WorldWideScience

Sample records for expected electron densities

  1. Probability density of quantum expectation values

    Science.gov (United States)

    Campos Venuti, L.; Zanardi, P.

    2013-10-01

    We consider the quantum expectation value A= of an observable A over the state |ψ>. We derive the exact probability distribution of A seen as a random variable when |ψ> varies over the set of all pure states equipped with the Haar-induced measure. To illustrate our results we compare the exact predictions for few concrete examples with the concentration bounds obtained using Levy's lemma. We also comment on the relevance of the central limit theorem and finally draw some results on an alternative statistical mechanics based on the uniform measure on the energy shell.

  2. Probability density of quantum expectation values

    Energy Technology Data Exchange (ETDEWEB)

    Campos Venuti, L., E-mail: lcamposv@usc.edu; Zanardi, P.

    2013-10-30

    We consider the quantum expectation value A=〈ψ|A|ψ〉 of an observable A over the state |ψ〉. We derive the exact probability distribution of A seen as a random variable when |ψ〉 varies over the set of all pure states equipped with the Haar-induced measure. To illustrate our results we compare the exact predictions for few concrete examples with the concentration bounds obtained using Levy's lemma. We also comment on the relevance of the central limit theorem and finally draw some results on an alternative statistical mechanics based on the uniform measure on the energy shell. - Highlights: • We compute the probability distribution of quantum expectation values for states sampled uniformly. • As a special case we consider in some detail the degenerate case where A is a one-dimensional projector. • We compare the concentration results obtained using Levy's lemma with the exact values obtained using our exact formulae. • We comment on the possibility of a Central Limit Theorem and show approach to Gaussian for a few physical operators. • Some implications of our results for the so-called “Quantum Microcanonical Equilibration” (Refs. [5–9]) are derived.

  3. An experimental electron density investigation

    Indian Academy of Sciences (India)

    Unknown

    based on X-ray diffraction measurements at 130 K. The electron density and its associated properties have been evaluated at the bond and the ring critical points for the naphthalene residues as well as for the central ring. The variation of the Laplacian along the axis, above and below the ring plane, is found to be symmetric ...

  4. Determination of electron temperature and electron density in ...

    African Journals Online (AJOL)

    The electron temperatures and electron densities of air and argon have been measured at various pds (pressure times distance). The electron temperatures have been computed using the Johnson-Malter double-probe method. The electron densities have been computed using the total positive ion current and the ...

  5. Analyticity of the density of electronic wavefunctions

    DEFF Research Database (Denmark)

    Sørensen, Thomas Østergaard; Fournais, S.; Hoffmann-Ostenhof, M.

    2004-01-01

    We prove that the electronic densities of atomic and molecular eigenfunctions are real analytic in R^3 away from the nuclei.......We prove that the electronic densities of atomic and molecular eigenfunctions are real analytic in R^3 away from the nuclei....

  6. Electron Density and Temperature Measurements, and Abundance ...

    Indian Academy of Sciences (India)

    Using spectra obtained from the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory), we investigate the height dependence of electron density, temperature and abundance anomalies in the solar atmosphere. In particular, we present ...

  7. Hospitalized smokers' expectancies for electronic cigarettes versus tobacco cigarettes.

    Science.gov (United States)

    Hendricks, Peter S; Cases, Mallory G; Thorne, Christopher B; Cheong, JeeWon; Harrington, Kathleen F; Kohler, Connie L; Bailey, William C

    2015-02-01

    The objectives of the current study were to compare hospitalized smokers' expectancies for electronic cigarettes (e-cigarettes) against their expectancies for tobacco cigarettes and evaluate relationships between e-cigarette expectancies and intention to use e-cigarettes. Analysis of baseline data from a one-year longitudinal observational study. The setting was a tertiary care academic center hospital in the Southeastern U.S. Participants were 958 hospitalized tobacco cigarette smokers. A questionnaire of e-cigarette expectancies based on the Brief Smoking Consequences Questionnaire-Adult (BSCQ-A) was developed and administered along with the original, tobacco-specific, BSCQ-A. Intention to use e-cigarettes was assessed with a single 10-point Likert scale item. Participants reported significantly weaker expectancies for e-cigarettes relative to tobacco cigarettes on all 10 BSCQ-A scales. Participants held sizably weaker expectancies that e-cigarettes pose health risks (p<.001, Cohen's d=-2.07), relieve negative affect (p<.001, Cohen's d=-1.01), satisfy the desire for nicotine (p<.001, Cohen's d=-.83), and taste pleasant (p<.001, Cohen's d=-.73). Among the strongest predictors of intention to use e-cigarettes were greater expectancies that e-cigarettes taste pleasant (p<.001, adjusted β=.34), relieve negative affect (p<.001, adjusted β=.32), and satisfy the desire for nicotine (p<.001, adjusted β=.31). Hospitalized tobacco smokers expect fewer negative and positive outcomes from e-cigarettes versus tobacco cigarettes. This suggests that e-cigarettes might be viable though imperfect substitutes for tobacco cigarettes. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Hospitalized Smokers’ Expectancies for Electronic Cigarettes versus Tobacco Cigarettes

    Science.gov (United States)

    Hendricks, Peter S.; Cases, Mallory G.; Thorne, Christopher B.; Cheong, JeeWon; Harrington, Kathleen F.; Kohler, Connie L.; Bailey, William C.

    2016-01-01

    Introduction To compare hospitalized smokers’ expectancies for electronic cigarettes (e-cigarettes) against their expectancies for tobacco cigarettes and evaluate relationships between e-cigarette expectancies and intention to use e-cigarettes. Methods Analysis of baseline data from a one-year longitudinal observational study. The setting was a tertiary care academic center hospital in the Southeastern U.S. Participants were 958 hospitalized tobacco cigarette smokers. A questionnaire of e-cigarette expectancies based on the Brief Smoking Consequences Questionnaire-Adult (BSCQ-A) was developed and administered along with the original, tobacco-specific, BSCQ-A. Intention to use e-cigarettes was assessed with a single 10-point Likert scale item. Results Participants reported significantly weaker expectancies for e-cigarettes relative to tobacco cigarettes on all 10 BSCQ-A scales. Participants held sizably weaker expectancies for the health risks of e-cigarettes (p < .001, Cohen's d = −2.07) as well as the ability of e-cigarettes to relieve negative affect (p < .001, Cohen's d = −1.01), satisfy the desire for nicotine (p < .001, Cohen's d = −.83), and taste pleasant (p < .001, Cohen's d = −.73). Among the strongest predictors of intention to use e-cigarettes were greater expectancies that e-cigarettes taste pleasant (p < .001, adjusted β = .34), relieve negative affect (p < .001, adjusted β = .32), and satisfy the desire for nicotine (p < .001, adjusted β = .31). Conclusions Hospitalizedtobacco smokers expect fewer negative and positive outcomes from e-cigarettes versus tobacco cigarettes. This suggests that e-cigarettes might be viable though imperfect substitutes for tobacco cigarettes. PMID:25452052

  9. Extraction of market expectations from risk-neutral density

    Directory of Open Access Journals (Sweden)

    Josip Arnerić

    2015-12-01

    Full Text Available The purpose of this paper is to investigate which of the proposed parametric models for extracting risk-neutral density; among Black-Scholes Merton, mixture of two log-normals and generalized beta; give the best fit. The model that fits sample data better is used to describe different characteristics (moments of the ex ante probability distribution. The empirical findings indicate that no matter which parametric model is used, the best fit is always obtained for short maturity horizon, but when comparing models in short-run, the mixture of two log-normals gives statistically significant smaller MSE. According to the pair-wise comparison results, the basic conclusion is that the mixture of two log-normals is superior to the other parametric models and has proven to be very flexible in capturing commonly observed characteristics of the underlying financial assets, such as asymmetries and “fat-tails” in implied probability distribution.

  10. Valence electronic state density in thorium dioxide

    Directory of Open Access Journals (Sweden)

    Teterin Anton Yu.

    2008-01-01

    Full Text Available This work analyses the fine low energy (0-40 eV X-ray photoelectron spectra of ThO2, taking into account relativistic Xα-discrete variation electronic structure calculations for the ThO8 (D4h cluster reflecting thorium's close environment in ThO2. As a result, it was theoretically shown and experimentally confirmed that Th5f electrons in ThO2 can participate directly (~0.6 Th5f electrons in chemical bond formation.Th6p electrons were shown to be a significant part (~0.44 Th6p electrons not only of inner valence molecular orbitals, but to play a significant role in outer valence molecular orbitals formation, as well. Inner valence molecular orbitals composition and sequent order were established to belong to the binding energy range of 13 eV to 40 eV. The valence electronic state density in the range of 0-40 eV in ThO2 was also calculated. For the first time, these data allowed an interpretation of the fine X-ray photoelectron spectra (0-40 eV and high resolution O4,5(Th X-ray emition spectral structure (~60 - ~85 eV of ThO2.

  11. Electron density distribution and bonding in ZnSe and PbSe using ...

    Indian Academy of Sciences (India)

    Unknown

    directions are relatively low in conformity with the loosely packed structure of ZnSe. (The interaction of atomic charges will be less and hence the electron densities along directions other than bonding are expected to be minimum). Figure 8(b) of PbSe shows unequal electron densities along the three directions. This is due ...

  12. Experimental charge density from electron microscopic maps.

    Science.gov (United States)

    Wang, Jimin

    2017-08-01

    The charge density (CD) distribution of an atom is the difference per unit volume between the positive charge of its nucleus and the distribution of the negative charges carried by the electrons that are associated with it. The CDs of the atoms in macromolecules are responsible for their electrostatic potential (ESP) distributions, which can now be visualized using cryo-electron microscopy at high resolution. CD maps can be recovered from experimental ESP density maps using the negative Laplacian operation. CD maps are easier to interpret than ESP maps because they are less sensitive to long-range electrostatic effects. An ESP-to-CD conversion involves multiplication of amplitudes of structure factors as Fourier transforms of these maps in reciprocal space by 1/d2 , where d is the resolution of reflections. In principle, it should be possible to determine the charges carried by the individual atoms in macromolecules by comparing experimental CD maps with experimental ESP maps. © 2017 The Protein Society.

  13. Density-dependent electron scattering in photoexcited GaAs

    DEFF Research Database (Denmark)

    Mics, Zoltán; D'’Angio, Andrea; Jensen, Søren A.

    2013-01-01

    —In a series of systematic optical pump - terahertz probe experiments we study the density-dependent electron scattering rate in photoexcited GaAs in a large range of carrier densities. The electron scattering time decreases by as much as a factor of 4, from 320 to 60 fs, as the electron density...

  14. Equation satisfied by electron-electron mutual Coulomb repulsion energy density functional

    OpenAIRE

    Joubert, Daniel P.

    2011-01-01

    The electron-electron mutual Coulomb repulsion energy density functional satisfies an equation that links functionals and functional derivatives at N-electron and (N-1)-electron densities for densities determined from the same adiabatic scaled external potential for the N-electron system.

  15. Expectations

    DEFF Research Database (Denmark)

    depend on the reader’s own experiences, individual feelings, personal associations or on conventions of reading, interpretive communities and cultural conditions? This volume brings together narrative theory, fictionality theory and speech act theory to address such questions of expectations...

  16. Electron-density topology in molecular systems: Paired and unpaired densities

    Science.gov (United States)

    Lobayan, Rosana M.; Bochicchio, Roberto C.; Lain, Luis; Torre, Alicia

    2005-10-01

    This work studies the partitioning of the electron density into two contributions which are interpreted as the paired and the effectively unpaired electron densities. The topological features of each density field as well as of the total density are described localizing the corresponding critical points in simple selected molecules (local formalism). The results show that unpaired electron-density concentrations occur out of the topological bonding regions whereas the paired electron densities present accumulations inside those regions. A comparison of these results with those arising from population analysis techniques (nonlocal or integrated formalisms) is reported.

  17. Extremal Density Matrices for the Expectation Value of a Qudit Hamiltonian

    Science.gov (United States)

    Castaños, O.; Figueroa, A.; López, J.; López-Peña, R.

    2017-05-01

    An algebraic procedure to find extremal density matrices for the expectation value of a finite Hamiltonian matrix is established. The extremal density matrices for pure states provide a complete description of the system, that is, its corresponding energy spectrum and projectors. For density matrices representing mixed states, one gets the most probable eigenstates that yield extremal mean values of the energy. The procedure uses mainly the stationary solutions of the von Neumann equation of motion, the orbits of the Hamiltonian, and the positivity conditions of the density matrix. The method is illustrated for matrix Hamiltonians of dimensions d = 2 and d = 3.

  18. Electronic cigarette use outcome expectancies among college students.

    Science.gov (United States)

    Pokhrel, Pallav; Little, Melissa A; Fagan, Pebbles; Muranaka, Nicholas; Herzog, Thaddeus A

    2014-06-01

    E-cigarette use outcome expectancies and their relationships with demographic and e-cigarette use variables are not well understood. Based on past cigarette as well as e-cigarette use research, we generated self-report items to assess e-cigarette outcome expectancies among college students. The objective was to determine different dimensions of e-cigarette use expectancies and their associations with e-cigarette use and use susceptibility. Self-report data were collected from 307 multiethnic 4- and 2-year college students [M age=23.5 (SD=5.5); 65% Female; 35% current cigarette smokers] in Hawaii. Data analyses were conducted by using factor and regression analyses. Exploratory factor analysis among e-cigarette ever-users indicated 7 factors: 3 positive expectancy factors (social enhancement, affect regulation, positive sensory experience) and 4 negative expectancy factors (negative health consequences, addiction concern, negative appearance, negative sensory experience). Confirmatory factor analysis among e-cigarette never-users indicated that the 7-factor model fitted reasonably well to the data. Being a current cigarette smoker was positively associated with positive expectancies and inversely with negative expectancies. Higher positive expectancies were significantly associated with greater likelihood of past-30-day e-cigarette use. Except addiction concern, higher negative expectancies were significantly associated with lower likelihood of past-30-day e-cigarette use. Among e-cigarette never-users, positive expectancy variables were significantly associated with higher intentions to use e-cigarettes in the future, adjusting for current smoker status and demographic variables. E-cigarette use expectancies determined in this study appear to predict e-cigarette use and use susceptibility among young adults and thus have important implications for future research. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Analytical Schwartz density applied to heavy two-electron ions

    Energy Technology Data Exchange (ETDEWEB)

    Romera, E.; Dehesa, J.S. [Universidad de Granada (Spain); Koga, Toshikatsu [Muroran Institute of Technology (Japan)

    1997-01-20

    An analytical expression of the electron density function p(r) due to Schwartz for two-electron atomic systems is applied to a detailed study of density-dependent properties of relatively heavy two-electron ions. Comparison of the Schwartz results with those from accurate Hartree-Fock and Hylleraas wave functions shows that despite its simple yet analytical form, the Schwartz density has a quantitative applicability in the density study of two-electron atoms within the nonrelativistic framework. 13 refs., 4 tabs.

  20. Electronic DC transformer with high power density

    NARCIS (Netherlands)

    Pavlovský, M.

    2006-01-01

    This thesis is concerned with the possibilities of increasing the power density of high-power dc-dc converters with galvanic isolation. Three cornerstones for reaching high power densities are identified as: size reduction of passive components, reduction of losses particularly in active components

  1. The ELENA Electron Cooler: Parameter choice and expected performance

    CERN Document Server

    Tranquille, G; Joergensen, L

    2013-01-01

    Electron cooling will be central to the success of the ELENA project which aims to increase by a factor of up to 100 the number of antiprotons available for the trap experiments. Because of the tight space constraints, the design of the device will be based on the compact electron cooler in operation on the S-LSR ring in Kyoto. The biggest challenge will be to generate a cold and stable electron beam at an energy of just 55 eV in order to cool the 100 KeV antiprotons. The use of photocathodes is excluded because their relatively short lifetime would require too many vacuum interventions during operation. We present the design parameters of our cooler as well as the results of the cooling performance simulations made with BetaCool and on-going work into "cold" cathodes.

  2. Polar cap electron densities from DE 1 plasma wave observations

    Science.gov (United States)

    Persoon, A. M.; Gurnett, D. A.; Shawhan, S. D.

    1983-01-01

    Electric-field-spectum measurements from the plasma-wave instrument on the Dynamics Explorer 1 spacecraft are used to study the local electron density at high altitudes in the northern polar-cap region. The electron density is determined from the upper cutoff of whistler-mode radiation at the electron plasma frequency. Median density values over the polar cap at L greater than 10 are found to vary from 35.2 + or - 8.5 cu cm at 2.1 earth radii to 0.99 + or - 0.51 cu cm at 4.66 earth radii. The steady-state radial-outflow model is examined for consistency with the observed density profile. A power-law fit to the radial variation of the electron density yields an exponent of - 3.85 + or - 0.32, which for the radial-outflow model implies a flow velocity increasing nearly linearly with incresing radial distance. Comparison of the observed electron densities with theoretical polar-wind densities yields consistent results up to 2.8 earth radii. A comparison of the observed electron densities with low-altitude density profiles from the Alouette II and ISIS 1 spacecraft illustrates transitions in the slope of the profile at 1.16 earth radii and between 1.55 and 2.0 earth radii. The changes in the density profile suggest that changes occur in the basic radial-transport processes at these altitudes.

  3. Electron localization in low-density quantum rings

    Science.gov (United States)

    Pederiva, F.; Emperador, A.; Lipparini, E.

    2002-10-01

    We present a systematic study of ground and excited states of the six-electron nanoscopic ring by fixed-node diffusion Monte Carlo calculations for a wide range of ring diameters and strengths of the harmonic confinement. We compare the density and correlation energies to the predictions of local spin density approximation theory, Hartree-Fock theory, and a model in which electrons are localized along the vertices of an hexagon, and analyze the electron-electron pair-correlation functions. We find evidence for a Wigner crystallization transition as the density is lowered. Conversely, evidence for a spin polarization transition is not found.

  4. The topology of the Coulomb potential density. A comparison with the electron density, the virial energy density, and the Ehrenfest force density.

    Science.gov (United States)

    Ferreira, Lizé-Mari; Eaby, Alan; Dillen, Jan

    2017-12-15

    The topology of the Coulomb potential density has been studied within the context of the theory of Atoms in Molecules and has been compared with the topologies of the electron density, the virial energy density and the Ehrenfest force density. The Coulomb potential density is found to be mainly structurally homeomorphic with the electron density. The Coulomb potential density reproduces the non-nuclear attractor which is observed experimentally in the molecular graph of the electron density of a Mg dimer, thus, for the first time ever providing an alternative and energetic foundation for the existence of this critical point. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  5. MGS RS: IONOSPHERIC ELECTRON DENSITY PROFILES V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains 5600 ionospheric electron density profiles (EDS files) derived from Mars Global Surveyor (MGS) radio occultation data. The profiles were...

  6. QTAIM electron density study of natural chalcones

    Science.gov (United States)

    González Moa, María J.; Mandado, Marcos; Cordeiro, M. Natália D. S.; Mosquera, Ricardo A.

    2007-09-01

    QTAIM atomic and bond properties, ionization potential, and O-H bond dissociation energies calculated at the B3LYP/6-311++G(2d,2p) level indicate the natural chalcones bear a significant radical scavenging activity. However, their ionization potentials indicate they decrease the electron-transfer rate between antioxidant and oxygen that yields the pro-oxidative cations less than other natural antioxidants. Rings A and B display slight and similar positive charges, whereas ring B is involved in exocycle delocalization at a larger extension.

  7. Wigner-like crystallization of Anderson-localized electron systems with low electron densities

    CERN Document Server

    Slutskin, A A; Pepper, M

    2002-01-01

    We consider an electron system under conditions of strong Anderson localization, taking into account interelectron long-range Coulomb repulsion. We establish that at sufficiently low electron densities and sufficiently low temperatures the Coulomb electron interaction brings about ordering of the Anderson-localized electrons into a structure that is close to an ideal (Wigner) crystal lattice, provided the dimension of the system is > 1. This Anderson-Wigner glass (AWG) is a new macroscopic electron state that, on the one hand, is beyond the conventional Fermi glass concept, and on the other hand, qualitatively differs from the known 'plain' Wigner glass (inherent in self-localized electron systems) in that the random slight electron displacements from the ideal crystal sites essentially depend on the electron density. With increasing electron density the AWG is found to turn into the plain Wigner glass or Fermi glass, depending on the width of the random spread of the electron levels. It is shown that the res...

  8. Measurement of electron density profile by microwave reflectometry on tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Simonet, F.

    1985-05-01

    A new method for measuring the electron density spatial profile has been successfully tested on the tokamak of Fontenay aux Roses (TFR). This method is based on the total reflection experienced by a wave of frequency F on the layer where F = F/sub p/e(r). The experimental results show that the maximum electron density in the discharge is also easily measured and that accurate determination of a density profile can be obtained with a time resolution of 5 ms. This diagnostic is well adapted to all fusion devices where access to the total plasma cross section is limited, particularly for large tokamaks.

  9. Tomography of the ionospheric electron density with geostatistical inversion

    Directory of Open Access Journals (Sweden)

    D. Minkwitz

    2015-08-01

    Full Text Available In relation to satellite applications like global navigation satellite systems (GNSS and remote sensing, the electron density distribution of the ionosphere has significant influence on trans-ionospheric radio signal propagation. In this paper, we develop a novel ionospheric tomography approach providing the estimation of the electron density's spatial covariance and based on a best linear unbiased estimator of the 3-D electron density. Therefore a non-stationary and anisotropic covariance model is set up and its parameters are determined within a maximum-likelihood approach incorporating GNSS total electron content measurements and the NeQuick model as background. As a first assessment this 3-D simple kriging approach is applied to a part of Europe. We illustrate the estimated covariance model revealing the different correlation lengths in latitude and longitude direction and its non-stationarity. Furthermore, we show promising improvements of the reconstructed electron densities compared to the background model through the validation of the ionosondes Rome, Italy (RO041, and Dourbes, Belgium (DB049, with electron density profiles for 1 day.

  10. Ionospheric topside models compared with experimental electron density profiles

    Directory of Open Access Journals (Sweden)

    S. M. Radicella

    2005-06-01

    Full Text Available Recently an increasing number of topside electron density profiles has been made available to the scientific community on the Internet. These data are important for ionospheric modeling purposes, since the experimental information on the electron density above the ionosphere maximum of ionization is very scarce. The present work compares NeQuick and IRI models with the topside electron density profiles available in the databases of the ISIS2, IK19 and Cosmos 1809 satellites. Experimental electron content from the F2 peak up to satellite height and electron densities at fixed heights above the peak have been compared under a wide range of different conditions. The analysis performed points out the behavior of the models and the improvements needed to be assessed to have a better reproduction of the experimental results. NeQuick topside is a modified Epstein layer, with thickness parameter determined by an empirical relation. It appears that its performance is strongly affected by this parameter, indicating the need for improvements of its formulation. IRI topside is based on Booker's approach to consider two parts with constant height gradients. It appears that this formulation leads to an overestimation of the electron density in the upper part of the profiles, and overestimation of TEC.

  11. Precision Electron Density Measurements in the SSX MHD Wind Tunnel

    Science.gov (United States)

    Suen-Lewis, Emma M.; Barbano, Luke J.; Shrock, Jaron E.; Kaur, Manjit; Schaffner, David A.; Brown, Michael R.

    2017-10-01

    We characterize fluctuations of the line averaged electron density of Taylor states produced by the magnetized coaxial plasma gun of the SSX device using a 632.8 nm HeNe laser interferometer. The analysis method uses the electron density dependence of the refractive index of the plasma to determine the electron density of the Taylor states. Typical magnetic field and density values in the SSX device approach about B ≅ 0.3 T and n = 0 . 4 ×1016 cm-3 . Analysis is improved from previous density measurement methods by developing a post-processing method to remove relative phase error between interferometer outputs and to account for approximately linear phase drift due to low-frequency mechanical vibrations of the interferometer. Precision density measurements coupled with local measurements of the magnetic field will allow us to characterize the wave composition of SSX plasma via density vs. magnetic field correlation analysis, and compare the wave composition of SSX plasma with that of the solar wind. Preliminary results indicate that density and magnetic field appear negatively correlated. Work supported by DOE ARPA-E ALPHA program.

  12. Electron densities in the upper ionosphere of Mars from the excitation of electron plasma oscillations

    Science.gov (United States)

    Duru, F.; Gurnett, D. A.; Morgan, D. D.; Modolo, R.; Nagy, A. F.; Najib, D.

    2008-07-01

    In addition to remote radio sounding of the ionosphere of Mars, the MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) instrument on the Mars Express spacecraft is also able to measure the in situ electron density from the excitation of local electron plasma oscillations. This paper presents an investigation of the electron density in the upper ionosphere of Mars based on the frequency of these oscillations. The advantage of this method is that electron densities can be measured at much higher altitudes than can be determined from remote radio soundings. Using this technique electron densities from 503 orbits have been analyzed over the period from 4 August 2005 to 31 July 2007 for altitudes ranging from about 275 to 1300 km. Although there is considerable variability from orbit to orbit, the median electron density at a given solar zenith angle (SZA) on the dayside of Mars decreases systematically with increasing altitude with a characteristic plasma scale height varying from about 80 to 145 km. At a fixed altitude, the electron density remains almost constant for SZAs less than about 80°. For SZAs greater than about 80° the electron density decreases rapidly with increasing SZA, approaching very low values on the nightside. Simulations performed using both magnetohydrodynamic and hybrid codes show that the nearly constant density at a given altitude is caused by the horizontal transport of plasma from the dayside toward the nightside due to interaction with the solar wind.

  13. Time-dependent density functional theory for many-electron systems interacting with cavity photons.

    Science.gov (United States)

    Tokatly, I V

    2013-06-07

    Time-dependent (current) density functional theory for many-electron systems strongly coupled to quantized electromagnetic modes of a microcavity is proposed. It is shown that the electron-photon wave function is a unique functional of the electronic (current) density and the expectation values of photonic coordinates. The Kohn-Sham system is constructed, which allows us to calculate the above basic variables by solving self-consistent equations for noninteracting particles. We suggest possible approximations for the exchange-correlation potentials and discuss implications of this approach for the theory of open quantum systems. In particular we show that it naturally leads to time-dependent density functional theory for systems coupled to the Caldeira-Leggett bath.

  14. Auroral E-region electron density gradients measured

    Directory of Open Access Journals (Sweden)

    C. Haldoupis

    2000-09-01

    Full Text Available In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ∇Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz=Ne/(dNe/dz, at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities  

  15. Auroral E-region electron density gradients measured

    Directory of Open Access Journals (Sweden)

    G. Hussey

    Full Text Available In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ∇Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz=Ne/(dNe/dz, at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities  

  16. Electron density and plasma dynamics of a colliding plasma experiment

    Energy Technology Data Exchange (ETDEWEB)

    Wiechula, J., E-mail: wiechula@physik.uni-frankfurt.de; Schönlein, A.; Iberler, M.; Hock, C.; Manegold, T.; Bohlender, B.; Jacoby, J. [Plasma Physics Group, Institute of Applied Physics, Goethe University, 60438 Frankfurt am Main (Germany)

    2016-07-15

    We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH{sub 2} at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 10{sup 15} cm{sup −3} for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 10{sup 16} cm{sup −3} for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.

  17. Electronic Structure of Matter Wave Functions and Density Functionals.

    CERN Document Server

    Kohn, W

    1999-01-01

    Since the 1920's Schroedinger wave functions have been the principal theoretical concept for understanding and computing the electronic structure of matter. More recently, Density Functional Theory (DFT), couched in terms of the electronic density distribution, n(r), has provided a new perspective and new computational possibilities, especially for systems consisting of very many (up to ~1000) atoms. In this talk some fundamental limitations of wave function methods for very-many-atom-systems will be discussed. The DFT approach will be explained together with some physical/chemical applications and a discussion of its strenghts and weaknesses.

  18. Analysis of the IMAGE RPI electron density data and CHAMP plasmasphere electron density reconstructions with focus on plasmasphere modelling

    Science.gov (United States)

    Gerzen, T.; Feltens, J.; Jakowski, N.; Galkin, I.; Reinisch, B.; Zandbergen, R.

    2016-09-01

    The electron density of the topside ionosphere and the plasmasphere contributes essentially to the overall Total Electron Content (TEC) budget affecting Global Navigation Satellite Systems (GNSS) signals. The plasmasphere can cause half or even more of the GNSS range error budget due to ionospheric propagation errors. This paper presents a comparative study of different plasmasphere and topside ionosphere data aiming at establishing an appropriate database for plasmasphere modelling. We analyze electron density profiles along the geomagnetic field lines derived from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite/Radio Plasma Imager (RPI) records of remote plasma sounding with radio waves. We compare these RPI profiles with 2D reconstructions of the topside ionosphere and plasmasphere electron density derived from GNSS based TEC measurements onboard the Challenging Minisatellite Payload (CHAMP) satellite. Most of the coincidences between IMAGE profiles and CHAMP reconstructions are detected in the region with L-shell between 2 and 5. In general the CHAMP reconstructed electron densities are below the IMAGE profile densities, with median of the CHAMP minus IMAGE residuals around -588 cm-3. Additionally, a comparison is made with electron densities derived from passive radio wave RPI measurements onboard the IMAGE satellite. Over the available 2001-2005 period of IMAGE measurements, the considered combined data from the active and passive RPI operations cover the region within a latitude range of ±60°N, all longitudes, and an L-shell ranging from 1.2 to 15. In the coincidence regions (mainly 2 ⩽ L ⩽ 4), we check the agreement between available active and passive RPI data. The comparison shows that the measurements are well correlated, with a median residual of ∼52 cm-3. The RMS and STD values of the relative residuals are around 22% and 21% respectively. In summary, the results encourage the application of IMAGE RPI data for

  19. Automatic temporal expectancy: a high-density event-related potential study.

    Directory of Open Access Journals (Sweden)

    Giovanni Mento

    Full Text Available How we compute time is not fully understood. Questions include whether an automatic brain mechanism is engaged in temporally regular environmental structure in order to anticipate events, and whether this can be dissociated from task-related processes, including response preparation, selection and execution. To investigate these issues, a passive temporal oddball task requiring neither time-based motor response nor explicit decision was specifically designed and delivered to participants during high-density, event-related potentials recording. Participants were presented with pairs of audiovisual stimuli (S1 and S2 interspersed with an Inter-Stimulus Interval (ISI that was manipulated according to an oddball probabilistic distribution. In the standard condition (70% of trials, the ISI lasted 1,500 ms, while in the two alternative, deviant conditions (15% each, it lasted 2,500 and 3,000 ms. The passive over-exposition to the standard ISI drove participants to automatically and progressively create an implicit temporal expectation of S2 onset, reflected by the time course of the Contingent Negative Variation response, which always peaked in correspondence to the point of S2 maximum expectation and afterwards inverted in polarity towards the baseline. Brain source analysis of S1- and ISI-related ERP activity revealed activation of sensorial cortical areas and the supplementary motor area (SMA, respectively. In particular, since the SMA time course synchronised with standard ISI, we suggest that this area is the major cortical generator of the temporal CNV reflecting an automatic, action-independent mechanism underlying temporal expectancy.

  20. Electron-beam guiding by a reduced-density channel

    Science.gov (United States)

    Welch, D. R.; Bieniosek, F. M.; Godfrey, B. B.

    1990-12-01

    A new regime of density-channel guiding of a relativistic electron beam in air has been found using a three-dimensional charged-particle simulation code, and confirmed in a double-pulse electron-beam experiment. The guiding results from the temperature dependence of the electron-neutral momentum-transfer frequency nu(m). The mechanism does not require a deep channel to obtain a significant guiding force. For the 13-kA MEDEA II (and beams of similar parameters), guiding persists 10 nsec into the beam pulse, with the force per channel displacement as high as 4 G/cm.

  1. Electron density distribution in Si and Ge using multipole, maximum ...

    Indian Academy of Sciences (India)

    In this work, the local structural information has also been obtained by analyzing the atomic pair distribution function. An attempt has been made in the present work to utilize the X-ray powder data sets to refine the structure and electron density distribution using the currently available versatile methods, MEM, multipole ...

  2. Effective atomic number, electron density and kerma of gamma ...

    Indian Academy of Sciences (India)

    Abstract. An attempt has been made to estimate the effective atomic number, electron density. (0.001 to 105 MeV) and kerma (0.001 to 20 MeV) of gamma radiation for a wide range of oxides of lanthanides using mass attenuation coefficient from WinXCom and mass energy absorption coef- ficient from Hubbell and Seltzer.

  3. Monitoring the three-dimensional ionospheric electron density ...

    Indian Academy of Sciences (India)

    In this paper, an IRI model assisted GPS-based Computerized Ionospheric Tomography (CIT) technique is developed to inverse the ionospheric electron density (IED) distribution over China. Essentially, an improved algebraic reconstruction technique (IART) is first proposed to reconstruct the ionospheric images with high ...

  4. The electron-propagator approach to conceptual density-functional ...

    Indian Academy of Sciences (India)

    Both electron propagator theory and density-functional theory provide conceptually useful information about chemical reactivity and, most especially, charge transfer. This paper elucidates thequalitative and quantitative links between the two theories, with emphasis on how the reactivity indicators of conceptual ...

  5. Measurements of plasma temperature and electron density in laser ...

    Indian Academy of Sciences (India)

    Abstract. Plasma produced by a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a copper solid sample in air at atmospheric pressure is studied spectroscopically. The temperature and electron density characterizing the plasma are measured by time-resolved spectroscopy of neutral atom and ion ...

  6. Bottomside Ionospheric Electron Density Specification using Passive High Frequency Signals

    Science.gov (United States)

    Kaeppler, S. R.; Cosgrove, R. B.; Mackay, C.; Varney, R. H.; Kendall, E. A.; Nicolls, M. J.

    2016-12-01

    The vertical bottomside electron density profile is influenced by a variety of natural sources, most especially traveling ionospheric disturbances (TIDs). These disturbances cause plasma to be moved up or down along the local geomagnetic field and can strongly impact the propagation of high frequency radio waves. While the basic physics of these perturbations has been well studied, practical bottomside models are not well developed. We present initial results from an assimilative bottomside ionosphere model. This model uses empirical orthogonal functions based on the International Reference Ionosphere (IRI) to develop a vertical electron density profile, and features a builtin HF ray tracing function. This parameterized model is then perturbed to model electron density perturbations associated with TIDs or ionospheric gradients. Using the ray tracing feature, the model assimilates angle of arrival measurements from passive HF transmitters. We demonstrate the effectiveness of the model using angle of arrival data. Modeling results of bottomside electron density specification are compared against suitable ancillary observations to quantify accuracy of our model.

  7. Electron Densities in the Upper Ionosphere of Mars from the Excitation of Local Electron Plasma Oscillations

    Science.gov (United States)

    Duru, F.; Gurnett, D. A.; Morgan, D. D.; Modolo, R.; Nagy, A. F.; Najib, D.; Plaut, J. J.; Picardi, G.

    2007-12-01

    In addition to the remote sounding of the ionosphere, the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on the Mars Express spacecraft, also excites local electron plasma oscillations. This paper summarizes the investigation of the local electron density using measurements of the locally excited electron plasma oscillation frequency. One of the advantages of this method is that the electron densities can be measured at very high altitudes, where remote ionospheric echoes cannot be detected. Measurements from 503 orbits over the period from August 4, 2005 to July 31, 2007 show that the average electron densities at a given solar zenith angle (SZA) decrease exponentially with increasing altitude. There is considerable variability at a given altitude due to the fact that the data at a specific altitude are obtained from different orbits. On the dayside of Mars, this exponential behavior continues up to altitudes of around 750 km. The scale height, in this altitude region, ranges between 130 km and 190 km. The average electron density is almost constant throughout the dayside in a given altitude range, but decreases rapidly as the spacecraft goes into the nightside. Simulations performed using different methods, show that the nearly constant density at a given altitude is due to transport effects. Investigation of individual orbits shows that the electron density throughout a pass often has large fluctuations, sometimes as much as ne/ne ~ 50 %, on time scales as small as 8 s.

  8. Fast electronic resistance switching involving hidden charge density wave states

    Science.gov (United States)

    Vaskivskyi, I.; Mihailovic, I. A.; Brazovskii, S.; Gospodaric, J.; Mertelj, T.; Svetin, D.; Sutar, P.; Mihailovic, D.

    2016-05-01

    The functionality of computer memory elements is currently based on multi-stability, driven either by locally manipulating the density of electrons in transistors or by switching magnetic or ferroelectric order. Another possibility is switching between metallic and insulating phases by the motion of ions, but their speed is limited by slow nucleation and inhomogeneous percolative growth. Here we demonstrate fast resistance switching in a charge density wave system caused by pulsed current injection. As a charge pulse travels through the material, it converts a commensurately ordered polaronic Mott insulating state in 1T-TaS2 to a metastable electronic state with textured domain walls, accompanied with a conversion of polarons to band states, and concurrent rapid switching from an insulator to a metal. The large resistance change, high switching speed (30 ps) and ultralow energy per bit opens the way to new concepts in non-volatile memory devices manipulating all-electronic states.

  9. Electron Density Determination, Bonding and Properties of Tetragonal Ferromagnetic Intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Wiezorek, Jorg [Univ. of Pittsburgh, PA (United States)

    2016-09-01

    The project developed quantitative convergent-beam electron diffraction (QCBED) methods by energy-filtered transmission electron microscopy (EFTEM) and used them in combination with density functional theory (DFT) calculations to study the electron density distribution in metallic and intermetallic phases with different cubic and non-cubic crystal structures that comprise elements with d-electron shells. The experimental methods developed here focus on the bonding charge distribution as one of the quantum mechanical characteristics central for understanding of intrinsic properties and validation of DFT calculations. Multiple structure and temperature factors have been measured simultaneously from nano-scale volumes of high-quality crystal with sufficient accuracy and precision for comparison with electron density distribution calculations by DFT. The often anisotropic temperature factors for the different atoms and atom sites in chemically ordered phases can differ significantly from those known for relevant pure element crystals due to bonding effects. Thus they have been measured from the same crystal volumes from which the structure factors have been determined. The ferromagnetic ordered intermetallic phases FePd and FePt are selected as model systems for 3d-4d and 3d-5d electron interactions, while the intermetallic phases NiAl and TiAl are used to probe 3d-3p electron interactions. Additionally, pure transition metal elements with d-electrons have been studied. FCC metals exhibit well defined delocalized bonding charge in tetrahedral sites, while less directional, more distributed bonding charge attains in BCC metals. Agreement between DFT calculated and QCBED results degrades as d-electron levels fill in the elements, and for intermetallics as d-d interactions become prominent over p-d interactions. Utilizing the LDA+U approach enabled inclusion of onsite Coulomb-repulsion effects in DFT calculations, which can afford improved agreements with QCBED results

  10. Maps for electron cloud density in Large Hadron Collider dipoles

    Directory of Open Access Journals (Sweden)

    T. Demma

    2007-11-01

    Full Text Available The generation of a quasistationary electron cloud inside the beam pipe through beam-induced multipacting processes has become an area of intensive study. The analyses performed so far have been based on heavy computer simulations taking into account photoelectron production, secondary emission, electron dynamics, and space charge effects, providing a detailed description of the electron-cloud evolution. Iriso and Peggs [U. Iriso and S. Peggs, Phys. Rev. ST Accel. Beams 8, 024403 (2005PRABFM1098-440210.1103/PhysRevSTAB.8.024403] have shown that, for the typical parameters of RHIC, the bunch-to-bunch evolution of the average electron-cloud density at a point can be represented by a cubic map. Simulations based on this map formalism are orders of magnitude faster compared to those based on standard particle tracking codes. In this communication we show that the map formalism is also applicable to the case of the Large Hadron Collider (LHC, and that, in particular, it reproduces the average electron-cloud densities computed using a reference code to within ∼15% for general LHC bunch filling patterns. We also illustrate the dependence of the polynomial map coefficients on the physical parameters affecting the electron cloud (secondary emission yield, bunch charge, bunch spacing, etc..

  11. The electron density of Saturn's magnetosphere

    Directory of Open Access Journals (Sweden)

    M. W. Morooka

    2009-07-01

    Full Text Available We have investigated statistically the electron density below 5 cm−3 in the magnetosphere of Saturn (7–80 RS, Saturn radii using 44 orbits of the floating potential data from the RPWS Langmuir probe (LP onboard Cassini. The density distribution shows a clear dependence on the distance from the Saturnian rotation axis (√X2+Y2 as well as on the distance from the equatorial plane (|Z|, indicating a disc-like structure. From the characteristics of the density distribution, we have identified three regions: the extension of the plasma disc, the magnetodisc region, and the lobe regions. The plasma disc region is at L<15, where L is the radial distance to the equatorial crossing of the dipole magnetic field line, and confined to |Z|<5 RS. The magnetodisc is located beyond L=15, and its density has a large variability. The variability has quasi-periodic characteristics with a periodicity corresponding to the planetary rotation. For Z>15 RS, the magnetospheric density distribution becomes constant in Z. However, the density still varies quasi-periodically with the planetary rotation also in this region. In fact, the quasi-periodic variation has been observed all over the magnetosphere beyond L=15. The region above Z=15 RS is identified as the lobe region. We also found that the magnetosphere can occasionally move latitudinally under the control of the density in the magnetosphere and the solar wind. From the empirical distributions of the electron densities obtained in this study, we have constructed an electron density model of the Saturnian nightside magnetosphere beyond 7 RS. The obtained model can well reproduce the observed density distribution, and can thus be useful for magnetospheric modelling studies.

  12. Nearly degenerate electron distributions and superluminal radiation densities

    Energy Technology Data Exchange (ETDEWEB)

    Tomaschitz, Roman, E-mail: tom@geminga.or [Department of Physics, Hiroshima University, 1-3-1 Kagami-yama, Higashi-Hiroshima 739-8526 (Japan)

    2010-02-01

    Polylogarithmic fugacity expansions of the partition function, the caloric and thermal equations of state, and the specific heat of fermionic power-law distributions are derived in the nearly degenerate low-temperature/high-density quantum regime. The spectral functions of an ultra-relativistic electron plasma are obtained by averaging the tachyonic radiation densities of inertial electrons with Fermi power-laws, whose entropy is shown to be extensive and stable. The averaged radiation densities are put to test by performing tachyonic cascade fits to the gamma-ray spectrum of the TeV blazar Markarian 421 in a low and high emission state. Estimates of the thermal electron plasma in this active galactic nucleus are extracted from the spectral fits, such as temperature, number count, and internal energy. The tachyonic cascades reproduce the quiescent as well as a burst spectrum of the blazar obtained with imaging atmospheric Cherenkov detectors. Double-logarithmic plots of the differential tachyon flux exhibit intrinsic spectral curvature, caused by the Boltzmann factor of the electron gas.

  13. One-electron reduced density matrices of strongly correlated harmonium atoms.

    Science.gov (United States)

    Cioslowski, Jerzy

    2015-03-21

    Explicit asymptotic expressions are derived for the reduced one-electron density matrices (the 1-matrices) of strongly correlated two- and three-electron harmonium atoms in the ground and first excited states. These expressions, which are valid at the limit of small confinement strength ω, yield electron densities and kinetic energies in agreement with the published values. In addition, they reveal the ω(5/6) asymptotic scaling of the exchange components of the electron-electron repulsion energies that differs from the ω(2/3) scaling of their Coulomb and correlation counterparts. The natural orbitals of the totally symmetric ground state of the two-electron harmonium atom are found to possess collective occupancies that follow a mixed power/Gaussian dependence on the angular momentum in variance with the simple power-law prediction of Hill's asymptotics. Providing rigorous constraints on energies as functionals of 1-matrices, these results are expected to facilitate development of approximate implementations of the density matrix functional theory and ensure their proper description of strongly correlated systems.

  14. Maps for electron cloud density in Large Hadron Collider dipoles

    CERN Document Server

    Demma, T; Ruggiero, F; Rumolo, G; Zimmermann, F

    2007-01-01

    The generation of a quasistationary electron cloud inside the beam pipe through beam-induced multipacting processes has become an area of intensive study. The analyses performed so far have been based on heavy computer simulations taking into account photoelectron production, secondary emission, electron dynamics, and space charge effects, providing a detailed description of the electron-cloud evolution. Iriso and Peggs [U. Iriso and S. Peggs, Phys. Rev. ST Accel. Beams 8, 024403 (2005)] have shown that, for the typical parameters of RHIC, the bunch-to-bunch evolution of the average electron-cloud density at a point can be represented by a cubic map. Simulations based on this map formalism are orders of magnitude faster compared to those based on standard particle tracking codes. In this communication we show that the map formalism is also applicable to the case of the Large Hadron Collider (LHC), and that, in particular, it reproduces the average electron-cloud densities computed using a reference code to wi...

  15. Excess electrons in ice: a density functional theory study.

    Science.gov (United States)

    Bhattacharya, Somesh Kr; Inam, Fakharul; Scandolo, Sandro

    2014-02-21

    We present a density functional theory study of the localization of excess electrons in the bulk and on the surface of crystalline and amorphous water ice. We analyze the initial stages of electron solvation in crystalline and amorphous ice. In the case of crystalline ice we find that excess electrons favor surface states over bulk states, even when the latter are localized at defect sites. In contrast, in amorphous ice excess electrons find it equally favorable to localize in bulk and in surface states which we attribute to the preexisting precursor states in the disordered structure. In all cases excess electrons are found to occupy the vacuum regions of the molecular network. The electron localization in the bulk of amorphous ice is assisted by its distorted hydrogen bonding network as opposed to the crystalline phase. Although qualitative, our results provide a simple interpretation of the large differences observed in the dynamics and localization of excess electrons in crystalline and amorphous ice films on metals.

  16. Electron momentum spectroscopy study of amantadine: binding energy spectra and valence orbital electron density distributions

    Science.gov (United States)

    Litvinyuk, I. V.; Zheng, Y.; Brion, C. E.

    2000-11-01

    The electron binding energy spectrum and valence orbital electron momentum density distributions of amantadine (1-aminoadamantane), an important anti-viral and anti-Parkinsonian drug, have been measured by electron momentum spectroscopy. Theoretical momentum distributions, calculated at the 6-311++G** and AUG-CC-PVTZ levels within the target Hartree-Fock and also the target Kohn-Sham density functional theory approximations, show good agreement with the experimental results. The results for amantadine are also compared with those for the parent molecule, adamantane, reported earlier (Chem. Phys. 253 (2000) 41). Based on the comparison tentative assignments of the valence region ionization bands of amantadine have been made.

  17. Application of the maximum entropy method to electron density determination

    Energy Technology Data Exchange (ETDEWEB)

    Wei Wendo

    1985-12-01

    The principle of maximum entropy is adopted to derive a procedure for obtaining the electron density distribution in crystals from incomplete X-ray diffraction data. This method was applied to cementite and the result proved to be better than the conventional Fourier inversion in resolution as well as in the absence of ripples. The potential advantages of this method are: (1) the amount of subjective judgment imposed on unavailable data is significantly limited, and (2) the result of this method is consistent with the known information and maximally noncommittal with regard to the unknowns. It is shown that the method is especially well suited to the problem of the determination of a high-resolution electron density map from insufficient experimental data. (orig.).

  18. Simple Fully Nonlocal Density Functionals for Electronic Repulsion Energy.

    Science.gov (United States)

    Vuckovic, Stefan; Gori-Giorgi, Paola

    2017-07-06

    From a simplified version of the mathematical structure of the strong coupling limit of the exact exchange-correlation functional, we construct an approximation for the electronic repulsion energy at physical coupling strength, which is fully nonlocal. This functional is self-interaction free and yields energy densities within the definition of the electrostatic potential of the exchange-correlation hole that are locally accurate and have the correct asymptotic behavior. The model is able to capture strong correlation effects that arise from chemical bond dissociation, without relying on error cancellation. These features, which are usually missed by standard density functional theory (DFT) functionals, are captured by the highly nonlocal structure, which goes beyond the "Jacob's ladder" framework for functional construction, by using integrals of the density as the key ingredient. Possible routes for obtaining the full exchange-correlation functional by recovering the missing kinetic component of the correlation energy are also implemented and discussed.

  19. Temperature dependence of electron density and electron-electron interactions in monolayer epitaxial graphene grown on SiC

    Science.gov (United States)

    Liu, Chieh-Wen; Chuang, Chiashain; Yang, Yanfei; Elmquist, Randolph E.; Ho, Yi-Ju; Lee, Hsin-Yen; Liang, Chi-Te

    2017-06-01

    We report carrier density measurements and electron-electron (e-e) interactions in monolayer epitaxial graphene grown on SiC. The temperature (T)-independent carrier density determined from the Shubnikov-de Haas (SdH) oscillations clearly demonstrates that the observed logarithmic temperature dependence of the Hall slope in our system must be due to e-e interactions. Since the electron density determined from conventional SdH measurements does not depend on e-e interactions based on Kohn’s theorem, SdH experiments appear to be more reliable compared with the classical Hall effect when one studies the T dependence of the carrier density in the low T regime. On the other hand, the logarithmic T dependence of the Hall slope δR xy /δB can be used to probe e-e interactions even when the conventional conductivity method is not applicable due to strong electron-phonon scattering.

  20. Quantum electrodynamical time-dependent density functional theory for many-electron systems on a lattice

    Science.gov (United States)

    Farzanehpour, Mehdi; Tokatly, Ilya; Nano-Bio Spectroscopy Group; ETSF Scientific Development Centre Team

    2015-03-01

    We present a rigorous formulation of the time-dependent density functional theory for interacting lattice electrons strongly coupled to cavity photons. We start with an example of one particle on a Hubbard dimer coupled to a single photonic mode, which is equivalent to the single mode spin-boson model or the quantum Rabi model. For this system we prove that the electron-photon wave function is a unique functional of the electronic density and the expectation value of the photonic coordinate, provided the initial state and the density satisfy a set of well defined conditions. Then we generalize the formalism to many interacting electrons on a lattice coupled to multiple photonic modes and prove the general mapping theorem. We also show that for a system evolving from the ground state of a lattice Hamiltonian any density with a continuous second time derivative is locally v-representable. Spanish Ministry of Economy and Competitiveness (Grant No. FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT578-13), COST Actions CM1204 (XLIC) and MP1306 (EUSpec).

  1. Quantum electrodynamical time-dependent density-functional theory for many-electron systems on a lattice

    Science.gov (United States)

    Farzanehpour, M.; Tokatly, I. V.

    2014-11-01

    We present a rigorous formulation of the time-dependent density-functional theory for interacting lattice electrons strongly coupled to cavity photons. We start with an example of one particle on a Hubbard dimer coupled to a single photonic mode, which is equivalent to the single mode spin-boson model or the quantum Rabi model. For this system we prove that the electron-photon wave function is a unique functional of the electronic density and the expectation value of the photonic coordinate, provided the initial state and the density satisfy a set of well defined conditions. Then we generalize the formalism to many interacting electrons on a lattice coupled to multiple photonic modes and prove the general mapping theorem. We also show that for a system evolving from the ground state of a lattice Hamiltonian any density with a continuous second time derivative is locally v representable.

  2. Deducing fast electron density changes in randomly orientated uncrystallized biomolecules in a pump-probe experiment.

    Science.gov (United States)

    Pande, K; Schwander, P; Schmidt, M; Saldin, D K

    2014-07-17

    We propose a method for deducing time-resolved structural changes in uncrystallized biomolecules in solution. The method relies on measuring the angular correlations of the intensities, when averaged over a large number of diffraction patterns from randomly oriented biomolecules in solution in a liquid solvent. The experiment is somewhat like a pump-probe version of an experiment on small angle X-ray scattering, except that the data expected by the algorithm are not just the radial variation of the averaged intensities. The differences of these correlation functions as measured from a photoexcited and dark structure enable the direct calculation of the difference electron density with a knowledge of only the dark structure. We exploit a linear relation we derive between the difference in these correlation functions and the difference electron density, applicable for small structural changes.

  3. The effective density of randomly moving electrons and related characteristics of materials with degenerate electron gas

    Directory of Open Access Journals (Sweden)

    V. Palenskis

    2014-04-01

    Full Text Available Interpretation of the conductivity of metals, of superconductors in the normal state and of semiconductors with highly degenerate electron gas remains a significant issue if consideration is based on the classical statistics. This study is addressed to the characterization of the effective density of randomly moving electrons and to the evaluation of carrier diffusion coefficient, mobility, and other parameters by generalization of the widely published experimental results. The generalized expressions have been derived for various kinetic parameters attributed to the non-degenerate and degenerate electron gas, by analyzing a random motion of the single type carriers in homogeneous materials. The values of the most important kinetic parameters for different metals are also systematized and discussed. It has been proved that Einstein's relation between the diffusion coefficient and the drift mobility of electrons is held for any level of degeneracy if the effective density of randomly moving carriers is properly taken into account.

  4. A study of effective atomic numbers and electron densities of some vitamins for electron, H, He and C ion interactions

    Science.gov (United States)

    Büyükyıldız, M.

    2017-09-01

    The radiological properties of some vitamins such as Retinol, Beta-carotene, Riboflavin, Niacin, Niacinamide, Pantothenic acid, Pyridoxine, Pyridoxamine, Pyridoxal, Biotin, Folic acid, Ascorbic acid, Cholecalciferol, Alpha-tocopherol, Gamma-tocopherol, Phylloquinone have been investigated with respect to total electron interaction and some heavy charged particle interaction as means of effective atomic numbers (Z_{eff}) and electron densities (N_{eff}) for the first time. Calculations were performed for total electron interaction and heavy ions such as H, He and C ion interactions in the energy region 10keV-10MeV by using a logarithmic interpolation method. Variations in Z_{eff}'s and N_{eff}'s of given vitamins have been studied according to the energy of electron or heavy charged particles, and significant variations have been observed for all types of interaction in the given energy region. The maximum values of Z_{eff} have been found in the different energy regions for different interactions remarkably and variations in N_{eff} seem approximately to be the same with variation in Z_{eff} for the given vitamins as expected. Z_{eff} values of some vitamins were plotted together and compared with each other for electron, H, He and C interactions and the ratios of Z_{eff}/ have been changed in the range of 0.25-0.36, 0.20-0.36, 0.22-0.35 and 0.20-0.35 for electron, H, He and C interactions, respectively.

  5. Automated segmentation of molecular subunits in electron cryomicroscopy density maps.

    Science.gov (United States)

    Baker, Matthew L; Yu, Zeyun; Chiu, Wah; Bajaj, Chandrajit

    2006-12-01

    Electron cryomicroscopy (cryoEM) is capable of imaging large macromolecular machines composed of multiple components. However, it is currently only possible to achieve moderate resolution at which it may be possible to computationally extract the individual components in the machine. In this work, we present application details of an automated method for detecting and segmenting the components of a large machine in an experimentally determined density map. This method is applicable to object with and without symmetry and takes advantage of global and local symmetry axes if present. We have applied this segmentation algorithm to several cryoEM data sets already deposited in EMDB with various complexities, symmetries and resolutions and validated the results using manually segmented density and available structures of the components in the PDB. As such, automated segmentation could become a useful tool for the analysis of the ever-increasing number of structures of macromolecular machines derived from cryoEM.

  6. Density-functional method for nonequilibrium electron transport

    DEFF Research Database (Denmark)

    Brandbyge, Mads; Mozos, J.L.; Ordejon, P.

    2002-01-01

    We describe an ab initio method for calculating the electronic structure, electronic transport, and forces acting on the atoms, for atomic scale systems connected to semi-infinite electrodes and with an applied voltage bias. Our method is based on the density-functional theory (DFT) as implemented...... the contact and the electrodes on the same footing. The effect of the finite bias (including self-consistency and the solution of the electrostatic problem) is taken into account using nonequilibrium Green's functions. We relate the nonequilibrium Green's function expressions to the more transparent scheme...... wires connected to aluminum electrodes with extended or finite cross section, (ii) single atom gold wires, and finally (iii) large carbon nanotube systems with point defects....

  7. Inversion of Ionospheric Electron Density from GPS Beacon Observations

    Institute of Scientific and Technical Information of China (English)

    Zou Yu-hua; Xu Ji-sheng

    2003-01-01

    This paper studies the mathematical foundation of time-dependent three-dimensional (3-D) computerized ionospheric tomography (CIT) for reconstructing ionospheric electron density, Ne, from ground-based GPS beacon observations. After simplifying the relation between Ne and time,the time-dependent 3-D inversion in consideration is reduced to a 3-D tomography with incomplete projections.To see clearly the effects of the incompleteness on the quality of reconstruction under 3-D condition, the formula of 3-D parallel-beam tomography is deduced theoretically. After establishing the mathematical foundation, simulations based on actual GPS ray paths with the help of the IRI-90 model are performed,and reasonable time-dependent 3-D distribution images of Neare obtained when taking proper layout of the network and allowing variable resolutions. The quality of the reconstruction is rather good when compared with the images from the IRI-90 model directly. Therefore, results in this paper demon-strate that imaging of the ionospheric electron density distri-bution from GPS beacon observations is reasonable in theory and feasible in practice.

  8. Inversion of Ionospheric Electron Density from GPS Beacon Observations

    Institute of Scientific and Technical Information of China (English)

    ZouYu-hua; XuJi-sheng

    2003-01-01

    This paper studies the mathematical foundation of time-dependent three-dimensional (3-D) computerized ionospheric tomography (CIT) for reconstructing ionospheric electron density, N~, from ground-based GPS beacon observations. After simplifying the relation between N. and time,the time-dependent 3-D inversion in consideration is reduced to a 3-D tomography with incomplete projections. To see clearly the effects of the incompleteness on the quality of reconstruction under 3-D condition, the formula of 3-D parallelbeam tomogtTaphy is deduced theoretically. After establishing the mathematical foundation, simulations based on actual GPS ray paths with the help of the IRI-90 model are performed,and reasonable time-dependent 3-D distribution images of Ne are obtained when taking proper layout of the network and allowing variable resolutions. The quality of the reconstruction is rather good when compared with the images from the IRI-90 model directly. Therefore, results in this paper demonstrate that imaging of the ionospheric electron density distribution from GPS beacon observations is reasonable in theor yand feasible in practice.

  9. Effective atomic numbers and electron density of dosimetric material

    Directory of Open Access Journals (Sweden)

    Kaginelli S

    2009-01-01

    Full Text Available A novel method for determination of mass attenuation coefficient of x-rays employing NaI (Tl detector system and radioactive sources is described.in this paper. A rigid geometry arrangement and gating of the spectrometer at FWHM position and selection of absorber foils are all done following detailed investigation, to minimize the effect of small angle scattering and multiple scattering on the mass attenuation coefficient, m/r, value. Firstly, for standardization purposes the mass attenuation coefficients of elemental foils such as Aluminum, Copper, Molybdenum, Tantalum and Lead are measured and then, this method is utilized for dosimetric interested material (sulfates. The experimental mass attenuation coefficient values are compared with the theoretical values to find good agreement between the theory and experiment within one to two per cent. The effective atomic numbers of the biological substitute material are calculated by sum rule and from the graph. The electron density of dosimetric material is calculated using the effective atomic number. The study has discussed in detail the attenuation coefficient, effective atomic number and electron density of dosimetric material/biological substitutes.

  10. Structure of the electron momentum density of atomic systems

    Energy Technology Data Exchange (ETDEWEB)

    Romera, E.; Dehesa, J.S. [Granada Univ. (Spain). Dept. de Fisica Moderna; Koga, T. [Department of Applied Chemistry, Muroran Institute of Technology, Muroran, Hokkaido 050 (Japan)

    1997-12-01

    The present paper addresses the controversial problem on the nonmonotonic behavior of the spherically-averaged momentum density {gamma}(p) observed previously for some ground-state atoms based on the Roothaan-Hartree-Fock (RHF) wave functions of Clementi and Roetti. Highly accurate RHF wave functions of Koga et al. are used to study the existence of extrema in the momentum density {gamma}(p) of all the neutral atoms from hydrogen to xenon. Three groups of atoms are clearly identified according to the nonmonotonicity parameter {mu}, whose value is either equal to, larger, or smaller than unity. Additionally, it is found that the function p{sup -{alpha}} {gamma}(p) is (i) monotonically decreasing from the origin for {alpha}{>=}0.75, (ii) convex for {alpha}{>=}1.35, and (iii) logarithmically convex for {alpha}{>=}3.64 for all the neutral atoms with nuclear charges Z = 1-54. Finally, these monotonicity properties are applied to derive simple yet general inequalities which involve three momentum moments left angle p{sup t} right angle. These inequalities not only generalize similar inequalities reported so far but also allow us to correlate some fundamental atomic quantities, such as the electron-electron repulsion energy and the peak height of Compton profile, in a simple manner. (orig.) 40 refs.

  11. Polar observations of electron density distribution in the Earth’s magnetosphere. 2. Density profiles

    Directory of Open Access Journals (Sweden)

    H. Laakso

    Full Text Available Using spacecraft potential measurements of the Polar electric field experiment, we investigate electron density variations of key plasma regions within the magnetosphere, including the polar cap, cusp, trough, plasmapause, and auroral zone. The statistical results were presented in the first part of this study, and the present paper reports detailed structures revealed by individual satellite passes. The high-altitude (> 3 RE polar cap is generally one of the most tenuous regions in the magnetosphere, but surprisingly, the polar cap boundary does not appear as a steep density decline. At low altitudes (1 RE in summer, the polar densities are very high, several 100 cm-3 , and interestingly, the density peaks at the central polar cap. On the noonside of the polar cap, the cusp appears as a dense, 1–3° wide region. A typical cusp density above 4 RE distance is between several 10 cm-3 and a few 100 cm-3 . On some occasions the cusp is crossed multiple times in a single pass, simultaneously with the occurrence of IMF excursions, as the cusp can instantly shift its position under varying solar wind conditions, similar to the magnetopause. On the nightside, the auroral zone is not always detected as a simple density cavity. Cavities are observed but their locations, strengths, and sizes vary. Also, the electric field perturbations do not necessarily overlap with the cavities: there are cavities with no field disturbances, as well as electric field disturbances observed with no clear cavitation. In the inner magnetosphere, the density distributions clearly show that the plasmapause and trough densities are well correlated with geomagnetic activity. Data from individual orbits near noon and midnight demonstrate that at the beginning of geomagnetic disturbances, the retreat speed of the plasmapause can be one L-shell per hour, while during quiet intervals the

  12. Polar observations of electron density distribution in the Earth’s magnetosphere. 2. Density profiles

    Directory of Open Access Journals (Sweden)

    H. Laakso

    2002-11-01

    Full Text Available Using spacecraft potential measurements of the Polar electric field experiment, we investigate electron density variations of key plasma regions within the magnetosphere, including the polar cap, cusp, trough, plasmapause, and auroral zone. The statistical results were presented in the first part of this study, and the present paper reports detailed structures revealed by individual satellite passes. The high-altitude (> 3 RE polar cap is generally one of the most tenuous regions in the magnetosphere, but surprisingly, the polar cap boundary does not appear as a steep density decline. At low altitudes (1 RE in summer, the polar densities are very high, several 100 cm-3 , and interestingly, the density peaks at the central polar cap. On the noonside of the polar cap, the cusp appears as a dense, 1–3° wide region. A typical cusp density above 4 RE distance is between several 10 cm-3 and a few 100 cm-3 . On some occasions the cusp is crossed multiple times in a single pass, simultaneously with the occurrence of IMF excursions, as the cusp can instantly shift its position under varying solar wind conditions, similar to the magnetopause. On the nightside, the auroral zone is not always detected as a simple density cavity. Cavities are observed but their locations, strengths, and sizes vary. Also, the electric field perturbations do not necessarily overlap with the cavities: there are cavities with no field disturbances, as well as electric field disturbances observed with no clear cavitation. In the inner magnetosphere, the density distributions clearly show that the plasmapause and trough densities are well correlated with geomagnetic activity. Data from individual orbits near noon and midnight demonstrate that at the beginning of geomagnetic disturbances, the retreat speed of the plasmapause can be one L-shell per hour, while during quiet intervals the plasmapause can expand anti-earthward at the same speed. For the trough region, it is found

  13. User identified positive outcome expectancies of electronic cigarette use: A concept mapping study.

    Science.gov (United States)

    Soule, Eric K; Maloney, Sarah F; Guy, Mignonne C; Eissenberg, Thomas; Fagan, Pebbles

    2017-05-01

    Electronic cigarette (ECIG) use is growing in popularity, but little is known about the perceived positive outcomes of ECIG use. This study used concept mapping (CM) to examine positive ECIG outcome expectancies. Sixty-three past 30-day ECIG users (38.1% female) between the ages of 18 and 64 (M = 37.8, SD = 13.3) completed a CM module. In an online program, participants provided statements that completed a prompt: "A specific positive, enjoyable, or exciting effect (i.e., physical or psychological) that I have experienced WHILE USING or IMMEDIATELY AFTER USING an electronic cigarette/electronic vaping device is. . . ." Participants (n = 35) sorted 123 statements into "piles" of similar content and rated (n = 43) each statement on a 7-point scale (1 = Definitely NOT a positive effect to 7 = Definitely a positive effect). A cluster map was created using data from the sorting task, and analysis indicated a 7 cluster model of positive ECIG use outcome expectancies: Therapeutic/Affect Regulation, High/Euphoria, Sensation Enjoyment, Perceived Health Effects, Benefits of Decreased Cigarette Use, Convenience, and Social Impacts. The Perceived Health Effects cluster was rated highest, although all mean ratings were greater than 4.69. Mean cluster ratings were compared, and females, younger adults, past 30-day cigarette smokers, users of more "advanced" ECIG devices, and nonlifetime (less than 100 lifetime cigarettes) participants rated certain clusters higher than comparison groups (ps < 0.05). ECIG users associate positive outcomes with ECIG use. ECIG outcome expectancies may affect product appeal and tobacco use behaviors and should be examined further to inform regulatory policies. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  14. Ultra-Stretchable Interconnects for High-Density Stretchable Electronics

    Directory of Open Access Journals (Sweden)

    Salman Shafqat

    2017-09-01

    Full Text Available The exciting field of stretchable electronics (SE promises numerous novel applications, particularly in-body and medical diagnostics devices. However, future advanced SE miniature devices will require high-density, extremely stretchable interconnects with micron-scale footprints, which calls for proven standardized (complementary metal-oxide semiconductor (CMOS-type process recipes using bulk integrated circuit (IC microfabrication tools and fine-pitch photolithography patterning. Here, we address this combined challenge of microfabrication with extreme stretchability for high-density SE devices by introducing CMOS-enabled, free-standing, miniaturized interconnect structures that fully exploit their 3D kinematic freedom through an interplay of buckling, torsion, and bending to maximize stretchability. Integration with standard CMOS-type batch processing is assured by utilizing the Flex-to-Rigid (F2R post-processing technology to make the back-end-of-line interconnect structures free-standing, thus enabling the routine microfabrication of highly-stretchable interconnects. The performance and reproducibility of these free-standing structures is promising: an elastic stretch beyond 2000% and ultimate (plastic stretch beyond 3000%, with <0.3% resistance change, and >10 million cycles at 1000% stretch with <1% resistance change. This generic technology provides a new route to exciting highly-stretchable miniature devices.

