WorldWideScience

Sample records for residual electron density

  1. Solar corona electron density distribution

    International Nuclear Information System (INIS)

    Esposito, P.B.; Edenhofer, P.; Lueneburg, E.

    1980-01-01

    Three and one-half months of single-frequency (f= 0 2.2 x 10 9 Hz) time delay data (earth-to-spacecraft and return signal travel time) were acquired from the Helios 2 spacecraft around the time of its solar occupation (May 16, 1976). Following the determination of the spacecraft trajectory the excess time delay due to the integrated effect of free electrons along the signal's ray path could be separated and modeled. An average solar corona, equatorial, electron density profile, during solar minimum, was deduced from time delay measurements acquired within 5--60 solar radii (R/sub S/) of the sun. As a point of reference, at 10 R/sub S/ from the sun we find an average electron density of 4500 el cm -3 . However, there appears to be an asymmtry in the electron density as the ray path moved from the west (preoccultation) to east (post-occulation) solar limb. This may be related to the fact that during entry into occulation the heliographic latitude of the ray path (at closes approach to the sun) was about 6 0 , whereas during exit it became -7 0 . The Helios electron density model is compared with similar models deduced from a variety of different experimental techniques. Within 5--20 R/sub S/ of the sun the models separate according to solar minimum or maximum conditions; however, anomalies are evident

  2. Statistical theory of electron densities

    International Nuclear Information System (INIS)

    Pratt, L.R.; Hoffman, G.G.; Harris, R.A.

    1988-01-01

    An optimized Thomas--Fermi theory is proposed which retains the simplicity of the original theory and is a suitable reference theory for Monte Carlo density functional treatments of condensed materials. The key ingredient of the optimized theory is a neighborhood sampled potential which contains effects of the inhomogeneities in the one-electron potential. In contrast to the traditional Thomas--Fermi approach, the optimized theory predicts a finite electron density in the vicinity of a nucleus. Consideration of the example of an ideal electron gas subject to a central Coulomb field indicates that implementation of the approach is straightforward. The optimized theory is found to fail completely when a classically forbidden region is approached. However, these circumstances are not of primary interest for calculations of interatomic forces. It is shown how the energy functional of the density may be constructed by integration of a generalized Hellmann--Feynman relation. This generalized Hellmann--Feynman relation proves to be equivalent to the variational principle of density functional quantum mechanics, and, therefore, the present density theory can be viewed as a variational consequence of the constructed energy functional

  3. Electron densities in planetary nebulae

    International Nuclear Information System (INIS)

    Stanghellini, L.; Kaler, J.B.

    1989-01-01

    Electron densities for 146 planetary nebulae have been obtained for analyzing a large sample of forbidden lines by interpolating theoretical curves obtained from solutions of the five-level atoms using up-to-date collision strengths and transition probabilities. Electron temperatures were derived from forbidden N II and/or forbidden O III lines or were estimated from the He II 4686 A line strengths. The forbidden O II densities are generally lower than those from forbidden Cl III by an average factor of 0.65. For data sets in which forbidden O II and forbidden S II were observed in common, the forbidden O II values drop to 0.84 that of the forbidden S II, implying that the outermost parts of the nebulae might have elevated densities. The forbidden Cl II and forbidden Ar IV densities show the best correlation, especially where they have been obtained from common data sets. The data give results within 30 percent of one another, assuming homogeneous nebulae. 106 refs

  4. The new method for the residual gas density measurements

    CERN Document Server

    Anashin, V V; Krasnov, A A; Malyshev, O B; Nas'mov, V P; Pyata, E I; Shaftan, T V

    2001-01-01

    A new method of measurement for residual gas density in the vacuum chambers in presence of synchrotron radiation (SR) is described. The method is based on using a photomultiplier tube for the detection of the SR-stimulated residual gas luminescence, which is proportional to the residual gas density and SR intensity. The design of the experimental setup and results of the measurements of densities of residual gases (H sub 2 , CO sub 2 , CO, N sub 2 , Ar and O sub 2) are submitted.

  5. Density of primes in l-th power residues

    Indian Academy of Sciences (India)

    Introduction. In a recent paper [1] the authors have computed the relative density of primes for which a given finite string S = {a1,..., am} of integers are quadratic residues simultaneously. It turns out, via Chebotarev density theorem, that this density is reciprocal to the degree of the multiquadratic extension given by square ...

  6. 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....

  7. 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

  8. Electron velocity and momentum density

    International Nuclear Information System (INIS)

    Perkins, G.A.

    1978-01-01

    A null 4-vector eta + sigma/sub μ/based on Dirac's relativistic electron equation, is shown explicitly for a plane wave and various Coulomb states. This 4-vector constitutes a mechanical ''model'' for the electron in those staes, and expresses the important spinor quantities represented conventionally by n, f, g, m, j, kappa, l, and s. The model for a plane wave agrees precisely with the relation between velocity and phase gradient customarily used in quantum theory, but the models for Coulomb states contradict that relation

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

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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.

  10. Electron density measurements in STPX plasmas

    Science.gov (United States)

    Clark, Jerry; Williams, R.; Titus, J. B.; Mezonlin, E. D.; Akpovo, C.; Thomas, E.

    2017-10-01

    Diagnostics have been installed to measure the electron density of Spheromak Turbulent Physics Experiment (STPX) plasmas at Florida A. & M. University. An insertable probe, provided by Auburn University, consisting of a combination of a triple-tipped Langmuir probe and a radial array consisting of three ion saturation current / floating potential rings has been installed to measure instantaneous plasma density, temperature and plasma potential. As the ramp-up of the experimental program commences, initial electron density measurements from the triple-probe show that the electron density is on the order of 1019 particles/m3. For a passive measurement, a CO2 interferometer system has been designed and installed for measuring line-averaged densities and to corroborate the Langmuir measurements. We describe the design, calibration, and performance of these diagnostic systems on large volume STPX plasmas.

  11. Residual carrier density in GaSb grown on Si substrates

    International Nuclear Information System (INIS)

    Akahane, Kouichi; Yamamoto, Naokatsu; Gozu, Shin-ichiro; Ueta, Akio; Ohtani, Naoki

    2006-01-01

    The relationships between the densities of residual carriers and those of dislocation in GaSb films grown on Si substrates were investigated. Dislocation density was evaluated by cross-sectional transmission electron microscopy (TEM). The TEM images indicated that the dislocation density after a 5-μm-thick GaSb film was grown was below 1 x 10 8 /cm 2 although the density near the interface between the Si substrate and the GaSb film was about 3 x 10 9 /cm 2 . Forming a dislocation loop by growing a thick GaSb layer may decrease the dislocation density. The density and mobility of the residual carrier were investigated by Hall measurement using the van der Pauw method. The residual carriers in GaSb grown on Si substrates were holes, and their densities decreased significantly from 4.2 x 10 18 to 1.4 x 10 17 /cm 3 as GaSb thickness was increased from 500 to 5500 nm

  12. Bone mineral density and mandibular residual ridge resorption.

    Science.gov (United States)

    Springe, Baiba; Slaidina, Anda; Soboleva, Una; Lejnieks, Aivars

    2014-01-01

    This prospective, cross-sectional study evaluated the relationship between bone mineral density (BMD) and the width and height parameters of the mandibular residual ridge. BMD was determined in the lumbar spine and femoral necks by dual energy x-ray absorptiometry (DXA) in 45 edentulous, postmenopausal women (mean age, 72.08 ± 8.53 years) who had used conventional complete dentures for at least 3 years. Measurements of the mandibular residual ridge were performed using cone beam computed tomography (CBCT). Height and width measurements were performed in the midline and adjacent to the mental foramina. Data were analyzed with descriptive and analytic statistics. The relationship between BMD and mandibular height and width measurements was assessed using analysis of variance as well as linear and multivariate regression analyses. Eight patients were excluded from the study because they did not complete both of the required imaging analyses (DXA and/or CBCT). There was no statistically significant relationship between BMD and mandibular bone height measurements in the midline and both regions of the mental foramina, and no statistically significant relationship existed between BMD and mandibular bone width measurements in the midline and both of the mental foramina regions. Postmenopausal women with reduced general BMD do not appear to have a reduction in the size of the mandibular residual ridge.

  13. Teaching Chemistry with Electron Density Models

    Science.gov (United States)

    Shusterman, Gwendolyn P.; Shusterman, Alan J.

    1997-07-01

    Linus Pauling once said that a topic must satisfy two criteria before it can be taught to students. First, students must be able to assimilate the topic within a reasonable amount of time. Second, the topic must be relevant to the educational needs and interests of the students. Unfortunately, the standard general chemistry textbook presentation of "electronic structure theory", set as it is in the language of molecular orbitals, has a difficult time satisfying either criterion. Many of the quantum mechanical aspects of molecular orbitals are too difficult for most beginning students to appreciate, much less master, and the few applications that are presented in the typical textbook are too limited in scope to excite much student interest. This article describes a powerful new method for teaching students about electronic structure and its relevance to chemical phenomena. This method, which we have developed and used for several years in general chemistry (G.P.S.) and organic chemistry (A.J.S.) courses, relies on computer-generated three-dimensional models of electron density distributions, and largely satisfies Pauling's two criteria. Students find electron density models easy to understand and use, and because these models are easily applied to a broad range of topics, they successfully convey to students the importance of electronic structure. In addition, when students finally learn about orbital concepts they are better prepared because they already have a well-developed three-dimensional picture of electronic structure to fall back on. We note in this regard that the types of models we use have found widespread, rigorous application in chemical research (1, 2), so students who understand and use electron density models do not need to "unlearn" anything before progressing to more advanced theories.

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

    African Journals Online (AJOL)

    It is seen that the electron temperature increases from 5.8 × 102 oK to 7.83 × 104 oK as the pd is reduced from 130mm Hg × mm to 60 mm Hg × mm for argon. The electron densities increases from 2.8 × 1011/cm3 to 3.2 × 1011 /cm3 for the same variation of pds. For air the electron temperature increases from 3.6 × 104 oK to ...

  15. Topside electron density at low latitudes

    International Nuclear Information System (INIS)

    Ezquer, R.G.; Cabrera, M.A.; Flores, R.F.; Mosert, M.

    2002-01-01

    The validity of IRI to predict the electron density at the topside electron density profile over the low latitude region is checked. The comparison with measurements obtained with the Taiyo satellite during low solar activity shows that, the disagreement between prediction and measurement is lower than 40% for 70% of considered cases. These IRI predictions are better than those obtained in a previous work at the southern peak of the equatorial anomaly for high solar activity. Additional studies for low solar activity, using ionosonde data as input parameters in the model, are needed in order to check if the observed deviations are due to the predicted peak characteristics or to the predicted shape of the topside profile. (author)

  16. Electron density measurement for steady state plasmas

    International Nuclear Information System (INIS)

    Kawano, Yasunori; Chiba, Shinichi; Inoue, Akira

    2000-01-01

    Electron density of a large tokamak has been measured successfully by the tangential CO 2 laser polarimeter developed in JT-60U. The tangential Faraday rotation angles of two different wavelength of 9.27 and 10.6 μm provided the electron density independently. Two-color polarimeter concept for elimination of Faraday rotation at vacuum windows is verified for the first time. A system stability for long time operation up to ∼10 hours is confirmed. A fluctuation of a signal baseline is observed with a period of ∼3 hours and an amplitude of 0.4 - 0.7deg. In order to improve the polarimeter, an application of diamond window for reduction of the Faraday rotation at vacuum windows and another two-color polarimeter concept for elimination of mechanical rotation component are proposed. (author)

  17. Aromaticity in benzene-like rings-An experimental electron density ...

    Indian Academy of Sciences (India)

    An experimental charge density study has been carried out on perylene 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 ...

  18. Electronic structure and electron momentum density in TiSi

    Energy Technology Data Exchange (ETDEWEB)

    Ghaleb, A.M. [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq); Mohammad, F.M. [Department of Physics, College of Science, University of Tikreet, Tikreet (Iraq); Sahariya, Jagrati [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Sharma, Mukesh [Physics Division, Forensic Science Laboratory, Jaipur, Rajasthan (India); Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India)

    2013-03-01

    We report the electron momentum density in titanium monosilicide using {sup 241}Am Compton spectrometer. Experimental Compton profile has been compared with the theoretical profiles computed using linear combination of atomic orbitals (LCAO). The energy bands, density of states and Fermi surface structures of TiSi are reported using the LCAO and the full potential linearized augmented plane wave methods. Theoretical anisotropies in directional Compton profiles are interpreted in terms of energy bands. To confirm the conducting behavior, we also report the real space analysis of experimental Compton profile of TiSi.

  19. Electronic structure and electron momentum density in TiSi

    International Nuclear Information System (INIS)

    Ghaleb, A.M.; Mohammad, F.M.; Sahariya, Jagrati; Sharma, Mukesh; Ahuja, B.L.

    2013-01-01

    We report the electron momentum density in titanium monosilicide using 241 Am Compton spectrometer. Experimental Compton profile has been compared with the theoretical profiles computed using linear combination of atomic orbitals (LCAO). The energy bands, density of states and Fermi surface structures of TiSi are reported using the LCAO and the full potential linearized augmented plane wave methods. Theoretical anisotropies in directional Compton profiles are interpreted in terms of energy bands. To confirm the conducting behavior, we also report the real space analysis of experimental Compton profile of TiSi

  20. New description of the electron density profile

    International Nuclear Information System (INIS)

    Rawer, K.

    1984-01-01

    Several methods are described by which the entire electron density profile of the International Reference Ionosphere (IRI) could be respresented analytically while emphasizing the most important physical features. Consideration is given to the use of absolute values as a sum of individual Ne (height) functions in order to eliminate conventional time-consuming fitting procedures. It is recommended that three Epstein steps be integrated in the skeleton function, thereby providing a total of eleven parameters for the profile. Some of the parameters might be only slowly variable (HX2, HX3, SC2, SC3). 9 references

  1. Electron Density Calibration for Radiotherapy Treatment Planning

    International Nuclear Information System (INIS)

    Herrera-Martinez, F.; Rodriguez-Villafuerte, M.; Martinez-Davalos, A.; Ruiz-Trejo, C.; Celis-Lopez, M. A.; Larraga-Gutierrez, J. M.; Garcia-Garduno, A.

    2006-01-01

    Computed tomography (CT) images are used as basic input data for most modern radiosurgery treatment planning systems (TPS). CT data not only provide anatomic information to delineate target volumes, but also allow the introduction of corrections for tissue inhomogeneities into dose calculations during the treatment planning procedure. These corrections involve the determination of a relationship between tissue electron density (ρe) and their corresponding Hounsfield Units (HU). In this work, an elemental analysis of different commercial tissue equivalent materials using Scanning Electron Microscopy was carried out to characterize their chemical composition. The tissue equivalent materials were chosen to ensure a large range of ρe to be included in the CT scanner calibration. A phantom was designed and constructed with these materials to simulate the size of a human head

  2. Determination of Thermal Properties and Morphology of Eucalyptus Wood Residue Filled High Density Polyethylene Composites

    Directory of Open Access Journals (Sweden)

    Ayse Kabakci

    2008-02-01

    Full Text Available Thermal behaviors of eucalyptus wood residue (EWR filled recycled high density polyethylene (HDPE composites have been measured applying the thermogravimetric analysis (TGA and differential scanning calorimetry (DSC. Morphology of the materials was also studied using scanning electron microscope (SEM. Addition of the EWR into the recycled HDPE matrix reduced the starting of degradation temperature. EWR filled recycled HDPE had two main decomposition peaks, one for EWR around 350 °C and one for recycled HDPE around 460 °C. Addition of EWR did not affect the melting temperature of the recycled HDPE. Morphological study showed that addition of coupling agent improved the compatibility between wood residue and recycled HDPE.

  3. Electron density measurements for plasma adaptive optics

    Science.gov (United States)

    Neiswander, Brian W.

    Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications. When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber. Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system's capabilities.

  4. 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...

  5. Interaction effects in liquids with low electron densities

    International Nuclear Information System (INIS)

    Warren, W.W. Jr.

    1987-01-01

    The author discusses two complementary classes of systems in which strong electron-electron or electron-ion interactions appear at low electron densities. The first are the expanded liquid alkali metals (cesium) in which electron correlation effects have a profound effect on the magnetic properties on the metallic side of the metal-nonmetal transition. The second group are molten alkali halides containing low densities of localized electrons introduced, say, by dissolution of small amounts of excess metal. (Auth.)

  6. Existence of time-dependent density-functional theory for open electronic systems: time-dependent holographic electron density theorem.

    Science.gov (United States)

    Zheng, Xiao; Yam, ChiYung; Wang, Fan; Chen, GuanHua

    2011-08-28

    We present the time-dependent holographic electron density theorem (TD-HEDT), which lays the foundation of time-dependent density-functional theory (TDDFT) for open electronic systems. For any finite electronic system, the TD-HEDT formally establishes a one-to-one correspondence between the electron density inside any finite subsystem and the time-dependent external potential. As a result, any electronic property of an open system in principle can be determined uniquely by the electron density function inside the open region. Implications of the TD-HEDT on the practicality of TDDFT are also discussed.

  7. Metastable atom probe for measuring electron beam density profiles

    Science.gov (United States)

    Lockhart, J. M.; Zorn, J. C.

    1972-01-01

    Metastable atom probe was developed for measuring current density in electron beam as function of two arbitrary coordinates, with spatial resolution better than 0.5 mm. Probe shows effects of space charge, magnetic fields, and other factors which influence electron current density, but operates with such low beam densities that introduced perturbation is very small.

  8. Study of Chromium Multilayers Properties Obtained by Pulsed Current Density: Residual Stress and Microhardness

    Directory of Open Access Journals (Sweden)

    Julieta TORRES-GONZÁLEZ

    2010-12-01

    Full Text Available Chromium multilayers deposits were obtained from three different bath solutions, they were prepared by switching current density between 10 and 70 Adm-2. Two temperatures were studied, 35°C and 55°C. At 35°C two different microstructures are alternated: columnar obtained at 10 Adm-2 and equiaxial obtained at 70 Adm-2. At 55°C only the columnar type microstructure is present, at 10 and 70 Adm-2, the only difference among the layers is a slight disorientation of grains. The properties of these chromium multilayers were characterized by scanning electron microscopy (SEM and X-ray diffraction (XRD. In general the deposits are microcracked with a high microhardness, high residual stress and a small grain size.

  9. 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.

  10. Probing Electron Dynamics with the Laplacian of the Momentum Density

    Energy Technology Data Exchange (ETDEWEB)

    Sukumar, N.; MacDougall, Preston J. [Middle Tennessee State University; Levit, M. Creon [Nasa Ames Research Center

    2012-09-24

    This chapter in the above-titled monograph presents topological analysis of the Laplacian of the electron momentum density in organic molecules. It relates topological features in this distribution to chemical and physical properties, particularly aromaticity and electron transport.

  11. Continuous localization-delocalization transition at intermediate electron densities

    International Nuclear Information System (INIS)

    Neilson, D.; Thakur, J.S.

    1999-01-01

    We find in 2D electron layers in quantum transistors that the interplay between the electron correlations and their interactions with defects in the semiconductor substrate generates a continuous localisation-delocalisation transition for intermediate electron densities (5 ≤ r s≤ 9). We distinguish this transition from the discontinuous metal-insulator transition which is observed at lower electron densities (r s≥ 10). The approach we use is based on the behaviour of electrons at low densities. We take into account the interactions between electrons and also their interactions with disorder. We determine a zero temperature phase diagram of localised and delocalised states as a function of electron and impurity densities. The phase boundary of the continuous transition is determined by the localisation length of the electrons. Copyright (1999) CSIRO Australia

  12. Density of primes in l-th power residues

    Indian Academy of Sciences (India)

    Given a prime number , a finite set of integers S={a1,…,am} and many -th roots of unity ril,i=1,…,m we study the distribution of primes in Q(l) such that the -th residue symbol of ai with respect to is ril, for all . We find out that this is related to the degree of the extension Q(a1l1,…,a1lm)/Q. We give an algorithm ...

  13. 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

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

    Indian Academy of Sciences (India)

    using the Boltzmann plot method and the electron density is determined using the Saha–. Boltzmann equation method ... Laser-induced plasma; spectroscopy; plasma temperature; electron density. PACS Nos 52.50.Jm; 52.70. ... trace sample in any phase (solid, liquid and gas) with no or minimal sample prepa- ration [2–4].

  15. On the regularity of the density of electronic wavefunctions

    DEFF Research Database (Denmark)

    Fournais, S.; Hoffmann-Ostenhof, M.; Hoffmann-Ostenhof, T.

      We prove that the electronic density of atomic and molecular eigenfunctions is smooth away from the nuclei. The result is proved without decay assumptions on the eighenfunctions.......  We prove that the electronic density of atomic and molecular eigenfunctions is smooth away from the nuclei. The result is proved without decay assumptions on the eighenfunctions....

  16. The Influence of Residual Stand Densities on Regeneration in Sugar Maple Stands

    Science.gov (United States)

    Carl H. Tubbs

    1968-01-01

    Studies of regeneration 2, 5, and 10 years after cutting mature and overmature sugar maple stands to several residual densities show that (1) sugar maple is still the predominant species under all stand densities (2) nearly all regeneration reaching larger size classes became established before cutting (3) heavier cuttings (30, 50, and 70 square feet) are more rapidly...

  17. Clinical impact of electron density calibration on dose calculation

    International Nuclear Information System (INIS)

    Fisher, S. T.; Bromley, R.; Oliver, L.D.

    2011-01-01

    Full text: 3D calculation of dose for radiotherapy planning requires accurate density data in the form of Hounsfield Units (HU) obtained from CT scans. This investigation aims to establish the clinical impact that inaccuracies in the definition of the relationship between HU and electron density may have on the dose distribution for a range of treatment sites. HU versus electron density calibration relationships were derived from RMI 465, Catphan and CTRS phantoms scanned on a GE Lightspeed RT CT. Dose calculations were performed using Eclipse AAA 8.6.14. A range of patient case studies were assessed in terms of reference point doses, off axis dose points, dose subtraction plots and dose volume histograms. The RMI electron density calibration was regarded as the gold standard. All plans used identical field parameters, monitor units and optimal fluence maps derived from the RMI reference plan to enable direct dosimetric comparison. Plans calculated with the CIRS and RMI electron density calibrations were comparable. In contrast, the electron density calibration derived from Catphan produced dose differences in the order of 8% for head and neck, 6% for pelvis and 2% for a simple spine case. Incorrect electron density calibration data can result in significant dosimetric error and should be validated against a gold standard prior to implementation in a TPS.

  18. 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...

  19. 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.

  20. Contamination characteristics and degradation behavior of low-density polyethylene film residues in typical farmland soils of China.

