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Sample records for anomalous hollow electron

  1. Observations And Measurements of Anomalous Hollow Electron Beams in a Storage Ring

    SciTech Connect

    Wu, Y.K.; Li, J.; Wu, J.; /SLAC

    2006-02-06

    Anomalous hollow electron beams have been recently observed in the Duke storage ring. With a single bunch beam in a lattice with a negative chromaticity, a hollow beam can be created. This beam consists of a solid core beam inside and a large ring beam outside. In this paper, we report the measurements of the hollow beam phenomenon, including its distinct image pattern and spectrum signature, and its evolution with time. By capturing the post-instability bursting beam, the hollow beam is a unique model system for studying transverse instabilities, in particular, the interplay of the wakefield and lattice nonlinearity. The hollow beam can also be used as a tool to study linear and nonlinear particle dynamics in the storage ring.

  2. Collimation with hollow electron beams.

    PubMed

    Stancari, G; Valishev, A; Annala, G; Kuznetsov, G; Shiltsev, V; Still, D A; Vorobiev, L G

    2011-08-19

    A novel concept of controlled halo removal for intense high-energy beams in storage rings and colliders is presented. It is based on the interaction of the circulating beam with a 5-keV, magnetically confined, pulsed hollow electron beam in a 2-m-long section of the ring. The electrons enclose the circulating beam, kicking halo particles transversely and leaving the beam core unperturbed. By acting as a tunable diffusion enhancer and not as a hard aperture limitation, the hollow electron beam collimator extends conventional collimation systems beyond the intensity limits imposed by tolerable losses. The concept was tested experimentally at the Fermilab Tevatron proton-antiproton collider. The first results on the collimation of 980-GeV antiprotons are presented. PMID:21929171

  3. Hollow cathode lamp based Faraday anomalous dispersion optical filter

    PubMed Central

    Pan, Duo; Xue, Xiaobo; Shang, Haosen; Luo, Bin; Chen, Jingbiao; Guo, Hong

    2016-01-01

    The Faraday anomalous dispersion optical filter (FADOF), which has acquired wide applications, is mainly limited to some gaseous elements and low melting-point metals before, for the restriction of the attainable atomic density. In conventional FADOF systems a high atomic density is usually achieved by thermal equilibrium at the saturated vapor pressure, hence for elements with high melting-points a high temperature is required. To avoid this restriction, we propose a scheme of FADOF based on the hollow cathode lamp (HCL), instead of atomic vapor cells. Experimental results in strontium atoms verified this scheme, where a transmission peak corresponding to the 88Sr (5s2)1S0 − (5s5p)1P1 transition (461 nm) is obtained, with a maximum transmittance of 62.5% and a bandwith of 1.19 GHz. The dependence of transmission on magnetic field and HCL discharge current is also studied. Since the state-of-art commercial HCLs cover about 70 elements, this scheme can greatly expand the applications of FADOFs, and the abundant atomic transitions they provide bring the HCL based FADOFs potential applications for frequency stabilization. PMID:27418112

  4. Hollow cathode lamp based Faraday anomalous dispersion optical filter

    NASA Astrophysics Data System (ADS)

    Pan, Duo; Xue, Xiaobo; Shang, Haosen; Luo, Bin; Chen, Jingbiao; Guo, Hong

    2016-07-01

    The Faraday anomalous dispersion optical filter (FADOF), which has acquired wide applications, is mainly limited to some gaseous elements and low melting-point metals before, for the restriction of the attainable atomic density. In conventional FADOF systems a high atomic density is usually achieved by thermal equilibrium at the saturated vapor pressure, hence for elements with high melting-points a high temperature is required. To avoid this restriction, we propose a scheme of FADOF based on the hollow cathode lamp (HCL), instead of atomic vapor cells. Experimental results in strontium atoms verified this scheme, where a transmission peak corresponding to the 88Sr (5s2)1S0 ‑ (5s5p)1P1 transition (461 nm) is obtained, with a maximum transmittance of 62.5% and a bandwith of 1.19 GHz. The dependence of transmission on magnetic field and HCL discharge current is also studied. Since the state-of-art commercial HCLs cover about 70 elements, this scheme can greatly expand the applications of FADOFs, and the abundant atomic transitions they provide bring the HCL based FADOFs potential applications for frequency stabilization.

  5. Hollow cathode lamp based Faraday anomalous dispersion optical filter.

    PubMed

    Pan, Duo; Xue, Xiaobo; Shang, Haosen; Luo, Bin; Chen, Jingbiao; Guo, Hong

    2016-01-01

    The Faraday anomalous dispersion optical filter (FADOF), which has acquired wide applications, is mainly limited to some gaseous elements and low melting-point metals before, for the restriction of the attainable atomic density. In conventional FADOF systems a high atomic density is usually achieved by thermal equilibrium at the saturated vapor pressure, hence for elements with high melting-points a high temperature is required. To avoid this restriction, we propose a scheme of FADOF based on the hollow cathode lamp (HCL), instead of atomic vapor cells. Experimental results in strontium atoms verified this scheme, where a transmission peak corresponding to the (88)Sr (5s(2))(1)S0 - (5s5p)(1)P1 transition (461 nm) is obtained, with a maximum transmittance of 62.5% and a bandwith of 1.19 GHz. The dependence of transmission on magnetic field and HCL discharge current is also studied. Since the state-of-art commercial HCLs cover about 70 elements, this scheme can greatly expand the applications of FADOFs, and the abundant atomic transitions they provide bring the HCL based FADOFs potential applications for frequency stabilization. PMID:27418112

  6. Anomalous optogalvanic line shapes of argon metastable transitions in a hollow cathode lamp

    NASA Technical Reports Server (NTRS)

    Ruyten, W. M.

    1993-01-01

    Anomalous optogalvanic line shapes were observed in a commercial hollow cathode lamp containing argon buffer gas. Deviations from Gaussian line shapes were particularly strong for transitions originating from the 3P2 metastable level of argon. The anomalous line shapes can be described reasonably well by the assumption that two regions in the discharge are excited simultaneously, each giving rise to a purely Gaussian line shape, but with different polarities, amplitudes, and linewidths.

  7. Three dimensional simulation of the operation of a hollow cathode electron emitter on the Shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Davis, V. A.; Katz, I.; Mandell, M. J.; Parks, D. E.

    1986-01-01

    Several researchers have suggested using hollow cathodes as plasma contactors for electrodynamic tethers, particularly to prevent the shuttle orbiter from charging to large negative potentials. Previous studies have shown that fluid models with anomalous scattering can describe the electron transport in hollow cathode generated plasmas. An improved theory of the hollow cathode plasmas is developed and computational results using the theory are compared with laboratory experiment. Numerical predictions for a hollow cathode plasma source of the type considered for use on the shuttle are presented as are three-dimensional NASCAP/LEO calculations of the emitted ion trajectories and the resulting potentials in the vicinity of the orbiter. The computer calculations show that the hollow cathode plasma source makes vastly superior contact with the ionospheric plasma compared with either an electron gun or passive ion collection by the orbiter.

  8. Hollow cathodes as electron emitting plasma contactors Theory and computer modeling

    NASA Technical Reports Server (NTRS)

    Davis, V. A.; Katz, I.; Mandell, M. J.; Parks, D. E.

    1987-01-01

    Several researchers have suggested using hollow cathodes as plasma contactors for electrodynamic tethers, particularly to prevent the Shuttle Orbiter from charging to large negative potentials. Previous studies have shown that fluid models with anomalous scattering can describe the electron transport in hollow cathode generated plasmas. An improved theory of the hollow cathode plasmas is developed and computational results using the theory are compared with laboratory experiments. Numerical predictions for a hollow cathode plasma source of the type considered for use on the Shuttle are presented, as are three-dimensional NASCAP/LEO calculations of the emitted ion trajectories and the resulting potentials in the vicinity of the Orbiter. The computer calculations show that the hollow cathode plasma source makes vastly superior contact with the ionospheric plasma compared with either an electron gun or passive ion collection by the Orbiter.

  9. Electronic properties of Si hollow nanowires

    SciTech Connect

    Di Mario, Lorenzo; Martelli, Faustino; Turchini, Stefano; Zema, Nicola; Cimino, Roberto

    2014-11-07

    The electronic and structural properties of amorphous and crystalline silicon hollow nanowires (HNWs) have been investigated by X-ray photoemission (XPS), Raman, and photoluminescence spectroscopies. The HNWs have an internal diameter of about 80 nm and sidewalls with a thickness of 8–15 nm. Crystalline HNWs are obtained by thermal annealing of the amorphous ones. XPS shows that although oxidation is a very important process in these suspended nanostructures, a clear Si 2p signal is detected in the crystalline HNWS, thus indicating that the sidewall surface maintains mainly a pure silicon nature. Raman shows that the thermal annealing gives rise to a very good crystal quality and a weak visible luminescence signal is detected in the crystalline HNWs.

  10. Development of hollow electron beams for proton and ion collimation

    SciTech Connect

    Stancari, G.; Drozhdin, A.I.; Kuznetsov, G.; Shiltsev, V.; Still, D.A.; Valishev, A.; Vorobiev, L.G.; Assmann, R.; Kabantsev, A.; /UC, San Diego

    2010-06-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

  11. Anomalous electronic transport in boron carbides

    NASA Astrophysics Data System (ADS)

    Emin, D.; Samara, G. A.; Wood, C.

    The boron carbides are composed of icosahedral units, B12 and B11C1, linked together by strong intericosahedral bonds. With such distributions of icosahedral and intericosahedral compositions, boron carbides, B/sub 1-x/C/sub x/, are single phase over 0.1 less than or equal to x less than or equal to 0.2. The electronic transport properties of the boron carbides were examined within this single-phase region. Results are inconsistent with conventional analyses of both itinerant and hopping transport. Most striking are Seebeck coefficients which are both large and rapidly increasing functions of temperature despite thermally activated dc conductivities. These results manifest the hopping of small bipolaronic holes between carbon-containing icosahedral that are inequivalent in energy and electron-lattice coupling strength. Under hydrostatic pressures up to approx. 25 kbar, the dc conductivities increase with pressure. This anomalous behavior for hopping conduction reflects the distinctive structure and bonding of these materials.

  12. Monodisperse Hollow Tricolor Pigment Particles for Electronic Paper

    PubMed Central

    2010-01-01

    A general approach has been designed to blue, green, and red pigments by metal ions doping hollow TiO 2. The reaction involves initial formation of PS at TiO2 core–shell nanoparticles via a mixed-solvent method, and then mixing with metal ions solution containing PEG, followed calcining in the atmosphere. The as-prepared hollow pigments exhibit uniform size, bright color, and tunable density, which are fit for electronic paper display. PMID:20651918

  13. Anomalous cross field electron transport in a Hall effect thruster

    SciTech Connect

    Boniface, C.; Garrigues, L.; Hagelaar, G. J. M.; Boeuf, J. P.; Gawron, D.; Mazouffre, S.

    2006-10-16

    The origin of anomalous electron transport across the magnetic field in the channel of a Hall effect thruster has been the subject of controversy, and the relative importance of electron-wall collisions and plasma turbulence on anomalous transport is not clear. From comparisons between Fabry-Perot measurements and hybrid model calculations of the ion velocity profile in a 5 kW Hall effect thruster, we deduce that one and the same mechanism is responsible for anomalous electron transport inside and outside the Hall effect thruster channel. This suggests that the previous assumption that Bohm anomalous conductivity is dominant outside the thruster channel whereas electron-wall conductivity prevails inside the channel is not valid.

  14. Anomalous confined electron states in graphene superlattices

    SciTech Connect

    Anh Le, H.; Chien Nguyen, D.; Nam Do, V.

    2014-07-07

    We show that periodic scalar potentials can induce the localization of some electronic states in graphene. Particularly, localized states are found at energies outside the potential variation range and embedded in the continuum spectrum of delocalized ones. The picture of the connection of wave functions with typical symmetries defined in relevant-edge nanoribbons is employed to explain the formation of the electronic structure and to characterize/classify eigen-states in graphene superlattices.

  15. Modeling of anomalous electron mobility in Hall thrusters

    SciTech Connect

    Koo, Justin W.; Boyd, Iain D.

    2006-03-15

    Accurate modeling of the anomalous electron mobility is absolutely critical for successful simulation of Hall thrusters. In this work, existing computational models for the anomalous electron mobility are used to simulate the UM/AFRL P5 Hall thruster (a 5 kW laboratory model) in a two-dimensional axisymmetric hybrid particle-in-cell Monte Carlo collision code. Comparison to experimental results indicates that, while these computational models can be tuned to reproduce the correct thrust or discharge current, it is very difficult to match all integrated performance parameters (thrust, power, discharge current, etc.) simultaneously. Furthermore, multiple configurations of these computational models can produce reasonable integrated performance parameters. A semiempirical electron mobility profile is constructed from a combination of internal experimental data and modeling assumptions. This semiempirical electron mobility profile is used in the code and results in more accurate simulation of both the integrated performance parameters and the mean potential profile of the thruster. Results indicate that the anomalous electron mobility, while absolutely necessary in the near-field region, provides a substantially smaller contribution to the total electron mobility in the high Hall current region near the thruster exit plane.

  16. In situ conversion of nanostructures from solid to hollow in transmission electron microscopes using electron beam

    NASA Astrophysics Data System (ADS)

    El Mel, Abdel-Aziz; Bittencourt, Carla

    2016-05-01

    With the current development of electron beam sources, the use of transmission electron microscopes is no more limited to imaging or chemical analysis but has rather been extended to nanoengineering. This includes the e-beam induced growth, etching and structural transformation of nanomaterials. In this review we summarize recent progress on the e-beam induced morphological transformation of nanostructures from solid to hollow. We provide a detailed account of the processes reported so far in the literature with a special emphasis on the mechanistic understanding of the e-beam induced hollowing of nanomaterials. Through an important number of examples, we discuss how one can achieve a precise control of such hollowing processes by understanding the fundamental mechanisms occurring at the atomic scale during the irradiation of solid nanostructures. Finally, we conclude with remarks and our own view on the prospective future directions of this research field.

  17. In situ conversion of nanostructures from solid to hollow in transmission electron microscopes using electron beam.

    PubMed

    El Mel, Abdel-Aziz; Bittencourt, Carla

    2016-06-01

    With the current development of electron beam sources, the use of transmission electron microscopes is no more limited to imaging or chemical analysis but has rather been extended to nanoengineering. This includes the e-beam induced growth, etching and structural transformation of nanomaterials. In this review we summarize recent progress on the e-beam induced morphological transformation of nanostructures from solid to hollow. We provide a detailed account of the processes reported so far in the literature with a special emphasis on the mechanistic understanding of the e-beam induced hollowing of nanomaterials. Through an important number of examples, we discuss how one can achieve a precise control of such hollowing processes by understanding the fundamental mechanisms occurring at the atomic scale during the irradiation of solid nanostructures. Finally, we conclude with remarks and our own view on the prospective future directions of this research field. PMID:27172892

  18. Anomalous broadening of energy distributions in photoemitted electron beams

    NASA Astrophysics Data System (ADS)

    Guidi, Vincenzo

    1996-06-01

    Photoemission is widely used to generate electron beams with an energy spread lower than by thermoemission. However, when a photocathode is illuminated by a multimode laser this feature is lost and an electron beam with several eV of energy spread is produced. We have developed an explanation for this anomalous behavior pointing out its origin in the combined effect of charge relaxation, taking place within the beam, together with the modulation of the laser power imposed by laser modes. The model permits a correct interpretation overall experimental evidences.

  19. Combinatorial approach to identify electronically cloaked hollow nanoparticles

    NASA Astrophysics Data System (ADS)

    Shen, Wenqing; Tian, Tao; Liao, Bolin; Zebarjadi, Mona

    2014-08-01

    The possibility of designing core-shell nanoparticles that are "invisible" to the conduction electrons has been demonstrated recently. A total scattering cross section smaller than 0.01% of the physical cross section was demonstrated by artificially adjusting the parameters of the barrier and the well in a core-shell geometry. In this paper, we aim to extend the developed concept and find realistic material combinations that satisfy the cloaking criteria. We report designs of hollow nanoparticles that could be used to realize the cloaking concept in III-V semiconductor host matrices. Such particles could be used in advanced materials design to enhance and tune the electrical and the thermoelectric properties of a given host matrix. This paper may also contribute to defect engineering by coating defect sites with a proper cloaking layer.

  20. Effects of anomalous transport on lower hybrid electron heating

    SciTech Connect

    McCoy, M.G.; Harvey, R.W.

    1981-02-01

    The transport of electron energy out of tokamaks is known to be far greater than that calculated using classical and neoclassical theory. However, low levels of non-axisymmetric magnetic field turbulence can couple the fast transport of electrons parallel to the magnetic field lines to radial transport, thus providing a plausible explanation for observed energy confinement. These models further predict that the electron loss rate is proportional to v/sub parallel bars/. This has subsequently been found to be consistent with data for runaway electrons in PLT, at energies up to 1 MeV. Recently it has been pointed out by Chan, Chiu and Ohkawa that anomalous transport processes should be taken into account in attempting to determine steady state electron distribution functions for cases involving RF electron tail heating, particularly in view of the v/sub parallel bars/ dependence of the loss rate. In this work these physical processes are modeled through a 2-D nonlinear program which describes the evolution of the electron distribution function in velocity magnitude; (v) and plasma radius (r), and which studies the efficiency of tail electron heating.

  1. Anomalous conductivity and secondary electron emission in Hall effect thrusters

    SciTech Connect

    Garrigues, L.; Hagelaar, G. J. M.; Boniface, C.; Boeuf, J. P.

    2006-12-15

    This paper is devoted to the study of the effects of electron-wall interactions on cross magnetic field electron momentum and energy losses in Hall effect thrusters. By coupling a semianalytical model of the wall sheath similar to models used by several authors in this context, with a two-dimensional hybrid simulation of a Hall effect thruster, we find that the cross magnetic field conductivity enhanced by electron-wall collisions and secondary electron emission is not sufficient to explain the conductivity deduced from experiments. Calculated current-voltage curves including electron-wall collisions from a standard sheath model as the sole 'anomalous' conductivity mechanism do not reproduce the measurements, especially at high discharge voltages, and for various wall ceramics. Results also show that a one-dimensional description of electron-wall collisions with a constant radial plasma density profile as used by many authors leads to an overestimation of the contribution of electron-wall interactions to cross magnetic field conductivity.

  2. Anomalous Skin Effect for Anisotropic Electron Velocity Distribution Function

    SciTech Connect

    Igor Kaganovich; Edward Startsev; Gennady Shvets

    2004-02-19

    The anomalous skin effect in a plasma with a highly anisotropic electron velocity distribution function (EVDF) is very different from skin effect in a plasma with the isotropic EVDF. An analytical solution was derived for the electric field penetrated into plasma with the EVDF described as a Maxwellian with two temperatures Tx >> Tz, where x is the direction along the plasma boundary and z is the direction perpendicular to the plasma boundary. The skin layer was found to consist of two distinctive regions of width of order nTx/w and nTz/w, where nTx,z/w = (Tx,z/m)1/2 is the thermal electron velocity and w is the incident wave frequency.

  3. Anomalous electron mobility in a coaxial Hall discharge plasma.

    PubMed

    Meezan, N B; Hargus, W A; Cappelli, M A

    2001-02-01

    A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various electrostatic probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical (collision-driven) Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electron-transport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of (omega(ce)tau)(eff) approximately 16. These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies (elastic collision induced plus fluctuation induced), as proposed by Boeuf and Garrigues [J. Appl. Phys. 84, 3541 (1998)]. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized. PMID:11308588

  4. The Electronic Properties of Superatom States of Hollow Molecules

    SciTech Connect

    Feng, Min; Zhao, Jin; Huang, Tian; Zhu, Xiaoyang; Petek, Hrvoje

    2011-05-17

    Electronic and optical properties of molecules and molecular solids are traditionally considered from the perspective of the frontier orbitals and their intermolecular interactions. How molecules condense into crystalline solids, however, is mainly attributed to the long-range polarization interaction. In this Account, we show that long-range polarization also introduces a distinctive set of diffuse molecular electronic states, which in quantum structures or solids can combine into nearly-free-electron (NFE) bands. These NFE properties, which are usually associated with good metals, are vividly evident in sp2 hybridized carbon materials, specifically graphene and its derivatives. The polarization interaction is primarily manifested in the screening of an external charge at a solid/vacuum interface. It is responsible for the universal image potential and the associated unoccupied image potential (IP) states, which are observed even at the He liquid/vacuum interface. The molecular electronic properties that we describe are derived from the IP states of graphene, which float above and below the molecular plane and undergo free motion parallel to it. Rolling or wrapping a graphene sheet into a nanotube or a fullerene transforms the IP states into diffuse atom-like orbitals that are bound primarily to hollow molecular cores, rather than the component atoms. Therefore, we named them the superatom molecular orbitals (SAMOs). Like the excitonic states of semiconductor nanostructures or the plasmonic resonances of metallic nanoparticles, SAMOs of fullerene molecules, separated by their van der Waals distance, can combine to form diatomic molecule-like orbitals of C60 dimers. For larger aggregates, they form NFE bands of superatomic quantum structures and solids. The overlap of the diffuse SAMO wavefunctions in van der Waals solids provides a different paradigm for band formation than the valence or conduction bands formed by interaction of the more tightly bound

  5. Anomalous skin effects in a weakly magnetized degenerate electron plasma

    NASA Astrophysics Data System (ADS)

    Abbas, G.; Sarfraz, M.; Shah, H. A.

    2014-09-01

    Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring the ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].

  6. Anomalous k⊥(-8/3) spectrum in electron magnetohydrodynamic turbulence.

    PubMed

    Meyrand, Romain; Galtier, Sébastien

    2013-12-27

    Electron magnetohydrodynamic turbulence is investigated under the presence of a relatively strong external magnetic field b0e∥ and through three-dimensional direct numerical simulations. Our study reveals the emergence of a k⊥(-8/3) scaling for the magnetic energy spectrum at scales k∥(D)≤k⊥≤k⊥(D), where k∥(D) and k⊥(D) are, respectively, the typical largest dissipative scales along and transverse to the b0 direction. Unlike standard magnetohydrodynamic, this turbulence regime is characterized by filaments of electric currents parallel to b0. The anomalous scaling is in agreement with a heuristic model in which the transfer in the parallel direction is negligible. Implications for solar wind turbulence are discussed. PMID:24483798

  7. Anomalous skin effects in a weakly magnetized degenerate electron plasma

    SciTech Connect

    Abbas, G. Sarfraz, M.; Shah, H. A.

    2014-09-15

    Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring the ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].

  8. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    SciTech Connect

    Sydorenko, D.; Kaganovich, I. D.; Chen, L.; Ventzek, P. L. G.

    2015-12-15

    Generation of anomalously energetic suprathermal electrons was observed in simulation of a high-voltage dc discharge with electron emission from the cathode. An electron beam produced by the emission interacts with the nonuniform plasma in the discharge via a two-stream instability. The energy transfer from the beam to the plasma electrons is ensured by the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The waves with short wavelength near the anode accelerate plasma bulk electrons to suprathermal energies. The sheath near the anode reflects some of the accelerated electrons back into the plasma. These electrons travel through the plasma, reflect near the cathode, and enter the accelerating area again but with a higher energy than before. Such particles are accelerated to energies much higher than after the first acceleration. This mechanism plays a role in explaining earlier experimental observations of energetic suprathermal electrons in similar discharges.

  9. Simulation of Hollow Electron Beam Collimation in the Fermilab Tevatron Collider

    SciTech Connect

    Morozov, I.A.; Stancari, G.; Valishev, A.; Shatilov, D.N.; /Novosibirsk, IYF

    2012-05-01

    The concept of augmenting the conventional collimation system of high-energy storage rings with a hollow electron beam was successfully demonstrated in experiments at the Tevatron. A reliable numerical model is required for understanding particle dynamics in the presence of a hollow beam collimator. Several models were developed to describe imperfections of the electron beam profile and alignment. The features of the imperfections are estimated from electron beam profile measurements. Numerical simulations of halo removal rates are compared with experimental data taken at the Tevatron.

  10. Conceptual design of hollow electron lenses for beam halo control in the Large Hadron Collider

    SciTech Connect

    Stancari, Giulio; Previtali, Valentina; Valishev, Alexander; Bruce, Roderik; Redaelli, Stefano; Rossi, Adriana; Salvachua Ferrando, Belen

    2014-06-26

    Collimation with hollow electron beams is a technique for halo control in high-power hadron beams. It is based on an electron beam (possibly pulsed or modulated in intensity) guided by strong axial magnetic fields which overlaps with the circulating beam in a short section of the ring. The concept was tested experimentally at the Fermilab Tevatron collider using a hollow electron gun installed in one of the Tevatron electron lenses. We are proposing a conceptual design for applying this technique to the Large Hadron Collider at CERN. A prototype hollow electron gun for the LHC was built and tested. The expected performance of the hollow electron beam collimator was based on Tevatron experiments and on numerical tracking simulations. Halo removal rates and enhancements of halo diffusivity were estimated as a function of beam and lattice parameters. Proton beam core lifetimes and emittance growth rates were checked to ensure that undesired effects were suppressed. Hardware specifications were based on the Tevatron devices and on preliminary engineering integration studies in the LHC machine. Required resources and a possible timeline were also outlined, together with a brief discussion of alternative halo-removal schemes and of other possible uses of electron lenses to improve the performance of the LHC.

  11. Positron Acceleration by Plasma Wakefields Driven by a Hollow Electron Beam.

    PubMed

    Jain, Neeraj; Antonsen, T M; Palastro, J P

    2015-11-01

    A scheme for positron plasma wakefield acceleration using hollow or donut-shaped electron driver beams is studied. An annular-shaped, electron-free region forms around the hollow driver beam, creating a favorable region (longitudinal field is accelerating and transverse field is focusing) for positron acceleration. For Facility for Advanced Accelerator Experimental Tests (FACET)-like parameters, the hollow beam driver produces accelerating gradients on the order of 10  GV/m. The accelerating gradient increases linearly with the total charge in the driver beam. Simulations show acceleration of a 23-GeV positron beam to 35.4 GeV with a maximum energy spread of 0.4% and very small emittance over a plasma length of 140 cm is possible. PMID:26588391

  12. Non-nuclear electron transport channels in hollow molecules

    NASA Astrophysics Data System (ADS)

    Zhao, Jin; Petek, Hrvoje

    2014-08-01

    Electron transport in inorganic semiconductors and metals occurs through delocalized bands formed by overlapping electron orbitals. Strong correlation of electronic wave functions with the ionic cores couples the electron and lattice motions, leading to efficient interaction and scattering that degrades coherent charge transport. By contrast, unoccupied electronic states at energies near the vacuum level with diffuse molecular orbitals may form nearly-free-electron bands with density maxima in non-nuclear interstitial voids, which are subject to weaker electron-phonon interaction. The position of such bands typically above the frontier orbitals, however, renders them unstable with respect to electronic interband relaxation and therefore unsuitable for charge transport. Through electronic-structure calculations, we engineer stable, non-nuclear, nearly-free-electron conduction channels in low-dimensional molecular materials by tailoring their electrostatic and polarization potentials. We propose quantum structures of graphane-derived Janus molecular sheets with spatially isolated conducting and insulating regions that potentially exhibit emergent electronic properties, as a paradigm for molecular-scale non-nuclear charge conductors; we also describe tuning of their electronic properties by application of external fields and calculate their electron-acoustic-phonon interaction.

  13. Turbulent anomalous transport and anisotropic electron heating in a return current system

    SciTech Connect

    Lee, Kuang Wu; Buechner, Joerg

    2011-02-15

    Anisotropic electron heating due to self-generated electromagnetic turbulences is observed in collisionless return current plasmas. The corresponding energy conversion, electron heating, and associated anomalous momentum transport are investigated by means of a two-dimensional electromagnetic particle-in-cell simulation code. The return current model consists of two counterstreaming electron beams with different temperatures and a stationary ion background. First, a general multifluid dispersion analyzer is presented in a clear matrix form that allows to study electron streaming instabilities. The numerical simulation confirms the predicted electrostatic electron-electron acoustic instability. Generating electromagnetic waves, the system evolves into a nonlinear stage. As a result, the electron drifts are slowed down due to turbulence-induced anomalous momentum exchange. Localized electric and magnetic field fluctuations play major roles in the energy conversion. Perpendicular electron heating follows the growth of magnetic field perturbations and the slowing of the electron drifts. Parallel and perpendicular electron heating occurs at different time scales. It is shown that the longer lasting perpendicular electron heating is caused by preheated parallel electron flows. The deflection of the preheated parallel electron flows in the localized turbulences, which is essentially a two-dimensional effect, leads to perpendicular electron heating even after the saturation of parallel electron heating. We conclude that the self-generated magnetic turbulence dominates the anomalous transport process in the late stage of return current system evolution.

  14. Non-nuclear Electron Transport Channels in Hollow Molecules

    SciTech Connect

    Zhao, Jin; Petek, Hrvoje

    2014-08-15

    Electron transport in inorganic semiconductors and metals occurs through delocalized bands formed by overlapping electron orbitals. Strong correlation of electronic wave functions with the ionic cores couples the electron and lattice motions, leading to efficient interaction and scattering that degrades coherent charge transport. By contrast, unoccupied electronic states at energies near the vacuum level with diffuse molecular orbitals may form nearly-free-electron bands with density maxima in non-nuclear interstitial voids, which are subject to weaker electron-phonon interaction. The position of such bands typically above the frontier orbitals, however, renders them unstable with respect to electronic interband relaxation and therefore unsuitable for charge transport. Through electronic-structure calculations, we engineer stable, non-nuclear, nearly-free-electron conduction channels in low-dimensional molecular materials by tailoring their electrostatic and polarization potentials. We propose quantum structures of graphane-derived Janus molecular sheets with spatially isolated conducting and insulating regions that potentially exhibit emergent electronic properties, as a paradigm for molecular-scale non-nuclear charge conductors; we also describe tuning of their electronic properties by application of external fields and calculate their electron–acoustic-phonon interaction.

  15. Plans for Deployment of Hollow Electron Lenses at the LHC for Enhanced Beam Collimation

    SciTech Connect

    Redaelli, S.; Bertarelli, A.; Bruce, R.; Perini, D.; Rossi, A.; Salvachua, B.; Stancari, G.; Valishev, A.

    2015-06-01

    Hollow electron lenses are considered as a possible means to improve the LHC beam collimation system, providing active control of halo diffusion rates and suppressing the population of transverse halos. After a very successful experience at the Tevatron, a conceptual design of a hollow e-lens optimized for the LHC was produced. Recent further studies have led to a mature preliminary technical design. In this paper, possible scenarios for the deployment of this technology at the LHC are elaborated in the context of the scheduled LHC long shutdowns until the full implementation of the HL-LHC upgrade in 2023. Possible setups of electron beam test stands at CERN and synergies with other relevant electron beam programmes are also discussed.

  16. Experimental study of magnetically confined hollow electron beams in the Tevatron as collimators for intense high-energy hadron beams

    SciTech Connect

    Stancari, G.; Annala, G.; Shiltsev, V.; Still, D.; Valishev, A.; Vorobiev, L.; /Fermilab

    2011-03-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable losses. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and tested at Fermilab for this purpose. It was installed in one of the Tevatron electron lenses in the summer of 2010. We present the results of the first experimental tests of the hollow-beam collimation concept on 980-GeV antiproton bunches in the Tevatron.

  17. Side-effects of the space charge field introduced by a hollow electron beam in the electron cooler of CSRm

    NASA Astrophysics Data System (ADS)

    Tang, Mei-Tang; Yang, Xiao-Dong; Mao, Li-Jun; Li, Jie; Ma, Xiao-Ming; Yan, Tai-Lai; Zheng, Wen-Heng; Zhao, He; Wu, Bo; Wang, Geng; Ruan, Shuang; Sha, Xiao-Ping

    2015-12-01

    An electron cooler is used to improve the quality of the ion beam in a synchrotron; however it also introduces a nonlinear electromagnetic field to the accelerator, which causes tune shift, tune spread and may drive resonances leading to ion beam loss. In this paper the tune shift and the tune spread caused by the nonlinear electromagnetic field of a hollow electron beam is investigated, and the resonance driving terms of the nonlinear electromagnetic field are analysed. The differences are presented compared with a solid electron beam. Calculations are performed for 238U32+ ions of energy 1.272 MeV stored in the main Cooler Storage Ring (CSRm) at the Institute of Modern Physics, Lanzhou. It is found that in this situation the nonlinear field caused by the hollow electron beam does not lead to serious resonances. Supported by National Natural Science Foundation of China (11375245)

  18. Development of a New Generation of Coolers with a Hollow Electron Beam and Electrostatic Bending

    SciTech Connect

    Parkhomchuk, V. V.

    2006-03-20

    The basic features and design of a new generation coolers made for CSRm,CSRe (Lanzhow, IMP) and for LEIR (Geneva, CERN) will discussed. The hollow profile electron beam help suppress recombination at the accumulation zone. The low electron beam density at the core of the intensive ion beam decrease the amplitude coherent electron-ion beam oscillations (so called electron heating effect). The electrostatic bending made the recuperation loss electron beam current less then 1 mkA for 1-2 Amp the main electron beam current. Decreasing out gassing by the electrons desorption the vacuum chamber cooler open perspective for obtain the high vacuum at cooler on level 1E-12 Torr (for LEIR cooler)

  19. Anomalous electron-ion energy coupling in electron drift wave turbulence

    NASA Astrophysics Data System (ADS)

    Zhao, Lei

    Turbulence is a ubiquitous phenomenon in nature, and it is well known that turbulence couples energy input to dissipation by cascade processes. Plasma turbulence play a critical role in tokamak confinement. Magnetized plasma turbulence is quasi 2D, anisotropic, wave like and two fluid (i.e. electrons and ions) in structure. Thus, weakly collisional plasma turbulence can mediate electron and ion energy transfer. The issue of anomalous electron and ion energy coupling is particularly important for low collisionality, electron heated plasmas, such as ITER. In this work, we reconsider the classic problem of turbulent heating and energy transfer pathways in drift wave turbulence. The total turbulent heating, composed of quasilinear electron cooling, quasilinear ion heating, nonlinear ion heating and zonal flow frictional heating, is analyzed. In Chapter 2, the electron and ion energy exchange via linear wave and particle resonance will be computed. To address net heating, we show the turbulent heating in an annulus arises due to a wave energy flux differential across this region. We show this net heating is proportional to the Reynolds work on the zonal flow. Zonal flow friction heats ions, thus the turbulence and zonal flow interaction enters as an important energy transfer channel. Since zonal flows are nonlinearly generated, it follows that we should apply weak turbulence theory to calculate the nonlinear ion turbulent heating via the virtual mode resonance in the electron drift wave turbulence, which will be discussed in Chapter 3. We defines a new collisionless turbulent energy transfer channel through nonlinear Landau damping in the electron and ion energy coupling process. The result shows that nonlinear ion heating can exceed quasilinear ion heating, so that nonlinear heating becomes the principal collisionless wave energy dissipation channel in electron drift wave turbulence. This follows since the beat mode resonates with the bulk of the ion distribution, in

  20. Intrashell Electron Interaction Mediated Photoformation of Hollow Atoms near Threshold

    SciTech Connect

    Houtari, S.; Kao, C.; Hamalainen, K.; Diamant, R.; Sharon, R.; Deutsch, M.

    2008-07-25

    Double photoionization (DPI) of an atom by a single photon is a direct consequence of electron-electron interactions within the atom. We have measured the evolution of the K-shell DPI from threshold up in transition metals by high-resolution x-ray emission spectroscopy of the K{sup h}a hypersatellites, photoexcited by monochromatized synchrotron radiation. The measured evolution of the single-to-double photoionization cross-section ratio with excitation energy was found to be universal. Theoretical fits suggest that near threshold DPI is predominantly a semiclassical knockout effect, rather than the purely quantum-mechanical shake-off observed at the infinite photon energy limit.

  1. Extraction of a steady state electron beam from HCD (hollow cathode discharge) plasmas for EBIS (electron beam ion source) applications

    SciTech Connect

    Hershcovitch, A.; Kovarik, V.; Prelec, K.

    1988-01-01

    Experiments to extract high brightness electron beams from hollow cathode discharge plasmas are now in progress. A unique feature of these plasmas, which in principle can facilitate the extraction of large current low emittance electron beams, is the existence of a relatively high energy electron population with a very narrow energy spread. This electron population was identified in a self-extraction experiment, which yielded a 35 eV, 600 mA electron beam with parallel energy spread of less than 0.5 eV. Preliminary, crude application of 2.5 kV extraction voltage yielded a steady state electron beam current of 1.2 A. The end result of this endeavor would be an Electron Beam Ion Source (EBIS) with an electron beam current of 6 A. 4 refs., 2 figs.

  2. Observation of New Hollow States of Li^+ in High-Resolution Electron-Spectroscopy Experiments

    NASA Astrophysics Data System (ADS)

    Diehl, S.; Cubaynes, D.; Bizau, J.-M.; Wuilleumier, F. J.; Mosnier, J.-P.; Kennedy, E. T.

    1998-05-01

    Using the synchrotron radiation emitted by the Super-ACO storage ring in Orsay and an electron spectrometer with decelerating optics, we have observed new highly-excited (2l,3l') and (2l, 4l'') hollow states of the singly-charged lithium ion. They were observed in the second step of the autoionization decay of atomic hollow states created by photoexcitation of lithium atoms at excitation energies below the triple-ionization potential (203 eV), and after direct ionization into the continuum at photon energies above 203 eV . We have measured the energies and widths of the new states, and found that they are in excellent agreement with theoretical calculations by K. T. Chung using the saddle point approximation.

  3. FEL indulators with the hollow-ring electron beam

    SciTech Connect

    Epp, V.; Bordovitsyn, V.; Kozhevnikov, A.

    1995-12-31

    A conceptual design of undulators with a modulated longitudinal magnetic field is proposed. The magnetic field is created by use of a solenoid with axis coincident with the electron beam axis. In order to modulate the magnetic field we propose an insertion of a row of alternating ferromagnetic and superconducting diaphragms in line with electron beam. The simulation of two-dimensional distribution of the magnetic field in the plane containing undulator axis was made using the computer code {open_quotes}Mermaid{close_quotes}. The magnetic field was analysed as a function of the system geometry. The dependence on the spacing l between superconducting diaphragms, inner a and outer b radii of the last ones is investigated. Two versions of the device are considered: with ferromagnetic rings made of magnetically soft material placed between the superconducting diaphragms and without them. It is shown that the field modulation depth increases with ratio of b/l and can exceed 50% in case of the ferromagnetic insertions. An approximate analytical calculation of the magnetic field distribution is performed as follows. The axial-symmetrical magnetic field can be defined by the vector potential with only one nonzero component A(r,{phi}) where r and {phi} are the cylindrical coordinates. The solution of the Laplace`s equation is found under the assumption that the magnetic field is infinitely extended and periodic along the z-axis. The boundary conditions are defined by the undulator design. The result is used for the calculation of the particle dynamics and for the investigations of the trajectory stability. The spectral and angular distribution of the radiation emitted from the described systems is found. The estimations show that the proposed design allows to create relatively high magnitude of the magnetic field (up to 1 T) with a short period about 1 cm or less.

  4. Numerical simulation of the creation of a hollow neutral-hydrogen channel by an electron beam.

    PubMed

    Ivanov, V V; Antsiferov, P S; Koshelev, K N; Akdim, M R; Bijkerk, F

    2006-11-17

    An experimental method is proposed for the creation of plasma optical waveguides at low electron densities. The method consists of creating a hollow neutral-hydrogen channel by means of fast local heating of a hydrogen volume by a needlelike electron beam, followed by laser ionization of the hydrogen to provide the plasma waveguide. Results of numerical simulations are presented which show that guiding with an axial electron density in the range of 10(17) cm-3 can be achieved with a matched spot size of 30 microm. Its application for laser wakefield acceleration of electrons is discussed. The method would enable guiding lengths up to 30 cm at maximal energies of accelerated electrons in the range 10-100 GeV. PMID:17155692

  5. Anomalous electronic structure and magnetoresistance in TaAs2

    PubMed Central

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  6. Anomalous electronic structure and magnetoresistance in TaAs2.

    PubMed

    Luo, Yongkang; McDonald, R D; Rosa, P F S; Scott, B; Wakeham, N; Ghimire, N J; Bauer, E D; Thompson, J D; Ronning, F

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  7. Anomalous electronic structure and magnetoresistance in TaAs2

    NASA Astrophysics Data System (ADS)

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-06-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.

  8. Anomalous electronic structure and magnetoresistance in TaAs2

    DOE PAGESBeta

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    We report that the change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. In conclusion, density functional calculations find that TaAs2 is a new topological semimetal [Z2 invariant (0;111)] withoutmore » Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.« less

  9. Anomalous Electronic Anisotropy Triggered by Ferroelastic Coupling in Multiferroic Heterostructures.

    PubMed

    Ju, Changcheng; Yang, Jan-Chi; Luo, Cheng; Shafer, Padraic; Liu, Heng-Jui; Huang, Yen-Lin; Kuo, Ho-Hung; Xue, Fei; Luo, Chih-Wei; He, Qing; Yu, Pu; Arenholz, Elke; Chen, Long-Qing; Zhu, Jinsong; Lu, Xiaomei; Chu, Ying-Hao

    2016-02-01

    The ferroelastic strain coupling in multiferroic heterostructures is explored aiming at novel physical effects and fascinating functionality. Ferroelastic domain walls in manganites induced by a stripe BiFeO3 template can modulate the electronic transfer and sufficiently block the magnetic ordering, creating a vast anisotropy. The findings suggest the great importance of ferroelastic strain engineering in material modifications. PMID:26640119

  10. Acceleration and evolution of a hollow electron beam in wakefields driven by a Laguerre-Gaussian laser pulse

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Bo; Chen, Min; Schroeder, C. B.; Luo, Ji; Zeng, Ming; Li, Fei-Yu; Yu, Lu-Le; Weng, Su-Ming; Ma, Yan-Yun; Yu, Tong-Pu; Sheng, Zheng-Ming; Esarey, E.

    2016-03-01

    We show that a ring-shaped hollow electron beam can be injected and accelerated by using a Laguerre-Gaussian laser pulse and ionization-induced injection in a laser wakefield accelerator. The acceleration and evolution of such a hollow, relativistic electron beam are investigated through three-dimensional particle-in-cell simulations. We find that both the ring size and the beam thickness oscillate during the acceleration. The beam azimuthal shape is angularly dependent and evolves during the acceleration. The beam ellipticity changes resulting from the electron angular momenta obtained from the drive laser pulse and the focusing forces from the wakefield. The dependence of beam ring radius on the laser-plasma parameters (e.g., laser intensity, focal size, and plasma density) is studied. Such a hollow electron beam may have potential applications for accelerating and collimating positively charged particles.

  11. Hollow Cone Electron Imaging for Single Particle 3D Reconstruction of Proteins

    NASA Astrophysics Data System (ADS)

    Tsai, Chun-Ying; Chang, Yuan-Chih; Lobato, Ivan; van Dyck, Dirk; Chen, Fu-Rong

    2016-06-01

    The main bottlenecks for high-resolution biological imaging in electron microscopy are radiation sensitivity and low contrast. The phase contrast at low spatial frequencies can be enhanced by using a large defocus but this strongly reduces the resolution. Recently, phase plates have been developed to enhance the contrast at small defocus but electrical charging remains a problem. Single particle cryo-electron microscopy is mostly used to minimize the radiation damage and to enhance the resolution of the 3D reconstructions but it requires averaging images of a massive number of individual particles. Here we present a new route to achieve the same goals by hollow cone dark field imaging using thermal diffuse scattered electrons giving about a 4 times contrast increase as compared to bright field imaging. We demonstrate the 3D reconstruction of a stained GroEL particle can yield about 13.5 Å resolution but using a strongly reduced number of images.

  12. Hollow Cone Electron Imaging for Single Particle 3D Reconstruction of Proteins.

    PubMed

    Tsai, Chun-Ying; Chang, Yuan-Chih; Lobato, Ivan; Van Dyck, Dirk; Chen, Fu-Rong

    2016-01-01

    The main bottlenecks for high-resolution biological imaging in electron microscopy are radiation sensitivity and low contrast. The phase contrast at low spatial frequencies can be enhanced by using a large defocus but this strongly reduces the resolution. Recently, phase plates have been developed to enhance the contrast at small defocus but electrical charging remains a problem. Single particle cryo-electron microscopy is mostly used to minimize the radiation damage and to enhance the resolution of the 3D reconstructions but it requires averaging images of a massive number of individual particles. Here we present a new route to achieve the same goals by hollow cone dark field imaging using thermal diffuse scattered electrons giving about a 4 times contrast increase as compared to bright field imaging. We demonstrate the 3D reconstruction of a stained GroEL particle can yield about 13.5 Å resolution but using a strongly reduced number of images. PMID:27292544

  13. Hollow Cone Electron Imaging for Single Particle 3D Reconstruction of Proteins

    PubMed Central

    Tsai, Chun-Ying; Chang, Yuan-Chih; Lobato, Ivan; Van Dyck, Dirk; Chen, Fu-Rong

    2016-01-01

    The main bottlenecks for high-resolution biological imaging in electron microscopy are radiation sensitivity and low contrast. The phase contrast at low spatial frequencies can be enhanced by using a large defocus but this strongly reduces the resolution. Recently, phase plates have been developed to enhance the contrast at small defocus but electrical charging remains a problem. Single particle cryo-electron microscopy is mostly used to minimize the radiation damage and to enhance the resolution of the 3D reconstructions but it requires averaging images of a massive number of individual particles. Here we present a new route to achieve the same goals by hollow cone dark field imaging using thermal diffuse scattered electrons giving about a 4 times contrast increase as compared to bright field imaging. We demonstrate the 3D reconstruction of a stained GroEL particle can yield about 13.5 Å resolution but using a strongly reduced number of images. PMID:27292544

  14. Controlling hollow relativistic electron beam orbits with an inductive current divider

    SciTech Connect

    Swanekamp, S. B.; Richardson, A. S.; Angus, J. R.; Cooperstein, G.; Hinshelwood, D. D.; Ottinger, P. F.; Rittersdorf, I. M.; Schumer, J. W.; Weber, B. V.; Zier, J. C.

    2015-02-06

    A passive method for controlling the trajectory of an intense, hollow electron beam is proposed using a vacuum structure that inductively splits the beam's return current. A central post carries a portion of the return current (I1), while the outer conductor carries the remainder (I2). An envelope equation appropriate for a hollow electron beam is derived and applied to the current divider. The force on the beam trajectory is shown to be proportional to (I2-I1), while the average force on the envelope (the beam width) is proportional to the beam current Ib = (I2 + I1). The values of I1 and I2 depend on the inductances in the return-current path geometries. Proper choice of the return-current geometries determines these inductances and offers control over the beam trajectory. As a result, solutions using realistic beam parameters show that, for appropriate choices of the return-current-path geometry, the inductive current divider can produce a beam that is both pinched and straightened so that it approaches a target at near-normal incidence with a beam diameter that is on the order of a few mm.

  15. Controlling hollow relativistic electron beam orbits with an inductive current divider

    DOE PAGESBeta

    Swanekamp, S. B.; Richardson, A. S.; Angus, J. R.; Cooperstein, G.; Hinshelwood, D. D.; Ottinger, P. F.; Rittersdorf, I. M.; Schumer, J. W.; Weber, B. V.; Zier, J. C.

    2015-02-06

    A passive method for controlling the trajectory of an intense, hollow electron beam is proposed using a vacuum structure that inductively splits the beam's return current. A central post carries a portion of the return current (I1), while the outer conductor carries the remainder (I2). An envelope equation appropriate for a hollow electron beam is derived and applied to the current divider. The force on the beam trajectory is shown to be proportional to (I2-I1), while the average force on the envelope (the beam width) is proportional to the beam current Ib = (I2 + I1). The values of I1more » and I2 depend on the inductances in the return-current path geometries. Proper choice of the return-current geometries determines these inductances and offers control over the beam trajectory. As a result, solutions using realistic beam parameters show that, for appropriate choices of the return-current-path geometry, the inductive current divider can produce a beam that is both pinched and straightened so that it approaches a target at near-normal incidence with a beam diameter that is on the order of a few mm.« less

  16. Controlling hollow relativistic electron beam orbits with an inductive current divider

    SciTech Connect

    Swanekamp, S. B.; Richardson, A. S.; Angus, J. R.; Cooperstein, G.; Hinshelwood, D. D.; Ottinger, P. F.; Rittersdorf, I. M.; Schumer, J. W.; Weber, B. V.; Zier, J. C.

    2015-02-15

    A passive method for controlling the trajectory of an intense, hollow electron beam is proposed using a vacuum structure that inductively splits the beam's return current. A central post carries a portion of the return current (I{sub 1}), while the outer conductor carries the remainder (I{sub 2}). An envelope equation appropriate for a hollow electron beam is derived and applied to the current divider. The force on the beam trajectory is shown to be proportional to (I{sub 2}-I{sub 1}), while the average force on the envelope (the beam width) is proportional to the beam current I{sub b} = (I{sub 2} + I{sub 1}). The values of I{sub 1} and I{sub 2} depend on the inductances in the return-current path geometries. Proper choice of the return-current geometries determines these inductances and offers control over the beam trajectory. Solutions using realistic beam parameters show that, for appropriate choices of the return-current-path geometry, the inductive current divider can produce a beam that is both pinched and straightened so that it approaches a target at near-normal incidence with a beam diameter that is on the order of a few mm.

  17. Visible light photocatalysis and electron emission from porous hollow spherical BiVO4 nanostructures synthesized by a novel route

    NASA Astrophysics Data System (ADS)

    Sarkar, Subrata; Chattopadhyay, K. K.

    2014-04-01

    Hollow spheres of BiVO4, made of pyramid like nanocrystals have been synthesized in an aqueous medium through a precursor solution mediated growth method with appropriate amount of polyvinyl alcohol (PVA). It was found that concentration of PVA in the precursor solution played a crucial role in determining the morphology of the product. Hollow spherical BiVO4 was formed with PVA concentration of 64 mg/mL in the precursor solution while with 32 mg/mL PVA concentration mixed morphology of hollow spherical and cubical structure was formed. Without adding PVA, only cubical (bulk like) BiVO4 powder was obtained. The structures have been characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), Fourier-transformed infrared (FTIR) spectroscopy, UV-Vis spectroscopy, thermogravimetry analysis (TGA) and differential thermal analysis (DTA). As-prepared hollow spherical BiVO4 samples were having monoclinic structure with energy band gap 2.42 eV. The hollow spherical BiVO4 exhibited excellent visible-light-driven photocatalytic efficiency for degrading N,N,N‧,N‧-tetraethylated rhodamine (RhB) organic dye, which was nearly 13 times efficient than that of the samples prepared by the same method but without PVA in the precursor solution. After five recycles, the hollow spherical BiVO4 catalyst did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst is essentially stable. The BiVO4 hollow spheres also exhibited electron field emission indicating that BiVO4 with tailored morphology can be used as a multi-functional material.

  18. Anomalous Coulomb Drag in Electron-Hole Bilayers due to the Formation of Excitons

    NASA Astrophysics Data System (ADS)

    Efimkin, Dmitry K.; Galitski, Victor

    2016-01-01

    Several recent experiments have reported an anomalous temperature dependence of the Coulomb drag effect in electron-hole bilayers. Motivated by these puzzling data, we study theoretically a low-density electron-hole bilayer, where electrons and holes avoid quantum degeneracy by forming excitons. We describe the ionization-recombination crossover between the electron-hole plasma and exciton gas and calculate both the intralayer and drag resistivity as a function of temperature. The latter exhibits a minimum followed by a sharp upturn at low temperatures, in qualitative agreement with the experimental observations [see, e.g., J. A. Seamons et al., Phys. Rev. Lett. 102, 026804 (2009)]. Importantly, the drag resistivity in the proposed scenario is found to be rather insensitive to a mismatch in electron and hole concentrations, in sharp contrast to the scenario of electron-hole Cooper pairing.

  19. Electrons on a spherical surface: Physical properties and hollow spherical clusters

    NASA Astrophysics Data System (ADS)

    Cricchio, Dario; Fiordilino, Emilio; Persico, Franco

    2012-07-01

    We discuss the physical properties of a noninteracting electron gas constrained to a spherical surface. In particular we consider its chemical potentials, its ionization potential, and its electric static polarizability. All these properties are discussed analytically as functions of the number N of electrons. The trends obtained with increasing N are compared with those of the corresponding properties experimentally measured or theoretically evaluated for quasispherical hollow atomic and molecular clusters. Most of the properties investigated display similar trends, characterized by a prominence of shell effects. This leads to the definition of a scale-invariant distribution of magic numbers which follows a power law with critical exponent -0.5. We conclude that our completely mechanistic and analytically tractable model can be useful for the analysis of self-assembling complex systems.

  20. High contrast hollow-cone dark field transmission electron microscopy for nanocrystalline grain size quantification.

    PubMed

    Yao, Bo; Sun, Tik; Warren, Andrew; Heinrich, Helge; Barmak, Katayun; Coffey, Kevin R

    2010-04-01

    In this paper, we describe hollow-cone dark field (HCDF) transmission electron microscopy (TEM) imaging, with a slightly convergent beam, as an improved technique that is suitable to form high contrast micrographs for nanocrystalline grain size quantification. We also examine the various factors that influence the HCDF TEM image quality, including the conditions of microscopy (alignment, focus and objective aperture size), the properties of the materials imaged (e.g., atomic number, strain, defects), and the characteristics of the TEM sample itself (e.g., thickness, ion milling artifacts). Sample preparation was found to be critical and an initial thinning by wet etching of the substrate (for thin film samples) or tripod polishing (for bulk samples), followed by low-angle ion milling was found to be the preferred approach for preparing high-quality electron transparent samples for HCDF imaging. PMID:20018512

  1. Nonperturbative renormalization and the electron{close_quote}s anomalous moment in large-{alpha} QED

    SciTech Connect

    Hiller, J.R.; Brodsky, S.J.

    1999-01-01

    We study the physical electron in quantum electrodynamics expanded on the light-cone Fock space in order to address two problems: (1) the physics of the electron{close_quote}s anomalous magnetic moment a{sub e} in nonperturbative QED and (2) the practical problems of ultraviolet regularization and renormalization in truncated nonperturbative light-cone Hamiltonian theory. We present results for a{sub e} computed in a light-cone gauge Fock space truncated to include one bare electron and at most two photons, i.e., up to two photons in flight. The calculational scheme uses an invariant mass cutoff, discretized light-cone quantization (DLCQ), a Tamm-Dancoff truncation of the Fock space, and a photon mass regulator. We introduce new weighting methods which greatly improve convergence to the continuum within DLCQ. Nonperturbative renormalization of the coupling and electron mass are carried out, and a limit on the magnitude of the effective physical coupling strength is computed. A large renormalized coupling strength {alpha}{sub R}=0.1 is then used to make the nonperturbative effects in the electron anomalous moment from the one-electron, two-photon Fock state sector numerically detectable. {copyright} {ital 1998} {ital The American Physical Society}

  2. Electron Anomalous Magnetic Moment in Basis Light-Front Quantization Approach

    SciTech Connect

    Zhao, Xingbo; Honkanen, Heli; Maris, Pieter; Vary, James P.; Brodsky, Stanley J.; /SLAC

    2012-02-17

    We apply the Basis Light-Front Quantization (BLFQ) approach to the Hamiltonian field theory of Quantum Electrodynamics (QED) in free space. We solve for the mass eigenstates corresponding to an electron interacting with a single photon in light-front gauge. Based on the resulting non-perturbative ground state light-front amplitude we evaluate the electron anomalous magnetic moment. The numerical results from extrapolating to the infinite basis limit reproduce the perturbative Schwinger result with relative deviation less than 1.2%. We report significant improvements over previous works including the development of analytic methods for evaluating the vertex matrix elements of QED.

  3. Anomalous giant piezoresistance in AlAs 2D electron systems with antidot lattices.

    PubMed

    Gunawan, O; Gokmen, T; Shkolnikov, Y P; De Poortere, E P; Shayegan, M

    2008-01-25

    An AlAs two-dimensional electron system patterned with an antidot lattice exhibits a giant piezoresistance effect at low temperatures, with a sign opposite to the piezoresistance observed in the unpatterned region. We suggest that the origin of this anomalous giant piezoresistance is the nonuniform strain in the antidot lattice and the exclusion of electrons occupying the two conduction-band valleys from different regions of the sample. This is analogous to the well-known giant magnetoresistance effect, with valley playing the role of spin and strain the role of magnetic field. PMID:18233015

  4. Calculation of the transverse kicks generated by the bends of a hollow electron lens

    SciTech Connect

    Stancari, Giulio

    2014-03-25

    Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam in high-energy accelerators. They were used in the Fermilab Tevatron collider for abort-gap clearing, beam-beam compensation, and halo scraping. A beam-beam compensation scheme based upon electron lenses is currently being implemented in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. This work is in support of a conceptual design of hollow electron beam scraper for the Large Hadron Collider. It also applies to the implementation of nonlinear integrable optics with electron lenses in the Integrable Optics Test Accelerator at Fermilab. We consider the axial asymmetries of the electron beam caused by the bends that are used to inject electrons into the interaction region and to extract them. A distribution of electron macroparticles is deposited on a discrete grid enclosed in a conducting pipe. The electrostatic potential and electric fields are calculated using numerical Poisson solvers. The kicks experienced by the circulating beam are estimated by integrating the electric fields over straight trajectories. These kicks are also provided in the form of interpolated analytical symplectic maps for numerical tracking simulations, which are needed to estimate the effects of the electron lens imperfections on proton lifetimes, emittance growth, and dynamic aperture. We outline a general procedure to calculate the magnitude of the transverse proton kicks, which can then be generalized, if needed, to include further refinements such as the space-charge evolution of the electron beam, magnetic fields generated by the electron current, and longitudinal proton dynamics.

  5. Anomalous charge transport in a quasi-one-dimensional electron system over liquid helium

    NASA Astrophysics Data System (ADS)

    Gladchenko, S. P.; Kovdrya, Yu. Z.; Nikolaenko, V. A.

    2003-11-01

    The conductivity σ in a quasi-one-dimensional electron system over liquid helium is measured in the temperature interval 0.5-1.7 K over a wide range of electron densities n. It is shown that the quantity σ/ne (e is the charge of the electron) initially increases with decreasing temperature and then, after passing through a maximum, begins to decline for T≈1 K. In this temperature region the value of σ/ne, above a certain value of the drift potential Vd, decreases with increasing Vd. It is conjectured that the anomalous charge transport observed in this study is due either to spatial ordering of the electrons in the quasi-one-dimensional channels or to the formation of many-electron polarons in the nonuniform potential along the channels.

  6. Electron contribution to the muon anomalous magnetic moment at four loops

    NASA Astrophysics Data System (ADS)

    Kurz, Alexander; Liu, Tao; Marquard, Peter; Smirnov, Alexander V.; Smirnov, Vladimir A.; Steinhauser, Matthias

    2016-03-01

    We present results for the QED contributions to the anomalous magnetic moment of the muon containing closed electron loops. The main focus is on perturbative corrections at four-loop order where the external photon couples to the external muon. Furthermore, all four-loop contributions involving simultaneously a closed electron and tau loop are computed. In combination with our recent results on the light-by-light-type corrections (see Ref. [1]), the complete four-loop electron-loop contribution to the anomalous magnetic moment of the muon has been obtained with an independent calculation. Our calculation is based on an asymptotic expansion in the ratio of the electron and the muon mass and shows the importance of higher-order terms in this ratio. We perform a detailed comparison with results available in the literature and find good numerical agreement. As a byproduct, we present analytic results for the on-shell muon mass and wave function renormalization constants at three-loop order including massive closed electron and tau loops, which we also calculated using the method of asymptotic expansion.

  7. Theory for the anomalous electron transport in Hall effect thrusters. II. Kinetic model

    NASA Astrophysics Data System (ADS)

    Lafleur, T.; Baalrud, S. D.; Chabert, P.

    2016-05-01

    In Paper I [T. Lafleur et al., Phys. Plasmas 23, 053502 (2016)], we demonstrated (using particle-in-cell simulations) the definite correlation between an anomalously high cross-field electron transport in Hall effect thrusters (HETs), and the presence of azimuthal electrostatic instabilities leading to enhanced electron scattering. Here, we present a kinetic theory that predicts the enhanced scattering rate and provides an electron cross-field mobility that is in good agreement with experiment. The large azimuthal electron drift velocity in HETs drives a strong instability that quickly saturates due to a combination of ion-wave trapping and wave-convection, leading to an enhanced mobility many orders of magnitude larger than that expected from classical diffusion theory. In addition to the magnetic field strength, B0, this enhanced mobility is a strong function of the plasma properties (such as the plasma density) and therefore does not, in general, follow simple 1 /B02 or 1 /B0 scaling laws.

