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1

Dielectrophoretic forces on particles in travelling electric fields  

Microsoft Academic Search

Computations are presented of the fields and forces experienced by dielectric uncharged particles subjected to travelling electric fields. The results provide an improved understanding of the various electrokinetic effects observed for particles exhibiting travelling wave dielectrophoresis, either over microelectrode structures or in channels between electrodes. The real and imaginary components of the complex dipole moment induced in a particle are

Michael P. Hughes; Ronald Pethig; Xiao-Bo Wang

1996-01-01

2

The effect of frequency on electric field induced surface force in red blood cell membrane  

Microsoft Academic Search

The use of electric field induced surface force acting on a red blood cell membrane to explain the observed sphering and hemolysis of the cell when exposed to the field is discussed. The frequency of the applied sinusoidal field inversely affects the field strengths at which sphering and hemolysis occur. Increase in frequency decreases the magnitude of the surface force.

Stephen K. W. Chang

1993-01-01

3

Electric Field Force Features-Harmonic Representation for 3D Shape Similarity  

Microsoft Academic Search

This paper proposes a novel shape representation “electric force features”, which is based on electric field theory. This\\u000a representation has several benefits. First, it is invariant to scale and rigid transform. Second, it can represent complex\\u000a and ill-defined models because of its physical background. 3D model supposed as charged body, we get the electric field force\\u000a distribution by placing some

Yujie Liu; Zongmin Li; Hua Li

2006-01-01

4

Characteristics of convection of an electrically conducting liquid in an additional external force field  

SciTech Connect

The authors analyze, theoretically and experimentally, the combined effects of gravitational and electric fields along with inertial forces on convective heat and mass transfer in liquid metals undergoing vortex flow in the presence of constant magnetic fields. The experimental data are derived for a eutectic indium-gallium-tin alloy. The flow model incorporates electrical conductivity and Hartmann number as well as other properties.

Mikel'son, A.E.; Karklin, Ya.Kh.

1987-07-01

5

Spinmotive force with static and uniform magnetization induced by a time-varying electric field  

NASA Astrophysics Data System (ADS)

A new spinmotive force is predicted in ferromagnets with spin-orbit coupling. By extending the theory of spinmotive force, we show that a time-varying electric field can induce a spinmotive force with static and uniform magnetization. This spinmotive has two advantages; it can be detected free from the inductive voltage owing to the absence of dynamical magnetization and it can be tuned by electric fields. To observe the effect, we propose two experimental setups: electric voltage measurement in a single ferromagnet and spin injection from a ferromagnet into an attached nonmagnetic conductor.

Yamane, Yuta; Ieda, Jun'ichi; Maekawa, Sadamichi

2013-07-01

6

Field-aligned electric field caused by the decay of force-free magnetic field and particle acceleration  

Microsoft Academic Search

Numerical simulation for the dynamics of a coronal filamentary magnetic loop has been made under the assumption that the field is initially force-free and an electric resistivity suddenly increases at a given moment due to an appearance of ion sound waves, which can be excited due to a high current density if a characteristic radius r0 of the magnetic loop

T. Takakura

1987-01-01

7

Force and torque on an electric dipole by spinning light fields  

NASA Astrophysics Data System (ADS)

We calculate the optical force and torque applied to an electric dipole by a spinning light field. We find that the dissipative part of the force depends on the orbital energy flow of the field only, because the latter is related to the phase gradient generalized for such a light field. As for the remaining spin energy flow, it gives rise to an optical torque. The resulting change in the optical force is detailed for different experimentally relevant configurations, and we show in particular how this change is critical when surface plasmon modes are involved.

Canaguier-Durand, Antoine; Cuche, Aurélien; Genet, Cyriaque; Ebbesen, Thomas W.

2013-09-01

8

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

9

Observation of the Intrinsic Abraham Force in Time-Varying Magnetic and Electric Fields  

NASA Astrophysics Data System (ADS)

The Abraham force exerted by a time-dependent electromagnetic field on neutral, polarizable matter has two contributions. The one induced by a time-varying magnetic field and a static electric field is reported here for the first time. We discuss our results in the context of the radiative momentum in matter. Our observations are consistent with Abraham’s and Nelson’s versions for radiative momentum.

Rikken, G. L. J. A.; van Tiggelen, B. A.

2012-06-01

10

Electric Field Force-Based Detection of Rotational Symmetry in 3D Model  

Microsoft Academic Search

In this paper, we propose a method to describe the rotational symmetry in 3D shapes. This symmetry is deterministically found through the use of a physical quantity: electric field force. He describes the measure of the shape's rotational symmetry with respect to every axis passing through the center mass. This algorithm can deal with complex and ill-defined models because of

Yujie Liu; Zongmin Li; Hua Li

2007-01-01

11

Non-uniform spatial distributions of both the magnitude and phase of AC electric fields determine dielectrophoretic forces  

Microsoft Academic Search

It is well known that the conventional dielectrophoretic force acting on a polarised particle in a non-uniform AC electric field is proportional to the in-phase component of the induced dipole moment and the non-uniformity of the field strength. In contrast, the travelling-wave-dielectrophoretic force that acts on a particle subjected to a travelling electric field is proportional to the out-of-phase component

X.-B Wang; M. P Hughes; Y Huang; F. F Becker; P. R. C Gascoyne

1995-01-01

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

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

14

Thermal noise, motional electromotive force, and electric fields in the human body  

Microsoft Academic Search

The human body is a parasitic antenna in which currents and electric fields are induced when it is near a 50-60 Hz transmission line or a 10-30 kHz transmitter. In a paper by Adair (see Phys. Rev. A, vol.43, p.1039-48, 1991) it is stated that “any effects on the cell level of fields in the body generated by weak external

Ronold W. P. King

1997-01-01

15

Laser focus accelerator by relativistic self-focusing and high electric fields in double layers of nonlinear force produced cavitons  

SciTech Connect

The laser focus accelerator with relativistic self-focusing for achieving Z-separated heavy ions of energies beyond 10 GeV was studied experimentally, in detailed numerical work and estimations on intense muon sources, heavy nuclear collisions and generation of new isotopes are on the way. The recently detected inverted double layers in the nonlinear (ponderomotive) force produced cavitons with 10/sup 9/ V/cm nearly static field can be used for electron acceleration. An upgraded present days Antares system with 20 phase-optimized steps should arrive at TeV electrons. The spontaneous high magnetic fields should produce highly directed non-Z-separated ion bunches where the E x B mechanism of Forslund and Brackbill with thermally created electric fields can be improved drastically by nonlinear force generated fields. Further studies were on acceleration by relativistic Doppler shift and by the transverse free electron laser.

Clark, P.J.; Eliezer, S.; Farley, F.J.M.; Goldsworthy, M.P.; Green, F.; Hora, H.; Kelly, J.C.; Lalousis, P.; Luther-Davies, B.; Stening, R.J.

1985-07-15

16

Laser focus accelerator by relativistic self-focusing and high electric fields in double layers of nonlinear force produced cavitons  

NASA Astrophysics Data System (ADS)

The laser focus accelerator with relativistic self-focusing for achieving Z-separated heavy ions of energies beyond 10 GeV was studied experimentally, in detailed numerical work and estimations on intense muon sources, heavy nuclear collisions and generation of new isotopes are on the way. The recently detected inverted double layers in the nonlinear (ponderomotive) force produced cavitons with 109 V/cm nearly static field can be used for electron acceleration. An upgraded present days Antares system with 20 phase-optimized steps should arrive at TeV electrons. The spontaneous high magnetic fields should produce highly directed non-Z-separated ion bunches where the E×B mechanism of Forslund and Brackbill with thermally created electric fields can be improved drastically by nonlinear force generated fields. Further studies were on acceleration by relativistic Doppler shift and by the transverse free electron laser.

Clark, P. J.; Eliezer, S.; Farley, F. J. M.; Goldsworthy, M. P.; Green, F.; Hora, H.; Kelly, J. C.; Lalousis, P.; Luther-Davies, B.; Stening, R. J.; Jin-Cheng, Wang

1985-07-01

17

Exploring Forces: Static Electricity  

NSDL National Science Digital Library

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

Network, Nanoscale I.; Sciencenter

2010-01-01

18

Influence of electric and gravitational force fields on nucleate boiling of FC72 on a wire: Results of a sounding rocket campaign  

NASA Astrophysics Data System (ADS)

The paper reports the main results obtained during a sounding rocket experiment about the effect of gravity and electric field on nucleate pool boiling of saturated FC72 on a wire. The effect of gravitational and electric forces on the nucleate pool boiling regime have been experimentally studied. The nucleate boiling region has been found to narrow at low gravity (corresponding to a decreasing critical heat flux, CHF) and to widen thanks to the action of an imposed electric field, that increases the CHF value. Both nucleate boiling heat transfer and CHF becomes insensitive to gravity beyond a certain threshold of the applied electric field. .

di Marco, P.; Grassi, W.

2002-01-01

19

Polarizable force fields  

Microsoft Academic Search

Standard force fields used in biomolecular computing describe electrostatic interactions in terms of fixed, usually atom-centered, charges. Real physical systems, however, polarize substantially when placed in a high-dielectric medium such as water — or even when a strongly charged system approaches a neutral body in the gas phase. Such polarization strongly affects the geometry and energetics of molecular recognition. First

Thomas A Halgren; Wolfgang Damm

2001-01-01

20

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

21

Electric Fields Quiz  

NSDL National Science Digital Library

This online quiz, from McGraw-Hill, focuses on electric fields. It is a 10-question quiz which can be checked at the end and covers electric potential, stored charge, illustrating an electric field, charge direction and other topics.

2010-03-05

22

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

23

Physics 2000: The Electric Force  

NSDL National Science Digital Library

This webpage demonstrates electric force exerted by positive and negative charges through a simulation of the behaviour of an electron in the presence of a proton. The concept is explained in the form of a conversation between two people to make learning more interesting. This webpage is a part of an extensive collection of physics tutorials.

2008-06-10

24

Electric and Magnetic Forces: Electromagnetism  

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

National Science Teachers Association (NSTA)

2008-10-30

25

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

NASA Astrophysics Data System (ADS)

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

Sheikin, E. G.; Wei, Yang Cheng

2013-01-01

26

Electric field replaces gravity in laboratory  

Microsoft Academic Search

For several years experiments in physical laboratories and in the fitotron have shown that one can replace gravitational field with electrical fields for plants. First obvious experiments in strong electrical fields in the MV\\/m regi on show that any materials and living plants respond immediately to Coulomb forces. Such fields are found in nature during thunderstorms. One has to be

S. Gorgolewski

2002-01-01

27

Electric Field Example 12  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario

2008-02-19

28

Forces Between Electrical Current Elements  

NASA Astrophysics Data System (ADS)

The momentum of a charged particle is p*=mv*-qA*, where m, v*, q and A* are respectively mass, velocity, charge and vector potential, and * denotes vector. Hence current element I'ds'* exerts a force on Ids*: ddF*=b(II'/r3)(r*.ds*)ds'*=ddF*(magnetic)+b(II'/r3)(ds*.ds'*)r*(nonmagnetic), where b=10-7 Newton/Ampere2. From ds'* to ds* is r*. This causes a nonuniform charge distribution along the circuit(s) containing Ids* and I'ds'* whose field transfers ddF* from conduction electrons to ions. The line integral of ddF* is tensile between points of a rectilinear portion of a circuit. The Lorentz force and Ampere's third law of magnetostatic force are invalid if ddF* is confirmed by a nonzero torque of a Marinov motor. If Ids* has velocity w* relative to I'ds'*: ddF* acts on conduction electrons of ds* as when w=0 and also acts on electrons and nuclei of ions of ds* as current elements w*dq=Dw*ds; D is linear charge density of ions. Resulting polarization by equal but opposite forces on electrons and nuclei of ions transfers ddF* from conduction electrons to ions. J. P. Wesley's intuitive assumption is justified.

Driscoll, Robert B.

2003-04-01

29

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

30

Simulated Static Electric Field (SSEF) Snake for Deformable Models  

Microsoft Academic Search

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

Dan Yuan; Siwei Lu

2002-01-01

31

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 A? 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

32

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

33

Electrical Measurement Techniques in Atomic Force Microscopy  

Microsoft Academic Search

A conductive tip in an atomic force microscope (AFM) has extended the capability from conventional topographic imaging to electrical surface characterization. The conductive tip acts as a voltage electrode to provide stimuli and monitor electrical surface properties. In this review article, we have organized the AFM electrical techniques based on whether the electrical properties are monitored at the cantilever tip

Alba Avila; Bharat Bhushan

2010-01-01

34

Electric field induced surface modification of Au  

Microsoft Academic Search

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.

T. M. Mayer; J. E. Houston; G. E. Franklin; A. A. Erchak; T. A. Michalske

1999-01-01

35

Laser focus accelerator by relativistic self-focusing and high electric fields in double layers of nonlinear force produced cavitons  

Microsoft Academic Search

The laser focus accelerator with relativistic self-focusing for achieving Z-separated heavy ions of energies beyond 10 GeV was studied experimentally, in detailed numerical work and estimations on intense muon sources, heavy nuclear collisions and generation of new isotopes are on the way. The recently detected inverted double layers in the nonlinear (ponderomotive) force produced cavitons with 109 V\\/cm nearly static

P. J. Clark; S. Eliezer; F. J. M. Farley; M. P. Goldsworthy; F. Green; H. Hora; J. C. Kelly; P. Lalousis; B. Luther-Davies; R. J. Stening; Wang Jin-Cheng

1985-01-01

36

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

SciTech Connect

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

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

1994-06-23

37

Experimental characterization of electrospinning: the electrically forced jet and instabilities  

Microsoft Academic Search

In the electrospinning process, polymer fibers with submicron-scale diameters are formed by subjecting a fluid jet to a high electric field. We report an experimental investigation of the electrically forced jet and its instabilities. The results are interpreted within the framework of a recently developed theory for electrified fluid jets. We find that the process can be described by a

Y. M. Shin; M. M. Hohman; M. P. Brenner; G. C. Rutledge

2001-01-01

38

Electric Field Hockey  

NSDL National Science Digital Library

Play hockey with electric charges. Place charges on the ice, then hit start to try to get the puck in the goal. View the electric field. Trace the puck's motion. Make the game harder by placing walls in front of the goal. This is a clone of the popular simulation of the same name marketed by Physics Academic Software and written by Prof. Ruth Chabay of the Dept of Physics at North Carolina State University.

Simulations, Phet I.; Dubson, Michael; Reid, Sam; Adams, Wendy; Harlow, Danielle

2004-07-01

39

Transmutation of electric into magnetic forces on a planar electron: Impurity spacing and band structure in strong magnetic fields  

NASA Astrophysics Data System (ADS)

We numerically investigate the eigenstates of an electron moving in two spatial dimensions in a strong, perpendicular magnetic field and a random impurity potential. Our work extends existing work at impurity densities greater than one per magnetic flux quantum to lower impurity densities and, reinterpreting the impurities as electrons, to the context of the fractional quantum Hall effect. We find that both the eigenenergies and the eigenstates of the single-particle spectrum depend qualitatively on the separation of the impurities. In general, this demonstrates that the moderate impurity density regime is interesting for the variety of phenomena present. In particular, we find that for moderate densities of impurities with widths on the order of the magnetic length it is possible to switch from a single energy band to multiple energy bands, with corresponding changes in the eigenstates including the dominance of large, ringlike states in the regions separating the energy bands, simply by the imposition of a hard-shell repulsion on the random impurity distribution. Further constraint of the impurities to a triangular lattice produces further qualitative changes in the spectrum, especially in the eigenstates, so that we find three distinct regimes for a single impurity density and width: random, random with a hard-shell repulsion, and triangular lattice. Focusing on the hard-shell case because of its analogy to the fractional quantum Hall effect, we find that the number and character of the states in the lowest energy band imply an effective magnetic field reduced from the applied field by half the amount predicted in composite fermion theory. Our initial motivation was based on an argument linking the effective magnetic field found in studying the Aharonov atom with the effective magnetic field of the fractional quantum Hall effect. Our results indicate that the viewpoint based on the Aharonov atom gives a correct qualitative insight into the fractional quantum Hall effect as well as the generic phenomenon of effective magnetic fields.

Horner, Margaret Lenore

40

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

41

Research on the effects of a history-based curriculum on the students' understanding of the concepts of electric field and lines of force  

NASA Astrophysics Data System (ADS)

The difficulties in learning the concepts of electric field and lines of force that have been signaled by the research in science education constitute the starting point of this research. Among the learning difficulties that students have, the assignment of the wrong ontological status to the to be learned concepts has proven to be a main one. Given that many students fail to achieve the scientific understanding of these concepts after a traditional instruction, this research was set out to design research-based instructional material and test its influence on the ontology assigned by the students to these concepts. The instructional material was designed using examples taken from the history of physics so that an ontological analysis of the early scientists' ideas was used to help students understand the ontology of the early conceptions compared to the ontology of the modern scientific ones. The instructional material was tested with a group physics major students at an Argentinean university. The predicates used by the students to describe an entity were taken as evidence of their ontological commitments with respect to field and lines of force. Differences in the proportion of correct predicates versus wrong ones were measured between two groups (experimental and control). These differences were detected using a quantitative measure taken from written data and were confirmed through oral interviews with some students. Although the wrong characterization of the learned entities was not absolutely eradicated from the students, a better characterization of them was present within the experimental ones. It was also found that the ontological understanding of a concept is not related to the success in solving traditional end-of-chapter problems. This result confirms that there is a part of the physics discipline that we are leaving aside when testing is limited to the ability to solve this type of problems.

Pocovi, Marta Cecilia

42

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

43

Effects of forced electromagnetic vibrations during the solidification of aluminum alloys: Part I. solidification in the presence of crossed alternating electric fields and stationary magnetic fields  

Microsoft Academic Search

A new magnetohydrodynamic method of transmitting forced vibrations to solidifying aluminum alloy melts has been developed.\\u000a Contrary to the case of the conventional mechanoacoustic systems, this device lends itself very well to a fundamental investigation.\\u000a The relatively accurate knowledge of both the electromagnetic pressure and the local velocity peaks has enabled us to reveal\\u000a the specific effects of the oscillatory

Charles Vivès

1996-01-01

44

Electric field replaces gravity in laboratory  

NASA Astrophysics Data System (ADS)

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

Gorgolewski, S.

45

Improving an all-atom force field  

NASA Astrophysics Data System (ADS)

Experimentally well-characterized proteins that are small enough to be computationally tractable provide useful information for refining existing all-atom force fields. This is used by us for reparametrizing a recently developed all-atom force field. Relying on high statistics parallel tempering simulations of a designed 20 residue ? -sheet peptide, we propose incremental changes that improve the force field’s range of applicability.

Mohanty, Sandipan; Hansmann, U. H. E.

2007-07-01

46

Global forces shape the electricity industry  

SciTech Connect

Whatever scenario for electricity comes to pass - one that emphasizes richness in energy supply or productivity in demand - expect to see increased complexity in the industry and its structures. Technology will be a key subversive element of this process of Schumpeterian creation and destruction. There are powerful global forces at work that are transforming whole economies and industries. Today`s electricity industry, with a century of tradition behind it, is also likely to be transformed in terms of its structure, competitive nature and the fuels that it uses. The electricity demand-Gross Domestic Product (GDP) relationship also stems from the increased share of electricity in energy markets. Overall, energy demand is declining relative to GDP, driven by increased efficiency and economic restructuring. Eventually (as indeed is already discernible in OECD countries) electricity demand will show the same characteristics.

Rainbow, R.

1996-05-01

47

Electric field forced vibration of a periodic piezocomposite plate with laminated structure and reflection and transmission of a plane wave at the fluid-composite interface  

Microsoft Academic Search

We address the problems of the vibration of a periodic piezocomposite plate (2-2 composite) under external electric fields and the reflection and transmission of a plane wave incident on the fluid-composite interface based on an analytical method developed recently, which takes into account explicitly the heterogeneous nature of the piezocomposites. It is shown that due to the finite thickness of

Q. M. Zhang; Xuecang Geng

1995-01-01

48

Bioanalytical separations using electric field gradient techniques.  

PubMed

The field of separations science will be strongly impacted by new electric-field-gradient-based strategies. Many new capabilities are being developed with analytical targets ranging from particles to small molecules, and soot to living cells. Here we review the emerging area of electric field gradient techniques, dividing the large variety of techniques by the target of separation. In doing so, we have contributions using dielectrophoresis, electric field gradient focusing (including dynamic, true moving bed, and pulsed field), electrocapture and electrophoretic focusing, temperature gradient focusing, and focusing with centrifugal force. We cover the literature from the start of 2007 to June 2008, along with some introductory discussions. Even with the relatively short time frame, this young and dynamic field of inquiry produced some 100 contributions describing new and unique techniques and several new applications. PMID:19197905

Meighan, Michelle M; Staton, Sarah J R; Hayes, Mark A

2009-03-01

49

On Electric Fields in Stellarator Equilibria  

SciTech Connect

The paper describes the electric field in stellarator equilibria and discusses the methods of how to compute the electric potential. The momentum balance in a given magnetic field including viscous and friction forces is considered in the frame of a multifluid model. A general ambipolar condition on closed pressure surfaces is derived that is still valid if magnetic surfaces do not exist. The need for an extended model originates from the singularities of the plasma current in the ideal magnetohydrodynamic model of stellarator equilibria, where parallel current density becomes singular leading to singular parallel electric fields. Viscosity and friction forces eliminate these singularities. The paper investigates the mathematical implications of the extended plasma model and discusses the existence of solutions using the methods of functional analysis.

Beidler, Craig D.; Igitkhanov, Yuri L.; Wobig, Horst F. G. [Max-Planck-Institut fuer Plasmaphysik (Germany)

2004-07-15

50

Improving an all-atom force field.  

PubMed

Experimentally well-characterized proteins that are small enough to be computationally tractable provide useful information for refining existing all-atom force fields. This is used by us for reparametrizing a recently developed all-atom force field. Relying on high statistics parallel tempering simulations of a designed 20 residue beta-sheet peptide, we propose incremental changes that improve the force field's range of applicability. PMID:17677516

Mohanty, Sandipan; Hansmann, U H E

2007-07-18

51

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

52

Electrosprays generated by a DC electric field  

NASA Astrophysics Data System (ADS)

The breakup of an electrified jet in a gas with an axially applied electric field is investigated theoretically. The jet fluid is taken to be a symmetric electrolyte and proper modelling of the cationic and anionic species is used by considering the Nernst-Planck equations in order to find the volume charge density that influences the electric field in the jet. The governing equations are investigated asymptotically in the long wave limit and the one dimensional model is solved numerically as a function of the hydrodynamic, electrical, and electrokinetic parameters. The electric field causes the jet to stretch and thin to a point where ion repulsion forces the jet to undergo Rayleigh fission. We measure the distance at which this point occurs by comparing the jet radius to the distance at which ion repulsion is important.

Papageorgiou, Demetrios; Conroy, Devin; Craster, Richard; Chang, Hsueh-Chia; Matar, Omar

2011-11-01

53

Force field feature extraction for ear biometrics  

Microsoft Academic Search

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

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

2005-01-01

54

Force Field for SiF4.  

National Technical Information Service (NTIS)

The force field of SiF4 has been determined using both Coriolis coupling constants obtained from an investigation of the band contour of v3 at 195 K and isotopic shifts. The force fields are equally well determined using both methods and are in agreement....

I. W. Levin S. Abramowitz

1968-01-01

55

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.

Daniels, Charlotte S.; Rubinsky, Boris

2011-01-01

56

Dynamics of vesicles in electric fields  

NASA Astrophysics Data System (ADS)

Electromechanical forces are widely used for cell manipulation. Knowledge of the physical mechanisms underlying the interaction of cells and external fields is essential for practical applications. Vesicles are model cells made of a lipid bilayer membrane. They are examples of ``soft'' particles, i.e., their shape when subjected to flow or electric field is not given a priori but it is governed by the balance of membrane, fluid and electrical stresses. This generic ``softness'' gives rise to a very complex vesicle dynamics in external fields. In an AC electric field, as the frequency is increased, vesicles filled with a fluid less conducting than the surrounding fluid undergo shape transition from prolate to oblate ellipsoids. The opposite effect is observed with drops. We present an electro- hydrodynamic theory based on the leaky dielectric model that quantitatively describes experimental observations. We compare drops and vesicles, and show how their distinct behavior stems from different interfacial properties.

Vlahovska, Petia; Gracia, Ruben

2007-11-01

57

Modeling solar force-free magnetic fields  

Microsoft Academic Search

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

B. C. Low; Y. Q. Lou

1990-01-01

58

Force Potentials in Quantum Field Theory  

Microsoft Academic Search

As early as 1935 Yukawa conjectured that the nuclear force, which ties together the component nucleons into a solid nucleus, could be attributed to an intermediate field with an intrinsic mass corresponding to the range of the nuclear force. The general success of the meson theory that followed the discovery of such particles in cosmic rays, has been so great

Y. Nambu

1950-01-01

59

Electric Field Example 11  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario

2008-02-19

60

Magnetic flux and lines of force for the Hertzian electric dipole and nonsinusoidal waves  

Microsoft Academic Search

The authors present computer plots of magnetic lines of force for the Hertzian electric dipole excited by sinusoidal currents that radiate to the far-field electromagnetic waves with the time variation of a Gaussian pulse. Plots of lines of force for sinusoidal waves are also presented for comparison. Since the density of the lines of force at any distance from the

M. G. M. Hussain; A. A. Omar

1990-01-01

61

Microfluidic droplets and electric fields  

NASA Astrophysics Data System (ADS)

Manipulating droplets through mazes of microchannels is a challenge faced by digital microfluidics (i.e microfluidics based on droplets). In this domain, using electric fields is an option. This option is justified by the fact that producing large electric fields in miniaturized systems is feasible, and dielectric contrasts between dispersed and continuous phases are typically large. Examples of devices reported in the literature are droplet guides, droplet mergers. In the present paper, we extend this approach by reporting two novel examples of droplet manipulations that exploit the action on an electric field in a microfluidic system: one is the control of droplet emission frequencies and the other is the inhibition of droplet breakup. Throughout the work, we analyze in some detail the various aspects of the action of the electric field. The experiments are performed in PDMS microfluidic systems using hexadecane and water for the continuous and dispersed phases respectively.

Tabeling, Patrick; Menetrier, Laure; McDonald, Alice; Willaime, Herve; Angelescu, Dan

2007-03-01

62

Assembly of LIGA using Electric Fields  

SciTech Connect

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

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

2002-04-01

63

Effects of Electric Fields on Block Copolymer Nanostructures  

Microsoft Academic Search

\\u000a In this chapter we overview electric-field-induced effects on block copolymer microdomains. First, we will consider the thin\\u000a film behavior and elucidate the parameters governing electric-field-induced alignment. We describe the structural evolution\\u000a of the alignment in an electric field via quasi in situ scanning force microscopy (SFM) using a newly developed SFM setup\\u000a that allows solvent vapor treatment in the presence

Heiko G. Schoberth; Violetta Olszowka; Kristin Schmidt; Alexander Böker

2010-01-01

64

Tokamak burn extension by radial electric field control  

SciTech Connect

This study considers a TFTR-sized plasma operating on a long cycle. The temperature profile is fixed in time, and the plasma is not refuelled. In order to isolate the electric field effects, this last condition is extended to prohibit the electric field at the plasma edge from returning more fuel to the plasma than gradient-driven forces expel.

Downum, W.B.; Miley, G.H.; Choi, C.K.

1980-01-01

65

Minds on Physics: Fundamental Forces & Fields, Teacher's Guide  

NSDL National Science Digital Library

This teacher's guide corresponds with the Fundamental Forces & Fields book, and consists of two parts: Answers and Instructional Aids for Teachers, and Answer Sheets. The Answers and Instructional Aids for Teachers provides advice for how to optimize the effectiveness of the activities, as well as brief explanations and comments on each question in the student activities. The Answer Sheets may be duplicated and distributed to students as desired. This is the fourth in a series of six teacher guides for the Minds On Physics Activities and Reader series. This volume deals with the basics of gravitational, electric, and magnetic forces and fields.

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

2007-05-25

66

Penetration electric fields: A Volland Stern approach  

NASA Astrophysics Data System (ADS)

This paper reformulates the Volland Stern model, separating contributions from corotation and convection to predict electric field penetration of the inner magnetosphere using data from the Advanced Composition Explorer (ACE) satellite. In the absence of shielding, the model electric field is EVS=?PC/2LYRE, where ?PC is the polar cap potential and 2LYRE is the width of the magnetosphere along the dawn dusk meridian. ?PC is estimated from the interplanetary electric field (IEF) and the dynamic pressure of the solar wind (PSW); values of LY were approximated using PSW and simple force-balance considerations. ACE measurements on 16 17 April 2002 were then used to calculate EVS for comparison with the eastward electric field component (EJ?) detected by the incoherent scatter radar at Jicamarca, Peru. While the interplanetary magnetic field (IMF) was southward, the model predicted observed ratios of EVS/IEF. During intervals of northward IMF, EJ? turned westward suggesting that a northward IMF BZ system of field-aligned currents affected the electrodynamics of the dayside ionosphere on rapid time scales.

Burke, William J.

2007-07-01

67

Additive empirical force field for hexopyranose monosaccharides.  

PubMed

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 alpha- and beta-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. Although 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

2008-11-30

68

Interactive calculations of electric fields  

SciTech Connect

In many experimental design situations it is valuable to know what the time-dependent electric and magnetic fields are likely to be so that such things as electric breakdown and ohmic heating as a result of magnetic field penetration canb e estimated. Because of the advent of extensions in the speed and memory of large electronic computers it has become easier to extend the scope of these calculations. Even so, it is necessary to use advanced sparse matrix techniques and to take as much advantage as possible of vectorization of code loops. In developing these codes extensive use has been made of the 2-D counterparts to test various aspects of the algorithms and of the code architecture. In addition, attempts have been made to make the user interface to these codes as simple and easy as possible. This paper addresses the problem of implementing this system for the 2-D calculation of electric fields. 3 refs., 4 figs.

