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1

Contrasting studentsâ understanding of electric field and electric force  

NSDL National Science Digital Library

Students may have greater difficulties in understanding electric interactions because they have less day to day experience with them than with mechanics. There may also be differences in understanding of different electric concepts like electric force and field. This study presents the results of studentsâ responses to two sequences of superposition principle isomorphic questions in which the only difference was that in one of the sequences, the electric force was used and in the other, the electric field. We administered one of the sequences to 249 students at a large private Mexican university after covering electrostatics in an Electricity and Magnetism class. The studentsâ answers, reasoning and drawings were analyzed. We found that students who took the force sequence were better able to correctly answer the questions using the superposition principle than those students with the field sequence. The analysis of the studentsâ reasoning and drawings helped us to examine their understanding of electric field and the use of electric field lines.

Garza, Alejandro; Zavala, Genaro

2014-04-11

2

Context Rich Problems Online Archives: Electric Field and Electric Force  

NSDL National Science Digital Library

This page provides a set of context-rich physics problems relating to electric forces and fields. Each context-rich problem is based on a real-world situation, and includes both information that is relevant to solving the problem and extraneous information. Strategies for problem solving are not explicitly provided. Each problem is formulated so it is too difficult for one student to solve alone, yet not too difficult for a group to master. This resource is based on the research results of the Minnesota Physics Education Research group. See Related items on this page for a link to the full collection.

Group, University O.; Heller, Kenneth; Heller, Patricia

2008-09-29

3

Ponderomotive force in the presence of electric fields  

SciTech Connect

This paper presents averaged equations of particle motion in an electromagnetic wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. The particle is also subjected to an E(vector sign) Multiplication-Sign B(vector sign) drift and a background electric field slowly changing in space and acting along the magnetic field line. The fields, wave amplitude, and the wave vector depend on the coordinate along the magnetic field line. The derivations of the ponderomotive forces are done by assuming that the drift velocity in the ambient magnetic field is comparable to the particle velocity. Such a scenario leads to new ponderomotive forces, dependent on the wave magnetic field intensity, and, as a result, to the additional energy exchange between the wave and the plasma particles. It is found that the parallel electric field can lead to the change of the particle-wave energy exchange rate comparable to that produced by the previously discussed ponderomotive forces.

Khazanov, G. V.; Krivorutsky, E. N. [NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2013-02-15

4

Electric Field How does a charge, q1, exert a force on  

E-print Network

Electric Field How does a charge, q1, exert a force on another charge, q2, when the charges don't touch? The charge, q1, sets up an electric field in its surrounding space This electric field has both magnitude and direction which determine the magnitude and direction of the force acting on q2 #12;Electric

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

5

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

PubMed

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

Geng, Yanan; Wu, Weida

2014-05-01

6

Impulsive force phenomenon of electric field stress causing serious particle contamination in plasma etching equipment  

NASA Astrophysics Data System (ADS)

To demonstrate electric field stress acting as an impulsive force, the action of the stress is investigated using a standard particle. Particles floated from a substrate owing to electric field stress are observed using an in situ particle monitoring system. The results indicate that the more rapidly an electric field changes, the more the stress increases, which demonstrates the impulsive force effect of electric field stress. From the results of this study, we can conclude that the cause of the instantaneous generation of many flaked particles in plasma etching chambers is electric field stress working as an impulsive force.

Kasashima, Yuji; Uesugi, Fumihiko

2014-11-01

7

Electricity: The Mysterious Force  

NSDL National Science Digital Library

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.

2008-01-01

8

Nonconservative forces between dielectric particles in a time-dependent electric field  

NASA Astrophysics Data System (ADS)

When a time-dependent external electric field is applied to a system of small dielectric particles, the time-averaged forces between the particles are enhanced if the external field has a frequency such that surface modes can be excited. We find that the forces are nonconservative if the dielectric function is dissipative; this occurs because the surface modes on nearby particles are coupled, causing their frequencies to depend on the interparticle distances. If a variable surface mode frequency crosses the fixed frequency of the external field at certain interparticle distances, the forces between the particles can change direction in such a way that the force lines spiral into fixed points, where the force is zero. We illustrate these ideas with a simple system for which an analytic solution exists: two identical spheres with a complex dielectric function, in vacuum.

Fuchs, Ronald; Claro, Francisco

2004-03-01

9

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

SciTech Connect

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.

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

1991-08-01

10

Lorentz Force Electrical Impedance Tomography  

E-print Network

This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers...

Grasland-Mongrain, Pol; Chapelon, Jean-Yves; Lafon, Cyril

2014-01-01

11

Gravitational Field and Electric Force Lines of a New 2-SOLITON Solution  

NASA Astrophysics Data System (ADS)

A new exact solution of the coupled Einstein-Maxwell equations is given and studied. It is found using the soliton method, adding one soliton to the Schwarzschild background. The solution is stationary and axial-symmetric, and has five physical parameters. The physical interpretation we give is that it describes a Kerr-Newman (KN) naked singularity linked by a "strut" to a charged black hole. Indeed, on the axis, between the two bodies an unavoidable anomaly region is present (g?? < 0 and a conic singularity). The solution is stationary also in the case with zero total angular momentum. Finally, we give the force lines of the electrical field in a general case, and in the case in which the KN singularity has a much smaller mass than the nearby black hole; we also considered the behavior at different distances of the charge. In spite of the naive interpretation suggested by the mathematical construction of the solution, what we expected to be a "Schwarzschild" black hole appears to be charged and rotating; we interpret this fact as a parameter-mixing phenomenon.

Pizzi, Marco

12

Fully Self-Consistent Ion-Drag-Force Calculations for Dust in Collisional Plasmas with an External Electric Field  

SciTech Connect

The ion drag force on a spherical dust particle immersed in a flowing plasma with an external electric field is self-consistently calculated using the particle-in-cell code SCEPTIC in the entire range of charge-exchange collisionality. Our results, not based on questionable approximations, extend prior analytic calculations valid only in a few limiting regimes. Particular attention is given to the force direction, shown never to be directed opposite to the flow except in the continuum limit, where other forces are of a much stronger magnitude.

Patacchini, Leonardo; Hutchinson, Ian H. [Plasma Science and Fusion Center and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2008-07-11

13

Microextraction of mebendazole across supported liquid membrane forced by pH gradient and electrical field.  

PubMed

In the present study, extraction of mebendazole across a supported-liquid membrane (SLM) was performed based on two different driving forces: (1) pH gradient over the SLM, and (2) electrical field sustained over the SLM. The extracted drug concentration was studied using reversed-phase HPLC-UV. At passive extraction conditions, mebendazole was extracted from alkaline samples (0.01 mmol L(-1) NaOH) into 1-undecanol immobilized in the pores of a porous hollow fiber of polypropylene (SLM), and then transported into 25 ?L of 100mM HCl as the acceptor solution. Under electrokinetic migration conditions, mebendazole transported under applied voltage from acidic solutions (100 mmol L(-1) HCl) through 2-nitrophenyl octyl ether (NPOE) immobilized in the pores of hollow fiber, into 25 ?L of 100 mmol L(-1) HCl as the acceptor solution. The effects of several factors including the nature of organic solvent, pH of donor and acceptor solutions, extraction time and stirring speed on the extraction efficiency of the drug were investigated and optimized. Under optimal conditions, preconcentration factors (PF) of 211 and 190 were obtained for the drug based on passive transport and electromembrane extraction (EME), respectively. Also, linear range of 0.5-1000 ?g L(-1) with estimation of coefficient higher than 0.994 was obtained for both of the proposed methods. The results showed that EME has higher speed in comparison with simple passive transport. The methods were successfully applied to extract mebendazole from plasma and urine samples and satisfactory results were obtained. PMID:21211924

Eskandari, Mahboube; Yamini, Yadollah; Fotouhi, Lida; Seidi, Shahram

2011-04-01

14

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

SciTech Connect

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.

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

1994-07-26

15

Polymer Size Effect on Shape and Position in DNA Trap by Electric and Hydrodynamic Force Fields  

Microsoft Academic Search

In recent years, a phenomenon has been discovered wherein charged particles are trapped near the constricted position of a microfluidic tapering channel when hydropressure and electric field are applied in opposite directions. By this phenomenon, the existence of various types of trapping patterns has already been demonstrated in a T4 phage DNA trapping experiment. In this study, we aim to

Kunimitsu Ueno; Wako Nagasaka; Yuichi Tomizawa; Yoshiteru Nakamori; Eiichi Tamiya; Yuzuru Takamura

2007-01-01

16

Study of electric field distribution in AlGalnP light-emitting diode by Kelvin probe force microscopy  

NASA Astrophysics Data System (ADS)

This work presents results of study of different AlGaInP light-emitting diodes by using Kelvin force probe microscopy. Study of current-voltage characteristics and electric field distribution had shown that for all type of experimental samples containing multiple quantum wells the most significant series resistance of heterostructures is determined by p-isotype heterojunction and confinement p-layer.

Oleynik, V. L.; Prudaev, I. A.; Novikov, Vad A.; Ryaboshtan, Yu L.; Gorlachuk, P. V.

2014-10-01

17

Pictures of Dynamic Electric Fields  

Microsoft Academic Search

The electric field of a point charge moving at relativistic velocities along a single plane of motion may be visualized in a physically intuitive way with the aid of pictures of the electric lines of force. A general derivation of exact parametric equations for these lines of force is described and applied to create the pictures presented here of synchrotron

Roger Y. Tsien

1972-01-01

18

Electric and Magnetic Forces  

NSDL National Science Digital Library

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

2010-02-10

19

Electric and Magnetic Forces: Electric Charges  

NSDL National Science Digital Library

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.

National Science Teachers Association (NSTA)

2008-10-30

20

Harnessing electrical forces for separation. Capillary zone electrophoresis, isoelectric focusing, field-flow fractionation, split-flow thin-cell continuous-separation and other techniques.  

PubMed

A simple analysis, first presented twenty years ago, showed that the effectiveness of a field-driven separation like electrophoresis, as expressed by the maximum number of theoretical plates (N), is given by the dimensionless ratio of two energies N = -delta mu ext/2RT in which -delta mu ext is the electrical potential energy drop of a charged species and RT is the thermal energy (R is the gas constant and T is the absolute temperature). Quantity -delta mu ext is the product of the force F acting on the species and the path length X of separation. The exceptional power of electrophoresis, for which often N approximately 10(6), can be traced directly to the enormous magnitude of the electrical force F. This paper explores the fundamentals underlying several different means for utilizing these powerful electrical forces for separation, including capillary zone electrophoresis, gel electrophoresis, isoelectric focusing, electrical field-flow fractionation and split-flow thin continuous separation cells. Remarkably, the above equation and its relatives are found to describe the approximate performance of all these diverse electrically driven systems. Factors affecting both the resolving power and separation speed of the systems are addressed; from these considerations some broad optimization criteria emerge. The capabilities of the different methods are compared using numerical examples. PMID:2592480

Giddings, J C

1989-10-20

21

Forces in electromagnetic field and gravitational field  

E-print Network

The force can be defined from the linear momentum in the gravitational field and electromagnetic field. But this definition can not cover the gradient of energy. In the paper, the force will be defined from the energy and torque in a new way, which involves the gravitational force, electromagnetic force, inertial force, gradient of energy, and some other new force terms etc. One of these new force terms can be used to explain why the solar wind varies velocity along the magnetic force line in the interplanetary space between the sun and the earth.

Zihua Weng

2008-06-21

22

Electric Field Containerless Processing Technology  

NASA Technical Reports Server (NTRS)

The objective of this task is to develop the science and technology base required to design and construct a high temperature electric field positioning module that could be used by materials scientists to conduct containerless science experiments in a low gravity environment. Containerless science modules that employ electric fields to position and manipulate samples offer several advantages over acoustic or electromagnetic systems. The electric field system will operate not only at atmospheric pressures but also in a vacuum, in contrast to the acoustic modules which can only operate in atmosphere where the acoustic forces are sufficient. The electric field technique puts minimum energy into the sample, whereas the electromagnetic system can deposit energy into the sample through eddy current heat as well as physical mixing in the sample. Two types of electric field modules have been constructed and tested to date. One employs a charged sample and uses electrostatic forces to position and control the sample. The second type of module induces electrical polarization of the sample and electric field gradients to position and control the sample.

Elleman, D. D.; Rhim, W. K.

1985-01-01

23

Electroreception Electric field properties  

E-print Network

) indicate direction and magnitude of force and electron flow · Electric potential isoclines (solid) indicate discharge of Apteronotus leptorhynchus (brown ghost knife fish) The top is a view looking down at the fish

Wilkinson, Gerald S.

24

Interpreting Kelvin probe force microscopy under an applied electric field: local electronic behavior of vapor-liquid-solid Si nanowires.  

PubMed

Kelvin probe force microscopy (KPFM) is used to characterize the electrical characteristics of vapor-liquid-solid (VLS) Si nanowires (NWs) that are grown in-place between two predefined electrodes. KPFM measurements are performed under an applied bias. Besides contact potential differences due to differing materials, the two other primary contributions to measured variations on Si NWs between electrodes are: trapped charges at interfaces, and the parallel and serial capacitance, which are accounted for with voltage normalization and oxide normalization. These two normalization processes alongside finite-element-method simulations are necessary to characterize the bias-dependent response of Si NWs. After applying both normalization methods on open-circuit NWs, which results in a baseline of zero, we conclude that we have accounted for all the major contributions to CPDs and we can isolate effects due to applied bias such as impurity states and charged carrier flow, as well as find open connections when NWs are connected in parallel. These characterization and normalization methods can also be used to determine that the specific contact resistance of electrodes to the NWs is on the order of ?? cm². Thus, the VLS growth method between predefined electrodes overcomes the challenge of making low-resistance contacts to nanoscale systems. Thereby, the experiments and analysis presented outline a systematic method for characterizing nanowires in parallel arrays under device operation conditions. PMID:23609527

Quitoriano, Nathaniel J; Sanderson, Robert N; Bae, Sung-Soo; Ragan, Regina

2013-05-24

25

LABORATORY II ELECTRIC FIELDS AND ELECTRIC POTENTIALS  

E-print Network

Lab II - 1 LABORATORY II ELECTRIC FIELDS AND ELECTRIC POTENTIALS In this lab you will continue to investigate the abstract concept of electric field. If you know the electric field at a point in space, you). With this simulation you can construct a complicated charge configuration and read out the resulting electric field

Minnesota, University of

26

1/00 E&M forces -1/8 ELECTRIC AND MAGNETIC FORCES  

E-print Network

a fluorescent screen. eVa As the electrons move in the horizontal (x) direction, an electric force may will remain constant. The electrons will move in a circular path of radius R with the force toward the center of electrons by electric and magnetic fields. APPARATUS: Electron beam tube, stand with coils, power supply

Glashausser, Charles

27

Electric Field Example 10  

NSDL National Science Digital Library

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.

Christian, Wolfgang; Belloni, Mario

2008-02-19

28

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

29

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

SciTech Connect

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.

Ganesh, Panchapakesan [ORNL; Kent, Paul R [ORNL; Mochalin, Vadym N [ORNL

2011-01-01

30

Distillation under electric fields  

SciTech Connect

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

Shah, V.M. [Univ. of Tennessee, Knoxville, TN (United States). Chemical Engineering Dept.; Blankenship, K.D.; Tsouris, C. [Oak Ridge National Lab., TN (United States)

1997-11-01

31

Computing nonlinear force free coronal magnetic fields  

E-print Network

Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.

T. Wiegelmann; T. Neukirch

2008-01-21

32

Anharmonic force field for methanol  

NASA Astrophysics Data System (ADS)

An ab initio quartic anharmonic force field for methanol has been calculated at the equilibrium position using the CCSD(T) method for the structure and the harmonic potential energy surface, and the MP4(SDQ) method for the anharmonic part of the surface. A triple zeta basis set was employed with symmetrized curvilinear internal valence coordinates in all calculations. The internal coordinate force field constants have been transformed into force constants in the dimensionless normal coordinate representation for various isotopomers. Vibrational term values for CH3OH, CH3OD, CD3OH, and CD3OD have been obtained using second order perturbation theory. Particular care has been devoted to the inclusion of Fermi resonance interactions between different vibrational states. A good accuracy has been achieved in the calculation of the fundamentals for all the isotopomers, the mean absolute error being 5.8 cm-1.

Miani, Andrea; Hänninen, Vesa; Horn, Matthias; Halonen, Lauri

33

Nonconservative electric and magnetic optical forces on submicron dielectric particles  

SciTech Connect

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.

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

34

Modeling solar force-free magnetic fields  

NASA Astrophysics Data System (ADS)

A class of nonlinear force-free magnetic fields is presented, described in terms of the solutions to a second-order, nonlinear ordinary differential equation. These magnetic fields are three-dimensional, filling the infinite half-space above a plane where the lines of force are anchored. They model the magnetic fields of the sun over active regions with a striking geometric realism. The total energy and the free energy associated with the electric current are finite and can be calculated directly from the magnetic field at the plane boundary using the virial theorem. In the study of solar magnetic fields with data from vector magnetographs, there is a long-standing interest in devising algorithms to extrapolate for the force-free magnetic field in a given domain from prescribed field values at the boundary. The closed-form magnetic fields of this paper open up an opportunity for testing the reliability and accuracy of algorithms that claim the capability of performing this extrapolation. The extrapolation procedure as an ill-posed mathematical problem is discussed.

Low, B. C.; Lou, Y. Q.

1990-03-01

35

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

E-print Network

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

Grasland-Mongrain, Pol

2014-01-01

36

Charge carrier dynamics and interactions in electric force microscopy.  

PubMed

In electric force microscopy, a charged atomic force microscope tip in vacuum senses a fluctuating electrical force generated by the sample. Such measurements can in principle probe electrical noise generated by moving charge carriers in an organic semiconductor. We present a theory of cantilever frequency fluctuations in electric force microscopy, driven by coupled charge carrier dynamics and dielectric fluctuations. The connection between observable frequency fluctuations in electric force microscopy and the Casimir-Lifshitz force is described. This classical electrodynamic calculation is based on Maxwell's equations coupled to diffusive carrier transport. The effects of carrier transport and inter-carrier interactions on the spectrum of cantilever frequency noise are elucidated. We find that a simplified model of freely diffusing carriers can overestimate cantilever frequency noise by several orders of magnitude because of the neglect of interactions. Electric force microscopy measurements on an organic field effect transistor are reported and qualitatively interpreted in terms of the suppression of electrical noise from charge carriers by Coulomb interactions. PMID:23020344

Lekkala, Swapna; Hoepker, Nikolas; Marohn, John A; Loring, Roger F

2012-09-28

37

Electrical Forces For Microscale Cell Manipulation  

E-print Network

differentiation (3) to detecting pathogenic bac- teria in food supplies (4), cell-based assays are crucial that our fingers cannot grasp. Many techniques exist to physically manipulate cells, including optical tweezers (5), acoustic forces (6), and surface modification (7). Electrical forces are an increas- ingly

Voldman, Joel

38

Electric Field and Potential Model  

NSDL National Science Digital Library

The EJS Electric Field and Potential Model shows the electric field and potential for cylindrical and spherical symmetry. In both symmetries, there are co-centric charged surfaces where the outer surface is grounded. The model reports the force on a test charge (yellow) between the co-centric surfaces as well as the voltage. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. The Electric Field and Potential model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_ElectricFieldPotential.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Cox, Anne

2009-11-06

39

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

E-print Network

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 ...

Grodzinsky, Alan J.

40

Equatorial electric field observations  

NASA Technical Reports Server (NTRS)

The paper reports both dc and ac measurements of equatorial electric fields from the San Marco D satellite. These measurements were performed with double floating probe sensors and have yielded a surprising number of new phenomena and effects in regions of equatorial spread-F. Among the phenomena observed are unexpected large-amplitude Rayleigh-Taylor updrafting velocities in equatorial bubbles.

Aggson, T. L.; Hanson, W. B.; Herrero, F. A.; Maynard, N. C.; Pfaff, R. F.; Saba, J. L.; Tsunoda, R. T.

1993-01-01

41

Electric Multipole Field Model  

NSDL National Science Digital Library

The EJS Electric Multipole Model of a point charge (monopole), a dipole, or a quadrupole can show either field vectors or the scalar potential (voltage). A slider changes the charge and a movable detector shows the electric field direction and magnitude or measures the potential. Detector values can be recorded into a data table and analyzed using a built-in data analysis tool. Users can modify this simulation by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. The Electric Multipole Field model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_ElectricMultipoleField.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Cox, Anne; Christian, Wolfgang; Franciscouembre

2010-01-31

42

Interaction Between Flames and Electric Fields Studied  

NASA Technical Reports Server (NTRS)

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.

Yuan, Zeng-Guang; Hegde, Uday

2003-01-01

43

Electric field imaging  

NASA Astrophysics Data System (ADS)

The physical user interface is an increasingly significant factor limiting the effectiveness of our interactions with and through technology. This thesis introduces Electric Field Imaging, a new physical channel and inference framework for machine perception of human action. Though electric field sensing is an important sensory modality for several species of fish, it has not been seriously explored as a channel for machine perception. Technological applications of field sensing, from the Theremin to the capacitive elevator button, have been limited to simple proximity detection tasks. This thesis presents a solution to the inverse problem of inferring geometrical information about the configuration and motion of the human body from electric field measurements. It also presents simple, inexpensive hardware and signal processing techniques for makin the field measurements, and several new applications of electric field sensing. The signal processing contribution includes synchronous undersampling, a narrowband, phase sensitive detection technique that is well matched to the capabilities of contemporary microcontrollers. In hardware, the primary contributions are the School of Fish, a scalable network of microcontroller-based transceive electrodes, and the LazyFish, a small footprint integrated sensing board. Connecting n School of Fish electrodes results in an array capable of making heterodyne measurements of any or all n(n - 1) off-diagonal entries in the capacitance matrix. The LazyFish uses synchronous undersampling to provide up to 8 high signal- to-noise homodyne measurements in a very small package. The inverse electrostatics portion of the thesis presents a fast, general method for extracting geometrical information about the configuration and motion of the human body from field measurements. The method is based on the Sphere Expansion, a novel fast method for generating approximate solutions to the Laplace equation. Finally, the thesis describes a variety of applications of electric field sensing, many enabled by the small footprint of the LazyFish. To demonstrate the School of Fish hardware and the Sphere Expansion inversion method, the thesis presents 3 dimensional position and orientation tracking of two hands. 1 (Copies available exclusively from MIT Libraries, Rm. 14- 0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) 1Please see the URL http://www.media.mit.edu/people/jrs/thesis.html for video clips, code, and other information related to this thesis.

Smith, Joshua Reynolds

44

Simulation of colloidal fouling by coupling a dynamically updating velocity profile and electric field interactions with Force Bias Monte Carlo methods for membrane filtration.  

PubMed

Pressure-driven flow through a channel with membrane walls is modeled for high particulate volume fractions of 10%. Particle transport is influenced by Brownian diffusion, shear-induced diffusion, and convection due to the axial crossflow. The particles are also subject to electrostatic double layer repulsion and van der Waals attraction, from both particle-particle and particle-membrane interactions. Force Bias Monte Carlo (FBMC) simulations predict the deposition of the particles onto the membranes, where both hydrodynamics and the change in particle potentials determine the probability that a proposed move is accepted. The particle volume fraction is used to determine an apparent local viscosity observed by the continuum flow. As particles migrate, the crossflow velocity field evolves in quasi-steady fashion with each time instance appearing fully developed in the downstream direction. Particles subject to combined hydrodynamic and electric effects (electrostatic double layer repulsion and van der Waals attraction) reach a more stable steady-state as compared to systems with only hydrodynamic effects considered. As expected, at higher crossflow Reynolds numbers more particles remain in the crossflow free stream. PMID:23540433

Boyle, Paul M; Houchens, Brent C; Kim, Albert S

2013-06-01

45

Electrical characterization of zinc oxide/aluminum nitride thin film precursor field effect transistor structures: A conducting atomic force microscopy and density functional theoretical study  

NASA Astrophysics Data System (ADS)

Electrical transport across pulsed laser deposited zinc oxide (ZnO)/aluminum nitride (AlN)/Si(100) thin film structures has been studied using conducting atomic force microscopy. Current versus voltage spectroscopy performed on the samples with varying AlN layer thickness (t), revealed asymmetric nonlinear behavior with a finite zero current region. The effective barrier height of the system is found to be (˜0.2 eV). The width of the zero current region was found to decrease exponentially with respect to t finally attaining the bulk band gap value. Density functional theory based calculations were carried out on the AlN and AlN-ZnO composite surface to investigate the band gap variation and ZnO adsorption on AlN. Results obtained by these calculations are in harmony with the experimental findings. Calculated values of the bulk cohesive energy explain the growth of the ZnO in an axis perpendicular to the surface supporting the experimentally observed results. Constant voltage current scans studies on the same sample showed the existence of current leakage spots. Current scans performed with varying bias voltages described an unambiguous growth profile of current leakage spots. These leakage spots were observed to evolve in a self similar pattern with the bias, which implied a possible existence of fractal dimension in the pattern of their growth. Mass fractal analysis is therefore carried out to model the growth pattern. Evolution of the mass-fractal with respect to the applied bias is found to be a case of Rayleigh distribution on a two-dimensional Poisson field, in the limiting case.

Dey, Shirshendu; Jejurikar, Suhas; Bhattacharya, Somesh Kumar; Banerji, Anirban; Adhi, K. P.; Dharmadhikari, C. V.

2010-11-01

46

Electric and Magnetic Forces: Electrostatics and Current Electricity  

NSDL National Science Digital Library

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 second of three Science Objects in the Electric and Magnetic Forces SciPack.

National Science Teachers Association (NSTA)

1900-01-01

47

Weyl-type fields with geodesic lines of force  

Microsoft Academic Search

The static electrogravitational equations are studied and it is shown that an aligned type D metric that has a Weyl-type relationship between the gravitational and electric potential has shear-free geodesic lines of force. All such fields are then found and turn out to be the fields of a charged sphere, charged infinite rod and charged infinite plate. A further solution

Brendan S. Guilfoyle

1999-01-01

48

Static and dynamical Meissner force fields  

NASA Astrophysics Data System (ADS)

The coupling between copper-based high temperature superconductors (HTS) and magnets is represented by a force field. Zero-field cooled experiments were performed with several forms of superconductors: 1) cold-pressed sintered cylindrical disks; 2) small particles fixed in epoxy polymers; and 3) small particles suspended in hydrocarbon waxes. Using magnets with axial field symmetries, direct spatial force measurements in the range of 0.1 to 10(exp 4) dynes were performed with an analytical balance and force constants were obtained from mechanical vibrational resonances. Force constants increase dramatically with decreasing spatial displacement. The force field displays a strong temperature dependence between 20 and 90 K and decreases exponentially with increasing distance of separation. Distinct slope changes suggest the presence of B-field and temperature-activated processes that define the forces. Hysteresis measurements indicated that the magnitude of force scales roughly with the volume fraction of HTS in composite structures. Thus, the net force resulting from the field interaction appears to arise from regions as small or smaller than the grain size and does not depend on contiguous electron transport over large areas. Results of these experiments are discussed.

Weinberger, B. R.; Lynds, L.; Hull, J. R.; Mulcahy, T. M.

1991-01-01

49

Cryosurgery with Pulsed Electric Fields  

PubMed Central

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

Daniels, Charlotte S.; Rubinsky, Boris

2011-01-01

50

Electric-field-induced phase transitions in electrorheological (ER) fluids in non-uniform electric fields  

NASA Astrophysics Data System (ADS)

In a uniform electric field, the structure of an ER fluid is governed by the interplay of long-ranged electric-field-induced interparticle interactions and thermal forces. When the ratio between the average electric energy of the interparticle interactions and the thermal energy exceeds a critical value an ER phase transition occurs (B. Khusid, A. Acrivos, Phys. Rev. E, 52, 1669, 1995). The application of a non-uniform electric field to an ER fluid will induce a translational motion of the particles, the so-called dielectrophoresis. We found that when the line of equal chemical potential for a non-uniform electric field in the phase diagram of the ER fluid intersects the critical line, the dielectrophoresis in a non-uniform AC electric field will be accompanied by ER phase transitions. In this case, the interplay of the both electric-field-induced effects leads to an abrupt change in the particle concentration distribution and, as a result, to the formation of a concentrated layer of particles in those regions, where, depending on the sign of the effective polarizability of a particle, the strength of the electric field is either higher or lower. The theoretical predictions of the theory which we have developed are consistent with the characteristic pearl-cell and diamond patterns of the particle aggregation observed previously in high-gradient electric fields generated in microelectrode systems (R. Pethig, Y. Huang, X.-B. Wang, J.P.H. Burt, J. Phys. D: Appl. Phys., 24, 881, 1992).