  8. Velocity space evolution of a minority energetic electron population undergoing the anomalous Doppler instability

    SciTech Connect

    Lai, W. N.; Chapman, S. C.; Dendy, R. O.

    2015-11-15

    The kinetic evolution in velocity space of a minority suprathermal electron population that is undergoing the anomalous Doppler instability (ADI) is investigated using the results from fully nonlinear numerical simulations that self-consistently evolve particles and fields in a plasma. Electron trajectories in phase space during different stages of the ADI are captured, and are analysed in relation to the characteristics of the excited electric fields and of the overall distribution of particles. For some electrons, trapping and mirroring effects are observed during the saturation phase. A relationship between the second order moments of the perpendicular electron distribution function and time is established, and is used to investigate the range of applicability of analytical approximations drawn from classical theory, that involve a quasilinear wave-driven diffusion operator.

  9. Hollow cone illumination for fast TEM, and outrunning damage with electrons

    NASA Astrophysics Data System (ADS)

    Spence, J. C. H.; Subramanian, G.; Musumeci, P.

    2015-11-01

    We consider the possibility of imaging individual bioparticles using snapshot diffraction from femotsecond pulses, using a 3 MeV electron beam, based on the recent experimental performance of these coherent beams. Assuming that radiation damage can be outrun using 100 fs pulses (or less), we find that a sufficient number of electrons are scattered per particle only if the beam diameter can be matched to that of the particle (e.g. a virus), about three orders of magnitude smaller than has currently been demonstrated (and limited by space-charge effects). We then propose the use of the hollow-cone illumination mode for fast transmission electron microscope imaging, because it can provide full-field atomic resolution imaging despite the use of the large incoherent annular source required for an efficient photocathode, so that coherent illumination is not needed for high-resolution imaging. Reciprocity arguments are used to compare this full-field mode with data aquisition times and source brightness in scanning transmission electron microscopy.

  10. Anomalous electron heating and energy balance in an ion beam generated plasma

    SciTech Connect

    Guethlein, G.

    1987-04-01

    The plasma described in this report is generated by a 15 to 34 kV ion beam, consisting primarily of protons, passing through an H/sub 2/ gas cell neutralizer. Plasma ions (or ion-electron pairs) are produced by electron capture from (or ionization of) gas molecules by beam ions and atoms. An explanation is provided for the observed anomalous behavior of the electron temperature (T/sub e/): a step-lite, nearly two-fold jump in T/sub e/ as the beam current approaches that which minimizes beam angular divergence; insensitivity of T/sub e/ to gas pressure; and the linear relation of T/sub e/ to beam energy.

  11. Anomalous electron heating effects on the E region ionosphere in TIEGCM

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Wang, Wenbin; Oppenheim, Meers; Dimant, Yakov; Wiltberger, Michael; Merkin, Slava

    2016-03-01

    We have recently implemented a new module that includes both the anomalous electron heating and the electron-neutral cooling rate correction associated with the Farley-Buneman Instability (FBI) in the thermosphere-ionosphere electrodynamics global circulation model (TIEGCM). This implementation provides, for the first time, a modeling capability to describe macroscopic effects of the FBI on the ionosphere and thermosphere in the context of a first-principle, self-consistent model. The added heating sources primarily operate between 100 and 130 km altitude, and their magnitudes often exceed auroral precipitation heating in the TIEGCM. The induced changes in E region electron temperature in the auroral oval and polar cap by the FBI are remarkable with a maximum Te approaching 2200 K. This is about 4 times larger than the TIEGCM run without FBI heating. This investigation demonstrates how researchers can add the important effects of the FBI to magnetosphere-ionosphere-thermosphere models and simulators.

  12. Nonlinear simulations of peeling-ballooning modes with anomalous electron viscosity and their role in edge localized mode crashes.

    PubMed

    Xu, X Q; Dudson, B; Snyder, P B; Umansky, M V; Wilson, H

    2010-10-22

    A minimum set of equations based on the peeling-ballooning (P-B) model with nonideal physics effects (diamagnetic drift, E×B drift, resistivity, and anomalous electron viscosity) is found to simulate pedestal collapse when using the new BOUT++ simulation code, developed in part from the original fluid edge code BOUT. Nonlinear simulations of P-B modes demonstrate that the P-B modes trigger magnetic reconnection, which leads to the pedestal collapse. With the addition of a model of the anomalous electron viscosity under the assumption that the electron viscosity is comparable to the anomalous electron thermal diffusivity, it is found from simulations using a realistic high-Lundquist number that the pedestal collapse is limited to the edge region and the edge localized mode (ELM) size is about 5%-10% of the pedestal stored energy. This is consistent with many observations of large ELMs. PMID:21231055

  13. Nonlinear simulations of peeling-ballooning modes with anomalous electron viscosity and their role in edge localized mode crashes

    DOE PAGESBeta

    Xu, X. Q.; Dudson, B.; Snyder, P. B.; Umansky, M. V.; Wilson, H.

    2010-10-22

    A minimum set of equations based on the peeling-ballooning (P-B) model with nonideal physics effects (diamagnetic drift, E×B drift, resistivity, and anomalous electron viscosity) is found to simulate pedestal collapse when using the new BOUT++ simulation code, developed in part from the original fluid edge code BOUT. Nonlinear simulations of P-B modes demonstrate that the P-B modes trigger magnetic reconnection, which leads to the pedestal collapse. With the addition of a model of the anomalous electron viscosity under the assumption that the electron viscosity is comparable to the anomalous electron thermal diffusivity, it is found from simulations using a realisticmore » high-Lundquist number that the pedestal collapse is limited to the edge region and the edge localized mode (ELM) size is about 5–10% of the pedestal stored energy. Furthermore, this is consistent with many observations of large ELMs.« less

  14. Nonlinear simulations of peeling-ballooning modes with anomalous electron viscosity and their role in edge localized mode crashes

    SciTech Connect

    Xu, X. Q.; Dudson, B.; Snyder, P. B.; Umansky, M. V.; Wilson, H.

    2010-10-22

    A minimum set of equations based on the peeling-ballooning (P-B) model with nonideal physics effects (diamagnetic drift, E×B drift, resistivity, and anomalous electron viscosity) is found to simulate pedestal collapse when using the new BOUT++ simulation code, developed in part from the original fluid edge code BOUT. Nonlinear simulations of P-B modes demonstrate that the P-B modes trigger magnetic reconnection, which leads to the pedestal collapse. With the addition of a model of the anomalous electron viscosity under the assumption that the electron viscosity is comparable to the anomalous electron thermal diffusivity, it is found from simulations using a realistic high-Lundquist number that the pedestal collapse is limited to the edge region and the edge localized mode (ELM) size is about 5–10% of the pedestal stored energy. Furthermore, this is consistent with many observations of large ELMs.

  15. Nonlinear Simulations of Peeling-Ballooning Modes with Anomalous Electron Viscosity and their Role in Edge Localized Mode Crashes

    SciTech Connect

    Xu, X. Q.; Umansky, M. V.; Dudson, B.; Wilson, H.; Snyder, P. B.

    2010-10-22

    A minimum set of equations based on the peeling-ballooning (P-B) model with nonideal physics effects (diamagnetic drift, ExB drift, resistivity, and anomalous electron viscosity) is found to simulate pedestal collapse when using the new BOUT++ simulation code, developed in part from the original fluid edge code BOUT. Nonlinear simulations of P-B modes demonstrate that the P-B modes trigger magnetic reconnection, which leads to the pedestal collapse. With the addition of a model of the anomalous electron viscosity under the assumption that the electron viscosity is comparable to the anomalous electron thermal diffusivity, it is found from simulations using a realistic high-Lundquist number that the pedestal collapse is limited to the edge region and the edge localized mode (ELM) size is about 5%-10% of the pedestal stored energy. This is consistent with many observations of large ELMs.

  16. Neutral cloud theory of the Jovian nebula: Anomalous ionization effect of superthermal electrons

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1994-01-01

    The standard model of the Jovian nebula postulates that its particle source is the extended cloud of neutral sulfur and oxygen atoms that escape from the satellite Io and become ionized through electron impact from the corotating plasma. Its energy source is the gyroenergy acquired by newly formed pickup ions as they are swept up to corotation velocity by the planetary magnetic field. Elastic collisions between plasma ions and electrons cool the ions and heat the electrons, while inelastic collisions cool the electrons and excite the ions to radiate intense line emission, which is the primary energy-loss mechanism for the plasma. This neutral cloud theory of the Io plasma torus, as it has come to be known, has been the subject of recent critcism which asserts that the theory cannot account for the observed charge state of the plasma which features O(+) and S(2+) as the dominant ions. It is shown in this work that the inclusion of a small population of super-thermal electrons is required to achieve the correct ion partitioning among various charge states. It is also argued that the anomalous ionization effect of the superthermal electrons is responsible for the overall spatial bifurcation of the nebula into a hot multiply charged plasma region outside of 5.7 Jovian radii and a cool singly ionized plasma inside this distance.

  17. Guide for 3D WARP simulations of hollow electron beam lenses. Practical explanation on basis of Tevatron electron lens test stand

    SciTech Connect

    Moens, Vince

    2014-06-08

    The purpose of this guide is to help successive students handle WARP. It outlines the installation of WARP on personal computers as well as super-computers and clusters. It furthermore teaches the reader how to handle the WARP environment and run basic scripts. Lastly it outlines how to execute the current Hollow Electron Beam Lens scripts.

  18. Anomalous skin effects in relativistic parallel propagating weakly magnetized electron plasma waves

    SciTech Connect

    Abbas, Gohar; Bashir, M. F.; Murtaza, G.

    2011-10-15

    Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized electron plasma is presented and general expressions for longitudinal and transverse permittivites are derived. It is found that the penetration depth for R- and L-waves increases as we move from non-relativistic to highly relativistic regime. The ambient magnetic field reduces/enhances the skin effects for R-wave/L-wave as the strength of the field is increased. In general, the weak magnetic field effects are pronounced for the weakly relativistic regime as compared with other relativistic cases. The results are also graphically illustrated. On switching off the magnetic field, previous results for field free case are retrieved [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Priniples of Plasma Electrodynamics (Springer-Verlag, Berlin, Heidelberg, 1984), Vol. 9, p. 106].

  19. Poker Flat Incoherent Scatter Radar observations of anomalous electron heating in the E region

    NASA Astrophysics Data System (ADS)

    Makarevich, R. A.; Koustov, A. V.; Nicolls, M. J.

    2013-07-01

    A comprehensive 2-year dataset collected with the Poker Flat Incoherent Scatter Radar (PFISR) located near Fairbanks, Alaska (MLAT = 65.4° N) is employed to identify and analyse 22 events of anomalous electron heating (AEH) in the auroral E region. The overall AEH occurrence probability is conservatively estimated to be 0.3% from nearly-continuous observations of the E region by PFISR, although it increases to 0.7-0.9% in the dawn and dusk sectors where all AEH events were observed. The AEH occurrence variation with MLT is broadly consistent with those of events with high convection velocity (>1000 m s-1) or electron temperature (> 800 K), except for much smaller AEH probability and absence of AEH events near magnetic midnight. This suggests that high convection electric field by itself is necessary but not sufficient for measurable electron heating by two-stream plasma waves. The multi-point observations are utilised to investigate the fundamental dependence of the electron temperature on the convection electric field, focusing on the previously-proposed saturation effects at extreme electric fields. The AEH dataset was found to exhibit considerable scatter and, on average, similar rate of the electron temperature increase with the electric field up to 100 mV m-1 as compared with previous studies. At higher (highest) electric fields, the electron temperatures are below the linear trend on average (within uncertainty). By employing a simple fluid model of AEH, it is demonstrated that some of this deviation from the linear trend may be due to a stronger vibrational cooling at very large temperatures and electric fields.

  20. Collisionless reversed magnetic shear trapped electron instability and contribution of sidebands to anomalous transport

    NASA Astrophysics Data System (ADS)

    Rogister, André L.; Singh, Raghvendra

    2005-11-01

    By keeping account of the trapped electron ∇B and curvature drifts, it is found that the spatial decay of the collisionless electron drift wave is governed either by the trapped electron response or by the resonant interaction of ions with the sidebands of the primary oscillation. In the former case, pairs of spatially bounded unstable and damped solutions are obtained for negative magnetic shear (ŝ<0) if, as usual, LTe=1/∂rlnTe<0; there are no bounded solutions if ŝLTe<0. In the latter case, there is either a set of bounded damped solutions if ηi>0 or a set of bounded unstable solutions if ηi<0. The unstable modes have a radiating character and the growth rates are γ ˜(2n+1)√1+2q2 ∣ŝ∣∣LNωe*/qR∣ (n is the Hermite polynomial solution index, q the safety factor, ŝ the magnetic shear parameter, R the major radius, ωe* the electron diamagnetic frequency, LN=1/∂rlnNe, and ηi=LN/LTi).The sidebands are responsible for unusually large ratios Qe/TeΓe, where Qe and Γe are the anomalous electron energy flux and the particle flux. These results may explain the box-type Te profile observed in lower hybrid current drive reversed magnetic shear plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60U Team, Phys. Fluids B 4, 2070 (1992)]. It is finally demonstrated that the ballooning hypothesis generally leads to conflicting requirements: it is thus hardly relevant for the electron drift branch! The "radiating" boundary condition that has formerly been imposed on the slab solution is finally discussed.

  1. Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2

    NASA Astrophysics Data System (ADS)

    Das, Pranab Kumar; di Sante, D.; Vobornik, I.; Fujii, J.; Okuda, T.; Bruyer, E.; Gyenis, A.; Feldman, B. E.; Tao, J.; Ciancio, R.; Rossi, G.; Ali, M. N.; Picozzi, S.; Yadzani, A.; Panaccione, G.; Cava, R. J.

    2016-02-01

    The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. Here we report angle- and spin-resolved photoemission spectroscopy of WTe2 single crystals, through which we disentangle the role of W and Te atoms in the formation of the band structure and identify the interplay of charge, spin and orbital degrees of freedom. Supported by first-principles calculations and high-resolution surface topography, we reveal the existence of a layer-dependent behaviour. The balance of electron and hole states is found only when considering at least three Te-W-Te layers, showing that the behaviour of WTe2 is not strictly two dimensional.

  2. Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2.

    PubMed

    Das, Pranab Kumar; Di Sante, D; Vobornik, I; Fujii, J; Okuda, T; Bruyer, E; Gyenis, A; Feldman, B E; Tao, J; Ciancio, R; Rossi, G; Ali, M N; Picozzi, S; Yadzani, A; Panaccione, G; Cava, R J

    2016-01-01

    The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. Here we report angle- and spin-resolved photoemission spectroscopy of WTe2 single crystals, through which we disentangle the role of W and Te atoms in the formation of the band structure and identify the interplay of charge, spin and orbital degrees of freedom. Supported by first-principles calculations and high-resolution surface topography, we reveal the existence of a layer-dependent behaviour. The balance of electron and hole states is found only when considering at least three Te-W-Te layers, showing that the behaviour of WTe2 is not strictly two dimensional. PMID:26924386

  3. Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2

    DOE PAGESBeta

    Das, Pranab Kumar; Di Sante, D.; Vobornik, I.; Fujii, J.; Okuda, T.; Bruyer, E.; Gyenis, A.; Feldman, B. E.; Tao, J.; Ciancio, R.; et al

    2016-02-29

    The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. We report angle- and spin-resolved photoemission spectroscopy of WTe2 single crystals, through which we disentangle the role of W and Te atoms in the formation of the band structure and identify the interplay of charge, spin and orbitalmore » degrees of freedom. Supported by first-principles calculations and high-resolution surface topography, we also reveal the existence of a layer-dependent behaviour. The balance of electron and hole states is found only when considering at least three Te–W–Te layers, showing that the behaviour of WTe2 is not strictly two dimensional.« less

  4. Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2

    PubMed Central

    Das, Pranab Kumar; Di Sante, D.; Vobornik, I.; Fujii, J.; Okuda, T.; Bruyer, E.; Gyenis, A.; Feldman, B. E.; Tao, J.; Ciancio, R.; Rossi, G.; Ali, M. N.; Picozzi, S.; Yadzani, A.; Panaccione, G.; Cava, R. J.

    2016-01-01

    The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. Here we report angle- and spin-resolved photoemission spectroscopy of WTe2 single crystals, through which we disentangle the role of W and Te atoms in the formation of the band structure and identify the interplay of charge, spin and orbital degrees of freedom. Supported by first-principles calculations and high-resolution surface topography, we reveal the existence of a layer-dependent behaviour. The balance of electron and hole states is found only when considering at least three Te–W–Te layers, showing that the behaviour of WTe2 is not strictly two dimensional. PMID:26924386

  5. Broadband 7-fs diffractive-optic-based 2D electronic spectroscopy using hollow-core fiber compression.

    PubMed

    Ma, Xiaonan; Dostál, Jakub; Brixner, Tobias

    2016-09-01

    We demonstrate noncollinear coherent two-dimensional (2D) electronic spectroscopy for which broadband pulses are generated in an argon-filled hollow-core fiber pumped by a 1-kHz Ti:Sapphire laser. Compression is achieved to 7 fs duration (TG-FROG) using dispersive mirrors. The hollow fiber provides a clean spatial profile and smooth spectral shape in the 500-700 nm region. The diffractive-optic-based design of the 2D spectrometer avoids directional filtering distortions and temporal broadening from time smearing. For demonstration we record data of cresyl-violet perchlorate in ethanol and use phasing to obtain broadband absorptive 2D spectra. The resulting quantum beating as a function of population time is consistent with literature data. PMID:27607681

  6. Gas pressure and electron density at the level of the active zone of hollow cathode arc discharges

    NASA Technical Reports Server (NTRS)

    Minoo, M. H.

    1984-01-01

    A model for the longitudinal variations of the partial pressures of electrons, ions, and neutral particles is proposed as a result of an experimental study of pressure variations at the level of the active zone as a function of the various discharge parameters of a hollow cathode arc. The cathode region where the temperature passes through its maximum is called active zone. The proposed model embodies the very important variations which the partial electron and neutral particles pressures undergo at the level of the active zone.

  7. Effects of Anomalous Electron Cross-Field Transport in a Low Temperature Magnetized Plasma

    NASA Astrophysics Data System (ADS)

    Raitses, Yevgeny

    2014-10-01

    The application of the magnetic field in a low pressure plasma can cause a spatial separation of low and high energy electrons. This so-called magnetic filter effect is used for many plasma applications, including ion and neutral beam sources, plasma processing of semiconductors and nanomaterials, and plasma thrusters. In spite of successful practical applications, the magnetic filter effect is not well understood. In this work, we explore this effect by characterizing the electron and ion energy distribution functions in a plasma column with crossed electric and magnetic fields. Experimental results revealed a strong dependence of spatial variations of plasma properties on the gas pressure. For xenon and argon gases, below ~ 1 mtorr, the increase of the magnetic field leads to a more uniform profile of the electron temperature. This surprising result is due to anomalously high electron cross-field transport that causes mixing of hot and cold electrons. High-speed imaging and probe measurements revealed a coherent structure rotating in E cross B direction with frequency of a few kHz. Theory and simulations describing this rotating structure has been developed and points to ionization and electrostatic instabilities as their possible cause. Similar to spoke oscillations reported for Hall thrusters, this rotating structure conducts the large fraction of the cross-field current. The use of segmented electrodes with an electrical feedback control is shown to mitigate these oscillations. Finally, a new feature of the spoke phenomenon that has been discovered, namely a sensitive dependence of the rotating oscillations on the gas pressure, can be important for many applications. This work was supported by DOE Contract DE-AC02-09CH11466.

  8. Protein structure determination by single-wavelength anomalous diffraction phasing of X-ray free-electron laser data

    PubMed Central

    Nass, Karol; Meinhart, Anton; Barends, Thomas R. M.; Foucar, Lutz; Gorel, Alexander; Aquila, Andrew; Botha, Sabine; Doak, R. Bruce; Koglin, Jason; Liang, Mengning; Shoeman, Robert L.; Williams, Garth; Boutet, Sebastien; Schlichting, Ilme

    2016-01-01

    Serial femtosecond crystallography (SFX) at X-ray free-electron lasers (XFELs) offers unprecedented possibilities for macromolecular structure determination of systems that are prone to radiation damage. However, phasing XFEL data de novo is complicated by the inherent inaccuracy of SFX data, and only a few successful examples, mostly based on exceedingly strong anomalous or isomorphous difference signals, have been reported. Here, it is shown that SFX data from thaumatin microcrystals can be successfully phased using only the weak anomalous scattering from the endogenous S atoms. Moreover, a step-by-step investigation is presented of the particular problems of SAD phasing of SFX data, analysing data from a derivative with a strong anomalous signal as well as the weak signal from endogenous S atoms. PMID:27158504

  9. Protein structure determination by single-wavelength anomalous diffraction phasing of X-ray free-electron laser data

    DOE PAGESBeta

    Nass, Karol; Meinhart, Anton; Barends, Thomas R. M.; Foucar, Lutz; Gorel, Alexander; Aquila, Andrew; Botha, Sabine; Doak, R. Bruce; Koglin, Jason; Liang, Mengning; et al

    2016-03-09

    Serial femtosecond crystallography (SFX) at X-ray free-electron lasers (XFELs) offers unprecedented possibilities for macromolecular structure determination of systems that are prone to radiation damage. However, phasing XFEL data de novo is complicated by the inherent inaccuracy of SFX data, and only a few successful examples, mostly based on exceedingly strong anomalous or isomorphous difference signals, have been reported. Here, it is shown that SFX data from thaumatin microcrystals can be successfully phased using only the weak anomalous scattering from the endogenous S atoms. Furthermore, a step-by-step investigation is presented of the particular problems of SAD phasing of SFX data, analysingmore » data from a derivative with a strong anomalous signal as well as the weak signal from endogenous S atoms.« less

  10. Anomalous conductivity in Hall thrusters: Effects of the non-linear coupling of the electron-cyclotron drift instability with secondary electron emission of the walls

    SciTech Connect

    Héron, A.; Adam, J. C.

    2013-08-15

    With the help of an implicit particle-in-cell code, we have shown in a previous paper that the electron-cyclotron drift instability was able to induce anomalous conductivity as well as anomalous heating. As such it can be a major actor among the mechanisms involved in the operation of Hall thrusters. However, experimental results show that the nature of wall material has a significant effect on the behavior of the thruster. The purpose of this paper is to study the plasma-wall interaction in the case where the plasma is heated self-consistently by electrostatic fluctuations induced by the electron-cyclotron drift instability.

  11. A kinetic cyclotron maser instability associated with a hollow beam of electrons

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Freund, H. P.

    1984-01-01

    A kinetic cyclotron maser instability associated with a hollow-beam distribution function is studied. The instability differs from that discussed for the gyrotron device in two respects: in the present case the momentum dispersion is substantial, and furthermore there exists a low-energy background plasma. On the basis of physical arguments it can be demonstrated that the hollow-beam distribution is far more unstable than the loss cone distribution which has been extensively investigated in recent years. A criterion for maximum growth rate is established on the basis of consideration of the resonance ellipse. The validity of this criterion is supported by the results of numerical calculation.

  12. Anomalous electronic transport features in a lateral quantum dot array sample

    NASA Astrophysics Data System (ADS)

    Pan, Wei; Dunn, R. G.; Reno, J. L.; Simmons, J. A.; Li, D.; Brueck, S. R. J.

    2006-03-01

    We will present in this talk experimental results obtained in a lateral quantum dot array sample, with a pitch size of ˜ 350 nm and a designed dot size of ˜ 150nm. The starting material is a high quality quantum well with the two-dimensional electron gas buried 200 nm below the surface. The quantum dot array is defined by a Ti/Au metal grid, which was fabricated using the interferometric lithograph and lift-off techniques. Around zero magnetic field, a pronounced positive magnetoresistance is observed, which can be explained by the semi-classical model of magnetic breakdown. The so-called commensurability oscillations together with the usual Shubnikov- de Hass oscillations are also observed. Surprisingly, in a pure DC measurement of longitudinal resistance, an anomalous resistance spike is clearly seen. The magnetic field position of this resistance spike depends on the amplitude of applied DC bias (Vds) between source and drain, and shows roughly a 1/Vds dependence.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  13. Study of nonlinear evolution of tearing modes induced by anomalous electron viscosity

    NASA Astrophysics Data System (ADS)

    He, Zhixiong; Dong, J. Q.; He, Hongda; Wang, Z. T.; Long, Y. X.; Mou, Z. Z.

    2015-12-01

    The nonlinear development of double tearing modes (DTMs) induced by anomalous electron viscosity, which may be present in magnetically confined plasmas due to electromagnetic turbulence and structures such as braiding of magnetic field lines, in a periodic cylinder is simulated. Comparing the evolution of the helical magnetic flux contours, the nonlinear development of magnetic reconnection of the DTMs is studied for different distances between the two resonant rational flux surfaces. There are three clear phases in the nonlinear evolution of DTMs when the distance between the two resonant flux surfaces is large: linear growing, nonlinearly driven growing, and saturation. There are four phases when the distance is medium: linear growing, nonlinearly driven growing, fast growing, and decaying. Finally, there are three phases of evolution when the distance is quite small, which are different from the phases when the distance is large: linear growing, nonlinearly driven growing, and decaying,. The coupling between the fastest-growing modes at the two resonant surfaces drives the nonlinear evolution of the system.

  14. Hydrothermal synthesis and magnetic properties of CuO hollow microspheres

    SciTech Connect

    Zhao, J.G.; Yin, J.Z.; Yang, M.

    2014-01-01

    Graphical abstract: - Highlights: • CuO hollow microspheres were synthesized through hydrothermal route. • The possible growth mechanism was proposed according to the experimental results. • CuO hollow microspheres show an anomalous ferromagnetic behavior at 5 K and 300 K. - Abstract: In the present work, CuO hollow microspheres with the diameter about 2 μm were successfully synthesized through a facile hydrothermal method. The phase purity, morphologies and structure features of the as obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy, respectively. It was found that reaction temperature, reaction time and different volume ratios of ethanol and distilled water played important roles on the morphologies of the obtained CuO hollow microspheres. The possible formation mechanism was also proposed according to the corresponding experimental results. The magnetic properties were investigated by superconducting quantum interference device, revealing that the CuO hollow microspheres exhibited an anomalous ferromagnetic behavior at 5 K and 300 K. At the same time, the origin of the ferromagnetism in CuO hollow microspheres was also discussed.

  15. Tenth-order electron anomalous magnetic moment: Contribution of diagrams without closed lepton loops

    NASA Astrophysics Data System (ADS)

    Aoyama, Tatsumi; Hayakawa, Masashi; Kinoshita, Toichiro; Nio, Makiko

    2015-02-01

    This paper presents a detailed account of the evaluation of the electron anomalous magnetic moment ae which arises from a gauge-invariant set, called Set V, consisting of 6354 tenth-order Feynman diagrams without closed lepton loops. The latest value of the sum of Set V diagrams evaluated by the Monte Carlo integration routine VEGAS is 8.726 (336 )(α /π )5 , which replaces the very preliminary value reported in 2012. Combining it with 6318 previously published tenth-order diagrams, we obtain 7.795 (336 )(α /π )5 as the complete mass-independent tenth-order term. Together with the improved value of the eighth-order term this leads to ae(theory)=1 159 652 181.643 (25 )(23 )(16 )(763 )×1 0-12 , where the first three uncertainties are from the eighth-order, tenth-order, and hadronic and elecroweak terms. The fourth and largest uncertainty is from α-1=137.035 999 049 (90 ) , the fine-structure constant derived from the rubidium recoil measurement. Thus, ae(experiment)-ae(theory)=-0.91 (0.82 )×1 0-12 . Assuming the validity of the standard model, we obtain the fine-structure constant α-1(ae)=137.035 999 1570 (29 )(27 )(18 )(331 ) , where uncertainties are from the eighth-order, tenth-order, and hadronic and electroweak terms, and the measurement of ae. This is the most precise value of α available at present and provides a stringent constraint on possible theories beyond the standard model.

  16. Role of electrostatic and magnetic electron confinement in a hollow-cathode glow discharge in a nonuniform magnetic field

    SciTech Connect

    Metel, A. S. Grigoriev, S. N.; Volosova, M. A.; Bolbukov, V. P.; Melnik, Yu. A.

    2015-02-15

    Glow discharge with electron confinement in an electrostatic trap has been studied. The trap is formed by a cylindrical hollow cathode, as well as by a flat target on its bottom and a grid covering its output aperture, both being negatively biased relative to the cathode. At a gas pressure of 0.2–0.4 Pa, the fraction of ions sputtering the target (δ = 0.13) in the entire number of ions emitted by the uniform discharge plasma corresponds to the ratio of the target surface area to the total surface area of the cathode, grid, and target. When a nonuniform magnetic field with force lines passing through the target center (where the magnetic induction reaches 35 mT), as well as through the grid, hollow cathode, and target periphery (where the field lines are arc-shaped), is applied to the trap, its influence on the discharge depends on the magnetic induction B{sub 0} at the target edge. At B{sub 0} = 1 mT, the electrons emitted from the target periphery and drifting azimuthally in the arc-shaped field insignificantly contribute to gas ionization. Nevertheless, since fast electrons that are emitted from the cathode and oscillate inside it are forced by the magnetic field to come more frequently to the target, thereby intensifying gas ionization near the latter, the fraction δ doubles and the plasma density near the target becomes more than twice as high as that near the grid. At B{sub 0} = 6 mT, the contribution of electrons emitted from the target surface to gas ionization near the target grows up and δ increases two more times. At cathode-target voltages in the range of 0–3 kV, the current in the target circuit vanishes as the voltage between the anode and the cathode decreases to zero.

  17. Role of electrostatic and magnetic electron confinement in a hollow-cathode glow discharge in a nonuniform magnetic field

    NASA Astrophysics Data System (ADS)

    Metel, A. S.; Grigoriev, S. N.; Volosova, M. A.; Bolbukov, V. P.; Melnik, Yu. A.

    2015-02-01

    Glow discharge with electron confinement in an electrostatic trap has been studied. The trap is formed by a cylindrical hollow cathode, as well as by a flat target on its bottom and a grid covering its output aperture, both being negatively biased relative to the cathode. At a gas pressure of 0.2-0.4 Pa, the fraction of ions sputtering the target (δ = 0.13) in the entire number of ions emitted by the uniform discharge plasma corresponds to the ratio of the target surface area to the total surface area of the cathode, grid, and target. When a nonuniform magnetic field with force lines passing through the target center (where the magnetic induction reaches 35 mT), as well as through the grid, hollow cathode, and target periphery (where the field lines are arc-shaped), is applied to the trap, its influence on the discharge depends on the magnetic induction B 0 at the target edge. At B 0 = 1 mT, the electrons emitted from the target periphery and drifting azimuthally in the arc-shaped field insignificantly contribute to gas ionization. Nevertheless, since fast electrons that are emitted from the cathode and oscillate inside it are forced by the magnetic field to come more frequently to the target, thereby intensifying gas ionization near the latter, the fraction δ doubles and the plasma density near the target becomes more than twice as high as that near the grid. At B 0 = 6 mT, the contribution of electrons emitted from the target surface to gas ionization near the target grows up and δ increases two more times. At cathode-target voltages in the range of 0-3 kV, the current in the target circuit vanishes as the voltage between the anode and the cathode decreases to zero.

  18. Tunable Microwave Absorption Frequency by Aspect Ratio of Hollow Polydopamine@α-MnO2 Microspindles Studied by Electron Holography.

    PubMed

    She, Wen; Bi, Han; Wen, Zhiwei; Liu, Qinghe; Zhao, Xuebing; Zhang, Jie; Che, Renchao

    2016-04-20

    A tunable response frequency is highly desirable for practical applications of microwave absorption materials but remains a great challenge. Here, hollow lightweight polydopamine@α-MnO2 microspindles were facilely synthesized with the tunable absorption frequency governed by the aspect ratio. The size of the hard template is a key factor to achieve the unique shape; the polymer layer with uniform thickness plays an important role in obtaining spindles with homogeneous size. With the aspect ratio increasing, the maximum reflection loss, as well as the absorption bandwidth (<-10 dB), increases and then decreases; meanwhile, the microwave absorption band shifts to the low frequency. The optimized aspect ratio of the cavity about the hollow polydopamine@α-MnO2 microspindles is ∼2.8. With 3 mm thickness at 9.7 GHz, the strongest reflection reaches -21.8 dB, and the width of the absorbing band (<-10 dB) is as wide as 3.3 GHz. Via electron holography, it is confirmed that strong charge accumulates around the interface between the polydopamine and α-MnO2 layers, which mainly contributes to the dielectric polarization absorption. This study proposes a reliable strategy to tune the absorption frequency via different aspect ratio polymer@α-MnO2 microspindles. PMID:27027922

  19. Wear Mechanisms in Electron Sources for Ion Propulsion, 2: Discharge Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Jameson, Kristina K.; Polk, James E.

    2008-01-01

    The wear of the keeper electrode in discharge hollow cathodes is a major impediment to the implementation of ion propulsion onboard long-duration space science missions. The development of a predictive theoretical model for hollow cathode keeper life has long been sought, but its realization has been hindered by the complexities associated with the physics of the partially ionized gas and the associated erosion mechanisms in these devices. Thus, although several wear mechanisms have been hypothesized, a quantitative explanation of life test erosion profiles has remained incomplete. A two-dimensional model of the partially ionized gas in a discharge cathode has been developed and applied to understand the mechanisms that drove the erosion of the keeper in two long-duration life tests of a 30-cm ion thruster. An extensive set of comparisons between predictions by the numerical simulations and measurements of the plasma properties and of the erosion patterns is presented. It is found that the near-plume plasma oscillations, predicted by theory and observed by experiment, effectively enhance the resistivity of the plasma as well as the energy of ions striking the keeper.

  20. Wear Mechanisms in Electron Sources for Ion Propulsion, 1: Neutralizer Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira

    2008-01-01

    Upon the completion of two long-duration life tests of a 30-cm ion engine, the orifice channel of the neutralizer hollow cathode was eroded away to as much as twice its original diameter. Whereas the neutralizer cathode orifice opened significantly, no noticeable erosion of the discharge cathode orifice was observed. Noquantitative explanation of these erosion trends has been established since the completion of the two life tests. A two-dimensional model of the partially ionized gas inside these devices has been developed and applied to the neutralizer hollow cathode. The numerical simulations show that the main mechanism responsible for the channel erosion is sputtering by Xe+. These ions are accelerated by the sheath along the channel and bombard the surface with kinetic energy/charge of about 17 V at the beginning of cathode life. The density of the ions inside the neutralizer orifice is computed to be as high as 2.1 x 10(sup 22) m(sup -3). Because of the 3.5-times larger diameter of the discharge cathode orifice, the ion density inside the orifice is more than 40 times lower and the sheath drop 7 V lower compared with the values in the neutralizer. At these conditions, Xe+ can cause no significant sputtering of the surface.

  1. Hollow cathode apparatus

    NASA Technical Reports Server (NTRS)

    Aston, G. (Inventor)

    1984-01-01

    A hollow cathode apparatus is described, which can be rapidly and reliably started. An ignitor positioned upstream from the hollow cathode, generates a puff of plasma that flows with the primary gas to be ionized through the cathode. The plasma puff creates a high voltage breakdown between the downstream end of the cathode and a keeper electrode, to heat the cathode to an electron-emitting temperature.

  2. The measurement of electron number density in helium micro hollow gas discharge using asymmetric He I lines

    NASA Astrophysics Data System (ADS)

    Jovović, J.; Šišović, N. M.

    2015-09-01

    The electron number density N e in helium micro hollow gas discharge (MHGD) is measured by means of optical emission spectroscopy (OES) techniques. The structure of MHGD is a gold-alumina-gold sandwich with 250 μm alumina thickness and 100 μm diameter hole. The electron temperature T e and gas temperature T g in the discharge is determined using the relative intensity of He I lines and {{\\text{N}}2}+≤ft({{\\text{B}}2}Σ\\text{u}+- {{X}2}Σ\\text{g}+\\right) R branch lines in the frame of BP technique, respectively. The simple procedure based on spectral line broadening theory was developed in MATLAB to generate synthetic neutral line asymmetric profiles. The synthetic profiles were compared with an experimental He I 447.1 nm and He I 492.2 nm line to obtain N e from the centre of a micro hollow gas discharge (MHGD) source in helium. The N e results were compared with N e values obtained from the forbidden-to-allowed (F/A) intensity ratio technique. The comparison confirmed higher N e determined using a F/A ratio due to large uncertainty of the method. Applying the fitting formula for a He I 492.2 nm line derived from computer simulation (CS) gives the same N e values as the one determined using the MATLAB procedure in this study. The dependence of N e on gas pressure and electric current is investigated as well.

  3. Performance of 75-millimeter-bore bearings using electron-beam-welded hollow balls with a diameter ratio of 1.26

    NASA Technical Reports Server (NTRS)

    Coe, H. H.; Parker, R. J.; Scibbe, H. W.

    1975-01-01

    An experimental investigation was performed to determine the rolling element fatigue life of electron beam-welded hollow balls with a diameter ratio (o.d./i.d.) of 1.26 and to determine the operating characteristics of bearings using these hollow balls. Similar bearings with solid balls were also tested and the data compared. The bearings were operated at shaft speeds up to 28,000 rpm with a thrust load of 2200 N (500 lb). Ball failures during the bearing tests were due to flexure fatigue. The solid and hollow ball bearings tested showed little difference in outer race temperatures and indicated the same bearing torque. The 17.5-mm (0.6875-in.) diameter balls were also tested in the five-ball fatigue tester and showed no significant difference in life when compared with the life of a solid ball.

  4. Anomalously enhanced electronic specific heat in Fe doped BISCO 2212 superconductors

    NASA Astrophysics Data System (ADS)

    Yu, M. K.; Franck, J. P.

    1994-12-01

    The specific heat of Fe substituted Bi 1.8Pb 0.2Sr 2Ca(Cu 1-xFe x) 2O 8 was measured for x = 1, 2, 4, 6, and 8%. A large anomalous contribution to the specific heat is observed below 15 K for the substituted samples. The anomaly suggests that Fe enters in the 3d 5 state, and that the samples are spin glasses in the superconducting state.

  5. Effect of entropy on anomalous transport in electron-temperature-gradient-modes

    SciTech Connect

    Yaqub Khan, M.; Iqbal, J.; Ul Haq, A.

    2014-05-15

    Due to the interconnection of entropy with temperature and density of plasma, it would be interesting to investigate plasma related phenomena with respect to entropy. By employing Braginskii transport equations, it is proved that entropy is proportional to a function of potential and distribution function of entropy is re-defined, ∇S–drift in obtained. New dispersion relation is derived; it is found that the anomalous transport depends on the gradient of the entropy.

  6. Formation and stability of a hollow electron beam in the presence of a plasma wake field driven by an ultra-short electron bunch

    NASA Astrophysics Data System (ADS)

    Tanjia, F.; Fedele, R.; De Nicola, S.; Akhter, T.; Jovanović, D.

    2016-09-01

    A numerical investigation on the spatiotemporal evolution of an electron beam, externally injected in a plasma in the presence of a plasma wake field, is carried out. The latter is driven by an ultra-short relativistic axially-symmetric femtosecond electron bunch. We first derive a novel Poisson-like equation for the wake potential where the driving term is the ultra-short bunch density, taking suitably into account the interplay between the sharpness and high energy of the bunch. Then, we show that a channel is formed longitudinally, through the externally injected beam while experiencing the effects of the bunch-driven plasma wake field, within the context of thermal wave model. The formation of the channel seems to be a final stage of the 3D evolution of the beam. This involves the appearance of small filaments and bubbles around the longitudinal axis. The bubbles coalesce forming a relatively stable axially-symmetric hollow beam structure.

  7. Spectroscopic studies of neutral erbium in a hollow cathode lamp: Electronic temperature and two-step optogalvanic spectroscopy

    NASA Astrophysics Data System (ADS)

    Bueno, Patricia; Victor, Alessandro R.; Santos, Jhonatha R. dos; Barreta, Luiz F. N.; Destro, Marcelo G.; Sbampato, Maria Esther; Neri, Jose W.; Silveira, Carlos A. B.

    2016-04-01

    This work reports the results obtained through spectroscopic studies developed on an erbium-neon hollow cathode lamp. First, emission spectra were obtained in order to estimate the electronic temperature of neutral erbium, which is an important plasma parameter for the calculation of atomic population in different energy levels. It was identified seven pairs of lines that can be used to estimate the electronic temperature of this metal by the two-line Boltzmann method. After these experiments, using the laser multistep excitation technique, three transitions for the first step excitation from the erbium ground state and eight transitions corresponding to the second step were observed. Four of these eight second steps correspond to erbium lines that were not reported in the literature before: 599.44 nm (17,157.31 → 33,844 cm- 1), 603.65 nm (17,073.80 → 33,635 cm- 1), 597.48 nm (17,029.06 → 33,761 cm- 1) and 597.56 nm (17,029.06 → 33,759 cm- 1).

  8. Theory for the anomalous electron transport in Hall effect thrusters. I. Insights from particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Lafleur, T.; Baalrud, S. D.; Chabert, P.

    2016-05-01

    Using a 1D particle-in-cell simulation with perpendicular electric, E0, and magnetic, B0, fields, and modelling the azimuthal direction (i.e., the E0 × B0 direction), we study the cross-field electron transport in Hall effect thrusters (HETs). For low plasma densities, the electron transport is found to be well described by classical electron-neutral collision theory, but at sufficiently high densities (representative of typical HETs), a strong instability is observed to significantly enhance the electron mobility, even in the absence of electron-neutral collisions. This instability is associated with correlated high-frequency (of the order of MHz) and short-wavelength (of the order of mm) fluctuations in both the electric field and the plasma density, which are shown to be the cause of the anomalous transport. Saturation of the instability is observed to occur due to a combination of ion-wave trapping in the E0 × B0 direction, and convection in the E0 direction.

  9. Electron, Ion and Atom Collisions Leading to Anomalous Doppler Broadening in Hydrogen

    NASA Astrophysics Data System (ADS)

    Petrović, Zoran Lj.; Stojanović, Vladimir D.; Nikitović, Željka D.

    2007-09-01

    DC high E/N swarm experiment (self sustained discharge operating in the Townsend regime) may be modeled directly and exactly as it does not require self consistent calculation of the electric field and is thus open to a simple Monte Carlo simulation that may include complexity at the level of representation of collisional events. Thus such an experiment operating under swarm conditions is the best way to test the mechanism of generation of anomalously large Doppler broadening that was often observed in low pressure discharges. In this paper we show revised results of modeling of Doppler profiles by using a well tested Monte Carlo procedure and revised models of heavy particle collisions. In particular we study the importance of fast H2 and fast H particles, the effect of different models of angular distribution of particles scattered of the surface and of the molecules and we study the role of the energy losses due to vibrational excitation.

  10. Electron's anomalous magnetic-moment effects on electron-hydrogen elastic collisions in the presence of a circularly polarized laser field

    SciTech Connect

    Elhandi, S.; Taj, S.; Attaourti, Y.; Manaut, B.; Oufni, L.

    2010-04-15

    The effect of the electron's anomalous magnetic moment on the relativistic electronic dressing for the process of electron-hydrogen atom elastic collisions is investigated. We consider a laser field with circular polarization and various electric field strengths. The Dirac-Volkov states taking into account this anomaly are used to describe the process in the first order of perturbation theory. The correlation between the terms coming from this anomaly and the electric field strength gives rise to the strong dependence of the spinor part of the differential cross section (DCS) with respect to these terms. A detailed study has been devoted to the nonrelativistic regime as well as the moderate relativistic regime. Some aspects of this dependence as well as the dynamical behavior of the DCS in the relativistic regime have been addressed.

  11. Thermal magnetic fluctuations and anomalous electron diffusion in a mirror-confined plasma

    SciTech Connect

    Murtaza, G.; Rahman, H.U.

    1983-09-01

    The electron test particle cross-field diffusion due to thermally excited magnetostatic modes with ergodic field lines is investigated. Estimate shows that in mirror-confined plasmas, the electron transport (and hence the electron thermal conduction) caused by the magnetostatic mode exceeds the convective as well as the classical transport.

  12. A hollow cathode ion source for production of primary ions for the BNL electron beam ion source

    NASA Astrophysics Data System (ADS)

    Alessi, James; Beebe, Edward; Carlson, Charles; McCafferty, Daniel; Pikin, Alexander; Ritter, John

    2014-02-01

    A hollow cathode ion source, based on one developed at Saclay, has been modified significantly and used for several years to produce all primary 1+ ions injected into the Relativistic Heavy Ion Collider Electron Beam Ion Source (EBIS) at Brookhaven. Currents of tens to hundreds of microamperes have been produced for 1+ ions of He, C, O, Ne, Si, Ar, Ti, Fe, Cu, Kr, Xe, Ta, Au, and U. The source is very simple, relying on a glow discharge using a noble gas, between anode and a solid cathode containing the desired species. Ions of both the working gas and ionized sputtered cathode material are extracted, and then the desired species is selected using an ExB filter before being transported into the EBIS trap for charge breeding. The source operates pulsed with long life and excellent stability for most species. Reliable ignition of the discharge at low gas pressure is facilitated by the use of capacitive coupling from a simple toy plasma globe. The source design, and operating experience for the various species, is presented.

  13. A hollow cathode ion source for production of primary ions for the BNL electron beam ion source

    SciTech Connect

    Alessi, James Beebe, Edward; Carlson, Charles; McCafferty, Daniel; Pikin, Alexander; Ritter, John

    2014-02-15

    A hollow cathode ion source, based on one developed at Saclay, has been modified significantly and used for several years to produce all primary 1+ ions injected into the Relativistic Heavy Ion Collider Electron Beam Ion Source (EBIS) at Brookhaven. Currents of tens to hundreds of microamperes have been produced for 1+ ions of He, C, O, Ne, Si, Ar, Ti, Fe, Cu, Kr, Xe, Ta, Au, and U. The source is very simple, relying on a glow discharge using a noble gas, between anode and a solid cathode containing the desired species. Ions of both the working gas and ionized sputtered cathode material are extracted, and then the desired species is selected using an ExB filter before being transported into the EBIS trap for charge breeding. The source operates pulsed with long life and excellent stability for most species. Reliable ignition of the discharge at low gas pressure is facilitated by the use of capacitive coupling from a simple toy plasma globe. The source design, and operating experience for the various species, is presented.

  14. A hollow cathode ion source for production of primary ions for the BNL electron beam ion source.

    PubMed

    Alessi, James; Beebe, Edward; Carlson, Charles; McCafferty, Daniel; Pikin, Alexander; Ritter, John

    2014-02-01

    A hollow cathode ion source, based on one developed at Saclay, has been modified significantly and used for several years to produce all primary 1+ ions injected into the Relativistic Heavy Ion Collider Electron Beam Ion Source (EBIS) at Brookhaven. Currents of tens to hundreds of microamperes have been produced for 1+ ions of He, C, O, Ne, Si, Ar, Ti, Fe, Cu, Kr, Xe, Ta, Au, and U. The source is very simple, relying on a glow discharge using a noble gas, between anode and a solid cathode containing the desired species. Ions of both the working gas and ionized sputtered cathode material are extracted, and then the desired species is selected using an ExB filter before being transported into the EBIS trap for charge breeding. The source operates pulsed with long life and excellent stability for most species. Reliable ignition of the discharge at low gas pressure is facilitated by the use of capacitive coupling from a simple toy plasma globe. The source design, and operating experience for the various species, is presented. PMID:24593637

  15. Electronic and optical device applications of hollow cathode plasma assisted atomic layer deposition based GaN thin films

    SciTech Connect

    Bolat, Sami Tekcan, Burak; Ozgit-Akgun, Cagla; Biyikli, Necmi; Okyay, Ali Kemal

    2015-01-15

    Electronic and optoelectronic devices, namely, thin film transistors (TFTs) and metal–semiconductor–metal (MSM) photodetectors, based on GaN films grown by hollow cathode plasma-assisted atomic layer deposition (PA-ALD) are demonstrated. Resistivity of GaN thin films and metal-GaN contact resistance are investigated as a function of annealing temperature. Effect of the plasma gas and postmetallization annealing on the performances of the TFTs as well as the effect of the annealing on the performance of MSM photodetectors are studied. Dark current to voltage and responsivity behavior of MSM devices are investigated as well. TFTs with the N{sub 2}/H{sub 2} PA-ALD based GaN channels are observed to have improved stability and transfer characteristics with respect to NH{sub 3} PA-ALD based transistors. Dark current of the MSM photodetectors is suppressed strongly after high-temperature annealing in N{sub 2}:H{sub 2} ambient.

  16. Hollow Retroreflectors

    NASA Technical Reports Server (NTRS)

    1993-01-01

    A hollow retroreflector is a mirror-like instrument that reflects light and other radiations back to the source. After developing a hollow retroreflector for NASA's Apollo-Soyuz mission, PLX, Inc. continued to expand the technology and develop a variety of retroreflector systems. The Lateral Transfer Hollow Retroreflector maintains precise separation, at any wavelength, of incoming and existing beams regardless of their orientation. It can be used as an instrument or as a component of an optical system. In the laboratory, it offers a new efficient means of beam positioning. In other applications, it connects laser resonators, aligns telescope mirrors and is useful in general boresighting and alignment.

  17. Direct electron transfer of glucose oxidase and biosensing of glucose on hollow sphere-nanostructured conducting polymer/metal oxide composite.

    PubMed

    Guo, Chun Xian; Li, Chang Ming

    2010-10-14

    A hollow sphere-nanostructured conductive polymer/metal oxide composite was synthesized and used to investigate the electrochemical behavior of glucose oxidase, demonstrating a significantly enhanced direct electron transfer ability of glucose oxidase. In particular, the long-standing puzzle of whether enzymatic glucose sensing involves an enzyme direct electron transfer process was studied. The results indicate the mechanism is indeed a glucose oxidase direct electron transfer process with competitive glucose oxidation and oxygen reduction to detect glucose. A glucose biosensor with the glucose oxidase-immobilized nanomaterial was further constructed, demonstrating superior sensitivity and reliability, and providing great potential in clinical applications. PMID:20714592

  18. Giant anomalous Hall effect in Fe-based microwires grown by focused-electron-beam-induced deposition

    NASA Astrophysics Data System (ADS)

    Córdoba, R.; Lavrijsen, R.; Fernández-Pacheco, A.; Ibarra, M. R.; Schoenaker, F.; Ellis, T.; Barcones-Campo, B.; Kohlhepp, J. T.; Swagten, H. J. M.; Koopmans, B.; Mulders, J. J. L.; De Teresa, J. M.

    2012-01-01

    We report the temperature dependence of the resistivity, the anisotropic magnetoresistance and the Hall effect of iron microwires grown by focused-electron-beam-induced deposition. By modifying the growth conditions in a controllable way, we study wires with iron compositions varying from 45% to 70%, which present different electrical conduction mechanisms, with resistivity values differing over three orders of magnitude. The magnetoresistance depends highly on the composition, and it can be understood by a subtle interplay between the anisotropic magnetoresistance and intergrain magnetoresistance due to their complex microstructure, consisting of an iron-carbon-oxygen amorphous matrix. A giant value for the anomalous Hall effect is found, which we explain by a large contribution of the skew scattering mechanism. The present results emphasize the correlation between the exotic microstructure of the microwires, and their magnetotransport properties.

  19. About a peculiar extra U(1): Z{sup '} discovery limit, muon anomalous magnetic moment, and electron electric dipole moment

    SciTech Connect

    Heo, Jae Ho

    2009-08-01

    The model (Lagrangian) with a peculiar extra U(1)[S. M. Barr and I. Dorsner, Phys. Rev. D 72, 015011 (2005); S. M. Barr and A. Khan, Phys. Rev. D 74, 085023 (2006)] is clearly presented. The assigned extra U(1) gauge charges give a strong constraint to build Lagrangians. The Z{sup '} discovery limits are estimated and predicted at the Tevatron and the LHC. The new contributions of the muon anomalous magnetic moment are investigated at one and two loops, and we predict that the deviation from the standard model may be explained. The electron electric dipole moment could also be generated because of the explicit CP-violation effect in the Higgs sector, and a sizable contribution is expected for a moderately sized CP phase [argument of the CP-odd Higgs], 0.1{<=}sin{delta}{<=}1[6 deg. {<=}arg(A){<=}90 deg.].

  20. Momentum and energy dependence of the anomalous high-energy dispersion in the electronic structure of high temperature superconductors.

    PubMed

    Inosov, D S; Fink, J; Kordyuk, A A; Borisenko, S V; Zabolotnyy, V B; Schuster, R; Knupfer, M; Büchner, B; Follath, R; Dürr, H A; Eberhardt, W; Hinkov, V; Keimer, B; Berger, H

    2007-12-01

    Using high-resolution angle-resolved photoemission spectroscopy we have studied the momentum and photon energy dependence of the anomalous high-energy dispersion, termed waterfalls, between the Fermi level and 1 eV binding energy in several high-T_{c} superconductors. We observe strong changes of the dispersion between different Brillouin zones and a strong dependence on the photon energy around 75 eV, which we associate with the resonant photoemission at the Cu3p-->3d_{x;{2}-y;{2}} edge. We conclude that the high-energy "waterfall" dispersion results from a strong suppression of the photoemission intensity at the center of the Brillouin zone due to matrix element effects and is, therefore, not an intrinsic feature of the spectral function. This indicates that the new high-energy scale in the electronic structure of cuprates derived from the waterfall-like dispersion may be incorrect. PMID:18233401

  1. Momentum and Energy Dependence of the Anomalous High-Energy Dispersion in the Electronic Structure of High Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Inosov, D. S.; Fink, J.; Kordyuk, A. A.; Borisenko, S. V.; Zabolotnyy, V. B.; Schuster, R.; Knupfer, M.; Büchner, B.; Follath, R.; Dürr, H. A.; Eberhardt, W.; Hinkov, V.; Keimer, B.; Berger, H.

    2007-12-01

    Using high-resolution angle-resolved photoemission spectroscopy we have studied the momentum and photon energy dependence of the anomalous high-energy dispersion, termed waterfalls, between the Fermi level and 1 eV binding energy in several high-Tc superconductors. We observe strong changes of the dispersion between different Brillouin zones and a strong dependence on the photon energy around 75 eV, which we associate with the resonant photoemission at the Cu3p→3dx2-y2 edge. We conclude that the high-energy “waterfall” dispersion results from a strong suppression of the photoemission intensity at the center of the Brillouin zone due to matrix element effects and is, therefore, not an intrinsic feature of the spectral function. This indicates that the new high-energy scale in the electronic structure of cuprates derived from the waterfall-like dispersion may be incorrect.

  2. Anomalous Electron Transport Due to Multiple High Frequency Beam Ion Driven Alfven Eigenmode

    SciTech Connect

    Gorelenkov, N. N.; Stutman, D.; Tritz, K.; Boozer, A.; Delgardo-Aparicio, L.; Fredrickson, E.; Kaye, S.; White, R.

    2010-07-13

    We report on the simulations of recently observed correlations of the core electron transport with the sub-thermal ion cyclotron frequency instabilities in low aspect ratio plasmas of the National Spherical Torus Experiment (NSTX). In order to model the electron transport of the guiding center code ORBIT is employed. A spectrum of test functions of multiple core localized Global shear Alfven Eigenmode (GAE) instabilities based on a previously developed theory and experimental observations is used to examine the electron transport properties. The simulations exhibit thermal electron transport induced by electron drift orbit stochasticity in the presence of multiple core localized GAE.

  3. Breaking all the invariants: Anomalous electron radiation belt diffusion by pitch angle scattering in the presence of split magnetic drift shells

    NASA Astrophysics Data System (ADS)

    O'Brien, T. P.

    2014-01-01

    Relativistic electron observations near geostationary orbit routinely show pitch angle distributions peaked away from 90 degrees. These "butterfly" distributions are consistent with magnetic drift shell splitting combined with a radial flux gradient. During magnetic storms, nature adds pitch angle scattering to split drift shells, breaking all three adiabatic invariants of the particle's motion. Therefore, some degree of anomalous radial diffusion is likely, and cross terms between the gyration and drift invariants and between the bounce and drift invariants arise. Using typical assumptions about the pitch angle scattering and the magnetic field topology, we calculate these anomalous diffusion coefficients near geostationary orbit. We show that the anomalous radial diffusion can exceed that due to more traditional drift-resonant wave-particle interactions. We also show that the neglected cross terms, particularly the bounce-drift cross term, can be significant. These results suggest necessary additions to some global electron radiation belt simulations.

  4. Anomalous Hall effect in ZnxFe3-xO4: Universal scaling law and electron localization below the Verwey transition

    NASA Astrophysics Data System (ADS)

    Jedrecy, N.; Hamieh, M.; Hebert, C.; Escudier, M.; Becerra, L.; Perriere, J.

    2016-08-01

    We show that the well-established universal scaling σxyAHE ˜ σxx1.6 between anomalous Hall and longitudinal conductivities in the low conductivity regime (σxx < 104 Ω-1 cm-1) transforms into the scaling σxyAHE ˜ σxx2 at the onset of strong electron localization. The crossover between the two relations is observed in magnetite-derived ZnxFe3-xO4 thin films where an insulating/hopping regime follows a bad metal/hopping regime below the Verwey transition temperature Tv. Our results demonstrate that electron localization effects come into play in the anomalous Hall effect (AHE) modifying significantly the scaling exponent. In addition, the thermal evolution of the anomalous Hall resistivity suggests the existence of spin polarons whose size would decrease below Tv.

  5. Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

    PubMed Central

    Wen, C. H. P.; Xu, H. C.; Chen, C.; Huang, Z. C.; Lou, X.; Pu, Y. J.; Song, Q.; Xie, B. P.; Abdel-Hafiez, Mahmoud; Chareev, D. A.; Vasiliev, A. N.; Peng, R.; Feng, D. L.

    2016-01-01

    FeSe layer-based superconductors exhibit exotic and distinctive properties. The undoped FeSe shows nematicity and superconductivity, while the heavily electron-doped KxFe2−ySe2 and single-layer FeSe/SrTiO3 possess high superconducting transition temperatures that pose theoretical challenges. However, a comprehensive study on the doping dependence of an FeSe layer-based superconductor is still lacking due to the lack of a clean means of doping control. Through angle-resolved photoemission spectroscopy studies on K-dosed thick FeSe films and FeSe0.93S0.07 bulk crystals, here we reveal the internal connections between these two types of FeSe-based superconductors, and obtain superconductivity below ∼46 K in an FeSe layer under electron doping without interfacial effects. Moreover, we discover an exotic phase diagram of FeSe with electron doping, including a nematic phase, a superconducting dome, a correlation-driven insulating phase and a metallic phase. Such an anomalous phase diagram unveils the remarkable complexity, and highlights the importance of correlations in FeSe layer-based superconductors. PMID:26952215

  6. Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy

    NASA Astrophysics Data System (ADS)

    Wen, C. H. P.; Xu, H. C.; Chen, C.; Huang, Z. C.; Lou, X.; Pu, Y. J.; Song, Q.; Xie, B. P.; Abdel-Hafiez, Mahmoud; Chareev, D. A.; Vasiliev, A. N.; Peng, R.; Feng, D. L.

    2016-03-01

    FeSe layer-based superconductors exhibit exotic and distinctive properties. The undoped FeSe shows nematicity and superconductivity, while the heavily electron-doped KxFe2-ySe2 and single-layer FeSe/SrTiO3 possess high superconducting transition temperatures that pose theoretical challenges. However, a comprehensive study on the doping dependence of an FeSe layer-based superconductor is still lacking due to the lack of a clean means of doping control. Through angle-resolved photoemission spectroscopy studies on K-dosed thick FeSe films and FeSe0.93S0.07 bulk crystals, here we reveal the internal connections between these two types of FeSe-based superconductors, and obtain superconductivity below ~46 K in an FeSe layer under electron doping without interfacial effects. Moreover, we discover an exotic phase diagram of FeSe with electron doping, including a nematic phase, a superconducting dome, a correlation-driven insulating phase and a metallic phase. Such an anomalous phase diagram unveils the remarkable complexity, and highlights the importance of correlations in FeSe layer-based superconductors.

  7. Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing.

