Science.gov

Sample records for electric field forces

  1. Average Lorentz self-force from electric field lines

    NASA Astrophysics Data System (ADS)

    Aashish, Sandeep; Haque, Asrarul

    2015-09-01

    We generalize the derivation of electromagnetic fields of a charged particle moving with a constant acceleration Singal (2011 Am. J. Phys. 79 1036) to a variable acceleration (piecewise constants) over a small finite time interval using Coulomb's law, relativistic transformations of electromagnetic fields and Thomson's construction Thomson (1904 Electricity and Matter (New York: Charles Scribners) ch 3). We derive the average Lorentz self-force for a charged particle in arbitrary non-relativistic motion via averaging the fields at retarded time.

  2. Real-space phase-field simulation of piezoresponse force microscopy accounting for stray electric fields

    NASA Astrophysics Data System (ADS)

    Yang, Lun; Dayal, Kaushik

    2012-04-01

    Piezoresponse force microscopy (PFM) is a powerful scanning-probe technique used to characterize important aspects of the microstructure in ferroelectrics. It has been widely applied to understand domain patterns, domain nucleation and the structure of domain walls. In this paper, we apply a real-space phase-field model to consistently simulate various PFM configurations. We model the PFM tip as a charged region that is external to the ferroelectric, and implement a boundary element method to efficiently and accurately account for the external stray fields that mediate the interactions between the tip and the ferroelectric. Our phase-field model and the solution method together are able to account for the electrical fields both within the specimen as well as those outside, and also consistently solve for the resulting electromechanical response with the same phase-field model. We apply this to various problems: first, the effect of crystal lattice orientation on the induced tip displacement and rotation; second, PFM scanning of a 90° domain wall that emerges at a free surface; third, the effect of closure domain microstructure on PFM response; fourth, the effect of surface modulations on PFM response; and fifth, the effect of surface charge compensation on PFM response.

  3. A "Sensitive Skin" for Robotic Companions Featuring Temperature, Force, and Electric Field Sensors

    E-print Network

    Breazeal, Cynthia

    A "Sensitive Skin" for Robotic Companions Featuring Temperature, Force, and Electric Field Sensors a wide variety of tactile inputs. Such "sensitive skins" can provide much benefit in human robot. In this paper we present a set of design criteria for how such "skins" should be designed. Based

  4. High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm

    NASA Astrophysics Data System (ADS)

    Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

    2015-10-01

    The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120?nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200?V/m at 1?KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection.

  5. High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm.

    PubMed

    Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

    2015-01-01

    The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120 nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200 V/m at 1 KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection. PMID:26507680

  6. High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm

    PubMed Central

    Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

    2015-01-01

    The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120?nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200?V/m at 1?KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection. PMID:26507680

  7. Electric/magnetic dipolein an electromagnetic field: force, torque and energy

    NASA Astrophysics Data System (ADS)

    Kholmetskii, Alexander; Missevitch, Oleg; Yarman, T.

    2014-10-01

    In this paper we collect the relativistic expressions for the force, torque and energy of a small electric/magnetic dipole in an electromagnetic field, which we recently obtained (A.L. Kholmetskii et al., Eur. J. Phys. 33, L7 (2011), Prog. Electromagn. Res. B 45, 83 (2012), Can. J. Phys. 9, 576 (2013)) and consider a number of subtle effects, characterized the behavior of the dipole in an external field, which seem interesting from the practical viewpoint.

  8. The Effect of Electric Fields In A Classic Introductory Physics Treatment of Eddy Current Forces

    E-print Network

    P. J. Salzman; John Robert Burke; Susan M. Lea

    2006-07-23

    A simple model of eddy currents in which current is computed solely from magnetic forces acting on electrons proves accessible to introductory students and gives a good qualitative account of eddy current forces. However, this model cannot be complete; it ignores the electric fields that drive current outside regions of significant magnetic field. In this paper we show how to extend the model to obtain a boundary value problem for current density. Solution of this problem in polar coordinates shows that the electric field significantly affects the quantitative results and presents an exercise suitable for upper division students. We apply elliptic cylindrical coordinates to generalize the result and offer an exercise useful for teaching graduate students how to use non-standard coordinate systems.

  9. Effects of auroral-particle anisotropies and mirror forces on high-latitude electric fields

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Schulz, M.; Cornwall, J. M.

    1981-01-01

    It is noted that, for most of the mechanisms for the strong electric fields that characterize the narrow regions in which there is acceleration and precipitation of ring current and/or plasma-sheet plasma, certain effects must be taken into account in simulations of auroral electric fields. The effects are those of auroral particle anisotropy, of mirror forces due to the inhomogeneous geomagnetic field, of auroral electron backscatter by the atmosphere, and of electron trapping by the combination of magnetic mirroring and electrostatic forces. What is more, the effects of the very strong perpendicular electric field must also be taken into account in a kinetic description of the Poisson equation in order to achieve a unified theory of the auroral electrostatic structure. Progress in these areas during the past few years is reviewed. It is shown that particle anisotropies and mirror forces can account for some basic electrostatic features of the quiet arc, while additional effects may be occurring in strong events in which the parallel potential drop is more than about 10 kV.

  10. Electric field and force modeling for electrostatic levitation of lossy dielectric plates

    NASA Astrophysics Data System (ADS)

    Woo, S. J.; Higuchi, T.

    2010-11-01

    Electrostatic levitation holds great promise for the semiconductor, solar panel, and flat-panel display industry where the handling of dielectrics in a contact-free manner can bring many advantages and solve long-standing contamination and particulate control problems. In this work an analytical model is developed for the electrostatic levitation field between a lossy dielectric plate and a generic stator electrode structure consisting of a regular planar array of parallel bar electrodes. Time-varying voltages of differing polarities are alternatingly applied to the bar electrodes. Atmospheric humidity-related surface conduction on the plate is explicitly taken into account in the model since it has a profound effect on the field dynamics. Based on this model, the electrostatic levitation force is calculated using the Maxwell stress tensor formulation. The levitation force dynamics are investigated by evaluating the transient response of the field under a step in the applied voltages. In this context, the rate of electric charge build up on the plate is characterized by the suspension initiation time (TSI), which is defined as the time elapsed between applying step voltages to the stator electrodes and start of lift-off of the dielectric plate from its initial position. TSI is theoretically predicted for 0.7 mm thick soda-lime glass substrates, typically used in the manufacturing of liquid crystal displays (LCDs), as a function of electrode geometry, air gap separation, ambient humidity, and step voltage magnitudes. The predicted results are shown to be in good agreement with previously published experimental data for soda-lime glass substrates.

  11. Mode Transition of RNA Trap by Electric and Hydraulic Force Field in Microfluidic Taper Shape Channel

    NASA Astrophysics Data System (ADS)

    Takamura, Yuzuru; Ueno, Kunimitsu; Nagasaka, Wako; Tomizawa, Yuichi; Tamiya, Eiichi

    2007-03-01

    We have discovered a phenomenon of accumulation of DNA near the constricted position of a microfluidic chip with taper shaped channel when both hydro pressure and electric field are applied in opposite directions. However, RNA has not been able to trap so far, unlike huge and uniformly double stranded DNA molecules, RNAs are smaller in size and single stranded with complicated conformation like blocks in lysed cell solution. In this paper, we will report not only large but also small RNA (100˜10b) are successfully trapped in relatively large microfluidic taper shape channel (width >10um). RNA are trapped in circular motion near the constricted position of taper shape channel, and the position and shape of the trapped RNA are controlled and make mode transition by changing the hydraulic and the electric force. Using this technique, smaller size molecule can be trapped in larger micro fluidic structure compared to the trap using dielectrophoresis. This technique is expected to establish easy and practical device as a direct total RNA extraction tool from living cells or tissues.

  12. 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.

  13. 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.

  14. Specific features of the thermal electromotive force in Bi quantum wires in transverse magnetic and electric fields

    NASA Astrophysics Data System (ADS)

    Sinyavskii, E. P.; Solovenko, V. G.

    2014-11-01

    The thermal electromotive force (emf) in Bi quantum wires has been calculated in the model of potential in the form of a paraboloid of revolution in a uniform magnetic field H, which is normal to the axis of the studied nanostructure, and in a direct-current (dc) electric field E ? H. It has been shown that, with an increase in E, the thermal emf ?xx is described by a nonmonotonic function at different values of H. A physical interpretation of this behavior of ?xx as a function of E is proposed with account for the interaction between carriers and the rough surface of the nanowire.

  15. The effect of electric field geometry on the performance of electromembrane extraction systems: Footprints of a third driving force along with migration and diffusion.

    PubMed

    Moazami, Hamid Reza; Hosseiny Davarani, Saied Saeed; Mohammadi, Jamil; Nojavan, Saeed; Abrari, Masoud

    2015-09-01

    The distribution of electric field vectors was first calculated for electromembrane extraction (EME) systems in classical and cylindrical electrode geometries. The results showed that supported liquid membrane (SLM) has a general field amplifying effect due to its lower dielectric constant in comparison with aqueous donor/acceptor solutions. The calculated norms of the electric field vector showed that a DC voltage of 50 V can create huge electric field strengths up to 64 kV m(-1) and 111 kV m(-1) in classical and cylindrical geometries respectively. In both cases, the electric field strength reached its peak value on the inner wall of the SLM. In the case of classical geometry, the field strength was a function of the polar position of the SLM whereas the field strength in cylindrical geometry was angularly uniform. In order to investigate the effect of the electrode geometry on the performance of real EME systems, the analysis was carried out in three different geometries including classical, helical and cylindrical arrangements using naproxen and sodium diclofenac as the model analytes. Despite higher field strength and extended cross sectional area, the helical and cylindrical geometries gave lower recoveries with respect to the classical EME. The observed decline of the signal was proved to be against the relations governing migration and diffusion processes, which means that a third driving force is involved in EME. The third driving force is the interaction between the radially inhomogeneous electric field and the analyte in its neutral form. PMID:26388374

  16. Lattice QCD with strong external electric fields.

    PubMed

    Yamamoto, Arata

    2013-03-15

    We study particle generation by a strong electric field in lattice QCD. To avoid the sign problem of the Minkowskian electric field, we adopt the "isospin" electric charge. When a strong electric field is applied, the insulating vacuum is broken down and pairs of charged particles are produced by the Schwinger mechanism. The competition against the color confining force is also discussed. PMID:25166523

  17. Fluid Mechanical and Electrical Fluctuation Forces in Colloids

    E-print Network

    D. Drosdoff; A. Widom

    2004-10-06

    Fluctuations in fluid velocity and fluctuations in electric fields may both give rise to forces acting on small particles in colloidal suspensions. Such forces in part determine the thermodynamic stability of the colloid. At the classical statistical thermodynamic level, the fluid velocity and electric field contributions to the forces are comparable in magnitude. When quantum fluctuation effects are taken into account, the electric fluctuation induced van der Waals forces dominate those induced by purely fluid mechanical motions. The physical principles are applied in detail for the case of colloidal particle attraction to the walls of the suspension container and more briefly for the case of forces between colloidal particles.

  18. Turbulent generation and mechanism analysis of forced-convective heat transfer enhancement by applying electric fields in the restricted region near the wall

    SciTech Connect

    Hasegawa, Masato; Yabe, Akira; Nariai, Hideki

    1999-07-01

    The heat transfer enhancement method of applying electric fields only near a heat transfer wall was numerically investigated. Generation of additional turbulence in the near-wall region occurs by the interaction between migrating electric charges and the turbulent flow of weakly electrically conductive fluids such as refrigerants, oils, and chlorofluorocarbon (CFC) alternatives. Based on electrostatic probe experiments, the authors assumed that the current was mainly transferred by the negative charges. They solved the Navier-Stokes equation with a Coulomb force term, the conservation equation of electric current, the Poisson equation of electric potential, and the energy equation. They used the Large Eddy Simulation (LES) method to represent the turbulence. The numerical analysis showed a heat transfer enhancement of 2.8 times for turbulent flow (Re = 1.8 x 10{sup 4}) when applying 5 kV to the near-wall region, 5 mm from the wall. The simulations for different distances between the coupled electrodes showed that an optimum location of the electrodes exists for achieving the lowest electric power input for a given electric field strength. They also evaluated the heat efficiency in a simple heat exchanger system using this heat transfer enhancement method. For the 5 kV/5 mm condition, where 19% of the total input power was consumed by the electric field, they achieved a heat transfer enhancement of 27 times compared to the case when an equivalent, additional amount of input power would be consumed by the pump to increase the flow rate of the heat-transfer fluid.

  19. Formation, characterization, and dynamics of onion-like carbon structures for electrical energy storage from nanodiamonds using reactive force fields

    NASA Astrophysics Data System (ADS)

    Ganesh, P.; Kent, P. R. C.; Mochalin, V.

    2011-10-01

    We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbon nanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core of the nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbon nanostructure appears, with a shell-shell spacing of about ˜3.4 Å for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large (˜29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.

  20. Formation, characterization and dynamics of onion like carbon structures from nanodiamonds using reactive force-fields for electrical energy storage

    SciTech Connect

    Kent, Paul R

    2011-01-01

    We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbon nanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core of the nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbon nanostructure appears, with a shell-shell spacing of about {approx}3.4 {angstrom} for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large ({approx}29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.

  1. Formation, characterization, and dynamics of onion-like carbon structures for electrical energy storage from nanodiamonds using reactive force fields

    SciTech Connect

    Ganesh, P.; Kent, P. R. C.; Mochalin, V.

    2011-10-01

    We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbonnanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core of the nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbonnanostructure appears, with a shell-shell spacing of about ~3.4 Å for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large (~29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.

  2. Distillation under electric fields

    SciTech Connect

    Shah, V.M.; Blankenship, K.D.; Tsouris, C.

    1997-11-01

    Distillation Is the most common separation process used in the chemical and petroleum industry. Major limitations in the applicability and efficiency of distillation come from thermodynamic equilibria, that is, vapor-liquid equilibria (VLE), and heat and mass transfer rates. In this work, electric fields are used to manipulate the VLE of mixtures. VLE experiments are performed for various binary mixtures in the presence of electric fields on the order of a few kilovolts per centimeter. The results show that the VLE is changed by electric fields, with changes in the separation factor as high as 10% being observed. Batch distillation experiments are also carried out for binary mixtures of 2-propanol and water with and without an applied electric field. Results show enhanced distillation rates and separation efficiency in the presence of an electric field but decreased separation enhancement when the electric current is increased. The latter phenomenon is caused by the formation at the surface of the liquid mixture of microdroplets that are entrained by the vapor. These observations suggest that there should be an electric field strength for each system for which the separation enhancement is maximum.

  3. Electric Field Mediated Droplet Centering

    SciTech Connect

    Bei, Z.-M.; Jones, T.B.; Tucker-Schwartz, A.; Harding, D.R.

    2010-03-12

    Double emulsion droplets subjected to a uniform ac electric field self-assemble into highly concentric structures via the dipole/dipole force if the outer droplet has a higher dielectric constant than the suspending liquid. The dielectric constant of the inner droplet has no influence. To minimize field-induced droplet distortion, the liquids must be density matched to ~0.1%. Centering of ~3 to 6 mm diameter droplets is achieved within ~60 s for field strengths of ~10^4 V_rms /m in liquids of viscosity ~10 cP. Effective centering depends strongly on frequency if the outer shell is conductive.

  4. Applications of Lorentz force in medical acoustics: Lorentz force hydrophone, Lorentz Force Electrical Impedance Tomography, Imaging of shear waves induced by Lorentz force

    E-print Network

    Grasland-Mongrain, Pol

    2014-01-01

    The ability of the Lorentz force to link a mechanical displacement to an electrical current presents a strong interest for medical acoustics, and three applications were studied in this thesis. In the first part of this work, a hydrophone was developed for mapping the particle velocity of an acoustic field. This hydrophone was constructed using a thin copper wire and an external magnetic field. A model was elaborated to determine the relationship between the acoustic pressure and the measured electrical current, which is induced by Lorentz force when the wire vibrates in the acoustic field of an ultrasound transducer. The built prototype was characterized and its spatial resolution, frequency response, sensitivity, robustness and directivity response were investigated. An imaging method called Lorentz Force Electrical Impedance Tomography was also studied. In this method, a biological tissue is vibrated by ultrasound in a magnetic field, which induces an electrical current by Lorentz force. The electrical imp...

  5. Revisiting the Corotation Electric Field

    NASA Astrophysics Data System (ADS)

    Rothwell, P. L.

    2001-05-01

    The rotation of the Earth's dipole magnetic field produces a corotation electric field in the nonrotating frame of reference. A quick calculation implies that this field might arise from the relative motion of an observer in the nonrotating frame and the motion of rotating magnetic field lines. However, upon applying Faraday's Law one finds that total time rate of change of the magnetic field as seen in the nonrotating frame is zero due to the azimuthal symmetry of the dipole. Therefore, classical EM theory(1) predicts a zero corotation electric field in the nonrotating frame for a vacuum. This conundrum has been traditionally treated in the following manner(2,3). 1) Start with a vacuum state with no conductors and plasma present. The transformation between E (the electric field in the nonrotating frame) and E' (the electric field in the rotating frame)implies that in the rotating frame E' is nonzero while E = 0. 2) In the presence of a thin conducting spherical shell (the ionosphere) polarization charges form in the shell due to the magnetic force on the electrons. A polarization electric field Ep is created such that in the idealized case the shell has a uniform electric potential. This Ep has a component along the magnetic field lines outside the shell. 3) Plasma will polarize along B, thus canceling the parallel component of Ep which allows the potential on the shell to be mapped along the magnetic field lines setting E' = 0. From the transformation equation E is now nonzero. This is the electric field required in the nonrotating frame for the plasma to corotate with the dipole. The presence of the corotation electric field is not a local result, but a nonlocal effect that requires the presence of an ionosphere and a conducting plasma. (1) W.K.H. Panofsky and M. Phillips, Classical Electricity and Magnetism, Addison-Wesley, 1956. (2) H. Alfven and C.-G. Falthammar, Cosmical Electrodynamics, 2nd ed., Oxford Press, 1963. (3) E.W.Hones and J.E.Bergeson, J. Geophys. Res. , 70, 4951, 1965.

  6. New equation of ion flux in a membrane. Inclusion of frictional force generated by the electric field

    SciTech Connect

    Higa, Mitsuru; Kira, Akira , Saitama )

    1994-06-23

    To describe the diffusion of ions in a water-swollen membrane, we improved the Nernst-Planck equation of ion flux by considering a frictional force generated by the collision of ions with membrane matrix which depends on membrane potential. This new equation of ion flux predicts that the apparent mobility of an ion in a membrane depends on both the membrane potential and the valence of the ion. The experimental data of diffusion in dialysis systems of KCl, LiCl, CaCl[sub 2], and LaCl[sub 3] were consistent with the predictions based on this equation. 34 refs., 6 figs.

  7. BE.430J Fields, Forces, and Flows in Biological Systems, Fall 2004

    E-print Network

    Grodzinsky, Alan J.

    This course covers the following topics: conduction, diffusion, convection in electrolytes; fields in heterogeneous media; electrical double layers; Maxwell stress tensor and electrical forces in physiological systems; and ...

  8. Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

    E-print Network

    Grasland-Mongrain, Pol; Mari, Jean-Martial; Souchon, Remi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy

    2015-01-01

    Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence ...

  9. Interaction Between Flames and Electric Fields Studied

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Hegde, Uday

    2003-01-01

    The interaction between flames and electric fields has long been an interesting research subject that has theoretical importance as well as practical significance. Many of the reactions in a flame follow an ionic pathway: that is, positive and negative ions are formed during the intermediate steps of the reaction. When an external electric field is applied, the ions move according to the electric force (the Coulomb force) exerted on them. The motion of the ions modifies the chemistry because the reacting species are altered, it changes the velocity field of the flame, and it alters the electric field distribution. As a result, the flame will change its shape and location to meet all thermal, chemical, and electrical constraints. In normal gravity, the strong buoyant effect often makes the flame multidimensional and, thus, hinders the detailed study of the problem.

  10. Electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.; Robinson, R. S.; Etters, R. D.

    1982-01-01

    A number of energy momentum anomalies are described that result from the use of Abraham-Lorentz electromagnetic theory. These anomalies have in common the motion of charged bodies or current carrying conductors relative to the observer. The anomalies can be avoided by using the nonflow approach, based on internal energy of the electromagnetic field. The anomalies can also be avoided by using the flow approach, if all contributions to flow work are included. The general objective of this research is a fundamental physical understanding of electric and magnetic fields which, in turn, might promote the development of new concepts in electric space propulsion. The approach taken is to investigate quantum representations of these fields.

  11. Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography.

    PubMed

    Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy

    2015-05-01

    Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an 'acousto-electrical speckle' in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging. PMID:25906432

  12. Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy

    2015-05-01

    Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.

  13. What Are Electric and Magnetic Fields? (EMF)

    MedlinePLUS

    ... Print this page Share What are Electric and Magnetic Fields? (EMF) Electric and Magnetic Fields Electricity is an essential part of our ... we take for granted. What are electric and magnetic fields? Electric and magnetic fields (EMF) are invisible ...

  14. Electric field replaces gravity in laboratory

    NASA Astrophysics Data System (ADS)

    Gorgolewski, S.

    For several years experiments in physical laboratories and in the fitotron have shown that one can replace gravitational field with electrical fields for plants. First obvious experiments in strong electrical fields in the MV/m regi on show that any materials and living plants respond immediately to Coulomb forces. Such fields are found in nature during thunderstorms. One has to be very careful in handling such strong fields for safety reasons. The fair weather global electrical field is about 20,000 times weaker. The coulomb forces are proportional to the square of the field strength and are thus 400 milion times weaker for a field of the order of 100 V/m.Yet it was found that some plants respond to such "weak" fields. We must remember that the electrical field is a factor of 10 38 times stronger than gravitational interaction. In plants we have dissociated in water mineral salts and the ions are subject to such ernormous forces. It was shown and published that the positive charges in the air in fields of the order of 3kV/m enhance lettuce growth by a factor of four relative to fields about 30 times weaker (100V/m). Reversal of the field polarity reverses the direction of plant growth and retards the plant's growth. Such fields overpower the gravitropism in the laboratory. More so horizontal electrical field is othogonal to gravity, now the fields do not see each other. Lettuce now growth horizontally ignoring the gravitational field. We can thus select the plants whose electrotropism even in the laboratory overwhelms gravity. This is important for the long space flights that we must grow vegetarian food for the crew. The successful harvesting of wheat in orbit does not contradict our experimental findings because wheat is not electrotropic like all plants from the grass family. The results of fitotron experiments with kV/m electrical fields are richly illustrated with colour digital photographs. We also subjected the candle flame to very strong horizontal electrical fields. The flame splits into two horizontal flames, ignoring the gravitational field in the laboratory. This result is similar to the behaviour of ions in plants which are responsible for the transport of nutrients from the roots to leaves and opposite ions to roots from the leaves. It shows that we can control the transport phenomena in the process of growth in plants as well as of combustion in space with proper electrical fields.

  15. Overview - Electric fields. [in magnetosphere

    NASA Technical Reports Server (NTRS)

    Cauffman, D. P.

    1979-01-01

    The electric fields session is designed to review progress in observation, theory, and modeling of magnetospheric electric fields, and to expose important new results. The present report comments on the state and prospects of electric field research, with particular emphasis on relevance to quantitative modeling of the magnetospheric processes. Attention is given to underlying theories and models. Modeling philosophy is discussed relative to explanatory models and representative models. Modeling of magnetospheric electric fields, while in its infancy, is developing rapidly on many fronts employing a variety of approaches. The general topic of magnetospheric electric fields is becoming of prime importance in understanding space plasmas.

  16. Atom based RF electric field sensing

    NASA Astrophysics Data System (ADS)

    Fan, Haoquan; Kumar, Santosh; Sedlacek, Jonathon; Kübler, Harald; Karimkashi, Shaya; Shaffer, James P.

    2015-10-01

    Atom-based measurements of length, time, gravity, inertial forces and electromagnetic fields are receiving increasing attention. Atoms possess properties that suggest clear advantages as self calibrating platforms for measurements of these quantities. In this review, we describe work on a new method for measuring radio frequency (RF) electric fields based on quantum interference using either Cs or Rb atoms contained in a dielectric vapor cell. Using a bright resonance prepared within an electromagnetically induced transparency window it is possible to achieve high sensitivities, <1 ?V cm-1 Hz-1/2, and detect small RF electric fields \\lt 1 ?V cm-1 with a modest setup. Some of the limitations of the sensitivity are addressed in the review. The method can be used to image RF electric fields and can be adapted to measure the vector electric field amplitude. Extensions of Rydberg atom-based electrometry for frequencies up to the terahertz regime are described.

  17. Magnetospheric electric fields and currents

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.; Zanetti, L. J.

    1987-01-01

    The progress made in the years 1983-1986 in understanding the character and operation of magnetospheric electric fields and electric currents is discussed, with emphasis placed on the connection with the interior regions. Special attention is given to determinations of global electric-field configurations, measurements of the response of magnetospheric particle populations to the electric-field configurations, and observations of the magnetospheric currents at high altitude and during northward IMF. Global simulations of current distributions are discussed, and the sources of global electric fields and currents are examined. The topics discussed in the area of impulsive and small-scale phenomena include substorm current systems, impulsive electric fields and associated currents, and field-aligned electrodynamics. A key finding of these studies is that the electric fields and currents are interrelated and cannot be viewed as separate entities.

  18. Electric field induced changes in protein conformation.

    PubMed

    Bekard, Innocent; Dunstan, Dave E

    2014-01-21

    The effect of a low strength oscillating electric field on the conformation of Bovine Serum Albumin (BSA) and Lysozyme in solution has been measured. A purpose built cell has been used to measure the real time autofluorescence and Circular Dichroism of the protein solutions exposed to electric fields of differing strength and frequency. Exposure to the electric fields results in protein unfolding for both Lysozyme and BSA. The applied field strengths are extremely small compared to the protein inter-chain intra-molecular forces. We propose a model whereby the electrophoretic motion of the proteins leads to a frictional force that results in protein unfolding. For BSA and Lysozyme in the electric fields used in this study, the shear rates at the protein surface under electrophoretic motion are of order 10(3) and 10(4) s(-1) respectively. Prolonged electric field exposure results in significant frictional energy dissipation in the proteins. The energy dissipated in the proteins results in protein unfolding, which is a critical initial step for protein aggregation and potentially amyloid fibril formation. PMID:24652412

  19. Polarization effects in molecular mechanical force fields

    PubMed Central

    Cieplak, Piotr; Dupradeau, François-Yves; Duan, Yong; Wang, Junmei

    2014-01-01

    The focus here is on incorporating electronic polarization into classical molecular mechanical force fields used for macromolecular simulations. First, we briefly examine currently used molecular mechanical force fields and the current status of intermolecular forces as viewed by quantum mechanical approaches. Next, we demonstrate how some components of quantum mechanical energy are effectively incorporated into classical molecular mechanical force fields. Finally, we assess the modeling methods of one such energy component—polarization energy—and present an overview of polarizable force fields and their current applications. Incorporating polarization effects into current force fields paves the way to developing potentially more accurate, though more complex, parameterizations that can be used for more realistic molecular simulations. PMID:21828594

  20. Sensing electric fields using single diamond spins

    E-print Network

    Florian Dolde; Helmut Fedder; Marcus W. Doherty; Tobias Nöbauer; Florian Rempp; Gopalakrishnan Balasubramanian; Thomas Wolf; Friedemann Reinhard; Lloyd C. L. Hollenberg; Fedor Jelezko; Jörg Wrachtrup

    2011-03-17

    The ability to sensitively detect charges under ambient conditions would be a fascinating new tool benefitting a wide range of researchers across disciplines. However, most current techniques are limited to low-temperature methods like single-electron transistors (SET), single-electron electrostatic force microscopy and scanning tunnelling microscopy. Here we open up a new quantum metrology technique demonstrating precision electric field measurement using a single nitrogen-vacancy defect centre(NV) spin in diamond. An AC electric field sensitivity reaching ~ 140V/cm/\\surd Hz has been achieved. This corresponds to the electric field produced by a single elementary charge located at a distance of ~ 150 nm from our spin sensor with averaging for one second. By careful analysis of the electronic structure of the defect centre, we show how an applied magnetic field influences the electric field sensing properties. By this we demonstrate that diamond defect centre spins can be switched between electric and magnetic field sensing modes and identify suitable parameter ranges for both detector schemes. By combining magnetic and electric field sensitivity, nanoscale detection and ambient operation our study opens up new frontiers in imaging and sensing applications ranging from material science to bioimaging.

  1. Optical force on toroidal nanostructures: Toroidal dipole versus renormalized electric dipole

    NASA Astrophysics Data System (ADS)

    Zhang, Xu-Lin; Wang, S. B.; Lin, Zhifang; Sun, Hong-Bo; Chan, C. T.

    2015-10-01

    We study the optical forces acting on toroidal nanostructures. A great enhancement of optical force is unambiguously identified as originating from the toroidal dipole resonance based on the source representation, where the distribution of the induced charges and currents is characterized by the three families of electric, magnetic, and toroidal multipoles. On the other hand, the resonant optical force can also be completely attributed to an electric dipole resonance in the alternative field representation, where the electromagnetic fields in the source-free region are expressed by two sets of electric and magnetic multipole fields based on symmetry. The confusion is resolved by conceptually introducing the irreducible electric dipole, toroidal dipole, and renormalized electric dipole. We demonstrate that the optical force is a powerful tool to identify toroidal response even when its scattering intensity is dwarfed by the conventional electric and magnetic multipoles.

  2. Electric field control of the cell orientation

    NASA Astrophysics Data System (ADS)

    Westman, Christopher; Sabirianov, Renat

    2008-03-01

    Many physiological processes depend on the response of biological cells to external forces. The natural electric field at a wound controls the orientation of the cell and its division.[1] We model the cell as an elongated elliptical particle with given Young's modulus with surface charge distribution in the external electric field. Using this simple theoretical model that includes the forces due to electrostatics and the elasticity of cells, we calculated analytically the response of the cell orientation and its dynamics in the presence of time varying electric field. The calculations reflect many experimentally observed features. Our model predicts the response of the cellular orientation to a sinusoidally varying applied electric field as a function of frequency similar to recent stress-induced effects.[2] *Bing Song, Min Zhao, John V. Forrester, and Colin D. McCaig, ``Electrical cues regulate the orientation and frequency of cell division and the rate of wound healing in vivo'', PNAS 2002, vol. 99 , 13577-13582. *R. De, A. Zemel, and S.A. Safran, ``Dynamics of cell orientation'', Nature Physics 2007, vol.3, 655.

  3. 49 CFR 236.758 - Lock, electric, forced drop.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Lock, electric, forced drop. 236.758 Section 236.758 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... § 236.758 Lock, electric, forced drop. An electric lock in which the locking member is...

  4. Electric and Magnetic Forces between Parallel-Wire Conductors.

    ERIC Educational Resources Information Center

    Morton, N.

    1979-01-01

    Discusses electric and magnetic forces between parallel-wire conductors and derives, in a simple fashion, order of magnitude estimates of the ratio of the likely electrostatic and electromagnetic forces for a simple parallel-wire balance. (Author/HM)

  5. Experimental Studies of Electrical Fields on a Breaking Rock Sample

    E-print Network

    Zhu, Zhenya

    2001-01-01

    When a rock sample is pressed by a force, the pressure on the crystal lattice generates an electrical field around the quart grains due to the piezoelectric effect. If a rock is saturated by conductive fluid, the relative ...

  6. Assembly of LIGA using Electric Fields

    SciTech Connect

    FEDDEMA, JOHN T.; WARNE, LARRY K.; JOHNSON, WILLIAM A.; OGDEN, ALLISON J.; ARMOUR, DAVID L.

    2002-04-01

    The goal of this project was to develop a device that uses electric fields to grasp and possibly levitate LIGA parts. This non-contact form of grasping would solve many of the problems associated with grasping parts that are only a few microns in dimensions. Scaling laws show that for parts this size, electrostatic and electromagnetic forces are dominant over gravitational forces. This is why micro-parts often stick to mechanical tweezers. If these forces can be controlled under feedback control, the parts could be levitated, possibly even rotated in air. In this project, we designed, fabricated, and tested several grippers that use electrostatic and electromagnetic fields to grasp and release metal LIGA parts. The eventual use of this tool will be to assemble metal and non-metal LIGA parts into small electromechanical systems.

  7. The harmonic force field of propane

    NASA Astrophysics Data System (ADS)

    Gough, K. M.; Murphy, W. F.; Raghavachari, Krishnan

    1987-09-01

    The quadratic vibrational force field of propane has been obtained by scaling calculated ab initio force fields to fit well determined vibrational frequencies from the Raman and infrared spectra of gaseous propane-h8, propane-d8, 1,1,1,2,3,3,3-propane-d7, and the two rotational isomers of 1,1,2,2,3,3,3-propane-d7. Two different ab initio force fields were investigated, one using Hartree-Fock theory (HF/6-31G*) and the other including electron correlation effects by means of second-order Møller-Plesset perturbation theory (MP2/6-31G*). The scaled MP2/6-31G* force field gives a significantly better fit of the experimental frequencies, especially for those involving contributions from the CC stretching coordinate.

  8. Introduction to power-frequency electric and magnetic fields.

    PubMed Central

    Kaune, W T

    1993-01-01

    This paper introduces the reader to electric and magnetic fields, particularly those fields produced by electric power systems and other sources using frequencies in the power-frequency range. Electric fields are produced by electric charges; a magnetic field also is produced if these charges are in motion. Electric fields exert forces on other charges; if in motion, these charges will experience magnetic forces. Power-frequency electric and magnetic fields induce electric currents in conducting bodies such as living organisms. The current density vector is used to describe the distribution of current within a body. The surface of the human body is an excellent shield for power-frequency electric fields, but power-frequency magnetic fields penetrate without significant attenuation; the electric fields induced inside the body by either exposure are comparable in magnitude. Electric fields induced inside a human by most environmental electric and magnetic fields appear to be small in magnitude compared to levels naturally occurring in living tissues. Detection of such fields thus would seem to require the existence of unknown biological mechanisms. Complete characterization of a power-frequency field requires measurement of the magnitudes and electrical phases of the fundamental and harmonic amplitudes of its three vector components. Most available instrumentation measures only a small subset, or some weighted average, of these quantities. Hand-held survey meters have been used widely to measure power-frequency electric and magnetic fields. Automated data-acquisition systems have come into use more recently to make electric- and magnetic-field recordings, covering periods of hours to days, in residences and other environments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8206045

  9. 6.641 Electromagnetic Fields, Forces, and Motion, Spring 2003

    E-print Network

    Zahn, Markus, 1946-

    Electric and magnetic quasistatic forms of Maxwell's equations applied to dielectric, conduction, and magnetization boundary value problems. Electromagnetic forces, force densities, and stress tensors, including magnetization ...

  10. Electric fields and quantum wormholes

    NASA Astrophysics Data System (ADS)

    Engelhardt, Dalit; Freivogel, Ben; Iqbal, Nabil

    2015-09-01

    Electric fields can thread a classical Einstein-Rosen bridge. Maldacena and Susskind have recently suggested that in a theory of dynamical gravity the entanglement of ordinary perturbative quanta should be viewed as creating a quantum version of an Einstein-Rosen bridge between the particles, or a "quantum wormhole." We demonstrate within low-energy effective field theory that there is a precise sense in which electric fields can also thread such quantum wormholes. We define a nonperturbative "wormhole susceptibility" that measures the ease of passing an electric field through any sort of wormhole. The susceptibility of a quantum wormhole is suppressed by powers of the U (1 ) gauge coupling relative to that for a classical wormhole but can be made numerically equal with a sufficiently large amount of entangled matter.

  11. FEA Simulation on Dielectric Composite and Semi-Crystalline Composite, and Analytical Computations and Approximations for the Charge, Force and Chemical Potential for a Prolate Spheroid Aligned with an Electric Field

    NASA Astrophysics Data System (ADS)

    Zhou, Kai

    2011-12-01

    A finite element study has been carried out to determine the effective dielectric constant of composite materials containing linear or nonlinear fillers. In the linear systems, spherical particles with field-independent dielectric constant are distributed randomly in a linear matrix. The effective dielectric constant is studied as a function of volume fraction and particle size. In the nonlinear system, a Landau thermodynamic model is employed to describe the field-dependent dielectric properties for both ferroelectric and antiferroelectric material. For the 2D ferroelectric-dielectric composite, the effective dielectric constant and dielectric tunability are examined based on filler volume fraction, size and shape, and then compared to classical effective medium theories. For the 3D antiferroelectric-dielectric composite, both the "hard" sphere and "soft" sphere models are examined at a volume fraction of 40%, which is above percolation for spherical filler. The finite element method is then adapted to determine the relaxation time constant, effective conductivity and electric field distribution of semi-crystalline composite. The simulated results show that both the effective conductivity of the composite and field distribution in the composite strongly depend on the crystalline volume fraction and the shape of the crystalline region. To achieve lower average electric field in the amorphous region, crystallites with larger length/thickness ratio are preferred. The charge and force on a conducting particle standing on a ground plane in a uniform background field are important to a range of technical areas, such as particle motion in gas-insulated substations. The charge, force and lifting field for such a particle is normally evaluated using approximate formulas in an obscure paper published over 40 years ago. Software technology now facilitates the solution of many such problems exactly, which allows evaluation of (i) the published approximation and (ii) the range of parameters over which the approximation is accurate. In the present contribution, we provide an exact solution to the charge and field-induced force for semi-spheroid standing on a ground plane, derive the commonly used approximation from the exact solution, and find that the commonly used approximate solution for the force on a rodlike particle agrees poorly with finite element computations of the force. We provide both "exact" and approximated formulas which agree well with finite element computations of the force on a rod-like particle for asperities from 2 to 100. An analytical expression is derived for the chemical potential of a water-filled spheroid in a dielectric medium based on Zeller's hypothesis for the chemical potential, against which Zeller's approximations for chemical potential could be compared for the same system. In doing so, we found that Zeller's approximation for DC component of the chemical potential is very good, although his expression for the conductivity at which the peak DC component occurs is not accurate at low spheroid asperities. However Zeller's approximation does not provide a very good approximation for the AC component of the chemical potential. Following Zeller's approach but with corrections, we have developed a much more accurate approximation for the AC component of the chemical potential which was compared with both the exact analytical solution and FEA computations.

  12. ECE 390 Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields.

    E-print Network

    ECE 390 ­ Electric & Magnetic Fields Catalog Description: Static and quasi-static electric), A. Jander (secondary) Course Content: · Introduction, review of vector analysis · Static electric fields in free space: Coulomb's law, Gauss's law, and electric potential, electric dipole · Static

  13. Current Status of Protein Force Fields for Molecular Dynamics

    PubMed Central

    Lopes, Pedro E.M.; Guvench, Olgun

    2015-01-01

    Summary The current status of classical force fields for proteins is reviewed. These include additive force fields as well as the latest developments in the Drude and AMOEBA polarizable force fields. Parametrization strategies developed specifically for the Drude force field are described and compared with the additive CHARMM36 force field. Results from molecular simulations of proteins and small peptides are summarized to illustrate the performance of the Drude and AMOEBA force fields. PMID:25330958

  14. Electrospinning and electrically forced jets. I. Stability theory

    NASA Astrophysics Data System (ADS)

    Hohman, Moses M.; Shin, Michael; Rutledge, Gregory; Brenner, Michael P.

    2001-08-01

    Electrospinning is a process in which solid fibers are produced from a polymeric fluid stream (solution or melt) delivered through a millimeter-scale nozzle. The solid fibers are notable for their very small diameters (<1 ?m). Recent experiments demonstrate that an essential mechanism of electrospinning is a rapidly whipping fluid jet. This series of papers analyzes the mechanics of this whipping jet by studying the instability of an electrically forced fluid jet with increasing field strength. An asymptotic approximation of the equations of electrohydrodynamics is developed so that quantitative comparisons with experiments can be carried out. The approximation governs both long wavelength axisymmetric distortions of the jet, as well as long wavelength oscillations of the centerline of the jet. Three different instabilities are identified: the classical (axisymmetric) Rayleigh instability, and electric field induced axisymmetric and whipping instabilities. At increasing field strengths, the electrical instabilities are enhanced whereas the Rayleigh instability is suppressed. Which instability dominates depends strongly on the surface charge density and radius of the jet. The physical mechanisms for the instability are discussed in the various possible limits.

  15. Electric fields in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.

    1972-01-01

    Two techniques, tracking the motions of Ba(+) clouds and measuring the differences in floating potential between symmetric double probes, were successful in: (1) demonstrating the basic convective nature of magnetospheric electric fields, (2) mapping global patterns of convection at upper ionosphere levels, and (3) revealing the physics of electric currents in the ionosphere and the importance of magnetosphere-ionosphere feedback in altering the imposed convection.

  16. Electric fields on quasiperiodic potentials

    NASA Astrophysics Data System (ADS)

    Salazar, F.; Naumis, G.

    2010-03-01

    The effects of an electric field on the electronic spectrum and localization properties of quasiperiodic chains are studied. As quasiperiodic systems, we use the Harper and the Fibonacci potentials since we prove that both are closely interrelated. In the limit of a strong field, a ladder spectrum with localized states is observed. The ladder structure can be understood by using perturbation theory. Then each local isomorphism class of the quasiperiodic potential reproduces its structure in the ladder. In the case of a weak field, we observed that the singular spectrum of the quasiperiodic potential tends to be smoothed, and the gaps decrease linearly with the field. Such an effect can be understood using a variational approach, perturbation theory and a series of approximants. When the electric field and the quasiperiodic potential have the same order of magnitude, it is possible to observe a delocalization effect due to local resonances.

  17. Speed, Acceleration, and Velocity: Level II, Unit 9, Lesson 1; Force, Mass, and Distance: Lesson 2; Types of Motion and Rest: Lesson 3; Electricity and Magnetism: Lesson 4; Electrical, Magnetic, and Gravitational Fields: Lesson 5; The Conservation and Conversion of Matter and Energy: Lesson 6; Simple Machines and Work: Lesson 7; Gas Laws: Lesson 8; Principles of Heat Engines: Lesson 9; Sound and Sound Waves: Lesson 10; Light Waves and Particles: Lesson 11; Program. A High.....

    ERIC Educational Resources Information Center

    Manpower Administration (DOL), Washington, DC. Job Corps.

    This self-study program for high-school level contains lessons on: Speed, Acceleration, and Velocity; Force, Mass, and Distance; Types of Motion and Rest; Electricity and Magnetism; Electrical, Magnetic, and Gravitational Fields; The Conservation and Conversion of Matter and Energy; Simple Machines and Work; Gas Laws; Principles of Heat Engines;…

  18. 7/15 Force current 1/7 FORCE ON A CURRENT IN A MAGNETIC FIELD

    E-print Network

    Gustafsson, Torgny

    7/15 Force current 1/7 FORCE ON A CURRENT IN A MAGNETIC FIELD PURPOSE: To study the force exerted in a magnetic field B, it experiences a magnetic force, called the Lorentz force, F qvBsin , (1) which results of the electrons with the ions, the wire itself experiences a magnetic force due to the interaction of the current

  19. Nanoscale Electric Field Sensor-Development and Testing

    NASA Astrophysics Data System (ADS)

    Brame, Jon; Woods, Nathan

    2008-10-01

    The goal of this project is to test a carbon nanotube based electric field sensing device. The device consists of a miniature gold needle suspended on a mat of carbon nanotubes over a trench on a Si/Si02 substrate. Field tests were made by recording the electric field inside dust devils in a Nevada desert, and those electric fields were simulated in a lab environment. Further tests to determine the device sensitivity were performed by manually manipulating the gold needle with an Atomic Force Microscope (AFM) tip. We report on fabrication techniques, field and lab test results and AFM testing results.

  20. Apparatuses and methods for generating electric fields

    DOEpatents

    Scott, Jill R; McJunkin, Timothy R; Tremblay, Paul L

    2013-08-06

    Apparatuses and methods relating to generating an electric field are disclosed. An electric field generator may include a semiconductive material configured in a physical shape substantially different from a shape of an electric field to be generated thereby. The electric field is generated when a voltage drop exists across the semiconductive material. A method for generating an electric field may include applying a voltage to a shaped semiconductive material to generate a complex, substantially nonlinear electric field. The shape of the complex, substantially nonlinear electric field may be configured for directing charged particles to a desired location. Other apparatuses and methods are disclosed.

  1. Electric field driven optical recording

    NASA Astrophysics Data System (ADS)

    Karpov, V. G.

    2010-07-01

    A physical mechanism of transformations between the amorphous and crystalline phases induced by the electric field of a laser beam is proposed. It creates needle-shaped crystal particles aligned to the beam polarization. The polarization driven orientation of particles can significantly increase the information storage capacity achievable with phase change optical recording. The nucleation and postnucleation stages of the laser field induced crystallization are discussed establishing the conditions under which the polarization aligned particles can be created.

  2. Electric field-assisted biosorption.

    PubMed

    Riordan, C R; Bustard, M T; Hughes, P; Reid, C N; McHale, A P

    2004-03-01

    A bisorption process using electric fields to facilitate contact between a sorbate and non-living biomass is described. The latter is enclosed within a semi-permeable membrane together with an electrode. The counter electrode is placed in the sorbate solution and an established potential across the electrodes facilitates electrokinetic movement of the sorbate to the biosorbant material. PMID:15127798

  3. Electric field divertor plasma pump

    DOEpatents

    Schaffer, M.J.

    1994-10-04

    An electric field plasma pump includes a toroidal ring bias electrode positioned near the divertor strike point of a poloidal divertor of a tokamak, or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix of the poloidal divertor contacts the ring electrode, which then also acts as a divertor plate. A plenum or other duct near the electrode includes an entrance aperture open to receive electrically-driven plasma. The electrode is insulated laterally with insulators, one of which is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode and a vacuum vessel wall, with the polarity of the bias applied to the electrode being relative to the vessel wall selected such that the resultant electric field E interacts with the magnetic field B already existing in the tokamak to create an E [times] B/B[sup 2] drift velocity that drives plasma into the entrance aperture. The pumped plasma flow into the entrance aperture is insensitive to variations, intentional or otherwise, of the pump and divertor geometry. Pressure buildups in the plenum or duct connected to the entrance aperture in excess of 10 mtorr are achievable. 11 figs.

  4. Linear electric field mass spectrometry

    DOEpatents

    McComas, David J. (Los Alamos, NM); Nordholt, Jane E. (Los Alamos, NM)

    1992-01-01

    A mass spectrometer and methods for mass spectrometry. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field.

  5. Linear electric field mass spectrometry

    DOEpatents

    McComas, D.J.; Nordholt, J.E.

    1992-12-01

    A mass spectrometer and methods for mass spectrometry are described. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field. 8 figs.

  6. Heliospheric Electric and Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Popescu, Adrian Sabin

    2007-09-01

    From the Maxwell equations in the local Minkowski spacetime chart (derived from the DEUS topology) we obtain the relations to be particularized for a solar type star and a massive star, and later to be used for a 3D representation of the electric and magnetic field topology (in heliosphere or in a stellar atmosphere) and of its evolution with the cosmological time.

  7. Measuring electric fields from surface contaminants with neutral atoms

    SciTech Connect

    Obrecht, J. M.; Wild, R. J.; Cornell, E. A.

    2007-06-15

    In this paper we demonstrate a technique of utilizing magnetically trapped neutral {sup 87}Rb atoms to measure the magnitude and direction of stray electric fields emanating from surface contaminants. We apply an alternating external electric field that adds to (or subtracts from) the stray field in such a way as to resonantly drive the trapped atoms into a mechanical dipole oscillation. The growth rate of the oscillation's amplitude provides information about the magnitude and sign of the stray field gradient. Using this measurement technique, we are able to reconstruct the vector electric field produced by surface contaminants. In addition, we can accurately measure the electric fields generated from adsorbed atoms purposely placed onto the surface and account for their systematic effects, which can plague a precision surface-force measurement. We show that baking the substrate can reduce the electric fields emanating from adsorbate and that the mechanism for reduction is likely surface diffusion, not desorption.

  8. Electric Field Induced Phase Transitions

    NASA Astrophysics Data System (ADS)

    Nardone, Marco; Karpov, Victor

    2012-02-01

    A novel theory of phase transitions that are driven by strong, symmetry-breaking electric fields is presented. The underlying mechanism is based on the formation of needle-shaped, metallic embryos that acquire strong dipole moments in the applied field. It is shown that the electrostatic contribution to the free energy can be so significant that it dominates the nucleation process and elongated metallic particles can form even in cases where they would be otherwise unstable in the bulk. As such, the theory predicts that any insulator will eventually form metallic inclusions when immersed in a sufficient electric field. Materials can thus be synthesized by the controlled application of a dc or laser field. In this work, the general mechanism is described and closed form expressions are presented for the field-dependent nucleation barrier and the effective field range as functions of material parameters. Overall, the theory presents a new parameter space to explore phase transitions and opens the venue of Field Induced Materials Synthesis (FIMS). As a provocative example, the potential for FIMS of metallic hydrogen at standard pressure is discussed; the effective field range is estimated to be 10^7 < E10^9 V/cm (laser intensity 10^12< I 10^16 W/cm^2).

  9. Derivation of Coulomb's Law of Forces Between Static Electric Charges Based on Spherical Source and Sink Model of Particles

    E-print Network

    Xiao-Song Wang

    2006-11-03

    We speculate that the universe may be filled with a continuum which may be called aether. Based on a spherical source and sink model of electric charges, we derive Coulomb's law of interactions between static electric charges in vacuum by methods of hydrodynamics. A reduced form of the Lorentz's force law of static electric charges is derived based on a definition of electric field.

  10. Longitudinal forces in pinched electric currents

    E-print Network

    F. O. Minotti

    2014-02-13

    It is shown that the theory of Mbelek and Lachi\\`eze-Rey predicts longitudinal forces of gravitational origin in pinched current distributions, with magnitudes large enough to have noticeable effects.

  11. Magnetic Fields Analogous to electric field, a magnet

    E-print Network

    Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University

    Magnetic Fields Analogous to electric field, a magnet produces a magnetic field, B Set up a B field two ways: Moving electrically charged particles Current in a wire Intrinsic magnetic field Basic characteristic of elementary particles such as an electron #12;Magnetic Fields Magnetic field lines Direction

  12. Energy buildup in sheared force-free magnetic fields

    NASA Technical Reports Server (NTRS)

    Wolfson, Richard; Low, Boon C.

    1992-01-01

    Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.

  13. GROUNDWATER AND SOIL REMEDIATION USING ELECTRICAL FIELD

    EPA Science Inventory

    Enhancements of contaminants removal and degradation in low permeability soils by electrical fields are achieved by the processes of electrical heating, electrokinetics, and electrochemical reactions. Electrical heating increases soil temperature resulting in the increase of cont...

  14. Comparison of a QM/MM Force Field and Molecular Mechanics Force Fields in Simulations of Alanine and

    E-print Network

    Richardson, David

    Comparison of a QM/MM Force Field and Molecular Mechanics Force Fields in Simulations of Alanine Department of Theoretical Physics, University of Paderborn, Paderborn, Germany ABSTRACT We compare mechanics (MM) force fields and with a fast com- bined quantum mechanics/molecular mechanics (QM/MM) force

  15. Lorentz force sigmometry: a novel technique for measuring the electrical conductivity of solid and liquid metals

    NASA Astrophysics Data System (ADS)

    Alkhalil, Shatha; Kolesnikov, Yurii; Thess, André

    2015-11-01

    In this paper, a novel method to measure the electrical conductivity of solid and molten metals is described. We term the method ‘Lorentz force sigmometry’, where the term ‘sigmometry’ refers to the letter sigma ?, often used to denote the electrical conductivity. The Lorentz force sigmometry method is based on the phenomenon of eddy currents generation in a moving conductor exposed to a magnetic field. Based on Ampere’s law, the eddy currents in turn generate a secondary magnetic field; as a result, the Lorentz force acts to brake the conductor. Owing to Newton’s third law, a measurable force, which is equal to the Lorentz force and is directly proportional to the electrical conductivity of the conductive fluid or solid, acts on the magnet. We present the results of the measurements performed on solids along with the initial measurements on fluids with a eutectic alloy composition of Ga67In20.5Sn12.5; detailed measurements on molten metals are still in progress and will be published in the future. We conducted a series of experiments and measured the properties of known electrical conductive metals, including aluminum and copper, to compute the calibration factor of the device, and then used the same calibration factor to estimate the unknown electrical conductivity of a brass bar. The predicted electrical conductivity of the brass bar was compared with the conductivity measured with a commercial device called ‘SigmaTest’ the observed error was less than 0.5%.

