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Sample records for ac applied field

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

    SciTech Connect

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

    2011-01-01

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

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

    SciTech Connect

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

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

  4. 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.

  5. 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.

  6. Manipulating Flames with AC Electric Fields

    NASA Astrophysics Data System (ADS)

    Bishop, Kyle

    2013-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-10-01

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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  10. AC Magnetic Field Frequency Dependence of Magnetoacoustic Emission

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  11. 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.

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

    SciTech Connect

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

    1997-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Ovadyahu, Z.

    2014-08-01

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

  15. Hierarchical assembly of anisotropic particles in AC electric fields

    NASA Astrophysics Data System (ADS)

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

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

  16. AC Electric Field Activated Shape Memory Polymer Composite

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  17. Critical field measurements in superconductors using ac inductive techniques

    NASA Astrophysics Data System (ADS)

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

    1983-09-01

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

  18. Electrohydrodynamics of suspension of liquid drops in AC fields

    NASA Astrophysics Data System (ADS)

    Abdul Halim, Md.; Esmaeeli, Asghar

    2012-11-01

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

  19. Rapid magnetic microfluidic mixer utilizing AC electromagnetic field.

    PubMed

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

    2009-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  1. Aligned Immobilization of Proteins Using AC Electric Fields.

    PubMed

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

    2016-03-01

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

  2. 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

  3. AC Electrostatic Field Study : Final Report.

    SciTech Connect

    Lebby, Gary L.

    1990-08-28

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

  4. 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.

  5. 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)

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

    NASA Astrophysics Data System (ADS)

    Demekhin, Evgeny; Korovyakovsky, Alex

    2006-11-01

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

  7. AC Electric Field Communication for Human-Area Networking

    NASA Astrophysics Data System (ADS)

    Kado, Yuichi; Shinagawa, Mitsuru

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

  8. Ion fluxes and electro-osmotic fluid flow in electrolytes around a metallic nanowire tip under large applied ac voltage.

    PubMed

    Poetschke, M; Bobeth, M; Cuniberti, G

    2013-09-10

    Motivated by the analysis of electrochemical growth of metallic nanowires from solution, we studied ion fluxes near nanoelectrodes in a binary symmetric electrolyte on the basis of the modified Poisson-Nernst-Planck equations in the strongly nonlinear region at large applied ac voltage. For an approximate calculation of the electric field near the nanowire tip, concentric spherical blocking electrodes were considered with radius of the inner electrode being of typically a few ten nanometers. The spatiotemporal evolution of the ion concentrations within this spherical model was calculated numerically by using the finite element method. The potential drop at the electric double layer, the electric field enhancement at the electrode surface, and the field screening in the bulk solution were determined for different bulk concentrations, ac voltages, and frequencies. The appearance of ac electro-osmotic fluid flow at the tip of a growing metallic nanowire is discussed, based on an estimation of the body force in the liquid near the nanowire tip, which was modeled by a cylinder with hemispherical cap. Electric field components tangential to the electrode surface exist near the contact between cylinder and hemisphere. Our analysis suggests that ac electro-osmotic flow causes an additional convective transport of metal complexes to the tip of the growing metal nanowire and thus affects the nanowire growth velocity. PMID:23927385

  9. Lipid Bilayer Vesicle Dynamics in AC Electric Fields

    NASA Astrophysics Data System (ADS)

    McConnell, Lane; Vlahovska, Petia; Miksis, Michael

    2014-11-01

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

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

    PubMed

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

    2015-06-01

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

  11. 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.

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

    PubMed

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

    2016-08-01

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

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

    PubMed Central

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

    2013-01-01

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

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

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

    SciTech Connect

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

    2010-12-15

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

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

    NASA Astrophysics Data System (ADS)

    Hatakeyama, Toyomasa; Tanji, Ayafumi; Yagi, Hiroshi

    1987-11-01

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

  1. 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 about 0.12 Pa were found to significantly 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 influenced 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 percent and 80 percent of the input power. The fraction of the input power deposited into the anode decreased with increasing applied field and anode radius. The highest performance measured, 20 percent efficiency at 3700 seconds specific impulse, was obtained using hydrogen propellant.

  2. Universal features of particle motion in ac electric fields

    NASA Astrophysics Data System (ADS)

    Niemeyer, L.; Seeger, M.

    2015-11-01

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

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

    PubMed

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

    2011-05-01

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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Liu, Minxian; Wang, Yan

    2012-01-01

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

  6. Thermodynamics of ferrofluids in applied magnetic fields.

    PubMed

    Elfimova, Ekaterina A; Ivanov, Alexey O; Camp, Philip J

    2013-10-01

    The thermodynamic properties of ferrofluids in applied magnetic fields are examined using theory and computer simulation. The dipolar hard sphere model is used. The second and third virial coefficients (B(2) and B(3)) are evaluated as functions of the dipolar coupling constant λ, and the Langevin parameter α. The formula for B(3) for a system in an applied field is different from that in the zero-field case, and a derivation is presented. The formulas are compared to results from Mayer-sampling calculations, and the trends with increasing λ and α are examined. Very good agreement between theory and computation is demonstrated for the realistic values λ≤2. The analytical formulas for the virial coefficients are incorporated in to various forms of virial expansion, designed to minimize the effects of truncation. The theoretical results for the equation of state are compared against results from Monte Carlo simulations. In all cases, the so-called logarithmic free energy theory is seen to be superior. In this theory, the virial expansion of the Helmholtz free energy is re-summed in to a logarithmic function. Its success is due to the approximate representation of high-order terms in the virial expansion, while retaining the exact low-concentration behavior. The theory also yields the magnetization, and a comparison with simulation results and a competing modified mean-field theory shows excellent agreement. Finally, the putative field-dependent critical parameters for the condensation transition are obtained and compared against existing simulation results for the Stockmayer fluid. Dipolar hard spheres do not undergo the transition, but the presence of isotropic attractions, as in the Stockmayer fluid, gives rise to condensation even in zero field. A comparison of the relative changes in critical parameters with increasing field strength shows excellent agreement between theory and simulation, showing that the theoretical treatment of the dipolar interactions

  7. 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.

  8. ACS Flat Field Corrections from Observations of 47 Tucanae

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

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

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

    PubMed

    Shafranjuk, S E

    2011-12-14

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

  10. Slip Line Field Applied To Deep Drawing

    SciTech Connect

    Miguel, V.; Coello, J.; Calatayud, A.; Martinez, A.; Benet, J

    2007-05-17

    Slip Line Field is a numerical method applied for modelling plane-strain processes. This method has been successfully checked properly for sheet drawing. Flange deformation in deep drawing is considered without change in thickness. A drawing mechanical test has been developed in order to reproduce the flange stresses state in sheet strips with the rolling direction selected. The fundamentals of this test, and some experimental results obtained from it, have been presented previously in different Congresses. In this work, an algorithm based on SLF has been implemented and theoretical results evaluated for different conditions. The algorithm have been applied to a mild DDQ steel and to a DDQ AISI 304 stainless steel. Theoretical and experimental results are compared. A good concordance in them has been found out under some conditions. One of the most important aspects is that it must not be considered tensile material properties but a modified behavior under multiaxial conditions.

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

    PubMed

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

    2014-05-01

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

  12. 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.

  13. 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.

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Liebrecht, C.

    2009-01-01

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

  17. 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.

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

    PubMed

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

    2010-10-01

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

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

    SciTech Connect

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

    2010-10-15

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

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

    SciTech Connect

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

    2002-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Amemiya, Naoyuki; Sato, Susumu; Ito, Takeshi

    2006-12-01

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

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

    PubMed

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

    2010-07-01

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

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Coombs, Timothy

    2015-05-01

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

  9. 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

  10. 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

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

    PubMed

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

    2016-01-01

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

  12. 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.

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

    PubMed

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

    De Marchi, Guido

    2002-07-01

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

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

    SciTech Connect

    Elesin, V. F.

    2013-11-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  17. 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.

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

    PubMed Central

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

    2015-01-01

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

  19. 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…

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2011-04-01

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

  4. 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.

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

    PubMed

    Jakova, Elisabet; Lee, Jeremy S

    2015-07-21

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

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

    NASA Astrophysics Data System (ADS)

    Mahmood, Bahar; Jaleh, Sojoodi; Yasaman, Yasaie

    2014-07-01

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

  8. Pipeline rehabilitation using field applied tape systems

    SciTech Connect

    Reeves, C.R.

    1998-12-31

    Bare steel pipelines were first installed years before the turn of the century. Pipeline operators soon realized the lie of bare steel could be greatly enhanced by applying coatings. Thus began ``pipeline rehabilitation.`` Many of the older pipelines were exposed, evaluated, coated and returned to service. This procedure has reached new heights in recent years as coated pipelines of the twentieth century, having lived past their original design life, are now subject to coating failure. Many operator companies with pipelines thirty years or older are faced with ``replace or recondition.`` Considering the emphasis on cost restraints and environmental issues, replacing an existing pipeline is often not the best decision. Rehabilitation is a preferred solution for many operators.

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

    PubMed

    Priede, Jānis; Etay, Jacqueline; Fautrelle, Yves

    2006-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    PubMed Central

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

    2009-01-01

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

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

    SciTech Connect

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

    1996-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  15. Experimental study on the effect of applying a crossed magnetic field on the insulator flashover behavior in high vacuum

    NASA Astrophysics Data System (ADS)

    Abu-Elabass, K.

    2015-09-01

    In this study, a possible method of reducing the flashover stress is achieved by the effect of an additional magnetic field in the transverse direction on the main applied electric field. The degree of vacuum used in this study was 5×10-5 Pa. The magnetic flux density B employed in this study extends from 4×10-3 to 24×10-3 T. From the results obtained throughout this work, the transverse magnetic field increases the flashover voltage and decreases the leakage current. The effect of the transverse magnetic field on the surface flashover of the dielectric solid in vacuum shows a marked dependence on the material and the thickness of the test specimen, the vacuum degree, the type of electric field (AC or DC) as well as the type of magnetic field (AC or DC).

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

    PubMed

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

    2009-01-16

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

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

    PubMed

    Holtappels, Moritz; Stubbe, Marco; Gimsa, Jan

    2009-02-01

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

  18. 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.

  19. Phase coexistence of a Stockmayer fluid in an applied field

    NASA Astrophysics Data System (ADS)

    Stevens, Mark J.; Grest, Gary S.

    1995-06-01

    We examine two apects of Stockmayer fluids, which consist of point dipoles that additionally interact via an attractive Lennard-Jones potential. We perform Monte Carlo simulations to examine the effect of an applied field on the liquid-gas phase coexistence and show that a magnetic fluid phase does exist in the absence of an applied field. As part of the search for the magnetic fluid phase, we perform Gibbs ensemble simulations to determine phase coexistence curves at large dipole moments, μ. The critical temperature is found to depend linearly on μ2 for intermediate values of μ beyond the initial nonlinear behavior near μ=0 and less than the μ where no liquid-gas phase coexistence has been found. For phase coexistence in an applied field, the critical temperatures as a function of the applied field for two different μ are mapped onto a single curve. The critical densities change very little as a function of applied field. We also verify that in an applied field the liquid droplets within the two-phase coexistence region become elongated in the direction of the field.

  20. 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).

  1. 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).

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

    PubMed

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

    2013-02-01

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

  3. 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.

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

    PubMed

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

    2014-01-01

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

  5. 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.

  6. 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…

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  9. 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.

  10. 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…

  11. Effect of applied magnetic field on a microwave plasma thruster

    SciTech Connect

    Yang Juan; Xu Yingqiao; Meng Zhiqiang; Yang Tielian

    2008-02-15

    Theoretical analysis and calculation show that applying a magnetic field in a microwave plasma thruster operating at 2.45 GHz can improve the thruster performance, whereby an electron cyclotron resonant layer at thruster startup state contributes to the increase of microwave energy dissipated in plasma, and a strong magnetic field up to 0.5 T can increase the peak temperature of inside plasma when the thruster operates in steady state. Experimental measurements of the thruster with applied field and operating on argon gas show high coupling efficiency. Plasma plume diagnostics deduce a high degree of gas ionization in the thruster cavity. This shows the feasibility of operating a microwave plasma thruster with an applied magnetic field.

  12. 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.

  13. 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).

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

    SciTech Connect

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

    1997-11-01

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

  15. Electromagnetic effects in an applied-field magnetoplasmadynamic thruster

    SciTech Connect

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

    1992-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1999-07-01

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

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

    SciTech Connect

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

    2014-08-20

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

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

    SciTech Connect

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

    2010-01-15

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

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

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

    SciTech Connect

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

    2008-06-25

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

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

  3. Spiral waves in oscillatory media with an applied electric field

    NASA Astrophysics Data System (ADS)

    Gabbay, Michael; Ott, Edward; Guzdar, Parvez N.

    1999-02-01

    Spiral waves in oscillatory reaction-diffusion systems under the influence of a uniform, time-independent electric field are modeled by the complex Ginzburg-Landau equation extended to include a convective term with complex coefficient. Results for the spiral drift, deformation, and frequency shift due to the electric field are obtained. The coefficient of the additional convective term is derived from the original reaction-diffusion system. The equation provides a good qualitative model of experimentally seen distortion of spiral waves in the presence of an applied electric field.

  4. 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.

  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. Thermodynamics of the Heisenberg ferromagnet in an applied magnetic field.

    NASA Technical Reports Server (NTRS)

    Flax, L.

    1972-01-01

    The anisotropic-Heisenberg-ferromagnet formalism developed previously is examined to include an applied magnetic field for the isotropic case in the random-phase approximation. Thermodynamic quantities such as magnetization, susceptibility, and the derivative of magnetization with respect to temperature are studied near the Curie point.

  7. Applying Sequential Fieldwork Skills across Two International Field Courses

    ERIC Educational Resources Information Center

    Rydant, A. L.; Shiplee, Brian A.; Smith, John P.; Middlekauff, Bryon D.

    2010-01-01

    This article addresses the development of a conceptual model of fieldwork practice and the creation of an associated set of skills for the geosciences. The set of eight generic and seventeen specific skills is applied in two international field courses to demonstrate the utility of such a skills-centered model across a broad range of venues,…

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

    PubMed

    Lee, Chee Kong; Gong, Jiangbin

    2011-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed

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

    2012-01-01

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

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  14. 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.

  15. Mechanical strains and electric fields applied to topologically imprinted elastomers

    NASA Astrophysics Data System (ADS)

    Burridge, D. J.; Mao, Y.; Warner, M.

    2006-08-01

    We analyze and predict the behavior of a chirally imprinted elastomer under a mechanical strain and an electric field, applied along the helical axis. As the strain and/or field increases, the system is deformed from a conical or transverse imprinted state towards an ultimately nematic one. At a critical strain and/or field there is a first-order transition to a low imprinting efficiency state. This transition is accompanied by a discontinuous global rotation of the director toward the axis of the imprinted helix, measured by the cone angle, θ . We show that the threshold electric field required for switching this transition can be conveniently low, provided an appropriate prestrain is imposed. We suggest that these properties may give rise to a “chiral pump.”

  16. Transverse voltage in superconductors at zero applied magnetic field

    NASA Astrophysics Data System (ADS)

    da Luz, M. S.; dos Santos, C. A. M.; Shigue, C. Y.; de Carvalho, F. J. H.; Machado, A. J. S.

    2009-01-01

    A systematic study of the transverse voltage at zero magnetic field in the superconducting state is reported. The effects of warming rate, temperature, applied magnetic field, and electrical current on the transversal resistance ( RXY) of polycrystalline superconducting sample are taken into account. At zero magnetic field two peaks are observed in RXY( T) curves which are related to the double superconducting transition in the RXX( T) component. In the superconducting ( RXX = zero) and normal states no transverse voltage has been detected at zero magnetic field as expected. The results are discussed within the framework of the motion of Abrikosov and Josephson vortices and anti-vortices. A new scaling relation between transverse and longitudinal components given by RXY ∼ d RXX/d T has been confirmed.

  17. External Horizontally Uniform Magnetic Field Applied to Steel Solidification

    NASA Astrophysics Data System (ADS)

    Mechighel, Farid; Kadja, Mahfoud

    Based on continuum model, a mathematical model for convection flow during directional solidification of steel, Fe-0.42wt%C, in an applied magnetic field is presented. The model includes mass, momentum, energy, species and electrical potential conservation equations. The geometry under study is rectangular. The permeability in the mushy zone is treated by means of the Blake-Kozeny equation. The system of equation has been discretized by means of Finite volume method. For solution of discretized equations SIMPLER Algorithm is used. The results show the strong effect of the magnetic field on the solidification process.

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

    NASA Astrophysics Data System (ADS)

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

    1999-02-01

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

  19. Applying field mapping refractive beam shapers to improve holographic techniques

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Williams, Gavin; McWilliam, Richard; Laskin, Vadim

    2012-03-01

    Performance of various holographic techniques can be essentially improved by homogenizing the intensity profile of the laser beam with using beam shaping optics, for example, the achromatic field mapping refractive beam shapers like πShaper. The operational principle of these devices presumes transformation of laser beam intensity from Gaussian to flattop one with high flatness of output wavefront, saving of beam consistency, providing collimated output beam of low divergence, high transmittance, extended depth of field, negligible residual wave aberration, and achromatic design provides capability to work with several laser sources with different wavelengths simultaneously. Applying of these beam shapers brings serious benefits to the Spatial Light Modulator based techniques like Computer Generated Holography or Dot-Matrix mastering of security holograms since uniform illumination of an SLM allows simplifying mathematical calculations and increasing predictability and reliability of the imaging results. Another example is multicolour Denisyuk holography when the achromatic πShaper provides uniform illumination of a field at various wavelengths simultaneously. This paper will describe some design basics of the field mapping refractive beam shapers and optical layouts of their applying in holographic systems. Examples of real implementations and experimental results will be presented as well.

  20. 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.

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

    PubMed

    Nishiguchi, Daiki; Sano, Masaki

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Low, Jonathan; Hogan, S. John

    2008-10-01

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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Beta Band Transcranial Alternating (tACS) and Direct Current Stimulation (tDCS) Applied After Initial Learning Facilitate Retrieval of a Motor Sequence

    PubMed Central

    Krause, Vanessa; Meier, Anna; Dinkelbach, Lars; Pollok, Bettina

    2016-01-01

    The primary motor cortex (M1) contributes to the acquisition and early consolidation of a motor sequence. Although the relevance of M1 excitability for motor learning has been supported, the significance of M1 oscillations remains an open issue. This study aims at investigating to what extent retrieval of a newly learned motor sequence can be differentially affected by motor-cortical transcranial alternating (tACS) and direct current stimulation (tDCS). Alpha (10 Hz), beta (20 Hz) or sham tACS was applied in 36 right-handers. Anodal or cathodal tDCS was applied in 30 right-handers. Participants learned an eight-digit serial reaction time task (SRTT; sequential vs. random) with the right hand. Stimulation was applied to the left M1 after SRTT acquisition at rest for 10 min. Reaction times were analyzed at baseline, end of acquisition, retrieval immediately after stimulation and reacquisition after eight further sequence repetitions. Reaction times during retrieval were significantly faster following 20 Hz tACS as compared to 10 Hz and sham tACS indicating a facilitation of early consolidation. tDCS yielded faster reaction times, too, independent of polarity. No significant differences between 20 Hz tACS and tDCS effects on retrieval were found suggesting that 20 Hz effects might be associated with altered motor-cortical excitability. Based on the behavioral modulation yielded by tACS and tDCS one might speculate that altered motor-cortical beta oscillations support early motor consolidation possibly associated with neuroplastic reorganization. PMID:26834593

  9. 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.

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

    SciTech Connect

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

    2007-06-01

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

  11. New method of applying conformal group to quantum fields

    NASA Astrophysics Data System (ADS)

    Han, Lei; Wang, Hai-Jun

    2015-09-01

    Most of previous work on applying the conformal group to quantum fields has emphasized its invariant aspects, whereas in this paper we find that the conformal group can give us running quantum fields, with some constants, vertex and Green functions running, compatible with the scaling properties of renormalization group method (RGM). We start with the renormalization group equation (RGE), in which the differential operator happens to be a generator of the conformal group, named dilatation operator. In addition we link the operator/spatial representation and unitary/spinor representation of the conformal group by inquiring a conformal-invariant interaction vertex mimicking the similar process of Lorentz transformation applied to Dirac equation. By this kind of application, we find out that quite a few interaction vertices are separately invariant under certain transformations (generators) of the conformal group. The significance of these transformations and vertices is explained. Using a particular generator of the conformal group, we suggest a new equation analogous to RGE which may lead a system to evolve from asymptotic regime to nonperturbative regime, in contrast to the effect of the conventional RGE from nonperturbative regime to asymptotic regime. Supported by NSFC (91227114)

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

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

  15. Scanning Hall probe measurements of field distributions of a coated conductor under applied fields

    NASA Astrophysics Data System (ADS)

    Yoo, Jaeun; Jung, Yonghwan; Lee, Jaeyoung; Lim, Sunme; Moo Lee, Sang; Jung, Ye Hyun; Youm, Dojun; Kim, Hosup; Ha, Hong Soo; Oh, Sangsoo

    2006-12-01

    We measured the field profiles near the surface of a coated conductor (CC) under various applied fields by using the scanning Hall probe method. The field, applied in the normal direction, was increased from zero to 171.5 Oe and then decreased to -58.8 Oe. We could not analyse our data completely by the direct use of Brandt's calculation but by a modification with unusual field dependences of the introduced parameters. Since Brandt's original calculation was based on homogeneous films, it was not suitable for CCs with coarse granular structures. The modified calculations with appropriate parameters are related to the coarse granular structures. Those parameters, D, Jc, and R, represent the three characteristics of the flux penetration network: the average distance of flux penetrations, the density of critical sheet currents, and the range of meandering of the flux penetration front, respectively. The external field dependences of these parameters were different from those of the classical critical state model.

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

    NASA Astrophysics Data System (ADS)

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

    1998-10-01

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

  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. 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.

  19. Experimental study of cooling enhancement using a Fe3O4 magnetic nanofluid, in an applied magnetic field

    NASA Astrophysics Data System (ADS)

    Stoian, F. D.; Holotescu, S.