Weiss, D.L.; Oliphant, T.A.

1986-07-01

69

Electric fields yield chaos in microflows  

PubMed Central

We present an investigation of chaotic dynamics of a low Reynolds number electrokinetic flow. Electrokinetic flows arise due to couplings of electric fields and electric double layers. In these flows, applied (steady) electric fields can couple with ionic conductivity gradients outside electric double layers to produce flow instabilities. The threshold of these instabilities is controlled by an electric Rayleigh number, Rae. As Rae increases monotonically, we show here flow dynamics can transition from steady state to a time-dependent periodic state and then to an aperiodic, chaotic state. Interestingly, further monotonic increase of Rae shows a transition back to a well-ordered state, followed by a second transition to a chaotic state. Temporal power spectra and time-delay phase maps of low dimensional attractors graphically depict the sequence between periodic and chaotic states. To our knowledge, this is a unique report of a low Reynolds number flow with such a sequence of periodic-to-aperiodic transitions. Also unique is a report of strange attractors triggered and sustained through electric fluid body forces.

Posner, Jonathan D.; Perez, Carlos L.; Santiago, Juan G.

2012-01-01

70

Apparatuses and methods for generating electric fields  

DOEpatents

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

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

2013-08-06

71

Electric Field of Bohr's Atom.  

National Technical Information Service (NTIS)

On the basis of the Lienard-Wiechert potential, it is shown that the electric field of the simplest Bohr atom oscillates though the mean (per period) value is equal to zero. The calculation with the use of the generally accepted presentation of the moving...

V. N. Strel'tsov

1994-01-01

72

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

73

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

74

Whole field decoupling of predistortion on polymeric cell force transducer  

NASA Astrophysics Data System (ADS)

Microfabricated polymer transducers have been developed to study cell mechanics. The key principle is to quantify the deformations on the sensor arrays induced by cell contractions and convert them into force distributions. The simplifications in deformation measurements come from the basic assumption that the deformation is solely attributed to cell contractions triggered by chemical or electrical stimuli. The diffraction moiré fringes via two polymer gratings provide whole field evolutions of distortion/strain on soft-lithography fabricated substrates. We found that the moiré patterns are able to decouple predistortions which were traditionally thought to be solely caused by cell contractile forces.

Zheng, Xiaoyu; Zhang, Xin

2011-04-01

75

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

76

Navigation guided by artificial force fields  

Microsoft Academic Search

This paper presents a new technique for controlling a user's navigation in a virtual environment. The approach intro- duces artificial force fields which act upon the user's vir- tual body such that he is guided around obstacles, rather than penetrating or colliding with them. The technique is extended to incorporate gravity into the environment. The problem of negotiating stairs during

Dongbo Xiao; Roger J. Hubbold

1998-01-01

77

Lessons Learned, Headquarters, I Field Force Vietnam Artillery.  

National Technical Information Service (NTIS)

During the period 1 November 1967 through 31 January 1968, I Field Force Vietnam Artillery continued to support United States, Vietnamese, and Free World Military Assistance Forces in II Corps Tactical Zone (CTZ). I Field Force Vietnam Artillery units, to...

1968-01-01

78

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

79

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.

80

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.

81

Nanoconfined water under electric field  

NASA Astrophysics Data System (ADS)

We study the effect of electric field on interfacial tension of nanoconfined water [1,2] using molecular simulations. Our analysis and simulations confirm that classical electrostriction characterizes usual electrowetting behavior in nanoscale hydrophobic channels and nanoporous materials [3]. We suggest a new mechanism to orient nanoparticles by an applied electric field even when the particles carry no charges or dipoles of their own. Coupling to the field can be accomplished trough solvent-mediated interaction between the electric field and a nanoparticle [4]. For nanoscale particles in water, we find the response to the applied field to be sufficiently fast to make this mechanism relevant for biological processes, design of novel nanostructures and sensors, and development of nanoengineering methods [5]. [1]C. D. Daub, D. Bratko, K. Leung and A. Luzar, J. Phys. Chem. C 111, 505 (2007). [2] D. Bratko, C. D. Daub, K. Leung and A. Luzar, J. Am. Chem. Soc. 129, 2504 (2007) [3] D. Bratko, C. D. Daub and A. Luzar, Phys. Chem. Chem. Phys. 10, 6807 (2008). [4] D. Bratko, C. D. Daub and A. Luzar, Faraday Discussions 141, 55 (2009). [5] C. D. Daub, D. Bratko, T. Ali and A. Luzar, Phys. Rev. Lett. 103, 207801 (2009).

Luzar, Alenka; Bratko, D.; Daub, C. D.

2010-03-01

82

Measuring electric fields from surface contaminants with neutral atoms  

SciTech Connect

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

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

2007-06-15

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

Storage of light-driven transthylakoid proton motive force as an electric field (??) under steady-state conditions in intact cells of Chlamydomonasreinhardtii  

Microsoft Academic Search

Proton motive force (pmf) is physiologically stored as either a ?pH or a membrane potential (??) across bacterial and mitochondrial energetic membranes. In the case of chloroplasts, previous work (Cruz et al. 2001, Biochemistry 40: 1226–1237) indicates that ?? is a significant fraction of pmf, in vivo, and in vitro as long as the activities of counterions are relatively low.

Jeffrey A. Cruz; Atsuko Kanazawa; Nathan Treff; David M. Kramer

2005-01-01

85

The Influence of Electric Field and Confinement on Cell Motility  

PubMed Central

The ability of cells to sense and respond to endogenous electric fields is important in processes such as wound healing, development, and nerve regeneration. In cell culture, many epithelial and endothelial cell types respond to an electric field of magnitude similar to endogenous electric fields by moving preferentially either parallel or antiparallel to the field vector, a process known as galvanotaxis. Here we report on the influence of dc electric field and confinement on the motility of fibroblast cells using a chip-based platform. From analysis of cell paths we show that the influence of electric field on motility is much more complex than simply imposing a directional bias towards the cathode or anode. The cell velocity, directedness, as well as the parallel and perpendicular components of the segments along the cell path are dependent on the magnitude of the electric field. Forces in the directions perpendicular and parallel to the electric field are in competition with one another in a voltage-dependent manner, which ultimately govern the trajectories of the cells in the presence of an electric field. To further investigate the effects of cell reorientation in the presence of a field, cells are confined within microchannels to physically prohibit the alignment seen in 2D environment. Interestingly, we found that confinement results in an increase in cell velocity both in the absence and presence of an electric field compared to migration in 2D.

Huang, Yu-Ja; Samorajski, Justin; Kreimer, Rachel; Searson, Peter C.

2013-01-01

86

Pumping of water through carbon nanotubes by rotating electric field and rotating magnetic field  

NASA Astrophysics Data System (ADS)

Using molecular dynamics simulations, we demonstrate pumping of water through a carbon nanotube by applying the combination of a rotating electric field and a rotating magnetic field. The driving force is a Lorentz force generated from the motion of charges in the magnetic field, and the motion is caused by the rotation of the electric field. We find that there exits a linear relationship between the average pumping velocity v and magnetic field strength B, which can be used to control the flux of the continuous unidirectional water flow. This approach is expected to be used in liquid circulation without a pressure gradient.

Li, Xiao-Peng; Kong, Gao-Pan; Zhang, Xing; He, Guo-Wei

2013-09-01

87

A 6-site force field for succinonitrile  

NASA Astrophysics Data System (ADS)

A 6-site succinonitrile force field has been developed. The model has produced proper proportions of the three succinonitrile conformers, which is necessary to avoid the thermal contraction of the plastic crystal phase around the melting point. The solid and liquid densities are about 1% lower or higher than the experimental values. The melting point of the model has been adjusted using the Gibbs-Duhem integration method. The theoretical melting point is in good agreement with experiment.

Feng, Xiaobing; Laird, Brian B.

88

Global Effects of Subauroral Electric Fields on the Thermosphere  

NASA Astrophysics Data System (ADS)

Ionospheric electric fields can have profound effects on the thermospheric composition and winds, particularly during geomagnetic activity. They influence numerous processes in the ionosphere/thermosphere (IT) system including plasma transport in the ionosphere, the ion drag force which affects neutral winds, and the Joule heating which drives much of the composition and structure of the IT system. They can extend to very low latitudes and can contribute substantially to the magnetospheric electric field structure, particularly during geomagnetic storms. Modelers have begun to understand the importance of the subauroral electric field coupling to the thermosphere, the inner magnetosphere and the plasmasphere and efforts to incorporate recent results are currently underway. We are examining the effect of the subauroral electric fields on IT coupling using an empirical model of the subauroral electric fields derived from data acquired by several low-Earth orbiting (LEO) spacecraft. The results are being incorporated into the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) to examine the global effects of the subauroral electric fields on the thermospheric structure. We will show our initial results, comparing the global thermospheric structure derived from TIME-GCM for a geomagnetic storm using a strictly high-latitude electric field model with thermospheric structure derived using an electric field model incorporating the subauroral electric field.

Anderson, P. C.; Crowley, G.; Johnston, W. R.

2007-05-01

89

Downward Mapping of Equatorial Ionospheric Electric Fields.  

National Technical Information Service (NTIS)

The problem of downward mapping of equatorial ionospheric electric fields is studied in two dimensions. Numerical solutions are shown and are compared with the corresponding ones for high latitudes. It is found that ionospheric electric fields can map dow...

W. D. Gonzalez S. L. G. Dutra A. L. C. Gonzalez A. E. C. Pereira

1985-01-01

90

Electric Field Measurement for HPM Research.  

National Technical Information Service (NTIS)

In this report, a description is given of the electric field measurement system at FOI Grids Jon Research Centre for HPM research. The system is intended for measurement of the electric field components in electromagnetic waves in the gigahertz region.

P. Appelgren T. Hultman A. Larsson

2003-01-01

91

Sustaining the US Air Force's Force Support Career Field through Officer Workforce Planning.  

National Technical Information Service (NTIS)

This dissertation recommends changes that can be made to the structure and management of the Air Force's Force Support officer career field to better align development of functional competencies with positional demand for those competencies. Data on Force...

K. O'Neill

2012-01-01

92

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

93

Dielectric fluid in inhomogeneous pulsed electric field.  

PubMed

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. PMID:23679510

Shneider, M N; Pekker, M

2013-04-09

94

A Parameterized, Global Model of the Subauroral Electric Fields  

NASA Astrophysics Data System (ADS)

Any models attempting to describe the structure of the thermosphere, the ionosphere, the plasmasphere, the inner magnetosphere and the ring current are dependent on the spatial and temporal distribution of the magnetospheric electric fields. As the inner magnetosphere is coupled to the subauroral ionosphere via magnetic field lines, the magnetospheric electric field structure is in turn dependent on the ionospheric electrodynamics. Electric fields influence numerous processes in the ionosphere/thermosphere (IT) system including plasma transport in the ionosphere, the ion drag force which affects neutral winds, and the Joule heating which drives much of the composition and structure of the IT system. These electric fields can extend to very low latitudes and can contribute substantially to the magnetospheric electric field structure, particularly during geomagnetic storms. The subauroral electric fields are known to reduce the ionospheric conductivity through fast chemistry and transport which produces a feedback mechanism into the magnetosphere through coupling along magnetic field lines further increasing the magnetospheric electric fields. They modify the plasmaspheric structure and drive the plasmasphere/electron plasmasheet interface (the plasmapause) inward. They are also extremely important to ring current formation and decay in that they enhance ring current formation during the storm main phase and slow storm recovery by providing a mechanism for transport of ring current particles to low L-values. Modelers have begun to understand the importance of the subauroral electric field coupling to the thermosphere, the inner magnetosphere and the plasmasphere and are clearly in need of an empirical model describing the global distribution of the subauroral electric fields. We are developing a parameterized, global model of the subauroral electric fields that will adjust to inputs of measured values of the equatorward edge of the auroral oval and the subauroral electric field and will present preliminary results of our efforts.

Anderson, P.; Johnston, W.

2007-05-01

95

A study on single fuel droplets combustion in vertical direct current electric fields  

Microsoft Academic Search

Both the electric force working on flames and the natural buoyancy are body forces, so there is a possibility to control the natural buoyancy by applying than electric field. It is important to discuss the body force in the flame because it induces the convective flow around flames. In this circumstance, combustion behavior of single droplets in vertical direct current

Osamu Imamura; Yasuyuki Kubo; Jun Osaka; Jun’ichi Sato; Mitsuhiro Tsue; Michikata Kono

2005-01-01

96

Fine Particle Flotation in a Centrifugal Force Field.  

National Technical Information Service (NTIS)

The effect of a centrifugal force field on hydrodynamic characteristics, flotation kinetics and separation behavior was examined. Flotation devices were designed that combine a centrifugal force field and flotation action in one apparatus. The relation be...

H. M. G. C. Tils

1990-01-01

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

Biomolecular simulations of membranes: Physical properties from different force fields  

Microsoft Academic Search

Phospholipid force fields are of ample importance for the simulation of artificial bilayers, membranes, and also for the simulation of integral membrane proteins. Here, we compare the two most applied atomic force fields for phospholipids, the all-atom CHARMM27 and the united atom Berger force field, with a newly developed all-atom generalized AMBER force field (GAFF) for dioleoylphosphatidylcholine molecules. Only the

Shirley W. I. Siu; Robert Vácha; Pavel Jungwirth; Rainer A. Böckmann

2008-01-01

99

Electric field probes for cellular phone dosimetry  

Microsoft Academic Search

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

Howard I. Bassen

1997-01-01

100

Ab initio based polarizable force field parametrization  

NASA Astrophysics Data System (ADS)

Experimental and simulation studies of anion-water systems have pointed out the importance of molecular polarization for many phenomena ranging from hydrogen-bond dynamics to water interfaces structure. The study of such systems at molecular level is usually made with classical molecular dynamics simulations. Structural and dynamical features are deeply influenced by molecular and ionic polarizability, which parametrization in classical force field has been an object of long-standing efforts. Although when classical models are compared to ab initio calculations at condensed phase, it is found that the water dipole moments are underestimated by ~30%, while the anion shows an overpolarization at short distances. A model for chloride-water polarizable interaction is parametrized here, making use of Car-Parrinello simulations at condensed phase. The results hint to an innovative approach in polarizable force fields development, based on ab initio simulations, which do not suffer for the mentioned drawbacks. The method is general and can be applied to the modeling of different systems ranging from biomolecular to solid state simulations.

Masia, Marco

2008-05-01

101

Ab initio based polarizable force field parametrization.  

PubMed

Experimental and simulation studies of anion-water systems have pointed out the importance of molecular polarization for many phenomena ranging from hydrogen-bond dynamics to water interfaces structure. The study of such systems at molecular level is usually made with classical molecular dynamics simulations. Structural and dynamical features are deeply influenced by molecular and ionic polarizability, which parametrization in classical force field has been an object of long-standing efforts. Although when classical models are compared to ab initio calculations at condensed phase, it is found that the water dipole moments are underestimated by approximately 30%, while the anion shows an overpolarization at short distances. A model for chloride-water polarizable interaction is parametrized here, making use of Car-Parrinello simulations at condensed phase. The results hint to an innovative approach in polarizable force fields development, based on ab initio simulations, which do not suffer for the mentioned drawbacks. The method is general and can be applied to the modeling of different systems ranging from biomolecular to solid state simulations. PMID:18532799

Masia, Marco

2008-05-14

102

Force field comparisons of the heat capacity of carbon nanotubes  

Microsoft Academic Search

The force fields Tersoff, CHARMM, COMPASS, CVFF and PCFF are compared using molecular calculations and simulations of SWNT thermal properties. The heat capacity results from the force fields vary significantly in the low (room) temperature range. The COMPASS force field best reproduces the phonon frequencies calculated from density functional theory and is consistent with the Raman scattering results. The temperature

C. Y. Guo; B. Montgomery Pettitt; L. T. Wheeler

2006-01-01

103

CHARMM general force field: A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields  

Microsoft Academic Search

The widely used CHARMM additive all-atom force field includes parameters for proteins, nucleic acids, lipids, and carbohydrates. In the present article, an extension of the CHARMM force field to drug-like molecules is presented. The resulting CHARMM General Force Field (CGenFF) covers a wide range of chemical groups present in biomolecules and drug-like molecules, including a large number of heterocyclic scaffolds.

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

2010-01-01

104

Pair-production in inhomogeneous electric fields  

SciTech Connect

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

Xue Shesheng [ICRANet, Piazzale della Repubblica, 10-65122 Pescara (Italy)

2008-01-03

105

Manipulation of red blood cells with electric field  

NASA Astrophysics Data System (ADS)

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

Saboonchi, Hossain; Esmaeeli, Asghar

2009-11-01

106

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

PubMed Central

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

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

2010-01-01

107

CHARMM general force field: A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields.  

PubMed

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

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

2010-03-01

108

Nonlinear cell response to strong electric fields  

Microsoft Academic Search

The response of living cells to externally applied electric fields is of widespread interest. In particular, the intensification of electric fields across cell membranes is believed to be responsible, through membrane rupture and reversible membrane breakdown processes, for certain types of tissue damage in electrical trauma cases which cannot be attributed to Joule heating. Large elongated cells such as skeletal

D. C. Bardos; C. J. Thompson; Y. S. Yang; K. H. Joyner

2000-01-01

109

Dielectrophoretic assembly of metallodielectric Janus particles in AC electric fields.  

PubMed

"Janus" particles with two hemispheres of different polarizability or charge demonstrate a multitude of interesting effects in external electric fields. We reported earlier how particles with one metallic hemisphere and one dielectric hemisphere self-propel in low-frequency alternating current (AC) electric fields. Here, we demonstrate the assembly of such Janus particles driven by AC electric fields at frequencies above 10 kHz. We investigated the relation between field-induced dielectrophoretic force, field distribution, and structure of the assemblies. The phase space for electric field intensity and frequency was explored for particle concentrations large enough to form a monolayer on a glass surface between two gold electrodes. A rich variety of metallodielectric particle structures and dynamics were uncovered, which are very different from those obtained from directed assembly of plain dielectric or plain conductive particles under the action of fields of similar frequency and intensity. The metallodielectric particles assemble into new types of chain structures, where the metallized halves of neighboring particles align into lanes along the direction of the electric field, while the dielectric halves face in alternating direction. The staggered chains may assemble in various orientations to form different types of two-dimensional metallodielectric crystals. The experimental results on the formation of staggered chains are interpreted by means of numerical simulations of the electric energy of the system. The assembly of Janus metallodielectric particles may find applications in liquid-borne microcircuits and materials with directional electric and heat transfer. PMID:18973307

Gangwal, Sumit; Cayre, Olivier J; Velev, Orlin D

2008-12-01

110

Point Charge Electric Field Demo Model  

NSDL National Science Digital Library

The Point Charge Electric Field Demo model shows the electric field with multiple point charge configurations and vector field visualizations. Users can select these configurations from a drop down menu or can create their own configurations. The Point Charge Electric Field Demo model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double click the ejs_em_PointChargeElectricFieldDemo.jar file to run the program if Java is installed.

Christian, Wolfgang

2010-08-11

111

Recent Developments and Applications of the CHARMM force fields  

PubMed Central

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

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

2011-01-01

112

Force field refinement from NMR scalar couplings  

NASA Astrophysics Data System (ADS)

NMR observables contain valuable information about the protein dynamics sampling a high-dimensional potential energy surface. Depending on the observable, the dynamics is sensitive to different time-windows. Scalar coupling constants J reflect the pico- to nanosecond motions associated with the intermolecular hydrogen bond network. Including an explicit H-bond in the molecular mechanics with proton transfer (MMPT) potential allows us to reproduce experimentally determined J couplings to within 0.02 Hz at best for ubiquitin and protein G. This is based on taking account of the chemically changing environment by grouping the H-bonds into up to seven classes. However, grouping them into two classes already reduces the RMSD between computed and observed J couplings by almost 50%. Thus, using ensemble-averaged data with two classes of H-bonds leads to substantially improved scalar couplings from simulations with accurate force fields.

Huang, Jing; Meuwly, Markus

2012-03-01

113

Lightning Location Using Electric Field Change Meters  

Microsoft Academic Search

Briefly introduced last year, the Huntsville Alabama Field Change Array (HAFCA) is a collection of electric field change meters deployed in and around Huntsville. Armed with accurate GPS timing, the array is able to sample electric field changes due to lightning strokes simultaneously at several locations. For the first time, different components of the lightning flash can be located in

P. M. Bitzer; H. Christian; J. Burchfield

2010-01-01

114

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

ERIC Educational Resources Information Center

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

Hustedde, Ron; Score, Michael

1995-01-01

115

Ionospheric electric fields, currents, and resulting magnetic fields variations  

NASA Astrophysics Data System (ADS)

This thesis uses an equivalent circuit model to calculate ionospheric electric fields, current densities and introduced magnetic fields variations on the ground. The role of the field aligned current is examined. Using different wind models, we studied the electric field variations with altitude, season and solar activity. The ionospheric eastward electric field changes very little within the whole ionosphere. The southward (equatorward) electric field is large and changes quickly with height in the E region although it is nearly constant in the F region. The prereversal enhancement of the eastward electric field is produced by the F region dynamo. We conclude that the Forbes and Gillette tidal wind can reproduce most features of the Jicamarca experiment and the AE-E and DE-2 satellite observations of the electric fields. The HWM90 empirical wind model failed to produce the observed electric field and it seems the semidiurnal wind in HWM90 is too strong. The field aligned current is located mainly in the E and low F region. The non-coincidence of the geomagnetic and geographic equators has a strong effect on the field aligned current in the equatorial zone. The field aligned currents driven by Forbes' winds for March equinox and December solstice flow mainly from the southern to northern hemisphere in the morning and vice versa in the afternoon at F region heights. The observed magnetic field variations on the ground are well reproduced in our simulations. The field aligned current is the main contributor to the eastward magnetic field component in the equatorial zone. The longitudinal inequality of the northward magnetic field is introduced mainly by the variations of the local magnetic field intensity. The electric field variations have only a minor effect. The northward magnetic field variations with the solar activity are introduced by changes of the E region equatorward electric field and the Hall conductivity.

Du, Junhu

116

Electric Field Analysis of Breast Tumor Cells  

PubMed Central

An attractive alternative treatment for malignant tumors that are refractive to conventional therapies, such as surgery, radiation, and chemotherapy, is electrical-pulse-mediated drug delivery. Electric field distribution of tissue/tumor is important for effective treatment of tissues. This paper deals with the electric field distribution study of a tissue model using MAXWELL 3D Simulator. Our results indicate that tumor tissue had lower electric field strength compared to normal cells, which makes them susceptible to electrical-pulse-mediated drug delivery. This difference could be due to the altered properties of tumor cells compared to normal cells, and our results corroborate this.

Sree, V. Gowri; Udayakumar, K.; Sundararajan, R.

2011-01-01

117

Electrical environment surrounding microbes exposed to pulsed electric fields  

Microsoft Academic Search

Inactivation of microbes by the application of intense pulsed electric fields (≃10 to 40 kV\\/cm) could result in low-temperature pasteurization of liquid foods. Advantages over conventional heat pasteurization include longer shelf-life, better flavor, and less enzyme damage. Numerical modeling of electrical parameters near the microbe during exposure to these intense electric fields is described. The continuity equation describes movement of

R. E. Bruhn; P. D. Pedrow; R. G. Olsen; G. V. Barbosa-Canovas; B. G. Swanson

1997-01-01

118

Lorentz force sigmometry: A contactless method for electrical conductivity measurements  

NASA Astrophysics Data System (ADS)

The present communication reports a new technique for the contactless measurement of the specific electrical conductivity of a solid body or an electrically conducting fluid. We term the technique ``Lorentz force sigmometry'' where the neologism ``sigmometry'' is derived from the Greek letter sigma, often used to denote the electrical conductivity. Lorentz force sigmometry (LoFoS) is based on similar principles as the traditional eddy current testing but allows a larger penetration depth and is less sensitive to variations in the distance between the sensor and the sample. We formulate the theory of LoFoS and compute the calibration function which is necessary for determining the unknown electrical conductivity from measurements of the Lorentz force. We conduct a series of experiments which demonstrate that the measured Lorentz forces are in excellent agreement with the numerical predictions. Applying this technique to an aluminum sample with a known electrical conductivity of ?Al=20.4MS/m and to a copper sample with ?Cu=57.92MS/m we obtain ?Al=21.59MS/m and ?Cu=60.08MS/m, respectively. This demonstrates that LoFoS is a convenient and accurate technique that may find application in process control and thermo-physical property measurements for solid and liquid conductors.

Uhlig, Robert P.; Zec, Mladen; Ziolkowski, Marek; Brauer, Hartmut; Thess, André

2012-05-01

119

New electric field in asymmetric magnetic reconnection.  

PubMed

We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site. PMID:24116786

Malakit, K; Shay, M A; Cassak, P A; Ruffolo, D

2013-09-23

120

Analysis of the electrically forced vibrations of piezoelectric mesa resonators  

NASA Astrophysics Data System (ADS)

We study the electrically forced thickness-shear and thickness-twist vibrations of stepped thickness piezoelectric plate mesa resonators made of polarized ceramics or 6-mm class crystals. A theoretical analysis based on the theory of piezoelectricity is performed, and an analytical solution is obtained using the trigonometric series. The electrical admittance, resonant frequencies, and mode shapes are calculated, and strong energy trapping of the modes is observed. Their dependence on the geometric parameters of the resonator is also examined.

He, Hui-Jing; Nie, Guo-Quan; Liu, Jin-Xi; Yang, Jia-Shi

2013-08-01

121

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

ERIC Educational Resources Information Center

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

Hart, Francis X.

1974-01-01

122

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

2013-09-10

123

Thermal Energy Storage in Forced-Air Electric Furnaces  

Microsoft Academic Search

Experimental data are presented for heat storage in forced-air electric furnaces using magnesite as the heat storage material. Charge and discharge data for temperature and flow, obtained in the laboratory, are compared with models used for the design of the furnace. Experience with the furnace operating in homes for a heating season and being charged during the off peak is

W. Bruce H. Cooke; R. H. Stephen Hardy; Michael T. Sulatisky

1980-01-01

124

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

2011-04-21

125

Optical fiber electric field intensity sensor  

Microsoft Academic Search

In this paper the results of the experimental investigation of fiber optic electric field intensity sensor are presented. These sensors are based on electroluminescent effect which consists in the light emission by some substances placed in variable electric field. The luminescent effect is observed in some composite semiconductors, among other - ZnS, doped by Mn, for high its concentration, order

Tadeusz Pustelny; Barbara M. Pustelny

2001-01-01

126

Theory of force-free electromagnetic fields. I. General theory  

Microsoft Academic Search

A general method to deal with the (relativistic) force-free electromagnetic field is developed. We formulate the theory without assuming symmetry of the electromagnetic field configuration. Thus we can apply it to any object where the force-free approximation is justified, e.g., the pulsar magnetosphere, the black-hole magnetosphere, and the magnetosphere around the accretion disk. We describe the force-free electromagnetic field by

Toshio Uchida

1997-01-01

127

DNA Polymorphism: A Comparison of Force Fields for Nucleic Acids  

Microsoft Academic Search

The improvements of the force fields and the more accurate treatment of long-range interactions are providing more reliable molecular dynamics simulations of nucleic acids. The abilities of certain nucleic acid force fields to represent the structural and conformational properties of nucleic acids in solution are compared. The force fields are AMBER 4.1, BMS, CHARMM22, and CHARMM27; the comparison of the

Swarnalatha Y. Reddy; Fabrice Leclerc; Martin Karplus

2003-01-01

128

Electric field mapping and auroral Birkeland currents  

SciTech Connect

Magnetic field lines, electric fields and equipotentials have been mapped throughout the magnetosphere in the vicinity of strong Birkeland currents. It was found that a uniform electric field at either the ionospheric or the equatorial end of a field line can map to a highly structured field at the other end if strong Birkeland currents are located nearby. The initiation of sheet currents of the region 1 - region 2 scale size and intensity resulted in magnetic field line displacements of about 1/2 hour in local time between equatorial and ionospheric end points. As a result, a uniform dawn to dusk electric field at the equator mapped to an ionospheric electric field with strong inward pointing components in the dusk hemisphere. Similar distortions were produced by Birkeland currents associated with narrow east-west-aligned auroral arcs. A specific model for the auroral current system, based on ionospheric measurements during a large substorm, was used to study effects seen during disturbed periods. An iterative procedure was developed to generate a self-consistent current system even in the presence of highly twisted field lines. The measured ionospheric electric field was projected tot he equatorial plane in the presence of the model Birkeland current system. Several physical processes were seen to influence ionospheric and equatorial electric fields, and the associated plasma convection, during a substorm.

Kaufmann, R.L.; Larson, D.J. (Univ. of New Hampshire, Durham (USA))

1989-11-01

129

Electrohydrodynamics of a drop under nonaxisymmetric electric fields.  