    Science.gov (United States)

    Xu, Gang; Wang, Qunhui; Gu, Qingbao; Cao, Yunzhe; DU, Xiaoming; Li, Fasheng

    2006-01-01

    Low-density polyethylene (LDPE) film residues left in farmlands due to agricultural activities were extensively investigated to evaluate the present pollution situation by selecting the typical areas with LDPE film application, including Harbin, Baoding, and Handan of China. The survey results demonstrated that the film residues were ubiquitous within the investigated areas and the amount reached 2,400-8,200 g ha(-1). Breakage rates of the film residues were almost at the same level in the studied fields. There were relatively small amounts of film residues remaining in neighboring farmland fields without application of LDPE film. The studies showed that the sheets of LDPE residues had the same oxidative deterioration, which was probably due to photodegradation instead of biodegradation. The higher molecular weight components of the LDPE film gradually decreased, which were reflected by the appearance of some small flakes detached from the film bodies. LDPE films in the investigated fields gradually deteriorated and the decomposing levels developed with their left time increasing. The degradation behaviors of LDPE films were confirmed by using Fourier transform infrared (FTIR), scanning electron microscopic (SEM), and gel permeation chromatography analyses.

  1. 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...

  2. Regional 4-D modeling of the ionospheric electron density

    Science.gov (United States)

    Schmidt, M.; Bilitza, D.; Shum, C. K.; Zeilhofer, C.

    2008-08-01

    The knowledge of the electron density is the key point in correcting ionospheric delays of electromagnetic measurements and in studying the ionosphere. During the last decade GNSS, in particular GPS, has become a promising tool for monitoring the total electron content (TEC), i.e., the integral of the electron density along the ray-path between the transmitting satellite and the receiver. Hence, geometry-free GNSS measurements provide informations on the electron density, which is basically a four-dimensional function depending on spatial position and time. In addition, these GNSS measurements can be combined with other available data including nadir, over-ocean TEC observations from dual-frequency radar altimetry (T/P, JASON, ENVISAT), and TECs from GPS-LEO occultation systems (e.g., FORMOSAT-3/COSMIC, CHAMP) with heterogeneous sampling and accuracy. In this paper, we present different multi-dimensional approaches for modeling spatio-temporal variations of the ionospheric electron density. To be more specific, we split the target function into a reference part, computed from the International Reference Ionosphere (IRI), and an unknown correction term. Due to the localizing feature of B-spline functions we apply tensor-product spline expansions to model the correction term in a certain multi-dimensional region either completely or partly. Furthermore, the multi-resolution representation derived from wavelet analysis allows monitoring the ionosphere at different resolutions levels. For demonstration we apply three approaches to electron density data over South America.

  3. 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.

  4. 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.

  5. 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.

  6. Residual Deconvolutional Networks for Brain Electron Microscopy Image Segmentation.

    Science.gov (United States)

    Fakhry, Ahmed; Zeng, Tao; Ji, Shuiwang

    2017-02-01

    Accurate reconstruction of anatomical connections between neurons in the brain using electron microscopy (EM) images is considered to be the gold standard for circuit mapping. A key step in obtaining the reconstruction is the ability to automatically segment neurons with a precision close to human-level performance. Despite the recent technical advances in EM image segmentation, most of them rely on hand-crafted features to some extent that are specific to the data, limiting their ability to generalize. Here, we propose a simple yet powerful technique for EM image segmentation that is trained end-to-end and does not rely on prior knowledge of the data. Our proposed residual deconvolutional network consists of two information pathways that capture full-resolution features and contextual information, respectively. We showed that the proposed model is very effective in achieving the conflicting goals in dense output prediction; namely preserving full-resolution predictions and including sufficient contextual information. We applied our method to the ongoing open challenge of 3D neurite segmentation in EM images. Our method achieved one of the top results on this open challenge. We demonstrated the generality of our technique by evaluating it on the 2D neurite segmentation challenge dataset where consistently high performance was obtained. We thus expect our method to generalize well to other dense output prediction problems.

  7. Idempotent Dirac density matrix for ten-electron central field inhomogeneous electron liquids in terms of electron- and kinetic energy-densities

    International Nuclear Information System (INIS)

    March, N.H.

    2006-08-01

    A differential equation for the Dirac density matrix γ(r, r'), given ground-state electron- and kinetic energy-densities, has been derived by March and Suhai for one- and two-level occupancy. For ten-electron spin-compensated spherical systems, it is shown here that γ ≡ γ[ρ, t g ] where ρ and t g are electron- and kinetic energy-densities. The philosophy of March and Suhai is confirmed beyond two-level filling. An important byproduct of the present approach is an explicit expression for the one-body potential of DFT in terms of the p-shell electron density. (author)

  8. Identification and discrimination of herbicide residues using a conducting polymer electronic nose

    Science.gov (United States)

    Alphus Dan Wilson

    2016-01-01

    The identification of herbicide residues on crop foliage is necessary to make crop-management decisions for weed pest control and to monitor pesticide residue levels on food crops. Electronic-nose (e-nose) methods were tested as a cheaper, alternative means of discriminating between herbicide residue types (compared with conventional chromatography methods), by...

  9. Proton cooling in ultracold low-density electron gas

    Science.gov (United States)

    Bobrov, A. A.; Bronin, S. Y.; Manykin, E. A.; Zelener, B. B.; Zelener, B. V.; Khikhlukha, D. R.

    2015-11-01

    A sole proton energy loss processes in an electron gas and the dependence of these processes on temperature and magnetic field are studied using molecular dynamics techniques in present work. It appears that for electron temperatures less than 100 K many body collisions affect the proton energy loss and these collisions must be taken into account. The influence of a strong magnetic field on the relaxation processes is also considered in this work. Calculations were performed for electron densities 10 cm-3, magnetic field 1-3 Tesla, electron temperatures 10-50 K, initial proton energies 100-10000 K.

  10. Density functional theory and an experimentally-designed energy functional of electron density.

    Science.gov (United States)

    Miranda, David A; Bueno, Paulo R

    2016-09-21

    We herein demonstrate that capacitance spectroscopy (CS) experimentally allows access to the energy associated with the quantum mechanical ground state of many-electron systems. Priorly, electrochemical capacitance, C [small mu, Greek, macron] [ρ], was previously understood from conceptual and computational density functional theory (DFT) calculations. Thus, we herein propose a quantum mechanical experiment-based variational method for electron charging processes based on an experimentally-designed functional of the ground state electron density. In this methodology, the electron state density, ρ, and an energy functional of the electron density, E [small mu, Greek, macron] [ρ], can be obtained from CS data. CS allows the derivative of the electrochemical potential with respect to the electron density, (δ[small mu, Greek, macron][ρ]/δρ), to be obtained as a unique functional of the energetically minimised system, i.e., β/C [small mu, Greek, macron] [ρ], where β is a constant (associated with the size of the system) and C [small mu, Greek, macron] [ρ] is an experimentally observable quantity. Thus the ground state energy (at a given fixed external potential) can be obtained simply as E [small mu, Greek, macron] [ρ], from the experimental measurement of C [small mu, Greek, macron] [ρ]. An experimental data-set was interpreted to demonstrate the potential of this quantum mechanical experiment-based variational principle.

  11. Ionospheric electron density profile estimation using commercial AM broadcast signals

    Science.gov (United States)

    Yu, De; Ma, Hong; Cheng, Li; Li, Yang; Zhang, Yufeng; Chen, Wenjun

    2015-08-01

    A new method for estimating the bottom electron density profile by using commercial AM broadcast signals as non-cooperative signals is presented in this paper. Without requiring any dedicated transmitters, the required input data are the measured elevation angles of signals transmitted from the known locations of broadcast stations. The input data are inverted for the QPS model parameters depicting the electron density profile of the signal's reflection area by using a probabilistic inversion technique. This method has been validated on synthesized data and used with the real data provided by an HF direction-finding system situated near the city of Wuhan. The estimated parameters obtained by the proposed method have been compared with vertical ionosonde data and have been used to locate the Shijiazhuang broadcast station. The simulation and experimental results indicate that the proposed ionospheric sounding method is feasible for obtaining useful electron density profiles.

  12. Electron temperature and density relationships in coronal mass ejections

    Science.gov (United States)

    Hammond, C. M.; Phillips, J. L.; Balogh, A.

    1995-01-01

    We examine 10 coronal mass ejections from the in-ecliptic portion of the Ulysses mission. Five of these CMEs are magnetic clouds. In each case we observe an inverse relationship between electron temperature and density. For protons this relationship is less clear. Earlier work has shown a similar inverse relationship for electrons inside magnetic clouds and interpreted it to mean that the polytropic index governing the expansion of electrons is less than unity. This requires electrons to be heated as the CME expands. We offer an alternative view that the inverse relationship between electron temperature and density is caused by more rapid cooling of the denser plasma through collisions. More rapid cooling of denser plasma has been shown for 1 AU measurements in the solar wind. As evidence for this hypothesis we show that the denser plasma inside the CMEs tends to be more isotropic indicating a different history of collisions for the dense plasma. Thus, although the electron temperature inside CMEs consistently shows an inverse correlation with the density, this is not an indication of the polytropic index of the plasma but instead supports the idea of collisional modification of the electrons during their transit from the sun.

  13. Effects of relative density and accumulated shear strain on post-liquefaction residual deformation

    Directory of Open Access Journals (Sweden)

    J. Kim

    2013-10-01

    Full Text Available The damage caused by liquefaction, which occurs following an earthquake, is usually because of settlement and lateral spreading. Generally, the evaluation of liquefaction has been centered on settlement, that is, residual volumetric strain. However, in actual soil, residual shear and residual volumetric deformations occur simultaneously after an earthquake. Therefore, the simultaneous evaluation of the two phenomena and the clarification of their relationship are likely to evaluate post-liquefaction soil behaviors more accurately. Hence, a quantitative evaluation of post-liquefaction damage will also be possible. In this study, the effects of relative density and accumulated shear strain on post-liquefaction residual deformations were reviewed through a series of lateral constrained-control hollow cylindrical torsion tests under undrained conditions. In order to identify the relationship between residual shear and residual volumetric strains, this study proposed a new test method that integrates monotonic loading after cyclic loading, and K0-drain after cyclic loading – in other words, the combination of cyclic loading, monotonic loading, and the K0 drain. In addition, a control that maintained the lateral constrained condition across all the processes of consolidation, cyclic loading, monotonic loading, and drainage was used to reproduce the anisotropy of in situ ground. This lateral constrain control was performed by controlling the axial strain, based on the assumption that under undrained conditions, axial and lateral strains occur simultaneously, and unless axial strain occurs, lateral strain does not occur. The test results confirmed that the recovery of effective stresses, which occur during monotonic loading and drainage after cyclic loading, respectively, result from mutually different structural restoration characteristics. In addition, in the ranges of 40–60% relative density and 50–100% accumulated shear strain, relative

  14. 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.

  15. Intramolecular cyclization of aspartic acid residues assisted by three water molecules: a density functional theory study

    Science.gov (United States)

    Takahashi, Ohgi; Kirikoshi, Ryota

    2014-01-01

    Aspartic acid (Asp) residues in peptides and proteins (l-Asp) are known to undergo spontaneous nonenzymatic reactions to form l-β-Asp, d-Asp, and d-β-Asp residues. The formation of these abnormal Asp residues in proteins may affect their three-dimensional structures and hence their properties and functions. Indeed, the reactions have been thought to contribute to aging and pathologies. Most of the above reactions of the l-Asp residues proceed via a cyclic succinimide intermediate. In this paper, a novel three-water-assisted mechanism is proposed for cyclization of an Asp residue (forming a gem-diol precursor of the succinimide) by the B3LYP/6-31 + G(d,p) density functional theory calculations carried out for an Asp-containing model compound (Ace-Asp-Nme, where Ace = acetyl and Nme = NHCH3). The three water molecules act as catalysts by mediating ‘long-range’ proton transfers. In the proposed mechanism, the amide group on the C-terminal side of the Asp residue is first converted to the tautomeric iminol form (iminolization). Then, reorientation of a water molecule and a conformational change occur successively, followed by the nucleophilic attack of the iminol nitrogen on the carboxyl carbon of the Asp side chain to form the gem-diol species. A satisfactory agreement was obtained between the calculated and experimental energetics.

  16. Evaporation of carbon using electrons of a high density plasma

    International Nuclear Information System (INIS)

    Muhl, S.; Camps, E.; Escobar A, L.; Garcia E, J.L.; Olea, O.

    1999-01-01

    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)

  17. Electron density measurements during ion beam transport on Gamble II

    International Nuclear Information System (INIS)

    Weber, B.V.; Hinshelwood, D.D.; Neri, J.M.; Ottinger, P.F.; Rose, D.V.; Stephanakis, S.J.; Young, F.C.

    1999-01-01

    High-sensitivity laser interferometry was used to measure the electron density created when an intense proton beam (100 kA, 1 MeV, 50 ns) from the Gamble II generator was transported through low-pressure gas as part of a project investigating Self-Pinched Transport (SPT) of intense ion beams. This measurement is non-perturbing and sufficiently quantitative to allow benchmarking of codes (particularly IPROP) used to model beam-gas interaction and ion-beam transport. Very high phase sensitivity is required for this measurement. For example, a 100-kA, 1-MeV, 10-cm-radius proton beam with uniform current density has a line-integrated proton density equal to n b L = 3 x 10 13 cm -2 . An equal electron line-density, n e L = n b L, (expected for transport in vacuum) will be detected as a phase shift of the 1.064 microm laser beam of only 0.05degree, or an optical path change of 1.4 x 10 -4 waves (about the size of a hydrogen atom). The time-history of the line-integrated electron density, measured across a diameter of the transport chamber at 43 cm from the input aperture, starts with the proton arrival time and decays differently depending on the gas pressure. The gas conditions included vacuum (10 -4 Torr air), 30 to 220 mTorr He, and 1 Torr air. The measured densities vary by three orders of magnitude, from 10 13 to 10 16 cm -2 for the range of gas pressures investigated. In vacuum, the measured electron densities indicate only co-moving electrons (n e L approximately n b L). In He, when the gas pressure is sufficient for ionization by beam particles and SPT is observed, n e L increases to about 10 n b L. At even higher pressures where electrons contribute to ionization, even higher electron densities are observed with an ionization fraction of about 2%. The diagnostic technique as used on the SPT experiment will be described and a summary of the results will be given. The measurements are in reasonable agreement with theoretical predictions from the IPROP code

  18. Electron and current density measurements on tokamak plasmas

    International Nuclear Information System (INIS)

    Lammeren, A.C.A.P. van.

    1991-01-01

    The first part of this thesis describes the Thomson-scattering diagnostic as it was present at the TORTUR tokamak. For the first time with this diagnostic a complete tangential scattering spectrum was recorded during one single laser pulse. From this scattering spectrum the local current density was derived. Small deviations from the expected gaussian scattering spectrum were observed indicating the non-Maxwellian character of the electron-velocity distribution. The second part of this thesis describes the multi-channel interferometer/ polarimeter diagnostic which was constructed, build and operated on the Rijnhuizen Tokamak Project (RTP) tokamak. The diagnostic was operated routinely, yielding the development of the density profiles for every discharge. When ECRH (Electron Cyclotron Resonance Heating) is switched on the density profile broadens, the central density decreases and the total density increases, the opposite takes place when ECRH is switched off. The influence of MHD (magnetohydrodynamics) activity on the density was clearly observable. In the central region of the plasma it was measured that in hydrogen discharges the so-called sawtooth collapse is preceded by an m=1 instability which grows rapidly. An increase in radius of this m=1 mode of 1.5 cm just before the crash is observed. In hydrogen discharges the sawtooth induced density pulse shows an asymmetry for the high- and low-field side propagation. This asymmetry disappeared for helium discharges. From the location of the maximum density variations during an m=2 mode the position of the q=2 surface is derived. The density profiles are measured during the energy quench phase of a plasma disruption. A fast flattening and broadening of the density profile is observed. (author). 95 refs.; 66 figs.; 7 tabs

  19. 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 ... The lanthanide oxides find remarkable applications in the field of medicine, biology, nuclear engineering and space technology.

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

    Indian Academy of Sciences (India)

    Unknown

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

  1. Measurements of plasma temperature and electron density in laser

    Indian Academy of Sciences (India)

    The temperature and electron density characterizing the plasma are measured by time-resolved spectroscopy of neutral atom and ion line emissions in the time window of 300–2000 ns. An echelle spectrograph coupled with a gated intensified charge coupled detector is used to record the plasma emissions.

  2. Behavior of the bottomside electron density profile over Pruhonice

    Czech Academy of Sciences Publication Activity Database

    Mosert, M.; Burešová, Dalia; Ezquer, R.; Mansilla, G.

    2004-01-01

    Roč. 34, č. 9 (2004), s. 1982-1989 ISSN 0273-1177 R&D Projects: GA AV ČR IAA3042102 Institutional research plan: CEZ:AV0Z3042911 Keywords : Electron density profiles * Variability Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.548, year: 2004

  3. 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 ...

  4. Reactivity descriptors and electron density analysis for ligand ...

    Indian Academy of Sciences (India)

    We discuss evaluation of local descriptors using relaxed as well as frozen approximation and characterize the / acceptance/donor characteristics of the above ligands. The intermolecular reactivity sequence for the same systems is examined by the global and local philicity index. In addition, electron density analysis has ...

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

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 74; Issue 6. Measurements of plasma temperature and electron density in laser-induced copper plasma by time-resolved spectroscopy of neutral atom and ion emissions. V K Unnikrishnan Kamlesh Alti V B Kartha C Santhosh G P Gupta B M Suri. Research Articles ...

  6. 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.

  7. Relations among several nuclear and electronic density functional reactivity indexes

    Science.gov (United States)

    Torrent-Sucarrat, Miquel; Luis, Josep M.; Duran, Miquel; Toro-Labbé, Alejandro; Solà, Miquel

    2003-11-01

    An expansion of the energy functional in terms of the total number of electrons and the normal coordinates within the canonical ensemble is presented. A comparison of this expansion with the expansion of the energy in terms of the total number of electrons and the external potential leads to new relations among common density functional reactivity descriptors. The formulas obtained provide explicit links between important quantities related to the chemical reactivity of a system. In particular, the relation between the nuclear and the electronic Fukui functions is recovered. The connection between the derivatives of the electronic energy and the nuclear repulsion energy with respect to the external potential offers a proof for the "Quantum Chemical le Chatelier Principle." Finally, the nuclear linear response function is defined and the relation of this function with the electronic linear response function is given.

  8. Analysis of Total Electron Content and Electron Density Profile during Different Geomagnetic Storms

    Science.gov (United States)

    Chapagain, N. P.; Rana, B.; Adhikari, B.

    2017-12-01

    Total Electron content (TEC) and electron density are the key parameters in the mitigation of ionospheric effects on radio communication system. Detail study of the TEC and electron density variations has been carried out during geomagnetic storms, with longitude and latitude, for four different locations: (13˚N -17˚N, 88˚E -98˚E), (30˚N-50˚N, 120˚W -95˚W), (29˚S-26˚S, 167˚W-163˚W,) and (60˚S-45˚S, 120˚W-105˚W) using the Gravity Recovery and Climate Experiment (GRACE) satellite observations. In order to find the geomagnetic activity, the solar wind parameters such as north-south component of inter planetary magnetic field (Bz), plasma drift velocity (Vsw), flow pressure (nPa), AE, Dst and Kp indices were obtained from Operating Mission as Nodes on the Internet (OMNI) web system. The data for geomagnetic indices have been correlated with the TEC and electron density for four different events of geomagnetic storms on 6 April 2008, 27 March 2008, 4 September 2008, and 11 October 2008. The result illustrates that the observed TEC and electron density profile significantly vary with longitudes and latitudes. This study illustrates that the values of TEC and the vertical electron density profile are influenced by the solar wind parameters associated with solar activities. The peak values of electron density and TEC increase as the geomagnetic storms become stronger. Similarly, the electron density profile varies with altitudes, which peaks around the altitude range of about 250- 350 km, depending on the strength of geomagnetic storms. The results clearly show that the peak electron density shifted to higher altitude (from about 250 km to 350 km) as the geomagnetic disturbances becomes stronger.

  9. Sorting carbon nanotubes by electronic structure using density differentiation.

    Science.gov (United States)

    Arnold, Michael S; Green, Alexander A; Hulvat, James F; Stupp, Samuel I; Hersam, Mark C

    2006-10-01

    The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) precludes their widespread application in electronics, optics and sensing. We report on the sorting of carbon nanotubes by diameter, bandgap and electronic type using structure-discriminating surfactants to engineer subtle differences in their buoyant densities. Using the scalable technique of density-gradient ultracentrifugation, we have isolated narrow distributions of SWNTs in which >97% are within a 0.02-nm-diameter range. Furthermore, using competing mixtures of surfactants, we have produced bulk quantities of SWNTs of predominantly a single electronic type. These materials were used to fabricate thin-film electrical devices of networked SWNTs characterized by either metallic or semiconducting behaviour.

  10. Identification of Critical Paraoxonase 1 Residues Involved in High Density Lipoprotein Interaction*

    Science.gov (United States)

    Gu, Xiaodong; Huang, Ying; Levison, Bruce S.; Gerstenecker, Gary; DiDonato, Anthony J.; Hazen, Leah B.; Lee, Joonsue; Gogonea, Valentin; DiDonato, Joseph A.; Hazen, Stanley L.

    2016-01-01

    Paraoxonase 1 (PON1) is a high density lipoprotein (HDL)-associated protein with atherosclerosis-protective and systemic anti-oxidant functions. We recently showed that PON1, myeloperoxidase, and HDL bind to one another in vivo forming a functional ternary complex (Huang, Y., Wu, Z., Riwanto, M., Gao, S., Levison, B. S., Gu, X., Fu, X., Wagner, M. A., Besler, C., Gerstenecker, G., Zhang, R., Li, X. M., Didonato, A. J., Gogonea, V., Tang, W. H., et al. (2013) J. Clin. Invest. 123, 3815–3828). However, specific residues on PON1 involved in the HDL-PON1 interaction remain unclear. Unambiguous identification of protein residues involved in docking interactions to lipid surfaces poses considerable methodological challenges. Here we describe a new strategy that uses a novel synthetic photoactivatable and click chemistry-taggable phospholipid probe, which, when incorporated into HDL, was used to identify amino acid residues on PON1 that directly interact with the lipoprotein phospholipid surface. Several specific PON1 residues (Leu-9, Tyr-185, and Tyr-293) were identified through covalent cross-links with the lipid probes using affinity isolation coupled to liquid chromatography with on-line tandem mass spectrometry. Based upon the crystal structure for PON1, the identified residues are all localized in relatively close proximity on the surface of PON1, defining a domain that binds to the HDL lipid surface. Site-specific mutagenesis of the identified PON1 residues (Leu-9, Tyr-185, and Tyr-293), coupled with functional studies, reveals their importance in PON1 binding to HDL and both PON1 catalytic activity and stability. Specifically, the residues identified on PON1 provide important structural insights into the PON1-HDL interaction. More generally, the new photoactivatable and affinity-tagged lipid probe developed herein should prove to be a valuable tool for identifying contact sites supporting protein interactions with lipid interfaces such as found on cell membranes

  11. Comparison of Satellite based Ion Density Measurements with Digisonde electron density measurements

    Science.gov (United States)

    Wilson, G.; Balthazor, R. L.; Reinisch, B. W.; McHarg, M.; Maldonado, C.