    2014-11-01

    This paper presents the results of an experimental study that envisaged the evaluation of the cooling capabilities of a transformer oil based magnetic nanofluid with the solid volume fraction of magnetite nanoparticles equal to 0.0162, in an AC applied magnetic field (f = 50 Hz). The heating and cooling regimes of a coil immersed in the magnetic nanofluid were compared to that corresponding to the base fluid (transformer oil). The results of our study indicate that the temperature rise rate of the magnetic nanofluid is lower than that corresponding to the transformer oil and a lower stationary temperature is obtained in the coil core, where the magnetic flux density is the largest.

  20. 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.

  1. 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.

  2. The Physics of a Spheromak with Applied Vertical Field

    NASA Astrophysics Data System (ADS)

    Woodruff, S.; Hill, D. N.; Hooper, E. B.; Holcomb, C. T.; Stallard, B. W.; Wood, R. D.; Bulmer, R. H.; Cohen, B. I.; Lodestro, L.; Pearlstein, L. D.; Sspx Team

    2000-10-01

    Lawrence Livermore National Laboratory, Livermore, California, USA. The physics basis of the initial flux configurations producible by the newly installed bias coils in SSPX is elucidated, and the anticipated results are explored. Broadly, the new configurations should increase the helicity injection rate, reduce the proportion of the spheromak flux that intersects the material boundary (‘field errors’) and increase particle confinement time. The effect of the applied field on equilibrium (CORSICA in SSPX geometry[1]) and stability (DCON[2]) will be discussed. Also, the effects on the dominant modes will be explored through 3D resistive MHD simulation (NIMROD[3]). Finally, a means for sustaining the spheromak in the absence of the n=1 mode, thought to be necessary for current drive, will be examined. [1] Hooper et al Nuc. Fusion v39, no.7, pp863-871 1999 [2] Glasser LANL report LA-UR-95-528 1995 [3] Glasser et al Plas. Phys. Cont. Fus. 41, A747 1999. Work performed under the auspices of US DOE by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.

  3. 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

  4. 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.

  5. A phenomenological performance model for applied-field MPD thrusters

    NASA Astrophysics Data System (ADS)

    Albertoni, R.; Paganucci, F.; Andrenucci, M.

    2015-02-01

    A theoretical model for the performance prediction of applied-field magnetoplasmadynamic thrusters (MPDTs) is presented. MPD thrusters have been long regarded as leading candidates for near-term, thrust-demanding missions due to their substantial thrust density and specific impulse even at moderate power levels (50-200 kW). However, the complicated physics behind the acceleration mechanism as well as the challenging on-ground testing have delayed their development and optimization leading to a slow but constant decline of interest in such a technology. Despite several theoretical efforts in the last few decades, no complete and definitive understanding of the scaling relations governing their performance is yet available. In this work, a simple phenomenological model for both the thrust and the terminal voltage is presented and discussed. The validity of the model is then assessed through a systematic comparison with the experimental data available in the literature. It was found that the suggested model can actually capture most of the characteristic features of this class of thrusters within a 20% error for a wide range of operational conditions.

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

    SciTech Connect

    Wong, P.S.; Sastre, A.

    1995-10-01

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

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

    PubMed

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

    2016-01-01

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

  10. 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

  11. 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.

  12. 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…

  13. 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…

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

    NASA Astrophysics Data System (ADS)

    Sánchez, Jorge H.; Rinaldi, Carlos

    2009-10-01

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

  15. 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.

  16. Fresnel field interaction applied to scattering from a vegetation layer

    NASA Technical Reports Server (NTRS)

    Fung, A. K.; Chen, M. F.; Lee, K. K.

    1987-01-01

    Models for scattering from a vegetation layer treated as a collection of discrete scatterers usually assume far field interaction among scatterers. In a real vegetation medium such as a deciduous forest or a soybean field it is not always true that each leaf is in the far field of other leaves. This paper examines the additional effect when scatterers are permitted to be in the Fresnel zone of one another. Both disc-shaped and needle-shaped leaves are considered. It is found that in general this causes the backscattering coefficient to be lower for the disk-shaped leaves and may be higher or lower for the needle-shaped leaves depending upon polarization, incidence angle, and frequency than those computed under the assumption of conventional far field interaction.

  17. 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.

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

    PubMed

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

    2015-07-01

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

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

    PubMed Central

    2010-01-01

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

  20. Controllability of brushite structural parameters using an applied magnetic field.

    PubMed

    Kuznetsov, V N; Yanovska, A A; Stanislavov, A S; Danilchenko, S N; Kalinkevich, A N; Sukhodub, L F

    2016-03-01

    The paper studies the influence of low intensity static magnetic field on brushite structural and microstructural parameters using the X-ray diffraction and the transmission electron microscopy. This effect was shown to have various influences on DCPD (Dicalcium Phosphate Dihydrate) structure depending on a magnetic field configuration or time of synthesis, which allows achieving controllability of the main properties of an obtained material. The influence of the magnetic field leads mostly to the decrease of crystallite sizes with no impact on the crystal lattice parameters. In (0 2 0) and (1 5 0) planes the growth of crystallite sizes is observed after 2 and 3 days of crystallization, respectively. The analysis of different contributions to peak broadening in [0 b 0] direction showed a similar trend for the crystallite sizes with the lower lattice microstrains after 2 days of synthesis. The effect similar to the preferred orientation was observed and classified with the Harris method. PMID:26706562

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  4. 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. PMID:24593382

  5. 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.

  6. 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.

  7. 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.

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

    PubMed

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

    2006-12-01

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

  9. Numerical Simulations for the Design of a Magnetoplasmadynamic Thruster with Coaxial Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Haag, D.; Auweter-Kurtz, M.; Fertig, M.

    2004-10-01

    In this paper, the plasma flow in applied field magneto-plasmadynamic (AFMPD) thrusters is described by conservation equations for heavy particles, electrons and the magnetic field for thermal and chemical non-equilibrium. To take into account the effects of the applied magnetic field a quasi-three dimensional approach with vanishing azimuthal derivatives is used for the velocity and magnetic field. The vector potential formulation has been chosen for the description of the applied magnetic field to handle the influences of solenoidal coils and induced azimuthal current density on the magnetic field. The numerical scheme is based on a two-dimensional, axisymmetric finite volume method on unstructured, adaptive meshes.

  10. Parallel computation of automatic differentiation applied to magnetic field calculations

    SciTech Connect

    Hinkins, R.L. |

    1994-09-01

    The author presents a parallelization of an accelerator physics application to simulate magnetic field in three dimensions. The problem involves the evaluation of high order derivatives with respect to two variables of a multivariate function. Automatic differentiation software had been used with some success, but the computation time was prohibitive. The implementation runs on several platforms, including a network of workstations using PVM, a MasPar using MPFortran, and a CM-5 using CMFortran. A careful examination of the code led to several optimizations that improved its serial performance by a factor of 8.7. The parallelization produced further improvements, especially on the MasPar with a speedup factor of 620. As a result a problem that took six days on a SPARC 10/41 now runs in minutes on the MasPar, making it feasible for physicists at Lawrence Berkeley Laboratory to simulate larger magnets.

  11. 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.

  12. 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.

  13. 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.

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

    DOE PAGESBeta

    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

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

    NASA Astrophysics Data System (ADS)

    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.

  16. 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…

  17. Experimental Study of a Two-Dimensional Applied-Field Magnetoplasmadynamic Thruster

    NASA Astrophysics Data System (ADS)

    Iwakawa, Akira; Nakata, Daisuke; Kuninaka, Hitoshi

    A two-dimensional applied-field magnetoplasmadynamic thruster (2D AF-MPDT) has been developed. A strong crossed magnetic field of more than 1 T can be applied to the 2D AF-MPDT. A thrust measurement system was newly developed. Successful operation with several applied magnetic field strengths from 0 T to 1 T was achieved and acceptable thrust efficiency was obtained. The discharge voltage increased when the magnetic field was applied. The thrust efficiency improves with increasing magnetic field. An operation limit such as a voltage hash was not observed. In this paper, the results indicate that the thrust efficiency of the 2D AF-MPDT can be improved with a strong applied crossed magnetic field.

  18. 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 0.20 T, 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 was strongly dependent on anode radius. Thruster efficiency increased monotonically with applied-field strength and propellant flow rate.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Mori, Hiroshi; Asahara, Yousuke

    1996-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1986-12-01

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

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    PubMed

    Zhadin, M N

    2001-01-01

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

  5. Control of molecular orientation in TTF TCNQ co-evaporated films by applying an electric field

    NASA Astrophysics Data System (ADS)

    Kato, N. A.; Fujimura, M.; Kuniyoshi, S.; Kudo, K.; Hara, M.; Tanaka, K.

    1998-06-01

    We have investigated the effect of an electric field on the molecular orientation of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) co-evaporated films, using an optical microscope, a scanning tunnelling microscope and X-ray diffraction. It is found that with an electric field applied TTF-TCNQ grows with the b-axis parallel to the electric field.

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

    PubMed

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

    2000-11-20

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

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

    NASA Astrophysics Data System (ADS)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

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

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

    SciTech Connect

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

    2013-10-15

    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 (10{sup 14}–10{sup 15} m{sup −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.

  9. 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.

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

    SciTech Connect

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

    2006-07-01

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

  11. 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

  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. PMID:26323781

  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. Macroscopic manifestations of broken inversion symmetry in noncentrosymmetric superconductors with applied magnetic field

    NASA Astrophysics Data System (ADS)

    Oka, Masatosi; Ichioka, Masanori; Machida, Kazushige

    2007-03-01

    We numerically investigate paramagnetic properties in noncentrosymmetric superconductors under applied magnetic fields, based on the time-dependent Ginzburg-Landau theory including the Pauli paramagnetic effect and the Rashba interaction. When an applied field is perpendicular to the polar axis, the paramagnetic effect breaks centrosymmetry in the Meissner state and cylindrical symmetry in the vortices, as macroscopic manifestations of broken inversion symmetry in the spatial structures of the screening current and the penetrating field. The paramagnetic supercurrent exists even at the vortex center by their asymmetric properties, therefore the flux flow is spontaneously induced without applying external currents.

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

    SciTech Connect

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

    2008-06-25

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

  16. 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.

  17. 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Logan, N. C.; Park, J.-K.; Paz-Soldan, C.; Lanctot, M. J.; Smith, S. P.; Burrell, K. H.

    2016-03-01

    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. 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.

  20. 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

  1. Field Test of Fiber-Optic Voltage and Current Sensors Applied to Gas Insulated Substation

    NASA Astrophysics Data System (ADS)

    Kuroda, Y.; Abe, Y.; Kuwahara, H.; Yoshinaga, K.

    1986-08-01

    The fiber-optic voltage and current sensors applied for 84kV three phase type gas insulated substation (GIS) were tested in order to see the advantages of these sensors practically in adverse field condition. The application technologies and field endurance test results of the sensors are described in this paper.

  2. Magnetoelectric and thermoelectric transport in graphene and helical metal: Effect of applied electric field

    NASA Astrophysics Data System (ADS)

    Chao, Sung-Po; Wei, Huazhou; Aji, Vivek

    2012-02-01

    We report on the electrical and thermoelectric transport properties of the surface state of the 3D topological insulator (TI) and graphene in a quantizing magnetic field. An unique feature of these systems is the evolution of the Landau level spectrum as a function of applied in plane electric field. We bench mark out results at small fields by computing conductivity and thermopower within linear response. We find that the universal values of thermopower in the clean limit depend on the gyromagnetic ratio in TIs, providing a clear distinction from graphene. In large electric fields we find an oscillation of conductivity as a function of applied electric field for fixed chemical potential, but not for fixed particle density. Signatures of the Landau level dependence on electric fields are also found in thermopower. These results are suggested as possible probes, in transport measurements of topological surface states.

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

    PubMed

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  5. 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

  6. 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.

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

    PubMed

    Sugioka, Hideyuki

    2016-08-01

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

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

    PubMed

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

    1996-03-01

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

  9. Selective Stabilization of the Fddd Diblock Copolymer Microphase in an Applied Electric Field

    NASA Astrophysics Data System (ADS)

    Martin, Jonathan; Li, Wei; Delaney, Kris; Fredrickson, Glenn

    Using self-consistent field theory, we explore the phase behavior of AB diblock copolymer melts in a uniform applied electric field. We assign an isotropic polarizability to each monomer type, such that the electric field selectively destabilizes AB interfaces that are perpendicular to the applied field. Under the mean-field approximation of the present model, lamellar and cylindrical structures align such that their AB interfaces are parallel to the electric field, and their relative stability with respect to the disordered phase is unchanged. Sphere and network phases do not have an axis of uniformity, so the preferred orientation for each of these phases must be identified by simulation. Small distortions in morphology are induced by the electric field for these phases, such that the free energy response includes non-harmonic terms. We compute the phase diagram for a melt in an applied electric field by comparing free energies of each morphology at its preferred orientation. We find that the stability regions for the sphere and network phases shrink with increasing electric field strength. Moreover, the double gyroid phase is relatively destabilized against the Fddd phase, extending the stability region for the Fddd phase to larger segregation strengths.

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

    PubMed Central

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

    2014-01-01

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

  11. 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.

  12. 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. PMID:27401088

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-04-01

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

  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. Performance of a 100 kW class applied field MPD thruster

    NASA Technical Reports Server (NTRS)

    Mantenieks, M. A.; Sovey, J. S.; Haag, T. W.; Raitano, P.; Myers, R. M.; Parkes, J. E.

    1989-01-01

    The performance of a 100 kW class, applied field 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.

  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. 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.

  1. Improving wave-packet revivals in circular billiards by applying constant magnetic fields

    SciTech Connect

    Delben, G. J.; Gusso, A.; Luz, M. G. E. da

    2006-05-15

    We show that the revivals structure of Gaussian wave packets for a charged particle with nonzero linear momentum placed in a circular billiard can be considerably improved by applying a perpendicular constant magnetic field of correct chosen intensity. To obtain the desired enhancement, the field must be turned on only at certain time values. We also briefly investigate how the shape of the evoluted packet at the revivals, with and without an external B, compares with the initial state.

  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. 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.

  4. 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.

  5. 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…

  6. 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)

  7. 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. PMID:7763365

  8. Effects of applied dc radial electric fields on particle transport in a bumpy torus plasma

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1978-01-01

    The influence of applied dc radial electric fields on particle transport in a bumpy torus plasma is studied. The plasma, magnetic field, and ion heating mechanism are operated in steady state. Ion kinetic temperature is more than a factor of ten higher than electron temperature. The electric fields raise the ions to energies on the order of kilovolts and then point radially inward or outward. Plasma number density profiles are flat or triangular across the plasma diameter. It is suggested that the radial transport processes are nondiffusional and dominated by strong radial electric fields. These characteristics are caused by the absence of a second derivative in the density profile and the flat electron temperature profiles. If the electric field acting on the minor radius of the toroidal plasma points inward, plasma number density and confinement time are increased.

  9. Bifurcation and chaos in spin-valve pillars in a periodic applied magnetic field.

    PubMed

    Murugesh, S; Lakshmanan, M

    2009-12-01

    We study the bifurcation and chaos scenario of the macromagnetization vector in a homogeneous nanoscale-ferromagnetic thin film of the type used in spin-valve pillars. The underlying dynamics is described by a generalized Landau-Lifshitz-Gilbert (LLG) equation. The LLG equation has an especially appealing form under a complex stereographic projection, wherein the qualitative equivalence of an applied field and a spin-current induced torque is transparent. Recently, chaotic behavior of such a spin vector has been identified by Li et al. [ Phys. Rev. B 74, 054417 (2006)] using a spin-polarized current passing through the pillar of constant polarization direction and periodically varying magnitude, owing to the spin-transfer torque effect. In this paper, we show that the same dynamical behavior can be achieved using a periodically varying applied magnetic field in the presence of a constant dc magnetic field and constant spin current, which is technically much more feasible, and demonstrate numerically the chaotic dynamics in the system for an infinitely thin film. Further, it is noted that in the presence of a nonzero crystal anisotropy field, chaotic dynamics occurs at much lower magnitudes of the spin current and dc applied field. PMID:20059207

  10. Bifurcation and chaos in spin-valve pillars in a periodic applied magnetic field

    NASA Astrophysics Data System (ADS)

    Murugesh, S.; Lakshmanan, M.

    2009-12-01

    We study the bifurcation and chaos scenario of the macromagnetization vector in a homogeneous nanoscale-ferromagnetic thin film of the type used in spin-valve pillars. The underlying dynamics is described by a generalized Landau-Lifshitz-Gilbert (LLG) equation. The LLG equation has an especially appealing form under a complex stereographic projection, wherein the qualitative equivalence of an applied field and a spin-current induced torque is transparent. Recently, chaotic behavior of such a spin vector has been identified by Li et al. [Li et al.Phys. Rev. B 74, 054417 (2006)] using a spin-polarized current passing through the pillar of constant polarization direction and periodically varying magnitude, owing to the spin-transfer torque effect. In this paper, we show that the same dynamical behavior can be achieved using a periodically varying applied magnetic field in the presence of a constant dc magnetic field and constant spin current, which is technically much more feasible, and demonstrate numerically the chaotic dynamics in the system for an infinitely thin film. Further, it is noted that in the presence of a nonzero crystal anisotropy field, chaotic dynamics occurs at much lower magnitudes of the spin current and dc applied field.

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

    DOE PAGESBeta

    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 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

  12. Identifying a cooperative control mechanism between an applied field and the environment of open quantum systems

    NASA Astrophysics Data System (ADS)

    Gao, Fang; Rey-de-Castro, Roberto; Wang, Yaoxiong; Rabitz, Herschel; Shuang, Feng

    2016-05-01

    Many systems under control with an applied field also interact with the surrounding environment. Understanding the control mechanisms has remained a challenge, especially the role played by the interaction between the field and the environment. In order to address this need, here we expand the scope of the Hamiltonian-encoding and observable-decoding (HE-OD) technique. HE-OD was originally introduced as a theoretical and experimental tool for revealing the mechanism induced by control fields in closed quantum systems. The results of open-system HE-OD analysis presented here provide quantitative mechanistic insights into the roles played by a Markovian environment. Two model open quantum systems are considered for illustration. In these systems, transitions are induced by either an applied field linked to a dipole operator or Lindblad operators coupled to the system. For modest control yields, the HE-OD results clearly show distinct cooperation between the dynamics induced by the optimal field and the environment. Although the HE-OD methodology introduced here is considered in simulations, it has an analogous direct experimental formulation, which we suggest may be applied to open systems in the laboratory to reveal mechanistic insights.

  13. Finite element modeling and analysis of piezo-integrated composite structures under large applied electric fields

    NASA Astrophysics Data System (ADS)

    Rao, M. N.; Tarun, S.; Schmidt, R.; Schröder, K.-U.

    2016-05-01

    In this article, we focus on static finite element (FE) simulation of piezoelectric laminated composite plates and shells, considering the nonlinear constitutive behavior of piezoelectric materials under large applied electric fields. Under the assumptions of small strains and large electric fields, the second-order nonlinear constitutive equations are used in the variational principle approach, to develop a nonlinear FE model. Numerical simulations are performed to study the effect of material nonlinearity for piezoelectric bimorph and laminated composite plates as well as cylindrical shells. In comparison to the experimental investigations existing in the literature, the results predicted by the present model agree very well. The importance of the present nonlinear model is highlighted especially in large applied electric fields, and it is shown that the difference between the results simulated by linear and nonlinear constitutive FE models cannot be omitted.

  14. Numerical Simulations and Accompanying Experimental Investigations of Magnetoplasmadynamic Thrusters with Coaxial Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Haag, Daniel; Auweter-Kurtz, Monika; Fertig, Markus; Herdrich, Georg

    An overview is given on a numerical simulation program for applied field magnetoplasmadynamic (AF-MPD) thrusters, which is currently under development at the Institute of Space Systems (IRS). The program allows the simulation of argon plasma flows in thermal and chemical non-equilibrium. The code is based on an axisymmetric finite volume method on unstructured, adaptive meshes. An externally applied magnetic field can be taken into account employing the vector potential formulation. Azimuthal velocity and magnetic field are handled by a quasi three-dimensional approach with vanishing azimuthal derivatives. Additionally, a laboratory AF-MPD thruster for the power range of 10-20 kW has been built up at IRS. The goal of the experimental investigations is the characterization of the operation and performance parameters of the thruster.

  15. Hydrogenic donor impurity in parallel-triangular quantum wires: Hydrostatic pressure and applied electric field effects

    NASA Astrophysics Data System (ADS)

    Restrepo, R. L.; Giraldo, E.; Miranda, G. L.; Ospina, W.; Duque, C. A.

    2009-12-01

    The combined effects of the hydrostatic pressure and in-growth direction applied electric field on the binding energy of hydrogenic shallow-donor impurity states in parallel-coupled-GaAs- Ga1-xAlxAs-quantum-well wires are calculated using a variational procedure within the effective-mass and parabolic-band approximations. Results are obtained for several dimensions of the structure, shallow-donor impurity positions, hydrostatic pressure, and applied electric field. Our results suggest that external inputs such us hydrostatic pressure and in-growth direction electric field are two useful tools in order to modify the binding energy of a donor impurity in parallel-coupled-quantum-well wires.