    PubMed

    Couto, Rafael C; Guarise, Marco; Nicolaou, Alessandro; Jaouen, Nicolas; Chiuzbăian, Gheorghe S; Lüning, Jan; Ekholm, Victor; Rubensson, Jan-Erik; Såthe, Conny; Hennies, Franz; Kimberg, Victor; Guimarães, Freddy F; Agren, Hans; Gel'mukhanov, Faris; Journel, Loïc; Simon, Marc

    2016-01-01

    The unique opportunity to study and control electron-nuclear quantum dynamics in coupled potentials offered by the resonant inelastic X-ray scattering (RIXS) technique is utilized to unravel an anomalously strong two-electron one-photon transition from core-excited to Rydberg final states in the CO molecule. High-resolution RIXS measurements of CO in the energy region of 12-14 eV are presented and analyzed by means of quantum simulations using the wave packet propagation formalism and ab initio calculations of potential energy curves and transition dipole moments. The very good overall agreement between the experimental results and the theoretical predictions allows an in-depth interpretation of the salient spectral features in terms of Coulomb mixing of "dark" with "bright" final states leading to an effective two-electron one-photon transition. The present work illustrates that the improved spectral resolution of RIXS spectra achievable today may call for more advanced theories than what has been used in the past. PMID:26860458

  8. Anomalous correlation effects and unique phase diagram of electron-doped FeSe revealed by photoemission spectroscopy.

    PubMed

    Wen, C H P; Xu, H C; Chen, C; Huang, Z C; Lou, X; Pu, Y J; Song, Q; Xie, B P; Abdel-Hafiez, Mahmoud; Chareev, D A; Vasiliev, A N; Peng, R; Feng, D L

    2016-01-01

    FeSe layer-based superconductors exhibit exotic and distinctive properties. The undoped FeSe shows nematicity and superconductivity, while the heavily electron-doped KxFe2-ySe2 and single-layer FeSe/SrTiO3 possess high superconducting transition temperatures that pose theoretical challenges. However, a comprehensive study on the doping dependence of an FeSe layer-based superconductor is still lacking due to the lack of a clean means of doping control. Through angle-resolved photoemission spectroscopy studies on K-dosed thick FeSe films and FeSe0.93S0.07 bulk crystals, here we reveal the internal connections between these two types of FeSe-based superconductors, and obtain superconductivity below ∼46 K in an FeSe layer under electron doping without interfacial effects. Moreover, we discover an exotic phase diagram of FeSe with electron doping, including a nematic phase, a superconducting dome, a correlation-driven insulating phase and a metallic phase. Such an anomalous phase diagram unveils the remarkable complexity, and highlights the importance of correlations in FeSe layer-based superconductors. PMID:26952215

  9. Magnetic and anomalous electronic transport properties of the quaternary Heusler alloys Co2Ti1-xFexGe

    NASA Astrophysics Data System (ADS)

    Venkateswarlu, B.; Midhunlal, P. V.; Babu, P. D.; Kumar, N. Harish

    2016-06-01

    The half-metallic Heusler alloy Co2TiGe has a ferromagnetic ground state with a low magnetic moment (2 μB). It is free of atomic antisite disorder but has low Curie temperature (~390 K). In contrast the other cobalt based Heusler alloy Co2FeGe has high Curie temperature (~980 K) and high magnetic moment (5.6 μB) while exhibiting antisite disorder and lack of half-metallicity. Hence it is of interest to investigate the magnetic and transport properties of solid solutions of these two materials with contrasting characteristics. We report the structural, magnetic and electronic transport properties of quaternary Co2Ti1-x FexGe (x=0.2, 0.4, 0.6, 0.8) Heusler alloys. The alloys crystallize in L21 structure but with antisite disorder. The magnetization measurements revealed that the alloys were of soft ferromagnetic type with high Curie temperatures. Deviation from Slater-Pauling behavior and drastic change in electronic transport properties with some anomalous features were observed.The complex electronic transport properties have been explained using different scattering mechanisms.

  10. Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing

    PubMed Central

    Couto, Rafael C.; Guarise, Marco; Nicolaou, Alessandro; Jaouen, Nicolas; Chiuzbăian, Gheorghe S.; Lüning, Jan; Ekholm, Victor; Rubensson, Jan-Erik; Såthe, Conny; Hennies, Franz; Kimberg, Victor; Guimarães, Freddy F.; Agren, Hans; Gel’mukhanov, Faris; Journel, Loïc; Simon, Marc

    2016-01-01

    The unique opportunity to study and control electron-nuclear quantum dynamics in coupled potentials offered by the resonant inelastic X-ray scattering (RIXS) technique is utilized to unravel an anomalously strong two-electron one-photon transition from core-excited to Rydberg final states in the CO molecule. High-resolution RIXS measurements of CO in the energy region of 12–14 eV are presented and analyzed by means of quantum simulations using the wave packet propagation formalism and ab initio calculations of potential energy curves and transition dipole moments. The very good overall agreement between the experimental results and the theoretical predictions allows an in-depth interpretation of the salient spectral features in terms of Coulomb mixing of “dark” with “bright” final states leading to an effective two-electron one-photon transition. The present work illustrates that the improved spectral resolution of RIXS spectra achievable today may call for more advanced theories than what has been used in the past. PMID:26860458

  11. Combined infrared multiphoton dissociation and electron capture dissociation with a hollow electron beam in Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Tsybin, Youri O; Witt, Matthias; Baykut, Gökhan; Kjeldsen, Frank; Håkansson, Per

    2003-01-01

    An electron injection system based on an indirectly heated ring-shaped dispenser cathode has been developed and installed in a 7 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. This new hardware design allows high-rate electron capture dissociation (ECD) to be carried out by a hollow electron beam coaxial with the ion cyclotron resonance (ICR) trap. Infrared multiphoton dissociation (IRMPD) can also be performed with an on-axis IR-laser beam passing through a hole at the centre of the dispenser cathode. Electron and photon irradiation times of the order of 100 ms are required for efficient ECD and IRMPD, respectively. As ECD and IRMPD generate fragments of different types (mostly c, z and b, y, respectively), complementary structural information that improves the characterization of peptides and proteins by FTICR mass spectrometry can be obtained. The developed technique enables the consecutive or simultaneous use of the ECD and IRMPD methods within a single FTICR experimental sequence and on the same ensemble of trapped ions in multistage tandem (MS/MS/MS or MS(n)) mass spectrometry. Flexible changing between ECD and IRMPD should present advantages for the analysis of protein digests separated by liquid chromatography prior to FTICRMS. Furthermore, ion activation by either electron or laser irradiation prior to, as well as after, dissociation by IRMPD or ECD increases the efficiency of ion fragmentation, including the w-type fragment ion formation, and improves sequencing of peptides with multiple disulfide bridges. The developed instrumental configuration is essential for combined ECD and IRMPD on FTICR mass spectrometers with limited access into the ICR trap. PMID:12872281

  12. Use of multiwavelength emission from hollow cathode lamp for measurement of state resolved atom density of metal vapor produced by electron beam evaporation

    SciTech Connect

    Majumder, A.; Dikshit, B.; Bhatia, M. S.; Mago, V. K.

    2008-09-15

    State resolved atom population of metal vapor having low-lying metastable states departs from equilibrium value. It needs to be experimentally investigated. This paper reports the use of hollow cathode lamp based atomic absorption spectroscopy technique to measure online the state resolved atom density (ground and metastable) of metal vapor in an atomic beam produced by a high power electron gun. In particular, the advantage of availability of multiwavelength emission in hollow cathode lamp is used to determine the atom density in different states. Here, several transitions pertaining to a given state have also been invoked to obtain the mean value of atom density thereby providing an opportunity for in situ averaging. It is observed that at higher source temperatures the atoms from metastable state relax to the ground state. This is ascribed to competing processes of atom-atom and electron-atom collisions. The formation of collision induced virtual source is inferred from measurement of atom density distribution profile along the width of the atomic beam. The total line-of-sight average atom density measured by absorption technique using hollow cathode lamp is compared to that measured by atomic vapor deposition method. The presence of collisions is further supported by determination of beaming exponent by numerically fitting the data.

  13. Use of multiwavelength emission from hollow cathode lamp for measurement of state resolved atom density of metal vapor produced by electron beam evaporation.

    PubMed

    Majumder, A; Dikshit, B; Bhatia, M S; Mago, V K

    2008-09-01

    State resolved atom population of metal vapor having low-lying metastable states departs from equilibrium value. It needs to be experimentally investigated. This paper reports the use of hollow cathode lamp based atomic absorption spectroscopy technique to measure online the state resolved atom density (ground and metastable) of metal vapor in an atomic beam produced by a high power electron gun. In particular, the advantage of availability of multiwavelength emission in hollow cathode lamp is used to determine the atom density in different states. Here, several transitions pertaining to a given state have also been invoked to obtain the mean value of atom density thereby providing an opportunity for in situ averaging. It is observed that at higher source temperatures the atoms from metastable state relax to the ground state. This is ascribed to competing processes of atom-atom and electron-atom collisions. The formation of collision induced virtual source is inferred from measurement of atom density distribution profile along the width of the atomic beam. The total line-of-sight average atom density measured by absorption technique using hollow cathode lamp is compared to that measured by atomic vapor deposition method. The presence of collisions is further supported by determination of beaming exponent by numerically fitting the data. PMID:19044405

  14. Anomalously Large Chiral Sensitivity in the Dissociative Electron Attachment of 10-Iodocamphor

    NASA Astrophysics Data System (ADS)

    Dreiling, J. M.; Lewis, F. W.; Mills, J. D.; Gay, T. J.

    2016-03-01

    We have studied dissociative electron attachment (DEA) between low energy (≤0.6 eV ) longitudinally polarized electrons and gas-phase chiral targets of 3-bromocamphor (C10 H15 BrO ), 3-iodocamphor (C10 H15 IO ), and 10-iodocamphor. The DEA rate depends on the sign of the incident electron helicity for a given target handedness, and it varies with both the atomic number (Z ) and location of the heaviest atom in the molecule. While simple dynamic mechanisms can account for the asymmetry dependence on Z , they fail to explain the large asymmetry variation with the heavy atom location.

  15. Anomalously Large Chiral Sensitivity in the Dissociative Electron Attachment of 10-Iodocamphor.

    PubMed

    Dreiling, J M; Lewis, F W; Mills, J D; Gay, T J

    2016-03-01

    We have studied dissociative electron attachment (DEA) between low energy (≤0.6  eV) longitudinally polarized electrons and gas-phase chiral targets of 3-bromocamphor (C_{10}H_{15}BrO), 3-iodocamphor (C_{10}H_{15}IO), and 10-iodocamphor. The DEA rate depends on the sign of the incident electron helicity for a given target handedness, and it varies with both the atomic number (Z) and location of the heaviest atom in the molecule. While simple dynamic mechanisms can account for the asymmetry dependence on Z, they fail to explain the large asymmetry variation with the heavy atom location. PMID:26991173

  16. Understanding the dramatic role of anomalous dispersion on the measurement of electron densities in plasmas using interferometers

    SciTech Connect

    Nilsen, J; Johnson, W R; Iglesias, C A; Scofield, J H

    2005-07-20

    For decades the electron density of plasmas has been measured using optical interferometers. With the availability of good X-ray laser sources in the last decade interferometers have been extended into the wavelength range 14-47 nm, which has enabled researchers to probe even higher density plasmas. The data analysis assumes the index of refraction is due only to the free electrons, which makes the index less than one. Recent interferometer experiments in Al plasmas observed plasmas with index of refraction greater than one at 14 nm and brought into question the validity of the usual formula for calculating the index. In this paper we show how the anomalous dispersion from bound electrons can dominate the free electron contribution to the index of refraction in many plasmas and make the index greater than one or enhance the contribution to the index such that one would greatly overestimate the density of the plasma using interferometers. Using a new average-atom code we calculate the index of refraction in many plasmas at different temperatures for photon energies from 0 to 100 eV and compare against calculations done with OPAL. We also present examples of other plasmas that may have index of refraction greater than one at X-ray laser energies. During the next decade X-ray free electron lasers and other X-ray sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential.

  17. Many-electron effects in anomalous elastic scattering of linearly polarized x-ray photons by Xe near the K-edge

    NASA Astrophysics Data System (ADS)

    Hopersky, A. N.; Yavna, V. A.; Popov, V. A.

    1997-11-01

    Within the non-relativistic approximation the effect of radial monopole rearrangement of electron shells within the field of a vacancy and of the processes of one-photon double excitation - ionization on the differential cross section of anomalous non-zero-angle elastic scattering of linearly polarized x-ray photons by the Xe atom in the region of its 1s-shell ionization threshold is studied. Theoretical results for the anomalous dispersion region of scattering demonstrate a strong dependence of the cross section value on the approximation used.

  18. Effect of anomalous electron cross-field transport on electron energy distribution function in a DC-RF magnetized plasma discharge

    NASA Astrophysics Data System (ADS)

    Raitses, Yevgeny; Donnelly, Vincent; Kaganovich, Igor; Godyak, Valery

    2013-09-01

    The application of the magnetic field in a low pressure plasma can cause a spatial separation of cold and hot electron groups. This so-called magnetic filter effect is not well understood and is the subject of our studies. In this work, we investigate electron energy distribution function in a DC-RF plasma discharge with crossed electric and magnetic field operating at sub-mtorr pressure range of xenon gas. Experimental studies showed that the increase of the magnetic field leads to a more uniform profile of the electron temperature across the magnetic field. This surprising result indicates the importance of anomalous electron transport that causes mixing of hot and cold electrons. High-speed imaging and probe measurements revealed a coherent structure rotating in E cross B direction with frequency of a few kHz. Similar to spoke oscillations reported for Hall thrusters, this rotating structure conducts the largest fraction of the cross-field current. This work was supported by the US DOE under Contract DE-AC02-09CH11466.

  19. Effect of anomalous electron cross-field transport on electron energy distribution function in a DC-RF magnetized plasma discharge

    NASA Astrophysics Data System (ADS)

    Raitses, Yevgeny; Donnelly, Vincent M.; Kaganovich, Igor D.; Godyak, Valery

    2013-10-01

    The application of the magnetic field in a low pressure plasma can cause a spatial separation of cold and hot electron groups. This so-called magnetic filter effect is not well understood and is the subject of our studies. In this work, we investigate electron energy distribution function in a DC-RF plasma discharge with crossed electric and magnetic field operating at sub-mtorr pressure range of xenon gas. Experimental studies showed that the increase of the magnetic field leads to a more uniform profile of the electron temperature across the magnetic field. This surprising result indicates the importance of anomalous electron transport that causes mixing of hot and cold electrons. High-speed imaging and probe measurements revealed a coherent structure rotating in E cross B direction with frequency of a few kHz. Similar to spoke oscillations reported for Hall thrusters, this rotating structure conducts the largest fraction of the cross-field current. This work was supported by DOE contract DE-AC02-09CH11466.

  20. Anomalous electronic structure and magnetoresistance in TaAs2

    SciTech Connect

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    We report that the change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. In conclusion, density functional calculations find that TaAs2 is a new topological semimetal [Z2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.

  1. Efficiency enhancement of anomalous-Doppler electron cyclotron masers with tapered magnetic field

    SciTech Connect

    Xie, Chao-Ran; Hou, Zhi-Ling; Kong, Ling-Bao E-mail: pkliu@pku.edu.cn; Beijing Key Laboratory of Harmful Chemicals Analysis and School of Science, Beijing University of Chemical Technology, Beijing 100029 ; Liu, Pu-Kun E-mail: pkliu@pku.edu.cn; Du, Chao-Hai; Jin, Hai-Bo

    2014-02-15

    The efficiency of slow-wave electron cyclotron masers (ECM) is usually low, thus limiting the practical applications. Here, a method of tapered magnetic field is introduced for the efficiency enhancement of the slow-wave ECM. The numerical calculations show that the tapered magnetic-field method can enhance the efficiency of slow-wave ECM significantly. The effect of beam electron velocity spread on the efficiency has also been studied. Although the velocity spread reduces the efficiency, a great enhancement of efficiency can still be obtained by the tapered magnetic field method.

  2. Hydrogen adsorption and anomalous electronic properties of nitrogen-doped graphene

    SciTech Connect

    Fujimoto, Yoshitaka; Saito, Susumu

    2014-04-21

    We investigate hydrogen adsorption effects on stabilities and electronic properties of nitrogen defects in graphene using first-principles electronic-structure calculations within the density-functional theory. We find that the adsorption of hydrogen atoms on the pyridine-type nitrogen defects in graphene becomes energetically favorable, whereas in the case of the substitutional nitrogen defect the hydrogen adsorption becomes unfavorable. We also find that a transition from p-type to n-type doping properties occurs by hydrogen adsorption on the pyridine-type defects, suggesting that even the carrier type is controllable in nitrogen-doped graphene.

  3. Electron energy-loss spectroscopy of anomalous plutonium behavior in nuclear waste materials.

    PubMed

    Buck, Edgar C; Finn, Patricia A; Bates, John K

    2004-01-01

    Plutonium-enriched layer has been observed in corroded spent uranium oxide fuel (CSNF). These Pu-enriched regions were examined with analytical transmission electron microscopy combined with electron energy-loss spectroscopy (EELS). The enriched region also contained U, Am, Ru, Zr, but only minor enrichment of rare earth elements. The Pu, possibly as Pu(V) according to EELS measurements, was dispersed within re-precipitated uranium oxide (identified as U3O8) nano-crystals between U(VI) secondary phases and the CSNF surface. The U, Pu, and Am enrichment was observed in the corrosion products with tests on different nuclear fuels. This may have implications for the long-term behavior of CSNF under storage in a geologic waste repository. Furthermore, there may be an increased potential for the generation of Pu-bearing colloids from this type of weathered CSNF. PMID:15003610

  4. Electron Energy-loss Spectroscopy of Anomalous Plutonium Behavior in Nuclear Waste Materials

    SciTech Connect

    Buck, Edgar C.; Finn, patricia A.; Bates, John K.

    2004-06-01

    Plutonium-enriched layer has been observed in corroded spent uranium oxide fuel (CSNF). These Pu-enriched regions were examined with analytical transmission electron microscopy combined with electron energy-loss spectroscopy. The enriched region also contained U, Am, Ru, Zr, but only minor enrichment of rare earth elements. The Pu, possibly as Pu(V) according to EELS measurements, was dispersed within re-precipitated uranium oxide (identified as U3O8) nano-crystals between U(VI) secondary phases and the CSNF surface. The U, Pu, and Am enrichment was observed in the corrosion products with tests on different nuclear fuels. This may have implications for the long-term behavior of CSNF under storage in a geologic waste repository. Furthermore, there may be an increased potential for the generation of Pu-bearing colloids from this type of weathered CSNF.

  5. Anomalous organic magnetoresistance from competing carrier-spin-dependent interactions with localized electronic and nuclear spins

    NASA Astrophysics Data System (ADS)

    Flatté, Michael E.

    Transport of carriers through disordered electronic energy landscapes occurs via hopping or tunneling through various sites, and can enhance the effects of carrier spin dynamics on the transport. When incoherent hopping preserves the spin orientation of carriers, the magnetic-field-dependent correlations between pairs of spins influence the charge conductivity of the material. Examples of these phenomena have been identified in hopping transport in organic semiconductors and colloidal quantum dots, as well as tunneling through oxide barriers in complex oxide devices, among other materials. The resulting room-temperature magnetic field effects on the conductivity or electroluminescence require external fields of only a few milliTesla. These magnetic field effects can be dramatically modified by changes in the local spin environment. Recent theoretical and experimental work has identified a regime for low-field magnetoresistance in organic semiconductors in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere1. The regime is studied experimentally by the controlled addition of localized electronic spins, through the addition of a stable free radical (galvinoxyl) to a material (MEH-PPV) that exhibits substantial room-temperature magnetoresistance (20 initially suppressed by the doping, as the localized electronic spin mixes one of the two spins whose correlation controls the transport. At intermediate doping, when one spin is fully decohered but the other is not, there is a regime where the magnetoresistance is insensitive to the doping level. For much greater doping concentrations the magnetoresistance is fully suppressed as both spins that control the charge conductivity of the material are mixed. The behavior is described within a theoretical model describing the effect of carrier spin dynamics on the current. Generalizations to amorphous and other disordered crystalline semiconductors will also be described. This work was

  6. Anomalous electron loading in SLAC 5045 klystron and relativistic klystron input cavities

    SciTech Connect

    Koontz, R.F.; Fowkes, R.W.; Lavine, T.L.; Miller, R.H.; Vlieks, A.E.

    1989-03-01

    Recent studies of RF breakup and instability in the SLAC 5045 klystrons have revealed that many production klystrons show loading of the input cavity by low energy electrons even under cold cathode no beam conditions. Sometime after the onset of the RF drive pulse, the input cavity absorbs a portion of the incident RF drive that would otherwise be reflected from the not-beam-loaded cavity. This power absorption is a function of drive level, and of axial magnetic field surrounding the cavity. No power absorption is present when the axial magnetic field is zero. This same phenomenon has been observed in the input cavity of relativistic klystron experiments being conducted as part of the SLAC-LBL-LLNL development program. The phenomenon may be associated with RF breakup and RF instability in SLAC 5045 klystrons, and with unstable pulse shortening in the relativistic klystron experiments. This paper outlines some old and new observations of microwave beam device malfunctions that probably are associated with low energy electron fluxes in the vacuum environments of microwave power devices. 2 refs., 5 figs.

  7. Anomalous behavior of LiF:Mg,Cu,P (TLD100H) irradiated with electron beams

    NASA Astrophysics Data System (ADS)

    Triolo, A.; Brai, M.; Bartolotta, A.; Marrale, M.

    2006-12-01

    Thermoluminescent dosimeters of LiF:Mg,Cu,P (TLD100H) were exposed to 60Co γ-ray, protons, high energy electrons and the glow curves were analyzed. We observed an unusual behavior of the TL response of dosimeters to 7 and 14 MeV electron beam. In fact the relative amplitude between two of the five peaks (2° and 3° peaks) assumes values smaller than the unity for doses up to 5 Gy and values greater than the unity for doses equal to or greater than 10 Gy. A possible explanation of this behavior is given adopting a model of the formation of the peaks 2° and 3° and examining the different ways of energy release in matter for each beam. To perform this analysis we deconvoluted the glow curve adopting general order kinetic (GOK) equation for the description of the peak shape, determining the number of peaks and their trapping parameter (E,s,n0).

  8. Anomalous electron cooling observed by the eiscat within the dusty nightside auroral dynamo layer

    NASA Astrophysics Data System (ADS)

    Timofeev, Evgeny; Kangas, Jorma; Vallinkoski, Matti; Shalimov, Sergey

    In the present study we analyze parameters of the lower ionosphere, measured by the EISCAT radar facility at the zenith of Tromsø auroral observatory during the ERRRIS campaign. Data used consists of 20 different nights of observations and includes approximately 2000 measurements. At that 75% and 25% of the data corresponds to measured ionospheric electric field that is below and above the threshold of the Farley-Buneman instability (which is 15-20 mV/m), respectively. In the first part of our analysis the height profiles of the electron and ion temperature difference (Te-Ti) (including standard deviation, STD) for both, small and large electric fields were calculated using the superimposed epoch method. It was shown that: 1) for the large electric fields the profile (Te-Ti) with Te>Ti takes the maximum (60-70 K) at 115 km in agreement with the standard conception; 2) for the small electric fields the thermal anomaly was revealed when Te

  9. Anomalous one-electron processes in the chemistry of uranium nitrogen multiple bonds.

    PubMed

    Mullane, Kimberly C; Lewis, Andrew J; Yin, Haolin; Carroll, Patrick J; Schelter, Eric J

    2014-09-01

    Novel reaction pathways are illustrated in the synthesis of uranium(IV), uranium(V), and uranium(VI) monoimido complexes. In contrast to the straightforward preparation of U(V)(═NSiMe3)[N(SiMe3)2]3 (1), the synthesis of a uranium(V) tritylimido complex, U(V)(═NCPh3)[N(SiMe3)2]3 (4), from U(III)[N(SiMe3)2]3 and Ph3CN3 was found to proceed through multiple one-electron steps. Whereas the oxidation of 1 with copper(II) salts produced the uranium(VI) monoimido complexes U(VI)(═NSiMe3)X[N(SiMe3)2]3 (X = Cl, Br), the reaction of 4 with CuBr2 undergoes sterically induced reduction to form the uranium(VI) monoimido complex U(VI)(═NCPh3)Br2[N(SiMe3)2]2, demonstrating a striking difference in reactivity based on imido substituent. The facile reduction of compounds 1 and 4 with KC8 allowed for the synthesis of the uranium(IV) monoimido derivatives, K[U(IV)(═NSiMe3)[N(SiMe3)2]3] (1-K) and K[U(IV)(═NCPh3)[N(SiMe3)2]3] (4-K), respectively. In contrast, an analogous uranium(IV) monoimido complex, K[U(IV)(═NPh(F))[N(SiMe3)Ph(F)

  10. Applications of anomalous diffraction systems, generation of attosecond electron and photon pulses and Raman amplification by stimulated emission of radiation

    NASA Astrophysics Data System (ADS)

    Vartak, Sameer Dinkar

    1998-10-01

    Anomalous diffraction is scattering process due to phase distortion introduced on incident phase front by scattering object. Phase mask or hologram, Christiansen filter, PDLC are examples of an anomalously diffracting systems. Phase hologram modulates an input wavefront to produce a wavefront which when Fourier transformed using a converging lens gives desired image on to a screen. We made a nonlinear optical element using phase mask made up of nonlinear material. It forms a lens because of nonlinear index of refraction when a high intensity beam is incident. This lens Fourier transforms the phase mask and images the phase mask. This nonlinear optical element can be used for various applications like image gating and 3-D memory writing and read out. Christiansen filter (CF) is a two component scattering system whose dispersion curves intersect at certain wavelength. Thus light corresponding to this wavelength traverses the filter without any scattering and light at other wavelengths gets scattered. This results in narrow wavelength dependent transmission curve centered at the index matching wavelength. When materials with an intensity dependent refractive index are used to make a CF, the index matching condition of CF becomes function of the input intensity resulting in intensity dependent beam size and transmittance through the filter. This property of nonlinear CF can be used to switch beam optically in both self and cross-modulation modes. Polymer Dispersed Liquid Crystal (PDLC) is dispersion of liquid crystal droplets in polymer whose index of refraction is same as ordinary refractive index of liquid crystal. PDLC shows voltage dependent scattering and are used in flat panel displays. We used this element as voltage controlled intracavity loss element in a laser cavity to make a lasing pixel projection display. Output of this pixel shows all desired properties for a projection display like narrow linewidth, high brightness, TTL switching compatibility and

  11. Fast Ignition relevant study of the flux of high intensity laser generated electrons via a hollow cone into a laser-imploded plasma

    SciTech Connect

    Key, M; Adam, J; Akli, K; Borgheshi, M; Chen, M; Evans, R; Freeman, R; Hatchett, S; Hill, J; Heron, A; King, J; Lancaster, K; Mackinnon, A; Norreys, P; Phillips, T; Romagnani, L; Snavely, R; Stephens, R; Stoeckl, C

    2005-10-11

    An integrated experiment relevant to fast ignition is described. A Cu doped CD spherical shell target is imploded around an inserted hollow Au cone by a six beam 600J, 1ns laser to a peak density of 4gcm{sup -3} and a diameter of 100 {micro}m. A 10 ps, 20TW laser pulse is focused into the cone at the time of peak compression. The flux of high-energy electrons through the imploded material is determined from the yield of Cu K{alpha} fluorescence by comparison with a Monte Carlo model and is estimated to carry 15% of the laser energy. Collisional and Ohmic heating are modeled. An electron spectrometer shows significantly greater reduction of the transmitted electron flux than is due to binary collisions and Ohmic potential. Enhanced scattering by instability-induced magnetic fields is suggested.

  12. Anomalous High-Energy Waterfall-Like Electronic Structure in 5 d Transition Metal Oxide Sr2IrO4 with a Strong Spin-Orbit Coupling

    PubMed Central

    Liu, Yan; Yu, Li; Jia, Xiaowen; Zhao, Jianzhou; Weng, Hongming; Peng, Yingying; Chen, Chaoyu; Xie, Zhuojin; Mou, Daixiang; He, Junfeng; Liu, Xu; Feng, Ya; Yi, Hemian; Zhao, Lin; Liu, Guodong; He, Shaolong; Dong, Xiaoli; Zhang, Jun; Xu, Zuyan; Chen, Chuangtian; Cao, Gang; Dai, Xi; Fang, Zhong; Zhou, X. J.

    2015-01-01

    The low energy electronic structure of Sr2IrO4 has been well studied and understood in terms of an effective Jeff = 1/2 Mott insulator model. However, little work has been done in studying its high energy electronic behaviors. Here we report a new observation of the anomalous high energy electronic structure in Sr2IrO4. By taking high-resolution angle-resolved photoemission measurements on Sr2IrO4 over a wide energy range, we have revealed for the first time that the high energy electronic structures show unusual nearly-vertical bands that extend over a large energy range. Such anomalous high energy behaviors resemble the high energy waterfall features observed in the cuprate superconductors. While strong electron correlation plays an important role in producing high energy waterfall features in the cuprate superconductors, the revelation of the high energy anomalies in Sr2IrO4, which exhibits strong spin-orbit coupling and a moderate electron correlation, points to an unknown and novel route in generating exotic electronic excitations. PMID:26267653

  13. Anomalous High-Energy Waterfall-Like Electronic Structure in 5 d Transition Metal Oxide Sr2IrO4 with a Strong Spin-Orbit Coupling.

    PubMed

    Liu, Yan; Yu, Li; Jia, Xiaowen; Zhao, Jianzhou; Weng, Hongming; Peng, Yingying; Chen, Chaoyu; Xie, Zhuojin; Mou, Daixiang; He, Junfeng; Liu, Xu; Feng, Ya; Yi, Hemian; Zhao, Lin; Liu, Guodong; He, Shaolong; Dong, Xiaoli; Zhang, Jun; Xu, Zuyan; Chen, Chuangtian; Cao, Gang; Dai, Xi; Fang, Zhong; Zhou, X J

    2015-01-01

    The low energy electronic structure of Sr2IrO4 has been well studied and understood in terms of an effective Jeff = 1/2 Mott insulator model. However, little work has been done in studying its high energy electronic behaviors. Here we report a new observation of the anomalous high energy electronic structure in Sr2IrO4. By taking high-resolution angle-resolved photoemission measurements on Sr2IrO4 over a wide energy range, we have revealed for the first time that the high energy electronic structures show unusual nearly-vertical bands that extend over a large energy range. Such anomalous high energy behaviors resemble the high energy waterfall features observed in the cuprate superconductors. While strong electron correlation plays an important role in producing high energy waterfall features in the cuprate superconductors, the revelation of the high energy anomalies in Sr2IrO4, which exhibits strong spin-orbit coupling and a moderate electron correlation, points to an unknown and novel route in generating exotic electronic excitations. PMID:26267653

  14. Anomalous High-Energy Waterfall-Like Electronic Structure in 5 d Transition Metal Oxide Sr2IrO4 with a Strong Spin-Orbit Coupling

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Yu, Li; Jia, Xiaowen; Zhao, Jianzhou; Weng, Hongming; Peng, Yingying; Chen, Chaoyu; Xie, Zhuojin; Mou, Daixiang; He, Junfeng; Liu, Xu; Feng, Ya; Yi, Hemian; Zhao, Lin; Liu, Guodong; He, Shaolong; Dong, Xiaoli; Zhang, Jun; Xu, Zuyan; Chen, Chuangtian; Cao, Gang; Dai, Xi; Fang, Zhong; Zhou, X. J.

    2015-08-01

    The low energy electronic structure of Sr2IrO4 has been well studied and understood in terms of an effective Jeff = 1/2 Mott insulator model. However, little work has been done in studying its high energy electronic behaviors. Here we report a new observation of the anomalous high energy electronic structure in Sr2IrO4. By taking high-resolution angle-resolved photoemission measurements on Sr2IrO4 over a wide energy range, we have revealed for the first time that the high energy electronic structures show unusual nearly-vertical bands that extend over a large energy range. Such anomalous high energy behaviors resemble the high energy waterfall features observed in the cuprate superconductors. While strong electron correlation plays an important role in producing high energy waterfall features in the cuprate superconductors, the revelation of the high energy anomalies in Sr2IrO4, which exhibits strong spin-orbit coupling and a moderate electron correlation, points to an unknown and novel route in generating exotic electronic excitations.

  15. Anomalous electrodynamic explosions in liquids

    SciTech Connect

    Aspden, H.

    1986-06-01

    The recently reported Graneau experiments on electrodynamic explosions in liquids, which reveal anomalous longitudinal electrodynamic forces of the order of 10/sup 4/ times greater than expected, verify the need for a term in the law of electrodynamics that corresponds to the ion/electron mass ratio. This confirms an earlier theoretical interpretation of the anomalous cathode reaction forces found in the vacuum arc.

  16. Anomalous Local Fermi Liquid in f2-Singlet Configuration: Impurity Model for Heavy-Electron System UPt3

    NASA Astrophysics Data System (ADS)

    Yotsuhashi, Satoshi; Miyake, Kazumasa; Kusunose, Hiroaki

    2016-03-01

    It is shown by the Wilson numerical renormalization group method that a strongly correlated impurity with a crystalline-electric-field singlet ground state in the f2-configuration exhibits an anomalous local Fermi liquid state in which the static magnetic susceptibility remains an uncorrelated value while the NMR relaxation rate is enhanced in proportion to the square of the mass enhancement factor. Namely, the Korringa-Shiba relation is apparently broken. This feature closely matches the anomalous behaviors observed in UPt3, i.e., the coexistence of an unenhanced value of the Knight shift due to quasiparticles contribution (the decrease across the superconducting transition) and the enhanced relaxation rate of NMR. Such an anomalous Fermi liquid behavior suggests that the Fermi liquid corrections for the susceptibility are highly anisotropic.

  17. Model of a Hollow Cathode Insert Plasma

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Polk, James E.

    2004-01-01

    A 2-D axisymmetric fluid model of the plasma in the insert region of a hollow cathode is presented. The level of sophistication included in the model is motivated in part by the need to determine quantitatively plasma fluxes to the emitter surface. The ultimate goal is to assess whether plasma effects can degrade the life of impregnated inserts beyond those documented throughout the 30-50 year history of vacuum cathode technologies. Results from simulations of a 1.2-cm diameter cathode operating at a discharge current of 25 A, and a gas flow rate of 5 sccm, suggest that approximately 10 A of electron current, and 3.5 A of ion current return to the emitter surface. The total emitted electron current computed by the model is about 35 A. Comparisons with plasma measurements suggest that anomalous heating of the plasma due to two-stream instabilities is possible near the orifice region. Solution to the heavy species energy equation, with classical transport and no viscous effects, predicts heavy species temperatures as high as 2640 K.

  18. The plasma properties and electron emission characteristics of near-zero differential resistance of hollow cathode-based plasma contactors with a discharge chamber

    SciTech Connect

    Xie, Kan; Farnell, Casey C.; Williams, John D.

    2014-08-15

    The formation of electron emission-bias voltage (I-V) characteristics of near-zero differential resistance in the cathodic plasma contactor for bare electrodynamic tether applications, based on a hollow cathode embedded in a ring-cusp ionization stage, is studied. The existence of such an I-V regime is important to achieve low impedance performance without being affected by the space plasma properties for a cathodic plasma contactor. Experimental data on the plasma structure and properties downstream from the ionization stage are presented as functions of the xenon flow rate and the electron emission current. The electrons were emitted from the cathode to the cylindrical vacuum chamber wall (r = 0.9 m) under ≈10{sup −5 }Torr of vacuum pressure. The ring-cusp configuration selected for the plasma contactor created a 125-Gauss axial field near the cathode orifice, along with a large-volume 50-Gauss magnitude pocket in the stage. A baseline ion energy cost of ≈300 eV/ion was measured in the ionization stage when no electrons were emitted to the vacuum chamber wall. In addition, the anode fall growth limited the maximum propellant unitization to below ≈75% in the discharge loss curves for this ion stage. Detailed measurements on the plasma properties were carried out for the no-electron emission and 3 A emission conditions. The experimental data are compared with 1-D models, and the effectiveness of the model is discussed. The four key issues that played important roles in the process of building the near-zero different resistance I-V regime are: a significant amount of ionization by the emission electrons, a decrease in the number of reflected electrons in the plume, the electron-temperature increment, and low initial ion energy at the source outlet.

  19. The plasma properties and electron emission characteristics of near-zero differential resistance of hollow cathode-based plasma contactors with a discharge chamber

    NASA Astrophysics Data System (ADS)

    Xie, Kan; Farnell, Casey C.; Williams, John D.

    2014-08-01

    The formation of electron emission-bias voltage (I-V) characteristics of near-zero differential resistance in the cathodic plasma contactor for bare electrodynamic tether applications, based on a hollow cathode embedded in a ring-cusp ionization stage, is studied. The existence of such an I-V regime is important to achieve low impedance performance without being affected by the space plasma properties for a cathodic plasma contactor. Experimental data on the plasma structure and properties downstream from the ionization stage are presented as functions of the xenon flow rate and the electron emission current. The electrons were emitted from the cathode to the cylindrical vacuum chamber wall (r = 0.9 m) under ≈10-5 Torr of vacuum pressure. The ring-cusp configuration selected for the plasma contactor created a 125-Gauss axial field near the cathode orifice, along with a large-volume 50-Gauss magnitude pocket in the stage. A baseline ion energy cost of ≈300 eV/ion was measured in the ionization stage when no electrons were emitted to the vacuum chamber wall. In addition, the anode fall growth limited the maximum propellant unitization to below ≈75% in the discharge loss curves for this ion stage. Detailed measurements on the plasma properties were carried out for the no-electron emission and 3 A emission conditions. The experimental data are compared with 1-D models, and the effectiveness of the model is discussed. The four key issues that played important roles in the process of building the near-zero different resistance I-V regime are: a significant amount of ionization by the emission electrons, a decrease in the number of reflected electrons in the plume, the electron-temperature increment, and low initial ion energy at the source outlet.

  20. Fast ignition relevant study of the flux of high intensity laser-generated electrons via a hollow cone into a laser-imploded plasma

    SciTech Connect

    Key, M. H.; Chen, M. H.; Hatchett, S. P.; Hill, J. M.; King, J. A.; MacKinnon, A. J.; Patel, P.; Phillips, T.; Snavely, R. A.; Town, R.; Adam, J. C.; Heron, A.; Akli, K. U.; Stephens, R.; Borghesi, M.; Romagnani, L.; Zepf, M.; Evans, R. G.; Freeman, R. R.; Habara, H.

    2008-02-15

    An integrated experiment relevant to fast ignition . A Cu-doped deuterated polymer spherical shell target with an inserted hollow Au cone is imploded by a six-beam 900-J, 1-ns laser. A 10-ps, 70-J laser pulse is focused into the cone at the time of peak compression. The flux of high-energy electrons through the imploded material is determined from the yield of Cu K{alpha} fluorescence by comparison with a Monte Carlo model. The electrons are estimated to carry about 15% of the laser energy. Collisional and Ohmic heating are modeled, and Ohmic effects are shown to be relatively unimportant. An electron spectrometer shows significantly greater reduction of the transmitted electron flux than is calculated in the model. Enhanced scattering by instability-induced magnetic fields is suggested. An extension of this fluor-based technique to measurement of coupling efficiency to the ignition hot spot in future larger-scale fast ignition experiments is outlined.

  1. Environmental Transmission Electron Microscopy Study of the Origins of Anomalous Particle Size Distributions in Supported Metal Catalysts

    SciTech Connect

    Benavidez, Angelica D.; Kovarik, Libor; Genc, Arda; Agrawal, Nitin; Larsson, Elin M.; Hansen, Thomas W.; Karim, Ayman M.; Datye, Abhaya K.

    2012-10-31

    In this Environmental TEM (ETEM) study of supported Pt and Pd model catalysts, individual nanoparticles were tracked during heat treatments at temperatures up to 600°C in H2, O2, and vacuum. We found anomalous growth of nanoparticles occurred during the early stages of catalyst sintering wherein some particles started to grow significantly larger than the mean, resulting in a broadening of the particle size distribution. We can rule out sample non-uniformity as a cause for the growth of these large particles, since images were recorded prior to heat treatments. The anomalous growth of these particles may help explain particle size distributions in heterogeneous catalysts which often show particles that are significantly larger than the mean, resulting in a long tail to the right. It has been suggested that particle migration and coalescence could be the likely cause for the broad size distributions. This study shows that anomalous growth of nanoparticles can occur under conditions where Ostwald ripening is the primary sintering mechanism.

  2. A New Geometric Method Based on Two-Dimensional Transmission Electron Microscopy for Analysis of Interior versus Exterior Pd Loading on Hollow Carbon Nanofibers

    SciTech Connect

    Shuai, Danmeng; Wang, Chong M.; Genc, Arda; Werth, Charles J.

    2011-04-18

    Hallow carbon nanofibers (CNFs) are being explored as catalyst supports because of their unique properties; catalytic activities with both interior and exterior metal loadings are being evaluated. Electron tomography (3D transmission electron microscopy, 3D TEM) has been used to estimate internal versus external loading of metal nanoclusters. However, this method is time consuming and requires a specialized TEM. We prepared three hollow CNF supported Pd samples with various Pd localizations, and developed a geometric analysis method based on 2D TEM images to estimate Pd internal versus external loading percentages. Results show the similar localization for the same sample in terms of the number, surface area, and mass of Pd nanoclusters but distinct values for different samples. To test our method, we compare results for one segment of a CNF using both 3D scanning transmission electron microscopy (3D TEM) and our new 2D geometic analysis method. Agreement is within 15.1%. Our results also agree with 3D TEM results from the literature for similarly prepared Pd on CNFs (within 5.6%). Our geometric analysis method is proposed as a more straightforward and fast way to evaluate metal nanocluster localizations on tubular supports.

  3. Anomalous Arms

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In this composite image of spiral galaxy M106 (NGC 4258), optical data from the Digitized Sky Survey is shown as yellow, radio data from the Very Large Array appears as purple, X-ray data from Chandra is coded blue, and infrared data from the Spitzer Space Telescope appears red. Two anomalous arms, which aren't visible at optical wavelengths, appear as purple and blue emission.

  4. Operating characteristics of a hollow-cathode neutralizer for 5 and 8 centimeter-diameter electron bombardment mercury ion thrusters

    NASA Technical Reports Server (NTRS)

    Weigand, A. J.

    1975-01-01

    Thin-tip 0.3-cm-outside-diameter hollow-cathode neutralizers were used to investigate causes of neutralizer tip erosion experienced in thruster endurance tests. Bell-jar tests indicated that neutralizers with new rolled tantalum foil inserts coated with an emissive mixture eroded very little over the neutral flow rates investigated (3 to 10 mA) for simulated 5- and 8-cm-diameter thruster neutralizer conditions. Tip erosion rates of neutralizers operated with no insert or emissive mixture increased by two orders of magnitude for both configurations as the neutral flow rate decreased. Spectroscopic analysis of the discharge plasma from neutralizers operated with inserts coated with the emissive mixture detected tungsten at all neutral flow rates for both thruster neutralizer conditions. The only source of tungsten was the tip. Therefore, detection of tungsten indicated neutralizer tip erosion. Barium, an element of the emissive mixture, was detected at low neutral flow rates for the 5-cm-diameter thruster neutralizer operating condition only.

  5. Channeling of high-power radio waves under conditions of strong anomalous absorption in the presence of an averaged electron heating source

    SciTech Connect

    Vas'kov, V. V.; Ryabova, N. A.

    2010-02-15

    Strong anomalous absorption of a high-power radio wave by small-scale plasma inhomogeneities in the Earth's ionosphere can lead to the formation of self-consistent channels (solitons) in which the wave propagates along the magnetic field, but has a soliton-like intensity distribution across the field. The structure of a cylindrical soliton as a function of the wave intensity at the soliton axis is analyzed. Averaged density perturbations leading to wave focusing were calculated using the model proposed earlier by Vas'kov and Gurevich (Geomagn. Aeron. 16, 1112 (1976)), in which an averaged electron heating source was used. It is shown that, under conditions of strong electron recombination, the radii of individual solitons do not exceed 650 m.

  6. Hollow cathodes for arcjet thrusters

    NASA Technical Reports Server (NTRS)

    Luebben, Craig R.; Wilbur, Paul J.

    1987-01-01

    In an attempt to prevent exterior spot emission, hollow cathode bodies and orifice plates were constructed from boron nitride which is an electrical insulator, but the orifice plates melted and/or eroded at high interelectrode pressures. The most suitable hollow cathodes tested included a refractory metal orifice plate in a boron nitride body, with the insert insulated electrically from the orifice plate. In addition, the hollow cathode interior was evacuated to assure a low pressure at the insert surface, thus promoting diffuse electron emission. At high interelectrode pressures, the electrons tended to flow through the orifice plate rather than through the orifice, which could result in overheating of the orifice plate. Using a carefully aligned centerline anode, electron flow through the orifice could be sustained at interelectrode pressures up to 500 torr - but the current flow path still occasionally jumped from the orifice to the orifice plate. Based on these tests, it appears that a hollow cathode would operate most effectively at pressures in the arcjet regime with a refractory, chemically stable, and electrically insulating cathode body and orifice plate.

  7. Hydrogen hollow cathode ion source

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J., Jr.; Sovey, J. S.; Roman, R. F. (Inventor)

    1980-01-01

    A source of hydrogen ions is disclosed and includes a chamber having at one end a cathode which provides electrons and through which hydrogen gas flows into the chamber. Screen and accelerator grids are provided at the other end of the chamber. A baffle plate is disposed between the cathode and the grids and a cylindrical baffle is disposed coaxially with the cathode at the one end of the chamber. The cylindrical baffle is of greater diameter than the baffle plate to provide discharge impedance and also to protect the cathode from ion flux. An anode electrode draws the electrons away from the cathode. The hollow cathode includes a tubular insert of tungsten impregnated with a low work function material to provide ample electrons. A heater is provided around the hollow cathode to initiate electron emission from the low work function material.

  8. Anomalous electronic transport in ξ'-Al-Pd-Mn complex metallic alloy studied by spectral conductivity analysis.

    PubMed

    Maciá, Enrique; Dolinšek, Janez

    2007-04-30

    The ξ' giant-unit-cell phase of the Al-Pd-Mn alloy system exhibits an almost temperature-independent electrical conductivity with a value typical of metallic alloys, but an anomalously low thermal conductivity comparable to that of thermal insulators. The origin of the T-independent conductivity is analysed by determining the spectral conductivity function σ(E) from a combined analysis of the electrical conductivity σ(T) and the thermoelectric power S(T) using a phenomenological approach. It is found that the T-independence of the conductivity results from the specific form of the spectral conductivity, which shows very weak variation over an energy scale of several k(B)T around the Fermi level, but exhibits fine structure that yields observable effects in σ(T) and S(T). PMID:21690958

  9. Cascade decays of hollow ions

    SciTech Connect

    Omar, G. ); Hahn, Y. )

    1991-05-01

    A multiple-electron-emission process for atoms with one or more inner-shell vacancies is treated using the radiative- and Auger-electron-emission cascade model, in which inner-shell holes are assumed to decay by sequentially emitting radiations and/or Auger electrons. Such hollow ions are produced by synchrotron irradiation of atomic targets and in ion-surface interactions with multiple-electron transfers. The final charge-state distribution is determined by the Auger and radiative branching ratios at each stage of the decay sequence. At intermediate stages of cascade, hollow ions with more than one hole in different ionization stages are created. The Ne, Mg, and Fe{sup 14+} ions with the initial 1{ital s}, 2{ital s}, and 2{ital p} vacancies are considered in detail, and the core charge dependence of the maximum charge state is studied. The hollow Mg ion with double initial 1{ital s} holes is analyzed, and the result compared with that for the case of one 1{ital s} hole. The peak is shifted more than two units to a higher degree of ionization. The correlated shake-off and shake-up multiple-electron processes are not considered, but they are expected to cause further shifts.

  10. Evidence of nonclassical plasma transport in hollow cathodes for electric propulsion

    SciTech Connect

    Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Jameson, Kristina K.

    2007-03-15

    Measurements, simplified analyses, and two-dimensional numerical simulations with a fluid plasma model show that classical resistivity cannot account for the elevated electron temperatures and steep plasma potential gradients measured in a 25-27.5 A electric propulsion hollow cathode. The cathode consisted of a 1.5 cm hollow tube with an {approx}0.28 cm diameter orifice and was operated with 5.5 SCCM (SCCM denotes cubic centimeter per minute at STP) of xenon flow using two different anode geometries: a segmented cone and a circular flat plate. The numerical simulations show that classical resistivity yields as much as four times colder electron temperatures compared to the measured values in the orifice and near-plume regions of the cathode. Classical transport and Ohm's law also predict exceedingly high electron-ion relative drift speeds compared to the electron thermal speed (>4). It is found that the addition of anomalous resistivity based on existing growth rate formulas for electron-ion streaming instabilities improves qualitatively the comparison between the numerical results and the time-averaged measurements. Simplified analyses that have been based largely on the axial measurements support the conclusion that additional resistivity is required in Ohm's law to explain the measurements. The combined results from the two-dimensional simulations and the analyses bound the range of enhanced resistivity to be 3-100 times the classical value.

  11. Direct observation of melting behaviors at the nanoscale under electron beam and heat to form hollow nanostructures

    NASA Astrophysics Data System (ADS)

    Huang, Chun-Wei; Hsin, Cheng-Lun; Wang, Chun-Wen; Chu, Fu-Hsuan; Kao, Chen-Yen; Chen, Jui-Yuan; Huang, Yu-Ting; Lu, Kuo-Chang; Wu, Wen-Wei; Chen, Lih-Juann

    2012-07-01

    We report the melting behaviours of ZnO nanowire by heating ZnO-Al2O3 core-shell heterostructures to form Al2O3 nanotubes in an in situ ultrahigh vacuum transmission electron microscope (UHV-TEM). When the ZnO-Al2O3 core-shell nanowire heterostructures were annealed at 600 °C under electron irradiation, the amorphous Al2O3 shell became single crystalline and then the ZnO core melted. The average vanishing rate of the ZnO core was measured to be 4.2 nm s-1. The thickness of the Al2O3 nanotubes can be precisely controlled by the deposition process. Additionally, the inner geometry of nanotubes can be defined by the initial ZnO core. The result shows a promising method to obtain the biocompatible Al2O3 nanotubes, which may be applied in drug delivery, biochemistry and resistive switching random access memory (ReRAM).We report the melting behaviours of ZnO nanowire by heating ZnO-Al2O3 core-shell heterostructures to form Al2O3 nanotubes in an in situ ultrahigh vacuum transmission electron microscope (UHV-TEM). When the ZnO-Al2O3 core-shell nanowire heterostructures were annealed at 600 °C under electron irradiation, the amorphous Al2O3 shell became single crystalline and then the ZnO core melted. The average vanishing rate of the ZnO core was measured to be 4.2 nm s-1. The thickness of the Al2O3 nanotubes can be precisely controlled by the deposition process. Additionally, the inner geometry of nanotubes can be defined by the initial ZnO core. The result shows a promising method to obtain the biocompatible Al2O3 nanotubes, which may be applied in drug delivery, biochemistry and resistive switching random access memory (ReRAM). Electronic supplementary information (ESI) available: Proof of the electron irradiation effect and three in situ TEM videos as dynamic observation of the ZnO-Al2O3 core-shell nanowire heterostructures forming the Al2O3 nanotube at 600 °C under electron irradiation and the disappearance of the ZnO core. See DOI: 10.1039/c2nr30724c

  12. Interface Electron Traps as a Source of Anomalous Capacitance in AlGaN/GaN Heterostructures

    NASA Astrophysics Data System (ADS)

    Osvald, J.

    2013-06-01

    We studied by modeling and simulation how deep traps at the AlGaN/GaN heterostructure interface influence the shape of capacitance-voltage ( C- V) curves of the heterostructure. Assuming donor and acceptor type of traps, we found differences in the C- V curves for sharp energy interface states or continuously distributed states with the same total concentration for the acceptor-type interface states. The background doping concentration of GaN had only a marginal influence on the shape of the C- V curves. We observed that an anomalous capacitance peak occurred for the continuous distribution of traps in the bandgap; a similar peak had been observed in experiment. We also saw that the capacitance curves shifted slightly to the right or to the left depending on the GaN doping concentration. A remarkable difference was found between the capacitance curves for the structures with the sharp acceptor trap level and continuous distribution of traps. For donor-type interface states, we found practically no influence on C- V curves since they remain populated and charge neutral during the measurement.

  13. Origin of anomalous electronic circular dichroism spectrum of RuPt2(tppz)2Cl2(PF6)4 in acetonitrile.

    PubMed

    Yu, Hua-Gen

    2014-07-24

    We report a theoretical study of the structures, energetics, and electronic spectra of the Pt(II)/Ru(II) mixed-metal complex RuPt2(tppz)2Cl2(PF6)4 (tppz = 2,3,5,6-tetra(2-pyridyl)pyrazine) in acetonitrile. The hybrid B3LYP density functional theory and its TDDFT methods were used with a complete basis set (CBS) extrapolation scheme and a conductor polarizable continuum model (C-PCM) for solvation effects. Results showed that the trinuclear complex has four types of stable conformers and/or enantiomers. They are separated by high barriers owing to the repulsive H/H geometrical constraints in tppz. A strong entropy effect was found for the dissociation of RuPt2(tppz)2Cl2(PF6)n in acetonitrile. The UV-visible and emission spectra of the complex were also simulated. They are in good agreement with experiments. In this work we have largely focused on exploring the origin of anomalous electronic circular dichroism (ECD) spectra of the RuPt2(tppz)2Cl2(PF6)4 complex in acetonitrile. As a result, a new mechanism has been proposed together with a clear illustration by using a physical model. PMID:25026322

  14. Anomalous tunneling in carbon/alkane/TiO(2)/gold molecular electronic junctions: energy level alignment at the metal/semiconductor interface.

    PubMed

    Yan, Haijun; McCreery, Richard L

    2009-02-01

    Carbon/TiO(2)/gold electronic junctions show slightly asymmetric electronic behavior, with higher current observed in current density (J)/voltage (V) curves when carbon is biased negative with respect to the gold top contact. When a approximately 1-nm-thick alkane film is deposited between the carbon and TiO(2), resulting in a carbon/alkane/TiO(2)/gold junction, the current increases significantly for negative bias and decreases for positive bias, thus creating a much less symmetric J/V response. Similar results were obtained when SiO(2) was substituted for the alkane layer, but Al(2)O(3) did not produce the effect. The observation that, by the addition of an insulating material between carbon and TiO(2), the junction becomes more conductive is unexpected and counterintuitive. Kelvin probe measurements revealed that while the apparent work function of the pyrolyzed photoresist film electrode is modulated by surface dipoles of different surface-bound molecular layers, the anomalous effect is independent of the direction of the surface dipole. We propose that by using a nanometer-thick film with a low dielectric constant as an insertion layer, most of the applied potential is dropped across this thin film, thus permitting alignment between the carbon Fermi level and the TiO(2) conduction band. Provided that the alkane layer is sufficiently thin, electrons can directly tunnel from carbon to the TiO(2) conduction band. Therefore, the electron injection barrier at the carbon/TiO(2) interface is effectively reduced by this energy-level alignment, resulting in an increased current when carbon is biased negative. The modulation of injection barriers by a low-kappa molecular layer should be generally applicable to a variety of materials used in micro- and nanoelectronic fabrication. PMID:20353235

  15. Electron temperature profile invariance on OH, L- and H-mode plasmas and consequences for the anomalous transport

    NASA Astrophysics Data System (ADS)

    Becker, G.

    1992-01-01

    The shapes of the electron temperature and electron density profiles in the OH, L- and H-mode confinement regimes of ASDEX are explored by statistical analysis. It is shown that the shape of Te(r) is conserved in the outer half of the plasma in these regimes and that it is invariant with respect to heating power, heating profile, density, density scale length, q value and ion mass. These results suggest that microturbulence constrains the shape of the temperature profile by adjusting the electron heat diffusivity χe(r). No such invariance is found for the temperature profile in the inner half of the plasma and for the density profile over the whole cross-section. Properties of the empirical electron heat diffusivity and the diffusion coefficient in different regimes can be described by Te profile invariance. The improved confinement with peaked density profiles, the reduction of χe in the bulk of H-mode plasmas and the power dependence of χe in the L-regime are discussed

  16. Hollow spherical supramolecular dendrimers.

    PubMed

    Percec, Virgil; Peterca, Mihai; Dulcey, Andrés E; Imam, Mohammad R; Hudson, Steven D; Nummelin, Sami; Adelman, Peter; Heiney, Paul A

    2008-10-01

    The synthesis of a library containing 12 conical dendrons that self-assemble into hollow spherical supramolecular dendrimers is reported. The design principles for this library were accessed by development of a method that allows the identification of hollow spheres, followed by structural and retrostructural analysis of their Pm3n cubic lattice. The first hollow spherical supramolecular dendrimer was made by replacing the tapered dendron, from the previously reported tapered dendritic dipeptide that self-assembled into helical pores, with its constitutional isomeric conical dendron. This strategy generated a conical dendritic dipeptide that self-assembled into a hollow spherical supramolecular dendrimer that self-organizes in a Pm3n cubic lattice. Other examples of hollow spheres were assembled from conical dendrons without a dipeptide at their apex. These are conical dendrons originated from tapered dendrons containing additional benzyl ether groups at their apex. The inner part of the hollow sphere assembled from the dipeptide resembles the path of a spherical helix or loxodrome and, therefore, is chiral. The spheres assembled from other conical dendrons are nonhelical, even when they contain stereocenters on the alkyl groups from their periphery. Functionalization of the apex of the conical dendrons with diethylene glycol allowed the encapsulation of LiOTf and RbOTf in the center of the hollow sphere. These experiments showed that hollow spheres function as supramolecular dendritic capsules and therefore are expected to display functions complementary to those of other related molecular and supramolecular structures. PMID:18771261

  17. Facile synthesis of hollow carbon nanospheres from hollow chitosan nanospheres.

    PubMed

    Ding, Ya; Xia, Xing-Hua

    2006-04-01

    Hollow carbon nanospheres (HCNS) with large surface area were synthesized from hollow chitosan nanospheres by one-step pyrolysis with a relatively low temperature (550 degrees C). The resulted HCNS is fully carbonized and partially graphitized under the experiment conditions. It is an important and facile method to prepare the uniform, shape- and size-controlled carbon nanomaterials by carbonization of the natural polysaccharide compounds and their derivatives. The as-prepared HCNS has a narrow size distribution in hollow carbon nanospheres (about 53 nm). The structure and size of HCNS are reproducible and could be tunable by changing the preparation conditions. The characterizations to estimate the composition, decompose properties, crystalline form, structure and surface property of the HCNS were investigated using FT-IR spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction measurement (XRD), transmission electron microscopy (TEM) analysis, and the N2 adsorption-desorption isothermal process. The present preparation method makes it feasible to synthesize carbon nanospheres in abundance in the lab, and the synthesized HCNS could be a promising support for metal catalysts, an ideal matrix connecting with DNA or other bioactive substances. PMID:16736772

  18. Self-contained hot-hollow cathode gun source assembly

    DOEpatents

    Zeren, J.D.

    1984-08-01

    A self-contained hot-hollow cathode gun source assembly for use in a vacuum chamber includes a crucible block having a hot-hollow cathode gun mounted underneath and providing a hole for the magnetic deflection of the ion/electron beam into a crucible on top the block.

  19. Self-contained hot-hollow cathode gun source assembly

    DOEpatents

    Zeren, Joseph D.

    1986-01-01

    A self-contained hot-hollow cathode gun source assembly for use in a vacuum chamber includes a crucible block having a hot-hollow cathode gun mounted underneath and providing a hole for the magnetic deflection of the ion/electron beam into a crucible on top the block.

  20. Pressure effect and electron diffraction on the anomalous transition in ternary superconductor Bi2Rh3Se2

    NASA Astrophysics Data System (ADS)

    Chen, C. Y.; Chan, C. L.; Mukherjee, S.; Chou, C. C.; Tseng, C. M.; Hsu, S. L.; Chu, M.-W.; Lin, J.-Y.; Yang, H. D.

    2014-01-01

    The effect of external hydrostatic pressure up to 22.23 kbar on the temperature-dependent transport properties of the ternary compound Bi2Rh3Se2 is investigated. Interestingly, the resistive anomaly at Ts~250 K, previously proposed as a charge-density-wave (CDW) transition, is shifted to higher temperature with increasing pressure, in distinct contrast to an established knowledge for CDW. Using temperature-dependent electron-diffraction characterizations, we have unraveled that this transition is, in effect, of a structural phase-transformation nature, experiencing the symmetry reduction from a high-symmetry C-centered monoclinic lattice to a low-symmetry primitive one below Ts. A more elaborately determined room-temperature C-centered lattice was also proposed.

  1. Facile Fabrication of Ultrafine Hollow Silica and Magnetic Hollow Silica Nanoparticles by a Dual-Templating Approach

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Xiao, Xiangheng; Zhang, Shaofeng; Fan, Lixia; Peng, Tangchao; Ren, Feng; Jiang, Changzhong

    2010-01-01

    The development of synthetic process for hollow silica materials is an issue of considerable topical interest. While a number of chemical routes are available and are extensively used, the diameter of hollow silica often large than 50 nm. Here, we report on a facial route to synthesis ultrafine hollow silica nanoparticles (the diameter of ca. 24 nm) with high surface area by using cetyltrimethylammmonium bromide (CTAB) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as co-templates and subsequent annealing treatment. When the hollow magnetite nanoparticles were introduced into the reaction, the ultrafine magnetic hollow silica nanoparticles with the diameter of ca. 32 nm were obtained correspondingly. Transmission electron microscopy studies confirm that the nanoparticles are composed of amorphous silica and that the majority of them are hollow.