  16. Electromechanical analysis of tapered piezoelectric bimorph at high electric field

    NASA Astrophysics Data System (ADS)

    Chattaraj, Nilanjan; Ganguli, Ranjan

    2015-04-01

    Piezoelectric bimorph laminar actuator of tapered width exhibits better performance for out-of-plane deflection compared to the rectangular surface area, while consuming equal surface area. This paper contains electromechanical analysis and modeling of a tapered width piezoelectric bimorph laminar actuator at high electric field in static state. The analysis is based on the second order constitutive equations of piezoelectric material, assuming small strain and large electric field to capture its behavior at high electric field. Analytical expressions are developed for block force, output strain energy, output energy density, input electrical energy, capacitance and energy efficiency at high electric field. The analytical expressions show that for fixed length, thickness, and surface area of the actuator, how the block force and output strain energy gets improved in a tapered surface actuator compared to a rectangular surface. Constant thickness, constant length and constant surface area of the actuator ensure constant mass, and constant electrical capacitance. We consider high electric field in both series and parallel electrical connection for the analysis. Part of the analytical results is validated with the experimental results, which are reported in earlier literature.

  17. Particle energization in a chaotic force-free magnetic field

    NASA Astrophysics Data System (ADS)

    Li, Xiaocan; Li, Gang; Dasgupta, Brahmananda

    2015-04-01

    A force-free field (FFF) is believed to be a reasonable description of the solar corona and in general a good approximation for low-beta plasma. The equations describing the magnetic field of FFF is similar to the ABC fluid equations which has been demonstrated to be chaotic. This implies that charged particles will experience chaotic magnetic field in the corona. Here, we study particle energization in a time-dependent FFF using a test particle approach. An inductive electric field is introduced by turbulent motions of plasma parcels. We find efficient particle acceleration with power-law like particle energy spectra. The power-law indices depend on the amplitude of plasma parcel velocity field and the spatial scales of the magnetic field fluctuation. The spectra are similar for different particle species. This model provide a possible mechanism for seed population generation for particle acceleration by, e.g., CME-driven shocks. Generalization of our results to certain non-force-free-field (NFFF) is straightforward as the sum of two or multiple FFFs naturally yield NFFF.

  18. Cell separation using electric fields

    NASA Technical Reports Server (NTRS)

    Mangano, Joseph (Inventor); Eppich, Henry (Inventor)

    2009-01-01

    The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

  19. Cell separation using electric fields

    NASA Technical Reports Server (NTRS)

    Mangano, Joseph A. (Inventor); Eppich, Henry M. (Inventor)

    2003-01-01

    The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

  20. Electric Field Controlled Self-Assembly of Hierarchically Ordered Membranes

    PubMed Central

    Velichko, Yuri S.; Mantei, Jason R.; Bitton, Ronit; Carvajal, Daniel; Shull, Kenneth R.; Stupp, Samuel I.

    2012-01-01

    Self-assembly in the presence of external forces is an adaptive, directed organization of molecular components under nonequilibrium conditions. While forces may be generated as a result of spontaneous interactions among components of a system, intervention with external forces can significantly alter the final outcome of self-assembly. Superimposing these intrinsic and extrinsic forces provides greater degrees of freedom to control the structure and function of self-assembling materials. In this work we investigate the role of electric fields during the dynamic self-assembly of a negatively charged polyelectrolyte and a positively charged peptide amphiphile in water leading to the formation of an ordered membrane. In the absence of electric fields, contact between the two solutions of oppositely charged molecules triggers the growth of closed membranes with vertically oriented fibrils that encapsulate the polyelectrolyte solution. This process of self-assembly is intrinsically driven by excess osmotic pressure of counterions, and the electric field is found to modify the kinetics of membrane formation, and also its morphology and properties. Depending on the strength and orientation of the field we observe a significant increase or decrease of up to nearly 100% in membrane thickness, as well as the controlled rotation of nanofiber growth direction by 90 degrees, resulting in a significant increase in mechanical stiffness. These results suggest the possibility of using electric fields to control structure in self-assembly processes involving diffusion of oppositely charged molecules. PMID:23166533

  1. Manipulation of red blood cells with electric field

    NASA Astrophysics Data System (ADS)

    Saboonchi, Hossain; Esmaeeli, Asghar

    2009-11-01

    Manipulation of bioparticles and macromolecules is the central task in many biological and biotechnological processes. The current methods for physical manipulation takes advantage of different forces such as acoustic, centrifugal, magnetic, electromagnetic, and electric forces, as well as using optical tweezers or filtration. Among all these methods, however, the electrical forces are particularly attractive because of their favorable scale up with the system size which makes them well-suited for miniaturization. Currently the electric field is used for transportation, poration, fusion, rotation, and separation of biological cells. The aim of the current research is to gain fundamental understanding of the effect of electric field on the human red blood cells (RBCs) using direct numerical simulation. A front tracking/finite difference technique is used to solve the fluid flow and electric field equations, where the fluid in the cell and the blood (plasma) is modeled as Newtonian and incompressible, and the interface separating the two is treated as an elastic membrane. The behavior of RBCs is investigated as a function of the controlling parameters of the problem such as the strength of the electric field.

  2. A conducting ball in an axial electric field

    E-print Network

    Alexander Savchenko

    2012-12-26

    We describe the distribution of a charge, the electric moments of arbitrary order and the force acting on a conducting ball on the axis of the axial electric field. We determine the full charge and the dipole moments of the first order for a conducting ball in an arbitrary inhomogeneous harmonic electric field. All statements are formulated in the form of theorems with proofs basing on properties of the matrix of moments of the Legendre polynomials. The analysis and proof of these properties are presented in Appendix.

  3. Conformal field theory of critical Casimir forces

    NASA Astrophysics Data System (ADS)

    Emig, Thorsten; Bimonte, Giuseppe; Kardar, Mehran

    2015-03-01

    Thermal fluctuations of a critical system induce long-ranged Casimir forces between objects that couple to the underlying field. For two dimensional conformal field theories (CFT) we derive exact results for the Casimir interaction for a deformed strip and for two compact objects of arbitrary shape in terms of the free energy of a standard region (circular ring or flat strip) whose dimension is determined by the mutual capacitance of two conductors with the objects' shape; and a purely geometric energy that is proportional to conformal charge of the CFT, but otherwise super-universal in that it depends only on the shapes and is independent of boundary conditions and other details. The effect of inhomogenous boundary conditions is also discussed.

  4. FORCE FIELD DEVELOPMENT FOR SIMULATIONS OF CONDENSED PHASES

    E-print Network

    1 FORCE FIELD DEVELOPMENT FOR SIMULATIONS OF CONDENSED PHASES A. Z. Panagiotopoulos1 IPST of this review is on development of force fields for simulations of technologically important properties properties over a broad range of temperatures and densities. Most existing force fields have been optimized

  5. Transferable force field for alcohols and polyalcohols.

    PubMed

    Ferrando, Nicolas; Lachet, Véronique; Teuler, Jean-Marie; Boutin, Anne

    2009-04-30

    A new force field has been developed for alcohol and polyalcohol molecules. Based on the anisotropic united-atom force field AUA4 developed for hydrocarbons, it only introduces one new anisotropic united atom corresponding to the hydroxyl group OH. In the case of polyalcohols and complex molecules, the calculation of the intramolecular electrostatic energy is revisited. These interactions are calculated between charges belonging to the different local dipoles of the molecule, one dipole being defined as a group of consecutive charges globally neutral. This new method allows avoiding the use of empirical scaling parameters commonly introduced to calculate 1-4 electrostatic interactions. The transferability of the proposed potential is demonstrated through the simulation of a wide variety of alcohol families: primary alcohols (methanol, ethanol, propan-1-ol, hexan-1-ol, octan-1-ol), secondary alcohols (propan-2-ol), tertiary alcohols (2-methylpropan-2-ol), phenol, and diols (1,2-ethanediol, 1,3-propanediol, 1,5-pentanediol). Monte Carlo simulations carried out in the Gibbs ensemble lead to a good agreement between calculated and experimental data for the thermodynamic properties along the liquid/vapor saturation curve, for the critical point coordinates and for the liquid structure at room temperature. Additional simulations were performed on the methanol + n-butane system showing the capability of the proposed potential to reproduce the azeotropic behavior of such mixtures with a good agreement. PMID:19344171

  6. Migration of amoeba cells in an electric field

    NASA Astrophysics Data System (ADS)

    Guido, Isabella; Bodenschatz, Eberhard

    2015-03-01

    Exogenous and endogenous electric fields play a role in cell physiology as a guiding mechanism for the orientation and migration of cells. Electrotaxis of living cells has been observed for several cell types, e.g. neurons, fibroblasts, leukocytes, neural crest cells, cancer cells. Dictyostelium discoideum (Dd), an intensively investigated chemotactic model organism, also exhibits a strong electrotactic behavior moving toward the cathode under the influence of electric fields. Here we report experiments on the effects of DC electric fields on the directional migration of Dd cells. We apply the electric field to cells seeded into microfluidic devices equipped with agar bridges to avoid any harmful effects of the electric field on the cells (ions formation, pH changes, etc.) and a constant flow to prevent the build-up of chemical gradient that elicits chemotaxis. Our results show that the cells linearly increase their speed over time when a constant electric field is applied for a prolonged duration (2 hours). This novel phenomenon cannot be attributed to mechanotaxis as the drag force of the electroosmotic flow is too small to produce shear forces that can reorient cells. It is independent of the cellular developmental stage and to our knowledge, it was not observed in chemotaxis. This work is supported by MaxSynBio project of the Max Planck Society.

  7. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Electric locks, force drop type; where required...Rules and Instructions: All Systems General § 236.10 Electric locks, force drop type; where required. Electric locks on new installations and...

  8. Pair-production in inhomogeneous electric fields

    SciTech Connect

    Xue Shesheng

    2008-01-03

    This is a preliminary study on the rate of electron-positron pair production in spatially inhomogeneous electric fields. We study the rate in the Sauter field and compare it to the rate in the homogeneous field.

  9. CHARMM General Force Field (CGenFF): A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields

    PubMed Central

    Vanommeslaeghe, K.; Hatcher, E.; Acharya, C.; Kundu, S.; Zhong, S.; Shim, J.; Darian, E.; Guvench, O.; Lopes, P.; Vorobyov, I.; MacKerell, A. D.

    2010-01-01

    The widely used CHARMM additive all-atom force field includes parameters for proteins, nucleic acids, lipids and carbohydrates. In the present paper an extension of the CHARMM force field to drug-like molecules is presented. The resulting CHARMM General Force Field (CGenFF) covers a wide range of chemical groups present in biomolecules and drug-like molecules, including a large number of heterocyclic scaffolds. The parametrization philosophy behind the force field focuses on quality at the expense of transferability, with the implementation concentrating on an extensible force field. Statistics related to the quality of the parametrization with a focus on experimental validation are presented. Additionally, the parametrization procedure, described fully in the present paper in the context of the model systems, pyrrolidine, and 3-phenoxymethylpyrrolidine will allow users to readily extend the force field to chemical groups that are not explicitly covered in the force field as well as add functional groups to and link together molecules already available in the force field. CGenFF thus makes it possible to perform “all-CHARMM” simulations on drug-target interactions thereby extending the utility of CHARMM force fields to medicinally relevant systems. PMID:19575467

  10. Electric Dipole Moment Experiment Systematic from Electric Field Discharge Current

    NASA Astrophysics Data System (ADS)

    Feinberg, B.; Gould, Harvey

    2014-09-01

    A magnetic field, in the direction of the electric field and synchronous with the electric field reversal, will mimic an EDM signal. One might expect a discharge across the electric field plates to produce magnetic fields with only small or vanishing components parallel to the electric field, minimizing its systematic effect. Our experimental model, using simulated discharge currents, found otherwise: the discharge current may be at an angle to the normal, and thus generate a normal magnetic field. Comparison of data from the experimental model with the results from calculations will be presented, along with estimates of the time-averaged normal magnetic field seen by atoms in an electron EDM experiment using a fountain of laser-cooled francium, as a function of discharge current.

  11. Enhanced Fair-Weather Electric Fields Soon After Sunrise

    NASA Technical Reports Server (NTRS)

    Marshall, T. C.; Rust, W. D.; Stolzenburg, M.; Roeder, W.; Krehbiel, P. R.

    1999-01-01

    The typical fair weather electric field at the ground is between -100 and -300 V/m. At the NASA Kennedy Space Center and US Air Force Cape Canaveral Air Station (KSC) the electric field at the ground sometimes reaches -400 to -1200 V/m within an hour or two after sunrise on days that otherwise seem to be fair weather. We refer to the enhanced negative electric fields as the "sunrise enhancement." To investigate the sunrise enhancement at KSC we measured the electric field (E) in the first few hundred meters above the ground before and during several sunrise enhancements. From these E soundings we can infer the presence of charge layers and determine their thickness and charge density.

  12. Charged Hadron Properties in Background Electric Fields

    SciTech Connect

    William Detmold, Brian C. Tiburzi, Andre Walker-Loud

    2010-02-01

    We report on a lattice calculation demonstrating a novel new method to extract the electric polarizability of charged pseudo-scalar mesons by analyzing two point correlation functions computed in classical background electric fields.

  13. Efficient forced vibration reanalysis method for rotating electric machines

    NASA Astrophysics Data System (ADS)

    Saito, Akira; Suzuki, Hiromitsu; Kuroishi, Masakatsu; Nakai, Hideo

    2015-01-01

    Rotating electric machines are subject to forced vibration by magnetic force excitation with wide-band frequency spectrum that are dependent on the operating conditions. Therefore, when designing the electric machines, it is inevitable to compute the vibration response of the machines at various operating conditions efficiently and accurately. This paper presents an efficient frequency-domain vibration analysis method for the electric machines. The method enables the efficient re-analysis of the vibration response of electric machines at various operating conditions without the necessity to re-compute the harmonic response by finite element analyses. Theoretical background of the proposed method is provided, which is based on the modal reduction of the magnetic force excitation by a set of amplitude-modulated standing-waves. The method is applied to the forced response vibration of the interior permanent magnet motor at a fixed operating condition. The results computed by the proposed method agree very well with those computed by the conventional harmonic response analysis by the FEA. The proposed method is then applied to the spin-up test condition to demonstrate its applicability to various operating conditions. It is observed that the proposed method can successfully be applied to the spin-up test conditions, and the measured dominant frequency peaks in the frequency response can be well captured by the proposed approach.

  14. Electric-field guiding of magnetic skyrmions

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Pramey; Yu, Guoqiang; Amiri, Pedram Khalili; Wang, Kang L.

    2015-10-01

    We theoretically study equilibrium and dynamic properties of nanosized magnetic skyrmions in thin magnetic films with broken inversion symmetry, where an electric field couples to magnetization via spin-orbit coupling. Based on a symmetry-based phenomenology and micromagnetic simulations we show that this electric-field coupling, via renormalizing the micromagnetic energy, modifies the equilibrium properties of the skyrmion. This change, in turn, results in a significant alteration of the current-induced skyrmion motion. Particularly, the speed and direction of the skyrmion can be manipulated by designing a desired energy landscape electrically, which we describe within Thiele's analytical model and demonstrate in micromagnetic simulations including electric-field-controlled magnetic anisotropy. We additionally use this electric-field control to construct gates for controlling skyrmion motion exhibiting a transistorlike and multiplexerlike function. The proposed electric-field effect can thus provide a low-energy electrical knob to extend the reach of information processing with skyrmions.

  15. Polyelectrolytes polarization in non-uniform electric fields

    E-print Network

    Farnoush Farahpour; Fathollah Varnik; Mohammad Reza Ejtehadi

    2014-11-16

    Stretching dynamics of polymers in microfluidics is of particular interest for polymer scientists. As a charged polymer, a polyelectrolyte can be deformed from its coiled equilibrium configuration to an extended chain by applying uniform or non-uniform electric fields. By means of hybrid lattice Boltzmann-molecular dynamics simulations, we investigate how the condensed counterions around the polyelectrolyte contribute to the polymer stretching in inhomogeneous fields. As an application, we discuss the translocation phenomena and entropic traps, when the driving force is an applied external electric field.

  16. The Energetics of Motivated Cognition: A Force-Field Analysis

    ERIC Educational Resources Information Center

    Kruglanski, Arie W.; Belanger, Jocelyn J.; Chen, Xiaoyan; Kopetz, Catalina; Pierro, Antonio; Mannetti, Lucia

    2012-01-01

    A force-field theory of motivated cognition is presented and applied to a broad variety of phenomena in social judgment and self-regulation. Purposeful cognitive activity is assumed to be propelled by a "driving force" and opposed by a "restraining force". "Potential" driving force represents the maximal amount of energy an individual is prepared…

  17. Force-Field Analysis: Incorporating Critical Thinking in Goal Setting.

    ERIC Educational Resources Information Center

    Hustedde, Ron; Score, Michael

    1995-01-01

    Force field analysis encourages members to examine the probability of reaching agreed-upon goals. It can help groups avoid working toward goals that are unlikely to be reached. In every situation are three forces: forces that encourage maintenance of the status quo or change; driving or helping forces that push toward change; and restraining…

  18. Entanglement generation by electric field background

    SciTech Connect

    Ebadi, Zahra Mirza, Behrouz

    2014-12-15

    The quantum vacuum is unstable under the influence of an external electric field and decays into pairs of charged particles, a process which is known as the Schwinger pair production. We propose and demonstrate that this electric field can generate entanglement. Using the Schwinger pair production for constant and pulsed electric fields, we study entanglement for scalar particles with zero spins and Dirac fermions. One can observe the variation of the entanglement produced for bosonic and fermionic modes with respect to different parameters.

  19. Plasma heating by electric field compression.

    PubMed

    Avinash, K; Kaw, P K

    2014-05-01

    Plasma heating by compression of electric fields is proposed. It is shown that periodic cycles of external compression followed by the free expansion of electric fields in the plasma cause irreversible, collisionless plasma heating and corresponding entropy generation. As a demonstration of general ideas and scalings, the heating is shown in the case of a dusty plasma, where electric fields are created due to the presence of charged dust. The method is expected to work in the cases of compression of low frequency or dc electric fields created by other methods. Applications to high power laser heating of plasmas using this scheme are discussed. PMID:24856702

  20. The Introduction of Fields in Relation to Force

    ERIC Educational Resources Information Center

    Brunt, Marjorie; Brunt, Geoff

    2012-01-01

    The introduction of force at age 14-16 years is considered, starting with elementary student experiments using magnetic force fields. The meaningless use of terms such as "action" and "reaction", or "agent" and "receiver" is discussed. (Contains 6 figures.)

  1. Electric fields in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.

    1975-01-01

    F-region drift velocities, measured by incoherent-scatter radar were analyzed in terms of diurnal, seasonal, magnetic activity, and solar cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days and the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component.

  2. Electric field soundings through thunderstorms

    NASA Technical Reports Server (NTRS)

    Marshall, Thomas C.; Rust, W. D.

    1991-01-01

    Twelve balloon soundings of the electric field in thunderstorms are reported. The maximum magnitude of E in the storms averaged 96 +/-28 kV/m, with the largest being 146 kV/m. The maximum was usually observed between vertically adjacent regions of opposite charge. Using a 1D approximation to Gauss' law, four to ten charge regions in the storms are inferred. The magnitude of the density in the charge regions varied between 0.2 and 13 nC/cu m. The vertical extent of the charge regions ranged from 130 to 2100 m. None of the present 12 storms had charge distributions that fit the long-accepted model of Simpson et al. (1937, 1941) of a lower positive charge, a main negative charge, and an upper positive charge. In addition to regions similar to the Simpson model, the present storms had screening layers at the upper and lower cloud boundaries and extra charge regions, usually in the lower part of the cloud.

  3. Demonstration of Three-Dimensional DNA Trapping Using Electric Force and Hydrodrag Force

    NASA Astrophysics Data System (ADS)

    Ukita, Yoshiaki; Mouez, Lassoued; Tomizawa, Yuichi; Takamura, Yuzuru

    2011-06-01

    This paper describes the first demonstration of DNA trapping in a stacked three-dimensional (3D) microchannel. To carry out the 3D trapping of DNA by using electric force and hydrodrag force, a 3D microchip with a stacked structure is fabricated by the conventional rapid prototyping process and SU-8 peel-off process. Experimental results show that DNA trapping is observed on the application of electric potential with continuous pumping of DNA, but it is not observed in the absence of an electric potential. Further, the results suggest that the trapping throughput of DNA clearly depends on the capillary diameter but not on the flow rate. Thus, we conclude that, for a constant trapping area, reduction in the size of capillary structures with a high density results in an increase in the efficiency of DNA trapping.

  4. Flute stabilization due to ponderomotive force created by an rf field with a variable gradient

    SciTech Connect

    Yasaka, Y.; Itatani, R.

    1986-06-30

    An rf-stabilization experiment was performed in the axisymmetric single-mirror device HIEI by controlling the radial-gradient scale length of the rf field with the aid of an azimuthally phased antenna array. The flute stability depends sensitively on the scale length of the perpendicular rf electric field, which shows that rf stabilization is caused by the ponderomotive force for ions.

  5. Reactive Force Fields via Explicit Valency

    NASA Astrophysics Data System (ADS)

    Kale, Seyit

    Computational simulations are invaluable in elucidating the dynamics of biological macromolecules. Unfortunately, reactions present a fundamental challenge. Calculations based on quantum mechanics can predict bond formation and rupture; however they suffer from severe length- and time-limitations. At the other extreme, classical approaches provide orders of magnitude faster simulations; however they regard chemical bonds as immutable entities. A few exceptions exist, but these are not always trivial to adopt for routine use. We bridge this gap by providing a novel, pseudo-classical approach, based on explicit valency. We unpack molecules into valence electron pairs and atomic cores. Particles bear ionic charges and interact via pairwise-only potentials. The potentials are informed of quantum effects in the short-range and obey dissociation limits in the long-range. They are trained against a small set of isolated species, including geometries and thermodynamics of small hydrides and of dimers formed by them. The resulting force field captures the essentials of reactivity, polarizability and flexibility in a simple, seamless setting. We call this model LEWIS, after the chemical theory that inspired the use of valence pairs. Following the introduction in Chapter 1, we initially focus on the properties of water. Chapter 2 considers gas phase clusters. To transition to the liquid phase, Chapter 3 describes a novel pairwise long-range compensation that performs comparably to infinite lattice summations. The approach is suited to ionic solutions in general. In Chapters 4 and 5, LEWIS is shown to correctly predict the dipolar and quadrupolar response in bulk liquid, and can accommodate proton transfers in both acid and base. Efficiency permits the study of proton defects at dilutions not accessible to experiment or quantum mechanics. Chapter 6 discusses explicit valency approaches in other hydrides, forming the basis of a reactive organic force field. Examples of simple proton transfer and more complex reactions are discussed. Chapter 7 provides a framework for variable electron spread. This addition resolves some of the inherent limitations of the former model which implicitly assumed that electron spread was not affected by the environment. A brief summary is provided in Chapter 8.

  6. Nonlinear force-free reconstruction of the global solar magnetic field: methodology

    E-print Network

    Contopoulos, Ioannis; Georgoulis, Manolis

    2010-01-01

    We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary surface on which only the distribution of the normal magnetic field component is given. The method relies on the theory of force-free electrodynamics and applies directly to the reconstruction of the solar coronal magnetic field for a given distribution of the photospheric radial field component. The method works as follows: we start with any initial magnetostatic global field configuration (e.g. zero, dipole), and along the boundary surface we create an evolving distribution of tangential (horizontal) electric fields that, via Faraday's equation, give rise to a respective normal field distribution approaching asymptotically the target distribution. At the same time, these electric fields are used as boundary condition to numerically evolve the resulting electromagnetic field above the boundary surface, modelled as a thin ideal plasma with non-reflecting, perfectly absorbing outer b...

  7. Substorm electric fields at nightside low latitude

    NASA Astrophysics Data System (ADS)

    Hashimoto, K. K.; Kikuchi, T.; Tomizawa, I.; Nagatsuma, T.

    2014-12-01

    The convection electric field penetrates from the polar ionosphere to low latitude and drives the DP2 currents in the global ionosphere with an intensified equatorial electrojet (EEJ). The electric field often reverses its direction, that is, the overshielding occurs and causes the equatorial counterelectrojet (CEJ) during storm and substorms. In this paper we report that the overshielding electric field is detected by the HF Doppler sounders at low latitude on the nightside. We analyzed the Doppler frequency of the HF radio signals propagated over 120 km in Japan at frequencies of 5 and 8 MHz and compared with the equatorial EEJ/CEJ during the substorm expansion phase. We found that the overshielding electric field reaches around 2 mV/m during major substorms (AL <-1800 nT). Taking the geometrical attenuation into account, we estimate the equatorial electric field to be about 1.5 mV/m. We also found that the correlation coefficient was 0.94 between the overshielding electric field and eastward equatorial electrojet at YAP on the night side. The electric field drives the eastward electrojets in the equatorial ionosphere on the night side. It is to be noted that the overshielding electric field is observed on the nightside at low latitude during the major substorms, while the convection electric field is dominant during smaller size substorms, as the CEJ flows on the dayside. These results suggest that the overshielding electric field associated with the Region-2 field-aligned currents becomes dominant during substorms at low latitude on the nightside as well as on the dayside.

  8. Dislocation core fields and forces in FCC metals

    SciTech Connect

    Henager, Charles H.; Hoagland, Richard G.

    2004-04-01

    Atomistic models were used to obtain dislocation core fields for edge, screw, and mixed dislocations in Al and Cu using EAM. Core fields are analyzed using a line force dipole representation, with dilatant and dipole terms. The core field contribution to the force between dislocations is shown to be significant for interactions within 50b.

  9. A novel high-sensitivity electrostatic biased electric field sensor

    NASA Astrophysics Data System (ADS)

    Huang, Jing'ao; Wu, Xiaoming; Wang, Xiaohong; Yan, Xiaojun; Lin, Liwei

    2015-09-01

    In this paper, an electric field sensor (EFS) with high sensitivity is proposed for low-frequency weak-strength ac electric field (E-field) measurements. The EFS is based on a piezoelectric cantilever biased by a strong electrostatic field. The electrostatic bias can enhance the electric field force of a weak ac E-field, thus the cantilever can oscillate in a weak ac E-field and the device sensitivity improves. Theoretical analyses have been established and suggest that a stronger strength of electrostatic field bias would produce a higher sensitivity improvement. In the experiment, a demonstrated sensor consisting of a polyvinylidene fluoride (PVDF) piezoelectric cantilever and a polytetrafluoroethylene (PTFE) electret was built and tested. Instead of extra voltage sources, the PTFE electret was charged to provide the electrostatic field, allowing the EFS a low energy consumption and a simple electric circuit design. The experiment results show good agreement with the simulation. The sensitivity of the cantilever E-field sensor reached 0.84 mV (kV/m)-1 when the surface potential of the electret was??-770?V.

  10. Horizontal electric fields from lightning return strokes

    NASA Technical Reports Server (NTRS)

    Thomson, E. M.; Medelius, P. J.; Rubinstein, M.; Uman, M. A.; Johnson, J.

    1988-01-01

    An experiment to measure simultaneously the wideband horizontal and vertical electric fields from lightning return strokes is described. Typical wave shapes of the measured horizontal and vertical fields are presented, and the horizontal fields are characterized. The measured horizontal fields are compared with calculated horizontal fields obtained by applying the wavetilt formula to the vertical fields. The limitations and sources of error in the measurement technique are discussed.

  11. Nanomechanical electric and electromagnetic field sensor

    DOEpatents

    Datskos, Panagiotis George; Lavrik, Nickolay

    2015-03-24

    The present invention provides a system for detecting and analyzing at least one of an electric field and an electromagnetic field. The system includes a micro/nanomechanical oscillator which oscillates in the presence of at least one of the electric field and the electromagnetic field. The micro/nanomechanical oscillator includes a dense array of cantilevers mounted to a substrate. A charge localized on a tip of each cantilever interacts with and oscillates in the presence of the electric and/or electromagnetic field. The system further includes a subsystem for recording the movement of the cantilever to extract information from the electric and/or electromagnetic field. The system further includes a means of adjusting a stiffness of the cantilever to heterodyne tune an operating frequency of the system over a frequency range.

  12. Axial Current Generation from Electric Field: Chiral Electric Separation Effect

    E-print Network

    Xu-Guang Huang; Jinfeng Liao

    2013-06-07

    We study a relativistic plasma containing charged chiral fermions in an external electric field. We show that with the presence of both vector and axial charge densities, the electric field can induce an axial current along its direction and thus cause chirality separation. We call it the Chiral Electric Separation Effect (CESE). On very general basis, we argue that the strength of CESE is proportional to $\\mu_V\\mu_A$ with $\\mu_V$ and $\\mu_A$ the chemical potentials for vector charge and axial charge. We then explicitly calculate this CESE conductivity coefficient in thermal QED at leading-log order. The CESE can manifest a new gapless wave mode propagating along the electric field. Potential observable of CESE in heavy-ion collisions is also discussed.

  13. Polarizable vacuum analysis of electric and magnetic fields

    E-print Network

    Xing-Hao Ye

    2009-08-22

    The electric and magnetic fields are investigated on the basis of quantum vacuum. The analysis of the electromagnetic energy and force indicates that an electric field is a polarized distribution of the vacuum virtual dipoles, and that a magnetic field in vacuum is a rearrangement of the vacuum polarization. It means that an electromagnetic wave is a successional changing of the vacuum polarization in space. Also, it is found that the average half length of the virtual dipoles around an elementary charge is a=2.8 *10^(-15)m. The result leads to the step distribution of the field energy around an electron, the relation between the fine structure constant and the vacuum polarization distribution, and an extremely high energy density of the electromagnetic field.

  14. Electrical Claims and Space Weather Measuring the visible effects of an invisible force

    E-print Network

    Schrijver, Karel

    Electrical Claims and Space Weather Measuring the visible effects of an invisible force Image the visible effects of an invisible force June 2015 #12;Electrical Claims and Space Weather Measuring .......................................................................... 16 #12;Electrical Claims and Space Weather Measuring the visible effects of an invisible force 1 1

  15. Nucleation of metals by strong electric fields

    NASA Astrophysics Data System (ADS)

    Nardone, M.; Karpov, V. G.

    2012-04-01

    Recent work on phase transitions in chalcogenides (underlying phase change memory) led to a theory of symmetry-breaking field effects, predicting needle-shaped metallic nuclei and exponentially accelerated nucleation rates. Here, we predict that, in general, any insulator will eventually form metallic inclusions if immersed in a sufficient electric field. These phase transitions are driven, not simply enhanced, by an electric field. Hence, metals can be formed under conditions where they would be otherwise unexpected. This opens the venue of field induced materials synthesis. As a technologically important example, we consider the field driven synthesis of metallic hydrogen at normal pressure.

  16. Dipole relaxation in an electric field

    NASA Astrophysics Data System (ADS)

    Neumann, Richard M.

    1980-07-01

    From Boltzmann's equation, S=k ln?, an expression for the orientational entropy, S of a rigid rod (electric dipole) is derived. The free energy of the dipole in an electric field is then calculated as a function of both the dipole's average orientation and the field strength. Application of the equilibrium criterion to the free energy yields the field dependence of the entropy of the dipole. Irreversible thermodynamics is used to derive the general form of the equation of motion of the dipole's average orientation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium.

  17. Lorentz Body Force Induced by Traveling Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.

    2003-01-01

    The Lorentz force induced by a traveling magnetic field (TMF) in a cylindrical container has been calculated. The force can be used to control flow in dectrically conducting melts and the direction of the magnetic field and resulting flow can be reversed. A TMF can be used to partially cancel flow driven by buoyancy. The penetration of the field into the cylinder decreases as the frequency increases, and there exists an optimal value of frequency for which the resulting force is a maximum. Expressions for the Lorentz force in the limiting cases of low frequency and infinite cylinder are also given and compared to the numerical calculations.

  18. Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

    PubMed Central

    Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

    2014-01-01

    Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

  19. Biomolecular simulations of membranes: Physical properties from different force fields

    E-print Network

    Siu, Weng In "Shirley"

    Received 28 December 2007; accepted 22 February 2008; published online 27 March 2008 Phospholipid force fields are of ample importance for the simulation of artificial bilayers, membranes, and also for phospholipids, the all-atom CHARMM27 and the united atom Berger force field, with a newly developed all

  20. Control of magnetism by electric fields

    NASA Astrophysics Data System (ADS)

    Matsukura, Fumihiro; Tokura, Yoshinori; Ohno, Hideo

    2015-03-01

    The electrical manipulation of magnetism and magnetic properties has been achieved across a number of different material systems. For example, applying an electric field to a ferromagnetic material through an insulator alters its charge-carrier population. In the case of thin films of ferromagnetic semiconductors, this change in carrier density in turn affects the magnetic exchange interaction and magnetic anisotropy; in ferromagnetic metals, it instead changes the Fermi level position at the interface that governs the magnetic anisotropy of the metal. In multiferroics, an applied electric field couples with the magnetization through electrical polarization. This Review summarizes the experimental progress made in the electrical manipulation of magnetization in such materials, discusses our current understanding of the mechanisms, and finally presents the future prospects of the field.

  1. Manipulating Colloids Charges & Electric Fields

    E-print Network

    Leunissen, Mirjam

    50 3.3.1 Normal phase behavior 50 3.3.2 Reentrant melting and freezing 55 3.3.3 Anomalous behavior 66 3.4 Conclusions & outlook 70 References 71 #12;4 Electrostatics at the oil ­ water interface 77 4 in an electric bottle

  2. Quantum electric field fluctuations and potential scattering

    NASA Astrophysics Data System (ADS)

    Huang, Haiyun; Ford, L. H.

    2015-06-01

    Some physical effects of time averaged quantum electric field fluctuations are discussed. The one loop radiative corrections to potential scattering are approximately derived from simple arguments which invoke vacuum electric field fluctuations. For both above barrier scattering and quantum tunneling, this effect increases the transmission probability. It is argued that the shape of the potential determines a sampling function for the time averaging of the quantum electric field operator. We also show that there is a nonperturbative enhancement of the transmission probability which can be inferred from the probability distribution for time averaged electric field fluctuations. The same method should be useful in understanding the effects of large quantum stress tensor fluctuations, which cannot be treated in perturbation theory.

  3. Collapse of DNA under alternating electric fields

    NASA Astrophysics Data System (ADS)

    Zhou, Chunda; Riehn, Robert

    2015-07-01

    Recent studies have shown that double-stranded DNA can collapse in the presence of a strong electric field. Here we provide an in-depth study of the collapse of DNA under weak confinement in microchannels as a function of buffer strength, driving frequency, applied electric-field strength, and molecule size. We find that the critical electric field at which DNA molecules collapse (tens of kV/m) is strongly dependent on driving frequency (100-800 Hz) and molecular size (20-160 kbp), and weakly dependent on the ionic strength (8-60 mM). We argue that an apparent stretching at very high electric fields is an artifact of the finite frame time of video microscopy.

  4. Enhanced momentum delivery by electric force to ions due to collisions of ions with neutrals

    SciTech Connect

    Makrinich, G.; Fruchtman, A.

    2013-04-15

    Ions in partially ionized argon, nitrogen, and helium gas discharges are accelerated across a magnetic field by an applied electric field, colliding with neutrals during the acceleration. The momentum delivered by the electric force to the ions, which is equal to the momentum carried by the mixed ion-neutral flow, is found by measuring the force exerted on a balance force meter by that flow exiting the discharge. The power deposited in the ions is calculated by measuring the ion flux and the accelerating voltage. The ratio of force over power is found for the three gases, while the gas flow rates and magnetic field intensities are varied over a wide range of values, resulting in a wide range of gas pressures and applied voltages. The measurements for the three different gases confirm our previous suggestion [G. Makrinich and A. Fruchtman, Appl. Phys. Lett. 95, 181504 (2009)] that the momentum delivered to the ions for a given power is enhanced by ion-neutral collisions during the acceleration and that this enhancement is proportional to the square root of the number of ion-neutral collisions.

  5. Electric field control of the magnetocaloric effect.

    PubMed

    Gong, Yuan-Yuan; Wang, Dun-Hui; Cao, Qing-Qi; Liu, En-Ke; Liu, Jian; Du, You-Wei

    2015-02-01

    Through strain-mediated magnetoelectric coupling, it is demonstrated that the magnetocaloric effect of a ferromagnetic shape-memory alloy can be controlled by an electric field. Large hysteresis and the limited operating temperature region are effectively overcome by applying an electric field on a laminate comprising a piezoelectric and the alloy. Accordingly, a model for an active magnetic refrigerator with high efficiency is proposed in principle. PMID:25522356

  6. Electric field gradient focusing in microchannels with embedded bipolar electrode.

    PubMed

    Hlushkou, Dzmitry; Perdue, Robbyn K; Dhopeshwarkar, Rahul; Crooks, Richard M; Tallarek, Ulrich

    2009-07-01

    The complex interplay of electrophoretic, electroosmotic, bulk convective, and diffusive mass/charge transport in a hybrid poly(dimethylsiloxane) (PDMS)/glass microchannel with embedded floating electrode is analyzed. The thin floating electrode attached locally to the wall of the straight microchannel results in a redistribution of local field strength after the application of an external electric field. Together with bulk convection based on cathodic electroosmotic flow, an extended field gradient is formed in the anodic microchannel segment. It imparts a spatially dependent electrophoretic force on charged analytes and, in combination with the bulk convection, results in an electric field gradient focusing at analyte-specific positions. Analyte concentration in the enriched zone approaches a maximum value which is independent of its concentration in the supplying reservoirs. A simple approach is shown to unify the temporal behavior of the concentration factors under general conditions. PMID:19532966

  7. Tuning Bimolecular Chemical Reactions by Electric Fields

    NASA Astrophysics Data System (ADS)

    Tscherbul, Timur V.; Krems, Roman V.

    2015-07-01

    We develop a theoretical method for solving the quantum mechanical reactive scattering problem in the presence of external fields based on a hyperspherical coordinate description of the reaction complex combined with the total angular momentum representation for collisions in external fields. The method allows us to obtain converged results for the chemical reaction LiF +H ?Li +HF in an electric field. Our calculations demonstrate that, by inducing couplings between states of different total angular momenta, electric fields with magnitudes <150 kV /cm give rise to resonant scattering and a significant modification of the total reaction probabilities, product state distributions, and the branching ratios for reactive versus inelastic scattering.

  8. Magnetic field and electric current structure in the chromosphere

    NASA Technical Reports Server (NTRS)

    Dravins, D.

    1974-01-01

    The three-dimensional vector magnetic field structure in the chromosphere above an active region is deduced by using high-resolution H-alpha filtergrams together with a simultaneous digital magnetogram. An analog model of the field is made with 400 metal wires representing field lines that outline the H-alpha structure. The height extent of the field is determined from vertical field-gradient observations around sunspots, from observed fibril heights, and from an assumption that the sources of the field are largely local. The computed electric currents (typically 10 mA/sq m) are found to flow in patterns not similar to observed features and not parallel to magnetic fields. Force structures correspond to observed solar features; the dynamics to be expected include: downward motion in bipolar areas in the lower chromosphere, an outflow of the outer chromosphere into the corona with radially outward flow above bipolar plage regions, and motion of arch filament systems.

  9. Calculations of the Electric Fields in Liquid Solutions

    PubMed Central

    Fried, Stephen D.; Wang, Lee-Ping; Boxer, Steven G.; Ren, Pengyu; Pande, Vijay S.

    2014-01-01

    The electric field created by a condensed phase environment is a powerful and convenient descriptor for intermolecular interactions. Not only does it provide a unifying language to compare many different types of interactions, but it also possesses clear connections to experimental observables, such as vibrational Stark effects. We calculate here the electric fields experienced by a vibrational chromophore (the carbonyl group of acetophenone) in an array of solvents of diverse polarities using molecular dynamics simulations with the AMOEBA polarizable force field. The mean and variance of the calculated electric fields correlate well with solvent-induced frequency shifts and band broadening, suggesting Stark effects as the underlying mechanism of these key solution phase spectral effects. Compared to fixed-charge and continuum models, AMOEBA was the only model examined that could describe non-polar, polar, and hydrogen bonding environments in a consistent fashion. Nevertheless, we found that fixed-charge force fields and continuum models were able to replicate some results of the polarizable simulations accurately, allowing us to clearly identify which properties and situations require explicit polarization and/or atomistic representations to be modeled properly, and for which properties and situations simpler models are sufficient. We also discuss the ramifications of these results for modeling electrostatics in complex environments, such as proteins. PMID:24304155

  10. MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2

    E-print Network

    Fornberg, Bengt

    MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy

  11. Crystal growth under external electric fields

    NASA Astrophysics Data System (ADS)

    Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo

    2014-10-01

    This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostaticallyeither through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

  12. Electric field measurements with stratospheric balloons

    NASA Astrophysics Data System (ADS)

    Iversen, I. B.

    1989-04-01

    Electric fields and currents in the middle atmosphere are important elements of the modern picture of this region. Balloon instruments, reaching the level of the stratosphere, were used extensively for the experimental work. The research has shown good progress, both in the MAP period and in the years before and after. The knowledge was increased about, e.g., the upper atmosphere potential, the electric properties of the medium itself and about the coupling with magnetospheric (ionospheric) fields and currents. Also various measurements have brought about a discussion of the possible existence of hitherto unknown sources. Throughout the MAP period the work on a possible definition of an electric index has continued.

  13. Crystal growth under external electric fields

    SciTech Connect

    Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo

    2014-10-06

    This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

  14. Drag forces on inclusions in classical fields with dissipative dynamics

    E-print Network

    Vincent Demery; D. S. Dean

    2010-04-01

    We study the drag force on uniformly moving inclusions which interact linearly with dynamical free field theories commonly used to study soft condensed matter systems. Drag forces are shown to be nonlinear functions of the inclusion velocity and depend strongly on the field dynamics. The general results obtained can be used to explain drag forces in Ising systems and also predict the existence of drag forces on proteins in membranes due to couplings to various physical parameters of the membrane such as composition, phase and height fluctuations.

  15. Computational Investigation of Helical Traveling Wave Tube Transverse RF Field Forces

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A.

    1998-01-01

    In a previous study using a fully three-dimensional (3D) helical slow-wave circuit cold- test model it was found, contrary to classical helical circuit analyses, that transverse FF electric fields have significant amplitudes compared with the longitudinal component. The RF fields obtained using this helical cold-test model have been scaled to correspond to those of an actual TWT. At the output of the tube, RF field forces reach 61%, 26% and 132% for radial, azimuthal and longitudinal components, respectively, compared to radial space charge forces indicating the importance of considering them in the design of electron beam focusing.

  16. Full 180° Magnetization Reversal with Electric Fields

    PubMed Central

    Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

    2014-01-01

    Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals. PMID:25512070

  17. Research of optical electric field probe

    NASA Astrophysics Data System (ADS)

    Zhang, Wan; Li, Bin; Chen, Jingyao; Wang, Jifeng; Lu, Guizhen

    2012-10-01

    As an important modern measurement equipment of the electromagnetic field, electric field probe can measure the industrial, scientific and medical aspects of the leakage field. In the Electro Magnetic Compatibility (EMC) experiment, it can also check the high-frequency-sensitive parts of the devices and the parasitic radiations due to the mechanical movement. Especially in the field of Electromagnetic Compatibility, electric field probe is one of the most important test equipment. This paper introduces a type of optical electric field probe. In the system, a kind of antenna, which could provide a response nearly isotropic for all polarizations of the incident field, is used for receiving the signal of the electric field. The high-frequency signal received by the antenna then is detected by Schottky barrier diode detector. This low-frequency or Direct Current (DC) signal can be modulated to the band of light by the Electro-Absorption-Distributed Feed Back (EA-DFB) modulator, thus the probe can provide a wild band responds. Through the optical fiber, the optical signal is sent to the photoelectric detector. Based on the optical power value, the field intensity can be calculated. In this system, compared with traditional transmission line, optical fiber can minimize the electromagnetic interference and transmission-line attenuation. In addition to this, the system also has high test sensitivity and wide measurement bandwidth. Furthermore, the whole system has a simple structure and low manufacturing cost.

  18. Evolution of Tachyon Kink with Electric Field

    E-print Network

    Inyong Cho; O-Kab Kwon; Chong Oh Lee

    2007-04-16

    We investigate the decay of an inhomogeneous D1-brane wrapped on a $S^1$ with an electric field. The model that we consider consists of an array of tachyon kink and anti-kink with a constant electric flux. Beginning with an initially static configuration, we numerically evolve the tachyon field with some perturbations under a fixed boundary condition at diametrically opposite points on the circle $S^1$. When the electric flux is smaller than the critical value, the tachyon kink becomes unstable; the tachyon field rolls down the potential, and the lower dimensional D0- and $\\bar {\\rm D}0$-brane become thin, which resembles the caustic formation known for this type of the system in the literature. For the supercritical values of the electric flux, the tachyon kink remains stable.

  19. Stability of Spherical Vesicles in Electric Fields

    PubMed Central

    2010-01-01

    The stability of spherical vesicles in alternating (ac) electric fields is studied theoretically for asymmetric conductivity conditions across their membranes. The vesicle deformation is obtained from a balance between the curvature elastic energies and the work done by the Maxwell stresses. The present theory describes and clarifies the mechanisms for the four types of morphological transitions observed experimentally on vesicles exposed to ac fields in the frequency range from 500 to 2 × 107 Hz. The displacement currents across the membranes redirect the electric fields toward the membrane normal to accumulate electric charges by the Maxwell?Wagner mechanism. These accumulated electric charges provide the underlying molecular mechanism for the morphological transitions of vesicles as observed on the micrometer scale. PMID:20575588

  20. Solidification processing superalloys in an electric field

    NASA Technical Reports Server (NTRS)

    Ahmed, Shaffiq; Bond, Robert; Mckannan, Eugene C.

    1991-01-01

    The phase morphology of a given superalloy's microstructure is established during solidification. Solidification-processing in an applied electric field is a technique currently undergoing experimental characterization at NASA-Marshall. The method is predicated on the simplest model of a metallic solid, in which ions are arranged in basic space lattices that are permeated by an 'electron gas' whose valence electrons are free to move in the solid. When in a superheated liquid state, the metal is seen as a dense 'cold plasma' of electrons and ions. The application of an electric field during solidification establishes a steady, continuous current flow; the direction of propagation of the plasma waves coincides with the direction of the electric field. Such an alignment introduces an ordered arrangement of the electric vectors and introduces an additional degree of order in an already highly ordered alloy.

  1. Electric field induced spin-polarized current

    DOEpatents

    Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

    2006-05-02

    A device and a method for generating an electric-field-induced spin current are disclosed. A highly spin-polarized electric current is generated using a semiconductor structure and an applied electric field across the semiconductor structure. The semiconductor structure can be a hole-doped semiconductor having finite or zero bandgap or an undoped semiconductor of zero bandgap. In one embodiment, a device for injecting spin-polarized current into a current output terminal includes a semiconductor structure including first and second electrodes, along a first axis, receiving an applied electric field and a third electrode, along a direction perpendicular to the first axis, providing the spin-polarized current. The semiconductor structure includes a semiconductor material whose spin orbit coupling energy is greater than room temperature (300 Kelvin) times the Boltzmann constant. In one embodiment, the semiconductor structure is a hole-doped semiconductor structure, such as a p-type GaAs semiconductor layer.

  2. Electric/magnetic field sensor

    DOEpatents

    Schill, Jr., Robert A. (Henderson, NV); Popek, Marc [Las Vegas, NV

    2009-01-27

    A UNLV novel electric/magnetic dot sensor includes a loop of conductor having two ends to the loop, a first end and a second end; the first end of the conductor seamlessly secured to a first conductor within a first sheath; the second end of the conductor seamlessly secured to a second conductor within a second sheath; and the first sheath and the second sheath positioned adjacent each other. The UNLV novel sensor can be made by removing outer layers in a segment of coaxial cable, leaving a continuous link of essentially uncovered conductor between two coaxial cable legs.

  3. Electric force microscopy of semiconductors: Theory of cantilever frequency fluctuations and noncontact friction

    SciTech Connect

    Lekkala, Swapna; Marohn, John A.; Loring, Roger F.

    2013-11-14

    An electric force microscope employs a charged atomic force microscope probe in vacuum to measure fluctuating electric forces above the sample surface generated by dynamics of molecules and charge carriers. We present a theoretical description of two observables in electric force microscopy of a semiconductor: the spectral density of cantilever frequency fluctuations (jitter), which are associated with low-frequency dynamics in the sample, and the coefficient of noncontact friction, induced by higher-frequency motions. The treatment is classical-mechanical, based on linear response theory and classical electrodynamics of diffusing charges in a dielectric continuum. Calculations of frequency jitter explain the absence of contributions from carrier dynamics to previous measurements of an organic field effect transistor. Calculations of noncontact friction predict decreasing friction with increasing carrier density through the suppression of carrier density fluctuations by intercarrier Coulomb interactions. The predicted carrier density dependence of the friction coefficient is consistent with measurements of the dopant density dependence of noncontact friction over Si. Our calculations predict that in contrast to the measurement of cantilever frequency jitter, a noncontact friction measurement over an organic semiconductor could show appreciable contributions from charge carriers.

  4. An electric force facilitator in descending vortex tornadogenesis

    NASA Astrophysics Data System (ADS)

    Patton, Forest S.; Bothun, Gregory D.; Sessions, Sharon L.

    2008-04-01

    We present a novel explanation of the physical processes behind one type of cloud and ground-level tornadogenesis within a supercell. We point out that the charge separation naturally found in these large thunderstorms can potentially serve to contract the preexisting angular momentum through the additional process of the electric force. On the basis of this, we present a plausible geometry that explains why many tornado vortices begin at storm midlevel and build downward into ground-level tornadoes. A simple model based on this geometry is used to demonstrate the strength of the electric force compared to the required centripetal acceleration to maintain cloud midlevel tornado vortices measurable as tornado vortex signatures (TVSs). Furthermore, a model based on this geometry is used to get a time estimate for tornado vortex formation. From this we are able to identify a plausible value for the threshold charge density that would lead to tornadogenesis and tornado maintenance on the timescale of a few minutes. We show that the proposed geometry can explain the observations that ground-level tornadoes thrive in regions with high shear and large convective available potential energy (CAPE) and are able to make some predictions of specific measurable quantities.

  5. Control of the Electric Field Profile in the Hall Thruster

    SciTech Connect

    A. Fruchtman; N. J. Fisch; Y. Raitses

    2000-10-05

    Control of the electric field profile in the Hall Thruster through the positioning of an additional electrode along the channel is shown theoretically to enhance the efficiency. The reduction of the potential drop near the anode by use of the additional electrode increases the plasma density there, through the increase of the electron and ion transit times, causing the ionization in the vicinity of the anode to increase. The resulting separation of the ionization and acceleration regions increases the propellant and energy utilizations. An abrupt sonic transition is forced to occur at the axial location of the additional electrode, accompanied by the generation of a large (theoretically infinite) electric field. This ability to generate a large electric field at a specific location along the channel, in addition to the ability to specify the electric potential there, allows one further control of the electric field profile in the thruster. In particular, when the electron temperature is high, a large abrupt voltage drop is induced at the vicinity of the additional electrode, a voltage drop that can comprise a significant part of the applied voltage.

  6. Approximate photochemical dynamics of azobenzene with reactive force fields

    NASA Astrophysics Data System (ADS)

    Li, Yan; Hartke, Bernd

    2013-12-01

    We have fitted reactive force fields of the ReaxFF type to the ground and first excited electronic states of azobenzene, using global parameter optimization by genetic algorithms. Upon coupling with a simple energy-gap transition probability model, this setup allows for completely force-field-based simulations of photochemical cis?trans- and trans?cis-isomerizations of azobenzene, with qualitatively acceptable quantum yields. This paves the way towards large-scale dynamics simulations of molecular machines, including bond breaking and formation (via the reactive force field) as well as photochemical engines (presented in this work).