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

    PubMed

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

    2016-08-01

    Bacillus thuringiensis (Bt) event DAS-81419-2 (Conkesta technology) in soybean, Glycine max (L.) Merrill, expresses Cry1F and Cry1Ac proteins to provide protection from feeding by several lepidopteran pests. A total of 27 field experiments across nine locations were conducted from 2011 to 2015 in southern and central Brazil to characterize the efficacy of DAS-81419-2 soybean infested with Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae), Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), Heliothis virescens (F.) (Lepidoptera: Noctuidae), and Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) during vegetative (V4) and reproductive (R2 and R4) crop developmental stages. The efficacy of DAS-81419-2 was compared to that of a non-Bt isogenic variety managed with or without applications of commercial foliar insecticides for lepidopteran control. DAS-81419-2 soybean consistently experienced defoliation levels of 0.5% or less (compared with 20.05-56.74% in the non-Bt, nonsprayed treatment) and larval survival of < 0.1% in all four species across the vegetative and reproductive plant stages evaluated. The efficacy of DAS-81419-2 was significantly higher than commercial foliar insecticides applied to the non-Bt variety. DAS-81419-2 soybeans containing two highly effective Bt proteins are expected to be a more robust IRM tool compared to single-trait Bt technologies. The consistent efficacy of DAS-81419-2 soybeans across years, locations, and crop stages suggests that it will be a valuable product for management of hard-to-control key lepidopteran pests in South American soybean production. PMID:27401112

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Kim, Sejong

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

  19. Controlling frustrated liquids and solids with an applied field in a kagome Heisenberg antiferromagnet.

    PubMed

    Nishimoto, Satoshi; Shibata, Naokazu; Hotta, Chisa

    2013-01-01

    Quantum spin-1/2 kagome Heisenberg antiferromagnet is the representative frustrated system possibly hosting a spin liquid. Clarifying the nature of this elusive topological phase is a key challenge in condensed matter; however, even identifying it still remains unsettled. Here we apply a magnetic field and discover a series of spin-gapped phases appearing at five different fractions of magnetization by means of a grand canonical density matrix renormalization group, an unbiased state-of-the-art numerical technique. The magnetic field dopes magnons and first gives rise to a possible Z₃ spin liquid plateau at 1/9 magnetization. Higher field induces a self-organized super-lattice unit, a six-membered ring of quantum spins, resembling an atomic orbital structure. Putting magnons into this unit one by one yields three quantum solid plateaus. We thus find that the magnetic field could control the transition between various emergent phases by continuously releasing the frustration. PMID:23912842

  20. Digitized quantitative electroencephalographic patterns applied as magnetic fields inhibit melanoma cell proliferation in culture.

    PubMed

    Karbowski, Lukasz M; Harribance, Sean L; Buckner, Carly A; Mulligan, Bryce P; Koren, Stanley A; Lafrenie, Robert M; Persinger, Michael A

    2012-08-15

    Weak (1 μT) physiologically patterned magnetic fields produce changes in behavioral, physiological, and cellular activity. In the present experiments 12 temporal samples of the electroencephalographic anomaly and normal activity of a person (SLH) whose proximity reliably affected the brain activity of others were extracted from QEEG data, digitized, and presented as equivalent magnetic field patterns to B16 mouse melanoma cells. Only two of the patterns, both originating from the primary source (right temporal lobe) of the EEG anomaly reduced the cell growth by one-third compared to the other patterns extracted from his QEEG or sham field exposures. In previous experiments these EEG transients were also associated with marked increases in photon emissions from the right side of SLH's head. The results suggest that the intrinsic complexity of electroencephalographic patterns of some people, when amplified appropriately and applied as computer-generated magnetic fields in the three spatial planes, could diminish cancer cell growth. PMID:22750152

  1. 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.

  2. AC electrophoretic deposition of organic-inorganic composite coatings.

    PubMed

    Yoshioka, T; Chávez-Valdez, A; Roether, J A; Schubert, D W; Boccaccini, A R

    2013-02-15

    Alternating current electrophoretic deposition (AC-EPD) of polyacrylic acid (PAA)-titanium oxide (TiO(2)) nanoparticle composites on stainless steel electrodes was investigated in basic aqueous solution. AC square wave with duty cycle of 80% was applied at a frequency of 1 kHz. FTIR-ATR spectra showed that both AC and direct current (DC) EPD successfully deposited PAA-TiO(2) composites. The deposition rate using AC-EPD was lower than that obtained in direct current DC-EPD. However, the microstructure and surface morphology of the deposited composite coatings were different depending on the type of electric field applied. AC-EPD applied for not more than 5 min led to smooth films without bubble formation, while DC-EPD for 1 min or more showed deposits with microstructural defects possibly as result of water electrolysis. AC-EPD was thus for the first time demonstrated to be a suitable technique to deposit organic-inorganic composite coatings from aqueous suspensions, showing that applying a square wave and frequency of 1 kHz leads to uniform PAA-TiO(2) composite coatings on conductive materials. PMID:23218240

  3. Forces acting on a particle in a concentration gradient under an externally applied oscillating electric field

    NASA Astrophysics Data System (ADS)

    Luo, Yuan; Yobas, Levent

    2014-09-01

    We report a force field on a particle in a concentration (conductivity) gradient under an externally applied oscillating electric field. The conductivity gradient was established through integrated microcapillaries bridging high- and low-conductivity streams in dedicated microchannels. Particles in low-conductivity electrolyte were observed to experience a strong force with the application of an oscillating field and pulled to the microcapillary openings where they were held against the flow. Particle trapping was accompanied by a concurrent electrolyte injection from high- to low-conductivity channel, triggered with the externally applied field and further contributed to the conductivity gradient near the trapping sites. We experimentally evaluated the force dependence on the magnitude and frequency of the excitation field for 10 μm polystyrene particles immersed at various conductivity levels. The experiments suggest that the observed force cannot be simply explained by dielectrophoresis or diffusiophoresis alone and further requires the consideration of a so-called concentration polarization force. This force has been rather recently postulated based on a theoretical treatment and yet to be experimentally validated. Using the theoretical treatment of this force, together with fluidic drag and diffusiophoresis, we correctly predicted trapping trajectories of particles based on a simultaneous solution of Poisson-Nernst-Planck and Stokes equations. The predicted and measured trapping velocities were found in reasonable agreement (within a factor of <1.6), suggesting that the consideration of the concentration polarization force is necessary for describing the observed particle behavior.

  4. 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.

  5. Kink instability in applied-field magneto-plasma-dynamic thrusters.

    PubMed

    Zuin, M; Cavazzana, R; Martines, E; Serianni, G; Antoni, V; Bagatin, M; Andrenucci, M; Paganucci, F; Rossetti, P

    2004-06-01

    Measurements of magnetic and electrostatic fluctuations in an applied field magneto-plasma-dynamic thruster have shown that a m/n=1/1 kink mode becomes unstable whenever the Kruskal-Shafranov limit is violated. A positive correlation is established between the kink and performance degradation at high current, which has until now prevented the use of this kind of thruster in space missions. PMID:15245232

  6. Self-pumped and double phase conjugation in GaAs with applied dc electric field

    NASA Technical Reports Server (NTRS)

    Chua, P. L.; Liu, D. T. H.; Cheng, L. J.

    1990-01-01

    Self-pumped and double phase conjugation are first demonstrated in undoped GaAs with applied dc electric field at 1.06 micron wavelength. Phase-conjugate reflectivities of up to 3 percent and 0.5 percent, respectively, are obtained and other dependences are reported. Reported values of the self-pumped phase-conjugate reflectivity are compared with those of InP.

  7. Control of Carbon Nanotube Morphology by Change of Applied Bias Field During Growth

    SciTech Connect

    Chen, L H.; AuBuchon, J F.; Gapin, A; Daraio, C; Bandaru, P; Jin, Sungho; Kim, D. W.; Yoo, I K.; Wang, Chong M.

    2004-10-21

    Carbon nanotube morphology has been engineered via simple control of applied voltage during dc plasma chemical vapor deposition growth. Below a critical applied voltage, a nanotube configuration of vertically aligned tubes with a constant diameter is obtained. Above the critical voltage, a nanocone-type configuration is obtained. The strongly field-dependent transition in morphology is attributed primarily to the plasma etching and decrease in the size of nanotube-nucleating catalyst particles. A two-step control of applied voltage allows a creation of dual-structured nanotube morphology consisting of a broad base nanocone ({approx}200 nm dia.) with a small diameter nanotube ({approx}7 nm) vertically emanating from the apex of the nanocone, which may be useful for atomic force microscopy.

  8. Temperature Dependence of Magnetization at Zero Applied Magnetic Field in Nearly Two Dimensional Ferromagnets

    NASA Astrophysics Data System (ADS)

    Widodo, Chomsin S.; Fujii, Muneaki

    2012-12-01

    NMR measurement have been made at low temperatures on the crystal structure of K2CuF4 and (C3H7NH3)2CuCl4 at zero applied magnetic field. 63Cu, 65Cu and 35Cl NMR have been used to measure spontaneous magnetization at the temperature range 2 K down to 30 mK. We have made the NMR experiments using a 3He-4He dilution refrigerator by conventional pulsed NMR method without external magnetic field. The magnetization at zero applied magnetic field in the nearly two-dimensional ferromagnet K2CuF4 of the experimental data is in a good agreement with Yamaji-Kondo theory and θc = 0.3, which is applied the double-time Green's function method incorporated with Tyablikov's decoupling. For temperature 1.1 K down to 0.26 K, the spontaneous magnetization of (C3H7NH3)2CuCl4 is support (t log t')-formalism from the spin wave theory.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  10. 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.

  11. Effect of applied magnetic fields during directional solidification of eutectic Bi-Mn

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    Samples of rod eutectics Bi/MnBi were directionally solidified in a growth-up Bridgman-Stockbarger configuration in the presence of a transverse magnetic field up to 3 kg to determine whether gravity-driven convective effects could be reduced or eliminated. The experiments were carried out over a range of furnace velocities, V, of 0.2 to 50 cm per hour with a thermal gradient at the liquid-solid interface of 100 C/cm and 150 C/cm. Morphological, thermal and magnetic analyses were carried out on samples grown with and without an applied magnetic field. For samples grown at V greater than 3 cm per hour in a transverse magnetic field, reduced mean rod diameter and interrod spacing occurred as well as undercooling and increased coercive strength. The data agreed with that obtained for low-g growth at 50 cm per hour and 30 cm per hour.

  12. 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.

  13. High resolution digital holographic synthetic aperture applied to deformation measurement and extended depth of field method.

    PubMed

    Claus, Daniel

    2010-06-01

    This paper discusses the potential of the synthetic-aperture method in digital holography to increase the resolution, to perform high accuracy deformation measurement, and to obtain a three-dimensional topology map. The synthetic aperture method is realized by moving the camera with a motorized x-y stage. In this way a greater sensor area can be obtained resulting in a larger numerical aperture (NA). A larger NA enables a more detailed reconstruction combined with a smaller depth of field. The depth of field can be increased by applying the extended depth of field method, which yields an in-focus reconstruction of all longitudinal object regions. Moreover, a topology map of the object can be obtained. PMID:20517390

  14. 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. PMID:2117228

  15. Investigation of Efficiency in Applied Field MagnetoPlasmaDynamic Thrusters

    NASA Astrophysics Data System (ADS)

    Lev, Dan

    An experimental and theoretical investigation of the scaling of thrust efficiency with the operational parameters (J,B,m˙) of applied-field magnetoplasmadynamic thrusters (AF-MPDTs) is carried out to provide guidelines for scaling and controlling AF-MDPT performance. This investigation is based on characterization of the various power dissipation mechanisms in AF-MPDTs with a focus on the acceleration and anode sheath power components. A semi-empirical model is derived for the anode sheath voltage fall in AF-MPDTs and verified by comparison to experimental data on a 30~kW lithium-fed steady-state AF-MPDT obtained using a hot langmuir probe. It is found that the anode sheath voltage fall increases approximately linearly with current and applied magnetic field and is inversely proportional to mass flow rate. It is shown that, although the electrons in the anode sheath are unmagnetized the voltage fall is attributed to plasma density reduction at the sheath edge, which is a result of increased plasma pinching at higher applied magnetic field values. It is also concluded that increased thermionic emission from the anode surface leads to an increase in the anode sheath voltage fall; therefore anode material with a high work function is preferred. A thrust efficiency model is formulated by employing a thrust formula previously derived and verified for the same thruster, and composing expressions for the different voltage components in AF-MPDTs. It is demonstrated that the efficiency increases with applied magnetic field for all current and mass flow rate values, and the enhancement of the efficiency by the applied magnetic field is greater when the mass flow rate is reduced. It is shown that the efficiency-current curves have a decreasing-increasing behavior due to an interchange between the different thrust components, each of which dominates in a different current regime and thus affects the scalability of the acceleration power component with current. It is

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

    NASA Astrophysics Data System (ADS)

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

    2005-10-01

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

  17. 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

  18. Thermionic triode generates ac power

    NASA Technical Reports Server (NTRS)

    Kniazzeh, A. G. F.; Scharz, F. C.

    1970-01-01

    Electrostatic grid controls conduction cycle of thermionic diode to convert low dc output voltages to high ac power without undesirable power loss. An ac voltage applied to the grid of this new thermionic triode enables it to convert heat directly into high voltage electrical power.

  19. 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.

  20. 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.

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

    PubMed Central

    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. PMID:25624018

  2. Single event AC - DC electrospraying

    NASA Astrophysics Data System (ADS)

    Stachewicz, U.; Dijksman, J. F.; Marijnissen, J. C. M.

    2008-12-01

    Electrospraying is an innovative method to deposit very small amounts of, for example, biofluids (far less than 1 p1) that include DNA or protein molecules. An electric potential is applied between a nozzle filled with liquid and a counter electrode placed at 1-2 millimeter distance from the nozzle. In our set-up we use an AC field superposed on a DC field to control the droplet generation process. Our approach is to create single events of electrospraying triggered by one single AC pulse. During this pulse, the equilibrium meniscus (determined by surface tension, static pressure and the DC field) of the liquid changes rapidly into a cone and subsequently into a jet formed at the cone apex. Next, the jet breaks-up into fine droplets and the spraying stops. The meniscus returns to its equilibrium shape again. So far we obtained a stable and reproducible single event process for ethanol and ethylene glycol with water using glass pipettes. The results will be used to generate droplets on demand in a controlled way and deposit them on a pre-defined place on the substrate.

  3. Electron and ion kinetics and anode plasma formation in two applied Br field ion diodes

    NASA Astrophysics Data System (ADS)

    Johnson, D. J.; Quintenz, J. P.; Sweeney, M. A.

    1985-02-01

    Two magnetically insulated ion diodes that utilize a radial applied-B field are described. Both diodes generate an annular beam that is extracted along the diode axis. The first diode operated at 1.2 MV and 600 kA for 25 ns and generated a 300-kA ion beam. The second operated at 300 kV, 100 kA and generated 15 kA of ion current. The first diode was used to study diode performance as a function of inner and outer anode-cathode gaps, the applied-B field, and transmission line current ratios. The second diode was used to study anode plasma formation. The diodes were operated below Bcrit, resulting in electron leakage to the anode, especially near the outer cathode. A definition of Bcrit applicable to extraction diodes is given and methods of improving ion production efficiency in these diodes are suggested. The strong correlation of ion production with visible light emission suggests, however, that the electron loss played an important role in anode turn-on. The breakdown of neutral gas desorbed by electron impact is thought to be the anode plasma production mechanism. The grazing incidence leakage electrons affect the breakdown by significantly enhancing space-charge-induced electric fields in the dielectric-filled anode grooves.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. 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.

  6. 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.

  7. 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.

  8. Applying the Aramid Joined v-belt high torque, low speed oil field pumping units

    SciTech Connect

    Stork, D.; Watson, J.

    1982-11-01

    This paper discusses the successful application of Aramid fiber-reinforced Torque Team Plus Joined Vbelts to low speed; (8-20 rpm) high torque, up to (320,000 in-lb); 100% belt driven oil field pumping units. Also discussed is a comparison in operating efficiency over gear or chain units, reduced initial expense, and lower overall maintenance effort. The Aramid reinforced Joined V-belts were applied to a double reduction drive (68-142:1 ratio) eliminating gear or chain reducers. Pumping units range in size from 57,000 in-lb to 320,000 in-lb.

  9. 100-kW class applied-field thruster component wear

    SciTech Connect

    Mantenieks, M.A. ); Myers, R.M. )

    1993-01-20

    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.

  10. 100-kW class applied-field MPD thruster component wear

    NASA Technical Reports Server (NTRS)

    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.

  11. A parallel finite-volume MHD code for plasma thrusters with an applied magnetic field

    NASA Astrophysics Data System (ADS)

    Norgaard, Peter; Choueiri, Edgar; Jardin, Stephen

    2006-10-01

    The Princeton Code for Advanced Plasma Propulsion Simulation (PCAPPS) is a recently developed parallel finite volume code that solves the resistive MHD equations in axisymmetric form. It is intended for simulating complex plasma flows, especially those in plasma thrusters. The code uses a flux function to represent the poloidal field. It allows for externally applied magnetic fields, necessary for efficient operation of magnetoplasmadynamic thrusters (MPDT) at low power. Separate electron and heavy species energy equations are employed, and model closure is achieved by a multi-level equilibrium ionization equation of state. We provide results from various validation tests, along with solver accuracy and parallel efficiency studies. Preliminary numerical studies of a lithium-fed MPDT are also presented.

  12. Highly selective water and fat imaging applying multislice sequences without sensitivity to B1 field inhomogeneities.

    PubMed

    Schick, F; Forster, J; Machann, J; Huppert, P; Claussen, C D

    1997-08-01

    Improved selectivity to one chemical shift component was obtained using simultaneous slice-selective and chemical shift-selective excitation in sequences with usual spin-echo refocusing. The new type of sequences can be applied on modern whole-body units and permits multislice operation. Spatial-spectral excitation is based on prior research in this field, but the proposed improved version provides off-center slice excitation by the usual processing of the RF pulse envelopes. In addition, no irregular gradient shapes are necessary. The required B0 homogeneity of the new method is similar to conventional "fat-sat" techniques. In contrast to fat-sat methods, selectivity to water is not reduced by unavoidable misadjustments of the transmitter or B1 field inhomogeneities in the newly developed approach. Thus, the reported method has the potential to replace standard frequency selective fat-sat sequences for most applications. PMID:9256107

  13. Applying Seismic Methods to National Security Problems: Matched Field Processing With Geological Heterogeneity

    SciTech Connect

    Myers, S; Larsen, S; Wagoner, J; Henderer, B; McCallen, D; Trebes, J; Harben, P; Harris, D

    2003-10-29

    Seismic imaging and tracking methods have intelligence and monitoring applications. Current systems, however, do not adequately calibrate or model the unknown geological heterogeneity. Current systems are also not designed for rapid data acquisition and analysis in the field. This project seeks to build the core technological capabilities coupled with innovative deployment, processing, and analysis methodologies to allow seismic methods to be effectively utilized in the applications of seismic imaging and vehicle tracking where rapid (minutes to hours) and real-time analysis is required. The goal of this project is to build capabilities in acquisition system design, utilization of full three-dimensional (3D) finite difference modeling, as well as statistical characterization of geological heterogeneity. Such capabilities coupled with a rapid field analysis methodology based on matched field processing are applied to problems associated with surveillance, battlefield management, finding hard and deeply buried targets, and portal monitoring. This project, in support of LLNL's national-security mission, benefits the U.S. military and intelligence community. Fiscal year (FY) 2003 was the final year of this project. In the 2.5 years this project has been active, numerous and varied developments and milestones have been accomplished. A wireless communication module for seismic data was developed to facilitate rapid seismic data acquisition and analysis. The E3D code was enhanced to include topographic effects. Codes were developed to implement the Karhunen-Loeve (K-L) statistical methodology for generating geological heterogeneity that can be utilized in E3D modeling. The matched field processing methodology applied to vehicle tracking and based on a field calibration to characterize geological heterogeneity was tested and successfully demonstrated in a tank tracking experiment at the Nevada Test Site. A three-seismic-array vehicle tracking testbed was installed on site

  14. 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.

  15. A model for the polarization of neurons by extrinsically applied electric fields.

    PubMed Central

    Tranchina, D; Nicholson, C

    1986-01-01

    A model is presented for the subthreshold polarization of a neuron by an applied electric field. It gives insight into how morphological features of a neuron affect its polarizability. The neuronal model consists of one or more extensively branched dendritic trees, a lumped somatic impedance, and a myelinated axon with nodes of Ranvier. The dendritic trees branch according to the 3/2-power rule of Rall, so that each tree has an equivalent cylinder representation. Equations for the membrane potential at the soma and at the nodes of Ranvier, given an arbitrary specified external potential, are derived. The solutions determine the contributions made by the dendritic tree and the axon to the net polarization at the soma. In the case of a spatially constant electric field, both the magnitude and sign of the polarization depend on simple combinations of parameters describing the neuron. One important combination is given by the ratio of internal resistances for longitudinal current spread along the dendritic tree trunk and along the axon. A second is given by the ratio between the DC space constant for the dendritic tree trunk and the distance between nodes of Ranvier in the axon. A third is given by the product of the electric field and the space constant for the trunk of the dendritic tree. When a neuron with a straight axon is subjected to a constant field, the membrane potential decays exponentially with distance from the soma. Thus, the soma seems to be a likely site for action potential initiation when the field is strong enough to elicit suprathreshold polarization. In a simple example, the way in which orientation of the various parts of the neuron affects its polarization is examined. When an axon with a bend is subjected to a spatially constant field, polarization is focused at the bend, and this is another likely site for action potential initiation. PMID:3801574

  16. Order reconstruction in inverse twisted nematic cell with an applied electric field

    NASA Astrophysics Data System (ADS)

    Sun, Yang; Ye, Wenjiang; Zhang, Zhidong

    2016-05-01

    Order reconstruction in an inverse twisted nematic (ITN) liquid crystal cell with an applied electric field is investigated based on Landau-de Gennes theory and the two-dimensional finite-difference iterative method. Twice eigenvalue exchange in three-axis layer configuration, thrice eigenvalue exchange in four-axis layer configuration, and negative order parameter uniaxial twisted state exist in this cell, which can be described by the order parameter tensor Q in equilibrium state. The twice eigenvalue exchange also has two degenerate configurations with reduced electric field E from 0.8 to 2.8 in 10ξ cell (ξ is the biaxial correlation length). Moreover, two critical cell gaps dc** = 7 ξ and dc* = 12 ξ are included in the study of the ITN cell. When d �**, only the eigenvalue change state exists. When d ≥ dc*, only a positive order parameter uniaxial twisted state exists near the threshold electric field. When dc** < d < dc*, a negative order parameter uniaxial twisted state exists near the threshold electric field. Comparison of the eigenvalue exchange solutions of different cell gaps of 5ξ, 10ξ, and 20ξ shows that smaller cell gap can inhibit the complexity of the eigenvalue exchange solution and reduce the number of axis layers. This research provides a theoretical basis for the change of multi-axis layer defect and promotes the concept of eigenvalue exchange.