Khusid, Boris; Acrivos, Andreas

1997-03-01

51

Molecular simulations: Force fields for carbon capture  

NASA Astrophysics Data System (ADS)

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.

Getman, Rachel B.

2012-10-01

52

Common Force Field Thermodynamics of Cholesterol  

PubMed Central

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

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

2013-01-01

53

MEASUREMENT OF VAN DER WAALS FORCE OF TONER ADHESION EMPLOYING A LINEARLY INCREASING ELECTRIC FIELD AND DETERMINING THE TONER JUMPING VOLTAGE  

Microsoft Academic Search

Both van der Waals and electrostatic forces of adhesion between toners and substrates play an important role in electrophotography processes employed in copying machines and laser printers. We report here a method of estimating van der Waals forces of adhesion between various substrates and toners of different particle sizes. The method involves the measurement of the detachment force and the

Y. HOSHINO; N. KUTSUWADA; Y. WATANABE; H. IZAWA

1996-01-01

54

Electric field statistics in MHD turbulence  

E-print Network

Electric field statistics in MHD turbulence Bernard Knaepen, Nicolas Denewet & Daniele Carati, ULB #12;Electric field statistics in MHD turbulence Outline Electric field in MHD? Particle acceleration Statistics of the electric & magnetic fields #12;Outline Electric field in MHD? Particle acceleration

Low, Robert

55

Weyl-type Fields with Geodesic Lines of Force  

Microsoft Academic Search

The static electrogravitational equations are studied and it is shown that an\\u000aaligned type D metric which has a Weyl-type relationship between the\\u000agravitational and electric potential has shearfree geodesic lines of force. All\\u000asuch fields are then found and turn out to be the fields of a charged sphere,\\u000acharged infinite rod and charged infinite plate. A further solution

Brendan S. Guilfoyle

1999-01-01

56

Weyl-type Fields with Geodesic Lines of Force  

E-print Network

The static electrogravitational equations are studied and it is shown that an aligned type D metric which has a Weyl-type relationship between the gravitational and electric potential has shearfree geodesic lines of force. All such fields are then found and turn out to be the fields of a charged sphere, charged infinite rod and charged infinite plate. A further solution is also found with shearing geodesic lines of force. This new solution can have $m>|e|$ or $m<|e|$, but cannot be in the Majumdar-Papapetrou class (in which $m = |e|$). It is algebraically general and has flat equipotential surfaces.

Brendan S. Guilfoyle

1999-05-18

57

Weyl-Type Fields with Geodesic Lines of Force  

E-print Network

The static electrogravitational equations are studied and it is shown that an aligned type D metric which has a Weyl-type relationship between the gravitational and electric potential has shearfree geodesic lines of force. All such fields are then found and turn out to be the fields of a charged sphere, charged infinite rod and charged infinite plate. A further solution is also found with shearing geodesic lines of force. This new solution can have $m>|e|$ or $m<|e|$, but cannot be in the Majumdar-Papapetrou class (in which $m = |e|$). It is algebraically general and has flat equipotential surfaces.

Guilfoyle, B S

1999-01-01

58

What Are Electric and Magnetic Fields? (EMF)  

MedlinePLUS

What are Electric and Magnetic Fields? (EMF) Electric and Magnetic Fields Electricity is an essential part of our lives. Electricity powers all sorts of things around us, from computers to refrigerators ...

59

Nanoribbons in external electric fields  

E-print Network

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.

Evgeny Korotyaev; Anton Kutsenko

2008-03-19

60

Additive empirical force field for hexopyranose monosaccharides  

PubMed Central

We present an all-atom additive empirical force field for the hexopyranose monosaccharide form of glucose and its diastereomers allose, altrose, galactose, gulose, idose, mannose, and talose. The model is developed to be consistent with the CHARMM all-atom biomolecular force fields, and the same parameters are used for all diastereomers, including both the ?- and ?-anomers of each monosaccharide. The force field is developed in a hierarchical manner and reproduces the gas-phase and condensed-phase properties of small-molecule model compounds corresponding to fragments of pyranose monosaccharides. The resultant parameters are transferred to the full pyranose monosaccharides and additional parameter development is done to achieve a complete hexopyranose monosaccharide force field. Parametrization target data include vibrational frequencies, crystal geometries, solute – water interaction energies, molecular volumes, heats of vaporization, and conformational energies, including those for over 1800 monosaccharide conformations at the MP2/cc-pVTZ//MP2/6-31G(d) level of theory. Though not targeted during parametrization, free energies of aqueous solvation for the model compounds compare favorably with experimental values. Also well-reproduced are monosaccharide crystal unit cell dimensions and ring pucker, densities of concentrated aqueous glucose systems, and the thermodynamic and dynamic properties of the exocyclic torsion in dilute aqueous systems. The new parameter set expands the CHARMM additive force field to allow for simulation of heterogeneous systems that include hexopyranose monosaccharides in addition to proteins, nucleic acids, and lipids. PMID:18470966

Guvench, Olgun; Greene, Shannon N.; Kamath, Ganesh; Brady, John W.; Venable, Richard M.; Pastor, Richard W.; MacKerell, Alexander D.

2010-01-01

61

6.641 Electromagnetic Fields, Forces, and Motion, Spring 2003  

E-print Network

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 ...

Zahn, Markus, 1946-

62

Introduction to power-frequency electric and magnetic fields.  

PubMed Central

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

Kaune, W T

1993-01-01

63

Electric Field: What is Wrong? Package  

NSDL National Science Digital Library

The EJS Electric Field: What is Wrong? Package is a collection of models for electrostatics with errors intentionally built into each model. Users can move charges around and see the force, observe the electric field generated by charge configurations, and observe the motion of test particles in electric fields to try to identify the errors in the simulation. Users can inspect, modify and correct any simulation in the package by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. The package also includes a brief overview of programming basics needed to correct the models. The Electric Field: What is Wrong? Package was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_electric_wiw.jar file will launch the package if Java is installed. Navigate within the package and click on a green triangle to run a particular simulation. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available on ComPADRE.

Cox, Anne; Christian, Wolfgang; Franciscouembre

2010-04-16

64

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)

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.

Zhou, Kai

65

Performance optimization in electric field gradient focusing.  

PubMed

Electric field gradient focusing (EFGF) is a technique used to simultaneously separate and concentrate biomacromolecules, such as proteins, based on the opposing forces of an electric field gradient and a hydrodynamic flow. Recently, we reported EFGF devices fabricated completely from copolymers functionalized with poly(ethylene glycol), which display excellent resistance to protein adsorption. However, the previous devices did not provide the predicted linear electric field gradient and stable current. To improve performance, Tris-HCl buffer that was previously doped in the hydrogel was replaced with a phosphate buffer containing a salt (i.e., potassium chloride, KCl) with high mobility ions. The new devices exhibited stable current, good reproducibility, and a linear electric field distribution in agreement with the shaped gradient region design due to improved ion transport in the hydrogel. The field gradient was calculated based on theory to be approximately 5.76 V/cm(2) for R-phycoerythrin when the applied voltage was 500 V. The effect of EFGF separation channel dimensions was also investigated; a narrower focused band was achieved in a smaller diameter channel. The relationship between the bandwidth and channel diameter is consistent with theory. Three model proteins were resolved in an EFGF channel of this design. The improved device demonstrated 14,000-fold concentration of a protein sample (from 2 ng/mL to 27 microg/mL). PMID:19081099

Sun, Xuefei; Farnsworth, Paul B; Tolley, H Dennis; Warnick, Karl F; Woolley, Adam T; Lee, Milton L

2009-01-01

66

Fiber Optic Electric Field Micro Sensor  

NASA Astrophysics Data System (ADS)

A novel method and apparatus for sensing AC and DC electric fields incorporating a fiber-optic transducer mounted directly on the tip of an optical fiber waveguide has been demonstrated. The transducer employs a conductive Fabry-Perot microcavity bounded by a conductive, thin and corrugated silicon diaphragm. When the conductive microcavity is placed into an electric field, the electric field is excluded from within the equipotential cavity, which acts as a Faraday cage, and a net electrostatic force exerted on the surface of the diaphragm. The diaphragm deflects linearly and uniformly under the influence of the extremely low electrostatic pressures which are induced. The diaphragm deflection modulates the reflectance within the optical fiber by varying the gap of the cavity. The change in reflected light is measured and correlated to the field strength using and improved dual-wavelength referencing technique which compensates for bending and transmission losses in the optical fiber. Electric fields in the range of 0 to 300KV/m were successfully measured. The minimum intensity detected was of the order of 40KV/m. This relatively low intensity is due to the high boron-diffusion of the fabricated silicon diaphragms. However, higher sensitivities are possible by thinning the diaphragm, increasing its radius, reducing the boss ratio or decreasing the corrugation depth. No corona or discharge effects were noticed and a good repeatability was observed in the measurements.

Mendez Chamorro, Alexis

67

Reactive Force Field & Molecular Dynamics Simulations  

E-print Network

: Parallel reactive molecular dynamics (MD) RMD ReaxFF · Applications: 1. Combustion of aluminum · Large scale (multimillion atoms) · Long time (nanosecond) #12;Reactive force field (RMD & ReaxFF (ReaxFF) #12;Classification of ReaxFF Potential Bonded Non-bonded E = Elp + Eover + Eunder + Ebond

Southern California, University of

68

Multi robot mapping using force field simulation  

Microsoft Academic Search

This paper describes a novel approach, called Force Field Simulation, to multi robot map- ping that works under the constraints given in autonomous search and rescue robotics. Extremely poor prealignment, lack of landmarks, and minimal overlap between scans are the main challenges. The presented algorithm solves the alignment problem of such laser scans utilizing a gradient descent approach motivated by

Rolf Lakaemper; Nagesh Adluru; Longin Jan Latecki; Raj Madhavan

2007-01-01

69

Multi Robot Mapping using Force Field Simulation  

Microsoft Academic Search

This paper describes a novel approach, called Force Field Simulation to multi robot mapping that works under the constraints given in autonomous search and rescue robotics. Extremely poor pre-alignment, lack of landmarks and minimal overlap between scans are the main challenges. The presented al- gorithm solves the alignment problem of such laser scans utilizing a gradient descent approach motivated by

Rolf Lakaemper; Raj Madhavan; Gaithersburg NIST

70

Minds on Physics: Fundamental Forces and Fields, Activities and Reader  

NSDL National Science Digital Library

This is the fourth in a series of six books which involves activities designed for students. This volume deals with the basics of gravitational, electric, and magnetic forces and fields. The activities part contains guidelines with which teachers can base activities and many questions which can be raised in class. The reader part creates opportunity for discussion and summarizes content covered after the activities have been performed.

Leonard, William J.; Dufresne, Robert J.; Gerace, William J.; Mestre, Jose P.

2006-07-22

71

Optical Near-field Interactions and Forces for Optoelectronic Devices  

NASA Astrophysics Data System (ADS)

Throughout history, as a particle view of the universe began to take shape, scientists began to realize that these particles were attracted to each other and hence came up with theories, both analytical and empirical in nature, to explain their interaction. The interaction pair potential (empirical) and electromagnetics (analytical) theories, both help to explain not only the interaction between the basic constituents of matter, such as atoms and molecules, but also between macroscopic objects, such as two surfaces in close proximity. The electrostatic force, optical force, and Casimir force can be categorized as such forces. A surface plasmon (SP) is a collective motion of electrons generated by light at the interface between two mediums of opposite signs of dielectric susceptibility (e.g. metal and dielectric). Recently, surface plasmon resonance (SPR) has been exploited in many areas through the use of tiny antennas that work on similar principles as radio frequency (RF) antennas in optoelectronic devices. These antennas can produce a very high gradient in the electric field thereby leading to an optical force, similar in concept to the surface forces discussed above. The Atomic Force Microscope (AFM) was introduced in the 1980s at IBM. Here we report on its uses in measuring these aforementioned forces and fields, as well as actively modulating and manipulating multiple optoelectronic devices. We have shown that it is possible to change the far field radiation pattern of an optical antenna-integrated device through modification of the near-field of the device. This modification is possible through change of the local refractive index or reflectivity of the "hot spot" of the device, either mechanically or optically. Finally, we have shown how a mechanically active device can be used to detect light with high gain and low noise at room temperature. It is the aim of several of these integrated and future devices to be used for applications in molecular sensing, and we believe that these methods show their potential for a chip-scale sensing device.

Kohoutek, John Michael

72

Influence of electric field on plant weight  

Microsoft Academic Search

This paper reports the influence of D.C. electric field on plant growth. We used the white radish sprout as the sample. The seeds of white radish sprout were grown under two circumstances; one is under electric fields, and the other is without electric fields. We have confirmed the following things: 1. The application of D.C. electric field improves the germination

T. Okumura; Y. Muramoto; N. Shimizu

2009-01-01

73

Electric field divertor plasma pump  

DOEpatents

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.

Schaffer, M.J.

1994-10-04

74

Human Tracking Using Electric Fields  

Microsoft Academic Search

In this paper we describe a simple, cheap, and unobtrusive demo system that can track multiple persons with low-frequency electric fields. The system's operation is based on measuring the capacitance between multiple floor tiles and a receiving electrode. The presented system is invisible to the user and uses a single-chip solution to measure the capacitances. The system was provided for

Miika Valtonen; Jukka Vanhala

2009-01-01

75

Electric field divertor plasma pump  

DOEpatents

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.

Schaffer, Michael J. (San Diego, CA)

1994-01-01

76

Electric fields in irradiated dielectrics  

NASA Technical Reports Server (NTRS)

An existing model for quantitatively predicting electric field build-up in dielectrics is used to demonstrate the importance of material parameters. Results indicate that electron irradiation will produce 10 to the 6th power V/cm in important materials. Parameters which can alter this build-up are discussed. Comparison to known irradiation induced dielectric charging experiments is discussed.

Frederickson, A. R.

1979-01-01

77

Linear electric field mass spectrometry  

DOEpatents

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.

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

1992-01-01

78

Linear electric field mass spectrometry  

DOEpatents

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.

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

1992-12-01

79

Electric Field Sensing and the \\  

Microsoft Academic Search

We have developed a novel input device called the "Flying Fish", which uses ElectricField (EF) sensing. We describe the basic physical principles of EF sensing, and show howit provides a simple, cheap mechanism for using hand gestures to navigate through virtualspaces, without the need for wearing or holding anything. We also discuss the implications ofthis type of device for interface

David Allport; Thomas G. Zimmerman; Joeseph A. Paradiso; R Joshua; Neil Gershenfeld

80

Electric Charge and Electric Field Electrostatics: Charge at rest  

E-print Network

Chapter 16 Electric Charge and Electric Field #12;Electrostatics: Charge at rest Electric Charges of conservation of Electric Charge: The net amount of electric charge produced in any process is zero. Model, neutral). #12;� All protons and electrons have same magnitude of electric charge but their masses

Yu, Jaehoon

81

Electric field induced surface modification of Au  

SciTech Connect

We discuss the role of localized high electric fields in the modification of Au surfaces with a W probe using the interfacial force microscope. Upon bringing a probe close to a Au surface, we measure both the interfacial force and the field emission current as a function of separation with a constant potential of 100 V between tip and sample. The current initially increases exponentially as the separation decreases. However, at a distance of less than {approximately}500 {Angstrom}, the current rises sharply as the surface begins to distort and rapidly close the gap. Retraction of the tip before contact is made reveals the formation of a mound on the surface. We propose a simple model, in which the localized high electric field under the tip assists the production of mobile Au adatoms by detachment from surface steps, and a radial field gradient causes a net flux of atoms toward the tip by surface diffusion. These processes give rise to an unstable surface deformation which, if left unchecked, results in a destructive mechanical contact. We discuss our findings with respect to earlier work using voltage pulses in the scanning tunneling microscope as a means of nanofabrication. {copyright} {ital 1999 American Institute of Physics.}

Mayer, T.M.; Houston, J.E.; Franklin, G.E.; Erchak, A.A.; Michalske, T.A. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1413 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185-1413 (United States)

1999-06-01

82

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

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;…

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

83

Electric-field-induced flame speed modification  

SciTech Connect

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.

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

84

General Multiobjective Force Field Optimization Framework, with Application to Reactive Force Fields for Silicon Carbide  

E-print Network

: (1) the ReaxFF reactive force field for modeling the adiabatic reactive dynamics of silicon carbide quantum mechanical data sets for demanding applications like ReaxFF, electronic fast forward (or electron

Goddard III, William A.

85

Force field calculation for inplane vibrations of ethylene using cndo \\/Force method  

Microsoft Academic Search

cndo\\/Force method is used to evaluate redundancy-free internal valence force field (rfivff) for inplane vibrations of ethylene. The bending force constants, the stretch-band and bend-bend interaction force constants\\u000a are predicted reasonably well in magnitude and sign by this method; whereas stretching force constants and stretch-stretch\\u000a interactions are overestimated. Initial force field is set up by transferring stretching force constants from

A Jothi; G Shanmugam; A Annamalai; Surjit Singh

1982-01-01

86

Perfluoroalkane force field for lipid membrane environments.  

PubMed

In this work, we present atomic parameters of perfluoroalkanes for use within the CHARMM force field. Perfluorinated alkanes represent a special class of molecules. On the one hand, they are considerably more hydrophobic than lipids, but on the other hand, they are not lipophilic either. Instead, they represent an independent class of philicity, enabling a whole portfolio of applications within both materials science and biochemistry. We performed a thorough parametrization of all bonded and nonbonded parameters with a particular focus on van der Waals parameters. Here, the general framework of the CHARMM and CGenFF force fields has been followed. The van der Waals parameters have been fitted to experimental densities over a wide range of temperatures and pressures. This newly parametrized class of molecules will open the gate for a variety of simulations of biologically relevant systems within the CHARMM force field. A particular perspective for the present work is the influence of polyphilic transmembrane molecules on membrane properties, aggregation phenomena, and transmembrane channels. PMID:25275859

von Rudorff, Guido Falk; Watermann, Tobias; Sebastiani, Daniel

2014-10-30

87

Forces on a spherical conducting particle in E × B fields  

NASA Astrophysics Data System (ADS)

The forces acting on a spherical conducting particle in a transversely flowing magnetized plasma are calculated in the entire range of magnetization and Debye length, using the particle code SCEPTIC3D (Patacchini and Hutchinson 2010 Plasma Phys. Control. Fusion 52 035005, 2011 Plasma Phys. Control. Fusion 53 025005). In short Debye length (i.e. high density) plasmas, both the ion-drag and Lorentz force arising from currents circulating inside the dust show strong components antiparallel to the convective electric field, suggesting that a free dust particle should gyrate faster than what predicted by its Larmor frequency. In intermediate to large Debye length conditions, by a downstream depletion effect already reported in unmagnetized strongly collisional regimes, the ion-drag in the direction of transverse flow can become negative. The internal Lorentz force, however, remains in the flow direction, and large enough in magnitude so that no spontaneous dust motion should occur.

Patacchini, Leonardo; Hutchinson, Ian H.

2011-06-01

88

Magnetic Fields Analogous to electric field, a magnet  

E-print Network

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

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

89

DFT SQM force field for cobalt corrinoids  

NASA Astrophysics Data System (ADS)

This Letter introduces a systematic development of a quantitative vibrational force field (FF) capable of modeling vibrational spectra of cobalt corrinoids (B 12 derivatives). The scaled quantum mechanical (SQM) method is used to refine density functional theory (DFT) based force constants calculated at the B3LYP level of theory. The reliability of the DFT-SQM FF for cobalt corrinoids is tested on a six-coordinate methylcobalamin Im-[Co III-corrin]-CH 3 model. It is shown that the computed frequencies and Raman intensities permit detailed vibrational assignment. This analysis illustrates the utility of DFT-SQM FF in making detailed connections between the structure of cobalt corrinoids and their vibrational spectra.

Andruniow, Tadeusz; Zgierski, Marek Z.; Kozlowski, Pawel M.

2000-12-01

90

A compact high field magnetic force microscope.  

PubMed

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

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

2014-12-01

91

Dielectric fluid in inhomogeneous pulsed electric field  

NASA Astrophysics Data System (ADS)

We consider the dynamics of a compressible fluid under the influence of electrostrictive ponderomotive forces in strong inhomogeneous nonstationary electric fields. It is shown that if the fronts of the voltage rise at a sharp, needlelike electrode are rather steep (less than or about nanoseconds), the region of negative pressure arises, which can reach values at which the fluid loses its continuity with the formation of cavitation ruptures. If the voltage on the electrode is not large enough or the front is flatter, the cavitation in the liquid does not occur. However, a sudden shutdown of the field results in a reverse flow of liquid from the electrode, which leads to appearance of negative pressure, and, possibly, cavitation.

Shneider, M. N.; Pekker, M.

2013-04-01

92

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

E-print Network

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.

Alexander J. Silenko

2006-04-11

93

Electric Field Induced Interfacial Instabilities  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

94

Reactive force fields for proton transfer dynamics.  

PubMed

A force field-inspired method based on fitted, high-quality multidimensional potential energy surfaces to follow proton transfer (PT) reactions in molecular dynamics simulations is presented. In molecular mechanics with proton transfer (MMPT) a system is partitioned into a region where proton transfer takes place and the remaining degrees of freedom which are treated with a conventional force field. The implementation of the method and applications to specific chemically and biologically relevant scenarios are presented. MMPT is developed in view of two primary areas in mind: to follow the molecular dynamics of proton transfer in the condensed phase on realistic time scales and to adapt the shape (morphing) of the potential energy surface for specific applications. MMPT is applied to PT in protonated ammonia dimer, double proton transfer in 2-pyridone-2-hydroxypyridine, and the first step of PT from a protein side-chain towards a buried [3Fe4S] cluster in ferredoxin I. Specific findings of the work include the fundamental role of the N-N vibration as the gating mode for PT in NH4+...NH3 and the qualitative understanding of PT from the protein to a metastable active-site water molecule in Ferredoxin I. PMID:18072179

Lammers, Sven; Lutz, Stephan; Meuwly, Markus

2008-05-01

95

Cell separation using electric fields  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

96

Cell separation using electric fields  

NASA Technical Reports Server (NTRS)

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.

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

2009-01-01

97

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...

98

Drag Forces, Neutral Wind and Electric Conductivity Changes in the Ionospheric E Region  

E-print Network

The neutrals in the Earth environment are in fact free and subjected to drag forces (by ions). In this study we show that drag or friction forces in the ionosphere-thermosphere system initiate changes in the plasma flow, neutral wind, and the conductivity, as well. Ions and electrons embedded in neutral wind field of velocity u acquire drifts perpendicular both to the initial neutral wind velocity and to the ambient magnetic field producing a perpendicular electric current. This perpendicular electric current is defined by a conductivity derived previously and the polarization electric field u x B. Self-consistently, the free neutrals acquires an additional neutral velocity component perpendicular to the initial neutral wind velocity u. The Pedersen and Hall currents wane within a specific time inversely proportional to neutral-ion collision frequency. These findings are relevant to a better understanding of electric current generation, distribution and closure in weakly ionized plasmas where charged particle...

Nenovski, Petko

2014-01-01

99

Computer Enhanced Electrics Fields Experiments  

NASA Astrophysics Data System (ADS)

A new quantitative experiment is described for plotting electric fields using a computer data acquisition system and an X-Y digitizing tablet. The experiment measures the equipotential points on a sheet of conductive paper on which electrodes have been placed with silver paint. Voltages are measured with a digital-to-analog converter and X-Y coordinates are determined with a commercial X-Y digitizing tablet. The X-Y coordinates can be determined with the conducting sheet randomly oriented on the X-Y digitizing tablet. Data are recorded and plotted in a spreadsheet for analysis. A control and measurement program written in VisualBasic for Windows controls and facilitates the acquisition, recording, and analysis of data. The apparatus and experiment will be described and demonstrated.

Parks, James E.; Manley, Richard J.; Elston, Stuart B.; Breinig, Marianne

1999-11-01

100

Electric Field Controlled Self-Assembly of Hierarchically Ordered Membranes  

PubMed Central

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

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

2012-01-01

101

Electric field N.M.R  

Microsoft Academic Search

Application of a strong de electric field to solutions of apolar molecules in an apolar solvent leads to partial orientation of the molecules. This orientation could be detected by N.M.R. spectroscopy through the anisotropic spin interactions that show up in the spectra. Subsequent analysis of the spectrum leads to information about the static electric polarizability tensor (a). The electric field

B. H. Ruessink; C. Maclean

1987-01-01

102

The Energetics of Motivated Cognition: A Force-Field Analysis  

ERIC Educational Resources Information Center

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…

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

2012-01-01

103

Work against an Electric Force: The Van De Graaff generator  

NSDL National Science Digital Library

This page illustrates the concept of work against an electric force using the examples of the Van de Graaff generator and lightening. There are also shorter examples of the Xerox machine and electric charge on transparency sheets as well as links to sites relating to the Van de Graaff machine or lightening. This is an optional section of "From Stargazers to Starships". French and Italian translations are available.

Stern, David

2005-01-04

104

Charged Hadron Properties in Background Electric Fields  

SciTech Connect

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.

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

2010-02-01

105

Predicted electric field near small superconducting ellipsoids.  

PubMed

We predict the existence of large electric fields near the surface of superconducting bodies of ellipsoidal shape of dimensions comparable to the penetration depth. The electric field is quadrupolar in nature with significant corrections from higher order multipoles. Prolate (oblate) superconducting ellipsoids are predicted to exhibit fields consistent with negative (positive) quadrupole moments, reflecting the fundamental charge asymmetry of matter. PMID:14754006

Hirsch, J E

2004-01-01

106

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

107

Polyelectrolytes polarization in non-uniform electric fields  

E-print Network

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

Farnoush Farahpour; Fathollah Varnik; Mohammad Reza Ejtehadi

2014-11-16

108

The Electric Field During Blowing Snow Events  

Microsoft Academic Search

A model is proposed to determine the electric field strength in blowing snow. To test this model, the electric field strength\\u000a was measured over an 80-day period during the Canadian Arctic Shelf Exchange Study (CASES) in 2004. The electric field strength\\u000a at 0.5 m correlates well with the difference between 10-m wind speed and a threshold wind speed, although there is

Mark Gordon; Peter A. Taylor

2009-01-01

109

An electric force facilitator in descending vortex tornadogenesis  

Microsoft Academic Search

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

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

2008-01-01

110

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Electric locks, force drop type; where required...All Systems General § 236.10 Electric locks, force drop type; where required. Electric locks on new installations and new...

2011-10-01

111

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

112

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Electric locks, force drop type; where required...All Systems General § 236.10 Electric locks, force drop type; where required. Electric locks on new installations and new...

2012-10-01

113

Electric field soundings through thunderstorms  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

114

Motor imagery facilitates force field learning.  

PubMed

Humans have the ability to produce an internal reproduction of a specific motor action without any overt motor output. Recent findings show that the processes underlying motor imagery are similar to those active during motor execution and both share common neural substrates. This suggests that the imagery of motor movements might play an important role in acquiring new motor skills. In this study we used haptic robot in conjunction with motor imagery technique to improve learning in a robot-based adaptation task. Two groups of subjects performed reaching movements with or without motor imagery in a velocity-dependent and position-dependent mixed force field. The groups performed movements with motor imagery produced higher after effects and decreased muscle co-contraction with respect to no-motor imagery group. These results showed a positive influence of motor imagery on acquiring new motor skill and suggest that motor learning can be facilitated by mental practice and could be used to increase the rate of adaptation. PMID:21555118

Anwar, Muhammad Nabeel; Tomi, Naoki; Ito, Koji

2011-06-13

115

Electric field driven torque in ATP synthase.  

