Sample records for electric field forces

  1. LABORATORY I ELECTRIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    of the object. (The magnitude of the gravitational field near the earth's surface is g = 9.8 m/s2 .) In the case as "action-at-a-distance". This means that an object can exert a force on another object that require some getting used to. First, it is hard to visualize objects interacting when

  2. Generation of Dielectrophoretic Force under Uniform Electric Field

    E-print Network

    Kua, C.H.

    Effective dipole moment method has been widely accepted as the de facto technique in predicting the dielectrophoretic force due to the non-uniform electric field. In this method, a finite-particle is modeled as an equivalent ...

  3. First-principles calculation of electrical forces among nanospheres in a uniform applied electric field

    Microsoft Academic Search

    David J. Bergman; Xiangting Li; Kwangmoo Kim; David Stroud

    2005-01-01

    We present a unified framework for a first-principles calculation of the electric force acting on dielectric or metallic nanospheres suspended in a dielectric host and subject to a uniform external electric field. This framework is based on the spectral representation of the local electric field in a composite medium. The quasi-static (or \\

  4. Mechanical Forces between Electric Currents and Saturated Magnetic Fields

    Microsoft Academic Search

    Vladimir Karapetoff

    1927-01-01

    The general case considered is that of N independent electric circuits placed in a medium of variable permeability and subject to saturation, in parts or as a whole. The problem is to determine the component (in a given direction) of the mechanical force acting upon one of the electric circuits, upon a group of circuits, or upon a group of

  5. Magnetoelectric force microscopy based on magnetic force microscopy with modulated electric field.

    PubMed

    Geng, Yanan; Wu, Weida

    2014-05-01

    We present the realization of a mesoscopic imaging technique, namely, the Magnetoelectric Force Microscopy (MeFM), for visualization of local magnetoelectric effect. The basic principle of MeFM is the lock-in detection of local magnetoelectric response, i.e., the electric field-induced magnetization, using magnetic force microscopy. We demonstrate MeFM capability by visualizing magnetoelectric domains on single crystals of multiferroic hexagonal manganites. Results of several control experiments exclude artifacts or extrinsic origins of the MeFM signal. The parameters are tuned to optimize the signal to noise ratio. PMID:24880381

  6. Forces and movement of water droplets in oil caused by applied electric field

    Microsoft Academic Search

    A. Pedersen; E. Ildstad; A. Nysveen

    2004-01-01

    The effect of applying an electric field to an emulsion of water and oil is to induce attractive forces and enhance the coalescence of adjacent water droplets. In the oil industry, it is common to utilize this process, called electrocoalescense, to enhance oil-water separation by enlarging the water droplets. The work presented here describes the forces influencing the kinematics of

  7. Electricity: The Mysterious Force

    NSDL National Science Digital Library

    2008-01-01

    This document examines the mysterious force of electricity. The reading will focus on the physical properties of electricity and discuss topics such as (1) The Atom of Carbon, (2) Static electricity, (3) Magnets are special, (4) Magnetic fields can produce electricity, (5) Batteries produce electricity, (6) Electricity travels in circuits, (7) Secondary energy source, (8) Making electricity, (9) Moving electricity from power plants to homes, (10) Fuels that make electricity, (11) Fossil fuel power plants, (12) Nuclear power plants, (13) Hydropower plants, (14) What's a Watt, and (15) Cost of electricity. The document also depicts illustrations of a bar magnet, turbine generator, transporting electricity, U.S. electricity production, peak demand, and energy efficiency. This resource is structured as an informational booklet to supplement your energy activities or to generate discussion questions.

  8. Students' conceptions and reasoning models of the electric force and field related questions in the interviewed CSEM test

    Microsoft Academic Search

    M Saarelainen; A Laaksonen; P E Hirvonen

    This study explores undergraduate students' conceptions and reasoning models of electric forces and fields. It is based on their answers and explanations given in the interviewed CSEM test questions 6 and 13. The results indicate that the students are able to apply Coulombian force only in relatively simple problems, but they fail in using appropriate electric field models in cases

  9. 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.

  10. Forces and torque on a pair of uncharged conducting spheres in an external electric field

    NASA Astrophysics Data System (ADS)

    Lekner, John

    2013-12-01

    Exact results are given for the forces acting on two conducting spheres in an applied electric field E. The torque acting on the two-sphere system is proportional to the difference between the longitudinal and transverse polarizabilities: ? =(??-?t)E2 sin? cos? (? is the angle between the applied field and the line-of-centers of the spheres). The forces acting on the two spheres are equal and opposite, and given by the derivatives of ?? and ?t with respect to the sphere separation. Simple analytic forms for the torque and forces are found at small and at large separations. At all separations, the torque always acts to align the line of centers of the spheres with the external field. Possible applications are to colloidal suspensions of spherical conducting particles.

  11. DOE Task Force meeting on Electrical Breakdown of Insulating Ceramics in a High Radiation Field

    SciTech Connect

    Green, P.H. (comp.) [comp.

    1991-08-01

    This volume contains the abstracts and presentation material from the Research Assistance Task Force Meeting Electrical Breakdown of Insulating Ceramics in a High-Radiation Field.'' The meeting was jointly sponsored by the Office of Basic Energy Sciences and the Office of Fusion Energy of the US Department of Energy in Vail, Colorado, May 28--June 1, 1991. The 26 participants represented expertise in fusion, radiation damage, electrical breakdown, ceramics, and semiconductor and electronic structures. These participants came from universities, industries, national laboratories, and government. The attendees represented eight nations. The Task Force meeting was organized in response to the recent discovery that a combination of temperature, electric field, and radiation for an extended period of time has an unexplained adverse effect in ceramics, termed radiation-enhanced electrical degradation (REED). REED occurs after an incubation period and continues to accelerate with irradiation until the ceramics can no longer be regarded as insulators. It appears that REED is irreversible and the ceramic insulators cannot be readily annealed or otherwise repaired for future services. This effect poses a serious threat for fusion reactors, which require electrical insulators in diagnostic devices, in radio frequency and neutral beam systems, and in magnetic assemblies. The problem of selecting suitable electrical insulating materials in thus far more serious than previously anticipated.

  12. Three-dimensional approximation of the total force on uncharged spheres in electric fields

    NASA Astrophysics Data System (ADS)

    Langemann, Dirk

    2007-02-01

    Droplets on outdoor high-voltage equipment suffer a total force which is non-vanishing in general. We consider a model problem of an uncharged and conductive sphere. We show that the total force can be given as a series of inhomogeneity indicators of the undisturbed electric field in the absence of the droplet. The proof of the series involves several aspects of the spherical harmonics in the three-dimensional Fourier technique. The series expansion establishes a relation between the solutions of two Poisson's equations on different domains. It is found that the expansion converges fast. The results are applied for droplets on a realistically shaped insulator.

  13. Studying electric field profiles in GaAs-based detector structures by Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Vilisova, M. D.; Germogenov, V. P.; Kaztaev, O. Zh.; Novikov, V. A.; Ponomarev, I. V.; Titkov, A. N.

    2010-05-01

    The method of scanning Kelvin probe force microscopy has been used to study the electric field distribution in GaAs-based p +-?- n- n + detector structures. In the active layer volume, two maxima in the field strength profiles have been found, which are localized in the regions of p +-? and ?- n junctions. A volt-age drop on the ?- n junction expands the region of collection of nonequilibrium holes, thus increasing the charge collection efficiency for the absorption of ? photons with an energy of 59.5 keV.

  14. Faraday's law of induction and the force on a body due to change in its magnetization in an electric field

    Microsoft Academic Search

    K. G. Ramanathan

    1962-01-01

    From arguments based on Faraday's Law of induction, it is shown that a body whose intensity of magnetization is changing should, in general, experience a force when situated in an electrostatic field in a manner analogous to the force experienced by a conductor carrying an electric current in a magnetic field.

  15. Effects of AC Electrical Field on the Dielectrophoresis Force of Dielectric Elastomers and Blends

    NASA Astrophysics Data System (ADS)

    Sirivat, Anuvat; Kunanuruksapong, Ruksapong

    2011-03-01

    The effects of frequency and amplitude of AC electric field on the deflection and the dielectrophoresis force of an acrylic elastomer (AR71), styrene copolymers (SAR and SBR), and the blends of doped PPP and AR71 are investigated. The dielectrophoresis forces of the dielectric elastomers and blends were measured by using a vertical cantilever fixture at various frequencies (0.3 to 60 Hz) and at AC electric field strengths of 200-800 Vpp/mm. The effects of the thicknesses of the specimens and the particle concentration are studied. The doped PPP particles are embedded in the AR71 with concentrations of 1, 10, and 20 %vol. The dielectrophoresis forces and deflection distance of the dielectric elastomers and blends generally increase with increasing amplitude but slightly decrease with increasing frequency; and they dramatically drop at the cut-off frequency. The cut-off frequencies are 7.84, 1.45, and 0.74 Hz for AR71, SAR, and SBR, respectively, at E of 800 Vpp/mm and a thickness of 0.7 to 0.8 mm. After blending the AR71 with doped PPP, the cut-off frequencies of the 1 %vol, 10 %vol and 20 %vol of doped PPP are 18.51, 15.28, and 10.67 Hz, respectively, at an E of 800 Vpp/mm and a thickness of 0.2 to 0.3 mm. The conductive polymer particles are shown here to improve the electromechanical responses at high frequency.

  16. Polyhedra Formation and Transient Cone Ejection of a Resonant Microdrop Forced by an ac Electric Field

    E-print Network

    Chang, Hsueh-Chia

    Polyhedra Formation and Transient Cone Ejection of a Resonant Microdrop Forced by an ac Electric of the diffuse layer. The selected polyhedra possess symmetries that ensure a global force balance of the Maxwell and frequencies, specific spherical har- monics are shown to evolve into specific polyhedra at comparatively low

  17. A finite-element analysis of the electrostatic force on a uniformly charged dielectric sphere resting on a dielectric-coated electrode in a detaching electric field

    Microsoft Academic Search

    James Q. Feng; Dan A. Hays

    1998-01-01

    In the electrophotographic process, charged toner particles are transferred from one surface to another with an electric field. To enable electric field transfer of toner, the externally applied field strength must be greater than a threshold value, so that the Coulomb force can overcome the toner adhesion force at the supporting surface. In this paper, the threshold field strength to

  18. Electric-field-induced forces between two surfaces filled with an insulating liquid: the role of adsorbed water

    NASA Astrophysics Data System (ADS)

    Wang, Yong Jian; Xu, Zuli; Sheng, Ping; Tong, Penger

    2014-06-01

    A systematic study of the electric-field-induced forces between a solid glass sphere and a flat gold-plated substrate filled with an insulating liquid has been carried out. Using atomic force microscopy, we measure the electrostatic force f(s, V) between the sphere and substrate as a function of the surface separation s and applied voltage V. The measured f(s, V) is found to be well described by an equation for a conducting sphere. Further force measurements for the "wet" porous glass spheres filled with an aqueous solution of urea and the dried porous glass spheres filled with (dry) air suggest that there is a water layer of a few nanometers in thickness adsorbed on the hydrophilic glass surface under ambient conditions. This adsorbed water layer is more conductive than the dielectric core of the glass sphere, making the sphere surface to be at a potential close to that of the cantilever electrode. As a result, the electric field is strongly concentrated in the gap region between the glass sphere and gold-plate substrate and thus their electrostatic attraction is enhanced. This surface conductivity effect is further supported by the thermal gravimetric analysis (TGA) and force response measurements to a time-dependent electric field. The experiment clearly demonstrates that the adsorption of a conductive water layer on a hydrophilic surface plays a dominant role in determining the electrostatic interaction between the dielectric sphere and substrate.

  19. Ionic velocities in an ionic liquid under high electric fields using all-atom and coarse-grained force field molecular dynamics

    Microsoft Academic Search

    John W. Daily; Michael M. Micci

    2009-01-01

    Molecular dynamics has been used to estimate ionic velocities and electrical conductivity in the ionic liquid 1-ethyl-3-methylimidazolium\\/tetraflouroborate (EMIM-BF4). Both an all-atom and coarse grained force fields were explored. The simulations were carried out at high electric fields where one might expect the Wien effect to become important in conventional electrolytes and that effect is observed. While the original Wilson theory

  20. Field Measurements of Heating Efficiency of Electric Forced-Air Furnaces in Six Manufactured Homes.

    SciTech Connect

    Davis, Bob; Palmiter, Larry S.; Siegel, Jeff

    1994-07-26

    This report presents the results of field measurements of heating efficiency for six manufactured homes in the Pacific Northwest heated with electric forced-air systems. This is the first in a series of regional and national efforts to measure in detail the heating efficiency of manufactured homes. Only six homes were included in this study because of budgetary constraints; therefore this is not a representative sample. These investigations do provide some useful information on the heating efficiency of these homes. Useful comparisons can be drawn between these study homes and site-built heating efficiencies measured with a similar protocol. The protocol used to test these homes is very similar to another Ecotope protocol used in the study conducted in 1992 and 1993 for the Bonneville Power Administration to test the heating efficiency of 24 homes. This protocol combined real-time power measurements of furnace energy usage with energy usage during co-heat periods. Accessory data such as house and duct tightness measurements and tracer gas measurements were used to describe these homes and their heating system efficiency. Ensuring that manufactured housing is constructed in an energy and resource efficient manner is of increasing concern to manufactured home builders and consumers. No comparable work has been done to measure the heating system efficiency of MCS manufactured homes, although some co-heat tests have been performed on manufactured homes heated with natural gas to validate HUD thermal standards. It is expected that later in 1994 more research of this kind will be conducted, and perhaps a less costly and less time-consuming method for testing efficiencies will be develops.

  1. Student interpretations of electric and magnetic fields and forces on the CSEM

    Microsoft Academic Search

    Marie Sanfilippo Plumb

    2004-01-01

    This study was undertaken to investigate the construct validity of ten purposefully selected items from the Conceptual Survey of Electricity and Magnetism (CSEM) (Maloney, O'Kuma, Hieggelke, & VanHeuvelen, 2001) and to probe into the mental models used by a group of post-instruction college physics students to answer the questions. The construct investigated was conceptual understanding of electric and magnetic fields

  2. Exploring Forces: Static Electricity

    NSDL National Science Digital Library

    Nanoscale Informal Science Education Network

    2010-01-01

    In this activity, learners investigate what happens when you build up static electricity on plastic balls. Learners discover that electrostatic forces cause smaller balls to suspend in a tube, while larger balls fall to the bottom. This activity shows learners that size can affect the way a material behaves. This activity is a great way to talk about how different things behave at the nanoscale.

  3. Tuning the instability in static mode atomic force spectroscopy as obtained in an AFM by applying an electric field between the tip and the substrate.

    PubMed

    Biswas, Soma; Raychaudhuri, A K; Sreeram, P A; Dietzel, Dirk

    2012-11-01

    We have investigated experimentally the role of cantilever instabilities in determination of the static mode force-distance curves in presence of a dc electric field. The electric field has been applied between the tip and the sample in an atomic force microscope working in ultra-high vacuum. We have shown how an electric field modifies the observed force (or cantilever deflection)-vs-distance curves, commonly referred to as the static mode force spectroscopy curves, taken using an atomic force microscope. The electric field induced instabilities shift the jump-into-contact and jump-off-contact points and also the deflection at these instability points. We explained the experimental results using a model of the tip-sample interaction and quantitatively established a relation between the observed static mode force spectroscopy curves and the applied electric field which modifies the effective tip-sample interaction in a controlled manner. The investigation establishes a way to quantitatively evaluate the electrostatic force in an atomic force microscope using the static mode force spectroscopy curves. PMID:22960002

  4. Forces acting on dielectric colloidal spheres at a water/nonpolar-fluid interface in an external electric field. 1. Uncharged particles.

    PubMed

    Danov, Krassimir D; Kralchevsky, Peter A

    2013-09-01

    Here, we calculate the electric forces acting on uncharged dielectric colloidal particles, which are attached to the interface between a nonpolar fluid (air, oil) and water, in the presence of an applied uniform external electric field directed normal to the interface. The uncharged particle becomes a source of dipolar electric field because it is polarized by the external field. Our goal is to calculate the normal (electrodipping) force acting on each separate particle, and the force of interaction between two identical particles. An exact analytical solution is obtained by solving the Laplace equation in toroidal coordinates and by separating the variables using the Mehler-Fock integral transform. The results show that the dependence of the normal force on particle contact angle is non-monotonic, with a maximum and a minimum. This force can be directed upward or downward depending on the particle contact angle and dielectric constant. An analytical asymptotic expression is derived for the force of interaction between two floating particles in external field. The magnitude of the latter force depends strongly on the particle contact angle ?. At a certain value of ?, the leading dipolar term becomes zero, and the interaction force is determined by the short-range octupolar term. Then, the attractive lateral capillary forces and van der Waals forces can overcome the electrostatic repulsion and can induce two-dimensional coagulation of the particles at the interface. The effects of the external electric field could find applications for control of the distances between particles in non-densely packed interfacial colloid crystals used in lithographic masks for the production of antireflective coatings, microlens arrays, etc. The case of charged particles in external field is considered in the second part of this study. PMID:23768629

  5. Electric and Magnetic Forces

    NSDL National Science Digital Library

    2010-02-10

    SciGuides are a collection of thematically aligned lesson plans, simulations, and web-based resources for teachers to use with their students centered on standards-aligned science concepts. People have known about and experienced electricity an

  6. Carbohydrate force fields

    PubMed Central

    Foley, B. Lachele; Tessier, Matthew B.; Woods, Robert J.

    2014-01-01

    Carbohydrates present a special set of challenges to the generation of force fields. First, the tertiary structures of monosaccharides are complex merely by virtue of their exceptionally high number of chiral centers. In addition, their electronic characteristics lead to molecular geometries and electrostatic landscapes that can be challenging to predict and model. The monosaccharide units can also interconnect in many ways, resulting in a large number of possible oligosaccharides and polysaccharides, both linear and branched. These larger structures contain a number of rotatable bonds, meaning they potentially sample an enormous conformational space. This article briefly reviews the history of carbohydrate force fields, examining and comparing their challenges, forms, philosophies, and development strategies. Then it presents a survey of recent uses of these force fields, noting trends, strengths, deficiencies, and possible directions for future expansion. PMID:25530813

  7. Electric and Magnetic Forces: Electric Charges

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2008-10-30

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach.This Science Object is the first of three Science Objects in the Electric and Magnetic Forces SciPack.

  8. Electric and Magnetic Forces: Electromagnetism

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2008-10-30

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach.This Science Object is the last of three Science Objects in the Electric and Magnetic Forces SciPack.

  9. 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.

  10. Force field of monoethanolamine

    SciTech Connect

    Alejandre, J.; Rivera, J.L.; Mora, M.A.; Garza, V. de la

    2000-02-17

    Ab initio calculations and canonical molecular dynamics simulations were performed to obtain a force field of monoethanolamine (MEA). The molecule is modeled by seven charged sites, and the force field includes intramolecular degrees of freedom and intermolecular interactions. The charges obtained in the energy minimization procedure reproduce the experimental geometry, dipole moment, and the most stable conformation. Molecular dynamics simulations were carried out in the liquid phase and in the liquid-vapor equilibrium state. Simulations in the liquid region give information about hydrogen bond formation, while simulations in the two-phase region allow the determination of coexisting densities and surface tension as functions of temperature. The hydrogen bond is favored when the hydrogen of the hydroxyl group is close to a nitrogen or to an oxygen of another molecule, and the strength in both cases is the same. Radial distribution functions involving hydrogens and oxygen in the hydroxyl group of MEA are compared with those of water at 298 K, and a similar structure is found for the first neighbor of atoms. The proposed force field gives a good description of the liquid-vapor coexistence of MEA. The liquid density obtained in simulations of the liquid-vapor equilibrium at 298 K is 1.003 g/cm{sup 3} versus the experimental value of 1.012 g/cm{sup 3}. The estimated critical point is located at 583.9 K and 0.32 g/cm{sup 3} in comparison with the experimental result of 614 K and 0.3116 g/cm{sup 3}, respectively. At 323 K the calculated surface tension if 43.2 {+-} 2.5 nM/m while the experimental value is 44.81 mN/m.

  11. Computation of the electric potential and the Lorentz force in a locally ionized magnetohydrodynamic flow in a nonuniform magnetic field for a transverse flow past a circular cylinder

    NASA Astrophysics Data System (ADS)

    Sheikin, E. G.; Wei, Yang Cheng

    2013-01-01

    An analytical solution to electrodynamic equations is obtained for the electric potential in a locally ionized magnetohydrodynamic (MHD) flow for a transverse flow past a circular cylinder in the non-uniform magnetic field of a rectilinear conductor. Analytical formulas for computing the volume density of the Lorentz force acting on the flow in a locally ionized MHD flow are obtained for the case of the conducting and nonconducting surfaces of the cylinder. The influence of the Hall parameter and width of the MHD interaction region on the value of the Lorentz force is analyzed. It is demonstrated that the Lorentz force, which accelerates and not decelerates the flow, appears under certain conditions near the surface of the cylinder in the neighborhood of the critical point.

  12. Field-regulated force by grafted polyelectrolytes

    E-print Network

    Christian Seidel; Yury A. Budkov; Nikolay V. Brilliantov

    2014-11-08

    Generation of mechanical force regulated by external electric field is studied both theoretically and by molecular dynamics (MD) simulations. The force arises in deformable bodies linked to the free end of a grafted polyelectrolyte chain which is exposed to electric field that favours its adsorption. We consider a few target bodies with different force-deformation relations including (i) linear and (ii) cubic dependences as well as (iii) Hertzian-like force. Such force-deformation relations mimic the behaviour of (i) coiled and (ii) stretched polymer chains, respectively, or (iii) that of a squeezed colloidal particle. The magnitude of the arising force varies over a wide interval although the electric field alters within a relatively narrow range only. The predictions of our theory agree quantitatively well with the results of numerical simulations. Both cases of zero and finite electrical current are investigated and we do not obtain substantial differences in the force generated. The phenomenon studied could possibly be utilised to design, e.g., vice-like devices to fix nano-sized objects.

  13. Electric Field Example 12

    NSDL National Science Digital Library

    Wolfgang Christian

    Four students have produced representations in the right box of the electric field they think produces the electric equipotential lines displayed in the left box. Click on each of their names and decide which student drew the best representation. The arrows in the field plot represent the direction and the colors represent the magnitude of the electric field. You can click-drag in the left-hand display to measure the potential.

  14. Electric Field Example 10

    NSDL National Science Digital Library

    Wolfgang Christian

    The square represents a cross section of a cube. Use the test charge to explore the direction of the electric field inside the cube. Click the cursor anywhere inside the cube to measure the magnitude of the electric field. Use it also to determine the dimensions of the cube. Find the flux through each side of the cube.

  15. Simulated Static Electric Field (SSEF) Snake for Deformable Models

    Microsoft Academic Search

    Dan Yuan; Siwei Lu

    2002-01-01

    In this paper a novel design of external force for snake is proposed. This kind of external force is actually a field, which we call the simulated static electric field. This field is created by simulated static electric charges, and the forces in this field are computed by the Coulomb law which is used in the analysis of static charge

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

    SciTech Connect

    Kent, Paul R [ORNL

    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.

  17. Nonconservative electric and magnetic optical forces on submicron dielectric particles

    SciTech Connect

    Gomez-Medina, Raquel; Nieto-Vesperinas, Manuel [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Campus de Cantoblanco, Madrid E-28049 (Spain); Saenz, Juan Jose [Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, 20018 Donostia-San Sebastian (Spain)

    2011-03-15

    We present a study of the total force on a small lossless dielectric particle, which presents both an electric and magnetic response, in a optical vortex wave field. We show that the force is a simple combination of conservative and nonconservative steady forces that can rectify the flow of magnetodielectric particles. In a vortex lattice the electric-magnetic dipolar interaction can spin the particles either in or out of the whirl sites leading to trapping or diffusion. Specifically, we analyze force effects on submicron silicon spheres in the near infrared, proving that the results previously discussed for hypothetical magnetodielectric particles can be observed for these Si particles.

  18. Drawing Electric Field Lines

    NSDL National Science Digital Library

    Wolfgang Christian

    The panel on the left displays an equipotential plot. The contours represent points at the exact same potential. Draw the electric field lines for this potential by dragging the pencil (at its tip) after clicking the "draw on" button.

  19. Electroreception Electric field properties

    E-print Network

    Wilkinson, Gerald S.

    (electron deficit) and negative charges (e.g. a dipole such as a battery) · Electric field lines (dashed in several fish families ­ Duplicate sodium channel gene is expressed only in electrocyte (Zakon 2006 PNAS

  20. Electric Field Example 8

    NSDL National Science Digital Library

    Wolfgang Christian

    One or more objects with uniform charge on them are located just off the screen on the left-hand side. Use the test charge to measure the electric field, and from that determine what type of object they are.

  1. Models of force-free magnetic fields in resistive media

    Microsoft Academic Search

    Rolf Bostrm

    1973-01-01

    A review is given of some of the basic properties of force-free fields under circumstances when the conductivity of the medium is finite. Then the electric current density is related not only to the magnetic field, but also by Ohm's law to the electric field and plasma velocity, which must be considered in the solutions. It is pointed out that

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

    SciTech Connect

    Higa, Mitsuru; Kira, Akira (Inst. of Physical and Chemical Research (RIKEN), Saitama (Japan))

    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.

  3. Turbulence generation by electric body forces

    Microsoft Academic Search

    J. H. Davidson; E. J. Shaughnessy

    1986-01-01

    The effect of an electric body force on vorticity production and turbulence generation in a gas is investigated by examination of the governing electrohydrodynamic equations. The theoretical concepts are illustrated by hot-film anemometer measurements of the electrically induced turbulence in a large scale electrostatic precipitator. The results indicate dramatic increases in turbulence and diffusivity due to the corona discharge and

  4. 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 ...

  5. Dynamic properties of force fields

    NASA Astrophysics Data System (ADS)

    Vitalini, F.; Mey, A. S. J. S.; No, F.; Keller, B. G.

    2015-02-01

    Molecular-dynamics simulations are increasingly used to study dynamic properties of biological systems. With this development, the ability of force fields to successfully predict relaxation timescales and the associated conformational exchange processes moves into focus. We assess to what extent the dynamic properties of model peptides (Ac-A-NHMe, Ac-V-NHMe, AVAVA, A10) differ when simulated with different force fields (AMBER ff99SB-ILDN, AMBER ff03, OPLS-AA/L, CHARMM27, and GROMOS43a1). The dynamic properties are extracted using Markov state models. For single-residue models (Ac-A-NHMe, Ac-V-NHMe), the slow conformational exchange processes are similar in all force fields, but the associated relaxation timescales differ by up to an order of magnitude. For the peptide systems, not only the relaxation timescales, but also the conformational exchange processes differ considerably across force fields. This finding calls the significance of dynamic interpretations of molecular-dynamics simulations into question.

  6. Electricity and Magnetic Fields

    NSDL National Science Digital Library

    VU Bioengineering RET Program,

    The grand challenge for this legacy cycle unit is for students to design a way to help a recycler separate aluminum from steel scrap metal. In previous lessons, they have looked at how magnetism might be utilized. In this lesson, students think about how they might use magnets and how they might confront the problem of turning the magnetic field off. Through the accompanying activity students explore the nature of an electrically induced magnetic field and its applicability to the needed magnet.

  7. 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.

  8. Device for measuring electric fields

    NASA Technical Reports Server (NTRS)

    Levine, S. H.; Harrison, S. R.

    1972-01-01

    Measurement of low-intensity electric fields in space and in presence of weak magnetic fields is accomplished by utilizing a device which permits determination of the extent a beam of cesium ions is deflected by an electric field.

  9. 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.

  10. Electrical Forces Determine Glomerular Permeability

    PubMed Central

    Hausmann, Ralf; Kuppe, Christoph; Egger, Herbert; Schweda, Frank; Knecht, Volker; Elger, Marlies; Menzel, Sylvia; Somers, Douglas; Braun, Gerald; Fuss, Astrid; Uhlig, Sandra; Kriz, Wilhelm; Tanner, George; Floege, Jrgen

    2010-01-01

    There is ongoing controversy about the mechanisms that determine the characteristics of the glomerular filter. Here, we tested whether flow across the glomerular filter generates extracellular electrical potential differences, which could be an important determinant of glomerular filtration. In micropuncture experiments in Necturus maculosus, we measured a potential difference across the glomerular filtration barrier that was proportional to filtration pressure (?0.045 mV/10 cm H2O). The filtration-dependent potential was generated without temporal delay and was negative within Bowman's space. Perfusion with the cationic polymer protamine abolished the potential difference. We propose a mathematical model that considers the relative contributions of diffusion, convection, and electrophoretic effects on the total flux of albumin across the filter. According to this model, potential differences of ?0.02 to ?0.05 mV can induce electrophoretic effects that significantly influence the glomerular sieving coefficient of albumin. This model of glomerular filtration has the potential to provide a mechanistic theory, based on experimental data, about the filtration characteristics of the glomerular filtration barrier. It provides a unique approach to the microanatomy of the glomerulus, renal autoregulation, and the pathogenesis of proteinuria. PMID:20947631

  11. Electric Potential Problem: Drawing Electric Fields

    NSDL National Science Digital Library

    Wolfgang Christian

    Draw the electric field lines for this potential by dragging the pencil (at its tip) after clicking the "draw on" button. After you have drawn your lines, determine which field best corresponds to your potential plot.

  12. LABORATORY II ELECTRIC FIELDS AND ELECTRIC POTENTIALS

    E-print Network

    Minnesota, University of

    of object A and the value of the potential at object A's location. As with forces, it would then be a simple the force exerted on object A by other objects, you first determine the field, at a location to be occupied's location. An advantage of this two-step approach is that if you make no changes but replace object

  13. 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.

  14. 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.

  15. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

    Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-Lun; Onuki, Akira

    1996-01-01

    The study of the interface in a charge-free, nonpolar, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In zero gravity, the interface is unstable at all long wavelengths in the presence of a field applied across it. It is conjectured that this will cause the binary fluid to break up into domains small enough to be outside the instability condition. The resulting pattern formation, and the effects on the critical properties as the domains approach the correlation length are of acute interest. With direct observation, laser light scattering, and interferometry, the phenomena can be probed to gain further understanding of interfacial instabilities and the pattern formation which results, and dimensional crossover in critical systems as the critical fluctuations in a particular direction are suppressed by external forces.

  16. A Simple Demonstration of Lorentz Force in Electrically-Conductive Fluid

    NASA Astrophysics Data System (ADS)

    Ribeiro, A.; Aurnou, J.

    2013-12-01

    Flows driven by electromagnetic Lorentz forces are ubiquitous in the universe. Lorentz forces are essential, for example, in the dynamics of planetary cores and astrophysical plasmas. In an electrically-conducting fluid, this force is defined as the vector cross product of the magnetic field with the electric current density. We have built an easily-replicated desktop device to demonstrate the effects of Lorentz forces in a copper sulfate solution. The electric current is controlled by a DC power supply, and the magnetic field is imposed using neodymium magnets. By varying the electric current, it is possible to tune the Lorentz forces and, thus, the resulting drive motions in the copper sulfate solution. Experiments will be carried out onsite, along with real time measurements of electric potential, magnetic field strength and local flow velocities.

  17. Sensing electric fields using single diamond spins

    E-print Network

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

  18. New Method to Calculate Electrical Forces Acting on a Sphere in an Electrorheological Fluid

    Microsoft Academic Search

    Kwangmoo Kim; Xiangting Li

    2005-01-01

    We describe a method to calculate the electrical force acting on a sphere in a suspension of dielectric spheres in a host with a different dielectric constant, under the assumption that a spatially uniform electric field is applied. The method uses a spectral representation for the total electrostatic energy of the composite. The force is expressed as a certain gradient

  19. Method to calculate electrical forces acting on a sphere in an electrorheological fluid

    Microsoft Academic Search

    Kwangmoo Kim; David Stroud; Xiangting Li; David J. Bergman

    2005-01-01

    We describe a method to calculate the electrical force acting on a sphere in a suspension of dielectric spheres in a host with a different dielectric constant, under the assumption that a spatially uniform electric field is applied. The method uses a spectral representation for the total electrostatic energy of the composite. The force is expressed as a certain gradient

  20. Polarization effects in molecular mechanical force fields

    PubMed Central

    Cieplak, Piotr; Dupradeau, Franois-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 componentpolarization energyand 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

  1. Cryosurgery with pulsed electric fields.

    PubMed

    Daniels, Charlotte S; Rubinsky, Boris

    2011-01-01

    This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to ablate cells in the high subzero freezing region of a cryosurgical lesion. PMID:22087224

  2. Force field feature extraction for ear biometrics

    Microsoft Academic Search

    David J. Hurley; Mark S. Nixon; John N. Carter

    2005-01-01

    The overall objective in defining feature space is to reduce the dimensionality of the original pattern space, whilst maintaining discriminatory power for classification. To meet this objec- tive in the context of ear biometrics a new force field transformation treats the image as an array of mutually attracting particles that act as the source of a Gaussian force field. Under-

  3. Electric & Magnetic Fields

    MedlinePLUS

    ... conventional power sources, such as power lines, electrical substations, or home appliances. While some of these studies ... about EMFs emitted by a power line or substation in your area, you can contact your local ...