PubMed

We consider the electrohydrodynamics of a spherical drop in a nonaxisymmetric electric field, which can be approximated by the sum of a uniform field and a linear straining field. We obtain the analytic solution of the three-dimensional flow fields inside and outside a drop for the Stokes flow regime by using Lamb's general solution and the leaky dielectric model. With the analytic solution, the dielectrophoretic migration velocity of a drop is obtained as a function of the type and the frequency of the imposed electric field. The direction of drop motion is found to be parallel to the dielectrophoretic force. The analytic solution is also used to investigate the characteristics of the interfacial flow under various nonaxisymmetric electric fields. While investigating the interfacial flow, we find a surface vortex structure under certain nonaxisymmetric electric fields, which is found to be related to the chaotic mixing inside the drop. Finally, we consider the chaotic features of three-dimensional flows inside the drop under static nonaxisymmetric electric fields. PMID:12957591

Im, Do Jin; Kang, In Seok

2003-10-01

130

Measurements of Electric Fields in Thunderclouds  

Microsoft Academic Search

A series of measurements of electric fields inside active thunderclouds in central New Mexico with instrumented rockets shows that very intense fields (up to 4 X 105 V\\/m) do exist, although they are rare. In a tabulation of the peak values of the electric field along each trajectory, 4.3 X 104 V\\/m is the median value. Peak values greater than

William P. Winn; G. W. Schwede; C. B. Moore

1974-01-01

131

DREIDING: A generic force field for molecular simulations  

Microsoft Academic Search

The authors report the parameters for a new generic force field, DREIDING, that they find useful for predicting structures and dynamics of organic, biological, and main-group inorganic molecules. The philosophy in DREIDING is to use general force constants and geometry parameters based on simple hybridization considerations rather than individual force constants and geometric parameters that depend on the particular combination

Stephen L. Mayo; Barry D. Olafson; Goddard Wa III

1990-01-01

132

Thin film transistors fabricated by evaporating pentacene under electric field  

NASA Astrophysics Data System (ADS)

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

Mandal, Tapendu; Garg, Ashish; Deepak

2013-10-01

133

Piezoresistive cantilevers and measurement system for characterizing low force electrical contacts  

Microsoft Academic Search

The continued miniaturization of integrated circuits (ICs), interconnects, relays, and packaging critically depends on the electrical properties of low force electrical contacts. This paper presents the design, fabrication, and characterization a micro-mechanical force sensor integrated with a four-wire electrical contact characterization capability to evaluate low force and small area electrical contacts comprised of thin films. The sensor consists of a

Beth L. Pruitt; Thomas W. Kenny

2003-01-01

134

Ionization induced by strong electromagnetic field in low dimensional systems bound by short range forces  

NASA Astrophysics Data System (ADS)

Ionization processes for a two dimensional quantum dot subjected to combined electrostatic and alternating electric fields of the same direction are studied using quantum mechanical methods. We derive analytical equations for the ionization probability in dependence on characteristic parameters of the system for both extreme cases of a constant electric field and of a linearly polarized electromagnetic wave. The ionization probabilities for a superposition of dc and low frequency ac electric fields of the same direction are calculated. The impulse distribution of ionization probability for a system bound by short range forces is found for a superposition of constant and alternating fields. The total probability for this process per unit of time is derived within exponential accuracy. For the first time the influence of alternating electric field on electron tunneling probability induced by an electrostatic field is studied taking into account the pre-exponential term.

Eminov, P. A.

2013-10-01

135

Propagation of Quantum Walks in Electric Fields  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

136

FORCE FIELD DEVELOPMENT FOR SIMULATIONS OF CONDENSED PHASES  

Microsoft Academic Search

The focus of this review is on development of force fields for simulations of technologically important properties of fluids and materials. Of particular interest are models that can reproduce thermodynamic and transport properties over a broad range of temperatures and densities. Most existing force fields have been optimized to the configurational properties of isolated molecules and thermodynamic or structural properties

A. Z. Panagiotopoulos

137

Chapter 1 Considerations for Lipid Force Field Development  

Microsoft Academic Search

The underlying approach to development of the CHARMM lipid force field, and the current ab initio and molecular dynamics methods for optimization of each term are reviewed. Results from the recent revision of the alkane force field and new results for esters illustrate the dependence of torsional surfaces on level of theory and basis set, and how changes in the

Jeffery B. Klauda; Richard M. Venable; Alexander D. MacKerell; Richard W. Pastor

2008-01-01

138

Empirical force fields for biological macromolecules: Overview and issues  

Microsoft Academic Search

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

Alexander D. MacKerell Jr.

2004-01-01

139

Magnetospheric observation of large sub-auroral electric fields  

SciTech Connect

An example of large sub-auroral poleward electric fields, similar to those observed on OGO-6, S3-2 and AE-C (recently referred to as SAID) has been found in the magnetosphere near L = 4 and 2300 MLT using ISEE-1 electric field data. The event is located adjacent to and outside the plasmapause and occurs 1 1/2 hours into a substorm. The event is accompanied by a significant penetration of the convection electric field inside the plasmasphere. Data from similar regions on the next orbit occurring near the beginning of a substorm did not exhibit these effects. Recent theoretical models predict SAID to occur in the trough regions, where substorm dynamics force currents to flow in regions of low conductivity: These models provide a first-order interpretation of this phenomena; however, the overall picture is more complex.

Maynard, N.C.; Aggson, T.L.; Heppner, J.P.

1980-11-01

140

Dynamics of water droplets breakup in electric fields  

SciTech Connect

In this paper the authors present an experimental and analytical study of the deformations and breakup of large water droplets that are approximately 1.4 cm in diameter, generated in microgravity, and subjected to an electric field. The deformations were recorded on films taken with a high-speed camera. The films show that under the electric field forces, the droplet extends along the direction of the electric field, forms Taylor cones at the elongated ends, and starts to eject several very small droplets form the tips of the cones before the entire mass breaks up in two or three droplets. The mathematical analysis and computer simulation presented in the paper show a successful reproduction of the various stages of the deformation process in time up to the formation of the Taylor cones.

Inculet, I.I. (Electrical Engineering Dept., Univ. of Western Ontario, London N6A 5B9 (Canada)); Floryan, J.M. (Mechanical Engineering Dept., Univ. of Western Ontario, London N6A 5B9 (Canada)); Haywood, R.J. (Waterloo Univ., ON (Canada). Dept. of Mechanical Engineering)

1992-10-01

141

Nonlinear cell response to strong electric fields  

NASA Astrophysics Data System (ADS)

The response of living cells to externally applied electric fields is of widespread interest. In particular, the intensification of electric fields across cell membranes is believed to be responsible, through membrane rupture and reversible membrane breakdown processes, for certain types of tissue damage in electrical trauma cases which cannot be attributed to Joule heating. Large elongated cells such as skeletal muscle fibres are particularly vulnerable to such damage. Previous theoretical studies of field intensification across cell membranes in such cells have assumed the membrane current to be linear in the applied field (Ohmic membrane conductivity) and were limited to sinusoidal applied fields. In this paper, we investigate a simple model of a long cylindrical cell, corresponding to nerve or skeletal muscle cells. Employing the electroquasistatic approximation, a system of coupled first-order differential equations for the membrane electric field is derived which incorporates arbitrary time dependence in the external field and nonlinear membrane response (non-Ohmic conductivity). The behaviour of this model is investigated for a variety of applied fields in both the linear and highly nonlinear regimes. We find that peak membrane fields predicted by the nonlinear model are approximately twice as intense, for low-frequency electrical trauma conditions, as those of the linear theory.

Bardos, D. C.; Thompson, C. J.; Yang, Y. S.; Joyner, K. H.

2000-07-01

142

Air Force Research Laboratory high power electric propulsion technology development  

Microsoft Academic Search

Space solar power generation systems have a significant impact on Electric Propulsion (EP) technology development.1,2,3 Recent advances in solar cell, deployment, and concentrator hardware have led to significant reductions in component mass, thereby decreasing power generation system specific mass. Combined with maneuvering requirements for Air Force and DoD missions of interest, propulsive requirements emerge that provide direction for technology investments.

Daniel L. Brown; Brian E. Beal; James M. Haas

2010-01-01

143

Electric Field Measuring and Display System.  

National Technical Information Service (NTIS)

An apparatus is described for monitoring the electric fields of cloud formations within a particular area. It utilizes capacitor plates that are alternately shielded from the clouds for generating an alternating signal corresponding to the intensity of th...

R. J. Wojtasinski D. D. Lovall

1974-01-01

144

Electrostatic Filters Generated by Electric Fields.  

National Technical Information Service (NTIS)

The 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 much higher efficiency and signific...

W. Bergman H. Hebard R. Taylor B. Lum

1979-01-01

145

Tendon Fibroplasia Induction by Exogenous Electrical Fields.  

National Technical Information Service (NTIS)

A parametric study is being undertaken of the effects of extra low frequency (ELF) conductive electric fields on chicken tendon explant fibroplasia, collagen synthesis and oriented migration. Independent variables are: pulse repetition rate, pulse duratio...

S. F. Cleary L. M. Liu R. Diegelmann

1986-01-01

146

High electrical field effects on cell membranes  

Microsoft Academic Search

Electrical charging of lipid membranes causes electroporation with sharp membrane conductance increases. Several recent observations, especially at very high field strength, are not compatible with the simple electroporation picture. Here we present several relevant experiments on cell electrical responses to very high external voltages. We hypothesize that, not only are aqueous pores created within the lipid membranes, but that nanoscale

U. Pliquett; R. P. Joshi; V. Sridhara; K. H. Schoenbach

2007-01-01

147

Field Emitter Cathodes and Electric Propulsion Systems  

Microsoft Academic Search

Replacing hollow and filament cathodes with field emitter (FE) cathodes could significantly improve the scalability, power, and performance of some meso- and microscale Electric Propulsion (EP) systems. This article discusses the motivation and challenges of integrating of FE and Electric Propulsion systems. The demands on cathode performance and lifetime and the propulsion system environments are described in this article. The

Colleen M. Marrese; James E. Polk; Juergen Mueller

2000-01-01

148

Towards a force field based on density fitting  

NASA Astrophysics Data System (ADS)

Total intermolecular interaction energies are determined with a first version of the Gaussian electrostatic model (GEM-0), a force field based on a density fitting approach using s-type Gaussian functions. The total interaction energy is computed in the spirit of the sum of interacting fragment ab initio (SIBFA) force field by separately evaluating each one of its components: electrostatic (Coulomb), exchange repulsion, polarization, and charge transfer intermolecular interaction energies, in order to reproduce reference constrained space orbital variation (CSOV) energy decomposition calculations at the B3LYP/aug-cc-pVTZ level. The use of an auxiliary basis set restricted to spherical Gaussian functions facilitates the rotation of the fitted densities of rigid fragments and enables a fast and accurate density fitting evaluation of Coulomb and exchange-repulsion energy, the latter using the overlap model introduced by Wheatley and Price [Mol. Phys. 69, 50718 (1990)]. The SIBFA energy scheme for polarization and charge transfer has been implemented using the electric fields and electrostatic potentials generated by the fitted densities. GEM-0 has been tested on ten stationary points of the water dimer potential energy surface and on three water clusters (n=16,20,64). The results show very good agreement with density functional theory calculations, reproducing the individual CSOV energy contributions for a given interaction as well as the B3LYP total interaction energies with errors below kBT at room temperature. Preliminary results for Coulomb and exchange-repulsion energies of metal cation complexes and coupled cluster singles doubles electron densities are discussed.

Piquemal, Jean-Philip; Cisneros, G. Andrés; Reinhardt, Peter; Gresh, Nohad; Darden, Thomas A.

2006-03-01

149

Towards a force field based on density fitting.  

PubMed

Total intermolecular interaction energies are determined with a first version of the Gaussian electrostatic model (GEM-0), a force field based on a density fitting approach using s-type Gaussian functions. The total interaction energy is computed in the spirit of the sum of interacting fragment ab initio (SIBFA) force field by separately evaluating each one of its components: electrostatic (Coulomb), exchange repulsion, polarization, and charge transfer intermolecular interaction energies, in order to reproduce reference constrained space orbital variation (CSOV) energy decomposition calculations at the B3LYP/aug-cc-pVTZ level. The use of an auxiliary basis set restricted to spherical Gaussian functions facilitates the rotation of the fitted densities of rigid fragments and enables a fast and accurate density fitting evaluation of Coulomb and exchange-repulsion energy, the latter using the overlap model introduced by Wheatley and Price [Mol. Phys. 69, 50718 (1990)]. The SIBFA energy scheme for polarization and charge transfer has been implemented using the electric fields and electrostatic potentials generated by the fitted densities. GEM-0 has been tested on ten stationary points of the water dimer potential energy surface and on three water clusters (n = 16,20,64). The results show very good agreement with density functional theory calculations, reproducing the individual CSOV energy contributions for a given interaction as well as the B3LYP total interaction energies with errors below kBT at room temperature. Preliminary results for Coulomb and exchange-repulsion energies of metal cation complexes and coupled cluster singles doubles electron densities are discussed. PMID:16542062

Piquemal, Jean-Philip; Cisneros, G Andrés; Reinhardt, Peter; Gresh, Nohad; Darden, Thomas A

2006-03-14

150

Towards a force field based on density fitting  

PubMed Central

Total intermolecular interaction energies are determined with a first version of the Gaussian electrostatic model (GEM-0), a force field based on a density fitting approach using s-type Gaussian functions. The total interaction energy is computed in the spirit of the sum of interacting fragment ab initio (SIBFA) force field by separately evaluating each one of its components: electrostatic (Coulomb), exchange repulsion, polarization, and charge transfer intermolecular interaction energies, in order to reproduce reference constrained space orbital variation (CSOV) energy decomposition calculations at the B3LYP/aug-cc-pVTZ level. The use of an auxiliary basis set restricted to spherical Gaussian functions facilitates the rotation of the fitted densities of rigid fragments and enables a fast and accurate density fitting evaluation of Coulomb and exchange-repulsion energy, the latter using the overlap model introduced by Wheatley and Price [Mol. Phys. 69, 50718 (1990)]. The SIBFA energy scheme for polarization and charge transfer has been implemented using the electric fields and electrostatic potentials generated by the fitted densities. GEM-0 has been tested on ten stationary points of the water dimer potential energy surface and on three water clusters (n=16,20,64). The results show very good agreement with density functional theory calculations, reproducing the individual CSOV energy contributions for a given interaction as well as the B3LYP total interaction energies with errors below kBT at room temperature. Preliminary results for Coulomb and exchange-repulsion energies of metal cation complexes and coupled cluster singles doubles electron densities are discussed.

Piquemal, Jean-Philip; Cisneros, G. Andres; Reinhardt, Peter; Gresh, Nohad; Darden, Thomas A.

2007-01-01

151

Sensitivity enhancements to photonic electric field sensor  

Microsoft Academic Search

This paper describes an electrode-less, all-optical, wideband electric field sensor fabricated in an electro-optic lithium niobate substrate. The sensor component is an integrated optic Mach-Zehnder interferometer. The electric field sensor uses the electro-optic properties of lithium niobate to modulate the phase of the light propagating in each arm of the Mach-Zehnder interferometer. The phase modulated light is then converted to

Sriram S. Sriram; Stuart A. Kingsley

2004-01-01

152

Lessons Learned, Headquarters, I Field Force Vietnam.  

National Technical Information Service (NTIS)

During February, March, and April 1968 the United States and Free World Military Forces and the Army Republic of Vietnam (ARVN) continued operations in the 2 Corps Tactical Zone (2 CTZ); in the west along the Cambodian/Laotion/Republic of Vietnam (RVN) bo...

1968-01-01

153

Parallel Microassembly with Electrostatic Force Fields  

Microsoft Academic Search

Assembly is a fundamental issue in the volume productionof products that include microscopic (submillimeter)parts. These parts are often fabricated in parallelat high density but must then be assembled intopatterns with lower spatial density. In this paper wepropose a new approach to microassembly using 1) ultrasonicvibration to eliminate friction and adhesion,and 2) electrostatic forces to position and align partsin parallel. We

Karl-friedrich Böhringer; Kenneth Y. Goldberg; Michael Cohn; Roger Howe; Al Pisano

1998-01-01

154

Lessons Learned, Headquarters, I Field Force Vietnam.  

National Technical Information Service (NTIS)

In November, December 1966 and January 1967, United States and Free World Military Forces (FWMAF) with 41 maneuver battalions, 23 US and 18 ROK, supported by 23 artillery battalions, and Army Vietnam (ARVN) with 30 maneuver battalions supported by 6 artil...

1967-01-01

155

Electric field gradient focusing in microchannels with embedded bipolar electrode.  

PubMed

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

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

2009-04-01

156

Fabrication and Characterization of Electric Field - Induced Resistive Sensor at the end of Scanning Probe Tip.  

National Technical Information Service (NTIS)

Fabrication and Characterization of Electrical Field were investigated to develop induced Resistive Sensor at the end of Scanning Probe Tip. The measurement and visual observation of doping profile were performed on Kelvin Prove Force Microscopy (KPFM) & ...

H. Shin

2006-01-01

157

Liquid crystal fiber optic electric field probe  

NASA Astrophysics Data System (ADS)

Polymer dispersed liquid crystal inserted between two multimode optical fiber end faces forms the basis of an electric field probe. This probe has an active volume of about 0.001 mm3 and approximates a point measurement. The linear relation between detector output and electric field in the 600-800 V/cm range is adequate for most electric power distribution systems. As the contrast ratio of this transducer is large, it can be used as an on-off detector for high voltage equipment.

Lacquet, Beatrys M.; Swart, Pieter L.; Spammer, Stephanus J.

1995-09-01

158

Detection of electric field around field-reversed configuration plasma  

SciTech Connect

Electric-field probes consisting of copper plates are developed to measure electric fields in a vacuum region around a plasma. The probes detect oscillating electric fields with a maximum strength of approximately 100 V/m through a discharge. Reproducible signals from the probes are obtained with an unstable phase dominated by a rotational instability. It is found that the azimuthal structure of the electric field can be explained by the sum of an n=2 mode charge distribution and a convex-surface electron distribution on the deformed separatrix at the unstable phase. The former distribution agrees with that anticipated from the diamagnetic drift motions of plasma when the rotational instability occurs. The latter distribution suggests that an electron-rich plasma covers the separatrix.

Ikeyama, Taeko; Hiroi, Masanori; Nogi, Yasuyuki [College of Science and Technology, Nihon University, Tokyo 101-8308 (Japan); Ohkuma, Yasunori [College of Industrial Technology, Nihon University, Chiba 275-8576 (Japan)

2010-01-15

159

Hormetic Electric Field Theory of Pattern Formation  

PubMed Central

The hormetic morphogen theory of curvature (Fosslien 2009) proposes that hormetic morphogen concentration gradients modulate the synthesis of adenosine triphosphate (ATP) by cells along the gradients (field cells) and thus regulate their proliferation and induce curvature such as vascular wall curvature; however, it is unclear whether such morphogen gradients can also determine the histological pattern of the walls. Here, I propose that the ATP gradients modulate export of H+ by vacuolar H+-ATPase (V-ATPase) located on the surface of field cells and generate extracellular ion concentration gradients, ion currents and electrical fields along the paths of morphogen gradients. In vitro, electrical fields can induce directional migration and elongation of vascular cells and align the cells with their long axis perpendicular to electrical field vectors (Bai et al. 2004). I suggest that likewise, in vivo vascular transmural electrical fields induced by hormetic morphogen concentration gradients can modulate cell shape i.e. cell elongation and cell curvature, and determine cell orientation. Moreover, I suggest that the electrical fields can modulate bidirectional cell migration and cell sorting via dynamic hormetic galvanotaxis analogous to in vitro isoelectric focusing in proton gradients, thus, hormetic morphogen gradients can determine the curvature of vessel walls and their histological patterns.

Fosslien, Egil

2010-01-01

160

Electric/magnetic field sensor  

DOEpatents

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

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

2009-01-27

161

Structural equilibrium of DNA represented with different force fields.  

PubMed

We have recently indicated preliminary evidence of different equilibrium average structures with the CHARMM and AMBER force fields in explicit solvent molecular dynamics simulations on the DNA duplex d(C5T5) . d(A5G5) (Feig, M. and B.M. Pettitt, 1997, Experiment vs. Force Fields: DNA conformation from molecular dynamics simulations. J. Phys. Chem. B. (101:7361-7363). This paper presents a detailed comparison of DNA structure and dynamics for both force fields from extended simulation times of 10 ns each. Average structures display an A-DNA base geometry with the CHARMM force field and a base geometry that is intermediate between A- and B-DNA with the AMBER force field. The backbone assumes B form on both strands with the AMBER force field, while the CHARMM force field produces heterogeneous structures with the purine strand in A form and the pyrimidine strand in dynamical equilibrium between A and B conformations. The results compare well with experimental data for the cytosine/guanine part but fail to fully reproduce an overall B conformation in the thymine/adenine tract expected from crystallographic data, particularly with the CHARMM force field. Fluctuations between A and B conformations are observed on the nanosecond time scale in both simulations, particularly with the AMBER force field. Different dynamical behavior during the first 4 ns indicates that convergence times of several nanoseconds are necessary to fully establish a dynamical equilibrium in all structural quantities on the time scale of the simulations presented here. PMID:9649374

Feig, M; Pettitt, B M

1998-07-01

162

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

163

Biological effects of electric fields: EPRI's role  

SciTech Connect

Since 1973 the Electric Power Research Institute (EPRI) has supported research to evaluate the biological effects which may result from exposure to electric fields produced by AC overhead transmission lines; more recently, EPRI has also begun DC research. Through 1981 EPRI will have expended $8.7M on these efforts. Ongoing AC projects are studying a variety of lifeforms exposed to electric fields; these include humans, miniature swine, rats, honeybees, chick embryos, and crops. The status of these projects is discussed. The DC program has not as yet produced data. These studies will add to the current data base so as to enable a more complete assessment of health risks which may be associated with exposure to electric fields at power frequencies.

Kavet, R.

1982-07-01

164

Stability of Spherical Vesicles in Electric Fields  

PubMed Central

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

2010-01-01

165

Influence of electric current on the Casimir forces between graphene sheets  

NASA Astrophysics Data System (ADS)

We investigate the dependence of the thermal Casimir force and the Casimir friction force between two graphene sheets on the drift velocity of the electrons in one graphene sheet. We show that the drift motion produces a measurable change of the thermal Casimir force due to the Doppler effect. The thermal Casimir force as well as the Casimir friction are strongly enhanced in the case of resonant photon tunneling when the energy of the emitted photon coincides with the energy of electron-hole pair excitations. In the case of resonant photon tunneling, even for temperatures above room temperature the Casimir friction is dominated by quantum friction due to quantum fluctuations. Quantum friction can be detected in frictional drag experiment between graphene sheets for high electric field.

Volokitin, A. I.; Persson, B. N. J.

2013-07-01

166

Is the solar chromospheric magnetic field force-free?  

NASA Astrophysics Data System (ADS)

We use observations of the Na I lambda 5896 spectral line, made with the Stokes Polarimeter at Mees Solar Observatory, to measure the chromospheric vector magnetic field in NOAA active region 7216. We compute the magnetic field from observations of the Stokes parameters at six wavelengths within this spectral line using a derivative method and calculate the height dependence of the net Lorentz force in the photosphere and low chromosphere. We conclude that the magnetic field is not force-free in the photosphere, but becomes force-free roughly 400 km above the photosphere.

Metcalf, Thomas R.; Jiao, Litao; McClymont, Alexander N.; Canfield, Richard C.; Uitenbroek, Han

1995-01-01

167

Combined shear force and near-field scanning optical microscopy  

NASA Astrophysics Data System (ADS)

A distance regulation method has been developed to enhance the reliability, versatility, and ease of use of near-field scanning optical microscopy (NSOM). The method relies on the detection of shear forces between the end of a near-field probe and the sample of interest. The system can be used solely for distance regulation in NSOM, for simultaneous shear force and near-field imaging, or for shear force microscopy alone. In the latter case, uncoated optical fiber probes are found to yield images with consistently high resolution.

Betzig, E.; Finn, P. L.; Weiner, J. S.

1992-05-01

168

New-generation amber united-atom force field.  

PubMed

We have developed a new-generation Amber united-atom force field for simulations involving highly demanding conformational sampling such as protein folding and protein-protein binding. In the new united-atom force field, all hydrogens on aliphatic carbons in all amino acids are united with carbons except those on Calpha. Our choice of explicit representation of all protein backbone atoms aims at minimizing perturbation to protein backbone conformational distributions and to simplify development of backbone torsion terms. Tests with dipeptides and solvated proteins show that our goal is achieved quite successfully. The new united-atom force field uses the same new RESP charging scheme based on B3LYP/cc-pVTZ//HF/6-31g** quantum mechanical calculations in the PCM continuum solvent as that in the Duan et al. force field. van der Waals parameters are empirically refitted starting from published values with respect to experimental solvation free energies of amino acid side-chain analogues. The suitability of mixing new point charges and van der Waals parameters with existing Amber covalent terms is tested on alanine dipeptide and is found to be reasonable. Parameters for all new torsion terms are refitted based on the new point charges and the van der Waals parameters. Molecular dynamics simulations of three small globular proteins in the explicit TIP3P solvent are performed to test the overall stability and accuracy of the new united-atom force field. Good agreements between the united-atom force field and the Duan et al. all-atom force field for both backbone and side-chain conformations are observed. In addition, the per-step efficiency of the new united-atom force field is demonstrated for simulations in the implicit generalized Born solvent. A speedup around two is observed over the Duan et al. all-atom force field for the three tested small proteins. Finally, the efficiency gain of the new united-atom force field in conformational sampling is further demonstrated with a well-known toy protein folding system, an 18 residue polyalanine in distance-dependent dielectric. The new united-atom force field is at least a factor of 200 more efficient than the Duan et al. all-atom force field for ab initio folding of the tested peptide. PMID:16805629

Yang, Lijiang; Tan, Chun-Hu; Hsieh, Meng-Juei; Wang, Junmei; Duan, Yong; Cieplak, Piotr; Caldwell, James; Kollman, Peter A; Luo, Ray

2006-07-01

169

Physlets Tour 8: Plotting Electric Fields  

NSDL National Science Digital Library

The panel on the left displays an equipotential plot. The contours represent points at the exact same potential. Draw the electric field lines for this potential by dragging the pencil (at its tip) after clicking the "draw on" button. After you have drawn your lines, determine which field best corresponds to your potential plot.

Christian, Wolfgang; Belloni, Mario

2006-01-13

170

Spiky electric fields in the magnetotail  

Microsoft Academic Search

Large-amplitude spiky electric fields which have been proposed to provide energization and heating of particles have been observed in many regions of the magnetosphere, including the bow shock, auroral zone, and plasma sheet boundary. We extend previous statistical studies of such fields in the magnetotail (which were limited to <~22RE) to cover the region explored by the Geotail satellite. Results

T. Streed; C. Cattell; F. Mozer; S. Kokubun; K. Tsuruda

2001-01-01

171

Nonlinear Force-Free Reconstruction of the Global Solar Magnetic Field: Methodology  

NASA Astrophysics Data System (ADS)

We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary surface on which only the distribution of the normal magnetic field component is given. The method relies on the theory of force-free electrodynamics and applies directly to the reconstruction of the solar coronal magnetic field for a given distribution of the photospheric radial field component. The method works as follows: we start with any initial magnetostatic global field configuration ( e.g. zero, dipole), and along the boundary surface we create an evolving distribution of tangential (horizontal) electric fields that, via Faraday's equation, give rise to a respective normal-field distribution approaching asymptotically the target distribution. At the same time, these electric fields are used as boundary condition to numerically evolve the resulting electromagnetic field above the boundary surface, modeled as a thin ideal plasma with non-reflecting, perfectly absorbing outer boundaries. The simulation relaxes to a nonlinear force-free configuration that satisfies the given normal-field distribution on the boundary. This is different from existing methods relying on a fixed boundary condition - the boundary evolves toward the a priori given one, at the same time evolving the three-dimensional field solution above it. Moreover, this is the first time that a nonlinear force-free solution is reached by using only the normal field component on the boundary. This solution is not unique, but it depends on the initial magnetic field configuration and on the evolutionary course along the boundary surface. To our knowledge, this is the first time that the formalism of force-free electrodynamics, used very successfully in other astrophysical contexts, is applied to the global solar magnetic field.

Contopoulos, I.; Kalapotharakos, C.; Georgoulis, M. K.

2011-04-01

172

Nonlinear force-free reconstruction of the global solar magnetic field  

NASA Astrophysics Data System (ADS)

We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary surface on which only the distribution of the normal magnetic field component is given. The method relies on the theory of force-free electrodynamics and applies directly to the reconstruction of the solar coronal magnetic field for a given distribution of the photospheric radial field component. The method works as follows: we start with any initial magnetostatic global field configuration (e.g. zero, dipole), and along the boundary surface we create an evolving distribution of tangential (horizontal) electric fields that, via Faraday's equation, give rise to a respective normal field distribution approaching asymptotically the target distribution. At the same time, these electric fields are used as boundary condition to numerically evolve the resulting electromagnetic field above the boundary surface, modeled as a thin ideal plasma with non-reflecting, perfectly absorbing outer boundaries. The simulation relaxes to a nonlinear force-free configuration that satisfies the given normal field distribution on the boundary. This is different from existing methods relying on a fixed boundary condition - the boundary evolves toward the a priori given one, at the same time evolving the three-dimensional field solution above it. Moreover, this is the first time a nonlinear force-free solution is reached by using only the normal field component on the boundary. This solution is not unique, but depends on the initial magnetic field configuration and on the evolutionary course along the boundary surface. To our knowledge, this is the first time that the formalism of force-free electrodynamics, used very successfully in other astrophysical contexts, is applied to the global solar magnetic field.

Contopoulos, I.

2012-01-01

173

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

174

Control of the Electric Field Profile in the Hall Thruster  

SciTech Connect

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

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

2000-10-05

175

Evolving Field Artillery Standard Tactical Missions for Force XXI.  

National Technical Information Service (NTIS)

This study examines the need to change the field artillery's four standard tactical missions because of the U.S. Army's evolution to Force XXI operations. Currently the field artillery organizes field artillery for combat and assigns a tactical mission (d...

