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Physics 2000: Electric Force Fields
NSDL National Science Digital Library
This page illustrates and describes electric fields and forces through a simulation. The explanation is given in the form of a conversation between two people. There is also a simple simulation which helps understand the concept better. This web page is part of a tutorial that introduces electric forces and fields.
Minnesota, University of
LABORATORY I ELECTRIC FIELDS AND FORCES Lab I - 1 The most fundamental forces are characterized as "action-at-a-distance". This means that an object can exert a force on another object that is not in contact with it. You have already learned about the gravitational force, which is of this type. You
Minnesota, University of
, electric, and magnetic) make up a common part of your everyday experiences. These forces are difficult energy as residing in the field. Using fields to study interactions solves the intellectual puzzle. The only reason we use field theory is because it leads us to a deeper understanding of natural phenomena
Chapter 19: Electric Charges, Forces, and Fields
Kioussis, Nicholas
of gravity on the proton. Set the magnitudes of the two forces equal to each other and solve for r. Set of electrons and protons are collected together into a single system. Use the total number of charges and the net electrical charge of the system to determine the number of protons and electrons. Sum the product
Ponderomotive force in the presence of electric fields
NASA Astrophysics Data System (ADS)
Khazanov, G. V.; Krivorutsky, E. N.
This paper presents averaged equations of particle motion in an electromagnetic wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. The particle is also subjected to an E?ūB? drift and a background electric field slowly changing in space and acting along the magnetic field line. The fields, wave amplitude, and the wave vector depend on the coordinate along the magnetic field line. The derivations of the ponderomotive forces are done by assuming that the drift velocity in the ambient magnetic field is comparable to the particle velocity. Such a scenario leads to new ponderomotive forces, dependent on the wave magnetic field intensity, and, as a result, to the additional energy exchange between the wave and the plasma particles. It is found that the parallel electric field can lead to the change of the particle-wave energy exchange rate comparable to that produced by the previously discussed ponderomotive forces.
Ponderomotive force in the presence of electric fields
Khazanov, G. V.; Krivorutsky, E. N. [NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)
This paper presents averaged equations of particle motion in an electromagnetic wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. The particle is also subjected to an E(vector sign) Multiplication-Sign B(vector sign) drift and a background electric field slowly changing in space and acting along the magnetic field line. The fields, wave amplitude, and the wave vector depend on the coordinate along the magnetic field line. The derivations of the ponderomotive forces are done by assuming that the drift velocity in the ambient magnetic field is comparable to the particle velocity. Such a scenario leads to new ponderomotive forces, dependent on the wave magnetic field intensity, and, as a result, to the additional energy exchange between the wave and the plasma particles. It is found that the parallel electric field can lead to the change of the particle-wave energy exchange rate comparable to that produced by the previously discussed ponderomotive forces.
Average Lorentz Self-Force From Electric Field Lines
Aashish, Sandeep
We generalize the derivation of electromagnetic fields of a charged particle moving with a constant acceleration [1] to a variable acceleration (piecewise constants) over a small finite time interval using Coulomb's law, relativistic transformations of electromagnetic fields and Thomson's construction [2]. We derive the average Lorentz self-force for a charged particle in arbitrary non-relativistic motion via averaging the fields at retarded time.
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.
Analysis of the electric field induced forces in erythrocyte membrane pores using a realistic cell model.
Sebastißn, J L; Mu±oz, S; Sancho, M; Miranda, J M
We calculate the induced electric stress forces on transient hydrophobic pores in the membrane of an erythrocyte exposed to an electric field. For this purpose, we use a finite element numerical technique and a realistic shape for the biconcave erythrocyte represented by a set of parametric equations in terms of Jacobi elliptic functions. The results clearly show that the electrical forces on the base and sidewalls of the pore favour the opening of the pore. A comparison of the force densities obtained for an unstretched flat membrane and for the realistic erythrocyte model shows that the thinning and curvature of the membrane cannot be neglected. We also show that the pore deformation depends strongly on the orientation of the pore with respect to the external field, and in particular is very small when the field is tangent to the membrane surface. PMID:17110781
Analytical solutions and validation of electric field and dielectrophoretic force in a bio-microfluidic channel.
Nerguizian, Vahķ; Alazzam, Anas; Roman, Dacian; Stiharu, Ion; Burnier, Miguel
In a microbiological device, cell or particle manipulation and characterization require the use of electric field on different electrodes in several configurations and shapes. To efficiently design microelectrodes within a microfluidic channel for dielectrophoresis focusing, manipulation and characterization of cells, the designer will seek the exact distribution of the electric potential, electric field and hence dielectrophoresis force exerted on the cell within the microdevice. In this paper we describe the approach attaining the analytical solution of the dielectrophoretic force expression within a microchannel with parallel facing same size electrodes present on the two faces of channel substrates, with opposite voltages on the pair electrodes. Simple Fourier series mathematical expressions are derived for electric potential, electric field and dielectric force between two distant finite-size electrodes. Excellent agreement is found by comparing the analytical results calculated using MATLABÖ with numerical ones obtained by Comsol. This analytical result can help the designer to perform simple design parametric analysis. Bio-microdevices are also designed and fabricated to illustrate the theoretical solution results with the experimental data. Experiments with red blood cells show the dielectrophoretic force contour plots of the analytical data matched to the experimental results. PMID:22287173
Centrifugal and electric field forces dual-pumping CD-like microfluidic platform for biomedical separation.
Wang, Gou-Jen; Hsu, Wen-Haw; Chang, Yau-Zin; Yang, Hsiharng
In this article, we propose a versatile CD-like multi-channel electrophoresis-based biomedical separation system that is driven by the interactive forces between the centrifugal force and the electric field force. The centrifugal force control of this system is realized through the velocity control of a DC servo motor, while the electric field is governed through the concentric conducting circuits, which are suitably designed and fabricated by sputtering on metal mask method, and can be adjusted to provide multi-stage voltages. Experimental results demonstrate that the electro-osmotic flow (EOF) effect can be effectively reduced when the electric field force and centrifugal force are in the opposite direction. Benefits from this are that the electrophoresis separation time can be prolonged and the length of the microfluidic channels can be shortened; therefore, more effective separation efficiency can be obtained. Moreover, other advantages, such as lower joule-heat generation, low-chemistry reaction, and no variation on the ion concentration during processes, make this biomedical separation system more useful. PMID:15307444
The Lorentz forces on an electrically conducting sphere in an alternating magnetic field
Udaya B. Sathuvalli; Yildiz Bayazitoglu
A method to calculate the Lorentz force on an electrically conducting sphere placed in an arbitrary sinusoidally varying magnetic field is developed. The crux of this method lies in expressing the external magnetic held and the eddy current density in the sphere in terms of a ōsource functionö of the current sources and a ōskin depth dependent functionö. The general
Study of electric fields parallel to the magnetic lines of force using artificially injected energetic electrons
NASA Technical Reports Server (NTRS)
Wilhelm, K.; Bernstein, W.; Whalen, B. A.
Electron beam experiments using rocket-borne instrumentation will be discussed. The observations indicate that reflections of energetic electrons may occur at possible electric field configurations parallel to the direction of the magnetic lines of force in an altitude range of several thousand kilometers above the ionosphere.
Effects of auroral-particle anisotropies and mirror forces on high-latitude electric fields
NASA Technical Reports Server (NTRS)
Chiu, Y. T.; Schulz, M.; Cornwall, J. M.
It is noted that, for most of the mechanisms for the strong electric fields that characterize the narrow regions in which there is acceleration and precipitation of ring current and/or plasma-sheet plasma, certain effects must be taken into account in simulations of auroral electric fields. The effects are those of auroral particle anisotropy, of mirror forces due to the inhomogeneous geomagnetic field, of auroral electron backscatter by the atmosphere, and of electron trapping by the combination of magnetic mirroring and electrostatic forces. What is more, the effects of the very strong perpendicular electric field must also be taken into account in a kinetic description of the Poisson equation in order to achieve a unified theory of the auroral electrostatic structure. Progress in these areas during the past few years is reviewed. It is shown that particle anisotropies and mirror forces can account for some basic electrostatic features of the quiet arc, while additional effects may be occurring in strong events in which the parallel potential drop is more than about 10 kV.
Non-uniform spatial distributions of both the magnitude and phase of AC electric fields determine dielectrophoretic forces
X.-B Wang; M. P Hughes; Y Huang; F. F Becker; P. R. C Gascoyne
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
Directly resolving particles in an electric field: local charge, force, torque, and applications
NASA Astrophysics Data System (ADS)
Liu, Qianlong
Prosperetti's seminal Physalis method for fluid flows with suspended particles is extended to electric fields to directly resolve finite-sized particles and to investigate accurately the mutual fluid-particle, particle-particle, and particle-boundary interactions. The method can be used for uncharged/charged dielectrics, uncharged/charged conductors, conductors with specified voltage, and general weak and strong discontinuous interface conditions. These interface conditions can be in terms of field variable, its gradients, and surface integration which has not been addesed by other numerical methods. In addition, for the first time, we rigorously derive the force and torque on the finite-sized particles resulting from the interactions between harmonics. The method, for the first time, directly resolves the particles with accurate local charge distribution, force, and torque on the particles, making many applications in engineering, mechanics, physics, chemistry, and biology possible, such as heterogeneous materials, microfluidics, electrophotography, electric double layer capacitors, and microstructures of nanodispersions. The efficiency of the method is demonstrated with up to one hundred thousand 3D particles, which suggests that the method can be used for many important engineering applications of broad interest. This research is supported by the Department of Energy under funding for an EFRC (the HeteroFoaM Center), grant no. DE-SC0001061.
Electric-field-induced force on a charged spherical colloid embedded in an electrolyte-saturated Brinkman medium
NASA Astrophysics Data System (ADS)
Hill, Reghan J.
When an electric field is applied to an electrolyte-saturated polymer gel immobilizing charged colloidal particles, the force that must be exerted by the hydrogel on each particle reflects a delicate balance of electrical and hydrodynamic stresses. This article adopts a simple boundary-layer analysis to derive a convenient formula for the force in terms of the particle, electrolyte and gel characteristics. Comparisons with numerically exact solutions of the full set of electrokinetic transport equations are presented. These reveal that a fortuitous cancellation of errors leads to reasonably accurate predictions of the force over a much wider range of the parameter space than should be expected. It is noteworthy that, in gels with low permeability, an adverse pressure gradient yields a net force that exceeds the bare electrical force. The analytical theory also provides a convenient formula for the incremental pore mobility, which is a convenient measure of the electro-osmotic pumping capacity of dilute random arrays of charged inclusions.
Polyhedra Formation and Transient Cone Ejection of a Resonant Microdrop Forced by an ac Electric Field
Chang, Hsueh-Chia
Polyhedra Formation and Transient Cone Ejection of a Resonant Microdrop Forced by an ac Electric of the diffuse layer. The selected polyhedra possess symmetries that ensure a global force balance of the Maxwell and frequencies, specific spherical har- monics are shown to evolve into specific polyhedra at comparatively low
NSDL National Science Digital Library
Reddy, B. Surendranath
This applet displays the electric field lines of force around one or two charged particle. The charged particle can be positive or negative. The magnitude of charge can be varied and the change in the electric field lines of force can be viewed. This is part of a large collection of physics and math applets by the author Surendrenath Reddy.
Molecular dynamics study of response of liquid N,N-dimethylformamide to externally applied electric field using a polarizable force field
Gao, Weimin; Niu, Haitao; Lin, Tong; Wang, Xungai; Kong, Lingxue [Institute for Frontier Materials, Deakin University, Waurn Ponds VIC 3216 (Australia)] [Institute for Frontier Materials, Deakin University, Waurn Ponds VIC 3216 (Australia)
The behavior of Liquid N,N-dimethylformamide subjected to a wide range of externally applied electric fields (from 0.001 V/nm to 1 V/nm) has been investigated through molecular dynamics simulation. To approach the objective the AMOEBA polarizable force field was extended to include the interaction of the external electric field with atomic partial charges and the contribution to the atomic polarization. The simulation results were evaluated with quantum mechanical calculations. The results from the present force field for the liquid at normal conditions were compared with the experimental and molecular dynamics results with non-polarizable and other polarizable force fields. The uniform external electric fields of higher than 0.01 V/nm have a significant effect on the structure of the liquid, which exhibits a variation in numerous properties, including molecular polarization, local cluster structure, rotation, alignment, energetics, and bulk thermodynamic and structural properties.
Microextraction of mebendazole across supported liquid membrane forced by pH gradient and electrical field.
Eskandari, Mahboube; Yamini, Yadollah; Fotouhi, Lida; Seidi, Shahram
In the present study, extraction of mebendazole across a supported-liquid membrane (SLM) was performed based on two different driving forces: (1) pH gradient over the SLM, and (2) electrical field sustained over the SLM. The extracted drug concentration was studied using reversed-phase HPLC-UV. At passive extraction conditions, mebendazole was extracted from alkaline samples (0.01 mmol L(-1) NaOH) into 1-undecanol immobilized in the pores of a porous hollow fiber of polypropylene (SLM), and then transported into 25 ?L of 100mM HCl as the acceptor solution. Under electrokinetic migration conditions, mebendazole transported under applied voltage from acidic solutions (100 mmol L(-1) HCl) through 2-nitrophenyl octyl ether (NPOE) immobilized in the pores of hollow fiber, into 25 ?L of 100 mmol L(-1) HCl as the acceptor solution. The effects of several factors including the nature of organic solvent, pH of donor and acceptor solutions, extraction time and stirring speed on the extraction efficiency of the drug were investigated and optimized. Under optimal conditions, preconcentration factors (PF) of 211 and 190 were obtained for the drug based on passive transport and electromembrane extraction (EME), respectively. Also, linear range of 0.5-1000 ?g L(-1) with estimation of coefficient higher than 0.994 was obtained for both of the proposed methods. The results showed that EME has higher speed in comparison with simple passive transport. The methods were successfully applied to extract mebendazole from plasma and urine samples and satisfactory results were obtained. PMID:21211924
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.
NSDL National Science Digital Library
Nave, Rod
In this free resource topics are connected in a well-organized concept map. One click takes the teacher from electric field to related topics such as Gauss' Law, capacitance, and calculations related to force and field potential. This item is part of a larger collection under continuing development by Dr. Rod Nave, Georgia State University.
Polymer Size Effect on Shape and Position in DNA Trap by Electric and Hydrodynamic Force Fields
NASA Astrophysics Data System (ADS)
Ueno, Kunimitsu; Nagasaka, Wako; Tomizawa, Yuichi; Nakamori, Yoshiteru; Tamiya, Eiichi; Takamura, Yuzuru
In recent years, a phenomenon has been discovered wherein charged particles are trapped near the constricted position of a microfluidic tapering channel when hydropressure and electric field are applied in opposite directions. By this phenomenon, the existence of various types of trapping patterns has already been demonstrated in a T4 phage DNA trapping experiment. In this study, we aim to explain the mechanism of this phenomenon. The relationship between DNA size and trapping pattern was examined using five different sizes of DNA samples. As a result, the trapping pattern and trapping condition extremely different with size when the most stable and clearest trapping image is observed. That is, the main trapping patterns change markedly in shapes and trapped positions, and large DNA traps occur under the conditions of low pressure and low voltage, whereas small size traps occur under the conditions of high pressure and high voltage. Another important result is that the ratio of the pressure and the voltage is independent of size when the main trap is observed. These findings suggest that this trap has size selectivity and molecular selectivity for extracting target molecules from a mixed solution.
Gap junctional regulation of pressure, fluid force, and electrical fields in the epigenetics of cardiac morphogenesis and remodeling.
Seki, Akiko; Nishii, Kiyomasa; Hagiwara, Nobuhisa
Epigenetic factors of pressure load, fluid force, and electrical fields that occur during cardiac contraction affect cardiac development, morphology, function, and pathogenesis. These factors are orchestrated by intercellular communication mediated by gap junctions, which synchronize action potentials and second messengers. Misregulation of the gap junction protein connexin (Cx) alters cardiogenesis, and can be a pathogenic factor causing cardiac conduction disturbance, fatal arrhythmia, and cardiac remodeling in disease states such as hypertension and ischemia. Changes in Cx expression can occur even when the DNA sequence of the Cx gene itself is unaltered. Posttranslational modifications might reduce arrhythmogenic substrates, improve cardiac function, and promote remodeling in a diseased heart. In this review, we discuss the epigenetic features of gap junctions that regulate cardiac morphology and remodeling. We further discuss potential clinical applications of current knowledge of the structure and function of gap junctions. PMID:25447447
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
Electric field and force modeling for electrostatic levitation of lossy dielectric plates
S. J. Woo; T. Higuchi
Electrostatic levitation holds great promise for the semiconductor, solar panel, and flat-panel display industry where the handling of dielectrics in a contact-free manner can bring many advantages and solve long-standing contamination and particulate control problems. In this work an analytical model is developed for the electrostatic levitation field between a lossy dielectric plate and a generic stator electrode structure consisting
Electric and Magnetic Forces: Electromagnetism
NSDL National Science Digital Library
National Science Teachers Association (NSTA)
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.
Generation of transverse fluid currents and forces by an electric field: Electro-osmosis on charge-modulated and undulated surfaces
Armand Ajdari
As in the usual paradigm for electro-osmosis, an electrolyte fluid confined between two parallel plates is considered, and an electric field E-->ext is applied parallel to the plates. Analyzing here the combined effect of charge and shape modulation on the surfaces, E-->ext is shown to generate flows in the slab and forces on the plates even if the plates (and
Nonsimilar, laminar, steady, electrically-conducting forced convection liquid metal boundary layer flow with induced magnetic field effects
O. Anwar Bķg; A. Y. Bakier; V. R. Prasad; J. Zueco; S. K. Ghosh
A nonsimilar steady laminar boundary layer model is described for the hydromagnetic convection flow of a Newtonian, electrically-conducting liquid metal past a translating, non-conducting plate with a magnetic field aligned with the plate direction. The non-dimensional boundary layer equations are solved with the Sparrow¢Quack¢Boerner local nonsimilarity method (LNM). An increase in magnetic Prandtl number (Prm) is found to strongly enhance
Novel scheme for drawing electric lines of force using scalar potential
Masashi Ohchi; Tatsuya Furukawa; Hideki Shimada
The electric lines of force are trajectories comprising the tangents of the lines of forces that act on the electric charge in the electric field. In the complicated system of the multi-dielectric and multi-conductor media, the lines of force are not necessarily continuous on the interface of the dielectric media. In the engineering application, the visualization of the electric fields
K. B. Maracas
Increasing electrification brings increased human exposures to electric and magnetic fields, commonly called EMFs, and growing evidence suggests that exposure to even low frequency, low energy, electric and magnetic fields may be related to adverse health effects. This paper focuses on magnetic fields and strategies that address them. The challenges faced by scientists in understanding magnetic field interactions with humans,
Outer hair cell length changes in an external electric field. II. The role of electrokinetic forces on the cell surface.
Jerry, R A; Popel, A S; Brownell, W E
An isolated cochlear outer hair cell can elongate or shorten when electrically stimulated, as discovered by Brownell et al. [Science 227, 194-196 (1985)]. In their experiments, the cylindrically shaped cell was fixed at one end, and was positioned between two electrodes which lie on the cell axis, but were far from the cell (transcellular stimulation). A model is developed to predict the component of the cell's elongation which arises from only electrokinetic phenomena. Outside the cell, electro-osmosis produces a drag on the lateral wall which almost exactly balances the electrophoretic force. In contrast to previous theories, we find that the electrokinetic response is governed by the free end of the cell, not the lateral wall. If the surface charge density of the free end lies between -0.004 and -0.07 C/m2 (corresponding to the zeta potential between -5 and -60 mV), then our model predicts elongations that are comparable in magnitude to experimentally measured values. PMID:7593923
Technology Transfer Automated Retrieval System (TEKTRAN)
The concept of pulsed electric fields (PEF) was first proposed in 1967 to change the behavior or microorganisms. The electric field phenomenon was identified as membrane rupture theory in the 1980s. Increasing the membrane permeability led to the application of PEF assisted extraction of cellular co...
NSDL National Science Digital Library
Wolfgang Christian
The square represents a cross section of a cube. Use the test charge to explore the direction of the electric field inside the cube. Click the cursor anywhere inside the cube to measure the magnitude of the electric field. Use it also to determine the dimensions of the cube. Find the flux through each side of the cube.
Nonconservative electric and magnetic optical forces on submicron dielectric particles
Gomez-Medina, Raquel; Nieto-Vesperinas, Manuel [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Campus de Cantoblanco, Madrid E-28049 (Spain); Saenz, Juan Jose [Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, 20018 Donostia-San Sebastian (Spain)
We present a study of the total force on a small lossless dielectric particle, which presents both an electric and magnetic response, in a optical vortex wave field. We show that the force is a simple combination of conservative and nonconservative steady forces that can rectify the flow of magnetodielectric particles. In a vortex lattice the electric-magnetic dipolar interaction can spin the particles either in or out of the whirl sites leading to trapping or diffusion. Specifically, we analyze force effects on submicron silicon spheres in the near infrared, proving that the results previously discussed for hypothetical magnetodielectric particles can be observed for these Si particles.
Formation, characterization and dynamics of onion like carbon structures from nanodiamonds using reactive force-fields for electrical energy storage
Kent, Paul R [ORNL
We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbon nanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core of the nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbon nanostructure appears, with a shell-shell spacing of about {approx}3.4 {angstrom} for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large ({approx}29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.
Electric lines of force of an electrically small dipole-loop antenna array
P. L. Overfelt
The electric lines of force of an electrically small dipole-loop antenna array have been determined analytically for both the near- and far-fields of the array. It has been found that the behavior of the families of electric contours are dependent upon a coupling parameter, which is the ratio of the loop and dipole sizes and currents. This parameter also controls
Revisiting the Corotation Electric Field
NASA Astrophysics Data System (ADS)
Rothwell, P. L.
The rotation of the Earth's dipole magnetic field produces a corotation electric field in the nonrotating frame of reference. A quick calculation implies that this field might arise from the relative motion of an observer in the nonrotating frame and the motion of rotating magnetic field lines. However, upon applying Faraday's Law one finds that total time rate of change of the magnetic field as seen in the nonrotating frame is zero due to the azimuthal symmetry of the dipole. Therefore, classical EM theory(1) predicts a zero corotation electric field in the nonrotating frame for a vacuum. This conundrum has been traditionally treated in the following manner(2,3). 1) Start with a vacuum state with no conductors and plasma present. The transformation between E (the electric field in the nonrotating frame) and E' (the electric field in the rotating frame)implies that in the rotating frame E' is nonzero while E = 0. 2) In the presence of a thin conducting spherical shell (the ionosphere) polarization charges form in the shell due to the magnetic force on the electrons. A polarization electric field Ep is created such that in the idealized case the shell has a uniform electric potential. This Ep has a component along the magnetic field lines outside the shell. 3) Plasma will polarize along B, thus canceling the parallel component of Ep which allows the potential on the shell to be mapped along the magnetic field lines setting E' = 0. From the transformation equation E is now nonzero. This is the electric field required in the nonrotating frame for the plasma to corotate with the dipole. The presence of the corotation electric field is not a local result, but a nonlocal effect that requires the presence of an ionosphere and a conducting plasma. (1) W.K.H. Panofsky and M. Phillips, Classical Electricity and Magnetism, Addison-Wesley, 1956. (2) H. Alfven and C.-G. Falthammar, Cosmical Electrodynamics, 2nd ed., Oxford Press, 1963. (3) E.W.Hones and J.E.Bergeson, J. Geophys. Res. , 70, 4951, 1965.
NSDL National Science Digital Library
Wolfgang Christian
One or more objects with uniform charge on them are located just off the screen on the left-hand side. Use the test charge to measure the electric field, and from that determine what type of object they are.
The dielectrophoretic force in its simplest implementation is the interaction of a nonuniform electric field with the dipole moment it induces in an object. The typical case is the induced
Voldman, Joel
of a nonuniform electric field with the dipole moment it induces in an object. The typical case is the induced and higher-order moments in the object. In addition, at field nulls the dipole moment is zero, because dipole in a lossy dielectric spherical particle. The force in this case, where the particle is much
49 CFR 236.758 - Lock, electric, forced drop.
Code of Federal Regulations, 2010 CFR
...2010-10-01 false Lock, electric, forced drop. 236.758 Section 236.758...Definitions ¦ 236.758 Lock, electric, forced drop. An electric lock in which the locking member is mechanically forced down to the locked...
49 CFR 236.758 - Lock, electric, forced drop.
Code of Federal Regulations, 2013 CFR
...2013-10-01 false Lock, electric, forced drop. 236.758 Section 236.758...Definitions ¦ 236.758 Lock, electric, forced drop. An electric lock in which the locking member is mechanically forced down to the locked...
49 CFR 236.758 - Lock, electric, forced drop.
Code of Federal Regulations, 2012 CFR
...2012-10-01 false Lock, electric, forced drop. 236.758 Section 236.758...Definitions ¦ 236.758 Lock, electric, forced drop. An electric lock in which the locking member is mechanically forced down to the locked...
49 CFR 236.758 - Lock, electric, forced drop.
Code of Federal Regulations, 2014 CFR
...2014-10-01 false Lock, electric, forced drop. 236.758 Section 236.758...Definitions ¦ 236.758 Lock, electric, forced drop. An electric lock in which the locking member is mechanically forced down to the locked...
49 CFR 236.758 - Lock, electric, forced drop.
Code of Federal Regulations, 2011 CFR
...2011-10-01 false Lock, electric, forced drop. 236.758 Section 236.758...Definitions ¦ 236.758 Lock, electric, forced drop. An electric lock in which the locking member is mechanically forced down to the locked...
Geometrical structures, vibrational frequencies, force constants and dissociation energies of isotopic water molecules (H2O, HDO, D2O, HTO, DTO, and T2O) under dipole electric field
Shun-Ping Shi; Quan Zhang; Li Zhang; Rong Wang; Zheng-He Zhu; Gang Jiang; Yi-Bei Fu
The dissociation limits of isotopic water molecules are derived for the ground state. The equilibrium geometries, the vibrational frequencies, the force constants and the dissociation energies for the ground states of all isotopic water molecules under the dipole electric fields from -0.05 a.u. to 0.05 a.u. are calculated using B3P86\\/6-311++G(3df,3pf). The results show that when the dipole electric fields change
Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography
Grasland-Mongrain, Pol; Mari, Jean-Martial; Souchon, Remi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy
Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence ...
Electricity and Magnetic Fields
NSDL National Science Digital Library
VU Bioengineering RET Program,
The grand challenge for this legacy cycle unit is for students to design a way to help a recycler separate aluminum from steel scrap metal. In previous lessons, they have looked at how magnetism might be utilized. In this lesson, students think about how they might use magnets and how they might confront the problem of turning the magnetic field off. Through the accompanying activity students explore the nature of an electrically induced magnetic field and its applicability to the needed magnet.
Dynamic properties of force fields
NASA Astrophysics Data System (ADS)
Vitalini, F.; Mey, A. S. J. S.; Noķ, F.; Keller, B. G.
Molecular-dynamics simulations are increasingly used to study dynamic properties of biological systems. With this development, the ability of force fields to successfully predict relaxation timescales and the associated conformational exchange processes moves into focus. We assess to what extent the dynamic properties of model peptides (Ac-A-NHMe, Ac-V-NHMe, AVAVA, A10) differ when simulated with different force fields (AMBER ff99SB-ILDN, AMBER ff03, OPLS-AA/L, CHARMM27, and GROMOS43a1). The dynamic properties are extracted using Markov state models. For single-residue models (Ac-A-NHMe, Ac-V-NHMe), the slow conformational exchange processes are similar in all force fields, but the associated relaxation timescales differ by up to an order of magnitude. For the peptide systems, not only the relaxation timescales, but also the conformational exchange processes differ considerably across force fields. This finding calls the significance of dynamic interpretations of molecular-dynamics simulations into question.
Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography.
Grasland-Mongrain, Pol; Destrempes, Franńois; Mari, Jean-Martial; Souchon, Rķmi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy
Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an 'acousto-electrical speckle' in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging. PMID:25906432
Simulation of colloidal fouling by coupling a dynamically updating velocity profile and electric field interactions with Force Bias Monte Carlo methods for membrane filtration.
Boyle, Paul M; Houchens, Brent C; Kim, Albert S
Pressure-driven flow through a channel with membrane walls is modeled for high particulate volume fractions of 10%. Particle transport is influenced by Brownian diffusion, shear-induced diffusion, and convection due to the axial crossflow. The particles are also subject to electrostatic double layer repulsion and van der Waals attraction, from both particle-particle and particle-membrane interactions. Force Bias Monte Carlo (FBMC) simulations predict the deposition of the particles onto the membranes, where both hydrodynamics and the change in particle potentials determine the probability that a proposed move is accepted. The particle volume fraction is used to determine an apparent local viscosity observed by the continuum flow. As particles migrate, the crossflow velocity field evolves in quasi-steady fashion with each time instance appearing fully developed in the downstream direction. Particles subject to combined hydrodynamic and electric effects (electrostatic double layer repulsion and van der Waals attraction) reach a more stable steady-state as compared to systems with only hydrodynamic effects considered. As expected, at higher crossflow Reynolds numbers more particles remain in the crossflow free stream. PMID:23540433
Force modulation for enhanced nanoscale electrical sensing
NASA Astrophysics Data System (ADS)
Koelmans, W. W.; Sebastian, A.; Abelmann, L.; Despont, M.; Pozidis, H.
Scanning probe microscopy employing conductive probes is a powerful tool for the investigation and modification of electrical properties at the nanoscale. Application areas include semiconductor metrology, probe-based data storage and materials research. Conductive probes can also be used to emulate nanoscale electrical contacts. However, unreliable electrical contact and tip wear have severely hampered the widespread usage of conductive probes for these applications. In this paper we introduce a force modulation technique for enhanced nanoscale electrical sensing using conductive probes. This technique results in lower friction, reduced tip wear and enhanced electrical contact quality. Experimental results using phase-change material stacks and platinum silicide conductive probes clearly demonstrate the efficacy of the proposed technique. Furthermore, conductive-mode imaging experiments on specially prepared platinum/carbon samples are presented to demonstrate the widespread applicability of this technique.
Force modulation for enhanced nanoscale electrical sensing.
Koelmans, W W; Sebastian, A; Abelmann, L; Despont, M; Pozidis, H
Scanning probe microscopy employing conductive probes is a powerful tool for the investigation and modification of electrical properties at the nanoscale. Application areas include semiconductor metrology, probe-based data storage and materials research. Conductive probes can also be used to emulate nanoscale electrical contacts. However, unreliable electrical contact and tip wear have severely hampered the widespread usage of conductive probes for these applications. In this paper we introduce a force modulation technique for enhanced nanoscale electrical sensing using conductive probes. This technique results in lower friction, reduced tip wear and enhanced electrical contact quality. Experimental results using phase-change material stacks and platinum silicide conductive probes clearly demonstrate the efficacy of the proposed technique. Furthermore, conductive-mode imaging experiments on specially prepared platinum/carbon samples are presented to demonstrate the widespread applicability of this technique. PMID:21821873
Work Performed Against an Electric Force
NSDL National Science Digital Library
Stern, David P. (David Peter), 1931-
This page, authored and curated by David P. Stern, illustrates the concept of work against an electric force using the examples of the Van de Graaff generator and lightening. There are also shorter examples of the Xerox machine and electric charge on transparency sheets as well as links to sites relating to the Van de Graaff machine or lightening. This is an optional section from a much larger collection of resources title "From Stargazers to Starships". A French and Italian translations of this lesson are available.
A hybrid technique for electromagnetic torque and force analysis of electric machines
T. S. Low; C. Bi; Z. J. Liu
In electric machines, the electromagnetic torques and forces are developed as a result of the interaction of the magnetic fields. These forces can be computed from the results of field analysis, using numerical or analytical methods. Describes a hybrid technique, which is suitable for the calculation and analysis of electromagnetic torques and forces. This method exploits the advantages of numerical
HOVEDOPPGAVE Polarizable force fields for flexible molecules
Izaguirre, Jes·s A.
HOVEDOPPGAVE 2004 Polarizable force fields for flexible molecules Kandidatens navn Asbj°rn Holt interactions. In this study a force field for flexible water molecules is constructed. To describe the electrostatic properties of the water molecules in this force fields, atomic charges and dipole moments are used
Electric field induced phase separation
Ludwik Leibler
In principle, magnetic and electric fields or gravity can control phase separation in liquid mixtures, but the coupling between these fields and the local concentration fluctuations is very weak and thus their use to control demixing seems limited to extreme conditions. Uniform electric fields induce detectable effects only very close to the transition temperature, at about few hundredths of degree
Optical force on toroidal nanostructures: toroidal dipole versus renormalized electric dipole
Zhang, Xu-Lin; Lin, Zhifang; Sun, Hong-Bo; Chan, C T
We study the optical forces acting on toroidal nanostructures. A great enhancement of optical force is unambiguously identified as originating from the toroidal dipole resonance based on the source-representation, where the distribution of the induced charges and currents is characterized by the three families of electric, magnetic, and toroidal multipoles. On the other hand, the resonant optical force can also be completely attributed to an electric dipole resonance in the alternative field-representation, where the electromagnetic fields in the source-free region are expressed by two sets of electric and magnetic multipole fields based on symmetry. The confusion is resolved by conceptually introducing the irreducible electric dipole, toroidal dipole, and renormalized electric dipole. We demonstrate that the optical force is a powerful tool to identify toroidal response even when its scattering intensity is dwarfed by the conventional electric and magnetic multipoles.
Electric Field Induced Interfacial Instabilities
NASA Technical Reports Server (NTRS)
Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-Lun; Onuki, Akira
The study of the interface in a charge-free, nonpolar, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In zero gravity, the interface is unstable at all long wavelengths in the presence of a field applied across it. It is conjectured that this will cause the binary fluid to break up into domains small enough to be outside the instability condition. The resulting pattern formation, and the effects on the critical properties as the domains approach the correlation length are of acute interest. With direct observation, laser light scattering, and interferometry, the phenomena can be probed to gain further understanding of interfacial instabilities and the pattern formation which results, and dimensional crossover in critical systems as the critical fluctuations in a particular direction are suppressed by external forces.
Cryosurgery with Pulsed Electric Fields
Daniels, Charlotte S.; Rubinsky, Boris
This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to ablate cells in the high subzero freezing region of a cryosurgical lesion. PMID:22087224
Electric and Magnetic Forces between Parallel-Wire Conductors.
ERIC Educational Resources Information Center
Morton, N.
Discusses electric and magnetic forces between parallel-wire conductors and derives, in a simple fashion, order of magnitude estimates of the ratio of the likely electrostatic and electromagnetic forces for a simple parallel-wire balance. (Author/HM)
Lipid14: The Amber Lipid Force Field
The AMBER lipid force field has been updated to create Lipid14, allowing tensionless simulation of a number of lipid types with the AMBER MD package. The modular nature of this force field allows numerous combinations of head and tail groups to create different lipid types, enabling the easy insertion of new lipid species. The Lennard-Jones and torsion parameters of both the head and tail groups have been revised and updated partial charges calculated. The force field has been validated by simulating bilayers of six different lipid types for a total of 0.5 ?s each without applying a surface tension; with favorable comparison to experiment for properties such as area per lipid, volume per lipid, bilayer thickness, NMR order parameters, scattering data, and lipid lateral diffusion. As the derivation of this force field is consistent with the AMBER development philosophy, Lipid14 is compatible with the AMBER protein, nucleic acid, carbohydrate, and small molecule force fields. PMID:24803855
Investigation on charge deterioration of electrically charged filter media using electric force microscopy
NASA Astrophysics Data System (ADS)
Kim, Jooyoun
Electret filter media is widely used in filtration application as the presence of embedded electrostatic charges allows for better particle capture efficiency with lower pressure drop. The effect of exposure to organic solvents on filtration performance of electret filter media was investigated using several different organic solvents and electret filter media. The exposure of electret filter media to liquid organic solvents caused a decrease in filtration performance without significant changes in resistance. It is hypothesized that the lowered performance of the electret filter media is due to the changes in electric field caused by the liquid organic solvents or to morphological changes. Scanning Electron Microscopy (SEM) was used to examine any observable morphological changes in the fibers after exposure to liquid organic solvents. There were no observable changes in morphology of fibers, suggesting the performance deterioration by chemical exposure was not caused by morphological changes in fibers. Electric Force Microscopy (EFM) was used to analyze the electric field of electret filter media prior to and after exposure to organic liquid solvents. Changes in the electric field were detected and quantified. Electric field gradient imaging (EFGI) by phase and frequency detection was shown to be a feasible method for the analysis of charge deterioration in electret filtration media. Two mathematical models based on electrostatics fundamentals were used to explain the behavior of EFM experimental data. Model I accounted for both a coulombic force and induced polarization phenomena. Model II incorporates a capacitance term. Both models exhibited good quantitative agreement with the experimental data hence the performance deterioration of the electret filter media after chemical immersion was proven to be directly related to changes in the electric field of the sample.
Cell membrane tethers generate mechanical force in response to electrical stimulation.
Brownell, William E; Qian, Feng; Anvari, Bahman
Living cells maintain a huge transmembrane electric field across their membranes. This electric field exerts a force on the membrane because the membrane surfaces are highly charged. We have measured electromechanical force generation by cell membranes using optically trapped beads to detach the plasma membrane from the cytoskeleton and form long thin cylinders (tethers). Hyperpolarizing potentials increased and depolarizing potentials decreased the force required to pull a tether. The membrane tether force in response to sinusoidal voltage signals was a function of holding potential, tether diameter, and tether length. Membrane electromechanical force production can occur at speeds exceeding those of ATP-based protein motors. By harnessing the energy in the transmembrane electric field, cell membranes may contribute to processes as diverse as outer hair cell electromotility, ion channel gating, and transport. PMID:20682262
United States of America Electric Energy Market Competition Task Force
Tesfatsion, Leigh
i United States of America Electric Energy Market Competition Task Force and the Federal Energy of competition within the wholesale and retail market for electric energy in the United States and to submit energy in the United States. The task force has 5 members: (1) an employee of the Department of Justice
Electric and magnetic field exposure
S. S. Sussman
The possible health hazards of low-level, power line frequency (50\\/60 Hz) electric and magnetic fields are considered. The historical background to this concern is briefly discussed. The types of studies being carried out and the results so far are summarized. It is concluded that while the scientific evidence on field effects is inconclusive, inferences of health effects justify further evaluation
Imaging Nanoscale Electromagnetic Near-Field Distributions Using Optical Forces.
Huang, Fei; Ananth Tamma, Venkata; Mardy, Zahra; Burdett, Jonathan; Kumar Wickramasinghe, H
We demonstrate the application of Atomic Force Microscopy (AFM) for mapping optical near-fields with nanometer resolution, limited only by the AFM probe geometry. By detecting the optical force between a gold coated AFM probe and its image dipole on a glass substrate, we profile the electric field distributions of tightly focused laser beams with different polarizations. The experimentally recorded focal force maps agree well with theoretical predictions based on a dipole-dipole interaction model. We experimentally estimate the aspect ratio of the apex of gold coated AFM probe using only optical forces. We also show that the optical force between a sharp gold coated AFM probe and a spherical gold nanoparticle of radius 15?nm, is indicative of the electric field distribution between the two interacting particles. Photo Induced Force Microscopy (PIFM) allows for background free, thermal noise limited mechanical imaging of optical phenomenon over wide range of wavelengths from Visible to RF with detection sensitivity limited only by AFM performance. PMID:26073331
6.641 Electromagnetic Fields, Forces, and Motion, Spring 2003
Zahn, Markus, 1946-
Electric and magnetic quasistatic forms of Maxwell's equations applied to dielectric, conduction, and magnetization boundary value problems. Electromagnetic forces, force densities, and stress tensors, including magnetization ...
Electric fields in the magnetosphere
NASA Technical Reports Server (NTRS)
Heppner, J. P.
Two techniques, tracking the motions of Ba(+) clouds and measuring the differences in floating potential between symmetric double probes, were successful in: (1) demonstrating the basic convective nature of magnetospheric electric fields, (2) mapping global patterns of convection at upper ionosphere levels, and (3) revealing the physics of electric currents in the ionosphere and the importance of magnetosphere-ionosphere feedback in altering the imposed convection.
FEA Simulation on Dielectric Composite and Semi-Crystalline Composite, and Analytical Computations and Approximations for the Charge, Force and Chemical Potential for a Prolate Spheroid Aligned with an Electric Field
NASA Astrophysics Data System (ADS)
Zhou, Kai
A finite element study has been carried out to determine the effective dielectric constant of composite materials containing linear or nonlinear fillers. In the linear systems, spherical particles with field-independent dielectric constant are distributed randomly in a linear matrix. The effective dielectric constant is studied as a function of volume fraction and particle size. In the nonlinear system, a Landau thermodynamic model is employed to describe the field-dependent dielectric properties for both ferroelectric and antiferroelectric material. For the 2D ferroelectric-dielectric composite, the effective dielectric constant and dielectric tunability are examined based on filler volume fraction, size and shape, and then compared to classical effective medium theories. For the 3D antiferroelectric-dielectric composite, both the "hard" sphere and "soft" sphere models are examined at a volume fraction of 40%, which is above percolation for spherical filler. The finite element method is then adapted to determine the relaxation time constant, effective conductivity and electric field distribution of semi-crystalline composite. The simulated results show that both the effective conductivity of the composite and field distribution in the composite strongly depend on the crystalline volume fraction and the shape of the crystalline region. To achieve lower average electric field in the amorphous region, crystallites with larger length/thickness ratio are preferred. The charge and force on a conducting particle standing on a ground plane in a uniform background field are important to a range of technical areas, such as particle motion in gas-insulated substations. The charge, force and lifting field for such a particle is normally evaluated using approximate formulas in an obscure paper published over 40 years ago. Software technology now facilitates the solution of many such problems exactly, which allows evaluation of (i) the published approximation and (ii) the range of parameters over which the approximation is accurate. In the present contribution, we provide an exact solution to the charge and field-induced force for semi-spheroid standing on a ground plane, derive the commonly used approximation from the exact solution, and find that the commonly used approximate solution for the force on a rodlike particle agrees poorly with finite element computations of the force. We provide both "exact" and approximated formulas which agree well with finite element computations of the force on a rod-like particle for asperities from 2 to 100. An analytical expression is derived for the chemical potential of a water-filled spheroid in a dielectric medium based on Zeller's hypothesis for the chemical potential, against which Zeller's approximations for chemical potential could be compared for the same system. In doing so, we found that Zeller's approximation for DC component of the chemical potential is very good, although his expression for the conductivity at which the peak DC component occurs is not accurate at low spheroid asperities. However Zeller's approximation does not provide a very good approximation for the AC component of the chemical potential. Following Zeller's approach but with corrections, we have developed a much more accurate approximation for the AC component of the chemical potential which was compared with both the exact analytical solution and FEA computations.