  7. Approximate photochemical dynamics of azobenzene with reactive force fields

    SciTech Connect

    Li, Yan; Hartke, Bernd

    2013-12-14

    We have fitted reactive force fields of the ReaxFF type to the ground and first excited electronic states of azobenzene, using global parameter optimization by genetic algorithms. Upon coupling with a simple energy-gap transition probability model, this setup allows for completely force-field-based simulations of photochemical cis?trans- and trans?cis-isomerizations of azobenzene, with qualitatively acceptable quantum yields. This paves the way towards large-scale dynamics simulations of molecular machines, including bond breaking and formation (via the reactive force field) as well as photochemical engines (presented in this work)

  8. Antiprotonic hydrogen in static electric field

    E-print Network

    G. Ya. Korenman; S. N. Yudin

    2005-01-12

    Effects of the static electric field on the splitting and annihilation widths of the levels of antiprotonic hydrogen with a large principal quantum number (n=30) are studied. Non-trivial aspects of the consideration is related with instability of (p\\bar{p})^*-atom in ns and np-states due to coupling of these states with the annihilation channels. Properties of the mixed nl-levels are investigated depending on the value of external static electric field. Specific resonance-like dependence of effective annihilation widths on the strength of the field is revealed.

  9. Electric fields associated with dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Sun, Wei-Jie; Fu, Suiyan; Parks, George K.; Pu, Zuyin; Zong, Qiu-Gang; Liu, Jiang; Yao, Zhonghua; Fu, Huishan; Shi, Quanqi

    2014-07-01

    Electric fields associated with dipolarization fronts (DFs) have been investigated in the magnetotail plasma sheet using Cluster observations. We have studied each term in the generalized Ohm's law using data obtained from the multispacecraft Cluster. Our results show that in the plasma flow frame, electric fields are directed normal to the DF in the magnetic dip region ahead of the DF as well as in the DF layer but in opposite directions. Case and statistical studies show that the Hall electric field is important while the electron pressure gradient term is much smaller. The ions decouple from the magnetic field in the DF layer and dip region (E + Vi×B ? 0), whereas electrons remain frozen-in (E + Ve×B=?pe/nee).

  10. Prediction of Mechanical Properties of Polymers With Various Force Fields

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The effect of force field type on the predicted elastic properties of a polyimide is examined using a multiscale modeling technique. Molecular Dynamics simulations are used to predict the atomic structure and elastic properties of the polymer by subjecting a representative volume element of the material to bulk and shear finite deformations. The elastic properties of the polyimide are determined using three force fields: AMBER, OPLS-AA, and MM3. The predicted values of Young s modulus and shear modulus of the polyimide are compared with experimental values. The results indicate that the mechanical properties of the polyimide predicted with the OPLS-AA force field most closely matched those from experiment. The results also indicate that while the complexity of the force field does not have a significant effect on the accuracy of predicted properties, small differences in the force constants and the functional form of individual terms in the force fields determine the accuracy of the force field in predicting the elastic properties of the polyimide.

  11. Electric field controlled columnar and planar patterning of cholesteric colloids.

    PubMed

    D'Adamo, G; Marenduzzo, D; Micheletti, C; Orlandini, E

    2015-05-01

    We study how dispersions of colloidal particles in a cholesteric liquid crystal behave under a time-dependent electric field. By controlling the amplitude and shape of the applied field wave, we show that the system can be reproducibly driven out of equilibrium through different kinetic pathways and navigated through a glassylike free energy landscape encompassing many competing metastable equilibria. Such states range from simple Saturn rings to complex structures featuring amorphous defect networks, or stacks of disclination loops. A nonequilibrium electric field can also trigger the alignment of particles into columnar arrays, through defect-mediated force impulses, or their repositioning within a plane. Our results are promising in terms of providing new avenues towards controlled patterning and self-assembly of soft colloid-liquid crystal composite materials. PMID:25978263

  12. Electric Field Controlled Columnar and Planar Patterning of Cholesteric Colloids

    NASA Astrophysics Data System (ADS)

    D'Adamo, G.; Marenduzzo, D.; Micheletti, C.; Orlandini, E.

    2015-05-01

    We study how dispersions of colloidal particles in a cholesteric liquid crystal behave under a time-dependent electric field. By controlling the amplitude and shape of the applied field wave, we show that the system can be reproducibly driven out of equilibrium through different kinetic pathways and navigated through a glassylike free energy landscape encompassing many competing metastable equilibria. Such states range from simple Saturn rings to complex structures featuring amorphous defect networks, or stacks of disclination loops. A nonequilibrium electric field can also trigger the alignment of particles into columnar arrays, through defect-mediated force impulses, or their repositioning within a plane. Our results are promising in terms of providing new avenues towards controlled patterning and self-assembly of soft colloid-liquid crystal composite materials.

  13. Lipid nanotube formation using space-regulated electric field above interdigitated electrodes.

    PubMed

    Bi, Hongmei; Fu, Dingguo; Wang, Lei; Han, Xiaojun

    2014-04-22

    Lipid nanotubes have great potential in biology and nanotechnology. Here we demonstrate a method to form lipid nanotubes using space-regulated AC electric fields above coplanar interdigitated electrodes. The AC electric field distribution can be regulated by solution height above the electrodes. The ratio of field component in x axis (Ex) to field component in z axis (Ez) increases dramatically at solution height below 50 ?m; therefore, at lower solution height, the force from Ex predominantly drives lipids to form lipid nanotubes along with the electric field direction. The forces exerted on the lipid nanotube during its formation were analyzed in detail, and an equation was obtained to describe the relationship among nanotube length and field frequency, amplitude, and time. We believe that the presented approach opens a way to design and prepare nanoscale materials with unique structural and functional properties using space-regulated electric fields. PMID:24669822

  14. Molecular dynamics simulations of methane hydrate using polarizable force fields

    SciTech Connect

    Jiang, H.N.; Jordan, K.D.; Taylor, C.E.

    2007-06-14

    Molecular dynamics simulations of methane hydrate have been carried out using the polarizable AMOEBA and COS/G2 force fields. Properties calculated include the temperature dependence of the lattice constant, the OC and OO radial distribution functions, and the vibrational spectra. Both the AMOEBA and COS/G2 force fields are found to successfully account for the available experimental data, with overall somewhat better agreement with experiment being found for the AMOEBA model. Comparison is made with previous results obtained using TIP4P and SPC/E effective two-body force fields and the polarizable TIP4P-FQ force field, which allows for in-plane polarization only. Significant differences are found between the properties calculated using the TIP4P-FQ model and those obtained using the other models, indicating an inadequacy of restricting explicit polarization to in-plane onl

  15. A Molecular Mechanics Force Field for Biologically Important Sterols

    E-print Network

    Ullmann, G. Matthias

    of the cholesterol crystal structure. The experimental geometry and cell dimensions are well reproduced. The force field derived here is also useful for simulating other sterols such as the phytosterols sigmasterol

  16. Generative morphologies of architectural organization in matter force field

    E-print Network

    Mutlu, Murat

    2010-01-01

    This thesis investigates generative methods of architectural form finding in matter force fields that produce spatial subdivision and organizational variation. Unlike the style driven contemporary free-form architecture ...

  17. Turbulent relaxation to a force-free field-reversed state

    NASA Technical Reports Server (NTRS)

    Dahlburg, J. P.; Montgomery, D.; Doolen, G. D.; Turner, L.

    1986-01-01

    The evolution of nonequilibrium initial conditions of an incompressible magnetohydrodynamic Z pinch is described by a three-dimensional, pseudospectral numerical code. Magnetohydrodynamic turbulence develops in the resistive, nonviscous magnetofluid, resulting in the selective decay of the energy relative to the magnetic helicity, at Lundquist numbers of only a few hundred. An interior force-free region grows with time and achieves spontaneous reversal of the toroidal magnetic field at the wall, without the necessity of an external electric field.

  18. Electric field controlled emulsion phase contactor

    DOEpatents

    Scott, T.C.

    1995-01-31

    A system is described for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity. 5 figs.

  19. Electric field controlled emulsion phase contactor

    DOEpatents

    Scott, Timothy C. (Knoxville, TN)

    1995-01-01

    A system for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity.

  20. Gravitational self-force in nonvacuum spacetimes: An effective field theory derivation

    NASA Astrophysics Data System (ADS)

    Zimmerman, Peter

    2015-09-01

    In this paper we investigate the motion of small compact objects in nonvacuum spacetimes using methods from effective field theory in curved spacetime. Although a vacuum formulation is sufficient in many astrophysical contexts, there are applications such as the role of the self-force in enforcing cosmic censorship in the context of the overcharging problem, which necessitate an extension into the nonvacuum regime. The defining feature of the self-force problem in nonvacuum spacetimes is the coupling between gravitational and nongravitational field perturbations. The formulation of the self-force problem for nonvacuum spacetimes was recently provided in simultaneous papers by Zimmerman and Poisson [Gravitational self-force in nonvacuum spacetimes, Phys. Rev. D 90, 084030 (2014)] and Linz, Friedmann, and Wiseman [Combined gravitational and electromagnetic self-force on charged particles in electrovac spacetimes, Phys. Rev. D 90, 084031 (2014)]. Here we distinguish ourselves by working with the effective action rather than the field equations. The formalism utilizes the multi-index notation developed by Zimmerman and Poisson [Gravitational self-force in nonvacuum spacetimes, Phys. Rev. D 90, 084030 (2014) to accommodate the coupling between the different fields. Using dimensional regularization, we arrive at a finite expression for the local self-force expressed in terms of multi-index quantities evaluated in the background spacetime. We then apply the formalism to compute the coupled gravitational self-force in two explicit cases. First, we calculate the self-force on a massive particle possessing scalar charge and moving in a scalarvac spacetime. We then derive an expression for the self-force on an electrically charged, massive particle moving in an electrovac spacetime. In both cases, the force is expressed as a sum of local terms involving tensors defined in the background spacetime and evaluated at the current position of the particle, as well as tail integrals that depend on the past history of the particle.

  1. Mitigated-force carriage for high magnetic field environments

    DOEpatents

    Ludtka, Gerard M.; Ludtka, Gail M.; Wilgen, John B.; Murphy, Bart L.

    2015-05-19

    A carriage for high magnetic field environments includes a plurality of work-piece separators disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla for supporting and separating a plurality of work-pieces by a preselected, essentially equal spacing, so that, as a first work-piece is inserted into the magnetic field, a second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

  2. A transferable ab initio based force field for aqueous ions

    NASA Astrophysics Data System (ADS)

    Tazi, Sami; Molina, John J.; Rotenberg, Benjamin; Turq, Pierre; Vuilleumier, Rodolphe; Salanne, Mathieu

    2012-03-01

    We present a new polarizable force field for aqueous ions (Li+, Na+, K+, Rb+, Cs+, Mg2 +, Ca2 +, Sr2 +, and Cl-) derived from condensed phase ab initio calculations. We use maximally localized Wannier functions together with a generalized force and dipole-matching procedure to determine the whole set of parameters. Experimental data are then used only for validation purposes and a good agreement is obtained for structural, dynamic, and thermodynamic properties. The same procedure applied to crystalline phases allows to parametrize the interaction between cations and the chloride anion. Finally, we illustrate the good transferability of the force field to other thermodynamic conditions by investigating concentrated solutions.

  3. Field-aligned currents and large scale magnetospheric electric fields

    NASA Technical Reports Server (NTRS)

    Dangelo, N.

    1980-01-01

    D'Angelo's model of polar cap electric fields (1977) was used to visualize how high-latitude field-aligned currents are driven by the solar wind generator. The region 1 and region 2 currents of Iijima and Potemra (1976) and the cusp field-aligned currents of Wilhjelm et al. (1978) and McDiarmid et al. (1978) are apparently driven by different generators, although in both cases the solar wind is their ultimate source.

  4. Acceleration of particles in an isotropic random force field

    E-print Network

    Hector Javier Durand-Manterola

    2012-04-18

    If we have a particle immersed in a field of random forces, each interaction of the particle with the field can enlarge or diminish its kinetic energy. In this work is shown that in general, for any field of random force with uniform distribution of directions, the probability to gain kinetic energy is larger that the probability to lose it. Therefore, if the particle is submitted to a great number of interactions with the force stochastic field, the final result will be that the particle will gain energy. The probability to gain energy in each interaction is Pg=1/2 (1+T/(2Po)), where T is the impulse given by the field and Po is the momentum of the particle before the interaction. The probability to lose energy in each interaction is Pl=1/2 (1-T/(2Po)).

  5. Electric Field Effects in RUS Measurements

    SciTech Connect

    Darling, Timothy W; Ten Cate, James A; Allured, Bradley; Carpenter, Michael A

    2009-09-21

    Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static and RF electric fields. Non-contact optical, buffered, or shielded transducers permit the application of charge and externally applied electric fields while making RUS measurements. For conducting samples, in vacuum, charging produces a small negative pressure in the volume of the material - a state rarely explored. At very high charges we influence the electron density near the surface so the propagation of surface waves and their resonances may give us a handle on the relationship of electron density to bond strength and elasticity. Our preliminary results indicate a charge sign dependent effect, but we are studying a number of possible other effects induced by charging. In dielectric materials, external electric fields influence the strain response, particularly in ferroelectrics. Experiments to study this connection at phase transformations are planned. The fact that many geological samples contain single crystal quartz suggests a possible use of the piezoelectric response to drive vibrations using applied RF fields. In polycrystals, averaging of strains in randomly oriented crystals implies using the 'statistical residual' strain as the drive. The ability to excite vibrations in quartzite polycrystals and arenites is explored. We present results of experimental and theoretical approaches to electric field effects using RUS methods.

  6. Parallel electric fields from ionospheric winds

    SciTech Connect

    Nakada, M.P. )

    1987-10-01

    The possible production of electric fields parallel to the magnetic field by dynamo winds in the E region is examined, using a jet stream wind model. Current return paths through the F region above the stream are examined as well as return paths through the conjugate ionosphere. The Wulf geometry with horizontal winds moving in opposite directions one above the other is also examined. Parallel electric fields are found to depend strongly on the width of current sheets at the edges of the jet stream. If these are narrow enough, appreciable parallel electric fields are produced. These appear to be sufficient to heat the electrons which reduces the conductivity and produces further increases in parallel electric fields and temperatures. Calculations indicate that high enough temperatures for optical emission can be produced in less than 0.3 s. Some properties of auroras that might be produced by dynamo winds are examined; one property is a time delay in brightening at higher and lower altitudes.

  7. Electric fields and double layers in plasmas

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Thiemann, H.; Schunk, R. W.

    1987-01-01

    Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamical features of the double layers are discussed. These features, as seen in simulations, laboratory experiments, and theory, indicate that double layers and the currents through them undergo slow oscillations which are determined by the ion transit time across an effective length of the system in which double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations were considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields and double layers in an expanding plasma is discussed.

  8. DC Electric Fields at the Magnetopause

    NASA Astrophysics Data System (ADS)

    Laakso, H. E.; Escoubet, C. P.; Masson, A.

    2014-12-01

    In order to understand the transfer of energy, momentum and mass through the magnetopause one needs to know several plasma and field parameters including the DC electric field which is known to be challenging to measure in tenuous plasma regions, e.g. in the inner side of the magnetopause where the density drops below 1/cc. However, each of the Cluster spacecraft carries five different experiments that can provide information about DC electric fields, i.e. double probe antenna (EFW) and electron drift meter (EDI) as well as electron and ion spectrometers (PEACE, CIS-HIA, CIS-CODIF). Each technique is very different and has its own strengths and limitations. Therefore it is important to compare all available measurements before making a judgement on DC electric field variation at the magnetopause; note that only very rarely all five measurements are available at the same time. Although the full-resolution observations in the Cluster archive are calibrated, they can still contain various errors. However, when two experiments show the same field, it is quite likely that this is the right field because the different measurements are based on so complimentary techniques and the field varies so much when the spacecraft moves from the magnetosheath through the magnetopause into the magnetosphere, or vice versa. In this presentation we present several cases of the magnetopause crossings and how the different measurements agree and disagree around the magnetopause region.

  9. Force Field Parameter Estimation of Functional Perfluoropolyether Lubricants

    SciTech Connect

    Smith, R.; Chung, P.S.; Steckel, J; Jhon, M.S.; Biegler, L.T.

    2011-01-01

    The head disk interface in a hard disk drive can be considered to be one of the hierarchical multiscale systems, which require the hybridization of multiscale modeling methods with coarse-graining procedure. However, the fundamental force field parameters are required to enable the coarse-graining procedure from atomistic/molecular scale to mesoscale models. In this paper, we investigate beyond molecular level and perform ab initio calculations to obtain the force field parameters. Intramolecular force field parameters for Zdol and Ztetraol were evaluated with truncated PFPE molecules to allow for feasible quantum calculations while still maintaining the characteristic chemical structure of the end groups. Using the harmonic approximation to the bond and angle potentials, the parameters were derived from the Hessian matrix, and the dihedral force constants are fit to the torsional energy profiles generated by a series of constrained molecular geometry optimization.

  10. Alternating Magnetic Field Forces for Satellite Formation Flying

    NASA Technical Reports Server (NTRS)

    Youngquist, Robert C.; Nurge, Mark A.; Starr, Stnaley O.

    2012-01-01

    Selected future space missions, such as large aperture telescopes and multi-component interferometers, will require the precise positioning of a number of isolated satellites, yet many of the suggested approaches for providing satellites positioning forces have serious limitations. In this paper we propose a new approach, capable of providing both position and orientation forces, that resolves or alleviates many of these problems. We show that by using alternating fields and currents that finely-controlled forces can be induced on the satellites, which can be individually selected through frequency allocation. We also show, through analysis and experiment, that near field operation is feasible and can provide sufficient force and the necessary degrees of freedom to accurately position and orient small satellites relative to one another. In particular, the case of a telescope with a large number of free mirrors is developed to provide an example of the concept. We. also discuss the far field extension of this concept.

  11. Apparatus having reduced mechanical forces for supporting high magnetic fields

    DOEpatents

    Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)

    1991-01-01

    The present invention identifies several configurations of conducting elements capable of supporting extremely high magnetic fields suitable for plasma confinement, wherein forces experienced by the conducting elements are significantly reduced over those which are present as a result of the generation of such high fields by conventional techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency.

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

    NASA Technical Reports Server (NTRS)

    El-Kaddah, N.; Szekely, J.

    1982-01-01

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

  13. The unification of the fundamental interaction within Maxwell electromagnetism: Model of hydrogen atom. Gravity as the secondary electric force. Calculation of the unified inertia force

    E-print Network

    L. Neslusan

    2010-12-28

    Considering two static, electrically charged, elementary particles, we demonstrate a possible way of proving that all known fundamental forces in the nature are the manifestations of the single, unique interaction. We re-define the gauging of integration constants in the Schwarzschild solution of Einstein field equations. We consider the potential energy in this context regardless it is gravitational or electric potential energy. With the newly gauged constants, we sketch how the unique interaction can be described with the help of an appropriate solution of the well-known Maxwell equations. According the solution, there are two zones, in the system of two oppositely charged particles, where the force is oscillating. The first particle can be in a stable, constant distance from the second particle, between the neighbouring regions of repulsion and attraction. In an outer oscillation zone, the corresponding energy levels in the proton-electron systems are identical (on the level of accuracy of values calculated by the Dirac's equations) to some experimentally determined levels in the hydrogen atom. For each system of two particles, there is also the zone with the macroscopic, i.e. monotonous behavior of the force. As well, the solution can be used to demonstrate that the net force between two assemblies consisting each (or at least one) of the same numbers of both positively and negatively charged particles is never zero. A secondary electric force, having the same orientation as the primary electric force between the oppositely charged particles, is always present. It can be identified to the gravity. Finally, the solution of the Maxwell equations can be used to calculate the inertia force of a particle. The consistent formulas for both acting and inertia forces enable to construct the dimensionless (without gravitational constant, permitivity of vacuum, etc.) equation of motion.

  14. Using impedance measurements for detecting pathogens trapped in an electric field

    DOEpatents

    Miles, Robin R.

    2004-07-20

    Impedance measurements between the electrodes in an electric field is utilized to detect the presence of pathogens trapped in the electric field. Since particles trapped in a field using the dielectiphoretic force changes the impedance between the electrodes by changing the dielectric material between the electrodes, the degree of particle trapping can be determined by measuring the impedance. This measurement is used to determine if sufficient pathogen have been collected to analyze further or potentially to identify the pathogen.

  15. Role of inductive electric fields in substorm development

    NASA Technical Reports Server (NTRS)

    Heikkila, Walter J.

    1992-01-01

    A study discussing and investigating the role of inductive electric fields in substorm development is presented. It is common to use the scalar potential phi to calculate the electrostatic field E(sup ES)-(inverted Delta)(phi). However, vector potential A has not been extensively used to analyze results by the relation for the inductive electric field E(sup IND)-delta A/delta t. Because of the weak dependence in distance (1/r) these potentials show the effect of distant sources, unlike MHD (Magnetohydrodynamic) theory which is strictly local. The two can be separated by the choice of the Coulomb (transverse) gauge. It is proper to consider that the plasma polarizes to counteract the activation of the inductive electric field; this is a matter of cause and effect. However, such polarization produces a curl free electrostatic field and thus cannot alter the electromotive force due to induction. This idea has some interesting consequences for plasma physics, including violations of MHD theory, creation of the substorm current diversion, and a fresh look at dayside merging via plasma transfer events.

  16. Health of workers exposed to electric fields.

    PubMed

    Broadbent, D E; Broadbent, M H; Male, J C; Jones, M R

    1985-02-01

    The results of health questionnaire interviews with 390 electrical power transmission and distribution workers, together with long term estimates of their exposure to 50 Hz electric fields, and short term measurements of the actual exposure for 287 of them are reported. Twenty eight workers received measurable exposures, averaging about 30 kVm-1h over the two week measurement period. Estimated exposure rates were considerably greater, but showed fair correlation with the measurements. Although the general level of health was higher than we have found in manual workers in other industries, there were significant differences in the health measures between different categories of job, different parts of the country, and in association with factors such as overtime, working alone, or frequently changing shift. After allowing for the effects of job and location, however, we found no significant correlations of health with either measured or estimated exposure to electric fields. PMID:3970875

  17. Motional Spin Relaxation in Large Electric Fields

    E-print Network

    Schmid, Riccardo; Filippone, B W

    2008-01-01

    We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}\\mathrm{He}$ atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}\\mathrm{He}$ samples. The spin relaxation times $T_{1}$ (longitudinal) and $T_{2}$ (transverse) of spin-polarized UCN and $^{3}\\mathrm{He}$ atoms are important considerations in a new search for the neutron Electric Dipole Moment at the SNS \\emph{nEDM} experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional $v\\times E$ field for UCN and for $^{3}\\mathrm{He}$ atoms at temperatures below $600 \\mathrm{mK}$. We find the relaxation times for the neutron due to the $v\\times E$ effect to be long compared to the neutron lifetime, ...

  18. Nonthermal processing by radio frequency electric fields

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Radio frequency electric fields (RFEF) processing is relatively new and has been shown to inactivate bacteria in apple juice, orange juice and apple cider at moderately low temperatures. Key equipment components of the process include a radio frequency power supply and a treatment chamber that is ca...

  19. PHASE EQUILIBRIA MODIFICATION BY ELECTRIC FIELDS

    EPA Science Inventory

    The primary focus of this program is to obtain a fundamental understanding of the effects of electric fields on polar and nonpolar mixtures in gas and liquid phases, with the ultimate goal of using this understanding in devising novel means to dramatically improve existing enviro...

  20. Visualization of Force Fields in Protein Structure Prediction

    SciTech Connect

    Crawford, Clark; Kreylos, Oliver; Hamann, Bernd; Crivelli, Silvia

    2005-04-26

    The force fields used in molecular computational biology are not mathematically defined in such a way that their mathematical representation would facilitate the straightforward application of volume visualization techniques. To visualize energy, it is necessary to define a spatial mapping for these fields. Equipped with such a mapping, we can generate volume renderings of the internal energy states in a molecule. We describe our force field, the spatial mapping that we used for energy, and the visualizations that we produced from this mapping. We provide images and animations that offer insight into the computational behavior of the energy optimization algorithms that we employ.

  1. Analog of electric and magnetic fields in stationary gravitational systems

    SciTech Connect

    Embacher, F.

    1984-08-01

    Newtonian and Machian aspects of the stationary gravitational field are brought into formal analogy with a stationry electromagnetic field. The electromagnetic vector potential equals (up to a factor) the timelike Killing vector field. The current density is given by the contraction of the Killing vector with the Ricci tensor. A coordinate-dependent split in electric and magnetic field vectors is given, and some results of classical electrodynamics are used to illustrate the analogy. In the linearized theory, the usual Maxwell equations are obtained. The analogy also holds from the point of view of particle motion. The geodesic equation is brought into a special form that exhibits an analog to the Lorentz force. Two examples (which have played an important role in the theoretical discovery of Machian effects) are considered.

  2. Effects of nanosecond pulse electric fields on cellular elasticity.

    PubMed

    Dutta, Diganta; Asmar, Anthony; Stacey, Michael

    2015-05-01

    We investigated the effects of a single 60 nanosecond pulsed electric field (nsPEF) of low (15 kV/cm) and high (60 kV/cm) field strengths on cellular morphology and membrane elasticity in Jurkat cells using fluorescent microscopy and atomic force microscopy (AFM). We performed force displacement measurements on cells using AFM and calculated the Young's modulus for membrane elasticity. Differential effects were observed depending upon pulsing conditions. We found that a single nsPEF of low field strength did not induce any apparent cytoskeletal breakdown and had minor morphological changes. Interestingly, force measurements and calculation of Young's modulus showed a significant decrease in membrane elasticity. A single nsPEF of high field strength induced stark morphological changes due to disruption of the actin cytoskeleton and a marked decrease in elasticity likely caused by irreversible membrane damage. We suggest that the cellular morphology is mainly dependent on stabilization by the actin cytoskeleton, while the elasticity changes are partially dependent on the cytoskeletal integrity. PMID:25732004

  3. Electric field distribution on knife-edge field emitters

    NASA Astrophysics Data System (ADS)

    Miller, Ryan; Lau, Yue Ying; Booske, John

    2007-11-01

    Of critical importance to advanced High Power Microwave (HPM) generators is the development and understanding of robust cold cathodes with low turn-on electric fields. Recent interesting candidates include ridged metallic cathodes fabricated by either laser ablation or other microfabrication methods [1]. We use conformal mapping to calculate the electric field on a knife-edge cathode. We find that the field enhancement factor scales approximately as the square root of the height-width ratio of the knife-edge [2]. An analytic approximation for the divergent electric field in the immediate vicinity of the sharp edge is derived. A smaller knife-edge placed on top of a larger one demonstrates that the composite field enhancement factor is approximately equal to the product of the field enhancement factor of the individual knife-edges. This proves the conjecture [3] on multiplication of field enhancement factors for one special case. This work was supported by AFOSR/MURI and by AFRL. [1] M.C. Jones, et al, Rev .Sci.Instrum.,75, 2976 (2004) [2] R. Miller, Y. Y. Lau, J. H. Booske, Appl. Phys. Lett., (to be published) [3] W. Schottky, Z. Physik, 14, 63 (1923).

  4. Reversible shear thickening at low shear rates of electrorheological fluids under electric fields

    NASA Astrophysics Data System (ADS)

    Tian, Yu; Zhang, Minliang; Jiang, Jile; Pesika, Noshir; Zeng, Hongbo; Israelachvili, Jacob; Meng, Yonggang; Wen, Shizhu

    2011-01-01

    By shearing electrorheological (ER) fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (<1 s-1) and a high critical electric field strength (>100 V/mm), which can be characterized by a critical apparent viscosity. Shear thickening and electrostatic particle interaction-induced interparticle friction forces are considered to play an important role in the origin of lateral shear resistance of ER fluids, while the applied electric field controls the extent of shear thickening. The electric-field-controlled reversible shear thickening has implications for high-performance electrorheological -magnetorheological fluid design, clutch fluids with high friction forces triggered by applying a local electric field, other field-responsive materials, and intelligent systems.

  5. Reversible shear thickening at low shear rates of electrorheological fluids under electric fields

    E-print Network

    Yu Tian; Minliang Zhang; Jile Jiang; Noshir Pesika; Hongbo Zeng; Jacob Israelachvili; Yonggang Meng; Shizhu Wen

    2010-08-24

    Shear thickening is a phenomenon of significant viscosity increase of colloidal suspensions. While electrorheological (ER) fluids can be turned into a solid-like material by applying an electric field, their shear strength is widely represented by the attractive electrostatic interaction between ER particles. By shearing ER fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (100 V/mm), which could be characterized by a modified Mason number. Shear thickening and electrostatic particle interaction-induced inter-particle friction forces is considered to be the real origin of the high shear strength of ER fluids, while the applied electric field controls the extent of shear thickening. The electric field-controlled reversible shear thickening has implications for high-performance ER/magnetorheological (MR) fluid design, clutch fluids with high friction forces triggered by applying local electric field, other field-responsive materials and intelligent systems.

  6. Reversible shear thickening at low shear rates of electrorheological fluids under electric fields.

    PubMed

    Tian, Yu; Zhang, Minliang; Jiang, Jile; Pesika, Noshir; Zeng, Hongbo; Israelachvili, Jacob; Meng, Yonggang; Wen, Shizhu

    2011-01-01

    By shearing electrorheological (ER) fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (<1?s(-1)) and a high critical electric field strength (>100 V/mm), which can be characterized by a critical apparent viscosity. Shear thickening and electrostatic particle interaction-induced interparticle friction forces are considered to play an important role in the origin of lateral shear resistance of ER fluids, while the applied electric field controls the extent of shear thickening. The electric-field-controlled reversible shear thickening has implications for high-performance electrorheological-magnetorheological fluid design, clutch fluids with high friction forces triggered by applying a local electric field, other field-responsive materials, and intelligent systems. PMID:21405692

  7. Benchmarking of Force Fields for Molecule-Membrane Interactions.

    PubMed

    Paloncýová, Markéta; Fabre, Gabin; DeVane, Russell H; Trouillas, Patrick; Berka, Karel; Otyepka, Michal

    2014-09-01

    Studies of drug-membrane interactions witness an ever-growing interest, as penetration, accumulation, and positioning of drugs play a crucial role in drug delivery and metabolism in human body. Molecular dynamics simulations complement nicely experimental measurements and provide us with new insight into drug-membrane interactions; however, the quality of the theoretical data dramatically depends on the quality of the force field used. We calculated the free energy profiles of 11 molecules through a model dimyristoylphosphatidylcholine (DMPC) membrane bilayer using five force fields, namely Berger, Slipids, CHARMM36, GAFFlipids, and GROMOS 43A1-S3. For the sake of comparison, we also employed the semicontinuous tool COSMOmic. High correlation was observed between theoretical and experimental partition coefficients (log K). Partition coefficients calculated by all-atomic force fields (Slipids, CHARMM36, and GAFFlipids) and COSMOmic differed by less than 0.75 log units from the experiment and Slipids emerged as the best performing force field. This work provides the following recommendations (i) for a global, systematic and high throughput thermodynamic evaluations (e.g., log K) of drugs COSMOmic is a tool of choice due to low computational costs; (ii) for studies of the hydrophilic molecules CHARMM36 should be considered; and (iii) for studies of more complex systems, taking into account all pros and cons, Slipids is the force field of choice. PMID:26588554

  8. Swarm equatorial electric field chain: First results

    NASA Astrophysics Data System (ADS)

    Alken, P.; Maus, S.; Chulliat, A.; Vigneron, P.; Sirol, O.; Hulot, G.

    2015-02-01

    The eastward equatorial electric field (EEF) in the E region ionosphere drives many important phenomena at low latitudes. We developed a method of estimating the EEF from magnetometer measurements of near-polar orbiting satellites as they cross the magnetic equator, by recovering a clean signal of the equatorial electrojet current and modeling the observed current to determine the electric field present during the satellite pass. This algorithm is now implemented as an official Level-2 Swarm product. Here we present first results of EEF estimates from nearly a year of Swarm data. We find excellent agreement with independent measurements from the ground-based coherent scatter radar at Jicamarca, Peru, as well as horizontal field measurements from the West African Magnetometer Network magnetic observatory chain. We also calculate longitudinal gradients of EEF measurements made by the A and C lower satellite pair and find gradients up to about 0.05 mV/m/deg with significant longitudinal variability.

  9. Observations of large transient magnetospheric electric fields

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Heppner, J. P.

    1977-01-01

    Transient electric field events were observed with the long, double probe instrumentation carried by the IMP-6 satellite. Nine, clearly defined, exceptionally large amplitude events are presented here. The events are observed in the midnight sector at geocentric distances 3.5 to .5.5 R sub e at middle latitudes within a magnetic L-shell range of 4.8 to 7.5. They usually have a total duration of one to several minutes, with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions, and in most cases they can be associated with negative dH/dt excursions at magnetic observatories located near the foot of the magnetic field line intersecting IMP-6. The magnetospheric motions calculated for these electric fields indicated a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity.

  10. Field-aligned currents and ionospheric electric fields

    NASA Technical Reports Server (NTRS)

    Yasuhara, F.; Akasofu, S.-I.

    1977-01-01

    It is shown that the observed distribution of the ionospheric electric field can be deduced from an equation combining Ohm's law with the current continuity equation by using the 'observed' distribution of field-aligned currents as the boundary condition for two models of the ionosphere. The first model has one conductive annular ring representing the quiet-time auroral precipitation belt; the second has two conductive annular rings that simulate the discrete and diffuse auroral regions. An analysis is performed to determine how well the electric-field distribution can be reproduced. The results indicate that the first model reproduces the Sq(p)-type distribution, the second model reproduces reasonably well a substorm-type potential and ionospheric current patterns together with the Harang discontinuity, and that the distribution of field-aligned currents is the same for both models.

  11. Tunable control of antibody immobilization using electric field

    PubMed Central

    Emaminejad, Sam; Javanmard, Mehdi; Gupta, Chaitanya; Chang, Shuai; Davis, Ronald W.; Howe, Roger T.

    2015-01-01

    The controlled immobilization of proteins on solid-state surfaces can play an important role in enhancing the sensitivity of both affinity-based biosensors and probe-free sensing platforms. Typical methods of controlling the orientation of probe proteins on a sensor surface involve surface chemistry-based techniques. Here, we present a method of tunably controlling the immobilization of proteins on a solid-state surface using electric field. We study the ability to orient molecules by immobilizing IgG molecules in microchannels while applying lateral fields. We use atomic force microscopy to both qualitatively and quantitatively study the orientation of antibodies on glass surfaces. We apply this ability for controlled orientation to enhance the performance of affinity-based assays. As a proof of concept, we use fluorescence detection to indirectly verify the modulation of the orientation of proteins bound to the surface. We studied the interaction of fluorescently tagged anti-IgG with surface immobilized IgG controlled by electric field. Our study demonstrates that the use of electric field can result in more than 100% enhancement in signal-to-noise ratio compared with normal physical adsorption. PMID:25650429

  12. Nonequilibrium forces between neutral atoms mediated by a quantum field

    SciTech Connect

    Behunin, Ryan O.; Hu, Bei-Lok

    2010-08-15

    We study forces between two neutral atoms, modeled as three-dimensional harmonic oscillators, arising from mutual influences mediated by an electromagnetic field but not from their direct interactions. We allow as dynamical variables the center-of-mass motion of the atom, its internal degrees of freedom, and the quantum field treated relativistically. We adopt the method of nonequilibrium quantum field theory which can provide a first-principles, systematic, and unified description including the intrinsic and induced dipole fluctuations. The inclusion of self-consistent back-actions makes possible a fully dynamical description of these forces valid for general atom motion. In thermal equilibrium we recover the known forces--London, van der Waals, and Casimir-Polder--between neutral atoms in the long-time limit. We also reproduce a recently reported force between atoms when the system is out of thermal equilibrium at late times. More noteworthy is the discovery of the existence of a type of (or identification of the source of some known) interatomic force which we call the ''entanglement force,'' originating from the quantum correlations of the internal degrees of freedom of entangled atoms.

  13. Interaction Forces Between Multiple Bodies in a Magnetic Field

    NASA Technical Reports Server (NTRS)

    Joffe, Benjamin

    1996-01-01

    Some of the results from experiments to determine the interaction forces between multiple bodies in a magnetic field are presented in this paper. It is shown how the force values and the force directions depend on the configuration of the bodies, their relative positions to each other, and the vector of the primary magnetic field. A number of efficient new automatic loading and assembly machines, as well as manipulators and robots, have been created based on the relationship between bodies and magnetic fields. A few of these patented magnetic devices are presented. The concepts involved open a new way to design universal grippers for robot and other kinds of mechanisms for the manipulation of objects. Some of these concepts can be used for space applications.

  14. Water-Silica Force Field for Simulating Nanodevices

    PubMed Central

    Cruz-Chu, Eduardo R.; Aksimentiev, Aleksei; Schulten, Klaus

    2008-01-01

    Amorphous silica is an inorganic material that is central for many nanotechnology appplications, such as nanoelectronics, microfluidics, and nanopore technology. In order to use molecular dynamics (MD) simulations to study the behavior of biomolecules with silica, we developed a force field for amorphous silica surfaces based on their macroscopic wetting properties that is compatible with the CHARMM force field and TIP3P water model. The contact angle of a water droplet with silica served as a criterion to tune the intermolecular interactions. The resulting force field was used to study the permeation of water through silica nanopores, illustrating the influence of the surface topography and the intermolecular parameters on permeation kinetics. We find that minute modeling of the amorphous surface is critical for MD studies, since the particular arrangement of surface atoms controls sensitively electrostatic interactions between silica and water. PMID:17064100

  15. Transferable force fields for adsorption of small gases in zeolites.

    PubMed

    Martin-Calvo, A; Gutiérrez-Sevillano, J J; Parra, J B; Ania, C O; Calero, S

    2015-10-01

    We provide transferable force fields for oxygen, nitrogen, and carbon monoxide that are able to reproduce experimental adsorption in both pure silica and alumino-substituted zeolites at cryogenic and high temperatures. The force field parameters can be combined with those previously reported for carbon dioxide, methane, and argon, opening the possibility for studying mixtures of interest containing the six components. Using these force field parameters we obtained some adsorption isotherms at cryogenic temperatures that at first sight were in discrepancies with experimental values for certain molecules and structures. We attribute these discrepancies to the sensitiveness of the equipment and to kinetic impedimenta that can lead to erratic results. Additional problems can be found during simulations when extra-framework cations are present in the system as their lack of mobility at low temperatures could lead to kinetic effects that hinder experimental adsorption. PMID:26313242

  16. Force-free field model of ball lightning

    NASA Astrophysics Data System (ADS)

    Tsui, K. H.

    2001-03-01

    Due to the nature that the force-free magnetic field, whose current carried by the conducting plasma is everywhere parallel to the magnetic field it generates, is the minimum energy configuration under the constraint of magnetic helicity conservation, ball lightning is considered as a self-organized phenomenon with a plasma fireball immersed in a spherical force-free magnetic field. Since this field does not exert force on the plasma, the plasma pressure, by itself, is in equilibrium with the surrounding environment, and the force-free magnetic field can take on any value without affecting the plasma. Due to this second feature, singular solutions of the magnetic field that are otherwise excluded are allowed, which enable a large amount of energy to be stored to sustain the ball lightning. The singularity is truncated only by the physical limit of current density that a plasma can carry. Scaling the customary soccer-size fireball to larger dimensions could account for day and night sightings of luminous objects in the sky.

  17. Electric Eels Concentrate Their Electric Field to Induce Involuntary Fatigue in Struggling Prey.

    PubMed

    Catania, Kenneth C

    2015-11-16

    Nature is replete with predator venoms that immobilize prey by targeting ion channels. Electric eels (Electrophorus electricus) take a different tactic to accomplish the same end. Striking eels emit electricity in volleys of 1 ms, high-voltage pulses. Each pulse is capable of activating prey motor neuron efferents, and hence muscles. In a typical attack, eel discharges cause brief, immobilizing tetanus, allowing eels to swallow small prey almost immediately. Here I show that when eels struggle with large prey or fish held precariously, they commonly curl to bring their own tail to the opposite side of prey, sandwiching it between the two poles of their powerful electric organ. They then deliver volleys of high-voltage pulses. Shortly thereafter, eels juggle prey into a favorable position for swallowing. Recordings from electrodes placed within prey items show that this curling behavior at least doubles the field strength within shocked prey, most likely ensuring reliable activation of the majority of prey motor neurons. Simulated pulse trains, or pulses from an eel-triggered stimulator, applied to a prey muscle preparations result in profound muscle fatigue and loss of contractile force. Consistent with this result, video recordings show that formerly struggling prey are temporarily immobile after this form of attack, allowing the manipulation of prey that might otherwise escape. These results reveal a unique use of electric organs to a unique end; eels superimpose electric fields from two poles, ensuring maximal remote activation of prey efferents that blocks subsequent prey movement by inducing involuntary muscle fatigue. PMID:26521183

  18. Design and development of scanning eddy current force microscopy for characterization of electrical, magnetic and ferroelectric properties with nanometer resolution

    NASA Astrophysics Data System (ADS)

    Nalladega, Vijayaraghava

    This dissertation describes the design and development of a new high-resolution electrical conductivity imaging technique combining the basic principles of eddy currents and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents induced in the sample are detected and measured with a magnetic tip attached to the AFM cantilever. The interaction of eddy currents with the magnetic tip-cantilever is theoretically modeled. The model is then used to estimate the eddy current forces generated in a typical metallic material placed in induced current field. The magnitude of the eddy current force is directly proportional to the electrical conductivity of the sample. The theoretical eddy current forces are used to design a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the development of a high-resolution, high sensitivity electrical conductivity imaging technique. The technique is used to experimentally measure eddy current forces in metals of different conductivities and compared with theoretical and finite element models. The experimental results show that the technique is capable of measuring pN range eddy current forces. The experimental eddy current forces are used to determine the electrical resistivity of a thin copper wire and the experimental value agrees with the bulk resistivity of copper reported in literature. The imaging capabilities of the new technique are demonstrated by imaging the electrical conductivity variations in a composite sample and a dual-phase titanium alloy in lift mode AFM. The results indicate that this technique can be used to detect very small variations in electrical conductivity. The spatial resolution of the technique is determined to be about 25 nm by imaging carbon nanofibers reinforced in polymer matrix. Since AFM is extensively used to characterize nanomaterials, the newly developed technique is used to characterize metallic nanoparticles. The results showed for the first time that it is possible to image helicons in nanometallic particles at low electromagnetic frequencies using an AFM. The theoretical analysis of the helicons in nanostructured materials is presented using the concept of effective mass of electrons. The primary objective of the research work reported in this dissertation is to develop a high-resolution electrical conductivity imaging system. However, the interaction of induced currents with different materials gives rise to different interaction forces. If an appropriate probe and an imaging mode are used, different material properties can be characterized using the same experimental setup. Therefore, in this study, magneto-acoustic, magnetic and dielectric properties of materials placed in induced current fields are studied. The modifications necessary to image these properties are discussed in detail. The advantages, limitations and applications of the new methodology are discussed.

  19. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Electric locks, force drop type; where required. 236.10 Section 236.10 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Rules and Instructions: All Systems General § 236.10 Electric locks, force drop type; where...

  20. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Electric locks, force drop type; where required. 236.10 Section 236.10 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Rules and Instructions: All Systems General § 236.10 Electric locks, force drop type; where...

  1. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Electric locks, force drop type; where required. 236.10 Section 236.10 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Rules and Instructions: All Systems General § 236.10 Electric locks, force drop type; where...

  2. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Electric locks, force drop type; where required. 236.10 Section 236.10 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Rules and Instructions: All Systems General § 236.10 Electric locks, force drop type; where...

  3. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Electric locks, force drop type; where required. 236.10 Section 236.10 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Rules and Instructions: All Systems General § 236.10 Electric locks, force drop type; where...

  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. Electric Field Quench, Equilibration and Universal Behavior

    E-print Network

    Ali-Akbari, M; Sepangi, H R

    2015-01-01

    We study electric field quench in N=2 strongly coupled gauge theory, using the AdS/CFT correspondence. To do so, we consider the aforementioned system which is subjected to a time-dependent electric field indicating an out of equilibrium system. Defining the equilibration time t_{eq}, at which the system relaxes to its final equilibrium state after injecting the energy, we find that the rescaled equilibriation time k^{-1}t_{eq} decreases as the transition time k increases. Therefore, we expect that for sufficiently large transition time, k ->infinity, the relaxation of the system to its final equilibrium can be an adiabatic process. On the other hand, we observe a universal behavior for the fast quenches, k universalization process which seems to be a typical feature of all strongly coupled gauge theories th...

  6. Electric Field Quench, Equilibration and Universal Behavior

    E-print Network

    M. Ali-Akbari; S. Amiri-Sharifi; H. R. Sepangi

    2015-04-14

    We study electric field quench in N=2 strongly coupled gauge theory, using the AdS/CFT correspondence. To do so, we consider the aforementioned system which is subjected to a time-dependent electric field indicating an out of equilibrium system. Defining the equilibration time t_{eq}, at which the system relaxes to its final equilibrium state after injecting the energy, we find that the rescaled equilibriation time k^{-1}t_{eq} decreases as the transition time k increases. Therefore, we expect that for sufficiently large transition time, k ->infinity, the relaxation of the system to its final equilibrium can be an adiabatic process. On the other hand, we observe a universal behavior for the fast quenches, k universalization process which seems to be a typical feature of all strongly coupled gauge theories that admit a gravitational dual.

  7. Electric Field and Humidity Trigger Contact Electrification

    NASA Astrophysics Data System (ADS)

    Zhang, Yanzhen; Pähtz, Thomas; Liu, Yonghong; Wang, Xiaolong; Zhang, Rui; Shen, Yang; Ji, Renjie; Cai, Baoping

    2015-01-01

    Here, we study the old problem of why identical insulators can charge one another on contact. We perform several experiments showing that, if driven by a preexisting electric field, charge is transferred between contacting insulators. This transfer happens because the insulator surfaces adsorb small amounts of water from a humid atmosphere. We believe the electric field then separates positively from negatively charged ions prevailing within the water, which we believe to be hydronium and hydroxide ions, such that at the point of contact, positive ions of one insulator neutralize negative ions of the other one, charging both of them. This mechanism can explain for the first time the observation made four decades ago that wind-blown sand discharges in sparks if and only if a thunderstorm is nearby.

  8. Electric Field and Humidity Trigger Contact Electrification

    E-print Network

    Yanzhen Zhang; Thomas Pähtz; Yonghong Liu; Xiaolong Wang; Rui Zhang; Yang Shen; Renjie Ji; Baoping Cai

    2015-01-14

    Here, we study the old problem of why identical insulators can charge one another on contact. We perform several experiments showing that, if driven by a preexisting electric field, charge is transferred between contacting insulators. This happens because the insulator surfaces adsorb small amounts of water from a humid atmosphere. We believe the electric field then separates positively from negatively charged ions prevailing within the water, which we believe to be hydronium and hydroxide ions, such that at the point of contact, positive ions of one insulator neutralize negative ions of the other one, charging both of them. This mechanism can explain for the first time the observation made four decades ago that wind-blown sand discharges in sparks if and only if a thunderstorm is nearby.

  9. Electric Field and Humidity Trigger Contact Electrification

    E-print Network

    Zhang, Yanzhen; Liu, Yonghong; Wang, Xiaolong; Zhang, Rui; Shen, Yang; Ji, Renjie; Cai, Baoping

    2015-01-01

    Here, we study the old problem of why identical insulators can charge one another on contact. We perform several experiments showing that, if driven by a preexisting electric field, charge is transferred between contacting insulators. This happens because the insulator surfaces adsorb small amounts of water from a humid atmosphere. We believe the electric field then separates positively from negatively charged ions prevailing within the water, which we believe to be hydronium and hydroxide ions, such that at the point of contact, positive ions of one insulator neutralize negative ions of the other one, charging both of them. This mechanism can explain for the first time the observation made four decades ago that wind-blown sand discharges in sparks if and only if a thunderstorm is nearby.

  10. ON THE FORCE-FREE NATURE OF PHOTOSPHERIC SUNSPOT MAGNETIC FIELDS AS OBSERVED FROM HINODE (SOT/SP)

    SciTech Connect

    Tiwari, Sanjiv Kumar

    2012-01-01

    A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic fields (computed from the force-free parameter {alpha}), and any kind of extrapolation, heavily hinges on the force-free approximation of the photospheric sunspot magnetic fields. Thus, it is of vital importance to inspect the force-free behavior of sunspot magnetic fields. The force-free nature of sunspot magnetic fields has been examined earlier by some researchers, ending with incoherent results. Accurate photospheric vector field measurements with high spatial resolution are required to inspect the force-free nature of sunspots. For this purpose, we use several vector magnetograms of high spatial resolution obtained from the Solar Optical Telescope/Spectro-Polarimeter on board Hinode. Both the necessary and sufficient conditions for force-free nature are examined by checking the global and local nature of equilibrium magnetic forces over sunspots. We find that sunspot magnetic fields are not very far from the force-free configuration, although they are not completely force-free on the photosphere. The umbral and inner penumbral fields are more force-free than the middle and outer penumbral fields. During their evolution, sunspot magnetic fields are found to maintain their proximity to force-free field behavior. Although a dependence of net Lorentz force components is seen on the evolutionary stages of the sunspots, we do not find a systematic relationship between the nature of sunspot magnetic fields and the associated flare activity. Further, we examine whether the fields at the photosphere follow linear or nonlinear force-free conditions. After examining this in various complex and simple sunspots, we conclude that, in either case, photospheric sunspot magnetic fields are closer to satisfying the nonlinear force-free field approximation.

  11. Manipulation of nano-entities in suspension by electric fields

    NASA Astrophysics Data System (ADS)

    Fan, Donglei

    Nanoscale entities, including nanospheres, nanodisks, nanorings, nanowires and nanotubes are potential building blocks for nanoscale devices. Among them, nanowires is an important type of nanoparticles, due to the potential application in microelectronics and bio-diagnosis. Manipulation of nanowires in suspension has been a formidable problem. As described in this thesis, using AC electric fields applied to strategically designed microelectrodes, nanowires in suspension can be driven to align, to chain, to accelerate in directions parallel and perpendicular to its orientation, to concentrate onto designated places, and to disperse in a controlled manner with high efficiency despite an extremely low Reynolds number at the level of 10-5. Randomly oriented nanowires in suspension can be rapidly assembled into extended nonlinear structures within seconds. We show that both the electric field and its gradient play the essential roles of aligning and transporting the nanowires into scaffolds according to the electric field distributions inherent to the geometry of the microelectrodes. The assembling efficiency depends strongly on the frequency of the applied AC voltages and varies as square of the voltage. Furthermore, nanowires have been rotated by AC electric fields applied to strategically designed electrodes. The rotation of the nanowires can be instantly switched on or off with precisely controlled rotation speed (to at least 25000 rpm), definite chirality, and total angle of rotation. This new method has been used to controllably rotate magnetic and non-magnetic nanowires as well as multi-wall carbon nanotubes. We have also produced a micromotor using a rotating nanowire that can drive particles into circular motion. This has application to microfluidic devices, micro-stirrers, and micro electromechanical systems (MEMS). To move and place nanowires onto designated locations with high precision, electrophoretic force has been combined with dielectrophoretic force to transport charged Au nanowires with length longer than 4 mum. The surface of Au nanowires has been chemical functionalized by either positive or negative charges. High frequency AC electric field has been applied to align and fix the orientation of the charged nanowires, though not to induce any motions, whereas a small DC voltage causes linear motion. The velocity of nanowires increases linearly with the DC electric field. The moving direction can be either parallel or perpendicular to the orientation of nanowires. Nanowires modified with different charges behave differently due to the electroosmosis flow induced by the DC electric field on the negatively charged quartz substrate. The zeta potential of quartz surface and the ratio of Stokes coefficients for longitudinal nano-entities suspended in a low Reynolds number regime (< 10-5) has been determined. Due to the small size of the nanowires, the nanowires suspended in liquids such as DI water are in extremely low Reynolds number regime (< 10-5). Manipulation due to DEP and EP forces are versatile and precise. Nanowires have been set into motion with prescribed tracks, such as squares and zigzags. The manipulation is also so precise that oppositely charged nanowires with radius of 150 nm have been moved to contact and connected end to end. A nanowire clipper have been assembled by this technique and set into oscillation. This method is not only applicable to nanowires, it has been successfully applied to multiwall carbon nanotubes as well. To demonstrate the complete control and flexibility of manipulating nanoparticles by E field, we have programmed nanowires to dance with music by Mozart with regard to clearly demonstrating the versatility of manipulating small entities of metallic, semiconductor, and biological materials. This work has been conducted under the guidance of the author's thesis advisors, Prof. Robert C. Cammarata, chair of the Department of Materials Science and Engineering of the Johns Hopkins University, and Prof. Chia-Ling Chien in the Department of Physics and Astronomy, and the

  12. Observations of large transient magnetospheric electric fields

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Heppner, J. P.