PubMed

FO-ATP synthase (FO) is a rotary motor that converts potential energy from ions, usually protons, moving from high- to low-potential sides of a membrane into torque and rotary motion. Here we propose a mechanism whereby electric fields emanating from the proton entry and exit channels act on asymmetric charge distributions in the c-ring, due to protonated and deprotonated sites, and drive it to rotate. The model predicts a scaling between time-averaged torque and proton motive force, which can be hindered by mutations that adversely affect the channels. The torque created by the c-ring of FO drives the ?-subunit to rotate within the ATP-producing complex (F1) overcoming, with the aid of thermal fluctuations, an opposing torque that rises and falls with angular position. Using the analogy with thermal Brownian motion of a particle in a tilted washboard potential, we compute ATP production rates vs. proton motive force. The latter shows a minimum, needed to drive ATP production, which scales inversely with the number of proton binding sites on the c-ring. PMID:24040370

Miller, John H; Rajapakshe, Kimal I; Infante, Hans L; Claycomb, James R

2013-01-01

116

Electric-field-induced crack patterns: Experiments and simulation  

NASA Astrophysics Data System (ADS)

We report a study of crack patterns formed in laponite gel drying in an electric field. The sample dries in a circular petri dish and the field is radial, acting inward or outward. A system of radial cracks forms in the setup with the center terminal positive, while predominantly cross-radial cracks form when the center is at a negative potential. The laponite accumulates near the negative terminal making the layer thicker at this end. A spring model on a square lattice is used to simulate the desiccation crack formation, with an additional radial force acting due to the electric field. With the radial force acting outward, radial cracks form and for the reversed field cross-radial cracks form. This conforms to the observation that laponite platelets become effectively positive due to overcharging and are attracted towards the negative terminal.

Khatun, Tajkera; Choudhury, Moutushi Dutta; Dutta, Tapati; Tarafdar, Sujata

2012-07-01

117

Electric-field-induced crack patterns: experiments and simulation.  

PubMed

We report a study of crack patterns formed in laponite gel drying in an electric field. The sample dries in a circular petri dish and the field is radial, acting inward or outward. A system of radial cracks forms in the setup with the center terminal positive, while predominantly cross-radial cracks form when the center is at a negative potential. The laponite accumulates near the negative terminal making the layer thicker at this end. A spring model on a square lattice is used to simulate the desiccation crack formation, with an additional radial force acting due to the electric field. With the radial force acting outward, radial cracks form and for the reversed field cross-radial cracks form. This conforms to the observation that laponite platelets become effectively positive due to overcharging and are attracted towards the negative terminal. PMID:23005498

Khatun, Tajkera; Choudhury, Moutushi Dutta; Dutta, Tapati; Tarafdar, Sujata

2012-07-01

118

Electric fields in the ionosphere and magnetosphere.  

NASA Technical Reports Server (NTRS)

Review of current techniques for measuring ionospheric and magnetospheric electric fields and existing measurements. Considerable progress in understanding electric fields has been made in the auroral regions where fields originating basically from convection patterns in the magnetosphere and modified by ionospheric interaction have been detected by both the barium ion cloud and double floating probe techniques and have been compared against predictions. The anticorrelation of electric fields and auroral arcs, the establishment of the auroral electrojet currents as Hall currents, the irregular nature of the electric fields, and the reversal of the electric fields between the eastward and westward electrojet regions have been some of the important observations. Recent barium ion cloud observations in the polar cap have indicated that the long assumed electrojet return current across the polar cap does not exist.

Maynard, N. C.

1972-01-01

119

Estimating Electric Fields from Vector Magnetogram Sequences  

NASA Astrophysics Data System (ADS)

We describe a new technique for estimating the three-dimensional vector electric field in the solar atmosphere by using a time-sequence of vector magnetograms to find an electric field distribution that obeys all 3 components of Faraday's law. The technique uses a ``poloidal-toroidal'' decomposition (PTD) to describe the electric field in terms of two scalar functions. The ``inductive'' PTD solutions to Faraday's Law are not unique, however, since additional contributions to the electric field from a potential function have no effect on Faraday's law. We then describe how estimates for the total electric field including both the inductive and potential components can be made by using variational techniques. The variational approach we develop is similar to Longcope's ``Minimum Energy Fit'' technique, in that the electric field obeys the vertical component of the magnetic induction equation, while also minimizing a positive definite functional. The purely potential part of the electric field can then be recovered by subtracting the PTD electric field from the total field.

Fisher, George H.; Welsch, B. T.; Abbett, W. P.; Bercik, D. J.

2009-05-01

120

Localized induced electric field within the magnetotail  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

121

ELECTRIC FIELDS, ELECTRON PRECIPITATION, AND VLF RADIATION  

Microsoft Academic Search

A balloon payload instrumented with thunderstorm dynamics (see Herman and Goldberg, a double-probe electric field detector and an X 1978; Markson, 1978; and references therein). ray scintillation counter was launched from This paper presents electric field, conducti- Roberval, Quebec, Canada (L = 4.1) at 0828 UT vity, and bremsstrahlung X ray data from a (0328 LT) on July 9, 1975.

E. A. Bering; T. J. Rosenberg; J. R. Benbrook; D. Detrick; D. L. Matthews; M. J. Rycroft; M. A. Saunders; W. R. Sheldon

1980-01-01

122

Ch 16 Electric Charge &Ch 16. Electric Charge & Electric Field  

E-print Network

move aroundSemiconductors: some Metals Insulators: almost none free electrons that can move around charges attract Liu UCD Phy1B 2012 #12;Electric ChargeElectric Charge Electron charge: -eElectron charge;Insulators & ConductorsInsulators & Conductors Conductors: lots ofConductors: lots of free electrons that can

Yoo, S. J. Ben

123

Estimating Electric Fields from Vector Magnetogram Sequences  

NASA Astrophysics Data System (ADS)

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.

Fisher, George H.; Welsch, B. T.; Abbett, W. P.; Bercik, D. J.

2010-05-01

124

Atoms in Crossed Electric and Magnetic Fields  

NASA Astrophysics Data System (ADS)

In this dissertation, extensive experimental and theoretical work pertaining to three interesting aspects of the interaction of atoms with crossed electric and magnetic fields is presented. The first experiment discussed deals with the effects of weak crossed fields on sodium atoms. A fluorescence spectrum of laser excited sodium n = 11 states in an electric field of 2560 V/cm perpendicular to a magnetic field of 4.4 kG is presented, along with a comparison to theory. The data show the important effects of m-mixing and residual degeneracies which remain in the crossed fields. The next topic presented is the theoretical prediction of novel resonances, termed "quasi-Penning resonances," corresponding to electron states localized away from the nucleus at the Stark saddlepoint in strong crossed electric and magnetic fields. The stability and possibility for observation of these resonances is explored. Finally, extensive experimental maps of data are presented which compare laser induced ionization spectra of sodium atoms in crossed electric and magnetic fields to spectra in an electric field atone. The experiment explores the energy region of the electric field saddlepoint, where quasi-Penning resonances are predicted to occur. The magnetic field is too weak for the observation of these resonances, but the experiment provides important groundwork for the understanding of future experiments in strong crossed fields. The magnetic field is seen to cause splitting of some transitions due to the interaction of the electron spin with the magnetic field. Also, magnetic field induced state mixing causes a redistribution of oscillator strengths leading to changes in peak heights and auto-ionizing line widths. On the whole, however, the effect of the weak crossed magnetic field on the sodium Stark spectra remains small.

Korevaar, Eric John

1987-09-01

125

Estimating Electric Fields from Vector Magnetogram Sequences  

NASA Astrophysics Data System (ADS)

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.

Fisher, G. H.; Welsch, B. T.; Abbett, W. P.; Bercik, D. J.

2010-05-01

126

ESTIMATING ELECTRIC FIELDS FROM VECTOR MAGNETOGRAM SEQUENCES  

SciTech Connect

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.

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

127

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

E-print Network

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

Fornberg, Bengt

128

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

PubMed Central

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

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

2014-01-01

129

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

PubMed

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

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

2014-01-01

130

Pair production in rotating electric fields  

NASA Astrophysics Data System (ADS)

We explore Schwinger pair production in rotating time-dependent electric fields using the real-time Dirac-Heisenberg-Wigner formalism. We determine the time evolution of the Wigner function as well as asymptotic particle distributions neglecting backreactions on the electric field. Whereas qualitative features can be understood in terms of effective Keldysh parameters, the field rotation leaves characteristic imprints in the momentum distribution that can be interpreted in terms of interference and multiphoton effects. These phenomena may seed characteristic features of QED cascades created in the antinodes of a high-intensity standing wave laser field.

Blinne, Alexander; Gies, Holger

2014-04-01

131

Comparison of Cellulose Ib Simulations with Three Carbohydrate Force Fields  

SciTech Connect

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.

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

2012-02-14

132

Approximate photochemical dynamics of azobenzene with reactive force fields.  

PubMed

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

Li, Yan; Hartke, Bernd

2013-12-14

133

Approximate photochemical dynamics of azobenzene with reactive force fields  

SciTech Connect

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)

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

134

Approximate photochemical dynamics of azobenzene with reactive force fields  

NASA Astrophysics Data System (ADS)

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).

Li, Yan; Hartke, Bernd

2013-12-01

135

Electrical Force Lines of a 2-S0LITON Solution of the Einstein-Maxwell Equations  

NASA Astrophysics Data System (ADS)

We briefly summarize the main features of a 2-soliton solution which describes an exact (nonlinear) superposition of a Schwarzschild black hole near a Kerr-Newman (KN) naked singularity. Then we give the force lines of the electrical field showing that also the black hole has a charge in the resulting solution (parameter-mixing phenomenon). At the same time we suggest that the plotting of the force lines can be a useful tool to understand complicated solutions of the Einstein-Maxwell, whose deep understanding is still lacking in literature.

Pizzi, M.

2008-09-01

136

Crystal growth under external electric fields  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

137

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

PubMed

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

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

2010-09-01

138

Calculations of the electric fields in liquid solutions.  

PubMed

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

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

2013-12-19

139

Solidification processing superalloys in an electric field  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

140

Rotationally Vibrating Electric-Field Mill  

NASA Technical Reports Server (NTRS)

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.

Kirkham, Harold

2008-01-01

141

Solutions and symmetries of force-free magnetic fields  

SciTech Connect

New analytical results concerning force-free magnetic fields are presented. A number of examples of exact solutions for two-dimensional nonlinear force-free fields described by the Liouville equation are shown. These include classical solutions, such as, the Gold-Hoyle field and the force-free Harris sheet as special cases. The connection between these solutions and the Lie point symmetries of the Liouville equation is illustrated. Lie point symmetries of the equation describing force-free magnetic fields in helical symmetry in cylindrical geometry are also investigated and an infinitesimal generator that, in the vicinity of the cylinder axis, makes it possible to transform purely radially dependent solutions into helically symmetric solutions, is found. Finally we point out the existence of a formal analogy between the equations for the vector potential components of a class of force-free fields and the equations of motion of a charged particle in a magnetic field. This analogy makes it possible to transfer known results from the theory of the motion of a charged particle, into the context of force-free magnetic fields. Explicit examples of such application are given.

Tassi, E. [Burning Plasma Research Group, Dipartimento di Energetica and CNISM, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Pegoraro, F. [Dipartimento di Fisica, E. Fermi and CNISM, Pisa (Italy); Cicogna, G. [Dipartimento di Fisica, E. Fermi and INFN, Pisa (Italy)

2008-09-15

142

Electric field measurements across the Harang discontinuity  

Microsoft Academic Search

The Harang discontinuity, the area separating the positive and negative bay regions in the midnight sector of the auroral zone, is a focal point for changes in behavior of many phenomena. Through this region the electric field, in a frame corotating with the earth, rotates through the west froma basically northward field in the positive bay region to a basically

Nelson C. Maynard

1974-01-01

143

Gravitationally Induced Electric Fields in Conductors  

Microsoft Academic Search

An estimate for the gravitationally induced electric field is presented that is based on a statistical model for the electrons in a metal in which their long-range electrostatic interaction with a differentially compressed lattice of positive ions is taken into account. The field is in the upward direction and is estimated to be of the order of magnitude E~Mge, where

A. J. Dessler; F. C. Michel; H. E. Rorschach; G. T. Trammell

1968-01-01

144

Numerical modeling of motion trajectory and deformation behavior of a cell in a nonuniform electric field  

PubMed Central

The motion trajectory and deformation behavior of a neutral red blood cell (RBC) in a microchannel subjected to an externally applied nonuniform electric field are numerically investigated, where both the membrane mechanical force and the dielectrophoresis (DEP) force are considered. The simulation results demonstrate that the DEP force is significantly influenced by several factors, namely, the RBC size, electrode potential, electric frequency, RBC permittivity, and conductivity, which finally results in the different behaviors of the cell motion and deformation in the nonuniform electric field. PMID:21523249

Li, Hua; Ye, Ting; Lam, K. Y.

2011-01-01

145

Nuclear forces from chiral effective field theory: a primer  

E-print Network

This paper is a write-up of introductory lectures on the modern approach to the nuclear force problem based on chiral effective field theory given at the 2009 Joliot-Curie School, Lacanau, France, 27 September - 3 October 2009.

Evgeny Epelbaum

2010-01-19

146

Nuclear forces from chiral effective field theory: a primer  

E-print Network

This paper is a write-up of introductory lectures on the modern approach to the nuclear force problem based on chiral effective field theory given at the 2009 Joliot-Curie School, Lacanau, France, 27 September - 3 October 2009.

Epelbaum, Evgeny

2010-01-01

147

Generative morphologies of architectural organization in matter force field  

E-print Network

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

Mutlu, Murat

2010-01-01

148

Nonequilibrium Forces Between Neutral Atoms Mediated by a Quantum Field  

E-print Network

We study all known and as yet unknown 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 principle, systematic and unified description including the intrinsic field fluctuations 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 forces -- between neutral atoms in the long-time limit but also discover the existence of two new types of interatomic forces. The first, a `nonequilibrium force', arises when the field and atoms are not in thermal equilibrium, and the second, which we call an `entanglement force', originates from the correlations of the internal degrees of freedom of entangled atoms.

Ryan Orson Behunin; Bei-Lok Hu

2010-02-13

149

A reactive force field (ReaxFF) for zinc oxide  

Microsoft Academic Search

We have developed a reactive force field (FF) within the ReaxFF framework, for use in molecular dynamics (MD) simulations to investigate structures and reaction dynamics for ZnO catalysts. The force field parameters were fitted to a training set of data points (energies, geometries, charges) derived from quantum-mechanical (QM) calculations. The data points were chosen to give adequate descriptions of (the

David Raymand; Adri C. T. van Duin; Micael Baudin; Kersti Hermansson

2008-01-01

150

Pair production from an external electric field  

SciTech Connect

We solve numerically the problem of pair production from an external electric field in 1 + 1 dimensions including the quantum back-reaction from the produced pairs. We find that in the linear regime our numerical results agree perfectly with analytic calculations. In the strong field regime where tunnelling is uninhibited we determine the time it takes for the electric field to degrade due to energy transfer to the large number of pion field degrees of freedom. The problem has three time scales--the oscillation frequency of the charged quanta, the induced plasma oscillation frequency due to the production of pairs and finally the time scale for energy to be transferred from the electromagnetic field to the pion field. 4 refs., 5 figs.

Cooper, F.; Mottola, E. (Los Alamos National Lab., NM (USA)); Rogers, B. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Physics); Anderson, P. (Mission Research Corp., Santa Barbara, CA (USA))

1990-01-01

151

Focused Fields of given Power with Maximum Electric Field Components  

E-print Network

Closed formulas are derived for the field in the focal region of a diffraction limited lens, such that the electric field component in a given direction at the focal point is larger than that of all other focused fields with the same power in the entrance pupil of the lens. Furthermore, closed formulas are derived for the corresponding optimum field distribution in the lens pupil. Focused fields with maximum longitudinal or maximum transverse are considered in detail. The latter field is similar, but not identical, to the focused linearly polarized plane wave.

Pereira, H P Urbach S F

2008-01-01

152

Web Assignments: Electric Field for Point Charges  

NSDL National Science Digital Library

This student activity uses a Java applet to show the electric field due to a point charge. The strength of the field can be measured at any coordinate in the x-y plane. The user is asked to calculate the magnitude of the charge, plot the strength of the field as a function of the radial distance from the charge, and compare this to Coulomb's Law This is part of a larger collection of applet-based learning activities.

Walkup, John

2008-11-18

153

Brownian motion in a non-homogeneous force field and photonic force microscope  

E-print Network

The Photonic Force Microscope (PFM) is an opto-mechanical technique based on an optical trap that can be assumed to probe forces in microscopic systems. This technique has been used to measure forces in the range of pico- and femto-Newton, assessing the mechanical properties of biomolecules as well as of other microscopic systems. For a correct use of the PFM, the force field to measure has to be invariable (homogeneous) on the scale of the Brownian motion of the trapped probe. This condition implicates that the force field must be conservative, excluding the possibility of a rotational component. However, there are cases where these assumptions are not fulfilled Here, we show how to improve the PFM technique in order to be able to deal with these cases. We introduce the theory of this enhanced PFM and we propose a concrete analysis workflow to reconstruct the force field from the experimental time-series of the probe position. Furthermore, we experimentally verify some particularly important cases, namely the case of a conservative or rotational force-field.

Giorgio Volpe; Giovanni Volpe; Dmitri Petrov

2007-08-03

154

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

SciTech Connect

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.

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

155

Alternating Magnetic Field Forces for Satellite Formation Flying  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

156

Force Field Parameter Estimation of Functional Perfluoropolyether Lubricants  

SciTech Connect

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.

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

2011-01-01

157

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

NASA Technical Reports Server (NTRS)

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.

El-Kaddah, N.; Szekely, J.

1982-01-01

158

Electric fields in the dayside auroral oval  

NASA Technical Reports Server (NTRS)

The results from four independent electric field experiments flown on three Black Brant 4 rockets in the forenoon dayside auroral oval in December 1974 and January 1975 are correlated with ground-based observations and rocket particle data. The electric field varied from zero to 150 mV/m. The predominant plasma convection was toward noon along the auroral oval with a smaller component directed toward the polar cap. In one case, however, a reversal occurred within the oval with plasma convection away from noon. Comparisons with magnetometer data indicate that in the dayside auroral oval, Hall currents sometimes are responsible for magnetic fluctuations observed on the ground. Comparisons with particle data show that the magnitude of the electric fields is inversely correlated with the electron energy flux.

Jorgensen, T. S.; Mikkelsen, I. S.; Lassen, K.; Haerendel, G.; Reiger, E.; Valenzuela, A.; Mozer, F. S.; Temerin, M.; Holback, B.; Bjoern, L.

1980-01-01

159

Temperature/electric field scaling in Ferroelectrics  

NASA Astrophysics Data System (ADS)

The effects of the field amplitude ( E) and temperature on the polarization and their scaling relations were investigated on rhombohedral PMN- xPT ceramics. The scaling law was based on the physical symmetries of the problem and rendered it possible to express the temperature variation (? ?) as an electric field equivalent ? Eeq=( ?+2 ?× P( E, ?0))×? ?. Consequently, this was also the case for the relationship between the entropy ( ?) and polarization ( P). Rhombohedral Pb(Mg 1/3Nb 2/3) 0.75Ti 0.25O 3 ceramics were used for the verification. It was found that such an approach permitted the prediction of the maximal working temperature, using only purely electrical measurements. It indicates that the working temperature should not exceed 333 K. This value corresponds to the temperature maximum before the dramatic decrease of piezoelectric properties. Reciprocally, the polarization behavior under electrical field can be predicted, using only purely thermal measurements. The scaling law enabled a prediction of the piezoelectric properties (for example, d31) under an electrical field replacing the temperature variation (? ?) by ? E/( ?+2 ?× p( E, ?0)). Inversely, predictions of the piezoelectric properties ( d31) as a function of temperature were permitted using purely only electrical measurements.

Hajjaji, Abdelowahed; Guyomar, Daniel; Pruvost, Sebastien; Touhtouh, Samira; Yuse, Kaori; Boughaleb, Yahia

2010-07-01

160

Microwave ovens: mapping the electrical field distribution.  

PubMed

Uniformity of electric field intensity of microwaves within the microwave oven cavity is necessary to ensure even load-heating, and is particularly important in pathology procedures where small volume irradiation is carried out. A simple and rapid method for mapping electric field distribution, using reversible thermographic paint, is described. Spatial heating patterns for various positions, and the effects of introducing dummy loads to modify heating distributions, have been obtained for a dedicated microwave processor, and comparison made with a domestic microwave oven. PMID:1787775

Ng, K H

1991-07-01

161

Flame propagation in an electric field  

Microsoft Academic Search

Conclusions  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a Under the influence of a transverse electric field the propagation velocity of the flame front up increases. The value of up has been found to depend on the potential difference between the capacitor plates.\\u000a \\u000a \\u000a \\u000a \\u000a 2. \\u000a \\u000a It has been shown that the increase in the flame propagation velocity in an electric field is due to the increase in the

G. D. Salamandra

1969-01-01

162

Pattern forced geophysical vector field segmentation based on Clifford FFT  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

163

Electric Field Effects in RUS Measurements  

SciTech Connect

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.

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

164

Electric field effects in RUS measurements.  

PubMed

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. PMID:19850314

Darling, Timothy W; Allured, Bradley; Tencate, James A; Carpenter, Michael A

2010-02-01

165

Visualization of Force Fields in Protein StructurePrediction  

SciTech Connect

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

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

2005-04-26

166

Electric field mediated colloidal assembly and control  

NASA Astrophysics Data System (ADS)

This dissertation presents video microscopy measurements and computer simulations of colloidal particle interactions in inhomogeneous, high-frequency AC electric fields. The interactions of particles with each other and inhomogeneous electric fields are quantified as a function of concentration, field amplitude, and frequency. Visual state diagrams show that these interactions in concentrated systems produce quasi-two dimensional microstructures including confined hard disk fluids, oriented dipolar chains, and oriented hexagonal close packed crystals. The interaction of a particle interacting with an electric field is directly measured with analyses of a single diffusing colloid within electric fields in the absence of many body effects. Concentrated systems are characterized in terms of density profiles across the electrode gap and angular pair distribution functions. An inverse Monte Carlo analysis extracted the induced dipole-induced dipole interaction from concentrated measurements. A single adjustable parameter consistently modified the induced dipole-field potential and the induced dipole-induced dipole potential to account for modification of the local electric field as the result of the local particle concentration, frequency and configuration. Confocal laser scanning microscopy (CLSM) perform sensitive measurements of internal three dimensional structure of crystals assembled in an interfacial quadrupole electrode device. Radial distributions as functions of elevation are used to characterize the equilibrium structure. A single adjustable parameter modified known potentials to match Monte Carlo simulations with experiment. The local density from experiment and simulation matched the expected density calculated from a balance of osmotic pressure and dielectrophoretic compression. Simulations qualitatively matched experimental observations of microstructure as a function of field amplitude. Programmable assembly for colloidal crystals is implemented in the quadrupole electrode device by guiding the dynamic evolution of a colloidal ensemble. A feedback method is used to control electric field mediated assembly based on real-time sensing and actuation single and multiple electrokinetic mechanisms. Sensing is achieved using particle tracking and order parameter computation to quantify the degree of order during the assembly process. A geometrical parameter for hexagonal close packing and radius of gyration are investigated as order parameters for quantifying condensation and crystallization. Colloidal crystal assembly and disassembly is actuated using electroosmosis and negative and positive dielectrophoresis (i.e. dipole-field interactions).

Juarez, Jaime Javier

167

The effect of electric fields upon liquid extraction. Progress report  

SciTech Connect

A series of mass transfer studies were conducted for the extraction of solute from droplets falling in an electric field. The experiments were planned such that the dispersed phase resistance was controlling. In one series of experiments single drops were formed from a charged nozzle and allowed to fall through a continuous, dielectric phase. The drop size and velocity were correlated by means of a simple force balance. Drop mass transfer coefficients were calculated for the drop free fall period and were compared to predictions based upon literature correlations for an oscillating droplet in-the absence of an electric field. Droplet size and velocity were approximately predicted by a staple force balance whereas the mass transfer coefficient was approximately 25--250% higher than that predicted. Droplet extraction efficiencies Increased about 20--30% in the presence of electric fields up to 2 kv/cm. For the same field, the drop diameter decreased 30--50% and the terminal velocity increased by up to 50%. The enhancements for the toluene-water system can be ascribed to increases in terminal velocity and decreases in drop diameter. The mass transfer model for freely falling drops proposed by Skelland and Wellek roughly predicts the moderate mass transfer efficiency increases (about 18% at 1 kv/cm) for the toluene water system but failed to predict the increases (about 25% at 0.5 kv/cm) for the heptane furfural system. The second series of experiments involved the formation of a swarm of droplets In a three stage sieve tray column. In a separate series of experiments. the effect of the electric field upon mass transfer from drops exhibiting interfacial turbulence was evaluated.

Carleson, T.E.

1988-04-13

168

The effect of electric fields upon liquid extraction  

SciTech Connect

A series of mass transfer studies were conducted for the extraction of solute from droplets falling in an electric field. The experiments were planned such that the dispersed phase resistance was controlling. In one series of experiments single drops were formed from a charged nozzle and allowed to fall through a continuous, dielectric phase. The drop size and velocity were correlated by means of a simple force balance. Drop mass transfer coefficients were calculated for the drop free fall period and were compared to predictions based upon literature correlations for an oscillating droplet in-the absence of an electric field. Droplet size and velocity were approximately predicted by a staple force balance whereas the mass transfer coefficient was approximately 25--250% higher than that predicted. Droplet extraction efficiencies Increased about 20--30% in the presence of electric fields up to 2 kv/cm. For the same field, the drop diameter decreased 30--50% and the terminal velocity increased by up to 50%. The enhancements for the toluene-water system can be ascribed to increases in terminal velocity and decreases in drop diameter. The mass transfer model for freely falling drops proposed by Skelland and Wellek roughly predicts the moderate mass transfer efficiency increases (about 18% at 1 kv/cm) for the toluene water system but failed to predict the increases (about 25% at 0.5 kv/cm) for the heptane furfural system. The second series of experiments involved the formation of a swarm of droplets In a three stage sieve tray column. In a separate series of experiments. the effect of the electric field upon mass transfer from drops exhibiting interfacial turbulence was evaluated.

Carleson, T.E.

1988-04-13

169

Electric field sensors based on MEMS technology  

Microsoft Academic Search

The design and optimization of two types of novel miniature vibrating Electric Field Sensors (EFSs) based on MicroElectroMechanical\\u000a Systems (MEMS) technology are presented. They have different structures and vibrating modes. The volume is much smaller than\\u000a other types of charge-induced EFSs such as field-mills. As miniaturizing, the induced signal is reduced enormously and a high\\u000a sensitive circuit is needed to

Chao Gong; Shanhong Xia; Kai Deng; Qiang Bai; Shaofeng Chen

2005-01-01

170

MAGNETIC EXPLOSIONS: ROLE OF THE INDUCTIVE ELECTRIC FIELD  

SciTech Connect

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.

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

2012-04-10

171

Health of workers exposed to electric fields.  

PubMed Central

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

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

1985-01-01

172

Electric field N.M.R.  

NASA Astrophysics Data System (ADS)

Application of a strong de electric field to solutions of apolar molecules in an apolar solvent leads to partial orientation of the molecules. This orientation could be detected by N.M.R. spectroscopy through the anisotropic spin interactions that show up in the spectra. Subsequent analysis of the spectrum leads to information about the static electric polarizability tensor (a). The electric field N.M.R. (EFNMR) method was applied to measure, from the 2H EFNMR spectrum of naphthalene-d8, the anisotropy of a (i.e. ??), and asymmetry (??). The result is: 7·1 ± 0·3 and -(4·4 ± 0·5) × 10-24 cm3 for ?? and ?? respectively. For triphenylene-d12 the value of ?? is measured to be -(14·4 ± 1·4) × 10-24 cm3. The results from the EFNMR method and from other methods are compared and discussed

Ruessink, B. H.; Maclean, C.

173

Estimation of Cellular Adhesion Forces Using Mean Field Theory  

Microsoft Academic Search

A complete understanding of the interaction of the cell with the surrounding substrate requires a quantitative understanding\\u000a of the force with which they adhere to the matrix. Using mean field theory, we provide a new and robust method to calculate\\u000a this force of cellular adhesion to a ligand coated substrate in a system that contains receptors, ligands and solvent. Our

Tianyi Yang; Muhammad H. Zaman

2010-01-01

174

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...