  4. Lipid14: The Amber Lipid Force Field

    PubMed Central

    2015-01-01

    The AMBER lipid force field has been updated to create Lipid14, allowing tensionless simulation of a number of lipid types with the AMBER MD package. The modular nature of this force field allows numerous combinations of head and tail groups to create different lipid types, enabling the easy insertion of new lipid species. The Lennard-Jones and torsion parameters of both the head and tail groups have been revised and updated partial charges calculated. The force field has been validated by simulating bilayers of six different lipid types for a total of 0.5 ?s each without applying a surface tension; with favorable comparison to experiment for properties such as area per lipid, volume per lipid, bilayer thickness, NMR order parameters, scattering data, and lipid lateral diffusion. As the derivation of this force field is consistent with the AMBER development philosophy, Lipid14 is compatible with the AMBER protein, nucleic acid, carbohydrate, and small molecule force fields. PMID:24803855

  5. 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)

  6. Magnetic Braiding and Parallel Electric Fields

    E-print Network

    A. L. Wilmot-Smith; G. Hornig; D. I. Pontin

    2008-10-08

    The braiding of the solar coronal magnetic field via photospheric motions - with subsequent relaxation and magnetic reconnection -- is one of the most widely debated ideas of solar physics. We readdress the theory in the light of developments in three-dimensional magnetic reconnection theory. It is known that the integrated parallel electric field along field lines is the key quantity determining the rate of reconnection, in contrast with the two-dimensional case where the electric field itself is the important quantity. We demonstrate that this difference becomes crucial for sufficiently complex magnetic field structures. A numerical method is used to relax a braided magnetic field to an ideal force-free equilibrium; that equilibrium is found to be smooth, with only large- scale current structures. However, the equilibrium is shown to have a highly filamentary integrated parallel current structure with extremely short length- scales. An analytical model is developed to show that, in a coronal situation, the length scales associated with the integrated parallel current structures will rapidly decrease with increasing complexity, or degree of braiding, of the magnetic field. Analysis shows the decrease in these length scales will, for any finite resistivity, eventually become inconsistent with the stability of a force- free field. Thus the inevitable consequence of the magnetic braiding process is shown to be a loss of equilibrium of the coronal field, probably via magnetic reconnection events.

  7. Electric field disturbance in the Earth-ionosphere layer

    Microsoft Academic Search

    V. M. Sorokin; A. K. Yaschenko

    2000-01-01

    Theoretical studies of the electric field disturbance due to a variation of the atmospheric current, flowing between ionosphere and the Earth, are carried out. This variation is caused by a conductivity variation and the electromotive force generation in the near-ground atmospheric layer. The increase of the atmosphere radioactivity level near the ground results in substantial increase of electric field in

  8. Electric Field Disturbance in the Earth - Ionosphere Layer

    Microsoft Academic Search

    V. M. Sorokin; A. K. Yaschenko

    2000-01-01

    Theoretical studies of the electric field disturbance due to a variation of the atmospheric current, flowing between ionosphere and the Earth, are carried out. This variation is caused by a conductivity variation and the electromotive force generation in the near-ground atmospheric layer. The increase of the atmosphere radioactivity level near the ground results in substantial increase of electric field in

  9. Contactless manipulation of microparts by electric field traps

    Microsoft Academic Search

    Felix M. Moesner; Toshiro Higuchi

    1998-01-01

    In an earlier paper by the authors, down-scaled devices for microparts handling utilizing an AC electric field boundary wave were proposed. Devices that instantly generate contactless microparts driving forces through electric field creation have been designed and fabricated. In a further attempt, the mechanisms behind microparts conveyance are here subsequently validated in experiments and simulations. Particles as micropart substitute are

  10. Electric Field Example 11

    NSDL National Science Digital Library

    Wolfgang Christian

    Click start to place several charges on the field. Then rearrange them so that the net flux out of the top of the box (as measured by the field lines) is twice that out of the bottom, with the same sign.

  11. 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

  12. Nanoribbons in external electric fields

    E-print Network

    Evgeny Korotyaev; Anton Kutsenko

    2008-03-19

    We consider the Schr\\"odinger operator on nanoribbons (tight-binding models) in an external electric potentials $V$. The corresponding electric field is perpendicular to the axis of the nanoribbon. If V=0, then the spectrum of the Schr\\"odinger operator consists of two spectral bands and the flat band (i.e., the eigenvalue with infinite multiplicity) between them. If we switch on an weak electric potential $V\\to 0$, then we determine the asymptotics of the spectral bands for small fields. In particular, we describe all potentials when the unperturbed eigenvalue remains the flat band and when one becomes the small band of the continuous spectrum.

  13. Thunderstorm electric field modelling

    NASA Technical Reports Server (NTRS)

    Tan, A.

    1982-01-01

    Calculation of eletric field vectors within and near an isolated thundercloud (which has a given volume charge distribution) is envisaged. The maximum field strength within the thundercloud is calculated. The effects of screening layers, both above and below the thundercloud may be investigated, as well time-dependent potential problem. The study can lead to a better understanding of the charge distributions in a thundercloud, which in turn may shed some light on the actual mechanism of charging of a thundercloud.

  14. Molecular simulations: Force fields for carbon capture

    NASA Astrophysics Data System (ADS)

    Getman, Rachel B.

    2012-10-01

    Force fields have been generated that enable accurate simulations of interactions occurring between CO2 molecules and metal-organic frameworks featuring 'open' metal sites, which are promising for carbon capture applications.

  15. Common Force Field Thermodynamics of Cholesterol

    PubMed Central

    Giangreco, Francesco; Yamamoto, Eiji; Hirano, Yoshinori; di Giosia, Matteo; Zerbetto, Francesco; Yasuoka, Kenji; Narumi, Tetsu; Yasui, Masato; Hfinger, Siegfried

    2013-01-01

    Four different force fields are examined for dynamic characteristics using cholesterol as a case study. The extent to which various types of internal degrees of freedom become thermodynamically relevant is evaluated by means of principal component analysis. More complex degrees of freedom (angle bending, dihedral rotations) show a trend towards force field independence. Moreover, charge assignments for membrane-embedded compounds are revealed to be critical with significant impact on biological reasoning. PMID:24302856

  16. Photocatalysts with internal electric fields.

    PubMed

    Li, Li; Salvador, Paul A; Rohrer, Gregory S

    2014-01-01

    The photocatalytic activity of materials for water splitting is limited by the recombination of photogenerated electron-hole pairs as well as the back-reaction of intermediate species. This review concentrates on the use of electric fields within catalyst particles to mitigate the effects of recombination and back-reaction and to increase photochemical reactivity. Internal electric fields in photocatalysts can arise from ferroelectric phenomena, p-n junctions, polar surface terminations, and polymorph junctions. The manipulation of internal fields through the creation of charged interfaces in hierarchically structured materials is a promising strategy for the design of improved photocatalysts. PMID:24084897

  17. Lorentz Force Electrical Impedance Tomography Pol Grasland-Mongrain1

    E-print Network

    Paris-Sud XI, Universit de

    -69003, France Resume-- This article describes a method cal- led Lorentz Force Electrical Impedance. This method offers an alternative to detecting pathologies invisible to standard ultrasonogra- phy. MotsLorentz Force Electrical Impedance Tomography Pol Grasland-Mongrain1 , Jean-Martial Mari1 , Jean

  18. United States of America Electric Energy Market Competition Task Force

    E-print Network

    Tesfatsion, Leigh

    i United States of America Electric Energy Market Competition Task Force and the Federal Energy of competition within the wholesale and retail market for electric energy in the United States and to submit energy in the United States. The task force has 5 members: (1) an employee of the Department of Justice

  19. 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 ...

  20. 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.

  1. COLLECTION OF INERTIALESS PARTICLES ON SPHEROIDS AND SPHERES WITH ELECTRICAL FORCES AND GRAVITATIO

    Microsoft Academic Search

    KENNETH A NIELSEN; JAMES C. HILL

    1981-01-01

    Collection efficiencies are predicted for the capture of fine, incrtialess, charged particles on a single spheroidal collector in a gaseous flow field by the action of coulombic and external electric field forces and gravity. With the flow and external fields parallel to the axis of symmetry, collection efficiencies for spheroidal collectors are found by determining particle trajectories. For three-dimensional nonsymmetric

  2. 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;

  3. 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.

  4. Electrophoresis in strong electric fields.

    PubMed

    Barany, Sandor

    2009-01-01

    Two kinds of non-linear electrophoresis (ef) that can be detected in strong electric fields (several hundred V/cm) are considered. The first ("classical" non-linear ef) is due to the interaction of the outer field with field-induced ionic charges in the electric double layer (EDL) under conditions, when field-induced variations of electrolyte concentration remain to be small comparatively to its equilibrium value. According to the Shilov theory, the non-linear component of the electrophoretic velocity for dielectric particles is proportional to the cubic power of the applied field strength (cubic electrophoresis) and to the second power of the particles radius; it is independent of the zeta-potential but is determined by the surface conductivity of particles. The second one, the so-called "superfast electrophoresis" is connected with the interaction of a strong outer field with a secondary diffuse layer of counterions (space charge) that is induced outside the primary (classical) diffuse EDL by the external field itself because of concentration polarization. The Dukhin-Mishchuk theory of "superfast electrophoresis" predicts quadratic dependence of the electrophoretic velocity of unipolar (ionically or electronically) conducting particles on the external field gradient and linear dependence on the particle's size in strong electric fields. These are in sharp contrast to the laws of classical electrophoresis (no dependence of V(ef) on the particle's size and linear dependence on the electric field gradient). A new method to measure the ef velocity of particles in strong electric fields is developed that is based on separation of the effects of sedimentation and electrophoresis using videoimaging and a new flowcell and use of short electric pulses. To test the "classical" non-linear electrophoresis, we have measured the ef velocity of non-conducting polystyrene, aluminium-oxide and (semiconductor) graphite particles as well as Saccharomice cerevisiae yeast cells as a function of the electric field strength, particle size, electrolyte concentration and the adsorbed polymer amount. It has been shown that the electrophoretic velocity of the particles/cells increases with field strength linearly up to about 100 and 200 V/cm (for cells) without and with adsorbed polymers both in pure water and in electrolyte solutions. In line with the theoretical predictions, in stronger fields substantial non-linear effects were recorded (V(ef)~E(3)). The ef velocity of unipolar ion-type conducting (ion-exchanger particles and fibres), electron-type conducting (magnesium and Mg/Al alloy) and semiconductor particles (graphite, activated carbon, pyrite, molybdenite) increases significantly with the electric field (V(ef)~E(2)) and the particle's size but is almost independent of the ionic strength. These trends are inconsistent with Smoluchowski's equation for dielectric particles, but are consistent with the Dukhin-Mishchuk theory of superfast electrophoresis. PMID:19041962

  5. Electric field divertor plasma pump

    DOEpatents

    Schaffer, Michael J. (San Diego, CA)

    1994-01-01

    An electric field plasma pump includes a toroidal ring bias electrode (56) positioned near the divertor strike point of a poloidal divertor of a tokamak (20), or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix (40) of the poloidal divertor contacts the ring electrode (56), which then also acts as a divertor plate. A plenum (54) or other duct near the electrode (56) includes an entrance aperture open to receive electrically-driven plasma. The electrode (56) is insulated laterally with insulators (63,64), one of which (64) is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode (56) and a vacuum vessel wall (22), 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.

  6. 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.

  7. 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.

  8. 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.

  9. Measuring electric fields from surface contaminants with neutral atoms

    SciTech Connect

    Obrecht, J. M.; Wild, R. J.; Cornell, E. A. [JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440 (United States) and Department of Physics, University of Colorado, Boulder, Colorado 80309-0390 (United States)

    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.

  10. 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) Opposite magnetic poles attract like magnetic poles repel #12;Like the electric field lines

  11. 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.

  12. Electric-field-induced flame speed modification

    SciTech Connect

    Marcum, S.D. [Department of Physics, Miami University, Oxford, OH 45056 (United States); Ganguly, B.N. [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433 (United States)

    2005-10-01

    The effects of pulsed and continuous DC electric fields on the reaction zones of premixed propane-air flames have been investigated using several types of experimental measurements. All observed effects on the flame are dependent on the applied voltage polarity, indicating that negatively charged flame species do not play a role in the perturbation of the reaction zone. Experiments designed to characterize the electric-field-induced modifications of the shape and size of the inner cone, and the concomitant changes in the temperature profiles of flames with equivalence ratios between 0.8 and 1.7, are also reported. High-speed two-dimensional imaging of the flame response to a pulsed DC voltage shows that the unperturbed conical flame front (laminar flow) is driven into a wrinkled laminar flamelet (cellular) geometry on a time scale of the order of 5 ms. Temperature distributions derived from thin filament pyrometry (TFP) measurements in flames perturbed by continuous DC fields show similar large changes in the reaction zone geometry, with no change in maximum flame temperature. All measurements are consistent with the observed flame perturbations being a fluid mechanical response to the applied field brought about by forcing positive flame ions counter to the flow. The resulting electric pressure decreases Lewis numbers of the ionic species and drives the effective flame Lewis number below unity. The observed increases in flame speed and the flame fronts trend toward turbulence can be described in terms of the flame front wrinkling and concomitant increase in reaction sheet area. This effect is a potentially attractive means of controlling flame fluid mechanical characteristics. The observed effects require minimal input electrical power (<1 W for a 1 kW burner) due to the much better electric field coupling achieved in the present experiments compared to the previous studies.

  13. 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.

  14. Magnetic forces and magnetostriction in electrical machines and transformer cores

    Microsoft Academic Search

    Lieven Vandevelde; Jan A. A. Melkebeek

    2003-01-01

    This paper presents an original method for computing the deformation due to both magnetic forces and magnetostriction in ferromagnetic material. The method is applied to rotating electrical machines and transformers and is compared with other methods found in literature.

  15. Electric field detachment of a nonuniformly charged dielectric sphere on a dielectric coated electrode

    Microsoft Academic Search

    James Q. Feng; Elliott A. Eklund; Dan A. Hays

    1997-01-01

    In the electrophotographic process, charged toner particles are transferred from one surface to another with an electric field. To enable electric field transfer of toner, the externally applied field strength must be greater than a threshold value so that the Coulomb force can overcome the toner adhesion force at the residing surface. Toner particles in electrophotography are often charged by

  16. Effect of Electric and Magnetic Fields on Spin Dynamics in the Resonant Electric Dipole Moment Experiment

    E-print Network

    Alexander J. Silenko

    2007-10-02

    A buildup of the vertical polarization in the resonant electric dipole moment (EDM) experiment [Y. F. Orlov, W. M. Morse, and Y. K. Semertzidis, Phys. Rev. Lett. 96, 214802 (2006)] is affected by a horizontal electric field in the particle rest frame oscillating at a resonant frequency. This field is defined by the Lorentz transformation of an oscillating longitudinal electric field and a uniform vertical magnetic one. The effect of a longitudinal electric field is significant, while the contribution from a magnetic field caused by forced coherent longitudinal oscillations of particles is dominant. The effect of electric field on the spin dynamics was not taken into account in previous calculations. This effect is considerable and leads to decreasing the EDM effect for the deuteron and increasing it for the proton. The formula for resonance strengths in the EDM experiment has been derived. The spin dynamics has been calculated.

  17. Dark forces and atomic electric dipole moments

    E-print Network

    Heman Gharibnejad; Andrei Derevianko

    2015-01-17

    Postulating the existence of a fnite-mass mediator of T,P-odd coupling between atomic electrons and nucleons we consider its effect on permanent electric dipole moment (EDM) of diamagnetic atoms. We present both numerical and analytical analysis for such mediator-induced EDMs and compare it with EDM results for the conventional contact interaction. Based on this analysis we derive limits on coupling strengths and carrier masses from experimental limits on EDM of 199Hg atom.

  18. Dark forces and atomic electric dipole moments

    NASA Astrophysics Data System (ADS)

    Gharibnejad, Heman; Derevianko, Andrei

    2015-02-01

    Postulating the existence of a finite-mass mediator of T,P-odd coupling between atomic electrons and nucleons, we consider its effect on the permanent electric dipole moment (EDM) of diamagnetic atoms. We present both numerical and analytical analysis for such mediator-induced EDMs and compare it with EDM results for the conventional contact interaction. Based on this analysis, we derive limits on coupling strengths and carrier masses from experimental limits on EDM of the 199Hg atom.

  19. ELECTRIC-FIELD-ENHANCED FABRIC FILTRATION OF ELECTRICALLY CHARGED FLYASH

    EPA Science Inventory

    The paper summarizes measurements in which both external electric field (applied by electrodes at the fabric surface) and flyash electrical charge (controlled by an upstream corona precharger) are independent variables in a factorial performance experiment carried out in a labora...

  20. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

    Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-lun; Onuki, Akira

    1999-01-01

    The study of the interface in a charge-free, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In this paper, the flat interface of a marginally polar binary fluid mixture is stressed by a perpendicular alternating electric field and the resulting instability is characterized by the critical electric field E(sub c) and the pattern observed. The character of the surface dynamics at the onset of instability is found to be strongly dependent on the frequency f of the field applied. The plot of E(sub c) vs. f for a fixed temperature shows a sigmoidal shape, whose low and high frequency limits are well described by a power-law relationship, E(sub c) = epsilon(exp zeta) with zeta = 0.35 and zeta = 0.08, respectively. The low-limit exponent compares well with the value zeta = 4 for a system of conducting and non-conducting fluids. On the other hand, the high-limit exponent coincides with what was first predicted by Onuki. The instability manifests itself as the conducting phase penetrates the non-conducting phase. As the frequency increases, the shape of the pattern changes from an array of bifurcating strings to an array of column-like (or rod-like) protrusions, each of which spans the space between the plane interface and one of the electrodes. For an extremely high frequency, the disturbance quickly grows into a parabolic cone pointing toward the upper plate. As a result, the interface itself changes its shape from that of a plane to that of a high sloping pyramid.

  1. 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.

  2. 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.

  3. 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.

  4. Electric Charge and Magnetic Flux on Rotating Black Holes in a Force-Free Magnetosphere

    E-print Network

    Hyun Kyu Lee; Chul H. Lee; Maurice H. P. M. van Putten

    2001-02-13

    The electric charge on rotating black holes is calculated to be ~ BJ in the force-free configuration of Ghosh (2000), with a horizon flux of ~ BM^2. This charge is gravitationally weak for B ~ 10^{15} G, so that the Kerr metric applies. Being similar to the electric charge of a magnetar, both electric charge and magnetic flux should be, in sign and order of magnitude, continuous during stellar collapse into a black hole. Extraction of the rotational energy from newly formed black holes may proceed by interaction with the magnetic field. Keywords:black hole physics --magnetic fields

  5. Electric field probes for cellular phone dosimetry

    Microsoft Academic Search

    Howard I. Bassen

    1997-01-01

    Miniature implantable electric field probes (E-field Probes) enable the measurements of microwave electric fields induced in biological subjects by relatively low level exposures. Using these instruments, the rate of energy deposition (Specific Absorption Rate or SAR) can be determined throughout models or actual bodies of laboratory animals and humans exposed to emissions from cellular phones and other radiators. E-field probes

  6. A compact high field magnetic force microscope.

    PubMed

    Zhou, Haibiao; Wang, Ze; Hou, Yubin; Lu, Qingyou

    2014-12-01

    We present the design and performance of a simple and compact magnetic force microscope (MFM), whose tip-sample coarse approach is implemented by the piezoelectric tube scanner (PTS) itself. In brief, a square rod shaft is axially spring-clamped on the inner wall of a metal tube which is glued inside the free end of the PTS. The shaft can thus be driven by the PTS to realize image scan and inertial stepping coarse approach. To enhance the inertial force, each of the four outer electrodes of the PTS is driven by an independent port of the controller. The MFM scan head is so compact that it can easily fit into the 52mm low temperature bore of a 20T superconducting magnet. The performance of the MFM is demonstrated by imaging a manganite thin film at low temperature and in magnetic fields up to 15T. PMID:25189114

  7. Self-forces from generalized Killing fields

    NASA Astrophysics Data System (ADS)

    Harte, Abraham I.

    2008-12-01

    A non-perturbative formalism is developed that simplifies the understanding of self-forces and self-torques acting on extended scalar charges in curved spacetimes. Laws of motion are locally derived using momenta generated by a set of generalized Killing fields. Self-interactions that may be interpreted as arising from the details of a body's internal structure are shown to have very simple geometric and physical interpretations. Certain modifications to the usual definition for a center-of-mass are identified that significantly simplify the motions of charges with strong self-fields. A derivation is also provided for a generalized form of the Detweiler Whiting axiom that pointlike charges should react only to the so-called regular component of their self-field. Standard results are shown to be recovered for sufficiently small charge distributions.

  8. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 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...

  9. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 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...

  10. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 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...

  11. 49 CFR 236.10 - Electric locks, force drop type; where required.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 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...

  12. 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...

  13. Measuring q/m for Water Drops--An Introduction to the Effects of Electrical Forces

    ERIC Educational Resources Information Center

    Hart, Francis X.

    1974-01-01

    Discusses an experiment which introduces students to the effects of electrical forces on the motion of macroscopic objects. Included are the proecedures of measuring the charge-to-mass ratio from deflections of charged water drops in horizontal fields and the overall charges delivered in a Faraday cup. (CC)

  14. 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.

  15. On the electric and magnetic field generation in expanding plasmas

    Microsoft Academic Search

    Herman Johannes Gertrudis Gielen

    1989-01-01

    A general method that decomposes each of the forces terms in Ohm's law in a component that induces a charge separation in the plasma and a component that can drive current is given. This decomposition is unambiguous and depends on the boundary conditions for the electric potential. It is shown that in calculating the electromagnetic field quantities in a plasma

  16. Relation between magnetic fields and electric currents in plasmas

    Microsoft Academic Search

    V. M. Vasyliunas

    2005-01-01

    Maxwell's equations allow the magnetic field B to be calculated if the electric current density J is assumed to be completely known as a function of space and time. The charged particles that constitute the current, however, are subject to Newton's laws as well, and J can be changed by forces acting on charged particles. Particularly in plasmas, where the

  17. 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.

  18. Magnetic Fields and Forces in Permanent Magnet Levitated Bearings

    Microsoft Academic Search

    Kevin D. Bachovchin; James F. Hoburg; Richard F. Post

    2012-01-01

    Magnetic fields and magnetic forces from magnetic bearings made of circular Halbach permanent-magnet arrays are computed and analyzed. The magnetic fields are calculated using superposition of fields due to patches of magnetization charge at surfaces where the magnetization is discontinuous. The magnetic force from the magnetic bearing is computed using superposition of forces on each patch of magnetization charge. The

  19. Electrical field distribution in transformer oil

    Microsoft Academic Search

    Uno Gafvert; Albert Jaksts; C. Tornkvist; L. Walfridsson

    1992-01-01

    Developments in Kerr electro-optic measurement technology at the laboratory have made possible high resolution electric field measurements in nonpolar liquids. The electric field distribution in transformer oil has been studied at service stress levels in both the transient and steady state. The field distributions observed are well described by a one-dimensional quantitative model (with measurable parameters) based on charge carrier

  20. Entanglement generation by electric field background

    NASA Astrophysics Data System (ADS)

    Ebadi, Zahra; Mirza, Behrouz

    2014-12-01

    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.

  1. Development of eddy current microscopy for high resolution electrical conductivity imaging using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Nalladega, V.; Sathish, S.; Jata, K. V.; Blodgett, M. P.

    2008-07-01

    We present a high resolution electrical conductivity imaging technique based on the principles of eddy current and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents generated in the conducting sample are detected and measured with a magnetic tip attached to a flexible cantilever of an AFM. The eddy current generation and its interaction with the magnetic tip cantilever are theoretically modeled using monopole approximation. The model is used to estimate the eddy current force between the magnetic tip and the electrically conducting sample. The theoretical model is also used to choose a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the design of a high resolution electrical conductivity imaging system. The force between the tip and the sample due to eddy currents is measured as a function of the separation distance and compared to the model in a single crystal copper. Images of electrical conductivity variations in a polycrystalline dual phase titanium alloy (Ti-6Al-4V) sample are obtained by scanning the magnetic tip-cantilever held at a standoff distance from the sample surface. The contrast in the image is explained based on the electrical conductivity and eddy current force between the magnetic tip and the sample. The spatial resolution of the eddy current imaging system is determined by imaging carbon nanofibers in a polymer matrix. The advantages, limitations, and applications of the technique are discussed.

  2. 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

  3. Plasma Heating by Electric Field Compression

    NASA Astrophysics Data System (ADS)

    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.

  4. Quantum Electric Field Fluctuations and Potential Scattering

    E-print Network

    Huang, Haiyun

    2015-01-01

    Some physical effects of time averaged quantum electric field fluctuations are discussed. The one loop radiative correction 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 suggest that there is a nonperturbative enhancement of the transmission probability which can be inferred from the probability distribution for time averaged electric field fluctuations.

  5. Photodetachment Spectroscopy in an Electric Field

    NASA Astrophysics Data System (ADS)

    Moore, Kim; Zawistowski, D. A.; Gasda, M. D.; Gibson, N. D.; Walter, C. W.

    2000-10-01

    Photodetachment from negative sulfur ions has been studied in external electric fields of approximately 240 V/cm. Photodetachment cross sections were measured both in an electric field and with zero electric field using a 4 keV S^- ion beam perpendicularly intersected with a pulsed, tunable laser beam. The cross section for the electric field case deviates from the Wigner law due to both below threshold detachment and the self-interference of the electron wave due to reflection by the electric field barrier. Analysis of the resulting modulation factor (a ratio of the field to zero field cross sections) reveals that the data are in excellent agreement with theoretical calculations(I.I. Fabrikant, J. Phys. B 27), 4545 (1994). The amplitude modification factor between data and theory is found to be 1.000(3), which supports the theoretical prediction that the rescattering effect for the negative sulfur ion is <1%.

  6. Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.

    PubMed

    Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

    2014-08-01

    Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180 polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results. PMID:24953042

  7. Recent Developments and Applications of the CHARMM force fields

    PubMed Central

    Zhu, Xiao; Lopes, Pedro E.M.; MacKerell, Alexander D.

    2011-01-01

    Empirical force fields commonly used to describe the condensed phase properties of complex systems such as biological macromolecules are continuously being updated. Improvements in quantum mechanical (QM) methods used to generate target data, availability of new experimental target data, incorporation of new classes of compounds and new theoretical developments (eg. polarizable methods) make force-field development a dynamic domain of research. Accordingly, a number of improvements and extensions of the CHARMM force fields have occurred over the years. The objective of the present review is to provide an up-to-date overview of the CHARMM force fields. A limited presentation on the historical aspects of force fields will be given, including underlying methodologies and principles, along with a brief description of the strategies used for parameter development. This is followed by information on the CHARMM additive and polarizable force fields, including examples of recent applications of those force fields. PMID:23066428

  8. 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.

  9. 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

  10. Localized induced electric field within the magnetotail

    NASA Technical Reports Server (NTRS)

    Heikkila, W. J.; Pellinen, R. J.

    1977-01-01

    The conversion of magnetic energy, stored within the magnetotail during the growth phase, into particle kinetic energy is studied by taking induced electric fields, due to explicit time dependence of magnetic fields, into consideration. The polarization of a plasma in the presence of such a field is discussed, and the topological difference between a polarized and an induced electric field, namely that one is irrotational and the other is not, is pointed out. A localized perturbation in neutral sheet current is also discussed.

  11. Total screening and finite range forces from ultramassive scalar fields

    NASA Astrophysics Data System (ADS)

    Arod?, H.; Karkowski, J.; ?wierczy?ski, Z.

    2013-06-01

    Force between static point particles coupled to a classical ultramassive scalar field is calculated. The field potential is proportional to the modulus of the field. It turns out that the force exactly vanishes when the distance between the particles exceeds certain finite value. Moreover, each isolated particle is surrounded by a compact cloud of the scalar field that completely screens its scalar charge.

  12. Electric field statistics in MHD turbulence

    E-print Network

    Low, Robert

    = 0 ? B = µ0j + 1 c2 E t In MHD the displacement current is neglected. j = 1 µ0 ? B #12;Electric field in MHD? An additional equation is still needed: It is obtained by using a generalized Ohm's law: · FluidElectric field statistics in MHD turbulence Bernard Knaepen, Nicolas Denewet & Daniele Carati, ULB

  13. Electric Field Control of the Photodetachment of H? Ion near a Repulsive Center

    NASA Astrophysics Data System (ADS)

    Wang, De-hua; Chen, Qiang; Xu, Qin-feng

    2014-01-01

    The influence of electric field on the photodetachment of H? ion near a repulsive center is investigated for the first time. The classical motion of the detached electron has been studied and the photodetachment cross section has been derived. It is found that the electric field has significant effect on the photodetachment of H? ion near a repulsive center. If the electric field is put upward, the electric field force acting on the detached electron has an opposite direction with the Coulomb repulsive force. Under this condition, the motion of the detached electron is relatively complex. Both the number of the closed orbits and the oscillating structure of the photodetachment cross section depend on the electric field strength. If the electric field is put downward, the electric field force acting on the detached electron has the same direction with the Coulomb repulsive force. Under this circumstance, the electric field can always strengthen the oscillation in the photodetachment cross section. Therefore, we can control the photodetachment of negative ion near repulsive center by changing the electric field. Our study will be useful in directing the future experimental research of the photodetachment processes of multiply charged anions in the presence of external fields.

  14. 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.)

  15. 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.

  16. MolStruc: a force field calculation program allowing interactive modifications of the force field parameters.

    PubMed

    Siri, D; Ppe, G; Bernassau, J M

    1990-12-01

    To analyze the influence of parameters and functions on the energy and geometry obtained through different force field calculations, we have developed program MolStruc. This software allows the user to choose between two sets of functions and parameters, MM2 and AMBER. The MM2 option of the program was developed to compute the coulombic energy in a dipole or monopole approximation. To establish comparisons between the energy values, the coulombic contribution is computed in the same way in the Amber and MM2 options of the program. The force field parameters can be handled interactively (through addition or modification). The program was used to study molecules of a representative sample displaying most of the problems encountered in molecular mechanics (MM). PMID:2282362

  17. 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.

  18. Thin film transistors fabricated by evaporating pentacene under electric field

    NASA Astrophysics Data System (ADS)

    Mandal, Tapendu; Garg, Ashish; Deepak

    2013-10-01

    Organizing the pentacene molecules with respect to the substrate is an essential prerequisite for achieving high field effect mobility in organic thin film transistors. Here, we report electrical characteristics of bottom gate, top contact Sin++/SiO2/pentacene/gold thin film transistors using electric field assisted thermal evaporation of pentacene. We find that the field assisted devices exhibit a five-fold enhancement in the field effect mobility, along with improvement in the saturation current as compared with a standard device. Simulation of electric field distribution in the substrate-electrode arrangement due to the application of external voltage during pentacene deposition shows an existence of a non-uniform electric field in the bottom gate top contact configuration and hence another configuration that avoids metal before pentacene deposition is proposed. The observed improvement in the transistor characteristics of field assisted device is explained by ab-initio calculation of anisotropy in the polarizability of isolated pentacene molecule, followed by an estimate of molecules that would align due to the field. Furthermore, the preferential molecular alignment in field deposited pentacene films is confirmed using X-ray diffraction and atomic force microscopy.

  19. Fiber-Optic Electric-Field Meter

    NASA Technical Reports Server (NTRS)

    Johnston, A. R.

    1986-01-01

    Sensor for measuring electric-field strength does not greatly alter field in which placed. Sensor used to map fields in electric power substation or under high-voltage transmission line. Also used for laboratory measurements. Fused-silica fibers guide light from source to photometer. Light emerges from tip of source fiber, passes through curved coupler, and enters tip of photometer fiber. Attenuation of coupler changes with distance between fiber tips.

  20. Axial current generation from electric field: chiral electric separation effect.

    PubMed

    Huang, Xu-Guang; Liao, Jinfeng

    2013-06-01

    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 a very general basis, we argue that the strength of CESE is proportional to ?(V)?(A) with ?(V) and ?(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 effects of CESE in heavy-ion collisions are also discussed. PMID:25167486

  1. General Physics II Exam 1 -Chs. 16,17,18 -Electric Fields, Potential, Current Feb. 11, 2013 Name Rec. Instr. Rec. Time

    E-print Network

    Wysin, Gary

    General Physics II Exam 1 - Chs. 16,17,18 - Electric Fields, Potential, Current Feb. 11, 2013 Name charge can experience an electric force. 4. (2) T F The smallest magnitude (non-zero) net charge of the electric force on Q1 due to Q2. b) (3) The direction of the electric force acting on Q1 is a. pushing Q1

  2. 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.

  3. ESTIMATING ELECTRIC FIELDS FROM VECTOR MAGNETOGRAM SEQUENCES

    SciTech Connect

    Fisher, G. H.; Welsch, B. T.; Abbett, W. P.; Bercik, D. J. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)

    2010-05-20

    Determining the electric field distribution on the Sun's photosphere is essential for quantitative studies of how energy flows from the Sun's photosphere, through the corona, and into the heliosphere. This electric field also provides valuable input for data-driven models of the solar atmosphere and the Sun-Earth system. We show how observed vector magnetogram time series can be used to estimate the photospheric electric field. Our method uses a 'poloidal-toroidal decomposition' (PTD) of the time derivative of the vector magnetic field. These solutions provide an electric field whose curl obeys all three components of Faraday's Law. The PTD solutions are not unique; the gradient of a scalar potential can be added to the PTD electric field without affecting consistency with Faraday's Law. We then present an iterative technique to determine a potential function consistent with ideal MHD evolution; but this field is also not a unique solution to Faraday's Law. Finally, we explore a variational approach that minimizes an energy functional to determine a unique electric field, a generalization of Longcope's 'Minimum Energy Fit'. The PTD technique, the iterative technique, and the variational technique are used to estimate electric fields from a pair of synthetic vector magnetograms taken from an MHD simulation; and these fields are compared with the simulation's known electric fields. The PTD and iteration techniques compare favorably to results from existing velocity inversion techniques. These three techniques are then applied to a pair of vector magnetograms of solar active region NOAA AR8210, to demonstrate the methods with real data. Careful examination of the results from all three methods indicates that evolution of the magnetic vector by itself does not provide enough information to determine the true electric field in the photosphere. Either more information from other measurements, or physical constraints other than those considered here are necessary to find the true electric field. However, we show it is possible to construct physically reasonable electric field distributions whose curl matches the evolution of all three components of B. We also show that the horizontal and vertical Poynting flux patterns derived from the three techniques are similar to one another for the cases investigated.