  15. Electron correlation in solids via density embedding theory

    Energy Technology Data Exchange (ETDEWEB)

    Bulik, Ireneusz W.; Chen, Weibing [Department of Chemistry, Rice University, Houston, Texas 77005 (United States); Scuseria, Gustavo E. [Department of Chemistry, Rice University, Houston, Texas 77005 (United States); Department of Physics and Astronomy, Rice University, Houston, Texas 77005 (United States)

    2014-08-07

    Density matrix embedding theory [G. Knizia and G. K.-L. Chan, Phys. Rev. Lett. 109, 186404 (2012)] and density embedding theory [I. W. Bulik, G. E. Scuseria, and J. Dukelsky, Phys. Rev. B 89, 035140 (2014)] have recently been introduced for model lattice Hamiltonians and molecular systems. In the present work, the formalism is extended to the ab initio description of infinite systems. An appropriate definition of the impurity Hamiltonian for such systems is presented and demonstrated in cases of 1, 2, and 3 dimensions, using coupled cluster theory as the impurity solver. Additionally, we discuss the challenges related to disentanglement of fragment and bath states. The current approach yields results comparable to coupled cluster calculations of infinite systems even when using a single unit cell as the fragment. The theory is formulated in the basis of Wannier functions but it does not require separate localization of unoccupied bands. The embedding scheme presented here is a promising way of employing highly accurate electronic structure methods for extended systems at a fraction of their original computational cost.

  16. Interaction of the electron density fluctuations with electron cyclotron waves from the equatorial launcher in ITER

    Science.gov (United States)

    Snicker, A.; Poli, E.; Maj, O.; Guidi, L.; Köhn, A.; Weber, H.; Conway, G. D.; Henderson, M.; Saibene, G.

    2018-01-01

    We present a numerical investigation of electron cyclotron beams interacting with electron density fluctuations in the ITER 15 MA H-mode scenario. In particular, here we study how the beam from the equatorial launcher, which shall be utilized to influence the sawtooth instability, is affected by the fluctuations. Moreover, we present the theory and first estimates of the power that is scattered from the injected O-mode to a secondary X-mode in the presence of the fluctuations. It is shown that for ITER parameters the scattered power stays within acceptable limits and broadening of the equatorial beams is less than those from the upper launcher.

  17. First test of BNL electron beam ion source with high current density electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Pikin, Alexander, E-mail: pikin@bnl.gov; Alessi, James G., E-mail: pikin@bnl.gov; Beebe, Edward N., E-mail: pikin@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973 (United States); Shornikov, Andrey; Mertzig, Robert; Wenander, Fredrik; Scrivens, Richard [CERN, CH-1211 Geneva 23 (Switzerland)

    2015-01-09

    A new electron gun with electrostatic compression has been installed at the Electron Beam Ion Source (EBIS) Test Stand at BNL. This is a collaborative effort by BNL and CERN teams with a common goal to study an EBIS with electron beam current up to 10 A, current density up to 10,000 A/cm{sup 2} and energy more than 50 keV. Intensive and pure beams of heavy highly charged ions with mass-to-charge ratio < 4.5 are requested by many heavy ion research facilities including NASA Space Radiation Laboratory (NSRL) at BNL and HIE-ISOLDE at CERN. With a multiampere electron gun, the EBIS should be capable of delivering highly charged ions for both RHIC facility applications at BNL and for ISOLDE experiments at CERN. Details of the electron gun simulations and design, and the Test EBIS electrostatic and magnetostatic structures with the new electron gun are presented. The experimental results of the electron beam transmission are given.

  18. Reduced density matrix hybrid approach: Application to electronic energy transfer

    Energy Technology Data Exchange (ETDEWEB)

    Berkelbach, Timothy C.; Reichman, David R. [Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 (United States); Markland, Thomas E. [Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305 (United States)

    2012-02-28

    Electronic energy transfer in the condensed phase, such as that occurring in photosynthetic complexes, frequently occurs in regimes where the energy scales of the system and environment are similar. This situation provides a challenge to theoretical investigation since most approaches are accurate only when a certain energetic parameter is small compared to others in the problem. Here we show that in these difficult regimes, the Ehrenfest approach provides a good starting point for a dynamical description of the energy transfer process due to its ability to accurately treat coupling to slow environmental modes. To further improve on the accuracy of the Ehrenfest approach, we use our reduced density matrix hybrid framework to treat the faster environmental modes quantum mechanically, at the level of a perturbative master equation. This combined approach is shown to provide an efficient and quantitative description of electronic energy transfer in a model dimer and the Fenna-Matthews-Olson complex and is used to investigate the effect of environmental preparation on the resulting dynamics.

  19. Investigation of Multiconfigurational Short-Range Density Functional Theory for Electronic Excitations in Organic Molecules

    DEFF Research Database (Denmark)

    Hubert, Mickaël; Hedegård, Erik D.; Jensen, Hans Jørgen Aa

    2016-01-01

    -srDFT for a selected benchmark set of electronic excitations of organic molecules, covering the most common types of organic chromophores. This investigation confirms the expectation that the MC-srDFT method is accurate for a broad range of excitations and comparable to accurate wave function methods such as CASPT2......Computational methods that can accurately and effectively predict all types of electronic excitations for any molecular system are missing in the toolbox of the computational chemist. Although various Kohn-Sham density-functional methods (KS-DFT) fulfill this aim in some cases, they become...... and double excitations have been promising, it is nevertheless important that the accuracy of MC-srDFT is at least comparable to the best KS-DFT methods also for organic molecules that are typically of single-reference character. In this paper we therefore systematically investigate the performance of MC...

  20. Two-electron Rabi oscillations in real-time time-dependent density-functional theory.

    Science.gov (United States)

    Habenicht, Bradley F; Tani, Noriyuki P; Provorse, Makenzie R; Isborn, Christine M

    2014-11-14

    We investigate the Rabi oscillations of electrons excited by an applied electric field in several simple molecular systems using time-dependent configuration interaction (TDCI) and real-time time-dependent density-functional theory (RT-TDDFT) dynamics. While the TDCI simulations exhibit the expected single-electron Rabi oscillations at a single resonant electric field frequency, Rabi oscillations in the RT-TDDFT simulations are a two-electron process. The existence of two-electron Rabi oscillations is determined both by full population inversion between field-free molecular orbitals and the behavior of the instantaneous dipole moment during the simulations. Furthermore, the Rabi oscillations in RT-TDDFT are subject to an intensity threshold of the electric field, below which Rabi oscillations do not occur and above which the two-electron Rabi oscillations occur at a broad range of frequencies. It is also shown that at field intensities near the threshold intensity, the field frequency predicted to induce Rabi oscillations by linear response TDDFT only produces detuned Rabi oscillations. Instead, the field frequency that yields the full two-electron population inversion and Rabi oscillation behavior is shown to be the average of single-electron transition frequencies from the ground S0 state and the doubly-excited S2 state. The behavior of the two-electron Rabi oscillations is rationalized via two possible models. The first model is a multi-photon process that results from the electric field interacting with the three level system such that three level Rabi oscillations may occur. The second model suggests that the mean-field nature of RT-TDDFT induces paired electron propagation.

  1. Harmonic analysis of the ionospheric electron densities retrieved from FORMOSAT-3/COSMIC radio occultation measurements

    Science.gov (United States)

    Masoumi, S.; Safari, A.; Sharifi, M.; Sam Khaniani, A.

    2011-12-01

    In order to investigate regular variations of the ionosphere, the least-squares harmonic estimation is applied to the time series of ionospheric electron densities in the region of Iran derived from about five years of Global Positioning System Radio Occultation (GPS RO) observations by FORMOSAT-3/COSMIC satellites. Although the obtained results are slightly different from the expected ones due to the low horizontal resolution of RO measurements, high vertical resolution of the observations enables us to detect not only the Total Electron Content (TEC) variations, but also periodic patterns of electron densities in different altitudes of the ionosphere. Dominant diurnal and annual signals, together with their Fourier series decompositions, and also periods close to 27 days are obtained, which is consistent with the previous analyses on TEC. In the equatorial anomaly band, the annual component is weaker than its Fourier decomposition periods. In particular, the semiannual period dominates the annual component, which is probably due to the effect of geomagnetic field. By the investigation of the frequencies at different local times, the semiannual signal is more significant than the annual one in the daytime, while the annual frequency is dominant at night. By the detection of the phases of the components, it is revealed that the annual signal has its maximum in summer at high altitudes, and in winter at lower altitudes. This suggests the effect of neutral compositions in the lower atmosphere. Further, the semiannual component peaks around equinox during the day, while its maximum mostly occurs in solstice at night. Since RO measurements can be used to derive TEC along the signal path between a GPS satellite and a receiver, study on the potentiality of using these observations for the prediction of electron densities and its application to the ionospheric correction of the single frequency receivers is suggested.

  2. Efficient Density Functional Approximation for Electronic Properties of Conjugated Systems

    Science.gov (United States)

    Caldas, Marília J.; Pinheiro, José Maximiano, Jr.; Blum, Volker; Rinke, Patrick

    2014-03-01

    There is on-going discussion about reliable prediction of electronic properties of conjugated oligomers and polymers, such as ionization potential IP and energy gap. Several exchange-correlation (XC) functionals are being used by the density functional theory community, with different success for different properties. In this work we follow a recent proposal: a fraction α of exact exchange is added to the semi-local PBE XC aiming consistency, for a given property, with the results obtained by many-body perturbation theory within the G0W0 approximation. We focus the IP, taken as the negative of the highest occupied molecular orbital energy. We choose α from a study of the prototype family trans-acetylene, and apply this same α to a set of oligomers for which there is experimental data available (acenes, phenylenes and others). Our results indicate we can have excellent estimates, within 0,2eV mean ave. dev. from the experimental values, better than through complete EN - 1 -EN calculations from the starting PBE functional. We also obtain good estimates for the electrical gap and orbital energies close to the band edge. Work supported by FAPESP, CNPq, and CAPES, Brazil, and DAAD, Germany.

  3. Smaller = denser, and the brain knows it: natural statistics of object density shape weight expectations.

    Directory of Open Access Journals (Sweden)

    Megan A K Peters

    Full Text Available If one nondescript object's volume is twice that of another, is it necessarily twice as heavy? As larger objects are typically heavier than smaller ones, one might assume humans use such heuristics in preparing to lift novel objects if other informative cues (e.g., material, previous lifts are unavailable. However, it is also known that humans are sensitive to statistical properties of our environments, and that such sensitivity can bias perception. Here we asked whether statistical regularities in properties of liftable, everyday objects would bias human observers' predictions about objects' weight relationships. We developed state-of-the-art computer vision techniques to precisely measure the volume of everyday objects, and also measured their weight. We discovered that for liftable man-made objects, "twice as large" doesn't mean "twice as heavy": Smaller objects are typically denser, following a power function of volume. Interestingly, this "smaller is denser" relationship does not hold for natural or unliftable objects, suggesting some ideal density range for objects designed to be lifted. We then asked human observers to predict weight relationships between novel objects without lifting them; crucially, these weight predictions quantitatively match typical weight relationships shown by similarly-sized objects in everyday environments. These results indicate that the human brain represents the statistics of everyday objects and that this representation can be quantitatively abstracted and applied to novel objects. Finally, that the brain possesses and can use precise knowledge of the nonlinear association between size and weight carries important implications for implementation of forward models of motor control in artificial systems.

  4. Density variation in the electron-hole liquid in stressed germanium and silicon

    Energy Technology Data Exchange (ETDEWEB)

    Kelso, S.M.

    1979-08-01

    A detailed study is presented of the variation in electron-hole pair density in the electron-hole liquid (EHL) in stressed Ge and Si. First, the variation of the density and other properties of the EHL is studied theoretically as a function of uniaxial stress in both Ge and Si. Second, the variation of the density with position is studied both theoretically and experimentally in the strain-confined electron-hole liquid (SCEHL) in Ge.

  5. On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector.

    Science.gov (United States)

    Aray, Yosslen; Paredes, Ricardo; Álvarez, Luis Javier; Martiz, Alejandro

    2017-06-14

    The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such as α-Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au, was studied using a localized electrons detector defined in the local moment representation. Our results clearly show an opposite pattern of the electron density localization for the cubic ceramic and transition metal materials. It was found that, for the elemental ceramic materials, the zone of low electron localization is very small and is mainly localized on the atomic basin edges. On the contrary, for the transition metals, there are low-valued localized electrons detector isocontours defining a zone of highly delocalized electrons that extends throughout the material. We have found that the best conductors are those in which the electron density at this low-value zone is the lowest.

  6. Temporal and spatial variations in ionospheric electron density profiles over South Africa during strong magnetic storms

    National Research Council Canada - National Science Library

    Yao, Y. B; Chen, P; Zhang, S; Chen, J. J

    2013-01-01

    ...) and vertical total electron content (VTEC) data from the Jason-1 satellite were used to analyze the variations in ionospheric electron density profiles over South Africa before and after the severe geomagnetic storms on 15 May 2005...

  7. Electron Cyclotron Resonance Heating of a High-Density Plasma

    DEFF Research Database (Denmark)

    Hansen, F. Ramskov

    1986-01-01

    Various schemes for electron cyclotron resonance heating of tokamak plasmas with the ratio of electron plasma frequency to electron cyclotron frequency, "»pe/^ce* larger than 1 on axis, are investigated. In particular, a mode conversion scheme is investigated using ordinary waves at the fundamental...

  8. Assimilation of FORMOSAT-3/COSMIC electron density profiles into a coupled Thermosphere/Ionosphere model

    Science.gov (United States)

    Lee, I.-Te; Matsuo, Tomoko; Richmond, Arthur D.; Tiger Liu, Jann-Yeng

    2013-04-01

    This paper presents our effort to assimilate FORMOSAT-3/COSMIC (F3/C) GPS Occultation Experiment observations into the National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) by means of ensemble Kalman filtering (EnKF). The F3/C EDP are combined with the TIE-GCM simulations by EnKF algorithms implemented in the NCAR Data Assimilation Research Testbed open-source community facility to compute the expected value of electron density, which is 'the best' estimate of the current ionospheric state. Assimilation analyses obtained with real F3/C electron density profiles during geomagnetic quiet time and disturbed period are further compared with independent ground-based observations and global ionospheric map as well as the F3/C profiles themselves. The comparison shows the improvement of the primary ionospheric parameters such as NmF2 and hmF2 and further display some small scale physical meaning structures which might either generally ionospheric features or storm effects. Nevertheless some unrealistic signatures appearing in the results and high rejection rates of observations due to the applied outlier threshold and quality control are also found in the assimilation experiments. These features are additionally analyzed to identify and correct the model biases in the future.

  9. Extension of electron cyclotron heating at ASDEX Upgrade with respect to high density operation

    Science.gov (United States)

    Schubert, Martin; Stober, Jörg; Herrmann, Albrecht; Kasparek, Walter; Leuterer, Fritz; Monaco, Francesco; Petzold, Bernhard; Plaum, Burkhard; Vorbrugg, Stefan; Wagner, Dietmar; Zohm, Hartmut

    2017-10-01

    The ASDEX Upgrade electron cyclotron resonance heating operates at 105 GHz and 140 GHz with flexible launching geometry and polarization. In 2016 four Gyrotrons with 10 sec pulse length and output power close to 1 MW per unit were available. The system is presently being extended to eight similar units in total. High heating power and high plasma density operation will be a part of the future ASDEX Upgrade experiment program. For the electron cyclotron resonance heating, an O-2 mode scheme is proposed, which is compatible with the expected high plasma densities. It may, however, suffer from incomplete single-pass absorption. The situation can be improved significantly by installing holographic mirrors on the inner column, which allow for a second pass of the unabsorbed fraction of the millimetre wave beam. Since the beam path in the plasma is subject to refraction, the beam position on the holographic mirror has to be controlled. Thermocouples built into the mirror surface are used for this purpose. As a protective measure, the tiles of the heat shield on the inner column were modified in order to increase the shielding against unabsorbed millimetre wave power.

  10. Extension of electron cyclotron heating at ASDEX Upgrade with respect to high density operation

    Directory of Open Access Journals (Sweden)

    Schubert Martin

    2017-01-01

    Full Text Available The ASDEX Upgrade electron cyclotron resonance heating operates at 105 GHz and 140 GHz with flexible launching geometry and polarization. In 2016 four Gyrotrons with 10 sec pulse length and output power close to 1 MW per unit were available. The system is presently being extended to eight similar units in total. High heating power and high plasma density operation will be a part of the future ASDEX Upgrade experiment program. For the electron cyclotron resonance heating, an O-2 mode scheme is proposed, which is compatible with the expected high plasma densities. It may, however, suffer from incomplete single-pass absorption. The situation can be improved significantly by installing holographic mirrors on the inner column, which allow for a second pass of the unabsorbed fraction of the millimetre wave beam. Since the beam path in the plasma is subject to refraction, the beam position on the holographic mirror has to be controlled. Thermocouples built into the mirror surface are used for this purpose. As a protective measure, the tiles of the heat shield on the inner column were modified in order to increase the shielding against unabsorbed millimetre wave power.

  11. Grand-canonical-ensemble representability problem for the one-electron reduced density matrix

    Science.gov (United States)

    Alcoba, D. R.; Bochicchio, R. C.; Massacessi, G. E.; Lain, L.; Torre, A.

    2007-01-01

    We deal with many-electron systems having a noninteger number of electrons, which cannot be described properly by means of pure states or by canonical statistical ensemble states. The study of the one-electron reduced density matrix for these systems raises the problem of its representability in statistical ensembles of grand canonical type. We derive the necessary and sufficient conditions for the representability of the one-electron reduced density matrix of grand-canonical statistical ensembles.

  12. Density-dependent electron scattering in photoexcited GaAs in strongly diffusive regime

    DEFF Research Database (Denmark)

    Mics, Zoltán; D’Angio, Andrea; Jensen, Søren A.

    2013-01-01

    In a series of systematic optical pump–terahertz probe experiments, we study the density-dependent electron scattering rate in photoexcited GaAs in the regime of strong carrier diffusion. The terahertz frequency-resolved transient sheet conductivity spectra are perfectly described by the Drude...... model, directly yielding the electron scattering rates. A diffusion model is applied to determine the spatial extent of the photoexcited electron-hole gas at each moment after photoexcitation, yielding the time-dependent electron density, and hence the density-dependent electron scattering time. We find...

  13. Experimental core electron density of cubic boron nitride

    DEFF Research Database (Denmark)

    Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse

    candidate because of its many similarities with diamond: bonding pattern in the extended network structure, hardness, and the quality of the crystallites.3 However, some degree ionic interaction is a part of the bonding in boron nitride, which is not present in diamond. By investigating the core density...... beyond multipolar modeling of the valence density. As was recently shown in a benchmark study of diamond by Bindzus et al.1 The next step is to investigate more complicated chemical bonding motives, to determine the effect of bonding on the core density. Cubic boron nitride2 lends itself as a perfect...... in boron nitride we may obtain a deeper understanding of the effect of bonding on the total density. We report here a thorough investigation of the charge density of cubic boron nitride with a detailed modelling of the inner atom charge density. By combining high resolution powder X-ray diffraction data...

  14. Characteristics of recycled and electron beam irradiated high density polyethylene samples

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, Jessica R.; Gabriel, Leandro; Geraldo, Aurea B.C.; Moura, Eduardo, E-mail: jrcardoso@ipen.br, E-mail: lgabriell@gmail.com, E-mail: ageraldo@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Polymers modification by irradiation is a well-known process that allows degradation and cross-linking in concurrent events; this last is expected when an increase of mechanical properties is required. Actually, the interest of recycling and reuse of polymeric material is linked to the increase of plastics ending up in waste streams. Therefore, these both irradiation and recycling process may be conducted to allow a new use to this material that would be discarded by an improvement of its mechanical properties. In this work, the High Density Polyethylene (HDPE) matrix has been recycled five times from original substrate. The electron beam irradiation process was applied from 50 kGy to 200 kGy in both original and recycled samples; in this way, mechanical properties and thermal characteristics were evaluated. The results of applied process and material characterization are discussed. (author)

  15. Electron momentum density and the momentum density of positron annihilation pairs in alkali metals: high-momentum components

    Energy Technology Data Exchange (ETDEWEB)

    Sob, M.

    1985-08-01

    The valence electron momentum density (EMD) and the momentum density of positron annihilation pairs (MDAP) are calculated ab initio for alkali metals from Li to Cs. It is shown that the proportion of valence electrons having their momenta within the central Fermi surface ranges from 75% (Cs) to 93% (Na); the momenta of the remaining valence electrons lie in the Umklapp Fermi surfaces centred at the surrounding reciprocal lattice points. In the calculation of the MDAP, various enhancement factors describing the effect of the many-body electron-positron interaction are examined; it seems that the recent model of enhancement of Umklapp terms presented by Sormann et al is not fully adequate. A relation between the EMD and MDAP is briefly discussed and the connection between the occupation of the central Fermi surface and other parameters of the electronic structure is pointed out.

  16. Investigation of the Electron Acceleration by a High-Power Laser and a Density-Tapered Mixed-Gas Cell

    Science.gov (United States)

    Kim, Jinju; Phung, Vanessa L. J.; Kim, Minseok; Hur, Min-Sup; Suk, Hyyong

    2017-10-01

    Plasma-based accelerators can generate about 1000 times stronger acceleration field compared with RF-based conventional accelerators, which can be done by high power laser and plasma. There are many issues in this research and one of them is development of a good plasma source for higher electron beam energy. For this purpose, we are investigating a special type of plasma source, which is a density-tapered gas cell with a mixed-gas for easy injection. By this type of special gas cell, we expect higher electron beam energies with easy injection in the wakefield. In this poster, some experimental results for electron beam generation with the density-tapered mixed-gas cell are presented. In addition to the experimental results, CFD (Computational-Fluid-Dynamics) and PIC (Particle-In-Cell) simulation results are also presented for comparison studies.

  17. A phase contrast imaging-interferometer system for detection of multiscale electron density fluctuations on DIII-D

    Science.gov (United States)

    Davis, E. M.; Rost, J. C.; Porkolab, M.; Marinoni, A.; Van Zeeland, M. A.

    2016-11-01

    Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI-interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz electron-scale instabilities. Further, correlating our interferometer's measurements with those from DIII-D's pre-existing, toroidally separated interferometer allows core-localized, low-n MHD studies that may otherwise be inaccessible via external magnetic measurements. The combined diagnostic's small port requirements and minimal access restrictions make it well-suited to the harsh neutron environments and limited port space expected in next-step devices.

  18. Tuning the conductivity threshold and carrier density of two-dimensional electron gas at oxide interfaces through interface engineering

    Directory of Open Access Journals (Sweden)

    H. J. Harsan Ma

    2015-08-01

    Full Text Available The two-dimensional electron gas (2DEG formed at the perovskite oxides heterostructures is of great interest because of its potential applications in oxides electronics and nanoscale multifunctional devices. A canonical example is the 2DEG at the interface between a polar oxide LaAlO3 (LAO and non-polar SrTiO3 (STO. Here, the LAO polar oxide can be regarded as the modulating or doping layer and is expected to define the electronic properties of 2DEG at the LAO/STO interface. However, to practically implement the 2DEG in electronics and device design, desired properties such as tunable 2D carrier density are necessary. Here, we report the tuning of conductivity threshold, carrier density and electronic properties of 2DEG in LAO/STO heterostructures by insertion of a La0.5Sr0.5TiO3 (LSTO layer of varying thicknesses, and thus modulating the amount of polarization of the oxide over layers. Our experimental result shows an enhancement of carrier density up to a value of about five times higher than that observed at the LAO/STO interface. A complete thickness dependent metal-insulator phase diagram is obtained by varying the thickness of LAO and LSTO providing an estimate for the critical thickness needed for the metallic phase. The observations are discussed in terms of electronic reconstruction induced by polar oxides.

  19. Exploring the Interaction Natures in Plutonyl (VI) Complexes with Topological Analyses of Electron Density.

    Science.gov (United States)

    Du, Jiguang; Sun, Xiyuan; Jiang, Gang

    2016-04-11

    The interaction natures between Pu and different ligands in several plutonyl (VI) complexes are investigated by performing topological analyses of electron density. The geometrical structures in both gaseous and aqueous phases are obtained with B3LYP functional, and are generally in agreement with available theoretical and experimental results when combined with all-electron segmented all-electron relativistic contracted (SARC) basis set. The Pu- O y l bond orders show significant linear dependence on bond length and the charge of oxygen atoms in plutonyl moiety. The closed-shell interactions were identified for Pu-Ligand bonds in most complexes with quantum theory of atoms in molecules (QTAIM) analyses. Meanwhile, we found that some Pu-Ligand bonds, like Pu-OH(-), show weak covalent. The interactive nature of Pu-ligand bonds were revealed based on the interaction quantum atom (IQA) energy decomposition approach, and our results indicate that all Pu-Ligand interactions is dominated by the electrostatic attraction interaction as expected. Meanwhile it is also important to note that the quantum mechanical exchange-correlation contributions can not be ignored. By means of the non-covalent interaction (NCI) approach it has been found that some weak and repulsion interactions existed in plutonyl(VI) complexes, which can not be distinguished by QTAIM, can be successfully identified.

  20. Exploring the Interaction Natures in Plutonyl (VI Complexes with Topological Analyses of Electron Density

    Directory of Open Access Journals (Sweden)

    Jiguang Du

    2016-04-01

    Full Text Available The interaction natures between Pu and different ligands in several plutonyl (VI complexes are investigated by performing topological analyses of electron density. The geometrical structures in both gaseous and aqueous phases are obtained with B3LYP functional, and are generally in agreement with available theoretical and experimental results when combined with all-electron segmented all-electron relativistic contracted (SARC basis set. The Pu– O y l bond orders show significant linear dependence on bond length and the charge of oxygen atoms in plutonyl moiety. The closed-shell interactions were identified for Pu-Ligand bonds in most complexes with quantum theory of atoms in molecules (QTAIM analyses. Meanwhile, we found that some Pu–Ligand bonds, like Pu–OH−, show weak covalent. The interactive nature of Pu–ligand bonds were revealed based on the interaction quantum atom (IQA energy decomposition approach, and our results indicate that all Pu–Ligand interactions is dominated by the electrostatic attraction interaction as expected. Meanwhile it is also important to note that the quantum mechanical exchange-correlation contributions can not be ignored. By means of the non-covalent interaction (NCI approach it has been found that some weak and repulsion interactions existed in plutonyl(VI complexes, which can not be distinguished by QTAIM, can be successfully identified.

  1. The effects of incident electron current density and temperature on the total electron emission yield of polycrystalline CVD diamond

    Energy Technology Data Exchange (ETDEWEB)

    Belhaj, M; Tondu, T; Inguimbert, V [ONERA/DESP 2, Avenue Edouard Belin, 31400 Toulouse Cedex (France); Barroy, Pierre; Silva, Francois; Gicquel, Alix, E-mail: Mohamed.Belhaj@onera.f [LIMHP, Universite Paris 13, CNRS Institut Galilee, 99 Avenue Jean-Baptiste Clement, 93430 Villetaneuse (France)

    2010-04-07

    The effects of temperature and incident electron current density on the total electron emission yield (TEEY) of polycrystalline diamond deposited by the chemical vapour deposition technique (CVD) were investigated at low electron beam fluence. It was found that the TEEY reversibly increases with the temperature and reversibly decreases with the current density. This behaviour is explained on the basis of a dynamic competition between the accumulation of holes (positive space charge), which internally reduces the secondary electron emission, and the thermally activated conductivity that tends to reduce the space charge formation.

  2. High-energy-density electron beam from interaction of two successive laser pulses with subcritical-density plasma

    Directory of Open Access Journals (Sweden)

    J. W. Wang

    2016-02-01

    Full Text Available It is shown by particle-in-cell simulations that a narrow electron beam with high energy and charge density can be generated in a subcritical-density plasma by two consecutive laser pulses. Although the first laser pulse dissipates rapidly, the second pulse can propagate for a long distance in the thin wake channel created by the first pulse and can further accelerate the preaccelerated electrons therein. Given that the second pulse also self-focuses, the resulting electron beam has a narrow waist and high charge and energy densities. Such beams are useful for enhancing the target-back space-charge field in target normal sheath acceleration of ions and bremsstrahlung sources, among others.

  3. Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points

    Energy Technology Data Exchange (ETDEWEB)

    Bučinský, Lukáš, E-mail: lukas.bucinsky@stuba.sk [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Kucková, Lenka; Malček, Michal; Kožíšek, Jozef; Biskupič, Stanislav [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Jayatilaka, Dylan [University of Western Australia, Department of Chemistry, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Büchel, Gabriel E. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria); King Abdullah University of Science and Technology, Division for Physical Sciences and Engineering and KAUST Catalysis Center, Thuwal (Saudi Arabia); Arion, Vladimir B. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria)

    2014-06-25

    Highlights: • Quasirelativistic study of electron density topology of Os and Ru complexes. • Electron/spin densities and negative Laplacian of electron density presented. • Analytic correction of picture change error at IOTC level. • Relativistic and spin–orbit effects are considered, IOTC vs. DKH2 compared. - Abstract: The change of picture of the quasirelativistic Hartree–Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl{sub 5}(Hpz)]{sup −} and [RuCl{sub 5}(NO)]{sup 2−} transition metal complexes are considered. Both, scalar relativistic and spin–orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.

  4. Four ways to determine the electron density in low-temperature plasmas

    NARCIS (Netherlands)

    Meulenbroeks, R.F.G.; Steenbakkers, M.F.M.; Qing, Z.; van de Sanden, M.C.M.; Schram, D.C.

    Four ways to measure the electron density in low-temperature plasmas are presented: Thomson scattering, Langmuir probe, optical-emission spectroscopy, and continuum-radiation analysis. The results of the four methods are compared to each other and discussed. For the electron-density range of

  5. Tuning the electron energy by controlling the density perturbation position in laser plasma accelerators

    CERN Document Server

    Brijesh, P; Phuoc, K T; Corde, S; Lambert, G; Malka, V; Mangles, S P D; Bloom, M; Kneip, S

    2012-01-01

    A density perturbation produced in an underdense plasma was used to improve the quality of electron bunches produced in the laser-plasma wakefield acceleration scheme. Quasi-monoenergetic electrons were generated by controlled injection in the longitudinal density gradients of the density perturbation. By tuning the position of the density perturbation along the laser propagation axis, a fine control of the electron energy from a mean value of 60 MeV to 120 MeV has been demonstrated with a relative energy-spread of 15 +/- 3.6%, divergence of 4 +/- 0.8 mrad and charge of 6 +/- 1.8 pC.

  6. Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points

    KAUST Repository

    Bučinský, Lukáš

    2014-06-01

    The change of picture of the quasirelativistic Hartree-Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl5(Hpz)]- and [RuCl5(NO)]2- transition metal complexes are considered. Both, scalar relativistic and spin-orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.©2014 Elsevier B.V. All rights reserved.

  7. A non-tomographic method for imaging the global ionospheric electron density

    Science.gov (United States)

    Brunini, C.; Meza, A.; Azpilicueta, F.; Schmidt, M.; Nava, B.; Coïson, P.; Radicella, S.

    There are today a variety of approaches for processing dual-frequency GPS observations and to produce global ionospheric maps of TEC. The majority of these researches use ground-based GPS observations from the worldwide tracking network of the International GPS Service. While ground-based ionospheric maps represent a big advance for ionosphere weather, the radial geometry of the ground-based observations limits their capability for providing information on the vertical electron distribution. This limitation can be removed by the introduction of horizontal cuts through the ionosphere, affordable by space-born GPS receivers flying on low-Earth orbiting satellites (e.g. GPS-Met, CHAMP, GRACE, SAC-C). Several empirical models are currently used to describe the electron density distribution in the ionosphere. Among them, the NeQuick model is being used by the ESA EGNOS project for assessment analysis and has been proposed for single-frequency operation in the Galileo project. NeQuick is mostly droved by the two parameters NmF2 and hmF2, whose values are usually computed as function of position and time, using the CCIR climatologic database. Since the CCIR provides monthly averaged values, so significant day-to-day deviations between the actual and predicted TEC can be expected. Therefore, it seems suitable to determine appropriate corrections for the CCIR values in order to better fit the observed TEC. In this contribution we present a non-tomographic method for 3-D imaging of the global electron density distribution that uses the NeQuick model and two-dimensional spherical wavelet expansions for representing the spatial variability of the driving parameters of NeQuick. The coefficients of the wavelet series are computable from TEC observations using parameter estimation methods.

  8. Topology of electron charge density for chemical bonds from valence bond theory: a probe of bonding types.

    Science.gov (United States)

    Zhang, Lixian; Ying, Fuming; Wu, Wei; Hiberty, Philippe C; Shaik, Sason

    2009-01-01

    To characterize the nature of bonding we derive the topological properties of the electron charge density of a variety of bonds based on ab initio valence bond methods. The electron density and its associated Laplacian are partitioned into covalent, ionic, and resonance components in the valence bond spirit. The analysis provides a density-based signature of bonding types and reveals, along with the classical covalent and ionic bonds, the existence of two-electron bonds in which most of the bonding arises from the covalent-ionic resonance energy, so-called charge-shift bonds. As expected, the covalent component of the Laplacian at the bond critical point is found to be largely negative for classical covalent bonds. In contrast, for charge-shift bonds, the covalent part of the Laplacian is small or positive, in agreement with the weakly attractive or repulsive character of the covalent interaction in these bonds. On the other hand, the resonance component of the Laplacian is always negative or nearly zero, and it increases in absolute value with the charge-shift character of the bond, in agreement with the decrease of kinetic energy associated with covalent-ionic mixing. A new interpretation of the topology of the total density at the bond critical point is proposed to characterize covalent, ionic, and charge-shift bonding from the density point of view.

  9. Density functional study of : Electronic and optical properties

    Indian Academy of Sciences (India)

    K C Bhamu

    2017-06-20

    Jun 20, 2017 ... the refractive index in zero frequency limits is 2.42. The absorption coefficient predicts the applicability of AgScO2 in solar cells and flat panel liquid crystal display as a transparent top window layer. Keywords. Density functional theory; band structure; optical properties. PACS Nos 71.15.Mb; 71.20.−b; 78.20.

  10. High Power Density Power Electronic Converters for Large Wind Turbines

    DEFF Research Database (Denmark)

    Senturk, Osman Selcuk

    assessments of these specific VSCs so that their power densities and reliabilities are quantitatively determined, which requires extensive utilization of the electro-thermal models of the VSCs under investigation. In this thesis, the three-level neutral-point-clamped VSCs (3L-NPC-VSCs), which are classified...

  11. Molecular Electron Density Theory: A Modern View of Reactivity in Organic Chemistry.

    Science.gov (United States)

    Domingo, Luis R

    2016-09-30

    A new theory for the study of the reactivity in Organic Chemistry, named Molecular Electron Density Theory (MEDT), is proposed herein. MEDT is based on the idea that while the electron density distribution at the ground state is responsible for physical and chemical molecular properties, as proposed by the Density Functional Theory (DFT), the capability for changes in electron density is responsible for molecular reactivity. Within MEDT, the reactivity in Organic Chemistry is studied through a rigorous quantum chemical analysis of the changes of the electron density as well as the energies associated with these changes along the reaction path in order to understand experimental outcomes. Studies performed using MEDT allow establishing a modern rationalisation and to gain insight into molecular mechanisms and reactivity in Organic Chemistry.

  12. PMSE strength during enhanced D region electron densities: Faraday rotation and absorption effects at VHF frequencies

    Science.gov (United States)

    Chau, Jorge L.; Röttger, Jürgen; Rapp, Markus

    2014-10-01

    In this paper we study the effects of absorption and Faraday rotation on measurements of polar mesosphere summer echoes (PMSE). We found that such effects can produce significant reduction of signal-to-noise ratio (SNR) when the D region electron densities (Ne) are enhanced, and VHF radar systems with linearly polarized antennas are used. In particular we study the expected effects during the strong solar proton event (SPE) of July 2000, also known as the Bastille day flare event. During this event, a strong anti-correlation between the PMSE SNR and the D-region Ne was found over three VHF radar sites at high latitudes: Andøya, Kiruna, and Svalbard. This anti-correlation has been explained (a) in terms of transport effects due to strong electric fields associated to the SPE and (b) due to a limited amount of aerosol particles as compared to the amount of D-region electrons. Our calculations using the Ne profiles used by previous researchers explain most, if not all, of the observed SNR reduction in both time (around the SPE peak) and altitude. This systematic effect, particularly the Faraday rotation, should be recognized and tested, and possibly avoided (e.g., using circular polarization), in future observations during the incoming solar maximum period, to contribute to the understanding of PMSE during enhanced D region Ne.

  13. Long-term observations of D-region electron densities at high and middle northern latitudes

    Science.gov (United States)

    Singer, Werner; Keuer, Dieter; Friedrich, Martin; Strelnikova, Irina; Latteck, Ralph

    D-region electron densities are estimated using Doppler radars at frequencies around 3 MHz in Andenes, Norway (69.3°N, 16.0°E) since summer 2003 and in Juliusruh, Germany (54.6°N, 13.4°E) since summer 2006. Both experiments utilize partial reflections of ordinary and extraordinary component waves from scatterers in the altitude range 50-90 km to estimate electron number densities from differential absorption (DAE) and differential phase (DPE) measurements. Height profiles of electron density are obtained between about 55 km and 90 km with sampling times of 2-3 minutes and height resolution of 1.5 km at Andenes and 3 km at Juliusruh. The electron density profiles independently derived from DAE and DPE measurements agree remarkably well. The radar results are compared with co-located simultaneously measured electron densities by rocket-borne radio wave propagation experiments (differential absorption, Faraday rotation, and impedance probe) in Andenes with good agreement between insitu and ground-based measurements. The diurnal and seasonal variability of electron densities as observed at high and mid-latitudes under quiet ionospheric conditions is presented and compared to the corresponding electron density profiles of the International Reference Ionosphere. The response of D-region ionization to regular solar activity variation as well as to solar activity storms and geomagnetic disturbances has been studied at polar latitudes. Characteristic electron density variations are found during downwelling events of nitric oxide due to strong vertical coupling during stratospheric warming events. In addition, we discuss the inter-relation between D-region electron densities from radar observations, riometer absorption, and the empirical model IMAZ at different levels of solar activity and during particle precipitation events.

  14. The electron-propagator approach to conceptual density-functional ...

    Indian Academy of Sciences (India)

    Unknown

    theory) to evaluate the quantities appearing in (16). In fact, the terms in (16) are often discussed using vocabulary more often associated with molecular- orbital theory. Using Klopman's classification of different chemical reaction types,32 the terms on the second line, which depend on the change in the number of electrons ...

  15. Measurements of plasma temperature and electron density in laser ...

    Indian Academy of Sciences (India)

    nique to provide remote, in-situ, rapid and multi-elemental analysis of bulk and trace sample in any phase (solid, liquid and gas) with no or minimal sample prepa- ration [2–4]. The characterization of LIPs by determining their temperature and electron den- sity is essential and has gained considerable interest in recent years ...

  16. Electron-positron momentum density in TTF-TCNQ

    DEFF Research Database (Denmark)

    Ishibashi, S.; Manuel, A.A.; Hoffmann, L.

    1997-01-01

    We present measurements of the positron two-dimensional angular correlation of annihilation radiation (2D-ACAR) in TTF-TCNQ. We report also theoretical simulations of the 2D-ACAR in which the electron wave functions were expressed as TTF or TCNQ molecular orbitals obtained from self-consistent qu...

  17. Experimental electron density determinations on penicillins and a fullerene derivative

    OpenAIRE

    Wagner, Armin

    2010-01-01

    The number of experimental charge density studies increased during the past years. This is prior to technical developments, especially the now widely spread area detectors which allow to measure high resolution X-ray diffraction data sets in a reasonable time. With the program system XD a computer program is available which enables the user to easily handle the substantial parameters in the Hansen-Coppens multipole formalism. The combination of the area detection technique with the high...

  18. The influence of the edge density fluctuations on electron cyclotron wave beam propagation in tokamaks

    DEFF Research Database (Denmark)

    Bertelli, N.; Balakin, A.A.; Westerhof, E.

    2010-01-01

    A numerical analysis of the electron cyclotron (EC) wave beam propagation in the presence of edge density fluctuations by means of a quasi-optical code [Balakin A. A. et al, Nucl. Fusion 48 (2008) 065003] is presented. The effects of the density fluctuations on the wave beam propagation are estim......A numerical analysis of the electron cyclotron (EC) wave beam propagation in the presence of edge density fluctuations by means of a quasi-optical code [Balakin A. A. et al, Nucl. Fusion 48 (2008) 065003] is presented. The effects of the density fluctuations on the wave beam propagation...

  19. Electron density variability of nighttime D region ionosphere in Vietnamese and Japanese sectors

    Science.gov (United States)

    Tan, Le Minh; Shiokawa, Kazuo; Thu, Nguyen Ngoc; Ha, Tran Quoc

    2017-06-01

    Recording tweek atmospherics on geomagnetically quiet days in 2014 at Tay Nguyen University (TNU) (12.65°N, 108.02°E), Vietnam, and at Kagoshima (KAG) (31.48°N, 130.72°E), Japan, we investigated the nighttime electron density variability of the D region ionosphere between the equatorial-low-latitude Vietnamese and the low- to middle-latitude Japanese sectors. We estimated the reflection height and electron density of the D region ionosphere using the first-order mode cutoff frequency of tweek atmospherics. The results observed at both stations show that the mean electron density at the reflection height during winter season was higher than that during summer and equinox seasons. The electron density observed at TNU gradually decreased from 20:15 to 4:15 LT from winter to equinox and to summer. The electron density observed at KAG increased from 20:20 to 4:20 LT during summer and winter seasons. The mean electron density during 2014 observed at TNU (25.0 cm-3) was higher by 2.1 cm-3 than that observed at KAG (22.9 cm-3). During 2014, the nighttime electron density variations show a moderate positive correlation with the sunspot number but show weak to no correlation with the galactic cosmic rays. We suggest that the seasonal variations in the nighttime electron density could be significantly caused by the enhancement of geocoronal hydrogen Lyman α intensity and seasonal variation of nitric oxide density in the lower ionosphere.

  20. A tunable electron beam source using trapping of electrons in a density down-ramp in laser wakefield acceleration.

    Science.gov (United States)

    Ekerfelt, Henrik; Hansson, Martin; Gallardo González, Isabel; Davoine, Xavier; Lundh, Olle

    2017-09-25

    One challenge in the development of laser wakefield accelerators is to demonstrate sufficient control and reproducibility of the parameters of the generated bunches of accelerated electrons. Here we report on a numerical study, where we demonstrate that trapping using density down-ramps allows for tuning of several electron bunch parameters by varying the properties of the density down-ramp. We show that the electron bunch length is determined by the difference in density before and after the ramp. Furthermore, the transverse emittance of the bunch is controlled by the steepness of the ramp. Finally, the amount of trapped charge depends both on the density difference and on the steepness of the ramp. We emphasize that both parameters of the density ramp are feasible to vary experimentally. We therefore conclude that this tunable electron accelerator makes it suitable for a wide range of applications, from those requiring short pulse length and low emittance, such as the free-electron lasers, to those requiring high-charge, large-emittance bunches to maximize betatron X-ray generation.

  1. Electron number density profiles derived from radio occultation on the CASSIOPE spacecraft

    Science.gov (United States)

    Shume, Esayas B.; Vergados, Panagiotis; Komjathy, Attila; Langley, Richard B.; Durgonics, Tibor

    2017-09-01

    This paper presents electron number density profiles derived from high-resolution Global Positioning System (GPS) radio occultation (RO) observations performed using the Enhanced Polar Outflow Probe payload on the high inclination CAScade, Smallsat and IOnospheric Polar Explorer (CASSIOPE) spacecraft. We have developed and applied a novel inverse Abel transform algorithm on high rate RO total electron content measurements performed along GPS to CASSIOPE radio links to recover electron density profiles. The high-resolution density profiles inferred from the CASSIOPE RO are (1) in very good agreement with density profiles estimated from ionosonde data, measured over stations nearby to the latitude and longitude of the RO tangent points; (2) in good agreement with density profiles inferred from GPS RO measured by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC); and (3) in general agreement with density profiles estimated using the International Reference Ionosphere climatological model. Using both CASSIOPE and COSMIC RO observations, we identify, for the first time, that there exist differences in the characteristics of the electron number density profiles retrieved over landmasses and oceans. The density profiles over oceans exhibit widespread values and scale heights compared to density profiles over landmasses. We provide an explanation for the ocean-landmass discrepancy in terms of the unique wave coupling mechanisms operating over oceans and landmasses.

  2. Density Functional Theory Study on the Electronic Structures of Oxadiazole Based Dyes as Photosensitizer for Dye Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Umer Mehmood

    2015-01-01

    Full Text Available The molecular structures and UV-visible absorption spectra of complex photosensitizers comprising oxadiazole isomers as the π-bridges were analyzed by density functional theory (DFT and time-dependent DFT. The ground state and excited state oxidation potentials, HOMOs and LUMOs energy levels, and electron injection from the dyes to semiconductor TiO2 have been computed in vacuum here. The results show that all of the dyes may potentially be good photosensitizers in DSSC. To justify the simulation basis, N3 dye was also simulated under the similar conditions. Simulated absorption spectrum, HOMO, LUMO, and band gap values of N3 were compared with the experimental values. We also computed the electronic structure properties and absorption spectra of dye/(TiO28 systems to elucidate the electron injection efficiency at the interface. This work is expected to give proper orientation for experimental synthesis.

  3. Seasonal and solar activity variability of D-region electron density at 69°N

    Science.gov (United States)

    Singer, Werner; Latteck, Ralph; Friedrich, Martin; Wakabayashi, Makato; Rapp, Markus

    2011-06-01

    A narrow beam Doppler radar operating at 3.17 MHz and installed close to the Andøya Rocket Range in Andenes, Norway, (69.3°N, 16.0°E) has been providing electron densities in the lower ionosphere since summer 2003. The experiment utilizes partial reflection of ordinary and extraordinary component waves from scatterers in the altitude range 50-95 km to estimate electron densities from differential absorption and differential phase measurements. These ground-based observations are in good agreement with concurrent rocket-borne radio wave propagation measurements at Andenes. Results of the diurnal and seasonal variability of electron densities and the response of D-region electron densities to solar activity storms are presented.

  4. Plasma sheath: An equivalent nonlinear mirror between electron density and transmitted electromagnetic signal

    Science.gov (United States)

    Yao, Bo; Li, Xiaoping; Shi, Lei; Liu, Yanming; Lei, Fan; Zhu, Congying

    2017-10-01

    An experiment on the propagation of electromagnetic (EM) signals in continuous time-varying plasma is designed to establish the nonlinear mirror between electron density and transmission coefficient. The nonlinearity is confirmed from the theoretical and experimental results. The amplitude and phase can be considered nonlinear functions of electron density when the complex interaction between plasma and EM waves is ignored. Results show that amplitude and phase distributions are asymmetrical when electron density follows symmetric distribution. The skewness of amplitude is positive, whereas the skewness of phase is negative. The nonlinear degree is closely related to the ratio of plasma frequency to the incident wave frequency and the range of electron density. The conclusions are crucial to the modeling of plasma sheath channels and understanding the blackout problem.

  5. CASSINI RSS: IONOSPHERIC ELECTRON DENSITY PROFILES EDP1 V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains the complete collection of the published Cassini radio occultation electron density profiles of the Titan ionosphere as of September 2008.

  6. A simple and straightforward expression for curling probe electron density diagnosis in reactive plasmas

    Science.gov (United States)

    Arshadi, Ali; Brinkmann, Ralf Peter; Hotta, Masaya; Nakamura, Keiji

    2017-04-01

    Active plasma resonance spectroscopy (APRS) refers to the family of plasma diagnostic methods which utilize the ability of plasmas to resonate at frequencies close to the plasma frequency. APRS operates by exciting the plasma with a weak RF signal by means of a small electric probe. The response of the plasma is recorded by a network analyzer (NA). A mathematical model is applied to derive characteristics like the electron density and the electron temperature. The curling probe is a promising realization of APRS. The curling probe is well-qualified for the local measurement of the electron density in reactive plasmas. This spiral probe resonates in plasma at a larger density dependent frequency than the plasma frequency. This manuscript represents a simple and straightforward expression relating this resonance frequency to the electron density of the plasma. A good agreement is observed between the proposed expression and the results obtained from previous studies and numerical simulations.

  7. Imaging Near-Earth Electron Densities Using Thomson Scattering

    Science.gov (United States)

    2009-01-15

    telescopes (left and right squares). In these simulated images, we have assumed an input aperture diameter of 23.5 cm and a pixel plate scale of 270...diameter of 23.8 cm and a pixel plate scale of 120 km. The inner field of view begins near 320 km in altitude, which Imaging Near-Earth Electron...LFM) Global MHD Magnetospheric Simulation Code,” J. Atmos. Sol. Terres . Phys. 66, 1333. Meier, R.R., 1991. “Ultraviolet Spectroscopy and Remote

  8. Analysis of the enhanced negative correlation between electron density and electron temperature related to earthquakes

    Directory of Open Access Journals (Sweden)

    X. H. Shen

    2015-04-01

    Full Text Available Ionospheric perturbations in plasma parameters have been observed before large earthquakes, but the correlation between different parameters has been less studied in previous research. The present study is focused on the relationship between electron density (Ne and temperature (Te observed by the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions satellite during local nighttime, in which a positive correlation has been revealed near the equator and a weak correlation at mid- and low latitudes over both hemispheres. Based on this normal background analysis, the negative correlation with the lowest percent in all Ne and Te points is studied before and after large earthquakes at mid- and low latitudes. The multiparameter observations exhibited typical synchronous disturbances before the Chile M8.8 earthquake in 2010 and the Pu'er M6.4 in 2007, and Te varied inversely with Ne over the epicentral areas. Moreover, statistical analysis has been done by selecting the orbits at a distance of 1000 km and ±7 days before and after the global earthquakes. Enhanced negative correlation coefficients lower than −0.5 between Ne and Te are found in 42% of points to be connected with earthquakes. The correlation median values at different seismic levels show a clear decrease with earthquakes larger than 7. Finally, the electric-field-coupling model is discussed; furthermore, a digital simulation has been carried out by SAMI2 (Sami2 is Another Model of the Ionosphere, which illustrates that the external electric field in the ionosphere can strengthen the negative correlation in Ne and Te at a lower latitude relative to the disturbed source due to the effects of the geomagnetic field. Although seismic activity is not the only source to cause the inverse Ne–Te variations, the present results demonstrate one possibly useful tool in seismo-electromagnetic anomaly differentiation, and a comprehensive analysis with multiple

  9. Maximum current density and beam brightness achievable by laser-driven electron sources

    Directory of Open Access Journals (Sweden)

    D. Filippetto

    2014-02-01

    Full Text Available This paper discusses the extension to different electron beam aspect ratio of the Child-Langmuir law for the maximum achievable current density in electron guns. Using a simple model, we derive quantitative formulas in good agreement with simulation codes. The new scaling laws for the peak current density of temporally long and transversely narrow initial beam distributions can be used to estimate the maximum beam brightness and suggest new paths for injector optimization.

  10. Maximum current density and beam brightness achievable by laser-driven electron sources

    Science.gov (United States)

    Filippetto, D.; Musumeci, P.; Zolotorev, M.; Stupakov, G.

    2014-02-01

    This paper discusses the extension to different electron beam aspect ratio of the Child-Langmuir law for the maximum achievable current density in electron guns. Using a simple model, we derive quantitative formulas in good agreement with simulation codes. The new scaling laws for the peak current density of temporally long and transversely narrow initial beam distributions can be used to estimate the maximum beam brightness and suggest new paths for injector optimization.

  11. Multipole electron-density modelling of synchrotron powder diffraction data: the case of diamond

    DEFF Research Database (Denmark)

    Svendsen, H.; Overgaard, J.; Busselez, R.

    2010-01-01

    Accurate structure factors are extracted from synchrotron powder diffraction data measured on crystalline diamond based on a novel multipole model division of overlapping reflection intensities. The approach limits the spherical-atom bias in structure factors extracted from overlapping powder data...... parameter. This directly exposes a correlation between electron density and thermal parameters even for a light atom such as carbon, and it also underlines that in organic systems proper deconvolution of thermal motion is important for obtaining correct static electron densities....

  12. Some new features of electron density irregularities over SHAR during strong spread F

    Directory of Open Access Journals (Sweden)

    S. Raizada

    Full Text Available An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR (14°N, 80°E, dip latitude 5.5°N to study electron density and electric field irregularities during spread F. The rocket was launched at 2130 local time (LT and it attained an apogee of 348 km. Results of electron density fluctuations are presented here. Two extremely sharp layers of very high electron density were observed at 105 and 130 km. The electron density increase in these layers was by a factor of 50 in a vertical extent of 10 km. Large depletions in electron density were observed around 175 and 238 km. Both sharp layers as well as depletions were observed also during the descent. The presence of sharp layers and depletions during the ascent and the descent of the rocket as well as an order of magnitude less electron density, in 150-300 km region during the descent, indicate the presence of strong large-scale horizontal gradients in the electron density. Some of the valley region irregularities (165-178 km, in the intermediate scale size range, observed during this flight, show spectral peaks at 2 km and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of new type. The growth rate of intermediate scale size irregularities, produced through generalized Rayleigh Taylor instability, was calculated for the 200-330 km altitude, using observed values of electron density gradients and an assumed vertically downward wind of 20 ms-1. These growth rate calculations suggest that the observed irregularities could be produced by the gradient drift instability.

    Key words: Ionosphere (equatorial ionosphere; ionospheric irregularities - Radio science (ionospheric physics

  13. Some new features of electron density irregularities over SHAR during strong spread F

    Directory of Open Access Journals (Sweden)

    S. Raizada

    2000-02-01

    Full Text Available An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR (14°N, 80°E, dip latitude 5.5°N to study electron density and electric field irregularities during spread F. The rocket was launched at 2130 local time (LT and it attained an apogee of 348 km. Results of electron density fluctuations are presented here. Two extremely sharp layers of very high electron density were observed at 105 and 130 km. The electron density increase in these layers was by a factor of 50 in a vertical extent of 10 km. Large depletions in electron density were observed around 175 and 238 km. Both sharp layers as well as depletions were observed also during the descent. The presence of sharp layers and depletions during the ascent and the descent of the rocket as well as an order of magnitude less electron density, in 150-300 km region during the descent, indicate the presence of strong large-scale horizontal gradients in the electron density. Some of the valley region irregularities (165-178 km, in the intermediate scale size range, observed during this flight, show spectral peaks at 2 km and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of new type. The growth rate of intermediate scale size irregularities, produced through generalized Rayleigh Taylor instability, was calculated for the 200-330 km altitude, using observed values of electron density gradients and an assumed vertically downward wind of 20 ms-1. These growth rate calculations suggest that the observed irregularities could be produced by the gradient drift instability.Key words: Ionosphere (equatorial ionosphere; ionospheric irregularities - Radio science (ionospheric physics

  14. Simulations of Nanocrystals Under Pressure: Combining Electronic Enthalpy and Linear-Scaling Density-Functional Theory

    OpenAIRE

    Corsini, NR; Greco, A.; Hine, ND; Molteni, C.; Haynes, PD

    2013-01-01

    We present an implementation in a linear-scaling density-functional theory code of an electronic enthalpy method, which has been found to be natural and efficient for the ab initio calculation of finite systems under hydrostatic pressure. Based on a definition of the system volume as that enclosed within an electronic density isosurface [M. Cococcioni, F. Mauri, G. Ceder, and N. Marzari, Phys. Rev. Lett. 94, 145501 (2005)], it supports both geometry optimizations and molecular dynamics simula...

  15. Advanced High Energy Density Secondary Batteries with Multi?Electron Reaction Materials

    OpenAIRE

    Chen, Renjie; Luo, Rui; Huang, Yongxin; Wu, Feng; Li, Li

    2016-01-01

    Secondary batteries have become important for smart grid and electric vehicle applications, and massive effort has been dedicated to optimizing the current generation and improving their energy density. Multi?electron chemistry has paved a new path for the breaking of the barriers that exist in traditional battery research and applications, and provided new ideas for developing new battery systems that meet energy density requirements. An in?depth understanding of multi?electron chemistries i...

  16. Electron density and temperature measurements in a laser produced carbon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, S.S.; Bindhu, C.V.; Issac, R.C.; Nampoori, V.P.; Vallabhan, C.P. [Laser Division, International School of Photonics, Cochin University of Science Technology, Cochin 682 022 (India)

    1997-09-01

    Plasma generated by fundamental radiation from a Nd:YAG laser focused onto a graphite target is studied spectroscopically. Measured line profiles of several ionic species were used to infer electron temperature and density at several sections located in front of the target surface. Line intensities of successive ionization states of carbon were used for electron temperature calculations. Stark broadened profiles of singly ionized species have been utilized for electron density measurements. Electron density as well as electron temperature were studied as functions of laser irradiance and time elapsed after the incidence of laser pulse. The validity of the assumption of local thermodynamic equilibrium is discussed in light of the results obtained. {copyright} {ital 1997 American Institute of Physics.}

  17. Path integrals for electronic densities, reactivity indices, and localization functions in quantum systems.

    Science.gov (United States)

    Putz, Mihai V

    2009-11-10

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr's quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions - all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems.

  18. First-principle calculation of electrons charge density in the diamond ...

    African Journals Online (AJOL)

    . It has been found that in each crystal, the total electrons charge density along the [100] and [010] directions are equal, however, the charge densities at a given distance from the center of the cell along [001] and [100] directions are not exactly

  19. Path Integrals for Electronic Densities, Reactivity Indices, and Localization Functions in Quantum Systems

    Directory of Open Access Journals (Sweden)

    Mihai V. Putz

    2009-11-01

    Full Text Available The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr’s quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions – all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving many-electronic systems.

  20. High energy density plasma science with an ultrarelativistic electron beam

    Science.gov (United States)

    Joshi, C.; Blue, B.; Clayton, C. E.; Dodd, E.; Huang, C.; Marsh, K. A.; Mori, W. B.; Wang, S.; Hogan, M. J.; O'Connell, C.; Siemann, R.; Watz, D.; Muggli, P.; Katsouleas, T.; Lee, S.

    2002-05-01

    An intense, high-energy electron or positron beam can have focused intensities rivaling those of today's most powerful laser beams. For example, the 5 ps (full-width, half-maximum), 50 GeV beam at the Stanford Linear Accelerator Center (SLAC) at 1 kA and focused to a 3 micron rms spot size gives intensities of >1020 W/cm-2 at a repetition rate of >10 Hz. Unlike a ps or fs laser pulse which interacts with the surface of a solid target, the particle beam can readily tunnel through tens of cm of steel. However, the same particle beam can be manipulated quite effectively by a plasma that is a million times less dense than air! This is because of the incredibly strong collective fields induced in the plasma by the Coulomb force of the beam. The collective fields in turn react back onto the beam leading to many clearly observable phenomena. The beam paraticles can be: (1) Deflected leading to focusing, defocusing, or even steering of the beam; (2) undulated causing the emission of spontaneous betatron x-ray radiation and; (3) accelerated or decelerated by the plasma fields. Using the 28.5 GeV electron beam from the SLAC linac a series of experiments have been carried out that demonstrate clearly many of the above mentioned effects. The results can be compared with theoretical predictions and with two-dimensional and three-dimensional, one-to-one, particle-in-cell code simulations. These phenomena may have practical applications in future technologies including optical elements in particle beam lines, synchrotron light sources, and ultrahigh gradient accelerators.

  1. On the exact formulation of multi-configuration density-functional theory: electron density versus orbitals occupation

    CERN Document Server

    Fromager, Emmanuel

    2014-01-01

    The exact formulation of multi-configuration density-functional theory (DFT) is discussed in this work. As an alternative to range-separated methods, where electron correlation effects are split in the coordinate space, the combination of Configuration Interaction methods with orbital occupation functionals is explored at the formal level through the separation of correlation effects in the orbital space. When applied to model Hamiltonians, this approach leads to an exact Site-Occupation Embedding Theory (SOET). An adiabatic connection expression is derived for the complementary bath functional and a comparison with Density Matrix Embedding Theory (DMET) is made. Illustrative results are given for the simple two-site Hubbard model. SOET is then applied to a quantum chemical Hamiltonian, thus leading to an exact Complete Active Space Site-Occupation Functional Theory (CASSOFT) where active electrons are correlated explicitly within the CAS and the remaining contributions to the correlation energy are described...

  2. Electronic Reading and Digital Library Technologies: Understanding Learner Expectation and Usage Intent for Mobile Learning

    Science.gov (United States)

    Hyman, Jack A.; Moser, Mary T.; Segala, Laura N.

    2014-01-01

    Mobile information technology is changing the education landscape by offering learners the opportunity to engage in asynchronous, ubiquitous instruction. While there is a proliferation of mobile content management systems being developed for the mobile Web and stand-alone mobile applications, few studies have addressed learner expectations and…

  3. Assessment studies on the inversion of satellite to satellite electron content to obtain electron density profiles in the ionosphere

    CERN Document Server

    Hochegger, G P

    2000-01-01

    The electron content data, obtained by satellite-to-satellite occultations of radio signals can lead to height profiles of electron density by discrete inversion. Since there is no possibility to verify such profiles by means of other measurements (practically never measurements at the same time and same location) it was necessary to simulate occultation scenarios by means of an ionosphere model to obtain a large number of comparisons sufficient for investigations on a statistical basis. The obtained electron contents were inverted and compared with electron density height profiles, obtained with the same ionospheric model for the occultation point. The differences between these profiles were investigated (difference between the F2-peak maxima, the height of the maxima, the shape of the topside and bottom side ionosphere). Since simulations were done for chosen locations (250 randomly spread on the globe) for every month and every second hour and for two solar activity levels (HSA and LSA), a whole year was '...

  4. Strain-confined electron-hole liquid in Ge: Density variations and compressibility

    Energy Technology Data Exchange (ETDEWEB)

    Kelso, S.M.

    1982-07-15

    We present a detailed theoretical and experimental investigation of a spatial variation in the electron-hole--pair density in the strain-confined electron-hole liquid in Ge. The density variation can be dramatic: We observed a compression of the central density by a factor of 3 for our largest drop radius, Rroughly-equal0.7 mm. Our experimental density profiles, obtained using Abel transforms of spatial luminescence profiles, are in good agreement with the theoretical predictions of approximately parabolic profiles with densities larger than the equilibrium value at the center of the drop. Our previous first-order theory has been extended to include the full density dependence of the pair free energy at finite stress and temperature. We discuss the shape and power dependence of spatial luminescence profiles and luminescence spectra, since the spatial density variation increases with drop size. We use the central densities for drop sizes ranging over an order of magnitude to measure the density dependence of the electron-hole--liquid chemical potential, providing a sensitive test of many-body theories for the correlation energy. We obtain an improved value for the isothermal compressibility of the strain-confined liquid: K/sub T/ = 0.067 +- 0.017 cm/sup 2//dyn for n = 0.47 x 10/sup 17/ cm/sup -3/, T = 1.9 K, and -sigma = 5.5 kgf/mm/sup 2/, where kgf represents kilogram force.