Speed, Acceleration, and Velocity: Level II, Unit 9, Lesson 1; Force, Mass, and Distance: Lesson 2; Types of Motion and Rest: Lesson 3; Electricity and Magnetism: Lesson 4; Electrical, Magnetic, and Gravitational Fields: Lesson 5; The Conservation and Conversion of Matter and Energy: Lesson 6; Simple Machines and Work: Lesson 7; Gas Laws: Lesson 8; Principles of Heat Engines: Lesson 9; Sound and Sound Waves: Lesson 10; Light Waves and Particles: Lesson 11; Program. A High.....
ERIC Educational Resources Information Center
Manpower Administration (DOL), Washington, DC. Job Corps.
This self-study program for high-school level contains lessons on: Speed, Acceleration, and Velocity; Force, Mass, and Distance; Types of Motion and Rest; Electricity and Magnetism; Electrical, Magnetic, and Gravitational Fields; The Conservation and Conversion of Matter and Energy; Simple Machines and Work; Gas Laws; Principles of Heat Engines;ģ
Apparatuses and methods for generating electric fields
Scott, Jill R; McJunkin, Timothy R; Tremblay, Paul L
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.
Linear electric field mass spectrometry
McComas, D.J.; Nordholt, J.E.
A mass spectrometer and methods for mass spectrometry are described. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field. 8 figs.
Electric field-assisted biosorption.
Riordan, C R; Bustard, M T; Hughes, P; Reid, C N; McHale, A P
A bisorption process using electric fields to facilitate contact between a sorbate and non-living biomass is described. The latter is enclosed within a semi-permeable membrane together with an electrode. The counter electrode is placed in the sorbate solution and an established potential across the electrodes facilitates electrokinetic movement of the sorbate to the biosorbant material. PMID:15127798
Electric field divertor plasma pump
Schaffer, Michael J. (San Diego, CA)
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.
Electromagnetic circulatory forces and rotordynamic instability in electric machines
Holopainen TP; Tenhunen A; Arkkio A
The electromechanical interaction in electric machines induces additional forces between the rotor and stator. To study this interaction, a simple electromechanical model was developed. The mechanical behaviour was modelled by the Jeffcott rotor. The electromagnetic forces were described by a simple parametric model including two electormagnetic variables. The aim of the study was to investigate the effects of electromechanical interaction
Enhancements of contaminants removal and degradation in low permeability soils by electrical fields are achieved by the processes of electrical heating, electrokinetics, and electrochemical reactions. Electrical heating increases soil temperature resulting in the increase of cont...
Minnesota, University of
. Ę Calculate the motion of a particle with a constant acceleration. Ę Calculate the motion of a particle of the universe, the atomic structure of materials, and the quark structure of elementary particles. Magnetic; Ę Calculate the magnetic force on a charged particle moving in a uniform magnetic field and describe its
Magnetic Fields Analogous to electric field, a magnet
Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University
Magnetic Fields Analogous to electric field, a magnet produces a magnetic field, B Set up a B field two ways: Moving electrically charged particles Current in a wire Intrinsic magnetic field Basic characteristic of elementary particles such as an electron #12;Magnetic Fields Magnetic field lines Direction
Electric Field and Gauss's Law Let's do another experiment
Tobar, Michael
we picture this? F = q1q2 r2 k What is the meaning of k? 2 A Force Field.... 3 The Electroscope http://upload.wikimedia.org/wikipedia/commons/b/b5/Electroscope.png http://www.engr.uky.edu/~gedney/courses/ee468/expmnt/escope-graph.gif 4 #12;What(x,y,z) ... Electric Field Units: Newtons/Coulomb 8 #12;Picturing Field 9 Measuring fields - The Electroscope http
Electrical Current in Sinai Billiards Under General Small Forces
NASA Astrophysics Data System (ADS)
Chernov, Nikolai; Zhang, Hong-Kun; Zhang, Pengfei
The Lorentz gas of -periodic scatterers (or the so called Sinai billiards) can be used to model motion of electrons on a metal. We investigate the linear response for the system under various external forces (during both the flight and the collision). We give some characterizations under which the forced system is time-reversible, and derive an estimate of the electrical current generated by the forced system. Moreover, applying Pesin entropy formula and Young dimension formula, we get several characterizations of the non-equilibrium steady state of the forced system.
Field study on moving force identification
NASA Astrophysics Data System (ADS)
Chan, Hung-tin Tommy; Yung, Tak H.; Law, S. S.
A field measurement to validate a moving force identification method was carried out on an existing prestressed concrete highway bridge with a span length of 28 m. The test bridge is located at Ma Tau Wai, Kowloon, Hong Kong. A heavy 2-axle truck with known axle loads was used as a control vehicle. Besides the control vehicle, axle load data of in-service vehicles were also collected. The bridge responses acquired for the identification were indirectly measured using strain gauges. Results show that dynamic axle loads induced from both control and in-service vehicles can be identified indicating the method is valid for identification of moving forces.
Force sensing control for electric powered wheelchairs
Rory A. Cooper; Lana M. Widman; Daniel K. Jones; Rick N. Robertson
People with many types of disabilities use electric powered wheelchairs (EPWs) for mobility. Excessive intention tremor, limited range of motion, athetoid motions, and spastic rigidity can reduce or prohibit the control over an EPW. This study focused on the design and testing of a newly developed isometric joystick (IJ) for EPW control. The IJ was tested against existing performance standards
SOLAR WIND ELECTRIC FIELDS IN THE ION CYCLOTRON FREQUENCY RANGE P. J. Kellogg,1
California at Berkeley, University of
SOLAR WIND ELECTRIC FIELDS IN THE ION CYCLOTRON FREQUENCY RANGE P. J. Kellogg,1 S. D. Bale,2 F. S in the plasma frame. The electric fields are large enough to provide the dominant force on the ions of the solar of the conservation of magnetic mo- ment in the solar wind, it was pointed out that electric fields in the range
Stark Spectroscopy: Measuring Electric Fields in Plasmas
Mark Bowden
The electric field is one of the most important parameters in discharge plasmas. Many applications that use discharges depend on behavior at the boundary, and the electric field is closely connected with other discharge parameters, such as charge densities, fluxes of electrons and ions, and energy distribution functions. It is therefore necessary to understand the spatial distribution of electric field
Energy buildup in sheared force-free magnetic fields
NASA Technical Reports Server (NTRS)
Wolfson, Richard; Low, Boon C.
Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.
Dielectric fluid in inhomogeneous pulsed electric field.
Shneider, M N; Pekker, M
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
Particle Energization in a Chaotic Force-free/Non-Force-free Magnetic field
NASA Astrophysics Data System (ADS)
Li, X.; Dasgupta, B.; Li, G.
Force-free field is believed to be a reasonable description of the quiet sun and a good approximation for low-beta plasma, like the lower region of solar corona. This field is similar to ABC field, which has been demonstrated to be chaotic. Here, we study the particle transport behavior in this field. We are particularly interested in particle energization if there is an electric field, which can be introduced by turbulent motion of plasma parcels. We expect a second order Fermi acceleration. Different spectra for turbulent motions are used, and particles with various mass-to-charge ratio are investigated. This process can provide a seed population generation mechanism for CME-driven shocks.
Lukas Novotny
In this article we use classical electrodynamics to derive the conservation law for linear momentum in an optical field. The\\u000a net force exerted on an arbitrary object is determined by MaxwellÆs stress tensor. It is shown that in the limiting case of\\u000a an infinitely extended object, the formalism renders the known expressions for radiation pressure. Similarly, in the small\\u000a object
Electric Charge and Magnetic Flux on Rotating Black Holes in a Force-Free Magnetosphere
Hyun Kyu Lee; Chul H. Lee; Maurice H. P. M. van Putten
The electric charge on rotating black holes is calculated to be ~ BJ in the force-free configuration of Ghosh (2000), with a horizon flux of ~ BM^2. This charge is gravitationally weak for B ~ 10^{15} G, so that the Kerr metric applies. Being similar to the electric charge of a magnetar, both electric charge and magnetic flux should be, in sign and order of magnitude, continuous during stellar collapse into a black hole. Extraction of the rotational energy from newly formed black holes may proceed by interaction with the magnetic field. Keywords:black hole physics --magnetic fields
Manipulation of red blood cells with electric field
NASA Astrophysics Data System (ADS)
Saboonchi, Hossain; Esmaeeli, Asghar
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.
Electric Field Controlled Self-Assembly of Hierarchically Ordered Membranes
Velichko, Yuri S.; Mantei, Jason R.; Bitton, Ronit; Carvajal, Daniel; Shull, Kenneth R.; Stupp, Samuel I.
Self-assembly in the presence of external forces is an adaptive, directed organization of molecular components under nonequilibrium conditions. While forces may be generated as a result of spontaneous interactions among components of a system, intervention with external forces can significantly alter the final outcome of self-assembly. Superimposing these intrinsic and extrinsic forces provides greater degrees of freedom to control the structure and function of self-assembling materials. In this work we investigate the role of electric fields during the dynamic self-assembly of a negatively charged polyelectrolyte and a positively charged peptide amphiphile in water leading to the formation of an ordered membrane. In the absence of electric fields, contact between the two solutions of oppositely charged molecules triggers the growth of closed membranes with vertically oriented fibrils that encapsulate the polyelectrolyte solution. This process of self-assembly is intrinsically driven by excess osmotic pressure of counterions, and the electric field is found to modify the kinetics of membrane formation, and also its morphology and properties. Depending on the strength and orientation of the field we observe a significant increase or decrease of up to nearly 100% in membrane thickness, as well as the controlled rotation of nanofiber growth direction by 90 degrees, resulting in a significant increase in mechanical stiffness. These results suggest the possibility of using electric fields to control structure in self-assembly processes involving diffusion of oppositely charged molecules. PMID:23166533
Cell separation using electric fields
NASA Technical Reports Server (NTRS)
Mangano, Joseph A. (Inventor); Eppich, Henry M. (Inventor)
The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.
Cell separation using electric fields
NASA Technical Reports Server (NTRS)
Mangano, Joseph (Inventor); Eppich, Henry (Inventor)
The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.
Migration of amoeba cells in an electric field
NASA Astrophysics Data System (ADS)
Guido, Isabella; Bodenschatz, Eberhard
Exogenous and endogenous electric fields play a role in cell physiology as a guiding mechanism for the orientation and migration of cells. Electrotaxis of living cells has been observed for several cell types, e.g. neurons, fibroblasts, leukocytes, neural crest cells, cancer cells. Dictyostelium discoideum (Dd), an intensively investigated chemotactic model organism, also exhibits a strong electrotactic behavior moving toward the cathode under the influence of electric fields. Here we report experiments on the effects of DC electric fields on the directional migration of Dd cells. We apply the electric field to cells seeded into microfluidic devices equipped with agar bridges to avoid any harmful effects of the electric field on the cells (ions formation, pH changes, etc.) and a constant flow to prevent the build-up of chemical gradient that elicits chemotaxis. Our results show that the cells linearly increase their speed over time when a constant electric field is applied for a prolonged duration (2 hours). This novel phenomenon cannot be attributed to mechanotaxis as the drag force of the electroosmotic flow is too small to produce shear forces that can reorient cells. It is independent of the cellular developmental stage and to our knowledge, it was not observed in chemotaxis. This work is supported by MaxSynBio project of the Max Planck Society.
Measuring q/m for Water Drops--An Introduction to the Effects of Electrical Forces
ERIC Educational Resources Information Center
Hart, Francis X.
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)
A compact high field magnetic force microscope.
Zhou, Haibiao; Wang, Ze; Hou, Yubin; Lu, Qingyou
We present the design and performance of a simple and compact magnetic force microscope (MFM), whose tip-sample coarse approach is implemented by the piezoelectric tube scanner (PTS) itself. In brief, a square rod shaft is axially spring-clamped on the inner wall of a metal tube which is glued inside the free end of the PTS. The shaft can thus be driven by the PTS to realize image scan and inertial stepping coarse approach. To enhance the inertial force, each of the four outer electrodes of the PTS is driven by an independent port of the controller. The MFM scan head is so compact that it can easily fit into the 52mm low temperature bore of a 20T superconducting magnet. The performance of the MFM is demonstrated by imaging a manganite thin film at low temperature and in magnetic fields up to 15T. PMID:25189114
Charged Hadron Properties in Background Electric Fields
William Detmold, Brian C. Tiburzi, Andre Walker-Loud
We report on a lattice calculation demonstrating a novel new method to extract the electric polarizability of charged pseudo-scalar mesons by analyzing two point correlation functions computed in classical background electric fields.
Electric fields in plasmas under pulsed currents
Tsigutkin, K; Stambulchik, E; Bernshtam, V; Maron, Y
Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spectroscopy and line-shape analysis. Plasma doping allows for 3D spatially resolved measurements. The measured peak magnitude and propagation velocity of the electric field is found to match those of the Hall electric field, inferred from the magnetic-field front propagation measured previously.
Development of eddy current microscopy for high resolution electrical conductivity imaging using atomic force microscopy.
Nalladega, V; Sathish, S; Jata, K V; Blodgett, M P
We present a high resolution electrical conductivity imaging technique based on the principles of eddy current and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents generated in the conducting sample are detected and measured with a magnetic tip attached to a flexible cantilever of an AFM. The eddy current generation and its interaction with the magnetic tip cantilever are theoretically modeled using monopole approximation. The model is used to estimate the eddy current force between the magnetic tip and the electrically conducting sample. The theoretical model is also used to choose a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the design of a high resolution electrical conductivity imaging system. The force between the tip and the sample due to eddy currents is measured as a function of the separation distance and compared to the model in a single crystal copper. Images of electrical conductivity variations in a polycrystalline dual phase titanium alloy (Ti-6Al-4V) sample are obtained by scanning the magnetic tip-cantilever held at a standoff distance from the sample surface. The contrast in the image is explained based on the electrical conductivity and eddy current force between the magnetic tip and the sample. The spatial resolution of the eddy current imaging system is determined by imaging carbon nanofibers in a polymer matrix. The advantages, limitations, and applications of the technique are discussed. PMID:18681706
Biological\\/medical pulsed electric field treatments
Karl H. Schoenbach; Robert H. Stark; Jingdong Deng; Ramy El-Sayed Aly; Stephen J. Beebe; E. Stephen Buescher
The application of electric fields to a medium, which contains biological cells, causes build-up of charges at the cell membrane, and consequently a change in the transmembrane potential of cells. For low electric fields, this causes voltage-gating, the voltage-induced opening of channels in the cell membrane. With increasing electric field, at transmembrane voltages on the order of 1 V, the
Multi-layered resonators for optimized electric field detection
NASA Astrophysics Data System (ADS)
Ioppolo, Tindaro; ųt³gen, Volkan
In this study, we carry out an analytical investigation to determine the efficacy of multi-layer dielectric micro-sphere resonators as high-resolution electric field sensors. The use of a large number of layers with different electrical and mechanical properties allows for optimum dielectric constant and elastic modulus gradients within the sphere to optimize sphere resonator's sensitivity to external electric field. The external electric field applied to a dielectric sphere induces an elastic deformation of the resonator (electrostriction effect), leading to shifts in its whispering gallery optical modes (WGM). The non-uniform distribution of the dielectric constant leads to a gradient in the electric field within the sphere. This in turn induces non-uniform body force on the sphere when subjected to an external electric field. By also appropriately varying the elastic modulus of the layers, the electrostictive deformation of the sphere can be optimized. In this paper we present a mathematical model describing the effect of the electric field on the WGM shift of layered micro-spherical resonators.
Field emission study of diamond like carbon films with scanned probe field emission force microscopy
Inoue, Takahito; Ogletree, D.Frank; Salmeron, Miquel
Using a tip as an anode, a scanning force microscope (SFM) with an electrically conducting tip allows simultaneous measurement of both field emitted currents and surface electronic properties with high lateral resolution. The principle of the method and its application to field emission from CVD diamond-like carbon films are presented. By simultaneously imaging the topography and field emission current distribution with a 100 nm tip-surface separation, we correlated emission, topography and dielectric properties. Subsequent contact SFM images of the same regions correlated topography and conductivity on the nanometer scale. The electrostatic force between tip and surface showed fluctuations on a millisecond time scale during field emission. This is probably due to charging and discharging of deep traps in the diamond film.
Microwave Circuit Electric Field Imaging Systems.
NASA Astrophysics Data System (ADS)
Budka, Thomas Philip
This thesis reports on the basic theory of operation and the experimental results obtained from an electric field imaging system for planar microwave circuits that employs the method of near-field modulated scattering. The system developed is capable of mapping the normal and tangential electric field intensities and electrical phase delays at each position within 10 ?m above a microwave circuit in the frequency range of 0.5 GHz to 18 GHz with a spatial electric field resolution of better than 100 mum. Two types of probe designs are used: hybrid probes and monolithically integrated probes. The hybrid electric field probes consist of electrically small dipoles or monopoles with high frequency diodes hybrid mounted with the antennas on 125 ?m thick low loss quartz. The monolithically integrated probes consist of Schottky diodes integrated with electrically small dipole and monopole antennas on a 40 mu m thick high resistivity silicon substrate. Both types of probes are used to measure the electric field intensities of the normal and tangential components over microstrip and coplanar waveguide transmission lines. The experimentally measured electric field intensity maps are presented and agree well with theory. Calibration techniques are presented that relate the measured electric field amplitudes and phases at one frequency with another frequency. Electric field intensity and electrical phase delay images are presented for a 50 Omega three turn microstrip meander line, a 10 GHz microstrip coupled line directional coupler and a 12.8 GHz microstrip patch antenna. Finally, a comparison between the experimentally measured and theoretically calculated electric fields using an FDTD approach is presented for a three stage coupled-line bandpass filter in the frequency range of 9 GHz to 12 GHz. The dissertation concludes with proposals for future work.
New electric field in asymmetric magnetic reconnection.
Malakit, K; Shay, M A; Cassak, P A; Ruffolo, D
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
Electrically small, complementary electric-field-coupled resonator antennas
NASA Astrophysics Data System (ADS)
Odabasi, H.; Teixeira, F. L.; Guney, D. O.
We study the radiation properties of electrically small resonant antennas (ka <1) composed of electric-field-coupled (ELC) and complementary electric-field-coupled (CELC) resonators and a monopole antenna. We use such parasitic ELC and CELC "metaresonators" to design various electrically small antennas. In particular, monopole-excited and bent-monopole-excited CELC resonator antennas are proposed that provide very low profiles on the order of ?0/20. We compare the performance of the proposed ELC and CELC antennas against more conventional designs based upon split-ring resonators.
Electric field variability and model uncertainty: A classification of source terms in estimating the squared electric field from an electric field model
R. B. Cosgrove; M. Codrescu
Joule heating by high-latitude electric fields is thought to be underestimated by electric field models, and it has been conjectured that the source of the underestimation is ōelectric field variability,ö although the interpretation of this term is not necessarily straightforward. We perform a classification of source terms in estimating the squared magnitude of electric field from an electric field model,
Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy
NASA Astrophysics Data System (ADS)
Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin
Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180░ polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results.
Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.
Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin
Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180░ polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results. PMID:24953042
Electric Field Driven Torque in ATP Synthase
Miller, John H.; Rajapakshe, Kimal I.; Infante, Hans L.; Claycomb, James R.
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
Hessian biased force field for polysilane polymers
Musgrave, C.B.; Dasgupta, S.; Goddard, W.A. III [California Inst. of Technology, Pasadena, CA (United States)
We report a force field (FF) suitable for molecular dynamics simulations of polysilane polymers. This FF, denoted MSXX, was developed using the Hessian biased method to describe accurately the vibrational states, the ab initio torsional potential energy surface, and the ab initio electrostatic charges of polysilane oligomers. This MSXX FF was used to calculate various spectroscopic and mechanical properties of the polysilane crystal. Stress-strain curves and surface energies are reported. Gibbs molecular dynamics calculations (Nose, Rahman-Parrinello) were used to predict various materials properties at higher temperatures. Phonon dispersion curves and elastic constants were calculated at various temperatures. Although this polymer is of increasing industrial interest, we could find no experimental data with which to compare these predictions. 20 refs., 6 figs., 16 tabs.
General Physics II Exam 1 -Chs. 16,17,18 -Electric Fields, Potential, Current Feb. 11, 2013 Name Rec. Instr. Rec. Time
Wysin, Gary
General Physics II Exam 1 - Chs. 16,17,18 - Electric Fields, Potential, Current Feb. 11, 2013 Name charge can experience an electric force. 4. (2) T F The smallest magnitude (non-zero) net charge of the electric force on Q1 due to Q2. b) (3) The direction of the electric force acting on Q1 is a. pushing Q1
Large electric fields in the magnetosphere
NASA Technical Reports Server (NTRS)
Mozer, F. S.; Boehm, M. H.; Cattell, C. A.; Temerin, M.; Wygant, J. R.
The Langmuir solitonlike structures which contain plasma frequency oscillations of 500 mV/m and parallel electric fields of about 100 mV/m, observed in the auroral zone below 1000 km, are studied. The characteristics of electrostatic shocks that contain perpendicular fields of 1000 mV/m and parallel fields of 100 mV/m, and of double layers that have parallel fields of 10 mV/m are described. Observations of the geomagnetic tail reveal the presence of 100 mV/m turbulent electric fields and 5-10 mV/m quasi-static fields in the high latitude boundary of the plasma sheet, and inside the plasma sheet fields of 5-10 mV/m are detected. The large amplitude quasi-static electric field fluctuations of 100 mV/m and the dc fields of approximately 5 mV/m observed in the bow shock are examined.
The Introduction of Fields in Relation to Force
ERIC Educational Resources Information Center
Brunt, Marjorie; Brunt, Geoff
The introduction of force at age 14-16 years is considered, starting with elementary student experiments using magnetic force fields. The meaningless use of terms such as "action" and "reaction", or "agent" and "receiver" is discussed. (Contains 6 figures.)
Fiber-Optic Electric-Field Meter
NASA Technical Reports Server (NTRS)
Johnston, A. R.
Sensor for measuring electric-field strength does not greatly alter field in which placed. Sensor used to map fields in electric power substation or under high-voltage transmission line. Also used for laboratory measurements. Fused-silica fibers guide light from source to photometer. Light emerges from tip of source fiber, passes through curved coupler, and enters tip of photometer fiber. Attenuation of coupler changes with distance between fiber tips.
Thermodynamics of Blue Phases In Electric Fields
O. Henrich; D. Marenduzzo; K. Stratford; M. E. Cates
We present extensive numerical studies to determine the phase diagrams of cubic and hexagonal blue phases in an electric field. We confirm the earlier prediction that hexagonal phases, both 2 and 3 dimensional, are stabilized by a field, but we significantly refine the phase boundaries, which were previously estimated by means of a semi-analytical approximation. In particular, our simulations show that the blue phase I -- blue phase II transition at fixed chirality is largely unaffected by electric field, as observed experimentally.
Polarizable vacuum analysis of electric and magnetic fields
Xing-Hao Ye
The electric and magnetic fields are investigated on the basis of quantum vacuum. The analysis of the electromagnetic energy and force indicates that an electric field is a polarized distribution of the vacuum virtual dipoles, and that a magnetic field in vacuum is a rearrangement of the vacuum polarization. It means that an electromagnetic wave is a successional changing of the vacuum polarization in space. Also, it is found that the average half length of the virtual dipoles around an elementary charge is a=2.8 *10^(-15)m. The result leads to the step distribution of the field energy around an electron, the relation between the fine structure constant and the vacuum polarization distribution, and an extremely high energy density of the electromagnetic field.
Dislocation core fields and forces in FCC metals
Henager, Charles H.; Hoagland, Richard G.
Atomistic models were used to obtain dislocation core fields for edge, screw, and mixed dislocations in Al and Cu using EAM. Core fields are analyzed using a line force dipole representation, with dilatant and dipole terms. The core field contribution to the force between dislocations is shown to be significant for interactions within 50b.
The effect of electrical deformation forces on the electropermeabilization of erythrocyte membranes in low- and high-conductivity media.
Sukhorukov, V L; Mussauer, H; Zimmermann, U
Electrical breakdown of erythrocytes induces hemoglobin release which increases markedly with decreasing conductivity of the pulse medium. This effect presumably results from the transient, conductivity-dependent deformation forces (elongation or compression) on the cell caused by Maxwell stress. The deformation force is exerted on the plasma membrane of the cell, which can be viewed as a transient dipole induced by an applied DC electric field pulse. The induced dipole arises from the free charges that accumulate at the cell interfaces via the Maxwell-Wagner polarization mechanism. The polarization response of erythrocytes to a DC field pulse was estimated from the experimental data obtained by using two complementary frequency-domain techniques. The response is very rapid, due to the highly conductive cytosol. Measurements of the electrorotation and electrodeformation spectra over a wide conductivity range yielded the information and data required for the calculation of the deformation force as a function of frequency and external conductivity and for the calculation of the transient development of the deformation forces during the application of a DC-field pulse. These calculations showed that (i) electric force precedes and accompanies membrane charging (up to the breakdown voltage) and (ii) that under low-conductivity conditions, the electric stretching force contributes significantly to the enlargement of "electroleaks" in the plasma membrane generated by electric breakdown. PMID:9625780
Forces between Dislocations due to Dislocation Core Fields
Henager, Charles H.; Hoagland, Richard G.
Atomistic dislocation models were used to determine the properties of dislocation core fields in Al using an EAM potential. Equilibrium atom configurations were compared with initial configurations displaced according to the Volterra field to determine core displacement fields for edge, screw, and mixed (60? and 30?) geometries. The core field was approximated by a line force defect field lying parallel to the dislocation line direction. Best-fit parameters for the core fields were obtained in terms of the anisotropic elastic solution for a line force defect, from which the line force strengths and the origin of the line forces were determined. The line force stress fields were then used to compute the forces between dislocations for several dislocation configurations. The Volterra field dominates beyond 50b but core field forces modify the equilibrium angle of edge dislocation dipoles and determine the force between otherwise non-interacting edge and screw dislocations at distances out to 50b compared to the Volterra-only forces.
Heat Transfer Control in Quiescent Air with Thermal Gradient by Magnetizing Force Under both Gravitational and Nongravitational Fields
Masato Akamatsu; Mitsuo Higano; Yoshio Takahashi; Hiroyuki Ozoe
Two-dimensional numerical computations were carried out to clarify the influence of magnetizing force on quiescent air with thermal gradient in a vertical cylindrical container under both gravitational and nongravitational fields. Several sizes and axial positions of a circular electric coil were tested so that the magnetizing force depended on the magnetic gradient. Under both gravitational and nongravitational fields, the convection
Friction forces arising from fluctuating thermal fields
Zurita-Sanchez, Jorge R.; Greffet, Jean-Jacques; Novotny, Lukas [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Laboratoire Energetique Moleculaire et Macroscopique, Combustion, Ecole Centrale Paris, 92295 Chatenay-Malabry Cedex (France); Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)
We calculate the damping of a classical oscillator induced by the electromagnetic field generated by thermally fluctuating currents in the environment. The fluctuation-dissipation theorem is applied to derive the linear-velocity damping coefficient {gamma}. It turns out that {gamma} is the result of fourth-order correlation functions. The theory is applied to a particle oscillating parallel to a flat substrate and numerical values for {gamma} are evaluated for particle and substrate materials made of silver and glass. We find that losses are much higher for dielectric materials than for metals because of the higher resistivity. We predict that measurements performed on metal films are strongly affected by the underlying dielectric substrate and we show that our theory reproduces existing theoretical results in the nonretarded limit. The theory provides an explanation for the observed distance-dependent damping in shear-force microscopy and it gives guidance for future experiments. Also, the theory should be of importance for the design of nanoscale mechanical systems and for understanding the trade-offs of miniaturization.
Energy partitioning of gaseous ions in an electric field.
NASA Technical Reports Server (NTRS)
Hahn, H.-S.; Mason, E. A.
The partitioning of ion energy among thermal energy, drift energy, and random-field energy is studied by solution of the Boltzmann equation. An expansion in powers of the square of the electric field strength is obtained by Kihara's method. Numerical calculations for several ion-neutral force laws show that Wannier's constant mean-free-time model gives a reasonable first approximation. The formal extension to multicomponent mixtures is also given. The matrix elements obtained are tabulated, and can be used to study the field dependence of other moments of the ion-distribution function.
Enhanced momentum delivery by electric force to ions due to collisions of ions with neutrals
Makrinich, G.; Fruchtman, A. [H.I.T.-Holon Institute of Technology, Holon 5810201 (Israel)
Ions in partially ionized argon, nitrogen, and helium gas discharges are accelerated across a magnetic field by an applied electric field, colliding with neutrals during the acceleration. The momentum delivered by the electric force to the ions, which is equal to the momentum carried by the mixed ion-neutral flow, is found by measuring the force exerted on a balance force meter by that flow exiting the discharge. The power deposited in the ions is calculated by measuring the ion flux and the accelerating voltage. The ratio of force over power is found for the three gases, while the gas flow rates and magnetic field intensities are varied over a wide range of values, resulting in a wide range of gas pressures and applied voltages. The measurements for the three different gases confirm our previous suggestion [G. Makrinich and A. Fruchtman, Appl. Phys. Lett. 95, 181504 (2009)] that the momentum delivered to the ions for a given power is enhanced by ion-neutral collisions during the acceleration and that this enhancement is proportional to the square root of the number of ion-neutral collisions.
Bloch electrons in electric and magnetic fields
Alejandro Kunold; Manuel Torres
We investigate Bloch electrons in two dimensions subject to constant electric and magnetic fields. The model that results from our pursuit is governed by a finite difference equation with a quasienergy spectrum that interpolates between a butterfly-like structure and a Stark ladder structure. These findings ensued from the use of electric and magnetic translation operators.
Quantum electric field fluctuations and potential scattering
NASA Astrophysics Data System (ADS)
Huang, Haiyun; Ford, L. H.
Some physical effects of time averaged quantum electric field fluctuations are discussed. The one loop radiative corrections to potential scattering are approximately derived from simple arguments which invoke vacuum electric field fluctuations. For both above barrier scattering and quantum tunneling, this effect increases the transmission probability. It is argued that the shape of the potential determines a sampling function for the time averaging of the quantum electric field operator. We also show that there is a nonperturbative enhancement of the transmission probability which can be inferred from the probability distribution for time averaged electric field fluctuations. The same method should be useful in understanding the effects of large quantum stress tensor fluctuations, which cannot be treated in perturbation theory.
Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient
Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo
Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971
Localized instabilities of colloidal motion in ac electric field gradients
NASA Astrophysics Data System (ADS)
Zhao, Jinyu; Vollmer, Doris; Butt, Hans-J³rgen; Auernhammer, G³nter K.
We investigated the behavior of suspensions of polymethylmethacrylate (PMMA) colloids in a density-matching solvent mixture of trans-decalin and cyclohexyl bromide in ac electric field gradients. Due to the difference of the dielectric constants of PMMA and the solvent mixture, these gradients exert a dielectrophoretic force on the colloids and drive them towards lower electric field strength. At sufficiently high field gradients, the initially homogeneous migration of colloids becomes unstable against local flows. We observed a wave-like instability of the interface between colloid-rich and colloid-poor regions. The wavelength does not depend on intrinsic time and length scales but seems to be determined by sample thickness. At higher field gradients the instability develops faster. The observed instability shows a number of similarities to the Rayleigh-Taylor instability.
Electric Field Effects Near Critical Points
Akira Onuki
We present a general Ginzburg-Landau theory of electrostatic interactions and electric field effects for the order parameter,\\u000a the polarization, and the charge density. Electric field effects are then investigated in fluids near the critical points\\u000a and liquid crystals near the isotropic-nematic phase transition. We also examine the liquid-liquid phase transition in polar\\u000a binary mixtures with a small fraction of ions.
CRRES electric field\\/Langmuir probe instrument
J. R. Wygant; P. R. Harvey; D. Pankow; F. S. Mozer; N. Maynard; H. Singer; M. Smiddy; W. Sullivan; P. Anderson
The CRRES spacecraft's electric field\\/Langmuir probe instruments, which consist of a main electronics package on the body of the spacecraft and two pairs of orthogonal sensors with a 100-m separation on the spin-plane of the spacecraft, measures the quasi-static 2D electric field in this spin plane at 32 samples\\/sec. Sensitivity is 0.1 mV\\/m, over a dynamic range of 1000 mV\\/m.
Analysis of options for structural reform in electric-utility regulation. Report of the NGA Task Force on electric utility regulation
Not Available
In June of 1982, an Electric Utility Task Force was formed under the auspices of the National Governors' Association. The Task Force members were charged with developing recommendations for any needed changes in the regulation of electric utilities and with identifying consensus solutions to the myriad of associated regulatory problems. This report represents the consensus view of the Task Force on the problems and potential options for addressing these problems. The Task Force members agree that the primacy of state regulation has been a desirable aspect of our traditional electric utility regulatory system and that any preemption of state authority in this field should be vigorously opposed. They also concluded that changes in three areas - regional power planning and regulation, sorting out of federal and state responsibilities, and benefit-sharing approaches - would be desirable in order to reduce multi-state conflicts and increase the opportunity for regulation which insures system reliability at the lowest possible long term cost. (DMC)
ECE 390 Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields.
ECE 390 Ł Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields. Credits: 4 Terms Offered: Fall Prerequisites: MTH 255, ENGR 203 (concurrent enrollment fields in free space, Ampere's circuital law, vector magnetic potential Ę Biot-Savart law, magnetic
Full 180░ Magnetization Reversal with Electric Fields
Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.
Achieving 180░ magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180░ magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90░ magnetization rotations, thereby leading to full 180░ magnetization reversals. PMID:25512070
Full 180░ magnetization reversal with electric fields.
Wang, J J; Hu, J M; Ma, J; Zhang, J X; Chen, L Q; Nan, C W
Achieving 180░ magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180░ magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90░ magnetization rotations, thereby leading to full 180░ magnetization reversals. PMID:25512070
Full 180░ Magnetization Reversal with Electric Fields
NASA Astrophysics Data System (ADS)
Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.
Achieving 180░ magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180░ magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90░ magnetization rotations, thereby leading to full 180░ magnetization reversals.
Empirical force fields for biological macromolecules: Overview and issues
Alexander D. MacKerell Jr.
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
Electric field induced spin-polarized current
Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng
A device and a method for generating an electric-field-induced spin current are disclosed. A highly spin-polarized electric current is generated using a semiconductor structure and an applied electric field across the semiconductor structure. The semiconductor structure can be a hole-doped semiconductor having finite or zero bandgap or an undoped semiconductor of zero bandgap. In one embodiment, a device for injecting spin-polarized current into a current output terminal includes a semiconductor structure including first and second electrodes, along a first axis, receiving an applied electric field and a third electrode, along a direction perpendicular to the first axis, providing the spin-polarized current. The semiconductor structure includes a semiconductor material whose spin orbit coupling energy is greater than room temperature (300 Kelvin) times the Boltzmann constant. In one embodiment, the semiconductor structure is a hole-doped semiconductor structure, such as a p-type GaAs semiconductor layer.
Electric-field-induced spin injection enhancement.
Park, Youn Ho; Kim, Kyung Ho; Kim, Hyung-Jun; Chang, Joonyeon; Han, Suk Hee; Koo, Hyun Cheol
The spin diffusion process can be modified by the electric field in a semiconductor channel. The electric field generated by the bias current improves the spin injection efficiency as well as the spin diffusion length at a ferromagnet-semiconductor hybrid system. Spin-polarized electrons from the ferromagnetic electrode were electrically investigated in an inverted heterostructure with an In0.53Ga0.47As active layer. Using local and non-local spin valve geometries, the interfacial spin polarizations with and without an electric field are extracted from the magnitude of spin transport signals. The interfacial spin polarization is increased from 3.2% to 7.0% with a current of 1 mA at T = 20 K. When the electric field assists the spin injection at the junction, the interfacial spin polarization remains 7% at the temperature ranged from 20 K to 200 K. Temperature dependence of the injected polarization shows that the electric field can compensate the thermal smearing of injection efficiency even at higher temperature. PMID:25942892
Magnetic field sensor based on the Ampere's force using dual-polarization DBR fiber laser
NASA Astrophysics Data System (ADS)
Yao, Shuang; Zhang, Yang; Guan, Baiou
A novel magnetic field sensor using distributed Bragg reflector (DBR) fiber laser by Ampere's force effect is proposed and experimentally demonstrated. The key sensing element, that is the dual-polarization DBR fiber laser, is fixed on the middle part of two copper plates which carry the current. Ampere's force is applied onto the coppers due to an external magnetic field generated by a DC solenoid. Thus, the lateral force from the coppers is converted to a corresponding beat frequency signal shift produced by the DBR laser. The electric current sensing is also realized by the same configuration and same principle simultaneously in an intuitive manner. Good agreement between the theory calculation and the experimental results is obtained, which shows a good linearity. This sensor's sensitivity to the magnetic field and to the electric current finally reaches ~258.92 kHz/mT and ~1.08727 MHz/A, respectively.
Polarizable and nonpolarizable force fields for alkyl nitrates.
Borodin, Oleg; Smith, Grant D; Sewell, Thomas D; Bedrov, Dmitry
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 nonpolarizable force field were determined by fitting the dipole moments and electrostatic potential to values for PETN molecules in the crystal phase obtained from molecular dynamics simulations using the polarizable force field. Molecular dynamics simulations of alkyl nitrate liquids and two polymorphs of PETN crystal demonstrate the ability of the quantum-chemistry-based force fields to accurately predict thermophysical and mechanical properties of these materials. PMID:18085767
Physlets Tour 8: Plotting Electric Fields
NSDL National Science Digital Library
Wolfgang Christian
The panel on the left displays an equipotential plot. The contours represent points at the exact same potential. Draw the electric field lines for this potential by dragging the pencil (at its tip) after clicking the "draw on" button. After you have drawn your lines, determine which field best corresponds to your potential plot.
Electric field measurements across the Harang discontinuity
Nelson C. Maynard
The Harang discontinuity, the area separating the positive and negative bay regions in the midnight sector of the auroral zone, is a focal point for changes in behavior of many phenomena. Through this region the electric field, in a frame corotating with the earth, rotates through the west froma basically northward field in the positive bay region to a basically
Electric field effects in RUS measurements
Timothy W. Darling; Bradley Allured; James A. Tencate; Michael A. Carpenter
Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static
Electric Field Effects in RUS Measurements
Timothy W Darling; James A Tencate; Bradley Allured; Michael A Carpenter
Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static
Computational Investigation of Helical Traveling Wave Tube Transverse RF Field Forces
NASA Technical Reports Server (NTRS)
Kory, Carol L.; Dayton, James A.
In a previous study using a fully three-dimensional (3D) helical slow-wave circuit cold- test model it was found, contrary to classical helical circuit analyses, that transverse FF electric fields have significant amplitudes compared with the longitudinal component. The RF fields obtained using this helical cold-test model have been scaled to correspond to those of an actual TWT. At the output of the tube, RF field forces reach 61%, 26% and 132% for radial, azimuthal and longitudinal components, respectively, compared to radial space charge forces indicating the importance of considering them in the design of electron beam focusing.
On electric fields created by quantized vortices
NASA Astrophysics Data System (ADS)
Rukin, A. S.; Shevchenko, S. I.
It is shown that in a magnetic field the quantized vortices in a superfluid acquire a real quantized electric charge concentrated in the vortex core. This charge is compensated by an opposite surface charge, located at macroscopic distance from the vortex axis. It is found that polarization caused by the vortex velocity field does not give rise to electric fields outside an infinite cylinder. The vortex-created electric fields can be observed only near the cylinder end surfaces, which must be covered by dielectric covers in order to prevent leakage of the superfluid. The influence of cover properties on the vortex-created potential is studied here. The potentials created by vortices on point and ring electrodes are calculated.
Electric fields associated with dipolarization fronts
NASA Astrophysics Data System (ADS)
Sun, Wei-Jie; Fu, Suiyan; Parks, George K.; Pu, Zuyin; Zong, Qiu-Gang; Liu, Jiang; Yao, Zhonghua; Fu, Huishan; Shi, Quanqi
Electric fields associated with dipolarization fronts (DFs) have been investigated in the magnetotail plasma sheet using Cluster observations. We have studied each term in the generalized Ohm's law using data obtained from the multispacecraft Cluster. Our results show that in the plasma flow frame, electric fields are directed normal to the DF in the magnetic dip region ahead of the DF as well as in the DF layer but in opposite directions. Case and statistical studies show that the Hall electric field is important while the electron pressure gradient term is much smaller. The ions decouple from the magnetic field in the DF layer and dip region (E + ViūB ? 0), whereas electrons remain frozen-in (E + VeūB=?pe/nee).
A model for polar cap electric fields
NASA Technical Reports Server (NTRS)
Dangelo, N.
A model is proposed relating polar cap ionospheric electric fields to the parameters of the solar wind near the orbit of the earth. The model ignores the notion of field line merging. An essential feature is the role played by velocity shear instabilities in regions of the outer magnetosphere, in which mapping of the magnetosheath electric field would produce sunward convection. The anomalous resistivity which arises from velocity shear turbulence, suffices to essentially disconnect the magnetosphere from the magnetosheath, at any place where that resistivity is large enough. The magnetosheath-magnetosphere system, as a consequence, acts as a kind of diode or rectifier for the magnetosheath electric fields. Predictions of the model are compared with several observations related to polar cap convection.
Electric field controlled columnar and planar patterning of cholesteric colloids.
D'Adamo, G; Marenduzzo, D; Micheletti, C; Orlandini, E
We study how dispersions of colloidal particles in a cholesteric liquid crystal behave under a time-dependent electric field. By controlling the amplitude and shape of the applied field wave, we show that the system can be reproducibly driven out of equilibrium through different kinetic pathways and navigated through a glassylike free energy landscape encompassing many competing metastable equilibria. Such states range from simple Saturn rings to complex structures featuring amorphous defect networks, or stacks of disclination loops. A nonequilibrium electric field can also trigger the alignment of particles into columnar arrays, through defect-mediated force impulses, or their repositioning within a plane. Our results are promising in terms of providing new avenues towards controlled patterning and self-assembly of soft colloid-liquid crystal composite materials. PMID:25978263
Electric Field Controlled Columnar and Planar Patterning of Cholesteric Colloids
NASA Astrophysics Data System (ADS)
D'Adamo, G.; Marenduzzo, D.; Micheletti, C.; Orlandini, E.