175

Nonequilibrium forces between neutral atoms mediated by a quantum field  

SciTech Connect

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.

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

176

Force-field calculation and geometry of the HOOO radical  

NASA Astrophysics Data System (ADS)

High-level ab initio calculations using the Davidson-corrected multireference configuration interaction (MRCI) level of theory with Dunning's correlation consistent basis sets and force-field calculations were performed for the HOOO radical. The harmonic vibrational frequencies and their anharmonic constants obtained by the force-field calculations reproduce the IR-UV experimental vibrational frequencies with errors less than 19 cm-1. The rotational constants for the ground vibrational state obtained using the vibration-rotation interaction constants of the force-field calculations also reproduce the experimentally determined rotational constants with errors less than 0.9%, indicating that the present quantum chemical calculations and the derived spectroscopic constants have high accuracy. The equilibrium structure was determined from the experimentally determined rotational constants combined with the theoretically derived vibration-rotation interaction constants. The determined geometrical parameters agree well with the results of the present MRCI calculation.

Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

2013-09-01

177

Molecular Dynamics Simulation of Tri-n-Butyl-Phophate Liquid: A Force Field Comparative Study  

SciTech Connect

Molecular dynamics (MD) simulations were conducted to compare the performance of four force fields in predicting thermophysical properties of tri-n-butyl-phosphate (TBP) in the liquid phase. The intramolecular force parameters used were from the Assisted Model Building with Energy Refinement (AMBER) force field model. The van der Waals parameters were based on either the AMBER or the Optimized Potential for Liquid Simulation (OPLS) force fields. The atomic partial charges were either assigned by performing quantum chemistry calculations or utilized previously published data, and were scaled to approximate the average experimental value of the electric dipole moment. Canonical ensemble computations based on the aforementioned parameters were performed near the atmospheric pressure and temperature to obtain the electric dipole moment, mass density, and self-diffusion coefficient. In addition, the microscopic structure of the liquid was characterized via pair correlation functions between selected atoms. It has been demonstrated that the electric dipole moment can be approximated within 1% of the average experimental value by virtue of scaled atomic partial charges. The liquid mass density can be predicted within 0.5-1% of its experimentally determined value when using the corresponding charge scaling. However, in all cases the predicted self- diffusion coefficient is significantly smaller than a commonly quoted experimental measurement; this result is qualified by the fact that the uncertainty of the experimental value was not available.

Cui, Shengting [ORNL; de Almeida, Valmor F [ORNL; Hay, Benjamin [ORNL; Ye, Xianggui [ORNL; Khomami, Bamin [ORNL

2012-01-01

178

Role of inductive electric fields in substorm development  

NASA Technical Reports Server (NTRS)

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

Heikkila, Walter J.

1992-01-01

179

PRIMO: A Transferable Coarse-grained Force Field for Proteins  

PubMed Central

We describe here the PRIMO (PRotein Intermediate Model) force field, a physics-based fully transferable additive coarse-grained potential energy function that is compatible with an all-atom force field for multi-scale simulations. The energy function consists of standard molecular dynamics energy terms plus a hydrogen-bonding potential term and is mainly parameterized based on the CHARMM22/CMAP force field in a bottom-up fashion. The solvent is treated implicitly via the generalized Born model. The bonded interactions are either harmonic or distance-based spline interpolated potentials. These potentials are defined on the basis of all-atom molecular dynamics (MD) simulations of dipeptides with the CHARMM22/CMAP force field. The non-bonded parameters are tuned by matching conformational free energies of diverse set of conformations with that of CHARMM all-atom results. PRIMO is designed to provide a correct description of conformational distribution of the backbone (?/?) and side chains (?1) for all amino acids with a CMAP correction term. The CMAP potential in PRIMO is optimized based on the new CHARMM C36 CMAP. The resulting optimized force field has been applied in MD simulations of several proteins of 36–155 amino acids and shown that the root-mean-squared-deviation of the average structure from the corresponding crystallographic structure varies between 1.80 and 4.03 Å. PRIMO is shown to fold several small peptides to their native-like structures from extended conformations. These results suggest the applicability of the PRIMO force field in the study of protein structures in aqueous solution, structure predictions as well as ab initio folding of small peptides. PMID:23997693

Kar, Parimal; Gopal, Srinivasa Murthy; Cheng, Yi-Ming; Predeus, Alexander; Feig, Michael

2013-01-01

180

Observations of large transient magnetospheric electric fields  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

181

Modeling Electric Field Influences on Plasmaspheric Refilling  

NASA Technical Reports Server (NTRS)

We have a new model of ion transport that we have applied to the problem of plasmaspheric flux tube refilling after a geomagnetic disturbance. This model solves the Fokker-Planck kinetic equation by applying discrete difference numerical schemes to the various operators. Features of the model include a time-varying ionospheric source, self-consistent Coulomb collisions, field-aligned electric field, hot plasma interactions, and ion cyclotron wave heating. We see refilling rates similar to those of earlier observations and models, except when the electric field is included. In this case, the refilling rates can be quite different that previously predicted. Depending on the populations included and the values of relevant parameters, trap zone densities can increase or decrease. In particular, the inclusion of hot populations near the equatorial region (specifically warm pancake distributions and ring current ions) can dramatically alter the refilling rate. Results are compared with observations as well as previous hydrodynamic and kinetic particle model simulations.

Liemohn, M. W.; Kozyra, J. U.; Khazanov, G. V.; Craven, Paul D.

1998-01-01

182

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

E-print Network

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

L. Neslusan

2010-12-28

183

Electric force microscopy investigation of the microstructure of thick film resistors  

NASA Astrophysics Data System (ADS)

Maps of the electric field distribution on the surface of thick film resistors (TFRs) have been acquired by using electric force microscopy (EFM). TFRs based on various types of conducting phases (Bi-ruthenate, Pb-ruthenate, or RuO2) and with different volume fractions in the glassy matrix have been examined. Scanning electron microscopy, x-ray energy dispersive spectroscopy and x-ray diffraction have been used to correlate the EFM results to the morphological, microchemical, and structural characteristics of the samples. The evolution of the TFRs microstructure and the segregation characteristic with the firing conditions have been investigated. The results showed that the concentration of the electric field around the conductive grains is a general feature of all the films, independently of the resistor composition, and a meander-like path of charge carriers on a microscopic scale has been assessed. The observations also indicated that at high firing temperatures the segregated structure did not disappear, but on the contrary was enhanced. All the results are critically discussed in relation to the electrical and piezoresistive properties of the TFRs and suggestions for new models to correlate the microstructure and the electric properties are presented.

Alessandrini, A.; Valdrè, G.; Morten, B.; Prudenziati, M.

2002-10-01

184

Charged particles in higher dimensional homogeneous gravitational field: Self-energy and self-force  

E-print Network

A problem of self-energy and self-force for a charged point-like particle in a higher dimensional homogeneous gravitational field is considered. We study two cases, when a particle has usual electric charge and a case when it has a scalar charge, which is a source of a scalar massless minimally coupled field. We assume that a particle is at rest in the gravitational field, so that its motion is not geodesic and it has an acceleration a directed from the horizon. The self-energy of a point charge is divergent and the strength of the divergence grows with the number of dimensions. In order to obtain a finite contribution to the self- energy we use a covariant regularization method which is a modification of the proper time cut-off and other covariant regularizations. We analyze a relation between the self-energy and self-force and obtain explicit expressions for the self-forces for the electric and scalar charge in the spacetimes with the number of dimensions up to eight. General expressions for the case of higher dimensions are also obtained. We discuss special logarithmic factors ln(a), which are present both in the self-energy and self-force in odd dimensions. Finally, we compare the obtained results with the earlier known results both for the homogeneous gravitational field and for particles near black holes.

Valeri P. Frolov; Andrei Zelnikov

2014-07-11

185

Analysis Of Shifts In Students' Reasoning Regarding Electric Field And Potential Concepts  

NASA Astrophysics Data System (ADS)

Students' reasoning regarding the relationships among electric fields, forces, and equipotential line patterns was explored using pre- and post-test responses to selected multiple-choice questions on the Conceptual Survey of Electricity and Magnetism. Students' written explanations of their reasoning, provided both pre- and post-instruction, allowed additional assessment of the changes in their thinking. In particular, the data indicate that although students largely abandon an initial tendency to associate stronger fields with wider equipotential line spacing, many of them persist in incorrectly associating electric field magnitude at a point with the electric potential at that point.

Meltzer, David E.

2007-01-01

186

Periodic deformation of microsize droplets in a microchannel induced by a transverse alternating electric field.  

PubMed

When a water droplet is suspended in an immiscible, insulating liquid medium of essentially infinite dimensions and is subjected to a periodically alternating electric field, it will undergo periodic deformation at a frequency twice that of the field. This work examined the periodic deformation and bursting of microsize water droplets in silicone oil moving through a PTFE microchannel with an inner diameter nearly twice that of the droplets, under a periodically alternating electric field normal to the direction of flow. When the sinusoidal electric field was either relatively weak or had a low frequency, the droplets displayed periodic deformation alternating between a prolate ellipsoidal along the electric field direction and a sphere. In contrast, droplets alternated between prolate and oblate shapes when the electric field strength was high or the frequency of the electric field was high. When the applied electric field strength was increased, a constriction formed in the central portion of droplets which had deformed into a prolate ellipsoid. When the electric field strength was further increased, droplets broke into two or more smaller droplets as the result of the inertial force acting on the water in the droplet and the electrostatic force at the interface of the droplet and the surrounding liquid. The majority of the small droplets formed by such breakups subsequently merged into single droplets over the course of time. PMID:24090269

Mochizuki, Takaaki

2013-10-15

187

Interaction of Electric Fields with Vascular Cells  

NASA Astrophysics Data System (ADS)

Electrical stimulation has been shown to be effective in improving healing rate of the non-healing or slow-healing wounds, a significant high-cost clinical issue. In order to optimize this process, identifying the mechanisms underlying the interaction of vascular cells with electric field (EF) is of interest. We have developed a 3D model of the cultured cells to simulate EF distribution in the cell membrane. The electrical stimulation of cells has been performed using our novel device that generates EF without any contact between electrodes and cells. The results indicate that cells respond to EF by releasing a specific growth factor (PlGF) which is important for blood vessel growth during wound healing.

Taghian, Toloo; Sheikh, Abdul; Narmoneva, Daria; Kogan, Andrei

2012-04-01

188

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

NASA Astrophysics Data System (ADS)

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.

Fu, Jinxin; Ou-Yang, H. Daniel

2014-09-01

189

Subdiffusion in a time-dependent force field  

SciTech Connect

Based on the random-barrier model and using the mean-field approximation, we derive an equation that describes the subdiffusion of particles in an external time-varying force field. The derived equation predicts the frequency dependence of the conductivity and, in this regard, is consistent with the experiment. We show that the response of the system to an external perturbation depends significantly on the structure of the inhomogeneous medium.

Shkilev, V. P., E-mail: shkilevv@ukr.net [National Academy of Sciences of Ukraine, Institute of Surface Chemistry (Ukraine)

2012-05-15

190

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

DOEpatents

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.

Stevens, Fred J. (Naperville, IL)

1992-01-01

191

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

PubMed

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

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

2011-01-01

192

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

E-print Network

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

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

2010-08-24

193

Force, current and field effects in single atom manipulation  

E-print Network

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

Hla, Saw-Wai

194

Lattice Dynamics of Black Phosphorus. I. Valence Force Field Model  

Microsoft Academic Search

Calculation of the lattice dynamical properties of black phosphorus, which is a narrow-gap covalent semiconductor with a layered structure, based on the valence force field model is presented. The results obtained are in good agreement with the experiments, except for infrared active optical modes. The results are discussed in connection with the crystal structure and the chemical-bonding nature of black

Chioko Kaneta; Hiroshi Katayama-Yoshida; Akira Morita

1986-01-01

195

AFMM: A molecular mechanics force field vibrational parametrization program  

Microsoft Academic Search

AFMM (Automated Frequency Matching Method) is a program package for molecular mechanics force field parametrization. The method used fits the molecular mechanics potential function to both vibrational frequencies and eigenvector projections derived from quantum chemical calculations. The program optimizes an initial parameter set (either pre-existing or using chemically-reasonable estimation) by iteratively changing them until the optimal fit with the reference

A. C. Vaiana; Z. Cournia; I. B. Costescu; J. C. Smith

2005-01-01

196

The Role of Search for Field Force Knowledge Management  

E-print Network

Chapter 8 The Role of Search for Field Force Knowledge Management Dyaa Albakour, Ge´ry Ducatel technical information and vital regulatory information, a knowledge management solution is concerned to innovative knowledge management applications for mobile workers. Integration of mobile devices

Kruschwitz, Udo

197

Using Force Fields as a User Interface Device  

Microsoft Academic Search

This paper discusses the use of force fields as a means of passing advice from a computer program to a user. It is suggested that this mechanism can be used as a replacement for traditional user interface pop-ups or other widgets when the task is a three dimensional one and a haptic device is available. The benefits and limitations are

Chris Gunn

198

Observed electric fields associated with lightning initiation  

Microsoft Academic Search

In situ electric field (E) measurements and inferred lightning initiation locations of three cloud-to-ground flashes are used to identify a thunderstorm region in which the preflash E exceeded the threshold for runaway breakdown. The maximum measured E in the region was 186 kV m?1 at 5.77 km altitude, which for runaway electrons is equivalent to 370 kV m?1 at sea

T. C. Marshall; M. Stolzenburg; C. R. Maggio; L. M. Coleman; P. R. Krehbiel; T. Hamlin; R. J. Thomas; W. Rison

2005-01-01

199

Measurement of electric fields in the stratosphere  

NASA Astrophysics Data System (ADS)

A balloon-borne experiment for electric field measurement with data coding, small enough to be used in a combined payload simultaneously measuring, e.g., X-ray fluxes, is described. Measurement apparatus assembly is depicted. System integration is shown, including direction finder (azimuth), spin motor, and inertia real winch. Electronics design is given. Procedures for prelaunch payload preparation and launch checkout are covered.

Slamanig, H.

1981-06-01

200

Killing of microorganisms by pulsed electric fields  

Microsoft Academic Search

Lethal effects of pulsed electric fields (PEF) on suspensions of various bacteria, yeast, and spores in buffer solutions and\\u000a liquid foodstuffs were examined. Living-cell counts of vegetative cell types were reduced by PEF treatment by up to more than\\u000a four orders of magnitude (> 99.99%). On the other hand, endoand ascospores were not inactivated or killed to any great extent.

T. Grahl; H. Märkl

1996-01-01

201

Electric field shielding in dielectric nanosolutions  

E-print Network

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.

Sergey Bastrukov; Pik-Yin Lai; Irina Molodtsova

2011-09-20

202

Influence of an external magnetic field on forced turbulence in a swirling flow of liquid metal  

E-print Network

We report an experimental investigation on the influence of an external magnetic field on forced 3D turbulence of liquid gallium in a closed vessel. We observe an exponential damping of the turbulent velocity fluctuations as a function of the interaction parameter N (ratio of Lorentz force over inertial terms of the Navier-Stokes equation). The flow structures develop some anisotropy but do not become bidimensional. From a dynamical viewpoint, the damping first occurs homogeneously over the whole spectrum of frequencies. For larger values of N, a very strong additional damping occurs at the highest frequencies. However, the injected mechanical power remains independent of the applied magnetic field. The simultaneous measurement of induced magnetic field and electrical potential differences shows a very weak correlation between magnetic field and velocity fluctuations. The observed reduction of the fluctuations is in agreement with a previously proposed mechanism for the saturation of turbulent dynamos and wit...

Gallet, Basile; Mordant, Nicolas

2009-01-01

203

Electric and magnetic fields at power frequencies.  

PubMed

Exposures to electric and magnetic fields are among the most ubiquitous exposures that the Canadian population experiences. Sources of electric and magnetic field exposures may be occupational or residential and include proximity to certain types of electrical equipment, transmission and distribution power lines as well as appliance use. The early studies of children tended toward a consistent association between risks for leukemia and brain cancer and residential proximity to power lines having high wire configuration. More recent studies-and studies which have attempted to improve upon the measurement of exposure by using calculated fields, point-in-time or personal monitoring-have been inconsistent, with some suggesting increased risk and others not. Occupational exposures have suggested an increase in risk for leukemia, and to a lesser extent brain cancer and Non-Hodgkin lymphoma. However, studies of residential exposures and cancer in adults generally have suggested no effect. Laboratory work has been unable to demonstrate a biological mechanism which might explain the epidemiological findings. In spite of extensive efforts over the past 20 years and many expert reviews, it has been difficult to reach consensus regarding the carcinogenic effects of electric and magnetic fields. Exposure assessment has proven to be complex, and agreement on the relevant exposure metric has not yet been obtained. There is justification to question whether point-in-time measures in homes are appropriate indices of the relevant etiological exposure, as they fail to account for changes over time, peak exposures or time-varying fields. Nevertheless, it is probably desirable to err on the side of caution in not placing too much weight on the inconsistencies. The IARC has classified EMF as a "possible carcinogen" which refers to the circumstances where there is limited evidence of carcinogenicity in humans and inadequate evidence in experimental animals. The IARC review indicated limited evidence for the carcinogenicity of extremely low-frequency magnetic fields in relation to childhood leukemia at high level exposure in the residential environment (average residential magnetic field strength >0.4 ?T). Even higher levels of exposure in the occupational environment may increase the risk of leukemia in adults. PMID:21199600

Miller, Anthony B; Green, Lois M

2010-01-01

204

Manipulation of nano-entities in suspension by electric fields  

NASA Astrophysics Data System (ADS)

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

Fan, Donglei

205

Collision avoidance and task planning using impedance force fields  

NASA Astrophysics Data System (ADS)

A recent progression of heavy lift assist device is to place the human operator closer to the end effector to provide close coupling of the operator input and the payload. This close coupling of the human for control and the power of a heavy lift assist device provides improved accuracy with ease of handling in the case of heavy and bulk objects. However, collisions with obstacles may still occur in a crowded manufacturing environment due to the large work piece inertia characteristics, inappropriate motion command from the operator and inattention or fatigue of the human operator. In this research, a fictitious force field is assigned to each obstacle in the workspace. As a work piece moves closer to an object, an impedance force is calculated and combined with the control forces, in order to prevent collisions. In addition, a set of impedance fields are developed and applied that associate desired trajectories with the layout of the workspace. Thus, the force fields guide the work piece to achieve advantageous orientations and positions during the material handling operation. This includes adjustment of the height of the work piece for placement on tables, orientation to preset positions, and optimizing the configuration of the lift assist robot during motion. Experimental results show that this approach to augmentation provides the operator with a natural and effective interface to the heavy lift assist device.

Luecke, Greg R.; Tan, Kok-Leong; Zafer, Naci

1999-11-01

206

Forced cooling of underground electric power transmission lines : design manual  

E-print Network

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

Brown, Jay A.

1978-01-01

207

Atomistic force field for alumina fit to density functional theory  

SciTech Connect

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.

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

208

Two Cases of Calculation of Mechanical Forces in Electric Circuits  

Microsoft Academic Search

A formula is derived for the mechanical force in a circle of round wire, due to its own current. A formula, F = I2 logh a1\\/a2, is also derived for the longitudinal force exerted on a round conductor, due to its own current, where it changes its diameter. Where there is a constriction in a liquid conductor, this force acts

H. B. Dwight

1927-01-01

209

Field measurement of basal forces generated by erosive debris flows  

USGS Publications Warehouse

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.

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

2013-01-01

210

Biofouling prevention with pulsed electric fields  

SciTech Connect

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.

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

2000-02-01

211

Electric Force Lines of the Double Reissner-Nordstrom Exact Solution  

NASA Astrophysics Data System (ADS)

Recently Alekseev and Belinski have presented a new exact solution to the Einstein-Maxwell equation which describes two Reissner-Nordstrom (RN) sources in reciprocal equilibrium (no struts or strings); one source is a naked singularity, the other is a black hole: this is the only possible configuration for two separable objects, apart from the well-known extreme case (mi = ei). In the present paper, after a brief summary of this solution, we study in some detail the coordinate systems used and the main features of the gravitational and electric fields. In particular, we graph the plots of the electric force lines in three qualitatively different situations: equal-sign charges, opposite charges and the case of a naked singularity near a neutral black hole.

Paolino, Armando; Pizzi, Marco

212

Electric force lines of the double Reissner-Nordstrom exact solution  

E-print Network

Recently, Alekseev and Belinski have presented a new exact solution of the Einstein-Maxwell equations which describes two Reissner-Nordstrom (RN) sources in reciprocal equilibrium (no struts nor strings); one source is a naked singularity, the other is a black hole: this is the only possible configuration for separable object, apart from the well-known extreme case ($m_i=e_i$). In the present paper, after a brief summary of this solution, we study in some detail the coordinate systems used and the main features of the gravitational and electric fields. In particular we graph the plots of the electric force lines in three qualitatively different situations: equal-signed charges, opposite charges and the case of a naked singularity near a neutral black hole.

A. Paolino; M. Pizzi

2008-04-03

213

PRELIMINARY EXPERIMENTS IN THE RESPONSE OF PARTICLES TO MAGNETIC AND ELECTRIC FIELDS  

Microsoft Academic Search

In the presence of a magnetic field, iron particles that are suspended ; in a viscous fluid will respond by arranging themselves in a lines-of-force ; pattern. With weak uniform fields of a few gauss and with fine iron powder of a ; few microns, the pattern becomes one of many parallel micronsize electrical ; conductors. In the presence of

Lonse

1959-01-01

214

PHYSICAL REVIEW E 83, 026704 (2011) Atomistic modeling of metal surfaces under electric fields: Direct coupling of electric fields to a  

E-print Network

field is assessed by applying the classical Gauss law. The electric forces acting on the partially such as linear accelerators with the sophisticated design of the accelerating structures [10]. A number- lation of the charge on an atom is not done in correspondence with Gauss law. Instead, some

Nordlund, Kai

215

Motional sideband excitation using rotating electric fields  

NASA Astrophysics Data System (ADS)

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.

Isaac, C. A.

2013-04-01

216

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

E-print Network

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.

Lionel Foret; Alois Würger

2003-10-28

217

Solar wind control of the earth's electric field  

Microsoft Academic Search

The sun-weather problem is placed within an electrical framework subject to experimental investigation. An explanation is suggested for how solar variability modulates the earth's electric field. The solar wind velocity is inversely correlated with the electrical potential of the ionosphere, a measure of the overall intensity of the earth's fair-weather atmospheric electric field. In seeking a physical cause of this

R. Markson; M. Muir

1980-01-01

218

Radial-Electric-Field Piezoelectric Diaphragm Pumps  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

219

Impact of electric fields on honey bees  

SciTech Connect

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.

Bindokas, V.P.

1985-01-01

220

Four-nucleon force in chiral effective field theory  

SciTech Connect

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.

Evgeny Epelbaum

2005-10-25

221

Quantum mechanical force field for water with explicit electronic polarization  

PubMed Central

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

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

2013-01-01

222

Quantum mechanical force field for water with explicit electronic polarization  

SciTech Connect

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.

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

223

Tuning the mass of chameleon fields in Casimir force experiments.  

PubMed

We have calculated the chameleon pressure between two parallel plates in the presence of an intervening medium that affects the mass of the chameleon field. As intuitively expected, the gas in the gap weakens the chameleon interaction mechanism with a screening effect that increases with the plate separation and with the density of the intervening medium. This phenomenon might open up new directions in the search of chameleon particles with future long-range Casimir force experiments. PMID:20867290

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

2010-06-18

224

Electrostatic air filters generated by electric fields  

SciTech Connect

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

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

1981-01-27

225

Behavioral effects of electric and magnetic fields  

NASA Astrophysics Data System (ADS)

Two sets of behavioral studies were conducted. In the first, three procedures were used to determine how aversive a 100 kV/m 60-Hz electric field is for a rat. Each of the procedures enabled rats to respond in order to reduce exposure to the field. The rats did reduce exposure slightly with one, but not with the other two, whereas they reduced their exposure to moderate illumination in all three procedures. The results show that while the procedures were appropriate for assessing stimulus aversiveness, 100 kV/m is not a generally aversive stimulus for the rat. It was previously reported that immediately after exposure for 30 minutes to a horizontal 60-Hz, 5 x 10(exp -5)T field combined with a total static field of 2.61 x 10(exp -5)T, the rate of lever pressing by rats increased during the DRL component of a multiple fixed ratio, DRL schedule of food reinforcement. This project failed to confirm those observations in an experiment that duplicated the behavioral baseline and the magnetic field exposure conditions, with the exception that the total DC vector was greater in these experiments than it was in others.

Laties, V. G.

1992-04-01

226

Computer simulation of trifluoromethane properties with ab initio force field.  

PubMed

Intermolecular interaction potentials of the trifluoromethane dimer in 15 orientations have been calculated using the Hartree-Fock (HF) self-consistent theory and the second-order Møller-Plesset (MP2) perturbation theory. Single point energies at important geometries were also calibrated by the coupled cluster with single and double and perturbative triple excitation [CCSD(T)] calculations. We have employed Pople's medium size basis sets [up to 6-311++G(3df,3pd)] and Dunning's correlation consistent basis sets (up to aug-cc-pVQZ). Basis set limit potential values were obtained through well-studied extrapolation methods. The calculated MP2 potential data were employed to parameterize a 5-site force field for molecular simulations. We performed molecular dynamics simulations using the constructed ab initio force field and compared the simulation results with experiments. Quantitative agreements for the atom-wise radial distribution functions and the self-diffusion coefficients over a wide range of experimental conditions can be obtained, thus validating the ab initio force field without using experimental data a priori. PMID:21598276

Chung, Yi-Hsing; Li, Arvin Huang-Te; Chao, Sheng D

2011-08-01

227

An oppositely charged insect exclusion screen with gap-free multiple electric fields  

NASA Astrophysics Data System (ADS)

An electric field screen was constructed to examine insect attraction mechanisms in multiple electric fields generated inside the screen. The screen consisted of two parallel insulated conductor wires (ICWs) charged with equal but opposite voltages and two separate grounded nets connected to each other and placed on each side of the ICW layer. Insects released inside the fields were charged either positively or negatively as a result of electricity flow from or to the insect, respectively. The force generated between the charged insects and opposite ICW charges was sufficient to capture all insects.

Matsuda, Yoshinori; Kakutani, Koji; Nonomura, Teruo; Kimbara, Junji; Kusakari, Shin-ichi; Osamura, Kazumi; Toyoda, Hideyoshi

2012-12-01

228

Experimental Study of Cloud Formation by Intense Electric Fields  

Microsoft Academic Search

Cloud and fog formation under an electric field has been studied experimentally using a Wilson's cloud chamber with a supercooled atmosphere of ethanol. The threshold electric field to generate dense clouds using parallel plate electrodes was about 4 kV\\/m as estimated from the generated cloud position and from a model experiment of an electric field simulation using a water bath.

Kazuhiko Teramoto; Motoji Ikeya

2000-01-01

229

Applying electric field sensing to human-computer interfaces  

Microsoft Academic Search

A non-contact sensor based on the interaction of a person with electric fields for human-computer interface is investigated. Two sensing modes are explored: an external electric field shunted to ground through a human body, and an external electric field transmitted through a human body to stationary receivers. The sensors are low power (milliwatts), high resolution (millimeter) low cost (a few

Thomas G. Zimmerman; Joshua R. Smith; Joseph A. Paradiso; David Allport; Neil Gershenfeld

1995-01-01

230

Direct Evidence of Solar Flare Modification of Stratospheric Electric Fields  

Microsoft Academic Search

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

R. H. Holzworth; F. S. Mozer

1979-01-01

231

PH 222-3A Spring 2007 ELECTRIC FIELDSELECTRIC FIELDS  

E-print Network

PH 222-3A Spring 2007 ELECTRIC FIELDSELECTRIC FIELDS L 2 3Lectures 2,3 Chapter 22 (Halliday/Resnick/Walker, Fundamentals of Physics 8th edition) 1 #12;Chapter 22 Electric FieldsElectric Fields In this chapter we

Mirov, Sergey B.