N. R. Brehm

1995-01-01

176

Electric Fields Produced by Florida Thunderstorms  

Microsoft Academic Search

Electric fields produced by air mass thunderstorms have been recorded at 25 field mill sites at the NASA Kennedy Space Center (KSC) during the summers of 1975 and 1976. Time- and area-averaged fields produced by individual storms are typically -0.8 to -2.1 kV m - during periods of intense lightning activity and usually 2-4 times larger (-2.3 to -4.3 kV

John M. Livingston; E. Philip Krider

1978-01-01

177

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

178

Kelvin probe force microscopy using near-field optical tips  

Microsoft Academic Search

We report on the use of near-field optical force sensors for Kelvin probe force microscopy (KPFM) and surface potential measurements. It is shown that a very good potential sensitivity of less than 5 mV can be obtained using such tips. In addition, it is found that the contact potential difference measured using these tips is independent of the scanning height,

R. Shikler; Y Rosenwaks

2000-01-01

179

Body-force stress fields defined by caustic rosettes  

Microsoft Academic Search

The method of reflected caustics was extended to the study of elastic fields due to body forces. It was shown that gage perforations create caustics under the influence of body forces which are different in shape and size than those developed in usual cases. The elastic solution of a perforated strip under the influence of an external loadp and body

P. S. Theocaris

1988-01-01

180

Acculturation in Acquired Organizations: A Force-Field Perspective  

Microsoft Academic Search

The acculturation process involved when one organization is acquired by another, and the two organizational cultures merge, has not been adequately conceptualized in the strategic management literature. It is argued here that the acculturation process can be more fully understood by utilizing Lewin's (1951) force-field approach. In addition, major forces of cultural differentiation and organizational integration are identified. It is

Priscilla M. Elsass; John F. Veiga

1994-01-01

181

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

DOEpatents

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

Stevens, F.J.

1990-03-15

182

Vertical Lorentz Force and Cross-Field Currents in the Photospheric Magnetic Fields of Solar Active Regions  

NASA Astrophysics Data System (ADS)

We demonstrate that the vertical Lorentz force and a corresponding lower limit of the cross-field electric current density can be calculated from vector magnetograms of solar active regions obtained at a single height in the solar atmosphere, provided that the vertical gradient of the magnetic field strength is known at this height. We use a predicted vertical magnetic field gradient derived from a previous analysis. By testing various force-free solutions, we find that the numerical accuracy of our method is satisfactory. Applying the method to active region photospheric vector magnetograms, we find vertical Lorentz forces ranging from several hundredths to a few tenths of the typical photospheric gravitational force, and typical cross-field current densities up to several times 10 mA m-2. The typical vertical current density is found to be 2-3 times smaller, on the order of 10-15 mA m-2. These differences are above the associated uncertainties. The values of the cross-field currents decrease in an averaged vector magnetogram, but the ratio of the cross-field to the vertical current density increases, also above the uncertainties. We conclude that the photospheric active region magnetic fields are not force-free, contrary to the conjectures of some recent studies.

Georgoulis, Manolis K.; LaBonte, Barry J.

2004-11-01

183

Molecular dynamics simulations of methane hydrate using polarizable force fields  

SciTech Connect

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

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

2007-06-14

184

Comparison of protein force fields for molecular dynamics simulations.  

PubMed

In the context of molecular dynamics simulations of proteins, the term "force field" refers to the combination of a mathematical formula and associated parameters that are used to describe the energy of the protein as a function of its atomic coordinates. In this review, we describe the functional forms and parameterization protocols of the widely used biomolecular force fields Amber, CHARMM, GROMOS, and OPLS-AA. We also summarize the ability of various readily available noncommercial molecular dynamics packages to perform simulations using these force fields, as well as to use modern methods for the generation of constant-temperature, constant-pressure ensembles and to treat long-range interactions. Finally, we finish with a discussion of the ability of these force fields to support the modeling of proteins in conjunction with nucleic acids, lipids, carbohydrates, and/or small molecules. PMID:18446282

Guvench, Olgun; MacKerell, Alexander D

2008-01-01

185

Forces in Toroidal Magnetic Field Coils on the Current Unbalance.  

National Technical Information Service (NTIS)

Calculation values of mechanical loadings are presented, which influence the elements of construction and separate coils of the longitudinal field of the tokamak type device. These forces appear at the unbalance of currents neighbouring sectionized parts ...

A. S. Simakov

1980-01-01

186

Correlated High Speed Video, Medium Range Electric-Field, and Magnetic-field observations of Sprites  

NASA Astrophysics Data System (ADS)

A high-speed (10,000-12,000 frames/sec) telescopic video observing program was conducted at Langmuir Laboratory in New Mexico by a joint group from the University of Alaska and the US Air Force Academy. The group recorded 25 sprites 300-450 km from the lab (generally due East) on the nights 7/13 through 7/15/2010. On 7/13 and 7/15, the Langmuir Electric Field Array (LEFA) acquired electric field-change data simultaneous to the video observations. LEFA currently comprises eight slow-antenna stations collecting electric field data sampled 50,000 times per second and high-passed at roughly one Hz. Three stations of the electric-field array were operating during the sprite studies. These stations were roughly equally spaced on an East-West baseline with a total length of 25 km. The closest sprite of the set was 275 km from the nearest slow-antenna. For nine sprites that have been checked so far against electric field records, an electric field-change precursor was seen in seven cases. The electric field precursor corresponds to a positive cloud-to-ground (CG) flash, as expected. For these same seven cases, NLDN data showed positive CG flashes typically within 2 millisec of the LEFA-observed field-change. Scrutiny of the electric field-change peak measured by the LEFA discerns that it preceded the first video frame on which sprite activity was visible by 3.6 millisec on average. An initial analysis shows no recognizable feature in the electric field-change record that is coincident (with appropriate propagation delays) with the optically observed sprite activity. The electric field-change appears to be entirely due to the +CG that precedes the sprite. In addition to the electric field data, magnetic field data from more distant stations operated by the Duke University group is being analyzed to get a more complete picture of the sprite-producing flash.

Sonnenfeld, R. G.; Kanmae, T.; Stenbaek-Nielsen, H. C.; McHarg, M. G.; Li, J.; Lu, G.; Cummer, S. A.; Hager, W. W.; Haaland, R. K.

2010-12-01

187

Constructing ab initio force fields for molecular dynamics simulations  

Microsoft Academic Search

We explore and discuss several important issues concerning the derivation of many-body force fields from ab initio quantum chemical data. In particular, we seek a general methodology for constructing ab initio force fields that are “chemically accurate” and are computationally efficient for large-scale molecular dynamics simulations. We investigate two approaches for modeling many-body interactions in extended molecular systems. The interactions

Yi-Ping Liu; Kyungsun Kim; B. J. Berne; Richard A. Friesner; Steven W. Rick

1998-01-01

188

Constructing ab initio force fields for molecular dynamics simulations  

Microsoft Academic Search

We explore and discuss several important issues concerning the derivation of many-body force fields from ab initio quantum chemical data. In particular, we seek a general methodology for constructing ab initio force fields that are ``chemically accurate'' and are computationally efficient for large-scale molecular dynamics simulations. We investigate two approaches for modeling many-body interactions in extended molecular systems. The interactions

Yi-Ping Liu; Kyungsun Kim; B. J. Berne; Richard A. Friesner; Steven W. Rick

1998-01-01

189

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

190

Polarizable and Nonpolarizable Force Fields for Alkyl Nitrates  

Microsoft Academic Search

Quantum-chemistry-based many-body polarizable and two-body nonpolarizable atomic force fields were developed for alkyl nitrate liquids and pentaerythritol tetranitrate (PETN) crystal. Bonding, bending, and torsional parameters, partial charges, and atomic polarizabilities for the polarizable force field were determined from gas-phase quantum chemistry calculations for alkyl nitrate oligomers and PETN performed at the MP2\\/ aug-cc-pvDz level of theory. Partial charges for the

Oleg Borodin; Grant D. Smith; Thomas D. Sewell; Dmitry Bedrov

2008-01-01

191

Structural Equilibrium of DNA Represented with Different Force Fields  

Microsoft Academic Search

We have recently indicated preliminary evidence of different equilibrium average structures with the CHARMM and AMBER force fields in explicit solvent molecular dynamics simulations on the DNA duplex d(C5T5) · d(A5G5) (Feig, M. and B. M. Pettitt, 1997, Experiment vs. Force fields: DNA conformation from molecular dynamics simulations. J. Phys. Chem. B. 101:7361–7363). This paper presents a detailed comparison of

Michael Feig; B. Montgomery Pettitt

1998-01-01

192

MATCH: An Atom- Typing Toolset for Molecular Mechanics Force Fields  

PubMed Central

We introduce a toolset of program libraries collectively titled MATCH (Multipurpose Atom-Typer for CHARMM) for the automated assignment of atom types and force field parameters for molecular mechanics simulation of organic molecules. The toolset includes utilities for the conversion from multiple chemical structure file formats into a molecular graph. A general chemical pattern-matching engine using this graph has been implemented whereby assignment of molecular mechanics atom types, charges and force field parameters is achieved by comparison against a customizable list of chemical fragments. While initially designed to complement the CHARMM simulation package and force fields by generating the necessary input topology and atom-type data files, MATCH can be expanded to any force field and program, and has core functionality that makes it extendable to other applications such as fragment-based property prediction. In the present work, we demonstrate the accurate construction of atomic parameters of molecules within each force field included in CHARMM36 through exhaustive cross validation studies illustrating that bond increment rules derived from one force field can be transferred to another. In addition, using leave-one-out substitution it is shown that it is also possible to substitute missing intra and intermolecular parameters with ones included in a force field to complete the parameterization of novel molecules. Finally, to demonstrate the robustness of MATCH and the coverage of chemical space offered by the recent CHARMM CGENFF force field (Vanommeslaeghe, et al., JCC., 2010, 31, 671–690), one million molecules from the PubChem database of small molecules are typed, parameterized and minimized.

Yesselman, Joseph D.; Price, Daniel J.; Knight, Jennifer L.; Brooks, Charles L.

2011-01-01

193

Tumor treatment with nanosecond pulsed electric fields  

Microsoft Academic Search

Nanosecond pulsed electric fields have demonstrated remarkable potential as tumor therapy. The application of 300-ns pulses with amplitudes of 40-50 kV\\/cm to melanomas grown in mice caused complete remission of the tumors. It is believed that the primary process that kills the tumor cells is the induction of apoptosis. Electrical models predict that for the application of shorter pulses, higher

J. F. Kolb; X. Chen; J. Zhuang; W. Ren; N. Scully; R. J. Swanson; S. J. Beebe; K. H. Schoenbach

2009-01-01

194

The Electric Field Instrument (EFI) for THEMIS  

Microsoft Academic Search

The design, performance, and on-orbit operation of the three-axis electric field instrument (EFI) for the NASA THEMIS mission\\u000a is described. The 20 radial wire boom and 10 axial stacer boom antenna systems making up the EFI sensors on the five THEMIS\\u000a spacecraft, along with their supporting electronics have been deployed and are operating successfully on-orbit without any\\u000a mechanical or electrical

J. W. Bonnell; F. S. Mozer; G. T. Delory; A. J. Hull; R. E. Ergun; C. M. Cully; V. Angelopoulos; P. R. Harvey

2008-01-01

195

Force field parameters for the simulation of modified histone tails.  

PubMed

We describe the development of force field parameters for methylated lysines and arginines, and acetylated lysine for the CHARMM all-atom force field. We also describe a CHARMM united-atom force field for modified sidechains suitable for use with fragment-based docking methods. The development of these parameters is based on results of ab initio quantum mechanics calculations of model compounds with subsequent refinement and validation by molecular mechanics and molecular dynamics simulations. The united-atom parameters are tested by fragment docking to target proteins using the MCSS procedure. The all-atom force field is validated by molecular dynamics simulations of multiple experimental structures. In both sets of calculations, the computational predictions using the force field were compared to the corresponding experimental structures. We show that the parameters yield an accurate reproduction of experimental structures. Together with the existing CHARMM force field, these parameters will enable the general modeling of post-translational modifications of histone tails. PMID:20652987

Grauffel, Cédric; Stote, Roland H; Dejaegere, Annick

2010-10-01

196

Vibrational spectrum and force field of dimethyldimethoxysilane  

SciTech Connect

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

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

1986-01-01

197

Electric field controlled emulsion phase contactor  

DOEpatents

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

Scott, Timothy C. (Knoxville, TN)

1995-01-01

198

Electric field controlled emulsion phase contactor  

DOEpatents

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

Scott, T.C.

1995-01-31

199

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

200

A transferable ab initio based force field for aqueous ions  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

201

The Electric Field Instrument (EFI) for THEMIS  

NASA Astrophysics Data System (ADS)

The design, performance, and on-orbit operation of the three-axis electric field instrument (EFI) for the NASA THEMIS mission is described. The 20 radial wire boom and 10 axial stacer boom antenna systems making up the EFI sensors on the five THEMIS spacecraft, along with their supporting electronics have been deployed and are operating successfully on-orbit without any mechanical or electrical failures since early 2007. The EFI provides for waveform and spectral three-axis measurements of the ambient electric field from DC up to 8 kHz, with a single, integral broadband channel extending up to 400 kHz. Individual sensor potentials are also measured, providing for on-board and ground-based estimation of spacecraft floating potential and high-resolution plasma density measurements. Individual antenna baselines are 50- and 40-m in the spin plane, and 6.9-m along the spin axis. The EFI has provided for critical observations supporting a clear and definitive understanding of the electrodynamics of both the boundaries of the terrestrial magnetosphere, as well as internal processes, such as relativistic particle acceleration and substorm dynamics. Such multi-point electric field observations are key for pushing forward the understanding of electrodynamics in space, in that without high-quality estimates of the electric field, the underlying electromagnetic processes involved in current sheets, reconnection, and wave-particle interactions may only be inferred, rather than measured, quantified, and used to discriminate between competing hypotheses regarding those processes.

Bonnell, J. W.; Mozer, F. S.; Delory, G. T.; Hull, A. J.; Ergun, R. E.; Cully, C. M.; Angelopoulos, V.; Harvey, P. R.

2008-12-01

202

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(Mg1/3Nb2/3)0.75Ti0.25O3 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

203

Field forced antiferroelectric-to-ferroelectric switching in modified lead zirconate titanate stannate ceramics  

Microsoft Academic Search

Electric-field-forced antiferroelectric- to-ferroelectric phase transitions in several compositions of modified lead zirconate titanate stannate antiferroelectric ceramics are studied for ultra-high-field-induced strain actuator applications. Two types of fatigue effects are observed in these ceramic compositions. In one, the fatigue effects only proceed to a limited extent and the properties may be restored by annealing above the Curie temperature, while in the

Wuyi Pan; Qiming Zhang; Amar Bhalla; Leslie E. Cross

1989-01-01

204

Students' understanding of superposition of electric fields  

NSDL National Science Digital Library

In this article an analysis of the difficulties experienced by students when applying the principle of superposition to electric fields is presented. A study of university level students in France and Sweden revealed the existence of difficulties arising out of two issues: (1) a causal interpretation of some relationships, (2) the student's need for an effect, motion of some kind, to accept the existence of a field. The links between these obstacles and a lack of a unified view on electric phenomena are discussed from a pedagogical point of view.

Rainson, Sylvie; Transtrã¶mer, G.; Viennot, Laurence

2005-10-24

205

An electric force facilitator in descending vortex tornadogenesis  

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

206

Force Field Parameter Estimation of Functional Perfluoropolyether Lubricants  

SciTech Connect

The head disk interface in hard disk drive can be considered 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 the 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

207

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

208

Force field parameter estimation of functional perfluoropolyether lubricants  

NASA Astrophysics Data System (ADS)

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, Robert; Seung Chung, Pil; Steckel, Janice A.; Jhon, Myung S.; Biegler, Lorenz T.

2011-04-01

209

Alternating magnetic field forces for satellite formation flying  

NASA Astrophysics Data System (ADS)

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 satellite 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, Stanley O.

2013-03-01

210

Earth magnetic field effects on Swarm electric field instrument  

NASA Astrophysics Data System (ADS)

Earth magnetic field effects on the particle sensors carried by the Swarm satellites are investigated using particle in cell (PIC) and test-particle modelling. In the reference frame of the spacecraft in which plasma flows at relative velocity v?, Earth magnetic field leads to an ambient electric field E?=-v?×B?, which affects the shape of particle distribution functions at the particle sensors. This in turn impacts the distribution of particle fluxes on the microchannel plate (MCP) in the ram face mounted thermal ion imagers (TIIs). Shifts in the centroid of these distributions depend on the direction and magnitude of the local magnetic field and, as such, are expected to vary periodically along the spacecraft orbit. The magnitude of these shifts is estimated quantitatively, and the effect of their variation on the calibration and interpretation of the electric field instrument (EFI) are also discussed.

Rehman, S.; Burchill, J.; Eriksson, A.; Marchand, R.

2012-12-01

211

Atomic emission spectroscopy in high electric fields  

SciTech Connect

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

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

1995-12-31

212

Trajectories in Electric and Magnetic Fields Model  

NSDL National Science Digital Library

The Trajectories in Electric and Magnetic Fields model computes a family of trajectories of charges emitted from a point source isotropically and with the same energy. These trajectories create focal points and caustic surfaces meeting the symmetry line in conical cusps. The simulation enables users to study these trajectories in both crossed and parallel magnetic fields. The user can vary the initial particle velocity and the field strengths. The Trajectories in Electric and Magnetic Fields model was developed using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. 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.

Christian, Wolfgang

2012-10-25

213

Magnetic Explosions: Role of the Inductive Electric Field  

NASA Astrophysics Data System (ADS)

Inclusion of the inductive electric field, E ind, due to the temporally changing B, in magnetic explosions is discussed, with emphasis on solar flares. Several roles played by E ind are identified: on a global scale, E ind produces the electromotive force that drives the explosion; the associated E ind × B drift is identified with the inflow of magnetic field lines into a reconnection region; the polarization current, associated with ?E ind/?t, implies a J × B force that accelerates this inflow; and the component of E 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.

2012-04-01

214

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

215

Electric field effects in multicomponent fluid lipid membranes  

SciTech Connect

A thermodynamic model of multicomponent fluid membranes under the influence of lateral forces is described. Membrane components are characterized by their effective molecular areas, molecular charges, and the set of critical demixing coefficients (differential interaction energies) between each of the different species present. This model is useful in the analysis of electric field induced concentration gradients in supported lipid bilayer membranes. It has been employed to determine the critical temperature for spontaneous lateral phase separation of a mixture of cardiolipin and phosphatidylcholine from field-induced concentration profiles of a fluorescent probe. More generally, it provides a convenient way of interpreting critical demixing effects in multicomponent membranes and exploring the way these influence the response of a membrane to lateral forces.

Groves, J.T.; Boxer, S.G.; McConnell, H.M.

2000-01-13

216

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

217

Force-Field Compensation in a Manual Tracking Task  

PubMed Central

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

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

2010-01-01

218

Effective Interatomic Forces from One-Particle Crystal Field Parameters.  

National Technical Information Service (NTIS)

Theoretical results are obtained for the crystal field coefficient which enable to develop an approach to the use of the crystal field data for the derivation of information on the effective interatomic forces in crystals. The method is applied to the mag...

S. Adam G. Adam A. Corciovei

1982-01-01

219

Magnetic clouds and force-free fields with constant alpha  

Microsoft Academic Search

Magnetic clouds observed at 1 AU are modeled as cylindrically symmetric, constant alpha force-free magnetic fields. The model satisfactorily explains the types of variations of the magnetic field direction that are observed as a magnetic cloud moves past a spacecraft in terms of the possible orientations of the axis of a magnetic cloud. The model also explains why the magnetic

L. F. Burlaga

1988-01-01

220

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

221

Optical forces on Mie particles in an Airy evanescent field.  

PubMed

Using vector potential and spectrum representation, we derive the expressions of the Airy evanescent field existed at the interface. Utilizing these expressions and the Arbitrary Beam Theory, the optical forces exerted on a Mie dielectric particle in the Airy evanescent field were theoretically investigated in detail. Numerical results show that the optical forces exhibit strong oscillations which are corresponding to the distributions of the evanescent field. With the increasing the size of particle radius, Morphology Dependent Resonance occurs for the particle with specific refractive index. PMID:23187386

Yang, Yang; Zang, Wei-Ping; Zhao, Zhi-Yu; Tian, Jian-Guo

2012-11-01

222

Effect of the electric current on the Casimir force between graphene sheets  

NASA Astrophysics Data System (ADS)

The dependence of the thermal component of the Casimir force and Casimir friction between graphene sheets on the drift velocity of charge carriers in one of the sheets has been analyzed. It has been shown that the drift motion results in the measurable change in the thermal Casimir force owing to the Doppler effect. The thermal Casimir force, as well as Casimir friction, increases strongly in the case of resonant photon tunneling, when the energy of an emitted photon coincides with the excitation energy of an electron-hole pair. In the case of resonant photon tunneling, the dominant contribution to the Casimir friction even at temperatures above room temperature comes from quantum friction caused by quantum fluctuations. Quantum friction can be detected in an experiment on the friction drag between graphene sheets in a high electric field.

Volokitin, A. I.; Persson, B. N. J.

2013-10-01

223

Plasma Shape Effect on Tokamak Electric Fields  

NASA Astrophysics Data System (ADS)

This work considers the effects of tokamak plasma shape, mainly ellipticity and triangularity, on the different components of the electric field. The plasma shape parameters influence mainly the poloidal and transversal electric fields, however the effect on the toroidal electric field is also analyzed. Resistive MHD equations are used for this treatment, as well as, new differential equations obtained by applying the curl operator on the original equations. Curvilinear coordinates described in previous papers are used [1]. In our treatment first, the transversal, poloidal and toroidal velocities are obtained as a function of some geometric parameters and values along some radius lines. The electric field determination comes after that. Axisymmetric conditions are used. Though our treatment is general, some simplifications can be obtained when additional up-down geometry symmetry is assumed. Application of our equation to different tokamaks is performed and compared with the results of previous authors. [4pt] [1] P. Martin, E. Castro and M. Haines, Phys. Plasmas14, 052502 (2007)

Martin, Pablo; Castro, Enrique

2010-11-01

224

Electro-optic polymer electric field sensor  

Microsoft Academic Search

Modern electronics are often shielded with metallic packaging to protect them from harmful electromagnetic radiation. In order to determine the effectiveness of the electronic shielding, there is a need to perform non-intrusive measurements of the electric field within the shielding. The requirement to be non-intrusive requires the sensor to be all dielectric and the sensing area needs to be very

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

2011-01-01

225

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...

226

Droplets profiles and wetting transitions in electric fields  

NASA Astrophysics Data System (ADS)

This paper presents current work in electrowetting. In the first part, we discuss experimental measurements of curvature of a conductive liquid drop in an electrical field. A recent theoretical and numerical study [8] predicts that diverging electric fields give rise to deviations close to the contact line from the usual spherical cap shape. We present here the first experimental measurements, compared to numerical simulations. In the second part, we recall how electrowetting is likely to induce wetting transitions, and describe the experimental setup designed to this purpose. Ellipsometry monitoring of film thickness is intended to follow total towards pseudo-partial wetting transition, allowing to reconstruct the effective interface potential of the system, acting like the electrostatic counterpart to the mechanical Surface Force Apparatus.

Bienia, Marguerite; Mugele, Frieder; Quilliet, Catherine; Ballet, Patrice

2004-08-01

227

Electrically Mediated Neuronal Guidance with Applied Alternating Current Electric Fields  

Microsoft Academic Search

Applied electric fields (EFs) have previously been presented as a potential method of inducing functional recovery after neural\\u000a trauma. To date, most of this research has focused on the application of a direct current (DC) stimulus to produce the desired\\u000a EF and induce neuronal growth. We propose that high duty-cycle alternating current (AC) stimulation is capable of inducing\\u000a similar EFs

Matthew S. Graves; Travis Hassell; Brooke L. Beier; Gabriel O. Albors; Pedro P. Irazoqui

2011-01-01

228

Electric current quadratic in an applied electric field  

NASA Astrophysics Data System (ADS)

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

Deyo, Eric

229

Sensitivity enhancements to photonic electric field sensor  

NASA Astrophysics Data System (ADS)

This paper describes an electrode-less, all-optical, wideband electric field sensor fabricated in an electro-optic lithium niobate substrate. The sensor component is an integrated optic Mach-Zehnder interferometer. The electric field sensor uses the electro-optic properties of lithium niobate to modulate the phase of the light propagating in each arm of the Mach-Zehnder interferometer. The phase modulated light is then converted to intensity modulation at the output of the interferometer. The unique feature of the sensor device is that the orientation of the crystal in one arm of the Mach-Zehnder interferometer is inverted to provide push-pull optical modulation for an applied electric field. Optical fibers are connected to the input and output of the sensor device. The basic device is an all-dielectric intensity modulator. The ability to operate the sensor without the use of any metal antenna permits its use in extremely high field conditions without any danger of damaging the sensor. The optical fiber connections provide optical isolation to the instrumentation to protect the instrumentation from possible overload conditions. The electrode-less sensor is designed specially for measuring high field strengths similar to the conditions in electromagnetic pulse, high power microwave and high voltage power lines. Sensitivity improvements are possible by using carrier suppression techniques.

Sriram, Sriram S.; Kingsley, Stuart A.

2004-08-01

230

Interfacial force field characterization in a constrained vapor bubble thermosyphon  

Microsoft Academic Search

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

Sunando Dasgupta; Joel L. Plawsky; Peter C. Wayner

1995-01-01

231

Artificial electric field in fermi liquids.  

PubMed

Based on the Keldysh formalism, we derive an effective Boltzmann equation for a quasiparticle constrained within a particular Fermi surface in an interacting Fermi liquid. This provides a many-body derivation of Berry curvatures in electron dynamics with spin-orbit coupling, which has received much attention in recent years in noninteracting models. As is well known, the Berry curvature in momentum space modifies naïve band dynamics via an "artificial magnetic field" in momentum space. Our Fermi liquid formulation completes the reinvention of modified band dynamics by introducing in addition an artificial electric field, related to Berry curvature in frequency and momentum space. We show explicitly how the artificial electric field affects the renormalization factor and transverse conductivity of interacting U(1) Fermi liquids with nondegenerate bands. PMID:17155760

Shindou, Ryuichi; Balents, Leon

2006-11-20

232

Dynamics of the structure of electric currents and electrodynamic forces in current sheets  

SciTech Connect

Specific features of the spatial distributions of the electric current and electrodynamic forces in current sheets are examined by studying the magnetic fields in them. It is shown that the j Multiplication-Sign B forces should lead to a gradual increase in the kinetic energy of the plasma accelerated along the current sheet surface. Excitation of currents directed oppositely to the main current in the central part of the sheet is observed for the first time, and the time evolution of the forward and reverse currents is investigated. Generation of reversed currents is a manifestation of the dynamic effects caused by the motion of plasma flows in the magnetic field and leading to a change in the magnetic structure of the current sheet.

Frank, A. G.; Satunin, S. N. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

2011-10-15

233

Magnitude of the Electric Field Near Thunderstorm-Associated Clouds.  

National Technical Information Service (NTIS)

Electric field measurements made in and near clouds during two airborne field mill programs are presented. Aircraft equipped with multiple electric field mills and cloud physics sensors were flown near active convection and into thunderstorm anvil and deb...

D. M. Mach F. J. Merceret J. E. Dye J. G. Ward M. G. Bateman

2013-01-01

234

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

Microsoft Academic Search

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

James S. Cloyd; Wright-Patterson AFB

1997-01-01

235

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

2013-10-03

236

Two-Droplet Combustion of N-Octane in a Direct Current Electric Field Under Microgravity  

Microsoft Academic Search

The combustion experiments of two droplets of n-octane arrayed in the direction of the electric field were carried out under microgravity. Experiments with different electrode distances are carried out and two individual flames were observed. The increase in the burning rate constant of the cathode-side flame was arranged reasonably using the representative electric body force, which was expressed by the

Osamu Imamura; Kiyotaka Yamashita; Shunsuke Nishida; George Ianus; Mitsuhiro Tsue; Michikata Kono

2011-01-01

237

Investigation of acoustic fields generated by eddy currents using an atomic force microscope  

NASA Astrophysics Data System (ADS)

This paper reports the experimental measurement and imaging of the acoustic fields generated by low-frequency eddy currents in metals in the absence of an external static magnetic field using a modified atomic force microscope. Acoustic displacements in a typical metal placed in eddy current field without static magnetic field were theoretically computed and found to be in the range of few hundred picometers. A modified atomic force microscope was used to detect and measure the acoustic displacements in a single crystal copper. The setup was also used to image acoustic fields in a titanium alloy sample. Details of the modified AFM to measure and image acoustic displacements are presented. The role of electrical and elastic properties on the contrast in acoustic images of Ti-6Al-4V sample is discussed.

Nalladega, V.; Sathish, S.; Blodgett, M.

2013-01-01

238

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

239

Picosecond Electrical Sampling with a Scanning Force Microscope.  

NASA Astrophysics Data System (ADS)

The miniaturization of electronic devices and circuits has been progressing at an astounding pace. Advance research devices are using linewidths in the tens of nanometers, with frequency cutoffs beyond 100 GHz. Conventional measurement techniques lack the ability to probe signals on specific lines with both fine lateral resolution and high bandwidth. Recently, electrical sampling with an atomic force microscope (AFM) has been demonstrated at Stanford. This technique makes use of an AFM to sample voltage waveforms with nanometer scale lateral resolution and temporal resolution limited only by the bandwidth of the sampling signal source. This thesis describes advances in this technique which bring the measurement bandwidth into the GHz range, with measured frequencies as high as 333 GHz and measured signal transients as fast as 1 ps. This technique involves the use of a specially designed AFM cantilever with a conductive tip floating over a sample under test. The electrical force on the tip is proportional to the square of the voltage between the tip and the sample. This square law dependence is then used to perform equivalent-time sampling, so that the measured deflection of the cantilever is proportional to a time-expanded version of the signal under test. The measurement bandwidth of this technique is limited to that of the sampling voltage source. Therefore, in order to obtain the highest measurement frequencies, nonlinear transmission line (NLTL) technology (which can generate voltage transients as fast as 480 fs) has been used. The fastest results have been obtained with devices which monolithically integrate the NLTL circuits with specially designed AFM cantilevers and tips.