    1977-01-01

    Transient electric field events were studied by means of the long double-probe instrumentation carried by the Imp 6 satellite, and nine clearly defined exceptionally large amplitude events are described. The events were observed in the midnight sector at geocentric distances of 3.5 to 5.5 earth radii at middle latitudes within a magnetic L shell range of 4.8 to 7.5; the duration is from one to several minutes with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions and are often associated with negative dH/dt excursions. The magnetospheric motions calculated for these electric fields indicate a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity. It is likely that the transient electric fields are responsible for the impulsive acceleration and injection of plasma to populate the outer radiation belt.

  13. Forced cooling of underground electric power transmission lines : design manual

    E-print Network

    Brown, Jay A.

    1978-01-01

    The methodology utilized for the design of a forced-cooled pipe-type underground transmission system is presented. The material is divided into three major parts: (1) The Forced-cooled Pipe-Type Underground Transmission ...

  14. Gravitational self-force in non-vacuum spacetimes: an effective field theory derivation

    E-print Network

    Peter Zimmerman

    2015-07-13

    In this paper we investigate the motion of small compact objects in non-vacuum spacetimes using methods from effective field theory in curved spacetime. Although a vacuum formulation is sufficient in many astrophysical contexts, there are applications such as the role of the self-force in enforcing cosmic-censorship in the context of the overcharging problem, which necessitate an extension into the non-vacuum regime. The defining feature of the self-force problem in non-vacuum spacetimes is the coupling between gravitational and non-gravitational field perturbations. The formulation of the self-force problem for non-vacuum spacetimes was recently provided in simultaneous papers by Zimmerman and Poisson [1] and Linz, Friedmann, Wiseman [2]. Here we distinguish ourselves by working with the effective action rather than the field equations. The formalism utilizes the multi-index notation developed by Zimmerman and Poisson [1] to accommodate the coupling between the different fields. Using dimensional regularization, we arrive at a finite expression for the local self-force expressed in terms of multi-index quantities evaluated in the background spacetime. We then apply the formalism to compute the coupled gravitational self-force in two explicit cases. First, we calculate the self-force on a massive particle possessing scalar charge and moving in an scalarvac spacetime. We then derive an expression for the self-force on an electrically charged, massive particle moving in an electrovac spacetime. In both cases, the force is expressed as a sum of local terms involving tensors defined in the background spacetime and evaluated at the current position of the particle, as well as tail integrals that depend on the past history of the particle.

  15. Mitigated-force carriage for high magnetic field environments

    SciTech Connect

    Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Murphy, Bart L

    2014-05-20

    A carriage for high magnetic field environments includes a first work-piece holding means for holding a first work-piece, the first work-piece holding means being disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla. The first work-piece holding means is further disposed in operable connection with a second work-piece holding means for holding a second work-piece so that, as the first work-piece is inserted into the magnetic field, the second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

  16. Einstein's osmotic equilibrium of colloidal suspensions in conservative force fields

    NASA Astrophysics Data System (ADS)

    Fu, Jinxin; Ou-Yang, H. Daniel

    2014-09-01

    Predicted by Einstein in his 1905 paper on Brownian motion, colloidal particles in suspension reach osmotic equilibrium under gravity. The idea was demonstrated by J.B. Perrin to win Nobel Prize in Physics in 1926. We show Einstein's equation for osmotic equilibrium can be applied to colloids in a conservative force field generated by optical gradient forces. We measure the osmotic equation of state of 100nm Polystyrene latex particles in the presence of KCl salt and PEG polymer. We also obtain the osmotic compressibility, which is important for determining colloidal stability and the internal chemical potential, which is useful for predicting the phase transition of colloidal systems. This generalization allows for the use of any conservative force fields for systems ranging from colloidal systems to macromolecular solutions.

  17. Electron transport in argon in crossed electric and magnetic fields

    PubMed

    Ness; Makabe

    2000-09-01

    An investigation of electron transport in argon in the presence of crossed electric and magnetic fields is carried out over a wide range of values of electric and magnetic field strengths. Values of mean energy, ionization rate, drift velocity, and diffusion tensor are reported here. Two unexpected phenomena arise; for certain values of electric and magnetic field we find regions where the swarm mean energy decreases with increasing electric fields for a fixed magnetic field and regions where swarm mean energy increases with increasing magnetic field for a fixed electric field. PMID:11088933

  18. Force, current and field effects in single atom manipulation

    E-print Network

    Braun, Kai-Felix

    Force, current and field effects in single atom manipulation K.-F. Braun , S.-W. Hla , N. Pertaya present a detailed investigation of the manipulation of Ag and Au atoms with a STM tip on the Ag(111 of the atom during manipulation. The threshold tunnelling resistance and tip-height to move a Au/Ag atom have

  19. Comparison of different force fields for the study of disaccharides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Eighteen empirical force fields and the semi-empirical quantum method PM3CARB-1 were compared for studying ß-cellobiose, a-maltose, and a-galabiose [a-D-Galp-(1'4)-a-D-Galp]. For each disaccharide, the energies of 54 conformers with differing hydroxymethyl, hydroxyl and glycosidic linkage orientatio...

  20. Force-Field Analysis: A Functional Management System

    ERIC Educational Resources Information Center

    Sanders, Stanley G.

    1977-01-01

    Force field analysis combines the advantages of the basic organization, objectivity, and science of systems theory and systems methods, with a simplicity and clarity that allows its mastery by policy-makers and administrators who are not specialists in engineering, data processing, or programming. (Author/IRT)

  1. Dynamics of drop formation in an electric field

    SciTech Connect

    Notz, P.K.; Basaran, O.A.

    1999-05-01

    The effect of an electric field on the formation of a drop of an inviscid, perfectly conducting liquid from a capillary which protrudes from the top plate of a parallel-plate capacitor into a surrounding dynamically inactive, insulating gas is studied computationally. This free boundary problem which is comprised of the surface Bernoulli equation for the transient drop shape and the Laplace equation for the velocity potential inside the drop and the electrostatic potential outside the drop is solved by a method of lines incorporating the finite element method for spatial discretization. The finite element algorithm employed relies on judicious use of remeshing and element addition to a two-region adaptive mesh to accommodate large domain deformations, and allows the computations to proceed until the thickness of the neck connecting an about to form drop to the rest of the liquid in the capillary is less than 0.1% of the capillary radius. The accuracy of the computations is demonstrated by showing that in the absence of an electric field predictions made with the new algorithm are in excellent agreement with boundary integral calculations and experimental measurements on water drops. Computational predictions of the primary drop volume and drop length at breakup are reported over a wide range of values of the ratios of electrical gravitational, and inertial forces to surface tension force. When the magnitude of the step change in field strength is small, the results of the new transient calculations accord well with those of an earlier stability analysis and thereby provide yet another testament to the accuracy of the new algorithm.

  2. Selective and directed growth of silicon nanowires by tip-enhanced local electric field

    NASA Astrophysics Data System (ADS)

    Ryu, Sang-gil; Kim, Eunpa; Hwang, David J.; Grigoropoulos, Costas P.

    2015-10-01

    We present a method to trigger highly selective and directed growth of individual silicon nanowires based on an electrically biased atomic force microscope (AFM) tip. The biased tip affects the nanowire growth behavior right from the initial stage. In particular, the locally intensified electric field at the AFM tip apex assists the dissociation of the precursor gas molecules and exerts augmented electrostatic force on the catalyst/NW assembly. Therefore, the electrically biased tip can be a candidate tool for the direct synthesis/integration of semiconductor nanomaterials on temperature-sensitive substrates.

  3. GLYCAM06: A Generalizable Biomolecular Force Field. Carbohydrates

    PubMed Central

    KIRSCHNER, KARL N.; YONGYE, AUSTIN B.; TSCHAMPEL, SARAH M.; GONZÁLEZ-OUTEIRIÑO, JORGE; DANIELS, CHARLISA R.; FOLEY, B. LACHELE; WOODS, ROBERT J.

    2015-01-01

    A new derivation of the GLYCAM06 force field, which removes its previous specificity for carbohydrates, and its dependency on the AMBER force field and parameters, is presented. All pertinent force field terms have been explicitly specified and so no default or generic parameters are employed. The new GLYCAM is no longer limited to any particular class of biomolecules, but is extendible to all molecular classes in the spirit of a small-molecule force field. The torsion terms in the present work were all derived from quantum mechanical data from a collection of minimal molecular fragments and related small molecules. For carbohydrates, there is now a single parameter set applicable to both ?- and ?-anomers and to all monosaccharide ring sizes and conformations. We demonstrate that deriving dihedral parameters by fitting to QM data for internal rotational energy curves for representative small molecules generally leads to correct rotamer populations in molecular dynamics simulations, and that this approach removes the need for phase corrections in the dihedral terms. However, we note that there are cases where this approach is inadequate. Reported here are the basic components of the new force field as well as an illustration of its extension to carbohydrates. In addition to reproducing the gas-phase properties of an array of small test molecules, condensed-phase simulations employing GLYCAM06 are shown to reproduce rotamer populations for key small molecules and representative biopolymer building blocks in explicit water, as well as crystalline lattice properties, such as unit cell dimensions, and vibrational frequencies. PMID:17849372

  4. Electric field-free gas breakdown in explosively driven generators

    SciTech Connect

    Shkuratov, Sergey I.; Baird, Jason; Talantsev, Evgueni F.; Altgilbers, Larry L.

    2010-07-15

    All known types of gas discharges require an electric field to initiate them. We are reporting on a unique type of gas breakdown in explosively driven generators that does not require an electric field.

  5. Spontaneous electric fields in solid carbon monoxide.

    PubMed

    Lasne, Jérôme; Rosu-Finsen, Alexander; Cassidy, Andrew; McCoustra, Martin R S; Field, David

    2015-11-28

    Reflection-absorption infrared spectroscopy (RAIRS) is shown to provide a means of observing the spontelectric phase of matter, the defining characteristic of which is the occurrence of a spontaneous and powerful static electric field within a film of material. The presence of such a field is demonstrated here through the study of longitudinal-transverse optical splitting in RAIR spectra in films of carbon monoxide, based upon the deposition temperature dependence of this splitting. Analysis of spectral data, in terms of the vibrational Stark effect, allows the measurement of the polarization of spontelectric films, showing for example that solid carbon monoxide at 20 K may maintain a spontelectric field of 3.78 × 10(7) V m(-1), representing a polarization of 3.34 × 10(-4) cm(-2). We comment on the astrophysical implications of polarized carbon monoxide ices, on the surface of cosmic grains in star-forming regions. PMID:26419192

  6. Electrical Grounding - a Field for Geophysicists and Electrical Engineers Partnership

    NASA Astrophysics Data System (ADS)

    Freire, P. F.; Pane, E.; Guaraldo, N.

    2012-12-01

    Technology for designing ground electrodes for high-voltage direct current transmission systems (HVDC) has being using in the last years, deep soil models based on a wide range of geophysical methods. These models shall include detailed representation of shallow soil, down to 100 meters, in order to allow the evaluation of the soil conditions where the ground electrodes will be buried. Also deep soil models are needed, to be used for the interference studies, which shall represent a soil volume of about 15 km deep and a surface area of about 15 to 30 km radius. Large facilities for power plants (hydroelectric and wind farms, for example) and industrial complexes (such as petrochemical plants) has become usual at the current stage of Brazil industrialization. Grounding mats for these facilities are made of a buried cooper mesh, interconnected to a wide variety of metallic masses, such as steel reinforced concrete foundations, ducts in general etc. These grounding systems may present dimensions with the order of hundreds of meters, and, at least in Brazil, are usually calculated by using electrical resistivity soil models, based on short spacing Wenner measurements (with maximum spacing of about 64 m.). The soil model shall be the best possible representation of the environment in which the grounding electrodes are immersed, for the purpose of calculation of resistance or for digital simulation. The model to be obtained is limited by the amount and quality of soil resistivity measurements are available, and the resources to be used in the calculations and simulations. Geophysics uses a wide range of technologies for exploring subsoil, ranging from surface measurements to wells logging - seismic, gravimetric, magnetic, electrical, electromagnetic and radiometric. The electrical and electromagnetic methods includes various measurement techniques (Wenner, Schlumberger, TDEM, Magneto-telluric etc.), which together allow the development of complex resistivity soil models, layered stratified or showing lateral variations, ranging down to several tens of kilometers deep, reaching the crust-mantle interface (typically with the order of 30-40 km). This work aims to analyze the constraints of the current soil models being used for grounding electrodes design, and suggests the need of a soil modeling methodology compatible with large grounding systems. Concerning the aspects related to soil modeling, electrical engineers need to get aware of geophysics resources, such as: - geophysical techniques for soil electrical resistivity prospection (down to about 15 kilometers deep); and - techniques for converting field measured data, from many different geophysical techniques, into adequate soil models for grounding grid simulation. It is also important to equalize the basic knowledge for the professionals that are working together for the specific purpose of soil modeling for electrical grounding studies. The authors have experienced the situation of electrical engineers working with geophysicists, but it was not clear for the latter the effective need of the electrical engineers, and for the engineers it was unknown the available geophysical resources, and also, what to do convert the large amount of soil resistivity data into a reliable soil model.

  7. Vectorial electric field measurement using isotropic electro-optic crystals

    SciTech Connect

    Gaborit, G.; Coutaz, J.-L.; Duvillaret, L.

    2007-06-11

    The authors present a two-component electric field measurement using a single electro-optic crystal and a single laser probe beam. This vectorial electric field measurement based on polarization state modulation is possible using isotropic electro-optic crystals for which directions of the eigendielectric axes are directly linked to the direction of the applied electric field. The proposed method can be used either for continuous wave or single shot measurements as the two electric field components are measured simultaneously.

  8. A planar lipid bilayer in an electric field: membrane instability, flow field and electrical impedance

    E-print Network

    Falko Ziebert; David Lacoste

    2011-02-22

    For many biotechnological applications it would be useful to better understand the effects produced by electric fields on lipid membranes. This review discusses several aspects of the electrostatic properties of a planar lipid membrane with its surrounding electrolyte in a normal DC or AC electric field. In the planar geometry, the analysis of electrokinetic equations can be carried out quite far, allowing to characterize analytically the steady state and the dynamics of the charge accumulation in the Debye layers, which results from the application of the electric field. For a conductive membrane in an applied DC electric field, we characterize the corrections to the elastic moduli, the appearance of a membrane undulation instability and the associated flows which are built up near the membrane. For a membrane in an applied AC electric field, we analytically derive the impedance from the underlying electrokinetic equations. We discuss different relevant effects due to the membrane conductivity or due to the bulk diffusion coefficients of the ions. Of particular interest is the case where the membrane has selective conductivity for only one type of ion. These results, and future extensions thereof, should be useful for the interpretation of impedance spectroscopy data used to characterize e.g. ion channels embedded in planar bilayers.

  9. Developing accurate molecular mechanics force fields for conjugated molecular systems.

    PubMed

    Do, Hainam; Troisi, Alessandro

    2015-10-14

    A rapid method to parameterize the intramolecular component of classical force fields for complex conjugated molecules is proposed. The method is based on a procedure of force matching with a reference electronic structure calculation. It is particularly suitable for those applications where molecular dynamics simulations are used to generate structures that are therefore analysed by electronic structure methods, because it is possible to build force fields that are consistent with electronic structure calculations that follow classical simulations. Such applications are commonly encountered in organic electronics, spectroscopy of complex systems and photobiology (e.g. photosynthetic systems). We illustrate the method by parameterizing the force fields of a molecule used in molecular semiconductors (2,2-dicyanovinyl-capped S,N-heteropentacene or DCV-SN5), a polymeric semiconductor (thieno[3,2-b]thiophene-diketopyrrolopyrrole TT-DPP) and a chromophore embedded in a protein environment (15,16-dihydrobiliverdin or DBV) where several hundreds of parameters need to be optimized in parallel. PMID:26349916

  10. Atomistic force field for alumina fit to density functional theory

    SciTech Connect

    Sarsam, Joanne; Thomas Young Centre, Imperial College London, London SW7 2AZ ; Finnis, Michael W.; Tangney, Paul; Thomas Young Centre, Imperial College London, London SW7 2AZ; Department of Physics, Imperial College London, London SW7 2AZ

    2013-11-28

    We present a force field for bulk alumina (Al{sub 2}O{sub 3}), which has been parametrized by fitting the energies, forces, and stresses of a large database of reference configurations to those calculated with density functional theory (DFT). We use a functional form that is simpler and computationally more efficient than some existing models of alumina parametrized by a similar technique. Nevertheless, we demonstrate an accuracy of our potential that is comparable to those existing models and to DFT. We present calculations of crystal structures and energies, elastic constants, phonon spectra, thermal expansion, and point defect formation energies.

  11. Lorentz and "apparent" transformations of the electric and magnetic fields

    E-print Network

    Tomislav Ivezic

    2006-07-21

    It is recently discovered that the usual transformations of the three-dimensional (3D) vectors of the electric and magnetic fields differ from the Lorentz transformations (LT) (boosts) of the corresponding 4D quantities that represent the electric and magnetic fields. In this paper, using geometric algebra formalism, this fundamental difference is examined representing the electric and magnetic fields by bivectors.

  12. Force enhancement following muscle stretch of electrically stimulated and voluntarily activated human adductor pollicis

    PubMed Central

    Lee, Hae-Dong; Herzog, Walter

    2002-01-01

    For electrically stimulated muscles, it has been observed that maximal muscle force during and after stretch is substantially greater than the corresponding isometric force. However, this observation has not been made for human voluntary contractions. We investigated the effects of active muscle stretch on muscle force production for in vivo human adductor pollicis (n = 12) during maximal voluntary contractions and electrically induced contractions. Peak forces during stretch, steady-state isometric forces following stretch, and passive forces following muscle deactivation were compared to the corresponding isometric forces obtained at optimal muscle length. Contractions with different stretch magnitudes (10, 20, and 30 deg at a constant speed of 10 deg s?1) and different speeds (10, 20, and 60 deg s?1 over a range of 30 deg) were performed in triplicate in a random order, balanced design. We found three novel results: (i) there was steady-state force enhancement following stretch in voluntarily contracted muscles; (ii) some force enhancement persisted following relaxation of the muscle and (iii) force enhancement, for some stretch conditions, exceeded the maximum isometric force at optimal muscle length. We conclude from these results that voluntary muscle contraction produces similar force enhancement to that observed in the past with electrically stimulated preparations. Therefore, steady-state force enhancement may play a role in everyday movements. Furthermore, these results suggest that non-uniformities in sarcomere length do not, at least not exclusively, account for the force enhancement following active muscle stretch, and that the stretch magnitude-dependent passive force enhancement observed here may be responsible for the enhancement of force above the isometric reference force at optimal muscle length. PMID:12433972

  13. Theoretical and experimental study of inclusion removal from molten metal under an alternating electromagnetic force field

    NASA Astrophysics Data System (ADS)

    Patel, Ashish D.

    One of the emerging technologies for the production of clean metals is electromagnetic filtration. This dissertation describes the work done on the theory of electromagnetic separation in alternating electromagnetic fields together with the experimental results obtained on the removal of silica particles from molten aluminum from an induced current separator. Analytical expressions have been developed for describing the electric and magnetic fields, and the separation force for a spherical particle in an infinite conducting medium subjected to an alternating magnetic field. It was found that the magnitude and direction of the separation force depends on the ratio of electrical conductivity of the fluid and the sphere as well as the frequency of the applied field. Analytical expressions were also developed for the MHD flow in and around the particle. The solutions revealed two characteristic secondary flows; one is driven by the distortion of the electric current around the particle, while the other is driven by forces resulting from the interaction of the current and the applied magnetic field. The results of the experimental study on removal of silica particles from aluminum showed complete removal of the particles from the melt, and the rate of inclusion removal was found to depend on the applied magnetic field strength and the particle size. A mathematical model has been developed for describing the rate of inclusion removal from the metal in the induced current separator. The model was found to accurately predict the measured removal rates. The effects of the processing parameters on time for complete removal of inclusions in induced current separators are discussed.

  14. Field measurement of basal forces generated by erosive debris flows

    USGS Publications Warehouse

    McCoy, S.W.; Tucker, G.E.; Kean, J.W.; Coe, J.A.

    2013-01-01

    It has been proposed that debris flows cut bedrock valleys in steeplands worldwide, but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows. Here we present and analyze measurements made using an automated sensor network, erosion bolts, and a 15.24?cm by 15.24?cm force plate installed in the bedrock channel floor of a steep catchment. These measurements allow us to quantify the distribution of basal forces from natural debris?flow events that incised bedrock. Over the 4?year monitoring period, 11 debris?flow events scoured the bedrock channel floor. No clear water flows were observed. Measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64?mm. The basal force during these erosive debris?flow events had a large?magnitude (up to 21?kN, which was approximately 50 times larger than the concurrent time?averaged mean force), high?frequency (greater than 1?Hz) fluctuating component. We interpret these fluctuations as flow particles impacting the bed. The resulting variability in force magnitude increased linearly with the time?averaged mean basal force. Probability density functions of basal normal forces were consistent with a generalized Pareto distribution, rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces. When the bed sediment thickness covering the force plate was greater than ~?20 times the median bed sediment grain size, no significant fluctuations about the time?averaged mean force were measured, indicating that a thin layer of sediment (~?5?cm in the monitored cases) can effectively shield the subjacent bed from erosive impacts. Coarse?grained granular surges and water?rich, intersurge flow had very similar basal force distributions despite differences in appearance and bulk?flow density. These results demonstrate that debris flows can have strong control on rates of steepland evolution and contribute to a foundation needed for modeling debris?flow incision stochastically.

  15. Extracting Nucleon Magnetic Moments and Electric Polarizabilities from Lattice QCD in Background Electric Fields

    SciTech Connect

    William Detmold, Brian Tiburzi, Andre Walker-Loud

    2010-03-01

    Nucleon properties are investigated in background electric fields. As the magnetic moments of baryons affect their relativistic propagation in constant electric fields, electric polarizabilities cannot be determined without knowledge of magnetic moments. We devise combinations of baryon two-point functions in external electric fields to isolate both observables. Using an ensemble of anisotropic gauge configurations with dynamical clover fermions, we demonstrate how magnetic moments and electric polarizabilities can be determined from lattice QCD simulations in background electric fields. We obtain results for both the neutron and proton. Our study is currently limited to electrically neutral sea quarks.

  16. Electric field induced Lyman-? emission of a hydrogen beam for electric field measurements.

    PubMed

    Chérigier-Kovacic, L; Ström, P; Lejeune, A; Doveil, F

    2015-06-01

    Electric field induced Lyman-? emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-? radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied. PMID:26133836

  17. Radial-Electric-Field Piezoelectric Diaphragm Pumps

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G.; Working, Dennis C.; Mossi, Karla; Castro, Nicholas D.; Mane, Pooma

    2009-01-01

    In a recently invented class of piezoelectric diaphragm pumps, the electrode patterns on the piezoelectric diaphragms are configured so that the electric fields in the diaphragms have symmetrical radial (along-the-surface) components in addition to through-the-thickness components. Previously, it was accepted in the piezoelectric-transducer art that in order to produce the out-of-plane bending displacement of a diaphragm needed for pumping, one must make the electric field asymmetrical through the thickness, typically by means of electrodes placed on only one side of the piezoelectric material. In the present invention, electrodes are placed on both sides and patterned so as to produce substantial radial as well as through-the-thickness components. Moreover, unlike in the prior art, the electric field can be symmetrical through the thickness. Tests have shown in a given diaphragm that an electrode configuration according to this invention produces more displacement than does a conventional one-sided electrode pattern. The invention admits of numerous variations characterized by various degrees of complexity. Figure 1 is a simplified depiction of a basic version. As in other piezoelectric diaphragm pumps of similar basic design, the prime mover is a piezoelectric diaphragm. Application of a suitable voltage to the electrodes on the diaphragm causes it to undergo out-of-plane bending. The bending displacement pushes a fluid out of, or pulls the fluid into, a chamber bounded partly by the diaphragm. Also as in other diaphragm pumps in general, check valves ensure that the fluid flows only in through one port and only out through another port.

  18. The impact of space electric field research on atmospheric studies

    NASA Technical Reports Server (NTRS)

    Mozer, F. S.

    1974-01-01

    Space measurements of electric fields have provided instrumentation for measuring atmospheric parameters and a better basis for understanding the electrical coupling between the magnetosphere and the atmosphere. Applications of an incoherent scatter radar (developed for ionospheric electric field research) to the measurement of atmospheric winds and turbulence and of Langmuir double probes (also developed for space research) for measurement of atmospheric electric fields are described. The increased knowledge of magnetospheric electric fields has focused attention on the electrical coupling between the magnetosphere and the atmosphere with conclusions that should considerably modify previous physical concepts in both domains.

  19. Electrostatic air filters generated by electric fields

    SciTech Connect

    Bergman, W.; Biermann, A.H.; Hebard, H.D.; Lum, B.Y.; Kuhl, W.D.

    1981-01-27

    This paper presents theoretical and experimental findings on fibrous filters converted to electrostatic operation by a nonionizing electric field. Compared to a conventional fibrous filter, the electrostatic filter has a higher efficiency and a longer, useful life. The increased efficiency is attributed to a time independent attraction between polarized fibers and charged, polarized particles and a time dependent attraction between charged fibers and charged, polarized particles. The charge on the fibers results from a dynamic process of charge accumulation due to the particle deposits and a charge dissipation due to the fiber conductivity.

  20. Impact of electric fields on honey bees

    SciTech Connect

    Bindokas, V.P.

    1985-01-01

    Biological effects in honey bee colonies under a 765-kV, 60-Hz transmission line (electric (E) field = 7 kV/m) were confirmed using controlled dosimetry and treatment reversal to replicate findings within the same season. Hives in the same environment but shielded from E field are normal, suggesting effects are caused by interaction of E field with the hive. Bees flying through the ambient E field are not demonstrably affected. Different thresholds and severity of effects were found in colonies exposed to 7, 5.5, 4.1, 1.8, and 0.65 to 0.85 kV/m at incremental distances from the line. Most colonies exposed at 7 kV/m failed in 8 weeks and failed to overwinter at greater than or equal to4.1 kV/m. Data suggest the limit of a biological effects corridor lies between 15 and 27 m (4.1 and 1.8 kV/m) beyond the outer phase of the transmission line. Mechanisms to explain colony disturbance fall into two categories, direct perception of enhanced in-hive E fields, and perception of shock from induced currents. The same effects induced in colonies with total-hive E-field exposure can be reproduced with shock or E-field exposure of worker bees in extended hive entranceways (= porches). Full-scale experiments demonstrate bee exposure to E fields including 100 kV/m under moisture-free conditions within a non-conductive porch causes no detectable effect on colony behavior. Exposure of bees on a conductive (e.g. wet) substrate produces been disturbance, increased mortality, abnormal propolization, and possible impairment of colony growth. Thresholds for effects caused by step-potential-induced currents are: 275-350 nA - disturbance of single bees; 600 nA - onset of abnormal propolization; and 900 nA - sting.

  1. The mechanical transduction of physiological strength electric fields.

    PubMed

    Hart, Francis X

    2008-09-01

    In this article it is proposed that electric fields of physiological strength (approximately 100 V/m) are transduced by the mechanical torque they exert on glycoproteins. The resulting mechanical signal is then transmitted to the cytoskeleton and propagated throughout the cell interior. This mechanical coupling is analyzed for transmembrane glycoproteins, such as integrins and the glycocalyx, and for glycoproteins in the extracellular matrix of cartilage. The applied torque is opposed by viscous fluid drag and restoring forces exerted by adjacent molecules in the membrane or cartilage. The resulting system represents a damped, driven harmonic oscillator. The amplitude of oscillation is constant at low frequencies, but falls off rapidly in the range 1-1000 Hz. The transition frequency depends on parameters such as the viscosity of the surrounding fluid and the restoring force exerted by the surrounding structure. The amplitude increases as the fourth power of the length of the transmembrane glycoproteins and as the square of the applied field. This process may operate in concert with other transduction mechanisms, such as the opening of voltage-gated channels and electrodiffusion/osmosis for DC fields. PMID:18381594

  2. Levitation forces of a bulk YBCO superconductor in gradient varying magnetic fields

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Gong, Y. M.; Wang, G.; Zhou, D. J.; Zhao, L. F.; Zhang, Y.; Zhao, Y.

    2015-09-01

    The levitation forces of a bulk YBCO superconductor in gradient varying high and low magnetic fields generated from a superconducting magnet were investigated. The magnetic field intensity of the superconducting magnet was measured when the exciting current was 90 A. The magnetic field gradient and magnetic force field were both calculated. The YBCO bulk was cooled by liquid nitrogen in field-cooling (FC) and zero-field-cooling (ZFC) condition. The results showed that the levitation forces increased with increasing the magnetic field intensity. Moreover, the levitation forces were more dependent on magnetic field gradient and magnetic force field than magnetic field intensity.

  3. Electric contributions to magnetic force microscopy response from graphene and MoS{sub 2} nanosheets

    SciTech Connect

    Li, Lu Hua Chen, Ying

    2014-12-07

    Magnetic force microscopy (MFM) signals have recently been detected from whole pieces of mechanically exfoliated graphene and molybdenum disulfide (MoS{sub 2}) nanosheets, and magnetism of the two nanomaterials was claimed based on these observations. However, non-magnetic interactions or artefacts are commonly associated with MFM signals, which make the interpretation of MFM signals not straightforward. A systematic investigation has been done to examine possible sources of the MFM signals from graphene and MoS{sub 2} nanosheets and whether the MFM signals can be correlated with magnetism. It is found that the MFM signals have significant non-magnetic contributions due to capacitive and electrostatic interactions between the nanosheets and conductive cantilever tip, as demonstrated by electric force microscopy and scanning Kevin probe microscopy analyses. In addition, the MFM signals of graphene and MoS{sub 2} nanosheets are not responsive to reversed magnetic field of the magnetic cantilever tip. Therefore, the observed MFM response is mainly from electric artefacts and not compelling enough to correlate with magnetism of graphene and MoS{sub 2} nanosheets.

  4. Controlling Positronium Annihilation with Electric Fields.

    PubMed

    Alonso, A M; Cooper, B S; Deller, A; Hogan, S D; Cassidy, D B

    2015-10-30

    We show that the annihilation dynamics of excited positronium (Ps) atoms can be controlled using parallel electric and magnetic fields. To achieve this, Ps atoms were optically excited to n=2 sublevels in fields that were adjusted to control the amount of short-lived and long-lived character of the resulting mixed states. Inclusion of the former offers a practical approach to detection via annihilation radiation, whereas the increased lifetimes due to the latter can be exploited to optimize resonance-enhanced two-photon excitation processes (e.g., 1^{3}S?2^{3}P?nS/nD), either by minimizing losses through intermediate state decay, or by making it possible to separate the excitation laser pulses in time. In addition, photoexcitation of mixed states with a 2^{3}S_{1} component represents an efficient route to producing long-lived pure 2^{3}S_{1} atoms via single-photon excitation. PMID:26565466

  5. Soil Identification using Field Electrical Resistivity Method

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Rosli, S.; Chitral, W. D.; Fauziah, A.; Azhar, A. T. S.; Aziman, M.; Ismail, B.

    2015-06-01

    Geotechnical site investigation with particular reference to soil identification was important in civil engineering works since it reports the soil condition in order to relate the design and construction of the proposed works. In the past, electrical resistivity method (ERM) has widely being used in soil characterization but experienced several black boxes which related to its results and interpretations. Hence, this study performed a field electrical resistivity method (ERM) using ABEM SAS (4000) at two different types of soils (Gravelly SAND and Silty SAND) in order to discover the behavior of electrical resistivity values (ERV) with type of soils studied. Soil basic physical properties was determine thru density (p), moisture content (w) and particle size distribution (d) in order to verify the ERV obtained from each type of soil investigated. It was found that the ERV of Gravelly SAND (278 ?m & 285 ?m) was slightly higher than SiltySAND (223 ?m & 199 ?m) due to the uncertainties nature of soils. This finding has showed that the results obtained from ERM need to be interpreted based on strong supported findings such as using direct test from soil laboratory data. Furthermore, this study was able to prove that the ERM can be established as an alternative tool in soil identification provided it was being verified thru other relevance information such as using geotechnical properties.

  6. Inhibition of brain tumor cell proliferation by alternating electric fields

    SciTech Connect

    Jeong, Hyesun; Oh, Seung-ick; Hong, Sunghoi E-mail: radioyoon@korea.ac.kr; Sung, Jiwon; Jeong, Seonghoon; Yoon, Myonggeun E-mail: radioyoon@korea.ac.kr; Koh, Eui Kwan

    2014-11-17

    This study was designed to investigate the mechanism by which electric fields affect cell function, and to determine the optimal conditions for electric field inhibition of cancer cell proliferation. Low-intensity (<2?V/cm) and intermediate-frequency (100–300 kHz) alternating electric fields were applied to glioblastoma cell lines. These electric fields inhibited cell proliferation by inducing cell cycle arrest and abnormal mitosis due to the malformation of microtubules. These effects were significantly dependent on the intensity and frequency of applied electric fields.

  7. Advancement of polarizable force field and its use for molecular modeling and design.

    PubMed

    Xu, Peijun; Wang, Jinguang; Xu, Yong; Chu, Huiying; Liu, Jiahui; Zhao, Meixia; Zhang, Depeng; Mao, Yingchen; Li, Beibei; Ding, Yang; Li, Guohui

    2015-01-01

    The most important requirement of biomolecular modeling is to deal with electrostatic energies. The electrostatic polarizability is an important part of electrostatic interaction for simulation systems. However, AMBER, CHARMM, OPLS, GROMOS, MMFF force fields etc. used in the past mostly apply fixed atomic center point charge to describe electrostatic energies, and are not sufficient for considering the influence of the electrostatic polarization. The emergence of polarizable force fields has solved this problem. In recent years, quickly developed polarizable force fields have involved a lot of fields. The chapter relating to polarizable force fields spread over several aspects. Firstly, we reviewed the history of the classical force fields and compared with polarizable force fields to elucidate the advancements of polarizable force fields. Secondly, it is introduced that the application of polarizable force fields to small molecules and biological macromolecules simulation, including molecular design. Finally, a brief development trend and perspective is given on rapidly growing polarizable force fields. PMID:25387957

  8. An electrohydraulic actuated ankle foot orthosis to generate force fields and to test proprioceptive reflexes during human walking.

    PubMed

    Noël, Martin; Cantin, Benoit; Lambert, Sébastien; Gosselin, Clément M; Bouyer, Laurent J

    2008-08-01

    The control of human walking can be temporarily modified by applying forces to the leg. To study the neural mechanisms underlying this adaptive capacity, a device delivering controlled forces and high-velocity displacements to the ankle was designed. A new solution, involving a closed circuit hydraulic system composed of two cylinders (master-slave) mutually connected by hoses and controlled by an electric motor was preferred over classical mechanical/electrical approaches. The slave cylinder delivers desired torques to the ankle using a light weight, custom-designed ankle-foot orthosis. This electrohydraulic orthosis (EHO) can produce several types of force fields during walking, including constant, position-dependent, and phase-dependent. With phase-dependent force fields, active torque cancellation maintains low-residual torques ( < or = 1.85 Nm root mean square) outside of the zone of force application for walking speeds ranging from 0.2 to 4.5 km/h. Rapid ankle stretches/unloads ( > 200 degrees/s) can also be produced alone or during force field application, and elicited proprioceptive reflexes in ankle muscles. In conclusion, the EHO is capable of delivering controlled force fields and of activating proprioceptive reflexes during human walking. It will provide the flexibility needed to test the adaptability of healthy and pathological gait control, and to address some of its underlying neural mechanisms. PMID:18701385

  9. Saturation of the Electric Field Transmitted to the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Lyatsky, Wladislaw; Khazanov, George V.; Slavin, James A.

    2010-01-01

    We reexamined the processes leading to saturation of the electric field, transmitted into the Earth's ionosphere from the solar wind, incorporating features of the coupled system previously ignored. We took into account that the electric field is transmitted into the ionosphere through a region of open field lines, and that the ionospheric conductivity in the polar cap and auroral zone may be different. Penetration of the electric field into the magnetosphere is linked with the generation of the Alfven wave, going out from the ionosphere into the solar wind and being coupled with the field-aligned currents at the boundary of the open field limes. The electric field of the outgoing Alfven wave reduces the original electric field and provides the saturation effect in the electric field and currents during strong geomagnetic disturbances, associated with increasing ionospheric conductivity. The electric field and field-aligned currents of this Alfven wave are dependent on the ionospheric and solar wind parameters and may significantly affect the electric field and field-aligned currents, generated in the polar ionosphere. Estimating the magnitude of the saturation effect in the electric field and field-aligned currents allows us to improve the correlation between solar wind parameters and resulting disturbances in the Earth's magnetosphere.

  10. Nonlinear response of electric fields at a neutral point

    NASA Astrophysics Data System (ADS)

    Berkovsky, Mikhail; Dufty, James W.; Calisti, Annette; Stamm, Roland; Talin, Bernard

    1995-05-01

    The complex dynamics of electric fields at a neutral point in a plasma is studied via a model of noninteracting ``quasiparticles.'' The simplicity of the model allows the reduction of the many-body problem to an effective single-particle analysis-all properties of interest can be reduced to quadratures. Still, the final calculations to extract a quantitative or even qualitative understanding of the field dynamics can be difficult. Attention here is focused on the dynamics of the conditional electric field: the field value at time t for a given initial value of the field. In addition to the relevant linear response function (electric field time correlation function), this property provides the complete nonlinear response of the electric field to arbitrary initial field perturbations. The static properties (distribution of electric fields and field time derivatives) and the electric field time correlation function have been known for some time for this model. We compare these results and the present result for the conditional electric field with molecular dynamics simulations including interactions. The comparisons suggest that the model provides a quantitative representation of electric field dynamics in real plasmas, except at strong coupling. The exact theoretical results are compared also with those obtained by modeling the electric field as a stochastic variable obeying a kangaroo process. The latter can be constructed to yield both the exact stationary distribution and the exact electric field time correlation function. However, we find that the conditional field is never well approximated by this process. An alternative representation of the joint distribution for electric fields, consistent with the exact stationary distribution, field correlation function, and conditional electric field, is suggested.

  11. Double-charge model for classical force-field simulations

    NASA Astrophysics Data System (ADS)

    Barrett, Christopher; Wang, Lin-Wang

    2015-06-01

    In a traditional classical force-field model, the atomic point charge that generates the electrostatic potential, and the Born charge induced by atomic movement, are represented by the same charge parameter. But their actual values can be very different, and correct values for both of them are needed in order to yield the correct atomic structure (electrostatic charge) and phonon spectrum (Born charge). This is particularly true for nanostructure calculations. Here, we introduce a double-charge model (DCM) to reconcile the difference between the electrostatic charge and Born charge. The DCM allows us to reproduce the accurate ab initio phonon spectrum not only in bulk systems, but also for nanostructures (slabs and nanowires). This enables the use of classical force fields to study phonon spectra of large nanostructures, which are important for many phenomena from carrier dynamics to thermo conductivities.

  12. Four-nucleon force in chiral effective field theory

    SciTech Connect

    Evgeny Epelbaum

    2005-10-25

    We derive the leading contribution to the four--nucleon force within the framework of chiral effective field theory. It is governed by the exchange of pions and the lowest--order nucleon--nucleon contact interaction and includes effects due to the nonlinear pion--nucleon couplings and the pion self interactions constrained by the chiral symmetry of QCD. The resulting 4NF does not contain any unknown parameters and can be tested in future few--and many--nucleon studies.

  13. Parmbsc1: a refined force field for DNA simulations.

    PubMed

    Ivani, Ivan; Dans, Pablo D; Noy, Agnes; Pérez, Alberto; Faustino, Ignacio; Hospital, Adam; Walther, Jürgen; Andrio, Pau; Goñi, Ramon; Balaceanu, Alexandra; Portella, Guillem; Battistini, Federica; Gelpí, Josep Lluis; González, Carlos; Vendruscolo, Michele; Laughton, Charles A; Harris, Sarah A; Case, David A; Orozco, Modesto

    2016-01-01

    We present parmbsc1, a force field for DNA atomistic simulation, which has been parameterized from high-level quantum mechanical data and tested for nearly 100 systems (representing a total simulation time of ?140 ?s) covering most of DNA structural space. Parmbsc1 provides high-quality results in diverse systems. Parameters and trajectories are available at http://mmb.irbbarcelona.org/ParmBSC1/. PMID:26569599

  14. Tuning the Mass of Chameleon Fields in Casimir Force Experiments

    E-print Network

    Ph. Brax; C. van de Bruck; A. C. Davis; D. J. Shaw; D. Iannuzzi

    2010-03-08

    We have calculated the chameleon pressure between two parallel plates in the presence of an intervening medium that affects the mass of the chameleon field. As intuitively expected, the gas in the gap weakens the chameleon interaction mechanism with a screening effect that increases with the plate separation and with the density of the intervening medium. This phenomenon might open up new directions in the search of chameleon particles with future long range Casimir force experiments.

  15. Current Status of the AMOEBA Polarizable Force Field

    PubMed Central

    Ponder, Jay W.; Wu, Chuanjie; Ren, Pengyu; Pande, Vijay S.; Chodera, John D.; Schnieders, Michael J.; Haque, Imran; Mobley, David L.; Lambrecht, Daniel S.; DiStasio, Robert A.; Head-Gordon, Martin; Clark, Gary N. I.; Johnson, Margaret E.

    2010-01-01

    Molecular force fields have been approaching a generational transition over the past several years, moving away from well-established and well-tuned, but intrinsically limited, fixed point charge models towards more intricate and expensive polarizable models that should allow more accurate description of molecular properties. The recently introduced AMOEBA force field is a leading publicly available example of this next generation of theoretical model, but to date has only received relatively limited validation, which we address here. We show that the AMOEBA force field is in fact a significant improvement over fixed charge models for small molecule structural and thermodynamic observables in particular, although further fine-tuning is necessary to describe solvation free energies of drug-like small molecules, dynamical properties away from ambient conditions, and possible improvements in aromatic interactions. State of the art electronic structure calculations reveal generally very good agreement with AMOEBA for demanding problems such as relative conformational energies of the alanine tetrapeptide and isomers of water sulfate complexes. AMOEBA is shown to be especially successful on protein-ligand binding and computational X-ray crystallography where polarization and accurate electrostatics are critical. PMID:20136072

  16. Kelvin Probe Force Microscopy for in situ Electrical Characterization of Organic Solar Cells

    E-print Network

    Fisher, Frank

    Kelvin Probe Force Microscopy for in situ Electrical Characterization of Organic Solar Cells., University of Pittsburgh The most efficient organic solar cell today is made from blending conjugated donors and acceptors in bulk heterojunction organic solar cells. Most microscopic characterization

  17. Design and optimization of force-reduced high field magnets

    NASA Astrophysics Data System (ADS)

    Rembeczki, Szabolcs

    High field magnets have many important applications in different areas of research, in the power industry and also for military purposes. For example, high field magnets are particularly useful in: material sciences, high energy physics, plasma physics (as fusion magnets), high power applications (as energy storage devices), and space applications (in propulsion systems). One of the main issues with high-field magnets is the presence of very large electromagnetic stresses that must be counteracted and therefore require heavy support structures. In superconducting magnets, the problems caused by Lorentz forces are further complicated by the fact that superconductors for high field applications are pressure sensitive. The current carrying capacity is greatly reduced under stress and strain (especially in the case of Nb 3Sn and the new high temperature superconductors) so the reduction of the acting forces is of even greater importance. Different force-reduced magnet concepts have been studied in the past, both numerical and analytical methods have been used to solve this problem. The developed concepts are based on such complex winding geometries that the realization and manufacturing of such coils is extremely difficult and these concepts are mainly of theoretical interest. In the presented research, a novel concept for force-reduced magnets has been developed and analyzed which is easy to realize and therefore is of practical interest. The analysis has been performed with a new methodology, which does not require the time consuming finite element calculations. The developed computer models describe the 3-dimensional winding configuration by sets of filaments (filamentary approximation). This approach is much faster than finite element analysis and therefore allows rapid optimization of concepts. The method has been extensively tested on geometries of force-reduced solenoids where even analytical solutions exist. As a further cross check, the developed computer codes have been tested against qualified finite element codes and found to be in excellent agreement. The developed concept of force-reduced coils is directly applicable to pulsed magnets and a conceptual design of a 25 Tesla magnet has been developed. Although no experimental proof was possible within the scope of this research, there is strong evidence to believe that the developed concept is also applicable to superconducting magnets operating in a constant current mode.

  18. Electric field effect in ultrathin black phosphorus

    SciTech Connect

    Koenig, Steven P.; Schmidt, Hennrik; Doganov, Rostislav A.; Castro Neto, A. H.; Özyilmaz, Barbaros

    2014-03-10

    Black phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer black phosphorus field effect devices on Si/SiO{sub 2} and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm{sup 2}/Vs and drain current modulation of over 10{sup 3}. At low temperatures, the on-off ratio exceeds 10{sup 5}, and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin black phosphorus crystals over the course of 1 h after exfoliation.

  19. Electric field effect in ultrathin black phosphorus

    NASA Astrophysics Data System (ADS)

    Koenig, Steven P.; Doganov, Rostislav A.; Schmidt, Hennrik; Castro Neto, A. H.; Özyilmaz, Barbaros

    2014-03-01

    Black phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer black phosphorus field effect devices on Si/SiO2 and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm2/Vs and drain current modulation of over 103. At low temperatures, the on-off ratio exceeds 105, and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin black phosphorus crystals over the course of 1 h after exfoliation.

  20. Secondary Structure of Rat and Human Amylin across Force Fields

    PubMed Central

    Hoffmann, Kyle Quynn; McGovern, Michael; Chiu, Chi-cheng; de Pablo, Juan J.

    2015-01-01

    The aggregation of human amylin has been strongly implicated in the progression of Type II diabetes. This 37-residue peptide forms a variety of secondary structures, including random coils, ?-helices, and ?-hairpins. The balance between these structures depends on the chemical environment, making amylin an ideal candidate to examine inherent biases in force fields. Rat amylin differs from human amylin by only 6 residues; however, it does not form fibrils. Therefore it provides a useful complement to human amylin in studies of the key events along the aggregation pathway. In this work, the free energy of rat and human amylin was determined as a function of ?-helix and ?-hairpin content for the Gromos96 53a6, OPLS-AA/L, CHARMM22/CMAP, CHARMM22*, Amberff99sb*-ILDN, and Amberff03w force fields using advanced sampling techniques, specifically bias exchange metadynamics. This work represents a first systematic attempt to evaluate the conformations and the corresponding free energy of a large, clinically relevant disordered peptide in solution across force fields. The NMR chemical shifts of rIAPP were calculated for each of the force fields using their respective free energy maps, allowing us to quantitatively assess their predictions. We show that the predicted distribution of secondary structures is sensitive to the choice of force-field: Gromos53a6 is biased towards ?-hairpins, while CHARMM22/CMAP predicts structures that are overly ?-helical. OPLS-AA/L favors disordered structures. Amberff99sb*-ILDN, AmberFF03w and CHARMM22* provide the balance between secondary structures that is most consistent with available experimental data. In contrast to previous reports, our findings suggest that the equilibrium conformations of human and rat amylin are remarkably similar, but that subtle differences arise in transient alpha-helical and beta-strand containing structures that the human peptide can more readily adopt. We hypothesize that these transient states enable dynamic pathways that facilitate the formation of aggregates and, eventually, amyloid fibrils. PMID:26221949

  1. Secondary structure of rat and human amylin across force fields

    DOE PAGESBeta

    Hoffmann, Kyle Quynn; McGovern, Michael; Chiu, Chi -cheng; de Pablo, Juan J.; Paci, Emanuele

    2015-07-29

    The aggregation of human amylin has been strongly implicated in the progression of Type II diabetes. This 37-residue peptide forms a variety of secondary structures, including random coils, ?-helices, and ?-hairpins. The balance between these structures depends on the chemical environment, making amylin an ideal candidate to examine inherent biases in force fields. Rat amylin differs from human amylin by only 6 residues; however, it does not form fibrils. Therefore it provides a useful complement to human amylin in studies of the key events along the aggregation pathway. In this work, the free energy of rat and human amylin wasmore »determined as a function of ?-helix and ?-hairpin content for the Gromos96 53a6, OPLS-AA/L, CHARMM22/CMAP, CHARMM22*, Amberff99sb*-ILDN, and Amberff03w force fields using advanced sampling techniques, specifically bias exchange metadynamics. This work represents a first systematic attempt to evaluate the conformations and the corresponding free energy of a large, clinically relevant disordered peptide in solution across force fields. The NMR chemical shifts of rIAPP were calculated for each of the force fields using their respective free energy maps, allowing us to quantitatively assess their predictions. We show that the predicted distribution of secondary structures is sensitive to the choice of force-field: Gromos53a6 is biased towards ?-hairpins, while CHARMM22/CMAP predicts structures that are overly ?-helical. OPLS-AA/L favors disordered structures. Amberff99sb*-ILDN, AmberFF03w and CHARMM22* provide the balance between secondary structures that is most consistent with available experimental data. In contrast to previous reports, our findings suggest that the equilibrium conformations of human and rat amylin are remarkably similar, but that subtle differences arise in transient alpha-helical and beta-strand containing structures that the human peptide can more readily adopt. We hypothesize that these transient states enable dynamic pathways that facilitate the formation of aggregates and, eventually, amyloid fibrils.« less

  2. Secondary structure of rat and human amylin across force fields

    SciTech Connect

    Hoffmann, Kyle Quynn; McGovern, Michael; Chiu, Chi -cheng; de Pablo, Juan J.; Paci, Emanuele

    2015-07-29

    The aggregation of human amylin has been strongly implicated in the progression of Type II diabetes. This 37-residue peptide forms a variety of secondary structures, including random coils, ?-helices, and ?-hairpins. The balance between these structures depends on the chemical environment, making amylin an ideal candidate to examine inherent biases in force fields. Rat amylin differs from human amylin by only 6 residues; however, it does not form fibrils. Therefore it provides a useful complement to human amylin in studies of the key events along the aggregation pathway. In this work, the free energy of rat and human amylin was determined as a function of ?-helix and ?-hairpin content for the Gromos96 53a6, OPLS-AA/L, CHARMM22/CMAP, CHARMM22*, Amberff99sb*-ILDN, and Amberff03w force fields using advanced sampling techniques, specifically bias exchange metadynamics. This work represents a first systematic attempt to evaluate the conformations and the corresponding free energy of a large, clinically relevant disordered peptide in solution across force fields. The NMR chemical shifts of rIAPP were calculated for each of the force fields using their respective free energy maps, allowing us to quantitatively assess their predictions. We show that the predicted distribution of secondary structures is sensitive to the choice of force-field: Gromos53a6 is biased towards ?-hairpins, while CHARMM22/CMAP predicts structures that are overly ?-helical. OPLS-AA/L favors disordered structures. Amberff99sb*-ILDN, AmberFF03w and CHARMM22* provide the balance between secondary structures that is most consistent with available experimental data. In contrast to previous reports, our findings suggest that the equilibrium conformations of human and rat amylin are remarkably similar, but that subtle differences arise in transient alpha-helical and beta-strand containing structures that the human peptide can more readily adopt. We hypothesize that these transient states enable dynamic pathways that facilitate the formation of aggregates and, eventually, amyloid fibrils.

  3. Dust particles under the influence of crossed electric and magnetic fields in the sheath of an rf discharge

    SciTech Connect

    Puttscher, M. Melzer, A.

    2014-12-15

    Experimental studies on the interaction of micron-sized dust particles in plasmas with external magnetic fields are presented. The particles are levitated in the sheath region of an rf discharge by gravity and electric field force under the presence of a horizontal magnetic field of up to 50?mT. It is observed that the dust particles are pushed either in the E{sup ?}×B{sup ?}- or in the opposite direction depending on magnetic field strength, particle properties, and discharge conditions. This transport behavior is described by a competition between horizontal ambipolar electric field force and ion and neutral drag.