232

2.6 ELECTRIC AND MAGNETIC FIELDS Introduction  

E-print Network

325 §2.6 ELECTRIC AND MAGNETIC FIELDS Introduction In electromagnetic theory the mks system MKS units Replacement symbol GAUSSIAN units E (Electric field) volt/m E statvolt/cm B (Magnetic field gauss-cm V (Electric potential) volt V statvolt (Dielectric constant) 4 µ (Magnetic permeability) 4µ c2

California at Santa Cruz, University of

233

GASEOUS ELECTRONICS In this chapter we study the properties of a plasma in an electric field. Our  

E-print Network

field, ignoring the effects of collisions. Under these conditions, we retrieve the Boltzmann relation side of the equation vanishes. Substituting for p from Eq. (2.101) (the electrons have high thermal positive charge generates an electric field. The force F e opposes the pressure gardient force F p.[4

Howard, John

234

Manipulating nanoscale contact electrification by an applied electric field.  

PubMed

Contact electrification is about the charge transfer between the surfaces of two materials in a contact-separation process. This effect has been widely utilized in particle separation and energy harvesting, where the charge transfer is preferred to be maximized. However, this effect is always undesirable in some areas such as electronic circuit systems due to the damage from the accumulated electrostatic charges. Herein, we introduced an approach to purposely manipulate the contact electrification process both in polarity and magnitude of the charge transfer through an applied electric field between two materials. Theoretical modeling and the corresponding experiments for controlling the charge transfer between a Pt coated atomic force microscopy tip and Parylene film have been demonstrated. The modulation effect of the electric field on contact electrification is enhanced for a thinner dielectric layer. This work can potentially be utilized to enhance the output performance of energy harvesting devices or nullify contact electric charge transfer in applications where this effect is undesirable. PMID:24479730

Zhou, Yu Sheng; Wang, Sihong; Yang, Ya; Zhu, Guang; Niu, Simiao; Lin, Zong-Hong; Liu, Ying; Wang, Zhong Lin

2014-03-12

235

Force-free magnetic fields - Generating functions and footpoint displacements  

NASA Technical Reports Server (NTRS)

This paper presents analytic and numerical calculations that explore equilibrium sequences of bipolar force-free magnetic fields in relation to displacments of their magnetic footpoints. It is shown that the appearance of magnetic islands - sometimes interpreted as marking the loss of equilibrium in models of the solar atmosphere - is likely associated only with physically unrealistic footpoint displacements such as infinite separation or 'tearing' of the model photosphere. The work suggests that the loss of equilibrium in bipolar configurations, sometimes proposed as a mechanism for eruptive solar events, probably requires either fully three-dimensional field configurations or nonzero plasma pressure. The results apply only to fields that are strictly bipolar, and do not rule out equilibrium loss in more complex structures such as quadrupolar fields.

Wolfson, Richard; Verma, Ritu

1991-01-01

236

Large Electric Field-Enhanced-Hardness Effect in a SiO2 Film  

NASA Astrophysics Data System (ADS)

Silicon dioxide films are extensively used in nano and micro-electromechanical systems. Here we studied the influence of an external electric field on the mechanical properties of a SiO2 film by using nanoindentation technique of atomic force microscopy (AFM) and friction force microscopy (FFM). A giant augmentation of the relative elastic modulus was observed by increasing the localized electric field. A slight decrease in friction coefficients was also clearly observed by using FFM with the increase of applied tip voltage. The reduction of the friction coefficients is consistent with the great enhancement of sample hardness by considering the indentation-induced deformation during the friction measurements.

Revilla, Reynier I.; Li, Xiao-Jun; Yang, Yan-Lian; Wang, Chen

2014-03-01

237

Large Electric Field-Enhanced-Hardness Effect in a SiO2 Film  

PubMed Central

Silicon dioxide films are extensively used in nano and micro–electromechanical systems. Here we studied the influence of an external electric field on the mechanical properties of a SiO2 film by using nanoindentation technique of atomic force microscopy (AFM) and friction force microscopy (FFM). A giant augmentation of the relative elastic modulus was observed by increasing the localized electric field. A slight decrease in friction coefficients was also clearly observed by using FFM with the increase of applied tip voltage. The reduction of the friction coefficients is consistent with the great enhancement of sample hardness by considering the indentation–induced deformation during the friction measurements. PMID:24681517

Revilla, Reynier I.; Li, Xiao-Jun; Yang, Yan-Lian; Wang, Chen

2014-01-01

238

On the nature of large auroral zone electric fields at 1-R/E/ altitude  

NASA Technical Reports Server (NTRS)

Mechanisms that may support magnetic-field-aligned electric fields in collisionless plasma are discussed in the light of recent magnetospheric observations, which for the first time allow a quantitative test of the theoretical models. Data from barium ion releases which indicate large field-aligned potential drops and direct electric field probe measurements at high altitude which reveal electric fields of several hundred millivolts per meter are discussed. It is concluded that the large field strengths observed (1) cannot be explained by anomalous resistivity or thermoelectric effects based on wave-particle interaction, (2) are much larger than required merely to balance the local mirror forces, and (3) are compatible with electric double layers of the same nature as those observed in the laboratory.

Shawhan, S. D.; Falthammar, C.-G.; Block, L. P.

1978-01-01

239

Nonlinear Force-Free Modeling of Coronal Magnetic Fields Part I: A Quantitative Comparison of Methods  

NASA Astrophysics Data System (ADS)

We compare six algorithms for the computation of nonlinear force-free (NLFF) magnetic fields (including optimization, magnetofrictional, Grad Rubin based, and Green's function-based methods) by evaluating their performance in blind tests on analytical force-free-field models for which boundary conditions are specified either for the entire surface area of a cubic volume or for an extended lower boundary only. Figures of merit are used to compare the input vector field to the resulting model fields. Based on these merit functions, we argue that all algorithms yield NLFF fields that agree best with the input field in the lower central region of the volume, where the field and electrical currents are strongest and the effects of boundary conditions weakest. The NLFF vector fields in the outer domains of the volume depend sensitively on the details of the specified boundary conditions; best agreement is found if the field outside of the model volume is incorporated as part of the model boundary, either as potential field boundaries on the side and top surfaces, or as a potential field in a skirt around the main volume of interest. For input field (B) and modeled field (b), the best method included in our study yields an average relative vector error E n = < |B-b|>/< |B|> of only 0.02 when all sides are specified and 0.14 for the case where only the lower boundary is specified, while the total energy in the magnetic field is approximated to within 2%. The models converge towards the central, strong input field at speeds that differ by a factor of one million per iteration step. The fastest-converging, best-performing model for these analytical test cases is the Wheatland, Sturrock, and Roumeliotis (2000) optimization algorithm as implemented by Wiegelmann (2004).

Schrijver, Carolus J.; De Rosa, Marc L.; Metcalf, Thomas R.; Liu, Yang; McTiernan, Jim; Régnier, Stéphane; Valori, Gherardo; Wheatland, Michael S.; Wiegelmann, Thomas

2006-05-01

240

Electric field effect in ultrathin black phosphorus  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

241

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

E-print Network

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.

John Swain; Allan Widom; Yogendra Srivastava

2014-04-29

242

Convolutional virtual electric field for image segmentation using active contours.  

PubMed

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

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

2014-01-01

243

Convolutional Virtual Electric Field for Image Segmentation Using Active Contours  

PubMed Central

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

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

2014-01-01

244

Coarse-grained force field; general folding theory  

PubMed Central

We review the coarse-grained UNited RESidue (UNRES) force field for the simulations of protein structure and dynamics, which is being developed in our laboratory over the last several years. UNRES is a physics-based force field, the prototype of which is defined as a potential of mean force of polypeptide chains in water, where all the degrees of freedom except the coordinates of ?-carbon atoms and side-chain centers have been integrated out. We describe the initial implementation of UNRES to protein-structure prediction formulated as a search for the global minimum of the potential-energy function and its subsequent molecular dynamics and extensions of molecular-dynamics implementation, which enabled us to study protein-folding pathways and thermodynamics, as well as to reformulate the protein-structure prediction problem as a search for the conformational ensemble with the lowest free energy at temperatures below the folding-transition temperature. Applications of UNRES to study biological problems are also described. PMID:21643583

Liwo, Adam; He, Yi; Scheraga, Harold A.

2012-01-01

245

Casimir force for a scalar field in warped brane worlds  

SciTech Connect

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

Linares, Roman; Morales-Tecotl, Hugo A. [Departamento de Fisica, Universidad Autonoma Metropolitana Iztapalapa, San Rafael Atlixco 186, C.P. 09340, Mexico D.F. (Mexico); Pedraza, Omar [Departamento de Fisica, Universidad Autonoma Metropolitana Iztapalapa, San Rafael Atlixco 186, C.P. 09340, Mexico D.F. (Mexico); Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Legaria, Instituto Politecnico Nacional, Av. Legaria 694, C.P. 11500, Mexico D.F. (Mexico)

2008-03-15

246

Saturation of the Electric Field Transmitted to the Magnetosphere  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

247

Interfacial Force Field Characterization in a Constrained Vapor Bubble Thermosyphon  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

248

Liquid/vapour phase separation in He-4 using electric fields  

NASA Technical Reports Server (NTRS)

In space, a replacement must be found for gravity to physically control and, in certain instances, contain cryogenic liquids. A program has been started at the Jet Propulsion Laboratory to study the use of electric field generated forces to establish the required orienting effects. Measurements which show that it is possible to apply strong enough electric fields to a liquid/vapor interface of He-4 to obtain an orienting force comparable to gravity are presented. Our measurements span the temperature range 1.7-4.2 K and demonstrate the applicability of Pashen's law for maximum attainable field before breakdown occurs. Some advantages of the electric field separator as opposed to passive surface tension devices are identified.

Israelsson, U. E.; Jackson, H. W.; Petrac, D.

1988-01-01

249

Empirical models of high latitude electric fields  

NASA Technical Reports Server (NTRS)

Model cross sections of the high latitude dawn-dusk electric field based on OGO-6 data are presented for the signature profiles, most frequently encountered for both + and -Y orientations of the interplanetary magnetic field. Line integrals give a total potential of 76 keV in each case. To illustrate extremes, examples of model cross-sections with total potentials of 23 keV and 140 keV are also given. Model convection patterns are also presented utilizing OGO-6 data on boundary locations at other magnetic local times. When this information is combined with characteristic field geometries in the region of the Harang discontinuity, and is supplemented by data from Ba+ cloud motions in the polar cap, it becomes possible to construct realistic convection patterns on the nightside which deviate from the usual sun-aligned patterns. The observational models presented are of limited applicability as a consequence of the variability of observed distributions. These limitations are emphasized with particular attention given to several types of recurrent deviations which have not previously been discussed.

Heppner, J. P.

1976-01-01

250

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

SciTech Connect

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.

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

251

Nonlinear gravitational self-force: Field outside a small body  

NASA Astrophysics Data System (ADS)

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 body’s 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 body’s 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.

Pound, Adam

2012-10-01

252

Electric field observations of equatorial bubbles  

NASA Technical Reports Server (NTRS)

Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

1992-01-01

253

Electropumping of water with rotating electric fields.  

PubMed

Pumping of fluids confined to nanometer dimension spaces is a technically challenging yet vitally important technological application with far reaching consequences for lab-on-a-chip devices, biomimetic nanoscale reactors, nanoscale filtration devices and the like. All current pumping mechanisms require some sort of direct intrusion into the nanofluidic system, and involve mechanical or electronic components. In this paper, we present the first nonequilibrium molecular dynamics results to demonstrate that non-intrusive electropumping of liquid water on the nanoscale can be performed by subtly exploiting the coupling of spin angular momentum to linear streaming momentum. A spatially uniform rotating electric field is applied to water molecules, which couples to their permanent electric dipole moments. The resulting molecular rotational momentum is converted into linear streaming momentum of the fluid. By selectively tuning the degree of hydrophobicity of the solid walls one can generate a net unidirectional flow. Our results for the linear streaming and angular velocities of the confined water are in general agreement with the extended hydrodynamical theory for this process, though also suggest refinements to the theory are required. These numerical experiments confirm that this new concept for pumping of polar nanofluids can be employed under laboratory conditions, opening up significant new technological possibilities. PMID:23614441

De Luca, Sergio; Todd, B D; Hansen, J S; Daivis, Peter J

2013-04-21

254

Electropumping of water with rotating electric fields  

NASA Astrophysics Data System (ADS)

Pumping of fluids confined to nanometer dimension spaces is a technically challenging yet vitally important technological application with far reaching consequences for lab-on-a-chip devices, biomimetic nanoscale reactors, nanoscale filtration devices and the like. All current pumping mechanisms require some sort of direct intrusion into the nanofluidic system, and involve mechanical or electronic components. In this paper, we present the first nonequilibrium molecular dynamics results to demonstrate that non-intrusive electropumping of liquid water on the nanoscale can be performed by subtly exploiting the coupling of spin angular momentum to linear streaming momentum. A spatially uniform rotating electric field is applied to water molecules, which couples to their permanent electric dipole moments. The resulting molecular rotational momentum is converted into linear streaming momentum of the fluid. By selectively tuning the degree of hydrophobicity of the solid walls one can generate a net unidirectional flow. Our results for the linear streaming and angular velocities of the confined water are in general agreement with the extended hydrodynamical theory for this process, though also suggest refinements to the theory are required. These numerical experiments confirm that this new concept for pumping of polar nanofluids can be employed under laboratory conditions, opening up significant new technological possibilities.

De Luca, Sergio; Todd, B. D.; Hansen, J. S.; Daivis, Peter J.

2013-04-01

255

AFMM: A molecular mechanics force field vibrational parametrization program  

NASA Astrophysics Data System (ADS)

AFMM (Automated Frequency Matching Method) is a program package for molecular mechanics force field parametrization. The method used fits the molecular mechanics potential function to both vibrational frequencies and eigenvector projections derived from quantum chemical calculations. The program optimizes an initial parameter set (either pre-existing or using chemically-reasonable estimation) by iteratively changing them until the optimal fit with the reference set is obtained. By implementing a Monte Carlo-like algorithm to vary the parameters, the tedious task of manual parametrization is replaced by an efficient automated procedure. The program is best suited for optimization of small rigid molecules in a well-defined energy minimum, for which the harmonic approximation to the energy surface is appropriate for describing the intra-molecular degrees of freedom. Program summaryTitle of program: AFMM Catalogue identifier: ADUZ Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUZ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: x86 PC, SGI, Sun Microsystems Operating system: GNU/Linux, BSD, IRIX, Solaris Programming language used: Python Memory required: 10 Mbytes No. of bits in a word: 32 or 64 No. of processors used: 1 Parallelized?: No No. of lines in distributed program, including test data, etc.:13 127 No. of bytes in distributed program, including test data, etc.: 182 550 Distribution format: tar.gz Typical running time: 24 h Nature of the physical problem: Molecular mechanics force field parametrization. Method of solution:Fitting of the molecular mechanics potential to normal modes derived from quantum chemical calculations. The missing force field parameters are optimized via a merit function to obtain the optimal fit with the reference quantum mechanical set.

Vaiana, A. C.; Cournia, Z.; Costescu, I. B.; Smith, J. C.

2005-04-01

256

The Anharmonic Force Field of BeH2 Revisited  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

257

Force Field Parametrization through Fitting on Inflection Points in Isotherms  

NASA Astrophysics Data System (ADS)

We present a method to determine potential parameters in molecular simulations of confined systems through fitting on experimental isotherms with inflection points. The procedure uniquely determines the adsorbent-adsorbate interaction parameters and is very sensitive to the size parameter. The inflection points in the isotherms are often related to a subtle interplay between different adsorption sites. If a force field can predict this interplay, it also reproduces the remaining part of the isotherm correctly, i.e., the Henry coefficients and saturation loadings.

Dubbeldam, D.; Calero, S.; Vlugt, T. J.; Krishna, R.; Maesen, T. L.; Beerdsen, E.; Smit, B.

2004-08-01

258

Electric fields in fluidic channels and sensor applications with capacitance  

Microsoft Academic Search

The application of common printed circuit board (PCB) technology to fluidic microsystems allows the generation of an electric field around two opposite copper walls of a fluidic channel. The shape of the electric field depends on the geometry of the channel construction and the fluid inside the channel. When passing a fluid between the tracks, the electrical capacitance changes as

Tobias Merkel; Lienhard Pagel; Hans-Walter Glock

2000-01-01

259

2.6 ELECTRIC AND MAGNETIC FIELDS Introduction  

E-print Network

325 §2.6 ELECTRIC AND MAGNETIC FIELDS Introduction In electromagnetic theory the mks system MKS units Replacement symbol GAUSSIAN units # E (Electric field) volt/m # E statvolt/cm # B (Magnetic potential) weber/m # A c gauss­cm V (Electric potential) volt V statvolt # (Dielectric constant) # 4# µ

California at Santa Cruz, University of

260

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

E-print Network

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

Fisher, Frank

261

Role of random electric fields in relaxors  

PubMed Central

PbZr1–xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1–xTixO3 (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

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

2014-01-01

262

Role of random electric fields in relaxors.  

PubMed

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

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

2014-02-01

263

Thermomechanical properties of graphene: valence force field model approach.  

PubMed

Using the valence force field model of Perebeinos and Tersoff (2009 Phys. Rev. B 79 241409(R)), different energy modes of suspended graphene subjected to tensile or compressive strain are studied. By carrying out Monte Carlo simulations it is found that: (i) only for small strains (|?| force field model results in a temperature independent bending modulus for graphene, and (viii) the Grüneisen parameter is estimated to be 0.64. PMID:22475745

Lajevardipour, A; Neek-Amal, M; Peeters, F M

2012-05-01

264

Electric field magnitudes and lightning initiation in thunderstorms  

Microsoft Academic Search

Lightning may be initiated via an electron avalanche that may occur when energetic electrons (~1 MeV) are accelerated by thunderstorm electric fields to velocities sufficient to produce new energetic electrons during ionizing collisions with nitrogen or oxygen molecules. For the avalanche to occur, the thunderstorm electric field must exceed a critical value called the breakeven field. At any altitude the

Thomas C. Marshall; Michael P. McCarthy; W. David Rust

1995-01-01

265

The electric field gradient in heavy rare earth metals  

Microsoft Academic Search

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

J. Pelzl; Fachbereich Physik

1972-01-01

266

Contour-clamped homogeneous electric field electrophoresis of Staphylococcus aureus  

Microsoft Academic Search

Contour-clamped homogeneous electric field (CHEF) electrophoresis is a technique of pulsed-field gel electrophoresis that enables the resolution of large fragments of DNA that cannot be resolved by conventional gel electrophoresis. The procedure involves the application of controlled electric fields that change direction at a predetermined angle to samples of DNA that have been embedded in an agarose gel matrix and

Warren B Grubb; Frances G O'Brien; Edet E Udo

2007-01-01

267

Computation of induced electric field for the sacral nerve activation  

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

268

Spiking patterns of a hippocampus model in electric fields  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

269

Neutral winds and electric fields in the dusk auroral oval. I - Measurements  

NASA Technical Reports Server (NTRS)

Two rockets carrying an upleg and downleg trimethyl aluminum chemical trail release and three barium cannisters were launched from Poker Flat, Alaska on Feb. 28, 1978 and Mar. 2, 1978 in order to study neutral winds and electric fields in the dusk auroral oval. Electric field measurements were also made with a radar system to supplement the barium cloud data. The barium cloud drifts on both days showed intense poleward electric fields in the subauroral region. The drifts were nearly latitude-independent and were equivalent to electric fields of 60 mV/m of February 2 and 40 mV/m on March 2. The data indicate that the Lorentz force and Joule heating had a strong influence on the observed neutral winds.

Mikkelsen, I. S.; Jorgensen, T. S.; Kelley, M. C.; Larsen, M. F.; Pereira, E.; Vickrey, J.

1981-01-01

270

Quantitative assessment of flow and electric fields for electrophoretic focusing at a converging channel entrance with interfacial electrode  

PubMed Central

The electric field and flow field gradients near an electrified converging channel are amenable to separating and focusing specific classes of electrokinetic material, but the detailed local electric field and flow dynamics in this region have not been thoroughly investigated. Finite elemental analysis was used to develop a model of a buffer reservoir connected to a smaller channel to simulate the electrophoretic and flow velocities (which correspond directly to the respective electric and flow fields) at a converging entrance. A detailed PTV (Particle Tracking Velocimetry) study using charged fluorescent microspheres was performed to assess the model validity both in the absence and presence of an applied electric field. The predicted flow velocity gradient from the model agreed with the PTV data when no electric field was present. Once the additional forces that act on the large particles required for tracing (dielectrophoresis) were included, the model accurately described the velocity of the charged particles in electric fields. PMID:22806456

Keebaugh, Michael W.; Mahanti, Prasun; Hayes, Mark A.

2013-01-01

271

ELECTRON ACCELERATION BY A STOCHASTIC ELECTRIC FIELD  

Microsoft Academic Search

The kinetic theory for runaway electrons is developed in a stochastic electric eld, consisting of short-scale electric cells. The general kinetic equation for the isotropic part of electron distribution function is derived, which includes eects of electron acceleration and slowing-down of spatial diusion of electrons in a region occupied by electric cells. The solutions are analyzed for some particular cases.

Victor Y. Trakhtengerts; Anton V. Kulchitsky; Dmitriy I. Iudin; Masashi Hayakawa

272

DC Electric Fields and Associated Plasma Drifts Observed with the C/NOFS Satellite  

NASA Technical Reports Server (NTRS)

Initial DC electric field observations and associated plasma drifts are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite. We present statistical averages of the vector fields for the first year of operations that include both the zonal and radial components of the resulting E x B plasma flows at low latitudes. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. The DC electric field detector reveals zonal and radial electric fields that undergo strong diurnal variations, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. There is considerable variation in the large scale DC electric field data, in both the daytime and nighttime cases, with enhanced structures typically observed at night. In general, the measured zonal DC electric field amplitudes include excursions that extend within the 0.4 - 2 m V/m range, corresponding to E x B drifts of the order of 30-150 m/s. The average vertical or radial electric fields may exceed the zonal fields in amplitude by a factor of 1.5 to 2. Although the data compare well, in a general sense, with previous satellite observations and statistical patterns of vertical ion drifts, the E x B drifts we report from C/NOFS rarely show a pronounced pre-reversal enhancement after sunset. We attribute this to a combination of extreme solar minimum conditions and the fact that the C/NOFS orbit of 401 by 867 km carries the probes essentially above the lower altitude regions where the wind-driven dynamo might be expected to create enhanced upwards drifts in the early evening. Evidence for wavenumber 4 tidal effects and other longitudinal signatures have been detected and will be presented. We also discuss off-equatorial electric fields and their relation to the ambient plasma density.

Pfaff, R.; Freudenreich, H.; Bromund, K.; Rowland, D.

2009-01-01

273

Partition Between Volitional and Induced Forces in Electrically Augmented Dynamic Isometric Muscle Contractions  

Microsoft Academic Search

Augmentation of force in partially deficient muscles can be achieved by combining electrical stimulation (ES) with their volitional activation (hybrid activation). However, while the overall torque results from the combination of the volitional and the electrically-induced torque components, the exact share between these components is not known. In a previous work, we described a method to resolve the share between

Eran Langzam; Yael Nemirovsky; Eli Isakov; Joseph Mizrahi

2006-01-01

274

Electric field induced bacterial flocculation of enteroaggregative Escherichia coli 042  

NASA Astrophysics Data System (ADS)

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.

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

2011-06-01

275

Electric field induced bacterial flocculation of Enteroaggregative Escherichia coli 042  

SciTech Connect

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

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

2011-01-01

276

Surface Heat Transfer in Electric Machines with Forced Air Flow  

Microsoft Academic Search

Since the insulation of windings in electric machines has comparatively low temperature limits, the problem of cooling these machines with the most economical use of material becomes one of major importance. The design of such machines from a temperature standpoint is usually based on tests of a previously made similar machine or else is of the ``cut arnd try'' type

G. E. Luke

1926-01-01

277

Linear electric field time-of-flight ion mass spectrometer  

DOEpatents

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.

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

2008-06-10

278

Electric Field Enhanced Diffusion of Salicylic Acid through Polyacrylamide Hydrogels  

NASA Astrophysics Data System (ADS)

The release mechanisms and the diffusion coefficients of salicylic acid -loaded polyacrylamide hydrogels were investigated experimentally by using a modified Franz-diffusion cell at 37 ^oC to determine the effects of crosslinking ratio and electric field strength. A significant amount of salicylic acid is released within 48 hours from the hydrogels of various crosslinking ratios, with and without electric field. The release characteristic follows the Q vs. t^1/2 linear relationship. Diffusion coefficient initially increases with increasing electric field strength and reaches the maximum value at electric field strength of 0.1 V; beyond that it decreases with electric field strength and becomes saturated at electric field strength of 5 V. The diffusion coefficient increases at low electric field strength (less 0.1 V) as a result of the electrophoresis of the salicylic acid, the expansion of pore size, and the induced pathway in pigskin. For electric field strength higher than 0.1 V, the decrease in the diffusion coefficient is due to the reduction of the polyacrylamide pore size. The diffusion coefficient obeys the scaling behavior D/Do=(drug size/pore size)^m, with the scaling exponent m equal to 0.93 and 0.42 at electric fields of 0 and 0.1 V, respectively.

Niamlang, Sumonman; Sirivat, Anuvat

2008-03-01

279

Distinguishing axions from generic light scalars using electric dipole moment and fifth-force experiments  

NASA Astrophysics Data System (ADS)

We derive electric dipole moment (EDM) constraints on possible new macroscopic time-reversal and parity-violating (TVPV) spin-dependent forces. These constraints are compared to those derived from direct searches in fifth-force experiments and from combining laboratory searches with astrophysical bounds on stellar energy loss. For axion-mediated TVPV spin-dependent forces, EDM constraints dominate over fifth-force limits by several orders of magnitude. However, we show that for a generic light scalar, unrelated to the strong CP problem, present bounds from direct fifth-force searches are more stringent than those inferred from EDM limits for the interaction ranges explored by fifth-force experiments. Thus, correlating observations in EDM and fifth-force experiments could help distinguish axions from more generic light scalar scenarios.

Mantry, Sonny; Pitschmann, Mario; Ramsey-Musolf, Michael J.

2014-09-01

280

Embedding Circular Force-Free Flux Ropes in Potential Magnetic Fields  

NASA Astrophysics Data System (ADS)

We propose a method for constructing approximate force-free equilibria in active regions that locally have a potential bipolar-type magnetic field with a thin force-free flux rope embedded inside it. The flux rope has a circular-arc axis and circular cross-section in which the interior magnetic field is predominantly toroidal (axial). Its magnetic pressure is balanced outside by that of the poloidal (azimuthal) field created at the boundary by the electric current sheathing the flux rope. To facilitate the implementation of the method in our numerical magnetohydrodynamic (MHD) code, the entire solution is described in terms of the vector potential of the magnetic field. The parameters of the flux rope can be chosen so that a subsequent MHD relaxation of the constructed configuration under line-tied conditions at the boundary provides a numerically exact equilibrium. Such equilibria are an approximation for the magnetic configuration preceding solar eruptions, which can be triggered in our model by imposing suitable photospheric flows beneath the flux rope. The proposed method is a useful tool for constructing pre-eruption magnetic fields in data-driven simulations of solar active events. Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD.

Titov, V. S.; Torok, T.; Mikic, Z.; Linker, J.

2013-12-01

281

Uplift and Outflow of Bacterial Spores via Electric Field  

NASA Astrophysics Data System (ADS)

The questions of how did life arise and is there life on other planets are some of the most profound questions that humanity asks Although there has been controversial signs of past bacterial life in meteorites which originated on Mars and there are current claims of bacterial life high in the atmosphere the issues of origin by chemical process or contamination make these types of results arguable and they will likely remain that way until a comprehensive theory is developed to explain why the claims might be true This paper proposes a complete theory for the spread of bacterial life throughout the galaxy by combining current knowledge from the fields of bacteriology stellar evolution and space weather Here we show the possibility that the forces of uplift on a charged bacteria particle are sufficient bring at least some lighter types of bacteria high into the ionosphere and subsequently move the charged spore onto magnetic field lines The bacteria spore is then driven down the magnetotail where during a solar storm a structure known as a plasmoid is propelled radially outward into space at velocities exceeding solar system escape velocity From that point the plasmoids are capable of reaching Mars the outer planets and even others systems eventually depositing the bacterial spores either via comets or direct interaction with the receiving planet The solid observational evidence for the strength of the electric fields and the speeds that the plasmoids leave the magnetotail during geomagnetic storms provide a firm

Dehel, T.