We study how dispersions of colloidal particles in a cholesteric liquid crystal behave under a time-dependent electric field. By controlling the amplitude and shape of the applied field wave, we show that the system can be reproducibly driven out of equilibrium through different kinetic pathways and navigated through a glassylike free energy landscape encompassing many competing metastable equilibria. Such states range from simple Saturn rings to complex structures featuring amorphous defect networks, or stacks of disclination loops. A nonequilibrium electric field can also trigger the alignment of particles into columnar arrays, through defect-mediated force impulses, or their repositioning within a plane. Our results are promising in terms of providing new avenues towards controlled patterning and self-assembly of soft colloid-liquid crystal composite materials.
A status of the United States Air Force's More Electric Aircraft initiative
James S. Cloyd; Wright-Patterson AFB
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)
Surface electric fields of tourmaline
S. Yamaguchi
The N2, O2, H2O, and CO2 molecules that have condensed on the surface of a pyroelectric tourmaline crystal were degassed successively by means of electron bombardment. The temperature dependence of the electrostatic field strength on the specimen surface was observed by electron diffraction; it decreased as the degassing advanced. The tourmaline surface behaved as a gas Chromatographic adsorbent.
MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2
Fornberg, Bengt
MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy
Cholesteric elastomers in external mechanical and electric fields.
Menzel, Andreas M; Brand, Helmut R
In our studies, we focus on the reaction of cholesteric side-chain liquid single-crystal elastomers (SCLSCEs) to static external mechanical and electric fields. By means of linearized continuum theory, different geometries are investigated: The mechanical forces are oriented in a direction either parallel or perpendicular to the axis of the cholesteric helix such that they lead to a compression or dilation of the elastomer. Whereas only a homogeneous deformation of the system is found for the parallel case, perpendicularly applied mechanical forces cause either twisting or untwisting of the cholesteric helix. This predominantly depends on the direction in which the director of the cholesteric phase is anchored at the boundaries of the elastomer, and on the sign of a material parameter that describes how deformations of the elastomer couple to the relative rotations between the elastomer and the director. It is also this material parameter that leads to an anisotropy of the mechanical reaction of the system to compression and dilation, due to the liquid crystalline order. The effect of an external electric field is studied when applied parallel to the helix axis of a perfect electric insulator. Here an instability arises at a threshold value of the field amplitude, where the latter results from a competition between the effects of the external electric field on the one hand and the influences of the boundaries of the system, the cholesteric order, and the coupling between the director and the polymer network on the other hand. The instability is either homogeneous in space in the directions perpendicular to the external electric field and includes homogeneous shearing, or, for certain values of the material parameters, there arise undulations of the elastomer and the director orientation perpendicular to the direction of the external electric field at onset. This describes a qualitatively new phenomenon not observed in cholesteric systems yet, as these undulations are due to the coupling of the director orientation to the deformations of the elastomer. Furthermore, we find that theoretically it should be possible to synthesize cholesteric and nematic SCLSCEs in which the director can be reoriented by an external electric field without macroscopically distorting the sample; the latter applies for one specific set of values for the material parameters involved. We also propose ways of experimental access to the material parameters in the general situation. PMID:17358173
Minnesota, University of
of a particle with a constant acceleration. Ę Calculate the motion of a particle with an acceleration structure of materials, and the quark structure of elementary particles. The magnetic interaction can best current-carrying wires, and coils of wire. Ę Calculate the magnetic force on a charged particle moving
Minnesota, University of
with a constant acceleration. Ę Calculate the motion of a particle with an acceleration of constant magnitude, the atomic structure of materials, and the quark structure of elementary particles. In this set of laboratory-carrying wires, and coils of wire. Ę Calculate the magnetic force on a charged particle moving in a uniform
Dynamics of the structure of electric currents and electrodynamic forces in current sheets
Frank, A. G.; Satunin, S. N. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)
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.
Fundamentals of ion motion in electric radio-frequency multipole fields
M. H. Friedman; A. L. Yergey; J. E. Campana
The fundamentals of ion motion in electromagnetic fields are reviewed in detail with a special emphasis on electric radio-frequency (RF) fields which are used frequently in dynamic mass spectrometry. Forces and effects on ions in electromagnetic fields which are typically neglected, but which may be important in practical applications are reviewed and discussed for completeness. A method, based on complex
ForceFit: a code to fit classical force fields to quantum mechanical potential energy surfaces.
Waldher, Benjamin; Kuta, Jadwiga; Chen, Samuel; Henson, Neil; Clark, Aurora E
The ForceFit program package has been developed for fitting classical force field parameters based upon a force matching algorithm to quantum mechanical gradients of configurations that span the potential energy surface of the system. The program, which runs under UNIX and is written in C++, is an easy-to-use, nonproprietary platform that enables gradient fitting of a wide variety of functional force field forms to quantum mechanical information obtained from an array of common electronic structure codes. All aspects of the fitting process are run from a graphical user interface, from the parsing of quantum mechanical data, assembling of a potential energy surface database, setting the force field, and variables to be optimized, choosing a molecular mechanics code for comparison to the reference data, and finally, the initiation of a least squares minimization algorithm. Furthermore, the code is based on a modular templated code design that enables the facile addition of new functionality to the program. PMID:20340109
Efficient global optimization of reactive force-field parameters.
Dittner, Mark; M³ller, Julian; Aktulga, Hasan Metin; Hartke, Bernd
Reactive force fields make low-cost simulations of chemical reactions possible. However, optimizing them for a given chemical system is difficult and time-consuming. We present a high-performance implementation of global force-field parameter optimization, which delivers parameter sets of the same quality with much less effort and in far less time than before, and also offers excellent parallel scaling. We demonstrate these features with example applications targeting the ReaxFF force field. ® 2015 Wiley Periodicals, Inc. PMID:26085201
Magnetic Forces and Field Line Density
NSDL National Science Digital Library
This is an activity about depicting the relative strength of magnetic fields using field line density. Learners will use the magnetic field line drawing of six magnetic poles created in a previous activity and identify the areas of strong, weak, and medium magnetic intensity using the density of magnetic field lines. This is the fifth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website. How to Draw Magnetic Fields - II in the Magnetic Math booklet must be completed prior to this activity.
The unification of the fundamental interaction within Maxwell electromagnetism: Model of hydrogen atom. Gravity as the secondary electric force. Calculation of the unified inertia force
L. Neslusan
Considering two static, electrically charged, elementary particles, we demonstrate a possible way of proving that all known fundamental forces in the nature are the manifestations of the single, unique interaction. We re-define the gauging of integration constants in the Schwarzschild solution of Einstein field equations. We consider the potential energy in this context regardless it is gravitational or electric potential energy. With the newly gauged constants, we sketch how the unique interaction can be described with the help of an appropriate solution of the well-known Maxwell equations. According the solution, there are two zones, in the system of two oppositely charged particles, where the force is oscillating. The first particle can be in a stable, constant distance from the second particle, between the neighbouring regions of repulsion and attraction. In an outer oscillation zone, the corresponding energy levels in the proton-electron systems are identical (on the level of accuracy of values calculated by the Dirac's equations) to some experimentally determined levels in the hydrogen atom. For each system of two particles, there is also the zone with the macroscopic, i.e. monotonous behavior of the force. As well, the solution can be used to demonstrate that the net force between two assemblies consisting each (or at least one) of the same numbers of both positively and negatively charged particles is never zero. A secondary electric force, having the same orientation as the primary electric force between the oppositely charged particles, is always present. It can be identified to the gravity. Finally, the solution of the Maxwell equations can be used to calculate the inertia force of a particle. The consistent formulas for both acting and inertia forces enable to construct the dimensionless (without gravitational constant, permitivity of vacuum, etc.) equation of motion.
Prediction of Mechanical Properties of Polymers With Various Force Fields
NASA Technical Reports Server (NTRS)
Odegard, Gregory M.; Clancy, Thomas C.; Gates, Thomas S.
The effect of force field type on the predicted elastic properties of a polyimide is examined using a multiscale modeling technique. Molecular Dynamics simulations are used to predict the atomic structure and elastic properties of the polymer by subjecting a representative volume element of the material to bulk and shear finite deformations. The elastic properties of the polyimide are determined using three force fields: AMBER, OPLS-AA, and MM3. The predicted values of Young s modulus and shear modulus of the polyimide are compared with experimental values. The results indicate that the mechanical properties of the polyimide predicted with the OPLS-AA force field most closely matched those from experiment. The results also indicate that while the complexity of the force field does not have a significant effect on the accuracy of predicted properties, small differences in the force constants and the functional form of individual terms in the force fields determine the accuracy of the force field in predicting the elastic properties of the polyimide.
Electric Field Effects in RUS Measurements
Darling, Timothy W [Los Alamos National Laboratory; Ten Cate, James A [Los Alamos National Laboratory; Allured, Bradley [UNIV NEVADA, RENO; Carpenter, Michael A [CAMBRIDGE UNIV. UK
Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static and RF electric fields. Non-contact optical, buffered, or shielded transducers permit the application of charge and externally applied electric fields while making RUS measurements. For conducting samples, in vacuum, charging produces a small negative pressure in the volume of the material - a state rarely explored. At very high charges we influence the electron density near the surface so the propagation of surface waves and their resonances may give us a handle on the relationship of electron density to bond strength and elasticity. Our preliminary results indicate a charge sign dependent effect, but we are studying a number of possible other effects induced by charging. In dielectric materials, external electric fields influence the strain response, particularly in ferroelectrics. Experiments to study this connection at phase transformations are planned. The fact that many geological samples contain single crystal quartz suggests a possible use of the piezoelectric response to drive vibrations using applied RF fields. In polycrystals, averaging of strains in randomly oriented crystals implies using the 'statistical residual' strain as the drive. The ability to excite vibrations in quartzite polycrystals and arenites is explored. We present results of experimental and theoretical approaches to electric field effects using RUS methods.
Electric field effects in RUS measurements.
Darling, Timothy W; Allured, Bradley; Tencate, James A; Carpenter, Michael A
Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static and RF electric fields. Non-contact optical, buffered, or shielded transducers permit the application of charge and externally applied electric fields while making RUS measurements. For conducting samples, in vacuum, charging produces a small negative pressure in the volume of the material--a state rarely explored. At very high charges we influence the electron density near the surface so the propagation of surface waves and their resonances may give us a handle on the relationship of electron density to bond strength and elasticity. Our preliminary results indicate a charge sign dependent effect, but we are studying a number of possible other effects induced by charging. In dielectric materials, external electric fields influence the strain response, particularly in ferroelectrics. Experiments to study this connection at phase transformations are planned. The fact that many geological samples contain single crystal quartz suggests a possible use of the piezoelectric response to drive vibrations using applied RF fields. In polycrystals, averaging of strains in randomly oriented crystals implies using the "statistical residual" strain as the drive. The ability to excite vibrations in quartzite polycrystals and arenites is explored. We present results of experimental and theoretical approaches to electric field effects using RUS methods. PMID:19850314
Magnetic phase control by an electric field.
Lottermoser, Thomas; Lonkai, Thomas; Amann, Uwe; Hohlwein, Dietmar; Ihringer, J÷rg; Fiebig, Manfred
The quest for higher data density in information storage is motivating investigations into approaches for manipulating magnetization by means other than magnetic fields. This is evidenced by the recent boom in magnetoelectronics and 'spintronics', where phenomena such as carrier effects in magnetic semiconductors and high-correlation effects in colossal magnetoresistive compounds are studied for their device potential. The linear magnetoelectric effect-the induction of polarization by a magnetic field and of magnetization by an electric field-provides another route for linking magnetic and electric properties. It was recently discovered that composite materials and magnetic ferroelectrics exhibit magnetoelectric effects that exceed previously known effects by orders of magnitude, with the potential to trigger magnetic or electric phase transitions. Here we report a system whose magnetic phase can be controlled by an external electric field: ferromagnetic ordering in hexagonal HoMnO3 is reversibly switched on and off by the applied field via magnetoelectric interactions. We monitor this process using magneto-optical techniques and reveal its microscopic origin by neutron and X-ray diffraction. From our results, we identify basic requirements for other candidate materials to exhibit magnetoelectric phase control. PMID:15282600
Electric fields and double layers in plasmas
NASA Technical Reports Server (NTRS)
Singh, Nagendra; Thiemann, H.; Schunk, R. W.
Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamical features of the double layers are discussed. These features, as seen in simulations, laboratory experiments, and theory, indicate that double layers and the currents through them undergo slow oscillations which are determined by the ion transit time across an effective length of the system in which double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations were considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields and double layers in an expanding plasma is discussed.
Field forced antiferroelectric-to-ferroelectric switching in modified lead zirconate titanate stannate ceramics
Wuyi Pan; Qiming Zhang; Amar Bhalla; Leslie E. Cross
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
Turbulent relaxation to a force-free field-reversed state
NASA Technical Reports Server (NTRS)
Dahlburg, J. P.; Montgomery, D.; Doolen, G. D.; Turner, L.
The evolution of nonequilibrium initial conditions of an incompressible magnetohydrodynamic Z pinch is described by a three-dimensional, pseudospectral numerical code. Magnetohydrodynamic turbulence develops in the resistive, nonviscous magnetofluid, resulting in the selective decay of the energy relative to the magnetic helicity, at Lundquist numbers of only a few hundred. An interior force-free region grows with time and achieves spontaneous reversal of the toroidal magnetic field at the wall, without the necessity of an external electric field.
DC Electric Fields at the Magnetopause
NASA Astrophysics Data System (ADS)
Laakso, H. E.; Escoubet, C. P.; Masson, A.
In order to understand the transfer of energy, momentum and mass through the magnetopause one needs to know several plasma and field parameters including the DC electric field which is known to be challenging to measure in tenuous plasma regions, e.g. in the inner side of the magnetopause where the density drops below 1/cc. However, each of the Cluster spacecraft carries five different experiments that can provide information about DC electric fields, i.e. double probe antenna (EFW) and electron drift meter (EDI) as well as electron and ion spectrometers (PEACE, CIS-HIA, CIS-CODIF). Each technique is very different and has its own strengths and limitations. Therefore it is important to compare all available measurements before making a judgement on DC electric field variation at the magnetopause; note that only very rarely all five measurements are available at the same time. Although the full-resolution observations in the Cluster archive are calibrated, they can still contain various errors. However, when two experiments show the same field, it is quite likely that this is the right field because the different measurements are based on so complimentary techniques and the field varies so much when the spacecraft moves from the magnetosheath through the magnetopause into the magnetosphere, or vice versa. In this presentation we present several cases of the magnetopause crossings and how the different measurements agree and disagree around the magnetopause region.
Using impedance measurements for detecting pathogens trapped in an electric field
Miles, Robin R.
Impedance measurements between the electrodes in an electric field is utilized to detect the presence of pathogens trapped in the electric field. Since particles trapped in a field using the dielectiphoretic force changes the impedance between the electrodes by changing the dielectric material between the electrodes, the degree of particle trapping can be determined by measuring the impedance. This measurement is used to determine if sufficient pathogen have been collected to analyze further or potentially to identify the pathogen.
Solutions and symmetries of force-free magnetic fields
Tassi, E. [Burning Plasma Research Group, Dipartimento di Energetica and CNISM, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Pegoraro, F. [Dipartimento di Fisica, E. Fermi and CNISM, Pisa (Italy); Cicogna, G. [Dipartimento di Fisica, E. Fermi and INFN, Pisa (Italy)
New analytical results concerning force-free magnetic fields are presented. A number of examples of exact solutions for two-dimensional nonlinear force-free fields described by the Liouville equation are shown. These include classical solutions, such as, the Gold-Hoyle field and the force-free Harris sheet as special cases. The connection between these solutions and the Lie point symmetries of the Liouville equation is illustrated. Lie point symmetries of the equation describing force-free magnetic fields in helical symmetry in cylindrical geometry are also investigated and an infinitesimal generator that, in the vicinity of the cylinder axis, makes it possible to transform purely radially dependent solutions into helically symmetric solutions, is found. Finally we point out the existence of a formal analogy between the equations for the vector potential components of a class of force-free fields and the equations of motion of a charged particle in a magnetic field. This analogy makes it possible to transfer known results from the theory of the motion of a charged particle, into the context of force-free magnetic fields. Explicit examples of such application are given.
Generative morphologies of architectural organization in matter force field
Mutlu, Murat
This thesis investigates generative methods of architectural form finding in matter force fields that produce spatial subdivision and organizational variation. Unlike the style driven contemporary free-form architecture ...
The convection electric field in auroral substorms
NASA Astrophysics Data System (ADS)
Gjerloev, J. W.; Hoffman, R. A.
Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained by DE 1. The selected passes, which occurred during substorm expansion phase, maximum, or early recovery phase, cover the entire nighttime substorm. The organization of the data used the method developed by Fujii et al. [1994], which divided the data into six local time sectors covering the nighttime substorm region. Following the procedures employed in the paper by Gjerloev and Hoffman [2000b], the latitudinal width and location of each auroral oval crossing was then adjusted to fit the sector average. In addition to the detailed study of the characteristics of the field within each sector this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection channel is coincident with the highest conductances located just poleward of the Harang region. This channel drives the substorm current wedge component of the westward electrojet in the surge and middle surge sectors. It is present in all premidnight passes and consequently is an integral part of the three-dimensional substorm current wedge system.
Electric field heating and reaction rate effects
S. M. A. Ibrahim; D. Bradley
The effects are described of electrical fields upon heating and reaction rates of the reacting gases of methane-air and methane-oxygen in the recirculation zone of a jet-stirred reactor. The effects of thermal and field gas heatings on concentrations of CO and COŌ were also studied. The experiments included measurements of gas temperature distribution across the reactor, current-voltage characteristics for dc
Health of workers exposed to electric fields.
Broadbent, D E; Broadbent, M H; Male, J C; Jones, M R
The results of health questionnaire interviews with 390 electrical power transmission and distribution workers, together with long term estimates of their exposure to 50 Hz electric fields, and short term measurements of the actual exposure for 287 of them are reported. Twenty eight workers received measurable exposures, averaging about 30 kVm-1h over the two week measurement period. Estimated exposure rates were considerably greater, but showed fair correlation with the measurements. Although the general level of health was higher than we have found in manual workers in other industries, there were significant differences in the health measures between different categories of job, different parts of the country, and in association with factors such as overtime, working alone, or frequently changing shift. After allowing for the effects of job and location, however, we found no significant correlations of health with either measured or estimated exposure to electric fields. PMID:3970875
Motional spin relaxation in large electric fields
NASA Astrophysics Data System (ADS)
Schmid, Riccardo; Plaster, B.; Filippone, B. W.
We discuss the precession of spin-polarized ultracold neutrons (UCNs) and He3 atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional vūE magnetic fields. Particle motion in an electric field creates a motional vūE magnetic field, which when combined with collisions produces variations of the total magnetic field and results in spin relaxation of neutron and He3 samples. The spin relaxation times T1 (longitudinal) and T2 (transverse) of spin-polarized UCNs and He3 atoms are important considerations in a new search for the neutron electric dipole moment at the Spallation Neutron Source nEDM experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional vūE field for UCNs and for He3 atoms at temperatures below 600mK . We find the relaxation times for the neutron due to the vūE effect to be long compared to the neutron lifetime, while the He3 relaxation times may be important for the nEDM experiment.
Exposure assessment for electric and magnetic fields
Exposure assessment for extremely low frequency (ELF) electric and magnetic fields (EMF) is discussed. It is suggested that such assessments can be designed by attempting to mimic the receptor's experience of interest. Present efforts are, however, hampered by the lack of clearly defined human health effects, or even important interaction mechanisms, which might be used to define the appropriate exposure
Electric fields close to ground lightning flashes
Electric field changes have been measured at distances close to artificially triggered ground lightning flashes. These measurements confirmed that triggered discharges often comprise several strokes, and that strokes subsequent to the first are similar to those of natural lighting flashes. Channel charge density, current, and velocity have been calculated for a number of such subsequent strokes. It is inferred from
Empirical high-latitude electric field models
J. P. Heppner; N. C. Maynard
Electric field measurements from the Dynamics Explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn-dusk OGO 6 measurements (J.P. Heppner, 1977). The analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones. Paralleling the previous analysis, the modeling is based on the distinctly
Electric field observations of equatorial bubbles
T. L. Aggson; N. C. Maynard; W.B. Hanson; Jack L. Saba
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
Reversible shear thickening at low shear rates of electrorheological fluids under electric fields
Yu Tian; Minliang Zhang; Jile Jiang; Noshir Pesika; Hongbo Zeng; Jacob Israelachvili; Yonggang Meng; Shizhu Wen
Shear thickening is a phenomenon of significant viscosity increase of colloidal suspensions. While electrorheological (ER) fluids can be turned into a solid-like material by applying an electric field, their shear strength is widely represented by the attractive electrostatic interaction between ER particles. By shearing ER fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (100 V/mm), which could be characterized by a modified Mason number. Shear thickening and electrostatic particle interaction-induced inter-particle friction forces is considered to be the real origin of the high shear strength of ER fluids, while the applied electric field controls the extent of shear thickening. The electric field-controlled reversible shear thickening has implications for high-performance ER/magnetorheological (MR) fluid design, clutch fluids with high friction forces triggered by applying local electric field, other field-responsive materials and intelligent systems.
Effects of nanosecond pulse electric fields on cellular elasticity.
Dutta, Diganta; Asmar, Anthony; Stacey, Michael
We investigated the effects of a single 60 nanosecond pulsed electric field (nsPEF) of low (15 kV/cm) and high (60 kV/cm) field strengths on cellular morphology and membrane elasticity in Jurkat cells using fluorescent microscopy and atomic force microscopy (AFM). We performed force displacement measurements on cells using AFM and calculated the Young's modulus for membrane elasticity. Differential effects were observed depending upon pulsing conditions. We found that a single nsPEF of low field strength did not induce any apparent cytoskeletal breakdown and had minor morphological changes. Interestingly, force measurements and calculation of Young's modulus showed a significant decrease in membrane elasticity. A single nsPEF of high field strength induced stark morphological changes due to disruption of the actin cytoskeleton and a marked decrease in elasticity likely caused by irreversible membrane damage. We suggest that the cellular morphology is mainly dependent on stabilization by the actin cytoskeleton, while the elasticity changes are partially dependent on the cytoskeletal integrity. PMID:25732004
Brownian motion in a non-homogeneous force field and photonic force microscope
Giorgio Volpe; Giovanni Volpe; Dmitri Petrov
The Photonic Force Microscope (PFM) is an opto-mechanical technique based on an optical trap that can be assumed to probe forces in microscopic systems. This technique has been used to measure forces in the range of pico- and femto-Newton, assessing the mechanical properties of biomolecules as well as of other microscopic systems. For a correct use of the PFM, the force field to measure has to be invariable (homogeneous) on the scale of the Brownian motion of the trapped probe. This condition implicates that the force field must be conservative, excluding the possibility of a rotational component. However, there are cases where these assumptions are not fulfilled Here, we show how to improve the PFM technique in order to be able to deal with these cases. We introduce the theory of this enhanced PFM and we propose a concrete analysis workflow to reconstruct the force field from the experimental time-series of the probe position. Furthermore, we experimentally verify some particularly important cases, namely the case of a conservative or rotational force-field.
Nanoplasmonic surfaces enabling strong surface-normal electric field enhancement
Demir, Hilmi Volkan
Nanoplasmonic surfaces enabling strong surface- normal electric field enhancement Kivanń G³ng÷r,1) plasmonic arrays provide electric field intensity enhancement in the plane, typically with a surface% surface coverage enabling strong surface-normal field enhancement. Experimental measurements are found
Swarm SCARF equatorial electric field inversion chain
NASA Astrophysics Data System (ADS)
Alken, Patrick; Maus, Stefan; Vigneron, Pierre; Sirol, Olivier; Hulot, Gauthier
The day-time eastward equatorial electric field (EEF) in the ionospheric E-region plays a crucial role in equatorial ionospheric dynamics. It is responsible for driving the equatorial electrojet (EEJ) current system, equatorial vertical ion drifts, and the equatorial ionization anomaly (EIA). Due to its importance, there is much interest in accurately measuring and modeling the EEF for both climatological and near real-time studies. The Swarm satellite mission offers a unique opportunity to estimate the equatorial electric field from measurements of the geomagnetic field. Due to the near-polar orbits of each satellite, the on-board magnetometers record a full profile in latitude of the ionospheric current signatures at satellite altitude. These latitudinal magnetic profiles are then modeled using a first principles approach with empirical climatological inputs specifying the state of the ionosphere. Since the EEF is the primary driver of the low-latitude ionospheric current system, the observed magnetic measurements can then be inverted for the EEF. This paper details the algorithm for recovering the EEF from Swarm geomagnetic field measurements. The equatorial electric field estimates are an official Swarm level-2 product developed within the Swarm SCARF (Satellite Constellation Application Research Facility). They will be made freely available by ESA after the commissioning phase.
Application of the drag force method to evaluate magnetic property degradation near the cut edges of electrical steels
NASA Astrophysics Data System (ADS)
Garshelis, Ivan J.; Crevecoeur, Guillaume; Tollens, Stijn P. L.; Dupre, Luc
The increase in hysteresis loss associated with the altered microstructure and residual stress fields in regions near the cut edges of electrical steels is investigated by means of drag force measurements. Measurements are made using relatively narrow magnets on samples of two grades of nonoriented steels cut by laser or mechanical processes. Largest drag forces, hence losses, are consistently found in slow laser cut samples, smallest drag forces with fast laser cut samples, and moderately higher losses in mechanically cut samples. These results are consistent with other measurement methods.
Observations of large transient magnetospheric electric fields
NASA Technical Reports Server (NTRS)
Aggson, T. L.; Heppner, J. P.
Transient electric field events were observed with the long, double probe instrumentation carried by the IMP-6 satellite. Nine, clearly defined, exceptionally large amplitude events are presented here. The events are observed in the midnight sector at geocentric distances 3.5 to .5.5 R sub e at middle latitudes within a magnetic L-shell range of 4.8 to 7.5. They usually have a total duration of one to several minutes, with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions, and in most cases they can be associated with negative dH/dt excursions at magnetic observatories located near the foot of the magnetic field line intersecting IMP-6. The magnetospheric motions calculated for these electric fields indicated a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity.
Swarm equatorial electric field chain: First results
NASA Astrophysics Data System (ADS)
Alken, P.; Maus, S.; Chulliat, A.; Vigneron, P.; Sirol, O.; Hulot, G.
The eastward equatorial electric field (EEF) in the E region ionosphere drives many important phenomena at low latitudes. We developed a method of estimating the EEF from magnetometer measurements of near-polar orbiting satellites as they cross the magnetic equator, by recovering a clean signal of the equatorial electrojet current and modeling the observed current to determine the electric field present during the satellite pass. This algorithm is now implemented as an official Level-2 Swarm product. Here we present first results of EEF estimates from nearly a year of Swarm data. We find excellent agreement with independent measurements from the ground-based coherent scatter radar at Jicamarca, Peru, as well as horizontal field measurements from the West African Magnetometer Network magnetic observatory chain. We also calculate longitudinal gradients of EEF measurements made by the A and C lower satellite pair and find gradients up to about 0.05 mV/m/deg with significant longitudinal variability.
Transverse electric field in a mesoscopic Luttinger-liquid ring
NASA Astrophysics Data System (ADS)
Ŗimßnek, E.
The electric field within a ring containing repulsively interacting electrons is estimated using the spinless Luttinger-liquid model extended to allow transverse excitations due to the radial centrifugal force. The radial voltage drop across a ring, threaded by the Aharonov-Bohm flux, consists of a flux-periodic part that is independent of the interaction, and a flux-independent part that is proportional to the square root of the inverse compressibility of the electron gas. The voltage drop obtained from perturbation theory is consistent with Bernoulli's equation.
Biological cell¢electrical field interaction: stochastic approach
Dubey, A. K.; Banerjee, M.
The present work demonstrates how a stochastic model can be implemented to obtain a realistic description of the interaction of a biological cell with an external electric field. In our model formulation, the stochasticity is adopted by introducing various levels of forcing intensities in model parameters. The presence of noise in nuclear membrane capacitance has the most significant effect on the current flow through a biological cell. A plausible explanation based on underlying physics and biological structure of the nuclear membrane is proposed to explain such results. PMID:22210959
Acceleration of particles in an isotropic random force field
Hector Javier Durand-Manterola
If we have a particle immersed in a field of random forces, each interaction of the particle with the field can enlarge or diminish its kinetic energy. In this work is shown that in general, for any field of random force with uniform distribution of directions, the probability to gain kinetic energy is larger that the probability to lose it. Therefore, if the particle is submitted to a great number of interactions with the force stochastic field, the final result will be that the particle will gain energy. The probability to gain energy in each interaction is Pg=1/2 (1+T/(2Po)), where T is the impulse given by the field and Po is the momentum of the particle before the interaction. The probability to lose energy in each interaction is Pl=1/2 (1-T/(2Po)).
Tunable control of antibody immobilization using electric field.
Emaminejad, Sam; Javanmard, Mehdi; Gupta, Chaitanya; Chang, Shuai; Davis, Ronald W; Howe, Roger T
The controlled immobilization of proteins on solid-state surfaces can play an important role in enhancing the sensitivity of both affinity-based biosensors and probe-free sensing platforms. Typical methods of controlling the orientation of probe proteins on a sensor surface involve surface chemistry-based techniques. Here, we present a method of tunably controlling the immobilization of proteins on a solid-state surface using electric field. We study the ability to orient molecules by immobilizing IgG molecules in microchannels while applying lateral fields. We use atomic force microscopy to both qualitatively and quantitatively study the orientation of antibodies on glass surfaces. We apply this ability for controlled orientation to enhance the performance of affinity-based assays. As a proof of concept, we use fluorescence detection to indirectly verify the modulation of the orientation of proteins bound to the surface. We studied the interaction of fluorescently tagged anti-IgG with surface immobilized IgG controlled by electric field. Our study demonstrates that the use of electric field can result in more than 100% enhancement in signal-to-noise ratio compared with normal physical adsorption. PMID:25650429
Alternating Magnetic Field Forces for Satellite Formation Flying
NASA Technical Reports Server (NTRS)
Youngquist, Robert C.; Nurge, Mark A.; Starr, Stnaley O.
Selected future space missions, such as large aperture telescopes and multi-component interferometers, will require the precise positioning of a number of isolated satellites, yet many of the suggested approaches for providing satellites positioning forces have serious limitations. In this paper we propose a new approach, capable of providing both position and orientation forces, that resolves or alleviates many of these problems. We show that by using alternating fields and currents that finely-controlled forces can be induced on the satellites, which can be individually selected through frequency allocation. We also show, through analysis and experiment, that near field operation is feasible and can provide sufficient force and the necessary degrees of freedom to accurately position and orient small satellites relative to one another. In particular, the case of a telescope with a large number of free mirrors is developed to provide an example of the concept. We. also discuss the far field extension of this concept.
Force Field Parameter Estimation of Functional Perfluoropolyether Lubricants
Smith, R.; Chung, P.S; Steckel, J.A.; Jhon, M.S; Biegler, L.T.
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.
Force Field Parameter Estimation of Functional Perfluoropolyether Lubricants
Smith, R.; Chung, P.S.; Steckel, J; Jhon, M.S.; Biegler, L.T.
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.
Molecular Dynamics Simulation of Tri-n-Butyl-Phophate Liquid: A Force Field Comparative Study
Cui, Shengting [ORNL; de Almeida, Valmor F [ORNL; Hay, Benjamin [ORNL; Ye, Xianggui [ORNL; Khomami, Bamin [ORNL
Molecular dynamics (MD) simulations were conducted to compare the performance of four force fields in predicting thermophysical properties of tri-n-butyl-phosphate (TBP) in the liquid phase. The intramolecular force parameters used were from the Assisted Model Building with Energy Refinement (AMBER) force field model. The van der Waals parameters were based on either the AMBER or the Optimized Potential for Liquid Simulation (OPLS) force fields. The atomic partial charges were either assigned by performing quantum chemistry calculations or utilized previously published data, and were scaled to approximate the average experimental value of the electric dipole moment. Canonical ensemble computations based on the aforementioned parameters were performed near the atmospheric pressure and temperature to obtain the electric dipole moment, mass density, and self-diffusion coefficient. In addition, the microscopic structure of the liquid was characterized via pair correlation functions between selected atoms. It has been demonstrated that the electric dipole moment can be approximated within 1% of the average experimental value by virtue of scaled atomic partial charges. The liquid mass density can be predicted within 0.5-1% of its experimentally determined value when using the corresponding charge scaling. However, in all cases the predicted self- diffusion coefficient is significantly smaller than a commonly quoted experimental measurement; this result is qualified by the fact that the uncertainty of the experimental value was not available.
Apparatus having reduced mechanical forces for supporting high magnetic fields
Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)
The present invention identifies several configurations of conducting elements capable of supporting extremely high magnetic fields suitable for plasma confinement, wherein forces experienced by the conducting elements are significantly reduced over those which are present as a result of the generation of such high fields by conventional techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency.
Design and development of scanning eddy current force microscopy for characterization of electrical, magnetic and ferroelectric properties with nanometer resolution
NASA Astrophysics Data System (ADS)
Nalladega, Vijayaraghava
This dissertation describes the design and development of a new high-resolution electrical conductivity imaging technique combining the basic principles of eddy currents and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents induced in the sample are detected and measured with a magnetic tip attached to the AFM cantilever. The interaction of eddy currents with the magnetic tip-cantilever is theoretically modeled. The model is then used to estimate the eddy current forces generated in a typical metallic material placed in induced current field. The magnitude of the eddy current force is directly proportional to the electrical conductivity of the sample. The theoretical eddy current forces are used to design a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the development of a high-resolution, high sensitivity electrical conductivity imaging technique. The technique is used to experimentally measure eddy current forces in metals of different conductivities and compared with theoretical and finite element models. The experimental results show that the technique is capable of measuring pN range eddy current forces. The experimental eddy current forces are used to determine the electrical resistivity of a thin copper wire and the experimental value agrees with the bulk resistivity of copper reported in literature. The imaging capabilities of the new technique are demonstrated by imaging the electrical conductivity variations in a composite sample and a dual-phase titanium alloy in lift mode AFM. The results indicate that this technique can be used to detect very small variations in electrical conductivity. The spatial resolution of the technique is determined to be about 25 nm by imaging carbon nanofibers reinforced in polymer matrix. Since AFM is extensively used to characterize nanomaterials, the newly developed technique is used to characterize metallic nanoparticles. The results showed for the first time that it is possible to image helicons in nanometallic particles at low electromagnetic frequencies using an AFM. The theoretical analysis of the helicons in nanostructured materials is presented using the concept of effective mass of electrons. The primary objective of the research work reported in this dissertation is to develop a high-resolution electrical conductivity imaging system. However, the interaction of induced currents with different materials gives rise to different interaction forces. If an appropriate probe and an imaging mode are used, different material properties can be characterized using the same experimental setup. Therefore, in this study, magneto-acoustic, magnetic and dielectric properties of materials placed in induced current fields are studied. The modifications necessary to image these properties are discussed in detail. The advantages, limitations and applications of the new methodology are discussed.
Ampere force based magnetic field sensor using dual-polarization fiber laser.
Cheng, Linghao; Guo, Zhenzhen; Han, Jianlei; Jin, Long; Guan, Bai-Ou
A magnetic field sensor is proposed by placing a dual-polarization fiber grating laser under a copper wire. With a perpendicular magnetic field applied, an electrical current flowing through the copper wire can generate Ampere force to squeeze the fiber grating laser, resulting in the birefringence change inside the laser cavity and hence the change of the beat note frequency. When an alternating current is injected into the copper wire, the magnetic field induced beat note frequency change can be discriminated from environment disturbances. A novel fiber-optic magnetic field sensor is therefore demonstrated with high sensitivity and inherent immunity to disturbances. PMID:23736594
Field-aligned currents and ionospheric electric fields
NASA Technical Reports Server (NTRS)
Yasuhara, F.; Akasofu, S.-I.
It is shown that the observed distribution of the ionospheric electric field can be deduced from an equation combining Ohm's law with the current continuity equation by using the 'observed' distribution of field-aligned currents as the boundary condition for two models of the ionosphere. The first model has one conductive annular ring representing the quiet-time auroral precipitation belt; the second has two conductive annular rings that simulate the discrete and diffuse auroral regions. An analysis is performed to determine how well the electric-field distribution can be reproduced. The results indicate that the first model reproduces the Sq(p)-type distribution, the second model reproduces reasonably well a substorm-type potential and ionospheric current patterns together with the Harang discontinuity, and that the distribution of field-aligned currents is the same for both models.
Disruption of cancer cell replication by alternating electric fields.
Kirson, Eilon D; Gurvich, Zoya; Schneiderman, Rosa; Dekel, Erez; Itzhaki, Aviran; Wasserman, Yoram; Schatzberger, Rachel; Palti, Yoram
Low-intensity, intermediate-frequency (100-300 kHz), alternating electric fields, delivered by means of insulated electrodes, were found to have a profound inhibitory effect on the growth rate of a variety of human and rodent tumor cell lines (Patricia C, U-118, U-87, H-1299, MDA231, PC3, B16F1, F-98, C-6, RG2, and CT-26) and malignant tumors in animals. This effect, shown to be nonthermal, selectively affects dividing cells while quiescent cells are left intact. These fields act in two modes: arrest of cell proliferation and destruction of cells while undergoing division. Both effects are demonstrated when such fields are applied for 24 h to cells undergoing mitosis that is oriented roughly along the field direction. The first mode of action is manifested by interference with the proper formation of the mitotic spindle, whereas the second results in rapid disintegration of the dividing cells. Both effects, which are frequency dependent, are consistent with the computed directional forces exerted by these specific fields on charges and dipoles within the dividing cells. In vivo treatment of tumors in C57BL/6 and BALB/c mice (B16F1 and CT-26 syngeneic tumor models, respectively), resulted in significant slowing of tumor growth and extensive destruction of tumor cells within 3-6 days. These findings demonstrate the potential applicability of the described electric fields as a novel therapeutic modality for malignant tumors. PMID:15126372
Conically shaped drops in electric fields
NASA Astrophysics Data System (ADS)
Stone, Howard A.; Brenner, Michael P.; Lister, John R.
When an electric field is applied to a dielectric liquid containing a suspended immiscible fluid drop, the drop deforms into a prolate ellipsoidal shape. Above a critical field strength the drop develops conical ends, as first observed by Zeleny [Phys. Rev. 10, 1 (1917)] and Wilson & Taylor [Proc. Camb. Phil. Soc. 22, 728 (1925)] for, respectively, the case of conducting drops and soap films in air. The case of two dielectric liquids was studied recently using a slender drop approximation by Li, Halsey & Lobkovsky [Europhys. Lett 27, 575 (1994)]. In this presentation we further develop the slender body approximation to obtain coupled ordinary differential equations for the electric field and the drop shape. Analytical formulae are derived which approximately give the cone angle as a function of the dielectric constant ratio between the two fluids, and the minimum applied electric field at which conical tips first form as a function of the dielectric constant ratio. Finally, drops shapes are calculated numerically and compared with the common prolate shape assumption.
Control of the interface between (He-3)-rich and (He-4)-rich phases using electric fields
NASA Technical Reports Server (NTRS)
Israelsson, Ulf E.; Jackson, H. W.; Petrac, D.
A microgravity dilution refrigerator is considered, and it is shown that electric-field generated forces can be used to control the interface line between (He-3)-rich and (He-3)-poor phases. Fields as high as 13 MV/m are obtained in the present v-shaped geometry which correspond to positioning forces comparable to gravity. Good agreement is found between experimental results on the movements of the interface line and calculations obtained with a two-fluid model.
Comparing Molecular Dynamics Force Fields in the Essential Subspace
Gomez-Puertas, Paulino; Boomsma, Wouter; Lindorff-Larsen, Kresten
The continued development and utility of molecular dynamics simulations requires improvements in both the physical models used (force fields) and in our ability to sample the Boltzmann distribution of these models. Recent developments in both areas have made available multi-microsecond simulations of two proteins, ubiquitin and Protein G, using a number of different force fields. Although these force fields mostly share a common mathematical form, they differ in their parameters and in the philosophy by which these were derived, and previous analyses showed varying levels of agreement with experimental NMR data. To complement the comparison to experiments, we have performed a structural analysis of and comparison between these simulations, thereby providing insight into the relationship between force-field parameterization, the resulting ensemble of conformations and the agreement with experiments. In particular, our results show that, at a coarse level, many of the motional properties are preserved across several, though not all, force fields. At a finer level of detail, however, there are distinct differences in both the structure and dynamics of the two proteins, which can, together with comparison with experimental data, help to select force fields for simulations of proteins. A noteworthy observation is that force fields that have been reparameterized and improved to provide a more accurate energetic description of the balance between helical and coil structures are difficult to distinguish from their ōunbalancedö counterparts in these simulations. This observation implies that simulations of stable, folded proteins, even those reaching 10 microseconds in length, may provide relatively little information that can be used to modify torsion parameters to achieve an accurate balance between different secondary structural elements. PMID:25811178
Electric force lines of the double Reissner-Nordstrom exact solution
A. Paolino; M. Pizzi
Recently, Alekseev and Belinski have presented a new exact solution of the Einstein-Maxwell equations which describes two Reissner-Nordstrom (RN) sources in reciprocal equilibrium (no struts nor strings); one source is a naked singularity, the other is a black hole: this is the only possible configuration for separable object, apart from the well-known extreme case ($m_i=e_i$). In the present paper, after a brief summary of this solution, we study in some detail the coordinate systems used and the main features of the gravitational and electric fields. In particular we graph the plots of the electric force lines in three qualitatively different situations: equal-signed charges, opposite charges and the case of a naked singularity near a neutral black hole.
Electric-field induced magnetization reversal using multiferroics
NASA Astrophysics Data System (ADS)
Trassin, Morgan
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.