Nechay, Bettina Anne

240

Electric field driven transition in magnetite  

NASA Astrophysics Data System (ADS)

Magnetite, Fe3O4, is a strongly electronically correlated system and thus exhibits remarkable electrical and magnetic properties, including the Verwey transition at TV˜122 K, which has attracted much attention since its 1939 discovery. Fe3O4 has recently revealed a new effect. By performing experiments at the nanoscale, we have discovered a novel electric-field driven transition (EFT) in magnetite below TV, from high- to low-resistance states driven by high electric field. The EFT is detected both in Fe3O4 nanoparticles and thin films, is hysteretic in voltage under continuous biasing, and is not caused by self- heating (S. Lee et. al., Nature Mater. 7, 130 (2008)). In this work we report on a thorough investigation of this new EFT. First, we unveil the origin of hysteresis observed in I-V curves. By applying voltage in a pulsed manner with controlled parameters we unambiguously demonstrate that while the transition is field-driven, hysteresis results from Joule heating in the low-resistance state. A simple relaxation-time thermal model captures the essentials of the hysteresis mechanism (A. Fursina et al., Phys. Rev. B 79, 245131 (2009)). Second, by doing multilead electrical measurements, we quantitatively separate the contributions of the Fe3O4 channel and each electrode interfaces and explore the contact effects upon testing several different contact metals. On the onset of the transition, contact resistances at both source and drain electrodes and the resistance of Fe3O4 channel decrease abruptly. This behavior is consistent with a theoretically predicted transition mechanism of charge gap closure by electric field. Finally, we report recent measurements of the distribution of switching voltages and its evolution with temperature. These studies demonstrate that nanoscale, nonequilibrium probes can reveal much about the underlying physics of strongly correlated materials.

Lee, Sungbae

2010-03-01

241

Electric field observations of equatorial bubbles  

SciTech Connect

The authors present here results from the double floating probe experiment carried on the San Marco D satellite, with emphasis on the observations of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. This study concentrates on isolated bubble structures in the upper ionospheric F region and divides these observed bubble encounters into two types, type 1 (live bubbles) and type 2(dead bubbles). Type 1 bubbles show varying degrees of plasma density depletion and upward velocities ranging from 100 to 1,000 m/s. Type 2 bubbles show plasma density depletion but no appreciable upward convection. Both types of events are often surrounded by a halo of plasma turbulence extending considerably outside the region's plasma depletion. Most type 1 events show some evidence for local continuity in the eastward (y) electric current, where the y component of the observed electric field (E{sub y}) shows hyperbolic correlation with the plasma density (n), as dictated by horizontal current continuity. This model stresses the importance of including magnetic field aligned currents in deriving the electric potential equation from the divergence equation {del} {times} j = 0. All of the type 1 (live) events examined exhibit a striking and systematic lack of conservation of the vertical component (x) of the electric field vector (E{sub x}) on crossing these structures. This lack of conservation of E{sub x} is of the order of 1.5 mV/m from west to east, directly implying that type 1 bubbles are not steady state plasma structures. A straightforward interpretation of this jump phenomenon in E{sub x} leads to the conclusion that the walls of most of the type 1 bubbles are collapsing inward at the rate of some 50 m/s.

Aggson, T.L. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Maynard, N.C. (Air Force Geophysics Lab., Hanscom AFB, MA (United States)); Hanson, W.B. (Univ. of Texas, Dallas (United States)); Saba, J.L. (ST Systems Corp., Lanham, MD (United States))

1992-03-01

242

Electric fields in polymers during dynamic deformation  

NASA Astrophysics Data System (ADS)

The transverse vibrations of a beam and the propagation of tension, compression, and shear deformation waves along the axis of a rod are studied by recording the electric field that appears under these conditions near the rod. Experiments are performed on samples made of various plastic materials in order to compare the effect of the properties of a material on the electric response during dynamic deformation, all other things being equal. Dynamic Young’s moduli are determined during bending vibrations and the propagation of longitudinal waves. It is shown that the location and type of antenna should be taken into account to adequately interpret a recorded signal and a dynamic mechanical process.

Bivin, Yu. K.

2010-06-01

243

Force-field calculation and geometry of the HOOO radical.  

PubMed

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. PMID:24028111

Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

2013-09-01

244

An all-atom force field for metallocenes.  

PubMed

A new all-atom force field, for the molecular modeling of metallocenes was constructed. Quantum chemical calculations were performed to obtain several force field terms not yet defined in the literature. The remainder were transferred from the OPLS-AA/AMBER framework. The parametrization work included the obtention of geometrical parameters, torsion energy profiles, and distributions of atomic charges that blend smoothly with the OPLS-AA specification for a variety of organic molecular fragments. Validation was carried out by comparing simulated and experimental data for five different ferrocene derivatives in the crystalline phase. The present model can be regarded as a step toward a general force field for metallocenes, built in a systematic way, easily integrated with OPLS-AA, and transferable between different metal-ligand combinations. PMID:17181343

Lopes, José N Canongia; do Couto, P Cabral; da Piedade, Manuel E Minas

2006-12-28

245

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

2011-01-05

246

Electrical stunning of fish: the relationship between the electric field strength and water conductivity  

Microsoft Academic Search

The electric field in water required to stun trout is investigated experimentally. The results show how the electric field depends on water conductivity. The electric fields in water required to generate permanent insensibility in trout following exposure durations of 15, 30 and 60 s are identified. A mathematical model of the electric field in the stunning tank is constructed and

Jeff Lines; Steve Kestin

2004-01-01

247

Dynamics of Drop Formation in an Electric Field.  

PubMed

The effect of an electric field on the formation of a drop of an inviscid, perfectly conducting liquid from a capillary which protrudes from the top plate of a parallel-plate capacitor into a surrounding dynamically inactive, insulating gas is studied computationally. This free boundary problem which is comprised of the surface Bernoulli equation for the transient drop shape and the Laplace equation for the velocity potential inside the drop and the electrostatic potential outside the drop is solved by a method of lines incorporating the finite element method for spatial discretization. The finite element algorithm employed relies on judicious use of remeshing and element addition to a two-region adaptive mesh to accommodate large domain deformations, and allows the computations to proceed until the thickness of the neck connecting an about to form drop to the rest of the liquid in the capillary is less than 0.1% of the capillary radius. The accuracy of the computations is demonstrated by showing that in the absence of an electric field predictions made with the new algorithm are in excellent agreement with boundary integral calculations (Schulkes, R. M. S. M. J. Fluid Mech. 278, 83 (1994)) and experimental measurements on water drops (Zhang, X., and Basaran, O. A. Phys. Fluids 7(6), 1184 (1995)). In the presence of an electric field, the algorithm predicts that as the strength of the applied field increases, the mode of drop formation changes from simple dripping to jetting to so-called microdripping, in accordance with experimental observations (Cloupeau, M., and Prunet-Foch, B. J. Aerosol Sci. 25(6), 1021 (1994); Zhang, X., and Basaran, O. A. J. Fluid Mech. 326, 239 (1996)). Computational predictions of the primary drop volume and drop length at breakup are reported over a wide range of values of the ratios of electrical, gravitational, and inertial forces to surface tension force. In contrast to previously mentioned cases where both the flow rate in the tube and the electric field strength are nonzero, situations are also considered in which the flow rate is zero and the dynamics are initiated by impulsively changing the field strength from a certain value to a larger value. When the magnitude of the step change in field strength is small, the results of the new transient calculations accord well with those of an earlier stability analysis (Basaran, O. A., and Scriven, L. E. J. Colloid Interface Sci. 140(1), 10 (1990)) and thereby provide yet another testament to the accuracy of the new algorithm. Copyright 1999 Academic Press. PMID:10191025

Notz; Basaran

1999-05-01

248

Lightning Location Using Electric Field Change Meters  

NASA Astrophysics Data System (ADS)

Briefly introduced last year, the Huntsville Alabama Field Change Array (HAFCA) is a collection of electric field change meters deployed in and around Huntsville. Armed with accurate GPS timing, the array is able to sample electric field changes due to lightning strokes simultaneously at several locations. For the first time, different components of the lightning flash can be located in three dimensions using only electric field change records. In particular, this research will show spacetime locations throughout entire lightning strokes, from preliminary breakdown pulses to the return stroke and later processes that may be related to charge neutralization. To find the spacetime locations, standard time of arrival methods will be used: finding the parameters that best fit the model using the Marquardt method. However, we will also discuss using Markov Chain Monte Carlo methods which yield a better estimation of errors. With this information, we will discuss selected cases from the array to date. In particular, we will discuss the inter-comparison of HAFCA with two other well known lightning location arrays, NLDN and NALMA. Specifically, we will explore the relationship between the first LMA pulse in a lightning stroke and the locations of preliminary breakdown pulses and the implications on lightning initiation. Further, the return stroke locations will be shown to agree reasonably well with NLDN locations. We will also locate compact intracloud discharges (CIDs) and compare with NLDN locations.

Bitzer, P. M.; Christian, H.; Burchfield, J.

2010-12-01

249

The effect of electric field on heat and mass transfer  

SciTech Connect

The process of evaporation from flat and cylindrical surfaces into an air stream flowing tangentially to them has been experimentally investigated. An electric field has been induced in the system from an emitting electrode in the form of needles arranged in a plate placed above the grounded water surface. A decisive effect of the ion-drag force on the evaporation process has been confirmed in the experiments proving that the ionic wind had intensified the process. About 8-fold increase in the average values of the heat and mass transfer coefficients caused by an electric field of an intensity 5 kV/cm in comparison with those obtained without the field has been observed. General correlations relating the evaporation rate to the process parameters have been suggested. The system under consideration can be treated as a model one for a solid dried at a constant rate period. The drying experiments with a kaolin plate have been carried out under conditions corresponding to those applied in water evaporation from a flat surface to provide the same values of the heat and mass transfer coefficients. Intensification of the drying process by the electric field, similar to that of water evaporation, has been recorded.

Wolny, A.; Kaniuk, R. [Warsaw Univ. of Technology (Poland). Faculty of Chemical and Process Engineering

1996-05-01

250

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

251

Pulsed Direct Current Electric Fields Enhance Osteogenesis in Adipose-Derived Stromal Cells  

PubMed Central

Adipose-derived stromal cells (ASCs) constitute a promising source of cells for regenerative medicine applications. Previous studies of osteogenic potential in ASCs have focused on chemicals, growth factors, and mechanical stimuli. Citing the demonstrated role electric fields play in enhancing healing in bone fractures and defects, we investigated the ability of pulsed direct current electric fields to drive osteogenic differentiation in mouse ASCs. Employing 50?Hz direct current electric fields in concert with and without osteogenic factors, we demonstrated increased early osteoblast-specific markers. We were also able to establish that commonly reported artifacts of electric field stimulation are not the primary mediators of the observed effects. The electric fields caused marked changes in the cytoskeleton. We used atomic force microscopy–based force spectroscopy to record an increase in the cytoskeletal tension after treatment with electric fields. We abolished the increased cytoskeletal stresses with the rho-associated protein kinase inhibitor, Y27632, and did not see any decrease in osteogenic gene expression, suggesting that the pro-osteogenic effects of the electric fields are not transduced via cytoskeletal tension. Electric fields may show promise as candidate enhancers of osteogenesis of ASCs and may be incorporated into cell-based strategies for skeletal regeneration.

Hammerick, Kyle E.; James, Aaron W.; Huang, Zubin; Prinz, Fritz B.

2010-01-01

252

Carbon Nanotubes Oscillation under Electric Field  

NASA Astrophysics Data System (ADS)

Oscillation mechanism of carbon nanotubes (CNTs) under various external electric fields is investigated by performing first principles molecular dynamics (MD) calculations on closed and open-ended CNTs. From MD calculations we observe that, in addition to the strength of the induced dipole moment, temperature, chirality, and moment of inertia of a CNT affect its oscillation frequency. We propose a procedure to discriminate CNTs with different moments of inertia and/or chiralities based on their different oscillation frequencies. The implication of our results in the process of nanotube insertion into biological cells, where the existing field across the cell membrane facilitates CNT penetration, is also discussed.

Khazaei, Mohammad; Farajian, Amir Abbas; Lee, Sang Uck; Belosludov, Rodion Vladimir; Kawazoe, Yoshiyuki

2010-11-01

253

Apricot Nectar Processing by Pulsed Electric Fields  

Microsoft Academic Search

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

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

2011-01-01

254

HIGH ELECTRIC FIELD DRYING OF JAPANESE RADISH  

Microsoft Academic Search

Japanese radish (Raphanus sativus L.) slices were dried under an alternating current (AC) high electric field (HEF) of 430 kV\\/m using a multiple point electrode and a grounded copper mesh. HEF with multipoint to a mesh electrode system could evaporate 87.5% of the total moisture from fresh radish slices on 7 h exposure. Oven-drying at 60°C and ambient air at

T. R. Bajgai; F. Hashinaga

2001-01-01

255

Phase measurement for electric field tomography.  

PubMed

The basic principles of electric field tomography (EFT) are briefly explained. EFT system numerical simulation results are given. The comparison of images reconstructed by systems with planar and round electrode arrays is presented. Some aspects of transmitting and measuring stages are discussed. The accuracy of the phase-sensitive demodulator, which is the key element of an EFT measuring system, is evaluated experimentally. PMID:18544795

Korjenevsky, A V; Tuykin, T S

2008-06-10

256

Strictly Polyhedral Colloids Challenged by Electric Field  

NASA Astrophysics Data System (ADS)

We have succeeded in fabricating monodisperse polyhedral metal-organic framework (MOF) crystals. Here, the micron-sized rhombic dodecahedra are suspended in liquid as candidates for directed self-assembly. The application of AC electric field is found to produce assembly at various facets truncations, probably owing to induced dipole attraction, with linear chaining that we observe and analyze based on direct in-situ imaging. The facet-to-facet preference during assembly produces striking selectivity for these1D chains.

Yanai, Nobuhiro; Sindoro, Melinda; Yan, Jing; Granick, Steve

2013-03-01

257

The Cell in the Electric Field  

Microsoft Academic Search

\\u000a An exposure of a cell to an external electric field results in the induced transmembrane voltage (??m) that superimposes to the resting voltage. This can have a range of effects, from modification of the activity of voltage-gated\\u000a channels to membrane electroporation, and accurate knowledge of spatial distribution and time course of ??m is important for the understanding of these effects.

Tadej Kotnik; Gorazd Pucihar; Damijan Miklav?i?

258

Food Industry Applications for Pulsed Electric Fields  

Microsoft Academic Search

\\u000a In this chapter the potential of pulsed electric fields (PEF) to enhance or create alternatives to conventional methods in\\u000a food processing will be summarized. After a brief introduction of the historical background, some applications for gentle\\u000a food preservation will be presented. The enhancement of mass transfer processes like extraction or drying by PEF-pretreatment\\u000a will be pointed out by showing examples

Henry Jaeger; Ana Balasa; Dietrich Knorr

259

Biological effects of narrow band pulsed electric fields  

Microsoft Academic Search

This paper describes the process of narrow band pulsed electric fields (NPEFs) and its effect on mammalian cells. The NPEF consists of a pulse modulated sinusoidal wave (PMSW), which allows delivery of well-defined electric fields in terms of frequency, field strength and deposition energy to the biological systems. 100 mus long sinusoidal electric fields with a frequency of 0.02, 2

Sunao Katsuki; Naoyuki Nomura; Hideto Koga; Hidenori Akiyama; Ichiro Uchida; Shin-ichi Abe

2007-01-01

260

Electric-field induced magnetization reversal using multiferroics  

NASA Astrophysics Data System (ADS)

Controlling magnetism using solely electric fields is interesting not only from a fundamental standpoint, but presents great potential for ultimately low energy consumption logic and memory. The evidence of the electrically controllable antiferromagnetic ordering in the multiferroic magnetoelectric bismuth ferrite (BiFeO3) drew an increasing interest in the pursuit for new emerging devices. To use such functionality for device applications, deterministic control not only of antiferromagnetism, but also ferromagnetism is essential. To achieve this goal, a ferromagnet/multiferroic heterostructure has been proposed based on the combination of magnetoelectric coupling in BiFeO3 and exchange coupling between magnetic materials and offers a new pathway for the electrical control of magnetism. By combination of a piezoresponse force microscopy, photoemission electron microscopy and anisotropic magnetoresistance measurements, we demonstrated the non-volatile reversal of a CoFe layer magnetization induced solely by the application of an electric field at room temperature. This 180 degree rotation of the magnetization of the ferromagnetic layer is mediated by a strong interfacial coupling. The correlation between the ferroelectric state in the multiferroic layer and the CoFe ferromagnetic domain architecture is evidenced. The projection of this strong magnetoelectric coupling in an out-of-plane configuration, allowing the reduction by an order of magnitude of voltage required, will be discussed. Our results show the high potential of magnetoelectric-based heterostructures for future low energy consumption data storage devices.

Trassin, Morgan

2012-02-01

261

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

262

Nucleon dynamics in effective field theory of nuclear forces  

Microsoft Academic Search

Low energy nucleon dynamics in the effective field theory (EFT) of nuclear forces is investigated by using the formalism of the generalized quantum dynamics (GQD). This formalism is based on a generalized dynamical equation derived as the most general equation of motion consistent with the current concepts of quantum theory and allows one to extend quantum dynamics to the case

Renat Kh. Gainutdinov; Aigul A. Mutygullina

2002-01-01

263

A force field for virtual atom molecular mechanics of proteins.  

PubMed

Activities of many biological macromolecules involve large conformational transitions for which crystallography can specify atomic details of alternative end states, but the course of transitions is often beyond the reach of computations based on full-atomic potential functions. We have developed a coarse-grained force field for molecular mechanics calculations based on the virtual interactions of C alpha atoms in protein molecules. This force field is parameterized based on the statistical distribution of the energy terms extracted from crystallographic data, and it is formulated to capture features dependent on secondary structure and on residue-specific contact information. The resulting force field is applied to energy minimization and normal mode analysis of several proteins. We find robust convergence in minimizations to low energies and energy gradients with low degrees of structural distortion, and atomic fluctuations calculated from the normal mode analyses correlate well with the experimental B-factors obtained from high-resolution crystal structures. These findings suggest that the virtual atom force field is a suitable tool for various molecular mechanics applications on large macromolecular systems undergoing large conformational changes. PMID:19717427

Korkut, Anil; Hendrickson, Wayne A

2009-08-28

264

Evaluation of DNA Force Fields in Implicit Solvation  

PubMed Central

DNA structural deformations and dynamics are crucial to its interactions in the cell. Theoretical simulations are essential tools to explore the structure, dynamics, and thermodynamics of biomolecules in a systematic way. Molecular mechanics force fields for DNA have benefited from constant improvements during the last decades. Several studies have evaluated and compared available force fields when the solvent is modeled by explicit molecules. On the other hand, few systematic studies have assessed the quality of duplex DNA models when implicit solvation is employed. The interest of an implicit modeling of the solvent consists in the important gain in the simulation performance and conformational sampling speed. In this study, respective influences of the force field and the implicit solvation model choice on DNA simulation quality are evaluated. To this end, extensive implicit solvent duplex DNA simulations are performed, attempting to reach both conformational and sequence diversity convergence. Structural parameters are extracted from simulations and statistically compared to available experimental and explicit solvation simulation data. Our results quantitatively expose the respective strengths and weaknesses of the different DNA force fields and implicit solvation models studied. This work can lead to the suggestion of improvements to current DNA theoretical models.

Gaillard, Thomas; Case, David A.

2011-01-01

265

Evaluation of TiO2 Force Fields.  

National Technical Information Service (NTIS)

A total of nine force fields for TiO2 have been compared and evaluated using bulk lattice and surface energy minimization procedures. Calculated crystal properties of four polymorphs of TiO2 (rutile, anatase, brookite and a high pressure phase TiO2(ii)) a...

D. R. Collins W. Smith

1996-01-01

266

The MARTINI Force Field: Coarse Grained Model for Biomolecular Simulations  

Microsoft Academic Search

We present an improved and extended version of our coarse grained lipid model. The new version, coined the MARTINI force field, is parametrized in a systematic way, based on the reproduction of partitioning free energies between polar and apolar phases of a large number of chemical compounds. To reproduce the free energies of these chemical building blocks, the number of

Siewert J. Marrink; H. Jelger Risselada; Serge Yefimov; D. Peter Tieleman; Alex H. de Vries

2007-01-01

267

Force field energy functionals for image feature extraction  

Microsoft Academic Search

The overall objective in defining feature space is to reduce the dimensionality of pattern space yet maintaining discriminatory power for classification and invariant description. To meet this objective, in the context of ear biometrics, a novel force field transformation has been developed in which the image is treated as an array of Gaussian attractors that act as the source of

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

2002-01-01

268

A force field for virtual atom molecular mechanics of proteins  

PubMed Central

Activities of many biological macromolecules involve large conformational transitions for which crystallography can specify atomic details of alternative end states, but the course of transitions is often beyond the reach of computations based on full-atomic potential functions. We have developed a coarse-grained force field for molecular mechanics calculations based on the virtual interactions of C? atoms in protein molecules. This force field is parameterized based on the statistical distribution of the energy terms extracted from crystallographic data, and it is formulated to capture features dependent on secondary structure and on residue-specific contact information. The resulting force field is applied to energy minimization and normal mode analysis of several proteins. We find robust convergence in minimizations to low energies and energy gradients with low degrees of structural distortion, and atomic fluctuations calculated from the normal mode analyses correlate well with the experimental B-factors obtained from high-resolution crystal structures. These findings suggest that the virtual atom force field is a suitable tool for various molecular mechanics applications on large macromolecular systems undergoing large conformational changes.

Korkut, Anil; Hendrickson, Wayne A.

2009-01-01

269

Destabilization of Pickering emulsions using external electric fields  

NASA Astrophysics Data System (ADS)

It is known that emulsions can be stabilized by the presence of particles which get trapped at fluid-fluid interfaces and prevent adjacent drops from coalescing with each other. We show here that such emulsions, or Pickering emulsions, can be destabilized by applying external electric fields. This is demonstrated experimentally by studying water drops in decane and using various types of particles, including micro and nanoparticles. It is conjectured that the destabilization occurs due to the motion of particles on the surface of drops in presence of a uniform electric field. Although there should be no electrostatic forces acting on neutral particles in a uniform electric field, the presence of the drop itself introduces some non-uniformity which is responsible for particle motions along the surface. Particles translate either to the poles or equator of the drop, depending on the relative dielectric constants of the particles, the surrounding fluid and the fluid within the drop. Such motions break the particle barrier, thus allowing for drops to merge into one another.

Hwang, Kyuho; Singh, Pushpendra; Aubry, Nadine

2008-11-01

270

Super resolution mapping of the near optical field and the gradient optical force  

NASA Astrophysics Data System (ADS)

We have developed a NSOM technique that can map both the near optical field and the optical force using an atomic force microscope. This technique could be very useful for characterizing MEMs/NEMs devices, plasmonic nanoantennas, nano-photonic devices and biologically active substrates. Unlike conventional NSOM techniques that rely on an aperture fabricated on the end of an AFM tip to collect the optical signal this apertureless technique uses a lockin amplifier locked to the AFM tip vibrational frequency, to correlate the amplitude modulation of the back reflected optical signal to the strength of the optical field. And since we are not limited by the fabrication of an aperture the spatial resolution of the map is limited only by the size of a sharp AFM tip which for metallic coated tips can have a radius of curvature of 10 to 20 nm. For optical force mapping the incident laser is modulated and the lock-in amplifier is used to correlate the amplitude modulation of the vibrating AFM tip to strength of the optical gradient force. And in this way one can get a very accurate mapping of both the optical force and the optical field for any substrate of interest as long as it can be back illuminated. Lastly with an electrically monolithic substrate it is possible to correlate the amplitude modulation of the tunneling current to the optical field and obtain a spatial mapping that has a resolution of an STM, about 1 nm or maybe less.

Gelfand, Ryan M.; Bonakdar, Alireza; Memis, O. Gokalp; Mohseni, Hooman

2013-09-01

271

Inertial effects on electrically conducting fluids in the presence of transverse magnetic fields: An example problem  

Microsoft Academic Search

When an electric current flowing within a conducting fluid crosses magnetic field lines, a body force is created, which may significantly affect the motion of the fluid. This paper treats the flow of a conducting fluid in a toroidal duct. A transverse magnetic field is present, and a portion of one surface of the toroidal duct serves as an electrode.

K. A. Cliffe

1998-01-01

272

An investigation of behaviours of a single bubble in a uniform electric field  

SciTech Connect

The effects of a d.c. electric field on bubble behaviours such as bubble growth, deformation and detachment are investigated. The bubble behaviours are simulated experimentally and the electric force acting on bubble is calculated numerically. The results indicate that bubbles are compressed intensely by the horizontal component of the electric stress and elongated by the vertical component, thus prolate spherical bubbles in the direction of electric field are formed. The investigation shows that both the rate of bubble deformation and the contact angle increase with electric field strength. Under the action of the electric field at a certain voltage, a larger bubble normally breaks into smaller ones while departing from the wall. In addition, the effects of the EHD induced bubble behaviours on boiling heat transfer are discussed. (author)

Dong, W.; Li, R.Y.; Yu, H.L. [CPE, University of Shanghai for Science and Technology, Shanghai (China); Yan, Y.Y. [School of the Built Environment, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

2006-06-15

273

Stochastic dynamics of electric dipole in external electric fields: A perturbed nonlinear pendulum approach  

NASA Astrophysics Data System (ADS)

The motion of a dipole in external electric fields is considered in the framework of nonlinear pendulum dynamics. A stochastic layer is formed near the separatrix of the dipole pendulum in a restoring static electric field under the periodic perturbation by plane-polarized electric fields. The width of the stochastic layer depends on the direction of the forcing field variation, and this width can be evaluated as a function of perturbation frequency, amplitude, and duration. A numerical simulation of the approximate stochastic layer width of a perturbed pendulum yields a multi-peak frequency spectrum. It is described well enough at high perturbation amplitudes by an analytical estimation based on the separatrix map with an introduced expression of the most effective perturbation phase. The difference in the fractal dimensions of the phase spaces calculated geometrically and using the time-delay reconstruction is attributed to the predominant development of periodic and chaotic orbits, respectively. The correlation of the stochastic layer width with the phase space fractal dimensions is discussed.

Kapranov, Sergey V.; Kouzaev, Guennadi A.

2013-06-01

274

Minute electric field reduced membrane fouling and improved performance of membrane bioreactor  

Microsoft Academic Search

Effective application of a low voltage and low intensity electric field in EMBR (a membrane bioreactor attached with electric field) may reduce fouling, energy consumption, while enhance treatment efficiency. For that, electrodes and membrane modules were re-arranged in EMBR to maintain constant electrophoresis forces against deposition\\/adsorption of extra-cellular polymeric substances (EPS) or sludge particles on the membrane. The copper wire

Lifen Liu; Jiadong Liu; Bo Gao; Fenglin Yang

275

Separation of seed by-products by an AC electric field  

Microsoft Academic Search

A method for separating constituents of the by-products derived from agricultural processes offers the possibility of recovering\\u000a their valuable components. Partial sorting by a unique electric field enriches the protein concentration in sunflower-seed\\u000a meal and cottonseed meal by removing objectionable components such as hulls or gossypol. Enrichment is accomplished by the\\u000a dynamic forces from an electric field that is created

Louis C. Weiss; Devron P. Thibodeaux

1984-01-01

276

Dynamics of drop formation in an electric field  

SciTech Connect

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

Notz, P.K.; Basaran, O.A. [Purdue Univ., West Lafayette, IN (United States). School of Chemical Engineering

1999-05-01

277

Spark Discharge Characteristics of Vehicles Energized by AC Electric Fields.  

National Technical Information Service (NTIS)

This study examined certain characteristics of spark discharges from vehicles energized by an electric field. Vehicles were placed in an electric field produced by a 500-kv transmission line. Spark dischargers were delivered through a resistor to a driven...

J. P. Reilly

1980-01-01

278

Radiation and Scattering from Large Polygonal Cylinders, Transverse Electric Fields.  

National Technical Information Service (NTIS)

The report deals with the computation of radiation and scattering of electromagnetic fields by electrically large convex conducting cylinders. A general computer program is developed for the case of transverse electric fields using the geometrical theory ...

J. R. Mautz R. F. Harrington

1975-01-01

279

Electric field-free gas breakdown in explosively driven generators  

SciTech Connect

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

Shkuratov, Sergey I. [Loki Incorporated, Rolla, Missouri 65409 (United States); Baird, Jason [Loki Incorporated, Rolla, Missouri 65409 (United States); Department of Mining and Nuclear Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409-0450 (United States); Talantsev, Evgueni F. [Pulsed Power LLC, Lubbock, Texas 79416 (United States); Altgilbers, Larry L. [U.S. Army Space and Missile Defense Command/Army Forces Strategic Command, Huntsville, Alabama 35807 (United States)

2010-07-15

280

Rydberg state decay in inhomogeneous electric fields  

NASA Astrophysics Data System (ADS)

An extension of the model of Merkt and Zare [J. Chem. Phys. 101, 3495 (1994)] is presented to describe the effects of static inhomogeneous electric fields, which arise experimentally from combinations of applied (or stray) homogeneous fields and the presence of charged particles, on Rydberg states of atoms and molecules. The effect of an arbitrary number of charged particles is included and the effects of nonzero quantum defects are investigated. A quantization axis rotation procedure is defined, allowing clear distinction between homogeneous and inhomogeneous field effects. Calculations are reported of the time-dependent decay of a coherent population of eigenstates for n=20, 33, and 50, involving diagonalization of the full n2×n2 matrix. Calculations are also carried out for n=100 by pre-diagonalization of the full homogeneous field perturbation followed by a restricted basis set diagonalization for the inhomogeneous part of the perturbation. The inclusion of nonzero quantum defects has a substantial impact on the ml mixing, confining significant mixing to a narrow range of radial and angular positions of the ion. An applied homogeneous field of order the Inglis-Teller field is required in combination with the field due to the ions. The dynamics are very different according to whether np or nf series carry the transition probability. For np-state population, the maximum stabilization is achieved at ion-Rydberg distances of around 5n2a0, with the ion almost perpendicular to the applied homogeneous field. For an initial nf population the ion perturbation may have a destabilizing effect at sufficiently small homogeneous field (<=0.1FIT). Significant effects of laser polarization on the stability are reported. Calculations for a realistic pseudo-random distribution of ions and Rydbergs suggest that ml mixing by ions will never reach the complete mixing limit, but that at least an order of magnitude stabilization is achievable under a restricted range of conditions.