  2. Direct phase selection of initial phases from single-wavelength anomalous dispersion (SAD) for the improvement of electron density and ab initio structure determination

    SciTech Connect

    Chen, Chung-De; Huang, Yen-Chieh; Chiang, Hsin-Lin; Hsieh, Yin-Cheng; Guan, Hong-Hsiang; Chuankhayan, Phimonphan; Chen, Chun-Jung

    2014-09-01

    A novel direct phase-selection method to select optimized phases from the ambiguous phases of a subset of reflections to replace the corresponding initial SAD phases has been developed. With the improved phases, the completeness of built residues of protein molecules is enhanced for efficient structure determination. Optimization of the initial phasing has been a decisive factor in the success of the subsequent electron-density modification, model building and structure determination of biological macromolecules using the single-wavelength anomalous dispersion (SAD) method. Two possible phase solutions (ϕ{sub 1} and ϕ{sub 2}) generated from two symmetric phase triangles in the Harker construction for the SAD method cause the well known phase ambiguity. A novel direct phase-selection method utilizing the θ{sub DS} list as a criterion to select optimized phases ϕ{sub am} from ϕ{sub 1} or ϕ{sub 2} of a subset of reflections with a high percentage of correct phases to replace the corresponding initial SAD phases ϕ{sub SAD} has been developed. Based on this work, reflections with an angle θ{sub DS} in the range 35–145° are selected for an optimized improvement, where θ{sub DS} is the angle between the initial phase ϕ{sub SAD} and a preliminary density-modification (DM) phase ϕ{sub DM}{sup NHL}. The results show that utilizing the additional direct phase-selection step prior to simple solvent flattening without phase combination using existing DM programs, such as RESOLVE or DM from CCP4, significantly improves the final phases in terms of increased correlation coefficients of electron-density maps and diminished mean phase errors. With the improved phases and density maps from the direct phase-selection method, the completeness of residues of protein molecules built with main chains and side chains is enhanced for efficient structure determination.

  3. Production of hollow aerogel microspheres

    SciTech Connect

    Upadhye, R.S.; Henning, S.A.

    1990-12-31

    A method is described for making hollow aerogel microspheres of 800--1200{mu} diameter and 100--300{mu} wall thickness by forming hollow alcogel microspheres during the sol/gel process in a catalytic atmosphere and capturing them on a foam surface containing catalyst. Supercritical drying of the formed hollow alcogel microspheres yields hollow aerogel microspheres which are suitable for ICF targets.

  4. Production of hollow aerogel microspheres

    DOEpatents

    Upadhye, Ravindra S.; Henning, Sten A.

    1993-01-01

    A method is described for making hollow aerogel microspheres of 800-1200 .mu. diameter and 100-300 .mu. wall thickness by forming hollow alcogel microspheres during the sol/gel process in a catalytic atmosphere and capturing them on a foam surface containing catalyst. Supercritical drying of the formed hollow alcogel microspheres yields hollow aerogel microspheres which are suitable for ICF targets.

  5. Effects of crystal orientation on electronic band structure and anomalous shift of higher critical point in VO2 thin films during the phase transition process

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Huang, Ting; You, Qinghu; Zhang, Jinzhong; Li, Wenwu; Wu, Jiada; Hu, Zhigao; Chu, Junhao

    2015-12-01

    The phase transition behaviour of vanadium dioxide (VO2) with different thicknesses has been investigated by temperature-dependent optical transmittance and Raman spectra. It is found that the crystal orientation has a great effect on the metal-insulator transition (MIT) of VO2 films. The x-ray diffraction (XRD) analysis shows that the films are polycrystalline and exhibit the characteristics of the monoclinic phase. The preferential growth crystal orientation (0 2 0) is converted to the (\\bar{1} 1 1) plane with the film thickness increasing. It is believed that the (\\bar{1} 1 1) plane is the reflection of a twinned structure with (0 1 1) crystal orientation, which will lead to the arrangements of oxygen atoms and vanadium atoms deviating from the pure monoclinic structure. It is found that the highest order transition (E 3) is highly susceptible to the crystal orientation, whereas the lowest order transition (E 1) is nearly unaffected by it. The E 3 exhibits an anomalous temperature dependence with an abrupt blue-shift (˜0.5 eV) in the vicinity of the metal-insulator transition (MIT) for VO2 film with a thickness of 84 nm. The findings show that the empty {σ*} band can be driven close to the Fermi level when the (0 2 0) orientation is converted to the (\\bar{1} 1 1) orientation. Compared to the VO2 films with thicknesses of 39 and 57 nm, the E 3 decreases by 0.8 eV and the E 2 increases by about 0.1 eV at the insulator state for the VO2 film with a thickness of 84 nm. The abnormal electronic transition and the variation of energy band is likely caused by the lattice distortion and V-V dimerisation deviation from the monoclinic {{a}\\text{m}} axis.

  6. Hollow-Fiber Clinostat

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Miller, Teresa Y.; Snyder, Robert S.

    1990-01-01

    Hollow-fiber clinostat, is bioreactor used to study growth and other behavior of cells in simulated microgravity. Cells under study contained in porous hollow fiber immersed in culture medium inside vessel. Bores in hollow fiber allow exchange of gases, nutrients, and metabolic waste products between living cells and external culture media. Hollow fiber lies on axis of vessel, rotated by motor equipped with torque and speed controls. Desired temperature maintained by operating clinostat in standard tissue-culture incubator. Axis of rotation made horizontal or vertical. Designed for use with conventional methods of sterilization and sanitation to prevent contamination of specimen. Also designed for asepsis in assembly, injection of specimen, and exchange of medium.

  7. Wanted: A Positive Control for Anomalous Subdiffusion

    PubMed Central

    Saxton, Michael J.

    2012-01-01

    Anomalous subdiffusion in cells and model systems is an active area of research. The main questions are whether diffusion is anomalous or normal, and if it is anomalous, its mechanism. The subject is controversial, especially the hypothesis that crowding causes anomalous subdiffusion. Anomalous subdiffusion measurements would be strengthened by an experimental standard, particularly one able to cross-calibrate the different types of measurements. Criteria for a calibration standard are proposed. First, diffusion must be anomalous over the length and timescales of the different measurements. The length-scale is fundamental; the time scale can be adjusted through the viscosity of the medium. Second, the standard must be theoretically well understood, with a known anomalous subdiffusion exponent, ideally readily tunable. Third, the standard must be simple, reproducible, and independently characterizable (by, for example, electron microscopy for nanostructures). Candidate experimental standards are evaluated, including obstructed lipid bilayers; aqueous systems obstructed by nanopillars; a continuum percolation system in which a prescribed fraction of randomly chosen obstacles in a regular array is ablated; single-file diffusion in pores; transient anomalous subdiffusion due to binding of particles in arrays such as transcription factors in randomized DNA arrays; and computer-generated physical trajectories. PMID:23260043

  8. A hollow cathode hydrogen ion source

    NASA Technical Reports Server (NTRS)

    Sovey, J. S.; Mirtich, M. J.

    1977-01-01

    High current density ion sources have been used to heat plasmas in controlled thermonuclear reaction experiments. High beam currents imply relatively high emission currents from cathodes which have generally taken the form of tungsten filaments. A hydrogen ion source is described which was primarily developed to assess the emission current capability and design requirements for hollow cathodes for application in neutral injection devices. The hydrogen source produced ions by electron bombardment via a single hollow cathode. Source design followed mercury ion thruster technology, using a weak magnetic field to enhance ionization efficiency.

  9. Stabilized Hollow Ions Extracted in Vacuum

    SciTech Connect

    Ninomiya, S.; Yamazaki, Y.; Azuma, T.; Komaki, K.; Koike, F.; Masuda, H.; Kuroki, K.; Sekiguchi, M.

    1997-06-01

    K x rays emitted from 2.1 keV/uN{sup 6+} ions passed through a thin Ni microcapillary foil were measured in coincidence with the exit charge states. Ions with a K hole but with several electrons in outershells, i.e., hollow ions formed above a surface (in the first generation), were successfully extracted in vacuum. It was found that a considerable fraction of extracted hollow ions had extremely long lifetimes of the order of ns. {copyright} {ital 1997} {ital The American Physical Society}

  10. 20. Detail, crack in southeast end wall showing hollow brick ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. Detail, crack in southeast end wall showing hollow brick lining of exterior wall; view to south, 135mm lens plus electronic flash illumination. - Benicia Arsenal, Powder Magazine No. 5, Junction of Interstate Highways 680 & 780, Benicia, Solano County, CA

  11. Submicrometer-sized hollow nickel spheres synthesized by autocatalytic reduction

    SciTech Connect

    Deng Yida . E-mail: denyda@sjtu.edu.cn; Zhao Ling; Liu Lei; Shen Bin; Hu Wenbin

    2005-10-06

    A facile method to fabricate submicrometer-sized hollow nickel spheres by autocatalyzing the redox reaction around a sacrificial colloidal particle surface is presented in this paper. The size distribution of these spheres can be controlled by regulating the concentration of the alkali solution. The hollow nickel particles were characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray powder diffraction. The hollow spheres produced by this process may have potential applications in many fields, including chemistry, biotechnology and materials science.

  12. The Quantum Anomalous Hall Effect: Theory and Experiment

    NASA Astrophysics Data System (ADS)

    Liu, Chao-Xing; Zhang, Shou-Cheng; Qi, Xiao-Liang

    2016-03-01

    The quantum anomalous Hall effect is defined as a quantized Hall effect realized in a system without an external magnetic field. The quantum anomalous Hall effect is a novel manifestation of topological structure in many-electron systems and may have potential applications in future electronic devices. In recent years, the quantum anomalous Hall effect was proposed theoretically and realized experimentally. In this review article, we provide a systematic overview of the theoretical and experimental developments in this field.

  13. Anomalous Diffraction in Crystallographic Phase Evaluation

    PubMed Central

    Hendrickson, Wayne A.

    2014-01-01

    X-ray diffraction patterns from crystals of biological macromolecules contain sufficient information to define atomic structures, but atomic positions are inextricable without having electron-density images. Diffraction measurements provide amplitudes, but the computation of electron density also requires phases for the diffracted waves. The resonance phenomenon known as anomalous scattering offers a powerful solution to this phase problem. Exploiting scattering resonances from diverse elements, the methods of multiwavelength anomalous diffraction (MAD) and single-wavelength anomalous diffraction (SAD) now predominate for de novo determinations of atomic-level biological structures. This review describes the physical underpinnings of anomalous diffraction methods, the evolution of these methods to their current maturity, the elements, procedures and instrumentation used for effective implementation, and the realm of applications. PMID:24726017

  14. The Smokey Hollow Community The Smokey Hollow Community, Informal ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    The Smokey Hollow Community - The Smokey Hollow Community, Informal boundaries by street name: North to South: East Jefferson Street to East Van Buren Street. West to East: South Gadsden Street to Marvin Street., Tallahassee, Leon County, FL

  15. Smokey Hollow Ethnographic Landscape Circa 1955 The Smokey Hollow ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Smokey Hollow Ethnographic Landscape Circa 1955 - The Smokey Hollow Community, Informal boundaries by street name: North to South: East Jefferson Street to East Van Buren Street. West to East: South Gadsden Street to Marvin Street., Tallahassee, Leon County, FL

  16. Electrochemical performance and electronic properties of shell LiNi0.5Mn1.5O4 hollow spheres for lithium ion battery

    NASA Astrophysics Data System (ADS)

    Cui, Yongli; Wang, Jiali; Wang, Mingzhen; Zhuang, Quanchao

    2016-03-01

    Shell spinel LiNi0.5Mn1.5O4 hollow microspheres were successfully synthesized by MnCO3 template, and characterized by XRD, SEM, and TEM. The results show that the hollow LiNi0.5Mn1.5O4 cathode has good cycle stability to reach 124.5, 119.8, and 96.6mAh/g at 0.5, 1, and 5 C, the corresponding retention rate of 98.1%, 98.2%, and 98.0% after 50 cycles at 20∘C, and the reversible capacity of 94.6mAh/g can be obtained at 1 C rate at 55∘C, 83.3% retention after 100 cycles. As the temperature decreases from 10∘C to ‑20∘C, the resistance of RSEI increases from 5.5 Ω to 135 Ω, Re from 27 Ω to 353.2 Ω, and Rct from 12.7 Ω to 73.0 Ω. Moreover, the B constant and Ea activation energy are 4480K and 37.22KJ/mol for the NTC spinel material, respectively.

  17. Hot hollow cathode gun assembly

    DOEpatents

    Zeren, J.D.

    1983-11-22

    A hot hollow cathode deposition gun assembly includes a hollow body having a cylindrical outer surface and an end plate for holding an adjustable heat sink, the hot hollow cathode gun, two magnets for steering the plasma from the gun into a crucible on the heat sink, and a shutter for selectively covering and uncovering the crucible.

  18. Hollow-Core Fiber Lamp

    NASA Technical Reports Server (NTRS)

    Yi, Lin (Inventor); Tjoelker, Robert L. (Inventor); Burt, Eric A. (Inventor); Huang, Shouhua (Inventor)

    2016-01-01

    Hollow-core capillary discharge lamps on the millimeter or sub-millimeter scale are provided. The hollow-core capillary discharge lamps achieve an increased light intensity ratio between 194 millimeters (useful) and 254 millimeters (useless) light than conventional lamps. The capillary discharge lamps may include a cone to increase light output. Hollow-core photonic crystal fiber (HCPCF) may also be used.

  19. Boron nitride hollow nanospheres: Synthesis, formation mechanism and dielectric property

    SciTech Connect

    Zhong, B.; Tang, X.H.; Huang, X.X.; Xia, L.; Zhang, X.D.; Wang, C.J.; Wen, G.W.

    2015-04-15

    Highlights: • BN hollow nanospheres are fabricated in large scale via a new CVD method. • Morphology and structure are elucidated by complementary analytical techniques. • Formation mechanism is proposed based on experimental observations. • Dielectric properties are investigated in the X-band microwave frequencies. • BN hollow nanospheres show lower dielectric loss than regular BN powders. - Abstract: Boron nitride (BN) hollow nanospheres have been successfully fabricated by pyrolyzing vapors decomposed from ammonia borane (NH{sub 3}BH{sub 3}) at 1300 °C. The final products have been extensively characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The BN hollow nanospheres were ranging from 100 to 300 nm in diameter and around 30–100 nm in thickness. The internal structure of the products was found dependent on the reaction temperatures. A possible formation mechanism of the BN hollow nanospheres was proposed on the basis of the experimental observations. Dielectric measurements in the X-band microwave frequencies (8–12 GHz) showed that the dielectric loss of the paraffin filled by the BN hollow nanospheres was lower than that filled by regular BN powders, which indicated that the BN hollow nanospheres could be potentially used as low-density fillers for microwave radomes.

  20. Anomalous Enhancement of the Superconducting Transition Temperature of Electron-doped La2-xCexCuO4 and Pr2-xCexCuO4 Cuprate Heterostructures

    SciTech Connect

    K Jin; P Vach; X Zhang; U Grupel; E Zohar; I Diamant; Y Dagan; S Smadici; P Abbamonte; R Greene

    2011-12-31

    The superconducting transition temperature T{sub c} of multilayers of electron-doped cuprates, composed of underdoped (or undoped) and overdoped La{sub 2-x}Ce{sub x}CuO{sub 4} (LCCO) and Pr{sub 2-x}Ce{sub x}CuO{sub 4} (PCCO) thin films, is found to increase significantly with respect to the T{sub c} of the corresponding single-phase films. By investigating the critical current density of superlattices with different doping levels and layer thicknesses, we find that the T{sub c} enhancement is caused by a redistribution of charge over an anomalously large distance.

  1. ACS SBC Recovery from Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2012-10-01

    This proposal is designed to permit recovery of the SBC {FUV MAMA} detector after an anomalous shutdown. Anomalous shutdowns can occur as a result of bright object violations which trigger the Bright Scene Detection or Software Global Monitor. Anomalous shutdowns can also occur as a result of SBC hardware problems. The recovery from anomalous shutdown procedure consists of four tests: 1} a signal processing electronics check, 2} a slow high voltage ramp-up to an intermediate voltage, 3} a slow high-voltage ramp-up to the full operating voltage, and 4} a Fold Test. During the two high-voltage ramp-ups, dark ACCUM exposures are taken. At high voltage, dark ACCUM exposures and diagnostics are taken. This proposal is based on Proposal 12738 from Cycle 19.

  2. ACS SBC Recovery from Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2010-09-01

    This proposal is designed to permit recovery of the SBC {FUV MAMA} detector after an anomalous shutdown. Anomalous shutdowns can occur as a result of bright object violations which trigger the Bright Scene Detection or Software Global Monitor. Anomalous shutdowns can also occur as a result of SBC hardware problems. The recovery from anomalous shutdown procedure consists of four tests: a signal processing electronics check, a slow high voltage ramp-up to an intermediate voltage, a slow high-voltage ramp-up to the full operating voltage, and lastly, a Fold Test. During the two high-voltage ramp-ups, dark ACCUM exposures are taken. At high voltage, dark ACCUM exposures and diagnostics are taken. This proposal is based on proposal 11884, visits 1 to 4.

  3. Nonlocal anomalous Hall effect

    NASA Astrophysics Data System (ADS)

    Zhang, Shulei; Vignale, Giovanni

    Anomalous Hall effect (AHE) is a distinctive transport property of ferromagnetic metals arising from spin orbit coupling (SOC) in concert with spontaneous spin polarization. Nonetheless, recent experiments have shown that the effect also appears in a nonmagnetic metal in contact with a magnetic insulator. The main puzzle lies in the apparent absence of spin polarized electrons in the non-magnetic metal. Here, we theoretically demonstrate that the scattering of electrons from a rough metal-insulator interface is generally spin-dependent, which results in mutual conversion between spin and charge currents flowing in the plane of the layer. It is the current-carrying spin polarized electrons and the spin Hall effect in the bulk of the metal layer that conspire to generate the AH current. This novel AHE differs from the conventional one only in the spatial separation of the SOC and the magnetization, so we name it as nonlocal AHE. In contrast to other previously proposed mechanisms (e.g., spin Hall AHE and magnetic proximity effect (MPE)), the nonlocal AHE appears on the first order of spin Hall angle and does not rely on the induced moments in the metal layer, which make it experimentally detectable by contrasting the AH current directions of two layered structures such as Pt/Cu/YIG and β -Ta/Cu/YIG (with a thin inserted Cu layer to eliminate the MPE). We predict that the directions of the AH currents in these two trilayers would be opposite since the spin Hall angles of Pt and β -Ta are of opposite signs. Work supported by NSF Grants DMR-1406568.

  4. Harnessing thermal expansion mismatch to form hollow nanoparticles.

    PubMed

    Jen-La Plante, Ilan; Mokari, Taleb

    2013-01-14

    Nano popcorn: a new formation mechanism for the synthesis of hollow metal oxide nanoparticles through a melt fracture mechanism. The hollow nanoparticles are formed via brittle fracture following the generation of tensile stresses arising due to liquid-phase thermal expansion of a low melting point core metal. The progress of this physical process can be monitored using in situ transmission electron microscopy for a model system of indium/indium oxide. PMID:23125049

  5. Laser-plasma-based linear collider using hollow plasma channels

    NASA Astrophysics Data System (ADS)

    Schroeder, C. B.; Benedetti, C.; Esarey, E.; Leemans, W. P.

    2016-09-01

    A linear electron-positron collider based on laser-plasma accelerators using hollow plasma channels is considered. Laser propagation and energy depletion in the hollow channel is discussed, as well as the overall efficiency of the laser-plasma accelerator. Example parameters are presented for a 1-TeV and 3-TeV center-of-mass collider based on laser-plasma accelerators.

  6. Synthesis of ZrC hollow nanospheres at low temperature

    NASA Astrophysics Data System (ADS)

    Shen, Guozhen; Chen, Di; Liu, Yuanfang; Tang, Kaibin; Qian, Yitai

    2004-02-01

    A novel chemical synthetic route has been developed to prepare ZrC hollow nanospheres at 600°C, using ZrCl 4 and C 6Cl 6 as source materials, and metallic Na as the reductant. The samples were characterized by X-ray powder diffraction and transmission electron microscopy. And an in situ template reduction-carbonization mechanism for ZrC hollow nanospheres was proposed.

  7. Fabrication and photocatalytic properties of SnO2 double-shelled and triple-shelled hollow spheres

    NASA Astrophysics Data System (ADS)

    Niu, Shanshan; Wang, Yong; Lu, Shan; Wang, Dongxia; Wang, Ping

    2016-06-01

    SnO2 double-shelled and triple-shelled hollow spheres were tailored by adjusting concentration of tin (IV) chloride solution during the process of the tin (IV) ions infused carbonaceous spheres. The structures of these SnO2 multi-shelled hollow spheres were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and their possible formation mechanism were also discussed. In virtue of triple-shelled hollow porous structure and higher specific surface area, SnO2 triple-shelled hollow spheres exhibited enhanced photocatalytic properties compared to SnO2 double-shelled hollow spheres.

  8. Anomalous Hall effect

    NASA Astrophysics Data System (ADS)

    Nagaosa, Naoto; Sinova, Jairo; Onoda, Shigeki; MacDonald, A. H.; Ong, N. P.

    2010-04-01

    The anomalous Hall effect (AHE) occurs in solids with broken time-reversal symmetry, typically in a ferromagnetic phase, as a consequence of spin-orbit coupling. Experimental and theoretical studies of the AHE are reviewed, focusing on recent developments that have provided a more complete framework for understanding this subtle phenomenon and have, in many instances, replaced controversy by clarity. Synergy between experimental and theoretical works, both playing a crucial role, has been at the heart of these advances. On the theoretical front, the adoption of the Berry-phase concepts has established a link between the AHE and the topological nature of the Hall currents. On the experimental front, new experimental studies of the AHE in transition metals, transition-metal oxides, spinels, pyrochlores, and metallic dilute magnetic semiconductors have established systematic trends. These two developments, in concert with first-principles electronic structure calculations, strongly favor the dominance of an intrinsic Berry-phase-related AHE mechanism in metallic ferromagnets with moderate conductivity. The intrinsic AHE can be expressed in terms of the Berry-phase curvatures and it is therefore an intrinsic quantum-mechanical property of a perfect crystal. An extrinsic mechanism, skew scattering from disorder, tends to dominate the AHE in highly conductive ferromagnets. The full modern semiclassical treatment of the AHE is reviewed which incorporates an anomalous contribution to wave-packet group velocity due to momentum-space Berry curvatures and correctly combines the roles of intrinsic and extrinsic (skew-scattering and side-jump) scattering-related mechanisms. In addition, more rigorous quantum-mechanical treatments based on the Kubo and Keldysh formalisms are reviewed, taking into account multiband effects, and demonstrate the equivalence of all three linear response theories in the metallic regime. Building on results from recent experiment and theory, a

  9. Hollow fission fragment tracks in fluorapatite

    NASA Astrophysics Data System (ADS)

    Li, Weixing

    Spontaneous fission of uranium in minerals creates a damaged "track" along the trajectory of the fission fragments. Fission tracks in fluorapatite, enlarged by chemical etching, are widely used in geologic age-dating and the reconstruction of the thermal history of Earth's crust. However, despite this wide spread application, there have been no systematic studies of the internal structure of unetched fission tracks or the atomic-scale process of track annealing. In this research, fission tracks in fluorapatite are demonstrated to be nano-channels instead of amorphous cores as had been assumed. The formation of hollow tracks is ascribed to the highly ionizing energy deposition of fission fragments inducing radiolytic decomposition of fluorapatite accompanied by the loss of volatile elements. The mechanism for thermal annealing of hollow tracks in fluorapatite is shown to be entirely different from that of amorphous tracks in zircon. The discontinuity of fission tracks, in addition to the shrinkage, prevents chemicals from entering into the hollow tracks for further etching, and then significantly reduces the etched length. The shrinkage of hollow fission tracks results from thermo-emission of vacancies or gaseous species from the cavities to surrounding solids instead of atomic-scale recovery of the amorphous core. The high diffusivity of atoms on the surface of hollow tracks causes the discontinuity of tracks either by Rayleigh instability, by Brownian motion, or by preferential motion of track segments. The preferential motion of atoms along c-axis causes more rapid annealing of fission tracks perpendicular to the c-axis. Under the electron beam, the hollow tracks segment into droplets and the track segments randomly move at room temperature or preferentially move along c-axis at high temperatures. The radiolytic annealing results from beam-enhanced diffusion, which is similar to thermally enhanced diffusion. The similarity in the morphology of fission tracks and

  10. Anomalous Diffraction in Cold Magnetized Plasma

    NASA Astrophysics Data System (ADS)

    Abelson, Z.; Gad, R.; Bar-Ad, S.; Fisher, A.

    2015-10-01

    Cold magnetized plasma possesses an anisotropic permittivity tensor with a unique dispersion relation that for adequate electron density and magnetic field results in anomalous diffraction of a right-hand circularly polarized beam. In this work, we demonstrate experimentally anomalous diffraction of a microwave beam in plasma. Additionally, decreasing the electron density enables observation of the transition of the material from a hyperbolic to a standard material. Manipulation of the control parameters will enable plasma to serve as a reconfigurable metamaterial-like medium.

  11. Anomalous Diffraction in Cold Magnetized Plasma.

    PubMed

    Abelson, Z; Gad, R; Bar-Ad, S; Fisher, A

    2015-10-01

    Cold magnetized plasma possesses an anisotropic permittivity tensor with a unique dispersion relation that for adequate electron density and magnetic field results in anomalous diffraction of a right-hand circularly polarized beam. In this work, we demonstrate experimentally anomalous diffraction of a microwave beam in plasma. Additionally, decreasing the electron density enables observation of the transition of the material from a hyperbolic to a standard material. Manipulation of the control parameters will enable plasma to serve as a reconfigurable metamaterial-like medium. PMID:26551813

  12. Hollow fiber liquid-liquid-liquid microextraction followed by solid-phase microextraction and in situ derivatization for the determination of chlorophenols by gas chromatography-electron capture detection.

    PubMed

    Saraji, Mohammad; Ghani, Milad

    2015-10-30

    A method based on the combination of hollow fiber liquid-liquid-liquid microextraction and solid-phase microextraction (SPME) followed by gas chromatography-electron capture detection was developed for the determination of chlorophenols in water and wastewater samples. Silica microstructures fabricated on the surface of a stainless steel wire were coated by an organic solvent and used as a SPME fiber. The analytes were extracted through a hollow fiber membrane containing n-decane from sample solution to an alkaline aqueous acceptor phase. They were then extracted and in situ derivatized on the SPME fiber using acetic anhydride. Experimental parameters such as the type of extraction solvent, acceptor phase NaOH concentration, donor phase HCl concentration, the amount of derivatizing reagent, salt concentration, stirring rate and extraction time were investigated and optimized. The precision of the method for the analytes at 0.02-30μgL(-1) concentration level ranged from 7.1 to 10.2% (as intra-day relative standard deviation) and 6.4 to 9.8% (as inter-day relative standard deviation). The linear dynamic ranges were in the interval of 5-500μgL(-1), 0.05-5μgL(-1), 0.02-1μgL(-1) and 0.001-0.5μgL(-1) for 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol, respectively. The enrichment factors were between 432 and 785. The limits of detection were in the range of 0.0004-1.2μgL(-1). Tap water, well water and wastewater samples were also analyzed to evaluate the method capability for real sample analysis. PMID:26411480

  13. Hollow Cathode With Multiple Radial Orifices

    NASA Technical Reports Server (NTRS)

    Brophy, John R.

    1992-01-01

    Improved hollow cathode serving as source of electrons has multiple radial orifices instead of single axial orifice. Distributes ion current more smoothly, over larger area. Prototype of high-current cathodes for ion engines in spacecraft. On Earth, cathodes used in large-diameter ion sources for industrial processing of materials. Radial orientation of orifices in new design causes current to be dispersed radially in vicinity of cathode. Advantageous where desireable to produce plasma more nearly uniform over wider region around cathode.

  14. Preparation and surface encapsulation of hollow TiO nanoparticles for electrophoretic displays

    NASA Astrophysics Data System (ADS)

    Zhao, Qian; Tan, Tingfeng; Qi, Peng; Wang, Shirong; Bian, Shuguang; Li, Xianggao; An, Yong; Liu, Zhaojun

    2011-02-01

    Hollow black TiO nanosparticles were obtained via deposition of inorganic coating on the surface of hollow core-shell polymer latex with Ti(OBu)4 as precursor and subsequent calcination in ammonia gas. Hollow TiO particles were characterized by scanning electron microscope, transmission electronic microscopy, X-ray diffraction, and thermogravimetric analysis. Encapsulation of TiO via dispersion polymerization was promoved by pretreating the pigments with 3-(trimethoxysilyl) propyl methacrylate, making it possible to prepare hollow TiO-polymer particles. When St and DVB were used as polymerization monomer, hollow TiO-polymer core-shell particles came into being via dispersion polymerization, and the lipophilic degree is 28.57%. Glutin-arabic gum microcapsules containing TiO-polymer particles electrophoretic liquid were prepared using via complex coacervation. It was founded that hollow TiO-polymer particles had enough electrophoretic mobility after coating with polymer.

  15. On Anomalous Quark Triangles

    NASA Astrophysics Data System (ADS)

    Vainshtein, Arkady

    2011-04-01

    Anomalous quark triangles with one axial and two vector currents are studied in special kinematics when one of the vector currents carries a soft momentum. According to the Adler-Bardeen theorem the anomalous longitudinal part of the triangle is not renormalized in the chiral limit. We show that perturbative corrections the transversal part of the triangle is also absent. This nonrenormalization, in difference with the longitudinal part, holds on only perturbatively.

  16. Hollow spherical shell manufacture

    DOEpatents

    O'Holleran, T.P.

    1991-11-26

    A process is disclosed for making a hollow spherical shell of silicate glass composition in which an aqueous suspension of silicate glass particles and an immiscible liquid blowing agent is placed within the hollow spherical cavity of a porous mold. The mold is spun to reduce effective gravity to zero and to center the blowing agent, while being heated so as to vaporize the immiscible liquid and urge the water carrier of the aqueous suspension to migrate into the body of the mold, leaving a green shell compact deposited around the mold cavity. The green shell compact is then removed from the cavity, and is sintered for a time and a temperature sufficient to form a silicate glass shell of substantially homogeneous composition and uniform geometry. 3 figures.

  17. Hollow Microporous Organic Capsules

    NASA Astrophysics Data System (ADS)

    Li, Buyi; Yang, Xinjia; Xia, Lingling; Majeed, Muhammad Irfan; Tan, Bien

    2013-07-01

    Fabrication of hollow microporous organic capsules (HMOCs) could be very useful because of their hollow and porous morphology, which combines the advantages of both microporous organic polymers and non-porous nanocapsules. They can be used as storage materials or reaction chambers while supplying the necessary path for the design of controlled uptake/release systems. Herein, the synthesis of HMOCs with high surface area through facile emulsion polymerization and hypercrosslinking reactions, is described. Due to their tailored porous structure, these capsules possessed high drug loading efficiency, zero-order drug release kinetics and are also demonstrated to be used as nanoscale reactors for the prepareation of nanoparticles (NPs) without any external stabilizer. Moreover, owing to their intrinsic biocompatibility and fluorescence, these capsules exhibit promising prospect for biomedical applications.

  18. HOLLOW CARBON ARC DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-10-11

    A device is described for producing an energetic, direct current, hollow, carbon-arc discharge in an evacuated container and within a strong magnetic field. Such discharges are particularly useful not only in dissociation and ionization of high energy molecular ion beams, but also in acting as a shield or barrier against the instreaming of lowenergy neutral particles into a plasma formed within the hollow discharge when it is used as a dissociating mechanism for forming the plasma. There is maintained a predetermined ratio of gas particles to carbon particles released from the arc electrodes during operation of the discharge. The carbon particles absorb some of the gas particles and are pumped along and by the discharge out of the device, with the result that smaller diffusion pumps are required than would otherwise be necessary to dispose of the excess gas.

  19. Hollow spherical shell manufacture

    DOEpatents

    O'Holleran, Thomas P.

    1991-01-01

    A process for making a hollow spherical shell of silicate glass composition in which an aqueous suspension of silicate glass particles and an immiscible liquid blowing agent is placed within the hollow spherical cavity of a porous mold. The mold is spun to reduce effective gravity to zero and to center the blowing agent, while being heated so as to vaporize the immiscible liquid and urge the water carrier of the aqueous suspension to migrate into the body of the mold, leaving a green shell compact deposited around the mold cavity. The green shell compact is then removed from the cavity, and is sintered for a time and a temperature sufficient to form a silicate glass shell of substantially homogeneous composition and uniform geometry.

  20. Hollow Microporous Organic Capsules

    PubMed Central

    Li, Buyi; Yang, Xinjia; Xia, Lingling; Majeed, Muhammad Irfan; Tan, Bien

    2013-01-01

    Fabrication of hollow microporous organic capsules (HMOCs) could be very useful because of their hollow and porous morphology, which combines the advantages of both microporous organic polymers and non-porous nanocapsules. They can be used as storage materials or reaction chambers while supplying the necessary path for the design of controlled uptake/release systems. Herein, the synthesis of HMOCs with high surface area through facile emulsion polymerization and hypercrosslinking reactions, is described. Due to their tailored porous structure, these capsules possessed high drug loading efficiency, zero-order drug release kinetics and are also demonstrated to be used as nanoscale reactors for the prepareation of nanoparticles (NPs) without any external stabilizer. Moreover, owing to their intrinsic biocompatibility and fluorescence, these capsules exhibit promising prospect for biomedical applications. PMID:23820511

  1. Anomalous fluorescence line intensity in megavoltage bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Pereira, Nino; Litz, Marc; Merkel, George; Schumer, Joseph; Seely, John; Carroll, Jeff

    2009-11-01

    A Cauchois transmission crystal spectrometer intended for laser plasma diagnostics has measured an anomalous ratio between the fluorescence lines in megavoltage bremsstrahlung. When observed in reflection, Kα1 fluorescence is twice as strong as the Kβ line, as is usual. However, in forward-directed bremsstrahlung from a 2 MV end point linear accelerator with a tungsten converter, the Kα1 and Kβ fluorescence are approximately equal. The anomalous fluorescence line ratio, unity, reflects the large amount of fluorescence generated on the side of the converter where the electrons enter, and the differential attenuation of the fluorescence photons as they pass through the converter to opposite side. Understanding of fluorescence in megavoltage bremsstrahlung is relevant to the explanation of anomalous line ratios in spectra produced by high-energy electrons generated by intense femtosecond laser irradiation.

  2. Hollow cathode plasma coupling study, 1986

    NASA Technical Reports Server (NTRS)

    Wilbur, Paul J.

    1986-01-01

    The electron collection and emission characteristics of a simple hollow cathode contactor, an extended anode hollow cathode contactor supplied by JSC, and a ring cusp magnetic field contactor are presented and the effects of discharge power and argon or xenon expellant flowrate on these characteristics are examined. All of the contactors are shown to exhibit good electron emission performance over a wide range of discharge power and expellant type and flowrate. Good electron performance is shown to be more difficult to achieve. Results suggest that the extended anode and ring cusp contactors should perform satisfactorily to electron emission currents beyond 1000 mA and electron collection currents beyond 500 mA. All contactors performed better on xenon than argon. A general theory of plasma contactor operation in both the electron collection and electron emission modes, which describes the current-limiting effects of space-charge phenomena is given. This current-limiting and collecting phenomenon is shown to be a function of driving potential differences and emitting and collecting surface radius ratio for the case of a spherical geometry. Discharge power did not appear to influence the electron collection current substantially in the experiments so it is suggested in light of the model that the contactors are generally not limited by their ion production capabilities under conditions at which they were tested.

  3. Anomalous is ubiquitous

    SciTech Connect

    Eliazar, Iddo; Klafter, Joseph

    2011-09-15

    Brownian motion is widely considered the quintessential model of diffusion processes-the most elemental random transport processes in Science and Engineering. Yet so, examples of diffusion processes displaying highly non-Brownian statistics-commonly termed 'Anomalous Diffusion' processes-are omnipresent both in the natural sciences and in engineered systems. The scientific interest in Anomalous Diffusion and its applications is growing exponentially in the recent years. In this Paper we review the key statistics of Anomalous Diffusion processes: sub-diffusion and super-diffusion, long-range dependence and the Joseph effect, Levy statistics and the Noah effect, and 1/f noise. We further present a theoretical model-generalizing the Einstein-Smoluchowski diffusion model-which provides a unified explanation for the prevalence of Anomalous Diffusion statistics. Our model shows that what is commonly perceived as 'anomalous' is in effect ubiquitous. - Highlights: > The article provides an overview of Anomalous Diffusion (AD) statistics. > The Einstein-Smoluchowski diffusion model is extended and generalized. > The generalized model universally generates AD statistics. > A unified 'universal macroscopic explanation' for AD statistics is established. > AD statistics are shown to be fundamentally connected to robustness.

  4. Preparation and Application of Hollow Silica/magnetic Nanocomposite Particle

    NASA Astrophysics Data System (ADS)

    Wang, Cheng-Chien; Lin, Jing-Mo; Lin, Chun-Rong; Wang, Sheng-Chang

    The hollow silica/cobalt ferrite (CoFe2O4) magnetic microsphere with amino-groups were successfully prepared via several steps, including preparing the chelating copolymer microparticles as template by soap-free emulsion polymerization, manufacturing the hollow cobalt ferrite magnetic microsphere by in-situ chemical co-precipitation following calcinations, and surface modifying of the hollow magnetic microsphere by 3-aminopropyltrime- thoxysilane via the sol-gel method. The average diameter of polymer microspheres was ca. 200 nm from transmission electron microscope (TEM) measurement. The structure of the hollow magnetic microsphere was characterized by using TEM and scanning electron microscope (SEM). The spinel-type lattice of CoFe2O4 shell layer was identified by using XRD measurement. The diameter of CoFe2O4 crystalline grains ranged from 54.1 nm to 8.5 nm which was estimated by Scherrer's equation. Additionally, the hollow silica/cobalt ferrite microsphere possesses superparamagnetic property after VSM measurement. The result of BET measurement reveals the hollow magnetic microsphere which has large surface areas (123.4m2/g). After glutaraldehyde modified, the maximum value of BSA immobilization capacity of the hollow magnetic microsphere was 33.8 mg/g at pH 5.0 buffer solution. For microwave absorption, when the hollow magnetic microsphere was compounded within epoxy resin, the maximum reflection loss of epoxy resins could reach -35dB at 5.4 GHz with 1.9 mm thickness.

  5. Novel hollow all-carbon structures

    NASA Astrophysics Data System (ADS)

    Sundholm, Dage; Wirz, Lukas N.; Schwerdtfeger, Peter

    2015-09-01

    A new family of cavernous all-carbon structures is proposed. These molecular cage structures are constructed by edge subdivisions and leapfrog transformations from cubic polyhedra or their duals. The obtained structures were then optimized at the density functional level. These hollow carbon structures represent a new class of carbon allotropes which could lead to many interesting applications.A new family of cavernous all-carbon structures is proposed. These molecular cage structures are constructed by edge subdivisions and leapfrog transformations from cubic polyhedra or their duals. The obtained structures were then optimized at the density functional level. These hollow carbon structures represent a new class of carbon allotropes which could lead to many interesting applications. Electronic supplementary information (ESI) available: Cartesian coordinates of the studied molecules. See DOI: 10.1039/c5nr04370k

  6. Mercury - the hollow planet

    NASA Astrophysics Data System (ADS)

    Rothery, D. A.

    2012-04-01

    Mercury is turning out to be a planet characterized by various kinds of endogenous hole (discounting impact craters), which are compared here. These include volcanic vents and collapse features on horizontal scales of tens of km, and smaller scale depressions ('hollows') associated with bright crater-floor deposits (BCFD). The BCFD hollows are tens of metres deep and kilometres or less across and are characteristically flat-floored, with steep, scalloped walls. Their form suggests that they most likely result from removal of surface material by some kind of mass-wasting process, probably associated with volume-loss caused by removal (via sublimation?) of a volatile component. These do not appear to be primarily a result of undermining. Determining the composition of the high-albedo bluish surface coating in BCFDs will be a key goal for BepiColombo instruments such as MIXS (Mercury Imaging Xray Spectrometer). In contrast, collapse features are non-circular rimless pits, typically on crater floors (pit-floor craters), whose morphology suggests collapse into void spaces left by magma withdrawal. This could be by drainage of either erupted lava (or impact melt) or of shallowly-intruded magma. Unlike the much smaller-scale BCFD hollows, these 'collapse pit' features tend to lack extensive flat floors and instead tend to be close to triangular in cross-section with inward slopes near to the critical angle of repose. The different scale and morphology of BCFD hollows and collapse pits argues for quite different modes of origin. However, BCFD hollows adjacent to and within the collapse pit inside Scarlatti crater suggest that the volatile material whose loss was responsible for the growth of the hollows may have been emplaced in association with the magma whose drainage caused the main collapse. Another kind of volcanic collapse can be seen within a 25 km-wide volcanic vent outside the southern rim of the Caloris basin (22.5° N, 146.1° E), on a 28 m/pixel MDIS NAC image

  7. Hollow Polyimide Microspheres

    NASA Technical Reports Server (NTRS)

    Weiser, Erik S. (Inventor); St.Clair, Terry L. (Inventor); Echigo, Yoshiaki (Inventor); Kaneshiro, Hisayasu (Inventor)

    2001-01-01

    A shaped article composed of an aromatic polyimide has a hollow, essentially spherical structure and a particle size of about 100 to about 1500 micrometers, a density of about 1 to about 6 pounds/cubic foot and a volume change of 1 to about 20% by a pressure treatment of 30 psi for 10 minutes at room temperature. A syntactic foam, made of a multiplicity of the shaped articles which are bonded together by a matrix resin to form an integral composite structure, has a density of about 3 to about 30 pounds/cubic feet and a compression strength of about 100 to about 1400 pounds/sq inch.

  8. Hollow Polyimide Microspheres

    NASA Technical Reports Server (NTRS)

    Weiser, Erik S. (Inventor); St.Clair, Terry L. (Inventor); Echigo, Yoshiaki (Inventor); Kaneshiro, Hisayasu (Inventor)

    1999-01-01

    A shaped article composed of an aromatic polyimide has a hollow, essentially spherical structure and a particle size of about 100 to about 1500 microns, a density of about I to about 6 pounds/ft3 and a volume change of 1 to about 20% by a pressure treatment of 30 psi for 10 minutes at room temperature. A syntactic foam, made of a multiplicity of the shaped articles which are bounded together by a matrix resin to form an integral composite structure, has a density of about 3 to about 30 pounds/cu ft and a compression strength of about 100 to about 1400 pounds/sq in.

  9. Hollow Polyimide Microspheres

    NASA Technical Reports Server (NTRS)

    Weiser, Erik S. (Inventor); St.Clair, Terry L. (Inventor); Echigo, Yoshiaki (Inventor); Kaneshiro, Hisayasu (Inventor)

    2000-01-01

    A shaped article composed of an aromatic polyimide has a hollow, essentially spherical structure and a particle size of about 100 to about 1500 microns a density of about 1 to about 6 pounds/cubic ft and a volume change of 1 to about 20 percent by a pressure treatment of 30 psi for 10 minutes at room temperature. A syntactic foam, made of a multiplicity of the shaped articles which are bonded together by a matrix resin to form an integral composite structure, has a density of about 3 to about 30 pounds/cubic ft and a compression strength 2 of about 100 to about 1400 pounds/sq in.

  10. 28,000 Hour Xenon Hollow Cathode LifeTest Results

    NASA Technical Reports Server (NTRS)

    Sarver-Verhey, Timothy R.

    1997-01-01

    The International Space Station Plasma Contactor System requires a hollow cathode assembly (HCA) with a lifetime of at least 18,000 hours. Critical components of the HCA include the hollow cathode and electron emitter. A series of hollow cathode wear tests was performed which included a life test operated at the maximum current of the HCA. This test sought to verify the hollow cathode design and contamination control protocols. The life test accumulated 27,800 hours of operation before failing to ignite. The hollow cathode exhibited relatively small changes in operating parameters over the course of the test. This life test is the longest duration test of a high current xenon hollow cathode reported to date.

  11. Anomalous law of cooling

    SciTech Connect

    Lapas, Luciano C.; Ferreira, Rogelma M. S.; Rubí, J. Miguel; Oliveira, Fernando A.

    2015-03-14

    We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton’s law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics.

  12. Anomalous law of cooling.

    PubMed

    Lapas, Luciano C; Ferreira, Rogelma M S; Rubí, J Miguel; Oliveira, Fernando A

    2015-03-14

    We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton's law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics. PMID:25770525

  13. Anomalous law of cooling

    NASA Astrophysics Data System (ADS)

    Lapas, Luciano C.; Ferreira, Rogelma M. S.; Rubí, J. Miguel; Oliveira, Fernando A.

    2015-03-01

    We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton's law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics.

  14. Anomalous gauge boson interactions

    SciTech Connect

    Aihara, H.; Barklow, T.; Baur, U. |

    1995-03-01

    We discuss the direct measurement of the trilinear vector boson couplings in present and future collider experiments. The major goals of such experiments will be the confirmation of the Standard Model (SM) predictions and the search for signals of new physics. We review our current theoretical understanding of anomalous trilinear gauge-boson self interactions. If the energy scale of the new physics is {approximately} 1 TeV, these low energy anomalous couplings are expected to be no larger than {Omicron}(10{sup {minus}2}). Constraints from high precision measurements at LEP and low energy charged and neutral current processes are critically reviewed.

  15. Experimental realization of quantized anomalous Hall effect

    NASA Astrophysics Data System (ADS)

    Xue, Qi-Kun

    2014-03-01

    Anomalous Hall effect was discovered by Edwin Hall in 1880. In this talk, we report the experimental observation of the quantized version of AHE, the quantum anomalous Hall effect (QAHE) in thin films of Cr-doped (Bi,Sb)2Te3 magnetic topological insulator. At zero magnetic field, the gate-tuned anomalous Hall resistance exhibits a quantized value of h /e2 accompanied by a significant drop of the longitudinal resistance. The longitudinal resistance vanishes under a strong magnetic field whereas the Hall resistance remains at the quantized value. The realization of QAHE paves a way for developing low-power-consumption electronics. Implications on observing Majorana fermions and other exotic phenomena in magnetic topological insulators will also be discussed. The work was collaborated with Ke He, Yayu Wang, Xucun Ma, Xi Chen, Li Lv, Dai Xi, Zhong Fang and Shoucheng Zhang.

  16. Graphene-based hollow spheres as efficient electrocatalysts for oxygen reduction.

    PubMed

    Wu, Longfei; Feng, Hongbin; Liu, Mengjia; Zhang, Kaixiang; Li, Jinghong

    2013-11-21

    A facile and straightforward approach is developed for the construction of graphene-based hollow spheres. An electron rich sodium-ammonia solution is used to effectively restore the π-conjugation of graphene. The hollow spheres exhibit excellent electrocatalytic activity towards oxygen reduction without catalyst deactivation. PMID:24089043

  17. Preparation and characterization of optical-functional diblock copolymer brushes on hollow sphere surface via atom transfer radical polymerization

    SciTech Connect

    Wang, Li-Ping; Li, Wen-Zhi; Zhao, Li-Min; Zhang, Chun-Juan; Wang, Yan-Dong; Kong, Li-Li; Li, Ling-Ling

    2010-09-15

    The optical-functional poly(methyl methacrylate)-block-Tb complex diblock copolymer brushes grafted from hollow sphere surface via atom transfer radical polymerization were investigated in this work. A sufficient amount of azo initiator was introduced onto hollow sphere surface firstly. Then the monomer methyl methacrylate was polymerized via surface-initiated reverse atom transfer radical polymerization using azo group modified hollow sphere as initiator. Following, the poly(methyl methacrylate) modified hollow sphere was used as maroinitiator for surface-initiated atom transfer radical polymerization of Tb complex. The samples were characterized by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance, gel permeation chromatographer and transmission electron microscopy, respectively. The results indicated that the poly(methyl methacrylate) had grafted from hollow sphere surface and the average diameter of hollow core was about 1 {mu}m. The optical properties of the poly(methyl methacrylate)-block-Tb copolymer modified hollow sphere were also reported.

  18. Effect of growth temperature on the electronic transport and anomalous Hall effect response in co-sputtered Co2FeSi thin films

    NASA Astrophysics Data System (ADS)

    Yadav, Anjali; Chaudhary, Sujeet

    2015-11-01

    Co-sputtered Co2FeSi thin films are studied by varying the growth temperature (Ts) as a control parameter in terms of the appreciable change in the disorder. The effect of Ts on structural, magnetic, electrical, and magneto-transport properties was investigated. As Ts is increased from room temperature to 400 °C, an improvement in the crystallinity and atomic ordering are observed. These are found to be correlated with the associated reduction in residual resistivity ( ρ x x 0 ) from 410 to 88 μΩ cm, an increment in residual resistivity ratio (r) from 0.8 to 1.23, and an increase in saturation magnetization from 1074 to 1196 emu/cc. The spin wave stiffness constant in these films is found to increase with Ts, with a reasonably high value of 358 meVÅ2 at the optimum value of Ts of 400 °C. Further, the obtained high carrier concentration and mobility values (at 10 K) of ˜30 e-s/f.u. and ˜0.11 cm2 V-1 s-1 for the films deposited at Ts = 400 °C shows the presence of compensated Fermi surface. The transport properties are investigated qualitatively from the scaling of anomalous Hall resistivity ρx y s (T) with the longitudinal resistivity ρ x x ( T ) data, employing the extrinsic (skew- and side-jump scatterings) and intrinsic scattering contributions. The variation in the intrinsic scattering contributions observed via the variation in linear dependence of ρx y s on ρx x 2 with the change in Ts is found to be associated with the improvement in the crystallinity of these films.

  19. Multi-shelled CeO₂ hollow microspheres as superior photocatalysts for water oxidation.

    PubMed

    Qi, Jian; Zhao, Kun; Li, Guodong; Gao, Yan; Zhao, Huijun; Yu, Ranbo; Tang, Zhiyong

    2014-04-21

    A general self-templating method is introduced to construct triple-shelled CeO₂ hollow microspheres, which are composed of tiny CeO₂ nanoparticles. When the triple-shelled CeO₂ hollow microspheres are used as photocatalysts for direct water oxidation with AgNO₃ as the electron scavenger, excellent activity and enhanced stability for O₂ evolution are achieved, in contrast with commercial CeO₂ nanoparticles, single-shelled CeO₂ hollow microspheres and double-shelled CeO₂ hollow microspheres. Such an outstanding performance is attributed to the unique properties of the triple-shelled CeO₂ hollow microspheres including more efficient multiple reflections of the incident light by the inner shells, the larger surface area and more active sites for improving separation of electron-hole pairs, and the more curved surfaces unfavorable for deposition of in situ generated Ag nanoparticles. PMID:24608859

  20. Hollow-cathode evaporators

    SciTech Connect

    Saenko, V.A.; Kravatskii, V.A.; Veremeichenko, G.N.; Vladimirov, A.I.

    1985-08-01

    This paper describes devices for producing plasma from the vapor of a solid substance under vacuum and depositing films from the plasma. The plasma is produced by a discharge between a hollow cathode crucible and an anode, which are placed in a magnetic field longitudinal in relation to the vapor flow. The basic parameters are: film deposition rate 1-70 nm/sec, consumption of working substance 1-30 mg/sec, ionization factor for the working substance in the flow 1-10%, ion-current density at the substrate 0.1-10 mA/cm/sup 2/. Films of Cu, Au, Ag, Cr, and A1 have been made with parameters better than those of films deposited without ionization.

  1. Catalytic hollow spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1986-01-01

    The improved, heterogeneous catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitably formed of a shell (12) of metal such as aluminum having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be, itself, catalytic or the catalyst can be coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  2. Catalytic, hollow, refractory spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1987-01-01

    Improved, heterogeneous, refractory catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitable formed of a shell (12) of refractory such as alumina having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be itself catalytic or a catalytically active material coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  3. Catalytic hollow spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1989-01-01

    The improved, heterogeneous catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitably formed of a shell (12) of metal such as aluminum having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be, itself, catalytic or the catalyst can be coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  4. Colored models for anomalous nuclei

    SciTech Connect

    Watson, P.J.S.; Saly, R.; Romo, W.J.; Sundaresan, M.K.; Campbell, B.; Elias, V.

    1983-04-01

    There seems to be good experimental evidence that anomalous nuclei are produced in heavy-ion collisions; they are anomalous in that they have an abnormally short mean free path, for example, in nuclear emulsions. Here we consider the possibility that anomalous nuclei are combinations of a colored anomalous particle fragment (based on theories with spontaneous breakdown of color symmetry) with ordinary nucleons. Phenomenological implications of various possible models in which the anomalous particle fragment is considered to be a colored particle with the color symmetry SU(3)/sub c/ explicitly broken are given.

  5. Demystifying fluorine chemical shifts: electronic structure calculations address origins of seemingly anomalous (19)F-NMR spectra of fluorohistidine isomers and analogues.

    PubMed

    Kasireddy, Chandana; Bann, James G; Mitchell-Koch, Katie R

    2015-11-11

    Fluorine NMR spectroscopy is a powerful tool for studying biomolecular structure, dynamics, and ligand binding, yet the origins of (19)F chemical shifts are not well understood. Herein, we use electronic structure calculations to describe the changes in (19)F chemical shifts of 2F- and 4F-histidine/(5-methyl)-imidazole upon acid titration. While the protonation of the 2F species results in a deshielded chemical shift, protonation of the 4F isomer results in an opposite, shielded chemical shift. The deshielding of 2F-histidine/(5-methyl)-imidazole upon protonation can be rationalized by concomitant decreases in charge density on fluorine and a reduced dipole moment. These correlations do not hold for 4F-histidine/(5-methyl)-imidazole, however. Molecular orbital calculations reveal that for the 4F species, there are no lone pair electrons on the fluorine until protonation. Analysis of a series of 4F-imidazole analogues, all with delocalized fluorine electron density, indicates that the deshielding of (19)F chemical shifts through substituent effects correlates with increased C-F bond polarity. In summary, the delocalization of fluorine electrons in the neutral 4F species, with gain of a lone pair upon protonation may help explain the difficulty in developing a predictive framework for fluorine chemical shifts. Ideas debated by chemists over 40 years ago, regarding fluorine's complex electronic effects, are shown to have relevance for understanding and predicting fluorine NMR spectra. PMID:26524669

  6. Method for sizing hollow microspheres

    DOEpatents

    Farnum, E.H.; Fries, R.J.

    1975-10-29

    Hollow Microspheres may be effectively sized by placing them beneath a screen stack completely immersed in an ultrasonic bath containing a liquid having a density at which the microspheres float and ultrasonically agitating the bath.

  7. Anomalous In-Plane Electronic Scattering in Charge Ordered Na0.41CoO2·0.6H2O

    NASA Astrophysics Data System (ADS)

    Cao, Guixin; Korshunov, Maxim M.; Gao, Yuze; Le Tacon, Mathieu; Singh, David J.; Lin, Chengtian

    2012-06-01

    We report electronic transport measurements on high quality floating zone grown NaxCoO2 and Na0.41CoO2·0.6H2O single crystals. We find an in-plane electronic scattering minimum near 11 K and a clear charge ordering at approximately 50 K. The electronic and magnetic properties in hydrated and nonhydrated Na0.41CoO2 samples are similar at higher temperature, but evolve in markedly different ways below ˜50K, where a strong ferromagnetic tendency is observed in the hydrated sample. Model calculations show the relationship of this tendency to the structure of the Fermi surface. The results, particularly the clear differences between the hydrated and nonhydrated material show a substantially enhanced ferromagnetic tendency upon hydration. Implications for superconductivity are discussed.

  8. Nonlocal Anomalous Hall Effect

    NASA Astrophysics Data System (ADS)

    Zhang, Steven S.-L.; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.

  9. High efficiency ionizer using a hollow cathode discharge plasma

    SciTech Connect

    Alessi, J.G.; Prelec, K.

    1984-01-01

    A proposal for an ionizer using a hollow cathode discharge plasma is described. Ionization is via the very high current density electron beam component in the plasma, as well as from charge exchange with plasma ions. Extraction of a He/sup +/ current corresponding to approximately 50% of the incoming atomic beam flux should be possible.

  10. Hollow Retroreflectors Offer Solid Benefits

    NASA Technical Reports Server (NTRS)

    2001-01-01

    A technician who lead a successful team of scientists, engineers, and other technicians in the design, fabrication, and characterization of cryogenic retroreflectors for the NASA Cassini/Composite Infrared Spectrometer (CIRS) mission to Saturn, developed a hollow retroreflector technology while working at NASA Goddard Space Flight Center. With 16 years of NASA experience, the technician teamed up with another NASA colleague and formed PROSystems, Inc., of Sharpsburg, Maryland, to provide the optics community with an alternative source for precision hollow retroreflectors. The company's hollow retroreflectors are front surface glass substrates assembled to provide many advantages over existing hollow retroreflectors and solid glass retroreflectors. Previous to this new technology, some companies chose not to use hollow retroreflectors due to large seam widths and loss of signal. The "tongue and groove" facet design of PROSystems's retroreflector allows for an extremely small seam width of .001 inches. Feedback from users is very positive regarding this characteristic. Most of PROSystems's primary customers mount the hollow retroreflectors in chrome steel balls for laser tracker targets in applications such as automobile manufacturing and spacecraft assembly.

  11. Phase coherent transport in hollow InAs nanowires

    SciTech Connect

    Wenz, T.; Rosien, M.; Haas, F.; Rieger, T.; Lepsa, M. I.; Lüth, H.; Grützmacher, D.; Schäpers, Th.; Demarina, N.

    2014-09-15

    Hollow InAs nanowires are produced from GaAs/InAs core/shell nanowires by wet chemical etching of the GaAs core. At room temperature, the resistivity of several nanowires is measured before and after removal of the GaAs core. The observed change in resistivity is explained by simulating the electronic states in both structures. At cryogenic temperatures, quantum transport in hollow InAs nanowires is studied. Flux periodic conductance oscillations are observed when the magnetic field is oriented parallel to the nanowire axis.

  12. STIS MAMA Recovery from Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2013-10-01

    This proposal is designed to permit a safe and orderly recovery of the STIS FUV MAMA or NUV MAMA detector after an anomalous shutdown. This is accomplished by using slower-than-normal MCP high-voltage ramp-ups and diagnostics. Anomalous shutdowns can occur because of bright object violations which trigger the Global Hardware Monitor or the Global Software Monitor. Anomalous shutdowns can also occur because of MAMA hardware anomalies or failures. The cause of the shutdown should be thoroughly investigated and understood prior to recovery. Twenty-four hour wait intervals are required after each test for MCP gas desorption and data analysis. Event flags are used to prevent inadvertent MAMA usage.The recovery procedure consists of three separate tests {i.e. visits} to check the MAMA's health after an anomalous shutdown: 1} signal processing electronics check, 2} slow, intermediate voltage high voltage ramp-up, and 3} ramp-up to full operating voltage followed by a fold analysis test {See STIS ISR 98-02R}. Each must be successfully completed before proceeding onto the next. This proposal executes the same steps as Cycle 20 proposal 13150.

  13. COS NUV Detector Recovery after Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2013-10-01

    This proposal is designed to permit a safe and orderly recovery of the NUV-MAMA detector after an anomalous shutdown. This is accomplished by using slower-than-normal MCP high-voltage ramp-ups and diagnostics. Anomalous shutdowns can occur because of bright object violations which trigger the Global Hardware Monitor or the Global Software Monitor. Anomalous shutdowns can also occur because of MAMA hardware anomalies or failures. The cause of the shutdown should be thoroughly investigated and understood prior to recovery. Twenty-four hour wait intervals are required after each test for MCP gas desorption and data analysis. Event flag 2 is used to prevent inadvertent MAMA usage.The recovery procedure consists of four separate tests {i.e. visits} to check the MAMA's health after an anomalous shutdown: 1} signal processing electronics check, 2} slow, intermediate voltage high-voltage ramp-up, 3} ramp-up to full operating voltage, and 4} fold analysis test {See COS TIR 2010-01}. Each must be successfully completed before proceeding onto the next. This proposal executes the same steps as Cycle 20 proposal 13129. Adjustments were made the the Software Global Monitor {SGM} to account for an increase in the dark counts due to window glow and to align the SGM to previously obtained Fold Analysis event data.