    2017-12-01

    The integrated Miniaturized Electrostatic Analyzer (IMESA) flying on the STPSat-3 satellite has collected more than 3 years of ion density data. This instrument is the first in a constellation of up to 6 instruments. We plan on integrating the data from all IMESAs into an approiate ionospheric model. OUr first step is to validate the IMESA data and calibrate the instrument. In this presentation we discuss our process for preparing IMESA data and comparing it to ground based measurements. Lastly, we present a number of comparisons between IMESA ion density measurements and digisonde electron density measurements.

  12. 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

  13. 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..

  14. Dry cleaning of fluorocarbon residues by low-power electron cyclotron resonance hydrogen plasma

    CERN Document Server

    Lim, S H; Yuh, H K; Yoon Eui Joon; Lee, S I

    1988-01-01

    A low-power ( 50 W) electron cyclotron resonance hydrogen plasma cleaning process was demonstrated for the removal of fluorocarbon residue layers formed by reactive ion etching of silicon dioxide. The absence of residue layers was confirmed by in-situ reflection high energy electron diffraction and cross-sectional high resolution transmission electron microscopy. The ECR hydrogen plasma cleaning was applied to contact cleaning of a contact string structure, resulting in comparable contact resistance arising during by a conventional contact cleaning procedure. Ion-assisted chemical reaction involving reactive atomic hydrogen species generated in the plasma is attributed for the removal of fluorocarbon residue layers.

  15. Electron charge densities at conduction-band edges of semiconductors

    International Nuclear Information System (INIS)

    Richardson, S.L.; Cohen, M.L.; Louie, S.G.; Chelikowsky, J.R.

    1986-01-01

    We demonstrate that both the empirical pseudopotential method (EPM) and the linear combination of atomiclike orbitals (LCAO) approach are capable of producing consistent electronic charge distributions in a compound semiconductor. Since the EPM approach is known to produce total valence electron charge densities which compare well with experimental x-ray data (e.g., Si), this work serves as a further test for the LCAO method. In particular, the EPM scheme, which uses an extended plane-wave basis, and the LCAO scheme, which employs a localized Gaussian basis, are used, with the same empirical potential as input, to analyze both the total valence electron charge density and the charge density of the first conduction band at the GAMMA, L, and X k points of the Brillouin zone. These charge densities are decomposed into their s-, p-, and d-orbital contributions, and this information is used to interpret the differences in the topologies of the conduction bands at GAMMA, L, and X. Such differences are crucial for a comprehensive understanding of interstitial impurities and the response of specific band states to perturbations in compound semiconductors

  16. Effect of Solder Flux Residues on Corrosion of Electronics

    DEFF Research Database (Denmark)

    Hansen, Kirsten Stentoft; Jellesen, Morten Stendahl; Møller, Per

    2009-01-01

    that no cleaning after the solder process is required. In some cases, however, this statement is not correct. Experiments with ‘No Clean’ wave solder flux have been performed, and the results show, that the solder temperature plays an important role; temperatures below 170°C cause more flux residues than solder......Flux from ‘No Clean’ solder processes can cause reliability problems in the field due to aggressive residues, which may be electrical conducting or corrosive in humid environments. The solder temperature during a wave solder process is of great importance to the amount of residues left on a PCBA...... of dust, which can act as a humidity absorber. The experiments have been made on SnPb wave solder flux, later experiments will show if the problems are less for Lead-free reflow and wave soldering, because the solder temperature is about 20°C higher. Furthermore an example of failure after humidity...

  17. 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.

  18. Electron correlation effects in third-order densities.

    Science.gov (United States)

    Rodriguez-Mayorga, Mauricio; Ramos-Cordoba, Eloy; Feixas, Ferran; Matito, Eduard

    2017-02-08

    The electronic energy of a system of fermions can be obtained from the second-order reduced density matrix through the contracted Schrödinger equation or its anti-Hermitian counterpart. Both energy expressions depend on the third-order reduced density matrix (3-RDM) which is usually approximated from lower-order densities. The accuracy of these methods depends critically on the set of N-representability conditions enforced in the calculation and the quality of the approximate 3-RDM. There are no benchmark studies including most 3-RDM approximations and, thus far, no assessment of the deterioration of the approximations with correlation effects has been performed. In this paper we introduce a series of tests to assess the performance of 3-RDM approximations in a model system with varying electron correlation effects, the three-electron harmonium atom. The results of this work put forward several limitations of the currently most used 3-RDM approximations for systems with important electron correlation effects.

  19. Electron density interferometry measurement in laser-matter interaction

    International Nuclear Information System (INIS)

    Popovics-Chenais, C.

    1981-05-01

    This work is concerned with the laser-interferometry measurement of the electronic density in the corona and the conduction zone external part. Particularly, it is aimed at showing up density gradients and at their space-time localization. The first chapter recalls the density profile influence on the absorption principal mechanisms and the laser energy transport. In chapter two, the numerical and analytical hydrodynamic models describing the density profile are analysed. The influence on the density profile of the ponderomotive force associated to high oscillating electric fields is studied, together with the limited thermal conduction and suprathermal electron population. The mechanism action, in our measurement conditions, is numerically simulated. Calculations are made with experimental parameters. The measurement interaction conditions, together with the diagnostic method by high resolution laser interferometry are detailed. The results are analysed with the help of numerical simulation which is the experiment modeling. An overview of the mechanisms shown up by interferometric measurements and their correlation with other diagnostics is the conclusion of this work [fr

  20. Density effects on electronic configurations in dense plasmas

    Science.gov (United States)

    Faussurier, Gérald; Blancard, Christophe

    2018-02-01

    We present a quantum mechanical model to describe the density effects on electronic configurations inside a plasma environment. Two different approaches are given by starting from a quantum average-atom model. Illustrations are shown for an aluminum plasma in local thermodynamic equilibrium at solid density and at a temperature of 100 eV and in the thermodynamic conditions of a recent experiment designed to characterize the effects of the ionization potential depression treatment. Our approach compares well with experiment and is consistent in that case with the approach of Stewart and Pyatt to describe the ionization potential depression rather than with the method of Ecker and Kröll.

  1. Reduction of heavy metals in residues from the dismantling of waste electrical and electronic equipment before incineration.

    Science.gov (United States)

    Long, Yu-Yang; Feng, Yi-Jian; Cai, Si-Shi; Hu, Li-Fang; Shen, Dong-Sheng

    2014-05-15

    Residues disposal from the dismantling of waste electrical and electronic equipment are challenging because of the large waste volumes, degradation-resistance, low density and high heavy metal content. Incineration is advantageous for treating these residues but high heavy metal contents may exist in incinerator input and output streams. We have developed and studied a specialized heavy metal reduction process, which includes sieving and washing for treating residues before incineration. The preferable screen aperture for sieving was found to be 2.36mm (8 meshes) in this study; using this screen aperture resulted in the removal of approximately 47.2% Cu, 65.9% Zn, 26.5% Pb, 55.4% Ni and 58.8% Cd from the residues. Subsequent washing further reduces the heavy metal content in the residues larger than 2.36mm, with preferable conditions being 400rpm rotation speed, 5min washing duration and liquid-to-solid ratio of 25:1. The highest cumulative removal efficiencies of Cu, Zn, Pb, Ni and Cd after sieving and washing reached 81.1%, 61.4%, 75.8%, 97.2% and 72.7%, respectively. The combined sieving and washing process is environmentally friendly, can be used for the removal of heavy metals from the residues and has benefits in terms of heavy metal recycling. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Identification of insecticide residues with a conducting-polymer electronic nose

    Science.gov (United States)

    A.D. Wilson

    2014-01-01

    The identification of insecticide residues on crop foliage is needed to make periodic pest management decisions. Electronic-nose (e-nose) methods were developed and tested as a means of acquiring rapid identifications of insecticide residue types at relatively low cost by detection of headspace volatiles released from inert surfaces in vitro. Detection methods were...

  3. Fungicide residue identification and discrimination using a conducting polymer electronic-nose

    Science.gov (United States)

    Alphus D. Wilson

    2013-01-01

    The identification of fungicide residues on crop foliage is necessary to make periodic pest management decisions. The determination of fungicide residue identities currently is difficult and time consuming using conventional chemical analysis methods such as gas chromatography-mass spectroscopy. Different fungicide types produce unique electronic aroma signature...

  4. An electron density measurement using an analyzer based imaging system

    International Nuclear Information System (INIS)

    Bewer, Brian

    2011-01-01

    Using a monochromatic X-ray beam from a synchrotron source the electron density of a homogeneous target was determined by measuring the refraction that occurs at the air-target interface for a known angle of incidence. The angle of deviation that these X-rays undergo at the transition between materials is micro-radian to submicro-radian in scale. Existing analyzer based imaging systems are designed to measure submicro-radian angle changes and commonly use monochromatic hard X-ray beams generated from synchrotron sources. A preliminary experiment using the analyzer based imaging apparatus at the Canadian Light Source Biomedical Imaging and Therapy beamline and a half cylinder shaped plastic target will be presented. By measuring the angle of deviation of the photon beam at several discrete angular positions of the target the electron density of the target material was determined.

  5. New Data on the Topside Electron Density Distribution

    Science.gov (United States)

    Huang, Xue-Qin; Reinisch, Bodo; Bilitza, Dieter; Benson, Robert F.

    2001-01-01

    The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from hmF2 to approx. 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms and most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350,000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis-status.html. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2) down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The automatic topside ionogram scaler with true height algorithm TOPIST software developed for this task is successfully scaling approx.70 % of the ionograms. An 'editing process' is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle. The ISIS data restoration efforts are supported through NASA's Applied Systems and Information Research Program.

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

    Indian Academy of Sciences (India)

    In the present work, the effective atomic num- bers and electron densities have been computed for 14 oxides of lanthanides which are shown in table 1 in the energy region of 0.001 MeV to 105 MeV using mass attenuation coefficient values from WinXCom. The kerma relative to air has also been computed and reported in ...

  7. Stopping power of degenerate electron liquid at metallic densities

    International Nuclear Information System (INIS)

    Tanaka, Shigenori; Ichimaru, Setsuo

    1985-01-01

    We calculate the stopping power of the degenerate electron liquid at metallic densities in the dielectric formalism. The strong Coulomb-coupling effects beyond the random-phase approximation are taken into account through the static and dynamic local-field corrections. It is shown that those strong-coupling and dynamic effects act to enhance the stopping power substantially in the low-velocity regime, leading to an improved agreement with experimental data. (author)

  8. The electronic density of states of disordered compounds

    International Nuclear Information System (INIS)

    Geertsma, W.; Dijkstra, J.

    1984-11-01

    Recently, the electronic properties of liquid alkali (Li, Na, K, Rb, Cs)-group IV (Si, Ge, Sn, Pb) alloys have been discussed by the present authors using a tight-binding model. Only anion orbitals (= group IV) are taken into account. Disorder is described by a pseudo lattice, which takes into account local coordination in one of the sublattices (cation or anion) only. In the first part of this paper it is shown that this approximation is consistent with the usual valence rules used by structural chemists for crystalline structures. In the second part of the paper the solutions for the density of states of the tight-binding Hamiltonian are studied for a number of pseudolattices. The infinite set of Green function equations is solved by using the effective transfer method, which replaces the famous Block condition. It is shown that such a model can explain the formation of bandgaps in disordered systems. By choosing the proper smallest cluster(s) of transfer loops to model the real structure by a pseudolattice, a density of states is obtained which represents properly that of the corresponding crystalline structure. Structures reminiscent to those caused by van Hove singularities already appear in the electronic density of states when relatively small cluster(s) of transfer loops are used. The approach outlined in this paper is capable of describing the electronic density of states due to various degrees of local order in a sublattice. Some of the peculiarities occurring in the solution of the density of states of certain pseudolattices, such as poles outside the band, are discussed in an appendix. (author)

  9. 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...... in the well tested SIESTA approach (which uses nonlocal norm-conserving pseudopotentials to describe the effect of the core electrons, and linear combination of finite-range numerical atomic orbitals to describe the valence states). We fully deal with the atomistic structure of the whole system, treating both...... 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...

  10. Equations of electron hydrodynamics in low-density pinches

    International Nuclear Information System (INIS)

    Bobrova, N.A.; Sasarov, P.V.

    1990-01-01

    The equations of electron hydrodynamics that describe axisymmetric configurations with a purely toroidal magnetic field in the case when ρ He /α ei /α He , where ρ He is the gyroradius of the electrons and α is the inverse density gradient, are derived. These equations generalize the electron part of the well-known Braginskii system of equations and contain additional dissipative terms, proportional to v ei -1 , which for l ei > α are ∼(l ei /α) 2 times greater than the well-known dissipative effects. The derived system of equations can be employed to describe the later stages of the development of sausages in not very dense z-pinches and to describe the phenomena occurring in plasma switches

  11. Identification of Critical Paraoxonase 1 Residues Involved in High Density Lipoprotein Interaction.

    Science.gov (United States)

    Gu, Xiaodong; Huang, Ying; Levison, Bruce S; Gerstenecker, Gary; DiDonato, Anthony J; Hazen, Leah B; Lee, Joonsue; Gogonea, Valentin; DiDonato, Joseph A; Hazen, Stanley L

    2016-01-22

    Paraoxonase 1 (PON1) is a high density lipoprotein (HDL)-associated protein with atherosclerosis-protective and systemic anti-oxidant functions. We recently showed that PON1, myeloperoxidase, and HDL bind to one another in vivo forming a functional ternary complex (Huang, Y., Wu, Z., Riwanto, M., Gao, S., Levison, B. S., Gu, X., Fu, X., Wagner, M. A., Besler, C., Gerstenecker, G., Zhang, R., Li, X. M., Didonato, A. J., Gogonea, V., Tang, W. H., et al. (2013) J. Clin. Invest. 123, 3815-3828). However, specific residues on PON1 involved in the HDL-PON1 interaction remain unclear. Unambiguous identification of protein residues involved in docking interactions to lipid surfaces poses considerable methodological challenges. Here we describe a new strategy that uses a novel synthetic photoactivatable and click chemistry-taggable phospholipid probe, which, when incorporated into HDL, was used to identify amino acid residues on PON1 that directly interact with the lipoprotein phospholipid surface. Several specific PON1 residues (Leu-9, Tyr-185, and Tyr-293) were identified through covalent cross-links with the lipid probes using affinity isolation coupled to liquid chromatography with on-line tandem mass spectrometry. Based upon the crystal structure for PON1, the identified residues are all localized in relatively close proximity on the surface of PON1, defining a domain that binds to the HDL lipid surface. Site-specific mutagenesis of the identified PON1 residues (Leu-9, Tyr-185, and Tyr-293), coupled with functional studies, reveals their importance in PON1 binding to HDL and both PON1 catalytic activity and stability. Specifically, the residues identified on PON1 provide important structural insights into the PON1-HDL interaction. More generally, the new photoactivatable and affinity-tagged lipid probe developed herein should prove to be a valuable tool for identifying contact sites supporting protein interactions with lipid interfaces such as found on cell membranes

  12. Measuring charge density of electron beam single nanosecond pulses

    International Nuclear Information System (INIS)

    Gonchar, A.I.; Nesterenko, V.S.; Fazkullin, V.A.

    1982-01-01

    A description is presented of a probe design and electrometric repeater circuit and technique for measuring the charge (current) density of electron beam single pulses by integrating current at a reference capacitor with a subsequent registering of voltage across the capacitor. The probe consists of a band-type signal electrodes and two oval cross-section sleeves: external and internal with larger and smaller rectangular openings, respectively. The external sleeve has antidynatron grid located over the hole. The design employs integer nickel sleever - the cores of electron tube cathodes. The signal electrode is made of nickel band 0.15 mm thick. The probe elements are insulated from each other along the whole length with a layer of teflon band (30 μm), with rectangular openings cut in compliance with the sleeve openings. The measurement range is from 0.4x10 - 9 to 1x10 - 7 C/cm 2 . The rated accuracy of measurements is no worse than +-5% for the beam energy of 0.2 to 3 KeV. The ultimate parameters the charge density - 6 C/cm 2 and direct current density 3 mA/cm 2 - are specified by the breakdown voltage (200 V) of the input capacitor and probe insulation

  13. A new software routine that automates the fitting of protein X-ray crystallographic electron-density maps.

    Science.gov (United States)

    Levitt, D G

    2001-07-01

    The classical approach to building the amino-acid residues into the initial electron-density map requires days to weeks of a skilled investigator's time. Automating this procedure should not only save time, but has the potential to provide a more accurate starting model for input to refinement programs. The new software routine MAID builds the protein structure into the electron-density map in a series of sequential steps. The first step is the fitting of the secondary alpha-helix and beta-sheet structures. These 'fits' are then used to determine the local amino-acid sequence assignment. These assigned fits are then extended through the loop regions and fused with the neighboring sheet or helix. The program was tested on the unaveraged 2.5 A selenomethionine multiple-wavelength anomalous dispersion (SMAD) electron-density map that was originally used to solve the structure of the 291-residue protein human heart short-chain L-3-hydroxyacyl-CoA dehydrogenase (SHAD). Inputting just the map density and the amino-acid sequence, MAID fitted 80% of the residues with an r.m.s.d. error of 0.43 A for the main-chain atoms and 1.0 A for all atoms without any user intervention. When tested on a higher quality 1.9 A SMAD map, MAID correctly fitted 100% (418) of the residues. A major advantage of the MAID fitting procedure is that it maintains ideal bond lengths and angles and constrains phi/psi angles to the appropriate Ramachandran regions. Recycling the output of this new routine through a partial structure-refinement program may have the potential to completely automate the fitting of electron-density maps.

  14. Current density monitor for intense relativistic electron beams

    International Nuclear Information System (INIS)

    Fiorito, R.B.; Raleigh, M.; Seltzer, S.M.

    1986-01-01

    We describe a new type of electric probe which is capable of measuring the time-resolved current density profile of a stable, reproducible, high-energy (>4-MeV) high-current (>1-kA) electron beam. The sensing element of this probe is an open-ended but capped-off 50-Ω coaxial line constructed of graphite. The graphite sensor is 4.3 mm in diameter, 6 cm long, and is range thin to the primary beam electrons. The probe produces a signal proportional to the intercepted beam current. When the sensor is scanned radially through the beam during repeated pulses, a curve of signal versus depth of insertion is produced from which the radial current density profile can be determined. Measurements are presented of the profile of the electron beam from the Experimental Test Accelerator (4.5 MeV, 10 kA) at Lawrence Livermore National Laboratory. Good agreement is shown between measurements made with this probe and the beam radius as predicted by transport codes. The advantage of the electric probe lies in its ruggedness, simplicity, inherent fast rise time, and low cost. In contrast to other systems it requires no radiation shielding, water cooling, or auxiliary support equipment to operate in an intense beam environment

  15. Automated Processing of ISIS Topside Ionograms into Electron Density Profiles

    Science.gov (United States)

    Reinisch, bodo W.; Huang, Xueqin; Bilitza, Dieter; Hills, H. Kent

    2004-01-01

    Modeling of the topside ionosphere has for the most part relied on just a few years of data from topside sounder satellites. The widely used Bent et al. (1972) model, for example, is based on only 50,000 Alouette 1 profiles. The International Reference Ionosphere (IRI) (Bilitza, 1990, 2001) uses an analytical description of the graphs and tables provided by Bent et al. (1972). The Alouette 1, 2 and ISIS 1, 2 topside sounder satellites of the sixties and seventies were ahead of their times in terms of the sheer volume of data obtained and in terms of the computer and software requirements for data analysis. As a result, only a small percentage of the collected topside ionograms was converted into electron density profiles. Recently, a NASA-funded data restoration project has undertaken and is continuing the process of digitizing the Alouette/ISIS ionograms from the analog 7-track tapes. Our project involves the automated processing of these digital ionograms into electron density profiles. The project accomplished a set of important goals that will have a major impact on understanding and modeling of the topside ionosphere: (1) The TOPside Ionogram Scaling and True height inversion (TOPIST) software was developed for the automated scaling and inversion of topside ionograms. (2) The TOPIST software was applied to the over 300,000 ISIS-2 topside ionograms that had been digitized in the fkamework of a separate AISRP project (PI: R.F. Benson). (3) The new TOPIST-produced database of global electron density profiles for the topside ionosphere were made publicly available through NASA s National Space Science Data Center (NSSDC) ftp archive at . (4) Earlier Alouette 1,2 and ISIS 1, 2 data sets of electron density profiles from manual scaling of selected sets of ionograms were converted fiom a highly-compressed binary format into a user-friendly ASCII format and made publicly available through nssdcftp.gsfc.nasa.gov. The new database for the topside ionosphere established

  16. Experimental electron density in crystalline H3PO4.

    Science.gov (United States)

    Souhassou, M; Espinosa, E; Lecomte, C; Blessing, R H

    1995-10-01

    X-ray diffraction data for H3PO4 crystals have been measured to dmin = 0.46 A resolution, and used to model the electron-density distribution with the hydrogen structure of the crystals adopted from an earlier neutron diffraction analysis. The molecule is asymmetric in the crystal with site symmetry 1 (C1), but the local symmetries of the pseudoatomic densities are, within experimental error, equivalent as they would be under idealized 3m (C3v) molecular symmetry. Although the experimental analysis entailed substantial problems with absorption and extinction corrections, the static deformation density from the experiment agrees very well with that from a polarized split-valence molecular orbital wavefunction for an isolated molecule with the crystallographic molecular geometry. Hydrogen bonding in the crystal polarizes the molecule's P==O acceptor group towards P(+)--O-, and appears to relocalize the lone-pair density of the P--OH donor groups. Crystal data: anhydrous orthophosphoric acid, H3PO4, M(r) = 98.00, room temperature, P2(1)/c, a = 5.7572 (13), b = 4.8310 (17), c = 11.5743 (21) A, beta = 95.274 (12) degrees, V = 320.55 (25) A3, Z = 4, dx = 2.030 mg mm-3, mu = 0.660 mm-1 for lambda(Mo K alpha) = 0.7107 A, F(000) = 200 e-, R(parallel F) = 0.026 for 3512 unique reflections.

  17. Communication: Investigation of the electron momentum density distribution of nanodiamonds by electron energy-loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhenbao; Yang, Bing; Lin, Yangming; Su, Dangsheng, E-mail: dssu@imr.ac.cn [Shenyang National Laboratory of Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Wenhua Road 72, Shenyang 110016 (China)

    2015-12-07

    The electron momentum distribution of detonation nanodiamonds (DND) was investigated by recording electron energy-loss spectra at large momentum transfer in the transmission electron microscope (TEM), which is known as electron Compton scattering from solid (ECOSS). Compton profile of diamond film obtained by ECOSS was found in good agreement with prior photon experimental measurement and theoretical calculation that for bulk diamond. Compared to the diamond film, the valence Compton profile of DND was found to be narrower, which indicates a more delocalization of the ground-state charge density for the latter. Combining with other TEM characterizations such as high-resolution transmission electron spectroscopy, diffraction, and energy dispersive X-ray spectroscopy measurements, ECOSS was shown to be a great potential technique to study ground-state electronic properties of nanomaterials.