  4. 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.

  5. Propagation of quantum walks in electric fields.

    PubMed

    Cedzich, C; Rybr, T; Werner, A H; Alberti, A; Genske, M; Werner, R F

    2013-10-18

    We study one-dimensional quantum walks in a homogenous electric field. The field is given by a phase which depends linearly on position and is applied after each step. The long time propagation properties of this system, such as revivals, ballistic expansion, and Anderson localization, depend very sensitively on the value of the electric field, ?, e.g., on whether ?/(2?) is rational or irrational. We relate these properties to the continued fraction expansion of the field. When the field is given only with finite accuracy, the beginning of the expansion allows analogous conclusions about the behavior on finite time scales. PMID:24182244

  6. Propagation of Quantum Walks in Electric Fields

    NASA Astrophysics Data System (ADS)

    Cedzich, C.; Rybr, T.; Werner, A. H.; Alberti, A.; Genske, M.; Werner, R. F.

    2013-10-01

    We study one-dimensional quantum walks in a homogenous electric field. The field is given by a phase which depends linearly on position and is applied after each step. The long time propagation properties of this system, such as revivals, ballistic expansion, and Anderson localization, depend very sensitively on the value of the electric field, ?, e.g., on whether ?/(2?) is rational or irrational. We relate these properties to the continued fraction expansion of the field. When the field is given only with finite accuracy, the beginning of the expansion allows analogous conclusions about the behavior on finite time scales.

  7. 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.

  8. Control of magnetism by electric fields.

    PubMed

    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. PMID:25740132

  9. New Method to Calculate Electrical Forces Acting on a Sphere in an Electrorheological Fluid

    E-print Network

    Kwangmoo Kim; David Stroud; Xiangting Li; David J. Bergman

    2005-01-09

    We describe a method to calculate the electrical force acting on a sphere in a suspension of dielectric spheres in a host with a different dielectric constant, under the assumption that a spatially uniform electric field is applied. The method uses a spectral representation for the total electrostatic energy of the composite. The force is expressed as a certain gradient of this energy, which can be expressed in a closed analytic form rather than evaluated as a numerical derivative. The method is applicable even when both the spheres and the host have frequency-dependent dielectric functions and nonzero conductivities, provided the system is in the quasistatic regime. In principle, it includes all multipolar contributions to the force, and it can be used to calculate multi-body as well as pairwise forces. We also present several numerical examples, including host fluids with finite conductivities. The force between spheres approaches the dipole-dipole limit, as expected, at large separations, but departs drastically from that limit when the spheres are nearly in contact. The force may also change sign as a function of frequency when the host is a slightly conducting fluid.

  10. Schwinger effect in inhomogeneous electric fields

    E-print Network

    Florian Hebenstreit

    2011-06-29

    The vacuum of quantum electrodynamics is unstable against the formation of many-body states in the presence of an external electric field, manifesting itself as the creation of electron-positron pairs (Schwinger effect). This effect has been a long-standing but still unobserved prediction as the generation of the required field strengths has not been feasible so far. However, due to the advent of a new generation of high-intensity laser systems such as the European XFEL or the Extreme Light Infrastructure (ELI), this effect might eventually become observable within the next decades. Based on the equal-time Wigner formalism, various aspects of the Schwinger effect in electric fields showing both temporal and spatial variations are investigated. Regarding the Schwinger effect in time-dependent electric fields, analytic expressions for the equal-time Wigner function in the presence of a static as well as a pulsed electric field are derived. Moreover, the pair creation process in the presence of a pulsed electric field with sub-cycle structure, which acts as a model for a realistic laser pulse, is examined. Finally, an ab initio simulation of the Schwinger effect in a simple space- and time-dependent electric field is performed for the first time, allowing for the calculation of the time evolution of various observables like the charge density, the particle number density or the number of created particles.

  11. Superimposed electrical stimulation decreases maximal grip force Boisgontier M.1,2

    E-print Network

    Paris-Sud XI, Université de

    Superimposed electrical stimulation decreases maximal grip force Boisgontier M.1,2 , Vuillerme N.1 muscular contraction (MVC) and electrical stimulation superimposed on voluntary muscular contraction (SES) to better understand mechanisms and effectiveness of electrical stimulation of the hand

  12. Local electric-field-induced oxidation of titanium nitride films

    Microsoft Academic Search

    S. Gwo; C.-L. Yeh; P.-F. Chen; Y.-C. Chou; T. T. Chen; T.-S. Chao; S.-F. Hu; T.-Y. Huang

    1999-01-01

    Nanometer-scale patterning of TiN films grown on SiO2\\/Si(001) has been demonstrated using the local electric-field-induced oxidation process with a conductive-probe atomic force microscope. The chemical composition of the modified TiN region was determined by micro-Auger electron spectroscopy and was found to consist of Ti, some trace amount of N, and O, suggesting the formation of titanium oxynitride in the near

  13. Electric field induced hydrogenation of silicene.

    PubMed

    Wu, Weichang; Ao, Zhimin; Wang, Tao; Li, Changming; Li, Sean

    2014-08-21

    An alternative approach for hydrogenation of silicene is proposed through applying an external electric field in order to reduce the reaction energy barrier based on density functional theory calculations. It is found that a positive perpendicular electric field F can act as a catalyst to reduce the energy barrier of H2 dissociative adsorption on silicene, which facilitates the hydrogenation of silicene. In addition, it is found that the barrier decreases as F increases, and when F is above 0.05 a.u. (1 a.u. = 5.14 10(11) V m(-1)), the barrier is quite low and hydrogenation of silicene can take place efficiently at room temperature. The catalytic effect of the electric field on hydrogenation of silicene is induced by the redistribution of atomic charge under the electric field, which would change the chemical activity of silicene significantly. PMID:24988182

  14. CRRES electric field\\/Langmuir probe instrument

    Microsoft Academic Search

    J. R. Wygant; P. R. Harvey; D. Pankow; F. S. Mozer; N. Maynard; H. Singer; M. Smiddy; W. Sullivan; P. Anderson

    1992-01-01

    The CRRES spacecraft's electric field\\/Langmuir probe instruments, which consist of a main electronics package on the body of the spacecraft and two pairs of orthogonal sensors with a 100-m separation on the spin-plane of the spacecraft, measures the quasi-static 2D electric field in this spin plane at 32 samples\\/sec. Sensitivity is 0.1 mV\\/m, over a dynamic range of 1000 mV\\/m.

  15. Longitudinal plasma oscillations in an electric field

    Microsoft Academic Search

    B. D. Fried; M. Gell-mann; J. D. Jackson; H. W. Wyld

    1960-01-01

    The properties of longitudinal plasma oscillations in an external electric field are investigated. In a completely linear approximation, it is found that the direct-current electric field introduces essentially no new effects. A quasi-linear approximation is also considered, in which couplings between different plasma modes are neglected while the space-averaged distribution functions are assumed to be approximately independent of time. In

  16. 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

  17. Characterization of the extremely low frequency (ELF) electric field interactions with living tissue

    Microsoft Academic Search

    Kenneth J. McLeod; Clinton T. Rubin; Henry J. Donahue; Farshid Guilak; Carol A. Mase

    1992-01-01

    Review of the empirical observations of extremely low frequency (ELF) electric field effects on tissue in vivo and cells in vitro, has led us to propose that these effects occur through the action of the electric polarization forces which develop at the cell surface. Such an interaction mechanism predicts that the field effects should be time dependent response and associated

  18. On the mechanism of extremely low frequency (ELF) electric field interactions with living tissue

    Microsoft Academic Search

    K. J. McLeod; C. T. Rubin; H. J. Donahue; F. Guilak

    1992-01-01

    A review of the empirical observations of ELF electric field effects on living tissue has led the authors to propose that effects occur through the action of the electric polarization forces which develop at the cell surface. Such an interaction mechanism predicts that the field effects should be associated with a time-development response as well as an actual deformation of

  19. 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

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

    PubMed

    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

  1. Empirical force fields for biological macromolecules: Overview and issues

    Microsoft Academic Search

    Alexander D. MacKerell Jr.

    2004-01-01

    Empirical force field-based studies of biological macromolecules are becoming a common tool for investigating their structure-activity relationships at an atomic level of detail. Such studies facilitate interpretation of experimental data and allow for information not readily accessible to experimental methods to be obtained. A large part of the success of empirical force field-based methods is the quality of the force

  2. Three-body Forces from a Classical Nonlinear Field

    NASA Astrophysics Data System (ADS)

    Arod?, H.; Karkowski, J.; ?wierczy?ski, Z.

    Forces in the systems of two opposite sign and three identical charges coupled to the dynamical scalar field of the signum-Gordon model are investigated. Three-body force is present, and the exact formula for it is found. Flipping the sign of one of the two charges changes not only the sign but also the magnitude of the force. Both effects are due to nonlinearity of the field equation.

  3. Three-body forces from a classical nonlinear field

    E-print Network

    Arodz, H; Swierczynski, Z

    2013-01-01

    Forces in the systems of two opposite sign and three identical charges coupled to the dynamical scalar field of the signum-Gordon model are investigated. Three-body force is present, and the exact formula for it is found. Flipping the sign of one of the two charges changes not only the sign but also the magnitude of the force. Both effects are due to nonlinearity of the field equation.

  4. Three-body forces from a classical nonlinear field

    E-print Network

    H. Arodz; J. Karkowski; Z. Swierczynski

    2013-10-02

    Forces in the systems of two opposite sign and three identical charges coupled to the dynamical scalar field of the signum-Gordon model are investigated. Three-body force is present, and the exact formula for it is found. Flipping the sign of one of the two charges changes not only the sign but also the magnitude of the force. Both effects are due to nonlinearity of the field equation.

  5. Full 180 Magnetization Reversal with Electric Fields

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  6. Full 180 magnetization reversal with electric fields.

    PubMed

    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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Rotationally Vibrating Electric-Field Mill

    NASA Technical Reports Server (NTRS)

    Kirkham, Harold

    2008-01-01

    A proposed instrument for measuring a static electric field would be based partly on a conventional rotating-split-cylinder or rotating-split-sphere electric-field mill. However, the design of the proposed instrument would overcome the difficulty, encountered in conventional rotational field mills, of transferring measurement signals and power via either electrical or fiber-optic rotary couplings that must be aligned and installed in conjunction with rotary bearings. Instead of being made to rotate in one direction at a steady speed as in a conventional rotational field mill, a split-cylinder or split-sphere electrode assembly in the proposed instrument would be set into rotational vibration like that of a metronome. The rotational vibration, synchronized with appropriate rapid electronic switching of electrical connections between electric-current-measuring circuitry and the split-cylinder or split-sphere electrodes, would result in an electrical measurement effect equivalent to that of a conventional rotational field mill. A version of the proposed instrument is described.

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

    SciTech Connect

    Lekkala, Swapna; Marohn, John A.; Loring, Roger F., E-mail: roger.loring@cornell.edu [Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 (United States)

    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.

  15. Electric force microscopy of semiconductors: theory of cantilever frequency fluctuations and noncontact friction.

    PubMed

    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. PMID:24320286

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  17. Magnetospheric electric field measurements during sudden commencements

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Skillman, T. L.

    1973-01-01

    Direction measurements of electric fields were made in the outer magnetosphere during two sudden commencements in 1972. These measurements were observed with the double floating probe experiment carried aboard the IMP 6 satellite. The initial variations of the measured electric field consisted of an increase from a background of about 1 mv/meter to some 10 mv/meter at about 7 rE (earth radi) and to some 4 mv/meter at 3 rE. These initial electric field disturbances were longitudinal, oriented counter clockwise about an axis pointed north. A solution of Maxwell's third equation is derived for these measurements using a quasi-static version of Mead's model of the magnetosphere B (t). This solution seems to describe well the magnitude and direction of the initial perturbation of the electric field vectors observed during these two sudden commencements. After the initial increase, the measured electric field rings several times with periods of the order of minutes. This observed oscillatory behavior correlates with magnetic observatory records taken near the foot of the magetic field line passing through the satellite.

  18. What supports the parallel electric field in Birkeland current regions?

    NASA Astrophysics Data System (ADS)

    Jasperse, John; Basu, Bamandas; Lund, Eric

    Quasi-steady electric fields parallel to the background magnetic field exist in both upward and downward Birkeland-current regions above the aurora. These fields, together with the turbulence found on auroral field lines, energize the plasma particles as they flow either away from or toward the earth. In general, these parallel electric fields are supported by one or more strong double layers, the mirror force, the generalized pressure gradient, and the anomalous resistivity due to the turbulence. Recently, we have developed a new kinetic and multi-moment fluid theory for the Birkeland current system that contains the effect of plasma turbulence [1, 2]. Applying the new theory [1, 2] to observations in the long-range potential region of a downwardcurrent sheet, we show that anomalous resistivity accounts for only a small portion of the parallel electric field and that the contributions from the mirror-force and generalized pressuregradient terms in the generalized Ohm's law for the problem are more important. Calculations in the double layer and transition propagation region for a downward-current sheet show that a strong double layer forms, propagates upward at the local ion-acoustic speed, is destabilized as the current density falls below the local critical value, and reforms at a lower altitude. These results have important implications in other regions of space such as magnetospheric reconnection sites and solar coronal loops where parallel electric fields are likely to exist. [1] J. R. Jasperse et al. (2006), Phys. Plasmas 13, 072903 [2] J. R. Jasperse et al. (2006), Phys. Plasmas 13, 112902

  19. Pair production in a strong electric field

    SciTech Connect

    Kluger, Y.; Eisenberg, J.M.; Svetitsky, B. (School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, 69978 Tel-Aviv (Israel)); Cooper, F.; Mottola, E. (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico (USA))

    1991-10-28

    We investigate the mechanism of pair creation in scalar QED from spatially homogeneous strong electric fields in 1+1 dimensions. Solution of the semiclassical field equations shows particle creation followed by plasma oscillations. We compare our results with a model based on a relativistic Boltzmann-Vlasov equation with a pair-creation source term related to the Schwinger mechanism. The time evolution of the electric field and the current obtained from the Boltzmann-Vlasov model is surprisingly similar to that found in the semiclassical calculation.

  20. 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.

  1. 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 + ViB ? 0), whereas electrons remain frozen-in (E + VeB=?pe/nee).

  2. Horizontal electric fields from lightning return strokes

    SciTech Connect

    Thomson, E.M.; Uman, M.A.; Johnson, J.; Stone, J.W.; Medelius, P.; Rubenstein, M.

    1985-01-01

    Measurements are presented of simultaneous horizontal and vertical electric fields from both close and distant lightning return strokes. The data were obtained during summer 1984 at the Kennedy Space Center, Florida, using an electrically isolated spherical antenna having a system bandwidth of 3 Hz to 5 MHz. Lightning signals were obtained from flashes at distances from a few to 100 kilometers. Since the horizontal electric field is in part determined by the local ground conductivity, that parameter was measured as a function of depth. The horizontal fields from lightning return strokes had typically 1/50 the peak amplitude of the vertical fields and waveshapes which were consistant with available theory, as expressed by the ''wavetilt'' formula.

  3. Electric Fields and Moving Media

    Microsoft Academic Search

    James R. Melcher

    1974-01-01

    Case studies for use in the teaching of basic field theory and electromechanics ideally illustrate the classic analytical solutions while both motivating discussions of engineering applications and dramatizing the physical phenomena. Experiments are particularly valuable for achieving this last purpose if they are visualized directly. To this end, a series of experiments are developed in the educational film, \\

  4. 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.

  5. Force-Free Magnetic Fields of Closed Configuration Having More Energy Than Open Fields

    NASA Astrophysics Data System (ADS)

    Choe, G.; Cheng, C.

    2002-05-01

    Observations of CMEs show an apparent opening of a coronal magnetic field which has assumed a closed configuration before the eruption. In order for this transition of field configuration to occur spontaneously, the pre-eruption closed field must have more energy than the open field. However, as far as force-free fields are concerned, such a transition is energetically forbidden according to the Aly-Sturrock theorem. The theorem states that the maximum energy of the closed force-free fields with the same boundary-normal field distribution and the same field topology is the energy of the corresponding open field. The force-free fields treated in Aly and Sturrock's proofs of the theorem are force-free fields that can be generated from closed potential fields by footpoint motions conserving the boundary normal field distribution and the field topology. The force-free fields investigated in this paper are force-free fields which are not governed by Aly and Sturrock's proofs. We have constructed force-free fields in weak equilibrium, which can be generated in multiple flux systems by a footpoint motion not conserving the boundary normal field distribution. It is found that there exist force-free fields having more magnetic energy than the corresponding open fields. The relevance with observations and the possible mechanisms of CMEs will be discussed.

  6. Can a Closed Force-Free Field Have More Energy Than the Open Field?

    NASA Astrophysics Data System (ADS)

    Choe, G. S.; Cheng, C. Z.

    2001-12-01

    Observations of CMEs show an apparent opening of a coronal magnetic field which has assumed a closed configuration before the eruption. In order for this transition of field configuration to occur spontaneously, the pre-eruption closed field must have more energy than the open field. However, as far as force-free fields are concerned, such a transition is energetically forbidden according to the Aly-sturrock theorem. The theorem states that the maximum energy of the closed force-free fields with the same boundary-normal field distribution and the same field topology is the energy of the corresponding open field. The force-free fields treated in Aly and Sturrock's proofs of the theorem are force-free fields that can be generated from closed potential fields by footpoint motions conserving the boundary normal field distribution and the field topology. The force-free fields investigated in this paper are force-free fields which are not governed by Aly and Sturrock's proofs. We will construct force-free fields in weak equilibrium by a footpoint motion not conserving the boundary normal field distribution and show that there exist force-free fields having more magnetic energy than the corresponding open fields. The relevance with observations and the possible mechanisms of CMEs will also be discussed.

  7. A method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

    SciTech Connect

    Stevens, F.J.

    1990-03-15

    Field flow fractionation, a method obtaining high resolution separations of organic and inorganic colloids and soluble molecules, has been known in the art for approximately twenty years. The term field flow fractionation uses the word field in a generic sense. The field may comprise an electric field, a temperature gradient, a pH gradient, gravitational sedimentation or sedimentation through the application of a centrifugal force. The field is made to act upon a flowing solution or colloidal suspension and causes segregation or fractionation of the solute molecules or colloid particles. A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation. 11 figs.

  8. Models of force-free magnetic fields in resistive media

    Microsoft Academic Search

    Bostroem

    1973-01-01

    A review is given of some of the basic properties of forcefree fields ; under circumstances when the conductivity of the medium is finite. Then the ; electric current density is related not only to the magnetic field, but also by ; Ohm's law to the electric fleld and plasma velocity, which must be considered in ; the solutions. It

  9. Magnetic Forces and Field Line Density

    NSDL National Science Digital Library

    This is an activity about depicting the relative strength of magnetic fields using field line density. Learners will use the magnetic field line drawing of six magnetic poles created in a previous activity and identify the areas of strong, weak, and medium magnetic intensity using the density of magnetic field lines. This is the fifth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website. How to Draw Magnetic Fields - II in the Magnetic Math booklet must be completed prior to this activity.

  10. A status of the United States Air Force's More Electric Aircraft initiative

    Microsoft Academic Search

    James S. Cloyd; Wright-Patterson AFB

    1997-01-01

    Since the early 1990s, the United States Air Force has been successfully pursuing advancement in aircraft electrical power system technologies as a means of collectively establishing the capability to dramatically reduce or eliminate centralized hydraulics aboard aircraft and replace it with electrical power as the motive force for all aircraft functions. This overall approach (called the More Electric Aircraft, MEA)

  11. Comparison of Cellulose Ib Simulations with Three Carbohydrate Force Fields

    SciTech Connect

    Matthews, J. F.; Beckham, G. T.; Bergenstrahle, M.; Brady, J. W.; Himmel, M. E.; Crowley, M. F.

    2012-02-14

    Molecular dynamics simulations of cellulose have recently become more prevalent due to increased interest in renewable energy applications, and many atomistic and coarse-grained force fields exist that can be applied to cellulose. However, to date no systematic comparison between carbohydrate force fields has been conducted for this important system. To that end, we present a molecular dynamics simulation study of hydrated, 36-chain cellulose I{beta} microfibrils at room temperature with three carbohydrate force fields (CHARMM35, GLYCAM06, and Gromos 45a4) up to the near-microsecond time scale. Our results indicate that each of these simulated microfibrils diverge from the cellulose I{beta} crystal structure to varying degrees under the conditions tested. The CHARMM35 and GLYCAM06 force fields eventually result in structures similar to those observed at 500 K with the same force fields, which are consistent with the experimentally observed high-temperature behavior of cellulose I. The third force field, Gromos 45a4, produces behavior significantly different from experiment, from the other two force fields, and from previously reported simulations with this force field using shorter simulation times and constrained periodic boundary conditions. For the GLYCAM06 force field, initial hydrogen-bond conformations and choice of electrostatic scaling factors significantly affect the rate of structural divergence. Our results suggest dramatically different time scales for convergence of properties of interest, which is important in the design of computational studies and comparisons to experimental data. This study highlights that further experimental and theoretical work is required to understand the structure of small diameter cellulose microfibrils typical of plant cellulose.

  12. ForceFit: a code to fit classical force fields to quantum mechanical potential energy surfaces.

    PubMed

    Waldher, Benjamin; Kuta, Jadwiga; Chen, Samuel; Henson, Neil; Clark, Aurora E

    2010-09-01

    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. PMID:20340109

  13. Approximate photochemical dynamics of azobenzene with reactive force fields

    SciTech Connect

    Li, Yan; Hartke, Bernd [Institute for Physical Chemistry, Christian-Albrechts-University, Olshausenstr. 40, 24098 Kiel (Germany)] [Institute for Physical Chemistry, Christian-Albrechts-University, Olshausenstr. 40, 24098 Kiel (Germany)

    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)

  14. 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).

  15. Approximate photochemical dynamics of azobenzene with reactive force fields.

    PubMed

    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). PMID:24329064

  16. 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.

  17. 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.

  18. A Laboratory Investigation of the Effect of Particle Collisions on the Generation of Electric Fields in Thunderstorms

    Microsoft Academic Search

    A. K. Kamra; B. Vonnegut

    1971-01-01

    A laboratory experiment has been performed to study the relative effect of aerodynamic and electrical forces an small electrically conducting particles of radii 100-200 colliding with a particle of 2 mm radius suspended in an upward moving vertical air stream of a wind tunnel and placed in a vertical polarizing electric field. It has been observed, in a low electric

  19. Electric Field Effects in RUS Measurements

    SciTech Connect

    Darling, Timothy W [Los Alamos National Laboratory; Ten Cate, James A [Los Alamos National Laboratory; Allured, Bradley [UNIV NEVADA, RENO; Carpenter, Michael A [CAMBRIDGE UNIV. UK

    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.

  20. 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.

  1. Parallel electric fields from ionospheric winds

    SciTech Connect

    Nakada, M.P. (NASA Goddard Space Flight Center, Greenbelt, MD (United States))

    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.

  2. Fabrication of a nanoscale electric field sensor

    NASA Astrophysics Data System (ADS)

    Zheng, Yun; King, Todd; Stewart, Daniel; Getty, Stephanie

    2009-05-01

    A new nanoscale electric field sensor was developed for studying triboelectric charging in terrestrial and Martian dust devils. The sensor was fabricated using MEMS techniques, integrated at the system level, and deployed during a dust devil field campaign. The two-terminal piezoresistive sensor consists of a micron-scale network of suspended singlewalled carbon nanotubes (SWCNTs) that are mechanically coupled to a free-standing electrically conductor. Electrostatic coupling of the conductor to the electric field is expected to produce a deflection of the conductor and a corresponding change in nanotube device resistance, based on the known piezoresistive properties of SWCNTs. The projected device performance will allow measurement of the large electric fields for large dust devils without saturation. With dimensions on the 100 ?m scale and power consumption of only tens of nW, the sensor features dramatically reduced mass, power, and footprint. Recent field testing of the sensor demonstrated the robustness of suspended SWCNT devices to temperature fluctuations, mechanical shock, dust, and other environmental factors.

  3. Electric Fields within Martian Dust Storms

    NASA Astrophysics Data System (ADS)

    Barth, E. L.; Rafkin, S. C.; Farrell, W. M.

    2010-12-01

    Mars analog and laboratory studies and field campaigns on Earth provide strong evidence for the existence of active electrodynamic processes on Mars. Dust charging studies using Mars soil simulant suggest that the triboelectric charging of dust observed within terrestrial dust disturbances is very possible on Mars. Recent microwave detection of a lightning signature correlated with a Martian dust storm suggests large electric fields do exist. We have developed a physically consistent model of triboelectric dust charging and atmospheric dynamics by coupling the Microscopic Triboelectric Simulator (MTS) with the Mars Regional Atmospheric Modeling System (MRAMS). We have used the combined model to simulate the dynamics of charged particles in Martian dust devils and examine the resulting electric field environment. We have shown that the mixing of negatively charged (metallic) and positively charged (basaltic) particles within a dust devil typically results in electric fields of order a few kV/m. In some cases, brief periods (few minutes) of much higher electric fields, 10s - 100s kV/m, are seen.

  4. 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 total azimuthal flux with a power-law distribution over the poloidal field. Particular attention is paid

  5. MAGNETIC EXPLOSIONS: ROLE OF THE INDUCTIVE ELECTRIC FIELD

    SciTech Connect

    Melrose, D. B. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)

    2012-04-10

    Inclusion of the inductive electric field, E{sub ind}, due to the temporally changing B, in magnetic explosions is discussed, with emphasis on solar flares. Several roles played by E{sub ind} are identified: on a global scale, E{sub ind} produces the electromotive force that drives the explosion; the associated E{sub ind} Multiplication-Sign B drift is identified with the inflow of magnetic field lines into a reconnection region; the polarization current, associated with {partial_derivative}E{sub ind}/{partial_derivative}t, implies a J Multiplication-Sign B force that accelerates this inflow; and the component of E{sub ind} parallel to B accelerates the energetic electrons that cause hard X-ray emission and type III radio bursts. Some simple models that describe these effects are presented. A resolution of the long-standing 'number problem' in solar flares is suggested.

  6. LABORATORY V MAGNETIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    's technology. Magnets are used today to image parts of the body, to explore the mysteries of the human brain to combine magnets to change the magnetic field at any point. You decide to determine the form

  7. LABORATORY V MAGNETIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    's technology. Magnets are used today to image parts of the body, to explore the mysteries of the human brain to combine magnets to change the magnetic field at any point. You must determine the map of the magnetic

  8. Wetting and motion behaviors of water droplet on graphene under thermal-electric coupling field

    NASA Astrophysics Data System (ADS)

    Zhang, Zhong-Qiang; Dong, Xin; Ye, Hong-Fei; Cheng, Guang-Gui; Ding, Jian-Ning; Ling, Zhi-Yong

    2015-02-01

    Wetting dynamics and motion behaviors of a water droplet on graphene are characterized under the electric-thermal coupling field using classical molecular dynamics simulation method. The water droplet on graphene can be driven by the temperature gradient, while the moving direction is dependent on the electric field intensity. Concretely, the water droplet on graphene moves from the low temperature region to the high temperature region for the relatively weak electric field intensity. The motion acceleration increases with the electric field intensity on graphene, whereas the moving direction switches when the electric field intensity increases up to a threshold. The essence is the change from hydrophilic to hydrophobic for the water droplet on graphene at a threshold of the electric field intensity. Moreover, the driven force of the water droplet caused by the overall oscillation of graphene has important influence on the motion behaviors. The results are helpful to control the wettability of graphene and further develop the graphene-based fluidic nanodevices.

  9. Atomic emission spectroscopy in high electric fields

    SciTech Connect

    Bailey, J.E.; Filuk, A.B.; Carlson, A.L. [and others

    1995-12-31

    Pulsed-power driven ion diodes generating quasi-static, {approximately}10 MV/cm, 1-cm scale-length electric fields are used to accelerate lithium ion beams for inertial confinement fusion applications. Atomic emission spectroscopy measurements contribute to understanding the acceleration gap physics, in particular by combining time- and space-resolved measurements of the electric field with the Poisson equation to determine the charged particle distributions. This unique high-field configuration also offers the possibility to advance basic atomic physics, for example by testing calculations of the Stark-shifted emission pattern, by measuring field ionization rates for tightly-bound low-principal-quantum-number levels, and by measuring transition-probability quenching.

  10. Models of the earth's electric field

    NASA Technical Reports Server (NTRS)

    Stern, D.

    1974-01-01

    Detailed models of the electric field of the magnetosphere are derived in several stages. For all, the conductivity along field lines is assumed to be high enough to ensure the vanishing of E B everywhere except in the ionosphere. At first the rotation of the earth is ignored completely and a simple model is constructed which fits certain observed properties. Next, the rotation of the earth is taken into account, but the field is assumed to be that of a magnetic dipole rotating around its symmetry axis. This allows the concept of the electric potential to be retained, which permits the derivation of interesting properties including the use of a conjugate potential which paces the drift of charged particles in the field. Finally, the general case involving asymmetrical rotation is briefly discussed.

  11. Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

    SciTech Connect

    Stevens, F.J.

    1992-07-28

    This patent describes a method of field flow fractionation for fractionating solute molecules form a solution. It comprises: causing the solution to flow through a fractionating conduit, under conditions of laminar fluid flow, applying an electric field across the flowing solution, between the input end and the discharge end of the conduit, periodically reversing the polarity of the electric field while the solution flows through the conduit.

  12. Electric field heating and reaction rate effects

    Microsoft Academic Search

    S. M. A. Ibrahim; D. Bradley

    1986-01-01

    The effects are described of electrical fields upon heating and reaction rates of the reacting gases of methane-air and methane-oxygen in the recirculation zone of a jet-stirred reactor. The effects of thermal and field gas heatings on concentrations of CO and CO were also studied. The experiments included measurements of gas temperature distribution across the reactor, current-voltage characteristics for dc

  13. Health of workers exposed to electric fields.

    PubMed Central

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

    1985-01-01

    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

  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. Vibrational spectrum and force field of dimethyldimethoxysilane

    SciTech Connect

    Tenisheva, T.F.; Lazarev, A.N.

    1986-01-01

    Experimental data is presented on the spectra of (CH/sub 3/)/sub 2/Si(OCH/sub 3/)/sub 2/ (I), (CH/sub 3/)/sub 2/Si(OCD/sub 3/)/sub 2/ (II), and (CD/sub 3/)/sub 2/Si(OCH/sub 3/)/sub 2/ (III). The results of the determination of the force constants on the basis of the optimization of the solution of the inverse mechanical problem of the theory of molecular vibrations with consideration of all the internal degrees of freedom with the exception of the coordinates corresponding to internal rotations are discussed. Raman spectra of I, II, and III in the liquid phase is shown and the IR spectra of amorphous films of I, II, and III are illustrated.

  16. Electric-field-induced flame speed modification

    Microsoft Academic Search

    S. D. Marcum; B. N. Ganguly

    2005-01-01

    The effects of pulsed and continuous DC electric fields on the reaction zones of premixed propaneair flames have been investigated using several types of experimental measurements. All observed effects on the flame are dependent on the applied voltage polarity, indicating that negatively charged flame species do not play a role in the perturbation of the reaction zone. Experiments designed to

  17. Electric Field Sensing For Graphical Interfaces

    Microsoft Academic Search

    Joshua R. Smith; Tom White; Christopher Dodge; Joseph A. Paradiso; Neil Gershenfeld; David Allport

    1998-01-01

    Low frequency electric fields provide a means to build contact and non-contact user interfaces that are unobtrusive, responsive, inexpensive, and simple to configure. In this paper, we outline the theory and implementation of such sensing techniques, contrasting them with more familiar alternatives. We then present a range of applications that we have developed for interacting with computer graphics.

  18. Non-intrusive electric field sensing

    NASA Astrophysics Data System (ADS)

    Schultz, S. M.; Selfridge, R.; Chadderdon, S.; Perry, D.; Stan, N.

    2014-04-01

    This paper presents an overview of non-intrusive electric field sensing. The non-intrusive nature is attained by creating a sensor that is entirely dielectric, has a small cross-sectional area, and has the interrogation electronics a long distance away from the system under test. One non-intrusive electric field sensing technology is the slab coupled optical fiber sensor (SCOS). The SCOS consists of an electro-optic crystal attached to the surface of a D-shaped optical fiber. It is entirely dielectric and has a cross-sectional area down to 0.3mm by 0.3mm. The SCOS device functions as an electric field sensor through use of resonant mode coupling between the crystal waveguide and the core of a D-shaped optical fiber. The resonant mode coupling of a SCOS device occurs at specific wavelengths whose spectral locations are determined in part by the effective refractive index of the modes in the slab. An electric field changes the refractive index of the slab causing a shift in the spectral position of the resonant modes. This paper describes an overview of the SCOS technology including the theory, fabrication, and operation. The effect of crystal orientation and crystal type are explained with respect to directional sensitivity and frequency response.