  4. Dust particles under the influence of crossed electric and magnetic fields in the sheath of an rf discharge

    NASA Astrophysics Data System (ADS)

    Puttscher, M.; Melzer, A.

    2014-12-01

    Experimental studies on the interaction of micron-sized dust particles in plasmas with external magnetic fields are presented. The particles are levitated in the sheath region of an rf discharge by gravity and electric field force under the presence of a horizontal magnetic field of up to 50 mT. It is observed that the dust particles are pushed either in the E ? × B ? - or in the opposite direction depending on magnetic field strength, particle properties, and discharge conditions. This transport behavior is described by a competition between horizontal ambipolar electric field force and ion and neutral drag.

  5. Electromagnetic and gravitational self-force on a relativistic particle from quantum fields in curved space

    E-print Network

    Galley, C R; Lin, S Y; Galley, Chad R.; Lin, Shih-Yuin

    2006-01-01

    We provide a quantum field theoretical derivation of the Abraham-Lorentz-Dirac (ALD) equation, describing the motion of an electric point charge sourcing an electromagnetic field, which back-reacts on the charge as a self-force, and the Mino-Sasaki-Tanaka-Quinn-Wald (MSTQW) equation describing the motion of a point mass with self-force interacting with the linearized metric perturbations caused by the mass off an otherwise vacuous curved background spacetime. We regularize the formally divergent self-force by smearing the direct part of the retarded Green's function and using a quasilocal expansion. We also derive the ALD-Langevin and the MSTQW-Langevin equations with a classical stochastic force accounting for the effect of the quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. These equations will be useful for studying the stochastic motion of charges and small masses under the influence of both quantum and classical noise sources, derived either self-consistentl...

  6. Electromagnetic and gravitational self-force on a relativistic particle from quantum fields in curved space

    E-print Network

    Chad R. Galley; B. L. Hu; Shih-Yuin Lin

    2006-03-24

    We provide a quantum field theoretical derivation of the Abraham-Lorentz-Dirac (ALD) equation, describing the motion of an electric point charge sourcing an electromagnetic field, which back-reacts on the charge as a self-force, and the Mino-Sasaki-Tanaka-Quinn-Wald (MSTQW) equation describing the motion of a point mass with self-force interacting with the linearized metric perturbations caused by the mass off an otherwise vacuous curved background spacetime. We regularize the formally divergent self-force by smearing the direct part of the retarded Green's function and using a quasilocal expansion. We also derive the ALD-Langevin and the MSTQW-Langevin equations with a classical stochastic force accounting for the effect of the quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. These equations will be useful for studying the stochastic motion of charges and small masses under the influence of both quantum and classical noise sources, derived either self-consistently or put in by hand phenomenologically. We also show that history-dependent noise-induced drift motions could arise from such stochastic sources on the trajectory that could be a hidden feature of gravitational wave forms hitherto unknown.

  7. Thermodynamically consistent force fields for the assembly of inorganic, organic, and biological nanostructures: the INTERFACE force field.

    PubMed

    Heinz, Hendrik; Lin, Tzu-Jen; Mishra, Ratan Kishore; Emami, Fateme S

    2013-02-12

    The complexity of the molecular recognition and assembly of biotic-abiotic interfaces on a scale of 1 to 1000 nm can be understood more effectively using simulation tools along with laboratory instrumentation. We discuss the current capabilities and limitations of atomistic force fields and explain a strategy to obtain dependable parameters for inorganic compounds that has been developed and tested over the past decade. Parameter developments include several silicates, aluminates, metals, oxides, sulfates, and apatites that are summarized in what we call the INTERFACE force field. The INTERFACE force field operates as an extension of common harmonic force fields (PCFF, COMPASS, CHARMM, AMBER, GROMACS, and OPLS-AA) by employing the same functional form and combination rules to enable simulations of inorganic-organic and inorganic-biomolecular interfaces. The parametrization builds on an in-depth understanding of physical-chemical properties on the atomic scale to assign each parameter, especially atomic charges and van der Waals constants, as well as on the validation of macroscale physical-chemical properties for each compound in comparison to measurements. The approach eliminates large discrepancies between computed and measured bulk and surface properties of up to 2 orders of magnitude using other parametrization protocols and increases the transferability of the parameters by introducing thermodynamic consistency. As a result, a wide range of properties can be computed in quantitative agreement with experiment, including densities, surface energies, solid-water interface tensions, anisotropies of interfacial energies of different crystal facets, adsorption energies of biomolecules, and thermal and mechanical properties. Applications include insight into the assembly of inorganic-organic multiphase materials, the recognition of inorganic facets by biomolecules, growth and shape preferences of nanocrystals and nanoparticles, as well as thermal transitions and nanomechanics. Limitations and opportunities for further development are also described. PMID:23276161

  8. Relationship between the ion drag and electric forces in dense dust clouds

    SciTech Connect

    Yaroshenko, V. V.; Khrapak, S. A.; Morfill, G. E.

    2013-04-15

    It is shown that the relation between the ion drag and electric forces is strongly dependent on the dust number density in complex plasmas. The effect of the particle size and discharge parameters on the force balance is investigated. Examples are given for realistic complex plasma parameters and comparison with microgravity experiments is presented.

  9. Liquid methanol under a static electric field.

    PubMed

    Cassone, Giuseppe; Giaquinta, Paolo V; Saija, Franz; Saitta, A Marco

    2015-02-01

    We report on an ab initio molecular dynamics study of liquid methanol under the effect of a static electric field. We found that the hydrogen-bond structure of methanol is more robust and persistent for field intensities below the molecular dissociation threshold whose value (?0.31 V/Å) turns out to be moderately larger than the corresponding estimate obtained for liquid water. A sustained ionic current, with ohmic current-voltage behavior, flows in this material for field intensities above 0.36 V/Å, as is also the case of water, but the resulting ionic conductivity (?0.40 S cm(-1)) is at least one order of magnitude lower than that of water, a circumstance that evidences a lower efficiency of proton transfer processes. We surmise that this study may be relevant for the understanding of the properties and functioning of technological materials which exploit ionic conduction, such as direct-methanol fuel cells and Nafion membranes. PMID:25662649

  10. Moving antiphase boundaries using an external electric field

    NASA Astrophysics Data System (ADS)

    Vaideeswaran, Kaushik; Shapovalov, Konstantin; Yudin, Petr V.; Tagantsev, Alexander K.; Setter, Nava

    2015-11-01

    Antiphase boundaries (APBs) are unique domain walls that may demonstrate switchable polarization in otherwise non-ferroelectric materials such as SrTiO3 and PbZrO3. The current study explores the possibility of displacing such domain walls at the nanoscale. We suggest the possibility of manipulating APBs using the inhomogeneous electric field of an Atomic Force Microscopy (AFM) tip with an applied voltage placed in their proximity. The displacement is studied as a function of applied voltage, film thickness, and initial separation of the AFM tip from the APB. It is established, for example, that for films with thickness of 15 nm, an APB may be attracted under the tip with a voltage of 25 V from initial separation of 30 nm. We have also demonstrated that the displacement is appreciably retained after the voltage is removed, rendering it favorable for potential applications.

  11. Casimir force for a scalar field in warped brane worlds

    E-print Network

    Roman Linares; Hugo A. Morales-Tecotl; Omar Pedraza

    2007-12-24

    In looking for imprints of extra dimensions in brane world models one usually builts these so that they are compatible with known low energy physics and thus focuses on high energy effects. Nevertheless, just as submillimeter Newton's law tests probe the mode structure of gravity other low energy tests might apply to matter. As a model example, in this work we determine the 4D Casimir force corresponding to a scalar field subject to Dirichlet boundary conditions on two parallel planes lying within the single brane of a Randall-Sundrum scenario extended by one compact extra dimension. Using the Green's function method such a force picks the contribution of each field mode as if it acted individually but with a weight given by the square of the mode wave functions on the brane. In the low energy regime one regains the standard 4D Casimir force that is associated to a zero mode in the massless case or to a quasilocalized or resonant mode in the massive one whilst the effect of the extra dimensions gets encoded as an additional term.

  12. Casimir force for a scalar field in warped brane worlds

    SciTech Connect

    Linares, Roman; Morales-Tecotl, Hugo A.; Pedraza, Omar

    2008-03-15

    In looking for imprints of extra dimensions in braneworld models one usually builds these so that they are compatible with known low energy physics and thus focuses on high energy effects. Nevertheless, just as submillimeter Newton's law tests probe the mode structure of gravity other low energy tests might apply to matter. As a model example, in this work we determine the 4D Casimir force corresponding to a scalar field subject to Dirichlet boundary conditions on two parallel planes lying within the single brane of a Randall-Sundrum scenario extended by one compact extra dimension. Using the Green's function method such a force picks the contribution of each field mode as if it acted individually but with a weight given by the square of the mode wave functions on the brane. In the low energy regime one regains the standard 4D Casimir force that is associated to a zero mode in the massless case or to a quasilocalized or resonant mode in the massive one while the effect of the extra dimensions gets encoded as an additional term.

  13. Casimir force for a scalar field in warped brane worlds

    NASA Astrophysics Data System (ADS)

    Linares, Román; Morales-Técotl, Hugo A.; Pedraza, Omar

    2008-03-01

    In looking for imprints of extra dimensions in braneworld models one usually builds these so that they are compatible with known low energy physics and thus focuses on high energy effects. Nevertheless, just as submillimeter Newton’s law tests probe the mode structure of gravity other low energy tests might apply to matter. As a model example, in this work we determine the 4D Casimir force corresponding to a scalar field subject to Dirichlet boundary conditions on two parallel planes lying within the single brane of a Randall-Sundrum scenario extended by one compact extra dimension. Using the Green’s function method such a force picks the contribution of each field mode as if it acted individually but with a weight given by the square of the mode wave functions on the brane. In the low energy regime one regains the standard 4D Casimir force that is associated to a zero mode in the massless case or to a quasilocalized or resonant mode in the massive one while the effect of the extra dimensions gets encoded as an additional term.

  14. Silica microwire-based interferometric electric field sensor.

    PubMed

    Han, Chunyang; Lv, Fangxing; Sun, Chen; Ding, Hui

    2015-08-15

    Silica microwire, as an optical waveguide whose diameter is close to or smaller than the wavelength of the guided light, is of great interest because it exhibits a number of excellent properties such as tight confinement, large evanescent fields, and great configurability. Here, we report a silica microwire-based compact photonic sensor for real-time detection of high electric field. This device contains an interferometer with propylene carbonate cladding. Based on the Kerr electro-optic effect of propylene carbonate, the applied intensive transient electric field can change the refractive index of propylene carbonate, which shifts the interferometric fringe. Therefore, the electric field could be demodulated by monitoring the fringe shift. The sensor was successfully used to detect alternating electric field with frequency of 50 Hz and impulse electric field with duration time of 200 ?s. This work lays a foundation for future applications in electric field sensing. PMID:26274634

  15. Pairwise-additive force fields for selected aqueous monovalent ions from adaptive force matching

    NASA Astrophysics Data System (ADS)

    Li, Jicun; Wang, Feng

    2015-11-01

    Simple non-polarizable potentials were developed for Na+, K+, Cl-, and Br- using the adaptive force matching (AFM) method with ab initio MP2 method as reference. Our MP2-AFM force field predicts the solvation free energies of the four salts formed by the ions with an error of no more than 5%. Other properties such as the ion-water radial distribution functions, first solvation shell water tilt angle distributions, ion diffusion constants, concentration dependent diffusion constant of water, and concentration dependent surface tension of the solutions were calculated with this potential. Very good agreement was achieved for these properties. In particular, the diffusion constants of the ions are within 6% of experimental measurements. The model predicts bromide to be enriched at the interface in the 1.6M KBr solution but predicts the ion to be repelled for the surface at lower concentration.

  16. Pairwise-additive force fields for selected aqueous monovalent ions from adaptive force matching.

    PubMed

    Li, Jicun; Wang, Feng

    2015-11-21

    Simple non-polarizable potentials were developed for Na(+), K(+), Cl(-), and Br(-) using the adaptive force matching (AFM) method with ab initio MP2 method as reference. Our MP2-AFM force field predicts the solvation free energies of the four salts formed by the ions with an error of no more than 5%. Other properties such as the ion-water radial distribution functions, first solvation shell water tilt angle distributions, ion diffusion constants, concentration dependent diffusion constant of water, and concentration dependent surface tension of the solutions were calculated with this potential. Very good agreement was achieved for these properties. In particular, the diffusion constants of the ions are within 6% of experimental measurements. The model predicts bromide to be enriched at the interface in the 1.6M KBr solution but predicts the ion to be repelled for the surface at lower concentration. PMID:26590540

  17. Observations of field-aligned currents, waves, and electric fields at substorm onset

    NASA Technical Reports Server (NTRS)

    Smits, D. P.; Hughes, W. J.; Cattell, C. A.; Russell, C. T.

    1986-01-01

    Substorm onsets, identified Pi 2 pulsations observed on the Air Force Geophysics Laboratory Magnetometer Network, are studied using magnetometer and electric field data from ISEE 1 as well as magnetometer data from the geosynchronous satellites GOES 2 and 3. The mid-latitude magnetometer data provides the means of both timing and locating the substorm onset so that the spacecraft locations with respect to the substorm current systems are known. During two intervals, each containing several onsets or intensifications, ISEE 1 observed field-aligned current signatures beginning simultaneously with the mid-latitude Pi 2 pulsation. Close to the earth broadband bursts of wave noise were observed in the electric field data whenever field-aligned currents were detected. One onset occurred when ISEE 1 and GOES 2 were on the same field line but in opposite hemispheres. During this onset ISEE 1 and GOES 2 saw magnetic signatures which appear to be due to conjugate field-aligned currents flowing out of the western end of the westward auroral electrojets. The ISEE 1 signature is of a line current moving westward past the spacecraft. During the other interval, ISEE 1 was in the near-tail region near the midnight meridian. Plasma data confirms that the plasma sheet thinned and subsequently expanded at onset. Electric field data shows that the plasma moved in the opposite direction to the plasma sheet boundary as the boundary expanded which implies that there must have been an abundant source of hot plasma present. The plasma motion was towards the center of the plasma sheet and earthwards and consisted of a series of pulses rather than a steady flow.

  18. Temperature gradient and electric field driven electrostatic instabilities

    NASA Technical Reports Server (NTRS)

    Morrison, P. J.; Ionson, J. A.

    1982-01-01

    The stability of electrostatic waves to thermodynamic and electric potential gradients was investigated. It is shown that thermodynamic gradients drive instabilities even when the internal electric field vanishes. Skewing of the distribution function is not included in the dielectric.

  19. Mechanics 1: Motion in a Central Force Field We now study the properties of a particle of (constant) mass m moving in a particular type of force

    E-print Network

    Kerswell, Rich

    Mechanics 1: Motion in a Central Force Field We now study the properties of a particle of (constant) mass m moving in a particular type of force field, a central force field. Central forces are very important in physics and engineering. For example, the gravitional force of attraction between two point

  20. Sodium Chloride, NaCl/? : New Force Field

    E-print Network

    Raul Fuentes-Azcatl; Marcia C. Barbosa

    2015-08-08

    A new computational model for Sodium Chloride, the NaCl/{\\epsilon}, is proposed. The Force Fields employed here for the description of the NaCl is based on a set of radial particle-particle pair potentials involving Lennard-Jones (LJ) and Coulombic forces. The parameterization is obtained fitting the density of the crystal and the density and the dielectric constant of the mixture of salt with water at diluted solution. Our model shows good agreement with the experimental values for the density and surface tension for the pure system and for the density, the viscosity, the diffusion, and the dielectric constant for the mixture with water at various molal concentrations. The NaCl/{\\epsilon} together with the water TIP4P/{\\epsilon} model provide a good approximation for studying electrolyte solutions.

  1. Interfacial Force Field Characterization in a Constrained Vapor Bubble Thermosyphon

    NASA Technical Reports Server (NTRS)

    DasGupta, Sunando; Plawsky, Joel L.; Wayner, Peter C., Jr.

    1995-01-01

    Isothermal profiles of the extended meniscus in a quartz cuvette were measured in the earth's gravitational field using an image-analyzing interferometer that is based on computer-enhanced video microscopy of the naturally occurring interference fringes. These profiles are a function of the stress field. Experimentally, the augmented Young-Laplace equation is an excellent model for the force field at the solid-liquid-vapor interfaces for heptane and pentane menisci on quartz and tetradecane on SFL6. The effects of refractive indices of the solid and liquid on the measurement techniques were demonstrated. Experimentally obtained values of the disjoining pressure and dispersion constants were compared to those predicted from the Dzyaloshinskii - Lifshitz - Pilaevskii theory for an ideal surface and reasonable agreements were obtained. A parameter introduced gives a quantitative measurement of the closeness of the system to equilibrium. The nonequilibrium behavior of this parameter is also presented

  2. Interfacial force field characterization in a constrained vapor bubble thermosyphon

    SciTech Connect

    DasGupta, S.; Plawsky, J.L.; Wayner, P.C. Jr.

    1995-09-01

    isothermal profiles of the extended meniscus in a quartz cuvette were measured in the earth`s gravitational field using an image analyzing interferometer that is based on computer-enhanced video microscopy of the naturally occurring interference fringes. These profiles are a function of the stress field. Experimentally, the augmented Young-Laplace equation is an excellent model for the force field at the solid-liquid-vapor interfaces for heptane and pentane menisci on quartz and tetradecane on SFL6. Effects of refractive indices of the solid and liquid on the measurement techniques were demonstrated. Experimentally obtained values of the disjoining pressure and dispersion constants were compared to those predicted from the Dzyaloshinskii-Lifshitz-Pitaevskii theory for an ideal surface and reasonable agreements were obtained. A parameter introduced gives a quantitative measurement of the closeness of the system to equilibrium. The nonequilibrium behavior of this parameter is also presented.

  3. Effect of rotating electric field on 3D complex (dusty) plasma

    NASA Astrophysics Data System (ADS)

    Wörner, L.; Nosenko, V.; Ivlev, A. V.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E.; Kroll, M.; Schablinski, J.; Block, D.

    2011-06-01

    The effect of rotating electric field on 3D particle clusters suspended in rf plasma was studied experimentally. Spheroidal clusters were suspended inside a glass box mounted on the lower horizontal rf electrode, with gravity partially balanced by thermophoretic force. Clusters rotated in the horizontal plane, in response to rotating electric field that was created inside the box using conducting coating on its inner surfaces ("rotating wall" technique). Cluster rotation was always in the direction of applied field and had a shear in the vertical direction. The angular speed of rotation was 104-107 times lower than applied frequency. The experiment is compared to a recent theory.

  4. Rapid parameterization of small molecules using the Force Field Toolkit

    PubMed Central

    Mayne, Christopher G.; Saam, Jan; Schulten, Klaus; Tajkhorshid, Emad; Gumbart, James C.

    2013-01-01

    The inability to rapidly generate accurate and robust parameters for novel chemical matter continues to severely limit the application of molecular dynamics (MD) simulations to many biological systems of interest, especially in fields such as drug discovery. Although the release of generalized versions of common classical force fields, e.g., GAFF and CGenFF, have posited guidelines for parameterization of small molecules, many technical challenges remain that have hampered their wide-scale extension. The Force Field Toolkit (ffTK), described herein, minimizes common barriers to ligand parameterization through algorithm and method development, automation of tedious and error-prone tasks, and graphical user interface design. Distributed as a VMD plugin, ffTK facilitates the traversal of a clear and organized workflow resulting in a complete set of CHARMM-compatible parameters. A variety of tools are provided to generate quantum mechanical target data, set up multidimensional optimization routines, and analyze parameter performance. Parameters developed for a small test set of molecules using ffTK were comparable to existing CGenFF parameters in their ability to reproduce experimentally measured values for pure-solvent properties (<15% error from experiment) and free energy of solvation (±0.5 kcal/mol from experiment). PMID:24000174

  5. Role of random electric fields in relaxors.

    PubMed

    Phelan, Daniel; Stock, Christopher; Rodriguez-Rivera, Jose A; Chi, Songxue; Leão, Juscelino; Long, Xifa; Xie, Yujuan; Bokov, Alexei A; Ye, Zuo-Guang; Ganesh, Panchapakesan; Gehring, Peter M

    2014-02-01

    PbZr(1-x)Ti(x)O3 (PZT) and Pb(Mg1/3Nb2/3)(1-x)Ti(x)O3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter. PMID:24449912

  6. Controlling Positronium Annihilation with Electric Fields

    NASA Astrophysics Data System (ADS)

    Alonso, A. M.; Cooper, B. S.; Deller, A.; Hogan, S. D.; Cassidy, D. B.

    2015-10-01

    We show that the annihilation dynamics of excited positronium (Ps) atoms can be controlled using parallel electric and magnetic fields. To achieve this, Ps atoms were optically excited to n =2 sublevels in fields that were adjusted to control the amount of short-lived and long-lived character of the resulting mixed states. Inclusion of the former offers a practical approach to detection via annihilation radiation, whereas the increased lifetimes due to the latter can be exploited to optimize resonance-enhanced two-photon excitation processes (e.g., 1 S 3 ?2 P 3 ?n S /n D ), either by minimizing losses through intermediate state decay, or by making it possible to separate the excitation laser pulses in time. In addition, photoexcitation of mixed states with a 2 S1 3 component represents an efficient route to producing long-lived pure 2 S1 3 atoms via single-photon excitation.

  7. Continuum Polarizable Force Field within the Poisson-Boltzmann Framework

    PubMed Central

    Tan, Yu-Hong; Tan, Chunhu; Wang, Junmei; Luo, Ray

    2008-01-01

    We have developed and tested a complete set of nonbonded parameters for a continuum polarizable force field. Our analysis shows that the new continuum polarizable model is consistent with B3LYP/cc-pVTZ in modeling electronic response upon variation of dielectric environment. Comparison with experiment also shows that the new continuum polarizable model is reasonable, with similar accuracy as B3LYP/cc-pVTZ in reproduction of dipole moments of selected organic molecules in the gas phase. We have further tested the validity to interchange the Amber van der Waals parameters between the explicit and continuum polarizable force fields with a series of dimers. It can be found that the continuum polarizable model agrees well with MP2/cc-pVTZ, with deviations in dimer binding energies less than 0.9 kcal/mol in the aqueous dielectric environment. Finally we have optimized atomic cavity radii with respect to experimental solvation free energies of 177 training molecules. To validate the optimized cavity radii, we have tested these parameters against 176 test molecules. It is found that the optimized PB atomic cavity radii transfer well from the training set to the test set, with an overall root-mean-squared deviation of 1.30 kcal/mol, unsigned average error of 1.07 kacl/mol, and correlation coefficient of 92% for all 353 molecules in both the training and test sets. Given the development documented here, the next natural step is the construction of a full protein/nucleic acid force field within the new continuum polarization framework. PMID:18507452

  8. The polarization electric field and its effects in an anisotropic rotating magnetospheric plasma

    NASA Technical Reports Server (NTRS)

    Huang, T. S.; Birmingham, T. J.

    1992-01-01

    Spatial variations of density and temperature along a magnetic field line are evaluated for a plasma undergoing adiabatic motion in a rotating magnetosphere. The effects of centrifugal and gravitational forces are accounted for, as is anisotropy in the pitch angle distribution functions of individual species. A polarization electric field is invoked to eliminate the net electric charge density resulting from the aforementioned mass dependent forces and different anisotropies. The position of maximum density in a two-component, electron-ion plasma is determined both in the absence and in the presence of the polarization effect and compared. A scale height, generalized to include anisotropies, is derived for the density fall-off. The polarization electric field is also included in the parallel guiding center equation; equilibrium points are determined and compared in both individual and average senses with the position of density maximum. Finally a transverse (to magnetic field lines) electric component is deduced as a consequence of dissimilar charge neutralization on adjacent field lines. The E x B velocity resultant from such a 'fringing' electric field is calculated and compared with the magnitude of other drifts.

  9. Electric field induced bacterial flocculation of enteroaggregative Escherichia coli 042

    NASA Astrophysics Data System (ADS)

    Kumar, Aloke; Mortensen, Ninell P.; Mukherjee, Partha P.; Retterer, Scott T.; Doktycz, Mitchel J.

    2011-06-01

    A response of the aggregation dynamics of enteroaggregative Escherichia coli under low magnitude steady and oscillating electric fields is presented. The presence of uniform electric fields hampered microbial adhesion and biofilm formation on a transverse glass surface, but instead promoted the formation of flocs. Extremely heterogenous distribution of live and dead cells was observed among the flocs. Moreover, floc formation was largely observed to be independent of the frequency of alternating electric fields.

  10. Electric field induced bacterial flocculation of Enteroaggregative Escherichia coli 042

    SciTech Connect

    Kumar, Aloke; Mortensen, Ninell P; Mukherjee, Partha P; Retterer, Scott T; Doktycz, Mitchel John

    2011-01-01

    A response of the aggregation dynamics of enteroaggregative Escherichia coli under low magnitude steady and oscillating electric fields is presented. The presence of uniform electric fields hampered microbial adhesion and biofilm formation on a transverse glass surface, but instead promoted the formation of flocs. Extremely heterogeneous distribution of live and dead cells was observed among the flocs. Moreover, floc formation was largely observed to be independent of the frequency of alternating electric fields.

  11. Linear electric field time-of-flight ion mass spectrometer

    DOEpatents

    Funsten, Herbert O. (Los Alamos, NM); Feldman, William C. (Los Alamos, NM)

    2008-06-10

    A linear electric field ion mass spectrometer having an evacuated enclosure with means for generating a linear electric field located in the evacuated enclosure and means for injecting a sample material into the linear electric field. A source of pulsed ionizing radiation injects ionizing radiation into the linear electric field to ionize atoms or molecules of the sample material, and timing means determine the time elapsed between ionization of atoms or molecules and arrival of an ion out of the ionized atoms or molecules at a predetermined position.

  12. Validating empirical force fields for molecular-level simulation of cellulose dissolution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The calculations presented here, which include dynamics simulations using analytical force fields and first principles studies, indicate that the COMPASS force field is preferred over the Dreiding and Universal force fields for studying dissolution of large cellulose structures. The validity of thes...

  13. Three Force Fields' Views of the 310 Helix Kalliopi K. Patapati and Nicholas M. Glykos*

    E-print Network

    Glykos, Nikolaos

    Three Force Fields' Views of the 310 Helix Kalliopi K. Patapati and Nicholas M. Glykos* Department force fields as evidenced from simulations of proteins in the folded state does not hold true different force fields show irreconcilable differ- ences in their folding predictions, even

  14. AMBER Force Field Parameters for the Naturally Occurring Modified Nucleosides in RNA

    E-print Network

    Schlegel, H. Bernhard

    AMBER Force Field Parameters for the Naturally Occurring Modified Nucleosides in RNA Raviprasad of biological macromolecules, ultimately, resulting in elucidation of biological function. The AMBER force field functional RNAs. We developed force field parameters for the 107 modified nucleotides currently known

  15. Accounting for electronic polarization in nonpolarizable force fields

    E-print Network

    Leontyev, Igor

    2015-01-01

    The issues of electronic polarizability in molecular dynamics simulations are discussed. We argue that the charges of ionized groups in proteins, and charges of ions in conventional non-polarizable force fields such as CHARMM, AMBER, GROMOS, etc should be scaled by a factor about 0.7. Our model explains why a neglect of electronic solvation energy, which typically amounts to about a half of total solvation energy, in non-polarizable simulations with un-scaled charges can produce a correct result; however, the correct solvation energy of ions does not guarantee the correctness of ion-ion pair interactions in many non-polarizable simulations. The inclusion of electronic screening for charged moieties is shown to result in significant changes in protein dynamics and can give rise to new qualitative results compared with the traditional non-polarizable force field simulations. The model also explains the striking difference between the value of water dipole $\\mu$~3D reported in recent ab initio and experimental s...

  16. Development of force field parameters for molecular simulation of polylactide

    PubMed Central

    McAliley, James H.; Bruce, David A.

    2011-01-01

    Polylactide is a biodegradable polymer that is widely used for biomedical applications, and it is a replacement for some petroleum based polymers in applications that range from packaging to carpeting. Efforts to characterize and further enhance polylactide based systems using molecular simulations have to this point been hindered by the lack of accurate atomistic models for the polymer. Thus, we present force field parameters specifically suited for molecular modeling of PLA. The model, which we refer to as PLAFF3, is based on a combination of the OPLS and CHARMM force fields, with modifications to bonded and nonbonded parameters. Dihedral angle parameters were adjusted to reproduce DFT data using newly developed CMAP dihedral cross terms, and the model was further adjusted to reproduce experimentally resolved crystal structure conformations, melt density, volume expansivity, and the glass transition temperature of PLA. We recommend the use of PLAFF3 in modeling PLA in its crystalline or amorphous states and have provided the necessary input files required for the publicly available molecular dynamics code GROMACS. PMID:22180734

  17. Extracting nucleon magnetic moments and electric polarizabilities from lattice QCD in background electric fields

    SciTech Connect

    Detmold, W.; Tiburzi, B. C.; Walker-Loud, A.

    2010-03-01

    Nucleon properties are investigated in background electric fields. As the magnetic moments of baryons affect their relativistic propagation in constant electric fields, electric polarizabilities cannot be determined without knowledge of magnetic moments. This is analogous to the experimental situation, for which determination of polarizabilities from the Compton amplitude requires subtraction of Born terms. With the background field method, we devise combinations of nucleon correlation functions in constant electric fields that isolate magnetic moments and electric polarizabilities. Using an ensemble of anisotropic gauge configurations with dynamical clover fermions, we demonstrate how both observables can be determined from lattice QCD simulations in background electric fields. We obtain results for the neutron and proton, however, our study is currently limited to electrically neutral sea quarks. The value we extract for the nucleon isovector magnetic moment is comparable to those obtained from measuring lattice three-point functions at similar pion masses.

  18. Interaction of a stream of dielectric spheres in an electric field in a high vacuum

    SciTech Connect

    Hendricks, C.D.; Kim, K.

    1983-06-14

    The interaction of a stream of dielectric spheres in an electric field in a high vacuum is investigated both theoretically and experimentally. This investigation is motivated by an elaborate attempt to detect fractional electric charges which might exist in matter, namely, a search for isolated quarks in matter. The theoretical analysis is intended for pinpointing the basic interaction mechanism by which a stream of dielectric spheres becomes destablized in an electric field. One important result of this analysis is a suggested method by which to eliminate the destabilizing forces. The experiments performed are intended to study the behavior of a stream of monodisperse dielectric liquid drops in an electric field in a high vacuum. It is seen from these experiments that the deflections of any two drops in the stream with charges differing by one electronic charge is not always the same due to the destabilization effects.

  19. Direct numerical simulation of the effect of an electric field on flame stability

    SciTech Connect

    Belhi, Memdouh; Domingo, Pascale; Vervisch, Pierre

    2010-12-15

    The role of electric fields in stabilising combustion is a well-known phenomenon. Among the possible mechanisms favouring the anchorage of the flame base, the ion-driven wind acting directly on flow momentum ahead of the flame base could be the leading one. Direct numerical simulation has been used to verify this hypothesis and lead to a better understanding of diffusion flame base anchoring in the presence of an externally applied voltage. In this context, a simplified modelling approach is proposed to describe combustion in the presence of electric body forces. The model reproduces the tendencies of experimental observations found in the literature. The sensitivity of the flame lift-off height to the applied voltage is studied and the modification of the velocity field ahead of the flame base induced by the electric volume forces is highlighted. (author)

  20. Self-force on an electric dipole in the spacetime of a cosmic string

    SciTech Connect

    Muniz, C.R.; Bezerra, V.B.

    2014-01-15

    We calculate the electrostatic self-force on an electric dipole in the spacetime generated by a static, thin, infinite and straight cosmic string. The electric dipole is held fixed in different configurations, namely, parallel, perpendicular to the cosmic string and oriented along the azimuthal direction around this topological defect, which is stretched along the z axis. We show that the self-force is equivalent to an interaction of the electric dipole with an effective dipole moment which depends on the linear mass density of the cosmic string and on the configuration. The plots of the self-forces as functions of the parameter which determines the angular deficit of the cosmic string are shown for those different configurations. -- Highlights: •Review of regularized Green’s function applied to the problem. •Self-force on an electric dipole in the string spacetime for some orientations. •Representation via graphs of the self-forces versus angular parameter of the cosmic string. •Self-force induced by the string seen as an interaction between two dipoles. •Discussion about the superposition principle in this non-trivial background.

  1. Evaluation of Contact Separation Force Testing as a Screening Methodology for Electrical Socket Contacts

    NASA Technical Reports Server (NTRS)

    Green, Chris; Greenwell, Chris; Brusse, jay; Krus, Dennis; Leidecker, Henning

    2009-01-01

    During system level testing intermittent and permanent open circuit failures of mated, crimp removable, electrical contact pairs were experienced. The root cause of the failures was determined to be low (but not zero) contact forces applied by the socket contact tines against the engaging pin. The low contact force reduces the effectiveness of the wiping action of the socket tines against the pin. The observed failure mode may be produced when insufficient wiping during mate, demate and small relative movement in use allows for the accumulation of debris or insulating films that electrically separate the contact pair. The investigation identified at least three manufacturing process control problems associated with the socket contacts that enabled shipment of contacts susceptible to developing low contact forces: (1) Improper heat treatment of the socket tines resulting in plastic rather than elastic behavior; (2) Overly thinned socket tines at their base resulting in reduced pin retention forces; (3) insufficient screening tests to identify parts susceptible to the aforementioned failure mechanisms. The results from an extensive screening program of socket contacts utilizing the industry standard contact separation force test procedures are described herein. The investigation shows this method to be capable of identifying initially weak sockets. However, sockets whose contact retention forces may degrade during use may not be screened out by pin retention testing alone. Further investigations are required to correlate low contact retention forces with increased electrical contact resistance in the presence of insulating films that may accumulate in the use environment.

  2. Pulsed electric field assisted assembly of polyaniline.

    PubMed

    Kumar, Arun; Kazmer, David O; Barry, Carol M F; Mead, Joey L

    2012-08-24

    Assembling conducting polyaniline (PANi) on pre-patterned nano-structures by a high rate, commercially viable route offers an opportunity for manufacturing devices with nanoscale features. In this work we report for the first time the use of pulsed electric field to assist electrophoresis for the assembly of conducting polyaniline on gold nanowire interdigitated templates. This technique offers dynamic control over heat build-up, which has been a main drawback in the DC electrophoresis and AC dielectrophoresis as well as the main cause of nanowire template damage. The use of this technique allowed higher voltages to be applied, resulting in shorter assembly times (e.g., 17.4 s, assembly resolution of 100 nm). Moreover, the area coverage increases with the increase in number of pulses. A similar trend was observed with the deposition height and the increase in deposition height followed a linear trend with a correlation coefficient of 0.95. When the experimental mass deposited was compared with Hamaker's theoretical model, the two were found to be very close. The pre-patterned templates with PANi deposition were subsequently used to transfer the nanoscale assembled PANi from the rigid templates to thermoplastic polyurethane using the thermoforming process. PMID:22863729

  3. Evidences of seismo-generated electric field

    NASA Astrophysics Data System (ADS)

    Liu, J. G.

    2009-12-01

    The global ionospheric map (GIM) is used to observe variations in the total electron content (TEC) of the global positioning system (GPS) associated with the 21 September 21 1999 M7.6 Chi-Chi earthquake, 26 December 2004 M9.3 Sumatra Earthquake, and 12 May 2008 M7.9 Wenchuan Earthquake. Spatial distributions of the TEC anomalies associated with the three earthquakes reveal remarkable conjugate signatures. The electron density profiles probed by six micro satellites of FORMOSAT3/COSMIC (F3/C) are further employed to simultaneously observe seismo-ionospheric anomalies during the Wenchuan earthquake. It is found that the ionospheric F2-peak electron density NmF2 and height hmF2 over the epicenter and its conjugate point significantly decreases approximately 40% and descends about 50-80km, respectively, when the GPS TEC anomalously reduces, while the NmF2 at the geomagnetic remarkable enhanced. This is an alternative evidence of the seismo-generated electric field being observed.

  4. The intra-spine electric force can drive vesicles for fusion: a theoretical model for long-term potentiation

    E-print Network

    Benuskova, Luba

    The intra-spine electric force can drive vesicles for fusion: a theoretical model for long 1999; accepted 7 December 1999 Abstract We have estimated the intensity of intra-spine electric ®elds triggered by stimulation of excitatory spine synapses. We show that this electric force can cause fast

  5. High-frequency electric field measurement using a toroidal antenna

    SciTech Connect

    Lee, Ki Ha

    2002-01-01

    A simple and compact method and apparatus for detecting high frequency electric fields, particularly in the frequency range of 1 MHz to 100 MHz, uses a compact toroidal antenna. For typical geophysical applications the sensor will be used to detect electric fields for a wide range of spectrum starting from about 1 MHz, in particular in the frequency range between 1 to 100 MHz, to detect small objects in the upper few meters of the ground. Time-varying magnetic fields associated with time-varying electric fields induce an emf (voltage) in a toroidal coil. The electric field at the center of (and perpendicular to the plane of) the toroid is shown to be linearly related to this induced voltage. By measuring the voltage across a toroidal coil one can easily and accurately determine the electric field.

  6. EFFECT OF FIELD POLARITY IN GUIDING SALMON FINGERLINGS BY ELECTRICITY

    E-print Network

    319 EFFECT OF FIELD POLARITY IN GUIDING SALMON FINGERLINGS BY ELECTRICITY SPECIAL SCIENTIFIC REPORT SALMON FINGERLINGS BY ELECTRICITY by H. William Newman Fishery Research Biologist Bureau of Commercial 3 The experiment 5 Results 6 Discussion and conclusions Sample size 6 Electrical treatments 7

  7. Simultaneous electric-field measurements on nearby balloons.

    NASA Technical Reports Server (NTRS)

    Mozer, F. S.

    1972-01-01

    Electric-field payloads were flown simultaneously on two balloons from Great Whale River, Canada, on September 21, 1971, to provide data at two points in the upper atmosphere that differed in altitude by more than one atmospheric density scale height and in horizontal position by 30-140 km. The altitude dependences in the two sets of data prove conclusively that the vertical electric field at balloon altitudes stems from fair-weather atmospheric electricity sources and that the horizontal fields are mapped down ionospheric fields, since the weather-associated horizontal fields were smaller than 2 mV/m.

  8. Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

    NASA Technical Reports Server (NTRS)

    Dye, J. E.; Bateman, M. G.; Christian, H. J.; Grainger, C. A.; Hall, W. D.; Krider, E. P.; Lewis, S. A.; Mach, D. M.; Merceret, F. J.; Willett, J. C.; Willis, P. T.

    2006-01-01

    A coordinated aircraft - radar project that investigated the electric fields, cloud microphysics and radar reflectivity of thunderstorm anvils near Kennedy Space Center is described. Measurements from two cases illustrate the extensive nature of the microphysics and electric field observations. As the aircraft flew from the edges of anvils into the interior, electric fields very frequently increased abruptly from approx.1 to >10 kV/m even though the particle concentrations and radar reflectivity increased smoothly. The abrupt increase in field usually occurred when the aircraft entered regions with a reflectivity of 10 to 15 dBZ. It is suggested that the abrupt increase in electric field may be because the charge advection from the storm core did not occur across the entire breadth of the anvil and was not constant in time. Screening layers were not detected near the edges of the anvils. Some long-lived anvils showed subsequent enhancement of electric field and reflectivity and growth of particles, which if localized, might be a factor in explaining the abrupt change of field in some cases. Comparisons of electric field magnitude with particle concentration or reflectivity for a combined data set that included all anvil measurements showed a threshold behavior. When the average reflectivity, such as in a 3-km cube, was less than approximately 5 dBZ, the electric field magnitude was <3 kV/m. Based on these findings, the Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) is now being used by NASA, the Air Force and Federal Aviation Administration in new Lightning Launch Commit Criteria as a diagnostic for high electric fields in anvils.

  9. Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

    NASA Technical Reports Server (NTRS)

    Dye, J. E.; Bateman, M. G.; Christian, H. J.; Defer, E.; Grainger, C. A.; Hall, W. D.; Krider, E. P.; Lewis, S. A.; Mach, D. M.; Merceret, F. J.; Willett, J. C.; Willis, P. T.

    2007-01-01

    A coordinated aircraft - radar project that investigated the electric fields, cloud microphysics and radar reflectivity of thunderstorm anvils near Kennedy Space Center is described. Measurements from two cases illustrate the extensive nature of the microphysics and electric field observations. As the aircraft flew from the edges of anvils into the interior, electric fields very frequently increased abruptly from approximately 1 to more than 10 kV m(exp -1) even though the particle concentration and radar reflectivity increased smoothly. The abrupt increase in field usually occurred when the aircraft entered regions with a reflectivity of 10 to 15 dBZ. It is suggested that the abrupt increase in electric field may be because the charge advection from the storm core did not occur across the entire breadth of the anvil and was not constant in time. Screening layers were not detected near the edges of the anvils. Some long-lived anvils showed subsequent enhancement of electric field and reflectivity and growth of particles, which if localized, might be a factor in explaining the abrupt change of field in some cases. Comparisons of electric field magnitude with particle concentration or reflectivity for a combined data set that included all anvil measurements showed a threshold behavior. When the average reflectivity, such as in a 3-km cube, was less than approximately 5 dBZ, the electric field magnitude was les than kV m(exp -1). Based on these findings, the Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) is now being used by NASA, the Air Force and Federal Aviation Administration in new Lightning Launch Commit Criteria as a diagnostic for high electric fields in anvils.

  10. Resonance tuning of electric field enhancement of nanogaps

    NASA Astrophysics Data System (ADS)

    Kang, Taehee; Rhie, Jiyeah; Park, Joohyun; Bahk, Young-Mi; Ahn, Jae Sung; Jeon, Hyeongtag; Kim, Dai-Sik

    2015-09-01

    We study the electric near-field enhancement of a metallic nanogap by far-field transmission measurement in the 0.6-2.3 µm wavelength range. The electric field is resonantly enhanced at the gap and the enhancement factor is quantified experimentally. The resonance condition of field enhancement can be controlled to various wavelengths by changing the gap size, which is confirmed by theoretical calculation using a mode expansion method.

  11. Enhanced roughness of lipid membranes caused by external electric fields

    E-print Network

    M Neek-Amal; H. Rafii-Tabar; H. R. Sepangi

    2007-05-17

    The behavior of lipid membranes in the presence of an external electric field is studied and used to examine the influence of such fields on membrane parameters such as roughness and show that for a micro sized membrane, roughness grows as the field increases. The dependence of bending rigidity on the electric field is also studied and an estimation of thickness of the accumulated charges around lipid membranes in a free-salt solution is presented.

  12. Reception and learning of electric fields in bees

    PubMed Central

    Greggers, Uwe; Koch, Gesche; Schmidt, Viola; Dürr, Aron; Floriou-Servou, Amalia; Piepenbrock, David; Göpfert, Martin C.; Menzel, Randolf

    2013-01-01

    Honeybees, like other insects, accumulate electric charge in flight, and when their body parts are moved or rubbed together. We report that bees emit constant and modulated electric fields when flying, landing, walking and during the waggle dance. The electric fields emitted by dancing bees consist of low- and high-frequency components. Both components induce passive antennal movements in stationary bees according to Coulomb's law. Bees learn both the constant and the modulated electric field components in the context of appetitive proboscis extension response conditioning. Using this paradigm, we identify mechanoreceptors in both joints of the antennae as sensors. Other mechanoreceptors on the bee body are potentially involved but are less sensitive. Using laser vibrometry, we show that the electrically charged flagellum is moved by constant and modulated electric fields and more strongly so if sound and electric fields interact. Recordings from axons of the Johnston organ document its sensitivity to electric field stimuli. Our analyses identify electric fields emanating from the surface charge of bees as stimuli for mechanoreceptors, and as biologically relevant stimuli, which may play a role in social communication. PMID:23536603

  13. ForceFit: a code to fit classical force fields to ab-initio potential energy surfaces

    SciTech Connect

    Henson, Neil Jon; Waldher, Benjamin; Kuta, Jadwiga; Clark, Aurora; Clark, Aurora E

    2009-01-01

    The ForceFit program package has been developed for fitting classical force field parameters based upon a force matching algorithm to quantum mechanical gradients of configurations that span the potential energy surface of the system. The program, which runs under Unix and is written in C++, is an easy to use, nonproprietary platform that enables gradient fitting of a wide variety of functional force field forms to quantum mechanical information obtained from an array of common electronic structure codes. All aspects of the fitting process are run from a graphical user interface, from the parsing of quantum mechanical data, assembling of a potential energy surface database, setting the force field and variables to be optimized, choosing a molecular mechanics code for comparison to the reference data, and finally, the initiation of a least squares minimization algorithm. Furthermore, the code is based on a modular templated code design that enables the facile addition of new functionality to the program.

  14. Self-force on an electric dipole in the spacetime of a cosmic string

    E-print Network

    C. R. Muniz; V. B Bezerra

    2013-10-16

    We calculate the electrostatic self-force on an electric dipole in the spacetime generated by a static, thin, infinite and straight cosmic string. The electric dipole is held fixed in different configurations, namely, parallel, perpendicular to the cosmic string and oriented along the azimuthal direction around this topological defect, which is stretched along the z axis. We show that the self-force is equivalent to an interaction of the electric dipole with an effective dipole moment which depends on the linear mass density of the cosmic string and on the configuration. The plots of the self-forces as functions of the parameter which determines the angular deficit of the cosmic string are shown for those different configurations.

  15. Influence of the dielectrophoretic force in mixed electrical double layers.

    PubMed

    López-García, José Juan; Horno, José; Grosse, Constantino

    2013-09-01

    The equilibrium properties of a charged plane immersed in an aqueous electrolyte solution are examined using a generalized Poisson-Boltzmann equation that takes into account the finite ion size by modeling the solution as a suspension of polarizable insulating spheres in water. This formalism is applied to a general solution composed of two or more counterion species with different valences, sizes, and effective permittivity values. It is shown that, due to the dependence of the dielectrophoretic force on the ion size and effective permittivity value, the concentration of the smaller counterion strongly increases while that of the larger one decreases in the immediate vicinity of the charged surface. As a result the surface potential value strongly increases as compared to the usual modified Poisson-Boltzmann theory that only includes steric interactions among ions. This effect is particularly important in the case of mixtures of univalent and divalent counterions, being significant even for relatively low surface charge values. PMID:23786835

  16. Fetal exposure to low frequency electric and magnetic fields

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

  17. Effects of a multichannel dynamic functional electrical stimulation system on hemiplegic gait and muscle forces.

    PubMed

    Qian, Jing-Guang; Rong, Ke; Qian, Zhenyun; Wen, Chen; Zhang, Songning

    2015-11-01

    [Purpose] The purpose of the study was to design and implement a multichannel dynamic functional electrical stimulation system and investigate acute effects of functional electrical stimulation of the tibialis anterior and rectus femoris on ankle and knee sagittal-plane kinematics and related muscle forces of hemiplegic gait. [Subjects and Methods] A multichannel dynamic electrical stimulation system was developed with 8-channel low frequency current generators. Eight male hemiplegic patients were trained for 4 weeks with electric stimulation of the tibia anterior and rectus femoris muscles during walking, which was coupled with active contraction. Kinematic data were collected, and muscle forces of the tibialis anterior and rectus femoris of the affected limbs were analyzed using a musculoskelatal modeling approach before and after training. A paired sample t-test was used to detect the differences between before and after training. [Results] The step length of the affected limb significantly increased after the stimulation was applied. The maximum dorsiflexion angle and maximum knee flexion angle of the affected limb were both increased significantly during stimulation. The maximum muscle forces of both the tibia anterior and rectus femoris increased significantly during stimulation compared with before functional electrical stimulation was applied. [Conclusion] This study established a functional electrical stimulation strategy based on hemiplegic gait analysis and musculoskeletal modeling. The multichannel functional electrical stimulation system successfully corrected foot drop and altered circumduction hemiplegic gait pattern. PMID:26696734

  18. Effects of a multichannel dynamic functional electrical stimulation system on hemiplegic gait and muscle forces

    PubMed Central

    Qian, Jing-guang; Rong, Ke; Qian, Zhenyun; Wen, Chen; Zhang, Songning

    2015-01-01

    [Purpose] The purpose of the study was to design and implement a multichannel dynamic functional electrical stimulation system and investigate acute effects of functional electrical stimulation of the tibialis anterior and rectus femoris on ankle and knee sagittal-plane kinematics and related muscle forces of hemiplegic gait. [Subjects and Methods] A multichannel dynamic electrical stimulation system was developed with 8-channel low frequency current generators. Eight male hemiplegic patients were trained for 4 weeks with electric stimulation of the tibia anterior and rectus femoris muscles during walking, which was coupled with active contraction. Kinematic data were collected, and muscle forces of the tibialis anterior and rectus femoris of the affected limbs were analyzed using a musculoskelatal modeling approach before and after training. A paired sample t-test was used to detect the differences between before and after training. [Results] The step length of the affected limb significantly increased after the stimulation was applied. The maximum dorsiflexion angle and maximum knee flexion angle of the affected limb were both increased significantly during stimulation. The maximum muscle forces of both the tibia anterior and rectus femoris increased significantly during stimulation compared with before functional electrical stimulation was applied. [Conclusion] This study established a functional electrical stimulation strategy based on hemiplegic gait analysis and musculoskeletal modeling. The multichannel functional electrical stimulation system successfully corrected foot drop and altered circumduction hemiplegic gait pattern. PMID:26696734

  19. INACTIVATION OF SACCHAROMYCES CEREVISIAE USING RADIO FREQUENCY ELECTRIC FIELDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The application of radio frequency (RF) electric fields was investigated as a nonthermal alternative to thermal inactivation of microorganisms in liquids. A novel RF system was developed and produced frequencies in the range of 20 kHz to 60 kHz. Electric field strengths of 20 kV/cm and 30 kV/cm we...

  20. PULSED ELECTRIC FIELD PROCESSING FACT SHEET FOR FOOD PROCESSORS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pulsed Electric Fields (PEF) apply intensive, high voltage electric field pulses to biological materials and cause cell membrane, primarily lipid bi-layers, to breakdown. PEF may be used to pasteurize fluid and pumpable foods. The benefit of PEF is the retention of product quality and freshness. A p...

  1. Adhesive Emulsion Bilayers under an Electric Field: From Unzipping to Fusion

    NASA Astrophysics Data System (ADS)

    Thiam, Abdou R.; Bremond, Nicolas; Bibette, Jérôme

    2011-08-01

    Water-in-oil emulsion drops are formed and stabilized with phospholipids which can adhere and form a bilayer. Using microfluidics, adhesive drop pairs are then trapped and submitted to an ac electric field. We observe three distinct states as a function of the adhesion energy and the electric field intensity. The pair can be either stable, though slightly deformed, or unzip and separate, or coalesce. The frontiers between the different states directly reflect vesicle detachment forces and electroporation theories. The experimental approach that we propose for probing liquid interface wetting between monolayers allows us to finely tuned the tension in the bilayer and gives access to bilayer unzipping.

  2. Adhesive emulsion bilayers under an electric field: from unzipping to fusion.

    PubMed

    Thiam, Abdou R; Bremond, Nicolas; Bibette, Jérôme

    2011-08-01

    Water-in-oil emulsion drops are formed and stabilized with phospholipids which can adhere and form a bilayer. Using microfluidics, adhesive drop pairs are then trapped and submitted to an ac electric field. We observe three distinct states as a function of the adhesion energy and the electric field intensity. The pair can be either stable, though slightly deformed, or unzip and separate, or coalesce. The frontiers between the different states directly reflect vesicle detachment forces and electroporation theories. The experimental approach that we propose for probing liquid interface wetting between monolayers allows us to finely tuned the tension in the bilayer and gives access to bilayer unzipping. PMID:21902373

  3. The exterior source surface for force-free fields. [solar atmosphere magnetic field model

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1978-01-01

    Consideration is given to the exterior source surface for force-free fields. The spherical harmonic expansion is presented for boundary values on two concentric spheres. An upper limit on a constant which measures the strength of coronal currents is found to be a function of the lowest multipole moment of the prescribed boundary values. The solar atmosphere is in the class of magnetic fields for which the study is applicable.