  18. Pre-storm electron density enhancements at middle latitudes

    Czech Academy of Sciences Publication Activity Database

    Burešová, Dalia; Laštovička, Jan

    2008-01-01

    Roč. 70, č. 15 (2008), s. 1848-1855 ISSN 1364-6826 R&D Projects: GA MŠk OC 091; GA MŠk 1P05OC030; GA AV ČR 1QS300120506; GA ČR GA205/08/1356 Grant - others:European Union(XE) COST 296 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * Electron density * Pre-stormenhancement Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.667, year: 2008

  19. Evidence for a continuous, power law, electron density irregularity spectrum

    Science.gov (United States)

    Cronyn, W. M.

    1972-01-01

    The spectral form of the irregularities in electron density that cause interplanetary scintillation (IPS) of small angular diameter radio sources is discussed. The intensity scintillation technique always yields an irregularity scale size, which is of the order of the first Fresnel zone for the wavelength at which the observations are taken. This includes not only the radio wavelength measurements of the structure of the interplanetary medium, but also radio wavelength measurements of the irregularity structure of the ionosphere and interstellar medium, and optical wavelength measurements of the irregularity structure of the atmosphere.

  20. Recycling of a fine, heavy fluff automobile shredder residue by density and differential fragmentation.

    Science.gov (United States)

    Gent, M R; Menéndez, M; Muñiz, H; Torno, S

    2015-09-01

    A compilation of the physical properties of materials which might typically occur in automobile shredder residue and an analysis of their suitability for the separation of materials in fine (<15mm) heavy fluff ASR (fhf-ASR) is presented. Differences in density and resistance to crushing of fhf-ASR materials were identified as potentially the most suitable low cost, technologically simple means for the separating this waste into its three principal components - metals, minerals (glass/stones) and organics (plastics). Results presented of laboratory scale tests demonstrate that fhf-ASR can in large part be separated into three principal components. Tests were conducted with 0.63-2.0mm and 2-10mm fractions. Recovery of plastics by density separations were conducted with water only jigs for the 2-10mm fraction and shaker tables for the 0.63-2mm fraction. Comparisons are presented of the separations of glass and stones from metals obtained by linear screening and vibratory screening of roller mill and impact mill crushing products of the high density 2-10mm fraction. Equipment used for these tests are of a laboratory or demonstrative scale. It is reasonable to anticipate that industrial scale processing would produce significantly better results. The 2-15mm fraction was found to constitute 91.6% of the fhf-ASR sampled. The metals content of the 2-10mm portion of this fraction was upgraded from 2.5% to 31% and 76.9% with recoveries varying inversely with grade from 91.9% to 40.1%. From 63.6% to 17.1% with a recovery of 93.5% of the organic materials. A residual product of fine sand of crushed glass/stones of 99.4% purity recovered 71.3% of these. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. 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 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.

  2. 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.

  3. 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.

  4. Scanning electron microscope/energy dispersive x ray analysis of impact residues in LDEF tray clamps

    Science.gov (United States)

    Bernhard, Ronald P.; Durin, Christian; Zolensky, Michael E.

    1993-01-01

    Detailed optical scanning of tray clamps is being conducted in the Facility for the Optical Inspection of Large Surfaces at JSC to locate and document impacts as small as 40 microns in diameter. Residues from selected impacts are then being characterized by Scanning Electron Microscopy/Energy Dispersive X-ray Analysis at CNES. Results from this analysis will be the initial step to classifying projectile residues into specific sources.

  5. Electron density fluctuation measurements in the TORTUR tokamak

    International Nuclear Information System (INIS)

    Remkes, G.J.J.

    1990-01-01

    This thesis deals with measurements of electron-density fluctuations in the TORTUR tokamak. These measurements are carried out by making use of collective scattering of electromagnetic beams. The choice of the wavelength of the probing beam used in collective scattering experiments has important consequences. in this thesis it is argued that the best choice for a wavelength lies in the region 0.1 - 1 mm. Because sources in this region were not disposable a 2 mm collective scattering apparatus has been used as a fair compromise. The scattering theory, somewhat adapted to the specific TORTUR situation, is discussed in Ch. 2. Large scattering angles are admitted in scattering experiments with 2 mm probing beams. This had consequences for the spatial response functions. Special attention has been paid to the wave number resolution. Expressions for the minimum source power have been determined for two detection techniques. The design and implementation of the scattering apparatus has been described in Ch. 3. The available location of the scattering volume and values of the scattering angle have been determined. The effect of beam deflection due to refraction effects is evaluated. The electronic system is introduced. Ch. 4 presents the results of measurements of density fluctuations in the TORTUR tokamak in the frequency range 1 kHz to 100 MHz end the wave number region 400 - 4000 m -1 in different regions of the plasma. Correlation between density and magnetic fluctuations has been found in a number of cases. During the current decay at the termination of several plasma discharges minor disruptions occurred. The fluctuations during these disruptions have been monitored. Measurements have been performed in hydrogen as well as deuterium. A possible dependence of the wave number on the ion gyroradius has been investigated. The isotropy of the fluctuations in the poloidal plane was investigated. A theoretical discussion of the measured results is given in ch. 5. ( H.W.). 63

  6. Preparation and characterization of high density polyethylene and residual fibre of Attalea funifera Mart (piacava) composites

    International Nuclear Information System (INIS)

    Agrela, Sara P.; Guimaraes, Danilo H.; Jose, Nadia M.; Carvalho, Gleidson G.P.; Carvalho, Ricardo F.

    2009-01-01

    The use of natural fiber reinforcement thermoplastic polymer is continuously increasing. This fact is manly due to its advantages as low cost, availability, recyclability, low energy demand and then environmental appeal if compared to synthetics fibers. The composites were prepared in different fiber volume ratios (5%, 10% and 20%) mixed with high density polyethylene (HDPE) and heated at 190 deg C. Thermogravimetric analysis and differential scanning calorimetry were used to investigate thermal stability. The composites structure was characterized by Fourier Transform Infrared spectroscopy, X-ray diffractometry. Fiber and residue of piassava (Attalea funifera Mart) chemical composition were determined by Van Soest Method. The results indicate that thermo stability of the composites of HDPE prepared with fiber volume ratios up to 20% is only slightly lowered. (author)

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

    African Journals Online (AJOL)

    structure semiconductor crystals has been performed. In a typical modern electronic structure calculation, the charge density is obtained from a certain density functional, however, the charge density in this work was obtained from first principles.

  8. Vacuum stability and residual gas density estimation for the vacuum chamber upgrade of the ATLAS interaction region of the Large Hadron Collider

    CERN Document Server

    Bregliozzi, G; Baglin, V; Jimenez, J M

    2012-01-01

    The CERN Large Hadron Collider (LHC) has 54 km of ultra-high vacuum (UHV) beam chambers out of which about 90% are at cryogenic temperature (1.9 K) and the rest at room temperature. During operation, the residual gas density in the beam pipes is dominated by beam induced effect such ion, electron and photon-stimulated gas desorption. Therefore, the computation of gas density profile is of great importance to confirm the vacuum stability, and to estimate the beam lifetime. Moreover, the gas density profiles are essential to determine the machine induced background in the experimental areas, and to define the pressure profile in the cryogenic sectors where there is no vacuum instrumentation available. In this paper, the vacuum stability is studied for a newly proposed upgrade of the vacuum chamber at the ATLAS interaction point, using the vacuum stability code called VASCO. The residual gas density profile along the ATLAS vacuum chambers and the effects of photon and electron flux hitting the vacuum chamber wal...

  9. first-principle calculation of electrons charge density in the diamond

    African Journals Online (AJOL)

    DR. AMINU

    ABSTRACT. A computational study of the total electrons charge density in the diamond-structure semiconductor crystals has been performed. In a typical modern electronic structure calculation, the charge density is obtained from a certain density functional, however, the charge density in this work was obtained from.

  10. Accuracy of ab initio electron correlation and electron densities in vanadium dioxide

    Science.gov (United States)

    Kylänpää, Ilkka; Balachandran, Janakiraman; Ganesh, Panchapakesan; Heinonen, Olle; Kent, Paul R. C.; Krogel, Jaron T.

    2017-11-01

    Diffusion quantum Monte Carlo results are used as a reference to analyze properties related to phase stability and magnetism in vanadium dioxide computed with various formulations of density functional theory. We introduce metrics related to energetics, electron densities and spin densities that give us insight on both local and global variations in the antiferromagnetic M1 and R phases. Importantly, these metrics can address contributions arising from the challenging description of the 3 d orbital physics in this material. We observe that the best description of energetics between the structural phases does not correspond to the best accuracy in the charge density, which is consistent with observations made recently by Medvedev et al. [Science 355, 371 (2017), 10.1126/science.aag0410] in the context of isolated atoms. However, we do find evidence that an accurate spin density connects to correct energetic ordering of different magnetic states in VO2, although local, semilocal, and meta-GGA functionals tend to erroneously favor demagnetization of the vanadium sites. The recently developed SCAN functional stands out as remaining nearly balanced in terms of magnetization across the M1-R transition and correctly predicting the ground state crystal structure. In addition to ranking current density functionals, our reference energies and densities serve as important benchmarks for future functional development. With our reference data, the accuracy of both the energy and the electron density can be monitored simultaneously, which is useful for functional development. So far, this kind of detailed high accuracy reference data for correlated materials has been absent from the literature.

  11. Study of residual stresses in CT test specimens welded by electron beam

    Science.gov (United States)

    Papushkin, I. V.; Kaisheva, D.; Bokuchava, G. D.; Angelov, V.; Petrov, P.

    2018-03-01

    The paper reports result of residual stress distribution studies in CT specimens reconstituted by electron beam welding (EBW). The main aim of the study is evaluation of the applicability of the welding technique for CT specimens’ reconstitution. Thus, the temperature distribution during electron beam welding of a CT specimen was calculated using Green’s functions and the residual stress distribution was determined experimentally using neutron diffraction. Time-of-flight neutron diffraction experiments were performed on a Fourier stress diffractometer at the IBR-2 fast pulsed reactor in FLNP JINR (Dubna, Russia). The neutron diffraction data estimates yielded a maximal stress level of ±180 MPa in the welded joint.

  12. Electronic structure and momentum density distribution of titanium dioxide

    International Nuclear Information System (INIS)

    Joshi, K.B.; Sharma, B.K.

    2007-01-01

    LCAO calculations have been performed for the electronic and structural properties of the rutile TiO 2 under the periodic HF and DFT schemes. The methods have been applied to study Compton profiles and the structure factors. The experimental Compton profile based on Am 241 Compton spectrometer for polycrystalline TiO 2 has been compared with the calculations. The calculated Compton profile from HF-LCAO has been found to be in good agreement with the measurement compared to the ionic model and DFT-LCAO method. The published experimental X-ray structure factors support the FLAPW method more than the periodic HF-LCAO method. Signatures of charge transfer on compound formation are observed. Partial ionic as well as covalent character of bonding is observed on the basis of structure factor as well as momentum density analysis. The present work enables to examine the DFT and HF approaches in terms of structure factor and the Compton profile studies

  13. Electronic properties of graphene nanoribbons: A density functional investigation

    International Nuclear Information System (INIS)

    Kumar, Sandeep; Sharma, Hitesh

    2015-01-01

    Density functional theory calculations have been performed on graphene nano ribbons (GNRs) to investigate the electronic properties as a function of chirality, size and hydrogenation on the edges. The calculations were performed on GNRs with armchair and zigzag configurations with 28, 34, 36, 40, 50, 56, 62, 66 carbon atoms. The structural stability of AGNR and ZGNR increases with the size of nanoribbon where as hydrogenation of GNR tends to lowers their structural stability. All GNRs considered have shown semiconducting behavior with HOMO-LUMO gap decreasing with the increase in the GNR size. The hydrogenation of GNR decreases its HOMO-LUMO gap significantly. The results are in agreement with the available experimental and theoretical results

  14. Dynamic effects of soil bulk density on denitrification and mineralisation by 15N labelled lettuce residue and paper wastes

    International Nuclear Information System (INIS)

    Hua Luo; Cheng Qing; Vinten, A.J.A.

    1997-10-01

    Two laboratory incubation experiments aimed to study the denitrification and mineralisation influenced by different additives ( 15 N labelled lettuce residue, paper wastes and mixture of both) and soil bulk densities were carried out by means of acetylene inhibition at the constant 15 degree C for 107 and 90 days, respectively. The results showed that the changes of N 2 O, CO 2 emission rates, inorganic nitrogen (NO 3 - and NH 4 + ), total N and 15 N abundance in the soils which were affected by adding lettuce residue, paper wastes and mixture of both were investigated. Soil denitrification rate increased after lettuce residue was added into soil for 8 days. The maximum rate of N 2 O emission was 15 times higher than that in soil without any additive. However, paper wastes did not increase N 2 O emission in the first 8 days compared with other treatments, mixed residue and paper wastes could promote soil microbial activity, but N 2 O emission was lower than that in the soil with lettuce residue added and higher than that with paper wastes, indicating that mixture of residue and paper wastes was benefit to soil nitrogen immobilisation. CO 2 emission in all the treatments were declined to the same level on the 107 th day. In the treatment added mixed residues and paper wastes, the released CO 2 quantities were higher than those in other treatments every day. Effect of different bulk density on N 2 O and CO 2 emission were response to the change of bulk density, it seems that N 2 O and CO 2 emission increased with bulk density. High bulk density could affect decomposition of paper wastes and NO 3 - , NH 4 + concentration. (30 ref., 10 tabs.)

  15. Homogenization mechanism of the residual surface potential of insulating specimens under electron beam irradiation

    International Nuclear Information System (INIS)

    Li Jingjing; Zhang Haibo; Feng Renjian

    2007-01-01

    A homogenized surface potential is desirable for the observation of a pre-irradiated insulating specimen using a scanning electron microscope because the residual surface potential may affect the imaging properties of the specimen. To homogenize the residual surface potential, the specimen should be subjected to the irradiation of an electron beam with the total electron yield greater than one. The expression of the equilibrium potential is derived based on the charge balance condition in the equilibrium state and the potential value is found to increase mainly with the secondary electron (SE) yield and the most probable emission energy of SEs. Further numerical calculations of SE trajectories show that affected by different surface potentials, SEs leave or return to the specimen surface to change the net charge flux into the specimen. This thereby increases the surface potential below the equilibrium potential and decreases that above the equilibrium potential, homogenizing the surface potential

  16. 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.

  17. One-electron densities of freely rotating Wigner molecules

    Science.gov (United States)

    Cioslowski, Jerzy

    2017-12-01

    A formalism enabling computation of the one-particle density of a freely rotating assembly of identical particles that vibrate about their equilibrium positions with amplitudes much smaller than their average distances is presented. It produces densities as finite sums of products of angular and radial functions, the length of the expansion being determined by the interplay between the point-group and permutational symmetries of the system in question. Obtaining from a convolution of the rotational and bosonic components of the parent wavefunction, the angular functions are state-dependent. On the other hand, the radial functions are Gaussians with maxima located at the equilibrium lengths of the position vectors of individual particles and exponents depending on the scalar products of these vectors and the eigenvectors of the corresponding Hessian as well as the respective eigenvalues. Although the new formalism is particularly useful for studies of the Wigner molecules formed by electrons subject to weak confining potentials, it is readily adaptable to species (such as ´balliums’ and Coulomb crystals) composed of identical particles with arbitrary spin statistics and permutational symmetry. Several examples of applications of the present approach to the harmonium atoms within the strong-correlation regime are given.

  18. Comparing two iteration algorithms of Broyden electron density mixing through an atomic electronic structure computation

    International Nuclear Information System (INIS)

    Zhang Man-Hong

    2016-01-01

    By performing the electronic structure computation of a Si atom, we compare two iteration algorithms of Broyden electron density mixing in the literature. One was proposed by Johnson and implemented in the well-known VASP code. The other was given by Eyert. We solve the Kohn-Sham equation by using a conventional outward/inward integration of the differential equation and then connect two parts of solutions at the classical turning points, which is different from the method of the matrix eigenvalue solution as used in the VASP code. Compared to Johnson’s algorithm, the one proposed by Eyert needs fewer total iteration numbers. (paper)

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

    International Nuclear Information System (INIS)

    Pikin, Alexander; Alessi, James G.; Beebe, Edward N.; Shornikov, Andrey; Mertzig, Robert; Wenander, Fredrik; Scrivens, Richard

    2015-01-01

    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 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

  20. Electron density enhancement in a quasi isochronous storage ring

    International Nuclear Information System (INIS)

    Pellegrini, C.; Robin, D.

    1991-01-01

    The six dimensional phase-space density of an electron beam in a storage ring is determined by the emission of synchrotron radiation, and by the transverse and longitudinal focusing forces determining the particle trajectories. In the simplest case of uncoupled horizontal, vertical and longitudinal motion, the phase space volume occupied by the beam can be characterized by the product of its three projections on the single degree of freedom planes, the horizontal, vertical, and longitudinal emittances. To minimize the beam phase space volume the authors can minimize the transverse and longitudinal emittances. In the case of transverse emittances this problem is very important for synchrotron radiation sources, and has been studied by several authors. A method to minimize the longitudinal emittance, and produce electron bunches with a short pulse length, small energy spread and large peak current has been proposed and discussed recently by C. Pellegrini and D. Robin. This method uses a ring in which the revolution period is weakly dependent on the particle energy, Quasi Isochronous Ring (QIR), in other words a ring with a momentum compaction nearly zero. In this paper they will extend the previous analysis of the conditions for stable single particle motion in such a ring, and give simple criteria for the estimate of the energy spread and phase acceptance of a QIR

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

    OpenAIRE

    Luis R. Domingo

    2016-01-01

    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 ...

  2. Accuracy of the Hartree-Fock and local density approximations for electron densities: a study for light atoms

    International Nuclear Information System (INIS)

    Almbladh, C.-O.; Ekenberg, U.; Pedroza, A.C.

    1983-01-01

    The authors compare the electron densities and Hartree potentials in the local density and the Hartree-Fock approximations to the corresponding quantities obtained from more accurate correlated wavefunctions. The comparison is made for a number of two-electron atoms, Li, and for Be. The Hartree-Fock approximation is more accurate than the local density approximation within the 1s shell and for the spin polarization in Li, while the local density approximation is slightly better than the Hartree-Fock approximation for charge densities in the 2s shell. The inaccuracy of the Hartree-Fock and local density approximations to the Hartree potential is substantially smaller than the inaccuracy of the local density approximation to the ground-state exchange-correlation potential. (Auth.)

  3. The Talbot-Lau x-ray deflectometer: a refraction-based electron density diagnostic for High Energy Density experiments

    Science.gov (United States)

    Valdivia, Maria Pia; Stutman, Dan; Stoeckl, Christian; Mileham, Chad; Begishev, Ildar; Theobald, Wolfgang; Bromage, Jake; Regan, Sean; Klein, Sallee; Vescovi, Milenko; Munoz-Cordovez, Gonzalo; Valenzuela-Villaseca, Vicente; Villanueva, Francisca; Veloso, Felipe

    2017-10-01

    Talbot-Lau X-ray Deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The diagnostic delivers refraction, attenuation, elemental composition, and scatter information from a single-shot Moiré image. A Talbot-Lau interferometer was benchmarked using laser-target and X-pinch x-ray backlighters. Grating survival and electron density mapping were demonstrated for: a) 25-29 J, 8-30 ps laser pulses using Cu targets and b) a 4 x 25 µm copper X-pinch driven by a 400kA/350ns generator. X-ray backlighter quality was assessed in order to optimize areal electron density gradient retrieval and electron density mapping. TXD enabled accurate areal electron density detection with high contrast (>25%) and spatial resolution of 50 µm in the high-power laser experiments, while a higher spatial resolution <27 µm and lower contrast (<15%) were found in pulsed power experiments, thus demonstrating the potential of TXD as an electron density diagnostic for HED plasmas. DENA0002955; FONDECYT N1171412.

  4. Analytical description of generation of the residual current density in the plasma produced by a few-cycle laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Silaev, A. A., E-mail: silaev@appl.sci-nnov.ru; Vvedenskii, N. V., E-mail: vved@appl.sci-nnov.ru [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); University of Nizhny Novgorod, Nizhny Novgorod 603950 (Russian Federation)

    2015-05-15

    When a gas is ionized by a few-cycle laser pulse, some residual current density (RCD) of free electrons remains in the produced plasma after the passage of the laser pulse. This quasi-dc RCD is an initial impetus to plasma polarization and excitation of the plasma oscillations which can radiate terahertz (THz) waves. In this work, the analytical model for calculation of RCD excited by a few-cycle laser pulse is developed for the first time. The dependences of the RCD on the carrier-envelope phase (CEP), wavelength, duration, and intensity of the laser pulse are derived. It is shown that maximum RCD corresponding to optimal CEP increases with the laser pulse wavelength, which indicates the prospects of using mid-infrared few-cycle laser pulses in the schemes of generation of high-power THz pulses. Analytical formulas for optimal pulse intensity and maximum efficiency of excitation of the RCD are obtained. Basing on numerical solution of the 3D time-dependent Schrödinger equation for hydrogen atoms, RCD dependence on CEP is calculated in a wide range of wavelengths. High accuracy of analytical formulas is demonstrated at the laser pulse parameters which correspond to the tunneling regime of ionization.

  5. Measurement of electron density in the atmospheric pressure helium plasma jet by using a dielectric probe

    International Nuclear Information System (INIS)

    Qi Bing; Zhou Qiujiao; Pan Lizhu; Zhang Mengdie; Huang Jianjun

    2014-01-01

    The electron densities in the atmospheric pressure helium plasma were calculated by means of electron drift velocity and the jet velocity respectively. The electron velocity and jet velocity can be calculated by means of helium plasma jet current measured by a dielectric probe and plasma discharge current signal measured by voltage probes. The results show that the estimated electron densities of the helium plasma jet calculated from electron drift velocity and the jet velocity are in the order of 10 11 cm -3 and they increase with applied voltage. There is a little fluctuation in the value of the electron density along the jet axis of the plasma. This result is the same as the measured electron density in atmospheric pressure helium non-thermal plasma jet by using a Rogowski coil and a Langmuir probe. This is in one order lower than the electron density measured by microwave antenna. (authors)

  6. Electron space charge effects in ion sources for residual gas analysis

    International Nuclear Information System (INIS)

    Cowen, M.C.; Allison, W.

    1993-01-01

    An electron impact ionization source suitable for residual gas analysis (RGA) with a quadrupole mass spectrometer has been studied both experimentally and by computer simulation. The electronic space charge is shown to play a role in limiting the extracted current from RGA ion sources and the simulation treats this aspect of the problem self-consistently. Under certain source conditions, the ion extraction efficiency is observed to decrease for electron currents above approximately 1 mA - well below the current at which space charge limiting of the electron emission is expected. The observed effects are well reproduced by the simulation. We show that whereas the electron trajectories are only weakly perturbed by space charge effects, the loss of ionization efficiency can be attributed to drastic changes in the ion trajectories. (author)

  7. Bacillus cereus as indicator in the sterilization of residual water with high energy electrons

    International Nuclear Information System (INIS)

    Mejia Z, E.