  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. Empirical high-latitude electric field models

    Microsoft Academic Search

    J. P. Heppner; N. C. Maynard

    1987-01-01

    Electric field measurements from the Dynamics Explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn-dusk OGO 6 measurements (J.P. Heppner, 1977). The analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones. Paralleling the previous analysis, the modeling is based on the distinctly

  1. Electric and magnetic field measurements in a high voltage center.

    PubMed

    Safigianni, Anastasia S; Spyridopoulos, Anastasios I; Kanas, Vasilis L

    2012-01-01

    This paper investigates the electric and magnetic fields inside a large high voltage center constituted both of 400/150 and 150/20 kV substation areas. Results of previous field measurements and calculations in substations, made by the authors of this paper or other researchers, are presented first. The basic data distinguishing the examined center from previously examined substations follow. The main results of the field measurements in the areas of the above-mentioned center are presented in relevant diagrams. General conclusions arising from the comparison of the measured field values with relevant reference levels in force for safe public and occupational exposure as well as with the results of previous research are finally given. PMID:21917821

  2. 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.

  3. 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.

  4. 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 (15kV/cm) and high (60kV/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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Particle-Particle Interaction in Electromagnetic Fields for Force-Field Tailoring

    Microsoft Academic Search

    Sameh S. Wanis; Thilini Rangedera; Narayanan M. Komerath

    2007-01-01

    Tailored electromagnetic force fields offer the possibility of forming structures having diverse geometries at various length scales from loose particles. The analogy of the responses of a neutral particle placed in an acoustic or electromagnetic field pointed to the existence of a unified governing force field expression. This was shown to be based on a dipole model of the particle

  10. Ampere force based magnetic field sensor using dual-polarization fiber laser.

    PubMed

    Cheng, Linghao; Guo, Zhenzhen; Han, Jianlei; Jin, Long; Guan, Bai-Ou

    2013-06-01

    A magnetic field sensor is proposed by placing a dual-polarization fiber grating laser under a copper wire. With a perpendicular magnetic field applied, an electrical current flowing through the copper wire can generate Ampere force to squeeze the fiber grating laser, resulting in the birefringence change inside the laser cavity and hence the change of the beat note frequency. When an alternating current is injected into the copper wire, the magnetic field induced beat note frequency change can be discriminated from environment disturbances. A novel fiber-optic magnetic field sensor is therefore demonstrated with high sensitivity and inherent immunity to disturbances. PMID:23736594

  11. 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.

  12. Force-Field Compensation in a Manual Tracking Task

    PubMed Central

    Squeri, Valentina; Masia, Lorenzo; Casadio, Maura; Morasso, Pietro; Vergaro, Elena

    2010-01-01

    This study addresses force/movement control in a dynamic hybrid task: the master sub-task is continuous manual tracking of a target moving along an eight-shaped Lissajous figure, with the tracking error as the primary performance index; the slave sub-task is compensation of a disturbing curl viscous field, compatibly with the primary performance index. The two sub-tasks are correlated because the lateral force the subject must exert on the eight-shape must be proportional to the longitudinal movement speed in order to perform a good tracking. The results confirm that visuo-manual tracking is characterized by an intermittent control mechanism, in agreement with previous work; the novel finding is that the overall control patterns are not altered by the presence of a large deviating force field, if compared with the undisturbed condition. It is also found that the control of interaction-forces is achieved by a combination of arm stiffness properties and direct force control, as suggested by the systematic lateral deviation of the trajectories from the nominal path and the comparison between perturbed trials and catch trials. The coordination of the two sub-tasks is quickly learnt after the activation of the deviating force field and is achieved by a combination of force and the stiffness components (about 80% vs. 20%), which is a function of the implicit accuracy of the tracking task. PMID:20567516

  13. Comparing Molecular Dynamics Force Fields in the Essential Subspace

    PubMed Central

    Gomez-Puertas, Paulino; Boomsma, Wouter; Lindorff-Larsen, Kresten

    2015-01-01

    The continued development and utility of molecular dynamics simulations requires improvements in both the physical models used (force fields) and in our ability to sample the Boltzmann distribution of these models. Recent developments in both areas have made available multi-microsecond simulations of two proteins, ubiquitin and Protein G, using a number of different force fields. Although these force fields mostly share a common mathematical form, they differ in their parameters and in the philosophy by which these were derived, and previous analyses showed varying levels of agreement with experimental NMR data. To complement the comparison to experiments, we have performed a structural analysis of and comparison between these simulations, thereby providing insight into the relationship between force-field parameterization, the resulting ensemble of conformations and the agreement with experiments. In particular, our results show that, at a coarse level, many of the motional properties are preserved across several, though not all, force fields. At a finer level of detail, however, there are distinct differences in both the structure and dynamics of the two proteins, which can, together with comparison with experimental data, help to select force fields for simulations of proteins. A noteworthy observation is that force fields that have been reparameterized and improved to provide a more accurate energetic description of the balance between helical and coil structures are difficult to distinguish from their unbalanced counterparts in these simulations. This observation implies that simulations of stable, folded proteins, even those reaching 10 microseconds in length, may provide relatively little information that can be used to modify torsion parameters to achieve an accurate balance between different secondary structural elements. PMID:25811178

  14. Pattern forced geophysical vector field segmentation based on Clifford FFT

    NASA Astrophysics Data System (ADS)

    Yuan, Linwang; Yu, Zhaoyuan; Luo, Wen; Yi, Lin; Hu, Yong

    2013-10-01

    Vector field segmentation is gaining increasing importance in geophysics research. Existing vector field segmentation methods usually can only handle the statistical characteristics of the original data. It is hard to integrate the patterns forced by certain geophysical phenomena. In this paper, a template matching method is firstly constructed on the foundation of the Clifford Fourier Transformation (CFT). The geometric meanings of both inner and outer components can provide more attractive information about the similarities between original vector field and template data. A composed similarity field is constructed based on the coefficients fields. After that, a modified spatial consistency preserving K-Means cluster algorithm is proposed. This algorithm is applied to the similarity fields to extract the template forced spatial distribution pattern. The complete algorithm for the overall processing is given and the experiments of ENSO forced global ocean surface wind segmentation are configured to test our method. The results suggest that the pattern forced segmentation can extract more latent information that cannot be directly measured from the original data. And the spatial distribution of ENSO influence on the surface wind field is clearly given in the segmentation result. All the above suggest that the method we proposed provides powerful and new thoughts and tools for geophysical vector field data analysis.

  15. Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

    DOEpatents

    Stevens, Fred J. (Naperville, IL)

    1992-01-01

    A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

  16. 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.

  17. Tracing optical force fields within graded-index media

    NASA Astrophysics Data System (ADS)

    Akbarzadeh, Alireza; Danesh, Mohammad; Qiu, Cheng-Wei; Danner, Aaron J.

    2014-05-01

    The mechanical interaction between light and graded index media (both isotropic and anisotropic) is presented from the geometrical optics (GO) perspective. Utilizing Hamiltonian equations to determine ray trajectories combined with a description of the Lorentz force exerted on bound currents and charges, we provide a general method that we denote force tracing for determining the direction and magnitude of the bulk and surface force density in arbitrarily anisotropic and inhomogeneous media. This technique provides the optical community with machinery which can give a good estimation of the force field distribution in different complex media, and with significantly faster computation speeds than full-wave methods allow. Comparison of force tracing against analytical solutions shows some unusual limitations of GO, which we also illustrate.

  18. 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.

  19. Electric Field and Humidity Trigger Contact Electrification

    E-print Network

    Yanzhen Zhang; Thomas Phtz; 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.

  20. Electric Field and Humidity Trigger Contact Electrification

    NASA Astrophysics Data System (ADS)

    Zhang, Yanzhen; Phtz, 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.

  1. TWO FREEDERICKSZ TRANSITIONS IN CROSSED ELECTRIC AND MAGNETIC FIELDS

    E-print Network

    Boyer, Edmond

    965 TWO FREEDERICKSZ TRANSITIONS IN CROSSED ELECTRIC AND MAGNETIC FIELDS H. J. DEULING by external electric or magnetic fields. The resulting distortion is governed by a balance of stabilizing magnetic field to induce twist and uses a vertical electric field to induce splay and bend. If we turn

  2. E-Government Field Force Automation: Promises, Challenges, and Stakeholders

    Microsoft Academic Search

    Hans Jochen Scholl; Raya Fidel; Michael Paulsmeyer; Kristene Unsworth

    2007-01-01

    With the growing pervasiveness and maturity of fully mobile and wirelessly connected technologies (FMWC), many organizations\\u000a have begun to equip their field workforce with such information and communication technologies (ICT). The aim of these projects\\u000a is to automate fieldwork operations, that is, to make them more effective, to improve field force responsiveness, and to speed\\u000a up the field processes, while

  3. Deriving forces from 2D velocity field measurements

    NASA Astrophysics Data System (ADS)

    Albrecht, Thomas; del Campo, Vanessa; Weier, Tom; Metzkes, Hans; Stiller, Jrg

    2013-03-01

    We discuss how to derive a force or a force density from a measured velocity field. The first part focuses on the integral force a fluid exerts on a body, e.g. lift and drag on an airfoil. Obtaining the correct pressure is crucial; however, it cannot be measured within the flow non-intrusively. Using numerical and experimental test cases, we compare the accuracy achievable with three methods: pressure reconstruction from velocity fields via (1) the differential momentum equation, or (2) the Poisson equation, furthermore, (3) Noca's momentum equation [Noca, JFS 13(5), 1999], which does not require pressure explicitly. The latter gives the best results for the lift, whereas the first or second approach should be used for the drag. The second part deals with obtaining the distribution of a body force density generated by an actuator. Using a stream function ansatz, we obtain a Laplace equation that allows us to compute the solenoidal part of the force distribution; however, the irrotational part is lost. Furthermore, the wall pressure must be known. We validate this approach using numerical data from a wall jet flow in a rectangular box, driven by a fictitious, solenoidal body force. Reconstructing the force distribution yields an error of less than 10-2 for most of the domain.

  4. Extremely low frequency electric fields and cancer: assessing the evidence.

    PubMed

    Kheifets, Leeka; Renew, David; Sias, Glenn; Swanson, John

    2010-02-01

    Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric-fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric-field exposures and appliance use does not support the conclusion of adverse health effects from electric-field exposure. Workers in close proximity to high-voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields. PMID:19650076

  5. Apricot Nectar Processing by Pulsed Electric Fields

    Microsoft Academic Search

    Gulsun Akdemir Evrendilek; Julide Altuntas; Mustafa Kemal Sangun; Howard Q. Zhang

    2011-01-01

    Application of Pulsed Electric Fields (PEF's) to process apricot nectar by determining the pH, Brix, total acidity, conductivity, color, non-enzymatic browning index, concentration of mineral ions and retention of ascorbic acid and beta carotene as well as inactivation of Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Pseudomonas syringae subs. syringae, Erwinia carotowora, Penicillum expansum and Botrytis cinerea was explored in

  6. Electric Field Generation in Martian Dust Devils

    NASA Astrophysics Data System (ADS)

    Barth, E. L.; Farrell, W. M.; Rafkin, S. C. R.

    2011-10-01

    Triboelectric dust charging physics via the Macroscopic Triboelectric Simulation (MTS) code has been added to the Mars Regional Atmospheric Modeling System (MRAMS) in order to simulate the electrodynamics of dust devils and dust disturbances on Mars. Using the model, we explore how macroscopic electric fields are generated within storms and attempt to quantify the time evolution of the electrodynamical system. This research was supported by the Mars Fundamental Research Program, NASA Grant NX07AR69G.

  7. Simulation of Forces between Humid Amorphous Silica Surfaces: A Comparison of Empirical Atomistic Force Fields

    PubMed Central

    2012-01-01

    Atmospheric humidity strongly influences the interactions between dry granular particles in process containers. To reduce the energy loss in industrial production processes caused by particle agglomeration, a basic understanding of the dependence of particle interactions on humidity is necessary. Hence, in this study, molecular dynamic simulations were carried out to calculate the adhesion between silica surfaces in the presence of adsorbed water. For a realistic description, the choice of force field is crucial. Because of their frequent use and transferability to biochemical systems, the Clay and CWCA force fields were investigated with respect to their ability to describe the watersilica interface in comparison to the more advanced Reax force field, ab initio calculations, and experiments. PMID:23378869

  8. 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

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

    SciTech Connect

    Behunin, Ryan O. [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Hu, Bei-Lok [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States)

    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.

  10. Electric field effect in graphite crystallites

    NASA Astrophysics Data System (ADS)

    Sagar, Adarsh; Balasubramanian, Kannan; Burghard, Marko; Kern, Klaus

    2012-05-01

    Graphite is a highly anisotropic crystal with a quasi-two-dimensional electronic structure exhibiting high intrinsic charge carrier mobility. Here, we investigate the effect of an electric field on the resistance of individual graphite crystallites with a thickness on the order of 40 nm. Ambipolar field-effect behavior was achieved with the aid of a polymer electrolyte gate. By optimizing the device geometry, devices with an on/off current ratio of up to 4 and carrier mobilities of around 100 cm2/Vs could be attained directly on the crystallites.

  11. Electric field shielding in dielectric nanosolutions

    E-print Network

    Sergey Bastrukov; Pik-Yin Lai; Irina Molodtsova

    2014-03-26

    To gain some insight into electrochemical activity of dielectric colloids of technical and biomedical interest we investigate a model of dielectric nanosolution whose micro-constitution is dominated by dipolarions -- positively and negatively charged spherically symmetric nano-structures composed of ionic charge surrounded by cloud of radially polarized dipoles of electrically neutral molecules of solvent. Combing the standard constitutive equations of an isotropic dielectric liquid with Maxwell equation of electrostatics and presuming the Boltzmann shape of the particle density of bound-charge we derive equation for the in-medium electrostatic field. Particular attention is given to numerical analysis of obtained analytic solutions of this equation describing the exterior fields of dipolarions with dipolar atmospheres of solvent molecules endowed with either permanent or field-induced dipole moments radially polarized by central symmetric field of counterions. The presented computations show that the electric field shielding of dipolarions in dielectric nanosolutions is quite different from that of counterionic nano-complexes of Debye-H\\"uckel theory of electrolytes.

  12. 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.

  13. Electric field induced variations in the wettability of stainless steel by ionic surfactant and electrolyte solutions

    Microsoft Academic Search

    Sanjay Wahal; Clarice Owiti; Arijit Bose

    1993-01-01

    Sessile drops of aqueous electrolyte as well as cationic and anionic surfactant solutions are placed on the lower plate of a stainless steel parallel plate capacitor and the variation of static advanced contact angles with the field strength between the plates is monitored. Even at field strengths where changes in electrical body forces are negligible, these drops spreads outward, irreversibly,

  14. Electric-field induced capillary interaction of charged particles at a polar interface

    E-print Network

    Lionel Foret; Alois Wrger

    2014-02-07

    We study the electric-field induced capillary interaction of charged particles at a polar interface. The algebraic tails of the electrostatic pressure of each charge results in a deformation of the interface $u\\sim \\rho ^{-4}$. The resulting capillary interaction is repulsive and varies as $\\rho ^{-6}$ with the particle distance. As a consequence, electric-field induced capillary forces cannot be at the origin of the secondary minimum observed recently for charged PMMA particles at on oil-water interface.

  15. PIV Measurements of Particle and Fluid Motion Induced by AC Electric Fields

    Microsoft Academic Search

    Dazhi Wang; Carl Meinhart; Marin Sigurdson

    2003-01-01

    The techniques to induce particle and fluid motion inside microsystems using ac electric fields have important applications in sensing and manipulating bioparticles. Micron-Resolution Particle Image Velocimetry (m-PIV) is a powerful tool to measure the spatially resolved motion with resolution approaching 1mm. In the presence of nonuniform ac electric fields, the particles experience dielectrophoretic (DEP) forces due to polarization and drag

  16. Mechanical and electrical properties of CdTe tetrapods studied by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Fang, Liang; Park, Jeong Young; Cui, Yi; Alivisatos, Paul; Shcrier, Joshua; Lee, Byounghak; Wang, Lin-Wang; Salmeron, Miquel

    2007-11-01

    The mechanical and electrical properties of CdTe tetrapod-shaped nanocrystals have been studied with atomic force microscopy. Tapping mode images of tetrapods deposited on silicon wafers revealed that they contact the surface with three of its arms. The length of these arms was found to be 13010nm. A large fraction of the tetrapods had a shortened vertical arm as a result of fracture during sample preparation. Fracture also occurs when the applied load is a few nanonewtons. Compression experiments with the atomic force microscope tip indicate that tetrapods with the shortened vertical arm deform elastically when the applied force was less than 50nN. Above 90nN additional fracture events occurred that further shortened the vertical arm. Loads above 130nN produced irreversible damage to the other arms as well. Current-voltage characteristics of tetrapods deposited on gold revealed a semiconducting behavior with a current gap of 2eV at low loads (<50nN) and a narrowing to about 1eV at loads between 60 and 110nN. Atomistic force field calculations of the deformation suggest that the ends of the tetrapod arms are stuck during compression so that the deformations are due to bending modes. Empirical pseudopotential calculation of the electron states indicates that the reduction of the current gap is due to electrostatic effects, rather than strain deformation effects inside the tetrapod.

  17. Superadiabatic optical forces on a dipole: exactly solvable model for a vortex field

    NASA Astrophysics Data System (ADS)

    Berry, M. V.; Shukla, Pragya

    2014-03-01

    The forces exerted by light on a small particle are modified by the particle's motion, giving a series of superadiabatic corrections to the lowest-order approximation in which the motion is neglected. The correction forces can be calculated recursively for an electric dipole modelled as a damped oscillator. In lowest order, there is, as is known, a non-potential though non-dissipative curl force, in addition to the familiar gradient force. In the next order, there are forces of geometric magnetism and friction, related to the geometric phase 2-form and the metric of the driving field. For the paraxial field of an optical vortex, the hierarchy of superadiabatic forces can be calculated explicitly, revealing a four-sheeted Riemann surface on which fast and slow dynamics are connected. This leads to an exact slow manifold, on which the dipole is driven without oscillations by the same forces as in the first two adiabatic orders, but with frequency-renormalized strengths.

  18. PhET: Electric Field Hockey

    NSDL National Science Digital Library

    This webpage contains an activity that allows users to guide a charged object, or "puck", through a maze using the electric field created by point charges placed by the user. Options exist to control the mass and sign of the charge of the puck. There are four levels of difficulty that change the barrier placement. Barriers do not affect the fields, only define the path of the puck. The user can view a vector representation of the electric field, as well as trace the path of the puck. After each attempt the user may move the existing charge or place more charges and try again. This activity gives users an immediate experience with the interaction between fields and charges. The page also contains samples of learning goals as well as user-submitted ideas and activities for use with the simulation. This simulation is part of a large and growing collection. It has been designed using principles from physics education research and refined based on student interviews.

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

    SciTech Connect

    Tiwari, Sanjiv Kumar, E-mail: tiwari@mps.mpg.de [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur 313 001 (India)

    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.

  20. Spatial aspects of the electric fields generated by weakly electric fish

    Microsoft Academic Search

    Eric I. Knudsen

    1975-01-01

    1.The electric fields of four species of wave type, gymnotid fishes were measured and mapped using a technique that allowed accurate assessment of small electric fields, free of unknown field compression and distortion artifacts.2.Dipole moment values were calculated for each fish's electric field from measurements made at a sufficient distance (Table 1). A dipole moment is an absolute evaluation of

  1. Measurements of electric-field strengths in ionization fronts during breakdown.

    PubMed

    Wagenaars, E; Bowden, M D; Kroesen, G M W

    2007-02-16

    Using laser-induced fluorescence-dip Stark spectroscopy, we performed time-resolved, direct measurements of electric-field strengths during the breakdown phase of a low-pressure, pulsed discharge in xenon. With this experimental technique we could for the first time quantitatively measure the time evolution of the driving force of the plasma breakdown process: the electric field. Moving ionization fronts were measured with submicrosecond resolution. These ionization fronts were sustained by a spatially narrow, rapidly moving region of strong electric field. PMID:17359030

  2. Measurements of Electric-Field Strengths in Ionization Fronts during Breakdown

    NASA Astrophysics Data System (ADS)

    Wagenaars, E.; Bowden, M. D.; Kroesen, G. M. W.

    2007-02-01

    Using laser-induced fluorescence-dip Stark spectroscopy, we performed time-resolved, direct measurements of electric-field strengths during the breakdown phase of a low-pressure, pulsed discharge in xenon. With this experimental technique we could for the first time quantitatively measure the time evolution of the driving force of the plasma breakdown process: the electric field. Moving ionization fronts were measured with submicrosecond resolution. These ionization fronts were sustained by a spatially narrow, rapidly moving region of strong electric field.

  3. Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, C.

    2000-01-01

    The research carried out in the Heat Transfer Laboratory of the Johns Hopkins University was motivated by previous studies indicating that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 when 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 influence of electric fields on bubble formation has been investigated both experimentally and theoretically.

  4. Electron distribution functions in electric field environments

    NASA Technical Reports Server (NTRS)

    Rudolph, Terence H.

    1991-01-01

    The amount of current carried by an electric discharge in its early stages of growth is strongly dependent on its geometrical shape. Discharges with a large number of branches, each funnelling current to a common stem, tend to carry more current than those with fewer branches. The fractal character of typical discharges was simulated using stochastic models based on solutions of the Laplace equation. Extension of these models requires the use of electron distribution functions to describe the behavior of electrons in the undisturbed medium ahead of the discharge. These electrons, interacting with the electric field, determine the propagation of branches in the discharge and the way in which further branching occurs. The first phase in the extension of the referenced models , the calculation of simple electron distribution functions in an air/electric field medium, is discussed. Two techniques are investigated: (1) the solution of the Boltzmann equation in homogeneous, steady state environments, and (2) the use of Monte Carlo simulations. Distribution functions calculated from both techniques are illustrated. Advantages and disadvantages of each technique are discussed.

  5. Biofouling prevention with pulsed electric fields

    SciTech Connect

    Abou-Ghazala, A.; Schoenbach, K.H.

    2000-02-01

    Temporary immobilization of aquatic nuisance species through application of short electric pulses has been explored as a method to prevent biofouling in cooling water systems where untreated lake, river, or sea water is used. In laboratory experiments, electrical pulses with amplitudes on the order of kilovolts/centimeter and submicrosecond duration were found to be most effective in stunning time in a temporal range from minutes to hours. The temporary immobilization is assumed to be caused by reversible membrane breakdown. This assumption is supported by results of measurements of the energy required for stunning. Based on the data obtained in laboratory experiments, field experiments in a tidal water environment have been performed. The flow velocity was such that the residence time of the aquatic nuisance species in the system was approximately half a minute. The results showed that the pulsed electric field method provides full protection against biofouling when pulses of 0.77 {micro}s width and 6 kV/cm amplitude are applied to the water at the inlet of such a cooling water system. Even at amplitudes of 1 kV/cm, the protection is still in the 90% range, at an energy expenditure of 1 kWh for the treatment of 60,000 gallons of water.

  6. Liquid methanol under a static electric field

    NASA Astrophysics Data System (ADS)

    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/) 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/, 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.

  7. Low frequency electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1989-01-01

    Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.

  8. The force exerting on cosmic bodies in a quaternionc field

    E-print Network

    V. Majernik

    2003-09-03

    The expression of a time-dependent cosmological constant $\\lambda \\propto 1/t^2$ is interpreted as the energy density of a special type of the quaternionic field. The Lorenz-like force acting on the moving body in the presence of this quaternionic field is determined. The astronomical and terrestrial effects of this field are presented, and the ways how it can be observably detected is discussed. Finally, a new mechanism of the particle creation and an alternative cosmological scenario in the presence of the cosmic quatertionic field is suggested.

  9. Mitigated-force carriage for high magnetic field environments

    DOEpatents

    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.

  10. 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.

  11. Introduction of periodic boundary conditions into UNRES force field.

    PubMed

    Sieradzan, Adam K

    2015-05-01

    In this article, implementation of periodic boundary conditions (PBC) into physics-based coarse-grained UNited RESidue (UNRES) force field is presented, which replaces droplet-like restraints previously used. Droplet-like restraints are necessary to keep multichain systems together and prevent them from dissolving to infinitely low concentration. As an alternative for droplet-like restrains cuboid PBCs with imaging of the molecules were introduced. Owing to this modification, artificial forces which arose from restraints keeping a droplet together were eliminated what leads to more realistic trajectories. Due to computational reasons cutoff and smoothing functions were introduced on the long range interactions. The UNRES force field with PBC was tested by performing microcanonical simulations. Moreover, to asses the behavior of the thermostat in PBCs Langevin and Berendsen thermostats were studied. The influence of PBCs on association pattern was compared with droplet-like restraints on the ??? hetero tetramer 1 protein system. 2015 Wiley Periodicals, Inc. PMID:25753584

  12. 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.

  13. Direct Evidence of Solar Flare Modification of Stratospheric Electric Fields

    Microsoft Academic Search

    R. H. Holzworth; F. S. Mozer

    1979-01-01

    Direct evidence of solar flare modification of stratospheric electric fields is presented through comparison of atmospheric electric field variations with fluxes of solar protons that bombarded the atmosphere during the August 1972 solar flares. Observed order of magnitude variations of the vertical electric field at 30-km altitude in anticorrelation with the intensity of solar protons are quantitatively interpreted in terms

  14. Multilayer graphene nanoribbon under vertical electric field

    NASA Astrophysics Data System (ADS)

    Bala Kumar, S.; Guo, Jing

    2011-08-01

    We study the effect of vertical electric-field (E-field) on the electronic properties of the multilayer armchair graphene nanoribbon (aGNR). Under E-field, the band structure of a bilayer aGNR undergoes interesting transformations, such as change in the electron velocity, sign of the electron effective mass, bandgap, and the position of the bandgap in the momentum space. Depending on the width of the aGNR and the applied E-field, the bandgap of the aGNR may either be increased or decreased. When the applied E-field is above a critical value, the bandgap of the bilayer aGNR is identical to that of the bilayer graphene, independent of the width. We also show that, for semiconducting multilayer aGNR with more than two layers, the bandgap decreases with increasing E-field, resulting in a semiconductor-to-metallic transition. This can be utilized to enhance the performance of graphene based transistor devices.

  15. Frequency-dependent force fields for QMMM calculations.

    PubMed

    Harczuk, Ignat; Vahtras, Olav; gren, Hans

    2015-03-11

    We outline the construction of frequency-dependent polarizable force fields. The force fields are derived from analytic response theory for different frequencies using a generalization of the LoProp algorithm giving a decomposition of a molecular dynamical polarizability to localized atomic dynamical polarizabilities. These force fields can enter in a variety of applications - we focus on two such applications in this work: firstly, they can be incorporated in a physical, straightforward, way for current existing methods that use polarizable embeddings, and we can show, for the first time, the effect of the frequency dispersion within the classical environment of a quantum mechanics-molecular mechanics (QMMM) method. Our methodology is here evaluated for some test cases comprising water clusters and organic residues. Secondly, together with a modified Silberstein-Applequist procedure for interacting inducible point-dipoles, these frequency-dependent polarizable force fields can be used for a classical determination of frequency-dependent cluster polarizabilities. We evaluate this methodology by comparing with the corresponding results obtained from quantum mechanics or QMMM where the absolute mean [small alpha, Greek, macron] is determined with respect to the size of the QM and MM parts of the total system. PMID:25714984

  16. 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 -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...

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

    E-print Network

    Hla, Saw-Wai

    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

  18. Force Field Modeling of Conformational Energies: Importance of Multipole

    E-print Network

    Ponder, Jay

    Force Field Modeling of Conformational Energies: Importance of Multipole Moments and Intramolecular the correlation, and both contributions are of similar importance. 2006 Wiley Periodicals, Inc. Int J Quantum little influence on con- formational degrees of freedom. The nonbonded Correspondence to: F. Jensen; e

  19. ADVANCES IN FORCE FIELD TAILORING FOR CONSTRUCTION IN SPACE

    E-print Network

    reports the status of adapting this new technology to a mission plan to build a 5-module, 1-G radiation a reference mission architecture and engineering solutions to the other issues in building large1 ADVANCES IN FORCE FIELD TAILORING FOR CONSTRUCTION IN SPACE Sam Wanis, Narayanan Komerath School

  20. Cylindrical Magnets and Coils: Fields, Forces, and Inductances

    Microsoft Academic Search

    R. Ravaud; G. Lemarquand; S. Babic; V. Lemarquand; C. Akyel

    2010-01-01

    This paper presents a synthesis of analytical calculations of magnetic parameters (field, force, torque, stiffness) in cylindrical magnets and coils. By using the equivalence between the amperian current model and the coulombian model of a magnet, we show that a thin coil or a cylindrical magnet axially magnetized have the same mathematical model. Consequently, we present first the analytical expressions

  1. Motional sideband excitation using rotating electric fields

    NASA Astrophysics Data System (ADS)

    Isaac, C. A.

    2013-04-01

    A form of motional sideband excitation is described in which a rotating dipole electric field is applied asymmetrically onto a Penning-type trap in the presence of a mechanism for cooling the axial motion of the trapped particles. In contrast to the traditional motional sideband excitation, which uses an oscillating electric field, the rotating field results in only one active sideband in each sense of rotation and so avoids accidental excitation of the other sideband making it applicable to Penning-type traps with a large degree of anharmonicity. Expressions are derived for the magnetron radius expansion and compression rates attainable, and approximations are made for the case of strong and weak drives. A comparison is made with data, taken using a two-stage positron accumulator presented by Isaac [C. A. Isaac, C. J. Baker, T. Mortensen, D. P. van der Werf, and M. Charlton, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.033201 107, 033201 (2011)], showing good agreement between the model and experiment.

  2. Electric current generation in photorefractive bismuth silicon oxide without application of external electric field

    NASA Astrophysics Data System (ADS)

    Buchhave, Preben; Kukhtarev, Nickolai; Kukhtareva, Tatiana; Edwards, Matthew E.; Reagan, Michael A.; Lyuksyutov, Sergei F.

    2003-10-01

    A holographic radial diffraction grating (HRDG) is an efficient optical element for splitting single laser beam on three 0, -1st, and +1st- diffraction order beams. The rotation of the grating at certain velocity allows a window for quality control over the frequency detuning between -1st, and +1st diffracted beams. The running interference fringes produced by the beams and projected on photorefractive crystal induce running holographic gratings in the crystal. This simple configuration is an effective tool for the study of such phenomena as space charge waves [1], domains motion [2], and electric current generation [3]. Specifics of photorefractive mechanism in cubic photorefractive crystals (BSO, BTO) normally require a use of external electric field to produce reasonable degree of refractive index modulation to observe associated with it phenomena. In this work we provide a direct experimental observation of the electric current generated in photorefractive BSO using running grating technique without an applied electric field. Moving interference fringes modulate a photoconductivity and an electric field in photorefractive crystal thus creating the photo electro-motive force (emf) and the current. The magnitude of the current varies between 1 and 10 nA depending on the rotation speed of HRDG. The peculiarities of the current behavior include a backward current flow, and current oscillations. The holographic current generated through this technique can find applications in non-destructive testing for ultra-sensitive vibrometry, materials characterization, and for motion sensors. References [1] S.F. Lyuksyutov, P. Buchhave, and M.V. Vasnetsov, Physical Review Letters, 79, No.1, 67-70 (1997) [2] P. Buchhave, S. Lyuksyutov, M. Vasnetsov, and C. Heyde, Journal Optical Society of America B, 13, No.11 2595-2602 (1996) [3] M. Vasnetsov, P. Buchhave, and S. Lyuksyutov Optics Communications, 137, 181-191 (1997)

  3. A phenomenological model that predicts forces generated when electrical stimulation is superimposed on submaximal volitional contractions

    PubMed Central

    Perumal, Ramu; Wexler, Anthony S.; Kesar, Trisha M.; Jancosko, Angela; Laufer, Yocheved

    2010-01-01

    Superimposition of electrical stimulation during voluntary contractions is used to produce functional movements in individuals with central nervous system impairment, to evaluate the ability to activate a muscle, to characterize the nature of fatigue, and to improve muscle strength during postsurgical rehabilitation. Currently, the manner in which voluntary contractions and electrically elicited forces summate is not well understood. The objective of the present study is to develop a model that predicts the forces obtained when electrical stimulation is superimposed on a volitional contraction. Quadriceps femoris muscles of 12 able-bodied subjects were tested. Our results showed that the total force produced when electrical stimulation was superimposed during a volitional contraction could be modeled by the equation T = V + S[(MaxForce ? V)/MaxForce]N, where T is the total force produced, V is the force in response to volitional contraction alone, S is the force response to the electrical stimulation alone, MaxForce is the maximum force-generating ability of the muscle, and N is a parameter that we posit depends on the differences in the motor unit recruitment order and firing rates between volitional and electrically elicited contractions. In addition, our results showed that the model predicted accurately (intraclass correlation coefficient ?0.97) the total force in response to a wide range of stimulation intensities and frequencies superimposed on a wide range of volitional contraction levels. Thus the model will be helpful to clinicians and scientists to predict the amount of stimulation needed to produce the targeted force levels in individuals with partial paralysis. PMID:20299613

  4. Effects of external force fields on peptide self-assembly and biomimetic silica synthesis

    NASA Astrophysics Data System (ADS)

    Yu, Jun; Wang, Qinrong; Zhang, Xin

    2014-08-01

    This study investigated the influence of physical parameters on the dynamic self-assembly of short peptide amphiphiles (A6K and V6K) and the peptide-mediated silica morphologies by applying external force fields (electric and flow fields). Diverse self-assembled structures (nanofibers, nanorods, or lamellar stacks) can be obtained depending on field intensities and molecular architectures. Although the trend in the structural transitions observed from the electrostatic stimulation differed from that obtained in flow field, the common features indicate that the formed structures exhibit a higher extent of end-to-end merging or lateral association. These self-assembled peptide-based nanostructures then were used as organic templates to tailor silica deposition. It was found that the application of flow fields can stably produce fibril morphology. However, in the case of electric fields, different silica structures were obtained by using different systems. The silica morphologies directed by V6K peptide were transformed from fibrils to plate-like structures, and A6K peptide produced fibril silica materials. The difference may be attributed to different biomimetic conditions, including external forces, solubility of hydrophobic blocks, and intensity of peptide-silicate interactions. This understanding of the mechanism by which external fields affect the self-assembled amphiphilic peptide nanostructures and the silicification process allows us to manipulate the role of short amphiphilic peptides in silica formation in vitro.