Softley, T. P.; Rednall, R. J.

2000-05-01

281

Control of the radial electric field shear by modification of the magnetic field configuration in LHD  

Microsoft Academic Search

Control of the radial electric field, Er, is considered to be important in helical plasmas, because the radial electric field and its shear are expected to reduce neoclassical and anomalous transport, respectively. In general, the radial electric field can be controlled by changing the collisionality, and positive or negative electric fields have been obtained by decreasing or increasing the electron

K. Ida; M. Yoshinuma; M. Yokoyama; S. Inagaki; N. Tamura; B. J. Peterson; T. Morisaki; S. Masuzaki; A. Komori; Y. Nagayama; K. Tanaka; K. Narihara; K. Y. Watanabe; C. D. Beidler

2005-01-01

282

Interplanetary electric fields and their relationship to low-latitude electric fields under disturbed conditions  

NASA Astrophysics Data System (ADS)

Recent studies have demonstrated that ground-based magnetometer observations can be used to infer realistic, daytime vertical E×B drift velocities in the Peruvian and Philippine longitude sectors. It has also been demonstrated that under certain conditions the time variability in the interplanetary electric field (IEF)—minutes to hours—is reflected in the daytime, prompt penetration of high-latitude electric fields to low latitudes. In this paper, we incorporate magnetometer-inferred E×B drift techniques to extend this study to include the Indian sector E×B drift velocities and to investigate the relationships between IEF conditions and daytime, low-latitude electric field observations under both geomagnetically quiet and disturbed conditions. This paper addresses several basic questions related to the relationships between IEF conditions and low-latitude east west electric fields. (1) When low-latitude electric fields exhibit quiet-time, Sq-type behavior, what are the IEF conditions? (2) Under disturbed conditions, what are the relationships between the IEF parameters and the low-latitude electric fields in the Peruvian, Philippine, and Indian longitude sectors? (3) If the three longitude sector electric field responses are similar under disturbed conditions, is the response consistent with the current ideas put forward at the Millstone Hill Workshop on promptly penetrating electric fields and over-shielding effects at low latitudes? We address the above questions by analyzing magnetometer-inferred E×B drift velocities between January 2001 and December 2004 when there exists more than 500 quiet days and more than 235 geomagnetically disturbed days, defined by daily Ap values greater than 20. It is suggested that the neural network approach that provides realistic E×B drift velocities based on magnetometer observations can be applied at any longitude where appropriately placed magnetometers exist. It is found that: (1) the average quiet, daytime upward E×B drift velocity vs. LT in the Indian sector is comparable to the average velocity vs. LT in the Peruvian sector and both are roughly 3 5 m/s less than the values in the Philippine sector; (2) under quiet conditions, the peak velocity occurs at 1100 LT in the Peruvian sector and at 1000 LT in both the Philippine and Indian sectors; and (3) during disturbed conditions, it is observed that daytime, promptly penetrating electric fields occur, simultaneously, in the Philippine, Indian and Peruvian sectors, in response to fluctuating IEF conditions.

Anghel, Adela; Anderson, David; Maruyama, Naomi; Chau, Jorge; Yumoto, Kiyo; Bhattacharyya, Archana; Alex, S.

2007-07-01

283

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

284

Electrical field control of interface magnetic anisotropy  

NASA Astrophysics Data System (ADS)

The interface magnetic anisotropy of ferromagnetic metals comes from the spin-orbit interaction. By explicitly taking into account the interaction between the symmetry-broken interface potential and the spin-dependent electric dipoles of the Bloch states, we find that the interface spin-orbit coupling can be modeled by the Rashba spin-orbit Hamiltonian (RSOH). Due to the presence of the RSOH, the spin up and down states of the ferromagnet are spin mixed at the interface. Among other consequences, the RSOH induces a perpendicular surface magnetic anisotropy whose magnitude is comparable to the observed values in transition metals. When an external electric field is applied across the interface, the induced screening potential modifies the RSOH and thus the perpendicular anisotropy can be manipulated. Our calculated results are in agreement with the experiments [1]. [4pt] [1] Endo et al., Appl. Phys. Lett. 96, 212503 (2010); T. Nozaki et al, Appl. Phys. Lett. 96, 022506 (2010).

Xu, Lei; Zhang, Shufeng

2011-03-01

285

Electric field control of interface magnetic anisotropy  

NASA Astrophysics Data System (ADS)

The interface magnetic anisotropy of ferromagnetic metals comes from the spin-orbit interaction. But unlike the semiconductor heterostructures, the strong electron screening would make the Rashba spin-orbit coupling (RSOC) localized within the election screening length at metallic interface. Now by explicitly taking into account the interaction between the symmetry-broken interface potential and the spin-dependent electric dipoles of the Bloch states, we find that this interaction may generate a RSOC, which is much stronger than the direct Pauli spin-orbit coupling. Due to the presence of the RSOC, the spin up and down states of the ferromagnet are spin mixed at the interface. Among other consequences, the RSOC induces a perpendicular surface magnetic anisotropy whose magnitude is comparable to the observed values in transition metals. When we apply an external electric field across the interface, the induced screening potential modifies the RSOC and thus the perpendicular anisotropy can be manipulated.

Xu, Lei; Zhang, Shufeng

2011-10-01

286

Development and testing of a general amber force field.  

PubMed

We describe here a general Amber force field (GAFF) for organic molecules. GAFF is designed to be compatible with existing Amber force fields for proteins and nucleic acids, and has parameters for most organic and pharmaceutical molecules that are composed of H, C, N, O, S, P, and halogens. It uses a simple functional form and a limited number of atom types, but incorporates both empirical and heuristic models to estimate force constants and partial atomic charges. The performance of GAFF in test cases is encouraging. In test I, 74 crystallographic structures were compared to GAFF minimized structures, with a root-mean-square displacement of 0.26 A, which is comparable to that of the Tripos 5.2 force field (0.25 A) and better than those of MMFF 94 and CHARMm (0.47 and 0.44 A, respectively). In test II, gas phase minimizations were performed on 22 nucleic acid base pairs, and the minimized structures and intermolecular energies were compared to MP2/6-31G* results. The RMS of displacements and relative energies were 0.25 A and 1.2 kcal/mol, respectively. These data are comparable to results from Parm99/RESP (0.16 A and 1.18 kcal/mol, respectively), which were parameterized to these base pairs. Test III looked at the relative energies of 71 conformational pairs that were used in development of the Parm99 force field. The RMS error in relative energies (compared to experiment) is about 0.5 kcal/mol. GAFF can be applied to wide range of molecules in an automatic fashion, making it suitable for rational drug design and database searching. PMID:15116359

Wang, Junmei; Wolf, Romain M; Caldwell, James W; Kollman, Peter A; Case, David A

2004-07-15

287

Aggregation and electrorheology in nanotube suspensions under applied electric field  

NASA Astrophysics Data System (ADS)

We consider the electrostatic response, i.e., polarization, mutual interactions and aggregation, of the nanotubes in solution under applied electric field. We model the nanotubes as rigid cylindrical rods with hemispherical ends. The surface charge densities of the nanotubes are obtained by solving an integral equation numerically. The calculated charge densities are then used to derive the interaction energies of the nanotubes with the applied field, as well as among each other. In addition to the electrostatic response, this would be a reasonable estimate of the radio-frequency (RF) electrodynamic response, as the RF wavelength is typically much larger than the nanotubes lengths. Our results show that nanotubes alignment with the electric field is very sensitive to their diameter. Nanotubes with larger diameters, e.g. multiwall or bundles, can overcome Brownian aggitation of the solvent molecules more effectively. The semiconducting nanotubes response is around two orders of magnitude lower than that of the metallic ones. The response is also proportional to the square of the applied field. The conditions for chain-like aggregation of the nanotubes are also explored using our results. We find that the calculated rupturing forces provide an estimate for the yield stress, which is in qualitative agreement with experimental results.

Farajian, Amir; Pupysheva, Olga; Schmidt, Howard; Yakobson, Boris

2007-03-01

288

Phosphate vibrations probe local electric fields and hydration in biomolecules  

PubMed Central

The role of electric fields in important biological processes like binding and catalysis has been studied almost exclusively by computational methods. Experimental measurements of the local electric field in macromolecules are possible using suitably calibrated vibrational probes. Here we demonstrate that the vibrational transitions of phosphate groups are highly sensitive to an electric field and quantify that sensitivity, allowing local electric field measurements to be made in phosphate-containing biological systems without chemical modification.

Levinson, Nicholas M.; Bolte, Erin E.; Miller, Carrie S.

2011-01-01

289

Effect of magnetic fields on combustion electromotive force  

Microsoft Academic Search

A magnetic field is observed to affect the electrical response of a system burning under self-propagating high-temperature\\u000a synthesis conditions. With the synthesis of lithium ferrite as an example, it is shown that, depending on its strength and\\u000a direction, applying a magnetic field induces different forms of response. The greatest effect is observed in the postprocess\\u000a region. Possible reasons for the

Yu. G. Morozov; M. V. Kuznetsov

1999-01-01

290

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

291

Spatial aspects of the electric fields generated by weakly electric fish  

Microsoft Academic Search

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

Eric I. Knudsen

1975-01-01

292

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

293

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

294

ENHANCEMENT OF METHANE CONVERSION USING ELECTRIC FIELDS  

SciTech Connect

This report summarizes the conditions and results of this multifaceted program. Detailed experimental descriptions and results and discussion can be found in the publications cited in the Appendix. The goal of this project is the development of novel, economical, processes for the conversion of natural gas to more valuable projects such as synthesis gas or direct conversion to methanol, ethylene and other organic oxygenates or higher hydrocarbons. The methodologies of the project are to investigate and develop low temperature electric discharges and electric discharge-enhanced catalysis for carrying out these conversions. With the electric discharge-enhanced conversion, the operating temperatures are expected to be far below those currently required for such processes as oxidative coupling, thereby allowing for a higher degree of catalytic selectivity while maintaining high activity. In the case of low temperature discharges, the conversion is carried out at ambient temperature, trading high temperature thermal energy for electric energy as the driving force for conversion. The low operating temperatures remove thermodynamic constraints on the product distribution due to the non-equilibrium nature of the low temperature plasma. This also removes the requirements of large thermal masses that need very large-scale operation to maximize efficiency that is the characteristic of current technologies, including high temperature plasma processes. This potentially allows much smaller scale processes to be efficient. Additionally, a gas conversion process that is electrically driven provides an internal use for excess power generated by proposed Fischer Tropsch gas-to-liquids processes and can increase their internal thermal efficiency and reduce capital costs. This project has studied three primary types of low temperature plasma reactor and operating conditions. The organization of this program is shown schematically in the report. Typical small scale laboratory reactor systems were developed that used mass flow controllers for feed gas mixture delivery and GC and MS analysis of products. The range of operation included flow rates from a few sccm to a few hundred sccm with residence times from less than a tenth of a second to about 30 minutes. Temperatures used were generally from ambient to 100 C, but were from as low as about 0 to a high of 800 C. Pressures were generally atmospheric, but for most of the configurations pressures up to 3 atmosphered were also used.

Richard G. Mallinson; Lance L. Lobban

2000-05-01

295

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

296

ELF electrostimulation on macrophages: possibility of immunomodulation by electric field  

Microsoft Academic Search

Among the biological effects of an ELF electric field, we have been interested in the effect on immune cells. If an electric field can modulate the immunoresponse, it will provide a potentially useful technique in clinical practice. The effects of ELF electrostimulation on macrophages were investigated to pursue the possibility of immunomodulation using apparatus designed for electric field therapy. First,

T. Shimookal; Koichi Ushida; Itaru Nakata; Kazuo Ohsaki; Koichi Shimizu

2000-01-01

297

The effect of electromotive-force generation on electrical properties of thin samarium sulfide films  

SciTech Connect

Electrical properties of thin SmS polycrystalline films with various values of the lattice constant at T = 300-580 K are studied. Specific features of the temperature dependences of electrical conductivity at T > 450 K are revealed. The effect of generation of the electromotive force with magnitude as large as 1.3 V at T = 440-470 K is observed when the films were subjected to the pressure of a spherical indenter. It is shown that it is possible to transform SmS films into a high-resistivity state (with the difference in the resistivity by three orders of magnitude) by applying an electric field with the strength higher than 100 V/cm. All the results obtained are accounted for using a model of the phenomenon of the electromotive-force generation in SmS under uniform heating of the sample and can also be attributed to the variable valence of samarium ions with respect to the lattice defects.

Kaminskii, V. V., E-mail: Vladimir.Kaminski@mail.ioffe.ru; Kazanin, M. M.; Solov'ev, S. M.; Sharenkova, N. V.; Volodin, N. M. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2006-06-15

298

Destabilization of Turing Structures by Electric Fields  

NASA Astrophysics Data System (ADS)

The dynamic behavior of hexagonal Turing patterns in the chlorine dioxide-iodine-malonic acid reaction was studied in a newly developed open reactor under the influence of externally applied weak directed current up to 17.5mA. A transition from stationary hexagonal patterns to spots moving parallel to the direction of the applied electric field could be observed. The velocity of the drift increases monotonously with the applied current. Experimental results could be qualitatively reproduced in numerical simulations with a reaction-diffusion-advection model, based on a realistic kinetic mechanism.

Schmidt, B.; de Kepper, P.; Müller, S. C.

2003-03-01

299

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

300

Electrohydrodynamic Model of Vesicle Deformation in Alternating Electric Fields  

PubMed Central

Abstract We develop an analytical theory to explain the experimentally observed morphological transitions of quasispherical giant vesicles induced by alternating electric fields. The model treats the inner and suspending media as lossy dielectrics, and the membrane as an impermeable flexible incompressible–fluid sheet. The vesicle shape is obtained by balancing electric, hydrodynamic, bending, and tension stresses exerted on the membrane. Our approach, which is based on force balance, also allows us to describe the time evolution of the vesicle deformation, in contrast to earlier works based on energy minimization, which are able to predict only stationary shapes. Our theoretical predictions for vesicle deformation are consistent with experiment. If the inner fluid is more conducting than the suspending medium, the vesicle always adopts a prolate shape. In the opposite case, the vesicle undergoes a transition from a prolate to oblate ellipsoid at a critical frequency, which the theory identifies with the inverse membrane charging time. At frequencies higher than the inverse Maxwell-Wagner polarization time, the electrohydrodynamic stresses become too small to alter the vesicle's quasispherical rest shape. The model can be used to rationalize the transient and steady deformation of biological cells in electric fields.

Vlahovska, Petia M.; Gracia, Ruben Serral; Aranda-Espinoza, Said; Dimova, Rumiana

2009-01-01

301

Field forced antiferroelectric-to-ferroelectric switching in modified lead zirconate titanate stannate ceramics  

SciTech Connect

Electric-field-forced antiferroelectric- to-ferroelectric phase transitions in several compositions of modified lead zirconate titanate stannate antiferroelectric ceramics are studied for ultra-high-field-induced strain actuator applications. Two types of fatigue effects are observed in these ceramic compositions. In one, the fatigue effects only proceed to a limited extent and the properties may be restored by annealing above the Curie temperature, while in the other, the fatigue effects proceed to a large extent and the properties cannot be restored completely by heat treatment.

Pan, W.; Zhang, Q.; Bhalla, A.; Cross, L.E. (Materials Research Lab., Pennsylvania State Univ., University Park, PA (US))

1989-04-01

302

In-plane force fields and elastic properties of graphene  

NASA Astrophysics Data System (ADS)

Bond stretching and angle bending force fields, appropriate to describe in-plane properties of graphene sheets, are derived using first principles' methods. The obtained force fields are fitted by analytical anharmonic potential energy functions, providing efficient means of calculations in molecular mechanics simulations. Using both molecular dynamics simulations and first principles' methods, numerical results regarding the mechanical behavior of graphene monolayers under various loads, like uniaxial tension in different directions or hydrostatic tension, are presented and compared. Graphene's response in shear stress is also investigated using molecular dynamics, where a noticeable asymmetric mechanical behavior is found. Stress-strain curves and elastic constants, such as, Young modulus, Poisson's ratio, bulk modulus, and shear modulus, are calculated. Our results are compared with available experimental estimates, as well as, with corresponding theoretical calculations. Finally, the effects of the anharmonicity of the extracted bond stretching and angle bending potentials on the mechanical properties of graphene are discussed.

Kalosakas, G.; Lathiotakis, N. N.; Galiotis, C.; Papagelis, K.

2013-04-01

303

Influence of relative humidity on analyzing electric field exposure using ELF electric field measurements.  

PubMed

The objective of the study was to investigate the influence of humidity on analyzing electric field exposure using extremely low frequency (ELF) electric field measurements. The study included 322 measurements in a climate room. We used two commercial three-axis meters, EFA-3 and EFA-300, and employed two measurement techniques in the climate room where we varied the temperature from 15 to 25?°C, the relative humidity from 55% to 95%, and the electric field from 1 to 25?kV/m. We calculated Pearson correlations between humidity and percentage errors for all data and for data at different levels of humidity. When the relative humidity was below 70%, the results obtained by the different measurement methods in terms of percentage errors were of the same order of magnitude for the considered temperatures and field strength, but the results were less reliable when the relative humidity was higher than 80%. In the future, it is important to take humidity into account when electric field measurement results will be compared to the values given in different exposure guidelines. PMID:23315970

Korpinen, Leena H; Kuisti, Harri A; Tarao, Hiroo; Elovaara, Jarmo A

2013-01-11

304

Magnetic resonance electrical impedance tomography for determining electric field distribution during electroporation  

NASA Astrophysics Data System (ADS)

Electroporation is a phenomenon caused by externally applied electric field to cells that results in an increase of cell membrane permeability to various molecules. Accurate coverage of the tissue with a sufficiently large electric field presents one of the most important conditions for successful membrane permeabilization. Applications based on electroporation would greatly benefit with a method for monitoring the electric field, especially if it could be done in situ. As the membrane electroporation is a consequence of an induced transmembrane potential, which is directly proportional to the local electric field, we have been investigating current density imaging and magnetic resonance electrical impedance tomography techniques to determine the electric field distribution during electroporation. In this paper, we present comparison of current density and electric field distribution in an agar phantom and in a liver tissue exposed to electroporation pulses. As expected, a region of increased electrical conductivity was observed in the liver tissue exposed to sufficiently high electric field but not in agar phantom.

Kranjc, Matej; Bajd, Franci; Serša, Igor; Miklav?i?, Damijan

2013-04-01

305

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

NASA Astrophysics Data System (ADS)

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

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

2003-10-01

306

Quantum mechanical force field for water with explicit electronic polarization.  

PubMed

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(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. PMID:23927266

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

2013-08-01

307

The FoldX web server: an online force field  

Microsoft Academic Search

FoldX is an empirical force field that was developed for the rapid evaluation of the effect of mutations on the stability, folding and dynamics of proteins and nucleicacids.ThecorefunctionalityofFoldX,namely the calculation of the free energy of a macromolecule based on its high-resolution 3D structure, is now publicly available through a web server at http:\\/\\/ foldx.embl.de\\/. The current release allows the cal-

Joost Schymkowitz; Jesper Borg; Francois Stricher; Robby Nys; Frederic Rousseau; Luis Serrano

2005-01-01

308

Comparison of different force fields for the study of disaccharides  

Microsoft Academic Search

Eighteen empirical force fields and the semi-empirical quantum method PM3CARB-1 were compared for studying ?-cellobiose, ?-maltose, and ?-galabiose [?-d-Galp-(1?4)-?-d-Galp]. For each disaccharide, the energies of 54 conformers with differing hydroxymethyl, hydroxyl, and glycosidic linkage orientations were minimized by the different methods, some at two dielectric constants. By comparing these results and the available crystal structure data and\\/or higher level density

Carlos A. Stortz; Glenn P. Johnson; Alfred D. French; Gábor I. Csonka

2009-01-01

309

Charge sensitivity analysis in force-field-atom resolution  

Microsoft Academic Search

Charge sensitivity analysis (CSA) was extended to AMBER force-field resolution. The effective electronegativity and hardness\\u000a data were found using evolutionary algorithms. Four model hardness matrices based on the classical electrostatic, Mataga–Nishimoto,\\u000a Ohno, and Louwen–Vogt interpolation formulae were considered. Mulliken population analysis and electrostatically derived charges\\u000a (CHELPG) were taken into account. It was demonstrated that the Ohno interpolation formula gives the

Anna Stachowicz; Anna Styrcz; Jacek Korchowiec

310

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

311

Planned waveguide electric field breakdown studies  

SciTech Connect

This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

Wang Faya; Li Zenghai [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

2012-12-21

312

Distinct Haptic Cues Do Not Reduce Interference when Learning to Reach in Multiple Force Fields  

Microsoft Academic Search

Background: Previous studies of learning to adapt reaching movements in the presence of novel forces show that learning multiple force fields is prone to interference. Recently it has been suggested that force field learning may reflect learning to manipulate a novel object. Within this theoretical framework, interference in force field learning may be the result of static tactile or haptic

Nicholas Cothros; Jeremy Wong; Paul L. Gribble

2008-01-01

313

Transient filamentous network structure of a colloidal suspension excited by stepwise electric fields.  

PubMed

Jamming and force networks observed in electrorheological (ER) fluids bear many similarities to those observed in various granular and colloidal systems. We have measured the time evolution (transient stresses) of filamentous networks of colloidal particles in suspensions subjected to continuous tensile strain concomitant with the switching on and off of electric fields. The density of particle chains was found to increase exponentially with the applied tensile strain via a rapid formation of single chains followed by a slower coarsening (aggregation) of the chains. The two processes can be ascribed to the field-induced short-range and long-range interparticle forces, respectively, along with the tensile viscous force. PMID:17358152

Tian, Yu; Zeng, Hongbo; Anderson, Travers H; Zhao, Boxin; McGuiggan, Patricia; Israelachvili, Jacob

2007-01-25

314

Comparison of different force fields for the study of disaccharides.  

PubMed

Eighteen empirical force fields and the semi-empirical quantum method PM3CARB-1 were compared for studying beta-cellobiose, alpha-maltose, and alpha-galabiose [alpha-D-Galp-(1-->4)-alpha-D-Galp]. For each disaccharide, the energies of 54 conformers with differing hydroxymethyl, hydroxyl, and glycosidic linkage orientations were minimized by the different methods, some at two dielectric constants. By comparing these results and the available crystal structure data and/or higher level density functional theory results, it was concluded that the newer parameterizations for force fields (GROMOS, GLYCAM06, OPLS-2005 and CSFF) give results that are reasonably similar to each other, whereas the older parameterizations for Amber, CHARMM or OPLS were more divergent. However, MM3, an older force field, gave energy and geometry values comparable to those of the newer parameterizations, but with less sensitivity to dielectric constant values. These systems worked better than MM2 variants, which were still acceptable. PM3CARB-1 also gave adequate results in terms of linkage and exocyclic torsion angles. GROMOS, GLYCAM06, and MM3 appear to be the best choices, closely followed by MM4, CSFF, and OPLS-2005. With GLYCAM06 and to a lesser extent, CSFF, and OPLS-2005, a number of the conformers that were stable with MM3 changed to other forms. PMID:19758584

Stortz, Carlos A; Johnson, Glenn P; French, Alfred D; Csonka, Gábor I

2009-08-22

315

Current Status of the AMOEBA Polarizable Force Field  

PubMed Central

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

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

2010-01-01

316

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

317

A Fast Current-Field Iteration Method for Calculating Nonlinear Force-Free Fields  

Microsoft Academic Search

Existing methods for calculating nonlinear force-free magnetic fields are slow, and are likely to be inadequate for reconstructing\\u000a coronal magnetic fields based on high-resolution vector magnetic field data from a new generation of spectro-polarimetric\\u000a instruments. In this paper a new implementation of the current-field iteration method is presented, which is simple, fast,\\u000a and accurate. The time taken by the method

M. S. Wheatland

2006-01-01

318

A Fast Current-Field Iteration Method for Calculating Nonlinear Force-Free Fields  

Microsoft Academic Search

Existing methods for calculating nonlinear force-free magnetic fields are slow, and are likely to be inadequate for reconstructing coronal magnetic fields based on high-resolution vector magnetic field data from a new generation of spectro-polarimetric instruments. In this paper a new implementation of the current-field iteration method is presented, which is simple, fast, and accurate. The time taken by the method

M. S. Wheatland

2006-01-01

319

Full-disk nonlinear force-free field extrapolation of SDO/HMI and SOLIS/VSM magnetograms  

NASA Astrophysics Data System (ADS)

Context. The magnetic field configuration is essential for understanding solar explosive phenomena, such as flares and coronal mass ejections. To overcome the unavailability of coronal magnetic field measurements, photospheric magnetic field vector data can be used to reconstruct the coronal field. Two complications of this approach are that the measured photospheric magnetic field is not force-free and that one has to apply a preprocessing routine to achieve boundary conditions suitable for the force-free modeling. Furthermore the nonlinear force-free extrapolation code should take uncertainties into account in the photospheric field data. They occur due to noise, incomplete inversions, or azimuth ambiguity-removing techniques. Aims: Extrapolation codes in Cartesian geometry for modeling the magnetic field in the corona do not take the curvature of the Sun's surface into account and can only be applied to relatively small areas, e.g., a single active region. Here we apply a method for nonlinear force-free coronal magnetic field modeling and preprocessing of photospheric vector magnetograms in spherical geometry using the optimization procedure to full disk vector magnetograms. We compare the analysis of the photospheric magnetic field and subsequent force-free modeling based on full-disk vector maps from Helioseismic and Magnetic Imager (HMI) onboard the solar dynamics observatory (SDO) and Vector Spectromagnetograph (VSM) of the Synoptic Optical Long-term Investigations of the Sun (SOLIS). Methods: We used HMI and VSM photospheric magnetic field measurements to model the force-free coronal field above multiple solar active regions, assuming magnetic forces to dominate. We solved the nonlinear force-free field equations by minimizing a functional in spherical coordinates over a full disk and excluding the poles. After searching for the optimum modeling parameters for the particular data sets, we compared the resulting nonlinear force-free model fields. We compared quantities, such as the total magnetic energy content, free magnetic energy, the longitudinal distribution of the magnetic pressure, and surface electric current density, using our spherical geometry extrapolation code. Results: The magnetic field lines obtained from nonlinear force-free extrapolation based on HMI and VSM data show good agreement. However, the nonlinear force-free extrapolation based on HMI data contain more total magnetic energy, free magnetic energy, the longitudinal distribution of the magnetic pressure, and surface electric current density than do the VSM data.

Tadesse, T.; Wiegelmann, T.; Inhester, B.; MacNeice, P.; Pevtsov, A.; Sun, X.

2013-02-01

320

Understanding Electric Interactions in Suspensions in Gradient AC Electric Fields II:. Simulations and Application Exploration  

NASA Astrophysics Data System (ADS)

We used numerical simulations of a continuous model and the molecular dynamics model to understand the particle instability, formation of island-like structures and existence of one critical particle concentration of 1% (v/v) for formation of island-like structures in the suspension in a gradient AC electric field reported in Paper I. The simulations of the continuous model show that the critical concentration of 1% (v/v) is the concentration of which the particles of a suspension are just fully filling the lower field region finally. According to the MD simulations, the particles instability does exist in the corn oil in a gradient AC electric field, anisotropic polarization interactions among the particles are responsible for the particle instability and have memory, and the memory is still kept even when the particles are transported by a dielectrophoresis force. The island-like structures can be regarded as signature of the memory. We explored possibilities to apply our findings in biomedical fields.

Tada, Shigeru; Shen, Yan; Jacqmin, David; Fu, Bingmei; Qiu, Zhiyong

321

Switch-toughening of ferroelectrics subjected to electric fields  

Microsoft Academic Search

Electric fields can influence the fracture toughness of ferroelectrics. For example, poled ferroelectrics exhibit fracture toughness anisotropy: the material is tougher for a crack parallel to the poling direction but less tough for a crack perpendicular to it. When an electric field is applied to a poled sample, a positive field reduces its fracture toughness but a negative field enhances

W. Yang; T. Zhu

1998-01-01

322

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

PubMed

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

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

2008-08-01

323

Electric charges and forces in atomic force microscopy and nano-xerography  

NASA Astrophysics Data System (ADS)

Electrostatic forces generated by contact potential differences, localized charges, or externally applied voltages play a crucial role in atomic force microscopy. Electrostatic forces mediate the non-contact measurement of local potentials by the Kelvin probe technique, enabling compositional mapping of surfaces. However, if not compensated properly, electrostatic forces lead to height errors in topography images acquired in tapping mode. We present a single scan Kelvin probe force microscopy technique that compensates local electrostatic forces and allows simultaneous height and potential measurements in tapping mode. Electrostatic forces also direct the localized assembly of structures in nano-xerography. Here we describe how positive charges, written into a thin film of poly(methyl)methacrylate with the conductive tip of an atomic force microscope, guide the deposition of carboxyl-functionalized multiwalled carbon nanotubes suspended in isopropyl-acohol.

Stemmer, A.; Ziegler, D.; Seemann, L.; Rychen, J.; Naujoks, N.

2008-12-01

324

Additional dc magnetic field response of magnetostrictive/piezoelectric magnetoelectric Laminates by Lorentz force effect  

NASA Astrophysics Data System (ADS)

We have discovered that traditional long-type magnetoelectric laminate composite of magnetostrictive Tb1-xDyxFe2-y and piezoelectric materials possesses additional ability of detecting dc magnetic field, using the product effect of the Lorentz force effect from Terfenol-D metal strips in dc magnetic field applied with an ac electrical current and the piezoelectric effect from piezoelectric material. The output voltage between the two faces of piezoelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystal shows a good linear response to applied dc magnetic field of 100-1200 Oe under different ac electrical current inputs (0.4-200 mA). The magnetoelectric coefficient is about ~64.1 mV/T A. The additional dc magnetic field response of magnetostrictive/piezoelectric magnetoelectric laminates driven by Lorentz force makes this composite hopeful for application in coil-free ac/dc magnetic-sensitive sensors. At the same time, for this composite, the additional ability will not affect the primal ability for detecting ac magnetic field.