  17. [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. PMID:26094455

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

    PubMed Central

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

    2013-01-01

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

  19. Particle tracking velocimetry applied to estimate the pressure field around a Savonius turbine

    NASA Astrophysics Data System (ADS)

    Murai, Yuichi; Nakada, Taishi; Suzuki, Takao; Yamamoto, Fujio

    2007-08-01

    Particle tracking velocimetry (PTV) is applied to flows around a Savonius turbine. The velocity vector field measured with PTV is utilized to estimate the pressure field around the turbine, as well as to evaluate the torque performance. The main objective of the work is the establishment of the pressure estimation scheme required to discuss the turbine performance. First, the PTV data are interpolated on a regular grid with a fourth-order ellipsoidal differential equation to generate velocity vectors satisfying the third-order spatio-temporal continuity both in time and space. Second, the phase-averaged velocity vector information with respect to the turbine angle is substituted into three different types of pressure-estimating equations, i.e. the Poisson equation, the Navier-Stokes equation and the sub-grid scale model of turbulence. The results obtained based on the Navier-Stokes equation are compared with those based on the Poisson equation, and have shown several merits in employing the Navier-Stokes-based method for the PTV measurement. The method is applied to a rotating turbine with the tip-speed ratio of 0.5 to find the relationship between torque behaviour and flow structure in a phase-averaged sense. We have found that a flow attached to the convex surface of the blades induces low-pressure regions to drive the turbine, namely, the lift force helps the turbine blades to rotate even when the drag force is insufficient. Secondary mechanisms of torque generation are also discussed.

  20. 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

  1. Low ac loss geometries in YBCO coated conductors and impact on conductor stability

    SciTech Connect

    Duckworth, Robert C; List III, Frederick Alyious; Paranthaman, Mariappan Parans; Rupich, M. W.; Zhang, W.; Xie, Y. Y.; Selvamanickam, V.

    2007-01-01

    Reduction of ac losses in applied ac fields can be accomplished through either the creation of filaments and bridging in YBCO coated conductors or an assembly of narrow width YBCO tapes. The ac losses for each of these geometries were measured at 77 K in perpendicular ac fields up to 100 mT. While ac loss reduction was achieved with YBCO filaments created through laser scribing and inkjet deposition, the assembly of stacked YBCO conductor provides an alternative method of ac loss reduction. When compared to a 4-mm wide YBCO coated conductor with a critical current of 60 A, the ac loss in a stack of 2-mm wide YBCO coated conductors with a similar total critical current was reduced. While the reduction in ac loss in a 2-mm wide stack coincided with the reduction in the engineering current density of the conductor, further reduction of ac loss was obtained through the splicing of the 2-mm wide tapes with low resistance solders. To better determine the practicality of these methods from a stability point of view, a numerical analysis was carried out to determine the influence of bridging and splicing on stability of a YBCO coated conductor for both liquid nitrogen-cooled and conduction cooled geometries.

  2. Magnetic Reconnection of an Externally Applied Magnetic Field in a High-Energy Density Plasma

    NASA Astrophysics Data System (ADS)

    Fiksel, G.; Barnak, D.; Chang, P.-Y.; Hu, S. X.; Nilson, P. M.; Betti, R.; Fox, W.; Germaschewski, K.; Bhattacharjee, A.

    2013-10-01

    An experiment on magnetic reconnection of an externally applied magnetic field in counter-propagating high-energy density plasmas was conducted on the OMEGA EP Laser System. Two counter-propagating plasma flows were created by irradiating oppositely placed plastic (CH) targets with 1.8-kJ, 2-ns laser beams. An external magnetic field was imposed perpendicular to the plasma flow by MIFEDS (magneto-inertial fusion electrical discharge system). The magnetic field has a null-x-point geometry with B = 5 T at the targets. The plasma interaction was imaged by laser-driven, fast-proton radiography. The radiography images demonstrate formation of a pair of counter-propagating magnetized ``ribbons'' that collide and reconnect at the midplane. The results will be compared with particle-in-cell simulations and interpreted with predictions from the DRACO code. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944, and NLUF Grant DE-SC0008655.

  3. 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.

  4. 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

  5. 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.

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

    PubMed

    Zhang, Shaohui; Hua, Yumei; Deng, Liangwei

    2016-04-01

    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

  7. 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.

    1974-01-01

    The drift field model used by Wolf (1963) 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 air mass zero sunlight. Voltages were calculated using an expression for the drift field diode saturation current. The model, applied to the oxygen-rich (C-13 group) lithium solar cells, was used to calculate the pre- and post-electron bombardment trends of the open-circuit voltage, maximum power, and short-circuit current for lithium gradients in the range from 10 to the 18th power to 10 to the 19th power Li/cm to the 4th power. Diffusion length degradation and carrier removal effects were sufficient to predict the cell performance up to 3 x 10 to the 14th electrons per sq cm. Beyond this fluence it was necessary to include drift field removal effects.

  8. 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.

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

    DOE PAGESBeta

    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

  10. 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.

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  13. Oscillation of electron mobility in parabolic double quantum well structure due to applied electric field

    SciTech Connect

    Sahoo, Narayan; Sahu, Trinath

    2014-12-15

    We show that oscillation of low temperature electron mobility μ can be obtained by applying an electric field F along the growth direction of the asymmetrically barrier delta doped Al{sub x}Ga{sub 1-x}As parabolic double quantum well structure. The drastic changes in the subband Fermi energies and distributions of subband wave functions as a function of F yield nonmonotonic intra- and intersubband scattering rate matrix elements mediated by intersubband effects. The oscillatory enhancement of μ, which is attributed to the subband mobilities governed by the ionized impurity scattering, magnifies with increase in well width and decrease in height of the parabolic structure potential. The results can be utilized for nanoscale low temperature device applications.

  14. 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.

  15. 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

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

    PubMed

    Walid Rezanoor, Md; Dutta, Prashanta

    2016-03-01

    Electrorotation is widely used for characterization of biological cells and materials using a rotating electric field. Generally, multiphase AC electric fields and quadrupolar electrode configuration are needed to create a rotating electric field for electrorotation. In this study, we demonstrate a simple method to rotate dielectrophoretically trapped microparticles using a stationary AC electric field. Coplanar interdigitated electrodes are used to create a linearly polarized nonuniform AC electric field. This nonuniform electric field is employed for dielectrophoretic trapping of microparticles as well as for generating electroosmotic flow in the vicinity of the electrodes resulting in rotation of microparticles in a microfluidic device. The rotation of barium titanate microparticles is observed in 2-propanol and methanol solvent at a frequency below 1 kHz. A particle rotation rate as high as 240 revolutions per minute is observed. It is demonstrated that precise manipulation (both rotation rate and equilibrium position) of the particles is possible by controlling the frequency of the applied electric field. At low frequency range, the equilibrium positions of the microparticles are observed between the electrode edge and electrode center. This method of particle manipulation is different from electrorotation as it uses induced AC electroosmosis instead of electric torque as in the case of electrorotation. Moreover, it has been shown that a microparticle can be rotated along its own axis without any translational motion. PMID:27014394

  17. 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.

  18. 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.

  19. 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. PMID:26541560

  20. Accurate field mapping in the presence of B0 inhomogeneities, applied to MR thermometry

    PubMed Central

    Mei, Chang-Sheng; Chu, Renxin; Hoge, W. Scott; Panych, Lawrence P.; Madore, Bruno

    2014-01-01

    Purpose To describe how B0 inhomogeneities can cause errors in proton resonance frequency (PRF) shift thermometry, and to correct for these errors. Methods With PRF thermometry, measured phase shifts are converted into temperature measurements through the use of a scaling factor proportional to the echo time, TE. However, B0 inhomogeneities can deform, spread, and translate MR echoes, potentially making the ‘true’ echo time vary spatially within the imaged object and take on values that differ from the prescribed TE value. Acquisition and reconstruction methods able to avoid or correct for such errors are presented. Results Tests were performed in a gel phantom during sonication, and temperature measurements were made with proper shimming as well as with intentionally-introduced B0 inhomogeneities. Errors caused by B0 inhomogeneities were observed, described, and corrected by the proposed methods. No statistical difference was found between the corrected results and the reference results obtained with proper shimming, while errors by more than 10% in temperature elevation were corrected for. The approach was also applied to an abdominal in vivo dataset. Conclusion Field variations induce errors in measured field values, which can be detected and corrected. The approach was validated for a PRF thermometry application. PMID:24975329

  1. Calcium dependent plasticity applied to repetitive transcranial magnetic stimulation with a neural field model.

    PubMed

    Wilson, M T; Fung, P K; Robinson, P A; Shemmell, J; Reynolds, J N J

    2016-08-01

    The calcium dependent plasticity (CaDP) approach to the modeling of synaptic weight change is applied using a neural field approach to realistic repetitive transcranial magnetic stimulation (rTMS) protocols. A spatially-symmetric nonlinear neural field model consisting of populations of excitatory and inhibitory neurons is used. The plasticity between excitatory cell populations is then evaluated using a CaDP approach that incorporates metaplasticity. The direction and size of the plasticity (potentiation or depression) depends on both the amplitude of stimulation and duration of the protocol. The breaks in the inhibitory theta-burst stimulation protocol are crucial to ensuring that the stimulation bursts are potentiating in nature. Tuning the parameters of a spike-timing dependent plasticity (STDP) window with a Monte Carlo approach to maximize agreement between STDP predictions and the CaDP results reproduces a realistically-shaped window with two regions of depression in agreement with the existing literature. Developing understanding of how TMS interacts with cells at a network level may be important for future investigation. PMID:27259518

  2. 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.

  3. The creation of 360 degree domain walls in ferromagnetic nanorings by circular applied magnetic fields

    NASA Astrophysics Data System (ADS)

    Bickel, Jessica; Smith, Spencer; Aidala, Katherine

    2014-03-01

    360° domain walls (DWs) are the proposed transition state of ferromagnetic nanorings which are candidate devices for magnetic memory. Using micromagnetic simulations, we examine the formation of 360° DWs created by the application of a circular Oersted field for the transition of a 5nm thick ring from a CCW to a CW vortex. The magnetic reversal begins by canting of the magnetization either inward or outward. As the spin continues to rotate, exchange interactions result in the rotation of adjacent spins. Finally, the rotate spin aligns with the applied magnetic field, creating a transition state made of two 180° DWs of opposite winding number. As the center of the rotated domain grows, the 180° walls of adjacent domains meet. Adjacent domains cant in opposite directions to lower the magnetostatic energy relative to canting in the same direction. Therefore 180° DWs at the boundaries have the same winding number and combine to form 360° DWs. Each pair of rotated domains results in a pair of two 360° DWs of opposite winding number. This work provides better understanding of the formation of 360° DWs and may lead to the ability to control the formation of DWs via geometry.

  4. A Novel Microaneurysms Detection Method Based on Local Applying of Markov Random Field.

    PubMed

    Ganjee, Razieh; Azmi, Reza; Moghadam, Mohsen Ebrahimi

    2016-03-01

    Diabetic Retinopathy (DR) is one of the most common complications of long-term diabetes. It is a progressive disease and by damaging retina, it finally results in blindness of patients. Since Microaneurysms (MAs) appear as a first sign of DR in retina, early detection of this lesion is an essential step in automatic detection of DR. In this paper, a new MAs detection method is presented. The proposed approach consists of two main steps. In the first step, the MA candidates are detected based on local applying of Markov random field model (MRF). In the second step, these candidate regions are categorized to identify the correct MAs using 23 features based on shape, intensity and Gaussian distribution of MAs intensity. The proposed method is evaluated on DIARETDB1 which is a standard and publicly available database in this field. Evaluation of the proposed method on this database resulted in the average sensitivity of 0.82 for a confidence level of 75 as a ground truth. The results show that our method is able to detect the low contrast MAs with the background while its performance is still comparable to other state of the art approaches. PMID:26779642

  5. 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.

  6. 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.

  7. The effects of applied electric fields on Micrasterias. I. Morphogenesis and the pattern of cell wall deposition.

    PubMed

    Brower, D L; McIntosh, J R

    1980-04-01

    Applied electric fields of approximately 14 V/cm have profound effects on the morphogenesis of the unicellular green alga, Micrasterias denticulata. This field corresponds to a potential drop of 15-40 mV across lobes oriented perpendicular to the applied field. These lobes show a galvanotropism toward the cathode. Lobes growing parallel to the field are stunted to varying degrees, depending on their orientation. As shown by other investigators, most cell wall material is normally deposited at the tips of growing lobes. If, however, cell expansion is osmotically inhibited in electric fields, wall material also accumulates along the cathode-facing (CF) sides of lobes oriented perpendicular to the field. Similarly, in cells growing under the influence of an applied field, radioactively labelled glucose and the methyl groups from methionine are incorporated along the CF sides of lobes as well as the lobe tips. This is also true when the label is added immediately after cells are removed from the fields, indicating that the wall-depositing machinery itself has been temporarily altered by the field. These results demonstrate that applied electric fields can be a valuable tool in elucidating the mechanisms of growth localization in Micrasterias cells. PMID:7400236

  8. 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

  9. 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

  10. Large-timestep techniques for particle-in-cell simulation of systems with applied fields that vary rapidly in space

    SciTech Connect

    Friedman, A.; Grote, D.P.

    1996-10-01

    Under conditions which arise commonly in space-charge-dominated beam applications, the applied focusing, bending, and accelerating fields vary rapidly with axial position, while the self-fields (which are, on average, comparable in strength to the applied fields) vary smoothly. In such cases it is desirable to employ timesteps which advance the particles over distances greater than the characteristic scales over which the applied fields vary. Several related concepts are potentially applicable: sub-cycling of the particle advance relative to the field solution, a higher-order time-advance algorithm, force-averaging by integration along approximate orbits, and orbit-averaging. We report on our investigations into the utility of such techniques for systems typical of those encountered in accelerator studies for heavy-ion beam-driven inertial fusion.

  11. Donor impurity in vertically-coupled quantum-dots under hydrostatic pressure and applied electric field

    NASA Astrophysics Data System (ADS)

    Duque, C. M.; Barseghyan, M. G.; Duque, C. A.

    2010-02-01

    In this work we make a predictive study on the binding energy of the ground state for hydrogenic donor impurity in vertically-coupled quantum-dot structure, considering the combined effects of hydrostatic pressure and in growth-direction applied electric field. The approach uses a variational method within the effective mass approximation. The low dimensional structure consists of three cylindrical shaped GaAs quantum-dots, grown in the z-direction and separated by Ga1-xAlxAs barriers. In order to include the pressure dependent Γ - X crossover in the barrier material a phenomenological model is followed. The main findings can be summarized as follows: 1) for symmetrical and asymmetrical dimensions of the structures, the binding energy as a function of the impurity position along the growth direction of the heterostructure has a similar behavior to that shown by the non-correlated electron wave function with maxima for the impurity in the well regions and minima for the impurity in the barrier regions, 2) for increasing radius of the system, the binding energy decreases and for R large enough reaches the limit of the binding energy in a coupled quantum well heterostructure, 3) the binding energy increases for higher Aluminum concentration in the barrier regions, 4) depending of the impurity position and of the structural dimensions of the system (well width and barrier thickness) - and because changing the height of the potential barrier makes possible to induce changes in the degree of symmetry of the carrier-wave function -, the electric field and hydrostatic pressure can cause the impurity binding energy increases or decreases, and finally 5) the line-shape of the binding energy curves are mainly given by the line-shape of the Coulomb interaction.

  12. Method and apparatus for dissipating remanent fields and preserving diamagnetism of ceramic superconductors

    SciTech Connect

    Youngdahl, C.A.

    1991-12-31

    A method for dissipating a remanent field, created when a magnetic field is brought into contact with a superconductor, comprising the steps of (1) providing a ceramic superconductor; (2) continuously or intermittently applying an AC current to the ceramic superconductor; (3) gradually removing the AC current until the undesired remanent field is dissipated.

  13. 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.

  14. Dynamics of Chemi-Ion Driven Flows in an Applied Electric Field

    NASA Astrophysics Data System (ADS)

    Tinajero, Jesse A.

    Chemi-ions are produced during combustion of a hydrocarbon fuel. If an external electric field is present, a charge separation occurs due to the electrical force acting on the positively and negatively charged species. These ions traverse in the direction of the electrode of opposite potential. Along their path, they continuously collide with neutral molecules within the surrounding bulk gas until they are able to recombine and neutralize at the downstream electrode. During each collision, the charged species give up their acquired momentum to the neutral molecules. Macroscopically, this transfer of momentum has been best described mathematically as a body force acting on the bulk gas. The effect is commonly referred to as an ion wind effect. Gravity effects make the electric field effects on combustion difficult to study with earth- based experiments. This is because the gravity-driven buoyancy effects behave as a body force also acting on the bulk gas. Buoyancy and electrical body forces act on the same order of magnitude. The two forces are coupled through temperature since the production of ions is temperature dependent. Between the two, the contribution to the net momentum of the gas is then difficult to distinguish. On the other hand, micro-gravity experiments allow for the direct study of electric field effects in the absence of gravity. Micro-gravity experiments on-board the International Space Station through NASA's Advanced Combustion via Micro- gravity Experiments program, or ACME, are planned for 2016--17. Nevertheless, preliminary studies are needed in preparation for the ISS experiments. These studies are described in this thesis. A replica of the ISS experiment for the electric field effects on laminar diffusion flames (EFIELD Flames) that is part of ACME was recreated in a ground based laboratory. A schlieren system was built to visualize the effect an applied electric field has on the flame's buoyant thermal plume when the electric field is given a

  15. Forced magnetic reconnection and field penetration of an externally applied rotating helical magnetic field in the TEXTOR tokamak.

    PubMed

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

    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. PMID:17026312

  16. Applying linear spectral unmixing to airborne hyperspectral imagery for mapping yield variability in grain sorghum and cotton fields

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examined linear spectral unmixing techniques for mapping the variation in crop yield for precision agriculture. Both unconstrained and constrained linear spectral unmixing models were applied to airborne hyperspectral imagery collected from a grain sorghum field and a cotton field. A pair...

  17. Improved performance of the pulsed copper-vapor-laser CuCl-vapor-laser with a compact device by applying an ac continuous-glow-discharge

    NASA Astrophysics Data System (ADS)

    Saito, H.; Taniguchi, H.; Ohgami, K.

    1985-10-01

    An additional continuous-glow-discharge was applied to the aperiodic pulsed CuCl-vapor laser. The experimental results exhibited an increase of up to 60 percent the laser-output average power at the maximum point, an increase of 1.5 times the peak power and pulse repetition frequency, and twice the pulse width in the laser oscillation against the laser without the continuous-glow discharge. Further, the additional technique led the CuCl-vapor-laser to operate in the higher operating-temperature region.

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. Applied electric field enhances DRG neurite growth: influence of stimulation media, surface coating and growth supplements

    NASA Astrophysics Data System (ADS)

    Wood, Matthew D.; Willits, Rebecca Kuntz

    2009-08-01

    Electrical therapies have been found to aid repair of nerve injuries and have been shown to increase and direct neurite outgrowth during stimulation. This enhanced neural growth existed even after the electric field (EF) or stimulation was removed, but the factors that may influence the enhanced growth, such as stimulation media or surface coating, have not been fully investigated. This study characterized neurite outgrowth and branching under various conditions: EF magnitude and application time, ECM surface coating, medium during EF application and growth supplements. A uniform, low-magnitude EF (24 or 44 V m-1) was applied to dissociated chick embryo dorsal root ganglia seeded on collagen or laminin-coated surfaces. During the growth period, cells were either exposed to NGF or N2, and during stimulation cells were exposed to either unsupplemented media (Ca2+) or PBS (no Ca2+). Parallel controls for each experiment included cells exposed to the chamber with no stimulation and cells remaining outside the chamber. After brief electrical stimulation (10 min), neurite length significantly increased 24 h after application for all conditions studied. Of particular interest, increased stimulation time (10-100 min) further enhanced neurite length on laminin but not on collagen surfaces. Neurite branching was not affected by stimulation on any surface, and no preferential growth of neurites was noted after stimulation. Overall, the results of this report suggest that short-duration electric stimulation is sufficient to enhance neurite length under a variety of conditions. While further data are needed to fully elucidate a mechanism for this increased growth, these data suggest that one focus of those investigations should be the interaction between the growth cone and the substrata.

  4. Applied electric field enhances DRG neurite growth: influence of stimulation media, surface coating and growth supplements.

    PubMed

    Wood, Matthew D; Willits, Rebecca Kuntz

    2009-08-01

    Electrical therapies have been found to aid repair of nerve injuries and have been shown to increase and direct neurite outgrowth during stimulation. This enhanced neural growth existed even after the electric field (EF) or stimulation was removed, but the factors that may influence the enhanced growth, such as stimulation media or surface coating, have not been fully investigated. This study characterized neurite outgrowth and branching under various conditions: EF magnitude and application time, ECM surface coating, medium during EF application and growth supplements. A uniform, low-magnitude EF (24 or 44 V m(-1)) was applied to dissociated chick embryo dorsal root ganglia seeded on collagen or laminin-coated surfaces. During the growth period, cells were either exposed to NGF or N2, and during stimulation cells were exposed to either unsupplemented media (Ca(2+)) or PBS (no Ca(2+)). Parallel controls for each experiment included cells exposed to the chamber with no stimulation and cells remaining outside the chamber. After brief electrical stimulation (10 min), neurite length significantly increased 24 h after application for all conditions studied. Of particular interest, increased stimulation time (10-100 min) further enhanced neurite length on laminin but not on collagen surfaces. Neurite branching was not affected by stimulation on any surface, and no preferential growth of neurites was noted after stimulation. Overall, the results of this report suggest that short-duration electric stimulation is sufficient to enhance neurite length under a variety of conditions. While further data are needed to fully elucidate a mechanism for this increased growth, these data suggest that one focus of those investigations should be the interaction between the growth cone and the substrata. PMID:19494423

  5. 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. PMID:26800316

  6. Control of transmission of right circularly polarized laser light in overdense plasma by applied magnetic field pulses.