  4. A new model for electric force microscopy and its application for electrostatically generated phase difference in tapping mode AFM

    E-print Network

    Stone, Peter (Peter Robert)

    2005-01-01

    The harmonic force balance method was used to model and simulate electric force microscopy (EFM) and electrostatically generated phase difference in tapping mode AFM (EPTA) measurements. Simulations show that the harmonic ...

  5. Satellite measurements of high latitude convection electric fields.

    NASA Technical Reports Server (NTRS)

    Cauffman, D. P.; Gurnett, D. A.

    1972-01-01

    This paper reviews the first results of satellite experiments to measure magnetospheric convection electric fields using the double-probe technique. The earliest successful measurements were made with the low-altitude (680-2530 km) polar orbiting Injun-5 spacecraft. The Injun-5 results are compared with the initial findings of the electric field experiment on the polar orbiting OGO-6 satellite. Electric field measurements from the OGO-6 satellite have substantiated many of the initial Injun-5 observations with improved accuracy and sensitivity. The OGO-6 detector revealed the persistent occurrence of anti-sunward convection across the polar cap region at velocities not generally detectable with the Injun-5 experiment. The OGO-6 observations also provided information indicating that the location of the electric field reversal shifts equatorward during periods of increased magnetic activity. The implications of the electric field measurements for magnetospheric and auroral structure are summarized, and a list of specific recommendations for improving future experiments is presented.

  6. Magnetic phase diagram of graphene nanorings in an electric field.

    PubMed

    Zhou, Aiping; Sheng, Weidong

    2015-10-14

    Magnetic properties of graphene nanorings are investigated in the presence of an electric field. Within the formalism of Hubbard model, the graphene nanorings of various geometric configurations are found to exhibit rich phase diagram. For a nanoring system which has degenerate states at the Fermi level, the system is shown to undergo an abrupt phase transition from the antiferromagnetic to a nonmagnetic state in an electric field applied cross its zigzag edges. However, the nanoring is found to always stay in the antiferromagnetic state when the electric field is applied cross its armchair edges. For the other nanoring system with a finite single-particle gap, the magnetic moments of its antiferromagnetic ground state is seen to decrease gradually to zero with the electric field applied cross the zigzag edges. When the electric field is applied cross the armchair edges, the nanoring is shown to undergo several magnetic phase transitions before settling itself in a nonmagnetic ordering. PMID:26401952

  7. Application of polarizable ellipsoidal force field model to pnicogen bonds.

    PubMed

    Liu, Fang; Du, Likai; Gao, Jun; Wang, Lili; Song, Bo; Liu, Chengbu

    2015-03-15

    Noncovalent interactions, such as hydrogen bonds and halogen bonds, are frequently used in drug designing and crystal engineering. Recently, a novel noncovalent pnicogen bonds have been identified as an important driving force in crystal structures with similar bonding mechanisms as hydrogen bond and halogen bond. Although the pnicogen bond is highly anisotropic, the pnicogen bond angles range from 160° to 180° due to the complicated substituent effects. To understand the anisotropic characters of pnicogen bond, a modification of the polarizable ellipsoidal force field (PEff) model previously used to define halogen bonds was proposed in this work. The potential energy surfaces (PESs) of mono- and polysubstituted PH3 -NH3 complexes were calculated at CCSD(T), MP2, and density functional theory levels and were used to examine the modified PEff model. The results indicate that the modified PEff model can precisely characterize pnicogen bond. The root mean squared error of PES obtained with PEff model is less than 0.5 kcal/mol, compared with MP2 results. In addition, the modified PEff model may be applied to other noncovalent bond interactions, which is important to understand the role of intermolecular interactions in the self-assembly structures. PMID:25565043

  8. Microwave near-field imaging of electric fields in a superconducting microstrip resonator

    E-print Network

    Anlage, Steven

    Microwave near-field imaging of electric fields in a superconducting microstrip resonator Ashfaq S describe the use of a cryogenic near-field scanning microwave microscope to image microwave electric fields of about 200 m. We describe the operation of the system and present microwave images of Cu and Tl2Ba2CaCu2O

  9. Semiconductor crystal growth in crossed electric and magnetic fields: Center Director's Discretionary Fund

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.

    1996-01-01

    A unique growth cell was designed in which crossed electric and magnetic fields could be separately or simultaneously applied during semiconductor crystal growth. A thermocouple was inserted into an InSb melt inside the growth cell to examine the temperature response of the fluid to applied electromagnetic fields. A static magnetic field suppressed time-dependent convection when a destabilizing thermal field was applied. The simultaneous application of electric and magnetic fields resulted in forced convection in the melt. The InSb ingots grown in the cell were polycrystalline. An InGaSb crystal, 0.5 cm in diameter and 23-cm long, was grown without electromagnetic fields applied. The axial composition results indicated that complete mixing in the melt occurred for this large aspect ratio.

  10. Middle atmospheric electric fields over thunderstorms

    NASA Technical Reports Server (NTRS)

    Holzworth, Robert H.

    1992-01-01

    This grant has supported a variety of investigations all having to do with the external electrodynamics of thunderstorms. The grant was a continuation of work begun while the PI was at the Aerospace Corporation (under NASA Grant NAS6-3109) and the general line of investigation continues today under NASA Grants NAG5-685 and NAG6-111. This report will briefly identify the subject areas of the research and associated results. The period actually covered by the grant NAG5-604 included the following analysis and flights: (1) analysis of five successful balloon flights in 1980 and 1981 (under the predecessor NASA grant) in the stratosphere over thunderstorms; (2) development and flight of the Hy-wire tethered balloon system for direct measurement of the atmospheric potential to 250 kV (this involved multiple tethered balloon flight periods from 1981 through 1986 from several locations including Wallops Island, VA, Poker Flat and Ft. Greely, AK and Holloman AFB, NM.); (3) balloon flights in the stratosphere over thunderstorms to measure vector electric fields and associated parameters in 1986 (2 flights), 1987 (4 flights), and 1988 (2 flights); and (4) rocket-borne optical lightning flash detectors on two rocket flights (1987 and 1988) (the same detector design that was used for the balloon flights listed under #3). In summary this grant supported 8 stratospheric zero-pressure balloon flights, tethered aerostat flights every year between 1982-1985, instruments on 2 rockets, and analysis of data from 6 stratospheric flights in 1980/81.

  11. Dipole Relaxation in an Electric Field.

    ERIC Educational Resources Information Center

    Neumann, Richard M.

    1980-01-01

    Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)

  12. Investigation of crossed SAW fields by scanning acoustic force microscopy.

    PubMed

    Behme, G; Hesjedal, T

    2001-07-01

    We used multimode scanning acoustic force microscopy (SAFM) for studying noncollinearly propagating Rayleigh and Love wave fields. By analyzing torsion and bending movement of SAFM cantilever, normal and in-plane wave oscillation components are accessible. The SAFM principle is the down-conversion of surface oscillations into cantilever vibrations caused by the nonlinearity of the tip-sample interaction. Through mixing of complementary oscillation components, phase velocities of crossed Rayleigh waves on GaAs and crossed Rayleigh and Love waves on the layered system SiO2/ST-cut quartz were obtained simultaneously. Now, it is possible to investigate elastic properties of submicron areas through multimode SAFM measurements. Finally, we present mixing experiments of four SAWs on GaAs and discuss the various influences on the measured SAFM amplitude and phase contrast. PMID:11477772

  13. On the Use of Quartic Force Fields in Variational Calculations

    NASA Technical Reports Server (NTRS)

    Fortenberry, Ryan C.; Huang, Xinchuan; Yachmenev, Andrey; Thiel, Walter; Lee, Timothy J.

    2013-01-01

    The use of quartic force fields (QFFs) has been shown to be one of the most effective ways to efficiently compute vibrational frequencies for small molecules. In this paper we outline and discuss how the simple-internal or bond-length bond-angle (BLBA) coordinates can be transformed into Morse-cosine(-sine) coordinates which produce potential energy surfaces from QFFs that possess proper limiting behavior and can effectively describe the vibrational (or rovibrational) energy levels of an arbitrary molecular system. We investigate parameter scaling in the Morse coordinate, symmetry considerations, and examples of transformed QFFs making use of the MULTIMODE, TROVE, and VTET variational vibrational methods. Cases are referenced where variational computations coupled with transformed QFFs produce accuracies compared to experiment for fundamental frequencies on the order of 5 cm(exp -1) and often as good as 1 cm(exp -1).

  14. Molecular dynamics simulations of methane hydrate using polarizable force fields

    SciTech Connect

    Jiang, H.N.; Jordan, K.D.; Taylor, C.E.

    2007-03-01

    Molecular dynamics simulations of methane hydrate have been carried out using the AMOEBA and COS/G2 polarizable force fields. Properties examined include the temperature dependence of the lattice constant, the OC and OO radial distribution functions and the vibrational spectra. Both the AMOEBA and COS/G2 models are found to successfully account for the available experimental data, with overall slightly better agreement with experiment being found for the AMOEBA model. Several properties calculated using the AMOEBA and COS/G2 models differ appreciable from the corresponding results obtained previously using the polarizable TIP4P-FQ model. This appears to be due to the inadequacy of the treatment of polarization, especially, the restriction of polarization to in-plane only, in the TIP4P-FQ model.

  15. Enthalpy of formation and anharmonic force field of diacetylene.

    PubMed

    Simmonett, Andrew C; Schaefer, Henry F; Allen, Wesley D

    2009-01-28

    The enthalpy of formation of diacetylene (C4H2) is pinpointed using state-of-the-art theoretical methods, accounting for high-order electron correlation, relativistic effects, non-Born-Oppenheimer corrections, and vibrational anharmonicity. Molecular energies are determined from coupled cluster theory with single and double excitations (CCSD), perturbative triples [CCSD(T)], full triples (CCSDT), and perturbative quadruples [CCSDT(Q)], in concert with correlation-consistent basis sets (cc-pVXZ, X=D, T, Q, 5, 6) that facilitate extrapolations to the complete basis set limit. The first full quartic force field of diacetylene is determined at the highly accurate all-electron CCSD(T) level with a cc-pCVQZ basis, which includes tight functions for core correlation. Application of second-order vibrational perturbation theory to our anharmonic force field yields fundamental frequencies with a mean absolute difference of only 3.9 cm(-1) relative to the experimental band origins, without the use of any empirical scale factors. By a focal point approach, we converge on an enthalpy change for the isogyric reaction 2 H-C[triple bond]C-H-->H-C[triple bond]C-C[triple bond]C-H+H2 of (+0.03, +0.81) kcal mol(-1) at (0, 298.15) K. With the precisely established fHdegrees of acetylene, we thus obtain DeltafHdegrees(C4H2)=(109.4,109.7)+/-0.3 kcal mol(-1) at (0, 298.15) K. Previous estimates of the diacetylene enthalpy of formation range from 102 to 120 kcal mol(-1). PMID:19191379

  16. Enthalpy of formation and anharmonic force field of diacetylene

    NASA Astrophysics Data System (ADS)

    Simmonett, Andrew C.; Schaefer, Henry F.; Allen, Wesley D.

    2009-01-01

    The enthalpy of formation of diacetylene (C4H2) is pinpointed using state-of-the-art theoretical methods, accounting for high-order electron correlation, relativistic effects, non-Born-Oppenheimer corrections, and vibrational anharmonicity. Molecular energies are determined from coupled cluster theory with single and double excitations (CCSD), perturbative triples [CCSD(T)], full triples (CCSDT), and perturbative quadruples [CCSDT(Q)], in concert with correlation-consistent basis sets (cc-pVXZ, X =D, T, Q, 5, 6) that facilitate extrapolations to the complete basis set limit. The first full quartic force field of diacetylene is determined at the highly accurate all-electron CCSD(T) level with a cc-pCVQZ basis, which includes tight functions for core correlation. Application of second-order vibrational perturbation theory to our anharmonic force field yields fundamental frequencies with a mean absolute difference of only 3.9 cm-1 relative to the experimental band origins, without the use of any empirical scale factors. By a focal point approach, we converge on an enthalpy change for the isogyric reaction 2H-C?C-H?H-C?C-C?C-H+H2 of (+0.03, +0.81) kcal mol-1 at (0, 298.15) K. With the precisely established ?fH° of acetylene, we thus obtain ?fH°(C4H2)=(109.4,109.7)±0.3 kcal mol-1 at (0, 298.15) K. Previous estimates of the diacetylene enthalpy of formation range from 102 to 120 kcal mol-1.

  17. Charge and current reservoirs for electric and magnetic field enhancement.

    PubMed

    Wang, Dongxing; Yang, Tian; Crozier, Kenneth B

    2010-05-10

    Two optical antenna designs incorporating structures termed charge and current reservoirs are proposed to realize localized high electric and magnetic field enhancement, respectively. Simulation results show that the fan-rod electric antenna design combines the advantages of the rod antenna and the bowtie antenna, and has higher field enhancement than either. The performance of a loop shaped magnetic antenna consisting of a pair of metallic strips with offsets is also verified numerically, with high magnetic field enhancement being observed in the simulation. In both of the designs, the concepts of charge and current reservoirs contribute to high electric and magnetic field enhancement. PMID:20588894

  18. Electric field effects on the dynamics of bubble detachment from an inclined surface

    NASA Astrophysics Data System (ADS)

    Di Marco, P.; Morganti, N.; Saccone, G.

    2015-11-01

    An experimental apparatus to study bubble detachment from an inclined surface under the action of electric forces is described. It consists of a container filled with FC72 at room temperature and pressure where a train of gas bubbles is injected from an orifice. An electrostatic field can be imposed around the bubble, while the cell can be tilted from 0 to 90°. It is possible to study interface growth with the aid of high-speed cinematography. Since the interface is asymmetrical, a mirror system allowed to acquire, in the same frame, two images at 90° of the bubble. Different inclinations, injection rates and voltages were tested in order to couple the effects of shear gravity and electric field. Curvature and contact angles have been derived with appropriate interpolation methods of the profile. Force balances on the bubble were checked, finding an electric force, which, at first pulls the bubbles from the orifice, then pushes it against the surface. The motion of the center of gravity confirms this behaviour. A power balance has been developed to determine the energy contributions, revealing that surface growth incorporates both the effects of inlet power and electric field.

  19. Effects of an Electric Field on White Sharks: In Situ Testing of an Electric Deterrent

    PubMed Central

    Huveneers, Charlie; Rogers, Paul J.; Semmens, Jayson M.; Beckmann, Crystal; Kock, Alison A.; Page, Brad; Goldsworthy, Simon D.

    2013-01-01

    Elasmobranchs can detect minute electromagnetic fields, <1 nVcm–1, using their ampullae of Lorenzini. Behavioural responses to electric fields have been investigated in various species, sometimes with the aim to develop shark deterrents to improve human safety. The present study tested the effects of the Shark Shield Freedom7™ electric deterrent on (1) the behaviour of 18 white sharks (Carcharodon carcharias) near a static bait, and (2) the rates of attacks on a towed seal decoy. In the first experiment, 116 trials using a static bait were performed at the Neptune Islands, South Australia. The proportion of baits taken during static bait trials was not affected by the electric field. The electric field, however, increased the time it took them to consume the bait, the number of interactions per approach, and decreased the proportion of interactions within two metres of the field source. The effect of the electric field was not uniform across all sharks. In the second experiment, 189 tows using a seal decoy were conducted near Seal Island, South Africa. No breaches and only two surface interactions were observed during the tows when the electric field was activated, compared with 16 breaches and 27 surface interactions without the electric field. The present study suggests that the behavioural response of white sharks and the level of risk reduction resulting from the electric field is contextually specific, and depends on the motivational state of sharks. PMID:23658766

  20. Formation of magnetic discontinuities through superposition of force-free magnetic fields: Periodic boundaries

    SciTech Connect

    Kumar, Dinesh; Bhattacharyya, R.; Smolarkiewicz, P. K.

    2013-11-15

    In ideal magnetohydrodynamics characterized by an infinite electrical conductivity, the magnetic flux across an arbitrary fluid surface is conserved in time. The magnetofluid then can be partitioned into contiguous subvolumes of fluid, each of which entraps its own subsystem of magnetic flux. During dynamical evolution of the magnetofluid, these subvolumes press into each other; and in the process, two such subvolumes may come into direct contact while ejecting a third interstitial subvolume. Depending on the orientations of magnetic fields of the two interacting subvolumes, the magnetic field at the common surface of interaction may become discontinuous and a current sheet is formed there. This process of current sheet formation and their subsequent decay is believed to be a plausible mechanism for coronal heating and may also be responsible for various eruptive phenomena at the solar corona. In this work, we explore this theoretical concept through numerical simulations of a viscous, incompressible magnetofluid characterized by infinite electrical conductivity. In particular, we show that if the initial magnetic field is prescribed by superposition of two linear force-free fields with different torsion coefficients, then formation of current sheets are numerically realizable in the neighborhood of magnetic nulls.

  1. Enhanced Translational Dynamics of Water under Electric Field

    SciTech Connect

    Omar Diallo, Souleymane; Mamontov, Eugene; Wada, Nobuo; Inagaki, S; Fukushima, Y

    2012-01-01

    High resolution quasielastic neutron scattering measurements have been used to study the effects of applied electric field on the dynamics of water molecules confined in the pores of folded silica sheet material FSM-12 with an average pore diameter (apd) of 16 Angstroms. In the absence of field, there is a significant slowing down of the water molecule diffusion as the temperature is lowered, in agreement with previous observations. The application of a moderate electric field of 2.5 kV/mm remarkably enhances the translational diffusion of water molecules. We interpret this as being due to a disruption of the hydrogen bonding by the electric field. This new observation suggests that existing theories valid at large electric field strengths may have to be corrected at moderate fields.

  2. Computed modeling of alternating electric fields therapy for recurrent glioblastoma

    PubMed Central

    Lok, Edwin; Hua, Van; Wong, Eric T

    2015-01-01

    Tumor treating fields (TTFields) are alternating electric fields frequency tuned to 200 kHz for the treatment of recurrent glioblastoma. We report a patient treated with TTFields and determined the distribution of TTFields intracranially by computerized simulation using co-registered postgadolinium T1-weighted, T2, and MP RAGE images together with pre-specified conductivity and relative permittivity values for various cerebral structures. The distribution of the electric fields within the brain is inhomogeneous. Higher field intensities were aggregated near the ventricles, particularly at the frontal and occipital horns. The recurred tumor was found distant from the primary glioblastoma and it was located at a site of relatively lower electric field intensity. Future improvement in TTFields treatment may need to take into account the inhomogeneity of the electric field distribution within the brain. PMID:26311253

  3. Pair creation by a photon in an electric field

    E-print Network

    V. N. Baier; V. M. Katkov

    2009-12-29

    The process of pair creation by a photon in a constant and homogeneous electric field is investigated basing on the polarization operator in the field. The total probability of the process is found in a relatively simple form. At high energy the quasiclassical approximation is valid. The corrections to the standard quasiclassical approximation (SQA) are calculated. In the region relatively low photon energies, where SQA is unapplicable, the new approximation is used. It is shown that in this energy interval the probability of pair creation by a photon in electric field exceeds essentially the corresponding probability in a magnetic field. This approach is valid at the photon energy much larger than "vacuum" energy in electric field: $\\omega\\gg eE/m$. For smaller photon energies the low energy approximation is developed. At $\\omega\\ll eE/m$ the found probability describes the absorption of soft photon by the particles created by an electric field.

  4. Computed modeling of alternating electric fields therapy for recurrent glioblastoma.

    PubMed

    Lok, Edwin; Hua, Van; Wong, Eric T

    2015-11-01

    Tumor treating fields (TTFields) are alternating electric fields frequency tuned to 200 kHz for the treatment of recurrent glioblastoma. We report a patient treated with TTFields and determined the distribution of TTFields intracranially by computerized simulation using co-registered postgadolinium T1-weighted, T2, and MP RAGE images together with pre-specified conductivity and relative permittivity values for various cerebral structures. The distribution of the electric fields within the brain is inhomogeneous. Higher field intensities were aggregated near the ventricles, particularly at the frontal and occipital horns. The recurred tumor was found distant from the primary glioblastoma and it was located at a site of relatively lower electric field intensity. Future improvement in TTFields treatment may need to take into account the inhomogeneity of the electric field distribution within the brain. PMID:26311253

  5. Electric-field-induced rotation of Brownian metal nanowires.

    PubMed

    Arcenegui, Juan J; García-Sánchez, Pablo; Morgan, Hywel; Ramos, Antonio

    2013-09-01

    We describe the physical mechanism responsible for the rotation of Brownian metal nanowires suspended in an electrolyte exposed to a rotating electric field. The electric field interacts with the induced charge in the electrical double layer at the metal-electrolyte interface, causing rotation due to the torque on the induced dipole and to the induced-charge electro-osmotic flow around the particle. Experiments demonstrate that the primary driving mechanism is the former of these two. Our analysis contrasts with previous work describing the electrical manipulation of metallic particles with electric fields, which neglected the electrical double layer. Theoretical values for the rotation speed are calculated and good agreement with experiments is found. PMID:24125362

  6. Enhancement of methane conversion using electric fields. Quarterly report, December 1994--March 1995

    SciTech Connect

    Mallinson, R.G.; Lobban, L.L.

    1995-04-01

    The goal of this project is the development of novel, economical, processes for the conversion of natural gas to more valuable projects such as methanol, ethylene and other organic oxygenates or higher hydrocarbons. The methodologies of the project are to investigate and develop low temperature electric discharges and electric field-enhanced catalysis for carrying out these conversions. In the case of low temperature discharges, the conversion is carried out at ambient temperature which in effect trades high temperature thermal energy for electric energy as the driving force for conversion. The low operating temperature relax and thermodynamic constraints on the product distribution found at high temperature and also removes the requirements of large thermal masses required for current technologies. With the electric field-enhanced conversion, the operating temperatures are expected to be below those currently required for such processes as oxidative coupling, thereby allowing for a higher degree of catalytic selectivity while maintaining high activity.

  7. Ab initio parameterization of an all-atom polarizable and dissociable force field for water.

    PubMed

    Pinilla, Carlos; Irani, Amir H; Seriani, Nicola; Scandolo, Sandro

    2012-03-21

    A novel all-atom, dissociative, and polarizable force field for water is presented. The force field is parameterized based on forces, stresses, and energies obtained form ab initio calculations of liquid water at ambient conditions. The accuracy of the force field is tested by calculating structural and dynamical properties of liquid water and the energetics of small water clusters. The transferability of the force field to dissociated states is studied by considering the solvation of a proton and the ionization of water at extreme conditions of pressure and temperature. In the case of the solvated proton, the force field properly describes the presence of both Eigen and Zundel configurations. In the case of the pressure-induced ice VIII/ice X transition and the temperature-induced transition to a superionic phase, the force field is found to describe accurately the proton symmetrization and the melting of the proton sublattice, respectively. PMID:22443781

  8. Electric field in 3D gravity with torsion

    SciTech Connect

    Blagojevic, M.; Cvetkovic, B.

    2008-08-15

    It is shown that in static and spherically symmetric configurations of the system of Maxwell field coupled to 3D gravity with torsion, at least one of the Maxwell field components has to vanish. Restricting our attention to the electric sector of the theory, we find an interesting exact solution, corresponding to the azimuthal electric field. Its geometric structure is to a large extent influenced by the values of two different central charges, associated to the asymptotic AdS structure of spacetime.

  9. Electric Field-Mediated Processing of Polymers. Appendix 1

    NASA Technical Reports Server (NTRS)

    Wnek, G. E.; Bowlin, G. L.; Haas, T. W.

    2000-01-01

    Significant opportunities exist for the processing of polymers (homopolymers and blends) using electric fields. We suggest that a broad range of properties can be achieved using a relatively small number of polymers, with electric fields providing the ability to tailor properties via the control of shape, morphology, and orientation. Specific attention is given to electrospinning, but we note that electroaerosol formation and field-modulated film casting represent additional processing options.

  10. Comparison of Nonlinear Force-Free Field and Potential Field in the Quiet Sun

    NASA Astrophysics Data System (ADS)

    Liu, S.; Zhang, H. Q.; Su, J. T.

    2011-05-01

    In this paper, a potential field extrapolation and three nonlinear force-free (NLFF) field extrapolations (optimization, direct boundary integral (DBIE), and approximate vertical integration (AVI) methods) are used to study the spatial configuration of magnetic field in the quiet Sun. It is found that differences in the computed field strengths among the three NLFF and potential fields exist in the low layers. However, they tend to disappear as the height increases, and the differences are of the order of 0.1 gauss when the height exceeds ? 2000 km above the photosphere. The difference in azimuth angles between each NLFF field model and the potential field is as follows: for the optimization field, it decreases evidently as the height increases; for the DBIE field, it almost stays constant and shows no significant change as the height increases; for the AVI field, it increases slowly as the height increases. Our analysis shows that the reconstructed NLFF fields deviate significantly from the potential field in the quiet Sun.

  11. Dynamics of ultracold molecules in confined geometry and electric field

    SciTech Connect

    Quemener, Goulven; Bohn, John L.

    2011-01-15

    We present a time-independent quantum formalism to describe the dynamics of molecules with permanent electric dipole moments in a two-dimensional confined geometry such as a one-dimensional optical lattice, in the presence of an electric field. Bose versus Fermi statistics and selection rules play a crucial role in the dynamics. As examples, we compare the dynamics of confined fermionic and bosonic polar KRb molecules under different confinements and electric fields. We show how chemical reactions can be suppressed, either by a 'statistical suppression' which applies for fermions at small electric fields and confinements, or by a 'potential energy suppression', which applies for both fermions and bosons at high electric fields and confinements. We also explore collisions that transfer molecules from one state of the confining potential to another. Although these collisions can be significant, we show that they do not play a role in the loss of the total number of molecules in the gas.

  12. Electric toothbrushes induce electric current in fixed dental appliances by creating magnetic fields.

    PubMed

    Kameda, Takashi; Ohkuma, Kazuo; Ishii, Nozomu; Sano, Natsuki; Ogura, Hideo; Terada, Kazuto

    2012-01-01

    Magnetic fields can represent a health problem, especially low frequency electromagnetic fields sometimes induced by electric current in metallic objects worn or used in or on the body (as opposed to high frequency electromagnetic fields that produce heat). Electric toothbrushes are widely used because of their convenience, but the electric motors that power them may produce electromagnetic waves. In this study, we showed that electric toothbrushes generate low frequency (1-2000 Hz) magnetic fields and induce electric current in dental appliances (e. g. orthodontic and prosthetic appliances and dental implants). Current induced by electric toothbrushes might be dependent on the quantity and types of metals used, and the shape of the appliances. Furthermore, these induced currents in dental appliances could impact upon human oral health, producing pain and discomfort. PMID:23037851

  13. Transient Charge Accumulation Applied Electric Field

    E-print Network

    Anlage, Steven

    bottom plate. Discussion Repeatability of initially increasing signal suggests electrical mechanism. Experimental Apparatus Cell Acceleration Acknowledgments Sand Mass Cell Acceleration Sand Mass Charging increases with time up to saturation point. Sand Mass Signal insensitive to sand mass in this configuration

  14. Variations in Gravitational Field, Tidal Force, Electromagnetic Waves and Earthquakes

    NASA Astrophysics Data System (ADS)

    Strasser, Valentino

    2010-12-01

    This paper is the report on an experiment carried out between the month of December 2009 and the month of April 2010 between the Venetian Lagoon and the Northern Apennines in Italy, to check on a potential relationship between earthquakes and variations in the local gravitational field, the effect on the tide exercised by the interaction between the moon and the Sun, the appearance of anomalous light effects in the atmosphere ("Earth lights"), and the emission of radio waves caused by stresses in the Earth's crust. The cases studied show that there is indeed some concomitance between the periodic rising and falling of the sea level and the terrestrial tide effect, due to the gravitational attraction of the moon and sun on the Earth. In fact, changes in the local force of gravity coincided with the cycle of high and low tides and, in certain cases, with a variation in the electromagnetic field that preceded the occurrence of a seismic event by just a few hours. The o! bservations in the article are limited to the magnitude range discussed in the paper.

  15. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  16. The hydrogen atom in plasmas with an external electric field

    SciTech Connect

    Bahar, M. K.; Soylu, A.

    2014-09-15

    We numerically solve the Schrödinger equation, using a more general exponential cosine screened Coulomb (MGECSC) potential with an electric field, in order to investigate the screening and weak external electric field effects on the hydrogen atom in plasmas. The MGECSC potential is examined for four different cases, corresponding to different screening parameters of the potential and the external electric field. The influences of the different screening parameters and the weak external electric field on the energy eigenvalues are determined by solving the corresponding equations using the asymptotic iteration method (AIM). It is found that the corresponding energy values shift when a weak external electric field is applied to the hydrogen atom in a plasma. This study shows that a more general exponential cosine screened Coulomb potential allows the influence of an applied, weak, external electric field on the hydrogen atom to be investigated in detail, for both Debye and quantum plasmas simultaneously. This suggests that such a potential would be useful in modeling similar effects in other applications of plasma physics, and that AIM is an appropriate method for solving the Schrödinger equation, the solution of which becomes more complex due to the use of the MGECSC potential with an applied external electric field.

  17. Nanoscale Lubrication of Ionic Surfaces Controlled via a Strong Electric Field

    NASA Astrophysics Data System (ADS)

    Strelcov, Evgheni; Kumar, Rajeev; Bocharova, Vera; Sumpter, Bobby G.; Tselev, Alexander; Kalinin, Sergei V.

    2015-01-01

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip and salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. The demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems.

  18. Nanoscale lubrication of ionic surfaces controlled via a strong electric field.

    PubMed

    Strelcov, Evgheni; Kumar, Rajeev; Bocharova, Vera; Sumpter, Bobby G; Tselev, Alexander; Kalinin, Sergei V

    2015-01-01

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip and salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. The demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems. PMID:25623295

  19. Nanoscale Lubrication of Ionic Surfaces Controlled via a Strong Electric Field

    PubMed Central

    Strelcov, Evgheni; Kumar, Rajeev; Bocharova, Vera; Sumpter, Bobby G.; Tselev, Alexander; Kalinin, Sergei V.

    2015-01-01

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip and salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. The demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems. PMID:25623295

  20. FEASIBILITY OF PRODUCING COMMODITIES AND ELECTRICITY FOR SPACE SHUTTLE OPERATIONS AT VANDENBERG AIR FORCE BASE

    EPA Science Inventory

    The report gives results of a preliminary screening study of the technical and economic feasibility of the on-site production of commodities (liquid propellant and gases) and electricity to support space shuttle launch activities at Vandenberg Air Force Base (VAFB). Both commerci...

  1. Video: Animals; Electric Current; Force; Science Activities. Learning in Science Project. Working Papers 51-54.

    ERIC Educational Resources Information Center

    Bell, Beverley; And Others

    Four papers to be used in conjunction with video-tapes developed by the Learning in Science Project are presented. Topic areas of the papers focus on: (1) animals; (2) electric current; (3) force; and (4) science activities. The first paper presents transcripts of class discussions focusing on the scientific meaning of the word animal. The second…

  2. A method for embedding circular force-free flux ropes in potential magnetic fields

    SciTech Connect

    Titov, V. S.; Török, T.; Mikic, Z.; Linker, J. A.

    2014-08-01

    We propose a method for constructing approximate force-free equilibria in pre-eruptive configurations in which a thin force-free flux rope is embedded into a locally bipolar-type potential magnetic field. The flux rope is assumed to have a circular-arc axis, a circular cross-section, and electric current that is either concentrated in a thin layer at the boundary of the rope or smoothly distributed across it with a maximum of the current density at the center. The entire solution is described in terms of the magnetic vector potential in order to facilitate the implementation of the method in numerical magnetohydrodynamic (MHD) codes that evolve the vector potential rather than the magnetic field itself. The parameters of the flux rope can be chosen so that its subsequent MHD relaxation under photospheric line-tied boundary conditions leads to nearly exact numerical equilibria. To show the capabilities of our method, we apply it to several cases with different ambient magnetic fields and internal flux-rope structures. These examples demonstrate that the proposed method is a useful tool for initializing data-driven simulations of solar eruptions.

  3. Molecular-scale measurements of electric fields at electrochemical interfaces.

    SciTech Connect

    Hayden, Carl C.; Farrow, Roger L.

    2011-01-01

    Spatially resolved measurements of electric fields at electrochemical interfaces would be a critical step toward further understanding and modeling the detailed structure of electric double layers. The goal of this project was to perform proof-of-principle experiments to demonstrate the use of field-sensitive dyes for optical measurements of fields in electrochemical systems. A confocal microscope was developed that provides sensitive detection of the lifetime and high resolution spectra of excited fluorescence for dyes tethered to electrically conductive surfaces. Excited state lifetimes for the dyes were measured and found to be relatively unquenched when linked to indium tin oxide, but strongly quenched on gold surfaces. However, our fluorescence detection is sufficiently sensitive to measure spectra of submonolayer dye coatings even when the fluorescence was strongly quenched. Further work to create dye labeled interfaces on flat, uniform and durable substrates is necessary to make electric field measurements at interfaces using field sensitive dyes.

  4. Independent Manipulation of Electric and Thermal Fields with Bilayer Structure

    E-print Network

    Lan, Chuwen; Wu, Lingling; Li, Bo; Zhou, Ji

    2015-01-01

    Recently, increasing attention has been focused on the employment of transformation and metamaterial for manipulation of various physical fields, which requires complicated configuration and usually limits in single field. Here, for the first time, we propose and experimentally demonstrated bilayer structure to achieve simultaneously independent manipulation of multi-physics field (dc electric fields and thermal) by directly solving the dc electric/ thermal field equations. This structure is composed of two layers: the outer layer is made of isotropic and homogeneous material, while the inner layer is fan-shape layer. Since it is not based on TO, it can be readily experimentally fabricated with naturally occurring materials. Experimentally, we has designed, fabricated and characterized two structures simultaneously behaving as dc electric cloak/ thermal concentrator and dc electric concentrator/ thermal cloak, respectively. The simulation results agree well with the experiment ones, thus confirming the feasib...

  5. Electron propagation in crossed magnetic and electric fields

    E-print Network

    Tobias Kramer; Christian Bracher; Manfred Kleber

    2003-07-30

    Laser-atom interaction can be an efficient mechanism for the production of coherent electrons. We analyze the dynamics of monoenergetic electrons in the presence of uniform, perpendicular magnetic and electric fields. The Green function technique is used to derive analytic results for the field--induced quantum mechanical drift motion of i) single electrons and ii) a dilute Fermi gas of electrons. The method yields the drift current and, at the same time it allows us to quantitatively establish the broadening of the (magnetic) Landau levels due to the electric field: Level number k is split into k+1 sublevels that render the $k$th oscillator eigenstate in energy space. Adjacent Landau levels will overlap if the electric field exceeds a critical strength. Our observations are relevant for quantum Hall configurations whenever electric field effects should be taken into account.

  6. Electric field induced selective disordering in lamellar block copolymers.

    PubMed

    Ruppel, Markus; Pester, Christian W; Langner, Karol M; Sevink, Geert J A; Schoberth, Heiko G; Schmidt, Kristin; Urban, Volker S; Mays, Jimmy W; Böker, Alexander

    2013-05-28

    External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the order-disorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the order-disorder transition and well below it. PMID:23573901

  7. Galvanotactic behavior of Tetrahymena pyriformis under electric fields

    NASA Astrophysics Data System (ADS)

    Kim, Dal Hyung; Kim, Paul Seung Soo; Lee, Kyoungwoo; Kim, JinSeok; Kim, Min Jun

    2013-12-01

    Tetrahymena pyriformis, a eukaryotic ciliate, swims toward a cathode in straight or cross-shaped microchannels under an applied electric field, a behavioral response called cathodal galvanotaxis. In straight channel experiments, a one-dimensional electric field was applied, and the galvanotactic swimming behavior of Tetrahymena pyriformis was observed and described in detail while the polarity of this field is switched. In most individual cases, the cell would immediately switch its direction toward the cathode; however, exceptional cases have been observed where cells exhibit a turning delay or do not turn after a polarity switch. In cross-channel experiments, feedback control using vision-based tracking was used to steer a cell in the microchannel intersection using a two-dimensional electric field generated by four electrodes placed at four ends of the cross channel. The motivation for this work is to study the swimming behavior of Tetrahymena pyriformis as a microrobot under the control of electric fields.

  8. Generation of strong electric fields in an ice film capacitor

    NASA Astrophysics Data System (ADS)

    Shin, Sunghwan; Kim, Youngsoon; Moon, Eui-seong; Lee, Du Hyeong; Kang, Hani; Kang, Heon

    2013-08-01

    We present a capacitor-type device that can generate strong electrostatic field in condensed phase. The device comprises an ice film grown on a cold metal substrate in vacuum, and the film is charged by trapping Cs+ ions on the ice surface with thermodynamic surface energy. Electric field within the charged film was monitored through measuring the film voltage using a Kelvin work function probe and the vibrational Stark effect of acetonitrile using IR spectroscopy. These measurements show that the electric field can be increased to ˜4 × 108 V m-1, higher than that achievable by conventional metal plate capacitors. In addition, the present device may provide several advantages in studying the effects of electric field on molecules in condensed phase, such as the ability to control the sample composition and structure at molecular scale and the spectroscopic monitoring of the sample under electric field.

  9. The source of the electric field in the nightside magnetosphere

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1975-01-01

    In the open magnetosphere model magnetic field lines from the polar caps connect to the interplanetary magnetic field and conduct an electric field from interplanetary space to the polar ionosphere. By examining the magnetic flux involved it is concluded that only slightly more than half of the magnetic flux in the polar caps belongs to open field lines and that such field lines enter or leave the magnetosphere through narrow elongated windows stretching the tail. These window regions are identified with the tail's boundary region and shift their position with changes in the interplanetary magnetic field, in particular when a change of interplanetary magnetic sector occurs. The circuit providing electric current in the magnetopause and the plasma sheet is extended across those windows; thus energy is drained from the interplanetary electric field and an electric potential drop is produced across the plasma sheet. The polar cap receives its electric field from interplanetary space on the day side from open magnetic field lines and on the night side from closed field lines leading to the plasma sheet. The theory described provides improved understanding of magnetic flux bookkeeping, of the origin of Birkeland currents, and of the boundary layer of the geomagnetic tail.

  10. Early trimpi events from lightning-induced electric fields in the ionosphere: An alternative explanation. (Reannouncement with new availability information)

    SciTech Connect

    Burke, W.J.

    1992-12-31

    Two classes of Trimpi modulation of VLF signals in the Earth-ionosphere waveguide have been identified in the literature. The more common type occurs 1 s or more after causative lightning strokes, the second in less than 100 ms. The authors explore the possibility that these early Trimpi events result from lightning-generated, electric field impulses lowering the mirror altitudes of trapped electrons. To overcome the mirror force on energetic electrons, upward-directed electric fields with strength of a few tens of mV/m are required. This is well within the range of electric field observed on sounding rockets above thunderstorms.

  11. Electric-field-driven Phenomena for Manipulating Particles in Micro-Devices

    NASA Technical Reports Server (NTRS)

    Khusid, Boris; Acrivos, Andreas

    2004-01-01

    Compared to other available methods, ac dielectrophoresis is particularly well-suited for the manipulation of minute particles in micro- and nano-fluidics. The essential advantage of this technique is that an ac field at a sufficiently high frequency suppresses unwanted electric effects in a liquid. To date very little has been achieved towards understanding the micro-scale field-and shear driven behavior of a suspension in that, the concepts currently favored for the design and operation of dielectrophoretic micro-devices adopt the approach used for macro-scale electric filters. This strategy considers the trend of the field-induced particle motions by computing the spatial distribution of the field strength over a channel as if it were filled only with a liquid and then evaluating the direction of the dielectrophoretic force, exerted on a single particle placed in the liquid. However, the exposure of suspended particles to a field generates not only the dielectrophoretic force acting on each of these particles, but also the dipolar interactions of the particles due to their polarization. Furthermore, the field-driven motion of the particles is accompanied by their hydrodynamic interactions. We present the results of our experimental and theoretical studies which indicate that, under certain conditions, these long-range electrical and hydrodynamic interparticle interactions drastically affect the suspension behavior in a micro-channel due to its small dimensions.

  12. Vertical Electric Field Measurements with Copper Plates by Sounding Balloon

    NASA Astrophysics Data System (ADS)

    Wen, Shao-Chun; Chiu, Cheng-Hsiu; Bing-Chih Chen, Alfred; Hsu, Rue-Ron; Su, Han-Tzong

    2015-04-01

    The vertical electric field plays an important role in driving the circulation of the global electric circuit, and crucial to the formation of the transient luminous events (TLEs). The in-situ measurement of the electric field in the upper atmosphere, especially from cloud top to the bottom of the ionosphere is very challenging but essential. Limited by the flight vehicle, the measurements of the electric field in and above cloud, especiall thundercloud, is rare up to now. A light-weight electric field meter was developed independently and sent to 30 km height by small meteorological balloons successfully. Other than the existing long-spaced, spherical probe design, an improved electric field meter has been built and tested carefully. A new circuit with ultra high input impedance and a high voltage amplifier is implemented to reduce the AC noise induced by the voltage divider. Two copper plates are used to replace the double spherical probes which is spaced by a long fiberglass boom. The in-lab calibration and tests show that this new model is superior to the existing design and very sensitive to the variation of the DC electric field. In this poster, the design and the in-lab tests will be presented, and preliminary results of the flight experiments are also discussed.

  13. On radiation forces acting on a transparent nanoparticle in the field of a focused laser beam

    NASA Astrophysics Data System (ADS)

    Afanas'ev, A. A.; Gaida, L. S.; Guzatov, D. V.; Rubinov, A. N.; Svistun, A. Ch

    2015-10-01

    Radiation forces acting on a transparent spherical nanoparticle in the field of a focused Gaussian laser beam are studied theoretically in the Rayleigh scattering regime. Expressions are derived for the scattering force and Cartesian components of the gradient force. The resultant force acting on a nanoparticle located in the centre of a laser beam is found. The parameters of the focused beam and optical properties of the nanoparticle for which the longitudinal component of the gradient force exceeds the scattering force are determined. Characteristics of the transverse gradient force are discussed.

  14. Generating ``Superponderomotive'' Electrons due to a Non-Wake-Field Interaction between a Laser Pulse and a Longitudinal Electric Field

    NASA Astrophysics Data System (ADS)

    Robinson, A. P. L.; Arefiev, A. V.; Neely, D.

    2013-08-01

    It is shown that electrons with momenta exceeding the “free electron” limit of meca02/2 can be produced when a laser pulse and a longitudinal electric field interact with an electron via a non-wake-field mechanism. The mechanism consists of two stages: the reduction of the electron dephasing rate ?-px/mec by an accelerating region of electric field and electron acceleration by the laser via the Lorentz force. This mechanism can, in principle, produce electrons that have longitudinal momenta that is a significant multiple of meca02/2. 2D particle-in-cell simulations of a relatively simple laser-plasma interaction indicate that the generation of superponderomotive electrons is strongly affected by this “antidephasing” mechanism.

  15. Ion trap electric field measurements using slab coupled optical sensors

    NASA Astrophysics Data System (ADS)

    Shumway, L.; Chadderdon, S.; Powell, A.; Li, A.; Austin, D.; Hawkins, A.; Selfridge, R.; Schultz, S.

    2014-03-01

    Ion traps are widely used in the field of mass spectrometry. These devices use high electric fields to mass-selectively trap, eject, and count the particles of a material, producing a mass spectrum of the given material. Because of their usefulness, technology pushes for smaller, more portable ion traps for field use. Making internal ion trap field measurements not yet feasible because current electric field sensors are often too bulky or their metallic composition perturbs field measurements. Using slab coupled optical sensor (SCOS) technology, we are able to build sensors that are compatible with the spacing constraints of the ion trap. These sensors are created by attaching a nonlinear crystal slab waveguide to an optical fiber. When a laser propagates through the fiber, certain wavelengths of light couple out of the fiber via the crystal and create "resonances" in the output light spectrum. These resonances shift in proportion to a given applied electric field, and by measuring that shift, we can approximate the electric field. Developing a sensor that can effectively characterize the electric fields within an ion trap will greatly assist in ion trap design, fabrication, and troubleshooting techniques.

  16. Static Electric Field Mapping Using a Mosquito Racket and Baby Oil

    ERIC Educational Resources Information Center

    Rediansyah, Herfien; Khairurrijal; Viridi, Sparisoma

    2015-01-01

    The aim of this research was to design a simple experimental device to see electric field force lines using common components which are readily available in everyday life. A solution of baby oil was placed in a plastic container, 4.5 × 4.5 × 1 inches, with both ends of the electrodes (metal wire) immersed in the solution at a depth of 0.2 inches.…

  17. Electric field effect in ultrathin zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Xing; Liu, Yun-Xiao; Tian, Hua; Xu, Jun-Wei; Feng, Lin

    2015-07-01

    The electric field effect in ultrathin zigzag graphene nanoribbons containing only three or four zigzag carbon chains is studied by first-principles calculations, and the change of conducting mechanism is observed with increasing in-plane electric field perpendicular to the ribbon. Wider zigzag graphene nanoribbons have been predicted to be spin-splitted for both valence band maximum (VBM) and conduction band minimum (CBM) with an applied electric field and become half-metal due to the vanishing band gap of one spin with increasing applied field. The change of VBM for the ultrathin zigzag graphene nanoribbons is similar to that for the wider ones when an electric field is applied. However, in the ultrathin zigzag graphene nanoribbons, there are two kinds of CBMs, one is spin-degenerate and the other is spin-splitted, and both are tunable by the electric field. Moreover, the two CBMs are spatially separated in momentum space. The conducting mechanism changes from spin-degenerate CBM to spin-splitted CBM with increasing applied electric field. Our results are confirmed by density functional calculations with both LDA and GGA functionals, in which the LDA always underestimates the band gap while the GGA normally produces a bigger band gap than the LDA. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204201 and 11147142) and the Natural Science Foundation for Young Scientists of Shanxi Province, China (Grant No. 2013021010-1).

  18. Polarizable Mean-Field Model of Water for Biological Simulations with Amber and Charmm force fields

    E-print Network

    Leontyev, Igor

    2015-01-01

    Although a great number of computational models of water are available today, the majority of current biological simulations are done with simple models, such as TIP3P and SPC, developed almost thirty years ago and only slightly modified since then. The reason is that the non-polarizable force fields that are mostly used to describe proteins and other biological molecules are incompatible with more sophisticated modern polarizable models of water. The issue is electronic polarizability: in liquid state, in protein, and in vacuum the water molecule is polarized differently, and therefore has different properties; thus the only way to describe all these different media with the same model is to use a polarizable water model. However, to be compatible with the force field of the rest of the system, e.g. a protein, the latter should be polarizable as well. Here we describe a novel model of water that is in effect polarizable, and yet compatible with the standard non-polarizable force fields such as AMBER, CHARMM,...

  19. Monte Carlo simulations of air showers in atmospheric electric fields

    E-print Network

    Buitink, S; Falcke, H; Heck, D; Kuijpers, J

    2009-01-01

    The development of cosmic ray air showers can be influenced by atmospheric electric fields. Under fair weather conditions these fields are small, but the strong fields inside thunderstorms can have a significant effect on the electromagnetic component of a shower. Understanding this effect is particularly important for radio detection of air showers, since the radio emission is produced by the shower electrons and positrons. We perform Monte Carlo simulations to calculate the effects of different electric field configurations on the shower development. We find that the electric field becomes important for values of the order of 1 kV/cm. Not only can the energy distribution of electrons and positrons change significantly for such field strengths, it is also possible that runaway electron breakdown occurs at high altitudes, which is an important effect in lightning initiation.

  20. Semiclassical pair production rate for rotating electric fields

    NASA Astrophysics Data System (ADS)

    Strobel, Eckhard; Xue, She-Sheng

    2015-02-01

    We semiclassically investigate Schwinger pair production for pulsed rotating electric fields depending on time. To do so we solve the Dirac equation for two-component fields in a Wentzel-Kramers-Brillouin-like approximation. The result shows that for two-component fields the spin distribution of produced pairs is generally not 1 ?1 . As a result the pair creation rates of spinor and scalar QED are different even for one pair of turning points. For rotating electric fields, the pair creation rate is dominated by particles with a specific spin depending on the sense of rotation for a certain range of pulse lengths and frequencies. We present an analytical solution for the momentum spectrum of the constant rotating field. We find interference effects not only in the momentum spectrum but also in the total particle number of rotating electric fields.

  1. Effective critical electric field for runaway-electron generation.

    PubMed

    Stahl, A; Hirvijoki, E; Decker, J; Embréus, O; Fülöp, T

    2015-03-20

    In this Letter we investigate factors that influence the effective critical electric field for runaway-electron generation in plasmas. We present numerical solutions of the kinetic equation and discuss the implications for the threshold electric field. We show that the effective electric field necessary for significant runaway-electron formation often is higher than previously calculated due to both (1) extremely strong dependence of primary generation on temperature and (2) synchrotron radiation losses. We also address the effective critical field in the context of a transition from runaway growth to decay. We find agreement with recent experiments, but show that the observation of an elevated effective critical field can mainly be attributed to changes in the momentum-space distribution of runaways, and only to a lesser extent to a de facto change in the critical field. PMID:25839283

  2. Insurance for electric and magnetic field litigation: Are you covered

    SciTech Connect

    Anderson, E.R.; Stewart, C.A. III

    1993-04-01

    Electrical power generating companies, power transmission companies and large generators and users of electrical power recently felt the sting of a second shock. The first shock came when lawsuits were first filed against companies in the electrical power industry claiming real or imagined damages from electrical and magnetic fields ([open quotes]EMFs[close quotes]). The new and second shock is potentially more devastating because it comes from the [open quotes]safe hands[close quotes] of the insurance industry. Standard-form comprehensive general liability ([open quotes]CGL[close quotes]) insurance policies purchased by nearly every company in the electrical power industry for generations are supposed to cover EMF bodily injury and property damage claims. Not so, say the lawyers for the most prominent insurance company selling insurance coverage to electric utilities, Associated Electric Gas Insurance Services, Ltd. ([open quotes]AEGIS[close quotes]).

  3. Stability of a liquid drop in an electric field

    SciTech Connect

    Popova, L.N.; Fedorenko, A.I.

    1982-04-01

    The boundary-value problem is solved for the critical electric field that causes a loss of stability of a dielectric electric drop. The theory is compared to experimental results on water, glycerin, N, N-dimethylformamide, and diethylene glycol.(AIP)

  4. Force Field Model of Periodic Trends in Biomolecular Halogen Bonds.

    PubMed

    Scholfield, Matthew R; Ford, Melissa Coates; Vander Zanden, Crystal M; Billman, M Marie; Ho, P Shing; Rappé, Anthony K

    2015-07-23

    The study of the noncovalent interaction now defined as a halogen bond (X-bond) has become one of the fastest growing areas in experimental and theoretical chemistry--its applications as a design tool are highly extensive. The significance of the interaction in biology has only recently been recognized, but has now become important in medicinal chemistry. We had previously derived a set of empirical potential energy functions to model the structure-energy relationships for bromines in biomolecular X-bonds (BXBs). Here, we have extended this force field for BXBs (ffBXB) to the halogens (Cl, Br, and I) that are commonly seen to form stable X-bonds. The ffBXB calculated energies show a remarkable one-to-one linear relationship to explicit BXB energies determined from an experimental DNA junction system, thereby validating the approach and the model. The resulting parameters allow us to interpret the stabilizing effects of BXBs in terms of well-defined physical properties of the halogen atoms, including their size, shape, and charge, showing periodic trends that are predictable along the Group VII column of elements. Consequently, we have established the ffBXB as an accurate computational tool that can be applied, for example, for the design of new therapeutic compounds against clinically important targets and new biomolecular-based materials. PMID:25338128

  5. Pulsed laser deposition of semiconductor-ITO composite films on electric-field-applied substrates

    NASA Astrophysics Data System (ADS)

    Narazaki, Aiko; Sato, Tadatake; Kawaguchi, Yoshizo; Niino, Hiroyuki; Yabe, Akira; Sasaki, Takeshi; Koshizaki, Naoto

    2002-09-01

    The DC electric-field effect on the crystallinity of II-VI semiconductor in composite systems has been investigated for CdS-ITO films fabricated via alternative pulsed laser deposition (PLD) of CdS and indium tin oxide (ITO) on electric-field-applied substrates. The alternative laser ablation was performed under irradiation of ArF excimer laser in mixture gas of helium and oxygen. The application of electric-field facilitated the preferential crystal-growth of CdS in nanometer scale at low pressure, whereas all the films grown without the field were amorphous. There is a large difference in the crystallization between the films grown on field-applied and heated substrates; the latter showed the crystal-growth with random orientations. This difference indicates that the existence of electric-field has an influence on the transformation from amorphous to crystalline phase of CdS. The driving force for the field-induced crystallization is also discussed in the light of the Joule heat.