  5. X-ray emission from relativistically moving electron density cusps

    Energy Technology Data Exchange (ETDEWEB)

    Kando, M.; Pirozhkov, A. S.; Nakamura, T.; Hayashi, Y.; Kotaki, H.; Kawase, K.; Esirkepov, T. Zh.; Fukuda, Y.; Kiriyama, H.; Okada, H.; Daito, I.; Kameshima, T.; Mori, M.; Koga, J. K.; Daido, H.; Faenov, A. Ya.; Pikuz, T.; Ma, J.; Chen, L.-M.; Ragozin, E. N. [Japan Atomic Energy Agency (Japan); Osaka University (Japan); Joint Institute for High Temperature of the Russian Academy of Science, Moscow (Russian Federation); Institute of Physics, Chinese Academy of Sciences, Beijing (China); P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky prospekt 53, 119991 Moscow (Russian Federation); Japan Atomic Energy Agency and Graduate School for the Creation of New Photonics Industries (Japan); Ludwig-Maximilians-University (Germany); and others

    2012-07-11

    We report on novel methods to generate ultra-short, coherent, X-rays using a laserplasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example, wake waves excited in an underdense plasma by an intense, short-pulse laser become dense and propagate along with the laser pulse. This is called a relativistic flying mirror. The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation, with a frequency multiplication factor of {approx} 4{gamma}{sup 2} and pulse shortening with the same factor. After the proof-of-principle experiments, we observed that the photon number generated in the flying mirror is close to the theoretical estimate. We present the details of the experiment in which a 9 TW laser pulse focused into a He gas jet generated the Flying Mirror, which partly reflected a 1 TW pulse, giving up to {approx} 10{sup 10} photons, 60 nJ (1.4 Multiplication-Sign 10{sup 12} photons/sr) in the XUV spectral region (12.8-22 nm).

  6. Ion and electron sheath characteristics in a low density and low temperature plasma

    Science.gov (United States)

    Borgohain, Binita; Bailung, H.

    2017-11-01

    Ion and electron sheath characteristics in a low electron temperature (Te ˜ 0.25-0.40 eV) and density (ne ˜ 106-107 cm-3) plasma are described. The plasma is produced in the experimental volume through diffusion from a hot cathode discharge plasma source by using a magnetic filter. The electron energy distribution function in the experimental plasma volume is measured to be a narrow Maxwellian distribution indicating the absence of primary and energetic electrons which are decoupled in the source side by the cusp magnetic field near the filter. An emissive probe is used to measure the sheath potential profiles in front of a metal plate biased negative and positive with respect to the plasma potential. For a positive plate bias, the electron density decreases considerably and the electron sheath expands with a longer presheath region compared to the ion sheath. The sheath potential structures are found to follow the Debye sheath model.

  7. A unifying probabilistic Bayesian approach to derive electron density from MRI for radiation therapy treatment planning.

    Science.gov (United States)

    Gudur, Madhu Sudhan Reddy; Hara, Wendy; Le, Quynh-Thu; Wang, Lei; Xing, Lei; Li, Ruijiang

    2014-11-07

    MRI significantly improves the accuracy and reliability of target delineation in radiation therapy for certain tumors due to its superior soft tissue contrast compared to CT. A treatment planning process with MRI as the sole imaging modality will eliminate systematic CT/MRI co-registration errors, reduce cost and radiation exposure, and simplify clinical workflow. However, MRI lacks the key electron density information necessary for accurate dose calculation and generating reference images for patient setup. The purpose of this work is to develop a unifying method to derive electron density from standard T1-weighted MRI. We propose to combine both intensity and geometry information into a unifying probabilistic Bayesian framework for electron density mapping. For each voxel, we compute two conditional probability density functions (PDFs) of electron density given its: (1) T1-weighted MRI intensity, and (2) geometry in a reference anatomy, obtained by deformable image registration between the MRI of the atlas and test patient. The two conditional PDFs containing intensity and geometry information are combined into a unifying posterior PDF, whose mean value corresponds to the optimal electron density value under the mean-square error criterion. We evaluated the algorithm's accuracy of electron density mapping and its ability to detect bone in the head for eight patients, using an additional patient as the atlas or template. Mean absolute HU error between the estimated and true CT, as well as receiver operating characteristics for bone detection (HU > 200) were calculated. The performance was compared with a global intensity approach based on T1 and no density correction (set whole head to water). The proposed technique significantly reduced the errors in electron density estimation, with a mean absolute HU error of 126, compared with 139 for deformable registration (p = 2  ×  10(-4)), 283 for the intensity approach (p = 2  ×  10(-6)) and 282 without density

  8. Exploring the Interaction Natures in Plutonyl (VI) Complexes with Topological Analyses of Electron Density

    OpenAIRE

    Jiguang Du; Xiyuan Sun; Gang Jiang

    2016-01-01

    The interaction natures between Pu and different ligands in several plutonyl (VI) complexes are investigated by performing topological analyses of electron density. The geometrical structures in both gaseous and aqueous phases are obtained with B3LYP functional, and are generally in agreement with available theoretical and experimental results when combined with all-electron segmented all-electron relativistic contracted (SARC) basis set. The Pu– O y l bond orders show significant line...

  9. Hot-electron-assisted femtochemistry at surfaces: A time-dependent density functional theory approach

    DEFF Research Database (Denmark)

    Gavnholt, Jeppe; Rubio, Angel; Olsen, Thomas

    2009-01-01

    Using time-evolution time-dependent density functional theory (TDDFT) within the adiabatic local-density approximation, we study the interactions between single electrons and molecular resonances at surfaces. Our system is a nitrogen molecule adsorbed on a ruthenium surface. The surface is modeled...... at two levels of approximation, first as a simple external potential and later as a 20-atom cluster. We perform a number of calculations on an electron hitting the adsorbed molecule from inside the surface and establish a picture, where the resonance is being probed by the hot electron. This enables us...

  10. A theoretical-electron-density databank using a model of real and virtual spherical atoms.

    Science.gov (United States)

    Nassour, Ayoub; Domagala, Slawomir; Guillot, Benoit; Leduc, Theo; Lecomte, Claude; Jelsch, Christian

    2017-08-01

    A database describing the electron density of common chemical groups using combinations of real and virtual spherical atoms is proposed, as an alternative to the multipolar atom modelling of the molecular charge density. Theoretical structure factors were computed from periodic density functional theory calculations on 38 crystal structures of small molecules and the charge density was subsequently refined using a density model based on real spherical atoms and additional dummy charges on the covalent bonds and on electron lone-pair sites. The electron-density parameters of real and dummy atoms present in a similar chemical environment were averaged on all the molecules studied to build a database of transferable spherical atoms. Compared with the now-popular databases of transferable multipolar parameters, the spherical charge modelling needs fewer parameters to describe the molecular electron density and can be more easily incorporated in molecular modelling software for the computation of electrostatic properties. The construction method of the database is described. In order to analyse to what extent this modelling method can be used to derive meaningful molecular properties, it has been applied to the urea molecule and to biotin/streptavidin, a protein/ligand complex.

  11. Organizational Leader Sensemaking in Healthcare Process Changes: The Development of the Electronic Medical Records Expectation Questionnaire

    Science.gov (United States)

    Riesenmy, Kelly Rouse

    2011-01-01

    Physicians play a unique role in the adoption of electronic medical records (EMR) within the healthcare organization. As leaders, they are responsible for setting the standards for this new technology within their sphere of influence while concurrently being required to learn and integrate EMR into their own workflow and process as the recipients…

  12. Exploring electron pair behaviour in chemical bonds using the extracule density.

    Science.gov (United States)

    Proud, Adam J; Mackenzie, Dalton E C K; Pearson, Jason K

    2015-08-21

    We explore explicit electron pair behaviour within the chemical bond (and lone pairs) by calculating the probability distribution for the center-of-mass (extracule) of an electron pair described by single localized orbitals. Using Edmiston-Ruedenberg localized orbitals in a series of 61 chemical systems, we demonstrate the utility of the extracule density as an interpretive tool in chemistry. By accessing localized regions of chemical space we simplify the interpretation of the extracule density and afford a quantum mechanical interpretation of "chemically intuitive" features of electronic structure. Specifically, we describe the localized effects on chemical bonds due to changes in electronegativities of bonded neighbours, bond strain, and non-covalent interactions. We show that the extracule density offers unique insight into electronic structure and allows one to readily quantify the effects of changing the chemical environment.

  13. Diurnal and seasonal Variability of D-Region Electron Densities at 69°N

    Science.gov (United States)

    Singer, Werner; Rapp, Markus; Latteck, Ralph; Friedrich, Martin

    Electron densities of the lower ionosphere are estimated with the Saura MF Doppler radar since summer 2004. The radar is located near country-regioncountry-regionAndenes, countryregionNorway (69.3° N, 16.0° E) and operates at 3.17 MHz with a peak power of 116 kW. The narrow beam transmitting/receiving antenna consists of 29 crossed half-wave dipoles arranged as a Mills Cross resulting in a beam width of about 7° . Antenna and transceiver system provide high flexibility in beam forming as well as the capability forming beams with left and right circular polarization at alternate pulses. The experiment utilizes partial reflections of ordinary and extraordinary component waves from scatterers in the altitude range 50-90 km to estimate electron number densities from differential absorption (DAE) and differential phase (DPE) measurements. Height profiles are obtained between about 55 km and 90 km with a time resolution of 9 minutes and a height resolution of 1 km. The electron density profiles independently derived from DAE and DPE measurements are in remarkable good agreement. Electron number densities are given if the results of the DAE and DPE experiments are in agreement within a factor of two. We discuss the diurnal and seasonal variability of electron densities obtained at Andenes and the response of D-region electron densities to solar activity storms and geomagnetic disturbances. The radar results are compared with previous rocket-borne radio wave propagation measurements at Andenes as well as with recent co-located simultaneous insitu observations using radio wave propagation experiments (differential absorption and Faraday rotation) which showed good agreement between the two techniques. In addition, monthly mean electron densities obtained with the MF radar are compared the recent dedicated auroral-zone, empirical model IMAZ.

  14. Effect of morphology and defect density on electron transfer of electrochemically reduced graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yan, E-mail: yanzhang@sues.edu.cn [School of Material Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Hao, Huilian, E-mail: huilian.hao@sues.edu.cn [School of Material Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Wang, Linlin, E-mail: wlinlin@mail.ustc.edu.cn [College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China)

    2016-12-30

    Highlights: • Different morphologies of ERGO on the surface of GCE were prepared via different methods. • The defect densities of ERGO were controlled by tuning the mass or concentration of GO. • A higher defect density of ERGO accelerates electron transfer rate. • ERGO with more exposed edge planes shows significantly higher electron transfer kinetics. • Both edge planes and defect density contribute to electron transfer of ERGO. - Abstract: Electrochemically reduced graphene oxide (ERGO) is widely used to construct electrochemical sensors. Understanding the electron transfer behavior of ERGO is essential for its electrode material applications. In this paper, different morphologies of ERGO were prepared via two different methods. Compared to ERGO/GCEs prepared by electrochemical reduction of pre-deposited GO, more exposed edge planes of ERGO are observed on the surface of ERGO-GCE that was constructed by electrophoretic deposition of GO. The defect densities of ERGO were controlled by tuning the mass or concentration of GO. The electron transfer kinetics (k{sup 0}) of GCE with different ERGOs was comparatively investigated. Owing to increased surface areas and decreased defect density, the k{sup 0} values of ERGO/GCE initially increase and then decrease with incrementing of GO mass. When the morphology and surface real areas of ERGO-GCE are the same, an increased defect density induces an accelerated electron transfer rate. k{sup 0} valuesof ERGO-GCEs are about 1 order of magnitude higher than those of ERGO/GCEs due to the difference in the amount of edge planes. This work demonstrates that both defect densities and edge planes of ERGO play crucial roles in electron transfer kinetics.

  15. NATO Advanced Study Institute on Electron and Magnetization Densities in Molecules and Crystals

    CERN Document Server

    1980-01-01

    The interest of describing the ground state properties of a system in terms of one electron density (or its two spin components) is obvious, in particular due to the simple physical significance of this function. Recent experimental progress in diffraction made the measurement of charge and magnetization densities in crystalline solids possible, with an accuracy at least as good as theoretical accuracy. Theoretical developments of the many-body problem have proved the extreme importance of the one electron density function and presently, accurate methods of band structure determination become available. Parallel to the diffraction techniques, other domains of research (inelastic scattering, resonance, molecular spectroscopy) deal with quantities directly related to the one particle density. But the two types of studies do not interfere enough and one should obviously gain more information by interpreting all experiments that are related to the density together. It became necessary to have an International Sch...

  16. The density functional study of electronic structure, electronic charge density, linear and nonlinear optical properties of single crystal alpha-LiAlTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Khan, Wilayat, E-mail: walayat76@gmail.com [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic)

    2014-04-01

    Highlights: • FP-LAPW technique is used for calculating the electronic structure. • The band structure shows that the calculated compound is semiconductor. • The complex dielectric function has been calculated. • Nonlinear optical properties has also been calculated. • This compound can be used for molecular engineering of the crystals. - Abstract: Self-consistent calculations is performed using the full potential linear augmented plane wave (FP-LAPW) technique based on density functional theory (DFT) to investigate the electronic band structure, density of states, electronic charge density, linear and non-linear optical properties of α-LiAlTe{sub 2} compound having tetragonal symmetry with space group I4{sup ¯}2d. The electronic structure are calculated using the Ceperley Alder local density approach (CA-LDA), Perdew Burke and Ernzerhof generalize gradient approach (PBE-GGA), Engel–Vosko generalize gradient approach (EVGGA) and modified Becke Johnson approach (mBJ). Band structure calculations of (α-LiAlTe{sub 2}) depict semiconducting nature with direct band gap of 2.35 eV (LDA), 2.48 eV (GGA), 3.05 eV (EVGGA) and 3.13 eV (mBJ), which is comparable to experimental value. The calculated electronic charge density show ionic interaction between Te and Li atoms and polar covalent interaction between Al and Te atoms. Some optical susceptibilities like dielectric constants, refractive index, extension co-efficient, reflectivity and energy loss function have been calculated and analyzed on the basis of electronic structure. The compound α-LiAlTe{sub 2} provides a considerable negative value of birefringence of −0.01. Any anisotropy observed in the linear optical properties which are in favor to enhance the nonlinear optical properties. The symbol χ{sub abc}{sup (2)}(ω) represents the second order nonlinear optical susceptibilities, possess six non-zero components in this symmetry (tetragonal), called: 1 2 3, 2 1 3, 2 3 1, 1 3 2, 3 1 2 and 3 2 1

  17. Consistent Atomic Geometries and Electronic Structure of Five Phases of Potassium Niobate from Density-Functional Theory

    Directory of Open Access Journals (Sweden)

    Falko Schmidt

    2017-01-01

    Full Text Available We perform a comprehensive theoretical study of the structural and electronic properties of potassium niobate (KNbO3 in the cubic, tetragonal, orthorhombic, monoclinic, and rhombohedral phase, based on density-functional theory. The influence of different parametrizations of the exchange-correlation functional on the investigated properties is analyzed in detail, and the results are compared to available experimental data. We argue that the PBEsol and AM05 generalized gradient approximations as well as the RTPSS meta-generalized gradient approximation yield consistently accurate structural data for both the external and internal degrees of freedom and are overall superior to the local-density approximation or other conventional generalized gradient approximations for the structural characterization of KNbO3. Band-structure calculations using a HSE-type hybrid functional further indicate significant near degeneracies of band-edge states in all phases which are expected to be relevant for the optical response of the material.

  18. Creating books for the National electronic Library for Health: expected barriers and useful lessons.

    Science.gov (United States)

    O'Brien, C

    2000-12-01

    The National electronic Library for Health (NeLH) is now taking shape, as the virtual branch libraries begin to accumulate 'books', among their resources. In the Primary Care branch (http://www.nelh-pc.nhs.uk), one of the first available books was the Statement of Fees and Allowances (otherwise known as the Red Book). While being held up as an example of what the NeLH can offer, this book and the story of its transformation from paper to Internet format is a powerful example of how much further the National Health Service (NHS) must go before it can claim to be fully exploiting the benefits of information technology (IT). This article refers to the author's experience in producing electronic books for primary care using WaX software, and an example of a process change from paper to screen that was managed within a university administrative office. The author suggests that to reap optimal benefits from IT, the NeLH and its collaborators must address the fundamental issues of people and the paper-based processes used by information providers. The NeLH must work with both NHS IT trainers and information providers in a three-way collaboration involving key people and processes, to achieve the efficient production of an updateable and user-friendly library of electronic books.

  19. Development and application of a 2-electron reduced density matrix approach to electron transport via molecular junctions

    Science.gov (United States)

    Hoy, Erik P.; Mazziotti, David A.; Seideman, Tamar

    2017-11-01

    Can an electronic device be constructed using only a single molecule? Since this question was first asked by Aviram and Ratner in the 1970s [Chem. Phys. Lett. 29, 277 (1974)], the field of molecular electronics has exploded with significant experimental advancements in the understanding of the charge transport properties of single molecule devices. Efforts to explain the results of these experiments and identify promising new candidate molecules for molecular devices have led to the development of numerous new theoretical methods including the current standard theoretical approach for studying single molecule charge transport, i.e., the non-equilibrium Green's function formalism (NEGF). By pairing this formalism with density functional theory (DFT), a wide variety of transport problems in molecular junctions have been successfully treated. For some systems though, the conductance and current-voltage curves predicted by common DFT functionals can be several orders of magnitude above experimental results. In addition, since density functional theory relies on approximations to the exact exchange-correlation functional, the predicted transport properties can show significant variation depending on the functional chosen. As a first step to addressing this issue, the authors have replaced density functional theory in the NEGF formalism with a 2-electron reduced density matrix (2-RDM) method, creating a new approach known as the NEGF-RDM method. 2-RDM methods provide a more accurate description of electron correlation compared to density functional theory, and they have lower computational scaling compared to wavefunction based methods of similar accuracy. Additionally, 2-RDM methods are capable of capturing static electron correlation which is untreatable by existing NEGF-DFT methods. When studying dithiol alkane chains and dithiol benzene in model junctions, the authors found that the NEGF-RDM predicts conductances and currents that are 1-2 orders of magnitude below

  20. Measurements of electron cloud density in the CERN Super Proton Synchrotron with the microwave transmission method

    CERN Document Server

    Federmann, S; Mahner, E

    2011-01-01

    The electron cloud effect can pose severe performance limitations in high-energy particle accelerators as the CERN Super Proton Synchrotron (SPS). Mitigation techniques such as vacuum chamber thin film coatings with low secondary electron yields (SEY < 1.3) aim to reduce or even suppress this effect. The microwave transmission method, developed and first applied in 2003 at the SPS, measures the integrated electron cloud density over a long section of an accelerator. This paper summarizes the theory and measurement principle and describes the new SPS microwave transmission setup used to study the electron cloud mitigation of amorphous carbon coated SPS dipole vacuum chambers. Comparative results of carbon coated and bare stainless steel dipole vacuum chambers are given for the beam with nominal LHC 25 ns bunch-to-bunch spacing in the SPS and the electron cloud density is derived.

  1. Two-resonance probe for measuring electron density in low-pressure plasmas

    Science.gov (United States)

    Kim, D. W.; You, S. J.; Kim, S. J.; Kim, J. H.; Oh, W. Y.

    2017-04-01

    A technique for measuring double-checked electron density using two types of microwave resonance is presented. Simultaneous measurement of the resonances (plasma and quarter-wavelength resonator resonances), which were used for the cutoff probe (CP) and hairpin probe (HP), was achieved by the proposed microwave resonance probe. The developed two-resonance probe (TRP) consists of parallel separated coaxial cables exposing the radiation and detection tips. The structure resembles that of the CP, except the gapped coaxial cables operate not only as a microwave feeder for the CP but also as a U- shaped quarter-wavelength resonator for the HP. By virtue of this structure, the microwave resonances that have typically been used for measuring the electron density for the CP and HP were clearly identified on the microwave transmission spectrum of the TRP. The two types of resonances were measured experimentally under various power and pressure conditions for the plasma. A three-dimensional full-wave simulation model for the TRP is also presented and used to investigate and reproduce the resonances. The electron densities inferred from the resonances were compared and showed good agreement. Quantitative differences between the densities were attributed to the effects of the sheath width and spatial density gradient on the resonances. This accessible technique of using the TRP to obtain double-checked electron densities may be useful for comparative study and provides complementary uses for the CP and HP.

  2. A simple image based method for obtaining electron density and atomic number in dual energy CT

    Science.gov (United States)

    Szczykutowicz, Timothy P.; Qi, Zhihua; Chen, Guang-Hong

    2011-03-01

    The extraction of electron density and atomic number information in computed tomography is possible when image values can be sampled using two different effective energies. The foundation for this extraction lies in the ability to express the linear attenuation coefficient using two basis functions that are dependent on electron density and atomic number over the diagnostic energy range used in CT. Material basis functions separate images into clinically familiar quantities such as 'bone' images and 'soft tissue' images. Physically, all basis function choices represent the expression of the linear attenuation coefficient in terms of a photoelectric and a Compton scattering term. The purpose of this work is to develop a simple dual energy decomposition method that requires no a priori knowledge about the energy characteristics of the imaging system. It is shown that the weighted sum of two basis images yields an electron density image where the weights for each basis image are the electron density of that basis image's basis material. Using the electron density image, effective atomic number information can also be obtained. These methods are performed solely in the image domain and require no spectrum or detector energy response information as required by some other dual energy decomposition methods.

  3. A density-temperature description of the outer electron radiation belt during geomagnetic storms

    Energy Technology Data Exchange (ETDEWEB)

    Borovsky, Joseph E [Los Alamos National Laboratory; Cayton, Thomas E [Los Alamos National Laboratory; Denton, Michael H [LANCASTER UNIV

    2009-01-01

    Electron flux measurements from 7 satellites in geosynchronous orbit from 1990-2007 are fit with relativistic bi-Maxwellians, yielding a number density n and temperature T description of the outer electron radiation belt. For 54.5 spacecraft years of measurements the median value ofn is 3.7x10-4 cm-3 and the median value ofT is 142 keY. General statistical properties of n, T, and the 1.1-1.5 MeV flux J are investigated, including local-time and solar-cycle dependencies. Using superposed-epoch analysis triggered on storm onset, the evolution of the outer electron radiation belt through high-speed-steam-driven storms is investigated. The number density decay during the calm before the storm is seen, relativistic-electron dropouts and recoveries from dropout are investigated, and the heating of the outer electron radiation belt during storms is examined. Using four different triggers (SSCs, southward-IMF CME sheaths, southward-IMF magnetic clouds, and minimum Dst), CME-driven storms are analyzed with superposed-epoch techniques. For CME-driven storms an absence of a density decay prior to storm onset is found, the compression of the outer electron radiation belt at time of SSC is analyzed, the number-density increase and temperature decrease during storm main phase is seen, and the increase in density and temperature during storm recovery phase is observed. Differences are found between the density-temperature and the flux descriptions, with more information for analysis being available in the density-temperature description.

  4. Laser Thomson scattering measurements of electron temperature and density in a hall-effect plasma

    Science.gov (United States)

    Washeleski, Robert L.

    Hall-effect thrusters (HETs) are compact electric propulsion devices with high specific impulse used for a variety of space propulsion applications. HET technology is well developed but the electron properties in the discharge are not completely understood, mainly due to the difficulty involved in performing accurate measurements in the discharge. Measurements of electron temperature and density have been performed using electrostatic probes, but presence of the probes can significantly disrupt thruster operation, and thus alter the electron temperature and density. While fast-probe studies have expanded understanding of HET discharges, a non-invasive method of measuring the electron temperature and density in the plasma is highly desirable. An alternative to electrostatic probes is a non-perturbing laser diagnostic technique that measures Thomson scattering from the plasma. Thomson scattering is the process by which photons are elastically scattered from the free electrons in a plasma. Since the electrons have thermal energy their motion causes a Doppler shift in the scattered photons that is proportional to their velocity. Like electrostatic probes, laser Thomson scattering (LTS) can be used to determine the temperature and density of free electrons in the plasma. Since Thomson scattering measures the electron velocity distribution function directly no assumptions of the plasma conditions are required, allowing accurate measurements in anisotropic and non-Maxwellian plasmas. LTS requires a complicated measurement apparatus, but has the potential to provide accurate, non-perturbing measurements of electron temperature and density in HET discharges. In order to assess the feasibility of LTS diagnostics on HETs non-invasive measurements of electron temperature and density in the near-field plume of a Hall thruster were performed using a custom built laser Thomson scattering diagnostic. Laser measurements were processed using a maximum likelihood estimation method

  5. An adaptive Expectation-Maximization algorithm with GPU implementation for electron cryomicroscopy.

    Science.gov (United States)

    Tagare, Hemant D; Barthel, Andrew; Sigworth, Fred J

    2010-09-01

    Maximum-likelihood (ML) estimation has very desirable properties for reconstructing 3D volumes from noisy cryo-EM images of single macromolecular particles. Current implementations of ML estimation make use of the Expectation-Maximization (EM) algorithm or its variants. However, the EM algorithm is notoriously computation-intensive, as it involves integrals over all orientations and positions for each particle image. We present a strategy to speedup the EM algorithm using domain reduction. Domain reduction uses a coarse grid to evaluate regions in the integration domain that contribute most to the integral. The integral is evaluated with a fine grid in these regions. In the simulations reported in this paper, domain reduction gives speedups which exceed a factor of 10 in early iterations and which exceed a factor of 60 in terminal iterations. Copyright 2010 Elsevier Inc. All rights reserved.

  6. Analysis of Expectations of Electronic Grocery Shopping for Potential Customer Segments

    Directory of Open Access Journals (Sweden)

    Heikkila Jukka

    1998-11-01

    Full Text Available The special nature of groceries, especially perishables, challenges the possibilities of digital channels i.e. computers and networks to improve customer service. We report the findings of theme interviews on the potential of electronic commerce (EC of groceries with 33 experts of grocery industry and EC, most of them senior executives, in 23 organisations in Finland during the Autumn of 1997. The specific areas of interest in the study are the predicted volume of EC in grocery shopping, the most potential customer segments, the anticipated benefits of EC to customers, and supplier strategies and infrastructure alternatives. Benefits of ECS (electronic grocery shopping are analysed for three selected potential customer groups in terms of phases in consumer buying process as well as two different infrastructure solutions. It seems that an EGS build on top of current grocery industry infrastructure can only satisfy one major consumer group. In order to gain momentum EGS needs a dedicated infrastructure within which logistic efficiency can be increased.

  7. Electron density and temperature diagnostics in laser-induced hydrogen plasma

    Science.gov (United States)

    Gautam, G.; Parigger, C. G.

    2017-02-01

    Laser-induced optical breakdown is achieved by using Q-switched, Nd:YAG radiation focused into ultra-high-purity (UHP) hydrogen gas at a pressure of 1.08 ± 0.03 × 105 Pa inside a cell. The plasma emission spectra are dispersed by a Czerny-Turner type spectrometer and detected with an intensified charge-coupled device (ICCD). Stark-broadened hydrogen Balmer series H α and Hβ line profiles are used as a spectroscopic tool for the determination of electron density and excitation temperature. Spatial variation of electron density and temperature at 0.40 µs are extracted from the recorded intensities of H α and Hβ lines. Temporal variations of electron density and excitation temperature are also presented for the time delay range of 0.15 µs to 1.4 µs.

  8. Measuring the Density of a Molecular Cluster Injector via Visible Emission from an Electron Beam

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, D. P.; Kaita, R.; Majeski, R. M.; Stotler, D. P.

    2010-06-28

    A method to measure the density distribution of a dense hydrogen gas jet is pre- sented. A Mach 5.5 nozzle is cooled to 80K to form a flow capable of molecular cluster formation. A 250V, 10mA electron beam collides with the jet and produces Hα emission that is viewed by a fast camera. The high density of the jet, several 1016cm-3, results in substantial electron depletion, which attenuates the Hα emission. The attenuated emission measurement, combined with a simplified electron-molecule collision model, allows us to determine the molecular density profile via a simple iterative calculation.

  9. Applications of electron density studies in molecular and solid state science

    DEFF Research Database (Denmark)

    Overgaard, Jacob

    2015-01-01

    the research in the area is directed. The method of electron density determination itself, as we shall see later, is strongly dependent on the access to very accurate X-ray structure factors collected to a high scattering angle. Data that fulfill these criteria are now becoming increasingly available due......The present dissertation contains the distillate of my scientific output in the field of experimental and theoretical electron density studies roughly over the last decade and a little more, since earning my PhD-degree in 2001. There are several reasons that I have chosen to write my dissertation...... of electron density studies in connection with the UN declared International Year of Crystallography in 2014. In addition, a number of reviews on the method have very recently appeared showing that the time is ripe to look back on the achievements of the last 10 years and also to look ahead to see where...

  10. Electron density increases due to Lightning activity as deduced from LWPC code and VLF signal perturbations.

    Science.gov (United States)

    Samir, Nait Amor; Bouderba, Yasmina

    VLF signal perturbations in association with thunderstorm activity appear as changes in the signal amplitude and phase. Several papers reported on the characteristics of thus perturbations and their connection to the lightning strokes amplitude and polarity. In this contribution, we quantified the electrons density increases due to lightning activity by the use of the LWPC code and VLF signal perturbations parameters. The method is similar to what people did in studying the solar eruptions effect. the results showed that the reference height (h') decreased to lower altitudes (between 70 and 80 km). From the LWPC code results the maximum of the electron density was then deduced. Therefore, a numerical simulation of the atmospheric species times dependences was performed to study the recovery times of the electrons density at different heights. The results showed that the recovery time last for several minutes and explain the observation of long recovery Early signal perturbations.

  11. Applications of electron density studies in molecular and solid state science

    DEFF Research Database (Denmark)

    Overgaard, Jacob

    2015-01-01

    The present dissertation contains the distillate of my scientific output in the field of experimental and theoretical electron density studies roughly over the last decade and a little more, since earning my PhD-degree in 2001. There are several reasons that I have chosen to write my dissertation...... of electron density studies in connection with the UN declared International Year of Crystallography in 2014. In addition, a number of reviews on the method have very recently appeared showing that the time is ripe to look back on the achievements of the last 10 years and also to look ahead to see where...... the research in the area is directed. The method of electron density determination itself, as we shall see later, is strongly dependent on the access to very accurate X-ray structure factors collected to a high scattering angle. Data that fulfill these criteria are now becoming increasingly available due...

  12. Plasma density transition trapping as a possible high-brightness electron beam source

    Directory of Open Access Journals (Sweden)

    M. C. Thompson

    2004-01-01

    Full Text Available Plasma density transition trapping is a recently proposed self-injection scheme for plasma wakefield accelerators. This technique uses a sharp downward plasma density transition to trap and accelerate background plasma electrons in a plasma wakefield. This paper examines the quality of electron beams captured using this scheme in terms of emittance, energy spread, and brightness. Two-dimensional particle-in-cell simulations show that these parameters can be optimized by manipulating the plasma density profile. We also develop, and support with simulations, a set of scaling laws that predicts how the brightness of transition trapping beams scales with the plasma density of the system. These scaling laws indicate that transition trapping can produce beams with brightness ≥5×10^{14}   A/(mrad^{2}. A proof-of-principle transition trapping experiment is planned for the near future. The proposed experiment is described in detail.

  13. Electronic density of states of amorphous Si and Ge: Application of a molecular-liquid model

    Science.gov (United States)

    Halder, N. C.

    1980-01-01

    The electronic structures of a-Si and a-Ge have been investigated by introducing the molecular-liquid model (MLM). The theoretical structure factors have been expressed in terms of three simple parameters-nearest-neighbor distance, packing density, and coordination number. For the electronic density of states (EDS), nonlocal energy-dependent pseudopotentials have been considered to second order in perturbation theory. When compared with the experimental structure factors, the MLM structure factors agree well for the momentum transfer in the region of 0agreement with recent theoretical and experimental results.

  14. [The reconstruction of welding arc 3D electron density distribution based on Stark broadening].

    Science.gov (United States)

    Zhang, Wang; Hua, Xue-Ming; Pan, Cheng-Gang; Li, Fang; Wang, Min

    2012-10-01

    The three-dimensional electron density is very important for welding arc quality control. In the present paper, Side-on characteristic line profile was collected by a spectrometer, and the lateral experimental data were approximated by a polynomial fitting. By applying an Abel inversion technique, the authors obtained the radial intensity distribution at each wavelength and thus constructed a profile for the radial positions. The Fourier transform was used to separate the Lorentz linear from the spectrum reconstructed, thus got the accurate Stark width. And we calculated the electronic density three-dimensional distribution of the TIG welding are plasma.

  15. Applications of electron density studies in molecular and solid state science

    DEFF Research Database (Denmark)

    Overgaard, Jacob

    2015-01-01

    The present dissertation contains the distillate of my scientific output in the field of experimental and theoretical electron density studies roughly over the last decade and a little more, since earning my PhD-degree in 2001. There are several reasons that I have chosen to write my dissertation...... to the technical developments driven not least by the efforts from large commercial manufacturers such as Bruker AXS and Agilent Technologies. It is also not unwarranted to claim that the electron density community is a driving force in this technological improvement as it is essential to push these instruments...

  16. A phase contrast imaging–interferometer system for detection of multiscale electron density fluctuations on DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Davis, E. M.; Rost, J. C.; Porkolab, M.; Marinoni, A. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Van Zeeland, M. A. [General Atomics, San Diego, California 92121 (United States)

    2016-11-15

    Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI–interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz electron-scale instabilities. Further, correlating our interferometer’s measurements with those from DIII-D’s pre-existing, toroidally separated interferometer allows core-localized, low-n MHD studies that may otherwise be inaccessible via external magnetic measurements. The combined diagnostic’s small port requirements and minimal access restrictions make it well-suited to the harsh neutron environments and limited port space expected in next-step devices.

  17. Structural, electronic, mechanical and quantum transport of ultrathin gold nanowire: A density functional approach

    Science.gov (United States)

    Jariwala, P. H.; Gupta, Sanjeev K.; Sonvane, Y. A.; Thakor, P. B.

    2017-06-01

    We have scrutinized the gold (Au) nanowires with distinct cross-section with 1-10 Au atoms for each unit cell by density-functional approach and performed first-principles computation. Here, we have investigated structural, electronic, transport and mechanical characteristic of Au nanowires. The structural characteristic of cubic bulk and nanowires of Au are very diverse from each other. The electronic density of state (DOS) and band structures of different formations express that all the nanowires are very good conductor in nature. The figure of conduction channels leans on number of atoms for each unit cell, diameter and structure of nanowires. We also inspect that the electronic thermal conductivities dependency on the temperature and we found that all the considered AuNWs have low conductivity than that of the bulk Au. Our results show that AuNWs have potential application in electronic devices like nanoelectro-mechanical systems (NEMS).

  18. Dynamics of the spatial electron density distribution of EUV-induced plasmas

    Science.gov (United States)

    van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Banine, V. Y.

    2015-11-01

    We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure.

  19. Determination of the vertical electron-density profile in ionospheric tomography: experimental results

    Directory of Open Access Journals (Sweden)

    C. N. Mitchell

    Full Text Available The reconstruction of the vertical electron-density profile is a fundamental problem in ionospheric tomography. Lack of near-horizontal ray paths limits the information available on the vertical profile, so that the resultant image of electron density is biased in a horizontal sense. The vertical profile is of great importance as it affects the authenticity of the entire tomographic image. A new method is described whereby the vertical profile is selected using relative total-electron-content measurements. The new reconstruction process has been developed from modelling studies. A range of background ionospheres, representing many possible peak heights, scale heights and electron densities are formed from a Chapman profile on the bottomside with a range of topside profiles. The iterative reconstruction process is performed on all of these background ionospheres and a numerical selection criterion employed to select the final image. The resulting tomographic images show excellent agreement in electron density when compared with independent verification provided by the EISCAT radar.

  20. Advanced High Energy Density Secondary Batteries with Multi‐Electron Reaction Materials

    Science.gov (United States)

    Luo, Rui; Huang, Yongxin; Li, Li

    2016-01-01

    Secondary batteries have become important for smart grid and electric vehicle applications, and massive effort has been dedicated to optimizing the current generation and improving their energy density. Multi‐electron chemistry has paved a new path for the breaking of the barriers that exist in traditional battery research and applications, and provided new ideas for developing new battery systems that meet energy density requirements. An in‐depth understanding of multi‐electron chemistries in terms of the charge transfer mechanisms occuring during their electrochemical processes is necessary and urgent for the modification of secondary battery materials and development of secondary battery systems. In this Review, multi‐electron chemistry for high energy density electrode materials and the corresponding secondary battery systems are discussed. Specifically, four battery systems based on multi‐electron reactions are classified in this review: lithium‐ and sodium‐ion batteries based on monovalent cations; rechargeable batteries based on the insertion of polyvalent cations beyond those of alkali metals; metal–air batteries, and Li–S batteries. It is noted that challenges still exist in the development of multi‐electron chemistries that must be overcome to meet the energy density requirements of different battery systems, and much effort has more effort to be devoted to this. PMID:27840796

  1. Advanced High Energy Density Secondary Batteries with Multi-Electron Reaction Materials.

    Science.gov (United States)

    Chen, Renjie; Luo, Rui; Huang, Yongxin; Wu, Feng; Li, Li

    2016-10-01

    Secondary batteries have become important for smart grid and electric vehicle applications, and massive effort has been dedicated to optimizing the current generation and improving their energy density. Multi-electron chemistry has paved a new path for the breaking of the barriers that exist in traditional battery research and applications, and provided new ideas for developing new battery systems that meet energy density requirements. An in-depth understanding of multi-electron chemistries in terms of the charge transfer mechanisms occuring during their electrochemical processes is necessary and urgent for the modification of secondary battery materials and development of secondary battery systems. In this Review, multi-electron chemistry for high energy density electrode materials and the corresponding secondary battery systems are discussed. Specifically, four battery systems based on multi-electron reactions are classified in this review: lithium- and sodium-ion batteries based on monovalent cations; rechargeable batteries based on the insertion of polyvalent cations beyond those of alkali metals; metal-air batteries, and Li-S batteries. It is noted that challenges still exist in the development of multi-electron chemistries that must be overcome to meet the energy density requirements of different battery systems, and much effort has more effort to be devoted to this.

  2. Electronic Properties of Antiperovskite Materials from State-of-the-Art Density Functional Theory

    OpenAIRE

    Bilal, M.; Jalali-Asadabadi, S.; Ahmad, Rashid; Ahmad, Iftikhar

    2015-01-01

    We present a review on the research developments on the theoretical electronic properties of the antiperovskite materials. The antiperovskite materials have perovskite type structure with the positions of cations and anions interchanged. The electronic structures are used to explain different physical properties of materials; therefore it is crucial to understand band structures and densities of states of materials for their effective use in technology. The theoretical results of ...

  3. Development and application of diagnostic instrumentation for measurement of electron density and conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Bauman, L.E.

    1990-05-01

    The purpose of this contract was to assemble and demonstrate in the laboratory a Faraday rotation system for measurement of electron density and conductivity, with the intent to produce a system suitable for diagnostic support of the development of pulsed, space-based magnetohydrodynamic (MHD) power systems. Two system configurations were tested: (1) a rotating polarizer and (2) a beam splitting polarizer. Due to the short path length plasma produced in the laboratory flame, the long wavelength 496 {mu}m methyl fluoride laser line was used and only the more sensitive rotating polarizer configuration was used for the demonstration experiments. Electron number densities from 2 {times} 10{sup 19} to 9 {times} 10{sup 19} were measured with good agreement to statistical equilibrium (Saha) calculations using emission absorption-measured flame temperatures and neutral seed atom number seed atom nuclear densities. The electron collision frequencies were measured by transmission measurements. Combining these two measurements gave measured electron conductivities of between 4 and 12 mohs/m. These results compared reasonably well with those found with an electron collision frequency model combined with chemical equilibrium calculations and the emission absorption measurements. Ellipticity measurements of electron collision frequency were not possible due to the short path length of the laboratory plasma. 46 refs., 25 figs., 9 tabs.

  4. Probing the electron density in HiPIMS plasmas by target inserts

    Science.gov (United States)

    Hecimovic, Ante; Held, Julian; Schulz-von der Gathen, Volker; Breilmann, Wolfgang; Maszl, Christian; von Keudell, Achim

    2017-12-01

    High power impulse magnetron sputtering (HiPIMS) is a versatile technology to deposit thin films with superior properties. During HiPIMS, the power is applied in short pulses of the order of 100 μs at power densities of kW cm-2 to a magnetron target creating a torus shaped dynamic high density plasma. This plasma torus is not homogeneous, but individual ionization zones become visible, which rotate along the torus with velocities of 10 km s-1 . Up to now, however, any direct measurement of the electron density inside these rotating ionization zones is missing. Here, we probe the electron density by measuring the target current locally by using small inserts embedded in an aluminium target facing the plasma torus. By applying simple sheath theory, a plasma density of the order of 1019 m-3 at the sheath edge can be inferred. The plasma density increases with increasing target current. In addition, the dynamics of the local target current variation is consistent with the dynamics of the traveling ionization zone causing a modulation of the local current density by 25%.

  5. The effects of nicotine stimulus and response expectancies on male and female smokers' responses to nicotine-free electronic cigarettes.

    Science.gov (United States)

    Copp, Sebastian R; Collins, Jamie L; Dar, Reuven; Barrett, Sean P

    2015-01-01

    Electronic cigarettes (e-cigarettes) have been reported to reduce tobacco craving and withdrawal; however, the mechanisms underlying these effects have not been elucidated. This study examined the contributions of nicotine stimulus and response expectancies to responses to nicotine-free e-cigarettes in 21 e-cigarette naïve smokers (12 male). Participants completed two randomized experimental sessions in which they administered a nicotine-free e-cigarette. During one session they were informed that the e-cigarette contained nicotine and during the other session they were informed that the e-cigarette was nicotine-free. Participants completed subjective assessments before and immediately after sampling ten puffs from the e-cigarette and were then invited to earn additional puffs using a computerized progressive ratio task. Prior to their enrolment in the study, participants provided an estimate of the relative importance of the nicotine content of e-cigarettes for craving relief. Instructions that the e-cigarette contained nicotine were found to reduce both intention to smoke (p=0.017) and withdrawal-related (p=0.018) craving, regardless of a-priori reported beliefs regarding the relative importance of nicotine. Nicotine content instructions were also found to be associated with a shorter latency to self-administration (p=0.005); however, a Sex×Instructions×Response Expectancy interaction (p=0.008) revealed that this effect was specific to women who had strong a-priori nicotine content craving relief expectations. Neither nicotine content instructions nor response expectancies impacted the number of puffs self-administered. Findings suggest that nicotine content expectations contribute to smokers' responses to e-cigarettes, and that a-priori beliefs about nicotine effects may be especially important in women. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Relationships between electron density, height and sub-peak ionospheric thickness in the night equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    K. J. W. Lynn

    2006-07-01

    Full Text Available The development and decay of the southern equatorial anomaly night-time peak in electron density as seen at a number of ionosonde reflection points extending from New Guinea and Indonesia into northern Australia was examined in terms of the characteristic rise and fall in height associated with the sunset ionisation-drift vortex at the magnetic equator. The observations relate to measurements made in November 1997. Following sunset, the ionospheric profile was observed to narrow as the maximum electron density increased during a fall in height that took the peak of the layer at Vanimo and Sumedang down to some 240 km. The fall was followed by a strong rise in which the electron density sub-peak profile expanded from a slab width (as given by POLAN of 20 km to over 100km with no corresponding change in peak electron density. The post-sunset equatorial fall in height and associated changes in profile density and thickness continued to be seen with diminishing amplitude and increasing local time delay in moving from the anomaly peak at Vanimo to the southernmost site of observation at Townsville. Secondary events on a lesser scale sometimes occurred later in the night and may provide evidence of the multiple vortices suggested by Kudeki and Bhattacharyya (1999. Doppler measurements of vertical velocity as seen at Sumedang in Java are compared with the observed changes in electron density profile in the post-sunset period. The normal post-sunset variation in ionospheric parameters was disrupted on the night of 7 November, the night before a negative ionospheric storm was observed.

  7. Mechanisms of the electron density depletion in the SAR arc region

    Directory of Open Access Journals (Sweden)

    A. V. Pavlov

    1996-02-01

    Full Text Available This study compares the measurements of electron density and temperature and the integral airglow intensity at 630 nm in the SAR arc region and slightly south of this (obtained by the Isis 2 spacecraft during the 18 December 1971 magnetic storm, with the model results obtained using the time dependent one-dimensional mathematical model of the Earth\\'s ionosphere and plasmasphere. The explicit expression in the third Enskog approximation for the electron thermal conductivity coefficient in the multicomponent mixture of ionized gases and a simplified calculation method for this coefficient presents an opportunity to calculate more exactly the electron temperature and density and 630 nm emission within SAR arc region are used in the model. Collisions between N2 and hot thermal electrons in the SAR arc region produce vibrationally excited nitrogen molecules. It appears that the loss rate of O+(4S due to reactions with the vibrationally excited nitrogen is enough to explain electron density depression by a factor of two at F-region heights and the topside ionosphere density variations within the SAR arc if the erosion of plasma within geomagnetic field tubes, during the main phase of the geomagnetic storm and subsequent filling of geomagnetic tubes during the recovery phase, are considered. To explain the disagreement by a factor 1.5 between the observed and modeled SAR arc electron densities an additional plasma drift velocity ~–30 m s–1 in the ion continuity equations is needed during the recovery phase. This additional plasma drift velocity is likely caused by the transition from convecting to corotating flux tubes on the equatorward wall of the trough. The electron densities and temperatures and 630 nm integral intensity at the SAR arc and slightly south of this region as measured for the 18 December 1971 magnetic storm were correctly described by the model without perpendicular electric fields. Within this model framework the effect of the

  8. Mechanisms of the electron density depletion in the SAR arc region

    Directory of Open Access Journals (Sweden)

    A. V. Pavlov

    Full Text Available This study compares the measurements of electron density and temperature and the integral airglow intensity at 630 nm in the SAR arc region and slightly south of this (obtained by the Isis 2 spacecraft during the 18 December 1971 magnetic storm, with the model results obtained using the time dependent one-dimensional mathematical model of the Earth's ionosphere and plasmasphere. The explicit expression in the third Enskog approximation for the electron thermal conductivity coefficient in the multicomponent mixture of ionized gases and a simplified calculation method for this coefficient presents an opportunity to calculate more exactly the electron temperature and density and 630 nm emission within SAR arc region are used in the model. Collisions between N2 and hot thermal electrons in the SAR arc region produce vibrationally excited nitrogen molecules. It appears that the loss rate of O+(4S due to reactions with the vibrationally excited nitrogen is enough to explain electron density depression by a factor of two at F-region heights and the topside ionosphere density variations within the SAR arc if the erosion of plasma within geomagnetic field tubes, during the main phase of the geomagnetic storm and subsequent filling of geomagnetic tubes during the recovery phase, are considered. To explain the disagreement by a factor 1.5 between the observed and modeled SAR arc electron densities an additional plasma drift velocity ~–30 m s–1 in the ion continuity equations is needed during the recovery phase. This additional plasma drift velocity is likely caused by the transition from convecting to corotating flux tubes on the equatorward wall of the trough. The electron densities and temperatures and 630 nm integral intensity at the SAR arc and slightly south of this region as measured for the 18 December 1971 magnetic storm were correctly described by the model without perpendicular electric fields

  9. Electron acceleration by a radially polarized laser pulse during ionization of low density gases

    Directory of Open Access Journals (Sweden)

    Kunwar Pal Singh

    2011-03-01

    Full Text Available The acceleration of electrons by a radially polarized intense laser pulse has been studied. The axial electric field of the laser is responsible for electron acceleration. The axial electric field increases with decreasing laser spot size; however, the laser pulse gets defocused sooner for smaller values and the electrons do not experience high electric field for long, reducing the energy they can reach. The electron remains confined in the electric field of the laser for longer and the electron energy peaks for the normalized laser spot size nearly equal to the normalized laser intensity parameter. Electron energy peaks for initial laser phase ϕ_{0}=π due to accelerating laser phase and decreases with transverse initial position of the electrons. The energy and angle of the emittance spectrum of the electrons generated during ionization of krypton and argon at low densities have been obtained and a right choice of laser parameters has been suggested to obtain high energy quasimonoenergetic collimated electron beams. It has been found that argon is more suitable than krypton to obtain high energy electron beams due to higher ionization potential of inner shells for the former.

  10. Density of one-particle states for 2-D electron gas in magnetic field

    Directory of Open Access Journals (Sweden)

    Dubrovskyi

    2013-03-01

    Full Text Available The density of states of a particle in a 2-D area is independent both of the energy and form of the area only at the region of large values of energy. If energy is small, the density of states in the rectangular potential well essentially depends on the form of the area. If the bottom of the potential well has a potential relief, it can define the small eigenvalues as the discrete levels. In this case, dimensions and form of the area would not have any importance. If the conservation of zero value of the angular momentum is taken into account, the effective one-particle Hamiltonian for the 2-D electron gas in the magnetic field in the circle is the Hamiltonian with the parabolic potential and the reflecting bounds. It is supposed that in the square, the Hamiltonian has the same view. The 2-D density of states in the square can be computed as the convolution of 1-D densities. The density of one-particle states for 2-D electron gas in the magnetic field is obtained. It consists of three regions. There is a discrete spectrum at the smallest energy. In the intervening region the density of states is the sum of the piecewise continuous function and the density of the discrete spectrum. At great energies, the density of states is a continuous function. The Fermi energy dependence on the magnetic field is obtained when the field is small and the Fermi energy is located in the region of continuous spectrum. The Fermi energy oscillates and in the average it increases proportionally to the square of the magnetic induction. Total energy of electron gas in magnetic field also oscillates and increases when the magnetic field increases monotonously.

  11. Quasi-monoenergetic electron beams production in a sharp density transition

    CERN Document Server

    Fourmaux, S; Lassonde, P; Corde, S; Lebrun, G; Malka, V; Rousse, A; Kieffer, J C; 10.1063/1.4752114

    2012-01-01

    Using a laser plasma accelerator, experiments with a 80 TW and 30 fs laser pulse demonstrated quasi-monoenergetic electron spectra with maximum energy over 0.4 GeV. This is achieved using a supersonic He gas jet and a sharp density ramp generated by a high intensity laser crossing pre-pulse focused 3 ns before the main laser pulse. By adjusting this crossing pre-pulse position inside the gas jet, among the laser shots with electron injection more than 40% can produce quasi-monoenergetic spectra. This could become a relatively straight forward technique to control laser wakefield electron beams parameters.

  12. Low-latitude Model Electron Density Profiles using the IRI and CCIR ...

    African Journals Online (AJOL)

    ... electron density profiles under different solar-geophysical conditions are highlighted. The need for additional ionosonde stations in the African sector in order to incorporate the results of studies on equatorial anomaly into the models is emphasized. Nigeria Journal of Pure and Applied Physics VOLUME 1, AUGUST 2000, ...

  13. A Method to Improve Electron Density Measurement of Cone-Beam CT Using Dual Energy Technique

    Directory of Open Access Journals (Sweden)

    Kuo Men

    2015-01-01

    Full Text Available Purpose. To develop a dual energy imaging method to improve the accuracy of electron density measurement with a cone-beam CT (CBCT device. Materials and Methods. The imaging system is the XVI CBCT system on Elekta Synergy linac. Projection data were acquired with the high and low energy X-ray, respectively, to set up a basis material decomposition model. Virtual phantom simulation and phantoms experiments were carried out for quantitative evaluation of the method. Phantoms were also scanned twice with the high and low energy X-ray, respectively. The data were decomposed into projections of the two basis material coefficients according to the model set up earlier. The two sets of decomposed projections were used to reconstruct CBCT images of the basis material coefficients. Then, the images of electron densities were calculated with these CBCT images. Results. The difference between the calculated and theoretical values was within 2% and the correlation coefficient of them was about 1.0. The dual energy imaging method obtained more accurate electron density values and reduced the beam hardening artifacts obviously. Conclusion. A novel dual energy CBCT imaging method to calculate the electron densities was developed. It can acquire more accurate values and provide a platform potentially for dose calculation.

  14. Density functional study of AgScO 2: Electronic and optical properties

    Indian Academy of Sciences (India)

    2017-06-20

    Jun 20, 2017 ... Electronic properties deal with energy bands and density of states (DOSs), while optical properties describe refractive index and absorption coefficient.The energy bands are interpreted in terms of DOSs. The computed value of band gap is in agreement with that reported in the literature. Our results predict ...

  15. On the definition of the effectively unpaired electron density matrix: A similarity measure approach

    Science.gov (United States)

    Alcoba, Diego R.; Bochicchio, Roberto C.; Lain, Luis; Torre, Alicia

    2006-09-01

    The mathematical concepts of similarity and distance in metric spaces are used to relate Takatsuka et al. and Head-Gordon definitions of the effectively unpaired electron density matrix. This approach opens the possibility of new suitable definitions of this quantity to given purposes.

  16. High-order ionospheric effects on electron density estimation from Fengyun-3C GPS radio occultation

    Science.gov (United States)

    Li, Junhai; Jin, Shuanggen

    2017-03-01

    GPS radio occultation can estimate ionospheric electron density and total electron content (TEC) with high spatial resolution, e.g., China's recent Fengyun-3C GPS radio occultation. However, high-order ionospheric delays are normally ignored. In this paper, the high-order ionospheric effects on electron density estimation from the Fengyun-3C GPS radio occultation data are estimated and investigated using the NeQuick2 ionosphere model and the IGRF12 (International Geomagnetic Reference Field, 12th generation) geomagnetic model. Results show that the high-order ionospheric delays have large effects on electron density estimation with up to 800 el cm-3, which should be corrected in high-precision ionospheric density estimation and applications. The second-order ionospheric effects are more significant, particularly at 250-300 km, while third-order ionospheric effects are much smaller. Furthermore, the high-order ionospheric effects are related to the location, the local time, the radio occultation azimuth and the solar activity. The large high-order ionospheric effects are found in the low-latitude area and in the daytime as well as during strong solar activities. The second-order ionospheric effects have a maximum positive value when the radio occultation azimuth is around 0-20°, and a maximum negative value when the radio occultation azimuth is around -180 to -160°. Moreover, the geomagnetic storm also affects the high-order ionospheric delay, which should be carefully corrected.

  17. Studies on effective atomic number, electron density and kerma for some fatty acids and carbohydrates

    DEFF Research Database (Denmark)

    Manohara, S.R.; Hanagodimath, S.M.; Gerward, Leif

    2008-01-01

    The effective atomic number, Z(eff), the effective electron density, N-el, and kerma have been calculated for some fatty acids and carbohydrates for photon interaction in the extended energy range from 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCo...

  18. YUP.SCX: coaxing atomic models into medium resolution electron density maps.

    Science.gov (United States)

    Tan, Robert K-Z; Devkota, Batsal; Harvey, Stephen C

    2008-08-01

    The structures of large macromolecular complexes in different functional states can be determined by cryo-electron microscopy, which yields electron density maps of low to intermediate resolutions. The maps can be combined with high-resolution atomic structures of components of the complex, to produce a model for the complex that is more accurate than the formal resolution of the map. To this end, methods have been developed to dock atomic models into density maps rigidly or flexibly, and to refine a docked model so as to optimize the fit of the atomic model into the map. We have developed a new refinement method called YUP.SCX. The electron density map is converted into a component of the potential energy function to which terms for stereochemical restraints and volume exclusion are added. The potential energy function is then minimized (using simulated annealing) to yield a stereochemically-restrained atomic structure that fits into the electron density map optimally. We used this procedure to construct an atomic model of the 70S ribosome in the pre-accommodation state. Although some atoms are displaced by as much as 33A, they divide themselves into nearly rigid fragments along natural boundaries with smooth transitions between the fragments.

  19. Corrections to the density-functional theory electronic spectrum: Copper phthalocyanine

    DEFF Research Database (Denmark)

    Vazquez, Hector; Jelinek, P.; Brandbyge, Mads

    2009-01-01

    A method for improving the electronic spectrum of standard Density-Functional Theory (DFT) calculations (i.e., LDA or GGA approximations) is presented, and its application is discussed for the case of the copper phthalocyanine (CuPc) molecule. The method is based on a treatment of exchange...

  20. Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains

    Science.gov (United States)

    Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.

    2016-09-01

    The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.

  1. A new interferometry-based electron density fluctuation diagnostic on Alcator C-Moda)

    Science.gov (United States)

    Kasten, C. P.; Irby, J. H.; Murray, R.; White, A. E.; Pace, D. C.

    2012-10-01

    The two-color interferometry diagnostic on the Alcator C-Mod tokamak has been upgraded to measure fluctuations in the electron density and density gradient for turbulence and transport studies. Diagnostic features and capabilities are described. In differential mode, fast phase demodulation electronics detect the relative phase change between ten adjacent, radially-separated (ΔR = 1.2 cm, adjustable), vertical-viewing chords, which allows for measurement of the line-integrated electron density gradient. The system can be configured to detect the absolute phase shift of each chord by comparison to a local oscillator, measuring the line-integrated density. Each chord is sensitive to density fluctuations with kR < 20.3 cm-1 and is digitized at up to 10 MS/s, resolving aspects of ion temperature gradient-driven modes and other long-wavelength turbulence. Data from C-Mod discharges is presented, including observations of the quasi-coherent mode in enhanced D-alpha H-mode plasmas and the weakly coherent mode in I-mode.

  2. Pairing and unpairing electron densities in organic systems: Two-electron three center through space and through bonds interactions

    Science.gov (United States)

    Lobayan, Rosana M.; Bochicchio, Roberto C.

    2014-05-01

    Two-electron three-center bonding interactions in organic ions like methonium (CH5+), ethonium (C2H7+), and protonated alkanes n-C4H_{11}+ isomers (butonium cations) are described and characterized within the theoretical framework of the topological analysis of the electron density decomposition into its effectively paired and unpaired contributions. These interactions manifest in some of this type of systems as a concentration of unpaired electron cloud around the bond paths, in contrast to the well known paradigmatic boron hydrids in which it is not only concentrated close to the atomic nucleus and the bond paths but out of them and over the region defined by the involved atoms as a whole. This result permits to propose an attempt of classification for these interactions based in such manifestations. In the first type, it is called as interactions through bonds and in the second type as interactions through space type.

  3. Theoretical estimation of the electron affinity for quinone derivatives by means of density functional theory

    Science.gov (United States)

    Kalimullina, L. R.; Nafikova, E. P.; Asfandiarov, N. L.; Chizhov, Yu. V.; Baibulova, G. Sh.; Zhdanov, E. R.; Gadiev, R. M.

    2015-03-01

    A number of compounds related to quinone derivatives is investigated by means of density functional theory in the B3LYP/6-31G(d) mode. Vertical electron affinity E va and/or electron affinity E a for the investigated compounds are known from experiments. The correlation between the calculated energies of π* molecular orbitals with the E va values measured via electron transmission spectroscopy is determined with a coefficient of 0.96. It is established that theoretical values of the adiabatic electron affinity, calculated as the difference between the total energies of a neutral molecule and a radical anion, correlate with E a values determined from electron transfer experiments with a correlation coefficient of 0.996.

  4. Escape of laser-accelerated MeV electrons through an extended low-density pre-plasma

    Science.gov (United States)

    Feister, Scott; Orban, C.; Morrison, J. T.; Ngirmang, G. K.; Smith, J.; Frische, K. D.; Peterson, A. C.; Klim, A. J.; Chowdhury, E. A.; Freeman, R. R.; Roquemore, W. M.

    2016-10-01

    Ultra-intense laser experiments at the Air Force Research Laboratory demonstrated larger than expected conversion efficiencies from laser energy to MeV electrons from short pulse irradiation of a water stream target. We present Particle-in-cell (PIC) simulations of the pulse interaction that include highly-realistic 3D modeling of the pre-plasma phase of the target expansion using the FLASH hydrodynamic code. The addition of this FLASH pre-pulse modeling step resulted in a dramatic increase in over-120-keV electrons exiting the LSP simulation space. Removal of the low-density pre-plasma region in the LSP initial conditions was shown to re-create low efficiency results from earlier simulations due to energetic electrons failing to escape an isolated target. Analysis of particle trajectories indicates that energetic electrons travel relatively unimpeded through the extended pre-plasma, increasing the conversion efficiency significantly. This research was sponsored by the Quantum and Non-Equilibrium Processes Division of the AFOSR, under the management of Dr. Enrique Parra, and support from the DOD HPCMP Internship Program.

  5. Density functional study of AgScO_2: Electronic and optical properties

    Science.gov (United States)

    Bhamu, K. C.; Sahariya, Jagrati; Vyas, Rishi; Priolkar, K. R.

    2017-07-01

    This paper focusses on the electronic and optical properties of scandium-based silver delafossite (AgScO_2) semiconductor. The density functional theory (DFT) in the framework of full potential linearized augmented plane wave (FP-LAPW) scheme has been used for the present calculations with local density approximation (LDA) and generalized gradient approximation (GGA). Electronic properties deal with energy bands and density of states (DOSs), while optical properties describe refractive index and absorption coefficient. The energy bands are interpreted in terms of DOSs. The computed value of band gap is in agreement with that reported in the literature. Our results predict AgScO_2 as indirect band-gap semiconductor. Our calculated value of the refractive index in zero frequency limits is 2.42. The absorption coefficient predicts the applicability of AgScO_2 in solar cells and flat panel liquid crystal display as a transparent top window layer.

  6. International Workshop on Electronic Density Functional Theory : Recent Progress and New Directions

    CERN Document Server

    Vignale, Giovanni; Das, Mukunda

    1998-01-01

    This book is an outcome of the International Workshop on Electronic Density Functional Theory, held at Griffith University in Brisbane, Australia, in July 1996. Density functional theory, standing as it does at the boundary between the disciplines of physics, chemistry, and materials science, is a great mixer. Invited experts from North America, Europe, and Australia mingled with students from several disciplines, rapidly taking up the informal style for which Australia is famous. A list of participants is given at the end of the book. Density functional theory (DFT) is a subtle approach to the very difficult problem of predicting the behavior of many interacting particles. A major application is the study of many-electron systems. This was the workshop theme, embracing inter alia computational chemistry and condensed matter physics. DFT circumvents the more conceptually straightforward (but more computationally intensive) approach in which one solves the many-body Schrodinger equation. It relies instead on r...

  7. Characteristics of temporal evolution of particle density and electron temperature in helicon discharge

    Science.gov (United States)

    Yang, Xiong; Cheng, Mousen; Guo, Dawei; Wang, Moge; Li, Xiaokang

    2017-10-01

    On the basis of considering electrochemical reactions and collision relations in detail, a direct numerical simulation model of a helicon plasma discharge with three-dimensional two-fluid equations was employed to study the characteristics of the temporal evolution of particle density and electron temperature. With the assumption of weak ionization, the Maxwell equations coupled with the plasma parameters were directly solved in the whole computational domain. All of the partial differential equations were solved by the finite element solver in COMSOL MultiphysicsTM with a fully coupled method. In this work, the numerical cases were calculated with an Ar working medium and a Shoji-type antenna. The numerical results indicate that there exist two distinct modes of temporal evolution of the electron and ground atom density, which can be explained by the ion pumping effect. The evolution of the electron temperature is controlled by two schemes: electromagnetic wave heating and particle collision cooling. The high RF power results in a high peak electron temperature while the high gas pressure leads to a low steady temperature. In addition, an OES experiment using nine Ar I lines was conducted using a modified CR model to verify the validity of the results by simulation, showing that the trends of temporal evolution of electron density and temperature are well consistent with the numerically simulated ones.

  8. Laser-wakefield acceleration of electron beams in a low density plasma channel

    Directory of Open Access Journals (Sweden)

    T. P. A. Ibbotson

    2010-03-01

    Full Text Available The generation of quasimonoenergetic electron beams, with energies greater than 500 MeV, in a laser-plasma accelerator driven by 2.5 J, 80 fs laser pulses guided in a low density plasma channel, is investigated. The laser energy required to achieve electron injection is found to depend strongly on the quality of the input laser focal spot. Simulations show that, although the matched spot size of the plasma channel is greater than the self-focused spot size, the channel assists relativistic self-focusing and enables electron injection to occur at lower plasma densities and laser powers than would be possible without a waveguide.

  9. Reduction of electron density in a plasma by injection of liquids

    Science.gov (United States)

    Sodha, M. S.; Evans, J. S.

    1974-01-01

    In this paper, the authors have investigated the physics of various processes relevant to the reduction of electron density in a plasma by addition of water droplets; two processes have in particular been analyzed in some detail, viz, the electron attachment to charged dielectric droplets and the emission of negative ions by vaporization from these droplets. The results of these analyses have been applied to a study of the kinetics of reduction of electron density and charging of droplets in an initially overionized plasma, after addition of water droplets. A number of simplifying assumptions including uniform size and charge on droplets and negligible change in the radius of the droplet due to evaporation have been made.

  10. Vertical and longitudinal electron density structures of equatorial E- and F-regions

    Directory of Open Access Journals (Sweden)

    P. S. Brahmanandam

    2011-01-01

    Full Text Available From global soundings of ionospheric electron density made with FORMOSAT 3/COSMIC satellites for September 2006–August 2009, day-night variations in vertical and longitudinal structures of the electron densities in equatorial E- and F-regions for different seasons are investigated for the first time. The results reveal that the wavenumber-3 and wavenumber-4 patterns dominated the nighttime (22:00–04:00 LT F-region longitudinal structures in solstice and in equinox seasons, respectively. In daytime (08:00–18:00 LT F-region, the wavenumber-4 patterns governed the longitudinal structures in the September equinox and December solstice, and wavenumber-3 in March equinox and June solstice respectively. A comparison of the daytime and nighttime longitudinal electron density structures indicates that they are approximately 180° out of phase with each other. It is believed that this out of phase relation is very likely the result of the opposite phase relation between daytime and nighttime nonmigrating diurnal tidal winds that modulate background E-region dynamo electric field at different places, leading to the day-night change in the locations of the equatorial plasma fountains that are responsible for the formation of the F-region longitudinal structures. Further, a good consistency between the locations of the density structures in the same seasons of the different years for both daytime and nighttime epochs has been noticed indicating that the source mechanism for these structures could be the same.