    2000-01-01

    One of the main causes of water pollution is the presence of microorganisms that provoke infections, moreover of chemical substances. The processes of residual water treatment finally require of the disinfection for its use or final disposition. The radiation technology for the residual water treatment by mean of electron beams is an innovator process because as well as decomposing the chemical substance or to degrade them, also it provokes a disinfection by which this is proposed as alternative for disinfection of residual water, with the purpose in reusing the water treated in the agriculture, recreation and industry among others secondary activities, solving environmental or health problems. The objective of this work is to evaluate the use of Bacillus cereus as biological indicator in the disinfection by radiation, using High Energy Electrons. To fulfil with this objective, the work was developed in three stages, the first one consisted in the acquisition, propagation and conservation of the Bacillus cereus stumps, considering Escherichia coli and Salmonella typhimurium as pathogenic germs present in residual water. Moreover, the inocule standardization and the conditions of the Electron accelerator Type Pelletron. In the second stage it was performed the irradiation of aqueous samples of the microorganisms simulating biological pollution and the application to problem samples of a treatment plant sited in the Lerma River zone of mixed residual water. And in the third stage was performed a regression analysis to the reported survival for each kind of microorganisms. The results obtained show that with the use of Electron beams was reduced 6 logarithmic units de E. coli at 129 Gy, for S. typhimurium it was reduced 8 logarithmic units at 383 Gy and the B. cereus at 511 Gy was reduced 6.8 logarithmic units. Of the problem samples irradiated at 500 Gy, the concentration of the total account diminished from 8.70 x 10 7 UFC/ml to 550 UFC/ml, the presence of B. Cereus

  8. Corrosion failure due to flux residues in an electronic add-on device

    DEFF Research Database (Denmark)

    Jellesen, Morten Stendahl; Minzari, Daniel; Rathinavelu, Umadevi

    2010-01-01

    Corrosion of components and sub-assemblies on an electronic Printed Circuit Board Assembly (PCBA) is a major reliability concern. Both process and user related contamination will influence the corrosion reliability of a PCBA and the electronic device as a whole. An important process related...... contamination is solder flux residues which can act as a corrosion promoter in humid atmosphere due to the presence of ionic substances and a resin component. The presence of ionic substances will increase the conductivity of a condensed water layer and influence corrosion processes, depending on the species...... of the electrochemical behavior metallic materials (alloys) used in the switch and risk of electrochemical migration (ECM) between the switch components in presence of flux residues was also carried out. Investigations included potentiodynamic polarization measurements on the switch electrodes using a micro...

  9. An x-ray backlit Talbot-Lau deflectometer for high-energy-density electron density diagnostics

    Science.gov (United States)

    Valdivia, M. P.; Stutman, D.; Stoeckl, C.; Theobald, W.; Mileham, C.; Begishev, I. A.; Bromage, J.; Regan, S. P.

    2016-02-01

    X-ray phase-contrast techniques can measure electron density gradients in high-energy-density plasmas through refraction induced phase shifts. An 8 keV Talbot-Lau interferometer consisting of free standing ultrathin gratings was deployed at an ultra-short, high-intensity laser system using K-shell emission from a 1-30 J, 8 ps laser pulse focused on thin Cu foil targets. Grating survival was demonstrated for 30 J, 8 ps laser pulses. The first x-ray deflectometry images obtained under laser backlighting showed up to 25% image contrast and thus enabled detection of electron areal density gradients with a maximum value of 8.1 ± 0.5 × 1023 cm-3 in a low-Z millimeter sized sample. An electron density profile was obtained from refraction measurements with an error of x-ray source-size, similar to conventional radiography.

  10. Stopping powers for channeled helium ions in silicon using electron densities from bandstructure calculations

    Science.gov (United States)

    van Dijk, P. W. L.; van Ijzendoorn, L. J.; de Koning, M.; Bobbert, P.; van Haeringen, W.; de Voigt, M. J. A.

    1994-03-01

    Stopping powers for channeled He ions have been calculated with a modified version of the Monte Carlo code LAROSE [J.H. Barrett, Phys. Rev. B 3 (1971) 1527]. The spatial distribution of the valence electron density in Si was obtained from bandstructure calculations. The stopping power was calculated using Lindhard's free-electron gas approach within the framework of the local density approximation. Spatial variations of the electron density along individual trajectories produce a significant contribution to the energy loss distribution. The average energy loss of 4 MeV He ions channeled in the axial , and directions have been calculated and compared with measured values. The contribution of the core electrons to the energy loss is investigated by adding the spherically symmetric Hartree-Fock-Slater electron densities of the closed shells to the valence electron density. Calculations show a high energy loss tail in the spectrum qualitatively in agreement with published experimental results.

  11. Determination of electron density, mass density and calcium fraction by mass of soft and osseous tissues by dual energy CT

    International Nuclear Information System (INIS)

    Henson, P.W.

    1989-01-01

    Techniques of CT analysis of trabecular regions are concerned with bone mineral assessment, with considerable attention being paid to the effect of unknown fat content. Information concerning mass density and electron density might provide a more complete picture but is not normally obtained. A method for the calculation of mass and electron density, as well as the fraction of calcium by mass, is described and requires only a measurement of effective beam energy on the skin in addition to the CT numbers from a dual energy scan. The method uses the six major elements, H, C, N, O, P and Ca as compartments for the analysis and can also be applied to soft tissue by using only the first four. The calculated mass fraction of Ca is found to be sensitive to fat content and difference between surface and internal energies which can lead to serious underestimates below a fraction of about 0.04. Mass and electron density results are independent of fat content and only marginally affected by energy differences. Results were obtained with simple materials confirming mass density can be calculated to the order of 3% and electron density to considerably better than 1%. 23 refs., 8 tabs

  12. Ligand identification using electron-density map correlations

    International Nuclear Information System (INIS)

    Terwilliger, Thomas C.; Adams, Paul D.; Moriarty, Nigel W.; Cohn, Judith D.

    2007-01-01

    An automated ligand-fitting procedure is applied to (F o − F c )exp(iϕ c ) difference density for 200 commonly found ligands from macromolecular structures in the Protein Data Bank to identify ligands from density maps. A procedure for the identification of ligands bound in crystal structures of macromolecules is described. Two characteristics of the density corresponding to a ligand are used in the identification procedure. One is the correlation of the ligand density with each of a set of test ligands after optimization of the fit of that ligand to the density. The other is the correlation of a fingerprint of the density with the fingerprint of model density for each possible ligand. The fingerprints consist of an ordered list of correlations of each the test ligands with the density. The two characteristics are scored using a Z-score approach in which the correlations are normalized to the mean and standard deviation of correlations found for a variety of mismatched ligand-density pairs, so that the Z scores are related to the probability of observing a particular value of the correlation by chance. The procedure was tested with a set of 200 of the most commonly found ligands in the Protein Data Bank, collectively representing 57% of all ligands in the Protein Data Bank. Using a combination of these two characteristics of ligand density, ranked lists of ligand identifications were made for representative (F o − F c )exp(iϕ c ) difference density from entries in the Protein Data Bank. In 48% of the 200 cases, the correct ligand was at the top of the ranked list of ligands. This approach may be useful in identification of unknown ligands in new macromolecular structures as well as in the identification of which ligands in a mixture have bound to a macromolecule

  13. One-electron properties of several small molecules calculated using the local density approximation within density functional theory

    Science.gov (United States)

    Duffy, Patrick; Chong, Delano P.; Dupuis, Michel

    1995-02-01

    Density functional theory (DFT) is a field enjoying a tremendous recent surge in popularity among theoretical and practical chemists alike because of its ability to more easily handle larger molecular systems than conventional ab initio methods. Until recently, however, assessment of the quality of the properties predicted (and therefore the charge density) from DFT had been limited mainly to dipole moments and their nuclear coordinate and electric field derivatives. This paper presents the calculated results for some of the one-electron properties of the eight small molecules (NH3, PH3, H2O, H2S, HF, HCl, CO, and N2). The properties chosen weight different regions of the charge density, from either very close in or at the nucleus (e.g., δ, the electron density at the nucleus) to regions farther out from the nucleus (e.g., the diamagnetic susceptibility ). It is found that properties which depend on an accurate knowledge of the electron density near to the nucleus are predicted poorly by the local density approximation (LDA), while others more dependent on the charge density farther out from the nucleus are predicted much more accurately, possibly due to cancellation of errors. Use of the LDA is therefore not recommended for ``tight'' properties; use of a functional employing gradient corrections would be more suitable for this purpose.

  14. Experimental core electron density of cubic boron nitride

    DEFF Research Database (Denmark)

    Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse

    and an extended multipolar model an experimental modeling of the core density is possible.4 The thermal motion is a problem since it is strongly correlated to the changes of the core density, but by combining the average displacement from a Wilson plot and a constrained refinement, a reasonable result has been...

  15. 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...... that the electron scattering time decreases from 320 to 60 fs, as the electron density changes from 1015 to 1019 cm−3....

  16. EISCAT observations of large scale electron temperture and electron density perturbations caused by high power HF radio waves

    Science.gov (United States)

    Stocker, A. J.; Honary, F.; Robinson, T. R.; Jones, T. B.; Stubbe, P.; Kopka, H.

    In this paper EISCAT observations of the effect of artificial modification on the F-region electron temperature and electron density during several heating experiments at Tromsø are reported. During O-mode heating at full power ( ERP = 240 MW) the electron temperature is increased by up to 55% of its ambient value at altitudes close to the heater interaction height. Measurements of the electron density have revealed both enhancements and depletions in the vicinity of the heater reflection height. These differences are indicative of variations in the balance between the transport and chemical effects. These results are compared with a time dependent numerical model developed from the perturbation equations of VAS'KOV and GUREVICH [(1975) Geomagn. Aeron.15, 51]. The results of numerical modelling of the electron temperature are in good agreement with the EISCAT observations, whereas there is less good agreement with regard to electron density.

  17. 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 ...

  18. Sensitivity analysis of crustal correction and its error propagation to upper mantle residual gravity and density anomalies

    DEFF Research Database (Denmark)

    Herceg, Matija; Artemieva, Irina; Thybo, Hans

    2013-01-01

    We investigate the effect of the crustal structure heterogeneity and uncertainty in its determination on stripped gravity field. The analysis is based on interpretation of residual upper mantle gravity anomalies which are calculated by subtracting (stripping) the gravitational effect of the crust...... a relatively small range of expected density variations in the lithospheric mantle, knowledge on the uncertainties associated with incomplete knowledge of density structure of the crust is of utmost importance for further progress in such studies......) uncertainties in the velocity-density conversion and (ii) uncertainties in knowledge of the crustal structure (thickness and average Vp velocities of individual crustal layers, including the sedimentary cover). In this study, we address both sources of possible uncertainties by applying different conversions...... from velocity to density and by introducing variations into the crustal structure which corresponds to the uncertainty of its resolution by high-quality and low-quality seismic models. We examine the propagation of these uncertainties into determinations of lithospheric mantle density. The residual...

  19. Measurements of electron density profiles using an angular filter refractometer

    Energy Technology Data Exchange (ETDEWEB)

    Haberberger, D., E-mail: dhab@lle.rochester.edu; Ivancic, S.; Hu, S. X.; Boni, R.; Barczys, M.; Craxton, R. S.; Froula, D. H. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14636 (United States)

    2014-05-15

    A novel diagnostic technique, angular filter refractometry (AFR), has been developed to characterize high-density, long-scale-length plasmas relevant to high-energy-density physics experiments. AFR measures plasma densities up to 10{sup 21} cm{sup −3} with a 263-nm probe laser and is used to study the plasma expansion from CH foil and spherical targets that are irradiated with ∼9 kJ of ultraviolet (351-nm) laser energy in a 2-ns pulse. The data elucidate the temporal evolution of the plasma profile for the CH planar targets and the dependence of the plasma profile on target radius for CH spheres.

  20. Understanding the properties of inorganic benzenes based on π-electron densities.

    Science.gov (United States)

    Wu, Wenjie; Li, Xiaoyan; Meng, Lingpeng; Zheng, Shijun; Zeng, Yanli

    2015-03-12

    The properties of inorganic benzenes have been investigated by means of second-order Møller-Plesset perturbation theory (MP2) calculations and quantum theory of atoms in molecules (QTAIM) studies. In this work, the σ- and π-electron densities were separated from the total electron densities, and it was therefore possible to evaluate the contributions of σ and π electrons to the chemical bonds and properties of inorganic benzenes. The following conclusions are given: (1) The π-attractors' positions correlate to their respective atomic radii. With increasing atomic number in the same period, the attractor of π-electron densities becomes closer to its respective nucleus. With increasing atomic number in the main group, the position of the π attractor becomes farther from its respective nucleus. (2) The strength of the chemical bonds of the inorganic benzene rings is determined by σ-electron densities, not π-electron densities; their bonding character is mainly determined by the σ-electron density; however, the role of the π-electron density cannot be neglected. (3) For the inorganic benzenes studied, the electron localization function for π (ELFπ) values are related to the differences of the electronegativity between the neighboring atoms of the inorganic benzene rings, Δχ(X,Y). The smaller the difference of Δχ(X,Y), the higher the value of ELFπ, resulting in more aromatic properties of the inorganic benzenes.

  1. Time-dependent density-functional and reduced density-matrix methods for few electrons: Exact versus adiabatic approximations

    International Nuclear Information System (INIS)

    Helbig, N.; Fuks, J.I.; Tokatly, I.V.; Appel, H.; Gross, E.K.U.; Rubio, A.

    2011-01-01

    Graphical abstract: We solve a 1D N-electron system, with N small, by mapping it onto an N-dimensional one-electron problem. We compare the exact solutions to the results from adiabatic density and density matrix functionals for different physical situations. Highlights: ► Static and dynamical correlations. ► Memory dependence of exchange-correlation functionals in TDDFT. ► Linear and non-linear response. ► Laser-induced population control. - Abstract: To address the impact of electron correlations in the linear and non-linear response regimes of interacting many-electron systems exposed to time-dependent external fields, we study one-dimensional (1D) systems where the interacting problem is solved exactly by exploiting the mapping of the 1D N-electron problem onto an N-dimensional single electron problem. We analyze the performance of the recently derived 1D local density approximation as well as the exact-exchange orbital functional for those systems. We show that the interaction with an external resonant laser field shows Rabi oscillations which are detuned due to the lack of memory in adiabatic approximations. To investigate situations where static correlations play a role, we consider the time-evolution of the natural occupation numbers associated to the reduced one-body density matrix. Those studies shed light on the non-locality and time-dependence of the exchange and correlation functionals in time-dependent density and density-matrix functional theories.

  2. All-electron density functional theory and time-dependent density functional theory with high-order finite elements

    OpenAIRE

    Lehtovaara, Lauri; Havu, Ville; Puska, Martti

    2009-01-01

    We present for static density functional theory and time-dependent density functional theory calculations an all-electron method which employs high-order hierarchical finite-element bases. Our mesh generation scheme, in which structured atomic meshes are merged to an unstructured molecular mesh, allows a highly nonuniform discretization of the space. Thus it is possible to represent the core and valence states using the same discretization scheme, i.e., no pseudopotentials or similar treatmen...

  3. 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.

  4. Profile shape parameterization of JET electron temperature and density profiles

    International Nuclear Information System (INIS)

    Schunke, B.

    1997-01-01

    The temperature and density profiles of the Joint European Torus (JET) are parametrized using log additive models in the control variables. Predictive error criteria are used to determine which terms in the log linear model to include. The density and temperature profiles are normalized to their line averages (n-bar and T-bar). The normalized ohmic density shape depends primarily on the parameter n-bar/B t , where B t is the toroidal magnetic field. Both the low mode (L mode) and the edge localized mode-free (ELM-free) high mode (H mode) temperature profiles shapes depend strongly on the type of heating power, with ion cyclotron resonant heating (ICRH) producing a more peaked profile than neutral beam injection (NBI). Given the heating type dependence, the L mode temperature shape is nearly independent of the other control variables. The H mode temperature shape broadens as the effective charge, Z eff , increases. The line average L mode temperature scales as B 0.96 t (power per particle) 0.385 . The L mode normalized density shape depends primarily on the ratio of line average density, n-bar, to the edge safety factor, q 95 . As n-bar/q 95 increases, the profile shape broadens. The current, I p , is the most important control variable for the normalized H mode density. As the current increases, the profile broadens and the gradient at the edge sharpens. Increasing the heating power, especially ICRH, or decreasing the average density, peaks the H mode density profile slightly. (author). 15 refs, 12 figs, 10 tabs

  5. Assessment of pesticide residues in some fruits using gas chromatography coupled with micro electron capture detector

    International Nuclear Information System (INIS)

    Latif, Y.; Sherazi, S.T.H.; Bhanger, M.I.

    2011-01-01

    A very sensitive analytical method for the determination of 26 pesticides in some fruits based on solid phase extraction (SPE) cleanup was developed using gas chromatography (GC) coupled with micro electron capture detector (mu ECD). The identity of the pesticides was confirmed by gas chromatography mass spectroscopy (GC-MS) using selected ion monitoring (SIM) mode. Ethyl acetate was used as a solvent for the extraction of pesticide residues with assistance of sonication. For cleanup an octadecyl, C18 SPE column was used. A linear response of mu ECD was observed for all pesticides with good correlation coefficients (>0.9992). Proposed method was successfully applied for the determination of pesticide residues in the orange, apple, and grape fruits. Average recoveries achieved for all of the pesticides at fortification levels of 0.05, 1.0 and 2.0 mu g g/sup -1/ in analyzed fruits were above 90% with relative standard deviations (RSD) less than 6%. (author)

  6. Simulation of electron beam from two strip electron guns and control of power density by rotation of gun

    International Nuclear Information System (INIS)

    Sahu, G K; Baruah, S; Thakur, K B

    2012-01-01

    Electron beam is preferably used for large scale evaporation of refractory materials. Material evaporation from a long and narrow source providing a well collimated wedge shaped atomic beam has applications in isotopic purification of metals relevant to nuclear industry. The electron beam from an electron gun with strip type filament provides a linear heating source. However, the high power density of the electron beam can lead to turbulence of the melt pool and undesirable splashing of molten metal. For obtaining quiet surface evaporation, the linear electron beam is generally scanned along its length. To further reduce the power density to maintain quiet evaporation the width of the vapour source can be controlled by rotating the electron gun on its plane, thereby scanning an inclined beam over the molten pool. The rotation of gun has further advantages. When multiple strip type electron guns are used for scaling up evaporation length, a dark zone appears between two beams due to physical separation of adjacent guns. This dark zone can be reduced by rotating the gun and thereby bringing two adjacent beams closer. The paper presented here provides the simulation results of the electron beam trajectory and incident power density originating from two strip electron guns by using in-house developed code. The effect of electron gun rotation on the electron beam trajectory and power density is studied. The simulation result is experimentally verified with the image of molten pool and heat affected zone taken after experiment. This technique can be gainfully utilized in controlling the time averaged power density of the electron beam and obtaining quiet evaporation from the metal molten pool.

  7. Electron density dynamics in the electronic ground state: motion along the Kekulé mode of benzene.

    Science.gov (United States)

    Schild, Axel; Choudhary, Deepanshu; Sambre, Vaibhav D; Paulus, Beate

    2012-11-26

    If the Born-Oppenheimer approximation is invoked for the description of chemical reactions, the electron density rearranges following the motion of the nuclei. Even though this approach is central to theoretical chemistry, the explicit time dependence of the electron density is rarely studied, especially if the nuclei are treated quantum mechanically. In this article, we model the motion of benzene along the Kekulé vibrational coordinate to simulate the nuclear dynamics and electron density dynamics in the electronic ground state. Details of the change of core, valence, and π electrons are determined and analyzed. We show how the pictures anticipated by drawing Lewis structures of the rearrangement correlate with the time-dependent quantum description of the process.

  8. 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......-relativistic plasma. Radial profiles for the power deposition and the non-inductive wave-driven current due to the Bernstein waves are calculated for realistic antenna radiation patterns with parameters corresponding to the Danish tokamak DANTE and to Princeton's PLT....

  9. Scanning electron microscope/energy dispersive x ray analysis of impact residues on LDEF tray clamps

    Science.gov (United States)

    Bernhard, Ronald P.; Durin, Christian; Zolensky, Michael E.

    1992-01-01

    To better understand the nature of particulates in low-Earth orbit (LEO), and their effects on spacecraft hardware, we are analyzing residues found in impacts on the Long Duration Exposure Facility (LDEF) tray clamps. LDEF experiment trays were held in place by 6 to 8 chromic-anodized aluminum (6061-T6) clamps that were fastened to the spacecraft frame using three stainless steel hex bolts. Each clamp exposed an area of approximately 58 sq cm (4.8 cm x 12.7 cm x .45 cm, minus the bolt coverage). Some 337 out of 774 LDEF tray clamps were archived at JSC and are available through the Meteoroid & Debris Special Investigation Group (M&D SIG). Optical scanning of clamps, starting with Bay/Row A01 and working toward H25, is being conducted at JSC to locate and document impacts as small as 40 microns. These impacts are then inspected by Scanning Electron Microscopy/Energy Dispersive X-ray Analysis (SEM/EDXA) to select those features which contain appreciable impact residue material. Based upon the composition of projectile remnants, and using criteria developed at JSC, we have made a preliminary discrimination between micrometeoroid and space debris residue-containing impact features. Presently, 13 impacts containing significant amounts of unmelted and semi-melted micrometeoritic residues were forwarded to Centre National d'Etudes Spatiales (CNES) in France. At the CNES facilities, the upgraded impacts were analyzed using a JEOL T330A SEM equipped with a NORAN Instruments, Voyager X-ray Analyzer. All residues were quantitatively characterized by composition (including oxygen and carbon) to help understand interplanetary dust as possibly being derived from comets and asteroids.

  10. Decay of the electron number density in the nitrogen afterglow using a hairpin resonator probe

    International Nuclear Information System (INIS)

    Siefert, Nicholas S.; Ganguly, Biswa N.; Sands, Brian L.; Hebner, Greg A.

    2006-01-01

    A hairpin resonator was used to measure the electron number density in the afterglow of a nitrogen glow discharge (p=0.25-0.75 Torr). Electron number densities were measured using a time-dependent approach similar to the approach used by Spencer et al. [J. Phys. D 20, 923 (1987)]. The decay time of the electron number density was used to determine the electron temperature in the afterglow, assuming a loss of electrons via ambipolar diffusion to the walls. The electron temperature in the near afterglow remained between 0.4 and 0.6 eV, depending on pressure. This confirms the work by Guerra et al. [IEEE Trans. Plasma. Sci. 31, 542 (2003)], who demonstrated experimentally and numerically that the electron temperature stays significantly above room temperature via superelastic collisions with highly vibrationally excited ground state molecules and metastables, such as A 3 Σ u +

  11. 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.