  14. COS NUV Detector Recovery After Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2011-10-01

    This proposal is designed to permit a safe and orderly recovery of the NUV-MAMA detector after an anomalous shutdown. This is accomplished by using slower-than-normal MCP high-voltage ramp-ups and diagnostics. Anomalous shutdowns can occur because of bright object violations, which trigger the Global Hardware Monitor or the Global Software Monitor. Anomalous shutdowns can also occur because of MAMA hardware anomalies or failures. The cause of the shutdown should be thoroughly investigated and understood prior to recovery. Twenty-four hour wait intervals are required after each test for MCP gas desorption and data analysis. Event flag 2 is used to prevent inadvertent MAMA usage.The recovery procedure consists of four separate tests {i.e. visits} to check the MAMAâ??s health after an anomalous shutdown: signal processing electronics check, slow, intermediate voltage high-voltage ramp-up, ramp-up to full operating voltage, and fold analysis test {See COS TIR 2010-01}. Each must be successfully completed before proceeding onto the next. This proposal executes the same steps as Cycle 18 proposal 12430.

  15. COS NUV Detector Recovery After Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2012-10-01

    This proposal is designed to permit a safe and orderly recovery of the NUV-MAMA detector after an anomalous shutdown. This is accomplished by using slower-than-normal MCP high-voltage ramp-ups and diagnostics. Anomalous shutdowns can occur because of bright object violations, which trigger the Global Hardware Monitor or the Global Software Monitor. Anomalous shutdowns can also occur because of MAMA hardware anomalies or failures. The cause of the shutdown should be thoroughly investigated and understood prior to recovery. Twenty-four hour wait intervals are required after each test for MCP gas desorption and data analysis. Event flag 2 is used to prevent inadvertent MAMA usage.The recovery procedure consists of four separate tests {i.e. visits} to check the MAMAâ_Ts health after an anomalous shutdown: 1} signal processing electronics check, 2} slow, intermediate voltage high-voltage ramp-up, 3} ramp-up to full operating voltage, and 4} fold analysis test {See COS TIR 2010-01}. Each must be successfully completed before proceeding onto the next. This proposal executes almost the same steps as Cycle 19 proposal 12723. Adjustments were made the the Software Global Monitor {SGM} to account for an increase in the dark counts due to window glow and to align the SGM to previously obtained Fold Analysis event data.

  16. ACS SBC Recovery from Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2013-10-01

    This proposal is designed to permit a safe and orderly recovery of the SBC {FUV MAMA} detector after an anomalous shutdown. This is accomplished by using slower-than-normal MCP high-voltage ramp-ups and diagnostics. Anomalous shutdowns can occur because of bright object violations, which trigger the Global Hardware Monitor or the Global Software Monitor. Anomalous shutdowns can also occur because of MAMA hardware anomalies or failures. The cause of the shutdown should be thoroughly investigated and understood prior to recovery. Twenty-four hour wait intervals are required after each test for MCP gas desorption and data analysis. Event flag 2 is used to prevent inadvertent MAMA usage. The recovery procedure consists of four separate tests {i.e. visits} to check the MAMA's health after an anomalous shutdown: 1} signal processing electronics check, 2} slow, high-voltage ramp-up to an intermediate voltage, 3} a slow high-voltage ramp-up to the nominal operating HV, and 4} fold analysis test. Each must be completed successfully before proceeding onto the next. During the two high-voltage ramp-ups, dark ACCUM exposures are taken. At high voltage, dark ACCUM exposures and diagnostics are taken. This proposal is based on Proposal 13163 from Cycle 20. For additional MAMA recovery information, see STIS ISR 98-02R.

  17. STIS MAMA Recovery from Anomalous Shutdown

    NASA Astrophysics Data System (ADS)

    Wheeler, Thomas

    2012-10-01

    This proposal is designed to permit a safe and orderly recovery of the STIS FUV MAMA or NUV MAMA detector after an anomalous shutdown. This is accomplished by using slower-than-normal MCP high-voltage ramp-ups and diagnostics. Anomalous shutdowns can occur because of bright object violations, which trigger the Global Hardware Monitor or the Global Software Monitor. Anomalous shutdowns can also occur because of MAMA hardware anomalies or failures. The cause of the shutdown should be thoroughly investigated and understood prior to recovery. Twenty-four hour wait intervals are required after each test for MCP gas desorption and data analysis. Event flags are used to prevent inadvertent MAMA usage.The recovery procedure consists of three separate tests {i.e. visits} to check the MAMAâ_Ts health after an anomalous shutdown: 1} signal processing electronics check, 2} slow, intermediate voltage high voltage ramp-up, and 3} ramp-up to full operating voltage followed by a fold analysis test {See STIS ISR 98-02R}. Each must be successfully completed before proceeding onto the next. This proposal executes the same steps as Cycle 19 proposal 12779.

  18. 12Cao-7Al2o3 Electride Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Rand, Lauren P. (Inventor); Williams, John D. (Inventor); Martinez, Rafael A. (Inventor)

    2016-01-01

    The use of the electride form of 12CaO-7Al.sub.2O.sub.3, or C12A7, as a low work function electron emitter in a hollow cathode discharge apparatus is described. No heater is required to initiate operation of the present cathode, as is necessary for traditional hollow cathode devices. Because C12A7 has a fully oxidized lattice structure, exposure to oxygen does not degrade the electride. The electride was surrounded by a graphite liner since it was found that the C12A7 electride converts to it's eutectic (CA+C3A) form when heated (through natural hollow cathode operation) in a metal tube.

  19. Hollowness of the observed auroral kilometric radiation pattern

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1987-01-01

    Presumably also generated by electron cyclotron emission, the earth's auroral kilometric radiation would be expected to exhibit a hollow pattern in the direction of the source magnetic field, similar to that reported for the comparable emissions from Jupiter. Although previously overlooked, such hollowness is clearly present in the new pattern measurements of Green and Gallagher (1985) at 56 kHz, occupying source-centered latitudes of 30 to 45 deg and hence occurring exactly where it was predicted and previously observed. Being distributed in longitude and spanning the entire evening sector, presumably reflecting a similar longitudinal distribution of auroral zone sources, this hollowness is attributed to sources beamed preferentially in the poleward magnetic meridian.

  20. Hollow fiber catalytic membranes

    SciTech Connect

    Ma, Yi Hua; Moser, W.; Shelekhin, A.; Pien, Shyhing

    1993-09-01

    The objective of the present research is to investigate the possibility of the enhancement of the H{sub 2}S thermal decomposition in the IGCC system by employing the hollow fiber catalytic membrane reactor. To accomplish the objective, the following major components in the analysis of the high temperature membrane reactor must be investigated: high-temperature stability of the porous glass membrane; catalytic properties of MoS{sub 2} and of the porous glass membrane; catalytic decomposition of H{sub 2}S in a packed bed reactor; catalytic decomposition of 100%, 8.6%, and 1.1% H{sub 2}S gas mixtures in the membrane reactor. The study has been shown that the conversion of the H{sub 2}S can be increased in the packed bed membrane reactor compared to the equilibrium conversion on the shell side. The development of a mathematical model for the proposed process is in progress. The model will enable optimization of the H{sub 2}S decomposition. These conditions include selectivity factors and pressure drop across the membrane.

  1. Anomalous diffusion in quantum Brownian motion with colored noise

    SciTech Connect

    Ford, G. W.; O'Connell, R. F.

    2006-03-15

    Anomalous diffusion is discussed in the context of quantum Brownian motion with colored noise. It is shown that earlier results follow simply and directly from the fluctuation-dissipation theorem. The limits on the long-time dependence of anomalous diffusion are shown to be a consequence of the second law of thermodynamics. The special case of an electron interacting with the radiation field is discussed in detail. We apply our results to wave-packet spreading.

  2. Numerical Simulations of the Partially-Ionized Gas in a 100-A LaB6 Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Goebel, Dan M.; Jorns, Benjamin A.; Polk, James E.; Guerrero, Pablo

    2013-01-01

    Numerical simulations of a hollow cathode with a LaB6 emitter operating at 100 A have been performed for the first time using the 2-D Orificed Cathode (OrCa2D) code. Results for a variety of plasma properties are presented and compared with laboratory measurements. The large size of the device permits peak electron number densities in the cathode interior that are lower than those established in the NSTAR hollow cathode, which operates with a 7.3x lower discharge current and 3.2x lower mass flow rate. Also, despite the higher discharge current in the LaB6 cathode, the maximum electron current density is lower, by 4.2x, than that in the NSTAR cathode due to the larger orifice size. Simulations and direct measurements show that at 12 sccm of xenon flow the peak emitter temperature is in the range of 1594-1630 C. It is also found that the conditions for the excitement of current-driven streaming instabilities and ion-acoustic turbulence (IAT) are satisfied in this cathode, similarly to what was found in the past in its smaller counterparts like the NSTAR cathode. Based on numerical simulations, it has long been argued that these instabilities may be responsible for the anomalously large ion energies that have been measured in these discharges as well as for the enhancement of the plasma resistivity. Confirmation of the presence of IAT in this cathode is presented for the first time in a companion paper.

  3. Comparison of Cu-II 781 nm lasers using high-voltage hollow-cathode and hollow-anode-cathode discharges

    SciTech Connect

    Peard, K.A.; Tobin, R.C. . Dept. of Physics); Donko, Z.; Rozsa, K. ); Szalai, L. )

    1994-09-01

    Voltage-current characteristics and the Cu-II 780.8 nm laser performances are described for a novel segmented hollow cathode and for three- and four-slot hollow-anode cathode (HAC) tubes. Each of these operate at a higher voltage and with higher slope resistance than a conventional hollow cathode and produce improved laser performance. The best laser performance is obtained with the segmented tube. The application of a longitudinal magnetic field raises the discharge voltage and enhances the laser performance for the segmented tube and raises the voltage for the four-slot HAC tube. The magnetic field lowers the voltage and reduces the laser performance with the three-slot HAC tube. The voltage effects are attributed to the deflection of the fast electrons by the magnetic field and represent experimental evidence for the oscillation of electrons in a hollow-cathode discharge.

  4. Beta function and anomalous dimensions

    SciTech Connect

    Pica, Claudio; Sannino, Francesco

    2011-06-01

    We demonstrate that it is possible to determine the coefficients of an all-orders beta-function linear in the anomalous dimensions using as data the 2-loop coefficients together with the first one of the anomalous dimensions which are universal. The beta function allows us to determine the anomalous dimension of the fermion masses at the infrared fixed point, and the resulting values compare well with the lattice determinations.

  5. Anomalous backscattered electron behavior of MoB and Mo{sub 5}SiB{sub 2} (T{sub 2}) phases in an as-cast Mo-B-Si alloy

    SciTech Connect

    Fournelle, J.H.; Nunes, C.A.; Perepezko, J.H.

    1996-12-31

    It is well established that backscattered electron (BSE) image contrast in SEM is primarily associated with differences in mean atomic number (Z) of the phases. The BSE coefficient increases with higher Z with slight dependence on beam energy E{sub 0}, except for some materials at <5 keV. We report here the anomalous BSE behavior of MoB and T{sub 2} (Mo{sub 5}SiB{sub 2}) phases observed imaging a 60Mo-30B-10Si (at%) alloy with a CAMECA SX-50. Specifies of the material and EMPA are reported in a companion communication. Mo-ss and Mo{sub 3}Si are also present. The drastic differences in BSE behavior are shown in Figures 1 (7 keV), 2 (15 keV), 2 (15 keV) and 3 (25 keV). The material has not been coated; addition of 100 {angstrom} carbon does not change the observed behavior.

  6. Flashing anomalous color contrast.

    PubMed

    Pinna, Baingio; Spillmann, Lothar; Werner, John S

    2004-01-01

    A new visual phenomenon that we call flashing anomalous color contrast is described. This phenomenon arises from the interaction between a gray central disk and a chromatic annulus surrounded by black radial lines. In an array of such figures, the central gray disk no longer appears gray, but assumes a color complementary to that of the surrounding annulus. The induced color appears: (1) vivid and saturated; (2) self-luminous, not a surface property; (3) flashing with eye or stimulus movement; (4) floating out of its confines; and (5) stronger in extrafoveal than in foveal vision. The strength of the effect depends on the number, length, width, and luminance contrast of the radial lines. The results suggest that the chromatic ring bounding the inner tips of the black radial lines induces simultaneous color contrast, whereas the radial lines elicit, in conjunction with the gray disk and the ring, the flashing, vividness, and high saturation of the effect. The stimulus properties inducing the illusion suggest that flashing anomalous color contrast may be based on asynchronous interactions among multiple visual pathways. PMID:15518215

  7. Fickian dispersion is anomalous

    SciTech Connect

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  8. Fickian dispersion is anomalous

    DOE PAGESBeta

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion wemore » illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.« less

  9. Co-Flow Hollow Cathode Technology

    NASA Technical Reports Server (NTRS)

    Hofer, Richard R.; Goebel, Dan M.

    2011-01-01

    Hall thrusters utilize identical hollow cathode technology as ion thrusters, yet must operate at much higher mass flow rates in order to efficiently couple to the bulk plasma discharge. Higher flow rates are necessary in order to provide enough neutral collisions to transport electrons across magnetic fields so that they can reach the discharge. This higher flow rate, however, has potential life-limiting implications for the operation of the cathode. A solution to the problem involves splitting the mass flow into the hollow cathode into two streams, the internal and external flows. The internal flow is fixed and set such that the neutral pressure in the cathode allows for a high utilization of the emitter surface area. The external flow is variable depending on the flow rate through the anode of the Hall thruster, but also has a minimum in order to suppress high-energy ion generation. In the co-flow hollow cathode, the cathode assembly is mounted on thruster centerline, inside the inner magnetic core of the thruster. An annular gas plenum is placed at the base of the cathode and propellant is fed throughout to produce an azimuthally symmetric flow of gas that evenly expands around the cathode keeper. This configuration maximizes propellant utilization and is not subject to erosion processes. External gas feeds have been considered in the past for ion thruster applications, but usually in the context of eliminating high energy ion production. This approach is adapted specifically for the Hall thruster and exploits the geometry of a Hall thruster to feed and focus the external flow without introducing significant new complexity to the thruster design.

  10. New route for hollow materials

    PubMed Central

    Rivaldo-Gómez, C. M.; Ferreira, F. F.; Landi, G. T.; Souza, J. A.

    2016-01-01

    Hollow micro/nano structures form an important family of functional materials. We have used the thermal oxidation process combined with the passage of electric current during a structural phase transition to disclose a colossal mass diffusion transfer of Ti ions. This combination points to a new route for fabrication of hollow materials. A structural phase transition at high temperature prepares the stage by giving mobility to Ti ions and releasing vacancies to the system. The electric current then drives an inward delocalization of vacancies, condensing into voids, and finally turning into a big hollow. This strong physical phenomenon leading to a colossal mass transfer through ionic diffusion is suggested to be driven by a combination of phase transition and electrical current followed by chemical reaction. We show this phenomenon for Ti leading to TiO2 microtube formation, but we believe that it can be used to other metals undergoing structural phase transition at high temperatures. PMID:27554448

  11. Hollow nanotubular toroidal polymer microrings

    NASA Astrophysics Data System (ADS)

    Lee, Jiyeong; Baek, Kangkyun; Kim, Myungjin; Yun, Gyeongwon; Ko, Young Ho; Lee, Nam-Suk; Hwang, Ilha; Kim, Jeehong; Natarajan, Ramalingam; Park, Chan Gyung; Sung, Wokyung; Kim, Kimoon

    2014-02-01

    Despite the remarkable progress made in the self-assembly of nano- and microscale architectures with well-defined sizes and shapes, a self-organization-based synthesis of hollow toroids has, so far, proved to be elusive. Here, we report the synthesis of polymer microrings made from rectangular, flat and rigid-core monomers with anisotropically predisposed alkene groups, which are crosslinked with each other by dithiol linkers using thiol-ene photopolymerization. The resulting hollow toroidal structures are shape-persistent and mechanically robust in solution. In addition, their size can be tuned by controlling the initial monomer concentrations, an observation that is supported by a theoretical analysis. These hollow microrings can encapsulate guest molecules in the intratoroidal nanospace, and their peripheries can act as templates for circular arrays of metal nanoparticles.

  12. Novel hollow powder porous structures

    SciTech Connect

    Sypeck, D.J.; Parrish, P.A.; Wadley, H.N.G.

    1998-12-31

    Recent finite element calculations indicate that structures constructed from partially compacted hollow spheres exhibit a greater stiffness and strength than many other cellular structures at comparable density. It has been observed that gas atomization of metallic powders often leads to entrapment of the flow field gas. The resulting hollow powders are an unwanted by-product in the sense that they lead to porosity and future sites of defect in solid parts. Here a method is developed to separate the hollow powders according to their size, shape and density. They are then consolidated to a porous structure. Examples of this are given for both a titanium alloy and a nickel-base superalloy. The compressive mechanical properties are measured and compared to those of other porous structures.

  13. New route for hollow materials.

    PubMed

    Rivaldo-Gómez, C M; Ferreira, F F; Landi, G T; Souza, J A

    2016-01-01

    Hollow micro/nano structures form an important family of functional materials. We have used the thermal oxidation process combined with the passage of electric current during a structural phase transition to disclose a colossal mass diffusion transfer of Ti ions. This combination points to a new route for fabrication of hollow materials. A structural phase transition at high temperature prepares the stage by giving mobility to Ti ions and releasing vacancies to the system. The electric current then drives an inward delocalization of vacancies, condensing into voids, and finally turning into a big hollow. This strong physical phenomenon leading to a colossal mass transfer through ionic diffusion is suggested to be driven by a combination of phase transition and electrical current followed by chemical reaction. We show this phenomenon for Ti leading to TiO2 microtube formation, but we believe that it can be used to other metals undergoing structural phase transition at high temperatures. PMID:27554448

  14. Communication: Localized molecular orbital analysis of the effect of electron correlation on the anomalous isotope effect in the NMR spin-spin coupling constant in methane

    SciTech Connect

    Zarycz, M. Natalia C. Provasi, Patricio F.; Sauer, Stephan P. A.

    2014-10-21

    We discuss the effect of electron correlation on the unexpected differential sensitivity (UDS) in the {sup 1}J(C–H) coupling constant of CH{sub 4} using a decomposition into contributions from localized molecular orbitals and compare with the {sup 1}J(N–H) coupling constant in NH{sub 3}. In particular, we discuss the well known fact that uncorrelated coupled Hartree-Fock (CHF) calculations are not able to reproduce the UDS in methane. For this purpose we have implemented for the first time a localized molecular orbital analysis for the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes—SOPPA(CCSD) in the DALTON program. Comparing the changes in the localized orbital contributions at the correlated SOPPA and SOPPA(CCSD) levels and at the uncorrelated CHF level, we find that the latter overestimates the effect of stretching the bond between the coupled atoms on the contribution to the coupling from the localized bonding orbital between these atoms. This disturbs the subtle balance between the molecular orbital contributions, which lead to the UDS in methane.

  15. Hollow sphere ceramic particles for abradable coatings

    SciTech Connect

    Longo, F.N.; Bader, N.F. III; Dorfman, M.R.

    1984-05-22

    A hollow sphere ceramic flame spray powder is disclosed. The desired constituents are first formed into agglomerated particles in a spray drier. Then the agglomerated particles are introduced into a plasma flame which is adjusted so that the particles collected are substantially hollow. The hollow sphere ceramic particles are suitable for flame spraying a porous and abradable coating. The hollow particles may be selected from the group consisting of zirconium oxide and magnesium zirconate.

  16. The hollow cathode effect in a radio-frequency driven microhollow cathode discharge in nitrogen

    NASA Astrophysics Data System (ADS)

    Zhang, Lianzhu; Zhao, Guoming; Wang, Jing; Han, Qing

    2016-02-01

    A two-dimensional particle-in-cell Monte-Carlo code has been developed to study the physical mechanism of the hollow cathode effect (HCE) in an rf microhollow cathode discharge (rf-MHCD). Under the simulated conditions, the HCE in the rf-MHCD is the result of sheath-superposition, and both α ionization and γ ionization play a role. However, α ionization mode is predominant. Electrons undergo a pendular motion during the negative portion of the rf cycle. When the rf hollow electrode has a positive voltage, the majority of the electrons move toward the rf electrode, and the mean electron energy near the rf electrode is higher than that in a dc hollow cathode discharge, resulting in a large number of energetic electrons bombarding the hollow cathode wall, an important characteristic of the rf-MHCD. When the hollow cathode aperture is sufficiently small, many electrons strike the hollow electrode and are removed from the discharge space, so that the plasma density decreases. The average energy of the ions in the quasi-neutral plasma region near the axis is greater than the thermal energy in a molecular gas. Therefore, high density, high energy, and high chemical activity are characteristic advantages of rf-MHCD plasma sources.

  17. Hollow tin/chromium whiskers

    NASA Astrophysics Data System (ADS)

    Cheng, Jing; Vianco, Paul T.; Li, James C. M.

    2010-05-01

    Tin whiskers have been an engineering challenge for over five decades. The mechanism has not been agreed upon thus far. This experiment aimed to identify a mechanism by applying compressive stresses to a tin film evaporated on silicon substrate with an adhesion layer of chromium in between. A phenomenon was observed in which hollow whiskers grew inside depleted areas. Using focused ion beam, the hollow whiskers were found to contain both tin and chromium. At the bottom of the depleted areas, thin tin/tin oxide film remained over the chromium layer. It indicates that tin transport occurred along the interface between tin and chromium layers.

  18. A Hollow Cathode Magnetron (HCM)

    SciTech Connect

    S.A. Cohen; Z. Wang

    1998-04-01

    A new type of plasma sputtering device, named the hollow cathode magnetron (HCM), has been developed by surrounding a planar magnetron cathode with a hollow cathode structure (HCS). Operating characteristics of HCMs, current-voltage ( I-V ) curves for fixed discharge pressure and voltage-pressure ( V-p ) curves for fixed cathode current, are measured. Such characteristics are compared with their planar magnetron counterparts. New operation regimes, such as substantially lower pressures (0.3 mTorr), were discovered for HCMs. Cathode erosion profiles show marked improvement over planar magnetron in terms of material utilization. The use of HCMs for thin film deposition are discussed.

  19. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Yen, S. P. S.; Klein, E. (Inventor)

    1976-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, crosslinked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  20. Hollow waveguide for urology treatment

    NASA Astrophysics Data System (ADS)

    Jelínková, H.; Němec, M.; Koranda, P.; Pokorný, J.; Kőhler, O.; Drlík, P.; Miyagi, M.; Iwai, K.; Matsuura, Y.

    2010-02-01

    The aim of our work was the application of the special sealed hollow waveguide system for the urology treatment - In our experimental study we have compared the effects of Ho:YAG (wavelength 2100 nm) and Er:YAG (wavelength 2940 nm) laser radiation both on human urinary stones (or compressed plaster samples which serve as a model) fragmentation and soft ureter tissue incision in vitro. Cyclic Olefin Polymer - coated silver (COP/Ag) hollow glass waveguides with inner and outer diameters 700 and 850 μm, respectively, were used for the experiment. To prevent any liquid to diminish and stop the transmission, the waveguide termination was utilized.

  1. Quartz antenna with hollow conductor

    DOEpatents

    Leung, Ka-Ngo; Benabou, Elie

    2002-01-01

    A radio frequency (RF) antenna for plasma ion sources is formed of a hollow metal conductor tube disposed within a glass tube. The hollow metal tubular conductor has an internal flow channel so that there will be no coolant leakage if the outer glass tube of the antenna breaks. A portion of the RF antenna is formed into a coil; the antenna is used for inductively coupling RF power to a plasma in an ion source chamber. The antenna is made by first inserting the metal tube inside the glass tube, and then forming the glass/metal composite tube into the desired coil shape.

  2. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Klein, Elias (Inventor)

    1980-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, cross-linked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  3. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Klein, Elias (Inventor)

    1977-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, cross-linked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  4. Anomalous reflections from the ionosphere

    NASA Astrophysics Data System (ADS)

    Givishvili, G. V.; Leshchenko, L. N.

    2013-09-01

    The existence of anomalous ionospheric reflections was shown on the basis of vertical soundings at the Moskow station. They are observed at heights of 100-200 km. These anomalous reflections are not related to the main Ne( h) ionospheric profile. Morphological characteristics of such reflections are presented: the daily, seasonal, and cyclic dependences of their appearance.

  5. Application of anomalous diffusion in production of negative ions

    NASA Astrophysics Data System (ADS)

    Jimbo, Kouichi

    1984-11-01

    The production of negative hydrogen ions is investigated in the reflex-type negative ion sources. When anomalous diffusion in the positive column was found by Hoh and Lehnert [Phys. Fluids 3, 600 (1960)], it was pointed out that the large particle loss produced by anomalous diffusion is compensated for by the larger particle production inside the plasma. In the present experiments anomalous diffusion was artificially encouraged by changing the radial electric field inside the reflex discharge. Apparent encouragement of negative ion current by the increase of the density fluctuation amplitude is observed. Twice as much negative ion current was obtained with the artificial encouragement as without. On the other hand, the larger extracted negative ion current was observed with a lower electron temperature, which is calculated from the anomalous diffusion coefficient derived from a simple nonlinear theory. This result is consistent with Wadehra's calculated results [Appl. Phys. Lett. 35, 917 (1979)].

  6. Application of anomalous diffusion in production of negative ions

    SciTech Connect

    Jimbo, K.

    1984-11-01

    The production of negative hydrogen ions is investigated in the reflex-type negative ion sources. When anomalous diffusion in the positive column was found by Hoh and Lehnert (Phys. Fluids 3, 600 (1960)), it was pointed out that the large particle loss produced by anomalous diffusion is compensated for by the larger particle production inside the plasma. In the present experiments anomalous diffusion was artificially encouraged by changing the radial electric field inside the reflex discharge. Apparent encouragement of negative ion current by the increase of the density fluctuation amplitude is observed. Twice as much negative ion current was obtained with the artificial encouragement as without. On the other hand, the larger extracted negative ion current was observed with a lower electron temperature, which is calculated from the anomalous diffusion coefficient derived from a simple nonlinear theory. This result is consistent with Wadehra's calculated results (Appl. Phys. Lett. 35, 917 (1979)).

  7. Spectrum of anomalous magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2016-05-01

    The equations of anomalous magnetohydrodynamics describe an Abelian plasma where conduction and chiral currents are simultaneously present and constrained by the second law of thermodynamics. At high frequencies the magnetic currents play the leading role, and the spectrum is dominated by two-fluid effects. The system behaves instead as a single fluid in the low-frequency regime where the vortical currents induce potentially large hypermagnetic fields. After deriving the physical solutions of the generalized Appleton-Hartree equation, the corresponding dispersion relations are scrutinized and compared with the results valid for cold plasmas. Hypermagnetic knots and fluid vortices can be concurrently present at very low frequencies and suggest a qualitatively different dynamics of the hydromagnetic nonlinearities.

  8. Detection of anomalous events

    DOEpatents

    Ferragut, Erik M.; Laska, Jason A.; Bridges, Robert A.

    2016-06-07

    A system is described for receiving a stream of events and scoring the events based on anomalousness and maliciousness (or other classification). The system can include a plurality of anomaly detectors that together implement an algorithm to identify low-probability events and detect atypical traffic patterns. The anomaly detector provides for comparability of disparate sources of data (e.g., network flow data and firewall logs.) Additionally, the anomaly detector allows for regulatability, meaning that the algorithm can be user configurable to adjust a number of false alerts. The anomaly detector can be used for a variety of probability density functions, including normal Gaussian distributions, irregular distributions, as well as functions associated with continuous or discrete variables.

  9. Anomalous gauge boson couplings

    SciTech Connect

    Barklow, T.; Rizzo, T.; Baur, U.

    1997-01-13

    The measurement of anomalous gauge boson self couplings is reviewed for a variety of present and planned accelerators. Sensitivities are compared for these accelerators using models based on the effective Lagrangian approach. The sensitivities described here are for measurement of {open_quotes}generic{close_quotes} parameters {kappa}{sub V}, {lambda}{sub V}, etc., defined in the text. Pre-LHC measurements will not probe these coupling parameters to precision better than O(10{sup -1}). The LHC should be sensitive to better than O(10{sup -2}), while a future NLC should achieve sensitivity of O(10{sup -3}) to O(10{sup -4}) for center of mass energies ranging from 0.5 to 1.5 TeV.

  10. RHETT/EPDM Flight Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Manzella, David; Patterson, Michael; Pastel, Michael

    1997-01-01

    Under the sponsorship of the BMDO Russian Hall Electric Thruster Technology program two xenon hollow cathodes, a flight unit and a flight spare were fabricated, acceptance tested and delivered to the Naval Research Laboratory for use on the Electric Propulsion Demonstration Module. These hollow cathodes, based on the International Space Station plasma contactor design, were fabricated at the NASA Lewis Research Center for use with a D-55 anode layer thruster in the first on-orbit operational application of this technology. The 2.2 Ampere nominal emission current of this device was obtained with a xenon flow rate of 0.6 mg/s. Ignition of the cathode discharge was accomplished through preheating the active electron emitter with a resistive heating element before application of a 650 volt ignition pulse between the emitter and an external starting electrode. The successful acceptance testing of the Electric Propulsion Demonstration Module utilizing these cathodes demonstrated the suitability of cathodes based on barium impregnated inserts in an enclosed keeper configuration for use with Hall thruster propulsion systems.

  11. Growth of solid and hollow gold particles through the thermal annealing of nanoscale patterned thin films

    SciTech Connect

    Lin, Junhao; He, Weidong; Vilayur Ganapathy, Subramanian; Peppernick, Samuel J.; Wang, Bin; Palepu, Sandeep; Remec, Miroslav; Hess, Wayne P.; Hmelo, Anthony B.; Pantelides, Sokrates T.; Dickerson, James

    2013-11-27

    Through thermally annealing well-arrayed, circular, nanoscale thin films of gold, deposited onto [111] silicon/silicon dioxide substrates, both solid and hollow gold particles of different morphologies with controllable sizes were obtained. The thin film could form individual particle or clusters of particles by tuning the diameter of it. Hollow gold particles were featured by their large size whose diameter was larger than 500 nm and confirmed by a cross-section view. Hollow gold particles show greater plasmonic field enhancement under photoemission electron microscopy. Potential growth mechanisms for these structures are explored

  12. Polypyrrole-Coated Zinc Ferrite Hollow Spheres with Improved Cycling Stability for Lithium-Ion Batteries.

    PubMed

    Sun, Xiaoran; Zhang, Hongwei; Zhou, Liang; Huang, Xiaodan; Yu, Chengzhong

    2016-07-01

    Here, ZnFe2 O4 double-shell hollow microspheres are designed to accommodate the large volume expansion during lithiation. A facile and efficient vapor-phase polymerization method has been developed to coat the ZnFe2 O4 hollow spheres with polypyrrole (PPY). The thin PPY coating improves not only the electronic conductivity but also the structural integrity, and thus the cycling stability of the ZnFe2 O4 hollow spheres. Our work sheds light on how to enhance the electrochemical performance of transition metal oxide-based anode materials by designing delicate nanostructures. PMID:27259158

  13. Oriented-assembly of hollow FePt nanochains with tunable catalytic and magnetic properties

    NASA Astrophysics Data System (ADS)

    Liu, Jialong; Xia, Tianyu; Wang, Shouguo; Yang, Guang; Dong, Bowen; Wang, Chao; Ma, Qidi; Sun, Young; Wang, Rongming

    2016-06-01

    structures. Compared with commercial Pt/C, well aligned hollow FePt nanochains show greatly enhanced catalytic activities in the methanol oxidation reaction (MOR) due to more favorable mass flow. Magnetic measurements indicate that the magnetic properties including Curie temperature and saturation magnetization can be tuned by the control of the size and shape of hollow nanochains. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00883f

  14. Hollow vortices in weakly compressible flows

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Vikas; Crowdy, Darren

    2014-11-01

    In a two-dimensional, inviscid and steady fluid flow, hollow vortices are bounded regions of constant pressure with non-zero circulation. It is known that for an infinite row of incompressible hollow vortices, analytical solutions for the flow field and the shape of the hollow vortex boundary can be obtained using conformal mapping methods. In this talk, we show how to derive analytical expressions for a weakly compressible hollow vortex row. This is done by introducing a new method based on the Imai-Lamla formula. We will also touch upon how to extend these results to a von-Karman street of hollow vortices.

  15. Hollow vortices in weakly compressible flows

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Vikas; Crowdy, Darren

    2015-11-01

    In a two-dimensional, inviscid and steady fluid flow, hollow vortices are bounded regions of constant pressure with non-zero circulation. It is known that for an infinite row of incompressible hollow vortices, analytical solutions for the flow field and the shape of the hollow vortex boundary can be obtained using conformal mapping methods. In this talk, we show how to derive analytical expressions for a weakly compressible hollow vortex row. This is done by introducing a new method based on the Imai-Lamla formula. We will also touch upon how to extend these results to a von-Karman street of hollow vortices.

  16. Hollow waveguide cavity ringdown spectroscopy

    NASA Technical Reports Server (NTRS)

    Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

    2012-01-01

    Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

  17. Hollow Plasma in a Solenoid

    SciTech Connect

    Anders, Andre; Kauffeldt, Marina; Oks, Efim M.; Roy, Prabir K.

    2010-11-30

    A ring cathode for a pulsed, high-current, multi-spot cathodic arc discharge was placed inside a pulsed magnetic solenoid. Photography is used to evaluate the plasma distribution. The plasma appears hollow for cathode positions close the center of the solenoid, and it is guided closer to the axis when the cathode is away from the center.

  18. Numerical simulation of the sustaining discharge in radio frequency hollow cathode discharge in argon

    SciTech Connect

    Jiang, Xin-Xian; He, Feng Ouyang, Ji-Ting; Chen, Qiang Ge, Teng

    2014-03-15

    In this paper, a two-dimensional fluid model was developed to study the radio frequency (RF) hollow cathode discharge (HCD) in argon at 1 Torr. The evolutions of the particle density distribution and the ionization rate distribution in RF HCD at 13.56 MHz indicate that the discharge mainly occurs inside the hollow cathode. The spatio-temporal distributions of the ionization rate and the power deposition within the hollow cathode imply that sheath oscillation heating is the primary mechanism to sustain the RF HCD, whereas secondary electron emission plays a negligible role. However, as driving frequency decreases, secondary electron heating becomes a dominant mechanism to sustain the discharge in RF hollow cathode.

  19. Hollow mesoporous TiO2 microspheres for enhanced photocatalytic degradation of acetaminophen in water.

    PubMed

    Lin, Chin Jung; Yang, Wen-Ta; Chou, Chen-Yi; Liou, Sofia Ya Hsuan

    2016-06-01

    Hollow core-shell mesoporous TiO2 microspheres were synthesized by a template-free solvothermal route for efficient photocatalytic degradation of acetaminophen. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Barrett-Joyner-Halenda data revealed a micrometer-sized mesoporous anatase TiO2 hollow sphere with large surface area and efficient light harvesting. For the photocatalytic degradation of acetaminophen in 60 min, the conversion fraction of the drug increased from 88% over commercial Degussa P25 TiO2 to 94% over hollow spheres with about 25% increase in the initial reaction rate. Even after 10 repeated runs, the recycled hollow spheres showed good photodegradation activity. The intermediates generated in the photocatalytic reactions were eventually converted into molecules that are easier to handle. The simple fabrication route would facilitate the development of photocatalysts for the decomposition of environmental contaminants. PMID:27003371

  20. Shape-controlled synthesis and properties of dandelion-like manganese sulfide hollow spheres

    SciTech Connect

    Ma, Wei; Chen, Gen; Zhang, Dan; Zhu, Jianyu; Qiu, Guanzhou; Liu, Xiaohe

    2012-09-15

    Graphical abstract: Dandelion-like MnS hollow spheres assembled with nanorods could be successfully synthesized in large quantities through a simple and convenient hydrothermal synthetic method under mild conditions using soluble hydrated manganese chloride as Mn source, L-cysteine as both a precipitator and complexing reagent. The dandelion-like MnS hollow spheres might have potential applications in microdevices and magnetic cells. Highlights: ► MnS hollow spheres assembled with nanorods could be synthesized. ► The morphologies and sizes of final products could be controlled. ► Possible formation mechanism of MnS hollow spheres is proposed. -- Abstract: Dandelion-like gamma-manganese (II) sulfide (MnS) hollow spheres assembled with nanorods have been prepared via a hydrothermal process in the presence of L-cysteine and polyvinylpyrrolidone (PVP). L-cysteine was employed as not only sulfur source, but also coordinating reagent for the synthesis of dandelion-like MnS hollow spheres. The morphology, structure and properties of as-prepared products have been investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM) and photoluminescence spectra (PL). The probable formation mechanism of as-prepared MnS hollow spheres was discussed on the basis of the experimental results. This strategy may provide an effective method for the fabrication of other metal sulfides hollow spheres.

  1. Anomalous behavior of LEED beam intensity during annealing

    NASA Astrophysics Data System (ADS)

    Fu, Tsu-Yi; Liu, T. F.; Su, C. W.; Shern, C. S.; Chen, R. H.

    2000-10-01

    Low-energy electron diffraction was used to study the annealing effects of 1 ML Ag on the ultra-thin-film Co/Pt (111). The behavior of the specular beam intensity versus temperature is anomalous. Besides the normal Debye-Waller effect, a bend occurs at 550 K, and a dramatic increase occurs at a higher temperature. A corresponding study by Auger electron spectroscopy and ultraviolet photoelectron spectroscopy indicates that the bend results from the Co inter-diffusion. The anomalous increase indicates that a more stable state forms at a higher temperature. The Co coverage plays an important role in determining the turning temperature. Possible mechanisms are discussed.

  2. In situ precipitation preparation of ZnO hollow spheres and their photocatalysis and gas-sensing properties

    NASA Astrophysics Data System (ADS)

    Jia, Xiaohua; Tian, Minggang; Liu, Yingying; Wu, Xiangyang; Song, Haojie

    2015-06-01

    ZnO hollow spheres were synthesized by in situ precipitation method in the presence of surfactant polyvinylpyrrolidone combined with subsequent calcination. The prepared ZnO was characterized using scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy. The results indicated that the prepared ZnO hollow spheres were well crystalline with wurtzite hexagonal phase. The formation mechanism of ZnO hollow spheres was discussed. Furthermore, the gas-sensing properties for detection of organic gas and photocatalytic activities for the degradation of rhodamine B (RhB) of the prepared ZnO hollow spheres were investigated. The results indicated that the prepared ZnO hollow spheres exhibited superior photocatalysis properties on decomposition of RhB and high gas-sensing properties for detection of acetone gas.

  3. A hollow cathode hydrogen ion source. [for controlled fusion

    NASA Technical Reports Server (NTRS)

    Sovey, J. S.; Mirtich, M. J.

    1977-01-01

    High current density ion sources have been used to heat plasmas in controlled thermonuclear reaction experiments. High beam currents imply relatively high emission currents from cathodes which have generally taken the form of tungsten filaments. This paper describes a hydrogen ion source which was primarily developed to assess the emission current capability and design requirements for hollow cathodes for application in neutral injection devices. The hydrogen source produced ions by electron bombardment via a single hollow cathode. Source design followed mercury ion thruster technology, using a weak magnetic field to enhance ionization efficiency. A 1.3-cm-diam hollow cathode using a low work function material dispenser performed satisfactorily over a discharge current range of 10-90 A. Cylindrical probe measurements taken without ion extraction indicate maximum ion number densities on the order of 10 trillion/cu cm. Discharge durations ranged from 30 sec to continuous operation. Tests with beam extraction at 2.5 keV and 30 A discharge current yield average ion beam current densities of 0.1 A/sq cm over a 5-cm extraction diameter. Results of this study can be used to supply the baseline information needed to scale hollow cathodes for operation at discharge currents of hundreds of amperes using distributed cathodes.

  4. Coprecipitation-assisted hydrothermal synthesis of PLZT hollow nanospheres

    SciTech Connect

    Zhu, Renqiang; Zhu, Kongjun; Qiu, Jinhao; Bai, Lin; Ji, Hongli

    2010-08-15

    Lanthanum-modified lead zirconate titanate Pb{sub 1-x}La{sub x}(Zr{sub 1-y}Ti{sub y})O{sub 3} (PLZT) hollow nanospheres have been successfully prepared via a template-free hydrothermal method using the well-mixed coprecipitated precursors and the KOH mineralizer. The structure, composition, and morphology of the PLZT hollow nanospheres were characterized by XRD (X-ray diffraction), ICP (inductive coupled plasma emission spectrometer), FTIR (Fourier transform infrared spectra), TG/DTA (thermogravimetric analysis and differential thermal analysis), TEM (transmission electron microscopy) and SEAD (selected area diffraction). The results show that the composition and the morphology control of the PLZT products are determined by the KOH concentration. The PLZT hollow nanospheres with uniform size of about 4 nm were synthesized in the presence of 5 M KOH. The crystalline nanoparticles can be prepared at dilute KOH, in contrast to the amorphous powders prepared at concentrated KOH. Formation mechanisms of the PLZT hollow nanospheres are also discussed.

  5. Preparation and optical property of anatase hollow microsphere with mesoporosity

    SciTech Connect

    Li Guohua Zhu Jingtao; Tian Wei; Ma Chunan

    2009-02-04

    Anatase hollow sphere with mesoporosity was prepared by sol pyrogenation used TiCl{sub 4} as precursor only. The samples were characterized by X-ray diffraction and scan electron microscopy, their specific surface area was measured by N{sub 2} adsorption. The results show that the sample calcined at 500 deg. C for 2 h is phase pure anatase, the morphology of the particle of the sample is hollow sphere, and the wall of the hollow sphere is constituted of anatase nanoparticle and mesoporosity. The crystallinity, the crystal size, the pore width, the specific surface area and the crystal phase of the sample are changing along with the calcined temperature. The optical property was measured by ultraviolet radiation vis absorption spectra of the suspension of the samples. The results show that the optical property of the sample is better than that of nanoanatase particle, and the optical property of hollow sphere titania with mesoporosity is related to its crystal phase, specific surface area, crystal size, porosity size and crystallinity.

  6. Ontogeny of an iridescent nanostructure composed of hollow melanosomes.

    PubMed

    Shawkey, Matthew D; D'Alba, Liliana; Xiao, Ming; Schutte, Matthew; Buchholz, Richard

    2015-04-01

    Iridescent colors in feathers are some of the brightest in nature, and are produced by coherent light scattering from periodic arrangements of melanosomes (melanin-containing organelles). Hollow melanosomes, an evolutionary innovation largely restricted to birds, contain an optically powerful combination of high and low refractive indices (from the melanin and air, respectively) that enables production of brighter and more saturated colors than solid melanosomes. However, despite their significance to avian color and potential utility as optical biomaterials, little is known about the ontogeny of either the melanosomes themselves or the nanostructures they comprise. We used light and electron microscopy to characterize nanostructural development in regenerating feathers of wild turkeys, a species with iridescent color produced by a hexagonally close-packed array of hollow melanosomes. We found that melanosomes form as solid bodies in melanocytes. Later in development, largely after placement in developing barbules, their interiors dissolve and leave hollow cores. These now hollow melanosomes are initially disorganized in the barbule, but become close-packed as they are pulled to the edge of the barbule, likely through a combination of forces including depletion-attraction. These data suggest that these structurally colored tissues are self-assembled and represent novel pathways of development. PMID:25427951

  7. Post-annealing reinforced hollow carbon nitride nanospheres for hydrogen photosynthesis

    NASA Astrophysics Data System (ADS)

    Zheng, Dandan; Huang, Caijing; Wang, Xinchen

    2014-12-01

    Hollow-structured g-C3N4 polymers with a high thermal stability up to 550 °C and an enhanced photocatalytic activity have been developed by post-annealing treatment, which effectively modifies the textural, crystal, and electronic properties of the g-C3N4 semiconductors without extra chemical assistance. This is a unique example of thermally and chemically stable conjugated polymers with hollow nanostructures and optoelectronic properties, promising the development of functional hollow g-C3N4 nanocomposites by chemical modifications like doping, surface grafting, and coupling with other inorganic/polymeric semiconductors with the aid of thermal treatment at high temperatures.Hollow-structured g-C3N4 polymers with a high thermal stability up to 550 °C and an enhanced photocatalytic activity have been developed by post-annealing treatment, which effectively modifies the textural, crystal, and electronic properties of the g-C3N4 semiconductors without extra chemical assistance. This is a unique example of thermally and chemically stable conjugated polymers with hollow nanostructures and optoelectronic properties, promising the development of functional hollow g-C3N4 nanocomposites by chemical modifications like doping, surface grafting, and coupling with other inorganic/polymeric semiconductors with the aid of thermal treatment at high temperatures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06011c

  8. Double autoionization of hollow-atom states

    NASA Astrophysics Data System (ADS)

    Pindzola, M. S.; Robicheaux, F.; Colgan, J.

    2005-08-01

    A time-dependent close-coupling method for three-electron atomic systems is formulated to calculate the double autoionization of hollow-atom states. Initial excited states are obtained by relaxation of the Schrödinger equation in imaginary time, while autoionization rates are obtained by propagation in real time. A 12-coupled-channels nonperturbative calculation on a three-dimensional radial lattice yields a double-autoionization rate for the Li(2s22p)→Li2+(1s)+2e- transition that that is somewhat smaller than earlier many-body perturbation theory calculations and in reasonable agreement with rates extracted from resonance profiles found in more recent γ+Li experiments.

  9. Cetyltrimethyl ammonium bromide assisted hydrothermal growth of hematite hollow cubes

    SciTech Connect

    Wang, Wei-Wei; Yao, Jia-Liang

    2010-11-15

    Hematite hollow cubes have been prepared by forced hydrolysis of ferric chloride solutions under hydrothermal conditions. The effects of reaction time, reaction temperature and cetyltrimethyl ammonium bromide on the transformation process from akageneite to hematite were investigated in detail. The products were characterized by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. It is found that cetyltrimethyl ammonium bromide was a critical factor influencing the phase transformation process of akageneite and the final morphology of the as-prepared products. With cetyltrimethyl ammonium bromide, hematite hollow cubes and porous spheres were obtained. Otherwise only dense cubes were observed even prolonging reaction time or increasing reaction temperature. The mechanism was proposed.

  10. Linear ion source with magnetron hollow cathode discharge

    SciTech Connect

    Tang, D.L.; Pu, S.H.; Wang, L.S.; Qiu, X.M.; Chu, Paul K.

    2005-11-15

    A linear ion source with magnetron hollow cathode discharge is described in this paper. The linear ion source is based on an anode layer thruster with closed-drift electrons that move in a closed path in the ExB fields. An open slit configuration is designed at the end of the ion source for the extraction of the linear ion beam produced by the magnetron hollow cathode discharge. The special configurations enable uninterrupted and expanded operation with oxygen as well as other reactive gases because of the absence of an electron source in the ion source. The ion current density and uniformity were experimentally evaluated. Using the ion source, surface modification was conducted on polyethylene terephthalate polymer films to improve the adhesion strength with ZnS coatings.

  11. Anomalous - viscosity current drive

    DOEpatents

    Stix, Thomas H.; Ono, Masayuki

    1988-01-01

    An apparatus and method for maintaining a steady-state current in a toroidal magnetically confined plasma. An electric current is generated in an edge region at or near the outermost good magnetic surface of the toroidal plasma. The edge current is generated in a direction parallel to the flow of current in the main plasma and such that its current density is greater than the average density of the main plasma current. The current flow in the edge region is maintained in a direction parallel to the main current for a period of one or two of its characteristic decay times. Current from the edge region will penetrate radially into the plasma and augment the main plasma current through the mechanism of anomalous viscosity. In another aspect of the invention, current flow driven between a cathode and an anode is used to establish a start-up plasma current. The plasma-current channel is magnetically detached from the electrodes, leaving a plasma magnetically insulated from contact with any material obstructions including the cathode and anode.

  12. Anomalous discrete symmetry

    SciTech Connect

    Huang, Z. )

    1992-12-01

    We examine an interesting scenario to solve the domain-wall problem recently suggested by Preskill, Trivedi, Wilczek, and Wise. The effective potential is calculated in the presence of the QCD axial anomaly. It is shown that some discrete symmetries such as {ital CP} and {ital Z}{sub 2} can be anomalous due to a so-called {ital K} term induced by instantons. We point out that the {ital Z}{sub 2} domain-wall problem in the two-doublet standard model can be resolved by two types of solutions: the {ital CP}-conserving one and the {ital CP}-breaking one. In the first case, there exist two {ital Z}{sub 2}-related local minima whose energy splitting is provided by the instanton effect. In the second case, there is only one unique vacuum so that the domain walls do not form at all. The consequences of this new source of {ital CP} violation are discussed and shown to be well within the experimental limits in weak interactions.

  13. Multiple Hollow Cathode Wear Testing

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    1994-01-01

    A hollow cathode-based plasma contactor has been baselined for use on the Space Station to reduce station charging. The plasma contactor provides a low impedance connection to space plasma via a plasma produced by an arc discharge. The hollow cathode of the plasma contactor is a refractory metal tube, through which xenon gas flows, which has a disk-shaped plate with a centered orifice at the downstream end of the tube. Within the cathode, arc attachment occurs primarily on a Type S low work function insert that is next to the orifice plate. This low work function insert is used to reduce cathode operating temperatures and energy requirements and, therefore, achieve increased efficiency and longevity. The operating characteristics and lifetime capabilities of this hollow cathode, however, are greatly reduced by oxygen bearing contaminants in the xenon gas. Furthermore, an optimized activation process, where the cathode is heated prior to ignition by an external heater to drive contaminants such as oxygen and moisture from the insert absorbed during exposure to ambient air, is necessary both for cathode longevity and a simplified power processor. In order to achieve the two year (approximately 17,500 hours) continuous operating lifetime requirement for the plasma contactor, a test program was initiated at NASA Lewis Research Center to demonstrate the extended lifetime capabilities of the hollow cathode. To date, xenon hollow cathodes have demonstrated extended lifetimes with one test having operated in excess of 8000 hours in an ongoing test utilizing contamination control protocols developed by Sarver-Verhey. The objectives of this study were to verify the transportability of the contamination control protocols developed by Sarver-Verhey and to evaluate cathode contamination control procedures, activation processes, and cathode-to-cathode dispersions in operating characteristics with time. These were accomplished by conducting a 2000 hour wear test of four hollow

  14. Anomalous transport modelling of tokamak plasmas

    SciTech Connect

    Kinsey, J.; Singer, C.; Malone, G.; Tiouririne, N.

    1992-12-31

    Theory based transport simulations of DIII-D, JET, ITER are compared to experimental data using a combination of anamolous transport models. The Multiple-mode Transport Model is calibrated to a give set of L-mode and H-mode discharges with an emphasis on testing the adequacy of anomalous flux contributions from drift/{eta}{sub i} and resistive ballooning mode theories. A survey of possible additions and/or alternatives to the model from recent theories on neoclassical MHD effects, hot ion modes, circulating electron modes, and high-m tearing modes is also included.

  15. Anomalous transport modelling of tokamak plasmas

    SciTech Connect

    Kinsey, J.; Singer, C.; Malone, G.; Tiouririne, N.

    1992-01-01

    Theory based transport simulations of DIII-D, JET, ITER are compared to experimental data using a combination of anamolous transport models. The Multiple-mode Transport Model is calibrated to a give set of L-mode and H-mode discharges with an emphasis on testing the adequacy of anomalous flux contributions from drift/[eta][sub i] and resistive ballooning mode theories. A survey of possible additions and/or alternatives to the model from recent theories on neoclassical MHD effects, hot ion modes, circulating electron modes, and high-m tearing modes is also included.

  16. The origin of anomalous muonium in semiconductors

    NASA Astrophysics Data System (ADS)

    Eshchenko, D. G.; Storchak, V. G.; Brewer, J. H.; Morris, G. D.; Clarker-Gayther, M. A.; Cottrell, S. P.; Cox, S. F. J.; Lord, J. S.

    2000-08-01

    The origin of muonium defect centers in semi-insulating GaAs has been studied using newly developed μSR techniques employing alternating electric fields. This technique prevents the accumulation of near-surface charges which may screen the external field. The screening effect was tested at ISIS by the measurements of the current induced by muon beam. Suppression of anomalous muonium signal with electric field suggests that muonium formation proceeds via transport of excess electrons from the ionization track to the muons.

  17. Anomalous thermal confinement in ohmically heated tokamaks

    SciTech Connect

    Romanelli, F.; Tang, W.M.; White, R.B.

    1986-02-01

    A model is proposed to explain the behavior of the gross energy confinement time in ohmically heated tokamak plasmas. The analysis takes into account the effect of the anomalous thermal conductivity due to small scale turbulence and of the macroscopic MHD behavior, which provides some constraints on the temperature profile. Results indicate that the thermal conductivity associated with the dissipative trapped-electron mode and with the ion temperature gradient (eta/sub i/) mode can account, respectively, for the Neo-Alcator scaling and the saturation of the energy confinement time with density. Comparisons with experimental results show reasonable agreement. 32 refs., 12 figs.

  18. Microinstability-based model for anomalous thermal confinement in tokamaks

    SciTech Connect

    Tang, W.M.

    1986-03-01

    This paper deals with the formulation of microinstability-based thermal transport coefficients (chi/sub j/) for the purpose of modelling anomalous energy confinement properties in tokamak plasmas. Attention is primarily focused on ohmically heated discharges and the associated anomalous electron thermal transport. An appropriate expression for chi/sub e/ is developed which is consistent with reasonable global constraints on the current and electron temperature profiles as well as with the key properties of the kinetic instabilities most likely to be present. Comparisons of confinement scaling trends predicted by this model with the empirical ohmic data base indicate quite favorable agreement. The subject of anomalous ion thermal transport and its implications for high density ohmic discharges and for auxiliary-heated plasmas is also addressed.

  19. Uniform hollow magnetite spheres: Facile synthesis, growth mechanism, and their magnetic properties

    SciTech Connect

    Zhou, Xing; Zhao, Guizhe; Liu, Yaqing

    2014-11-15

    Highlights: • Uniform Fe{sub 3}O{sub 4} hollow spheres with high saturation magnetization were synthesized through a simple solvothermal process. • Without using any hard templates or external magnetic field. • The as-prepared magnetite hollow spheres exhibit a ferromagnetic behavior with high Ms of ca. 85.9 emu/g at room temperature. • The morphology of Fe{sub 3}O{sub 4} with nanoparticles, hollow, and irregular structures could be adjusted by changing the reactive conditions. - Abstract: Hierarchical porous Fe{sub 3}O{sub 4} hollow spheres with high saturation magnetization were synthesized through a simple solvothermal process in ethylene glycol (EG) in the presence of Tetrabutylammonium chloride (TBAC) and urea. By investigating the effect of reaction temperature, time, the amount of urea, and concentration of iron ion on the formation of hollow spheres, it was proposed that the main formation mechanism of hollow spheres is Ostwald ripening process combined with assembly-then-inside-out evacuation process. Additionally, it is found that the morphology of Fe{sub 3}O{sub 4} with nanoparticles, hollow, and irregular structures could be adjusted by changing the above factors. The resulting products were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometer (VSM). The hierarchical porous Fe{sub 3}O{sub 4} hollow spheres exhibited enhanced saturation magnetization as compared with Fe{sub 3}O{sub 4} nanoparticles.

  20. Temporal Fluctuations in a 100-A LaB6 Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Jorns, Benjamin A.; Mikellides, Ioannis G.; Goebel, Dan M.

    2013-01-01

    The temporal fluctuations in the near plume of a 100-Amperes LaB6 (Lanthanum hexaboride) hollow cathode are experimentally investigated. At high currents, turbulent oscillations may contribute to two of the anomalous processes of hollow cathode operation - anomalous resistivity and the production of energetic ions. A detailed study of the properties of the oscillations in a high current cathode is necessary to determine the impact of the fluctuation spectrum on these two effects. In this investigation, a probe array is employed to measure the amplitude and dispersion of axial modes in the plume while a retarding potential analyzer yields estimates of the radial ion energy distribution. The onset of the ion acoustic turbulence (IAT) is observed at high current values, and the character of the turbulent spectrum is shown to agree with weak turbulent theory: the amplitude of the spectrum decreases with flow rate but increases with discharge current. Estimates of the anomalous collision frequency based on experimental observations indicate that the IAT collision frequency can exceed the classical collision frequency at sufficiently high discharge current densities. Additionally, the onset of the IAT is shown to be correlated with the appearance of a high energy ion tail and that the energy in this tail is comparable to the energy in the experimentally-observed IAT.

  1. Petrology of Anomalous Eucrites

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Peng, Z. X.; Ross, D. K.

    2015-01-01

    Most mafic achondrites can be broadly categorized as being "eucritic", that is, they are composed of a ferroan low-Ca clinopyroxene, high-Ca plagioclase and a silica phase. They are petrologically distinct from angritic basalts, which are composed of high-Ca, Al-Ti-rich clinopyroxene, Carich olivine, nearly pure anorthite and kirschsteinite, or from what might be called brachinitic basalts, which are composed of ferroan orthopyroxene and high-Ca clinopyroxene, intermediate-Ca plagioclase and ferroan olivine. Because of their similar mineralogy and composition, eucrite-like mafic achondrites formed on compositionally similar asteroids under similar conditions of temperature, pressure and oxygen fugacity. Some of them have distinctive isotopic compositions and petrologic characteristics that demonstrate formation on asteroids different from the parent of the HED clan (e.g., Ibitira, Northwest Africa (NWA) 011). Others show smaller oxygen isotopic distinctions but are otherwise petrologically and compositionally indistinguishable from basaltic eucrites (e.g., Pasamonte, Pecora Escarpment (PCA) 91007). The degree of uniformity in delta O-17 of eucrites and diogenites is one piece of evidence considered to favor of a magma-ocean scenario for their petrogenesis. Given that the O isotopic differences separating Pasamonte and PCA 91007 from other eucrites are small, and that there is an absence of other distinguishing characteristics, a legitimate question is: Did the HED parent asteroid fail to homogenize via a magma-ocean stage, thus explaining outliers like Pasamonte? We are initiating a program of study of anomalous eucrite-like achondrites as one part of our effort to seek a resolution of this issue. Here we present preliminary petrologic information on Asuka (A-) 881394, Elephant Moraine (EET) 87520 and EET 87542. We will have studied several more by conference time.

  2. Hollow Spheres in Composite Materials and Metallic Hollow Sphere Composites (MHSC)

    NASA Astrophysics Data System (ADS)

    Baumeister, Erika; Molitor, Martin

    The newly developed metallic hollow spheres are used in combination with a polymeric matrix for producing metallic hollow-sphere-composites (MSHC), which have been developed for mechanical engineering applications in the “InnoZellMet” project.

  3. Purification of nanoparticles by hollow fiber diafiltration

    NASA Astrophysics Data System (ADS)

    Veeken, J.

    2012-09-01

    Hollow Fiber Diafiltration (Hollow Fiber Tangential Flow Filtration) is an efficient and rapid alternative to traditional methods of nanoparticle purification such as ultracentrifugation, stirred cell filtration, dialysis or chromatography. Hollow Fiber Diafiltration can be used to purify a wide range of nanoparticles including liposomes, colloids, magnetic particles and nanotubes. Hollow Fiber Diafiltration is a membrane based method where pore size determines the retention or transmission of solution components. It is a flow process where the sample is gently circulated through a tubular membrane. With controlled replacement of the permeate or (dialysate), pure nanoparticles can be attained. Hollow Fiber Diafiltration can be directly scaled up from R&D volumes to production. By adding more membrane fibers and maintaining the operating parameters, large volumes can be processed in the same time with the same pressure, and flow dynamics as bench-scale volumes. Keywords: hollow fiber, Diafiltration, filtration, purification, tangential flow filtration.

  4. Microemulsion-based synthesis of nanoscale TiO 2 hollow spheres

    NASA Astrophysics Data System (ADS)

    Zurmühl, C.; Popescu, R.; Gerthsen, D.; Feldmann, C.

    2011-08-01

    Nanoscale TiO 2 hollow spheres are prepared based on gelatine-filled reversed microemulsions. The resulting nanomaterial exhibits an outer diameter of 25-35 nm, a thickness of the sphere wall of 4-6 nm and an inner cavity of 15-20 nm in diameter. The as-prepared hollow spheres are characterized based on different electron microscopic techniques, infrared spectroscopy and optical spectroscopy. Thermogravimetry, X-ray powder diffraction and sorption measurements according to the Brunauer-Emmett-Teller analysis are used to elucidate the thermal properties as well as the specific surface of the hollow spheres. Finally, the photocatalytic properties of as-prepared TiO 2 hollow spheres are studied.

