Debye potentials for heterogeneous media

NASA Astrophysics Data System (ADS)

Panamarev, N. S.; Donchenko, V. A.; Zemlyanov, Al. A.; Samokhvalov, I. V.; Apeksimov, D. V.; Panamaryova, A. N.; Trifonova, A. V.

2017-11-01

The paper presents the results of the Helmholtz equation solution by the method of perturbation theory in the spherical coordinate system for the Debye potentials for weakly heterogeneous media based on metal nanoparticles and the dielectric matrix. In that case, the dielectric function of a composite changes in space in the radial direction.

Analytical Debye-Huckel model for electrostatic potentials around dissolved DNA.

PubMed Central

Wagner, K; Keyes, E; Kephart, T W; Edwards, G

1997-01-01

We present an analytical, Green-function-based model for the electric potential of DNA in solution, treating the surrounding solvent with the Debye-Huckel approximation. The partial charge of each atom is accounted for by modeling DNA as linear distributions of atoms on concentric cylindrical surfaces. The condensed ions of the solvent are treated with the Debye-Huckel approximation. The resultant leading term of the potential is that of a continuous shielded line charge, and the higher order terms account for the helical structure. Within several angstroms of the surface there is sufficient information in the electric potential to distinguish features and symmetries of DNA. Plots of the potential and equipotential surfaces, dominated by the phosphate charges, reflect the structural differences between the A, B, and Z conformations and, to a smaller extent, the difference between base sequences. As the distances from the helices increase, the magnitudes of the potentials decrease. However, the bases and sugars account for a larger fraction of the double helix potential with increasing distance. We have found that when the solvent is treated with the Debye-Huckel approximation, the potential decays more rapidly in every direction from the surface than it did in the concentric dielectric cylinder approximation. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 7 PMID:9199767

Effective Coulomb force modeling for spacecraft in Earth orbit plasmas

NASA Astrophysics Data System (ADS)

Seubert, Carl R.; Stiles, Laura A.; Schaub, Hanspeter

2014-07-01

Coulomb formation flight is a concept that utilizes electrostatic forces to control the separations of close proximity spacecraft. The Coulomb force between charged bodies is a product of their size, separation, potential and interaction with the local plasma environment. A fast and accurate analytic method of capturing the interaction of a charged body in a plasma is shown. The Debye-Hückel analytic model of the electrostatic field about a charged sphere in a plasma is expanded to analytically compute the forces. This model is fitted to numerical simulations with representative geosynchronous and low Earth orbit (GEO and LEO) plasma environments using an effective Debye length. This effective Debye length, which more accurately captures the charge partial shielding, can be up to 7 times larger at GEO, and as great as 100 times larger at LEO. The force between a sphere and point charge is accurately captured with the effective Debye length, as opposed to the electron Debye length solutions that have errors exceeding 50%. One notable finding is that the effective Debye lengths in LEO plasmas about a charged body are increased from centimeters to meters. This is a promising outcome, as the reduced shielding at increased potentials provides sufficient force levels for operating the electrostatically inflated membrane structures concept at these dense plasma altitudes.

On the Debye-Hückel effect of electric screening

NASA Astrophysics Data System (ADS)

Campos, L. M. B. C.; Lau, F. J. P.

2014-07-01

The paper considers non-linear self-consistent electric potential equation (Sec. I), due to a cloud made of a single species of electric charges, satisfying a Boltzmann distribution law (Sec. II). Exact solutions are obtained in a simple logarithmic form, in three cases: (Sec. III) spherical radial symmetry; (Sec. IV) plane parallel symmetry; (Sec. V) a special case of azimuthal-cylindrical symmetry. All these solutions, and their transformations (Sec. VI), involve the Debye-Hückel radius; the latter was originally defined from a solution of the linearized self-consistent potential equation. Using an exact solution of the self-consistent potential equation, the distance at which the potential vanishes differs from the Debye-Hückel radius by a factor of √2 . The preceding (Secs. II-VI) simple logarithmic exact solutions of the self-consistent potential equations involve no arbitrary constants, and thus are special or singular integrals not the general integral. The general solution of the self-consistent potential equation is obtained in the plane parallel case (Sec. VII), and it involves two arbitrary constants that can be reduced to one via a translation (Sec. VIII). The plots of dimensionless potential (Figure 1), electric field (Figure 2), charge density (Figure 3), and total charge between ζ and infinity (Figure 4), versus distance normalized to Debye-Hückel radius ζ ≡ z/a, show that (Sec. IX) there is a continuum of solutions, ranging from a charge distribution concentrated inside the Debye-Hückel radius to one spread-out beyond it. The latter case leads to the limiting case of logarithmic potential, and stronger electric field; the former case, of very concentrated charge distribution, leads to a fratricide effect and weaker electric field.

Radiation Force Caused by Scattering, Absorption, and Emission of Light by Nonspherical Particles

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)

2001-01-01

General formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived. For randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory, whereas the average radiation force caused by emission vanishes.

Superb electromagnetic wave-absorbing composites based on large-scale graphene and carbon nanotube films.

PubMed

Li, Jinsong; Lu, Weibang; Suhr, Jonghwan; Chen, Hang; Xiao, John Q; Chou, Tsu-Wei

2017-05-24

Graphene has sparked extensive research interest for its excellent physical properties and its unique potential for application in absorption of electromagnetic waves. However, the processing of stable large-scale graphene and magnetic particles on a micrometer-thick conductive support is a formidable challenge for achieving high reflection loss and impedance matching between the absorber and free space. Herein, a novel and simple approach for the processing of a CNT film-Fe 3 O 4 -large scale graphene composite is studied. The Fe 3 O 4 particles with size in the range of 20-200 nm are uniformly aligned along the axial direction of the CNTs. The composite exhibits exceptionally high wave absorption capacity even at a very low thickness. Minimum reflection loss of -44.7 dB and absorbing bandwidth of 4.7 GHz at -10 dB are achieved in composites with one-layer graphene in six-layer CNT film-Fe 3 O 4 prepared from 0.04 M FeCl 3 . Microstructural and theoretical studies of the wave-absorbing mechanism reveal a unique Debye dipolar relaxation with an Eddy current effect in the absorbing bandwidth.

Effects of weakly coupled and dense quantum plasmas environments on charge exchange and ionization processes in Na+ + Rb(5s) atom collisions

NASA Astrophysics Data System (ADS)

Pandey, Mukesh Kumar; Lin, Yen-Chang; Ho, Yew Kam

2017-02-01

The effects of weakly coupled or classical and dense quantum plasmas environment on charge exchange and ionization processes in Na+ + Rb(5s) atom collision at keV energy range have been investigated using classical trajectory Monte Carlo (CTMC) method. The interaction of three charged particles are described by the Debye-Hückel screen potential for weakly coupled plasma, whereas exponential cosine-screened Coulomb potential have been used for dense quantum plasma environment and the effects of both conditions on the cross sections are compared. It is found that screening effects on cross sections in high Debye length condition is quite small in both plasma environments. However, enhanced screening effects on cross sections are observed in dense quantum plasmas for low Debye length condition, which becomes more effective while decreasing the Debye length. Also, we have found that our calculated results for plasma-free case are comparable with the available theoretical results. These results are analyzed in light of available theoretical data with the choice of model potentials.

Enhanced absorption of microwave radiations through flexible polyvinyl alcohol-carbon black/barium hexaferrite composite films

NASA Astrophysics Data System (ADS)

Kumar, Sushil; Datt, Gopal; Santhosh Kumar, A.; Abhyankar, A. C.

2016-10-01

Flexible microwave absorber composite films of carbon black (CB)/barium hexaferrite nano-discs (BaF) in polyvinyl alcohol (PVA) matrix, fabricated by gel casting, exhibit ˜99.5% attenuation of electromagnetic waves in the entire 8-18 GHz (X and Ku-band) range. The X-ray diffraction and Raman spectroscopy studies confirm the formation of CB-BaF-PVA composite films. The electromagnetic absorption properties of composite films are found to be enhanced with CB content due to the synergetic effect of multiple dielectric and magnetic losses. The 25 wt. % CB grafted PVA-BaF flexible composite films with a thickness of ˜ 2 mm exhibit effective electromagnetic shielding of 23.6 dB with a dominant contribution from absorption mechanism (SEA ˜ 21 dB). The dielectric properties of composite films are further discussed by using the Debye model. The detailed analysis reveals that major contribution to dielectric losses is from dipolar and interfacial polarizations, whereas magnetic losses are predominantly from domain wall displacement.

Debye ring diffraction elucidation of 2D photonic crystal self-assembly and ordering at the air-water interface.

PubMed

Smith, N L; Coukouma, A; Dubnik, S; Asher, S A

2017-12-06

We fabricate 2D photonic crystals (2DPC) by spreading a dispersion of charged colloidal particles (diameters = 409, 570, and 915 nm) onto the surface of electrolyte solutions using a needle tip flow method. When the interparticle electrostatic interaction potential is large, particles self-assemble into highly ordered hexagonal close packed (hcp) monolayers. Ordered 2DPC efficiently forward diffract monochromatic light to produce a Debye ring on a screen parallel to the 2DPC. The diameter of the Debye ring is inversely proportional to the 2DPC particle spacing, while the Debye ring brightness and thickness depends on the 2DPC ordering. The Debye ring thickness increases as the 2DPC order decreases. The Debye ring ordering measurements of 2DPC attached to glass slides track measurements of the 2D pair correlation function order parameter calculated from SEM micrographs. The Debye ring method was used to investigate the 2DPC particle spacing, and ordering at the air-solution interface of NaCl solutions, and for 2DPC arrays attached to glass slides. Surprisingly, the 2DPC ordering does not monotonically decrease as the salt concentration increases. This is because of chloride ion adsorption onto the anionic particle surfaces. This adsorption increases the particle surface charge and compensates for the decreased Debye length of the electric double layer when the NaCl concentration is below a critical value.

Free-Free Transitions in the Presence of Laser Fields and Debye Potential at Very Low Incident Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, Anand

2012-01-01

We study the free-free transition in electron-helium ion in the ground state and embedded in a Debye potential in the presence of an external laser field at very low incident electron energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen as monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing Volkov wave function for it. The scattering wave function for the incident electron on the target embedded in a Debye potential is solved numerically by taking into account the effect of electron exchange. We calculate the laser-assisted differential and total cross sections for free-free transition for absorption/emission of a single photon or no photon exchange. The results will be presented at the conference.

Introduction to the theory and application of a unified Bohm criterion for arbitrary-ion-temperature collision-free plasmas with finite Debye lengths

NASA Astrophysics Data System (ADS)

Kos, L.; Jelić, N.; Kuhn, S.; Tskhakaya, D. D.

2018-04-01

At present, identifying and characterizing the common plasma-sheath edge (PSE) in the conventional fluid approach leads to intrinsic oversimplifications, while the kinetic one results in unusable over-generalizations. In addition, none of these approaches can be justified in realistic plasmas, i.e., those which are characterized by non-negligible Debye lengths and a well-defined non-negligible ion temperature. In an attempt to resolve this problem, we propose a new formulation of the Bohm criterion [D. Bohm, The Characteristics of Electrical Discharges in Magnetic Fields (McGraw-Hill, New York, 1949)], which is here expressed in terms of fluid, kinetic, and electrostatic-pressure contributions. This "unified" Bohm criterion consists of a set of two equations for calculating the ion directional energy (i.e., the mean directional velocity) and the plasma potential at the common PSE, and is valid for arbitrary ion-to-electron temperature ratios. It turns out to be exact at any point of the quasi-neutral plasma provided that the ion differential polytropic coefficient function (DPCF) of Kuhn et al. [Phys. Plasmas 13, 013503 (2006)] is employed, with the advantage that the DPCF is an easily measurable fluid quantity. Moreover, our unified Bohm criterion holds in plasmas with finite Debye lengths, for which the famous kinetic criterion formulated by Harrison and Thompson [Proc. Phys. Soc. 74, 145 (1959)] fails. Unlike the kinetic criterion in the case of negligible Debye length, the kinetic contribution to the unified Bohm criterion, arising due to the presence of negative and zero velocities in the ion velocity distribution function, can be calculated separately from the fluid term. This kinetic contribution disappears identically at the PSE, yielding strict equality of the ion directional velocity there and the ion sound speed, provided that the latter is formulated in terms of the present definition of DPCFs. The numerical values of these velocities are found for the Tonks-Langmuir collision-free, plane-parallel discharge model [Phys. Rev. 34, 876 (1929)], however, with the ion-source temperature extended here from the original (zero) value to arbitrary high ones. In addition, it turns out, that the charge-density derivative (in the potential "space") with respect to the potential exhibits two characteristic points, i.e., potentials, namely the points of inflection and maximum of that derivative (in the potential space), which stay "fixed" at their respective potentials independent of the Debye length until it is kept fairly small. Plasma quasi-neutrality appears well satisfied up to the first characteristic point/potential, so we identify that one as the plasma edge (PE). Adopting the convention that the sheath is a region characterized by considerable electrostatic pressure (energy density), we identify the second characteristic point/potential as the sheath edge (SE). Between these points, the charge density increases from zero to a finite value. Thus, the interval between the PE and SE, with the "fixed" width (in the potential "space") of about one third of the electron temperature, will be named the plasma-sheath transition (PST). Outside the PST, the electrostatic-pressure term and its derivatives turn out to be nearly identical with each other, independent of the particular values of the ion temperature and Debye length. In contrast, an increase in Debye lengths from zero to finite values causes the location of the sonic point/potential (laying inside the PST) to shift from the PE (for vanishing Debye length) towards the SE, while at the same time, the absolute value of the corresponding ion-sound velocity slightly decreases. These shifts turn out to be manageable with employing the mathematical concept of the plasma-to-sheath transition (different from, but related to our natural PST concept), resulting in approximate, but sufficiently reliable semi-analytic expressions, which are functions of the ion temperature and Debye length.

Monitoring processing properties of high performance thermoplastics using frequency dependent electromagnetic sensing

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.; Delos, S. E.; Hoff, M. S.; Weller, L. W.; Haverty, P. D.

1987-01-01

An in situ NDE dielectric impedance measurement method has been developed for ascertaining the cure processing properties of high temperature advanced thermoplastic and thermosetting resins, using continuous frequency-dependent measurements and analyses of complex permittivity over 9 orders of magnitude and 6 decades of frequency at temperatures up to 400 C. Both ionic and Debye-like dipolar relaxation processes are monitored. Attention is given to LARC-TPI, PEEK, and poly(arylene ether) resins' viscosity, glass transition temperature, recrystallization, and residual solvent content and evolution properties.

A numerical method for electro-kinetic flow with deformable fluid interfaces

NASA Astrophysics Data System (ADS)

Booty, Michael; Ma, Manman; Siegel, Michael

2013-11-01

We consider two-phase flow of ionic fluids whose motion is driven by an imposed electric field. At a fluid interface, a screening cloud of ions develops and forms an electro-chemical double layer or Debye layer. The imposed field acts on this induced charge distribution, resulting in a strong slip flow near the interface. We formulate a ``hybrid'' or multiscale numerical method in the thin Debye layer limit that incorporates an asymptotic analysis of the electrostatic potential and fluid dynamics in the Debye layer into a boundary integral solution of the full moving boundary problem. Results of the method are presented that show time-dependent deformation and steady state drop interface shapes when the timescale for charge-up of the Debye layer is either much less than or comparable to the timescale of the flow.

FDTD computation of human eye exposure to ultra-wideband electromagnetic pulses.

PubMed

Simicevic, Neven

2008-03-21

With an increase in the application of ultra-wideband (UWB) electromagnetic pulses in the communications industry, radar, biotechnology and medicine, comes an interest in UWB exposure safety standards. Despite an increase of the scientific research on bioeffects of exposure to non-ionizing UWB pulses, characterization of those effects is far from complete. A numerical computational approach, such as a finite-difference time domain (FDTD) method, is required to visualize and understand the complexity of broadband electromagnetic interactions. The FDTD method has almost no limits in the description of the geometrical and dispersive properties of the simulated material, it is numerically robust and appropriate for current computer technology. In this paper, a complete calculation of exposure of the human eye to UWB electromagnetic pulses in the frequency range of 3.1-10.6, 22-29 and 57-64 GHz is performed. Computation in this frequency range required a geometrical resolution of the eye of 0.1 mm and an arbitrary precision in the description of its dielectric properties in terms of the Debye model. New results show that the interaction of UWB pulses with the eye tissues exhibits the same properties as the interaction of the continuous electromagnetic waves (CWs) with the frequencies from the pulse's frequency spectrum. It is also shown that under the same exposure conditions the exposure to UWB pulses is from one to many orders of magnitude safer than the exposure to CW.

On the Debye–Hückel effect of electric screening

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campos, L. M. B. C.; Lau, F. J. P.

2014-07-15

The paper considers non-linear self-consistent electric potential equation (Sec. I), due to a cloud made of a single species of electric charges, satisfying a Boltzmann distribution law (Sec. II). Exact solutions are obtained in a simple logarithmic form, in three cases: (Sec. III) spherical radial symmetry; (Sec. IV) plane parallel symmetry; (Sec. V) a special case of azimuthal-cylindrical symmetry. All these solutions, and their transformations (Sec. VI), involve the Debye-Hückel radius; the latter was originally defined from a solution of the linearized self-consistent potential equation. Using an exact solution of the self-consistent potential equation, the distance at which the potentialmore » vanishes differs from the Debye-Hückel radius by a factor of √(2). The preceding (Secs. II–VI) simple logarithmic exact solutions of the self-consistent potential equations involve no arbitrary constants, and thus are special or singular integrals not the general integral. The general solution of the self-consistent potential equation is obtained in the plane parallel case (Sec. VII), and it involves two arbitrary constants that can be reduced to one via a translation (Sec. VIII). The plots of dimensionless potential (Figure 1), electric field (Figure 2), charge density (Figure 3), and total charge between ζ and infinity (Figure 4), versus distance normalized to Debye-Hückel radius ζ ≡ z/a, show that (Sec. IX) there is a continuum of solutions, ranging from a charge distribution concentrated inside the Debye-Hückel radius to one spread-out beyond it. The latter case leads to the limiting case of logarithmic potential, and stronger electric field; the former case, of very concentrated charge distribution, leads to a fratricide effect and weaker electric field.« less

Dissociation of heavy quarkonium in hot QCD medium in a quasiparticle model

NASA Astrophysics Data System (ADS)

Agotiya, Vineet Kumar; Chandra, Vinod; Jamal, M. Yousuf; Nilima, Indrani

2016-11-01

Following a recent work on the effective description of the equations of state for hot QCD obtained from a hard thermal loop expression for the gluon self-energy, in terms of the quasigluons and quasiquarks and antiquarks with respective effective fugacities, the dissociation process of heavy quarkonium in hot QCD medium has been investigated. This has been done by investigating the medium modification to a heavy quark potential. The medium-modified potential has a quite different form (a long-range Coulomb tail in addition to the usual Yukawa term) in contrast to the usual picture of Debye screening. The flavor dependence binding energies of the heavy quarkonia states and the dissociation temperature have been obtained by employing the Debye mass for pure gluonic and full QCD case computed employing the quasiparticle picture. Thus, estimated dissociation patterns of the charmonium and bottomonium states, considering Debye mass from different approaches in the pure gluonic case and full QCD, have shown good agreement with the other potential model studies.

Low energy electron-impact ionization of hydrogen atom for coplanar equal-energy-sharing kinematics in Debye plasmas

NASA Astrophysics Data System (ADS)

Li, Jun; Zhang, Song Bin; Ye, Bang Jiao; Wang, Jian Guo; Janev, R. K.

2016-12-01

Low energy electron-impact ionization of hydrogen atom in Debye plasmas has been investigated by employing the exterior complex scaling method. The interactions between the charged particles in the plasma have been represented by Debye-Hückel potentials. Triple differential cross sections (TDCS) in the coplanar equal-energy-sharing geometry at an incident energy of 15.6 eV for different screening lengths are reported. As the screening strength increases, TDCS change significantly. The evolutions of dominant typical peak structures of the TDCS are studied in detail for different screening lengths and for different coplanar equal-energy-sharing geometries.

Repulsion Between Finite Charged Plates with Strongly Overlapped Electric Double Layers.

PubMed

Ghosal, Sandip; Sherwood, John D

2016-09-20

Screened Coulomb interactions between uniformly charged flat plates are considered at very small plate separations for which the Debye layers are strongly overlapped, in the limit of small electrical potentials. If the plates are of infinite length, the disjoining pressure between the plates decays as an inverse power of the plate separation. If the plates are of finite length, we show that screening Debye layer charges close to the edge of the plates are no longer constrained to stay between the plates, but instead spill out into the surrounding electrolyte. The resulting change in the disjoining pressure is calculated analytically: the force between the plates is reduced by this edge correction when the charge density is uniform over the surface of the plates, and is increased when the surface is at constant potential. A similar change in disjoining pressure due to loss of lateral confinement of the Debye layer charges should occur whenever the sizes of the interacting charged objects become small enough to approach the Debye scale. We investigate the effect here in the context of a two-dimensional model problem that is sufficiently simple to yield analytical results.

Tunneling effects in electromagnetic wave scattering by nonspherical particles: A comparison of the Debye series and physical-geometric optics approximations

NASA Astrophysics Data System (ADS)

Bi, Lei; Yang, Ping

2016-07-01

The accuracy of the physical-geometric optics (PG-O) approximation is examined for the simulation of electromagnetic scattering by nonspherical dielectric particles. This study seeks a better understanding of the tunneling effect on the phase matrix by employing the invariant imbedding method to rigorously compute the zeroth-order Debye series, from which the tunneling efficiency and the phase matrix corresponding to the diffraction and external reflection are obtained. The tunneling efficiency is shown to be a factor quantifying the relative importance of the tunneling effect over the Fraunhofer diffraction near the forward scattering direction. Due to the tunneling effect, different geometries with the same projected cross section might have different diffraction patterns, which are traditionally assumed to be identical according to the Babinet principle. For particles with a fixed orientation, the PG-O approximation yields the external reflection pattern with reasonable accuracy, but ordinarily fails to predict the locations of peaks and minima in the diffraction pattern. The larger the tunneling efficiency, the worse the PG-O accuracy is at scattering angles less than 90°. If the particles are assumed to be randomly oriented, the PG-O approximation yields the phase matrix close to the rigorous counterpart, primarily due to error cancellations in the orientation-average process. Furthermore, the PG-O approximation based on an electric field volume-integral equation is shown to usually be much more accurate than the Kirchhoff surface integral equation at side-scattering angles, particularly when the modulus of the complex refractive index is close to unity. Finally, tunneling efficiencies are tabulated for representative faceted particles.

Eddies in a bottleneck: an arbitrary Debye length theory for capillary electroosmosis.

PubMed

Park, Stella Y; Russo, Christopher J; Branton, Daniel; Stone, Howard A

2006-05-15

Using an applied electrical field to drive fluid flows becomes desirable as channels become smaller. Although most discussions of electroosmosis treat the case of thin Debye layers, here electroosmotic flow (EOF) through a constricted cylinder is presented for arbitrary Debye lengths (kappa(-1)) using a long wavelength perturbation of the cylinder radius. The analysis uses the approximation of small potentials. The varying diameter of the cylinder produces radially and axially varying effective electric fields, as well as an induced pressure gradient. We predict the existence of eddies for certain constricted geometries and propose the possibility of electrokinetic trapping in these regions. We also present a leading-order criterion which predicts central eddies in very narrow constrictions at the scale of the Debye length. Eddies can be found both in the center of the channel and along the perimeter, and the presence of the eddies is a consequence of the induced pressure gradient that accompanies electrically driven flow into a narrow constriction.

Eddies in a Bottleneck: An Arbitrary Debye Length Theory for Capillary Electroosmosis

PubMed Central

Park, Stella Y.; Russo, Christopher J.; Branton, Daniel; Stone, Howard A.

2011-01-01

Using an applied electrical field to drive fluid flows becomes desirable as channels become smaller. Although most discussions of electroosmosis treat the case of thin Debye layers, here electroosmotic flow (EOF) through a constricted cylinder is presented for arbitrary Debye lengths (κ−1) using a long wavelength perturbation of the cylinder radius. The analysis uses the approximation of small potentials. The varying diameter of the cylinder produces radially and axially varying effective electric fields, as well as an induced pressure gradient. We predict the existence of eddies for certain constricted geometries and propose the possibility of electrokinetic trapping in these regions. We also present a leading-order criterion which predicts central eddies in very narrow constrictions at the scale of the Debye length. Eddies can be found both in the center of the channel and along the perimeter, and the presence of the eddies is a consequence of the induced pressure gradient that accompanies electrically driven flow into a narrow constriction. PMID:16376361

FAST TRACK COMMUNICATION: Oscillation structures in elastic and electron capture cross sections for H+-H collisions in Debye plasmas

NASA Astrophysics Data System (ADS)

Wu, Y.; Wang, J. G.; Krstic, P. S.; Janev, R. K.

2010-10-01

We find that the number of vibrational states in the ground potential of a H2+ molecular ion embedded in the Debye plasma and the number of Regge oscillations in the resonant charge transfer cross section of the H+ + H collision system in the plasma are quasi-conserved when the Debye radius D is larger than 1.4a0. The elastic and resonant charge transfer processes in the H+ + H collision have been studied in the 0.1 meV-100 eV collision energy range for a wide range of Debye radii using a highly accurate calculation based on the modified ab initio multireference configuration interaction code. Remarkable plasma screening effects have been found in both the molecular structure and the collision dynamics of this system. Shape resonances, Regge and glory oscillations have been found in the integral cross sections in the considered energy range even for strong interaction screening, showing their ubiquitous nature.

Ionization potential depression and optical spectra in a Debye plasma model

NASA Astrophysics Data System (ADS)

Lin, Chengliang; Röpke, Gerd; Reinholz, Heidi; Kraeft, Wolf-Dietrich

2017-11-01

We show how optical spectra in dense plasmas are determined by the shift of energy levels as well as the broadening owing to collisions with the plasma particles. In lowest approximation, the interaction with the plasma particles is described by the RPA dielectric function, leading to the Debye shift of the continuum edge. The bound states remain nearly un-shifted, their broadening is calculated in Born approximation. The role of ionization potential depression as well as the Inglis-Teller effect are shown. The model calculations have to be improved going beyond the lowest (RPA) approximation when applying to WDM spectra.

Joule heating effects on electromagnetohydrodynamic flow through a peristaltically induced micro-channel with different zeta potential and wall slip

NASA Astrophysics Data System (ADS)

Ranjit, N. K.; Shit, G. C.

2017-09-01

This paper aims to develop a mathematical model for magnetohydrodynamic flow of biofluids through a hydrophobic micro-channel with periodically contracting and expanding walls under the influence of an axially applied electric field. The velocity slip effects have been taken into account at the channel walls by employing different slip lengths due to hydrophobic gating. Different temperature jump factors have also been used to investigate the thermomechanical interactions at the fluid-solid interface. The electromagnetohydrodynamic flow in a microchannel is simplified under the framework of Debye-Hückel linearization approximation. We have derived the closed-form solutions for the linearized dimensionless boundary value problem under the assumptions of long wave length and low Reynolds number. The axial velocity, temperature, pressure distribution, stream function, wall shear stress and the Nusselt number have been appraised for diverse values of the parameters approaching into the problem. Our main focus is to determine the effects of different zeta potential on the axial velocity and temperature distribution under electromagnetic environment. This study puts forward an important observation that the different zeta potential plays an important role in controlling fluid velocity. The study further reveals that the temperature increases significantly with the Joule heating parameter and the Brinkman number (arises due to the dissipation of energy).

Charged plate in asymmetric electrolytes: One-loop renormalization of surface charge density and Debye length due to ionic correlations.

PubMed

Ding, Mingnan; Lu, Bing-Sui; Xing, Xiangjun

2016-10-01

Self-consistent field theory (SCFT) is used to study the mean potential near a charged plate inside a m:-n electrolyte. A perturbation series is developed in terms of g=4πκb, where band1/κ are Bjerrum length and bare Debye length, respectively. To the zeroth order, we obtain the nonlinear Poisson-Boltzmann theory. For asymmetric electrolytes (m≠n), the first order (one-loop) correction to mean potential contains a secular term, which indicates the breakdown of the regular perturbation method. Using a renormalizaton group transformation, we remove the secular term and obtain a globally well-behaved one-loop approximation with a renormalized Debye length and a renormalized surface charge density. Furthermore, we find that if the counterions are multivalent, the surface charge density is renormalized substantially downwards and may undergo a change of sign, if the bare surface charge density is sufficiently large. Our results agrees with large MC simulation even when the density of electrolytes is relatively high.

Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas

NASA Astrophysics Data System (ADS)

Li, Jun; Zhang, Song Bin; Ye, Bang Jiao; Wang, Jian Guo; Janev, R. K.

2017-09-01

Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas have been investigated by employing the exterior complex scaling method. The interactions between charged particles in the plasmas have been represented by Debye-Hückel potentials. The 1 s -1 s elastic collision strengths below the n =2 excitation threshold of He+ dominated by resonance structures are calculated for different screening lengths. As the screening strength increases, the resonance peaks studied [2(1,0) 2 +1Se,3Po,1De , and 2(0,1) 2 +1Po] exhibit blueshifts and then redshifts with a further increase of the screening strength, which results in dramatic changes of the collision strengths. It is found that these dynamic variation features of the resonances are related to the changes of energy levels of He+ in the screened potential and geometric configurations of resonances. Triple-differential-ionization cross sections in coplanar geometries at 6-Ry incident electron energy are also reported, significant changes are observed with varying screening length.

Charged particle layers in the Debye limit.

PubMed

Golden, Kenneth I; Kalman, Gabor J; Kyrkos, Stamatios

2002-09-01

We develop an equivalent of the Debye-Hückel weakly coupled equilibrium theory for layered classical charged particle systems composed of one single charged species. We consider the two most important configurations, the charged particle bilayer and the infinite superlattice. The approach is based on the link provided by the classical fluctuation-dissipation theorem between the random-phase approximation response functions and the Debye equilibrium pair correlation function. Layer-layer pair correlation functions, screened and polarization potentials, static structure functions, and static response functions are calculated. The importance of the perfect screening and compressibility sum rules in determining the overall behavior of the system, especially in the r--> infinity limit, is emphasized. The similarities and differences between the quasi-two-dimensional bilayer and the quasi-three-dimensional superlattice are highlighted. An unexpected behavior that emerges from the analysis is that the screened potential, the correlations, and the screening charges carried by the individual layers exhibit a marked nonmonotonic dependence on the layer separation.

Magnetic field tunable dielectric dispersion in successive field-induced magnetic phases of the geometrically frustrated magnet CuFeO2 up to 28 T

NASA Astrophysics Data System (ADS)

Tamatsukuri, H.; Mitsuda, S.; Hiroura, K.; Nakajima, T.; Fujihala, M.; Yamano, M.; Toshioka, Y.; Kaneko, C.; Takehana, K.; Imanaka, Y.; Terada, N.; Kitazawa, H.

2018-06-01

We find magnetic-field-dependent dielectric dispersions specific to successive field-induced magnetic phases of a geometrically frustrated magnet CuFeO2 up to 28 T. The dielectric dispersions in the three field-induced collinear-commensurate magnetic phases are well described by the superposition of Debye-type relaxations, and the number of contributions to the Debye-type dispersions differs in these phases. In contrast, the dielectric dispersions in the noncollinear-incommensurate phase, known as a spin-driven ferroelectric phase, cannot be simply described by the Debye-type relaxations. In addition, we find that the temperature dependence of the Debye relaxation frequencies follows the Arrhenius law, and that the activation energies derived from the Arrhenius equation also depend on the magnetic field. Considering the magnetostriction effect in combination with elongation/contraction of spins resulting from the application of a magnetic field, we show that the number of Debye relaxation components is equivalent to the number of states of local Fe3O clusters determined by oxygen displacement within a triangular Fe lattice. Based on this correspondence, we propose a possible explanation that excess charges resulting from a lack of stoichiometry hop over the double-well potentials within each local Fe3O cluster, like small polarons.

A fully-implicit Particle-In-Cell Monte Carlo Collision code for the simulation of inductively coupled plasmas

NASA Astrophysics Data System (ADS)

Mattei, S.; Nishida, K.; Onai, M.; Lettry, J.; Tran, M. Q.; Hatayama, A.

2017-12-01

We present a fully-implicit electromagnetic Particle-In-Cell Monte Carlo collision code, called NINJA, written for the simulation of inductively coupled plasmas. NINJA employs a kinetic enslaved Jacobian-Free Newton Krylov method to solve self-consistently the interaction between the electromagnetic field generated by the radio-frequency coil and the plasma response. The simulated plasma includes a kinetic description of charged and neutral species as well as the collision processes between them. The algorithm allows simulations with cell sizes much larger than the Debye length and time steps in excess of the Courant-Friedrichs-Lewy condition whilst preserving the conservation of the total energy. The code is applied to the simulation of the plasma discharge of the Linac4 H- ion source at CERN. Simulation results of plasma density, temperature and EEDF are discussed and compared with optical emission spectroscopy measurements. A systematic study of the energy conservation as a function of the numerical parameters is presented.

Passage of the discharge current through the plasma-electrode interface in the electromagnetic rail accelerator channel

NASA Astrophysics Data System (ADS)

Zhukov, B. G.; Reznikov, B. I.; Kurakin, R. O.; Ponyaev, S. A.; Bobashev, S. V.

2016-11-01

We investigate the phenomena that accompany the acceleration of a free plasma piston (without a striker) in the electromagnetic rail accelerator channel filled with different gases (argon, helium). An intense glow appears in the shock-compressed layer (SCL) in the case of strong shock waves that produce a high electron concentration ( 1017-1018 cm-3) behind the front. We have proposed that explosive electron emission (EEE) ensures the high-intensity emission of electrons, the passage of a part of the discharge current through the SCL, and the glow of the SCL. The velocity of a shock wave for which the strong electric field in the Debye layer at the cathode causes EEE from its surface and the passage of the current in the SCL has been determined. It has been concluded that, for high velocities of the plasma, the EEE is a universal mechanism that ensure the passage of a strong current through the interface between the cold electrode and the plasma.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length.

PubMed

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-10-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length

PubMed Central

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-01-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes. PMID:24465094

LEO high voltage solar array arcing response model, continuation 5

NASA Technical Reports Server (NTRS)

Metz, Roger N.

1989-01-01

The modeling of the Debye Approximation electron sheaths in the edge and strip geometries was completed. Electrostatic potentials in these sheaths were compared to NASCAP/LEO solutions for similar geometries. Velocity fields, charge densities and particle fluxes to the biased surfaces were calculated for all cases. The major conclusion to be drawn from the comparisons of our Debye Approximation calculations with NASCAP-LEO output is that, where comparable biased structures can be defined and sufficient resolution obtained, these results are in general agreement. Numerical models for the Child-Langmuir, high-voltage electron sheaths in the edge and strip geometries were constructed. Electrostatic potentials were calculated for several cases in each of both geometries. Velocity fields and particle fluxes were calculated. The self-consistent solution process was carried through one cycle and output electrostatic potentials compared to NASCAP-type input potentials.

High correlation of double Debye model parameters in skin cancer detection.

PubMed

Truong, Bao C Q; Tuan, H D; Fitzgerald, Anthony J; Wallace, Vincent P; Nguyen, H T

2014-01-01

The double Debye model can be used to capture the dielectric response of human skin in terahertz regime due to high water content in the tissue. The increased water proportion is widely considered as a biomarker of carcinogenesis, which gives rise of using this model in skin cancer detection. Therefore, the goal of this paper is to provide a specific analysis of the double Debye parameters in terms of non-melanoma skin cancer classification. Pearson correlation is applied to investigate the sensitivity of these parameters and their combinations to the variation in tumor percentage of skin samples. The most sensitive parameters are then assessed by using the receiver operating characteristic (ROC) plot to confirm their potential of classifying tumor from normal skin. Our positive outcomes support further steps to clinical application of terahertz imaging in skin cancer delineation.

Theory of waves incoherently scattered

NASA Technical Reports Server (NTRS)

Bauer, P.

1974-01-01

Electromagnetic waves impinging upon a plasma at frequencies larger than the plasma frequency, suffer weak scattering. The scattering arises from the existence of electron density fluctuations. The received signal corresponds to a particular spatial Fourier component of the fluctuations, the wave vector of which is a function of the wavelength of the radiowave. Wavelengths short with respect to the Debye length of the medium relate to fluctuations due to non-interacting Maxwellian electrons, while larger wavelengths relate to fluctuations due to collective Coulomb interactions. In the latter case, the scattered signal exhibits a spectral distribution which is characteristic of the main properties of the electron and ion gases and, therefore, provides a powerful diagnosis of the state of the ionosphere.

Weak polyelectrolyte complexation driven by associative charging.

PubMed

Rathee, Vikramjit S; Zervoudakis, Aristotle J; Sidky, Hythem; Sikora, Benjamin J; Whitmer, Jonathan K

2018-03-21

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly. In this study, we elucidate the novel interplay between weak polyelectrolyte charging and complexation behavior through coupled molecular dynamics and Monte Carlo simulations. Specifically, we investigate a model of two equal-length and oppositely charging polymer chains in an implicit salt solution represented through Debye-Hückel interactions. The charging tendency of each chain, along with the salt concentration, is varied to determine the existence and extent of cooperativity in charging and complexation. Strong cooperation in the charging of these chains is observed at large Debye lengths, corresponding to low salt concentrations, while at lower Debye lengths (higher salt concentrations), the chains behave in apparent isolation. When the electrostatic coupling is long-ranged, we find that a highly charged chain strongly promotes the charging of its partner chain, even if the environment is unfavorable for an isolated version of that partner chain. Evidence of this phenomenon is supported by a drop in the potential energy of the system, which does not occur at the lower Debye lengths where both potential energies and charge fractions converge for all partner chain charging tendencies. The discovery of this cooperation will be helpful in developing "smart" drug delivery mechanisms by allowing for better predictions for the dissociation point of delivery complexes.

Weak polyelectrolyte complexation driven by associative charging

NASA Astrophysics Data System (ADS)

Rathee, Vikramjit S.; Zervoudakis, Aristotle J.; Sidky, Hythem; Sikora, Benjamin J.; Whitmer, Jonathan K.

2018-03-01

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly. In this study, we elucidate the novel interplay between weak polyelectrolyte charging and complexation behavior through coupled molecular dynamics and Monte Carlo simulations. Specifically, we investigate a model of two equal-length and oppositely charging polymer chains in an implicit salt solution represented through Debye-Hückel interactions. The charging tendency of each chain, along with the salt concentration, is varied to determine the existence and extent of cooperativity in charging and complexation. Strong cooperation in the charging of these chains is observed at large Debye lengths, corresponding to low salt concentrations, while at lower Debye lengths (higher salt concentrations), the chains behave in apparent isolation. When the electrostatic coupling is long-ranged, we find that a highly charged chain strongly promotes the charging of its partner chain, even if the environment is unfavorable for an isolated version of that partner chain. Evidence of this phenomenon is supported by a drop in the potential energy of the system, which does not occur at the lower Debye lengths where both potential energies and charge fractions converge for all partner chain charging tendencies. The discovery of this cooperation will be helpful in developing "smart" drug delivery mechanisms by allowing for better predictions for the dissociation point of delivery complexes.

Influence of Plasma Environment on K-Line Emission in Highly Ionized Iron Atoms Evaluated Using a Debye-Huckel Model

NASA Technical Reports Server (NTRS)

Deprince, J.; Fritzsche, S.; Kallman, T. R.; Palmeri, P.; Quinet, P.

2017-01-01

The influence of plasma environment on the atomic parameters associated with the K-vacancy states has been investigated theoretically for several iron ions. To do this, a time-averaged Debye-Huckel potential for both the electron-nucleus and electron-electron interactions has been considered in the framework of relativistic multiconfiguration Dirac-Fock computations. More particularly, the plasma screening effects on ionization potentials, K-thresholds, transition energies, and radiative rates have been estimated in the astrophysical context of accretion disks around black holes. In the present paper, we describe the behavior of those atomic parameters for Ne-, Na-, Ar-, and K-like iron ions.

Finite-element time-domain algorithms for modeling linear Debye and Lorentz dielectric dispersions at low frequencies.

PubMed

Stoykov, Nikolay S; Kuiken, Todd A; Lowery, Madeleine M; Taflove, Allen

2003-09-01

We present what we believe to be the first algorithms that use a simple scalar-potential formulation to model linear Debye and Lorentz dielectric dispersions at low frequencies in the context of finite-element time-domain (FETD) numerical solutions of electric potential. The new algorithms, which permit treatment of multiple-pole dielectric relaxations, are based on the auxiliary differential equation method and are unconditionally stable. We validate the algorithms by comparison with the results of a previously reported method based on the Fourier transform. The new algorithms should be useful in calculating the transient response of biological materials subject to impulsive excitation. Potential applications include FETD modeling of electromyography, functional electrical stimulation, defibrillation, and effects of lightning and impulsive electric shock.

A molecular Debye-Hückel theory and its applications to electrolyte solutions: The size asymmetric case

DOE PAGES

Xiao, Tiejun; Song, Xueyu

2017-03-28

We developed a molecular Debye-Hückel theory for electrolyte solutions with size asymmetry, where the dielectric response of an electrolyte solution is described by a linear combination of Debye-Hückel-like response modes. Furthermore, as the size asymmetry of an electrolyte solution leads to a charge imbalanced border zone around a solute, the dielectric response to the solute is characterized by two types of charge sources, namely, a bare solute charge and a charge distribution due to size asymmetry. These two kinds of charge sources are screened by the solvent differently, our theory presents a method to calculate the mean electric potential asmore » well as the electrostatic contributions to thermodynamic properties. Finally, the theory was successfully applied to binary as well as multi-component primitive models of electrolyte solutions.« less

Plasma-screening effects on the electron-impact excitation of hydrogenic ions in dense plasmas

NASA Technical Reports Server (NTRS)

Jung, Young-Dae

1993-01-01

Plasma-screening effects are investigated on electron-impact excitation of hydrogenic ions in dense plasmas. Scaled cross sections Z(exp 4) sigma for 1s yields 2s and 1s yields 2p are obtained for a Debye-Hueckel model of the screened Coulomb interaction. Ground and excited bound wave functions are modified in the screened Coulomb potential (Debye-Hueckel model) using the Ritz variation method. The resulting atomic wave functions and their eigenenergies agree well with the numerical and high-order perturbation theory calculations for the interesting domain of the Debye length not less than 10. The Born approximation is used to describe the continuum states of the projectile electron. Plasma screening effects on the atomic electrons cannot be neglected in the high-density cases. Including these effects, the cross sections are appreciably increased for 1s yields 2s transitions and decreased for 1s yields 2p transitions.

Electromagnetic plasma particle simulations on Solar Probe Plus spacecraft interaction with near-Sun plasma environment

NASA Astrophysics Data System (ADS)

Miyake, Yohei; Usui, Hideyuki

It is necessary to predict the nature of spacecraft-plasma interactions in extreme plasma conditions such as in the near-Sun environment. The spacecraft environment immersed in the solar corona is characterized by the small Debye length due to dense (7000 mathrm{/cc}) plasmas and a large photo-/secondary electron emission current emitted from the spacecraft surfaces, which lead to distinctive nature of spacecraft-plasma interactions [1,2,3]. In the present study, electromagnetic field perturbation around the Solar Probe Plus (SPP) spacecraft is examined by using our original EM-PIC (electromagnetic particle-in-cell) plasma simulation code called EMSES. In the simulations, we consider the SPP spacecraft at perihelion (0.04 mathrm{AU} from the Sun) and important physical effects such as spacecraft charging, photoelectron and secondary electron emission, solar wind plasma flow including the effect of spacecraft orbital velocity, and the presence of a background magnetic field. Our preliminary results show that both photoelectrons and secondary electrons from the spacecraft are magnetized in a spatial scale of several meters, and make drift motion due the presence of the background convection electric field. This effect leads to non-axisymmetric distributions of the electron density and the resultant electric potential near the spacecraft. Our simulations predict that a strong (˜ 100 mathrm{mV/m}) spurious electric field can be observed by the probe measurement on the spacecraft due to such a non-axisymmetric effect. We also confirm that the large photo-/secondary electron current alters magnetic field intensity around the spacecraft, but the field variation is much smaller than the background magnetic field magnitude (a few mathrm{nT} compared to a few mathrm{mu T}). [1] Ergun et al., textit{Phys. Plasmas}, textbf{17}, 072903, 2010. [2] Guillemant et al., textit{Ann. Geophys.}, textbf{30}, 1075-1092, 2012. [3] Guillemant et al., textit{IEEE Trans. Plasma Sci.}, textbf{41}, 3338-3348, 2013.

Full-Potential Calculation of Structural, Electronic, and Thermodynamic Properties of Fluoroperovskite { CsMF}3 (M = Be and Mg)

NASA Astrophysics Data System (ADS)

Harmel, M.; Khachai, H.; Ameri, A.; Baki, N.; Haddou, A.; Khalfa, M.; Abbar, B.; Omran, S. Bin; Uğur, G.; Uğur, Ş.; Khenata, R.

2012-12-01

The structural and electronic properties of the cubic fluoroperoveskite { CsBeF}3 and { CsMgF}3 have been investigated using the full-potential-linearized augmented plane wave method within the density functional theory. The exchange-correlation potential was treated with the local density approximation and the generalized gradient approximation. The calculations of the electronic band structures show that { CsBeF}_{3 } has an indirect bandgap, whereas { CsMgF}3 has a direct bandgap. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the effect of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and the heat capacity for { CsBeF}3 and { CsMgF}3 compounds are investigated for the first time.

Correlation potential of a test ion near a strongly charged plate.

PubMed

Lu, Bing-Sui; Xing, Xiangjun

2014-03-01

We analytically calculate the correlation potential of a test ion near a strongly charged plate inside a dilute m:-n electrolyte. We do this by calculating the electrostatic Green's function in the presence of a nonlinear background potential, the latter having been obtained using the nonlinear Poisson-Boltzmann theory. We consider the general case where the dielectric constants of the plate and the electrolyte are distinct. The following generic results emerge from our analyses: (1) If the distance to the plate Δz is much larger than a Gouy-Chapman length, the plate surface will behave effectively as an infinitely charged surface, and the dielectric constant of the plate effectively plays no role. (2) If Δz is larger than a Gouy-Chapman length but shorter than a Debye length, the correlation potential can be interpreted in terms of an image charge that is three times larger than the source charge. This behavior is independent of the valences of the ions. (3) The Green's function vanishes inside the plate if the surface charge density is infinitely large; hence the electrostatic potential is constant there. In this respect, a strongly charged plate behaves like a conductor plate. (4) If Δz is smaller than a Gouy-Chapman length, the correlation potential is dominated by the conventional image charge due to the dielectric discontinuity at the interface. (5) If Δz is larger than a Debye length, the leading order behavior of the correlation potential will depend on the valences of the ions in the electrolyte. Furthermore, inside an asymmetric electrolyte, the correlation potential is singly screened, i.e., it undergoes exponential decay with a decay width equal to the Debye length.

Effects of laser radiation field on energies of hydrogen atom in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahar, M. K., E-mail: mussiv58@gmail.com

2015-09-15

In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye andmore » quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.« less

The double layers in the plasma sheet boundary layer during magnetic reconnection

NASA Astrophysics Data System (ADS)

Guo, J.; Yu, B.

2014-11-01

We studied the evolutions of double layers which appear after the magnetic reconnection through two-dimensional electromagnetic particle-in-cell simulation. The simulation results show that the double layers are formed in the plasma sheet boundary layer after magnetic reconnection. At first, the double layers which have unipolar structures are formed. And then the double layers turn into bipolar structures, which will couple with another new weak bipolar structure. Thus a new double layer or tripolar structure comes into being. The double layers found in our work are about several ten Debye lengths, which accords with the observation results. It is suggested that the electron beam formed during the magnetic reconnection is responsible for the production of the double layers.

Conditions for similitude and the effect of finite Debye length in electroosmotic flows.

PubMed

Oh, Jung Min; Kang, Kwan Hyoung

2007-06-15

Under certain conditions, the velocity field is similar to the electric field for electroosmotic flow (EOF) inside a channel. There was a disagreement between investigators on the necessity of the infinitesimal-Reynolds-number condition for the similarity when the Helmholtz-Smoluchowski relation is applied throughout the boundaries. What is puzzling is a recent numerical result that showed, contrary to the conventional belief, an evident Reynolds number dependence of the EOF. We show here that the notion that the infinitesimal-Reynolds-number condition is required originates from the misunderstanding that the EOF is the Stokes flow. We point out that the EOF becomes the potential flow when the Helmholtz-Smoluchowski relation is applied at the boundaries. We carry out a numerical simulation to investigate the effect of finiteness of the Debye length and the vorticity layer inherently existing at the channel wall. We show that the Reynolds number dependence of the previous numerical simulation resulted from the finiteness of the Debye length and subsequent convective transport of vorticity toward the bulk flow. We discuss in detail how the convection of vorticity occurs and what factors are involved in the transport process, after carrying out the simulation for different Reynolds numbers, Debye lengths, corner radii, and geometries.

Debye screening in single-molecule carbon nanotube field-effect sensors.

PubMed

Sorgenfrei, Sebastian; Chiu, Chien-Yang; Johnston, Matthew; Nuckolls, Colin; Shepard, Kenneth L

2011-09-14

Point-functionalized carbon nanotube field-effect transistors can serve as highly sensitive detectors for biomolecules. With a probe molecule covalently bound to a defect in the nanotube sidewall, two-level random telegraph noise (RTN) in the conductance of the device is observed as a result of a charged target biomolecule binding and unbinding at the defect site. Charge in proximity to the defect modulates the potential (and transmission) of the conductance-limiting barrier created by the defect. In this Letter, we study how these single-molecule electronic sensors are affected by ionic screening. Both charge in proximity to the defect site and buffer concentration are found to affect RTN amplitude in a manner that follows from simple Debye length considerations. RTN amplitude is also dependent on the potential of the electrolyte gate as applied to the reference electrode; at high enough gate potentials, the target DNA is completely repelled and RTN is suppressed.

Debye screening in single-molecule carbon nanotube field-effect transistors

PubMed Central

Sorgenfrei, Sebastian; Chiu, Chien-yang; Johnston, Matthew; Nuckolls, Colin; Shepard, Kenneth L.

2013-01-01

Point-functionalized carbon nanotube field-effect transistors can serve as highly sensitive detectors for biomolecules. With a probe molecule covalently bound to a defect in the nanotube sidewall, two-level random telegraph noise (RTN) in the conductance of the device is observed as a result of a charged target biomolecule binding and unbinding at the defect site. Charge in proximity to the defect modulates the potential (and transmission) of the conductance-limiting barrier created by the defect. In this Letter, we study how these single-molecule electronic sensors are affected by ionic screening. Both charge in proximity to the defect site and buffer concentration are found to affect RTN amplitude in a manner that follows from simple Debye length considerations. RTN amplitude is also dependent on the potential of the electrolyte gate as applied to the reference electrode; at high enough repulsive potentials, the target DNA is completely repelled and RTN is suppressed. PMID:21806018

Long Range Debye-Hückel Correction for Computation of Grid-based Electrostatic Forces Between Biomacromolecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mereghetti, Paolo; Martinez, M.; Wade, Rebecca C.

Brownian dynamics (BD) simulations can be used to study very large molecular systems, such as models of the intracellular environment, using atomic-detail structures. Such simulations require strategies to contain the computational costs, especially for the computation of interaction forces and energies. A common approach is to compute interaction forces between macromolecules by precomputing their interaction potentials on three-dimensional discretized grids. For long-range interactions, such as electrostatics, grid-based methods are subject to finite size errors. We describe here the implementation of a Debye-Hückel correction to the grid-based electrostatic potential used in the SDA BD simulation software that was applied to simulatemore » solutions of bovine serum albumin and of hen egg white lysozyme.« less

Angular Distribution and Linear Polarization of X-ray Radiation Resulting from Electron Impact Excitation of Highly Charged Ions in Debye Plasmas

NASA Astrophysics Data System (ADS)

Chen, Zhanbin

2018-05-01

Plasma-screening effects on the 1s _{1/2} → 2l (l = s , p ) and 1s _{1/2} → 3d _{3/2} electron-impact excitation of highly charged ions are investigated, together with their subsequent radiative decay. The analysis is performed based on the multi-configuration Dirac-Fock method and the fully relativistic distorted-wave method incorporating the Debye-Hückel potential. To explore the nature of the effects, calculations are carried out based on detailed analyses of the integrated total and magnetic sublevel cross sections, the alignment parameters, the linear polarizations, and the angular distribution of the X-ray photoemission, as well as on corresponding data calculated in various Debye lengths/environments, taking the 2p _{3/2}→ 1s _{1/2} and 3d _{3/2}→ 1s _{1/2} characteristic lines of H-like Fe^{25+} ion as an example. The present results are compared with experimental data and other theoretical predictions where available.

Hydrodynamic dispersion in a combined magnetohydrodynamic- electroosmotic-driven flow through a microchannel with slowly varying wall zeta potentials

NASA Astrophysics Data System (ADS)

Vargas, C.; Arcos, J.; Bautista, O.; Méndez, F.

2017-09-01

The effective dispersion coefficient of a neutral solute in the combined electroosmotic (EO) and magnetohydrodynamic (MHD)-driven flow of a Newtonian fluid through a parallel flat plate microchannel is studied. The walls of the microchannel are assumed to have modulated and low zeta potentials that vary slowly in the axial direction in a sinusoidal manner. The flow field required to obtain the dispersion coefficient is solved using the lubrication approximation theory. The solution of the electrical potential is based on the Debye-Hückel approximation for a symmetric (Z :Z ) electrolyte solution. The EO and MHD effects, together with the variations in the zeta potentials of the walls, are observed to notably modify the axial distribution of the effective dispersion coefficient. The problem is formulated for two cases of the zeta potential function. Note that the dispersion coefficient primarily depends on the Hartmann number, on the ratio of the half height of the microchannel to the Debye length, and on the assumed variation in the zeta potentials of the walls.

On the non-exponentiality of the dielectric Debye-like relaxation of monoalcohols

NASA Astrophysics Data System (ADS)

Arrese-Igor, S.; Alegría, A.; Colmenero, J.

2017-03-01

We have investigated the Debye-like relaxation in a series of monoalcohols (MAs) by broadband dielectric spectroscopy and thermally stimulated depolarization current techniques in order to get further insight on the time dispersion of this intriguing relaxation. Results indicate that the Debye-like relaxation of MAs is not always of exponential type and conforms well to a dispersion of Cole-Davidson type. Apart from the already reported non-exponentiality of the Debye-like relaxation in 2-hexyl-1-decanol and 2-butyl-1-octanol, a detailed analysis of the dielectric permittivity of 5-methyl-3-heptanol shows that this MA also presents some extent of dispersion on its Debye-like relaxation which strongly depends on the temperature. Results suggest that the non-exponential character of the Debye-like relaxation might be a general characteristic in the case of not so intense Debye-like relaxations relative to the α relaxation. Finally, we briefly discuss on the T-dependence and possible origin for the observed dispersion.

Tight ceramic UF membrane as RO pre-treatment: the role of electrostatic interactions on phosphate rejection.

PubMed

Shang, Ran; Verliefde, Arne R D; Hu, Jingyi; Zeng, Zheyi; Lu, Jie; Kemperman, Antoine J B; Deng, Huiping; Nijmeijer, Kitty; Heijman, Sebastiaan G J; Rietveld, Luuk C

2014-01-01

Phosphate limitation has been reported as an effective approach to inhibit biofouling in reverse osmosis (RO) systems for water purification. The rejection of dissolved phosphate by negatively charged TiO2 tight ultrafiltration (UF) membranes (1 kDa and 3 kDa) was observed. These membranes can potentially be adopted as an effective process for RO pre-treatment in order to constrain biofouling by phosphate limitation. This paper focuses on electrostatic interactions during tight UF filtration. Despite the larger pore size, the 3 kDa ceramic membrane exhibited greater phosphate rejection than the 1 kDa membrane, because the 3 kDa membrane has a greater negative surface charge and thus greater electrostatic repulsion against phosphate. The increase of pH from 6 to 8.5 led to a substantial increase in phosphate rejection by both membranes due to increased electrostatic repulsion. At pH 8.5, the maximum phosphate rejections achieved by the 1 kDa and 3 kDa membrane were 75% and 86%, respectively. A Debye ratio (ratio of the Debye length to the pore radius) is introduced in order to evaluate double layer overlapping in tight UF membranes. Threshold Debye ratios were determined as 2 and 1 for the 1 kDa and 3 kDa membranes, respectively. A Debye ratio below the threshold Debye ratio leads to dramatically decreased phosphate rejection by tight UF membranes. The phosphate rejection by the tight UF, in combination with chemical phosphate removal by coagulation, might accomplish phosphate-limited conditions for biological growth and thus prevent biofouling in the RO systems. Copyright © 2013 Elsevier Ltd. All rights reserved.

The origin of the Debye relaxation in liquid water and fitting the high frequency excess response.

PubMed

Elton, Daniel C

2017-07-19

We critically review the literature on the Debye absorption peak of liquid water and the excess response found on the high frequency side of the Debye peak. We find a lack of agreement on the microscopic phenomena underlying both of these features. To better understand the molecular origin of Debye peak we ran large scale molecular dynamics simulations and performed several different distance-dependent decompositions of the low frequency dielectric spectra, finding that it involves processes that take place on scales of 1.5-2.0 nm. We also calculated the k-dependence of the Debye relaxation, finding it to be highly dispersive. These findings are inconsistent with models that relate Debye relaxation to local processes such as the rotation/translation of molecules after H-bond breaking. We introduce the spectrumfitter Python package for fitting dielectric spectra and analyze different ways of fitting the high frequency excess, such as including one or two additional Debye peaks. We propose using the generalized Lydanne-Sachs-Teller (gLST) equation as a way of testing the physicality of model dielectric functions. Our attempts at fitting the experimental spectrum using the gLST relation as a constraint indicate that the traditional way of fitting the excess response with secondary and tertiary Debye relaxations is problematic. All of our work is consistent with the recent theory of Popov et al. (2016) that Debye relaxation is due to the migration of Bjerrum-like defects in the hydrogen bond network. Under this theory, the mechanism of Debye relaxation in liquid water is similar to the mechanism in ice, but the heterogeneity and power-law dynamics of the H-bond network in water results in excess response on the high frequency side of the peak.

Theoretical investigations on structural, elastic and electronic properties of thallium halides

NASA Astrophysics Data System (ADS)

Singh, Rishi Pal; Singh, Rajendra Kumar; Rajagopalan, Mathrubutham

2011-04-01

Theoretical investigations on structural, elastic and electronic properties, viz. ground state lattice parameter, elastic moduli and density of states, of thallium halides (viz. TlCl and TlBr) have been made using the full potential linearized augmented plane wave method within the generalized gradient approximation (GGA). The ground state lattice parameter and bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameter have also been calculated for these compounds. Calculated structural, elastic and other parameters are in good agreement with the available data.