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

    DEFF Research Database (Denmark)

    Senturk, Osman Selcuk

    In large wind turbines (in MW and multi-MW ranges), which are extensively utilized in wind power plants, full-scale medium voltage (MV) multi-level (ML) voltage source converters (VSCs) are being more preferably employed nowadays for interfacing these wind turbines with electricity grids. For the......In large wind turbines (in MW and multi-MW ranges), which are extensively utilized in wind power plants, full-scale medium voltage (MV) multi-level (ML) voltage source converters (VSCs) are being more preferably employed nowadays for interfacing these wind turbines with electricity grids....... For these VSCs, high power density is required due to limited turbine nacelle space. Also, high reliability is required since maintenance cost of these remotely located wind turbines is quite high and these turbines operate under harsh operating conditions. In order to select a high power density and reliability...... VSC solution for wind turbines, first, the VSC topology and the switch technology to be employed should be specified such that the highest possible power density and reliability are to be attained. Then, this qualitative approach should be complemented with the power density and reliability...

  13. Exploring the temporally resolved electron density evolution in extreme ultra-violet induced plasmas

    International Nuclear Information System (INIS)

    Van der Horst, R M; Beckers, J; Nijdam, S; Kroesen, G M W

    2014-01-01

    We measured the electron density in an extreme ultra-violet (EUV) induced plasma. This is achieved in a low-pressure argon plasma by using a method called microwave cavity resonance spectroscopy. The measured electron density just after the EUV pulse is 2.6 × 10 16  m −3 . This is in good agreement with a theoretical prediction from photo-ionization, which yields a density of 4.5 × 10 16  m −3 . After the EUV pulse the density slightly increases due to electron impact ionization. The plasma (i.e. electron density) decays in tens of microseconds. (fast track communication)

  14. 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.

  15. The study of dynamics of electrons in the presence of large current densities

    International Nuclear Information System (INIS)

    Garcia, G.

    2007-11-01

    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

  16. Angular distribution of electron temperature and density in a laser-ablation plume

    DEFF Research Database (Denmark)

    Toftmann, B.; Schou, Jørgen; Hansen, T.N.

    2000-01-01

    The angular distribution of electron temperature and density in a laser-ablation plume has been studied for the first time. The electron temperature ranges from 0.1 to 0.5 eV and is only weakly dependent on the angle in the low-intensity range studied here. In contrast, the typical ion energy is ...... is about 2 orders of magnitude larger, and its angular distribution is mon peaked about the target normal. The derived Values of the electron density are in agreement with the measured values of ion density.......The angular distribution of electron temperature and density in a laser-ablation plume has been studied for the first time. The electron temperature ranges from 0.1 to 0.5 eV and is only weakly dependent on the angle in the low-intensity range studied here. In contrast, the typical ion energy...

  17. 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

    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 (e-POP) 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 (TEC) 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...... 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...

  18. Trabecular bone microstructure and mineral density in human residual ridge at various intervals over a long period after tooth extraction.

    Science.gov (United States)

    Tanaka, Mikako; Yamashita-Mikami, Emi; Akazawa, Kohei; Yoshizawa, Michiko; Arai, Yoshiaki; Ejiri, Sadakazu

    2018-03-06

    Long-term changes of trabecular microstructure in human tooth extraction socket have not been investigated. To examine the trabecular microstructure of human residual ridges at various intervals following tooth extraction, and to determine whether bone remodeling activity can attain points of relative stability and when such points are reached. Forty-four bone biopsy specimens were obtained from lower molar or premolar regions of residual ridges. Postextraction times ranged from 1.6 to 360 months. Samples were analyzed using micro-computed tomography and three-dimensional bone morphometry with histological analyses. Trabecular bone parameters were plotted against postextraction times, and a stepwise piecewise linear regression analysis was performed to determine at which points of time these parameters either increased or decreased. Using piecewise linear regression, "inflection points" were found in most trabecular bone parameters between 7 and 12 months postextraction. Among the residual ridge samples, woven trabecular structure became mature, consisting of thick lamellar trabeculae with sufficient bone density, under dynamic bone remodeling until the 7th to 12th month post-tooth extraction. After this period, the mature network structure remained stable with low remodeling activity. Bone remodeling of trabecular structure in human residual ridge after tooth extraction had a stabilization period. © 2018 Wiley Periodicals, Inc.

  19. Density functional theory study of structure, electronic and magnetic ...

    Indian Academy of Sciences (India)

    Keywords. Rhodium; boron; aluminium; gallium; methanol activation. Abstract. Rhodium clusters are very important finite size materials because of their unique electronic, magneticand catalytic properties. Tuning the physical and chemical properties of rhodium clusters by incorporatingdifferent metal and non-metal atoms ...

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

    Indian Academy of Sciences (India)

    The local, average and electronic structure of the semiconducting materials Si and Ge has been studied using multipole, maximum entropy method (MEM) and pair distribution function (PDF) analyses, using X-ray powder data. The covalent nature of bonding and the interaction between the atoms are clearly revealed by the ...

  1. 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...

  2. Density functional study of : Electronic and optical properties

    Indian Academy of Sciences (India)

    K C Bhamu

    2017-06-20

    Jun 20, 2017 ... used as an inner layer of solar cells for electricity gen- eration. This peculiar characteristic has established a benchmark in invisible electronics and opened a new era in solar cell technology [5–9]. Dietrich and Jansen [10] synthesized and reported the 3R phase of AgScO2. Shannon et al [11] reported.

  3. Density functional theory study of structure, electronic and magnetic ...

    Indian Academy of Sciences (India)

    ABHIJIT DUTTA

    2018-01-30

    Jan 30, 2018 ... Abstract. Rhodium clusters are very important finite size materials because of their unique electronic, magnetic and catalytic properties. Tuning the physical and chemical properties of rhodium clusters by incorporating different metal and non-metal atoms have found a great research interest in recent years.

  4. Experimental electron density profiles of the mid-latitude lower ionosphere and winter anomaly

    International Nuclear Information System (INIS)

    Rapoport, Z.Ts.; Sinel'nikov, V.M.

    1996-01-01

    Summarized measurements of high-latitude electron density profiles of N e lower ionosphere, obtained at M100B meteorological rockets by precision method of coherent frequencies during 1979-1990 at the Volgograd test site (φ = 48 deg 41' N; λ = 44 deg 21 E), are presented. The profiles obtained represent average values of electron density at various altitudes of lower ionosphere (h = 70-100 km) during night and day time hours in winter and non winter periods. Increased electron density values during daytime hours in winter are related to winter anomaly phenomenon. 36 refs.; 1 fig

  5. Basis set representation of the electron density at an atomic nucleus.

    Science.gov (United States)

    Mastalerz, Remigius; Widmark, Per-Olof; Roos, Björn Olof; Lindh, Roland; Reiher, Markus

    2010-10-14

    In this paper a detailed investigation of the basis set convergence for the calculation of relativistic electron densities at the position of finite-sized atomic nuclei is presented. The development of Gauss-type basis sets for such electron densities is reported and the effect of different contraction schemes is studied. Results are then presented for picture-change corrected calculations based on the Douglas-Kroll-Hess Hamiltonian. Moreover, the role of electron correlation, the effect of the numerical integration accuracy in density functional calculations, and the convergence with respect to the order of the Douglas-Kroll-Hess Hamiltonian and the picture-change-transformed property operator are studied.

  6. CO2 laser interferometer for temporally and spatially resolved electron density measurements

    Science.gov (United States)

    Brannon, P. J.; Gerber, R. A.; Gerardo, J. B.

    1982-09-01

    A 10.6-μm Mach-Zehnder interferometer has been constructed to make temporally and spatially resolved measurements of electron densities in plasmas. The device uses a pyroelectric vidicon camera and video memory to record and display the two-dimensional fringe pattern and a Pockels cell to limit the pulse width of the 10.6-μm radiation. A temporal resolution of 14 ns has been demonstrated. The relative sensitivity of the device for electron density measurements is 2×1015 cm-2 (the line integral of the line-of-sight length and electron density), which corresponds to 0.1 fringe shift.

  7. CO2 laser interferometer for temporally and spatially resolved electron density measurements

    International Nuclear Information System (INIS)

    Brannon, P.J.; Gerber, R.A.; Gerardo, J.B.

    1982-01-01

    A 10.6-μm Mach--Zehnder interferometer has been constructed to make temporally and spatially resolved measurements of electron densities in plasmas. The device uses a pyroelectric vidicon camera and video memory to record and display the two-dimensional fringe pattern and a Pockels cell to limit the pulse width of the 10.6-μm radiation. A temporal resolution of 14 ns has been demonstrated. The relative sensitivity of the device for electron density measurements is 2 x 10 15 cm -2 (the line integral of the line-of-sight length and electron density), which corresponds to 0.1 fringe shift

  8. Theoretical calculation of electron density and temperature in the edge of tokamak

    Science.gov (United States)

    Asif, Muhammad; Asif, Anila

    2017-06-01

    In this work, we use a method based on the concept of particle confinement time (τp) uniqueness to calculate the electron density and temperature in ohmically heated, edge plasma of the Hefei tokamak-7. Here, with the help of the data taken from Johnson and Hinnov’s table, we have done an extensive work to find electron densities and temperatures that satisfy the τp uniqueness to evaluate the temporal evolution of electron density (ne) and temperature (Te). The results are in good agreement as measured from the Langmuir probe array in previous works.

  9. Mapping the Local Density of States by Very-Low-Energy Scanning Electron Microscope

    Czech Academy of Sciences Publication Activity Database

    Pokorná, Zuzana; Frank, Luděk

    2010-01-01

    Roč. 51, č. 2 (2010), s. 214-218 ISSN 1345-9678 Institutional research plan: CEZ:AV0Z20650511 Keywords : density of states * scanning low energy electron microscopy * aluminum * very-low-energy scanning electron microscopy * electron band structure Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.779, year: 2010 http://www.jim.or.jp/journal/e/51/02/214.html

  10. Holographic electron density shape theorem and its role in drug design and toxicological risk assessment.

    Science.gov (United States)

    Mezey, P G

    1999-01-01

    Each complete, boundaryless molecular electron density is fully determined by any nonzero volume piece of the electron density cloud. This inherent feature of molecules, called the "holographic" property of molecular electron densities, provides a strong foundation for the local, quantum chemical shape analysis of various functional groups, pharmacophores, and other local molecular moieties. A proof is presented for the relevant molecular shape theorem, the "holographic electron density shape theorem", and the role of this theorem in quantum chemical, quantitative shape-activity relations (QShAR) is discussed. The quantum chemical methods of molecular shape analysis can be extended to ab initio quality electron densities of macromolecules, such as proteins, as well as to local molecular moieties, such as functional groups or pharmacophores, based on the transferability and additivity of local, fuzzy density fragments and the associated local density matrixes within the framework of the ADMA (Adjustable Density Matrix Assembler) approach. In addition to new results on chemical bonding and the development of macromolecular force methods, the new methodologies are also applicable to QShAR studies in computer-aided drug discovery and in toxicological risk assessment.

  11. Communication: Near-locality of exchange and correlation density functionals for 1- and 2-electron systems

    International Nuclear Information System (INIS)

    Sun, Jianwei; Yang, Zenghui; Peng, Haowei; Perdew, John P.

    2016-01-01

    The uniform electron gas and the hydrogen atom play fundamental roles in condensed matter physics and quantum chemistry. The former has an infinite number of electrons uniformly distributed over the neutralizing positively charged background, and the latter only one electron bound to the proton. The uniform electron gas was used to derive the local spin density approximation to the exchange-correlation functional that undergirds the development of the Kohn-Sham density functional theory. We show here that the ground-state exchange-correlation energies of the hydrogen atom and many other 1- and 2-electron systems are modeled surprisingly well by a different local spin density approximation (LSDA0). LSDA0 is constructed to satisfy exact constraints but agrees surprisingly well with the exact results for a uniform two-electron density in a finite, curved three-dimensional space. We also apply LSDA0 to excited or noded 1-electron densities, where it works less well. Furthermore, we show that the localization of the exact exchange hole for a 1- or 2-electron ground state can be measured by the ratio of the exact exchange energy to its optimal lower bound.

  12. 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.

  13. Two-dimensional electron density characterisation of arc interruption phenomenon in current-zero phase

    Science.gov (United States)

    Inada, Yuki; Kamiya, Tomoki; Matsuoka, Shigeyasu; Kumada, Akiko; Ikeda, Hisatoshi; Hidaka, Kunihiko

    2018-01-01

    Two-dimensional electron density imaging over free burning SF6 arcs and SF6 gas-blast arcs was conducted at current zero using highly sensitive Shack-Hartmann type laser wavefront sensors in order to experimentally characterise electron density distributions for the success and failure of arc interruption in the thermal reignition phase. The experimental results under an interruption probability of 50% showed that free burning SF6 arcs with axially asymmetric electron density profiles were interrupted with a success rate of 88%. On the other hand, the current interruption of SF6 gas-blast arcs was reproducibly achieved under locally reduced electron densities and the interruption success rate was 100%.

  14. Generalized expressions for variations in critical frequencies, electron densities and altitudes of the ionospheric layers

    International Nuclear Information System (INIS)

    Njau, E.C.

    1990-12-01

    We develop generalized mathematical expressions for time and space variations of peak electron densities of the ionospheric D, E, F1 and F2 layers as well as corresponding variations in the altitudes of the electron density peaks in each of these layers. On the basis of the Chapman characteristics of the E and F1 layers and other techniques, a generalized expression is developed for the electron density height profile of each of the four ionospheric layers. Consequently a generalized mathematical expression is developed for the entire electron density height profile of the whole ionosphere as a function of time, latitude and longitude. The latter mathematical expression may be used to compute or predict ionospheric parameters associated with ratio and satellite communications. Finally we show that some well documented equations on ionospheric parameters are simplified (or approximated) versions of some of our mathematical expressions. (author). 29 refs

  15. 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.

  16. Electron-density-sensitive Line Ratios of Fe XIII– XVI from Laboratory Sources Compared to CHIANTI

    Science.gov (United States)

    Weller, M. E.; Beiersdorfer, P.; Soukhanovskii, V. A.; Scotti, F.; LeBlanc, B. P.

    2018-02-01

    We present electron-density-sensitive line ratios for Fe XIII– XVI measured in the spectral wavelength range of 200–440 Å and an electron density range of (1–4) × 1013 cm‑3. The results provide a test at the high-density limit of density-sensitive line ratios useful for astrophysical studies. The measurements were performed on the National Spherical Torus Experiment-Upgrade, where electron densities were measured independently by the laser Thomson scattering diagnostic. Spectra were collected with a flat-field grazing-incidence spectrometer, which provided a spectral resolution of up to 0.3 Å, i.e., high resolution across the broad wavelength range. The response of the instrument was relatively calibrated using spectroscopic techniques in order to improve accuracy. The line ratios are compared to other laboratory sources and the latest version of CHIANTI (8.0.2), and an agreement within 30% is found.

  17. Electron heating caused by parametrically driven turbulence near the critical density

    International Nuclear Information System (INIS)

    Mizuno, K.; DeGroot, J.S.; Estabrook, K.G.

    1986-01-01

    Microwave-driven experiments and particle simulation calculations are presented that model s-polarized laser light incident on a pellet. In the microwave experiments, the incident microwaves are observed to decay into ion and electron waves near the critical density if the microwave power is above a well-defined threshold. Significant absorption, thermal electron heating, and hot electron generation are observed for microwave powers above a few times threshold. Strong absorption, strong profile modification, strongly heated hot electrons with a Maxwellian distribution, a hot-electron temperature that increases slowly with power, and a hot-electron density that is almost constant, are all observed in both the microwave experiments and simulation calculations for high powers. In addition, the thermal electrons are strongly heated for high powers in the microwave experiments

  18. Spectroscopic measurements of the density and electronic temperature at the plasma edge in Tore Supra

    International Nuclear Information System (INIS)

    Lediankine, A.

    1996-01-01

    The profiles of temperature and electronic density at the plasma edge are important to study the wall-plasma interaction and the radiative layers in the Tokamak plasmas. The laser ablation technique of the lithium allows to measure the profile of electronic density. To measure the profile of temperature, it has been used for the first time, the injection of a fluorine neutral atoms beam. The experiments, the results are described in this work. (N.C.)

  19. 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.

  20. 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.

  1. Inertial electron instability of current-carrying low-density plasma

    International Nuclear Information System (INIS)

    Basova, S.V.; Varentsova, S.A.; Gordeev, A.V.; Gulin, A.V.; Shuvaev, V.Yu.

    1991-01-01

    Current-carrying low-density plasma instability is investigated taking into account electron inertia at stationary ions. By analytic and numeric methods it is shown that in a constant density plasma the instability occurs under condition that the value H-tilde=H+(m e c/e)dv/dr, where H is the magnetic field, v - electron current velocity, changes the sign as the function of coordinate. Numeric calculations allowed to derive the increments for specific current configurations

  2. Self-consistent calculation of electron density distribution in metals in HNC approximation

    Energy Technology Data Exchange (ETDEWEB)

    Stachowiak, H.; Boronski, E.; Banach, G. [Polska Akademia Nauk, Wroclaw (Poland). Inst. Niskich Temperatur i Badan Strukturalnych

    1997-12-01

    A nonlinear integro-differential equation is introduced for density amplitude of conduction electrons in simple metals as a consequence of the results obtained within the theory of liquids. The simplicity of this equation in comparison with the usual Kohn-Sham approach gives the possibility to determine the self- consistent density of conduction electrons without assuming a muffin-tin lattice potential. Calculations have been performed for lithium. Perspectives connected with this approach are discussed. (author). 8 refs, 2 figs.

  3. Fast-electron self-collimation in a plasma density gradient

    International Nuclear Information System (INIS)

    Yang, X. H.; Borghesi, M.; Robinson, A. P. L.

    2012-01-01

    A theoretical and numerical study of fast electron transport in solid and compressed fast ignition relevant targets is presented. The principal aim of the study is to assess how localized increases in the target density (e.g., by engineering of the density profile) can enhance magnetic field generation and thus pinching of the fast electron beam through reducing the rate of temperature rise. The extent to which this might benefit fast ignition is discussed.

  4. 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

  5. An empirical topside electron density model for calculation of absolute ion densities in IRI

    Czech Academy of Sciences Publication Activity Database

    Třísková, Ludmila; Truhlík, Vladimír; Šmilauer, Jan

    2006-01-01

    Roč. 37, č. 5 (2006), s. 928-934 ISSN 0273-1177 R&D Projects: GA ČR GP205/02/P037; GA AV ČR IAA3042201; GA MŠk ME 651 Grant - others:National Science Foundation(US) 0245457 Institutional research plan: CEZ:AV0Z30420517 Keywords : Plasma density * Topside ionosphere * Ion composition * Empirical models Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.706, year: 2005

  6. 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.

  7. 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.

  8. Role of substituents on the reactivity and electron density profile of ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 125; Issue 5. Role of substituents on the reactivity and electron density profile of diimine ligands: A density functional theory based study. Bhakti S Kulkarni Deepti Mishra Sourav Pal. Volume 125 Issue 5 September 2013 pp 1247-1258 ...

  9. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Y; Mazzucato, E; Guttenfelder, W; Bell, R E; Domier, C W; LeBlanc, B P; Lee, K C; Luhmann Jr, N C; Smith, D R

    2011-03-21

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k⊥ρs ≤10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  10. Density matrix renormalization group with efficient dynamical electron correlation through range separation

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Knecht, Stefan; Kielberg, Jesper Skau

    2015-01-01

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electroncorrelation...... effects in multiconfigurational electronic structure problems....

  11. Proton and neutron densities from elastic electron scattering

    International Nuclear Information System (INIS)

    Frois, B.

    1979-01-01

    Elastic electron scattering has now determined extremely fine details of the shape of the nuclear groound state. The combination of (e,e) and muonic X-rays data are giving informations that are among the most precise on nuclear structure. This enables to see all the limitations of existing theories. However, we begin to have a very coherent description of nuclei with the self consistent field theories to a few percent. A very significant progress has been achieved with the calculations of RPA correlations in the round state in a self consistent way. Only recent experiments (on medium and heavy nuclei) of some significance for the understanding of the structure of the nucleus are reviewed

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

    Science.gov (United States)

    Shen, X. H.; Zhang, X.; Liu, J.; Zhao, S. F.; Yuan, G. P.

    2015-04-01

    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 parameters helps to

  13. Residual gas entering high density hydrogen plasma: rarefaction due to rapid heating

    NARCIS (Netherlands)

    N. den Harder,; D.C. Schram,; W. J. Goedheer,; de Blank, H. J.; M. C. M. van de Sanden,; van Rooij, G. J.

    2015-01-01

    The interaction of background molecular hydrogen with magnetized (0.4 T) high density (1–5 × 10 20  m −3 ) low temperature (∼3 eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center,

  14. Characterising electron beam welded dissimilar metal joints to study residual stress relaxation from specimen extraction

    International Nuclear Information System (INIS)

    Abburi Venkata, K.; Truman, C.E.; Smith, D.J.; Bhaduri, A.K.

    2016-01-01

    Nuclear power plants require dissimilar metal weld joints to connect the primary steam generator made from ferritic steel to the intermediate heat exchanger made from austenitic steel. Such joints are complex because of the mismatch in the thermal and the mechanical properties of the materials used in the joint. Electron Beam (EB) welding is emerging as a promising technique to manufacture dissimilar joints providing a great many advantages over conventional welding techniques, in terms of low heat input, high heat intensity, narrow fusion and heat affected zones, deeper penetration and increased welding speeds. However before this method can be considered for implementation in an actual plant, it is essential for a careful and a comprehensive outlining of the joint characteristics and the apparent effects on performance during service. In the present study, an EB welded joint was manufactured using austenitic AISI 316LN stainless steel and a ferritic-martensitic P91 steel, without the addition of filler material. Neutron diffraction measurement was conducted on the welded plate to measure the residual stress distribution across the weld as well as through the thickness of the plate. A finite element analysis was conducted on a two-dimensional cross-sectional model using ABAQUS code to simulate the welding process and predict the residual stresses, implementing the effects of solid-state phase transformation experienced by P91 steel. The predicted residual stresses were transferred to a 3D finite element model of the plate to simulate the machining and extraction of a C(T) blank specimen from the welded plate and the extent of stress relaxation is studied.

  15. Status of electron temperature and density measurement with beam emission spectroscopy on thermal helium at TEXTOR

    NARCIS (Netherlands)

    Schmitz, O.; Beigman, I. L.; Vainshtein, L. A.; Schweer, B.; Kantor, M.; Pospieszczyk, A.; Xu, Y.; Krychowiak, M.; Lehnen, M.; Samm, U.; Unterberg, B.

    2008-01-01

    Beam emission spectroscopy on thermal helium is used at the TEXTOR tokamak as a reliable method to obtain radial profiles of electron temperature T-e(r, t) and electron density ne(r, t). In this paper the experimental realization of this method at TEXTOR and the status of the atomic physics employed

  16. Electron-nuclear coupling in time-dependent multicomponent density functional theory

    NARCIS (Netherlands)

    Butriy, Olena O.