    PubMed

    Ma, Guangjin; Yu, Wei; Yu, M Y; Luan, Shixia; Wu, Dong

    2016-05-01

    The effect of a transient magnetic field on right-hand circularly polarized (RHCP) laser light propagation in overcritical-density plasma is investigated. When the electron gyrofrequency is larger than the wave frequency, RHCP light can propagate along the external magnetic field in an overcritical density plasma without resonance or cutoff. However, when the magnetic field falls to below the cyclotron resonance point, the propagating laser pulse will be truncated and the local plasma electrons resonantly heated. Particle-in-cell simulation shows that when applied to a thin slab, the process can produce intense two-cycle light pulses as well as long-lasting self-magnetic fields. PMID:27300997

  7. Control of transmission of right circularly polarized laser light in overdense plasma by applied magnetic field pulses

    NASA Astrophysics Data System (ADS)

    Ma, Guangjin; Yu, Wei; Yu, M. Y.; Luan, Shixia; Wu, Dong

    2016-05-01

    The effect of a transient magnetic field on right-hand circularly polarized (RHCP) laser light propagation in overcritical-density plasma is investigated. When the electron gyrofrequency is larger than the wave frequency, RHCP light can propagate along the external magnetic field in an overcritical density plasma without resonance or cutoff. However, when the magnetic field falls to below the cyclotron resonance point, the propagating laser pulse will be truncated and the local plasma electrons resonantly heated. Particle-in-cell simulation shows that when applied to a thin slab, the process can produce intense two-cycle light pulses as well as long-lasting self-magnetic fields.

  8. Three dimensional adaptive meshing scheme applied to the control of the spatial representation of complex field pattern in electromagnetics

    NASA Astrophysics Data System (ADS)

    Grosges, T.; Borouchaki, H.; Barchiesi, D.

    2010-12-01

    We present an improved adaptive mesh process based on Riemannian transformation to control the accuracy in high field gradient representation for diffraction problems. Such an adaptive meshing is applied in representing the electromagnetic intensity around a metallic submicronic spherical particle, which is known to present high gradients in limited zones of space including the interference pattern of the electromagnetic field. We show that, the precision of the field variation being controlled, this improved scheme permits drastically decreasing the computational time as well as the memory requirements by adapting the number and the position of nodes where the electromagnetic field must be computed and represented.

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

    PubMed

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

    2016-01-01

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

  10. 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

  11. 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.

  12. 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.

  13. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  15. 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.…

  16. 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

  17. Patch nearfield acoustic holography combined with sound field separation technique applied to a non-free field

    NASA Astrophysics Data System (ADS)

    Bi, ChuanXing; Jing, WenQian; Zhang, YongBin; Xu, Liang

    2015-02-01

    The conventional nearfield acoustic holography (NAH) is usually based on the assumption of free-field conditions, and it also requires that the measurement aperture should be larger than the actual source. This paper is to focus on the problem that neither of the above-mentioned requirements can be met, and to examine the feasibility of reconstructing the sound field radiated by partial source, based on double-layer pressure measurements made in a non-free field by using patch NAH combined with sound field separation technique. And also, the sensitivity of the reconstructed result to the measurement error is analyzed in detail. Two experiments involving two speakers in an exterior space and one speaker inside a car cabin are presented. The experimental results demonstrate that the patch NAH based on single-layer pressure measurement cannot obtain a satisfied result due to the influences of disturbing sources and reflections, while the patch NAH based on double-layer pressure measurements can successfully remove these influences and reconstruct the patch sound field effectively.

  18. Bouncing of a Droplet on Superhydrophobic Surface in AC Electrowetting

    NASA Astrophysics Data System (ADS)

    Kang, Kwan Hyoung; Lee, Seung Jun; Hong, Jiwoo

    2009-11-01

    Oscillation of a droplet is induced in ac electrowetting by time-dependent electrical wetting tension. A droplet placed on a superhydrophobic surface bounces up like a rubber ball when an ac signal is applied. The bouncing pattern is highly frequency dependent. We investigated how the shape deformation and bouncing of a droplet are affected by applied frequency. The droplet motion is analyzed with the spectral method. The droplet is modeled as a simple linear oscillator, and the mass and spring constants are determined based on analytical results. We found that bouncing occurs periodically at a resonance frequency of the droplet. The motion of a sessile droplet released from a fixed shape is analyzed based on the phase field method. The numerical results show qualitative agreement with the experimental results for a bouncing droplet. Details on the flow field inside a bouncing droplet will be discussed based on numerical results.

  19. A flux-coupled ac/dc magnetizing device

    NASA Astrophysics Data System (ADS)

    Gopman, D. B.; Liu, H.; Kent, A. D.

    2013-06-01

    We report on an instrument for applying ac and dc magnetic fields by capturing the flux from a rotating permanent magnet and projecting it between two adjustable pole pieces. This can be an alternative to standard electromagnets for experiments with small samples or in probe stations in which an applied magnetic field is needed locally, with advantages that include a compact form-factor, very low power requirements and dissipation as well as fast field sweep rates. This flux capture instrument (FLUXCAP) can produce fields from -400 to +400 mT, with field resolution less than 1 mT. It generates static magnetic fields as well as ramped fields, with ramping rates as high as 10 T/s. We demonstrate the use of this apparatus for studying the magnetotransport properties of spin-valve nanopillars, a nanoscale device that exhibits giant magnetoresistance.

  20. 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. PMID:26551119

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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. Using genetic algorithms to characterize ferrofluid topographies in externally applied magnetic fields

    NASA Astrophysics Data System (ADS)

    Spinella-Mamo, V.; Paranjape, M.

    2009-02-01

    Both ferrofluidics and genetic algorithms are relatively new fields. Due to complex physical interactions, ferrofluidic topographies and assemblies have only been solved using finite time step, Lattice Boltzmann, and finite-element methods in very simple magnetic field configurations. In this paper, we show that it is possible (and highly advantageous) to employ genetic algorithms to solve for the fluid topographies, which can be extended to include more complex magnetic fields.

  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. PMID:27281285

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  5. Intense laser effects on the optical properties of asymmetric GaAs double quantum dots under applied electric field

    NASA Astrophysics Data System (ADS)

    Bejan, Doina; Niculescu, Ecaterina Cornelia

    2016-06-01

    We investigated the combined effects of a non-resonant intense laser field and a static electric field on the electronic structure and the nonlinear optical properties (absorption, optical rectification) of a GaAs asymmetric double quantum dot under a strong probe field excitation. The calculations were performed within the compact density-matrix formalism under steady state conditions using the effective mass approximation. Our results show that: (i) the electronic structure and optical properties are sensitive to the dressed potential; (ii) under applied electric fields, an increase of the laser intensity induces a redshift of the optical absorption and rectification spectra; (iii) the augment of the electric field strength leads to a blueshift of the spectra; (iv) for high electric fields the optical spectra show a shoulder-like feature, related with the occurrence of an anti-crossing between the two first excited levels.

  6. 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.

  7. Molecular dynamics study of response of liquid N,N-dimethylformamide to externally applied electric field using a polarizable force field

    SciTech Connect

    Gao, Weimin; Niu, Haitao; Lin, Tong; Wang, Xungai; Kong, Lingxue

    2014-01-28

    The behavior of Liquid N,N-dimethylformamide subjected to a wide range of externally applied electric fields (from 0.001 V/nm to 1 V/nm) has been investigated through molecular dynamics simulation. To approach the objective the AMOEBA polarizable force field was extended to include the interaction of the external electric field with atomic partial charges and the contribution to the atomic polarization. The simulation results were evaluated with quantum mechanical calculations. The results from the present force field for the liquid at normal conditions were compared with the experimental and molecular dynamics results with non-polarizable and other polarizable force fields. The uniform external electric fields of higher than 0.01 V/nm have a significant effect on the structure of the liquid, which exhibits a variation in numerous properties, including molecular polarization, local cluster structure, rotation, alignment, energetics, and bulk thermodynamic and structural properties.

  8. Molecular dynamics study of response of liquid N,N-dimethylformamide to externally applied electric field using a polarizable force field

    NASA Astrophysics Data System (ADS)

    Gao, Weimin; Niu, Haitao; Lin, Tong; Wang, Xungai; Kong, Lingxue

    2014-01-01

    The behavior of Liquid N,N-dimethylformamide subjected to a wide range of externally applied electric fields (from 0.001 V/nm to 1 V/nm) has been investigated through molecular dynamics simulation. To approach the objective the AMOEBA polarizable force field was extended to include the interaction of the external electric field with atomic partial charges and the contribution to the atomic polarization. The simulation results were evaluated with quantum mechanical calculations. The results from the present force field for the liquid at normal conditions were compared with the experimental and molecular dynamics results with non-polarizable and other polarizable force fields. The uniform external electric fields of higher than 0.01 V/nm have a significant effect on the structure of the liquid, which exhibits a variation in numerous properties, including molecular polarization, local cluster structure, rotation, alignment, energetics, and bulk thermodynamic and structural properties.

  9. Characteristics of divertor heat and particle deposition with intrinsic and applied 3-D fields in NSTX H-mode plasmas

    SciTech Connect

    Ahn, J.W.; Canik, John; Maingi, Rajesh; Gray, Travis K; Lore, Jeremy D; McLean, Adam G; Park, J.-K.; Roquemore, A. L.; Soukhanovskii, V. A.

    2011-01-01

    Divertor heat and particle flux profiles are modified by externally imposed non-axisymmetric magnetic perturbations in the National Spherical Torus Experiment. The applied 3-D field causes strike point splitting that is represented as local peaks and valleys in the divertor profiles. The plasma response in an ideal perturbed equilibrium approach was included in the field line tracing by taking account of the B-field generated by the plasma current up to a certain fraction of normalized flux inside the separatrix and being superposed to the vacuum field. The inclusion of this type of plasma response does not significantly affect the location and spacing of the split strike points at the divertor surface. A modest level of divertor profile modification is found to occur even without the application of 3-D fields in certain high triangularity (delta = 0.65-0.8) discharges, with the location of local peaks and valleys same before and after the application. The intrinsic error field from the non-circularity of PF5 coil is known to have primarily n = 3 component in NSTX and was modeled to be included in the vacuum field line tracing. The produced puncture plot of the field line along with the connection length profile shows that the radial location of local peaks agrees well with the measurement, identifying intrinsic error field as a possible source of intrinsic strike point splitting. The radial location of local peaks in the profiles during the triggered ELM by the applied n = 3 field is the same before and after the 3-D field application. This shows that the heat flux from the triggered ELMs appears to follow the imposed n = 3 field structure.

  10. 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)

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

    PubMed Central

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

    2010-01-01

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

  12. 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

  13. 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

  14. LOW PERMEABLE TARPS REDUCE EMISSIONS FROM DRIP-APPLIED INLINE IN A STRAWBERRY FIELD TRIAL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plastic tarps are often used to reduce fumigant emissions in raised-bed strawberry fields. In September 2007 near Oxnard, CA, a field study was conducted to determine the emission reductions under four tarp treatments: standard polyethylene (PE), virtually impermeable film (VIF), semi-impermeable fi...

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Effects of an applied magnetic field on directional solidification of off-eutectic Bi-Mn alloys

    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. 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 field. Conductivity gradients in the melt are suggested as a possible mechanism for the observed results.

  18. 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.

  19. 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…

  20. Process Challenges and Learning-Based Interactions in Stage 2 of Doctoral Education: Implications from Two Applied Social Science Fields

    ERIC Educational Resources Information Center

    Baker, Vicki L.; Pifer, Meghan J.; Flemion, Blair

    2013-01-01

    This article reports on an exploratory study that examined the transition to independence in Stage 2 of the doctoral student experience in two applied social science fields. We rely on an interdisciplinary framework that integrates developmental networks and sociocultural perspectives of learning to better understand the connection between the…

  1. 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.

  2. 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...

  3. 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.

  4. Think different: applying the old macintosh mantra to the computability of the SUSY auxiliary field problem

    NASA Astrophysics Data System (ADS)

    Calkins, Mathew; Gates, D. E. A.; Gates, S. James; Golding, William M.

    2015-04-01

    Starting with valise supermultiplets obtained from 0-branes plus field redefinitions, valise adinkra networks, and the "Garden Algebra," we discuss an architecture for algorithms that (starting from on-shell theories and, through a well-defined computation procedure), search for off-shell completions. We show in one dimension how to directly attack the notorious "off-shell auxiliary field" problem of supersymmetry with algorithms in the adinkra network-world formulation.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  6. Expert knowledge techniques applied to the analysis of electric field mill data

    NASA Technical Reports Server (NTRS)

    Nicholson, James R.; Mulvehill, Alice M.

    1990-01-01

    NASA operates a network of ground-based electric field mills at Kennedy Space Center (KSC) to identify clouds which might be an electrical hazard to space vehicle prior to and during launch or to the various ground operations performed at the center. Artificial intelligence has been used to develop an expert system for analyzing electric field mill data. The application of the system to expert system to small thunderstorms at KSC is shown.

  7. Modification of divertor heat and article flux profiles with applied 3D fields in NSTX H-mode plasmas

    SciTech Connect

    Ahn, Joon-Wook; Canik, John; Soukhanovskii, V. A.; Maingi, Rajesh; Battaglia, D. J.

    2010-04-01

    Externally imposed non-axisymmetric magnetic perurbations are observed to alter divertor heat and particle flux profiles in the National Spherical Torus Experiment (NSTX). The divertor profiles are foud to have a modust level of multiple local peaks, characteristic of strike poimt splitting or the "magnetis lob" structure, even before the application of the 3D fields in some (but not all) NSTX discharges. This is thought to be due to the intrinsic error fields. The applied 3D fields augmented the intrinsic strike point splitting, making the ampliture of local peaks, and valleys larger in the divertor profile and striations at the divertor surface brighter. The measured heat flux profile shows that the radial location and spacing of the strations are qualitativel consistent witth a vacuum field tracing calcultion. 3D field application did not change the peak divertor heat and particle fluxes at the toroidal location of measurement. Spatial characteristics of the observed patterns are also reported in the paper.

  8. The influence of applied magnetic fields on the optical properties of zero- and one-dimensional CdSe nanocrystals

    NASA Astrophysics Data System (ADS)

    Blumling, Daniel E.; McGill, Stephen; Knappenberger, Kenneth L.

    2013-09-01

    Shape-dependent exciton relaxation dynamics of CdSe 0-D nanocrystals and 1-D nanorods were studied using low-temperature (4.2 K), time-resolved and intensity-integrated magneto-photoluminscence (MPL) spectroscopy. Analysis of the average MPL rate constants from several different nanocrystal quantum dots and rods excited by 400 nm light in applied magnetic fields up to 17.5 T revealed size-dependent energy gaps separating bright and dark exciton fine-structure states. For 1-D nanorods under strong cross-sectional confinement and large length-to-diameter aspect ratios, efficient mixing of bright and dark exciton states was achieved using relatively low applied field strengths (<=4 T). The effect was attributed, in part, to decreased confinement of CdSe hole states associated with the long axis of the nanorod, which resulted in reduction of the energy gaps separating the bright and dark states. Increased control over the angle formed between the applied field vectors and the nanocrystal c-axis led to more efficient and uniform mixing of nanorod exciton states than for quantum dots. The findings suggest 1-D nanostructures are advantageous over 0-D ones for field-responsive applications.Shape-dependent exciton relaxation dynamics of CdSe 0-D nanocrystals and 1-D nanorods were studied using low-temperature (4.2 K), time-resolved and intensity-integrated magneto-photoluminscence (MPL) spectroscopy. Analysis of the average MPL rate constants from several different nanocrystal quantum dots and rods excited by 400 nm light in applied magnetic fields up to 17.5 T revealed size-dependent energy gaps separating bright and dark exciton fine-structure states. For 1-D nanorods under strong cross-sectional confinement and large length-to-diameter aspect ratios, efficient mixing of bright and dark exciton states was achieved using relatively low applied field strengths (<=4 T). The effect was attributed, in part, to decreased confinement of CdSe hole states associated with the long

  9. 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.

  10. 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.

  11. 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. PMID:22554532

  12. Runoff and degradation of aerially applied dinotefuran in paddy fields and river.

    PubMed

    Yokoyama, Sayako; Ito, Masataka; Nagasawa, Shunsuke; Morohashi, Masayuki; Ohno, Masaki; Todate, Yukitaka; Kose, Tomohiro; Kawata, Kuniaki

    2015-06-01

    Variation, run-off and degradation characteristics of the insecticide dinotefuran, (EZ)-(RS)-1-methyl-2-nitro-3-(tetrahydro-3-furyl-methyl)guanidine, in water and soil from two paddy fields after aerial application was investigated as well as in river water. Maximum concentrations of dinotefuran were 290 and 720 µg/L in the two paddy waters, 25 and 28 µg/kg dry in the two paddy soils, and 10 µg/L in the river water. Runoff ratios of dinotefuran from the paddy fields were calculated as 14%-41%. Mean half-lives of dinotefuran were 5.4 days in the paddy water and 12 days in the paddy soil. Results obtained in this study are important for the evaluation of the actual behavior of dinotefuran in paddy fields and rivers. PMID:25917847

  13. The effects of applied electric fields on Micrasterias. II. The distributions of cytoplasmic and plasma membrane components.

    PubMed

    Brower, D L; Giddings, T H

    1980-04-01

    The accompanying paper describes the effects of applied electric fields on the morphogenesis and patterns of wall deposition of growing cells of Micrasterias denticulata. This paper details the effects of electric fields (approximately 14 V cm-1) on the subcellular components of Micrasterias, including a description of the plasma membrane of growing semi-cells as visualized by freeze-fracturing. There are no gross cytoplasmic abnormalities or asymmetrics in the distributions of cytoplasmic organelles caused by the fields. In particular, neither the Large Vesicles nor Dark Vesicles are concentrated in the cathode-facing (CF) halves of lobes oriented perpendicular to the fields, where extra deposition of wall material has been shown to occur. In freeze-fracture replicas, there are about twice as many plasma membrane particles near the tips of growing lobes as there are in proximal regions of the lobes. Additionally, rosettes, consisting of 6 membrane particles, are seen predominantly in the distal parts of the lobes, and these rosettes are believed to be important in the synthesis of cell wall microfibrils. The applied fields cause a large asymmetry in the distributions of membrane particles, with larger numbers being found on the CF sides of lobes oriented perpendicular to the fields. We were not able to detect a specific effect on any class of particles. Taken all together, the data support the hypothesis that some of the factors responsible for growth localization in Micrasterias reside in the plasma membrane. PMID:7400237

  14. Three-spin interaction Ising model with a nondegenerate ground state at zero applied field

    NASA Astrophysics Data System (ADS)

    Bidaux, R.; Boccara, N.; Forgàcs, G.

    1986-10-01

    The field-temperature phase diagram of a two-dimensional, three-spin interaction Ising model is studied using two different methods: mean field approximation and numerical transfer matrix techniques. The former leads to a rather rich phase diagram in which two separate phases with different symmetries can be found, and which presents first-order transition lines, a triple point, and a critical end point, like the solid-liquid-gas phase diagram of a pure compound. The numerical transfer matrix study confirms part of these results, but does not clearly evidence the existence of the less symmetric phase.

  15. Distribution patterns of MCA-coated granules aerially applied to corn fields of Southern Hungary between 2000 and 2002.

    PubMed

    Wennemann, L; Hummel, H E

    2003-01-01

    Field studies in corn (Zea mays L.) were conducted to evaluate distribution patterns of 4-methoxy-cinnamaldehyde (MCA) coated corn grits after aerial application with a Dromader fixed wing aircraft. The kairomone mimic MCA is synthetically available and a quite specific and efficient adult attractant for the invasive alien maize pest western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte. Orientation disruptive properties of MCA for WCR when applied at unphysiologically high concentrations are currently under investigation. For successful implementation of the MCA disruption technique, the distribution patterns of MCA coated corn granules ('grits') in the field are important. Grits are degrained corn cobs, shredded to different sizes, coated with MCA and used as a carrier material to disseminate MCA vapors into corn fields. Granules of 10-12 mesh size were aerially applied eight times at rates ranging from 12.4 to 25.0 kg/ha. The goal is to evaluate distribution patterns of corn grits treated with MCA in three fields located at Csanadpalota, Kardoskút and Mezöhegyes in Southern Hungary between 2000 and 2002. Increasing rates reflect our attempts in finding and optimising the most even distribution of granules in the field. Field experiments were evaluated by collecting grits in 30-cm plastic saucers and by counting grits accumulated on corn plant parts. Variation in grit number per unit area and frequency of corn granule number per plant showed some transient technical application problems. Analysis of grits collected in the saucers revealed some statistical difference between the different application dates as well as differences in rates applied. Altogether grits in saucers were more evenly distributed in comparison to the grits collected on plant parts. As the corn plants age, their leaves and whorls present a smaller and smaller surface area where granules can accumulate. Altogether, however, grit distribution patterns indicate that aerial

  16. Applying Wireless Information Technology in Field Trips--A Hong Kong Experience

    ERIC Educational Resources Information Center

    So, Koon Keung Teddy

    2004-01-01

    In 2002, the Honk Kong government launched a pilot scheme "e-school bag" promoting the use of wireless technology in ten primary and ten secondary schools for classroom teaching and learning. In 2003, a secondary school successfully received a grant from the Quality Education Fund (QEF) to implement a wireless network for outdoor field trips. This…

  17. Parallel simulation of particle transport in an advection field applied to volcanic explosive eruptions

    NASA Astrophysics Data System (ADS)

    Künzli, Pierre; Tsunematsu, Kae; Albuquerque, Paul; Falcone, Jean-Luc; Chopard, Bastien; Bonadonna, Costanza

    2016-04-01

    Volcanic ash transport and dispersal models typically describe particle motion via a turbulent velocity field. Particles are advected inside this field from the moment they leave the vent of the volcano until they deposit on the ground. Several techniques exist to simulate particles in an advection field such as finite difference Eulerian, Lagrangian-puff or pure Lagrangian techniques. In this paper, we present a new flexible simulation tool called TETRAS (TEphra TRAnsport Simulator) based on a hybrid Eulerian-Lagrangian model. This scheme offers the advantages of being numerically stable with no numerical diffusion and easily parallelizable. It also allows us to output particle atmospheric concentration or ground mass load at any given time. The model is validated using the advection-diffusion analytical equation. We also obtained a good agreement with field observations of the tephra deposit associated with the 2450 BP Pululagua (Ecuador) and the 1996 Ruapehu (New Zealand) eruptions. As this kind of model can lead to computationally intensive simulations, a parallelization on a distributed memory architecture was developed. A related performance model, taking into account load imbalance, is proposed and its accuracy tested.