  11. Electron density measurement of non-equilibrium atmospheric pressure plasma using dispersion interferometer

    Science.gov (United States)

    Yoshimura, Shinji; Kasahara, Hiroshi; Akiyama, Tsuyoshi

    2017-10-01

    Medical applications of non-equilibrium atmospheric plasmas have recently been attracting a great deal of attention, where many types of plasma sources have been developed to meet the purposes. For example, plasma-activated medium (PAM), which is now being studied for cancer treatment, has been produced by irradiating non-equilibrium atmospheric pressure plasma with ultrahigh electron density to a culture medium. Meanwhile, in order to measure electron density in magnetic confinement plasmas, a CO2 laser dispersion interferometer has been developed and installed on the Large Helical Device (LHD) at the National Institute for Fusion Science, Japan. The dispersion interferometer has advantages that the measurement is insensitive to mechanical vibrations and changes in neutral gas density. Taking advantage of these properties, we applied the dispersion interferometer to electron density diagnostics of atmospheric pressure plasmas produced by the NU-Global HUMAP-WSAP-50 device, which is used for producing PAM. This study was supported by the Grant of Joint Research by the National Institutes of Natural Sciences (NINS).

  12. Temporal variation of the electron density in afterglow of high-density CF_4, C_4F_8, and CF_4--H2 plasmas

    Science.gov (United States)

    Sasaki, K.; Kadota, K.

    1998-10-01

    The kinetics of electrons in electronegative plasmas is greatly affected by dissociative attachment to neutral molecules, which is a major process for the formation of negative ions. In fluorocarbon plasmas, negative fluorine ions (F^-) are produced by electron attachment to various reaction products as well as the parent gas. In the present work, we have measured the temporal variation of the electron density in the afterglow of high-density CF_4, C_4F_8, and CF_4--H2 plasmas. A conventional microwave interferometer at 35 GHz was adopted for the measurement. The electron loss frequency was evaluated from the temporal variation of the electron density which was calculated from the interferometry signal digitized with a high sampling rate of 100 MHz. In CF4 plasmas, the variation of the electron loss frequency roughly corresponded to that of the neutral radical densities. In C_4F8 plasmas, the electron loss frequency was higher for the discharge condition with lower dissociation degree. These results indicates that reaction products play important roles for the production of F^- in CF4 plasmas, while in C_4F8 plasmas, the production of F^- is governed by the parent gas. No correlations were found between the electron loss frequency and the F atom density in CF_4--H2 plasmas, which suggests that the production of F^- from F2 is nearly negligible.

  13. Variations of the ionospheric electron density during the Bhuj seismic event

    Directory of Open Access Journals (Sweden)

    A. Trigunait

    2004-12-01

    Full Text Available Ionospheric perturbations by natural geophysical activity, such as volcanic eruptions and earthquakes, have been studied since the great Alaskan earthquake in 1964. Measurements made from the ground show a variation of the critical frequency of the ionosphere layers before and after the shock. In this paper, we present an experimental investigation of the electron density variations around the time of the Bhuj earthquake in Gujarat, India. Several experiments have been used to survey the ionosphere. Measurements of fluctuations in the integrated electron density or TEC (Total Electron Content between three satellites (TOPEX-POSEIDON, SPOT2, SPOT4 and the ground have been done using the DORIS beacons. TEC has been also evaluated from a ground-based station using GPS satellites, and finally, ionospheric data from a classical ionospheric sounder located close to the earthquake epicenter are utilized. Anomalous electron density variations are detected both in day and night times before the quake. The generation mechanism of these perturbations is explained by a modification of the electric field in the global electric circuit induced during the earthquake preparation. Key words. Ionosphere (ionospheric disturbances – Radio Science (ionospheric physics – History of geophysics (seismology

  14. Coupled electron-hole bilayer graphene sheets: Superfluidity, Charge Density Waves, and Coupled Wigner Crystals

    Science.gov (United States)

    Zarenia, Mohammad; Peeters, Francois; Neilson, David

    The juxtaposition of superconducting and charge density wave (CDW) phases that is often observed in connection with High-Temperature Superconductors, is attracting considerable attention. In these systems, the crystal lattice provides a polarizable background, needed to drive the CDW phase. We report on a different system that exhibits the association of superfluid and CDW phases, but in which the polarizable background is uniform. Our system consists of two coupled two-dimensional bilayers of graphene, one bilayer containing electrons and the other holes interacting through the long range Coulomb interaction. To account for the inter-layer correlation energy accurately, we introduce a new approach which is based on the random phase approximation at high densities and interpolation between the weakly- and strongly-interacting regimes. We determine the zero temperature phase diagram in which the two control parameters are the equal electron and hole densities and the thickness of the insulating barrier separating the two bilayers. We find in addition to an electron-hole superfluid and a one-dimensional CDW phases that there exist also a coupled electron-hole Wigner crystal. The structure of the crystal background plays no role in determining the phase diagram. This work was supported by the Flemish Science Foundation (FWO).

  15. Effect of current density on electron beam induced charging in MgO

    Energy Technology Data Exchange (ETDEWEB)

    Boughariou, Aicha [LaMaCoP, Universite de Sfax, Faculte des Sciences, 3038 Sfax (Tunisia)]. E-mail: aicha_boughariou@yahoo.fr; Hachicha, Olfa [LaMaCoP, Universite de Sfax, Faculte des Sciences, 3038 Sfax (Tunisia); Kallel, Ali [LaMaCoP, Universite de Sfax, Faculte des Sciences, 3038 Sfax (Tunisia); Blaise, Guy [LPS, Universite Paris-Sud XI, Batiment 510, Orsay 91405 (France)

    2005-11-15

    It is well known that the presence of space charge in an insulator is correlated with an electric breakdown. Many studies have been carried out on the experimental characterization of space charges. In this paper, we outline the dependence on the current density of the charge-trapping phenomenon in magnesium oxide. Our study was performed with a dedicated scanning electron microscope (SEM) on the electrical property evolution of surface of magnesium oxide (1 0 0) (MgO) single crystal, during a 1.1, 5 and 30 keV electron irradiation. The types of charges trapped on the irradiated areas and the charging kinetics are determined by measuring the total secondary electron emission (SEE) {sigma} during the injection process by means of two complementary detectors. At low energies 1.1 and 5 keV, two different kinds of self-regulated regime ({sigma} = 1) were observed as a function of current density. At 30 keV energy, the electron emission appears to be stimulated by the current density, due to the Poole-Frenkel effect.

  16. The effect of longitudinal density gradient on electron plasma wake field acceleration

    CERN Document Server

    Tsiklauri, David

    2016-01-01

    3-, 2- and 1-dimensional, particle-in-cell, fully electromagnetic simulations of electron plasma wake field acceleration in the blow out regime are presented. Earlier results are extended by (i) studying the effect of longitudinal density gradient; (ii) avoiding use of co-moving simulation box; (iii) inclusion of ion motion; and (iv) studying fully electromagnetic plasma wake fields. It is established that injecting driving and trailing electron bunches into a positive density gradient of ten-fold increasing density over 10 cm long Lithium vapor plasma, results in spatially more compact and three times larger, compared to the uniform density case, electric fields (-6.4 x 10^{10} V/m), leading to acceleration of the trailing bunch up to 24.4 GeV (starting from initial 20.4 GeV), with an energy transfer efficiencies from leading to trailing bunch of 75 percent. In the uniform density case -2.5 x 10^{10} V/m wake is created leading to acceleration of the trailing bunch up to 22.4 GeV, with an energy transfer eff...

  17. Density-Gradient-Driven trapped-electron-modes in improved-confinement RFP plasmas

    Science.gov (United States)

    Duff, James; Sarff, John; Ding, Weixing; Brower, David; Parke, Eli; Chapman, Brett; Terry, Paul; Pueschel, M. J.; Williams, Zach

    2017-10-01

    Short wavelength density fluctuations in improved-confinement MST plasmas exhibit multiple features characteristic of the trapped-electron-mode (TEM). Core transport in the RFP is normally governed by magnetic stochasticity stemming from long wavelength tearing modes that arise from current profile peaking, which are suppressed via inductive control for this work. The improved confinement is associated with an increase in the pressure gradient that can destabilize drift waves. The measured density fluctuations have f 50 kHz, kϕρs , and propagate in the electron drift direction. Their spectral emergence coincides with a sharp decrease in global tearing mode associated fluctuations, their amplitude increases with local density gradient, and they exhibit a density-gradient threshold at R /Ln 15 . The GENE code, modified for the RFP, predicts the onset of density-gradient-driven TEM for these strong-gradient plasma conditions. While nonlinear analysis shows a large Dimits shift associated with predicted strong zonal flows, the inclusion of residual magnetic fluctuations, comparable to experimental magnetic fluctuations, causes a collapse of the zonal flows and an increase in the predicted transport to a level close to the experimentally measured heat flux. Work supported by US DOE.

  18. Variations of topside ionospheric electron density near the dawn terminator in relation to geomagnetic activity

    Science.gov (United States)

    Tam, Sunny W. Y.; Chen, Chien-Han; Wang, Kaiti

    2017-11-01

    A statistical study to determine the influence of geomagnetic disturbances on the ionosphere across the dawn terminator at subauroral and middle latitudes is performed, based on the vertical electron density profiles measured by the GPS Occultation Experiment aboard the FORMOSAT-3/COSMIC satellites from August 2006 to July 2009. Three ranges of solar zenith angles are adopted to characterize transitions between the pre- and post-dawn ionosphere. Results indicate opposing plasma density effects at the darkened and sunlit locations between 50° and 65° magnetic latitude (λm). The darkened topside ionosphere features density increases associated with geomagnetic activity, while density reductions mark its sunlit counterpart. The average electron peak density in the F2 region can increase by up to 44% in the darkened ionosphere and decrease by up to 20% in the sunlit ionosphere as Kp changes from 0-1 to 4-5. In the λm = 55°-65° range, the dominant contributors to the density perturbation are auroral electron precipitation for the darkened region and enhanced penetration electric fields for the sunlit region, with the transition occurring across the terminator local times. Dominance shifts first to electric fields at 50°-55°, then to aurora-induced neutral wind at 45°-50°, suggesting that during disturbed times electric fields seldom penetrate below λm = 50°. Findings presented in this statistical study should contribute to the study of space weather and the understanding of non-local influences of geomagnetic disturbances on topside dynamics.

  19. Density Functional Reactivity Theory Characterizes Charge Separation Propensity in Proton-Coupled Electron Transfer Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shubin [Univ. of North Carolina, Chapel Hill, NC (United States); Ess, Daniel H. [Brigham Young Univ., Provo, UT (United States); Univ. of North Carolina, Chapel Hill, NC (United States); Schauer, Cynthia [Univ. of North Carolina, Chapel Hill, NC (United States)

    2011-04-20

    Proton-coupled electron transfer (PCET) reactions occur in many biological and artificial solar energy conversion processes. In these reactions the electron is often transferred to a site distant to the proton acceptor site. In this work, we employ the dual descriptor and the electrophilic Fukui function from density functional reactivity theory (DFRT) to characterize the propensity for an electron to be transferred to a site other than the proton acceptor site. The electrophilic regions of hydrogen bond or van der Waal reactant complexes were examined using these DFRT descriptors to determine the region of space to which the electron is most likely to be transferred. This analysis shows that in PCET reactions the electrophilic region of the reactant complex does not include the proton acceptor site.

  20. Validation of COSMIC radio occultation electron density profiles by incoherent scatter radar data

    Science.gov (United States)

    Cherniak, Iurii; Zakharenkova, Irina

    The COSMIC/FORMOSAT-3 is a joint US/Taiwan radio occultation mission consisting of six identical micro-satellites. Each microsatellite has a GPS Occultation Experiment payload to operate the ionospheric RO measurements. FS3/COSMIC data can make a positive impact on global ionosphere study providing essential information about height electron density distribu-tion. For correct using of the RO electron density profiles for geophysical analysis, modeling and other applications it is necessary to make validation of these data with electron density distributions obtained by another measurement techniques such as proven ground based facili-ties -ionosondes and IS radars. In fact as the ionosondes provide no direct information on the profile above the maximum electron density and the topside ionosonde profile is obtained by fitting a model to the peak electron density value, the COSMIC RO measurements can make an important contribution to the investigation of the topside part of the ionosphere. IS radars provide information about the whole electron density profile, so we can estimate the agreement of topside parts between two independent measurements. To validate the reliability of COS-MIC data we have used the ionospheric electron density profiles derived from IS radar located near Kharkiv, Ukraine (geographic coordinates: 49.6N, 36.3E, geomagnetic coordinates: 45.7N, 117.8E). The Kharkiv radar is a sole incoherent scatter facility on the middle latitudes of Eu-ropean region. The radar operates with 100-m zenith parabolic antenna at 158 MHz with peak transmitted power 2.0 MW. The Kharkiv IS radar is able to determine the heights-temporal distribution of ionosphere parameters in height range of 70-1500 km. At the ionosphere in-vestigation by incoherent scatter method there are directly measured the power spectrum (or autocorrelation function) of scattered signal. With using of rather complex procedure of the received signal processing it is possible to estimate the

  1. Line Shape Modeling for the Diagnostic of the Electron Density in a Corona Discharge

    Directory of Open Access Journals (Sweden)

    Joël Rosato

    2017-09-01

    Full Text Available We present an analysis of spectra observed in a corona discharge designed for the study of dielectrics in electrical engineering. The medium is a gas of helium and the discharge was performed at the vicinity of a tip electrode under high voltage. The shape of helium lines is dominated by the Stark broadening due to the plasma microfield. Using a computer simulation method, we examine the sensitivity of the He 492 nm line shape to the electron density. Our results indicate the possibility of a density diagnostic based on passive spectroscopy. The influence of collisional broadening due to interactions between the emitters and neutrals is discussed.

  2. Determination of the electronic density of states near buried interfaces: Application to Co/Cu multilayers

    DEFF Research Database (Denmark)

    Nilsson, A.; Sthör, J.; Wiell, T.

    1996-01-01

    High-resolution L(3) x-ray absorption and emission spectra of Co and Cu in Co/Cu multilayers are shown to provide unique information on the occupied and unoccupied density of d states near buried interfaces. The d bands of both Co and Cu interfacial layers are shown to be considerably narrowed re...... relative to the bulk metals, and for Cu interface layers the d density of states is found to be enhanced near the Fermi level. The experimental results are confirmed by self-consistent electronic structure calculations....

  3. RENNSH: a novel α-helix identification approach for intermediate resolution electron density maps.

    Science.gov (United States)

    Ma, Lingyu; Reisert, Marco; Burkhardt, Hans

    2012-01-01

    Accurate identification of protein secondary structures is beneficial to understand three-dimensional structures of biological macromolecules. In this paper, a novel refined classification framework is proposed, which treats alpha-helix identification as a machine learning problem by representing each voxel in the density map with its Spherical Harmonic Descriptors (SHD). An energy function is defined to provide statistical analysis of its identification performance, which can be applied to all the α-helix identification approaches. Comparing with other existing α-helix identification methods for intermediate resolution electron density maps, the experimental results demonstrate that our approach gives the best identification accuracy and is more robust to the noise.

  4. The Kinetic Energy of Hydrocarbons as a Function of Electron Density and Convolutional Neural Networks

    CERN Document Server

    Yao, Kun

    2015-01-01

    We demonstrate a convolutional neural network trained to reproduce the Kohn-Sham kinetic energy of hydrocarbons from electron density. The output of the network is used as a non-local correction to the conventional local and semi-local kinetic functionals. We show that this approximation qualitatively reproduces Kohn-Sham potential energy surfaces when used with conventional exchange correlation functionals. Numerical noise inherited from the non-linearity of the neural network is identified as the major challenge for the model. Finally we examine the features in the density learned by the neural network to anticipate the prospects of generalizing these models.

  5. Modelling coronal electron density and temperature profiles based on solar magnetic field observations

    Science.gov (United States)

    Rodríguez Gómez, J. M.; Antunes Vieira, L. E.; Dal Lago, A.; Palacios, J.; Balmaceda, L. A.; Stekel, T.

    2017-10-01

    The density and temperature profiles in the solar corona are complex to describe, the observational diagnostics is not easy. Here we present a physics-based model to reconstruct the evolution of the electron density and temperature in the solar corona based on the configuration of the magnetic field imprinted on the solar surface. The structure of the coronal magnetic field is estimated from Potential Field Source Surface (PFSS) based on magnetic field from both observational synoptic charts and a magnetic flux transport model. We use an emission model based on the ionization equilibrium and coronal abundances from CHIANTI atomic database 8.0. The preliminary results are discussed in details.

  6. Spatial and temporal variations of electron temperatures and densities from EUV-emitting lithium plasmas.

    Science.gov (United States)

    Coons, R W; Harilal, S S; Polek, M; Hassanein, A

    2011-07-01

    Planar slabs of pure Li were irradiated with 1.064 nm, 6 ns Nd:YAG laser pulses. Determination of plasma densities at both the earliest times of plasma formation and near the target surface was performed using Nomarski interferometry. The plasma parameters at later times were evaluated using optical emission spectroscopy. The space- and time-dependent electron densities and temperatures of the plasma were determined from their Stark broadening and the relative intensities of the spectral lines, respectively. The advantages and disadvantages of both of these techniques are evaluated and discussed.

  7. Analog front-end electronics for the outer layers of the SuperB SVT: Design and expected performances

    Science.gov (United States)

    Bombelli, Luca; Fiorini, Carlo; Nasri, Bayan; Trigilio, Paolo; Citterio, Mauro; Neri, Nicola

    2013-08-01

    The Silicon Vertex Tracker (SVT) of the new SuperB collider will be composed of 6 different detector layers [1]. The innermost layer (L0) will be composed by striplets or pixels [2]; the other 5 detector layers will be double-sided long-strip detectors. The strip geometries and the foreseen hit-rates will change according to the different layers. As a consequence, different optimization of the analog read-out electronics is needed in order to provide high detection-efficiency and low noise level in the different layers. Two readout ASICs are currently developed, one for layers 0-3, another for layers 4 and 5; they differ mainly in the analog front-end. In this work, we present the design and the expected performances of the analog front-end for layers 4 and 5. For these layers, the strip detectors show a very high stray capacitance and high series resistance. In this condition, the noise optimization is our primary concern. A necessary compromise on the best peaking time to achieve an acceptable noise level together with efficiency and timing accuracy has been found. We will present the design of preamplifier and shaper and the results of simulation of noise performance and efficiency (with the expected background rates). In addition, the design of the time-over-threshold and its use to correct the time-walk of the event trigger is discussed as well as the achievable timing accuracy of the circuit.

  8. Correlated electron dynamics and memory in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Thiele, Mark

    2009-07-28

    Time-dependent density functional theory (TDDFT) is an exact reformulation of the time-dependent many-electron Schroedinger equation, where the problem of many interacting electrons is mapped onto the Kohn-Sham system of noninteracting particles which reproduces the exact electronic density. In the Kohn-Sham system all non-classical many-body effects are incorporated in the exchange-correlation potential which is in general unknown and needs to be approximated. It is the goal of this thesis to investigate the connection between memory effects and correlated electron dynamics in strong and weak fields. To this end one-dimensional two-electron singlet systems are studied. At the same time these systems include the onedimensional helium atom model, which is an established system to investigate the crucial effects of correlated electron dynamics in external fields. The studies presented in this thesis show that memory effects are negligible for typical strong field processes. Here the approximation of the spatial nonlocality is of primary importance. For the photoabsorption spectra on the other hand the neglect of memory effects leads to qualitative and quantitative errors, which are shown to be connected to transitions of double excitation character. To develop a better understanding of the conditions under which memory effects become important quantum fluid dynamics has been found to be especially suitable. It represents a further exact reformulation of the quantum mechanic many-body problem which is based on hydrodynamic quantities such as density and velocity. Memory effects are shown to be important whenever the velocity field develops strong gradients and dissipative effects contribute. (orig.)

  9. Current densities due to electron-hole puddles in graphene flakes at the charge neutrality point

    Science.gov (United States)

    Lima, Leandro; Lewenkopf, Caio

    2014-03-01

    Graphene flakes show a typical conductivity minimum of about e2 / h , almost independent of sample mobility, at the charge neutrality point. This is at odds with the notion that as the mobility increases, and graphene becomes more ballistic, its density of states (DOS) and conductivity at the charge neutrality point should vanish. The observed conductivity minimum is often attributed to the presence of electron-hole charge puddles, that give rise to an effective local-dependent chemical potential. In this way, the local chemical potential fluctuates creating p and n-doped regions and the electronic transport is facilitated by Klein tunneling through the p and n-doped domains. Although very attractive, there is little quantitative support for this this picture. We revisit this problem and analyze the transport properties using a self-consistent recursive Green's functions technique with spin resolution that includes the electronic interaction modeled by a mean field Hubbard term. We calculate electronic current densities between neighboring carbon sites near the p-n interface and relate the electronic propagation to the puddles charge, size and shapes.

  10. Ground-state properties and density response of quasi-one-dimensional electron systems

    Science.gov (United States)

    Agosti, Daniele; Pederiva, Francesco; Lipparini, Enrico; Takayanagi, Kazuo

    1998-06-01

    Ground-state properties of the quasi-one-dimensional electron gas in a quantum wire are calculated in the random-phase approximation (RPA), the ladder approximation, and the Singwi-Tosi-Land-Sjölander approximation. Numerical results are given for the exchange-correlation energy and the compressibility as a function of the electron density and the width of the wire. The dielectric response of the system has been calculated in the local field approximation and compared with the RPA result.

  11. The charger transfer electronic coupling in diabatic perspective: A multi-state density functional theory study

    Science.gov (United States)

    Guo, Xinwei; Qu, Zexing; Gao, Jiali

    2018-01-01

    The multi-state density functional theory (MSDFT) provides a convenient way to estimate electronic coupling of charge transfer processes based on a diabatic representation. Its performance has been benchmarked against the HAB11 database with a mean unsigned error (MUE) of 17 meV between MSDFT and ab initio methods. The small difference may be attributed to different representations, diabatic from MSDFT and adiabatic from ab initio calculations. In this discussion, we conclude that MSDFT provides a general and efficient way to estimate the electronic coupling for charge-transfer rate calculations based on the Marcus-Hush model.

  12. Generation of a neutral, high-density electron-positron plasma in the laboratory

    CERN Document Server

    Sarri, G; Cole, J; Schumaker, W; Di Piazza, A; Reville, B; Doria, D; Dromey, B; Gizzi, L; Green, A; Grittani, G; Kar, S; Keitel, C H; Krushelnick, K; Kushel, S; Mangles, S; Najmudin, Z; Thomas, A G R; Vargas, M; Zepf, M

    2013-01-01

    We report on the laser-driven generation of purely neutral, relativistic electron-positron pair plasmas. The overall charge neutrality, high average Lorentz factor ($\\gamma_{e/p} \\approx 15$), small divergence ($\\theta_{e/p} \\approx 10 - 20$ mrad), and high density ($n_{e/p}\\simeq 10^{15}$cm$^{-3}$) of these plasmas open the pathway for the experimental study of the dynamics of this exotic state of matter, in regimes that are of relevance to electron-positron astrophysical plasmas.

  13. Communication: Reduced density matrices in molecular systems: Grand-canonical electron states

    Energy Technology Data Exchange (ETDEWEB)

    Bochicchio, Roberto C., E-mail: rboc@df.uba.ar [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Miranda-Quintana, Ramón A. [Laboratory of Computational and Theoretical Chemistry, Faculty of Chemistry, University of Havana, Zapata e G y Mazón, 10400 Havana (Cuba); Rial, Diego [Departamento de Matemática, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IMAS, CONICET, Ciudad Universitaria, 1428 Buenos Aires (Argentina)

    2013-11-21

    Grand-canonical like descriptions of many electron atomic and molecular open systems which are characterized by a non-integer number of electrons are presented. Their associated reduced density matrices (RDMs) are obtained by introducing the contracting mapping for this type of distributions. It is shown that there is loss of information when connecting RDMs of different order by partial contractions. The energy convexity property of these systems simplifies the description. Consequently, this formulation opens the possibility to a new look for chemical descriptors such as chemical potential and reactivity among others. Examples are presented to discuss the theoretical aspects of this work.

  14. Communication: Reduced density matrices in molecular systems: Grand-canonical electron states

    Science.gov (United States)

    Bochicchio, Roberto C.; Miranda-Quintana, Ramón A.; Rial, Diego

    2013-11-01

    Grand-canonical like descriptions of many electron atomic and molecular open systems which are characterized by a non-integer number of electrons are presented. Their associated reduced density matrices (RDMs) are obtained by introducing the contracting mapping for this type of distributions. It is shown that there is loss of information when connecting RDMs of different order by partial contractions. The energy convexity property of these systems simplifies the description. Consequently, this formulation opens the possibility to a new look for chemical descriptors such as chemical potential and reactivity among others. Examples are presented to discuss the theoretical aspects of this work.

  15. Irradiation tests and expected performance of readout electronics of the ATLAS hadronic endcap calorimeter for the HL-LHC

    CERN Document Server

    Cheplakov, A; The ATLAS collaboration

    2014-01-01

    The readout electronics of the ATLAS Hadronic Endcap Calorimeter (HEC) will have to withstand a much more demanding radiation environment at the future high-luminosity LHC (HL-LHC) compared to LHC design values. The heart of the HEC read-out electronics is the pre-amplifier and summing (PAS) system which is realized in GaAs ASIC technology. The PAS devices are installed inside the LAr cryostat directly on the detector. They have been proven to operate reliably in LHC conditions up to luminosities of 1000 fb-1, within safety margins. However, at the HL-LHC a total luminosity of 3000 fb-1 is expected, which corresponds to radiation levels being increased by a factor 3-5. On top of that a safety factor of at least 2 needs to be accounted for to reflect our confidence in the simulations. The GaAs ASIC has therefore been exposed to neutron and proton radiation with integrated fluences in excess of 4∙10^15 n/cm2 and 2.6∙10^14 p/cm2, several factors above the levels corresponding to ten years of HL-LHC running. ...

  16. Irradiation Tests and Expected Performance of Readout Electronics of the ATLAS Hadronic Endcap Calorimeter for the HL-LHC

    CERN Document Server

    Cheplakov, A; The ATLAS collaboration

    2014-01-01

    The readout electronics of the ATLAS Hadronic Endcap Calorimeter (HEC) will have to withstand a much more demanding radiation environment at the future high-luminosity LHC (HL-LHC) compared to LHC design values. The heart of the HEC read-out electronics is the pre-amplifier and summing (PAS) system which is realized in GaAs ASIC technology. The PAS devices are installed inside the LAr cryostat directly on the detector. They have been proven to operate reliably in LHC conditions up to luminosities of 1000 fb-1, within safety margins. However, at the HL-LHC a total luminosity of 3000 fb-1 is expected, which corresponds to radiation levels being increased by a factor 3-5. On top of that a safety factor of at least 2 needs to be accounted for to reflect our confidence in the simulations. The GaAs ASIC has therefore been exposed to neutron and proton radiation with integrated fluences in excess of 4x10^15 n/cm2 and 2.6x10^14 p/cm2, several factors above the levels corresponding to ten years of HL-LHC running. In-s...

  17. Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Tierno, S. P., E-mail: sp.tierno@upm.es; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L. [Department of Applied Physics, E.T.S.I. Aeronáutica y del Espacio. Universidad Politécnica de Madrid, 28040 Madrid (Spain)

    2016-01-15

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

  18. Generation of attosecond electron bunches in a laser-plasma accelerator using a plasma density upramp

    Energy Technology Data Exchange (ETDEWEB)

    Weikum, M.K., E-mail: maria.weikum@desy.de [Deutsches Elektronensynchrotron (DESY), Bdg. 30b, Notkestr. 85, 22607 Hamburg (Germany); Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Li, F.Y. [Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Assmann, R.W. [Deutsches Elektronensynchrotron (DESY), Bdg. 30b, Notkestr. 85, 22607 Hamburg (Germany); Sheng, Z.M. [Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom); Laboratory for Laser Plasmas and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Jaroszynski, D. [Department of Physics, University of Strathclyde, G4 0NG Glasgow (United Kingdom)

    2016-09-01

    Attosecond electron bunches and attosecond radiation pulses enable the study of ultrafast dynamics of matter in an unprecedented regime. In this paper, the suitability for the experimental realization of a novel scheme producing sub-femtosecond duration electron bunches from laser-wakefield acceleration in plasma with self-injection in a plasma upramp profile has been investigated. While it has previously been predicted that this requires laser power above a few hundred terawatts typically, here we show that the scheme can be extended with reduced driving laser powers down to tens of terawatts, generating accelerated electron pulses with minimum length of around 166 attoseconds and picocoulombs charge. Using particle-in-cell simulations and theoretical models, the evolution of the accelerated electron bunch within the plasma as well as simple scalings of the bunch properties with initial laser and plasma parameters are presented. - Highlights: • LWFA with an upramp density profile can trap and accelerate sub-fs electron beams. • A reduction of the necessary threshold laser intensity by a factor 4 is presented. • Electron properties are tuned by varying initial laser and plasma parameters. • Simulations predict electron bunch lengths below 200 attoseconds with pC charge. • Strong bunch evolution effects and a large energy spread still need to be improved.

  19. Communication: Hilbert-space partitioning of the molecular one-electron density matrix with orthogonal projectors.

    Science.gov (United States)

    Vanfleteren, Diederik; Van Neck, Dimitri; Bultinck, Patrick; Ayers, Paul W; Waroquier, Michel

    2010-12-21

    A double-atom partitioning of the molecular one-electron density matrix is used to describe atoms and bonds. All calculations are performed in Hilbert space. The concept of atomic weight functions (familiar from Hirshfeld analysis of the electron density) is extended to atomic weight matrices. These are constructed to be orthogonal projection operators on atomic subspaces, which has significant advantages in the interpretation of the bond contributions. In close analogy to the iterative Hirshfeld procedure, self-consistency is built in at the level of atomic charges and occupancies. The method is applied to a test set of about 67 molecules, representing various types of chemical binding. A close correlation is observed between the atomic charges and the Hirshfeld-I atomic charges.

  20. Fragment transition density method to calculate electronic coupling for excitation energy transfer

    Energy Technology Data Exchange (ETDEWEB)

    Voityuk, Alexander A., E-mail: alexander.voityuk@icrea.cat [Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain and Institut de Química Computacional i Catàlisi (IQCC), Universitat de Girona 17071 Girona (Spain)

    2014-06-28

    A general approach, the Fragment Transition Density (FTD) scheme, is introduced to estimate electronic coupling for excitation energy transfer in a molecular system. Within this method, the excitation energies and transition densities of the system are used to derive the coupling matrix element. The scheme allows one to treat systems where exciton donor and acceptor are close together and their exchange interaction and orbital overlap are significant. The FTD method can be applied in combination with any quantum mechanical approach to treat excited states of general nature including single-, double-, and higher excitations. Using FTD approach, we derive excitonic couplings for several systems computed with the CIS, TD DFT and MS-CASPT2 methods. In particular, it is shown that the estimated coupling values in DNA π-stacks are strongly affected by the short-range electronic interaction of adjacent nucleobases.

  1. Comparison of F-region electron density observations by satellite radio tomography and incoherent scatter methods

    Directory of Open Access Journals (Sweden)

    T. Nygrén

    1996-12-01

    Full Text Available In November 1995 a campaign of satellite radiotomography supported by the EISCAT incoherent scatter radar and several other instruments was arranged in Scandinavia. A chain of four satellite receivers extending from the north of Norway to the south of Finland was installed approximately along a geomagnetic meridian. The receivers carried out difference Doppler measurements using signals from satellites flying along the chain. The EISCAT UHF radar was simultaneously operational with its beam swinging either in geomagnetic or in geographic meridional plane. With this experimental set-up latitudinal scans of F-region electron density are obtained both from the radar observations and by tomographic inversion of the phase observations given by the difference Doppler experiment. This paper shows the first results of the campaign and compares the electron densities given by the two methods.

  2. From Metal Cluster to Metal Nanowire: A Topological Analysis of Electron Density and Band Structure Calculation

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2002-01-01

    Full Text Available Abstract:We investigate a theoretical model of molecular metalwire constructed from linear polynuclear metal complexes. In particular we study the linear Crn metal complex and Cr molecular metalwire. The electron density distributions of the model nanowire and the linear Crn metal complexes, with n = 3, 5, and 7, are calculated by employing CRYSTAL98 package with topological analysis. The preliminary results indicate that the bonding types between any two neighboring Cr are all the same, namely the polarized open-shell interaction. The pattern of electron density distribution in metal complexes resembles that of the model Cr nanowire as the number of metal ions increases. The conductivity of the model Cr nanowire is also tested by performing the band structure calculation.

  3. Temporal Behavior of the Ionospheric Electron Density at Low Latitudes: First Glimpse

    Science.gov (United States)

    Gjerloev, J. W.; Humberset, B. K.; Gonzalez, S. A.; Garnett Marques Brum, C.

    2013-12-01

    In this paper we address the spatiotemporal characteristics of the electron density at 150 km altitude in the low latitude ionosphere above the Arecibo Observatory. We utilize a new pointing mode that allows us to probe the same volume in the ionosphere for a continuous period of approximately 25 min. or more. The ISR profiles have 150 m range resolution and samples have a 10-second time resolution; we probed 60 individual regions uniformly spaced in local times and covering the full 24 hours. For each time series we determine the total derivative of the electron density using a narrow Hanning bandpass filter that allow us to determine the variability at different frequencies. This is done for each of the 60 local time regions. We further compare to widely used static statistical models and test their underlying assumption: Dynamics can be ignored.

  4. Measurements of electron density irregularities in the ionosphere of Jupiter by Pioneer 10

    Science.gov (United States)

    Woo, R.; Yang, F.-C.

    1976-01-01

    It is demonstrated that when the frequency spectrum of log amplitude fluctuations is used, the radio-occultation experiment is a powerful tool for detecting, identifying, and studying ionospheric irregularities. Analysis of Pioneer 10 radio-occultation measurements reveals that the Jovian ionosphere possesses electron-density irregularities which are very similar to those found in the earth's ionosphere. This is the first time such irregularities have been found in a planetary ionosphere other than that of the earth. The Pioneer 10 results indicate that the spatial wave-number spectrum of the electron-density irregularities is close to the Kolmogorov spectrum and that the outer scale size is greater than the Fresnel size (6.15 km). This type of spectrum suggests that the irregularities are probably produced by the turbulent dissipation of irregularities larger than the outer scale size.

  5. Applications of electron density studies in molecular and solid state science

    DEFF Research Database (Denmark)

    Overgaard, Jacob

    2015-01-01

    The present dissertation contains the distillate of my scientific output in the field of experimental and theoretical electron density studies roughly over the last decade and a little more, since earning my PhD-degree in 2001. There are several reasons that I have chosen to write my dissertation...... of electron density studies in connection with the UN declared International Year of Crystallography in 2014. In addition, a number of reviews on the method have very recently appeared showing that the time is ripe to look back on the achievements of the last 10 years and also to look ahead to see where...... at this point in time. Given the development in the underlying technology of X-ray diffraction in the last two decades it is relevant to describe the impact that this has had on the possible output, and this is well exemplified by the studies that I have been involved in. It is also timely to present a status...

  6. textbf{Tomography of Ionosphere electron density and its abnormity analysis during Wenchuan earthquake }

    Science.gov (United States)

    Wang, Xiaoya; Xing, Nan

    2010-05-01

    A multiple-arc method and Kriging interpolation are applied to obtain VTEC as well as DCB using ground-based GPS data. Given by the time variation characteristics of VTEC and DCB, VTEC is calculated every 30 minutes as local variables, and DCB is calculated every day as global variables. Kriging method, taking the spatial information of VTEC into account, is useful to make VTEC more precise and stable. Meanwhile, based on 3-variable spline basis function, we expand electron density into a linear combination of a set of grid points. Tomography of Ionosphere electron density is made by MART. The results show the coherence with CHAMP occultation results. We applied these two ways to process the ground-based GPS data of Yangzi River Triangle Region in May, 2008 when the shocking earthquake happened in Wenchuan. A simple statistic analysis reveals the response of ionosphere to the earthquake and also the abnormal signal occurred before the earthquake.

  7. Expectation values for low-resolution slit-scan flow prescreening: influence of nuclear shape and DNA density

    Energy Technology Data Exchange (ETDEWEB)

    Mullaney, P.F.; Mann, R.; Seger, G.H.; Achatz, M.

    1982-06-01

    We conducted high-resolution fluorescent image analysis with mithramycin-stained cells from clinical gynecologic specimens. Features characteristic of the usual, low-resolution, one-dimensional, slit-scan flow cytometric measurements were extracted from 250 high-resolution nuclear images. In addition to the measurement of the usual parameters, nuclear ellpticity and DNA density (DNA per unit nuclear size) were also determined. Our preliminary results indicate that both of these features offer increasded discrimination. When nuclear shape was included as a global feature, at least 77% of the diagnostic cells could be distinguished from normal cells, with no overlap. Both features hold promise for improving the discrimination possible with flow cytometry.

  8. Density changes in shear bands of a metallic glass determined by correlative analytical transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rösner, Harald, E-mail: rosner@uni-muenster.de [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Peterlechner, Martin [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Kübel, Christian [Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology (INT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Schmidt, Vitalij [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Wilde, Gerhard [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China)

    2014-07-01

    Density changes between sheared zones and their surrounding amorphous matrix as a result of plastic deformation in a cold-rolled metallic glass (melt-spun Al{sub 88}Y{sub 7}Fe{sub 5}) were determined using high-angle annular dark-field (HAADF) detector intensities supplemented by electron-energy loss spectroscopy (EELS), energy-dispersive X-ray (EDX) and nano-beam diffraction analyses. Sheared zones or shear bands were observed as regions of bright or dark contrast arising from a higher or lower density relative to the matrix. Moreover, abrupt contrast changes from bright to dark and vice versa were found within individual shear bands. We associate the decrease in density mainly with an enhanced free volume in the shear bands and the increase in density with concomitant changes of the mass. This interpretation is further supported by changes in the zero loss and Plasmon signal originating from such sites. The limits of this new approach are discussed. - Highlights: • We describe a novel approach for measuring densities in shear bands of metallic glasses. • The linear relation of the dark-field intensity I/I{sub 0} and the mass thickness ρt was used. • Individual shear bands showed abrupt contrast changes from bright to dark and vice versa. • Density changes ranging from about −10% to +6% were found for such shear bands. • Mixtures of amorphous/medium range ordered domains were found within the shear bands.

  9. Local and global properties of eigenfunctions and one-electron densities of Coulombic Schrödinger operators

    DEFF Research Database (Denmark)

    Fournais, Søren; Hoffmann-Ostenhof, Maria; Hoffmann-Ostenhof, Thomas

    2008-01-01

    We review recent results by the authors on the regularity of molecular eigenfunctions ψ and their corresponding one-electron densities ρ, as well as of the spherically averaged one-electron atomic density ρ. Furthermore, we prove an exponentially decreasing lower bound for ρ in the case when the ...

  10. Correlated magnetic impurities in a superconductor: electron density profiles and robustness of superconductivity.

    Science.gov (United States)

    Sacramento, P D; Dugaev, V K; Vieira, V R; Araújo, M A N

    2010-01-20

    The insertion of magnetic impurities in a conventional superconductor leads to various effects. In this work we show that the electron density is affected by the spins (considered as classical) both locally and globally. The charge accumulation is solved self-consistently. This affects the transport properties along magnetic domain walls. Also, we show that superconductivity is more robust if the spin locations are not random but correlated. © 2010 IOP Publishing Ltd

  11. Variability in the Fl and F2 region electron density during a ...

    African Journals Online (AJOL)

    This paper investigates the variation in the F1 and F2 region electron density during a geomagnetic activity, at East Asian mid-latitude stations. In this analysis, we have employed D(foF1) and D(foF2) representing deviation of the critical frequency for the F1 and F2 ionospheric regions respectively. The F1 region appears to ...

  12. Electronic properties and charge density of BexZn1−xTe alloys

    Indian Academy of Sciences (India)

    Mater. Sci., Vol. 34, No. 3, June 2011, pp. 499–506. c Indian Academy of Sciences. Electronic properties and charge density of BexZn1−xTe alloys. C B SWARNKAR†, U PALIWAL, N N PATEL‡ and K B JOSHI. ∗. Department of Physics, M.L. Sukhadia University, Udaipur 313 001, India. †Department of Physics, S.G.G. Govt.

  13. Tracing the Fingerprint of Chemical Bonds within the Electron Densities of Hydrocarbons: A Comparative Analysis of the Optimized and the Promolecule Densities.

    Science.gov (United States)

    Keyvani, Zahra Alimohammadi; Shahbazian, Shant; Zahedi, Mansour

    2016-10-18

    The equivalence of the molecular graphs emerging from the comparative analysis of the optimized and the promolecule electron densities in two hundred and twenty five unsubstituted hydrocarbons was recently demonstrated [Keyvani et al. Chem. Eur. J. 2016, 22, 5003]. Thus, the molecular graph of an optimized molecular electron density is not shaped by the formation of the C-H and C-C bonds. In the present study, to trace the fingerprint of the C-H and C-C bonds in the electron densities of the same set of hydrocarbons, the amount of electron density and its Laplacian at the (3, -1) critical points associated with these bonds are derived from both optimized and promolecule densities, and compared in a newly proposed comparative analysis. The analysis not only conforms to the qualitative picture of the electron density build up between two atoms upon formation of a bond in between, but also quantifies the resulting accumulation of the electron density at the (3, -1) critical points. The comparative analysis also reveals a unified mode of density accumulation in the case of 2318 studied C-H bonds, but various modes of density accumulation are observed in the case of 1509 studied C-C bonds and they are classified into four groups. The four emerging groups do not always conform to the traditional classification based on the bond orders. Furthermore, four C-C bonds described as exotic bonds in previous studies, for example the inverted C-C bond in 1,1,1-propellane, are naturally distinguished from the analysis. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Measurements of transient electron density distributions by femtosecond X-ray diffraction; Messungen transienter Elektronendichteverteilungen durch Femtosekunden-Roentgenbeugung

    Energy Technology Data Exchange (ETDEWEB)

    Freyer, Benjamin

    2013-05-02

    This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

  15. Correlation energy, correlated electron density, and exchange-correlation potential in some spherically confined atoms.

    Science.gov (United States)

    Vyboishchikov, Sergei F

    2016-12-05

    We report correlation energies, electron densities, and exchange-correlation potentials obtained from configuration interaction and density functional calculations on spherically confined He, Be, Be(2+) , and Ne atoms. The variation of the correlation energy with the confinement radius Rc is relatively small for the He, Be(2+) , and Ne systems. Curiously, the Lee-Yang-Parr (LYP) functional works well for weak confinements but fails completely for small Rc . However, in the neutral beryllium atom the CI correlation energy increases markedly with decreasing Rc . This effect is less pronounced at the density-functional theory level. The LYP functional performs very well for the unconfined Be atom, but fails badly for small Rc . The standard exchange-correlation potentials exhibit significant deviation from the "exact" potential obtained by inversion of Kohn-Sham equation. The LYP correlation potential behaves erratically at strong confinements. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  16. HF produced ionospheric electron density irregularities diagnosed by UHF radio star scintillations

    Science.gov (United States)

    Frey, A.; Gordon, W. E.

    1982-01-01

    Three observations of radio star intensity fluctuations at UHF are reported for HF ionospheric modification experiments carried out at the Arecibo Observatory. Two observations at 430 MHz and one at 1400 MHz suggest that the the thin phase screen theory is a good approximation to the observed power spectra. It is noted, however, that the theory has to be extended to include antenna filtering. This type of filtering is important for UHF radio star scintillations since the antenna usually has a narrow beamwidth. HF power densities of less than 37 microwatts/sq m incident on the ionosphere give rise to electron density irregularities larger than 13% of the ambient density (at 260 km) having scale sizes of approximately 510 m perpendicular to the geomagnetic field. The irregularities are found to form within 20-25 s after the HF power is turned on. The drift velocities of the irregularities can be estimated from the observed power spectra.

  17. Grand canonical electronic density-functional theory: Algorithms and applications to electrochemistry

    Science.gov (United States)

    Sundararaman, Ravishankar; Goddard, William A.; Arias, Tomas A.

    2017-03-01

    First-principles calculations combining density-functional theory and continuum solvation models enable realistic theoretical modeling and design of electrochemical systems. When a reaction proceeds in such systems, the number of electrons in the portion of the system treated quantum mechanically changes continuously, with a balancing charge appearing in the continuum electrolyte. A grand-canonical ensemble of electrons at a chemical potential set by the electrode potential is therefore the ideal description of such systems that directly mimics the experimental condition. We present two distinct algorithms: a self-consistent field method and a direct variational free energy minimization method using auxiliary Hamiltonians (GC-AuxH), to solve the Kohn-Sham equations of electronic density-functional theory directly in the grand canonical ensemble at fixed potential. Both methods substantially improve performance compared to a sequence of conventional fixed-number calculations targeting the desired potential, with the GC-AuxH method additionally exhibiting reliable and smooth exponential convergence of the grand free energy. Finally, we apply grand-canonical density-functional theory to the under-potential deposition of copper on platinum from chloride-containing electrolytes and show that chloride desorption, not partial copper monolayer formation, is responsible for the second voltammetric peak.

  18. Retrieval of Electron Density Profile for KOMPSAT-5 GPS Radio Occultation

    Directory of Open Access Journals (Sweden)

    Woo-Kyoung Lee

    2007-12-01

    Full Text Available The AOPOD (Atmosphere Occultation and Precision Orbit Determination system, the secondary payload of KOMPSAT (KOrea Multi-Purpose SATellite-5 scheduled to be launched in 2010, shall provide GPS radio occultation data. In this paper, we simulated the GPS radio occultation characteristic of KOMPSAT-5 and retrieved electron density profiles using KROPS (KASI Radio Occultation Processing Software. The electron density retrieved from CHAMP (CHAllenging Minisatellite Payload GPS radio occultation data on June 20, 2004 was compared with IRI (International Reference Ionosphere - 2001, PLP (Planar Langmuir Probe, and ionosonde measurements. When the result was compared with ionosonde measurements, the discrepancies were 5 km on the F_2 peak height (hmF_2 and 3×10^{10} el/m^3 on the electron density of the F_2 peak height (NmF_2. By comparing with the Langmuir Probe measurements of CHAMP satellite (PLP, both agrees with 1.6×10^{11} el/m^3 at the height of 365.6 km.

  19. Polyquant CT: direct electron and mass density reconstruction from a single polyenergetic source

    Science.gov (United States)

    Mason, Jonathan H.; Perelli, Alessandro; Nailon, William H.; Davies, Mike E.

    2017-11-01

    Quantifying material mass and electron density from computed tomography (CT) reconstructions can be highly valuable in certain medical practices, such as radiation therapy planning. However, uniquely parameterising the x-ray attenuation in terms of mass or electron density is an ill-posed problem when a single polyenergetic source is used with a spectrally indiscriminate detector. Existing approaches to single source polyenergetic modelling often impose consistency with a physical model, such as water-bone or photoelectric-Compton decompositions, which will either require detailed prior segmentation or restrictive energy dependencies, and may require further calibration to the quantity of interest. In this work, we introduce a data centric approach to fitting the attenuation with piecewise-linear functions directly to mass or electron density, and present a segmentation-free statistical reconstruction algorithm for exploiting it, with the same order of complexity as other iterative methods. We show how this allows both higher accuracy in attenuation modelling, and demonstrate its superior quantitative imaging, with numerical chest and metal implant data, and validate it with real cone-beam CT measurements.

  20. Estimation of dislocation density from precession electron diffraction data using the Nye tensor.

    Science.gov (United States)

    Leff, A C; Weinberger, C R; Taheri, M L

    2015-06-01

    The Nye tensor offers a means to estimate the geometrically necessary dislocation density of a crystalline sample based on measurements of the orientation changes within individual crystal grains. In this paper, the Nye tensor theory is applied to precession electron diffraction automated crystallographic orientation mapping (PED-ACOM) data acquired using a transmission electron microscope (TEM). The resulting dislocation density values are mapped in order to visualize the dislocation structures present in a quantitative manner. These density maps are compared with other related methods of approximating local strain dependencies in dislocation-based microstructural transitions from orientation data. The effect of acquisition parameters on density measurements is examined. By decreasing the step size and spot size during data acquisition, an increasing fraction of the dislocation content becomes accessible. Finally, the method described herein is applied to the measurement of dislocation emission during in situ annealing of Cu in TEM in order to demonstrate the utility of the technique for characterizing microstructural dynamics. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Two-dimensional electron density measurement of pulsed positive primary streamer discharge in atmospheric-pressure air

    Science.gov (United States)

    Inada, Yuki; Aono, Kaiho; Ono, Ryo; Kumada, Akiko; Hidaka, Kunihiko; Maeyama, Mitsuaki

    2017-05-01

    Elucidating the electron density of streamer discharges propagating in atmospheric-pressure air is critical for achieving a systematic understanding of the production mechanisms of reactive species. Using Shack-Hartmann-type laser wavefront sensors with a temporal resolution of 2 ns, we carried out single-shot two-dimensional electron density measurements for positive primary streamers generated in a 13 mm air gap between pin-to-plate electrodes. The electron density over the positive primary streamers decayed from 1015 to {{10}14}\\text{c}{{\\text{m}}-3} during the propagation. The decay time constant of the electron density in the primary streamer channels was estimated to be  ˜2 ns. The distribution widths of the electron density were in good agreement with those of the light emission, typically ranging from 0.8 to 1.5 mm.

  2. Plasma Wave and Electron Density Structure Observed in the Cusp with a Dual-Rocket Experiment

    Science.gov (United States)

    Colpitts, C. A.; Labelle, J. W.; Kletzing, C.; Bounds, S.; Cairns, I.

    2008-12-01

    The Twin Rockets to Investigate Cusp Electrodynamics (TRICE) were launched on December 10, 2007, from Andoya Research Range in Andenes, Norway, into the active cusp. Both payloads traveled north over Svalbard, with one payload reaching an apogee of ~1100 km, and the other reaching ~600 km. The payloads were separated by 100-400 km during the main portion of the flight. Both payloads included waveform receivers with 5 MHz bandwidth. These recorded several distinct types of auroral waves including whistler mode waves below ~1000 kHz and Langmuir-upper hybrid waves at 300-3000 kHz for several hundred km. Both payloads concurrently encountered a distinct period of Langmuir turbulence. Clearly defined wave cutoffs provide measurements of electron density and reveal significant density structure with density enhancements having amplitudes up to 100 percent and scale sizes from meters to tens of kilometers. Analysis of the inferred density profiles using windowed Fourier Transforms or Lomb-Scargle periodograms generates dynamic spectra of the density, which provide estimates of the spectral composition of the density irregularities for time intervals sufficiently short that the stationarity of the spectra can be investigated. The large-scale structures through which the two payloads propagated were measured by both the EISCAT and SuperDARN radars as well as by all-sky cameras operated at Longyearbyen and Ny-Alesund on Svalbard. Using this data when available, comparison of the density irregularity waveforms and spectra from the two flights is studied in relation to spatial and altitude variations of the turbulence. This examination of wave and density structures and the large scale formations with which they are associated will add to the understanding of the large scale electrodynamics of the cusp region.

  3. Measurement of electrons from albedo neutron decay and neutron density in near-Earth space.

    Science.gov (United States)

    Li, Xinlin; Selesnick, Richard; Schiller, Quintin; Zhang, Kun; Zhao, Hong; Baker, Daniel N; Temerin, Michael A

    2017-12-21

    The Galaxy is filled with cosmic-ray particles, mostly protons with kinetic energies greater than hundreds of megaelectronvolts. Around Earth, trapped energetic protons, electrons and other particles circulate at altitudes from about 500 to 40,000 kilometres in the Van Allen radiation belts. Soon after these radiation belts were discovered six decades ago, it was recognized that the main source of inner-belt protons (with kinetic energies of tens to hundreds of megaelectronvolts) is cosmic-ray albedo neutron decay (CRAND). In this process, cosmic rays that reach the upper atmosphere interact with neutral atoms to produce albedo neutrons, which, being prone to β-decay, are a possible source of geomagnetically trapped protons and electrons. These protons would retain most of the kinetic energy of the neutrons, while the electrons would have lower energies, mostly less than one megaelectronvolt. The viability of CRAND as an electron source has, however, been uncertain, because measurements have shown that the electron intensity in the inner Van Allen belt can vary greatly, while the neutron-decay rate should be almost constant. Here we report measurements of relativistic electrons near the inner edge of the inner radiation belt. We demonstrate that the main source of these electrons is indeed CRAND, and that this process also contributes to electrons in the inner belt elsewhere. Furthermore, measurement of the intensity of electrons generated by CRAND provides an experimental determination of the neutron density in near-Earth space-2 × 10-9 per cubic centimetre-confirming theoretical estimates.

  4. Measurement of electrons from albedo neutron decay and neutron density in near-Earth space

    Science.gov (United States)

    Li, Xinlin; Selesnick, Richard; Schiller, Quintin; Zhang, Kun; Zhao, Hong; Baker, Daniel N.; Temerin, Michael A.

    2017-12-01

    The Galaxy is filled with cosmic-ray particles, mostly protons with kinetic energies greater than hundreds of megaelectronvolts. Around Earth, trapped energetic protons, electrons and other particles circulate at altitudes from about 500 to 40,000 kilometres in the Van Allen radiation belts. Soon after these radiation belts were discovered six decades ago, it was recognized that the main source of inner-belt protons (with kinetic energies of tens to hundreds of megaelectronvolts) is cosmic-ray albedo neutron decay (CRAND). In this process, cosmic rays that reach the upper atmosphere interact with neutral atoms to produce albedo neutrons, which, being prone to β-decay, are a possible source of geomagnetically trapped protons and electrons. These protons would retain most of the kinetic energy of the neutrons, while the electrons would have lower energies, mostly less than one megaelectronvolt. The viability of CRAND as an electron source has, however, been uncertain, because measurements have shown that the electron intensity in the inner Van Allen belt can vary greatly, while the neutron-decay rate should be almost constant. Here we report measurements of relativistic electrons near the inner edge of the inner radiation belt. We demonstrate that the main source of these electrons is indeed CRAND, and that this process also contributes to electrons in the inner belt elsewhere. Furthermore, measurement of the intensity of electrons generated by CRAND provides an experimental determination of the neutron density in near-Earth space—2 × 10‑9 per cubic centimetre—confirming theoretical estimates.

  5. Weak-beam scanning transmission electron microscopy for quantitative dislocation density measurement in steels.

    Science.gov (United States)

    Yoshida, Kenta; Shimodaira, Masaki; Toyama, Takeshi; Shimizu, Yasuo; Inoue, Koji; Yoshiie, Toshimasa; Milan, Konstantinovic J; Gerard, Robert; Nagai, Yasuyoshi

    2017-04-01

    To evaluate dislocations induced by neutron irradiation, we developed a weak-beam scanning transmission electron microscopy (WB-STEM) system by installing a novel beam selector, an annular detector, a high-speed CCD camera and an imaging filter in the camera chamber of a spherical aberration-corrected transmission electron microscope. The capabilities of the WB-STEM with respect to wide-view imaging, real-time diffraction monitoring and multi-contrast imaging are demonstrated using typical reactor pressure vessel steel that had been used in an European nuclear reactor for 30 years as a surveillance test piece with a fluence of 1.09 × 1020 neutrons cm-2. The quantitatively measured size distribution (average loop size = 3.6 ± 2.1 nm), number density of the dislocation loops (3.6 × 1022 m-3) and dislocation density (7.8 × 1013 m m-3) were carefully compared with the values obtained via conventional weak-beam transmission electron microscopy studies. In addition, cluster analysis using atom probe tomography (APT) further demonstrated the potential of the WB-STEM for correlative electron tomography/APT experiments. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  6. Quasi-optical design for systems to diagnose the electron temperature and density fluctuations on EAST

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qifo; Liu, Yong; Zhao, Hailin, E-mail: zhaohailin@ipp.ac.cn; Zhou, Tianfu; Ti, Ang; Hu, Liqun [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-11-15

    A system to simultaneously diagnose the electron temperature and density fluctuations is proposed for Experimental Advanced Superconducting Tokamak device. This system includes a common quasi-optical antenna, a correlation electron cyclotron emission (CECE) system that is used to measure the electron temperature fluctuations and a Doppler backscattering (DBS) system that is used to measure the electron density fluctuations. The frequency range of the proposed CECE system is 108-120 GHz, and this corresponds to a radial coverage of normalized radius ((R − R{sub 0})/a, R{sub 0} = 1850 mm, a = 450 mm) from 0.2 to 0.67 for the plasma operation with a toroidal magnetic field of 2.26 T. This paper focuses on the design of the quasi-optical antenna and aims at optimizing the poloidal resolution for different frequency bands. An optimum result gives the beam radius for the CECE system of 13-15 mm and this corresponds to a wave number range of k{sub θ} < 2.4 cm{sup −1}. The beam radius is 20-30 mm for V band (50-75 GHz) and 15-20 mm for W band (75-110 GHz).

  7. Counterintuitive electron localisation from density-functional theory with polarisable solvent models

    Energy Technology Data Exchange (ETDEWEB)

    Dale, Stephen G., E-mail: sdale@ucmerced.edu [Chemistry and Chemical Biology, School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343 (United States); Johnson, Erin R., E-mail: erin.johnson@dal.ca [Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2 (Canada)

    2015-11-14

    Exploration of the solvated electron phenomena using density-functional theory (DFT) generally results in prediction of a localised electron within an induced solvent cavity. However, it is well known that DFT favours highly delocalised charges, rendering the localisation of a solvated electron unexpected. We explore the origins of this counterintuitive behaviour using a model Kevan-structure system. When a polarisable-continuum solvent model is included, it forces electron localisation by introducing a strong energetic bias that favours integer charges. This results in the formation of a large energetic barrier for charge-hopping and can cause the self-consistent field to become trapped in local minima thus converging to stable solutions that are higher in energy than the ground electronic state. Finally, since the bias towards integer charges is caused by the polarisable continuum, these findings will also apply to other classical polarisation corrections, as in combined quantum mechanics and molecular mechanics (QM/MM) methods. The implications for systems beyond the solvated electron, including cationic DNA bases, are discussed.

  8. High-quality stable electron beams from laser wakefield acceleration in high density plasma

    Directory of Open Access Journals (Sweden)

    B. S. Rao

    2014-01-01

    Full Text Available High-quality, stable electron beams are produced from self-injected laser wakefield acceleration using the interaction of moderate 3 TW, 45 fs duration Ti:sapphire laser pulses with high density (>5×10^{19}   cm^{−3} helium gas jet plasma. The electron beam has virtually background-free quasimonoenergetic distribution with energy 35.6_{−2.5}^{+3.9}  MeV, charge 3.8_{−1.2}^{+2.8}  pC, divergence and pointing variation ∼10  mrad. The stable and high quality of the electron beam opens an easy way for applications of the laser wakefield accelerator in the future, particularly due to the widespread availability of sub-10 TW class lasers with a number of laser plasma laboratories around the world.

  9. Generation of neutral and high-density electron-positron pair plasmas in the laboratory.

    Science.gov (United States)

    Sarri, G; Poder, K; Cole, J M; Schumaker, W; Di Piazza, A; Reville, B; Dzelzainis, T; Doria, D; Gizzi, L A; Grittani, G; Kar, S; Keitel, C H; Krushelnick, K; Kuschel, S; Mangles, S P D; Najmudin, Z; Shukla, N; Silva, L O; Symes, D; Thomas, A G R; Vargas, M; Vieira, J; Zepf, M

    2015-04-23

    Electron-positron pair plasmas represent a unique state of matter, whereby there exists an intrinsic and complete symmetry between negatively charged (matter) and positively charged (antimatter) particles. These plasmas play a fundamental role in the dynamics of ultra-massive astrophysical objects and are believed to be associated with the emission of ultra-bright gamma-ray bursts. Despite extensive theoretical modelling, our knowledge of this state of matter is still speculative, owing to the extreme difficulty in recreating neutral matter-antimatter plasmas in the laboratory. Here we show that, by using a compact laser-driven setup, ion-free electron-positron plasmas with unique characteristics can be produced. Their charge neutrality (same amount of matter and antimatter), high-density and small divergence finally open up the possibility of studying electron-positron plasmas in controlled laboratory experiments.

  10. The study of dynamics of electrons in the presence of large current densities; Etude de la dynamique des electrons en presence de fortes densites de courant

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, G

    2007-11-15

    The runaway electron effect is considered in different fields: nuclear fusion, or the heating of the solar corona. In this thesis, we are interested in runaway electrons in the ionosphere. We consider the issue of electrons moving through an ionospheric gas of positive ions and neutrals under the influence of a parallel electric field. We develop a kinetic model of collisions including electrons/electrons, electrons/ions and electrons/neutrals collisions. We use a Fokker-Planck approach to describe binary collisions between charged particles with a long-range interaction. A computational example is given illustrating the approach to equilibrium and the impact of the different terms. Then, a static electric field is applied in a new sample run. In this run, the electrons move in the z direction, parallel to the electric field. The first results show that all the electron distribution functions are non-Maxwellian. Furthermore, runaway electrons can carry a significant part of the total current density up to 20% of the total current density. Nevertheless, we note that the divergence free of the current density is not conserved. We introduce major changes in order to take into account the variation of the different moments of the ion distribution functions. We observe that the electron distribution functions are still non-Maxwellian. Runaway electrons are created and carry the current density. The core distribution stay at rest. As these electrons undergo less collisions, they increase the plasma conductivity. We make a parametric study. We fit the electron distribution function by two Maxwellian. We show that the time to reach the maximal current density is a key point. Thus, when we increase this time, we modify the temperatures. The current density plays a primary role. When the current density increases, all the moments of the distributions increase: electron density and mean velocity of the suprathermal distribution and the electron temperature of the core and

  11. Spatially separated charge densities of electrons and holes in organic-inorganic halide perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dan; Liang, Chunjun, E-mail: chjliang@bjtu.edu.cn, E-mail: zhqhe@bjtu.edu.cn; Zhang, Huimin; You, Fangtian; He, Zhiqun, E-mail: chjliang@bjtu.edu.cn, E-mail: zhqhe@bjtu.edu.cn [Key Laboratory of Luminescence and Optical Information, Ministry of Education, School of Science, Beijing Jiaotong University, Beijing 100044 (China); Zhang, Chunxiu [Information Recording Materials Lab, Beijing Institute of Graphic Communication, Beijing 102600 (China)

    2015-02-21

    Solution-processable methylammonium lead trihalide perovskites exhibit remarkable high-absorption and low-loss properties for solar energy conversion. Calculation from density functional theory indicates the presence of non-equivalent halogen atoms in the unit cell because of the specific orientation of the organic cation. Considering the 〈100〉 orientation as an example, I{sub 1}, one of the halogen atoms, differs from the other iodine atoms (I{sub 2} and I{sub 3}) in terms of its interaction with the organic cation. The valance-band-maximum (VBM) and conduction-band-minimum (CBM) states are derived mainly from 5p orbital of I{sub 1} atom and 6p orbital of Pb atom, respectively. The spatially separated charge densities of the electrons and holes justify the low recombination rate of the pure iodide perovskite. Chlorine substitution further strengthens the unique position of the I{sub 1} atom, leading to more localized charge density around the I{sub 1} atom and less charge density around the other atoms at the VBM state. The less overlap of charge densities between the VBM and CBM states explains the relatively lower carrier recombination rate of the iodine-chlorine mixed perovskite. Chlorine substitution significantly reduces the effective mass at a direction perpendicular to the Pb-Cl bond and organic axis, enhancing the carrier transport property of the mixed perovskite in this direction.

  12. The 10 sheath-accelerated electrons and ions. [atmospheric models of plasma sheaths and ionospheric electron density

    Science.gov (United States)

    Shawhan, S. D.

    1975-01-01

    A model is presented that suggests that plasma sheaths form between the ionospheric plasma moving with Io and the ambient plasma corotating with Jupiter. Potentials across these sheaths could be as high as 580 kV which is the motional emf across Io's ionosphere. Electrons and ions can be accelerated across these sheaths. The sheaths may exist at the top of the Io ionosphere with characteristic thicknesses of 1/4 kilometers. The model is consistent with the Pioneer observations of 0.15 MeV electrons at the inner edge of Io's L-shell and the enhanced number density of low-energy protons at the outer edge. Ion sputtering of the Io surface is discussed and may explain the presence of atomic hydrogen and sodium in the vicinity of Io. Also these accelerated particles may be important to the formation of the Io ionosphere. High electron flux which may lead to decametric radio emissions, Jovian atmospheric heating and optical and X-ray emissions is also discussed.