  5. 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.

  6. The spatially averaged electric field in the near field and far field of a circular aperture

    Microsoft Academic Search

    Charles J. Daly; Todd W. Nuteson; Navalgund A. H. K. Rao

    2003-01-01

    This paper presents a theoretical and numerical investigation of the spatially averaged electric field in the beam of a circular aperture. The investigation leads to closed-form analytical expressions, based on scalar diffraction theory, which describe the spatially averaged electric field in the Fresnel region of a circular aperture excited by a spatially uniform, harmonic plane wave. The expressions ultimately permit

  7. Electric and magnetic field exposure, chemical exposure, and leukemia risk in electrical'' occupations

    SciTech Connect

    Bowman, J.D.; Sobel, E.; London, S.J.; Thomas, D.C.; Garabrant, D.H.; Pearce, N.; Peters, J.M. (University of Southern California, Los Angeles, CA (United States). Dept. of Preventive Medicine)

    1992-12-01

    This project was conducted to address what are the extremely low frequency (ELF) magnetic and electric field exposures of workers in electrical'' occupations and do they exceed exposures encountered in non-electrical'' occupations and what are the chemical and physical exposures in the electrical'' occupations and do they exceed exposures encountered in non-electrical'' occupations Two subsidiary issues were does characterization and quantification of ELF magnetic field exposure in the electrical'' occupations provide data to support a dose response relationship between leukemia risk and electric or magnetic field exposure and do dffferences in chemical exposure between the occupations help explain the previously observed leukemia risk associated with these electrical'' occupations Data were collected in 3 regions in which electrical workers had been reported to have an excess of leukemia - New Zealand, Los Angeles and Seattle Measurements of magnetic fields were made on 493 electrical workers and 163 non-electrical workers.

  8. The role of magnetic-field-aligned electric fields in auroral acceleration

    Microsoft Academic Search

    L. P. Block; C. G. Faelthammar

    1990-01-01

    Electric field measurements on the Swedish satellite Viking have confirmed and extended earlier observations on S3-3 and provided further evidence of the role of dc electric fields in auroral acceleration processes. On auroral magnetic field lines the electric field is strongly fluctuating both transverse and parallel to the magnetic field. The significance of these fluctuations for the auroral acceleration process

  9. Quantitative estimates of magnetic field reconnection properties from electric and magnetic field measurements

    E-print Network

    California at Berkeley, University of

    Quantitative estimates of magnetic field reconnection properties from electric and magnetic field there are positive electric field components tangential to the magnetopause and a magnetic field component normal to it. Because these three components are the smallest of the six electric and magnetic fields

  10. 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.

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

    SciTech Connect

    Sarsam, Joanne [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Finnis, Michael W.; Tangney, Paul, E-mail: p.tangney@imperial.ac.uk [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)

    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.

  12. Convolutional Virtual Electric Field for Image Segmentation Using Active Contours

    PubMed Central

    Wang, Yuanquan; Zhu, Ce; Zhang, Jiawan; Jian, Yuden

    2014-01-01

    Gradient vector flow (GVF) is an effective external force for active contours; however, it suffers from heavy computation load. The virtual electric field (VEF) model, which can be implemented in real time using fast Fourier transform (FFT), has been proposed later as a remedy for the GVF model. In this work, we present an extension of the VEF model, which is referred to as CONvolutional Virtual Electric Field, CONVEF for short. This proposed CONVEF model takes the VEF model as a convolution operation and employs a modified distance in the convolution kernel. The CONVEF model is also closely related to the vector field convolution (VFC) model. Compared with the GVF, VEF and VFC models, the CONVEF model possesses not only some desirable properties of these models, such as enlarged capture range, u-shape concavity convergence, subject contour convergence and initialization insensitivity, but also some other interesting properties such as G-shape concavity convergence, neighboring objects separation, and noise suppression and simultaneously weak edge preserving. Meanwhile, the CONVEF model can also be implemented in real-time by using FFT. Experimental results illustrate these advantages of the CONVEF model on both synthetic and natural images. PMID:25360586

  13. Effective charge of a small absorbing body in highly collisional plasma subject to an external electric field

    SciTech Connect

    Chaudhuri, M.; Khrapak, S. A.; Morfill, G. E. [Max-Planck Institut fuer Extraterrestrische Physik, D-85741 Garching (Germany)

    2007-05-15

    The total force which is the resultant of the electric, ion, and electron drag forces has been calculated for a small absorbing spherical grain immersed in a highly collisional, weakly ionized plasma subject to a weak external electric field. Linear dielectric response formalism has been used and both ion and electron absorption on the grain have been taken into account. It is shown that the total force is always directed along the direction of the electric force. The 'effective' charge of the grain which can be defined as the ratio of the total force to the strength of the electric field is calculated. It is shown that its magnitude is comparable to the magnitude of the actual grain's charge.

  14. Coherent Control of a Single Electron Spin with Electric Fields

    Microsoft Academic Search

    K. C. Nowack; F. H. L. Koppens; Yu. V. Nazarov; L. M. K. Vandersypen

    2007-01-01

    Manipulation of single spins is essential for spin-based quantum information\\u000aprocessing. Electrical control instead of magnetic control is particularly\\u000aappealing for this purpose, since electric fields are easy to generate locally\\u000aon-chip. We experimentally realize coherent control of a single electron spin\\u000ain a quantum dot using an oscillating electric field generated by a local gate.\\u000aThe electric field induces

  15. 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.

  16. What Supports the Parallel Electric Field in the Birkeland (Field-Aligned) Current Regions of the Earth's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Jasperse, John; Basu, Bamandas; Lund, Eric; Grossbard, Neil

    2008-11-01

    Quasi-steady electric fields parallel to the geomagnetic field exist in both upward and downward Birkeland (field-aligned) current regions above the aurora. These fields, together with the turbulence found on auroral field lines, energize the plasma particles as they flow either away from or toward the earth. In general, these parallel electric fields are supported by one or more strong double layers, mirror force, generalized pressure gradient, and anomalous resistivity due to the turbulence. Recently, and for the first time, we have developed a new kinetic and multi-moment fluid theory for the Birkeland current system that contains the effect of turbulence for the inhomogeneous, non-uniformly magnetized plasma. Applying the new theory to observations in a downward-current sheet, we show that anomalous resistivity accounts for only a small portion of the parallel electric field and that contributions from the double layer, mirror force, and generalized pressure gradient terms in the generalized Ohm's law for the problem are more important. These results have important implications in other regions of space such as magnetospheric reconnection sites and solar coronal loops where parallel electric fields are likely to exist.

  17. Which electric fields are realizable in conducting January 8, 2013

    E-print Network

    Paris-Sud XI, Université de

    u represents the electric field, while u is the current field according to Ohm's law. AlternativelyWhich electric fields are realizable in conducting materials? January 8, 2013 Marc Brianea , Graeme such that u is a divergence free current field. The construction is shown to be always possible locally in Rd

  18. Gene delivery in conjunction with gold nanoparticle and tumor treating electric field

    NASA Astrophysics Data System (ADS)

    Tiwari, Pawan K.; Soo Lee, Yeon

    2013-08-01

    The advances in electrotherapy to treat the diseased biological cell instigate its extension in gene therapy through the delivery of gene into the nucleus. The objective of this study is to investigate the application of moderate intensity alternating electric field, also known as tumor treating electric field on a carrier system consisting of a charged gene complex conjugated to the surface of a gold nanoparticle. The gene delivery mechanism relies on the magnitude and direction of the induced electric field inside the cytoplasm in presence of carrier system. The induced electric field strength is significant in breaking the gene complex-gold nanoparticle bonding, and exerting an electric force pushing the charged gene into the nucleus. The electric force orientation is dependent on the aspect ratio (AR) of the gold nanoparticle and a relationship between them is studied via Maxwell two-dimensional (2D) finite element simulation analyzer. The development of charge density on the surface of carrier system and the required electric field strength to break the bonding are investigated utilizing the Gouy-Chapman-Grahame-Stern (GCGS) theoretical model. A carrier system having the aspect ratio of the gold nanoparticle in the range 1 < AR ? 5 and AR = 1 are substantial delivering cationic and anionic genes into the nucleus, respectively.

  19. Sensing local inhomogeneity in electrical steels by the drag force method

    NASA Astrophysics Data System (ADS)

    Garshelis, Ivan J.; Kari, Ryan J.; Tollens, Stijn P. L.; Sergeant, Peter; Vandenbossche, Lode P.; Dupr, Luc R.

    2008-04-01

    Variations in the longitudinal drag force on a magnet close to a slowly moving strip sample of electrical steel are shown to provide sensitive, nondestructive indications of local inhomogeneity in the permeability, dimensions, and hysteresis loss of the sample. Measurements of both grain-oriented and nonoriented electrical steels showed drag force variations of unexpectedly large amplitude for movements of just a few millimeters, often with quasiperiodic features. Hysteresis variations were smaller and less drastic.

  20. The United Theory of the Two Fields of the Electric and Magnetic Nature

    E-print Network

    Sharafiddinov, R S

    2002-01-01

    Each of electrically charged particles testifies in favor of the existence of a kind of the magnetically charged monoparticle. As a consequence, only the corresponding mononeutrinos answer for quantization of the electric charges of all the neutrinos. Therefore, to understand the nature of matter at the fundamental level one must use the electromagnetic field as the field of the unified system of the photon and monophoton where the electric and magnetic forces of the nature are united. Some logical and laboratory confirmations of the availability of compound structure of gauge invariance have been listed which say also about the connection between the states of elementary particles and monoparticles

  1. The United Theory of the Two Fields of the Electric and Magnetic Nature

    E-print Network

    Rasulkhozha S. Sharafiddinov

    2010-12-07

    Each of electrically charged particles testifies in favor of the existence of a kind of the magnetically charged monoparticle. As a consequence, only the corresponding mononeutrinos answer for quantization of the electric charges of all neutrinos. Therefore, to understand the nature of matter at the fundamental level, one must use the electromagnetic field as the field of the unified system of the photon and monophoton where the electric and magnetic forces of the nature are united. Some logical and laboratory confirmations of the availability of compound structure of gauge invariance have been listed which say also about the connection between the states of elementary particles and monoparticles.

  2. Electric field effect in ultrathin black phosphorus

    NASA Astrophysics Data System (ADS)

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

  3. Electric field effect in ultrathin black phosphorus

    SciTech Connect

    Koenig, Steven P.; Schmidt, Hennrik [Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Doganov, Rostislav A.; Castro Neto, A. H.; zyilmaz, Barbaros [Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, 28 Medical Drive, Singapore 117456 (Singapore)

    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.

  4. Mapping the force field of a hydrogen-bonded assembly

    PubMed Central

    Sweetman, A. M.; Jarvis, S. P.; Sang, Hongqian; Lekkas, I.; Rahe, P.; Wang, Yu; Wang, Jianbo; Champness, N.R.; Kantorovich, L.; Moriarty, P.

    2014-01-01

    Hydrogen bonding underpins the properties of a vast array of systems spanning a wide variety of scientific fields. From the elegance of base pair interactions in DNA to the symmetry of extended supramolecular assemblies, hydrogen bonds play an essential role in directing intermolecular forces. Yet fundamental aspects of the hydrogen bond continue to be vigorously debated. Here we use dynamic force microscopy (DFM) to quantitatively map the tip-sample force field for naphthalene tetracarboxylic diimide molecules hydrogen-bonded in two-dimensional assemblies. A comparison of experimental images and force spectra with their simulated counterparts shows that intermolecular contrast arises from repulsive tip-sample interactions whose interpretation can be aided via an examination of charge density depletion across the molecular system. Interpreting DFM images of hydrogen-bonded systems therefore necessitates detailed consideration of the coupled tip-molecule system: analyses based on intermolecular charge density in the absence of the tip fail to capture the essential physical chemistry underpinning the imaging mechanism. PMID:24875276

  5. Mapping the force field of a hydrogen-bonded assembly

    NASA Astrophysics Data System (ADS)

    Sweetman, A. M.; Jarvis, S. P.; Sang, Hongqian; Lekkas, I.; Rahe, P.; Wang, Yu; Wang, Jianbo; Champness, N. R.; Kantorovich, L.; Moriarty, P.

    2014-05-01

    Hydrogen bonding underpins the properties of a vast array of systems spanning a wide variety of scientific fields. From the elegance of base pair interactions in DNA to the symmetry of extended supramolecular assemblies, hydrogen bonds play an essential role in directing intermolecular forces. Yet fundamental aspects of the hydrogen bond continue to be vigorously debated. Here we use dynamic force microscopy (DFM) to quantitatively map the tip-sample force field for naphthalene tetracarboxylic diimide molecules hydrogen-bonded in two-dimensional assemblies. A comparison of experimental images and force spectra with their simulated counterparts shows that intermolecular contrast arises from repulsive tip-sample interactions whose interpretation can be aided via an examination of charge density depletion across the molecular system. Interpreting DFM images of hydrogen-bonded systems therefore necessitates detailed consideration of the coupled tip-molecule system: analyses based on intermolecular charge density in the absence of the tip fail to capture the essential physical chemistry underpinning the imaging mechanism.

  6. 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

  7. Effect of Contact Force Between Rough Surfaces on Real Contact Area and Electrical Contact Resistance

    E-print Network

    Paris-Sud XI, Universit de

    Effect of Contact Force Between Rough Surfaces on Real Contact Area and Electrical Contact and the real contact area between rough surfaces as a function of the contact force. This application, surface roughness effects were ignored in the analysis, due to the difficulty to generate a rough surface

  8. 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.

  9. Magnetic forces for type II superconductors in a levitation field

    NASA Astrophysics Data System (ADS)

    Torng, Terry; Chen, Q. Y.

    1993-02-01

    A complete loop of hysteretic force has been calculated for hard superconductors in an almost-constant-gradient magnetic suspension system, which consists of a pair of oppositely wound superconducting coils. The dependences of levitation forces on the sample size, critical current density, external field strength, field gradient, and the magnetic history were investigated. Dynamic spring constants as well as magnetic damping coefficients were inferred from minor loop calculations. The minor loops, similar to the Rayleigh loops for ferromagnetic materials, could be described in quadratic terms. The major loops strongly depend on the magnetic passage, a flux-trap effect which is responsible for the subtlety in obtaining reproducible hysteresis loop. The basic physics of levitation and inverse levitation will be quantitatively illustrated.

  10. Lost at Sea: Hurricane Force Wind Fields and the North Pacific Ocean Environment

    E-print Network

    Businger, Steven

    Lost at Sea: Hurricane Force Wind Fields and the North Pacific Ocean Environment 1 Steven Businger: Hurricane Force Wind Fields and the North Pacific Ocean Environment 2 Hurricane Force (HF) Wind Fields in this talk is to help raise awareness of the hazards created by hurricane force winds in extratropical

  11. Materials Bound by Non-Chemical Forces: External Fields and the Quantum Vacuum

    E-print Network

    John Swain; Allan Widom; Yogendra Srivastava

    2014-04-29

    We discuss materials which owe their stability to external fields. These include: 1) external electric or magnetic fields, and 2) quantum vacuum fluctuations in these fields induced by suitable boundary conditions (the Casimir effect). Instances of the first case include the floating water bridge and ferrofluids in magnetic fields. An example of the second case is taken from biology where the Casimir effect provides an explanation of the formation of stacked aggregations or "rouleaux" by negatively charged red blood cells. We show how the interplay between electrical and Casimir forces can be used to drive self-assembly of nano-structured materials, and could be generalized both as a probe of Casimir forces and as a means of manufacturing nanoscale structures. Interestingly, all the cases discussed involve the generation of the somewhat exotic negative pressures. We note that very little is known about the phase diagrams of most materials in the presence of external fields other than those represented by the macroscopic scalar quantities of pressure and temperature. Many new and unusual states of matter may yet be undiscovered.

  12. Quantum mechanical force field for water with explicit electronic polarization

    SciTech Connect

    Han, Jaebeom; Mazack, Michael J. M.; Zhang, Peng; Truhlar, Donald G.; Gao, Jiali [Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street, SE, Minneapolis, Minnesota 55455-0431 (United States)] [Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street, SE, Minneapolis, Minnesota 55455-0431 (United States)

    2013-08-07

    A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensed-phase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen- and hydrogen-containing compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a three-point charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with three-point-charge potential) model, is suitable for modeling both gas-phase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 10{sup 6} self-consistent-field calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as across biological ion channels through membranes.

  13. Quantum mechanical force field for water with explicit electronic polarization

    PubMed Central

    Han, Jaebeom; Mazack, Michael J. M.; Zhang, Peng; Truhlar, Donald G.; Gao, Jiali

    2013-01-01

    A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensed-phase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen- and hydrogen-containing compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a three-point charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with three-point-charge potential) model, is suitable for modeling both gas-phase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 106 self-consistent-field calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as across biological ion channels through membranes. PMID:23927266

  14. 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.

  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. Electric field representation of pulsar intensity spectra

    E-print Network

    Mark Walker; Dan Stinebring

    2005-08-08

    Pulsar dynamic spectra exhibit high visibility fringes arising from interference between scattered radio waves. These fringes may be random or highly ordered patterns, depending on the nature of the scattering or refraction. Here we consider the possibility of decomposing pulsar dynamic spectra -- which are intensity measurements -- into their constituent scattered waves, i.e. electric field components. We describe an iterative method of achieving this decomposition and show how the algorithm performs on data from the pulsar B0834+06. The match between model and observations is good, although not formally acceptable as a representation of the data. Scattered wave components derived in this way are immediately useful for qualitative insights into the scattering geometry. With some further development this approach can be put to a variety of uses, including: imaging the scattering and refracting structures in the interstellar medium; interstellar interferometric imaging of pulsars at very high angular resolution; and mitigating pulse arrival time fluctuations due to interstellar scattering.

  17. Electro-optic polymer electric field sensor

    NASA Astrophysics Data System (ADS)

    Perry, D.; Chadderdon, S.; Gibson, Richard; Shreeve, B.; Selfridge, Richard H.; Schultz, Stephen M.; Wang, Wen C.; Forber, Richard; Luo, J.

    2011-04-01

    Modern electronics are often shielded with metallic packaging to protect them from harmful electromagnetic radiation. In order to determine the effectiveness of the electronic shielding, there is a need to perform non-intrusive measurements of the electric field within the shielding. The requirement to be non-intrusive requires the sensor to be all dielectric and the sensing area needs to be very small. The non-intrusive sensor is attained by coupling a slab of non-linear optical material to the surface of a D shaped optical fiber and is called a slab coupled optical fiber sensor (SCOS). The sensitivity of the SCOS is increased by using an organic electro-optic (EO) polymer.

  18. Silicone oil contamination and electrical contact resistance degradation of low-force gold contacts.

    SciTech Connect

    Dugger, Michael Thomas; Dickrell, Daniel John, III

    2006-02-01

    Hot-switched low-force gold electrical contact testing was performed using a nanomechanical test apparatus to ascertain the sensitivity of simulated microelectromechanical systems (MEMS) contact to silicone oil contamination. The observed cyclic contact resistance degradation was dependent on both closure rate and noncontact applied voltage. The decomposition of silicone oil from electrical arcing was hypothesized as the degradation mechanism.

  19. MIT OpenCourseWare: Fields, Forces, and Flows in Biological Systems

    NSDL National Science Digital Library

    Materials from this intriguingly titled Massachusetts Institute of Technology (MIT) course about biological systems are freely available to students, educators, and others through MIT's OpenCourseWare. The course covers a variety of topics including "conduction, diffusion, convection in electrolytes; fields in heterogeneous media; electrical double layers; Maxwell stress tensor and electrical forces in physiological systems; and fluid and sold continua: equations of motion useful for porous, hydrated biological tissues. Case studies considered include membrane transport; electrode interfaces; electrical, mechanical, and chemical transduction in tissues; electrophoretic and electroosmotic flows; diffusion/reaction; and ECG." This OpenCourseWare website provides downloadable notes for 25 lectures; seven downloadable assignments with solutions; and a pdf version of the final exam. The site links to an open, online discussion group for the course as well.

  20. 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.

  1. Ab initio and density functional studies of the structure, vibrational spectra and force field of trimethylsilane

    NASA Astrophysics Data System (ADS)

    McKean, D. C.

    1999-07-01

    Ab initio and density functional Q-M treatments have been carried out on trimethylsilane, SiHMe 3. The harmonic force fields so obtained are scaled to frequencies selected from four isotopic species, SiH(CH 3) 3, SiD(CH 3) 3, SiH(CD 3) 3 and SiD(CD 3) 3, some new infrared data for the d 0 species being employed. The region 250-200 cm -1 is reinterpreted in terms of the skeletal bending modes ?8( a1) and ?23( e), with ?8> ?23. Microwave information regarding the positions of the methyl torsions apparently conflicts with evidence both from the Q-M calculations and from infrared combination bands, which favour values less than 160 cm -1. All the scaled force fields give a poor fit to frequencies in the E symmetry species and nine force constants there are further refined. The spread of scale factors narrows when a larger basis set or density functional theory is employed, but widens slightly when electron correlation is introduced through an MP2 calculation. Valence interaction constants are reported for bond stretching motions and their significance assessed. Coriolis and centrifugal distortion constants are listed for the preferred B3LYP/6-311G** based force field. Electrical properties of the atoms and bonds are discussed.

  2. 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.

  3. DNA Electromagnetophoresis under the Condition of Magnetic Fields Perpendicular to Electric Fields

    Microsoft Academic Search

    Shun Ozawa; Daiki Kurosaka; Isao Yamamoto; Tadashi Takamasu

    2011-01-01

    The effects of magnetic fields on DNA electrophoresis have been studied under the condition of horizontal electric fields and vertical homogeneous magnetic fields. The migration course of DNA bends to the cross-product direction of the electric field and the magnetic field. The electrophoretic distance of the DNA differs between magnetic fields of 0 and 13 T. The decreases in the

  4. Current Practices in Field Force Automation: Decision Support and Information Management for the Field Force

    Microsoft Academic Search

    Gwen Trentham; Hans Jochen Scholl

    2008-01-01

    Abstract Inthe past, field operations have mostly been a stepchild,of information ,and ,communication technology,(ICT) enabled ,organizational ,overhaul and process re-design. Recently, increased technological,(mobile ,wirelessly ,connected) capability, economic necessity, and new external factors (such as the ,higher frequency of large-scale emergencies, for example, of the magnitude of hurricanes Katrina and Rita in the US) have raised interest in and ,commitment ,to

  5. The electric field gradient in heavy rare earth metals

    Microsoft Academic Search

    J. Pelzl; Fachbereich Physik

    1972-01-01

    Estimates of the electric field gradient in heavy rare earth metals have been evaluated from experimental hyperfine interaction data. In addition, the magnetic hyperfine fields are analyzed. In the metals the effective radial integrals r-3>4f of the magnetic and quadrupole hyperfine interaction are reduced at most by 10% compared with the free ion values. The electric field gradients due to

  6. Ambipolar edge electric field with energy dependence

    NASA Astrophysics Data System (ADS)

    Spizzo, G.; White, R. B.; Agostini, M.; Scarin, P.; Vianello, N.

    2012-10-01

    In a recent work,footnotetextG.Spizzo et al., Nucl. Fusion 52 (2012) 054015 it was shown that in the edge of toroidal confinement devices a sheath potential can arise when the ambipolarity constraint is applied to ion and electron motion in proximity of edge islands: in this way, the symmetry of the electric field is the same as the generating island. This was shown by analyzing ion and electron motion in presence of an electrostatic potential in a 8 ion Larmor radius layer next the wall, by means of the guiding-center code Orbit. Simulations show that there is a phase shift between the potential ``island'' and the magnetic island, with this difference ?pot-?island ?/2 for monoenergetic ions and electrons with bulk energy. Measurements in the RFX reversed field pinch show that in experiment the phase shift depends on collision frequency, the value ?/2 being its collisionless extrapolation. This suggests that there is an energy dependence during the potential formation. In this paper we will show initial results with the implementation of a full profile Monte Carlo operator, based on the energy scattering formula of Boozer-Kuo.footnotetextA. H. Boozer A.H. and G. Kuo-Petravic, Phys. Fluids 24 (1981) 851

  7. Role of random electric fields in relaxors

    PubMed Central

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

    2014-01-01

    PbZr1xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1xTixO3 (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

  8. Models between Barkhausen noise and coercive force of grain-oriented electrical steel

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Li, Changsheng; Cai, Ban; Perin, Deniz; Chukwuchekwa, Nkwachukwu

    2013-05-01

    Effect of ball scribing on relational models between coercive force and Barkhausen noise of conventional grain-oriented (CGO) and high-permeability grain-oriented (HGO) electrical steel was investigated. Models between two parameters in both CGO and HGO electrical steel were established. The results show that after ball scribing, Barkhausen noise of CGO steel increases (26% after 4mm's scribing at 1.0T) and that of HGO electrical steel apparently decreases (17.3% with 16mm's scribing at 1.0T), while coercive force of both CGO and HGO electrical steel decreases. Models between coercive force and magnetic Barkhausen noise after scribing were also constructed according to experimental data, and the experimental data curves were analyzed in the magnetizing process, which provides reference for correlation of different magnetic parameters.

  9. Computation of induced electric field for the sacral nerve activation

    NASA Astrophysics Data System (ADS)

    Hirata, Akimasa; Hattori, Junya; Laakso, Ilkka; Takagi, Airi; Shimada, Takuo

    2013-11-01

    The induced electric field/current in the sacral nerve by stimulation devices for the treatment of bladder overactivity is investigated. Implanted and transcutaneous electrode configurations are considered. The electric field induced in the sacral nerve by the implanted electrode is largely affected by its surrounding tissues, which is attributable to the variation in the input impedance of the electrode. In contrast, the electric field induced by the transcutaneous electrode is affected by the tissue conductivity and anatomical composition of the body. In addition, the electric field induced in the subcutaneous fat in close proximity of the electrode is comparable with the estimated threshold electric field for pain. These computational findings explain the clinically observed weakness and side effect of each configuration. For the transcutaneous stimulator, we suggest that the electrode contact area be increased to reduce the induced electric field in the subcutaneous fat.

  10. Spiking patterns of a hippocampus model in electric fields

    NASA Astrophysics Data System (ADS)

    Men, Cong; Wang, Jiang; Qin, Ying-Mei; Wei, Xi-Le; Che, Yan-Qiu; Deng, Bin

    2011-12-01

    We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.

  11. Electronic properties of ?-graphyne nanoribbons under the electric field effect

    NASA Astrophysics Data System (ADS)

    Jafarzadeh, H.; Roknabadi, M. R.; Shahtahmasebi, N.; Behdani, M.

    2015-03-01

    In this paper, we investigate the electronic structure of both armchair and zigzag ?-graphyne nanoribbons. We use a simple tight binding model to study the variation of the electronic band gap in ?-graphyne nanoribbon. The effects of ribbon width, transverse electric field and edge shape on the electronic structure have been studied. Our results show that in the absence of external electric field, zigzag ?-graphyne nanoribbons are semimetal and the electronic band gap in armchair ?-graphyne nanoribbon oscillates and decreases with ribbon's width. By applying an external electric field the band gap in the electronic structure of zigzag ?-graphyne nanoribbon opens and oscillates with ribbon width and electric field magnitude. Also the band gap of armchair ?-graphyne nanoribbon decreases in low electric field, but it has an oscillatory growth behavior for high strength of external electric field.

  12. 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.

  13. 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.

  14. 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

  15. Dipole and quadrupole forces exerted on atoms in laser fields: The nonperturbative approach

    NASA Astrophysics Data System (ADS)

    indelka, Milan; Moiseyev, Nimrod; Cederbaum, Lorenz S.

    2006-11-01

    Manipulation of cold atoms by lasers has so far been studied solely within the framework of the conventional dipole approximation, and the atom-light interaction has been treated using low order perturbation theory. Laser control of atomic motions has been ascribed exclusively to the corresponding light-induced dipole forces. In this work, we present a general theory to derive the potential experienced by an atom in a monochromatic laser field in a context analogous to the Born-Oppenheimer approximation for molecules in the field-free case. The formulation goes beyond the dipole approximation and gives rise to the field-atom coupling potential terms which so far have not been taken into consideration in theoretical or experimental studies. Contrary to conventional approaches, our method is based upon the many electron Floquet theory and remains valid also for high intensity laser fields (i.e., for a strongly nonperturbative atom-light interaction). As an illustration of the developed theory, we investigate the trapping of cold atoms in optical lattices. We find that for some atoms for specific laser parameters, despite the absence of the dipole force, the laser trapping is still possible due to the electric quadrupole forces. Namely, we show that by using realistic laser parameters one can form a quadrupole optical lattice which is sufficiently strong to trap Ca and Na atoms.

  16. Scattering Polarization in the Presence of Magnetic and Electric Fields

    E-print Network

    Yee Yee Oo; M. Sampoorna; K. N. Nagendra; Sharath Ananthamurthy; G. Ramachandran

    2007-02-12

    The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Limiting cases of scattering under Zeeman effect and Hanle effect in weak magnetic fields are discussed. The theory is general enough to handle scattering in intermediate magnetic fields (Hanle-Zeeman effect) and for arbitrary orientation of magnetic field. The quadrupolar electric field produces asymmetric line shifts and causes interesting level-crossing phenomena either in the absence of an ambient magnetic field or in its presence. It is shown that the quadrupolar electric field produces an additional depolarization in the $Q/I$ profiles and rotation of the plane of polarization in the $U/I$ profile over and above that arising from magnetic field itself. This characteristic may have a diagnostic potential to detect steady state and time varying electric fields that surround radiating atoms in Solar atmospheric layers.

  17. Surface electric fields for North America during historical geomagnetic storms

    USGS Publications Warehouse

    Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

    2013-01-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic stormsthe 1989 Quebec storm and the 2003 Halloween storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  18. Lost at Sea: Hurricane Force Wind Fields and the North Pacific Ocean Environment

    E-print Network

    Lost at Sea: Hurricane Force Wind Fields and the North Pacific Ocean Environment 1 Unidata Policy Lost at Sea: Hurricane Force Wind Fields and the North Pacific Ocean Environment 2 Hurricane Force (HF to help raise awareness of the hazards created by hurricane force winds in extratropical cyclones

  19. A Comparison Between Nonlinear Force-Free Field and Potential Field Models Using Full-Disk SDO/HMI Magnetogram

    NASA Astrophysics Data System (ADS)

    Tadesse, Tilaye; Wiegelmann, T.; MacNeice, P. J.; Inhester, B.; Olson, K.; Pevtsov, A.

    2014-03-01

    Measurements of magnetic fields and electric currents in the pre-eruptive corona are crucial to the study of solar eruptive phenomena, like flares and coronal mass ejections (CMEs). However, spectro-polarimetric measurements of certain photospheric lines permit a determination of the vector magnetic field only at the photosphere. Therefore, there is considerable interest in accurate modeling of the solar coronal magnetic field using photospheric vector magnetograms as boundary data. In this work, we model the coronal magnetic field above multiple active regions with the help of a potential field and a nonlinear force-free field (NLFFF) extrapolation code over the full solar disk using Helioseismic and Magnetic Imager (SDO/HMI) data as boundary conditions. We compare projections of the resulting magnetic field lines with full-disk coronal images from the Atmospheric Imaging Assembly (SDO/AIA) for both models. This study has found that the NLFFF model reconstructs the magnetic configuration closer to observation than the potential field model for full-disk magnetic field extrapolation. We conclude that many of the trans-equatorial loops connecting the two solar hemispheres are current-free.

  20. Far-field mapping of the longitudinal magnetic and electric optical fields C. Ecoffey, T. Grosjean

    E-print Network

    Boyer, Edmond

    Far-field mapping of the longitudinal magnetic and electric optical fields C. Ecoffey, T. Grosjean of the longitudinal magnetic and electric optical fields with a standard scanning microscope that involves a high filter aimed at transmitting selectively to the detector the signal from the magnetic or electric

  1. A Bidirectional Brain-Machine Interface Algorithm That Approximates Arbitrary Force-Fields

    PubMed Central

    Semprini, Marianna; Mussa-Ivaldi, Ferdinando A.; Panzeri, Stefano

    2014-01-01

    We examine bidirectional brain-machine interfaces that control external devices in a closed loop by decoding motor cortical activity to command the device and by encoding the state of the device by delivering electrical stimuli to sensory areas. Although it is possible to design this artificial sensory-motor interaction while maintaining two independent channels of communication, here we propose a rule that closes the loop between flows of sensory and motor information in a way that approximates a desired dynamical policy expressed as a field of forces acting upon the controlled external device. We previously developed a first implementation of this approach based on linear decoding of neural activity recorded from the motor cortex into a set of forces (a force field) applied to a point mass, and on encoding of position of the point mass into patterns of electrical stimuli delivered to somatosensory areas. However, this previous algorithm had the limitation that it only worked in situations when the position-to-force map to be implemented is invertible. Here we overcome this limitation by developing a new non-linear form of the bidirectional interface that can approximate a virtually unlimited family of continuous fields. The new algorithm bases both the encoding of position information and the decoding of motor cortical activity on an explicit map between spike trains and the state space of the device computed with Multi-Dimensional-Scaling. We present a detailed computational analysis of the performance of the interface and a validation of its robustness by using synthetic neural responses in a simulated sensory-motor loop. PMID:24626393

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

    SciTech Connect

    Muniz, C.R., E-mail: celiomuniz@yahoo.com [Grupo de Fsica Terica (GFT), Universidade Estadual do Cear, UECE-FECLI, Iguatu, Cear (Brazil); Bezerra, V.B., E-mail: valdir@ufpb.br [Departamento de Fsica, Universidade Federal da Paraba, Caixa Postal 5008, CEP 58051-970, Joo Pessoa, PB (Brazil)

    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 Greens 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.