On force-field models of the spacecraft flyby anomaly
Wolfgang Hasse; Emrah Birsin; Philipp Haehnel
Recently, Anderson et al. published an empirical prediction formula for the so far unexplained parts of the velocity changes of spacecrafts during Earth flybys. In the framework of a perturbational approach, we show that there is no velocity-independent force field of the Earth - in addition to its Newtonian gravity field - that is to reproduce this formula. However, we
Classical motion in force fields with short range correlations
B. Aguer; S. De Bievre; P. Lafitte; P. Parris
We study the long time motion of fast particles moving through time-dependent random force fields with correlations that decay rapidly in space, but not necessarily in time. The time dependence of the averaged kinetic energy and mean-squared displacement is shown to exhibit a large degree of universality; it depends only on whether the force is, or is not, a gradient vector field. When it is, p^{2}(t) ~ t^{2/5} independently of the details of the potential and of the space dimension. Motion is then superballistic in one dimension, with q^{2}(t) ~ t^{12/5}, and ballistic in higher dimensions, with q^{2}(t) ~ t^{2}. These predictions are supported by numerical results in one and two dimensions. For force fields not obtained from a potential field, the power laws are different: p^{2}(t) ~ t^{2/3} and q^{2}(t) ~ t^{8/3} in all dimensions d\\geq 1.
Extremely low frequency electric fields and cancer: assessing the evidence.
Kheifets, Leeka; Renew, David; Sias, Glenn; Swanson, John
Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric-fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric-field exposures and appliance use does not support the conclusion of adverse health effects from electric-field exposure. Workers in close proximity to high-voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields. PMID:19650076
Field emission study of diamond-like carbon films with scanned-probe field-emission force microscopy
Inoue, Takahito [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); Ogletree, D. Frank [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); Salmeron, Miquel [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)
Using a tip as an anode, a scanning force microscope (SFM) with an electrically conducting tip allows simultaneous measurement of both field-emitted currents and surface electronic properties with high lateral resolution. The principle of the method and its application to field emission from chemical vapor deposition diamond-like carbon films are presented. By simultaneously imaging the topography and field-emission current distribution with a 100 nm tip-surface separation, we correlated emission, topography, and dielectric properties. Subsequent contact SFM images of the same regions correlated topography and conductivity on the nanometer scale. The electrostatic force between tip and surface showed fluctuations on a millisecond time scale during field emission. This is probably due to charging and discharging of deep traps in the diamond-like carbon film. (c) 2000 American Institute of Physics.
Fiber optic electric field sensor technology
NASA Technical Reports Server (NTRS)
Jarzynski, J.; De Paula, R. P.
The properties of piezoactive plastics are reviewed as well as the fiber-optic electric field sensors studied so far. A particular configuration consisting of a concentric piezoactive jacket on the glass fiber is discussed in detail and the frequency response of this sensor is projected over a wide range of frequencies. The present design has the practical advantages of leading to a compact lightweight sensor; longer fiber lengths may be used to increase sensitivity. It is predicted that, at low frequencies, a fiber-optic antenna using a 1-km length of fiber would be capable of detecting a minimum electric field of 43 microV/m assuming a minimum phase sensitivity of 10 to the -6th radians for the optical Mach-Zehnder interferometer.
Evaluation of electric belt grill, forced-air convection oven, and electric broiler cookery methods for beef tenderness research
T. E Lawrence; D. A King; E Obuz; E. J Yancey; M. E Dikeman
Five muscles from USDA Select beef carcasses were cooked on an electric belt grill at three temperatures (93, 117, and 163░C), in a forced-air convection oven, and on an electric broiler to determine effects of cooking treatment and muscle on Warner-Bratzler shear force values, cooking traits (cooking loss, cooking time, and endpoint temperature), and repeatability of duplicate measurements. All cooking
Charged particles in higher dimensional homogeneous gravitational field: self-energy and self-force
NASA Astrophysics Data System (ADS)
Frolov, Valeri P.; Zelnikov, Andrei
A problem of self-energy and self-force for a charged point-like particle in a higher dimensional homogeneous gravitational field is considered. We study two cases, when a particle has the usual electric charge, and when it has a scalar charge, which is a source of a scalar massless minimally coupled field. We assume that a particle is at rest in the gravitational field, so that its motion is not geodesic, and it has an acceleration a directed away from the horizon. The self-energy of a point charge is divergent and the strength of the divergence grows with the number of dimensions. In order to obtain a finite contribution to the self-energy, we use a covariant regularization method which is a modification of the proper time cut-off and other covariant regularizations. We analyze the relation between the self-energy and the self-force and obtain explicit expressions for the self-forces for the electric and the scalar charge in spacetimes with the number of dimensions up to eight. General expressions for the case of higher dimensions are also obtained. We discuss special logarithmic factors ln a, which are present in both the self-energy and the self-force in odd dimensions. Finally, we compare the obtained results with the earlier known results both for the homogeneous gravitational field and for particles near black holes.
Charged particles in higher dimensional homogeneous gravitational field: Self-energy and self-force
Valeri P. Frolov; Andrei Zelnikov
A problem of self-energy and self-force for a charged point-like particle in a higher dimensional homogeneous gravitational field is considered. We study two cases, when a particle has usual electric charge and a case when it has a scalar charge, which is a source of a scalar massless minimally coupled field. We assume that a particle is at rest in the gravitational field, so that its motion is not geodesic and it has an acceleration a directed from the horizon. The self-energy of a point charge is divergent and the strength of the divergence grows with the number of dimensions. In order to obtain a finite contribution to the self- energy we use a covariant regularization method which is a modification of the proper time cut-off and other covariant regularizations. We analyze a relation between the self-energy and self-force and obtain explicit expressions for the self-forces for the electric and scalar charge in the spacetimes with the number of dimensions up to eight. General expressions for the case of higher dimensions are also obtained. We discuss special logarithmic factors ln(a), which are present both in the self-energy and self-force in odd dimensions. Finally, we compare the obtained results with the earlier known results both for the homogeneous gravitational field and for particles near black holes.
Killing of microorganisms by pulsed electric fields
T. Grahl; H. Mõrkl
Lethal effects of pulsed electric fields (PEF) on suspensions of various bacteria, yeast, and spores in buffer solutions and\\u000a liquid foodstuffs were examined. Living-cell counts of vegetative cell types were reduced by PEF treatment by up to more than\\u000a four orders of magnitude (> 99.99%). On the other hand, endoand ascospores were not inactivated or killed to any great extent.
Force field-dependent solution properties of glycine oligomers.
Drake, Justin A; Pettitt, B Montgomery
Molecular simulations can be used to study disordered polypeptide systems and to generate hypotheses on the underlying structural and thermodynamic mechanisms that govern their function. As the number of disordered protein systems investigated with simulations increase, it is important to understand how particular force fields affect the structural properties of disordered polypeptides in solution. To this end, we performed a comparative structural analysis of Gly3 and Gly10 in aqueous solution from all atom, microsecond molecular dynamics (MD) simulations using the CHARMM 27 (C27), CHARMM 36 (C36), and Amber ff12SB force fields. For each force field, Gly3 and Gly10 were simulated for at least 300 ns and 1 ?s, respectively. Simulating oligoglycines of two different lengths allows us to evaluate how force field effects depend on polypeptide length. Using a variety of structural metrics (e.g., end-to-end distance, radius of gyration, dihedral angle distributions), we characterize the distribution of oligoglycine conformers for each force field and show that each sample conformation space differently, yielding considerably different structural tendencies of the same oligoglycine model in solution. Notably, we find that C36 samples more extended oligoglycine structures than both C27 and ff12SB. ® 2015 Wiley Periodicals, Inc. PMID:25952623
Forced cooling of underground electric power transmission lines : design manual
Brown, Jay A.
The methodology utilized for the design of a forced-cooled pipe-type underground transmission system is presented. The material is divided into three major parts: (1) The Forced-cooled Pipe-Type Underground Transmission ...
Mott insulators in strong electric fields
NASA Astrophysics Data System (ADS)
Sachdev, S.; Sengupta, K.; Girvin, S. M.
Recent experiments on ultracold atomic gases in an optical lattice potential have produced a Mott insulating state of 87Rb atoms. This state is stable to a small applied potential gradient (an ┬Ī┬«┬Ī┬«electric┬Ī┬»┬Ī┬» field), but a resonant response was observed when the potential energy drop per lattice spacing (E), was close to the repulsive interaction energy (U) between two atoms in the same lattice potential well. We identify all states which are resonantly coupled to the Mott insulator for Eś=U via an infinitesimal tunneling amplitude between neighboring potential wells. The strong correlation between these states is described by an effective Hamiltonian for the resonant subspace. This Hamiltonian exhibits quantum phase transitions associated with an Ising density wave order and with the appearance of superfluidity in the directions transverse to the electric field. We suggest that the observed resonant response is related to these transitions and propose experiments to directly detect the order parameters. The generalizations to electric fields applied in different directions and to a variety of lattices should allow study of numerous other correlated quantum phases. This work is supported by U.S. NSF Grant Nos. DMR 0098226 and DMR 0196503.
Electric field quench, equilibration, and universal behavior
NASA Astrophysics Data System (ADS)
Amiri-Sharifi, S.; Ali-Akbari, M.; Sepangi, H. R.
We study electric field quench in N =2 strongly coupled gauge theory, using the AdS/CFT correspondence. To do so, we consider the aforementioned system which is subjected to a time-dependent electric field indicating an out of equilibrium system. Defining the equilibration time teq , at which the system relaxes to its final equilibrium state after injecting the energy, we find that the rescaled equilibration time k-1teq decreases as the transition time k increases. Therefore, we expect that for sufficiently large transition time, k ??, the relaxation of the system to its final equilibrium can be an adiabatic process. On the other hand, we observe a universal behavior for the fast quenches, k ?1 , meaning that the rescaled equilibration time does not depend on the final value of the time-dependent electric field. Our calculations generalized to systems in various dimensions also confirm the universalization process which seems to be a typical feature of all strongly coupled gauge theories that admit a gravitational dual.
Electric field effects in oxide perovskite systems.
NASA Astrophysics Data System (ADS)
Ogale, Satishchandra
Recently, the suggested and partly demonstrated existence of stripe phases in oxide perovskite systems, and the suggestion of percolative phase separation as a primary transport mechanism in manganites, have raised interesting questions about the nature of response of such electronically inhomogeneous systems to external perturbations such as strain, defects and applied fields. We have explored the status of such perovskites as a channel in an electric field effect configuration. Our recent data on a modified and improved manganite/PZT based heterostructure show colossal electric field effects, which along with their systematics under applied magnetic field strongly favor an electronically inhomogeneous picture for the manganite channel over the traditional uniform channel picture. In fact the magneto-resistance and electro-resistance are found to exhibit complimentary behavior. It will be argued based on the various length-scale related physical considerations that nanometer scale channels could lead to even more novel features in field induced perturbations. 1. D. M. Newns et al. Appl. Phys. Lett. 73, 780 (1998). 2. S. B. Ogale et al. Phys. Rev. Letts. 77, 1159 (1996). 3. Emery, V. J. et al. Phys. Rev. B. 56, 6120 (1997). 4. M. Uehara et al. Nature 399, 560 (1999).
Deriving forces from 2D velocity field measurements
NASA Astrophysics Data System (ADS)
Albrecht, Thomas; del Campo, Vanessa; Weier, Tom; Metzkes, Hans; Stiller, J÷rg
We discuss how to derive a force or a force density from a measured velocity field. The first part focuses on the integral force a fluid exerts on a body, e.g. lift and drag on an airfoil. Obtaining the correct pressure is crucial; however, it cannot be measured within the flow non-intrusively. Using numerical and experimental test cases, we compare the accuracy achievable with three methods: pressure reconstruction from velocity fields via (1) the differential momentum equation, or (2) the Poisson equation, furthermore, (3) Noca's momentum equation [Noca, JFS 13(5), 1999], which does not require pressure explicitly. The latter gives the best results for the lift, whereas the first or second approach should be used for the drag. The second part deals with obtaining the distribution of a body force density generated by an actuator. Using a stream function ansatz, we obtain a Laplace equation that allows us to compute the solenoidal part of the force distribution; however, the irrotational part is lost. Furthermore, the wall pressure must be known. We validate this approach using numerical data from a wall jet flow in a rectangular box, driven by a fictitious, solenoidal body force. Reconstructing the force distribution yields an error of less than 10-2 for most of the domain.
On force-field models of the spacecraft flyby anomaly
Hasse, Wolfgang; Haehnel, Philipp
Recently, Anderson et al. published an empirical prediction formula for the so far unexplained parts of the velocity changes of spacecrafts during Earth flybys. In the framework of a perturbational approach, we show that there is no velocity-independent force field of the Earth - in addition to its Newtonian gravity field - that is to reproduce this formula. However, we give examples for fields modeling exactly the flyby anomaly which are quadratic functions of the velocity of the spacecraft.
On force-field models of the spacecraft flyby anomaly
Wolfgang Hasse; Emrah Birsin; Philipp Haehnel
Recently, Anderson et al. published an empirical prediction formula for the so far unexplained parts of the velocity changes of spacecrafts during Earth flybys. In the framework of a perturbational approach, we show that there is no velocity-independent force field of the Earth - in addition to its Newtonian gravity field - that is to reproduce this formula. However, we give examples for fields modeling exactly the flyby anomaly which are quadratic functions of the velocity of the spacecraft.
Nonequilibrium forces between neutral atoms mediated by a quantum field
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)
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.
Superadiabatic optical forces on a dipole: exactly solvable model for a vortex field
NASA Astrophysics Data System (ADS)
Berry, M. V.; Shukla, Pragya
The forces exerted by light on a small particle are modified by the particle's motion, giving a series of superadiabatic corrections to the lowest-order approximation in which the motion is neglected. The correction forces can be calculated recursively for an electric dipole modelled as a damped oscillator. In lowest order, there is, as is known, a non-potential though non-dissipative æcurl forceÆ, in addition to the familiar gradient force. In the next order, there are forces of geometric magnetism and friction, related to the geometric phase 2-form and the metric of the driving field. For the paraxial field of an optical vortex, the hierarchy of superadiabatic forces can be calculated explicitly, revealing a four-sheeted Riemann surface on which fast and slow dynamics are connected. This leads to an exact æslow manifoldÆ, on which the dipole is driven without oscillations by the same forces as in the first two adiabatic orders, but with frequency-renormalized strengths.
Kelvin Probe Force Microscopy for in situ Electrical Characterization of Organic Solar Cells
Fisher, Frank
Kelvin Probe Force Microscopy for in situ Electrical Characterization of Organic Solar Cells solar cell performance. Guangyong Li is currently an Assistant Professor in the Department of Electrical Wednesday October 19, 2011, Babbio 122, 11am Professor Guangyong Li Dep. of Electrical and Computer Eng
Driving force characteristics of 40kW switched reluctance motor for electric vehicle
K. Watanabe; S. Aida; A. Komatsuzaki; I. Miki
There is a growing interest in an electric vehicle (EV), a hybrid-electric vehicle and a fuel-cell vehicle due to air pollution and exhaustion of fossil fuels. These vehicles use motors to obtain the driving force. Switched reluctance motors (SRMs) have a simple structure, high reliability and low cost. Furthermore, these are desirable features for electric vehicle. Our purpose is conversion
Status of the United States Air Force's More Electric Aircraft initiative
James S. Cloyd
Since the early 1990's, the USAF has been successfully pursuing advancement in aircraft electrical power system technologies as a means of collectively establishing the capability to reduce dramatically or eliminate centralized hydraulics aboard aircraft and replace them with electrical power as the motive force for all aircraft functions. This overall approach (called the More Electric Aircraft, MEA) has been analytically
Force-free magnetic fields - The magneto-frictional method
NASA Technical Reports Server (NTRS)
Yang, W. H.; Sturrock, P. A.; Antiochos, S. K.
The problem under discussion is that of calculating magnetic field configurations in which the Lorentz force j x B is everywhere zero, subject to specified boundary conditions. We choose to represent the magnetic field in terms of Clebsch variables in the form B = grad alpha x grad beta. These variables are constant on any field line so that each field line is labeled by the corresponding values of alpha and beta. When the field is described in this way, the most appropriate choice of boundary conditions is to specify the values of alpha and beta on the bounding surface. We show that such field configurations may be calculated by a magneto-frictional method. We imagine that the field lines move through a stationary medium, and that each element of magnetic field is subject to a frictional force parallel to and opposing the velocity of the field line. This concept leads to an iteration procedure for modifying the variables alpha and beta, that tends asymptotically towards the force-free state. We apply the method first to a simple problem in two rectangular dimensions, and then to a problem of cylindrical symmetry that was previously discussed by Barnes and Sturrock (1972). In one important respect, our new results differ from the earlier results of Barnes and Sturrock, and we conclude that the earlier article was in error.
Development of a novel fouling suppression system in membrane bioreactors using an intermittent electric field.
Akamatsu, Kazuki; Lu, Wei; Sugawara, Takashi; Nakao, Shin-ichi
A novel membrane bioreactor system that uses an intermittent electric field was successfully developed to suppress membrane fouling, caused mainly by activated sludge. We found that the surface of the activated sludge is negatively charged, and propose the utilization of an electric repulsive force to move the sludge away from the membrane by applying an electric field only when the permeate flux has drastically declined because of membrane fouling. The experimental results showed that a field of 6 V cm(-1), switched on and off every 90 s, significantly improved the removal of the activated sludge from the membrane and accordingly improved the average permeate flux. PMID:19897224
Force field inside the void in complex plasmas under microgravity conditions
Kretschmer, M.; Khrapak, S.A.; Zhdanov, S.K.; Thomas, H.M.; Morfill, G.E.; Fortov, V.E.; Lipaev, A.M.; Molotkov, V.I.; Ivanov, A.I.; Turin, M.V. [Centre for Interdisciplinary Plasma Science, Max-Planck-Institut fuer extraterrestrische Physik, D-85741 Garching (Germany); Institute for High Energy Densities, Russian Academy of Sciences, Izhorskaya 13/19, 125412 Moscow (Russian Federation); RSC 'Energia' Korolev, 141070 Moscow Region (Russian Federation)
Observations of complex plasmas under microgravity conditions onboard the International Space Station performed with the Plasma-Kristall experiment-Nefedov facility are reported. A weak instability of the boundary between the central void (region free of microparticles) and the microparticle cloud is observed at low gas pressures. The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called the 'trampoline effect'). The trajectories of injected particles are analyzed providing information on the force field inside the void. The experimental results are compared with theory which assumes that the most important forces inside the void are the electric and the ion drag forces. Good agreement is found clearly indicating that under conditions investigated the void formation is caused by the ion drag force.
Force field inside the void in complex plasmas under microgravity conditions
NASA Astrophysics Data System (ADS)
Kretschmer, M.; Khrapak, S. A.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E.; Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Ivanov, A. I.; Turin, M. V.
Observations of complex plasmas under microgravity conditions onboard the International Space Station performed with the Plasma-Kristall experiment-Nefedov facility are reported. A weak instability of the boundary between the central void (region free of microparticles) and the microparticle cloud is observed at low gas pressures. The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called the ōtrampoline effectö). The trajectories of injected particles are analyzed providing information on the force field inside the void. The experimental results are compared with theory which assumes that the most important forces inside the void are the electric and the ion drag forces. Good agreement is found clearly indicating that under conditions investigated the void formation is caused by the ion drag force.
Electric and magnetic fields at power frequencies.
Miller, Anthony B; Green, Lois M
Exposures to electric and magnetic fields are among the most ubiquitous exposures that the Canadian population experiences. Sources of electric and magnetic field exposures may be occupational or residential and include proximity to certain types of electrical equipment, transmission and distribution power lines as well as appliance use. The early studies of children tended toward a consistent association between risks for leukemia and brain cancer and residential proximity to power lines having high wire configuration. More recent studies-and studies which have attempted to improve upon the measurement of exposure by using calculated fields, point-in-time or personal monitoring-have been inconsistent, with some suggesting increased risk and others not. Occupational exposures have suggested an increase in risk for leukemia, and to a lesser extent brain cancer and Non-Hodgkin lymphoma. However, studies of residential exposures and cancer in adults generally have suggested no effect. Laboratory work has been unable to demonstrate a biological mechanism which might explain the epidemiological findings. In spite of extensive efforts over the past 20 years and many expert reviews, it has been difficult to reach consensus regarding the carcinogenic effects of electric and magnetic fields. Exposure assessment has proven to be complex, and agreement on the relevant exposure metric has not yet been obtained. There is justification to question whether point-in-time measures in homes are appropriate indices of the relevant etiological exposure, as they fail to account for changes over time, peak exposures or time-varying fields. Nevertheless, it is probably desirable to err on the side of caution in not placing too much weight on the inconsistencies. The IARC has classified EMF as a "possible carcinogen" which refers to the circumstances where there is limited evidence of carcinogenicity in humans and inadequate evidence in experimental animals. The IARC review indicated limited evidence for the carcinogenicity of extremely low-frequency magnetic fields in relation to childhood leukemia at high level exposure in the residential environment (average residential magnetic field strength >0.4 ?T). Even higher levels of exposure in the occupational environment may increase the risk of leukemia in adults. PMID:21199600
Generation and measurement of dc electric fields with space charge
Martin Misakian
Characterization of the electrical environment in the vicinity of high voltage dc transmission lines requires measurement of a number of electrical parameters associated with the lines. These parameters include the electric field strength with significant space-charge contributions. This report describes an experimental effort to generate known dc electric fields containing controlled amounts of space charge. An apparatus which has been
Dielectric Force Microscopy: Imaging Charge Carriers in Nanomaterials without Electrical Contacts.
Zhang, Jie; Lu, Wei; Li, Yize Stephanie; Cai, Jinhua; Chen, Liwei
Nanomaterials are increasingly used in electronic, optoelectronic, bioelectronic, sensing, and energy nanodevices. Characterization of electrical properties at nanometer scales thus becomes not only a pursuit in basic science but also of widespread practical need. The conventional field-effect transistor (FET) approach involves making electrical contacts to individual nanomaterials. This approach faces serious challenges in routine characterization due to the small size and the intrinsic heterogeneity of nanomaterials, as well as the difficulties in forming Ohmic contact with nanomaterials. Since the charge carrier polarization in semiconducting and metallic materials dominates their dielectric response to external fields, detecting dielectric polarization is an alternative approach in probing the carrier properties and electrical conductivity in nanomaterials. This Account reviews the challenges in the electrical conductivity characterization of nanomaterials and demonstrates that dielectric force microscopy (DFM) is a powerful tool to address the challenges. DFM measures the dielectric polarization via its force interaction with charges on the DFM tip and thus eliminates the need to make electrical contacts with nanomaterials. Furthermore, DFM imaging provides nanometer-scaled spatial resolution. Single-walled carbon nanotubes (SWNTs) and ZnO nanowires are used as model systems. The transverse dielectric permittivity of SWNTs is quantitatively measured to be ?10, and the differences in longitudinal dielectric polarization are exploited to distinguish metallic SWNTs from semiconducting SWNTs. By application of a gate voltage at the DFM tip, the local carrier concentration underneath the tip can be accumulated or depleted, depending on charge carrier type and the density of states near the Fermi level. This effect is exploited to identify the conductivity type and carrier type in nanomaterials. By making comparison between DFM and FET measurements on the exact same SWNTs, it is found that the DFM gate modulation ratio, which is the ratio of DFM signal strengths at different gate voltage, is linearly proportional to the logarithm of FET device on/off ratio. A Drude-level model is established to explain the semilogarithmic correlation between DFM gate modulation ration and FET device on/off ratio and simulate the dependence of DFM force on charge carrier concentration and mobility. Future developments towards DFM imaging of charge carrier concentration or mobility in nanomaterials and nanodevices can thus be expected. PMID:26061707
Tiwari, Sanjiv Kumar, E-mail: email@example.com [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur 313 001 (India)
A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic fields (computed from the force-free parameter {alpha}), and any kind of extrapolation, heavily hinges on the force-free approximation of the photospheric sunspot magnetic fields. Thus, it is of vital importance to inspect the force-free behavior of sunspot magnetic fields. The force-free nature of sunspot magnetic fields has been examined earlier by some researchers, ending with incoherent results. Accurate photospheric vector field measurements with high spatial resolution are required to inspect the force-free nature of sunspots. For this purpose, we use several vector magnetograms of high spatial resolution obtained from the Solar Optical Telescope/Spectro-Polarimeter on board Hinode. Both the necessary and sufficient conditions for force-free nature are examined by checking the global and local nature of equilibrium magnetic forces over sunspots. We find that sunspot magnetic fields are not very far from the force-free configuration, although they are not completely force-free on the photosphere. The umbral and inner penumbral fields are more force-free than the middle and outer penumbral fields. During their evolution, sunspot magnetic fields are found to maintain their proximity to force-free field behavior. Although a dependence of net Lorentz force components is seen on the evolutionary stages of the sunspots, we do not find a systematic relationship between the nature of sunspot magnetic fields and the associated flare activity. Further, we examine whether the fields at the photosphere follow linear or nonlinear force-free conditions. After examining this in various complex and simple sunspots, we conclude that, in either case, photospheric sunspot magnetic fields are closer to satisfying the nonlinear force-free field approximation.
Spatial aspects of the electric fields generated by weakly electric fish
Eric I. Knudsen
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
Rocket borne instrument to measure electric fields inside electrified clouds
NASA Technical Reports Server (NTRS)
Ruhnke, L. H.
Simple electric field measuring system is mounted on small rocket and consists of two voltage probes, one extending from nose and other on tail fin. Electric field through which rocket passes is determined by potential difference between probes.
Electrical Grounding - a Field for Geophysicists and Electrical Engineers Partnership
NASA Astrophysics Data System (ADS)
Freire, P. F.; Pane, E.; Guaraldo, N.
Technology for designing ground electrodes for high-voltage direct current transmission systems (HVDC) has being using in the last years, deep soil models based on a wide range of geophysical methods. These models shall include detailed representation of shallow soil, down to 100 meters, in order to allow the evaluation of the soil conditions where the ground electrodes will be buried. Also deep soil models are needed, to be used for the interference studies, which shall represent a soil volume of about 15 km deep and a surface area of about 15 to 30 km radius. Large facilities for power plants (hydroelectric and wind farms, for example) and industrial complexes (such as petrochemical plants) has become usual at the current stage of Brazil industrialization. Grounding mats for these facilities are made of a buried cooper mesh, interconnected to a wide variety of metallic masses, such as steel reinforced concrete foundations, ducts in general etc. These grounding systems may present dimensions with the order of hundreds of meters, and, at least in Brazil, are usually calculated by using electrical resistivity soil models, based on short spacing Wenner measurements (with maximum spacing of about 64 m.). The soil model shall be the best possible representation of the environment in which the grounding electrodes are immersed, for the purpose of calculation of resistance or for digital simulation. The model to be obtained is limited by the amount and quality of soil resistivity measurements are available, and the resources to be used in the calculations and simulations. Geophysics uses a wide range of technologies for exploring subsoil, ranging from surface measurements to wells logging - seismic, gravimetric, magnetic, electrical, electromagnetic and radiometric. The electrical and electromagnetic methods includes various measurement techniques (Wenner, Schlumberger, TDEM, Magneto-telluric etc.), which together allow the development of complex resistivity soil models, layered stratified or showing lateral variations, ranging down to several tens of kilometers deep, reaching the crust-mantle interface (typically with the order of 30-40 km). This work aims to analyze the constraints of the current soil models being used for grounding electrodes design, and suggests the need of a soil modeling methodology compatible with large grounding systems. Concerning the aspects related to soil modeling, electrical engineers need to get aware of geophysics resources, such as: - geophysical techniques for soil electrical resistivity prospection (down to about 15 kilometers deep); and - techniques for converting field measured data, from many different geophysical techniques, into adequate soil models for grounding grid simulation. It is also important to equalize the basic knowledge for the professionals that are working together for the specific purpose of soil modeling for electrical grounding studies. The authors have experienced the situation of electrical engineers working with geophysicists, but it was not clear for the latter the effective need of the electrical engineers, and for the engineers it was unknown the available geophysical resources, and also, what to do convert the large amount of soil resistivity data into a reliable soil model.
The effect of force feedback delay on stiffness perception and grip force modulation during tool-mediated interaction with elastic force fields.
Leib, Raz; Karniel, Amir; Nisky, Ilana
During interaction with objects, we form an internal representation of their mechanical properties. This representation is used for perception and for guiding actions, such as in precision grip, where grip force is modulated with the predicted load forces. In this study, we explored the relationship between grip force adjustment and perception of stiffness during interaction with linear elastic force fields. In a forced-choice paradigm, participants probed pairs of virtual force fields while grasping a force sensor that was attached to a haptic device. For each pair, they were asked which field had higher level of stiffness. In half of the pairs, the force feedback of one of the fields was delayed. Participants underestimated the stiffness of the delayed field relatively to the nondelayed, but their grip force characteristics were similar in both conditions. We analyzed the magnitude of the grip force and the lag between the grip force and the load force in the exploratory probing movements within each trial. Right before answering which force field had higher level of stiffness, both magnitude and lag were similar between delayed and nondelayed force fields. These results suggest that an accurate internal representation of environment stiffness and time delay was used for adjusting the grip force. However, this representation did not help in eliminating the bias in stiffness perception. We argue that during performance of a perceptual task that is based on proprioceptive feedback, separate neural mechanisms are responsible for perception and action-related computations in the brain. PMID:25717155
Charge dissipation measurement on the surface of polymeric materials using modified surface potential electric force microscopy
NASA Astrophysics Data System (ADS)
Reagan, Michael; Lyuksyutov, Sergei; Dolog, Ivan; Mallik, Robert; Juhl, Shane; Vaia, Richard; Durstock, Michael; Ferguson, John
The AFMEN technique when combined with surface potential electric force microscopy (SP-EFM) reveals the pattern of electric charge build-up and dissipation in polymeric and organic materials. This information can be used to develop an adequate description of nanoconductivity in these materials. The description includes effects due to local electric field variations and charge transport mechanisms. Charge evolution was estimated by measuring electric currents using AFM. In addition to the SP-EFM and AFM work outlined above, we also use Inelastic Electron Tunneling Spectroscopy (IETS) to characterize the electronic and vibrational properties of polymer and composite materials. IETS has been used in the past by one of the authors to investigate ultra-thin (roughly 1 nm) polymer films, including PMMA. The films were deposited either by spin coating from or by plasma polymerization. This work is being extended to study the adsorption of spin-coated PMMA on photovoltaic materials such as CdS. Temperature dependent current-voltage and conductance voltage data obtained from tunnel diodes containing CdS/PMMA heterolayers can be used to determine the conduction mechanisms in these layers.
The electromagnetic force field, fluid flow field, and temperature profiles in levitated metal droplets
N. El-Kaddah; J. Szekely
A mathematical representation has been developed for the electromagnetic force field, the fluid flow field, the temperature\\u000a field (and for transport controlled kinetics), in a levitation melted metal droplet. The technique of mutual inductances was\\u000a employed for the calculation of the electromagnetic force field, while the turbulent Navier-Stokes equations and the turbulent\\u000a convective transport equations were used to represent the
Large Electric Field¢Enhanced¢Hardness Effect in a SiO2 Film
Revilla, Reynier I.; Li, Xiao-Jun; Yang, Yan-Lian; Wang, Chen
Silicon dioxide films are extensively used in nano and micro¢electromechanical systems. Here we studied the influence of an external electric field on the mechanical properties of a SiO2 film by using nanoindentation technique of atomic force microscopy (AFM) and friction force microscopy (FFM). A giant augmentation of the relative elastic modulus was observed by increasing the localized electric field. A slight decrease in friction coefficients was also clearly observed by using FFM with the increase of applied tip voltage. The reduction of the friction coefficients is consistent with the great enhancement of sample hardness by considering the indentation¢induced deformation during the friction measurements. PMID:24681517
Super resolution mapping of the near optical field and the gradient optical force
NASA Astrophysics Data System (ADS)
Gelfand, Ryan M.; Bonakdar, Alireza; Memis, O. Gokalp; Mohseni, Hooman
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.
Electron distribution functions in electric field environments
NASA Technical Reports Server (NTRS)
Rudolph, Terence H.
The amount of current carried by an electric discharge in its early stages of growth is strongly dependent on its geometrical shape. Discharges with a large number of branches, each funnelling current to a common stem, tend to carry more current than those with fewer branches. The fractal character of typical discharges was simulated using stochastic models based on solutions of the Laplace equation. Extension of these models requires the use of electron distribution functions to describe the behavior of electrons in the undisturbed medium ahead of the discharge. These electrons, interacting with the electric field, determine the propagation of branches in the discharge and the way in which further branching occurs. The first phase in the extension of the referenced models , the calculation of simple electron distribution functions in an air/electric field medium, is discussed. Two techniques are investigated: (1) the solution of the Boltzmann equation in homogeneous, steady state environments, and (2) the use of Monte Carlo simulations. Distribution functions calculated from both techniques are illustrated. Advantages and disadvantages of each technique are discussed.
Gravitational self-force in non-vacuum spacetimes: an effective field theory derivation
Peter Zimmerman
In this paper we investigate the motion of small compact objects in non-vacuum spacetimes using methods from effective field theory in curved spacetime. Although a vacuum formulation is sufficient in many astrophysical contexts, there are applications such as the role of the self-force in enforcing cosmic-censorship in the context of the overcharging problem, which necessitate an extension into the non-vacuum regime. The defining feature of the self-force problem in non-vacuum spacetimes is the coupling between gravitational and non-gravitational field perturbations. The formulation of the self-force problem for non-vacuum spacetimes was recently provided in simultaneous papers by Zimmerman and Poisson [1] and Linz, Friedmann, Wiseman [2]. Here we distinguish ourselves by working with the effective action rather than the field equations. The formalism utilizes the multi-index notation developed by Zimmerman and Poisson [1] to accommodate the coupling between the different fields. Using dimensional regularization, we arrive at a finite expression for the local self-force expressed in terms of multi-index quantities evaluated in the background spacetime. We then apply the formalism to compute the coupled gravitational self-force in two explicit cases. First, we calculate the self-force on a massive particle possessing scalar charge and moving in an scalarvac spacetime. We then derive an expression for the self-force on an electrically charged, massive particle moving in an electrovac spacetime. In both cases, the force is expressed as a sum of local terms involving tensors defined in the background spacetime and evaluated at the current position of the particle, as well as tail integrals that depend on the past history of the particle.
Gravitational self-force in non-vacuum spacetimes: an effective field theory derivation
Peter Zimmerman
In this paper we investigate the motion of small compact objects in non-vacuum spacetimes using methods from effective field theory in curved spacetime. Although a vacuum formulation is sufficient in many astrophysical contexts, there are applications such as the role of the self-force in enforcing cosmic-censorship in the context of the overcharging problem, which necessitate an extension into the non-vacuum regime. The defining feature of the self-force problem in non-vacuum spacetimes is the coupling between gravitational and non-gravitational field perturbations. The formulation of the self-force problem for non-vacuum spacetimes was recently provided in simultaneous papers by Zimmerman and Poisson [1] and Linz, Friedmann, Wiseman [2]. Here we distinguish ourselves by working with the effective action rather than the field equations. The formalism utilizes the multi-index notation developed by Zimmerman and Poisson [1] to accommodate the coupling between the different fields. Using dimensional regularization, we arrive at a finite expression for the local self-force expressed in terms of multi-index quantities evaluated in the background spacetime. We then apply the formalism to compute the coupled gravitational self-force in two explicit cases. First, we calculate the self-force on a massive particle possessing scalar charge and moving in an scalarvac spacetime. We then derive an expression for the self-force on an electrically charged, massive particle moving in an electrovac spacetime. In both cases, the force is expressed as a sum of local terms involving tensors defined in the background spacetime and evaluated at the current position of the particle, as well as tail integrals that depend on the past history of the particle.
DIVERSION OF ADULT SALMON BY AN ELECTRICAL FIELD Marine Biological Laboratory : -1958 WOODS HOLE OF ADULT SALMON BY AN ELECTRICAL FIELD By Roger E. Burrows Fishery Research Biologist Entiat, Wash. Bureau line has proved satisfactory for the diversion of adult salmon. The electrical field is created by 110
Electric field distribution in resonant reflection filters under normal incidence
Tianyu Sun; Jianyong Ma; Jianpeng Wang; Yunxia Jin; Hongbo He; Jianda Shao; Zhengxiu Fan
Electric field distributions inside resonant reflection filters constructed using planar periodic waveguides are investigated in this paper. The electric fields may be intensified by resonance effects. Although the resonant reflection peaks can be quite narrow using weakly modulated planar periodic waveguides, the strong electric field enhancement limits their use in high-power laser systems. Strongly modulated waveguides may be used to
Inactivation of viruses using pulsed high electric field
Akira Mizuno; Toru Inoue; Shigeo Yamaguchi; Ken-ichi Sakamoto; Takakiyo Saeki; Yoichi Matsumoto; Koichi Minamiyama
The effect of pulsed high electric field on viruses in liquid was studied. Swine vesicular disease virus (SVDV) and equine herpes virus-1 (EHV-1) were used in the experiment. Pulsed high voltage was applied repetitively to the converged electric field type electrode, which had an insulating plate with pinholes between parallel-plate electrodes. A pulsed high electric field was formed at the
Applying electric field sensing to human-computer interfaces
Thomas G. Zimmerman; Joshua R. Smith; Joseph A. Paradiso; David Allport; Neil Gershenfeld
A non-contact sensor based on the interaction of a person with electric fields for human-computer interface is investigated. Two sensing modes are explored: an external electric field shunted to ground through a human body, and an external electric field transmitted through a human body to stationary receivers. The sensors are low power (milliwatts), high resolution (millimeter) low cost (a few
Lorentz and "apparent" transformations of the electric and magnetic fields
Tomislav Ivezic
It is recently discovered that the usual transformations of the three-dimensional (3D) vectors of the electric and magnetic fields differ from the Lorentz transformations (LT) (boosts) of the corresponding 4D quantities that represent the electric and magnetic fields. In this paper, using geometric algebra formalism, this fundamental difference is examined representing the electric and magnetic fields by bivectors.
Experimental Study of Cloud Formation by Intense Electric Fields
Kazuhiko Teramoto; Motoji Ikeya
Cloud and fog formation under an electric field has been studied experimentally using a Wilson's cloud chamber with a supercooled atmosphere of ethanol. The threshold electric field to generate dense clouds using parallel plate electrodes was about 4 kV\\/m as estimated from the generated cloud position and from a model experiment of an electric field simulation using a water bath.
Electrohydrodynamic Model of Vesicle Deformation in Alternating Electric Fields
Vlahovska, Petia M.; GraciÓ, RubĶn Serral; Aranda-Espinoza, Said; Dimova, Rumiana
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. PMID:19527639
The force exerting on cosmic bodies in a quaternionc field
V. Majernik
The expression of a time-dependent cosmological constant $\\lambda \\propto 1/t^2$ is interpreted as the energy density of a special type of the quaternionic field. The Lorenz-like force acting on the moving body in the presence of this quaternionic field is determined. The astronomical and terrestrial effects of this field are presented, and the ways how it can be observably detected is discussed. Finally, a new mechanism of the particle creation and an alternative cosmological scenario in the presence of the cosmic quatertionic field is suggested.
Mitigated-force carriage for high magnetic field environments
Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Murphy, Bart L
A carriage for high magnetic field environments includes a first work-piece holding means for holding a first work-piece, the first work-piece holding means being disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla. The first work-piece holding means is further disposed in operable connection with a second work-piece holding means for holding a second work-piece so that, as the first work-piece is inserted into the magnetic field, the second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.
Electric field induced Lyman-? emission of a hydrogen beam for electric field measurements
NASA Astrophysics Data System (ADS)
Chķrigier-Kovacic, L.; Str÷m, P.; Lejeune, A.; Doveil, F.
Electric field induced Lyman-? emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-? radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.
Three-dimensional tree simulation of composite system considering an interface perpendicular or parallel to the electric force line
H. Uehara; T. Fujimoto; N. Nanba; K. Kudo
We carried out a three-dimensional tree simulation of a composite system with an interface perpendicular or parallel to the electric force line based on a dielectric breakdown model (DBM) considering the growth probability. It was found that an interface perpendicular to the electric force line exhibits a positive barrier effect and that an interface parallel to the electric force line
Effective charge of a small absorbing body in highly collisional plasma subject to an external electric field
Chaudhuri, M.; Khrapak, S. A.; Morfill, G. E. [Max-Planck Institut fuer Extraterrestrische Physik, D-85741 Garching (Germany)
The total force which is the resultant of the electric, ion, and electron drag forces has been calculated for a small absorbing spherical grain immersed in a highly collisional, weakly ionized plasma subject to a weak external electric field. Linear dielectric response formalism has been used and both ion and electron absorption on the grain have been taken into account. It is shown that the total force is always directed along the direction of the electric force. The 'effective' charge of the grain which can be defined as the ratio of the total force to the strength of the electric field is calculated. It is shown that its magnitude is comparable to the magnitude of the actual grain's charge.
Radial-Electric-Field Piezoelectric Diaphragm Pumps
NASA Technical Reports Server (NTRS)
Bryant, Robert G.; Working, Dennis C.; Mossi, Karla; Castro, Nicholas D.; Mane, Pooma
In a recently invented class of piezoelectric diaphragm pumps, the electrode patterns on the piezoelectric diaphragms are configured so that the electric fields in the diaphragms have symmetrical radial (along-the-surface) components in addition to through-the-thickness components. Previously, it was accepted in the piezoelectric-transducer art that in order to produce the out-of-plane bending displacement of a diaphragm needed for pumping, one must make the electric field asymmetrical through the thickness, typically by means of electrodes placed on only one side of the piezoelectric material. In the present invention, electrodes are placed on both sides and patterned so as to produce substantial radial as well as through-the-thickness components. Moreover, unlike in the prior art, the electric field can be symmetrical through the thickness. Tests have shown in a given diaphragm that an electrode configuration according to this invention produces more displacement than does a conventional one-sided electrode pattern. The invention admits of numerous variations characterized by various degrees of complexity. Figure 1 is a simplified depiction of a basic version. As in other piezoelectric diaphragm pumps of similar basic design, the prime mover is a piezoelectric diaphragm. Application of a suitable voltage to the electrodes on the diaphragm causes it to undergo out-of-plane bending. The bending displacement pushes a fluid out of, or pulls the fluid into, a chamber bounded partly by the diaphragm. Also as in other diaphragm pumps in general, check valves ensure that the fluid flows only in through one port and only out through another port.