  13. Pairing and unpairing electron densities in organic systems: Two-electron three center through space and through bonds interactions

    Energy Technology Data Exchange (ETDEWEB)

    Lobayan, Rosana M., E-mail: rmlb@exa.unne.edu.ar [Departamento de Física, Facultad de Ciencias Exactas, Naturales y Agrimensura, Universidad Nacional del Nordeste, 3400, Corrientes (Argentina); Bochicchio, Roberto C., E-mail: rboc@df.uba.ar [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, and IFIBA, CONICET, Ciudad Universitaria, 1428, Buenos Aires (Argentina)

    2014-05-07

    Two-electron three-center bonding interactions in organic ions like methonium (CH{sub 5}{sup +}), ethonium (C{sub 2}H{sub 7}{sup +}), and protonated alkanes n−C{sub 4}H{sub 11}{sup +} isomers (butonium cations) are described and characterized within the theoretical framework of the topological analysis of the electron density decomposition into its effectively paired and unpaired contributions. These interactions manifest in some of this type of systems as a concentration of unpaired electron cloud around the bond paths, in contrast to the well known paradigmatic boron hydrids in which it is not only concentrated close to the atomic nucleus and the bond paths but out of them and over the region defined by the involved atoms as a whole. This result permits to propose an attempt of classification for these interactions based in such manifestations. In the first type, it is called as interactions through bonds and in the second type as interactions through space type.

  14. Electron densities by the maximum entropy method (MEM) for various types of prior densities: a case study on three amino acids and a tripeptide.

    Science.gov (United States)

    Prathapa, Siriyara Jagannatha; Mondal, Swastik; van Smaalen, Sander

    2013-04-01

    Dynamic model densities according to Mondal et al. [(2012), Acta Cryst. A68, 568-581] are presented for independent atom models (IAM), IAMs after high-order refinements (IAM-HO), invariom (INV) models and multipole (MP) models of α-glycine, DL-serine, L-alanine and Ala-Tyr-Ala at T ≃ 20 K. Each dynamic model density is used as prior in the calculation of electron density according to the maximum entropy method (MEM). We show that at the bond-critical points (BCPs) of covalent C-C and C-N bonds the IAM-HO and INV priors produce reliable MEM density maps, including reliable values for the density and its Laplacian. The agreement between these MEM density maps and dynamic MP density maps is less good for polar C-O bonds, which is explained by the large spread of values of topological descriptors of C-O bonds in static MP densities. The density and Laplacian at BCPs of hydrogen bonds have similar values in MEM density maps obtained with all four kinds of prior densities. This feature is related to the smaller spatial variation of the densities in these regions, as expressed by small magnitudes of the Laplacians and the densities. It is concluded that the use of the IAM-HO prior instead of the IAM prior leads to improved MEM density maps. This observation shows interesting parallels to MP refinements, where the use of the IAM-HO as an initial model is the accepted procedure for solving MP parameters. A deconvolution of thermal motion and static density that is better than the deconvolution of the IAM appears to be necessary in order to arrive at the best MP models as well as at the best MEM densities.

  15. Directed high-power THz radiation from transverse laser wakefield excited in an electron density filament

    Science.gov (United States)

    Kalmykov, Serge; Englesbe, Alexander; Elle, Jennifer; Domonkos, Matthew; Schmitt-Sody, Andreas

    2017-10-01

    A tightly focused femtosecond, weakly relativistic laser pulse partially ionizes the ambient gas, creating a string (a ``filament'') of electron density, locally reducing the nonlinear index and compensating for the self-focusing effect caused by bound electrons. While maintaining the filament over many Rayleigh lengths, the pulse drives inside it a three-dimensional (3D) wave of charge separation - the plasma wake. If the pulse waist size is much smaller than the Langmuir wavelength, electron current in the wake is mostly transverse. Electrons, driven by the wake across the sharp radial boundary of the filament, lose coherence within 2-3 periods of wakefield oscillations, and the wake decays. The laser pulse is thus accompanied by a short-lived, almost aperiodic electron current coupled to the sharp index gradient. The comprehensive 3D hydrodynamic model shows that this structure emits a broad-band THz radiation, with the highest power emitted in the near-forward direction. The THz radiation pattern contains information on wake currents surrounding the laser pulse, thus serving as an all-optical diagnostic tool. The results are tested in cylindrical and full 3D PIC simulations using codes WAKE and EPOCH.

  16. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics.

    Science.gov (United States)

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Jaung, Jae Yun; Kim, Yong-Hoon; Park, Sung Kyu

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  17. Recoverable Wire-Shaped Supercapacitors with Ultrahigh Volumetric Energy Density for Multifunctional Portable and Wearable Electronics.

    Science.gov (United States)

    Shi, Minjie; Yang, Cheng; Song, Xuefeng; Liu, Jing; Zhao, Liping; Zhang, Peng; Gao, Lian

    2017-05-24

    Wire-shaped supercapacitors (SCs) based on shape memory materials are of considerable interest for next-generation portable and wearable electronics. However, the bottleneck in this field is how to develop the devices with excellent electrochemical performance while well-maintaining recoverability and flexibility. Herein, a unique asymmetric electrode concept is put forward to fabricate smart wire-shaped SCs with ultrahigh energy density, which is realized by using porous carbon dodecahedra coated on NiTi alloy wire and flexible graphene fiber as yarn electrodes. Notably, the wire-shaped SCs not only exhibit high flexibility that can be readily woven into real clothing but also represent the available recoverable ability. When irreversible plastic deformations happen, the deformed shape of the devices can automatically resume the initial predesigned shape in a warm environment (about 35 °C). More importantly, the wire-shaped SCs act as efficient energy storage devices, which display high volumetric energy density (8.9 mWh/cm(3)), volumetric power density (1080 mW/cm(3)), strong durability in multiple mechanical states, and steady electrochemical behavior after repeated shape recovery processes. Considering their relative facile fabrication technology and excellent electrochemical performance, this asymmetric electrode strategy produced smart wire-shaped supercapacitors desirable for multifunctional portable and wearable electronics.

  18. The effect of density fluctuations on electron cyclotron beam broadening and implications for ITER

    Science.gov (United States)

    Snicker, A.; Poli, E.; Maj, O.; Guidi, L.; Köhn, A.; Weber, H.; Conway, G.; Henderson, M.; Saibene, G.

    2018-01-01

    We present state-of-the-art computations of propagation and absorption of electron cyclotron waves, retaining the effects of scattering due to electron density fluctuations. In ITER, injected microwaves are foreseen to suppress neoclassical tearing modes (NTMs) by driving current at the q=2 and q=3/2 resonant surfaces. Scattering of the beam can spoil the good localization of the absorption and thus impair NTM control capabilities. A novel tool, the WKBeam code, has been employed here in order to investigate this issue. The code is a Monte Carlo solver for the wave kinetic equation and retains diffraction, full axisymmetric tokamak geometry, determination of the absorption profile and an integral form of the scattering operator which describes the effects of turbulent density fluctuations within the limits of the Born scattering approximation. The approach has been benchmarked against the paraxial WKB code TORBEAM and the full-wave code IPF-FDMC. In particular, the Born approximation is found to be valid for ITER parameters. In this paper, we show that the radiative transport of EC beams due to wave scattering in ITER is diffusive unlike in present experiments, thus causing up to a factor of 2–4 broadening in the absorption profile. However, the broadening depends strongly on the turbulence model assumed for the density fluctuations, which still has large uncertainties.

  19. Analysis of local dislocation densities in cold-rolled alloy 690 using transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Tae-Young; Kim, Sung Woo; Hwang, Seong Sik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Service failure of alloy 690 in NPP has not been reported. However, some research groups reported that primary water stress corrosion cracking (PWSCC) occurred in severely cold-rolled alloy 690. Transgranular craking was also reported in coll-rolled alloy 690 with a banded structure. In order to understand the effect of cold rolling on the cracking of alloy 690, many research groups have focused on the local strain and the cracked carbide induced by cold-rolling, by using electron backscatter diffraction (EBSD). Transmission electron microscopy (TEM) has been widely used to characterize structural materials because this technique has superior spatial resolution and allows for the analysis of crystallographic and chemical information. The aim of the present study is to understand the mechanism of the abnormally high crack growth rate (CGR) in cold-rolled alloy 690 with a banded structure. The local dislocation density was measured by TEM to confirm the effects of local strain on the stress corrosion cracking (SCC) of alloy 690 with a banded structure. The effects of intragranular carbides on the SCC were also evaluated in this study. The local dislocation densities were directly measured using TEM to understand the effect of local strain on the SCC of Ni-based alloy 690 with a banded structure. The dislocation densities in the interior of the grains sharply increased in highly cold-rolled specimens due to intragranular carbide, which acted as a dislocation source.

  20. Structural, electronic, and thermodynamic properties of curium dioxide: Density functional theory calculations

    Science.gov (United States)

    Hou, Ling; Li, Wei-Dong; Wang, Fangwei; Eriksson, Olle; Wang, Bao-Tian

    2017-12-01

    We present a systematic investigation of the structural, magnetic, electronic, mechanical, and thermodynamic properties of CmO2 with the local density approximation (LDA)+U and the generalized gradient approximation (GGA)+U approaches. The strong Coulomb repulsion and the spin-orbit coupling (SOC) effects on the lattice structures, electronic density of states, and band gaps are carefully studied, and compared with other A O2 (A =U , Np, Pu, and Am). The ferromagnetic configuration with half-metallic character is predicted to be energetically stable while a charge-transfer semiconductor is predicted for the antiferromagnetic configuration. The elastic constants and phonon spectra show that the fluorite structure is mechanically and dynamically stable. Based on the first-principles phonon density of states, the lattice vibrational energy is calculated using the quasiharmonic approximation. Then, the Gibbs free energy, thermal expansion coefficient, specific heat, and entropy are obtained and compared with experimental data. The mode Grüneisen parameters are presented to analyze the anharmonic properties. The Slack relation is applied to obtain the lattice thermal conductivity in temperature range of 300-1600 K. The phonon group velocities are also calculated to investigate the heat transfer. For all these properties, if available, we compare the results of CmO2 with other A O2 .

  1. Reconstructing Regional Ionospheric Electron Density: A Combined Spherical Slepian Function and Empirical Orthogonal Function Approach

    Science.gov (United States)

    Farzaneh, Saeed; Forootan, Ehsan

    2017-11-01

    The computerized ionospheric tomography is a method for imaging the Earth's ionosphere using a sounding technique and computing the slant total electron content (STEC) values from data of the global positioning system (GPS). The most common approach for ionospheric tomography is the voxel-based model, in which (1) the ionosphere is divided into voxels, (2) the STEC is then measured along (many) satellite signal paths, and finally (3) an inversion procedure is applied to reconstruct the electron density distribution of the ionosphere. In this study, a computationally efficient approach is introduced, which improves the inversion procedure of step 3. Our proposed method combines the empirical orthogonal function and the spherical Slepian base functions to describe the vertical and horizontal distribution of electron density, respectively. Thus, it can be applied on regional and global case studies. Numerical application is demonstrated using the ground-based GPS data over South America. Our results are validated against ionospheric tomography obtained from the constellation observing system for meteorology, ionosphere, and climate (COSMIC) observations and the global ionosphere map estimated by international centers, as well as by comparison with STEC derived from independent GPS stations. Using the proposed approach, we find that while using 30 GPS measurements in South America, one can achieve comparable accuracy with those from COSMIC data within the reported accuracy (1 × 1011 el/cm3) of the product. Comparisons with real observations of two GPS stations indicate an absolute difference is less than 2 TECU (where 1 total electron content unit, TECU, is 1016 electrons/m2).

  2. First assimilations of COSMIC radio occultation data into the Electron Density Assimilative Model (EDAM

    Directory of Open Access Journals (Sweden)

    M. J. Angling

    2008-02-01

    Full Text Available Ground based measurements of slant total electron content (TEC can be assimilated into ionospheric models to produce 3-D representations of ionospheric electron density. The Electron Density Assimilative Model (EDAM has been developed for this purpose. Previous tests using EDAM and ground based data have demonstrated that the information on the vertical structure of the ionosphere is limited in this type of data. The launch of the COSMIC satellite constellation provides the opportunity to use radio occultation data which has more vertical information. EDAM assimilations have been run for three time periods representing quiet, moderate and disturbed geomagnetic conditions. For each run, three data sets have been ingested – only ground based data, only COSMIC data and both ground based and COSMIC data. The results from this preliminary study show that both ground and space based data are capable of improving the representation of the vertical structure of the ionosphere. However, the analysis is limited by the incomplete deployment of the COSMIC constellation and the use of auto-scaled ionosonde data. The first of these can be addressed by repeating this type of study once full deployment has been achieved. The latter requires the manual scaling of ionosonde data; ideally an agreed data set would be scaled and made available to the community to facilitate comparative testing of assimilative models.

  3. Imaging of fast moving electron-density structures in the polar cap

    Directory of Open Access Journals (Sweden)

    C. N. Mitchell

    2007-06-01

    Full Text Available The imaging of fast-moving electron-density structures in the polar cap presents a unique set of challenges that are not encountered in other ionospheric imaging problems. GPS observations of total electron content in the polar cap are sparse compared to other regions in the Northern Hemisphere. Furthermore, the slow relative motion of the satellites across the sky complicates the problem since the velocity of the plasma can be large in comparison and traditional approaches could result in image blurring. This paper presents a Kalman-filter based method that incorporates a forward projection of the solution based on a model plasma drift velocity field. This is the first time that the plasma motion, rather than just integrations of electron density, has been used in an ionospheric imaging algorithm. The motion is derived from the Weimer model of the electric field. It is shown that this novel approach to the implementation of a Kalman filter provides a detailed view of the polar cap ionosphere under severe storm conditions. A case study is given for the October 2003 Halloween storm where verification is provided by incoherent scatter radars.

  4. Pressure-Dependent Electronic and Transport Properties of Bulk Platinum Oxide by Density Functional Theory

    Science.gov (United States)

    Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh; Nekrasov, Kirill A.; Kichigina, Natalia V.

    2018-02-01

    The structural, electronic, and vibrational properties of bulk platinum oxide (PtO) at compressive pressures in the interval from 0 GPa to 35 GPa are investigated using the density functional theory. The calculated electronic band structure of PtO shows poor metallicity at very low density of states on the Fermi level. However, the hybrid pseudopotential calculation yielded 0.78 eV and 1.30 eV direct band and indirect gap, respectively. Importantly, our results predict that PtO has a direct band gap within the framework of HSE06, and it prefers equally zero magnetic order at different pressures. In the Raman spectra, peaks are slightly shifted towards higher frequency with the decrease in pressure. We have also calculated the thermoelectric properties, namely the electronic thermal conductivity and electrical conductivity, with respect to temperature and thermodynamic properties such as entropy, specific heat at constant volume, enthalpy and Gibbs free energy with respect to pressure. The result shows that PtO is a promising candidate for use as a catalyst, in sensors, as a photo-cathode in water electrolysis, for thermal decomposition of inorganic salt and fuel cells.

  5. Controlling Side Chain Density of Electron Donating Polymers for Improving VOC in Polymer Solar Cells

    Science.gov (United States)

    Kim, B. J.; Kim, K. H.; Cho, C. H.; Kang, H.; Yoon, S. C.

    2012-02-01

    The ability to tune the LUMO/HOMO levels of electroactive materials in active layer of polymer solar cells is critical in controlling their optical and electrochemical properties because the HOMO and LUMO offsets between the polymer donor and the electron acceptor strongly affect charge separation and the open circuit voltage (VOC) of a solar cell. Here, we developed two series of electroactive materials for improving VOC in polymer solar cells. First, we enable facile control over the number of solubilizing groups ultimately tethered to the fullerene by tuning the molar ratio between reactants from 1:1 to 1:3, thus producing o-xylenyl C60 mono-, bis-, and tris-adducts (OXCMA, OXCBA, and OXCTA) as electron acceptors with different LUMO levels. As the number of solubilizing groups increased, VOC values of the P3HT-based BHJ solar cells increased from 0.63, 0.83, to 0.98 V. Second, we present a series of novel poly[3-(4-n-octyl)phenylthiophene] (POPT) derivatives (POPT, POPTT, and POTQT) as electron donors with different side-chain density. As a result of lower HOMO levels by decrease in the side-chain density of the polymers, the devices consisting of POPT, POPTT, and POPQT with PCBM showed increased VOC values of 0.58, 0.63, and 0.75 V, respectively.

  6. Pressure-Dependent Electronic and Transport Properties of Bulk Platinum Oxide by Density Functional Theory

    Science.gov (United States)

    Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh; Nekrasov, Kirill A.; Kichigina, Natalia V.

    2017-11-01

    The structural, electronic, and vibrational properties of bulk platinum oxide (PtO) at compressive pressures in the interval from 0 GPa to 35 GPa are investigated using the density functional theory. The calculated electronic band structure of PtO shows poor metallicity at very low density of states on the Fermi level. However, the hybrid pseudopotential calculation yielded 0.78 eV and 1.30 eV direct band and indirect gap, respectively. Importantly, our results predict that PtO has a direct band gap within the framework of HSE06, and it prefers equally zero magnetic order at different pressures. In the Raman spectra, peaks are slightly shifted towards higher frequency with the decrease in pressure. We have also calculated the thermoelectric properties, namely the electronic thermal conductivity and electrical conductivity, with respect to temperature and thermodynamic properties such as entropy, specific heat at constant volume, enthalpy and Gibbs free energy with respect to pressure. The result shows that PtO is a promising candidate for use as a catalyst, in sensors, as a photo-cathode in water electrolysis, for thermal decomposition of inorganic salt and fuel cells.

  7. Charge constrained density functional molecular dynamics for simulation of condensed phase electron transfer reactions.

    Science.gov (United States)

    Oberhofer, Harald; Blumberger, Jochen

    2009-08-14

    We present a plane-wave basis set implementation of charge constrained density functional molecular dynamics (CDFT-MD) for simulation of electron transfer reactions in condensed phase systems. Following the earlier work of Wu and Van Voorhis [Phys. Rev. A 72, 024502 (2005)], the density functional is minimized under the constraint that the charge difference between donor and acceptor is equal to a given value. The classical ion dynamics is propagated on the Born-Oppenheimer surface of the charge constrained state. We investigate the dependence of the constrained energy and of the energy gap on the definition of the charge and present expressions for the constraint forces. The method is applied to the Ru2+-Ru3+ electron self-exchange reaction in aqueous solution. Sampling the vertical energy gap along CDFT-MD trajectories and correcting for finite size effects, a reorganization free energy of 1.6 eV is obtained. This is 0.1-0.2 eV lower than a previous estimate based on a continuum model for solvation. The smaller value for the reorganization free energy can be explained by the fact that the Ru-O distances of the divalent and trivalent Ru hexahydrates are predicted to be more similar in the electron transfer complex than for the separated aqua ions.

  8. Topside ionospheric vertical electron density profile reconstruction using GPS and ionosonde data: possibilities for South Africa

    Directory of Open Access Journals (Sweden)

    P. Sibanda

    2011-02-01

    Full Text Available Successful empirical modeling of the topside ionosphere relies on the availability of good quality measured data. The Alouette, ISIS and Intercosmos-19 satellite missions provided large amounts of topside sounder data, but with limited coverage of relevant geophysical conditions (e.g., geographic location, diurnal, seasonal and solar activity by each individual mission. Recently, methods for inferring the electron density distribution in the topside ionosphere from Global Positioning System (GPS-based total electron content (TEC measurements have been developed. This study is focused on the modeling efforts in South Africa and presents the implementation of a technique for reconstructing the topside ionospheric electron density (Ne using a combination of GPS-TEC and ionosonde measurements and empirically obtained Upper Transition Height (UTH. The technique produces reasonable profiles as determined by the global models already in operation. With the added advantage that the constructed profiles are tied to reliable measured GPS-TEC and the empirically determined upper transition height, the technique offers a higher level of confidence in the resulting Ne profiles.

  9. Topological Properties of Chemical Bonds from Static and Dynamic Electron Densities.

    Science.gov (United States)

    Jagannatha Prathapa, Siriyara; Held, Jeanette; van Smaalen, Sander

    2013-09-01

    Dynamic and static electron densities (EDs) based on the independent spherical atom model (IAM) and multipole (MP) models of crambin were successfully computed, holding no series-termination effects. The densities are compared to EDs of small biological molecules at diverse temperatures. It is outlined that proteins exhibit an intrinsic flexibility, present as frozen disorder at 100 K, in contrast to small molecules. The flexibility of the proteins is reflected by atomic displacement parameters (B-factors), which are considerably larger than for small molecules at 298 K. Thus, an optimal deconvolution of deformation density and thermal motion is not guaranteed, which prevents a free refinement of MP parameters but allows an application of transferable, fixed MP parameters. The analysis of the topological properties, such as the density at bond critical points (BCPs) and the Laplacian, reveals systematic differences between static and dynamic EDs. Zero-point-vibrations, yet present in dynamic EDs at low temperature, affect but marginally the EDs of small molecules. The zero-point-vibrations cause a smearing of the ED, which becomes more pronounced with increasing temperature. Topological properties, primarily the Laplacian, of covalent bonds appear to be more sensitive to effects by temperature and the polarity of the bonds. However, dynamic EDs at ca. 20 K based on MP models provide a good characterization of chemical bonding. Both the density at BCPs and the Laplacian of hydrogen bonds constitute similar values from static and dynamic EDs for all studied temperatures. Deformation densities demonstrate the necessity of the employment of MP parameters in order to comprise the nature of covalent bonds. The character of hydrogen bonds can be roughly pictured by IAM, whereas MP parameters are recommended for a classification of hydrogen bonds beyond a solely interpretation of topological properties.

  10. Behavior of Parameters of Nighttime Electron Density Enhancements of the Ionospheric F2 Layer

    Science.gov (United States)

    Yakovets, Artur; Gordienko, Galina

    2017-04-01

    There is known a wide class of disturbances of the F2-layer of the ionosphere, which are superimposed on the regular diurnal variations of the electron density. Different types of disturbances are characterized by different mechanisms of their generation. Traveling ionospheric disturbances appear to be the most characteristic features of the inhomogeneous structure of the ionosphere. Another type of ionospheric disturbances presents the nighttime electron density enhancements in the ionospheric F2- layer maximum (NmF2). This type of irregularities is described in numerous papers. There is a concept that, in spite of the various mechanisms of ionospheric disturbances generation a response of F2-layer parameters exhibits similar features associated with the upward lift and the simultaneous expansion of the layer and then its subsequent downward movement, including layer compression, which results in the formation of the electron density peak in the layer maximum at the moment of greatest compression. The aim of this study is a verification of this concept on the example of disturbances related with the nighttime electron density enhancements, and the definition of precise quantitative relationships between the variations of different F2-layer parameters for such disturbances. By using the data of the ionospheric vertical sounding in Almaty, (76° 55'E, 43°15'N) during 2001-2012, analysis of the behavior the F2-layer parameters during the night electron density enhancements was carried out within framework of a single concept of effects of various types of ionospheric plasma perturbations in variations of height and half-thickness of the F2-layer, accompanied by increasing and decreasing NmF2 at moments of maximum compression and expansion of the layer. For a quantitative analysis of the parameters of nighttime enhancements we have selected 20 nights characterized by low magnetic activity (Dst> - 50 nT) and evident manifestations of the nighttime electron density

  11. Vacuum expectation values of the current density and energy-momentum tensor for a charged scalar field in curved spacetime with toroidally compactified spatial dimensions

    Science.gov (United States)

    Saharian, Aram; Kotanjyan, Anna; Sargsyan, Hayk; Simonyan, David

    2016-07-01

    The models with compact spatial dimensions appear in a number of fundamental physical theories. In particular, the idea of compactified dimensions has been extensively used in supergravity and superstring theories. In quantum field theory, the modification of the vacuum fluctuations spectrum by the periodicity conditions imposed on the field operator along compact dimensions leads to a number of interesting physical effects. A well known example of this kind, demonstrating the close relation between quantum phenomena and global geometry, is the topological Casimir effect. In models with extra compact dimensions, the Casimir energy creates a nontrivial potential for the compactification radius. This can serve as a stabilization mechanism for moduli fields and for the effective gauge couplings. The Casimir effect has also been considered as a possible origin for the dark energy in Kaluza-Klein-type and braneworld models. In the resent presentation we investigate the effects of the gravity and topology on the local properties of the quantum vacuum for a charged scalar field in the presence of a classical gauge field. Vacuum expectation value of the energy-momentum tensor and current density are investigated for a charged scalar field in dS spacetime with toroidally compact spatial dimensions in the presence of a classical constant gauge field. Due to the nontrivial topology, the latter gives rise to Aharonov-Bohm-like effect on the vacuum characteristics. The vacuum current density, energy density and stresses are even periodic functions of the magnetic flux enclosed by compact dimensions. For small values of the comoving lengths of compact dimensions, compared with the dS curvature radius, the effects of gravity on the topological contributions are small and the expectation values are expressed in terms of the corresponding quantities in the Minkowski bulk by the standard conformal relation. For large values of the comoving lengths, depending on the field mass, two

  12. PIC-simulation of the electron beam interaction with modulated density plasma

    Science.gov (United States)

    Berendeev, E. A.; Dudnikova, G. I.; Efimova, A. A.

    2017-10-01

    In this paper, the processes of electromagnetic radiation generation as a result of the interaction of a relativistic electron beam with hydrogen and argon plasma are studied on the basis of numerical modeling by the particle-in-cells method (PIC). Series of numerical experiments for different background plasma parameters, beam and magnetic field have been performed using modern computer systems with massively parallel architecture. Estimates of the radiation efficiency for both the initially homogeneous plasma and for longitudinal density modulation are obtained. It is shown that the change in the plasma density due to the development of the modulation instability makes it possible to increase substantially the power of the generated sub-THz radiation. The parameters used in numerical experiments correspond to the conditions of laboratory experiments on GOL-3 facility (BINP SB RAS, Novosibirsk, Russia).

  13. Analysis of electronic models for solar cells including energy resolved defect densities

    Energy Technology Data Exchange (ETDEWEB)

    Glitzky, Annegret

    2010-07-01

    We introduce an electronic model for solar cells including energy resolved defect densities. The resulting drift-diffusion model corresponds to a generalized van Roosbroeck system with additional source terms coupled with ODEs containing space and energy as parameters for all defect densities. The system has to be considered in heterostructures and with mixed boundary conditions from device simulation. We give a weak formulation of the problem. If the boundary data and the sources are compatible with thermodynamic equilibrium the free energy along solutions decays monotonously. In other cases it may be increasing, but we estimate its growth. We establish boundedness and uniqueness results and prove the existence of a weak solution. This is done by considering a regularized problem, showing its solvability and the boundedness of its solutions independent of the regularization level. (orig.)

  14. Ionic and electronic transport properties in dense plasmas by orbital-free density functional theory.

    Science.gov (United States)

    Sjostrom, Travis; Daligault, Jérôme

    2015-12-01

    We validate the application of our recent orbital-free density functional theory (DFT) approach [Phys. Rev. Lett. 113, 155006 (2014);] for the calculation of ionic and electronic transport properties of dense plasmas. To this end, we calculate the self-diffusion coefficient, the viscosity coefficient, the electrical and thermal conductivities, and the reflectivity coefficient of hydrogen and aluminum plasmas. Very good agreement is found with orbital-based Kohn-Sham DFT calculations at lower temperatures. Because the computational costs of the method do not increase with temperature, we can produce results at much higher temperatures than is accessible by the Kohn-Sham method. Our results for warm dense aluminum at solid density are inconsistent with the recent experimental results reported by Sperling et al. [Phys. Rev. Lett. 115, 115001 (2015)].

  15. BioMEA: a versatile high-density 3D microelectrode array system using integrated electronics.

    Science.gov (United States)

    Charvet, Guillaume; Rousseau, Lionel; Billoint, Olivier; Gharbi, Sadok; Rostaing, Jean-Pierre; Joucla, Sébastien; Trevisiol, Michel; Bourgerette, Alain; Chauvet, Philippe; Moulin, Céline; Goy, François; Mercier, Bruno; Colin, Mikael; Spirkovitch, Serge; Fanet, Hervé; Meyrand, Pierre; Guillemaud, Régis; Yvert, Blaise

    2010-04-15

    Microelectrode arrays (MEAs) offer a powerful tool to both record activity and deliver electrical microstimulations to neural networks either in vitro or in vivo. Microelectronics microfabrication technologies now allow building high-density MEAs containing several hundreds of microelectrodes. However, dense arrays of 3D micro-needle electrodes, providing closer contact with the neural tissue than planar electrodes, are not achievable using conventional isotropic etching processes. Moreover, increasing the number of electrodes using conventional electronics is difficult to achieve into compact devices addressing all channels independently for simultaneous recording and stimulation. Here, we present a full modular and versatile 256-channel MEA system based on integrated electronics. First, transparent high-density arrays of 3D-shaped microelectrodes were realized by deep reactive ion etching techniques of a silicon substrate reported on glass. This approach allowed achieving high electrode aspect ratios, and different shapes of tip electrodes. Next, we developed a dedicated analog 64-channel Application Specific Integrated Circuit (ASIC) including one amplification stage and one current generator per channel, and analog output multiplexing. A full modular system, called BIOMEA, has been designed, allowing connecting different types of MEAs (64, 128, or 256 electrodes) to different numbers of ASICs for simultaneous recording and/or stimulation on all channels. Finally, this system has been validated experimentally by recording and electrically eliciting low-amplitude spontaneous rhythmic activity (both LFPs and spikes) in the developing mouse CNS. The availability of high-density MEA systems with integrated electronics will offer new possibilities for both in vitro and in vivo studies of large neural networks. 2010 Elsevier B.V. All rights reserved.

  16. Computed tomography as a source of electron density information for radiation treatment planning

    Energy Technology Data Exchange (ETDEWEB)

    Skrzynski, Witold; Slusarczyk-Kacprzyk, Wioletta; Bulski, Wojciech [Medical Physics Dept., Center of Oncology, Warsaw (Poland); Zielinska-Dabrowska, Sylwia; Wachowicz, Marta; Kukolowicz, Pawel F. [Medical Physics Dept., Holycross Cancer Center, Kielce (Poland)

    2010-06-15

    Purpose: to evaluate the performance of computed tomography (CT) systems of various designs as a source of electron density ({rho}{sub el}) data for treatment planning of radiation therapy. Material and methods: dependence of CT numbers on relative electron density of tissue-equivalent materials (HU-{rho}{sub el} relationship) was measured for several general-purpose CT systems (single-slice, multislice, wide-bore multislice), for radiotherapy simulators with a single-slice CT and kV CBCT (cone-beam CT) options, as well as for linear accelerators with kV and MV CBCT systems. Electron density phantoms of four sizes were used. Measurement data were compared with the standard HU-{rho}{sub el} relationships predefined in two commercial treatment-planning systems (TPS). Results: the HU-{rho}{sub el} relationships obtained with all of the general-purpose CT scanners operating at voltages close to 120 kV were very similar to each other and close to those predefined in TPS. Some dependency of HU values on tube voltage was observed for bone-equivalent materials. For a given tube voltage, differences in results obtained for different phantoms were larger than those obtained for different CT scanners. For radiotherapy simulators and for kV CBCT systems, the information on {rho}{sub el} was much less precise because of poor uniformity of images. For MV CBCT, the results were significantly different than for kV systems due to the differing energy spectrum of the beam. Conclusion: the HU-{rho}{sub el} relationships predefined in TPS can be used for general-purpose CT systems operating at voltages close to 120 kV. For nontypical imaging systems (e.g., CBCT), the relationship can be significantly different and, therefore, it should always be measured and carefully analyzed before using CT data for treatment planning. (orig.)

  17. Response of the ionospheric electron density to different types of seismic events

    Directory of Open Access Journals (Sweden)

    Y. He

    2011-08-01

    Full Text Available The electron density data recorded by the Langmuir Probe Instrument (ISL, Instrument Sonde de Langmuir onboard the DEMETER satellite have been collected for nearly 4 yr (during 2006–2009 to perform a statistical analysis. During this time, more than 7000 earthquakes with a magnitude larger than or equal to 5.0 occurred all over the world. For the statistical studies, all these events have been divided into various categories on the basis of the seismic information, including Southern or Northern Hemisphere earthquakes, inland or sea earthquakes, earthquakes at different magnitude levels, earthquakes at different depth levels, isolated events and all events. To distinguish the pre-earthquake anomalies from the possible ionospheric anomalies related to the geomagnetic activity, the data were filtered with the Kp index. The statistical results obviously show that the electron density increases close to the epicentres both in the Northern and the Southern Hemisphere, but the position of the anomaly is slightly shifted to the north in the Northern Hemisphere and to the south in the Southern Hemisphere. The electron density related to both inland and sea earthquakes presents an anomaly approximately close to the epicentres, but the anomaly for sea earthquakes is more significant than for inland earthquakes. The intensity of the anomalies is enhanced when the magnitude increases and is reduced when the depth increases. A similar anomaly can also be seen in the statistical results concerning the isolated earthquakes. All these statistical results can help to better understand the preparation process of the earthquakes and their influence up to the ionospheric levels.

  18. 2D hydrodynamic simulations of a variable length gas target for density down-ramp injection of electrons into a laser wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kononenko, O., E-mail: olena.kononenko@desy.de [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany); Lopes, N.C.; Cole, J.M.; Kamperidis, C.; Mangles, S.P.D.; Najmudin, Z. [The John Adams Institute for Accelerator Science, The Blackett Laboratory, Imperial College London, SW7 2BZ UK (United Kingdom); Osterhoff, J. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany); Poder, K. [The John Adams Institute for Accelerator Science, The Blackett Laboratory, Imperial College London, SW7 2BZ UK (United Kingdom); Rusby, D.; Symes, D.R. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom); Warwick, J. [Queens University Belfast, North Ireland (United Kingdom); Wood, J.C. [The John Adams Institute for Accelerator Science, The Blackett Laboratory, Imperial College London, SW7 2BZ UK (United Kingdom); Palmer, C.A.J. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany)

    2016-09-01

    In this work, two-dimensional (2D) hydrodynamic simulations of a variable length gas cell were performed using the open source fluid code OpenFOAM. The gas cell was designed to study controlled injection of electrons into a laser-driven wakefield at the Astra Gemini laser facility. The target consists of two compartments: an accelerator and an injector section connected via an aperture. A sharp transition between the peak and plateau density regions in the injector and accelerator compartments, respectively, was observed in simulations with various inlet pressures. The fluid simulations indicate that the length of the down-ramp connecting the sections depends on the aperture diameter, as does the density drop outside the entrance and the exit cones. Further studies showed, that increasing the inlet pressure leads to turbulence and strong fluctuations in density along the axial profile during target filling, and consequently, is expected to negatively impact the accelerator stability.

  19. Applications of electron density studies in molecular and solid state science

    DEFF Research Database (Denmark)

    Overgaard, Jacob

    2015-01-01

    The present dissertation contains the distillate of my scientific output in the field of experimental and theoretical electron density studies roughly over the last decade and a little more, since earning my PhD-degree in 2001. There are several reasons that I have chosen to write my dissertation...... to their limits to obtain the required data resolution and quality. The apparent variation in subjects of the presented chapters is not a sign of a lack of scientific direction but merely underlines the fact that the method is applicable throughout chemistry and that I have also taken advantage...

  20. The electronic structure of TiCl: ligand field versus density functional calculations

    Science.gov (United States)

    Focsa, C.; Bencheikh, M.; Pettersson, L. G. M.

    1998-07-01

    The electronic structures of titanium chloride and its cation have been analysed by means of both ligand field (LFT) and density functional (DFT) theories. Despite the discrepancy between the DFT and LFT concerning the assignment of the ground state of 0953-4075/31/13/006/img6, an overall agreement is seen for TiCl. The observed 0953-4075/31/13/006/img7 ground state is found to result from our calculated 0953-4075/31/13/006/img8 ground state by a 0953-4075/31/13/006/img9 ionization process with an energy of 0953-4075/31/13/006/img10.

  1. Electronic health record in the internal medicine clinic of a Brazilian university hospital: Expectations and satisfaction of physicians and patients.

    Science.gov (United States)

    Duarte, Jurandir Godoy; Azevedo, Raymundo Soares

    2017-06-01

    To evaluate the satisfaction and expectations of patients and physicians before and after the implementation of an electronic health record (EHR) in the outpatient clinic of a university hospital. We conducted 389 interviews with patients and 151 with physicians before and after the implementation of a commercial EHR at the internal medicine clinic of Hospital das Clínicas of the Faculty of Medicine of the University of São Paulo (HC-FMUSP), Brazil. The physicians were identified by their connection to the outpatient clinic and categorized by their years since graduation: residents and preceptors (with 10 years or less of graduation) or assistants (with more than 10 years of graduation). The answers to the questionnaire given by the physicians were classified as favorable or against the use of EHR, before and after the implementation of this system in this clinic, receiving 1 or 0 points, respectively. The sum of these points generated a multiple regression score to determine which factors contribute to the acceptance of EHR by physicians. We also did a third survey, after the EHR was routinely established in the outpatient clinic. The degree of patient satisfaction was the same before and after implementation, with more than 90% positive evaluations. They noted the use of the computer during the consultation and valued such use. Resident (younger) physicians had more positive expectations than assistants (older physicians) before EHR implementation. This optimism was reduced after implementation. In the third evaluation the use of EHR was higher among resident physicians. Resident physicians perceived and valued the EHR more and used it more. In 28 of the 57 questions on performance of clinical tasks, resident physicians found it easier to use EHR than assistant physicians with significant differences (psatisfaction, resident physicians responded "good" and "excellent" to a greater extent than assistant physicians (p=0.002). Our results reinforce the idea that

  2. Reliability of High I/O High Density CCGA Interconnect Electronic Packages under Extreme Thermal Environment

    Science.gov (United States)

    Ramesham, Rajeshuni

    2012-01-01

    This paper provides the experimental test results of advanced CCGA packages tested in extreme temperature thermal environments. Standard optical inspection and x-ray non-destructive inspection tools were used to assess the reliability of high density CCGA packages for deep space extreme temperature missions. Ceramic column grid array (CCGA) packages have been increasing in use based on their advantages such as high interconnect density, very good thermal and electrical performances, compatibility with standard surface-mount packaging assembly processes, and so on. CCGA packages are used in space applications such as in logic and microprocessor functions, telecommunications, payload electronics, and flight avionics. As these packages tend to have less solder joint strain relief than leaded packages or more strain relief over lead-less chip carrier packages, the reliability of CCGA packages is very important for short-term and long-term deep space missions. We have employed high density CCGA 1152 and 1272 daisy chained electronic packages in this preliminary reliability study. Each package is divided into several daisy-chained sections. The physical dimensions of CCGA1152 package is 35 mm x 35 mm with a 34 x 34 array of columns with a 1 mm pitch. The dimension of the CCGA1272 package is 37.5 mm x 37.5 mm with a 36 x 36 array with a 1 mm pitch. The columns are made up of 80% Pb/20%Sn material. CCGA interconnect electronic package printed wiring polyimide boards have been assembled and inspected using non-destructive x-ray imaging techniques. The assembled CCGA boards were subjected to extreme temperature thermal atmospheric cycling to assess their reliability for future deep space missions. The resistance of daisy-chained interconnect sections were monitored continuously during thermal cycling. This paper provides the experimental test results of advanced CCGA packages tested in extreme temperature thermal environments. Standard optical inspection and x-ray non

  3. Threading dislocation density characterization in III-V photovoltaic materials by electron channeling contrast imaging

    Science.gov (United States)

    Yaung, Kevin Nay; Kirnstoetter, Stefan; Faucher, Joseph; Gerger, Andy; Lochtefeld, Anthony; Barnett, Allen; Lee, Minjoo Larry

    2016-11-01

    Accurate and rapid threading dislocation density (TDD) characterization of III-V photovoltaic materials using electron channeling contrast imaging (ECCI) is demonstrated. TDDs measured using ECCI showed close agreement with those from electron beam-induced current mapping (EBIC) and defect selective etching (DSE). ECCI is shown to be well-suited for measuring TDD values over a range of 5×106-5×108 cm-2. ECCI can distinguish individual dislocations in clusters closer than 0.2 μm, highlighting its excellent spatial resolution compared to DSE and EBIC. Taken together, ECCI is shown to be a versatile and complementary method to rapidly quantify TDD in III-V solar cells.

  4. Approximation of charge-deposition density in thin slabs irradiated by electrons

    CERN Document Server

    Alouani-Bibi, F; Rogov, Y V; Tabata, T

    2000-01-01

    Charge-deposition distributions in thin slabs irradiated by plane-parallel electron beams are studied. The slabs considered are made of elements with atomic numbers ranging from 4 to 79. The slab thicknesses are from 0.5 to 50 mg/cm sup 2 , and the electron beam energies are from 1 to 10 MeV. Using a new Monte Carlo method (called the trajectory translation method), data on the charge-deposition density have been obtained. Theoretical analysis of these data has been performed. Based on this analysis, a semiempirical model that describes charge-deposition distributions in thin slabs has been developed. The results obtained by the semiempirical model have been compared with those obtained by the PENELOPE Monte Carlo code and show moderate agreement.

  5. Modelling of the electron density height profiles in the mid-latitude ionospheric D-region

    Directory of Open Access Journals (Sweden)

    P. Y. Mukhtarov

    1996-06-01

    Full Text Available A new mid-latitude D-region (50-105 km model of the electron density is presented obtained on the basis of a full wave theory and by a trial-and-error inversion method. Daytime (at different solar zenith angles absorption measurements by A3-technique made in Bulgaria yielded data with the aid of which the seasonal and diurnal courses of the Ne(h-profiles were derived. Special attention is drawn to the event diurnal asymmetry, or uneven formation of the ionosphere as a function of insulation. The latter is probably connected with the influence of the diurnal fluctuations in the local temperature on the chemistry involved in the electron loss rate, as well as the diurnal variations of the main ionizing agent (NO in the D-region. That is why the Ne(h-profiles in the midlatitude D-region are modelled separately for morning and afternoon hours.

  6. Analysis of vibrational, structural, and electronic properties of rivastigmine by density functional theory

    Science.gov (United States)

    Prasad, O.; Sinha, L.; Misra, N.; Narayan, V.; Kumar, N.; Kumar, A.

    2010-09-01

    The present work deals with the structural, electronic, and vibrational analysis of rivastigmine. Rivastigmine, an antidementia medicament, is credited with significant therapeutic effects on the cognitive, functional, and behavioural problems that are commonly associated with Alzheimer’s dementia. For rivastigmine, a number of minimum energy conformations are possible. The geometry of twelve possible conformers has been analyzed and the most stable conformer was further optimized at a higher basis set. The electronic properties and vibrational frequencies were then calculated using a density functional theory at the B3LYP level with the 6-311+G(d, p) basis set. The different molecular surfaces have also been drawn to understand the activity of the molecule. A narrower frontier orbital energy gap in rivastigmine makes it softer and more reactive than water and dimethylfuran. The calculated value of the dipole moment is 2.58 debye.

  7. Electron and Negative Ion Densities in C(2)F(6) and CHF(3) Containing Inductively Coupled Discharges

    Energy Technology Data Exchange (ETDEWEB)

    HEBNER,GREGORY A.; MILLER,PAUL A.

    1999-12-07

    Electron and negative ion densities have been measured in inductively coupled discharges containing C{sub 2}F{sub 6} and CHF{sub 3}. Line integrated electron density was determined using a microwave interferometer, negative ion densities were inferred using laser photodetachment spectroscopy, and electron temperature was determined using a Langmuir probe. For the range of induction powers, pressures and bias power investigated, the electron density peaked at 9 x 10{sup 12} cm{sup -2} (line-integrated) or approximately 9 x 10{sup 11} cm{sup -3}. The negative ion density peaked at approximately 1.3 x 10{sup 11} cm{sup -3}. A maximum in the negative ion density as a function of induction coil power was observed. The maximum is attributed to a power dependent change in the density of one or more of the potential negative ion precursor species since the electron temperature did not depend strongly on power. The variation of photodetachment with laser wavelength indicated that the dominant negative ion was F{sup -}. Measurement of the decay of the negative ion density in the afterglow of a pulse modulated discharge was used to determine the ion-ion recombination rate for CF{sub 4}, C{sub 2}F{sub 6} and CHF{sub 3} discharges.

  8. Gradual Diffusion and Punctuated Phase Space Density Enhancements of Highly Relativistic Electrons: Van Allen Probes Observations

    Science.gov (United States)

    Baker, D. N.; Jaynes, A. N.; Li, X.; Henderson, M. G.; Kanekal, S. G.; Reeves, G. D.; Spence, H. E.; Claudepierre, S. G.; Fennell, J. F.; Hudson, M. K.

    2014-01-01

    The dual-spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth's radiation belts. Observations (up to E (is) approximately 10MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi-MeV electron flux and phase space density (PSD) changes during March 2013 in the context of the first year of Van Allen Probes operation. This March period demonstrates the classic signatures both of inward radial diffusive energization and abrupt localized acceleration deep within the outer Van Allen zone (L (is) approximately 4.0 +/- 0.5). This reveals graphically that both 'competing' mechanisms of multi-MeV electron energization are at play in the radiation belts, often acting almost concurrently or at least in rapid succession.

  9. Study of argon ions density and electron temperature and density in magnetron plasma by optical emission spectroscopy and collisional-radiative model

    Directory of Open Access Journals (Sweden)

    Kirill E. Evdokimov

    2017-06-01

    Full Text Available Optical emission spectroscopy (OES combined with the models of plasma light emission becomes non-intrusive and versatile method of plasma parameters determination. In this paper we have studied the densities of charge carriers and electron temperature in Ar plasma of pulsed DC magnetron in different experimental conditions. Electron density and temperature were determined by fitting of relative emission line intensities calculated from collisional-radiative model (CRM to experimental ones. The model describes the kinetics of the first 40 excited states of neutral argon Ar and takes into account the following processes: electron impact excitation/deexcitation, spontaneous light emission, radiation trapping, electron impact ionization, and metastable quenching due to diffusion to walls. Then, ions density was determined from relative intensity of 488 nm Ar+ emission line and simple CRM accounting excitation from ground states of neutral Ar and ion Ar+. The values of electron and ion density agree very well. To test the stability of results, we performed Monte-Carlo calculations with random variation of experimental spectrum as well as of excitation cross-sections and estimated confidence intervals and errors for plasma parameters. Also, we validated OES study by comparison with Langmuir probe measurements. The agreement between optical and probe techniques is satisfactory.

  10. Calculation of induced current densities for humans by magnetic fields from electronic article surveillance devices

    Science.gov (United States)

    Gandhi, Om P.; Kang, Gang

    2001-11-01

    This paper illustrates the use of the impedance method to calculate the electric fields and current densities induced in millimetre resolution anatomic models of the human body, namely an adult and 10- and 5-year-old children, for exposure to nonuniform magnetic fields typical of two assumed but representative electronic article surveillance (EAS) devices at 1 and 30 kHz, respectively. The devices assumed for the calculations are a solenoid type magnetic deactivator used at store checkouts and a pass-by panel-type EAS system consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to obtain induced current densities averaged over a cross section of 1 cm2 perpendicular to the direction of induced currents. This is done to compare the peak current densities with the limits or the basic restrictions given in the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm2 area-averaged current densities for the CNS tissues such as the brain and the spinal cord are increasingly larger for smaller models and are the highest for the model of the 5-year-old child. For both the EAS devices, the maximum 1 cm2 area-averaged current densities for the brain of the model of the adult are lower than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10- and 5-year-old children if sufficiently strong magnetic fields are used.

  11. Measurement of electron density and electron temperature of a cascaded arc plasma using laser Thomson scattering compared to an optical emission spectroscopic approach

    Science.gov (United States)

    Yong, WANG; Cong, LI; Jielin, SHI; Xingwei, WU; Hongbin, DING

    2017-11-01

    As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering (LTS) system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5 × 1019 m-3 to 7.1 × 1020 m-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison, an optical emission spectroscopy (OES) system was established as well. The results showed that the electron excitation temperature (configuration temperature) measured by OES is significantly higher than the electron temperature (kinetic electron temperature) measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium (LTE). This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.

  12. Electron Density Profile Data Contains Virtual Height/Frequency Pairs from a Profile or Profiles (Composite Months) of Ionograms

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Electron Density Profile, N(h), data set contains both individual profiles and composite months. The data consist of virtual height/frequency pairs from a...

  13. Influence of the electron density on the characteristics of terahertz waves generated under laser–cluster interaction

    Energy Technology Data Exchange (ETDEWEB)

    Frolov, A. A., E-mail: frolov@ihed.ras.ru [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

    2016-12-15

    A theory of generation of terahertz radiation under laser–cluster interaction, developed earlier for an overdense cluster plasma [A. A. Frolov, Plasma Phys. Rep. 42. 637 (2016)], is generalized for the case of arbitrary electron density. The spectral composition of radiation is shown to substantially depend on the density of free electrons in the cluster. For an underdense cluster plasma, there is a sharp peak in the terahertz spectrum at the frequency of the quadrupole mode of a plasma sphere. As the electron density increases to supercritical values, this spectral line vanishes and a broad maximum at the frequency comparable with the reciprocal of the laser pulse duration appears in the spectrum. The dependence of the total energy of terahertz radiation on the density of free electrons is analyzed. The radiation yield is shown to increase significantly under resonance conditions, when the laser frequency is close to the eigenfrequency of the dipole or quadrupole mode of a plasma sphere.

  14. Increasing positive ion number densities below the peak of ion-electron pair production in Titan's ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Vigren, E.; Galand, M. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Shebanits, O.; Wahlund, J.-E. [Swedish Institute of Space Physics, P.O. Box 537, SE-751 21 Uppsala (Sweden); Geppert, W. D. [Department of Physics, Stockholm University, SE-10691 Stockholm (Sweden); Lavvas, P. [Groupe de Spectrométrie Moléculaire et Atmosphérique, Université Reims Champagne-Ardenne, UMR 7331, F-51687 Reims (France); Vuitton, V. [Institut de Planétologie et d' Astrophysique de Grenoble (IPAG), UJF-Grenoble/CNRS-INSU, UMR 5274, F-38041 Grenoble (France); Yelle, R. V., E-mail: erik.vigren@irfu.se [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092 (United States)

    2014-05-01

    We combine derived ion-electron pair formation rates with Cassini Radio Plasma Wave Science Langmuir Probe measurements of electron and positive ion number densities in Titan's sunlit ionosphere. We show that positive ion number densities in Titan's sunlit ionosphere can increase toward significantly lower altitudes than the peak of ion-electron pair formation despite that the effective ion-electron recombination coefficient increases. This is explained by the increased mixing ratios of negative ions, which are formed by electron attachment to neutrals. While such a process acts as a sink for free electrons, the positive ions become longer-lived as the rate coefficients for ion-anion neutralization reactions are smaller than those for ion-electron dissociative recombination reactions.

  15. Spin-orbit interaction in a two-dimensional electron gas in a InAs/AlSb quantum well with gate-controlled electron density

    NARCIS (Netherlands)

    Heida, J.P.; Wees, B.J. van; Kuipers, J.J.; Klapwijk, T.M.; Borghs, G.

    1998-01-01

    We present experiments on the tuning of the spin-orbit interaction in a two-dimensional electron gas in an asymmetric InAs/AlSb quantum well using a gate. The observed dependence of the spin splitting energy on the electron density can be attributed solely to the change in the Fermi wave vector. The

  16. Effective atomic numbers, electron densities and kinetic energy released in matter of vitamins for photon interaction

    Science.gov (United States)

    Shantappa, A.; Hanagodimath, S. M.

    2014-01-01

    Effective atomic numbers, electron densities of some vitamins (Retinol, Riboflavin, Niacin, Biotin, Folic acid, Cobalamin, Phylloquinone and Flavonoids) composed of C, H, O, N, Co, P and S have been calculated for total and partial photon interactions by the direct method for energy range 1 keV-100 GeV by using WinXCOM and kinetic energy released in matter (Kerma) relative to air is calculated in energy range of 1 keV-20 MeV. Change in effective atomic number and electron density with energy is calculated for all photon interactions. Variation of photon mass attenuation coefficients with energy are shown graphically only for total photon interaction. It is observed that change in mass attenuation coefficient with composition of different chemicals is very large below 100 keV and moderate between 100 keV and 10 MeV and negligible above 10 MeV. Behaviour of vitamins is almost indistinguishable except biotin and cobalamin because of large range of atomic numbers from 1(H) to 16 (S) and 1(H) to 27(Co) respectively. K a value shows a peak due to the photoelectric effect around K-absorption edge of high- Z constituent of compound for biotin and cobalamin.

  17. ELECTRON BEAM CURING OF EPOXY ACRYLATE COATINGS ON MEDIUM-DENSITY FIBERBOARD

    Directory of Open Access Journals (Sweden)

    Sugiarto Danu

    2010-06-01

    Full Text Available Most of the medium-density fiberboard (MDF as an engineered woods need surface coating process before entering final products, such as furniture and building materials. The wood surface should be covered for surface protection from damage during service life as well as to enhance its appearance. Surface coating of MDF was conducted using epoxy acrylate resin either for clear and pigmented coatings. Titanium dioxide was used for white pigmented coatings. Coating was conducted at variation thickness level of 30 to 150 μm. Curing was carried out by using 350 kV electron beam accelerator at 1.35 mA current and 1.6 m/min conveyor speed to get the absorbed dose of 3 Mrad. Effect of coating thickness was evaluated by measuring the physical, mechanical and chemical properties of cured samples, i.e., hardness, gloss, transparency, adhesion, abrasion resistance, and chemical, solvent and stain resistance. Experimental results showed that pendulum hardness and abrasion resistance slightly increased whereas gloss, transparency and adhesion resistance decreased with increasing coating thickness, while chemical, solvent and stain resistance remains similar. In general, clear coating provides better properties than pigmented coating.   Keywords: electron-beam; coating; epoxy-acrylate; pigment; medium-density fiberboard

  18. Electron Temperature and Density in Local Helicity Injection and High betat Plasmas

    Science.gov (United States)

    Schlossberg, David J.

    Tokamak startup in a spherical torus (ST) and an ST-based fusion nuclear science facility can greatly benefit from using non-inductive methods. The Pegasus Toroidal Experiment has developed a non-inductive startup technique using local helicity injection (LHI). Electron temperature, T e(r), and density, ne( r), profiles during LHI are unknown. These profiles are critical for understanding both the physics of the injection and relaxation mechanisms, as well as for extrapolating this technique to larger devices. A new Thomson scattering system has been designed, installed, and used to characterize Te(r, t) and ne(r, t) during LHI. The diagnostic leverages new technology in image intensified CCD cameras, high-efficiency diffraction gratings, and reliable Nd:YAG lasers. Custom systems for stray light mitigation, fast shuttering, and precision timing have been developed and implemented. The overall system provides a low-maintenance, economic, and effective means to explore novel physics regimes in Pegasus. Electron temperature and density profiles during LHI have been measured for the first time. Results indicate Te(r) peaked in the core of plasmas, and sustained while plasmas are coupled to injection drive. Electron densities also peak near the core of the tokamak, up to local values of n e ˜ 1.5 x 1019 m -3. A comparison of Te( r, t) has been made between discharges with dominant drive voltage from induction versus helicity injection. In both cases Te ( r, t) profiles remain peaked, with values for Te ,max > 150 eV in dominantly helicity-driven plasmas using high-field side LHI. Sustained values of betat ˜ 100% have been demonstrated in a tokamak for the first time. Plasmas are created and driven entirely non-solenoidally, and exhibit MHD stability. Measured temperature and density profiles are used to constrain magnetic equilibrium reconstructions, which calculate 80% ramp-down. For a continued decrease in the toroidal field these plasmas disrupt near the ideal MHD

  19. A global scale picture of ionospheric peak electron density changes during geomagnetic storms

    Science.gov (United States)

    Kumar, Vickal V.; Parkinson, Murray L.

    2017-04-01

    Changes in ionospheric plasma densities can affect society more than ever because of our increasing reliance on communication, surveillance, navigation, and timing technology. Models struggle to predict changes in ionospheric densities at nearly all temporal and spatial scales, especially during geomagnetic storms. Here we combine a 50 year (1965-2015) geomagnetic disturbance storm time (Dst) index with plasma density measurements from a worldwide network of 132 vertical incidence ionosondes to develop a picture of global scale changes in peak plasma density due to geomagnetic storms. Vertical incidence ionosondes provide measurements of the critical frequency of the ionospheric F2 layer (foF2), a direct measure of the peak electron density (NmF2) of the ionosphere. By dissecting the NmF2 perturbations with respect to the local time at storm onset, season, and storm intensity, it is found that (i) the storm-associated depletions (negative storm effects) and enhancements (positive storm effects) are driven by different but related physical mechanisms, and (ii) the depletion mechanism tends to dominate over the enhancement mechanism. The negative storm effects, which are detrimental to HF radio links, are found to start immediately after geomagnetic storm onset in the nightside high-latitude ionosphere. The depletions in the dayside high-latitude ionosphere are delayed by a few hours. The equatorward expansion of negative storm effects is found to be regulated by storm intensity (farthest equatorward and deepest during intense storms), season (largest in summer), and time of day (generally deeper on the nightside). In contrast, positive storm effects typically occur on the dayside midlatitude and low-latitude ionospheric regions when the storms are in the main phase, regardless of the season. Closer to the magnetic equator, moderate density enhancements last up to 40 h during the recovery phase of equinox storms, regardless of the local time. Strikingly, high

  20. Ionospheric electron density perturbations during the 7-10 March 2012 geomagnetic storm period

    Science.gov (United States)

    Belehaki, Anna; Kutiev, Ivan; Marinov, Pencho; Tsagouri, Ioanna; Koutroumbas, Kostas; Elias, Panagiotis

    2017-02-01

    From 7 to 10 March 2012 a series of magnetospheric disturbances caused perturbations in the ionospheric electron density. Analyzing the interplanetary causes in each phase of this disturbed period, in comparison with the total electron content (TEC) disturbances, we have concluded that the interplanetary solar wind controls largely the ionospheric response. An interplanetary shock detected at 0328UT on 7 March caused the formation of prompt penetrating electric fields in the dayside that transported plasma from the near-equatorial region to higher in attitudes and latitudes forming a giant plasma fountain which is part of the so-called dayside ionospheric super-fountain. The super-fountain produces an increase in TEC which is the dominant effect at middle latitude, masking the effect of the negative storm. Simultaneously, inspecting the TEC maps, we found evidence for a turbulence in TEC propagating southward probably caused by large scale travelling ionospheric disturbances (LSTIDs) linked to auroral electrojet intensification. On 8 March, a magnetospheric sudden impulse at 1130UT accompanied with strong pulsations in all interplanetary magnetic field (IMF) components and with northward Bz component during the growth phase of the storm. These conditions triggered a pronounced directly driven substorm phase during which we observe LSTID. However, the analysis of DMSP satellite observations, provided with strong evidence for Sub-Auroral Polarization Streams (SAPS) formation that erode travelling ionospheric disturbances (TID) signatures. The overall result of these mechanisms can be detected in maps of de-trended TEC, but it is difficult to identify separately each of the sources of the observed perturbations, i.e. auroral electrojet activity and LSTIDs, super-fountain and SAPS. In order to assess the capability of the ionospheric profiler called Topside Sounder Model - assisted Digisonde (TaD model) to detect such perturbations in the electron density, electron

  1. Comment on ?Characterizing unpaired electrons from one-particle density matrix? 6M. Head-Gordon, Chem. Phys. Lett. 372 (2003) 508?5119

    Science.gov (United States)

    Bochicchio, R. C.; Torre, A.; Lain, L.

    2003-10-01

    A recent theoretical study published in this journal has proposed a new definition of the unpaired electron density in molecular systems. This comment attempts to clarify the difference between the concept reported there and that of 'effectively' unpaired electron density.

  2. Signal acquisition and scale calibration for beam power density distribution of electron beam welding

    Science.gov (United States)

    Peng, Yong; Li, Hongqiang; Shen, Chunlong; Guo, Shun; Zhou, Qi; Wang, Kehong

    2017-06-01

    The power density distribution of electron beam welding (EBW) is a key factor to reflect the beam quality. The beam quality test system was designed for the actual beam power density distribution of high-voltage EBW. After the analysis of characteristics and phase relationship between the deflection control signal and the acquisition signal, the Post-Trigger mode was proposed for the signal acquisition meanwhile the same external clock source was shared by the control signal and the sampling clock. The power density distribution of beam cross-section was reconstructed using one-dimensional signal that was processed by median filtering, twice signal segmentation and spatial scale calibration. The diameter of beam cross-section was defined by amplitude method and integral method respectively. The measured diameter of integral definition is bigger than that of amplitude definition, but for the ideal distribution the former is smaller than the latter. The measured distribution without symmetrical shape is not concentrated compared to Gaussian distribution.

  3. Supersonic helium beam diagnostic for fluctuation measurements of electron temperature and density at the Tokamak TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Kruezi, U.; Stoschus, H.; Schweer, B.; Sergienko, G.; Samm, U. [Institute of Energy and Climate Research, Plasma Physics, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Partner in the Trilateral Euregio Cluster, Juelich (Germany)

    2012-06-15

    A supersonic helium beam diagnostic, based on the line-ratio technique for high resolution electron density and temperature measurements in the plasma edge (r/a > 0.9) was designed, built, and optimised at TEXTOR (Torus Experiment for Technology Oriented Research). The supersonic injection system, based on the Campargue skimmer-nozzle concept, was developed and optimised in order to provide both a high neutral helium beam density of n{sub 0}= 1.5 Multiplication-Sign 10{sup 18} m{sup -3} and a low beam divergence of {+-}1 Degree-Sign simultaneously, achieving a poloidal resolution of {Delta}{sub poloidal}= 9 mm. The setup utilises a newly developed dead volume free piezo valve for operation in a high magnetic field environment of up to 2 T with a maximum repetition rate of 80 Hz. Gas injections are realised for a duration of 120 ms at a repetition rate of 2 Hz (duty cycle 1/3). In combination with a high sensitivity detection system, consisting of three 32 multi-channel photomultipliers (PMTs), measurements of edge electron temperature and density with a radial resolution of {Delta}{sub radial}= 2 mm and a maximum temporal resolution of {Delta}t Asymptotically-Equal-To 2 {mu}s (470 kHz) are possible for the first time. The diagnostic setup at TEXTOR is presented. The newly developed injection system and its theoretical bases are discussed. The applicability of the stationary collisional-radiative model as basis of the line-ratio technique is shown. Finally, an example of a fluctuation analysis demonstrating the unique high temporal and spatial resolution capabilities of this new diagnostic is presented.

  4. TEMPERATURE AND ELECTRON DENSITY DIAGNOSTICS OF A CANDLE-FLAME-SHAPED FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Guidoni, S. E. [NASA Goddard Space Flight Center/CUA, Code 674, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); McKenzie, D. E.; Longcope, D. W.; Yoshimura, K. [Department of Physics, Montana State University, Bozeman, MT 59717-3840 (United States); Plowman, J. E., E-mail: silvina.e.guidoni@nasa.gov [High Altitude Observatory, National Center for Atmospheric Research P.O. Box 3000, Boulder, CO 80307-3000 (United States)

    2015-02-10

    Candle-flame-shaped flares are archetypical structures that provide indirect evidence of magnetic reconnection. A flare resembling Tsuneta's famous 1992 candle-flame flare occurred on 2011 January 28; we present its temperature and electron density diagnostics. This flare was observed with Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), Hinode/X-Ray Telescope (XRT), and Solar Terrestrial Relations Observatory Ahead (STEREO-A)/Extreme Ultraviolet Imager, resulting in high-resolution, broad temperature coverage, and stereoscopic views of this iconic structure. The high-temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the posteruption flare arcade, a feature that has been observed in other long-duration events. Despite the extensive work on the standard reconnection scenario, there is no complete agreement among models regarding the nature of this high-intensity elongated structure. Electron density maps reveal that reconnected loops that are successively connected at their tops to the tower develop a density asymmetry of about a factor of two between the two legs, giving the appearance of ''half-loops''. We calculate average temperatures with a new fast differential emission measure (DEM) method that uses SDO/AIA data and analyze the heating and cooling of salient features of the flare. Using STEREO observations, we show that the tower and the half-loop brightenings are not a line-of-sight projection effect of the type studied by Forbes and Acton. This conclusion opens the door for physics-based explanations of these puzzling, recurrent solar flare features, previously attributed to projection effects. We corroborate the results of our DEM analysis by comparing them with temperature analyses from Hinode/XRT.

  5. Study of electron densities of normal and neoplastic human breast tissues by Compton scattering using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Antoniassi, M.; Conceicao, A.L.C. [Departamento de Fisica-Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto-Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil); Poletti, M.E., E-mail: poletti@ffclrp.usp.br [Departamento de Fisica-Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto-Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil)

    2012-07-15

    Electron densities of 33 samples of normal (adipose and fibroglangular) and neoplastic (benign and malignant) human breast tissues were determined through Compton scattering data using a monochromatic synchrotron radiation source and an energy dispersive detector. The area of Compton peaks was used to determine the electron densities of the samples. Adipose tissue exhibits the lowest values of electron density whereas malignant tissue the highest. The relationship with their histology was discussed. Comparison with previous results showed differences smaller than 4%. - Highlights: Black-Right-Pointing-Pointer Electron density of normal and neoplastic breast tissues was measured using Compton scattering. Black-Right-Pointing-Pointer Monochromatic synchrotron radiation was used to obtain the Compton scattering data. Black-Right-Pointing-Pointer The area of Compton peaks was used to determine the electron densities of samples. Black-Right-Pointing-Pointer Adipose tissue shows the lowest electron density values whereas the malignant tissue the highest. Black-Right-Pointing-Pointer Comparison with previous results showed differences smaller than 4%.