Thermodynamic properties of fullerite C70

NASA Astrophysics Data System (ADS)

Rekhviashvili, S. Sh.

2017-08-01

A new expression for the isochoric heat capacity and the equation of state of fullerite C70 are obtained in the framework of a quantum-statistical method. Analogs of the Debye law and Dulong-Petit law for this fullerite are formulated. Fullerene C70 molecules are modeled by isotropic quantum oscillators under the assumption that their nonsphericity weakly influences the thermodynamic properties of the condensed phase. The intramolecular oscillations of carbon atoms are described using the Debye theory and the cold contribution to the free energy of fullerite is calculated using the Lennard-Jones pair potential for fullerene molecules. A comparison of the proposed theory to experiment shows good agreement.

Thermodynamic properties of semiconductor compounds studied based on Debye-Waller factors

NASA Astrophysics Data System (ADS)

Van Hung, Nguyen; Toan, Nguyen Cong; Ba Duc, Nguyen; Vuong, Dinh Quoc

2015-08-01

Thermodynamic properties of semiconductor compounds have been studied based on Debye-Waller factors (DWFs) described by the mean square displacement (MSD) which has close relation with the mean square relative displacement (MSRD). Their analytical expressions have been derived based on the statistical moment method (SMM) and the empirical many-body Stillinger-Weber potentials. Numerical results for the MSDs of GaAs, GaP, InP, InSb, which have zinc-blende structure, are found to be in reasonable agreement with experiment and other theories. This paper shows that an elements value for MSD is dependent on the binary semiconductor compound within which it resides.

Dusty plasma ring model

NASA Astrophysics Data System (ADS)

Sheridan, T. E.

2009-12-01

A model of a dusty plasma (Yukawa) ring is presented. We consider n identical particles confined in a two-dimensional (2D) annular potential well and interacting through a Debye (i.e. Yukawa or screened Coulomb) potential. Equilibrium configurations are computed versus n, the Debye shielding parameter and the trap radius. When the particle separation exceeds a critical value the particles form a 1D chain with a ring topology. Below the critical separation the zigzag instability gives a 2D configuration. Computed critical separations are shown to agree well with a theoretical prediction for the zigzag threshold. Normal mode spectra for 1D rings are computed and found to be in excellent agreement with the longitudinal and transverse dispersion relations for unbounded straight chains. When the longitudinal and transverse dispersion relations intersect we observe a resonance due to the finite curvature of the ring.

Electromagnetic pulse distortion in living tissue.

PubMed

Lepelaars, E S

1996-05-01

Insight into the distortion of electromagnetic (EM) signals in living tissue is important for optimising medical applications. To obtain this insight, field calculations have been carried out for a plane-stratified configuration of air, skin, fat, muscle and bone tissue. In this configuration, an EM field is generated by a prescribed pulsed current in a circular loop. Debye dispersion models have been developed for the description of the permittivity of the tissues. The field problem is solved analytically with the aid of a temporal Fourier transformation and a spatial Hankel transformation. The corresponding inverse transformations have been carried out numerically. To demonstrate the influences of stratification and dispersion separately, the EM fields in the stratified configuration, in a completely muscle-filled space and in vacuum are compared. Two different pulses have been considered; narrow and wide. It emerges that dispersion results in a retardation and an attenuation of the field. Stratification causes additional fluctuations of the time-dependent field. Furthermore, the conductivity of tissue at high frequencies is mainly determined by its water content. Tissues with high water content, like muscle and skin, exhibit higher conductivity at high frequencies than fat and bone. Muscle and skin tissue therefore behave as low-pass filters to EM signals.

Non Debye approximation on specific heat of solids

NASA Astrophysics Data System (ADS)

Bhattacharjee, Ruma; Das, Anamika; Sarkar, A.

2018-05-01

A simple non Debye frequency spectrum is proposed. The normalized frequency spectrum is compared to that of Debye spectrum. The proposed spectrum, provides a good account of low frequency phonon density of states, which gives a linear temperature variation at low temperature in contrast to Debye T3 law. It has been analyzed that the proposed model provides a good account of excess specific heat for nanostructure solid.

Simulations of free-solution electrophoresis of polyelectrolytes with a finite Debye length using the Debye-Hückel approximation.

PubMed

Hickey, Owen A; Shendruk, Tyler N; Harden, James L; Slater, Gary W

2012-08-31

We introduce a mesoscale simulation method based on multiparticle collision dynamics (MPCD) for the electrohydrodynamics of polyelectrolytes with finite Debye lengths. By applying the Debye-Hückel approximation to assign an effective charge to MPCD particles near charged monomers, our simulations are able to reproduce the rapid rise in the electrophoretic mobility with respect to the degree of polymerization for the shortest polymer lengths followed by a small decrease for longer polymers due to charge condensation. Moreover, these simulations demonstrate the importance of a finite Debye length in accurately determining the mobility of uniformly charged polyelectrolytes and net neutral polyampholytes.

Debye-Scherrer simulation and its use for nano-materials testing

NASA Astrophysics Data System (ADS)

Kalabushkin, Alexander E.

2005-04-01

Nano-material specimens of metallic glass were tested with the Debye-Scherrer x-ray diffraction method. For data simulation and data treatment new Debye-Scherrer simulator was devised. The simulator and test results are discussed.

Study of microvascular non-Newtonian blood flow modulated by electroosmosis.

PubMed

Tripathi, Dharmendra; Yadav, Ashu; Anwar Bég, O; Kumar, Rakesh

2018-05-01

An analytical study of microvascular non-Newtonian blood flow is conducted incorporating the electro-osmosis phenomenon. Blood is considered as a Bingham rheological aqueous ionic solution. An externally applied static axial electrical field is imposed on the system. The Poisson-Boltzmann equation for electrical potential distribution is implemented to accommodate the electrical double layer in the microvascular regime. With long wavelength, lubrication and Debye-Hückel approximations, the boundary value problem is rendered non-dimensional. Analytical solutions are derived for the axial velocity, volumetric flow rate, pressure gradient, volumetric flow rate, averaged volumetric flow rate along one time period, pressure rise along one wavelength and stream function. A plug swidth is featured in the solutions. Via symbolic software (Mathematica), graphical plots are generated for the influence of Bingham plug flow width parameter, electrical Debye length and Helmholtz-Smoluchowski velocity (maximum electro-osmotic velocity) on the key hydrodynamic variables. This study reveals that blood flow rate accelerates with decreasing the plug width (i.e. viscoplastic nature of fluids) and also with increasing the Debye length parameter. Copyright © 2018 Elsevier Inc. All rights reserved.

Simulation of radial expansion of an electron beam injected into a background plasma

NASA Technical Reports Server (NTRS)

Koga, J.; Lin, C. S.

1989-01-01

A 2-D electrostatic particle code was used to study the beam radial expansion of a nonrelativistic electron beam injected from an isolated equipotential conductor into a background plasma. The simulations indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. The simulations also suggest that the charge buildup at the beam stagnation point causes the beam radial expansion. From a survey of the simulation results, it is found that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. This dependence is explained in terms of the ratio of the beam electron Debye length to the ambient electron Debye length. These results are most applicable to the SEPAC electron beam injection experiments from Spacelab 1, where high charging potential was observed.

Electron-ion collision rates in noble gas clusters irradiated by femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Dey, R.; Roy, A. C.

2012-05-01

We report a theoretical analysis of electron-ion collision rates in xenon gas clusters irradiated by femtosecond laser pulses. The present analysis is based on the eikonal approximation (EA), the first Born approximation (FBA) and the classical (CL) methods. The calculations are performed using the plasma-screened Rogers potential introduced by Moll et al. [J. Phys. B. 43, 135103 (2010)] as well as the Debye potential for a wide range of experimental parameters. We find that the magnitudes of electron-ion collision frequency obtained in the EA do not fall as rapidly with the kinetic energy of electrons as in the FBA and CL methods for higher charge states of xenon ion (Xe8+ and Xe14+). Furthermore, EA shows that the effect of the inner structure of ion is most dominant for the lowest charge state of xenon ion (Xe1+). In the case of the present effective potential, FBA overestimates the CL results for all three different charge states of xenon, whereas for the Debye potential, both the FBA and CL methods predict collision frequencies which are nearly close to each other.

Structural, electronic and thermal properties of super hard ternary boride, WAlB

NASA Astrophysics Data System (ADS)

Rajpoot, Priyanka; Rastogi, Anugya; Verma, U. P.

2018-04-01

A first principle study of the structural, electronic and thermal properties of Tungsten Aluminum Boride (WAlB) using full-potential linearized augmented plane wave (FP-LAPW) in the frame work of density function theory (DFT) have been calculated. The calculated equilibrium structural parameters are in excellent agreement with available experimental results. The calculated electronic band structure reveals that WAlB is metallic in nature. The quasi-harmonic Debye model is applied to study of the temperature and pressure effect on volume, Debye temperature, thermal expansion coefficient and specific heat at constant volume and constant pressure. To the best of our knowledge theoretical investigation of these properties of WAlB is reported for the first time.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filippov, A. V., E-mail: fav@triniti.ru

The interaction of two charged point macroparticles located in Wigner–Seitz cells of simple cubic (SC), body-centered cubic (BCC), or face-centered cubic (FCC) lattices in an equilibrium plasma has been studied within the Debye approximation or, more specifically, based on the linearized Poisson–Boltzmann model. The shape of the outer boundary is shown to exert a strong influence on the pattern of electrostatic interaction between the two macroparticles, which transforms from repulsion at small interparticle distances to attraction as the interparticle distance approaches half the length of the computational cell. The macroparticle pair interaction potential in an equilibrium plasma is shown tomore » be nevertheless the Debye one and purely repulsive for likely charged macroparticles.« less

Understanding light scattering by a coated sphere part 2: time domain analysis.

PubMed

Laven, Philip; Lock, James A

2012-08-01

Numerical computations were made of scattering of an incident electromagnetic pulse by a coated sphere that is large compared to the dominant wavelength of the incident light. The scattered intensity was plotted as a function of the scattering angle and delay time of the scattered pulse. For fixed core and coating radii, the Debye series terms that most strongly contribute to the scattered intensity in different regions of scattering angle-delay time space were identified and analyzed. For a fixed overall radius and an increasing core radius, the first-order rainbow was observed to evolve into three separate components. The original component faded away, while the two new components eventually merged together. The behavior of surface waves generated by grazing incidence at the core/coating and coating/exterior interfaces was also examined and discussed.

Free-energy functional of the Debye-Hückel model of simple fluids

NASA Astrophysics Data System (ADS)

Piron, R.; Blenski, T.

2016-12-01

The Debye-Hückel approximation to the free energy of a simple fluid is written as a functional of the pair correlation function. This functional can be seen as the Debye-Hückel equivalent to the functional derived in the hypernetted chain framework by Morita and Hiroike, as well as by Lado. It allows one to obtain the Debye-Hückel integral equation through a minimization with respect to the pair correlation function, leads to the correct form of the internal energy, and fulfills the virial theorem.

Effective surface Debye temperature for NiMnSb(100) epitaxial films

NASA Astrophysics Data System (ADS)

Borca, C. N.; Komesu, Takashi; Jeong, Hae-kyung; Dowben, P. A.; Ristoiu, D.; Hordequin, Ch.; Pierre, J.; Nozières, J. P.

2000-07-01

The surface Debye temperature of the NiMnSb (100) epitaxial films has been obtained using low energy electron diffraction, inverse photoemission, and core-level photoemission. The normal dynamic motion of the (100) surface results in a value for the effective surface Debye temperature of 145±13 K. This is far smaller than the bulk Debye temperature of 312±5 K obtained from wave vector dependent inelastic neutron scattering. The large difference between these measures of surface and bulk dynamic motion indicates a soft and compositionally different (100) surface.

Elucidation of spin echo small angle neutron scattering correlation functions through model studies.

PubMed

Shew, Chwen-Yang; Chen, Wei-Ren

2012-02-14

Several single-modal Debye correlation functions to approximate part of the overall Debey correlation function of liquids are closely examined for elucidating their behavior in the corresponding spin echo small angle neutron scattering (SESANS) correlation functions. We find that the maximum length scale of a Debye correlation function is identical to that of its SESANS correlation function. For discrete Debye correlation functions, the peak of SESANS correlation function emerges at their first discrete point, whereas for continuous Debye correlation functions with greater width, the peak position shifts to a greater value. In both cases, the intensity and shape of the peak of the SESANS correlation function are determined by the width of the Debye correlation functions. Furthermore, we mimic the intramolecular and intermolecular Debye correlation functions of liquids composed of interacting particles based on a simple model to elucidate their competition in the SESANS correlation function. Our calculations show that the first local minimum of a SESANS correlation function can be negative and positive. By adjusting the spatial distribution of the intermolecular Debye function in the model, the calculated SESANS spectra exhibit the profile consistent with that of hard-sphere and sticky-hard-sphere liquids predicted by more sophisticated liquid state theory and computer simulation. © 2012 American Institute of Physics

Effects of overlapping electric double layer on mass transport of a macro-solute across porous wall of a micro/nanochannel for power law fluid.

PubMed

Bhattacharjee, Saikat; Mondal, Mrinmoy; De, Sirshendu

2017-05-01

Effects of overlapping electric double layer and high wall potential on transport of a macrosolute for flow of a power law fluid through a microchannel with porous walls are studied in this work. The electric potential distribution is obtained by coupling the Poisson's equation without considering the Debye-Huckel approximation. The numerical solution shows that the center line potential can be 16% of wall potential at pH 8.5, at wall potential -73 mV and scaled Debye length 0.5. Transport phenomena involving mass transport of a neutral macrosolute is formulated by species advective equation. An analytical solution of Sherwood number is obtained for power law fluid. Effects of fluid rheology are studied in detail. Average Sherwood number is more for a pseudoplastic fluid compared to dilatant upto the ratio of Poiseuille to electroosmotic velocity of 5. Beyond that, the Sherwood number is independent of fluid rheology. Effects of fluid rheology and solute size on permeation flux and concentration of neutral solute are also quantified. More solute permeation occurs as the fluid changes from pseudoplastic to dilatant. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

One-dimensional conduction through supporting electrolytes: two-scale cathodic Debye layer.

PubMed

Almog, Yaniv; Yariv, Ehud

2011-10-01

Supporting-electrolyte solutions comprise chemically inert cations and anions, produced by salt dissolution, together with a reactive ionic species that may be consumed and generated on bounding ion-selective surfaces (e.g., electrodes or membranes). Upon application of an external voltage, a Faraday current is thereby established. It is natural to analyze this ternary-system process through a one-dimensional transport problem, employing the thin Debye-layer limit. Using a simple model of ideal ion-selective membranes, we have recently addressed this problem for moderate voltages [Yariv and Almog, Phys. Rev. Lett. 105, 176101 (2010)], predicting currents that scale as a fractional power of Debye thickness. We address herein the complementary problem of moderate currents. We employ matched asymptotic expansions, separately analyzing the two inner thin Debye layers adjacent to the ion-selective surfaces and the outer electroneutral region outside them. A straightforward calculation following comparable singular-perturbation analyses of binary systems is frustrated by the prediction of negative ionic concentrations near the cathode. Accompanying numerical simulations, performed for small values of Debye thickness, indicate a number unconventional features occurring at that region, such as inert-cation concentration amplification and electric-field intensification. The current-voltage correlation data of the electrochemical cell, obtained from compilation of these simulations, does not approach a limit as the Debye thickness vanishes. Resolution of these puzzles reveals a transformation of the asymptotic structure of the cathodic Debye layer. This reflects the emergence of an internal boundary layer, adjacent to the cathode, wherein field and concentration scaling differs from those of the Gouy-Chapman theory. The two-scale feature of the cathodic Debye layer is manifested through a logarithmic voltage scaling with Debye thickness. Accounting for this scaling, the complied current-voltage data collapses upon a single curve. This curve practically coincides with an asymptotically calculated universal current-voltage relation.

On behavior peculiarity of electron plasma

NASA Astrophysics Data System (ADS)

Gordeeva, N. M.; Yushkanov, A. A.

2018-03-01

The analysis of the analytical solution of the problem of the behavior of electron plasma in the AC electric field is fulfilled. Debye mode describes shielding of the external electric field in the plasma. The analysis of the region of existence of Debye mode, depending on the plasma parameters has been realized. A non-trivial dependence of the region of existence of Debye mode on the degree of degeneracy of the electron gas are revealed. For the case of nearly degenerate electron gas Debye mode has several areas of existence, depending on the frequency of the electric field.

Strong and weak adsorptions of polyelectrolyte chains onto oppositely charged spheres

NASA Astrophysics Data System (ADS)

Cherstvy, A. G.; Winkler, R. G.

2006-08-01

We investigate the complexation of long thin polyelectrolyte (PE) chains with oppositely charged spheres. In the limit of strong adsorption, when strongly charged PE chains adapt a definite wrapped conformation on the sphere surface, we analytically solve the linear Poisson-Boltzmann equation and calculate the electrostatic potential and the energy of the complex. We discuss some biological applications of the obtained results. For weak adsorption, when a flexible weakly charged PE chain is localized next to the sphere in solution, we solve the Edwards equation for PE conformations in the Hulthén potential, which is used as an approximation for the screened Debye-Hückel potential of the sphere. We predict the critical conditions for PE adsorption. We find that the critical sphere charge density exhibits a distinctively different dependence on the Debye screening length than for PE adsorption onto a flat surface. We compare our findings with experimental measurements on complexation of various PEs with oppositely charged colloidal particles. We also present some numerical results of the coupled Poisson-Boltzmann and self-consistent field equation for PE adsorption in an assembly of oppositely charged spheres.

Electron capture and excitation processes in H+-H collisions in dense quantum plasmas

NASA Astrophysics Data System (ADS)

Jakimovski, D.; Markovska, N.; Janev, R. K.

2016-10-01

Electron capture and excitation processes in proton-hydrogen atom collisions taking place in dense quantum plasmas are studied by employing the two-centre atomic orbital close-coupling (TC-AOCC) method. The Debye-Hückel cosine (DHC) potential is used to describe the plasma screening effects on the Coulomb interaction between charged particles. The properties of a hydrogen atom with DHC potential are investigated as a function of the screening strength of the potential. It is found that the decrease in binding energy of nl levels with increasing screening strength is considerably faster than in the case of the Debye-Hückel (DH) screening potential, appropriate for description of charged particle interactions in weakly coupled classical plasmas. This results in a reduction in the number of bound states in the DHC potential with respect to that in the DH potential for the same plasma screening strength, and is reflected in the dynamics of excitation and electron capture processes for the two screened potentials. The TC-AOCC cross sections for total and state-selective electron capture and excitation cross sections with the DHC potential are calculated for a number of representative screening strengths in the 1-300 keV energy range and compared with those for the DH and pure Coulomb potential. The total capture cross sections for a selected number of screening strengths are compared with the available results from classical trajectory Monte Carlo calculations.

Quadrupole terms in the Maxwell equations: Debye-Hückel theory in quadrupolarizable solvent and self-salting-out of electrolytes.

PubMed

Slavchov, Radomir I

2014-04-28

If the molecules of a given solvent possess significant quadrupolar moment, the macroscopic Maxwell equations must involve the contribution of the density of the quadrupolar moment to the electric displacement field. This modifies the Poisson-Boltzmann equation and all consequences from it. In this work, the structure of the diffuse atmosphere around an ion dissolved in quadrupolarizable medium is analyzed by solving the quadrupolar variant of the Coulomb-Ampere's law of electrostatics. The results are compared to the classical Debye-Hückel theory. The quadrupolar version of the Debye-Hückel potential of a point charge is finite even in r = 0. The ion-quadrupole interaction yields a significant expansion of the diffuse atmosphere of the ion and, thus, it decreases the Debye-Hückel energy. In addition, since the dielectric permittivity of the electrolyte solutions depends strongly on concentration, the Born energy of the dissolved ions alters with concentration, which has a considerable contribution to the activity coefficient γ± known as the self-salting-out effect. The quadrupolarizability of the medium damps strongly the self-salting-out of the electrolyte, and thus it affects additionally γ±. Comparison with experimental data for γ± for various electrolytes allows for the estimation of the quadrupolar length of water: LQ ≈ 2 Å, in good agreement with previous assessments. The effect of quadrupolarizability is especially important in non-aqueous solutions. Data for the activity of NaBr in methanol is used to determine the quadrupolarizability of methanol with good accuracy.

Theory of a cylindrical probe in a collisionless magnetoplasma

NASA Technical Reports Server (NTRS)

Laframboise, J. G.; Rubinstein, J.

1976-01-01

A theory is presented for a cylindrical electrostatic probe in a collisionless plasma in the case where the probe axis is inclined at an angle to a uniform magnetic field. The theory is applicable to electron collection, and under more restrictive conditions, to ion collection. For a probe at space potential, the theory is exact in the limit where probe radius is much less than Debye length. At attracting probe potentials, the theory yields an upper bound and an adiabatic limit for current collection. At repelling probe potentials, it provides a lower bound. The theory is valid if the ratios of probe radius to Debye length and probe radius to mean gyroradius are not simultaneously large enough to produce extrema in the probe sheath potential. The numerical current calculations are based on the approximation that particle orbits are helices near the probe, together with the use of kinetic theory to relate velocity distributions near the probe to those far from it. Probe characteristics are presented for inclination angles from 0 to 90 deg and for probe-radius mean-gyroradius ratios from 0.1 to infinity. For an angle of 0 deg, the end-effect current is calculated separately.

The defect level and ideal thermal conductivity of graphene uncovered by residual thermal reffusivity at the 0 K limit

NASA Astrophysics Data System (ADS)

Xie, Yangsu; Xu, Zaoli; Xu, Shen; Cheng, Zhe; Hashemi, Nastaran; Deng, Cheng; Wang, Xinwei

2015-05-01

Due to its intriguing thermal and electrical properties, graphene has been widely studied for potential applications in sensor and energy devices. However, the reported value for its thermal conductivity spans from dozens to thousands of W m-1 K-1 due to different levels of alternations and defects in graphene samples. In this work, the thermal diffusivity of suspended four-layered graphene foam (GF) is characterized from room temperature (RT) down to 17 K. For the first time, we identify the defect level in graphene by evaluating the inverse of thermal diffusivity (termed ``thermal reffusivity'': Θ) at the 0 K limit. By using the Debye model of Θ = Θ0 + C × e-θ/2T and fitting the Θ-T curve to the point of T = 0 K, we identify the defect level (Θ0) and determine the Debye temperature of graphene. Θ0 is found to be 1878 s m-2 for the studied GF and 43-112 s m-2 for three highly crystalline graphite materials. This uncovers a 16-43-fold higher defect level in GF than that in pyrolytic graphite. In GF, the phonon mean free path solely induced by defects and boundary scattering is determined as 166 nm. The Debye temperature of graphene is determined to be 1813 K, which is very close to the average theoretical Debye temperature (1911 K) of the three acoustic phonon modes in graphene. By subtracting the defect effect, we report the ideal thermal diffusivity and conductivity (κideal) of graphene presented in the 3D foam structure in the range of 33-299 K. Detailed physics based on chemical composition and structure analysis are given to explain the κideal-T profile by comparing with those reported for suspended graphene.Due to its intriguing thermal and electrical properties, graphene has been widely studied for potential applications in sensor and energy devices. However, the reported value for its thermal conductivity spans from dozens to thousands of W m-1 K-1 due to different levels of alternations and defects in graphene samples. In this work, the thermal diffusivity of suspended four-layered graphene foam (GF) is characterized from room temperature (RT) down to 17 K. For the first time, we identify the defect level in graphene by evaluating the inverse of thermal diffusivity (termed ``thermal reffusivity'': Θ) at the 0 K limit. By using the Debye model of Θ = Θ0 + C × e-θ/2T and fitting the Θ-T curve to the point of T = 0 K, we identify the defect level (Θ0) and determine the Debye temperature of graphene. Θ0 is found to be 1878 s m-2 for the studied GF and 43-112 s m-2 for three highly crystalline graphite materials. This uncovers a 16-43-fold higher defect level in GF than that in pyrolytic graphite. In GF, the phonon mean free path solely induced by defects and boundary scattering is determined as 166 nm. The Debye temperature of graphene is determined to be 1813 K, which is very close to the average theoretical Debye temperature (1911 K) of the three acoustic phonon modes in graphene. By subtracting the defect effect, we report the ideal thermal diffusivity and conductivity (κideal) of graphene presented in the 3D foam structure in the range of 33-299 K. Detailed physics based on chemical composition and structure analysis are given to explain the κideal-T profile by comparing with those reported for suspended graphene. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02012c

Kinetic Theory of Plasmas

DTIC Science & Technology

2009-09-01

RTO-EN-AVT-162 means of a Coulomb potential screened at the Debye length (Delcroix and Bers, 1984; Balescu , 1988). 4. The plasma is composed of...Theory of Plasmas 2 - 28 RTO-EN-AVT-162 References Balescu , R. (1988). Transport Processes in Plasmas. Elsevier, Amsterdam. Barth, T. (2008

Sum-Frequency Generation from a Thin Cylindrical Layer

NASA Astrophysics Data System (ADS)

Shamyna, A. A.; Kapshai, V. N.

2018-01-01

In the Rayleigh-Gans-Debye approximation, we have solved the problem of the sum-frequency generation by two plane elliptically polarized electromagnetic waves from the surface of a dielectric particle of a cylindrical shape that is coated by a thin layer possessing nonlinear optical properties. The formulas that describe the sum-frequency field have been presented in the tensor and vector forms for the second-order nonlinear dielectric susceptibility tensor, which was chosen in the general form, containing chiral components. Expressions describing the sum-frequency field from the cylindrical particle ends have been obtained for the case of a nonlinear layer possessing chiral properties. Three-dimensional directivity patterns of the sum-frequency radiation have been analyzed for different combinations of parameters (angles of incidence, degrees of ellipticity, orientations of polarization ellipses, cylindrical particle dimensions). The mathematical properties of the spatial distribution functions of the sum-frequency field, which characterize the symmetry of directivity patterns, have been revealed.

Potential of mean force of DNA guided assemblies past Debye-Hückel regime

NASA Astrophysics Data System (ADS)

Girard, Martin; Seo, Soyoung; Li, Yaohua; Mirkin, Chad; Olvera de La Cruz, Monica

Many of the bioinspired systems make use of biopolymers such as polypeptides or DNA. The latter is widely used in self-assembled systems, from colloidal crystals to origami construction. In these systems, salt is commonly required to screen the electrostatic repulsion between the strands. In the classical Debye-Hückel picture, salt ions are point particles and the screening distance is a decreasing monotonic function of salt concentration. This picture breaks down at moderate salt concentrations, where the behavior becomes non-monotonic. In this talk, we will show results for potential of mean force of DNA grafted colloids obtained through multiscale molecular dynamics. In this picture, the highly charged DNA causes non-trivial behavior at moderate salt concentrations (c 0 . 3 - 0 . 7 M), namely increase of repulsion for non-complementary DNA strands while repulsion decreases for complementary strands. We will show spatial cluster distribution as function of size and charge as well as implications for experimental systems.

Effects of temperature and pressure on thermodynamic properties of Cd0.50 Zn0.50 Se alloy

NASA Astrophysics Data System (ADS)

Aarifeen, Najm ul; Afaq, A.

2017-09-01

Thermodynamic properties of \\text{C}{{\\text{d}}0.50} \\text{Z}{{\\text{n}}0.50} Se alloy are studied using quasi harmonic model for pressure range 0-10 GPa and temperature range 0-1000 K. The structural optimization is obtained by self consistent field calculations and full-potential linear muffin-tin orbital method with GGA+U as an exchange correlation functional where U=2.3427 eV is the hubbard potential. The effects of temperature and pressure on the bulk modulus, Helmholtz free energy, internal energy, entropy, Debye temperature, Grüneisen parameter, thermal expansion coefficient and heat capacities of the material are observed and discussed. The bulk modulus, Helmholtz free energy and Debye temperature are found to decrease with increasing temperature while there is an increasing behavior when the pressure rises. Whereas internal energy has increasing trend with rises in temperature and it almost remains insensitive to pressure. The entropy of the system increases (decreases) with a rise of pressure (temperature).

Two-dimensional potential double layers and discrete auroras

NASA Technical Reports Server (NTRS)

Kan, J. R.; Lee, L. C.; Akasofu, S.-I.

1979-01-01

This paper is concerned with the formation of the acceleration region for electrons which produce the visible auroral arc and with the formation of the inverted V precipitation region. The former is embedded in the latter, and both are associated with field-aligned current sheets carried by plasma sheet electrons. It is shown that an electron current sheet driven from the plasma sheet into the ionosphere leads to the formation of a two-dimensional potential double layer. For a current sheet of a thickness less than the proton gyrodiameter solutions are obtained in which the field-aligned potential drop is distributed over a length much greater than the Debye length. For a current sheet of a thickness much greater than the proton gyrodiameter solutions are obtained in which the potential drop is confined to a distance on the order of the Debye length. The electric field in the two-dimensional double-layer model is the zeroth-order field inherent to the current sheet configuration, in contrast to those models in which the electric field is attributed to the first-order field due to current instabilities or turbulences. The maximum potential in the two-dimensional double-layer models is on the order of the thermal energy of plasma sheet protons, which ranges from 1 to 10 keV.

Effect of screening on the transport of polyelectrolytes through nanopores

NASA Astrophysics Data System (ADS)

Oukhaled, G.; Bacri, L.; Mathé, J.; Pelta, J.; Auvray, L.

2008-05-01

We study the transport of dextran sulfate molecules (Mw=8000 Da) through a bacterial α-hemolysin channel inserted into a bilayer lipid membrane submitted to an external electric field. We detect the current blockades induced by the molecules threading through one pore and vary the ionic strength in an unexplored range starting at 10-3 M. In the conditions of the experiment, the polyelectrolyte molecules enter the pore only if the Debye screening length is smaller than the pore radius in agreement with theory. We also observe that large potentials favour the passage of the molecules. The distribution of blockade durations suggests that a complex process governs the kinetics of the molecules. The dwelling time increases sharply as the Debye length increases and approaches the pore radius.

Electrostatic attraction between overall neutral surfaces.

PubMed

Adar, Ram M; Andelman, David; Diamant, Haim

2016-08-01

Two overall neutral surfaces with positively and negatively charged domains ("patches") have been shown in recent experiments to exhibit long-range attraction when immersed in an ionic solution. Motivated by the experiments, we calculate analytically the osmotic pressure between such surfaces within the Poisson-Boltzmann framework, using a variational principle for the surface-averaged free energy. The electrostatic potential, calculated beyond the linear Debye-Hückel theory, yields an overall attraction at large intersurface separations, over a wide range of the system's controlled length scales. In particular, the attraction is stronger and occurs at smaller separations for surface patches of larger size and charge density. In this large patch limit, we find that the attraction-repulsion crossover separation is inversely proportional to the square of the patch-charge density and to the Debye screening length.

Resonant charge exchange for H-H+ in Debye plasmas

NASA Astrophysics Data System (ADS)

Laricchiuta, Annarita; Colonna, Gianpiero; Capitelli, Mario; Kosarim, Alexander; Smirnov, Boris M.

2017-11-01

The dynamics of resonant charge exchange in proton-hydrogen collisions embedded in plasma is investigated in the framework of the asymptotic approach, modified to account for the effect of Debye-Hückel screening in particle interactions. The cross sections exhibit a marked dependence on the Debye length in regimes of severe plasma confinement. Processes involving excited states H( n)-H+ are also discussed.

Electrostatic stability of electron-positron plasmas in dipole geometry

NASA Astrophysics Data System (ADS)

Mishchenko, Alexey; Plunk, Gabriel G.; Helander, Per

2018-04-01

The electrostatic stability of electron-positron plasmas is investigated in the point-dipole and Z-pinch limits of dipole geometry. The kinetic dispersion relation for sub-bounce-frequency instabilities is derived and solved. For the zero-Debye-length case, the stability diagram is found to exhibit singular behaviour. However, when the Debye length is non-zero, a fluid mode appears, which resolves the observed singularity, and also demonstrates that both the temperature and density gradients can drive instability. It is concluded that a finite Debye length is necessary to determine the stability boundaries in parameter space. Landau damping is investigated at scales sufficiently smaller than the Debye length, where instability is absent.

A molecular Debye-Huckel theory of solvation in polar fluids: An extension of the Born model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Tiejun; Song, Xueyu

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated inmore » a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. In conclusion, our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.« less

A molecular Debye-Huckel theory of solvation in polar fluids: An extension of the Born model

DOE PAGES

Xiao, Tiejun; Song, Xueyu

2017-12-06

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated inmore » a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. In conclusion, our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.« less

A molecular Debye-Hückel theory of solvation in polar fluids: An extension of the Born model

NASA Astrophysics Data System (ADS)

Xiao, Tiejun; Song, Xueyu

2017-12-01

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated in a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. Our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.

A molecular Debye-Hückel theory of solvation in polar fluids: An extension of the Born model.

PubMed

Xiao, Tiejun; Song, Xueyu

2017-12-07

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated in a self-consistent way and can be used to evaluate the electrostatic contribution to the thermodynamic properties of a polar fluid. Our theory is applied to a dipolar hard sphere fluid as well as interaction site models of polar fluids such as water, where the electrostatic contribution to their thermodynamic properties can be obtained accurately.

Important Variation in Vibrational Properties of LiFePO4 and FePO4 Induced by Magnetism

PubMed Central

Seifitokaldani, Ali; Gheribi, Aïmen E.; Phan, Anh Thu; Chartrand, Patrice; Dollé, Mickaël

2016-01-01

A new thermodynamically self-consistent (TSC) method, based on the quasi-harmonic approximation (QHA), is used to obtain the Debye temperatures of LiFePO4 (LFP) and FePO4 (FP) from available experimental specific heat capacities for a wide temperature range. The calculated Debye temperatures show an interesting critical and peculiar behavior so that a steep increase in the Debye temperatures is observed by increasing the temperature. This critical behavior is fitted by the critical function and the adjusted critical temperatures are very close to the magnetic phase transition temperatures in LFP and FP. Hence, the critical behavior of the Debye temperatures is correlated with the magnetic phase transitions in these compounds. Our first-principle calculations support our conjecture that the change in electronic structures, i.e. electron density of state and electron localization function, and consequently the change in thermophysical properties due to the magnetic transition may be the reason for the observation of this peculiar behavior of the Debye temperatures. PMID:27604551

Important Variation in Vibrational Properties of LiFePO4 and FePO4 Induced by Magnetism

NASA Astrophysics Data System (ADS)

Seifitokaldani, Ali; Gheribi, Aïmen E.; Phan, Anh Thu; Chartrand, Patrice; Dollé, Mickaël

2016-09-01

A new thermodynamically self-consistent (TSC) method, based on the quasi-harmonic approximation (QHA), is used to obtain the Debye temperatures of LiFePO4 (LFP) and FePO4 (FP) from available experimental specific heat capacities for a wide temperature range. The calculated Debye temperatures show an interesting critical and peculiar behavior so that a steep increase in the Debye temperatures is observed by increasing the temperature. This critical behavior is fitted by the critical function and the adjusted critical temperatures are very close to the magnetic phase transition temperatures in LFP and FP. Hence, the critical behavior of the Debye temperatures is correlated with the magnetic phase transitions in these compounds. Our first-principle calculations support our conjecture that the change in electronic structures, i.e. electron density of state and electron localization function, and consequently the change in thermophysical properties due to the magnetic transition may be the reason for the observation of this peculiar behavior of the Debye temperatures.

Important Variation in Vibrational Properties of LiFePO4 and FePO4 Induced by Magnetism.

PubMed

Seifitokaldani, Ali; Gheribi, Aïmen E; Phan, Anh Thu; Chartrand, Patrice; Dollé, Mickaël

2016-09-08

A new thermodynamically self-consistent (TSC) method, based on the quasi-harmonic approximation (QHA), is used to obtain the Debye temperatures of LiFePO4 (LFP) and FePO4 (FP) from available experimental specific heat capacities for a wide temperature range. The calculated Debye temperatures show an interesting critical and peculiar behavior so that a steep increase in the Debye temperatures is observed by increasing the temperature. This critical behavior is fitted by the critical function and the adjusted critical temperatures are very close to the magnetic phase transition temperatures in LFP and FP. Hence, the critical behavior of the Debye temperatures is correlated with the magnetic phase transitions in these compounds. Our first-principle calculations support our conjecture that the change in electronic structures, i.e. electron density of state and electron localization function, and consequently the change in thermophysical properties due to the magnetic transition may be the reason for the observation of this peculiar behavior of the Debye temperatures.

Electron Debye scale Kelvin-Helmholtz instability: Electrostatic particle-in-cell simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Sang-Yun; Lee, Ensang, E-mail: eslee@khu.ac.kr; Kim, Khan-Hyuk

2015-12-15

In this paper, we investigated the electron Debye scale Kelvin-Helmholtz (KH) instability using two-dimensional electrostatic particle-in-cell simulations. We introduced a velocity shear layer with a thickness comparable to the electron Debye length and examined the generation of the KH instability. The KH instability occurs in a similar manner as observed in the KH instabilities in fluid or ion scales producing surface waves and rolled-up vortices. The strength and growth rate of the electron Debye scale KH instability is affected by the structure of the velocity shear layer. The strength depends on the magnitude of the velocity and the growth ratemore » on the velocity gradient of the shear layer. However, the development of the electron Debye scale KH instability is mainly determined by the electric field generated by charge separation. Significant mixing of electrons occurs across the shear layer, and a fraction of electrons can penetrate deeply into the opposite side fairly far from the vortices across the shear layer.« less

Assessing the feasibility of low temperature XAFS experiments at Indus-2, India: First results

NASA Astrophysics Data System (ADS)

Ramanan, Nitya; Rajput, Parasmani; Jha, S. N.; Lahiri, Debdutta

2015-05-01

In this work, we report installation of displex cryostat XAFS sample holder at XAFS beamline (BL-09) of Indus-2 synchrotron facility, India and make critical assessment of feasibility of low-temperature XAFS experiments in terms of data quality and reproducibility, temperature range, calibration and attainable resolution. We adopted the Debye Model-based calibration method by measuring XAFS of standard Au foil with known Debye temperature (ΘDebye)Autheory = 165 K. The data is of good quality and reproducible with international data. By fitting Debye Waller Factor (σexpt2 (T)), we deduced (ΘDebye)Auexpt = 163 K which implies calibration within 2 K. Error bars for σexpt2 (T) correspond to temperature uncertainty ΔT ≤ 5 K, which defines the temperature resolution for low temperature XAFS experiments. Thus, from both calibration and resolution points-of-view, this work demonstrates the feasibility of low temperature XAFS experiments at BL-09, Indus-2. Feasibility of extending XAFS experiments to lower temperature and unknown samples is discussed.

Temperature and pressure dependent thermodynamic behavior of 2H-CuInO2

NASA Astrophysics Data System (ADS)

Bhamu, K. C.

2018-05-01

Density functional theory and quasi-harmonic Debye model has been used to study the thermodynamic properties of 2H-CuInO2. At the optimized structural parameters, pressure (0 to 80 GPa) dependent variation in the various thermodynamic properties, i.e. unit cell volume (V), bulk modulus (B), specific heat (Cv), Debye temperature (θD), Grüneisen parameter (γ) and thermal expansion coefficient (α) are calculated for various temperature values. The results predict that the pressure has significant effect on unit cell volume and bulk modulus while the temperature shows negligible effect on both parameters. With increasing temperature thermal expansion coefficient increase while with increasing pressure it decreases. The specific heat remains close to zero for ambient pressure and temperature values and it increases with increasing temperature. It is observed that the pressure has high impact on Debye temperature and Grüneisen parameter instead of temperature. Debye temperature and Grüneisen parameter both remains almost constant for the temperature range (0-300K) while Grüneisen parameter decrease with increasing pressure at constant temperature and Debye temperature increases rapidly with increasing pressure. An increase in Debye temperature with respect to pressure shows that the thermal vibration frequency changes rapidly.

Two independent measurements of Debye lengths in doped nonpolar liquids.

PubMed

Prieve, D C; Hoggard, J D; Fu, R; Sides, P J; Bethea, R

2008-02-19

Electric current measurements were performed between 2.5 cm x 7.5 cm parallel-plate electrodes separated by 1.2 mm of heptane doped with 0-15% w/w poly(isobutylene succinimide) (PIBS) having a molecular weight of about 1700. The rapid (microsecond) initial charging of the capacitor can be used to infer the dielectric constant of the solution. The much slower decay of current arising from the polarization of electrodes depends on the differential capacitance of the diffuse clouds of charge carriers accumulating next to each electrode and on the ohmic resistance of the fluid. Using the Gouy-Chapman model for the differential capacitance, Debye lengths of 80-600 nm were deduced that decrease with increasing concentration of PIBS. Values of the Debye lengths were confirmed by performing independent measurements of double-layer repulsion between a 6 microm polystyrene (PS) latex sphere and a PS-coated glass plate using total internal reflection microscopy in the same solutions. The charge carriers appear to be inverted PIBS micelles having apparent Stokes diameters of 20-40 nm. Dynamic light scattering reveals a broad distribution of sizes having an intensity-averaged diameter of 15 nm. This smaller size might arise (1) from overestimating the electrophoretic mobility of micelles by treating them as point charges or (2) because charged micelles are larger on average than uncharged micelles. When Faradaic reactions and zeta potentials on the electrodes can be neglected, such current versus time experiments yield values for the Debye length and ionic strength with less effort than force measurements. To obtain the concentration of charge carriers from measurements of conductivity, the mobility of the charge carriers must be known.

The defect level and ideal thermal conductivity of graphene uncovered by residual thermal reffusivity at the 0 K limit.

PubMed

Xie, Yangsu; Xu, Zaoli; Xu, Shen; Cheng, Zhe; Hashemi, Nastaran; Deng, Cheng; Wang, Xinwei

2015-06-14

Due to its intriguing thermal and electrical properties, graphene has been widely studied for potential applications in sensor and energy devices. However, the reported value for its thermal conductivity spans from dozens to thousands of W m(-1) K(-1) due to different levels of alternations and defects in graphene samples. In this work, the thermal diffusivity of suspended four-layered graphene foam (GF) is characterized from room temperature (RT) down to 17 K. For the first time, we identify the defect level in graphene by evaluating the inverse of thermal diffusivity (termed "thermal reffusivity": Θ) at the 0 K limit. By using the Debye model of Θ = Θ0 + C× e(-θ/2T) and fitting the Θ-T curve to the point of T = 0 K, we identify the defect level (Θ0) and determine the Debye temperature of graphene. Θ0 is found to be 1878 s m(-2) for the studied GF and 43-112 s m(-2) for three highly crystalline graphite materials. This uncovers a 16-43-fold higher defect level in GF than that in pyrolytic graphite. In GF, the phonon mean free path solely induced by defects and boundary scattering is determined as 166 nm. The Debye temperature of graphene is determined to be 1813 K, which is very close to the average theoretical Debye temperature (1911 K) of the three acoustic phonon modes in graphene. By subtracting the defect effect, we report the ideal thermal diffusivity and conductivity (κideal) of graphene presented in the 3D foam structure in the range of 33-299 K. Detailed physics based on chemical composition and structure analysis are given to explain the κideal-T profile by comparing with those reported for suspended graphene.

Transport of Multivalent Electrolyte Mixtures in Micro- and Nanochannels

DTIC Science & Technology

2013-11-08

equations for this process are the unsteady Navier-Stokes equations along with continuity and the Poisson- Nernst -Planck system for the electro- static part...about five times the Debye screening length D (the 1/e lengthscale for the potential from the solution of the linearized Poisson- Boltzmann equation

The Debye-Huckel Approximation in Electroosmotic Flow in Micro- and Nano-channels

NASA Astrophysics Data System (ADS)

Conlisk, A. Terrence

2002-11-01

In this work we consider the electroosmotic flow in a rectangular channel. We consider a mixture of water or other neutral solvent and a salt compound such as sodium chloride and other buffers for which the ionic species are entirely dissociated. Results are produced for the case where the channel height is much greater than the electric double layer(EDL)(microchannel) and for the case where the channel height is of the order or slightly greater than the width of the EDL(nanochannel). At small cation, anion concentration differences the Debye-Huckel approximation is appropriate; at larger concentration differences, the Gouy-Chapman picture of the electric double emerges naturally. In the symmetric case for the electroosmotic flow so induced, the velocity field and the potential are similar. We specifically focus in this paper on the limits of the Debye-Huckel approximation for a simplified version of a phosphate buffered saline(PBS) mixture. The fluid is assumed to behave as a continuum and the volume flow rate is observed to vary linearly with channel height for electrically driven flow in contrast to pressure driven flow which varies as height cubed. This means that very large pressure drops are required to drive flows in small channels. However, useful volume flow rates may be obtained at a very low driving voltage.

Polarizabilites and Rydberg States in the Presence of a Debye Potential

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Drachman, Richard J.

2010-01-01

Polarizabilities and hyperpolarizabilities, alpha(1), beta(1),gamma(1), alpha(2), beta(2),gamma(2), alpha(3), beta(3),gamma(3), delta and epsilon of hydrogenic systems have been calculated by Drachman. We have now calculated these quantities by using pseudostates for the S. P. D and F states. All of them converge very fast as the number of terms in the pseudostates is increased, and are essentially independent of the nonlinear parameters. All the results are in good agreement with the results obtained by Drachman. except for delta, which is of the third-order in perturbation formalism. We have calculated Rydberg states of He for high N and L. The effective potential is -alpha(sub 1)/x(exp 4)+{6 * Beta(sub 1) -alpha(sub 2)/x(exp6), where x is the distance of the outer electron from the nucleus. The exchange and electron-electron correlations are unimportant because the outer electron is far away from the nucleus. This implies that the conventional variational calculations are not necessary. The results agree well with the results of Drachman. We have generalized this approach in the presence of a Debye potential.

Estimation of the reduction of sputtering for fusion grade materials after disappearance of the Debye sheath

NASA Astrophysics Data System (ADS)

Adhikari, S.; Moulick, R.; Goswami, K. S.

2018-02-01

The effect of grazing angle on a solid surface (divertor) erosion due to ion sputtering is studied by 1D-3V fluid approach. For an oblique magnetic field, there exists a region in front of the solid surface called Chodura sheath (CS). It is assumed that the CS is additive to the Debye sheath (DS). For a certain value of the grazing angle, it has been observed that the DS vanishes and the entire potential drop occurs across the CS. This new analysis of the event provides some facts of pragmatic importance in improving the solutions of edge impurity codes. Important factors, such as ion energy, impact angle for physical sputtering are highlighted. The dependence of these two parameters on the grazing angle is also investigated in detail.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Gyeong Won; Shim, Jaewon; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

The influence of renormalization plasma screening on the entanglement fidelity for the elastic electron-atom scattering is investigated in partially ionized dense hydrogen plasmas. The partial wave analysis and effective interaction potential are employed to obtain the scattering entanglement fidelity in dense hydrogen plasmas as functions of the collision energy, the Debye length, and the renormalization parameter. It is found that the renormalization plasma shielding enhances the scattering entanglement fidelity. Hence, we show that the transmission of the quantum information can be increased about 10% due to the renormalization shielding effect in dense hydrogen plasmas. It is also found that themore » renormalization shielding effect on the entanglement fidelity for the electron-atom collision increases with an increase of the collision energy. In addition, the renormalization shielding function increases with increasing collision energy and saturates to the unity with an increase of the Debye length.« less

Vibrational properties of nanocrystals from the Debye Scattering Equation

DOE PAGES

Scardi, P.; Gelisio, L.

2016-02-26

One hundred years after the original formulation by Petrus J.W. Debije (aka Peter Debye), the Debye Scattering Equation (DSE) is still the most accurate expression to model the diffraction pattern from nanoparticle systems. A major limitation in the original form of the DSE is that it refers to a static domain, so that including thermal disorder usually requires rescaling the equation by a Debye-Waller thermal factor. The last is taken from the traditional diffraction theory developed in Reciprocal Space (RS), which is opposed to the atomistic paradigm of the DSE, usually referred to as Direct Space (DS) approach. Besides beingmore » a hybrid of DS and RS expressions, rescaling the DSE by the Debye-Waller factor is an approximation which completely misses the contribution of Temperature Diffuse Scattering (TDS). The present work proposes a solution to include thermal effects coherently with the atomistic approach of the DSE. Here, a deeper insight into the vibrational dynamics of nanostructured materials can be obtained with few changes with respect to the standard formulation of the DSE, providing information on the correlated displacement of vibrating atoms.« less

Influence of the Debye length on the interaction of a small molecule-modified Au nanoparticle with a surface-bound bioreceptor.

PubMed

Bukar, Natalia; Zhao, Sandy Shuo; Charbonneau, David M; Pelletier, Joelle N; Masson, Jean-Francois

2014-05-18

We report that a shorter Debye length and, as a consequence, decreased colloidal stability are required for the molecular interaction of folic acid-modified Au nanoparticles (Au NPs) to occur on a surface-bound receptor, human dihydrofolate reductase (hDHFR). The interaction measured using surface plasmon resonance (SPR) sensing was optimal in a phosphate buffer at pH 6 and ionic strength exceeding 300 mM. Under these conditions, the aggregation constant of the Au NPs was approximately 10(4) M(-1) s(-1) and the Debye length was below 1 nm, on the same length scale as the size of the folate anion (approximately 0.8 nm). Longer Debye lengths led to poorer SPR responses, revealing a reduced affinity of the folic acid-modified Au NPs for hDHFR. While high colloidal stability of Au NPs is desired in most applications, these conditions may hinder molecular interactions due to Debye lengths exceeding the size of the ligand and thus preventing close interactions with the surface-bound molecular receptor.

Thermodynamic properties of α-uranium

NASA Astrophysics Data System (ADS)

Ren, Zhiyong; Wu, Jun; Ma, Rong; Hu, Guichao; Luo, Chao

2016-11-01

The lattice constants and equilibrium atomic volume of α-uranium were calculated by Density Functional Theory (DFT). The first principles calculation results of the lattice for α-uranium are in agreement with the experimental results well. The thermodynamic properties of α-uranium from 0 to 900 K and 0-100 GPa were calculated with the quasi-harmonic Debye model. Volume, bulk modulus, entropy, Debye temperature, thermal expansion coefficient and the heat capacity of α-uranium were calculated. The calculated results show that the bulk modulus and Debye temperature increase with the increasing pressure at a given temperature while decreasing with the increasing temperature at a given pressure. Volume, entropy, thermal expansion coefficient and the heat capacity decrease with the increasing pressure while increasing with the increasing temperature. The theoretical results of entropy, Debye temperature, thermal expansion coefficient and the heat capacity show good agreement with the general trends of the experimental values. The constant-volume heat capacity shows typical Debye T3 power-law behavior at low temperature limit and approaches to the classical asymptotic Dulong-Petit limit at high temperature limit.

First-principles study of the structural, electronic and thermal properties of CaLiF3

NASA Astrophysics Data System (ADS)

Chouit, N.; Amara Korba, S.; Slimani, M.; Meradji, H.; Ghemid, S.; Khenata, R.

2013-09-01

Density functional theory calculations have been performed to study the structural, electronic and optical properties of CaLiF3 cubic fluoroperovskite. Our calculations were carried out by means of the full-potential linearized augmented plane-wave method. The exchange-correlation potential is treated by the local density approximation and the generalized gradient approximation (GGA) (Perdew, Burke and Ernzerhof). Moreover, the alternative form of GGA proposed by Engel and Vosko is also used for band structure calculations. The calculated total energy versus volume allows us to obtain structural properties such as the lattice constant (a0), bulk modulus (B0) and pressure derivative of the bulk modulus (B'0 ). Band structure, density of states and band gap pressure coefficients are also given. Our calculations show that CaLiF3 has an indirect band gap (R-Γ). Following the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature and pressure effects on the lattice constant, bulk modulus, thermal expansion coefficient, Debye temperature and heat capacities are calculated.

A novel pressure variation study on electronic structure, mechanical stability and thermodynamic properties of potassium based fluoroperovskite

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2017-09-01

The effect of pressure variation on stability, structural parameters, elastic constants, mechanical, electronic and thermodynamic properties of cubic SrKF3 fluoroperovskite have been investigated by using the full-potential linearized augmented plane wave (FP-LAPW) method combined with Quasi-harmonic Debye model in which the phonon effects are considered. The calculated lattice parameters show a prominent decrease in lattice constant and bonds length with the increase in pressure. The application of pressure from 0 to 25 GPa reveals a predominant characteristic associated with widening of bandgap with GGA and GGA plus Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The influence of pressure on elastic constants and their related mechanical parameters have been discussed in detail. Apart of linear dependence of elastic coefficients, transition from brittle to ductile behavior is also observed at elevated pressure ranges. We have successfully computed variation of lattice constant, volume expansion, bulk modulus, Debye temperature and specific heat capacities at pressure and temperature in the range of 0-25 GPa and 0-600 K.

Determination of molecular configuration by debye length modulation.

PubMed

Vacic, Aleksandar; Criscione, Jason M; Rajan, Nitin K; Stern, Eric; Fahmy, Tarek M; Reed, Mark A

2011-09-07

Silicon nanowire field effect transistors (FETs) have emerged as ultrasensitive, label-free biodetectors that operate by sensing bound surface charge. However, the ionic strength of the environment (i.e., the Debye length of the solution) dictates the effective magnitude of the surface charge. Here, we show that control of the Debye length determines the spatial extent of sensed bound surface charge on the sensor. We apply this technique to different methods of antibody immobilization, demonstrating different effective distances of induced charge from the sensor surface.

Debye-Waller Factor in Neutron Scattering by Ferromagnetic Metals

NASA Astrophysics Data System (ADS)

Paradezhenko, G. V.; Melnikov, N. B.; Reser, B. I.

2018-04-01

We obtain an expression for the neutron scattering cross section in the case of an arbitrary interaction of the neutron with the crystal. We give a concise, simple derivation of the Debye-Waller factor as a function of the scattering vector and the temperature. For ferromagnetic metals above the Curie temperature, we estimate the Debye-Waller factor in the range of scattering vectors characteristic of polarized magnetic neutron scattering experiments. In the example of iron, we compare the results of harmonic and anharmonic approximations.

Ab initio studies of structural, electronic, optical, elastic and thermal properties of silver gallium dichalcogenides (AgGaX{sub 2}: X = S, Se, Te)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Sheetal; Department of Physics, Panjab University, Chandigarh 160014; Verma, A.S., E-mail: ajay_phy@rediffmail.com

2014-05-01

Graphical abstract: - Highlights: • FP-LAPW method has been used to compute the solid state properties of AgGaX{sub 2} (X = S, Se, Te). • Electronic and optical properties reported with recently developed mBJ potential. • Thermal expansion, heat capacity, Debye temperature, entropy and Grüneisen parameter were evaluated. • Hardness was calculated for the first time at different temperature and pressure. - Abstract: We have performed ab initio calculations for the structural, electronic, optical, elastic and thermal properties of the silver gallium dichalcogenides (AgGaX{sub 2}: X = S, Se, Te). In this study, we have used the accurate full potentialmore » linearized augmented plane wave (FP-LAPW) method to find the equilibrium structural parameters and to compute the six elastic constants (C{sub 11}, C{sub 12}, C{sub 13}, C{sub 33}, C{sub 44} and C{sub 66}). We have reported electronic and optical properties with the recently developed density functional theory of Tran and Blaha, and this theory is used along with the Wu-Cohen generalized gradient approximation (WC-GGA) for the exchange-correlation potential. Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients and optical conductivities were calculated for photon energies up to 40 eV. The thermodynamical properties such as thermal expansion, heat capacity, debye temperature, entropy, Grüneisen parameter and bulk modulus were calculated employing the quasi-harmonic Debye model at different temperatures (0–900 K) and pressures (0–8 GPa) and the silent results were interpreted. Hardness of the materials was calculated for the first time at different temperatures and pressures.« less

Electromagnetic potential vectors and the Lagrangian of a charged particle

NASA Technical Reports Server (NTRS)

Shebalin, John V.

1992-01-01

Maxwell's equations can be shown to imply the existence of two independent three-dimensional potential vectors. A comparison between the potential vectors and the electric and magnetic field vectors, using a spatial Fourier transformation, reveals six independent potential components but only four independent electromagnetic field components for each mode. Although the electromagnetic fields determined by Maxwell's equations give a complete description of all possible classical electromagnetic phenomena, potential vectors contains more information and allow for a description of such quantum mechanical phenomena as the Aharonov-Bohm effect. A new result is that a charged particle Lagrangian written in terms of potential vectors automatically contains a 'spontaneous symmetry breaking' potential.

Laboratory observation of electron phase-space holes during magnetic reconnection.

PubMed

Fox, W; Porkolab, M; Egedal, J; Katz, N; Le, A

2008-12-19

We report the observation of large-amplitude, nonlinear electrostatic structures, identified as electron phase-space holes, during magnetic reconnection experiments on the Versatile Toroidal Facility at MIT. The holes are positive electric potential spikes, observed on high-bandwidth ( approximately 2 GHz) Langmuir probes. Investigations with multiple probes establish that the holes travel at or above the electron thermal speed and have a three-dimensional, approximately spherical shape, with a scale size approximately 2 mm. This corresponds to a few electron gyroradii, or many tens of Debye lengths, which is large compared to holes considered in simulations and observed by satellites, whose length scale is typically only a few Debye lengths. Finally, a statistical study over many discharges confirms that the holes appear in conjunction with the large inductive electric fields and the creation of energetic electrons associated with the magnetic energy release.

Surface forces between colloidal particles at high hydrostatic pressure

NASA Astrophysics Data System (ADS)

Pilat, D. W.; Pouligny, B.; Best, A.; Nick, T. A.; Berger, R.; Butt, H.-J.

2016-02-01

It was recently suggested that the electrostatic double-layer force between colloidal particles might weaken at high hydrostatic pressure encountered, for example, in deep seas or during oil recovery. We have addressed this issue by means of a specially designed optical trapping setup that allowed us to explore the interaction of a micrometer-sized glass bead and a solid glass wall in water at hydrostatic pressures of up to 1 kbar. The setup allowed us to measure the distance between bead and wall with a subnanometer resolution. We have determined the Debye lengths in water for salt concentrations of 0.1 and 1 mM. We found that in the pressure range from 1 bar to 1 kbar the maximum variation of the Debye lengths was <1 nm for both salt concentrations. Furthermore, the magnitude of the zeta potentials of the glass surfaces in water showed no dependency on pressure.

Numerical study of the influence of solid polarization on electrophoresis at finite Debye thickness.

PubMed

Bhattacharyya, Somnath; De, Simanta

2015-09-01

The influence of solid polarization on the electrophoresis of a uniformly charged dielectric particle for finite values of the particle-to-fluid dielectric permittivity ratio is analyzed quantitatively without imposing the thin Debye length or weak-field assumption. Present analysis is based on the computation of the coupled Poisson-Nernst-Planck and Stokes equations in the fluid domain along with the Laplace equation within the solid. The electrophoretic velocity is determined through the balance of forces acting on the particle. The solid polarization of the charged particle produces a reduction on its electrophoretic velocity compared to a nonpolarizable particle of the same surface charge density. In accordance with the existing thin-layer analysis, our computed results for thin Debye layer shows that the solid polarization is important only when the applied electric field is strong. When the Debye length is in the order of the particle size, the electrophoretic velocity decreases with the rise of the particle permittivity and attains a saturation limit at large values of the permittivity. Our computed solution for electrophoretic velocity is in agreement with the existing asymptotic analyses based on a thin Debye layer for limiting cases.