Jia, Yanmin; Tang, Yanxue; Zhao, Xiangyong; Luo, Haosu; Or, Siu Wing; Chan, Helen Lai Wa

2006-12-01

325

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

Microsoft Academic Search

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

Gwen Trentham; Hans Jochen Scholl

2008-01-01

326

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

327

Evaluation of Electromagnetic Force and Magnetic Laval Nozzle Acceleration in an Applied-Field MPD Thruster  

NASA Astrophysics Data System (ADS)

A magneto-plasma-dynamic thruster (MPDT) is expected as one of the promising electric propulsion systems owing to features of a relatively large thrust, high specific impulse that is unattainable by conventional chemical or nuclear propulsion required for space missions such as a manned Mars mission. To clarify the electromagnetic acceleration mechanism of a plasma flow in an applied-field MPDT, detailed flow field and electromagnetic force field are evaluated experimentally with spectroscopic technique and magnetic probe array. It is found that an axial drag force generated by an interaction between azimuthal plasma current and radial magnetic field cancels an acceleration force in a uniform magnetic field. A thermal energy component is much larger than a flow energy component in Bernoulli's equation and ion acoustic Mach number is limited less than unity in the muzzle region of MPD arcjet. In order to convert the thermal energy to the flow energy, magnetic Laval nozzle acceleration with a local magnetic coil is attempted. The ion Mach number after passing through the nozzle throat exceeds unity and a production of supersonic plasma flow is achieved. An optimum magnetic nozzle configuration is discussed with the experimental results.

Tobari, Hiroyuki; Sato, Ryuichi; Harata, Kenji; Hattori, Kunihiko; Ando, Akira; Inutake, Masaaki

2003-10-01

328

The Source of the Electric Field in the Nightside Magnetosphere.  

National Technical Information Service (NTIS)

In the open magnetosphere model magnetic field lines from the polar caps connect to the interplanetary magnetic field and conduct an electric field from interplanetary space to the polar ionosphere. By examining the magnetic flux involved it is concluded ...

D. P. Stern

1975-01-01

329

Dynamics of an electric dipole moment in a stochastic electric field  

NASA Astrophysics Data System (ADS)

The mean-field dynamics of an electric dipole moment in a deterministic and a fluctuating electric field is solved to obtain the average over fluctuations of the dipole moment and the angular momentum as a function of time for a Gaussian white-noise stochastic electric field. The components of the average electric dipole moment and the average angular momentum along the deterministic electric-field direction do not decay to zero, despite fluctuations in all three components of the electric field. This is in contrast to the decay of the average over fluctuations of a magnetic moment in a stochastic magnetic field with Gaussian white noise in all three components. The components of the average electric dipole moment and the average angular momentum perpendicular to the deterministic electric-field direction oscillate with time but decay to zero, and their variance grows with time.

Band, Y. B.

2013-08-01

330

Dynamics of an electric dipole moment in a stochastic electric field.  

PubMed

The mean-field dynamics of an electric dipole moment in a deterministic and a fluctuating electric field is solved to obtain the average over fluctuations of the dipole moment and the angular momentum as a function of time for a Gaussian white-noise stochastic electric field. The components of the average electric dipole moment and the average angular momentum along the deterministic electric-field direction do not decay to zero, despite fluctuations in all three components of the electric field. This is in contrast to the decay of the average over fluctuations of a magnetic moment in a stochastic magnetic field with Gaussian white noise in all three components. The components of the average electric dipole moment and the average angular momentum perpendicular to the deterministic electric-field direction oscillate with time but decay to zero, and their variance grows with time. PMID:24032795

Band, Y B

2013-08-15

331

Molecular dynamics simulation of nanosized water droplet spreading in an electric field.  

PubMed

Molecular dynamics (MD) simulations are performed for the spreading of a nanosized water droplet on a solid substrate subject to a parallel electric field. A combined electrostatic and Lennard-Jones potential is employed to represent the intermolecular interactions. Results show that in response to the applied field, polar water molecules realign themselves and this microscopic reorientation of molecular dipoles combines with the intermolecular forces to produce a macroscopic deformation of a free spherical water droplet into an ellipsoid. The applied field has a strong effect on the spreading of the water droplet on a solid substrate. For a weaker parallel field, the droplet spreading is asymmetric with the leading contact angle being greater than the trailing contact angle. With an increase in field strength, this asymmetry continues to increase, culminates, and then decreases until it disappears. The symmetric spreading remains with a further increase in the field strength until the saturation point is reached. This transition from the asymmetric to symmetric spreading is a manifestation of the interaction of the electric field with polar water molecules and the intermolecular forces within the droplet and between the water and solid; the interaction also leads to a change in hydrogen bonds along the droplet surface. The dynamics of the droplet spreading is entailed by the electrically induced motion of molecules along the liquid surface toward the solid substrate and is controlled by a competing mechanism among the electric, water-water, and water-solid intermolecular forces. PMID:23488748

Song, F H; Li, B Q; Liu, C

2013-03-21

332

Effects of electric fields on ultracold Rydberg atom interactions  

NASA Astrophysics Data System (ADS)

The behaviour of interacting ultracold Rydberg atoms in both constant electric fields and laser fields is important for designing experiments and constructing realistic models of them. In this paper, we briefly review our prior work and present new results on how electric fields affect interacting ultracold Rydberg atoms. Specifically, we address the topics of constant background electric fields on Rydberg atom pair excitation and laser-induced Stark shifts on pair excitation.

Cabral, J. S.; Kondo, J. M.; Gonçalves, L. F.; Nascimento, V. A.; Marcassa, L. G.; Booth, D.; Tallant, J.; Schwettmann, A.; Overstreet, K. R.; Sedlacek, J.; Shaffer, J. P.

2011-09-01

333

Plasma Expansion in Presence of Electric and Magnetic Fields  

SciTech Connect

The presence of electric and magnetic fields in high enthalpy nozzle flows can produce strong effects. In particular, non equilibrium conditions can be observed when this field are present. In this work we have investigated two different field configurations in supersonic nozzle: first of all we have studied the cooperative effect of electric and magnetic field applied inside the nozzle and secondly we have investigated the role of non equilibrium distribution produced in the reservoir by electric discharge (plasma jet)

Colonna, Gianpiero; Capitelli, Mario [Dipartimento di Chimica, Universita di Bari (Italy); CNR-IMIP, Bari Section (Italy)

2005-05-16

334

Fetal exposure to low frequency electric and magnetic fields  

Microsoft Academic Search

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

R. Cech; N. Leitgeb; M. Pediaditis

2007-01-01

335

Observation of Dusk Electric Field in LLBL  

NASA Astrophysics Data System (ADS)

A big magnetic storm with Dst of order - 472 nT occurred on November 20, 2003. Cluster spacecrafts passed through the magnetopause at about 16:33:20 on the dusk flank, and crossed LLBL between 14:4:00 and 16:13:20. The dusk electric field component Edusk was observed in LLBL. Edusk is about order of 0 °C 45 mV/m during big magnetic storm, but Edusk is about order of (-1) °C 1 mV/m during quiet time. At the same time Edusk is about order of 20-70 mV/m during big magnetic storm in the magnetosheath, and the variance of Edusk is correlative with Bz and V.

Wang, N.; Chen, T.; Liu, Z.; Luo, J.; Balogh, A.; Carr, C.; Zhang, T.; Reme, H.; Gustafsson, G.

2005-12-01

336

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

337

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

338

Deformation field of the soft substrate induced by capillary force  

NASA Astrophysics Data System (ADS)

Prediction on the deformation of a soft substrate induced by capillary force has been widely paid attention in the broad range of applications, such as metallurgy, material science, astronavigation, micro/nano-technology, etc., which is also a supplementary result to the classical Young's equation. We quantitatively analyzed the deformation of an elastic substrate under capillary force by means of the energy principle and the continuum mechanics method. The actual drop's morphology was investigated and was compared with that calculated based on the classical spherical shape assumption of the droplet. The displacement field of the substrate was obtained, especially, its singularity at the droplet edge was also discussed. The results are beneficial to engineering application and micro/nano-measurement.

Liu, J. L.; Nie, Z. X.; Jiang, W. G.

2009-05-01

339

Theoretical prediction of electric fields in wind-blown sand  

NASA Astrophysics Data System (ADS)

Existing experimental and theoretical studies have identified the existence of an electric field in wind-blown sand, whose strength is hundreds to thousands of times larger than that of the fair-weather electric field (around 120v m- 1) and is related to the intensity of the wind-blown sand transport. The direction of electric field is often upward pointing and opposite to that of the fair-weather electric field. In this study, we performed theoretical predictions of electric fields in wind-blown sand transport by assuming a constant charge-to-mass ratio (i.e., - 60µc kg- 1) of the saltating particles and considering the streamwise spatial variation of particle concentration in the evolution of wind-blown sand. Our results show that there exist both vertical and horizontal electric fields in wind-blown sand transport. The numerical results of vertical electric fields and mass flux are in good agreement with the experimental data measured by Schmidt et al. [1998] and Shao and Raupach [1992], respectively, which suggests that our model is valid. The horizontal electric field demonstrates a vertical stratification feature and is about one order of magnitude bigger than the fair-weather electric field. Finally, the effects of the wind speed and the sand grain diameter on electric fields are discussed.

Bo, Tianli; Zhang, Huan; Zhu, Wei; Zheng, Xiaojing

2013-05-01

340

Ambipolar edge electric field with energy dependence  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

341

Neutral winds and electric fields in the dust auroral oval. II - Theory and model  

Microsoft Academic Search

A two-dimensional numerical model of the thermosphere is applied to the auroral zone neutral wind, electric field, and plasma density data set, presented in an earlier paper. The model shows that the action of the Lorentz force can be responsible to a great extent for the large zonal velocities near the 150-km altitude. Model equations are described, an explanation of

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

1981-01-01

342

Dynamic motion of a conductive particle in viscous fluid under DC electric field  

Microsoft Academic Search

When plastic waste is liquefied for recycling, the impurities present could influence the quality of the reprocessed products. In order to explore the possible method for removing solid impurities using electrostatic forces, the motion of spherical conductive particles under a uniform electric field has been carefully investigated. In this paper, a solid impurity and liquefied plastics are simulated by a

Changrag Choi; Kyoko Yatsuzuka; Kazutoshi Asano

2001-01-01

343

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

SciTech Connect

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

Sindelka, Milan; Moiseyev, Nimrod [Department of Chemistry and Minerva Center of Nonlinear Physics in Complex Systems, Technion, Israel Institute of Technology, Haifa 32000 (Israel); Cederbaum, Lorenz S. [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany)

2006-11-15

344

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.

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

2013-01-01

345

The Physics Classroom: Electric Force - Inverse Square Law  

NSDL National Science Digital Library

This tutorial for introductory physics explores the inverse square relationship between electrostatic force and separation distance, with descriptions, definitions and explanations of how electrostatic forces obey the inverse square law. An interactive question-and-answer set allows students to self-test their understanding. This page is part of The Physics Classroom tutorials for students of introductory physics. SEE RELATED ITEMS on this page for a link to a closely related tutorial on Coulomb's Law by the same author.

Henderson, Tom; Foundation, National S.

2006-11-18

346

A Nonlinear Force-Free Magnetic Field Approximation Suitable for Fast Forward-Fitting to Coronal Loops. I. Theory  

NASA Astrophysics Data System (ADS)

We derive an analytical approximation of nonlinear force-free magnetic field solutions (NLFFF) that can efficiently be used for fast forward-fitting to solar magnetic data, constrained either by observed line-of-sight magnetograms and stereoscopically triangulated coronal loops, or by 3D vector-magnetograph data. The derived NLFFF solutions provide the magnetic field components B x ( x), B y ( x), B z ( x), the force-free parameter ?( x), the electric current density j( x), and are accurate to second-order (of the nonlinear force-free ?-parameter). The explicit expressions of a force-free field can easily be applied to modeling or forward-fitting of many coronal phenomena.

Aschwanden, Markus J.

2013-10-01

347

Vector field statistical analysis of kinematic and force trajectories.  

PubMed

When investigating the dynamics of three-dimensional multi-body biomechanical systems it is often difficult to derive spatiotemporally directed predictions regarding experimentally induced effects. A paradigm of 'non-directed' hypothesis testing has emerged in the literature as a result. Non-directed analyses typically consist of ad hoc scalar extraction, an approach which substantially simplifies the original, highly multivariate datasets (many time points, many vector components). This paper describes a commensurately multivariate method as an alternative to scalar extraction. The method, called 'statistical parametric mapping' (SPM), uses random field theory to objectively identify field regions which co-vary significantly with the experimental design. We compared SPM to scalar extraction by re-analyzing three publicly available datasets: 3D knee kinematics, a ten-muscle force system, and 3D ground reaction forces. Scalar extraction was found to bias the analyses of all three datasets by failing to consider sufficient portions of the dataset, and/or by failing to consider covariance amongst vector components. SPM overcame both problems by conducting hypothesis testing at the (massively multivariate) vector trajectory level, with random field corrections simultaneously accounting for temporal correlation and vector covariance. While SPM has been widely demonstrated to be effective for analyzing 3D scalar fields, the current results are the first to demonstrate its effectiveness for 1D vector field analysis. It was concluded that SPM offers a generalized, statistically comprehensive solution to scalar extraction's over-simplification of vector trajectories, thereby making it useful for objectively guiding analyses of complex biomechanical systems. PMID:23948374

Pataky, Todd C; Robinson, Mark A; Vanrenterghem, Jos

2013-07-31

348

Ab initio quantum force field for simulations of nanostructures  

NASA Astrophysics Data System (ADS)

It is demonstrated that the third generation of a recently introduced quantum mechanical polarizable force field (QMPFF) successfully reproduces experimental data on binding energies of polycyclic aromatic hydrocarbons and fullerene C60 with graphite. The QMPFF also provides an accurate description of bulk graphite and solid C60 properties. In all the studied systems, the electrostatics due to the penetration effect was found to be important and comparable in magnitude with the total interaction energy. The QMPFF predicts graphite exfoliation energy of 55meV /atom in agreement with the relatively large experimental value of 52±5meV /atom recently suggested by Zacharia [Phys. Rev. B 69, 155406 (2004)].

Donchev, A. G.

2006-12-01

349

Force Simulation and Ergonomic Assessment of Electric Care Beds  

Microsoft Academic Search

This study aims at evaluating and predicting the feasibility of electric care bed (ECB). Subjective evaluation were utilized to quantify the usage limitation of ECB and depict direction of shear in the passive motion process, Two groups of people were asked to finish a series of experiments on two types of electric care beds. The results were utilized in a

Qi. Wang; Zhonghai Yu

2010-01-01

350

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

Microsoft Academic Search

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

Masatoshi Sakai; Masaaki Iizuka; Masakazu Nakamura; Kazuhiro Kudo

2005-01-01

351

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

352

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

NASA Astrophysics Data System (ADS)

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 mV/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. F.; Freudenreich, H.; Bromund, K.; Rowland, D.

2009-05-01

353

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

354

Lattice vacancies in silicon film exposed to external electric field  

NASA Astrophysics Data System (ADS)

Density functional calculations based on wavelet basis set are performed to investigate the structure, internal electric-charge distribution, and formation energy of lattice vacancies in silicon film under electric fields. It was found that the formation energies of vacancies both in JT? (Jahn-Teller distortion orthogonal to electric field) and JT|| (Jahn-Teller distortion parallel to electric field) distortions are decreased with the increasing of field strength, due to the charge polarization in the whole space of silicon film. For the split vacancy, it can lower its energy by moving further away from the split space to form a tetragonal JT? vacancy under electric field. Our results also demonstrate the importance of the potential fluctuations induced by the electric fields on the charge redistribution within the vacancy defects.

Mao, Yuliang; Caliste, Damien; Pochet, Pascal

2013-07-01

355

Computation of induced electric field for the sacral nerve activation.  

PubMed

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. PMID:24140875

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

2013-10-18

356

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

357

The Topological Nature of Boundary Value Problems for Force-Free Magnetic Fields  

NASA Astrophysics Data System (ADS)

The difficulties of constructing a three-dimensional, continuous force-free magnetic field in the solar corona are investigated through a boundary value problem posed for the unbounded domain external to a unit sphere. The normal field component Bn and the boundary value ?b of the twist function ? on the unit sphere, combined with the demand for a vanishing field at infinity, do constitute sufficient conditions for determining a solution if it exists, but Bn and ?b cannot be prescribed independently. An exhaustive classification of the admissible (Bn,?b)-pairs is developed, using the topological properties of the ? flux surfaces implied by their footprints described by the constant-?b curves on the unit sphere. The incompatibilities arising from boundary conditions contradicting the field equations are distinguished from the interesting one of (Bn,?b) being, in principle, admissible but requiring a weak solution describing a force-free field containing inevitable magnetic tangential discontinuities. This particular incompatibility relates the boundary value problem to the Parker theory of spontaneous current sheets in magnetic fields embedded in electrically perfectly conducting fluids. Our investigation strategically skirts around some important but formidable mathematical problems to arrive at physically definite conclusions and insights on the construction of force-free fields, both in the practical task of modeling coronal magnetic fields with magnetopolarimetric data and in the basic understanding of the Parker theory. Two specific demonstrations of (Bn,?b) are given to illustrate circumstances under which a continuous solution to the boundary value may or may not exist.

Low, B. C.; Flyer, N.

2007-10-01

358

EFFECT OF ELECTRIC FIELD INDUCED PERTURBATION OF THE DISTRIBUTION OF IONS NEAR THE CELL SURFACE ON MIGRATION OF CHARGED MEMBRANE COMPONENTS  

EPA Science Inventory

It has demonstrated that an externally applied electric field perturbs the distribution of some of the macromolecules in biological membranes. Various electrostatic, hydrodynamic and structural forces resulting from the external field influence the movement of intramembraneous pa...

359

Reorganization of microfilament structure induced by ac electric fields  

SciTech Connect

AC electric fields induce redistribution of integral membrane proteins. Cell-surface receptor redistribution does not consistently follow electric field lines and depends critically on the frequency of the applied ac electric fields, suggesting that mechanisms other than electroosmosis are involved. We hypothesized that cytoskeletal reorganization is responsible for electric field-induced cell-surface receptor redistribution, and used fluorescence video microscopy to study the reorganization of microfilaments in human hepatoma (Hep3B) cells exposed to low-frequency electric fields ranging in strength from 25 mV/cm to 20 V/cm (peak to peak). The frequency of the applied electric field was varied from 1 to 120 Hz and the field exposure duration from 1 to 60 min. In control cells, cytoplasmic microfilaments were aligned in the form of continuous parallel cables along the longitudinal axis of the cell. Exposure of cells to ac electric fields induced alterations in microfilament structure in a manner that depended on the frequency of the applied field. A 1 or 10 Hz ac field caused microfilament reorganization from continuous, aligned cable structures to discontinuous globular patches. In contrast, the structure of microfilaments in cells exposed to 20-120 Hz electric fields did not offer from that in control cells. The extent of microfilament reorganization increased nonlinearly with the electric field strength. The characteristic time for microfilament reorganization in cells exposed to a 1 Hz, 20 V/cm electric field was {approx} 5 min. Applied ac electric fields could initiate signal transduction cascades, which in turn cause reorganization of cytoskeletal structures. 39 refs., 5 figs., 1 tab.

Cho, M.R.; Thatte, H.S.; Golan, D.E. [Harvard Medical School, Boston, MA (United States); Lee, R.C. [Univ. of Chicago, IL (United States)

1996-11-01

360

Dynamics of rotating gaseous ellipsoid in external force fields  

NASA Astrophysics Data System (ADS)

General and computationally-tractable equations are presented for the large-amplitude motion of a uniform gaseous ellipsoid rotating in an external force field. When this force is expressed as a linear function of the rectangular coordinates in the space under consideration, the equation of motion is reduced to a set of ordinary differential equations for the angular velocity, semimajor-axes of the ellipsoid, circulation, and temperature of the gaseous medium; they are integrated as an initial-value problem. Ad hoc (though fairly realistic) equations are used for cooling and viscosity to reproduce the gravitational contractions of the rotating gaseous ellipsoid. As one application, a series of equilibrium states of a uniform interstellar gas cloud in the tidal force of the Galaxy was determined, and their gravitational contraction was followed to a compact elongated structure. Two types of contractions are also found; the one is smooth contraction and the other is a violent one in which the prolate ellipsoid tumbles end-over-end with large-scale gas circulation within it.

Tatematsu, Yoshinori; Fujimoto, Mitsuaki

1990-04-01

361

Local plasma membrane permeabilization of living cells by nanosecond electric pulses using atomic force microscopy  

NASA Astrophysics Data System (ADS)

Numerous studies provide evidence that nanosecond electric pulses (nsEPs) can trigger the formation of nanopores in the plasma membranes of cells. However, the biophysical mechanism responsible for nanopore formation is not well understood. In this study, we hypothesize that membrane damage induced by nsEPs is primarily dependent on the local molecular composition and mechanical strength of the plasma membrane. To test this hypothesis, we positioned metal-coated, nanoscale cantilever tips using an atomic force microscope (AFM) to deliver nsEPs to localized areas on the surface of the plasma membrane. We conducted computational modeling simulations to verify that the electric field provided by the nsEP is concentrated between the tip and the plasma membrane. The results show that we could effectively deliver nsEPs using the AFM tips at very low voltages. Using scanning electron microscopy we analyzed the tips after applying 10V over 5 seconds duration and found no damage to the tip or loss of platinum coating. As a proof of concept, we applied a 1 and 10V, 5 second pulse to HeLa cells causing large morphological changes. We also applied both a mechanical indention and 600ns electrical pulse stimulus and measured positive propidium ion uptake into the cytoplasm suggesting formation of membrane pores. In future studies, we plan to elucidate the effect that specific, local molecular structures and compositions have on efficacy of electroporation using the newly constructed nano-electrode system.

Thompson, Gary; Payne, Jason A.; Roth, Caleb C.; Wilmink, Gerald J.; Ibey, Bennett L.

2011-02-01

362

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

363

Pulsed electric field enhanced ultrafiltration of synthetic and fruit juice  

Microsoft Academic Search

An experimental investigation of electric field assisted clarification of synthetic juice (a mixture of pectin and sucrose) and mosambi (Citrus Sinensis (L.) Osbeck) juice using a 30kDa molecular weight cut-off membrane in cross-flow ultrafiltration mode under laminar flow regime is reported herein. Electric field is applied in both continuous as well as pulse mode. Application of d.c. electric field has

Biswajit Sarkar; Sirshendu De; Sunando DasGupta

2008-01-01

364

THE ELECTRIC FIELD AND WAVE EXPERIMENT FOR THE CLUSTER MISSION  

Microsoft Academic Search

The electric-field and wave experiment (EFW) on Cluster is designed to measure the electric-field and density fluctuations with sampling rates up to 36000 samples s-1. Langmuir probe sweeps can also be made to determine the electron density and temperature. The instrument has several important capabilities. These include (1) measurements of quasi-static electric fields of amplitudes up to 700 mV m-1

G. Gustafsson; R. Bostrom; B. Holback; G. Holmgren; A. Lundgren; K. Stasiewicz; L. ÅHLÉN; F. S. Mozer; D. Pankow; P. Harvey; P. Berg; R. Ulrich; A. Pedersen; R. Schmidt; A. Butler; A. W. C. Fransen; D. Klinge; M. Thomsen; C.-G. FÄLTHAMMAR; P.-A. Lindqvist; S. Christenson; J. Holtet; B. Lybekk; T. A. Sten; P. Tanskanen; K. Lappalainen; J. Wygant

1997-01-01

365

60Hertz Electric-Field Exposures in Transmission Line Towers  

Microsoft Academic Search

This article reports on an investigation of 60-Hz electric-field exposures of line workers in 230- to 765-kV transmission line towers. The exposures were based on computations of the unperturbed electric field along climbing routes and at work positions on the towers and on insulated ladders suspended in towers. Computed exposures were expressed in terms of the unperturbed electric field averaged

T. Bracken; Russell Senior; Joseph Dudman

2005-01-01

366

Atmospheric Electric Fields: A Numerical Approach.  

National Technical Information Service (NTIS)

In this work some numerical methods for the resolution of the atmospheric electric potential equation are presented and discussed. Some applications related to different sources of the atmospheric electric potential for equatorial latitudes are also given...

S. L. G. Dutra A. E. C. Pereira A. L. C. Gonzalez W. D. Gonzalez

1985-01-01

367

Influence of a radial electrical field on the electrical breakdown along the exploding tungsten wire  

Microsoft Academic Search

Experimental results on the influence of a radial electrical field on the electrical breakdown along exploding W wires in vacuum are presented. To create a radial electrical field a wire was set inside of a metal tubule fixed on one of the electrodes. It is shown that a wire explosion inside of the tubule (when the tubule has a negative

Alexander G. Rousskikh; Rina B. Baksht; Alexey Yu. Labetsky; Vladimir I. Oreshkin; Alexander V. Shishlov

2004-01-01

368

Electric and magnetic fields at three pulp and paper mills.  

PubMed

Extremely low frequency (60 Hz) electric and magnetic field levels were measured at three Canadian pulp and paper mills, using area point-in-time measurements. Most electric field levels were below the limit of detection of 1 V/m (92 of 132 measurements); the highest measured field was 47 V/m. Measured magnetic field strengths ranged from less than the limit of detection (0.125 mG, 2 of 132 measurements) to 706 mG, with a median of 1.6 mG. Magnetic field levels were higher in mills that consume more electric power, but worker exposures could not be predicted according to plant power consumption. Overall, electric and magnetic field levels in the three pulp and paper mills were similar to those experienced by the general population. However, maximum magnetic field intensities in some areas were as high as those experienced by electrical workers. PMID:8209842

Barroetavena, M C; Ross, R; Teschke, K

1994-04-01

369

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

370

Development of force field parameters for molecular simulation of polylactide  

PubMed Central

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

McAliley, James H.; Bruce, David A.

2011-01-01

371

Reactive force field potential for carbon deposition on silicon surfaces  

NASA Astrophysics Data System (ADS)

In this paper a new interatomic potential based on the Kieffer force field and designed to perform molecular dynamics (MD) simulations of carbon deposition on silicon surfaces is implemented. This potential is a third-order reactive force field that includes a dynamic charge transfer and allows for the formation and breaking of bonds. The parameters for Si-C and C-C interactions are optimized using a genetic algorithm. The quality of the potential is tested on its ability to model silicon carbide and diamond physical properties as well as the formation energies of point defects. Furthermore, MD simulations of carbon deposition on reconstructed (100) silicon surfaces are carried out and compared to similar simulations using a Tersoff-like bond order potential. Simulations with both potentials produce similar results showing the ability to extend the use of the Kieffer potential to deposition studies. The investigation reveals the presence of a channelling effect when depositing the carbon at 45° incidence angle. This effect is due to channels running in directions symmetrically equivalent to the (110) direction. The channelling is observed to a lesser extent for carbon atoms with 30° and 60° incidence angles relative to the surface normal. On a pristine silicon surface, sticking coefficients were found to vary between 100 and 73%, depending on deposition conditions.

Briquet, Ludovic G. V.; Jana, Arindam; Mether, Lotta; Nordlund, Kai; Henrion, Gérard; Philipp, Patrick; Wirtz, Tom

2012-10-01

372

Developing Force Fields from the Microscopic Structure of Solutions  

PubMed Central

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

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

2009-01-01

373

Reactive force field potential for carbon deposition on silicon surfaces.  

PubMed

In this paper a new interatomic potential based on the Kieffer force field and designed to perform molecular dynamics (MD) simulations of carbon deposition on silicon surfaces is implemented. This potential is a third-order reactive force field that includes a dynamic charge transfer and allows for the formation and breaking of bonds. The parameters for Si-C and C-C interactions are optimized using a genetic algorithm. The quality of the potential is tested on its ability to model silicon carbide and diamond physical properties as well as the formation energies of point defects. Furthermore, MD simulations of carbon deposition on reconstructed (100) silicon surfaces are carried out and compared to similar simulations using a Tersoff-like bond order potential. Simulations with both potentials produce similar results showing the ability to extend the use of the Kieffer potential to deposition studies. The investigation reveals the presence of a channelling effect when depositing the carbon at 45° incidence angle. This effect is due to channels running in directions symmetrically equivalent to the (110) direction. The channelling is observed to a lesser extent for carbon atoms with 30° and 60° incidence angles relative to the surface normal. On a pristine silicon surface, sticking coefficients were found to vary between 100 and 73%, depending on deposition conditions. PMID:22914286

Briquet, Ludovic G V; Jana, Arindam; Mether, Lotta; Nordlund, Kai; Henrion, Gérard; Philipp, Patrick; Wirtz, Tom

2012-08-23

374

Modeling enzymatic transition states by force field methods  

NASA Astrophysics Data System (ADS)

The SEAM method, which models a transition structure as a minimum on the seam of two diabatic surfaces represented by force field functions, has been used to generate 20 transition structures for the decarboxylation of orotidine by the orotidine-5prime-monophosphate decarboxylase enzyme. The dependence of the TS geometry on the flexibility of the system has been probed by fixing layers of atoms around the active site and using increasingly larger nonbonded cutoffs. The variability over the 20 structures is found to decrease as the system is made more flexible. Relative energies have been calculated by various electronic structure methods, where part of the enzyme is represented by a force field description and the effects of the solvent are represented by a continuum model. The relative energies vary by several hundreds of kJ/mol between the transition structures, and tests showed that a large part of this variation is due to changes in the enzyme structure at distances more than 5 Å from the active site. There are significant differences between the results obtained by pure quantum methods and those from mixed quantum and molecular mechanics methods.