  6. Polymer ring resonators for high density photonic and electronic-photonic integration

    Science.gov (United States)

    Sun, Haishan

    2009-12-01

    Electrical interconnect based on the copper wires will be the bottleneck for the future performance improvement of multi-core CPUs. Chip scale optical interconnect based on high density photonic and electronic-photonic integration is one of the feasible solutions. Ring resonators are promising photonic components serving as building blocks. High density integration of ring resonators is also important for high throughput lab-on-a-chip biosensors and opto-microwave integrated circuits. Polymer materials are compatible with most semiconductor fabrication processes. Polymers can be easily doped with rare earth ions, quantum dots etc. to make active optical devices. Especially, over several hundreds pm/V electro-optic (EO) coefficients and femtosecond scale response time of EO polymers enables photonic devices with sub 1V to millivolt drive voltages and terahertz bandwidth. This dissertation describes several technologies about design, simulation, fabrication, integration with electronic circuits and fiber optics of polymer ring resonators, and demonstrates three application examples of polymer ring resonators in communications and biochemical sensing. First the Beam Propagation Method (BPM) and the matrix analysis are combined to provide a fast circuit level simulation and design procedure of polymer ring resonators. Several low cost fabrication techniques based on electron beam irradiation effects on EO polymers are introduced. For the practical electronicphotonic integration, a hybrid integration scheme of EO polymer waveguide devices with Si integrated circuits is developed. One application is an all-dielectric RF sensor or receiver with sensitivity of 100 V/m and theoretical bandwidth over 100 GHz. This device is based on a novel structure with polymer ring resonator directly coupled to a side polished optical fiber. The other two examples are biochemical sensors based on multi-slot waveguide and ring resonator reflector structures.

  7. Electronic structure of the substitutional vacancy in graphene: density-functional and Green's function studies

    Science.gov (United States)

    Nanda, B. R. K.; Sherafati, M.; Popović, Z. S.; Satpathy, S.

    2012-08-01

    We study the electronic structure of graphene with a single substitutional vacancy using a combination of the density-functional, tight-binding and impurity Green's function approaches. Density-functional studies are performed with the all-electron spin-polarized linear augmented plane wave (LAPW) method. The three sp2σ dangling bonds adjacent to the vacancy introduce localized states (Vσ) in the mid-gap region, which split due to the crystal field and a Jahn-Teller distortion, while the pzπ states introduce a sharp resonance state (Vπ) in the band structure. For a planar structure, symmetry strictly forbids hybridization between the σ and the π states, so that these bands are clearly identifiable in the calculated band structure. As to the magnetic moment of the vacancy, the Hund's rule coupling aligns the spins of the four localized Vσ1↑↓, Vσ2↑ and Vπ↑ electrons, resulting in an S = 1 state, with a magnetic moment of 2μB, which is reduced by about 0.3μB due to the anti-ferromagnetic spin polarization of the π band itinerant states in the vicinity of the vacancy. This results in the net magnetic moment of 1.7μB. Using the Lippmann-Schwinger equation, we reproduce the well-known ˜1/r decay of the localized Vπ wave function with distance, and in addition, find an interference term coming from the two Dirac points, previously unnoticed in the literature. The long-range nature of the Vπ wave function is a unique feature of the graphene vacancy and we suggest that this may be one of the reasons for the widely varying relaxed structures and magnetic moments reported from the supercell band calculations in the literature.

  8. Regional 3-D ionospheric electron density specification on the basis of data assimilation of ground-based GNSS and radio occultation data

    Science.gov (United States)

    Aa, Ercha; Liu, Siqing; Huang, Wengeng; Shi, Liqin; Gong, Jiancun; Chen, Yanhong; Shen, Hua; Li, Jianyong

    2016-06-01

    In this paper, a regional 3-D ionospheric electron density specification over China and adjacent areas (70°E-140°E in longitude, 15°N-55°N in latitude, and 100-900 km in altitude) is developed on the basis of data assimilation technique. The International Reference Ionosphere (IRI) is used as a background model, and a three-dimensional variational technique is used to assimilate both the ground-based Global Navigation Satellite System (GNSS) observations from the Crustal Movement Observation Network of China (CMONOC) and International GNSS Service (IGS) and the ionospheric radio occultation (RO) data from FORMOSAT-3/COSMIC (F3/C) satellites. The regional 3-D gridded ionospheric electron densities can be generated with temporal resolution of 5 min in universal time, horizontal resolution of 2° × 2° in latitude and longitude, and vertical resolution of 20 km between 100 and 500 km and 50 km between 500 and 900 km. The data assimilation results are validated through extensive comparison with several sources of electron density information, including (1) ionospheric total electron content (TEC); (2) Abel-retrieved F3/C electron density profiles (EDPs); (3) ionosonde foF2 and bottomside EDPs; and (4) the Utah State University Global Assimilation of Ionospheric Measurements (USU-GAIM) under both geomagnetic quiet and disturbed conditions. The validation results show that the data assimilation procedure pushes the climatological IRI model toward the observation, and a general accuracy improvement of 15-30% can be expected. Thecomparisons also indicate that the data assimilation results are more close to the Center for Orbit Determination of Europe (CODE) TEC and Madrigal TEC products than USU-GAIM. These initial results might demonstrate the effectiveness of the data assimilation technique in improving specification of local ionospheric morphology.

  9. Generating high brightness electron beams using density down ramp injection in nonlinear plasma wakefields

    Science.gov (United States)

    Dalichaouch, Thamine; Xu, Xinlu; Davidson, Asher; Yu, Peicheng; An, Weiming; Joshi, Chan; Zhang, Chaojie; Mori, Warren; Li, Fei; Lu, Wei; Fonseca, Ricardo

    2017-10-01

    In the past few decades, there has been much progress in theory, simulation, and experiment towards using Plasma wakefield acceleration (PWFA) and Laser wakefield acceleration (LWFA) as the basis for designing and building compact x-ray free-electron-lasers (XFEL) as well as a next generation linear collider. Recently, ionization injection and density downramp injection have been proposed and demonstrated as controllable injection schemes for generating high quality relativistic electron beams. We present the concepts and full 3D simulation results using OSIRIS which show that downramp injection can generate electron beams with unprecedented brightnesses. However, full-3D simulations of plasma-based acceleration can be computationally intensive, sometimes taking millions of cpu-hours. Due to the near azimuthal symmetry in PWFA and LWFA, quasi-3D simulations using a cylindrical geometry are computationally more efficient than 3D Cartesian simulations since only the first few harmonics are needed in ϕ to capture the 3D physics of most problems. We also present results from the quasi-3D approach on downramp injection and compare the results against full 3D simulations. Work supported by NSF and DOE.

  10. Electronic structure of oxygen-terminated zigzag graphene nanoribbons: A hybrid density functional theory study

    Science.gov (United States)

    Ramasubramaniam, Ashwin

    2010-06-01

    The size-dependent electronic structure of oxygen-terminated zigzag graphene nanoribbons is investigated using standard density functional theory (DFT) with an exchange-correlation functional of the generalized gradient approximation form as well as hybrid DFT calculations with two different exchange-correlation functionals. Hybrid DFT calculations, which typically provide more accurate band gaps than standard DFT, are found to predict semiconducting behavior in oxygen-terminated zigzag graphene nanoribbons; this is in distinct contrast to standard DFT with (semi)local exchange-correlation functionals, which have been widely employed in previous studies and shown to predict metallic behavior. (Semi)local exchange-correlation functionals employed in standard DFT calculations cause unphysical delocalization of lone pairs from the oxygen atoms due to self-interaction errors and lead to metallic behavior. Hybrid DFT calculations do not suffer from this spurious effect and produce a clear size-dependent band gap. Appreciable fundamental band gaps (˜1eV) are found for the smallest ribbons (two zigzag rows); the band gap decreases rapidly with increasing ribbon width, resulting eventually in a zero band-gap semiconductor at about 4-5 zigzag rows. This finding could have useful implications for molecular electronics, in particular, since oxygen-terminated zigzag graphene nanoribbons are thermodynamically stable unlike their hydrogenated counterparts. More generally, through a concrete example, this study suggests caution when employing (semi)local functionals in DFT studies of functionalized graphene/graphene derivatives when the functional groups contain electron lone pairs.

  11. Density functional investigation of structural, electronic and optical properties of Ge-doped ZnO

    Science.gov (United States)

    Lv, Ying-bo; Dai, Ying; Yang, Kesong; Zhang, Zhenkui; Wei, Wei; Guo, Meng; Huang, Baibiao

    2011-10-01

    Recent experiments reported fascinating phenomenon of photoluminescence (PL) blueshift in Ge-doped ZnO. To understand it, we examined the structural, electronic and optical properties of Ge-doped ZnO (ZnO:Ge) systematically by means of density functional theory calculations. Our results show that Ge atoms tend to cluster in heavily doped ZnO. Ge clusters can limit the conductivity of doped ZnO but reinforce the near-band-edge emission. The substitutional Ge for Zn leads to Fermi level pinning in the conduction band, which indicates Ge-doped ZnO is of n-type conductivity character. It is found that the delocalized Ge 4s states hybridize with conduction band bottom, and is dominant in the region near the Fermi level, suggesting that Ge-4s states provides major free carriers in ZnO:Ge crystal. The observed blueshift of PL in Ge-doped ZnO originates from the electron transition energy from the valence band to the empty levels above Fermi level larger than the gap of undoped ZnO. The electron transition between the gap states induced by oxygen vacancy and conduction band minimum may be the origin of the new PL peak at 590 nm.

  12. Carbon Nanotubes with Tailored Density of Electronic States for Electrochemical Applications.

    Science.gov (United States)

    Song, Yingpan; Hu, Huifang; Feng, Miao; Zhan, Hongbing

    2015-11-25

    The density of electronic states (DOS) is an intrinsic electronic property that works conclusively in the electrochemistry of carbon materials. However, seldom has it been reported how the DOS at the Fermi level influences the electrochemical activity. In this work, we synthesized partially and fully unzipped carbon nanotubes by longitudinally unzipping pristine carbon nanotubes (CNTs). We then studied the electrochemical activity and biosensitivity of carbon materials by means of the CNTs and their derivatives to elucidate the effect of the DOS on their electrochemical performances. Tailoring of the DOS for the CNT derivatives could be conveniently realized by varying the sp(2)/sp(3) ratio (i.e., graphite concentration) through manipulating the oxidative unzipping degree. Despite the diverse electron transfer mechanisms and influence factors of the four investigated redox probes (IrCl6(2-), [Fe(CN)6](3-), Fe(3+), and ascorbic acid), the CNT derivatives exhibited consistent kinetic behaviors, wherein CNTs with a high DOS showed superior electrochemical response compared with partially and fully unzipped carbon nanotubes. For biological detection, the CNTs could simultaneously distinguish ascorbic acid, dopamine, and uric acid, while the three CNT derivatives could all differentiate phenethylamine and epinephrine existed in the newborn calf serum. Moreover, the three CNT derivatives all presented wide linear detection ranges with high sensitivities for dopamine, phenethylamine, and epinephrine.

  13. Noncovalent interactions from electron density topology and solvent effects on spectral properties of Schiff bases

    Science.gov (United States)

    Gandhimathi, S.; Balakrishnan, C.; Theetharappan, M.; Neelakantan, M. A.; Venkataraman, R.

    2017-03-01

    Two Schiff bases were prepared by the condensation of o-allyl substituted 2,4-dihydroxy acetophenone with 1,2-diaminopropane (L1) and ethanediamine (L2) and characterized by elemental analysis, and ESI-MS, IR, UV-Vis, 1H and 13C NMR spectral techniques. The effect of solvents with respect to different polarities on UV-Vis and emission spectra of L1 and L2 was investigated at room temperature show that the compounds exist in keto and enol forms in solution and may be attributed to the intramolecular proton transfer in the ground state. The solute-solvent interactions, change in dipole moment and solvatochromic properties of the compounds were studied based on the solvent polarity parameters. For L1 and L2, the ground and excited state electronic structure calculations were carried out by DFT and TD-DFT at B3LYP/6-311G (d,p) level, respectively. The IR, NMR and electronic absorption spectra computed were compared with the experimental observations. The intramolecular charge transfer within the molecule is evidenced from the HOMO and LUMO energy levels and surface analysis. The noncovalent interactions like hydrogen bonding and van der Waals interactions were identified from the molecular geometry and electron localization function. These interactions in molecules have been studied by using reduced density gradient and graphed by Multiwfn.

  14. Commensurate and incommensurate spin-density waves in heavy electron systems

    Directory of Open Access Journals (Sweden)

    P. Schlottmann

    2016-05-01

    Full Text Available The nesting of the Fermi surfaces of an electron and a hole pocket separated by a nesting vector Q and the interaction between electrons gives rise to itinerant antiferromagnetism. The order can gradually be suppressed by mismatching the nesting and a quantum critical point (QCP is obtained as the Néel temperature tends to zero. The transfer of pairs of electrons between the pockets can lead to a superconducting dome above the QCP (if Q is commensurate with the lattice, i.e. equal to G/2. If the vector Q is not commensurate with the lattice there are eight possible phases: commensurate and incommensurate spin and charge density waves and four superconductivity phases, two of them with modulated order parameter of the FFLO type. The renormalization group equations are studied and numerically integrated. A re-entrant SDW phase (either commensurate or incommensurate is obtained as a function of the mismatch of the Fermi surfaces and the magnitude of |Q − G/2|.

  15. Robust Estimation of Electron Density From Anatomic Magnetic Resonance Imaging of the Brain Using a Unifying Multi-Atlas Approach

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Shangjie [Tianjin Key Laboratory of Process Measurement and Control, School of Electrical Engineering and Automation, Tianjin University, Tianjin (China); Department of Radiation Oncology, Stanford University School of Medicine, Palo Alto, California (United States); Hara, Wendy; Wang, Lei; Buyyounouski, Mark K.; Le, Quynh-Thu; Xing, Lei [Department of Radiation Oncology, Stanford University School of Medicine, Palo Alto, California (United States); Li, Ruijiang, E-mail: rli2@stanford.edu [Department of Radiation Oncology, Stanford University School of Medicine, Palo Alto, California (United States)

    2017-03-15

    Purpose: To develop a reliable method to estimate electron density based on anatomic magnetic resonance imaging (MRI) of the brain. Methods and Materials: We proposed a unifying multi-atlas approach for electron density estimation based on standard T1- and T2-weighted MRI. First, a composite atlas was constructed through a voxelwise matching process using multiple atlases, with the goal of mitigating effects of inherent anatomic variations between patients. Next we computed for each voxel 2 kinds of conditional probabilities: (1) electron density given its image intensity on T1- and T2-weighted MR images; and (2) electron density given its spatial location in a reference anatomy, obtained by deformable image registration. These were combined into a unifying posterior probability density function using the Bayesian formalism, which provided the optimal estimates for electron density. We evaluated the method on 10 patients using leave-one-patient-out cross-validation. Receiver operating characteristic analyses for detecting different tissue types were performed. Results: The proposed method significantly reduced the errors in electron density estimation, with a mean absolute Hounsfield unit error of 119, compared with 140 and 144 (P<.0001) using conventional T1-weighted intensity and geometry-based approaches, respectively. For detection of bony anatomy, the proposed method achieved an 89% area under the curve, 86% sensitivity, 88% specificity, and 90% accuracy, which improved upon intensity and geometry-based approaches (area under the curve: 79% and 80%, respectively). Conclusion: The proposed multi-atlas approach provides robust electron density estimation and bone detection based on anatomic MRI. If validated on a larger population, our work could enable the use of MRI as a primary modality for radiation treatment planning.

  16. Public and physician's expectations and ethical concerns about electronic health record: Benefits outweigh risks except for information security.

    Science.gov (United States)

    Entzeridou, Eleni; Markopoulou, Evgenia; Mollaki, Vasiliki

    2018-02-01

    Electronic Health Record systems (EHRs) offer numerous benefits in health care but also pose certain risks. As we progress toward the implementation of EHRs, a more in-depth understanding of attitudes that influence overall levels of EHR support is required. To record public and physicians' awareness, expectations for, and ethical concerns about the use of EHRs. A convenience sample was surveyed for both the public and physicians. The Public's Questionnaire was distributed to the public in a printed and an online version. The Physicians' Questionnaire was distributed to physicians in an online version. The questionnaires requested demographic characteristics followed by close-ended questions enquiring about awareness, perceived impact, perceived risks, and ethical issues raised by EHR use. In total, 46% of the public and 91% of physicians were aware of EHRs. Physicians' and public opinions were comparable concerning the positive impact of EHRs on better, more effective, and faster decisions on the patients' health, on better coordination between hospitals/clinics and on quality and reduced cost of health care. However, physicians were concerned that an EHR system would be a burden for their finances, for their time concerning training on the system, for their everyday workload and workflow. The majority of the public generally agreed that they would worry about the possibility that a non-authorized, third party might gain access to their personal health information (48.8%), and that they would worry about future discriminations due to possible disclosure of their health information (48.8%). Most physicians disagreed that EHRs will disrupt the doctor-patient relationship (58.1%) but they would worry about the safety of their patients' information (53.1%). Overall, both the public and physicians were in favor of the implementation of an EHR system, evaluating that possible benefits are more important than possible risks. The majority of the public believed that

  17. Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

    Science.gov (United States)

    Haider, S. A.; Kim, J.; Nagy, A. F.; Keller, C. N.; Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Szego, K.; Kiraly, P.

    1992-01-01

    The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

  18. Injection of auxiliary electrons for increasing the plasma density in highly charged and high intensity ion sources.

    Science.gov (United States)

    Odorici, F; Malferrari, L; Montanari, A; Rizzoli, R; Mascali, D; Castro, G; Celona, L; Gammino, S; Neri, L

    2016-02-01

    Different electron guns based on cold- or hot-cathode technologies have been developed since 2009 at INFN for operating within ECR plasma chambers as sources of auxiliary electrons, with the aim of boosting the source performances by means of a higher plasma lifetime and density. Their application to microwave discharge ion sources, where plasma is not confined, has required an improvement of the gun design, in order to "screen" the cathode from the plasma particles. Experimental tests carried out on a plasma reactor show a boost of the plasma density, ranging from 10% to 90% when the electron guns are used, as explained by plasma diffusion models.

  19. Stationary Conditions of the Electron Density Along the Reaction Path: Connection with Conceptual DFT and Information Theory.

    Science.gov (United States)

    Gonzalez, Carlos A; Squitieri, Emilio; Franco, Hector J; Rincon, Luis C

    2017-01-26

    The Kohn-Sham density functional theory (DFT) formalism has been used to investigate the influence of the stationary behavior of the electron density (ρ(r⃗;s)) along a minimum energy path on the corresponding stationary conditions observed in the total potential energy of the reactive system, information theory measures (Shannon information entropy and Onicescu information energy), and chemical reactivity indexes (the chemical hardness). The theoretical treatment presented in this work, combined with DFT calculations on 3 different test reactions: Ḣ' + H 2 , Ḣ' + CH 4 and H - + CH 4 , suggest that for any reactive system, properties that can be cast as a functional of the electron density, must exhibit stationary points along the IRC path modulated by the corresponding stationary behavior of the electron density.

  20. Strong correlation between D 2 density and electron temperature at the target of divertors found in SOLPS analysis

    Science.gov (United States)

    Stangeby, P. C.; Sang, Chaofeng

    2017-05-01

    A companion paper (Sang et al 2016 Nucl. Fusion (https://doi.org/10.1088/1741-4326/aa6548)) reports an assessment, using the SOLPS5.0 (B2-EIRENE) code, of the relative importance of two key aspects of divertor-baffle geometry: (i) divertor closure, and (ii) field-target angle. A wide range of the degree of divertor closure and field-target angle were modeled. An unexpectedly strong and simple correlation has been discovered in these data (and is reported here) between the electron temperature, T et, and the D 2 density, n{{D2}t}{} at the target, for T et  grid spanning two power decay widths outward from the separatrix. This may imply that achievement of low T et reduces, essentially, to identifying the divertor-baffle geometry which achieves the highest gas density near the target. To try to identify the controlling physics involved, two-point model formatting (2PMF) has been applied to the code output; it finds an equally strong and simple correlation between the 2PMF volumetric power-loss factor, {{f}\\text{vol-\\text{pwr}-\\text{loss}}} , and n{{D2}t}{} for each flux tube: {{f}\\text{vol-\\text{pwr}-\\text{loss}}}=1.2× {{10}29}n{{D2}t}-1.54~ with R 2 = 0.93. While these trends are broadly as would be expected, the simplicity, tightness and span of the correlations are not understood at present. Additionally, since more of the volumetric power loss is due to impurities than to deuterium, and as the impurities do not radiate just at the target, it is not evident why {{f}\\text{vol-\\text{pwr}-\\text{loss}}} is so strongly correlated with n{{D2}t}{} . To address these questions, in future work 2PMF analysis will be extended to compute the individual contributions to {{f}\\text{vol-\\text{pwr}-\\text{loss}}} .

  1. The Peruvian Citizen Perception and Expectation toward the e-Government. The Electronic Tax Payment as a Successful e-Gov Project

    Directory of Open Access Journals (Sweden)

    Diego Cardona

    2010-05-01

    Full Text Available In this chapter, the authors try to stand out how the Latin American governments, specifically the Peruvian government, can evaluate its efforts implementing electronic administration initiatives, identifying what the citizen expects from the electronic administration and how he or she perceives it, applying an evaluation model to the electronic tax payment service implemented, as a successful initiative at Latin-America. The proposed model to achieve this, was developed by one of the authors during his doctoral dissertation (Cardona, 2004 and evaluated by the other one as dissertation judge. It includes five different independent and latent constructs, Attitude, Aptitude, Trust, Relevance and Satisfaction that affect two dependent and latent constructs, the Citizen Perception and the Citizen Expectative towards its relationship with the Public Administration through the use of Information and Communication Technologies - ICT, under the effect of illustrative variables related with citizen, institutions and context.

  2. Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration

    Energy Technology Data Exchange (ETDEWEB)

    Awad, Wael [Lund University, Box 124, 221 00 Lund (Sweden); Cairo University, Cairo (Egypt); Svensson Birkedal, Gabriel [Lund University, Biomedical Center A13, 221 84 Lund (Sweden); Thunnissen, Marjolein M. G. M. [Lund University, Box 124, 221 00 Lund (Sweden); Lund University, Box 188, 221 00 Lund (Sweden); Mani, Katrin [Lund University, Biomedical Center A13, 221 84 Lund (Sweden); Logan, Derek T., E-mail: derek.logan@biochemistry.lu.se [Lund University, Box 124, 221 00 Lund (Sweden)

    2013-12-01

    The anisotropy of crystals of glypican-1 was significantly reduced by controlled dehydration using the HC1 device, allowing the building of previously disordered parts of the structure. The use of controlled dehydration for improvement of protein crystal diffraction quality is increasing in popularity, although there are still relatively few documented examples of success. A study has been carried out to establish whether controlled dehydration could be used to improve the anisotropy of crystals of the core protein of the human proteoglycan glypican-1. Crystals were subjected to controlled dehydration using the HC1 device. The optimal protocol for dehydration was developed by careful investigation of the following parameters: dehydration rate, final relative humidity and total incubation time T{sub inc}. Of these, the most important was shown to be T{sub inc}. After dehydration using the optimal protocol the crystals showed significantly reduced anisotropy and improved electron density, allowing the building of previously disordered parts of the structure.

  3. Transmission of electromagnetic waves through a two-layer plasma structure with spatially nonuniform electron density.

    Science.gov (United States)

    Denysenko, I B; Ivko, S; Smolyakov, A; Azarenkov, N A

    2012-11-01

    Transmission of a p-polarized electromagnetic wave through a two-layer plasma structure with spatially nonuniform distributions of electron density in the layers is studied. The case, when the electromagnetic wave is obliquely incident on the structure and is evanescent in both plasma layers, is considered. The conditions for total transparency of the two-layer structure are found for the thin slab case and when the plasma inhomogeneity is weak. It is shown that the transmission coefficient of the p-polarized wave can be about unity, even if the plasma inhomogeneity is large. The effects of plasma inhomogeneity on transparency of the structure are more important if the slabs are thick, comparing with the case of thin layers.

  4. Diffuse scattering provides material parameters and electron density profiles of biomembranes.

    Science.gov (United States)

    Liu, Yufeng; Nagle, John F

    2004-04-01

    Fully hydrated stacks of DOPC lipid bilayer membranes generate large diffuse x-ray scattering that corrupts the Bragg peak intensities that are used in conventional biophysical structural analysis, but the diffuse scattering actually contains more information. Using an efficient algorithm for fitting extensive regions of diffuse data to classical smectic liquid crystalline theory we first obtain the compressional modulus B= 10(13) erg/ cm(4), which involves interactions between membranes, and the bending modulus K(c) =8x 10(-13) erg of the membranes. The membrane form factor F ( q(z) ) is then obtained for most values of q(z) up to 0.8 A(-1). The electron density profile rho(z) is obtained by fitting models to F( q(z) ). Constraining the models to conform to other measurements provides structural quantities such as area A=72.1+/-0.5 A(2) per lipid at the interface.

  5. eRDF Analyser: An interactive GUI for electron reduced density function analysis

    Directory of Open Access Journals (Sweden)

    Janaki Shanmugam

    2017-01-01

    Full Text Available eRDF Analyser is an interactive MATLAB GUI for reduced density function (RDF or pair distribution function (PDF analysis of amorphous and polycrystalline materials to study their local structure. It is developed as an integrated tool with an easy-to-use interface that offers a streamlined approach to extract RDF from electron diffraction data without the need for external routines. The software incorporates recent developments in scattering factor parameterisation and an automated fitting routine for the atomic scattering curve. It also features an automated optimisation routine for determination of the position of the centre of diffraction patterns recorded using both central and off-centre locations of the incident beam. It is available in both open source code (MATLAB m-file and executable form.

  6. Cancer therapy using non-thermal atmospheric pressure plasma with ultra-high electron density

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Hiromasa [Institute of Innovation for Future Society, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Center for Advanced Medicine and Clinical Research, Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Mizuno, Masaaki [Center for Advanced Medicine and Clinical Research, Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Toyokuni, Shinya [Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Maruyama, Shoichi [Department of Nephrology, Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Kodera, Yasuhiro [Department of Gastroenterological Surgery (Surgery II), Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Terasaki, Hiroko [Department of Ophthalmology, Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Adachi, Tetsuo [Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, 501-1196 Gifu (Japan); Kato, Masashi [Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Kikkawa, Fumitaka [Department of Obstetrics and Gynecology, Nagoya University Graduate School of Medicine, Tsurumai-cho 65, Showa-ku, Nagoya 466-8550 (Japan); Hori, Masaru [Institute of Innovation for Future Society, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2015-12-15

    Cancer therapy using non-thermal atmospheric pressure plasma is a big challenge in plasma medicine. Reactive species generated from plasma are key factors for treating cancer cells, and thus, non-thermal atmospheric pressure plasma with high electron density has been developed and applied for cancer treatment. Various cancer cell lines have been treated with plasma, and non-thermal atmospheric plasma clearly has anti-tumor effects. Recent innovative studies suggest that plasma can both directly and indirectly affect cells and tissues, and this observation has widened the range of applications. Thus, cancer therapy using non-thermal atmospheric pressure plasma is promising. Animal experiments and understanding the mode of action are essential for clinical application in the future. A new academic field that combines plasma science, the biology of free radicals, and systems biology will be established.

  7. eRDF Analyser: An interactive GUI for electron reduced density function analysis

    Science.gov (United States)

    Shanmugam, Janaki; Borisenko, Konstantin B.; Chou, Yu-Jen; Kirkland, Angus I.

    eRDF Analyser is an interactive MATLAB GUI for reduced density function (RDF) or pair distribution function (PDF) analysis of amorphous and polycrystalline materials to study their local structure. It is developed as an integrated tool with an easy-to-use interface that offers a streamlined approach to extract RDF from electron diffraction data without the need for external routines. The software incorporates recent developments in scattering factor parameterisation and an automated fitting routine for the atomic scattering curve. It also features an automated optimisation routine for determination of the position of the centre of diffraction patterns recorded using both central and off-centre locations of the incident beam. It is available in both open source code (MATLAB m-file) and executable form.

  8. Trap density of GeNx/Ge interface fabricated by electron-cyclotron-resonance plasma nitridation

    Science.gov (United States)

    Fukuda, Yukio; Otani, Yohei; Toyota, Hiroshi; Ono, Toshiro

    2011-07-01

    We have investigated GeNx/Ge interface properties using Si3N4(7 nm)/GeNx(2 nm)/Ge metal-insulator-semiconductor structures fabricated by the plasma nitridation of Ge substrates using an electron-cyclotron-resonance-generated nitrogen plasma. The interface trap density (Dit) measured by the conductance method is found to be distributed symmetrically in the Ge band gap with a minimum Dit value lower than 3 × 1011 cm-2eV-1 near the midgap. This result may lead to the development of processes for the fabrication of p- and n-Ge Schottky-barrier (SB) source/drain metal-insulator-semiconductor field-effect transistors using chemically and thermally robust GeNx dielectrics as interlayers for SB source/drain contacts and high-κ gate dielectrics.

  9. Large-scale all-electron density functional theory calculations using an enriched finite element basis

    CERN Document Server

    Kanungo, Bikash

    2016-01-01

    We present a computationally efficient approach to perform large-scale all-electron density functional theory calculations by enriching the classical finite element basis with compactly supported atom-centered numerical basis functions that are constructed from the solution of the Kohn-Sham (KS) problem for single atoms. We term these numerical basis functions as enrichment functions, and the resultant basis as the enriched finite element basis. The enrichment functions are compactly supported through the use of smooth cutoff functions, which enhances the conditioning and maintains the locality of the basis. The integrals involved in the evaluation of the discrete KS Hamiltonian and overlap matrix in the enriched finite element basis are computed using an adaptive quadrature grid based on the characteristics of enrichment functions. Further, we propose an efficient scheme to invert the overlap matrix by using a block-wise matrix inversion in conjunction with special reduced-order quadrature rules to transform...

  10. Reproducibility of the cutoff probe for the measurement of electron density

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Oh, W. Y. [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); You, S. J., E-mail: sjyou@cnu.ac.kr [Department of Physics, Chungnam National University, Daejeon 305-701 (Korea, Republic of); Kwon, J. H.; You, K. H.; Seo, B. H.; Kim, J. H., E-mail: jhkim86@kriss.re.kr [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); Yoon, J.-S. [Plasma Technology Research Center, National Fusion Research Institute, Gunsan 573-540 (Korea, Republic of)

    2016-06-15

    Since a plasma processing control based on plasma diagnostics attracted considerable attention in industry, the reproducibility of the diagnostics using in this application has become a great interest. Because the cutoff probe is one of the potential candidates for this application, knowing the reproducibility of the cutoff probe measurement becomes quit important in the cutoff probe application research. To test the reproducibility of the cutoff probe measurement, in this paper, a comparative study among the different cutoff probe measurements was performed. The comparative study revealed remarkable result: the cutoff probe has a great reproducibility for the electron density measurement, i.e., there are little differences among measurements by different probes made by different experimenters. The discussion including the reason for the result was addressed via this paper by using a basic measurement principle of cutoff probe and a comparative experiment with Langmuir probe.

  11. Seasonal dependence of the longitudinal variations of nighttime ionospheric electron density and equivalent winds at southern midlatitudes

    Directory of Open Access Journals (Sweden)

    X. Luan

    2013-10-01

    Full Text Available It has been indicated that the observed Weddell Sea anomaly (WSA appeared to be an extreme manifestation of the longitudinal variations in the Southern Hemisphere, since the WSA is characterized by greater evening electron density than the daytime density in the region near the Weddell Sea. In the present study, the longitudinal variations of the nighttime F2-layer peak electron density at southern midlatitudes are analyzed using the observations of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC satellites between 2006 and 2008. It is found that significant longitudinal difference (> 150% relative to the minimum density at each local time prevails in all seasons, although the WSA phenomenon is only evident in summer under this solar minimum condition. Another interesting feature is that in summer, the maximum longitudinal differences occur around midnight (~ 23:00–00:00 LT rather than in the evening (19:00–21:00 LT in the evening, when the most prominent electron density enhancement occurs for the WSA phenomenon. Thus the seasonal–local time patterns of the electron density longitudinal variations during nighttime at southern midlatitudes cannot be simply explained in terms of the WSA. Meanwhile, the variations of the geomagnetic configuration and the equivalent magnetic meridional winds/upward plasma drifts are analyzed to explore their contributions to the longitudinal variations of the nighttime electron density. The maximum longitudinal differences are associated with the strongest wind-induced vertical plasma drifts after 21:00 LT in the Western Hemisphere. Besides the magnetic declination–zonal wind effects, the geographic meridional winds and the magnetic inclination also have significant effects on the upward plasma drifts and the resultant electron density.

  12. Optical excitation and electron relaxation dynamics at semiconductor surfaces: a combined approach of density functional and density matrix theory applied to the silicon (001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Buecking, N.

    2007-11-05

    In this work a new theoretical formalism is introduced in order to simulate the phononinduced relaxation of a non-equilibrium distribution to equilibrium at a semiconductor surface numerically. The non-equilibrium distribution is effected by an optical excitation. The approach in this thesis is to link two conventional, but approved methods to a new, more global description: while semiconductor surfaces can be investigated accurately by density-functional theory, the dynamical processes in semiconductor heterostructures are successfully described by density matrix theory. In this work, the parameters for density-matrix theory are determined from the results of density-functional calculations. This work is organized in two parts. In Part I, the general fundamentals of the theory are elaborated, covering the fundamentals of canonical quantizations as well as the theory of density-functional and density-matrix theory in 2{sup nd} order Born approximation. While the formalism of density functional theory for structure investigation has been established for a long time and many different codes exist, the requirements for density matrix formalism concerning the geometry and the number of implemented bands exceed the usual possibilities of the existing code in this field. A special attention is therefore attributed to the development of extensions to existing formulations of this theory, where geometrical and fundamental symmetries of the structure and the equations are used. In Part II, the newly developed formalism is applied to a silicon (001)surface in a 2 x 1 reconstruction. As first step, density-functional calculations using the LDA functional are completed, from which the Kohn-Sham-wave functions and eigenvalues are used to calculate interaction matrix elements for the electron-phonon-coupling an the optical excitation. These matrix elements are determined for the optical transitions from valence to conduction bands and for electron-phonon processes inside the

  13. Biomolecular Force Field Parameterization via Atoms-in-Molecule Electron Density Partitioning.

    Science.gov (United States)

    Cole, Daniel J; Vilseck, Jonah Z; Tirado-Rives, Julian; Payne, Mike C; Jorgensen, William L

    2016-05-10

    Molecular mechanics force fields, which are commonly used in biomolecular modeling and computer-aided drug design, typically treat nonbonded interactions using a limited library of empirical parameters that are developed for small molecules. This approach does not account for polarization in larger molecules or proteins, and the parametrization process is labor-intensive. Using linear-scaling density functional theory and atoms-in-molecule electron density partitioning, environment-specific charges and Lennard-Jones parameters are derived directly from quantum mechanical calculations for use in biomolecular modeling of organic and biomolecular systems. The proposed methods significantly reduce the number of empirical parameters needed to construct molecular mechanics force fields, naturally include polarization effects in charge and Lennard-Jones parameters, and scale well to systems comprised of thousands of atoms, including proteins. The feasibility and benefits of this approach are demonstrated by computing free energies of hydration, properties of pure liquids, and the relative binding free energies of indole and benzofuran to the L99A mutant of T4 lysozyme.

  14. High-speed digital holography for neutral gas and electron density imaging

    Energy Technology Data Exchange (ETDEWEB)

    Granstedt, E. M., E-mail: egranstedt@gmail.com [Princeton University, Princeton, New Jersey 08540 (United States); Thomas, C. E. [Third Dimension Technologies, Oak Ridge, Tennessee 37831 (United States); Kaita, R.; Majeski, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Baylor, L. R.; Meitner, S. J.; Combs, S. K. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2016-05-15

    An instrument was developed using digital holographic reconstruction of the wavefront from a CO{sub 2} laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1–25 μs pulses from a continuous-wave CO{sub 2} laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.

  15. Anomalous electron density events in the quiet summer ionosphere at solar minimum over Millstone Hill

    Directory of Open Access Journals (Sweden)

    A. V. Pavlo

    1998-04-01

    Full Text Available This study compares the observed behavior of the F region ionosphere over Millstone Hill with calculations from the IZMIRAN model for solar minimum for the geomagnetically quiet period 23-25 June 1986, when anomalously low values of hmF2(<200 km were observed. We found that these low values of hmF2 (seen as a G condition on ionograms exist in the ionosphere due to a decrease of production rates of oxygen ions resulting from low values of atomic oxygen density. Results show that determination of a G condition using incoherent scatter radar data is sensitive both to the true concentration of O+ relative to the molecular ions, and to the ion composition model assumed in the data reduction process. The increase in the O++ N 2 loss rate due to vibrationally excited N2 produces a reduction in NmF2 of typically 5-10% , but as large as 15% , bringing the model and data into better agreement. The effect of vibrationally excited NO+ ions on electron densities is negligible.Key words. Ionosphere (Ion chemistry and composition; Ionosphere-atmosphere interactions; Mid-latitude ionosphere.

  16. The mechanical, electronic and optical properties of KH under high pressure: a density functional theory study

    Science.gov (United States)

    Xinyou, An; Feng, Geng; Weiyi, Ren; Hui, Yang; Ziqi, He; Feiyu, Wang; Tixian, Zeng

    2017-03-01

    The mechanical, electronic and optical properties of KH under high pressure have been studied using the generalized gradient approximation and Heyd-Scuseria-Ernzerh of hybrid method within density functional theory. Based on the usual condition of equal enthalpies, high pressure phase transition of KH from B 1 to B 2 was confirmed, is about 4.1 GPa, and normalized volume collapse ΔV P /V 0 is about 11.09%. The calculated equilibrium structural parameters and elastic modulus are in excellent agreement with the experimental and other theoretical results. At ground states, B 1 KH is elastic stable, but B 2 KH is unstable. C 11 and c‧ are the main factors, which cause the structural phase transition under the pressures. The band structures and density of states of KH were calculated and analyzed in detail. Valance bands are local and conduction bands are continuous. The VBs mainly originate from K 3s, 3p and H 1s states, and the CBs consist of K 3s, 3p states, some hybridized levels are found between K 3s and 3p states. Mulliken population analysis of KH indicate that the charge populations of H 1s and K 3p states are very obvious but K 3s states are relatively weak, the charge transfers are from K to H. The linear response optical properties of KH were emphatically predicted combing with the band structures and frequency-dependent and dielectric function ε(ω).

  17. Vibrational analysis, electronic structure and nonlinear optical properties of Levofloxacin by density functional theory

    Science.gov (United States)

    Gunasekaran, Sethu; Rajalakshmi, K.; Kumaresan, Subramanian

    2013-08-01

    The Fourier transform (FT-IR) spectrum of Levofloxacin was recorded in the region 4000-400 cm-1 and a complete vibrational assignment of fundamental vibrational modes of the molecule was carried out using density functional method. The observed fundamental modes have been compared with the harmonic vibrational frequencies computed using DFT (B3LYP) method by employing 6-31 G (d, p) basis sets. The most stable geometry of the molecule under investigation has been determined from the potential energy scan. The first-order hyperpolarizability (βo) and other related properties (μ, αo) of Levofloxacin are calculated using density functional theory (DFT) on a finite field approach. UV-vis spectrum of the molecule was recorded and the electronic properties, such as HOMO and LUMO energies were performed by DFT using 6-31 G (d, p) basis sets. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that, the charge transfer occurs within the molecule. The other molecular properties like molecular electrostatic potential (MESP), Mulliken population analysis and thermodynamic properties of the title molecule have been calculated.

  18. Static and Dynamic Electronic (Hyperpolarizabilities of Dimethylnaphthalene Isomers: Characterization of Spatial Contributions by Density Analysis

    Directory of Open Access Journals (Sweden)

    Andrea Alparone

    2013-01-01

    Full Text Available Static and frequency-dependent electronic (hyperpolarizabilities of the dimethylnaphthalene (DMN isomers were computed in vacuum using the Coulomb-attenuating Density Functional Theory method. The nonlinear optical Second Harmonic Generation (SHG and Electro-Optical Pockels Effect (EOPE were investigated at the characteristic Nd:YAG laser wavelength of 1064 nm. The response electric properties especially the longitudinal polarizability, polarizability anisotropy, and first-order hyperpolarizability are significantly affected by the position of the methyl groups. The SHG and EOPE techniques can be potentially useful to discriminate the ,-DMN isomers (2,6-DMN < 2,7-DMN < 2,3-DMN as well as the ,-DMN isomers (1,5-DMN < 1,4-DMN < 1,8-DMN. The (hyperpolarizability differences among the investigated DMNs were elucidated through density analysis calculations. The predicted polarizabilities exhibit good linear relationships with the experimental first-order biomass-normalized rate coefficient, a physicochemical property connected to the rates of biodegradation processes of polycyclic aromatic hydrocarbons.

  19. Structural, elastic, electronic, and thermodynamic properties of MgAgSb investigated by density functional theory

    Science.gov (United States)

    Wang, Jun-Fei; Fu, Xiao-Nan; Zhang, Xiao-Dong; Wang, Jun-Tao; Li, Xiao-Dong; Jiang, Zhen-Yi

    2016-08-01

    The structural, elastic, electronic, and thermodynamic properties of thermoelectric material MgAgSb in γ,β,α phases are studied with first-principles calculations based on density functional theory. The optimized lattice constants accord well with the experimental data. According to the calculated total energy of the three phases, the phase transition order is determined from α to γ phase with cooling, which is in agreement with the experimental result. The physical properties such as elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and anisotropy factor are also discussed and analyzed, which indicates that the three structures are mechanically stable and each has a ductile feature. The Debye temperature is deduced from the elastic properties. The total density of states (TDOS) and partial density of states (PDOS) of the three phases are investigated. The TDOS results show that the γ phase is most stable with a pseudogap near the Fermi level, and the PDOS analysis indicates that the conduction band of the three phases is composed mostly of Mg-3s, Ag-4d, and Sb-5p. In addition, the changes of the free energy, entropy, specific heat, thermal expansion of γ-MgAgSb with temperature are obtained successfully. The obtained results above are important parameters for further experimental and theoretical tuning of doped MgAgSb as a thermoelectric material at high temperature. Project supported by the National Natural Science Foundation of China (Grant No. 11504088), the Fund from Henan University of Technology, China (Grant Nos. 2014YWQN08 and 2013JCYJ12), the Natural Science Fund from the Henan Provincial Education Department, China (Grant No. 16A140027), the Natural Science Foundation of Shaanxi Province of China (Grant Nos. 2013JQ1018 and 15JK1759), and the Science Foundation of Northwest University of China (Grant No. 14NW23).

  20. Oxide heterostructures for high density 2D electron gases on GaAs

    Science.gov (United States)

    Kornblum, Lior; Faucher, Joseph; Morales-Acosta, Mayra D.; Lee, Minjoo L.; Ahn, Charles H.; Walker, Frederick J.

    2018-01-01

    2D electron gases (2DEGs) that form at oxide interfaces provide a rich testbed of phenomena for condensed matter research, with emerging implementations in devices. Integrating such oxide systems with semiconductors advances these interesting phenomena toward technological applications. This approach further opens prospects of new functionalities arising from the potential to couple the 2DEG carriers with the semiconductor. In this work, we demonstrate the first integration of oxide 2DEGs with a direct bandgap III-V semiconductor. The growth and structural characteristics of (001) GdTiO3-SrTiO3 (GTO-STO) heterostructures on (001) GaAs are described. Analysis of the magnetotransport data yields a high electron density of ˜2 × 1014 cm-2 per GTO-STO interface, and points to the oxide interface as the source of the carriers. The effect of structure and defects on the transport properties is discussed within the context of the growth conditions and their limitations. These results provide a route for integrating oxide 2DEGs and other functional oxides with GaAs toward future device prospects and integration schemes.

  1. Analytical nuclear derivatives for the parametric two-electron reduced density matrix method

    Science.gov (United States)

    Valentine, Andrew J. S.; Mazziotti, David A.

    2017-10-01

    Efficient and accurate nuclear gradients are essential to performing molecular optimizations. Here for the first time we present analytical nuclear gradients for the parametric two-electron reduced-density-matrix method (p2-RDM), which uses the 2-RDM as the primary variable in calculations in lieu of the many-electron wavefunction. While numerical gradients require six energy evaluations for each atom, analytical gradients require only a single calculation for each geometry sampled. We present benchmark p2-RDM geometry optimizations that show analytical gradients reduce CPU times by as much as 80%, even for small molecules. We also use p2-RDM to evaluate the bond length alternation (BLA), or the difference in length between adjacent single and double bonds, of trans-polyacetylene (PA). We find that the BLA in the extrapolated limit to be 0.080 Å, in agreement with experiment and closely mirroring the prediction of the more expensive coupled-cluster with single and double excitations with perturbative triples (CCSD(T)).

  2. A density functional theory investigation of the electronic structure and spin moments of magnetite

    KAUST Repository

    Noh, Junghyun

    2014-08-01

    We present the results of density functional theory (DFT) calculations on magnetite, Fe3O4, which has been recently considered as electrode in the emerging field of organic spintronics. Given the nature of the potential applications, we evaluated the magnetite room-temperature cubic phase in terms of structural, electronic, and magnetic properties. We considered GGA (PBE), GGA + U (PBE + U), and range-separated hybrid (HSE06 and HSE(15%)) functionals. Calculations using HSE06 and HSE(15%) functionals underline the impact that inclusion of exact exchange has on the electronic structure. While the modulation of the band gap with exact exchange has been seen in numerous situations, the dramatic change in the valence band nature and states near the Fermi level has major implications for even a qualitative interpretation of the DFT results. We find that HSE06 leads to highly localized states below the Fermi level while HSE(15%) and PBE + U result in delocalized states around the Fermi level. The significant differences in local magnetic moments and atomic charges indicate that describing room-temperature bulk materials, surfaces and interfaces may require different functionals than their low-temperature counterparts.

  3. Europium Luminescence: Electronic Densities and Superdelocalizabilities for a Unique Adjustment of Theoretical Intensity Parameters

    Science.gov (United States)

    Dutra, José Diogo L.; Lima, Nathalia B. D.; Freire, Ricardo O.; Simas, Alfredo M.

    2015-09-01

    We advance the concept that the charge factors of the simple overlap model and the polarizabilities of Judd-Ofelt theory for the luminescence of europium complexes can be effectively and uniquely modeled by perturbation theory on the semiempirical electronic wave function of the complex. With only three adjustable constants, we introduce expressions that relate: (i) the charge factors to electronic densities, and (ii) the polarizabilities to superdelocalizabilities that we derived specifically for this purpose. The three constants are then adjusted iteratively until the calculated intensity parameters, corresponding to the 5D0→7F2 and 5D0→7F4 transitions, converge to the experimentally determined ones. This adjustment yields a single unique set of only three constants per complex and semiempirical model used. From these constants, we then define a binary outcome acceptance attribute for the adjustment, and show that when the adjustment is acceptable, the predicted geometry is, in average, closer to the experimental one. An important consequence is that the terms of the intensity parameters related to dynamic coupling and electric dipole mechanisms will be unique. Hence, the important energy transfer rates will also be unique, leading to a single predicted intensity parameter for the 5D0→7F6 transition.

  4. Electronic structures of one-dimensional poly-fused selenophene radical cations: density functional theory study

    Directory of Open Access Journals (Sweden)

    Hiroshi Kawabata et al

    2008-01-01

    Full Text Available Hybrid density functional theory (DFT calculations have been carried out for neutral and radical cation species of a fused selenophene oligomer, denoted by Se(n, where n represents the number of selenophene rings in the oligomer, to elucidate the electronic structures at ground and low-lying excited states. A polymer of fused selenophene was also investigated using one-dimensional periodic boundary conditions (PBC for comparison. It was found that the reorganization energy of a radical cation of Se(n from a vertical hole trapping point to its relaxed structure is significantly small. Also, the reorganization energy decreased gradually with increasing n, indicating that Se(n has an effective intramolecular hole transport property. It was found that the radical cation species of Se(n has a low-energy band in the near-IR region, which is strongly correlated to hole conductivity. The relationship between the electronic states and intramolecular hole conductivity was discussed on the basis of theoretical calculations.

  5. Benchmarks for electronically excited states: Time-dependent density functional theory and density functional theory based multireference configuration interaction

    DEFF Research Database (Denmark)

    Silva-Junior, Mario R.; Schreiber, Marko; Sauer, Stephan P. A.

    2008-01-01

    Time-dependent density functional theory (TD-DFT) and DFT-based multireference configuration interaction (DFT/MRCI) calculations are reported for a recently proposed benchmark set of 28 medium-sized organic molecules. Vertical excitation energies, oscillator strengths, and excited-state dipole...

  6. Investigation of the causes of the longitudinal variation of the electron density in the Weddell Sea Anomaly

    Science.gov (United States)

    Richards, P. G.; Meier, R. R.; Chen, Shih-Ping; Drob, D. P.; Dandenault, P.

    2017-06-01

    This paper investigates and quantifies the causes of the Weddell Sea Anomaly (WSA), a region near the tip of South America extending from approximately 30° to 120°W geographic longitude and 50° to 75°S geographic latitude at solar minimum between 2007 and 2010. This region is unusual because the midnight peak electron density exceeds the midday peak electron density in summer. This study is far more quantitative than previous studies because, unlike other models, it assimilates selected data parameters to constrain a physical model in order to investigate other aspects of the data. It is shown that the commonly accepted explanation that the WSA is related to the magnetic field declination and inclination effects on the neutral wind does not explain the longitudinal variation of the electron density. Rather, longitudinal changes in the neutral winds and neutral densities are the most likely explanation for the WSA. These longitudinal wind and density changes are attributed to the varying latitudinal distance from the auroral zone energy input. No contributions from the plasmasphere or other sources are required. Furthermore, it is shown that a widely used empirical thermosphere density model overestimates the longitudinal changes in the WSA region.type="synopsis">type="main">Plain Language SummaryThis paper investigates and quantifies the causes of the Weddell Sea Anomaly (WSA), a region near the tip of South America extending from approximately 30° to 120°W geographic longitude and 50° to 75°S geographic latitude at solar minimum between 2007 and 2010. This region is unusual because the midnight peak electron density exceeds the midday peak electron density in summer. This study is far more quantitative than previous studies because, unlike other models, it assimilates selected data parameters to constrain a physical model in order to investigate other aspects of the data. It is shown that the commonly accepted explanation that the WSA is related to the

  7. D-region electron densities obtained by differential absorption and phase measurements with a 3-MHz-Doppler radar

    Science.gov (United States)

    Singer, W.; Latteck, R.; Friedrich, M.; Dalin, P.; Kirkwood, S.; Engler, N.; Holdsworth, D.

    2005-08-01

    A Doppler radar at 3.17 MHz has been installed close to the Andøya Rocket Range as part of the ALOMAR observatory at Andenes, Norway (69.3°N, 16.0°E) in summer 2002 to improve the ground based capabilities for measurements of small scale features and electron number densities in the mesosphere. The main feature of the new radar is the transmitting/receiving antenna which is arranged as a Mills Cross of 29 crossed half-wave dipoles with a minimum beam width of about 7°. The modular transceiver system provides high flexibility in beam forming and pointing as well as in switching of the polarisation between ordinary and extraordinary mode on transmission and reception. Doppler winds and electron number densities can be measured between about 55 km and 90 km with a time resolution of 9 minutes. The electron number density profiles derived with differential absorption (DAE) and differential phase (DPE) measurements are in remarkable good agreement. We discuss the diurnal and seasonal variability of electron densities obtained at Andenes in 2004/2005, the response of D-region electron densities to geomagnetic disturbances and solar proton events. The results are compared with rocket measurements from Andenes and with observations from EISCAT VHF radar at Tromsø.

  8. D-region electron density and effective recombination coefficients during twilight – experimental data and modelling during solar proton events

    Directory of Open Access Journals (Sweden)

    A. Osepian

    2009-10-01

    Full Text Available Accurate measurements of electron density in the lower D-region (below 70 km altitude are rarely made. This applies both with regard to measurements by ground-based facilities and by sounding rockets, and during both quiet conditions and conditions of energetic electron precipitation. Deep penetration into the atmosphere of high-energy solar proton fluxes (during solar proton events, SPE produces extra ionisation in the whole D-region, including the lower altitudes, which gives favourable conditions for accurate measurements using ground-based facilities. In this study we show that electron densities measured with two ground-based facilities at almost the same latitude but slightly different longitudes, provide a valuable tool for validation of model computations. The two techniques used are incoherent scatter of radio waves (by the EISCAT 224 MHz radar in Tromsø, Norway, 69.6° N, 19.3° E, and partial reflection of radio-waves (by the 2.8 MHz radar near Murmansk, Russia, 69.0° N, 35.7° E. Both radars give accurate electron density values during SPE, from heights 57–60 km and upward with the EISCAT radar and between 55–70 km with the partial reflection technique. Near noon, there is little difference in the solar zenith angle between the two locations and both methods give approximately the same values of electron density at the overlapping heights. During twilight, when the difference in solar zenith angles increases, electron density values diverge. When both radars are in night conditions (solar zenith angle >99° electron densities at the overlapping altitudes again become equal. We use the joint measurements to validate model computations of the ionospheric parameters f+, λ, αeff and their variations during solar proton events. These parameters are important characteristics of the lower ionosphere structure which cannot be determined by other methods.

  9. D-region electron density and effective recombination coefficients during twilight - experimental data and modelling during solar proton events

    Science.gov (United States)

    Osepian, A.; Kirkwood, S.; Dalin, P.; Tereschenko, V.

    2009-10-01

    Accurate measurements of electron density in the lower D-region (below 70 km altitude) are rarely made. This applies both with regard to measurements by ground-based facilities and by sounding rockets, and during both quiet conditions and conditions of energetic electron precipitation. Deep penetration into the atmosphere of high-energy solar proton fluxes (during solar proton events, SPE) produces extra ionisation in the whole D-region, including the lower altitudes, which gives favourable conditions for accurate measurements using ground-based facilities. In this study we show that electron densities measured with two ground-based facilities at almost the same latitude but slightly different longitudes, provide a valuable tool for validation of model computations. The two techniques used are incoherent scatter of radio waves (by the EISCAT 224 MHz radar in Tromsø, Norway, 69.6° N, 19.3° E), and partial reflection of radio-waves (by the 2.8 MHz radar near Murmansk, Russia, 69.0° N, 35.7° E). Both radars give accurate electron density values during SPE, from heights 57-60 km and upward with the EISCAT radar and between 55-70 km with the partial reflection technique. Near noon, there is little difference in the solar zenith angle between the two locations and both methods give approximately the same values of electron density at the overlapping heights. During twilight, when the difference in solar zenith angles increases, electron density values diverge. When both radars are in night conditions (solar zenith angle >99°) electron densities at the overlapping altitudes again become equal. We use the joint measurements to validate model computations of the ionospheric parameters f+, λ, αeff and their variations during solar proton events. These parameters are important characteristics of the lower ionosphere structure which cannot be determined by other methods.

  10. Density function theory study on structures and electronic properties of 2Meq2AlOPh and its derivatives

    Science.gov (United States)

    Ji, Yanju; Liu, Xiaocun; Fu, Gang; Chen, Ying; Wang, Fengxiang; Zhao, Junqing

    2015-07-01

    Structures and electronic properties of 2Meq2AlOC6H4R (R=CN, Cl, H, OMe, NMe2) have been studied in the scheme of density function theory with the B3LYP and the 6-31G (d) basis set. The substitutions of the electron-withdrawing groups (CN, Cl) increase the band gap while the substitutions of the electron-donating groups (OMe, NMe2) decrease the gap. The substitutions of electron-withdrawing groups enhance the electron injection ability. In addition, the vertical ionization energies (IEV), the vertical electronic affinities (EAV) and reorganization energies of 2Meq2AlOPh and its derivatives are calculated in the work. All complexes are better electron transport materials.

  11. Evaporation of carbon using electrons of a high density plasma; Evaporacion de carbono usando los electrones de un plasma de alta densidad

    Energy Technology Data Exchange (ETDEWEB)

    Muhl, S.; Camps, E.; Escobar A, L.; Garcia E, J.L.; Olea, O. [Instituto de Investigaciones en Materiales, UNAM, C.P. 04510 Mexico D.F. (Mexico)

    2000-07-01

    The high density plasmas are used frequently in the preparation of thin films or surface modification, for example to nitridation. In these processes, are used mainly the ions and the neutrals which compose the plasma. However, the electrons present in the plasma are not used, except in the case of chemical reactions induced by collisions, although the electron bombardment usually get hot the work piece. Through the adequate polarization of a conductor material, it is possible to extract electrons from a high density plasma at low pressure, that could be gotten the evaporation of this material. As result of the interaction between the plasma and the electron flux with the vapor produced, this last will be ionized. In this work, it is reported the use of this novelty arrangement to prepare carbon thin films using a high density argon plasma and a high purity graphite bar as material to evaporate. It has been used substrates outside plasma and immersed in the plasma. Also it has been reported the plasma characteristics (temperature and electron density, energy and ions flux), parameters of the deposit process (deposit rate and ion/neutral rate) as well as the properties of the films obtained (IR absorption spectra and UV/Vis, elemental analysis, hardness and refractive index). (Author)

  12. In Silico Modeling of Indigo and Tyrian Purple Single-Electron Nano-Transistors Using Density Functional Theory Approach

    Science.gov (United States)

    Shityakov, Sergey; Roewer, Norbert; Förster, Carola; Broscheit, Jens-Albert

    2017-07-01

    The purpose of this study was to develop and implement an in silico model of indigoid-based single-electron transistor (SET) nanodevices, which consist of indigoid molecules from natural dye weakly coupled to gold electrodes that function in a Coulomb blockade regime. The electronic properties of the indigoid molecules were investigated using the optimized density-functional theory (DFT) with a continuum model. Higher electron transport characteristics were determined for Tyrian purple, consistent with experimentally derived data. Overall, these results can be used to correctly predict and emphasize the electron transport functions of organic SETs, demonstrating their potential for sustainable nanoelectronics comprising the biodegradable and biocompatible materials.

  13. Gaussian Mixture Density based Analytical Model of Noise Induced Variation in Key Parameter of Electronically Tunable Device

    Directory of Open Access Journals (Sweden)

    Rawid Banchuin

    2015-03-01

    Full Text Available In this research, the Gaussian mixture density based analytical model of variation in key parameter of electronically tunable device has been originally proposed. The proposed model is applicable to any electronically tunable device with its tuning variable has been affected by any kind of noise with arbitrary parameters. It has been found from the verification by using different electronically tunable device based empirical distributions and the Kolmogorov-Smirnov tests that this novel model is very accurate. So, it has been found to be a convenient mathematical tool for the analysis and design of various electronically tunable device based circuits.

  14. PMSE observations with the EISCAT VHF- and UHF-radars: Ice particles and their effect on ambient electron densities

    Science.gov (United States)

    Li, Qiang; Rapp, Markus

    2013-11-01

    It is now well understood that the occurrence of PMSE is closely connected to the presence of ice particles. These ice particles modify the ambient electron density by electron attachment which occasionally leads to large electron density depletions which have also been called ‘biteouts’. There has been some debate in the literature regarding the relative depth of such depletions which is usually expressed by the parameter Λ=|ZA|NA/ne. Here, |ZA|NA is the charge number density of ice particles and ne is the electron density. In this paper, we present, for the first time, the statistical distribution of Λ using measurements with the EISCAT VHF- and UHF-radars. Based on 25 h of simultaneous observations, we derived a total of 757 Λ values based on 15 min of data each. In each of these cases, PMSE were observed with the EISCAT VHF-radar but not with the UHF-radar and the UHF-measurement were hence used to determine the electron density profile. From these 757 cases, there are 699 cases with Λ⪡1, and only 33 cases with Λ>0.5 (21 cases with Λ>1). A correlation analysis of Λ versus PMSE volume reflectivities further reveals that there is no strong dependence between the two parameters. This is in accordance with current PMSE-theory based on turbulence in combination with a large Schmidt-number. The maxima of Λ from each profile show a negative relationship with the undisturbed electron densities deduced at the same altitudes. This reveals that the variability of Λ mainly depends on the variability of the electron densities. In addition, variations of aerosol number densities may also play a role. Although part of the observations were conducted during the HF heating experiments, the so-called overshoot effects did not significantly bias our statistical results. In order to avoid missing biteouts because of a superposition of coherent and incoherent scatter in the UHF-data, we finally calculated spectral parameters n by applying a simple fit to auto

  15. A method for 3D electron density imaging using single scattered x-rays with application to mammographic screening

    Energy Technology Data Exchange (ETDEWEB)

    Van Uytven, Eric [National Research Council Institute for Biodiagnostics, 435 Ellice Ave, Winnipeg, Manitoba, R3B 1Y6 (Canada); Pistorius, Stephen [Division of Medical Physics, CancerCare Manitoba, 675 McDermot Ave, Winnipeg, Manitoba, R3A 1R9 (Canada); Gordon, Richard [Department of Radiology, University of Manitoba, Winnipeg, Manitoba (Canada)], E-mail: eric.vanuytven@nrc-cnrc.gc.ca, E-mail: Stephen.Pistorius@cancercare.mb.ca, E-mail: gordonr@cc.umanitoba.ca

    2008-10-07

    Screening mammography is the current standard in detecting breast cancer. However, its fundamental disadvantage is that it projects a 3D object into a 2D image. Small lesions are difficult to detect when superimposed over layers of normal, heterogeneous tissue. In this work, we examine the potential of single scattered photon electron density imaging in a mammographic environment. Simulating a low-energy (<20 keV) scanning pencil beam, we have developed an algorithm capable of producing 3D electron density images from a single projection. We have tested the algorithm by imaging parts of a simulated mammographic accreditation phantom containing lesions of various sizes. The results indicate that the group of imaged lesions differ significantly from background breast tissue (p < 0.005), confirming that electron density imaging may be a useful diagnostic test for the presence of breast cancer.

  16. Stockholder projector analysis: a Hilbert-space partitioning of the molecular one-electron density matrix with orthogonal projectors.

    Science.gov (United States)

    Vanfleteren, Diederik; Van Neck, Dimitri; Bultinck, Patrick; Ayers, Paul W; Waroquier, Michel

    2012-01-07

    A previously introduced partitioning of the molecular one-electron density matrix over atoms and bonds [D. Vanfleteren et al., J. Chem. Phys. 133, 231103 (2010)] is investigated in detail. Orthogonal projection operators are used to define atomic subspaces, as in Natural Population Analysis. The orthogonal projection operators are constructed with a recursive scheme. These operators are chemically relevant and obey a stockholder principle, familiar from the Hirshfeld-I partitioning of the electron density. The stockholder principle is extended to density matrices, where the orthogonal projectors are considered to be atomic fractions of the summed contributions. All calculations are performed as matrix manipulations in one-electron Hilbert space. Mathematical proofs and numerical evidence concerning this recursive scheme are provided in the present paper. The advantages associated with the use of these stockholder projection operators are examined with respect to covalent bond orders, bond polarization, and transferability.

  17. Influence of plasma density on the generation of 100's MeV electrons via Direct Laser Acceleration

    Science.gov (United States)

    Hussein, Amina; Batson, T.; Arefiev, A. V.; Chen, H.; Craxton, R. S.; Davies, A.; Froula, D. H.; Haberberger, D.; Jansen, O.; Krushelnick, K.; Nilson, P. M.; Theobald, W.; Wang, T.; Williams, G. J.; Willingale, L.

    2017-10-01

    The role of plasma density and quasi-static fields in the acceleration of electrons to many times the ponderomotive energies (exceeding 400 MeV) by high-energy, picosecond duration laser pulses via Direct Laser Acceleration (DLA) from underdense CH plasma was investigated. Experiments using the OMEGA EP laser facility and two-dimensional particle-in-cell simulations using the EPOCH code were performed. The existence of an optimal plasma density for the generation of high-energy, low-divergence electron beams is demonstrated. The role of quasi-static channel fields on electron energy enhancement, beam pointing and divergence elucidate the mechanisms and action of DLA at different plasma densities. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-FOA-0001109.

  18. Ionospheric electron density irregularities observed by satellite-to-satellite, dual-frequency, low-low Doppler tracking link

    Science.gov (United States)

    Estes, R. D.; Grossi, M. D.

    1984-01-01

    A low-low, satellite-to-satellite, dual-frequency, Doppler tracking experiment was performed. The data are analyzed here for irregularities in electron density at the altitude of 212 km. The differential Doppler data with the relative motion term removed are integrated to obtain a representation of the electron density variation along the satellite path. Well-known large-scale features such as the equatorial geomagnetic anomaly and day/night ionization level differences are clearly observed in the integrated data. The larger crest of the morning geomagnetic anomaly is seen to occur in the southern (winter) hemisphere in agreement with previous observations. In addition, a sharp peak in the electron density at the day-to-night transition point is observed in two consecutive revolutions. This effect may be due to the previously postulated atmospheric shock wave generated by supersonic motion of the terminator.

  19. Radio science electron density profiles of lunar ionosphere based on the service module of circumlunar return and reentry spacecraft

    Science.gov (United States)

    Wang, M.; Han, S.; Ping, J.; Tang, G.; Zhang, Q.