  3. Nonlinear gravitational self-force: Field outside a small body

    NASA Astrophysics Data System (ADS)

    Pound, Adam

    2012-10-01

    A small extended body moving through an external spacetime g?? creates a metric perturbation h??, which forces the body away from geodesic motion in g??. The foundations of this effect, called the gravitational self-force, are now well established, but concrete results have mostly been limited to linear order. Accurately modeling the dynamics of compact binaries requires proceeding to nonlinear orders. To that end, I show how to obtain the metric perturbation outside the body at all orders in a class of generalized wave gauges. In a small buffer region surrounding the body, the form of the perturbation can be found analytically as an expansion for small distances r from a representative worldline. Given only a specification of the bodys multipole moments, the field obtained in the buffer region suffices to find the metric everywhere outside the body via a numerical puncture scheme. Following this procedure at first and second order, I calculate the field in the buffer region around an arbitrarily structured compact body at sufficiently high order in r to numerically implement a second-order puncture scheme, including effects of the bodys spin. I also define nth-order (local) generalizations of the Detweiler-Whiting singular and regular fields and show that in a certain sense, the body can be viewed as a skeleton of multipole moments.

  4. Structural explanation of the rheology of a colloidal suspension under high dc electric fields.

    PubMed

    Espn, Manuel J; Delgado, Angel V; Gonzlez-Caballero, Fernando

    2006-04-01

    In this work we describe the electrorheology of suspensions consisting of hematite (alpha-Fe2O3) particles dispersed in silicone oil in the presence of large dc electric fields. If an electric field pulse is applied to the systems, it is possible to estimate the time that the electrorheological (ER) fluid takes to reach its final microstructure in the presence of the field. Our results indicate that response times of several seconds are typical, and that this time decreases with the field strength. Conventional shear-rate sweeps indicate the existence of a well-defined dynamic yield stress and a shear-thinning behavior. Interestingly, both the yield stress and the shear-thinning slope alpha [relating the viscosity, eta, and the shear rate, .gamma, as eta=alphagamma(.-b) + eta (infinity)] show a linear dependence on the field strength, E, in disagreement with the E2 dependence often reported. This deviation is associated with changes in the conductivity of the dispersion medium with the field strength. A simple calculation of the interactions present in our ER fluid demonstrates that the ER behavior is entirely controlled by hydrodynamic (proportional to .gamma) and electrical forces (proportional to E). This is confirmed by the collapse of all experimental results in a single master curve when the relative viscosity is plotted against the ratio .gamma/E. Careful attention has been paid in this work to the microstructure of the suspensions in the presence of both shear and electric fields simultaneously: the particles gather themselves on the walls of the electrorheological measurement cell, forming aggregates with cylindrical symmetry, shaped as rings or lamellas of solids. The electric field induced increase in viscosity is the consequence of the balance between two actions: that of the electric field, tending to keep particles together, and that of the shear field, forcing the flow of the liquid phase in the regions between rings or between rings and walls. PMID:16711805

  5. Faint electric dynamic forces in atmosphere is a possible precursor for a Seismic events phenomena

    NASA Astrophysics Data System (ADS)

    Grigoropoulos, K. N.; Nastos, P. T.; Tselentis, G.; Saragas, E.; Ifantis, A.

    2009-04-01

    The objective of this paper is to monitor the propagation of faint electric forces (D.C. potentials) in Athens' atmosphere before an earthquake. Many authors refer to radio emissions (ELF,HF,VLF,UHF ) before an event. Several other researches have been done with ICE (Instrument Champ Electrique), measurement of quasi-continuous electric fields and electric components of waves, from DC up to 3.5 MHz, or IMSC (Measuring the magnetic components of waves), for measuring magnetic field from a few Hz up to 18 kHz. More studies, within the last twenty years are correlated also with monitoring underground electromagnetic fields from different countries, but few are dealing with D.C.field. The concept is that, the aerosols are injected into the lower atmosphere due to intensifying soil gas content during the increase of seismic activity. At our station in Athens, a continuous monitoring has been conducted by three D.C.detectors which follow the ionosphere variations of the electric field daily, for the years 2007-2008. Multiple antennas have been posted and tested up to the height of thirty meters above the ground. The faint electro potentials received, had been continuously registered by two electrometers. A cross over study of aerosols simulation has been simultaneously done with photo detectors. For this purpose an array of four photo diodes, posted in infrared and visible band in function, and was connected to electro meters too. Several approaches have been taken in past years by researchers attempting to correlate changes in geophysical parameters with earthquake phenomena. In particular, many works examine possible connections of Geoelectric Field (Long and Sort Term Geoelectric Potential) variations to seismic activity and their possible use as precursors of seismic events. Long Term Geoelectric Potential (LTGP) acquisition data consists of potential difference measured between pairs of electrodes placed in the ground at specific location and distance. The electric field is continuously monitored, usually in two perpendicular directions (e.g. N-S and E-W), by two pairs of electrodes, each corresponding to a separate channel. Here we examine such possible correlations between recorded Long Term Geoelectric Potential (LTGP) acquisition data and the seismic activity observed during the same period. In collaboration with the University of Athens, Laboratory of Climatology and Atmospheric Environment and according their given data, we avoided measurements during periods of rain, snow, storms, lightning or extreme variations of temperature and atmospheric pressure. During these observations we observed an enormous variation in the voltage signals and several potential peaks were registered before the quakes in both detectors and photodiodes. The variations noted before the events, become with an optimum peak between four hours to fourteen days. All cases are related with eight earthquakes, registered in the southern part of Greece. Our conclusions demonstrate that charged aerosol emissions in the atmosphere are possible to influence and increase electro potentials before an earthquake event, under certain atmospheric conditions.

  6. Dielectrophoresis Force and Deflection of Dielectric Elastomers and Blends under AC field

    NASA Astrophysics Data System (ADS)

    Kunanuraksapong, Ruksapong; Sirivat, Anuvat

    2010-03-01

    The effects of frequency and amplitude of AC electric field on the deflection distance and the dielectrophoresis force of the of acrylic elastomers (AR71), styrene copolymers (SAR and SBR), and blends with poly(p-phenylene) (AR71:PPP and SAR:PPP) were investigated. The dielectrophoresis forces of the dielectric elastomers and blends were measured by a vertical cantilever under various frequencies (0.3-60 Hz) and at the amplitudes of 200, 300, 500, 600 and 800 Vpp/mm. In addition, the effect of thickness of specimens and the particle concentration on the dielectrophoresis force were studied. Poly(p-phenylene) particles were added into AR71 and SAR with particle concentrations of 5, 10, 15 and 20 vol%. The forces were calculated from the non-linear deflection theory of the cantilever. The dielectrophoresis forces and deflection distances of the dielectric elastomers and blends generally increase with increasing amplitude but slightly decrease with increasing frequency, and they dramatically drop at the cut-off frequency. The cutoff frequencies are 12.0, 1.5 and 1.5 Hz for AR71, SAR, and SBR, at E = 800 Vpp/mm, respectively.

  7. Influence of polyelectrolyte shape on its sedimentation behavior: effect of relaxation electric field.

    PubMed

    Yeh, Pin-Hua; Hsu, Jyh-Ping; Tseng, Shiojenn

    2014-11-28

    The sedimentation of an isolated, charged polyelectrolyte (PE) subjected to an applied field is modeled theoretically, taking into account the variation of its shape. In particular, the effects of double-layer relaxation, effective charge density, and strength of the induced relaxation electric field are examined. We show that the interaction of these effects yields complex and interesting sedimentation behaviors. For example, the behavior of the electric force acting on a loosely structured PE can be different from that on a compactly structured one; the former is dominated mainly by the convective fluid flow. For thick double layers, electric force has a local maximum as the Reynolds number varies, but tends to increase monotonically with increasing Reynolds number if the layer is thin. The drag factor is found to behave differently from literature results. The shape of a PE significantly influences its sedimentation behavior by affecting the amount of counterions attracted to its interior and the associated local electric field. Interestingly, a more stretched PE has a higher effective charge density but experiences a weaker electric force. PMID:25283952

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

    SciTech Connect

    Belhi, Memdouh; Domingo, Pascale; Vervisch, Pierre [CORIA - CNRS and INSA de Rouen, Technopole du Madrillet, BP 8, 76801 Saint-Etienne-du-Rouvray (France)

    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)

  9. 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.

  10. Transferability of coarse-grained force fields: the polymer case.

    PubMed

    Carbone, Paola; Varzaneh, Hossein Ali Karimi; Chen, Xiaoyu; Mller-Plathe, Florian

    2008-02-14

    A key question for all coarse-graining methodologies is the degree of transferability of the resulting force field between various systems and thermodynamic conditions. Here we present a detailed study of the transferability over different thermodynamic states of a coarse-grained (CG) force field developed using the iterative Boltzmann inversion method. The force field is optimized against distribution functions obtained from atomistic simulations. We analyze the polymer case by investigating the bulk of polystyrene and polyamide-6,6 whose coarse-grained models differ in the chain length and in the number of atoms lumped in one bead. The effect of temperature and pressure on static, dynamic, and thermodynamic properties is tested by comparing systematically the coarse-grain results with the atomistic ones. We find that the CG model describing the polystyrene is transferable only in a narrow range of temperature and it fails in describing the change of the bulk density when temperature is 80 K lower than the optimization one. Moreover the calculation of the self-diffusion coefficient shows that the CG model is characterized by a faster dynamics than the atomistic one and that it overestimates the isothermal compressibility. On the contrary, the polyamide-6,6 CG model turns out to be fully transferable between different thermodynamic conditions. The transferability is checked by changing either the temperature or the pressure of the simulation. We find that, in this case, the CG model is able to follow all the intra- and interstructural rearrangements caused by the temperature changes. In addition, while at low temperature the difference between the CG and atomistic dynamics is remarkable due to the presence of hydrogen bonds in the atomistic systems, for high temperatures, the speedup of the CG dynamics is strongly reduced, leading to a CG diffusion coefficient only six times bigger than the atomistic one. Moreover, the isothermal compressibility calculated at different temperatures agrees very well with the experimental one. We find that the polymer chain length does not affect the transferability of the force field and we attribute such transferability mainly to the finer model used in describing the polyamide-6,6 than the polystyrene. PMID:18282071

  11. The Anharmonic Force Field of BeH2 Revisited

    NASA Technical Reports Server (NTRS)

    Martin, Jan M. L.; Lee, Timothy J.

    2003-01-01

    The anharmonic force field of BeH2 has been calculated near the basis set and n-particle space limits. The computed antisymmetric stretch frequencies of BeH2 and BeD2 are in excellent agreement with recent high-resolution gas-phase measurements. The agreement between theory and experiment for the other spectroscopic constants is also excellent, except for omega(sub 3) and X(sub 33) for BeH2 and G(sub 22) for BeD2. It is concluded that further experimental work is needed in order to resolve these discrepancies.

  12. Electric Fields Caused by Blood Flow Modulate Vascular Endothelial Electrophysiology and Nitric Oxide Production

    PubMed Central

    Trivedi, Darshan P.; Hallock, Kevin J.; Bergethon, Peter R.

    2012-01-01

    Endothelial cells are exposed to a ubiquitous, yet unexamined electrical force caused by blood flow: the electrokinetic vascular streaming potential (EVSP). In this study, the hypothesis that extremely low frequency (ELF) electric fields parameterized by the EVSP have significant biological effects on endothelial cell properties was studied by measuring membrane potential and nitric oxide production under ELF stimulation between 02 Hz and 06.67 volts per meter. Using membrane potential and nitric oxide sensitive fluorescent dyes, bovine aortic endothelial cells (BAECs) in culture were studied in the presence and absence of EVSP-modeled electric fields. The transmembrane potential of BAECs was shown to depolarize between 17 mV with a strong dependency on both the magnitude and frequency of the isolated ELF field. The findings also support a field interaction with a frequency-dependent tuning curve. The ELF field complexly modulates the nitric oxide response to adenosine triphosphate stimulation with potentiation seen with up to a seven-fold increase. This potentiation was also frequency and magnitude dependent. An early logarithmic phase of NO production is enhanced in a field strength- dependent manner, but the ELF field does not modify a later exponential phase. This study shows that using electric fields on the order of those generated by blood flow influences the essential biology of endothelial cells. The inclusion of ELF electric fields in the paradigm of vascular biology may create novel opportunities for advancing both the understanding and therapies for treatment of vascular diseases. PMID:22674251

  13. A Single Universal Force Field Can Uniquely Orient Non-Symmetric Parts

    E-print Network

    Richardson, David

    grippers, conveyor belts, or vibratory bowl feeders, these devices generate force fields in which the parts with trans- versely vibrating plates. The flexibility and dexter- ity that programmable force fields offer

  14. 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.

  15. Crystalline electric fields in mixed valent systems

    SciTech Connect

    Shapiro, S.M.

    1980-01-01

    The inelastic neutron studies of rare-earth-based mixed valent systems have all shown remarkably similar results: a broad quasielastic line with half width on the order of 10 MeV. This width exhibits a strong temperature dependence in those systems which undergo a valence transition and is only weakly temperature dependent in those systems which show no transition. A surprising result was the absence of crystalline electric field (CEF) excitations. Recent measurements on the alloy Ce/sub .9-x/La/sub x/Th/sub .1/ have revealed the existence of CEF excitations. For x = 0, the valence transition is strongly first order and occurs near T/sub 0/ approx. 150 K. The inelastic spectra exhibit the typical broad quasielastic scattering. As x increases, T/sub 0/ decreases due to internal pressure effects, and a well-defined, but broad, excitation appears near E = 15 MeV. This is interpreted as a CEF excitation between the GAMMA/sub 7/ and GAMMA/sub 8/ levels of the Ce/sup 3/+ ion. For x = 0.40, the valence transition is almost completely suppressed and the excitation becomes even sharper.

  16. Electric field breakdown in single molecule junctions.

    PubMed

    Li, Haixing; Su, Timothy A; Zhang, Vivian; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha

    2015-04-22

    Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ?1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level. PMID:25675085

  17. Substorm electric fields in the earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Cattell, C. A.; Mozer, F. S.

    1984-01-01

    A survey has been made of all the electric field data from the University of California, Berkeley, double probe experiment on ISEE-1 (apogee approximately 22 earth radii) during 1980 when the satellite was in the magnetotail. This study was restricted to the 74 events where E cross B flows could be calculated and were equal to or greater than 100 km/s. Substorm times were determined by examining the Ae index for peaks equal to or greater than 250 gamma. In association with substorms, approximately 70 percent of the flows were earthward, and approximately 20 percent had a signature called 'near satellite reconnection' (first described by Nishida et al. (1983) of tailward flow followed by earthward flow which can be interpreted in terms of a model where the x-line forms earthward of the satellite and subsequently propagates tailward of X(GSM) = -21 earth radii and within the absolute value of Y(GSM) equal to or less than 4.5 earth radii. These data suggest that the near earth x-line usually forms tailward of X(GSM) approximately -20 earth radii.

  18. Role of electrical field in quantum Hall effect of graphene

    NASA Astrophysics Data System (ADS)

    Luo, Ji

    2013-01-01

    The ballistic motion of carriers of graphene in an orthogonal electromagnetic field is investigated to explain quantum Hall effect of graphene under experimental conditions. With the electrical field, all electronic eigen-states have the same expectation value of the velocity operator, or classically, all carriers move in cycloid-like curves with the same average velocity. This velocity is the origin of the Hall conductance and its magnitude is just appropriate so that the quantized Hall conductance is exactly independent of the external field. Electrical field changes each Landau level into a bundle of energies. Hall conductance plateaus occur in small fields as bundle gaps exist and are destroyed in intermediate fields as bundles overlap. As the electrical field tends to the critical point, all bundles have the same width, and bundle gaps increase to infinity rapidly. As a result, saturation of the Hall conductance may be observed. Electrical field thus demonstrates nonlinear effects on the Hall conductance.

  19. Biological Effects of Electrical and Magnetic Fields: Is It Real?

    E-print Network

    Durham, M. O.

    The hazardous effect of electric and magnetic fields on biological systems is the subject of considerable debate. Traditional methods have failed to provide a correlation between the fields and biological effects. A model is presented that solves...

  20. 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.

  1. Kinetic theory of runaway breakdown in inhomogeneous thundercloud electric field

    NASA Astrophysics Data System (ADS)

    Gurevich, A. V.; Carlson, H. C.; Medvedev, Yu. V.; Zybin, K. P.

    2001-04-01

    Kinetic theory of runaway breakdown in inhomogeneous thunderstorm electric field is developed. The kinetic equation, boundary and initial conditions are formulated. Spectrum of X-ray emission generated by runaway electrons is calculated. It has quite a specific form: a sharp maximum at energies 50-60 keV and a rapid fall both to the smaller and higher energies. The intensity of the emission is growing effectively with the relation Em/ Ec (of maximal electric field Em to critical field Ec) and falling down sharply with the distance near the point z where electric field E( z) is equal to critical field Ec.

  2. Anisotropy of magnetic emulsions induced by magnetic and electric fields

    E-print Network

    Yury I. Dikansky; Alexander N. Tyatyushkin; Arthur R. Zakinyan

    2011-09-10

    The anisotropy of magnetic emulsions induced by simultaneously acting electric and magnetic fields is theoretically and experimentally investigated. Due to the anisotropy, the electric conductivity and magnetic permeability of a magnetic emulsion are no longer scalar coefficients, but are tensors. The electric conductivity and magnetic permeability tensors of sufficiently diluted emulsions in sufficiently weak electric and magnetic fields are found as functions of the electric and magnetic intensity vectors. The theoretically predicted induced anisotropy was verified experimentally. The experimental data are analyzed and compared with theoretical predictions. The results of the analysis and comparison are discussed.

  3. Decoherence and coherence in gravitational, electric and strong nuclear fields

    E-print Network

    P. R. Silva

    2010-10-25

    Inspired in the work of Erich Joos which appreciated the role played by matter in making the decoherence of the gravitational field, we developed an alternative way of treating the former problem. Besides this, we used the alternative approach to examine the decoherence of the electric field performed by the conduction electrons in metals. As a counterpoint, we studied the coherence of the electric color field inside nucleons, which renders the strong field a totally quantum character.

  4. 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.

  5. Exposure assessment for power frequency electric and magnetic fields.

    PubMed

    Bracken, T D

    1993-04-01

    Over the past decade considerable data have been collected on electric and magnetic fields in occupational environments. These data have taken the form of area measurements, source characterizations, and personal exposure measurements. Occupational EMF levels are highly variable in space and time. Exposures associated with these fields exhibit similar large variations during a day, between days, and between individuals within a group. The distribution of exposure measures is skewed over several decades with only a few values occurring at the maximum field levels. The skewness of exposure measures implies that large sample sizes may be required for assessments and that multiple statistical descriptors are preferred to describe individual and group exposures. Except for the relatively few occupational settings where high voltage sources are prevalent, electric fields encountered in the workplace are probably similar to residential exposures. Consequently, high electric field exposures are essentially limited to utility environments and occupations. Within the electric utility industry, it is definitely possible to identify occupations with high electric field exposures relative to those of office workers or other groups. The highly exposed utility occupations are linemen, substation operators, and utility electricians. The distribution of electric field exposures in the utility worker population is very skewed even within a given occupation. As with electric fields, magnetic fields in the workplace appear to be comparable with residential levels, unless a clearly defined high-current source is present. Since high-current sources are more prevalent than high-voltage sources, environments with relatively high magnetic field exposures encompass a more diverse set of occupations than do those with high electric fields. Within the electric utility industry, it is possible to identify occupational environments with high magnetic field exposure relative to the office environment. Utility job categories with the highest exposures are generation facility workers, substation operators, utility linemen, and utility electricians. There are also higher exposures among traditional "electrical worker" job categories. Outside the electrical utility industry, potential sources of high occupational magnetic field exposures at ELF are induction furnaces, welding machines, electrical transportation systems, and electrical distribution vaults. However, the use of low power electrical equipment such as small motors in close proximity to workers and possibly for long periods of time could also lead to high exposure situations. Handheld survey instruments are available to perform area measurements of electric and magnetic fields at power frequencies but not aat all frequencies within the ELF range. Sophisticated personal computer-based instruments are available to characterize areas and sources across the entire frequency range.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8480632

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

    PubMed

    Lpez-Garca, Jos Juan; Horno, Jos; 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

  7. Reception and learning of electric fields in bees

    PubMed Central

    Greggers, Uwe; Koch, Gesche; Schmidt, Viola; Drr, Aron; Floriou-Servou, Amalia; Piepenbrock, David; Gpfert, 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

  8. EHD behavior of nitrogen bubbles in DC electric fields

    SciTech Connect

    Chen, F.; Peng, Y.; Song, Y.Z.; Chen, M. [Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2007-10-15

    The deformation of nitrogen bubbles injected into transformer oil with various DC electric fields was studied experimentally and theoretically. The bubble deformation was visualized by a high speed camera. The major axis of the bubble was elongated along the direction parallel to the electric field, with the elongation increasing as the electric field strength was raised. The electrical Weber number (We) was used to correlate the electric field strength and the dielectric permittivity of the working fluid to the bubble relative aspect ratio (AR{sub e}/AR{sub 0}). The experimental results show that the relative aspect ratio increases with increasing We. The electric stresses were calculated on an actual bubble shape including the electrostriction stresses to analyze the bubble elongation. (author)

  9. Electrical Field Effects in Phthalocyanine Film Growth by Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Banks, Curtis E.; Zhu, Shen; Frazier, Donald O.; Penn, Benjamin; Abdeldayem, Hossin; Hicks, Roslin; Sarkisov, Sergey

    1999-01-01

    Phthalocyanine, an organic material, is a very good candidate for non-linear optical application, such as high-speed switching and optical storage devices. Phthalocyanine films have been synthesized by vapor deposition on quartz substrates. Some substrates were coated with a very thin gold film for introducing electrical field. These films have been characterized by surface morphology, material structure, chemical and thermal stability, non-linear optical parameters, and electrical behaviors. The films have excellent chemical and optical stability. However, the surface of these films grown without electrical field shows flower-like morphology. When films are deposited under an electrical field ( an aligned structure is revealed on the surface. A comparison of the optical and electrical properties and the growth mechanism for these films grown with and without an electrical field will be discussed.

  10. Relativistic ponderomotive forces in the field of intense laser radiation

    NASA Astrophysics Data System (ADS)

    Castillo, A. J.; Milant'ev, V. P.

    2014-09-01

    The motion of a relativistic charged particle in the presence of the field of high-power laser radiation represented in the form of a Gaussian beam of arbitrary mode is analyzed. The vector potential of the radiation field is expanded in terms of a small parameter (the ratio of the wavelength to the Gaussian beam waist). A specific feature of averaging with respect to the phases of the high-mode Gaussian beams is demonstrated. The averaged equations for the motion of particle and a general expression for the ponderomotive relativistic force for the circularly polarized radiation are derived. It is demonstrated that relativistic effects suppress the averaged action of high-power laser radiation on the particle.

  11. On the force between an electrically polarizable atom and a magnetically polarizable one

    NASA Astrophysics Data System (ADS)

    Farina, C.; Santos, F. C.; Tort, A. C.

    2002-03-01

    In this paper we re-obtain the retarded as well as the non-retarded force between an electrically polarizable atom and a magnetically polarizable one in a very simple and suggestive way. Using a perturbative approach, we show that while the retarded force between these two atoms is proportional to 1/r8, the non-retarded force is proportional to 1/r5, in agreement with Feinberg and Sucher's result (Feinberg G and Sucher J 1970 Phys. Rev. A 2 2395). This rather surprising result should be contrasted with the 1/r7 behaviour of the London-van der Waals force between two electrically polarizable atoms. Our approach permits us to give a physical interpretation for such a result.

  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. On the controllability of the Vlasov-Poisson system in the presence of external force fields

    E-print Network

    Paris-Sud XI, Universit de

    On the controllability of the Vlasov-Poisson system in the presence of external force fields Olivier Glass Daniel Han-Kwan May 3, 2011 Abstract In this work, we are interested in the controllability of Vlasov-Poisson systems in the presence of an external force field (namely a bounded force field

  14. Quantum Chemistry Based Force Field for Simulations of HMX Grant D. Smith* and Rishikesh K. Bharadwaj

    E-print Network

    Utah, University of

    Quantum Chemistry Based Force Field for Simulations of HMX Grant D. Smith* and Rishikesh K kcal/mol. The force field, parametrized to reproduce the quantum chemistry geometries and energies the quantum chemistry based force field accurately reproduced the gas-phase structure of DMNA as determined

  15. 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...

  16. Effects of Radial Electric Fields on ICRF Waves

    SciTech Connect

    C.K. Phillips; J.C. Hosea; M. Ono; J.R. Wilson

    2001-06-18

    Equilibrium considerations infer that large localized radial electric fields are associated with internal transport barrier structures in tokamaks and other toroidal magnetic confinement configurations. In this paper, the effects of an equilibrium electric field on fast magnetosonic wave propagation are considered in the context of a cold plasma model.

  17. Simulation of electric field effects in premixed methane flames

    Microsoft Academic Search

    T. Pedersen; R. C. Brown

    1993-01-01

    The objective of this study is to predict the effect of electric fields on the ionic structure of one-dimensional methane flames. An understanding of this phenomenon could be important in attempts to control blowoff limits, flame speed, and soot formation by the application of electric fields. The chemical kinetic mechanism devised for this study combines existing methane oxidation mechanisms with

  18. Robotic Electrolocation: Active Underwater Target Localization with Electric Fields

    Microsoft Academic Search

    James R. Solberg; Kevin M. Lynch; Malcolm A. Maciver

    2007-01-01

    We explore the capabilities of a robot designed to locate objects underwater through active movement of an electric field emitter and sensor apparatus. The robot is inspired by the biological phenomenon of active electrolocation, a sensing strategy found in two groups of freshwater fishes known to emit weak electric fields for target localization and communication. We characterize the performance of

  19. Reconfigurable assemblies of Janus rods in AC electric fields.

    PubMed

    Chaudhary, Kundan; Jurez, Jaime J; Chen, Qian; Granick, Steve; Lewis, Jennifer A

    2014-03-01

    We investigate the electric field-induced assembly of Janus colloids composed of silica rods patterned with gold patches in both side- and tip-coated motifs. These shape and chemically anisotropic particles assemble into reconfigurable chains, whose structure depends on patch location, AC electric field strength, and frequency. PMID:24652478

  20. Electric and Magnetic Field control of Exchange Bias

    Microsoft Academic Search

    Christian Binek

    2007-01-01

    Exchange bias (EB) and its accompanying training effect are fundamental interface phenomena in coupled magnetic thin films with significant impact in spintronic applications. Here we report on the electric field control of the EB in innovative antiferromagnetic (AF)\\/ferromagnetic (FM) heterostructures and the magnetic field control of the EB training effect in exchange coupled all FM bilayer systems. Electric control of

  1. 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...

  2. Electric Field Intensity of the Lightning Return Stroke

    Microsoft Academic Search

    Martin A. Uman; D. Kenneth McLain; Richard J. Fisher; E. Philip Krider

    1973-01-01

    From an examination of about 1000 electric field wave forms produced by lightning return strokes in 16 storms at distances between 20 and 100 km from an observation site at the Kennedy Space Center, Florida, a typical return stroke current wave form is derived. For this current wave form, the electric field intensity at distances between 0.5 and 100 km

  3. Electric field calculations with the boundary element method

    Microsoft Academic Search

    S. S. Bamji; A. T. Bulinski; K. M. Prasad

    1993-01-01

    The boundary element method is used to calculate the electric field profiles at needle tips commonly used for electrical treeing tests. Field distributions are also obtained for polyethylene containing a space charge, at the needle tip, and are compared with the values previously obtained by the finite difference method

  4. An auroral effect on the fair weather electric field

    Microsoft Academic Search

    L. C. Hale; C. L. Croskey

    1979-01-01

    Evidence is presented for coupling between the upper and lower atmosphere by means of the shorting out of the vertical mesospheric electric field by auroral radiation, which causes a transfer of mesospheric potential to the lower atmosphere. Measurements were made by an electric field antenna which was part of a parachute-borne payload, launched by rocket from near Fairbanks, Alaska. Data

  5. Developing Force Fields from the Microscopic Structure of Solutions.

    PubMed

    Ploetz, Elizabeth A; Bentenitis, Nikolaos; Smith, Paul E

    2010-03-25

    We have been developing force fields designed for the eventual simulation of peptides and proteins using the Kirkwood-Buff (KB) theory of solutions as a guide. KB theory provides exact information on the relative distributions for each species present in solution. This information can also be obtained from computer simulations. Hence, one can use KB theory to help test and modify the parameters commonly used in biomolecular studies. A series of small molecule force fields representative of the fragments found in peptides and proteins have been developed. Since this approach is guided by the KB theory, our results provide a reasonable balance in the interactions between self-association of solutes and solute solvation. Here, we present our progress to date. In addition, our investigations have provided a wealth of data concerning the properties of solution mixtures, which is also summarized. Specific examples of the properties of aromatic (benzene, phenol, p-cresol) and sulfur compounds (methanethiol, dimethylsulfide, dimethyldisulfide) and their mixtures with methanol or toluene are provided as an illustration of this kind of approach. PMID:20161692

  6. The Effect of Electric Field Magnitude and Frequency on Caenorhabditis Elegans

    NASA Astrophysics Data System (ADS)

    Chuang, Han-Sheng; Raizen, David; Dabbish, Nooreen; Lamb, Annesai; Bau, Haim

    2010-11-01

    Low magnitude, DC electric fields have been used to guide the motion of the wild-type nematode (worm) Caenorhabditis elegans. Low intensity AC fields (<100 Hz) can even be utilized to localize the worm. However, the worm appears oblivious to the electric field as the frequency is higher than several hundreds of Hz. In contrast, in the presence of nonuniform, moderate AC fields (15--50 kV/m) at higher frequencies (>10 kHz), the worm is restrained by the field's maximum. This is the first demonstration of dielectrophoretic trapping of an animal. With certain electrode arrangements, only the worm's tail is immobilized, and the worm's swimming motion does not appear to be affected by the trapping force. Similar trapping conditions with transitional frequencies (10--100 kHz) can cause paralysis. The worm is (irreversibly) paralyzed with lower frequencies (e.g. 45 kV/m, 2 kHz) or electrified with higher electric field intensities (e.g. 10 Hz, 70 kV/m). We report on the results of a parametric study that delineates the effect of the electric field on the worm as a function of the worm's stage and the electric field intensity and frequency. Worm-dielectrophoresis can be used, among other things, to sort worms by size, to temporarily immobilize worms to enable their characterization and study, and to use worms to induce fluid motion and mixing.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  8. Why the OPLS-AA force field cannot produce the ?-hairpin structure of H1 peptide in solution when comparing with the GROMOS 43A1 force field?

    PubMed

    Cao, Zanxia; Liu, Lei; Wang, Jihua

    2011-12-01

    The optimal combination of force field and water model is an essential problem that is able to increase molecular dynamics simulation quality for different types of proteins and peptides. In this work, an attempt has been made to explore the problem by studying H1 peptide using four different models based on different force fields, water models and electrostatic schemes. The driving force for H1 peptide conformation transition and the reason why the OPLS-AA force field cannot produce the ?-hairpin structure of H1 peptide in solution while the GROMOS 43A1 force field can do were investigated by temperature replica exchange molecular dynamics simulation (T-REMD). The simulation using the GROMOS 43A1 force field preferred to adopt a ?-hairpin structure, which was in good agreement with the several other simulations and the experimental evidences. However, the simulation using the OPLS-AA force field has a significant difference from the simulations with the GROMOS 43A1 force field simulation. The results show that the driving force in H1 peptide conformation transition is solvent exposure of its hydrophobic residues. However, the subtle balances between residue-residue interactions and residue-solvent interaction are disrupted by using the OPLS-AA force field, which induced the reduction in the number of residue-residue contact. Similar solvent exposure of the hydrophobic residues is observed for all the conformations sampled using the OPLS-AA force field. For H1 peptide which exhibits large solvent exposure of the hydrophobic residues, the GROMOS 43A1 force field with the SPC water model can provide more accurate results. PMID:22066538

  9. Reversible Electric-Field-Driven Magnetic Domain-Wall Motion

    NASA Astrophysics Data System (ADS)

    Franke, Kvin J. A.; Van de Wiele, Ben; Shirahata, Yasuhiro; Hmlinen, Sampo J.; Taniyama, Tomoyasu; van Dijken, Sebastiaan

    2015-01-01

    Control of magnetic domain-wall motion by electric fields has recently attracted scientific attention because of its potential for magnetic logic and memory devices. Here, we report on a new driving mechanism that allows for magnetic domain-wall motion in an applied electric field without the concurrent use of a magnetic field or spin-polarized electric current. The mechanism is based on elastic coupling between magnetic and ferroelectric domain walls in multiferroic heterostructures. Pure electric-field-driven magnetic domain-wall motion is demonstrated for epitaxial Fe films on BaTiO3 with in-plane and out-of-plane polarized domains. In this system, magnetic domain-wall motion is fully reversible and the velocity of the walls varies exponentially as a function of out-of-plane electric-field strength.