The surface stability of Cr 2O 3 (0 0 0 1)

DOE PAGES

Cao, Shi; Wu, Ning; Echtenkamp, William; ...

2015-05-28

The surface of chromia (Cr 2O 3) has a surface electronic structure distinct from the bulk and a packing density distinct from the bulk. More than a demarcation between the solid and the vacuum, the surface differs from the bulk of chromia, not just because of a partial occupancy of chromium sites, but also because of an increased number of unoccupied surface oxygen sites (vacancy sites), evident in angle-resolved core level photoemission. In spite of the structural differences that exist at the surface, there is, as yet, no evidence that these complications affect the surface Debye temperature beyond the mostmore » simple of assumptions regarding the lower coordination of the surface. Using low-energy electron diffraction (LEED), the effective surface Debye temperature (similar to 490 K) is found to be lower than the bulk (similar to 645 K) Debye temperature of Cr 2O 3(0 0 0 1). This surface effective Debye temperature, indicative of vibrations along the surface normal, uncorrected for anharmonic effects, has a value reduced from the effective bulk Debye temperature yet close to the value root 2 expected from a simple mean field argument.« less

Self-Consistent Approach to Global Charge Neutrality in Electrokinetics: A Surface Potential Trap Model

NASA Astrophysics Data System (ADS)

Wan, Li; Xu, Shixin; Liao, Maijia; Liu, Chun; Sheng, Ping

2014-01-01

In this work, we treat the Poisson-Nernst-Planck (PNP) equations as the basis for a consistent framework of the electrokinetic effects. The static limit of the PNP equations is shown to be the charge-conserving Poisson-Boltzmann (CCPB) equation, with guaranteed charge neutrality within the computational domain. We propose a surface potential trap model that attributes an energy cost to the interfacial charge dissociation. In conjunction with the CCPB, the surface potential trap can cause a surface-specific adsorbed charge layer σ. By defining a chemical potential μ that arises from the charge neutrality constraint, a reformulated CCPB can be reduced to the form of the Poisson-Boltzmann equation, whose prediction of the Debye screening layer profile is in excellent agreement with that of the Poisson-Boltzmann equation when the channel width is much larger than the Debye length. However, important differences emerge when the channel width is small, so the Debye screening layers from the opposite sides of the channel overlap with each other. In particular, the theory automatically yields a variation of σ that is generally known as the "charge regulation" behavior, attendant with predictions of force variation as a function of nanoscale separation between two charged surfaces that are in good agreement with the experiments, with no adjustable or additional parameters. We give a generalized definition of the ζ potential that reflects the strength of the electrokinetic effect; its variations with the concentration of surface-specific and surface-nonspecific salt ions are shown to be in good agreement with the experiments. To delineate the behavior of the electro-osmotic (EO) effect, the coupled PNP and Navier-Stokes equations are solved numerically under an applied electric field tangential to the fluid-solid interface. The EO effect is shown to exhibit an intrinsic time dependence that is noninertial in its origin. Under a step-function applied electric field, a pulse of fluid flow is followed by relaxation to a new ion distribution, owing to the diffusive counter current. We have numerically evaluated the Onsager coefficients associated with the EO effect, L21, and its reverse streaming potential effect, L12, and show that L12=L21 in accordance with the Onsager relation. We conclude by noting some of the challenges ahead.

Assessing the contributions of surface waves and complex rays to far-field Mie scattering by use of the Debye series

NASA Technical Reports Server (NTRS)

Hovenac, Edward A.; Lock, James A.

1991-01-01

The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with the Debye series. Interference effects between surface waves, complex waves, and geometrical waves are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface wave-geometrical pattern is presented.

Large divalent cations and electrostatic potentials adjacent to membranes. Experimental results with hexamethonium.

PubMed Central

Alvarez, O; Brodwick, M; Latorre, R; McLaughlin, A; McLaughlin, S; Szabo, G

1983-01-01

A simple extension of the Gouy-Chapman theory predicts that the ability of a divalent cation to screen charges at a membrane-solution interface decreases significantly if the distance between the charges on the cation is comparable with the Debye length. We tested this prediction by investigating the effect of hexamethonium on the electrostatic potential adjacent to negatively charged phospholipid bilayer membranes. The distance between the two charges of an extended hexamethonium molecule is approximately 1 nm, which is the Debye length in the 0.1 M monovalent salt solutions used in these experiments. Six different experimental approaches were utilized. We measured the electrophoretic mobility of multilamellar vesicles to determine the zeta potential, the line width of the 31P nuclear magnetic resonance (NMR) signal from sonicated vesicles to calculate the change in potential at the phosphodiester moiety of the lipid, and the conductance of planar bilayer membranes exposed to either carriers (nonactin) or pore formers (gramicidin) to estimate the change in potential within the membrane. We also measured directly the effect of hexamethonium on the potential above a monolayer formed from negative lipids, and attempted to calculate the change in the surface potential of a bilayer membrane from capacitance measurements. With the exception of the capacitance calculations, each of the techniques gave comparable results: hexamethonium exerts a smaller effect on the potential than that predicted by the classic screening theory. The results are consistent with the predictions of the extended Gouy-Chapman theory and are relevant to the interpretation of physiological and pharmacological experiments that utilize hexamethonium and other large divalent cations. PMID:6198001

Determination of Debye temperatures and Lamb-Mössbauer factors for LnFeO3 orthoferrite perovskites (Ln  =  La, Nd, Sm, Eu, Gd)

NASA Astrophysics Data System (ADS)

Scrimshire, A.; Lobera, A.; Bell, A. M. T.; Jones, A. H.; Sterianou, I.; Forder, S. D.; Bingham, P. A.

2018-03-01

Lanthanide orthoferrites have wide-ranging industrial uses including solar, catalytic and electronic applications. Here a series of lanthanide orthoferrite perovskites, LnFeO3 (Ln  =  La Nd; Sm; Eu; Gd), prepared through a standard stoichiometric wet ball milling route using oxide precursors, has been studied. Characterisation through x-ray diffraction and x-ray fluorescence confirmed the synthesis of phase-pure or near-pure LnFeO3 compounds. 57Fe Mössbauer spectroscopy was performed over a temperature range of 10 K-293 K to observe hyperfine structure and to enable calculation of the recoil-free fraction and Debye temperature (θ D) of each orthoferrite. Debye temperatures (Ln  =  La 474 K Nd 459 K Sm 457 K Eu 452 K Gd 473 K) and recoil-free fractions (Ln  =  La 0.827; Nd 0.817; Sm 0.816; Eu 0.812; Gd 0.826) were approximated through minimising the difference in the temperature dependent experimental centre shift and theoretical isomer shift, by allowing the Debye temperature and isomer shift values to vary. This method of minimising the difference between theoretical and actual values yields Debye temperatures consistent with results from other studies determined through thermal analysis methods. This displays the ability of variable-temperature Mössbauer spectroscopy to approximate Debye temperatures and recoil-free fractions, whilst observing temperature induced transitions over the temperature range observed. X-ray diffraction and Rietveld refinement show an inverse relationship between FeO6 octahedral volume and approximated Debye temperatures. Raman spectroscopy show an increase in the band positions attributed to soft modes of Ag symmetry, Ag(3) and Ag(5) from La to GdFeO3 corresponding to octahedral rotations and tilts in the [0 1 0] and [1 0 1] planes respectively.

Long range Debye-Hückel correction for computation of grid-based electrostatic forces between biomacromolecules

PubMed Central

2014-01-01

Background Brownian dynamics (BD) simulations can be used to study very large molecular systems, such as models of the intracellular environment, using atomic-detail structures. Such simulations require strategies to contain the computational costs, especially for the computation of interaction forces and energies. A common approach is to compute interaction forces between macromolecules by precomputing their interaction potentials on three-dimensional discretized grids. For long-range interactions, such as electrostatics, grid-based methods are subject to finite size errors. We describe here the implementation of a Debye-Hückel correction to the grid-based electrostatic potential used in the SDA BD simulation software that was applied to simulate solutions of bovine serum albumin and of hen egg white lysozyme. Results We found that the inclusion of the long-range electrostatic correction increased the accuracy of both the protein-protein interaction profiles and the protein diffusion coefficients at low ionic strength. Conclusions An advantage of this method is the low additional computational cost required to treat long-range electrostatic interactions in large biomacromolecular systems. Moreover, the implementation described here for BD simulations of protein solutions can also be applied in implicit solvent molecular dynamics simulations that make use of gridded interaction potentials. PMID:25045516

Universal Non-Debye Scaling in the Density of States of Amorphous Solids.

PubMed

Charbonneau, Patrick; Corwin, Eric I; Parisi, Giorgio; Poncet, Alexis; Zamponi, Francesco

2016-07-22

At the jamming transition, amorphous packings are known to display anomalous vibrational modes with a density of states (DOS) that remains constant at low frequency. The scaling of the DOS at higher packing fractions remains, however, unclear. One might expect to find a simple Debye scaling, but recent results from effective medium theory and the exact solution of mean-field models both predict an anomalous, non-Debye scaling. Being mean-field in nature, however, these solutions are only strictly valid in the limit of infinite spatial dimension, and it is unclear what value they have for finite-dimensional systems. Here, we study packings of soft spheres in dimensions 3 through 7 and find, away from jamming, a universal non-Debye scaling of the DOS that is consistent with the mean-field predictions. We also consider how the soft mode participation ratio evolves as dimension increases.

First principles electronic and thermal properties of some AlRE intermetallics

NASA Astrophysics Data System (ADS)

Srivastava, Vipul; Sanyal, Sankar P.; Rajagopalan, M.

2008-10-01

A study on structural and electronic properties of non-magnetic cubic B 2-type AlRE (RE=Sc, Y, La, Ce, Pr and Lu) intermetallics has been done theoretically. The self-consistent tight binding linear muffin tin orbital method is used to describe the electronic properties of these intermetallics at ambient and at high pressure. These compounds show metallic behavior under ambient conditions. The variation of density of states under compression indicates some possibility of structural phase transformation in AlLa, AlCe and AlPr. Thermal properties like Debye temperature and Grüneisen constant are calculated at T=0 K and at ambient pressure within the Debye-Grüneisen model and compared with the others’ theoretical results. Our results are in good agreement. We have also performed a pressure-induced variation of Debye temperature and have found a decrease in Debye temperature around 40 kbar in AlRE (RE=La, Ce, Pr) intermetallics.

Estimation of Phonon and Carrier Thermal Conductivities for Bulk Thermoelectric Materials Using Transport Properties

NASA Astrophysics Data System (ADS)

Otsuka, Mioko; Homma, Ryoei; Hasegawa, Yasuhiro

2017-05-01

The phonon and carrier thermal conductivities of thermoelectric materials were calculated using the Wiedemann-Franz law, Boltzmann equation, and a method we propose in this study called the Debye specific heat method. We prepared polycrystalline n-type doped bismuth telluride (BiTe) and bismuth antimony (BiSb) bulk alloy samples and measured six parameters (Seebeck coefficient, resistivity, thermal conductivity, thermal diffusivity, magneto-resistivity, and Hall coefficient). The carrier density and mobility were estimated for calculating the carrier thermal conductivity by using the Boltzmann equation. In the Debye specific heat method, the phonon thermal diffusivity, and thermal conductivity were calculated from the temperature dependence of the effective specific heat by using not only the measured thermal conductivity and Debye model, but also the measured thermal diffusivity. The carrier thermal conductivity was also evaluated from the phonon thermal conductivity by using the specific heat. The ratio of carrier thermal conductivity to thermal conductivity was evaluated for the BiTe and BiSb samples, and the values obtained using the Debye specific heat method at 300 K were 52% for BiTe and <5.5% for BiSb. These values are either considerably larger or smaller than those obtained using other methods. The Dulong-Petit law was applied to validate the Debye specific heat method at 300 K, which is significantly greater than the Debye temperature of the BiTe and BiSb samples, and it was confirmed that the phonon specific heat at 300 K has been accurately reproduced using our proposed method.

Improving the Electromagnetic Wave Absorption Properties of the Layered MoS2 by Cladding with Ni Nanoparticles

NASA Astrophysics Data System (ADS)

Zhang, Zilong; Wang, Zilin; Heng, Liuyang; Wang, Shuai; Chen, Xiqiao; Fu, Xiquan; Zou, Yanhong; Tang, Zhixiang

2018-05-01

MoS2 is a promising material with microwave absorption performance due to its high dielectric properties and low density. However, pure MoS2 is non-magnetic and has a bad impedance matching characteristic. In this study we prepared the Ni/MoS2 nanocomposites by cladding the MoS2 micrometer slices with magnetic Ni nanoparticles. Our results show that the microwave absorption properties of Ni/MoS2 nanocomposites have been improved obviously compared with the pure MoS2. Because of the introduction of Ni particles, the permeability of the nanocomposites has been turned from one to a complex, indicating a newly added magnetic loss. Meanwhile, the big gap between the permittivity and permeability of the Ni/MoS2 nanocomposites has been properly narrowed, which suggests an improved impedance matching. Moreover, the dielectric Cole-Cole semicircle shows that there are more Debye relaxation processes for the Ni/MoS2 nanocomposites, which further enhances the dielectric loss. Due to its improved electromagnetic properties, the minimum reflection loss (RL) value of the Ni/MoS2 nanocomposites with 60 wt % loading reaches -55 dB and the absorption bandwidth (<-10 dB) is up to 4.0 GHz (10.8-14.8 GHz) with a matching thickness of 1.5 mm. The results provide an excellent candidate for microwave absorbing materials with a broad effective absorption bandwidth at thin thicknesses.

Phase-sensitive detection of acoustically stimulated electromagnetic response in steel

NASA Astrophysics Data System (ADS)

Yamada, Hisato; Yotsuji, Junichi; Ikushima, Kenji

2018-07-01

The signal amplitude and the phase of acoustically stimulated electromagnetic (ASEM) response have been investigated in steel. In the ASEM method, magnetization is temporally modulated with the radio frequency (rf) of irradiated ultrasonic waves through magnetomechanical coupling. The first-harmonic components of the induced rf dipolar magnetic fields are detected using a resonant loop antenna. The signal amplitude of ASEM waves is determined by the magnitude of local piezomagnetic coefficients on an acoustically excited spot. Here, we divided the ASEM waves into the “in-phase” and “quadrature” components by phase-sensitive detection (PSD). On the basis of the linear response theory, we provided the theoretical formalism of ASEM response by introducing local complex piezomagnetic coefficients, d loc = d‧ + id‧‧. We investigated the magnetic field (H) dependence of the individual components on the different surface conditions of steel plates. The in-phase component [∝ d‧(H)] shows a hysteresis loop on the machined surface of a steel plate, in which d‧(H) switches sign at two finite field values, ±H 0. The inversion of magnetization associated with the applied static fields is thus definitely observed in the PSD measurements. In addition, we measured the hysteresis behaviors on a steel surface with a thin mill scale (iron oxide layers). The hysteresis loop broadens and a significant contribution of the quadrature component [∝ d‧‧(H)] is found. We discuss the origin of the hysteresis behaviors of d‧ and d‧‧ using the Debye relaxation model.

Modeling of spacecraft charging

NASA Technical Reports Server (NTRS)

Whipple, E. C., Jr.

1977-01-01

Three types of modeling of spacecraft charging are discussed: statistical models, parametric models, and physical models. Local time dependence of circuit upset for DoD and communication satellites, and electron current to a sphere with an assumed Debye potential distribution are presented. Four regions were involved in spacecraft charging: (1) undisturbed plasma, (2) plasma sheath region, (3) spacecraft surface, and (4) spacecraft equivalent circuit.

Electro-osmotic flow in a rotating rectangular microchannel

PubMed Central

Ng, Chiu-On; Qi, Cheng

2015-01-01

An analytical model is presented for low-Rossby-number electro-osmotic flow in a rectangular channel rotating about an axis perpendicular to its own. The flow is driven under the combined action of Coriolis, pressure, viscous and electric forces. Analytical solutions in the form of eigenfunction expansions are developed for the problem, which is controlled by the rotation parameter (or the inverse Ekman number), the Debye parameter, the aspect ratio of the channel and the distribution of zeta potentials on the channel walls. Under the conditions of fast rotation and a thin electric double layer (EDL), an Ekman–EDL develops on the horizontal walls. This is essentially an Ekman layer subjected to electrokinetic effects. The flow structure of this boundary layer as a function of the Ekman layer thickness normalized by the Debye length is investigated in detail in this study. It is also shown that the channel rotation may have qualitatively different effects on the flow rate, depending on the channel width and the zeta potential distributions. Axial and secondary flows are examined in detail to reveal how the development of a geostrophic core may lead to a rise or fall of the mean flow. PMID:26345088

Effect of Trapped Ions on Shielding of a Charged Spherical Object in a Plasma

NASA Astrophysics Data System (ADS)

Lampe, Martin; Ganguli, Gurudas; Joyce, Glenn; Gavrishchaka, Valeriy

2001-04-01

The problem of electrostatic shielding around a small spherical collector immersed in plasma, and the related problem of electron and ion flow to the collector, date to the origins of plasma physics. Beginning with Langmuir[1], all calculations have neglected collisions, on the grounds that the mean free path is long compared to shielding length scales, i.e. the Debye length. However, investigators beginning with Bernstein and Rabinowitz[2] have known that negative-energy trapped ions, created by occasional collisions, might be important. We present an analytic calculation of the density of trapped and untrapped ions, self-consistent with a calculation of the potential. We show that under typical conditions for dust grains immersed in a discharge plasma, trapped ions dominate the shielding cloud in steady state, even in the limit of very long mean free path. As a result the shielded potential is quite different from the Debye form or the results of orbital motion limited theory. Collisions also modify the ion current to the grain, but to a lesser extent. [1]H. Mott-Smith and I. Langmuir, Phys. Rev. 28, 27 (1926). [2]I. Bernstein and I. Rabinowitz, Phys. Fluids 2,112(1959).

Nonlinear dust-lattice waves: a modified Toda lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cramer, N. F.

Charged dust grains in a plasma interact with a Coulomb potential, but also with an exponential component to the potential, due to Debye shielding in the background plasma. Here we investigate large-amplitude oscillations and waves in dust-lattices, employing techniques used in Toda lattice analysis. The lattice consists of a linear chain of particles, or a periodic ring as occurs in experimentally observed dust particle clusters. The particle motion has a triangular waveform, and chaotic motion for large amplitude motion of a grain.

THERMODYNAMIC PROPERTIES OF MC (M = V, Nb, Ta): FIRST-PRINCIPLES CALCULATIONS

NASA Astrophysics Data System (ADS)

Cao, Yong; Zhu, Jingchuan; Liu, Yong; Long, Zhishen

2013-07-01

Through the quasi-harmonic Debye model, the pressure and temperature dependences of linear expansion coefficient, bulk modulus, Debye temperature and heat capacity have been investigated. The calculated thermodynamic properties were compared with experimental data and satisfactory agreement is reached.

Calculation of Debye-Scherrer diffraction patterns from highly stressed polycrystalline materials

DOE PAGES

MacDonald, M. J.; Vorberger, J.; Gamboa, E. J.; ...

2016-06-07

Calculations of Debye-Scherrer diffraction patterns from polycrystalline materials have typically been done in the limit of small deviatoric stresses. Although these methods are well suited for experiments conducted near hydrostatic conditions, more robust models are required to diagnose the large strain anisotropies present in dynamic compression experiments. A method to predict Debye-Scherrer diffraction patterns for arbitrary strains has been presented in the Voigt (iso-strain) limit. Here, we present a method to calculate Debye-Scherrer diffraction patterns from highly stressed polycrystalline samples in the Reuss (iso-stress) limit. This analysis uses elastic constants to calculate lattice strains for all initial crystallite orientations, enablingmore » elastic anisotropy and sample texture effects to be modeled directly. Furthermore, the effects of probing geometry, deviatoric stresses, and sample texture are demonstrated and compared to Voigt limit predictions. An example of shock-compressed polycrystalline diamond is presented to illustrate how this model can be applied and demonstrates the importance of including material strength when interpreting diffraction in dynamic compression experiments.« less

XAFS Debye-Waller Factors Temperature-Dependent Expressions for Fe+2-Porphyrin Complexes

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas; Bunker, Grant

2007-02-01

We present an efficient and accurate method for directly calculating single and multiple scattering X-ray absorption fine structure (XAFS) thermal Debye-Waller factors for Fe+2 -porphiryn complexes. The number of multiple scattering Debye-Waller factors on metal porphyrin centers exceeds the number of available parameters that XAFS experimental data can support during fitting with simulated spectra. Using the Density Functional Theory (DFT) under the hybrid functional of X3LYP, phonon normal mode spectrum properties are used to express the mean square variation of the half-scattering path length for a Fe+2 -porphiryn complex as a function of temperature for the most important single and multiple scattering paths of the complex thus virtually eliminating them from the fitting procedure. Modeled calculations are compared with corresponding values obtained from DFT-built and optimized Fe+2 -porphyrin bis-histidine structure as well as from experimental XAFS spectra previously reported. An excellent agreement between calculated and reference Debye-Waller factors for Fe+2-porphyrins is obtained.

Structure determination from XAFS using high-accuracy measurements of x-ray mass attenuation coefficients of silver, 11 keV-28 keV, and development of an all-energies approach to local dynamical analysis of bond length, revealing variation of effective thermal contributions across the XAFS spectrum.

PubMed

Tantau, L J; Chantler, C T; Bourke, J D; Islam, M T; Payne, A T; Rae, N A; Tran, C Q

2015-07-08

We use the x-ray extended range technique (XERT) to experimentally determine the mass attenuation coefficient of silver in the x-ray energy range 11 kev-28 kev including the silver K absorption edge. The results are accurate to better than 0.1%, permitting critical tests of atomic and solid state theory. This is one of the most accurate demonstrations of cross-platform accuracy in synchrotron studies thus far. We derive the mass absorption coefficients and the imaginary component of the form factor over this range. We apply conventional XAFS analytic techniques, extended to include error propagation and uncertainty, yielding bond lengths accurate to approximately 0.24% and thermal Debye-Waller parameters accurate to 30%. We then introduce the FDMX technique for accurate analysis of such data across the full XAFS spectrum, built on full-potential theory, yielding a bond length accuracy of order 0.1% and the demonstration that a single Debye parameter is inadequate and inconsistent across the XAFS range. Two effective Debye-Waller parameters are determined: a high-energy value based on the highly-correlated motion of bonded atoms (σ(DW) = 0.1413(21) Å), and an uncorrelated bulk value (σ(DW) = 0.1766(9) Å) in good agreement with that derived from (room-temperature) crystallography.

Computer models of the spacecraft wake

NASA Technical Reports Server (NTRS)

Rubin, A. G.; Heinemann, M.; Tautz, M.; Cooke, D.

1986-01-01

Until recently, computations of space plasma flow over a spacecraft have been unstable for ratios of spacecraft dimension to Debye length typical of the low Earth orbit environment. Calculations are presented of the spacecraft/environment interaction based on two computer codes, MACH and POLAR. MACH, an inside-out particle tracking code, was developed for the purpose of validating the physics of POLAR in regimes where these are no comprehensive theoretical or experimental results. While the spacecraft which can be treated by MACH are restricted to simple geometries, the methodology is more fundamental than POLAR. MACH generates self-consistent solutions within the context of quasisteady Vlasov plasma flow and achieves Debye ratios previously unobtainable. POLAR uses a three-dimensional finite-element representation of the vehicle in a staggered mesh. The plasma sheath is modeled by outside-in particle tracking. Solutions for the plasma flow, wake and vehicle charging are obtained by Vlasov-Poisson iteration; charge stabilization techniques make the results virtually insensitive to the Debye ratio. POLAR reproduces the Laframboise static plasma solutions for sperical probes and fits the Makita-Kuriki probe data for spheres in a flowing plasma in regions where comparisons are valid. POLAR and MACH solutions for the particle and electrostatic potential structure of the wake of a charged disk in a low-altitude flow are shown for Mach numbers 4, 5, and 8. New features of the solutions include ion focussing in the wake and a definitive determination of the sheath edge in the wake which shows that the sheath is not an equipotential.

Measurement of Debye length in laser-produced plasma.

NASA Technical Reports Server (NTRS)

Ehler, W.

1973-01-01

The Debye length of an expanded plasma created by placing an evacuated chamber with an entrance slit in the path of a freely expanding laser produced plasma was measured, using the slab geometry. An independent measurement of electron density together with the observed value for the Debye length also provided a means for evaluating the plasma electron temperature. This temperature has applications in ascertaining plasma conductivity and magnetic field necessary for confinement of the laser produced plasma. Also, the temperature obtained would be useful in analyzing electron-ion recombination rates in the expanded plasma and the dynamics of the cooling process of the plasma expansion.

The nuclear size and mass effects on muonic hydrogen-like atoms embedded in Debye plasma

NASA Astrophysics Data System (ADS)

Poszwa, A.; Bahar, M. K.; Soylu, A.

2016-10-01

Effects of finite nuclear size and finite nuclear mass are investigated for muonic atoms and muonic ions embedded in the Debye plasma. Both nuclear charge radii and nuclear masses are taken into account with experimentally determined values. In particular, isotope shifts of bound state energies, radial probability densities, transition energies, and binding energies for several atoms are studied as functions of Debye length. The theoretical model based on semianalytical calculations, the Sturmian expansion method, and the perturbative approach has been constructed, in the nonrelativistic frame. For some limiting cases, the comparison with previous most accurate literature results has been made.

Optical Simulation of Debye-Scherrer Crystal Diffraction

ERIC Educational Resources Information Center

Logiurato, F.; Gratton, L. M.; Oss, S.

2008-01-01

In this paper we describe and discuss simple, inexpensive optical experiments used to simulate x-ray and electron diffraction according to the Debye-Scherrer theory. The experiment can be used to address, at the high school level, important subjects related to fundamental quantum and solid-state physics.

Wakes and differential charging of large bodies in low Earth orbit

NASA Technical Reports Server (NTRS)

Parker, L. W.

1985-01-01

Highlights of earlier results using the Inside-Out WAKE code on wake structures of LEO spacecraft are reviewed. For conducting bodies of radius large compared with the Debye length, a high Mach number wake develops a negative potential well. Quasineutrality is violated in the very near wake region, and the wake is relatively empty for a distance downstream of about one half of a Mach number of radii. There is also a suggestion of a core of high density along the axis. A comparison of rigorous numerical solutions with in situ wake data from the AE-C satellite suggests that the so called neutral approximation for ions (straight line trajectories, independent of fields) may be a reasonable approximation except near the center of the near wake. This approximation is adopted for very large bodies. Work concerned with the wake point potential of very large nonconducting bodies such as the shuttle orbiter is described. Using a cylindrical model for bodies of this size or larger in LEO (body radius up to 10 to the 5th power Debye lengths), approximate solutions are presented based on the neutral approximation (but with rigorous trajectory calculations for surface current balance). There is a negative potential well if the body is conducting, and no well if the body is nonconducting. In the latter case the wake surface itself becomes highly negative. The wake point potential is governed by the ion drift energy.

Electronic structure, thermodynamic properties and hydrogenation of LaPtIn and CePtIn compounds by ab-initio methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jezierski, Andrzej, E-mail: andrzej.jezierski@ifmpan.poznan.pl; Szytuła, Andrzej

2016-02-15

The electronic structures and thermodynamic properties of LaPtIn and CePtIn are studied by means of ab-initio full-relativistic full-potential local orbital basis (FPLO) method within densities functional (DFT) methodologies. We have also examined the influence of hydrogen on the electronic structure and stability of CePtInH and LaPtInH systems. The positions of the hydrogen atoms have been found from the minimum of the total energy. Our calculations have shown that band structure and topology of the Fermi surfaces changed significantly during the hydrogenation. The thermodynamic properties (bulk modulus, Debye temperatures, constant pressure heat capacity) calculated in quasi-harmonic Debye-Grüneisen model are in amore » good agreement with the experimental data. We have applied different methods of the calculation of the equation of states (EOS) (Murnaghan, Birch-Murnaghan, Poirier–Tarantola, Vinet). The thermodynamic properties are presented for the pressure 0« less

Thermodynamics of Thomas-Fermi screened Coulomb systems

NASA Technical Reports Server (NTRS)

Firey, B.; Ashcroft, N. W.

1977-01-01

We obtain in closed analytic form, estimates for the thermodynamic properties of classical fluids with pair potentials of Yukawa type, with special reference to dense fully ionized plasmas with Thomas-Fermi or Debye-Hueckel screening. We further generalize the hard-sphere perturbative approach used for similarly screened two-component mixtures, and demonstrate phase separation in this simple model of a liquid mixture of metallic helium and hydrogen.

Spectra of confined positronium

NASA Astrophysics Data System (ADS)

Munjal, D.; Silotia, P.; Prasad, V.

2017-12-01

Positronium is studied under the effect of spherically confined plasma environment. Exponentially Cosine Screened Coulomb potential (ECSC) has been used to include the dense plasma screening effect on positronium. Time independent Schrodinger equation is solved numerically. Various physical parameters such as energy eigenvalues, radial matrix elements, oscillator strengths, and polarizability are well explored as a function of confinement parameters. Oscillator strength gets drastically modified under confinement. We have also obtained the results for Ps confined under spherically confined Debye potential and compared with results of ECSC potential. Also incidental degeneracy for different values of confinement parameters has been reported for the first time for positronium.

Direct measurement of the plasma screening length and surface potential near the lunar terminator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, J.

1977-05-01

Direct measurement of the lunar dayside surface potential and screening length has been made by the suprathermal ion detector experiment (Side) near the terminator. In a region 20degree--30degree from the terminator at the Apollo 14 and 15 sites the surface potential is found to be approximately 50 V negative, and the screening length to be about 1 km. This value of the screening length is more than 2 orders of magnitude greater than the solar wind 'Debye' length. The strong negative surface potential in this region may be due to enhanced temperature and density of the solar wind plasma.

Direct measurement of the plasma screening length and surface potential near the lunar terminator

NASA Technical Reports Server (NTRS)

Benson, J.

1977-01-01

Direct measurement of the lunar dayside surface potential and screening length has been made by the suprathermal ion detector experiment (Side) near the terminator. In a region 20-30 deg from the terminator at the Apollo 14 and 15 sites the surface potential is found to be approximately 50 V negative, and the screening length to be about 1 km. This value of the screening length is more than 2 orders of magnitude greater than the solar wind 'Debye' length. The strong negative surface potential in this region may be due to enhanced temperature and density of the solar wind plasma.

A molecular Debye-Hückel approach to the reorganization energy of electron transfer reactions in an electric cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Tiejun; Department of Chemistry, Iowa State University, Ames, Iowa 50011; Song, Xueyu

2014-10-07

Electron transfer near an electrode immersed in ionic fluids is studied using the linear response approximation, namely, mean value of the vertical energy gap can be used to evaluate the reorganization energy, and hence any linear response model that can treat Coulomb interactions successfully can be used for the reorganization energy calculation. Specifically, a molecular Debye-Hückel theory is used to calculate the reorganization energy of electron transfer reactions in an electric cell. Applications to electron transfer near an electrode in molten salts show that the reorganization energies from our molecular Debye-Hückel theory agree well with the results from MD simulations.

Correlated Debye model for atomic motions in metal nanocrystals

NASA Astrophysics Data System (ADS)

Scardi, P.; Flor, A.

2018-05-01

The Correlated Debye model for the mean square relative displacement of atoms in near-neighbour coordination shells has been extended to include the effect of finite crystal size. This correctly explains the increase in Debye-Waller coefficient observed for metal nanocrystals. A good match with Molecular Dynamics simulations of Pd nanocrystals is obtained if, in addition to the phonon confinement effect of the finite domain size, proper consideration is also given to the static disorder component caused by the undercoordination of surface atoms. The new model, which addresses the analysis of the Pair Distribution Function and powder diffraction data collected at different temperatures, was preliminarily tested on recently published experimental data on nanocrystalline Pt powders.

Modulation of a compressional electromagnetic wave in a magnetized electron-positron quantum plasma.

PubMed

Amin, M R

2015-09-01

Amplitude modulation of a compressional electromagnetic wave in a strongly magnetized electron-positron pair plasma is considered in the quantum magnetohydrodynamic regime. The important ingredients of this study are the inclusion of the external strong magnetic field, Fermi quantum degeneracy pressure, particle exchange potential, quantum diffraction effects via the Bohm potential, and dissipative effect due to collision of the charged carriers. A modified-nonlinear Schödinger equation is developed for the compressional magnetic field of the electromagnetic wave by employing the standard reductive perturbation technique. The linear and nonlinear dispersions of the electromagnetic wave are discussed in detail. For some parameter ranges, relevant to dense astrophysical objects such as the outer layers of white dwarfs, neutron stars, and magnetars, etc., it is found that the compressional electromagnetic wave is modulationally unstable and propagates as a dissipated electromagnetic wave. It is also found that the quantum effects due to the particle exchange potential and the Bohm potential are negligibly small in comparison to the effects of the Fermi quantum degeneracy pressure. The numerical results on the growth rate of the modulation instability is also presented.

Continuum limit of the vibrational properties of amorphous solids.

PubMed

Mizuno, Hideyuki; Shiba, Hayato; Ikeda, Atsushi

2017-11-14

The low-frequency vibrational and low-temperature thermal properties of amorphous solids are markedly different from those of crystalline solids. This situation is counterintuitive because all solid materials are expected to behave as a homogeneous elastic body in the continuum limit, in which vibrational modes are phonons that follow the Debye law. A number of phenomenological explanations for this situation have been proposed, which assume elastic heterogeneities, soft localized vibrations, and so on. Microscopic mean-field theories have recently been developed to predict the universal non-Debye scaling law. Considering these theoretical arguments, it is absolutely necessary to directly observe the nature of the low-frequency vibrations of amorphous solids and determine the laws that such vibrations obey. Herein, we perform an extremely large-scale vibrational mode analysis of a model amorphous solid. We find that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that follow another universal non-Debye scaling law.

Numerical analysis of finite Debye-length effects in induced-charge electro-osmosis.

PubMed

Gregersen, Misha Marie; Andersen, Mathias Baekbo; Soni, Gaurav; Meinhart, Carl; Bruus, Henrik

2009-06-01

For a microchamber filled with a binary electrolyte and containing a flat unbiased center electrode at one wall, we employ three numerical models to study the strength of the resulting induced-charge electro-osmotic (ICEO) flow rolls: (i) a full nonlinear continuum model resolving the double layer, (ii) a linear slip-velocity model not resolving the double layer and without tangential charge transport inside this layer, and (iii) a nonlinear slip-velocity model extending the linear model by including the tangential charge transport inside the double layer. We show that, compared to the full model, the slip-velocity models significantly overestimate the ICEO flow. This provides a partial explanation of the quantitative discrepancy between observed and calculated ICEO velocities reported in the literature. The discrepancy increases significantly for increasing Debye length relative to the electrode size, i.e., for nanofluidic systems. However, even for electrode dimensions in the micrometer range, the discrepancies in velocity due to the finite Debye length can be more than 10% for an electrode of zero height and more than 100% for electrode heights comparable to the Debye length.

Continuum limit of the vibrational properties of amorphous solids

PubMed Central

Mizuno, Hideyuki; Ikeda, Atsushi

2017-01-01

The low-frequency vibrational and low-temperature thermal properties of amorphous solids are markedly different from those of crystalline solids. This situation is counterintuitive because all solid materials are expected to behave as a homogeneous elastic body in the continuum limit, in which vibrational modes are phonons that follow the Debye law. A number of phenomenological explanations for this situation have been proposed, which assume elastic heterogeneities, soft localized vibrations, and so on. Microscopic mean-field theories have recently been developed to predict the universal non-Debye scaling law. Considering these theoretical arguments, it is absolutely necessary to directly observe the nature of the low-frequency vibrations of amorphous solids and determine the laws that such vibrations obey. Herein, we perform an extremely large-scale vibrational mode analysis of a model amorphous solid. We find that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that follow another universal non-Debye scaling law. PMID:29087941

Dark-field transmission electron microscopy and the Debye-Waller factor of graphene

PubMed Central

Hubbard, William A.; White, E. R.; Dawson, Ben; Lodge, M. S.; Ishigami, Masa; Regan, B. C.

2014-01-01

Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary. PMID:25242882

Dark-field transmission electron microscopy and the Debye-Waller factor of graphene.

PubMed

Shevitski, Brian; Mecklenburg, Matthew; Hubbard, William A; White, E R; Dawson, Ben; Lodge, M S; Ishigami, Masa; Regan, B C

2013-01-15

Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary.

Calculation of Debye-Scherrer diffraction patterns from highly stressed polycrystalline materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J., E-mail: macdonm@umich.edu; SLAC National Accelerator Laboratory, Menlo Park, California 94025; Vorberger, J.

2016-06-07

Calculations of Debye-Scherrer diffraction patterns from polycrystalline materials have typically been done in the limit of small deviatoric stresses. Although these methods are well suited for experiments conducted near hydrostatic conditions, more robust models are required to diagnose the large strain anisotropies present in dynamic compression experiments. A method to predict Debye-Scherrer diffraction patterns for arbitrary strains has been presented in the Voigt (iso-strain) limit [Higginbotham, J. Appl. Phys. 115, 174906 (2014)]. Here, we present a method to calculate Debye-Scherrer diffraction patterns from highly stressed polycrystalline samples in the Reuss (iso-stress) limit. This analysis uses elastic constants to calculate latticemore » strains for all initial crystallite orientations, enabling elastic anisotropy and sample texture effects to be modeled directly. The effects of probing geometry, deviatoric stresses, and sample texture are demonstrated and compared to Voigt limit predictions. An example of shock-compressed polycrystalline diamond is presented to illustrate how this model can be applied and demonstrates the importance of including material strength when interpreting diffraction in dynamic compression experiments.« less

Attractive potential around a thermionically emitting microparticle.

PubMed

Delzanno, G L; Lapenta, G; Rosenberg, M

2004-01-23

We present a simulation study of the charging of a dust grain immersed in a plasma, considering the effect of thermionic electron emission from the grain. It is shown that the orbit motion limited theory is no longer reliable when electron emission becomes large: screening can no longer be treated within the Debye-Huckel approach and an attractive potential well can form, leading to the possibility of attractive forces on other grains with the same polarity. We suggest to perform laboratory experiments where emitting dust grains could be used to create nonconventional dust crystals or macromolecules.

Effective Debye length in closed nanoscopic systems: a competition between two length scales.

PubMed

Tessier, Frédéric; Slater, Gary W

2006-02-01

The Poisson-Boltzmann equation (PBE) is widely employed in fields where the thermal motion of free ions is relevant, in particular in situations involving electrolytes in the vicinity of charged surfaces. The applications of this non-linear differential equation usually concern open systems (in osmotic equilibrium with an electrolyte reservoir, a semi-grand canonical ensemble), while solutions for closed systems (where the number of ions is fixed, a canonical ensemble) are either not appropriately distinguished from the former or are dismissed as a numerical calculation exercise. We consider herein the PBE for a confined, symmetric, univalent electrolyte and quantify how, in addition to the Debye length, its solution also depends on a second length scale, which embodies the contribution of ions by the surface (which may be significant in high surface-to-volume ratio micro- or nanofluidic capillaries). We thus establish that there are four distinct regimes for such systems, corresponding to the limits of the two parameters. We also show how the PBE in this case can be formulated in a familiar way by simply replacing the traditional Debye length by an effective Debye length, the value of which is obtained numerically from conservation conditions. But we also show that a simple expression for the value of the effective Debye length, obtained within a crude approximation, remains accurate even as the system size is reduced to nanoscopic dimensions, and well beyond the validity range typically associated with the solution of the PBE.

A new insight on the dynamics of sodium dodecyl sulfate aqueous micellar solutions by dielectric spectroscopy.

PubMed

Lanzi, Leandro; Carlà, Marcello; Lanzi, Leonardo; Gambi, Cecilia M C

2009-02-01

Aqueous sodium dodecyl sulfate micellar solutions were investigated by a recently developed double-differential dielectric spectroscopy technique in the frequency range 100 MHz-3 GHz at 22 degrees C, in the surfactant concentration range 29.8-524 mM, explored for the first time above 104 mM. The micellar contribution to dielectric spectra was analyzed according to three models containing, respectively, a single Debye relaxation, a Cole-Cole relaxation and a double Debye relaxation. The single Debye model is not accurate enough. Both Cole-Cole and double Debye models fit well the experimental dielectric spectra. With the double Debye model, two characteristic relaxation times were identified: the slower one, in the range 400-900 ps, is due to the motion of counterions bound to the micellar surface (lateral motion); the faster one, in the range 100-130 ps, is due to interfacial bound water. Time constants and amplitudes of both processes are in fair agreement with Grosse's theoretical model, except at the largest concentration values, where interactions between micelles increase. For each sample, the volume fraction of bulk water and the effect of bound water as well as the conductivity in the low frequency limit were computed. The bound water increases as the surfactant concentration increases, in quantitative agreement with the micellar properties. The number of water molecules per surfactant molecule was also computed. The conductivity values are in agreement with Kallay's model over the whole surfactant concentration range.

Electrostatic interactions between diffuse soft multi-layered (bio)particles: beyond Debye-Hückel approximation and Deryagin formulation.

PubMed

Duval, Jérôme F L; Merlin, Jenny; Narayana, Puranam A L

2011-01-21

We report a steady-state theory for the evaluation of electrostatic interactions between identical or dissimilar spherical soft multi-layered (bio)particles, e.g. microgels or microorganisms. These generally consist of a rigid core surrounded by concentric ion-permeable layers that may differ in thickness, soft material density, chemical composition and degree of dissociation for the ionogenic groups. The formalism allows the account of diffuse interphases where distributions of ionogenic groups from one layer to the other are position-dependent. The model is valid for any number of ion-permeable layers around the core of the interacting soft particles and covers all limiting situations in terms of nature of interacting particles, i.e. homo- and hetero-interactions between hard, soft or entirely porous colloids. The theory is based on a rigorous numerical solution of the non-linearized Poisson-Boltzmann equation including radial and angular distortions of the electric field distribution within and outside the interacting soft particles in approach. The Gibbs energy of electrostatic interaction is obtained from a general expression derived following the method by Verwey and Overbeek based on appropriate electric double layer charging mechanisms. Original analytical solutions are provided here for cases where interaction takes place between soft multi-layered particles whose size and charge density are in line with Deryagin treatment and Debye-Hückel approximation. These situations include interactions between hard and soft particles, hard plate and soft particle or soft plate and soft particle. The flexibility of the formalism is highlighted by the discussion of few situations which clearly illustrate that electrostatic interaction between multi-layered particles may be partly or predominantly governed by potential distribution within the most internal layers. A major consequence is that both amplitude and sign of Gibbs electrostatic interaction energy may dramatically change depending on the interplay between characteristic Debye length, thickness of ion-permeable layers and their respective protolytic features (e.g. location, magnitude and sign of charge density). This formalism extends a recent model by Ohshima which is strictly limited to interaction between soft mono-shell particles within Deryagin and Debye-Hückel approximations under conditions where ionizable sites are completely dissociated.

Effects of geometric modulation and surface potential heterogeneity on electrokinetic flow and solute transport in a microchannel

NASA Astrophysics Data System (ADS)

Bera, Subrata; Bhattacharyya, S.

2017-12-01

A numerical investigation is performed on the electroosmotic flow (EOF) in a surface-modulated microchannel to induce enhanced solute mixing. The channel wall is modulated by placing surface-mounted obstacles of trigonometric shape along which the surface potential is considered to be different from the surface potential of the homogeneous part of the wall. The characteristics of the electrokinetic flow are governed by the Laplace equation for the distribution of external electric potential; the Poisson equation for the distribution of induced electric potential; the Nernst-Planck equations for the distribution of ions; and the Navier-Stokes equations for fluid flow simultaneously. These nonlinear coupled set of governing equations are solved numerically by a control volume method over the staggered system. The influence of the geometric modulation of the surface, surface potential heterogeneity and the bulk ionic concentration on the EOF is analyzed. Vortical flow develops near a surface modulation, and it becomes stronger when the surface potential of the modulated region is in opposite sign to the surface potential of the homogeneous part of the channel walls. Vortical flow also depends on the Debye length when the Debye length is in the order of the channel height. Pressure drop along the channel length is higher for a ribbed wall channel compared to the grooved wall case. The pressure drop decreases with the increase in the amplitude for a grooved channel, but increases for a ribbed channel. The mixing index is quantified through the standard deviation of the solute distribution. Our results show that mixing index is higher for the ribbed channel compared to the grooved channel with heterogeneous surface potential. The increase in potential heterogeneity in the modulated region also increases the mixing index in both grooved and ribbed channels. However, the mixing performance, which is the ratio of the mixing index to pressure drop, reduces with the rise in the surface potential heterogeneity.

Effects of geometric modulation and surface potential heterogeneity on electrokinetic flow and solute transport in a microchannel

NASA Astrophysics Data System (ADS)

Bera, Subrata; Bhattacharyya, S.

2018-04-01

A numerical investigation is performed on the electroosmotic flow (EOF) in a surface-modulated microchannel to induce enhanced solute mixing. The channel wall is modulated by placing surface-mounted obstacles of trigonometric shape along which the surface potential is considered to be different from the surface potential of the homogeneous part of the wall. The characteristics of the electrokinetic flow are governed by the Laplace equation for the distribution of external electric potential; the Poisson equation for the distribution of induced electric potential; the Nernst-Planck equations for the distribution of ions; and the Navier-Stokes equations for fluid flow simultaneously. These nonlinear coupled set of governing equations are solved numerically by a control volume method over the staggered system. The influence of the geometric modulation of the surface, surface potential heterogeneity and the bulk ionic concentration on the EOF is analyzed. Vortical flow develops near a surface modulation, and it becomes stronger when the surface potential of the modulated region is in opposite sign to the surface potential of the homogeneous part of the channel walls. Vortical flow also depends on the Debye length when the Debye length is in the order of the channel height. Pressure drop along the channel length is higher for a ribbed wall channel compared to the grooved wall case. The pressure drop decreases with the increase in the amplitude for a grooved channel, but increases for a ribbed channel. The mixing index is quantified through the standard deviation of the solute distribution. Our results show that mixing index is higher for the ribbed channel compared to the grooved channel with heterogeneous surface potential. The increase in potential heterogeneity in the modulated region also increases the mixing index in both grooved and ribbed channels. However, the mixing performance, which is the ratio of the mixing index to pressure drop, reduces with the rise in the surface potential heterogeneity.

Inertial effects in systems with magnetic charge

NASA Astrophysics Data System (ADS)

Armitage, N. P.

2018-05-01

This short article sets out some of the basic considerations that go into detecting the mass of quasiparticles with effective magnetic charge in solids. Effective magnetic charges may be appear as defects in particular magnetic textures. A magnetic monopole is a defect in this texture and as such these are not monopoles in the actual magnetic field B, but instead in the auxiliary field H. They may have particular properties expected for such quasiparticles such as magnetic charge and mass. This effective mass may-in principle-be detected in the same fashion that the mass is detected of other particles classically e.g. through their inertial response to time-dependent electromagnetic fields. I discuss this physics in the context of the "simple" case of the quantum spin ices, but aspects are broadly applicable. Based on extensions to Ryzkhin's model for classical spin ice, a hydrodynamic formulation can be given that takes into account inertial and entropic forces. Ultimately, a form for the susceptibility is obtained that is equivalent to the Rocard equation, which is a classic form used to account for inertial effects in the context of Debye-like relaxation.

Second-harmonic generation from a thin spherical layer and No-generation conditions

NASA Astrophysics Data System (ADS)

Kapshai, V. N.; Shamyna, A. A.

2017-09-01

In the Rayleigh-Gans-Debye approximation, we solve the problem of second-harmonic generation by an elliptically polarized electromagnetic wave incident on the surface of a spherical particle that is coated by an optically nonlinear layer and is placed in a dielectric. The formulas obtained characterize the spatial distribution of the electric field of the second harmonic in the far-field zone. The most general form of the second-order dielectric susceptibility tensor is considered, which contains four independent components, with three of them being nonchiral and one, chiral. Consistency and inconsistencies between the obtained solution and formulas from works of other authors are found. We analyze the directivity patterns that characterize the spatial distribution of the generated radiation for the nonchiral layer and their dependences on the anisotropy and ellipticity coefficients of the incident wave. It is found that, with increasing radius of the nonlinear layer, the generated radiation becomes more directional. Combinations of parameters for which no radiation is generated are revealed. Based on this, we propose methods for experimental determination of the anisotropy coefficients.

Review of Work Done with Professor Nussenzveig Regarding the Mie Theory

NASA Technical Reports Server (NTRS)

Wiscombe, W.

2003-01-01

Prof. Nussenzveig has dedicated part of his career to a surprising and unusual pursuit harking back to the heyday of classical physics: Mie theory, or the scattering of electromagnetic radiation by a homogeneous sphere. M e theory was not put forward until around 1908 (nearly simultaneously by Debye in a different form) and was quickly forgotten in the rush to the then-new quantum mechanics. It remained somewhat of a backwater until Prof. Nussenzveig brought it back by adapting complex angular momentum ideas from Regge pole theory, which had originally been invented for quantum mechanics. Since 1960, he has made fundamental contributions to actually understanding (as opposed to merely calculating) Mie theory. I became involved with this work in 1978 by inviting Prof. Nussenzveig to visit me at the National Center for Atmospheric Research. Since then we have written several papers together on approximate methods for Mie cross-sections, bubble scattering, and other subjects. This lecture will review that work, ending with his recent work on Mie resonances. The emphasis will be on the applications in atmospheric sciences.

First-Principles Study of Structural, Electronic, Optical, and Thermal Properties of BeSiSb2 and MgSiSb2

NASA Astrophysics Data System (ADS)

Benlamari, S.; Boukhtouta, M.; Taïri, L.; Meradji, H.; Amirouche, L.; Ghemid, S.

2018-03-01

Structural, electronic, optical, and thermal properties of ternary II-IV-V2 (BeSiSb2 and MgSiSb2) chalcopyrite semiconductors have been calculated using the full-potential linearized augmented plane wave scheme␣in the generalized gradient approximation. The optimized equilibrium structural parameters ( a, c, and u) are in good agreement with theoretical results obtained using other methods. The band structure and density of states reveal that BeSiSb2 has an indirect (Γ-Z) bandgap of about 0.61 eV, whereas MgSiSb2 has a direct (Γ-Γ) bandgap of 0.80 eV. The dielectric function, refractive index, and extinction coefficient were calculated to investigate the optical properties, revealing that BeSiSb2 and MgSiSb2 present very weak birefringence. The temperature dependence of the volume, bulk modulus, Debye temperature, and heat capacities ( C v and C p) was predicted using the quasiharmonic Debye model at different pressures. Significant differences in properties are observed at high pressure and high temperature. We predict that, at 300 K and 0 GPa, the heat capacity at constant volume C v, heat capacity at constant pressure C P, Debye temperature θ D, and Grüneisen parameter γ will be about 94.91 J/mol K, 98.52 J/mol K, 301.30 K, and 2.11 for BeSiSb2 and about 96.08 J/mol K, 100.47 J/mol K, 261.38 K, and 2.20 for MgSiSb2, respectively.

Redshift of the Heα emission line of He-like ions under a plasma environment

NASA Astrophysics Data System (ADS)

Fang, T. K.; Wu, C. S.; Gao, X.; Chang, T. N.

2017-11-01

By carefully following the spatial and temporal criteria of the Debye-Hückel (DH) approximation, we present a detailed theoretical study on the redshifts of the spectroscopically isolated Heα lines corresponding to the 1 s 2 p 1P →1 s21S emission from two-electron ions embedded in external dense plasma. We first focus our study on the ratio R =Δ ωα/ωo between the redshift Δ ωα due to the external plasma environment and the energy ωo of the Heα line in the absence of the plasma. Interestingly, the result of our calculation shows that this ratio R turns out to vary as a nearly universal function of a reduced Debye length λD(Z ) =(Z -1 ) D . Since the ratio R dictates the necessary energy resolution for a quantitative measurement of the redshifts and, at the same time, the Debye length D is linked directly to the plasma density and temperature, the dependence of R on D should help to facilitate the potential experimental efforts for a quantitative measurement of the redshifts for the Heα line of the two-electron ions. In addition, our study has led to a nearly constant redshift Δ ωα at a given D for all He-like ions with Z between 5 and 18 based on our recent critical assessment of the applicability of the DH approximation to atomic transitions. These two general features, if confirmed by observation, would offer a viable and easy alternative in the diagnostic efforts of the dense plasma.

Information-theoretic measures of hydrogen-like ions in weakly coupled Debye plasmas

NASA Astrophysics Data System (ADS)

Zan, Li Rong; Jiao, Li Guang; Ma, Jia; Ho, Yew Kam

2017-12-01

Recent development of information theory provides researchers an alternative and useful tool to quantitatively investigate the variation of the electronic structure when atoms interact with the external environment. In this work, we make systematic studies on the information-theoretic measures for hydrogen-like ions immersed in weakly coupled plasmas modeled by Debye-Hückel potential. Shannon entropy, Fisher information, and Fisher-Shannon complexity in both position and momentum spaces are quantified in high accuracy for the hydrogen atom in a large number of stationary states. The plasma screening effect on embedded atoms can significantly affect the electronic density distributions, in both conjugate spaces, and it is quantified by the variation of information quantities. It is shown that the composite quantities (the Shannon entropy sum and the Fisher information product in combined spaces and Fisher-Shannon complexity in individual space) give a more comprehensive description of the atomic structure information than single ones. The nodes of wave functions play a significant role in the changes of composite information quantities caused by plasmas. With the continuously increasing screening strength, all composite quantities in circular states increase monotonously, while in higher-lying excited states where nodal structures exist, they first decrease to a minimum and then increase rapidly before the bound state approaches the continuum limit. The minimum represents the most reduction of uncertainty properties of the atom in plasmas. The lower bounds for the uncertainty product of the system based on composite information quantities are discussed. Our research presents a comprehensive survey in the investigation of information-theoretic measures for simple atoms embedded in Debye model plasmas.

75 FR 5009 - Proximity Detection Systems for Underground Mines

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-01

... electromagnetic field based systems. After reviewing the different types of systems, MSHA determined that the electromagnetic field based system offers the greatest potential for reducing pinning, crushing, and striking... near RCCMs. An electromagnetic field based system consists of a combination of electromagnetic field...

Structural Origin of Enhanced Dynamics at the Surface of a Glassy Alloy

NASA Astrophysics Data System (ADS)

Sun, Gang; Saw, Shibu; Douglass, Ian; Harrowell, Peter

2017-12-01

The enhancement of mobility at the surface of an amorphous alloy is studied using a combination of molecular dynamic simulations and normal mode analysis of the nonuniform distribution of Debye-Waller factors. The increased mobility at the surface is found to be associated with the appearance of Arrhenius temperature dependence. We show that the transverse Debye-Waller factor exhibits a peak at the surface. Over the accessible temperature range, we find that the bulk and surface diffusion coefficients obey the same empirical relationship with the respective Debye-Waller factors. Extrapolating this relationship to lower T , we argue that the observed decrease in the constraint at the surface is sufficient to account for the experimentally observed surface enhancement of mobility.

Slow test charge response in a dusty plasma with Kappa distributed electrons and ions

NASA Astrophysics Data System (ADS)

Ali, S.; Eliasson, B.

2017-08-01

The electrostatic potential around a slowly moving test charge is studied in a dusty plasma where the ions and electrons follow a powerlaw Kappa distribution in velocity space. A test charge moving with a speed much smaller than the dust thermal speed gives rise to a short-scale Debye-Hückel potential as well as a long-range far-field potential decreasing as inverse cube of the distance to the test charge along the propagation direction. The potentials are significantly modified in the presence of high-energy tails, modeled by lower spectral indices in the ion and electron Kappa distribution functions. Plasma parameters relevant to laboratory dusty plasmas are discussed.

Computation on collisionless steady-state plasma flow past a charged disk

NASA Technical Reports Server (NTRS)

Parker, L. W.

1976-01-01

A computer method is presented using the 'inside-out' approach, for predicting the structure of the disturbed zone near a moving body in space. The approach uses fewer simplifying assumptions than other available methods, and is applicable to large ranges of the values of body and plasma parameters. Two major advances concerning 3-dimensional bodies are that thermal motions of ions as well as of electrons are treated realistically by following their trajectories in the electric field, and the technique for achieving self-consistency is promising for very large bodies. Three sample solutions were obtained for a disk-shaped body, charged negatively to a potential 4kT/e. With ion Mach number 4, and equal ion and electron temperatures, the wakes of a relatively small body (radius 5 Debye lengths) and a relatively large body (radius 100 Debye lengths) both begin to fill up between 2 and 3 body radii downstream. For the large body there is in addition a potential well (about 6kT/e deep) behind the body. Increasing the ion Mach number to 8 for the large body causes the potential well to become wider and longer but not deeper. For the large body, the quasineutrality assumption is validated outside of a cone-shaped region in the very near wake. For the large as well as the small body, the disturbed zone behind the body extends transversely no more than 2 or 3 body radii, a result of significance for the design of spacecraft boom instrumentation.

Theoretical analysis of the electronic, optical and thermal properties of lead strontium telluride alloys Pb1-xSrxTe (x = 0.0-1.0)

NASA Astrophysics Data System (ADS)

Chouit, F.; Sifi, C.; Slimani, M.; Meradji, H.; Ghemid, S.; Khenata, R.; Rai, D. P.; Bin Omran, S.

2018-02-01

We have simulated different physical properties of Pb1-xSrxTe semiconductors, using the Ab-initio full potential augmented plane wave (FP-LAPW) method. The two commonly used exchange potentials viz., PBE-GGA and WC-GGA are used along with the most recently developed modified Becke and Johnson (mBJ) potential to study the electronic and optical properties. In this study, we have observed an increase in band gap values as well as the lattice parameter with increasing the concentration of Sr atoms in Pb1-xSrxTe alloys while the bulk modulus and the refractive index have reverse effect. The microscopic origin of the band gap bowing is explained using the approach of Zunger and co-workers. At ambient conditions (p = 0, T = 0), the calculations indicate that Pb1-xSrxTe is a direct band gap semiconductor R-R with x = 0.125, 0.25, 0.375, 0.5, 0.625, 0.75 and 0.875. The refractive indices are also calculated using the FP-LAPW method and the models of Moss, Ravindra and the Herve-Vandame. The obtained results are in consistent with the previous available data. To study the thermal effects, the temperature effect on the lattice parameters, thermal expansions, heat capacities the quasi-harmonic Debye model is applied. The Debye temperature is determined from the non-equilibrium Gibbs function.

SEPAC data analysis in support of the environmental interaction program

NASA Technical Reports Server (NTRS)

Lin, Chin S.