  18. Three-dimensional seismic survey applied to field development in Williston basin

    SciTech Connect

    Robinson, G.C.; Baixas, F.; Hooyman, P.J.

    1983-03-01

    The Medicine Lake field of Sheridan County, Montana, was discovered in March 1979. In October 1981, a mini-3-D seismic survey covering 2.5 mi/sup 2/ (6.2 km/sup 2/) was acquired over this field in order to facilitate development drilling by delineating the field's reservoirs and obtaining a more accurate image of the subsurface structure. A multiline system, consisting of 240 geophone groups distributed on 8 lines, was used. The energy source was shothole dynamite using 5 lbs (2.3 kg) charges at 250 ft (46 m). The shotpoints were arranged in a cross pattern with extra shotpoints included to provide necessary control on the weathered zone. The average subsurface coverage was 600%, with CDP bins 165 ft (50 m) square. Prior to the actual shooting, a computer simulation of the resulting fold was performed to verify the field geometry. The entire survey was recorded in one day with no movement of the geophones, thus minimizing costs. The objective of the stratigraphic interpretation was to outline zones of possible porosity, particularly in the Madison and Red River intervals. The horizontal and vertical inverted sections were particularly useful for ascertaining the location and lateral extent of those anomalous zones. The results correlate well with known production, and should aid in the location of future development wells.

  19. 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…

  20. 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. PMID:21800184

  1. Applying "Best Practices" to Preparation of Future Educators Using Exemplary Field Experiences.

    ERIC Educational Resources Information Center

    Ramey, Linda K.; Cole, Donna J.

    This paper provides an overview of the components of Wright State University's (WSU's) present teacher preparation program and addresses the changes envisioned with Ohio's recently approved licensure programs. The paper explains how WSU's current program offers field experiences in three phases. Student teachers have the opportunity to work under…

  2. Comparison of Shank-and-Drip-Applied Methyl Bromide Alternatives in Perenial Crop Field Nurseries.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methyl bromide has been used extensively at open-field perennial crop nurseries to ensure the production of plants that are free of soilborne pests and pathogens. California regulations require that nursery stock for farm planting be commercially clean with respect to economically important nematod...

  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. PMID:25651571

  4. 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

  5. Spinor-unit field representation of electromagnetism applied to a model inflationary cosmology

    NASA Astrophysics Data System (ADS)

    Nash, Patrick L.

    2012-09-01

    The new spinor-unit field representation of the electromagnetism (Nash in J Math Phys 51:042501-1-042501-27, 2010) (with quark and lepton sources) is integrated via minimal coupling with standard Einstein gravitation, to formulate a Lagrangian model of the very early universe. A completely new solution to the coupled Einstein-Maxwell equations, with sources, is derived. These equations are generalized somewhat, but not in a way that violates any physical principles. The solution of the coupled Euler-Lagrange field equations yields a scale factor a( t) (comoving coordinates) that initially exponentially increases N e-folds from a(0) ≈ 0 to a 1 = a(0) e N ( N = 60 is illustrated), then exponentially decreases, then exponentially increases to a 1, and so on almost periodically. (Oscillatory cosmological models are not knew, and have been derived from string theory and loop quantum gravity.) It is not known if the scale factor escapes this periodic trap. This model is noteworthy in several respects: 1. All fundamental fields other than gravity are realized by spinor fields. 2. A plausible connection between the unit field u and the generalization of the photon wave function with a form of Dark Energy is described, and a simple natural scenario is outlined that allocates a fraction of the total energy of the Universe to this form of Dark Energy. 3. A solution of an analog of the pure Einstein-Maxwell equations is found using an approach that is in marked contrast with the method followed to obtain a solution of the well known Friedmann model of a radiation-dominated universe.

  6. Energy saving in ac generators

    NASA Technical Reports Server (NTRS)

    Nola, F. J.

    1980-01-01

    Circuit cuts no-load losses, without sacrificing full-load power. Phase-contro circuit includes gate-controlled semiconductor switch that cuts off applied voltage for most of ac cycle if generator idling. Switch "on" time increases when generator is in operation.

  7. 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.

  8. Three-dimensional seismic survey applied to field development in Williston basin

    SciTech Connect

    Robinson, G.C.; Baixas, F.; Hooyman, P.J.

    1983-08-01

    The Medicine Lake field of Sheridan County, Montana, was discovered in March 1979 by the drilling of a seismic anomaly. Production is obtained from Paleozoic carbonate reservoirs ranging in age from Ordovician to Mississippian. Cumulative production from the field, as of March 1982, is 1.2 million bbl. A mini-3D seismic survey was acquired in October 1981 to facilitate development drilling. The survey covered 2.4 mi/sup 2/ (6.2 km/sup 2/), encompassing the field's seven producing wells and two dry holes. The purpose of this survey was to provide an accurate image of the subsurface structure and delineate the extent of the producing formations. The areal coverage and improved subsurface imaging of the 3D survey provided a detailed view of the Medicine Lake anomaly. The seismic data reveals that the structure results from a local basement (Precambrian) high. Mapping of the Ordovician Winnipeg Formation revealed a domal structure covering approximately 0.6 mi/sup 2/ (1.5 km/sup 2/) with closure in excess of 180 ft (55 m). Although all producing wells are located on the Medicine Lake structure, stratigraphic variations within the reservoirs may localized production within structural closure. Porosity in several producing formations is diagenetic; prediction of reservoir trends from well data alone is difficult. Inversion and interactive modeling were used to study these stratigraphic variations. A correlation between relative acoustic impedance and porosity was established for several formations. Vertical and horizontal relative acoustic impedance sections were then employed to locate zones of possible porosity. This information, combined with the improved structural data, should aid in further development of the Medicine lake field.

  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. Spin echo dynamics under an applied drift field in graphene nanoribbon superlattices

    SciTech Connect

    Prabhakar, Sanjay; Melnik, Roderick; Bonilla, Luis L.; Raynolds, James E.

    2013-12-02

    We investigate the evolution of spin dynamics in graphene nanoribbon superlattices (GNSLs) with armchair and zigzag edges in the presence of a drift field. We determine the exact evolution operator and show that it exhibits spin echo phenomena due to rapid oscillations of the quantum states along the ribbon. The evolution of the spin polarization is accompanied by strong beating patterns. We also provide detailed analysis of the band structure of GNSLs with armchair and zigzag edges.

  11. 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.

  12. 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.

  13. 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.

  14. Field-scale monitoring of pharmaceutical compounds applied to active golf courses by recycled water.

    PubMed

    Young, M H; Green, R L; Conkle, J L; McCullough, M; Devitt, D A; Wright, L; Vanderford, B J; Snyder, S A

    2014-03-01

    The scarcity of potable water in arid and semiarid environments has led to the wider use of recycled water for irrigating agricultural fields, parks, golf courses, and other areas. One concern using recycled water as a source of irrigation has been the presence, fate, and transport of pharmaceutical compounds in water that percolates below the root zone of plants; however, very few multiyear field studies have been reported in the peer-reviewed literature. Here, we assessed compound mass flux of 13 pharmaceuticals in the fairways of four golf courses in the southwestern United States during a 2-yr field study. The sites varied by climate and soil type but were similar regarding turfgrass management. The results showed the presence of at least one pharmaceutical compound in nearly all samples collected, although concentrations were substantially lower after transport through the soil. Percent reduction in compound mass fluxes in drainage water was effectively 100% in 22 of 52 cases, 98 to 100% in 27 of 52 cases, and 73 to 94% in 3 of 52 cases (a case is defined as a specific compound measured at a specific site). Mass fluxes migrating below the root zone were calculated as <250 × 10 g ha for all compounds and >100 × 10 g ha in only two cases. For cases where the majority of the analyses were reportable, all fluxes were <8.80 × 10 g ha. Carbamazepine, meprobamate, and sulfamethoxazole were most commonly found in drainage water, representing nearly 80% of all reportable detections. This research demonstrates the potential of turfgrass/soil systems to reduce contaminant loading below the root zone and potentially toward groundwater. PMID:25602667

  15. Lasing characteristics of a pendant drop deformed by an applied electric field.

    PubMed

    Pu, X Y; Lee, W K

    2000-04-01

    The lasing properties of an oval-shaped resonant cavity (ORC) with a continuously variable aspect ratio have been studied. The ORC was formed with a dye-doped pendant drop placed inside a variable static electric field. When the drop ORC was pumped by a nitrogen laser, lasing from the ORC was found to have strong directional emission characteristics and an intensity enhancement factor as great as 19.5. Calculated results of light rays escaping from ORC's by refraction are in good agreement with the experimental data. PMID:18064081

  16. 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.

  17. Effect of nonlinear absorption on electric field applied lead chloride by Z-scan technique

    NASA Astrophysics Data System (ADS)

    Rejeena, I.; Lillibai, Rahimkutty, M. H.; Nampoori, V. P. N.; Radhakrishnan, P.

    2014-10-01

    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 PbCl2 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.

  18. 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.

  19. 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.

  20. Ion sensitive field effect transistors applied to the measurement of the pH of brines

    SciTech Connect

    Chen, J

    1991-07-01

    The ability to measure the pH (the negative logarithm of the hydrogen ion activity) of harsh fluids such as geothermal oil field brines is important, since pH is a fundamental property; as one chemist stated: very often pH is a critical test because its accuracy lays the foundation for other measurements''. In our research, we focus on the analysis of brines similar to those found in underground geothermal reservoirs. Since the brines are deep under the ground, the values of the pressure and the temperature are high (up to 14 Mpa and 150[degrees]C); therefore the usual methods of pH measurement, e.g., glass electrode, are not applicable. The hydrogen ion sensitive ISFET (Ion Selective Field Effect Transistor) was studied as a pH sensor in this research. An ISFET can detect the electrochemical potential difference between the solution and the semiconductor due to the concentration of H[sup +] ions in the solution. Because of its solid state construction, an ISFET should work properly under high pressure and high temperature conditions. Earlier results, have indicated that it is possible to use ISFETs under the harsh conditions presented by geothermal brines.

  1. Ion sensitive field effect transistors applied to the measurement of the pH of brines

    SciTech Connect

    Chen, J.

    1991-12-31

    The ability to measure the pH (the negative logarithm of the hydrogen ion activity) of harsh fluids such as geothermal oil field brines is important, since pH is a fundamental property; as one chemist stated: ``very often pH is a critical test because its accuracy lays the foundation for other measurements``. In our research, we focus on the analysis of brines similar to those found in underground geothermal reservoirs. Since the brines are deep under the ground, the values of the pressure and the temperature are high (up to 14 Mpa and 150{degrees}C); therefore the usual methods of pH measurement, e.g., glass electrode, are not applicable. The hydrogen ion sensitive ISFET (Ion Selective Field Effect Transistor) was studied as a pH sensor in this research. An ISFET can detect the electrochemical potential difference between the solution and the semiconductor due to the concentration of H{sup +} ions in the solution. Because of its solid state construction, an ISFET should work properly under high pressure and high temperature conditions. Earlier results, have indicated that it is possible to use ISFETs under the harsh conditions presented by geothermal brines.

  2. Gravitomagnetic response of an irrotational body to an applied tidal field

    NASA Astrophysics Data System (ADS)

    Landry, Philippe; Poisson, Eric

    2015-05-01

    The deformation of a nonrotating body resulting from the application of a tidal field is measured by two sets of Love numbers associated with the gravitoelectric and gravitomagnetic pieces of the tidal field, respectively. The gravitomagnetic Love numbers were previously computed for fluid bodies under the assumption that the fluid is in a strict hydrostatic equilibrium that requires the complete absence of internal motions. A more realistic configuration, however, is an irrotational state that establishes, in the course of time, internal motions driven by the gravitomagnetic interaction. We recompute the gravitomagnetic Love numbers for this irrotational state and show that they are dramatically different from those associated with the strict hydrostatic equilibrium: while the Love numbers are positive in the case of strict hydrostatic equilibrium, they are negative in the irrotational state. Our computations are carried out in the context of perturbation theory in full general relativity and in a post-Newtonian approximation that reproduces the behavior of the Love numbers when the body's compactness is small.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Feasibility analysis of digital single lens reflex applied in the field of aerospace measurement

    NASA Astrophysics Data System (ADS)

    Feng, Xinghao; Li, Manliang; Tang, Xuehai

    2015-10-01

    The mainstrean digital single lens reflex (DSLR) image has the characteristics of true color and high quality, this paper proposes apply DSLR to probe spacecraft in order to obtain better quality Color images. Firstly, the performance parameters of mainstream DSLR and industrial-grade optical detector are analysed and compared detailedly; Secondly, the performance and positioning ways etc. of optical detector and DSLR system integrated special telephoto lens are analysed and compared. Furthermore, some experiments have been done in different conditions. The experiments indicate that the performances of DSLR and optical detector are similar. In addition, DSLR has the advantage of small size, low cost and Easy positioning, which can be used to obtain the scene of spacecraft in the takeoff phase and part of reentry phase.

  8. 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

    2016-01-01

    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

  9. 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

  10. AC Loss Reduction in Filamentized YBCO Coated Conductors with Virtual Transverse Cross-cuts

    SciTech Connect

    Zhang, Yifei; Duckworth, Robert C; Ha, Tam T; List III, Frederick Alyious; Gouge, Michael J; Chen, Y; X, Xiong,; Selvamanickam, V.

    2011-01-01

    While the performance of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO)-based coated conductors under dc currents has improved significantly in recent years, filamentization is being investigated as a technique to reduce ac loss so that the 2nd generation (2G) high temperature superconducting (HTS) wires can also be utilized in various ac power applications such as cables, transformers and fault current limiters. Experimental studies have shown that simply filamentizing the superconducting layer is not effective enough to reduce ac loss because of incomplete flux penetration in between the filaments as the length of the tape increases. To introduce flux penetration in between the filaments more uniformly and further reduce the ac loss, virtual transverse cross-cuts were made in superconducting filaments of the coated conductors fabricated using the metal organic chemical vapor deposition (MOCVD) method. The virtual transverse cross-cuts were formed by making cross-cuts (17 - 120 {micro}m wide) on the IBAD (ion beam assisted deposition)-MgO templates using laser scribing followed by depositing the superconducting layer ({approx} 0.6 {micro}m thick). AC losses were measured and compared for filamentized conductors with and without the cross-cuts under applied peak ac fields up to 100 mT. The results were analyzed to evaluate the efficacy of filament decoupling and the feasibility of using this method to achieve ac loss reduction.

  11. Automated decision algorithm applied to a field experiment with multiple research objectives: The DC3 campaign

    NASA Astrophysics Data System (ADS)

    Hanlon, C. J.; Small, A.; Bose, S.; Young, G. S.; Verlinde, J.

    2013-12-01

    In airborne field campaigns, investigators confront complex decision challenges concerning when and where to deploy aircraft to meet scientific objectives within constraints of time and budgeted flight hours. An automated flight decision recommendation system was developed to assist investigators leading the Deep Convective Clouds and Chemistry (DC3) campaign in spring--summer 2012. In making flight decisions, DC3 investigators needed to integrate two distinct, potentially competing objectives: to maximize the total harvest of data collected, and also to maintain an approximate balance of data collected from each of three geographic study regions. Choices needed to satisfy several constraint conditions including, most prominently, a limit on the total number of flight hours, and a bound on the number of calendar days in the field. An automated recommendation system was developed by translating these objectives and bounds into a formal problem of constrained optimization. In this formalization, a key step involved the mathematical representation of investigators' scientific preferences over the set of possible data collection outcomes. Competing objectives were integrated into a single metric by means of a utility function, which served to quantify the value of alternative data portfolios. Flight recommendations were generated to maximize the expected utility of each daily decision, conditioned on that day's forecast. A calibrated forecast probability of flight success in each study region was generated according to a forecasting system trained on numerical weather prediction model output, as well as expected climatological probability of flight success on future days. System performance was evaluated by comparing the data yielded by the actual DC3 campaign, compared with the yield that would have been realized had the algorithmic recommendations been followed. It was found that the algorithmic system would have achieved 19%--59% greater utility than the decisions

  12. Metachronal wave of artificial cilia array actuated by applied magnetic field

    NASA Astrophysics Data System (ADS)

    Tsumori, Fujio; Marume, Ryuma; Saijou, Akinori; Kudo, Kentaro; Osada, Toshiko; Miura, Hideshi

    2016-06-01

    In this paper, a biomimetic microstructure related to cilia, which are effective fluidic and conveying systems in nature, is described. Authors have already reported that a magnetic elastomer pillar actuated by a rotating magnetic field can work like a natural cilium. In the present work, we show examples of a cilia array with a metachronal wave as the next step. A metachronal wave is a sequential action of a number of cilia. It is theoretically known that a metachronal wave gives a higher fluidic efficiency; however, there has been no report on a metachronal wave by artificial cilia. We prepared magnetic elastomer pillars that contain chainlike clusters of magnetic particles. The orientation of chains was set to be different in each pillar so that each pillar will deform with a different phase.

  13. Field test of infrared thermography applied to biogas controlling in landfill sites

    NASA Astrophysics Data System (ADS)

    Madruga, Francisco J.; Muñoz, Jaime M.; González, Daniel A.; Tejero, Juan I.; Cobo, Adolfo; Gil, José L.; Conde, Olga M.; López-Higuera, Jose M.

    2007-04-01

    The gases accumulated inside the landfill as result of the fermentation of Municipal Solid Waste (MSW) known as biogas, are taking into consideration all possible uses as direct transformation into electricity. The system for collecting, regulating and controlling the biogas must include all the necessary safety features where the biogas leakage presents a high impact. Infrared thermography can be use to detect gas leakages due to the differences in temperature between the gas and the immediate surroundings. This method is able to monitor a wide area of landfill sites, quickly. This technology will not be effective if the differences in temperature are not better than five degrees. This paper describes a field test conducted to study the limitations of the infrared thermography caused by weather conditions and the moment of day or/and season when the thermal images was captured. Pipelines, borders, cells, covers, slopes and leakage (hot spots) are studied and optimum conditions are defined.

  14. Analytic treatment of vortex states in cylindrical superconductors in applied axial magnetic field

    SciTech Connect

    Ludu, A.; Van Deun, J.; Cuyt, A.; Milosevic, M. V.; Peeters, F. M.

    2010-08-15

    We solve the linear Ginzburg-Landau (GL) equation in the presence of a uniform magnetic field with cylindrical symmetry and we find analytic expressions for the eigenfunctions in terms of the confluent hypergeometric functions. The discrete spectrum results from an implicit equation associated to the boundary conditions and it is resolved in analytic form using the continued fractions formalism. We study the dependence of the spectrum and the eigenfunctions on the sample size and the surface conditions for solid and hollow cylindrical superconductors. Finally, the solutions of the nonlinear GL formalism are constructed as expansions in the linear GL eigenfunction basis and selected by minimization of the free energy. We present examples of vortex states and their energies for different samples in enhancing/suppressing superconductivity surroundings.

  15. Adsorption of gas molecules on monolayer MoS2 and effect of applied electric field

    NASA Astrophysics Data System (ADS)

    Yue, Qu; Shao, Zhengzheng; Chang, Shengli; Li, Jingbo

    2013-10-01

    Using first-principles calculations, we investigate the adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO) on monolayer MoS2. The most stable adsorption configuration, adsorption energy, and charge transfer are obtained. It is shown that all the molecules are weakly adsorbed on the monolayer MoS2 surface and act as charge acceptors for the monolayer, except NH3 which is found to be a charge donor. Furthermore, we show that charge transfer between the adsorbed molecule and MoS2 can be significantly modulated by a perpendicular electric field. Our theoretical results are consistent with the recent experiments and suggest MoS2 as a potential material for gas sensing application.

  16. Adsorption of gas molecules on monolayer MoS2 and effect of applied electric field.

    PubMed

    Yue, Qu; Shao, Zhengzheng; Chang, Shengli; Li, Jingbo

    2013-01-01

    : Using first-principles calculations, we investigate the adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO) on monolayer MoS2. The most stable adsorption configuration, adsorption energy, and charge transfer are obtained. It is shown that all the molecules are weakly adsorbed on the monolayer MoS2 surface and act as charge acceptors for the monolayer, except NH3 which is found to be a charge donor. Furthermore, we show that charge transfer between the adsorbed molecule and MoS2 can be significantly modulated by a perpendicular electric field. Our theoretical results are consistent with the recent experiments and suggest MoS2 as a potential material for gas sensing application. PMID:24134512

  17. Effect of barrier width on the exciton states in coupled quantum wells in an applied electric field

    NASA Astrophysics Data System (ADS)

    Sivalertporn, Kanchana

    2016-05-01

    The effect of barrier width on the exciton states in coupled quantum wells has been theoretically studied using an efficient approach. By solving the Schrödinger equation in real space, the electron and hole energies and wave functions are calculated in the presence of an applied electric field. It is found that with zero electric field the energy splitting of the doublets is large in the case of thin barrier width. However for thicker barrier width, the Stark effect is stronger at large electric field. The exciton states, binding energies and oscillator strength are also calculated as a function of electric field. There is shown the direct-to-indirect crossover of the exciton ground state at approximately F = 10 kV/cm and F = 5 kV/cm for Lb = 2 nm and Lb = 4 nm respectively, corresponding to the dramatic decrease of its binding energy and oscillator strength. This direct-to-indirect crossover happens at lower electric field for thicker barrier width. We have also studied the light-matter coupling and calculated the DX, IX and CM components of the polariton states as a function of electric field.

  18. Isothermal martensitic transformation in a 12Cr-9Ni-4Mo-2Cu stainless steel in applied magnetic fields

    NASA Astrophysics Data System (ADS)

    San Martín, D.; Aarts, K. W. P.; Rivera-Díaz-del-Castillo, P. E. J.; van Dijk, N. H.; Brück, E.; van der Zwaag, S.