    2017-09-01

    The existence of lunar ionosphere has been under debate for a long time. Radio occultation experiments had been performed by both Luna 19/22 and SELENE missions and electron column density of lunar ionosphere was provided. The Apollo 14 mission also acquired the electron density with in situ measurements. But the results of these missions don't well-matched. In order to explore the lunar ionosphere, radio occultation with the service module of Chinese circumlunar return and reentry spacecraft has been performing. One coherent S-band and X-band radio signals were recorded by China deep space stations, and local correlation was adopted to compute carrier phases of both signals. Based on the above work, the electron density profiles of lunar ionosphere was obtained and analyzed.

  20. Eliciting end-user expectations to guide the implementation process of a new electronic health record: A case study using concept mapping.

    Science.gov (United States)

    Joukes, Erik; Cornet, Ronald; de Bruijne, Martine C; de Keizer, Nicolette F

    2016-03-01

    To evaluate the usability of concept mapping to elicit the expectations of healthcare professionals regarding the implementation of a new electronic health record (EHR). These expectations need to be taken into account during the implementation process to maximize the chance of success of the EHR. Two university hospitals in Amsterdam, The Netherlands, in the preparation phase of jointly implementing a new EHR. During this study the hospitals had different methods of documenting patient information (legacy EHR vs. paper-based records). Concept mapping was used to determine and classify the expectations of healthcare professionals regarding the implementation of a new EHR. A multidisciplinary group of 46 healthcare professionals from both university hospitals participated in this study. Expectations were elicited in focus groups, their relevance and feasibility were assessed through a web-questionnaire. Nonmetric multidimensional scaling and clustering methods were used to identify clusters of expectations. We found nine clusters of expectations, each covering an important topic to enable the healthcare professionals to work properly with the new EHR once implemented: usability, data use and reuse, facility conditions, data registration, support, training, internal communication, patients, and collaboration. Average importance and feasibility of each of the clusters was high. Concept mapping is an effective method to find topics that, according to healthcare professionals, are important to consider during the implementation of a new EHR. The method helps to combine the input of a large group of stakeholders at limited efforts. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  1. Pnicogen bonds: a theoretical study based on the Laplacian of electron density.

    Science.gov (United States)

    Eskandari, K; Mahmoodabadi, N

    2013-12-05

    Although, most of the authors classify the pnicogen bonds as σ-hole bonding, there are some evidence that show they do not require any positive electrostatic potential around interacting molecules. In this work, the Laplacian of electron density is used to study pnicogen bonds in different dimer and trimer complexes. It is shown that the noncovalent P···P, P···N, and N···N bonds can be categorized as lump-hole interactions; a region of charge depletion and excess kinetics energy (hole) in the valence shell charge concentration (VSCC) of pnicogen atom combines with a region of charge concentration and excess potential energy (lump) in the VSCC of another molecule and form a pnicogen bond. In fact, since the full quantum potential (according to the local statement of virial theorem) has been used in the definition of the Laplacian, the lump-hole concept is more useful than the σ-hole in which the electrostatic part of potential is only considered. It is shown that the existence of hole in the VSCC of pnicogen atom is responsible for formation and (in the absence of other interactions) geometry of pnicogen bonded complexes. Because there is (at least) one hole in their VSCC, the pnicogen atoms in PH3, PH2F, H2C═PH, H2C═PF, and NH2F can engage in direct pnicogen-pnicogen interactions. However, the VSCC of nitrogen atom in the NH3 is devoid of hole and hence cannot act as an electron acceptor in pnicogen-bonded complexes.

  2. Small scale density variations of electrons and charged particles in the vicinity of polar mesosphere summer echoes

    Directory of Open Access Journals (Sweden)

    M. Rapp

    2003-01-01

    Full Text Available We present small scale variations of electron number densities and particle charge number densities measured in situ in the presence of polar mesosphere summer echoes. It turns out that the small scale fluctuations of electrons and negatively charged particles show a strong anticorrelation down to the smallest scales observed. Comparing these small scale structures with the simultaneously measured radar signal to noise profile, we find that the radar profile is well described by the power spectral density of both electrons and charged particles at the radar half wavelength (=the Bragg scale. Finally, we consider the shape of the power spectra of the observed plasma fluctuations and find that both charged particles and electrons show spectra that can be explained in terms of either neutral air turbulence acting on the distribution of a low diffusivity tracer or the fossil remnants of a formerly active turbulent region. All these results are consistent with the theoretical ideas by Rapp and Lübken (2003 suggesting that PMSE can be explained by a combination of active and fossil neutral air turbulence acting on the large and heavy charged aerosol particles which are subsequently mirrored in the electron number density distribution that becomes visible to a VHF radar when small scale fluctuations are present.

  3. The probability density function of energy loss for an electron by bremsstrahlung radiation in a thickness of a target

    Science.gov (United States)

    Kia, Mohammad Reza

    2017-10-01

    The probability density function (PDF) of energy loss for an electron by bremsstrahlung radiation in a thickness of a target is obtained by solving the collision term of the Boltzmann equation for the Bethe-Heitler differential cross section. It is demonstrated that the values of the energy loss for an electron by bremsstrahlung radiation will be important in order to calculate the total energy loss when the amount of screening from the atomic electrons becomes important. In this case, a stochastic equation based on the electron energy and the target properties is derived to calculate the energy loss of an electron by bremsstrahlung radiation in a thickness of a target. The results obtained from this analysis are in good agreement with the experimental data and the folding theory for the PDFs of total energy loss for an electron at a certain depth of a target reported in the literature.

  4. Density functional investigations of the properties and thermochemistry of UF6 and UF5 using valence-electron and all-electron approaches.

    Science.gov (United States)

    Batista, Enrique R; Martin, Richard L; Hay, P Jeffrey; Peralta, Juan E; Scuseria, Gustavo E

    2004-08-01

    The structural properties and thermochemistry of UF6 and UF5 have been investigated using both Hartree-Fock and density functional theory (DFT) approximations. Within the latter approach, the local spin-density approximation, the generalized gradient approximation, and hybrid density functionals were considered. To describe the uranium atom we employed small-core (60 electrons) and large-core (78 electrons) relativistic effective core potentials (RECPs), as well as the all-electron approximation based on the two-component third-order Douglas-Kroll-Hess Hamiltonian. For structural properties, we obtained very good agreement with experiment with DFT and both large and small-core RECPs. The best match with experiment is given by the hybrid functionals with the small-core RECP. The bond dissociation energy (BDE) was obtained from the relative energies of the fragments [UF6 --> UF5 + F], corrected for zero-point energy and spin-orbit interaction. Very good agreement was found between the BDE obtained from all-electron calculations and those calculated with the small-core RECP, while those from the large-core RECP are off by more than 50%. In order to obtain good agreement with experiment in the BDE it is imperative to work with hybrid density functionals and a small-core RECP. (c) 2004 American Institute of Physics.

  5. The effect of electron cyclotron heating on density fluctuations at ion and electron scales in ITER baseline scenario discharges on the DIII-D tokamak

    Science.gov (United States)

    Marinoni, A.; Pinsker, R. I.; Porkolab, M.; Rost, J. C.; Davis, E. M.; Burrell, K. H.; Candy, J.; Staebler, G. M.; Grierson, B. A.; McKee, G. R.; Rhodes, T. L.; The DIII-D Team

    2017-12-01

    Experiments simulating the ITER baseline scenario on the DIII-D tokamak show that torque-free pure electron heating, when coupled to plasmas subject to a net co-current beam torque, affects density fluctuations at electron scales on a sub-confinement time scale, whereas fluctuations at ion scales change only after profiles have evolved to a new stationary state. Modifications to the density fluctuations measured by the phase contrast imaging diagnostic (PCI) are assessed by analyzing the time evolution following the switch-off of electron cyclotron heating (ECH), thus going from mixed beam/ECH to pure neutral beam heating at fixed βN . Within 20 ms after turning off ECH, the intensity of fluctuations is observed to increase at frequencies higher than 200 kHz in contrast, fluctuations at lower frequency are seen to decrease in intensity on a longer time scale, after other equilibrium quantities have evolved. Non-linear gyro-kinetic modeling at ion and electron scales scales suggest that, while the low frequency response of the diagnostic is consistent with the dominant ITG modes being weakened by the slow-time increase in flow shear, the high frequency response is due to prompt changes to the electron temperature profile that enhance electron modes and generate a larger heat flux and an inward particle pinch. These results suggest that electron heated regimes in ITER will feature multi-scale fluctuations that might affect fusion performance via modifications to profiles.

  6. A Quantitative Analysis of Light-Driven Charge Transfer Processes Using Voronoi Partitioning of Time Dependent DFT-Derived Electron Densities

    NARCIS (Netherlands)

    Rombouts, J.A.; Ehlers, A.W.; Lammertsma, K.

    2017-01-01

    An analytical method is presented that provides quantitative insight into light-driven electron density rearrangement using the output of standard time-dependent density functional theory (TD-DFT) computations on molecular compounds. Using final and initial electron densities for photochemical

  7. Reduced-Density-Matrix Description of Decoherence and Relaxation Processes for Electron-Spin Systems

    Science.gov (United States)

    Jacobs, Verne

    2017-04-01

    Electron-spin systems are investigated using a reduced-density-matrix description. Applications of interest include trapped atomic systems in optical lattices, semiconductor quantum dots, and vacancy defect centers in solids. Complimentary time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations are self-consistently developed. The general non-perturbative and non-Markovian formulations provide a fundamental framework for systematic evaluations of corrections to the standard Born (lowest-order-perturbation) and Markov (short-memory-time) approximations. Particular attention is given to decoherence and relaxation processes, as well as spectral-line broadening phenomena, that are induced by interactions with photons, phonons, nuclear spins, and external electric and magnetic fields. These processes are treated either as coherent interactions or as environmental interactions. The environmental interactions are incorporated by means of the general expressions derived for the time-domain and frequency-domain Liouville-space self-energy operators, for which the tetradic-matrix elements are explicitly evaluated in the diagonal-resolvent, lowest-order, and Markov (short-memory time) approximations. Work supported by the Office of Naval Research through the Basic Research Program at The Naval Research Laboratory.

  8. FPGA based phase detection technique for electron density measurement in SST-1 tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Pramila, E-mail: pramila@ipr.res.in; Mandaliya, Hitesh; Rajpal, Rachana; Kaur, Rajwinder

    2016-11-15

    A multi-channel signal-conditioning and phase-detection concept is implemented in the prototype design using the high-precision OPAMP, high-speed comparators, high Q filters, high-density FPGA (Field Programmable Gate array), 10 MHz parallel-multiplying DACs (Digital to Analog Converter), etc. The complete digital-logic for the phase-detection is implemented inside the logic cells of FPGA using VHDL code, with high speed 100 MHz clock generated from Digital Clock Manager (DCM), which is used to measure the time elapsed between zero crossings of the two signals coming from reference and probe paths of the diagnostics. The logic is implemented to measure either leading or lagging phase and also to accumulate the total phase difference throughout the shot duration with the maximum value of accumulated phase of 5760 (16 cycles × 360°) degree and a resolution of 3.6 °. A precision high speed and high bandwidth (80 MHz) operational amplifiers are used as the front end-electronics component for conditioning the high-frequency (1 MHz) and low amplitude signal (μV). The hardware detail, implementation concept in FPGA and testing results will be presented in the paper.

  9. A method for estimating the temperature in high energy density free electron laser experiments

    Energy Technology Data Exchange (ETDEWEB)

    Principi, Emiliano, E-mail: emiliano.principi@unicam.i [CNISM, Dipartimento di Fisica, Universita degli Studi di Camerino via Madonna delle Carceri, I-62032 Camerino (Italy); Ferrante, Carino; Filipponi, Adriano [Dipartimento di Fisica, Universita degli Studi dell' Aquila, Via Vetoio, I-67100 L' Aquila (Italy); Bencivenga, Filippo; D' Amico, Francesco; Masciovecchio, Claudio [Synchrotron ELETTRA, Strada Statale 14-I-34149 Basovizza, Trieste (Italy); Di Cicco, Andrea [CNISM, Dipartimento di Fisica, Universita degli Studi di Camerino via Madonna delle Carceri, I-62032 Camerino (Italy); IMPMC, Universite Paris 6, CNRS, 140 rue de Lourmel, 75015 Paris (France)

    2010-09-21

    Present and forthcoming free electron laser (FEL) large scale facilities deliver high fluence ultrafast soft and hard X-ray pulses able to create and probe warm dense matter (WDM). Proper diagnostic for basic physical quantities, like temperature and density, is necessary, but the short lifetime of the WDM state (few ps) makes their measurements a challenging task. In this work we propose a method to estimate the WDM temperature using the experimental information from a slow temperature pyrometric probe exploiting the properties of the heat diffusion equation. Numerical simulations show that for typical thin foil samples, a temperature measurement with 1-10{mu}s temporal resolution at the distance of about 300-500{mu}m from the beam center contains sufficient information to retrieve the initial spatial temperature distribution with sufficient accuracy providing information on the temperature reached in the WDM regime. The inversion of the experimental information is obtained by means of a Bayesian approach exploiting a Metropolis Monte Carlo numerical procedure. The model and calculations presented in this work provide the theoretical background for the development of a device for temperature diagnostics of the TIMEX end-station at the Fermi-Elettra FEL facility.

  10. Determination of effective atomic number and electron density of heavy metal oxide glasses

    Science.gov (United States)

    Ali, A. M.; El-Khayatt, A. M.; Akkurt, I.

    2016-03-01

    The effective atomic number (Zeff) and effective electron density (Neff) of eight heavy metal oxide (HMO) glasses have been determined using the Monte Carlo simulation code MCNP for the energy range of 10 keV-10 MeV. The interpolation method was employed to extract Zeff and Neff values from the simulation and that calculated with the help of XCOM program. Comparisons are also made with predictions from the Auto-Zeff software in the same energy region. Wherever possible, the simulated values of Zeff and Neff are compared with experimental data. In general, a very good agreement was noticed. It was found that the Zeff and Neff vary with photon energy and do not have extended intermediate regions where Compton scattering is truly dominating; only dips slightly above ∼1.5 MeV were recorded. Zeff and Neff are found to increase with PbO and Bi2O3 contents. It was found that the Zeff value rather than the Neff value is a better indicator for PbO and/or Bi2O3 contents.

  11. Beta-Barrel Detection for Medium Resolution Cryo-Electron Microscopy Density Maps Using Genetic Algorithms and Ray Tracing.

    Science.gov (United States)

    Ng, Albert; Si, Dong

    2017-10-16

    Cryo-electron microscopy (cryo-EM) is a technique that produces three-dimensional density maps of large protein complexes. This allows for the study of the structure of these proteins. Identifying the secondary structures within proteins is vital to understanding the overall structure and function of the protein. The [Formula: see text]-barrel is one such secondary structure, commonly found in lipocalins and membrane proteins. In this article, we present a novel approach that utilizes genetic algorithms, kd-trees, and ray tracing to automatically detect and extract [Formula: see text]-barrels from cryo-EM density maps. This approach was tested on simulated and experimental density maps with zero, one, or multiple barrels in the density map. The results suggest that the proposed approach is capable of performing automatic detection of [Formula: see text]-barrels from medium resolution cryo-EM density maps.

  12. Assessment of oscillator strengths with multiconfigurational short-range density functional theory for electronic excitations in organic molecules

    DEFF Research Database (Denmark)

    Hedegård, Erik Donovan

    2017-01-01

    considered the large collection of organic molecules whose excited states were investigated with a range of electronic structure methods by Thiel et al. As a by-product of our calculations of oscillator strengths, we also obtain electronic excitation energies, which enable us to compare the performance......We have in a series of recent papers investigated electronic excited states with a hybrid between a complete active space self-consistent field (CASSCF) wave function and density functional theory (DFT). This method has been dubbed the CAS short-range DFT method (CAS–srDFT). The previous papers...

  13. An all-electron calculation of an antihypertensive protein with the Gaussian-based density functional method

    Science.gov (United States)

    Sato, Fumitoshi; Yoshihiro, Tamotsu; Okazaki, Isao; Kashiwagi, Hiroshi

    1999-09-01

    An all-electron calculation of the antihypertensive and antiviral protein BDS-I from the sea anemone Anemonia sulcata was carried out using the density functional method based on Gaussian-type orbitals with workstations. Our computer program ProteinDF coded by the object-oriented language C++, was originally designed for all-electron calculations of proteins and controlled in parallel with high efficiency. The numbers of residues, atoms, orbitals and auxiliary functions of the calculated protein were 43, 629, 3615 and 6545, respectively. This Letter reports timing data of the computation and some calculated electronic properties. Our program will open the door for advanced studies of larger proteins.

  14. Charge and current density profiles of a degenerate magnetized free-electron gas near a hard wall

    NARCIS (Netherlands)

    Kettenis, M.M.; Suttorp, L.G.

    1998-01-01

    The charge and current densities of a completely degenerate free-electron gas in a uniform magnetic field are found to have a damped oscillatory spatial dependence near a wall that is parallel to the magnetic field. For large distances from the wall the behaviour of the associated profile functions

  15. Electron-pair densities of group 2 atoms in their {sup 1}P and {sup 3}P terms

    Energy Technology Data Exchange (ETDEWEB)

    Koga, T. [Muroran Inst. of Tech., Hokkaido (Japan). Dept. of Applied Chemistry]|[Institute Carlos I de Fisica Teorica y Computacional, Facultad de Ciencias, Universidad de Granada, Granada 18071 (Spain); Matsuyama, H. [Muroran Inst. of Tech., Hokkaido (Japan). Dept. of Applied Chemistry; Molina, J.M. [Grupo de Modelizacion y Dise no Molecular, Instituto de Biotecnologia, Universidad de Granada, Granada 18071 (Spain); Dehesa, J.S. [Institute Carlos I de Fisica Teorica y Computacional, Facultad de Ciencias, Universidad de Granada, Granada 18071 (Spain)

    1999-08-01

    Electron-pair intracule (relative motion) and extracule (center-of-mass motion) densities are studied in both position and momentum spaces for the {sup 1}P and {sup 3}P terms of the group 2 atoms Be (atomic number Z=4), Mg (Z=12), Ca (Z=20), Sr (Z=38), Ba (Z=56), and Ra (Z=88). In position space, the {sup 1}P-{sup 3}P difference in the intracule densities shows that the probability of a small interelectronic distance is larger in the triplet for all the six atoms, as reported for the lightest Be atom in the literature. The position-space extracule density clarifies that the triplet electrons are more likely to be at opposite positions with respect to the nucleus than the singlet electrons for all the atoms. In momentum space, the singlet generally has a larger probability of a small relative momentum between two electrons as a naive manifestation of the Fermi hole in the triplet. The extracule density in momentum space shows that the {sup 1}P term has a distribution larger in a large center-of-mass momentum region than the {sup 3}P term. (orig.) 27 refs.

  16. MODEL-OBSERVATION COMPARISONS OF ELECTRON NUMBER DENSITIES IN THE COMA OF 67P/CHURYUMOV–GERASIMENKO DURING 2015 JANUARY

    Energy Technology Data Exchange (ETDEWEB)

    Vigren, E.; Edberg, N. J. T.; Eriksson, A. I.; Johansson, F.; Odelstad, E. [Swedish Institute of Space Physics, Uppsala (Sweden); Altwegg, K.; Tzou, C.-Y. [Physikalisches Institut, University of Bern, Bern (Switzerland); Galand, M. [Department of Physics, Imperial College London, London (United Kingdom); Henri, P.; Valliéres, X., E-mail: erik.vigren@irfu.se [Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, Orleans (France)

    2016-09-01

    During 2015 January 9–11, at a heliocentric distance of ∼2.58–2.57 au, the ESA Rosetta spacecraft resided at a cometocentric distance of ∼28 km from the nucleus of comet 67P/Churyumov–Gerasimenko, sweeping the terminator at northern latitudes of 43°N–58°N. Measurements by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Comet Pressure Sensor (ROSINA/COPS) provided neutral number densities. We have computed modeled electron number densities using the neutral number densities as input into a Field Free Chemistry Free model, assuming H{sub 2}O dominance and ion-electron pair formation by photoionization only. A good agreement (typically within 25%) is found between the modeled electron number densities and those observed from measurements by the Mutual Impedance Probe (RPC/MIP) and the Langmuir Probe (RPC/LAP), both being subsystems of the Rosetta Plasma Consortium. This indicates that ions along the nucleus-spacecraft line were strongly coupled to the neutrals, moving radially outward with about the same speed. Such a statement, we propose, can be further tested by observations of H{sub 3}O{sup +}/H{sub 2}O{sup +} number density ratios and associated comparisons with model results.

  17. Density dependence of electron-spin polarization and relaxation in intrinsic GaAs at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Teng, L H; Chen, K; Wen, J H; Lin, W Z; Lai, T S, E-mail: stslts@mail.sysu.edu.c [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Zhongshan (Sen Yat-Sen) University, Guangzhou, Guangdong 510275 (China)

    2009-07-07

    Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier-density dependence of the electron-spin polarization and spin relaxation dynamics in bulk intrinsic GaAs near the bottom of the conduction band. The experimental result shows that the initial degree of the electron-spin polarization is less than 0.5, and both the initial degree of spin polarization and the spin relaxation time decrease with increasing carrier densities. The simulation calculation shows that the band-gap renormalization effect has a significant influence on the initial degree of spin polarization, but it is not the physical origin of the decrease in the electron-spin polarization. Contrarily, the initial degree of spin polarization can be greatly enhanced by the band-gap renormalization effect for carrier densities above 3.5 x 10{sup 17} cm{sup -3}. In intrinsic GaAs, both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms play an important role. The Bir-Aronov-Pikus mechanism becomes stronger with the increase in the carrier density, and becomes dominant at high carrier density.

  18. Density dependence of electron-spin polarization and relaxation in intrinsic GaAs at room temperature

    Science.gov (United States)

    Teng, L. H.; Chen, K.; Wen, J. H.; Lin, W. Z.; Lai, T. S.

    2009-07-01

    Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier-density dependence of the electron-spin polarization and spin relaxation dynamics in bulk intrinsic GaAs near the bottom of the conduction band. The experimental result shows that the initial degree of the electron-spin polarization is less than 0.5, and both the initial degree of spin polarization and the spin relaxation time decrease with increasing carrier densities. The simulation calculation shows that the band-gap renormalization effect has a significant influence on the initial degree of spin polarization, but it is not the physical origin of the decrease in the electron-spin polarization. Contrarily, the initial degree of spin polarization can be greatly enhanced by the band-gap renormalization effect for carrier densities above 3.5 × 1017 cm-3. In intrinsic GaAs, both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms play an important role. The Bir-Aronov-Pikus mechanism becomes stronger with the increase in the carrier density, and becomes dominant at high carrier density.

  19. Time-dependent quantum many-body systems. Linear response, electronic transport, and reduced density matrices

    Energy Technology Data Exchange (ETDEWEB)

    Appel, H.

    2007-05-15

    In part I of this work we present a double-pole approximation (DPA) to the response equations of time-dependent density functional theory (TDDFT). The double-pole approximation provides an exact description of systems with two strongly coupled excitations which are isolated from the rest of the spectrum. In contrast to the traditional single-pole approximation of TDDFT the DPA also yields corrections to the Kohn-Sham oscillator strengths. We also demonstrate how to invert the double-pole solution which allows us to predict matrix elements of the exchange-correlation kernel f{sub xc} from experimental input. We attempt some first steps towards a time-dependent generalization of reduced density matrix functional theory (RDMFT). In part II we derive equations of motion for natural orbitals and occupation numbers. Using the equation of motion for the occupation numbers we show that an adiabatic extension of presently known ground-state functionals of static RDMFT always leads to occupation numbers which are constant in time. From the stationary conditions of the equations of motion for the N-body correlations (correlated parts of the N-body matrices) we derive a new class of ground-state functionals which can be used in static RDMFT. Applications are presented for a one-dimensional model system where the time-dependent many-body Schroedinger equation can be propagated numerically. We use optimal control theory to find optimized laser pulses for transitions in a model for atomic Helium. From the numerically exact correlated wavefunction we extract the exact time evolution of natural orbitals and occupation numbers for (i) laser-driven Helium and (ii) electron-ion scattering. Part III of this work considers time-dependent quantum transport within TDDFT. We present an algorithm for the calculation of extended eigenstates of single-particle Hamiltonians which is especially tailored to a finite-difference discretization of the Schroedinger equation. We consider the

  20. A Statistical Test of the Relationship Between Chorus Wave Activation and Anisotropy of Electron Phase Space Density

    Directory of Open Access Journals (Sweden)

    Dong-Hee Lee

    2014-12-01

    Full Text Available Whistler mode chorus wave is considered to play a critical role in accelerating and precipitating the electrons in the outer radiation belt. In this paper we test a conventional scenario of triggering chorus using THEMIS satellite observations of waves and particles. Specifically, we test if the chorus onset is consistent with development of anisotropy in the electron phase space density (PSD. After analyzing electron PSD for 73 chorus events, we find that, for ~80 % of them, their onsets are indeed associated with development of the positive anisotropy in PSD where the pitch angle distribution of electron velocity peaks at 90 degrees. This PSD anisotropy is prominent mainly at the electron energy range of ≤ ~20 keV. Interestingly, we further find that there is sometimes a time delay among energies in the increases of the anisotropy: A development of the positive anisotropy occurs earlier by several minutes for lower energy than for an adjacent higher energy.

  1. Measuring the magnetic-field-dependent chemical potential of a low-density three-dimensional electron gas in n -GaAs and extracting its magnetic susceptibility

    Science.gov (United States)

    Roy Choudhury, Aditya N.; Venkataraman, V.

    2016-01-01

    We report the magnetic-field-dependent shift of the electron chemical potential in bulk, n -type GaAs at room temperature. A transient voltage of ˜100 μ V was measured across a Au-Al2O3 -GaAs metal-oxide-semiconductor capacitor in a pulsed magnetic field of ˜6 T . Several spurious voltages larger than the signal that had plagued earlier researchers performing similar experiments were carefully eliminated. The itinerant magnetic susceptibility of GaAs is extracted from the experimentally measured data for four different doping densities, including one as low as 5 ×1015cm-3 . Though the susceptibility in GaAs is dominated by Landau-Peierls diamagnetism, the experimental technique demonstrated can be a powerful tool for extracting the total free carrier magnetization of any electron system. The method is also virtually independent of the carrier concentration and is expected to work better in the nondegenerate limit. Such experiments had been successfully performed in two-dimensional electron gases at cryogenic temperatures. However, an unambiguous report on having observed this effect in any three-dimensional electron gas has been lacking. We highlight the 50 year old literature of various trials and discuss the key details of our experiment that were essential for its success. The technique can be used to unambiguously yield only the itinerant part of the magnetic susceptibility of complex materials such as magnetic semiconductors and hexaborides, and thus shed light on the origin of ferromagnetism in such systems.

  2. Quantitative evaluation of magnetic flux density in a magnetic recording head and pseudo soft underlayer by electron holography.

    Science.gov (United States)

    Xia, Weixing; Hirata, Kei; Yanagisawa, Keiichi; Ishida, Yoichi; Kasai, Hiroto; Yanagiuchi, Katsuaki; Shindo, Daisuke; Tonomura, Akira

    2010-01-01

    The magnetic interaction between the pole tip of a single-pole head and a pseudo soft underlayer in perpendicular magnetic recording was observed by electron holography. The magnetic flux density inside the soft underlayer was quantitatively evaluated. The distribution of magnetic flux density was calculated using the finite element method, and the influences of the modulation of the reference wave and stray fields were investigated by comparison with experimental results. The flux density observed was found to be underestimated due to the modulation of the phase shift in reference wave. The magnetic flux measured experimentally was larger than that inside the specimen because of the relatively large stray fields above and below the specimen in the direction of the electron beam.

  3. Femtosecond laser high-efficiency drilling of high-aspect-ratio microholes based on free-electron-density adjustments.

    Science.gov (United States)

    Jiang, Lan; Fang, Juqiang; Cao, Qiang; Zhang, Kaihu; Wang, Peng; Yu, Yanwu; Huang, Qiang; Lu, Yongfeng

    2014-11-01

    We studied the micromachining of high-aspect-ratio holes in poly(methylmethacrylate) using a visible double-pulse femtosecond laser based on free-electron-density adjustments. Hole depth and aspect ratio increased simultaneously upon decreasing the wavelength in the visible-light zone. When the pulse energy reached a high level, the free-electron density was adjusted by using a double-pulse laser, which induced fewer free electrons, a lower reflectivity plasma plume, and more pulse energy deposition in the solid bottom. Thus, the aspect ratio of the hole was improved considerably. At a moderate pulse energy level, a 1.3-1.4 times enhancement of both the ablation depth and the aspect ratio was observed when the double-pulse delay was set between 100 and 300 fs, probably due to an enhanced photon-electron coupling effect through adjusting the free-electron density. At a lower pulse energy level, this effect also induced the generation of a submicrometer string. In addition, the ablation rate was improved significantly by using visible double pulses.

  4. Neural-network-based depth-resolved multiscale structural optimization using density functional theory and electron diffraction data

    Science.gov (United States)

    Pennington, Robert S.; Coll, Catalina; Estradé, Sònia; Peiró, Francesca; Koch, Christoph T.

    2018-01-01

    Iterative neural-network-based three-dimensional structural optimization of atomic positions over tens of nanometers is performed using transmission electron microscope (TEM) diffraction data simulated from density functional theory (DFT) all-electron densities, thus retrieving parameter variations along the beam direction. We first use experimental data to show that the GPAW DFT code's all-electron densities are considerably more accurate for electron diffraction calculations compared to conventional isolated-atom scattering factors, and they also compare well to Wien2K DFT simulations. This DFT-TEM combination is then integrated into an iterative neural-network-optimization-based algorithm (PRIMES, parameter retrieval and inversion from multiple electron scattering) to retrieve nanometer-scale ferroelectric polarization domains and strain in theoretical bulklike specimens from TEM data. DFT and isolated-atom methods produce substantially different diffraction patterns and retrieved polarization domain parameters, and DFT is sufficient to retrieve strain properties from a silicon specimen simulated using experimentally derived structure factors. Thus, we show that the improved accuracy, fast computation, and intuitive integration make the GPAW DFT code well suited for three-dimensional materials characterization and demonstrate this using an iterative neural-network algorithm that is verifiable on the mesoscale and, with DFT integration, self-consistent on the nanoscale.

  5. Electron number density profiles derived from radio occultation on the CASSIOPE spacecraft

    DEFF Research Database (Denmark)

    Shume, E. B.; Vergados, P.; Komjathy, A.

    2017-01-01

    good agreement with density profiles estimated from ionosonde data, measured over nearby stations to the latitude and longitude of the RO tangent points, (2) in good agreement with density profiles inferred from GPS RO measured by the Constellation Observing System for Meteorology, Ionosphere...... number density profiles retrieved over landmasses and oceans. The density profiles over oceans exhibit wide-spread values and scale heights compared to density profiles over landmasses. We provide an explanation for the ocean-landmass discrepancy in terms of the unique wave coupling mechanisms operating...

  6. Irradiation Tests and Expected Performance of Readout Electronics of the ATLAS Hadronic Endcap Calorimeter for the HL-LHC

    CERN Document Server

    Nagel, M; The ATLAS collaboration

    2013-01-01

    The readout electronics of the ATLAS Hadronic Endcap Calorimeter will have to withstand an about 10 times larger radiation environment at the future high-luminosity LHC (HL-LHC) compared to their design values. The GaAs ASIC, which comprises the heart of the readout electronics and consists of a Pre-Amplification and a Summing stage (PAS), has been exposed to neutron and proton radiation with fluences corresponding to ten years of running of the HL-LHC. Neutron tests were performed at the NPI in Rez, Czech Republic, where a 36 MeV proton beam is directed on a thick heavy water target to produce neutrons. The proton irradiation was done with 200 MeV protons at the PROSCAN area of the Proton Irradiation Facility at the PSI in Villigen, Switzerland. In-situ measurements of S-parameters in both tests allow the evaluation of frequency dependent performance parameters, like gain and input impedance, as a function of fluence. The non-linearity of the ASIC response has been measured directly in the neutron tests with...

  7. Irradiation Tests and Expected Performance of Readout Electronics of the ATLAS Hadronic Endcap Calorimeter for the HL-LHC

    CERN Document Server

    INSPIRE-00030110; The ATLAS collaboration

    2013-01-01

    The readout electronics of the ATLAS Hadronic Endcap Calorimeter (HEC) will have to withstand an about 3-5 times larger radiation environment at the future high-luminosity LHC (HLLHC) compared to their design values. The preamplifier and summing boards (PSBs), which are equipped with GaAs ASICs and comprise the heart of the readout electronics, were irradiated with neutrons and protons with fluences surpassing several times ten years of operation of the HL-LHC. Neutron tests were performed at the NPI in Rez, Czech Republic, where a 36 MeV proton beam was directed on a thick heavy water target to produce neutrons. The proton irradiation was done with 200 MeV protons at the PROSCAN area of the Proton Irradiation Facility at the PSI in Villigen, Switzerland. In-situ measurements of S-parameters in both tests allow the evaluation of frequency dependent performance parameters, like gain and input impedance, as a function of fluence. The linearity of the ASIC response was measured directly in the neutron tests with...

  8. Approximating the nonlinear density dependence of electron transport coefficients and scattering rates across the gas–liquid interface

    Science.gov (United States)

    Garland, N. A.; Boyle, G. J.; Cocks, D. G.; White, R. D.

    2018-02-01

    This study reviews the neutral density dependence of electron transport in gases and liquids and develops a method to determine the nonlinear medium density dependence of electron transport coefficients and scattering rates required for modeling transport in the vicinity of gas–liquid interfaces. The method has its foundations in Blanc’s law for gas-mixtures and adapts the theory of Garland et al (2017 Plasma Sources Sci. Technol. 26) to extract electron transport data across the gas–liquid transition region using known data from the gas and liquid phases only. The method is systematically benchmarked against multi-term Boltzmann equation solutions for Percus–Yevick model liquids. Application to atomic liquids highlights the utility and accuracy of the derived method.

  9. Dispersion and density of states of phonons and electrons in an α-B12 crystal determined from first principles

    Science.gov (United States)

    Mavrin, B. N.; Reshetnyak, V. V.

    2017-07-01

    Using the DFT method, we study the phonon properties of an α-B12 rhombohedral crystal in the basis set of plane waves and its electronic structure in the localized basis set of Gaussians. It follows from the phonon dispersion that the crystal possesses a dynamical stability. The effective Born charges, the oscillator strengths, the transverse-longitudinal splitting, and the dielectric functions of dipole modes are calculated. We show that charge transfer from polar to equatorial atoms takes place in a B12 icosahedron, while B-B bonds have predominantly a covalent character. In the density of states of acoustic modes, we reveal a structure that can manifest itself in the spectra of disordered boron compounds. From the dispersion of electronic bands, the occurrence of an indirect energy gap follows. The overlap of partial densities implies the hybridization of s and p electronic states in boron atoms.

  10. Determination of the Electron Density and Electron Temperature in A Magnetron Discharge Plasma Using Optical Spectroscopy and the Collisional-Radiative Model of Argon

    Science.gov (United States)

    Evdokimov, K. E.; Konishchev, M. E.; Pichugin, V. F.; Pustovalova, A. A.; Ivanova, N. M.; Sun', Ch.

    2017-09-01

    A method for determining the electron temperature and electron density in a plasma is proposed that is based on minimization of the difference between the experimental relative intensities of the spectral argon (Ar) lines and those same intensities calculated with the aid of the collisional-radiative model. The model describes the kinetics of the ground state and 40 excited states of the Ar atom and takes into account the following processes: excitation and deactivation of the states of the atom by electron impact, radiative decay of the excited states, self-absorption of radiation, ionization of excited states by electron impact, and quenching of metastable states as a consequence of collisions with the chamber walls. Using the given method, we have investigated the plasma of a magnetron discharge on a laboratory setup for intermediate-frequency magnetron sputtering for a few selected operating regimes.

  11. Effects of rf power on electron density and temperature, neutral temperature, and Te fluctuations in an inductively coupled plasma

    Science.gov (United States)

    Camparo, James; Fathi, Gilda

    2009-05-01

    Atomic clocks that fly on global-navigation satellites such as global positioning system (GPS) and Galileo employ light from low-temperature, inductively coupled plasmas (ICPs) for atomic signal generation and detection (i.e., alkali/noble-gas rf-discharge lamps). In this application, the performance of the atomic clock and the capabilities of the navigation system depend sensitively on the stability of the ICP's optical emission. In order to better understand the mechanisms that might lead to instability in these rf-discharge lamps, and hence the satellite atomic clocks, we studied the optical emission from a Rb/Xe ICP as a function of the rf power driving the plasma. Surprisingly, we found that the electron density in the plasma was essentially independent of increases in rf power above its nominal value (i.e., "rf-power gain") and that the electron temperature was only a slowly varying function of rf-power gain. The primary effect of rf power was to increase the temperature of the neutrals in the plasma, which was manifested by an increase in Rb vapor density. Interestingly, we also found evidence for electron temperature fluctuations (i.e., fluctuations in the plasma's high-energy electron content). The variance of these fluctuations scaled inversely with the plasma's mean electron temperature and was consistent with a simple model that assumed that the total electron density in the discharge was independent of rf power. Taken as a whole, our results indicate that the electrons in alkali/noble-gas ICPs are little affected by slight changes in rf power and that the primary effect of such changes is to heat the plasma's neutral species.

  12. Electron Beam Welding of a Depleted Uranium Alloy to Niobium Using a Calibrated Electron Beam Power Density Distribution

    Science.gov (United States)

    Elmer, J. W.; Teruya, A. T.; Terrill, P. E.

    2000-08-01

    Electron beam test welds were made joining flat plates of commercially pure niobium to a uranium-6wt%Nb (binary) alloy. The welding parameters and joint design were specifically developed to minimize mixing of the niobium with the U-6%Nb alloy. A Modified Faraday Cup (MFC) technique using computer-assisted tomography was employed to determine the precise power distribution of the electron beam so that the welding parameters could be directly transferred to other welding machines and/or to other facilities.

  13. Density profiles of different negative ion mass groups at Titan as observed by Cassini's CAPS electron spectrometer

    Science.gov (United States)

    Wellbrock, A.; Coates, A. J.; Jones, G. H.; Waite, J. H.

    2013-12-01

    The discovery of heavy negative ions by Cassini's CAPS electron spectrometer (ELS) in Titan's ionosphere (Coates et al., 2007, Waite et al., 2007) suggests that complex hydrocarbon and nitrile processes occur in Titan's upper atmosphere which are also linked to haze formation. Negative ions are observed during Titan encounters at altitudes different mass groups as reported by Coates et al. (2007). These have been updated by Wellbrock et al. (2013) who performed a study investigating trends of mass groups with altitude using data from 34 negative ion encounters. We continue this work here by studying individual flybys in more detail. We investigate density profiles for different mass groups and total densities.

  14. Slit disk for modified faraday cup diagnostic for determining power density of electron and ion beams

    Science.gov (United States)

    Teruya, Alan T [Livermore, CA; Elmer,; John, W [Danville, CA; Palmer, Todd A [State College, PA

    2011-03-08

    A diagnostic system for characterization of an electron beam or an ion beam includes an electrical conducting disk of refractory material having a circumference, a center, and a Faraday cup assembly positioned to receive the electron beam or ion beam. At least one slit in the disk provides diagnostic characterization of the electron beam or ion beam. The at least one slit is located between the circumference and the center of the disk and includes a radial portion that is in radial alignment with the center and a portion that deviates from radial alignment with the center. The electron beam or ion beam is directed onto the disk and translated to the at least one slit wherein the electron beam or ion beam enters the at least one slit for providing diagnostic characterization of the electron beam or ion beam.

  15. Time-dependent density-functional theory simulation for electron-ion dynamics in molecules under intense laser pulses.

    Science.gov (United States)

    Kawashita, Y; Nakatsukasa, T; Yabana, K

    2009-02-11

    We have developed a simulation method to describe three-dimensional dynamics of electrons and ions in a molecule based on the time-dependent density-functional theory. We solve the time-dependent Kohn-Sham equation for electrons employing the real-space and real-time method, while the ion dynamics are described in classical mechanics by the Ehrenfest method. For an efficient calculation in massively parallel computers, the code is parallelized dividing the spatial grid points. We apply the method to the Coulomb explosion of the H(2)S molecule under an intense and ultrashort laser pulse and investigate the mechanism of the process.

  16. Development of a Method for Local Electron Temperature and Density Measurements in the Divertor of the JET Tokamak

    Science.gov (United States)

    Jupen, C.; Meigs, A.; Bhatia, A. K.; Brezinsek, S.; OMullane, M.

    2004-01-01

    Plasma volume recombination in the divertor, a process in which charged particles recombine to neutral atoms, contributes to plasma detachment and hence cooling at the divertor target region. Detachment has been observed at JET and other tokamaks and is known to occur at low electron temperatures (T(sub e)10(exp 20)/m(exp 3)). The ability to measure such low temperatures is therefore of interest for modelling the divertor. In present work we report development of a new spectroscopic technique for investigation of local electron density (n(sub e)) and temperature (T,) in the outer divertor at JET.

  17. Investigating the effect of acene-fusion and trifluoroacetyl substitution on the electronic and charge transport properties by density functional theory

    Directory of Open Access Journals (Sweden)

    Ahmad Irfan

    2016-05-01

    Full Text Available We designed novel derivatives of 4,6-di(thiophen-2-ylpyrimidine (DTP. Two benchmark strategies including mesomerically deactivating group, as well as the extension of π-conjugation bridge (acene-fusion have been employed to enhance the electrical and charge transport properties. The density functional theory (DFT and time dependent DFT methods have been used to get optimized geometries in ground and first excited state, respectively. The structural properties (geometric parameters, electronic properties (frontier molecular orbitals; highest occupied and lowest unoccupied molecular orbitals, photophysical properties (absorption, fluorescence and phosphorescence, and important charge transport properties are discussed to establish a molecular level structure–property relationship among these derivatives. Our calculated electronic spectra i.e., absorption, fluorescence and phosphorescence have been found in good semi-quantitative agreement with available experimental data. All the newly designed derivatives displayed significantly improved electron injection ability than those of the parent molecule. The values of reorganization energy and transfer integral elucidate that DTP is a potential hole transport material. Based on our present investigation, it is expected that the naphtho and anthra derivatives of DTP are better hole transporters than those of some well-known charge transporter materials like naphthalene, anthracene, tetracene and pentacene.

  18. Exploring the electron density localization in single MoS2 monolayers by means of a localize-electrons detector and the quantum theory of atoms in molecules

    Science.gov (United States)

    Aray, Yosslen

    2017-11-01

    The nature of the electron density localization in a MoS2 monolayer under 0 % to 11% tensile strain has been systematically studied by means of a localized electron detector function and the Quantum Theory of atoms in molecules. At 10% tensile strain, this monolayer become metallic. It was found that for less than 6.5% of applied stress, the same atomic structure of the equilibrium geometry (0% strain) is maintained; while over 6.5% strain induces a transformation to a structure where the sulfur atoms placed on the top and bottom layer form S2 groups. The localized electron detector function shows the presence of zones of highly electron delocalization extending throughout the Mo central layer. For less than 10% tensile strain, these zones comprise the BCPs and the remainder CPs in separates regions of the space; while for the structures beyond 10% strain, all the critical points are involved in a region of highly delocalized electrons that extends throughout the material. This dissimilar electron localization pattern is like to that previously reported for semiconductors such as Ge bulk and metallic systems such as transition metals bulk.

  19. Examining real-time time-dependent density functional theory nonequilibrium simulations for the calculation of electronic stopping power

    Science.gov (United States)

    Yost, Dillon C.; Yao, Yi; Kanai, Yosuke

    2017-09-01

    In ion irradiation processes, electronic stopping power describes the energy transfer rate from the irradiating ion to the target material's electrons. Due to the scarcity and significant uncertainties in experimental electronic stopping power data for materials beyond simple solids, there has been growing interest in the use of first-principles theory for calculating electronic stopping power. In recent years, advances in high-performance computing have opened the door to fully first-principles nonequilibrium simulations based on real-time time-dependent density functional theory (RT-TDDFT). While it has been demonstrated that the RT-TDDFT approach is capable of predicting electronic stopping power for a wide range of condensed matter systems, there has yet to be an exhaustive examination of the physical and numerical approximations involved and their effects on the calculated stopping power. We discuss the results of such a study for crystalline silicon with protons as irradiating ions. We examine the influences of key approximations in RT-TDDFT nonequilibrium simulations on the calculated electronic stopping power, including approximations related to basis sets, finite size effects, exchange-correlation approximation, pseudopotentials, and more. Finally, we propose a simple and efficient correction scheme to account for the contribution from core-electron excitations to the stopping power, as it was found to be significant for large proton velocities.

  20. The effect of sample matrix on electron density, electron temperature and gas temperature in the argon inductively coupled plasma examined by Thomson and Rayleigh scattering

    Science.gov (United States)

    Hanselman, D. S.; Sesi, N. N.; Huang, M.; Hieftje, G. M.

    1994-05-01

    Spatially-resolved electron temperature ( Te), electron number density ( ne) and gas-kinetic temperature ( Tg) maps of the inductively coupled plasma (ICP) have been obtained for two central-gas flow rates, four heights above the load coil (ALC) and in the presence and absence of interferants with a wide range of first ionization potentials. The radial profiles demonstrate how the directly measured fundamental parameters neTe and Tg can be significantly enhanced and/or depressed with added interferent, depending upon plasma operating conditions and observation region. In general, the magnitude of ne, and Te change is found to be an inverse function of interferent ionization potential; furthermore, ne enhancements in the central channel might be the result of electron redistribution from high to low electron density regions rather than from ionization of the matrix. The large measured increases in ne cannot be attributed solely to matrix ionization, especially when measurement uncertainties and the probable over-estimation in calculated ne, enhancements are taken into account. Changes in ne and Te have been correlated with axial Ca atom and ion emission profiles. A brief review of the mechanisms most likely involved in interelement matrix interferences is given within the context of the present study. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk for the Macintosh computer with data files stored in ASCII format. The main article discusses the scientific aspects of the subject and gives an interpretation of the results contained in the data files.

  1. Permutation-blocking path-integral Monte Carlo approach to the static density response of the warm dense electron gas.

    Science.gov (United States)

    Dornheim, Tobias; Groth, Simon; Vorberger, Jan; Bonitz, Michael

    2017-08-01

    The static density response of the uniform electron gas is of fundamental importance for numerous applications. Here we employ the recently developed ab initio permutation blocking path integral Monte Carlo (PB-PIMC) technique [T. Dornheim et al., New J. Phys. 17, 073017 (2015)10.1088/1367-2630/17/7/073017] to carry out extensive simulations of the harmonically perturbed electron gas at warm dense matter conditions. In particular, we investigate in detail the validity of linear response theory and demonstrate that PB-PIMC allows us to obtain highly accurate results for the static density response function and, thus, the static local field correction. A comparison with dielectric approximations to our new ab initio data reveals the need for an exact treatment of correlations. Finally, we consider a superposition of multiple perturbations and discuss the implications for the calculation of the static response function.

  2. Full-Potential Electronic Structure Method Energy and Force Calculations with Density Functional and Dynamical Mean Field Theory

    CERN Document Server

    Wills, John M; Andersson, Per; Delin, Anna; Grechnyev, Oleksiy; Alouani, Mebarek

    2010-01-01

    This book covers the theory of electronic structure of materials, with special emphasis on the usage of linear muffin-tin orbitals. Methodological aspects are given in detail as are examples of the method when applied to various materials. Different exchange and correlation functionals are described and how they are implemented within the basis of linear muffin-tin orbitals. Functionals covered are the local spin density approximation, generalised gradient approximation, self-interaction correction and dynamical mean field theory.

  3. Automatic Atlas Based Electron Density and Structure Contouring for MRI-based Prostate Radiation Therapy on the Cloud

    Science.gov (United States)

    Dowling, J. A.; Burdett, N.; Greer, P. B.; Sun, J.; Parker, J.; Pichler, P.; Stanwell, P.; Chandra, S.; Rivest-Hénault, D.; Ghose, S.; Salvado, O.; Fripp, J.

    2014-03-01

    Our group have been developing methods for MRI-alone prostate cancer radiation therapy treatment planning. To assist with clinical validation of the workflow we are investigating a cloud platform solution for research purposes. Benefits of cloud computing can include increased scalability, performance and extensibility while reducing total cost of ownership. In this paper we demonstrate the generation of DICOM-RT directories containing an automatic average atlas based electron density image and fast pelvic organ contouring from whole pelvis MR scans.

  4. Faradaic processes beyond Nernst's law: density functional theory assisted modelling of partial electron delocalisation and pseudocapacitance in graphene oxides.

    Science.gov (United States)

    Li, Junfu; O'Shea, James; Hou, Xianghui; Chen, George Z

    2017-09-25

    The study of electron delocalisation in oxygen atom segregated zones in graphene, aided by the first-principles density functional theory, has revealed extra energy bands of ≥2 eV wide around the Fermi level, predicting Faradaic charge storage occurring in a wide range of potentials, which disagrees with Nernst's law but accounts well for the so called pseudocapacitance of heteroatom-modified graphene based electrode materials in supercapacitors.

  5. Saturable absorption of an x-ray free-electron-laser heated solid-density aluminum plasma.

    Science.gov (United States)

    Rackstraw, D S; Ciricosta, O; Vinko, S M; Barbrel, B; Burian, T; Chalupský, J; Cho, B I; Chung, H-K; Dakovski, G L; Engelhorn, K; Hájková, V; Heimann, P; Holmes, M; Juha, L; Krzywinski, J; Lee, R W; Toleikis, S; Turner, J J; Zastrau, U; Wark, J S

    2015-01-09

    High-intensity x-ray pulses from an x-ray free-electron laser are used to heat and probe a solid-density aluminum sample. The photon-energy-dependent transmission of the heating beam is studied through the use of a photodiode. Saturable absorption is observed, with the resulting transmission differing significantly from the cold case, in good agreement with atomic-kinetics simulations.

  6. Electron density and plasma waves in mid-latitude sporadic-E layer observed during the SEEK-2 campaign

    Directory of Open Access Journals (Sweden)

    H. Mori

    2005-10-01

    Full Text Available The SEEK-2 campaign was carried out over Kyushu Island in Japan on 3 August 2002, by using the two sounding rockets of S310-31 and S310-32. This campaign was planned to elucidate generation mechanisms of Quasi-Periodic Echoes (QPEs associated with mid-latitude sporadic-E (Es layers. Electron number densities were successfully measured in the Es layers by using the impedance probe on board two rockets. The plasma waves in the VLF and ELF ranges were also observed on board the S310-32 rocket. Results of electron density measurement showed that there were one or two major peaks in the Es layers along the rockets' trajectories near the altitude of about 10km. There were some smaller peaks associated with the main Es layers in the altitude range from 90 to 120 km. These density peaks were distributed in a very large extent during the SEEK-2 campaign. The Es layer structure is also measured by using the Fixed Bias Probe (FBP, which has a high spatial resolution of several meters (the impedance probe has an altitude resolution of about 400 m. The comparison with the total electron content (TEC measured by the Dual Band Beacon revealed that the Es layer was also modulated in the horizontal direction with the scale size of 30–40 km. It was shown that the QP echoes observed by the ground-based coherent radar come from the major density peak of the Es layer. The plasma wave instrument detected the enhancement of VLF and ELF plasma waves associated with the operation of the TMA release, and also with the passage of the Es layers. Keywords. Ionosphere (Ionospheric irregularities; Midlatitude ionosphere; Plasma temeperature and density

  7. The nematicity induced d-symmetry charge density wave in electron-doped iron-pnictide superconductors

    Science.gov (United States)

    Chou, Chung-Pin; Chen, Hong-Yi; Ting, C. S.

    2018-03-01

    The interplay among the nematicity, the stripe spin-density-wave (SDW) order and superconductivity in iron-pnictides is studied in a self-consistent Bogoliubov-de Gennes equations. Our calculations have shown that the nematic-order breaks the degeneracy of dxz and dyz orbitals and causes the elliptic Fermi surface near the Γ point in the normal state. In addition, the appearance of the orthorhombic magnetic fluctuations generates two uneven pairs of peaks at ( ± π, 0) and (0, ± π) in its Fourier transformation. All these are comparing favorably with experimental measurements. In the nematic phase, our results indicate that the charge density and its spatial image in the local density of states exhibit a dx2 -y2-like symmetry. Finally, the complete phase diagram is obtained and the nematic phase is found to be in a narrow region close to the SDW transition in the electron-doped iron-pnictide superconductors.

  8. Recent progress in predicting structural and electronic properties of organic solids with the van der Waals density functional

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Susumu, E-mail: shou@sci.u-ryukyu.ac.jp [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 (Japan); Okuma, Koji; Inaoka, Takeshi [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 (Japan); Hamada, Ikutaro, E-mail: Hamada.Ikutaro@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan)

    2015-10-01

    Highlights: • Review of theoretical studies on organic solids with the density-functional methods. • van der Waals (vdW)-inclusive methods to predict cohesive properties of oligoacenes. • A variant of the vdW density functional describes the structures accurately. • The molecular configuration and conformation crucially affects the band dispersion. - Abstract: We review recent studies on electronic properties of the organic solids with the first-principles electronic structure methods, with the emphasis on the roles of the intermolecular van der Waals (vdW) interaction in electronic properties of the organic semiconductors. After a brief summary of the recent vdW inclusive first-principle theoretical methods, we discuss their performance in predicting cohesive properties of oligoacene crystals as examples of organic crystals. We show that a variant of the van der Waals density functional describes structure and energetics of organic crystals accurately. In addition, we review our recent study on the zinc phthalocyanine crystal and discuss the importance of the intermolecular distance and orientational angle in the band dispersion. Finally, we draw some general conclusions and the future perspectives.

  9. Density-functional calculation of van der Waals forces for free-electron-like surfaces

    DEFF Research Database (Denmark)

    Hult, E.; Hyldgaard, P.; Rossmeisl, Jan

    2001-01-01

    A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well...... as for the interaction between the surfaces themselves. The densities and static image-plane positions that are needed as input in the van der Waals functional are calculated self-consistently within density-functional theory using the generalized-gradient approximation, pseudopotentials, and plane waves. This study...... shows that the van der Waals density functional is applicable to realistic surfaces. The need for physically correct surface models, especially for open surfaces, is also illustrated. Finally the parameters for the anisotropic interaction of O-2 with Al are calculated....

  10. Validation of Spherically Symmetric Inversion by Use of a Tomographically Reconstructed Three-Dimensional Electron Density of the Solar Corona

    Science.gov (United States)

    Wang, Tongjiang; Davila, Joseph M.

    2014-01-01

    Determining the coronal electron density by the inversion of white-light polarized brightness (pB) measurements by coronagraphs is a classic problem in solar physics. An inversion technique based on the spherically symmetric geometry (spherically symmetric inversion, SSI) was developed in the 1950s and has been widely applied to interpret various observations. However, to date there is no study of the uncertainty estimation of this method. We here present the detailed assessment of this method using a three-dimensional (3D) electron density in the corona from 1.5 to 4 solar radius as a model, which is reconstructed by a tomography method from STEREO/COR1 observations during the solar minimum in February 2008 (Carrington Rotation, CR 2066).We first show in theory and observation that the spherically symmetric polynomial approximation (SSPA) method and the Van de Hulst inversion technique are equivalent. Then we assess the SSPA method using synthesized pB images from the 3D density model, and find that the SSPA density values are close to the model inputs for the streamer core near the plane of the sky (POS) with differences generally smaller than about a factor of two; the former has the lower peak but extends more in both longitudinal and latitudinal directions than the latter. We estimate that the SSPA method may resolve the coronal density structure near the POS with angular resolution in longitude of about 50 deg. Our results confirm the suggestion that the SSI method is applicable to the solar minimum streamer (belt), as stated in some previous studies. In addition, we demonstrate that the SSPA method can be used to reconstruct the 3D coronal density, roughly in agreement with the reconstruction by tomography for a period of low solar activity (CR 2066). We suggest that the SSI method is complementary to the 3D tomographic technique in some cases, given that the development of the latter is still an ongoing research effort.

  11. Feasibility Studies of the Two Filters Method in TJ-II for Electron Temperature Measurements in High Density Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Baiao, D.; Medina, F.; Ochando, M.; Varandas, C.

    2009-07-01

    The TJ-II plasma soft X-ray emission was studied in order to establish an adequate setup for an electron temperature diagnostic suitable for high density, with spatial and temporal resolutions, based on the two-filters method. The preliminary experimental results reported were obtained with two diagnostics (an X-ray PHA based on a Ge detector and a tomography system) already installed in TJ-II stellarator. These results lead to the conclusion that the two-filters method was a suitable option for an electron temperature diagnostic for high-density plasmas in TJ-II. We present the design and fi rst results obtained with a prototype for the measurement of electron temperature in TJ-II plasmas heated with energetic neutral beams. This system consists in two AXUV20A detectors which measure the soft X-ray plasma emissivity trough beryllium filters of different thickness. From the two-filters technique it is possible to estimate the electron temperature. The analyses carried out allowed concluding which filter thicknesses are most suited for TJ-II plasmas, and enhanced the need of a computer code to simulate signals and plasma compositions. (Author) 7 refs.

  12. Electron cloud at the KEKB Low-Energy Ring Simulations of central cloud density, bunch filling, patterns, magnetic fields, and lost electrons

    CERN Document Server

    Zimmermann, Frank

    2000-01-01

    We report various electron-cloud simulations for the Low Energy Ring (LER) of KEKB. These address the evolution of the electron-cloud density at the center of the vacuum chamber,the effect of z-dependent quadrupole, dipole and solenoid fields,the response of the electron cloud to several bunch trains and filling patterns,the spatial electron distribution, and the characteristics of electrons lost to the wall. Comparing simulations and measurements, the present vertical blow up appears to be more consistent with simulations for field-free regions than with those for a quadrupole field.Thus, we recommend that further C yoke magnets be installed to cover as much of the ring circumference as possible,including the straight sections.In addition, we show that a C yoke magnet configuration with adjacent magnets of alternating polarity is about two times more effective than one of equal polarity.More efficient still would be a solenoid field,which promises a suppression by an additional factor of 3-6. Our simulations...

  13. Plasma density enhancements created by the ionization of the Earth's upper atmosphere by artificial electron beams

    DEFF Research Database (Denmark)

    Neubert, Torsten; Banks, P.M.

    line) and down-going differential energy flux. The equations are solved numerically, using the MSIS atmospheric model and the IRI ionospheric model. The results from the model compare well with recent observations from the CHARGE 2 sounding rocket experiment. Two aspects of the beam-neutral atmosphere...... electrons and thereby limits the ionization of the neutral atmosphere. As an example we find from CHARGE 2 observations and from the model calculations that below about 180 km, secondary electrons generated through the ionization of the neutral atmosphere by 1-10 keV electron beams from sounding rockets...

  14. Immobilization of bilirubin oxidase on graphene oxide flakes with different negative charge density for oxygen reduction. The effect of GO charge density on enzyme coverage, electron transfer rate and current density.

    Science.gov (United States)

    Filip, Jaroslav; Andicsová-Eckstein, Anita; Vikartovská, Alica; Tkac, Jan

    2017-03-15

    Previously we showed that an effective bilirubin oxidase (BOD)-based biocathode using graphene oxide (GO) could be prepared in 2 steps: 1. electrostatic adsorption of BOD on GO; 2. electrochemical reduction of the BOD-GO composite to form a BOD-ErGO (electrochemically reduced GO) film on the electrode. In order to identify an optimal charge density of GO for BOD-ErGO composite preparation, several GO fractions differing in an average flake size and ζ-potential were prepared using centrifugation and consequently employed for BOD-ErGO biocathode preparation. A simple way to express surface charge density of these particular GO nanosheets was developed. The values obtained were then correlated with biocatalytic and electrochemical parameters of the prepared biocathodes, i.e. electrocatalytically active BOD surface coverage (Γ), heterogeneous electron transfer rate (kS) and a maximum biocatalytic current density. The highest bioelectrocatalytic current density of (597±25)μAcm(-2) and the highest Γ of (23.6±0.9)pmolcm(-2) were obtained on BOD-GO composite having the same moderate negative charge density, but the highest kS of (79.4±4.6)s(-1) was observed on BOD-GO composite having different negative charge density. This study is a solid foundation for others to consider the influence of a charge density of GO on direct bioelectrochemistry/bioelectrocatalysis of other redox enzymes applicable for construction of biosensors, bioanodes, biocathodes or biofuel cells. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. An accurate density functional theory calculation for electronic excitation energies: the least-squares support vector machine.

    Science.gov (United States)

    Gao, Ting; Sun, Shi-Ling; Shi, Li-Li; Li, Hui; Li, Hong-Zhi; Su, Zhong-Min; Lu, Ying-Hua

    2009-05-14

    Support vector machines (SVMs), as a novel type of learning machine, has been very successful in pattern recognition and function estimation problems. In this paper we introduce least-squares (LS) SVMs to improve the calculation accuracy of density functional theory. As a demonstration, this combined quantum mechanical calculation with LS-SVM correction approach has been applied to evaluate the electronic excitation energies of 160 organic molecules. The newly introduced LS-SVM approach reduces the root-mean-square deviation of the calculated electronic excitation energies of 160 organic molecules from 0.32 to 0.11 eV for the B3LYP/6-31G(d) calculation. Thus, the LS-SVM correction on top of B3LYP/6-31G(d) is a better method to correct electronic excitation energies and can be used as the approximation of experimental results which are impossible to obtain experimentally.

  16. Advanced High Energy Density Secondary Batteries with Multi‐Electron Reaction Materials

    National Research Council Canada - National Science Library

    Chen, Renjie; Luo, Rui; Huang, Yongxin; Wu, Feng; Li, Li

    2016-01-01

    ...‐electron chemistry has paved a new path for the breaking of the barriers that exist in traditional battery research and applications, and provided new ideas for developing new battery systems...

  17. Ultraviolet Thomson Scattering from Two-Plasmon-Decay Driven Electron Plasma Waves at Quarter-Critical Densities

    Science.gov (United States)

    Follett, R. K.; Michel, D. T.; Hu, S. X.; Myatt, J. F.; Henchen, R. J.; Katz, J.; Froula, D. H.

    2013-10-01

    Thomson scattering (TS) was used to probe electron plasma waves (EPW's) driven by the two-plasmon-decay (TPD) instability near quarter-critical density. TPD-driven EPW's were observed at densities consistent with the common-wave TPD model. Five laser beams (λ3ω = 351nm) produced 400- μm-diam (FWHM) laser spots with overlapped intensities up to 3 ×1014W/cm2 . A 263-nm TS beam was used to probe densities ranging from 0.18 to 0.26 nc, where nc is the critical density for 351-nm light. The experimental geometry was chosen to match the five-beam TPD common wave k vector. The TS spectrum shows a large amplitude, narrow (~1.6-nm FHWM) feature centered around 423.4 nm. This wavelength corresponds to scattering from EPW's with a normalized wave vector k / k3 ω = 1 . 3 , a density of ne/nc = 0.243, and a temperature of Te = 2 keV. This is consistent with the predicted values given by the dispersion relations and TPD maximum growth hyperbola. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  18. Interpretation of monoclinic hafnia valence electron energy-loss spectra by time-dependent density functional theory

    Science.gov (United States)

    Hung, L.; Guedj, C.; Bernier, N.; Blaise, P.; Olevano, V.; Sottile, F.

    2016-04-01

    We present the valence electron energy-loss spectrum and the dielectric function of monoclinic hafnia (m -HfO2) obtained from time-dependent density-functional theory (TDDFT) predictions and compared to energy-filtered spectroscopic imaging measurements in a high-resolution transmission-electron microscope. Fermi's golden rule density-functional theory (DFT) calculations can capture the qualitative features of the energy-loss spectrum, but we find that TDDFT, which accounts for local-field effects, provides nearly quantitative agreement with experiment. Using the DFT density of states and TDDFT dielectric functions, we characterize the excitations that result in the m -HfO2 energy-loss spectrum. The sole plasmon occurs between 13 and 16 eV, although the peaks ˜28 and above 40 eV are also due to collective excitations. We furthermore elaborate on the first-principles techniques used, their accuracy, and remaining discrepancies among spectra. More specifically, we assess the influence of Hf semicore electrons (5 p and 4 f ) on the energy-loss spectrum, and find that the inclusion of transitions from the 4 f band damps the energy-loss intensity in the region above 13 eV. We study the impact of many-body effects in a DFT framework using the adiabatic local-density approximation (ALDA) exchange-correlation kernel, as well as from a many-body perspective using "scissors operators" matched to an ab initio G W calculation to account for self-energy corrections. These results demonstrate some cancellation of errors between self-energy and excitonic effects, even for excitations from the Hf 4 f shell. We also simulate the dispersion with increasing momentum transfer for plasmon and collective excitation peaks.