282

Surface electric fields for North America during historical geomagnetic storms  

NASA Astrophysics Data System (ADS)

To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 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.

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

2013-08-01

283

Parametrization of a reactive force field for aluminum hydride  

NASA Astrophysics Data System (ADS)

A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFFAlH3 is used to study the dynamics governing hydrogen desorption in AlH3. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFFAlH3. Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH4.

Ojwang, J. G. O.; van Santen, Rutger A.; Kramer, Gert Jan; van Duin, Adri C. T.; Goddard, William A.

2009-07-01

284

Parametrization of a reactive force field for aluminum hydride.  

PubMed

A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFF(AlH(3)) is used to study the dynamics governing hydrogen desorption in AlH(3). During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFF(AlH(3)). Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH(4). PMID:19655888

Ojwang, J G O; van Santen, Rutger A; Kramer, Gert Jan; van Duin, Adri C T; Goddard, William A

2009-07-28

285

Derivation of a Molecular Mechanics Force Field for Cholesterol  

SciTech Connect

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.

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

2004-01-01

286

Parametrization of a reactive force field for aluminum hydride  

SciTech Connect

A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFF{sub AlH{sub 3}} is used to study the dynamics governing hydrogen desorption in AlH{sub 3}. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFF{sub AlH{sub 3}}. Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH{sub 4}.

Ojwang, J. G. O. [Schuit Institute of Catalysis, Eindhoven University of Technology, Postbus 513, Den Dolech 2, Eindhoven 5600 MB (Netherlands); Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington D.C. 20012 (United States); Santen, Rutger A. van; Kramer, Gert Jan [Schuit Institute of Catalysis, Eindhoven University of Technology, Postbus 513, Den Dolech 2, Eindhoven 5600 MB (Netherlands); Duin, Adri C. T. van [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Goddard, William A. III [Materials and Process Simulation Center (MSC), California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125 (United States)

2009-07-28

287

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

SciTech Connect

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.

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

2009-01-01

288

A Modified Electric Field Mill and Measurements of Cloud Electric Field with it at a Tropical Coastal Station  

Microsoft Academic Search

Electric field mills are kept away from a recording station in an open field. During times of deviation of data from a known diurnal pattern and at times of malfunctioning of an element of the measurement system, a necessity to instantly check the functioning of the field mill arises. A modification to a field deployable inverted field mill to do

R. Vishnu; S. Muralidas; G. Mohankumar; S. Sampath

2010-01-01

289

Electric and magnetic fields measured during a sudden impulse  

NASA Technical Reports Server (NTRS)

The electric field in the ionosphere and the magnetic field at the earth's surface in the mid-latitude region were both measured during a sudden impulse. Ionospheric conductivities deduced from this data were consistent with expectations, thus suggesting that the fluctuations in the magnetic field at the earth's surface were caused by overhead ionospheric currents that were driven by an electric field associated with the sudden impulse.

Schutz, S.; Adams, G. J.; Mozer, F. S.

1974-01-01

290

A Wearable Force Plate Designed Using Pressure Sensitive Electric Conductive Rubber  

NASA Astrophysics Data System (ADS)

To perform 3D ground reaction force (GRF) and moments measurement with a comfortable interface for the foot, this paper presents a new 3D force sensor cell designed using pressure sensitive electric conductive rubber (PSECR). A wearable force plate with a four-support mechanism was proposed for measuring triaxial forces and moments. A compact electrical hardware system including amplifier modules, conditioning circuits, and then a micro-computer controller was developed and integrated into the sensor system. A shoes-based sensor system composed of two developed force plates was constructed for GRF and moment measurement. Calibration experiments were conducted, and a stationary force plate was used as a reference device to verify the measures of GRF and moment using the sensor system in trials by a normal walking speed. The results show a good correspondence between the developed sensor system and the reference system, which was examined by a root mean square (RMS) difference of 7.2N for x-axial force, 11.1N for y-axial force, and 9.5N for z-axial force. The RMS difference of the measured x-, y-, and z- directional moments was 6.4Nm, 1.9Nm, and 1.4Nm, respectively.

Liu, Tao; Inoue, Yoshio; Shibata, Kyoko

291

Temperature Modulation of Electric Fields in Biological Matter  

PubMed Central

Pulsed electric fields (PEF) have become an important minimally invasive surgical technology for various applications including genetic engineering, electrochemotherapy and tissue ablation. This study explores the hypothesis that temperature dependent electrical parameters of tissue can be used to modulate the outcome of PEF protocols, providing a new means for controlling and optimizing this minimally invasive surgical procedure. This study investigates two different applications of cooling temperatures applied during PEF. The first case utilizes an electrode which simultaneously delivers pulsed electric fields and cooling temperatures. The subsequent results demonstrate that changes in electrical properties due to temperature produced by this configuration can substantially magnify and confine the electric fields in the cooled regions while almost eliminating electric fields in surrounding regions. This method can be used to increase precision in the PEF procedure, and eliminate muscle contractions and damage to adjacent tissues. The second configuration considered introduces a third probe that is not electrically active and only applies cooling boundary conditions. This second study demonstrates that in this probe configuration the temperature induced changes in electrical properties of tissue substantially reduce the electric fields in the cooled regions. This novel treatment can potentially be used to protect sensitive tissues from the effect of the PEF. Perhaps the most important conclusion of this investigation is that temperature is a powerful and accessible mechanism to modulate and control electric fields in biological tissues and can therefore be used to optimize and control PEF treatments. PMID:21695144

Daniels, Charlotte S.; Rubinsky, Boris

2011-01-01

292

Middle atmospheric electric fields over thunderstorms  

NASA Technical Reports Server (NTRS)

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.

Holzworth, Robert H.

1992-01-01

293

Dielectrophoretic spectra of translational velocity and critical frequency for a spheroid in traveling electric field.  

PubMed

An analysis has been made of the dielectrophoretic (DEP) forces acting on a spheroidal particle in a traveling alternating electric field. The traveling field can be generated by application of alternating current signals to an octapair electrode array arranged in phase quadrature sequence. The frequency dependent force can be resolved into two orthogonal forces that are determined by the real and the imaginary parts of the Clausius-Mossotti factor. The former is determined by the gradient in the electric field and directs the particle either toward or away from the tip of the electrodes in the electrode array. The force determined by the imaginary component is in a direction along the track of the octapair interdigitated electrode array. The DEP forces are related to the dielectric properties of the particle. Experiments were conducted to determine the DEP forces in such an electrode arrangement using yeast cells (Saccharomyces cervisiate TISTR 5088) with media of various conductivities. Experimental data are presented for both viable and nonviable cells. The dielectric properties so obtained were similar to those previously reported in literature using other DEP techniques. PMID:20644671

Bunthawin, Sakshin; Wanichapichart, Pikul; Tuantranont, Adisorn; Coster, Hans G L

2010-01-01

294

Probing university students' understanding of electromotive force in electricity  

NASA Astrophysics Data System (ADS)

The goal of this study is to identify students' difficulties with learning the concepts of electromotive force (emf) and potential difference in the context of transitory currents and resistive direct-current circuits. To investigate these difficulties, we developed a questionnaire based on an analysis of the theoretical and epistemological framework of physics, which was then administered to first-year engineering and physics students at universities in Spain, Colombia, and Belgium. The results of the study show that student difficulties seem to be strongly linked to the absence of an analysis of the energy balance within the circuit and that most university students do not clearly understand the usefulness of and the difference between the concepts of potential difference and emf.

Garzón, Isabel; De Cock, Mieke; Zuza, Kristina; van Kampen, Paul; Guisasola, Jenaro

2014-01-01

295

Simulating the interplay between plasma transport, electric field, and magnetic field in the near-earth nightside magnetosphere  

NASA Astrophysics Data System (ADS)

The convection electric field resulting from the coupling of the Earth's magnetosphere with the solar wind and interplanetary magnetic field (IMF) drives plasma in the tail plasma sheet earthward. This transport and the resulting energy storage in the near Earth plasma sheet are important for setting up the conditions that lead to major space weather disturbances, such as storms and substorms. Penetration of plasma sheet particles into the near-Earth magnetosphere in response to enhanced convection is crucial to the development of the Region 2 field-aligned current system and large-scale magnetosphere-ionosphere (M-I) coupling, which results in the shielding of the convection electric field. In addition to the electric field, plasma transport is also strongly affected by the magnetic field, which is distinctly different from dipole field in the inner plasma sheet and changes with plasma pressure in maintaining force balance. The goal of this dissertation is to investigate how the plasma transport into the inner magnetosphere is affected by the interplay between plasma, electric field and magnetic field. For this purpose, we conduct simulations using the Rice Convection Model (RCM), which self-consistently calculates the electric field resulting from M-I coupling. In order to quantitatively evaluate the interplay, we improved the RCM simulations by establishing realistic plasma sheet particle sources, by incorporating it with a modified Dungey force balance magnetic field solver (RCM-Dungey runs), and by adopting more realistic electron loss rates. We found that plasma sheet particle sources strongly affect the shielding of the convection electric field, with a hotter and more tenuous plasma sheet resulting in less shielding than a colder and denser one and thus in more earthward penetration of the plasma sheet. The Harang reversal, which is closely associated with the shielding of the convection electric field and the earthward penetration of low-energy protons, is found to be located at lower latitudes and extend more dawnward for a hotter and more tenuous plasma sheet. In comparison with simulation runs under an empirical but not force balance magnetic field from the Tsyganenko 96 model, the simulation results show that transport under force-balanced magnetic field results in weaker pressure gradients and thus weaker R2 FAC in the near-earth region, weaker shielding of the penetration electric field and, as a result, more earthward penetration of plasma sheet protons and electrons with their inner edges being closer together and more azimuthally symmetric. To evaluate the effect of electron loss rate on ionospheric conductivity, a major contributing factor to M-I coupling, we run RCM-Dungey with a more realistic, MLT dependent electron loss rate established from observed wave activity. Comparing our results with those using a strong diffusion everywhere rate, we found that under the MLT dependent loss rate, the dawn-dusk asymmetry in the precipitating electron energy fluxes agrees better with statistical DMSP observations. The more realistic loss rate is much weaker than the strong diffusion limit in the inner magnetosphere. This allows high-energy electrons in the inner magnetosphere to remain much longer and produce substantial conductivity at lower latitudes. The higher conductivity at lower latitudes under the MLT dependent loss rate results in less efficient shielding in response to an enhanced convection electric field, and thus to deeper penetration of the ion plasma sheet into the inner magnetosphere than under the strong diffusion everywhere rate.

Gkioulidou, Malamati

296

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

SciTech Connect

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)

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

297

Analysis of shifts in students' reasoning regarding electric field and potential concepts  

NASA Astrophysics Data System (ADS)

Students' reasoning regarding the relationships among electric fields, forces, and equipotential line patterns was explored using pre- and post-test responses to selected multiple-choice questions on the Conceptual Survey of Electricity and Magnetism. Students' written explanations of their reasoning, provided both pre- and post-instruction, allowed additional assessment of the changes in their thinking. The data indicate that although students largely abandon an initial tendency to associate stronger fields with wider equipotential line spacing, many of them persist in incorrectly associating electric field magnitude at a point with the electric potential at that point. Analysis of the data also illustrated that the accuracy of specific multiple-choice responses in reflecting student thinking can be strongly time dependent. In our sample, a strong and consistent pattern of correct answers on a specific question (administered before instruction) was demonstrated to provide a highly misleading impression of students' understanding.

Meltzer, David E.

2007-03-01

298

Biofouling prevention with pulsed electric fields  

Microsoft Academic Search

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

A. Abou-Ghazala; Karl H. Schoenbach

2000-01-01

299

Dipole Relaxation in an Electric Field.  

ERIC Educational Resources Information Center

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

Neumann, Richard M.

1980-01-01

300

Fetal exposure to low frequency electric and magnetic fields  

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

301

Modular Approach to Physics: Electric Potential in Uniform Field Simulation  

NSDL National Science Digital Library

This simulation can be used to trace the electric potential lines and the electrical field lines in a region where the electrical field is uniform. It also allows the user to visualize the motion, and energy of a charge placed in this region. The user can change the electrical field, the charge, its mass, and its initial velocity. Details on how to use the applet are available under Applet Help on the top left corner of the simulation window. This item is part of a larger collection of simulation-based physics modules sponsored by the MAP project (Modular Approach to Physics).

Austin, David; Martin, Brian

2011-03-06

302

Electric and magnetic field sensing for high-voltage applications  

Microsoft Academic Search

Electric and magnetic fields can be measured optically, either directly via Pockels and Faraday effect or indirectly via Piezo effect. In high voltage applications fiber optic sensors are especially attractive for their ability of easy potential separation. For electric fields the Pockels effect in BSO, BGO crystals is mostly read out polarimetrically. The current is mostly measured via the Faraday

Thomas Bosselmann

1997-01-01

303

Electric Field Intensity of the Lightning Return Stroke  

Microsoft Academic Search

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

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

1973-01-01

304

MICROSECOND-SCALE ELECTRIC FIELD PULSES IN CLOUD LIGHTNING FLASHES  

E-print Network

in three geographical locations as recorded with the same measurement system: in Socorro, New Mexico discharge, can have for lightning-related EMC Electric field data (see Table 1) were acquired with a system-149- 30F3 MICROSECOND-SCALE ELECTRIC FIELD PULSES IN CLOUD LIGHTNING FLASHES Y. Villanueva, V

Florida, University of

305

The genotoxic potential of electric and magnetic fields: an update  

Microsoft Academic Search

We review 23 studies on the potential genotoxicity of electric and magnetic fields that have appeared in the published literature since our 1993 review of 55 published studies (McCann et al., Mutat. Res. 297 (1993) 61–95) and six additional studies published prior to 1993, which were not previously reviewed. As in our previous review, internal electric fields present in media

Joyce McCann; Fred Dietrich; Charles Rafferty

1998-01-01

306

Alternating electric field induced agglomeration of carbon black filled resins  

Microsoft Academic Search

This letter reports on our observation that an alternating electric field is able to induce the formation of an electrically conducting network in carbon black (CB) filled resins well below the zero-field percolation threshold. Compared with the recently presented dc method, the ac agglomeration is more efficient in two respects: it proceeds significantly faster under equivalent conditions and is still

Matthias-Klaus Schwarz; Wolfgang Bauhofer; Karl Schulte

2002-01-01

307

Electric Field Analysis of the Insulation Structure of Power Transformer  

Microsoft Academic Search

Electric field and dielectric conditions were analysed in an oil immersed power transformer. The particularity of the transformer’s design we are dealing with is an attempt to eliminate the stress-control ring above the low voltage (LV) winding. Using the finite element method (FEM) we analysed the steady state electric field that suited conditions during dielectric test with a separate AC

Danilo Makuc; Juso Ikanovi?; Konrad Lenasi

308

A fundamental limit on electric fields in air  

Microsoft Academic Search

By modifying the avalanche mode of runaway breakdown to include positive feedback from gamma-rays and positrons, it is found that enormous bursts of energetic radiation can be produced in strong electric fields in air, with peak fluxes up to one billion times greater than from conventional models. These bursts generate so many runaway electrons that the electric field is very

J. R. Dwyer

2003-01-01

309

Dynamics of the generation of magnetic-field-aligned electric fields by drift currents  

Microsoft Academic Search

A study is made of the process of generation and evolution of parallel electric fields on closed geomagnetic field lines. Charge separation that is due to the different character of the drift of energetic electrons and protons of inhomogeneous magnetospheric plasma in the geomagnetic field is considered to be the factor responsible for the generation of the electric field. In

Sergey V. Fridman

1994-01-01

310

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

NASA Astrophysics Data System (ADS)

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 forces due to viscous interaction with the suspending medium, and the fluid is put into motion by electrothermal effect, ac electroosmosis, or both. Typically, m-PIV measures the fluid velocity by tracking the motion of fluorescent particles with an assumption that the particles faithfully follow the fluid flow. But in our experiments the particle velocity is different from the underlining fluid velocity due to the DEP forces on the particles induced by the applied electric fields. In order to determine fluid velocity under nonuniform electric fields, we used a technique called Two-color m-PIV (Meinhart et al., 2003). In an effort to find the mechanisms behind the fluid motion, we measured fluid velocity at several regions within a microchannel over a range of applied voltages. The results indicate that the fluid motion is caused by combination of electrothermal effect and ac electroosmosis, and that electrothermal effect is more important at the bulk fluid.

Wang, Dazhi; Meinhart, Carl; Sigurdson, Marin

2003-11-01

311

Nonlinear piezoelectricity in epitaxial ferroelectrics at high electric fields  

SciTech Connect

Non-linear effects in the coupling of polarization with elastic strain have been predicted to occur in ferroelectric materials subjected to high electric fields. Such predictions are tested here for a Pb(Zr0.2,Ti0.8)O3 ferroelectric thin film at electric fields in the range of several MV/cm. Thermal runaway and subsequent low-frequency dielectric breakdown are overcome by using nanosecond electrical pulses to apply high electric fields, which made the probing of the film's structure possible at piezoelectric strains reaching up to 2.7%. The piezoelectric strain exceeds predictions based on constant piezoelectric coefficients at electric fields from 2 to 4 MV/cm, which is consistent with a non-linear effect predicted to occur at concomitant piezoelectric distortions. At higher fields, the piezoelectric response decreases, suggesting that elastic interactions between atoms enter a new regime.

Grigoriev, Alexei [University of Wisconsin, Madison; Sichel, Rebecca [University of Wisconsin, Madison; Lee, Ho Nyung [ORNL; Landahl, Eric C. [Argonne National Laboratory (ANL); Adams, Bernhard [Argonne National Laboratory (ANL); Dufresne, Eric M. [Argonne National Laboratory (ANL); Evans, Paul G. [University of Wisconsin, Madison

2008-01-01

312

Electric field quench in AdS/CFT  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

313

Electric Field Distribution of Cadmium Zinc Telluride (CZT)  

SciTech Connect

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.

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

2009-08-02

314

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

315

Electric field-mediated processing of polymer blend solutions  

NASA Technical Reports Server (NTRS)

Multiphase polymer blends in which the minor phases are oriented in a desired direction may demonstrate unique optical, electrical, and mechanical properties. While morphology development in shear fields was studied extensively, little work has focused on effects of electric fields on phase structure. The use of electric fields for blend morphology modulation with particular attention given to solvent casting of blends in d.c. fields was explored. Both homopolymer blends (average phase sizes of several microns) and diblock copolymer/homopolymer blends (average phase sizes of hundreds of Angstroms) were investigated. Summarized are important observations and conclusions.

Wnek, G. E.; Krause, S.

1993-01-01

316

Trapping of ion conics by downward parallel electric fields  

NASA Technical Reports Server (NTRS)

Energetic particle data from electrostatic analyzers aboard the S3-3 satellite indicative of a downward parallel electric field at low altitudes are presented to argue for a causal connection between downward parallel electric fields and ion heating. The data include observations of upward field-aligned electron beams in regions where precipitating electron fluxes are suppressed. Evidence of downward acceleration of ions and locally mirroring ion conics is also presented. It is argued that the presence of a downward electric field may have important consequences for ion conic heating and might in fact be required for the observed heating of ions to several hundred electron volts.

Gorney, D. J.; Chiu, Y. T.; Croley, D. R., Jr.

1985-01-01

317

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

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

318

Electric field measurements during the MAC/EPSILON campaign  

NASA Technical Reports Server (NTRS)

The MAC/EPSILON observational campaign in northern Norway involved the taking of three-axis electric field measurements of the middle atmosphere by means of five rocketborne payloads during October and November, 1987. Simultaneous horizontal electric field measurements made by two of the rocket flights were in general agreement in their limited overlap region. The more extensive horizontal E-field measurements exhibited a decreasing mapping function with decreasing altitude, thereby indicating the presence of fields from a local auroral patch. Small-scale variations in the horizontal fields of the lights were similar to observed wavelike variations in the neutral wind field.

Croskey, C. L.; Hale, L. C.; Mitchell, J. D.; Schmidlin, F. J.; Hoppe, U.-P.

1990-01-01

319

Self-organized growth of tetrathiafulvalene-tetracyanoquinodimethane molecular wires using the coevaporation method under a static electric field  

NASA Astrophysics Data System (ADS)

Wire-like crystals of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) charge-transfer complexes were grown under a static electric field by employing electric-field assisted evaporation. TTF-TCNQ molecular wires grew from the edges of two gold electrodes opposite to each other along the electric lines of force, and finally make a connection at their front end to form a single wire. Self-organization of the wire bridge is derived from a higher local electric field between the tips of the opposing molecular wires. Oriented molecular wires, which have diffuse branches, exhibit the effects of a local electric field. Preferential growth of TCNQ at the tip of the molecular wire during coevaporation of TTF and TCNQ is clearly revealed by microscopic Raman spectroscopy. Asymmetrical growth of coevaporated TTF-TCNQ wire under a static electric field is dominated by the drift motion of TCNQ-.

Sakai, Masatoshi; Iizuka, Masaaki; Nakamura, Masakazu; Kudo, Kazuhiro

2005-03-01

320

Lipid membranes in external electric fields: kinetics of large pore formation causing rupture.  

PubMed

About 40 years ago, Helfrich introduced an elastic model to explain shapes and shape transitions of cells (Z Naturforsch C, 1973; 28:693). This seminal article stimulated numerous theoretical as well as experimental investigations and created new research fields. In particular, the predictive power of his approach was demonstrated in a large variety of lipid model system. Here in this review, we focus on the development with respect to planar lipid membranes in external electric fields. Stimulated by the early work of Helfrich on electric field forces acting on liposomes, we extended his early approach to understand the kinetics of lipid membrane rupture. First, we revisit the main forces determining the kinetics of membrane rupture followed by an overview on various experiments. Knowledge on the kinetics of defect formation may help to design stable membranes or serve for novel mechanism for controlled release. PMID:24485595

Winterhalter, Mathias

2014-06-01

321

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

NASA Technical Reports Server (NTRS)

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

Mazuruk, K.; Volz, M. P.

1996-01-01

322

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

PubMed Central

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 individual’s 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 (0.22±0.17 N for the healthy subjects; 0.17±0.13 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 individual’s available workspace into account. With feedback, more accurate control of muscle force can be achieved. PMID:24103414

2013-01-01

323

Controlling Factors of the Electric Field at the Triple Junction  

NASA Astrophysics Data System (ADS)

The metal-dielectric-vacuum junction is defined as the triple junction owned enhanced electric field, thus this special region is regarded as the location where primary electrons emission is favored. For electron emission, triple junction could affect both the flashover breakdown of insulators and the electron emission property of ferroelectric cathodes. In this study, we theoretically investigate the electric field enhancement in the triple-junction region. It is found that the key parameter to determine the field enhancement is the taper angle of the electrode and the relative permittivity of the dielectric. In addition, we first deduce the accurate expression of the electric field in this special region. The controlling parameters for determining the field enhancement are discussed in detail. We also discover the way to reduce the electric field of this region through simulation. The current analysis would be useful for both the electron emission enhancement and the issue of flashover breakdown.

Liu, Yang; Huang, Xu-Dong; Feng, Yu-Jun; He, Hong-Liang

2014-02-01

324

Enhanced Translational Dynamics of Water under Electric Field  

SciTech Connect

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.

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

325

Atomic force microscopy modified for studying electric properties of thin films and crystals. Review  

Microsoft Academic Search

Probe force microscopy continues growing in popularity as a method for studying surfaces of solids and control over crystals\\u000a and thin films that are grown on various scientific and industrial setups. New modifications of the method increase the possibilities\\u000a for recording various characteristics of the objects studied. An important role here is played by “electricalforce microscopy,\\u000a the various modifications

K. L. Sorokina; A. L. Tolstikhina

2004-01-01

326

Force.  

ERIC Educational Resources Information Center

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)

Gamble, Reed

1989-01-01

327

Electrical field-induced extraction and separation techniques: promising trends in analytical chemistry--a review.  

PubMed

Sample preparation is an important issue in analytical chemistry, and is often a bottleneck in chemical analysis. So, the major incentive for the recent research has been to attain faster, simpler, less expensive, and more environmentally friendly sample preparation methods. The use of auxiliary energies, such as heat, ultrasound, and microwave, is one of the strategies that have been employed in sample preparation to reach the above purposes. Application of electrical driving force is the current state-of-the-art, which presents new possibilities for simplifying and shortening the sample preparation process as well as enhancing its selectivity. The electrical driving force has scarcely been utilized in comparison with other auxiliary energies. In this review, the different roles of electrical driving force (as a powerful auxiliary energy) in various extraction techniques, including liquid-, solid-, and membrane-based methods, have been taken into consideration. Also, the references have been made available, relevant to the developments in separation techniques and Lab-on-a-Chip (LOC) systems. All aspects of electrical driving force in extraction and separation methods are too specific to be treated in this contribution. However, the main aim of this review is to provide a brief knowledge about the different fields of analytical chemistry, with an emphasis on the latest efforts put into the electrically assisted membrane-based sample preparation systems. The advantages and disadvantages of these approaches as well as the new achievements in these areas have been discussed, which might be helpful for further progress in the future. PMID:24528839

Yamini, Yadollah; Seidi, Shahram; Rezazadeh, Maryam

2014-03-01

328

On intense diverging electric fields associated with black aurora  

Microsoft Academic Search

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

Göran Marklund; Lars Blomberg; Carl-Gunne Fälthammar; Per-Arne Lindqvist

1994-01-01

329

Trapping of ion conics by downward parallel electric fields  

Microsoft Academic Search

Energetic particle data from electrostatic analyzers aboard the S3-3 satellite indicative of a downward parallel electric field at low altitudes are presented to argue for a causal connection between downward parallel electric fields and ion heating. The data include observations of upward field-aligned electron beams in regions where precipitating electron fluxes are suppressed. Evidence of downward acceleration of ions and

D. J. Gorney; Y. T. Chiu; D. R. Jr. Croley

1985-01-01

330

Beyond Orientation: The Impact of Electric Fields on Block Copolymers  

SciTech Connect

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.

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

331

Axial-Field Electrical Machines - Design and Applications  

Microsoft Academic Search

Axial-field electrical machines offer an alternative to the conventional machines. In the axial-field machine, the airgap flux is axial in direction and the active current carrying conductors are radially positioned. This paper presents the design characteristics, special features, manufacturing aspects and potential applications for axial-field electrical machines. The experimental results from several prototypes, including d.c. machines, synchronous machines and single-phase

C. C. Chan

1987-01-01

332

A New Design Approach for Axial-Field Electrical Machines  

Microsoft Academic Search

The laminated core of an axial-field electrical machine is usually made of a strip-wound circular core which is machined to form the slots. This paper presents a new design and method of construction for the laminated cores of axial-field electrical machines. The laminated core, viz. armature or stator core, is sandwiched between two field cores. As there is no yoke

Wai Leung; James C. Chan

1980-01-01

333

Electric field in 3D gravity with torsion  

E-print Network

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

M. Blagojevi?; B. Cvetkovi?

2008-04-11

334

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

PubMed Central

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

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

2013-01-01

335

Changes in corticospinal excitability during reach adaptation in force fields  

PubMed Central

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

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

2013-01-01

336

A reactive force field for aqueous-calcium carbonate systems.  

PubMed

A new reactive force field has been derived that allows the modelling of speciation in the aqueous-calcium carbonate system. Using the ReaxFF methodology, which has now been implemented in the program GULP, calcium has been simulated as a fixed charge di-cation species in both crystalline phases, such as calcite and aragonite, as well as in the solution phase. Excluding calcium from the charge equilibration process appears to have no adverse effects for the simulation of species relevant to the aqueous environment. Based on this model, the speciation of carbonic acid, bicarbonate and carbonate have been examined in microsolvated conditions, as well as bulk water. When immersed in a droplet of 98 water molecules and two hydronium ions, the carbonate ion is rapidly converted to bicarbonate, and ultimately carbonic acid, which is formed as the metastable cis-trans isomer under kinetic control. Both first principles and ReaxFF calculations exhibit the same behaviour, but the longer timescale accessible to the latter allows the diffusion of the carbonic acid to the surface of the water to be observed, where it is more stable at the interface. Calcium carbonate is also examined as ion pairs in solution for both CaCO(3)(0)((aq)) and CaHCO(3)(+)((aq)), in addition to the (1014) surface in contact with water. PMID:21850319

Gale, Julian D; Raiteri, Paolo; van Duin, Adri C T

2011-10-01

337

Force Field Independent Metal Parameters Using a Nonbonded Dummy Model  

PubMed Central

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

2014-01-01

338

Dynamics of ultracold molecules in confined geometry and electric field  

SciTech Connect

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

Quemener, Goulven; Bohn, John L. [JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2011-01-15

339

Excitation energies and ionization potentials at high electric fields for molecules relevant for electrically insulating liquids  

NASA Astrophysics Data System (ADS)

The electric-field dependence of the molecular ionization potential and excitation energies is investigated by density-functional theory calculations. It is demonstrated that the ionization potential has a strong field dependence and decreases with increasing field. The excitation energies depend weakly on the field and the number of available excited states decreases with increasing field since the ionization potential has a stronger field dependence. Above a specific field, different for each molecule, a two-state model is obtained consisting of the electronic ground state and the ionized state. Implications for streamer propagation and electrically insulating materials are discussed.