  5. Hollow CoFe2O4-Co3Fe7 microspheres applied in electromagnetic absorption

    NASA Astrophysics Data System (ADS)

    Li, Wanxi; Wang, Liancheng; Li, Guomin; Xu, Yao

    2015-03-01

    In this work, monodisperse hollow cobalt ferrite (CoFe2O4) microspheres with mean diameter of 150 nm and shell thickness of 50 nm have been successfully prepared via a one-pot solvothermal method. In order to improve the microwave absorption, a thermal reduction process was designed to synthesize hollow CoFe2O4-Co3Fe7 microspheres. Scanning electron microscopy and transmission electron microscopy images showed that the CoFe2O4-Co3Fe7 microspheres retained hollow structure. Microwave absorption results revealed that hollow CoFe2O4-Co3Fe7 microspheres exhibited much stronger electromagnetic absorption than the original hollow CoFe2O4 microspheres. Most importantly, when the sample thickness was 1.3 mm, the reflection loss (RL) less than -10 dB was obtained in the frequency range of 12.5-17.7 GHz, which nearly covered the entire Ku-band. When the sample thickness increased to 2 mm, the minimum RL was as high as -41.6 dB with the effective bandwidth (the bandwidth of RL at -10 dB) of 3 GHz. The enhanced microwave absorption was attributed to efficient complement between dielectric loss and magnetic loss. These results indicated that the hollow CoFe2O4-Co3Fe7 microspheres could be used as a new candidate for microwave absorbents, especially in Ku-band.

  6. Controlled Synthesis of Hollow Manganese Oxide Nanocrystals.

    PubMed

    Nam, Ki Min; Oh, Kyung Hee; Ham, Kyung-Sik

    2016-02-01

    Carbon spheres have been prepared from glucose under hydrothermal conditions to facilitate the synthesis of hollow manganese oxides. The phases of manganese oxide are controlled by changing annealing temperature of the manganese monoxide on a carbon sphere template. The particles on the carbon surface get an agglomeration and make dense oxide shell during the calcination step, which result in typical hollow structures. The electrochemical properties of hollow manganese oxides have been investigated to elucidate their relative catalytic activities. PMID:27433689

  7. Process for making hollow carbon spheres

    DOEpatents

    Luhrs, Claudia C.; Phillips, Jonathan; Richard, Monique N.; Knapp, Angela Michelle

    2013-04-16

    A hollow carbon sphere having a carbon shell and an inner core is disclosed. The hollow carbon sphere has a total volume that is equal to a volume of the carbon shell plus an inner free volume within the carbon shell. The inner free volume is at least 25% of the total volume. In some instances, a nominal diameter of the hollow carbon sphere is between 10 and 180 nanometers.

  8. Method to fabricate hollow microneedle arrays

    DOEpatents

    Kravitz, Stanley H.; Ingersoll, David; Schmidt, Carrie; Flemming, Jeb

    2006-11-07

    An inexpensive and rapid method for fabricating arrays of hollow microneedles uses a photoetchable glass. Furthermore, the glass hollow microneedle array can be used to form a negative mold for replicating microneedles in biocompatible polymers or metals. These microneedle arrays can be used to extract fluids from plants or animals. Glucose transport through these hollow microneedles arrays has been found to be orders of magnitude more rapid than natural diffusion.

  9. Improved Rare-Earth Emitter Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Goebel, Dan M.

    2011-01-01

    An improvement has been made to the design of the hollow cathode geometry that was created for the rare-earth electron emitter described in Compact Rare Earth Emitter Hollow Cathode (NPO-44923), NASA Tech Briefs, Vol. 34, No. 3 (March 2010), p. 52. The original interior assembly was made entirely of graphite in order to be compatible with the LaB6 material, which cannot be touched by metals during operation due to boron diffusion causing embrittlement issues in high-temperature refractory materials. Also, the graphite tube was difficult to machine and was subject to vibration-induced fracturing. This innovation replaces the graphite tube with one made out of refractory metal that is relatively easy to manufacture. The cathode support tube is made of molybdenum or molybdenum-rhenium. This material is easily gun-bored to near the tolerances required, and finish machined with steps at each end that capture the orifice plate and the mounting flange. This provides the manufacturability and robustness needed for flight applications, and eliminates the need for expensive e-beam welding used in prior cathodes. The LaB6 insert is protected from direct contact with the refractory metal tube by thin, graphite sleeves in a cup-arrangement around the ends of the insert. The sleeves, insert, and orifice plate are held in place by a ceramic spacer and tungsten spring inserted inside the tube. To heat the cathode, an insulating tube is slipped around the refractory metal hollow tube, which can be made of high-temperature materials like boron nitride or aluminum nitride. A screw-shaped slot, or series of slots, is machined in the outside of the ceramic tube to constrain a refractory metal wire wound inside the slot that is used as the heater. The screw slot can hold a single heater wire that is then connected to the front of the cathode tube by tack-welding to complete the electrical circuit, or it can be a double slot that takes a bifilar wound heater with both leads coming out

  10. Barium Depletion in Hollow Cathode Emitters

    NASA Technical Reports Server (NTRS)

    Polk, James E.; Capece, Angela M.; Mikellides, Ioannis G.; Katz, Ira

    2009-01-01

    The effect of tungsten erosion, transport and redeposition on the operation of dispenser hollow cathodes was investigated in detailed examinations of the discharge cathode inserts from an 8200 hour and a 30,352 hour ion engine wear test. Erosion and subsequent re-deposition of tungsten in the electron emission zone at the downstream end of the insert reduces the porosity of the tungsten matrix, preventing the ow of barium from the interior. This inhibits the interfacial reactions of the barium-calcium-aluminate impregnant with the tungsten in the pores. A numerical model of barium transport in the internal xenon discharge plasma shows that the barium required to reduce the work function in the emission zone can be supplied from upstream through the gas phase. Barium that flows out of the pores of the tungsten insert is rapidly ionized in the xenon discharge and pushed back to the emitter surface by the electric field and drag from the xenon ion flow. This barium ion flux is sufficient to maintain a barium surface coverage at the downstream end greater than 0.6, even if local barium production at that point is inhibited by tungsten deposits. The model also shows that the neutral barium pressure exceeds the equilibrium vapor pressure of the impregnant decomposition reaction over much of the insert length, so the reactions are suppressed. Only a small region upstream of the zone blocked by tungsten deposits is active and supplies the required barium. These results indicate that hollow cathode failure models based on barium depletion rates in vacuum dispenser cathodes are very conservative.

  11. Rational synthesis of carbon-coated hollow Ge nanocrystals with enhanced lithium-storage properties

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Chu, Xiaoqing; Chen, Chaoji; Xiang, Jingwei; Liu, Xiaoxiao; Huang, Yunhui; Hu, Xianluo

    2016-06-01

    capability. The small size and the high structural integrity of hollow Ge@C structures contribute to the superior lithium-storage performances. Electronic supplementary information (ESI) available: TEM/SEM images, XRD pattern, TG results, XPS spectra, and electrochemical properties. See DOI: 10.1039/c6nr00937a

  12. A general approach towards multi-faceted hollow oxide composites using zeolitic imidazolate frameworks

    NASA Astrophysics Data System (ADS)

    Wu, Renbing; Wang, Dan Ping; Han, Jianyu; Liu, Hai; Zhou, Kun; Huang, Yizhong; Xu, Rong; Wei, Jun; Chen, Xiaodong; Chen, Zhong

    2014-12-01

    that these complex hollow oxide composites, especially the Co3O4/SiO2 hollow dodecahedra, exhibit a significantly enhanced photocatalytic performance as oxygen evolution photocatalysts. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05135a

  13. A Fiber Supercapacitor with High Energy Density Based on Hollow Graphene/Conducting Polymer Fiber Electrode.

    PubMed

    Qu, Guoxing; Cheng, Jianli; Li, Xiaodong; Yuan, Demao; Chen, Peining; Chen, Xuli; Wang, Bin; Peng, Huisheng

    2016-05-01

    A hollow graphene/conducting polymer composite fiber is created with high mechanical and electronic properties and used to fabricate novel fiber-shaped supercapacitors that display high energy densities and long life stability. The fiber supercapacitors can be woven into flexible powering textiles that are particularly promising for portable and wearable electronic devices. PMID:27001216

  14. Evidence for Anomalous Effects on the Current Evolution in Tokamak Operating Scenarios

    SciTech Connect

    Casper, T; Jayakumar, R; Allen, S; Holcomb, C; Makowski, M; Pearlstein, L; Berk, H; Greenfield, C; Luce, T; Petty, C; Politzer, P; Wade, M; Murakami, M; Kessel, C

    2006-10-03

    Alternatives to the usual picture of advanced tokamak (AT) discharges are those that form when anomalous effects alter the plasma current and pressure profiles and those that achieve stationary characteristics through mechanisms so that a measure of desired AT features is maintained without external current-profile control. Regimes exhibiting these characteristics are those where the safety factor (q) evolves to a stationary profile with the on-axis and minimum q {approx} 1 and those with a deeply hollow current channel and high values of q. Operating scenarios with high fusion performance at low current and where the inductively driven current density achieves a stationary configuration with either small or non-existing sawteeth may enhance the neutron fluence per pulse on ITER and future burning plasmas. Hollow current profile discharges exhibit high confinement and a strong ''box-like'' internal transport barrier (ITB). We present results providing evidence for current profile formation and evolution exhibiting features consistent with anomalous effects or with self-organizing mechanisms. Determination of the underlying physical processes leading to these anomalous effects is important for scaling of current experiments for application in future burning plasmas.

  15. Ring cusp/hollow cathode discharge chamber performance studies

    NASA Technical Reports Server (NTRS)

    Vaughn, J. A.; Wilbur, P. J.

    1988-01-01

    An experimental study performed to determine the effects of hollow cathode position, anode position, and ring cusp magnetic field configuration and strength on discharge chamber performance is described. The results are presented in terms of comparative plasma ion energy cost, extracted ion fraction, and beam profile data. Results show that the rate of primary electron loss to the anode decreases as the anode is moved downstream of the ring cusp toward the screen grid and that the loss rate of ions to hollow cathode surfaces are excessive if the cathode is located upstream of a point of peak magnetic flux density at the discharge chamber centerline. Moreover, the fraction of the ions produced that are lost to discharge chamber walls and ring magnet surfaces is reduced by positioning of the magnet rings so the plasma density is uniform over the grid surface, and adjusting their strength to a level where it is sufficient to prevent excessive ion losses by Bohm diffusion.

  16. A new method for the preparation of monoporous hollow microspheres.

    PubMed

    Chang, Ming-Wei; Stride, Eleanor; Edirisinghe, Mohan

    2010-04-01

    The feasibility of producing a hollow microsphere with a single hole in its shell by coaxial electrohydrodynamic atomization (CEHDA) is demonstrated. Polymethylsilsesquioxane (PMSQ) was used as a model shell material encapsulating a core of a volatile liquid, perfluorohexane (PFH), which was subsequently evaporated to produce the hollow microspheres. The diameters of the microspheres and of the single surface pore were controlled by varying the flow rate of the components, the concentration of the PMSQ solution, and the applied voltage in the CEHDA process. The particles were characterized by scanning electron microscopy, and the ranges obtained were 275-860 nm for the microsphere diameter and 35-135 nm for the pore size. The process overcomes several of the key problems associated with existing methods of monoporous microsphere formation including removing the need for elevated temperatures, multiple processing steps, and the use of surfactants and other additives. PMID:20095539

  17. Hollow cathode and ion accelerator system for current ion sources

    SciTech Connect

    Aston, G.

    1981-01-01

    A small self-heating hollow cathode has been designed and tested which uses a novel flowing plasma starting concept to eliminate the need for cathode heating elements and low work function insert materials. In a magnetic field free ion source, this cathode has reliably and repeatedly produced arc currents, using argon, of 100 ampere (the power supply limit) at arc voltages of 22 volts. The cathode operates with a high gas stagnation pressure and plasma density to produce field enhanced thermionic emission from the electron emitting surface, a 0.02mm thick rolled tungsten foil cylinder, without appreciable erosion of this surface. Possible applications of larger versions of this hollow cathode for use in neutral beam injector ion sources are discussed. An ion accelerator system has also been designed and tested which combines a unique arrangement of multiple hole and slit apertures to amplify the extracted ion current density by a factor of four during the ion acceleration process.

  18. Fabrication and upconversion luminescence properties of YF3:Er3+ hollow nanofibers via monoaxial electrospinning combined with fluorination method.

    PubMed

    Li, Dan; Dong, Xiangting; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

    2014-06-01

    YF3:Er3+ hollow nanofibers were successfully fabricated via fluorination of the relevant Y2O3:Er3+ hollow nanofibers which were obtained by calcining the electrospun PVP/[Y(NO3)3 + Er(NO3)3] composite nanofibers. The morphology and properties of the products were investigated in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and fluorescence spectrometer. YF3:Er3+ hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with the mean diameter of 172 +/- 23 nm, and YF3:Er3+ hollow nanofibers were composed of nanoparticles with the diameter ranging from 30 nm to 50 nm. Upconversion emission spectrum analysis manifested that YF3:Er3+ hollow nanofibers emitted strong green and weak red upconversion emission centering at 524 nm, 543 nm and 653 nm, respectively. The green emissions and the red emission were respectively originated from 2H11/2/4S3/2 --> 4I15/2 and 4F9/2 --> 4I15/2 energy levels transitions of the Er3+ ions. Moreover, the emitting colors of YF3:Er3+ hollow nanofibers were located in the green region in CIE chromaticity coordinates diagram. The luminescent intensity of YF3:Er3+ hollow nanofibers was increased remarkably with the increasing doping concentration of Er3+ ions. The possible formation mechanism of YF3:Er3+ upconversion luminescence hollow nanofibers was also discussed. This preparation technique could be applied to prepare other rare earth fluoride upconversion luminescence hollow nanofibers. PMID:24738372

  19. Structural analysis of hollow blades: Torsional stress analysis of hollow fan blades for aircraft jet engines

    NASA Technical Reports Server (NTRS)

    Ogawa, A.; Sofue, Y.; Isobe, T.

    1979-01-01

    A torsional stress analysis of hollow fans blades by the finite element method is presented. The fans are considered to be double circular arc blades, hollowed 30 percent, and twisted by a component of the centrifugal force by the rated revolution. The effects of blade hollowing on strength and rigidity are discussed. The effects of reinforcing webs, placed in the hollowed section in varying numbers and locations, on torsional rigidity and the convergence of stresses, are reported. A forecast of the 30 percent hollowing against torsional loadings is discussed.

  20. Instability of plasma plume of micro-hollow cathode discharge

    SciTech Connect

    Levko, D.; Bliokh, Y. P.; Gurovich, V. Tz.; Krasik, Ya. E.

    2015-11-15

    The micro-hollow cathode gas discharge driven by thermionic emission is studied using the two-dimensional particle-in-cell Monte Carlo collisions simulation. The electron current is extracted from the plasma plume penetrating into the keeper–anode space through a small keeper orifice from the cathode-keeper space. The results of simulations and a simplified analytical model showed that the plasma density and extracted current can exhibit deep modulation in the range of frequencies of tens of MHz. This modulation appears when the space-charge limited current between the plume boundary and the anode exceeds the plasma thermal electron current through the orifice.

  1. Microanalysis of extended-test xenon hollow cathodes

    NASA Technical Reports Server (NTRS)

    Verhey, Timothy R.; Patterson, Michael J.

    1991-01-01

    Four hollow cathode electron sources were analyzed via boroscopy, scanning electron microscopy, energy dispersive x ray analysis, and x ray diffraction analysis. These techniques were used to develop a preliminary understanding of the chemistry of the devices that arise from contamination due to inadequate feed-system integrity and improper insert activation. Two hollow cathodes were operated in an ion thruster simulator at an emission current of 23.0 A for approximately 500 hrs. The two tests differed in propellant-feed systems, discharge power supplies, and activation procedures. Tungsten deposition and barium tungstate formation on the internal cathode surfaces occurred during the first test, which were believed to result from oxygen contamination of the propellant feed-system. Consequently, the test facility was upgraded to reduce contamination, and the test was repeated. The second hollow cathode was found to have experienced significantly less tungsten deposition. A second pair of cathodes examined were the discharge and the neutralizer hollow cathodes used in a life-test of a 30-cm ring-cusp ion thruster at a 5.5 kW power level. The cathodes' test history was documented and the post-test microanalyses are described. The most significant change resulting from the life-test was substantial tungsten deposition on the internal cathode surfaces, as well as removal of material from the insert surface. In addition, barium tungstate and molybdate were found on insert surfaces. As a result of the cathode examinations, procedures and approaches were proposed for improved discharge ignition and cathode longevity.

  2. Anomalous Diffraction at Ultra-High Energy for Protein Crystallography

    SciTech Connect

    Jakoncic,J.; Di Michiel, M.; Zhong, Z.; Honkimaki, V.; Jouanneau, Y.; Stojanoff, V.

    2006-01-01

    Single-wavelength anomalous diffraction (SAD), multiwavelength anomalous diffraction (MAD) and single isomorphous replacement with anomalous scattering (SIRAS) phasing at ultra-high X-ray energy, 55 keV, are used successfully to determine a high-quality and high-resolution experimental electronic density map of hen egg-white lysozyme, a model protein. Several combinations, between single- and three-wavelength, with native data were exploited to demonstrate that standard phasing procedures with standard equipment and software can successfully be applied to three-dimensional crystal structure determination of a macromolecule, even at these very short wavelengths. For the first time, a high-quality three-dimensional molecular structure is reported from SAD phasing with ultra-high-energy X-rays. The quality of the crystallographic data and the experimental electron density maps meet current standards. The 2.7% anomalous signal from three Ho atoms, at the Ho K edge, was sufficient to obtain a remarkable electron density and build the first lanthanide structure for HEWL in its entirety.

  3. Anomalous positrons from heavy ion collisions: Past results and future plans

    SciTech Connect

    Betts, R.R.

    1989-01-01

    The current status of the experimental study of anomalous lines observed in the spectra of positrons produced in heavy ion collisions is reviewed. A new experiment to measure positron-electron coincidences is discussed. 26 refs., 14 figs., 2 tabs.

  4. Anomalous Quasiparticles on the Domain Wall Between Topological Insulators and Spin Ice Compounds

    NASA Astrophysics Data System (ADS)

    Kanazawa, I.; Sasaki, T.

    We have discussed the behavior of anomalous quasiparticle with fractional electronic charge on the domain wall between topological insulators and spin ice compounds from the standpoint of the field-theoretical formula.

  5. Developments in Hollow Graphite Fiber Technology

    NASA Technical Reports Server (NTRS)

    Stallcup, Michael; Brantley, Lott W., Jr. (Technical Monitor)

    2002-01-01

    Hollow graphite fibers will be lighter than standard solid graphite fibers and, thus, will save weight in optical components. This program will optimize the processing and properties of hollow carbon fibers developed by MER and to scale-up the processing to produce sufficient fiber for fabricating a large ultra-lightweight mirror for delivery to NASA.

  6. Scaling theory for anomalous semiclassical quantum transport

    NASA Astrophysics Data System (ADS)

    Sena-Junior, M. I.; Macêdo, A. M. S.

    2016-01-01

    Quantum transport through devices coupled to electron reservoirs can be described in terms of the full counting statistics (FCS) of charge transfer. Transport observables, such as conductance and shot-noise power are just cumulants of FCS and can be obtained from the sample's average density of transmission eigenvalues, which in turn can be obtained from a finite element representation of the saddle-point equation of the Keldysh (or supersymmetric) nonlinear sigma model, known as quantum circuit theory. Normal universal metallic behavior in the semiclassical regime is controlled by the presence of a Fabry-Pérot singularity in the average density of transmission eigenvalues. We present general conditions for the suppression of Fabry-Pérot modes in the semiclassical regime in a sample of arbitrary shape, a disordered conductor or a network of ballistic quantum dots, which leads to an anomalous metallic phase. Through a double-scaling limit, we derive a scaling equation for anomalous metallic transport, in the form of a nonlinear differential equation, which generalizes the ballistic-diffusive scaling equation of a normal metal. The two-parameter stationary solution of our scaling equation generalizes Dorokhov's universal single-parameter distribution of transmission eigenvalues. We provide a simple interpretation of the stationary solution using a thermodynamic analogy with a spin-glass system. As an application, we consider a system formed by a diffusive wire coupled via a barrier to normal-superconductor reservoirs. We observe anomalous reflectionless tunneling, when all perfectly transmitting channels are suppressed, which cannot be explained by the usual mechanism of disorder-induced opening of tunneling channels.

  7. High Current Hollow Cathode Plasma Plume Measurements

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Kamhawi, Hani; Williams, George J., Jr.

    2014-01-01

    Plasma plume measurements are reported for a hollow cathode assembly (HCA) operated at discharge currents of 50, 70, and 100 A at xenon flow rates between 19 - 46 standard cubic centimeter per minute. The HCA was centrally mounted in the NASA-300MS Hall Thruster and was operated in the "spot" and "plume" modes with additional data taken with an applied magnetic field. Langmuir probes, retarding potential analyzers, and optical emission spectroscopy were employed to measure plasma properties near the orifice of the HCA and to assess the charge state of the near-field plasma. Electron temperatures (2-6 electron volt) and plasma potentials are consistent with probe-measured values in previous investigations. Operation with an applied-field yields higher discharge voltages, increased Xe III production, and increased signals from the 833.5 nm C I line. While operating in plume mode and with an applied field, ion energy distribution measurements yield ions with energies significantly exceeding the applied discharge voltage. These findings are correlated with high-frequency oscillations associated with each mode.

  8. Synthesis of Hollow β-Phase GeO2 Nanoparticles.

    PubMed

    Zou, Xu; Liu, Bingbing; Li, Quanjun; Li, Zepeng; Liu, Bo; We, Wei; Li, Dongmei; Zou, Bo; Cui, Tian; Zou, Guangtian; Mao, Ho-kwang

    2015-02-01

    We fabricated mono-dispersed hollow waxberry shaped β-quartz GeO2 by a facile one-step synthesis in emulsion at room temperature. TEM images indicated that hollow waxberry shaped GeO2 were consisted of nano-sphere whose average size were estimated to be 20 nm. The growth mechanism and optical properties of the products were also investigated. It was found that addition of n-butanol and PVP were crucial factors to control the morphology of GeO2. The possible formation mechanism of the hollow interior is proposed as the Ostwald ripening. The optical properties of the β-GeO2 nanoparticles with hollow shapes were also studied with photoluminescence spectrum, which reveals a broad emission, suggesting potential applications in electronic and optoelectronic nanodevices. These attractive results provide us a new simple method further used to fabricate other specific hollow structure and indicate hollow waxberry shaped GeO2 may have potential applications in light-emitting nanodevices. PMID:26353722

  9. Model of the Plasma Potential Distribution in the Plume of a Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Katz, Ira; Mikellides, Ioannis G.; Goebel, Dan M.

    2004-01-01

    In this paper we present results from a new model of the plasma potentials in the plume just downstream of the hollow cathode keeper. We examine the electron drift velocity as the hollow cathode plasma and neutral gas expand downstream of the keeper. If the drift velocity exceeds the thermal velocity a double layer potential structure develops that is the source of hot electrons. Ions are accelerated upstream through the double layer. The locations of the double layers are calculated using a simple model. It is shown that as the cathode gas flow increases, the location of the double layer moves farther downstream.

  10. Geometrical Aspects of a Hollow-cathode Magnetron (HCM)

    SciTech Connect

    Cohen, Samuel, A.; Wang, Zhehui

    1998-11-01

    A hollow-cathode magnetron (HCM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS), is operable at substantially lower pressures than its planar-magnetron counterpart. We have studied the dependence of magnetron operational parameters on the inner diameter D and length L of a cylindrical HCS. Only when L is greater than L sub zero, a critical length, is the HCM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic or primary electron transport. At pressures above 1 mTorr, an electron-impact ionization model with Bohm diffusion at a temperature equivalent to one-half the primary electron energy and with an ambipolar constraint can explain the ion-electron pair creation required to sustain the discharge. The critical length L sub zero is determined by the magnetization length of the primary electrons.

  11. Anomalous-viscosity current drive

    DOEpatents

    Stix, T.H.; Ono, M.

    1986-04-25

    The present invention relates to a method and apparatus for maintaining a steady-state current for magnetically confining the plasma in a toroidal magnetic confinement device using anomalous viscosity current drive. A second aspect of this invention relates to an apparatus and method for the start-up of a magnetically confined toroidal plasma.

  12. POROUS WALL, HOLLOW GLASS MICROSPHERES

    SciTech Connect

    Sexton, W.

    2012-06-30

    Hollow Glass Microspheres (HGM) is not a new technology. All one has to do is go to the internet and Google{trademark} HGM. Anyone can buy HGM and they have a wide variety of uses. HGM are usually between 1 to 100 microns in diameter, although their size can range from 100 nanometers to 5 millimeters in diameter. HGM are used as lightweight filler in composite materials such as syntactic foam and lightweight concrete. In 1968 a patent was issued to W. Beck of the 3M{trademark} Company for 'Glass Bubbles Prepared by Reheating Solid Glass Particles'. In 1983 P. Howell was issued a patent for 'Glass Bubbles of Increased Collapse Strength' and in 1988 H. Marshall was issued a patent for 'Glass Microbubbles'. Now Google{trademark}, Porous Wall, Hollow Glass Microspheres (PW-HGMs), the key words here are Porous Wall. Almost every article has its beginning with the research done at the Savannah River National Laboratory (SRNL). The Savannah River Site (SRS) where SRNL is located has a long and successful history of working with hydrogen and its isotopes for national security, energy, waste management and environmental remediation applications. This includes more than 30 years of experience developing, processing, and implementing special ceramics, including glasses for a variety of Department of Energy (DOE) missions. In the case of glasses, SRS and SRNL have been involved in both the science and engineering of vitreous or glass based systems. As a part of this glass experience and expertise, SRNL has developed a number of niches in the glass arena, one of which is the development of porous glass systems for a variety of applications. These porous glass systems include sol gel glasses, which include both xerogels and aerogels, as well as phase separated glass compositions, that can be subsequently treated to produce another unique type of porosity within the glass forms. The porous glasses can increase the surface area compared to 'normal glasses of a 1 to 2 order of

  13. Anomalous transport induced by sheath instability in Hall effect thrusters

    SciTech Connect

    Taccogna, Francesco; Schneider, Ralf

    2009-06-22

    It is well recognized to ascribe the anomalous cross-field conductivity inside Hall-effect thrusters to fluctuation-induced transport due to gradient-driven instabilities (Rayleigh or electron drift) and to electron-wall interaction (near-wall conductivity). In this letter, we have performed numerical experiments showing the possibility of another mechanism inducing azimuthal fluctuations: the lateral sheath instability. It is created by a negative differential resistance of the current-voltage I-V characteristic of the floating wall as a consequence of high secondary electron emission. The contribution from this effect to the anomalous axial current is calculated and it accounts of more than 80% of the experimental value.

  14. A simple route to synthesize ZnFe2O4 hollow spheres and their magnetorheological characteristics

    NASA Astrophysics Data System (ADS)

    Jiang, Wanquan; Cao, Zhen; Gu, Rui; Ye, Xingzhu; Jiang, Cuifeng; Gong, Xinglong

    2009-12-01

    In this paper, a simple route to synthesize hollow spheres of ZnFe2O4 without the assistance of a template is reported. The crystal structure and morphology of these particles were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). It was found that the final products were hollow spheres with perfect morphology, and their size and the thickness of their shells decreased with the increase of urea precursor. Ferromagnetism was observed from the magnetic hysteresis loops of the ZnFe2O4 hollow spheres at room temperature. The possible formation mechanism of the hollow spheres is discussed. In addition, ZnFe2O4 magnetorheological (MR) fluids were prepared and then their MR effect was investigated on a rotational rheometer equipped with a magnetic field generator.

  15. Cobalt oxide hollow microspheres with micro- and nano-scale composite structure: Fabrication and electrochemical performance

    NASA Astrophysics Data System (ADS)

    Tao, Feifei; Gao, Cuiling; Wen, Zhenhai; Wang, Qiang; Li, Jinghong; Xu, Zheng

    2009-05-01

    Co 3O 4 hollow microspheres with micro- and nano-scale composite structure self-assembled by nanosheets were successfully fabricated by the template-free wet-chemical approach. This method is simple, facile and effective. The Co 3O 4 hollow microspheres with good purity and homogeneous size were well characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR (FTIR), thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectrometer (ICP). The formation mechanism was deeply studied. The micro- and nano-scale composite structure constructed by the porous nanosheets promotes to improve the electrochemical properties of Co 3O 4 hollow microspheres. The high discharge capacity of 1048 mAh g -1 indicates it to be the potential application in electrode materials of Li-ion battery.

  16. Controllable synthesis of helical, straight, hollow and nitrogen-doped carbon nanofibers and their magnetic properties

    SciTech Connect

    Li, Xun; Xu, Zheng

    2012-12-15

    Graphical abstract: The helical, straight and hollow carbon nanofibers can be selectively synthesized by adjusting either the reaction temperature or feed gas composition. Display Omitted Highlights: ► CNFs were synthesized via pyrolysis of acetylene on copper NPs. ► The helical, straight, hollow and N-doped CNFs can be selectively synthesized. ► The growth mechanism of different types of CNFs was proposed. -- Abstract: Carbon nanofibers (CNFs) with various morphologies were synthesized by catalytic pyrolysis of acetylene on copper nanoparticles which were generated from the in situ decomposition of copper acetylacetonate. The morphology of the pristine and acid-washed CNFs was investigated by field emission scanning electron microscope and high-resolution transmission electron microscope. Helical, straight and hollow CNFs can be selectively synthesized by adjusting either the reaction temperature or feed gas composition. The growth mechanism for these three types of CNFs was proposed.

  17. Two-dimensional model of orificed micro-hollow cathode discharge for space application

    SciTech Connect

    Levko, D.; Krasik, Ya. E.; Vekselman, V.; Haber, I.

    2013-08-15

    In this paper, we describe results of self-consistent two-dimensional (x-z) particle-in-cell simulations, with a Monte Carlo collision model, of an orificed micro-hollow cathode operating in a planar diode geometry. The model includes thermionic electron emission with Schottky effect, secondary electron emission due to cathode bombardment by the plasma ions, several different collision processes, and a non-uniform xenon background gas density in the cathode-anode gap. Simulated results showing behavior of the plasma density, potential distribution, and energy flux towards the hollow cathode and orifice walls, are discussed. In addition, results of simulations showing the effect of different Xe gas pressures, orifice size, and cathode voltage, on operation of the micro-hollow cathode are presented.

  18. Revisiting the Anomalous rf Field Penetration into a Warm Plasma

    SciTech Connect

    Igor D. Kaganovich; Oleg V. Polomarov; Constantine E. Theodosiou

    2005-06-24

    Radio-frequency [rf] waves do not penetrate into a plasma and are damped within it. The electric field of the wave and plasma current are concentrated near the plasma boundary in a skin layer. Electrons can transport the plasma current away from the skin layer due to their thermal motion. As a result, the width of the skin layer increases when electron temperature effects are taken into account. This phenomenon is called anomalous skin effect. The anomalous penetration of the rf electric field occurs not only for transversely propagating to the plasma boundary wave (inductively coupled plasmas) but also for the wave propagating along the plasma boundary (capacitively coupled plasmas). Such anomalous penetration of the rf field modifies the structure of the capacitive sheath. Recent advances in the nonlinear, non-local theory of the capacitive sheath are reported. It is shown that separating the electric field profile into exponential and non-exponential parts yields an efficient qualitative and quantitative description of the anomalous skin effect in both inductively and capacitively coupled plasma.

  19. Hollow GdPO4:Eu3+ microspheres: Luminescent properties and applications as drug carrier

    NASA Astrophysics Data System (ADS)

    Tang, Yanxia; Mei, Rui; Yang, Shaokun; Tang, Hongxia; Yin, Wenzhong; Xu, Yongchun; Gao, Yaping

    2016-04-01

    GdPO4:Eu3+ samples were synthesized by a hydrothermal process using melamine formaldehyde (MF) as template. The X-ray diffraction (XRD) patterns and the Fourier Transform Infrared (FTIR) spectrum suggested that GdPO4:Eu3+ has a hexagonal phase. The scanning electron microscope (SEM) and transmission electron microscope (TEM) images showed that the obtained GdPO4:Eu3+ are hollow microspheres with diameters in the range of 1-1.5 μm. Under the excitation at 245 nm, hexagonal GdPO4:Eu3+ hollow microspheres showed emission bands originating from the 5D0 → 7FJ (J = 1, 2, 3 and 4) transitions of Eu3+. The drug release properties of hexagonal GdPO4:Eu3+ hollow microspheres were exhibited by the doxorubicin hydrochloride (DOX) release test. The biocompatibility of hexagonal GdPO4:Eu3+ hollow microsphere was tested by the standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results indicated that hollow GdPO4:Eu3+ microspheres have potential applications in biomedicine fields.

  20. Non-lead hollow point bullet

    DOEpatents

    Vaughn, Norman L.; Lowden, Richard A.

    2003-04-15

    The non-lead hollow point bullet of the instant invention comprises a mixed construction slug further comprising, a monolithic metal insert having a tapered (preferred conical) hollow point tip and a tapered (preferred conical) tail protrusion, and an unsintered powdered metal composite core in tandem alignment with the insert. The core has a hollow tapered (preferred conical) cavity tip portion coupled with the tapered (preferred conical) tail protrusion on the insert. An open tip jacket envelops at least a portion of the insert and the core. The jacket is swaged at the open tip.

  1. Designing Hollow Nano Gold Golf Balls

    PubMed Central

    2015-01-01

    Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core. Selective gold plating of the core followed by removal of the polystyrene beads produced a golf ball-like nanostructure with 100 nm pits. Dissolution of the silica core produced a hollow/porous golf ball-like nanostructure. PMID:24937196

  2. Microring embedded hollow polymer fiber laser

    SciTech Connect

    Linslal, C. L. Sebastian, S.; Mathew, S.; Radhakrishnan, P.; Nampoori, V. P. N.; Girijavallabhan, C. P.; Kailasnath, M.

    2015-03-30

    Strongly modulated laser emission has been observed from rhodamine B doped microring resonator embedded in a hollow polymer optical fiber by transverse optical pumping. The microring resonator is fabricated on the inner wall of a hollow polymer fiber. Highly sharp lasing lines, strong mode selection, and a collimated laser beam are observed from the fiber. Nearly single mode lasing with a side mode suppression ratio of up to 11.8 dB is obtained from the strongly modulated lasing spectrum. The microring embedded hollow polymer fiber laser has shown efficient lasing characteristics even at a propagation length of 1.5 m.

  3. Method for producing small hollow spheres

    DOEpatents

    Hendricks, C.D.

    1979-01-09

    Method is disclosed for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T [approx gt] 600 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10[sup 3] [mu]m) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants. 1 fig.

  4. Method for producing small hollow spheres

    DOEpatents

    Hendricks, Charles D. [Livermore, CA

    1979-01-09

    Method for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T .gtorsim. 600.degree. C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10.sup.3 .mu.m) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants.

  5. Anomalous nonlinear X-ray Compton scattering

    NASA Astrophysics Data System (ADS)

    Fuchs, Matthias; Trigo, Mariano; Chen, Jian; Ghimire, Shambhu; Shwartz, Sharon; Kozina, Michael; Jiang, Mason; Henighan, Thomas; Bray, Crystal; Ndabashimiye, Georges; Bucksbaum, Philip H.; Feng, Yiping; Herrmann, Sven; Carini, Gabriella A.; Pines, Jack; Hart, Philip; Kenney, Christopher; Guillet, Serge; Boutet, Sébastien; Williams, Garth J.; Messerschmidt, Marc; Seibert, M. Marvin; Moeller, Stefan; Hastings, Jerome B.; Reis, David A.

    2015-11-01

    X-ray scattering is typically used as a weak linear atomic-scale probe of matter. At high intensities, such as produced at free-electron lasers, nonlinearities can become important, and the probe may no longer be considered weak. Here we report the observation of one of the most fundamental nonlinear X-ray-matter interactions: the concerted nonlinear Compton scattering of two identical hard X-ray photons producing a single higher-energy photon. The X-ray intensity reached 4 × 1020 W cm-2, corresponding to an electric field well above the atomic unit of strength and within almost four orders of magnitude of the quantum-electrodynamic critical field. We measure a signal from solid beryllium that scales quadratically in intensity, consistent with simultaneous non-resonant two-photon scattering from nearly-free electrons. The high-energy photons show an anomalously large redshift that is incompatible with a free-electron approximation for the ground-state electron distribution, suggesting an enhanced nonlinearity for scattering at large momentum transfer.

  6. Anomalous magnetic properties of VOx multiwall nanotubes

    NASA Astrophysics Data System (ADS)

    Demishev, S. V.; Chernobrovkin, A. L.; Glushkov, V. V.; Goodilin, E. A.; Grigorieva, A. V.; Ishchenko, T. V.; Kuznetsov, A. V.; Sluchanko, N. E.; Tretyakov, Yu D.; Semeno, A. V.

    2010-01-01

    Basing on the high frequency (60 GHz) electron spin resonance (ESR) and magnetic susceptibility study of the VOx multiwall nanotubes (VOx-NTs) in the range 4.2-300 K we report the ESR evidence of the presence of the antiferromagnetic V4+ dimers in VOx-NTs and the observation of an anomalous low temperature (T<50 K) growth of the magnetic susceptibility for V4+ quasi-free spins, which obey power law χ(T)~1/Tα with the exponent αapprox0.6. The estimates of the concentrations for various spin species (clusters) indicate that the non-interacting dimers should be an essential element in the VOx-NTs structure. The possibility of the disorder driven quantum critical regime in VOx-NTs is discussed.

  7. Photoinduced Anomalous Hall Effects in Weyl Semimetals

    NASA Astrophysics Data System (ADS)

    Chan, Ching-Kit; Lee, Patrick A.; Burch, Kenneth S.; Han, Jung Hoon; Ran, Ying

    We examine theoretically the interplay between chiral photons and chiral electrons in Weyl semimetals. Owing to its monopole nature, a three-dimensional Weyl node is topologically-robust against a circularly polarized light. A driven Weyl system exhibits node shifts in the momentum space, in sharp contrast to the gap opening in a driven two-dimensional Dirac system. We show that the node shift leads to a change of the Chern vector which gives arise to a net photoinduced anomalous Hall conductivity, in the plane perpendicular to the light propagation. We shall describe the basic idea behind this generic photoinduced Hall effect, illustrate it with a concrete microscope model, and estimate its feasibility based on current optical experimental techniques.

  8. Dielectric barrier structure with hollow electrodes and its recoil effect

    SciTech Connect

    Yu, Shuang; Chen, Qunzhi; Liu, Jiahui; Wang, Kaile; Jiang, Zhe; Sun, Zhili; Zhang, Jue; Fang, Jing

    2015-06-15

    A dielectric barrier structure with hollow electrodes (HEDBS), in which gas flow oriented parallel to the electric field, was proposed. Results showed that with this structure, air can be effectively ignited, forming atmospheric low temperature plasma, and the proposed HEDBS could achieve much higher electron density (5 × 10{sup 15}/cm{sup 3}). It was also found that the flow condition, including outlet diameter and flow rate, played a key role in the evolution of electron density. Optical emission spectroscopy diagnostic results showed that the concentration of reactive species had the same variation trend as the electron density. The simulated distribution of discharge gas flow indicated that the HEDBS had a strong recoil effect on discharge gas, and could efficiently promote generating electron density as well as reactive species.

  9. Electron beam device

    DOEpatents

    Beckner, E.H.; Clauser, M.J.

    1975-08-12

    This patent pertains to an electron beam device in which a hollow target is symmetrically irradiated by a high energy, pulsed electron beam about its periphery and wherein the outer portion of the target has a thickness slightly greater than required to absorb the electron beam pulse energy. (auth)

  10. High Current Hollow Cathode Plasma Plume Measurements

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Kamhawi, Hani; Williams, George J., Jr.

    2013-01-01

    Plasma plume measurements are reported for a hollow cathode assembly (HCA) oper-ated at discharge currents of 50, 70, and 100 A at xenon ow rates between 19 - 46 sccm.The HCA was centrally mounted in the annulus of the NASA-300MS Hall Thruster andwas operated in the spot and plume modes with additional data taken with an appliedmagnetic eld. Langmuir probes, retarding potential analyzers, and optical emission spec-troscopy were employed to measure plasma properties near the orice of the HCA and toassess the charge state of the near-eld plasma. Electron temperatures (2-6 eV) and plasmapotentials are consistent with probe-measured values in previous investigations. Operationwith an applied-eld yields higher discharge voltages, increased Xe III production, andincreased signals from the 833.5 nm C I line. While operating in plume mode and with anapplied eld, ion energy distribution measurements yield ions with energies signicantlyexceeding the applied discharge voltage. These ndings are correlated with high-frequencyoscillations associated with each mode.

  11. Magnetic effects in anomalous dispersion

    SciTech Connect

    Blume, M.

    1992-12-31

    Spectacular enhancements of magnetic x-ray scattering have been predicted and observed experimentally. These effects are the result of resonant phenomena closely related to anomalous dispersion, and they are strongest at near-edge resonances. The theory of these resonances will be developed with particular attention to the symmetry properties of the scatterer. While the phenomena to be discussed concern magnetic properties the transitions are electric dipole or electric quadrupole in character and represent a subset of the usual anomalous dispersion phenomena. The polarization dependence of the scattering is also considered, and the polarization dependence for magnetic effects is related to that for charge scattering and to Templeton type anisotropic polarization phenomena. It has been found that the strongest effects occur in rare-earths and in actinides for M shell edges. In addition to the scattering properties the theory is applicable to ``forward scattering`` properties such as the Faraday effect and circular dichroism.

  12. O/W/O double emulsion-assisted synthesis and catalytic properties of CeO 2 hollow microspheres

    NASA Astrophysics Data System (ADS)

    Zhang, DongEn; Xie, Qing; Wang, MingYan; Zhang, XiaoBo; Li, ShanZhong; Han, GuiQuan; Ying, AiLing; Chen, AiMei; Gong, JunYan; Tong, ZhiWei

    2010-09-01

    CeO 2 hollow microspheres have been fabricated through a simple thermal decomposition of precursor approach. The precursor with an average size of 10 μm was prepared in a reverse microemulsions containing Ce(NO 3) 3·6H 2O and CO(NH 2) 2 at 160 °C. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), selected area electron diffraction (SAED) and scanning electron microscopy (SEM). The possible formation mechanism of hollow spheres was discussed. In addition, the CeO 2 hollow microspheres modified glassy carbon electrode exhibit excellent sensing performance towards methyl orange, which provide a new application of CeO 2 hollow spheres. The catalytic activity of CeO 2 hollow spheres on the thermal decomposition of ammonium perchlorate (AP) also was investigated by TGA. The catalytic performance of CeO 2 hollow spheres is superior to that of commercial CeO 2 powder.

  13. Hollow Alveolus-Like Nanovesicle Assembly with Metal-Encapsulated Hollow Zeolite Nanocrystals.

    PubMed

    Dai, Chengyi; Zhang, Anfeng; Liu, Min; Gu, Lin; Guo, Xinwen; Song, Chunshan

    2016-08-23

    Inspired by the vesicular structure of alveolus which has a porous nanovesicle structure facilitating the transport of oxygen and carbon dioxide, we designed a hollow nanovesicle assembly with metal-encapsulated hollow zeolite that would enhance diffusion of reactants/products and inhibit sintering and leaching of active metals. This zeolitic nanovesicle has been successfully synthesized by a strategy which involves a one-pot hydrothermal synthesis of hollow assembly of metal-containing solid zeolite crystals without a structural template and a selective desilication-recrystallization accompanied by leaching-hydrolysis to convert the metal-containing solid crystals into metal-encapsulated hollow crystals. We demonstrate the strategy in synthesizing a hollow nanovesicle assembly of Fe2O3-encapsulated hollow crystals of ZSM-5 zeolite. This material possesses a microporous (0.4-0.6 nm) wall of hollow crystals and a mesoporous (5-17 nm) shell of nanovesicle with macropores (about 350 nm) in the core. This hierarchical structure enables excellent Fe2O3 dispersion (3-4 nm) and resistance to sintering even at 800 °C; facilitates the transport of reactant/products; and exhibits superior activity and resistance to leaching in phenol degradation. Hollow nanovesicle assembly of Fe-Pt bimetal-encapsulated hollow ZSM-5 crystals was also prepared. PMID:27429013

  14. One-Dimensional Solutions for Transient Thermal Stresses in Functionally Graded Hollow Cylinders and Hollow Spheres

    NASA Astrophysics Data System (ADS)

    Ootao, Yoshihiro; Tanigawa, Yoshinobu

    2008-02-01

    This paper is concerned with the theoretical treatment of transient thermoelastic problems involving functionally graded hollow cylinders and hollow spheres due to uniform heat supply. The thermal and thermoelastic coefficients of the hollow cylinders and hollow spheres are expressed as power functions of the radial coordinate. The one-dimensional solutions for the temperature changes in a transient state and the thermoelastic response are obtained herein. Some numerical results are shown in figures. Furthermore, the influence of the material nonhomogeneity on the temperature change, displacements and stresses is investigated.

  15. Three-dimensional reconstruction of anomalous eutectic in laser remelted Ni-30 wt.% Sn alloy

    NASA Astrophysics Data System (ADS)

    Cao, Yong-Qing; Lin, Xin; Wang, Zhi-Tai; Wang, Li-Lin; Song, Meng-Hua; Yang, Hai-Ou; Huang, Wei-Dong

    2015-12-01

    Laser remelting has been performed on Ni-30 wt.% Sn hypoeutectic alloy. An anomalous eutectic formed at the bottom of the molten pool when the sample was remelted thoroughly. 3D morphologies of the α-Ni and Ni3Sn phases in the anomalous eutectic region were obtained and investigated using serial sectioning reconstruction technology. It is found that the Ni3Sn phase has a continuous interconnected network structure and the α-Ni phase is distributed as separate particles in the anomalous eutectic, which is consistent with the electron backscatter diffraction pattern examinations. The α-Ni particles in the anomalous eutectic are supersaturated with Sn element as compared with the equilibrium phase diagram. Meanwhile, small wavy lamella eutectics coexist with anomalous eutectics. The Trivedi-Magnin-Kurz model was used to estimate undercooling with lamellar spacing. The results suggest that the critical undercooling found in undercooling solidification is not a sufficient condition for anomalous eutectic formation. Besides, α-Ni particles in the anomalous eutectic do not exhibit a completely random misorientation and some neighboring α-Ni particles have the same orientation. It is shown that both the coupled and decoupled growth of the eutectic two phases can generate the α-Ni + Ni3Sn anomalous eutectic structure.

  16. Synthesis of mesoporous hollow silica nanospheres using polymeric micelles as template and their application as a drug-delivery carrier.

    PubMed

    Sasidharan, Manickam; Zenibana, Haruna; Nandi, Mahasweta; Bhaumik, Asim; Nakashima, Kenichi

    2013-10-01

    Mesoporous hollow silica nanospheres with uniform particle sizes of 31-33 nm have been successfully synthesized by cocondensation of tetramethoxysilane (TMOS) and alkyltrimethoxysilanes [RSi(OR)3], where the latter also acts as a porogen. ABC triblock copolymer micelles of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) with a core-shell-corona architecture have been employed as a soft template at pH 4. The cationic shell block with 2-vinyl pyridine groups facilitates the condensation of silica precursors under the sol-gel reaction conditions. Phenyltrimethoxysilane, octyltriethoxysilane, and octadecyltriethoxysilanes were used as porogens for generating mesopores in the shell matrix of hollow silica and the octadecyl precursor produced the largest mesopore among the different porogens, of dimension ca. 4.1 nm. The mesoporous hollow particles were thoroughly characterized by small-angle X-ray diffraction (SXRD), thermal (TG/DTA) and nitrogen sorption analyses, infra-red (FTIR) and nuclear magnetic resonance ((13)C-CP MAS NMR and (29)Si MAS NMR) spectroscopies, and transmission electron microscopy (TEM). The mesoporous hollow silica nanospheres have been investigated for drug-delivery application by an in vitro method using ibuprofen as a model drug. The hollow silica nanospheres exhibited higher storage capacity than the well-known mesoporous silica MCM-41. Propylamine functionalized hollow particles show a more sustained release pattern than their unfunctionalized counterparts, suggesting a huge potential of hollow silica nanospheres in the controlled delivery of small drug molecules. PMID:23887599

  17. Formation and stability of hollow MgO nanoshells.

    PubMed

    Krishnan, Gopi; Palasantzas, G; Kooi, B J

    2010-07-01

    High temperature annealing of gas phase synthesized Mg nanoparticles surrounded by an MgO shell leads to formation of hollow MgO nanoshells due to the evaporation assisted Kirkendall effect. Under electron beam exposure in TEM, the (220) MgO facets reduce their high surface energy by forming cube facets, which is followed by nanoshell size reduction and collapse within a few minutes. However, in ambient conditions the nanoshells remain stable for significant periods of time and further degrade by becoming filled with carbon while lossing any MgO identity. Finally, in moderate low vacuum they remained stable for months indicating promise for applications. PMID:21128428

  18. Comparative Spectroscopic Temperature Measurements In Hydrogen Hollow Cathode Glow Discharge

    NASA Astrophysics Data System (ADS)

    Majstorovic, G. Lj.; Šišovic, N. M.; Konjevic, N.

    2010-07-01

    We report results of optical emission spectroscopy measurements of rotational Trot and translational temperature Ttr of hydrogen molecules. The light source was hollow cathode glow discharge with titanium cathode operated in hydrogen at low pressure. The rotational temperature of excited electronic states of H2 was determined either from relative line intensities of the R branch of the GK ? B band or from the Q branch of the Fulcher-a diagonal band. The population of excited energy levels, determined from relative line intensities, was used to derive ro-vibronic temperature of the ground state of hydrogen molecule.

  19. Hollow rhodoliths increase Svalbard's shelf biodiversity

    PubMed Central

    Teichert, Sebastian

    2014-01-01

    Rhodoliths are coralline red algal assemblages that commonly occur in marine habitats from the tropics to polar latitudes. They form rigid structures of high-magnesium calcite and have a good fossil record. Here I show that rhodoliths are ecosystem engineers in a high Arctic environment that increase local biodiversity by providing habitat. Gouged by boring mussels, originally solid rhodoliths become hollow ecospheres intensely colonised by benthic organisms. In the examined shelf areas, biodiversity in rhodolith-bearing habitats is significantly greater than in habitats without rhodoliths and hollow rhodoliths yield a greater biodiversity than solid ones. This biodiversity, however, is threatened because hollow rhodoliths take a long time to form and are susceptible to global change and anthropogenic impacts such as trawl net fisheries that can destroy hollow rhodoliths. Rhodoliths and other forms of coralline red algae play a key role in a plurality of environments and need improved management and protection plans. PMID:25382656

  20. Hollow rhodoliths increase Svalbard's shelf biodiversity

    NASA Astrophysics Data System (ADS)

    Teichert, Sebastian

    2014-11-01

    Rhodoliths are coralline red algal assemblages that commonly occur in marine habitats from the tropics to polar latitudes. They form rigid structures of high-magnesium calcite and have a good fossil record. Here I show that rhodoliths are ecosystem engineers in a high Arctic environment that increase local biodiversity by providing habitat. Gouged by boring mussels, originally solid rhodoliths become hollow ecospheres intensely colonised by benthic organisms. In the examined shelf areas, biodiversity in rhodolith-bearing habitats is significantly greater than in habitats without rhodoliths and hollow rhodoliths yield a greater biodiversity than solid ones. This biodiversity, however, is threatened because hollow rhodoliths take a long time to form and are susceptible to global change and anthropogenic impacts such as trawl net fisheries that can destroy hollow rhodoliths. Rhodoliths and other forms of coralline red algae play a key role in a plurality of environments and need improved management and protection plans.

  1. Low Dielectric Constant Materials from Hollow Fibers and Plant Oil

    NASA Astrophysics Data System (ADS)

    Hong, Chang K.; Wool, Richard P.

    2003-03-01

    A new low dielectric constant (k) material suited to electronic materials applications was developed using hollow keratin fibers (HF) and chemically modified soyoil. High-speed microelectronics are facilitated by preventing the ``rubber necking", or slow-down of electrons on the printed wires through the use of low-k dielectrics. The unusual low k-value of the HF composite material derives both from the air (k = 1) in the hollow microcrystalline keratin fibers (k = 1.6), and the triglyceride molecules (k = 2.3), and is in the range of 1.7 to 2.7 at 100 MHz, depending on the HF fraction. These values are lower than that of the conventional silicon dioxide, (k = 3.8 to 4.2) or epoxy dielectric insulators. Also, the HF dielectric is lightweight (SG < 1) and rigid (Modulus > 2 GPa), with fracture toughness (1.0 MPa m^1/2) (and approximates the shape and feel of a silicon dioxide insulator. Multi-Chip-Module circuit printing results suggest that the low-cost composite made with HF (from avian sources) and plant oil (from soybean) has the potential to replace the dielectric in microchips and circuit boards in the ever-growing electronic materials field, in addition to many applications as a new lightweight composite material. Supported by EPA and DoE

  2. BOX-DEATH HOLLOW ROADLESS AREA, UTAH.

    USGS Publications Warehouse

    Weir, Gordon W.; Lane, Michael

    1984-01-01

    Geologic mapping, geochemical sampling, and a search for prospects and mineralized rock in the Box-Death Hollow Roadless Area, Utah indicate that there is little promise for the occurrence of mineral or energy resources in the area. Additional exploratory drilling by industry seems warranted if wells elsewhere in the region find oil or gas in strata as yet untested in the Box-Death Hollow Roadless Area.

  3. Liquid molded hollow cell core composite articles

    NASA Technical Reports Server (NTRS)

    Bernetich, Karl R. (Inventor)

    2005-01-01

    A hollow core composite assembly 10 is provided, including a hollow core base 12 having at least one open core surface 14, a bondable solid film 22 applied to the open core surface 14, at least one dry face ply 30 laid up dry and placed on top of the solid film 22, and a liquid resin 32 applied to the at least one dry face ply 30 and then cured.

  4. Nanotubes within transition metal silicate hollow spheres: Facile preparation and superior lithium storage performances

    SciTech Connect

    Zhang, Fan; An, Yongling; Zhai, Wei; Gao, Xueping; Feng, Jinkui; Ci, Lijie; Xiong, Shenglin

    2015-10-15

    Highlights: • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were successfully prepared by a facile hydrothermal method using SiO{sub 2} nanosphere. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were tested as anode materials for lithium batteries. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} delivered superior electrochemical performance. • The lithium storage mechanism is probe via cyclic voltammetry and XPS. - Abstract: A series of transition metal silicate hollow spheres, including cobalt silicate (Co{sub 2}SiO{sub 4}), manganese silicate (MnSiO{sub 3}) and copper silicate (CuSiO{sub 3}.2H{sub 2}O, CuSiO{sub 3} as abbreviation in the text) were prepared via a simple and economic hydrothermal method by using silica spheres as chemical template. Time-dependent experiments confirmed that the resultants formed a novel type of hierarchical structure, hollow spheres assembled by numerous one-dimensional (1D) nanotubes building blocks. For the first time, the transition metal silicate hollow spheres were characterized as novel anode materials of Li-ion battery, which presented superior lithium storage capacities, cycle performance and rate performance. The 1D nanotubes assembly and hollow interior endow this kind of material facilitate fast lithium ion and electron transport and accommodate the big volume change during the conversion reactions. Our study shows that low-cost transition metal silicate with rationally designed nanostructures can be promising anode materials for high capacity lithium-ion battery.

  5. Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries

    NASA Astrophysics Data System (ADS)

    Sasidharan, Manickam; Nakashima, Kenichi; Gunawardhana, Nanda; Yokoi, Toshiyuki; Ito, Masanori; Inoue, Masamichi; Yusa, Shin-Ichi; Yoshio, Masaki; Tatsumi, Takashi

    2011-11-01

    Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance (29Si MAS NMR and 13CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and

  6. Titania coated hollow glass microspheres for environmental applications

    NASA Astrophysics Data System (ADS)

    Koopman, Mark C.

    The potential applicability of titania coated hollow glass microspheres (HGMs) to the photocatalytic degradation of microbiological and organic chemical water pollutants could have dramatic positive effects on improving the quality of industrial wastewaters that empty into rivers and streams, as well as potential use in economically improving the quality of drinking water. Heterogeneous photocatalysis using titania has been extensively studied since the 1990's because of its non-toxic nature, its high quantum yield of electrons and photo-holes, and its ability to use ambient solar radiation as a power source. Although titania embodies extraordinarily attractive properties for a range of environmental applications, a viable substrate or method of using the material effectively has not been recognized. HGMs are particularly attractive as a support for titania because of their low density and high surface area to volume ratio, but details of how they react to imposed loading, wear, and impact have not been addressed, nor have materials engineering analyses that could maximize their utility been made. In this study we have examined the microstructure, morphology and micro-compression properties of two types of titania coated hollow microspheres, a commercially produced HGM and cenospheres, a derivative of fly ash. Comparisons of uncoated and titania coated hollow microspheres showed improved failure loads and facture energies for the titania coated materials over the uncoated hollow microspheres. Also, the relationship between failure load and hollow microsphere diameter was characterized and the function employed to explain part of the gain in average failure load for the HGMs. Microscopic examination of titania coated HGMs that were subjected to various turbulent conditions, as well as intentional fracture, indicated good interfacial integrity, which supports the viability of both types of HGMs for potential applications. The photocatalytic reactivity of the titania

  7. Measuring anomalous Wtb couplings at e^-p collider

    NASA Astrophysics Data System (ADS)

    Dutta, Sukanta; Goyal, Ashok; Kumar, Mukesh; Mellado, Bruce

    2015-12-01

    We study the accuracy with which the lowest order CP conserving anomalous Wtb couplings in the single top-quark production at the proposed large hadron electron collider can be probed. The one-dimensional distribution of various kinematic observables at the parton level MC and their asymmetries arising due to the presence of anomalous couplings both in the hadronic and leptonic W decay is examined. We find that at 95 % CL the anomalous coupling associated with the left-handed vector current can be measured at an accuracy of the order of ˜ 10^{-2}-10^{-3}, while those associated with the right-handed vector and left- as well as right-handed tensor currents have a sensitivity at the order of ˜ 10^{-1}-10^{-2} for the systematic uncertainty varying between 10-1 % at an integrated luminosity of 100 fb^{-1}. A comprehensive analysis of the combined covariance matrix derived from all one-dimensional distributions of kinematical observables is used to compute the errors in the anomalous couplings.

  8. Anomalous signal of solvent bromides used for phasing of lysozyme.

    PubMed

    Dauter, Z; Dauter, M

    1999-05-28

    The anomalous signal of bromide ions, present in the crystal structure of tetragonal hen egg-white lysozyme through the substitution of NaCl by NaBr in the crystallization medium, was used for phasing of X-ray data collected to 1.7 A resolution with a wavelength near the absorption edge of bromine. Phasing of a single wavelength data set, based purely on anomalous deltaf " contribution, led to easily interpretable electron density, equivalent to the complete multiwavelength anonalous dispersion phasing based on four-wavelength data. The classic small-structure direct methods program SHELXS run against all anomalous differences gave a successful solution of six highest peaks corresponding to six bromide ions in the structure with data limited up to a resolution of 3.5 A. Interpretable maps were obtained at a resolution up to 3.0 A using programs MLPHARE and DM. Bromide ions occupy well ordered positions at the protein surface. Phasing based on the single wavelength signal of anomalous scatterers introduced into the ordered solvent shell can be proposed as a tool for solving structures of well diffracting crystals. PMID:10339408

  9. Influence of the floating potential on micro-hollow cathode operation

    SciTech Connect

    Levko, D.; Bliokh, Y. P.; Krasik, Ya. E.

    2015-06-15

    The influence of a keeper electrode with a floating potential on the operation of a micro-hollow cathode is studied using the two-dimensional particle-in-cell Monte Carlo collisions model. The floating potential is determined self-consistently, taking into account the electron and ion charges collected by the keeper and the potential induced by the plasma non-compensated space charge. It is shown that the parameters of the micro-hollow cathode operation vary significantly, according to whether the keeper potential is floating or has a specified constant value.

  10. Chemical vapor deposition synthesis and photoluminescence properties of ZnS hollow microspheres

    SciTech Connect

    Pi Zhengbang; Su Xiaolu; Yang Chao; Tian Xike Pei Fang; Zhang Suxin; Zhen Jianhua

    2008-08-04

    ZnS hollow microspheres were prepared via a facile template-free chemical vapor deposition (CVD) route using metallic zinc powders and sulphur sublimed as reactants. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometer (EDX). The results showed that the as-prepared ZnS hollow spheres had uniform size about 4-8 {mu}m in diameter. The growth mechanism of such interesting was discussed. The optical property of the products was also recorded by means of photoluminescence (PL) spectroscopy.