  19. Creation and diagnosis of a solid-density plasma with an X-ray free-electron laser.

    Science.gov (United States)

    Vinko, S M; Ciricosta, O; Cho, B I; Engelhorn, K; Chung, H-K; Brown, C R D; Burian, T; Chalupský, J; Falcone, R W; Graves, C; Hájková, V; Higginbotham, A; Juha, L; Krzywinski, J; Lee, H J; Messerschmidt, M; Murphy, C D; Ping, Y; Scherz, A; Schlotter, W; Toleikis, S; Turner, J J; Vysin, L; Wang, T; Wu, B; Zastrau, U; Zhu, D; Lee, R W; Heimann, P A; Nagler, B; Wark, J S

    2012-01-25

    Matter with a high energy density (>10(5) joules per cm(3)) is prevalent throughout the Universe, being present in all types of stars and towards the centre of the giant planets; it is also relevant for inertial confinement fusion. Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities. With the advent of the Linac Coherent Light Source (LCLS) X-ray laser, high-intensity radiation (>10(17) watts per cm(2), previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated. An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 10(6) kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray-matter interactions, and illustrate the importance of electron-ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.

  20. Changes of the electron density distribution during MHD activity in CHS

    Energy Technology Data Exchange (ETDEWEB)

    Soltwish, H. [Ruhr-University Bochum, Institute for Experimental Physics, Bochum (Germany); Tanaka, K. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    2000-09-01

    Density oscillations induced by MHD activities were observed in NBI heated plasmas on CHS by using an HCN laser interferometer. The accompanied changes of the density profiles were also observed. The oscillations are composition of m=0 sawteeth like crash and m=2 sinusoidal oscillations as a post courser of the crash. Possible models of the oscillation structure are examined in order to explain experimental data of the interferometer. Rotating plasma core, which is hollow profile and keeps constant elongation of the flux surface can explain amplitude and phase distribution of the sinusoidal oscillation. (author)

  1. Analysis of Electronic Densities and Integrated Doses in Multiform Glioblastomas Stereotactic Radiotherapy

    Science.gov (United States)

    Barón-Aznar, C.; Moreno-Jiménez, S.; Celis, M. A.; Lárraga-Gutiérrez, J. M.; Ballesteros-Zebadúa, P.

    2008-08-01

    Integrated dose is the total energy delivered in a radiotherapy target. This physical parameter could be a predictor for complications such as brain edema and radionecrosis after stereotactic radiotherapy treatments for brain tumors. Integrated Dose depends on the tissue density and volume. Using CT patients images from the National Institute of Neurology and Neurosurgery and BrainScansoftware, this work presents the mean density of 21 multiform glioblastomas, comparative results for normal tissue and estimated integrated dose for each case. The relationship between integrated dose and the probability of complications is discussed.

  2. Spatial profiles of electron and metastable atom densities in positive polarity fast ionization waves sustained in helium

    Energy Technology Data Exchange (ETDEWEB)

    Weatherford, Brandon R., E-mail: brweathe@gmail.com, E-mail: zax@esi-group.com, E-mail: evbarna@sandia.gov, E-mail: mjkush@umich.edu; Barnat, E. V., E-mail: brweathe@gmail.com, E-mail: zax@esi-group.com, E-mail: evbarna@sandia.gov, E-mail: mjkush@umich.edu [Sandia National Laboratories, Albuquerque, New Mexico 87185-1423 (United States); Xiong, Zhongmin, E-mail: brweathe@gmail.com, E-mail: zax@esi-group.com, E-mail: evbarna@sandia.gov, E-mail: mjkush@umich.edu; Kushner, Mark J., E-mail: brweathe@gmail.com, E-mail: zax@esi-group.com, E-mail: evbarna@sandia.gov, E-mail: mjkush@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122, USA. (United States)

    2014-09-14

    Fast ionization waves (FIWs), often generated with high voltage pulses over nanosecond timescales, are able to produce large volumes of ions and excited states at moderate pressures. The mechanisms of FIW propagation were experimentally and computationally investigated to provide insights into the manner in which these large volumes are excited. The two-dimensional structure of electron and metastable densities produced by short-pulse FIWs sustained in helium were measured using laser-induced fluorescence and laser collision-induced fluorescence diagnostics for times of 100–120 ns after the pulse, as the pressure was varied from 1 to 20 Torr. A trend of center-peaked to volume-filling to wall-peaked electron density profiles was observed as the pressure was increased. Instantaneous FIW velocities, obtained from plasma-induced emission, ranged from 0.1 to 3×10⁹cm s⁻¹, depending on distance from the high voltage electrode and pressure. Predictions from two-dimensional modeling of the propagation of a single FIW correlated well with the experimental trends in electron density profiles and wave velocity. Results from the model show that the maximum ionization rate occurs in the wavefront, and the discharge continues to propagate forward after the removal of high voltage from the powered electrode due to the potential energy stored in the space charge. As the pressure is varied, the radial distribution of the ionization rate is shaped by changes in the electron mean free path, and subsequent localized electric field enhancement at the walls or on the centerline of the discharge.

  3. Measurement of electron temperatures of Argon Plasmas in a High-Density Inductively-Coupled Remote Plasma System by Langmuir Probe and Optical-Emission Spectroscopy

    NARCIS (Netherlands)

    Boogaard, A.; Kovalgin, Alexeij Y.; Aarnink, Antonius A.I.; Wolters, Robertus A.M.; Holleman, J.; Brunets, I.; Schmitz, Jurriaan

    2006-01-01

    We measured electron density and electron energy distribution function (EEDF) in our reactor by a Langmuir probe. The EEDF of Ar plasma in the reactor could largely be described by the Maxwell-Boltzmann distribution function, but it also contained a fraction (~10-3) of electrons which were much

  4. New method in computer simulations of electron and ion densities and temperatures in the plasmasphere and low-latitude ionosphere

    Directory of Open Access Journals (Sweden)

    A. V. Pavlov

    Full Text Available A new theoretical model of the Earth’s low- and mid-latitude ionosphere and plasmasphere has been developed. The new model uses a new method in ionospheric and plasmaspheric simulations which is a combination of the Eulerian and Lagrangian approaches in model simulations. The electron and ion continuity and energy equations are solved in a Lagrangian frame of reference which moves with an individual parcel of plasma with the local plasma drift velocity perpendicular to the magnetic and electric fields. As a result, only the time-dependent, one-dimension electron and ion continuity and energy equations are solved in this Lagrangian frame of reference. The new method makes use of an Eulerian computational grid which is fixed in space co-ordinates and chooses the set of the plasma parcels at every time step, so that all the plasma parcels arrive at points which are located between grid lines of the regularly spaced Eulerian computational grid at the next time step. The solution values of electron and ion densities Ne and Ni and temperatures Te and Ti at the Eulerian computational grid are obtained by interpolation. Equations which determine the trajectory of the ionospheric plasma perpendicular to magnetic field lines and take into account that magnetic field lines are "frozen" in the ionospheric plasma are derived and included in the new model. We have presented a comparison between the modeled NmF2 and hmF2 and NmF2 and hmF2 which were observed at the anomaly crest and close to the geomagnetic equator simultaneously by the Huancayo, Chiclayo, Talara, Bogota, Panama, and Puerto Rico ionospheric sounders during the 7 October 1957 geomagnetically quiet time period at solar maximum. The model calculations show that there is a need to revise the model local time dependence of the equatorial upward E × B drift velocity given by Scherliess and Fejer (1999 at solar maximum during quiet

  5. New method in computer simulations of electron and ion densities and temperatures in the plasmasphere and low-latitude ionosphere

    Directory of Open Access Journals (Sweden)

    A. V. Pavlov

    2003-07-01

    Full Text Available A new theoretical model of the Earth’s low- and mid-latitude ionosphere and plasmasphere has been developed. The new model uses a new method in ionospheric and plasmaspheric simulations which is a combination of the Eulerian and Lagrangian approaches in model simulations. The electron and ion continuity and energy equations are solved in a Lagrangian frame of reference which moves with an individual parcel of plasma with the local plasma drift velocity perpendicular to the magnetic and electric fields. As a result, only the time-dependent, one-dimension electron and ion continuity and energy equations are solved in this Lagrangian frame of reference. The new method makes use of an Eulerian computational grid which is fixed in space co-ordinates and chooses the set of the plasma parcels at every time step, so that all the plasma parcels arrive at points which are located between grid lines of the regularly spaced Eulerian computational grid at the next time step. The solution values of electron and ion densities Ne and Ni and temperatures Te and Ti at the Eulerian computational grid are obtained by interpolation. Equations which determine the trajectory of the ionospheric plasma perpendicular to magnetic field lines and take into account that magnetic field lines are "frozen" in the ionospheric plasma are derived and included in the new model. We have presented a comparison between the modeled NmF2 and hmF2 and NmF2 and hmF2 which were observed at the anomaly crest and close to the geomagnetic equator simultaneously by the Huancayo, Chiclayo, Talara, Bogota, Panama, and Puerto Rico ionospheric sounders during the 7 October 1957 geomagnetically quiet time period at solar maximum. The model calculations show that there is a need to revise the model local time dependence of the equatorial upward E × B drift velocity given by Scherliess and Fejer (1999 at solar maximum during quiet daytime equinox conditions. Uncertainties in the calculated Ni

  6. End-User Experiences and Expectations Regarding Data Registration and Reuse Before the Implementation of a (New) Electronic Health Record: A Case Study in Two University Hospitals.

    Science.gov (United States)

    Joukes, Erik; de Keizer, Nicolette; Abu-Hanna, Ameen; de Bruijne, Martine; Cornet, Ronald

    2015-01-01

    Patient data stored in Electronic Health Records (EHRs) are used during care provision but are also potentially usefully reused for other purposes. Data (re)use requires good data quality, which necessitates efforts by healthcare professionals for proper data registration. However, their commitment depends on their perception of the reuse benefits. We developed a questionnaire to investigate the perception and expectations of end-users on data registration and reuse in two university hospitals starting a joint EHR implementation. Especially personnel in direct patient care reports to spend much time (40%) on data registration and this group is not willing to spend more time with the new EHR. Additionally, approximately one third of the personnel did not yet have a clear view on future developments regarding data registration and reuse. We found only small differences between hospitals.

  7. Factors Influencing Mean Inner Potentials As Studied Using Electron Holography and Density Functional Theory

    DEFF Research Database (Denmark)

    Pennington, Robert S.

    to analyze diffraction effects on the amplitude and the phase. There is relatively good comparison between image simulation and experimental data, but the experimental absorption parameter is found to differ between strongly and weakly diffracting conditions. Density functional theory simulations of the mean...

  8. Calculation of electronic excitations using wave-function in wave-function frozen-density embedding

    NARCIS (Netherlands)

    Hoefener, S.; Visscher, L.

    2012-01-01

    Recently, a general framework suitable for general frozen-density embedding (FDE) methods was published [S. Höfener, A. S. P. Gomes, and L. Visscher, J. Chem. Phys. 136, 044104 (2012)]10.1063/1.3675845. In the present article, we report the fragmentation of a supermolecule while treating all

  9. Classification and assessment of retrieved electron density maps in coherent X-ray diffraction imaging using multivariate analysis.

    Science.gov (United States)

    Sekiguchi, Yuki; Oroguchi, Tomotaka; Nakasako, Masayoshi

    2016-01-01

    Coherent X-ray diffraction imaging (CXDI) is one of the techniques used to visualize structures of non-crystalline particles of micrometer to submicrometer size from materials and biological science. In the structural analysis of CXDI, the electron density map of a sample particle can theoretically be reconstructed from a diffraction pattern by using phase-retrieval (PR) algorithms. However, in practice, the reconstruction is difficult because diffraction patterns are affected by Poisson noise and miss data in small-angle regions due to the beam stop and the saturation of detector pixels. In contrast to X-ray protein crystallography, in which the phases of diffracted waves are experimentally estimated, phase retrieval in CXDI relies entirely on the computational procedure driven by the PR algorithms. Thus, objective criteria and methods to assess the accuracy of retrieved electron density maps are necessary in addition to conventional parameters monitoring the convergence of PR calculations. Here, a data analysis scheme, named ASURA, is proposed which selects the most probable electron density maps from a set of maps retrieved from 1000 different random seeds for a diffraction pattern. Each electron density map composed of J pixels is expressed as a point in a J-dimensional space. Principal component analysis is applied to describe characteristics in the distribution of the maps in the J-dimensional space. When the distribution is characterized by a small number of principal components, the distribution is classified using the k-means clustering method. The classified maps are evaluated by several parameters to assess the quality of the maps. Using the proposed scheme, structure analysis of a diffraction pattern from a non-crystalline particle is conducted in two stages: estimation of the overall shape and determination of the fine structure inside the support shape. In each stage, the most accurate and probable density maps are objectively selected. The validity

  10. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    outlines how the expectation-based explanation of IEO complements explanations stressing family resources as an important cause of IEO; it carefully defines "expectation," the core concept underlying the dissertation; it places the methodological contributions of the dissertation in the debate over...... for their educational futures. Focusing on the causes rather than the consequences of educational expectations, I argue that students shape their expectations in response to the signals about their academic performance they receive from institutionalized performance indicators in schools. Chapter II considers...... strongly suggest that students rely on information about their academic performances when considering their educational prospects. The two chapters thus highlight that educational expectations are subject to change over the educational career, and that educational systems play a prominent role in students...

  11. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    of the relation between the self and educational prospects; evaluations that are socially bounded in that students take their family's social position into consideration when forming their educational expectations. One important consequence of this learning process is that equally talented students tend to make...... different educational choices according to their family background. IEO thus appears to be mediated by the expectations students hold for their futures. Taken together, this research agenda argues that both researchers and policy-makers need to consider the expectation-based origin of educational...... outlines how the expectation-based explanation of IEO complements explanations stressing family resources as an important cause of IEO; it carefully defines "expectation," the core concept underlying the dissertation; it places the methodological contributions of the dissertation in the debate over...

  12. Periodic density functional theory study of structural and electronic properties of single-walled zinc oxide and carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Marana, Naiara L. [Modeling and Molecular Simulations Group, São Paulo State University, UNESP, 17033-360 Bauru, SP (Brazil); Albuquerque, Anderson R. [Federal Institute of Education, Science and Technology of Sertão Pernambucano, 56400-000 Floresta, PE (Brazil); La Porta, Felipe A. [Chemistry Department, Federal Technological University of Paraná, 86036-370 Londrina, PR (Brazil); Longo, Elson [São Paulo State University, Chemistry Institute, UNESP, 14801-907 Araraquara, SP (Brazil); Sambrano, Julio R. [Modeling and Molecular Simulations Group, São Paulo State University, UNESP, 17033-360 Bauru, SP (Brazil)

    2016-05-15

    Periodic density functional theory calculations with the B3LYP hybrid functional and all-electron Gaussian basis set were performed to simulate the structural and electronic properties as well as the strain and formation energies of single-walled ZnO nanotubes (SWZnONTs) and Carbon nanotubes (SWCNTs) with different chiralities as functions of their diameters. For all SWZnONTs, the band gap, strain energy, and formation energy converge to ~4.5 eV, 0.0 eV/atom, and 0.40 eV/atom, respectively. This result suggests that the nanotubes are formed more easily from the surface than from the bulk. For SWCNTs, the strain energy is always positive, while the formation energy is negative for armchair and zigzag nanotubes, therefore suggesting that these types of nanotubes can be preferentially formed from the bulk. The electronic properties of SWCNTs depend on the chirality; all armchair nanotubes are metallic, while zigzag and chiral nanotubes can be metallic or semiconducting, depending on the n and m vectors. - Graphical abstract: DFT/B3LYP were performed to simulate the structural and electronic properties as well as the strain and formation energies of SWZnONTs and SWCNTs with different chiralities as functions of their diameters. - Highlights: • The energies of SWZnONTs converge for chirality with diameters up 20 Å. • SWCNTs electronic properties depend on the chirality. • The properties of SWZnONTs are very similar to those of monolayer surface.

  13. Fast and accurate conversion of atomic models into electron density maps

    Directory of Open Access Journals (Sweden)

    Carlos O.S. Sorzano

    2015-03-01

    Full Text Available New image processing methodologies and algorithms have greatly contributed to the signi cant progress in three-dimensional electron microscopy (3DEM of biological complexes we have seen over the last decades. Naturally, the availability of accurate procedures for the objective testing of new algorithms is a crucial requirement for the further advancement of the eld. A good and accepted testing work ow involves the generation of realistic 3DEM-like maps of biological macromolecules from which some measure of ground truth can be derived, ideally because their 3D atomic structure is already known. In this work we propose a very accurate generation of maps using atomic form factors for electron scattering. We thoroughly review current approaches in the eld, quantitatively demonstrating the bene ts of the new methodology. Additionally, we study a concrete example of the use of this approach for hypothesis testing in 3D Electron Microscopy.

  14. Modeling Biophysical and Biological Properties From the Characteristics of the Molecular Electron Density, Electron Localization and Delocalization Matrices, and the Electrostatic Potential

    Science.gov (United States)

    Matta*, Chérif F

    2014-01-01

    The electron density and the electrostatic potential are fundamentally related to the molecular hamiltonian, and hence are the ultimate source of all properties in the ground- and excited-states. The advantages of using molecular descriptors derived from these fundamental scalar fields, both accessible from theory and from experiment, in the formulation of quantitative structure-to-activity and structure-to-property relationships, collectively abbreviated as QSAR, are discussed. A few such descriptors encode for a wide variety of properties including, for example, electronic transition energies, pKa's, rates of ester hydrolysis, NMR chemical shifts, DNA dimers binding energies, π-stacking energies, toxicological indices, cytotoxicities, hepatotoxicities, carcinogenicities, partial molar volumes, partition coefficients (log P), hydrogen bond donor capacities, enzyme–substrate complementarities, bioisosterism, and regularities in the genetic code. Electronic fingerprinting from the topological analysis of the electron density is shown to be comparable and possibly superior to Hammett constants and can be used in conjunction with traditional bulk and liposolubility descriptors to accurately predict biological activities. A new class of descriptors obtained from the quantum theory of atoms in molecules' (QTAIM) localization and delocalization indices and bond properties, cast in matrix format, is shown to quantify transferability and molecular similarity meaningfully. Properties such as “interacting quantum atoms (IQA)” energies which are expressible into an interaction matrix of two body terms (and diagonal one body “self” terms, as IQA energies) can be used in the same manner. The proposed QSAR-type studies based on similarity distances derived from such matrix representatives of molecular structure necessitate extensive investigation before their utility is unequivocally established. © 2014 The Author and the Journal of Computational Chemistry Published

  15. Energy densities of magnetic field and relativistic electrons at the innermost region of the M87 jet

    Directory of Open Access Journals (Sweden)

    Kino M.

    2013-12-01

    Full Text Available We explore energy densities of magnetic fields and relativistic electrons in M87 jet. Since the radio core at the base of the M87 jet is the optically thick surface against synchrotron self absorption (SSA, observations directly give the size and turnover frequency for SSA. Using the observed angular diameter 0.11 mas, which corresponds to 16 Schwarzschild radii of the central black hole with 6 × 109 solar mass, and the flux density of the radio core at 43 GHz, we estimate the energy densities of magnetic field (UB and relativistic electrons (Ue by comparing the standard SSA formula to the observed radio core. Together with the allowed total kinetic power of the M87 jet, we find that (i the allowed B is limited in the range 2 G ≤ B ≤ 13 G, and that (ii 0:18 ≤ Ue/UB ≤ 66 holds. Our results significantly constrain formation mechanism of relativistic jets in active galactic nuclei.

  16. High-spatial-resolution electron density measurement by Langmuir probe for multi-point observations using tiny spacecraft

    Science.gov (United States)

    Hoang, H.; Røed, K.; Bekkeng, T. A.; Trondsen, E.; Clausen, L. B. N.; Miloch, W. J.; Moen, J. I.

    2017-11-01

    A method for evaluating electron density using a single fixed-bias Langmuir probe is presented. The technique allows for high-spatio-temporal resolution electron density measurements, which can be effectively carried out by tiny spacecraft for multi-point observations in the ionosphere. The results are compared with the multi-needle Langmuir probe system, which is a scientific instrument developed at the University of Oslo comprising four fixed-bias cylindrical probes that allow small-scale plasma density structures to be characterized in the ionosphere. The technique proposed in this paper can comply with the requirements of future small-sized spacecraft, where the cost-effectiveness, limited space available on the craft, low power consumption and capacity for data-links need to be addressed. The first experimental results in both the plasma laboratory and space confirm the efficiency of the new approach. Moreover, detailed analyses on two challenging issues when deploying the DC Langmuir probe on a tiny spacecraft, which are the limited conductive area of the spacecraft and probe surface contamination, are presented in the paper. It is demonstrated that the limited conductive area, depending on applications, can either be of no concern for the experiment or can be resolved by mitigation methods. Surface contamination has a small impact on the performance of the developed probe.

  17. Deciphering effects of functional groups and electron density on azo dyes degradation by graphene loaded TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qian [College of Chemical Engineering, HuaQiao University, Xiamen 361021 (China); Liang, Xiao [School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Chen, Bor-Yann [Department of Chemical and Materials Engineering, National I-Lan University, 26047, Taiwan (China); Chang, Chang-Tang, E-mail: ctchang@niu.edu.tw [Department of Environmental Engineering, National I-Lan University, 26047, Taiwan (China)

    2015-12-01

    Highlights: • The degradation pathways of RB5, RB171 and RR198 have been identified. • The favorable bond to be broken under photo degradation was deciphered in this research. • The breakages of the bonds were due to the electron density changes around the bonds. • The hydroxyl radicals as the main oxidized species were confirmed by positive hole trapper and ESR. - Abstract: This study tended to decipher the mechanism of photo degradation of azo dyes, which bond was favorable to be broken for application of wastewater decolorization. That is, from chemical structure perspective, the critical substituents to affect electron donor/acceptor for dye degradation would be identified in this research. The model reactive blacks (RB5), reactive blue 171 (RB171) and reactive red 198 (RR198) were degraded by graphene loaded TiO{sub 2}, indicating how the electron withdrawing and releasing groups affect azo dye degradability. The byproducts and intermediate products were analyzed by ultraviolet–visible spectroscopy (UV–vis), gas chromatography–mass spectrometry (GC–MS) and ion chromatography (IC). Furthermore, the radicals involved in the reaction were found by electron paramagnetic resonance (ESR) to confirm the main oxidized species of hydroxyl radicals rather than the light generated positive holes. The finding revealed that the breakages of the bonds were due to the electron density changes around the bonds. This principle can be applicable not only for RB5 degradation, but also for reactive blue 171 (RB171), reactive red 198 (RR198) and some other textile dyes.

  18. Thermally driven hopping and electron transport in amorphous materials from density functional calculations

    Energy Technology Data Exchange (ETDEWEB)

    Abtew, Tesfaye A; Drabold, D A [Department of Physics and Astronomy, Ohio University, Athens, OH 45701-2979 (United States)

    2004-11-10

    In this paper we study electron dynamics and transport in models of amorphous silicon and amorphous silicon hydride. By integrating the time-dependent Kohn-Sham equation, we compute the time evolution of electron states near the gap, and study the spatial and spectral diffusion of these states due to lattice motion. We perform these calculations with a view to developing ab initio hopping transport methods. The techniques are implemented with the ab initio local basis code SIESTA, and may be applicable to molecular, biomolecular and other condensed matter systems.

  19. Approaching an experimental electron density model of the biologically active trans -epoxysuccinyl amide group-Substituent effects vs. crystal packing

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Ming W.; Stewart, Scott G.; Sobolev, Alexandre N.; Dittrich, Birger; Schirmeister, Tanja; Luger, Peter; Hesse, Malte; Chen, Yu-Sheng; Spackman, Peter R.; Spackman, Mark A.; Grabowsky, Simon (Heinrich-Heine); (Freie); (UC); (Bremen); (JG-UM); (UWA)

    2017-01-24

    The trans-epoxysuccinyl amide group as a biologically active moiety in cysteine protease inhibitors such as loxistatin acid E64c has been used as a benchmark system for theoretical studies of environmental effects on the electron density of small active ingredients in relation to their biological activity. Here, the synthesis and the electronic properties of the smallest possible active site model compound are reported to close the gap between the unknown experimental electron density of trans-epoxysuccinyl amides and the well-known function of related drugs. Intramolecular substituent effects are separated from intermolecular crystal packing effects on the electron density, which allows us to predict the conditions under which an experimental electron density investigation on trans-epoxysuccinyl amides will be possible. In this context, the special importance of the carboxylic acid function in the model compound for both crystal packing and biological activity is revealed through the novel tool of model energy analysis.

  20. Interaction of electrons with cisplatin and the subsequent effect on DNA damage: a density functional theory study.

    Science.gov (United States)

    Chen, Hsing-Yin; Chen, Hui-Fen; Kao, Chai-Lin; Yang, Po-Yu; Hsu, Sodio C N

    2014-09-28

    Cisplatin, Pt(NH3)2Cl2, is a leading chemotherapeutic agent that has been widely used for various cancers. Recent experiments show that combining cisplatin and electron sources can dramatically enhance DNA damage and the cell-killing rate and, therefore, is a promising way to overcome the side effects and the resistance of cisplatin. However, the molecular mechanisms underlying this phenomenon are not clear yet. By using density functional theory calculations, we confirm that cisplatin can efficiently capture the prehydrated electrons and then undergo dissociation. The first electron attachment triggers a spontaneous departure of the chloride ion, forming a T-shaped [Pt(NH3)2Cl]˙ neutral radical, whereas the second electron attachment leads to a spontaneous departure of ammine, forming a linear [Pt(NH3)Cl](-) anion. We further recognize that the one-electron reduced product [Pt(NH3)2Cl]˙ is extremely harmful to DNA. It can abstract hydrogen atoms from the C-H bonds of the ribose moiety and the methyl group of thymine, which in turn leads to DNA strand breaks and cross-link lesions. The activation energies of these hydrogen abstraction reactions are relatively small compared to the hydrolysis of cisplatin, a prerequisite step in the normal mechanism of action of cisplatin. These results rationalize the improved cytotoxicity of cisplatin by supplying electrons. Although the biological effects of the two-electron reduced product [Pt(NH3)Cl](-) are not clear at this stage, our calculations indicate that it might be protonated by the surrounding water.

  1. Using the electron localization function to correct for confinement physics in semi-local density functional theory.

    Science.gov (United States)

    Hao, Feng; Armiento, Rickard; Mattsson, Ann E

    2014-05-14

    We have previously proposed that further improved functionals for density functional theory can be constructed based on the Armiento-Mattsson subsystem functional scheme if, in addition to the uniform electron gas and surface models used in the Armiento-Mattsson 2005 functional, a model for the strongly confined electron gas is also added. However, of central importance for this scheme is an index that identifies regions in space where the correction provided by the confined electron gas should be applied. The electron localization function (ELF) is a well-known indicator of strongly localized electrons. We use a model of a confined electron gas based on the harmonic oscillator to show that regions with high ELF directly coincide with regions where common exchange energy functionals have large errors. This suggests that the harmonic oscillator model together with an index based on the ELF provides the crucial ingredients for future improved semi-local functionals. For a practical illustration of how the proposed scheme is intended to work for a physical system we discuss monoclinic cupric oxide, CuO. A thorough discussion of this system leads us to promote the cell geometry of CuO as a useful benchmark for future semi-local functionals. Very high ELF values are found in a shell around the O ions, and take its maximum value along the Cu-O directions. An estimate of the exchange functional error from the effect of electron confinement in these regions suggests a magnitude and sign that could account for the error in cell geometry.

  2. first-principle calculation of electrons charge density in the diamond

    African Journals Online (AJOL)

    DR. AMINU

    the direct lattice. Table 1, below lists some elements which exhibit the diamond structure. The nearest neighbor distance, d is calculated from the appropriate ..... Slater, J. C. (1955). One-Electron Energies of Atoms,. Molecules and Solids Phys. Rev. 98, 1039. Seeger, K. (2004). Semiconductor Physics (Springer-Verlag.

  3. Electronic properties and charge density of BexZn1− xTe alloys

    Indian Academy of Sciences (India)

    Electronic band structure calculations are performed for the BeZn1−Te (0 ≤ ≤ 1 in steps of 0.2) alloys following the empirical pseudopotential method. The alloying effects are modelled through the modified virtual crystal approximation. Throughout the composition, valence band maximum resides at the point.

  4. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    outlines how the expectation-based explanation of IEO complements explanations stressing family resources as an important cause of IEO; it carefully defines "expectation," the core concept underlying the dissertation; it places the methodological contributions of the dissertation in the debate over......' expectation formation. Chapters IV and V constitute the methodological contribution of the dissertation. Chapter IV develops a general method for decomposing total effects into its direct and indirect counterparts in nonlinear probability models such as the logistic response model. The method forms a solution...

  5. Density Determination and Metallographic Surface Preparation of Electron Beam Melted Ti6Al4V

    Science.gov (United States)

    2015-06-02

    Dossett and LtCol. Todd Lincoln of the United States Air Force – Dental Evaluation and Consultation Service for performing X-ray micro computed tomography...technique that is currently used to produce customized titanium-6aluminum-4vanadium (Ti6Al4V) cranial implants for wounded warfighters who require cranial... implant that favors bacterial contact and adhesion. Objective: The objective of this study was to establish density determination and metallographic

  6. Development of an air-stable, high energy density printed silver oxide battery for printed electronics

    OpenAIRE

    Braam, Kyle

    2014-01-01

    Printed batteries are an emerging battery technology that has the potential to enable the production of cheap, small form factor, flexible batteries capable of powering a diverse set of existing and emerging applications such as RFID tags, flexible displays, and distributed sensors. Partially printed battery systems have been demonstrated with various chemistries, but what is needed is a low cost, air stable method of fully printing a high energy density battery. The silver oxide chemistry i...

  7. Determination of total mass attenuation coefficients, effective atomic numbers and electron densities for different shielding materials used in radiation protection

    Energy Technology Data Exchange (ETDEWEB)

    Almeida J, A. T. [FUNDACENTRO, Centro Regional de Minas Gerais, Brazilian Institute for Safety and Health at Work, Belo Horizonte, 30180-100 Minas Gerais (Brazil); Nogueira, M. S. [Center of Development of Nuclear Technology / CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil); Santos, M. A. P., E-mail: mnogue@cdtn.br [Regional Center for Nuclear Science / CNEN, 50.740-540 Recife, Pernambuco (Brazil)

    2015-10-15

    Full text: In this paper, the interaction of X-rays with some shielding materials has been studied for materials containing different amounts of barite and aggregates. The total mass attenuation coefficient (μ{sub t}) for three shielding materials has been calculated by using WinXCOM program in the energy range from RQR qualities (RQR-4, RQR-6, RQR-9, and RQR-10). They were: cream barite (density 2.99 g/cm{sup 3} collected in the State of Sao Paulo), purple barite (density 2.95 g/cm{sup 3} collected in the State of Bahia) and white barite (density 3.10 g/cm{sup 3} collected in the State of Paraiba). The chemical analysis was carried out by an X-ray fluorescence spectrometer model EDX-720, through dispersive energy. The six elements of the higher concentration found in the sample and analyzed by Spectrophotometry of Energy Dispersive X-ray for the samples were Ba(60.9% - white barite), Ca(17,92% - cream barite), Ce(3,60% - white barite), Fe(17,16% - purple barite), S(12,11% - white barite) and Si(29,61% - purple barite). Also, the effective atomic number (Z{sub eff}) and the effective electron density (N{sub eff}) were calculated using the values of the total mass attenuation coefficient. The dependence of these parameters on the incident photon energy and the chemical composition has been examined. (Author)

  8. Nature of non-nuclear (3, -3) π-attractor and π-bonding: Theoretical analysis on π-electron density

    Science.gov (United States)

    Lv, Jiao; Yang, Lihua; Sun, Zheng; Meng, Lingpeng; Li, Xiaoyan

    2018-01-01

    Understanding the nature of π-electron density is important to characterize the conjugate π molecular systems. In this work, the π-electron densities of some typical conjugated π molecular systems were separated from their total electron densities; the positions and natures of non-nuclear (3, -3) π-attractors and the π-bond critical points (π-BCPs) are investigated. The calculated results show that for the same element, the position of the π-attractor is constant, regardless of the chemical surroundings. The position of the π-BCP is closer to the atom with the larger electronegativity.

  9. Size dependent electronic properties of silicon quantum dots-An analysis with hybrid, screened hybrid and local density functional theory

    Science.gov (United States)

    Gabay, D.; Wang, X.; Lomakin, V.; Boag, A.; Jain, M.; Natan, A.

    2017-12-01

    We use an efficient projection scheme for the Fock operator to analyze the size dependence of silicon quantum dots (QDs) electronic properties. We compare the behavior of hybrid, screened hybrid and local density functionals as a function of the dot size up to ∼800 silicon atoms and volume of up to ∼20 nm3. This allows comparing the calculations of hybrid and screened hybrid functionals to experimental results over a wide range of QD sizes. We demonstrate the size dependent behavior of the band gap, density of states, ionization potential and HOMO level shift after ionization. We also demonstrate how the use of Graphical Processing Units (GPUs) can further accelerate such calculations.

  10. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    In this dissertation I examine the relationship between subjective beliefs about the outcomes of educational choices and the generation of inequality of educational opportunity (IEO) in post-industrial society. Taking my departure in the rational action turn in the sociology of educational...... different educational choices according to their family background. IEO thus appears to be mediated by the expectations students hold for their futures. Taken together, this research agenda argues that both researchers and policy-makers need to consider the expectation-based origin of educational...... for their educational futures. Focusing on the causes rather than the consequences of educational expectations, I argue that students shape their expectations in response to the signals about their academic performance they receive from institutionalized performance indicators in schools. Chapter II considers...

  11. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    different educational choices according to their family background. IEO thus appears to be mediated by the expectations students hold for their futures. Taken together, this research agenda argues that both researchers and policy-makers need to consider the expectation-based origin of educational...... inequalities if educational reform is to promote educational and social mobility in post-industrial society. I pursue my research agenda in five chapters. In the introductory Chapter I I situate my research contributions in the tradition of the sociology of educational stratification. This chapter also...... outlines how the expectation-based explanation of IEO complements explanations stressing family resources as an important cause of IEO; it carefully defines "expectation," the core concept underlying the dissertation; it places the methodological contributions of the dissertation in the debate over...

  12. Evolutionary Expectations

    DEFF Research Database (Denmark)

    Nash, Ulrik William

    2014-01-01

    cognitive bounds will perceive business opportunities identically. In addition, because cues provide information about latent causal structures of the environment, changes in causality must be accompanied by changes in cognitive representations if adaptation is to be maintained. The concept of evolutionary......, they are correlated among people who share environments because these individuals satisfice within their cognitive bounds by using cues in order of validity, as opposed to using cues arbitrarily. Any difference in expectations thereby arise from differences in cognitive ability, because two individuals with identical......The concept of evolutionary expectations descends from cue learning psychology, synthesizing ideas on rational expectations with ideas on bounded rationality, to provide support for these ideas simultaneously. Evolutionary expectations are rational, but within cognitive bounds. Moreover...

  13. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    strongly suggest that students rely on information about their academic performances when considering their educational prospects. The two chapters thus highlight that educational expectations are subject to change over the educational career, and that educational systems play a prominent role in students...... stratification, I argue that students facing significant educational transitions form their educational expectations by taking into account the foreseeable, yet inherently uncertain, consequences of potential educational pathways. This process of expectation formation, I posit, involves evaluations...... of the relation between the self and educational prospects; evaluations that are socially bounded in that students take their family's social position into consideration when forming their educational expectations. One important consequence of this learning process is that equally talented students tend to make...

  14. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    stratification, I argue that students facing significant educational transitions form their educational expectations by taking into account the foreseeable, yet inherently uncertain, consequences of potential educational pathways. This process of expectation formation, I posit, involves evaluations...... of the relation between the self and educational prospects; evaluations that are socially bounded in that students take their family's social position into consideration when forming their educational expectations. One important consequence of this learning process is that equally talented students tend to make...... the role of causal inference in social science; and it discusses the potential of the findings of the dissertation to inform educational policy. In Chapters II and III, constituting the substantive contribution of the dissertation, I examine the process through which students form expectations...

  15. Expected Value

    OpenAIRE

    Robert Lapson

    1992-01-01

    A procedure for decision-making under risk is developed and axiomatized. It provides another explanation for the Allais paradox as well as justification for some other preference patterns that can not be represented by the expected utility model, but it includes expected utility representation fo preferences as a particular case. The idea of the procedure is that evaluation of the lotteries takes two steps. First, a decision maker classifies a lottery as a "bad," "good" or "medium" one. Then ...

  16. Temperature dependence of persistent spin currents in a spin-orbit-coupled electron gas: A density-matrix approach

    Science.gov (United States)

    Bencheikh, K.; Vignale, G.

    2008-04-01

    We present a simple analytical method, based on the canonical density matrix, for the calculation of the equilibrium spin current as a function of temperature in a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling terms. We find that the persistent spin current is extremely robust against thermal disorder: its variation with temperature is exponentially small (∝e-TF/T) at temperatures much smaller than the Fermi temperature TF and changes to a power law TF/T for T≫TF .

  17. Electron-Ion Dynamics with Time-Dependent Density Functional Theory: Towards Predictive Solar Cell Modeling: Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Maitra, Neepa [Hunter College City University of New York, New York, NY (United States)

    2016-07-14

    This project investigates the accuracy of currently-used functionals in time-dependent density functional theory, which is today routinely used to predict and design materials and computationally model processes in solar energy conversion. The rigorously-based electron-ion dynamics method developed here sheds light on traditional methods and overcomes challenges those methods have. The fundamental research undertaken here is important for building reliable and practical methods for materials discovery. The ultimate goal is to use these tools for the computational design of new materials for solar cell devices of high efficiency.

  18. Density functional theory investigation of the electronic structure and defect chemistry of Sr1-xKxFeO3

    Energy Technology Data Exchange (ETDEWEB)

    Ritzmann, Andrew M.; Dieterich, Johannes M.; Carter, Emily A.

    2016-07-27

    Solid oxide fuel cells (SOFCs) efficiently generate electricity, but high operating temperatures (T op > 800 °C) limit their utility. Reducing T op requires mixed ion–electron conducting (MIEC) cathode materials. Density functional theory is used here to investigate the role of potassium substitutions in the MIEC material Sr1-x K x FeO3 (SKFO). We predict that such substitutions are endothermic. SrFeO3 and SKFO have nearly identical metallic electronic structures. Oxygen vacancy formation energies decrease by ~0.2 eV when x K increases from 0 to 0.0625. SKFO is a promising SOFC MIEC cathode material; however, further experimental investigations must assess its long-term stability at the desired operating temperatures.

  19. Nonlinear density excitations in a magnetorotating relativistic plasma with warm ions and non-Maxwellian electrons

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Ali [National Centre for Physics, Shahdara Valley Road, Islamabad (Pakistan); Masood, W. [National Centre for Physics, Shahdara Valley Road, Islamabad (Pakistan); COMSATS Institute of Information Technology, Park Road, Chak Shahzad, Islamabad (Pakistan)

    2016-05-15

    Linear and nonlinear electrostatic ion acoustic waves in a weakly relativistic magnetorotating plasma in the presence of non-Maxwellian electrons and warm ions have been examined. The system under consideration has yielded two solutions, namely, the fast and slow acoustic modes which have been observed to depend on the streaming velocity, ion to electron temperature ratio, and the nonthermality parameter of the non-Maxwellian electrons. Using the multiple time scale analysis, we have derived the three dimensional nonlinear Zakharov–Kuznetsov equation and also presented its solution. Both compressive and rarefactive solitary structures have been found in consonance with the satellite observations. It has been observed that although the linear dispersion relation gives both fast and slow ion acoustic waves, the solitary structures form only for the fast acoustic mode. The dependence of the characteristics of the solitary structures on several plasma parameters has also been explored. The present investigation may be beneficial to understanding the rotating plasma environments such as those found in the planetary magnetospheres of Saturn and Jupiter.

  20. Comparing density, electron temperature, and magnetic fluctuations with gyrokinetic simulations using new synthetic diagnostics

    Science.gov (United States)

    Ernst, D. R.; Bergerson, W.; Ennever, P.; Greenwald, M.; Hubbard, A.; Irby, J.; Phillips, P.; Porkolab, M.; Rowan, W.; Terry, J. L.; Xu, P.; Alcator C-Mod Team

    2013-10-01

    Three new synthetic turbulence diagnostics are implemented in GS2 and compared with measurements: phase contrast imaging, polarimetry, and electron-cyclotron (ECE) emission. Our new synthetic diagnostic framework is based on transforming to a real-space annulus in Cartesian coordinates. This allows straightforward convolution with diagnostic point-spread functions, or integration over viewing chords. Wavenumber spectra and fluctuation amplitudes, as well as transport fluxes, are compared with measurements. Both phase contrast imaging and newly observed ECE electron temperature fluctuations, closely follow the electron temperature in an internal transport barrier during on-axis heating pulses, consistent with the role of TEM turbulence. New C-Mod polarimetry measurements, showing strong broadband core magnetic fluctuations, will also be examined against gyrokinetic simulations. The new framework is readily extended to other fluctuation measurements such as two-color interferometry, beam emission spectroscopy, Doppler back-scattering, ECE imaging, and microwave imaging reflectometry. Supported by U.S. DoE awards DE-FC02-08ER54966, DE-FC02-99ER54512, DE-FG03-96ER54373.

  1. Electronic Structure of the d Bent-metallocene Cp(2)VCl(2): A Photoelectron and Density Functional Study.

    Science.gov (United States)

    Cranswick, Matthew A; Gruhn, Nadine E; Enemark, John H; Lichtenberger, Dennis L

    2008-04-15

    The Cp(2)VCl(2) molecule is a prototype for bent metallocene complexes with a single electron in the metal d shell, but experimental measure of the binding energy of the d electron by photoelectron spectroscopy eluded early attempts due to apparent decomposition in the spectrometer to Cp(2)VCl. With improved instrumentation, the amount of decomposition is reduced and subtraction of ionization intensity due to Cp(2)VCl from the Cp(2)VCl(2)/Cp(2)VCl mixed spectrum yields the Cp(2)VCl(2) spectrum exclusively. The measured ionization energies provide well-defined benchmarks for electronic structure calculations. Density functional calculations support the spectral interpretations and agree well with the ionization energy of the d(1) electron and the energies of the higher positive ion states of Cp(2)VCl(2). The calculations also account well for the trends to the other Group V bent metallocene dichlorides Cp(2)NbCl(2) and Cp(2)TaCl(2). The first ionization energy of Cp(2)VCl(2) is considerably greater than the first ionization energies of the second- and third-row transition metal analogues.

  2. Ab initio density functional theory study on the atomic and electronic structure of GaP/Si(001) heterointerfaces

    Science.gov (United States)

    Romanyuk, O.; Supplie, O.; Susi, T.; May, M. M.; Hannappel, T.

    2016-10-01

    The atomic and electronic band structures of GaP/Si(001) heterointerfaces were investigated by ab initio density functional theory calculations. Relative total energies of abrupt interfaces and mixed interfaces with Si substitutional sites within a few GaP layers were derived. It was found that Si diffusion into GaP layers above the first interface layer is energetically unfavorable. An interface with Si/Ga substitution sites in the first layer above the Si substrate is energetically the most stable one in thermodynamic equilibrium. The electronic band structure of the epitaxial GaP/Si(001) heterostructure terminated by the (2 ×2 ) surface reconstruction consists of surface and interface electronic states in the common band gap of two semiconductors. The dispersion of the states is anisotropic and differs for the abrupt Si-Ga, Si-P, and mixed interfaces. Ga 2 p , P 2 p , and Si 2 p core-level binding-energy shifts were computed for the abrupt and the lowest-energy heterointerface structures. Negative and positive core-level shifts due to heterovalent bonds at the interface are predicted for the abrupt Si-Ga and Si-P interfaces, respectively. The distinct features in the heterointerface electronic structure and in the core-level shifts open new perspectives in the experimental characterization of buried polar-on-nonpolar semiconductor heterointerfaces.

  3. Time-dependent density functional theory study on direction-dependent electron and hole transfer processes in molecular systems.

    Science.gov (United States)

    Partovi-Azar, Pouya; Kaghazchi, Payam

    2017-04-15

    We report on real-time time-dependent density functional theory calculations on direction-dependent electron and hole transfer processes in molecular systems. As a model system, we focus on α-sulfur. It is shown that time scale of the electron transfer process from a negatively charged S8 molecule to a neighboring neutral monomer is comparable to that of a strong infrared-active molecular vibrations of the dimer with one negatively charged monomer. This results in a strong coupling between the electrons and the nuclei motion which eventually leads to S8 ring opening before the electron transfer process is completed. The open-ring structure is found to be stable. The similar infrared-active peak in the case of hole transfer, however, is shown to be very weak and hence no significant scattering by the nuclei is possible. The presented approach to study the charge transfer processes in sulfur has direct applications in the increasingly growing research field of charge transport in molecular systems. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  4. Characteristics and sources of the electron density irregularities in the mid latitude E and Fregions

    Science.gov (United States)

    2017-05-10

    Investigators (PI and Co-PIs): Young-Sil Kwak (PI), Jaeheung Park , Tae-Yong Yang, Young-Sook Lee, Jong-Min Choi, and Woo Kyoung Lee - e-mail address : yskwak...decoded and integrated raw data signal samples are subjected to the process of fast Fourier transform for on-line computation of the Doppler power... Park , J., H. Luehr, G. Kervalishvili, J. Rauberg, C. Stolle, Y.-S. Kwak, and W. K. Lee (2017), Morphology of high-latitude plasma density

  5. Pairing and unpairing electron densities in organic systems: [1.1.1]Propellane case

    Science.gov (United States)

    Lobayan, Rosana M.; Bochicchio, Roberto C.

    2013-02-01

    We present a theoretical description of the case of the strained [1.1.1]propellane system by application of the local and nonlocal topological formalisms to the density decomposition into its effectively paired and unpaired contributions. The analysis is mainly focused on the nature of its carbon-carbon headbridge sequence and the existence of 2e-3c complex patterns of bonding. The results clearly indicate that the system only possess 2e-2c patterns, including a true carbon-carbon headbridge bond and no 3c-2e complex patterns of bonding appear.

  6. On the calculation of Δ for electronic excitations in time-dependent density-functional theory

    Science.gov (United States)

    Myneni, Hemanadhan; Casida, Mark E.

    2017-04-01

    Excited states are often treated within the context of time-dependent (TD) density-functional theory (DFT), making it important to be able to assign the excited spin-state symmetry. While there is universal agreement on how Δ , the difference between for ground and excited states, should be calculated in a wave-function-like formalism such as the Tamm-Dancoff approximation (TDA), confusion persists as to how to determine the spin-state symmetry of excited states in TD-DFT. We try to clarify the origins of this confusion by examining various possibilities for the parameters (σ1 ,σ2) in the formula

  7. N-representability-driven reconstruction of the two-electron reduced-density matrix for a real-time time-dependent electronic structure method

    Energy Technology Data Exchange (ETDEWEB)

    Jeffcoat, David B.; DePrince, A. Eugene, E-mail: deprince@chem.fsu.edu [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390 (United States)

    2014-12-07

    Propagating the equations of motion (EOM) for the one-electron reduced-density matrix (1-RDM) requires knowledge of the corresponding two-electron RDM (2-RDM). We show that the indeterminacy of this expression can be removed through a constrained optimization that resembles the variational optimization of the ground-state 2-RDM subject to a set of known N-representability conditions. Electronic excitation energies can then be obtained by propagating the EOM for the 1-RDM and following the dipole moment after the system interacts with an oscillating external electric field. For simple systems with well-separated excited states whose symmetry differs from that of the ground state, excitation energies obtained from this method are comparable to those obtained from full configuration interaction computations. Although the optimized 2-RDM satisfies necessary N-representability conditions, the procedure cannot guarantee a unique mapping from the 1-RDM to the 2-RDM. This deficiency is evident in the mean-field-quality description of transitions to states of the same symmetry as the ground state, as well as in the inability of the method to describe Rabi oscillations.

  8. Techniques for Remote Sensing of Ionospheric Electron Density from a Spacecraft.

    Science.gov (United States)

    1981-08-05

    DETECTORS Detectors to measure electron and proton intensity, angular distributions, and energy spectra SOFT PARTICLE SPECTROMETER Electrostatic...MMd LAE . AIRR 141T41 K HI IA I HI 4. CLOLD TOP HEIGTIS & S RFACE ALBEDO 1060 l. hd lAG1 FREQUENCY D01 RI, P QIRO P1441 . 1 ME I4I R .11 1111...p 1283, 1974. 75. Luhmann, J. G., and J. B. Blake, "Calculations of Soft Auroral Brems- strahlung and Ka Line Emission at Satellite Altitude," J

  9. Kinetic Temperature and Electron Density Measurement in an Inductively Coupled Plasma Torch using Degenerate Four-Wave Mixing

    Science.gov (United States)

    Schafer, Julia; Lyons, Wendy; Tong, WIlliam G.; Danehy, Paul M.

    2008-01-01

    Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively-coupled plasma. Measurements are performed in a 1 kW, 27 MHz RF plasma using a continuous-wave, tunable 811.5-nm diode laser to excite the 4s(sup 3)P2 approaches 4p(sup 3)D3 argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler-broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000 K+/-150 K. Electron densities measured range from 6.1 (+/-0.3) x 10(exp 15)/cu cm to 10.1 (+/-0.3) x 10(exp 15)/cu cm. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.

  10. Brickworx builds recurrent RNA and DNA structural motifs into medium- and low-resolution electron-density maps

    Energy Technology Data Exchange (ETDEWEB)

    Chojnowski, Grzegorz, E-mail: gchojnowski@genesilico.pl [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); Waleń, Tomasz [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); University of Warsaw, Banacha 2, 02-097 Warsaw (Poland); Piątkowski, Paweł; Potrzebowski, Wojciech [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); Bujnicki, Janusz M. [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); Adam Mickiewicz University, Umultowska 89, 61-614 Poznan (Poland)

    2015-03-01

    A computer program that builds crystal structure models of nucleic acid molecules is presented. Brickworx is a computer program that builds crystal structure models of nucleic acid molecules using recurrent motifs including double-stranded helices. In a first step, the program searches for electron-density peaks that may correspond to phosphate groups; it may also take into account phosphate-group positions provided by the user. Subsequently, comparing the three-dimensional patterns of the P atoms with a database of nucleic acid fragments, it finds the matching positions of the double-stranded helical motifs (A-RNA or B-DNA) in the unit cell. If the target structure is RNA, the helical fragments are further extended with recurrent RNA motifs from a fragment library that contains single-stranded segments. Finally, the matched motifs are merged and refined in real space to find the most likely conformations, including a fit of the sequence to the electron-density map. The Brickworx program is available for download and as a web server at http://iimcb.genesilico.pl/brickworx.

  11. Electronic structure of SnF{sub 3}: An example of valence skipper which forms charge density wave

    Energy Technology Data Exchange (ETDEWEB)

    Hase, I., E-mail: i.hase@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568 (Japan); Yanagisawa, T. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568 (Japan); Kawashima, K. [IMRA Material R& D Co., LTD., Kariya, Aichi 448-0032 (Japan)

    2016-11-15

    Highlights: • We calculated the electronic structure of SnF{sub 3} and BaBiO{sub 3} from first principles. • As for SnF{sub 3}, charge-density-wave (CDW) is found, which agrees with the experiment. • As for BaBiO{sub 3}, CDW is not found, contrary to the experiment. • We conclude that the CDW is hard in SnF{sub 3} and is soft in BaBiO{sub 3}. - Abstract: In the present study we calculated the electronic structure of the valence skipping compound SnF{sub 3} and BaBiO{sub 3} from first-principles. We confirmed that the charge-density-wave (CDW) is formed in SnF{sub 3}, and the Sn atoms in two crystallographic different sites take the valence Sn{sup 2+} and Sn{sup 4+}. Structure optimization study reveals that this CDW is stable, though the atomic position is slightly different from the experimental data. This behavior is in contrast with the case of BaBiO{sub 3}, where the structure optimization leads to the uniform state, which means that two Bi sites are equivalent. The CDW state is hard in SnF{sub 3}, which means that the CDW gap is large enough and it is difficult to melt this CDW order.

  12. Dependence of high density nitrogen-vacancy center ensemble coherence on electron irradiation doses and annealing time

    Science.gov (United States)

    Zhang, C.; Yuan, H.; Zhang, N.; Xu, L. X.; Li, B.; Cheng, G. D.; Wang, Y.; Gui, Q.; Fang, J. C.

    2017-12-01

    Negatively charged nitrogen-vacancy (NV‑) center ensembles in diamond have proved to have great potential for use in highly sensitive, small-package solid-state quantum sensors. One way to improve sensitivity is to produce a high-density NV‑ center ensemble on a large scale with a long coherence lifetime. In this work, the NV‑ center ensemble is prepared in type-Ib diamond using high energy electron irradiation and annealing, and the transverse relaxation time of the ensemble—T 2—was systematically investigated as a function of the irradiation electron dose and annealing time. Dynamical decoupling sequences were used to characterize T 2. To overcome the problem of low signal-to-noise ratio in T 2 measurement, a coupled strip lines waveguide was used to synchronously manipulate NV‑ centers along three directions to improve fluorescence signal contrast. Finally, NV‑ center ensembles with a high concentration of roughly 1015 mm‑3 were manipulated within a ~10 µs coherence time. By applying a multi-coupled strip-lines waveguide to improve the effective volume of the diamond, a sub-femtotesla sensitivity for AC field magnetometry can be achieved. The long-coherence high-density large-scale NV‑ center ensemble in diamond means that types of room-temperature micro-sized solid-state quantum sensors with ultra-high sensitivity can be further developed in the near future.

  13. Electrostatic properties of the pyrimethamine-2,4-dihydroxybenzoic acid cocrystal in methanol studied using transferred electron-density parameters.

    Science.gov (United States)

    Faroque, Muhammad Umer; Noureen, Sajida; Ahmed, Maqsood; Tahir, Muhammad Nawaz

    2018-01-01

    The crystal structure of the cocrystal salt form of the antimalarial drug pyrimethamine with 2,4-dihydroxybenzoic acid in methanol [systematic name: 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium 2,4-dihydroxybenzoate methanol monosolvate, C12H14ClN4+·C7H5O4-·CH3OH] has been studied using X-ray diffraction data collected at room temperature. The crystal structure was refined using the classical Independent Atom Model (IAM) and the Multipolar Atom Model by transferring electron-density parameters from the ELMAM2 database. The Cl atom was refined anharmonically. The results of both refinement methods have been compared. The intermolecular interactions have been characterized on the basis of Hirshfeld surface analysis and topological analysis using Bader's theory of Atoms in Molecules. The results show that the molecular assembly is built primarily on the basis of charge transfer between 2,4-dihydroxybenzoic acid and pyrimethamine, which results in strong intermolecular hydrogen bonds. This fact is further validated by the calculation of the electrostatic potential based on transferred electron-density parameters.

  14. A precision control method for plasma electron density and Faraday rotation angle measurement on HL-2A

    Science.gov (United States)

    Zhang, Wei; Wu, Tongyu; Ding, Baogang; Li, Yonggao; Zhou, Yan; Yin, Zejie

    2017-07-01

    The precision of plasma electron density and Faraday rotation angle measurement is a key indicator for far-infrared laser interferometer/polarimeter plasma diagnosis. To improve the precision, a new multi-channel high signal-to-noise ratio HCOOH interferometer/polarimeter has been developed on the HL-2A tokamak. It has a higher level requirement for phase demodulation precision. This paper introduces an improved real-time fast Fourier transform algorithm based on the field programmable gate array, which significantly improves the precision. We also apply a real-time error monitoring module (REMM) and a stable error inhibiting module (SEIM) for precision control to deal with the weak signal. We test the interferometer/polarimeter system with this improved precision control method in plasma discharge experiments and simulation experiments. The experimental results confirm that the plasma electron density precision is better than 1/3600 fringe and the Faraday rotation angle measurement precision is better than 1/900 fringe, while the temporal resolution is 80 ns. This performance can fully meet the requirements of HL-2A.

  15. Unequal Expectations

    DEFF Research Database (Denmark)

    Karlson, Kristian Bernt

    In this dissertation I examine the relationship between subjective beliefs about the outcomes of educational choices and the generation of inequality of educational opportunity (IEO) in post-industrial society. Taking my departure in the rational action turn in the sociology of educational...... different educational choices according to their family background. IEO thus appears to be mediated by the expectations students hold for their futures. Taken together, this research agenda argues that both researchers and policy-makers need to consider the expectation-based origin of educational...... strongly suggest that students rely on information about their academic performances when considering their educational prospects. The two chapters thus highlight that educational expectations are subject to change over the educational career, and that educational systems play a prominent role in students...

  16. Density functional study of electronic, charge density, and chemical bonding properties of 9-methyl-3-Thiophen-2-YI-Thieno [3,2-e] [1, 2, 4] Thriazolo [4,3-c] pyrimidine-8-Carboxylic acid ethyl ester crystals

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H., E-mail: maalidph@yahoo.co.uk [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Kamarudin, H. [Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Alahmed, Z.A. [Department of Physics and Astronomy, King Saud University, Riyadh 11451 (Saudi Arabia); Auluck, S. [CSIR-National Physical Laboratory, Dr. K S Krishnan Marg, New Delhi 110012 (India); Chyský, Jan [Department of Instrumentation and Control Engineering, Faculty of Mechanical Engineering, CTU in Prague, Technicka 4, 166 07 Prague 6 (Czech Republic)

    2014-06-01

    A comprehensive theoretical density functional investigation of the electronic crystal structure, chemical bonding, and the electron charge densities of 9-Methyl-3-Thiophen-2-YI-Thieno [3, 2-e] [1, 2, 4] Thriazolo [4,3-c] Pyrimidine-8-Carboxylic Acid Ethyl Ester (C{sub 15}H{sub 12}N{sub 4}O{sub 2}S{sub 2}) is performed. The density of states at Fermi level equal to 5.50 (3.45) states/Ry cell, and the calculated bare electronic specific heat coefficient is found to be 0.95 (0.59) mJ/mole-K{sup 2} for the local density approximation (Engel–Vosko generalized gradient approximation). The electronic charge density space distribution contours in (1 0 0) and (1 1 0) planes were calculated. We find that there are two independent molecules (A and B) in the asymmetric unit exhibit intramolecular C–H…O, C–H…N interactions. This intramolecular interaction is different in molecules A and B, where A molecule show C–H…O interaction while B molecule exhibit C–H…N interaction. We should emphasis that there is π–π interaction between the pyrimidine rings of the two neighbors B molecules gives extra strengths and stabilizations to the superamolecular structure. The calculated distance between the two neighbors pyrimidine rings found to be 3.345 Å, in good agreement with the measured one (3.424(1) Å). - Highlights: • Electronic structure, chemical bonding, and electron charge density were studied. • Density of states at Fermi level is 5.50 (3.45) states/Ry cell, for LDA (EVGGA). • Bare electronic specific heat coefficient is 0.95 (0.59) mJ/mole-K{sup 2} for LDA(EVGGA). • There are two independent molecules (A and B) in the asymmetric unit.

  17. Intermolecular Interactions in Crystalline Theobromine as Reflected in Electron Deformation Density and (13)C NMR Chemical Shift Tensors.

    Science.gov (United States)

    Bouzková, Kateřina; Babinský, Martin; Novosadová, Lucie; Marek, Radek

    2013-06-11

    An understanding of the role of intermolecular interactions in crystal formation is essential to control the generation of diverse crystalline forms which is an important concern for pharmaceutical industry. Very recently, we reported a new approach to interpret the relationships between intermolecular hydrogen bonding, redistribution of electron density in the system, and NMR chemical shifts (Babinský et al. J. Phys. Chem. A, 2013, 117, 497). Here, we employ this approach to characterize a full set of crystal interactions in a sample of anhydrous theobromine as reflected in (13)C NMR chemical shift tensors (CSTs). The important intermolecular contacts are identified by comparing the DFT-calculated NMR CSTs for an isolated theobromine molecule and for clusters composed of several molecules as selected from the available X-ray diffraction data. Furthermore, electron deformation density (EDD) and shielding deformation density (SDD) in the proximity of the nuclei involved in the proposed interactions are calculated and visualized. In addition to the recently reported observations for hydrogen bonding, we focus here particularly on the stacking interactions. Although the principal relations between the EDD and CST for hydrogen bonding (HB) and stacking interactions are similar, the real-space consequences are rather different. Whereas the C-H···X hydrogen bonding influences predominantly and significantly the in-plane principal component of the (13)C CST perpendicular to the HB path and the C═O···H hydrogen bonding modulates both in-plane components of the carbonyl (13)C CST, the stacking modulates the out-of-plane electron density resulting in weak deshielding (2-8 ppm) of both in-plane principal components of the CST and weak shielding (∼ 5 ppm) of the out-of-plane component. The hydrogen-bonding and stacking interactions may add to or subtract from one another to produce total values observed experimentally. On the example of theobromine, we demonstrate

  18. Inter-relation between D-region electron densities from 3-MHz Doppler radar observations, riometer absorption, and the empirical model IMAZ at 69N

    Science.gov (United States)

    Singer, Werner; Gausa, Michael; Latteck, Ralph; Honary, Farideh; Friedrich, Martin

    Electron densities of the lower ionosphere are estimated using the Saura MF Doppler radar data since summer 2003. The radar is located near Andenes, Norway (69.3N, 16.0E) and operates at 3.17 MHz. The experiment utilizes partial reflections of ordinary and extraordinary component waves from scatterers in the altitude range 50-90 km to estimate electron number densities from differential absorption (DAE) and differential phase (DPE) measurements. Height profiles of electron density are obtained between about 55 km and 90 km with a height resolution of 1 km. The diurnal and seasonal variability of electron densities as well as the response of D-region electron densities to solar activity storms, solar proton events, and geomagnetic disturbances have been estimated. The imaging riometer AIRIS near Andenes monitors excessive radio wave absorption due to precipitating energetic particles. The vertical beam of the Saura MF radar coincides with the volume observed with the vertical AIRIS beam. The data from both systems allow the verification of the lower part of the neural network-based ionospheric model for the Auroral zone IMAZ-2. The model provides electron density profiles between 60 and 140 km for a given riometer absorption, time, and ionospheric state. It is based on electron density profiles from EISCAT UHF/VHF radars for altitudes above about 85 km and high-latitude rocket measurements, but the data below 70 km is almost exclusively due to sounding rockets. Comparisons of the IMAZ model with measured electron density profiles are discussed for different levels of solar activity and various particle precipitation events.

  19. Modelling coronal electron density and temperature profiles of the Active Region NOAA 11855

    Science.gov (United States)

    Rodríguez Gómez, J. M.; Antunes Vieira, L. E.; Dal Lago, A.; Palacios, J.; Balmaceda, L. A.; Stekel, T.

    2017-10-01

    The magnetic flux emergence can help understand the physical mechanism responsible for solar atmospheric phenomena. Emerging magnetic flux is frequently related to eruptive events, because when emerging they can reconnected with the ambient field and release magnetic energy. We will use a physic-based model to reconstruct the evolution of the solar emission based on the configuration of the photospheric magnetic field. The structure of the coronal magnetic field is estimated by employing force-free extrapolation NLFFF based on vector magnetic field products (SHARPS) observed by HMI instrument aboard SDO spacecraft from Sept. 29 (2013) to Oct. 07 (2013). The coronal plasma temperature and density are described and the emission is estimated using the CHIANTI atomic database 8.0. The performance of the our model is compared to the integrated emission from the AIA instrument aboard SDO spacecraft in the specific wavelengths 171Å and 304Å.

  20. Storm-time variation of relativistic electron phase space density associated with potential mechanisms in the outer radiation belts

    Science.gov (United States)

    Liu, S.; Xiao, F.; Yang, C.; Zhou, Q.; He, Y.

    2016-12-01

    The possible acceleration mechanisms of relativistic electron fluxes in Earth's outer radiation belt are basically categorized into two groups: radial diffusion and in-situ acceleration. A physical understanding and modeling of the radiation belt dynamic require an investigation of the electron phase space density (PSD) to provide a delicate picture of the mechanisms. Here, we study the time evolution of relativistic electron PSD during two events. During 23 to 24 September, 2014, with minimum Dst=-27 nT and maximum Kp 4, relativistic (2.1 -3.4 MeV) electron fluxes and chorus waves were substantially enhanced at L=4.5-6 by the Van Allen Probes. Pronounced peaks in PSD radial profiles occurred at L*=4.9-5.2, suggesting a local acceleration process as the primary mechanism. Numerical calculation shows that bounce-averaged momentum diffusion coefficient from chorus wave approaches 10-5 s-1 at large pitch angle for 2 MeV electrons. Meanwhile, electromagnetic and electrostatic radial diffusion coefficients (DMLL and DELL) are smaller than approximately by 3-20 times and 25-100 times respectively. This indicates that chorus-electron interaction dominates the PSD evolution over the radial diffusion in this event. During 1 to 3 October, 2013, with minimum Dst=-67 nT and maximum Kp 8, relativistic electron fluxes increased by 1-2 orders at L=4.8-5.8, while chorus waves are not directly observed. The PSD radial profiles monotonically increases with L*. We find that DMLL and DELL can approach 10-4 s-1 and 10-5 s-1 respectively. Using inferred chorus intensity 50 pT, we obtain the momentum diffusion coefficient as about 10-6 s-1. The above calculations and observations indicated that the radial diffusion tends to be the dominant process for the PSD enhancement. The present results provide a direct support and reveal a typical picture for the previous statistical characteristics of radial PSD evolution related to different internal, magnetospheric processes. It further