    2008-01-01

    In this thesis we developed the time-dependent version of the multicomponent density functional approach to treat time-dependent electron-nuclear systems. The method enables to describe the electron-nuclear coupling fully quantum mechanically. No Born-Oppenheimer approximation is involved in the

  17. Detection of antibiotic residues in bovine milk by a voltammetric electronic tongue system

    International Nuclear Information System (INIS)

    Wei Zhenbo; Wang Jun

    2011-01-01

    A voltammetric electronic tongue (VE-tongue) was developed to detect antibiotic residues in bovine milk. Six antibiotics (Chloramphenicol, Erythromycin, Kanamycin sulfate, Neomycin sulfate, Streptomycin sulfate and Tetracycline HCl) spiked at four different concentration levels (0.5, 1, 1.5 and 2 maximum residue limits (MRLs)) were classified based on VE-tongue by two pattern recognition methods: principal component analysis (PCA) and discriminant function analysis (DFA). The VE-tongue was composed of five working electrodes (gold, silver, platinum, palladium, and titanium) positioned in a standard three-electrode configuration. The Multi-frequency large amplitude pulse voltammetry (MLAPV) which consisted of four segments (1 Hz, 10 Hz, 100 Hz and 1000 Hz) was applied as potential waveform. The six antibiotics at the MRLs could not be separated from bovine milk completely by PCA, but all the samples were demarcated clearly by DFA. Three regression models: Principal Component Regression Analysis (PCR), Partial Least Squares Regression (PLSR), and Least Squares-Support Vector Machines (LS-SVM) were used for concentrations of antibiotics prediction. All the regression models performed well, and PCR had the most stable results.

  18. Detection of antibiotic residues in bovine milk by a voltammetric electronic tongue system

    Energy Technology Data Exchange (ETDEWEB)

    Wei Zhenbo [Zhejiang University, Department of Bio-Systems Engineering, 268 Kaixuan Road, Hangzhou, Zhejiang 310029 (China); Wang Jun, E-mail: jwang@zju.edu.cn [Zhejiang University, Department of Bio-Systems Engineering, 268 Kaixuan Road, Hangzhou, Zhejiang 310029 (China)

    2011-05-23

    A voltammetric electronic tongue (VE-tongue) was developed to detect antibiotic residues in bovine milk. Six antibiotics (Chloramphenicol, Erythromycin, Kanamycin sulfate, Neomycin sulfate, Streptomycin sulfate and Tetracycline HCl) spiked at four different concentration levels (0.5, 1, 1.5 and 2 maximum residue limits (MRLs)) were classified based on VE-tongue by two pattern recognition methods: principal component analysis (PCA) and discriminant function analysis (DFA). The VE-tongue was composed of five working electrodes (gold, silver, platinum, palladium, and titanium) positioned in a standard three-electrode configuration. The Multi-frequency large amplitude pulse voltammetry (MLAPV) which consisted of four segments (1 Hz, 10 Hz, 100 Hz and 1000 Hz) was applied as potential waveform. The six antibiotics at the MRLs could not be separated from bovine milk completely by PCA, but all the samples were demarcated clearly by DFA. Three regression models: Principal Component Regression Analysis (PCR), Partial Least Squares Regression (PLSR), and Least Squares-Support Vector Machines (LS-SVM) were used for concentrations of antibiotics prediction. All the regression models performed well, and PCR had the most stable results.

  19. Assessment of Pesticide Residues in Some Fruits Using Gas Chromatography Coupled with Micro Electron Capture Detector

    Directory of Open Access Journals (Sweden)

    M. I. Bhanger

    2011-12-01

    Full Text Available A very sensitive analytical method for the determination of 26 pesticides in some fruits based on solid phase extraction (SPE cleanup was developed using gas chromatography (GC coupled with micro electron capture detector (μECD. The identity of the pesticides was confirmed by gas chromatography mass spectroscopy (GC-MS using selected ion monitoring (SIM mode. Ethyl acetate was used as a solvent for the extraction of pesticide residues with assistance of sonication. For cleanup an octadecyl, C18 SPE column was used. A linear response of μECD was observed for all pesticides with good correlation coefficients (>0.9992. Proposed method was successfully applied for the determination of pesticide residues in the orange, apple, and grape fruits. Average recoveries achieved for all of the pesticides at fortification levels of 0.05, 1.0 and 2.0 μg g-1 in analyzed fruits were above 90% with relative standard deviations (RSD less than 6

  20. Protein hydrogen exchange measured at single-residue resolution by electron transfer dissociation mass spectrometry

    DEFF Research Database (Denmark)

    Rand, Kasper D; Zehl, Martin; Jensen, Ole Nørregaard

    2009-01-01

    Because of unparalleled sensitivity and tolerance to protein size, mass spectrometry (MS) has become a popular method for measuring the solution hydrogen (1H/2H) exchange (HX) of biologically relevant protein states. While incorporated deuterium can be localized to different regions by pepsin...... proteolysis of the labeled protein, the assignment of deuteriums to individual residues is typically not obtained, thereby limiting a detailed understanding of HX and the dynamics of protein structure. Here we use gas-phase fragmentation of peptic peptides by electron transfer dissociation (ETD) to measure...... the HX of individual amide linkages in the amyloidogenic protein beta2-microglobulin. A comparison of the deuterium levels of 60 individual backbone amides of beta2-microglobulin measured by HX-ETD-MS analysis to the corresponding values measured by NMR spectroscopy shows an excellent correlation...

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

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

    Science.gov (United States)

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

    2014-11-01

    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

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

    International Nuclear Information System (INIS)

    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.

    2012-01-01

    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 ∼ 4γ 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 ∼ 10 10 photons, 60 nJ (1.4×10 12 photons/sr) in the XUV spectral region (12.8-22 nm).

  4. 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).

  5. Measurement of power density distribution and beam waist simulation for electron beam

    International Nuclear Information System (INIS)

    Shen, Chunlong; Peng, Yong; Wang, Kehong; Zhou, Qi

    2013-01-01

    The study aims to measure the power density distribution of the electron beam (EB) for further estimating its characteristics. A compact device combining deflection signal controller and current signal acquisition circuit of the EB was built. A software modelling framework was developed to investigate structural parameters of the electron beam. With an iterative algorithm, the functional relationship between the electron beam power and its power density was solved and the corresponding contour map of power density distribution was plotted through isoline tracking approach. The power density distribution of various layers of cross-section beam was reconstructed for beam volume by direct volume rendering technique. The further simulation of beam waist with all-known marching cubes algorithm reveals the evolution of spatial appearance and geometry measurement principle was explained in detail. The study provides an evaluation of promising to replace the traditional idea of EB spatial characteristics. - Highlights: ► We build a framework for measuring power density distribution for electron beam. ► We capture actual electron and build transient spatial power distribution for EB. ► Tracing algorithm of power density contour for cross-section was designed. ► The volume and waist of the beam are reconstructed in 4D mode. ► Geometry measurement is finished which is befit for designing of process welding.

  6. 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...

  7. Energy-momentum density of graphite by electron-momentum spectroscopy

    International Nuclear Information System (INIS)

    Vos, M.; Fang, Z.; Canney, S.; Kheifets, A.; McCarthy, I.E.; Weigold, E.

    1996-11-01

    The energy-resolved electron momentum density of graphite has been measured along a series of well-defined directions using electron momentum spectroscopy (EMS). This is the first measurement of this kind performed on a single-crystal target with a thoroughly controlled orientation which clearly demonstrates the different nature of the σ and π bands in graphite. Good agreement between the calculated density and the measured one is found, further establishing that fact that EMS yields more direct and complete information on the valence electronic structure that any other method. 12 refs., 2 figs

  8. The implementation of real-time plasma electron density calculations on EAST

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.C., E-mail: zzc@ipp.ac.cn; Xiao, B.J.; Wang, F.; Liu, H.Q.; Yuan, Q.P.; Wang, Y.; Yang, Y.

    2016-11-15

    Highlights: • The real-time density calculation system (DCS) has been applied to the EAST 3-wave polarimeter-interferometer (POINT) system. • The new system based on Flex RIO acquires data at high speed and processes them in a short time. • Roll-over module is developed for density calculation. - Abstract: The plasma electron density is one of the most fundamental parameters in tokamak experiment. It is widely used in the plasma control system (PCS) real-time control, as well as plasma physics analysis. The 3-wave polarimeter-interferometer (POINT) system had been used to measure the plasma electron density on the EAST since last campaign. This paper will give the way to realize the real-time measurement of plasma electron density. All intermediate frequency (IF) signals after POINT system, in the 0.5–3 MHz range, stream to the real-time density calculation system (DCS) to extract the phase shift information. All the prototype hardware is based on NI Flex RIO device which contains a high speed Field Programmable Gate Array (FPGA). The original signals are sampled at 10 M Samples/s, and the data after roll-over module are transmitted to PCS by reflective memory (RFM). With this method, real-time plasma electron density data with high accuracy and low noise had been obtained in the latest EAST tokamak experiment.

  9. 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.

  10. A Plasma Edge Electron Density Diagnostic Based on a Doppler-free Measurement of Stark Broadening

    Science.gov (United States)

    Zafar, Abdullah; Martin, Elijah; Shannon, Steve

    2017-10-01

    Passive spectroscopic measurements of Stark broadening have been reliably used to determine electron density for decades. A low-density limit of 1e19 m-3 exists using these passive techniques due to Doppler and instrument broadening. At Oak Ridge National Laboratory, a novel diagnostic approach for measuring electron density using Stark broadening is currently under development and is capable of extending the low-density limit to 1e16 m-3 . The diagnostic is based on measuring the spectral line profile of a Balmer series transition using Doppler-free saturation spectroscopy, a laser-based absorption technique. The spectrum is then fit to a quantum mechanical model using the Explicit Zeeman Stark Spectral Simulator (EZSSS) code to extract the electron density. The increased sensitivity to the electron density is realized because Doppler-free saturation spectroscopy (DFSS) can greatly reduce the Doppler broadening and essentially eliminate the instrument broadening. DFSS has been successfully employed to measure spectral data in a magnetized (500-800 G), low temperature (5 eV), low density (1e17-1e18 m-3), He/H2 and He/CH4 plasma in the mTorr pressure range. Experimentally measured pi and sigma H-alpha spectra, fit using the EZSSS code, will be presented. A quantitative model to accurately predict crossover peaks and dips will also be given. This work was supported by the US. D.O.E. contract DE-AC05-00OR22725.

  11. Topology of Electron Density of Cadmium Telluride Determined from Relief and Contour Plots

    International Nuclear Information System (INIS)

    Othman, A.P.; Gopir, G.A.

    2013-01-01

    The topology of the electron density yields a faithful and a reliable mapping of the concepts of atoms, molecular structure, bonds and structure, besides providing the basis for a theory of structural stability. In quantum mechanics, and in particular quantum chemistry, the electron density is a measure of the probability of an electron occupying an infinitesimal element of space surrounding any given point. Contour plots of electron density distribution of cadmium telluride (CdTe) were obtained using the density functional theory (DFT) method and were used as the basis to qualitatively study the bond, structure and stability of the molecule when it is in bulk. We looked at the way the electron density, ρ of CdTe defines the gradient field and hence the bonding type. We identified the bond paths that coincide with the contours of electron sharing. These bond paths indicated that the molecule was slightly covalent. Our topological analysis led us to conclude that CdTe was an n-type semiconductor with covalent bond and slight ionic character. (author)

  12. 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.

  13. Chemical bonding in view of electron charge density and kinetic energy density descriptors.

    Science.gov (United States)

    Jacobsen, Heiko

    2009-05-01

    Stalke's dilemma, stating that different chemical interpretations are obtained when one and the same density is interpreted either by means of natural bond orbital (NBO) and subsequent natural resonance theory (NRT) application or by the quantum theory of atoms in molecules (QTAIM), is reinvestigated. It is shown that within the framework of QTAIM, the question as to whether for a given molecule two atoms are bonded or not is only meaningful in the context of a well-defined reference geometry. The localized-orbital-locator (LOL) is applied to map out patterns in covalent bonding interaction, and produces results that are consistent for a variety of reference geometries. Furthermore, LOL interpretations are in accord with NBO/NRT, and assist in an interpretation in terms of covalent bonding. 2008 Wiley Periodicals, Inc.

  14. Pseudoclassical approach to electron and ion density correlations in simple liquid metals

    International Nuclear Information System (INIS)

    Vericat, F.; Tosi, M.P.; Pastore, G.

    1986-04-01

    Electron-electron and electron-ion structural correlations in simple liquid metals are treated by using effective pair potentials to incorporate quantal effects into a pseudoclassical description of the electron fluid. An effective pair potential between simultaneous electron density fluctuations is first constructed from known properties of the degenerate jellium model, which are the plasmon sum rule, the Kimball-Niklasson relation and Yasuhara's values of the electron pair distribution function at contact. An analytic expression is thereby obtained in the Debye-Hueckel approximation for the electronic structure factor in jellium over a range of density appropriate to metals, with results which compare favourably with those of fully quantal evaluations. A simple pseudoclassical model is then set up for a liquid metal: this involves a model of charged hard spheres for the ion-ion potential and an empty core model for the electron-ion potential, the Coulombic tails being scaled as required by the relation between the long-wavelength partial structure factors and the isothermal compressibility of the metal. The model is solved analytically by a pseudoclassical linear response treatment of the electron-ion coupling and numerical results are reported for partial structure factors in liquid sodium and liquid beryllium. Contact is made for the latter system with data on the electron-electron structure factor in the crystal from inelastic X-ray scattering experiments of Eisenberger, Marra and Brown. (author)

  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. Using Fe XXII to Determine the Electron Density of Stellar Coronae

    Science.gov (United States)

    Lepson, Jaan; Beiersdorfer, P.; Brown, G. V.; Clementson, J.; Gu, M. F.

    2010-03-01

    Lines from Fe XXII, both in the EUV and X-ray region, are known to be sensitive to the electron density and have in recent years been used as diagnostics of stellar coronae, such as AB Dor and Ex Hya. We have recently obtained spectral data from laboratory sources in which the electron density is known either from non-spectroscopic means or from K-shell density diagnostics. The densities of the laboratory sources range from 5x1011 cm-3 to 5x1014 cm-3. The measurements have been used to test the spectral models underlying the Fe XXII density diagnostic line ratios. This work was supported by the NASA APRA program and the DOE General Plasma Science program.

  17. Bayesian electron density inference from JET lithium beam emission spectra using Gaussian processes

    Science.gov (United States)

    Kwak, Sehyun; Svensson, J.; Brix, M.; Ghim, Y.-C.; Contributors, JET

    2017-03-01

    A Bayesian model to infer edge electron density profiles is developed for the JET lithium beam emission spectroscopy (Li-BES) system, measuring Li I (2p-2s) line radiation using 26 channels with  ∼1 cm spatial resolution and 10∼ 20 ms temporal resolution. The density profile is modelled using a Gaussian process prior, and the uncertainty of the density profile is calculated by a Markov Chain Monte Carlo (MCMC) scheme. From the spectra measured by the transmission grating spectrometer, the Li I line intensities are extracted, and modelled as a function of the plasma density by a multi-state model which describes the relevant processes between neutral lithium beam atoms and plasma particles. The spectral model fully takes into account interference filter and instrument effects, that are separately estimated, again using Gaussian processes. The line intensities are inferred based on a spectral model consistent with the measured spectra within their uncertainties, which includes photon statistics and electronic noise. Our newly developed method to infer JET edge electron density profiles has the following advantages in comparison to the conventional method: (i) providing full posterior distributions of edge density profiles, including their associated uncertainties, (ii) the available radial range for density profiles is increased to the full observation range (∼26 cm), (iii) an assumption of monotonic electron density profile is not necessary, (iv) the absolute calibration factor of the diagnostic system is automatically estimated overcoming the limitation of the conventional technique and allowing us to infer the electron density profiles for all pulses without preprocessing the data or an additional boundary condition, and (v) since the full spectrum is modelled, the procedure of modulating the beam to measure the background signal is only necessary for the case of overlapping of the Li I line with impurity lines.

  18. Electron mobility in supercritical pentanes as a function of density and temperature

    International Nuclear Information System (INIS)

    Itoh, Kengo; Nakagawa, Kazumichi; Nishikawa, Masaru

    1988-01-01

    The excess electron mobility in supercritical n-, iso- and neopentane was measured isothermally as a function of density. The density-normalized mobility μN in all three isomers goes through a minimum at a density below the respective critical densities, and the mobility is quite temperature-dependent in this region, then goes through a minimum. The μN behavior around the minimum in n-pentane is well accounted for by the Cohen-Lekner model with the structure factor S(K) estimated from the speed of sound, while that in iso- and neopentane is not. (author)

  19. Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

    Science.gov (United States)

    Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

    1976-01-01

    Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

  20. On-treatment non-high-density lipoprotein cholesterol, apolipoprotein B, triglycerides, and lipid ratios in relation to residual vascular risk after treatment with potent statin therapy

    DEFF Research Database (Denmark)

    Mora, Samia; Glynn, Robert J; Boekholdt, S Matthijs

    2012-01-01

    The goal of this study was to determine whether residual risk after high-dose statin therapy for primary prevention individuals with reduced levels of low-density lipoprotein cholesterol (LDL-C) is related to on-treatment apolipoprotein B, non-high-density lipoprotein cholesterol (non-HDL-C), tri...

  1. 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

  2. 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

  3. Deduction of edge electron density with multiply charged ions in ORNL volume-type electron cyclotron resonance ion source.

    Science.gov (United States)

    You, H-J; Woo, H-J; Chung, K-S; Liu, Y; Meyer, F W; Lho, T; Lee, M-J

    2008-02-01

    The electron densities in the argon plasmas of the ORNL 6 GHz electron cyclotron resonance (ECR) ion source with a flat central magnetic field have been deduced from the ion branches of the electric probe current-voltage curves measured in the edge region of the plasmas. To overcome the difficulties due to unknown velocities of multiply charged ions at the sheath edge, a modified generalized Bohm criterion for the ion sheath velocity is introduced and the mean velocity of all ionic charge states at the sheath edge is assumed to be equal to the sound velocity of the system of particles. The calculated electron densities and temperatures for different plasmas optimized for four charge state distributions are discussed.

  4. 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.

  5. 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.

  6. The Electron Density in Explosive Transition Region Events Observed by IRIS

    Science.gov (United States)

    Doschek, G. A.; Warren, H. P.; Young, P. R.

    2016-11-01

    We discuss the intensity ratio of the O IV line at 1401.16 Å to the Si IV line at 1402.77 Å in Interface Region Imaging Spectrograph (IRIS) spectra. This intensity ratio is important if it can be used to measure high electron densities that cannot be measured using line intensity ratios of two different O IV lines from the multiplet within the IRIS wavelength range. Our discussion is in terms of considerably earlier observations made from the Skylab manned space station and other spectrometers on orbiting spacecraft. The earlier data on the O IV and Si IV ratio and other intersystem line ratios not available to IRIS are complementary to IRIS data. In this paper, we adopt a simple interpretation based on electron density. We adopt a set of assumptions and calculate the electron density as a function of velocity in the Si IV line profiles of two explosive events. At zero velocity the densities are about 2-3 × 1011 cm-3, and near 200 km s-1 outflow speed the densities are about 1012 cm-3. The densities increase with outflow speed up to about 150 km s-1 after which they level off. Because of the difference in the temperature of formation of the two lines and other possible effects such as non-ionization equilibrium, these density measurements do not have the precision that would be available if there were some additional lines near the formation temperature of O IV.

  7. Electron density and temperature in NIO1 RF source operated in oxygen and argon

    Science.gov (United States)

    Barbisan, M.; Zaniol, B.; Cavenago, M.; Pasqualotto, R.; Serianni, G.; Zanini, M.

    2017-08-01

    The NIO1 experiment, built and operated at Consorzio RFX, hosts an RF negative ion source, from which it is possible to produce a beam of maximum 130 mA in H- ions, accelerated up to 60 kV. For the preliminary tests of the extraction system the source has been operated in oxygen, whose high electronegativity allows to reach useful levels of extracted beam current. The efficiency of negative ions extraction is strongly influenced by the electron density and temperature close to the Plasma Grid, i.e. the grid of the acceleration system which faces the source. To support the tests, these parameters have been measured by means of the Optical Emission Spectroscopy diagnostic. This technique has involved the use of an oxygen-argon mixture to produce the plasma in the source. The intensities of specific Ar I and Ar II lines have been measured along lines of sight close to the Plasma Grid, and have been interpreted with the ADAS package to get the desired information. This work will describe the diagnostic hardware, the analysis method and the measured values of electron density and temperature, as function of the main source parameters (RF power, pressure, bias voltage and magnetic filter field). The main results show that not only electron density but also electron temperature increase with RF power; both decrease with increasing magnetic filter field. Variations of source pressure and plasma grid bias voltage appear to affect only electron temperature and electron density, respectively.

  8. 'Anomalous electron transport' with 'Giant Current Density' at room temperature observed with nanogranular materials

    International Nuclear Information System (INIS)

    Koops, Hans W.P.

    2013-01-01

    Focused electron beam induced deposition is a novel bottom up nano-structurization technology. An electron beam of high power density is used to generate nano- structures with dimensions > 20 nm, but being composed from amorphous or nanogranular materials with crystals of 2 to 5 nm diameter embedded in a Fullerene matrix. Those compounds are generated in general by secondary or low energy electrons in layers of inorganic, organic, organometallic compounds absorbed to the sample. Those are converted into nanogranular materials by the electron beam following chemical and physical laws, as given by 'Mother Nature'. Metals and amorphous mixtures of chemical compounds from metals are normal resistors, which can carry a current density J 2 . Nanogranular composites like Au/C or Pt/C with metal nanocrystals embedded in a Fullerene matrix have hopping conduction with 0-dimensional Eigen-value characteristics and show 'anomalous electron transport' and can carry 'Giant Current Densities' with values from > 1 MA/cm 2 to 0.1 GA/cm 2 without destruction of the materials. However the area connecting the nanogranular material with a metal with a 3-dimensional electron gas needs to be designed, that the flowing current is reduced to the current density values which the 3-D metal can support without segregation. The basis for a theoretical explanation of the phenomenon can be geometry quantization for Coulomb blockade, of electron surface orbitals around the nanocrystals, hopping conduction, and the limitation of the density of states for phonons in geometry confined non percolated granular materials with strong difference in mass and orientation. Several applications in electronics, signal generators, light sources, detectors, and solar energy harvesting are suggested. (author)

  9. 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...... moments are computed using the same geometries (MP2/6-31G*) and basis set (TZVP) as in our previous ab initio benchmark study on electronically excited states. The results from TD-DFT (with the functionals BP86, B3LYP, and BHLYP) and from DFT/MRCI are compared against the previous high-level ab initio...

  10. 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.