1990-01-01

Injections of nonrelativistic electron beams from an isolated equipotential conductor into a uniform background of plasma and neutral gas were simulated using a two dimensional electrostatic particle code. The ionization effects of spacecraft charging are examined by including interactions of electrons with neutral gas. The simulations show that the conductor charging potential decreases with increasing neutral background density due to the production of secondary electrons near the conductor surface. In the spacecraft wake, the background electrons accelerated towards the charged space craft produced an enhancement of secondary electrons and ions. Simulations run for longer times indicate that the spacecraft potential is further reduced and short wavelength beam-plasma oscillations appear. The results are applied to explain the space craft charging potential measured during the SEPAC experiments from Spacelab 1. A second paper is presented in which a two dimensional electrostatic particle code was used to study the beam radial expansion of a nonrelativistic electron beam injected from an isolated equipotential conductor into a background plasma. The simulations indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. The simulations also suggest that the charge buildup at the beam stagnation point causes the beam radial expansion. From a survey of the simulation results, it is found that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. This dependence is explained in terms of the ratio of the beam electron Debye length to the ambient electron Debye length. These results are most applicable to the SEPAC electron beam injection experiments from Spacelab 1, where high charging potential was observed.

Dusty plasma (Yukawa) rings

NASA Astrophysics Data System (ADS)

Sheridan, T. E.; Gallagher, James C.

2016-11-01

One-dimensional and quasi-one-dimensional strongly coupled dusty plasma rings have been created experimentally. Longitudinal (acoustic) and transverse (optical) dispersion relations for the one-ring are measured and found to be in excellent agreement with the theory for an unbounded straight chain of particles interacting through a Yukawa (i.e., screened Coulomb or Debye-Hückel) potential. These rings provide a new experimental system to directly study one-dimensional and quasi-one-dimensional linear and nonlinear phenomena.

Comprehensive Study of Plasma-Wall Sheath Transport Phenomena

DTIC Science & Technology

2012-09-10

environment, a Langmuir probe and a Retarding Potential Analyzer (RPA). The Langmuir probe could be considered the seminal plasma diagnostic, and a large...plasma-sheath interface. Electric field is normalized by Te/LD (LD is the Debye length) and velocity is normalized by the Bohm speed. Figure 14...studying the interaction of the near-wall plasma sheath with a magnetic field , and modeled the plasma sheath of the GT thick-sheath (~10mm) plasma

Some Debye temperatures from single-crystal elastic constant data

USGS Publications Warehouse

Robie, R.A.; Edwards, J.L.

1966-01-01

The mean velocity of sound has been calculated for 14 crystalline solids by using the best recent values of their single-crystal elastic stiffness constants. These mean sound velocities have been used to obtain the elastic Debye temperatures ??De for these materials. Models of the three wave velocity surfaces for calcite are illustrated. ?? 1966 The American Institute of Physics.

Dielectric relaxation of 2-ethyl-1-hexanol around the glass transition by thermally stimulated depolarization currents.

PubMed

Arrese-Igor, S; Alegría, A; Colmenero, J

2015-06-07

We explore new routes for characterizing the Debye-like and α relaxation in 2-ethyl-1-hexanol (2E1H) monoalcohol by using low frequency dielectric techniques including thermally stimulated depolarization current (TSDC) techniques and isothermal depolarization current methods. In this way, we have improved the resolution of the overlapped processes making it possible the analysis of the data in terms of a mode composition as expected for a chain-like response. Furthermore the explored ultralow frequencies enabled to study dynamics at relatively low temperatures close to the glass transition (Tg). Results show, on the one hand, that Debye-like and α relaxation timescales dramatically approach to each other upon decreasing temperature to Tg. On the other hand, the analysis of partial polarization TSDC data confirms the single exponential character of the Debye-like relaxation in 2E1H and rules out the presence of Rouse type modes in the scenario of a chain-like response. Finally, on crossing the glass transition, the Debye-like relaxation shows non-equilibrium effects which are further emphasized by aging treatment and would presumably emerge as a result of the arrest of the structural relaxation below Tg.

Characterizing Flexible and Instrinsically Unstructured Biological Macromolecules by SAS using the Porod-Debye Law

PubMed Central

Rambo, Robert P.; Tainer, John A.

2011-01-01

Unstructured proteins, RNA or DNA components provide functionally important flexibility that is key to many macromolecular assemblies throughout cell biology. As objective, quantitative experimental measures of flexibility and disorder in solution are limited, small angle scattering (SAS), and in particular small angle X-ray scattering (SAXS), provides a critical technology to assess macromolecular flexibility as well as shape and assembly. Here, we consider the Porod-Debye law as a powerful tool for detecting biopolymer flexibility in SAS experiments. We show that the Porod-Debye region fundamentally describes the nature of the scattering intensity decay, which captures information needed for distinguishing between folded and flexible particles. Particularly for comparative SAS experiments, application of the law, as described here, can distinguish between discrete conformational changes and localized flexibility relevant to molecular recognition and interaction networks. This approach aids insightful analyses of fully and partly flexible macromolecules that is more robust and conclusive than traditional Kratky analyses. Furthermore, we demonstrate for prototypic SAXS data that the ability to calculate particle density by the Porod-Debye criteria, as shown here, provides an objective quality assurance parameter that may prove of general use for SAXS modeling and validation. PMID:21509745

Peter J. W. Debye - a whole life devoted to science.

PubMed

Dalba, Giuseppe

2016-11-01

In 1915 P. Debye, one of the most prominent scientists in the field of condensed-matter physics and physical chemistry, published an X-ray scattering equation for randomly oriented scattering sites. This formula, since then used for describing the structure of powders, liquids and gases, has become a model for material analysis at the nanoscale. This paper re-examines briefly Debye's works on the origin and evolution of the scattering equation and its first uses. The career of the great scientist and some of his other numerous and diverse contributions to science are also reviewed. Additionally the paper addresses aspects of his life as a teacher, as a science manager and as a man, including the recent controversy about his conduct during the Third Reich regime.

Calculation of Half-Metal, Debye and Curie Temperatures of Co2VAl Compound: First Principles Study

NASA Astrophysics Data System (ADS)

Arash, Boochani; Heidar, Khosravi; Jabbar, Khodadadi; Shahram, Solaymani; Masoud Majidiyan, Sarmazdeh; Rohollah Taghavi, Mendi; Sayed, Mohammad Elahi

2015-05-01

By FP-LAPW calculations, the structural, elastic, Debye and Curie temperatures, electronic and magnetic properties of Co2 VAl are investigated. The results indicate that Ferromagnetic (FM) phase is more stable than Anti-Ferromagnetic (AFM) and Non-magnetic (NM) ones. In addition, C11-C12 > 0, C44 > 0, and B > 0 so Co2VAl is an elastically stable material with high Debye temperature. Also, the B/G ratio exhibits a ductility behavior. The relatively high Curie temperature provides it as a favorable material for spintronic application. It's electronic and magnetic properties are studied by GGA+U approach leading to a 100% spin polarization at Fermi level. Supported by the simulation of Nano Physics Lab center of Kermanshah Branch, Islamic Azad University

Field-Assisted Splitting of Pure Water Based on Deep-Sub-Debye-Length Nanogap Electrochemical Cells.

PubMed

Wang, Yifei; Narayanan, S R; Wu, Wei

2017-08-22

Owing to the low conductivity of pure water, using an electrolyte is common for achieving efficient water electrolysis. In this paper, we have fundamentally broken through this common sense by using deep-sub-Debye-length nanogap electrochemical cells to achieve efficient electrolysis of pure water (without any added electrolyte) at room temperature. A field-assisted effect resulted from overlapped electrical double layers can greatly enhance water molecules ionization and mass transport, leading to electron-transfer limited reactions. We have named this process "virtual breakdown mechanism" (which is completely different from traditional mechanisms) that couples the two half-reactions together, greatly reducing the energy losses arising from ion transport. This fundamental discovery has been theoretically discussed in this paper and experimentally demonstrated in a group of electrochemical cells with nanogaps between two electrodes down to 37 nm. On the basis of our nanogap electrochemical cells, the electrolysis current density from pure water can be significantly larger than that from 1 mol/L sodium hydroxide solution, indicating the much better performance of pure water splitting as a potential for on-demand clean hydrogen production.

Dependence of ion density in the wake of the AE-C satellite on the ratio of body size to Debye length in an (O/sup +/)-dominated plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samir, U.; Kaufman, Y.J.; Brace, L.H.

Measurements of electron temperature, satellite potential, ion density and ion composition from the cylindrical electrostatic probe and the Bennett ion mass spectrometer on board the AE-C satellite were used to investigate the influence of the body size parameter R/sub D/=R/sub 0//lambda/sub D/ (where R/sub 0/ is the satellite radius and lambda/sub D/ is the ambient Debye length) on ion distribution in the very near wake. The investigation focused on (O/sup +/) plasmas. It was found that the ratio (..beta..) of density in the wake to ambient density varies with R/sub D/ and that the variation can be described by amore » simple exponential relationship of the form ..beta..=a/sub 0/ exp (a/sub 1/R/sub D/) for 37< or =R/sub D/< or =247 and a/sub 0/=0.006, a/sub 1/=-0.009. the present study extends that of Samir et al. (1979a).« less

Influence of collective nonideal shielding on fusion reaction in partially ionized classical nonideal plasmas

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Young-Dae

2017-04-01

The collective nonideal effects on the nuclear fusion reaction process are investigated in partially ionized classical nonideal hydrogen plasmas. The effective pseudopotential model taking into account the collective and plasma shielding effects is applied to describe the interaction potential in nonideal plasmas. The analytic expressions of the Sommerfeld parameter, the fusion penetration factor, and the cross section for the nuclear fusion reaction in nonideal plasmas are obtained as functions of the nonideality parameter, Debye length, and relative kinetic energy. It is found that the Sommerfeld parameter is suppressed due to the influence of collective nonideal shielding. However, the collective nonideal shielding is found to enhance the fusion penetration factor in partially ionized classical nonideal plasmas. It is also found that the fusion penetration factors in nonideal plasmas represented by the pseudopotential model are always greater than those in ideal plasmas represented by the Debye-Hückel model. In addition, it is shown that the collective nonideal shielding effect on the fusion penetration factor decreases with an increase of the kinetic energy.

Electromagnetic finite elements based on a four-potential variational principle

NASA Technical Reports Server (NTRS)

Schuler, James J.; Felippa, Carlos A.

1991-01-01

Electromagnetic finite elements based on a variational principle that uses the electromagnetic four-potential as a primary variable are derived. This choice is used to construct elements suitable for downstream coupling with mechanical and thermal finite elements for the analysis of electromagnetic/mechanical systems that involve superconductors. The main advantages of the four-potential as a basis for finite element formulation are that the number of degrees of freedom per node remains modest as the problem dimensionally increases, that jump discontinuities on interfaces are naturally accommodated, and that statics as well as dynamics may be treated without any a priori approximations. The new elements are tested on an axisymmetric problem under steady state forcing conditions. The results are in excellent agreement with analytical solutions.

Electromagnetic structure of light nuclei

DOE PAGES

Pastore, Saori

2016-03-25

Here, the present understanding of nuclear electromagnetic properties including electromagnetic moments, form factors and transitions in nuclei with A ≤ 10 is reviewed. Emphasis is on calculations based on nuclear Hamiltonians that include two- and three-nucleon realistic potentials, along with one- and two-body electromagnetic currents derived from a chiral effective field theory with pions and nucleons.

Electromagnetic structure of light nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pastore, Saori

Here, the present understanding of nuclear electromagnetic properties including electromagnetic moments, form factors and transitions in nuclei with A ≤ 10 is reviewed. Emphasis is on calculations based on nuclear Hamiltonians that include two- and three-nucleon realistic potentials, along with one- and two-body electromagnetic currents derived from a chiral effective field theory with pions and nucleons.

Rediscovering the Schulze-Hardy rule in competitive adsorption to an air-water interface.

PubMed

Stenger, Patrick C; Isbell, Stephen G; St Hillaire, Debra; Zasadzinski, Joseph A

2009-09-01

The ratio of divalent to monovalent ion concentration necessary to displace the surface-active protein, albumin, by lung surfactant monolayers and multilayers at an air-water interface scales as 2(-6), the same concentration dependence as the critical flocculation concentration (CFC) for colloids with a high surface potential. Confirming this analogy between competitive adsorption and colloid stability, polymer-induced depletion attraction and electrostatic potentials are additive in their effects; the range of the depletion attraction, twice the polymer radius of gyration, must be greater than the Debye length to have an effect on adsorption.

Electricity and Magnetism

NASA Astrophysics Data System (ADS)

Glazebrook, R. T.

2016-10-01

1. Electrostatics: fundamental facts; 2. Electricity as a measurable quantity; 3. Measurement of electric force and potential; 4. Condensers; 5. Electrical machines; 6. Measurement of potential and electric force; 7. Magnetic attraction and repulsion; 8. Laws of magnetic force; 9. Experiments with magnets; 10. Magnetic calculations; 11. Magnetic measurements; 12. Terrestrial magnetism; 13. The electric current; 14. Relation between electromagnetic force and current; 15. Measurement of current; 16. Measurement of resistance and electromotive force; 17. Measurement of quantity of electricity, condensers; 18. Thermal activity of a current; 19. The voltaic cell (theory); 20. Electromagnetism; 21. Magnetisation of iron; 22. Electromagnetic instruments; 23. Electromagnetic induction; 24. Applications of electromagnetic induction; 25. Telegraphy and telephony; 26. Electric waves; 27. Transference of electricity through gases: corpuscles and electrons; Answers to examples; Index.

Analogy between electromagnetic potentials and wave-like dynamic variables with connections to quantum theory

NASA Astrophysics Data System (ADS)

Yang, Chen

2018-05-01

The transitions from classical theories to quantum theories have attracted many interests. This paper demonstrates the analogy between the electromagnetic potentials and wave-like dynamic variables with their connections to quantum theory for audiences at advanced undergraduate level and above. In the first part, the counterpart relations in the classical electrodynamics (e.g. gauge transform and Lorenz condition) and classical mechanics (e.g. Legendre transform and free particle condition) are presented. These relations lead to similar governing equations of the field variables and dynamic variables. The Lorenz gauge, scalar potential and vector potential manifest a one-to-one similarity to the action, Hamiltonian and momentum, respectively. In the second part, the connections between the classical pictures of electromagnetic field and particle to quantum picture are presented. By characterising the states of electromagnetic field and particle via their (corresponding) variables, their evolution pictures manifest the same algebraic structure (isomorphic). Subsequently, pictures of the electromagnetic field and particle are compared to the quantum picture and their interconnections are given. A brief summary of the obtained results are presented at the end of the paper.

A simulation study of radial expansion of an electron beam injected into an ionospheric plasma

NASA Technical Reports Server (NTRS)

Koga, J.; Lin, C. S.

1994-01-01

Injections of nonrelativistic electron beams from a finite equipotential conductor into an ionospheric plasma have been simulated using a two-dimensional electrostatic particle code. The purpose of the study is to survey the simulation parameters for understanding the dependence of beam radius on physical variables. The conductor is charged to a high potential when the background plasma density is less than the beam density. Beam electrons attracted by the charged conductor are decelerated to zero velocity near the stagnation point, which is at a few Debye lengths from the conductor. The simulations suggest that the beam electrons at the stagnation point receive a large transverse kick and the beam expands radially thereafter. The buildup of beam electrons at the stagnation point produces a large electrostatic force responsible for the transverse kick. However, for the weak charging cases where the background plasma density is larger than the beam density, the radial expansion mechanism is different; the beam plasma instability is found to be responsible for the radial expansion. The simulations show that the electron beam radius for high spacecraft charging cases is of the order of the beam gyroradius, defined as the beam velocity divided by the gyrofrequency. In the weak charging cases, the beam radius is only a fraction of the beam gyroradius. The parameter survey indicates that the beam radius increases with beam density and decreases with magnetic field and beam velocity. The beam radius normalized by the beam gyroradius is found to scale according to the ratio of the beam electron Debye length to the ambient electron Debye length. The parameter dependence deduced would be useful for interpreting the beam radius and beam density of electron beam injection experiments conducted from rockets and the space shuttle.

Dynamics of human serum albumin studied by acoustic relaxation spectroscopy.

PubMed

Hushcha, T; Kaatze, U; Peytcheva, A

Sonic absorption spectra of solutions of human serum albumin (SA) in water and in aqueous phosphate buffer systems have been measured between 0.2 and 2000 MHz at different temperatures (15-35 degrees C), pH values (1.8-12.3), and protein concentrations (1-40 g/L). Several spectra, indicating relaxation processes in the whole frequency range, have been found. The spectra at neutral pH could be fitted well with an analytical function consisting of the asymptotic high frequency absorption and two relaxation contributions, a Debye-type relaxation term with discrete relaxation time and a term with asymmetric continuous distribution of relaxation times. Both relaxation contributions were observed in water and in buffer solutions and increased with protein concentration. The contribution represented by a Debye-type term is practically independent of temperature and was attributed to cooperative conformational changes of the polypeptide chain featuring a relaxation time of about 400 ns. The distribution of the relaxation times corresponding to the second relaxation contribution was characterized by a short time cutoff, between about 0.02 and 0.4 ns depending on temperature, and a long time tail extending to microseconds. Such relaxation behavior was interpreted in terms of solute-solvent interactions reflecting various hydration layers of HSA molecules. At acid and alkaline pH, an additional Debye-type contribution with relaxation time in the range of 30-100 ns exists. It seems to be due to proton transfer reactions of protein side-chain groups. The kinetic and thermodynamic parameters of these processes have been estimated from these first measurements to indicate the potential of acoustic spectra for the investigation of the elementary kinetics of albumin processes. Copyright 2004 Wiley Periodicals, Inc. Biopolymers, 2004

Improved analysis techniques for cylindrical and spherical double probes.

PubMed

Beal, Brian; Johnson, Lee; Brown, Daniel; Blakely, Joseph; Bromaghim, Daron

2012-07-01

A versatile double Langmuir probe technique has been developed by incorporating analytical fits to Laframboise's numerical results for ion current collection by biased electrodes of various sizes relative to the local electron Debye length. Application of these fits to the double probe circuit has produced a set of coupled equations that express the potential of each electrode relative to the plasma potential as well as the resulting probe current as a function of applied probe voltage. These equations can be readily solved via standard numerical techniques in order to determine electron temperature and plasma density from probe current and voltage measurements. Because this method self-consistently accounts for the effects of sheath expansion, it can be readily applied to plasmas with a wide range of densities and low ion temperature (T(i)/T(e) ≪ 1) without requiring probe dimensions to be asymptotically large or small with respect to the electron Debye length. The presented approach has been successfully applied to experimental measurements obtained in the plume of a low-power Hall thruster, which produced a quasineutral, flowing xenon plasma during operation at 200 W on xenon. The measured plasma densities and electron temperatures were in the range of 1 × 10(12)-1 × 10(17) m(-3) and 0.5-5.0 eV, respectively. The estimated measurement uncertainty is +6%∕-34% in density and +∕-30% in electron temperature.

Novel Separation of Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mariella, R

The separation of actinides and other elements of interest for nuclear forensics and threat reduction is currently performed using decades-old chemistries and ion-exchange columns. We propose to determine the technical feasibility of a novel method for separating actinide ions in solution. This method is based upon isotachophoresis (ITP), which has been applied in the purification of pharmaceuticals and other biochemical applications. This technique has the potential to separate inorganic ions more effectively than existing methods, which is key to analyzing very small samples. We will perform a quantitative assessment of the effectiveness of specific isotachophoretic approaches including predicting the physicalmore » and chemical properties, such as ion mobility, of inorganic ions under specific solvent conditions using a combination of ab initio calculations and semi-empirical methods. We expect to obtain a thorough understanding of the analytical systems parameters under which ITP is most effective for the separation of inorganic samples, including the influence of the double layer surrounding actinide ions, the Debye length for different ions and ion complexes, and Debye-Hueckel limits. Inorganic separations are key to nuclear forensics for countering terrorism and nuclear proliferation. If found to be feasible and potentially superior to currently used separation approaches, ITP could provide the conceptual basis for an improved means to separate samples of nuclear explosion debris for nuclear forensic analysis, in support of the Laboratory's missions in homeland and national security.« less

Structural, electronic, elastic, and thermal properties of CaNiH3 perovskite obtained from first-principles calculations

NASA Astrophysics Data System (ADS)

Benlamari, S.; Bendjeddou, H.; Boulechfar, R.; Amara Korba, S.; Meradji, H.; Ahmed, R.; Ghemid, S.; Khenata, R.; Omran, S. Bin

2018-03-01

A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carried out via first-principles full potential (FP) linearized augmented plane wave plus local orbital (LAPW+lo) method designed within the density functional theory (DFT). To treat the exchange–correlation energy/potential for the total energy calculations, the local density approximation (LDA) of Perdew–Wang (PW) and the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) are used. The three independent elastic constants (C 11, C 12, and C 44) are calculated from the direct computation of the stresses generated by small strains. Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant (a 0), bulk modulus (B 0), and its pressure derivative ({B}0^{\\prime }) are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride.

Dependence of Lunar Surface Charging on Solar Wind Plasma Conditions and Solar Irradiation

NASA Technical Reports Server (NTRS)

Stubbs, T. J.; Farrell, W. M.; Halekas, J. S.; Burchill, J. K.; Collier, M. R.; Zimmerman, M. I.; Vondrak, R. R.; Delory, G. T.; Pfaff, R. F.

2014-01-01

The surface of the Moon is electrically charged by exposure to solar radiation on its dayside, as well as by the continuous flux of charged particles from the various plasma environments that surround it. An electric potential develops between the lunar surface and ambient plasma, which manifests itself in a near-surface plasma sheath with a scale height of order the Debye length. This study investigates surface charging on the lunar dayside and near-terminator regions in the solar wind, for which the dominant current sources are usually from the pohotoemission of electrons, J(sub p), and the collection of plasma electrons J(sub e) and ions J(sub i). These currents are dependent on the following six parameters: plasma concentration n(sub 0), electron temperature T(sub e), ion temperature T(sub i), bulk flow velocity V, photoemission current at normal incidence J(sub P0), and photo electron temperature T(sub p). Using a numerical model, derived from a set of eleven basic assumptions, the influence of these six parameters on surface charging - characterized by the equilibrium surface potential, Debye length, and surface electric field - is investigated as a function of solar zenith angle. Overall, T(sub e) is the most important parameter, especially near the terminator, while J(sub P0) and T(sub p) dominate over most of the dayside.

Electronic structure, mechanical and thermodynamic properties of BaPaO3 under pressure.

PubMed

Khandy, Shakeel Ahmad; Islam, Ishtihadah; Gupta, Dinesh C; Laref, Amel

2018-05-07

Density functional theory (DFT)-based investigations have been put forward on the elastic, mechanical, and thermo-dynamical properties of BaPaO 3 . The pressure dependence of electronic band structure and other physical properties has been carefully analyzed. The increase in Bulk modulus and decrease in lattice constant is seen on going from 0 to 30 GPa. The predicted lattice constants describe this material as anisotropic and ductile in nature at ambient conditions. Post-DFT calculations using quasi-harmonic Debye model are employed to envisage the pressure-dependent thermodynamic properties like Debye temperature, specific heat capacity, Grüneisen parameter, thermal expansion, etc. Also, the computed Debye temperature and melting temperature of BaPaO 3 at 0 K are 523 K and 1764.75 K, respectively.

Mechanical and thermodynamic properties of AlX (X = N, P, As) compounds

NASA Astrophysics Data System (ADS)

Xu, Lifang; Bu, Wei

2017-09-01

The Vickers hardness of various AlX (X = N, P, As) compound polymorphs were calculated with the bond resistance model. Thermodynamic properties, such as vibrational entropy, constant volume specific heat and Debye temperatures, were calculated using phonon dispersion relations and phonon density of states (DOS). The calculated values are in good agreement with the previous experimental and theoretical data. For the same structure of AlX (X = N, P, As) compounds, their hardness and Debye temperatures both decrease with the X atomic number. The wurtzite (wz) and zincblende (zb) structures of the same compounds AlX share an almost identical hardness, but have different Debye temperatures. The difference between wz and zb structures increases as the atomic number of X increases. The thermodynamic properties reveal that the constant volume specific heat approaches the Dulong-Petit rule at high temperatures.

Ab-initio study of thermodynamic properties of boron nanowire at atomic scale

NASA Astrophysics Data System (ADS)

Bhuyan, Prabal D.; Gupta, Sanjeev K.; Sonvane, Y.; Gajjar, P. N.

2018-04-01

In the present work, we have optimized ribbon like zigzag structure of boron (B) nanowire (NW) and investigated vibrational and thermodynamic properties using quasi-harmonic approximations (QHA). All positive phonon in the phonon dispersive curve have confirmed dynamical stability of ribbon B-NW. The thermodynamic properties, like Debye temperature, internal energy and specific heat, are calculated as a function of temperature. The variation of specific heat is proportional to T3 Debye law at lower temperature for B-NW, while it becomes constant above room temperature at 1200K; obeys Dulong-Petit's law. The high Debye temperature of 1120K is observed at ambient temperature, which can be attributed to high thermal conductivity. Our study shows that B-NW with high thermal conductivity could be the next generation electron connector for nanoscale electronic devices.

Influence of semiclassical plasma on the energy levels and radiative transitions in highly charged ions★

NASA Astrophysics Data System (ADS)

Hu, Hong-Wei; Chen, Zhan-Bin; Chen, Wen-Cong; Liu, Xiao-Bin; Fu, Nian; Wang, Kai

2017-11-01

Considering the quantum effects of diffraction and the collective screening effects, the potential of test charge in semiclassical plasmas is derived. It is generalized exponential screened Coulomb potential. Using the Ritz variational method incorporating this potential, the effects of semiclassical plasma on the energy levels and radiative transitions are investigated systematically, taking highly charged H-like ion as an example. The Debye plasma model is also employed for comparison purposes. Comparisons and analysis are made between these two sets of results and the differences are discussed. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

76 FR 81516 - Homeland Security Advisory Council

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-28

... security; and provide information on the threat of an electromagnetic pulse attack and its associated... Operational Update. Electromagnetic Pulse (EMP) Threat--Lessons Learned and Areas of Vulnerability, and... and the potential threat of an electromagnetic pulse attack. Both will include lessons learned and...

Limitations of the paraxial Debye approximation.

PubMed

Sheppard, Colin J R

2013-04-01

In the paraxial form of the Debye integral for focusing, higher order defocus terms are ignored, which can result in errors in dealing with aberrations, even for low numerical aperture. These errors can be avoided by using a different integration variable. The aberrations of a glass slab, such as a coverslip, are expanded in terms of the new variable, and expressed in terms of Zernike polynomials to assist with aberration balancing. Tube length error is also discussed.

The thermo-elastic instability model of melting of alkali halides in the Debye approximation

NASA Astrophysics Data System (ADS)

Owens, Frank J.

2018-05-01

The Debye model of lattice vibrations of alkali halides is used to show that there is a temperature below the melting temperature where the vibrational pressure exceeds the electrostatic pressure. The onset temperature of this thermo-elastic instability scales as the melting temperature of NaCl, KCl, and KBr, suggesting its role in the melting of the alkali halides in agreement with a previous more rigorous model.

Light scattering by cylindrical nanoparticles: Limits of applicability of the Rayleigh-Gans-Debye approximation

NASA Astrophysics Data System (ADS)

Kanevskii, V. I.; Rozenbaum, V. M.

2014-08-01

Applicability of the Rayleigh-Gans-Debye (RGD) approximation for describing light scattering by nanoparticles with large dielectric losses (such as carbon nanotubes) is analyzed. By a comparison of the approximate results with exact ones, it is shown that the presence of dielectric losses expands the range of applicability of the RGD approximation. This conclusion is illustrated by a differential cross-section diagram of scattering by a multiwall carbon nanotube.

Water promotes the sealing of nanoscale packing defects in folding proteins.

PubMed

Fernández, Ariel

2014-05-21

A net dipole moment is shown to arise from a non-Debye component of water polarization created by nanoscale packing defects on the protein surface. Accordingly, the protein electrostatic field exerts a torque on the induced dipole, locally impeding the nucleation of ice at the protein-water interface. We evaluate the solvent orientation steering (SOS) as the reversible work needed to align the induced dipoles with the Debye electrostatic field and computed the SOS for the variable interface of a folding protein. The minimization of the SOS is shown to drive protein folding as evidenced by the entrainment of the total free energy by the SOS energy along trajectories that approach a Debye limit state where no torque arises. This result suggests that the minimization of anomalous water polarization at the interface promotes the sealing of packing defects, thereby maintaining structural integrity and committing the protein chain to fold.

Formation of negative hydrogen ion: polarization electron capture and nonthermal shielding.

PubMed

Ki, Dae-Han; Jung, Young-Dae

2012-09-07

The influence of the nonthermal shielding on the formation of the negative hydrogen ion (H(-)) by the polarization electron capture are investigated in partially ionized generalized Lorentzian plasmas. The Bohr-Lindhard method has been applied to obtain the negative hydrogen formation radius and cross section as functions of the collision energy, de Broglie wave length, Debye length, impact parameter, and spectral index of the plasma. The result shows that the nonthermal character of the plasma enhances the formation radius of the negative hydrogen, especially, for small Debye radii. It is found that the nonthermal effect increases the formation cross section of the negative hydrogen. It is also found that the maximum position of the formation cross section approaches to the collision center with an increase of the spectral index. In addition, it is found that the formation cross section significantly decreases with an increase of the Debye length, especially, for small spectral indices.

First-principles investigations on structural, elastic, electronic properties and Debye temperature of orthorhombic Ni3Ta under pressure

NASA Astrophysics Data System (ADS)

Li, Pan; Zhang, Jianxin; Ma, Shiyu; Jin, Huixin; Zhang, Youjian; Zhang, Wenyang

2018-06-01

The structural, elastic, electronic properties and Debye temperature of Ni3Ta under different pressures are investigated using the first-principles method based on density functional theory. Our calculated equilibrium lattice parameters at 0 GPa well agree with the experimental and previous theoretical results. The calculated negative formation enthalpies and elastic constants both indicate that Ni3Ta is stable under different pressures. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν are calculated by the Voigt-Reuss-Hill method. The bigger ratio of B/G indicates Ni3Ta is ductile and the pressure can improve the ductility of Ni3Ta. In addition, the results of density of states and the charge density difference show that the stability of Ni3Ta is improved by the increasing pressure. The Debye temperature ΘD calculated from elastic modulus increases along with the pressure.

The scaling of oblique plasma double layers

NASA Technical Reports Server (NTRS)

Borovsky, J. E.

1983-01-01

Strong oblique plasma double layers are investigated using three methods, i.e., electrostatic particle-in-cell simulations, numerical solutions to the Poisson-Vlasov equations, and analytical approximations to the Poisson-Vlasov equations. The solutions to the Poisson-Vlasov equations and numerical simulations show that strong oblique double layers scale in terms of Debye lengths. For very large potential jumps, theory and numerical solutions indicate that all effects of the magnetic field vanish and the oblique double layers follow the same scaling relation as the field-aligned double layers.

A Numerical Model of Laser-Induced Fluorescence in a Hydrogen Plasma

DTIC Science & Technology

1991-03-10

cross-sections. Lee, et al., cited screened Coulomb potential calculations by several groups to place an up- per limit of 30 A on the Debye length...intensity: RL(t)(1/sec) = B,,(cir 2/erg . sec) . (J,)(erg/sec .cm -. liz) (3.5) 35 The Einstein coefficients are related by the statistical weights of the...impact processes.) These rate matrices were then added together to obtain the total rate matrix for both groups of electrons. The total electron density

A dusty plasma 1-ring to rule them all

NASA Astrophysics Data System (ADS)

Sheridan, T. E.; Gallagher, James C.

2010-04-01

One-dimensional and quasi-one-dimensional strongly-coupled dusty plasma rings have been created experimentally in the DONUT (Dusty ONU experimenT) apparatus. Longitudinal (acoustic) and transverse (optical) dispersion relations for the 1-ring were measured and found to be in very good agreement with the theory for an unbounded straight chain of particles interacting through a Yukawa (i.e., screened Coulomb or Debye-H"uckel) potential. These rings provide a new system in which to study one-dimensional and quasi-one-dimensional physics.

The classical equation of state of fully ionized plasmas

NASA Astrophysics Data System (ADS)

Eisa, Dalia Ahmed

2011-03-01

The aim of this paper is to calculate the analytical form of the equation of state until the third virial coefficient of a classical system interacting via an effective potential of fully Ionized Plasmas. The excess osmotic pressure is represented in the forms of a convergent series expansions in terms of the plasma Parameter μ _{ab} = {{{e_a e_b χ } over {DKT}}}, where χ2 is the square of the inverse Debye radius. We consider only the thermal equilibrium plasma.

Additional application of the NASCAP code. Volume 1: NASCAP extension

NASA Technical Reports Server (NTRS)

Katz, I.; Cassidy, J. J.; Mandell, M. J.; Parks, D. E.; Schnuelle, G. W.; Stannard, P. R.; Steen, P. G.

1981-01-01

The NASCAP computer program comprehensively analyzes problems of spacecraft charging. Using a fully three dimensional approach, it can accurately predict spacecraft potentials under a variety of conditions. Several changes were made to NASCAP, and a new code, NASCAP/LEO, was developed. In addition, detailed studies of several spacecraft-environmental interactions and of the SCATHA spacecraft were performed. The NASCAP/LEO program handles situations of relatively short Debye length encountered by large space structures or by any satellite in low earth orbit (LEO).

Numerical modeling of the SNS H{sup −} ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veitzer, Seth A.; Beckwith, Kristian R. C.; Kundrapu, Madhusudhan

Ion source rf antennas that produce H- ions can fail when plasma heating causes ablation of the insulating coating due to small structural defects such as cracks. Reducing antenna failures that reduce the operating capabilities of the Spallation Neutron Source (SNS) accelerator is one of the top priorities of the SNS H- Source Program at ORNL. Numerical modeling of ion sources can provide techniques for optimizing design in order to reduce antenna failures. There are a number of difficulties in developing accurate models of rf inductive plasmas. First, a large range of spatial and temporal scales must be resolved inmore » order to accurately capture the physics of plasma motion, including the Debye length, rf frequencies on the order of tens of MHz, simulation time scales of many hundreds of rf periods, large device sizes on tens of cm, and ion motions that are thousands of times slower than electrons. This results in large simulation domains with many computational cells for solving plasma and electromagnetic equations, short time steps, and long-duration simulations. In order to reduce the computational requirements, one can develop implicit models for both fields and particle motions (e.g. divergence-preserving ADI methods), various electrostatic models, or magnetohydrodynamic models. We have performed simulations using all three of these methods and have found that fluid models have the greatest potential for giving accurate solutions while still being fast enough to perform long timescale simulations in a reasonable amount of time. We have implemented a number of fluid models with electromagnetics using the simulation tool USim and applied them to modeling the SNS H- ion source. We found that a reduced, single-fluid MHD model with an imposed magnetic field due to the rf antenna current and the confining multi-cusp field generated increased bulk plasma velocities of > 200 m/s in the region of the antenna where ablation is often observed in the SNS source. We report here on comparisons of simulated plasma parameters and code performance using more accurate physical models, such as two-temperature extended MHD models, for both a related benchmark system describing a inductively coupled plasma reactor, and for the SNS ion source. We also present results from scaling studies for mesh generation and solvers in the USim simulation code.« less

Boson-boson effective nonrelativistic potential for higher-derivative electromagnetic theories in D dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Accioly, Antonio; Dias, Marco

2004-11-15

The problem of computing the effective nonrelativistic potential U{sub D} for the interaction of charged-scalar bosons, within the context of D-dimensional electromagnetism with a cutoff, is reduced to quadratures. It is shown that U{sub 3} cannot bind a pair of identical charged-scalar bosons; nevertheless, numerical calculations indicate that boson-boson bound states do exist in the framework of three-dimensional higher-derivative electromagnetism augmented by a topological Chern-Simons term.

Characteristics of dust voids in a strongly coupled laboratory dusty plasma

NASA Astrophysics Data System (ADS)

Bailung, Yoshiko; Deka, T.; Boruah, A.; Sharma, S. K.; Pal, A. R.; Chutia, Joyanti; Bailung, H.

2018-05-01

A void is produced in a strongly coupled dusty plasma by inserting a cylindrical pin (˜0.1 mm diameter) into a radiofrequency discharge argon plasma. The pin is biased externally below the plasma potential to generate the dust void. The Debye sheath model is used to obtain the sheath potential profile and hence to estimate the electric field around the pin. The electric field force and the ion drag force on the dust particles are estimated and their balance accounts well for the maintenance of the size of the void. The effects of neutral density as well as dust density on the void size are studied.

EVALUATION OF THE POTENTIAL CARCINOGENICITY OF ELECTROMAGNETIC FIELDS (EXTERNAL REVIEW DRAFT)

EPA Science Inventory

The U.S. Environmental Protection Agency (EPA or Agency) is posting on this web site a draft document related to the potential adverse human health effects resulting from exposure to electromagnetic fields (EMF). This document was never finalized after EPA activities were discon...

Effect of High Pressure and Temperature on Structural, Thermodynamic and Thermoelectric Properties of Quaternary CoFeCrAl Alloy

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

2018-03-01

Employing first-principles based on density functional theory we have investigated the structural, magneto-electronic, thermoelectric and thermodynamic properties of quaternary Heusler alloy CoFeCrAl. Electronic band structure displays that CoFeCrAl is an indirect band gap semiconductor in spin-down state with the band gap value of 0.65 eV. Elastic constants reveal CoFeCrAl is a mechanically stable structure having a Debye temperature of 648 K along with a high melting temperature (2130 K). The thermoelectric properties in the temperature range 50-800 K have been calculated. CoFeCrAl possesses a high Seebeck coefficient of - 46 μV/K at room temperature along with the huge power factor of ˜ 4.8 (1012 μW cm-1 K-2 s-1) which maximizes the figure-of-merit up to ˜ 0.75 at 800 K temperature and suggesting CoFeCrAl as potential thermoelectric material. The effect of high pressure and high temperature on the thermal expansion, Grüneisen parameter and heat capacity were also studied by using the quasi-harmonic Debye model.

Order of wetting transitions in electrolyte solutions.

PubMed

Ibagon, Ingrid; Bier, Markus; Dietrich, S

2014-05-07

For wetting films in dilute electrolyte solutions close to charged walls we present analytic expressions for their effective interface potentials. The analysis of these expressions renders the conditions under which corresponding wetting transitions can be first- or second-order. Within mean field theory we consider two models, one with short- and one with long-ranged solvent-solvent and solvent-wall interactions. The analytic results reveal in a transparent way that wetting transitions in electrolyte solutions, which occur far away from their critical point (i.e., the bulk correlation length is less than half of the Debye length) are always first-order if the solvent-solvent and solvent-wall interactions are short-ranged. In contrast, wetting transitions close to the bulk critical point of the solvent (i.e., the bulk correlation length is larger than the Debye length) exhibit the same wetting behavior as the pure, i.e., salt-free, solvent. If the salt-free solvent is governed by long-ranged solvent-solvent as well as long-ranged solvent-wall interactions and exhibits critical wetting, adding salt can cause the occurrence of an ion-induced first-order thin-thick transition which precedes the subsequent continuous wetting as for the salt-free solvent.

Application of relativistic distorted-wave method to electron-impact excitation of highly charged Fe XXIV ion embedded in weakly coupled plasmas

NASA Astrophysics Data System (ADS)

Chen, Zhanbin

2018-05-01

The process of excitation of highly charged Fe XXIV ion embedded in weakly coupled plasmas by electron impact is studied, together with the subsequent radiative decay. For the target structure, the calculation is performed using the multiconfiguration Dirac-Hartree-Fock method incorporating the Debye-Hückel potential for the electron-nucleus interaction. Fine-structure levels of the 1s22p and 1s2s2p configurations and the transition properties among these levels are presented over a wide range of screening parameters. For the collision dynamics, the distorted-wave method in the relativistic frame is adopted to include the effect of plasma background, in which the interparticle interactions in the system are described by screened interactions of the Debye-Hückel type. The continuum wave function of the projectile electron is obtained by solving the modified Dirac equations. The influence of plasma strength on the cross section, the linear polarization, and the angular distribution of x-ray photon emission are investigated in detail. Comparison of the present results with experimental data and other theoretical predictions, when available, is made.

First-Principles Study on the Structural, Electronic, Magnetic and Thermodynamic Properties of Full Heusler Alloys Co2VZ (Z = Al, Ga)

NASA Astrophysics Data System (ADS)

Bentouaf, Ali; Hassan, Fouad H.; Reshak, Ali H.; Aïssa, Brahim

2017-01-01

We report on the investigation of the structural and physical properties of the Co2VZ (Z = Al, Ga) Heusler alloys, with L21 structure, through first-principles calculations involving the full potential linearized augmented plane-wave method within density functional theory. These physical properties mainly revolve around the electronic, magnetic and thermodynamic properties. By using the Perdew-Burke-Ernzerhof generalized gradient approximation, the calculated lattice constants and spin magnetic moments were found to be in good agreement with the experimental data. Furthermore, the thermal effects using the quasi-harmonic Debye model have been investigated in depth while taking into account the lattice vibrations, the temperature and the pressure effects on the structural parameters. The heat capacities, the thermal expansion coefficient and the Debye temperatures have also been determined from the non-equilibrium Gibbs functions. An application of the atom in molecule theory is presented and discussed in order to analyze the bonding nature of the Heusler alloys. The focus is on the mixing of the metallic and covalent behavior of Co2VZ (Z = Al, Ga) Heusler alloys.

Breakdown of the Debye polarization ansatz at protein-water interfaces

NASA Astrophysics Data System (ADS)

Fernández Stigliano, Ariel

2013-06-01

The topographical and physico-chemical complexity of protein-water interfaces scales down to the sub-nanoscale range. At this level of confinement, we demonstrate that the dielectric structure of interfacial water entails a breakdown of the Debye ansatz that postulates the alignment of polarization with the protein electrostatic field. The tendencies to promote anomalous polarization are determined for each residue type and a particular kind of structural defect is shown to provide the predominant causal context.

Project Physics Tests 4, Light and Electromagnetism.

ERIC Educational Resources Information Center

Harvard Univ., Cambridge, MA. Harvard Project Physics.

Test items relating to Project Physics Unit 4 are presented in this booklet. Included are 70 multiple-choice and 22 problem-and-essay questions. Concepts of light and electromagnetism are examined on charges, reflection, electrostatic forces, electric potential, speed of light, electromagnetic waves and radiations, Oersted's and Faraday's work,…

Science 101: Can Electromagnetic Waves Affect Emotions?

ERIC Educational Resources Information Center

Robertson, Bill

2017-01-01

The answer to this month's question, "Can electromagnetic waves affect emotions," is yes. Wherever there are electromagnetic (EM) waves (basically everywhere!), there is the potential for them directly or indirectly to affect the emotions. But what about the likely motivation behind the originally-posed question? Can EM waves affect your…

Floating potential in electronegative plasmas for non-zero ion temperatures

NASA Astrophysics Data System (ADS)

Regodón, Guillermo Fernando; Fernández Palop, José Ignacio; Tejero-del-Caz, Antonio; Díaz-Cabrera, Juan Manuel; Carmona-Cabezas, Rafael; Ballesteros, Jerónimo

2018-02-01

The floating potential of a Langmuir probe immersed in an electronegative plasma is studied theoretically under the assumption of radial positive ion fluid movement for non-zero positive ion temperature: both cylindrical and spherical geometries are studied. The model is solvable exactly. The special characteristics of the electronegative pre-sheath are found and the influence of the stratified electronegative pre-sheath is shown to be very small in practical applications. It is suggested that the use of the floating potential in the measurement of negative ions population density is convenient, in view of the numerical results obtained. The differences between the two radial geometries, which become very important for small probe radii of the order of magnitude of the Debye length, are studied.

Precise energy eigenvalues of hydrogen-like ion moving in quantum plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, S.; Saha, Jayanta K.; Mukherjee, T. K.

2015-06-15

The analytic form of the electrostatic potential felt by a slowly moving test charge in quantum plasma is developed. It has been shown that the electrostatic potential is composed of two parts: the Debye-Huckel screening term and the near-field wake potential. The latter depends on the velocity of the test charge as well as on the number density of the plasma electrons. Rayleigh-Ritz variational calculation has been done to estimate precise energy eigenvalues of hydrogen-like carbon ion under such plasma environment. A detailed analysis shows that the energy levels gradually move to the continuum with increasing plasma electron density whilemore » the level crossing phenomenon has been observed with the variation of ion velocity.« less

Relation between the microstructure and the electromagnetic properties of BaTiO3/Ni0.5Zn0.5Fe2O4 ceramic composite

NASA Astrophysics Data System (ADS)

Xiao, Bin; Tang, Yu; Ma, Guodong; Ma, Ning; Du, Piyi

2015-06-01

The microstructure-property relation in ferroelectric/ferromagnetic composite is investigated in detail, exemplified by typical sol-gel-derived 0.3BTO/0.7NZFO ceramic composite. The effect of microstructural factors including intergrain connectivity, grain size and interfaces on the dielectric and magnetic properties of the composite prepared by conventional ceramic method and three-step sintering method is discussed both experimentally and theoretically. It reveals that the dielectric behavior of the composite is controlled by a hybrid dielectric process that combines the contribution of Debye-like dipoles and Maxwell-Wagner (M-W or interfacial) polarization. Enhanced dielectric, magnetic and conductive behaviors appear in the composite with better intergrain connectivity and larger grain size derived by sol-gel route and three-step sintering method. The effective permittivity contributed by Debye-like dipoles exhibits a value of ~130,000 in three-step sintered composite, which is almost the same as that in conventionally sintered one, but that contributed by M-W response is much smaller in the former. Compared with conventionally prepared samples, the relaxation time ( τ) is 3.476 × 10-6 s, about one order of magnitude smaller, and the dc electrical conductivity is 3.890 × 10-3 S/m, one order of magnitude higher in three-step sintered composite. The minimum dielectric loss reveals almost the same (~0.2) for all samples, but shows distinguishable difference in low-frequency region. Meanwhile, an initial permeability of 84, twice as large as that of conventionally prepared composite and 56 % the value of single-phased NZFO ferrite (~150), and a saturation magnetization of 63.5 emu/g, 32 % higher than that of conventional one and approximately 84 % the value of single-phased NZFO ferrite (~76 emu/g), appear simultaneously in three-step sintered composite with larger grain size and better intergrain connectivity. It is clear that the discovery is helpful for establishing a more explicit view on the physics of multi-functional composite materials, while the composite with optimized microstructure is beneficial to be used as a high-performance material.

Moderately nonlinear diffuse-charge dynamics under an ac voltage.

PubMed

Stout, Robert F; Khair, Aditya S

2015-09-01

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

Quantum mechanical probability current as electromagnetic 4-current from topological EM fields

NASA Astrophysics Data System (ADS)

van der Mark, Martin B.

2015-09-01

Starting from a complex 4-potential A = αdβ we show that the 4-current density in electromagnetism and the probability current density in relativistic quantum mechanics are of identical form. With the Dirac-Clifford algebra Cl1,3 as mathematical basis, the given 4-potential allows topological solutions of the fields, quite similar to Bateman's construction, but with a double field solution that was overlooked previously. A more general nullvector condition is found and wave-functions of charged and neutral particles appear as topological configurations of the electromagnetic fields.

Identification of structural relaxation in the dielectric response of water

DOE PAGES

Hansen, Jesper S.; Kisliuk, Alexander; Sokolov, Alexei P.; ...

2016-06-09

One century ago pioneering dielectric results obtained for water and n-alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Here, comparing dielectric, viscoelastic, and light scattering results, we unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in monoalcohols.

Importance of the Debye Screening Length on Nanowire Field Effect Transistor Sensors

PubMed Central

Stern, Eric; Wagner, Robin; Sigworth, Fred J.; Breaker, Ronald; Fahmy, Tarek M.; Reed, Mark A.

2009-01-01

Nanowire field effect transistors (NW-FETs) can serve as ultrasensitive detectors for label-free reagents. The NW-FET sensing mechanism assumes a controlled modification in the local channel electric field created by the binding of charged molecules to the nanowire surface. Careful control of the solution Debye length is critical for unambiguous selective detection of macromolecules. Here we show the appropriate conditions under which the selective binding of macromolecules is accurately sensed with NW-FET sensors. PMID:17914853

Detection beyond Debye's length with an electrolyte-gated organic field-effect transistor.

PubMed

Palazzo, Gerardo; De Tullio, Donato; Magliulo, Maria; Mallardi, Antonia; Intranuovo, Francesca; Mulla, Mohammad Yusuf; Favia, Pietro; Vikholm-Lundin, Inger; Torsi, Luisa

2015-02-04

Electrolyte-gated organic field-effect transistors are successfully used as biosensors to detect binding events occurring at distances from the transistor electronic channel that are much larger than the Debye length in highly concentrated solutions. The sensing mechanism is mainly capacitive and is due to the formation of Donnan's equilibria within the protein layer, leading to an extra capacitance (CDON) in series to the gating system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Importance of the Debye screening length on nanowire field effect transistor sensors.

PubMed

Stern, Eric; Wagner, Robin; Sigworth, Fred J; Breaker, Ronald; Fahmy, Tarek M; Reed, Mark A

2007-11-01

Nanowire field effect transistors (NW-FETs) can serve as ultrasensitive detectors for label-free reagents. The NW-FET sensing mechanism assumes a controlled modification in the local channel electric field created by the binding of charged molecules to the nanowire surface. Careful control of the solution Debye length is critical for unambiguous selective detection of macromolecules. Here we show the appropriate conditions under which the selective binding of macromolecules is accurately sensed with NW-FET sensors.

Two loop renormalization of the magnetic coupling in hot QCD

NASA Astrophysics Data System (ADS)

Giovannangeli, P.

2004-04-01

Well above the critical temperature hot QCD is described by 3d electrostatic QCD with gauge coupling gE and Debye mass mE. We integrate out the Debye scales to two loop accuracy and find for the gauge coupling in the resulting magnetostatic action gM2=gE21-{1}/{48}{gE2N}/{πmE}-{17}/{4608}{gE2N}/{πmE}2+O{gE2N}/{πmE}3.

The electrostatics of a dusty plasma

NASA Technical Reports Server (NTRS)

Whipple, E. C.; Mendis, D. A.; Northrop, T. G.

1986-01-01

The potential distribution in a plasma containing dust grains were derived where the Debye length can be larger or smaller than the average intergrain spacing. Three models were treated for the grain-plasma system, with the assumption that the system of dust and plasma is charge-neutral: a permeable grain model, an impermeable grain model, and a capacitor model that does not require the nearest neighbor approximation of the other two models. A gauge-invariant form of Poisson's equation was used which is linearized about the average potential in the system. The charging currents to a grain are functions of the difference between the grain potential and this average potential. Expressions were obtained for the equilibrium potential of the grain and for the gauge-invariant capacitance between the grain and the plasma. The charge on a grain is determined by the product of this capacitance and the grain-plasma potential difference.

Electromagnetic fields and potentials generated by massless charged particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azzurli, Francesco, E-mail: francesco.azzurli@gmail.com; Lechner, Kurt, E-mail: lechner@pd.infn.it; INFN, Sezione di Padova, Via F. Marzolo, 8, 35131 Padova

2014-10-15

We provide for the first time the exact solution of Maxwell’s equations for a massless charged particle moving on a generic trajectory at the speed of light. In particular we furnish explicit expressions for the vector potential and the electromagnetic field, which were both previously unknown, finding that they entail different physical features for bounded and unbounded trajectories. With respect to the standard Liénard–Wiechert field the electromagnetic field acquires singular δ-like contributions whose support and dimensionality depend crucially on whether the motion is (a) linear, (b) accelerated unbounded, (c) accelerated bounded. In the first two cases the particle generates amore » planar shock-wave-like electromagnetic field traveling along a straight line. In the second and third cases the field acquires, in addition, a δ-like contribution supported on a physical singularity-string attached to the particle. For generic accelerated motions a genuine radiation field is also present, represented by a regular principal-part type distribution diverging on the same singularity-string. - Highlights: • First exact solution of Maxwell’s equations for massless charges in arbitrary motion. • Explicit expressions of electromagnetic fields and potentials. • Derivations are rigorous and based on distribution theory. • The form of the field depends heavily on whether the motion is bounded or unbounded. • The electromagnetic field contains unexpected Dirac-delta-function contributions.« less

Effective screening length and quasiuniversality for the restricted primitive model of an electrolyte solution.

PubMed

Janecek, Jirí; Netz, Roland R

2009-02-21

Monte Carlo simulations for the restricted primitive model of an electrolyte solution above the critical temperature are performed at a wide range of concentrations and temperatures. Thermodynamic properties such as internal energy, osmotic coefficient, activity coefficient, as well as spatial correlation functions are determined. These observables are used to investigate whether quasiuniversality in terms of an effective screening length exists, similar to the role played by the effective electron mass in solid-state physics. To that end, an effective screening length is extracted from the asymptotic behavior of the Fourier-transformed charge-correlation function and plugged into the Debye-Huckel limiting expressions for various thermodynamic properties. Comparison with numerical results is favorable, suggesting that correlation and other effects not captured on the Debye-Huckel limiting level can be successfully incorporated by a single effective parameter while keeping the functional form of Debye-Huckel expressions. We also compare different methods to determine mean ionic activity coefficient in molecular simulations and check the internal consistency of the numerical data.

The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration.

PubMed

Smith, Alexander M; Lee, Alpha A; Perkin, Susan

2016-06-16

According to classical electrolyte theories interactions in dilute (low ion density) electrolytes decay exponentially with distance, with the Debye screening length the characteristic length scale. This decay length decreases monotonically with increasing ion concentration due to effective screening of charges over short distances. Thus, within the Debye model no long-range forces are expected in concentrated electrolytes. Here we reveal, using experimental detection of the interaction between two planar charged surfaces across a wide range of electrolytes, that beyond the dilute (Debye-Hückel) regime the screening length increases with increasing concentration. The screening lengths for all electrolytes studied-including aqueous NaCl solutions, ionic liquids diluted with propylene carbonate, and pure ionic liquids-collapse onto a single curve when scaled by the dielectric constant. This nonmonotonic variation of the screening length with concentration, and its generality across ionic liquids and aqueous salt solutions, demonstrates an important characteristic of concentrated electrolytes of substantial relevance from biology to energy storage.

High-Temperature and High-Pressure Study of Electronic and Thermal Properties of PbTaO3 and SnAlO3 Metal Perovskites by Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Khandy, Shakeel Ahmad; Islam, Ishtihadah; Ganai, Zahid Saleem; Gupta, Dinesh C.; Parrey, Khursheed Ahmad

2018-01-01

First principles calculations on the thermodynamic properties of PbTaO3 and SnAlO3 in a temperature range from 0 K to 800 K and pressure range from 0 GPa to 30 GPa have been carried out within the framework of density functional theory (DFT). The band structures of these oxides at different pressures display an increase in metallic character with a concomitant decrease in lattice constants, while the bulk modulus increases with increasing pressure. The thermal concert of these materials has been analyzed in terms of the temperature and pressure variation in Debye temperature, thermal expansion, entropy, and the Grüneisen parameter. Debye temperatures have been calculated from the elastic parameters as well as the quasi-harmonic Debye model, which are 339.07 GPa for PbTaO3 and 714.36 GPa for SnAlO3.

First-principles study on the thermal expansion of Ni-X binary alloys based on the quasi-harmonic Debye model

NASA Astrophysics Data System (ADS)

Shin, Yongjin; Jung, Woo-Sang; Lee, Young-Su

2016-11-01

In this study, we use the quasi-harmonic Debye model to predict the coefficient of thermal expansion of Ni- X binary alloys. The method bridges between the macroscopic elastic behavior and thermodynamic properties of materials without an expensive calculation of the volume dependence of the phonon density of states. Furthermore, the Grüneisen parameter is derived from the volume dependence of the Debye temperature, which is calculated from the first-principles elastic stiffness constants. The experimental coefficient of thermal expansion (CTE) of pure nickel is well reproduced, especially in the low temperature region. Among the few alloying elements tested, Al is predicted to slightly decrease the CTE whereas Mo and W are more effective in reducing the CTE. For the cases of Ni-X binary alloy systems, where the variation in the CTE is relatively small, the method used here appears to perform better than certain other formulations that rely entirely on the energy vs. volume relationship.

Slow dielectric response of Debye-type in water and other hydrogen bonded liquids

NASA Astrophysics Data System (ADS)

Jansson, Helén; Bergman, Rikard; Swenson, Jan

2010-05-01

The slow dynamics of some hydrogen bonded glass-forming liquids has been investigated by broadband dielectric spectroscopy. We show that the polyalcohols glycerol, xylitol, and sorbitol, and mixtures of glycerol and water, and in fact, even pure water exhibit a process of Debye character at longer time-scales than the glass transition and viscosity related α-relaxation. Even if it is less pronounced, this process displays many similarities to the well-studied Debye-like process in monoalcohols. It can be observed in both the negative derivative of the real part of the permittivity or in the imaginary part of the permittivity, if the conductivity contribution is reduced. In the present study the conductivity contribution has been suppressed by use of a thin Teflon film placed between the sample and one of the electrodes. The new findings might have important implications for the structure and dynamics of hydrogen bonded liquids in general, and for water in particular.

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2014 CFR

2014-10-01

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47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

Low temperature heat capacities and thermodynamic functions described by Debye-Einstein integrals.

PubMed

Gamsjäger, Ernst; Wiessner, Manfred

2018-01-01

Thermodynamic data of various crystalline solids are assessed from low temperature heat capacity measurements, i.e., from almost absolute zero to 300 K by means of semi-empirical models. Previous studies frequently present fit functions with a large amount of coefficients resulting in almost perfect agreement with experimental data. It is, however, pointed out in this work that special care is required to avoid overfitting. Apart from anomalies like phase transformations, it is likely that data from calorimetric measurements can be fitted by a relatively simple Debye-Einstein integral with sufficient precision. Thereby, reliable values for the heat capacities, standard enthalpies, and standard entropies at T  = 298.15 K are obtained. Standard thermodynamic functions of various compounds strongly differing in the number of atoms in the formula unit can be derived from this fitting procedure and are compared to the results of previous fitting procedures. The residuals are of course larger when the Debye-Einstein integral is applied instead of using a high number of fit coefficients or connected splines, but the semi-empiric fit coefficients keep their meaning with respect to physics. It is suggested to use the Debye-Einstein integral fit as a standard method to describe heat capacities in the range between 0 and 300 K so that the derived thermodynamic functions are obtained on the same theory-related semi-empiric basis. Additional fitting is recommended when a precise description for data at ultra-low temperatures (0-20 K) is requested.

Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions.

PubMed

Rinne, Klaus F; Gekle, Stephan; Netz, Roland R

2014-12-07

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into different water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.

Differential photoelectric charging of nonconducting surfaces in space. [on sunlit strip

NASA Technical Reports Server (NTRS)

Pelizzari, M. A.; Criswell, D. R.