Quantum chemistry based force fields for soft matter
Matthew A. Glaser; Noel A. Clark; Edgardo Garcia; David M. Walba
We describe the use of ab initio electronic structure calculations in the development of high-quality classical interaction potentials for liquid crystal modeling. Our focus is on methods for the rapid, on-demand creation of force fields for use in mean field theory based calculations of materials properties, employed for routine pre-synthesis evaluation of novel liquid crystalline materials. The role of quantum
Subdiffusion in a time-dependent force field
Shkilev, V. P., E-mail: firstname.lastname@example.com [National Academy of Sciences of Ukraine, Institute of Surface Chemistry (Ukraine)
Based on the random-barrier model and using the mean-field approximation, we derive an equation that describes the subdiffusion of particles in an external time-varying force field. The derived equation predicts the frequency dependence of the conductivity and, in this regard, is consistent with the experiment. We show that the response of the system to an external perturbation depends significantly on the structure of the inhomogeneous medium.
Liquid/vapour phase separation in He-4 using electric fields
NASA Technical Reports Server (NTRS)
Israelsson, U. E.; Jackson, H. W.; Petrac, D.
In space, a replacement must be found for gravity to physically control and, in certain instances, contain cryogenic liquids. A program has been started at the Jet Propulsion Laboratory to study the use of electric field generated forces to establish the required orienting effects. Measurements which show that it is possible to apply strong enough electric fields to a liquid/vapor interface of He-4 to obtain an orienting force comparable to gravity are presented. Our measurements span the temperature range 1.7-4.2 K and demonstrate the applicability of Pashen's law for maximum attainable field before breakdown occurs. Some advantages of the electric field separator as opposed to passive surface tension devices are identified.
CRRES Electric Field Power Spectral Distributions
NASA Astrophysics Data System (ADS)
Brautigam, D. H.; Bass, J.; Wygant, J.
The ULF wave power during the CRRES mission is investigated using the CRRES electric field instrument. The wave power spectral characteristics are examined as a function of L in terms of long-term averages, and in terms of magnetic activity (Kp). Previous work has fit the power spectral density to activity-dependent power law spectra [Holzworth and Mozer, 1979]. Results from the current study are compared with these earlier results. There are a significant number of cases where the observed spectra deviate from a power law, exhibiting a secondary peak around 8 mHz . The regularity and nature of these spectra are examined as well.
Electrostatic air filters generated by electric fields
Bergman, W.; Biermann, A.H.; Hebard, H.D.; Lum, B.Y.; Kuhl, W.D.
This paper presents theoretical and experimental findings on fibrous filters converted to electrostatic operation by a nonionizing electric field. Compared to a conventional fibrous filter, the electrostatic filter has a higher efficiency and a longer, useful life. The increased efficiency is attributed to a time independent attraction between polarized fibers and charged, polarized particles and a time dependent attraction between charged fibers and charged, polarized particles. The charge on the fibers results from a dynamic process of charge accumulation due to the particle deposits and a charge dissipation due to the fiber conductivity.
Force field development from first principles for materials design
NASA Astrophysics Data System (ADS)
Chan, Maria; Kinaci, Alper; Narayanan, Badri; Sen, Fatih; Gray, Stephen; Davis, Michael; Sankaranaryanan, Subramanian
The ability to perform accurate calculations efficiently is crucial for computational materials design. In this talk, we will discuss a stream-lined approach to force field development using first principles density functional theory training data and machine learning algorithms. We will also discuss the validation of this approach on precious metal nanoparticles.
Force, current and field effects in single atom manipulation
Hla, Saw-Wai
Force, current and field effects in single atom manipulation K.-F. Braun , S.-W. Hla , N. Pertaya present a detailed investigation of the manipulation of Ag and Au atoms with a STM tip on the Ag(111 of the atom during manipulation. The threshold tunnelling resistance and tip-height to move a Au/Ag atom have
Evaluation of DNA Force Fields in Implicit Solvation
Gaillard, Thomas; Case, David A.
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. PMID:22043178
Frequency-dependent force fields for QMMM calculations.
Harczuk, Ignat; Vahtras, Olav; ┼gren, Hans
We outline the construction of frequency-dependent polarizable force fields. The force fields are derived from analytic response theory for different frequencies using a generalization of the LoProp algorithm giving a decomposition of a molecular dynamical polarizability to localized atomic dynamical polarizabilities. These force fields can enter in a variety of applications - we focus on two such applications in this work: firstly, they can be incorporated in a physical, straightforward, way for current existing methods that use polarizable embeddings, and we can show, for the first time, the effect of the frequency dispersion within the classical environment of a quantum mechanics-molecular mechanics (QMMM) method. Our methodology is here evaluated for some test cases comprising water clusters and organic residues. Secondly, together with a modified Silberstein-Applequist procedure for interacting inducible point-dipoles, these frequency-dependent polarizable force fields can be used for a classical determination of frequency-dependent cluster polarizabilities. We evaluate this methodology by comparing with the corresponding results obtained from quantum mechanics or QMMM where the absolute mean [small alpha, Greek, macron] is determined with respect to the size of the QM and MM parts of the total system. PMID:25714984
Impact of electric fields on honey bees
Bindokas, V.P.
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.
Electric Field Driven Torque in Biological Rotary Motors
Miller,, John H; Maric, Sladjana; Infante, Hans L; Claycomb, James R
Ion driven rotary motors, such as Fo-ATP synthase (Fo) and the bacterial flagellar motor, act much like a battery-powered electric motor. They convert energy from ions as they move from high to low potential across a membrane into torque and rotary motion. Here we propose a mechanism whereby electric fields, emanating from channels in one or more stators, act on asymmetric charge distributions due to protonated and deprotonated sites in the rotor and drive it to rotate. The model predicts an ideal scaling law between torque and ion motive force, which can be hindered by mitochondrial mutations. The rotor of Fo drives the gamma-subunit to rotate within the ATP-producing complex (F1), working against an opposing torque that rises and falls periodically with angular position. Drawing an analogy with Brownian motion of a particle in a tilted washboard potential, we compute the highly nonlinear ATP production rate vs. proton motive force (pmf), showing a minimum pmf needed to drive ATP production with important me...
Convolutional Virtual Electric Field for Image Segmentation Using Active Contours
Wang, Yuanquan; Zhu, Ce; Zhang, Jiawan; Jian, Yuden
Gradient vector flow (GVF) is an effective external force for active contours; however, it suffers from heavy computation load. The virtual electric field (VEF) model, which can be implemented in real time using fast Fourier transform (FFT), has been proposed later as a remedy for the GVF model. In this work, we present an extension of the VEF model, which is referred to as CONvolutional Virtual Electric Field, CONVEF for short. This proposed CONVEF model takes the VEF model as a convolution operation and employs a modified distance in the convolution kernel. The CONVEF model is also closely related to the vector field convolution (VFC) model. Compared with the GVF, VEF and VFC models, the CONVEF model possesses not only some desirable properties of these models, such as enlarged capture range, u-shape concavity convergence, subject contour convergence and initialization insensitivity, but also some other interesting properties such as G-shape concavity convergence, neighboring objects separation, and noise suppression and simultaneously weak edge preserving. Meanwhile, the CONVEF model can also be implemented in real-time by using FFT. Experimental results illustrate these advantages of the CONVEF model on both synthetic and natural images. PMID:25360586
Convolutional virtual electric field for image segmentation using active contours.
Wang, Yuanquan; Zhu, Ce; Zhang, Jiawan; Jian, Yuden
Gradient vector flow (GVF) is an effective external force for active contours; however, it suffers from heavy computation load. The virtual electric field (VEF) model, which can be implemented in real time using fast Fourier transform (FFT), has been proposed later as a remedy for the GVF model. In this work, we present an extension of the VEF model, which is referred to as CONvolutional Virtual Electric Field, CONVEF for short. This proposed CONVEF model takes the VEF model as a convolution operation and employs a modified distance in the convolution kernel. The CONVEF model is also closely related to the vector field convolution (VFC) model. Compared with the GVF, VEF and VFC models, the CONVEF model possesses not only some desirable properties of these models, such as enlarged capture range, u-shape concavity convergence, subject contour convergence and initialization insensitivity, but also some other interesting properties such as G-shape concavity convergence, neighboring objects separation, and noise suppression and simultaneously weak edge preserving. Meanwhile, the CONVEF model can also be implemented in real-time by using FFT. Experimental results illustrate these advantages of the CONVEF model on both synthetic and natural images. PMID:25360586
Soil Identification using Field Electrical Resistivity Method
NASA Astrophysics Data System (ADS)
Hazreek, Z. A. M.; Rosli, S.; Chitral, W. D.; Fauziah, A.; Azhar, A. T. S.; Aziman, M.; Ismail, B.
Geotechnical site investigation with particular reference to soil identification was important in civil engineering works since it reports the soil condition in order to relate the design and construction of the proposed works. In the past, electrical resistivity method (ERM) has widely being used in soil characterization but experienced several black boxes which related to its results and interpretations. Hence, this study performed a field electrical resistivity method (ERM) using ABEM SAS (4000) at two different types of soils (Gravelly SAND and Silty SAND) in order to discover the behavior of electrical resistivity values (ERV) with type of soils studied. Soil basic physical properties was determine thru density (p), moisture content (w) and particle size distribution (d) in order to verify the ERV obtained from each type of soil investigated. It was found that the ERV of Gravelly SAND (278 ?m & 285 ?m) was slightly higher than SiltySAND (223 ?m & 199 ?m) due to the uncertainties nature of soils. This finding has showed that the results obtained from ERM need to be interpreted based on strong supported findings such as using direct test from soil laboratory data. Furthermore, this study was able to prove that the ERM can be established as an alternative tool in soil identification provided it was being verified thru other relevance information such as using geotechnical properties.
Nonlinear response of electric fields at a neutral point
NASA Astrophysics Data System (ADS)
Berkovsky, Mikhail; Dufty, James W.; Calisti, Annette; Stamm, Roland; Talin, Bernard
The complex dynamics of electric fields at a neutral point in a plasma is studied via a model of noninteracting ``quasiparticles.'' The simplicity of the model allows the reduction of the many-body problem to an effective single-particle analysis-all properties of interest can be reduced to quadratures. Still, the final calculations to extract a quantitative or even qualitative understanding of the field dynamics can be difficult. Attention here is focused on the dynamics of the conditional electric field: the field value at time t for a given initial value of the field. In addition to the relevant linear response function (electric field time correlation function), this property provides the complete nonlinear response of the electric field to arbitrary initial field perturbations. The static properties (distribution of electric fields and field time derivatives) and the electric field time correlation function have been known for some time for this model. We compare these results and the present result for the conditional electric field with molecular dynamics simulations including interactions. The comparisons suggest that the model provides a quantitative representation of electric field dynamics in real plasmas, except at strong coupling. The exact theoretical results are compared also with those obtained by modeling the electric field as a stochastic variable obeying a kangaroo process. The latter can be constructed to yield both the exact stationary distribution and the exact electric field time correlation function. However, we find that the conditional field is never well approximated by this process. An alternative representation of the joint distribution for electric fields, consistent with the exact stationary distribution, field correlation function, and conditional electric field, is suggested.
Empirical high-latitude electric field models
Heppner, J.P. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Maynard, N.C. (Air Force Geophysics Lab., Hanscom AFB, MA (United States))
Electric field measurements from the Dynamics Explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn-dusk OGO 6 measurements (J.P. Heppner, 1977). The analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones. Paralleling the previous analysis, the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the Y component of the interplanetary magnetic field. The objective, which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns, is met by deriving one pattern (model BC) for the northern hemisphere with a +Y interplanetary magnetic field (IMF) and southern hemisphere with a {minus}Y IMF and two patterns (models A and DE) for the northern hemisphere with a {minus}Y IMF and southern hemisphere with a +Y IMF. The most significant large-scale revisions of the OGO 6 models are (1) on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the IMF Y component, (2) on the nightside where a westward flow region poleward from the Harang discontinuity appears under model BC conditions, and (3) magnetic local time shifts in the positions of the convection cell foci. The modeling above was followed by a detailed examination of cases where the IMF Z component was clearly positive (northward). Neglecting the seasonally dependent cases where irregularities obscure pattern recognition, the observations range from reasonable agreement with the new BC and DE models, to cases where different characteristics appeared primarily at dayside high latitudes.
Nonlinear relaxation field in charged systems under high electric fields
Klaus Morawetz
The influence of an external electric field on the current in charged systems is investigated. The results from the classical hierarchy of density matrices are compared with the results from the quantum kinetic theory. The kinetic theory yields a systematic treatment of the nonlinear current beyond linear response. To this end the dynamically screened and field-dependent Lenard-Balescu equation is integrated analytically and the nonlinear relaxation field is calculated. The classical linear response result known as Debye - Onsager relaxation effect is only obtained if asymmetric screening is assumed. Considering the kinetic equation of one specie the other species have to be screened dynamically while the screening with the same specie itself has to be performed statically. Different other approximations are discussed and compared.
Nonlinear relaxation field in charged systems under high electric fields
Morawetz, K
The influence of an external electric field on the current in charged systems is investigated. The results from the classical hierarchy of density matrices are compared with the results from the quantum kinetic theory. The kinetic theory yields a systematic treatment of the nonlinear current beyond linear response. To this end the dynamically screened and field-dependent Lenard-Balescu equation is integrated analytically and the nonlinear relaxation field is calculated. The classical linear response result known as Debye - Onsager relaxation effect is only obtained if asymmetric screening is assumed. Considering the kinetic equation of one specie the other species have to be screened dynamically while the screening with the same specie itself has to be performed statically. Different other approximations are discussed and compared.
Planned waveguide electric field breakdown studies
Wang Faya; Li Zenghai [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)
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.
Particle Acceleration in a 3D Reconnecting Current Sheet with the Polarization Electric Field
V. Zharkova; T. Siverskyj
Particle acceleration is investigated in a 3D magnetic field topology with a guiding field corresponding to reconnecting current sheets with different compressibility. The solutions are compared from solving 3D motion equation in the test particle and particle-in-cell approaches. Three types of electric fields are considered: a drifted one brought by the VxB force, the polarization one caused by a difference
Atomistic force field for alumina fit to density functional theory
Sarsam, Joanne [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Finnis, Michael W.; Tangney, Paul, E-mail: email@example.com [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)
We present a force field for bulk alumina (Al{sub 2}O{sub 3}), which has been parametrized by fitting the energies, forces, and stresses of a large database of reference configurations to those calculated with density functional theory (DFT). We use a functional form that is simpler and computationally more efficient than some existing models of alumina parametrized by a similar technique. Nevertheless, we demonstrate an accuracy of our potential that is comparable to those existing models and to DFT. We present calculations of crystal structures and energies, elastic constants, phonon spectra, thermal expansion, and point defect formation energies.
Finite Element Studies of Colloidal Mixtures Influenced by Electric FieldsĀ
Drummond, Franklin Jerrel
a finite element analysis of colloidal mixture electrokinetic behavior. Computations of particle forces as a function of applied frequency and particle shape were performed. An effective medium property method was also studied. Fluidic and electric...
Field forced antiferroelectric-to-ferroelectric switching in modified lead zirconate titanate stannate ceramics
Pan, W.; Zhang, Q.; Bhalla, A.; Cross, L.E. (Materials Research Lab., Pennsylvania State Univ., University Park, PA (US))
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.
Local plasma membrane permeabilization of living cells by nanosecond electric pulses using atomic force microscopy
NASA Astrophysics Data System (ADS)
Thompson, Gary; Payne, Jason A.; Roth, Caleb C.; Wilmink, Gerald J.; Ibey, Bennett L.
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.
Dependence on electric field intensities of cell biological effects induced by microsecond pulsed electric fields
Chengxiang Li; Chenguo Yao; Caixin Sun; Fei Guo; Wei Zhou; Zhengai Xiong
Some studies have been conducted on reversible electroporation (RE) and\\/or irreversible electroporation (IRE) induced by microsecond pulsed electric fields (?sPEF), while little attention has been paid to the apoptosis effect caused by ?sPEF. To the best of our knowledge, there have been no reports of relationships between the field intensities inducing apoptosis and those resulting in IRE\\/RE. This paper attempts
Parallel electric fields in nonlinear magnetosonic waves
Takahashi, Seiichi; Ohsawa, Yukiharu [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)
The electric field parallel to the magnetic field, E{sub parallel}, in nonlinear magnetosonic waves is studied theoretically and numerically. In the calculation of E{sub parallel} based on the conventional reductive perturbation method, the terms related to the magnetic pressure cancel, and E{sub parallel} is proportional to the electron temperature T{sub e}. With a modified perturbation scheme assuming that the wave amplitude is in the range (m{sub e}/m{sub i}){sup 1/2}<{epsilon}<1, an expression for E{sub parallel} is obtained that is proportional to the magnetic pressure in a cold plasma. Its integral along the magnetic field, F=-{integral}E{sub parallel}ds, is proportional to {epsilon}{sup 2}m{sub i}v{sub A}{sup 2}. One-dimensional, fully kinetic, electromagnetic particle simulations verify the theoretical predictions for small-amplitude waves. Further, they demonstrate that eF becomes of the order of {epsilon}(m{sub i}v{sub A}{sup 2}+{gamma}{sub e}T{sub e}) in large-amplitude [{epsilon}{approx}O(1)] oblique shock waves. These theory and simulations indicate that E{sub parallel} in magnetosonic waves can be strong in a strong magnetic field.
Electro-elastic fields of piezoelectric materials with an elliptic hole under uniform internal shearing forces
NASA Astrophysics Data System (ADS)
Du, Yanliang; Liu, Shuhong; Duan, Shijie; Li, Yanqiang
The existing investigations on piezoelectric materials containing an elliptic hole mainly focus on remote uniform tensile loads. In order to have a better understanding of the fracture behavior of piezoelectric materials under different loading conditions, theoretical and numerical solutions are presented for an elliptic hole in transversely isotropic piezoelectric materials subjected to uniform internal shearing forces based on the complex potential approach. By solving ten variable linear equations, the analytical solutions inside and outside the hole satisfying the permeable electric boundary conditions are obtained. Taking PZT-4 ceramic into consideration, numerical results of electro-elastic fields along the edge of the hole and axes, and the electric displacements in the hole are presented. Comparison with stresses in transverse isotropic elastic materials shows that the hoop stress at the ends of major axis in two kinds of material equals zero for the various ratios of major to minor axis lengths; If the ratio is greater than 1, the hoop stress in piezoelectric materials is smaller than that in elastic materials, and if the ratio is smaller than 1, the hoop stress in piezoelectric materials is greater than that in elastic materials; When it is a circle hole, the shearing stress in two materials along axes is the same. The distribution of electric displacement components shows that the vertical electric displacement in the hole and along axes in the material is always zero though under the permeable electric boundary condition; The horizontal and vertical electric displacement components along the edge of the hole are symmetrical and antisymmetrical about horizontal axis, respectively. The stress and electric displacement distribution tends to zero at distances far from the elliptical hole, which conforms to the conclusion usually made on the basis of Saint-Venant's principle. Unlike the existing work, uniform shearing forces acting on the edge of the hole, and the distribution of electro-elastic fields inside and outside the elliptic hole are considered.
Vibration analysis considering higher harmonics of electromagnetic forces for rotating electric machines
Shigeru SAKAMOTO; Tosuke HIRATA; Takashi KOBAYASHI; Kenzo KAJIWARA
A method is described to calculate vibration due to electromagnetic forces for rotating electric machines. This method can calculate the frequency response of vibration due to higher harmonics of electromagnetic forces. The usefulness of this method is verified through the agreement between calculated and measured results for a three-phase\\/four-pole induction motor. The authors also calculate the complicated dynamic behavior caused
Relationship between the ion drag and electric forces in dense dust clouds
Yaroshenko, V. V.; Khrapak, S. A.; Morfill, G. E. [Max-Planck-Institut fuer extraterrestrische Physik, D-85748 Garching (Germany)
It is shown that the relation between the ion drag and electric forces is strongly dependent on the dust number density in complex plasmas. The effect of the particle size and discharge parameters on the force balance is investigated. Examples are given for realistic complex plasma parameters and comparison with microgravity experiments is presented.
Field measurement of basal forces generated by erosive debris flows
McCoy, S.W.; Tucker, G.E.; Kean, J.W.; Coe, J.A.
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.
Electric Field Dependence of the Probability of Charge Carriers Recombination
M. Obarowska; J. Godlewski
The influence of an external electric field on the probability of charge carriers recombination in molecular solid state was investigated. From analytical approximations, the probability of charge carriers recombination is found to decrease with increasing electric field. The results could be useful to explain the decrease of electroluminescence efficiency in single layer organic light emitting diodes (OLEDs) at high electric
How Should One Optimize Nonlinear Force-Free Coronal Magnetic Field Extrapolations from SDO/HMI Vector Magnetograms?
NASA Astrophysics Data System (ADS)
Wiegelmann, T.; Thalmann, J. K.; Inhester, B.; Tadesse, T.; Sun, X.; Hoeksema, J. T.
The Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) provides photospheric vector magnetograms with a high spatial and temporal resolution. Our intention is to model the coronal magnetic field above active regions with the help of a nonlinear force-free extrapolation code. Our code is based on an optimization principle and has been tested extensively with semianalytic and numeric equilibria and applied to vector magnetograms from Hinode and ground-based observations. Recently we implemented a new version which takes into account measurement errors in photospheric vector magnetograms. Photospheric field measurements are often affected by measurement errors and finite nonmagnetic forces inconsistent for use as a boundary for a force-free field in the corona. To deal with these uncertainties, we developed two improvements: i) preprocessing of the surface measurements to make them compatible with a force-free field, and ii) new code which keeps a balance between the force-free constraint and deviation from the photospheric field measurements. Both methods contain free parameters, which must be optimized for use with data from SDO/HMI. In this work we describe the corresponding analysis method and evaluate the force-free equilibria by how well force-freeness and solenoidal conditions are fulfilled, by the angle between magnetic field and electric current, and by comparing projections of magnetic field lines with coronal images from the Atmospheric Imaging Assembly (SDO/AIA). We also compute the available free magnetic energy and discuss the potential influence of control parameters.
Review Of Fiber-Optic Electric-Field Sensors
NASA Technical Reports Server (NTRS)
De Paula, Ramon P.; Jarzynski, Jacek
Tutorial paper reviews state of art in fiber-optic sensors of alternating electric fields. Because such sensors are made entirely of dielectric materials, they are relatively transparent to incident electric fields; they do not distort fields significantly. Paper presents equations that express relationships among stress, strain, and electric field in piezoactive plastic and equations for phase shift in terms of photoelastic coefficients and strains in optical fiber.
Electric field effect in ultrathin black phosphorus
Koenig, Steven P.; Schmidt, Hennrik [Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Doganov, Rostislav A.; Castro Neto, A. H.; ųzyilmaz, Barbaros [Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, 28 Medical Drive, Singapore 117456 (Singapore)
Black phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer black phosphorus field effect devices on Si/SiO{sub 2} and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm{sup 2}/Vs and drain current modulation of over 10{sup 3}. At low temperatures, the on-off ratio exceeds 10{sup 5}, and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin black phosphorus crystals over the course of 1 h after exfoliation.
Subwavelength particles in an inhomogeneous light field: optical forces associated with the spin and orbital energy flows
NASA Astrophysics Data System (ADS)
Bekshaev, A. Ya
We analyse the ponderomotive action experienced by a small spherical particle immersed in an optical field, in relation to the internal energy flows (optical currents) and their spin and orbital constituents. The problem is studied analytically, on the basis of the dipole model, and numerically. The three sources of the field mechanical actionŚthe energy density gradient and the orbital and spin parts of the energy flowŚdiffer in their ponderomotive mechanisms, and their physical nature manifests itself in the dependence of the optical force on the particle radius a. If a ? ? (the radiation wavelength), the optical force behaves as a?, and integer ? can be used to classify the sources of the mechanical action. This classification correlates with the multipole representation of the field-particle interaction: the gradient force and the orbital momentum force appear due to the electric or magnetic dipole moments per se; the spin momentum force emerges due to interaction between the electric and magnetic dipoles or between the dipole and quadrupole moments (if the particle is polarizable electrically but not magnetically or vice versa). In principle, the spin and orbital currents can be measured separately through the probe particle motion, employing a special choice of particles with the necessary magnetic and/or electric properties.
An attempt in assessing contact forces from a kinematic field
NASA Astrophysics Data System (ADS)
Richefeu, Vincent; Combe, Gaļl; Maurin, Raphaļl
In granular materials, it is not so simple to assess experimentally the contact forces. Photoelasticity is generally used for this purpose but this technique involves some constraints that may limit its use. We propose a different solution, which implements both the digital image correlation (DIC) technique and the non-smooth contact dynamics (NSCD) formalism. In a nutshell, the technique aims to find a set of contact forces mechanically admissible given a set of measured contact velocities. We used photographs of a simple shear test of a two-dimensional analogue granular material (about 1000 aluminum rods) to apply the solution, and we showed that valuable information about the contact forces can be extracted from the kinematic field provided that no major rearrangement occurs for at least five image shots.
Advancement of polarizable force field and its use for molecular modeling and design.
Xu, Peijun; Wang, Jinguang; Xu, Yong; Chu, Huiying; Liu, Jiahui; Zhao, Meixia; Zhang, Depeng; Mao, Yingchen; Li, Beibei; Ding, Yang; Li, Guohui
The most important requirement of biomolecular modeling is to deal with electrostatic energies. The electrostatic polarizability is an important part of electrostatic interaction for simulation systems. However, AMBER, CHARMM, OPLS, GROMOS, MMFF force fields etc. used in the past mostly apply fixed atomic center point charge to describe electrostatic energies, and are not sufficient for considering the influence of the electrostatic polarization. The emergence of polarizable force fields has solved this problem. In recent years, quickly developed polarizable force fields have involved a lot of fields. The chapter relating to polarizable force fields spread over several aspects. Firstly, we reviewed the history of the classical force fields and compared with polarizable force fields to elucidate the advancements of polarizable force fields. Secondly, it is introduced that the application of polarizable force fields to small molecules and biological macromolecules simulation, including molecular design. Finally, a brief development trend and perspective is given on rapidly growing polarizable force fields. PMID:25387957
The Dynamics of an Electric Dipole Moment in a Stochastic Electric Field
Y. B. Band
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 mo- mentum 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 elec- tric 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.
Electrical Nanoprobing of Semiconducting Carbon Nanotubes Using an Atomic Force Microscope
McEuen, Paul L.
Electrical Nanoprobing of Semiconducting Carbon Nanotubes Using an Atomic Force Microscope Y. Yaish electrical nanoprobe (SEN). We show that, for Au contacts and p-type device operation, Schottky barriers schematically in Fig. 1(a), are made by chemical vapor deposition growth [22] of NTs at lithographically defined
Silicone oil contamination and electrical contact resistance degradation of low-force gold contacts.
Dugger, Michael Thomas; Dickrell, Daniel John, III
Hot-switched low-force gold electrical contact testing was performed using a nanomechanical test apparatus to ascertain the sensitivity of simulated microelectromechanical systems (MEMS) contact to silicone oil contamination. The observed cyclic contact resistance degradation was dependent on both closure rate and noncontact applied voltage. The decomposition of silicone oil from electrical arcing was hypothesized as the degradation mechanism.
Superimposed electrical stimulation decreases maximal grip force Boisgontier M.1,2
Paris-Sud XI, Universitķ de
protocols are widely accepted and routinely shown as beneficial in research studies as well as in clinical of electrical stimulation applied during voluntary muscular contraction can lead to refinement of its clinical force, hand, motor units recruitment, muscular synergies, superimposed electrical stimulation hal
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...
Force-free configurations in reversed-field pinches
Emets, Y.P.; Zamidra, A.I.; Kovbasenko, Y.P.
The structure of reversed-field pinches is analyzed on the basis of analytic solutions of equations describing force-free configurations. A model with a constant coefficient of the proportionality between the current density and the magnetic field is used to analyze the effect of the toroidal geometry on the field distribution and the F--THETA diagrams. A modified model is proposed in which the ratio of the current density to the magnetic field tends toward zero near the wall of the discharge chamber. This model yields a more accurate description of the experiments F--THETA diagrams and of the field distributions. It is preferable to the Bessel-function model from the energy standpoint.
Empirical models of high latitude electric fields
NASA Technical Reports Server (NTRS)
Heppner, J. P.
Model cross sections of the high latitude dawn-dusk electric field based on OGO-6 data are presented for the signature profiles, most frequently encountered for both + and -Y orientations of the interplanetary magnetic field. Line integrals give a total potential of 76 keV in each case. To illustrate extremes, examples of model cross-sections with total potentials of 23 keV and 140 keV are also given. Model convection patterns are also presented utilizing OGO-6 data on boundary locations at other magnetic local times. When this information is combined with characteristic field geometries in the region of the Harang discontinuity, and is supplemented by data from Ba+ cloud motions in the polar cap, it becomes possible to construct realistic convection patterns on the nightside which deviate from the usual sun-aligned patterns. The observational models presented are of limited applicability as a consequence of the variability of observed distributions. These limitations are emphasized with particular attention given to several types of recurrent deviations which have not previously been discussed.
Nonlinear Force-Free Modeling of Coronal Magnetic Fields Part I: A Quantitative Comparison of Methods
NASA Astrophysics Data System (ADS)
Schrijver, Carolus J.; De Rosa, Marc L.; Metcalf, Thomas R.; Liu, Yang; McTiernan, Jim; Rķgnier, Stķphane; Valori, Gherardo; Wheatland, Michael S.; Wiegelmann, Thomas
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).
MIT OpenCourseWare: Fields, Forces, and Flows in Biological Systems
NSDL National Science Digital Library
Materials from this intriguingly titled Massachusetts Institute of Technology (MIT) course about biological systems are freely available to students, educators, and others through MIT's OpenCourseWare. The course covers a variety of topics including "conduction, diffusion, convection in electrolytes; fields in heterogeneous media; electrical double layers; Maxwell stress tensor and electrical forces in physiological systems; and fluid and sold continua: equations of motion useful for porous, hydrated biological tissues. Case studies considered include membrane transport; electrode interfaces; electrical, mechanical, and chemical transduction in tissues; electrophoretic and electroosmotic flows; diffusion/reaction; and ECG." This OpenCourseWare website provides downloadable notes for 25 lectures; seven downloadable assignments with solutions; and a pdf version of the final exam. The site links to an open, online discussion group for the course as well.
Electric field observations of equatorial bubbles
NASA Astrophysics Data System (ADS)
Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.
Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.
Nonminimal black holes with regular electric field
Alexander B. Balakin; Alexei E. Zayats
We discuss the problem of identification of coupling constants, which describe interactions between photons and space-time curvature, using exact regular solutions to the extended equations of the nonminimal Einstein-Maxwell theory. We argue the idea that three nonminimal coupling constants in this theory can be reduced to the single guiding parameter, which plays the role of nonminimal radius. We base our consideration on two examples of exact solutions obtained earlier in our works: the first of them describes a nonminimal spherically symmetric object (star or black hole) with regular radial electric field; the second example represents a nonminimal Dirac-type object (monopole or black hole) with regular metric. We demonstrate that one of the inflexion points of the regular metric function identifies a specific nonminimal radius, thus marking the domain of dominance of nonminimal interactions.
Nonminimal black holes with regular electric field
Balakin, Alexander B
We discuss the problem of identification of coupling constants, which describe interactions between photons and space-time curvature, using exact regular solutions to the extended equations of the nonminimal Einstein-Maxwell theory. We argue the idea that three nonminimal coupling constants in this theory can be reduced to the single guiding parameter, which plays the role of nonminimal radius. We base our consideration on two examples of exact solutions obtained earlier in our works: the first of them describes a nonminimal spherically symmetric object (star or black hole) with regular radial electric field; the second example represents a nonminimal Dirac-type object (monopole or black hole) with regular metric. We demonstrate that one of the inflexion points of the regular metric function identifies a specific nonminimal radius, thus marking the domain of dominance of nonminimal interactions.
Direct computation of parameters for accurate polarizable force fields.
Verstraelen, Toon; Vandenbrande, Steven; Ayers, Paul W
We present an improved electronic linear response model to incorporate polarization and charge-transfer effects in polarizable force fields. This model is a generalization of the Atom-Condensed Kohn-Sham Density Functional Theory (DFT), approximated to second order (ACKS2): it can now be defined with any underlying variational theory (next to KS-DFT) and it can include atomic multipoles and off-center basis functions. Parameters in this model are computed efficiently as expectation values of an electronic wavefunction, obviating the need for their calibration, regularization, and manual tuning. In the limit of a complete density and potential basis set in the ACKS2 model, the linear response properties of the underlying theory for a given molecular geometry are reproduced exactly. A numerical validation with a test set of 110 molecules shows that very accurate models can already be obtained with fluctuating charges and dipoles. These features greatly facilitate the development of polarizable force fields. PMID:25416881
Double-charge model for classical force-field simulations
NASA Astrophysics Data System (ADS)
Barrett, Christopher; Wang, Lin-Wang
In a traditional classical force-field model, the atomic point charge that generates the electrostatic potential, and the Born charge induced by atomic movement, are represented by the same charge parameter. But their actual values can be very different, and correct values for both of them are needed in order to yield the correct atomic structure (electrostatic charge) and phonon spectrum (Born charge). This is particularly true for nanostructure calculations. Here, we introduce a double-charge model (DCM) to reconcile the difference between the electrostatic charge and Born charge. The DCM allows us to reproduce the accurate ab initio phonon spectrum not only in bulk systems, but also for nanostructures (slabs and nanowires). This enables the use of classical force fields to study phonon spectra of large nanostructures, which are important for many phenomena from carrier dynamics to thermo conductivities.
Efficient parametrization of complex molecule-surface force fields.
Gao, David Z; Federici Canova, Filippo; Watkins, Matthew B; Shluger, Alexander L
We present an efficient scheme for parametrizing complex molecule-surface force fields from ab initio data. The cost of producing a sufficient fitting library is mitigated using a 2D periodic embedded slab model made possible by the quantum mechanics/molecular mechanics scheme in CP2K. These results were then used in conjunction with genetic algorithm (GA) methods to optimize the large parameter sets needed to describe such systems. The derived potentials are able to well reproduce adsorption geometries and adsorption energies calculated using density functional theory. Finally, we discuss the challenges in creating a sufficient fitting library, determining whether or not the GA optimization has completed, and the transferability of such force fields to similar molecules. ® 2015 Wiley Periodicals, Inc. PMID:25891018
DC Electric Fields and Associated Plasma Drifts Observed with the C/NOFS Satellite
NASA Technical Reports Server (NTRS)
Pfaff, R.; Freudenreich, H.; Bromund, K.; Rowland, D.
Initial DC electric field observations and associated plasma drifts are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite. We present statistical averages of the vector fields for the first year of operations that include both the zonal and radial components of the resulting E x B plasma flows at low latitudes. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. The DC electric field detector reveals zonal and radial electric fields that undergo strong diurnal variations, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. There is considerable variation in the large scale DC electric field data, in both the daytime and nighttime cases, with enhanced structures typically observed at night. In general, the measured zonal DC electric field amplitudes include excursions that extend within the 0.4 - 2 m V/m range, corresponding to E x B drifts of the order of 30-150 m/s. The average vertical or radial electric fields may exceed the zonal fields in amplitude by a factor of 1.5 to 2. Although the data compare well, in a general sense, with previous satellite observations and statistical patterns of vertical ion drifts, the E x B drifts we report from C/NOFS rarely show a pronounced pre-reversal enhancement after sunset. We attribute this to a combination of extreme solar minimum conditions and the fact that the C/NOFS orbit of 401 by 867 km carries the probes essentially above the lower altitude regions where the wind-driven dynamo might be expected to create enhanced upwards drifts in the early evening. Evidence for wavenumber 4 tidal effects and other longitudinal signatures have been detected and will be presented. We also discuss off-equatorial electric fields and their relation to the ambient plasma density.
Effect of rotating electric field on 3D complex (dusty) plasma
Woerner, L.; Nosenko, V.; Ivlev, A. V.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E. [Max-Planck-Institut fuer extraterrestrische Physik, D-85741 Garching (Germany); Kroll, M.; Schablinski, J.; Block, D. [Christian-Albrechts Universitaet zu Kiel, D-24118 Kiel (Germany)
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 10{sup 4}-10{sup 7} times lower than applied frequency. The experiment is compared to a recent theory.
Force-Field Compensation in a Manual Tracking Task
Valentina Squeri; Lorenzo Masia; Maura Casadio; Pietro Morasso; Elena Vergaro; Paul L. Gribble
This study addresses force\\/movement control in a dynamic ōhybridö 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
Quantum mechanical force field for water with explicit electronic polarization
Han, Jaebeom; Mazack, Michael J. M.; Zhang, Peng; Truhlar, Donald G.; Gao, Jiali [Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street, SE, Minneapolis, Minnesota 55455-0431 (United States)] [Department of Chemistry and Supercomputing Institute, University of Minnesota, 207 Pleasant Street, SE, Minneapolis, Minnesota 55455-0431 (United States)
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 ū 10{sup 6} self-consistent-field calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as across biological ion channels through membranes.
Quantum mechanical force field for water with explicit electronic polarization.
Han, Jaebeom; Mazack, Michael J M; Zhang, Peng; Truhlar, Donald G; Gao, Jiali
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 ū 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
Electromagnetic and gravitational self-force on a relativistic particle from quantum fields in curved space
Chad R. Galley; B. L. Hu; Shih-Yuin Lin
We provide a quantum field theoretical derivation of the Abraham-Lorentz-Dirac (ALD) equation, describing the motion of an electric point charge sourcing an electromagnetic field, which back-reacts on the charge as a self-force, and the Mino-Sasaki-Tanaka-Quinn-Wald (MSTQW) equation describing the motion of a point mass with self-force interacting with the linearized metric perturbations caused by the mass off an otherwise vacuous curved background spacetime. We regularize the formally divergent self-force by smearing the direct part of the retarded Green's function and using a quasilocal expansion. We also derive the ALD-Langevin and the MSTQW-Langevin equations with a classical stochastic force accounting for the effect of the quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. These equations will be useful for studying the stochastic motion of charges and small masses under the influence of both quantum and classical noise sources, derived either self-consistently or put in by hand phenomenologically. We also show that history-dependent noise-induced drift motions could arise from such stochastic sources on the trajectory that could be a hidden feature of gravitational wave forms hitherto unknown.
Current Status of the AMOEBA Polarizable Force Field
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.
Molecular force fields have been approaching a generational transition over the past several years, moving away from well-established and well-tuned, but intrinsically limited, fixed point charge models towards more intricate and expensive polarizable models that should allow more accurate description of molecular properties. The recently introduced AMOEBA force field is a leading publicly available example of this next generation of theoretical model, but to date has only received relatively limited validation, which we address here. We show that the AMOEBA force field is in fact a significant improvement over fixed charge models for small molecule structural and thermodynamic observables in particular, although further fine-tuning is necessary to describe solvation free energies of drug-like small molecules, dynamical properties away from ambient conditions, and possible improvements in aromatic interactions. State of the art electronic structure calculations reveal generally very good agreement with AMOEBA for demanding problems such as relative conformational energies of the alanine tetrapeptide and isomers of water sulfate complexes. AMOEBA is shown to be especially successful on protein-ligand binding and computational X-ray crystallography where polarization and accurate electrostatics are critical. PMID:20136072
Demixing in simple fluids induced by electric field gradients
Yoav Tsori; Franńois Tournilhac; Ludwik Leibler
Phase separation in liquid mixtures is mainly controlled by temperature and pressure, but can also be influenced by gravitational, magnetic or electric fields. However, the weak coupling between such fields and concentration fluctuations limits this effect to extreme conditions. For example, mixing induced by uniform electric fields is detectable only at temperatures that are within a few hundredths of degree
The electric field gradient in heavy rare earth metals
J. Pelzl; Fachbereich Physik
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
Modelling of the electric field in HVDC cables
D. Carstea; I. Carstea
The scope of this paper is to present some aspects in modeling of electrical field in high-voltage direct-current (HVDC) cables. Some computation models for electrical fields are presented. Computation procedures are developed for DC cables with one and two imperfect dielectric insulation layers for capacitive and resistive field distribution
Spiking patterns of a hippocampus model in electric fields
NASA Astrophysics Data System (ADS)
Men, Cong; Wang, Jiang; Qin, Ying-Mei; Wei, Xi-Le; Che, Yan-Qiu; Deng, Bin
We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.
Electric field and plasma observations in the magnetosphere
NASA Technical Reports Server (NTRS)
Gurnett, D. A.
Satellite-borne electric field measurements using the double probe technique have now provided a comprehensive survey of convection electric fields at low altitudes in the magnetosphere. The most prominent features of the convection electric fields are reversals located at high magnetic latitudes, with generally anti-sunward convection poleward and sunward convection equatorward of the electric field reversal location. On the day side of the magnetosphere the electric field reversal is observed to coincide with the equatorward boundary of the polar cusp. In the local afternoon and evening regions inverted V electron precipitation bands occur at or near the electric field reversal and in regions usually characterized by large fluctuations in the electric field. In the local midnight region strong convection electric fields have also been observed deep within the magnetosphere, near the equatorward boundary of the plasma sheet. Recent measurements of electric fields near the inverted V electron precipitation bands suggests that these events are associated with large electrostatic potential gradients along the geomagnetic field.
Electric Field Effect in Epitaxial Graphene Devices
NASA Astrophysics Data System (ADS)
Li, Xuebin; Wu, Xiaosong; Sprinkle, Michael; Ming, Fan; Berger, Claire; Murali, Raghunath; Zaman, Farhana; Meindl, James; de Heer, Walter
The electric field effect has been observed on epitaxial graphene multilayers grown on SiC substrates by thermal decomposition of SiC. Carriers mobilities up to 2.5x10^4cm^2/Vs have been measured. Both side-gated and top-gated graphene field effect transistors (FETs) have been fabricated using standard semiconductor processes on both the Si and the C face of the SiC substrates. In side-gated FETs, the gates are located on both sides of narrow graphene ribbons; source-drain resistances decrease by several percent with a gate bias of several volts. For top-gated FETs the resistance swing reaches a factor of 25. At the gate voltage corresponding to the maximum source-drain resistance, the Hall voltage changes sign indicating a transition from hole- to electron- carried transport, consistent with the graphene band structure. These results indicate the potential of epitaxial graphene as a platform for large-scale graphene based electronics.
Role of random electric fields in relaxors.