Davari, N.; Åstrand, P.-O.; Ingebrigtsen, S.; Unge, M.

2013-04-01

340

The hydrogen atom in plasmas with an external electric field  

NASA Astrophysics Data System (ADS)

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

Bahar, M. K.; Soylu, A.

2014-09-01

341

Structured DC Electric Fields With and Without Associated Plasma Density Gradients Observed with the C/NOFS Satellite  

NASA Technical Reports Server (NTRS)

DC electric field observations and associated plasma drifts gathered with the Vector Electric Field Investigation on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite typically reveal considerable variation at large scales (approximately 100's of km), in both daytime and nighttime cases, with enhanced structures usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, as observed by the Planar Langmuir Probe on C/NOFS, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the relationship of such structured DC electric fields and the ambient plasma density in the C/NOFS satellite measurements observed thus far, taking into account both plasma density depletions and enhancements. We investigate the mapping of the electric fields along magnetic field lines from distant altitudes and latitudes to locations where the density structures, which presumably formed the original seat of the electric fields, are no longer discernible in the observations. In some cases, the electric field structures and spectral characteristics appear to mimic those associated with equatorial spread-F processes, providing important clues to their origins. We examine altitude, seasonal, and longitudinal effects in an effort to establish the origin of such structured DC electric fields observed both with, and without, associated plasma density gradients

Pfaff, R.; Rowland, D.; Klenzing, J.; Freudenreich, H.; Bromund, K.; Liebrecht, C.; Roddy, P.; Hunton, D.

2009-01-01

342

A low-temperature dynamic mode scanning force microscope operating in high magnetic fields  

E-print Network

-field optical microscope designed for operation at low temperatures.5 In this setup, an optical fiber is glued scanning near field optical microscopy,5,7­10 magnetic force microscopy,11 and acoustic near field as a friction- force sensor. The advantages of these piezoelectric sensors are the availability, the low cost

Ihn, Thomas

343

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

NASA Astrophysics Data System (ADS)

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 200pT , an electric field of 6MV/m lifts the degeneracy between states of unequal ?mF? and, along with the low (?3m/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.

Amini, Jason M.; Munger, Charles T., Jr.; Gould, Harvey

2007-06-01

344

Electric Field Induced Selective Disordering in Lamellar Block Copolymers  

SciTech Connect

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.

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

345

Non-volatile electrically-driven repeatable magnetization reversal with no applied magnetic field  

NASA Astrophysics Data System (ADS)

Repeatable magnetization reversal under purely electrical control remains the outstanding goal in magnetoelectrics. Here we use magnetic force microscopy to study a commercially manufactured multilayer capacitor that displays strain-mediated coupling between magnetostrictive Ni electrodes and piezoelectric BaTiO3-based dielectric layers. In an electrode exposed by polishing approximately normal to the layers, we find a perpendicularly magnetized feature that exhibits non-volatile electrically driven repeatable magnetization reversal with no applied magnetic field. Using micromagnetic modelling, we interpret this nominally full magnetization reversal in terms of a dynamic precession that is triggered by strain from voltage-driven ferroelectric switching that is fast and reversible. The anisotropy field responsible for the perpendicular magnetization is reversed by the electrically driven magnetic switching, which is, therefore, repeatable. Our demonstration of non-volatile magnetic switching via volatile ferroelectric switching may inspire the design of fatigue-free devices for electric-write magnetic-read data storage.

Ghidini, M.; Pellicelli, R.; Prieto, J. L.; Moya, X.; Soussi, J.; Briscoe, J.; Dunn, S.; Mathur, N. D.

2013-02-01

346

Field-tunable probe for combined electric and magnetic field measurements  

Microsoft Academic Search

A method to measure the magnitude and phase of electric and magnetic fields with a single probe is presented. The optically-based probe, consisting of a hybrid combination of gallium arsenide followed by terbium gallium garnet, employs the Pockels effect to measure electric fields and the Faraday effect to measure magnetic fields. Isolation between the two effects is achieved via external

Ronald M. Reano; John F. Whitaker; Linda P. B. Katehi

2002-01-01

347

Analysis of microwave generation by field emitted electrons moving in crossed electric and magnetic fields  

Microsoft Academic Search

A new microwave generating device is proposed and analysed theoretically. The device is based on the controlled motion of field emission (FE) electrons in a vacuum working space subject to crossed electric E and magnetic B fields. A cylindrical capacitor configuration is considered, the symmetry of the arrangement being cylindrical around the B axis whilst the radial electric field is

V. Filip; D. Nicolaescu; C. N. Plavitu; F. Okuyama

1997-01-01

348

Streamer discharges can move perpendicularly to the electric field  

NASA Astrophysics Data System (ADS)

Streamer discharges are a primary mode of electric breakdown in thunderstorms and high voltage technology; they are generally believed to grow along electric field lines. However, we here give experimental and numerical evidence that streamers can propagate nearly perpendicularly to the background electric field. These streamers are guided by pre-ionization that is orders of magnitude lower than the ionization density in a streamer channel, hardly affecting the background field. Positive streamers could be guided in nitrogen with 0.5% of oxygen or less, but not in air. This observation also tests the role of photo-ionization in gas mixtures with varying nitrogen–oxygen ratio.

Nijdam, S.; Takahashi, E.; Teunissen, J.; Ebert, U.

2014-10-01

349

TOPICAL REVIEW: Carbon nanotube electric field emitters and applications  

Microsoft Academic Search

Carbon nanotubes (CNTs) have recently emerged as a promising class of electron field emitters. They have low threshold electric field for emission and high emission current density, which make them attractive for technological applications. In this article we review recent progress on the understanding of CNT field emitters and discuss issues related to the applications of CNT based cold cathodes

M. I. Shakir; M. Nadeem; S. A. Shahid; N. M. Mohamed

2006-01-01

350

Inertia as a zero-point-field Lorentz force  

Microsoft Academic Search

Under the hypothesis that ordinary matter is ultimately made of subelementary constitutive primary charged entities or partons'' bound in the manner of traditional elementary Planck oscillators (a time-honored classical technique), it is shown that a heretofore uninvestigated Lorentz force (specifically, the magnetic component of the Lorentz force) arises in any accelerated reference frame from the interaction of the partons with

Bernhard Haisch; Alfonso Rueda; H. E. Puthoff

1994-01-01

351

Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC  

NASA Technical Reports Server (NTRS)

The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbational estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10,472 +/- 5, and 2051 +/-10/cm for omega1, omega2, and omega3, respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental v(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.

Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.

1993-01-01

352

Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC  

NASA Technical Reports Server (NTRS)

The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbation estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10, 472 +/- 5, and 2051 +/- 10 cm(exp -1) for omega(sub 1), omega(sub 2), and omega(sub 3), respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental nu(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.

Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.

1993-01-01

353

Effect of induced electric field on migration of a charged porous particle.  

PubMed

The effect of ambient fluid flow on a charged porous spherical particle suspended in an aqueous medium is analyzed. The porous particle is ion permeable and fluid penetrable. The induced electric field due to the polarization of the particle's electric double layer and counterion condensation leads to a hindrance effect on particle migration by producing an electric force. The influence of this retardation force on the hydrodynamics of the particle is studied through the Nernst-Planck equations, which are coupled with the Stokes-Brinkman equation. The interactions of the double-layer polarization, shielding effect, electroosmosis of unbalanced ions and fluid convection are analyzed. The settling velocity and fluid collection efficiency of the charged aggregate is determined. We have studied the electrokinetics for a wide range of fixed charge density and permeability of the particle with no assumption made on the thickness of the double layer relative to the dimension of the particle. PMID:25374308

Gopmandal, Partha P; Bhattacharyya, S; Barman, Bhanuman

2014-11-01

354

Ion trap electric field measurements using slab coupled optical sensors  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

355

Effects of high-latitude ionospheric electric field variability on global thermospheric Joule heating and mechanical energy transfer rate  

Microsoft Academic Search

Effects of high-latitude ionospheric electric field variability on the Joule heating and mechanical energy transfer rate are investigated by incorporating realistic spatial and temporal characteristics of electric field variability derived from observations into the forcing of a thermosphere ionosphere electrodynamic general circulation model. First, the characteristics of subgrid-scale variability are examined from a spectral analysis of Dynamic Explorer-2 (DE-2) plasma

Tomoko Matsuo

2008-01-01

356

Update of the cholesterol force field parameters in CHARMM.  

PubMed

A modification of the CHARMM36 lipid force field (C36) for cholesterol, henceforth, called C36c, is reported. A fused ring compound, decalin, was used to model the steroid section of cholesterol. For decalin, C36 inaccurately predicts the heat of vaporization (~10 kJ/mol) and molar volume (~10 cc/mol), but C36c resulted in near perfect comparison with experiment. MD simulations of decalin and heptane at various compositions were run to estimate the enthalpy and volumes of mixing to compare to experiment for this simple model of cholesterol in a chain environment. Superior estimates for these thermodynamic properties were obtained with C36c versus C36. These new parameters were applied to cholesterol, and quantum mechanical calculations were performed to modify the torsional potential of an acyl chain torsion for cholesterol. This model was tested through simulations of DMPC/10% cholesterol, DMPC/30% cholesterol, and DOPC/10% cholesterol. The C36 and C36c results were similar for surface areas per lipid, deuterium order parameters, electron density profiles, and atomic form factors and generally agree well with experiment. However, C36 and C36c produced slightly different cholesterol angle distributions with C36c adopting a more perpendicular orientation with respect to the bilayer plane. The new parameters in the C36c modification should enable more accurate simulations of lipid bilayers with cholesterol, especially for those interested in the free energy of lipid flip/flop or transfer of phospholipids and/or cholesterol. PMID:22136112

Lim, Joseph B; Rogaski, Brent; Klauda, Jeffery B

2012-01-12

357

Slow-Atom Electron EDM Experiment with Electric Field Quantization  

NASA Astrophysics Data System (ADS)

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 experiment. Electric field quantization of Cs atoms required nulling residual magnetic fields to < 200 pT, transport of polarized atoms through field-free (nulled) regions, and inducing transitions between closely spaced |mF| levels using separated short pulses in place of oscillatory fields. The possibility of improving the e-EDM limit with a Cs fountain experiment will be discussed.

Gould, Harvey; Amini, Jason; Munger, Charles, Jr.

2007-06-01

358

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

NASA Technical Reports Server (NTRS)

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.

Khusid, Boris; Acrivos, Andreas

2004-01-01

359

Electric fields and convection velocities associated with flux transfer events  

NASA Technical Reports Server (NTRS)

A survey of the electric field and (E x B)/B-squared convection velocities associated with 23 flux transfer events (FTEs) in the magnetosheath and magnetosphere is presented. Twelve-second averaged electric field data show perturbations in the component of the electric field perpendicular to the magnetopause, with an average magnitude of 3.5 mV/m associated with the FTEs. Direct flux transfer events have a northward, and reverse flux transfer events a southward, E x B velocity component, in agreement with the current FTE model. The flux tubes moved across the magnetopause plane at an average E x B speed of 125 km/s with respect to the ambient E x B flow, with events located on the dawn (dusk) side tending to move downward (duskward). No large spiky electric fields of the type observed elsewhere in the magnetosphere were detected.

Dailey, R.; Cattell, C. A.; Mozer, F. S.; Berchem, J.

1985-01-01

360

Effect of electric field on fracture of piezoelectric ceramics  

Microsoft Academic Search

Closed form solutions for all three modes of fracture for an infinite piezoelectric medium containing a center crack subjected to a combined mechanical and electrical loading were obtained. The explicit mechanical and electrical fields near the crack tip were derived, from which the strain energy release rate and the total potential energy release rate were obtained by using the crack

S. B. Park; C. T. Sun

1993-01-01

361

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

NASA Astrophysics Data System (ADS)

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.

Ben, Xue; Park, Harold S.

2014-11-01

362

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

PubMed

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 ([Formula: see text], [Formula: see text] and [Formula: see text]) 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 [Formula: see text] 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. PMID:25337694

Ben, Xue; Park, Harold S

2014-11-14

363

Satellite Measurements of High Latitude Convection Electric Fields  

Microsoft Academic Search

This paper reviews the first results of satellite experiments to measure magnetospheric convection electric fields using the double-probe technique.The earliest successful measurements were made with the low-altitude (680 2530 km) polar orbiting Injun-5 spacecraft (launched August, 1968). The Injun-5 data are discussed in detail. The Injun-5 results are compared with the initial findings of the electric field experiment on the

David P. Cauffman; Donald A. Gurnett

1972-01-01

364

Built-in electric field thickness design for betavoltaic batteries  

Microsoft Academic Search

Isotope source energy deposition along the thickness direction of a semiconductor is calculated, based upon which an ideal short current is evaluated for betavoltaic batteries. Electron-hole pair recombination and drifting length in a PN junction built-in electric field are extracted by comparing the measured short currents with the ideal short currents. A built-in electric field thickness design principle is proposed

Chen Haiyang; Li Darang; Yin Jianhua; Cai Shengguo

2011-01-01

365

Effects of nanosecond pulsed electric field exposure on arabidopsis thaliana  

Microsoft Academic Search

Seven days old seedlings of Arabidopsis thaliana, suspended in a 0.4 S\\/m buffer solution were exposed to nanosecond pulsed electric fields (nsPEF) with a duration of 10 ns, 25 ns and 100 ns. The electric field was varied from 5 kV\\/cm up to 50 kV\\/cm. The specific treatment energy ranged between 100 J\\/kg and 10 kJ\\/kg. Due to electroporation of

Christian J. Eing; Simone Bonnet; Michael Pacher; Holger Puchta; Wolfgang Frey

2009-01-01

366

Electric field vector characterization of terahertz surface plasmons  

Microsoft Academic Search

We demonstrate the ability to characterize independently the vector components of the electric field associated with terahertz surface plasmons. This is accomplished via electro-optic sampling, using an electro-optic crystal placed in close proximity to a corrugated metal foil. The individual electric field vector components are measured using two separate ZnTe crystals. Since ZnTe exhibits isotropic dielectric properties, all of the

Ajay Nahata; Wenqi Zhu

2007-01-01

367

Generation of conic ions by auroral electric fields  

SciTech Connect

Perpendicular accelerations of ions by the auroral electric fields are examined systematically using the test particle approach to assess their contribution to the ion conics observed on high-latitude field lines. The results show (1) that the existence of a nonzero parallel electric field component (E/sub parallel/not =0) is a necessary condition for the static auroral electric fields to accelerate ions continuously across auroral field lines, (2) that the highly nonuniform two-dimensional auroral arc electric fields (with latitudinal thickness L/sub x/< or =rho/sub i/; the ion gyroradius) can contribute to conic ions with energy up to a few keV; (3) that the moderately nonuniform two-dimensional electric field of the inverted V scale (L/sub x/>>rho/sub i/) can contribute to low energy conic ions less than a few tens electron volts, and (4) that the O/sup +/ ions can be accelerated across field lines more efficiently than the H/sup +/ ions, resulting in more energetic and more coniclike O/sup +/ ions than H/sup +/ ions.

Yang, W.H.; Kan, J.R.

1983-01-01

368

Computer Simulations of Charged Colloids in Alternating Electric Fields  

E-print Network

We briefly review recent theoretical and simulation studies of charged colloidal dispersions in alternating electric fields (AC fields). The response of single colloid to an external field can be characterized by a complex polarizability, which describes the dielectric properties of the colloid and its surrounding electrical double layer. We present computer simulation studies of single spherical colloid, using a coarse-grained mesoscale approach that accounts in full for hydrodynamic and electrostatic interactions as well as for thermal fluctuations. We investigate systematically a number of controlling parameters, such as the amplitude and frequency of the AC-fields. The results are in good agreement with recent theoretical predictions.

Jiajia Zhou; Friederike Schmid

2014-01-05

369

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

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)

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

2010-11-15

370

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

Microsoft Academic Search

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

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

2011-01-01

371

Effect of the radial electric field on turbulence  

SciTech Connect

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.

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

1990-01-01

372

Forces  

NSDL National Science Digital Library

This page provides the background for a basic laboratory exercise on force. Included is an explanation of force and vector components and an interactive java applet to demonstrate vectors and vector algebra.

Sorokin, Vladimir

2004-11-28

373

Takeoff and Landing Control using Force Sensor by Electrically-Powered Helicopters  

NASA Astrophysics Data System (ADS)

This paper introduces a takeoff and landing control technique related to a helicopter. The presented control system consists of a small toy electrically-powered helicopter for indoor flights, a flight base under which a focre sensor is set, and a helicopter control terminal which is connected to a system controller. The force sensor use is intended to realize soft takeoff and landing control. When the helicopter stands on the base, the force sensor outputs lift force data corresponding to the weight of the helicopter. As the operational voltage rises, the helicopter almost takes off from the base. Concurrently, the forse sensor output closes to 0. Thus, if the system controller controls the voltage arbitrarily, it is expected to realize the soft takeoff and landing control. This paper introduces the design process including modeling based on ststem identification technique, and shows the simulation and experimental results of the lift force control.

Fujita, Masanori; Shimada, Akira

374

Proteins in electric fields and pressure fields: experimental results.  

PubMed

Experimental results obtained by Stark effect and pressure tuning optical spectroscopy are discussed with the emphasis on studies aimed at unraveling the coupling of prosthetic groups to proteins. A comparative, detailed analysis is given concerning the coupling of the heme group to the apoprotein in various heme proteins based on spectral hole burning data. Electrochromism and electric dichroism experiments related to the coupling problem are also discussed in the context of other protein systems. PMID:9733987

Fidy, J; Balog, E; Köhler, M

1998-08-18

375

KINETIC ALFVEN TURBULENCE AND PARALLEL ELECTRIC FIELDS IN FLARE LOOPS  

SciTech Connect

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.

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

376

Alignment mechanisms of diblock copolymers in electric fields  

NASA Astrophysics Data System (ADS)

Precise control of the orientation of block copolymer domains is of interest for the production of self-assembling nanoporous media. Electric fields are effective in orienting copolymer domains normal to a surface. In thin films of poly(styrene-block-methyl methacrylate), a threshold electric field strength Et was found, which for film thicknesses greater than 10 ?m, was independent of film thickness and could be described by the difference in interfacial energies of the diblock components with the substrate. Neutron reflectivity, small angle neutron and x-ray scattering and off-specular scattering suggest that interfacial fluctuations are amplified by the electric field that leads to orientation of the cylinders along the field lines. In the case of poly(styrene-block-isoprene), a material with a smaller difference in dielectric constants, the microdomain orientation occurs at higher field strengths. Also the reorientation process is more rapid than in poly(styrene-block-methyl methacrylate).

Derouchey, Jason; Thurn-Albrecht, Thomas; Russell, Tom; Satija, Sushil

2000-03-01

377

Nonlinear spectroscopy of barium in parallel electric and magnetic fields  

NASA Astrophysics Data System (ADS)

We report on the experimental spectral observations of barium in parallel electric and magnetic fields. The laser pulse is linearly polarized along or perpendicular to the fields, leading to the states m = 0 and the states m = ±1 populated, respectively, by one photon excitation. By sweeping the electric field, we observe the linear and nonlinear splitting of the diamagnetic spectrum as the electric field increases. The spectral anticrossing is induced by the atomic core effect. The Stark spectrum also shows an obvious nonlinear quadratic behavior when the applied magnetic field varies strongly. All spectra are well explained by the full quantum calculation after taking the quantum defect effects of the channel ns up to nf into account.

Yang, Hai-Feng; Gao, Wei; Cheng, Hong; Liu, Hong-Ping

2014-10-01

378

Electric fields in nonhomogeneously doped silicon. Summary of simulations  

NASA Astrophysics Data System (ADS)

Variations of the doping concentration inside a silicon device result in electric field distortions. These distortions, "parasitic" fields, have been observed in Silicon Drift Detectors [D. Nouais, et al., Nucl. Instr. and Meth. A 501 (2003) 119; E. Crescio, et al., Nucl. Instr. and Meth. A 539 (2005) 250]. Electric fields inside a silicon device can be calculated for a given doping profile. In this study, the ATLAS device simulator. [ Silvaco International, 4701 Patrick Henry Drive, Bldg.2, Santa Clara, CA 95054, USA and ] was used to calculate the electric field inside an inhomogeneously doped device. Simulations were performed for 1D periodic doping profiles. Results show strong dependence of the parasitic field strength on the 'smoothness' of the doping profile.

Kotov, I. V.; Humanic, T. J.; Nouais, D.; Randel, J.; Rashevsky, A.; Alice-Its Collaboration

379

Finding Electric Fields, Poynting and Helicity Fluxes from Vector Magnetograms  

NASA Astrophysics Data System (ADS)

Existence of systematic measurements of vector magnetic fields allows us to estimate electric field in the photosphere, using Poloidal-Toroidal Decomposition of the magnetic field and its partial time derivative (Fisher et l. 2011). The PTD method is based on solving a set of Poisson equations which in the past has been done using Fast Fourier Transform techniques. We modify the existing PTD method by improving the poisson solver using a package of solvers for elliptic partial differential equations called Fishpack. We apply the PTD with a new Poisson equation solver to several test cases with a known electric field. We find that for the ANMHD simulation test case application of the new poisson solver yields a more accurate values of electric field, Poisson and helicity fluxes than before. We further investigate the applicability of our method to other test cases using simulations of M. Cheung and Y. Fan and also HMI vector magnetograms.

Kazachenko, Maria; Fisher, G. H.; Welsch, B. T.

2012-05-01

380

Ionisation of a quantum dot by electric fields  

SciTech Connect

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)

Eminov, P A; Gordeeva, S V

2012-08-31

381

Helical multiferroics for electric field controlled quantum information processing  

NASA Astrophysics Data System (ADS)

Magnetoelectric coupling in helical multiferroics allows us to steer spin order with electric fields. Here we show theoretically that in a helical multiferroic chain quantum information processing as well as quantum phases are highly sensitive to electric (E) field. Applying E field, the quantum state transfer fidelity can be increased and made directionally dependent. We also show that E field transforms the spin-density-wave/nematic or multipolar phases of a frustrated ferromagnetic spin-1/2 chain in chiral phase with a strong magnetoelectric coupling. We find sharp reorganization of the entanglement spectrum as well as a large enhancement of fidelity susceptibility at Ising quantum phase transition from nematic to chiral states driven by electric field. These findings point to a tool for quantum information with low power consumption.

Azimi, M.; Chotorlishvili, L.; Mishra, S. K.; Greschner, S.; Vekua, T.; Berakdar, J.

2014-01-01

382

Electrical properties of chain microstructure magnetic emulsions in magnetic field  

E-print Network

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.

Arthur Zakinyan; Yuri Dikansky; Marita Bedzhanyan

2014-02-05

383

Differences in end-point force trajectories elicited by electrical stimulation of individual human calf muscles  

PubMed Central

The purpose of this study was to investigate the end-point force trajectories of the fibularis longus (FIB), lateral gastrocnemius (LG) and medial gastrocnemius (MG) muscles. Most information about individual muscle function has come from studies which use models based on electromyographic (EMG) recordings. In this study (N=20 subjects) we used electrical stimulation (20Hz) to elicit activity in individual muscles, recorded the end-point forces at the foot and verified the selectivity of stimulation by using magnetic resonance imaging. Unexpectedly, no significant differences were found between LG and MG force directions. Stimulation of LG and MG resulted in downward and medial or lateral forces depending on the subject. We found FIB end-point forces to be significantly different than those of LG and MG. In all subjects, stimulation of FIB resulted in downward and lateral forces. Based on our results, we suggest that there are multiple factors determining when and whether LG or MG will produce a medial or lateral force and FIB consistently plays a significant role in eversion/abduction and plantarflexion. We suggest that the inter-subject variability we found is not simply an artifact of experimental or technical error but is functionally relevant and should be addressed in future studies and models. PMID:20095454

Giordano, S B; Segal, R L; Abelew, T A

2009-01-01

384

Electric fields in micro-gravity can replace gravity  

NASA Astrophysics Data System (ADS)

The influence of the world-wide atmospheric electric field on the growth of plants seems to have been neglected. The confirmation of the existence of electrotropism shows effects on some plants similar to gravity. I propose space ex eriments withp plants that grow in microgravity but are exposed to different electric field configurations with various field strengths and polarity. The electric field in terrestrial environment shows strong effects on some plants that can be regarded as due to phototropism. In microgravity we have full control of light and electric field, and thus we can practically eliminate the effects of gravity and we can study to what degree the electric field can replace the gravitational effects on plants. In this way we can create a new habitat for some plants and study its role in the rate of growth as well as in the sensing of free space for growth of plants in absence of gravity. By varying the strength and direction of illumination of plants we can also study the relative role of phototropism and electrotropism on different plants. This should enable us to select the most suitable plants for Advanced Life Support systems (ALS) for long-duration missions in microgravity environment. Some simple space experiments for verification of these assumptions are described that should answer the basic questions how should we design the ALS for the future high performance space stations and long duration manned space flights. The selection of the suitable plants for such ALS may go along two approaches: the self supporting electrotropic plants using the optimal electric field strength and its range of variation, non electrotropic plants that creep along the "ground" or other supporting plants or special structures. Ground based fitotron experiments have shown that several kV/m electric fields overwhelm the gravity better than clinostats can do. It happens in case of electrotropic plants but also after several days for non-electrotropic plants

Gorgolewski, S.

385

Electric field-induced motion of solid particles in two-dimensional fluids  

NASA Astrophysics Data System (ADS)

Electric field induced motion of spherical and cylindrical glass particles were studied in a smectic A liquid crystal octyl cyanobiphenyl (8CB) medium. The particles were dispersed in the smectic A medium, sandwiched between to glass plates with conductive inner surfaces. Under DC fields the smectic layers become parallel to the glass substrates. Such configuration corresponds to a two dimensional isotropic fluid structure along the film surface: the motion of solid particles results viscous forces along the substrates, whereas the motion across the layers is opposed by elastic permeation forces. Under DC fields above a threshold instability occurs and the particles move with constant speed in arbitrary directions normal to the electric field. The moving spheres and the cylinders rotate about their symmetry axis along the layers. When air bubbles are present in the film the, spheres tend to stick to the bubbles, and rotate collectively with a field- dependent speed that is independent of the radius of the bubbles (the angular velocity is inversely proportional to the radius). The details of the motion and the underlying physical mechanism will be discussed. The studies may have relevance of understanding particle motions in cell membranes under electric actuations and will contribute to our understanding of the hydrodynamic properties of two-dimensional fluid systems.

Jackli, Antal; Liao, Guangxun; Kelly, Jack R.

2004-03-01

386

Force  

NSDL National Science Digital Library

Instructions: This is a webquest designed to help students understand force. It is specifically meant to teach the idea that the greater the force applied to an object the greater the change in speed or direction of the object depending on the mass. This is also known as Newton's Second Law of Motion. Lets Learn about Force! For this project your students will understand force. They will use Newton's second law to solve the problem presented. UT Core Curriculum: Science 3rd Grade. Standard 3- Students will understand the relationship between the force applied to an object and resulting motion of the ...

Brownie, Mrs.

2010-04-07

387

Parametrization and Application of a Coarse Grained Force Field for Benzene/Fullerene Interactions with Lipids  

E-print Network

Parametrization and Application of a Coarse Grained Force Field for Benzene/Fullerene Interactions Recently, we reported new coarse grain (CG) force fields for lipids and phenyl/fullerene based molecules. In the C60 lipid systems, the fullerenes were shown to aggregate even at the lowest concentrations

Nielsen, Steven O.