1978-01-01

The photoelectric charging caused by an infinitely long strip of sunlight across a nonconducting plane is studied by use of a model which contains an electrical cutoff radius, and the results of numerical calculations are presented. The model simulates charging of a sunlit area with dimensions equal to the strip's width, exposed to a plasma with a comparatively large Debye length. Uniform potential is quickly established on a uniformly sunlit strip as a result of charge redistribution by low-energy photoelectrons. The results are in accord with a theoretical surface conductivity derived for photoelectron sheaths above highly charged sunlit areas. The surface potential, which drops sharply across the sunlight-shadow boundary, is discussed.

The Evolutional History of Electromagnetic Navigation Bronchoscopy: State of the Art.

PubMed

Mehta, Atul C; Hood, Kristin L; Schwarz, Yehuda; Solomon, Stephen B

2018-04-30

Electromagnetic navigation bronchoscopy (ENB) has come a long way from the early roots of electromagnetic theory. Current ENB devices have the potential to change the way lung cancer is detected and treated. This paper provides an overview of the history, current state, and future of ENB. Copyright © 2018. Published by Elsevier Inc.

47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.

Code of Federal Regulations, 2011 CFR

2011-10-01

... to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz,” ANSI/IEEE C95.1-1992... Electromagnetic Fields,” NCRP Report No. 86, Section 17.4.5. Copyright NCRP, 1986, Bethesda, Maryland 20814. SAR... Potentially Hazardous Electromagnetic Fields—RF and Microwave,” IEEE C95.3-1991. (4) For purposes of analyzing...

47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.

Code of Federal Regulations, 2010 CFR

2010-10-01

... to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz,” ANSI/IEEE C95.1-1992... Electromagnetic Fields,” NCRP Report No. 86, Section 17.4.5. Copyright NCRP, 1986, Bethesda, Maryland 20814. SAR... Potentially Hazardous Electromagnetic Fields—RF and Microwave,” IEEE C95.3-1991. (4) For purposes of analyzing...

Electromagnetic Imaging Methods for Nondestructive Evaluation Applications

PubMed Central

Deng, Yiming; Liu, Xin

2011-01-01

Electromagnetic nondestructive tests are important and widely used within the field of nondestructive evaluation (NDE). The recent advances in sensing technology, hardware and software development dedicated to imaging and image processing, and material sciences have greatly expanded the application fields, sophisticated the systems design and made the potential of electromagnetic NDE imaging seemingly unlimited. This review provides a comprehensive summary of research works on electromagnetic imaging methods for NDE applications, followed by the summary and discussions on future directions. PMID:22247693

Tabletop Models for Electrical and Electromagnetic Geophysics.

ERIC Educational Resources Information Center

Young, Charles T.

2002-01-01

Details the use of tabletop models that demonstrate concepts in direct current electrical resistivity, self-potential, and electromagnetic geophysical models. Explains how data profiles of the models are obtained. (DDR)

Oscillatory electroosmotic flow in a parallel-plate microchannel under asymmetric zeta potentials

NASA Astrophysics Data System (ADS)

Peralta, M.; Arcos, J.; Méndez, F.; Bautista, O.

2017-06-01

In this work, we conduct a theoretical analysis of the start-up of an oscillatory electroosmotic flow (EOF) in a parallel-plate microchannel under asymmetric zeta potentials. It is found that the transient evolution of the flow field is controlled by the parameters {R}ω , {R}\\zeta , and \\bar{κ }, which represent the dimensionless frequency, the ratio of the zeta potentials of the microchannel walls, and the electrokinetic parameter, which is defined as the ratio of the microchannel height to the Debye length. The analysis is performed for both low and high zeta potentials; in the former case, an analytical solution is derived, whereas in the latter, a numerical solution is obtained. These solutions provide the fundamental characteristics of the oscillatory EOFs for which, with suitable adjustment of the zeta potential and the dimensionless frequency, the velocity profiles of the fluid flow exhibit symmetric or asymmetric shapes.

Formation of the Electric Double Layer and its Effects on Moving Bodies in a Space Plasma Environment

NASA Technical Reports Server (NTRS)

Yang, Qianli; Wu, S. T.; Stone, N. H.; Li, Xiaoquing

1996-01-01

In this paper we solve the self-consistent Vlasov and Poisson equations by a numerical method to determine the local distribution function of the ion and the electron, within a thin layer near the moving body, respectively. Using these ion and electron distributions, the number density for the ions and electrons are determined, such that, the electric potential is obtained within this thin layer (i.e., measured by Debye length). Numerical results are presented for temporal evolution of the electron and ion density and its corresponding electric potential within the layer which shows the formation of electric double layer and its structures. From these numerical results, we are able to determine the maximum conditions of the electric potential, it may create satellite anomaly.

The forward rainbow scattering of low energy protons by a graphene sheet

NASA Astrophysics Data System (ADS)

Ćosić, M.; Petrović, S.; Nešković, N.

2018-05-01

This article studies the rainbow scattering of 5-keV protons by the single sheet of free-standing graphene and its possible use as a tool for investigation of the ion-graphene interaction. The proton-graphene interaction potential was constructed by using the Doyle-Turner, ZBL, and Molière proton-carbon interaction potentials. The thermal motion of carbon atoms was included by averaging the potentials according to the Debye model. Proton trajectories were obtained by numerical solution of the corresponding Newton equations of motion. They were used to obtain the mapping of the proton initial positions to their scattering angles. Morphological properties of the introduced mapping including its multiplicity and the rainbow singularities were used to explain important features of the obtained angular distributions of transmitted protons.

Exposure to electromagnetic fields aboard high-speed electric multiple unit trains.

PubMed

Niu, D; Zhu, F; Qiu, R; Niu, Q

2016-01-01

High-speed electric multiple unit (EMU) trains generate high-frequency electric fields, low-frequency magnetic fields, and high-frequency wideband electromagnetic emissions when running. Potential human health concerns arise because the electromagnetic disturbances are transmitted mainly into the car body from windows, and from there to passengers and train staff. The transmission amount and amplitude distribution characteristics that dominate electromagnetic field emission need to be studied, and the exposure level of electromagnetic field emission to humans should be measured. We conducted a series of tests of the on board electromagnetic field distribution on several high-speed railway lines. While results showed that exposure was within permitted levels, the possibility of long-term health effects should be investigated.

Permanent electric dipole moments of PtX (X = H, F, Cl, Br, and I) by the composite approach

NASA Astrophysics Data System (ADS)

Deng, Dan; Lian, Yongqin; Zou, Wenli

2017-11-01

Using the FPD composite approach of Peterson et. al. we calculate the permanent electric dipole moments of PtX (X = H, F, Cl, Br, and I) at the equilibrium geometries of their ground states. The dipole moment of PtF is estimated to be 3.421 Debye, being very close to the experimental value of 3.42(6) Debye. This research also suggests the ordering of dipole moments of PtX being proportional to the electronegativity of X.

Hypothesis on how to measure electromagnetic hypersensitivity.

PubMed

Tuengler, Andreas; von Klitzing, Lebrecht

2013-09-01

Electromagnetic hypersensitivity (EHS) is an ill-defined term to describe the fact that people who experience health symptoms in the vicinity of electromagnetic fields (EMFs) regard them as causal for their complaints. Up to now most scientists assume a psychological cause for the suffering of electromagnetic hypersensitive individuals. This paper addresses reasons why most provocation studies could not find any association between EMF exposure and EHS and presents a hypothesis on diagnosis and differentiation of this condition. Simultaneous recordings of heart rate variability, microcirculation and electric skin potentials are used for classification of EHS. Thus, it could be possible to distinguish "genuine" electromagnetic hypersensitive individuals from those who suffer from other conditions.

[Dynamics of biomacromolecules in coherent electromagnetic radiation field].

PubMed

Leshcheniuk, N S; Apanasevich, E E; Tereshenkov, V I

2014-01-01

It is shown that induced oscillations and periodic displacements of the equilibrium positions occur in biomacromolecules in the absence of electromagnetic radiation absorption, due to modulation of interaction potential between atoms and groups of atoms forming the non-valence bonds in macromolecules by the external electromagnetic field. Such "hyperoscillation" state causes inevitably the changes in biochemical properties of macromolecules and conformational transformation times.

Determining Detection and Classification Potential of Munitions using Advanced EMI Sensors in the Underwater Environment

DTIC Science & Technology

2016-11-01

focuses on characterizing Electromagnetic Induction (EMI) responses in the underwater setting through numerical and experimental studies with the...marine EMI sensing. 15. SUBJECT TERMS Munitions Response, Electromagnetic Induction, Unexploded Ordnance, Classification 16. SECURITY CLASSIFICATION...using Advanced EMI Sensors in the Underwater Environment.” The project focuses on characterizing Electromagnetic Induction (EMI) responses in the

Idiopathic environmental intolerance attributed to electromagnetic fields: a content analysis of British newspaper reports.

PubMed

Eldridge-Thomas, Buffy; Rubin, G James

2013-01-01

Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) is a controversial condition in which people describe symptoms following exposure to electromagnetic fields from everyday electrical devices. However, double-blind experiments have found no convincing evidence that electromagnetic fields cause these symptoms. In this study, we assessed whether recent newspaper reporting in the UK reflected this scientific evidence. We searched a database of newspaper articles to identify all those that contained IEI-EMF related keywords and selected a random sample of 60 for content analysis. For our primary outcomes, we assessed how many articles mainly or wholly presented an electromagnetic cause for IEI-EMF and how many discussed unproven treatments for the condition such as strategies intended to reduce exposure to electromagnetic fields or the use of complementary and alternative therapies. We also assessed whether the type of information source used by a newspaper article (e.g. scientist, person with IEI-EMF, politician) or the type of newspaper (broadsheet, tabloid, local or regional) was associated with either outcome. Of the 60 articles, 43 (71.7%) presented a mainly electromagnetic cause, compared to 13 (21.7%) which presented mainly non-electromagnetic causes and 4 (6.7%) which did not discuss a cause. 29 (48.3%) did not mention any potential treatment, while 24 (40.0%) mentioned eletromagnetic field related strategies and 12 (20.0%) mentioned complementary or alternative therapies. Articles which quoted someone with IEI-EMF were significantly more likely to report an electromagnetic cause and to present unproven treatments. Those which used a scientist as a source were more likely to present a non-electromagnetic cause for the condition. The widespread poor reporting we identified is disappointing and has the potential for to encourage more people to misattribute their symptoms to electromagnetic fields. Scientists should remain engaged with the media to counteract this effect.

Search for anisotropy in the Debye-Waller factor of HCP solid 4He

NASA Astrophysics Data System (ADS)

Barnes, Ashleigh L.; Hinde, Robert J.

2016-02-01

The properties of hexagonal close packed (hcp) solid 4He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid 4He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp 4He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp 4He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm3, and is found to be in good qualitative agreement with experimental data.

Statistics of Magnetic Reconnection X-Lines in Kinetic Turbulence

NASA Astrophysics Data System (ADS)

Haggerty, C. C.; Parashar, T.; Matthaeus, W. H.; Shay, M. A.; Wan, M.; Servidio, S.; Wu, P.

2016-12-01

In this work we examine the statistics of magnetic reconnection (x-lines) and their associated reconnection rates in intermittent current sheets generated in turbulent plasmas. Although such statistics have been studied previously for fluid simulations (e.g. [1]), they have not yet been generalized to fully kinetic particle-in-cell (PIC) simulations. A significant problem with PIC simulations, however, is electrostatic fluctuations generated due to numerical particle counting statistics. We find that analyzing gradients of the magnetic vector potential from the raw PIC field data identifies numerous artificial (or non-physical) x-points. Using small Orszag-Tang vortex PIC simulations, we analyze x-line identification and show that these artificial x-lines can be removed using sub-Debye length filtering of the data. We examine how turbulent properties such as the magnetic spectrum and scale dependent kurtosis are affected by particle noise and sub-Debye length filtering. We subsequently apply these analysis methods to a large scale kinetic PIC turbulent simulation. Consistent with previous fluid models, we find a range of normalized reconnection rates as large as ½ but with the bulk of the rates being approximately less than to 0.1. [1] Servidio, S., W. H. Matthaeus, M. A. Shay, P. A. Cassak, and P. Dmitruk (2009), Magnetic reconnection and two-dimensional magnetohydrodynamic turbulence, Phys. Rev. Lett., 102, 115003.

First-principle calculation on mechanical and thermal properties of B2-NiSc with point defects

NASA Astrophysics Data System (ADS)

Yuan, Zhipeng; Cui, Hongbao; Guo, Xuefeng

2017-01-01

Using the first-principles plane-wave pseudo-potential method based on density functional theory, the effect of vacancy and anti-position defect on the mechanical and thermal properties of B2-NiSc intermetallics were discussed in detail. Several parameters, such as the shear modulus, bulk modulus, modulus of elasticity, C 11-C 11, the Debye temperature and Poisson's ratio, have been calculated to evaluate the effect of vacancy and anti-position defect on the hardness, ductility and thermal properties of B2-NiSc intermetallics. The results show that VNi, ScNi, VSc and NiSc the four point defects all make the crystal hardness decrease and improve plasticity of B2-NiSc intermetallics. The entropy, enthalpy and free energy of VNi, ScNi, VSc and NiSc are monotonously changed as temperature changes. From the perspective of free energy, NiSc is the most stable, while ScNi is the most unstable. Debye temperature of NiSc intermetallics with four different point defects shows VNi, ScNi, VSc and NiSc the four point defects all reduce the stability of B2-NiSc intermetallics. Project supported by the National Natural Science Foundation of China (Nos. 51301063, 51571086) and the Talent Introduction Foundation of Henan Polytechnic University (No. Y-2009).

Electro-osmotic flow of couple stress fluids in a micro-channel propagated by peristalsis

NASA Astrophysics Data System (ADS)

Tripathi, Dharmendra; Yadav, Ashu; Anwar Bég, O.

2017-04-01

A mathematical model is developed for electro-osmotic peristaltic pumping of a non-Newtonian liquid in a deformable micro-channel. Stokes' couple stress fluid model is employed to represent realistic working liquids. The Poisson-Boltzmann equation for electric potential distribution is implemented owing to the presence of an electrical double layer (EDL) in the micro-channel. Using long wavelength, lubrication theory and Debye-Huckel approximations, the linearized transformed dimensionless boundary value problem is solved analytically. The influence of electro-osmotic parameter (inversely proportional to Debye length), maximum electro-osmotic velocity (a function of external applied electrical field) and couple stress parameter on axial velocity, volumetric flow rate, pressure gradient, local wall shear stress and stream function distributions is evaluated in detail with the aid of graphs. The Newtonian fluid case is retrieved as a special case with vanishing couple stress effects. With increasing the couple stress parameter there is a significant increase in the axial pressure gradient whereas the core axial velocity is reduced. An increase in the electro-osmotic parameter both induces flow acceleration in the core region (around the channel centreline) and it also enhances the axial pressure gradient substantially. The study is relevant in the simulation of novel smart bio-inspired space pumps, chromatography and medical micro-scale devices.

Modified Nose-Hoover thermostat for solid state for constant temperature molecular dynamics simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wen-Hwa, E-mail: whchen@pme.nthu.edu.tw; National Applied Research Laboratories, Taipei 10622, Taiwan, ROC; Wu, Chun-Hung

2011-07-10

Nose-Hoover (NH) thermostat methods incorporated with molecular dynamics (MD) simulation have been widely used to simulate the instantaneous system temperature and feedback energy in a canonical ensemble. The method simply relates the kinetic energy to the system temperature via the particles' momenta based on the ideal gas law. However, when used in a tightly bound system such as solids, the method may suffer from deriving a lower system temperature and potentially inducing early breaking of atomic bonds at relatively high temperature due to the neglect of the effect of the potential energy of atoms based on solid state physics. Inmore » this paper, a modified NH thermostat method is proposed for solid system. The method takes into account the contribution of phonons by virtue of the vibrational energy of lattice and the zero-point energy, derived based on the Debye theory. Proof of the equivalence of the method and the canonical ensemble is first made. The modified NH thermostat is tested on different gold nanocrystals to characterize their melting point and constant volume specific heat, and also their size and temperature dependence. Results show that the modified NH method can give much more comparable results to both the literature experimental and theoretical data than the standard NH. Most importantly, the present model is the only one, among the six thermostat algorithms under comparison, that can accurately reproduce the experimental data and also the T{sup 3}-law at temperature below the Debye temperature, where the specific heat of a solid at constant volume is proportional to the cube of temperature.« less

Electromagnetic induction and radiation-induced abnormality of wave propagation in excitable media

NASA Astrophysics Data System (ADS)

Ma, Jun; Wu, Fuqiang; Hayat, Tasawar; Zhou, Ping; Tang, Jun

2017-11-01

Continuous wave emitting from sinus node of the heart plays an important role in wave propagating among cardiac tissue, while the heart beating can be terminated when the target wave is broken into turbulent states by electromagnetic radiation. In this investigation, local periodical forcing is applied on the media to induce continuous target wave in the improved cardiac model, which the effect of electromagnetic induction is considered by using magnetic flux, then external electromagnetic radiation is imposed on the media. It is found that target wave propagation can be blocked to stand in a local area and the excitability of media is suppressed to approach quiescent but homogeneous state when electromagnetic radiation is imposed on the media. The sampled time series for membrane potentials decrease to quiescent state due to the electromagnetic radiation. It could accounts for the mechanism of abnormality in heart failure exposed to continuous electromagnetic field.

Role of nonthermal electron on the dynamics of relativistic electromagnetic soliton in the interaction of laser-plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rostampooran, Shabnam; Dorranian, Davoud, E-mail: doran@srbiau.ac.ir

A system of nonlinear one-dimensional equations of the electron hydrodynamics with Maxwell's equations was developed to describe electromagnetic (EM) solitons in plasma with nonthermal electrons. Equation of vector potential was derived in relativistic regime by implementing the multiple scales technique, and their solitonic answers were introduced. The allowed regions for bright and dark electromagnetic solitons were discussed in detail. Roles of number density of nonthermal electrons, temperature of electrons, and frequency of fast participate of vector potential on the Sagdeev potential and properties of EM soliton were investigated. Results show that with increasing the number of nonthermal electrons, the amplitudemore » of vector potential of bright solitons increases. By increasing the number of nonthermal electrons, dark EM solitons may be changed to bright solitons. Increasing the energy of nonthermal electrons leads to generation of high amplitude solitons.« less

Excitation of surface electromagnetic waves in a graphene-based Bragg grating

PubMed Central

Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

2012-01-01

Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc. PMID:23071901

Excitation of surface electromagnetic waves in a graphene-based Bragg grating.

PubMed

Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

2012-01-01

Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc.

Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rinne, Klaus F.; Netz, Roland R.; Gekle, Stephan

2014-12-07

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into differentmore » water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.« less

First principles and Debye model study of the thermodynamic, electronic and optical properties of MgO under high-temperature and pressure

NASA Astrophysics Data System (ADS)

Miao, Yurun; Li, Huayang; Wang, Hongjuan; He, Kaihua; Wang, Qingbo

2018-02-01

First principles and quasi-harmonic Debye model have been used to study the thermodynamic properties, enthalpies, electronic and optical properties of MgO up to the core-mantle boundary (CMB) condition (137 GPa and 3700 K). Thermodynamic properties calculation includes thermal expansion coefficient and capacity, which have been studied up to the CMB pressure (137 GPa) and temperature (3700 K) by the Debye model with generalized gradient approximation (GGA) and local-density approximation (LDA). First principles with hybrid functional method (PBE0) has been used to calculate the electronic and optical properties under pressure up to 137 GPa and 0 K. Our results show the Debye model with LDA and first principles with PBE0 can provide accurate thermodynamic properties, enthalpies, electronic and optical properties. Calculated enthalpies show that MgO keep NaCl (B1) structure up to 137 GPa. And MgO is a direct bandgap insulator with a 7.23 eV calculated bandgap. The bandgap increased with increasing pressure, which will induce a blue shift of optical properties. We also calculated the density of states (DOS) and discussed the relation between DOS and band, optical properties. Equations were used to fit the relations between pressure and bandgaps, absorption coefficient (α(ω)) of MgO. The equations can be used to evaluate pressure after careful calibration. Our calculations can not only be used to identify some geological processes, but also offer a reference to the applications of MgO in the future.

On the Connection Between Microbursts and Nonlinear Electronic Structures in Planetary Radiation Belts

NASA Technical Reports Server (NTRS)

Osmane, Adnane; Wilson, Lynn B., III; Blum, Lauren; Pulkkinen, Tuija I.

2016-01-01

Using a dynamical-system approach, we have investigated the efficiency of large-amplitude whistler waves for causing microburst precipitation in planetary radiation belts by modeling the microburst energy and particle fluxes produced as a result of nonlinear wave-particle interactions. We show that wave parameters, consistent with large amplitude oblique whistlers, can commonly generate microbursts of electrons with hundreds of keV-energies as a result of Landau trapping. Relativistic microbursts (greater than 1 MeV) can also be generated by a similar mechanism, but require waves with large propagation angles Theta (sub k)B greater than 50 degrees and phase-speeds v(sub phi) greater than or equal to c/9. Using our result for precipitating density and energy fluxes, we argue that holes in the distribution function of electrons near the magnetic mirror point can result in the generation of double layers and electron solitary holes consistent in scales (of the order of Debye lengths) to nonlinear structures observed in the radiation belts by the Van Allen Probes. Our results indicate a relationship between nonlinear electrostatic and electromagnetic structures in the dynamics of planetary radiation belts and their role in the cyclical production of energetic electrons (E greater than or equal to 100 keV) on kinetic timescales, which is much faster than previously inferred.

A New Energy Ordering and the Dipole Moment of Gas Phase Glycine via Plane-Wave Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Min, Byeong June

2018-03-01

The abundance of glycine (Gly), the simplest amino acid, in meteorites leads us to the next question about its extraterrestrial origin. However, astronomers have not yet found glycine signature in interstellar medium. Laboratory microwave spectroscopy experiments report the most stable Gly conformer has a dipole moment of 4.5 - 5.45 Debye. Theoretical calculations, so far performed only with Gaussian basis functions, has predicted a dipole moment of about 1 Debye. This discrepancy has baffled astronomers. We study the energetics of glycine and its isomers and conformers via plane-wave density functional theory calculations. The geometric structures of the isomers and their conformers are identified, along with their relative stability and their dipole moment. In the case of glycine, we obtain the most stable conformer with a dipole moment of 5.76 Debye, close to the microwave spectroscopy experiments. If the plane wave energy cutoff is reduced to a lower value ( 400 eV) on purpose, the energy ordering reverses to the case with Gaussian basis calculations.

Compliance of the Stokes-Einstein model and breakdown of the Stokes-Einstein-Debye model for a urea-based supramolecular polymer of high viscosity.

PubMed

Świergiel, Jolanta; Bouteiller, Laurent; Jadżyn, Jan

2014-11-14

Impedance spectroscopy was used for the study of the static and dynamic behavior of the electrical conductivity of a hydrogen-bonded supramolecular polymer of high viscosity. The experimental data are discussed in the frame of the Stokes-Einstein and Stokes-Einstein-Debye models. It was found that the translational movement of the ions is due to normal Brownian diffusion, which was revealed by a fulfillment of Ohm's law by the electric current and a strictly exponential decay of the current after removing the electric stimulus. The dependence of the dc conductivity on the viscosity of the medium fulfills the Stokes-Einstein model quite well. An extension of the model, by including in it the conductivity relaxation time, is proposed in this paper. A breakdown of the Stokes-Einstein-Debye model is revealed by the relations of the dipolar relaxation time to the viscosity and to the dc ionic conductivity. The importance of the C=O···H-N hydrogen bonds in that breakdown is discussed.

Epoxy-based hydrogels investigated by high-frequency dielectric relaxation spectroscopy.

PubMed

Krakovský, Ivan; Shikata, Toshiyuki; Hasegawa, Ryuta

2013-11-14

Using high-frequency dielectric relaxation spectroscopy, nanophase-separated structures of epoxy-based hydrogels were investigated as a function of water content at 25 °C. The dielectric spectra resulting from the hydrogels were reasonably decomposed into two Debye-type and two Cole-Cole-type relaxation modes. The fastest Debye-type mode, found at 8.3 ps, was attributed to the rotational relaxation process of free water molecules in the bulk state. The other Debye-type mode, at ca. 20-34 ps, originates from the exchange process of water molecules that are hydrogen-bonded to the hydrophilic epoxy network portions for free bulk ones. The first Cole-Cole-type mode observed, at ca. 20-370 ps, was assigned to the complicated dynamics for electric dipole moments of the hydrophilic groups in the epoxy networks (mainly monomeric oxyethylene units). The slowest major Cole-Cole-type mode, at 5-29 ns, was attributed to the Maxwell-Wagner-Sillars polarization process and confirmed the presence of the nanophase-separated structures as revealed by the previous small-angle neutron scattering experiments.

Slow Debye-type peak observed in the dielectric response of polyalcohols

NASA Astrophysics Data System (ADS)

Bergman, Rikard; Jansson, Helén; Swenson, Jan

2010-01-01

Dielectric relaxation spectroscopy of glass forming liquids normally exhibits a relaxation scenario that seems to be surprisingly general. However, the relaxation dynamics is more complicated for hydrogen bonded liquids. For instance, the dielectric response of monoalcohols is dominated by a mysterious Debye-like process at lower frequencies than the structural α-relaxation that is normally dominating the spectra of glass formers. For polyalcohols this process has been thought to be absent or possibly obscured by a strong contribution from conductivity and polarization effects at low frequencies. We here show that the Debye-like process, although much less prominent, is also present in the response of polyalcohols. It can be observed in the derivative of the real part of the susceptibility or directly in the imaginary part if the conductivity contribution is reduced by covering the upper electrode with a thin Teflon layer. We report on results from broadband dielectric spectroscopy studies of several polyalcohols: glycerol, xylitol, and sorbitol. The findings are discussed in relation to other experimental observations of ultraslow (i.e., slower than the viscosity related α-relaxation) dynamics in glass formers.

Ab Initio Calculation of XAFS Debye-Waller Factors for Crystalline Materials

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas

2007-02-01

A direct an accurate technique for calculating the thermal X-ray absorption fine structure (XAFS) Debye-Waller factors (DWF) for materials of crystalline structure is presented. Using the Density Functional Theory (DFT) under the hybrid X3LYP functional, a library of MnO spin—optimized clusters are built and their phonon spectrum properties are calculated; these properties in the form of normal mode eigenfrequencies and eigenvectors are in turn used for calculation of the single and multiple scattering XAFS DWF. DWF obtained via this technique are temperature dependent expressions and can be used to substantially reduce the number of fitting parameters when experimental spectra are fitted with a hypothetical structure without any ad hoc assumptions. Due to the high computational demand a hybrid approach of mixing the DFT calculated DWF with the correlated Debye model for inner and outer shells respectively is presented. DFT obtained DWFs are compared with corresponding values from experimental XAFS spectra on manganosite. The cluster size effect and the spin parameter on the DFT calculated DWFs are discussed.

Investigation of different physical aspects such as structural, mechanical, optical properties and Debye temperature of Fe2ScM (M=P and As) semiconductors: A DFT-based first principles study

NASA Astrophysics Data System (ADS)

Ali, Md. Lokman; Rahaman, Md. Zahidur

2018-04-01

By using first principles calculation dependent on the density functional theory (DFT), we have investigated the mechanical, structural properties and the Debye temperature of Fe2ScM (M=P and As) compounds under various pressures up to 60 GPa. The optical properties have been investigated under zero pressure. Our calculated optimized structural parameters of both the materials are in good agreement with other theoretical predictions. The calculated elastic constants show that Fe2ScM (M=P and As) compounds are mechanically stable under external pressure below 60 GPa. From the elastic constants, the shear modulus G, the bulk modulus B, Young’s modulus E, anisotropy factor A and Poisson’s ratio ν are calculated by using the Voigt-Reuss-Hill approximation. The Debye temperature and average sound velocities are also investigated from the obtained elastic constants. The detailed analysis of all optical functions reveals that both compounds are good dielectric material.

q-deformed Einstein's model to describe specific heat of solid

NASA Astrophysics Data System (ADS)

Guha, Atanu; Das, Prasanta Kumar

2018-04-01

Realistic phenomena can be described more appropriately using generalized canonical ensemble, with proper parameter sets involved. We have generalized the Einstein's theory for specific heat of solid in Tsallis statistics, where the temperature fluctuation is introduced into the theory via the fluctuation parameter q. At low temperature the Einstein's curve of the specific heat in the nonextensive Tsallis scenario exactly lies on the experimental data points. Consequently this q-modified Einstein's curve is found to be overlapping with the one predicted by Debye. Considering only the temperature fluctuation effect(even without considering more than one mode of vibration is being triggered) we found that the CV vs T curve is as good as obtained by considering the different modes of vibration as suggested by Debye. Generalizing the Einstein's theory in Tsallis statistics we found that a unique value of the Einstein temperature θE along with a temperature dependent deformation parameter q(T) , can well describe the phenomena of specific heat of solid i.e. the theory is equivalent to Debye's theory with a temperature dependent θD.

Delocalization via Sliding in Solid 4He: Is It Plausible?

NASA Astrophysics Data System (ADS)

Krainyukova, N. V.

2010-02-01

The modified Debye approach was used to calculate the Gibbs free energy for solid 4He and energetic profiles for different atomic displacements with respect to an equilibrium lattice. Atoms interact via the applied Aziz potential. We have found that individual atomic displacements may hardly give rise to any delocalization because of huge barriers but cooperative plane sliding is highly plausible especially in the intermediate phase, which was found to be more favorable than hcp for small cluster sizes. In the latter case the roughness of the potential profile is less than one kelvin. In some particular sliding cases the energy levels in the nearest wells nearly coincide that is a well-known precursor for the delocalization effect.

Static quark-antiquark potential in the quark-gluon plasma from lattice QCD.

PubMed

Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander

2015-02-27

We present a state-of-the-art determination of the complex valued static quark-antiquark potential at phenomenologically relevant temperatures around the deconfinement phase transition. Its values are obtained from nonperturbative lattice QCD simulations using spectral functions extracted via a novel Bayesian inference prescription. We find that the real part, both in a gluonic medium, as well as in realistic QCD with light u, d, and s quarks, lies close to the color singlet free energies in Coulomb gauge and shows Debye screening above the (pseudo)critical temperature T_{c}. The imaginary part is estimated in the gluonic medium, where we find that it is of the same order of magnitude as in hard-thermal loop resummed perturbation theory in the deconfined phase.

Concentration analysis of breast tissue phantoms with terahertz spectroscopy

PubMed Central

Truong, Bao C. Q.; Fitzgerald, Anthony J.; Fan, Shuting; Wallace, Vincent P.

2018-01-01

Terahertz imaging has been previously shown to be capable of distinguishing normal breast tissue from its cancerous form, indicating its applicability to breast conserving surgery. The heterogeneous composition of breast tissue is among the main challenges to progressing this potential research towards a practical application. In this paper, two concentration analysis methods are proposed for analyzing phantoms mimicking breast tissue. The dielectric properties and the double Debye parameters were used to determine the phantom composition. The first method is wholly based on the conventional effective medium theory while the second one combines this theoretical model with empirical polynomial models. Through assessing the accuracy of these methods, their potential for application to quantifying breast tissue pathology was confirmed. PMID:29541525

Non-Debye domain-wall-induced dielectric response in Sr0.61-xCexBa0.39Nb2O6

NASA Astrophysics Data System (ADS)

Kleemann, W.; Dec, J.; Miga, S.; Woike, Th.; Pankrath, R.

2002-06-01

Two different non-Debye dielectric spectra are observed in a polydomain relaxor-ferroelectric Sr0.61-xBa0.39Nb2O6:Ce3+x single crystal in the vicinity of its transition temperature, Tc~320 K. At infralow frequencies the susceptibility varies as χ*~ω-β, β~0.2, and is attributed to an irreversible creep-like viscous motion of domain walls, while logarithmic dispersion due to reversible wall relaxation [T. Nattermann, Y. Shapir, and I. Vilfan, Phys. Rev. B 42, 8577 (1990)] occurs at larger ω.

Direct measurement of sub-Debye-length attraction between oppositely charged surfaces.

PubMed

Kampf, Nir; Ben-Yaakov, Dan; Andelman, David; Safran, S A; Klein, Jacob

2009-09-11

Using a surface force balance with fast video analysis, we have measured directly the attractive forces between oppositely charged solid surfaces (charge densities sigma(+), sigma(-)) across water over the entire range of interaction, in particular, at surface separations D below the Debye screening length lambda(S). At very low salt concentration we find a long-ranged attraction between the surfaces (onset ca. 100 nm), whose variation at D

Debye screening of dislocations.

PubMed

Groma, I; Györgyi, G; Kocsis, B

2006-04-28

Debye-like screening by edge dislocations of some externally given stress is studied by means of a variational approach to coarse grained field theory. Explicitly given are the force field and the induced geometrically necessary dislocation (GND) distribution, in the special case of a single glide axis in 2D, for (i) a single edge dislocation and (ii) a dislocation wall. Numerical simulation demonstrates that the correlation in relaxed dislocation configurations is in good agreement with the induced GND in case (i). Furthermore, the result (ii) well predicts the experimentally observed decay length for the GND developing close to grain boundaries.

Three-dimensional particle-in-cell simulations of a plasma jet/cloud streaming across a transverse magnetic field

NASA Astrophysics Data System (ADS)

Voitcu, Gabriel; Echim, Marius

2014-05-01

The dynamics of collisionless plasma jets/clouds in magnetic field configurations typical for the terrestrial magnetotail and frontside magnetosheath is a topic of interest for understanding the physics of the magnetosphere and its interaction with the solar wind. The presence of high-speed jets in the frontside magnetosheath has been recently proved experimentally by Cluster and THEMIS spacecrafts. There is increasing evidence that the bursty bulk flows in the magnetotail have jet-like features. In the present paper we use fully electromagnetic 3D explicit particle-in-cell (PIC) simulations to investigate the interaction of a localized three-dimensional plasma element/jet/cloud with a transverse magnetic field. We consider a plasma jet/cloud that moves in vacuum and perpendicular to an ambient magnetic field. Ampère and Faraday's laws are used to compute the self-consistent electric and magnetic fields on a three-dimensional spatial grid having a step-size of the order of the Debye length and using a time-step that resolves the plasma frequency. The initial magnetic field inside the simulation domain is uniform and the plasma bulk velocity at the beginning of the simulation is normal to the magnetic field direction. The total time scale of the simulation is of the order of few ion Larmor periods. Space and time variations of the plasma parameters and of the electromagnetic field are analyzed and discussed. We emphasize non-MHD effects like the energy-dispersion signatures at the edges of the plasma element, similar to results previously reported by Voitcu and Echim (2012) using test-kinetic simulations. Acknowledgments: Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.

Proposed electromagnetic wave energy converter

NASA Technical Reports Server (NTRS)

Bailey, R. L.

1973-01-01

Device converts wave energy into electric power through array of insulated absorber elements responsive to field of impinging electromagnetic radiation. Device could also serve as solar energy converter that is potentially less expensive and fragile than solar cells, yet substantially more efficient.

On the evolution of Saturn's 'Spokes' - Theory

NASA Technical Reports Server (NTRS)

Morfill, G. E.; Gruen, E.; Goertz, C. K.; Johnson, T. V.

1983-01-01

Starting with the assumption that negatively charged micron-sized dust grains may be elevated above Saturn's ring plane by plasma interactions, the subsequent evolution of the system is discussed. The discharge of the fine dust by solar UV radiation produces a cloud of electrons which moves adiabatically in Saturn's dipolar magnetic field. The electron cloud is absorbed by the ring after one bounce, alters the local ring potential significantly, and reduces the local Debye length. As a result, more micron-sized dust particles may be elevated above the ring plane and the spoke grows. This process continues until the electron cloud has dissipated.

Periodical plasma structures controlled by external magnetic field

NASA Astrophysics Data System (ADS)

Schweigert, I. V.; Keidar, M.

2017-06-01

The characteristics of two-dimensional periodical structures in a magnetized plasma are studied using kinetic simulations. Ridges (i.e. spikes in electron and ion density) are formed and became more pronounced with an increase of magnetic field incidence angle in the plasma volume in the cylindrical chamber. These ridges are shifted relative to each other, which results in the formation of a two-dimensional double-layer structure. Depending on Larmor radius and Debye length up to 19 potential steps appear across the oblique magnetic field. The electrical current gathered into the channels is associated with the electron and ion density ridges.

Effect of Base Sequence "Defects" on the Electrostatic Potential of Dissolved DNA

NASA Astrophysics Data System (ADS)

Adams, Scott V.; Wagner, Katrina; Kephart, Thomas S.; Edwards, Glenn

1997-11-01

An analytical model of the electrostatic potential surrounding dissolved DNA has been developed. The model consists of an all-atom, mathematically helical structure for DNA, in which the atoms are arranged in infinite lines of discrete point charges on concentric cylindrical surfaces. The surrounding solvent and counterions are treated with the Debye-Huckel approximation (Wagner et al., Biophysical Journal 73, 21-30, 1997). Variation in the electrostatic potential due to structural differences between A, B, and Z conformations and homopolymer base sequence is apparent. The most recent modification to the model exploits the principle of superposition to calculate the potential of DNA with a base sequence containing `defects.' That is, the base sequence is no longer uniform along the polymer. Differences between the potential of homopolymer DNA and the potential of DNA containing base `defects' are immediately obvious. These results may aid in understanding the role of electrostatics in base-sequence specificity exhibited by DNA-binding proteins.

Spacetime algebra as a powerful tool for electromagnetism

NASA Astrophysics Data System (ADS)

Dressel, Justin; Bliokh, Konstantin Y.; Nori, Franco

2015-08-01

We present a comprehensive introduction to spacetime algebra that emphasizes its practicality and power as a tool for the study of electromagnetism. We carefully develop this natural (Clifford) algebra of the Minkowski spacetime geometry, with a particular focus on its intrinsic (and often overlooked) complex structure. Notably, the scalar imaginary that appears throughout the electromagnetic theory properly corresponds to the unit 4-volume of spacetime itself, and thus has physical meaning. The electric and magnetic fields are combined into a single complex and frame-independent bivector field, which generalizes the Riemann-Silberstein complex vector that has recently resurfaced in studies of the single photon wavefunction. The complex structure of spacetime also underpins the emergence of electromagnetic waves, circular polarizations, the normal variables for canonical quantization, the distinction between electric and magnetic charge, complex spinor representations of Lorentz transformations, and the dual (electric-magnetic field exchange) symmetry that produces helicity conservation in vacuum fields. This latter symmetry manifests as an arbitrary global phase of the complex field, motivating the use of a complex vector potential, along with an associated transverse and gauge-invariant bivector potential, as well as complex (bivector and scalar) Hertz potentials. Our detailed treatment aims to encourage the use of spacetime algebra as a readily available and mature extension to existing vector calculus and tensor methods that can greatly simplify the analysis of fundamentally relativistic objects like the electromagnetic field.

Electron Flow to a Satellite at High Positive Potential

NASA Technical Reports Server (NTRS)

Sheldon, John W.

1996-01-01

The Tethered Satellite System (TSS) is designed to deploy a 1.6 m diameter spherical satellite a distance of 20 km above the space shuttle orbiter on an insulated conducting tether. Because of the passage of the conducting tether through the earth's magnetic field, an emf is generated producing a positive satellite potential of about 5000 V. Electron flow under the influence of this high positive potential is the focus of the present analysis. The ionospheric parameters at TSS orbit altitude are; thermal velocity of electrons, 1.9 x 10(exp 5) M/S, thermal velocity of the ions, 1.1 x 10(exp 3) m/s, velocity of the satellite 8 x 10(exp 3) m/s. The electrons, with a Debye length, lambda(D) = 0.49 cm, spiral about the earth's magnetic field lines (0.4 Gauss) with a radius of about 3 cm and the ions spiral with a radius of 5 m. Under these conditions, the electron thermal energy, kT is 0.17 eV. The TSS satellite radius, r(p) is 163 Debye lengths. There is an extensive literature on the interaction of satellites with the near-earth ionospheric plasma. The space charge limitation to the electron current collected by a sphere at positive electrical potential was calculated by Langmuir and Blodgett (1924). Parker and Murphy (1967) recognized the importance of the influence of the earth's magnetic field and used the guiding center approximation to calculate the electron current collected by a positive charged satellite. More recently Ma and Schunk (1989) have calculated the time dependent flow of electrons to a spherical satellite at positive potential utilizing numerical methods and Sheldon (1994) used similar methods to solve this problem for the steady state. In order to analyze some of the phenomena that occurred in the ionosphere during the TSS flights, it would be useful to have analytic expressions for these electron flows. The governing equations are very complex and an exact analytical solution is not likely. An approximate analytical solution is feasible however, and the results of one attempt are presented herein.

[Electromagnetic pollution (electrosmog)--potential hazards of our electromagnetic future].

PubMed

Nowak, D; Radon, K

2004-02-26

The term electromagnetic environment encompasses the totality of all electric, magnetic and electromagnetic fields generated by natural and technical sources. A differentiation is made between low- and high-frequency electromagnetic fields. Typical sources of the former are domestic electricity Exposure to the latter is, for example, associated with the sue of mobile telephones. Studies on the health-related effects of electromagnetic fields are available in particular for the low-frequency range, based on an appropriate estimation of exposure. A number of these studies reveal an association between exposure to this type of electromagnetic fields and the occurrence of infantile leukemia in the highest exposure category. For high-frequency electromagnetic fields the number of epidemiological studies is limited. An increased risk of an accident occurring through the use of a cellular phone while driving has consistently been shown. Against the background of our limited knowledge about possible adverse effects of exposure to mobile phone transmitters, and the inability of the public to influence such exposure, transparency in the communication of the risks involved is of great importance.

Gauge Invariant Formulation of the Interaction of Electromagnetic Radiation and Matter

ERIC Educational Resources Information Center

Kobe, Donald H.; Smirl, Arthur L.

1978-01-01

Presents a discussion in Perturbation theory in quantum mechanics for the interaction of electromagnetic radiation with matter. Advocates the use of electric dipole interaction whenever it can be used as compared to the vector potential interaction. (GA)

Propagation of a plasma streamer in catalyst pores

NASA Astrophysics Data System (ADS)

Zhang, Quan-Zhi; Bogaerts, Annemie

2018-03-01

Although plasma catalysis is gaining increasing interest for various environmental applications, the underlying mechanisms are still far from understood. For instance, it is not yet clear whether and how plasma streamers can propagate in catalyst pores, and what is the minimum pore size to make this happen. As this is crucial information to ensure good plasma-catalyst interaction, we study here the mechanism of plasma streamer propagation in a catalyst pore, by means of a two-dimensional particle-in-cell/Monte Carlo collision model, for various pore diameters in the nm-range to μm-range. The so-called Debye length is an important criterion for plasma penetration into catalyst pores, i.e. a plasma streamer can penetrate into pores when their diameter is larger than the Debye length. The Debye length is typically in the order of a few 100 nm up to 1 μm at the conditions under study, depending on electron density and temperature in the plasma streamer. For pores in the range of ∼50 nm, plasma can thus only penetrate to some extent and at very short times, i.e. at the beginning of a micro-discharge, before the actual plasma streamer reaches the catalyst surface and a sheath is formed in front of the surface. We can make plasma streamers penetrate into smaller pores (down to ca. 500 nm at the conditions under study) by increasing the applied voltage, which yields a higher plasma density, and thus reduces the Debye length. Our simulations also reveal that the plasma streamers induce surface charging of the catalyst pore sidewalls, causing discharge enhancement inside the pore, depending on pore diameter and depth.

Debye sheath mechanism at laser plasma interaction and generalization to nuclear forces and quark-gluon plasma

NASA Astrophysics Data System (ADS)

Osman, Frederick; Ghahramani, Nader; Hora, Heinrich

2005-10-01

The studies of laser ablation have lead to a new theory of nuclei, endothermic nuclei generation, and quark-gluon plasmas. The surface of ablated plasma expanding into vacuum after high power laser irradiation of targets contains an electric double layer having the thickness of the Debye length. This led to the discovery of surface tension in plasmas, and led to the internal dynamic electric fields in all inhomogeneous plasmas. The surface tension causes stabilization by short length surface wave smoothing the expanding plasma plume and to stabilization against the Rayleigh Taylor instability. Generalizing this to the degenerate electrons in a metal with the Fermi energy instead of the temperature resulted in the first quantum theory of surface tension of metals in agreement with measurements. Taking the Fermi energy in the Debye length for nucleons results in a theory of nuclei with stable confinement of protons and neutrons just at the well-known nuclear density, and the Debye lengths equal to the Hofstadter decay of the nuclear surface. Increasing the nuclear density by a factor of 10 leads to a change of the Fermi energy into its relativistic branch where no surface energy is possible and the particle mass is not defined, permitting the quark gluon plasma. Expansion of this higher density at the big bang or in super-nova results in nucleation and element generation. The Boltzmann equilibrium permits the synthesis of nuclei even in the endothermic range, however with the limit to about uranium. A relation for the magic numbers leads to a quark structure of nuclear shells that can be understood as a duality property of nuclei with respect to nucleons and quarks

A Note on Feynman Path Integral for Electromagnetic External Fields

NASA Astrophysics Data System (ADS)

Botelho, Luiz C. L.

2017-08-01

We propose a Fresnel stochastic white noise framework to analyze the nature of the Feynman paths entering on the Feynman Path Integral expression for the Feynman Propagator of a particle quantum mechanically moving under an external electromagnetic time-independent potential.

Single-cone finite-difference schemes for the (2+1)-dimensional Dirac equation in general electromagnetic textures

NASA Astrophysics Data System (ADS)

Pötz, Walter

2017-11-01

A single-cone finite-difference lattice scheme is developed for the (2+1)-dimensional Dirac equation in presence of general electromagnetic textures. The latter is represented on a (2+1)-dimensional staggered grid using a second-order-accurate finite difference scheme. A Peierls-Schwinger substitution to the wave function is used to introduce the electromagnetic (vector) potential into the Dirac equation. Thereby, the single-cone energy dispersion and gauge invariance are carried over from the continuum to the lattice formulation. Conservation laws and stability properties of the formal scheme are identified by comparison with the scheme for zero vector potential. The placement of magnetization terms is inferred from consistency with the one for the vector potential. Based on this formal scheme, several numerical schemes are proposed and tested. Elementary examples for single-fermion transport in the presence of in-plane magnetization are given, using material parameters typical for topological insulator surfaces.

Ion strength limit of computed excess functions based on the linearized Poisson-Boltzmann equation.

PubMed

Fraenkel, Dan

2015-12-05

The linearized Poisson-Boltzmann (L-PB) equation is examined for its κ-range of validity (κ, Debye reciprocal length). This is done for the Debye-Hückel (DH) theory, i.e., using a single ion size, and for the SiS treatment (D. Fraenkel, Mol. Phys. 2010, 108, 1435), which extends the DH theory to the case of ion-size dissimilarity (therefore dubbed DH-SiS). The linearization of the PB equation has been claimed responsible for the DH theory's failure to fit with experiment at > 0.1 m; but DH-SiS fits with data of the mean ionic activity coefficient, γ± (molal), against m, even at m > 1 (κ > 0.33 Å(-1) ). The SiS expressions combine the overall extra-electrostatic potential energy of the smaller ion, as central ion-Ψa>b (κ), with that of the larger ion, as central ion-Ψb>a (κ); a and b are, respectively, the counterion and co-ion distances of closest approach. Ψa>b and Ψb>a are derived from the L-PB equation, which appears to conflict with their being effective up to moderate electrolyte concentrations (≈1 m). However, the L-PB equation can be valid up to κ ≥ 1.3 Å(-1) if one abandons the 1/κ criterion for its effectiveness and, instead, use, as criterion, the mean-field electrostatic interaction potential of the central ion with its ion cloud, at a radial distance dividing the cloud charge into two equal parts. The DH theory's failure is, thus, not because of using the L-PB equation; the lethal approximation is assigning a single size to the positive and negative ions. © 2015 Wiley Periodicals, Inc.

Effect of pressure variation on structural, elastic, mechanical, optoelectronic and thermodynamic properties of SrNaF3 fluoroperovskite

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2017-12-01

The effect of pressure variation on structural, electronic, elastic, mechanical, optical and thermodynamic characteristics of cubic SrNaF3 fluoroperovskite have been investigated by employing first-principles method within the framework of gradient approximation (GGA). For the total energy calculations, we have used the full-potential linearized augmented plane wave (FP-LAPW) method. Thermodynamic properties are computed in terms of quasi-harmonic Debye model. The pressure effects are determined in the range of 0-25 GPa, in which mechanical stability of SrNaF3 fluoroperovskite remains valid. A prominent decrease in lattice constant and bonds length is observed with the increase in pressure from 0 to 25 GPa. The effect of increase in pressure on band structure calculations with GGA and GGA plus Tran-Blaha modified Becke-Johnson (TB-mBJ) potential reveals a predominant characteristic associated with widening of bandgap. The influence of pressure on set of isotropic elastic parameters and their related properties are numerically estimated for SrNaF3 polycrystalline aggregate. Apart of linear dependence of elastic coefficients, transition from brittle to ductile behavior is observed as pressure is increased from 0 to 25 GPa. We have successfully obtained variation of lattice constant, volume expansion, bulk modulus, Debye temperature and specific heat capacities with pressure and temperature in the range of 0-25 GPa and 0-600 K. All the calculated optical properties such as the complex dielectric function ɛ(ω), optical conductivity σ(ω), energy loss function L(ω), absorption coefficient α(w), refractive index n(ω), reflectivity R(ω), and effective number of electrons n eff, via sum rules shift towards the higher energies under the application of pressure.

Pure axial flow of viscoelastic fluids in rectangular microchannels under combined effects of electro-osmosis and hydrodynamics

NASA Astrophysics Data System (ADS)

Reshadi, Milad; Saidi, Mohammad Hassan; Ebrahimi, Abbas

2018-02-01

This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien-Tanner (PTT) model with the Gordon-Schowalter convected derivative which covers the upper convected Maxwell, Johnson-Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson-Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid system and is verified against 1D analytical solution of the velocity profile with less than 0.06% relative error. Also, a parametric study is carried out to investigate the effect of channel aspect ratio (width to height), wall zeta potential and the Debye-Hückel parameter on 2D velocity profile, volumetric flow rate and the Poiseuille number in the mixed EO/PD flows of viscoelastic fluids with different Weissenberg numbers. Our results show that, for low channel aspect ratios, the previous 1D analytical models underestimate the velocity profile at the channel half-width centerline in the case of favorable pressure gradients and overestimate it in the case of adverse pressure gradients. The results reveal that the inapplicability of the Debye-Hückel approximation at high zeta potentials is more significant for higher Weissenberg number fluids. Also, it is found that, under the specified values of electrokinetic parameters, there is a threshold for velocity scale ratio in which the Poiseuille number is approximately independent of channel aspect ratio.

General Navier–Stokes-like momentum and mass-energy equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monreal, Jorge, E-mail: jmonreal@mail.usf.edu

2015-03-15

A new system of general Navier–Stokes-like equations is proposed to model electromagnetic flow utilizing analogues of hydrodynamic conservation equations. Such equations are intended to provide a different perspective and, potentially, a better understanding of electromagnetic mass, energy and momentum behaviour. Under such a new framework additional insights into electromagnetism could be gained. To that end, we propose a system of momentum and mass-energy conservation equations coupled through both momentum density and velocity vectors.

First-principles calculations for elastic properties of OsB 2 under pressure

NASA Astrophysics Data System (ADS)

Yang, Jun-Wei; Chen, Xiang-Rong; Luo, Fen; Ji, Guang-Fu

2009-11-01

The structure, elastic properties and elastic anisotropy of orthorhombic OsB 2 are investigated by density functional theory method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation (GGA) as well as local density approximation (LDA). The obtained structural parameters, elastic constants, elastic anisotropy and Debye temperature for OsB 2 under pressure are consistent with the available experimental data and other theoretical results. It is found that the elastic constants, bulk modulus and Debye temperature of OsB 2 tend to increase with increasing pressure. It is predicted that OsB 2 is not a superhard material from our calculations.

The polarized Debye sheath effect on Kadomtsev-Petviashvili electrostatic structures in strongly coupled dusty plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahmansouri, M.; Alinejad, H.

2015-04-15

We give a theoretical investigation on the dynamics of nonlinear electrostatic waves in a strongly coupled dusty plasma with strong electrostatic interaction between dust grains in the presence of the polarization force (i.e., the force due to the polarized Debye sheath). Adopting a reductive perturbation method, we derived a three-dimensional Kadomtsev-Petviashvili equation that describes the evolution of weakly nonlinear electrostatic localized waves. The energy integral equation is used to study the existence domains of the localized structures. The analysis provides the localized structure existence region, in terms of the effects of strong interaction between the dust particles and polarization force.

Solvent free tin oxide nanoparticle for gas sensing application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ranjan, Pranay, E-mail: pranjan@iitp.ac.in; Thakur, Ajay D.; Centre for Energy and Environment, Indian Institute of Technology Patna, Patliputra, Patna 800013 India

2016-05-06

A new modified technique of synthesizing tin oxide nanoparticles with crystallite size of 2 nm to 6 nm has been developed. Surface area of the nanoparticle has been increased as we approached towards the Debye length. Such a techniques for approaching the Debye length is expected to bring remarkable changes in the properties of resistive based gas sensors. The technique used here is less toxic, economical and has high yield. Phase purity, size, shape and composition has been investigated using x-ray diffraction, micro Raman, scanning electron microscopy and energy dispersive x ray spectroscopy. While surface area has been calculated through Brunaur-Emmett-Teller (BET).

A modified Rayleigh-Gans-Debye formula for small angle X-ray scattering by interstellar dust grains

NASA Astrophysics Data System (ADS)

Sharma, Subodh K.

2015-05-01

A widely used approximation in studies relating to small angle differential scattering cross-section of X-rays scattered by interstellar dust grains is the well known Rayleigh-Gans-Debye approximation (RGDA). The validity of this approximation, however, is limited only to X-ray energies greater than about 1 keV. At lower energies, this approximation overestimates the exact results. In this paper a modification to the RGDA is suggested. It is shown that a combination of the RGDA with Ramsauer approximation retains the formal simplicity of the RGDA and also yields good agreement with Mie computations at all X-ray energies.

Debye temperature of metallic nanowires--an experimental determination from the resistance of metallic nanowires in the temperature range 4.2 K-300 K.

PubMed

Bid, Aveek; Bora, Achyut; Raychaudhuri, A K

2007-06-01

We have studied the resistance of metallic nanowires (silver and copper) as a function of the wire diameter in the temperature range 4.2 K-300 K. The nanowires with an average diameter of 15 nm-200 nm and length 6 microm were electrochemically deposited using polycarbonate membranes as template from AgNO3 and CuSO4, respectively. The wires after growth were removed from the membranes by dissolving the polymer in dichloromethane and their crystalline nature confirmed by XRD and TEM studies. The TEM study establishes that the nanowires are single crystalline and can have twin in them. The resistivity data was fitted to Bloch-Gruneisen theorem with the values of Debye temperature and the electron-acoustic phonon coupling constant as the two fit variables. The value of the Debye temperature obtained for the Ag wires was seen to match well with that of the bulk while for Cu wires a significant reduction was observed. The observed increase in resistivity with a decrease in the wire diameter could be explained as due to diffuse surface scattering of the conduction electrons.

Low temperature and high pressure thermoelastic and crystallographic properties of SrZrO3 perovskite in the Pbnm phase

NASA Astrophysics Data System (ADS)

Knight, Kevin S.; Bull, Craig L.

2016-12-01

The thermoelastic and structural properties of SrZrO3 perovskite in the Pnma (Pbnm) phase have been studied using neutron powder diffraction at 82 temperatures between 11 K and 406 K at ambient pressure, and at sixteen pressures between 0.07 and 6.7 GPa at ambient temperature. The bulk modulus, derived by fitting the equation of state to a second order Birch-Murnaghan equation-of-state, 157(5) GPa, is in excellent agreement with that deduced in a recent resonant ultrasound investigation. Experimental axial compressional moduli are in agreement with those calculated from the elastic stiffness coefficients derived by ab-initio calculation, although the experimental bulk modulus is significantly softer than that calculated. Following low temperature saturation for temperatures less than 40 K, the unit cell monotonically increases with a predicted high temperature limit in the volume expansivity of ∼2.65 × 10-5 K-1. Axial linear thermal expansion coefficients are found to be in the order αb < αc < αa for all temperatures greater than 20 K with the b axis indicating a weak, low temperature negative expansion coefficient at low temperatures. The thermoelastic properties of SrZrO3 can be approximated by a two-term Debye model for the phonon density of states with Debye temperatures of 238(4) K and 713(6) K derived in a self-consistent manner by simultaneously fitting the isochoric heat capacity and the unit cell volume. Atomic displacement parameters have been fitted to a modified Debye model in which the zero-point term is an additional refinable variable and shows the cations and anions have well separated Debye temperatures, mirroring the need for two Debye-like distributions in the vibrational density of states. The temperature dependence of the crystal structure is presented in terms of the amplitudes of the seven symmetry-adapted basis vectors of the aristotype phase that are consistent with space group Pbnm, thus permitting a direct measure of the order parameter evolution in SrZrO3. The temperature variation of the in-phase tilt, which is lost at the phase transition at 973 K, is consistent with tricritical behaviour, in agreement with published results based on high temperature crystallographic data.

Thermal noise due to surface-charge effects within the Debye layer of endogenous structures in dendrites.

PubMed

Poznanski, Roman R

2010-02-01

An assumption commonly used in cable theory is revised by taking into account electrical amplification due to intracellular capacitive effects in passive dendritic cables. A generalized cable equation for a cylindrical volume representation of a dendritic segment is derived from Maxwell's equations under assumptions: (i) the electric-field polarization is restricted longitudinally along the cable length; (ii) extracellular isopotentiality; (iii) quasielectrostatic conditions; and (iv) homogeneous medium with constant conductivity and permittivity. The generalized cable equation is identical to Barenblatt's equation arising in the theory of infiltration in fissured strata with a known analytical solution expressed in terms of a definite integral involving a modified Bessel function and the solution to a linear one-dimensional classical cable equation. Its solution is used to determine the impact of thermal noise on voltage attenuation with distance at any particular time. A regular perturbation expansion for the membrane potential about the linear one-dimensional classical cable equation solution is derived in terms of a Green's function in order to describe the dynamics of free charge within the Debye layer of endogenous structures in passive dendritic cables. The asymptotic value of the first perturbative term is explicitly evaluated for small values of time to predict how the slowly fluctuating (in submillisecond range) electric field attributed to intracellular capacitive effects alters the amplitude of the membrane potential. It was found that capacitive effects are almost negligible for cables with electrotonic lengths L>0.5 , contributes up to 10% of the signal for cables with electrotonic lengths in the range between 0.25

Ab Initio Study of the Electronic Structure, Elastic Properties, Magnetic Feature and Thermodynamic Properties of the Ba2NiMoO6 Material

NASA Astrophysics Data System (ADS)

Deluque Toro, C. E.; Mosquera Polo, A. S.; Gil Rebaza, A. V.; Landínez Téllez, D. A.; Roa-Rojas, J.