Phelan, Daniel; Stock, Christopher; Rodriguez-Rivera, Jose A; Chi, Songxue; LeŃo, Juscelino; Long, Xifa; Xie, Yujuan; Bokov, Alexei A; Ye, Zuo-Guang; Ganesh, Panchapakesan; Gehring, Peter M
PbZr(1-x)Ti(x)O3 (PZT) and Pb(Mg1/3Nb2/3)(1-x)Ti(x)O3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter. PMID:24449912
Role of random electric fields in relaxors
Phelan, Daniel; Stock, Christopher; Rodriguez-Rivera, Jose A.; Chi, Songxue; LeŃo, Juscelino; Long, Xifa; Xie, Yujuan; Bokov, Alexei A.; Ye, Zuo-Guang; Ganesh, Panchapakesan; Gehring, Peter M.
PbZr1¢xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1¢xTixO3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter. PMID:24449912
Electric field induced bacterial flocculation of enteroaggregative Escherichia coli 042
NASA Astrophysics Data System (ADS)
Kumar, Aloke; Mortensen, Ninell P.; Mukherjee, Partha P.; Retterer, Scott T.; Doktycz, Mitchel J.
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.
G. Gustafsson; R. Bostrom; B. Holback; G. Holmgren; A. Lundgren; K. Stasiewicz; L. ┼HL╔N; 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. F─LTHAMMAR; P.-A. Lindqvist; S. Christenson; J. Holtet; B. Lybekk; T. A. Sten; P. Tanskanen; K. Lappalainen; J. Wygant
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
Electric field induced bacterial flocculation of Enteroaggregative Escherichia coli 042
Kumar, Aloke [ORNL; Mortensen, Ninell P [ORNL; Mukherjee, Partha P [ORNL; Retterer, Scott T [ORNL; Doktycz, Mitchel John [ORNL
A response of the aggregation dynamics of enteroaggregative Escherichia coli under low magnitude steady and oscillating electric fields is presented. The presence of uniform electric fields hampered microbial adhesion and biofilm formation on a transverse glass surface, but instead promoted the formation of flocs. Extremely heterogeneous distribution of live and dead cells was observed among the flocs. Moreover, floc formation was largely observed to be independent of the frequency of alternating electric fields.
Study of oxide breakdown under very low electric field
A. Teramoto; H. Umeda; K. Azamawari; K. Kobayashi; K. Shiga; J. Komori; Y. Ohno; H. Miyoshi
We have performed TDDB measurements at temperatures lower than 125░C in an electric field (Eox) range of 7-13.5 MV\\/cm and have evaluated the intrinsic lifetime in a wide electric field range, using both area and temperature dependences of oxide lifetime. For positive gate bias, log(tBD) of 7.1 and 9.6 nm oxides is not proportional to the electric field but is
Electric field measurements at subcritical, oblique bow shock crossings
NASA Technical Reports Server (NTRS)
Wygant, J. R.; Bensadoun, M.; Mozer, F. S.
ISEE-1 electric field measurements at three oblique, subcritical dispersive bow shock crossings are presented. The potential drops across the shock due to the large spatial scale normal component of the electric field were found to vary between 340 and 520 V. The measurements provide the first observations in a space plasma of the oscillations in the normal component of the electric field connected with the whistler precursor phase standing at a collisionless shock. Intense, rapidly varying electric fields with peak amplitudes ranging up to 100 mV/m were observed at the magnetic ramp of the shock in the high time resolution data.
Electric Field Enhanced Diffusion of Salicylic Acid through Polyacrylamide Hydrogels
NASA Astrophysics Data System (ADS)
Niamlang, Sumonman; Sirivat, Anuvat
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.
Strong gravitational force induced by static electromagnetic fields
B. V. Ivanov
It is argued that static electric or magnetic fields induce Weyl-Majumdar-Papapetrou solutions for the metric of spacetime. Their gravitational acceleration includes a term many orders of magnitude stronger than usual perturbative terms. It gives rise to a number of effects, which can be detected experimentally. Four electrostatic and four magnetostatic examples of physical set-ups with simple symmetries are proposed. The different ways in which mass sources enter and complicate the pure electromagnetic picture are described.
A Wearable Force Plate Designed Using Pressure Sensitive Electric Conductive Rubber
NASA Astrophysics Data System (ADS)
Liu, Tao; Inoue, Yoshio; Shibata, Kyoko
To perform 3D ground reaction force (GRF) and moments measurement with a comfortable interface for the foot, this paper presents a new 3D force sensor cell designed using pressure sensitive electric conductive rubber (PSECR). A wearable force plate with a four-support mechanism was proposed for measuring triaxial forces and moments. A compact electrical hardware system including amplifier modules, conditioning circuits, and then a micro-computer controller was developed and integrated into the sensor system. A shoes-based sensor system composed of two developed force plates was constructed for GRF and moment measurement. Calibration experiments were conducted, and a stationary force plate was used as a reference device to verify the measures of GRF and moment using the sensor system in trials by a normal walking speed. The results show a good correspondence between the developed sensor system and the reference system, which was examined by a root mean square (RMS) difference of 7.2N for x-axial force, 11.1N for y-axial force, and 9.5N for z-axial force. The RMS difference of the measured x-, y-, and z- directional moments was 6.4Nm, 1.9Nm, and 1.4Nm, respectively.
Self-force on an electric dipole in the spacetime of a cosmic string
Muniz, C.R., E-mail: firstname.lastname@example.com [Grupo de FĒsica Te¾rica (GFT), Universidade Estadual do Cearß, UECE-FECLI, Iguatu, Cearß (Brazil); Bezerra, V.B., E-mail: firstname.lastname@example.com [Departamento de FĒsica, Universidade Federal da ParaĒba, Caixa Postal 5008, CEP 58051-970, JoŃo Pessoa, PB (Brazil)
We calculate the electrostatic self-force on an electric dipole in the spacetime generated by a static, thin, infinite and straight cosmic string. The electric dipole is held fixed in different configurations, namely, parallel, perpendicular to the cosmic string and oriented along the azimuthal direction around this topological defect, which is stretched along the z axis. We show that the self-force is equivalent to an interaction of the electric dipole with an effective dipole moment which depends on the linear mass density of the cosmic string and on the configuration. The plots of the self-forces as functions of the parameter which determines the angular deficit of the cosmic string are shown for those different configurations. -- Highlights: ĢReview of regularized GreenÆs function applied to the problem. ĢSelf-force on an electric dipole in the string spacetime for some orientations. ĢRepresentation via graphs of the self-forces versus angular parameter of the cosmic string. ĢSelf-force induced by the string seen as an interaction between two dipoles. ĢDiscussion about the superposition principle in this non-trivial background.
The intra-spine electric force can drive vesicles for fusion: a theoretical model for long-term potentiation
Benuskova, Luba
The intra-spine electric force can drive vesicles for fusion: a theoretical model for long 1999; accepted 7 December 1999 Abstract We have estimated the intensity of intra-spine electric ®elds triggered by stimulation of excitatory spine synapses. We show that this electric force can cause fast
Surface electric fields for North America during historical geomagnetic storms
Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.
To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic stormsŚthe 1989 ōQuebecö storm and the 2003 ōHalloweenö 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.
Relative importance of electric fields and neutral winds in polar-cap Es formation
NASA Astrophysics Data System (ADS)
Voiculescu, Mirela; Nygren, Tuomo; Aikio, Anita
Previous statistical studies of sporadic E layers have shown that Es formation within the polar cap is, generally, controlled by the electric field. However, case studies show that the effect of neutral wind, which obviously has its own effect on ion motion, cannot be ruled out. Four Es layers, observed by the EISCAT Svalbard Radar (ESR), were chosen for investigating the role played by electric field and neutral wind in their formation and evolution. Estimates of the ionospheric electric field were obtained from the statistical APL model, which uses observations of F region plasma drift and interplanetary magnetic field as inputs. The neutral wind was obtained from the NRLMSISE-00 model. A flat height profile of metal ions was assumed in the beginning, and the time development of layers was constructed by integrating the continuity equation under the action of driving forces due to neutral wind and electric field. The results indicate that electric field and neutral wind, both separately and together, could create a layer at the times of radar observations. However, the agreement between the observed and calculated layer altitudes was poor. A better agreement was obtained, if the electric field was assumed to be stronger than the statistical value given by the APL model. In one case, when the observed layer lied below 100 km in altitude, it also seemed that neutral winds at these heights were weaker than given by the model.
A bidirectional brain-machine interface algorithm that approximates arbitrary force-fields.
Vato, Alessandro; Szymanski, Francois D; Semprini, Marianna; Mussa-Ivaldi, Ferdinando A; Panzeri, Stefano
We examine bidirectional brain-machine interfaces that control external devices in a closed loop by decoding motor cortical activity to command the device and by encoding the state of the device by delivering electrical stimuli to sensory areas. Although it is possible to design this artificial sensory-motor interaction while maintaining two independent channels of communication, here we propose a rule that closes the loop between flows of sensory and motor information in a way that approximates a desired dynamical policy expressed as a field of forces acting upon the controlled external device. We previously developed a first implementation of this approach based on linear decoding of neural activity recorded from the motor cortex into a set of forces (a force field) applied to a point mass, and on encoding of position of the point mass into patterns of electrical stimuli delivered to somatosensory areas. However, this previous algorithm had the limitation that it only worked in situations when the position-to-force map to be implemented is invertible. Here we overcome this limitation by developing a new non-linear form of the bidirectional interface that can approximate a virtually unlimited family of continuous fields. The new algorithm bases both the encoding of position information and the decoding of motor cortical activity on an explicit map between spike trains and the state space of the device computed with Multi-Dimensional-Scaling. We present a detailed computational analysis of the performance of the interface and a validation of its robustness by using synthetic neural responses in a simulated sensory-motor loop. PMID:24626393
Interfacial Force Field Characterization in a Constrained Vapor Bubble Thermosyphon
NASA Technical Reports Server (NTRS)
DasGupta, Sunando; Plawsky, Joel L.; Wayner, Peter C., Jr.
Isothermal profiles of the extended meniscus in a quartz cuvette were measured in the earth's gravitational field using an image-analyzing interferometer that is based on computer-enhanced video microscopy of the naturally occurring interference fringes. These profiles are a function of the stress field. Experimentally, the augmented Young-Laplace equation is an excellent model for the force field at the solid-liquid-vapor interfaces for heptane and pentane menisci on quartz and tetradecane on SFL6. The effects of refractive indices of the solid and liquid on the measurement techniques were demonstrated. Experimentally obtained values of the disjoining pressure and dispersion constants were compared to those predicted from the Dzyaloshinskii - Lifshitz - Pilaevskii theory for an ideal surface and reasonable agreements were obtained. A parameter introduced gives a quantitative measurement of the closeness of the system to equilibrium. The nonequilibrium behavior of this parameter is also presented
Self-organized growth of tetrathiafulvalene-tetracyanoquinodimethane molecular wires using the coevaporation method under a static electric field
Sakai, Masatoshi; Iizuka, Masaaki; Nakamura, Masakazu; Kudo, Kazuhiro [Department of Electronics and Mechanical Engineering, Faculty of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)
Wire-like crystals of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) charge-transfer complexes were grown under a static electric field by employing electric-field assisted evaporation. TTF-TCNQ molecular wires grew from the edges of two gold electrodes opposite to each other along the electric lines of force, and finally make a connection at their front end to form a single wire. Self-organization of the wire bridge is derived from a higher local electric field between the tips of the opposing molecular wires. Oriented molecular wires, which have diffuse branches, exhibit the effects of a local electric field. Preferential growth of TCNQ at the tip of the molecular wire during coevaporation of TTF and TCNQ is clearly revealed by microscopic Raman spectroscopy. Asymmetrical growth of coevaporated TTF-TCNQ wire under a static electric field is dominated by the drift motion of TCNQ{sup -}.
Mechanical stress in a dielectric solid from a uniform electric field
Anderson, R.A.
Mechanical stress in a dielectric solid from application of a uniform electric field is usually assumed to be described by ''Maxwell stress,'' proportional to the first power of the relative dielectric constant, kappa. Significant corrections are found from energy minimization when the dependence of permittivity on strain is included. Electrostriction coefficients are evaluated by the use of a model dielectric consisting of a simple-cubic lattice of linearly polarizable point dipoles. Compressive stress in the applied-field direction is larger than expected by more than a factor of kappa. The force density exerted on internal space charge needs to be corrected by the same factor. Stress components also have been calculated, with identical results, through direct summation of microscopic forces. This method permits identification of the origins of electrically induced stress. The dominant contribution is a compressive stress in the field direction, proportional to kappaS, from attraction between free charge at the electrodes. This component can attain tens of MPa at fields approaching the intrinsic dielectric strength. A lateral tensile stress independent of kappa also is present, which may assist electrical breakdown in some crystalline dielectrics. These stress components are augmented by short-range, dipolar forces throughout the bulk of the dielectric. Deformations accompanying poling of poly(vinylidene fluoride) are considered and found to be influenced by electrically induced stress.
Electric fields in unsteady wind-blown sand.
Zhang, Huan; Zheng, Xiao-Jing; Bo, Tian-Li
The electrification of wind-blown sand has been widely confirmed by field and wind-tunnel measurements. It plays an important role in the lifting and transport of sand particles. In this study we investigated the behavior of electric fields in unsteady saltation by adopting periodic variation wind sequences. The influence of electric fields on sand transport rate was also discussed. The results show that both horizontal and vertical electric fields exist in unsteady saltation, and the transport rate in unsteady saltation is less than that in steady saltation. An interesting result is that the directions of vertical electric field fluctuate upward and downward-pointing with time in the unsteady saltation. This provides a possible explanation for the bipolar pattern of the vertical electric field in wind-blown sand. PMID:24574056
Biological Effects of Electrical and Magnetic Fields: Is It Real?Ā
Durham, M. O.
The hazardous effect of electric and magnetic fields on biological systems is the subject of considerable debate. Traditional methods have failed to provide a correlation between the fields and biological effects. A model is presented that solves...
An Investigation of the Behaviour of Drops and Drop-Pairs Subjected to Strong Electrical Forces
P. R. Brazier-Smith; S. G. Jennings; J. Latham
A numerical model is described which simulates irrotational, incompressible flow on a computer. It has been applied to the problems of the deformation of uncharged drop-pairs separated in an electric field of critical strength and isolated drops charged to the Rayleigh limit in the absence of an electric field. In the case of pairs of drops of radius R, separated
Simulating the interplay between plasma transport, electric field, and magnetic field in the near-earth nightside magnetosphere
NASA Astrophysics Data System (ADS)
Gkioulidou, Malamati
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.
Exposure assessment for power frequency electric and magnetic fields.
Bracken, T D
Over the past decade considerable data have been collected on electric and magnetic fields in occupational environments. These data have taken the form of area measurements, source characterizations, and personal exposure measurements. Occupational EMF levels are highly variable in space and time. Exposures associated with these fields exhibit similar large variations during a day, between days, and between individuals within a group. The distribution of exposure measures is skewed over several decades with only a few values occurring at the maximum field levels. The skewness of exposure measures implies that large sample sizes may be required for assessments and that multiple statistical descriptors are preferred to describe individual and group exposures. Except for the relatively few occupational settings where high voltage sources are prevalent, electric fields encountered in the workplace are probably similar to residential exposures. Consequently, high electric field exposures are essentially limited to utility environments and occupations. Within the electric utility industry, it is definitely possible to identify occupations with high electric field exposures relative to those of office workers or other groups. The highly exposed utility occupations are linemen, substation operators, and utility electricians. The distribution of electric field exposures in the utility worker population is very skewed even within a given occupation. As with electric fields, magnetic fields in the workplace appear to be comparable with residential levels, unless a clearly defined high-current source is present. Since high-current sources are more prevalent than high-voltage sources, environments with relatively high magnetic field exposures encompass a more diverse set of occupations than do those with high electric fields. Within the electric utility industry, it is possible to identify occupational environments with high magnetic field exposure relative to the office environment. Utility job categories with the highest exposures are generation facility workers, substation operators, utility linemen, and utility electricians. There are also higher exposures among traditional "electrical worker" job categories. Outside the electrical utility industry, potential sources of high occupational magnetic field exposures at ELF are induction furnaces, welding machines, electrical transportation systems, and electrical distribution vaults. However, the use of low power electrical equipment such as small motors in close proximity to workers and possibly for long periods of time could also lead to high exposure situations. Handheld survey instruments are available to perform area measurements of electric and magnetic fields at power frequencies but not aat all frequencies within the ELF range. Sophisticated personal computer-based instruments are available to characterize areas and sources across the entire frequency range.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8480632
F. S. Mozer
Balloon-measured electric-field data for 5-hour periods during each of 19 substorms near local midnight between L -- 6.6 and 8.3 have been analyzed and averaged to show that the ionospheric electric field is made up of approximately equal contributions from a large-scale field and smallscale turbulence. The large-scale field in a nonrotating frame of reference develops a westward component during
Continuum Polarizable Force Field within the Poisson-Boltzmann Framework
Tan, Yu-Hong; Tan, Chunhu; Wang, Junmei; Luo, Ray
We have developed and tested a complete set of nonbonded parameters for a continuum polarizable force field. Our analysis shows that the new continuum polarizable model is consistent with B3LYP/cc-pVTZ in modeling electronic response upon variation of dielectric environment. Comparison with experiment also shows that the new continuum polarizable model is reasonable, with similar accuracy as B3LYP/cc-pVTZ in reproduction of dipole moments of selected organic molecules in the gas phase. We have further tested the validity to interchange the Amber van der Waals parameters between the explicit and continuum polarizable force fields with a series of dimers. It can be found that the continuum polarizable model agrees well with MP2/cc-pVTZ, with deviations in dimer binding energies less than 0.9 kcal/mol in the aqueous dielectric environment. Finally we have optimized atomic cavity radii with respect to experimental solvation free energies of 177 training molecules. To validate the optimized cavity radii, we have tested these parameters against 176 test molecules. It is found that the optimized PB atomic cavity radii transfer well from the training set to the test set, with an overall root-mean-squared deviation of 1.30 kcal/mol, unsigned average error of 1.07 kacl/mol, and correlation coefficient of 92% for all 353 molecules in both the training and test sets. Given the development documented here, the next natural step is the construction of a full protein/nucleic acid force field within the new continuum polarization framework. PMID:18507452
A new model for electric force microscopy and its application for electrostatically generated phase difference in tapping mode AFM
Stone, Peter (Peter Robert)
The harmonic force balance method was used to model and simulate electric force microscopy (EFM) and electrostatically generated phase difference in tapping mode AFM (EPTA) measurements. Simulations show that the harmonic ...
Micro-gravity: current distributions creating a uniform force field
NASA Astrophysics Data System (ADS)
Vincent-Viry, O.; Mailfert, A.; Colteu, A.; Dael, A.; Gourdin, C.; Quettier, L.
This paper presents two structures of superconducting coils able to give satisfactory solutions to the problem of generation of uniform field of high magnetic forces. The first structure is modeled by the use of purely surface current densities, whereas the second one can be described with volume current densities. Both of these structures proceed from the study of a particular expression of the complex magnetic potential introduced for structures with two-dimensional geometry. This work is carried out in a research collaboration between the GREEN and the DSM-DAPNIA department of the CEA Saclay.
On the force fields which are homogeneous of degree $-3$
Alain Albouy
The dynamics defined by a force field which is positively homogeneous of degree $-3$ can always be reduced, by simply constraining it. The dimension of the phase space is reduced by two dimensions, while it may only be reduced by one dimension if the degree of homogeneity is different from $-3$. This remark is an elegant foundation of Appell's projective dynamics. We show how it relates to Kn\\"orrer's remark on the correspondence between the Neumann potential on a sphere and the geodesic motion on an ellipsoid.
The Anharmonic Force Field of BeH2 Revisited
NASA Technical Reports Server (NTRS)
Martin, Jan M. L.; Lee, Timothy J.
The anharmonic force field of BeH2 has been calculated near the basis set and n-particle space limits. The computed antisymmetric stretch frequencies of BeH2 and BeD2 are in excellent agreement with recent high-resolution gas-phase measurements. The agreement between theory and experiment for the other spectroscopic constants is also excellent, except for omega(sub 3) and X(sub 33) for BeH2 and G(sub 22) for BeD2. It is concluded that further experimental work is needed in order to resolve these discrepancies.
Probing university students' understanding of electromotive force in electricity
NASA Astrophysics Data System (ADS)
Garz¾n, Isabel; De Cock, Mieke; Zuza, Kristina; van Kampen, Paul; Guisasola, Jenaro
The goal of this study is to identify students' difficulties with learning the concepts of electromotive force (emf) and potential difference in the context of transitory currents and resistive direct-current circuits. To investigate these difficulties, we developed a questionnaire based on an analysis of the theoretical and epistemological framework of physics, which was then administered to first-year engineering and physics students at universities in Spain, Colombia, and Belgium. The results of the study show that student difficulties seem to be strongly linked to the absence of an analysis of the energy balance within the circuit and that most university students do not clearly understand the usefulness of and the difference between the concepts of potential difference and emf.
Holographic confining gauge theory and response to the electric field
Kazuo Ghoroku; Masafumi Ishihara; Tomoki Taminato
We study the response of confining gauge theory to the external electric field by using holographic Yang-Mills theories in the large Nc limit. Although the theories are in the confinement phase, we find a transition from the insulator to the conductor phase when the electric field exceeds its critical value. Then, the baryon number current is generated in the conductor
Holographic confining gauge theory and response to the electric field
Kazuo Ghoroku; Masafumi Ishihara; Tomoki Taminato
We study the response of confining gauge theory to the external electric field by using holographic Yang-Mills theories in the large N{sub c} limit. Although the theories are in the confinement phase, we find a transition from the insulator to the conductor phase when the electric field exceeds its critical value. Then, the baryon number current is generated in the
Electric field phase diagram of thiourea determined by optical birefringence
Paris-Sud XI, Universitķ de
L-123 Electric field phase diagram of thiourea determined by optical birefringence J. P. Jamet the birefringence jump is zero, a second-order line T03BB(E) separating the paraelectric phase from the optical linear birefringence; some pre- liminary measurements with zero electric field made with the same
Spectroscopy of laboratory and space plasma with oscillating electrical fields
E. A. Oks
The spontaneous emission spectra of atoms and ions interacting with oscillating electrical fields in a plasma medium are investigated theoretically. The use of these phenomena for plama diagnosis under specific laboratory and space conditions is examined. The I (delta omega) contours of the emitted lines are investigated as a function of the electrical field parameters (the amplitude, the position of
Electric field calculations with the boundary element method
S. S. Bamji; A. T. Bulinski; K. M. Prasad
The boundary element method is used to calculate the electric field profiles at needle tips commonly used for electrical treeing tests. Field distributions are also obtained for polyethylene containing a space charge, at the needle tip, and are compared with the values previously obtained by the finite difference method
High-latitude day side electric field and particle measurements
Nelson C. Maynard; Alan D. Johnstone
Two rockets carrying electric field and low-energy particle instrumentation were launched near noon at 80 ° magnetic latitude. One flight encountered polar cap conditions only, whereas the other traversed part of the polar cusp. Although weak particle precipitation was measured on both flights, bursts of intense magnetosheath-type electron fluxes were detected on the latter. Strong electric fields such as would
Intense ionospheric electric and magnetic field pulses generated by lightning
M. C. Kelley; J. G. Ding; R. H. Holzworth
Electric and magnetic field measurements have been made in the ionosphere over an active thunderstorm and an optical detector onboard the same rocket yielded an excellent time base for the study of waves radiated into space from the discharge. In addition to detection of intense, but generally well understood whistler mode waves, very unusual electric and magnetic field pulses preceded
dc electric field meter with fiber-optic readout
Alan R. Johnston; Harold Kirkham; Bjorn T. Eng
The design of a dc electric field meter capable of measuring the magnitude and direction of the electric field at an arbitrary location above the ground plane is described. The meter is based on measuring induced charge on a split cylindrical electrode pair which is rotated around its axis of symmetry. Data readout is by fiber-optic cable using pulse frequency
Debye size microprobes for electric field measurements in laboratory plasmas
California at Los Angles, University of
Debye size microprobes for electric field measurements in laboratory plasmas P. Pribyl, W. Gekelman by their nature have a hierarchy of size and time scales. The relationship between these interaction scales the average electric field between them. A sheath several Debye lengths in size the Debye length is D kT 0/ne2
High intensity pulsed electric fields applied for food preservation
S. Toepfl; V. Heinz; D. Knorr
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
Polymer dispersed liquid crystal fiber optic electric field probe
Beatrys M. Lacquet; Pieter L. Swart; Stephanus J. Spammer
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 V\\/cm to 800 V\\/cm range is adequate for most electric power distribution systems.
Electric and Magnetic Field Detection in Elasmobranch Fishes
NASA Astrophysics Data System (ADS)
Kalmijn, Ad. J.
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.
Control of thumb force using surface functional electrical stimulation and muscle load sharing
Background Stroke survivors often have difficulties in manipulating objects with their affected hand. Thumb control plays an important role in object manipulation. Surface functional electrical stimulation (FES) can assist movement. We aim to control the 2D thumb force by predicting the sum of individual muscle forces, described by a sigmoidal muscle recruitment curve and a single force direction. Methods Five able bodied subjects and five stroke subjects were strapped in a custom built setup. The forces perpendicular to the thumb in response to FES applied to three thumb muscles were measured. We evaluated the feasibility of using recruitment curve based force vector maps in predicting output forces. In addition, we developed a closed loop force controller. Load sharing between the three muscles was used to solve the redundancy problem having three actuators to control forces in two dimensions. The thumb force was controlled towards target forces of 0.5 N and 1.0 N in multiple directions within the individualÆs thumb work space. Hereby, the possibilities to use these force vector maps and the load sharing approach in feed forward and feedback force control were explored. Results The force vector prediction of the obtained model had small RMS errors with respect to the actual measured force vectors (0.22▒0.17 N for the healthy subjects; 0.17▒0.13 N for the stroke subjects). The stroke subjects showed a limited work range due to limited force production of the individual muscles. Performance of feed forward control without feedback, was better in healthy subjects than in stroke subjects. However, when feedback control was added performances were similar between the two groups. Feedback force control lead, especially for the stroke subjects, to a reduction in stationary errors, which improved performance. Conclusions Thumb muscle responses to FES can be described by a single force direction and a sigmoidal recruitment curve. Force in desired direction can be generated through load sharing among redundant muscles. The force vector maps are subject specific and also suitable in feedforward and feedback control taking the individualÆs available workspace into account. With feedback, more accurate control of muscle force can be achieved. PMID:24103414
Validating empirical force fields for molecular-level simulation of cellulose dissolution
Technology Transfer Automated Retrieval System (TEKTRAN)
The calculations presented here, which include dynamics simulations using analytical force fields and first principles studies, indicate that the COMPASS force field is preferred over the Dreiding and Universal force fields for studying dissolution of large cellulose structures. The validity of thes...
Molecules as a Basis'for Modeling the Force Field of
Downs, Robert T.
6 Molecules as a Basis'for Modeling the Force Field of Silica G. v. Gibbs, F. C. Hill, M. B. Boisen in small molecules'. More recent studies indicate that a similar connection exists between the force field CONNECTION BETWEEN THE FORCE FIELD OF SILICA AND SMALL MOLECULES 2.1 Structural Evidence There is a wealth
Structured DC Electric Fields With and Without Associated Plasma Density Gradients Observed with the C/NOFS Satellite
NASA Technical Reports Server (NTRS)
Pfaff, R.; Rowland, D.; Klenzing, J.; Freudenreich, H.; Bromund, K.; Liebrecht, C.; Roddy, P.; Hunton, D.
DC electric field observations and associated plasma drifts gathered with the Vector Electric Field Investigation on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite typically reveal considerable variation at large scales (approximately 100's of km), in both daytime and nighttime cases, with enhanced structures usually confined to the nightside. Although such electric field structures are typically associated with plasma density depletions and structures, as observed by the Planar Langmuir Probe on C/NOFS, what is surprising is the number of cases in which large amplitude, structured DC electric fields are observed without a significant plasma density counterpart structure, including their appearance at times when the ambient plasma density appears relatively quiescent. We investigate the relationship of such structured DC electric fields and the ambient plasma density in the C/NOFS satellite measurements observed thus far, taking into account both plasma density depletions and enhancements. We investigate the mapping of the electric fields along magnetic field lines from distant altitudes and latitudes to locations where the density structures, which presumably formed the original seat of the electric fields, are no longer discernible in the observations. In some cases, the electric field structures and spectral characteristics appear to mimic those associated with equatorial spread-F processes, providing important clues to their origins. We examine altitude, seasonal, and longitudinal effects in an effort to establish the origin of such structured DC electric fields observed both with, and without, associated plasma density gradients
Plasma rotation by electric and magnetic fields in a discharge cylinder
NASA Technical Reports Server (NTRS)
Wilhelm, H. E.; Hong, S. H.
A theoretical model for an electric discharge consisting of a spatially diverging plasma sustained electrically between a small ring cathode and a larger ring anode in a cylindrical chamber with an axial magnetic field is developed to study the rotation of the discharge plasma in the crossed electric and magnetic fields. The associated boundary-value problem for the coupled partial differential equations which describe the electric potential and the plasma velocity fields is solved in closed form. The electric field, current density, and velocity distributions are discussed in terms of the Hartmann number and the Hall coefficient. As a result of Lorentz forces, the plasma rotates with speeds as high as 1 million cm/sec around its axis of symmetry at typical conditions. As an application, it is noted that rotating discharges of this type could be used to develop a high-density plasma-ultracentrifuge driven by j x B forces, in which the lighter (heavier) ion and atom components would be enriched in (off) the center of the discharge cylinder.
Electric Field Distribution of Cadmium Zinc Telluride (CZT)
Yang,G.; Bolotnikov, A.; Camarda, G.S.; Cui, Y.; Hossain, A.; Kim, K.; James, R.B.
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.
Electric Field Quench in AdS/CFT
Koji Hashimoto; Shunichiro Kinoshita; Keiju Murata; Takashi Oka
An electric field quench, a suddenly applied electric field, can induce nontrivial dynamics in confining systems which may lead to thermalization as well as a deconfinement transition. In order to analyze this nonequilibrium transitions,we use the AdS/CFT correspondence for $\\mathcal{N}=2$ supersymmetric QCD that has a confining meson sector. We find that the electric field quench causes the deconfinement transition even when the magnitude of the applied electric field is smaller than the critical value for the static case (which is the QCD Schwinger limit for quark-antiquark pair creation). The time dependence is crucial for this phenomenon, and the gravity dual explains it as an oscillation of a D-brane in the bulk AdS spacetime. Interestingly, the deconfinement time takes only discrete values as a function of the magnitude of the electric field. We advocate that the new deconfinement phenomenon is analogous to the exciton Mott transition.
Effects of an electric field on white sharks: in situ testing of an electric deterrent.
Huveneers, Charlie; Rogers, Paul J; Semmens, Jayson M; Beckmann, Crystal; Kock, Alison A; Page, Brad; Goldsworthy, Simon D
Elasmobranchs can detect minute electromagnetic fields, <1 nV cm(-1), using their ampullae of Lorenzini. Behavioural responses to electric fields have been investigated in various species, sometimes with the aim to develop shark deterrents to improve human safety. The present study tested the effects of the Shark Shield Freedom7Ö electric deterrent on (1) the behaviour of 18 white sharks (Carcharodon carcharias) near a static bait, and (2) the rates of attacks on a towed seal decoy. In the first experiment, 116 trials using a static bait were performed at the Neptune Islands, South Australia. The proportion of baits taken during static bait trials was not affected by the electric field. The electric field, however, increased the time it took them to consume the bait, the number of interactions per approach, and decreased the proportion of interactions within two metres of the field source. The effect of the electric field was not uniform across all sharks. In the second experiment, 189 tows using a seal decoy were conducted near Seal Island, South Africa. No breaches and only two surface interactions were observed during the tows when the electric field was activated, compared with 16 breaches and 27 surface interactions without the electric field. The present study suggests that the behavioural response of white sharks and the level of risk reduction resulting from the electric field is contextually specific, and depends on the motivational state of sharks. PMID:23658766
Effects of an Electric Field on White Sharks: In Situ Testing of an Electric Deterrent
Huveneers, Charlie; Rogers, Paul J.; Semmens, Jayson M.; Beckmann, Crystal; Kock, Alison A.; Page, Brad; Goldsworthy, Simon D.
Elasmobranchs can detect minute electromagnetic fields, <1 nVcm¢1, using their ampullae of Lorenzini. Behavioural responses to electric fields have been investigated in various species, sometimes with the aim to develop shark deterrents to improve human safety. The present study tested the effects of the Shark Shield Freedom7Ö electric deterrent on (1) the behaviour of 18 white sharks (Carcharodon carcharias) near a static bait, and (2) the rates of attacks on a towed seal decoy. In the first experiment, 116 trials using a static bait were performed at the Neptune Islands, South Australia. The proportion of baits taken during static bait trials was not affected by the electric field. The electric field, however, increased the time it took them to consume the bait, the number of interactions per approach, and decreased the proportion of interactions within two metres of the field source. The effect of the electric field was not uniform across all sharks. In the second experiment, 189 tows using a seal decoy were conducted near Seal Island, South Africa. No breaches and only two surface interactions were observed during the tows when the electric field was activated, compared with 16 breaches and 27 surface interactions without the electric field. The present study suggests that the behavioural response of white sharks and the level of risk reduction resulting from the electric field is contextually specific, and depends on the motivational state of sharks. PMID:23658766
Magnetic field induced rearrangement of the electric field domains in weakly coupled superlattices
W. H. M. Feu; D. C. Elias; L. A. Cury; G. S. Vieira; M. P. Pires; S. M. Landi; P. L. Souza
We present an investigation of the electric field domain configuration in the sequential tunneling regime in weakly coupled superlattices in the presence of a magnetic field applied parallel to the quantum well layers. We show that, for an applied bias such that two electric field domains are present in the sample, as the magnetic field is increased a succession of
Dipole Relaxation in an Electric Field.
ERIC Educational Resources Information Center
Neumann, Richard M.
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)
Middle atmospheric electric fields over thunderstorms
NASA Technical Reports Server (NTRS)
Holzworth, Robert H.
This grant has supported a variety of investigations all having to do with the external electrodynamics of thunderstorms. The grant was a continuation of work begun while the PI was at the Aerospace Corporation (under NASA Grant NAS6-3109) and the general line of investigation continues today under NASA Grants NAG5-685 and NAG6-111. This report will briefly identify the subject areas of the research and associated results. The period actually covered by the grant NAG5-604 included the following analysis and flights: (1) analysis of five successful balloon flights in 1980 and 1981 (under the predecessor NASA grant) in the stratosphere over thunderstorms; (2) development and flight of the Hy-wire tethered balloon system for direct measurement of the atmospheric potential to 250 kV (this involved multiple tethered balloon flight periods from 1981 through 1986 from several locations including Wallops Island, VA, Poker Flat and Ft. Greely, AK and Holloman AFB, NM.); (3) balloon flights in the stratosphere over thunderstorms to measure vector electric fields and associated parameters in 1986 (2 flights), 1987 (4 flights), and 1988 (2 flights); and (4) rocket-borne optical lightning flash detectors on two rocket flights (1987 and 1988) (the same detector design that was used for the balloon flights listed under #3). In summary this grant supported 8 stratospheric zero-pressure balloon flights, tethered aerostat flights every year between 1982-1985, instruments on 2 rockets, and analysis of data from 6 stratospheric flights in 1980/81.
Radial electric fields in the vicinity of locked magnetic islands
Nishimura, S.; Itoh, K.; Ida, K. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Yagi, M. [Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan); Itoh, S.-I. [Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)
The radial electric field in the vicinity of magnetic islands locked by resonant magnetic perturbations (static error fields) is numerically studied using a set of reduced two-fluid equations. The asymmetric radial electric fields across locked magnetic islands are observed, which are due to the symmetry breaking effects such as the cylindrical geometry and inhomogeneous electron diamagnetic drift. It is found that the magnitude of the difference (between maximum and minimum radial electric fields around O-point) is proportional to the averaged electron diamagnetic drift frequency inside magnetic islands and the square of the island width, but inversely proportional to the square root of the ion viscosity.
Accounting for electronic polarization in nonpolarizable force fields
Leontyev, Igor
The issues of electronic polarizability in molecular dynamics simulations are discussed. We argue that the charges of ionized groups in proteins, and charges of ions in conventional non-polarizable force fields such as CHARMM, AMBER, GROMOS, etc should be scaled by a factor about 0.7. Our model explains why a neglect of electronic solvation energy, which typically amounts to about a half of total solvation energy, in non-polarizable simulations with un-scaled charges can produce a correct result; however, the correct solvation energy of ions does not guarantee the correctness of ion-ion pair interactions in many non-polarizable simulations. The inclusion of electronic screening for charged moieties is shown to result in significant changes in protein dynamics and can give rise to new qualitative results compared with the traditional non-polarizable force field simulations. The model also explains the striking difference between the value of water dipole $\\mu$~3D reported in recent ab initio and experimental s...
Thermomechanical properties of graphene: valence force field model approach.
Lajevardipour, A; Neek-Amal, M; Peeters, F M
Using the valence force field model of Perebeinos and Tersoff (2009 Phys. Rev. B 79 241409(R)), different energy modes of suspended graphene subjected to tensile or compressive strain are studied. By carrying out Monte Carlo simulations it is found that: (i) only for small strains (|?| ? 0.02) is the total energy symmetrical in the strain, while it behaves completely differently beyond this threshold; (ii) the important energy contributions in stretching experiments are stretching, angle bending, an out-of-plane term, and a term that provides repulsion against ?-? misalignment; (iii) in compressing experiments the two latter terms increase rapidly, and beyond the buckling transition stretching and bending energies are found to be constant; (iv) from stretching-compressing simulations we calculated the Young's modulus at room temperature 350 ▒ 3.15 N m(-1 ), which is in good agreement with experimental results (340 ▒ 50 N m(-1 )) and with ab initio results (322-353) N m(-1 ); (v) molar heat capacity is estimated to be 24.64 J mol(-1 ) K(-1 ) which is comparable with the Dulong-Petit value, i.e. 24.94 J mol(-1) K(-1), and is almost independent of the strain; (vi) nonlinear scaling properties are obtained from height-height correlations at finite temperature; (vii) the used valence force field model results in a temperature independent bending modulus for graphene, and (viii) the Gr³neisen parameter is estimated to be 0.64. PMID:22475745
Development of force field parameters for molecular simulation of polylactide
McAliley, James H.; Bruce, David A.
Polylactide is a biodegradable polymer that is widely used for biomedical applications, and it is a replacement for some petroleum based polymers in applications that range from packaging to carpeting. Efforts to characterize and further enhance polylactide based systems using molecular simulations have to this point been hindered by the lack of accurate atomistic models for the polymer. Thus, we present force field parameters specifically suited for molecular modeling of PLA. The model, which we refer to as PLAFF3, is based on a combination of the OPLS and CHARMM force fields, with modifications to bonded and nonbonded parameters. Dihedral angle parameters were adjusted to reproduce DFT data using newly developed CMAP dihedral cross terms, and the model was further adjusted to reproduce experimentally resolved crystal structure conformations, melt density, volume expansivity, and the glass transition temperature of PLA. We recommend the use of PLAFF3 in modeling PLA in its crystalline or amorphous states and have provided the necessary input files required for the publicly available molecular dynamics code GROMACS. PMID:22180734
Electric toothbrushes induce electric current in fixed dental appliances by creating magnetic fields.
Kameda, Takashi; Ohkuma, Kazuo; Ishii, Nozomu; Sano, Natsuki; Ogura, Hideo; Terada, Kazuto
Magnetic fields can represent a health problem, especially low frequency electromagnetic fields sometimes induced by electric current in metallic objects worn or used in or on the body (as opposed to high frequency electromagnetic fields that produce heat). Electric toothbrushes are widely used because of their convenience, but the electric motors that power them may produce electromagnetic waves. In this study, we showed that electric toothbrushes generate low frequency (1-2000 Hz) magnetic fields and induce electric current in dental appliances (e. g. orthodontic and prosthetic appliances and dental implants). Current induced by electric toothbrushes might be dependent on the quantity and types of metals used, and the shape of the appliances. Furthermore, these induced currents in dental appliances could impact upon human oral health, producing pain and discomfort. PMID:23037851
Recent measurements of middle atmospheric electric fields and related parameters
NASA Astrophysics Data System (ADS)
Zadorozhny, A. M.; Tyutin, A. A.; Bragin, O. A.; Kikhtenko, V. N.
In 1989, two series of rocket measurements were carried out to investigate middle atmosphere electric fields. The measurements were taken both in the Northern Hemisphere on Heiss Island (80 deg 37 N and 58 deg 03 min E) and in the Southern Hemisphere in the Indian Ocean (40-60 deg S and approx. 45 deg E) on board the research vessel 'Akademik Shirshov'. Along with the vertical electric fields, aerosol content and positive ion density were also measured. Some of the rocket launches were made during the extremely strong solar proton events (SPE) of October 1989. The experiments showed the strong variability of the electric fields in the middle atmosphere at polar and high middle latitudes. In all the measurements the maximum of the vertical electric field height profile in the lower mesosphere was observed to be more than approx. 1 V/m. The electric field strength and the field direction at maximum varied considerably among the launches. A maximum value of +12 V/m was detected at a height of about 58 km at 58 deg 30 mins on 21 October 1989 during the SPE. The simultaneous measurements of the electric field strength, positive ion density and aerosols point out both an ion-aerosol interaction and a connection between the mesospheric electric fields and aerosol content.
Electric field measurements during the MAC/EPSILON campaign
NASA Technical Reports Server (NTRS)
Croskey, C. L.; Hale, L. C.; Mitchell, J. D.; Schmidlin, F. J.; Hoppe, U.-P.
The MAC/EPSILON observational campaign in northern Norway involved the taking of three-axis electric field measurements of the middle atmosphere by means of five rocketborne payloads during October and November, 1987. Simultaneous horizontal electric field measurements made by two of the rocket flights were in general agreement in their limited overlap region. The more extensive horizontal E-field measurements exhibited a decreasing mapping function with decreasing altitude, thereby indicating the presence of fields from a local auroral patch. Small-scale variations in the horizontal fields of the lights were similar to observed wavelike variations in the neutral wind field.