388

A reactive force field simulation of liquidliquid phase transitions in phosphorus  

E-print Network

A reactive force field simulation of liquid­liquid phase transitions in phosphorus P. Ballone 2004; accepted 6 August 2004 A force field model of phosphorus has been developed based on density T of the black P to arsenic A17 structure observed in the solid state, and also corresponds to a semiconductor

389

Development and Validation of ReaxFF Reactive Force Field for Hydrocarbon Chemistry Catalyzed by Nickel  

E-print Network

Development and Validation of ReaxFF Reactive Force Field for Hydrocarbon Chemistry Catalyzed as a function of temperature and pressure, we have developed the ReaxFF reactive force field to describe surface. The ReaxFF parameters were determined by fitting to the geometries and energy surfaces from

Goddard III, William A.

390

Multiparadigm Modeling of Dynamical Crack Propagation in Silicon Using a Reactive Force Field  

Microsoft Academic Search

We report a study of dynamic cracking in a silicon single crystal in which the ReaxFF reactive force field is used for several thousand atoms near the crack tip, while more than 100 000 atoms are described with a nonreactive force field. ReaxFF is completely derived from quantum mechanical calculations of simple silicon systems without any empirical parameters. Our results

Markus J. Buehler; Adri C. T. van Duin; William A. Goddard III

2006-01-01

391

The ReaxFF PolarizableReactiveForce Fields for Molecular Dynamics Simulationof  

E-print Network

The ReaxFF PolarizableReactiveForce Fields for Molecular Dynamics Simulationof Ferroelectrics. A key feature of the force field (denoted ReaxFF) is that charge transfer and atomic polarization) obtained using QM methods of cubic and tetragonal BaTiO3 over a wide pressure range. We then use the ReaxFF

Goddard III, William A.

392

ReaxFF SiO Reactive Force Field for Silicon and Silicon Oxide Systems  

Microsoft Academic Search

To predict the structures, properties, and chemistry of materials involving silicon and silicon oxides; interfaces between these materials; and hydrolysis of such systems, we have developed the ReaxFFSiO, reactive force field. The parameters for this force field were obtained from fitting to the results of quantum chemical (QC) calculations on the structures and energy barriers for a number of silicon

Adri C. T. van Duin; Alejandro Strachan; Shannon Stewman; Qingsong Zhang; Xin Xu; William A. Goddard

2003-01-01

393

The ReaxFF Polarizable Reactive Force Fields for Molecular Dynamics Simulation of Ferroelectrics  

E-print Network

The ReaxFF Polarizable Reactive Force Fields for Molecular Dynamics Simulation of Ferroelectrics. A key feature of the force field (denoted ReaxFF) is that charge transfer and atomic polarization pressure range obtained using QM methods. We then use the ReaxFF with MD to study thermal properties of Ba

Ã?agin, Tahir

394

A reactive force field for lithium-aluminum silicates with applications to eucryptite phases  

Microsoft Academic Search

We have parameterized a reactive force field (ReaxFF) for lithium-aluminum silicates using density functional theory (DFT) calculations of structural properties of a number of bulk phase oxides, silicates and aluminates, as well as of several representative clusters. The force field parameters optimized in this study were found to predict lattice parameters and heats of formation of selected condensed phases in

Badri Narayanan; Adri C. T. van Duin; Branden B. Kappes; Ivar E. Reimanis; Cristian V. Ciobanu

2012-01-01

395

Finger-Shaped GelForce: Sensor for Measuring Surface Traction Fields for Robotic Hand  

E-print Network

. In particular, a haptic sensor for a robotic finger is considered to be an important device because the fingerFinger-Shaped GelForce: Sensor for Measuring Surface Traction Fields for Robotic Hand Katsunari in a robotic hand. Index Terms--Force sensor, surface traction field, finger shape, robotic hand. Ã? 1

Tachi, Susumu

396

Electric field enhanced conductivity in strongly coupled dense metal plasma  

SciTech Connect

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.

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

2012-06-15

397

Limiting electric fields of HVDC overhead power lines.  

PubMed

As a consequence of the increased use of renewable energy and the now long distances between energy generation and consumption, in Europe, electric power transfer by high-voltage (HV) direct current (DC) overhead power lines gains increasing importance. Thousands of kilometers of them are going to be built within the next years. However, existing guidelines and regulations do not yet contain recommendations to limit static electric fields, which are one of the most important criteria for HVDC overhead power lines in terms of tower design, span width and ground clearance. Based on theoretical and experimental data, in this article, static electric fields associated with adverse health effects are analysed and various criteria are derived for limiting static electric field strengths. PMID:24573710

Leitgeb, N

2014-05-01

398

Excitation by Local Electric Fields in the Aurora and Airglow  

Microsoft Academic Search

We have developed a method for accurate calculation of the distribution of electron energies in the ionosphere under the influence of an electric field. From this calculation we can predict rates of excitation of radiating states of N., O., and O as a function of the strength of a hypothetical applied field. We find that it is unreasonable to expect

L. R. Megill; N. P. Carleton

1964-01-01

399

Structural Transition Produced by Electric Fields in Aqueous Sodium Deoxyribonucleate  

PubMed Central

It was found that the birefringence of aqueous solutions of sodium DNA is anomalous when electric fields of high intensity (?104 v/cm) are applied. The magnitude of the birefringence first rose upon application of the orienting pulse, then fell as the field was sustained above a critical value. The occurrence of the effect depended upon macromolecular and electrolyte concentrations. Upon removal of the field, the birefringence was rapidly restored and then it decayed with an increase of the reorientational relaxation times, relative to those observed below the critical field. It is proposed that the electric field may cause aggregation of the macromolecules and then produce a structural transition concomitant with the electric field orientation effect. This transition may correspond to the “B” ? “A” structures identified in x-ray studies, or to a “B” ? “V” structure change, where “V” is a postulated new helical form stabilized by cooperative interactions of base and dipoles in the electric field. Field induced transitions of this type would be of interest in connection with molecular mechanisms of transport through membranes, nerve impulse transmission, or information storage. PMID:5861709

O'Konski, Chester T.; Stellwagen, Nancy C.

1965-01-01

400

Abrupt Rabi oscillations in a superoscillating electric field  

E-print Network

We study counterintuitive dynamics of a two-level system (TLS) interacting with electric field superoscillating in time. We show that a TLS may be excited by an external light pulse whose spectral components are below the absorption line of the TLS. We attribute this unique dynamics to the Rabi oscillations of the TLS in a superoscillating driving field.

Baranov, D G; Lisyansky, A A

2014-01-01

401

Electric field distributions for Langmuir waves in planetary foreshocks  

Microsoft Academic Search

This paper addresses several key issues regarding the statistics of Langmuir wave fields E in planetary foreshocks by presenting (1) a detailed theory for the electric field strength probability distributions averaged over Earth's foreshock and (2) the first analyses of the distributions observed in the outer planets. First, existing theory is extended and generalized, describing in detail how lognormal distributions

Christopher R. Boshuizen; Iver H. Cairns; P. A. Robinson

2004-01-01

402

Magnetospheric Electric Field Properties Deduced from Simultaneous Balloon Flights  

Microsoft Academic Search

independent of altitude to within about a factor of 2 from L = 4 to 23, and its direction varies with a typical diurnal pattern. Short-term averages of these data show that this diurnal pattern is associated with magnetic bays, in that the east-west component of the ionospheric electric field in a rotating field of reference becomes westward about an

F. S. Mozer; R. H. Manka

1971-01-01

403

Resonant tunneling controlled by laser and constant electric fields  

E-print Network

We develop the concept of scattering matrix and we use it to perform stable numerical calculations of resonant tunneling of electrons through a multiple potential barrier in a semiconductor heterostructure. Electrons move in two external nonperturbative electric fields: constant and oscillating in time. We apply our algorithm for different strengths and spatial configurations of the fields.

J. Z. Kaminski; E. Saczuk

2011-01-01

404

Charge Equilibration Force Fields for Molecular Dynamics Simulations of Lipids, Bilayers, and Integral Membrane Protein Systems  

PubMed Central

With the continuing advances in computational hardware and novel force fields constructed using quantum mechanics, the outlook for non-additive force fields is promising. Our work in the past several years has demonstrated the utility of polarizable force fields, those based on the charge equilibration formalism, for a broad range of physical and biophysical systems. We have constructed and applied polarizable force fields for lipids and lipid bilayers. In this review of our recent work, we discuss the formalism we have adopted for implementing the charge equilibration (CHEQ) method for lipid molecules. We discuss the methodology, related issues, and briefly discuss results from recent applications of such force fields. Application areas include DPPC-water monolayers, potassium ion permeation free energetics in the gramicidin A bacterial channel, and free energetics of permeation of charged amino acid analogues across the water-bilayer interface. PMID:21967961

Lucas, Timothy R.; Bauer, Brad A.; Patel, Sandeep

2014-01-01

405

Electric field measurements with an airplane: A solution to problems caused by emitted charge  

Microsoft Academic Search

The growth of electrical energy inthundercloud prior tolightning fish cn be studied by measuring the electric field. The use ofirplnes to measure the electric field hs beenproblem because the intense electric field of  thunderstorm cuses electric breakdown inirt sharp metallic pointsnd edges. The electrical charge produced by the breakdown cn be confused with the charge in the thunderstorm itself,

Q. Mo; A. E. Ebneter; P. Fleischhacker; W. P. Winn

1998-01-01

406

Weak electric field interactions in the central nervous system.  

PubMed

Exposure to extremely low frequency electric and magnetic fields will induce electric fields and currents within the body, but these are almost always much lower than those that can stimulate peripheral nerve tissue. Guidance on exposure to such fields has been published by NRPB and ICNIRP, which is based on the avoidance of acute effects in the central nervous system. Weak electric field effects, below action potential thresholds, have been demonstrated in vitro in brain slice preparations; thresholds can be estimated to be above about 1 mV mm(-1) (around 100 mA m(-2), taking a brain tissue conductivity of around 0.1 S m(-1)), depending on stimulus conditions. Some studies suggest possible effects at lower induced field strengths. The intact nervous system might be expected to be more sensitive to induced electric fields and currents than in vitro preparations, due to a higher level of spontaneous activity and a greater number of interacting neurons. There is good evidence that electrically excitable cells in the retina can be affected in vivo by induced currents as low as 10 mA m(-2). It has been suggested that induced current densities above 10 mA m(-2) may have effects on other central nervous system functions but few studies have been carried out. Further research in experimental animals using both in vitro and in vivo approaches is needed to clarify this issue. PMID:12199550

Saunders, Richard D; Jefferys, John G R

2002-09-01

407

Relationship of electric field and charged particle density fluctuations to air turbulence in the mesosphere  

NASA Astrophysics Data System (ADS)

A theoretical model is developed that is applicable to the electric field fluctuations that arise in the polar summer mesosphere as a result of the coupling of the charged species to the neutral air turbulence. The motions of electrons, ions, and charged aerosol particles are described as harmonic oscillators both driven and damped by the drag force exerted by the neutral air. The relative fluctuations in the ion density are found to be nearly the same as those in the neutral air as a consequence of the ions' high-momentum transfer relaxation frequency. The aerosol density fluctuations follow those of the neutral air at frequencies below their relaxation frequency, which is in the acoustic range. The electrons move primarily in response to the electric force to partially cancel the net charge density of ions and aerosol particles except at wavelengths shorter than the Debye length. Electric field and charge density fluctuations are calculated for several sets of conditions. In "bite-out" regions in which the electron density is reduced as a consequence of attachment to the aerosol particles the electric field fluctuations are found to be enhanced, which is consistent with observations.

Robertson, Scott

2007-10-01

408

Schwinger pair production in electric and magnetic fields  

SciTech Connect

Charged particles in static electric and magnetic fields have Landau levels and tunneling states from the vacuum. Using the instanton method of Phys. Rev. D 65, 105002 (2002), we obtain the formulas for the pair-production rate in spinor and scalar QED, which sum over all Landau levels and recover exactly the well-known results. The pair-production rates are calculated for an electric field of finite extent, and for the Sauter potential, both with a constant magnetic field also present, and are shown to have finite-size effects.

Kim, Sang Pyo; Page, Don N. [Department of Physics, Kunsan National University, Kunsan 573-701, Korea and Asia Pacific Center for Theoretical Physics, Pohang 790-784 (Korea, Republic of); Theoretical Physics Institute, Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada)

2006-03-15

409

Streamer Initiation from Hydrometeors in Weak Thundercloud Electric Fields  

NASA Astrophysics Data System (ADS)

How atmospheric lightning initiates in thunderclouds has been a scientific puzzle for decades. One theory of air electrical breakdown that has been applied to explaining the initiation of lightning discharges is the conventional breakdown theory [e.g., MacGorman and Rust, p. 86, 1998; Rakov and Uman, p. 121, 2003]. A critical component of this theory is to demonstrate that streamers are able to form and propagate in the field with a magnitude similar to the observed thundercloud electric fields. The observed maximum value of this field varies from 0.13-0.3E_k [Stolzenburg et al., 2007], where E_k is the conventional breakdown threshold field. This value fails to provide a sufficient condition for the initiation of electron avalanches and then the electrical breakdown process. To overcome this obstacle, the theory of streamer initiation from thundercloud hydrometeors (water drops, ice crystals, etc.) was brought forward [e.g., Dawson, JGR, 74 (28), 6859, 1969; Griffiths and Latham, Quart. J. Roy. Meteorol. Soc., 100, 163, 1974; Griffiths and Phelps, Quart. J. Roy. Meteorol. Soc., 102, 4019, 1976]. Hydrometeors are abundant in thunderclouds and they can cause significant field enhancement in their vicinity. For this study, the streamer discharge model reported by Liu and Pasko [JGR, 109, A04301, 2004] is utilized and modified to investigate whether streamers can successfully originate from isolated hydrometeors in the thundercloud electric field. The thundercloud hydrometeors are modeled using a neutral plasma column. Our simulation results show successful formation of streamers from model hydrometeors in a uniform applied electric field below the conventional breakdown threshold field. We report detailed modeling results at thundercloud altitude for the applied electric fields close to the observed maximum thundercloud field. It is demonstrated that the dimensions, i.e., length and radius, of the plasma column have a critical effect on the initiation of streamers. The results also show that at lower applied electric fields for certain initial conditions, branching structures easily appear at the tip of the hydrometeor. To reduce the effects of branching, we investigate the possibility of using other geometries, specifically an ellipsoid, for the initial ionization column. So far, the minimum electric field value required for the stable formation of streamers from hydrometeors without the occurrence of branching structures has been observed to be 0.3E_k at 7 km from our modeling results.

Sadighi, S.; Liu, N.; Dwyer, J. R.; Rassoul, H. K.

2011-12-01

410

Relativistic Bosons in Time-Harmonic Electric Fields  

NASA Astrophysics Data System (ADS)

In the present paper, we consider a bi-dimensional thin sample, placed in a strong harmonically oscillating electric field and a static magnetic induction, both directed along the normal to the sample's plane. The Klein-Gordon equation describing the relativistic bosons leads to a Mathieu's type equation for the temporal part of the wave functions. It follows that, for the electric field pulsation inside a computable range, depending on the external fields intensities, the amplitude functions are turning from oscillatory to exponentially growing modes. For ultra-relativistic particles, one can recover the periodic stationary amplitude behavior.

Buhucianu, Ovidiu; Dariescu, Marina-Aura; Dariescu, Ciprian

2012-02-01

411

Tuning the mechanical behaviour of structural elements by electric fields  

NASA Astrophysics Data System (ADS)

This work reports on the adoption of electric fields to tune the mechanical behaviour of structural elements. A mechanical characterization procedure, consisting of double lap joint and 3-point bending tests, is conducted on copper-polyimide laminates while applying electric fields of varying intensity. Field dependence and, thus, adaptability of shear strength and bending stiffness are shown as a function of the overlapping length and interfaces number, respectively. Further, the impact of remaining charges is investigated in both testing configurations. The findings herein lay the foundation for the implementation of electro-adaptive components in structural applications.

Di Lillo, Luigi; Raither, Wolfram; Bergamini, Andrea; Zündel, Manuel; Ermanni, Paolo

2013-06-01

412

Vehicle Dynamics Control of In-wheel Electric Motor Drive Vehicles Based on Averaging of Tire Force Usage  

NASA Astrophysics Data System (ADS)

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.

Masaki, Nobuo; Iwano, Haruo; Kamada, Takayoshi; Nagai, Masao

413

Electric Field Enhancement and Light Transmission in Cylindrical Nanoholes  

SciTech Connect

The properties of electric fields in subwavelength cylindrical apertures are examined upon excitation by a far-field source. We find that the largest enhancements are localized at the edge of the aperture, close to its rim. Both the entrance and exit rims of the hole can produce intense fields, although at long wavelengths thick slabs lead to smaller fields at the exit rim. The fields display a two lobe angular pattern characteristic of a radiating dipole in the near field. The influence of aperture size and slab thickness on field enhancement is presented. Although there is often a connection between peak transmission and peak field, the two rarely occur at the same wavelength. Enhancements in the electric field intensity can be increased by an order of magnitude by adding a grooved structure around the aperture, which acts as a grating and permits coupling to surface plasmon polaritons. Our results indicate that nanohole systems can be optimized to yield large electric field enhancements, making them an attractive medium for surface enhanced spectroscopies.

Shuford, Kevin L [ORNL; Ratner, Mark A. [Northwestern University, Evanston; Gray, Stephen K. [Argonne National Laboratory (ANL); Schatz, George C. [Northwestern University, Evanston

2007-01-01

414

Critical Points of the Electric Field from a Collection of Point Charges  

SciTech Connect

The electric field around a molecule is generated by the charge distribution of its constituents: positively charged atomic nuclei, which are well approximated by point charges, and negatively charged electrons, whose probability density distribution can be computed from quantum mechanics. For the purposes of molecular mechanics or dynamics, the charge distribution is often approximated by a collection of point charges, with either a single partial charge at each atomic nucleus position, representing both the nucleus and the electrons near it, or as several different point charges per atom. The critical points in the electric field are useful in visualizing its geometrical and topological structure, and can help in understanding the forces and motion it induces on a charged ion or neutral dipole. Most visualization tools for vector fields use only samples of the field on the vertices of a regular grid, and some sort of interpolation, for example, trilinear, on the grid cells. There is less risk of missing or misinterpreting topological features if they can be derived directly from the analytic formula for the field, rather than from its samples. This work presents a method which is guaranteed to find all the critical points of the electric field from a finite set of point charges. To visualize the field topology, we have modified the saddle connector method to use the analytic formula for the field.

Max, N; Weinkauf, T

2007-02-16

415

Ionization of N2 in radio-frequent electric field  

NASA Astrophysics Data System (ADS)

Rate coefficients for the electron impact ionization of the N2 molecule are calculated in non-equilibrium conditions in the presence of time-dependent electric field. A Monte Carlo simulation has been developed in order to determine non-equilibrium electron energy distribution functions within one period of the radio-frequent (RF) electric field. By using these distribution functions, rate coefficients for ionization of the N2 molecule have been obtained time resolved within one period in the frequency range from 13.56 up to 500 MHz, at effective reduced electric field values up to 700 Td. This work presents an insight into the temporal characteristics of ionizing process and provides the ionization rate coefficients that can be of great use for correct implementation in modeling RF plasma discharges. A behavior of rate coefficients under the influence of magnitude and frequency of the fields was studied separately revealing some interesting features in time dependence.

Popovi?, M. P.; Vojnovi?, M. M.; Aoneas, M. M.; Risti?, M. M.; Vi?i?, M. D.; Popari?, G. B.

2014-06-01

416

Electric field for tuning quantum entanglement in supported clusters.  

PubMed

We show that quantum entanglement, nowadays so widely observed and used in a multitude of systems, can be traced in the atomic spins of metal clusters supported on metal surfaces. Most importantly, we show that it can be voluntarily altered with external electric fields. We use a combination of ab initio and model Heisenberg-Dirac-Van Vleck quantum spin Hamiltonian calculations to show, with the example of a prototype system (Mn dimers on Ag(0?0?1) surface), that, in an inherently unentangled system an electric field can 'switch on' the entanglement and significantly change its critical temperature parameter. The physical mechanism allowing such rigorous control of entanglement by an electric field is the field-induced change in the internal magnetic coupling of the supported nanostructure. PMID:25018555

Brovko, Oleg O; Farberovich, Oleg V; Stepanyuk, Valeri S

2014-08-01

417

Manipulating the self assembly of colloids in electric fields  

NASA Astrophysics Data System (ADS)

During the last decade the focus in colloid science on self-assembly has moved from mostly spherical particles and interaction potentials to more and more complex particle shapes, interactions and conditions. In this minireview we focus on how external electric fields, which in almost all cases can be replaced by magnetic particles and fields for similar effects, are used to manipulate the self-assembly process of ever more complex colloids. We will illustrate typical results from literature next to examples of our own work on how electric fields are used to achieve a broad range of different effects guiding the self-assembly of colloidal dispersions. In addition, preliminary measurements and calculations on how electric fields can be used to induce lock-and-key interactions will be presented as well.

van Blaaderen, A.; Dijkstra, M.; van Roij, R.; Imhof, A.; Kamp, M.; Kwaadgras, B. W.; Vissers, T.; Liu, B.

2013-11-01

418

Electric field control of multiferroic domain wall motion  

NASA Astrophysics Data System (ADS)

The dynamics of a multiferroic domain wall in which an electric field can couple to the magnetization via inhomogeneous magnetoelectric interaction is investigated by the collective-coordinate framework. We show how the electric field is capable of delaying the onset of the Walker breakdown of the domain wall motion, leading to a significant enhancement of the maximum wall velocity. Moreover, we show that in the stationary regime the chirality of the domain wall can be efficiently reversed when the electric field is applied along the direction of the magnetic field. These characteristics suggest that the multiferroic domain wall may provide a new prospective means to design faster and low-power-consumption domain wall devices.

Chen, Hong-Bo; Liu, Ye-Hua; Li, You-Quan

2014-04-01

419

PIC simulation of electrodeless plasma thruster with rotating electric field  

NASA Astrophysics Data System (ADS)

For longer lifetime of electric propulsion system, an electrodeless plasma thruster with rotating electric field have been proposed utilizing a helicon plasma source. The rotating electric field may produce so-called Lissajous acceleration of helicon plasma in the presence of diverging magnetic field through a complicated mechanism originating from many parameters. Two-dimensional simulations of the Lissajous acceleration were conducted by a code based on Particle-In-Cell (PIC) method and Monte Carlo Collision (MCC) method for understanding plasma motion in acceleration area and for finding the optimal condition. Obtained results show that azimuthal current depends on ratio of electron drift radius to plasma region length, AC frequency, and axial magnetic field. When ratio of cyclotron frequency to the AC frequency is higher than unity, reduction of the azimuthal current by collision effect is little or nothing.

Nomura, Ryosuke; Ohnishi, Naofumi; Nishida, Hiroyuki

2012-11-01

420

Theory of electric field measurements conducted in the magnetosphere with electric probes  

Microsoft Academic Search

From the preceding discussion of possible errors and from the probe dimensions given in Tables IV and V the conclusion can be drawn that there should be no great difficulties in making rough (10–20%) measurements of electric fields in the ionosphere. With moderate efforts (using metallized balloons) it should also be possible to obtain order of magnitude estimates of electric

U. Fahleson

1967-01-01

421

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

NASA Technical Reports Server (NTRS)

Boiling is an effective mode of heat transfer since high heat flux levels are possible driven by relatively small temperature differences. The high heat transfer coefficients associated with boiling have made the use of these processes increasingly attractive to aerospace engineering. Applications of this type include compact evaporators in the thermal control of aircraft avionics and spacecraft environments, heat pipes, and use of boiling to cool electronic equipment. In spite of its efficiency, cooling based on liquid-vapor phase change processes has not yet found wide application in aerospace engineering due to specific problems associated with the low gravity environment. After a heated surface has reached the superheat required for the initiation of nucleate boiling, bubbles will start forming at nucleation sites along the solid interface by evaporation of the liquid. Bubbles in contact with the wall will continue growing by this mechanism until they detach. In terrestrial conditions, bubble detachment is determined by the competition between body forces (e.g. buoyancy) and surface tension forces that act to anchor the bubble along the three phase contact line. For a given body force potential and a balance of tensions along the three phase contact line, bubbles must reach a critical size before the body force can cause them to detach from the wall. In a low gravity environment the critical bubble size for detachment is much larger than under terrestrial conditions, since buoyancy is a less effective means of bubble removal. Active techniques of heat transfer enhancement in single phase and phase change processes by utilizing electric fields have been the subject of intensive research during recent years. The field of electrohydrodynamics (EHD) deals with the interactions between electric fields, flow fields and temperature fields. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 as compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The goal of our research is to experimentally investigate the potential of EHD and the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions.

Herman, Cila

1996-01-01

422

Climate Field Reconstruction under Stationary and Nonstationary Forcing.  

NASA Astrophysics Data System (ADS)

The fidelity of climate reconstructions employing covariance-based calibration techniques is tested with varying levels of sparseness of available data during intervals of relatively constant (stationary) and increasing (nonstationary) forcing. These tests employ a regularized expectation-maximization algorithm using surface temperature data from both the instrumental record and coupled ocean-atmosphere model integrations. The results indicate that if radiative forcing is relatively constant over a data-rich calibration period and increases over a data-sparse reconstruction period, the imputed temperatures in the reconstruction period may be biased and may underestimate the true temperature trend. However, if radiative forcing is stationary over a data-sparse reconstruction period and increases over a data-rich calibration period, the imputed values in the reconstruction period are nearly unbiased. These results indicate that using the data-rich part of the twentieth-century instrumental record (which contains an increasing temperature trend plausibly associated with increasing radiative forcing) for calibration does not significantly bias reconstructions of prior climate.

Rutherford, S.; Mann, M. E.; Delworth, T. L.; Stouffer, R. J.

2003-02-01

423

ADVANCES IN FORCE FIELD TAILORING FOR CONSTRUCTION IN SPACE  

E-print Network

space is certainly a complex process requiring several years. It is essential meanwhile to have field, in microgravity. The hypothesis was that the particles would drift towards the nodal surfaces of the field and form walls, and this hypothesis was proven true. By tailoring field geometry, one can thus

424

Vibration damping of elastic waves in electrically conducting media subjected to high magnetic fields  

NASA Technical Reports Server (NTRS)

The propagation of vibrational energy in bulk, torsional, and flexural modes, in electrically conducting media can undergo strong attenuation if subjected to high magnetic fields in certain spatial arrangements. The reasons for this are induced Eddy currents which are generated by the volume elements in the media moving transversally to the magnetic field at acoustic velocities. In magnetic fields achievable with superconductors, the non-conservative (dissipative) forces are compared to the elastic and inertial forces for most metals. Strong dissipation of vibrational energy in the form of heat takes place as a result. A simplified theory is presented based on engineering representations of electrodynamics, attenuation values for representative metals are calculated, and problems encountered in formulating a generalized theory based on electrodynamics of moving media are discussed. General applications as well as applications specific to maglev are discussed.

Horwath, T. G.

1992-01-01

425

Experimental Study of Cloud Formation by Intense Electric Fields  

NASA Astrophysics Data System (ADS)

Cloud and fog formation under an electric field has been studied experimentally using a Wilson’s cloud chamber with a supercooled atmosphere of ethanol. The threshold electric field to generate dense clouds using parallel plate electrodes was about 4 kV/m as estimated from the generated cloud position and from a model experiment of an electric field simulation using a water bath. Positive ions produced by the ionization of the atmosphere condense nuclei for the generation of fogs and clouds. Old legends and retrospective reports on earthquake fogs (EQFs) and clouds (EQCs) prior to a major shock may be elucidated by the condensation of vapor under an intense electric field, similar to earthquake lightning (EQL) due to electro-atmospheric arc and dark discharges. A plume cloud like a streamer discharge was produced from a needle electrode, which exhibited similarities to tornado-type clouds photographed before the Kobe earthquake. Electric discharges of clouds by a wired rocket or laser-induced lightning are suggested to terminate the electric energy for the upward vortex flow of a tornado.

Teramoto, Kazuhiko; Ikeya, Motoji

2000-05-01