  10. Electric Field Distribution of Cadmium Zinc Telluride (CZT)

    SciTech Connect

    Yang,G.; Bolotnikov, A.; Camarda, G.S.; Cui, Y.; Hossain, A.; Kim, K.; James, R.B.

    2009-08-02

    Cadmium Zinc Telluride (CZT) is attracting increasing interest with its promise as a room-temperature nuclear-radiation-detector material. The distribution of the electric field in CZT detectors substantially affects their detection performance. At Brookhaven National Laboratory (BNL), we employed a synchrotron X-Ray mapping technique and a Pockels-effect measurement system to investigate this distribution in different detectors. Here, we report our latest experimental results with three detectors of different width/height ratios. A decrease in this ratio aggravates the non-uniform distribution of electric field, and focuses it on the central volume. Raising the bias voltage effectively can minimize such non-uniformity of the electric field distribution. The position of the maximum electric field is independent of the bias voltage; the difference between its maximum- and minimum-intensity of electric field increases with the applied bias voltage.

  11. Electric field quench in AdS/CFT

    NASA Astrophysics Data System (ADS)

    Hashimoto, Koji; Kinoshita, Shunichiro; Murata, Keiju; Oka, Takashi

    2014-09-01

    An electric field quench, a suddenly applied electric field, can induce nontrivial dynamics in confining systems which may lead to thermalization as well as a deconfinement transition. In order to analyze this nonequilibrium transitions, we use the AdS/CFT correspondence for supersymmetric QCD that has a confining meson sector. We find that the electric field quench causes the deconfinement transition even when the magnitude of the applied electric field is smaller than the critical value for the static case (which is the QCD Schwinger limit for quark-antiquark pair creation). The time dependence is crucial for this phenomenon, and the gravity dual explains it as an oscillation of a D-brane in the bulk AdS spacetime. Interestingly, the deconfinement time takes only discrete values as a function of the magnitude of the electric field. We advocate that the new deconfinement phenomenon is analogous to the exciton Mott transition.

  12. Electric Field Quench in AdS/CFT

    E-print Network

    Koji Hashimoto; Shunichiro Kinoshita; Keiju Murata; Takashi Oka

    2014-07-03

    An electric field quench, a suddenly applied electric field, can induce nontrivial dynamics in confining systems which may lead to thermalization as well as a deconfinement transition. In order to analyze this nonequilibrium transitions,we use the AdS/CFT correspondence for $\\mathcal{N}=2$ supersymmetric QCD that has a confining meson sector. We find that the electric field quench causes the deconfinement transition even when the magnitude of the applied electric field is smaller than the critical value for the static case (which is the QCD Schwinger limit for quark-antiquark pair creation). The time dependence is crucial for this phenomenon, and the gravity dual explains it as an oscillation of a D-brane in the bulk AdS spacetime. Interestingly, the deconfinement time takes only discrete values as a function of the magnitude of the electric field. We advocate that the new deconfinement phenomenon is analogous to the exciton Mott transition.

  13. Consistency restrictions on maximal electric field strength in QFT

    E-print Network

    S. P. Gavrilov; D. M. Gitman

    2008-08-26

    QFT 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 $eET^2$, one can see that the leading contributions to the energy are due to the creation of paticles 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

  14. Control of thumb force using surface functional electrical stimulation and muscle load sharing

    PubMed Central

    2013-01-01

    Background Stroke survivors often have difficulties in manipulating objects with their affected hand. Thumb control plays an important role in object manipulation. Surface functional electrical stimulation (FES) can assist movement. We aim to control the 2D thumb force by predicting the sum of individual muscle forces, described by a sigmoidal muscle recruitment curve and a single force direction. Methods Five able bodied subjects and five stroke subjects were strapped in a custom built setup. The forces perpendicular to the thumb in response to FES applied to three thumb muscles were measured. We evaluated the feasibility of using recruitment curve based force vector maps in predicting output forces. In addition, we developed a closed loop force controller. Load sharing between the three muscles was used to solve the redundancy problem having three actuators to control forces in two dimensions. The thumb force was controlled towards target forces of 0.5 N and 1.0 N in multiple directions within the individuals thumb work space. Hereby, the possibilities to use these force vector maps and the load sharing approach in feed forward and feedback force control were explored. Results The force vector prediction of the obtained model had small RMS errors with respect to the actual measured force vectors (0.220.17 N for the healthy subjects; 0.170.13 N for the stroke subjects). The stroke subjects showed a limited work range due to limited force production of the individual muscles. Performance of feed forward control without feedback, was better in healthy subjects than in stroke subjects. However, when feedback control was added performances were similar between the two groups. Feedback force control lead, especially for the stroke subjects, to a reduction in stationary errors, which improved performance. Conclusions Thumb muscle responses to FES can be described by a single force direction and a sigmoidal recruitment curve. Force in desired direction can be generated through load sharing among redundant muscles. The force vector maps are subject specific and also suitable in feedforward and feedback control taking the individuals available workspace into account. With feedback, more accurate control of muscle force can be achieved. PMID:24103414

  15. 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.

  16. Biofouling prevention with pulsed electric fields

    Microsoft Academic Search

    A. Abou-Ghazala; Karl H. Schoenbach

    2000-01-01

    Temporary immobilization of aquatic nuisance species through application of short electric pulses has been explored as a method to prevent biofouling in cooling water systems where untreated lake, river, or sea water is used. In laboratory experiments, electrical pulses with amplitudes on the order of kilovolts\\/centimeter and submicrosecond duration were found to be most effective in stunning hydrazoans, a common

  17. Radiated electric field measurements in U.S. Army helicopters

    Microsoft Academic Search

    James E. Bruckart

    1992-01-01

    Aircraft systems and medical devices generate electromagnetic fields. EMI can cause faulty operation of aircraft systems or medical devices and endanger patients or aircraft crewmembers. A ground and inflight study was conducted to describe the electromagnetic fields in typical operations. Broadband isotropic field sensors measured electric fields from 5 kHz to 3 MHz, 3 to 500 MHz, and 0.5 MHz

  18. Electric Field Enhancement and Light Transmission in Cylindrical Nanoholes

    Microsoft Academic Search

    Kevin L Shuford; Mark A. Ratner; Stephen K. Gray; George C. Schatz

    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

  19. Electromagnetic self-forces and generalized Killing fields

    NASA Astrophysics Data System (ADS)

    Harte, Abraham I.

    2009-08-01

    Building upon previous results in scalar field theory, a formalism is developed that uses generalized Killing fields to understand the behavior of extended charges interacting with their own electromagnetic fields. New notions of effective linear and angular momenta are identified, and their evolution equations are derived exactly in arbitrary (but fixed) curved spacetimes. A slightly modified form of the Detweiler-Whiting axiom that a charge's motion should only be influenced by the so-called regular component of its self-field is shown to follow very easily. It is exact in some interesting cases and approximate in most others. Explicit equations describing the center-of-mass motion, spin angular momentum and changes in mass of a small charge are also derived in a particular limit. The chosen approximationsalthough standardincorporate dipole and spin forces that do not appear in the traditional Abraham-Lorentz-Dirac or Dewitt-Brehme equations. They have, however, been previously identified in the test body limit.

  20. Unified Field Theory and Force Formulas of Interactions

    NASA Astrophysics Data System (ADS)

    Ma, Tian; Wang, Shouhong

    2013-04-01

    The main objective of this talk is to drive a unified field model coupling four interactions, based on the principle of interaction dynamics (PID) and the principle of representation invariance (PID). Intuitively, PID takes the variation of the action functional under energy-momentum conservation constraint. PRI requires that physical laws be independent of representations of the gauge groups. One important outcome of this unified field model is a natural duality between the interacting fields (g, A, W^a, S^k), corresponding to graviton, photon, intermediate vector bosons W^ and Z and gluons, and the adjoint bosonic fields (?,, ^aw, ^ks). This duality predicts two Higgs particles of similar mass with one due to weak interaction and the other due to strong interaction. PID and PRI can be applied directly to individual interactions, leading to 1) modified Einstein equations, giving rise to a unified theory for dark matter and dark energy, 2) three levels of strong interaction potentials for quark, nucleon/hadron, and atom respectively, and 3) a weak interaction potential. These potential/force formulas offer a clear mechanism for both quark confinement and asymptotic freedom.

  1. The Importance of Radial Electric Fields in Magnetic Confinement

    SciTech Connect

    Oost, Guido van [Ghent University (Belgium)

    2004-03-15

    The importance of radial electric fields was already recognised early in the research on controlled thermonuclear fusion. An initial description of electric field effects in toroidal confinement was given by Budker{sup 1} Such a configuration with combined magnetic and electric confinement ('magnetoelectric confinement', where the electric field provides a toroidal equilibrium configuration without rotational transform) was studied by Stix{sup 2}, who suggested that a reactor-grade plasma under magnetoelectric confinement (electric fields of order 1 MV/cm) may reach a quasi-steady-state with ambipolar loss of electrons and some suprathermal ions (e.g. 3.5 MeV {alpha}-particles). Experiments such as on the Electric Field Bumpy Torus EFBT{sup 3,4} provided quite favourable scaling for particle confinement. The possible importance of radial electric fields for transport was in the past repeatedly established{sup 5,6,7,8}. Since the early days the plasma potential has been measured in tokamaks such as ST{sup 9}, TM-4{sup 10} and ISX-B{sup 11}, but because no significant effects of the radial electric field E{sub r} on plasma transport were observed, no further research was conducted in tokamaks.

  2. 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 nVcm1, 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

  3. Electric field effects on the reactivity of heme model systems

    NASA Astrophysics Data System (ADS)

    De Biase, Pablo M.; Doctorovich, Fabio; Murgida, Daniel H.; Estrin, Dario A.

    2007-01-01

    Proteins integrated or transiently bound to membranes are subject to strong electric fields. However, the role of these fields on tuning the reactivity of redox proteins is still an open issue. High electric fields are also present in protein-based electrochemical devices. In this work we report DFT calculations of the electric field effects on ligand binding and on the redox potentials of porphyrin models representing the active sites of typical heme proteins such as cytochrome c, cytochrome c oxidase, cytochrome c peroxidase and cytochrome P450.

  4. Electrotaxis of oral squamous cell carcinoma cells in a multiple-electric-field chip with uniform flow field

    PubMed Central

    Tsai, Hsieh-Fu; Peng, Shih-Wei; Wu, Chun-Ying; Chang, Hui-Fang; Cheng, Ji-Yen

    2012-01-01

    We report a new design of microfluidic chip (Multiple electric Field with Uniform Flow chip, MFUF chip) to create multiple electric field strengths (EFSs) while providing a uniform flow field simultaneously. MFUF chip was fabricated from poly-methyl methacrylates (PMMA) substrates by using CO2 laser micromachining. A microfluidic network with interconnecting segments was utilized to de-couple the flow field and the electric field (EF). Using our special design, different EFSs were obtained in channel segments that had an identical cross-section and therefore a uniform flow field. Four electric fields with EFS ratio of 7.9:2.8:1:0 were obtained with flow velocity variation of only 7.8% CV (coefficient of variation). Possible biological effect of shear force can therefore be avoided. Cell behavior under three EFSs and the control condition, where there is no EF, was observed in a single experiment. We validated MFUF chip performance using lung adenocarcinoma cell lines and then used the chip to study the electrotaxis of HSC-3, an oral squamous cell carcinoma cell line. The MFUF chip has high throughput capability for studying the EF-induced cell behavior under various EFSs, including the control condition (EFS?=?0). PMID:24009650

  5. Adaptation and generalization in acceleration dependent force fields

    PubMed Central

    Hwang, Eun Jung; Smith, Maurice A.; Shadmehr, Reza

    2005-01-01

    Any passive rigid inertial object that we hold in our hand, e.g., a tennis racquet, imposes a field of forces on the arm that depends on limb position, velocity, and acceleration. A fundamental characteristic of this field is that the forces due to acceleration and velocity are linearly separable in the intrinsic coordinates of the limb. In order to learn such dynamics with a collection of basis elements, a control system would generalize correctly and therefore perform optimally if the basis elements that were sensitive to limb velocity were not sensitive to acceleration, and vice versa. However, in the mammalian nervous system proprioceptive sensors like muscle spindles encode a nonlinear combination of all components of limb state, with sensitivity to velocity dominating sensitivity to acceleration. Therefore, limb state in the space of proprioception is not linearly separable despite the fact that this separation is a desirable property of control systems that form models of inertial objects. In building internal models of limb dynamics, does the brain use a representation that is optimal for control of inertial objects, or a representation that is closely tied to how peripheral sensors measure limb state? Here we show that in humans, patterns of generalization of reaching movements in acceleration dependent fields are strongly inconsistent with basis elements that are optimized for control of inertial objects. Unlike a robot controller that models the dynamics of the natural world and represents velocity and acceleration independently, internal models of dynamics that people learn appear to be rooted in the properties of proprioception, nonlinearly responding to the pattern of muscle activation and representing velocity more strongly than acceleration. PMID:16292640

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

    SciTech Connect

    Henson, Neil Jon [Los Alamos National Laboratory; Waldher, Benjamin [WSU; Kuta, Jadwiga [WSU; Clark, Aurora [WSU; Clark, Aurora E [NON LANL

    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.

  7. Enhanced Translational Dynamics of Water under Electric Field

    SciTech Connect

    Omar Diallo, Souleymane [ORNL; Mamontov, Eugene [ORNL; Wada, Nobuo [Nagoya University, Japan; Inagaki, S [Toyota Central Research and Development Labs. Inc.; Fukushima, Y [Toyota Central Research and Development Labs. Inc.

    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.

  8. Electric and magnetic fields and field derivatives from lightning stepped leaders and first return strokes measured at distances

    E-print Network

    Florida, University of

    Electric and magnetic fields and field derivatives from lightning stepped leaders and first return; published 5 September 2008. [1] Using electric and magnetic field and field derivative sensors arrayed over-peak width of the stepped-leader/return-stroke electric field waveform; the stepped-leader electric field

  9. Enhancement of methane conversion using electric fields. Quarterly report, July--September 1995

    SciTech Connect

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

    1995-11-01

    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 temperatures relax the 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.

  10. 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.

  11. Nanosecond pulsed electric fields perturb membrane phospholipids in T lymphoblasts

    Microsoft Academic Search

    P. Thomas Vernier; Yinghua Sun; Laura Marcu; Cheryl M. Craft; Martin A. Gundersen

    2004-01-01

    Nanosecond, megavolt-per-meter pulsed electric fields scramble the asymmetric arrangement of phospholipids in cell membranes without the permeabilization associated with longer, lower-field pulses. A single 30 ns, 2.5 MV\\/m pulse produces perturbations consistent with phosphatidylserine (PS) externalization in Jurkat T lymphoblasts within milliseconds, polarized in the direction of the applied field, indicating an immediate interaction between membrane components and the electric

  12. Beyond Orientation: The Impact of Electric Fields on Block Copolymers

    SciTech Connect

    Liedel, Clemens [RWTH Aachen University; Boker, A. [Universitat Bayreuth; Pester, Christian [RWTH Aachen University; Ruppel, Markus A [ORNL; Urban, Volker S [ORNL

    2012-01-01

    Since the first report on electric field-induced alignment of block copolymers (BCPs) in 1991, electric fields have been shown not only to direct the orientation of BCP nanostructures in bulk, solution, and thin films, but also to reversibly induce order-order transitions, affect the order-disorder transition temperature, and control morphologies' dimensions with nanometer precision. Theoretical and experimental results of the past years in this very interesting field of research are summarized and future perspectives are outlined.

  13. On intense diverging electric fields associated with black aurora

    Microsoft Academic Search

    Gran Marklund; Lars Blomberg; Carl-Gunne Flthammar; Per-Arne Lindqvist

    1994-01-01

    Results are presented from the double-probe electric field instrument on the Freja satellite with particular focus on the fine-structured and dynamic plasma of the upper auroral ionosphere. The high-resolution measurements show frequently occurring intense and irregular fine-scale electric fields similar to those observed at higher altitudes by, for example, the S3-3 and Viking satellites. Whereas the high-altitude fields tend to

  14. The Electrical Structure of Terrestrial Dust Devils: Implications of Multiple Vertical Measurements of the Electric Field

    Microsoft Academic Search

    G. T. Delory; W. M. Farrell; B. Hillard; N. O. Renno; P. Smith; J. R. Marshall; A. Eatchel

    2002-01-01

    In this work we discuss observations of the electrical structure of dust devils made in the summer of 2001 and 2002 during the Mars Atmosphere and Dust in the Optical and Radio (MATADOR) field campaign outside of Tucson, Arizona. While it has long been known that Terrestrial dust devils can support large electric fields of magnitudes of up to 10

  15. Electron electric-dipole-moment experiment using electric-field quantized slow cesium atoms

    SciTech Connect

    Amini, Jason M.; Munger, Charles T. Jr.; Gould, Harvey [Mail Stop 71-259, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2007-06-15

    A proof-of-principle electron electric-dipole-moment (e-EDM) experiment using slow cesium atoms, nulled magnetic fields, and electric-field quantization has been performed. With the ambient magnetic fields seen by the atoms reduced to less than 200 pT, an electric field of 6 MV/m lifts the degeneracy between states of unequal |m{sub F}| and, along with the low ({approx_equal}3 m/s) velocity, suppresses the systematic effect from the motional magnetic field. The low velocity and small residual magnetic field have made it possible to induce transitions between states and to perform state preparation, analysis, and detection in regions free of applied static magnetic and electric fields. This experiment demonstrates techniques that may be used to improve the e-EDM limit by two orders of magnitude, but it is not in itself a sensitive e-EDM search, mostly due to limitations of the laser system.

  16. What Supports the Parallel Electric Field in the Birkeland (Field-Aligned) Current Regions of the Earth's Magnetosphere?

    NASA Astrophysics Data System (ADS)

    Basu, B.; Jasperse, J. R.; Lund, E. J.; Grossbard, N.

    2008-12-01

    Quasi-steady electric fields parallel to the background geomagnetic field exist in both upward and downward Birkeland (field-aligned) current regions above the aurora. These fields, together with the turbulence found on auroral field lines, energize the plasma particles as they flow either away from or toward the earth. In general, these parallel electric fields are supported by one or more strong double layers, the mirror force, the generalized pressure gradient, and the anomalous resistivity due to the turbulence. Recently, and for the first time, we have developed and published a new kinetic and multi-moment fluid, anomalous transport theory that contains the effect of electrostatic turbulence for inhomogeneous, non-uniformly magnetized plasmas [1, 2]. Applying the new theory to observations in a downward-current sheet, we show that anomalous resistivity accounts for only a small portion of the parallel electric field and that contributions from the double layer, mirror force, and generalized pressure gradient terms in the generalized Ohm's law for the problem are more important. Calculations in the double-layer-and-transition-propagation region for a downward-current sheet show that a strong double layer forms, propagates upward at the local ion-acoustic speed, is destabilized as the current falls below the local critical value, and reforms at a lower altitude. These results have important implications in other regions of space such as magnetospheric reconnection sites and solar coronal loops where parallel electric fields are likely to exist. [1] J. R. Jasperse et al. (2006), Phys. Plasmas 13, 072903, and [2] J. R. Jasperse et al. (2006), Phys. Plasmas 13, 112902.

  17. Variations of electric field and electric resistivity of air caused by dust motion

    NASA Astrophysics Data System (ADS)

    Seran, E.; Godefroy, M.; Renno, N.; Elliott, H.

    2013-08-01

    report results of a field campaign conducted in the Nevada desert with a suite of electric field instruments consisting of a field mill (FM) and a short dipole antenna (SDA). Furthermore, we show that a combination of the measurements of these two instruments allows the estimation of the electric resistivity of air, an important quantity that is extremely difficult to measure near the Earth's surface. The electric resistivity of air is found to vary between 1.5 1013 and 6 1013 ? m and to correlate with changes in electric field. Vertical DC electric fields with amplitudes up to 6 kV m-1 were observed to correspond to clouds of dust blowing through the measurement site. Enhanced DC and AC electric fields are measured during periods when horizontal wind speed exceeds 7 m s-1, or around twice the background value. We suggest that low-frequency emissions, below ~200 Hz, are generated by the motion of electrically charged particles in the vicinity of the SDA electrode and propose a simple model to reproduce the observed spectra. According to this model, the spectral response is controlled by three parameters, (i) the speed of the charged particles, (ii) the charge concentration, and (iii) the minimum distance between the particle and the electrode. In order to explain the electric fields measured with the FM sensors at different heights, we developed a multilayer model that relates the electric field to the charge distribution. For example, a nonlinear variation of the electric field observed by the FM sensors below 50 cm is simulated by a near-surface layer of tens of centimeters that is filled with electrically charged particles that carry a predominantly negative charge in the vicinity of the soil. The charge concentration inside this layer is estimated to vary between 1012 and 5 1013 electrons m-3.

  18. Exposure of workers in the electric power industry to electric and magnetic fields.

    PubMed

    Lindh, T; Andersson, L I

    1994-01-01

    A survey of 50 Hz electric and magnetic fields in the electric power industry has distinguished differences in exposure among the employees making it possible to compare health effects as a function of exposure. The workers that were most exposed to electric and magnetic fields were linemen and substation personnel who worked on facilities at operating voltages above 20 kV. On average, they were exposed to an electric field strength above 30 V/m for approximately 1.5 to 3 hours per day and to a magnetic flux density of around 1 to 2 microT. The least exposed group were linemen working in the 0.4 to 20 kV part of the network with exposure to a magnetic field of 0.10 microT. The electric field seldom exceeded 30 V/m. PMID:8047670

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

    SciTech Connect

    Bahar, M. K. [Department of Physics, Karamano?lu Mehmetbey University, 70100 Karaman (Turkey); Soylu, A. [Department of Physics, Ni?de University, 51240 Ni?de (Turkey)

    2014-09-15

    We numerically solve the Schrdinger 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 Schrdinger equation, the solution of which becomes more complex due to the use of the MGECSC potential with an applied external electric field.

  20. 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).

  1. Modification of the CHARMM force field for DMPC lipid bilayer.

    PubMed

    Hgberg, Carl-Johan; Nikitin, Alexei M; Lyubartsev, Alexander P

    2008-11-15

    The CHARMM force field for DMPC lipids was modified in order to improve agreement with experiment for a number of important properties of hydrated lipid bilayer. The modification consists in introduction of a scaling factor 0.83 for 1-4 electrostatic interactions (between atoms separated by three covalent bonds), which provides correct transgauche ratio in the alkane tails, and recalculation of the headgroup charges on the basis of HF/6-311(d,p) ab-initio computations. Both rigid TIP3P and flexible SPC water models were used with the new lipid model, showing similar results. The new model in a 75 ns simulation has shown a correct value of the area per lipid at zero surface tension, as well as good agreement with the experiment for the electron density, structure factor, and order parameters, including those in the headgroup part of lipids. PMID:18512235

  2. Derivation of a Molecular Mechanics Force Field for Cholesterol

    SciTech Connect

    Cournia, Zoe; Vaiana, Andrea C.; Smith, Jeremy C.; Ullmann, G. Matthias M.

    2004-01-01

    As a necessary step toward realistic cholesterol:biomembrane simulations, we have derived CHARMM molecular mechanics force-field parameters for cholesterol. For the parametrization we use an automated method that involves fitting the molecular mechanics potential to both vibrational frequencies and eigenvector projections derived from quantum chemical calculations. Results for another polycyclic molecule, rhodamine 6G, are also given. The usefulness of the method is thus demonstrated by the use of reference data from two molecules at different levels of theory. The frequency-matching plots for both cholesterol and rhodamine 6G show overall agreement between the CHARMM and quantum chemical normal modes, with frequency matching for both molecules within the error range found in previous benchmark studies.

  3. Force field development for cofactors in the photosystem II.

    PubMed

    Zhang, Lu; Silva, Daniel-Adriano; Yan, Yijing; Huang, Xuhui

    2012-09-30

    We present a set of force field (FF) parameters compatible with the AMBER03 FF to describe five cofactors in photosystem II (PSII) of oxygenic photosynthetic organisms: plastoquinone-9 (three redox forms), chlorophyll-a, pheophytin-a, heme-b, and ?-carotene. The development of a reliable FF for these cofactors is an essential step for performing molecular dynamics simulations of PSII. Such simulations are important for the calculation of absorption spectrum and the further investigation of the electron and energy transfer processes. We have derived parameters for partial charges, bonds, angles, and dihedral-angles from solid theoretical models using systematic quantum mechanics (QM) calculations. We have shown that the developed FF parameters are in good agreement with both ab initio QM and experimental structural data in small molecule crystals as well as protein complexes. PMID:22685077

  4. 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...

  5. An experimental study on the motion, deformation and electrical charging of water drops falling in oil in the presence of high voltage D.C. electric field

    SciTech Connect

    Jalaal, M.; Khorshidi, B.; Esmaeilzadeh, E. [Department of Mechanical Engineering, University of Tabriz, Tabriz 51666 (Iran)

    2010-11-15

    The motion, deformation and electrical charging of conducting water drops falling in an insulating liquid subjected to various electric fields strength were studied experimentally. The drop motion was recorded contentiously by high speed camera and their responses to deformation under the influence of electric field were digitally extracted by image processing of the sequential frames. Two parameters were defined for describing the deviation and deformation of the drops under the electric forces. Outcomes depicted that the deviation of the drops from the vertical line would be increased by adding to the applied electrical potential as well as reduction of drop size. Moreover, regarding to deformation diagram, the results revealed a dissimilar deformation manner between large and small drops, which can be helpful in describing the drop-drop electro coalescence phenomena and in design of electrically driven droplet-based systems. (author)

  6. Forces due to fluctuations in the anisotropic phase-field model of solidification

    Microsoft Academic Search

    Stanislav G. Pavlik; Robert F. Sekerka

    1999-01-01

    Stochastic forces due to thermodynamic fluctuations are derived for the anisotropic phase-field model of solidification. The stochastic forces turn out to be anisotropic. The derivation utilizes the general principles of irreversible thermodynamics. One of the forces is the divergence of the stochastic heat flux derived by Landau and Lifshitz (Statistical Physics, Pergamon Press, Oxford, 1958). The other force is the

  7. Accounting for electronic polarization in non-polarizable force fields.

    PubMed

    Leontyev, Igor; Stuchebrukhov, Alexei

    2011-02-21

    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 ?? 3D reported in recent ab initio and experimental studies with the value ?(eff)? 2.3D typically used in the empirical potentials, such as TIP3P or SPC/E. It is shown that the effective dipole of water can be understood as a scaled value ?(eff) = ?/??(el), where ?(el) = 1.78 is the electronic (high-frequency) dielectric constant of water. This simple theoretical framework provides important insights into the nature of the effective parameters, which is crucial when the computational models of liquid water are used for simulations in different environments, such as proteins, or for interaction with solutes. PMID:21212894

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

    SciTech Connect

    Kumar, Dinesh; Bhattacharyya, R. [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India)] [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)] [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)

    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.

  9. 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

  10. 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.

  11. 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

  12. THE UNITED THEORY OF THE TWO FIELDS OF THE ELECTRIC AND MAGNETIC NATURE

    E-print Network

    Rasulkhozha S. Sharafiddinov

    2003-01-01

    Each of electrically charged particles testifies in favor of the existence of a kind of the magnetically charged monoparticle. As a consequence, only the corresponding mononeutrinos answer for quantization of the electric charges of all the neutrinos. Therefore, to understand the nature of matter at the fundamental level one must use the electromagnetic field as the field of the unified system of the photon and monophoton where the electric and magnetic forces of the nature are united. Some logical and laboratory confirmations of the availability of compound structure of gauge invariance have been listed which say also about the connection between the states of elementary particles and monoparticles. 1 A study of the behavior of electrons and their neutrinos in a nucleus Coulomb field shows clearly that between the mass of a particle and its charge there exists a sharp dependence [1]. For the light Dirac neutrino (? = ?e) it has the form [2] e E ? = ? 3eGF(mE ?)2

  13. Electric-field-induced structure and optical properties of electrorheological fluids with attapulgite nanorods

    NASA Astrophysics Data System (ADS)

    Jin, Ting; Cheng, Yuchuan; He, Ru; Luo, Yuxia; Jiang, Meng; Chen, Chao; Xu, Gaojie

    2014-07-01

    Attapulgite (ATP) is a type of crystalloid hydrous magnesium-aluminum silicate mineral with natural one-dimensional (1D) fibrous morphology. In this study, the authors investigated the optical and mechanical performances of ATP nanorods in silicone oil under an electric field. It was observed that the optical transmittance of ATP suspensions decreased rapidly under the low electric field, using ultraviolet-visible (UV-Vis) spectroscopy. The results of optical microscopy and scanning electron microscopy (SEM) indicated that the electromigration of ATP nanorods was the major cause of such an aberrant optical phenomenon. Further, the electrorheological (ER) response of the samples was measured by the height-controlled method. The change trend of the normal force was illustrated by the dynamic assembly behavior of ATP in the applied electric field. This work provided intuitive evidence for an in-depth understanding of the mechanism of ER fluids containing 1D dielectric materials.

  14. Electric Field Induced Selective Disordering in Lamellar Block Copolymers

    SciTech Connect

    Ruppel, Markus A [ORNL; Pester, Christian W [ORNL; Langner, Karol M [Leiden Institute of Chemistry, Leiden University, The Netherlands; Sevink, Geert [Leiden Institute of Chemistry, Leiden University, The Netherlands; Schoberth, Heiko [University of Bayreuth; Schmidt, Kristin [ORNL; Urban, Volker S [ORNL; Mays, Jimmy [ORNL; Boker, Alexander [RWTH Aachen University

    2013-01-01

    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 orderdisorder 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 orderdisorder transition and well below it.

  15. 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...

  16. 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.

  17. Ground state of graphene slabs in an external electric field

    NASA Astrophysics Data System (ADS)

    Taut, M.; Xiao, Ruijuan

    2011-12-01

    Unlike graphene (AB) stacks, (ABC) stacks have two interesting properties: they are topological insulators with only surface states at the Fermi level, and they develop a tunable gap in an external electric field. The total energy of graphene (AB) stacks is lower than of (ABC) stacks which coincides with the empirical fact that graphite is mainly (AB) stacked. An external perpendicular electric field, however, makes (ABC) stacks energetically more favorable than (AB) stacks. Thus, growing or annealing stacks in an external electric field might become a device to increase the yield in (ABC) sequences or even to produce (ABC) stacks in a controlled way.

  18. Electric Field induced alignment and morphological transitions of triblock copolymers.

    NASA Astrophysics Data System (ADS)

    Isaacs-Sodeye, Akinbode

    2005-03-01

    The electric field induced microdomain alignment of poly (styrene-b-ethylene-co-butylene -b-styrene)(SEBS) and poly (styrene-b-isobutylene-b-Styrene)(SIBS) triblock copolymers were investigated using AFM and cross-sectional TEM. For the SIBS samples, evidence of a transition from cylindrical to spherical morphology of the minor polystyrene microdomains was observed. These spherical domains appear to impinge on one another, much like a string of beads, and preferentially align with the direction of the applied electric field. On the other hand the SEBS samples, which had lower molecular weights, showed significant microdomain orientation in the direction of the applied electric field.

  19. Structure of liquid ethylene glycol: A molecular dynamics simulation study with different force fields

    E-print Network

    Saiz, Leonor

    of the studied force fields have the same intermolecular parameters and different intramolecular interactionsStructure of liquid ethylene glycol: A molecular dynamics simulation study with different force simulation studies for several different liquid phase force fields. We compare the properties obtained

  20. Optimization of protein force-field parameters with the Protein Data Bank

    NASA Astrophysics Data System (ADS)

    Sakae, Yoshitake; Okamoto, Yuko

    2003-12-01

    We propose a novel method to optimize existing force-field parameters for protein systems. The method consists of minimizing the summation of the square of the force acting on each atom in the proteins with the structures from the Protein Data Bank. We performed this optimization to the partial-charge and torsion-energy parameters of the AMBER parm94 force field, using 100 molecules from the Protein Data Bank. We then performed folding simulations of ?-helical and ?-hairpin peptides. The optimized force-field parameters gave structures more consistent with the experimental implications than the original AMBER force field.