Electromagnetic self-forces and generalized Killing fields
Abraham I. Harte
Building upon previous results in scalar field theory, a formalism is developed that uses generalized Killing fields to understand the behavior of extended charges interacting with their own electromagnetic fields. New notions of effective linear and angular momenta are identified, and their evolution equations are derived exactly in arbitrary (but fixed) curved spacetimes. A slightly modified form of the Detweiler-Whiting axiom that a charge's motion should only be influenced by the so-called "regular" component of its self-field is shown to follow very easily. It is exact in some interesting cases, and approximate in most others. Explicit equations describing the center-of-mass motion, spin angular momentum, and changes in mass of a small charge are also derived in a particular limit. The chosen approximations -- although standard -- incorporate dipole and spin forces that do not appear in the traditional Abraham-Lorentz-Dirac or Dewitt-Brehme equations. They have, however, been previously identified in the test body limit.
Unified Field Theory and Force Formulas of Interactions
NASA Astrophysics Data System (ADS)
Ma, Tian; Wang, Shouhong
The main objective of this talk is to drive a unified field model coupling four interactions, based on the principle of interaction dynamics (PID) and the principle of representation invariance (PID). Intuitively, PID takes the variation of the action functional under energy-momentum conservation constraint. PRI requires that physical laws be independent of representations of the gauge groups. One important outcome of this unified field model is a natural duality between the interacting fields (g, A, W^a, S^k), corresponding to graviton, photon, intermediate vector bosons W^▒ and Z and gluons, and the adjoint bosonic fields (?,, ^aw, ^ks). This duality predicts two Higgs particles of similar mass with one due to weak interaction and the other due to strong interaction. PID and PRI can be applied directly to individual interactions, leading to 1) modified Einstein equations, giving rise to a unified theory for dark matter and dark energy, 2) three levels of strong interaction potentials for quark, nucleon/hadron, and atom respectively, and 3) a weak interaction potential. These potential/force formulas offer a clear mechanism for both quark confinement and asymptotic freedom.
Magnetic Control of Electric-Field Domains in Semiconductor Superlattices
T. Schmidt; A. G. M. Jansen; R. J. Haug; K. V. Klitzing; K. Eberl
Applying magnetic fields up to B = 29 T, we investigate the formation of electric-field domains in Landau-quantized semiconductor superlattices. Surprisingly, the electric-field distribution remains determined by the subband spacing rather than by the cyclotron energy. At the domain boundary, however, strong inter-Landau-level tunneling occurs, which leads to a magnetically tunable number of extra resonances in the current-voltage curve. In
Electric Field-Mediated Processing of Polymers. Appendix 1
NASA Technical Reports Server (NTRS)
Wnek, G. E.; Bowlin, G. L.; Haas, T. W.
Significant opportunities exist for the processing of polymers (homopolymers and blends) using electric fields. We suggest that a broad range of properties can be achieved using a relatively small number of polymers, with electric fields providing the ability to tailor properties via the control of shape, morphology, and orientation. Specific attention is given to electrospinning, but we note that electroaerosol formation and field-modulated film casting represent additional processing options.
CRRES electric field power spectra and radial diffusion coefficients
D. H. Brautigam; G. P. Ginet; J. M. Albert; J. R. Wygant; D. E. Rowland; A. Ling; J. Bass
Combined Release and Radiation Effects Satellite (CRRES) Electric Field Instrument (EFI) data are used to determine the electric field power spectral density as a function of L and Kp over the frequency range 0.2 to 15.9 mHz. The power at each frequency is fit to the function P(L, Kp) = a Lb exp(cKp). Assuming a purely electrostatic field and making
High electric field packaging of silicon carbide photoconductive switches
C. Hettler; C. James; J. Dickens
Photoconductive semiconductor switches (PCSS) made from semi-insulating (SI) silicon carbide (SiC) are promising candidates for high frequency, high voltage, and low jitter switching. However, existing switches fail at electric fields considerably lower than the intrinsic dielectric strength of SiC (3 MV\\/cm) because of the field enhancements near the electrode-semiconductor interfaces. Various geometries were identified which could reduce the electric field
Internal probe array for the measurement of radial electric field
NASA Astrophysics Data System (ADS)
Andreason, Samuel P.; Slough, John T.
A multipoint radial electric field probe, paired with a Langmuir triple probe has been operated on a RF sustained field reversed configuration. Langmuir probe measurements confirm the approximation that Te(r)śconstant, allowing for simpler interpretation of the floating potential, and the probe array was implemented with nonemissive, floating probes. Due to the large antenna potentials (multi-kilovolts), the electric field probe was designed taking advantage of the development of inexpensive, multichannel, portable digital storage oscilloscopes. This also made it possible to operate the internal plasma diagnostic with a minimum of electrical design work and fewer calibration issues. The diagnostic was electrically isolated (floated) separate from experiment ground, and has been used to measure transient electric fields as large as 2.5 kV/m.
The creation of electric fields within plasma shock fronts
NASA Astrophysics Data System (ADS)
Wilks, S. C.; Amendt, P. A.; Haines, M. G.; Kruer, W. L.; Li, C. K.; Petrasso, R. D.
The propagation of shocks in high temperature plasmas is, in general, a well understood phenomena in high energy density science. Although the creation of a self-consistent electric field that develops at the shock front was predicted decades ago, it has not been investigated in detail, since in most cases of interest this effect was deemed small and therefore is always ignored in hydrodynamic calculations of shocks. However, certain parameter regimes exist in which the strength of this electric field is sufficiently large that it can affect the shock width, owing to excessive diffusion of electrons across the shock interface. For example, in strong shocks a precursor electric field ahead of the shock is observed which can then give rise to a precursor electric shock. We present a number of examples from a variety of parameter regimes, and then compare theoretical predictions with results obtained from collisional particle-based plasma simulations (LSP) that include this self-consistent electric field.
Refinement of the AMBER Force Field for Nucleic Acids: Improving the Description of ?\\/ ? Conformers
Alberto Pķrez; Ivßn Marchßn; Daniel Svozil; Jiri Sponer; Thomas E. Cheatham; Charles A. Laughton; Modesto Orozco
We present here the parmbsc0 force field, a refinement of the AMBER parm99 force field, where emphasis has been made on the correct representation of the ?\\/? concerted rotation in nucleic acids (NAs). The modified force field corrects overpopulations of the ?\\/?=(g+,t) backbone that were seen in long (more than 10ns) simulations with previous AMBER parameter sets (parm94-99). The force
Effect of induced electric field on migration of a charged porous particle.
Gopmandal, Partha P; Bhattacharyya, S; Barman, Bhanuman
The effect of ambient fluid flow on a charged porous spherical particle suspended in an aqueous medium is analyzed. The porous particle is ion permeable and fluid penetrable. The induced electric field due to the polarization of the particle's electric double layer and counterion condensation leads to a hindrance effect on particle migration by producing an electric force. The influence of this retardation force on the hydrodynamics of the particle is studied through the Nernst-Planck equations, which are coupled with the Stokes-Brinkman equation. The interactions of the double-layer polarization, shielding effect, electroosmosis of unbalanced ions and fluid convection are analyzed. The settling velocity and fluid collection efficiency of the charged aggregate is determined. We have studied the electrokinetics for a wide range of fixed charge density and permeability of the particle with no assumption made on the thickness of the double layer relative to the dimension of the particle. PMID:25374308
Variations of electric field and electric resistivity of air caused by dust motion
NASA Astrophysics Data System (ADS)
Seran, E.; Godefroy, M.; Renno, N.; Elliott, H.
report results of a field campaign conducted in the Nevada desert with a suite of electric field instruments consisting of a field mill (FM) and a short dipole antenna (SDA). Furthermore, we show that a combination of the measurements of these two instruments allows the estimation of the electric resistivity of air, an important quantity that is extremely difficult to measure near the Earth's surface. The electric resistivity of air is found to vary between 1.5 Ę 1013 and 6 Ę 1013 ? m and to correlate with changes in electric field. Vertical DC electric fields with amplitudes up to 6 kV m-1 were observed to correspond to clouds of dust blowing through the measurement site. Enhanced DC and AC electric fields are measured during periods when horizontal wind speed exceeds 7 m s-1, or around twice the background value. We suggest that low-frequency emissions, below ~200 Hz, are generated by the motion of electrically charged particles in the vicinity of the SDA electrode and propose a simple model to reproduce the observed spectra. According to this model, the spectral response is controlled by three parameters, (i) the speed of the charged particles, (ii) the charge concentration, and (iii) the minimum distance between the particle and the electrode. In order to explain the electric fields measured with the FM sensors at different heights, we developed a multilayer model that relates the electric field to the charge distribution. For example, a nonlinear variation of the electric field observed by the FM sensors below 50 cm is simulated by a near-surface layer of tens of centimeters that is filled with electrically charged particles that carry a predominantly negative charge in the vicinity of the soil. The charge concentration inside this layer is estimated to vary between 1012 and 5 Ę 1013 electrons m-3.
The effect of an external electric field on the structure of liquid water using molecular dynamics simulations
NASA Astrophysics Data System (ADS)
Jung, Dong Hyun; Yang, Jung Hwan; Jhon, Mu Shik
Using molecular dynamics simulations with the rigid TIP4P water model, we have analyzed the structural change of liquid water induced by an external electric field. The temperature was controlled with a Nosķ-Hoover thermostat. In this paper, we report the acquisition of liquid water with the enhanced structural regularity by applying an electric field. From the simulations under various strengths of the electric field, we can see that the threshold for the significant structural change is thought to be between 0.2 and 0.15 V/┼. When the number of six-membered rings is increased by the external electric field, so that water is forced to have structural regularity, we calculate the diffusion coefficients and discover that water we make in the simulations is not solid but still liquid under the electric field.
The report gives results of a preliminary screening study of the technical and economic feasibility of the on-site production of commodities (liquid propellant and gases) and electricity to support space shuttle launch activities at Vandenberg Air Force Base (VAFB). Both commerci...
Indirect vector control of electric drives employing induction motor with forced dynamics
Jan VITTEK; Juraj ALTUS; Jozef BUDAY; M. Rapsik
The contribution presents an extension of indirect vector control of electric drives employing induction motors to 'forced dynamic control'. This control method offers an accurate realization of dynamic response profiles, which can be selected for given application by the user. The developed systems operate with shaft position encoder or shaft sensorless, when only the stator currents are measured, the applied
Shape memory alloy coil-shaped clamp for enhanced normal force in electrical connectors
Igor Kulisic; Gary L. Gray; S. E. Mohney
Many electrical connectors experience a significant degradation in performance due to fretting corrosion, which is particularly problematic when the connector undergoes vibration. Fretting corrosion can be reduced or eliminated if the relative motion between the pin and receptacle is reduced or eliminated. One practical means of reducing the relative motion is to increase the normal force between the pin and
Using evoked EMG as a synthetic force sensor of isometric electrically stimulated muscle
Abbas Erfanian; Howard Jay Chizeck; Reza M. Hashemi
A method for the estimation of the force generated by electrically stimulated muscle during isometric contraction is developed here. It is based upon measurements of the evoked electromyogram (EMG) [EEMG] signal. Muscle stimulation is provided to the quadriceps muscle of a paralyzed human subject using percutaneous intramuscular electrodes, and EEMG signals are collected using surface electrodes. Through the use of
Electric-field-induced structure and optical properties of electrorheological fluids with attapulgite nanorods
NASA Astrophysics Data System (ADS)
Jin, Ting; Cheng, Yuchuan; He, Ru; Luo, Yuxia; Jiang, Meng; Chen, Chao; Xu, Gaojie
Attapulgite (ATP) is a type of crystalloid hydrous magnesium-aluminum silicate mineral with natural one-dimensional (1D) fibrous morphology. In this study, the authors investigated the optical and mechanical performances of ATP nanorods in silicone oil under an electric field. It was observed that the optical transmittance of ATP suspensions decreased rapidly under the low electric field, using ultraviolet-visible (UV-Vis) spectroscopy. The results of optical microscopy and scanning electron microscopy (SEM) indicated that the electromigration of ATP nanorods was the major cause of such an aberrant optical phenomenon. Further, the electrorheological (ER) response of the samples was measured by the height-controlled method. The change trend of the normal force was illustrated by the dynamic assembly behavior of ATP in the applied electric field. This work provided intuitive evidence for an in-depth understanding of the mechanism of ER fluids containing 1D dielectric materials.
The gel edge electric field gradients in denaturing polyacrylamide gel electrophoresis.
Desruisseaux, C; Slater, G W; Drouin, G
It has previously been shown that zones of higher electric field form close to the loading end of the gel during denaturing polyacrylamide gel electrophoresis. Here we show that the field can reach up to three times its normal mean value a few cm in front of the loading wells when 44.5 mM Tris-44.5 mM boric acid-1 mM EDTA is used as the gel buffer. We also demonstrate that this electric field gradient is mostly due to the difference in ion transference numbers at the gel/buffer interface caused by the high viscosity of the urea solution contained in the gel. This field gradient leads to increased band widths and forces us to redefine both the electrophoretic mobility and the mean field intensity. We discuss some methods that can be used to minimize the effects of this gradient. PMID:9629888
The hydrogen atom in plasmas with an external electric field
Bahar, M. K. [Department of Physics, Karamano?lu Mehmetbey University, 70100 Karaman (Turkey); Soylu, A. [Department of Physics, Ni?de University, 51240 Ni?de (Turkey)
We numerically solve the Schr÷dinger equation, using a more general exponential cosine screened Coulomb (MGECSC) potential with an electric field, in order to investigate the screening and weak external electric field effects on the hydrogen atom in plasmas. The MGECSC potential is examined for four different cases, corresponding to different screening parameters of the potential and the external electric field. The influences of the different screening parameters and the weak external electric field on the energy eigenvalues are determined by solving the corresponding equations using the asymptotic iteration method (AIM). It is found that the corresponding energy values shift when a weak external electric field is applied to the hydrogen atom in a plasma. This study shows that a more general exponential cosine screened Coulomb potential allows the influence of an applied, weak, external electric field on the hydrogen atom to be investigated in detail, for both Debye and quantum plasmas simultaneously. This suggests that such a potential would be useful in modeling similar effects in other applications of plasma physics, and that AIM is an appropriate method for solving the Schr÷dinger equation, the solution of which becomes more complex due to the use of the MGECSC potential with an applied external electric field.
Electric Field Induced Selective Disordering in Lamellar Block Copolymers
Ruppel, Markus A [ORNL; Pester, Christian W [ORNL; Langner, Karol M [Leiden Institute of Chemistry, Leiden University, The Netherlands; Sevink, Geert [Leiden Institute of Chemistry, Leiden University, The Netherlands; Schoberth, Heiko [University of Bayreuth; Schmidt, Kristin [ORNL; Urban, Volker S [ORNL; Mays, Jimmy [ORNL; Boker, Alexander [RWTH Aachen University
External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the orderdisorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the orderdisorder transition and well below it.
Molecular-scale measurements of electric fields at electrochemical interfaces.
Hayden, Carl C.; Farrow, Roger L.
Spatially resolved measurements of electric fields at electrochemical interfaces would be a critical step toward further understanding and modeling the detailed structure of electric double layers. The goal of this project was to perform proof-of-principle experiments to demonstrate the use of field-sensitive dyes for optical measurements of fields in electrochemical systems. A confocal microscope was developed that provides sensitive detection of the lifetime and high resolution spectra of excited fluorescence for dyes tethered to electrically conductive surfaces. Excited state lifetimes for the dyes were measured and found to be relatively unquenched when linked to indium tin oxide, but strongly quenched on gold surfaces. However, our fluorescence detection is sufficiently sensitive to measure spectra of submonolayer dye coatings even when the fluorescence was strongly quenched. Further work to create dye labeled interfaces on flat, uniform and durable substrates is necessary to make electric field measurements at interfaces using field sensitive dyes.
A fundamental limit on electric fields in air
NASA Astrophysics Data System (ADS)
Dwyer, J. R.
By modifying the avalanche mode of runaway breakdown to include positive feedback from gamma-rays and positrons, it is found that enormous bursts of energetic radiation can be produced in strong electric fields in air, with peak fluxes up to one billion times greater than from conventional models. These bursts generate so many runaway electrons that the electric field is very rapidly discharged, resulting in a fundamental upper limit on the electric field strength achievable in air. This limit has important implications for the electrification of thunderstorms and the production of lightning.
High Dynamic Range Electric Field Sensor for Electromagnetic Pulse Detection
Lin, Che-Yun; Lee, Beom Suk; Zhang, Xingyu; Chen, Ray T
We design a high dynamic range electric field sensor based on domain inverted electro-optic (E-O) polymer Y-fed directional coupler for electromagnetic wave detection. This electrode-less, all optical, wideband electrical field sensor is fabricated using standard processing for E-O polymer photonic devices. Experimental results demonstrate effective detection of electric field from 16.7V/m to 750KV/m at a frequency of 1GHz, and spurious free measurement range of 70dB.
The use of electric fields in tissue engineering
The use of electric fields for measuring cell and tissue properties has a long history. However, the exploration of the use of electric fields in tissue engineering is only very recent. A review is given of the various methods by which electric fields may be used in tissue engineering, concentrating on the assembly of artificial tissues from its component cells using electrokinetics. A comparison is made of electrokinetic techniques with other physical cell manipulation techniques which can be used in the construction of artificial tissues. PMID:19279709
Application of polarizable ellipsoidal force field model to pnicogen bonds.
Liu, Fang; Du, Likai; Gao, Jun; Wang, Lili; Song, Bo; Liu, Chengbu
Noncovalent interactions, such as hydrogen bonds and halogen bonds, are frequently used in drug designing and crystal engineering. Recently, a novel noncovalent pnicogen bonds have been identified as an important driving force in crystal structures with similar bonding mechanisms as hydrogen bond and halogen bond. Although the pnicogen bond is highly anisotropic, the pnicogen bond angles range from 160░ to 180░ due to the complicated substituent effects. To understand the anisotropic characters of pnicogen bond, a modification of the polarizable ellipsoidal force field (PEff) model previously used to define halogen bonds was proposed in this work. The potential energy surfaces (PESs) of mono- and polysubstituted PH3 -NH3 complexes were calculated at CCSD(T), MP2, and density functional theory levels and were used to examine the modified PEff model. The results indicate that the modified PEff model can precisely characterize pnicogen bond. The root mean squared error of PES obtained with PEff model is less than 0.5 kcal/mol, compared with MP2 results. In addition, the modified PEff model may be applied to other noncovalent bond interactions, which is important to understand the role of intermolecular interactions in the self-assembly structures. PMID:25565043
Dipolar Radicals in Crossed Electric and Magnetic Fields
John L. Bohn; Goulven Quķmķner
Paramagnetic, dipolar Hund's case-a radicals are considered in the presence of arbitrary, non-collinear combinations of electric and magnetic fields. The field-dependent part of the Hamiltonian is found to be exactly diagonalizable, and described by quantum numbers given by the projection of the molecule's total angular momentum along a space-fixed axis that is determined by both the fields and the electric and magnetic dipole moments of the molecule. In cases of strong fields, this procedure identifies a set of quantum numbers for the molecule in crossed fields. We dub this set a "Hund's case-X" basis.
The source of the electric field in the nightside magnetosphere
NASA Technical Reports Server (NTRS)
Stern, D. P.
In the open magnetosphere model magnetic field lines from the polar caps connect to the interplanetary magnetic field and conduct an electric field from interplanetary space to the polar ionosphere. By examining the magnetic flux involved it is concluded that only slightly more than half of the magnetic flux in the polar caps belongs to open field lines and that such field lines enter or leave the magnetosphere through narrow elongated windows stretching the tail. These window regions are identified with the tail's boundary region and shift their position with changes in the interplanetary magnetic field, in particular when a change of interplanetary magnetic sector occurs. The circuit providing electric current in the magnetopause and the plasma sheet is extended across those windows; thus energy is drained from the interplanetary electric field and an electric potential drop is produced across the plasma sheet. The polar cap receives its electric field from interplanetary space on the day side from open magnetic field lines and on the night side from closed field lines leading to the plasma sheet. The theory described provides improved understanding of magnetic flux bookkeeping, of the origin of Birkeland currents, and of the boundary layer of the geomagnetic tail.
Atomistic simulations of electric field effects on the Young's modulus of metal nanowires.
Ben, Xue; Park, Harold S
We present a computational, atomistic study of electric field effects on the Young's modulus of metal nanowires. The simulations are electromechanically coupled, where the mechanical forces on the atoms are obtained from realistic embedded atom method potentials, and where the electrostatic forces on the atoms are obtained using a point dipole electrostatic model that is modified to account for the different polarizability and bonding environment of surface atoms. By considering three different nanowire axial orientations (left angle bracket 100 right angle bracket, left angle bracket 110 right angle bracket and right angle bracket 111 right angle bracket) of varying cross sectional sizes and aspect ratios, we find that the Young's modulus of the nanowires differs from that predicted for the purely mechanical case due to the elimination of nonlinear elastic stiffening or softening effects due to the electric field-induced positive relaxation strain relative to the relaxed mechanical configuration. We further find that left angle bracket 100 right angle bracket nanowires are most sensitive to the applied electric field, with Young's moduli that can be increased more than 20% with increasing aspect ratio. Finally, while the orientation of the transverse surfaces does impact the Young's modulus of the nanowires under applied electric field, the key factor controlling the magnitude of the stiffness change of the nanowires is the distance between atomic planes along the axial direction of the nanowire bulk. PMID:25337694
Atomistic simulations of electric field effects on the Young?s modulus of metal nanowires
NASA Astrophysics Data System (ADS)
Ben, Xue; Park, Harold S.
We present a computational, atomistic study of electric field effects on the Young?s modulus of metal nanowires. The simulations are electromechanically coupled, where the mechanical forces on the atoms are obtained from realistic embedded atom method potentials, and where the electrostatic forces on the atoms are obtained using a point dipole electrostatic model that is modified to account for the different polarizability and bonding environment of surface atoms. By considering three different nanowire axial orientations (< 100> , < 110> and < 111> ) of varying cross sectional sizes and aspect ratios, we find that the Young?s modulus of the nanowires differs from that predicted for the purely mechanical case due to the elimination of nonlinear elastic stiffening or softening effects due to the electric field-induced positive relaxation strain relative to the relaxed mechanical configuration. We further find that < 100> nanowires are most sensitive to the applied electric field, with Young?s moduli that can be increased more than 20% with increasing aspect ratio. Finally, while the orientation of the transverse surfaces does impact the Young?s modulus of the nanowires under applied electric field, the key factor controlling the magnitude of the stiffness change of the nanowires is the distance between atomic planes along the axial direction of the nanowire bulk.
Electromagnetic Forces and Fields in a Rotating Reference Frame
Paul N. Arendt, Jr
Maxwell's equations and the equations governing charged particle dynamics are presented for a rotating coordinate system with the global time coordinate of an observer on the rotational axis. Special care is taken in defining the relevant entities in these equations. Ambiguities in the definitions of the electromagnetic fields are pointed out, and in fact are shown to be essential in such a system of coordinates. The Lorentz force is found to have an extra term in this frame, which has its origins in relativistic mass. A related term in the energy equation, which allows inertia to be gained even during strict corotation, suggests ways existing pulsar magnetosphere models may be modified to match observed `braking indices' more closely.
Molecular Dynamics Simulation of Nitrobenzene Dioxygenase Using AMBER Force Field
Molecular dynamics simulation of the oxygenase component of nitrobenzene dioxygenase (NBDO) system, a member of the naphthalene family of Rieske nonheme iron dioxygenases, has been carried out using the AMBER force field combined with a new set of parameters for the description of the mononuclear nonheme iron center and iron¢sulfur Rieske cluster. Simulation results provide information on the structure and dynamics of nitrobenzene dioxygenase in an aqueous environment and shed light on specific interactions that occur in its catalytic center. The results suggest that the architecture of the active site is stabilized by key hydrogen bonds, and Asn258 positions the substrate for oxidation. Analysis of protein¢water interactions reveal the presence of a network of solvent molecules at the entrance to the active site, which could be of potential catalytic importance. PMID:24955078
Development of the CHARMM Force Field for Lipids
Pastor, R.W.; MacKerell, A.D.
The development of the CHARMM additive all-atom lipid force field (FF) is traced from the early 1990Æs 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. PMID:21760975
On the Use of Quartic Force Fields in Variational Calculations
NASA Technical Reports Server (NTRS)
Fortenberry, Ryan C.; Huang, Xinchuan; Yachmenev, Andrey; Thiel, Walter; Lee, Timothy J.
The use of quartic force fields (QFFs) has been shown to be one of the most effective ways to efficiently compute vibrational frequencies for small molecules. In this paper we outline and discuss how the simple-internal or bond-length bond-angle (BLBA) coordinates can be transformed into Morse-cosine(-sine) coordinates which produce potential energy surfaces from QFFs that possess proper limiting behavior and can effectively describe the vibrational (or rovibrational) energy levels of an arbitrary molecular system. We investigate parameter scaling in the Morse coordinate, symmetry considerations, and examples of transformed QFFs making use of the MULTIMODE, TROVE, and VTET variational vibrational methods. Cases are referenced where variational computations coupled with transformed QFFs produce accuracies compared to experiment for fundamental frequencies on the order of 5 cm(exp -1) and often as good as 1 cm(exp -1).
The Eccentric Frame Decomposition of Central Force Fields
Jared M. Maruskin; Daniel J. Scheeres; Fred C. Adams; Anthony M. Bloch
The rosette-shaped motion of a particle in a central force field is known to be classically solvable by quadratures. We present a new approach of describing and characterizing such motion based on the eccentricity vector of the two body problem. In general, this vector is not an integral of motion. However, the orbital motion, when viewed from the nonuniformly rotating frame defined by the orientation of the eccentricity vector, can be solved analytically and will either be a closed periodic circulation or libration. The motion with respect to inertial space is then given by integrating the argument of periapsis with respect to time. Finally we will apply the decomposition to a modern central potential, the spherical Hernquist-Newton potential, which models dark matter halos of galaxies with central black holes.
Vertical Electric Field Measurements with Copper Plates by Sounding Balloon
NASA Astrophysics Data System (ADS)
Wen, Shao-Chun; Chiu, Cheng-Hsiu; Bing-Chih Chen, Alfred; Hsu, Rue-Ron; Su, Han-Tzong
The vertical electric field plays an important role in driving the circulation of the global electric circuit, and crucial to the formation of the transient luminous events (TLEs). The in-situ measurement of the electric field in the upper atmosphere, especially from cloud top to the bottom of the ionosphere is very challenging but essential. Limited by the flight vehicle, the measurements of the electric field in and above cloud, especiall thundercloud, is rare up to now. A light-weight electric field meter was developed independently and sent to 30 km height by small meteorological balloons successfully. Other than the existing long-spaced, spherical probe design, an improved electric field meter has been built and tested carefully. A new circuit with ultra high input impedance and a high voltage amplifier is implemented to reduce the AC noise induced by the voltage divider. Two copper plates are used to replace the double spherical probes which is spaced by a long fiberglass boom. The in-lab calibration and tests show that this new model is superior to the existing design and very sensitive to the variation of the DC electric field. In this poster, the design and the in-lab tests will be presented, and preliminary results of the flight experiments are also discussed.
Non-bonded force field for the interaction between metals and organic molecules
Mueser, Martin
Non-bonded force field for the interaction between metals and organic molecules: A case study to parameterize the non-bonded force field for the interaction between organic molecules and metal surfaces. After reaching a local equilibration, molecules near the metal surfaces are isolated and the forces
Field measurements of interactions between furnaces and forced air distribution systems
LBNL 40587 Field measurements of interactions between furnaces and forced air distribution systems Vol. 104 Part 1 Field measurements of interactions between furnaces and forced air distribution performance of these furnaces and their interactions with their forced-air distribution systems
Anti-slip re-adhesion control of electric motor coach based on force control using disturbance observer
Kiyoshi Ohishi; Yasuaki Ogawa; Ichiro Miyashita; Shinobu Yasukawa
In electric motor coaches, when the adhesion force coefficient between rail and driving wheel decreases suddenly, the electric motor coach has slip phenomena. In order to overcome this problem, the authors have already proposed the anti-slip control system based on ordinary disturbance observer. However, on condition of large variation of adhesion force coefficient, it is sometimes difficult for this control
Comprehensive Analysis of Human Cells Motion under an Irrotational AC Electric Field in an Electro-Microfluidic Chip
Kermarrec, Frķdķrique; Gidrol, Xavier; Peyrade, David
AC electrokinetics is a versatile tool for contact-less manipulation or characterization of cells and has been widely used for separation based on genotype translation to electrical phenotypes. Cells responses to an AC electric field result in a complex combination of electrokinetic phenomena, mainly dielectrophoresis and electrohydrodynamic forces. Human cells behaviors to AC electrokinetics remain unclear over a large frequency spectrum as illustrated by the self-rotation effect observed recently. We here report and analyze human cells behaviors in different conditions of medium conductivity, electric field frequency and magnitude. We also observe the self-rotation of human cells, in the absence of a rotational electric field. Based on an analytical competitive model of electrokinetic forces, we propose an explanation of the cell self-rotation. These experimental results, coupled with our model, lead to the exploitation of the cell behaviors to measure the intrinsic dielectric properties of JURKAT, HEK and PC3 human cell lines. PMID:24736275
Electric-field-tunable electronic properties of graphene quantum dots
R. B. Chen; C. P. Chang; M. F. Lin
The tight-binding method is employed to investigate the electronic properties of a square graphene quantum dot subject to an in-plane electric field (F). The electronic properties are strongly modified by tuning the field strength or altering the field direction. F will change state energies, alter energy gaps, and induce energy gap modulations. State energies show oscillatory behavior with the change
DC-probes for electric field distribution measurements
S. P. Hornfeldt
It is desired to measure the external electric field distribution of components for high voltage DC transmission. This information is useful in the development of such components. By measuring the field under a variety of ambient conditions, the performance of both the external and the internal insulation of the component can be assessed. The principles of how DC fields can
Robotic Electrolocation: Active Underwater Target Localization with Electric Fields
Hartmann, Mitra J. Z.
filter and refined with each measurement. I. INTRODUCTION The ability of some aquatic animals to sense electric fields was discovered in the late 1950s [8] and is therefore one of the most recently discovered, such as the platypus, are able to sense weak bioelectric fields emitted by aquatic prey and use these fields to locate
Probing electric fields in proteins in solution by NMR spectroscopy.
Hass, Mathias A S; Jensen, Malene Ringkj°bing; Led, Jens J
Electric fields generated in native proteins affect almost every aspect of protein function. We present a method that probes changes in the electric field at specific locations within a protein. The method utilizes the dependence of the amide (1)H and (15)N NMR chemical shifts on electric charges in proteins. Charges were introduced at different positions in the blue copper protein plastocyanin, by protonation of side chains or by substitution of the metal ion. It is found that the associated chemical shift perturbations (CSPs) stem mainly from long-range electric field effects caused by the change in the electric charge. It is demonstrated that the CSPs can be used to estimate the dielectric constant at different locations in the protein, estimate the nuclear shielding polarizability, or position charges in proteins. PMID:18214953
Effects of Electric Current and Field on the Behavior of Metallic Materials
NASA Astrophysics Data System (ADS)
Cao, Wei-Di.
The effects of electric current and field on the behavior of metallic materials has been studied in terms of the drop in flow stress caused by an electric current pulse and the changes in superplastic behavior and phase transformation kinetics resulting from applying an external electric field. The experimental procedure employed previously by Conrad et al to investigate the electroplastic effect was modified to facilitate the elimination of side effects from the observed drop in flow stress due to a current pulse, to determine the electron wind force on dislocations and to establish the effect of electric current on each of the thermal activation parameters in the Arrhenius strain rate equation. The experimental values of the electron wind force were in general accord with those predicted by available theories for FCC metals, but a much higher value was obtained for BCC Nb. The measured electron wind force decreased with increasing stacking fault energy and in turn with decreasing width of extended dislocations in FCC metals. To fully evaluate the experimental values of the electron wind force, further improvement of present theories is necessary which take into account the band structure and Fermi surface geometry of individual metals. The electric current reduced the activation volume and free energy, most likely by changing the force-distance curve of the thermal activation process. It is concluded that the observed increase in the pre-exponential term produced by current pulse arises partly from the increase in the density of mobile dislocations and the area swept out per successful thermal fluctation, but mostly results from the difference between the static and dynamic responses of the test system to the pulsed load drop. An external electric field reduced the flow stress and work hardening, significantly suppressed the cavitation and retarded strain-enhanced grain growth of 7475 Al during superplastic deformation. In addition, the application of an external electric field during the heat treatment of two steels accelerated austenization, increased hardenability and retarded the dissociation of quenched martensite during tempering. Possible mechanism for these effects are discussed.
Progress in edge measurements of ion temperature and radial electric field
Hartmut Ehmler; Yuri Turkin; Kent McCormick; Matthias Reich; Elisabeth Wolfrum
The determination of plasma profiles at the edge is usually difficult due to limited spatial resolution and detection efficiency. Progress has been achieved with a narrow high-energy Lithium beam employed for charge-exchange spectroscopy. Impurity density, ion temperature and poloidal rotation are measured for C^6+ and C^5+. The radial electric field is derived from the radial force balance equation. Beam emission
Electric-field-induced fatigue crack growth in ferroelectric ceramics
Bin Liu; Daining Fang; Keh-Chih Hwang
The experimental results obtained in this investigation shows that the electric-field-induced fatigue displays distinct characters under different magnitudes of electric loading. It seems that there exists a transition of fatigue cracking from the micro-crack nucleation and growth to the main crack growth. The crack growth rate is nonlinearly related to the cyclic electric load. Similar to chemical fatigue, there exists
Poloidal Rotation and Radial Electric Field Measurements in TFTR
NASA Astrophysics Data System (ADS)
Bell, R. E.; Synakowski, E. J.; Ernst, D. R.; Leblanc, B. P.; Zarnstorff, M. C.; Levinton, F. M.
Measured impurity poloidal rotation, v_?, in TFTR reversed shear plasmas has been shown to differ significantly from neoclassically predicted values of v_?.(R. E. Bell, F. M. Levinton, S. H. Batha, et al.), Phys. Rev. Lett., to be published The core v_? is found to be offset in the ion diamagnetic direction, with respect to neoclassical v_?, yielding a positive core radial electric field, E_r. Er is determined spectroscopically using the radial force balance equation, E_r=nablap/(eZn)+v_?B_?-v_?B_?. A similar offset is found for v_? in TFTR supershot plasmas. The sign of v_? and in some cases the sign of Er are reversed compared to neoclassical predictions. For supershot plasmas with balanced beam injection, the core Er was also positive and dominated by the positive -v_?B_? term. Dynamic changes in v_? and Er were observed during pellet injection, helium gas puffing, and changes in the direction of neutral beam injection. The magnitude of v_? is found to vary with energy confinement time. L-mode plasmas exhibit little poloidal rotation.
Electric field effect in ultrathin zigzag graphene nanoribbons
NASA Astrophysics Data System (ADS)
Zhang, Wen-Xing; Liu, Yun-Xiao; Tian, Hua; Xu, Jun-Wei; Feng, Lin
The electric field effect in ultrathin zigzag graphene nanoribbons containing only three or four zigzag carbon chains is studied by first-principles calculations, and the change of conducting mechanism is observed with increasing in-plane electric field perpendicular to the ribbon. Wider zigzag graphene nanoribbons have been predicted to be spin-splitted for both valence band maximum (VBM) and conduction band minimum (CBM) with an applied electric field and become half-metal due to the vanishing band gap of one spin with increasing applied field. The change of VBM for the ultrathin zigzag graphene nanoribbons is similar to that for the wider ones when an electric field is applied. However, in the ultrathin zigzag graphene nanoribbons, there are two kinds of CBMs, one is spin-degenerate and the other is spin-splitted, and both are tunable by the electric field. Moreover, the two CBMs are spatially separated in momentum space. The conducting mechanism changes from spin-degenerate CBM to spin-splitted CBM with increasing applied electric field. Our results are confirmed by density functional calculations with both LDA and GGA functionals, in which the LDA always underestimates the band gap while the GGA normally produces a bigger band gap than the LDA. Project supported by the National Natural Science Foundation of China (Grant Nos.Ā11204201 and 11147142) and the Natural Science Foundation for Young Scientists of Shanxi Province, China (Grant No.Ā2013021010-1).
Electric and magnetic fields in medicine and biology
Not Available
Papers Include: The effects of low frequency (50 Hz) magnetic fields on neuro-chemical transmission in vitro; Morphological changes in E Coli subjected to DC electrical fields; An investigation of some claimed biological effects of electromagnetic fields; Electrical phenomena and bone healing - a comparison of contemporary techniques; Clinical evaluations of a portable module emitting pulsed RF energy; The design, construction and performance of a magnetic nerve stimulator; The principle of electric field tomography and its application to selective read-out of information from peripheral nerves; Applied potential tomography - clinical applications; Impendance imaging using a linear electrode array; Mathematics as an aid to experiment: human body currents induced by power frequency electric fields; Effects of electric field near 750KV transmission line and protection against their harmful consequences; Leukemia and electromagnetic fields: a case-control study; Overhead power lines and childhood cancer; Magnetic measurement of nerve action currents - a new intraoperative recording technique; The potential use of electron spin resonance or impedance measurement to image neuronal electrical activity in the human brain.
Effect of electric fields on fracture behavior of ferroelectric ceramics
H. G Beom; S. N Atluri
The asymptotic problem of a semi-infinite crack perpendicular to the poling direction in a ferroelectric ceramic subjected to combined electric and mechanical loading is analyzed to investigate effect of electric fields on fracture behavior. Electromechanical coupling induced by the piezoelectric effect is neglected in this paper. The shape and size of the switching zone is shown to depend strongly on
Influence of electric fields on the fracture of ferroelectric ceramics
Andreas Ricoeur; Meinhard Kuna
This paper deals with the fracture mechanics of piezoelectric solids. All investigations consider a single crack, which is exposed to combined electrical and mechanical loading. The main subject of interest is the influence of electric fields on the fracture toughness of ferroelectric ceramics and the derivation of an appropriate fracture criterion. Numerical techniques are presented, allowing for the calculation of
Effective critical electric field for runaway electron generation
Stahl, Adam; Decker, Joan; Embrķus, Ola; F³l÷p, T³nde
In this letter we investigate factors that influence the effective critical electric field for runaway electron generation in plasmas. We present numerical solutions of the kinetic equation, and discuss the implications for the threshold electric field. We show that the effective electric field necessary for significant runaway formation often is higher than previously calculated due to both (1) extremely strong dependence of primary generation on temperature, and (2) synchrotron radiation losses. We also address the effective critical field in the context of a transition from runaway growth to decay. We find agreement with recent experiments, but show that the observation of an elevated effective critical field can mainly be attributed to changes in the momentum-space distribution of runaways, and only to a lesser extent to a de facto change in the critical field.
Effective critical electric field for runaway-electron generation.
Stahl, A; Hirvijoki, E; Decker, J; Embrķus, O; F³l÷p, T
In this Letter we investigate factors that influence the effective critical electric field for runaway-electron generation in plasmas. We present numerical solutions of the kinetic equation and discuss the implications for the threshold electric field. We show that the effective electric field necessary for significant runaway-electron formation often is higher than previously calculated due to both (1)Āextremely strong dependence of primary generation on temperature and (2)Āsynchrotron radiation losses. We also address the effective critical field in the context of a transition from runaway growth to decay. We find agreement with recent experiments, but show that the observation of an elevated effective critical field can mainly be attributed to changes in the momentum-space distribution of runaways, and only to a lesser extent to a de facto change in the critical field. PMID:25839283
Semiclassical pair production rate for rotating electric fields
NASA Astrophysics Data System (ADS)
Strobel, Eckhard; Xue, She-Sheng
We semiclassically investigate Schwinger pair production for pulsed rotating electric fields depending on time. To do so we solve the Dirac equation for two-component fields in a Wentzel-Kramers-Brillouin-like approximation. The result shows that for two-component fields the spin distribution of produced pairs is generally not 1 ?1 . As a result the pair creation rates of spinor and scalar QED are different even for one pair of turning points. For rotating electric fields, the pair creation rate is dominated by particles with a specific spin depending on the sense of rotation for a certain range of pulse lengths and frequencies. We present an analytical solution for the momentum spectrum of the constant rotating field. We find interference effects not only in the momentum spectrum but also in the total particle number of rotating electric fields.
Mozer, F. S.; Chen, C. H. K., E-mail: email@example.com [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
By searching through more than 10 satellite years of THEMIS and Cluster data, 3 reliable examples of parallel electric field turbulence in the undisturbed solar wind have been found. The perpendicular and parallel electric field spectra in these examples have similar shapes and amplitudes, even at large scales (frequencies below the ion gyroscale), where Alfvenic turbulence with no parallel electric field component is thought to dominate. The spectra of the parallel electric field fluctuations are power laws with exponents near -5/3 below the ion scales ({approx}0.1 Hz), and with a flattening of the spectrum in the vicinity of this frequency. At small scales (above a few Hz), the spectra are steeper than -5/3 with values in the range of -2.1 to -2.8. These steeper slopes are consistent with expectations for kinetic Alfven turbulence, although their amplitude relative to the perpendicular fluctuations is larger than expected.
Electric fields and convection velocities associated with flux transfer events
NASA Technical Reports Server (NTRS)
Dailey, R.; Cattell, C. A.; Mozer, F. S.; Berchem, J.
A survey of the electric field and (E x B)/B-squared convection velocities associated with 23 flux transfer events (FTEs) in the magnetosheath and magnetosphere is presented. Twelve-second averaged electric field data show perturbations in the component of the electric field perpendicular to the magnetopause, with an average magnitude of 3.5 mV/m associated with the FTEs. Direct flux transfer events have a northward, and reverse flux transfer events a southward, E x B velocity component, in agreement with the current FTE model. The flux tubes moved across the magnetopause plane at an average E x B speed of 125 km/s with respect to the ambient E x B flow, with events located on the dawn (dusk) side tending to move downward (duskward). No large spiky electric fields of the type observed elsewhere in the magnetosphere were detected.
Electric field of a point charge in truncated hyperbolic motion
NASA Astrophysics Data System (ADS)
Franklin, Jerrold
We find the electric field of a point charge in ætruncated hyperbolic motionÆ, in which the charge moves at a constant velocity followed by motion with a constant acceleration in its instantaneous rest frame. The same Lienard¢Wiechert formula holds for the acceleration phase and the constant velocity phase of the chargeÆs motion. The only modification is that the formula giving the retarded time is different for the constant velocity motion than it was for the accelerated motion. The electric field lines are continuous as the retarded time increases through the transition time between constant velocity and accelerated motion. As the transition time approaches negative infinity the electric field develops a delta function contribution that has been introduced by others as necessary to preserve GaussÆs law for the electric field.