2018-04-01

We report first-principles calculations of the elastic properties, electronic structure and magnetic behavior performed over the Ba2NiMoO6 double perovskite. Calculations are carried out through the full-potential linear augmented plane-wave method within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient and Local Density Approximations, including spin polarization. The elastic properties calculated are bulk modulus (B), the elastic constants (C 11, C 12 and C 44), the Zener anisotropy factor (A), the isotropic shear modulus (G), the Young modulus (Y) and the Poisson ratio (υ). Structural parameters, total energies and cohesive properties of the perovskite are studied by means of minimization of internal parameters with the Murnaghan equation, where the structural parameters are in good agreement with experimental data. Furthermore, we have explored different antiferromagnetic configurations in order to describe the magnetic ground state of this compound. The pressure and temperature dependence of specific heat, thermal expansion coefficient, Debye temperature and Grüneisen parameter were calculated by DFT from the state equation using the quasi-harmonic model of Debye. A specific heat behavior C V ≈ C P was found at temperatures below T = 400 K, with Dulong-Petit limit values, which is higher than those, reported for simple perovskites.

High-pressure and high-temperature physical properties of LiF studied by density functional theory calculations and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Sun, Xiao-Wei; Liu, Zi-Jiang; Quan, Wei-Long; Song, Ting; Khenata, Rabah; Bin-Omran, Saad

2018-05-01

Using the revised Perdew-Burke-Ernzerhof generalized gradient approximation based on first-principles plane-wave pseudopotential density functional theory, the high-pressure structural phase transition of LiF is explored. From the analysis of Gibbs free energies, we find that no phase transition occurs for LiF in the presented pressure range from 0 to 1000 GPa, and this result is consistent with the theoretical prediction obtained via ab initio calculations [N.A. Smirnov, Phys. Rev. B 83 (2011) 014109]. Using the classical molecular dynamics technique with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction, the melting phase diagram of LiF is determined. The obtained normalized volumes under pressure are in good agreement with our density functional theory results and the available experimental data. Meanwhile, with the help of the quasi-harmonic Debye model in which the phononic effects are considered, the thermodynamic properties of interest, including the volume thermal expansion coefficient, isothermal bulk modulus and its first and second pressure derivatives, heat capacity at constant volume, entropy, Debye temperature, and Grüneisen parameter of LiF are predicted systematically. All the properties of LiF with the stable NaCl-type structure in the temperature range of 0-4900 K and the pressure up to 1000 GPa are summarized.

Magnetic Imaging: a New Tool for UK National Nuclear Security

NASA Astrophysics Data System (ADS)

Darrer, Brendan J.; Watson, Joe C.; Bartlett, Paul; Renzoni, Ferruccio

2015-01-01

Combating illicit trafficking of Special Nuclear Material may require the ability to image through electromagnetic shields. This is the case when the trafficking involves cargo containers. Thus, suitable detection techniques are required to penetrate a ferromagnetic enclosure. The present study considers techniques that employ an electromagnetic based principle of detection. It is generally assumed that a ferromagnetic metallic enclosure will effectively act as a Faraday cage to electromagnetic radiation and therefore screen any form of interrogating electromagnetic radiation from penetrating, thus denying the detection of any eventual hidden material. In contrast, we demonstrate that it is actually possible to capture magnetic images of a conductive object through a set of metallic ferromagnetic enclosures. This validates electromagnetic interrogation techniques as a potential detection tool for National Nuclear Security applications.

Magnetic Imaging: a New Tool for UK National Nuclear Security

PubMed Central

Darrer, Brendan J.; Watson, Joe C.; Bartlett, Paul; Renzoni, Ferruccio

2015-01-01

Combating illicit trafficking of Special Nuclear Material may require the ability to image through electromagnetic shields. This is the case when the trafficking involves cargo containers. Thus, suitable detection techniques are required to penetrate a ferromagnetic enclosure. The present study considers techniques that employ an electromagnetic based principle of detection. It is generally assumed that a ferromagnetic metallic enclosure will effectively act as a Faraday cage to electromagnetic radiation and therefore screen any form of interrogating electromagnetic radiation from penetrating, thus denying the detection of any eventual hidden material. In contrast, we demonstrate that it is actually possible to capture magnetic images of a conductive object through a set of metallic ferromagnetic enclosures. This validates electromagnetic interrogation techniques as a potential detection tool for National Nuclear Security applications. PMID:25608957

Electromagnetic thrusters for spacecraft prime propulsion

NASA Technical Reports Server (NTRS)

Rudolph, L. K.; King, D. Q.

1984-01-01

The benefits of electromagnetic propulsion systems for the next generation of US spacecraft are discussed. Attention is given to magnetoplasmadynamic (MPD) and arc jet thrusters, which form a subset of a larger group of electromagnetic propulsion systems including pulsed plasma thrusters, Hall accelerators, and electromagnetic launchers. Mission/system study results acquired over the last twenty years suggest that for future prime propulsion applications high-power self-field MPD thrusters and low-power arc jets have the greatest potential of all electromagnetic thruster systems. Some of the benefits they are expected to provide include major reductions in required launch mass compared to chemical propulsion systems (particularly in geostationary orbit transfer) and lower life-cycle costs (almost 50 percent less). Detailed schematic drawings are provided which describe some possible configurations for the various systems.

Magnetic imaging: a new tool for UK national nuclear security.

PubMed

Darrer, Brendan J; Watson, Joe C; Bartlett, Paul; Renzoni, Ferruccio

2015-01-22

Combating illicit trafficking of Special Nuclear Material may require the ability to image through electromagnetic shields. This is the case when the trafficking involves cargo containers. Thus, suitable detection techniques are required to penetrate a ferromagnetic enclosure. The present study considers techniques that employ an electromagnetic based principle of detection. It is generally assumed that a ferromagnetic metallic enclosure will effectively act as a Faraday cage to electromagnetic radiation and therefore screen any form of interrogating electromagnetic radiation from penetrating, thus denying the detection of any eventual hidden material. In contrast, we demonstrate that it is actually possible to capture magnetic images of a conductive object through a set of metallic ferromagnetic enclosures. This validates electromagnetic interrogation techniques as a potential detection tool for National Nuclear Security applications.

High Resolution, Low Altitude Aeromagnetic and Electromagnetic Survey of Mt Rainier

USGS Publications Warehouse

Rystrom, V.L.; Finn, C.; Deszcz-Pan, Maryla

2000-01-01

In October 1996, the USGS conducted a high resolution airborne magnetic and electromagnetic survey in order to discern through-going sections of exposed altered rocks and those obscured beneath snow, vegetation and surficial unaltered rocks. Hydrothermally altered rocks weaken volcanic edifices, creating the potential for catastrophic sector collapses and ensuing formation of destructive volcanic debris flows. This data once compiled and interpreted, will be used to examine the geophysical properties of the Mt. Rainier volcano, and help assist the USGS in its Volcanic Hazards Program and at its Cascades Volcano Observatory. Aeromagnetic and electromagnetic data provide a means for seeing through surficial layers and have been tools for delineating structures within volcanoes. However, previously acquired geophysical data were not useful for small-scale geologic mapping. In this report, we present the new aeromagnetic and electromagnetic data, compare results from previously obtained, low-resolution aeromagnetic data with new data collected at a low-altitude and closely spaced flightlines, and provide information on potential problems with using high-resolution data.

Quantum statistical mechanics of dense partially ionized hydrogen.

NASA Technical Reports Server (NTRS)

Dewitt, H. E.; Rogers, F. J.

1972-01-01

The theory of dense hydrogenic plasmas beginning with the two component quantum grand partition function is reviewed. It is shown that ionization equilibrium and molecular dissociation equilibrium can be treated in the same manner with proper consideration of all two-body states. A quantum perturbation expansion is used to give an accurate calculation of the equation of state of the gas for any degree of dissociation and ionization. In this theory, the effective interaction between any two charges is the dynamic screened potential obtained from the plasma dielectric function. We make the static approximation; and we carry out detailed numerical calculations with the bound and scattering states of the Debye potential, using the Beth-Uhlenbeck form of the quantum second virial coefficient. We compare our results with calculations from the Saha equation.

Measurement and mapping of the GSM-based electromagnetic pollution in the Black Sea region of Turkey.

PubMed

Tuysuz, Burak; Mahmutoglu, Yigit

2017-01-01

Electromagnetic pollution caused by mobile communication devices, a new form of environmental pollution, has been one of the most concerning problems to date. Consequences of long-term exposure to the electromagnetic radiation caused by cell phone towers are still unknown and can potentially be a new health hazard. It is important to measure, analyze and map the electromagnetic radiation levels periodically because of the potential risks. The electromagnetic pollution maps can be used for the detection of diseases caused by the radiation. With the help of the radiation maps of different regions, comparative analysis can be provided and distribution of the diseases can be investigated. In this article, Global System for Mobile communication (GSM)-based electromagnetic pollution map of the Rize Providence, which has high cancer rates because of the Chernobyl nuclear explosion, is generated. First, locations of the GSM base stations are identified and according to the antenna types of the base stations, safety distances are determined. Subsequently, 155 measurements are taken during November 2014 from the nearest living quarters of the Rize city center in Turkey. The measurements are then assessed statistically. Thenceforth, for visual judgment of the determined statistics, collected measurements are presented on the map. It is observed that national limits are not exceeded, but it is also discovered that the safety distance is waived at some of the measurement points and above the average radiation levels are noted. Even if the national limits are not exceeded, the long-term effects of the exposition to the electromagnetic radiation can cause serious health problems.

Simulation of plasma double-layer structures

NASA Technical Reports Server (NTRS)

Borovsky, J. E.; Joyce, G.

1982-01-01

Electrostatic plasma double layers are numerically simulated by means of a magnetized 2 1/2 dimensional particle in cell method. The investigation of planar double layers indicates that these one dimensional potential structures are susceptible to periodic disruption by instabilities in the low potential plasmas. Only a slight increase in the double layer thickness with an increase in its obliqueness to the magnetic field is observed. Weak magnetization results in the double layer electric field alignment of accelerated particles and strong magnetization results in their magnetic field alignment. The numerical simulations of spatially periodic two dimensional double layers also exhibit cyclical instability. A morphological invariance in two dimensional double layers with respect to the degree of magnetization implies that the potential structures scale with Debye lengths rather than with gyroradii. Electron beam excited electrostatic electron cyclotron waves and (ion beam driven) solitary waves are present in the plasmas adjacent to the double layers.

Numerical solution of a multi-ion one-potential model for electroosmotic flow in two-dimensional rectangular microchannels.

PubMed

Van Theemsche, Achim; Deconinck, Johan; Van den Bossche, Bart; Bortels, Leslie

2002-10-01

A new more general numerical model for the simulation of electrokinetic flow in rectangular microchannels is presented. The model is based on the dilute solution model and the Navier-Stokes equations and has been implemented in a finite-element-based C++ code. The model includes the ion distribution in the Helmholtz double layer and considers only one single electrical' potential field variable throughout the domain. On a charged surface(s) the surface charge density, which is proportional to the local electrical field, is imposed. The zeta potential results, then, from this boundary condition and depends on concentrations, temperature, ion valence, molecular diffusion coefficients, and geometric conditions. Validation cases show that the model predicts accurately known analytical results, also for geometries having dimensions comparable to the Debye length. As a final study, the electro-osmotic flow in a controlled cross channel is investigated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, S.; Saha, J. K.; Chandra, R.

The Rayleigh-Ritz variational technique with a Hylleraas basis set is being tested for the first time to estimate the structural modifications of a lithium atom embedded in a weakly coupled plasma environment. The Debye-Huckel potential is used to mimic the weakly coupled plasma environment. The wave functions for both the helium-like lithium ion and the lithium atom are expanded in the explicitly correlated Hylleraas type basis set which fully takes care of the electron-electron correlation effect. Due to the continuum lowering under plasma environment, the ionization potential of the system gradually decreases leading to the destabilization of the atom. Themore » excited states destabilize at a lower value of the plasma density. The estimated ionization potential agrees fairly well with the few available theoretical estimates. The variation of one and two particle moments, dielectric susceptibility and magnetic shielding constant, with respect to plasma density is also been discussed in detail.« less

Electromagnetic information transfer through aqueous system.

PubMed

Foletti, Alberto; Ledda, Mario; Lolli, Maria Grazia; Grimaldi, Settimio; Lisi, Antonella

2017-01-01

Several beneficial effects of the electromagnetic information transfer through aqueous system (EMITTAS) procedure have previously been reported in vitro. The clinical potential of this procedure has also started to be evaluated. Information flow in biological systems can be investigated through chemical and molecular approaches or by a biophysical approach focused on endogenous electrodynamic activities. Electromagnetic signals are endogenously generated at different levels of the biological organization and, likely, play an active role in synchronizing internal cell function or local/systemic adaptive response. Consequently, each adaptive response can be described by its specific electromagnetic pattern and, therefore, correlates with a unique and specific electromagnetic signature. A biophysical procedure synchronously integrating the EMITTAS procedure has already been applied for the treatment of articular pain, low-back pain, neck pain and mobility, fluctuating asymmetry, early-stage chronic kidney disease, refractory gynecological infections, minor anxiety and depression disorders. This clinical strategy involves a single treatment, since the EMITTAS procedure allows the patient to continue his/her own personal treatment at home by means of self-administration of the recorded aqueous system. A significant and long-lasting improvement has been reported, showing a potential beneficial use of this biophysical procedure in the management of common illnesses in an efficient, effective and personalized way. Data from recent studies suggest that aqueous systems may play a key role in providing the basis for recording, storing, transferring and retrieving clinically effective quanta of biological information. These features likely enable to trigger local and systemic self-regulation and self-regeneration potential of the organism.

Three dimensional α-tunneling in intense laser fields

NASA Astrophysics Data System (ADS)

Kis, Daniel P.; Szilvasi, Reka

2018-04-01

The width and life-time of the quasibound state of the α cluster in intense monochromatic electromagnetic (laser) field are discussed in details. The laser modified three dimensional potential barrier felt by the α particle is investigated analytically in long wave approximation and zero-order approximations with some different nuclear models: Coulomb potential with rectangular well, and with Woods-Saxon type potential. We show that the circularly polarized electromagnetic field and the special parameters of the nuclear potentials determine an enhancement of the decay probability, so the life-time of the quasibound state decreases in few times compared to the case of free field.

Kohn-Sham approach to quantum electrodynamical density-functional theory: Exact time-dependent effective potentials in real space.

PubMed

Flick, Johannes; Ruggenthaler, Michael; Appel, Heiko; Rubio, Angel

2015-12-15

The density-functional approach to quantum electrodynamics extends traditional density-functional theory and opens the possibility to describe electron-photon interactions in terms of effective Kohn-Sham potentials. In this work, we numerically construct the exact electron-photon Kohn-Sham potentials for a prototype system that consists of a trapped electron coupled to a quantized electromagnetic mode in an optical high-Q cavity. Although the effective current that acts on the photons is known explicitly, the exact effective potential that describes the forces exerted by the photons on the electrons is obtained from a fixed-point inversion scheme. This procedure allows us to uncover important beyond-mean-field features of the effective potential that mark the breakdown of classical light-matter interactions. We observe peak and step structures in the effective potentials, which can be attributed solely to the quantum nature of light; i.e., they are real-space signatures of the photons. Our findings show how the ubiquitous dipole interaction with a classical electromagnetic field has to be modified in real space to take the quantum nature of the electromagnetic field fully into account.

Key Technologies and Applications of Gas Drainage in Underground Coal Mine

NASA Astrophysics Data System (ADS)

Zhou, Bo; Xue, Sheng; Cheng, Jiansheng; Li, Wenquan; Xiao, Jiaping

2018-02-01

It is the basis for the long-drilling directional drilling, precise control of the drilling trajectory and ensuring the effective extension of the drilling trajectory in the target layer. The technology can be used to complete the multi-branch hole construction and increase the effective extraction distance of the coal seam. The gas drainage and the bottom grouting reinforcement in the advanced area are realized, and the geological structure of the coal seam can be proved accurately. It is the main technical scheme for the efficient drainage of gas at home and abroad, and it is applied to the field of geological structure exploration and water exploration and other areas. At present, the data transmission method is relatively mature in the technology and application, including the mud pulse and the electromagnetic wave. Compared with the mud pulse transmission mode, the electromagnetic wave transmission mode has obvious potential in the data transmission rate and drilling fluid, and it is suitable for the coal mine. In this paper, the key technologies of the electromagnetic wave transmission mode are analyzed, including the attenuation characteristics of the electromagnetic transmission channel, the digital modulation scheme, the channel coding method and the weak signal processing technology. A coal mine under the electromagnetic wave drilling prototype is developed, and the ground transmission experiments and down hole transmission test are carried out. The main work includes the following aspects. First, the equivalent transmission line method is used to establish the electromagnetic transmission channel model of coal mine drilling while drilling, and the attenuation of the electromagnetic signal is measured when the electromagnetic channel measured. Second, the coal mine EM-MWD digital modulation method is developed. Third, the optimal linear block code which suitable for EM-MWD communication channel in coal mine is proposed. Fourth, the noise characteristics of well near horizontal directional drilling are analyzed, and the multi-stage filter method is proposed to suppress the natural potential and strong frequency interference signal. And the weak electromagnetic communication signal is extracted from the received signal. Finally, the detailed design of the electromagnetic wave while drilling is given.

The influence of electromagnetic pollution on living organisms: historical trends and forecasting changes.

PubMed

Redlarski, Grzegorz; Lewczuk, Bogdan; Żak, Arkadiusz; Koncicki, Andrzej; Krawczuk, Marek; Piechocki, Janusz; Jakubiuk, Kazimierz; Tojza, Piotr; Jaworski, Jacek; Ambroziak, Dominik; Skarbek, Łukasz; Gradolewski, Dawid

2015-01-01

Current technologies have become a source of omnipresent electromagnetic pollution from generated electromagnetic fields and resulting electromagnetic radiation. In many cases this pollution is much stronger than any natural sources of electromagnetic fields or radiation. The harm caused by this pollution is still open to question since there is no clear and definitive evidence of its negative influence on humans. This is despite the fact that extremely low frequency electromagnetic fields were classified as potentially carcinogenic. For these reasons, in recent decades a significant growth can be observed in scientific research in order to understand the influence of electromagnetic radiation on living organisms. However, for this type of research the appropriate selection of relevant model organisms is of great importance. It should be noted here that the great majority of scientific research papers published in this field concerned various tests performed on mammals, practically neglecting lower organisms. In that context the objective of this paper is to systematise our knowledge in this area, in which the influence of electromagnetic radiation on lower organisms was investigated, including bacteria, E. coli and B. subtilis, nematode, Caenorhabditis elegans, land snail, Helix pomatia, common fruit fly, Drosophila melanogaster, and clawed frog, Xenopus laevis.

The Influence of Electromagnetic Pollution on Living Organisms: Historical Trends and Forecasting Changes

PubMed Central

Żak, Arkadiusz; Koncicki, Andrzej; Piechocki, Janusz; Jakubiuk, Kazimierz; Tojza, Piotr; Jaworski, Jacek; Ambroziak, Dominik; Skarbek, Łukasz

2015-01-01

Current technologies have become a source of omnipresent electromagnetic pollution from generated electromagnetic fields and resulting electromagnetic radiation. In many cases this pollution is much stronger than any natural sources of electromagnetic fields or radiation. The harm caused by this pollution is still open to question since there is no clear and definitive evidence of its negative influence on humans. This is despite the fact that extremely low frequency electromagnetic fields were classified as potentially carcinogenic. For these reasons, in recent decades a significant growth can be observed in scientific research in order to understand the influence of electromagnetic radiation on living organisms. However, for this type of research the appropriate selection of relevant model organisms is of great importance. It should be noted here that the great majority of scientific research papers published in this field concerned various tests performed on mammals, practically neglecting lower organisms. In that context the objective of this paper is to systematise our knowledge in this area, in which the influence of electromagnetic radiation on lower organisms was investigated, including bacteria, E. coli and B. subtilis, nematode, Caenorhabditis elegans, land snail, Helix pomatia, common fruit fly, Drosophila melanogaster, and clawed frog, Xenopus laevis. PMID:25811025

Measurement and Analysis of L-Band (1535-1660 MHz) Electromagnetic (EM) Noise on Ships

DOT National Transportation Integrated Search

1974-12-01

A program of L-band (1535-1660 MHz) electromagnetic (EM) noise measurements conducted on ships is described. The magnitude and duration of EM noise on ships is of particular significance in terms of potential radio frequency interference (RFI) to fut...

Electromagnetic Propulsion

NASA Technical Reports Server (NTRS)

Schafer, Charles

2000-01-01

The design and development of an Electromagnetic Propulsion is discussed. Specific Electromagnetic Propulsion Topics discussed include: (1) Technology for Pulse Inductive Thruster (PIT), to design, develop, and test of a multirepetition rate pulsed inductive thruster, Solid-State Switch Technology, and Pulse Driver Network and Architecture; (2) Flight Weight Magnet Survey, to determine/develop light weight high performance magnetic materials for potential application Advanced Space Flight Systems as these systems develop; and (3) Magnetic Flux Compression, to enable rapid/robust/reliable omni-planetary space transportation within realistic development and operational costs constraints.

The electromagnetic spectrum: current and future applications in oncology.

PubMed

Allison, Ron R

2013-05-01

The electromagnetic spectrum is composed of waves of various energies that interact with matter. When focused upon and directed at tumors, these energy sources can be employed as a means of lesion ablation. While the use of x-rays is widely known in this regard, a growing body of evidence shows that other members of this family can also achieve oncologic success. This article will review therapeutic application of the electromagnetic spectrum in current interventions and potential future applications.

A novel model of interaction between high frequency electromagnetic non-ionizing fields and microtubules viewed as coupled two-degrees of freedom harmonic oscillators.

PubMed

Caligiuri, Luigi Maxmilian

2015-01-01

The question regarding the potential biological and adverse health effects of non-ionizing electromagnetic fields on living organisms is of primary importance in biophysics and medicine. Despite the several experimental evidences showing such occurrence in a wide frequency range from extremely low frequency to microwaves, a definitive theoretical model able to explain a possible mechanism of interaction between electromagnetic fields and living matter, especially in the case of weak and very weak intensities, is still missing. In this paper it has been suggested a possible mechanism of interaction involving the resonant absorption of electromagnetic radiation by microtubules. To this aim these have been modeled as non-dissipative forced harmonic oscillators characterized by two coupled "macroscopic" degrees of freedom, respectively describing longitudinal and transversal vibrations induced by the electromagnetic field. We have shown that the proposed model, although at a preliminary stage, is able to explain the ability of even weak electromagnetic radiating electromagnetic fields to transfer high quantities of energy to living systems by means of a resonant mechanism, so capable to easily damage microtubules structure.

The Dirac equation in Schwarzschild black hole coupled to a stationary electromagnetic field

NASA Astrophysics Data System (ADS)

Al-Badawi, A.; Owaidat, M. Q.

2017-08-01

We study the Dirac equation in a spacetime that represents the nonlinear superposition of the Schwarzschild solution to an external, stationary electromagnetic field. The set of equations representing the uncharged Dirac particle in the Newman-Penrose formalism is decoupled into a radial and an angular parts. We obtain exact analytical solutions of the angular equations. We manage to obtain the radial wave equations with effective potentials. Finally, we study the potentials by plotting them as a function of radial distance and examine the effect of the twisting parameter and the frequencies on the potentials.

Energy deposition of heavy ions in the regime of strong beam-plasma correlations.

PubMed

Gericke, D O; Schlanges, M

2003-03-01

The energy loss of highly charged ions in dense plasmas is investigated. The applied model includes strong beam-plasma correlation via a quantum T-matrix treatment of the cross sections. Dynamic screening effects are modeled by using a Debye-like potential with a velocity dependent screening length that guarantees the known low and high beam velocity limits. It is shown that this phenomenological model is in good agreement with simulation data up to very high beam-plasma coupling. An analysis of the stopping process shows considerably longer ranges and a less localized energy deposition if strong coupling is treated properly.

Tight focusing of radially polarized circular Airy vortex beams

NASA Astrophysics Data System (ADS)

Chen, Musheng; Huang, Sujuan; Shao, Wei

2017-11-01

Tight focusing properties of radially polarized circular Airy vortex beams (CAVB) are studied numerically. The light field expressions for the focused fields are derived based on vectorial Debye theory. We also study the relationship between focal profiles, such as light intensity distribution, radius of focal spot and focal length, and the parameters of CAVB. Numerical results demonstrate that we can generate a radially polarized CAVB with super-long focal length, super-strong longitudinal intensity or subwavelength focused spot at the focal plane by properly choosing the parameters of incident light and high numerical aperture (NA) lens. These results have potential applications for optical trapping, optical storage and particle acceleration.

Electron transfer in proton-hydrogen collisions under dense quantum plasma

NASA Astrophysics Data System (ADS)

Nayek, Sujay; Bhattacharya, Arka; Kamali, Mohd Zahurin Mohamed; Ghoshal, Arijit; Ratnavelu, Kurunathan

2017-09-01

The effects of dense quantum plasma on 1 s → nlm charge transfer, for arbitrary n,l,m, in proton-hydrogen collisions have been studied by employing a distorted wave approximation. The interactions among the charged particles in the plasma have been represented by modified Debye-Huckel potentials. A detailed study has been made to explore the effects of background plasma environment on the differential and total cross sections for electron capture into different angular momentum states for the incident energy in the range 10-1000 keV. For the unscreened case, our results agree well with some of the most accurate results available in the literature.

The first principles study of elastic and thermodynamic properties of ZnSe

NASA Astrophysics Data System (ADS)

Khatta, Swati; Kaur, Veerpal; Tripathi, S. K.; Prakash, Satya

2018-05-01

The elastic and thermodynamic properties of ZnSe are investigated using thermo_pw package implemented in Quantum espresso code within the framework of density functional theory. The pseudopotential method within the local density approximation is used for the exchange-correlation potential. The physical parameters of ZnSe bulk modulus and shear modulus, anisotropy factor, Young's modulus, Poisson's ratio, Pugh's ratio and Frantsevich's ratio are calculated. The sound velocity and Debye temperature are obtained from elastic constant calculations. The Helmholtz free energy and internal energy of ZnSe are also calculated. The results are compared with available theoretical calculations and experimental data.

Thermo physical Properties of Multiferroic Rare Earth Manganite GdMnO3

NASA Astrophysics Data System (ADS)

Choithrani, Renu; Gaur, N. K.

2008-04-01

We have investigated the thermophysical properties of multiferroic rare earth manganite GdMnO3 in the temperature range 15 K⩽T⩽300 K. We have applied interatomic potential to study the Specific heat (C) as a function of temperature. The calculated Specific heat values are closer to the available experimental data. At room temperature, the orthorhombic GdMnO3 phase is indicative of a strong Jahn-Teller distortion. In addition, we have reported the cohesive energy (φ), molecular force constant (f), compressibility (β), Restrahalen frequency (ν0), Debye temperature (ΘD) and Groneisen parameter (γ) at temperature 15 K⩽T⩽300 K.

New electromagnetic mode in graphene.

PubMed

Mikhailov, S A; Ziegler, K

2007-07-06

A new, weakly damped, transverse electromagnetic mode is predicted in graphene. The mode frequency omega lies in the window 1.667<[see text]omega/micro < 2, where micro is the chemical potential, and can be tuned from radio waves to the infrared by changing the density of charge carriers through a gate voltage.

Spectral lines behavior of Be I and Na I isoelectronic sequence in Debye plasma environment

NASA Astrophysics Data System (ADS)

Chaudhuri, Rajat K.; Chattopadhyay, Sudip; Sinha Mahapatra, Uttam

2012-08-01

We report the plasma screening effect on the first ionization potential (IP) and [He]2s2(1S0)→[He]2s2p /2s3p allowed (P11) and inter-combination transitions (P31) in some selected Be-like ions. In addition, we investigate the spectral properties of [Ne]3s (2S1/2)→[Ne]np(2P1/2 and P23/2 for n = 3, 4) transitions in Ca X and Fe XVI ions (Na I isoelectronic sequence) and [He]3s(2S1/2)→[He]np(2P1/2 and P23/2 for n = 2, 3) transitions in Li, B II, and N IV (Li I isoelectronic sequence) under plasma environment. The state-of-the-art relativistic coupled cluster calculations using the Debye model of plasma for electron-nucleus interaction show that (a) the ionization potential decreases sharply with increasing plasma strength and (b) the gap between the [He]2s2(1S0)→[He]2s2p(1,3P1) energy levels increases with increasing plasma potential and nuclear charge. It is found that the [He]2s2 (1S0)→2s3p(1,3P1) transition energy decreases uniformly with increasing plasma potential and nuclear charge. In other words, the spectral lines associated with 2s-2p (i.e., Δn=0, where n corresponds to principle quantum number) transitions in Be I isoelectronic sequence exhibit a blue-shift (except for Be I, B II, and the lowest inter-combination line in C III, which exhibit a red-shift), whereas those associated with 2s-3p (i.e., Δn≠0) transitions are red-shifted. Similar trend is observed in Li I and Na I isoelectronic sequences, where spectral lines associated with Δn=0 (Δn≠0) are blue-shifted (red-shifted). The effect of Coulomb screening on the spectral lines of ions subjected to plasma is also addressed.

Electromagnetic micropores: fabrication and operation.

PubMed

Basore, Joseph R; Lavrik, Nickolay V; Baker, Lane A

2010-12-21

We describe the fabrication and characterization of electromagnetic micropores. These devices consist of a micropore encompassed by a microelectromagnetic trap. Fabrication of the device involves multiple photolithographic steps, combined with deep reactive ion etching and subsequent insulation steps. When immersed in an electrolyte solution, application of a constant potential across the micropore results in an ionic current. Energizing the electromagnetic trap surrounding the micropore produces regions of high magnetic field gradients in the vicinity of the micropore that can direct motion of a ferrofluid onto or off of the micropore. This results in dynamic gating of the ion current through the micropore structure. In this report, we detail fabrication and characterize the electrical and ionic properties of the prepared electromagnetic micropores.

Electromagnetic Radiation Disturbed the Photosynthesis of Microcystis aeruginosa at the Proteomics Level.

PubMed

Tang, Chao; Yang, Chuanjun; Yu, Hui; Tian, Shen; Huang, Xiaomei; Wang, Weiyi; Cai, Peng

2018-01-11

Photosynthesis of Microcystis aeruginosa under Electromagnetic Radiation (1.8 GHz, 40 V/m) was studied by using the proteomics. A total of 30 differentially expressed proteins, including 15 up-regulated and 15 down-regulated proteins, were obtained in this study. The differentially expressed proteins were significantly enriched in the photosynthesis pathway, in which the protein expression levels of photosystems II cytochrome b559 α subunit, cytochrome C550, PsbY, and F-type ATP synthase (a, b) decreased. Our results indicated that electromagnetic radiation altered the photosynthesis-related protein expression levels, and aimed at the function of photosynthetic pigments, photosystems II potential activity, photosynthetic electron transport process, and photosynthetic phosphorylation process of M. aeruginosa. Based on the above evidence, that photoreaction system may be deduced as a target of electromagnetic radiation on the photosynthesis in cyanobacteria; the photoreaction system of cyanobacteria is a hypothetical "shared target effector" that responds to light and electromagnetic radiation; moreover, electromagnetic radiation does not act on the functional proteins themselves but their expression processes.

Acute effects of electromagnetic stimulation of the brain on cortical activity, cortical blood flow, blood pressure and heart rate in the cat: an evaluation of safety.

PubMed Central

Eyre, J A; Flecknell, P A; Kenyon, B R; Koh, T H; Miller, S

1990-01-01

The influence of repeated high intensity electromagnetic stimulation of the brain on cortical activity, cortical blood flow, blood pressure and heart rate has been investigated in the cat, to evaluate the safety of the method. The observations have been made in preparations under propofol anaesthesia before, during and after periods of anoxia. Electromagnetic stimulation of the brain evoked activity in descending motor pathways and was recorded by activity in the median nerve and by muscle twitches. Following repeated series of high intensity stimulation there were no systematic changes in somatosensory evoked potentials or background EEG, nor were there signs of epileptogenic activity during electromagnetic stimulation, before, during or after periods of anoxia. No systematic changes in cortical blood flow, blood pressure or heart rate were observed during electromagnetic stimulation, before or after periods of anoxia. In conclusion, no acute adverse consequences following electromagnetic stimulation in the normal and anoxic cat brain were demonstrated. PMID:2380732

Synthetic electromagnetic knot in a three-dimensional skyrmion

PubMed Central

Lee, Wonjae; Gheorghe, Andrei H.; Tiurev, Konstantin; Ollikainen, Tuomas; Möttönen, Mikko; Hall, David S.

2018-01-01

Classical electromagnetism and quantum mechanics are both central to the modern understanding of the physical world and its ongoing technological development. Quantum simulations of electromagnetic forces have the potential to provide information about materials and systems that do not have conveniently solvable theoretical descriptions, such as those related to quantum Hall physics, or that have not been physically observed, such as magnetic monopoles. However, quantum simulations that simultaneously implement all of the principal features of classical electromagnetism have thus far proved elusive. We experimentally realize a simulation in which a charged quantum particle interacts with the knotted electromagnetic fields peculiar to a topological model of ball lightning. These phenomena are induced by precise spatiotemporal control of the spin field of an atomic Bose-Einstein condensate, simultaneously creating a Shankar skyrmion—a topological excitation that was theoretically predicted four decades ago but never before observed experimentally. Our results reveal the versatile capabilities of synthetic electromagnetism and provide the first experimental images of topological three-dimensional skyrmions in a quantum system. PMID:29511735

Electromagnetic tracking of motion in the proximity of computer generated graphical stimuli: a tutorial.

PubMed

Schnabel, Ulf H; Hegenloh, Michael; Müller, Hermann J; Zehetleitner, Michael

2013-09-01

Electromagnetic motion-tracking systems have the advantage of capturing the tempo-spatial kinematics of movements independently of the visibility of the sensors. However, they are limited in that they cannot be used in the proximity of electromagnetic field sources, such as computer monitors. This prevents exploiting the tracking potential of the sensor system together with that of computer-generated visual stimulation. Here we present a solution for presenting computer-generated visual stimulation that does not distort the electromagnetic field required for precise motion tracking, by means of a back projection medium. In one experiment, we verify that cathode ray tube monitors, as well as thin-film-transistor monitors, distort electro-magnetic sensor signals even at a distance of 18 cm. Our back projection medium, by contrast, leads to no distortion of the motion-tracking signals even when the sensor is touching the medium. This novel solution permits combining the advantages of electromagnetic motion tracking with computer-generated visual stimulation.

A Surrogate for Debye-Waller Factors from Dynamic Stokes Shifts

PubMed Central

Zhong, Qin; Johnson, Jerainne; Aamer, Khaled A.; Tyagi, Madhusudan

2011-01-01

We show that the short-time behavior of time-resolved fluorescence Stokes shifts (TRSS) are similar to that of the intermediate scattering function obtained from neutron scattering at q near the peak in the static structure factor for glycerol. This allows us to extract a Debye-Waller (DW) factor analog from TRSS data at times as short as 1 ps in a relatively simple way. Using the time-domain relaxation data obtained by this method we show that DW factors evaluated at times ≥ 40 ps can be directly influenced by α relaxation and thus should be used with caution when evaluating relationships between fast and slow dynamics in glassforming systems. PMID:21701673

Nanostructured Drugs Embedded into a Polymeric Matrix: Vinpocetine/PVP Hybrids Investigated by Debye Function Analysis.

PubMed

Hasa, Dritan; Giacobbe, Carlotta; Perissutti, Beatrice; Voinovich, Dario; Grassi, Mario; Cervellino, Antonio; Masciocchi, Norberto; Guagliardi, Antonietta

2016-09-06

Microcrystalline vinpocetine, coground with cross-linked polyvinylpyrrolidone, affords hybrids containing nanosized drug nanocrystals, the size and size distributions of which depend on milling times and drug-to-polymer weight ratios. Using an innovative approach to microstructural characterization, we analyzed wide-angle X-ray total scattering data by the Debye function analysis and demonstrated the possibility to characterize pharmaceutical solid dispersions obtaining a reliable quantitative view of the physicochemical status of the drug dispersed in an amorphous carrier. The microstructural properties derived therefrom have been successfully employed in reconciling the enigmatic difference in behavior between in vitro and in vivo solubility tests performed on nanosized vinpocetine embedded in a polymeric matrix.

Optical equivalence of isotropic ensembles of ellipsoidal particles in the Rayleigh-Gans-Debye and anomalous diffraction approximations and its consequences

NASA Astrophysics Data System (ADS)

Paramonov, L. E.

2012-05-01

Light scattering by isotropic ensembles of ellipsoidal particles is considered in the Rayleigh-Gans-Debye approximation. It is proved that randomly oriented ellipsoidal particles are optically equivalent to polydisperse randomly oriented spheroidal particles and polydisperse spherical particles. Density functions of the shape and size distributions for equivalent ensembles of spheroidal and spherical particles are presented. In the anomalous diffraction approximation, equivalent ensembles of particles are shown to also have equal extinction, scattering, and absorption coefficients. Consequences of optical equivalence are considered. The results are illustrated by numerical calculations of the angular dependence of the scattering phase function using the T-matrix method and the Mie theory.

Order-disorder effects on the elastic properties of CuMPt6 (M=Cr and Co) compounds

NASA Astrophysics Data System (ADS)

Huang, Shuo; Li, Rui-Zi; Qi, San-Tao; Chen, Bao; Shen, Jiang

2014-04-01

The elastic properties of CuMPt6 (M=Cr and Co) in disordered face-centered cubic (fcc) structure and ordered Cu3Au-type structure are studied with lattice inversion embedded-atom method. The calculated lattice constant and Debye temperature agree quite well with the comparable experimental data. The obtained formation enthalpy demonstrates that the Cu3Au-type structure is energetically more favorable. Numerical estimates of the elastic constants, bulk/shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy, and Debye temperature for both compounds are performed, and the results suggest that the disordered fcc structure is much softer than the ordered Cu3Au-type structure.

Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential

NASA Astrophysics Data System (ADS)

Darian, D.; Marholm, S.; Paulsson, J. J. P.; Miyake, Y.; Usui, H.; Mortensen, M.; Miloch, W. J.

2017-09-01

The charging of a sounding rocket in subsonic and supersonic plasma flows with external magnetic field is studied with numerical particle-in-cell (PIC) simulations. A weakly magnetized plasma regime is considered that corresponds to the ionospheric F2 layer, with electrons being strongly magnetized, while the magnetization of ions is weak. It is demonstrated that the magnetic field orientation influences the floating potential of the rocket and that with increasing angle between the rocket axis and the magnetic field direction the rocket potential becomes less negative. External magnetic field gives rise to asymmetric wake downstream of the rocket. The simulated wake in the potential and density may extend as far as 30 electron Debye lengths; thus, it is important to account for these plasma perturbations when analyzing in situ measurements. A qualitative agreement between simulation results and the actual measurements with a sounding rocket is also shown.

Dependent scattering and absorption by densely packed discrete spherical particles: Effects of complex refractive index

NASA Astrophysics Data System (ADS)

Ma, L. X.; Tan, J. Y.; Zhao, J. M.; Wang, F. Q.; Wang, C. A.; Wang, Y. Y.

2017-07-01

Due to the dependent scattering and absorption effects, the radiative transfer equation (RTE) may not be suitable for dealing with radiative transfer in dense discrete random media. This paper continues previous research on multiple and dependent scattering in densely packed discrete particle systems, and puts emphasis on the effects of particle complex refractive index. The Mueller matrix elements of the scattering system with different complex refractive indexes are obtained by both electromagnetic method and radiative transfer method. The Maxwell equations are directly solved based on the superposition T-matrix method, while the RTE is solved by the Monte Carlo method combined with the hard sphere model in the Percus-Yevick approximation (HSPYA) to consider the dependent scattering effects. The results show that for densely packed discrete random media composed of medium size parameter particles (equals 6.964 in this study), the demarcation line between independent and dependent scattering has remarkable connections with the particle complex refractive index. With the particle volume fraction increase to a certain value, densely packed discrete particles with higher refractive index contrasts between the particles and host medium and higher particle absorption indexes are more likely to show stronger dependent characteristics. Due to the failure of the extended Rayleigh-Debye scattering condition, the HSPYA has weak effect on the dependent scattering correction at large phase shift parameters.

Full-field drift Hamiltonian particle orbits in 3D geometry

NASA Astrophysics Data System (ADS)

Cooper, W. A.; Graves, J. P.; Brunner, S.; Isaev, M. Yu

2011-02-01

A Hamiltonian/Lagrangian theory to describe guiding centre orbit drift motion which is canonical in the Boozer coordinate frame has been extended to include full electromagnetic perturbed fields in anisotropic pressure 3D equilibria with nested magnetic flux surfaces. A redefinition of the guiding centre velocity to eliminate the motion due to finite equilibrium radial magnetic fields and the choice of a gauge condition that sets the radial component of the electromagnetic vector potential to zero are invoked to guarantee that the Boozer angular coordinates retain the canonical structure. The canonical momenta are identified and the guiding centre particle radial drift motion and parallel gyroradius evolution are derived. The particle coordinate position is linearly modified by wave-particle interactions. All the nonlinear wave-wave interactions appear explicitly only in the evolution of the parallel gyroradius. The radial variation of the electrostatic potential is related to the binormal component of the displacement vector for MHD-type perturbations. The electromagnetic vector potential projections can then be determined from the electrostatic potential and the radial component of the MHD displacement vector.

Electromagnetic potentials basis for energy density and power flux

NASA Astrophysics Data System (ADS)

Puthoff, H. E.

2016-09-01

In rounding out the education of students in advanced courses in applied electromagnetics it is incumbent on us as mentors to raise issues that encourage appreciation of certain subtle aspects that are often overlooked during first exposure to the field. One of these has to do with the interplay between fields and potentials, with the latter often seen as just a convenient mathematical artifice useful in solving Maxwell’s equations. Nonetheless, to those practiced in application it is well understood that various alternatives in the use of fields and potentials are available within electromagnetic (EM) theory for the definitions of energy density, momentum transfer, EM stress-energy tensor, and so forth. Although the various options are all compatible with the basic equations of electrodynamics (e.g., Maxwell’s equations, Lorentz force law, gauge invariance), nonetheless certain alternative formulations lend themselves to being seen as preferable to others with regard to the transparency of their application to physical problems of interest. Here we argue for the transparency of an energy density/power flux option based on the EM potentials alone.

Angular momentum and torque described with the complex octonion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weng, Zi-Hua, E-mail: xmuwzh@xmu.edu.cn

2014-08-15

The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of electromagnetic field andmore » of gravitational field can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic) dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory.« less

Effect of 935-MHz phone-simulating electromagnetic radiation on endometrial glandular cells during mouse embryo implantation.

PubMed

Liu, Wenhui; Zheng, Xinmin; Qu, Zaiqing; Zhang, Ming; Zhou, Chun; Ma, Ling; Zhang, Yuanzhen

2012-10-01

This study examined the impact of 935MHz phone-simulating electromagnetic radiation on embryo implantation of pregnant mice. Each 7-week-old Kunming (KM) female white mouse was set up with a KM male mouse in a single cage for mating overnight after induction of ovulation. In the first three days of pregnancy, the pregnant mice was exposed to electromagnetic radiation at low-intensity (150 μW/cm(2), ranging from 130 to 200 μW/cm(2), for 2- or 4-h exposure every day), mid-intensity (570 μW/cm(2), ranging from 400 to 700 μW/cm(2), for 2- or 4-h exposure every day) or high-intensity (1400 μW/cm(2), ranging from 1200 to 1500 μW/cm(2), for 2- or 4-h exposure every day), respectively. On the day 4 after gestation (known as the window of murine embryo implantation), the endometrium was collected and the suspension of endometrial glandular cells was made. Laser scanning microscopy was employed to detect the mitochondrial membrane potential and intracellular calcium ion concentration. In high-intensity, 2- and 4-h groups, mitochondrial membrane potential of endometrial glandular cells was significantly lower than that in the normal control group (P<0.05). The calcium ion concentration was increased in low-intensity 2-h group but decreased in high-intensity 4-h group as compared with the normal control group (P<0.05). However, no significant difference was found in mitochondrial membrane potential of endometrial glandular cells between low- or mid-intensity groups and the normal control group, indicating stronger intensity of the electromagnetic radiation and longer length of the radiation are required to inflict a remarkable functional and structural damage to mitochondrial membrane. Our data demonstrated that electromagnetic radiation with a 935-MHz phone for 4 h conspicuously decreased mitochondrial membrane potential and lowered the calcium ion concentration of endometrial glandular cells. It is suggested that high-intensity electromagnetic radiation is very likely to induce the death of embryonic cells and decrease the chance of their implantation, thereby posing a high risk to pregnancy.

Investigate the electrical and thermal properties of the low temperature resistant silver nanowire fabricated by two-beam laser technique

NASA Astrophysics Data System (ADS)

He, Gui-Cang; Dong, Xian-Zi; Liu, Jie; Lu, Heng; Zhao, Zhen-Sheng

2018-05-01

A two-beam laser fabrication technique is introduced to fabricate the single silver nanowire (AgNW) on polyethylene terephthalate (PET) substrate. The resistivity of the AgNW is (1.31 ± 0.05) × 10-7 Ω·m, which is about 8 times of the bulk silver resistivity (1.65 × 10-8 Ω·m). The AgNW electrical resistance is measured in temperature range of 10-300 K and fitted with the Bloch-Grüneisen formula. The fitting results show that the residue resistance is 153 Ω, the Debye temperature is 210 K and the electron-phonon coupling constant is (5.72 ± 0.24) × 10-8 Ω·m. Due to the surface scattering, the Debye temperature and the electron-phonon coupling constant are lower than those of bulk silver, and the residue resistance is bigger than that of bulk silver. Thermal conductivity of the single AgNW is calculated in the corresponding temperature range, which is the biggest at the temperature approaching the Debye temperature. The AgNW on PET substrate is the low temperature resistance material and is able to be operated stably at such a low temperature of 10 K.

Nonlinear effects on electrophoresis of a charged dielectric nanoparticle in a charged hydrogel medium

NASA Astrophysics Data System (ADS)

Bhattacharyya, S.; De, Simanta

2016-09-01

The impact of the solid polarization of a charged dielectric particle in gel electrophoresis is studied without imposing a weak-field or a thin Debye length assumption. The electric polarization of a dielectric particle due to an external electric field creates a non-uniform surface charge density, which in turn creates a non-uniform Debye layer at the solid-gel interface. The solid polarization of the particle, the polarization of the double layer, and the electro-osmosis of mobile ions within the hydrogel medium create a nonlinear effect on the electrophoresis. We have incorporated those nonlinear effects by considering the electrokinetics governed by the Stokes-Brinkman-Nernst-Planck-Poisson equations. We have computed the governing nonlinear coupled set of equations numerically by adopting a finite volume based iterative algorithm. Our numerical method is tested for accuracy by comparing with several existing results on free-solution electrophoresis as well as results based on the Debye-Hückel approximation. Our computed result shows that the electrophoretic velocity decreases with the rise of the particle dielectric permittivity constant and attains a saturation limit at large values of permittivity. A significant impact of the solid polarization is found in gel electrophoresis compared to the free-solution electrophoresis.

A Hierarchical Algorithm for Fast Debye Summation with Applications to Small Angle Scattering

PubMed Central

Gumerov, Nail A.; Berlin, Konstantin; Fushman, David; Duraiswami, Ramani

2012-01-01

Debye summation, which involves the summation of sinc functions of distances between all pair of atoms in three dimensional space, arises in computations performed in crystallography, small/wide angle X-ray scattering (SAXS/WAXS) and small angle neutron scattering (SANS). Direct evaluation of Debye summation has quadratic complexity, which results in computational bottleneck when determining crystal properties, or running structure refinement protocols that involve SAXS or SANS, even for moderately sized molecules. We present a fast approximation algorithm that efficiently computes the summation to any prescribed accuracy ε in linear time. The algorithm is similar to the fast multipole method (FMM), and is based on a hierarchical spatial decomposition of the molecule coupled with local harmonic expansions and translation of these expansions. An even more efficient implementation is possible when the scattering profile is all that is required, as in small angle scattering reconstruction (SAS) of macromolecules. We examine the relationship of the proposed algorithm to existing approximate methods for profile computations, and show that these methods may result in inaccurate profile computations, unless an error bound derived in this paper is used. Our theoretical and computational results show orders of magnitude improvement in computation complexity over existing methods, while maintaining prescribed accuracy. PMID:22707386

Experimental studies of Debye-like process and structural relaxation in mixtures of 2-ethyl-1-hexanol and 2-ethyl-1-hexyl bromide

NASA Astrophysics Data System (ADS)

Preuß, M.; Gainaru, C.; Hecksher, T.; Bauer, S.; Dyre, J. C.; Richert, R.; Böhmer, R.

2012-10-01

Binary solutions of 2-ethyl-1-hexanol (2E1H) with 2-ethyl-1-hexyl bromide (2E1Br) are investigated by means of dielectric, shear mechanical, near-infrared, and solvation spectroscopy as well as dielectrically monitored physical aging. For moderately diluted 2E1H the slow Debye-like process, which dominates the dielectric spectra of the neat monohydroxy alcohol, separates significantly from the α-relaxation. For example, the separation in equimolar mixtures amounts to four decades in frequency. This situation of highly resolved processes allows one to demonstrate unambiguously that physical aging is governed by the α-process, but even under these ideal conditions the Debye process remains undetectable in shear mechanical experiments. Furthermore, the solvation experiments show that under constant charge conditions the microscopic polarization fluctuations take place on the time scale of the structural process. The hydrogen-bond populations monitored via near-infrared spectroscopy indicate the presence of a critical alcohol concentration, xc ≈ 0.5-0.6, thereby confirming the dielectric data. In the pure bromide a slow dielectric process of reduced intensity is present in addition to the main relaxation. This is taken as a sign of intermolecular cooperativity probably mediated via halogen bonds.

Hydraulic continuity and biological effects of low strength very low frequency electromagnetic waves: Case of microbial biofilm growth in water treatment.

PubMed

Gérard, Merlin; Noamen, Omri; Evelyne, Gonze; Eric, Valette; Gilles, Cauffet; Marc, Henry

2015-10-15

This study aims to elucidate the interactions between water, subjected to electromagnetic waves of very low frequency (VLF) (kHz) with low strength electromagnetic fields (3.5 mT inside the coils), and the development of microbial biofilms in this exposed water. Experimental results demonstrate that in water exposed to VLF electromagnetic waves, the biomass of biofilm is limited if hydraulic continuity is achieved between the electromagnetic generator and the biofilm media. The measured amount of the biofilm's biomass is approximately a factor two lower for exposed biofilm than the non-exposed biofilm. Measurements of electromagnetic fields in the air and simulations exhibit very low intensities of fields (<10 nT and 2 V/m) in the biofilm-exposed region at a distance of 1 m from the electromagnetic generator. Exposure to electric and magnetic fields of the quoted intensities cannot explain thermal and ionizing effects on the biofilm. A variable electrical potential with a magnitude close to 20 mV was detected in the tank in hydraulic continuity with the electromagnetic generator. The application of quantum field theory may help to explain the observed effects in this case. Copyright © 2015 Elsevier Ltd. All rights reserved.

Some Student Conceptions of Electromagnetic Induction

NASA Astrophysics Data System (ADS)

Thong, Wai Meng; Gunstone, Richard

2008-01-01

Introductory electromagnetism is a central part of undergraduate physics. Although there has been some research into student conceptions of electromagnetism, studies have been sparse and separated. This study sought to explore second year physics students’ conceptions of electromagnetism, to investigate to what extent the results from the present study are similar to these results from other studies, and to uncover any new forms of alternative conceptions. Data for this study came from 15 in-depth interviews. Three previously unreported alternative conceptions were identified in the study: 1) induced current varies proportionately with current in solenoid; 2) there must be contact between magnetic flux and the external coil in order for any emf to be induced in the coil; 3) coulombic or electrostatic potential difference is present in an induced electric field. These alternative conceptions were manifested in these students’ explanations of electromagnetic phenomena presented to them during the interviews.

Electromagnetic Fields, Pulsed Radiofrequency Radiation, and Epigenetics: How Wireless Technologies May Affect Childhood Development

ERIC Educational Resources Information Center

Sage, Cindy; Burgio, Ernesto

2018-01-01

Mobile phones and other wireless devices that produce electromagnetic fields (EMF) and pulsed radiofrequency radiation (RFR) are widely documented to cause potentially harmful health impacts that can be detrimental to young people. New epigenetic studies are profiled in this review to account for some neurodevelopmental and neurobehavioral changes…

Electromagnetic banana kinetic equation and its applications in tokamaks

NASA Astrophysics Data System (ADS)

Shaing, K. C.; Chu, M. S.; Sabbagh, S. A.; Seol, J.

2018-03-01

A banana kinetic equation in tokamaks that includes effects of the finite banana width is derived for the electromagnetic waves with frequencies lower than the gyro-frequency and the bounce frequency of the trapped particles. The radial wavelengths are assumed to be either comparable to or shorter than the banana width, but much wider than the gyro-radius. One of the consequences of the banana kinetics is that the parallel component of the vector potential is not annihilated by the orbit averaging process and appears in the banana kinetic equation. The equation is solved to calculate the neoclassical quasilinear transport fluxes in the superbanana plateau regime caused by electromagnetic waves. The transport fluxes can be used to model electromagnetic wave and the chaotic magnetic field induced thermal particle or energetic alpha particle losses in tokamaks. It is shown that the parallel component of the vector potential enhances losses when it is the sole transport mechanism. In particular, the fact that the drift resonance can cause significant transport losses in the chaotic magnetic field in the hitherto unknown low collisionality regimes is emphasized.

REVIEWS OF TOPICAL PROBLEMS: "Magnetized" black holes

NASA Astrophysics Data System (ADS)

Aliev, A. N.; Gal'tsov, D. V.

1989-01-01

Physical aspects of the theory of black holes in an external electromagnetic field are reviewed. The "magnetized" black hole model is currently widely discussed in astrophysics because it provides a basis for the explanation of the high energy activity of galactic cores and quasars. The particular feature of this model is that it predicts unusual "gravimagnetic" phenomena that arise as a result of a natural combination of effects in electrodynamics and gravitation, namely, the appearance of an inductive potential difference during the rotation of a black hole in a magnetic field, the drift of a black hole in an external electromagnetic field, the change in the chemical potential of the event horizon, the creation of an effective ergosphere of a black hole in a magnetic field, and so on. Questions relating to the description of electromagnetic fields in Kerr space-time are examined, including their influence on the space-time metric, the interaction between a rotating charged black hole and an external electromagnetic field, the motion of charged particles near "magnetized" black holes, including their spontaneous and stimulated emission, and the influence of magnetic fields on quantum-mechanical processes in black holes.

Nonlinear properties of gated graphene in a strong electromagnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Avetisyan, A. A., E-mail: artakav@ysu.am; Djotyan, A. P., E-mail: adjotyan@ysu.am; Moulopoulos, K., E-mail: cos@ucy.ac.cy

We develop a microscopic theory of a strong electromagnetic field interaction with gated bilayer graphene. Quantum kinetic equations for density matrix are obtained using a tight binding approach within second quantized Hamiltonian in an intense laser field. We show that adiabatically changing the gate potentials with time may produce (at resonant photon energy) a full inversion of the electron population with high density between valence and conduction bands. In the linear regime, excitonic absorption of an electromagnetic radiation in a graphene monolayer with opened energy gap is also studied.

First-principles simulations of electrostatic interactions between dust grains

NASA Astrophysics Data System (ADS)

Itou, H.; Amano, T.; Hoshino, M.

2014-12-01

We investigated the electrostatic interaction between two identical dust grains of an infinite mass immersed in homogeneous plasma by employing first-principles N-body simulations combined with the Ewald method. We specifically tested the possibility of an attractive force due to overlapping Debye spheres (ODSs), as was suggested by Resendes et al. [Phys. Lett. A 239, 181-186 (1998)]. Our simulation results demonstrate that the electrostatic interaction is repulsive and even stronger than the standard Yukawa potential. We showed that the measured electric field acting on the grain is highly consistent with a model electrostatic potential around a single isolated grain that takes into account a correction due to the orbital motion limited theory. Our result is qualitatively consistent with the counterargument suggested by Markes and Williams [Phys. Lett. A 278, 152-158 (2000)], indicating the absence of the ODS attractive force.

Electronic and Transport Properties of LaNi4Sb12 Skutterudite: Modified Becke-Johnson Approach

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Singh, Srishti; Gupta, Dinesh C.

2018-05-01

We carried out an ab initio study of structural, electronic, thermodynamic, and thermoelectric properties of the lanthanum-filled skutterudite, LaNi4Sb12. Generalized gradient approximation and modified Becke-Johnson potentials were employed for the exchange-correlation potential. The electronic structure calculations display the metallic behavior of the compound. The alloy offers low lattice thermal conductivity along with a high Seebeck coefficient with a value of - 158 (μVK-1) at room temperature. The effect of high pressure and temperature on thermal properties like thermal expansion coefficient, heat capacity, and Grüneisen parameter are also investigated by means of a quasi-harmonic Debye model. The large Seebeck coefficient and high power factor exhibited by LaNi4Sb12 make it an attractive candidate for thermoelectric materials.

Electrostatic and hydrodynamics effects in a sedimented magnetorheological suspension.

PubMed

Domínguez-García, P; Pastor, J M; Melle, Sonia; Rubio, Miguel A

2009-08-01

We present experimental results on the equilibrium microstructure of a sedimented magnetorheological suspension, namely, an aqueous suspension of micron-sized superparamagnetic particles. We develop a study of the electrical interactions on the suspension by processing video-microscopy images of the sedimented particles. We calculate the pair distribution function, g(r), which yields the electrostatic pair potential u(r), showing an anomalous attractive interaction for distances on the order of twice the particle diameter, with characteristic parameters whose values show a dependence with the two-dimensional concentration of particles. The repulsive body of the potential is adjusted to a DLVO expression in order to calculate the Debye screening length and the effective surface charge density. Influence of confinement and variations on the Boltzmann sedimentation profile because of the electrostatic interactions appear to be essential for the interpretation of experimental results.

Coulomb interactions between cytoplasmic electric fields and phosphorylated messenger proteins optimize information flow in cells.