  11. Nb{sub 2}O{sub 5} hollow nanospheres as anode material for enhanced performance in lithium ion batteries

    SciTech Connect

    Sasidharan, Manickam; Gunawardhana, Nanda; Yoshio, Masaki; Nakashima, Kenichi

    2012-09-15

    Graphical abstract: Nb{sub 2}O{sub 5} hollow nanosphere constructed electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles and maintains structural integrity and excellent cycling stability. Highlights: ► Nb{sub 2}O{sub 5} hollow nanospheres synthesis was synthesized by soft-template. ► Nb{sub 2}O{sub 5} hollow nanospheres were investigated as anode material in Li-ion battery. ► Nanostructured electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles. ► The electrode maintains the structural integrity and excellent cycling stability. ► Nanosized shell domain facilitates fast lithium intercalation/deintercalation. -- Abstract: Nb{sub 2}O{sub 5} hollow nanospheres of average diameter ca. ∼29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb{sub 2}O{sub 5} hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g{sup −1}. The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb{sub 2}O{sub 5} shell domain that facilitates fast lithium intercalation/deintercalation kinetics.

  12. Method and device for detecting impact events on a security barrier which includes a hollow rebar allowing insertion and removal of an optical fiber

    DOEpatents

    Pies, Ross E.

    2016-03-29

    A method and device for the detection of impact events on a security barrier. A hollow rebar is farmed within a security barrier, whereby the hollow rebar is completely surrounded by the security barrier. An optical fiber passes through the interior of the hollow rebar. An optical transmitter and an optical receiver are both optically connected to the optical fiber and connected to optical electronics. The optical electronics are configured to provide notification upon the detection of an impact event at the security barrier based on the detection of disturbances within the optical fiber.

  13. Graphene-based hollow TiO2 composites with enhanced photocatalytic activity for removal of pollutants

    NASA Astrophysics Data System (ADS)

    Zhang, Lixin; Zhang, Jia; Jiu, Hongfang; Ni, Changhui; Zhang, Xia; Xu, Meiling

    2015-11-01

    Catalytically active graphene-based hollow TiO2 composites(TiO2/RGO) were successfully synthesized via the solvothermal method. Hollow TiO2 microspheres are uniformly dispersed on RGO. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) were used for the characterization of prepared photocatalysts. The mass of GO was optimized in the photocatalytic removal of rhodamine B (RhB) as a model dye pollutants. The results showed that graphene-based hollow TiO2 composites exhibit a significantly enhanced photocatalytic activity in degradation of RhB under either UV or visible light irradiation. The formation of the graphene-based hollow TiO2 composites and the photocatalytic mechanisms under UV and visible light were also discussed.

  14. A template-free method for stable CuO hollow microspheres fabricated from a metal organic framework (HKUST-1)

    NASA Astrophysics Data System (ADS)

    Zhang, Suoying; Liu, Hong; Liu, Pengfei; Yang, Zhuhong; Feng, Xin; Huo, Fengwei; Lu, Xiaohua

    2015-05-01

    Uniform CuO hollow microspheres were successfully achieved from a non-uniform metal organic framework by using a template-free method. The process mechanism has been revealed to be spherical aggregation and Ostwald ripening. When tested in CO oxidation and heat treatment, these assembled microspheres exhibited an excellent catalytic performance and show a much better stability than the inherited hollow structure from MOFs.Uniform CuO hollow microspheres were successfully achieved from a non-uniform metal organic framework by using a template-free method. The process mechanism has been revealed to be spherical aggregation and Ostwald ripening. When tested in CO oxidation and heat treatment, these assembled microspheres exhibited an excellent catalytic performance and show a much better stability than the inherited hollow structure from MOFs. Electronic supplementary information (ESI) available: The experiment details, auxiliary FESEM, XRD, BET and TG results of synthesized products. See DOI: 10.1039/c5nr01443c

  15. One-step synthesis of Zn/ZnO hollow nanoparticles by the laser ablation in liquid technique

    NASA Astrophysics Data System (ADS)

    Desarkar, H. S.; Kumbhakar, P.; Mitra, A. K.

    2013-05-01

    Here, one-step synthesis of Zn/ZnO hollow nanoparticles along with solid nanoparticles is reported using the laser ablation in liquid (LAL) technique. Laser radiation of the 1064 nm wavelength is emitted from a Q-switched Nd:YAG laser and is incident on a solid zinc target kept in a water medium. The as-obtained hollow and solid particles are characterized by transmission electron microscopy (TEM) and UV-visible absorption spectroscopy. Hollow nanoparticles are produced by the laser generated bubbles produced in water. The surface of a hollow nanoparticle is assembled from smaller solid nanoparticles. A strong laser-particle interaction is also observed when laser ablation is carried out for a longer time duration. Photoluminescence (PL) emission measurements at room temperature show that all samples exhibit PL emission in the UV-visible region. A reduction in size and an increase in concentration of the synthesized nanoparticles is observed with increasing laser ablation time.

  16. Template Synthesis of Shape-Tailorable NiS2 Hollow Prisms as High-Performance Supercapacitor Materials.

    PubMed

    Dai, Ziyang; Zang, Xiaoxian; Yang, Jun; Sun, Chencheng; Si, Weili; Huang, Wei; Dong, Xiaochen

    2015-11-18

    Uniform NiS2 hollow nanoprisms have been controllably synthesized by a facial sacrificial template method including two-step refluxed reactions. The morphology of the hollow NiS2 prisms can be easily tailored by the low cost nickel complex template. With unique hollow structure, efficient electron, and ion transport pathway as well as single crystal structure, the NiS2 hollow prisms electrode exhibits excellent pseudocapacitive performance in LiOH electrolyte. It can deliver a specific capacitance of 1725 F g(-1) at a current density of 5 A g(-1) and 1193 F g(-1) even at a current density of 40 A g(-1). Furthermore, the materials also present an amazing cycling stability, that is, the specific capacitance can increase from 1367 F g(-1) to 1680 F g(-1) after 10,000 cycles of charge-discharge at the current density of 20 A g(-1). PMID:26501765

  17. Up-conversion in rare earth-doped silica hollow spheres

    NASA Astrophysics Data System (ADS)

    Fortes, Luís M.; Li, Yigang; Réfega, Ricardo; Clara Gonçalves, M.

    2012-06-01

    In the present work, Er/Yb co-doped silica hollow spheres are prepared in a two-step process. In a first step, polystyrene-core is silica coated in situ by a modified Stöber sol-gel method and in the second one, the sacrificial polystyrene core is thermally removed. The core-shell and the hollow spheres are characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PL). PL measurements show up-conversion phenomena upon excitation at 975 nm, through the emission of blue (˜490 nm), green (˜523 nm and ˜536 nm) and red (˜655 nm) light. The up-conversion phenomena are discussed and modelled. The developed model explains the up-conversion phenomena of Er/Yb co-doped silica hollow spheres, with special agreement for high Yb/Er ratio.

  18. Interfacially Controlled Synthesis of Hollow Mesoporous Silica Spheres with Radially Oriented Pore Structures

    SciTech Connect

    Li, Juan; Liu, Jun; Wang, Donghai; Guo, Ruisong; Li, Xiaolin; Qi, Wen N.

    2010-06-24

    This paper reports an alternative process to prepare hollow mesoporous silica spheres (HMS) using a single cationic surfactant with a tunable wall thickness and radially oriented pore structures. Using N,N-dimethylformide (DMF) as the intermediate solvent bridging the organic and aqueous phase, hollow mesoporous silica spheres were synthesized with interfacial hydrolysis reactions at the surface of liquid droplets. These spheres have an ordered pore structure aligned along the radial direction, and the wall thickness and sphere sizes can be tuned by adjusting the experimental conditions. Transmission electron microscopy and nitrogen absorption techniques were used to characterize HMS and its formation procedure. A hypothetic formation mechanism was proposed on the basis of a morphology transformation with the correct amount of DMF and a careful observation of the early hydrolysis stages. Au and magnetic Fe3O4 nanoparticles have been encapsulated in the HMS hollow core for potential applications.

  19. Interfacially controlled synthesis of hollow mesoporous silica spheres with radially oriented pore structures.

    PubMed

    Li, Juan; Liu, Jun; Wang, Donghai; Guo, Ruisong; Li, Xiaolin; Qi, Wen

    2010-07-20

    This paper reports an alternative process to prepare hollow mesoporous silica spheres (HMS) using a single cationic surfactant with a tunable wall thickness and radially oriented pore structures. Using N,N-dimethylformide (DMF) as the intermediate solvent bridging the organic and aqueous phase, hollow mesoporous silica spheres were synthesized with interfacial hydrolysis reactions at the surface of liquid droplets. These spheres have an ordered pore structure aligned along the radial direction, and the wall thickness and sphere sizes can be tuned by adjusting the experimental conditions. Transmission electron microscopy and nitrogen absorption techniques were used to characterize HMS and its formation procedure. A hypothetic formation mechanism was proposed on the basis of a morphology transformation with the correct amount of DMF and a careful observation of the early hydrolysis stages. Au and magnetic Fe(3)O(4) nanoparticles have been encapsulated in the HMS hollow core for potential applications. PMID:20575542

  20. Efficient rapid microwave-assisted route to synthesize InP micrometer hollow spheres

    SciTech Connect

    Zheng Xiuwen Hu Qitu; Sun Chuansheng

    2009-01-08

    The efficiencies of two methods of synthesizing InP micro-scale hollow spheres are compared via the analogous solution-liquid-solid (ASLS) growth mechanism, either through a traditional solvothermal procedure, or via a microwave-assisted method. Scanning electronic microscopy (SEM) images show that most of the as-grown samples are micrometer hollow spheres, which indicates the efficiency of both methods. For traditional solvothermal route, long time (10 h) is necessary to obtain the desired samples, however, for the microwave-assisted route, 30 min is enough for hollow spherical products. An optimal choice of microwave irradiating time allows reducing the reaction time from hours to minutes. The proposed ASLS growth mechanism has also been discussed in detail.

  1. Hollow Block Copolymer Nanoparticles through a Spontaneous One-Step Structural Reorganization

    PubMed Central

    Petzetakis, Nikos; Robin, Mathew P.; Patterson, Joseph P.; Kelley, Elizabeth G.; Cotanda, Pepa; Bomans, Paul H. H.; Sommerdijk, Nico A. J. M.; Dove, Andrew P.; Epps, Thomas H.; O'Reilly, Rachel K.

    2013-01-01

    The spontaneous one-step synthesis of hollow nanocages and nanotubes from spherical and cylindrical micelles based on poly(acrylic acid)-b-polylactide (P(AA)-b-P(LA)) block copolymers (BCPs) has been achieved. This structural reorganization, which occurs simply upon drying of the samples, was elucidated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). We show that it was necessary to use stain-free imaging to examine these nanoscale assemblies, as the hollow nature of the particles was obscured by application of a heavy metal stain. Additionally, the internal topology of the P(AA)-b-P(LA) particles could be tuned by manipulating the drying conditions to give solid or compartmentalized structures. Upon re-suspension, these reorganized nanoparticles retain their hollow structure and can be display significantly enhanced loading of a hydrophobic dye compared to the original cylinders. PMID:23391297

  2. Destructive Evaluation of a Xenon Hollow Cathode after a 28,000 Hour Life Test

    NASA Technical Reports Server (NTRS)

    Sarver-Verhey, Timothy R.

    1998-01-01

    International Space Station (ISS) plasma contactor system requires a hollow cathode assembly (HCA) with a lifetime of at least 18,000 hours. In order to demonstrate the lifetime capability of the HCA, a series of hollow cathode wear tests was performed which included a life test operated at the maximum current of the HCA. This test sought to verify hollow cathode lifetime capability and contamination control protocols. This hollow cathode accumulated 27,800 hours of operation before it failed during a restart attempt. The cathode was subsequently destructively analyzed in order to determine the failure mechanism. Microscopic examination of the cathode interior determined that relatively small changes in the cathode physical geometry had occurred and barium tungstates, which are known to limit the emission process, had formed over a majority of the electron emitter surface. Because the final state of the insert was consistent with expected impregnate chemistry, the hollow cathode was believed to have reached the end of its usable life under the test conditions.

  3. Study Of Erosion Rates And Surface Effects of Different Hollow Cathode Materials During Vacuum Microarc Discharge

    SciTech Connect

    Atta Khedr, M.; Abdel Moneim, H.M.

    2005-03-17

    Studies of the properties of the emitted plasma from graphite, titanium, titanium Carbide, Stainless Steel, Cupper and Molybdenum Hollow Cathode materials during vacuum microarc were carried out. Using high voltage of 30 KV, short arc duration (0.5 - 4 {mu}s) and arc currents (100 - 450 A), each cathode material was subjected to 1000-3000 arc discharges under high vacuum (10-8 mbar) conditions. The angular distributions for the evaporants in each case were measured and show an exponential isotropic distribution in agreement with the theoretical predictions. The total erosion rates of evaporants and molten droplets were estimated and showed clearly their, dependence on the cathode material and on the hollow cathode geometry. The damages on the cathode surfaces and the inside of the hollow cathodes were investigated by the scanning electron microscope. Crater formation were formed spreading inside the hole of the hollow cathodes as well as on the rim surfaces and were found to differ according to both geometry and material of the hollow cathodes. The crater evacuation velocity and plasma pressure were determined. The damage on the anode tip showed erosion on the pen anode tip to the extent of drilling hole. The mechanism responsible for such phenomena is discussed.

  4. Hierarchical CoS2@C hollow microspheres constructed by nanosheets with superior lithium storage

    NASA Astrophysics Data System (ADS)

    Chen, Weiwei; Li, Tingting; Hu, Qian; Li, Chengpin; Guo, Hong

    2015-07-01

    An effective approach of alcoholysis is employed to prepare hollow CoS2@C hybrid nanosheets aggregates as anode materials for Li-ion batteries. Amorphous carbon can be loaded on the CoS2 nanoparticles uniformly in the solvothermal alcoholysis process, and the subsequent calcination results of the formation of hollow structures. The capacity of the sample can remain stable as high as 720 mAhg-1 after 200 cycles, and it also exhibits good rate capacity. The nano-scaled characteristics of CoS2 nanosheets embedded in the aggregates ensure the electrode having a high capacity and the fast Li-ion diffusion in the electrode. The in-situ introduction of carbon renders the electrode having a good electronic conductivity and can effectively prevent the formation of polysulfide anions. The unique hollow structures can shorten the length of Li-ion diffusion, which is benefit for the rate performance. The hollow structure also offers a sufficient void space, which sufficiently alleviates the mechanical stress caused by volume change. Therefore, the prepared hierarchical hollow CoS2@C materials constructed by nanosheets exhibit outstanding electrochemical performance.

  5. Broad beam gas ion source with hollow cathode discharge and four-grid accelerator system

    NASA Astrophysics Data System (ADS)

    Tang, Deli; Pu, Shihao; Huang, Qi; Tong, Honghui; Cui, Xirong; Chu, Paul K.

    2007-04-01

    A broad beam gas ion source based on low-pressure hollow cathode glow discharge is described. An axial magnetic filed produced by AlNiCo permanent magnets enhances the glow discharge in the ion source as a result of the magnetizing electrons between the hollow cathode and rod anode. The gas plasma is produced by magnetron hollow cathode glow discharge in the hollow cathode and a collimated broad ion beam is extracted by a four-grid accelerator system. A weak magnetic field of several millitesla is enough to ignite the magnetron glow discharge at pressure lower than 0.1 Pa, thereby enabling stable and continuous high-current discharge to form the homogeneous plasma. A four-grid accelerator, which separates the extraction and acceleration of the ion beam, is used in this design to generate the high-energy ion beam from 10 keV to 60 keV at a working pressure of 10-4 Torr. Although a higher gas pressure is necessary to maintain the low-pressure glow discharge when compared to hot filament discharge, the hollow cathode ion source is operational with reactive gases such as oxygen in the high-voltage continuous mode. A laterally uniform ion beam can be achieved by using the four-grid accelerator system. The effects of the rod anode length on the characteristics of the plasma discharge as well as ion beam extraction from the ion source are discussed.

  6. Anomalous behavior of 1/f noise in graphene near the charge neutrality point

    NASA Astrophysics Data System (ADS)

    Takeshita, Shunpei; Matsuo, Sadashige; Tanaka, Takahiro; Nakaharai, Shu; Tsukagoshi, Kazuhito; Moriyama, Takahiro; Ono, Teruo; Arakawa, Tomonori; Kobayashi, Kensuke

    2016-03-01

    We investigate the noise in single layer graphene devices from equilibrium to far-from equilibrium and found that the 1/f noise shows an anomalous dependence on the source-drain bias voltage (VSD). While the Hooge's relation is not the case around the charge neutrality point, we found that it is recovered at very low VSD region. We propose that the depinning of the electron-hole puddles is induced at finite VSD, which may explain this anomalous noise behavior.

  7. Hollow spherical carbonized polypyrrole/sulfur composite cathode materials for lithium/sulfur cells with long cycle life

    NASA Astrophysics Data System (ADS)

    Wang, Zhongbao; Zhang, Shichao; Zhang, Lan; Lin, Ruoxu; Wu, Xiaomeng; Fang, Hua; Ren, Yanbiao

    2014-02-01

    Hollow carbonized polypyrrole (PPy) spheres are synthesized using poly(methyl methacrylate-ethyl acrylate-acrylic acid) latex spheres as sacrificial templates. The hollow spherical carbonized PPy/sulfur composite cathode materials are prepared by heating the mixture of hollow carbonized PPy spheres and element sulfur at 155 °C for 24 h. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show the hollow structures of the carbonized PPy spheres and the homogeneous distribution of sulfur on the carbonized PPy shells. The hollow spherical carbonized PPy/sulfur composite with 60.9 wt.% S shows high specific capacity and excellent cycling stability when used as the cathode materials in lithium/sulfur cells, whose initial specific discharge capacity reaches as high as 1320 mA h g-1 and the reversible discharge capacity retains 758 mA h g-1 after 400 cycles at 0.2C. The excellent electrochemical properties benefit from the hollow structures and the flexible shells of the carbonized PPy spheres.

  8. Hollow glass for insulating layers

    NASA Astrophysics Data System (ADS)

    Merticaru, Andreea R.; Moagar-Poladian, Gabriel

    1999-03-01

    Common porous materials, some of which will be considered in the chapters of this book, include concrete, paper, ceramics, clays, porous semiconductors, chromotography materials, and natural materials like coral, bone, sponges, rocks and shells. Porous materials can also be reactive, such as in charcoal gasification, acid rock dissolution, catalyst deactivation and concrete. This study continues the investigations about the properties of, so-called, hollow glass. In this paper is presented a computer simulation approach in which the thermo-mechanical behavior of a 3D microstructure is directly computed. In this paper a computer modeling approach of porous glass is presented. One way to test the accuracy of the reconstructed microstructures is to computed their physical properties and compare to experimental measurement on equivalent systems. In this view, we imagine a new type of porous type of glass designed as buffer layer in multilayered printed boards in ICs. Our glass is a variable material with a variable pore size and surface area. The porosity could be tailored early from the deposition phases that permitting us to keep in a reasonable balance the dielectric constant and thermal conductivity.

  9. Anomalous phosphenes in ocular protontherapy

    NASA Astrophysics Data System (ADS)

    Khan, E.; Maréchal, F.; Dendale, R.; Mabit, C.; Calugaru, V.; Desjardin, L.; Narici, L.

    2010-04-01

    We have undertaken a clinical ground study of proton-induced light flashes (phosphenes). Patients treated at the Institut Curie - Centre de Protonthérapie in Orsay, France, received radiation therapy to cure ocular and skull-base cancers. Sixty percent of the patients treated for choroidal melanomas using 73 MeV protons report anomalous phosphenes. Delivering a radiation dose on the retina only is not sufficient to trigger the light flash. The present study may be the first indication of phosphenes triggered by protons of few tens of MeV.

  10. Khinchin Theorem and Anomalous Diffusion

    NASA Astrophysics Data System (ADS)

    Lapas, Luciano C.; Morgado, Rafael; Vainstein, Mendeli H.; Rubí, J. Miguel; Oliveira, Fernando A.

    2008-12-01

    A recent Letter [M. H. Lee, Phys. Rev. Lett. 98, 190601 (2007)PRLTAO0031-900710.1103/PhysRevLett.98.190601] has called attention to the fact that irreversibility is a broader concept than ergodicity, and that therefore the Khinchin theorem [A. I. Khinchin, Mathematical Foundations of Statistical Mechanics (Dover, New York, 1949)] may fail in some systems. In this Letter we show that for all ranges of normal and anomalous diffusion described by a generalized Langevin equation the Khinchin theorem holds.

  11. Photochemical preparation of CdS hollow microspheres at room temperature and their use in visible-light photocatalysis

    SciTech Connect

    Huang Yuying; Sun Fengqiang; Wu Tianxing; Wu Qingsong; Huang Zhong; Su Heng; Zhang Zihe

    2011-03-15

    CdS hollow microspheres have been successfully prepared by a photochemical preparation technology at room temperature, using polystyrene latex particles as templates, CdSO{sub 4} as cadmium source and Na{sub 2}S{sub 2}O{sub 3} as both sulphur source and photo-initiator. The process involved the deposition of CdS nanoparticles on the surface of polystyrene latex particles under the irradiation of an 8 W UV lamp and the subsequent removal of the latex particles by dispersing in dichloromethane. Photochemical reactions at the sphere/solution interface should be responsible for the formation of hollow spheres. The as-prepared products were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Such hollow spheres could be used in photocatalysis and showed high photocatalytic activities in photodegradation of methyl blue (MB) in the presence of H{sub 2}O{sub 2}. The method is green, simple, universal and can be extended to prepare other sulphide and oxide hollow spheres. -- Graphical abstract: Taking polystyrene spheres dispersed in a precursor solution as templates, CdS hollow microspheres composed of nanoparticles were successfully prepared via a new photochemical route at room temperature. Display Omitted Research highlights: {yields} Photochemical method was first employed to prepare hollow microspheres. {yields} CdS hollow spheres were first prepared at room temperature using latex spheres. {yields} The polystyrene spheres used as templates were not modified with special groups. {yields}The CdS hollow microspheres showed high visible-light photocatalytic activities.

  12. Anomalous Hall effect in localization regime

    NASA Astrophysics Data System (ADS)

    Wu, Lin; Zhu, Kai; Yue, Di; Tian, Yuan; Jin, Xiaofeng

    2016-06-01

    The anomalous Hall effect in the ultrathin film regime is investigated in Fe(001)(1-3 nm) films epitaxial on MgO(001). The logarithmic localization correction to longitudinal resistivity and anomalous Hall resistivity are observed at low temperature. We identify that the coefficient of skew scattering has a reduction from metallic to localized regime, while the contribution of side jump has inconspicuous change except for a small drop below 10 K. Furthermore, we discover that the intrinsic anomalous Hall conductivity decreases with the reduction of thickness below 2 nm. Our results provide unambiguous experimental evidence to clarify the problem of localization correction to the anomalous Hall effect.

  13. Nickel oxide hollow microsphere for non-enzyme glucose detection.

    PubMed

    Ci, Suqin; Huang, Taizhong; Wen, Zhenhai; Cui, Shumao; Mao, Shun; Steeber, Douglas A; Chen, Junhong

    2014-04-15

    A facile strategy has been developed to fabricate nickel oxide hollow microspheres (NiO-HMSs) through a solvothermal method by using a mixed solvent of ethanol and water with the assistance of sodium dodecyl sulfate (SDS). Various techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and powder X-ray diffraction (XRD), were used to characterize the morphology and the structure of as-prepared samples. It was confirmed that the products possess a hollow microsphere structure that is constructed by interconnecting porous nanoplate framework. Electrochemical studies indicate that the NiO-HMS exhibits excellent stability and high catalytic activity for electrocatalytic oxidation of glucose in alkaline solutions, which enables the NiO-HMS to be used in enzyme-free amperometric sensors for glucose determination. It was demonstrated that the NiO-HMS-based glucose biosensor offers a variety of merits, such as a wide linear response window for glucose concentrations of 1.67 μM-6.87 mM, short response time (3 s), a lower detection limit of 0.53 μM (S/N=3), high sensitivity (~2.39 mA mM(-1) cm(-2)) as well as good stability and repeatability. PMID:24287412

  14. Hollow gold nanorectangles: The roles of polarization and substrate

    NASA Astrophysics Data System (ADS)

    Near, Rachel D.; El-Sayed, Mostafa A.

    2013-07-01

    Dimers of hollow gold nanorectangles ((197 ± 4) × (134 ± 6) nm outside and (109 ± 5) × (53 ± 3) nm inside) were fabricated via electron beam lithography with interparticle separations ranging from 27 ± 2 nm to 596 ± 8 nm. Spectroscopic investigation of these arrays showed multiple peaks under illumination polarized both parallel and perpendicular to the interparticle axis. Discrete dipole approximation theoretical calculations were used to investigate the nature of these multiple peaks. These calculations demonstrate that the multiple peaks arise due to a combination of multiple plasmon modes and interactions with the substrate. The substrate effects are more pronounced for the parallel polarization because parallel polarization (along the long axis) of the nanorectangles results in a much stronger dipole mode than for the perpendicular polarization (along the short axis). Next, we show how these peaks change, as the hollow nanorectangles are brought within coupling range of one another. In this endeavor, we make use of our previously reported method to directly convert scanning electron microscope images of the nanoparticles into the shape files for the theoretical calculations.

  15. Hollow gold nanorectangles: the roles of polarization and substrate.

    PubMed

    Near, Rachel D; El-Sayed, Mostafa A

    2013-07-28

    Dimers of hollow gold nanorectangles ((197 ± 4) × (134 ± 6) nm outside and (109 ± 5) × (53 ± 3) nm inside) were fabricated via electron beam lithography with interparticle separations ranging from 27 ± 2 nm to 596 ± 8 nm. Spectroscopic investigation of these arrays showed multiple peaks under illumination polarized both parallel and perpendicular to the interparticle axis. Discrete dipole approximation theoretical calculations were used to investigate the nature of these multiple peaks. These calculations demonstrate that the multiple peaks arise due to a combination of multiple plasmon modes and interactions with the substrate. The substrate effects are more pronounced for the parallel polarization because parallel polarization (along the long axis) of the nanorectangles results in a much stronger dipole mode than for the perpendicular polarization (along the short axis). Next, we show how these peaks change, as the hollow nanorectangles are brought within coupling range of one another. In this endeavor, we make use of our previously reported method to directly convert scanning electron microscope images of the nanoparticles into the shape files for the theoretical calculations. PMID:23902009

  16. Controllable synthesis of Ce{sub 1-x}Zr{sub x}O{sub 2} hollow nanospheres via supercritical anti-solvent precipitation

    SciTech Connect

    Jiang Haoxi; Huang Pan; Liu Lin; Zhang Minhua

    2012-01-15

    Nanocrystalline Ce{sub 1-x}Zr{sub x}O{sub 2} hollow nanospheres were successfully synthesized via supercritical anti-solvent precipitation using supercritical CO{sub 2} as the anti-solvent. It was found that the as-produced samples exhibited hollow spherical structures with uniform diameters ranging from 30 to 50 nm and the sphere walls were composed of various oriented nanocrystallites, with sizes of 3-7 nm. The results of high-resolution transmission electron microscopy showed that the formation of the hollow structures could be controlled by adjusting the solution concentration. The results of temperature-programmed reduction and oxygen storage capacity measurements showed that the hollow nanospheres had enhanced redox properties. A possible mechanism for the formation of Ce{sub 1-x}Zr{sub x}O{sub 2} hollow nanospheres has also been proposed and experimental investigated.

  17. Criteria of radio-frequency ring-shaped hollow cathode discharge using H{sub 2} and Ar gases for plasma processing

    SciTech Connect

    Ohtsu, Yasunori; Kawasaki, Yujiro

    2013-01-21

    In order to achieve high-density capacitively coupled plasma, a radio-frequency (RF) ring-shaped hollow cathode discharge has been developed as a candidate for processing plasma sources. The plasma density in the hollow cathode discharge reaches a high magnitude of 10{sup 10}-10{sup 11} cm{sup -3}. The RF ring-shaped hollow cathode discharge depends on the pressure and mass of the working gas. Criteria required for producing a RF ring-shaped hollow cathode discharge have been investigated for various gas pressures using H{sub 2} and Ar gases for high-density plasma production. The results reveal that the criteria for the occurrence of the hollow cathode effect are that the trench width should be approximately equal to the sum of the electron-neutral mean free paths and twice the sheath thickness of the RF powered electrode.

  18. Intense short-pulse lasers irradiating wire and hollow plasma fibers.

    PubMed

    Zhou, C T; He, X T; Chew, L Y

    2011-03-15

    When an intense laser pulse irradiates a solid-density foil target, electrons produced at the relativistic critical density can be accelerated to relativistic energy by the ponderomotive force. When a plasma fiber is attached to the back of the foil, the produced relativistic electrons are guided to propagate along the fiber for a long distance, because the high-current electron beam induces strong radial electric fields in the fiber. Transport and heating of intense laser-driven relativistic electrons in both wire and hollow plasma fibers are compared theoretically and numerically. We found that the coupling efficiency from the laser to the plasma fiber depends on the fiber structure. Because of the enhanced return currents in the wire fiber, the temperature in the wire fiber is higher than that in the hollow fiber. PMID:21403730

  19. A green chemical approach to the synthesis of photoluminescent ZnO hollow spheres with enhanced photocatalytic properties

    SciTech Connect

    Patrinoiu, Greta; Tudose, Madalina; Calderon-Moreno, Jose Maria; Birjega, Ruxandra; Budrugeac, Petru; Ene, Ramona; Carp, Oana

    2012-02-15

    ZnO hollow spheres have been synthesized by a simple and environmentally friendly template assisted route. Starch-derived carbonaceous spheres were used as template, impregnated with Zn(CH{sub 3}COO){sub 2}{center_dot}2H{sub 2}O to obtain zinc-containing precursor spheres and thermally treatment at 600 Degree-Sign C, yielding hollow ZnO spherical shells. The precursor spheres and hollow shells were characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy, thermal analysis and room-temperature photoluminescence measurements. The hollow spherical shells with diameters of {approx}150 nm and wall thickness of {approx}20 nm, are polycrystalline, with a mean crystallite size of 22 nm, exhibiting interesting emission features, with a wide multi-peak band covering blue and green regions of the visible spectrum. The photocatalytic activities (under UV and visible light irradiations) of the ZnO spherical shells evaluated for the phenol degradation reaction in aqueous solutions are outstanding, a total phenol conversion being registered in the case of UV irradiation experiments. - Graphical abstract: The photocatalytic reaction initiated by the photoexcitation of the semiconductor (ZnO), leads to the formation of electron-hole, while part of the electron-hole pairs recombine, some holes combine with water to form {center_dot}OH radicals and some electrons convert oxygen to super oxide radical ({center_dot}O{sub 2}{sup -}). Highlights: Black-Right-Pointing-Pointer Green synthesis of ZnO hollow spheres. Black-Right-Pointing-Pointer Starch-derived carbonaceous spheres as spherical hard template. Black-Right-Pointing-Pointer ZnO hollow spheres with notable visible photoluminescence properties. Black-Right-Pointing-Pointer ZnO hollow spheres with photocatalytical activity in degradation/mineralization of phenol.

  20. Accurate hierarchical control of hollow crossed NiCo2O4 nanocubes for superior lithium storage

    NASA Astrophysics Data System (ADS)

    Guo, Hong; Liu, Lixiang; Li, Tingting; Chen, Weiwei; Liu, Jiajia; Guo, Yuanyuan; Guo, Yicheng

    2014-04-01

    . Therefore, hollow crossed NiCo2O4 nanocube electrodes exhibit excellent electrochemical performance. This method is simple and of low cost, which may open a new avenue for fast synthesis of hollow crossed structural nano-functional materials for energy storage, catalysts, sensors and other new applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00930d

  1. Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Fontheim, E. G.; Ong, R. S. B.; Roble, R. G.; Mayr, H. G.; Hoegy, W. H.; Ionson, J. A.; Baron, M. J.; Wickwar, V. B.; Vondrak, R. R.

    1978-01-01

    By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A = 1) disagrees considerably with the measured profile over most of the altitude range up to 450 km. It is shown that an anomaly coefficient with a sharp peak of the order of 10,000 centered around the F2 peak is consistent with observations.

  2. Modeling of Carbon Impurity Anomalous Transport

    NASA Astrophysics Data System (ADS)

    Stamm, Roland; Voitsekhovitch, Irina; Benkadda, Sadri; Beyer, Peter; Koubiti, Mohamed; Marandet, Yannick; Godbert-Mouret, Laurence; Bateman, Glenn; Kritz, Arnold; Pankin, Andre

    2001-10-01

    An improvement of plasma confinement by impurity seeding has been observed on different Tokamak. The understanding of the physics of the impurity transport is an important step towards the control of the plasma confinement in such regimes. Different physical mechanisms of the anomalous transport of carbon impurity and their impact on the evolution of the scenario of a tokamak discharge are analyzed in this work. This is done by using a self-consistent modeling of thermal electron and ion energy, and main ion and carbon impurity content with the multi-mode model taking into account the contributions from different types of plasma instabilities [1]. This study has been performed for the medium size tokamak with a central heating of the electron and ion species, and with both central (NBI) and wall particle source. The L-mode scenario and the scenario with an improved particle and energy confinement due to the reversed q-profile has been analyzed and the influence of the carbon impurity on the plasma evolution has been investigated by varying the starting time and the magnitude of the carbon influx. The effect of the main ion dilution on the growth rate as well as the effect of radiative cooling at the plasma edge on the power balance are analyzed under different conditions. 1. Bateman G., et al., Phys. Plasmas, 5 (1998) 1793

  3. ERTS-1 anomalous dark patches

    NASA Technical Reports Server (NTRS)

    Strong, A. E. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Through combined use of imagery from ERTS-1 and NOAA-2 satellites was found that when the sun elevation exceeds 55 degrees, the ERTS-1 imagery is subject to considerable contamination by sunlight even though the actual specular point is nearly 300 nautical miles from nadir. Based on sea surface wave slope information, a wind speed of 10 knots will theoretically provide approximately 0.5 percent incident solar reflectance under observed ERTS multispectral scanner detectors. This reflectance nearly doubles under the influence of a 20 knot wind. The most pronounced effect occurs in areas of calm water where anomalous dark patches are observed. Calm water at distances from the specular point found in ERTS scenes will reflect no solar energy to the multispectral scanner, making these regions stand out as dark areas in all bands in an ocean scene otherwise comprosed by a general diffuse sunlight from rougher ocean surfaces. Anomalous dark patches in the outer parts of the glitter zones may explain the unusual appearance of some scenes.

  4. Characterization of hollow cathode, ring cusp discharge chambers. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.

    1989-01-01

    An experimental study into the effects of changes in such physical design parameters as hollow cathode position, anode position and ring cusp magnetic field configuration and strength on discharge chamber performance, is described. The results are presented in terms of comparative plasma ion energy cost, extracted ion fraction and ion beam profile data. Such comparisons are used to demonstrate specific means by which changes in these design parameters induce changes in performance, i.e., through changes in the loss rates of primary electrons to the anode, of ions to discharge chamber walls or of ions to cathode and anode surfaces. Results show: (1) the rate of primary electron loss to the anode decreases as the anode is moved downstream of the ring cusp toward the screen grid, (2) the loss rate of ions to hollow cathode surfaces are excessive if the cathode is located upstream of a point of peak magnetic flux density on the discharge chamber centerline, and (3) the fraction of the ions produced that are lost to discharge chamber walls and ring magnet surfaces is reduced by positioning the magnet rings so the plasma density is uniform over the grid surface and so there are no steep magnetic flux density gradients near the walls through which ions can be lost by Bohm diffusion. The uniformity of the plasma density at the grids can also be improved by moving the point of primary electron injection into the discharge chamber off of the chamber centerline. Other results show the discharge chamber losses decrease when a filament cathode is substituted for a hollow cathode to the extent of the hollow cathode operating power. When plasma ion energy cost is determined in such a way that the cost of operating the hollow cathode is subtracted out, the performance using either electron source is similar.

  5. CuO hollow nanosphere-catalyzed cross-coupling of aryl iodides with thiols

    NASA Astrophysics Data System (ADS)

    Woo, Hyunje; Mohan, Balaji; Heo, Eunjung; Park, Ji Chan; Song, Hyunjoon; Park, Kang Hyun

    2013-09-01

    New functionalized CuO hollow nanospheres on acetylene black (CuO/AB) and on charcoal (CuO/C) have been found to be effective catalysts for C-S bond formation under microwave irradiation. CuO catalysts showed high catalytic activity with a wide variety of substituents which include electron-rich and electron-poor aryl iodides with thiophenols by the addition of two equivalents of K2CO3 as base in the absence of ligands.

  6. 44th Annual Anomalous Absorption Conference

    SciTech Connect

    Beg, Farhat

    2014-03-03

    Conference Grant Report July 14, 2015 Submitted to the U. S. Department of Energy Attn: Dr. Sean Finnegan By the University of California, San Diego 9500 Gilman Drive La Jolla, California 92093 On behalf of the 44th Annual Anomalous Absorption Conference 8-13 June 2014, in Estes Park, Colorado Support Requested: $10,100 Amount expended: $3,216.14 Performance Period: 1 March 20 14 to 28 February 20 15 Principal Investigator Dr. Farhat Beg Center for Energy Research University of California, San Diego 9500 Gilman Drive La Jolla, California 92093-0417 858-822-1266 (telephone) 858-534-4543 (fax) fbeg@ucsd.edu Administrative Point of Contact: Brandi Pate, 858-534-0851, blpate®ucsd.edu I. Background The forty-fourth Anomalous Absorption Conference was held in Estes Park, Colorado from June 5-8, 2014 (aac2014.ucsd.edu). The first Anomalous Absorption Conference was held in 1971 to assemble experts in the poorly understood area of laser-plasma absorption. The goal of that conference was to address the anomalously large laser absorption seen in plasma experiments with respect to the laser absorption predicted by linear plasma theory. Great progress in this research area has been made in the decades since that first meeting, due in part to the scientific interactions that have occurred annually at this conference. Specifically, this includes the development of nonlinear laser-plasma theory and the simulation of laser interactions with plasmas. Each summer since that first meeting, this week-long conference has been held at unique locations in North America as a scientific forum for intense scientific exchanges relevant to the interaction of laser radiation with plasmas. Responsibility for organizing the conference has traditional rotated each year between the major Inertial Confinement Fusion (ICF) laboratories and universities including LANL, LLNL, LLE, UCLA UC Davis and NRL. As the conference has matured over the past four decades, its technical footprint has expanded

  7. Magnetic and optical properties of electrospun hollow nanofibers of SnO2 doped with Ce-ion

    NASA Astrophysics Data System (ADS)

    Mohanapriya, P.; Pradeepkumar, R.; Victor Jaya, N.; Natarajan, T. S.

    2014-07-01

    Cerium doped SnO2 hollow nanofibers were synthesized by electrospinning. High resolution scanning electron microscope (HRSEM) and transmission electron microscopy (TEM) analysis showed hollow nanofibers with diameters around ˜200 nm. The optimized substitution of Ce ion into SnO2 lattices happened above 6 mol. % doping as confirmed by Powder X-ray diffraction (XRD) studies. Optical band gap was decreased by the doping confirming the direct energy transfer between f-electrons of rare earth ion and the SnO2 conduction or valence band. The compound also exhibited room temperature ferromagnetism with the saturation magnetization of 19 × 10-5 emu/g at 6 mol. %. This study demonstrates the Ce doped SnO2 hollow nanofibers for applications in magneto-optoelectronic devices.

  8. Magnetic and optical properties of electrospun hollow nanofibers of SnO{sub 2} doped with Ce-ion

    SciTech Connect

    Mohanapriya, P.; Victor Jaya, N.; Pradeepkumar, R.; Natarajan, T. S.

    2014-07-14

    Cerium doped SnO{sub 2} hollow nanofibers were synthesized by electrospinning. High resolution scanning electron microscope (HRSEM) and transmission electron microscopy (TEM) analysis showed hollow nanofibers with diameters around ∼200 nm. The optimized substitution of Ce ion into SnO{sub 2} lattices happened above 6 mol. % doping as confirmed by Powder X-ray diffraction (XRD) studies. Optical band gap was decreased by the doping confirming the direct energy transfer between f-electrons of rare earth ion and the SnO{sub 2} conduction or valence band. The compound also exhibited room temperature ferromagnetism with the saturation magnetization of 19 × 10{sup −5} emu/g at 6 mol. %. This study demonstrates the Ce doped SnO{sub 2} hollow nanofibers for applications in magneto-optoelectronic devices.

  9. Tuning the synthesis of platinum-copper nanoparticles with a hollow core and porous shell for the selective hydrogenation of furfural to furfuryl alcohol

    NASA Astrophysics Data System (ADS)

    Huang, Shuangshuang; Yang, Nating; Wang, Shibin; Sun, Yuhan; Zhu, Yan

    2016-07-01

    Pt-Cu nanoparticles constructed with a hollow core and porous shell have been synthesized in which Pt-Cu cages with multiporous outermost shells are formed at the initial stage and then the Pt and Cu atoms in solution continuously fed these hollow-core of cages by passing through the porous tunnels of the outermost shells, finally leading to the formation of hollow structures with different sizes. Furthermore, these hollow-core Pt-Cu nanoparticles are more effective than the solid-core Pt-Cu nanoparticles for the catalytic hydrogenation of furfural toward furfuryl alcohol. The former can achieve almost 100% conversion of furfural with 100% selectivity toward the alcohol.Pt-Cu nanoparticles constructed with a hollow core and porous shell have been synthesized in which Pt-Cu cages with multiporous outermost shells are formed at the initial stage and then the Pt and Cu atoms in solution continuously fed these hollow-core of cages by passing through the porous tunnels of the outermost shells, finally leading to the formation of hollow structures with different sizes. Furthermore, these hollow-core Pt-Cu nanoparticles are more effective than the solid-core Pt-Cu nanoparticles for the catalytic hydrogenation of furfural toward furfuryl alcohol. The former can achieve almost 100% conversion of furfural with 100% selectivity toward the alcohol. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr03894h

  10. Anomalous resistivity and heating in current-driven plasma thrusters

    NASA Astrophysics Data System (ADS)

    Choueiri, E. Y.

    1999-05-01

    A theory is presented of anomalous resistivity and particle heating in current-driven plasma accelerators such as the magnetoplasmadynamic thruster (MPDT). An electromagnetic dielectric tensor is used for a current-carrying, collisional and finite-beta plasma and it is found that an instability akin to the generalized lower hybrid drift instability (GLHDI) exists for electromagnetic modes (i.e., with finite polarization). Weak turbulence theory is then used to develop a second-order description of the heating rates of particles by the waves and the electron-wave momentum exchange rate that controls the anomalous resistivity effect. It is found that the electron Hall parameter strongly scales the level of anomalous dissipation for the case of the MPDT plasma. This scaling has recently been confirmed experimentally [Phys. Plasmas 5, 3581 (1997)]. Polynomial expressions of the relevant transport coefficients cast solely in terms of macroscopic parameters are also obtained for including microturbulence effects in numerical plasma fluid models used for thruster flow simulation.

  11. Method for the production of fabricated hollow microspheroids

    SciTech Connect

    Wickramanayake, Shan; Luebke, David R.

    2015-06-09

    The method relates to the fabrication of a polymer microspheres comprised of an asymmetric layer surrounding a hollow interior. The fabricated hollow microsphere is generated from a nascent hollow microsphere comprised of an inner core of core fluid surrounded by a dope layer of polymer dope, where the thickness of the dope layer is at least 10% and less than 50% of the diameter of the inner core. The nascent hollow microsphere is exposed to a gaseous environment, generating a vitrified hollow microsphere, which is subsequently immersed in a coagulation bath. Solvent exchange produces a fabricated hollow microsphere comprised of a densified outer skin surrounding a macroporous inner layer, which surrounds a hollow interior. In an embodiment, the polymer is a polyimide or a polyamide-imide, and the non-solvent in the core fluid and the coagulation bath is water. The fabricated hollow microspheres are particularly suited as solvent supports for gas separation processes.

  12. Hollow shaft integrated health monitoring system for railroad wheels

    NASA Astrophysics Data System (ADS)

    Frankenstein, B.; Hentschel, D.; Pridoehl, E.; Schubert, F.

    2005-05-01

    The economic efficiency and competitiveness of environment-friendly rail transportation depends on safety, availability and maintenance of single highly loaded structure components. Until now these components have been changed in fixed maintenance intervals irrespective of any usage related conditions. With the knowledge and evaluation of the component conditions, life cycle costs can be reduced by means of optimized maintenance and/or "fit for purpose" design. For example, rail-bound vehicle wheel sets are among the most highly stressed travelling gear components of the bogie. if such a component fails, a serious accident may occur. For this reason, a health monitoring system based on the interpretation of ultrasonic sound signatures has been developed. First, the ultrasonic waves generated by an artificial defect on the outer wheel tread of a railroad wheel towards an acoustic sensor, placed inside the hollow shaft of the railroad axis were simulated with a EFIT (Elastodynamic Finite Integration Technique). The results achieved proved that relevant signals can be found in a frequency range up to 300 kHz. Based on this a diagnostic unit was designed and built for application under rotation conditions, which consists of a piezo-electric sensor, primary electronics, an analog-to-digital converter, a digital signal processor, a trigger unit, and a telemetric transmitter. This diagnostic unit was integrated in the hollow shaft of a railroad wheel axis, a component of a special laboratory test rig. Algorithms which allow for the rotation-synchronized processing of acoustic signals were implemented into the rotating diagnostic unit. After successfully completing a campaign for this test rig, a second test was performed inside the wheel/railroad simulation test rig of the Deutsche Bahn AG under railroad-like conditions. The data generated inside the hollow shaft of the railroad wheel axis by the diagnostic unit were telemetrically transmitted to an industrial computer

  13. Normal and anomalous Doppler effects in periodic waveguide cyclotron maser

    SciTech Connect

    Korol, M.; Jerby, E.

    1995-12-31

    A linear analysis of the periodic-waveguide cyclotron (PWC) maser shows that the PWC interaction with fast-waves possesses properties of the known anomalous Doppler resonance interaction if the wave impedance of the resonant spatial harmonic, Z{sub n}, is much smaller than the free space impedance, i.e. if Z{sub n} {much_lt} Z{sub 0}. The feasibility of a fast-wave PWC interaction in a low impedance waveguide is examined theoretically in this paper. A practical scheme of a slotted-waveguide PWC operating in the fundamental harmonic near cutoff is proposed for a future experiment. The possible advantages of the quasi-anomalous Doppler effect in the fast-wave-PWC operating regime are the alleviation of the initial electron rotation and a high-efficiency operation.

  14. Anomalous Capacitive Sheath with Deep Radio Frequency Electric Field Penetration

    SciTech Connect

    Igor D. Kaganovich

    2002-01-18

    A novel nonlinear effect of anomalously deep penetration of an external radio-frequency electric field into a plasma is described. A self-consistent kinetic treatment reveals a transition region between the sheath and the plasma. Because of the electron velocity modulation in the sheath, bunches in the energetic electron density are formed in the transition region adjusted to the sheath. The width of the region is of order V(subscript T)/omega, where V(subscript T) is the electron thermal velocity, and w is frequency of the electric field. The presence of the electric field in the transition region results in a cooling of the energetic electrons and an additional heating of the cold electrons in comparison with the case when the transition region is neglected.

  15. Modeling the plasma plume of a hollow cathode

    NASA Astrophysics Data System (ADS)

    Boyd, Iain D.; Crofton, Mark W.

    2004-04-01

    In this study, a numerical model is developed to simulate the xenon plasma plume from a thermionic hollow cathode employing an orifice plate used for propellant ionization and beam neutralization in an electrostatic space propulsion system. The model uses a detailed fluid model to describe the electrons and a particle-based kinetic approach is used to model the heavy xenon ions and atoms. A number of key assumptions in terms of physical modeling and boundary conditions of the simulations are assessed through direct comparisons with experimental measurements. For two of the three cathode operating conditions considered, good agreement with the measured data is obtained. The third condition appears to lie in a different physical regime where elevated electron and ion temperatures and decreased transport coefficients are required in the simulation to provide agreement between the model and the measured data.

  16. Hollow Silicon Nanostructures via the Kirkendall Effect.

    PubMed

    Son, Yoonkook; Son, Yeonguk; Choi, Min; Ko, Minseong; Chae, Sujong; Park, Noejung; Cho, Jaephil

    2015-10-14

    The Kirkendall effect is a simple, novel phenomenon that may be applied for the synthesis of hollow nanostructures with designed pore structures and chemical composition. We demonstrate the use of the Kirkendall effect for silicon (Si) and germanium (Ge) nanowires (NWs) and nanoparticles (NPs) via introduction of nanoscale surface layers of SiO2 and GeO2, respectively. Depending on the reaction time, Si and Ge atoms gradually diffuse outward through the oxide layers, with pore formation in the nanostructural cores. Through the Kirkendall effect, NWs and NPs were transformed into nanotubes (NTs) and hollow NPs, respectively. The mechanism of the Kirkendall effect was studied via quantum molecular dynamics calculations. The hollow products demonstrated better electrochemical performance than their solid counterparts because the pores developed in the nanostructures resulted in lower external pressures during lithiation. PMID:26340592

  17. Polypyrrole hollow fiber for solid phase extraction.

    PubMed

    Tian, Tian; Deng, Jianjun; Xie, Zhuoying; Zhao, Yuanjin; Feng, Zhangqi; Kang, Xuejun; Gu, Zhongze

    2012-04-21

    We have developed a solid-phase extraction method based on conductive polypyrrole (PPy) hollow fibers which were fabricated by electrospinning and in situ polymerization. The electrospun poly (e-caprolactone) (PCL) fibers were employed as templates for the in situ surface polymerization of PPy under mechanical stirring or ultrasonication to obtain burr-shaped or smooth fiber shells, respectively. Hollow PPy fibers, achieved by removing the PCL templates, were the ideal sorbents for solid phase extraction of polar compounds due to their inherent multi-functionalities. By using the hollow PPy fibers, two important neuroendocrine markers of behavioural disorders, 5-hydroxyindole-3-acetic acid and homovanillic acid, were successfully extracted. Under the optimized conditions, the absolute recoveries of the above two neuroendocrine markers were 90.7% and 92.4%, respectively, in human plasma. Due to its simplicity, selectivity and sensitivity, the method may be applied to quantitatively analyse the concentrations of polar species in complex matrix samples. PMID:22398754

  18. Method of making a non-lead hollow point bullet

    DOEpatents

    Vaughn, Norman L.; Lowden, Richard A.

    2003-10-07

    The method of making a non-lead hollow point bullet has the steps of a) compressing an unsintered powdered metal composite core into a jacket, b) punching a hollow cavity tip portion into the core, c) seating an insert, the insert having a hollow point tip and a tail protrusion, on top of the core such that the tail protrusion couples with the hollow cavity tip portion, and d) swaging the open tip of the jacket.

  19. Anomalous inverse bremsstrahlung heating of laser-driven plasmas

    NASA Astrophysics Data System (ADS)

    Kundu, Mrityunjay

    2016-05-01

    Absorption of laser light in plasma via electron-ion collision (inverse bremsstrahlung) is known to decrease with the laser intensity as I 0 -3/2 or with the electron temperature as T e -3/2 where Coulomb logarithm ln Λ = 0.5ln(1 + k 2 min/k 2 max) in the expression of electron-ion collision frequency v ei is assumed to be independent of ponderomotive velocity v 0 = E0/ω which is unjustified. Here k -1 min = v th/max(ω, ω p), and k -1 max = Z/v 2 th are maximum and minimum cut-off distances of the colliding electron from the ion, v th = √T e is its thermal velocity, ω, ω p are laser and plasma frequency. Earlier with a total velocity v = (v 2 0 + v 2 th)1/2 dependent ln Λ(v) it was reported that v ei and corresponding fractional laser absorption (α) initially increases with increasing intensity, reaches a maximum value, and then fall according to the conventional I 0 -3/2 scaling. This anomalous increase in v ei and α may be objected due to an artifact introduced in ln Λ(v) through k-1 min ∝ v. Here we show similar anomalous increase of v ei and α versus I 0 (in the low temperature and under-dense density regime) with quantum and classical kinetic models of v ei without using ln Λ, but a proper choice of the total velocity dependent inverse cut-off length kmax -1 ∝ v 2 (in classical case) or kmax ∝ v (in quantum case). For a given I 0 < 5 × 1014Wcm-2, v ei versus T e also exhibits so far unnoticed identical anomalous increase as v ei versus Io, even if the conventional k max ∝ v2 th, or k max ∝ v th is chosen. However, for higher T e > 15 eV, anomalous growth of vei and a disappear. The total velocity dependent k max in kinetic models, as proposed here, may explain anomalous increase of a with I 0 measured in some earlier laser-plasma experiments. This work may be important to understand collisional absorption in the under-dense pre-plasma region due to low intensity pre-pulses and amplified spontaneous emission (ASE) pedestal in the

  20. Predicting clutter during anomalous propagation conditions

    NASA Astrophysics Data System (ADS)

    Lee, Susan C.; Maurer, Donald E.; Musser, Keith L.

    1988-06-01

    Excessive clutter caused by anomalous propagation conditions severely degrades radar performance in many regions of the world. This article describes methods that can be used to predict anomalous clutter amplitude for site-specific radar parameters, terrain features, and atmospheric conditions and to predict the effects of radar Doppler processing on evaporation-ducted sea clutter.

  1. Pine Hollow Watershed Project : FY 2000 Projects.

    SciTech Connect

    Sherman County Soil and Water Conservation District

    2001-06-01

    The Pine Hollow Project (1999-010-00) is an on-going watershed restoration effort administered by Sherman County Soil and Water Conservation District and spearheaded by Pine Hollow/Jackknife Watershed Council. The headwaters are located near Shaniko in Wasco County, and the mouth is in Sherman County on the John Day River. Pine Hollow provides more than 20 miles of potential summer steelhead spawning and rearing habitat. The watershed is 92,000 acres. Land use is mostly range, with some dryland grain. There are no water rights on Pine Hollow. Due to shallow soils, the watershed is prone to rapid runoff events which scour out the streambed and the riparian vegetation. This project seeks to improve the quality of upland, riparian and in-stream habitat by restoring the natural hydrologic function of the entire watershed. Project implementation to date has consisted of construction of water/sediment control basins, gradient terraces on croplands, pasture cross-fences, upland water sources, and grass seeding on degraded sites, many of which were crop fields in the early part of the century. The project is expected to continue through about 2007. From March 2000 to June 2001, the Pine Hollow Project built 6 sediment basins, 1 cross-fence, 2 spring developments, 1 well development, 1 solar pump, 50 acres of native range seeding and 1 livestock waterline. FY2000 projects were funded by BPA, Oregon Watershed Enhancement Board, US Fish and Wildlife Service and landowners. In-kind services were provided by Sherman County Soil and Water Conservation District, USDA Natural Resources Conservation Service, USDI Bureau of Land Management, Oregon Department of Fish and Wildlife, Pine Hollow/Jackknife Watershed Council, landowners and Wasco County Soil and Water Conservation District.

  2. Process for manufacturing hollow fused-silica insulator cylinder

    DOEpatents

    Sampayan, Stephen E.; Krogh, Michael L.; Davis, Steven C.; Decker, Derek E.; Rosenblum, Ben Z.; Sanders, David M.; Elizondo-Decanini, Juan M.

    2001-01-01

    A method for building hollow insulator cylinders that can have each end closed off with a high voltage electrode to contain a vacuum. A series of fused-silica round flat plates are fabricated with a large central hole and equal inside and outside diameters. The thickness of each is related to the electron orbit diameter of electrons that escape the material surface, loop, and return back. Electrons in such electron orbits can support avalanche mechanisms that result in surface flashover. For example, the thickness of each of the fused-silica round flat plates is about 0.5 millimeter. In general, the thinner the better. Metal, such as gold, is deposited onto each top and bottom surface of the fused-silica round flat plates using chemical vapor deposition (CVD). Eutectic metals can also be used with one alloy constituent on the top and the other on the bottom. The CVD, or a separate diffusion step, can be used to defuse the deposited metal deep into each fused-silica round flat plate. The conductive layer may also be applied by ion implantation or gas diffusion into the surface. The resulting structure may then be fused together into an insulator stack. The coated plates are aligned and then stacked, head-to-toe. Such stack is heated and pressed together enough to cause the metal interfaces to fuse, e.g., by welding, brazing or eutectic bonding. Such fusing is preferably complete enough to maintain a vacuum within the inner core of the assembled structure. A hollow cylinder structure results that can be used as a core liner in a dielectric wall accelerator and as a vacuum envelope for a vacuum tube device where the voltage gradients exceed 150 kV/cm.

  3. Self-assembly of poly(o-methoxyaniline) hollow nanospheres from a polymeric acid solution

    NASA Astrophysics Data System (ADS)

    Sui, Jing; Zhang, Lijuan; Peng, Hui; Travas-Sejdic, Jadranka; Kilmartin, Paul A.

    2009-10-01

    Self-assembled poly(o-methoxyaniline) (POMA) hollow nanospheres were prepared in a solution of poly(methyl vinyl ether-alt-maleic acid) (PMVEA) by oxidative polymerization using ammonium persulfate as the oxidant. The weight ratio of PMVEA to o-methoxyaniline in the solution had a significant effect on the morphology of the poly(o-methoxyaniline) nanospheres as determined by scanning electron microscopy. The diameter of the hollow nanospheres decreased from 440 to 210 nm with an increase in the PMVEA concentration from 1% to 5%. Freeze-fracture transmission electron microscopy results showed the presence of spherical micelles composed of PMVEA/ o-methoxyaniline prior to polymerization, which also decreased in size as more PMVEA was added to the solution, and can act as soft templates for the formation of the hollow POMA nanospheres. The POMA/PMVEA hollow nanospheres were characterized by means of Fourier transform infrared, UV-visible, x-ray photoelectron spectroscopy, elemental analysis and conductivity measurements.

  4. Characterization of hollow BaTiO3 nanofibers and intense visible photoluminescence

    NASA Astrophysics Data System (ADS)

    Woong Lee, Kui; Siva Kumar, Koppala; Heo, Gaeun; Seong, Maeng-Je; Yoon, Jong-Won

    2013-10-01

    BaTiO3 hollow nanofibers were fabricated by electrospinning and then subsequent calcination of as-spun nanofibers with a heating rate of 2.5 °C/min. Scanning electron microscope and transmission electron microscope (TEM) results indicated that the heating rate had a significant effect on the morphology of the BaTiO3 hollow nanofibers. The X-ray diffraction, Raman spectroscopy, and TEM results indicate the prepared BaTiO3 hollow nanofibers have tetragonal phases. From the results of the X-ray photoelectron spectroscopy analysis, in the amorphous BaTiO3 nanofiber, peaks at 457.2 eV for Ti 2p3/2 were also found, which corresponded to the Ti3+ ions. However, in the crystalline BaTiO3 nanofibers, peaks of Ti 2p3/2 showed the Ti4+ ions. Intense visible photoluminescence was observed in the amorphous BaTiO3 nanofiber, which is calcined below a temperature of 500 °C. The observed intense photoluminescence was ascribed to a multiphonon process with localized states within the band gap of the highly disordered states. In the crystalline BaTiO3 hollow fiber, low intensity of photoluminescence showed at the visible region, which is originated from an intrinsic Ba defect.

  5. Ultrasonic/surfactant assisted of CdS nano hollow sphere synthesis and characterization

    SciTech Connect

    Rafati, Amir Abbas; Borujeni, Ahmad Reza Afraz; Najafi, Mojgan; Bagheri, Ahmad

    2011-01-15

    CdS hollow nanospheres with diameters ranging from 40 to 150 nm have been synthesized by a surfactant-assisted sonochemical route. The successful vesicle templating indicates that the outer leaflet of the bilayer is the receptive surface in the controlled growth of CdS nanoparticles which provide the unique reactor for the nucleation and mineralization growth of CdS nanoparticles. The CdS nanostructures obtained were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and photoluminescence spectroscopy. Structural characterization of hollow CdS nanospheres indicates that these products packed with square subunits having sizes between 5 and 7 nm in diameter. The formation of the hollow nanostructure was explained by a vesicle template mechanism, in which sonication and surfactant play important roles. The band-edge emission and surface luminescence of the CdS nanoparticles were observed. -Research Highlights: {yields} CdS hollow nanospheres with diameters of 40-150 nm were synthesized. {yields} Nanoparticles were characterized by UV/Vis and photoluminescence. {yields} Nanospheres are composed of smaller nanocrystals with the average size of 6.8 nm. {yields} The band gap energy of the CdS nanoparticles is higher than its bulk value.