  6. Electric field effects on alanine tripeptide in sodium halide solutions.

    PubMed

    Astrakas, Loukas G; Gousias, Christos; Tzaphlidou, Margaret

    2015-12-01

    The electric field effects on conformational properties of trialanine in different halide solutions were explored with long-scale molecular dynamics simulations. NaF, NaCl, NaBr and NaI solutions of low (0.2?M) and high (2?M) concentrations were exposed to a constant electric field of 1000?V/m. Generally, the electric field does not disturb trialanine's structure. Large structural changes appear only in the case of the supersaturated 2.0?M NaF solution containing NaF crystals. Although the electric field affects in a complex way, all the ions-water-peptide interactions, it predominantly affects the electroselectivity effect, which describes specific interactions such as the ion-pair formation. PMID:25006865

  7. Controlling flow direction in nanochannels by electric field strength

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Zhao, Tianshou; Li, Zhigang

    2015-08-01

    Molecular dynamics simulations are conducted to study the flow behavior of CsF solutions in nanochannels under external electric fields E . It is found that the channel surface energy greatly affects the flow behavior. In channels of high surface energy, water molecules, on average, move in the same direction as that of the electric field regardless of the strength of E . In low surface energy channels, however, water transports in the opposite direction to the electric field at weak E and the flow direction is changed when E becomes sufficiently large. The direction change of water flow is attributed to the coupled effects of different water-ion interactions, inhomogeneous water viscosity, and ion distribution changes caused by the electric field. The flow direction change observed in this work may be employed for flow control in complex micro- or nanofluidic systems.

  8. PARALLEL ELECTRIC FIELD SPECTRUM OF SOLAR WIND TURBULENCE

    SciTech Connect

    Mozer, F. S.; Chen, C. H. K.

    2013-05-01

    By searching through more than 10 satellite years of THEMIS and Cluster data, 3 reliable examples of parallel electric field turbulence in the undisturbed solar wind have been found. The perpendicular and parallel electric field spectra in these examples have similar shapes and amplitudes, even at large scales (frequencies below the ion gyroscale), where Alfvenic turbulence with no parallel electric field component is thought to dominate. The spectra of the parallel electric field fluctuations are power laws with exponents near -5/3 below the ion scales ({approx}0.1 Hz), and with a flattening of the spectrum in the vicinity of this frequency. At small scales (above a few Hz), the spectra are steeper than -5/3 with values in the range of -2.1 to -2.8. These steeper slopes are consistent with expectations for kinetic Alfven turbulence, although their amplitude relative to the perpendicular fluctuations is larger than expected.

  9. Spin flip of electron in static electric fields

    E-print Network

    Richard T. Hammond

    2013-06-03

    The effects on the spin state of an electron in a time independent electric field are examined. The probability of spin flipping is calculated, and other effects are studied using the minimally coupled Dirac equation.

  10. Streamer inhibition for improving force and electric wind produced by DBD actuators

    NASA Astrophysics Data System (ADS)

    Debien, Antoine; Benard, Nicolas; Moreau, Eric

    2012-05-01

    The use of thin wires from 13 to 300 µm in diameter as the exposed electrode of a surface dielectric barrier discharge (SDBD) plasma actuator is experimentally investigated by electrical and optical diagnostics, electrohydrodynamic force measurements and produced electric wind characterization from time-averaged and time-resolved measurements. The streamer inhibition and glow discharge enhancement due to the use of a thin wire active electrode fully modify the topology and the temporal behaviour of the thrust and the electric wind production. With a typical plate-to-plate DBD, the electric wind velocity increases during the negative going cycle. With a wire-to-plate design, both positive and negative going-cycle discharges result in an electric wind velocity increase. The four main quantitative results are as follows: (1) for a power consumption of 1 W cm-1, the force is increased from 65 to 95 mN m-1 when a 13 µm wire is used, (2) this corresponds to a 15% electric wind velocity enhancement, (3) electromechanical efficiency can be increased from 0.1% to 0.25%, (4) these improvements are applied for definition of a new multi-DBD design plasma actuator that allows us to produce a mean velocity of 10.5 m s-1.

  11. Folding of gas-phase polyalanines in a static electric field: alignment, deformations, and polarization effects.

    PubMed

    Calvo, F; Dugourd, P

    2008-07-01

    Monte Carlo simulations of the temperature-induced unfolding of small gas-phase polyalanines in a static, homogeneous electric field are reported, based on the AMBER ff96 force field. The peptides exhibit a structural transition from the native alpha-helix state to entropically favored beta-sheet conformations, before eventually turning to extended coil at higher temperatures. Upon switching the electric field, the molecules undergo preferential alignment of their dipole moment vector toward the field axis and a shift of the alpha-beta transition to higher temperatures. At higher field strengths (>10(8) V/m) the molecules stretch and the alpha-beta and beta-coil transitions merge. A simple three-state model is shown to account for the observed behavior. Under even higher fields, density functional theory calculations and a polarizable force field both show that electronic rearrangements tend to further increase the dipole moment, polarization effects being approximately half in magnitude with respect to stretching effect. Finally a tentative (temperature, field-strength) phase diagram is sketched. PMID:18223004

  12. On the field-aligned electric field in the polar cap

    NASA Astrophysics Data System (ADS)

    Wing, Simon; Fairfield, Donald H.; Johnson, Jay R.; Ohtani, Shin-I.

    2015-07-01

    The Johns Hopkins University Applied Physics Laboratory open-field line particle precipitation model predicts downward field-aligned electric field to maintain charge quasi-neutrality. Previous studies confirmed the existence of such electric fields. However, the present study shows that upward field-aligned electric field can be found within upward field-aligned current (FAC) region. In the upward FAC region, upward electric field that accelerates electron downward is seen with the occurrence rates of 82%-96%. In contrast, the occurrence rates in the downward FAC regions are 3%-11%. Polar rain electrons located in the upward FAC region adjacent to closed field lines often show a ramping up of energy with increasing latitude before reaching a plateau. This plateau may be attributed to the magnetosheath electrons that progressively have higher antisunward velocity and lower density with increasing distance from the subsolar point before they asymptotically reach the solar wind values.

  13. Biopolymers under large external forces and mean-field RNA virus evolutionary dynamics

    NASA Astrophysics Data System (ADS)

    Ahsan, Syed Amir

    The modeling of the mechanical response of single-molecules of DNA and RNA under large external forces through statistical mechanical methods is central to this thesis with a small portion devoted to modeling the evolutionary dynamics of positive-sense single-stranded RNA viruses. In order to develop and test models of biopolymer mechanics and illuminate the mechanisms underlying biological processes where biopolymers undergo changes in energy on the order of the thermal energy, , entails measuring forces and lengths on the scale of piconewtons (pN) and nanometers (nm), respectively. A capacity achieved in the past two decades at the single-molecule level through the development of micromanipulation techniques such as magnetic and optical tweezers, atomic force microscopy, coupled with advances in micro- and nanofabrication. The statistical mechanical models of biopolymers developed in this dissertation are dependent upon and the outcome of these advancements and resulting experiments. The dissertation begins in chapter 1 with an introduction to the structure and thermodynamics of DNA and RNA, highlighting the importance and effectiveness of simple, two-state models in their description as a prelude to the emergence of two-state models in the research manuscripts. In chapter 2 the standard models of the elasticity of polymers and of a polymer gel are reviewed, characterizing the continuum and mean-field models, including the scaling behavior of DNA in confined spaces. The research manuscript presented in the last section of chapter 2 (section 2.5), subsequent to a review of a Flory gel and in contrast to it, is a model of the elasticity of RNA as a gel, with viral RNA illustrating an instance of such a network, and shown to exhibit anomalous elastic behavior, a negative Poisson ratio, and capable of facilitating viral RNA encapsidation with further context provided in section 5.1. In chapter 3 the experimental methods and behavior of DNA and RNA under mechanical forces are reviewed culminating with the research manuscript in section 3.4 of the development of the two-state worm-like chain, modeling the overstretching transition of B-DNA to S-DNA. Chapter 4 considers the behavior of DNA in an electric field, first reviewing DNA as a polyelectrolyte and of DNA electrophoresis in free solution and it's polarization and resulting stretched conformation as context for the study of the contrasting behavior of DNA in an AC electric field presented in the research manuscripts of the final two sections of chapter 4. In section 4.3 the collapse of DNA in ac electric fields is investigated with the experimental results and possible models for collapse presented with a scaling analysis of the frequency- and confinement-dependent critical field for collapse presented in section 4.4, contrasting a mean-field Flory-type model and a continuum, wormlike chain model. Chapter 5 investigates viral RNA; reviewing the encapsidation, life cycle and the evolutionary dynamics of single-stranded RNA viruses including the quasispecies model and it's prediction of the information or error catastrophe, providing context for the models developed in the research manuscripts presented in sections 2.5 and 5.3. In section 5.3, a simple ODE model of the evolution of positive-sense single-stranded RNA viruses is developed, adopting the two-state mean-field quasispecies model, to characterize the selection pressure associated with the encapsidation and independently, the degradation by RNAi of the wild-type relative to the mutant population and demonstrate their capacity to induce an information catastrophe and consequently support the evolution of intermediate encapsidation rates and of viral suppressors of RNA silencing, in addition to providing support for antiviral therapeutic pathways.

  14. Structural characterization of electric-field assisted dip-coating of gold nanoparticles on silicon

    NASA Astrophysics Data System (ADS)

    Dushaq, Ghada H.; Alkhatib, Amro; Rasras, Mahmoud S.; Nayfeh, Ammar M.

    2015-09-01

    We report the effect of applying an electric field on the surface coverage of 40nm gold colloidal nanoparticles on silicon wafer using dip-coating and electrochemical cell set up. By applying electric field during the dip-coating of silicon wafer in a solution of gold nano particles (GNP) the surface coverage increased by 10% when the electric field varied from 5V/cm to 25V/cm at fixed deposition time of 90s. Ultra High Resolution Scanning Electron Microscopy (HRSEM) images shows that the particle agglomeration becomes more noticeable at higher electric field and as the deposition time increases from 90 s to 20 min a thin film of gold is achieved. Moreover, the results are discussed in terms of chemical bonding, electrostatic force and electrophoretic mobility of Au nano particles during the electric field enhanced deposition on the Si surface. Applied voltage, time of dipping, concentration of the aqueous solution, and particles zeta potential are all can be controlled to enhance the uniformity and particles profile on the silicon surface.

  15. A New Electric Field in Asymmetric Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Malakit, K.; Shay, M. A.; Cassak, P.; Ruffolo, D. J.

    2013-12-01

    Magnetic reconnection is an important plasma process that drives the dynamics of the plasma in the magnetosphere and plays a crucial role in the interaction between magnetospheric and magnetosheath plasma. It has been shown that when a reconnection occurs in a collisionless plasma, it exhibits the Hall electric field, an in-plane electric field structure pointing toward the X-line. In this work, we show that when the reconnection has asymmetric inflow conditions such as the reconnection at the day-side magnetopause, a new in-plane electric field structure can exist. This electric field points away from the X-line and is distinct from the known Hall electric field. We argue that the origin of the electric field is associated with the physics of finite Larmor radius. A theory and predictions of the electric field properties are presented and backed up by results from fully kinetic particle-in-cell simulations of asymmetric reconnection with various inflow conditions. Under normal day-side reconnection inflow conditions, the electric field is expected to occur on the magnetospheric side of the X-line pointing Earthward. Hence, it has a potential to be used as a signature for satellites, such as the upcoming Magnetospheric Multi-Scale (MMS) mission, to locate the reconnection sites at the day-side magnetopause. This research was supported by the postdoctoral research sponsorship of Mahidol University (KM), NSF grants ATM-0645271 - Career Award (MAS) and AGS-0953463 (PAC), NASA grants NNX08A083G - MMS IDS, NNX11AD69G, and NNX13AD72G (MAS) and NNX10AN08A (PAC), and the Thailand Research Fund (DR).

  16. Average low-latitude meridional electric fields from DE 2 during solar maximum

    SciTech Connect

    Maynard, N.C. ); Aggson, T.L.; Herrero, F.A. ); Liebrecht, M.C. )

    1988-05-01

    Electric field data from the double probe vector electric field instrument (VEFI) on the DE 2 spacecraft have been analyzed to determine the average meridional electric field (zonal ion flow) patterns in the region between {plus minus} 30{degree} magnetic latitude during solar maximum conditions. The average data set displayed a rapid increase of the downward meridional electric field with local time near 1,800 MLT with the higher latitudes seeing the change first. A secondary nighttime maximum of this electric field component was observed post midnight with the crossover to upward electric fields (westward ion flow) occurring between 0400 and 0500 MLT. A sharp return to near zero was observed between 1,200 and 1,300. Typical average amplitudes range between 3 and 6 mV/m. No consistent variations with magnetic activity were observed. Although the daily variation in the zonal ion flow is dominated by the diurnal term, a net superrotation is evident in the harmonic analysis. The superrotation is strongest near the equator and decreases with latitude, because of the disturbance dynamo. The higher order harmonics up through the quatrediurnal term are also of significant magnitude in the analysis of the shape of the daily variation. Cose similarity is seen to the zonal neutral winds indicating that they form the principal driving force. The magnitudes of the electric field derived ion drift are somewhat higher than the average F region neutral wind values. This along with the higher order harmonic content argues for the need to develop fully coupled E and F region model depicting the ionosphere and thermosphere interactions in a self-consistent fashion.

  17. Electric field induced generation and dynamics of defects in drops of nematic cholesterics

    NASA Astrophysics Data System (ADS)

    Timirov, Yu. I.; Skaldin, O. A.; Basyrova, E. R.; Lebedev, Yu. A.

    2015-09-01

    The electric field induced dynamics and interconversion of defects in nematic cholesteric drops has been studied experimentally. It has been demonstrated that, depending on the applied voltage and the ratio of the drop radius to the equilibrium helix pitch, R/ P, orientational structural interconversions of different types can be realized. In particular, when the condition R/ P ? 1 is satisfied, drops with defects of only one type, namely, the Frank—Price defect, which rotates upon application of an alternating electric voltage, are observed. In the case of R/ P ? 1, the rotational dynamics of the defect is transformed during its disintegration into two surface defects with the force m = 1.

  18. Phase transition of dimyristoylphosphatidylglycerol bilayers induced by electric field pulses.

    PubMed

    Thürk, M; Porschke, D

    1991-08-26

    The phase transition of dimyristoylphosphatidylglycerol (DMPG) bilayers has been studied by measurements of light scattering under high electric field pulses. Midpoints of phase transitions have been identified by a clear discontinuity of field induced relaxation amplitudes. We show that the phase transition of DMPG suspensions in monovalent salt is virtually independent of the electric field strength up to approx. 35 kV/cm. A shift of the lipid phase by electric field pulses has been observed, however, for DMPG suspensions in the presence of Ca2+ ions. DMPG suspensions exhibit a jump of the phase transition temperature from 17 degrees C at Ca/DMPG molar ratios r less than 1/7 to 32 degrees C at r greater than 1/7. Field pulses of 60 to 100 microseconds applied to DMPG suspensions with Ca2+ at r greater than 1/7 induce discontinuities of relaxation amplitudes in the temperature range 15 to 22 degrees C in addition to the 'standard' one at 32 degrees C, when the electric field strength is above 15 kV/cm. These results indicate that electric field pulses induce a transition from the phase formed at 'high' Ca(2+)- to the one formed at 'low' Ca(2+)-ion concentrations. Our results are consistent with a dissociation field effect on Ca(2+)-lipid complexes which drives the phase transition. PMID:1878369

  19. Shape and oscillations of the water drops freely suspended in a horizontal electric field: A wind tunnel study

    NASA Astrophysics Data System (ADS)

    Bhalwankar, Rohini; Deshpande, C. G.; Kamra, A. K.

    2015-10-01

    The time-averaged axis ratios, frequency and amplitude of oscillations of water drops of 2.67-6.6 mm diameter were determined by suspending them in a vertical wind tunnel in the absence and presence of horizontal electric fields using a high speed camera at 1000 frames per second. A systematic decrease in the drop's axis-ratio is observed with increase in its diameter and/or horizontal electric field. The results revealed with high speed photography are in good agreement with earlier results. The drop distortion due to horizontal electric field is more pronounced for the drops in the size-range of 3.36-6 mm diameter showing that the electrical forces progressively enhance the horizontal elongation of the drop resulting in its instability at 6.6 mm. The drop oscillation frequency computed from temporal variation of axis ratio, decreases with increase in drop size but shows no significant change in oscillation frequency in the horizontal electric field of ?500 kV m-1. However, the oscillation amplitude increases with increase in drop size up to a threshold value and then flatten-off in the electric field of ?300 kV m-1 demonstrating the nonlinear effect of net forces acting on such large drops. In higher electric field of 500 kV m-1, gradual increase in the amplitude of oscillation with an increase in drop diameter has been observed. Moreover, for a particular drop size, the amplitude of oscillation decreases with increase in the electric field upto 500 kV m-1. The oscillation frequency of the waterdrops experiences multimode oscillations. The dominant fundamental mode of oscillations (2,0) always exists for all drops in our experiments along with the coexistence of higher modes of oscillations i.e. (2,1) and (2,2) mode. Possible effects of electrical forces on shape parameters and their implications on cloud microphysics and in radar meteorology are discussed.

  20. Differential twin receiving fiber-optic magnetic field and electric current sensor utilizing a microfiber coupler.

    PubMed

    Yan, Shao-cheng; Chen, Ye; Li, Cai; Xu, Fei; Lu, Yan-qing

    2015-04-01

    A magnetic field and electric current meter is proposed based on a differential twin receiving microfiber coupler (MC) sensor. The sensor is fabricated by bonding a MC and an aluminium (Al) wire together. With the small diameter of several micrometers, the output power at each port of the coupler shows high sensitivity to the distortion of Al wire from the Lorentz force induced by the magnetic field or the thermal expansion caused by the electric current. The ratio of the difference to the sum of the output signals from the two output ports can be used to eliminate the variation in the sensitivity. Using our proposed sensor, we measured a magnetic field sensitivity of ~0.0496 mT(-1), current sensitivity of ~1.0899 A(-1) without any magnetic field, and good repeatability are also shown in this paper. PMID:25968771

  1. Computer Simulations of Charged Colloids in Alternating Electric Fields

    E-print Network

    Jiajia Zhou; Friederike Schmid

    2014-01-07

    We briefly review recent theoretical and simulation studies of charged colloidal dispersions in alternating electric fields (AC fields). The response of single colloid to an external field can be characterized by a complex polarizability, which describes the dielectric properties of the colloid and its surrounding electrical double layer. We present computer simulation studies of single spherical colloid, using a coarse-grained mesoscale approach that accounts in full for hydrodynamic and electrostatic interactions as well as for thermal fluctuations. We investigate systematically a number of controlling parameters, such as the amplitude and frequency of the AC-fields. The results are in good agreement with recent theoretical predictions.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  3. Vehicle Dynamics Control of In-wheel Electric Motor Drive Vehicles Based on Averaging of Tire Force Usage

    NASA Astrophysics Data System (ADS)

    Masaki, Nobuo; Iwano, Haruo; Kamada, Takayoshi; Nagai, Masao

    For in-wheel electric motor drive vehicles, a new vehicle dynamics control which is based on the tire force usage rate is proposed. The new controller adopts non-linear optimal control could manage the interference between direct yaw-moment control and the tire force usage rate. The new control is considered total longitudinal and transverse tire force. Therefore the controller can prevent tire force saturation near tire force limit during cornering. Simulations and test runs by the custom made four wheel drive in-wheel motor electric vehicle show that higher driving stability performance compared to the performance of the same vehicle without control.

  4. Report on Non-Contact DC Electric Field Sensors

    SciTech Connect

    Miles, R; Bond, T; Meyer, G

    2009-06-16

    This document reports on methods used to measure DC electrostatic fields in the range of 100 to 4000 V/m using a non-contact method. The project for which this report is written requires this capability. Non-contact measurements of DC fields is complicated by the effect of the accumulation of random space-charges near the sensors which interfere with the measurement of the field-of-interest and consequently, many forms of field measurements are either limited to AC measurements or use oscillating devices to create pseudo-AC fields. The intent of this document is to report on methods discussed in the literature for non-contact measurement of DC fields. Electric field meters report either the electric field expressed in volts per distance or the voltage measured with respect to a ground reference. Common commercial applications for measuring static (DC) electric fields include measurement of surface charge on materials near electronic equipment to prevent arcing which can destroy sensitive electronic components, measurement of the potential for lightning to strike buildings or other exposed assets, measurement of the electric fields under power lines to investigate potential health risks from exposure to EM fields and measurement of fields emanating from the brain for brain diagnostic purposes. Companies that make electric field sensors include Trek (Medina, NY), MKS Instruments, Boltek, Campbell Systems, Mission Instruments, Monroe Electronics, AlphaLab, Inc. and others. In addition to commercial vendors, there are research activities continuing in the MEMS and optical arenas to make compact devices using the principles applied to the larger commercial sensors.

  5. KINETIC ALFVEN TURBULENCE AND PARALLEL ELECTRIC FIELDS IN FLARE LOOPS

    SciTech Connect

    Zhao, J. S.; Wu, D. J.; Lu, J. Y.

    2013-04-20

    This study investigates the spectral structure of the kinetic Alfven turbulence in the low-beta plasmas. We consider a strong turbulence resulting from collisions between counterpropagating wavepackets with equal energy. Our results show that (1) the spectra of the magnetic and electric field fluctuations display a transition at the electron inertial length scale, (2) the turbulence cascades mainly toward the magnetic field direction as the cascade scale is smaller than the electron inertial length, and (3) the parallel electric field increases as the turbulent scale decreases. We also show that the parallel electric field in the solar flare loops can be 10{sup 2}-10{sup 4} times the Dreicer field as the turbulence reaches the electron inertial length scale.

  6. Critical electric field for maximum tunability in nonlinear dielectrics

    NASA Astrophysics Data System (ADS)

    Akdogan, E. K.; Safari, A.

    2006-09-01

    The authors develop a self-consistent thermodynamic theory to compute the critical electric field at which maximum tunability is attained in a nonlinear dielectric. They then demonstrate that the stored electrostatic free energy functional has to be expanded at least up to the sixth order in electric field so as to define the critical field, and show that it depends solely on the fourth and sixth order permittivities. They discuss the deficiency of the engineering tunability metric in describing nonlinear dielectric phenomena, introduce a critical field renormalized tunability parameter, and substantiate the proposed formalism by computing the critical electric field for prototypical 0.9Pb(Mg1/3,Nb2/3)-0.1PbTiO3 and Ba(Ti0.85,Sn0.15)O3 paraelectrics.

  7. Reversible electric-field control of magnetization at oxide interfaces

    NASA Astrophysics Data System (ADS)

    Cuellar, F. A.; Liu, Y. H.; Salafranca, J.; Nemes, N.; Iborra, E.; Sanchez-Santolino, G.; Varela, M.; Hernandez, M. Garcia; Freeland, J. W.; Zhernenkov, M.; Fitzsimmons, M. R.; Okamoto, S.; Pennycook, S. J.; Bibes, M.; Barthélémy, A.; Te Velthuis, S. G. E.; Sefrioui, Z.; Leon, C.; Santamaria, J.

    2014-06-01

    Electric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field.

  8. Reversible electric-field control of magnetization at oxide interfaces.

    PubMed

    Cuellar, F A; Liu, Y H; Salafranca, J; Nemes, N; Iborra, E; Sanchez-Santolino, G; Varela, M; Garcia Hernandez, M; Freeland, J W; Zhernenkov, M; Fitzsimmons, M R; Okamoto, S; Pennycook, S J; Bibes, M; Barthélémy, A; te Velthuis, S G E; Sefrioui, Z; Leon, C; Santamaria, J

    2014-01-01

    Electric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field. PMID:24953219

  9. Electric field-induced softening of alkali silicate glasses

    NASA Astrophysics Data System (ADS)

    McLaren, C.; Heffner, W.; Tessarollo, R.; Raj, R.; Jain, H.

    2015-11-01

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

  10. Electric fields in nonhomogeneously doped silicon. Summary of simulations

    NASA Astrophysics Data System (ADS)

    Kotov, I. V.; Humanic, T. J.; Nouais, D.; Randel, J.; Rashevsky, A.; Alice-Its Collaboration

    2006-11-01

    Variations of the doping concentration inside a silicon device result in electric field distortions. These distortions, "parasitic" fields, have been observed in Silicon Drift Detectors [D. Nouais, et al., Nucl. Instr. and Meth. A 501 (2003) 119; E. Crescio, et al., Nucl. Instr. and Meth. A 539 (2005) 250]. Electric fields inside a silicon device can be calculated for a given doping profile. In this study, the ATLAS device simulator. [ Silvaco International, 4701 Patrick Henry Drive, Bldg.2, Santa Clara, CA 95054, USA and ] was used to calculate the electric field inside an inhomogeneously doped device. Simulations were performed for 1D periodic doping profiles. Results show strong dependence of the parasitic field strength on the 'smoothness' of the doping profile.

  11. Consistency Restrictions on Maximal Electric-Field Strength in Quantum Field Theory

    SciTech Connect

    Gavrilov, S. P.; Gitman, D. M.

    2008-09-26

    Quantum field theory with an external background can be considered as a consistent model only if backreaction is relatively small with respect to the background. To find the corresponding consistency restrictions on an external electric field and its duration in QED and QCD, we analyze the mean-energy density of quantized fields for an arbitrary constant electric field E, acting during a large but finite time T. Using the corresponding asymptotics with respect to the dimensionless parameter eET{sup 2}, one can see that the leading contributions to the energy are due to the creation of particles by the electric field. Assuming that these contributions are small in comparison with the energy density of the electric background, we establish the above-mentioned restrictions, which determine, in fact, the time scales from above of depletion of an electric field due to the backreaction.

  12. Submitted to Physical Review A Friction forces arising from fluctuating thermal fields

    E-print Network

    Novotny, Lukas

    Submitted to Physical Review A Friction forces arising from fluctuating thermal fields Jorge R-dependent damping in shear-force microscopy and it gives guidance for future experiments. Also, the theory should explored to what extent Casimir forces influence the performance of micrometer sized mechanical devices [1

  13. Current Status of the AMOEBA Polarizable Force Field Jay W. Ponder and Chuanjie Wu

    E-print Network

    Ponder, Jay

    #12;Current Status of the AMOEBA Polarizable Force Field Jay W. Ponder and Chuanjie Wu Department that should allow more accurate description of molecular properties. The recently introduced AMOEBA force, it has only received relatively limited validation, which we address here. We show that the AMOEBA force

  14. Rydberg-Stark states in oscillating electric fields

    E-print Network

    Zhelyazkova, V

    2015-01-01

    Experimental and theoretical studies of the effects of weak radio-frequency electric fields on Rydberg-Stark states with electric dipole moments as large as 10000 D are reported. High-resolution laser spectroscopic studies of Rydberg states with principal quantum number $n=52$ and $53$ were performed in pulsed supersonic beams of metastable helium with the excited atoms detected by pulsed electric field ionisation. Experiments were carried out in the presence of sinusoidally oscillating electric fields with frequencies of 20~MHz, amplitudes of up to 120~mV/cm, and dc offsets of up to 4.4~V/cm. In weak fields the experimentally recorded spectra are in excellent agreement with the results of calculations carried out using Floquet methods to account for electric dipole couplings in the oscillating fields. This highlights the validity of these techniques for the accurate calculation of the Stark energy level structure in such fields, and the limitations of the calculations in stronger fields where $n-$mixing and ...

  15. Internal electric field densities of metal nanoshells.

    PubMed

    Schelm, Stefan; Smith, Geoff B

    2005-02-10

    The internal field patterns for gold shells filled with the same material as the surrounding medium are calculated with Mie theory and in the quasistatic approximation and their properties compared to the response of homogeneous spheres and metallic rings. One major difference between the sphere and shell case is that the areas of highest field enhancement in metallic shells are located perpendicular to the incident polarization, whereas for metallic spheres they are along the polarization direction. Recent results based on the discrete dipole approximation (DDA) are shown to be misleading, which might be due to the use of a too coarse grid size. We also show that the type of resonance and the associated internal field pattern (low or high energy) has a strong impact on the external fields. PMID:16851144

  16. Tumour cell membrane poration and ablation by pulsed low-intensity electric field with carbon nanotubes.

    PubMed

    Wang, Lijun; Liu, Dun; Zhou, Ru; Wang, Zhigang; Cuschieri, Alfred

    2015-01-01

    Electroporation is a physical method to increase permeabilization of cell membrane by electrical pulses. Carbon nanotubes (CNTs) can potentially act like "lighting rods" or exhibit direct physical force on cell membrane under alternating electromagnetic fields thus reducing the required field strength. A cell poration/ablation system was built for exploring these effects of CNTs in which two-electrode sets were constructed and two perpendicular electric fields could be generated sequentially. By applying this system to breast cancer cells in the presence of multi-walled CNTs (MWCNTs), the effective pulse amplitude was reduced to 50 V/cm (main field)/15 V/cm (alignment field) at the optimized pulse frequency (5 Hz) of 500 pulses. Under these conditions instant cell membrane permeabilization was increased to 38.62%, 2.77-fold higher than that without CNTs. Moreover, we also observed irreversible electroporation occurred under these conditions, such that only 39.23% of the cells were viable 24 h post treatment, in contrast to 87.01% cell viability without presence of CNTs. These results indicate that CNT-enhanced electroporation has the potential for tumour cell ablation by significantly lower electric fields than that in conventional electroporation therapy thus avoiding potential risks associated with the use of high intensity electric pulses. PMID:25822874

  17. Electric field enhanced conductivity in strongly coupled dense metal plasma

    SciTech Connect

    Stephens, J.; Neuber, A.

    2012-06-15

    Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field ({approx}6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.

  18. Controlling Growth Orientation of Phthalocyanine Films by Electrical Fields

    NASA Technical Reports Server (NTRS)

    Zhu, S.; Banks, C. E.; Frazier, D. O.; Ila, D.; Muntele, I.; Penn, B. G.; Sharma, A.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Organic Phthalocyanine films have many applications ranging from data storage to various non-linear optical devices whose quality is affected by the growth orientation of Phthalocyanine films. Due to the structural and electrical properties of Phthalocyanine molecules, the film growth orientation depends strongly on the substrate surface states. In this presentation, an electrical field up to 4000 V/cm is introduced during film growth. The Phthalocyanine films are synthesized on quartz substrates using thermal evaporation. An intermediate layer is deposited on some substrates for introducing the electrical field. Scanning electron microscopy, x-ray diffraction, and Fourier transform infrared spectroscopy are used for measuring surface morphology, film structure, and optical properties, respectively. The comparison of Phthalocyanine films grown with and without the electrical field reveals different morphology, film density, and growth orientation, which eventually change optical properties of these films. These results suggest that the growth method in the electrical field can be used to synthesized Phthalocyanine films with a preferred crystal orientation as well as propose an interaction mechanism between the substrate surface and the depositing molecules. The details of growth conditions and of the growth model of how the Phthalocyanine molecules grow in the electrical field will be discussed.

  19. Critical Points of the Electric Field from a Collection of Point Charges

    SciTech Connect

    Max, N; Weinkauf, T

    2007-02-16

    The electric field around a molecule is generated by the charge distribution of its constituents: positively charged atomic nuclei, which are well approximated by point charges, and negatively charged electrons, whose probability density distribution can be computed from quantum mechanics. For the purposes of molecular mechanics or dynamics, the charge distribution is often approximated by a collection of point charges, with either a single partial charge at each atomic nucleus position, representing both the nucleus and the electrons near it, or as several different point charges per atom. The critical points in the electric field are useful in visualizing its geometrical and topological structure, and can help in understanding the forces and motion it induces on a charged ion or neutral dipole. Most visualization tools for vector fields use only samples of the field on the vertices of a regular grid, and some sort of interpolation, for example, trilinear, on the grid cells. There is less risk of missing or misinterpreting topological features if they can be derived directly from the analytic formula for the field, rather than from its samples. This work presents a method which is guaranteed to find all the critical points of the electric field from a finite set of point charges. To visualize the field topology, we have modified the saddle connector method to use the analytic formula for the field.

  20. Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila

    1996-01-01

    Boiling is an effective mode of heat transfer since high heat flux levels are possible driven by relatively small temperature differences. The high heat transfer coefficients associated with boiling have made the use of these processes increasingly attractive to aerospace engineering. Applications of this type include compact evaporators in the thermal control of aircraft avionics and spacecraft environments, heat pipes, and use of boiling to cool electronic equipment. In spite of its efficiency, cooling based on liquid-vapor phase change processes has not yet found wide application in aerospace engineering due to specific problems associated with the low gravity environment. After a heated surface has reached the superheat required for the initiation of nucleate boiling, bubbles will start forming at nucleation sites along the solid interface by evaporation of the liquid. Bubbles in contact with the wall will continue growing by this mechanism until they detach. In terrestrial conditions, bubble detachment is determined by the competition between body forces (e.g. buoyancy) and surface tension forces that act to anchor the bubble along the three phase contact line. For a given body force potential and a balance of tensions along the three phase contact line, bubbles must reach a critical size before the body force can cause them to detach from the wall. In a low gravity environment the critical bubble size for detachment is much larger than under terrestrial conditions, since buoyancy is a less effective means of bubble removal. Active techniques of heat transfer enhancement in single phase and phase change processes by utilizing electric fields have been the subject of intensive research during recent years. The field of electrohydrodynamics (EHD) deals with the interactions between electric fields, flow fields and temperature fields. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 as compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The goal of our research is to experimentally investigate the potential of EHD and the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions.

  1. Induced water condensation and bridge formation by electric fieldsin Atomic Force Microscopy

    SciTech Connect

    Sacha, G.M.; Verdaguer, A.; Salmeron, M.

    2006-02-22

    We present an analytical model that explains how in humidenvironments the electric field near a sharp tip enhances the formationof water meniscii and bridges between tip and sample. The predictions ofthe model are compared with experimental measurements of the criticaldistance where the field strength causes bridge formation.

  2. Improved electric field modelling for TDR

    NASA Astrophysics Data System (ADS)

    Woodhead, Ian; Buchan, Graeme; Platt, Ian; Christie, John

    2007-04-01

    Integral equation (IE) methods may be used to model the interaction between microwave signals and porous materials and hence lead to improvements in time-domain reflectometry (TDR) or other techniques for measurement of moisture content. Although they may employ pulse basis functions to represent the field in each cell of the discretized region, the inherent approximations limit accuracy. Higher order basis functions provide one alternative, but here we describe a method that retains the geometric and cell density advantages of delta functions, and improves accuracy by correcting for the field integration errors of the conventional moment method. Our approach circumvents errors that arise when assuming that the field of a cell is adequately represented by a source at its centre, and results in close agreement between empirical results and the model.

  3. Abrupt Rabi oscillations in a superoscillating electric field

    E-print Network

    Baranov, D G; Lisyansky, A A

    2014-01-01

    We study counterintuitive dynamics of a two-level system (TLS) interacting with electric field superoscillating in time. We show that a TLS may be excited by an external light pulse whose spectral components are below the absorption line of the TLS. We attribute this unique dynamics to the Rabi oscillations of the TLS in a superoscillating driving field.

  4. Mapping transient electric fields with picosecond electron bunches

    PubMed Central

    Chen, Long; Li, Runze; Chen, Jie; Zhu, Pengfei; Liu, Feng; Cao, Jianming; Sheng, Zhengming; Zhang, Jie

    2015-01-01

    Transient electric fields, which are an important but hardly explored parameter of laser plasmas, can now be diagnosed experimentally with combined ultrafast temporal resolution and field sensitivity, using femtosecond to picosecond electron or proton pulses as probes. However, poor spatial resolution poses great challenges to simultaneously recording both the global and local field features. Here, we present a direct 3D measurement of a transient electric field by time-resolved electron schlieren radiography with simultaneous 80-?m spatial and 3.7-ps temporal resolutions, analyzed using an Abel inversion algorithm. The electric field here is built up at the front of an aluminum foil irradiated with a femtosecond laser pulse at 1.9 × 1012 W/cm2, where electrons are emitted at a speed of 4 × 106 m/s, resulting in a unique “peak–valley” transient electric field map with the field strength up to 105 V/m. Furthermore, time-resolved schlieren radiography with charged particle pulses should enable the mapping of various fast-evolving field structures including those found in plasma-based particle accelerators. PMID:26554022

  5. -561 -105Pl LIGHTNING ELECTRIC AND MAGNETIC FIELDS

    E-print Network

    Florida, University of

    -561 - 105Pl LIGHTNING ELECTRIC AND MAGNETIC FIELDS V. A. Rakov University of Florida, Gainesville lightning processes are reviewed. Ground flashes of both polarities and cloud flashes are considered lightning discharges involve a number of processes that produce characteristic electromagnetic field

  6. Mapping transient electric fields with picosecond electron bunches.

    PubMed

    Chen, Long; Li, Runze; Chen, Jie; Zhu, Pengfei; Liu, Feng; Cao, Jianming; Sheng, Zhengming; Zhang, Jie

    2015-11-24

    Transient electric fields, which are an important but hardly explored parameter of laser plasmas, can now be diagnosed experimentally with combined ultrafast temporal resolution and field sensitivity, using femtosecond to picosecond electron or proton pulses as probes. However, poor spatial resolution poses great challenges to simultaneously recording both the global and local field features. Here, we present a direct 3D measurement of a transient electric field by time-resolved electron schlieren radiography with simultaneous 80-?m spatial and 3.7-ps temporal resolutions, analyzed using an Abel inversion algorithm. The electric field here is built up at the front of an aluminum foil irradiated with a femtosecond laser pulse at 1.9 × 10(12) W/cm(2), where electrons are emitted at a speed of 4 × 10(6) m/s, resulting in a unique "peak-valley" transient electric field map with the field strength up to 10(5) V/m. Furthermore, time-resolved schlieren radiography with charged particle pulses should enable the mapping of various fast-evolving field structures including those found in plasma-based particle accelerators. PMID:26554022

  7. Zigzag nanoribbons in external electric and magnetic fields

    E-print Network

    Korotyaev, Evgeny L

    2010-01-01

    We consider the Schr\\"odinger operators on zigzag nanoribbons (quasi-1D tight-binding models) in external magnetic fields and an electric potential $V$. The magnetic field is perpendicular to the plane of the ribbon and the electric field is perpendicular to the axis of the nanoribbon and the magnetic field. If the magnetic and electric fields are absent, then the spectrum of the Schr\\"odinger (Laplace) operator consists of two non-flat bands and one flat band (an eigenvalue with infinite multiplicity) between them. If we switch on the magnetic field, then the spectrum of the magnetic Schr\\"odinger operator consists of some non-flat bands and one flat band between them. Thus the magnetic field changes the continuous spectrum but does not the flat band. If we switch on a weak electric potential $V\\to 0$, then there are two cases: (1) the flat band splits into the small spectral band. We determine the asymptotics of the spectral bands for small fields. (2) the unperturbed flat band remains the flat band. We des...

  8. Experimental evidence that a high electric field acts as an efficient external parameter during crystalline growth of bulk oxide

    NASA Astrophysics Data System (ADS)

    Hicher, P.; Haumont, R.; Saint-Martin, R.; Mininger, X.; Berthet, P.; Revcolevschi, A.

    2015-01-01

    A new crystal growth device, in which a high static external electric voltage (up to 14 kV) is added to a floating zone method, is described. Our first experiments show that the application of such an electric field acts like an external force, introducing a pressure effect which is in direct competition with temperature in the solid/liquid thermodynamic equilibrium. High electric fields could therefore be an additional parameter in crystal growth, opening original routes to the synthesis of new materials.

  9. Proteins in electric fields and pressure fields: experimental results.

    PubMed

    Fidy, J; Balog, E; Köhler, M

    1998-08-18

    Experimental results obtained by Stark effect and pressure tuning optical spectroscopy are discussed with the emphasis on studies aimed at unraveling the coupling of prosthetic groups to proteins. A comparative, detailed analysis is given concerning the coupling of the heme group to the apoprotein in various heme proteins based on spectral hole burning data. Electrochromism and electric dichroism experiments related to the coupling problem are also discussed in the context of other protein systems. PMID:9733987

  10. Tuning the mechanical behaviour of structural elements by electric fields

    NASA Astrophysics Data System (ADS)

    Di Lillo, Luigi; Raither, Wolfram; Bergamini, Andrea; Zündel, Manuel; Ermanni, Paolo

    2013-06-01

    This work reports on the adoption of electric fields to tune the mechanical behaviour of structural elements. A mechanical characterization procedure, consisting of double lap joint and 3-point bending tests, is conducted on copper-polyimide laminates while applying electric fields of varying intensity. Field dependence and, thus, adaptability of shear strength and bending stiffness are shown as a function of the overlapping length and interfaces number, respectively. Further, the impact of remaining charges is investigated in both testing configurations. The findings herein lay the foundation for the implementation of electro-adaptive components in structural applications.

  11. Dirac oscillator in perpendicular magnetic and transverse electric fields

    SciTech Connect

    Nath, D.; Roy, P.

    2014-12-15

    We study (2+1) dimensional massless Dirac oscillator in the presence of perpendicular magnetic and transverse electric fields. Exact solutions are obtained and it is shown that there exists a critical magnetic field B{sub c} such that the spectrum is different in the two regions B>B{sub c} and Belectric field. • Exact solutions are found. • Critical cases have been examined.

  12. Vapor-liquid equilibrium in electric field gradients.

    PubMed

    Samin, Sela; Tsori, Yoav

    2011-01-13

    We investigate the vapor-liquid coexistence of polar and nonpolar fluids in the presence of a nonuniform electric field. We find that a large enough electric field can nucleate a gas bubble from the liquid phase or a liquid droplet from the vapor phase. The surface tension of the vapor-liquid interface is determined within squared-gradient theory. When the surface potential (charge) is controlled, the surface tension increases (decreases) compared to the zero-field interface. The effect of the electric field on the fluid phase diagram depends strongly on the constitutive relation for the dielectric constant. Finally, we show that gas bubbles can be nucleated far from the bounding surfaces. PMID:21142049

  13. Skin Rejuvenation with Non-Invasive Pulsed Electric Fields

    PubMed Central

    Golberg, Alexander; Khan, Saiqa; Belov, Vasily; Quinn, Kyle P.; Albadawi, Hassan; Felix Broelsch, G.; Watkins, Michael T.; Georgakoudi, Irene; Papisov, Mikhail; Mihm Jr., Martin C.; Austen Jr., William G.; Yarmush, Martin L.

    2015-01-01

    Degenerative skin diseases affect one third of individuals over the age of sixty. Current therapies use various physical and chemical methods to rejuvenate skin; but since the therapies affect many tissue components including cells and extracellular matrix, they may also induce significant side effects, such as scarring. Here we report on a new, non-invasive, non-thermal technique to rejuvenate skin with pulsed electric fields. The fields destroy cells while simultaneously completely preserving the extracellular matrix architecture and releasing multiple growth factors locally that induce new cells and tissue growth. We have identified the specific pulsed electric field parameters in rats that lead to prominent proliferation of the epidermis, formation of microvasculature, and secretion of new collagen at treated areas without scarring. Our results suggest that pulsed electric fields can improve skin function and thus can potentially serve as a novel non-invasive skin therapy for multiple degenerative skin diseases. PMID:25965851

  14. Skin Rejuvenation with Non-Invasive Pulsed Electric Fields

    NASA Astrophysics Data System (ADS)

    Golberg, Alexander; Khan, Saiqa; Belov, Vasily; Quinn, Kyle P.; Albadawi, Hassan; Felix Broelsch, G.; Watkins, Michael T.; Georgakoudi, Irene; Papisov, Mikhail; Mihm, Martin C., Jr.; Austen, William G., Jr.; Yarmush, Martin L.

    2015-05-01

    Degenerative skin diseases affect one third of individuals over the age of sixty. Current therapies use various physical and chemical methods to rejuvenate skin; but since the therapies affect many tissue components including cells and extracellular matrix, they may also induce significant side effects, such as scarring. Here we report on a new, non-invasive, non-thermal technique to rejuvenate skin with pulsed electric fields. The fields destroy cells while simultaneously completely preserving the extracellular matrix architecture and releasing multiple growth factors locally that induce new cells and tissue growth. We have identified the specific pulsed electric field parameters in rats that lead to prominent proliferation of the epidermis, formation of microvasculature, and secretion of new collagen at treated areas without scarring. Our results suggest that pulsed electric fields can improve skin function and thus can potentially serve as a novel non-invasive skin therapy for multiple degenerative skin diseases.

  15. Inversion of the electric field driven by ionic solvation energy

    NASA Astrophysics Data System (ADS)

    Guerrero Garcia, Guillermo; Solis, Francisco; Olvera de La Cruz, Monica

    2014-03-01

    In previous studies, Monte Carlo simulations have suggested the possibility of inverting the electric field near a liquid/liquid interface due to excluded volume effects, ionic size asymmetry, and image charges at high electrolyte concentrations in the absence of ion transfer. In this work, we develop a mean field theory and coarse grained simulations to study the ion transfer between the two immiscible electrolytes in the presence of an electric field. Our calculations suggest a novel mechanism to invert the electric field near confined oil/water interfaces based on differences of the ionic solvation energy in both liquid media. We thank the support of the Office of the Secretary of Defense under the NSSEFF program award number FA9550-10-1-0167.

  16. Role of confinement in water solidification under electric fields

    NASA Astrophysics Data System (ADS)

    Nie, Guo-Xi; Wang, Yu; Huang, Ji-Ping

    2015-10-01

    In contrast to the common belief that confinement promotes water solidification, here we show by molecular dynamics simulations that confinement can impede water solidification under electric fields. The behavior is evidenced by the increase in critical electric field strength for water solidification as the confinement progresses. We also show that the solidification occurs more easily with a parallel field than a perpendicular one. We understand and generalize these results by developing an energy theory incorporated with the anisotropic Clausius-Mossotti equation. It is revealed that the underlying mechanism lies in the confinement effect on molecules' electro-orientations. Thus, it becomes possible to achieve electro-freezing (i.e., room-temperature ice) by choosing both confinement and electric fields appropriately.

  17. Controlled limits of FORC theory: Mean field and Nucleation

    E-print Network

    fluctuations corrections 1.3 Test/verify theory experimentally on nanoparticle arrays 2. Strong exchange of pillar sample. FIG. 5. a The first-order reversal curve FORC data for nickel pillar sample. To make

  18. Electric Field Enhancement and Light Transmission in Cylindrical Nanoholes

    SciTech Connect

    Shuford, Kevin L; Ratner, Mark A.; Gray, Stephen K.; Schatz, George C.

    2007-01-01

    The properties of electric fields in subwavelength cylindrical apertures are examined upon excitation by a far-field source. We find that the largest enhancements are localized at the edge of the aperture, close to its rim. Both the entrance and exit rims of the hole can produce intense fields, although at long wavelengths thick slabs lead to smaller fields at the exit rim. The fields display a two lobe angular pattern characteristic of a radiating dipole in the near field. The influence of aperture size and slab thickness on field enhancement is presented. Although there is often a connection between peak transmission and peak field, the two rarely occur at the same wavelength. Enhancements in the electric field intensity can be increased by an order of magnitude by adding a grooved structure around the aperture, which acts as a grating and permits coupling to surface plasmon polaritons. Our results indicate that nanohole systems can be optimized to yield large electric field enhancements, making them an attractive medium for surface enhanced spectroscopies.

  19. Polarizable Atomic Multipole-Based AMOEBA Force Field for Proteins Jiajing Zhang,

    E-print Network

    Ponder, Jay

    Polarizable Atomic Multipole-Based AMOEBA Force Field for Proteins Yue Shi, Zhen Xia, Jiajing Zhang of the AMOEBA (atomic multi- pole optimized energetics for biomolecular simulation) force field for proteins is presented. The current version (AMOEBA- 2013) utilizes permanent electrostatic multipole moments through

  20. Coarse-Grained Model of Collagen Molecules Using an Extended MARTINI Force Field

    E-print Network

    Buehler, Markus J.

    Coarse-Grained Model of Collagen Molecules Using an Extended MARTINI Force Field Alfonso Gautieri, Massachusetts Received January 9, 2010 Abstract: Collagen is the most abundant protein in the human body of collagen molecules. We identify MARTINI force field parameters to describe hydroxyproline amino acid

  1. A reactive force field simulation of liquidliquid phase transitions in phosphorus

    E-print Network

    A reactive force field simulation of liquid­liquid phase transitions in phosphorus P. Ballone 2004; accepted 6 August 2004 A force field model of phosphorus has been developed based on density T of the black P to arsenic A17 structure observed in the solid state, and also corresponds to a semiconductor

  2. Parametrization and Application of a Coarse Grained Force Field for Benzene/Fullerene Interactions with Lipids

    E-print Network

    Nielsen, Steven O.

    Parametrization and Application of a Coarse Grained Force Field for Benzene/Fullerene Interactions Recently, we reported new coarse grain (CG) force fields for lipids and phenyl/fullerene based molecules. In the C60 lipid systems, the fullerenes were shown to aggregate even at the lowest concentrations

  3. Electric-field control of magnetic moment in Pd

    NASA Astrophysics Data System (ADS)

    Obinata, Aya; Hibino, Yuki; Hayakawa, Daichi; Koyama, Tomohiro; Miwa, Kazumoto; Ono, Shimpei; Chiba, Daichi

    2015-09-01

    Several magnetic properties have recently become tunable with an applied electric field. Particularly, electrically controlled magnetic phase transitions and/or magnetic moments have attracted attention because they are the most fundamental parameters in ferromagnetic materials. In this study, we showed that an electric field can be used to control the magnetic moment in films made of Pd, usually a non-magnetic element. Pd ultra-thin films were deposited on ferromagnetic Pt/Co layers. In the Pd layer, a ferromagnetically ordered magnetic moment was induced by the ferromagnetic proximity effect. By applying an electric field to the ferromagnetic surface of this Pd layer, a clear change was observed in the magnetic moment, which was measured directly using a superconducting quantum interference device magnetometer. The results indicate that magnetic moments extrinsically induced in non-magnetic elements by the proximity effect, as well as an intrinsically induced magnetic moments in ferromagnetic elements, as reported previously, are electrically tunable. The results of this study suggest a new avenue for answering the fundamental question of “can an electric field make naturally non-magnetic materials ferromagnetic?”

  4. Relationship between ionospheric electric fields and magnetic activity indices

    NASA Astrophysics Data System (ADS)

    Shirapov, D. Sh.

    2012-02-01

    The relations between electric fields in the daytime and nighttime sectors of the polar ionosphere and magnetic activity indices of auroral region (AL) and northern polar cap (PCN) are studied. It is found that the above relations do exist and are described by: a) equations U {pc/(1)} (kV) = 27.62 + 21.43PCN with a correlation coefficient R = 0.87 and U {pc/(1)} (kV) = 4.06 + 49.21PCN - 6.24 PCN2 between the difference in the electric potentials across the polar cap in the daytime sector U {pc/(1)} and PCN and b) regression equation U {pc/(2)} (kV) = 23.33 + 0.08|AL| with R = 0.86 between the difference in the electric potentials across the polar cap in the nighttime sector U {pc/(2)} and |AL|. It is shown that: a) it is possible to use the AL and PCN indices for real-time diagnostics of instantaneous values of the electric fields in the daytime and nighttime sectors of the polar ionosphere in the process of a substorm development; b) at the expansion phase of a substorm, due to calibration of PCN values by the values of the solar wind electric field E sw, the PCN index does not feel the contribution of the western electrojet and, accordingly, the contribution of the nighttime ionospheric electric field U {pc/(2)}, governed by the reconnection in the magnetospheric tail.