PubMed

Gatenby, Robert A; Frieden, B Roy

2010-08-11

Normal cell function requires timely and accurate transmission of information from receptors on the cell membrane (CM) to the nucleus. Movement of messenger proteins in the cytoplasm is thought to be dependent on random walk. However, Brownian motion will disperse messenger proteins throughout the cytosol resulting in slow and highly variable transit times. We propose that a critical component of information transfer is an intracellular electric field generated by distribution of charge on the nuclear membrane (NM). While the latter has been demonstrated experimentally for decades, the role of the consequent electric field has been assumed to be minimal due to a Debye length of about 1 nanometer that results from screening by intracellular Cl- and K+. We propose inclusion of these inorganic ions in the Debye-Huckel equation is incorrect because nuclear pores allow transit through the membrane at a rate far faster than the time to thermodynamic equilibrium. In our model, only the charged, mobile messenger proteins contribute to the Debye length. Using this revised model and published data, we estimate the NM possesses a Debye-Huckel length of a few microns and find this is consistent with recent measurement using intracellular nano-voltmeters. We demonstrate the field will accelerate isolated messenger proteins toward the nucleus through Coulomb interactions with negative charges added by phosphorylation. We calculate transit times as short as 0.01 sec. When large numbers of phosphorylated messenger proteins are generated by increasing concentrations of extracellular ligands, we demonstrate they generate a self-screening environment that regionally attenuates the cytoplasmic field, slowing movement but permitting greater cross talk among pathways. Preliminary experimental results with phosphorylated RAF are consistent with model predictions. This work demonstrates that previously unrecognized Coulomb interactions between phosphorylated messenger proteins and intracellular electric fields will optimize information transfer from the CM to the NM in cells.

Electron spin relaxation governed by Raman processes both for Cu2+ ions and carbonate radicals in KHCO3 crystals: EPR and electron spin echo studies

NASA Astrophysics Data System (ADS)

Hoffmann, Stanislaw K.; Goslar, Janina; Lijewski, Stefan

2012-08-01

EPR studies of Cu2+ and two free radicals formed by γ-radiation were performed for KHCO3 single crystal at room temperature. From the rotational EPR results we concluded that Cu2+ is chelated by two carbonate molecules in a square planar configuration with spin-Hamiltonian parameters g|| = 2.2349 and A|| = 18.2 mT. Free radicals were identified as neutral HOCOrad with unpaired electron localized on the carbon atom and a radical anion CO3·- with unpaired electron localized on two oxygen atoms. The hyperfine splitting of the EPR lines by an interaction with a single hydrogen atom of HOCOrad was observed with isotropic coupling constants ao = 0.31 mT. Two differently oriented radical sites were identified in the crystal unit cell. Electron spin-lattice relaxation measured by electron spin echo methods shows that both Cu2+ and free radicals relax via two-phonon Raman processes with almost the same relaxation rate. The temperature dependence of the relaxation rate 1/T1 is well described with the effective Debye temperature ΘD = 175 K obtained from a fit to the Debye-type phonon spectrum. We calculated a more realistic Debye temperature value from available elastic constant values of the crystal as ΘD = 246 K. This ΘD-value and the Debye phonon spectrum approximation give a much worse fit to the experimental results. Possible contributions from a local mode or an optical mode are considered and it is suggested that the real phonon spectrum should be used for the relaxation data interpretation. It is unusual that free radicals in KHCO3 relax similarly to the well localized Cu2+ ions, which suggests a small destruction of the host crystal lattice by the ionizing irradiation allowing well coupling between radical and lattice dynamics.

Modeling impacts of NH{sub 3} on uptake of H{sub 2}SO{sub 4} by charged nucleating nanoparticles in the Earth's atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nadykto, A. B., E-mail: anadykto@gmail.com; Department of Applied Mathematics, Moscow State University of Technology “STANKIN”, Vadkovsky per. 1, Moscow 127055; Nazarenko, K. M.

2016-06-08

The understanding of the role of ammonia, a well-known stabilizer of binary sulfuric acid-water clusters, in the gas-to-nanoparticle conversion in the Earth atmosphere is critically important for the assessment of aerosol radiative forcing associated with the climate changes. The sulfuric acid H{sub 2}SO{sub 4} is present in the atmosphere in the form of the gas-phase hydrates (H{sub 2}SO{sub 4})(H{sub 2}O){sub n}, whose interaction with NH{sub 3} leads to the formation of more stable bisulfate clusters (NH{sub 3})(H{sub 2}SO{sub 4})(H{sub 2}O){sub n}. Although the impact of NH{sub 3} on the thermochemical stability of binary clusters nucleating homogeneously has been studied inmore » some detail in the past, the effect of ammonia on other microphysical properties relevant to nucleation remains insufficiently well understood. In the present study, the effect of ammonia on the electrical dipole moment controlling the nucleation of airborne ions via the dipole-charge interaction has been investigated using the Density Functional Theory (DFT), ab initio MP2 and model chemistry G3 methods. The presence of ammonia in (H{sub 2}SO{sub 4})(H{sub 2}O){sub n} is found to lead to very large enhancement in the dipole moment, which exceeds 2.0-2.5 Debyes (∼60-80%), 3.7-5.0 Debyes (∼90-180%), 1.4-4.5 Debyes (∼50-150%) and 2.1-5.5 Debyes (∼60-700%) for n = 0, n = 1, n = 2 and n = 3, respectively. The implications of this include the significantly increased uptake of the sulfuric acid, the key atmospheric nucleation precursor, by airborne ions and neutrals (due to dipole-dipole interaction), enhanced nucleation rates and the elevated production of ultrafine particles, which cause adverse health impacts.« less

Dipole-Induced Electromagnetic Transparency

NASA Astrophysics Data System (ADS)

Puthumpally-Joseph, Raiju; Sukharev, Maxim; Atabek, Osman; Charron, Eric

2014-10-01

We determine the optical response of a thin and dense layer of interacting quantum emitters. We show that, in such a dense system, the Lorentz redshift and the associated interaction broadening can be used to control the transmission and reflection spectra. In the presence of overlapping resonances, a dipole-induced electromagnetic transparency (DIET) regime, similar to electromagnetically induced transparency (EIT), may be achieved. DIET relies on destructive interference between the electromagnetic waves emitted by quantum emitters. Carefully tuning material parameters allows us to achieve narrow transmission windows in, otherwise, completely opaque media. We analyze in detail this coherent and collective effect using a generalized Lorentz model and show how it can be controlled. Several potential applications of the phenomenon, such as slow light, are proposed.

Behavior of a spin-1/2 massive charged particle in Schwarzschild immersed in an electromagnetic universe

NASA Astrophysics Data System (ADS)

Al-Badawi, A.

2018-02-01

The Dirac equation is considered in a spacetime that represents a Schwarzschild metric coupled to a uniform external electromagnetic field. Due to the presence of electromagnetic field from the surroundings, the interaction with the spin-1/2 massive charged particle is considered. The equations of the spin-1/2 massive charged particle are separated into radial and angular equations by adopting the Newman-Penrose formalism. The angular equations obtained are similar to the Schwarzschild geometry. For the radial equations we manage to obtain the one dimensional Schrödinger-type wave equations with effective potentials. Finally, we study the behavior of the potentials by plotting them as a function of radial distance and expose the effect of the external parameter, charge and the frequency of the particle on them.

Using ISS Telescopes for Electromagnetic Follow-up of Gravitational Wave Detections of NS-NS and NS-BH Mergers

NASA Technical Reports Server (NTRS)

Camp, J.; Barthelmy, S.; Blackburn, L.; Carpenter, K. G.; Gehrels, N.; Kanner, J.; Marshall, F. E.; Racusin, J. L.; Sakamoto, T.

2013-01-01

The International Space Station offers a unique platform for rapid and inexpensive deployment of space telescopes. A scientific opportunity of great potential later this decade is the use of telescopes for the electromagnetic follow-up of ground-based gravitational wave detections of neutron star and black hole mergers. We describe this possibility for OpTIIX, an ISS technology demonstration of a 1.5 m diffraction limited optical telescope assembled in space, and ISS-Lobster, a wide-field imaging X-ray telescope now under study as a potential NASA mission. Both telescopes will be mounted on pointing platforms, allowing rapid positioning to the source of a gravitational wave event. Electromagnetic follow-up rates of several per year appear likely, offering a wealth of complementary science on the mergers of black holes and neutron stars.

Study of pressure variation effect on structural, opto-electronic, elastic, mechanical, and thermodynamic properties of SrLiF3

NASA Astrophysics Data System (ADS)

Erum, Nazia; Iqbal, Muhammad Azhar

2017-11-01

The structural, electronic, elastic, optical and thermodynamic properties of cubic fluoroperovskite SrLiF3 at ambient and high-pressure are investigated by using first-principles total energy calculations within the framework of Generalized Gradient Approximation (GGA), combined with Quasi-harmonic Debye model in which the phonon effects are considered. The pressure effects are determined in the range of 0-50 GPa, in which cubic stability of SrLiF3 fluoroperovskite remains valid. The computed lattice parameters agree well with experimental and previous theoretical results. Decrease in lattice constant and bonds length is observed with the increase in pressure from 0 to 50 GPa. The effect of increase in pressure on electronic band structure calculations with GGA and GGA plus Tran-Blaha modified Becke-Johnson (TB-mBJ) potential reveals a predominant characteristic associated with widening of bandgap. The influence of pressure on elastic constants and their related mechanical parameters have been discussed in detail. All the calculated optical properties such as the complex dielectric function Ԑ(ω), optical conductivity σ(ω), energy loss function L(ω), absorption coefficient α(w), refractive index n (ω), reflectivity R (ω), and effective number of electrons neff, via sum rules shift towards the higher energies under the application of pressure. Moreover, important thermodynamic properties heat capacities (Cp and Cv), volume expansion coefficient (α), and Debye temperature (θD) are predicted successfully in the wide temperature and pressure ranges.

Combining the AFLOW GIBBS and elastic libraries to efficiently and robustly screen thermomechanical properties of solids

NASA Astrophysics Data System (ADS)

Toher, Cormac; Oses, Corey; Plata, Jose J.; Hicks, David; Rose, Frisco; Levy, Ohad; de Jong, Maarten; Asta, Mark; Fornari, Marco; Buongiorno Nardelli, Marco; Curtarolo, Stefano

2017-06-01

Thorough characterization of the thermomechanical properties of materials requires difficult and time-consuming experiments. This severely limits the availability of data and is one of the main obstacles for the development of effective accelerated materials design strategies. The rapid screening of new potential materials requires highly integrated, sophisticated, and robust computational approaches. We tackled the challenge by developing an automated, integrated workflow with robust error-correction within the AFLOW framework which combines the newly developed "Automatic Elasticity Library" with the previously implemented GIBBS method. The first extracts the mechanical properties from automatic self-consistent stress-strain calculations, while the latter employs those mechanical properties to evaluate the thermodynamics within the Debye model. This new thermoelastic workflow is benchmarked against a set of 74 experimentally characterized systems to pinpoint a robust computational methodology for the evaluation of bulk and shear moduli, Poisson ratios, Debye temperatures, Grüneisen parameters, and thermal conductivities of a wide variety of materials. The effect of different choices of equations of state and exchange-correlation functionals is examined and the optimum combination of properties for the Leibfried-Schlömann prediction of thermal conductivity is identified, leading to improved agreement with experimental results than the GIBBS-only approach. The framework has been applied to the AFLOW.org data repositories to compute the thermoelastic properties of over 3500 unique materials. The results are now available online by using an expanded version of the REST-API described in the Appendix.

Effects of dielectric inhomogeneity on electrostatic twist rigidity of a helical biomolecule in Debye-Hückel regime

NASA Astrophysics Data System (ADS)

Rezaie-Dereshgi, Amir; Mohammad-Rafiee, Farshid

2018-04-01

The electrostatic interactions play a crucial role in biological systems. Here we consider an impermeable dielectric molecule in the solvent with a different dielectric constant. The electrostatic free energy in the problem is studied in the Debye-Hückel regime using the analytical Green function that is calculated in the paper. Using this electrostatic free energy, we study the electrostatic contribution to the twist rigidity of a double stranded helical molecule such as a DNA and an actin filament. The dependence of the electrostatic twist rigidity of the molecule to the dielectric inhomogeneity, structural parameters, and the salt concentration is studied. It is shown that, depending on the parameters, the electrostatic twist rigidity could be positive or negative.

Experimental confirmation of stable, small-debye-length, pure-electron-plasma equilibria in a stellarator.

PubMed

Kremer, J P; Pedersen, T Sunn; Lefrancois, R G; Marksteiner, Q

2006-09-01

The creation of the first small-Debye length, low temperature pure electron plasmas in a stellarator is reported. A confinement time of 20 ms has been measured. The long confinement time implies the existence of macroscopically stable equilibria and that the single particle orbits are well confined despite the lack of quasisymmetry in the device, the Columbia non-neutral torus. This confirms the beneficial confinement effects of strong electric fields and the resulting rapid E x B rotation of the electrons. The particle confinement time is presently limited by the presence of bulk insulating materials in the plasma, rather than any intrinsic plasma transport processes. A nearly flat temperature profile is seen in the inner part of the plasma.

Prediction study of structural, elastic and electronic properties of FeMP (M = Ti, Zr, Hf) compounds

NASA Astrophysics Data System (ADS)

Tanto, A.; Chihi, T.; Ghebouli, M. A.; Reffas, M.; Fatmi, M.; Ghebouli, B.

2018-06-01

First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy indexes, Pugh's criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal.

The therapeutic effect of a pulsed electromagnetic field on the reproductive patterns of male Wistar rats exposed to a 2.45-GHz microwave field

PubMed Central

Kumar, Sanjay; Kesari, Kavindra Kumar; Behari, Jitendra

2011-01-01

INTRODUCTION: Environmental exposure to man-made electromagnetic fields has been steadily increasing with the growing demand for electronic items that are operational at various frequencies. Testicular function is particularly susceptible to radiation emitted by electromagnetic fields. OBJECTIVES: This study aimed to examine the therapeutic effects of a pulsed electromagnetic field (100 Hz) on the reproductive systems of male Wistar rats (70 days old). METHODS: The experiments were divided into five groups: microwave sham, microwave exposure (2.45 GHz), pulsed electromagnetic field sham, pulsed electromagnetic field (100 Hz) exposure, and microwave/pulsed electromagnetic field exposure. The animals were exposed for 2 hours/day for 60 days. After exposure, the animals were sacrificed, their sperm was used for creatine and caspase assays, and their serum was used for melatonin and testosterone assays. RESULTS: The results showed significant increases in caspase and creatine kinase and significant decreases in testosterone and melatonin in the exposed groups. This finding emphasizes that reactive oxygen species (a potential inducer of cancer) are the primary cause of DNA damage. However, pulsed electromagnetic field exposure relieves the effect of microwave exposure by inducing Faraday currents. CONCLUSIONS: Electromagnetic fields are recognized as hazards that affect testicular function by generating reactive oxygen species and reduce the bioavailability of androgen to maturing spermatozoa. Thus, microwave exposure adversely affects male fertility, whereas pulsed electromagnetic field therapy is a non-invasive, simple technique that can be used as a scavenger agent to combat oxidative stress. PMID:21876981

Artificial electromagnetism for neutral atoms: Escher staircase and Laughlin liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, Erich J.

2004-10-01

We present a method for creating fields that couple to neutral atoms in the same way that electromagnetic fields couple to charged particles. We show that this technique opens the door for a range of neutral atom experiments, including probing the interplay between periodic potentials and quantum Hall effects. Furthermore, we propose, and analyze, seemingly paradoxical geometries which can be engineered through these techniques. For example, we show how to create a ring of sites where an atom continuously reduces its potential energy by moving in a clockwise direction.

Expanding the use of real-time electromagnetic tracking in radiation oncology.

PubMed

Shah, Amish P; Kupelian, Patrick A; Willoughby, Twyla R; Meeks, Sanford L

2011-11-15

In the past 10 years, techniques to improve radiotherapy delivery, such as intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT) for both inter- and intrafraction tumor localization, and hypofractionated delivery techniques such as stereotactic body radiation therapy (SBRT), have evolved tremendously. This review article focuses on only one part of that evolution, electromagnetic tracking in radiation therapy. Electromagnetic tracking is still a growing technology in radiation oncology and, as such, the clinical applications are limited, the expense is high, and the reimbursement is insufficient to cover these costs. At the same time, current experience with electromagnetic tracking applied to various clinical tumor sites indicates that the potential benefits of electromagnetic tracking could be significant for patients receiving radiation therapy. Daily use of these tracking systems is minimally invasive and delivers no additional ionizing radiation to the patient, and these systems can provide explicit tumor motion data. Although there are a number of technical and fiscal issues that need to be addressed, electromagnetic tracking systems are expected to play a continued role in improving the precision of radiation delivery.

Expanding the use of real‐time electromagnetic tracking in radiation oncology

PubMed Central

Kupelian, Patrick A.; Willoughby, Twyla R.; Meeks, Sanford L.

2011-01-01

In the past 10 years, techniques to improve radiotherapy delivery, such as intensity‐modulated radiation therapy (IMRT), image‐guided radiation therapy (IGRT) for both inter‐ and intrafraction tumor localization, and hypofractionated delivery techniques such as stereotactic body radiation therapy (SBRT), have evolved tremendously. This review article focuses on only one part of that evolution, electromagnetic tracking in radiation therapy. Electromagnetic tracking is still a growing technology in radiation oncology and, as such, the clinical applications are limited, the expense is high, and the reimbursement is insufficient to cover these costs. At the same time, current experience with electromagnetic tracking applied to various clinical tumor sites indicates that the potential benefits of electromagnetic tracking could be significant for patients receiving radiation therapy. Daily use of these tracking systems is minimally invasive and delivers no additional ionizing radiation to the patient, and these systems can provide explicit tumor motion data. Although there are a number of technical and fiscal issues that need to be addressed, electromagnetic tracking systems are expected to play a continued role in improving the precision of radiation delivery. PACS number: 87.63.‐d PMID:22089017

A resonant electromagnetic vibration energy harvester for intelligent wireless sensor systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiu, Jing, E-mail: jingqiu@cqu.edu.cn; Wen, Yumei; Li, Ping

Vibration energy harvesting is now receiving more interest as a means for powering intelligent wireless sensor systems. In this paper, a resonant electromagnetic vibration energy harvester (VEH) employing double cantilever to convert low-frequency vibration energy into electrical energy is presented. The VEH is made up of two cantilever beams, a coil, and magnetic circuits. The electric output performances of the proposed electromagnetic VEH have been investigated. With the enhancement of turns number N, the optimum peak power of electromagnetic VEH increases sharply and the resonance frequency deceases gradually. When the vibration acceleration is 0.5 g, we obtain the optimum output voltagemore » and power of 9.04 V and 50.8 mW at frequency of 14.9 Hz, respectively. In a word, the prototype device was successfully developed and the experimental results exhibit a great enhancement in the output power and bandwidth compared with other traditional electromagnetic VEHs. Remarkably, the proposed resonant electromagnetic VEH have great potential for applying in intelligent wireless sensor systems.« less

Electrodynamics; Problems and solutions

NASA Astrophysics Data System (ADS)

Ilie, Carolina C.; Schrecengost, Zachariah S.

2018-05-01

This book of problems and solutions is a natural continuation of Ilie and Schrecengost's first book Electromagnetism: Problems and Solutions. Aimed towards students who would like to work independently on more electrodynamics problems in order to deepen their understanding and problem-solving skills, this book discusses main concepts and techniques related to Maxwell's equations, conservation laws, electromagnetic waves, potentials and fields, and radiation.

Exact Electromagnetic Fields Produced by a Finite Wire with Constant Current

ERIC Educational Resources Information Center

Jimenez, J. L.; Campos, I.; Aquino, N.

2008-01-01

We solve exactly the problem of calculating the electromagnetic fields produced by a finite wire with a constant current, by using two methods: retarded potentials and Jefimenko's formalism. One result in this particular case is that the usual Biot-Savart law of magnetostatics gives the correct magnetic field of the problem. We also show…

From Fragmented Knowledge to a Knowledge Structure: Linking the Domains of Mechanics and Electromagnetism.

ERIC Educational Resources Information Center

Bagno, Esther; Eylon, Bat-Sheva; Ganiel, Uri

2000-01-01

Describes the MAOF physics education program which is designed to relate large parts of mechanics and electromagnetism to each other via the key concepts of field and potential, while at the same time treat students' conceptual difficulties. Finds that students who studied with the MAOF program significantly improved their physics knowledge…

Using Helicopter Electromagnetic Surveys to Identify Potential Hazards at Mine Waste Impoundments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammack, R.W.

2008-01-01

In July 2003, helicopter electromagnetic surveys were conducted at 14 coal waste impoundments in southern West Virginia. The purpose of the surveys was to detect conditions that could lead to impoundment failure either by structural failure of the embankment or by the flooding of adjacent or underlying mine works. Specifically, the surveys attempted to: 1) identify saturated zones within the mine waste, 2) delineate filtrate flow paths through the embankment or into adjacent strata and receiving streams, and 3) identify flooded mine workings underlying or adjacent to the waste impoundment. Data from the helicopter surveys were processed to generate conductivity/depthmore » images. Conductivity/depth images were then spatially linked to georeferenced air photos or topographic maps for interpretation. Conductivity/depth images were found to provide a snapshot of the hydrologic conditions that exist within the impoundment. This information can be used to predict potential areas of failure within the embankment because of its ability to image the phreatic zone. Also, the electromagnetic survey can identify areas of unconsolidated slurry in the decant basin and beneath the embankment. Although shallow, flooded mineworks beneath the impoundment were identified by this survey, it cannot be assumed that electromagnetic surveys can detect all underlying mines. A preliminary evaluation of the data implies that helicopter electromagnetic surveys can provide a better understanding of the phreatic zone than the piezometer arrays that are typically used.« less

Considerations for human exposure standards for fast-rise-time high-peak-power electromagnetic pulses.

PubMed

Merritt, J H; Kiel, J L; Hurt, W D

1995-06-01

Development of new emitter systems capable of producing high-peak-power electromagnetic pulses with very fast rise times and narrow pulse widths is continuing. Such directed energy weapons systems will be used in the future to defeat electronically vulnerable targets. Human exposures to these pulses can be expected during testing and operations. Development of these technologies for radar and communications purposes has the potential for wider environmental exposure, as well. Current IEEE C95.1-1991 human exposure guidelines do not specifically address these types of pulses, though limits are stated for pulsed emissions. The process for developing standards includes an evaluation of the relevant bioeffects data base. A recommendation has been made that human exposure to ultrashort electromagnetic pulses that engender electromagnetic transients, called precursor waves, should be avoided. Studies that purport to show the potential for tissue damage induced by such pulses were described. The studies cited in support of the recommendation were not relevant to the issues of tissue damage by propagated pulses. A number of investigations are cited in this review that directly address the biological effects of electromagnetic pulses. These studies have not shown evidence of tissue damage as a result of exposure to high-peak-power pulsed microwaves. It is our opinion that the current guidelines are sufficiently protective for human exposure to these pulses.

Calculation of sheath and wake structure about a pillbox-shaped spacecraft in a flowing plasma

NASA Technical Reports Server (NTRS)

Parker, L. W.

1977-01-01

A computer program was used for studies of the disturbed zones around bodies in flowing plasmas, particularly spacecraft and their associated sheaths and wakes. The program solved a coupled Poisson-Vlasov system of nonlinear partial differential integral equations to obtain distributions of electric potential and ion and electron density about a finite length cylinder in a plasma flow at arbitrary ion Mach numbers. The approach was applicable to a larger range of parameters than other available approaches. In sample calculations, bodies up to 100 Debye lengths in radius were treated, that is, larger than any previously treated realistically. Applications were made to in-situ satellite experiments.

Experimental investigation of plasma sheaths in magnetic mirror and cusp configurations

NASA Astrophysics Data System (ADS)

Jiang, Zhengqi; Wei, Zi-an; Ma, J. X.

2017-11-01

Sheath structures near a metal plate in a magnetized plasma were experimentally investigated in magnetic mirror and cusp configurations. Plasma parameters and the sheath potential distributions were probed by a planar and an emissive probe, respectively. The measured sheath profiles in the mirror configuration show that the sheath thickness first decreases and then increases when the magnetic strength is raised. A magnetic flux-tube model was used to explain this result. In the cusp configuration, the measured sheath thickness decreases with the increase of the coil current creating the magnetic cusp. However, when normalized by the electron Debye length, the dependence of the sheath thickness on the coil current is reversed.

The Influence of Particle Charge on Heterogeneous Reaction Rate Coefficients

NASA Technical Reports Server (NTRS)

Aikin, A. C.; Pesnell, W. D.

2000-01-01

The effects of particle charge on heterogeneous reaction rates are presented. Many atmospheric particles, whether liquid or solid are charged. This surface charge causes a redistribution of charge within a liquid particle and as a consequence a perturbation in the gaseous uptake coefficient. The amount of perturbation is proportional to the external potential and the square of the ratio of debye length in the liquid to the particle radius. Previous modeling has shown how surface charge affects the uptake coefficient of charged aerosols. This effect is now included in the heterogeneous reaction rate of an aerosol ensemble. Extension of this analysis to ice particles will be discussed and examples presented.

Additional extensions to the NASCAP computer code, volume 1

NASA Technical Reports Server (NTRS)

Mandell, M. J.; Katz, I.; Stannard, P. R.

1981-01-01

Extensions and revisions to a computer code that comprehensively analyzes problems of spacecraft charging (NASCAP) are documented. Using a fully three dimensional approach, it can accurately predict spacecraft potentials under a variety of conditions. Among the extensions are a multiple electron/ion gun test tank capability, and the ability to model anisotropic and time dependent space environments. Also documented are a greatly extended MATCHG program and the preliminary version of NASCAP/LEO. The interactive MATCHG code was developed into an extremely powerful tool for the study of material-environment interactions. The NASCAP/LEO, a three dimensional code to study current collection under conditions of high voltages and short Debye lengths, was distributed for preliminary testing.

On the Nature of Disorder in Solid 4He

NASA Astrophysics Data System (ADS)

Krainyukova, N. V.

2010-02-01

We apply a modified Debye approach to calculate the Gibbs free energy for different structural phases and crystallite sizes in 4He. Atoms are assumed to interact via the Aziz potential. We have found that some intermediate (between hcp and bcc) phase predicted previously is more favorable than hcp at low temperatures and for small sizes. We show that it can exist in a wide pressure range up to 60 bar in 4He for crystallite sizes about 3,000 atoms. For larger sizes (10,000 atoms or more) this phase becomes unfavorable. In multidomain structures the intermediate phase competes with hcp and metastable fcc that can be a reason for disorder in solid 4He.

Monte Carlo simulations of flexible polyanions complexing with whey proteins at their isoelectric point

NASA Astrophysics Data System (ADS)

de Vries, R.

2004-02-01

Electrostatic complexation of flexible polyanions with the whey proteins α-lactalbumin and β-lactoglobulin is studied using Monte Carlo simulations. The proteins are considered at their respective isoelectric points. Discrete charges on the model polyelectrolytes and proteins interact through Debye-Hückel potentials. Protein excluded volume is taken into account through a coarse-grained model of the protein shape. Consistent with experimental results, it is found that α-lactalbumin complexes much more strongly than β-lactoglobulin. For α-lactalbumin, strong complexation is due to localized binding to a single large positive "charge patch," whereas for β-lactoglobulin, weak complexation is due to diffuse binding to multiple smaller charge patches.

Periodical plasma structures controlled by external magnetic field

NASA Astrophysics Data System (ADS)

Schweigert, I. V.; Keidar, M.

2017-11-01

The plasma of Hall thruster type in external magnetic field is studied in 2D3V kinetic simulations using PIC MCC method. The periodical structure with maxima of electron and ion densities is formed and becomes more pronounced with increase of magnetic field incidence angle in the plasma. These ridges of electron and ion densities are aligned with the magnetic field vector and shifted relative each other. This leads to formation of two-dimensional double-layers structure in cylindrical plasma chamber. Depending on Larmor radius and Debye length up to nineteen potential steps appear across the oblique magnetic field. The electrical current gathered on the wall is associated with the electron and ion density ridges.

Analytical and numerical study of electroosmotic slip flows of fractional second grade fluids

NASA Astrophysics Data System (ADS)

Wang, Xiaoping; Qi, Haitao; Yu, Bo; Xiong, Zhen; Xu, Huanying

2017-09-01

This work investigates the unsteady electroosmotic slip flow of viscoelastic fluid through a parallel plate micro-channel under combined influence of electroosmotic and pressure gradient forcings with asymmetric zeta potentials at the walls. The generalized second grade fluid with fractional derivative was used for the constitutive equation. The Navier slip model with different slip coefficients at both walls was also considered. By employing the Debye-Hückel linearization and the Laplace and sin-cos-Fourier transforms, the analytical solutions for the velocity distribution are derived. And the finite difference method for this problem was also given. Finally, the influence of pertinent parameters on the generation of flow is presented graphically.

Theoretical prediction of the structural properties of uranium chalcogenides under high pressure

NASA Astrophysics Data System (ADS)

Kapoor, Shilpa; Yaduvanshi, Namrata; Singh, Sadhna

2018-05-01

Uranium chalcogenides crystallize in rock salt structure at normal condition and transform to Cesium Chloride structure at high pressure. We have investigated the transition pressure and volume drop of USe and UTe using three body potential model (TBIP). Present model includes long range Columbic, three body interaction forces and short range overlap forces operative up to next nearest neighbors. We have reported the phase transition pressure, relative volume collapses, the thermo physical properties such as molecular force constant (f), infrared absorption frequency (v0), Debye temperature (θD) and Gruneisen parameter (γ) of present chalcogenides and found that our results in general good agreement with experimental and other theoretical data.

Dusty plasma in the region of the lunar terminator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popel, S. I., E-mail: popel@iki.rssi.ru; Zelenyi, L. M.; Atamaniuk, B.

2016-05-15

Dusty plasma in the region of the lunar terminator is considered. It is shown that, in this region, a structure resembling a plasma sheath forms near the lunar surface. This sheath creates a potential barrier, due to which electrons over the illuminated part of the Moon are confined by electrostatic forces. The width of the sheath-like structure is on the order of the ion Debye length. In this structure, significant (about several hundred V/m) electric fields arise, which lift charged micron-size dust grains to heights of several tens of centimeters. The suggested effect may be used to explain the glowmore » observed by the Surveyor spacecraft over the lunar terminator.« less

Molecular dynamics study of the melting curve of NiTi alloy under pressure

NASA Astrophysics Data System (ADS)

Zeng, Zhao-Yi; Hu, Cui-E.; Cai, Ling-Cang; Chen, Xiang-Rong; Jing, Fu-Qian

2011-02-01

The melting curve of NiTi alloy was predicted by using molecular dynamics simulations combining with the embedded atom model potential. The calculated thermal equation of state consists well with our previous results obtained from quasiharmonic Debye approximation. Fitting the well-known Simon form to our Tm data yields the melting curves for NiTi: 1850(1 + P/21.938)0.328 (for one-phase method) and 1575(1 + P/7.476)0.305 (for two-phase method). The two-phase simulations can effectively eliminate the superheating in one-phase simulations. At 1 bar, the melting temperature of NiTi is 1575 ± 25 K and the corresponding melting slope is 64 K/GPa.

Electrokinetic energy conversion in a finite length superhydrophobic microchannel

NASA Astrophysics Data System (ADS)

Malekidelarestaqi, M.; Mansouri, A.; Chini, S. F.

2018-07-01

We investigated the effect of superhydrophobic walls on electrokinetics phenomena in a finite-length microchannel with superhydrophobic walls (in both transient and steady-state). We implemented the effect of superhydrophobicity using Navier's slip-length. To include the importance of the electric double-layer, we scaled the slip-length with respect to Debye-length (κ-1). By increasing the slip-length from 0 to 144 nm (1.5κ-1), streaming-current, streaming-potential, flow-rate and electrokinetic energy conversion increased by 2.55, 2.44, 1.8, and 3.4 folds, accordingly. The electrokinetic energy conversion of each microchannel was in the order of picowatt. To produce more energy, an array of microchannels should be used.

Electromagnetic wave propagating along a space curve

NASA Astrophysics Data System (ADS)

Lai, Meng-Yun; Wang, Yong-Long; Liang, Guo-Hua; Wang, Fan; Zong, Hong-Shi

2018-03-01

By using the thin-layer approach, we derive the effective equation for the electromagnetic wave propagating along a space curve. We find intrinsic spin-orbit, extrinsic spin-orbit, and extrinsic orbital angular-momentum and intrinsic orbital angular-momentum couplings induced by torsion, which can lead to geometric phase, spin, and orbital Hall effects. And we show the helicity inversion induced by curvature that can convert a right-handed circularly polarized electromagnetic wave into a left-handed polarized one, vice versa. Finally, we demonstrate that the gauge invariance of the effective dynamics is protected by the geometrically induced gauge potential.

Electromagnetic holographic sensitivity field of two-phase flow in horizontal wells

NASA Astrophysics Data System (ADS)

Zhang, Kuo; Wu, Xi-Ling; Yan, Jing-Fu; Cai, Jia-Tie

2017-03-01

Electromagnetic holographic data are characterized by two modes, suggesting that image reconstruction requires a dual-mode sensitivity field as well. We analyze an electromagnetic holographic field based on tomography theory and Radon inverse transform to derive the expression of the electromagnetic holographic sensitivity field (EMHSF). Then, we apply the EMHSF calculated by using finite-element methods to flow simulations and holographic imaging. The results suggest that the EMHSF based on the partial derivative of radius of the complex electric potential φ is closely linked to the Radon inverse transform and encompasses the sensitivities of the amplitude and phase data. The flow images obtained with inversion using EMHSF better agree with the actual flow patterns. The EMHSF overcomes the limitations of traditional single-mode sensitivity fields.

iPad2(R) use in patients with implantable cardioverter defibrillators causes electromagnetic interference: the EMIT Study.

PubMed

Kozik, Teri M; Chien, Gianna; Connolly, Therese F; Grewal, Gurinder S; Liang, David; Chien, Walter

2014-04-10

Over 140 million iPads(®) have been sold worldwide. The iPad2(®), with magnets embedded in its frame and Smart Cover and 3G cellular data capability, can potentially cause electromagnetic interference in implantable cardioverter defibrillators. This can lead to potentially life-threatening situations in patients. The goal of this study was to determine whether the iPad2(®) can cause electromagnetic interference in patients with implantable cardioverter defibrillators. Twenty-seven patients with implantable cardioverter defibrillators were studied. The iPad2(®) was held at reading distance and placed directly over the device with cellular data capability activated and deactivated. The manufacturers/models of devices and the patients' body mass index were noted. The presence of electromagnetic interference was detected by using a programmer supplied by each manufacturer. Magnet mode with suspension of anti-tachycardia therapy was triggered in 9 (33%) patients. All occurred when the iPad2(®) was placed directly over the device. The cellular data status did not cause interference and no noise or oversensing was noted. There was no significant difference between the mean body mass index of the groups with or without interference. The iPad2(®) can trigger magnet mode in implantable cardioverter defibrillators when laid directly over the device. This is potentially dangerous if patients should develop life-threatening arrhythmias at the same time. As new electronic products that use magnets are produced, the potential risk to patients with implantable defibrillators needs to be addressed.

Analysis of superconducting electromagnetic finite elements based on a magnetic vector potential variational principle

NASA Technical Reports Server (NTRS)

Schuler, James J.; Felippa, Carlos A.

1991-01-01

Electromagnetic finite elements are extended based on a variational principle that uses the electromagnetic four potential as primary variable. The variational principle is extended to include the ability to predict a nonlinear current distribution within a conductor. The extension of this theory is first done on a normal conductor and tested on two different problems. In both problems, the geometry remains the same, but the material properties are different. The geometry is that of a 1-D infinite wire. The first problem is merely a linear control case used to validate the new theory. The second problem is made up of linear conductors with varying conductivities. Both problems perform well and predict current densities that are accurate to within a few ten thousandths of a percent of the exact values. The fourth potential is then removed, leaving only the magnetic vector potential, and the variational principle is further extended to predict magnetic potentials, magnetic fields, the number of charge carriers, and the current densities within a superconductor. The new element produces good results for the mean magnetic field, the vector potential, and the number of superconducting charge carriers despite a relatively high system condition number. The element did not perform well in predicting the current density. Numerical problems inherent to this formulation are explored and possible remedies to produce better current predicting finite elements are presented.

Rovibrational states of Wigner molecules in spherically symmetric confining potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cioslowski, Jerzy

2016-08-07

The strong-localization limit of three-dimensional Wigner molecules, in which repulsively interacting particles are confined by a weak spherically symmetric potential, is investigated. An explicit prescription for computation of rovibrational wavefunctions and energies that are asymptotically exact at this limit is presented. The prescription is valid for systems with arbitrary angularly-independent interparticle and confining potentials, including those involving Coulombic and screened (i.e., Yukawa/Debye) interactions. The necessary derivations are greatly simplified by explicit constructions of the Eckart frame and the parity-adapted primitive wavefunctions. The performance of the new formalism is illustrated with the three- and four-electron harmonium atoms at their strong-correlation limits.more » In particular, the involvement of vibrational modes with the E symmetry is readily pinpointed as the origin of the “anomalous” weak-confinement behavior of the {sup 1}S{sub +} state of the four-electron species that is absent in its {sup 1}D{sub +} companion of the strong-confinement regime.« less

Renormalization group method based on the ionization energy theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arulsamy, Andrew Das, E-mail: sadwerdna@gmail.com; School of Physics, University of Sydney, Sydney, New South Wales 2006

2011-03-15

Proofs are developed to explicitly show that the ionization energy theory is a renormalized theory, which mathematically exactly satisfies the renormalization group formalisms developed by Gell-Mann-Low, Shankar and Zinn-Justin. However, the cutoff parameter for the ionization energy theory relies on the energy-level spacing, instead of lattice point spacing in k-space. Subsequently, we apply the earlier proofs to prove that the mathematical structure of the ionization-energy dressed electron-electron screened Coulomb potential is exactly the same as the ionization-energy dressed electron-phonon interaction potential. The latter proof is proven by means of the second-order time-independent perturbation theory with the heavier effective mass condition,more » as required by the electron-electron screened Coulomb potential. The outcome of this proof is that we can derive the heat capacity and the Debye frequency as a function of ionization energy, which can be applied in strongly correlated matter and nanostructures.« less

The aerodynamics of bodies in a rarefied ionized gas with applications to spacecraft environmental dynamics

NASA Technical Reports Server (NTRS)

Stone, N. H.

1981-01-01

The objectives are to provide a parametric description of the electrostatic interaction of a mesosonic, collisionless plasma with conducting bodies on the order of 1 to 10 Debye lengths in size, and to extend this description to the satellite-ionospheric interaction, where possible. Experimental findings include: the wake of the geometrically complex body appears to be a linear superposition of the wakes of its simple geometric components; and vector ion flux measurements show converging ion streams at the wake axis and direct evidence of ion streams deflected from the wake axis by the positive space charge potential associated with the axial ion peak. The extension to the satellite-ionospheric interaction utilizes qualitative scaling and indicates that similar, but smaller amplitude, wake structures may be expected for small or highly charged bodies. However, for large bodies at small potentials, the structure may be diffused by the thermal ion motion and the dispersion resulting for space charge potentials.

Ion and electron sheath characteristics in a low density and low temperature plasma

NASA Astrophysics Data System (ADS)

Borgohain, Binita; Bailung, H.

2017-11-01

Ion and electron sheath characteristics in a low electron temperature (Te ˜ 0.25-0.40 eV) and density (ne ˜ 106-107 cm-3) plasma are described. The plasma is produced in the experimental volume through diffusion from a hot cathode discharge plasma source by using a magnetic filter. The electron energy distribution function in the experimental plasma volume is measured to be a narrow Maxwellian distribution indicating the absence of primary and energetic electrons which are decoupled in the source side by the cusp magnetic field near the filter. An emissive probe is used to measure the sheath potential profiles in front of a metal plate biased negative and positive with respect to the plasma potential. For a positive plate bias, the electron density decreases considerably and the electron sheath expands with a longer presheath region compared to the ion sheath. The sheath potential structures are found to follow the Debye sheath model.

Anomalous properties of the acoustic excitations in glasses on the mesoscopic length scale.

PubMed

Monaco, Giulio; Mossa, Stefano

2009-10-06

The low-temperature thermal properties of dielectric crystals are governed by acoustic excitations with large wavelengths that are well described by plane waves. This is the Debye model, which rests on the assumption that the medium is an elastic continuum, holds true for acoustic wavelengths large on the microscopic scale fixed by the interatomic spacing, and gradually breaks down on approaching it. Glasses are characterized as well by universal low-temperature thermal properties that are, however, anomalous with respect to those of the corresponding crystalline phases. Related universal anomalies also appear in the low-frequency vibrational density of states and, despite a longstanding debate, remain poorly understood. By using molecular dynamics simulations of a model monatomic glass of extremely large size, we show that in glasses the structural disorder undermines the Debye model in a subtle way: The elastic continuum approximation for the acoustic excitations breaks down abruptly on the mesoscopic, medium-range-order length scale of approximately 10 interatomic spacings, where it still works well for the corresponding crystalline systems. On this scale, the sound velocity shows a marked reduction with respect to the macroscopic value. This reduction turns out to be closely related to the universal excess over the Debye model prediction found in glasses at frequencies of approximately 1 THz in the vibrational density of states or at temperatures of approximately 10 K in the specific heat.

First-Principles Calculations on the Origin of Mechanical Properties and Electronic Structures of 5d Transition Metal Monocarbides MC (M = Hf, Ta, W, Re, Os, Ir, and Pt)

NASA Astrophysics Data System (ADS)

Fukuichi, Masayuki; Momida, Hiroyoshi; Geshi, Masaaki; Michiuchi, Masato; Sogabe, Koichi; Oguchi, Tamio

2018-04-01

Much is not systematically known about the origin of mechanical properties among 5d transition metal carbides including tungsten carbide. In order to understand the microscopic origin of hardness, the mechanical properties and electronic structures of 5d transition metal monocarbides MC (M = Hf, Ta, W, Re, Os, Ir, and Pt) in five different structures (NaCl, WC, ZnS, CsCl, and NiAs type) are analyzed using first-principles calculations based on the density functional theory. Our results would indicate that WC-type WC and NiAs-type ReC have the highest and second highest hardness among all of the MC, respectively, in terms of the Debye temperature. By examining the Debye temperature in the series, it is found that MC in the range of less and more than half filled 5d shells are brittle and ductile, respectively. Our results would indicate that filling in the bonding and anti-bonding states contributes to brittleness and ductility. The Debye temperature could be a key to understanding hardness in terms of bulk and shear moduli. In addition, we evaluate some other structural properties such as equilibrium volume, formation enthalpy, and elastic constant to investigate structural stability. Based on the theoretical findings, the microscopic mechanisms of hardness and brittleness in the transition metal carbides are discussed.

Response to ``Comment on `Slow Debye-type peak observed in the dielectric response of polyalcohols' '' [J. Chem. Phys. 134, 037101 (2011)

NASA Astrophysics Data System (ADS)

Bergman, R.; Jansson, H.; Swenson, J.

2011-01-01

In our recent article [R. Bergman et al., J. Chem. Phys. 132, 044504 (2010)] we investigated some polyalcohols, i.e., glycerol, xylitol, and sorbitol by dielectric spectroscopy. In the study, a low-frequency peak of Debye character that normally is hidden by the large low-frequency dispersion due to conductivity was revealed by analyzing the real part of the permittivity and by using a thin Teflon film to suppress the low-frequency dispersion. We agree with the comment by Paluch et al. [J. Chem. Phys. 134, 037101 (2011)] that the Teflon film setup will indeed create a peak due to the dc conductivity. However, due to the fact that the location of the peak was almost identical in measurement with and without Teflon, we unfortunately mainly showed the data measured with Teflon, despite that it could also be observed in the real part of the permittivity without using the Teflon setup, as shown in our original article [R. Bergman et al., J. Chem. Phys. 132, 044504 (2010)]. Here, we show that the low-frequency peak of Debye character can also be observed by subtracting the dc conductivity. Furthermore, we show that the modulus representation used in Paluch et al. [J. Chem. Phys. 134, 037101 (2011).] is also not suitable for detecting processes hidden by the conductivity.

Anomalies in the equilibrium and nonequilibrium properties of correlated ions in complex molecular environments

NASA Astrophysics Data System (ADS)

Mahakrishnan, Sathiya; Chakraborty, Subrata; Vijay, Amrendra

2017-11-01

Emergent statistical attributes, and therefore the equations of state, of an assembly of interacting charge carriers embedded within a complex molecular environment frequently exhibit a variety of anomalies, particularly in the high-density (equivalently, the concentration) regime, which are not well understood, because they do not fall under the low-concentration phenomenologies of Debye-Hückel-Onsager and Poisson-Nernst-Planck, including their variants. To go beyond, we here use physical concepts and mathematical tools from quantum scattering theory, transport theory with the Stosszahlansatz of Boltzmann, and classical electrodynamics (Lorentz gauge) and obtain analytical expressions both for the average and the frequency-wave vector-dependent longitudinal and transverse current densities, diffusion coefficient, and the charge density, and therefore the analytical expressions for (a) the chemical potential, activity coefficient, and the equivalent conductivity for strong electrolytes and (b) the current-voltage characteristics for ion-transport processes in complex molecular environments. Using a method analogous to the notion of Debye length and thence the electrical double layer, we here identify a pair of characteristic length scales (longitudinal and the transverse), which, being wave vector and frequency dependent, manifestly exhibit nontrivial fluctuations in space-time. As a unifying theme, we advance a quantity (inverse length dimension), gscat(a ), which embodies all dynamical interactions, through various quantum scattering lengths, relevant to molecular species a, and the analytical behavior which helps us to rationalize the properties of strong electrolytes, including anomalies, in all concentration regimes. As an example, the behavior of gscat(a ) in the high-concentration regime explains the anomalous increase of the Debye length with concentration, as seen in a recent experiment on electrolyte solutions. We also put forth an extension of the standard diffusion equation, which manifestly incorporates the effects arising from the underlying microscopic collisions among constituent molecular species. Furthermore, we show a nontrivial connection between the current-voltage characteristics of electrolyte solutions and the Landauer's approach to electrical conduction in mesoscopic solids and thereby establish a definite conceptual bridge between the two disjoint subjects. For numerical insight, we present results on the aqueous solution of KCl as an example of strong electrolyte, and the transport (conduction as well as diffusion) of K+ ions in water, as an example of ion transport across the voltage-gated channels in biological cells.

Anomalies in the equilibrium and nonequilibrium properties of correlated ions in complex molecular environments.

PubMed

Mahakrishnan, Sathiya; Chakraborty, Subrata; Vijay, Amrendra

2017-11-01

Emergent statistical attributes, and therefore the equations of state, of an assembly of interacting charge carriers embedded within a complex molecular environment frequently exhibit a variety of anomalies, particularly in the high-density (equivalently, the concentration) regime, which are not well understood, because they do not fall under the low-concentration phenomenologies of Debye-Hückel-Onsager and Poisson-Nernst-Planck, including their variants. To go beyond, we here use physical concepts and mathematical tools from quantum scattering theory, transport theory with the Stosszahlansatz of Boltzmann, and classical electrodynamics (Lorentz gauge) and obtain analytical expressions both for the average and the frequency-wave vector-dependent longitudinal and transverse current densities, diffusion coefficient, and the charge density, and therefore the analytical expressions for (a) the chemical potential, activity coefficient, and the equivalent conductivity for strong electrolytes and (b) the current-voltage characteristics for ion-transport processes in complex molecular environments. Using a method analogous to the notion of Debye length and thence the electrical double layer, we here identify a pair of characteristic length scales (longitudinal and the transverse), which, being wave vector and frequency dependent, manifestly exhibit nontrivial fluctuations in space-time. As a unifying theme, we advance a quantity (inverse length dimension), g_{scat}^{(a)}, which embodies all dynamical interactions, through various quantum scattering lengths, relevant to molecular species a, and the analytical behavior which helps us to rationalize the properties of strong electrolytes, including anomalies, in all concentration regimes. As an example, the behavior of g_{scat}^{(a)} in the high-concentration regime explains the anomalous increase of the Debye length with concentration, as seen in a recent experiment on electrolyte solutions. We also put forth an extension of the standard diffusion equation, which manifestly incorporates the effects arising from the underlying microscopic collisions among constituent molecular species. Furthermore, we show a nontrivial connection between the current-voltage characteristics of electrolyte solutions and the Landauer's approach to electrical conduction in mesoscopic solids and thereby establish a definite conceptual bridge between the two disjoint subjects. For numerical insight, we present results on the aqueous solution of KCl as an example of strong electrolyte, and the transport (conduction as well as diffusion) of K^{+} ions in water, as an example of ion transport across the voltage-gated channels in biological cells.

Search for Effects of an Electrostatic Potential on Clocks in the Frame of Reference of a Charged Particle

NASA Technical Reports Server (NTRS)

Ringermacher, Harry I.; Conradi, Mark S.; Cassenti, Brice

2005-01-01

Results of experiments to confirm a theory that links classical electromagnetism with the geometry of spacetime are described. The theory, based on the introduction of a Torsion tensor into Einstein s equations and following the approach of Schroedinger, predicts effects on clocks attached to charged particles, subject to intense electric fields, analogous to the effects on clocks in a gravitational field. We show that in order to interpret this theory, one must re-interpret all clock changes, both gravitational and electromagnetic, as arising from changes in potential energy and not merely potential. The clock is provided naturally by proton spins in hydrogen atoms subject to Nuclear Magnetic Resonance trials. No frequency change of clocks was observed to a resolution of 6310(exp -9). A new "Clock Principle" was postulated to explain the null result. There are two possible implications of the experiments: (a) The Clock Principle is invalid and, in fact, no metric theory incorporating electromagnetism is possible; (b) The Clock Principle is valid and it follows that a negative rest mass cannot exist.

A look at the possible mechanism and potential of magneto therapy.

PubMed

Jacobson, J I

1991-03-07

A testable theoretical model for the mechanism of magneto-therapy is presented. The theory delineated is the equation mc2 = Bvl coulomb which sets in dual resonance gravitational and electromagnetic potentials. This proposed unification of Einstein's gravity and Maxwell's electromagnetism is designated Jacobson's resonance and is a general expression of Zeeman and cyclotron resonance. The application of this theory involves the utilization of exogenously sourced very weak magnetic fields on the order of magnitude 10(-8) gauss to reorient the atomic crystal lattice structures of genomic magnetic domains. Examples of genomic magnetic domains are homeoboxes and oncogenes and associated structures like peptide hormone trophic factors. Various phenomena are also analyzed in terms of how they may relate to biological systems such as solitons, phonons, cyclotron resonance, the piezoelectric effect, the fractional quantum Hall effect, string theory, and biologically closed electric circuits. The potential of magneto-therapy in the treatment of various genomic and associated disorders is explored. The ultimate question "Can an oncogene be electromagnetically induced into becoming a structurally homologous normal gene?" is posed.

Hybrid Method for Power Control Simulation of a Single Fluid Plasma Thruster

NASA Astrophysics Data System (ADS)

Jaisankar, S.; Sheshadri, T. S.

2018-05-01

Propulsive plasma flow through a cylindrical-conical diverging thruster is simulated by a power controlled hybrid method to obtain the basic flow, thermodynamic and electromagnetic variables. Simulation is based on a single fluid model with electromagnetics being described by the equations of potential Poisson, Maxwell and the Ohm's law while the compressible fluid dynamics by the Navier Stokes in cylindrical form. The proposed method solved the electromagnetics and fluid dynamics separately, both to segregate the two prominent scales for an efficient computation and for the delivery of voltage controlled rated power. The magnetic transport is solved for steady state while fluid dynamics is allowed to evolve in time along with an electromagnetic source using schemes based on generalized finite difference discretization. The multistep methodology with power control is employed for simulating fully ionized propulsive flow of argon plasma through the thruster. Numerical solution shows convergence of every part of the solver including grid stability causing the multistep hybrid method to converge for a rated power delivery. Simulation results are reasonably in agreement with the reported physics of plasma flow in the thruster thus indicating the potential utility of this hybrid computational framework, especially when single fluid approximation of plasma is relevant.

The interaction between electromagnetic fields at megahertz, gigahertz and terahertz frequencies with cells, tissues and organisms: risks and potential

PubMed Central

Begley, Ryan; Harvey, Alan R.; Hool, Livia; Wallace, Vincent P.

2017-01-01

Since regular radio broadcasts started in the 1920s, the exposure to human-made electromagnetic fields has steadily increased. These days we are not only exposed to radio waves but also other frequencies from a variety of sources, mainly from communication and security devices. Considering that nearly all biological systems interact with electromagnetic fields, understanding the affects is essential for safety and technological progress. This paper systematically reviews the role and effects of static and pulsed radio frequencies (100–109 Hz), millimetre waves (MMWs) or gigahertz (109–1011 Hz), and terahertz (1011–1013 Hz) on various biomolecules, cells and tissues. Electromagnetic fields have been shown to affect the activity in cell membranes (sodium versus potassium ion conductivities) and non-selective channels, transmembrane potentials and even the cell cycle. Particular attention is given to millimetre and terahertz radiation due to their increasing utilization and, hence, increasing human exposure. MMWs are known to alter active transport across cell membranes, and it has been reported that terahertz radiation may interfere with DNA and cause genomic instabilities. These and other phenomena are discussed along with the discrepancies and controversies from published studies. PMID:29212756

Consideration of the effects of intense tissue heating on the RF electromagnetic fields during MRI: simulations for MRgFUS in the hip

NASA Astrophysics Data System (ADS)

Xuegang Xin, Sherman; Gu, Shiyong; Carluccio, Giuseppe; Collins, Christopher M.

2015-01-01

Due to the strong dependence of tissue electrical properties on temperature, it is important to consider the potential effects of intense tissue heating on the RF electromagnetic fields during MRI, as can occur in MR-guided focused ultrasound surgery. In principle, changes of the RF electromagnetic fields could affect both efficacy of RF pulses, and the MRI-induced RF heating (SAR) pattern. In this study, the equilibrium temperature distribution in a whole-body model with 2 mm resolution before and during intense tissue heating up to 60 °C at the target region was calculated. Temperature-dependent electric properties of tissues were assigned to the model to establish a temperature-dependent electromagnetic whole-body model in a 3T MRI system. The results showed maximum changes in conductivity, permittivity, ≤ft|\\mathbf{B}1+\\right|, and SAR of about 25%, 6%, 2%, and 20%, respectively. Though the B1 field and SAR distributions are both temperature-dependent, the potential harm to patients due to higher SARs is expected to be minimal and the effects on the B1 field distribution should have minimal effect on images from basic MRI sequences.

Advanced electromagnetic methods for aerospace vehicles

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; El-Sharawy, El-Budawy; Hashemi-Yeganeh, Shahrokh; Aberle, James T.; Birtcher, Craig R.

1991-01-01

The Advanced Helicopter Electromagnetics is centered on issues that advance technology related to helicopter electromagnetics. Progress was made on three major topics: composite materials; precipitation static corona discharge; and antenna technology. In composite materials, the research has focused on the measurements of their electrical properties, and the modeling of material discontinuities and their effect on the radiation pattern of antennas mounted on or near material surfaces. The electrical properties were used to model antenna performance when mounted on composite materials. Since helicopter platforms include several antenna systems at VHF and UHF bands, measuring techniques are being explored that can be used to measure the properties at these bands. The effort on corona discharge and precipitation static was directed toward the development of a new two dimensional Voltage Finite Difference Time Domain computer program. Results indicate the feasibility of using potentials for simulating electromagnetic problems in the cases where potentials become primary sources. In antenna technology the focus was on Polarization Diverse Conformal Microstrip Antennas, Cavity Backed Slot Antennas, and Varactor Tuned Circular Patch Antennas. Numerical codes were developed for the analysis of two probe fed rectangular and circular microstrip patch antennas fed by resistive and reactive power divider networks.

Geophysical identification of subsurface cavities and fractures near a Superfund site south of Rockford, Illinois

NASA Astrophysics Data System (ADS)

Adams, Ryan Frye

The ACME Superfund site is one of many Superfund sites in Northern Illinois. This 20 acre (8.1 ha) site was contaminated by various volatile organic compounds (VOC's) and heavy metals during the 1960-1980s. To more fully understand the potential extent of the karst system and its interaction with contaminants, both surface and borehole geophysics including seismic refraction tomography, frequency domain electromagnetics, electrical resistivity, ground penetrating radar, as well as natural gamma and electromagnetic well logs, were undertaken over an approximately 3,000 square meter grid in a field immediately south of the ACME site. Seismic refraction tomography provided information on lithology and fluctuations in the bedrock surface in the depth range 6 to 8 m. Refraction, combined with electromagnetic conductivity, also allowed mapping of potential soil pipes and/or filled sinkholes in the overlying soils. These could channel surface waters into the karst conduit system. Frequency domain electromagnetics proved to be the most successful tool for the identifying possible karst conduits below the bedrock surface. Zones of reduced conductivity suggest a series of interconnected solutionally enlarged fractures in an orthogonal pattern at a depth of approximately 8 m immediately south of the ACME site.

Worldline approach for numerical computation of electromagnetic Casimir energies: Scalar field coupled to magnetodielectric media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mackrory, Jonathan B.; Bhattacharya, Tanmoy; Steck, Daniel A.

Here, we present a worldline method for the calculation of Casimir energies for scalar fields coupled to magnetodielectric media. The scalar model we consider may be applied in arbitrary geometries, and it corresponds exactly to one polarization of the electromagnetic field in planar layered media. Starting from the field theory for electromagnetism, we work with the two decoupled polarizations in planar media and develop worldline path integrals, which represent the two polarizations separately, for computing both Casimir and Casimir-Polder potentials. We then show analytically that the path integrals for the transverse-electric polarization coupled to a dielectric medium converge to themore » proper solutions in certain special cases, including the Casimir-Polder potential of an atom near a planar interface, and the Casimir energy due to two planar interfaces. We also evaluate the path integrals numerically via Monte Carlo path-averaging for these cases, studying the convergence and performance of the resulting computational techniques. Lastly, while these scalar methods are only exact in particular geometries, they may serve as an approximation for Casimir energies for the vector electromagnetic field in other geometries.« less

Worldline approach for numerical computation of electromagnetic Casimir energies: Scalar field coupled to magnetodielectric media

DOE PAGES

Mackrory, Jonathan B.; Bhattacharya, Tanmoy; Steck, Daniel A.

2016-10-12

Here, we present a worldline method for the calculation of Casimir energies for scalar fields coupled to magnetodielectric media. The scalar model we consider may be applied in arbitrary geometries, and it corresponds exactly to one polarization of the electromagnetic field in planar layered media. Starting from the field theory for electromagnetism, we work with the two decoupled polarizations in planar media and develop worldline path integrals, which represent the two polarizations separately, for computing both Casimir and Casimir-Polder potentials. We then show analytically that the path integrals for the transverse-electric polarization coupled to a dielectric medium converge to themore » proper solutions in certain special cases, including the Casimir-Polder potential of an atom near a planar interface, and the Casimir energy due to two planar interfaces. We also evaluate the path integrals numerically via Monte Carlo path-averaging for these cases, studying the convergence and performance of the resulting computational techniques. Lastly, while these scalar methods are only exact in particular geometries, they may serve as an approximation for Casimir energies for the vector electromagnetic field in other geometries.« less

Critical Infrastructure Protection: EMP Impacts on the U.S. Electric Grid

NASA Astrophysics Data System (ADS)

Boston, Edwin J., Jr.