Hansen, M. B.; Jensen, H. J. A.; Jensen, F.

375

Automated conformational energy fitting for force-field development  

PubMed Central

We present a general conformational-energy fitting procedure based on Monte Carlo simulated annealing (MCSA) for application in the development of molecular mechanics force fields. Starting with a target potential energy surface and an unparameterized molecular mechanics potential energy surface, an optimized set of either dihedral or grid-based correction map (CMAP) parameters is produced that minimizes the root mean squared error (RMSE) between the parameterized and targeted energies. The fitting is done using an MCSA search in parameter space and consistently converges to the same RMSE irrespective of the randomized parameters used to seed the search. Any number of dihedral parameters can be simultaneously parameterized, allowing for fitting to multi-dimensional potential energy scans. Fitting options for dihedral parameters include non-uniform weighting of the target data, constraining multiple optimized parameters to the same value, constraining parameters to be no greater than a user-specified maximum value, including all or only a subset of multiplicities defining the dihedral Fourier series, and optimization of phase angles in addition to force constants. The dihedral parameter fitting algorithm’s performance is characterized through multi-dimensional fitting of cyclohexane, tetrahydropyran, and hexopyranose monosaccharide energetics, with the latter case having a 30-dimensional parameter space. The CMAP fitting is applied in the context of polypeptides, and is used to develop a parameterization that simultaneously captures the ?, ? energetics of the alanine dipeptide and the alanine tetrapeptide. Because the dihedral energy term is common to many force fields, we have implemented the dihedral-fitting algorithm in the portable Python scripting language and have made it freely available as Supplementary Material.

Guvench, Olgun; MacKerell, Alexander D.

2010-01-01

376

A Second Generation Force Field for the Simulation of Proteins, Nucleic Acids, and Organic Molecules  

Microsoft Academic Search

We present the derivation of a new molecular mechanical force field for simulating the structures, conformational energies, and interaction energies of proteins, nucleic acids, and many related organic molecules in condensed phases. This effective two-body force field is the successor to the Weiner et al. force field and was developed with some of the same philosophies, such as the use

Wendy D. Cornell; Piotr Cieplak; Christopher I. Bayly; Ian R. Gould; Kenneth M. Merz; David M. Ferguson; David C. Spellmeyer; Thomas Fox; James W. Caldwell

1995-01-01

377

A comparison of different approaches based on force fields for coordination among multiple mobiles  

Microsoft Academic Search

This paper addresses the issue of real-time coordination among multiple mobiles, using the force fields approach. Firstly, a brief overview of different formulations of force fields is presented along with two techniques for handling multiple mobiles. Secondly, a new straight forward formulation of force fields is proposed based on the concept of closest point of approach, and following the principle

Karim ZEGHAL

1998-01-01

378

Computer simulation of electric field variations due to movements of electric charges.  

PubMed

Simulations were carried out for the orbit of electron-induced secondary electrons around a charged microfibril of a sciatic nerve tissue. In order to set the parameters for the simulation, the shape of the microfibril was determined from a transmission electron microscopy image, while the electric potential on the surface of the charged microfibril was evaluated from a reconstructed phase image obtained with electron holography. On the other hand, the passing point and the angle of secondary electrons at the microfibril surface were determined from a reconstructed amplitude image. Eventually, simulation of orbits of secondary electrons was carried out by changing the kinetic energy of the secondary electrons. Under the given conditions, the orbit of secondary electrons with a kinetic energy of 29.6 eV fits the observations. If there are thin layers of electrons, the secondary electrons do not reach the surface but they go over it due to the repulsive Coulomb force resulting in successive revolving motion around the charged microfibril. Furthermore, the electric field variation due to the movement of the electric charges resulting from the specimen drift is also discussed briefly comparing it with electron holography data. PMID:22595205

Inoue, Masao; Suzuki, Satoshi; Akase, Zentaro; Shindo, Daisuke

2012-05-16

379

Electric field and dewetting induced hierarchical structure formation in polymer/polymer/air trilayers.  

PubMed

Electrohydrodynamics were studied in a trilayer thin film system consisting of two different polymeric layers and air. A polymer with a higher dielectric constant, poly(methyl methacrylate), was sandwiched between air and a lower dielectric constant polymer, polystyrene. An electric field was applied normal to the interfaces. Along with electrostatic forces, dewetting forces were significant at two of the interfaces, namely, the polystyrene/silicon wafer and the polystyrene/poly(methyl methacrylate) interfaces. These two combined forces produce novel closed-cell structures that are difficult to produce by other existing techniques. PMID:16396599

Leach, K Amanda; Gupta, Suresh; Dickey, Michael D; Willson, C Grant; Russell, Thomas P

2005-12-01

380

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

381

Surface electric fields for North America during historical geomagnetic storms  

USGS Publications Warehouse

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, Nichole; Gannon, Jennifer L.

2013-01-01

382

Electric field-controlled rippling of graphene.  

PubMed

Metal-graphene interfaces generated by electrode deposition induce barriers or potential modulations influencing the electronic transport properties of graphene based devices. However, their impact on the local mechanical properties of graphene is much less studied. Here we show that graphene near a metallic interface can exhibit a set of ripples self-organized into domains whose topographic roughness is controlled by the tip bias of a scanning tunneling microscope. The reconstruction from topographic images of graphene bending energy maps sheds light on the local electro-mechanical response of graphene under STM imaging and unveils the role of the stress induced by the vicinity of the graphene-metal interface in the formation and the manipulation of these ripples. Since microscopic rippling is one of the important factors that limit charge carrier mobility in graphene, the control of rippling with a gate voltage may have important consequences in the conductance of graphene devices where transverse electric fields are created by contactless suspended gate electrodes. This opens up also the possibility to dynamically control the local morphology of graphene nanomembranes. PMID:24065072

Osváth, Zoltán; Lefloch, François; Bouchiat, Vincent; Chapelier, Claude

2013-09-25

383

Penetration electric fields driving main phase Dst  

NASA Astrophysics Data System (ADS)

On the basis of three selection criteria we have analyzed the main phase electrodynamics of 17 magnetic storms that occurred between 1999 and mid-2005: (1) the availability of solar wind measurements from the Advanced Composition Explorer (ACE) satellite, (2) a minimum Dst ? -100 nT, and (3) no significant recovery episode between the beginning and maximum epoch of the main phase (dDst/dt > 0). We combined the Volland-Stern and Siscoe-Hill models to estimate the intensities of electric fields (EVS) in the equatorial plane as the polar cap potential divided by the width of the magnetosphere along the dawn-dusk axis. A survey of provisional Dst and EVS traces over the 5.5 years of interest shows that all sustained excursions of EVS above quiet time levels of 0.22 ± 0.08 mV/m were closely tied to the main phases of storms. In every instance, EVS returned to background at or near the beginning of the recovery phase. The data indicate very high correlations between Dst and IVS = ?EVSdt during the main phase of all selected storms.

Burke, William J.; Gentile, Louise C.; Huang, Cheryl Y.

2007-07-01

384

Monte Carlo simulations of flexible molecules in a static electric field: electric dipole and conformation  

NASA Astrophysics Data System (ADS)

We have performed Monte Carlo replica-exchange method calculations on the gas phase tryptophan-glycine dipeptide in a static electric field. At low electric field, the average dipole of the molecule follows the Langevin-Debye equation. At high electric field, a deviation from this law is observed and the analysis of the results shows that the external field modifies the conformation of the molecules. This opens the way to a possible control of the conformation of gas phase biomolecules with static electric fields.

Poulain, P.; Antoine, R.; Broyer, M.; Dugourd, P.

2005-01-01

385

Experimental validation of magnetic and electric local force formulations associated to energy principle  

Microsoft Academic Search

In the design process of any device, the computation of the forces or the torque is often a decisive step. Finite element solutions give accurate solutions in terms of magnetic field or flux density. But for local force computation associated to a magnetic field, many formulations are available. They use different physical interpretations of the same phenomenon. Here, a new

Olivier Barré; Pascal Brochet; Michel Hecquet

2006-01-01

386

Planetary Magnetic Fields and Solar Forcing: Implications for Atmospheric Evolution  

NASA Astrophysics Data System (ADS)

The solar wind and the solar XUV/EUV radiation constitute a permanent forcing of the upper atmosphere of the planets in our solar system, thereby affecting the habitability and chances for life to emerge on a planet. The forcing is essentially inversely proportional to the square of the distance to the Sun and, therefore, is most important for the innermost planets in our solar system—the Earth-like planets. The effect of these two forcing terms is to ionize, heat, chemically modify, and slowly erode the upper atmosphere throughout the lifetime of a planet. The closer to the Sun, the more efficient are these process. Atmospheric erosion is due to thermal and non-thermal escape. Gravity constitutes the major protection mechanism for thermal escape, while the non-thermal escape caused by the ionizing X-rays and EUV radiation and the solar wind require other means of protection. Ionospheric plasma energization and ion pickup represent two categories of non-thermal escape processes that may bring matter up to high velocities, well beyond escape velocity. These energization processes have now been studied by a number of plasma instruments orbiting Earth, Mars, and Venus for decades. Plasma measurement results therefore constitute the most useful empirical data basis for the subject under discussion. This does not imply that ionospheric plasma energization and ion pickup are the main processes for the atmospheric escape, but they remain processes that can be most easily tested against empirical data. Shielding the upper atmosphere of a planet against solar XUV, EUV, and solar wind forcing requires strong gravity and a strong intrinsic dipole magnetic field. For instance, the strong dipole magnetic field of the Earth provides a “magnetic umbrella”, fending of the solar wind at a distance of 10 Earth radii. Conversely, the lack of a strong intrinsic magnetic field at Mars and Venus means that the solar wind has more direct access to their topside atmosphere, the reason that Mars and Venus, planets lacking strong intrinsic magnetic fields, have so much less water than the Earth? Climatologic and atmospheric loss process over evolutionary timescales of planetary atmospheres can only be understood if one considers the fact that the radiation and plasma environment of the Sun has changed substantially with time. Standard stellar evolutionary models indicate that the Sun after its arrival at the Zero-Age Main Sequence (ZAMS) 4.5 Gyr ago had a total luminosity of ?70% of the present Sun. This should have led to a much cooler Earth in the past, while geological and fossil evidence indicate otherwise. In addition, observations by various satellites and studies of solar proxies (Sun-like stars with different age) indicate that the young Sun was rotating more than 10 times its present rate and had correspondingly strong dynamo-driven high-energy emissions which resulted in strong X-ray and extreme ultraviolet (XUV) emissions, up to several 100 times stronger than the present Sun. Further, evidence of a much denser early solar wind and the mass loss rate of the young Sun can be determined from collision of ionized stellar winds of the solar proxies, with the partially ionized gas in the interstellar medium. Empirical correlations of stellar mass loss rates with X-ray surface flux values allows one to estimate the solar wind mass flux at earlier times, when the solar wind may have been more than 1000 times more massive. The main conclusions drawn on basis of the Sun-in-time-, and a time-dependent model of plasma energization/escape is that: 1. Solar forcing is effective in removing volatiles, primarily water, from planets,

Lundin, Rickard; Lammer, Helmut; Ribas, Ignasi

2007-03-01

387

Investigation of the Biological Effects of Pulsed Electrical Fields.  

National Technical Information Service (NTIS)

The investigation of the effects of pulsed electrical fields on mammalian erythrocytes indicates that such fields produce transient pores or channels in the cell membrane as evidenced by the release of intercellular potassium ions and hemoglobin (and perh...

S. F. Cleary R. Hoffman L. Liu

1977-01-01

388

Role of electrical field in quantum Hall effect of graphene  

NASA Astrophysics Data System (ADS)

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

Luo, Ji

2013-01-01

389

Crowd instability analysis using velocity-field based social force model  

Microsoft Academic Search

This paper proposes a novel method to locate crowd behavior instability spatio-temporally using a velocity-field based social force model. Considering the impacts of velocity field on interaction force between individuals, we establish an improved social force model by introducing collision probability in view of velocity distribution. As compared with commonly-used social force model, which defines interaction force as a dependent

Jing Zhao; Yi Xu; Xiaokang Yang; Qing Yan

2011-01-01

390

High-frequency electric field measurement using a toroidal antenna  

DOEpatents

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

Lee, Ki Ha (Lafayette, CA)

2002-01-01

391

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

392

Electric field effects on fluorescence quenching due to electron transfer  

Microsoft Academic Search

The effect of an external electric field on fluorescence quenching due to electron transfer from a photoexcited electron donor to an acceptor has been analyzed theoretically. The model predicts that at weak fields the variation DeltaI(c,F)\\/I(c,0) in the steady-state monomer fluorescence intensity induced by an external electric field is proportional to the square of the field strength F and to

Maria Hilczer; Sergey Traytak; M. Tachiya

2001-01-01

393

Electric and Magnetic Fields at Three Pulp and Paper Mills  

Microsoft Academic Search

Extremely low frequency (60 Hz) electric and magnetic field levels were measured at three Canadian pulp and paper mills, using area point-in-time measurements. Most electric field levels were below the limit of detection of 1 V\\/m (92 of 132 measurements); the highest measured field was 47 V\\/m. Measured magnetic field strengths ranged from less than the limit of detection (0.125

Maria Cristina Barroetavena; Randy Ross; Kay Teschke

1994-01-01

394

A new algorithm for simulating flows of conducting fluids in the presence of electric fields  

NASA Astrophysics Data System (ADS)

We propose an algorithm based on dissipative particle dynamics (DPD) for simulations of conducting fluids in the presence of an electric field. In this model, the electrostatic equations are solved in each DPD time step to determine the charge density at the fluid surfaces. These surface charges are distributed on a thin layer of fluid particles near the interface, and the corresponding interfacial electric forces are added to other DPD forces. The algorithm is applied to the electrospinning process at the Taylor cone formation stage. It is shown that, when the applied voltage is sufficiently high, the algorithm captures the formation of a Taylor cone with analytical apex angle 98.6°. Our results demonstrate the potential of the presented DPD algorithm for simulating two-phase problems in the presence of an electric field with non-periodic boundary conditions.

Joulaian, M.; Pishevar, A.; Khajepor, S.; Schmid, F.; Afshar, Y.

2012-11-01

395

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

396

Qualitative and quantitative analysis of dynamic deformation of a cell in nonuniform alternating electric field  

NASA Astrophysics Data System (ADS)

The present paper is dedicated to numerical modeling of the deformation of a cell in a nonuniform ac electric field. A two-fluid model is presented to characterize the flow mechanism of a cell suspending in a medium, in which the mechanical force of cell membranes and dielectrophoretic forces due to the nonuniform ac field are incorporated. The dielectrophoretic forces are then validated by comparing them with the dipole moment approximation. The simulation results demonstrate that the cell deformation depends on the frequency of the electric field. At low frequency, the cell is repelled away from the electrodes, and tilts clockwise. The lower part of the cell deforms thinner, whereas the upper part becomes fatter. At intermediate frequency, the cell moves almost along the centerline of the microchannel, and deforms slightly. The cell orientation oscillates with the average value of zero. At high frequency, however, the cell is attracted toward the electrodes, and tilts counterclockwise. The lower part of the cell becomes fatter, but the upper part deforms thinner. These behaviors are mainly attributed to the distribution of dielectrophoresis force strength generated by the nonuniform electric field.

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

2011-11-01

397

Ionospheric effects from different seismogenic electric field sources  

Microsoft Academic Search

The results of numerical simulations of the impact of different seismogenic electric field sources on TEC (Total Electron Content) of the ionosphere are presented. The external electric currents flowing between the faults and the ionosphere were used as lower boundary condition for the electric potential equation of the UAM (Upper Atmosphere Model). Different configurations and magnitudes of these currents were

Alexander A. Namgaladze; Oleg V. Zolotov

2011-01-01

398

Biological effects of power frequency electric and magnetic fields.  

PubMed

The Institute of Electrical and Electronics Engineers (IEEE) has made an analysis of six recent major scientific committee reports dealing with the biological effects of exposure to electric and magnetic fields associated with electric power distribution and utilization. The conclusions drawn from these committee reports are presented in this summary. PMID:18244086

1989-01-01

399

Reception and learning of electric fields in bees.  

PubMed

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

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

2013-03-27

400

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

401

Injury by electrical forces: pathophysiology, manifestations, and therapy.  

PubMed

The pathogenesis and pathophysiologic features of electrical injury are more complex than once thought. The relative contributions of thermal and pure electrical damage depend on the duration of electric current passage, the orientation of the cells in the current path, their location, and other factors. If the contact time is brief, nonthermal mechanisms of cell damage will be most important and the damage is relatively restricted to the cell membrane. When contact time is much longer, however, heat damage predominates and the whole cell is affected directly. These parameters also determine the anatomic tissue distribution of injury. Damage by Joule heating is not known to be dependent on cell size, whereas larger cells are more vulnerable to membrane breakdown by electroporation. Cells do survive transient plasma membrane rupture under appropriate circumstances or if therapy is instituted quickly. If membrane permeabilization is the primary cellular pathologic condition, then injured tissue may be salvageable and the challenge for the future is to identify a technique to reseal the damaged membranes promptly. Present standards of care for electrical injury require a fully staffed and well-equipped intensive care unit, available operating suites, and the availability of the full range of medical specialists. Major teaching hospitals with burn centers may be the ideal setting for the treatment of an electrical trauma victim. After the initial resuscitation, efforts are directed primarily towards preventing additional tissue loss mediated through the compartment syndrome, compressive neuropathies, or the presence of necrotic tissue. Renal and cardiac failure caused by the release of intracellular muscle contents into the circulation must be prevented. Attention can then be directed towards maximizing tissue salvage and preventing late skeletal and neuromuscular complications. Reconstructive procedures that transfer healthy tissue from a distance are necessary to optimize the functional value of the remaining tissue. Finally, unless the patient is rehabilitated psychologically, the real benefit from other sophisticated care will not be fully realized. These goals are important throughout the acute care of the patient. In the future, new guidelines for treating electrical trauma will be based on a clearer understanding of the relevant pathophysiologic features. These strategies will rely on improved diagnostic imaging and on reversing the fundamental problem of cell membrane damage. Moreover, complex biochemical and organ system pathophysiologic interactions will require careful management. If successful, research efforts presently underway should improve the prognosis of victims after electrical trauma. PMID:9365421

Lee, R C

1997-09-01

402

EHD behavior of nitrogen bubbles in DC electric fields  

SciTech Connect

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

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

2007-10-15

403

Possible DC electric field in the ionosphere related to seismicity  

NASA Astrophysics Data System (ADS)

This paper presents the method for calculation of DC electric field in the atmosphere and the ionosphere generated by model distribution of external electric current in the lower atmosphere. Appearance of such current is associated with enhancement of seismic activity that is accompanied by emanation of soil gases into the atmosphere. These gases transfer positive and negative charged aerosols. Atmospheric convection of charged aerosols forms external electric current, which works as a source of conductivity current in the atmosphere ionosphere electric circuit. It is shown that DC electric field generated in the ionosphere by this current reaches up to 10 mV/m, while the long-term vertical electric field disturbances excited near the Earth surface do not exceed 100 V/m. Such limitation of the near-ground field is caused by the formation of potential barrier for charged particles at the Earth surface in a process of their transport from soil to atmosphere.

Sorokin, V. M.; Chmyrev, V. M.; Yaschenko, A. K.

404

Electron acceleration by low frequency electric field fluctuations - Electron conics  

Microsoft Academic Search

Electron conics can be generated by fluctuations at roughly one Hz in a parallel electric field accelerating auroral electrons at altitudes of several thousand kilometers. The results from simulations including such time-varying electric fields are in good agreement with observed electron distributions. The simulation parameters are consistent with the ion beams and broadband waves associated with electron conics. Calculations are

Mats Andre; Lars Eliasson

1992-01-01

405

INACTIVATION OF SACCHAROMYCES CEREVISIAE USING RADIO FREQUENCY ELECTRIC FIELDS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

406

Equatorial Ionospheric Electric Fields During the November 2004 Magnetic Storm  

Microsoft Academic Search

We use radar measurements from the Jicamarca Radio Observatory, magnetometer observations from the Pacific sector and ionosonde data from Brazil to study equatorial ionospheric electric fields during the November 2004 geomagnetic storm. Our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in

B. G. Fejer; J. W. Jensen; T. Kikuchi; M. A. Abdu; J. L. Chau

2007-01-01

407

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

408

Vertical variations of the polarization electric field in the ionosphere  

NASA Astrophysics Data System (ADS)

Expressions to describe the vertical distribution of the polarization electric field in the ionosphere are proposed. The expressions are based on the analysis of the rocket sounding data presented by Serafimov and Kutiev (1980). Consideration is given to the relationship between height and the nullification of the polarization electric field.

Serafimov, K. B.

409

Empirical models of storm time equatorial zonal electric fields  

Microsoft Academic Search

Ionospheric plasma drifts often show highly complex and variable signatures during geomagnetically active periods due to the effects of different disturbance processes. We describe initially a methodology for the study of storm time dependent ionospheric electric fields. We present empirical models of equatorial disturbance zonal electric fields obtained using extensive F region vertical plasma drift measurements from the Jicamarca Observatory

Ludger Scherliess

1997-01-01

410

PULSED ELECTRIC FIELD PROCESSING FACT SHEET FOR FOOD PROCESSORS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

411

Underground Test Sensor Development. Volume 2. Electric Field Sensor Development.  

National Technical Information Service (NTIS)

A concept for the nonperturbative measurement of electric fields in a plasma is described. The concept is based on laser-induced fluorescence from Stark-mixed states. This work reviews the electric field measurement concept, the choices of an active mediu...

J. Bahns

1990-01-01

412

Nanosecond pulsed electric field effects on human cells  

Microsoft Academic Search

Electric fields have been used on intact cells for decades, most notably for effects on plasma membranes for cell fusion and transient electroporation to allow the entry of xenomolecules. Compared to electroporation pulses, new pulse power technology generates non-thermal pulses with shorter durations and higher electric fields (nsPEF) such that the charging time of the plasma membrane is not reached,

Stephen J. Beebe; Paula Fox; Laura Rec; Lauren Willis; Karl Schoenbach

2002-01-01

413

Electric field-treated MEAs for improved fuel cell performance  

Microsoft Academic Search

In this paper, electric field assisted fabrication of membrane electrode assemblies (MEAs) for fuel cells is proposed, with the aim of improving the electronic and ionic connections in the catalyst layers and increasing the efficiency of catalyst utilization. Anodic and cathodic electrodes have been prepared by the perpendicular application of a low-frequency ac electric field to the catalyst ink spread

Zhi-Tao Wang; Yu-Xin Wang; Li Xu; Qi-Jun Gao; Guo-Qiang Wei; Jun Lu

2009-01-01

414

A Dielectrophoretic Chip With a 3-D Electric Field Gradient  

Microsoft Academic Search

This paper presents the design, fabrication and testing of a new structure of dielectrophoresis (DEP) chip having a three-dimensional (3-D) electric field gradient and an asymmetric distribution of the electric field in the vertical plane. This achievement was possible due to the special configuration of the electrodes: a bulk silicon electrode and a thin amorphous silicon electrode. The thick electrode

Ciprian Iliescu; Liming Yu; Guolin Xu; Francis E. H. Tay

2006-01-01

415

Effects of Radial Electric Fields on ICRF Waves  

SciTech Connect

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

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

2001-06-18

416

High intensity pulsed electric fields applied for food preservation  

Microsoft Academic Search

Preservation of liquid foods by high intensity pulsed electric fields (PEF) is an interesting alternative to traditional techniques like thermal pasteurization. Based on the underlying mechanism of action, in this paper the crucial process parameters electrical field strength, total pulse energy input and treatment temperature were investigated experimentally. Inactivation studies were performed with three bacteria (E. coli, Bacillus megaterium, Listeria

S. Toepfl; V. Heinz; D. Knorr

2007-01-01

417

Subnanosecond Pulsed-Power Generated Electric Fields for Cancer Treatment  

Microsoft Academic Search

This article summarizes ongoing research on the use of pulsed power-generated electric fields as a delicate tool for skin cancer treatment. A prolate-spheroidal impulse radiating antenna is used as a noninvasive technique for generating an electromagnetic implosion to kill melanoma cells. Index Terms—Pulsed-power generated electric field, Impulse radiating antennas, Cancer treatment

Serhat Altunc; Andy Warhol

2009-01-01

418

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

419

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

420

Augmented electric- and magnetic-field integral equations  

Microsoft Academic Search

Augmented electric- and magnetic-field integral equations, which preserve the basic simplicity, solution capability, and pure electric- and magnetic-field character of Maue's original integral equations, are introduced to eliminate the spurious resonances from the exterior solution of the original integral equations. The exact dependence of the original and augmented integral equations on the geometry of the principal area (self patch) which

Arthur D. Yaghjian

1981-01-01

421

A Novel Electrical Field Bioreactor for Wound Healing Study  

Microsoft Academic Search

Wound healing is essential for maintaining the integrity of multicellular organisms. The disruption of an epithelial layer instantaneously generates endogenous electric fields, which play a key role in wound healing. In vitro, a variety of cells respond to DC electric fields of physiological strength by directional movement. Such experiments involve culturing cells in specially designed galvanotaxis chambers connected to a

Gang Yang; Haiyan Long; Jiang Wu; Hua Huang

2008-01-01

422

Using Gravitational Analogies to Introduce Elementary Electrical Field Theory Concepts  

Microsoft Academic Search

Since electrical field concepts are usually unfamiliar, abstract, and difficult to visualize, conceptual analogies from familiar gravitational phenomena are valuable for teaching. Such analogies emphasize the underlying continuity of field concepts in physics and support the spiral development of student understanding. We find the following four tables to be helpful in reviewing gravitational and electrical comparisons after students have worked

Susan Saeli; Dan MacIsaac

2007-01-01

423

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

424

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

425

Molecular dynamics simulations of methane hydrate using polarizable force fields  

SciTech Connect

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

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

2007-03-01

426

Development of the CHARMM Force Field for Lipids  

PubMed Central

The development of the CHARMM additive all-atom lipid force field (FF) is traced from the early 1990’s to the most recent version (C36) published in 2010. Though simulations with early versions yielded useful results, they failed to reproduce two important quantities: a zero surface tension at the experimental bilayer surface area, and the signature splitting of the deuterium order parameters in the glycerol and upper chain carbons. Systematic optimization of parameters based on high level quantum mechanical data and free energy simulations have resolved these issues, and bilayers with a wide range of lipids can be simulated in tensionless ensembles using C36. Issues associated with other all-atom lipid FFs, success and limitations in the C36 FF and ongoing developments are also discussed.

Pastor, R.W.; MacKerell, A.D.

2011-01-01

427

Accounting for electronic polarization in non-polarizable force fields.  

PubMed

The issues of electronic polarizability in molecular dynamics simulations are discussed. We argue that the charges of ionized groups in proteins, and charges of ions in conventional non-polarizable force fields such as CHARMM, AMBER, GROMOS, etc should be scaled by a factor about 0.7. Our model explains why a neglect of electronic solvation energy, which typically amounts to about a half of total solvation energy, in non-polarizable simulations with un-scaled charges can produce a correct result; however, the correct solvation energy of ions does not guarantee the correctness of ion-ion pair interactions in many non-polarizable simulations. The inclusion of electronic screening for charged moieties is shown to result in significant changes in protein dynamics and can give rise to new qualitative results compared with the traditional non-polarizable force field simulations. The model also explains the striking difference between the value of water dipole ?? 3D reported in recent ab initio and experimental studies with the value ?(eff)? 2.3D typically used in the empirical potentials, such as TIP3P or SPC/E. It is shown that the effective dipole of water can be understood as a scaled value ?(eff) = ?/??(el), where ?(el) = 1.78 is the electronic (high-frequency) dielectric constant of water. This simple theoretical framework provides important insights into the nature of the effective parameters, which is crucial when the computational models of liquid water are used for simulations in different environments, such as proteins, or for interaction with solutes. PMID:21212894

Leontyev, Igor; Stuchebrukhov, Alexei

2011-01-07

428

Electric and Magnetic Field Detection in Elasmobranch Fishes  

NASA Astrophysics Data System (ADS)

Sharks, skates, and rays receive electrical information about the positions of their prey, the drift of ocean currents, and their magnetic compass headings. At sea, dogfish and blue sharks were observed to execute apparent feeding responses to dipole electric fields designed to mimic prey. In training experiments, stingrays showed the ability to orient relative to uniform electric fields similar to those produced by ocean currents. Voltage gradients of only 5 nanovolts per centimeter would elicit either behavior.

Kalmijn, Ad. J.

1982-11-01

429

Cell Membrane Charging in Intense Nanosecond Pulsed Electric Fields  

Microsoft Academic Search

In order to study membrane charging in mammalian cells during exposure to pulsed electric fields of 60 ns duration we measured transmembrane voltage changes during and after exposure in real-time, i.e. with a resolution that is short compared to the duration of the administered electrical pulse. The applied electric field was varied between 5 kV\\/cm and 90 kV\\/cm. Under all

J. F. Kolb; W. Frey; J. A. White; S. J. Beebe; R. P. Joshi; K. H. Schoenbach

2006-01-01

430

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

431

Ultracold molecular collisions in combined electric and magnetic fields  

NASA Astrophysics Data System (ADS)

We consider collisions of electric and magnetic polar molecules, taking the OH radical as an example, subject to combined electric and magnetic static fields. We show that the relative orientation of the fields has an important effect on the collision processes for different fields' magnitudes at different collision energies. This is due to the way the molecules polarize in the combined electric and magnetic fields and hence the way the electric dipole-dipole interaction rises. If OH molecules are confined in magnetic quadrupole traps and if an electric field is applied, molecular collisions will strongly depend on the position as well as the velocity of the molecules. Consequences on the molecular dynamics are discussed.

Quéméner, Goulven; Bohn, John L.

2013-07-01

432

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

433