Computer model for the cardiac electrical field
H. Oumellal; P. d'Alche
A 2-D model of the cardiac electrical activity is proposed in order to define the methodology of computation. The automatic propagation of the activation in the schematic representation of the auricles and ventricles is in relation to the actual distribution of the nodal or conductive tissues in the heart. The innovative feature of the model is the possibility of computing
Lipidbook: a public repository for force field parameters used in membrane simulations
Beckstein, Oliver
Lipidbook: a public repository for force field parameters used in membrane. P. Sansom, and Oliver Beckstein. Lipidbook: a public repository for force via PubMed identifier and digital object identifier (DOI), and users can
Energy efficiency and the limits of market forces: The example of the electric motor market in France
Edmar Luiz Fagundes de Almeida
This paper addresses the limits of market forces as the exclusive driving force for energy efficiency. The electric motor market in France is analysed, with particular emphasis on the structure and functioning of the market, as well as the decision-making practices of the main agents. The study shows that market forces are constrained by the variety of transaction types and
Vehicle Dynamics Control of In-wheel Electric Motor Drive Vehicles Based on Averaging of Tire Force Usage
NASA Astrophysics Data System (ADS)
Masaki, Nobuo; Iwano, Haruo; Kamada, Takayoshi; Nagai, Masao
For in-wheel electric motor drive vehicles, a new vehicle dynamics control which is based on the tire force usage rate is proposed. The new controller adopts non-linear optimal control could manage the interference between direct yaw-moment control and the tire force usage rate. The new control is considered total longitudinal and transverse tire force. Therefore the controller can prevent tire force saturation near tire force limit during cornering. Simulations and test runs by the custom made four wheel drive in-wheel motor electric vehicle show that higher driving stability performance compared to the performance of the same vehicle without control.
Calculation of three-dimensional electromagnetic force field during arc welding
NASA Astrophysics Data System (ADS)
Kumar, A.; DebRoy, T.
Electromagnetic force is an important driving force for convection in the weld pool during arc welding. Accurate calculation of the electromagnetic force field requires complex numerical calculations of three-dimensional current density and magnetic flux fields. Several simplifying assumptions have been suggested to avoid the complex calculations. The resulting analytical expressions for the electromagnetic force field have been widely used without any critical evaluation of their intrinsic merit, since accurate numerical calculations were difficult in the past because of lack of fast computers. A numerical model has been developed to accurately calculate the current density and magnetic flux fields and the resulting electromagnetic force field in three dimensions in the entire weldment. The model can take into account any current distribution on the work piece surface and evaluate the effects of different arc locations and work piece geometry on the electromagnetic force field. Contributions of the electrode current, arc plasma, and current distribution inside the three-dimensional work piece to the magnetic field and the electromagnetic force field are determined. The electromagnetic force field computed from the model is compared with those obtained from the commonly used simplified expressions of electromagnetic force to examine the accuracy of the commonly used simplifying assumptions. The accuracy of the computed electromagnetic force field can be significantly improved by using the proposed numerical model.
A quadruple-scanning-probe force microscope for electrical property measurements of microscopic materials
NASA Astrophysics Data System (ADS)
Higuchi, Seiji; Kubo, Osamu; Kuramochi, Hiromi; Aono, Masakazu; Nakayama, Tomonobu
Four-terminal electrical measurement is realized on a microscopic structure in air, without a lithographic process, using a home-built quadruple-scanning-probe force microscope (QSPFM). The QSPFM has four probes whose positions are individually controlled by obtaining images of a sample in the manner of atomic force microscopy (AFM), and uses the probes as contacting electrodes for electrical measurements. A specially arranged tuning fork probe (TFP) is used as a self-detection force sensor to operate each probe in a frequency modulation AFM mode, resulting in simultaneous imaging of the same microscopic feature on an insulator using the four TFPs. Four-terminal electrical measurement is then demonstrated in air by placing each probe electrode in contact with a graphene flake exfoliated on a silicon dioxide film, and the sheet resistance of the flake is measured by the van der Pauw method. The present work shows that the QSPFM has the potential to measure the intrinsic electrical properties of a wide range of microscopic materials in situ without electrode fabrication.
Comparison of Nonlinear Force-Free Field and Potential Field in the Quiet Sun
NASA Astrophysics Data System (ADS)
Liu, S.; Zhang, H. Q.; Su, J. T.
In this paper, a potential field extrapolation and three nonlinear force-free (NLFF) field extrapolations (optimization, direct boundary integral (DBIE), and approximate vertical integration (AVI) methods) are used to study the spatial configuration of magnetic field in the quiet Sun. It is found that differences in the computed field strengths among the three NLFF and potential fields exist in the low layers. However, they tend to disappear as the height increases, and the differences are of the order of 0.1 gauss when the height exceeds ? 2000 km above the photosphere. The difference in azimuth angles between each NLFF field model and the potential field is as follows: for the optimization field, it decreases evidently as the height increases; for the DBIE field, it almost stays constant and shows no significant change as the height increases; for the AVI field, it increases slowly as the height increases. Our analysis shows that the reconstructed NLFF fields deviate significantly from the potential field in the quiet Sun.
Convective Heat Transfer Control Using Magnetic and Electric Fields
George S. Dulikravich; Marcelo J. Colańo
A practical approach to non-intrusively controlling electrically conducting melt flow-fields and heat transfer could be achieved by using externally applied magnetic and electric fields. Computational methods are needed to enhance our understanding of this phenomena and its potential in practical industrial processes. In addition, numerical simulation can be used together with optimization to determine distributions of magnets and\\/or electrodes on
An Updated Balloon-Borne Electric Field Sensor
W. Rison; P. R. Krehbiel; W. D. Rust; D. R. Macgorman; S. Fredrickson; D. Kennedy; E. Bruning; J. Young; I. Apostolakopoulos; D. Nealson
Most of the vertical profiles of the electric fields in thunderstorms come from low-mass balloon-borne electric field meters (EFM) based on the design originally developed by Winn and Byerley (Q. J. Royal Met. Soc., 101, 979-94, 1975). This instrument uses a pair of aluminum spheres as sensing electrodes, which spin about the horizontal axis with a frequency of about 2.5~Hz.
A New Electric Field in Asymmetric Magnetic Reconnection
NASA Astrophysics Data System (ADS)
Malakit, K.; Shay, M. A.; Cassak, P.; Ruffolo, D. J.
Magnetic reconnection is an important plasma process that drives the dynamics of the plasma in the magnetosphere and plays a crucial role in the interaction between magnetospheric and magnetosheath plasma. It has been shown that when a reconnection occurs in a collisionless plasma, it exhibits the Hall electric field, an in-plane electric field structure pointing toward the X-line. In this work, we show that when the reconnection has asymmetric inflow conditions such as the reconnection at the day-side magnetopause, a new in-plane electric field structure can exist. This electric field points away from the X-line and is distinct from the known Hall electric field. We argue that the origin of the electric field is associated with the physics of finite Larmor radius. A theory and predictions of the electric field properties are presented and backed up by results from fully kinetic particle-in-cell simulations of asymmetric reconnection with various inflow conditions. Under normal day-side reconnection inflow conditions, the electric field is expected to occur on the magnetospheric side of the X-line pointing Earthward. Hence, it has a potential to be used as a signature for satellites, such as the upcoming Magnetospheric Multi-Scale (MMS) mission, to locate the reconnection sites at the day-side magnetopause. This research was supported by the postdoctoral research sponsorship of Mahidol University (KM), NSF grants ATM-0645271 - Career Award (MAS) and AGS-0953463 (PAC), NASA grants NNX08A083G - MMS IDS, NNX11AD69G, and NNX13AD72G (MAS) and NNX10AN08A (PAC), and the Thailand Research Fund (DR).
Drying Characteristics of Pulsed Electric Field-Treated Carrot
T. K. Gachovska; A. A. Adedeji; M. Ngadi; G. V. S. Raghavan
This study was designed to establish the interaction effect of various components of pulsed electric field (PEF) system on drying characteristics of carrot, a vegetable rich in carotenoid. Carrots were treated in PEF system of 0.5, 1, and 1.5ĀkV\\/cm electric field strength, 0.5 and 1Ā?F capacitance, and pulse numbers of 10, 30, and 50. The samples were subsequently dried at
Built-in electric field thickness design for betavoltaic batteries
Chen Haiyang; Li Darang; Yin Jianhua; Cai Shengguo
Isotope source energy deposition along the thickness direction of a semiconductor is calculated, based upon which an ideal short current is evaluated for betavoltaic batteries. Electron-hole pair recombination and drifting length in a PN junction built-in electric field are extracted by comparing the measured short currents with the ideal short currents. A built-in electric field thickness design principle is proposed
Magnetospheric observation of large sub-auroral electric fields
N. C. Maynard; T. L. Aggson; J. P. Heppner
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
Electric-field distribution near current contacts of anisotropic materials
NASA Astrophysics Data System (ADS)
Slot, E.; van der Zant, H. S.; Thorne, R. E.
We have measured the nonuniformity of the electric field near lateral current contacts of the charge-density-wave materials NbSe3 and o-TaS3. In this contact geometry, the electric field increases considerably near a current contact. Fitting our data to an existing model yields values for the conduction anisotropy and a characteristic longitudinal length scale. This length scale is on the same order as the mesoscopic phenomena in charge-density-wave devices.
Ionizing gas breakdown waves in strong electric fields.
NASA Technical Reports Server (NTRS)
Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.
A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.
The average tangential electric field at the noon magnetopause
Lindqvist, P.A. (Royal Inst. of Tech., Stockholm (Sweden)); Mozer, F.S. (Univ. of California, Berkeley (United States))
The tangential electric field at the magnetopause in the magnetopause frame of reference has been estimated for 205 magnetopause crossings of the ISEE 1 satellite within 2 hours of local noon during 1977-1981. At most of these crossings, time variations of the electric field caused its fluctuations to be large compared with its mean value. This implies both that variations of the field (due, for example, to time varying reconnection) may be of fundamental significance, and that statistical analyses of a large number of crossings are required to determine the average dependence of the tangential electric field at the magnetopause on the magnetosheath magnetic field. A generalized least squares method, which takes into account uncertainties in both the electric and magnetic field measurements, has been developed and applied to the data. The results indicate that, on the average, reconnecton occurs at the subsolar magnetopause; that the average reconnecton flow speed of magnetosheath plasma toward the magnetopause is 20{sup +14}{sub {minus}6} km/s (which is about 15% of the local Alfven speed); and that the dependence of the average tangential electric field at the magnetopause on the magnetosheath north-south magnetic field is sufficient to account for a major part of the magnetospheric potential and convection.
Particle dynamics in a spatially varying electric field
Rothwell, P.L. [Hanscom Air Force Base, Bedford, MA (United States)] [Hanscom Air Force Base, Bedford, MA (United States); Silevitch, M.B. [Northeastern Univ., Boston, MA (United States)] [Northeastern Univ., Boston, MA (United States); Block, L.P.; Faelthammar, C.G. [Royal Institute of Technology, Stockhoms (Sweden)] [Royal Institute of Technology, Stockhoms (Sweden)
The particle dynamics of a plasma with finite first and second spatial derivatives in the electric field is solved. Macroscopic MHD phenomena are invalid in an explanation of single ion dynamics in a spatially varying one-dimensional electric field perpendicular to a magnetic field. We show there is no drift current in single ion motion in a magnetic field. We determine the ion drift velocity. Exact solutions are found in terms of Jacobian elliptic functions. We illustrate these results by application to the Harang discontinuity. 15 refs., 8 figs.
Electrical poling below coercive field for large piezoelectricity
NASA Astrophysics Data System (ADS)
Guo, Hanzheng; Ma, Cheng; Liu, Xiaoming; Tan, Xiaoli
Isotropic polycrystalline ferroelectric ceramics have to be electrically poled to develop a net macroscopic polarization and hence piezoelectricity. It is well accepted that a sufficient poling can only be realized under an electric field that is much higher than the coercive field. In this study, we observed in (Bi1/2Na1/2)TiO3-BaTiO3 ceramics that large piezoelectricity can develop at poling fields far below the measured coercive field. Using in situ transmission electron microscopy, such an unusual behavior, is interpreted with the polarization alignment of polar nanodomains in the non-ergodic relaxor phase.
ISEF 2009 -XIV International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering
Paris-Sud XI, Universitķ de
ISEF 2009 - XIV International Symposium on Electromagnetic Fields in Mechatronics, Electrical on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering, Arras : France (2009)" #12;ISEF 2009 - XIV International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic
Diffusion through ordered force fields in nanopores represented by Smoluchowski equation
Wang, F.Y.; Zhu, Z.H.; Rudolph, V. [University of Queensland, Brisbane, Qld. (Australia). School of Engineering
The classical Einstein or Fick diffusion equation was developed in random force fields. When the equation is applied to gas transport through coal, significant discrepancies are observed between experimental and simulation results. The explanation may be that the random force field assumption is violated. In this article, we analyze molecular transport driven by both random and ordered (directional) forces in nanopores. When applied to CO{sub 2} transport through cone-shaped carbon nano-tubes (CNTs) and Li{sup +} doped graphite pores, computational results show that directional force fields may significantly affect porous media flow. Directional forces may be generated by potential gradients arising from a range of non-uniform characteristics, such as variations in the pore-sizes and in local surface compositions. On the basis of the simulation and experimental results, the Smoluchowski and Fokker-Planck equations, which account for the directional force fields, are recommended for diffusion through ordered force fields in nanopores.
Computation of electromagnetic fields produced by electric power lines and residential electrical wiring
F. P. Dawalibi
Recent epidemiological research work suggesting a link between 50-60 Hz magnetic fields and certain forms of leukemia and brain cancer, has dramatically increased interest in evaluating electromagnetic fields emanating from a three-dimensional arbitrary network of energized overhead and buried conductors. This article presents electric and magnetic fields inside and outside an imaginary house located near a power distribution line. The
Derivation of magnetospheric electric fields from whistler data in a dynamic geomagnetic field
L. P. Block; D. L. Carpenter
The whistler method of determining magnetospheric electric fields has until recently been applied on the assumption of a static dipole geomagnetic field. We consider the effect on the whistler analysis of including both departures of the field from a dipole and temporal variations in the field. Departures from a dipole field appear to have relatively small effects on the analysis
Electric Field Coupling Antenna for Wide Band Near-Field File Transfer
T. Washiro; S. Kuroda; K. Tanaka
Electric field coupling antenna useful especially for wide band near-field file transfer in LWB (low band) frequency range was developed. It shows some remarkable characteristics, for example, polarization free, wide bandwidth, and strong coupling in near- and middle-field in spite of low radiation in far- field. New applications in near-field communication can be realized with this antenna.
Electric field line diagrams don't work
Alan Wolf; Stephen J. van Hook
Electric fields produced by coplanar point charges have often been represented by field line diagrams that depict two-dimensional slices of the three-dimensional field. Serious problems with these ``conventional'' field line diagrams (CFLDs) have been overlooked. Two of these problems, ``equatorial clumping'' and ``false monopole moment,'' occur because a two-dimensional slice lacks information vital to the accurate representation of an inherently
Sherwood 2000 Electric Field Structure in
Tracy, Eugene R.
for the analysis of linear wave conversion in tokamak geometry. Geometric optics is computationally much more(D -== HH ikE -= #12;Sherwood 2000 The tokamak as a resonant cavity Ę Launch a family of rays from field after first conversion 4. The H field between the 1st and 2nd conversions 5. Reflection
Electric field sensors in electromagnetic sounding
Wu Xiao Wu; D. V. Thiel
A staked and an insulated dipole antenna were used to monitor transmissions from a distant very-low-frequency transmitter. The field strength recorded from the staked antenna was found to be much larger than that recorded from the insulated antenna. It is shown that this can be adequately described as magnetic field induction. It is postulated that an insulated antenna is a
Tumour cell membrane poration and ablation by pulsed low-intensity electric field with carbon nanotubes.
Wang, Lijun; Liu, Dun; Zhou, Ru; Wang, Zhigang; Cuschieri, Alfred
Electroporation is a physical method to increase permeabilization of cell membrane by electrical pulses. Carbon nanotubes (CNTs) can potentially act like "lighting rods" or exhibit direct physical force on cell membrane under alternating electromagnetic fields thus reducing the required field strength. A cell poration/ablation system was built for exploring these effects of CNTs in which two-electrode sets were constructed and two perpendicular electric fields could be generated sequentially. By applying this system to breast cancer cells in the presence of multi-walled CNTs (MWCNTs), the effective pulse amplitude was reduced to 50 V/cm (main field)/15 V/cm (alignment field) at the optimized pulse frequency (5 Hz) of 500 pulses. Under these conditions instant cell membrane permeabilization was increased to 38.62%, 2.77-fold higher than that without CNTs. Moreover, we also observed irreversible electroporation occurred under these conditions, such that only 39.23% of the cells were viable 24 h post treatment, in contrast to 87.01% cell viability without presence of CNTs. These results indicate that CNT-enhanced electroporation has the potential for tumour cell ablation by significantly lower electric fields than that in conventional electroporation therapy thus avoiding potential risks associated with the use of high intensity electric pulses. PMID:25822874
Transverse migration of polyelectrolytes in microfluidic channels induced by combined shear and electric fields.
Arca, Mert; Butler, Jason E; Ladd, Anthony J C
If a dilute solution of a polyelectrolyte such as DNA is forced through a microcapillary by an electric field, while simultaneously driven by a pressure gradient, then the polymer will migrate in directions transverse to the field lines. Here we investigate the sharp increase in concentration in the center of the channel that arises when the flow and electric field drive the polymer in the same direction. We report the first systematic investigation of the effects of flow velocity, electric field, and ionic strength on the degree of migration. Our experiments show that migration increases with increasing shear and electric field as predicted by kinetic theory [Butler et al., Phys. Fluids, 2007, 19, 113101], but eventually saturates as suggested by computer simulations [Kekre et al., Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2010, 82, 050803(R)]. The addition of salt reduces the strength of the migration, consistent with a screening of long-range hydrodynamic flow fields by added salt. However, increasing the ionic strength of a Tris-acetate-EDTA buffer solution has much less effect on the degree of migration. PMID:25899578
Electrical distribution and substation system for heavy oil production field
Adams, E.R.; Patel, J.M.
California's Midway-Sunset oil field, located in the San Joaquin Valley, is one of the nations largest areas producing low gravity or heavy crude oil. Located on the west side of the southern portion of the valley, the Midway-Sunset oil field covers approximately 200 square miles. Santa Fe Energy Company is one of the largest oil producers in this field. Rapid expansion of oil producing and oil treating facilities over the last sixteen years has prompted some serious considerations of power distribution and electrical energy availability to meet the needs of this expanding producing field. Santa Fe's electrical load for this field has grown from 6.8MW to 13.5MW in just the last five years and is expected to increase to 30 MW by the year 1985. This paper shows the electrical needs of such an oil production facility due to the special demands of heavy, crude oil secondary-recovery methods.
Ionisation of a quantum dot by electric fields
Eminov, P A; Gordeeva, S V
We have derived analytical formulas for differential and total ionisation probabilities of a two-dimensional quantum dot by a constant electric field. In the adiabatic approximation, we have calculated the probability of this process in the field of a plane electromagnetic wave and in a superposition of constant and alternating electric fields. The imaginary-time method is used to obtain the momentum distribution of the ionisation probability of a bound system by an intense field generated by a superposition of parallel constant and alternating electric fields. The total probability of the process per unit time is calculated with exponential accuracy. The dependence of the results obtained on the characteristic parameters of the problem is investigated. (laser applications and other topics in quantum electronics)
Helical multiferroics for electric field controlled quantum information processing
NASA Astrophysics Data System (ADS)
Azimi, M.; Chotorlishvili, L.; Mishra, S. K.; Greschner, S.; Vekua, T.; Berakdar, J.
Magnetoelectric coupling in helical multiferroics allows us to steer spin order with electric fields. Here we show theoretically that in a helical multiferroic chain quantum information processing as well as quantum phases are highly sensitive to electric (E) field. Applying E field, the quantum state transfer fidelity can be increased and made directionally dependent. We also show that E field transforms the spin-density-wave/nematic or multipolar phases of a frustrated ferromagnetic spin-1/2 chain in chiral phase with a strong magnetoelectric coupling. We find sharp reorganization of the entanglement spectrum as well as a large enhancement of fidelity susceptibility at Ising quantum phase transition from nematic to chiral states driven by electric field. These findings point to a tool for quantum information with low power consumption.
Reversible electric-field control of magnetization at oxide interfaces
NASA Astrophysics Data System (ADS)
Cuellar, F. A.; Liu, Y. H.; Salafranca, J.; Nemes, N.; Iborra, E.; Sanchez-Santolino, G.; Varela, M.; Hernandez, M. Garcia; Freeland, J. W.; Zhernenkov, M.; Fitzsimmons, M. R.; Okamoto, S.; Pennycook, S. J.; Bibes, M.; Barthķlķmy, A.; Te Velthuis, S. G. E.; Sefrioui, Z.; Leon, C.; Santamaria, J.
Electric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field.
Converting wind energy to electrical energy using charged droplets in an electric field
D. Djairam; W. Nijdam; J. Balendonck; P. H. F. Morshuis; J. J. Smit
Conversion of wind energy to electrical energy can be achieved when charged droplets are transported against the direction of an electric field. This method is used in an electrostatic wind energy converter (EWICON). The charged droplets can either be created using electrohydrodynamic atomisation (EHDA) or by high pressure monodisperse spraying (HPMS) in combination with induction charging. In this paper, these
Simulation of near-field optical manipulator using the combination of a near-field scanning optical microscope probe and an atomic force microscope metallic probe
NASA Astrophysics Data System (ADS)
Liu, Binghui; Yang, Lijun; Wang, Yang
We propose a physical model to calculate the trapping force on a nanoparticle trapped by the system using the combination of a near-field scanning optical microscope (NSOM) probe and an atomic force microscope (AFM) metallic probe. Such a near-field trap is produced by evanescent illumination from the NSOM probe and light scattering at the tip of the AFM metallic probe. By using the Maxwell stress tensor through the electric field distribution obtained with the three-dimensional finite difference time domain (3-D FDTD) method, the dependence of the trapping force on the system parameters is discussed, and trapping properties including near-field distribution, trapping position, and the role of other forces versus trapping force are revealed. The results indicate that a particle down to tens of nanometers in size can be trapped toward the tip of an AFM probe with a lower laser intensity (ś1040 W/mm2) than that required by conventional optical manipulators (ś105 W/mm2).
Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields
NASA Technical Reports Server (NTRS)
Herman, Cila
Boiling is an effective mode of heat transfer since high heat flux levels are possible driven by relatively small temperature differences. The high heat transfer coefficients associated with boiling have made the use of these processes increasingly attractive to aerospace engineering. Applications of this type include compact evaporators in the thermal control of aircraft avionics and spacecraft environments, heat pipes, and use of boiling to cool electronic equipment. In spite of its efficiency, cooling based on liquid-vapor phase change processes has not yet found wide application in aerospace engineering due to specific problems associated with the low gravity environment. After a heated surface has reached the superheat required for the initiation of nucleate boiling, bubbles will start forming at nucleation sites along the solid interface by evaporation of the liquid. Bubbles in contact with the wall will continue growing by this mechanism until they detach. In terrestrial conditions, bubble detachment is determined by the competition between body forces (e.g. buoyancy) and surface tension forces that act to anchor the bubble along the three phase contact line. For a given body force potential and a balance of tensions along the three phase contact line, bubbles must reach a critical size before the body force can cause them to detach from the wall. In a low gravity environment the critical bubble size for detachment is much larger than under terrestrial conditions, since buoyancy is a less effective means of bubble removal. Active techniques of heat transfer enhancement in single phase and phase change processes by utilizing electric fields have been the subject of intensive research during recent years. The field of electrohydrodynamics (EHD) deals with the interactions between electric fields, flow fields and temperature fields. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 as compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The goal of our research is to experimentally investigate the potential of EHD and the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions.
Nonlinear force-free coronal magnetic field extrapolation scheme based on the direct boundary integral formulation
Han He; Huaning Wang
The boundary integral equation (BIE) method was first proposed by Yan and Sakurai (2000) and used to extrapolate the nonlinear force-free magnetic field in the solar atmosphere. Recently, Yan and Li (2006) improved the BIE method and proposed the direct boundary integral equation (DBIE) formulation, which represents the nonlinear force-free magnetic field by direct integration of the magnetic field on
Unified Field Theory and Force Formulas of Interactions Tian Ma, Shouhong Wang
Wang, Shouhong
Unified Field Theory and Force Formulas of Interactions Tian Ma, Shouhong Wang Supported in part by NSF, ONR and Chinese NSF http://www.indiana.edu/~fluid I. Two Roads to a Unified Field Theory II. Unified Field Theory of Four Interactions III. Potential and Force Formulas for Strong Interaction IV
Unified Field Equations Coupling Four Forces and Theory of Dark Matter and Dark Energy
Wang, Shouhong
Unified Field Equations Coupling Four Forces and Theory of Dark Matter and Dark Energy Tian Ma II. Principle of Interaction Dynamics III. Unified Field Equations Coupling Four Forces IV. Duality V, June, 2012, http://arxiv.org/abs/1206.5078 2. Tian Ma & Shouhong Wang, Unified Field Equations Coupling
Influence of varying electroosmotic flow on the effective diffusion in electric field gradient separations.
Maynes, Daniel; Tenny, Joseph; Webbd, Brent W; Lee, Milton L
Recently the use electric field gradient focusing (EFGF) to enhance focusing of proteins has been proposed and explored to provide significant improvement in separation resolution. The objective of EFGF is to focus proteins of specific electrophoretic mobilities at distinct stationary locations in a column or channel. This can be accomplished in a capillary by allowing the electric potential to vary in the streamwise direction. Because the electric field is varying, so also is the electrokinetic force exerted on the proteins and the electroosmotic velocity of the buffer solution. Due to the varying electric field, the Taylor diffusion characteristics will also vary along the column, causing a degradation of peak widths of some proteins, dependent on their equilibrium positions and local velocity distributions. The focus of this paper is an analysis that allows characterization of the local Taylor diffusion and resulting protein band peak width as a function of the local magnitude of the EOF relative to the average fluid velocity for both cylindrical and rectangular channels. In general the analysis shows that as the ratio of the local electroosmotic velocity to the average velocity deviates from unity, the effective diffusion increases significantly. The effectiveness of EFGF devices over a range of protein diffusivities, capillary diameters, flow velocities, and electric field gradient is discussed. PMID:18200632
Electric field enhanced conductivity in strongly coupled dense metal plasma
NASA Astrophysics Data System (ADS)
Stephens, J.; Neuber, A.
Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field (ś6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.
Limiting electric fields of HVDC overhead power lines.
Leitgeb, N
As a consequence of the increased use of renewable energy and the now long distances between energy generation and consumption, in Europe, electric power transfer by high-voltage (HV) direct current (DC) overhead power lines gains increasing importance. Thousands of kilometers of them are going to be built within the next years. However, existing guidelines and regulations do not yet contain recommendations to limit static electric fields, which are one of the most important criteria for HVDC overhead power lines in terms of tower design, span width and ground clearance. Based on theoretical and experimental data, in this article, static electric fields associated with adverse health effects are analysed and various criteria are derived for limiting static electric field strengths. PMID:24573710
Possibilities for Measurement and Compensation of Stray DC Electric Fields Acting on Drag-Free Test Masses
W. J. Weber; L. Carbone; A. Cavalleri; R. Dolesi; C. D. Hoyle; M. Hueller; S. Vitale
DC electric fields can combine with test mass charging and thermal dielectric voltage noise to create significant force noise acting on the drag-free test masses in the LISA (Laser Interferometer Space Antenna) gravitational wave mission. This paper proposes a simple technique to measure and compensate average stray DC potentials at the mV level, yielding substantial reduction in this source of force noise. We discuss the attainable resolution for both flight and ground based experiments.
Evidence that transduction of electromagnetic field is mediated by a force receptor.
Marino, Andrew A; Carrubba, Simona; Frilot, Clifton; Chesson, Andrew L
Low-strength magnetic fields triggered onset and offset evoked potentials, indicating that the detection process was a form of sensory transduction; whether the field interacted directly with an ion channel or indirectly via a signaling cascade is unknown. By analogy with electrosensory transduction in lower life forms, we hypothesized that the evoked potentials were initiated by a force exerted by the induced electric field on an ion channel in the plasma membrane. We applied a rapid magnetic stimulus (0.2 ms) and found that it produced evoked potentials indistinguishable in latency, magnitude, and frequency from those found previously when the stimulus was 50 times slower. The ability of the field-detection system in human subjects to respond to the rapid stimulus supported the theory that the receptor potentials necessary for production of evoked potentials originated from a direct interaction between the field and an ion channel in the plasma membrane that resulted in a change in the average probability of the channel to be in the open state. PMID:19383425
Modelling of ?- d-glucopyranose ring distortion in different force fields: a metadynamics study
Vojt?ch Spiwok; Blanka Krßlovß; Igor TvaroÜka
Modelling of carbohydrate conformations is a challenging task for force field developers. Three carbohydrate force fields, namely GLYCAM06, GROMOS 45a4 and OPLS were evaluated. Free energies of different ring conformations of ?-d-glucopyranose were calculated using metadynamics in vacuum as well as in explicitly modelled water. All three force fields model the 4C1 conformation as the most stable by at least
The influence of catch trials on the consolidation of motor memory in force field adaptation tasks.
Focke, Anne; Stockinger, Christian; Diepold, Christina; Taubert, Marco; Stein, Thorsten
In computational neuroscience it is generally accepted that human motor memory contains neural representations of the physics of the musculoskeletal system and the objects in the environment. These representations are called "internal models". Force field studies, in which subjects have to adapt to dynamic perturbations induced by a robotic manipulandum, are an established tool to analyze the characteristics of such internal models. The aim of the current study was to investigate whether catch trials during force field learning could influence the consolidation of motor memory in more complex tasks. Thereby, the force field was more than double the force field of previous studies (35 NĘs/m). Moreover, the arm of the subjects was not supported. A total of 46 subjects participated in this study and performed center-out movements at a robotic manipulandum in two different force fields. Two control groups learned force field A on day 1 and were retested in the same force field on day 3 (AA). Two test groups additionally learned an interfering force field B (= -A) on day 2 (ABA). The difference between the two test and control groups, respectively, was the absence (0%) or presence (19%) of catch trials, in which the force field was turned-off suddenly. The results showed consolidation of force field A on day 3 for both control groups. Test groups showed no consolidation of force field A (19% catch trials) and even poorer performance on day 3 (0% catch trials). In conclusion, it can be stated that catch trials seem to have a positive effect on the performance on day 3 but do not trigger a consolidation process as shown in previous studies that used a lower force field viscosity with supported arm. These findings indicate that the results of previous studies in which less complex tasks were analyzed, cannot be fully transferred to more complex tasks. Moreover, the effects of catch trials in these situations are insufficiently understood and further research is needed. PMID:23898319
The influence of catch trials on the consolidation of motor memory in force field adaptation tasks
Focke, Anne; Stockinger, Christian; Diepold, Christina; Taubert, Marco; Stein, Thorsten
In computational neuroscience it is generally accepted that human motor memory contains neural representations of the physics of the musculoskeletal system and the objects in the environment. These representations are called ōinternal modelsö. Force field studies, in which subjects have to adapt to dynamic perturbations induced by a robotic manipulandum, are an established tool to analyze the characteristics of such internal models. The aim of the current study was to investigate whether catch trials during force field learning could influence the consolidation of motor memory in more complex tasks. Thereby, the force field was more than double the force field of previous studies (35 NĘs/m). Moreover, the arm of the subjects was not supported. A total of 46 subjects participated in this study and performed center-out movements at a robotic manipulandum in two different force fields. Two control groups learned force field A on day 1 and were retested in the same force field on day 3 (AA). Two test groups additionally learned an interfering force field B (= ?A) on day 2 (ABA). The difference between the two test and control groups, respectively, was the absence (0%) or presence (19%) of catch trials, in which the force field was turned-off suddenly. The results showed consolidation of force field A on day 3 for both control groups. Test groups showed no consolidation of force field A (19% catch trials) and even poorer performance on day 3 (0% catch trials). In conclusion, it can be stated that catch trials seem to have a positive effect on the performance on day 3 but do not trigger a consolidation process as shown in previous studies that used a lower force field viscosity with supported arm. These findings indicate that the results of previous studies in which less complex tasks were analyzed, cannot be fully transferred to more complex tasks. Moreover, the effects of catch trials in these situations are insufficiently understood and further research is needed. PMID:23898319
Photodegradation versus hot-electron impact for electrical tree inception at low electric fields
S. S. Bamji; A. T. Bulinski; Y. Chen; R. J. Densley
A mechanism of degradation in polymeric insulation at fields lower than required for hot-electron transport is shown. Cable grade low-density polyethylene was aged under divergent and uniform fields, using needle-plane and dimple-plane geometries, respectively. It is shown that, at points of electric stress enhancement in the polymer, the light emitted during the initiation phase of electrical treeing is not due
Polarizable Mean-Field Model of Water for Biological Simulations with Amber and Charmm force fields
Leontyev, Igor
Although a great number of computational models of water are available today, the majority of current biological simulations are done with simple models, such as TIP3P and SPC, developed almost thirty years ago and only slightly modified since then. The reason is that the non-polarizable force fields that are mostly used to describe proteins and other biological molecules are incompatible with more sophisticated modern polarizable models of water. The issue is electronic polarizability: in liquid state, in protein, and in vacuum the water molecule is polarized differently, and therefore has different properties; thus the only way to describe all these different media with the same model is to use a polarizable water model. However, to be compatible with the force field of the rest of the system, e.g. a protein, the latter should be polarizable as well. Here we describe a novel model of water that is in effect polarizable, and yet compatible with the standard non-polarizable force fields such as AMBER, CHARMM,...
Electric field alignment of nanofibrillated cellulose (NFC) in silicone oil: impact on electrical properties.
Kadimi, Amal; Benhamou, Karima; Ounaies, Zoubeida; Magnin, Albert; Dufresne, Alain; Kaddami, Hamid; Raihane, Mustapha
This work aims to study how the magnitude, frequency, and duration of an AC electric field affect the orientation of two kinds of nanofibrillated cellulose (NFC) dispersed in silicone oil that differ by their surface charge density and aspect ratio. In both cases, the electric field alignment occurs in two steps: first, the NFC makes a gyratory motion oriented by the electric field; second, NFC interacts with itself to form chains parallel to the electric field lines. It was also observed that NFC chains become thicker and longer when the duration of application of the electric field is increased. In-situ dielectric properties have shown that the dielectric constant of the medium increases in comparison to the randomly dispersed NFC (when no electric field is applied). The optimal parameters of alignment were found to be 5000 Vpp/mm and 10 kHz for a duration of 20 min for both kinds of NFC. The highest increase in dielectric constant was achieved with NFC oxidized for 5 min (NFC-O-5 min) at the optimum conditions mentioned above. PMID:24848447
Linear oscillations and stability of a liquid bridge in an axial electric field
NASA Astrophysics Data System (ADS)
Pelekasis, N. A.; Economou, K.; Tsamopoulos, J. A.
Small amplitude oscillations of viscous, capillary bridges are studied in the presence of an electric dc field. The electric field is proposed as a means to maintain bridges longer than their perimeter and of uniform cylindrical shape. This is desired in the fabrication of semiconductor crystals. The material of the bridge and the surrounding medium is modeled either as a perfect or as a leaky dielectric. The frequency and the damping rate of the oscillations are calculated numerically by solving a generalized eigenvalue problem. It is shown that they depend on the ratios of the dielectric constants, ?=?in/?out, and conductivities, S=?in/?out, of the two materials, the aspect ratio of the bridge, ?=?Rś/Lś, the ratio of viscous to the capillary force, Oh=Re-1, which can also be viewed as the inverse Reynolds number of the flow, and, finally, the electrical Bond number, Cel, which is the ratio of the electric stresses to the capillary force. The stability limit of an initially cylindrical bridge is determined with respect to varicose disturbances. In agreement with previous studies it is shown that, if both materials are perfect dielectrics, application of an electric field has a stabilizing effect on the bridge, in the sense that the minimum value, ?min, of the aspect ratio for the bridge to remain stable drops below 0.5, irrespective of the specific value of the ratio ?. If both materials are leaky dielectrics, bridge stability is determined by the sign of (S-?) and (S-1)(?-1), with the positive sign indicating bridge stabilization. The factor (S-?) arises due to the appearance of a tangential electric stress in the perturbed state for leaky dielectrics. For both cases of leaky and perfect dielectrics, the most unstable mode is the one leading to amphora shaped bridges. It was also found that, when application of an electric field stabilizes the bridge, leaky dielectrics require a lower field than perfect dielectrics and that a large enough field tends to stabilize the bridge for almost the entire range of values of the aspect ratio ?. These findings concur with earlier analytical results for the stability of jets in longitudinal electric fields and, in conjunction with certain experimental observations, point to the usefulness of the leaky dielectric model pertaining to the stability of bridges.
Electric Field Driven Self-Assembly of Colloidal Rods
NASA Astrophysics Data System (ADS)
Juarez, Jaime; Chaudhary, Kundan; Chen, Qian; Granick, Steve; Lewis, Jennifer
The ability to assemble anisotropic colloidal building blocks into ordered configurations is of both scientific and technological importance. We are studying how electric field-induced interactions guide the self-assembly of these blocks into well aligned microstructures. Specifically, we present observations of the assembly of colloidal silica rods (L/D ś 4) within planar electrode cells as a function of different electric field parameters. Results from video microscopy and image analysis demonstrate that aligned microstructures form due to the competition between equilibrium interactions of induced dipoles and non-equilibrium processes (i.e., electro-osmosis). Under the appropriate electric field conditions (ś kHZ AC fields), aligned colloidal rod fluids form over large areas on the electrode surface. The superposition of a DC electric field to this aligned colloidal rod fluid initiates their condensation into a vertically oriented crystalline phase. Ongoing work is now focused on exploring how temporal changes to electric fields influence colloidal rod dynamics and, hence, the assembly kinetics of aligned colloidal monolayers.
Electric Field Control of Ferromagnetism and Magnetic Devices Using Multiferroics
NASA Astrophysics Data System (ADS)
Heron, John Thomas
This dissertation presents a study of a heterostructure composed of room temperature magnetoelectric multiferroic BiFeO3 and ferromagnetic Co.90Fe.10, with specific interest in understanding the interfacial coupling mechanisms in this system and establishing the electric field control of a magnetization and spintronic devices. The field of spintronics has been plagued with the problem of a large energy dissipation as a consequence of the resistive losses that come during the writing of the magnetic state (i.e. reversing the magnetization direction). The primary aim of the work presented here is to investigate and understand a novel heterostructure and materials interface that can be demonstrated as a pathway to low energy spintronics. In this dissertation, I will address the specific aspects of multiferroicity, magnetoelectricity, and interface coupling that must be addressed in order to reverse a magnetization with an electric field. Furthermore, I will demonstrate the reversal of a magnetization with an electric field in single and multilayer magnetic devices. The primary advances made as a result of the work described herein are the use of epitaxial constraints to control the nanoscale domain structure of a multiferroic which is then correlated to the domain structure of the exchange coupled ferromagnet. Additionally, the magnetization direction of the ferromagnetic layer is controlled with only an applied electric field at both macroscopic and microscopic scales. Lastly, using this electric field control of ferromagnetism, the first demonstration of a magnetoelectric memory bit is presented.
Weak electric field interactions in the central nervous system.
Saunders, Richard D; Jefferys, John G R
Exposure to extremely low frequency electric and magnetic fields will induce electric fields and currents within the body, but these are almost always much lower than those that can stimulate peripheral nerve tissue. Guidance on exposure to such fields has been published by NRPB and ICNIRP, which is based on the avoidance of acute effects in the central nervous system. Weak electric field effects, below action potential thresholds, have been demonstrated in vitro in brain slice preparations; thresholds can be estimated to be above about 1 mV mm(-1) (around 100 mA m(-2), taking a brain tissue conductivity of around 0.1 S m(-1)), depending on stimulus conditions. Some studies suggest possible effects at lower induced field strengths. The intact nervous system might be expected to be more sensitive to induced electric fields and currents than in vitro preparations, due to a higher level of spontaneous activity and a greater number of interacting neurons. There is good evidence that electrically excitable cells in the retina can be affected in vivo by induced currents as low as 10 mA m(-2). It has been suggested that induced current densities above 10 mA m(-2) may have effects on other central nervous system functions but few studies have been carried out. Further research in experimental animals using both in vitro and in vivo approaches is needed to clarify this issue. PMID:12199550
Wetting of sessile water drop under an external electrical field
NASA Astrophysics Data System (ADS)
Vancauwenberghe, Valerie; di Marco, Paolo; Brutin, David; Amu Collaboration; Unipi Collaboration
The enhancement of heat and mass transfer using a static electric field is an interesting process for industrial applications, due to its low energy consumption and potentially high level of evaporation rate enhancement. However, to date, this phenomenon is still not understood in the context of the evaporation of sessile drops. We previously synthesized the state of the art concerning the effect of an electric field on sessile drops with a focus on the change of contact angle and shape and the influence of the evaporation rate [1]. We present here the preliminary results of an new experiment set-up. The novelty of the set-up is the drop injection from the bottom that allows to generate safety the droplet under the electrostatic field. The evaporation at room temperature of water drops having three different volumes has been investigated under an electric field up to 10.5 kV/cm. The time evolutions of the contact angles, volumes and diameters have been analysed. As reported in the literature, the drop elongate along the direction of the electric field. Despite the hysteresis effect of the contact angle, the receding contact angle increases with the strength of the electric field. This is clearly observable for the small drops for which the gravity effect can be neglected.
Electric field detectors in a coupled ring configuration: preliminary results
Bruno Ando; Salvatore Baglio; Alberto Ascia; Adi R. Bulsara
A novel architecture for sensing weak dc magneticfields exploits the co- operation between nonlinear coupled systems and ferroelectric devices. Sensors for static electric fields (E-fields) based on unidirection- ally coupled nonlinear dynamical systems1 are currently un- der development. They will exploit the synergic use of bistable ferroelectric materials, micromachining technologies, and novel sensing strategies. Considerable practical interest in such de-