The purpose of this research is to identify the United States electric grid infrastructure systems vulnerabilities to electromagnetic pulse attacks and the cyber-based impacts of those vulnerabilities to the electric grid. Additionally, the research identifies multiple defensive strategies designed to harden the electric grid against electromagnetic pulse attack that include prevention, mitigation and recovery postures. Research results confirm the importance of the electric grid to the United States critical infrastructures system and that an electromagnetic pulse attack against the electric grid could result in electric grid degradation, critical infrastructure(s) damage and the potential for societal collapse. The conclusions of this research indicate that while an electromagnetic pulse attack against the United States electric grid could have catastrophic impacts on American society, there are currently many defensive strategies under consideration designed to prevent, mitigate and or recover from an electromagnetic pulse attack. However, additional research is essential to further identify future target hardening opportunities, efficient implementation strategies and funding resources.

Mechanical, electronic and thermodynamic properties of full Heusler compounds Fe2VX(X = Al, Ga)

NASA Astrophysics Data System (ADS)

Khalfa, M.; Khachai, H.; Chiker, F.; Baki, N.; Bougherara, K.; Yakoubi, A.; Murtaza, G.; Harmel, M.; Abu-Jafar, M. S.; Omran, S. Bin; Khenata, R.

2015-11-01

The electronic structure, mechanical and thermodynamic properties of Fe2VX, (with X = Al and Ga), have been studied self consistently by employing state-of-the-art full-potential linearized approach of augmented plane wave plus local orbitals (FP-LAPW + lo) method. The exchange-correlation potential is treated with the local density and generalized gradient approximations (LDA and GGA). Our predicted ground state properties such as lattice constants, bulk modulus and elastic constants appear more accurate when we employed the GGA rather than the LDA, and these results are in very good agreement with the available experimental and theoretical data. Further, thermodynamic properties of Fe2VAl and Fe2VGa are predicted with pressure and temperature in the ranges of 0-40 GPa and 0-1500 K using the quasi-harmonic Debye model. We have obtained successfully the variations of the heat capacities, primitive cell volume and volume expansion coefficient.

Computational investigations of the band structure, and thermodynamic and optical features of thorium-based oxide ThGeO4 using the full-potential linearized augmented plane-wave plus local orbital approach

NASA Astrophysics Data System (ADS)

Chiker, F.; Khachai, H.; Mathieu, C.; Bin-Omran, S.; Kada, Belkacem; Sun, Xiao-Wei; Sandeep; Rai, D. P.; Khenata, R.

2018-05-01

In this study, first-principles investigations were performed using the full-potential linearized augmented plane-wave method of the structural and optoelectronic properties of thorium germinate (ThGeO4), a high-K dielectric material. Under ambient conditions, the structural properties calculated for ThGeO4 in the zircon phase were in excellent agreement with the available experimental data. Furthermore, using the modified Becke -Johnson correction method, the calculated band gaps and optical constants accurately described this compound. Finally, the thermal properties were predicted over a temperature range of 0-700 K and pressures up to 11 GPa using the quasi-harmonic Debye model, where the variations in the heat capacity, primitive cell volume, and thermal expansion coefficients were determined successfully.

Gauge-invariant expectation values of the energy of a molecule in an electromagnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mandal, Anirban; Hunt, Katharine L. C.

In this paper, we show that the full Hamiltonian for a molecule in an electromagnetic field can be separated into a molecular Hamiltonian and a field Hamiltonian, both with gauge-invariant expectation values. The expectation value of the molecular Hamiltonian gives physically meaningful results for the energy of a molecule in a time-dependent applied field. In contrast, the usual partitioning of the full Hamiltonian into molecular and field terms introduces an arbitrary gauge-dependent potential into the molecular Hamiltonian and leaves a gauge-dependent form of the Hamiltonian for the field. With the usual partitioning of the Hamiltonian, this same problem of gaugemore » dependence arises even in the absence of an applied field, as we show explicitly by considering a gauge transformation from zero applied field and zero external potentials to zero applied field, but non-zero external vector and scalar potentials. We resolve this problem and also remove the gauge dependence from the Hamiltonian for a molecule in a non-zero applied field and from the field Hamiltonian, by repartitioning the full Hamiltonian. It is possible to remove the gauge dependence because the interaction of the molecular charges with the gauge potential cancels identically with a gauge-dependent term in the usual form of the field Hamiltonian. We treat the electromagnetic field classically and treat the molecule quantum mechanically, but nonrelativistically. Our derivation starts from the Lagrangian for a set of charged particles and an electromagnetic field, with the particle coordinates, the vector potential, the scalar potential, and their time derivatives treated as the variables in the Lagrangian. We construct the full Hamiltonian using a Lagrange multiplier method originally suggested by Dirac, partition this Hamiltonian into a molecular term H{sub m} and a field term H{sub f}, and show that both H{sub m} and H{sub f} have gauge-independent expectation values. Any gauge may be chosen for the calculations; but following our partitioning, the expectation values of the molecular Hamiltonian are identical to those obtained directly in the Coulomb gauge. As a corollary of this result, the power absorbed by a molecule from a time-dependent, applied electromagnetic field is equal to the time derivative of the non-adiabatic term in the molecular energy, in any gauge.« less

[The electroporation effects of high power pulse microwave and electromagnetic pulse irradiation on the membranes of cardiomyocyte cells and the mechanism therein involved].

PubMed

Deng, Hua; Wang, Dewen; Peng, Ruiyun; Wang, Shuiming; Chen, Jiankui; Zhang, Sa; Dong, Bo; Wang, Xiaomin

2005-08-01

Though there is ongoing public concern on potential hazards and risk of electromagnetic radiation, the bioeffects mechanism of electromagnetic fields remains obscure. Heart is one of the organs susceptive to electromagnetic fields (EMF). This study was designed to assess the influence of high power pulse microwave and electromagnetic pulse irradiation on cardiomyocytes, to explore the critical mechanism of electromagnetic fields, and to explain the regular course of injury caused by exposure to pulse EMF. Cultured cardiomyocytes were irradiated by high power pulse microwave and electromagnetic pulse first, then a series of apparatus including atom force microscope, laser scanning confocal microscope and flow cytometer were used to examine the changes of cell membrane conformation, structure and function. After irradiation, the cardiomyocytes pulsated slower or stop, the cells conformation was abnormal, the cells viability declined, and the percentage of apoptosis and necrosis increased significantly (P< 0.01). The cell membrane had pores unequal in size, and lost its penetration character. The concentration of Na+, K+, Ca2+, Cl-, Mg2+, Ca2+ and P3+ in cell culture medium increased significantly (P< 0.01). and the concentration of Ca2+ in cells ([Ca2+]i) decreased significantly (P<0.01). The results indicated that cardiomyocytes are susceptible to non-ionizing radiation. Pulse electromagnetic field can induce cardiomyocytes electroporation, and can do great damage to cells conformation, structure and function. Electroporation is one of the most critical mechanisms to explain the athermal effects of electromagnetic radiation.

Dressing effects on the occurrence scattering time retardation and advance in a dusty plasma

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Young-Dae; Hanyang Plasma Team

2017-10-01

The dressing effects on the occurrence scattering time for the dust-dust interaction are investigated in a complex plasma. The first-order eikonal analysis is applied to obtain the scattering amplitude and the occurrence scattering time for the dust-dust interaction. The result shows that dressing effect enhances the retardation phenomena of the occurrence scattering time in the forward scattering domain. It is shown that the oscillatory behavior of the scaled occurrence scattering time is getting more significant with an increase of the Debye length. It is also found that the retardation domain of the occurrence scattering time increases with a decrease of the Debye length. The variation of the occurrence scattering time retardation and advance due to the dressing effect is also discussed.

Study of 57Fe Mössbauer effect in RFe 2Zn 20 ( R = Lu, Yb, Gd)

DOE PAGES

Bud’ko, Sergey L.; Kong, Tai; Ma, Xiaoming; ...

2015-08-04

In this document we report measurements of 57Fe Mössbauer spectra for RFe 2Zn 20 ( R = Lu, Yb, Gd) from ~ 4.5 K to room temperature. The obtained isomer shift values are very similar for all three compounds, their temperature dependence was analyzed within the Debye model and resulted in an estimate of the Debye temperatures of 450-500 K. The values of quadrupole splitting at room temperature change with the cubic lattice constant a in a linear fashion. For GdFe 2Zn 20, ferromagnetic order is seen as an appearance of a sextet in the spectra. The 57Fe site hyperfinemore » field for T → 0 was evaluated to be ~ 2.4 T.« less

Interactive visualization of multi-data-set Rietveld analyses using Cinema:Debye-Scherrer.

PubMed

Vogel, Sven C; Biwer, Chris M; Rogers, David H; Ahrens, James P; Hackenberg, Robert E; Onken, Drew; Zhang, Jianzhong

2018-06-01

A tool named Cinema:Debye-Scherrer to visualize the results of a series of Rietveld analyses is presented. The multi-axis visualization of the high-dimensional data sets resulting from powder diffraction analyses allows identification of analysis problems, prediction of suitable starting values, identification of gaps in the experimental parameter space and acceleration of scientific insight from the experimental data. The tool is demonstrated with analysis results from 59 U-Nb alloy samples with different compositions, annealing times and annealing temperatures as well as with a high-temperature study of the crystal structure of CsPbBr 3 . A script to extract parameters from a series of Rietveld analyses employing the widely used GSAS Rietveld software is also described. Both software tools are available for download.

Interactive visualization of multi-data-set Rietveld analyses using Cinema:Debye-Scherrer

PubMed Central

Biwer, Chris M.; Rogers, David H.; Ahrens, James P.; Hackenberg, Robert E.; Onken, Drew; Zhang, Jianzhong

2018-01-01

A tool named Cinema:Debye-Scherrer to visualize the results of a series of Rietveld analyses is presented. The multi-axis visualization of the high-dimensional data sets resulting from powder diffraction analyses allows identification of analysis problems, prediction of suitable starting values, identification of gaps in the experimental parameter space and acceleration of scientific insight from the experimental data. The tool is demonstrated with analysis results from 59 U–Nb alloy samples with different compositions, annealing times and annealing temperatures as well as with a high-temperature study of the crystal structure of CsPbBr3. A script to extract parameters from a series of Rietveld analyses employing the widely used GSAS Rietveld software is also described. Both software tools are available for download. PMID:29896062

Lattice distortions in complex oxides and their relation to the thermal properties

NASA Astrophysics Data System (ADS)

Srivastava, Archana; Gaur, N. K.

2018-05-01

We have investigated the various lattice distortions in complex oxides Ca1-xLaxMnO3 and its effect on elastic and thermal properties of these perovskite manganites, especially Debye temperature of these complex oxides. The revealed data on Bulk modulus and Debye temperature studied as a function of lattice distortions using a novel atomistic approach of Atom in Molecules(AIM) theory and Modified Rigid Ion Model (MRIM) are in closer agreement with the available experimental data for some concentrations (x) of Ca1-xLaxMnO3. We demonstrate that the distortions introduced due to electron concentration, size mismatch and JT effects are the dominant factor, whereas charge mismatch and buckling of Mn-O-Mn angle influence the thermal properties to a lesser degree in the ferromagnetic state.

Electromagnetic Flow Meter Having a Driver Circuit Including a Current Transducer

NASA Technical Reports Server (NTRS)

Patel, Sandeep K. (Inventor); Karon, David M. (Inventor); Cushing, Vincent (Inventor)

2014-01-01

An electromagnetic flow meter (EMFM) accurately measures both the complete flow rate and the dynamically fluctuating flow rate of a fluid by applying a unipolar DC voltage to excitation coils for a predetermined period of time, measuring the electric potential at a pair of electrodes, determining a complete flow rate and independently measuring the dynamic flow rate during the "on" cycle of the DC excitation, and correcting the measurements for errors resulting from galvanic drift and other effects on the electric potential. The EMFM can also correct for effects from the excitation circuit induced during operation of the EMFM.

Mapping Emplaced Articulated Concrete Mattress Using Geoelectrical and Electromagnetic Techniques.

DTIC Science & Technology

1998-08-01

4 Articulated Concrete Mattress ........................... 4 Test Sites . ........................................ 5 3- Self -Potential M ethod...7 Self -Potential Theory . ................................ 7 Calculation of Self -Potential Response Profiles...45 Figures 1-53 Appendix A: Phase II Report - Investigation of Articulated Concrete Mattress Using Self -Potential and

Terahertz electromagnetic fields (0.106 THz) do not induce manifest genomic damage in vitro.

PubMed

Hintzsche, Henning; Jastrow, Christian; Kleine-Ostmann, Thomas; Kärst, Uwe; Schrader, Thorsten; Stopper, Helga

2012-01-01

Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment.Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm(2) to 2 mW/cm(2), representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction.

Terahertz Electromagnetic Fields (0.106 THz) Do Not Induce Manifest Genomic Damage In Vitro

PubMed Central

Hintzsche, Henning; Jastrow, Christian; Kleine-Ostmann, Thomas; Kärst, Uwe; Schrader, Thorsten; Stopper, Helga

2012-01-01

Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment. Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm2 to 2 mW/cm2, representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction. PMID:23029508

A Route to Chaotic Behavior of Single Neuron Exposed to External Electromagnetic Radiation.

PubMed

Feng, Peihua; Wu, Ying; Zhang, Jiazhong

2017-01-01

Non-linear behaviors of a single neuron described by Fitzhugh-Nagumo (FHN) neuron model, with external electromagnetic radiation considered, is investigated. It is discovered that with external electromagnetic radiation in form of a cosine function, the mode selection of membrane potential occurs among periodic, quasi-periodic, and chaotic motions as increasing the frequency of external transmembrane current, which is selected as a sinusoidal function. When the frequency is small or large enough, periodic, and quasi-periodic motions are captured alternatively. Otherwise, when frequency is in interval 0.778 < ω < 2.208, chaotic motion characterizes the main behavior type. The mechanism of mode transition from quasi-periodic to chaotic motion is also observed when varying the amplitude of external electromagnetic radiation. The frequency apparently plays a more important role in determining the system behavior.

A Route to Chaotic Behavior of Single Neuron Exposed to External Electromagnetic Radiation

PubMed Central

Feng, Peihua; Wu, Ying; Zhang, Jiazhong

2017-01-01

Non-linear behaviors of a single neuron described by Fitzhugh-Nagumo (FHN) neuron model, with external electromagnetic radiation considered, is investigated. It is discovered that with external electromagnetic radiation in form of a cosine function, the mode selection of membrane potential occurs among periodic, quasi-periodic, and chaotic motions as increasing the frequency of external transmembrane current, which is selected as a sinusoidal function. When the frequency is small or large enough, periodic, and quasi-periodic motions are captured alternatively. Otherwise, when frequency is in interval 0.778 < ω < 2.208, chaotic motion characterizes the main behavior type. The mechanism of mode transition from quasi-periodic to chaotic motion is also observed when varying the amplitude of external electromagnetic radiation. The frequency apparently plays a more important role in determining the system behavior. PMID:29089882

Measurement of the environmental broadband electromagnetic waves in a mid-size European city.

PubMed

Fernández-García, R; Gil, I

2017-10-01

In this paper, the level of exposure to broadband radiofrequency electromagnetic field in a mid-size European city was evaluated in accordance with the International Commission on Non-ionizing Radiation Protection guidelines from 1998. With the aim to analyse all the potential electromagnetic waves present in the city up to 18GHz, a total of 271 locations distributed along Terrassa (Spain) have been measured. To show the results in an easy-to-interpret way by the citizen, the results have been represented in a set of raster maps. The measurement results obtained showed that the electromagnetic wave measured in all broadband frequency range along the city is much lower than the safety level according to the international regulations for both public and occupational sectors. Copyright © 2017 Elsevier Inc. All rights reserved.

Confined states in photonic-magnonic crystals with complex unit cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dadoenkova, Yu. S.; Novgorod State University, 173003 Veliky Novgorod; Donetsk Physical and Technical Institute of the National Academy of Sciences of Ukraine, 83114 Donetsk

2016-08-21

We have investigated multifunctional periodic structures in which electromagnetic waves and spin waves can be confined in the same areas. Such simultaneous localization of both sorts of excitations can potentially enhance the interaction between electromagnetic waves and spin waves. The system we considered has a form of one dimensional photonic-magnonic crystal with two types of magnetic layers (thicker and thinner ones) separated by sections of the dielectric photonic crystals. We focused on the electromagnetic defect modes localized in the magnetic layers (areas where spin waves can be excited) and decaying in the sections of conventional (nonmagnetic) photonic crystals. We showedmore » how the change of relative thickness of two types of the magnetic layers can influence on the spectrum of spin waves and electromagnetic defect modes, both localized in magnetic parts of the system.« less

Investigation of the spatially isotropic component of the laterally averaged molecular hydrogen/Ag(111) physisorption potential

NASA Astrophysics Data System (ADS)

Yu, Chien-fan; Whaley, K. Birgitta; Hogg, C. S.; Sibener, S. J.

1985-10-01

A comprehensive study of the spatially isotropic component of the laterally averaged molecular hydrogen/Ag(111) physisorption potential is presented. Diffractive selective adsorption scattering resonances for rotationally state-selected H2 and D2 on Ag(111) have been mapped out as a function of incident polar angle for several crystal azimuths and beam energies. These resonances have been used to determine the bound eigenvalues, and subsequently the shape, of the potential well. Best fit Lennard-Jones, Morse, variable exponent, and exponential-3 potentials having well depths of ˜32 meV are derived from the data. These measurements are supported by rotationally inelastic scattering measurements for HD and exact close-coupled quantum scattering calculations. Debye-Waller attenuation measurements are also presented for H2, D2, and HD. The ability to detect these diffractively coupled resonances on a closest-packed metallic surface, i.e., a surface of extremely low corrugation, suggests that such measurements can be carried out on a much wider class of surfaces than previously envisioned.

Investigation of the spatially isotropic component of the laterally averaged molecular hydrogen/Ag(3) physisorption potential

NASA Astrophysics Data System (ADS)

Yu, C. F.; Whaley, K. B.; Hogg, C. S.; Sibener, S. J.

1985-08-01

A comprehensive study of the spatially isotropic component of the laterally averaged molecular hydrogen/Ag(111) physisorption potential is presented. Diffractive selective adsorption scattering resonances for rotationally state-selected H2 and D2 on Ag(111) have been mapped out as a function of incident polar angle for several crystal azimuths and beam energies. These resonances have been used to determine the bound eigenvalues, and subsequently the shape, of the potential well. Best fit Lennard-Jones, Morse, variable exponent, and exponential-3 potentials having well depths of approximately 32 MeV are derived from the data. These measurements are supported by rotationally inelastic scattering measurements for HD and exact close-coupled quantum scattering calculations. Debye-Waller attenuation measurements are also presented for H2, D2, and HD. The ability to detect these diffractively coupled resonances on a closest-packed metallic surface, i.e., a surface of extremely low corrugation, suggests that such measurements can be carried out on a much wider class of surfaces than previously envisioned.

Stability of parallel electroosmotic flow subject to an axial modulated electric field

NASA Astrophysics Data System (ADS)

Suresh, Vinod; Homsy, George

2001-11-01

The stability of parallel electroosmotic flow in a micro-channel subjected to an AC electric field is studied. A spatially uniform time harmonic electric field is applied along the length of a two-dimensional micro-channel containing a dilute electrolytic solution, resulting in a time periodic parallel flow. The top and bottom walls of the channel are maintained at constant potential. The base state ion concentrations and double layer potential are determined using the Poisson-Boltzmann equation in the Debye-Hückel approximation. Experiments by other workers (Santiago et. al., unpublished) have shown that such a system can exhibit instabilities that take the form of mixing motion occurring in the bulk flow outside the double layer. It is shown that such instabilities can potentially result from the coupling of disturbances in the ion concentrations or electric potential to the base state velocity or ion concentrations, respectively. The stability boundary of the system is determined using Floquet theory and its dependence on the modulation frequency and amplitude of the axial electric field is studied.

Effect of Trapped Ions on Shielding and Floating Potential of a Dust Grain in a Plasma

NASA Astrophysics Data System (ADS)

Lampe, Martin; Ganguli, Gurudas; Joyce, Glenn; Gavrishchaka, Valeriy

2001-10-01

The problem of electrostatic shielding around a small spherical collector immersed in plasma, and the related problem of electron and ion flow to the collector, date to the origins of plasma physics. Beginning with Mott-Smith and Langmuir (1926), calculations have typically neglected collisions, on the grounds that the mean free path is long compared to shielding length scales, i.e. the Debye length. However, investigators beginning with Bernstein and Rabinowitz (1959) have known that negative-energy trapped ions, created by occasional collisions, might be important. We present an analytic calculation of the density of trapped and untrapped ions, self-consistent with the potential. Under typical conditions for dust grains immersed in a discharge plasma, trapped ions dominate the shielding cloud in steady state, even in the limit of very long mean free path. As a result the shielded potential is different from the results of orbital motion limited theory. Collisions also greatly increase the ion current to the collector, thereby decreasing the floating potential and the grain charge by a factor as large as two to three.

Invariant Laws of Thermodynamics and Validity of Hasenöhrl Mass-Energy Equivalence Formula m = (4/3) E/c2 at Photonic, Electrodynamic, and Cosmic Scales

NASA Astrophysics Data System (ADS)

Sohrab, Siavash

2017-01-01

According to a scale-invariant statistical theory of fields electromagnetic photon mass is given as mem , k =√{ hk /c3 } . Since electromagnetic energy of photon is identified as amu =√{ hkc } , all baryonic matter is composed of light (photons) Eem = Nmem , kc2 =Mem , kc2 [ Joule ] or equivalently Mem , kc2 / 8338 [ kcal ] = Namu =Ma [ kg ] where 8338 is De Pretto number. Besides particle electromagnetic energy one requires potential energy associated with Poincaré stress for particle stability leading to rest enthalpy \\hcirco =\\ucirco +po \\vcirc =\\ucirco +\\ucirco / 3 = (4 / 3)mem , kc2 in accordance with Hasenöhrl. The 4/3 problem of electrodynamics (T. H. Boyer, Phys. Rev. Lett. 25, 1982) is also related to Poincaré stress thus the potential energy po \\vcirc =\\ucirco / 3 . Hence, the factor 4/3 is identified as Poisson polytropic index b =cp /cv and total particle rest mass will be composed of electromagnetic and gravitational parts mo =mem +mgr = (3 / 4) Eo /c2 + (1 / 4) Eo /c2 . At cosmological scale, respectively 3/4 and 1/4 of the total mass of closed universe will be electromagnetic (dark energy) and gravitational (dark matter) in nature as was emphasized by Pauli (Theory of Relativity, Dover, 1958). Also, Poincaré-Lorentz dynamic versus Einstein kinematic theory of relativity will be discussed.

Electromagnetic tracking for abdominal interventions in computer aided surgery

PubMed Central

Zhang, Hui; Banovac, Filip; Lin, Ralph; Glossop, Neil; Wood, Bradford J.; Lindisch, David; Levy, Elliot; Cleary, Kevin

2014-01-01

Electromagnetic tracking has great potential for assisting physicians in precision placement of instruments during minimally invasive interventions in the abdomen, since electromagnetic tracking is not limited by the line-of-sight restrictions of optical tracking. A new generation of electromagnetic tracking has recently become available, with sensors small enough to be included in the tips of instruments. To fully exploit the potential of this technology, our research group has been developing a computer aided, image-guided system that uses electromagnetic tracking for visualization of the internal anatomy during abdominal interventions. As registration is a critical component in developing an accurate image-guided system, we present three registration techniques: 1) enhanced paired-point registration (time-stamp match registration and dynamic registration); 2) orientation-based registration; and 3) needle shape-based registration. Respiration compensation is another important issue, particularly in the abdomen, where respiratory motion can make precise targeting difficult. To address this problem, we propose reference tracking and affine transformation methods. Finally, we present our prototype navigation system, which integrates the registration, segmentation, path-planning and navigation functions to provide real-time image guidance in the clinical environment. The methods presented here have been tested with a respiratory phantom specially designed by our group and in swine animal studies under approved protocols. Based on these tests, we conclude that our system can provide quick and accurate localization of tracked instruments in abdominal interventions, and that it offers a user friendly display for the physician. PMID:16829506

Effect of Ion Streaming on Diffusion of Dust Grains in Dissipative System

NASA Astrophysics Data System (ADS)

Begum, M.; Das, N.

2018-01-01

The presence of strong electric fields in the sheath region of laboratory complex plasma induces an ion drift and perturbs the field around dust grains. The downstream focusing of ions leads to the formation of oscillatory kind of attractive wake potential which superimpose with the normal Debye-Hückel (DH) potential. The structural properties of complex plasma and diffusion coefficient of dust grains in the presence of such a wake potential have been investigated using Langevin dynamics simulation in the subsonic regime of ion flow. The study reveals that the diffusion of dust grains is strongly affected by the ion flow, so that the diffusion changes its character in the wake potential to the DH potential dominant regimes. The dependence of the diffusion coefficient on the parameters, such as the neutral pressure, dust grain size, ion flow velocity, and Coulomb coupling parameter, have been calculated for the subsonic regime by using the Green-Kubo expression, which is based on the integrated velocity autocorrelation function. It is found that the diffusion and the structural property of the system is intimately connected with the interaction potential and significantly get affected in the presence of ion flow in the subsonic regime.

Analysis of electromagnetic interference from power system processing and transmission components for Space Station Freedom

NASA Technical Reports Server (NTRS)

Barber, Peter W.; Demerdash, Nabeel A. O.; Wang, R.; Hurysz, B.; Luo, Z.

1991-01-01

The goal is to analyze the potential effects of electromagnetic interference (EMI) originating from power system processing and transmission components for Space Station Freedom.The approach consists of four steps: (1) develop analytical tools (models and computer programs); (2) conduct parameterization studies; (3) predict the global space station EMI environment; and (4) provide a basis for modification of EMI standards.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pramanik, Souvik, E-mail: souvick.in@gmail.com; Ghosh, Subir, E-mail: subir_ghosh2@rediffmail.com; Pal, Probir, E-mail: probirkumarpal@rediffmail.com

In the present paper, dynamics of generalized charged particles are studied in the presence of external electromagnetic interactions. This particular extension of the free relativistic particle model lives in Non-Commutative κ-Minkowski space–time, compatible with Doubly Special Relativity, that is motivated to describe Quantum Gravity effects. Furthermore we have also considered the electromagnetic field to be dynamical and have derived the modified forms of Lienard–Wiechert like potentials for these extended charged particle models. In all the above cases we exploit the new and extended form of κ-Minkowski algebra where electromagnetic effects are incorporated in the lowest order, in the Dirac frameworkmore » of Hamiltonian constraint analysis.« less

Investigation of Electromagnetic Field Threat to Fuel Tank Wiring of a Transport Aircraft

NASA Technical Reports Server (NTRS)

Ely, Jay J.; Nguyen, Truong X.; Dudley, Kenneth L.; Scearce, Stephen A.; Beck, Fred B.; Deshpande, Manohar D.; Cockrell, C. R.

2000-01-01

National Transportation Safety Board investigators have questioned whether an electrical discharge in the Fuel Quantity Indication System (FQIS) may have initiated the TWA-800 center wing tank explosion. Because the FQIS was designed to be incapable of producing such a discharge on its own, attention has been directed to mechanisms of outside electromagnetic influence. To support the investigation, the NASA Langley Research Center was tasked to study the potential for radiated electromagnetic fields from external radio frequency (RF) transmitters and passenger carried portable electronic devices (PEDs) to excite the FQIS enough to cause arcing, sparking or excessive heating within the fuel tank.

Electromagnetic interference of power conditioners for solar electric propulsion

NASA Technical Reports Server (NTRS)

Whittlesey, A. C.; Macie, T. W.

1973-01-01

Electrical, multikilowatt power conditioning (PC) equipment needed on board a spacecraft utilizing solar electric propulsion creates an electromagnetic environment that is potentially deterimental to the science, navigation, and radio communication hardware. Within the scope of the solar electric propulsion system technology program, three lightweight, 2.5-kW PCs were evaluated in terms of their electromagnetic characteristics. It was found that the levels of radiated and conducted interference exceeded the levels anticipated for a solar electric propulsion mission. These noise emissions, however, were the result of deficient interference design in these models, rather than a basic inability to control interference in this type of PC.

Electromagnetic duality and the electric memory effect

NASA Astrophysics Data System (ADS)

Hamada, Yuta; Seo, Min-Seok; Shiu, Gary

2018-02-01

We study large gauge transformations for soft photons in quantum electrodynamics which, together with the helicity operator, form an ISO(2) algebra. We show that the two non-compact generators of the ISO(2) algebra correspond respectively to the residual gauge symmetry and its electromagnetic dual gauge symmetry that emerge at null infinity. The former is helicity universal (electric in nature) while the latter is helicity distinguishing (magnetic in nature). Thus, the conventional large gauge transformation is electric in nature, and is naturally associated with a scalar potential. We suggest that the electric Aharonov-Bohm effect is a direct measure for the electromagnetic memory arising from large gauge transformations.

Dimension-sensitive optical responses of electromagnetically induced transparency vapor in a waveguide

NASA Astrophysics Data System (ADS)

Qi Shen, Jian; He, Sailing

2006-12-01

A three-level EIT (electromagnetically induced transparency) vapor is used to manipulate the transparency and absorption properties of the probe light in a waveguide. The most remarkable feature of the present scheme is such that the optical responses resulting from both electromagnetically induced transparency and large spontaneous emission enhancement are very sensitive to the frequency detunings of the probe light as well as to the small changes of the waveguide dimension. The potential applications of the dimension- and dispersion-sensitive EIT responses are discussed, and the sensitivity limits of some waveguide-based sensors, including electric absorption modulator, optical switch, wavelength sensor, and sensitive magnetometer, are analyzed.

Development of Self-Potential Tomography for Early Warning System of rainfall induced Landslides: Electro-kinetic Effects and Sandbox Experiments

NASA Astrophysics Data System (ADS)

Hattori, K.; Yamazaki, T.; Terajima, T.; Huang, Q.

2017-12-01

Electro-kinetic effects is one of the possible mechanism for ULF electromagnetic phenomena preceeding landlisdes and large earthquakes. To understand general tendencies of electromagnetic changes related to electro-kinetic effects, we struggle with the integrated research to clarify the coupling among hydrological, geotechnical, and electromagnetic changes. Our final goal is to understand the ULF elecromagnetic phenomena in order to develop a simple technology for earthquake monitoring/forecasting. So, in this paper, we first show the observed waveforms possibly related to the Boso slow slip events in 2003 and 2007 and indoor landslide experiments with artificial rainfall. Then, numerical computations on the self-potential variation by the simulated groundwater flow, and compare the results with those observed by laboratory experiments. In the result, the simulated self-potential variation is consistent with observed one. FInally, we developed self-potential tomography to estimate the ground water condition. And we also characterize the pressure from the self-potential data, and compare the result with observed pressure head that is measured by pore-pressure gauge and found that the inverted pressure head is consistent with observed one. In addition, we apply the self-potential data observed by the flume test. The estimated pressure head from observed self-potential data shows the consistency with observed pressure head. And estimated pressure head also show the characteristic distribution before the landslide occurred. These facts are highly suggestive in effectiveness of the self-potential tomography to monitor groundwater changes associated with landslide. The details will be given in our presentation.

Motion of a Janus particle very near a wall

NASA Astrophysics Data System (ADS)

Rashidi, Aidin; Wirth, Christopher L.

2017-12-01

This article describes the simulated Brownian motion of a sphere comprising hemispheres of unequal zeta potential (i.e., "Janus" particle) very near a wall. The simulation tool was developed and used to assist in the methodology development for applying Total Internal Reflection Microscopy (TIRM) to anisotropic particles. Simulations of the trajectory of a Janus sphere with cap density matching that of the base particle very near a boundary were used to construct 3D potential energy landscapes that were subsequently used to infer particle and solution properties, as would be done in a TIRM measurement. Results showed that the potential energy landscape of a Janus sphere has a transition region at the location of the boundary between the two Janus halves, which depended on the relative zeta potential magnitude. The potential energy landscape was fit to accurately obtain the zeta potential of each hemisphere, particle size, minimum potential energy position and electrolyte concentration, or Debye length. We also determined the appropriate orientation bin size and regimes over which the potential energy landscape should be fit to obtain system properties. Our simulations showed that an experiment may require more than 106 observations to obtain a suitable potential energy landscape as a consequence of the multivariable nature of observations for an anisotropic particle. These results illustrate important considerations for conducting TIRM for anisotropic particles.

Electromagnetic Coupling of Negative Parity Nucleon Resonances N (1535) Based on Nonrelativistic Constituent Quark Model

NASA Astrophysics Data System (ADS)

Parsaei, Sara; Rajabi, Ali Akbar

2018-01-01

The electromagnetic transition between the nucleon and excited baryons has long been recognized as an important source of information for understanding strong interactions in the domain of quark confinement. We study the electromagnetic properties of the excitation of the negative parity the N*(1535) resonances in the nonrelativistic constituent quark model at large momentum transfers and have performed a calculation the longitudinal and transverse helicity amplitudes. Since the helicity amplitudes depend strongly on the quark wave function in this paper, we consider the baryon as a simple, non-relativistically three-body quark model and also consider a hypercentral potential scheme for the internal baryon structure, which makes three-body forces among three quarks. Since the hyper central potential depends only on the hyper radius, therefore, the Cornell potential which is a combination of the Coulombic-like term plus a linear confining term is considered as the potential for interaction between quarks. In our work, in solving the Schrodinger equation with the Cornell potential, the Nikiforov-Uvarov method employed, and the analytic eigen-energies and eigen-functions obtained. By using the obtained eigen-functions, the transition amplitudes calculated. We show that our results in the range {{{Q}}}2> 2 {{GeV}}2 lead to an overall better agreement with the experimental data in comparison with the other three non-relativistic quark models.

Theoretical simulations of the structural stabilities, elastic, thermodynamic and electronic properties of Pt3Sc and Pt3Y compounds

NASA Astrophysics Data System (ADS)

Boulechfar, R.; Khenioui, Y.; Drablia, S.; Meradji, H.; Abu-Jafar, M.; Omran, S. Bin; Khenata, R.; Ghemid, S.

2018-05-01

Ab-initio calculations based on density functional theory have been performed to study the structural, electronic, thermodynamic and mechanical properties of intermetallic compounds Pt3Sc and Pt3Y using the full-potential linearized augmented plane wave(FP-LAPW) method. The total energy calculations performed for L12, D022 and D024 structures confirm the experimental phase stability. Using the generalized gradient approximation (GGA), the values of enthalpies formation are -1.23 eV/atom and -1.18 eV/atom for Pt3Sc and Pt3Y, respectively. The densities of states (DOS) spectra show the existence of a pseudo-gap at the Fermi level for both compounds which indicate the strong spd hybridization and directing covalent bonding. Furthermore, the density of states at the Fermi level N(EF), the electronic specific heat coefficient (γele) and the number of bonding electrons per atom are predicted in addition to the elastic constants (C11, C12 and C44). The shear modulus (GH), Young's modulus (E), Poisson's ratio (ν), anisotropy factor (A), ratio of B/GH and Cauchy pressure (C12-C44) are also estimated. These parameters show that the Pt3Sc and Pt3Y are ductile compounds. The thermodynamic properties were calculated using the quasi-harmonic Debye model to account for their lattice vibrations. In addition, the influence of the temperature and pressure was analyzed on the heat capacities (Cp and Cv), thermal expansion coefficient (α), Debye temperature (θD) and Grüneisen parameter (γ).

Modified Bose-Einstein and Fermi-Dirac statistics if excitations are localized on an intermediate length scale: applications to non-Debye specific heat.

PubMed

Chamberlin, Ralph V; Davis, Bryce F

2013-10-01

Disordered systems show deviations from the standard Debye theory of specific heat at low temperatures. These deviations are often attributed to two-level systems of uncertain origin. We find that a source of excess specific heat comes from correlations between quanta of energy if excitations are localized on an intermediate length scale. We use simulations of a simplified Creutz model for a system of Ising-like spins coupled to a thermal bath of Einstein-like oscillators. One feature of this model is that energy is quantized in both the system and its bath, ensuring conservation of energy at every step. Another feature is that the exact entropies of both the system and its bath are known at every step, so that their temperatures can be determined independently. We find that there is a mismatch in canonical temperature between the system and its bath. In addition to the usual finite-size effects in the Bose-Einstein and Fermi-Dirac distributions, if excitations in the heat bath are localized on an intermediate length scale, this mismatch is independent of system size up to at least 10(6) particles. We use a model for correlations between quanta of energy to adjust the statistical distributions and yield a thermodynamically consistent temperature. The model includes a chemical potential for units of energy, as is often used for other types of particles that are quantized and conserved. Experimental evidence for this model comes from its ability to characterize the excess specific heat of imperfect crystals at low temperatures.

Structural, electronic, magnetic, elastic, and thermal properties of Co-based equiatomic quaternary Heusler alloys

NASA Astrophysics Data System (ADS)

Paudel, Ramesh; Zhu, Jingchuan

2018-05-01

In this research work, we have predicted the physical properties of CoFeZrGe and CoFeZrSb for the first time by utilizing first principle calculations based on density functional theory. The exchange-correlation potentials are treated within the generalized-gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). The investigated equilibrium lattice parameters of CoFeCrSi are in agreement with available theoretical data and for CoFeZrZ(Z = Ge,Sb) are 6.0013 and 6.2546 Å respectively. The calculated magnetic moments are 1.01μB /fu , 2μB /fu and 1μB /fu for CoFeZrZ(Z = Ge, Sb and Si) respectively, and agree with the Slater-Pauling rule, Mt =Zt - 24 . The CoFeZrGe, CoFeZrSb and CoFeZrSi composites showed half-metallic behaviour with 100 % spin polarization at equilibrium lattice parameters with band gap of 0.43, 0.70 and 0.59 eV for GGA and an improved band gap of 0.86, 1.01 and 1.08 for GGA + U respectively. Elastic properties are also discussed in this paper and it is found that all the materials are mechanically stable and ductile in nature. The CoFeZrSi alloy is found to be stiffer than CoFeZrZ(Z = Ge and Sb) alloys. The Debye temperatures are predicted by using calculated elastic constants. Moreover, the volume heat capacities (Cv) are investigated by utilizing the quasi-harmonic Debye model.

From single Debye-Hückel chains to polyelectrolyte solutions: Simulation results

NASA Astrophysics Data System (ADS)

Kremer, Kurt

1996-03-01

This lecture will present results from simulations of single weakly charged flexible chains, where the electrostatic part of the interaction is modeled by a Debye-Hückel potential,( with U. Micka, IFF, Forschungszentrum Jülich, 52425 Jülich, Germany) as well as simulations of polyelectrolyte solutions, where the counterions are explicitly taken into account( with M. J. Stevens, Sandia Nat. Lab., Albuquerque, NM 87185-1111) ( M. J. Stevens, K. Kremer, JCP 103), 1669 (1995). The first set of the simulations is meant to clear a recent contoversy on the dependency of the persistence length LP on the screening length Γ. While the analytic theories give Lp ~ Γ^x with either x=1 or x=2, the simulations find for all experimentally accessible chain lengths a varying exponent, which is significantly smaller than 1. This causes serious doubts on the applicability of this model for weakly charged polyelectrolytes in general. The second part deals with strongly charged flexible polyelectrolytes in salt free solution. These simulations are performed for multichain systems. The full Coulomb interactions of the monomers and counterions are treated explicitly. Experimental measurements of the osmotic pressure and the structure factor are reproduced and extended. The simulations reveal a new picture of the chain structure based on calculations of the structure factor, persistence length, end-to-end distance, etc. Even at very low density, the chains show significant bending. Furthermore, the chains contract significantly before they start to overlap. We also show that counterion condensation dramatically alters the chain structure, even for a good solvent backbone.

Graphene-Based Liquid-Gated Field Effect Transistor for Biosensing: Theory and Experiments

PubMed Central

Reiner-Rozman, Ciril; Larisika, Melanie; Nowak, Christoph; Knoll, Wolfgang

2015-01-01

We present an experimental and theoretical characterization for reduced Graphene-Oxide (rGO) based FETs used for biosensing applications. The presented approach shows a complete result analysis and theoretically predictable electrical properties. The formulation was tested for the analysis of the device performance in the liquid gate mode of operation with variation of the ionic strength and pH-values of the electrolytes in contact with the FET. The dependence on the Debye length was confirmed experimentally and theoretically, utilizing the Debye length as a working parameter and thus defining the limits of applicability for the presented rGO-FETs. Furthermore, the FETs were tested for the sensing of biomolecules (bovine serum albumin (BSA) as reference) binding to gate-immobilized anti-BSA antibodies and analyzed using the Langmuir binding theory for the description of the equilibrium surface coverage as a function of the bulk (analyte) concentration. The obtained binding coefficients for BSA are found to be same as in results from literature, hence confirming the applicability of the devices. The FETs used in the experiments were fabricated using wet-chemically synthesized graphene, displaying high electron and hole mobility (μ) and provide the strong sensitivity also for low potential changes (by change of pH, ion concentration, or molecule adsorption). The binding coefficient for BSA-anti-BSA interaction shows a behavior corresponding to the Langmuir adsorption theory with a Limit of Detection (LOD) in the picomolar concentration range. The presented approach shows high reproducibility and sensitivity and a good agreement of the experimental results with the calculated data. PMID:25791463

Broadband electromagnetic analysis of compacted kaolin

NASA Astrophysics Data System (ADS)

Bore, Thierry; Wagner, Norman; Cai, Caifang; Scheuermann, Alexander

2017-01-01

The mechanical compaction of soil influences not only the mechanical strength and compressibility but also the hydraulic behavior in terms of hydraulic conductivity and soil suction. At the same time, electric and dielectric parameters are increasingly used to characterize soil and to relate them with mechanic and hydraulic parameters. In the presented study electromagnetic soil properties and suction were measured under defined conditions of standardized compaction tests. The impact of external mechanical stress conditions of nearly pure kaolinite was analyzed on soil suction and broadband electromagnetic soil properties. An experimental procedure was developed and validated to simultaneously determine mechanical, hydraulic and broadband (1 MHz-3 GHz) electromagnetic properties of the porous material. The frequency dependent electromagnetic properties were modeled with a classical mixture equation (advanced Lichtenecker and Rother model, ALRM) and a hydraulic-mechanical-electromagnetic coupling approach was introduced considering water saturation, soil structure (bulk density, porosity), soil suction (pore size distribution, water sorption) as well as electrical conductivity of the aqueous pore solution. Moreover, the relaxation behavior was analyzed with a generalized fractional relaxation model concerning a high-frequency water process and two interface processes extended with an apparent direct current conductivity contribution. The different modeling approaches provide a satisfactory agreement with experimental data for the real part. These results show the potential of broadband electromagnetic approaches for quantitative estimation of the hydraulic state of the soil during densification.

Partial compilation and revision of basic data in the WATEQ programs

USGS Publications Warehouse

Nordstrom, D. Kirk; Valentine, S.D.; Ball, J.W.; Plummer, Niel; Jones, B.F.

1984-01-01

Several portions of the basic data in the WATEQ series of computer programs (WATEQ, WATEQF, WATEQ2, WATEQ3, and PHREEQE) are compiled. The density and dielectric constant of water and their temperature dependence are evaluated for the purpose of updating the Debye-Huckel solvent parameters in the activity coefficient equations. The standard state thermodynamic properties of the Fe2+ and Fe3+ aqueous ions are refined. The main portion of this report is a comprehensive listing of aluminum hydrolysis constants, aluminum fluoride, aluminum sulfate, calcium chloride, magnesium chloride, potassium sulfate and sodium sulfate stability constants, solubility product constants for gibbsite and amorphous aluminum hydroxide, and the standard electrode potentials for Fe (s)/Fe2+(aq) and Fe2 +(aq)/Fe3+(aq). (USGS)

Monte Carlo simulations of flexible polyanions complexing with whey proteins at their isoelectric point.

PubMed

de Vries, R

2004-02-15

Electrostatic complexation of flexible polyanions with the whey proteins alpha-lactalbumin and beta-lactoglobulin is studied using Monte Carlo simulations. The proteins are considered at their respective isoelectric points. Discrete charges on the model polyelectrolytes and proteins interact through Debye-Huckel potentials. Protein excluded volume is taken into account through a coarse-grained model of the protein shape. Consistent with experimental results, it is found that alpha-lactalbumin complexes much more strongly than beta-lactoglobulin. For alpha-lactalbumin, strong complexation is due to localized binding to a single large positive "charge patch," whereas for beta-lactoglobulin, weak complexation is due to diffuse binding to multiple smaller charge patches. Copyright 2004 American Institute of Physics

[Effect of electromagnetic radiation on discharge activity of neurons in the hippocampus CA1 in rats].

PubMed

Tong, Jun; Chen, Su; Liu, Xiang-Ming; Hao, Dong-Mei

2013-09-01

In order to explore effect of electromagnetic radiation on learning and memory ability of hippocampus neuron in rats, the changes in discharge patterns and overall electrical activity of hippocampus neuron after electromagnetic radiation were observed. Rat neurons discharge was recorded with glass electrode extracellular recording technology and a polygraph respectively. Radiation frequency of electromagnetic wave was 900 MHZ and the power was 10 W/m2. In glass electrode extracellular recording, the rats were separately irradiated for 10, 20, 30, 40, 50 and 60 min, every points repeated 10 times and updated interval of 1h, observing the changes in neuron discharge and spontaneous discharge patterns after electromagnetic radiation. In polygraph recording experiments, irradiation group rats for five days a week, 6 hours per day, repeatedly for 10 weeks, memory electrical changes in control group and irradiation group rats when they were feeding were repeatedly monitored by the implanted electrodes, observing the changes in peak electric digits and the largest amplitude in hippocampal CA1 area, and taking some electromagnetic radiation sampling sequence for correlation analysis. (1) Electromagnetic radiation had an inhibitory role on discharge frequency of the hippocampus CA1 region neurons. After electromagnetic radiation, discharge frequency of the hippocampus CA1 region neurons was reduced, but the changes in scale was not obvious. (2) Electromagnetic radiation might change the spontaneous discharge patterns of hippocampus CA1 region neurons, which made the explosive discharge pattern increased obviously. (3) Peak potential total number within 5 min in irradiation group was significantly reduced, the largest amplitude was less than that of control group. (4) Using mathematical method to make the correlation analysis of the electromagnetic radiation sampling sequence, that of irradiation group was less than that of control group, indicating that there was a tending to be inhibitory connection between neurons in irradiation group after electromagnetic radiation. Electromagnetic radiation may cause structure and function changes of transfer synaptic in global, make hippocampal CA1 area neurons change in the overall discharge characteristic and discharge patterns, thus lead to decrease in the ability of learning and memory.

The measurement procedure in the SEMONT monitoring system.

PubMed

Djuric, Nikola; Kljajic, Dragan; Kasas-Lazetic, Karolina; Bajovic, Vera

2014-03-01

The measurement procedure of the open area in situ electric field strength is presented, acquiring the real field data for testing of the Serbian electromagnetic field monitoring network (SEMONT) and its Internet portal. The SEMONT monitoring system introduces an advanced approach of wireless sensor network utilization for the continuous supervision of overall and cumulative level of electromagnetic field over the observed area. The aim of the SEMONT system is to become a useful tool for the national and municipal agencies for the environmental protection, regarding the electromagnetic pollution monitoring and the exposure assessment of the general population. Considering the public concern on the potentially harmful effects of the long-term exposure to electromagnetic radiation, as well as the public transparency principle that is incorporated into the Serbian law on non-ionizing radiation protection, the SEMONT monitoring system is designed for the long-term continuous monitoring, presenting real-time measurement results, and corresponding exposure assessment over the public Internet network.

Tunable electromagnetically induced transparency in coupled three-dimensional split-ring-resonator metamaterials

PubMed Central

Han, Song; Cong, Longqing; Lin, Hai; Xiao, Boxun; Yang, Helin; Singh, Ranjan

2016-01-01

Metamaterials have recently enabled coupling induced transparency due to interference effects in coupled subwavelength resonators. In this work, we present a three dimensional (3-D) metamaterial design with six-fold rotational symmetry that shows electromagnetically induced transparency with a strong polarization dependence to the incident electromagnetic wave due to the ultra-sharp resonance line width as a result of interaction between the constituent meta-atoms. However, when the six-fold rotationally symmetric unit cell design was re-arranged into a fourfold rotational symmetry, we observed the excitation of a polarization insensitive dual-band transparency. Thus, the 3-D split-ring resonators allow new schemes to observe single and multi-band classical analogues of electromagnetically induced transparencies that has huge potential applications in slowing down light, sensing modalities, and filtering functionalities either in the passive mode or the active mode where such effects could be tuned by integrating materials with dynamic properties. PMID:26857034

Electromagnetized gold nanoparticles mediate direct lineage reprogramming into induced dopamine neurons in vivo for Parkinson's disease therapy

NASA Astrophysics Data System (ADS)

Yoo, Junsang; Lee, Euiyeon; Kim, Hee Young; Youn, Dong-Ho; Jung, Junghyun; Kim, Hongwon; Chang, Yujung; Lee, Wonwoong; Shin, Jaein; Baek, Soonbong; Jang, Wonhee; Jun, Won; Kim, Soochan; Hong, Jongki; Park, Hi-Joon; Lengner, Christopher J.; Moh, Sang Hyun; Kwon, Youngeun; Kim, Jongpil

2017-10-01

Electromagnetic fields (EMF) are physical energy fields generated by electrically charged objects, and specific ranges of EMF can influence numerous biological processes, which include the control of cell fate and plasticity. In this study, we show that electromagnetized gold nanoparticles (AuNPs) in the presence of specific EMF conditions facilitate an efficient direct lineage reprogramming to induced dopamine neurons in vitro and in vivo. Remarkably, electromagnetic stimulation leads to a specific activation of the histone acetyltransferase Brd2, which results in histone H3K27 acetylation and a robust activation of neuron-specific genes. In vivo dopaminergic neuron reprogramming by EMF stimulation of AuNPs efficiently and non-invasively alleviated symptoms in mouse Parkinson's disease models. This study provides a proof of principle for EMF-based in vivo lineage conversion as a potentially viable and safe therapeutic strategy for the treatment of neurodegenerative disorders.

Radio Frequency Electromagnetic Radiation From Streamer Collisions

NASA Astrophysics Data System (ADS)

Luque, Alejandro

2017-10-01

We present a full electromagnetic model of streamer propagation where the Maxwell equations are solved self-consistently together with electron transport and reactions including photoionization. We apply this model to the collision of counter-propagating streamers in gaps tens of centimeters wide and with large potential differences of hundreds of kilovolts. Our results show that streamer collisions emit electromagnetic pulses that, at atmospheric pressure, dominate the radio frequency spectrum of an extended corona in the range from about 100 MHz to a few gigahertz. We also investigate the fast penetration, after a collision, of electromagnetic fields into the streamer heads and show that these fields are capable of accelerating electrons up to about 100 keV. By substantiating the link between X-rays and high-frequency radio emissions and by describing a mechanism for the early acceleration of runaway electrons, our results support the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges.

Electromagnetic containerless processing requirements and recommended facility concept and capabilities for space lab

NASA Technical Reports Server (NTRS)

Frost, R. T.; Bloom, H. L.; Napaluch, L. J.; Stockhoff, E. H.; Wouch, G.

1974-01-01

Containerless melting, reaction, and solidification experiments and processes which potentially can lead to new understanding of material science and production of new or improved materials in the weightless space environment are reviewed in terms of planning for spacelab. Most of the experiments and processes discussed are amenable to the employment of electromagnetic position control and electromagnetic induction or electron beam heating and melting. The spectrum of relevant properties of materials, which determine requirements for a space laboratory electromagnetic containerless processing facility are reviewed. Appropriate distributions and associated coil structures are analyzed and compared on the basis of efficiency, for providing the functions of position sensing, control, and induction heating. Several coil systems are found capable of providing these functions. Exchangeable modular coils in appropriate sizes are recommended to achieve the maximum power efficiencies, for a wide range of specimen sizes and resistivities, in order to conserve total facility power.

Radio Frequency Electromagnetic Radiation From Streamer Collisions.

PubMed

Luque, Alejandro

2017-10-16

We present a full electromagnetic model of streamer propagation where the Maxwell equations are solved self-consistently together with electron transport and reactions including photoionization. We apply this model to the collision of counter-propagating streamers in gaps tens of centimeters wide and with large potential differences of hundreds of kilovolts. Our results show that streamer collisions emit electromagnetic pulses that, at atmospheric pressure, dominate the radio frequency spectrum of an extended corona in the range from about 100 MHz to a few gigahertz. We also investigate the fast penetration, after a collision, of electromagnetic fields into the streamer heads and show that these fields are capable of accelerating electrons up to about 100 keV. By substantiating the link between X-rays and high-frequency radio emissions and by describing a mechanism for the early acceleration of runaway electrons, our results support the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges.

Constraints and stability in vector theories with spontaneous Lorentz violation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bluhm, Robert; Gagne, Nolan L.; Potting, Robertus

2008-06-15

Vector theories with spontaneous Lorentz violation, known as bumblebee models, are examined in flat spacetime using a Hamiltonian constraint analysis. In some of these models, Nambu-Goldstone modes appear with properties similar to photons in electromagnetism. However, depending on the form of the theory, additional modes and constraints can appear that have no counterparts in electromagnetism. An examination of these constraints and additional degrees of freedom, including their nonlinear effects, is made for a variety of models with different kinetic and potential terms, and the results are compared with electromagnetism. The Hamiltonian constraint analysis also permits an investigation of the stabilitymore » of these models. For certain bumblebee theories with a timelike vector, suitable restrictions of the initial-value solutions are identified that yield ghost-free models with a positive Hamiltonian. In each case, the restricted phase space is found to match that of electromagnetism in a nonlinear gauge.« less

Near Wake Depletion of Non-Magnetized Bodies Immersed in Mesosonic Plasma Flow

NASA Technical Reports Server (NTRS)

Wright, K. H.; Stone, N. H.; Samir, U.; Sorensen, J.; Winningham, J. D.

1997-01-01

During the recent TSS-1R mission, measurements of ion depletion in the near wake were obtained at a downstream distance of two body radii from the satellite center. The ratio of satellite radius to Debye length is approximately 150. Similar measurements were also obtained at the same downstream location in the wake of the shuttle during the Spacelab 2 mission of August 1985. In the case of the shuttle, the ratio of body radius to Debye length is greater than 1000. The wake depletion observed in the these two cases, together with data obtained from previous ionospheric satellites and from applicable laboratory experiments involving small bodies, will be compared in order to determine the influence of body size on wake filling. Extrapolation of these results to the case of the moon in the solar wind will be noted.

Calculation of Energy Diagram of Asymmetric Graded-Band-Gap Semiconductor Superlattices.

PubMed

Monastyrskii, Liubomyr S; Sokolovskii, Bogdan S; Alekseichyk, Mariya P

2017-12-01

The paper theoretically investigates the peculiarities of energy diagram of asymmetric graded-band-gap superlattices with linear coordinate dependences of band gap and electron affinity. For calculating the energy diagram of asymmetric graded-band-gap superlattices, linearized Poisson's equation has been solved for the two layers forming a period of the superlattice. The obtained coordinate dependences of edges of the conduction and valence bands demonstrate substantial transformation of the shape of the energy diagram at changing the period of the lattice and the ratio of width of the adjacent layers. The most marked changes in the energy diagram take place when the period of lattice is comparable with the Debye screening length. In the case when the lattice period is much smaller that the Debye screening length, the energy diagram has the shape of a sawtooth-like pattern.

First principle study of structural, elastic and electronic properties of APt3 (A=Mg, Sc, Y and Zr)

NASA Astrophysics Data System (ADS)

Benamer, A.; Roumili, A.; Medkour, Y.; Charifi, Z.

2018-02-01

We report results obtained from first principle calculations on APt3 compounds with A=Mg, Sc, Y and Zr. Our results of the lattice parameter a are in good agreement with experimental data, with deviations less than 0.8%. Single crystal elastic constants are calculated, then polycrystalline elastic moduli (bulk, shear and Young moduli, Poisson ration, anisotropy factor) are presented. Based on Debye model, Debye temperature ϴD is calculated from the sound velocities Vl, Vt and Vm. Band structure results show that the studied compounds are electrical conductors, the conduction mechanism is assured by Pt-d electrons. Different hybridisation states are observed between Pt-d and A-d orbitals. The study of the charge density distribution and the population analysis shows the coexistence of ionic, covalent and metallic bonds.

Effect of hydrostatic pressure on physical properties of strontium based fluoroperovskites for novel applications

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2018-02-01

Density functional theory (DFT) is employed to calculate the effect of pressure variation on electronic structure, elastic parameters, mechanical durability, and thermodynamic aspects of SrRbF3, in combination with Quasi-harmonic Debye model. The pressure effects are determined in the range of 0-25 GPa, in which cubic stability of SrRbF3 fluoroperovskite remains valid. Significant influence of compression on wide range of elastic parameters and related mechanical properties have been discussed, to utilize this material in low birefringence lens fabrication technology. Apart of linear dependence on elastic coefficients, transition from brittle to ductile behavior is also observed at elevated pressure ranges. Moreover, successful prediction of important thermodynamic aspects such as volume expansion coefficient (α), Debye temperature (θ D), heat capacities (Cp and Cv) are also done within wide pressure and temperature ranges.

Analysis of terahertz dielectric properties of pork tissue

NASA Astrophysics Data System (ADS)

Huang, Yuqing; Xie, Qiaoling; Sun, Ping

2017-10-01

Seeing that about 70% component of fresh biological tissues is water, many scientists try to use water models to describe the dielectric properties of biological tissues. The classical water dielectric models are Debye model, Double Debye model and Cole-Cole model. This work aims to determine a suitable model by comparing three models above with experimental data. These models are applied to fresh pork tissue. By means of least square method, the parameters of different models are fitted with the experimental data. Comparing different models on both dielectric function, the Cole-Cole model is verified the best to describe the experiments of pork tissue. The correction factor α of the Cole-Cole model is an important modification for biological tissues. So Cole-Cole model is supposed to be a priority selection to describe the dielectric properties for biological tissues in the terahertz range.

Measurements of the Casimir-Lifshitz force in fluids: The effect of electrostatic forces and Debye screening

NASA Astrophysics Data System (ADS)

Munday, J. N.; Capasso, Federico; Parsegian, V. Adrian; Bezrukov, Sergey M.

2008-09-01

We present detailed measurements of the Casimir-Lifshitz force between two gold surfaces (a sphere and a plate) immersed in ethanol and study the effect of residual electrostatic forces, which are dominated by static fields within the apparatus and can be reduced with proper shielding. Electrostatic forces are further reduced by Debye screening through the addition of salt ions to the liquid. Additionally, the salt leads to a reduction of the Casimir-Lifshitz force by screening the zero-frequency contribution to the force; however, the effect is small between gold surfaces at the measured separations and within experimental error. An improved calibration procedure is described and compared with previous methods. Finally, the experimental results are compared with Lifshitz’s theory and found to be consistent for the materials used in the experiment.