    This work concerns an in situ study of the isothermal formation of martensite in a stainless steel under the influence of magnetic fields up to 9 T at three different temperatures (213, 233 and 253 K). It is shown that the presence of a constant applied magnetic field promotes the formation of martensite significantly. The activation energy for the nucleation of martensite has been derived using a semi-empirical kinetic model. The experimental results have been analyzed using the Ghosh and Olson model. While this model describes the time and field dependences of the experimental data well, the thermal frictional energy and the defect size values are much lower than those expected from earlier work.

  19. Influence of applied magnetic field strength and frequency response of pick-up coil on the magnetic barkhausen noise profile

    NASA Astrophysics Data System (ADS)

    Vashista, M.; Moorthy, V.

    2013-11-01

    The influence of applied magnetic field strength and frequency response of the pick-up coil on the shape of Magnetic Barkhausen Noise (MBN) profile have been studied. The low frequency MBN measurements have been carried out using 5 different MBN pick-up coils at two different ranges of applied magnetic field strengths on quenched and tempered (QT) and case-carburised and tempered (CT) 18CrNiMo7 steel bar samples. The MBN pick-up coils have been designed to obtain different frequency response such that the peak frequency response varies from ˜4 kHz to ˜32 kHz and the amplitude of low frequency signals decreases gradually. At lower applied magnetic field strength of ±14,000 A/m, all the pick-up coils produced a single peak MBN profile for both QT and CT sample. However, at higher applied magnetic field strength of ±22,000 A/m, the MBN profile showed two peaks for both QT and CT samples for pick-up coils with peak frequency response up to ˜17 kHz. Also, there is systematic reduction in peak 2 for QT sample and asymmetric reduction in the heights of peak 1 and peak 2 for CT sample with increase in peak frequency response of the pick-up coils. The decreasing sensitivity of pick-up coils with increasing peak frequency response to MBN signal generation is indicated by the gradual reduction in width of MBN profile and height of peak 2 in the QT sample. The drastic reduction in peak 1 as compared to peak 2 in the CT sample shows the effect of decreasing low frequency response of the pick-up coils on lowering skin-depth of MBN signal detection. This study clearly suggests that it is essential to optimise both maximum applied magnetic field strength and frequency response of the MBN pick-up coil for maximising the shape of the MBN profile for appropriate correlation with the magnetisation process and hence the material properties.

  20. AC Electroosmotic Pumping in Nanofluidic Funnels.

    PubMed

    Kneller, Andrew R; Haywood, Daniel G; Jacobson, Stephen C

    2016-06-21

    We report efficient pumping of fluids through nanofluidic funnels when a symmetric AC waveform is applied. The asymmetric geometry of the nanofluidic funnel induces not only ion current rectification but also electroosmotic flow rectification. In the base-to-tip direction, the funnel exhibits a lower ion conductance and a higher electroosmotic flow velocity, whereas, in the tip-to-base direction, the funnel has a higher ion conductance and a lower electroosmotic flow velocity. Consequently, symmetric AC waveforms easily pump fluid through the nanofunnels over a range of frequencies, e.g., 5 Hz to 5 kHz. In our experiments, the nanofunnels were milled into glass substrates with a focused ion beam (FIB) instrument, and the funnel design had a constant 5° taper with aspect ratios (funnel tip width to funnel depth) of 0.1 to 1.0. We tracked ion current rectification by current-voltage (I-V) response and electroosmotic flow rectification by transport of a zwitterionic fluorescent probe. Rectification of ion current and electroosmotic flow increased with increasing electric field applied to the nanofunnel. Our results support three-dimensional simulations of ion transport and electroosmotic transport through nanofunnels, which suggest the asymmetric electroosmotic transport stems from an induced pressure at the junction of the nanochannel and nanofunnel tip. PMID:27230495

  1. Triatomicidal effect of new spot-on formulations applied to poultry in semi-field conditions.

    PubMed

    Juan, Laura W; Seccacini, Emilia A; Zerba, Eduardo N; Canale, Delmi; Alzogaray, Raúl A

    2013-01-01

    Chagas disease is an endemic disease affecting ten million people in the American continent. Produced by a parasite transmitted by triatomine insects, the main actions for reducing the incidence of this disease are focused on the control of insect vectors. This type of control has produced highly effective results within rural homes, but not in peridomestic areas (kitchens, warehouses, hen houses and other buildings not attached to the houses). The object of the present study was to assess the triatomicidal effect of new spot-on formulations developed by our laboratory in a semi-rural environment. The active ingredients of the formulations were β-cypermethrin, pyriproxyfen, or β-cypermethrin + pyriproxyfen. All formulations were applied to hens and tested in miniature replicas of rural households where experimental populations of Triatoma infestans, the main vector of Chagas disease in Argentina, had been previously released. The experimental populations exposed to formulations containing β-cypermethrin or β-cypermethrin + pyriproxyfen were noticeably reduced compared to non-treated control groups. However, no differences were observed between the effects produced by β-cypermethrin alone and β-cypermethrin + pyriproxyfen. Pyriproxyfen alone produced no significant reduction in the experimental populations of T. infestans. These results suggest that spot-on application of β-cypermethrin could be a useful complementary tool for controlling triatomine insects in the peridomestic areas of rural homes. PMID:23001549

  2. 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

  3. 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.

  4. 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.

  5. European empirical methods applied to subsidence in U. S. coal fields

    SciTech Connect

    Munson, D.E.; Eichfeld, W.F.

    1980-10-01

    The empirical methods commonly used in Europe to describe the shape of subsidence troughs are tested against the field data of the York Canyon Mine in Northern New Mexico. This mine is in a flat lying seam under rugged terrain. The subsidence data consists of time-correlated measurements of surface displacements above two longwall panels. While the profile fits from the graphical methods (United Kingdom) do not agree with the measured profiles, the profile functions of the error integral type used in Continental Europe fit the data well. The profile function analysis of the development curves also suggests a time-dependent response of the overburden. These results, except for the specific profile function used, are similar to those found previously for longwall subsidence at the Old Ben No. 24 Mine. Parameter values of the fit, i.e., the effective half range of the function and inflection point offset, were determined for all profiles. These parameters for the development curves and traveling profiles, which fundamentally result from the same raw data, exhibit markedly different apparent ''scatter.'' The rather narrow range of values for the development curves suggest that individual points subside in a well-behaved manner; and hence, the large variation in parameter values for the traveling profiles reflects an inadequacy in the analysis in correlation between points. Consequently, the use of influence functions appears to be a possible method for improving the empirical analysis of longwall subsidence.

  6. 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.

  7. Remote field eddy current technique applied to the inspection of nonmagnetic steam generator tubes

    NASA Astrophysics Data System (ADS)

    Shin, Young-Kil; Chung, Tae-Eon; Lord, William

    2001-04-01

    As steam generator (SG) tubes have aged, new and subtle degradations have appeared. Most of them start growing from outside the tubes. Since outer diameter defects might not be detected by conventional eddy current testing due to skin effect phenomena, this paper studies the feasibility of using the remote field eddy current (RFEC) technique, which has shown equal sensitivity to inner diameter (ID) and outer diameter (OD) defects in ferromagnetic pipe inspection. Finite element modeling studies show that the operating frequency needs to be increased up to a few hundred kHz in order for RFEC effects to occur in the nonmagnetic SG tube. The proper distance between exciter and sensor coils is also found to be 1.5 OD, which is half of the distance used in ferromagnetic pipe inspection. The resulting defect signals show equal sensitivity to ID and OD defects. These results demonstrate superior capability of the proposed RFEC probe compared to the differential ECT probe in detecting OD defects.

  8. Improved source reconstruction in Fourier-based Near-field Acoustic Holography applied to small apertures

    NASA Astrophysics Data System (ADS)

    Lopez Arteaga, I.; Scholte, R.; Nijmeijer, H.

    2012-10-01

    It is well known that Fourier-based Near-field Acoustic Holography fails to produce good source reconstructions when the aperture size of the microphone array is smaller than the source size. In this paper this problem is overcome by pre-conditioning the spatial hologram data using Linear Predictive Border Padding (LPBP) before it is Fourier-transformed to the wave-number domain. It is shown that LPBP allows for very small aperture sizes with a good reconstruction accuracy. An exhaustive analysis of LPBP is presented based on numerical experiments and measured data. The numerical experiments are performed on two different source types: modal patterns and point sources. These two types of sources represent the two limit situations that one can find in practice: modal patterns have a tonal spectrum in the spatial wave-number domain and are relatively easy to reconstruct accurately, while point sources have a broad-band wave-number spectrum which makes them very challenging to reconstruct. In order to illustrate the accuracy of the method in practice, results of measurements on a hard disk drive are presented as well. For a given distance to the source, the position and size of the hologram plane apertures is varied and the reconstructed source information is compared to the original source data. The reconstructed sources are compared both qualitatively and quantitatively. The results show that LPBP is an efficient and accurate extrapolation method, which leads to accurate reconstructions even for very small aperture sizes.

  9. 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.

  10. 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.

  11. Binary systems, star clusters and the Galactic-field population. Applied stellar dynamics

    NASA Astrophysics Data System (ADS)

    Kroupa, Pavel

    2002-01-01

    This book contains the results of recent theoretical work on the evolution of primordial binary systems in young star clusters, their effect on the evolution of their host clusters, implications for the distribution of young stars in the Milky Way, and the formation of bound star clusters. This work shows that if the Galactic-field binary population is a dynamically evolved version of the Taurus-Auriga pre-main sequence population, then most stars form in clusters with typically a few hundred binaries within a radius of about 0.5-1 pc. The results also suggest that the population I primordial binary-star orbital-parameter distribution functions may be universal, much like the initial mass function. Most solar-like planetary systems can survive in such clusters. The work presented here also establishes that most observed triple and quadruple systems must be primordial, but that α Cen A/B-Proxima Cen-like systems can form in clusters through dynamical capture. Precise N-body calculations using Aarseth's N-body codes of clusters containing up to 104 stars are used to create an extensive young-cluster library. These data demonstrate that the primordial binary systems are disrupted on a crossing-time scale, and that the truncation of the surviving period distribution measures the maximum concentration the cluster ever experienced. The N-body calculations demonstrate that Galactic star clusters form readily as nuclei of expanding OB associations despite a star-formation efficiency of typically 30 per cent and gas-expulsion over a time-span shorter than the cluster crossing time.

  12. In situ aquatic bioassessment of pesticides applied on rice fields using a microalga and daphnids.

    PubMed

    Marques, C R; Pereira, R; Antunes, S C; Cachada, A; Duarte, A C; Gonçalves, F

    2011-08-15

    This study assessed the effects of episodic contamination on a drainage canal adjacent to an area of intensive rice production (Coimbra, Portugal). Four monitoring periods were considered [i) before herbicide application (day-14), ii) at the first application day (day 0), iii) 3 or 5 and iv) 6days after]. Each one consisted in three complementary evaluation lines: a) physico-chemical analyses, b) whole effluent toxicity (WET) assays with Pseudokirchneriella subcapitata, c) in situ bioassays to assess microalgae (P. subcapitata) growth, and the feeding rate and survival of Daphnia longispina and Daphnia magna. Study sites were located upstream, in a protected wetland (L1), and downstream, in the vicinity of rice fields (L2). Along with the application of agrochemicals, there was a general decrease of the water quality, especially in L2, due to nutrient and herbicide inputs. Herbicide peaks (on days 0, 5 and 6) in L2 water samples were recorded concomitantly or immediately after their application. Regarding the in situ bioassessment, the algae growth decrease from day 0 onwards in L1, whilst in L2 its inhibition was generally coherent with the decline of the water quality. Apparently, WET tests indicated that the limitation of nutrients could be affecting algae growth in L1, however, conclusions should be cautious. The feeding depression of daphnids occurred on days 0 and 5 for D. longispina and only on day 0 for D. magna, while significant reductions on survival were restricted to day 0 for both species. The impairments occurring on day 0 were linked to a potential increased toxicity driven by the ingestion of particle-bound herbicides and suspended particles. The feeding rate of daphnids provided an earlier indication of toxic impairments, though it is prompted the use of complementary endpoints and trophic levels in order to understand the cumulative effects due to various herbicide pulses. PMID:21669452

  13. Nanocrystalline cellulose applied simultaneously as the gate dielectric and the substrate in flexible field effect transistors.

    PubMed

    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 cm(2) V (-1) s(-1)), drain-source current on/off modulation ratio higher than 10(5), 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. PMID:24522012

  14. 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

  15. 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. PMID:21174424

  16. ACS Quicklook PDF products

    NASA Astrophysics Data System (ADS)

    Suchkov, Anatoly

    1999-12-01

    This report details the features of the ACS quicklook PDF products produced by the HST data pipeline. The requirements closely follow the design of paper products recommended by the Data Quality Committee, with appropriate changes required to fully support ACS.

  17. Theory of NMR 1 /T1 relaxation in a quantum spin nematic in an applied magnetic field

    NASA Astrophysics Data System (ADS)

    Smerald, Andrew; Shannon, Nic

    2016-05-01

    There is now strong theoretical evidence that a wide range of frustrated magnets should support quantum spin-nematic order in an applied magnetic field. Nonetheless, the fact that spin-nematic order does not break time-reversal symmetry makes it very difficult to detect in experiment. In this article, we continue the theme begun in Phys. Rev. B 88, 184430 (2013), 10.1103/PhysRevB.88.184430, of exploring how spin-nematic order reveals itself in the spectrum of spin excitations. Building on an earlier analysis of inelastic neutron scattering [Phys. Rev. B 91, 174402 (2015), 10.1103/PhysRevB.91.174402], we show how the NMR 1 /T1 relaxation rate could be used to identify a spin-nematic state in an applied magnetic field. We emphasize the characteristic universal features of 1 /T1 using a symmetry-based description of the spin-nematic order parameter and its fluctuations. Turning to the specific case of spin-1/2 frustrated ferromagnets, we show that the signal from competing spin-wave excitations can be suppressed through a judicious choice of nuclear site and field direction. As a worked example, we show how 31P NMR in the square lattice frustrated ferromagnet BaCdVO (PO4)2 is sensitive to spin-nematic order.

  18. 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.}

  19. 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.

  20. 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.

  1. The effects of self-generated and applied magnetic fields on the computation of flow over a Mars return aerobrake

    NASA Technical Reports Server (NTRS)

    Palmer, Grant

    1991-01-01

    A CFD technique is developed to calculate the electromagnetic phenomena simultaneously with the fluid flow in the shock layer over an axisymmetric blunt body in a thermal-equilibrium chemical-nonequilibrium environment. The flowfield is solved using an explicit time-marching, first-order spatially accurate scheme. The electromagnetic phenomena are coupled to the real-gas flow solver through an iterative procedure. The electromagnetic terms introduce a strong stiffness, which was overcome by using significantly smaller time steps for the electromagnetic conservation equation. The technique is applied in calculating the flow over a Mars return aerobrake vehicle entering the Earth's atmosphere. For the case where no external field is applied, the electromagnetic effects have little impact on the flowfield.

  2. 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.

  3. 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.

  4. Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

    NASA Astrophysics Data System (ADS)

    Jing, C.; Chang, C.; Gold, S. H.; Konecny, R.; Antipov, S.; Schoessow, P.; Kanareykin, A.; Gai, W.

    2013-11-01

    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.

  5. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field.

    PubMed

    Klokkenburg, M; Erné, B H; Wiedenmann, A; Petukhov, A V; Philipse, A P

    2007-05-01

    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 (Fe3O4) 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, Phys. Rev. Lett. 97, 185702 (2006)] on the same ferrofluids. PMID:17677066

  6. Mitigation of Alfvén activity in a tokamak by externally applied static 3D fields.

    PubMed

    Bortolon, A; Heidbrink, W W; Kramer, G J; Park, J-K; Fredrickson, E D; Lore, J D; Podestà, M

    2013-06-28

    The application of static magnetic field perturbations to a tokamak plasma is observed to alter the dynamics of high-frequency bursting Alfvén modes that are driven unstable by energetic ions. In response to perturbations with an amplitude of δB/B∼0.01 at the plasma boundary, the mode amplitude is reduced, the bursting frequency is increased, and the frequency chirp is smaller. For modes of weaker bursting character, the magnetic perturbation induces a temporary transition to a saturated continuous mode. Calculations of the perturbed distribution function indicate that the 3D perturbation affects the orbits of fast ions that resonate with the bursting modes. The experimental evidence represents an important demonstration of the possibility of controlling fast-ion instabilities through "phase-space engineering" of the fast-ion distribution function, by means of externally applied perturbation fields. PMID:23848889

  7. 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.

  8. Fundamental study on filter effect of confronting divergent magnetic fields applied to low-pressure inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Sugawara, Hirotake; Ogino, So

    2016-07-01

    The electron motion under confronting divergent magnetic fields (CDMFs) applied to inductively coupled plasmas was simulated using a Monte Carlo method. The CDMFs induced by two coaxial dc coils confined electrons in one side of the separatrix of the CDMFs. However, electrons diffused across the separatrix mainly in two ways. One was the displacement of their gyrocenters due to scattering near the outer part of the separatrix. This process tended to occur for high-energy electrons with correspondingly large gyroradii. The other was passage through the weak magnetic field around the center. This process was allowed for low-energy electrons. The position-dependent selectivity about the electron energy was pointed out as a seed property for applications of the separatrix as a magnetic filter or shutter. The mechanism by which the functions of the separatrix emerge was explained from a viewpoint of electron motion under the CDMFs.

  9. Effects of field-applied composted cattle manure and chemical fertilizer on ammonia and particulate ammonium exchanges at an upland field

    NASA Astrophysics Data System (ADS)

    Hayashi, Kentaro; Koga, Nobuhisa; Yanai, Yosuke

    The present study aimed to investigate the NH 3 volatilization loss from field-applied compost and chemical fertilizer and evaluate the atmosphere-land exchange of NH 3 and particulate NH 4+ (pNH 4) at an upland field with volcanic ash soil (Andosol) in Hokkaido, northern Japan. Two-step basal fertilization was conducted on the bare soil surface. First, a moderately fermented compost of cattle manure was applied by surface incorporation (mixing depth, 0-15 cm) at a rate of 117 kg N ha -1 as total nitrogen (T-N) corresponding to 9.9 kg N ha -1 as ammoniacal nitrogen (NH 4-N). Twelve days later, a chemical fertilizer containing 10% (w/w) of NH 4-N as a mixture of ammonium sulfate and ammonium phosphates was applied by row placement (cover depth, 3 cm) at a rate of 100 kg N ha -1 as NH 4-N. The study period was divided into the first-half, beginning after the compost application (CCM period), and the second-half, beginning after the chemical fertilizer application (CF period). The mean air concentrations of NH 3 and pNH 4 (1.5 m height) were 7.6 and 3.0 μg N m -3, respectively, in the CCM period; the values were 3.7 and 3.9 μg N m -3, respectively, in the CF period. The composition ratios of NH 3 to the sum of NH 3 and pNH 4 (1.5 m height) were 72% and 49% in the CCM and CF periods, respectively. The NH 3 volatilization loss from the compost was 0.8% of the applied T-N (or 9.3% of the applied NH 4-N) and that from the chemical fertilizer was near zero. Excluding the period immediately after the compost application, the upland field acted as a net sink for NH 3 and pNH 4.

  10. 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

  11. 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.

  12. Generalizing the correlated chromophore domain model of reversible photodegradation to include the effects of an applied electric field

    NASA Astrophysics Data System (ADS)

    Anderson, Benjamin; Kuzyk, Mark G.

    2014-03-01

    All observations of photodegradation and self-healing follow the predictions of the correlated chromophore domain model [Ramini et al., Polym. Chem. 4, 4948 (2013), 10.1039/c3py00263b]. In the present work, we generalize the domain model to describe the effects of an electric field by including induced dipole interactions between molecules in a domain by means of a self-consistent field approach. This electric field correction is added to the statistical mechanical model to calculate the distribution of domains that are central to healing. Also included in the model are the dynamics due to the formation of an irreversibly damaged species, which we propose involves damage to the polymer mediated through energy transfer from a dopant molecule after absorbing a photon. As in previous studies, the model with one-dimensional domains best explains all experimental data of the population as a function of time, temperature, intensity, concentration, and now applied electric field. Though the precise nature of a domain is yet to be determined, the fact that only one-dimensional domain models are consistent with observations suggests that they might be made of correlated dye molecules along polymer chains. Furthermore, the voltage-dependent measurements suggest that the largest polarizability axis of the molecules are oriented perpendicular to the chain.

  13. Generalizing the correlated chromophore domain model of reversible photodegradation to include the effects of an applied electric field.

    PubMed

    Anderson, Benjamin; Kuzyk, Mark G

    2014-03-01

    All observations of photodegradation and self-healing follow the predictions of the correlated chromophore domain model [Ramini et al., Polym. Chem. 4, 4948 (2013)]. In the present work, we generalize the domain model to describe the effects of an electric field by including induced dipole interactions between molecules in a domain by means of a self-consistent field approach. This electric field correction is added to the statistical mechanical model to calculate the distribution of domains that are central to healing. Also included in the model are the dynamics due to the formation of an irreversibly damaged species, which we propose involves damage to the polymer mediated through energy transfer from a dopant molecule after absorbing a photon. As in previous studies, the model with one-dimensional domains best explains all experimental data of the population as a function of time, temperature, intensity, concentration, and now applied electric field. Though the precise nature of a domain is yet to be determined, the fact that only one-dimensional domain models are consistent with observations suggests that they might be made of correlated dye molecules along polymer chains. Furthermore, the voltage-dependent measurements suggest that the largest polarizability axis of the molecules are oriented perpendicular to the chain. PMID:24730866

  14. Field evaluation of soybean engineered with a synthetic cry1Ac transgene for resistance to corn earworm, soybean looper, velvetbean caterpillar (Lepidoptera: Noctuidae), and lesser cornstalk borer (Lepidoptera: Pyralidae).