  1. 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)

  2. A latent force model for describing electric propagation in deep brain stimulation: a simulation study.

    PubMed

    Alvarado, Pablo A; Alvarez, Mauricio A; Daza-Santacoloma, Genaro; Orozco, Alvaro; Castellanos-Dominguez, Germn

    2014-01-01

    Deep brain stimulation (DBS) is a neurosurgical method used to treat symptoms of movement disorders by implanting electrodes in deep brain areas. Often, the DBS modeling approaches found in the literature assume a quasi-static approximation, and discard any dynamic behavior. Nevertheless, in a real DBS system the stimulus corresponds to a wave that changes as a function of time. It is clear that DBS demands an approach that takes into account the time-varying behavior of the input stimulus. In this work, we present a novel latent force model for describing the dynamic electric propagation occurred during DBS. The performance of the proposed model was studied by simulations under different conditions. The results show that our approach is able to take into account the time variations of the source and the produced field. Moreover, by restricting our model it is possible to obtain solutions for electrostatic formulations, here experimental results were compared with the finite element method. Additionally, our approach allows a solution to the inverse problem, which is a valuable clinical application allowing the appropriate tuning of the DBS device by the expert physician. PMID:25570527

  3. Two dimensional measurements of electrical fields in transformer oil

    Microsoft Academic Search

    U. Gafvert

    1990-01-01

    It is demonstrated that the electro-optical Kerr effect with field modulation can be used for angularly resolved field mapping of two-dimensional objects in transformer oils. This technique can determine the amplitude as well as the direction of the electric field in liquid insulation systems relevant for converter transformers. As an example, the technique was applied to two overlapping Macrolon barriers

  4. Optical fiber current sensors in high electric field environments

    Microsoft Academic Search

    Allen H. Rose; S. M. Etzel; Kent B. Rochford

    1999-01-01

    This paper analyzes the response of optical fiber current sensors that are subjected to high electric fields, such as fields encountered in gas-insulated systems. This paper shows that through the electrooptic (EO) Kerr effect, these fields can cause harmonic distortion of the measured ac current waveform. This harmonic distortion was confirmed experimentally. Also, this paper shows that it is possible

  5. Electric Field Measurements during the Genesis and Rapid Intensification Processes (GRIP) Field Program

    Microsoft Academic Search

    M. G. Bateman; R. Blakeslee; D. M. Mach

    2010-01-01

    During the Genesis and Rapid Intensification Processes (GRIP) field program, a system of 6 electric field mills was flown on one of NASA's Global Hawk aircraft. We placed several mills on the aircraft to enable us to measure the vector electric field. We created a distributed, ethernet-connected system so that each sensor has its own embedded Linux system, complete with

  6. Evaluating shock absorption behavior of small-sized systems under programmable electric field

    NASA Astrophysics Data System (ADS)

    Jagtap, Piyush; Kumar, Praveen

    2014-11-01

    A simple ball-drop impact tester is developed for studying the dynamic response of hierarchical, complex, small-sized systems and materials. The developed algorithm and set-up have provisions for applying programmable potential difference along the height of a test specimen during an impact loading; this enables us to conduct experiments on various materials and smart structures whose mechanical behavior is sensitive to electric field. The software-hardware system allows not only acquisition of dynamic force-time data at very fast sampling rate (up to 2 106 samples/s), but also application of a pre-set potential difference (up to 10 V) across a test specimen for a duration determined by feedback from the force-time data. We illustrate the functioning of the set-up by studying the effect of electric field on the energy absorption capability of carbon nanotube foams of 5 5 1.2 mm3 size under impact conditions.

  7. 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.

  8. Critical Casimir forces in the presence of random surface fields

    NASA Astrophysics Data System (ADS)

    Macio?ek, A.; Vasilyev, O.; Dotsenko, V.; Dietrich, S.

    2015-03-01

    We study critical Casimir forces (CCFs) fC for films of thickness L which in the three-dimensional bulk belong to the Ising universality class and which are exposed to random surface fields (RSFs) on both surfaces. We consider the case in which, in the absence of RSFs, the surfaces of the film belong to the surface universality class of the so-called ordinary transition. We carry out a finite-size scaling analysis and show that for weak disorder, CCFs still exhibit scaling, acquiring a random field scaling variable w that is zero for pure systems. We confirm these analytic predictions by Monte Carlo (MC) simulations. Moreover, our MC data show that fC varies as fC(w ?0 ) -fC(w =0 ) w2 . Asymptotically, for large L , w scales as w L-0.26?0 , indicating that this type of disorder is an irrelevant perturbation of the ordinary surface universality class. However, for thin films such that w ?1 , we find that the presence of RSFs with vanishing mean value increases significantly the strength of CCFs, as compared to systems without them, and it shifts the extremum of the scaling function of fC toward lower temperatures. But fC remains attractive.

  9. Atomistic simulations of electric field effects on the Young?s modulus of metal nanowires

    NASA Astrophysics Data System (ADS)

    Ben, Xue; Park, Harold S.

    2014-11-01

    We present a computational, atomistic study of electric field effects on the Young?s modulus of metal nanowires. The simulations are electromechanically coupled, where the mechanical forces on the atoms are obtained from realistic embedded atom method potentials, and where the electrostatic forces on the atoms are obtained using a point dipole electrostatic model that is modified to account for the different polarizability and bonding environment of surface atoms. By considering three different nanowire axial orientations (< 100> , < 110> and < 111> ) of varying cross sectional sizes and aspect ratios, we find that the Young?s modulus of the nanowires differs from that predicted for the purely mechanical case due to the elimination of nonlinear elastic stiffening or softening effects due to the electric field-induced positive relaxation strain relative to the relaxed mechanical configuration. We further find that < 100> nanowires are most sensitive to the applied electric field, with Young?s moduli that can be increased more than 20% with increasing aspect ratio. Finally, while the orientation of the transverse surfaces does impact the Young?s modulus of the nanowires under applied electric field, the key factor controlling the magnitude of the stiffness change of the nanowires is the distance between atomic planes along the axial direction of the nanowire bulk.

  10. 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.

  11. Transient Charge Accumulation Applied Electric Field

    E-print Network

    Anlage, Steven

    in a poorly understood but broadly occurring process known as triboelectric charging. This phenomenon lightning discharges.1 Additionally, biological implications of triboelectric charging have been observed of triboelectric charging in sand by observing electrical discharge on metal plates under various conditions

  12. 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]).

  13. Detrimental effects of electrical fields on cardiac muscle

    Microsoft Academic Search

    LESLIE TUNG

    1996-01-01

    The use of controlled electrical shock as a therapy to manage cardiac arrhythmia is a practice commonly used today. High intensity electrical fields are generated near the shock electrodes, and if the electrodes are placed directly on or inside the heart as is often the case, tissue injury and dysfunction may result if the shock intensity is too high. Many

  14. Electric field at the ground in a large tornado

    Microsoft Academic Search

    W. P. Winn; S. J. Hunyady; G. D. Aulich

    2000-01-01

    A number of observers have reported lightning, diffuse luminosity, or other manifestations of electrical activity in tornadoes. To try to quantify these observations, eight instruments with sensors for electric field and other parameters were placed in front of a large tornado that passed by Allison, Texas, on June 8, 1995. The edge of the tornado vortex passed over two of

  15. DC link stabilized field oriented control of electric propulsion systems

    Microsoft Academic Search

    S. D. Sudhoff; K. A. Corzine; S. F. Glover; H. J. Hegner

    1998-01-01

    Induction motor based electric propulsion systems can be used in a wide variety of applications including locomotives, hybrid electric vehicles, and ships. Field oriented control of these drives is attractive since it allows the torque to be tightly and nearly instantaneously controlled. However, such systems can be prone to negative impedance instability of the DC link. This paper examines this

  16. Space charge behavior in polyethylene under AC electric fields

    Microsoft Academic Search

    J. Zhao; Z. Xu; G. Chen; P. L. Lewin

    2011-01-01

    Polyethylene has been widely used as the insulation of high voltage power cables due to its excellent dielectric properties and electrical performance. The existence of space charge in polymeric insulators is a significant issue with respect to life expectation. It can alter the local electric field and initiate possible partial discharge or eventual breakdown. This appears relatively more severe under

  17. Spatial confinement of ultrasonic force fields in microfluidic channels Otto Manneberg a

    E-print Network

    Spatial confinement of ultrasonic force fields in microfluidic channels Otto Manneberg a , S: 43.25.Gf Keywords: Ultrasonic manipulation Acoustic radiation force Microfluidic chip Particle image localized ultrasonic manipulation functions in series in micro- fluidic chips. The manipulation functions

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

    PubMed

    Stahl, A; Hirvijoki, E; Decker, J; Embrus, O; Flp, 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

  19. 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.

  20. Semiclassical pair production rate for rotating electric fields

    E-print Network

    Eckhard Strobel; She-Sheng Xue

    2015-02-09

    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 WKB-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 quantum electro dynamics (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

    NASA Astrophysics Data System (ADS)

    Stahl, A.; Hirvijoki, E.; Decker, J.; Embrus, O.; Flp, T.

    2015-03-01

    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.

  2. Calculating Electric Field Using Flux Detector and Gauss's Law

    NSDL National Science Digital Library

    Wolfgang Christian

    The learner is asked to calculate the electric field due to a charge filament as shown in the animation. Given are three different detectors and three different viewpoints: intermediate distance, very close, and very far from the filament.

  3. 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.

  4. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

    NASA Astrophysics Data System (ADS)

    Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

  5. Electric field effect in correlated oxide systems

    Microsoft Academic Search

    C. H. Ahn; J.-M. Triscone; J. Mannhart

    2003-01-01

    Semiconducting field-effect transistors are the workhorses of the modern electronics era. Recently, application of the field-effect approach to compounds other than semiconductors has created opportunities to electrostatically modulate types of correlated electron behaviourincluding high-temperature superconductivity and colossal magnetoresistanceand potentially tune the phase transitions in such systems. Here we provide an overview of the achievements in this field and discuss the

  6. Biological electric fields and rate equations for biophotons.

    PubMed

    Alvermann, M; Srivastava, Y N; Swain, J; Widom, A

    2015-04-01

    Biophoton intensities depend upon the squared modulus of the electric field. Hence, we first make some general estimates about the inherent electric fields within various biosystems. Generally, these intensities do not follow a simple exponential decay law. After a brief discussion on the inapplicability of a linear rate equation that leads to strict exponential decay, we study other, nonlinear rate equations that have been successfully used for biosystems along with their physical origins when available. PMID:25737231

  7. Ortho and Para Molecules of Water in Electric Field

    E-print Network

    S. N. Andreev; V. P. Makarov; V. I. Tikhonov; A. A. Volkov

    2007-03-04

    Stark effect is calculated by the perturbation theory method separately for the ortho and para water molecules. At room temperature, a 30%-difference in the energy change is found for the two species put in electric field. This implies a sorting of the ortho and para water molecules in non-uniform electric fields. The ortho/para water separation is suggested to occur in the course of steam sorption on a solid surface and of large-scale atmospheric processes.

  8. Quantifying electric field gradient fluctuations over polymers using ultrasensitive cantilevers

    PubMed Central

    Yazdanian, Showkat M.; Hoepker, Nikolas; Kuehn, Seppe; Loring, Roger F.; Marohn, John A.

    2009-01-01

    An ultrasensitive cantilever, oscillating parallel to a surface in vacuum, is used to probe weak thermal electric field gradient fluctuations over thin polymer films. We measure the power spectrum of cantilever frequency fluctuations as a function of cantilever height and voltage over polymers of various compositions and thicknesses. The data are well described by a linear-response theory that calculates stochastic electric fields arising from thermally-driven dielectric fluctuations. PMID:19435337

  9. Band structures of Bernal graphene modulated by electric fields

    Microsoft Academic Search

    Sing-Jyun Tsai; Jon-Hsu Ho; Yu-Huang Chiu; Ming-Fa Lin

    2010-01-01

    The tight-binding model is utilized to investigate the influence of modulation electric fields on bilayer Bernal graphene (BBG). The electric potential changes the parabolic bands into oscillatory ones, and induces more band-edge states. As the strength of field is strengthened, it would enhance the oscillation of energy band, affect larger range of energy, induced more band-edge states, and cause more

  10. Electric fields preceding cloud-to-ground lightning flashes

    Microsoft Academic Search

    W. Beasley; M. A. Uman; P. L. Rustan Jr.

    1982-01-01

    A detailed analysis is presented of the electric-field variations preceding the first return strokes of 80 cloud-to-ground lightning flashes in nine different storms observed at the NASA Kennedy Space Center during the summers of 1976 and 1977. It is suggested that the electric-field variations can best be characterized as having two sections: preliminary variations and stepped leader. The stepped-leader change

  11. Slow-Atom Electron EDM Experiment with Electric Field Quantization

    Microsoft Academic Search

    Harvey Gould; Jason Amini; Charles Munger Jr.

    2007-01-01

    Improving the electron electric dipole moment (e-EDM) upper limit has been a 40-year battle against systematic effects. Two new weapons in this battle are slow atoms and ground-state electric field quantization, both of which suppress motional magnetic field effects. They have been used effectively in a recently completed e-EDM experiment that is a prototype for a high-sensitivity Cs fountain e-EDM

  12. Longitudinal electric-field variations in the daytime equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Deminov, M. G.; Kochenova, N. A.; Sitnov, Iu. S.

    1988-02-01

    Longitudinal variations of vertical drift velocity and electric field above the magnetic equator are determined on the basis of Intercosmos-19 data on longitudinal f0F2 variations for near-midnight hours during the winter and summer high-activity periods. The longitudinal electric-field variations are explained by a mechanism involving the heating of the atmosphere and the conservation of the magnitude of the total current of the equatorial electrojet. The results obtained agree well with POGO satellite data.

  13. An Updated Balloon-Borne Electric Field Sensor

    Microsoft Academic Search

    W. Rison; P. R. Krehbiel; W. D. Rust; D. R. Macgorman; S. Fredrickson; D. Kennedy; E. Bruning; J. Young; I. Apostolakopoulos; D. Nealson

    2005-01-01

    Most of the vertical profiles of the electric fields in thunderstorms come from low-mass balloon-borne electric field meters (EFM) based on the design originally developed by Winn and Byerley (Q. J. Royal Met. Soc., 101, 979-94, 1975). This instrument uses a pair of aluminum spheres as sensing electrodes, which spin about the horizontal axis with a frequency of about 2.5~Hz.

  14. Is the 3-D magnetic null point with a convective electric field an efficient particle accelerator?

    NASA Astrophysics Data System (ADS)

    Guo, J.-N.; Bchner, J.; Otto, A.; Santos, J.; Marsch, E.; Gan, W.-Q.

    2010-04-01

    Aims: We study the particle acceleration at a magnetic null point in the solar corona, considering self-consistent magnetic fields, plasma flows and the corresponding convective electric fields. Methods: We calculate the electromagnetic fields by 3-D magnetohydrodynamic (MHD) simulations and expose charged particles to these fields within a full-orbit relativistic test-particle approach. In the 3-D MHD simulation part, the initial magnetic field configuration is set to be a potential field obtained by extrapolation from an analytic quadrupolar photospheric magnetic field with a typically observed magnitude. The configuration is chosen so that the resulting coronal magnetic field contains a null. Driven by photospheric plasma motion, the MHD simulation reveals the coronal plasma motion and the self-consistent electric and magnetic fields. In a subsequent test particle experiment the particle energies and orbits (determined by the forces exerted by the convective electric field and the magnetic field around the null) are calculated in time. Results: Test particle calculations show that protons can be accelerated up to 30 keV near the null if the local plasma flow velocity is of the order of 1000 km s-1 (in solar active regions). The final parallel velocity is much higher than the perpendicular velocity so that accelerated particles escape from the null along the magnetic field lines. Stronger convection electric field during big flare explosions can accelerate protons up to 2 MeV and electrons to 3 keV. Higher initial velocities can help most protons to be strongly accelerated, but a few protons also run the risk to be decelerated. Conclusions: Through its convective electric field and due to magnetic nonuniform drifts and de-magnetization process, the 3-D null can act as an effective accelerator for protons but not for electrons. Protons are more easily de-magnetized and accelerated than electrons because of their larger Larmor radii. Notice that macroscopic MHD simulations are blind to microscopic magnetic structures where more non-adiabatic processes might be taking place. In the real solar corona, we expect that particles could have a higher probability to experience a de-magnetization process and get accelerated. To trigger a significant acceleration of electrons and even higher energetic protons, however, the existence of a resistive electric field mainly parallel to the magnetic field is required. A physically reasonable resistivity model included in resistive MHD simulations is direly needed for the further investigations of electron acceleration by parallel electric fields.

  15. Structure and Morphology of Phthalocyanine Films Grown in Electrical Fields by Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Banks, Curtis E.; Frazier, Donald O.; Penn, Benjamin; Abdeldayem, Hossin; Hicks, Roslin

    1999-01-01

    Phthalocyanine is a very stable organic material in the atmosphere and has been used in numerous applications, such as optical switching and optical storage devices. Although this material has already been discovered for several decades and has had extensive studies conducted on it, many properties still need to be better understood, for example, the mechanisms of forming different solid phases and of changing film morphology by external forces. Phthalocyanine has two preferred solid phases (alpha and beta phases) for which the crystal structures, surface morphology and optical properties are different. In order to investigate these phenomena and the relationship among them, phthalocyanine films have been synthesized by vapor deposition on quartz substrates with and without an external electrical field. Some substrates were coated with a very thin gold film for the electrical field. These films have been characterized using x-ray diffraction, scanning electron microscopy, Fourier transfer infrared spectroscopy, and Z-scan technique. The films have excellent chemical and thermal stability. However, the surface of these films grown without the electrical field shows flower-like morphology. When films are deposited under an electrical field (approximately 3000 V/cm), an aligned structure is revealed on the surface. A comparison of the structure, morphology, optical properties, and the growth mechanism for these films with and without an electrical field will be discussed.

  16. 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.

  17. Electrical poling below coercive field for large piezoelectricity

    NASA Astrophysics Data System (ADS)

    Guo, Hanzheng; Ma, Cheng; Liu, Xiaoming; Tan, Xiaoli

    2013-03-01

    Isotropic polycrystalline ferroelectric ceramics have to be electrically poled to develop a net macroscopic polarization and hence piezoelectricity. It is well accepted that a sufficient poling can only be realized under an electric field that is much higher than the coercive field. In this study, we observed in (Bi1/2Na1/2)TiO3-BaTiO3 ceramics that large piezoelectricity can develop at poling fields far below the measured coercive field. Using in situ transmission electron microscopy, such an unusual behavior, is interpreted with the polarization alignment of polar nanodomains in the non-ergodic relaxor phase.

  18. Effect of the radial electric field on turbulence

    SciTech Connect

    Carreras, B.A.; Lynch, V.E.

    1990-01-01

    For many years, the neoclassical transport theory for three- dimensional magnetic configurations, such as magnetic mirrors, ELMO Bumpy Tori (EBTs), and stellarators, has recognized the critical role of the radial electric field in the confinement. It was in these confinement devices that the first experimental measurements of the radial electric field were made and correlated with confinement losses. In tokamaks, the axisymmetry implies that the neoclassical fluxes are ambipolar and, as a consequence, independent of the radial electric field. However, axisymmetry is not strict in a tokamak with turbulent fluctuations, and near the limiter ambipolarity clearly breaks down. Therefore, the question of the effect of the radial electric field on tokamak confinement has been raised in recent years. In particular, the radial electric field has been proposed to explain the transition from L-mode to H-mode confinement. There is some initial experimental evidence supporting this type of explanation, although there is not yet a self-consistent theory explaining the generation of the electric field and its effect on the transport. Here, a brief review of recent results is presented. 27 refs., 4 figs.

  19. Liquid Crystals in Electric Field Akira ONUKI

    E-print Network

    and that of the lower plate be ?ex. The total charge on the upper plate is Q ¼ Sex. The electric potential satisfies ¼ 0 at the bottom z ¼ 0 and ¼ ? at the top z ¼ L, where ? is the potential difference between the two of a capacitor and an inhomogeneous dielectric material at fixed capacitor charge Q. The potential difference ?

  20. Chronic exposure to a 60-Hz electric field: effects on neuromuscular function in the rat

    SciTech Connect

    Jaffe, R.A.; Laszewski, B.L.; Carr, D.B.

    1981-01-01

    Neuromuscular function in adult male rats was studied following 30 days of exposure to a 60-Hz electric field at 100 kV/m (unperturbed field strength). Isometric force transducters were attached to the tendons of the plantaris (predominantly fast twitch), and soleus (predominantly slow twitch) muscles in the urethan-anesthetized rat. Square-wave stimuli were delivered to the distal stump of the transected sciatic nerve. Several measurements were used to characterize neuromuscular function, including twitch characteristics, chronaxie, tetanic and posttetanic potentiation, and fatigue and recovery. The results from three independent series of experiments are reported. Only recovery from fatigue in slow-twitch muscles was consistently and significantly affected (enhanced) by electric-field exposure. This effect does not appear to be mediated by field-induced changes in either neuromuscular transmission, or in the contractile mechanism itself. It is suggested that the effect may be mediated secondary to an effect on mechanisms regulating muscle blood flow or metabolism.

  1. Radiation Damage of Myoglobin Crystals in Weak Stationary Electric and Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Trame, C. B.; Dragovic, M.; Chiu, H.-J.

    2014-03-01

    Radiation damage is one of the bottlenecks in the field of structural biology. Cryo-cooling of protein crystals provided a breakthrough in the 1980s and resulted in significant reductions in radiation damage. Other factors positively influencing the progression of damage include the application of radical scavengers and reductions in the experimental beam size. Here we study the impact on radiation damage of applying static magnetic and electric fields during protein diffraction experiments, ultimately probing the Lorenz force effect on primary photoelectrons and secondary Auger electrons, which both contribute to the damage process. The design of a special mounting pin using graphene for applying electric fields on a crystalline sample is described. Analyses of myoglobin protein crystals exposed to the fields of ~40 mT and -300 V show a slower global radiation damage rate and also changes in the progression of specific damage process on the molecular level, in particular at doses extending beyond the Garman limit of 30 MGy.

  2. 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.

  3. Scattering effects of electric and magnetic field probes

    Microsoft Academic Search

    John D. Norgard; Ronald M. Sega; Michael Harrison; Anthony Pesta; Mike Seifert

    1989-01-01

    Many electromagnetic measurements of electromagnetic pulse (EMP) interactions with electronic systems use B-dot and D-dot probes. The effect of the measurement probe on the field distribution being measured is considered. An infrared measurement technique is used to determine the field distributions with and without the presence of electric- or magnetic-field probes. Two-dimensional thermogram images of the scattered field patterns are

  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. Electrical properties of chain microstructure magnetic emulsions in magnetic field

    E-print Network

    Arthur Zakinyan; Yuri Dikansky; Marita Bedzhanyan

    2014-02-05

    The work deals with the experimental study of the emulsion whose dispersion medium is a magnetic fluid while the disperse phase is formed by a glycerin-water mixture. It is demonstrated that under effect of a magnetic field chain aggregates form from the disperse phase drops. Such emulsion microstructure change affects its macroscopic properties. The emulsion dielectric permeability and specific electrical conductivity have been measured. It is demonstrated that under the effect of relatively weak external magnetic fields (~ 1 kA/m) the emulsion electrical parameters may change several fold. The work theoretically analyzes the discovered regularities of the emulsion electrical properties.

  6. 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; Barthlmy, 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

  7. KINETIC ALFVEN TURBULENCE AND PARALLEL ELECTRIC FIELDS IN FLARE LOOPS

    SciTech Connect

    Zhao, J. S.; Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Lu, J. Y., E-mail: js_zhao@pmo.ac.cn [College of Math and Statistics, Nanjing University of Information Science and Technology, Nanjing 210044 (China)

    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.

  8. Ionisation of a quantum dot by electric fields

    SciTech Connect

    Eminov, P A; Gordeeva, S V

    2012-08-31

    We have derived analytical formulas for differential and total ionisation probabilities of a two-dimensional quantum dot by a constant electric field. In the adiabatic approximation, we have calculated the probability of this process in the field of a plane electromagnetic wave and in a superposition of constant and alternating electric fields. The imaginary-time method is used to obtain the momentum distribution of the ionisation probability of a bound system by an intense field generated by a superposition of parallel constant and alternating electric fields. The total probability of the process per unit time is calculated with exponential accuracy. The dependence of the results obtained on the characteristic parameters of the problem is investigated. (laser applications and other topics in quantum electronics)

  9. Liquid bulk rotation induced by electric field at free surface

    NASA Astrophysics Data System (ADS)

    Saghaei, Tayebeh; Moradi, Ali-Reza; Shirsavar, Reza; Habibi, Mehdi

    2015-02-01

    In this paper, we induce rotation in a bulk of polar liquid with one free surface, by applying external crossed electric fields. We show that the induced rotation is due to the imposed stresses at the free surface of the liquid. A simple theoretical model was developed based on solving the Navier-Stokes equation that enables us to calculate the average induced stress in the liquid bulk, using experimental measurements of the angular velocity of the liquid. Our results indicate that the induced stresses and the angular velocities of the rotating liquid are independent from the electrical conductivity of the liquid. However, the induced stresses linearly depend on the external electric field and the applied electric voltage for passing the electric current through the bulk. Both experimental results and the theoretical model show that the angular velocity, linearly changes with depth.

  10. Changes in corticospinal excitability during reach adaptation in force fields

    PubMed Central

    Ahmadi-Pajouh, Mohammad Ali; Harran, Michelle D.; Salimpour, Yousef; Shadmehr, Reza

    2013-01-01

    Both abrupt and gradually imposed perturbations produce adaptive changes in motor output, but the neural basis of adaptation may be distinct. Here, we measured the state of the primary motor cortex (M1) and the corticospinal network during adaptation by measuring motor-evoked potentials (MEPs) before reach onset using transcranial magnetic stimulation of M1. Subjects reached in a force field in a schedule in which the field was introduced either abruptly or gradually over many trials. In both groups, by end of the training, muscles that countered the perturbation in a given direction increased their activity during the reach (labeled as the on direction for each muscle). In the abrupt group, in the period before the reach toward the on direction, MEPs in these muscles also increased, suggesting a direction-specific increase in the excitability of the corticospinal network. However, in the gradual group, these MEP changes were missing. After training, there was a period of washout. The MEPs did not return to baseline. Rather, in the abrupt group, off direction MEPs increased to match on direction MEPs. Therefore, we observed changes in corticospinal excitability in the abrupt but not gradual condition. Abrupt training includes the repetition of motor commands, and repetition may be the key factor that produces this plasticity. Furthermore, washout did not return MEPs to baseline, suggesting that washout engaged a new network that masked but did not erase the effects of previous adaptation. Abrupt but not gradual training appears to induce changes in M1 and/or corticospinal networks. PMID:23034365

  11. Changes in corticospinal excitability during reach adaptation in force fields.

    PubMed

    Orban de Xivry, Jean-Jacques; Ahmadi-Pajouh, Mohammad Ali; Harran, Michelle D; Salimpour, Yousef; Shadmehr, Reza

    2013-01-01

    Both abrupt and gradually imposed perturbations produce adaptive changes in motor output, but the neural basis of adaptation may be distinct. Here, we measured the state of the primary motor cortex (M1) and the corticospinal network during adaptation by measuring motor-evoked potentials (MEPs) before reach onset using transcranial magnetic stimulation of M1. Subjects reached in a force field in a schedule in which the field was introduced either abruptly or gradually over many trials. In both groups, by end of the training, muscles that countered the perturbation in a given direction increased their activity during the reach (labeled as the on direction for each muscle). In the abrupt group, in the period before the reach toward the on direction, MEPs in these muscles also increased, suggesting a direction-specific increase in the excitability of the corticospinal network. However, in the gradual group, these MEP changes were missing. After training, there was a period of washout. The MEPs did not return to baseline. Rather, in the abrupt group, off direction MEPs increased to match on direction MEPs. Therefore, we observed changes in corticospinal excitability in the abrupt but not gradual condition. Abrupt training includes the repetition of motor commands, and repetition may be the key factor that produces this plasticity. Furthermore, washout did not return MEPs to baseline, suggesting that washout engaged a new network that masked but did not erase the effects of previous adaptation. Abrupt but not gradual training appears to induce changes in M1 and/or corticospinal networks. PMID:23034365

  12. Energy of Force-Free Magnetic Fields in Relation to Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Choe, G. S.; Cheng, C. Z.

    2002-05-01

    In typical observations of coronal mass ejections (CMEs), a magnetic structure of a helmet-shaped closed configuration bulges out and eventually opens up. In order for this transition of field configuration to occur spontaneously, the pre-eruption closed magnetic field must have more energy than the post-eruption open field. In force-free fields, however, such a possibility is denied by the Aly-Sturrock theorem. The theorem states that the maximum energy state of force-free fields with a given boundary normal field distribution is the open field. Here we note that the theorem implicitly assumes the existence of the maximum energy configuration. However, this may not be taken for granted because the limiting configuration of energy-increasing sequences of force-free fields does not necessarily have an energy equal to the energy supremum. In this study, we have constructed force-free fields containing tangential discontinuities in multiple flux systems. These force-free fields can be generated from a potential field by footpoint motions that do not conserve the boundary normal field distribution. Some of these force-free fields are found to have more magnetic energy than the corresponding open fields. The constructed force-free configurations are compared with observational features of CME-bearing active regions. Possible mechanisms of CMEs are also discussed.

  13. Force field independent metal parameters using a nonbonded dummy model.

    PubMed

    Duarte, Fernanda; Bauer, Paul; Barrozo, Alexandre; Amrein, Beat Anton; Purg, Miha; Aqvist, Johan; Kamerlin, Shina Caroline Lynn

    2014-04-24

    The cationic dummy atom approach provides a powerful nonbonded description for a range of alkaline-earth and transition-metal centers, capturing both structural and electrostatic effects. In this work we refine existing literature parameters for octahedrally coordinated Mn(2+), Zn(2+), Mg(2+), and Ca(2+), as well as providing new parameters for Ni(2+), Co(2+), and Fe(2+). In all the cases, we are able to reproduce both M(2+)-O distances and experimental solvation free energies, which has not been achieved to date for transition metals using any other model. The parameters have also been tested using two different water models and show consistent performance. Therefore, our parameters are easily transferable to any force field that describes nonbonded interactions using Coulomb and Lennard-Jones potentials. Finally, we demonstrate the stability of our parameters in both the human and Escherichia coli variants of the enzyme glyoxalase I as showcase systems, as both enzymes are active with a range of transition metals. The parameters presented in this work provide a valuable resource for the molecular simulation community, as they extend the range of metal ions that can be studied using classical approaches, while also providing a starting point for subsequent parametrization of new metal centers. PMID:24670003

  14. Force Field Independent Metal Parameters Using a Nonbonded Dummy Model

    PubMed Central

    2014-01-01

    The cationic dummy atom approach provides a powerful nonbonded description for a range of alkaline-earth and transition-metal centers, capturing both structural and electrostatic effects. In this work we refine existing literature parameters for octahedrally coordinated Mn2+, Zn2+, Mg2+, and Ca2+, as well as providing new parameters for Ni2+, Co2+, and Fe2+. In all the cases, we are able to reproduce both M2+O distances and experimental solvation free energies, which has not been achieved to date for transition metals using any other model. The parameters have also been tested using two different water models and show consistent performance. Therefore, our parameters are easily transferable to any force field that describes nonbonded interactions using Coulomb and Lennard-Jones potentials. Finally, we demonstrate the stability of our parameters in both the human and Escherichia coli variants of the enzyme glyoxalase I as showcase systems, as both enzymes are active with a range of transition metals. The parameters presented in this work provide a valuable resource for the molecular simulation community, as they extend the range of metal ions that can be studied using classical approaches, while also providing a starting point for subsequent parametrization of new metal centers. PMID:24670003

  15. The alignment of ice crystals in changing electric fields

    NASA Astrophysics Data System (ADS)

    Foster, T. C.; Hallett, J.

    Orientation of ice crystals in the form of thin plates (diameter up to 30 ?m, thickness 0.5 to a few ?m) was investigated optically for crystals nucleated in a supercooled cloud in a laboratory cold chamber. Random orientation caused by Brownian rotation of small crystals (apparent as twinkling) and alignment caused by airflow resulting from fall motion of larger crystals was changed by application of an electric field either as a step or as an oscillating square wave of variable frequency of order 1-10 Hz. Video records and time exposed still photographs demonstrated crystal fall, oscillation, and orientation changes with electric field magnitude and frequency. Thin film interference colours provided crystal thickness, mass, and moment of inertia. Realignment began for electric fields greater than 0.5-1 kV/m and was complete above 10 kV/m. Measurements of degree of alignment (from random orientation to completely parallel to the electric field) and its time dependence (of order tenths of seconds) are consistent with predictions of a theoretical oscillator model based on electrical torques on ellipsoids in viscous air. In a changing electric field at low frequency, the crystal realignment varies along with the variation field and at high frequency they remain aligned along the average field. These results are applied to larger crystals as occur in the atmosphere with implication for remote sensing of ice by radar and lidar as influenced by local electric fields and with the possibility of their remote measurement by optical observation of changing crystal orientations.

  16. 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.

  17. 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

  18. Electric field enhanced conductivity in strongly coupled dense metal plasma

    SciTech Connect

    Stephens, J.; Neuber, A. [Center for Pulsed Power and Power Electronics, Texas Tech University, Lubbock, Texas 79409 (United States)

    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.

  19. The influence of catch trials on the consolidation of motor memory in force field adaptation tasks

    PubMed Central

    Focke, Anne; Stockinger, Christian; Diepold, Christina; Taubert, Marco; Stein, Thorsten

    2013-01-01

    In computational neuroscience it is generally accepted that human motor memory contains neural representations of the physics of the musculoskeletal system and the objects in the environment. These representations are called internal models. Force field studies, in which subjects have to adapt to dynamic perturbations induced by a robotic manipulandum, are an established tool to analyze the characteristics of such internal models. The aim of the current study was to investigate whether catch trials during force field learning could influence the consolidation of motor memory in more complex tasks. Thereby, the force field was more than double the force field of previous studies (35 Ns/m). Moreover, the arm of the subjects was not supported. A total of 46 subjects participated in this study and performed center-out movements at a robotic manipulandum in two different force fields. Two control groups learned force field A on day 1 and were retested in the same force field on day 3 (AA). Two test groups additionally learned an interfering force field B (= ?A) on day 2 (ABA). The difference between the two test and control groups, respectively, was the absence (0%) or presence (19%) of catch trials, in which the force field was turned-off suddenly. The results showed consolidation of force field A on day 3 for both control groups. Test groups showed no consolidation of force field A (19% catch trials) and even poorer performance on day 3 (0% catch trials). In conclusion, it can be stated that catch trials seem to have a positive effect on the performance on day 3 but do not trigger a consolidation process as shown in previous studies that used a lower force field viscosity with supported arm. These findings indicate that the results of previous studies in which less complex tasks were analyzed, cannot be fully transferred to more complex tasks. Moreover, the effects of catch trials in these situations are insufficiently understood and further research is needed. PMID:23898319

  20. 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.