  5. Electric-field control of magnetic moment in Pd

    PubMed Central

    Obinata, Aya; Hibino, Yuki; Hayakawa, Daichi; Koyama, Tomohiro; Miwa, Kazumoto; Ono, Shimpei; Chiba, Daichi

    2015-01-01

    Several magnetic properties have recently become tunable with an applied electric field. Particularly, electrically controlled magnetic phase transitions and/or magnetic moments have attracted attention because they are the most fundamental parameters in ferromagnetic materials. In this study, we showed that an electric field can be used to control the magnetic moment in films made of Pd, usually a non-magnetic element. Pd ultra-thin films were deposited on ferromagnetic Pt/Co layers. In the Pd layer, a ferromagnetically ordered magnetic moment was induced by the ferromagnetic proximity effect. By applying an electric field to the ferromagnetic surface of this Pd layer, a clear change was observed in the magnetic moment, which was measured directly using a superconducting quantum interference device magnetometer. The results indicate that magnetic moments extrinsically induced in non-magnetic elements by the proximity effect, as well as an intrinsically induced magnetic moments in ferromagnetic elements, as reported previously, are electrically tunable. The results of this study suggest a new avenue for answering the fundamental question of “can an electric field make naturally non-magnetic materials ferromagnetic?” PMID:26391306

  6. Electric-field control of magnetic moment in Pd.

    PubMed

    Obinata, Aya; Hibino, Yuki; Hayakawa, Daichi; Koyama, Tomohiro; Miwa, Kazumoto; Ono, Shimpei; Chiba, Daichi

    2015-01-01

    Several magnetic properties have recently become tunable with an applied electric field. Particularly, electrically controlled magnetic phase transitions and/or magnetic moments have attracted attention because they are the most fundamental parameters in ferromagnetic materials. In this study, we showed that an electric field can be used to control the magnetic moment in films made of Pd, usually a non-magnetic element. Pd ultra-thin films were deposited on ferromagnetic Pt/Co layers. In the Pd layer, a ferromagnetically ordered magnetic moment was induced by the ferromagnetic proximity effect. By applying an electric field to the ferromagnetic surface of this Pd layer, a clear change was observed in the magnetic moment, which was measured directly using a superconducting quantum interference device magnetometer. The results indicate that magnetic moments extrinsically induced in non-magnetic elements by the proximity effect, as well as an intrinsically induced magnetic moments in ferromagnetic elements, as reported previously, are electrically tunable. The results of this study suggest a new avenue for answering the fundamental question of "can an electric field make naturally non-magnetic materials ferromagnetic?" PMID:26391306

  7. A microfluidic device based on gravity and electric force driving for flow cytometry and fluorescence activated cell sorting.

    PubMed

    Yao, Bo; Luo, Guo-an; Feng, Xue; Wang, Wei; Chen, Ling-xin; Wang, Yi-ming

    2004-12-01

    A novel method based on gravity and electric force driving of cells was developed for flow cytometry and fluorescence activated cell sorting in a microfluidic chip system. In the experiments cells flowed spontaneously under their own gravity in a upright microchip, passed through the detection region and then entered into the sorting electric field one by one at an average velocity of 0.55 mm s(-1) and were fluorescence activated cell sorted (FACS) by a switch-off activation program. In order to study the dynamical and kinematic characteristics of single cells in gravity and electric field of microchannels a physical and numerical module based on Newton's Law of motion was established and optimized. Hydroxylpropylmethyl cellulose (HPMC) was used to minimize cell assembling, sedimentation and adsorption to microchannels. This system was applied to estimate the necrotic and apoptotic effects of ultraviolet (UV) light on HeLa cells by exposing them to UV radiation for 10, 20 or 40 min and the results showed that UV radiation induced membrane damage contributed to the apoptosis and necrosis of HeLa cells. PMID:15570372

  8. Direct numerical simulations (DNS) of particles in spatially varying electric fields

    NASA Astrophysics Data System (ADS)

    Amah, E.; Janjua, M.; Fischer, I. S.; Singh, P.

    2013-11-01

    We have developed a direct numerical simulation (DNS) scheme to simulate the motion of dielectric particles suspended in a dielectric liquid in nonuniform electric fields. The motion of particles is tracked using a distributed Lagrange multiplier method (DLM) and the electric forces acting on the particles are calculated by an efficient scheme in which the Maxwell stress tensor (MST) is integrated over the surfaces of the particles to obtain the force. The code is validated by performing a convergence study and by comparing the particle trajectories in a dielectrophoretic cage with those given by the point-dipole method. We also show that the trajectories of the two or more interacting particles given by the MST method can be different from those obtained using the point-dipole method since the latter does not consider particle-particle interactions.

  9. Pre-breakdown cavitation nanopores in the dielectric fluid in the inhomogeneous, pulsed electric fields

    NASA Astrophysics Data System (ADS)

    Pekker, Mikhail; Shneider, Mikhail N.

    2015-10-01

    This paper discusses the nanopores emerging and developing in a liquid dielectric under the action of the ponderomotive electrostrictive forces in a nonuniform electric field. It is shown that the gradient of the electric field in the vicinity of the rupture (cavitation nanopore) substantially increases and determines whether the rupture grows or collapses. The cavitation rupture in the liquid (nanopore) tends to stretch along the lines of the original field. The mechanism of the breakdown associated with the generation of secondary ruptures in the vicinity of the poles of the nanopore is proposed. The estimations of the extension time for nanopore in water and oil (polar and nonpolar liquids, respectively) are presented. A new mechanism of nano- and subnanosecond breakdown in the insulating (transformer) oil that can be realized in the vicinity of water microdroplets in nanosecond high-voltage devices is considered.

  10. Cavitation nanopore in the dielectric fluid in the inhomogeneous, pulsed electric fields

    E-print Network

    M. Pekker; M. N. Shneider

    2014-12-19

    This paper discusses the nanopores emerging and developing in a liquid dielectric under the action of the ponderomotive electrostrictive forces in a nonuniform electric field. It is shown that the gradient of the electric field in the vicinity of the rupture (cavitation nanopore) substantially increases and determines whether the rupture grows or collapses. The cavitation rupture in the liquid (nanopore) tends to stretch along the lines of the original field. The mechanism of the breakdown associated with the generation of secondary ruptures in the vicinity of the poles of the nanopore is proposed. The estimations of the extension time for nanopore in water and oil (polar and nonpolar liquids, respectively) are presented. A new mechanism of nano- and subnanosecond breakdown in the insulating (transformer) oil that can be realized in the vicinity of water microdroplets in modern nanosecond high-voltage devices is considered

  11. Electric and magnetic fields in the astrophysics of wormholes

    NASA Astrophysics Data System (ADS)

    Beskin, V. S.; Kardashev, N. S.; Novikov, I. D.; Shatskii, A. A.

    2011-09-01

    We consider the properties of electric and magnetic fields in vacuum in the neighborhood of static, spherically symmetric wormholes. Although certain aspects of this problem have been considered before, some important features remained undiscovered. We study in detail the properties of electric and magnetic fields in the case of quasi-adiabatic motion of field sources near an Ellis-Bronnikov wormhole and the passage of such sources through the wormhole. An exact solution is found in closed form for a wormhole immersed in a magnetic field that is homogeneous at infinity, as well as an exact solution for a dipolar field without sources. The properties of electromagnetic fields are important for possible observational manifestations of wormholes in astrophysics.

  12. Electric-Field-Induced Reversible Phase Transitions in Two-Dimensional Colloidal Crystals.

    PubMed

    Collins, Kelsey A; Zhong, Xiao; Song, Pengcheng; Little, Neva R; Ward, Michael D; Lee, Stephanie S

    2015-09-29

    Two-dimensional colloidal crystals confined within electric field traps on the surface of a dielectrophoretic cell undergo reversible phase transitions that depend on the strength of the applied AC electric field. At low field strengths, the particles adopt a two-dimensional hexagonal close-packed lattice with p6m plane group symmetry and the maximum achievable packing fraction of ? = 0.91. Higher electric field strengths induce dipoles in the particles that provoke a phase transition to structures that depend on the number of particles confined in the trap. Whereas traps containing N = 24 particles transform to a square-packed lattice with p4m symmetry and ? = 0.79 is observed, traps of the same size containing N = 23 particles can also pack in a lattice with p2 symmetry and ? = 0.66. Traps with N = 21, 22, and 25 particles exhibit a mixture of packing structures, revealing the influence of lateral compressive forces, in addition to induced dipole interactions, in stabilizing loosely packed arrangements. These observations permit construction of a phase diagram based on adjustable parameters of electric field strength (0-750 V/cm) and particle number (N = 21-25). PMID:26343786

  13. Initial Results from the Vector Electric Field Investigation on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Rowland, D.; Acuna, M.; Le, G.; Farrell, W.; Holzworth, R.; Wilson, G.; Burke, W.; Freudenreich, H.; Bromund, K.; Liebrecht, C.; Martin, S.; Kujawski, J.; Uribe, P.; Fourre, R.; McCarthy, M.; Maynard, N.; Berthelier, J.-J.; Steigies, C.

    2009-01-01

    Initial results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. The DC electric field detector has revealed zonal and meridional electric fields that undergo a diurnal variation, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. In general, the measured DC electric field amplitudes are in the 0.5-2 mV/m range, corresponding to I3 x B drifts of the order of 30-150 m/s. What is surprising is the high degree of large-scale (10's to 100's of km) structure in the DC electric field, particularly at night, regardless of whether well-defined spread-F plasma density depletions are present. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. On some occasions, localized regions of low frequency (< 8 Hz) magnetic field broadband irregularities have been detected, suggestive of filamentary currents, although there is no one-to-one correspondence of these waves with the observed plasma density depletions, at least within the data examined thus far. Finally, the data set includes a wide range of ELF/VLF/HF waves corresponding to a variety of plasma waves, in particular banded ELF hiss, whistlers, and lower hybrid wave turbulence triggered by lightning-induced sferics. The VEFI data set represents a treasure trove of measurements that are germane to numerous fundamental aspects of the electrodynamics and irregularities inherent to the Earth's low latitude ionosphere.

  14. Modeling electron transport in the presence of electric and magnetic fields.

    SciTech Connect

    Fan, Wesley C.; Drumm, Clifton Russell; Pautz, Shawn D.; Turner, C. David

    2013-09-01

    This report describes the theoretical background on modeling electron transport in the presence of electric and magnetic fields by incorporating the effects of the Lorentz force on electron motion into the Boltzmann transport equation. Electromagnetic fields alter the electron energy and trajectory continuously, and these effects can be characterized mathematically by differential operators in terms of electron energy and direction. Numerical solution techniques, based on the discrete-ordinates and finite-element methods, are developed and implemented in an existing radiation transport code, SCEPTRE.

  15. Water-methanol separation with carbon nanotubes and electric fields

    NASA Astrophysics Data System (ADS)

    Winarto, Affa; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-07-01

    Methanol is used in various applications, such as fuel for transportation vehicles, fuel cells, and in chemical industrial processes. Conventionally, separation of methanol from aqueous solution is by distillation. However, this method consumes a large amount of energy; hence development of a new method is needed. In this work, molecular dynamics simulations are performed to investigate the effect of an electric field on water-methanol separation by carbon nanotubes (CNTs) with diameters of 0.81 to 4.07 nm. Without an electric field, methanol molecules fill the CNTs in preference to water molecules. The preference of methanol to occupy the CNTs over water results in a separation effect. This separation effect is strong for small CNT diameters and significantly decreases with increasing diameter. In contrast, under an electric field, water molecules strongly prefer to occupy the CNTs over methanol molecules, resulting in a separation effect for water. More interestingly, the separation effect for water does not decrease with increasing CNT diameter. Formation of water structures in CNTs induced by an electric field has an important role in the separation of water from methanol.Methanol is used in various applications, such as fuel for transportation vehicles, fuel cells, and in chemical industrial processes. Conventionally, separation of methanol from aqueous solution is by distillation. However, this method consumes a large amount of energy; hence development of a new method is needed. In this work, molecular dynamics simulations are performed to investigate the effect of an electric field on water-methanol separation by carbon nanotubes (CNTs) with diameters of 0.81 to 4.07 nm. Without an electric field, methanol molecules fill the CNTs in preference to water molecules. The preference of methanol to occupy the CNTs over water results in a separation effect. This separation effect is strong for small CNT diameters and significantly decreases with increasing diameter. In contrast, under an electric field, water molecules strongly prefer to occupy the CNTs over methanol molecules, resulting in a separation effect for water. More interestingly, the separation effect for water does not decrease with increasing CNT diameter. Formation of water structures in CNTs induced by an electric field has an important role in the separation of water from methanol. Electronic supplementary information (ESI) available: Molecule structures in carbon nanotubes. Water molecules vs. methanol molecules in carbon nanotubes under electric field. See DOI: 10.1039/c5nr02182k

  16. ELF electric and magnetic fields: Pacific Northwest Laboratory studies

    SciTech Connect

    Anderson, L.E.

    1992-06-01

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

  17. ELF electric and magnetic fields: Pacific Northwest Laboratory studies

    NASA Astrophysics Data System (ADS)

    Anderson, L. E.

    1992-06-01

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

  18. DFT-Derived Force Fields for Modeling Hydrocarbon Adsorption in MIL-47(V).

    PubMed

    Kulkarni, Ambarish R; Sholl, David S

    2015-08-01

    Generic force fields such as UFF and DREIDING are widely used for predicting molecular adsorption and diffusion in metal-organic frameworks (MOFs), but the accuracy of these force fields is unclear. We describe a general framework for developing transferable force fields for modeling the adsorption of alkanes in a nonflexible MIL-47(V) MOF using periodic density functional theory (DFT) calculations. By calculating the interaction energies for a large number of energetically favorable adsorbate configurations using DFT, we obtain a force field that gives good predictions of adsorption isotherms, heats of adsorption, and diffusion properties for a wide range of alkanes and alkenes in MIL-47(V). The force field is shown to be transferable to related materials such as MIL-53(Cr) and is used to calculate the free-energy differences for the experimentally observed phases of MIL-53(Fe). PMID:26158777

  19. Communication: Multiple atomistic force fields in a single enhanced sampling simulation.

    PubMed

    Hoang Viet, Man; Derreumaux, Philippe; Nguyen, Phuong H

    2015-07-14

    The main concerns of biomolecular dynamics simulations are the convergence of the conformational sampling and the dependence of the results on the force fields. While the first issue can be addressed by employing enhanced sampling techniques such as simulated tempering or replica exchange molecular dynamics, repeating these simulations with different force fields is very time consuming. Here, we propose an automatic method that includes different force fields into a single advanced sampling simulation. Conformational sampling using three all-atom force fields is enhanced by simulated tempering and by formulating the weight parameters of the simulated tempering method in terms of the energy fluctuations, the system is able to perform random walk in both temperature and force field spaces. The method is first demonstrated on a 1D system and then validated by the folding of the 10-residue chignolin peptide in explicit water. PMID:26178083

  20. Communication: Multiple atomistic force fields in a single enhanced sampling simulation

    NASA Astrophysics Data System (ADS)

    Hoang Viet, Man; Derreumaux, Philippe; Nguyen, Phuong H.

    2015-07-01

    The main concerns of biomolecular dynamics simulations are the convergence of the conformational sampling and the dependence of the results on the force fields. While the first issue can be addressed by employing enhanced sampling techniques such as simulated tempering or replica exchange molecular dynamics, repeating these simulations with different force fields is very time consuming. Here, we propose an automatic method that includes different force fields into a single advanced sampling simulation. Conformational sampling using three all-atom force fields is enhanced by simulated tempering and by formulating the weight parameters of the simulated tempering method in terms of the energy fluctuations, the system is able to perform random walk in both temperature and force field spaces. The method is first demonstrated on a 1D system and then validated by the folding of the 10-residue chignolin peptide in explicit water.

  1. Carrier heating in disordered conjugated polymers in electric field

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2010-01-26

    The electric field dependence of charge carrier transport and the effect of carrier heating in disordered conjugated polymers were investigated. A parameter-free multiscale methodology consisting of classical molecular dynamics simulation for the generation of the atomic structure, large system electronic structure and electron-phonon coupling constants calculations and the procedure for extracting the bulk polymer mobility, was used. The results suggested that the mobility of a fully disordered poly(3-hexylthiophene) (P3HT) polymer increases with electric field which is consistent with the experimental results on samples of regiorandom P3HT and different from the results on more ordered regioregular P3HT polymers, where the opposite trend is often observed at low electric fields. We calculated the electric field dependence of the effective carrier temperature and showed however that the effective temperature cannot be used to replace the joint effect of temperature and electric field, in contrast to previous theoretical results from phenomenological models. Such a difference was traced to originate from the use of simplified Miller-Abrahams hopping rates in phenomenological models in contrast to our considerations that explicitly take into account the electronic state wave functions and the interaction with all phonon modes.

  2. Electric Field Detection in Sawfish and Shovelnose Rays

    PubMed Central

    Wueringer, Barbara E.; Jnr, Lyle Squire; Kajiura, Stephen M.; Tibbetts, Ian R.; Hart, Nathan S.; Collin, Shaun P.

    2012-01-01

    In the aquatic environment, living organisms emit weak dipole electric fields, which spread in the surrounding water. Elasmobranchs detect these dipole electric fields with their highly sensitive electroreceptors, the ampullae of Lorenzini. Freshwater sawfish, Pristis microdon, and two species of shovelnose rays, Glaucostegus typus and Aptychotrema rostrata were tested for their reactions towards weak artificial electric dipole fields. The comparison of sawfishes and shovelnose rays sheds light on the evolution and function of the elongated rostrum (‘saw’) of sawfish, as both groups evolved from a shovelnose ray-like ancestor. Electric stimuli were presented both on the substrate (to mimic benthic prey) and suspended in the water column (to mimic free-swimming prey). Analysis of around 480 behavioural sequences shows that all three species are highly sensitive towards weak electric dipole fields, and initiate behavioural responses at median field strengths between 5.15 and 79.6 nVcm?1. The response behaviours used by sawfish and shovelnose rays depended on the location of the dipoles. The elongation of the sawfish’s rostrum clearly expanded their electroreceptive search area into the water column and enables them to target free-swimming prey. PMID:22848543

  3. Electric-field-induced interfacial instabilities of a soft elastic membrane confined between viscous layers

    NASA Astrophysics Data System (ADS)

    Dey, Mohar; Bandyopadhyay, Dipankar; Sharma, Ashutosh; Qian, Shizhi; Joo, Sang Woo

    2012-10-01

    We explore the electric-field-induced interfacial instabilities of a trilayer composed of a thin elastic film confined between two viscous layers. A linear stability analysis (LSA) is performed to uncover the growth rate and length scale of the different unstable modes. Application of a normal external electric field on such a configuration can deform the two coupled elastic-viscous interfaces either by an in-phase bending or an antiphase squeezing mode. The bending mode has a long-wave nature, and is present even at a vanishingly small destabilizing field. In contrast, the squeezing mode has finite wave-number characteristics and originates only beyond a threshold strength of the electric field. This is in contrast to the instabilities of the viscous films with multiple interfaces where both modes are found to possess long-wave characteristics. The elastic film is unstable by bending mode when the stabilizing forces due to the in-plane curvature and the elastic stiffness are strong and the destabilizing electric field is relatively weak. In comparison, as the electric field increases, a subdominant squeezing mode can also appear beyond a threshold destabilizing field. A dominant squeezing mode is observed when the destabilizing field is significantly strong and the elastic films are relatively softer with lower elastic modulus. In the absence of liquid layers, a free elastic film is also found to be unstable by long-wave bending and finite wave-number squeezing modes. The LSA asymptotically recovers the results obtained by the previous formulations where the membrane bending elasticity is approximately incorporated as a correction term in the normal stress boundary condition. Interestingly, the presence of a very weak stabilizing influence due to a smaller interfacial tension at the elastic-viscous interfaces opens up the possibility of fabricating submicron patterns exploiting the instabilities of a trilayer.

  4. Phenomenon of the time-reversal violating magnetic field generation by a static electric field in a medium and vacuum

    E-print Network

    Vladimir G. Baryshevsky

    1999-12-23

    It is shown that the T- and P-odd weak interactions yield to the existence of both electric field and magnetic (directed along the electric field) field around an electric charge. Similarly the assotiated magnetic field is directed along the vector of strength of stationary gravitational field.

  5. Nanomechanical Model of Microtubule Translocation in the Presence of Electric Fields

    PubMed Central

    Kim, Taesung; Kao, Ming-Tse; Hasselbrink, Ernest F.; Meyhöfer, Edgar

    2008-01-01

    Research efforts in recent years have been directed toward actively controlling the direction of translocation of microtubules on a kinesin-coated glass surface with E-fields (electric fields), opening up the possibility of engineering controllable nanodevices that integrate microtubules and motor proteins into their function. Here, we present a detailed, biophysical model that quantitatively describes our observations on the steering of microtubules by electric fields. A sudden application of an electric field parallel to the surface and normal to the translocation direction of a microtubule bends the leading end toward the anode, because Coulombic (electrophoretic) forces are dominant on negatively charged microtubules. Modeling this bending as a cantilever deflection with uniform loading requires accurate mechanical and electrical properties of microtubules, including their charge density, viscous drag, and flexural rigidity. We determined the charge density of microtubules from measurements of the electrophoretic mobility in a “zero flow” capillary electrophoresis column and estimate it to be 256 e? per micron of length. Viscous drag forces on deflecting microtubules in electroosmotic flows were studied theoretically and experimentally by directly characterizing flows using a caged dye imaging method. The flexural rigidity of microtubules was measured by applying E-fields to microtubules with biotinylated segments that were bound to streptavidin-coated surfaces. From the calculated loading, and the Bernoulli-Euler curvature and moment equation, we find that the flexural rigidity of microtubules depends on their length, suggesting microtubules are anisotropic. Finally, our model accurately predicts the biophysical properties and behavior of microtubules directed by E-fields, which opens new avenues for the design of biomolecular nanotransport systems. PMID:18234823

  6. Simulation on electrical field distribution and fiber falls in melt electrospinning.

    PubMed

    Wang, Xin; Liu, Yong; Zhang, Chi; An, Ying; He, Xuetao; Yang, Weimin

    2013-07-01

    Electrospinning is now a typical way of direct and consecutive producing nanofibers. In order to comprehensively understand the change of fiber chains in falling process of electrospinning, the article import dissipative particle dynamics (DPD) mesoscale simulation method into electrospinning study. In current work, an electrical force formula is proposed after simulation of the distribution of electrostatic field in electrospinning using Finite Element Method. Then, various electrostatic force, temperature and viscosity in electrospinning system are qualitatively simulated by DPD simulation. Results showed that the falling velocity of fiber increased with the increase of electrostatic force. It was found that the lower the polymer viscosity, the quicker the fiber falls. And the diameter of fiber significantly increased with augment of viscosity. Both of above are agree with experimental results. We also found that the falling velocity of fiber is in contrast with length of polymer chains, which has not been found in experiments. PMID:23901490

  7. Improvement in Electrical Conductivity of Indium Tin Oxide Films Prepared via Pulsed Laser Deposition on Electric-Field-Applied Substrates

    NASA Astrophysics Data System (ADS)

    Narazaki, Aiko; Kawaguchi, Yoshizo; Niino, Hiroyuki; Sasaki, Takeshi; Koshizaki, Naoto

    2002-06-01

    Indium tin oxide films were fabricated by pulsed laser deposition on electric-field-applied substrates. The volume resistivity was effectively reduced when the electric current passing through films showed a drastic increase accompanied by a subsequent small decrease. According to X-ray diffraction (XRD) measurements, the peculiar behavior of electric current is attributable to the electric-field-induced crystallization.

  8. Effects of a Guide Field on the Larmor Electric Field in Collisionless Asymmetric Reconnection

    NASA Astrophysics Data System (ADS)

    Ruffolo, D. J.; Malakit, K.; Ek-In, S.; Shay, M. A.; Cassak, P.

    2014-12-01

    Recently it has been pointed out that when the inflow conditions of magnetic reconnection are asymmetric, a new in-plane electric field can arise from the physics of finite ion Larmor radius, called the Larmor electric field. It is located next to the Hall electric field structure, making it a potential indicator of proximity to the diffusion region. However, the properties of the Larmor electric field have not previously been explored for the case of a nonzero guide field, which could occur for many reconnection sites, including the day-side magnetopause. In this study, we therefore further explore the properties of the Larmor electric field by adding guide fields with different strengths into our simulations. The results show that the width of the Larmor electric field structure will be smaller, but the strength of the field will be stronger as the guide field increases, consistent with what we expect from the existing theory. Moreover, we show that in the region where the Larmor electric field occurs, there also appears an electron anisotropy. The widths of the electron anisotropy and Larmor electric field structures are found to be similar, suggesting that observing the combination of these two signatures provides a useful indicator of proximity to a reconnection site. Partially supported by a Mahidol University Postdoctoral Fellowship and the Thailand Research Fund. This research was supported by the postdoctoral research sponsorship of Mahidol University (K. M.), the Thailand Research Fund (D. R.), NSF Grants No. ATM-0645271 (M. A. S.) and No. AGS-0953463 (P.A. C.), NASA Grants No. NNX08A083G—MMS IDS, No. NNX11AD69G, and No. NNX13AD72G(M. A. S.).

  9. Relation between mechanical dynamic processes and the accompanying electric fields

    NASA Astrophysics Data System (ADS)

    Bivin, Yu. K.

    2015-06-01

    The dependence of the electric field in the plane of motion of a nylon string on the string velocity is experimentally studied. The shape and number of the charges that accompany the motion of solid bodies, which have various geometric parameters, in air up to transonic velocities are determined. The formation and shape of electric charges of different signs in an initially neutral dielectric rod are investigated during the motion of a deformation pulse of the same sign along the rod.

  10. A CRITICAL ASSESSMENT OF NONLINEAR FORCE-FREE FIELD MODELING OF THE SOLAR CORONA FOR ACTIVE REGION 10953

    SciTech Connect

    DeRosa, Marc L.; Schrijver, Carolus J.; Aschwanden, Markus J.; Cheung, Mark C. M.; Lites, Bruce W.; Amari, Tahar; Canou, Aurelien; McTiernan, James M.; Regnier, Stephane; Thalmann, Julia K.; Wiegelmann, Thomas; Inhester, Bernd; Tadesse, Tilaye; Valori, Gherardo; Wheatland, Michael S.; Conlon, Paul A.; Fuhrmann, Marcel

    2009-05-10

    Nonlinear force-free field (NLFFF) models are thought to be viable tools for investigating the structure, dynamics, and evolution of the coronae of solar active regions. In a series of NLFFF modeling studies, we have found that NLFFF models are successful in application to analytic test cases, and relatively successful when applied to numerically constructed Sun-like test cases, but they are less successful in application to real solar data. Different NLFFF models have been found to have markedly different field line configurations and to provide widely varying estimates of the magnetic free energy in the coronal volume, when applied to solar data. NLFFF models require consistent, force-free vector magnetic boundary data. However, vector magnetogram observations sampling the photosphere, which is dynamic and contains significant Lorentz and buoyancy forces, do not satisfy this requirement, thus creating several major problems for force-free coronal modeling efforts. In this paper, we discuss NLFFF modeling of NOAA Active Region 10953 using Hinode/SOT-SP, Hinode/XRT, STEREO/SECCHI-EUVI, and SOHO/MDI observations, and in the process illustrate three such issues we judge to be critical to the success of NLFFF modeling: (1) vector magnetic field data covering larger areas are needed so that more electric currents associated with the full active regions of interest are measured, (2) the modeling algorithms need a way to accommodate the various uncertainties in the boundary data, and (3) a more realistic physical model is needed to approximate the photosphere-to-corona interface in order to better transform the forced photospheric magnetograms into adequate approximations of nearly force-free fields at the base of the corona. We make recommendations for future modeling efforts to overcome these as yet unsolved problems.

  11. E region electric field dependence of the solar activity

    NASA Astrophysics Data System (ADS)

    Denardini, C. M.; Moro, J.; Resende, L. C. A.; Chen, S. S.; Schuch, N. J.; Costa, J. E. R.

    2015-10-01

    We have being studying the zonal and vertical E region electric field components inferred from the Doppler shifts of type 2 echoes (gradient drift irregularities) detected with the 50 MHz backscatter coherent radar set at São Luis, Brazil (SLZ, 2.3°S, 44.2°W) during the solar cycle 24. In this report we present the dependence of the vertical and zonal components of this electric field with the solar activity, based on the solar flux F10.7. For this study we consider the geomagnetically quiet days only (Kp ? 3+). A magnetic field-aligned-integrated conductivity model was developed for proving the conductivities, using the IRI-2007, the MISIS-2000, and the IGRF-11 models as input parameters for ionosphere, neutral atmosphere, and Earth magnetic field, respectively. The ion-neutron collision frequencies of all the species are combined through the momentum transfer collision frequency equation. The mean zonal component of the electric field, which normally ranged from 0.19 to 0.35 mV/m between the 8 and 18 h (LT) in the Brazilian sector, show a small dependency with the solar activity. Whereas the mean vertical component of the electric field, which normally ranges from 4.65 to 10.12 mV/m, highlights the more pronounced dependency of the solar flux.

  12. OBLIQUELY ROTATING PULSARS: SCREENING OF THE INDUCTIVE ELECTRIC FIELD

    SciTech Connect

    Melrose, D. B.; Yuen Rai

    2012-02-01

    Pulsar electrodynamics has been built up by taking ingredients from two models, the vacuum-dipole model, which ignores the magnetosphere but includes the inductive electric field due to the obliquely rotating magnetic dipole, and the corotating-magnetosphere model, which neglects the vacuum inductive electric field and assumes a corotating magnetosphere. We argue that the inductive field can be neglected only if it is screened by a current, J{sub sc}, which we calculate for a rigidly rotating magnetosphere. Screening of the parallel component of the inductive field can be effective, but the perpendicular component cannot be screened in a pulsar magnetosphere. The incompletely screened inductive electric field has not been included in any model for a pulsar magnetosphere, and taking it into account has important implications. One effect is that it implies that the magnetosphere cannot be corotating, and we suggest that drift relative to corotation offers a natural explanation for the drifting of subpulses. A second effect is that this screening of the parallel inductive electric field must break down in the outer magnetosphere, and this offers a natural explanation for the acceleration of the electrons that produce pulsed gamma-ray emission.

  13. Electric field measurements within a severe thunderstorm anvil

    NASA Technical Reports Server (NTRS)

    Byrne, G. J.; Few, A. A.; Stewart, M. F.

    1989-01-01

    This paper presents the results of electric field measurements made within a severe thunderstorm in central Oklahoma on June 13, 1983. The observations show the electrical structure of a severe storm anvil to be more complex than the simple structure of a positive interior and thin, negative screening layers. Evidence is found of extensive regions of both positive and negative charge in the interior of the anvil, and the thicknesses of screening layers are found to be about an order of magnitude greater than calculated in previous models. A conceptual model for the development of the electrical structure of thunderstorm anvils is proposed in which anvil dynamics plays an important role.

  14. Dynamics of Three-Dimensional Vesicles in DC Electric fields

    E-print Network

    Ebrahim M. Kolahdouz; David Salac

    2015-03-02

    A numerical and systematic parameter study of three-dimensional vesicle electrohydrodynamics is presented to investigate the effects of different fluid and membrane properties. The dynamics of vesicles in the presence of DC electric fields is considered, both in the presence and absence of linear shear flow. For suspended vesicles it is shown that the conductivity ratio and viscosity ratio between the interior and exterior fluids, as well as the vesicle membrane capacitance, substantially affect the minimum electric field strength required to induce a full Prolate-Oblate-Prolate transition.In addition, there exists a critical electric field strength above which a vesicle will no longer tumble when exposed to linear shear flow.

  15. Equatorial Electric Fields Derived from Swarm Magnetometer Data

    NASA Astrophysics Data System (ADS)

    Alken, P.; Maus, S.; Vigneron, P.; Sirol, O.; Hulot, G.; Chulliat, A.

    2014-12-01

    The Swarm Level-2 operational equatorial electric field (EEF) productis producing estimates of the EEF for each dayside orbit of all threesatellites. The EEF plays a crucial role in E and F region daytimeequatorial ionospheric dynamics. It is responsible for driving theequatorial electrojet (EEJ) current system, equatorial vertical ion drifts,and the equatorial ionization anomaly (EIA). The EEF is recovered byanalyzing the EEJ signature seen in the Swarm absolute scalar magnetometer(ASM) data. We will present first results of Swarm-derived EEJ currentsand their corresponding EEF estimates, compare the results betweensatellites, and finally validate them against independent groundmeasurements. We will further compare the magnetometer-derived EEF inthe E-region with measurements from the Electric Field Instrument (EFI) toexplore vertical gradients in the equatorial electric field.

  16. Microspacecraft and Earth observation: Electrical Field (ELF) measurement project

    NASA Technical Reports Server (NTRS)

    1990-01-01

    There is a need for an inexpensive, extensive, long-lasting global electric field measurement system (ELF). The primary performance driver of this mission is the need to measure the attitude of each spacecraft in the Earth's electric field very accurately. In addition, it is necessary to know the electric charge generated by the satellite as it crosses the magnetic field lines (E equals V times B). In order to achieve the desired global coverage, a constellation of about 50 satellites in at least 18 different orbits will be used. To reduce the cost of each satellite, off-the-shelf, proven technology will be used whenever possible. Researchers have set a limit of $500,000 per satellite. Researchers expect the program cost, including the deployment of the entire constellation, to be less than $100 million. The minimum projected mission life is five years.

  17. Electric field suppression of ultracold confined chemical reactions

    SciTech Connect

    Quemener, Goulven; Bohn, John L.

    2010-06-15

    We consider ultracold collisions of polar molecules confined in a one-dimensional optical lattice. Using a quantum scattering formalism and a frame transformation method, we calculate elastic and chemical quenching rate constants for fermionic molecules. Taking {sup 40}K{sup 87}Rb molecules as a prototype, we find that the rate of quenching collisions is enhanced at zero electric field as the confinement is increased but that this rate is suppressed when the electric field is turned on. For molecules with 500 nK of collision energy, for realistic molecular densities, and for achievable experimental electric fields and trap confinements, we predict lifetimes for KRb molecules to be 1 s. We find a ratio of elastic to quenching collision rates of about 100, which may be sufficient to achieve efficient evaporative cooling of polar KRb molecules.

  18. Modeling Electric Fields of Peripheral Nerve Block Needles.

    NASA Astrophysics Data System (ADS)

    Davis, James Ch.; Ramirez, Jason G.

    2005-11-01

    Peripheral nerve blocks present an alternative to general anesthesia in certain surgical procedures and a means of acute pain relief through continuous blockades. They have been shown to decrease the incidence of postoperative nausea and vomiting, reduce oral narcotic side effects, and improve sleep quality. Injecting needles, which carry small stimulating currents, are often used to aid in locating the target nerve bundle. With this technique, muscle responses indicate needle proximity to the corresponding nerve bundle. Failure rates in first injection attempts prompted our study of electric field distributions. Finite difference methods were used to solve for the electric fields generated by two widely used needles. Differences in geometry between needles are seen to effect changes in electric field and current distributions. Further investigations may suggest needle modifications that result in a reduction of initial probing failures.

  19. Modeling Electric Fields of Peripheral Nerve Block Needles.

    NASA Astrophysics Data System (ADS)

    Davis, James Ch.; Anderson, Norman E.; Meisel, Mark W.; Ramirez, Jason G.; Kayser Enneking, F.

    2006-03-01

    Peripheral nerve blocks present an alternative to general anesthesia in certain surgical procedures and a means of acute pain relief through continuous blockades. They have been shown to decrease the incidence of postoperative nausea and vomiting, reduce oral narcotic side effects, and improve sleep quality. Injecting needles, which carry small stimulating currents, are often used to aid in locating the target nerve bundle. With this technique, muscle responses indicate needle proximity to the corresponding nerve bundle. Failure rates in first injection attempts prompted our study of electric field distributions. Finite difference methods were used to solve for the electric fields generated by two widely used needles. Geometric differences in the needles effect variations in their electric field and current distributions. Further investigations may suggest needle modifications that result in a reduction of initial probing failures.

  20. Method of using an electric field controlled emulsion phase contactor

    DOEpatents

    Scott, T.C.

    1993-11-16

    A system is described for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity. 5 figures.

  1. Method of using an electric field controlled emulsion phase contactor

    DOEpatents

    Scott, Timothy C. (Knoxville, TN)

    1993-01-01

    A system for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity.

  2. Electric currents and voltage drops along auroral field lines

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1983-01-01

    An assessment is presented of the current state of knowledge concerning Birkeland currents and the parallel electric field, with discussions focusing on the Birkeland primary region 1 sheets, the region 2 sheets which parallel them and appear to close in the partial ring current, the cusp currents (which may be correlated with the interplanetary B(y) component), and the Harang filament. The energy required by the parallel electric field and the associated particle acceleration processes appears to be derived from the Birkeland currents, for which evidence is adduced from particles, inverted V spectra, rising ion beams and expanded loss cones. Conics may on the other hand signify acceleration by electrostatic ion cyclotron waves associated with beams accelerated by the parallel electric field.

  3. Dielectronic recombination as a function of electric field strength

    NASA Technical Reports Server (NTRS)

    Reisenfeld, Daniel B.

    1992-01-01

    Dielectronic recombination (DR) is the dominant recombination mechanism at coronal temperatures and densities. We present a procedure for calculating DR rate coefficients as a function of electric field strength and apply this method to carbon ions. We focus on the competing effects of enhancement by plasma microfields and rate decrease through collisional excitation and ionization. We find that, in the case of C(3+), a significant rate enhancement results, leading to a reinterpretation of C IV emission-line intensities in the sun and late-type stars. We further consider how macroscopic electric fields, in particular motional electric fields, can affect DR rate coefficients, demonstrating dramatic rate increases for a number of the carbon ions.

  4. Anomalous Capacitive Sheath with Deep Radio Frequency Electric Field Penetration

    SciTech Connect

    Igor D. Kaganovich

    2002-01-18

    A novel nonlinear effect of anomalously deep penetration of an external radio-frequency electric field into a plasma is described. A self-consistent kinetic treatment reveals a transition region between the sheath and the plasma. Because of the electron velocity modulation in the sheath, bunches in the energetic electron density are formed in the transition region adjusted to the sheath. The width of the region is of order V(subscript T)/omega, where V(subscript T) is the electron thermal velocity, and w is frequency of the electric field. The presence of the electric field in the transition region results in a cooling of the energetic electrons and an additional heating of the cold electrons in comparison with the case when the transition region is neglected.

  5. Effects of Electric Fields on Proton Transport Through Water Chains

    PubMed Central

    Hassan, Sergio A.; Hummer, Gerhard; Lee, Yong-Sok

    2006-01-01

    Molecular dynamics simulations on quantum energy surfaces are carried out to study the effects of perturbing electric fields on proton transport (PT) in protonated water chains. As an idealized model of a hydrophobic cavity in the interior of a protein the water molecules are confined into a carbon nanotube (CNT). The water chain connects a hydrated hydroniumion (H3O+) at one end of the CNT and an imidazole molecule at the other end. Without perturbing electric fields PT from the hydronium proton donor to the imidazole acceptor occurs on a picosecond time scale. External perturbations to PT are created by electric fields of varying intensities, normal to the CNT axis, generated by a neutral pair of charges on the nanotube wall. For fields above ?0.5 V/Å, the hydronium ion is effectively trapped at the CNT center, and PT blocked. Fields of comparable strength are generated inside proteins by nearby polar/charged amino acids. At lower fields the system displays a rich dynamic behavior, where the excess charge shuttles back and forth along the water chain before reaching the acceptor group on the picosecond time scale. The effects of the perturbing field on the proton movement are analyzed in terms of structural and dynamic properties of the water chain. The implications of these observations on PT in biomolecular systems and its control by external perturbing fields are discussed. PMID:16774356

  6. Fourier analysis of polar cap electric field and current distributions

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1984-01-01

    A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

  7. The effects of electric fields on wind driven particulate detachment

    NASA Astrophysics Data System (ADS)

    Holstein-Rathlou, C.; Merrison, J. P.; Brædstrup, C. F.; Nornberg, P.

    2012-04-01

    The generation of electric fields close to the surface during sand and dust transport events occurs as a consequence of contact electrification of the sand and dust particulates. Albeit a well documented phenomena the effects of electric fields on the wind driven detachment and transport of granular materials is not well understood. To improve our understanding of the interaction of naturally occurring electric fields upon the transport of sand (and dust) within Aeolian events we have investigated the influence of the electrical conductivity of the surface on the wind driven detachment threshold for sand sized particulates at a surface. Small circular deposits of granular material were placed upon a surface in a parallel plate electrode system and the entire setup located within a re-circulating wind tunnel. This allowed for the application of various electric fields and wind speeds. The study has demonstrated that there is a qualitative difference in the behaviour of the wind driven detachment threshold for an insulating surface as compared to a conductive surface.

  8. Measurements of middle-atmosphere electric fields and associated electrical conductivities

    NASA Technical Reports Server (NTRS)

    Hale, L. C.; Croskey, C. L.; Mitchell, J. D.

    1981-01-01

    A simple antenna for measuring the vertical electric field in the 'middle atmosphere' has been flown on a number of rocket-launched parachute-borne payloads. The data from the first nine such flights, launched under a variety of geophysical conditions, are presented, along with electrical conductivities measured simultaneously. The data include indications of layered peaks of several volts per meter in the mesospheric field at high and low latitudes in situations of relatively low conductivity. During an auroral 'REP' event the electric field reversed direction in the lower stratosphere, accompanied by a substantial enhancement in conductivity. The data generally do not confirm speculations based only on the extension of the thunderstorm circuit from below or the mapping of ionospheric and magnetospheric fields from above, but seem to require, in addition, internal generation processes in the middle atmosphere.

  9. Visualizing Simulated Electrical Fields from Electroencephalography and Transcranial Electric Brain Stimulation: A Comparative Evaluation

    PubMed Central

    Eichelbaum, Sebastian; Dannhauer, Moritz; Hlawitschka, Mario; Brooks, Dana; Knösche, Thomas R.; Scheuermann, Gerik

    2014-01-01

    Electrical activity of neuronal populations is a crucial aspect of brain activity. This activity is not measured directly but recorded as electrical potential changes using head surface electrodes (electroencephalogram - EEG). Head surface electrodes can also be deployed to inject electrical currents in order to modulate brain activity (transcranial electric stimulation techniques) for therapeutic and neuroscientific purposes. In electroencephalography and noninvasive electric brain stimulation, electrical fields mediate between electrical signal sources and regions of interest (ROI). These fields can be very complicated in structure, and are influenced in a complex way by the conductivity profile of the human head. Visualization techniques play a central role to grasp the nature of those fields because such techniques allow for an effective conveyance of complex data and enable quick qualitative and quantitative assessments. The examination of volume conduction effects of particular head model parameterizations (e.g., skull thickness and layering), of brain anomalies (e.g., holes in the skull, tumors), location and extent of active brain areas (e.g., high concentrations of current densities) and around current injecting electrodes can be investigated using visualization. Here, we evaluate a number of widely used visualization techniques, based on either the potential distribution or on the current-flow. In particular, we focus on the extractability of quantitative and qualitative information from the obtained images, their effective integration of anatomical context information, and their interaction. We present illustrative examples from clinically and neuroscientifically relevant cases and discuss the pros and cons of the various visualization techniques. PMID:24821532

  10. Visualizing simulated electrical fields from electroencephalography and transcranial electric brain stimulation: a comparative evaluation.

    PubMed

    Eichelbaum, Sebastian; Dannhauer, Moritz; Hlawitschka, Mario; Brooks, Dana; Knösche, Thomas R; Scheuermann, Gerik

    2014-11-01

    Electrical activity of neuronal populations is a crucial aspect of brain activity. This activity is not measured directly but recorded as electrical potential changes using head surface electrodes (electroencephalogram - EEG). Head surface electrodes can also be deployed to inject electrical currents in order to modulate brain activity (transcranial electric stimulation techniques) for therapeutic and neuroscientific purposes. In electroencephalography and noninvasive electric brain stimulation, electrical fields mediate between electrical signal sources and regions of interest (ROI). These fields can be very complicated in structure, and are influenced in a complex way by the conductivity profile of the human head. Visualization techniques play a central role to grasp the nature of those fields because such techniques allow for an effective conveyance of complex data and enable quick qualitative and quantitative assessments. The examination of volume conduction effects of particular head model parameterizations (e.g., skull thickness and layering), of brain anomalies (e.g., holes in the skull, tumors), location and extent of active brain areas (e.g., high concentrations of current densities) and around current injecting electrodes can be investigated using visualization. Here, we evaluate a number of widely used visualization techniques, based on either the potential distribution or on the current-flow. In particular, we focus on the extractability of quantitative and qualitative information from the obtained images, their effective integration of anatomical context information, and their interaction. We present illustrative examples from clinically and neuroscientifically relevant cases and discuss the pros and cons of the various visualization techniques. PMID:24821532

  11. Transport of ions through a (6,6) carbon nanotube under electric fields

    NASA Astrophysics Data System (ADS)

    Shen, Li; Xu, Zhen; Zhou, Zhe-Wei; Hu, Guo-Hui

    2014-11-01

    The transport of water and ions through carbon nanotubes (CNTs) is crucial in nanotechnology and biotechnology. Previous investigation indicated that the ions can hardly pass through (6,6) CNTs due to their hydrated shells. In the present study, utilizing molecular dynamics simulation, it is shown that the energy barrier mainly originating from the hydrated water molecules could be overcome by applying an electric field large enough in the CNT axis direction. Potential of mean force is calculated to show the reduction of energy barrier when the electric field is present for (Na+, K+, Cl-) ions. Consequently, ionic flux through (6,6) CNTs can be found once the electric field becomes larger than a threshold value. The variation of the coordination numbers of ions at different locations from the bulk to the center of the CNT is also explored to elaborate this dynamic process. The thresholds of the electric field are different for Na+, K+, and Cl- due to their characteristics. This consequence might be potentially applied in ion selectivity in the future.

  12. Casimir force for a scalar field in a single brane world

    SciTech Connect

    Linares, R.; Morales-Tecotl, H. A.; Pedraza, O.

    2010-02-10

    Vacuum force is an interesting low energy test for brane worlds due to its dependence on field's modes and its role in submillimeter gravity experiments. In this contribution we obtain the scalar field vacuum force between two parallel plates lying in the brane of a Randall-Sundrum scenario extended by p compact dimensions (RSII-{sub p}). We obtain the force using the Green's function technique and we compare our results with the ones obtained by using the zeta function regularization method. As a result we obtain agreement in the expression for the force independently of the method used, thus we solve a previous discrepancy between the two approaches.

  13. Reduced dielectric response in spatially varying electric fields.

    PubMed

    Hansen, J S

    2015-11-21

    In this paper, the dynamical equation for polarization is derived. From this the dielectric response to a spatially varying electric field is analyzed showing a reduced response due to flux of polarization in the material. This flux is modeled as a diffusive process through linear constitutive relations between the flux and the gradient of the polarization. Comparison between the theory and molecular dynamics simulations confirms this effect. The effect is significant for small length scale electric field variations and the inclusion of the flux is thus important in nanoscale modeling of dielectric response. PMID:26590542

  14. Drifts of auroral structures and magnetospheric electric fields

    SciTech Connect

    Nakamura, Rumi; Oguti, Takasi )

    1987-10-01

    Drifts of pulsating auroral patches and discrete auroral arc fragments are analyzed on the basis of all-sky TV observations of auroras. The drifts of auroral structures in this study correspond on a gross scale with other measurements of magnetospheric convection. The result strongly suggests that not only auroral patches but also arc fragments, when detached from the main body of the discrete aurora, drift owing to the magnetospheric electric fields. The measurement of the drifts of auroral structures could possibly provide us with a convenient and accurate method to estimate the magnetospheric electric fields.

  15. Effect of electric field on spray deposited zinc sulphide films

    NASA Astrophysics Data System (ADS)

    Swami, Sanjay Kumar; Chaturvedi, Neha; Kumar, Anuj; Dutta, Viresh

    2015-06-01

    Zinc sulphide (ZnS) thin films were deposited on soda lime glass substrate using spray technique with a DC voltage (300 V) applied to the nozzle to create an electric field during the spray deposition. Spray deposition of ZnS film under an electric field, resulted in change of the surface morphology, transmission, and enhancement in crystallinity of the film. The band gap of the spray deposited ZnS film was found to be 3.62 eV. Transparent ZnS film with the benefit of large area and low cost spray technique can be suitable for solar cell window layer application.

  16. Electric field induced instabilities: waves and stationary patterns.

    PubMed

    Dutta, Sumana; Ray, Deb Shankar

    2006-02-01

    We examine a prototypical ionic reaction-diffusion system involving the well-known iodate-arsenous acid reaction in an electric field at a constant current density. By taking into consideration of the spatial inhomogeneities in electric field intensity and charge density due to ionic migration and diffusion using charge balance condition, we look for the different instability regions in the appropriate parameter space. We show that the model admits of both absolute and convective instability resulting in the development of propagating waves and also stationary spatial patterns at times. PMID:16605432

  17. Electron acceleration by low frequency electric field fluctuations - Electron conics

    NASA Technical Reports Server (NTRS)

    Andre, Mats; Eliasson, Lars

    1992-01-01

    Electron conics can be generated by fluctuations at roughly one Hz in a parallel electric field accelerating auroral electrons at altitudes of several thousand kilometers. The results from simulations including such time-varying electric fields are in good agreement with observed electron distributions. The simulation parameters are consistent with the ion beams and broadband waves associated with electron conics. Calculations are used to predict for example oscillations in the low altitude electron fluxes. These results can be used to compare different possible mechanisms for the generation of electron conics.

  18. Linear oscillations of a drop in uniform alternating electric fields

    SciTech Connect

    Yang, Wenrui; Carleson, T.E.

    1990-10-01

    Oscillations of a conducting drop immersed in a dielectric fluid in an alternating electric field has been modelled in order to understand the enhancement of the transport processes by the electric field. Numerical solutions for oscillation amplitude, velocity distribution, resonant frequency and streamlines were obtained. The effects of viscosity and density on the resonant frequency and the velocity distribution were investigated. It was found that the resonant frequency of viscous fluids was always smaller than the free oscillation frequency of the same droplet. The predicted scanning frequency response curve and the streamlines agree well with the experimental observations.

  19. Development of Field Excavator with Embedded Force Measurement

    NASA Technical Reports Server (NTRS)

    Johnson, K.; Creager, C.; Izadnegahdar, A.; Bauman, S.; Gallo, C.; Abel, P.

    2012-01-01

    A semi-intelligent excavation mechanism was developed for use with the NASA-built Centaur 2 rover prototype. The excavator features a continuously rotatable large bucket supported between two parallel arms, both of which share a single pivot axis near the excavator base attached to the rover. The excavator is designed to simulate the collection of regolith, such as on the Moon, and to dump the collected soil into a hopper up to one meter tall for processing to extract oxygen. Because the vehicle can be autonomous and the terrain is generally unknown, there is risk of damaging equipment or using excessive power when attempting to extract soil from dense or rocky terrain. To minimize these risks, it is critical for the rover to sense the digging forces and adjust accordingly. It is also important to understand the digging capabilities and limitations of the excavator. This paper discusses the implementation of multiple strain gages as an embedded force measurement system in the excavator's arms. These strain gages can accurately measure and resolve multi-axial forces on the excavator. In order to validate these sensors and characterize the load capabilities, a series of controlled excavation tests were performed at Glenn Research Center with the excavator at various depths and cut angles while supported by a six axis load cell. The results of these tests are both compared to a force estimation model and used for calibration of the embedded strain gages. In addition, excavation forces generated using two different types of bucket edge (straight vs. with teeth) were compared.

  20. Cardiovascular response of rats exposed to 60-Hz electric fields

    SciTech Connect

    Hilton, D.I.; Phillips, R.D.

    1980-01-01

    Recently, it has been reported that exposure to high-strength electric fields can influence electrocardiogram (ECG) patterns, heart rates, and blood pressures in various species of animals. Our studies were designed to evaluate these reported effects and to help clarify some of the disagreement present in the literature. Various cardiovascular variables were measured in Sprague-Dawley rats exposed or sham-exposed to 60-Hz electric fields at 80 to 100 kV/m for periods up to four months. No significant differences in heart rates, ECG patterns, blood pressures, or vascular reactivity were observed between exposed and sham-exposed rats after 8 hours, 40 hours, 1 month, or 4 months of exposure. Our studies cannot be directly compared to the work of other investigators because of differences in animal species and electric-field characteristics. However, our failure to detect any cardiovascular changes may have been the result of (1) eliminating secondary field effects such as shocks, audible noise, corona, and ozone; (2) minimizing steady-state microcurrents between the mouth of the animal and watering devices; and (3) minimizing electric-field-induced vibration of the electrodes and animal cages.