    PubMed

    Walker, D R; All, J N; McPherson, R M; Boerma, H R; Parrott, W A

    2000-06-01

    A transgenic line of the soybean 'Jack', Glycine max (L.) Merrill, expressing a synthetic cry1Ac gene from Bacillus thuringiensis variety kurstaki (Jack-Bt), was evaluated for resistance to four lepidopteran pests in the field. Jack-Bt and genotypes serving as susceptible and resistant controls were planted in field cages and artificially infested with larvae of corn earworm, Helicoverpa zea (Boddie), and velvetbean caterpillar, Anticarsia gemmatalis (Hübner), in 1996, 1997, and 1998, and also with soybean looper, Pseudoplusia includens (Walker), in 1996. Susceptible controls included Jack (1996-1998), 'Cobb' (1996), and Jack-HPH (1996). GatIR 81-296 was used as the resistant control in all 3 yr. Compared with untransformed Jack, Jack-Bt showed three to five times less defoliation from corn earworm and eight to nine times less damage from velvetbean caterpillar. Defoliation of GatIR 81-296 was intermediate between that of Jack and Jack-Bt for corn earworm, and similar to that of Jack for velveltbean caterpillar. Jack-Bt exhibited significant, but lower resistance to soybean looper. Jack-Bt also showed four times greater resistance than Jack to natural infestations of lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), in conventional field plots at two locations in 1998. Data from these experiments suggest that expression of this cry1Ac construct in soybean should provide adequate levels of resistance to several lepidopteran pests under field conditions. PMID:10902306

  15. Quenching of the initial ac Susceptibility in Single Domain Ni Nanobars

    SciTech Connect

    Gai, Zheng; Zhang, Xiaoguang; Kravchenko, Ivan I; Retterer, Scott T; Wendelken, J F

    2012-01-01

    The ac susceptibility measurement probes the dynamic properties of a magnetic material, which is believed to consist of magnetization rotation and domain wall motion contributions. Here we report the observation of a complete quenching of the initial ac susceptibility for a single domain Ni nanobar array, when the ac field is aligned with the long axis of the bars. The vanishing of the susceptibility in one direction is a unique nanoscale phenomena, allowing an unambiguous determination of the magnetic state of the nanostructure and a clean separation of different contributions to its dynamic properties. For example, an unambiguous determination of the surface anisotropy energy is obtained when the field is applied perpendicular to the long axis.

  16. ac susceptibility of an assembly of nanomagnets: Combined effects of surface anisotropy and dipolar interactions

    NASA Astrophysics Data System (ADS)

    Vernay, F.; Sabsabi, Z.; Kachkachi, H.

    2014-09-01

    We compute the ac susceptibility of a weakly dipolar-interacting monodisperse assembly of magnetic nanoclusters with oriented anisotropy. For this purpose, we first compute the relaxation rate in a longitudinal magnetic field of a single nanomagnet taking account of both dipolar interactions in the case of dilute assemblies and surface anisotropy. We then study the behavior of the real and imaginary components of the ac susceptibility as functions of temperature, frequency, surface anisotropy, and interparticle interactions. We find that the surface anisotropy induces an upward shift of the temperature at the maximum of the ac susceptibility components and that its effects may be tuned so as to screen out the effects of interactions. The phenomenological Vogel-Fulcher law for the effect of dipolar interaction on the relaxation rate is revisited within our formalism and a semianalytical expression is given for the effective temperature in terms of inter alia the applied field, surface anisotropy, and dipolar interaction.

  17. 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.

  18. The Behaviors of Ferro-Magnetic Nano-Particles In and Around Blood Vessels under Applied Magnetic Fields.

    PubMed

    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 (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

  19. 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

  20. The near field/far field model with constant application of chemical mass and exponentially decreasing emission of the mass applied.

    PubMed

    Nicas, Mark

    2016-07-01

    The near field/far field (NF/FF) model is a contaminant dispersion construct that permits making airborne contaminant exposure estimates for an individual located close to an emission source. In the present analysis, chemical emission involves a constant mass rate of chemical application to surfaces, denoted I (mg/min), and an exponentially decreasing rate of emission of the chemical from the surfaces with rate constant α (min(-1)). The time-dependent emission rate function is: G(t), mg/min = I - I exp(- αt), where time t is in minutes. The exact time-dependent equations for the contaminant concentration in the NF and the FF are presented. These equations are used to revise a previous analysis of a study in which a penetrant liquid containing benzene was applied to parts on a work table in a test room. The previous analysis assumed that the benzene was applied as a bolus at the start of a 15-min use period, whereas the present analysis assumes the same total benzene mass was applied at a uniform rate over the 15-min use period, but with the same evaporation rate constant α. The new G(t) function leads to a lower 15-min time weighted average NF benzene concentration that better matches the experimental data. It is also shown that the exact equation for the NF concentration is well approximated by combining two well-mixed single-zone equations. The approximation method is mathematically simpler and obviates the need to derive the exact NF equation. PMID:26861562

  1. 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

  2. Biasing a ferronematic - a new way to detect weak magnetic field.

    PubMed

    Tomašovičová, Natália; Kováč, Jozef; Raikher, Yuriy; Éber, Nándor; Tóth-Katona, Tibor; Gdovinová, Veronika; Jadżyn, Jan; Pinčák, Richard; Kopčanský, Peter

    2016-06-29

    The magnetic properties of a ferronematic, i.e., a nematic liquid crystal doped with magnetic nanoparticles in low volume concentration are studied, with the focus on the ac magnetic susceptibility. A weak dc bias magnetic field (a few Oe) applied to the ferronematic in its isotropic phase increases the ac magnetic susceptibility considerably. Passage of the isotropic-to-nematic phase transition resets this enhancement irreversibly (unless the dc bias field is applied again in the isotropic phase). PMID:27296792

  3. 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

  4. 360 Degree DW formation during vortex to vortex switching in thin ferromagnetic nanorings in an applied circular field

    NASA Astrophysics Data System (ADS)

    Sun, Yineng; Goldman, Abby; Licht, Abigail; Li, Yihan; Pradhan, Nihar; Yang, Tianyu; Tuominen, Mark; Aidala, Katherine

    2012-02-01

    We present simulations of the switching process between clockwise and counterclockwise vortex states in ferromagnetic nanorings in an applied circular field, relevant to potential data storage devices. This circular field can be experimentally generated by passing current through the solid metal tip of an atomic force microscope, which has achieved vortex-to-vortex switching in thicker asymmetric rings [1]. We find that in sufficiently thin rings, the vortex switching process occurs through the nucleation and annihilation of pairs of 360 degree domain walls (DW), with opposite topological indices. The DW with the same circulation as the vortex annihilates first. We can control which DW annihilates first by offsetting the center of our circular field to target a specific DW. Both exchange energy and demagnetization energy must be considered in predicting the energy barrier to DW annihilation. [1] T. Yang, N.R. Pradhan, A. Goldman, A.S. Licht, Y.Li, M. Kemei, M.T. Tuominen, K.E. Aidala. APL, 98, 242505 (2011).

  5. Direct numerical simulation of AC dielectrophoretic particle-particle interactive motions.

    PubMed

    Ai, Ye; Zeng, Zhenping; Qian, Shizhi

    2014-03-01

    Under an AC electric field, individual particles in close proximity induce spatially non-uniform electric field around each other, accordingly resulting in mutual dielectrophoretic (DEP) forces on these particles. The resulting attractive DEP particle-particle interaction could assemble individual colloidal particles or biological cells into regular patterns, which has become a promising bottom-up fabrication technique for bio-composite materials and microscopic functional structures. In this study, we developed a transient multiphysics model under the thin electric double layer (EDL) assumption, in which the fluid flow field, AC electric field and motion of finite-size particles are simultaneously solved using an Arbitrary Lagrangian-Eulerian (ALE) numerical approach. Numerical simulations show that negative DEP particle-particle interaction always tends to attract particles and form a chain parallel to the applied electric field. Particles usually accelerate at the first stage of the attractive motion due to an increase in the DEP interactive force, however, decelerate until stationary at the second stage due to a faster increase in the repulsive hydrodynamic force. Identical particles move at the same speed during the interactive motion. In contrast, smaller particles move faster than bigger particles during the attractive motion. The developed model explains the basic mechanism of AC DEP-based particle assembly technique and provides a versatile tool to design microfluidic devices for AC DEP-based particle or cell manipulation. PMID:24407661

  6. Fundamental Study on Filter Effect of Confronting Divergent Magnetic Fields Applied to a Low-Pressure Inductively Coupled Plasma

    NASA Astrophysics Data System (ADS)

    Sugawara, Hirotake

    2015-09-01

    Function of confronting divergent magnetic fields (CDMFs) applied to an inductively coupled plasma called the X-point plasma was investigated. The plasma is driven by a planar spiral rf antenna on the top of a cylindrical chamber. The CDMFs are induced by two coaxial coils with dc currents of opposite directions, and have cusps on their separatrix plane and a magnetic null point at its center. Electron motion in H2 at 1 Pa under the CDMFs was simulated using a Monte Carlo method. Electrons released form the chamber ceiling were captured in the upper region of the chamber by magnetic flux lines running between the ceiling and side wall. However, some of them diffused downward across the separatrix in two ways: passage through the weak magnetic field around the center, and displacement of electron gyrocenters from the upper region to the lower region due to scattering by gas molecules near the outer part of the separatrix. While the former was unselective about electron energy, the latter tended to occur for high-energy electrons with long gyroradii. This position-dependent selectivity in electron passage across the separatrix indicates applicability of the CDMFs as a magnetic filter or shutter. Work supported by JSPS KAKENHI Grant Number 25400528.

  7. In-situ lattice-strain analysis of a ferroelectric thin film under an applied pulse electric field

    SciTech Connect

    Sakata, O.; Yasui, S.; Yamada, T.; Funakubo, H.; Yabashi, M.

    2010-06-23

    We developed an in-situ measurement system for characterizing the relationship between ferroelectricity and lattice distortion of a ferroelectric thin film at BL13XU, SPring-8. The dielectric polarization obtained and the lattice strain evaluated provide us with the electrostrictive coefficient of the film. The system for the method consists of a refractive lens for two dimensional micron focusing, ferroelectric characterization system, high-precision four-circle diffractometer, and time-resolved photon counting system. It enables in-situ measurements of the electric polarization of the film and an electric-field-induced strain using nano-second order time-resolved synchrotron diffraction. We applied the method to determining the lattice constant distorted by the electric field and the polarization value of a 410 nm-thick BiFeO{sub 3} thin film. The piezoelectric constant d{sub 33} evaluated was about 28 pm/V. The polarization observed allowed us to evaluate an electrostrictive coefficient Q of 1{center_dot}4x10{sup -2} m{sup 4}/C{sup 2}.

  8. Phonon emission in germanium and silicon by electrons and holes in applied electric field at low temperature

    SciTech Connect

    Wang, G.

    2010-05-15

    The cryogenic dark matter search employs Ge and Si detectors to search for weakly interacting massive particle dark matter via its elastic-scattering interactions with nuclei while discriminating against interactions of background particles. These detectors distinguish nuclear recoils from electron recoils by simultaneously measuring phonon and ionization production in semiconducting substrates at sub-kelvin temperatures. They also reconstruct event position by quadrant-segmented measurement of the phonon signal. The ionization drift field does work on the electrons and holes. The charge carriers radiate this energy as acoustic phonons. At the typical applied field of 300 V/m in Ge (400 V/m in Si), we self-consistently model the behavior of the electrons and holes using independent drifted Maxwellian distributions, each characterized by an average drift velocity and an effective temperature, and including acoustic phonon emission. We calculate the phonon power angular and frequency distributions. We find that the bias polarity affects these distributions and, therefore, the phonon collection efficiency in Ge.

  9. Optical Flow Applied to Time-Lapse Image Series to Estimate Glacier Motion in the Southern Patagonia Ice Field

    NASA Astrophysics Data System (ADS)

    Lannutti, E.; Lenzano, M. G.; Toth, C.; Lenzano, L.; Rivera, A.

    2016-06-01

    In this work, we assessed the feasibility of using optical flow to obtain the motion estimation of a glacier. In general, former investigations used to detect glacier changes involve solutions that require repeated observations which are many times based on extensive field work. Taking into account glaciers are usually located in geographically complex and hard to access areas, deploying time-lapse imaging sensors, optical flow may provide an efficient solution at good spatial and temporal resolution to describe mass motion. Several studies in computer vision and image processing community have used this method to detect large displacements. Therefore, we carried out a test of the proposed Large Displacement Optical Flow method at the Viedma Glacier, located at South Patagonia Icefield, Argentina. We collected monoscopic terrestrial time-lapse imagery, acquired by a calibrated camera at every 24 hour from April 2014 until April 2015. A filter based on temporal correlation and RGB color discretization between the images was applied to minimize errors related to changes in lighting, shadows, clouds and snow. This selection allowed discarding images that do not follow a sequence of similarity. Our results show a flow field in the direction of the glacier movement with acceleration in the terminus. We analyzed the errors between image pairs, and the matching generally appears to be adequate, although some areas show random gross errors related to the presence of changes in lighting. The proposed technique allowed the determination of glacier motion during one year, providing accurate and reliable motion data for subsequent analysis.

  10. Non-invasive near-field measurement setup based on modulated scatterer technique applied to microwave tomography

    NASA Astrophysics Data System (ADS)

    Memarzadeh-Tehran, Hamidreza

    The main focus of this thesis is to address the design and development of a near-field (NF) imaging setup based on the modulated scatterer technique (MST). MST is a well-known approach used in applications where accurate and perturbation-free measurement results are necessary. Of the possible implementations available for making an MST probe, including electrical, optical and mechanical, the optically modulated scatterer OMS was considered in order to provide nearly perturbation-free measurement due to the invisibility of optical fiber to the radio-frequency electromagnetic fields. The OMS probe consists of a commercial, off-the-shelf (COTS) photodiode chip (nonlinear device), a short-dipole antenna acting as a scatterer and a matching network (passive circuit). The latter improves the scattering properties and also increases the sensitivity of the OMS probe within the frequency range in which the matching network is optimized. The radiation characteristics of the probe, including cross-polarization response and omnidirectional sensitivity, were both theoretically and experimentally investigated. Finally, the performance and reliability of the probe was studied by comparing measured near-field distributions on a known field distribution with simulations. Increased imaging speed was obtained using an array of OMS probes, which reduces mechanical movements. Mutual-coupling, switching time and shadowing effect, which all may affect the performance of the array, were investigated. Then, the results obtained by the array were validated in a NF imager by measuring the E-field distribution of an antenna under test (AUT) and comparing it with a simulation. Calibration and data averaging were applied to raw data to compensate the probes for uncertainties in fabrication and interaction between array/AUT and array/receiving antenna. Dynamic range and linearity of the developed NF imager was improved by adding a carrier canceller circuit to the front-end of the receiver. The

  11. 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

  12. Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell and Monte Carlo collision. II. Investigation of acceleration mechanisms

    NASA Astrophysics Data System (ADS)

    Tang, Hai-Bin; Cheng, Jiao; Liu, Chang; York, Thomas M.

    2012-07-01

    The particle-in-cell method previously described in paper (I) has been applied to the investigation of acceleration mechanisms in applied-field magnetoplasmadynamic thrusters. This new approach is an alternative to magnetohydrodynamics models and allows nonlocal dynamic effects of particles and improved transport properties. It was used to model a 100 kW, steady-state, applied-field, argon magnetoplasmadynamic thruster to study the physical acceleration processes with discharge currents of 1000-1500 A, mass flow rates of 0.025-0.1 g/s and applied magnetic field strengths of 0.034-0.102 T. The total thrust calculations were used to verify the theoretical approach by comparison with experimental data. Investigations of the acceleration model offer an underlying understanding of applied-field magnetoplasmadynamic thrusters, including the following conclusions: (1) swirl acceleration mechanism is the dominant contributor to the plasma acceleration, and self-magnetic, Hall, gas-dynamic, and swirl acceleration mechanisms are in an approximate ratio of 1:10:10:100; (2) the Hall acceleration produced mainly by electron swirl is insensitive to the change of externally applied magnetic field and shows only slight increases when the current is raised; (3) self-magnetic acceleration is normally negligible for all cases, while the gas-dynamic acceleration contribution increases with increasing applied magnetic field strength, discharge current, and mass flow rate.

  13. Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell and Monte Carlo collision. II. Investigation of acceleration mechanisms

    SciTech Connect

    Tang Haibin; Cheng Jiao; Liu Chang; York, Thomas M.

    2012-07-15

    The particle-in-cell method previously described in paper (I) has been applied to the investigation of acceleration mechanisms in applied-field magnetoplasmadynamic thrusters. This new approach is an alternative to magnetohydrodynamics models and allows nonlocal dynamic effects of particles and improved transport properties. It was used to model a 100 kW, steady-state, applied-field, argon magnetoplasmadynamic thruster to study the physical acceleration processes with discharge currents of 1000-1500 A, mass flow rates of 0.025-0.1 g/s and applied magnetic field strengths of 0.034-0.102 T. The total thrust calculations were used to verify the theoretical approach by comparison with experimental data. Investigations of the acceleration model offer an underlying understanding of applied-field magnetoplasmadynamic thrusters, including the following conclusions: (1) swirl acceleration mechanism is the dominant contributor to the plasma acceleration, and self-magnetic, Hall, gas-dynamic, and swirl acceleration mechanisms are in an approximate ratio of 1:10:10:100; (2) the Hall acceleration produced mainly by electron swirl is insensitive to the change of externally applied magnetic field and shows only slight increases when the current is raised; (3) self-magnetic acceleration is normally negligible for all cases, while the gas-dynamic acceleration contribution increases with increasing applied magnetic field strength, discharge current, and mass flow rate.

  14. ACS Data Handbook v.6.0

    NASA Astrophysics Data System (ADS)

    Gonzaga, S.; et al.

    2011-03-01

    ACS was designed to provide a deep, wide-field survey capability from the visible to near-IR using the Wide Field Camera (WFC), high resolution imaging from the near-UV to near-IR with the now-defunct High Resolution Camera (HRC), and solar-blind far-UV imaging using the Solar Blind Camera (SBC). The discovery efficiency of ACS's Wide Field Channel (i.e., the product of WFC's field of view and throughput) is 10 times greater than that of WFPC2. The failure of ACS's CCD electronics in January 2007 brought a temporary halt to CCD imaging until Servicing Mission 4 in May 2009, when WFC functionality was restored. Unfortunately, the high-resolution optical imaging capability of HRC was not recovered.

  15. 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.

  16. Environmental fate of the insecticide cypermethrin applied as microgranular and emulsifiable concentrate formulations in sunflower cultivated field plots.

    PubMed

    Mantzos, N; Karakitsou, A; Hela, D; Konstantinou, I

    2016-01-15

    A field dissipation and transport study of the insecticide cypermethrin applied as microgranular (MG) and emulsifiable concentrate (EC) formulations has been conducted in field sunflower cultivations and bare soil plots with two different slopes (1% and 5%). The dissipation of insecticide in soil (on planting rows) was monitored for a period of 193 days. Cypermethrin residual concentrations in the upper soil layer (0-10 cm), 2 days after soil application (DASA), ranged from 0.53 to 0.73 μg g(- 1) when the maximum values were observed 7 DASA, ranged from 1.06 to 1.23 μg g(-1). The dissipation rate was better described by first-order kinetics. The average half-life in cultivated (tilled and planted) plots was 23.07 and 24.24 days for soil slopes 5% and 1%, respectively. In uncultivated (tilled but not planted) plots the respective values were 22.01 and 22.37 days. The insecticide was found below the 10 cm soil layer occasionally in few samples at low concentrations (< 0.02 μg g(- 1)). In runoff water it was detected once (7 days after foliar application, at levels below LOQ), when in sediment it was detectable for seven samplings. The maximum values were observed 7 days after foliar application, when they reached 0.097 and 0.143 μg g(-1) in cultivated plots with soil slopes 1% and 5%; and 0.394 and 0.500 μg g(-1) in uncultivated plots, respectively. The amount of cypermethrin which was transferred by the sediment remained at low levels (less than 0.01% of the totally applied active ingredient), even in plots with 5% inclination. The insecticide was detected in leaves and stems of the sunflower plants after the foliar application up to the day of harvest. On the contrary, in roots it was detectable during the whole cultivation period. No residues were detected in flowers or seeds. PMID:26439647

  17. Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell code with Monte Carlo collision. I. Computation methods and physical processes

    SciTech Connect

    Tang Haibin; Cheng Jiao; Liu Chang; York, Thomas M.

    2012-07-15

    A two-dimensional axisymmetric electromagnetic particle-in-cell code with Monte Carlo collision conditions has been developed for an applied-field magnetoplasmadynamic thruster simulation. This theoretical approach establishes a particle acceleration model to investigate the microscopic and macroscopic characteristics of particles. This new simulation code was used to study the physical processes associated with applied magnetic fields. In this paper (I), detail of the computation procedure and results of predictions of local plasma and field properties are presented. The numerical model was applied to the configuration of a NASA Lewis Research Center 100-kW magnetoplasmadynamic thruster which has well documented experimental results. The applied magnetic field strength was varied from 0 to 0.12 T, and the effects on thrust were calculated as a basis for verification of the theoretical approach. With this confirmation, the changes in the distributions of ion density, velocity, and temperature throughout the acceleration region related to the applied magnetic fields were investigated. Using these results, the effects of applied field on physical processes in the thruster discharge region could be represented in detail, and those results are reported.

  18. Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell code with Monte Carlo collision. I. Computation methods and physical processes

    NASA Astrophysics Data System (ADS)

    Tang, Hai-Bin; Cheng, Jiao; Liu, Chang; York, Thomas M.

    2012-07-01

    A two-dimensional axisymmetric electromagnetic particle-in-cell code with Monte Carlo collision conditions has been developed for an applied-field magnetoplasmadynamic thruster simulation. This theoretical approach establishes a particle acceleration model to investigate the microscopic and macroscopic characteristics of particles. This new simulation code was used to study the physical processes associated with applied magnetic fields. In this paper (I), detail of the computation procedure and results of predictions of local plasma and field properties are presented. The numerical model was applied to the configuration of a NASA Lewis Research Center 100-kW magnetoplasmadynamic thruster which has well documented experimental results. The applied magnetic field strength was varied from 0 to 0.12 T, and the effects on thrust were calculated as a basis for verification of the theoretical approach. With this confirmation, the changes in the distributions of ion density, velocity, and temperature throughout the acceleration region related to the applied magnetic fields were investigated. Using these results, the effects of applied field on physical processes in the thruster discharge region could be represented in detail, and those results are reported.

  19. 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…

  20. 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