  6. Sacrificial Silver Nanoparticles: Reducing GeI2 To Form Hollow Germanium Nanoparticles by Electroless Deposition.

    PubMed

    Nolan, Bradley M; Chan, Eric K; Zhang, Xinming; Muthuswamy, Elayaraja; van Benthem, Klaus; Kauzlarich, Susan M

    2016-05-24

    Herein we report the electroless deposition of Ge onto sacrificial Ag nanoparticle (NP) templates to form hollow Ge NPs. The formation of AgI is a necessary component for this reaction. Through a systematic study of surface passivating ligands, we determined that tri-n-octylphosphine is necessary to facilitate the formation of hollow Ge NPs by acting as a transport agent for GeI2 and the oxidized Ag(+) cation (i.e., AgI product). Annular dark-field (ADF) scanning transmission electron microscopy (STEM) imaging of incomplete reactions revealed Ag/Ge core/shell NPs; in contrast, completed reactions displayed hollow Ge NPs with pinholes which is consistent with the known method for dissolution of the nanotemplate. Characterization of the hollow Ge NPs was performed by transmission electron microscopy, ADF-STEM, energy-dispersive X-ray spectroscopy, UV-vis spectrophotometry, and Raman spectroscopy. The galvanic replacement reaction of Ag with GeI2 offers a versatile method for controlling the structure of Ge nanomaterials. PMID:27096547

  7. Emergent primary PCI of anomalous LAD.

    PubMed

    Hershey, Jeffrey; Isada, Loretta; Fenster, Michael S

    2006-05-01

    Approximately 0.3% to 2% of patients may have anomalous origins of the coronary arteries. Anomalous origin of the left coronary artery (LCA) or left anterior descending (LAD) artery from the right sinus has been well described. In persons in whom the course involves an interarterial track between the aorta (Ao) and pulmonary artery (PA), an increased incidence of sudden death has been reported, particularly during or shortly after exercise. This has been felt to be due to transient occlusion of the anomalous LAD from increased blood flow through the Ao and PA as the anomalous LAD courses between them, possibly causing myocardial ischemia. In an elective setting, further anatomic delineation with other methodologies such as cardiac magnetic resonance (MR) imaging is recommended. In this case report we present an emergent percutaneous coronary intervention (PCI) of an anomalous LAD arising from the right sinus of Valsalva and coursing between the Ao and PA in a nonsurgical candidate. PMID:16670456

  8. Hollow needle used to cut metal honeycomb structures

    NASA Technical Reports Server (NTRS)

    Gregg, E. A.

    1966-01-01

    Hollow needle tool cuts metal honeycomb structures without damaging adjacent material. The hollow needle combines an electrostatic discharge and a stream of oxygen at a common point to effect rapid, accurate metal cutting. The tool design can be varied to use the hollow needle principle for cutting a variety of shapes.

  9. Plastic Hollow Tubes As Waveguides For IR Radiation

    NASA Astrophysics Data System (ADS)

    Croitoru, N.; Dror, J.; Mendlovic, D.

    1988-06-01

    A theoretical ray model was developed for energy distribution of IR radiation, transmitted through hollow straight and bent fibers. The theoretical results were compared with the experimental data obtained from measurements of our plastic hollow fibers. A satisfactory agreement between the experimental and theoretical data was achieved. Application of the plastic hollow fibers in surgery (on certain organic tissues) is described.

  10. Photoanode using hollow spherical TiO2 for duel functions in dye-sensitized solar cell.

    PubMed

    Ko, Hwan Ho; Yi, Sung; Jeong, Sung Hoon

    2013-12-01

    We report a new fabrication method of a bilayer photoanode for dye sensitized solar cell having highly crystalline TiO2 with hollow spherical nanoparticles. The hollow spherical TiO2 nanoparticles in DSSC work not only as scattering layer but also as channel of electrolyte. This is due to the fact that incident light is scattered by the hollow spherical nanoparticle according to Mie theory and spherical hollow spheres allow the empty space inside each sphere to circulate the electrolyte more effectively. The nanoparticles were synthesized by hydrothermal method. The space inside the spheres was fully developed by Ostwald Ripening process and the size of hollow spheres was controlled by concentration of PVPs and hydrothermal synthesis conditions (time and temperature). The nanoparticle size and photoanode morphology of the hollow spheres were measured by scanning electron microscope (SEM). Finally, the power conversion efficiency of 6.26% has been achieved under AM 1.5G simulated sunlights (100 mW cm(-2)). PMID:24266162

  11. Microemulsion-based synthesis of nanoscaled silver hollow spheres and direct comparison with massive particles of similar size

    NASA Astrophysics Data System (ADS)

    Kind, Christian; Popescu, Radian; Müller, Erich; Gerthsen, Dagmar; Feldmann, Claus

    2010-10-01

    Nanoscale silver hollow spheres are first prepared via a microemulsion approach with 15-20 nm as the outer diameter, 3-5 nm as the wall thickness, and 10-15 nm as the diameter of the inner cavity. The presence of hollow spheres is confirmed by electron microscopy (SEM, BF-/HAADF-STEM, HRTEM) as well as by X-ray diffraction with a line-shape analysis to characterize the microcrystalline properties. In addition to the hollow spheres, massive silver nanoparticles of similar size (outer diameter of 15-20 nm) are gained via microemulsions. Based on the similarity of experimental conditions and the resulting particle size, as-prepared silver hollow spheres and massive nanoparticles are used to compare their optical properties and surface-plasmon resonance. In contrast to reducing the diameter of massive particles, ``hollowing'' of silver nanoparticles leads to a red-shift of the plasmon resonance. With a red shift of about 33 nm in the case of the hollow spheres, a quantum-size effect is indeed observed and in accordance with the thin sphere wall.

  12. Xanthoceraside hollow gold nanoparticles, green pharmaceutics preparation for poorly water-soluble natural anti-AD medicine.

    PubMed

    Meng, Da-Li; Shang, Lei; Feng, Xiao-He; Huang, Xing-Fei; Che, Xin

    2016-06-15

    In order to increase the solubility of poorly water-soluble natural product, xanthoceraside, an effective anti-AD compound from Xanthoceras sorbifolia Bunge, and maintain its natural property, the xanthoceraside hollow gold nanoparticles were successively prepared by green ultrasonic method with silica spheres as templates and HF solution as selective etching solvent. Hollow gold nanoparticles and drug-loaded hollow gold nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The solubilities of xanthoceraside loaded on hollow gold nanoparticles were increased obviously from 3.0μg/ml and 2.5μg/ml to 12.7μg/ml and 10.7μg/ml at 25°C and 37°C, respectively. The results of XRD and DSC indicated that the reason for this increase was mainly due to the amorphous state of xanthoceraside loaded on the hollow gold nanoparticles. In summary, the method of loading xanthoceraside onto hollow gold nanoparticles was a green and useful strategy to improve the solubility and dissolution of poorly water-soluble natural products and worth to applying to other natural products. PMID:27102991

  13. Microemulsion-based synthesis of nanoscaled silver hollow spheres and direct comparison with massive particles of similar size.

    PubMed

    Kind, Christian; Popescu, Radian; Müller, Erich; Gerthsen, Dagmar; Feldmann, Claus

    2010-10-01

    Nanoscale silver hollow spheres are first prepared via a microemulsion approach with 15-20 nm as the outer diameter, 3-5 nm as the wall thickness, and 10-15 nm as the diameter of the inner cavity. The presence of hollow spheres is confirmed by electron microscopy (SEM, BF-/HAADF-STEM, HRTEM) as well as by X-ray diffraction with a line-shape analysis to characterize the microcrystalline properties. In addition to the hollow spheres, massive silver nanoparticles of similar size (outer diameter of 15-20 nm) are gained via microemulsions. Based on the similarity of experimental conditions and the resulting particle size, as-prepared silver hollow spheres and massive nanoparticles are used to compare their optical properties and surface-plasmon resonance. In contrast to reducing the diameter of massive particles, "hollowing" of silver nanoparticles leads to a red-shift of the plasmon resonance. With a red shift of about 33 nm in the case of the hollow spheres, a quantum-size effect is indeed observed and in accordance with the thin sphere wall. PMID:20694210

  14. Electrically tunable spin polarization of chiral edge modes in a quantum anomalous Hall insulator

    NASA Astrophysics Data System (ADS)

    Zhang, Rui-Xing; Hsu, Hsiu-Chuan; Liu, Chao-Xing

    2016-06-01

    In the quantum anomalous Hall effect, chiral edge modes are expected to conduct spin polarized current without dissipation and thus hold great promise for future electronics and spintronics with low energy consumption. However, spin polarization of chiral edge modes has never been established in experiments. In this work, we theoretically study spin polarization of chiral edge modes in the quantum anomalous Hall effect, based on both the effective model and more realistic tight-binding model constructed from first-principles calculations. We find that spin polarization can be manipulated by tuning either a local gate voltage or the Fermi energy. We also propose to extract spin information of chiral edge modes by contacting the quantum anomalous Hall insulator to a ferromagnetic lead. The establishment of spin polarization of chiral edge modes, as well as the manipulation and detection in a fully electrical manner, will pave the way to the applications of the quantum anomalous Hall effect in spintronics.

  15. Anomalous perturbative transport in tokamaks due to drift-wave turbulence

    SciTech Connect

    Thoul, A.A. ); Similon, P.L. ); Sudan, R.N. )

    1994-03-01

    A new method for calculating the anomalous transport in tokamak plasmas is presented. The renormalized nonlinear plasma response function is derived using the direct-interaction approximation (DIA). A complete calculation for the case of electrostatic drift-wave turbulence is presented. Explicit expressions for all coefficients of the anomalous transport matrix relating particle and heat fluxes to density and temperature gradients in the plasma are obtained. The anomalous transport matrix calculated using the DIA does not have the Onsager symmetry. As an example of application, the parameters of the Texas Experimental Tokamak (TEXT) [Nucl. Technol. Fusion [bold 1], 479 (1981)] are used to evaluate all transport coefficients numerically, as well as the spectrum modulation. The relation between the theoretical results and the experimental data is discussed. Although this paper focuses on electron transport for simplicity, the method can also be used to calculate anomalous transport due to ion instabilities, such as the ion-temperature-gradient instability.

  16. Mass balancing of hollow fan blades

    NASA Technical Reports Server (NTRS)

    Kielb, R. E.

    1986-01-01

    A typical section model is used to analytically investigate the effect of mass balancing as applied to hollow, supersonic fan blades. A procedure to determine the best configuration of an internal balancing mass to provide flutter alleviation is developed. This procedure is applied to a typical supersonic shroudless fan blade which is unstable in both the solid configuration and when it is hollow with no balancing mass. The addition of an optimized balancing mass is shown to stabilize the blade at the design condition.

  17. Hollow mesoporous raspberry-like colloids with removable caps as photoresponsive nanocontainers

    NASA Astrophysics Data System (ADS)

    Hu, Chi; West, Kevin R.; Scherman, Oren A.

    2016-04-01

    The fabrication, characterisation and controlled cargo release of hollow mesoporous raspberry-like colloids (HMRCs), which are assembled by utilising host-guest complexation of cucurbit[8]uril (CB[8]) are described. CB[8] is employed as a supramolecular linker to `stick' the viologen functionalised paramagnetic iron oxide nanoparticles onto an azobenzene functionalised hollow mesoporous silica core. The formed HMRCs are photoresponsive and can be reversibly disassembled upon light irradiation, endowing them with an ability to release loaded cargo under photocontrol. While the assembled HMRCs retain cargo inside their cavity, disassembled particles with their iron oxide nanoparticle `caps' removed will release the loaded cargo through the mesoporous shell of the hollow silica colloids. A model system using a boronic acid derivative as the cargo in the HMRCs and Alizarin Red salt as a sensor for the released boronic acid is demonstrated.The fabrication, characterisation and controlled cargo release of hollow mesoporous raspberry-like colloids (HMRCs), which are assembled by utilising host-guest complexation of cucurbit[8]uril (CB[8]) are described. CB[8] is employed as a supramolecular linker to `stick' the viologen functionalised paramagnetic iron oxide nanoparticles onto an azobenzene functionalised hollow mesoporous silica core. The formed HMRCs are photoresponsive and can be reversibly disassembled upon light irradiation, endowing them with an ability to release loaded cargo under photocontrol. While the assembled HMRCs retain cargo inside their cavity, disassembled particles with their iron oxide nanoparticle `caps' removed will release the loaded cargo through the mesoporous shell of the hollow silica colloids. A model system using a boronic acid derivative as the cargo in the HMRCs and Alizarin Red salt as a sensor for the released boronic acid is demonstrated. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR01016D

  18. Anomalous Growth of Aging Populations

    NASA Astrophysics Data System (ADS)

    Grebenkov, Denis S.

    2016-04-01

    We consider a discrete-time population dynamics with age-dependent structure. At every time step, one of the alive individuals from the population is chosen randomly and removed with probability q_k depending on its age, whereas a new individual of age 1 is born with probability r. The model can also describe a single queue in which the service order is random while the service efficiency depends on a customer's "age" in the queue. We propose a mean field approximation to investigate the long-time asymptotic behavior of the mean population size. The age dependence is shown to lead to anomalous power-law growth of the population at the critical regime. The scaling exponent is determined by the asymptotic behavior of the probabilities q_k at large k. The mean field approximation is validated by Monte Carlo simulations.

  19. Novel LaBO3 hollow nanospheres of size 34±2 nm templated by polymeric micelles.

    PubMed

    Sasidharan, Manickam; Gunawardhana, Nanda; Luitel, Hom Nath; Yokoi, Toshiyuki; Inoue, Masamichi; Yusa, Shin-ichi; Watari, Takanori; Yoshio, Masaki; Tatsumi, Takashi; Nakashima, Kenichi

    2012-03-15

    Novel lanthanum borate (LaBO(3)) hollow nanospheres of size 34±2 nm have been reported for the first time by soft-template self-assembly process. Poly(styrene-b-acrylic acid-b-ethylene oxide) (PS-PAA-PEO) micelle with core-shell-corona architecture serves as an efficient soft template for fabrication of LaBO(3) hollow particles using sodium borohydride (NaBH(4)) and LaCl(3)⋅7H(2)O as the precursors. In this template, the PS block (core) acts as a template of the void space of hollow particle, the anionic PAA block (shell) serves as reaction field for metal ion interactions, and the PEO block (corona) stabilizes the polymer/lanthana composite particles. The PS-PAA-PEO micelles and the resulting LaBO(3) hollow nanospheres were thoroughly characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), X-ray diffraction, magic angle spinning-nuclear magnetic resonance ((11)B MAS NMR), energy dispersive X-ray analysis, thermal analyses, Fourier transform infra red spectroscopy, and nitrogen adsorption/desorption analyses. The nitrogen adsorption/desorption analyses and TEM observation of the hollow particles confirmed the presence of disordered mesopores in the LaBO(3) shell domain. The solid state (11)B MAS NMR spectra of LaBO(3) hollow nanospheres revealed that the shell part contains both trigonal and tetrahedral boron species. The LaBO(3) hollow particles were applied to anode materials in lithium-ion rechargeable batteries (LIBs). The hollow particles exhibited high coulombic efficiency and charge-discharge cycling capacities of up to 100 cycles in the LIBs. PMID:22257959

  20. Anomalous extracellular diffusion in rat cerebellum.

    PubMed

    Xiao, Fanrong; Hrabe, Jan; Hrabetova, Sabina

    2015-05-01

    Extracellular space (ECS) is a major channel transporting biologically active molecules and drugs in the brain. Diffusion-mediated transport of these substances is hindered by the ECS structure but the microscopic basis of this hindrance is not fully understood. One hypothesis proposes that the hindrance originates in large part from the presence of dead-space (DS) microdomains that can transiently retain diffusing molecules. Because previous theoretical and modeling work reported an initial period of anomalous diffusion in similar environments, we expected that brain regions densely populated by DS microdomains would exhibit anomalous extracellular diffusion. Specifically, we targeted granular layers (GL) of rat and turtle cerebella that are populated with large and geometrically complex glomeruli. The integrative optical imaging (IOI) method was employed to evaluate diffusion of fluorophore-labeled dextran (MW 3000) in GL, and the IOI data analysis was adapted to quantify the anomalous diffusion exponent dw from the IOI records. Diffusion was significantly anomalous in rat GL, where dw reached 4.8. In the geometrically simpler turtle GL, dw was elevated but not robustly anomalous (dw = 2.6). The experimental work was complemented by numerical Monte Carlo simulations of anomalous ECS diffusion in several three-dimensional tissue models containing glomeruli-like structures. It demonstrated that both the duration of transiently anomalous diffusion and the anomalous exponent depend on the size of model glomeruli and the degree of their wrapping. In conclusion, we have found anomalous extracellular diffusion in the GL of rat cerebellum. This finding lends support to the DS microdomain hypothesis. Transiently anomalous diffusion also has a profound effect on the spatiotemporal distribution of molecules released into the ECS, especially at diffusion distances on the order of a few cell diameters, speeding up short-range diffusion-mediated signals in less permeable

  1. Nanostructural transformations during the reduction of hollow and porous nickel oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Medford, John A.; Johnston-Peck, Aaron C.; Tracy, Joseph B.

    2012-12-01

    Size-dependent nanostructural transformations occurring during the H2-mediated reduction of hollow and porous NiO nanoparticles were investigated for controlled nanoparticle sizes of ~10 to 100 nm. Transmission electron microscopy reveals that the location and number of reduction sites strongly depend on the nanoparticle size and structure.Size-dependent nanostructural transformations occurring during the H2-mediated reduction of hollow and porous NiO nanoparticles were investigated for controlled nanoparticle sizes of ~10 to 100 nm. Transmission electron microscopy reveals that the location and number of reduction sites strongly depend on the nanoparticle size and structure. Electronic supplementary information (ESI) available: Additional TEM images, SAED, and HRTEM images without color overlays. See DOI: 10.1039/c2nr33005a

  2. Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping

    NASA Astrophysics Data System (ADS)

    Frasinski, L. J.; Zhaunerchyk, V.; Mucke, M.; Squibb, R. J.; Siano, M.; Eland, J. H. D.; Linusson, P.; v. d. Meulen, P.; Salén, P.; Thomas, R. D.; Larsson, M.; Foucar, L.; Ullrich, J.; Motomura, K.; Mondal, S.; Ueda, K.; Osipov, T.; Fang, L.; Murphy, B. F.; Berrah, N.; Bostedt, C.; Bozek, J. D.; Schorb, S.; Messerschmidt, M.; Glownia, J. M.; Cryan, J. P.; Coffee, R. N.; Takahashi, O.; Wada, S.; Piancastelli, M. N.; Richter, R.; Prince, K. C.; Feifel, R.

    2013-08-01

    When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called “partial covariance mapping” to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

  3. Gastroretentive delivery systems: hollow beads.

    PubMed

    Talukder, R; Fassihi, R

    2004-04-01

    The objective of this study was to develop a floatable multiparticulate system with potential for intragastric sustained drug delivery. Cross-linked beads were made by using calcium and low methoxylated pectin (LMP), which is an anionic polysaccharide, and calcium, LMP, and sodium alginate. Beads were dried separately in an air convection type oven at 40 degrees C for 6 hours and in a freeze dryer to evaluate the changes in bead characteristics due to process variability. Riboflavin (B-2), tetracycline (TCN), and Methotrexate (MTX) were used as model drugs for encapsulation. Ionic and nonionic excipients were added to study their effects on the release profiles of the beads. The presence of noncross linking agents in low amounts (less than 2%) did not significantly interfere with release kinetics. For an amphoteric drug like TCN, which has pH dependent solubility, three different pHs (1.5, 5.0, and 8.0) of cross-linking media were used to evaluate the effects of pH on the drug entrapment capacity of the beads. As anticipated, highest entrapment was possible when cross-linking media pH coincided with least drug solubility. Evaluation of the drying process demonstrated that the freeze-dried beads remained buoyant over 12 hours in United States Pharmacopeia (USP) hydrochloride buffer at pH 1.5, whereas the air-dried beads remained submerged throughout the release study. Confocal laser microscopy revealed the presence of air-filled hollow spaces inside the freeze dried beads, which was responsible for the flotation property of the beads. However, the release kinetics from freeze dried beads was independent of hydrodynamic conditions. Calcium-pectinate-alginate beads released their contents at much faster rates than did calcium-pectinate beads (100% in 10 hours vs. 50% in 10 hours). It appears that the nature of cross-linking, drying method, drug solubility, and production approach are all important and provide the opportunity and potential for development of a

  4. The hollow cathode in the quasi-steady MPD discharge

    NASA Technical Reports Server (NTRS)

    Von Jaskowsky, W. F.; Jahn, R. G.; Clark, K. E.; Krishnan, M.

    1973-01-01

    A large hollow cathode has been operated in a quasi-steady MPD discharge over a range of current from 7 to 30 kA and argon mass flow from 0.04 to 6.0 g/sec. The 1.3-cm-i.d. cathode cavity attains steady emission characteristics in some tens of microseconds without the assistance of auxiliary heating, low work function inserts, or external keeper electrodes. Measured current and potential distributions within the cavity reveal that the current attaches in a zone 1 to 2 cm long with a surface current density greater than 1000 A/sq cm and a local axial electric field less than 10 V/cm. Electron densities within the cavity, estimated from spectroscopic records, are above 10 to the 17th power per cu cm, at least one order of magnitude greater than has been reported for either ion engine hollow cathodes or conventional solid cathodes in similar arc discharges.

  5. Hollow circular-truncated cone resonator and its hollow variable biconical laser beam

    NASA Astrophysics Data System (ADS)

    Liu, Jinglun; Chen, Mei; Wang, Qionghua; Sun, Nianchun

    2014-05-01

    To obtain a hollow variable biconical laser beam (HVBLB), a CO2 laser having a hollow circular-truncated cone resonator (HCTCR) is presented. This HCTCR comprises a rotationally symmetric total-reflecting concave mirror at the bottom, a rotationally symmetric part-reflecting convex mirror at the top, and a hollow circular-truncated cone discharge tube at the middle. The cross section of this generated biconical laser beam changes from annulus to circular to annulus and the size of this cross section from big to small to large as the propagation distance increases. So, a kind of laser beam with variable center intensity from zero to peak value to zero is obtained and is known as HVBLB. Due to the inclusion of part of the hollow laser beam (HLB) and solid laser beam, this HVBLB requires no additional beam-shaping element and has broad applications such as optical trapping and commercial manufacturing.

  6. Novel hollow mesoporous 1D TiO2 nanofibers as photovoltaic and photocatalytic materials.

    PubMed

    Zhang, Xiang; Thavasi, Velmurugan; Mhaisalkar, S G; Ramakrishna, Seeram

    2012-03-01

    Hollow mesoporous one dimensional (1D) TiO(2) nanofibers are successfully prepared by co-axial electrospinning of a titanium tetraisopropoxide (TTIP) solution with two immiscible polymers; polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) using a core-shell spinneret, followed by annealing at 450 °C. The annealed mesoporous TiO(2) nanofibers are found to having a hollow structure with an average diameter of 130 nm. Measurements using the Brunauer-Emmett-Teller (BET) method reveal that hollow mesoporous TiO(2) nanofibers possess a high surface area of 118 m(2) g(-1) with two types of mesopores; 3.2 nm and 5.4 nm that resulted from gaseous removal of PEO and PVP respectively during annealing. With hollow mesoporous TiO(2) nanofibers as the photoelectrode in dye sensitized solar cells (DSSC), the solar-to-current conversion efficiency (η) and short circuit current (J(sc)) are measured as 5.6% and 10.38 mA cm(-2) respectively, which are higher than those of DSSC made using regular TiO(2) nanofibers under identical conditions (η = 4.2%, J(sc) = 8.99 mA cm(-2)). The improvement in the conversion efficiency is mainly attributed to the higher surface area and mesoporous TiO(2) nanostructure. It facilitates the adsorption of more dye molecules and also promotes the incident photon to electron conversion. Hollow mesoporous TiO(2) nanofibers with close packing of grains and crystals intergrown with each other demonstrate faster electron diffusion, and longer electron recombination time than regular TiO(2) nanofibers as well as P25 nanoparticles. The surface effect of hollow mesoporous TiO(2) nanofibers as a photocatalyst for the degradation of rhodamine dye was also investigated. The kinetic study shows that the hollow mesoporous surface of the TiO(2) nanofibers influenced its interactions with the dye, and resulted in an increased catalytic activity over P25 TiO(2) nanocatalysts. PMID:22315140

  7. Anomalous frequency dependent diamagnetism in metal silicide

    NASA Astrophysics Data System (ADS)

    Dahal, Ashutosh; Gunasekera, Jagat; Harriger, Leland; Singh, David J.; Singh, Deepak K.; Leland Harriger Collaboration

    Discovery of superconductivity in PbO-type FeSe has generated a lot of interest. Among the samples we synthesize with similar structure, NiSi has showed anomalous but very interesting results. Nickel silicides are important electronic materials that have been used as contacts for field effect transistors, as interconnects and in nanoelectronic devices. The magnetic properties of NiSi are not well known, however. In this presentation, we report a highly unusual magnetic phenomenon in NiSi. The ac susceptibility measurements on NiSi reveal strong frequency dependence of static and dynamic susceptibilities that are primarily diamagnetic at room temperature. The static susceptibility is found to exhibit a strong frequency dependence of the diamagnetic response below 100K, while dynamic susceptibility showed peak type feature at 10KHz frequency around 50K. Detailed neutron scattering measurements on high quality powder sample of NiSi on SPINS cold spectrometer further revealed an inelastic peak around 1.5meV, even though no magnetic order is detected. The inelastic peak dissipates above 100K, which is where the static susceptibility starts to diverge with frequency. Research is supported by U.S. Department of Energy, Office of Basic Energy Sciences under Grant No. DE-SC0014461.

  8. Anomalous neuronal responses to fluctuated inputs

    NASA Astrophysics Data System (ADS)

    Hosaka, Ryosuke; Sakai, Yutaka

    2015-10-01

    The irregular firing of a cortical neuron is thought to result from a highly fluctuating drive that is generated by the balance of excitatory and inhibitory synaptic inputs. A previous study reported anomalous responses of the Hodgkin-Huxley neuron to the fluctuated inputs where an irregularity of spike trains is inversely proportional to an input irregularity. In the current study, we investigated the origin of these anomalous responses with the Hindmarsh-Rose neuron model, map-based models, and a simple mixture of interspike interval distributions. First, we specified the parameter regions for the bifurcations in the Hindmarsh-Rose model, and we confirmed that the model reproduced the anomalous responses in the dynamics of the saddle-node and subcritical Hopf bifurcations. For both bifurcations, the Hindmarsh-Rose model shows bistability in the resting state and the repetitive firing state, which indicated that the bistability was the origin of the anomalous input-output relationship. Similarly, the map-based model that contained bistability reproduced the anomalous responses, while the model without bistability did not. These results were supported by additional findings that the anomalous responses were reproduced by mimicking the bistable firing with a mixture of two different interspike interval distributions. Decorrelation of spike trains is important for neural information processing. For such spike train decorrelation, irregular firing is key. Our results indicated that irregular firing can emerge from fluctuating drives, even weak ones, under conditions involving bistability. The anomalous responses, therefore, contribute to efficient processing in the brain.

  9. Anomalous neuronal responses to fluctuated inputs.

    PubMed

    Hosaka, Ryosuke; Sakai, Yutaka

    2015-10-01

    The irregular firing of a cortical neuron is thought to result from a highly fluctuating drive that is generated by the balance of excitatory and inhibitory synaptic inputs. A previous study reported anomalous responses of the Hodgkin-Huxley neuron to the fluctuated inputs where an irregularity of spike trains is inversely proportional to an input irregularity. In the current study, we investigated the origin of these anomalous responses with the Hindmarsh-Rose neuron model, map-based models, and a simple mixture of interspike interval distributions. First, we specified the parameter regions for the bifurcations in the Hindmarsh-Rose model, and we confirmed that the model reproduced the anomalous responses in the dynamics of the saddle-node and subcritical Hopf bifurcations. For both bifurcations, the Hindmarsh-Rose model shows bistability in the resting state and the repetitive firing state, which indicated that the bistability was the origin of the anomalous input-output relationship. Similarly, the map-based model that contained bistability reproduced the anomalous responses, while the model without bistability did not. These results were supported by additional findings that the anomalous responses were reproduced by mimicking the bistable firing with a mixture of two different interspike interval distributions. Decorrelation of spike trains is important for neural information processing. For such spike train decorrelation, irregular firing is key. Our results indicated that irregular firing can emerge from fluctuating drives, even weak ones, under conditions involving bistability. The anomalous responses, therefore, contribute to efficient processing in the brain. PMID:26565270

  10. Growth of hollow nickel fluoride whiskers

    SciTech Connect

    Petrov, S. V.; Orekhov, Yu. F.; Fedorov, P. P.

    2009-07-15

    Hollow nickel fluoride whiskers have been obtained by condensation from the vapor phase onto a platinum substrate in a flow of hydrogen fluoride. Crystals up to 5 mm in length have a square cross section with a 300 {+-} 30-{mu}m side. The wall thickness is 85 {+-} 20 {mu}m.

  11. Precise microinjection into skin using hollow microneedles.

    PubMed

    Wang, Ping M; Cornwell, Megan; Hill, James; Prausnitz, Mark R

    2006-05-01

    Hollow needles of micron dimensions have previously been fabricated and envisioned for use with transdermal patches or infusion pumps to achieve painless delivery of drugs to the skin for local and systemic effects without the need for hypodermic needles. However, little work has been carried out to identify methods to effectively use hollow microneedles for drug delivery. To address this need, we inserted hollow, glass microneedles into hairless rat skin in vivo and human cadaver skin in vitro and then imaged infusion of dye molecules, insulin, polymer microparticles, and cells into the skin by brightfield and fluorescence microscopy. The depth of needle penetration into skin was controlled by inserting needles with a rotary drilling device, which enabled localized injection within the epidermis or dermis with +/-60 microm resolution. Although small quantities of fluid could be injected after needle insertion into skin, partial retraction of the needle by withdrawing back 100-300 microm or vibrating the microneedle array dramatically increased infusion flow rate. We conclude that hollow microneedles can be used for precise microinjection into skin, especially when a single needle is inserted by rotary drilling and then retracted part way before infusion or a microneedle array is inserted by mechanical vibration. PMID:16484988

  12. Method for preparing hollow metal oxide microsphere

    DOEpatents

    Schmitt, C.R.

    1974-02-12

    Hollow refractory metal oxide microspheres are prepared by impregnating resinous microspheres with a metallic compound, drying the impregnated microspheres, heating the microspheres slowly to carbonize the resin, and igniting the microspheres to remove the carbon and to produce the metal oxide. Zirconium oxide is given as an example. (Official Gazette)

  13. Evidence of high-n hollow-ion emission from Si ions pumped by ultraintense x-rays from relativistic laser plasma

    NASA Astrophysics Data System (ADS)

    Colgan, J.; Faenov, A. Ya.; Pikuz, S. A.; Tubman, E.; Butler, N. M. H.; Abdallah, J., Jr.; Dance, R. J.; Pikuz, T. A.; Skobelev, I. Yu.; Alkhimova, M. A.; Booth, N.; Green, J.; Gregory, C.; Andreev, A.; Lötzsch, R.; Uschmann, I.; Zhidkov, A.; Kodama, R.; McKenna, P.; Woolsey, N.

    2016-05-01

    We report on the first observation of high-n hollow ions (ions having no electrons in the K or L shells) produced in Si targets via pumping by ultra-intense x-ray radiation produced in intense laser-plasma interactions reaching the radiation dominant kinetics regime (RDKR). The existence of these new types of hollow ions in high-energy density plasma has been found via observation of highly resolved x-ray emission spectra of silicon plasma. This has been confirmed by plasma kinetics calculations, underscoring the ability of powerful radiation sources to fully strip electrons from the innermost shells of light atoms. Hollow-ions spectral diagnostics provide a unique opportunity to characterize powerful x-ray radiation of laboratory and astrophysical plasmas. With the use of this technique we provide evidence for the existence of the RDKR via observation of asymmetry in the observed radiation of hollow ions from the front and rear sides of the target.

  14. Hollow cobalt phosphonate spherical hybrid as high-efficiency Fenton catalyst

    NASA Astrophysics Data System (ADS)

    Zhu, Yun-Pei; Ren, Tie-Zhen; Yuan, Zhong-Yong

    2014-09-01

    catalytic oxidizing decomposition of methylene blue with sulfate radicals as compared to cobalt phosphonate nanoparticles synthesized in single water system, which could be attributed to enhanced mass transfer and high surface area for the hollow material. Some operational parameters, including pH and reaction temperature, were found to influence the oxidation process. The present results suggest that cobalt phosphonate material can perform as an efficient heterogeneous catalyst for the degradation of organic contaminants, providing insights into the rational design and development of alternative catalysts for wastewater treatment. Electronic supplementary information (ESI) available: XRD patterns and digital photographs of DTPMP. See DOI: 10.1039/c4nr02679a

  15. Synthesis and luminescence of hollow spherical Eu3+- or Tb3+ -doped MgAl2O4 phosphors.

    PubMed

    Wang, Jinghui; Ye, Junwei; Lin, Yuan; Chen, Wendan; Ning, Guiling

    2010-01-01

    Eu3+- or Tb3+ -doped MgAl2O4 hollow spheres have been successfully synthesized via facile hydrothermal method by using carbon spheres as template followed by a subsequent heat treatment. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed that the hollow microspheres possessed diameters in the range of 1-2.5 microm and shell thickness of 60-80 nm. A possible formation mechanism for hollow spheres was proposed. MgAl2O4:Eu3+ show strong red emission at 619 nm corresponding to the forced electric dipole (5)D0-->(7)F2 transition of Eu3+, and MgAl2O4:Tb3+ exhibit strong green emission at 545 nm corresponding to 5D4-->(7)F5 transition of Tb3+. PMID:20352894

  16. Experimental phasing using zinc anomalous scattering

    SciTech Connect

    Cha, Sun-Shin; An, Young Jun; Jeong, Chang-Sook; Kim, Min-Kyu; Lee, Sung-Gyu; Lee, Kwang-Hoon; Oh, Byung-Ha

    2012-09-01

    The surface of proteins can be charged with zinc ions and the anomalous signals from these zinc ions can be used for structure determination of proteins. Zinc is a suitable metal for anomalous dispersion phasing methods in protein crystallography. Structure determination using zinc anomalous scattering has been almost exclusively limited to proteins with intrinsically bound zinc(s). Here, it is reported that multiple zinc ions can easily be charged onto the surface of proteins with no intrinsic zinc-binding site by using zinc-containing solutions. Zn derivatization of protein surfaces appears to be a largely unnoticed but promising method of protein structure determination.

  17. Plasma processes inside dispenser hollow cathodes

    NASA Astrophysics Data System (ADS)

    Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Polk, James E.; Jameson, Kristina K.

    2006-06-01

    A two-dimensional fluid model of the plasma and neutral gas inside dispenser orificed hollow cathodes has been developed to quantify plasma processes that ultimately determine the life of the porous emitters inserted in these devices. The model self-consistently accounts for electron emission from the insert as well as for electron and ion flux losses from the plasma. Two cathodes, which are distinctively different in size and operating conditions, have been simulated numerically. It is found that the larger cathode, with outer tube diameter of 1.5cm and orifice diameter of 0.3cm, establishes an effective emission zone that spans approximately the full length of the emitter when operated at a discharge current of 25A and a flow rate of 5.5sccm. The net heating of the emitter is caused by ions that are produced by ionization of the neutral gas inside the tube and are then accelerated by the sheath along the emitter. The smaller cathode, with an outer diameter of 0.635cm and an orifice diameter of 0.1cm, does not exhibit the same operational characteristics. At a flow rate of 4.25sccm and discharge current of 12A, the smaller cathode requires 4.5 times the current density near the orifice and operates with more than 6 times the neutral particle density compared to the large cathode. As a result, the plasma particle density is almost one order of magnitude higher compared to the large cathode. The plasma density in this small cathode is high enough such that the Debye length is sufficiently small to allow "sheath funneling" into the pores of the emitter. By accessing areas deeper into the insert material, it is postulated that the overall emission of electrons is significantly enhanced. The maximum emission current density is found to be about 1A/mm2 in the small cathode, which is about one order of magnitude higher than attained in the large cathode. The effective emission zone in the small cathode extends to about 15% of the emitter length only, and the power

  18. Mechanism of hollow-core-fiber infrared-supercontinuum compression with bulk material

    SciTech Connect

    Bejot, P.; Schmidt, B. E.; Legare, F.; Kasparian, J.; Wolf, J.-P.

    2010-06-15

    We numerically investigate the pulse compression mechanism in the infrared spectral range based on the successive action of nonlinear pulse propagation in a hollow-core fiber followed by linear propagation through bulk material. We found an excellent agreement of simulated pulse properties with experimental results at 1.8 {mu}m in the two-optical-cycle regime close to the Fourier limit. In particular, the spectral phase asymmetry attributable to self-steepening combined with self-phase modulation is a necessary prerequisite for subsequent compensation by the phase introduced by glass material in the anomalous dispersion regime. The excellent agreement of the model enabled simulating pressure and wavelength tunability of sub-two cycles in the range from 1.5 to 4 {mu}m with this cost-efficient and robust approach.

  19. Experimental realization of acoustic metasurface with double-split hollow sphere

    NASA Astrophysics Data System (ADS)

    Ding, Chang-Lin; Wang, Zhen-Ru; Shen, Fang-Liang; Chen, Huai-Jun; Zhai, Shi-Long; Zhao, Xiao-Peng

    2016-03-01

    We experimentally present an acoustic metasurface (AMS) with sub-wavelength thickness based on the meta-molecule consisting of eight different sized double-split hollow spheres (DSHSs). By designing the discontinuous phase profile covered 2π span induced by the DSHSs, the AMS can manipulate the reflected acoustic waves in a way that could not be imitated by natural materials. Both simulations and experiments show that the AMS can realize anomalous reflection, i.e., a normal incident wave can be reflected into an oblique direction. Moreover, the reflection angle can be flexible controlled by mechanically tuning the spatial distance of the DSHSs in the AMS, which is consistent with the generalized Snell's law.

  20. Ion acoustic turbulence in a 100-A LaB₆ hollow cathode.

    PubMed

    Jorns, Benjamin A; Mikellides, Ioannis G; Goebel, Dan M

    2014-12-01

    The temporal fluctuations in the near plume of a 100-A LaB(6) hollow cathode are experimentally investigated. A probe array is employed to measure the amplitude and dispersion of axial modes in the plume, and these properties are examined parametrically as a function of cathode operating conditions. The onset of ion acoustic turbulence is observed at high current and is characterized by a power spectrum that exhibits a cutoff at low frequency and an inverse dependence on frequency at high values. The amplitude of the turbulence is found to decrease with flow rate but to depend nonmonotonically on discharge current. Estimates of the anomalous collision frequency based on experimental measurements indicate that the ion acoustic turbulence collision frequency can exceed the classical rate at high discharge current densities by nearly two orders of magnitude. PMID:25615204

  1. Preparation of hollow core/shell microspheres of hematite and its adsorption ability for samarium.

    PubMed

    Yu, Sheng-Hui; Yao, Qi-Zhi; Zhou, Gen-Tao; Fu, Sheng-Quan

    2014-07-01

    Hollow core/shell hematite microspheres with diameter of ca. 1-2 μm have been successfully achieved by calcining the precursor composite microspheres of pyrite and polyvinylpyrrolidone (PVP) in air. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) gas sorptometry. Temperature- and time-dependent experiments unveil that the precursor pyrite-PVP composite microspheres finally transform into hollow core/shell hematite microspheres in air through a multistep process including the oxidation and sulfation of pyrite, combustion of PVP occluded in the precursor, desulfation, aggregation, and fusion of nanosized hematite as well as mass transportation from the interior to the exterior of the microspheres. The formation of the hollow core/shell microspheres dominantly depends on the calcination temperature under current experimental conditions, and the aggregation of hematite nanocrystals and the core shrinking during the oxidation of pyrite are responsible for the formation of the hollow structures. Moreover, the adsorption ability of the hematite for Sm(III) was also tested. The results exhibit that the hematite microspheres have good adsorption activity for trivalent samarium, and that its adsorption capacity strongly depends on the pH of the solution, and the maximum adsorption capacity for Sm(III) is 14.48 mg/g at neutral pH. As samarium is a typical member of the lanthanide series, our results suggest that the hollow hematite microspheres have potential application in removal of rare earth elements (REEs) entering the water environment. PMID:24892188

  2. Fabrication of hollow mesoporous NiO hexagonal microspheres via hydrothermal process in ionic liquid

    SciTech Connect

    Zhao, Jinbo; Wu, Lili; Zou, Ke

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Ni(OH){sub 2} precursors were synthesized in ionic liquid and water solution by hydrothermal method. Black-Right-Pointing-Pointer NiO hollow microspheres were prepared by thermal treatment of Ni(OH){sub 2} precursors. Black-Right-Pointing-Pointer NiO hollow microspheres were self-assembled by mesoporous cubic and hexagonal nanocrystals with high specific surface area. Black-Right-Pointing-Pointer The mesoporous structure is stable at 773 K. Black-Right-Pointing-Pointer The ionic liquid absorbed on the O-terminate surface of the crystals to form hydrogen bond and played key roles in determining the final shape of the NiO novel microstructure. -- Abstract: The novel NiO hexagonal hollow microspheres have been successfully prepared by annealing Ni(OH){sub 2}, which was synthesized via an ionic liquid-assisted hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), N{sub 2} adsorption-desorption and Fourier transform infrared spectrometer (FTIR). The results show that the hollow NiO microstructures are self-organized by mesoporous cubic and hexagonal nanocrystals. The mesoporous structure possessed good thermal stability and high specific surface area (ca. 83 m{sup 2}/g). The ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim][BF{sub 4}]) was found to play a key role in controlling the morphology of NiO microstructures during the hydrothermal process. The special hollow mesoporous architectures will have potential applications in many fields, such as catalysts, absorbents, sensors, drug-delivery carriers, acoustic insulators and supercapacitors.

  3. Y2O3:Eu3+ core-in-multi-hollow microspheres: facile synthesis and luminescence properties.

    PubMed

    Liu, Guixia; Liu, Shujun; Dong, Xiangting; Wang, Jinxian

    2011-11-01

    Y2O3:Eu3+ core-in-multi-hollow microspheres were synthesized via a facile hydrothermal method in the presence of glucose followed by a subsequent heat-treatment process. X-ray diffraction (XRD) pattern shows that the as-obtained hollow spheres are cubic phase of Y2O3. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images indicate that the samples are three layer hollow spheres with a diameter of 2-4 microm and the outermost wall thickness of 100 nm, the size of the inner core is about 300-400 nm, and the sub-outer wall thickness is about 100 nm. X-ray energy dispersive spectrum (EDS) shows that the samples are composed of Y, Eu and O. Photoluminescence spectra show that the hollow spheres have a strong characteristic red emission corresponding to the 5D0 - 7F2 transition of Eu3+ ions under ultraviolet excitation. This method can be used to synthesize other rare earth oxide hollow luminescent materials. PMID:22413288

  4. Hierarchical NiO-SiO2 composite hollow microspheres with enhanced adsorption affinity towards Congo red in water.

    PubMed

    Lei, Chunsheng; Zhu, Xiaofeng; Zhu, Bicheng; Yu, Jiaguo; Ho, Wingkei

    2016-03-15

    Hollow microspheres and hierarchical porous nanostructured materials with desired morphologies have gained remarkable attention for their potential applications in environmental technology. In this study, NiO-SiO2 hollow microspheres were prepared by co-precipitation with SiO2 and nickel salt as precursors, followed by dipping in alkaline solution and calcination. The samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption, and X-ray photoelectron spectroscopy. The synthesized hollow spheres were composed of a SiO2 shell and hierarchical porous NiO nanosheets on the surface. Adsorption experiments suggested that NiO-SiO2 composite particles were powerful adsorbents for removal of Congo red from water, with a maximum adsorption capacity of 204.1 mg/g. The high specific surface areas, hollow structures, and hierarchical porous surfaces of the hollow composite particles are suitable for various applications, including adsorption of pollutants, chemical separation, and water purification. PMID:26724707

  5. Modelling anomalous extinction using nanodiamonds

    NASA Astrophysics Data System (ADS)

    Rai, Rakesh K.; Rastogi, Shantanu

    2012-07-01

    The modelling of extinction along anomalous/non-Cardelli, Clayton & Mathis sightlines, which are characterized by a broad 217.5-nm bump and steep far-ultraviolet (FUV) rise, is reported. The extinction along these sightlines, namely HD 210121, HD 204827, HD 29647 and HD 62542, is difficult to reproduce using standard silicate and graphite grains. A very good match with the observed extinction is obtained by considering a nanodiamond component as part of the carbonaceous matter. Most of these sightlines are rich in carbon and are invariably backed by a young hot stellar object. Nanodiamond is taken as a core within amorphous carbon and graphite. These core-mantle particles, taken as additional components along with graphite and silicates, lead to a reduction in the silicate requirement. The abundance of carbonaceous matter is not affected, as a very small fraction of nanodiamond is required. Extinction along sightlines that show steep FUV is also reported, demonstrating the importance of the nanodiamond component in all such regions.

  6. Electrospun manganese-cobalt oxide hollow nanofibres synthesized via combustion reactions and their lithium storage performance

    NASA Astrophysics Data System (ADS)

    Hwang, Soo Min; Kim, So Yeun; Kim, Jae-Geun; Kim, Ki Jae; Lee, Jong-Won; Park, Min-Sik; Kim, Young-Jun; Shahabuddin, Mohammed; Yamauchi, Yusuke; Kim, Jung Ho

    2015-04-01

    Mesoporous hollow fibres of MnCo2O4 and CoMn2O4 were synthesized by electrospinning and highly exothermic oxygen-mediated combustion reactions during calcination, in which the heating rate affected the final fibre morphology (e.g., single- or double-shell). The anodes consisting of hollow fibres showed excellent electrochemical properties for lithium-ion batteries.Mesoporous hollow fibres of MnCo2O4 and CoMn2O4 were synthesized by electrospinning and highly exothermic oxygen-mediated combustion reactions during calcination, in which the heating rate affected the final fibre morphology (e.g., single- or double-shell). The anodes consisting of hollow fibres showed excellent electrochemical properties for lithium-ion batteries. Electronic supplementary information (ESI) available: Experimental section; additional thermal analyses; XRD patterns; SEM and TEM results; N2 adsorption isotherms; differential capacity plots of galvanostatic voltage profiles and coulombic efficiency during cycling. See DOI: 10.1039/c5nr01145k

  7. Synthesis and characterization of Eu3+:Gd2O3 hollow spheres for biomedical applications

    NASA Astrophysics Data System (ADS)

    Kumari, Manisha; Sharma, Prashant K.

    2016-05-01

    Multifunctional magnetic Nanoparticles (MFMNPs) are potentially applicable in both drug delivery systems (DDS) and hyperthermia treatment. Structural, surface morphology and optical property were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and photoluminescence (PL) measurement. Uniform Eu3+:Gd2O3 hollow microspheres of 1.8-2.0 μm diameters were synthesized by template based approach. We found that synthesized Hollow spheres are 100 nm in thickness. FE-SEM images revealed that the synthesized material are hollow in structure with good porous structure and these pores work as pathway for releasing drugs from the hollow particle inside. Luminescent properties of material were studied by room temperature photoluminescence emission spectra under the excitation of 275 nm. Material exhibit bright red emission corresponding to the 5D0-7F2 transition of the activator ions under ultraviolet light excitation, which might find potential applications in fields such as drug delivery or biological labeling because of their excellent luminescence properties.

  8. Wakefield structure of plasma hollow channels self-driven by tightly focused beams

    NASA Astrophysics Data System (ADS)

    Amorim, Ligia D.; Vieira, Jorge; Fonseca, Ricardo A.; Silva, Luis O.

    2015-11-01

    Plasma based wakefield accelerators (PWFA) are promising alternatives to conventional configurations due to the high accelerating gradients they can sustain. For future linear colliders, however, PWFAs need to overcome the challenge of efficiently accelerating positrons. PWFAs regimes with high acceleration gradients typically defocus positron bunches. Several techniques have tried to solve this challenge. Here we explore how tightly focused positron bunches sent through homogeneous plasmas can radially expel the plasma ions generating a hollow channel with high accelerating and focusing fields. We modeled the hollow channel accelerating and focusing wakefields structures analytically, and found good agreement with 3D numerical simulations performed with the PIC code OSIRS. We demonstrated that this scheme could accelerate positrons to high energies. Furthermore, we analyzed the impact of the key drive bunch properties on the formation of the hollow channel, finding that bunches with short fall times (compared to electron bubble radius) and small transverse sizes (compared to plasma skin depth) maximize both accelerating and focusing fields. We also studied hollow channels driven by laser beams. Work supported by FCT grant SFRH/BD/84851/2012. We acknowledge PRACE for access to resources on SuperMUC (Leibniz Research Center).

  9. Hollow polycaprolactone composite fibers for controlled magnetic responsive antifungal drug release.

    PubMed

    Wang, Baolin; Zheng, Hongxia; Chang, Ming-Wei; Ahmad, Zeeshan; Li, Jing-Song

    2016-09-01

    Hollow magnetic fibers for trigger based drug release were synthesized using one-step co-axial electrospinning (COX-ES). This was achieved by encapsulating the antifungal active 'ketoconazole' (KCZ) and iron oxide (Fe3O4) nanoparticles (NPs) in composite form within the core shell polymeric matrix material (polycaprolactone, PCL) during the COX-ES process. Dimethyl silicone oil was used as the inner core (liquid) of co-flowing solutions, which subsequently perfused out of the two-phase electrospun microstructures to form hollow fibers. Resulting drug-loaded magnetic hollow fibers were characterized using optical microscopy, scanning electron microscopy and Fourier Transform Infra-Red. The tensile strength and magnetization properties of composite fibers were also assessed. KCZ drug concentration in electrospinning solutions strongly influenced resulting fiber morphology, drug loading efficiency and release. Expedited drug release during a slow-sustained phase was demonstrated through the application of an auxiliary magnetic field. Variations in tensile strength (∼1.3-6.3MPa) were due to composite fiber components compromising polymer chain integrity. In-vitro cell studies (using human cervical carcinoma cell lines) demonstrated fiber biocompatibility. The present study demonstrates the potential application of magnetic hollow fibers for controlled treatment of fungal infections and antimicrobial indications. PMID:27295492

  10. Preparation of hollow hydroxyapatite microspheres by the conversion of borate glass at near room temperature

    SciTech Connect

    Yao, Aihua; Ai, Fanrong; Liu, Xin; Wang, Deping; Huang, Wenhai; Xu, Wei

    2010-01-15

    Hollow hydroxyapatite microspheres, consisting of a hollow core and a porous shell, were prepared by converting Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres in dilute phosphate solution at 37 {sup o}C. The results confirmed that Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass was transformed to hydroxyapatite without changing the external shape and dimension of the original glass object. Scanning electron microscopy images showed the shell wall of the microsphere was built from hydroxyapatite particles, and these particles spontaneously align with one another to form a porous sphere with an interior cavity. Increase in phosphate concentration resulted in an increase in the reaction rate, which in turn had an effect on shell wall structure of the hollow hydroxyapatite microsphere. For the Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres reacted in low-concentration K{sub 2}HPO{sub 4} solution, lower reaction rate and a multilayered microstructure were observed. On the other hand, the glass microspheres reacted in higher phosphate solution converted more rapidly and produced a single hydroxyapatite layer. Furthermore, the mechanism of forming hydroxyapatite hollow microsphere was described.

  11. Gold nanorod-templated synthesis of polymetallic hollow nanostructures with enhanced electrocatalytic performance.

    PubMed

    Guo, Xia; Ye, Wei; Zhu, Rui; Wang, Wenxin; Xie, Fang; Sun, Hongyan; Zhao, Qing; Ding, Yi; Yang, Jian

    2014-10-21

    Anisotropic polymetallic hollow nanostructures are highly desired for many applications because of their unique morphology, large specific surface areas and attractive electronic effects. Here, a simple method using gold nanorods as a self-sacrificed template has been developed for the fabrication of hollow dumbbell-like nanorods of Au@PtAg. The formation of the hollow structures involves the growth of another metallic shell first, and then the etching of gold nanorods, which is induced by oxygen and ascorbic acid. The lattice mismatch and cohesive energy of the shell, along with its surface passivation, greatly affect the subsequent etching and the resulting products, as has been demonstrated by a positive control in the case of Rh and a negative control in the case of Pd. Hollow dumbbell-like nanorods of Au@PtAg show great enhancement for the dehydrogenation pathway in the oxidation of formic acid, as compared to solid Au@PtAg nanorods, PtAu nanotubes and commercial Pt/C. PMID:25155233

  12. Low-temperature solvothermal synthesis of EuS hollow microspheres

    SciTech Connect

    Peng, Yong; Wang, Hong; Li, Peng; Fu, Yao Xing, Mingming; Jiang, Tao; Luo, Xixian

    2014-09-15

    Graphical abstract: Synthesis of EuS hollow microspheres at low-temperature via solvothermal method for the first time. - Highlights: • We adopt an improved method to synthesise the (Phen)Eu(Et{sub 2}CNS{sub 2}){sub 3} in deionized water. • We have successfully synthesised the EuS hollow microsphere at 230 °C in acetonitrile. • The price of acetonitrile is more inexpensive, so the price of preparation was reduced. - Abstract: EuS crystals are synthesized by low-temperature solvothermal decomposition of the single source precursor complex (Phen)Eu(Et{sub 2}CNS{sub 2}){sub 3} in acetonitrile. X-ray powder diffraction, scanning electron microscopy, granulocyte diameter statistical analysis, surface energy-dispersive X-ray spectroscopy analysis, and UV–vis absorption spectroscopy are used to characterize the structure and properties of the obtained EuS crystals. The results show that the formed EuS crystals are uniform hollow microspheres with a typical cubic phase structure of rock salt and the average particle size of 2.01 μm. The mechanisms for the thermal decomposition of the precursor complex and the formation of the EuS hollow microspheres are postulated based on the experimental observations and previous reports.

  13. Anomalous right upper lobe venous drainage.

    PubMed

    Tarazi, M; Mayooran, N; Philip, B; Anjum, M N; O'Regan, K; Doddakula, K

    2016-01-01

    Lung resections are usually not associated with significant bleeding, but can be fatal, especially in cases of video-assisted thoracoscopic surgery (VATS). Anomalous vascular structures could be a major reason for unexpected bleeding in such surgeries. We present a case of an aberrant upper lobe pulmonary vein that was encountered posterior to the right upper lobe bronchus during a right upper lobectomy via thoracotomy. The anomalous pulmonary vein was identified preoperatively on a computed tomography (CT) scan and hence was looked for before dividing the bronchus. Many centres are adopting the VATS approach for performing lung resections. If an anomalous vein is present posterior to the bronchus, it might be in a blind spot and could be damaged inadvertently, leading to profuse and potentially fatal bleeding. We conclude that the identification of anomalous vascular structures prior to surgery with the help of CT helps in avoiding adverse outcomes. PMID:27016516

  14. Anomalous right upper lobe venous drainage

    PubMed Central

    Tarazi, M.; Mayooran, N.; Philip, B.; Anjum, M.N.; O'Regan, K.; Doddakula, K.

    2016-01-01

    Lung resections are usually not associated with significant bleeding, but can be fatal, especially in cases of video-assisted thoracoscopic surgery (VATS). Anomalous vascular structures could be a major reason for unexpected bleeding in such surgeries. We present a case of an aberrant upper lobe pulmonary vein that was encountered posterior to the right upper lobe bronchus during a right upper lobectomy via thoracotomy. The anomalous pulmonary vein was identified preoperatively on a computed tomography (CT) scan and hence was looked for before dividing the bronchus. Many centres are adopting the VATS approach for performing lung resections. If an anomalous vein is present posterior to the bronchus, it might be in a blind spot and could be damaged inadvertently, leading to profuse and potentially fatal bleeding. We conclude that the identification of anomalous vascular structures prior to surgery with the help of CT helps in avoiding adverse outcomes. PMID:27016516

  15. The charmonium dissociation in an ''anomalous wind''

    DOE PAGESBeta

    Sadofyev, Andrey V.; Yin, Yi

    2016-01-11

    We study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries "anomalous flow" induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the "anomalous flow" would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the "anomalous flow" experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and it qualitative difference between anomalous effects on the charmoniummore » color screening length which are model-dependent and those on the heavy quark drag force which are fixed by the second law of thermodynamics. As a result, we speculate on the possible charmonium dissociation induced by the chiral anomaly in heavy ion collisions.« less

  16. Tunneling Anomalous and Spin Hall Effects.

    PubMed

    Matos-Abiague, A; Fabian, J

    2015-07-31

    We predict, theoretically, the existence of the anomalous Hall effect when a tunneling current flows through a tunnel junction in which only one of the electrodes is magnetic. The interfacial spin-orbit coupling present in the barrier region induces a spin-dependent momentum filtering in the directions perpendicular to the tunneling current, resulting in a skew tunneling even in the absence of impurities. This produces an anomalous Hall conductance and spin Hall currents in the nonmagnetic electrode when a bias voltage is applied across the tunneling heterojunction. If the barrier is composed of a noncentrosymmetric material, the anomalous Hall conductance and spin Hall currents become anisotropic with respect to both the magnetization and crystallographic directions, allowing us to separate this interfacial phenomenon from the bulk anomalous and spin Hall contributions. The proposed effect should be useful for proving and quantifying the interfacial spin-orbit fields in metallic and metal-semiconductor systems. PMID:26274432

  17. The charmonium dissociation in an "anomalous wind"

    NASA Astrophysics Data System (ADS)

    Sadofyev, Andrey V.; Yin, Yi

    2016-01-01

    We study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries "anomalous flow" induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the "anomalous flow" would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the "anomalous flow" experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and qualitative difference between anomalous effects on the charmonium color screening length which are model-dependent and those on the heavy quark drag force which are fixed by the second law of thermodynamics. We speculate on the possible charmonium dissociation induced by the chiral anomaly in heavy ion collisions.

  18. Hollow spherical nanostructured polydiphenylamine for direct electrochemistry and glucose biosensor.

    PubMed

    Santhosh, P; Manesh, K M; Uthayakumar, S; Gopalan, A I; Lee, K-P

    2009-03-15

    Nanostructured, hollow spheres of polydiphenylamine (HS-PDPA) are prepared through a "soft template assisted self-assembly" approach. An enzymatic glucose biosensor is fabricated through immobilizing glucose oxidase (GOx) into HS-PDPA matrix. The HS-PDPA-GOx electrode exhibits a pair of well-defined reversible redox peaks with a fast heterogeneous electron transfer rate. At an applied potential of +0.65V, HS-PDPA-GOx electrode possesses high sensitivity (1.77 microAmM(-1)cm(-2)), stability and reproducibility towards glucose. The amperometric current response of HS-PDPA-GOx to glucose is linear in the concentration range between 1 and 28 mM with a detection limit of 0.05 mM (S/N=3). Also, HS-PDPA-GOx electrode shows high selectivity towards glucose in the presence of ascorbic acid, uric acid and acetaminophen at their maximum physiological concentrations. PMID:19041234

  19. An experimental investigation of a hollow cathode discharge

    NASA Technical Reports Server (NTRS)

    Wilbur, P. J.

    1971-01-01

    An experimental study of the effects of various modifications to the hollow cathode discharge region of a 20 cm electron bombardment ion thruster is presented. The introduction of electrical insulation between the main and cathode discharge regions is shown to have no significant effect on thruster performance. Adjustment of both the diameter and length of the cathode discharge region from the design condition are examined and the reduced sizes are shown to effect large improvements in propellant utilization when the thruster is operating at about 30% of the design thrust level. Performance improvements are shown to be less significant at higher thrust levels. The feasibility of using a high voltage tickler electrode to initiate the cathode-keeper discharge is considered and results obtained suggest this mode of startup is unsatisfactory.

  20. Hollow cathode plasma source for active spacecraft charge control

    NASA Technical Reports Server (NTRS)

    Deininger, William D.; Aston, Graeme; Pless, Lewis C.

    1987-01-01

    A prototype plasma source spacecraft discharge device has been developed to control overall and differential spacecraft surface charging. The plasma source is based on a unique hollow cathode discharge, where the plasma generation process is contained completely within the cathode. This device can be operated on argon, krypton, or xenon and has a rapid cold start time of less than 4 s. The discharge system design includes a spacecraft-discharge/net-charge sensing circuit which provides the ability to measure the polarity, magnitude, pulse shape, and time duration of a discharging event. Ion currents of up to 325 microA and electron currents ranging from 0.02 to 6.0 A have been extracted from the device. In addition, the spacecraft discharge device successfully discharged capacitively biased plates, from as high as + or - 2500 V, to ground potential, and discharged and clamped actively biased plates at +5 V with respect to ground potential during ground simulation testing.