  11. Assembling phosphorene flexagons for 2D electron-density-guided nanopatterning and nanofabrication.

    Science.gov (United States)

    Kang, Kisung; Jang, Woosun; Soon, Aloysius

    2017-07-27

    To build upon the rich structural diversity in the ever-increasing polymorphic phases of two-dimensional phosphorene, we propose different assembly methods (namely, the "bottom-up" and "top-down" approaches) that involve four commonly reported parent phases (i.e. the α-, β-, γ-, and δ-phosphorene) in combination with the lately reported remarkably low-energy one-dimensional defects in α-phosphorene. In doing so, we generate various periodically repeated phosphorene patterns in these so-called phosphorene flexagons and present their local electron density (via simulated scanning tunneling microscopy (STM) images). These interesting electron density patterns seen in the flexagons (mimicking symmetry patterns that one may typically see in a kaleidoscope) may assist as potential 2D templates where electron-density-guided nanopatterning and nanofabrication in complex organized nanoarchitectures are important.

  12. 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...

  13. 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.

  14. Likelihood-based modification of experimental crystal structure electron density maps

    Science.gov (United States)

    Terwilliger, Thomas C [Sante Fe, NM

    2005-04-16

    A maximum-likelihood method for improves an electron density map of an experimental crystal structure. A likelihood of a set of structure factors {F.sub.h } is formed for the experimental crystal structure as (1) the likelihood of having obtained an observed set of structure factors {F.sub.h.sup.OBS } if structure factor set {F.sub.h } was correct, and (2) the likelihood that an electron density map resulting from {F.sub.h } is consistent with selected prior knowledge about the experimental crystal structure. The set of structure factors {F.sub.h } is then adjusted to maximize the likelihood of {F.sub.h } for the experimental crystal structure. An improved electron density map is constructed with the maximized structure factors.

  15. Reassessment of the electron density in Cu2O using γ-ray diffraction.

    Science.gov (United States)

    Jauch, Wolfgang; Reehuis, Manfred

    2014-12-01

    The electron-density distribution in Cu2O has been critically reexamined to test controversial conclusions from earlier experimental and theoretical studies. The electron density is derived via multipole refinement of high-quality single-crystal diffraction data, collected at room temperature with 316.5 keV gamma radiation. Four γ-lines in the energy range 200-600 keV have been used to extrapolate extinction-free low-order structure factors. The remaining extinction corrections refine to a crystal mosaicity identical to the observed one. There is no support for anharmonic contributions to the thermal parameters. Important features of the derived electron density are (i) a partially filled d_{z^2} orbital, (ii) an incomplete ionization of Cu and O, and (iii) no interstitial Cu-Cu charge pileup, thereby refuting the covalent bonding hypothesis.

  16. Electron beam manipulation, injection and acceleration in plasma wakefield accelerators by optically generated plasma density spikes

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, Georg; Karger, Oliver S.; Knetsch, Alexander [Institute of Experimental Physics, University of Hamburg, 22761 Hamburg (Germany); Xi, Yunfeng; Deng, Aihua; Rosenzweig, James B. [Particle Beam Physics Laboratory, UCLA, Los Angeles, CA 90095 (United States); Bruhwiler, David L. [RadiaSoft LLC, Boulder, CO 80304 (United States); RadiaBeam Technologies LLC (United States); Smith, Jonathan [Tech-X UK Ltd, Daresbury, Cheshire WA4 4FS (United Kingdom); Sheng, Zheng-Ming; Jaroszynski, Dino A.; Manahan, Grace G. [Physics Department, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Hidding, Bernhard [Institute of Experimental Physics, University of Hamburg, 22761 Hamburg (Germany); Physics Department, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2016-09-01

    We discuss considerations regarding a novel and robust scheme for optically triggered electron bunch generation in plasma wakefield accelerators [1]. In this technique, a transversely propagating focused laser pulse ignites a quasi-stationary plasma column before the arrival of the plasma wake. This localized plasma density enhancement or optical “plasma torch” distorts the blowout during the arrival of the electron drive bunch and modifies the electron trajectories, resulting in controlled injection. By changing the gas density, and the laser pulse parameters such as beam waist and intensity, and by moving the focal point of the laser pulse, the shape of the plasma torch, and therefore the generated trailing beam, can be tuned easily. The proposed method is much more flexible and faster in generating gas density transitions when compared to hydrodynamics-based methods, and it accommodates experimentalists needs as it is a purely optical process and straightforward to implement.

  17. Diagnostics of electron density of laser-produced plasma from the XUV spectra of Ag XIX

    International Nuclear Information System (INIS)

    Huang Wenzhong; Zhang Tanxin; He Shaotang; Gu Yuqiu; You Yonglu; Jiang Wenmian

    1999-12-01

    The XUV spectra from Ag XIX of laser-produced plasma are measured. The density dependence of Δn = 0(4-4) transitions from Ag XIX has been studied in a density range 10 17 -10 22 cm -3 with the collisional radiative model. The theoretical model includes the effect of cascading from n = 5 states on the population of the n = 4 levels. In addition, optical depth effects on the line intensities were considered. The two transitions of 4d 2 D 5/2 -4f 2 F 7/2 and 4p 2 P 3/2 -4d 2 D 5/2 remain close to each other and are unblended with other lines. Calculations of their radiation intensity ratio vs the electron density are performed. Electron density of laser produced plasma has been deduced from the ratio

  18. Investigation of bulk electron densities for dose calculations on cone-beam CT images

    International Nuclear Information System (INIS)

    Lambert, J.; Parker, J.; Gupta, S.; Hatton, J.; Tang, C.; Capp, A.; Denham, J.W.; Wright, P.

    2010-01-01

    Full text: If cone-beam CT images are to be used for dose calculations, then the images must be able to provide accurate electron density information. Twelve patients underwent twice weekly cone-beam CT scans in addition to the planning CT scan. A standardised 5-field treatment plan was applied to 169 of the CBCT images. Doses were calculated using the original electron density values in the CBCT and with bulk electron densities applied. Bone was assigned a density of 288 HU, and all other tissue was assigned to be water equivalent (0 HU). The doses were compared to the dose calculated on the original planning CT image. Using the original HU values in the cone-beam images, the average dose del i vered by the plans from all 12 patients was I. I % lower than the intended 200 cOy delivered on the original CT plans (standard devia tion 0.7%, maximum difference -2.93%). When bulk electron densities were applied to the cone-beam images, the average dose was 0.3% lower than the original CT plans (standard deviation 0.8%, maximum difference -2.22%). Compared to using the original HU values, applying bulk electron densities to the CBCT images improved the dose calculations by almost I %. Some variation due to natural changes in anatomy should be expected. The application of bulk elec tron densities to cone beam CT images has the potential to improve the accuracy of dose calculations due to inaccurate H U values. Acknowledgements This work was partially funded by Cancer Council NSW Grant Number RG 07-06.

  19. Effect of plasma density around Io on local electron heating in the Io plasma torus

    Science.gov (United States)

    Tsuchiya, F.; Yoshioka, K.; Kagitani, M.; Kimura, T.; Murakami, G.; Yamazaki, A.; Misawa, H.; Kasaba, Y.; Yoshikawa, I.; Sakanoi, T.; Koga, R.; Ryo, A.; Suzuki, F.; Hikida, R.

    2017-12-01

    HISAKI observation of Io plasma torus (IPT) with extreme ultraviolet (EUV) wavelength range is a useful probe to access plasma environment in inner magnetosphere of Jupiter. Emissions from sulfur and oxygen ions in EUV range are caused by electron impact excitation and their intensity is well correlated with the abundance of hot electron in IPT. Previous observation showed that the brightness was enhanced downstream of the satellite Io, indicating that efficient electron heating takes place at Io and/or just downstream of Io. Detailed analysis of the emission intensity shows that the brightness depends on the magnetic longitude at Io and primary and secondary peaks appear in the longitude ranges of 100-130 and 250-340 degrees, respectively. The peak position and amplitude are slightly different between dawn and dusk sides. Here, we introduce inhomogeneous IPT density model in order to investigate relation between the emission intensity and local plasma density around Io in detail. An empirical IPT model is used for spatial distribution of ion and electron densities in the meridional plane. To include longitude and local time asymmetry in IPT, we consider (1)dawnward shift of IPT due to global convection electric field, (2) offset of Jupiter's dipole magnetic field, and (3) tilt of IPT with respect to Io's orbital plane. The modeled electron density at the position of Io as a function of magnetic longitude at Io shows similar profile with the ion emission intensity derived from the observation. This result suggests that energy extracted around Io and/or efficiency of electron heating is closely related to the plasma density around Io and longitude and local time dependences is explained by the spatial inhomogeneity of plasma density in IPT. A part of the energy extracted around Io could be transferred to the Jovian ionosphere along the magnetic field line and cause bright aurora spots and strong radio emissions.

  20. Modelling the experimental electron density: only the synergy of various approaches can tackle the new challenges

    Directory of Open Access Journals (Sweden)

    Piero Macchi

    2015-07-01

    Full Text Available Electron density is a fundamental quantity that enables understanding of the chemical bonding in a molecule or in a solid and the chemical/physical property of a material. Because electrons have a charge and a spin, two kinds of electron densities are available. Moreover, because electron distribution can be described in momentum or in position space, charge and spin density have two definitions and they can be observed through Bragg (for the position space or Compton (for the momentum space diffraction experiments, using X-rays (charge density or polarized neutrons (spin density. In recent years, we have witnessed many advances in this field, stimulated by the increased power of experimental techniques. However, an accurate modelling is still necessary to determine the desired functions from the acquired data. The improved accuracy of measurements and the possibility to combine information from different experimental techniques require even more flexibility of the models. In this short review, we analyse some of the most important topics that have emerged in the recent literature, especially the most thought-provoking at the recent IUCr general meeting in Montreal.

  1. 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...

  2. 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

    encountered in single-crystal studies of small-unit-cell inorganic structures can be overcome with synchrotron powder diffraction. It is shown that the standard Hansen-Coppens multipole model is not flexible enough to fit the static theoretical structure factors, whereas fitting of thermally smeared structure...... 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....

  3. Critical density for Landau damping in a two-electron-component plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rupp, Constantin F.; López, Rodrigo A.; Araneda, Jaime A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile)

    2015-10-15

    The asymptotic evolution of an initial perturbation in a collisionless two-electron-component plasma with different temperatures is studied numerically. The transition between linear and nonlinear damping regimes is determined by slowly varying the density of the secondary electron-component using high-resolution Vlasov-Poisson simulations. It is shown that, for fixed amplitude perturbations, this transition behaves as a critical phenomenon with time scales and field amplitudes exhibiting power-law dependencies on the threshold density, similar to the critical amplitude behavior in a single-component plasma.

  4. Simultaneous measurement of line electron density and Faraday rotation in the ISX-B tokamak

    International Nuclear Information System (INIS)

    Hutchinson, D.P.; Ma, C.H.; Staats, P.A.; Vander Sluis, K.L.

    1981-01-01

    A new diagnostic system utilizing a submillimetre-wave, phase-modulated polarimeter/interferometer has been used to simultaneously measure the time evolution of the line-averaged electron density and poloidal field-induced Faraday rotation in the ISX-B tokamak. The measurements, performed along four chords of the plasma column, have been correlated with poloidal field changes associated with a ramp in the Ohmic-heating current and by neutral-beam injection. These are the first simultaneous measurements of line electron density and Faraday rotation to be made along a chord of submillimetre laser beam in a tokamak plasma. (author)

  5. Diffuse Surface Scattering in the Plasmonic Resonances of Ultralow Electron Density Nanospheres.

    Science.gov (United States)

    Monreal, R Carmina; Antosiewicz, Tomasz J; Apell, S Peter

    2015-05-21

    Localized surface plasmon resonances (LSPRs) have recently been identified in extremely diluted electron systems obtained by doping semiconductor quantum dots. Here, we investigate the role that different surface effects, namely, electronic spill-out and diffuse surface scattering, play in the optical properties of these ultralow electron density nanosystems. Diffuse scattering originates from imperfections or roughness at a microscopic scale on the surface. Using an electromagnetic theory that describes this mechanism in conjunction with a dielectric function including the quantum size effect, we find that the LSPRs show an oscillatory behavior in both position and width for large particles and a strong blue shift in energy and an increased width for smaller radii, consistent with recent experimental results for photodoped ZnO nanocrystals. We thus show that the commonly ignored process of diffuse surface scattering is a more important mechanism affecting the plasmonic properties of ultralow electron density nanoparticles than the spill-out effect.

  6. Highly collimated monoenergetic target-surface electron acceleration in near-critical-density plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Mao, J. Y. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Kaiserslautern 67663 (Germany); Chen, L. M., E-mail: lmchen@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Huang, K.; Ma, Y.; Zhao, J. R.; Yan, W. C.; Ma, J. L.; Wei, Z. Y. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Li, D. Z. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Institute of High Energy Physics, CAS, Beijing 100049 (China); Aeschlimann, M. [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Kaiserslautern 67663 (Germany); Zhang, J. [Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-03-30

    Optimized-quality monoenergetic target surface electron beams at MeV level with low normalized emittance (0.03π mm mrad) and high charge (30 pC) per shot have been obtained from 3 TW laser-solid interactions at a grazing incidence. The 2-Dimension particle-in-cell simulations suggest that electrons are wake-field accelerated in a large-scale, near-critical-density preplasma. It reveals that a bubble-like structure as an accelerating cavity appears in the near-critical-density plasma region and travels along the target surface. A bunch of electrons are pinched transversely and accelerated longitudinally by the wake field in the bubble. The outstanding normalized emittance and monochromaticity of such highly collimated surface electron beams could make it an ideal beam for fast ignition or may serve as an injector in traditional accelerators.

  7. Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

    CERN Document Server

    Byrd, J; Sonnad, K; Caspers, Friedhelm; Kroyer, T; Krasnykh, A; Pivi, M

    2009-01-01

    Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solen...

  8. Isochoric heating and strong blast wave formation driven by fast electrons in solid-density targets

    Science.gov (United States)

    Santos, J. J.; Vauzour, B.; Touati, M.; Gremillet, L.; Feugeas, J.-L.; Ceccotti, T.; Bouillaud, R.; Deneuville, F.; Floquet, V.; Fourment, C.; Hadj-Bachir, M.; Hulin, S.; Morace, A.; Nicolaï, Ph; d'Oliveira, P.; Reau, F.; Samaké, A.; Tcherbakoff, O.; Tikhonchuk, V. T.; Veltcheva, M.; Batani, D.

    2017-10-01

    We experimentally investigate the fast (metallic foils and subsequent high-pressure hydrodynamics induced by energetic electrons driven by high-intensity, high-contrast laser pulses. The early-time temperature profile inside the target is measured from the streaked optical pyrometry of the target rear side. This is further characterized from benchmarked simulations of the laser-target interaction and the fast electron transport. Despite a modest laser energy (laser-based platform dedicated to high-energy-density physics studies.

  9. Inertial electron instability in low-density current-carrying plasmas

    International Nuclear Information System (INIS)

    Basova, S.V.; Varentsova, S.A.; Gordeev, A.V.; Gulin, A.V.; Shuvaev, V.Yu.

    1991-01-01

    The stability of a low-density current-carrying plasma with finite electron inertia and motionless ions is studied. It is shown analytically and numerically that an instability exists when the quantity H = H + (m e c/e)dv/dr changes sign as a function of position, where H is the magnetic field and v is the current drift velocity of the electrons. The growth rates for specific current configurations are obtained by numerical calculation

  10. Cooling of high-density and power electronics by means of heat pipes

    International Nuclear Information System (INIS)

    Hubbeling, L.

    1980-06-01

    This report describes how heat pipes can be used for cooling modern electronic equipment, with numerous advantages over air-cooled systems. A brief review of heat-pipe properties is given, with a detailed description of a functioning prototype. This is a single-width CAMAC unit containing high-density electronic circuits cooled by three heat pipes, and allowing a dissipation of over 120 W instead of the normal maximum of 20 W. (orig.)

  11. Study of electron density and its fluctuations in tokamaks plasmas by fast infrared interferometry

    International Nuclear Information System (INIS)

    Ryter, F.

    1982-10-01

    The electron density knowledge in tokamak plasma is fundamental for controlled fusion research. Its study can be made by interferometric measurement of plasma refraction index. Density and density fluctuation measurements are given for present and future tokamak, the wavelength used must be in the far infrared. The interferometer used type employs two identical lasers. Waveguide type submillimetric lasers, optically pumped by a CO 2 laser, have been developed and optimized. Detectors used are Schottky diodes. The interferometer allows a radial study of the plasma and presents a great stability during the measurement [fr

  12. 2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe.

    Science.gov (United States)

    Chen, Y H; Yang, X Y; Lin, C; Wang, L; Xu, M; Wang, X G; Xiao, C J

    2014-11-01

    A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

  13. Microwave Transmission Measurement of the Electron Cloud Density in the Positron Ring of PEP-II

    CERN Document Server

    Pivi, M T F; Byrd, J; De Santis, S; Sonnad, K G; Caspers, Friedhelm; Kroyer, T; Roncarolo, F

    2008-01-01

    Clouds of electrons in the vacuum chambers of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We applied a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave which is independently excited and transmitted over a straight section of the accelerator. The modulation in the wave transmission which appear to increase in depth when the clearing solenoids are switched off, seem to be directly correlated to the electron cloud density in the section. Furthermore, we expect a larger phase shift of a wave transmitted through magnetic dipole field regions if the transmitted wave couples with the gyration motion of the electrons. We have used this technique to measure the average electron cloud density (ECD) specifically for the first time in magnetic...

  14. 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 estimated in a vacuum beam propagation between the edge density layer and the EC resonance absorption layer. Consequences on the EC beam propagation are investigated by using a simplified model in which the density fluctuations are described by a single harmonic oscillation. In addition, quasi......-optical calculations are shown by using edge density fluctuations as calculated by two-dimensional interchange turbulence simulations and validated with the experimental data [O. E. Garcia et al, Nucl. Fusion 47 (2007) 667]...

  15. Electron momentum density and band structure calculations of {alpha}- and {beta}-GeTe

    Energy Technology Data Exchange (ETDEWEB)

    Vadkhiya, Laxman [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Arora, Gunjan [Department of Physics, Techno India NJR Institute of Technology, Udaipur 313002, Rajasthan (India); Rathor, Ashish [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India)

    2011-12-15

    We have measured isotropic experimental Compton profile of {alpha}-GeTe by employing high energy (662 keV) {gamma}-radiation from a {sup 137}Cs isotope. To compare our experiment, we have also computed energy bands, density of states, electron momentum densities and Compton profiles of {alpha}- and {beta}-phases of GeTe using the linear combination of atomic orbitals method. The electron momentum density is found to play a major role in understanding the topology of bands in the vicinity of the Fermi level. It is seen that the density functional theory (DFT) with generalised gradient approximation is relatively in better agreement with the experiment than the local density approximation and hybrid Hartree-Fock/DFT. - Highlights: > Compton profile of {alpha}-GeTe using a 20 Ci {sup 137}Cs Compton spectrometer. > Compared experimental Compton data with density functional theory. > Reported energy bands and density of states of {alpha}- and {beta}-GeTe. > EVED profiles analysed to check the covalent character.

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

    Science.gov (United States)

    Lynn, K. J. W.; Harris, T. J.; Sjarifudin, M.

    2006-07-01

    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.

  17. 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

  18. 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

  19. Investigation of the Electron Density Variation During the 21 August 2017 Solar Eclipse

    Science.gov (United States)

    Reinisch, B. W.; Dandenault, P. B.; Galkin, I. A.; Hamel, R.; Richards, P. G.

    2018-02-01

    This paper presents a comparison of modeled and measured electron densities for the 21 August 2017 solar eclipse across the USA. The location of the instrument was (43.81°N, 247.32°E) where the maximum obscuration of 99.6% occurred at 17.53 hr UT on 21 August. The solar apparent time was 9.96 hr, and the duration of the eclipse was 2.7 hr. It was found that if it is assumed that there are no chromosphere emissions at totality, 30% coronal emission remaining at totality gave the best fit to the electron density variation at 150 km. The 30% coronal emission estimate has uncertainties associated with respect to uncertainties in the solar spectrum, the measured electron density, and the amount of chromosphere emissions remaining at totality. The agreement between the modeled and measured electron densities is excellent at 150 km with the assumed 30% coronal emission at totality. At other altitudes, the agreement is very good, but the altitude profile would be improved if the model peak electron density (NmF2) decayed more slowly to better match the data. The minimum NmF2 in the model occurs 10 min after totality when it decreases to 0.55 from its noneclipse value. The minimum of the NmF2 data occurs between 6 and 10 min after totality but is 15% larger. The total electron content decreases to 0.65 of its preeclipse value. These relative changes agree well with those predicted by others prior to the eclipse.

  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. A new method of electron density measurement by Fabry-Perot interferometry

    International Nuclear Information System (INIS)

    Hojo, Hitoshi; Mase, Atsushi

    2004-01-01

    A new method for determining the electron density of a thin plasma by means of Fabry-Perot interferometry is proposed. The interferometer consists of two plasma layers and dielectric material surrounded by two plasma layers. The transmittance of electromagnetic waves across the interferometer is calculated, and Fabry-Perot resonances are frequency when the width of a plasma layer is known. (author)

  2. Influence of the curve density relative electron in dosimetry clinic in treatments stereo tactics

    International Nuclear Information System (INIS)

    Moreno Saiz, C.; Benitez Villegas, E. M.; Casado Villalon, F. J.; Parra Osorio, V.; Bodineau Gil, C.; Garcia Pareja, S.

    2013-01-01

    The objective of this study is to analyze the difference between clinical dosimetry in the treatments with radiosurgery and stereotactic radiotherapy fractional obtained from the relative Electron density curve (Schneider 1996) tabulated and provided with the scanner's radiation therapy. (Author)

  3. Relative electron density determination using a physics based parameterization of photon interactions in medical DECT

    NARCIS (Netherlands)

    van Abbema, Joanne K.; van Goethem, Marc-Jan; Greuter, Marcel J. W.; van der Schaaf, Arjen; Brandenburg, Sytze; van der Graaf, Emiel R.

    2015-01-01

    Radiotherapy and particle therapy treatment planning require accurate knowledge of the electron density and elemental composition of the tissues in the beam path to predict the local dose deposition. We describe a method for the analysis of dual energy computed tomography (DECT) images that provides

  4. Electron density in reasonably real metallic surfaces, including interchange and correlation effects

    International Nuclear Information System (INIS)

    Moraga, L.A.; Martinez, G.

    1981-01-01

    By means of a new method, the electron density in a jellium surface is calculated taking in account interchange and correlation effects; reproducing, in this way, the Lang and Kohn results. The new method is self-consistent but not iterative and hence is possible extend it to the solution of the same problem in more reasonably real metallic surfaces. (L.C.) [pt

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

    Indian Academy of Sciences (India)

    2017-06-20

    Jun 20, 2017 ... 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 densityapproximation (LDA) and generalized gradient approximation (GGA). Electronic properties deal with energy bands and ...

  6. Electron density and temperature determination in a Tokamak plasma using light scattering

    International Nuclear Information System (INIS)

    Perez-Navarro Gomerz, A.; Zurro Hernandez, B.

    1976-01-01

    A theoretical foundation review for light scattering by plasmas is presented. Furthermore, we have included a review of the experimental methods for electron density and temperature measurements, with spatial and time resolution, in a Tokamak plasma using spectral analysis of the scattered radiation. (Author) 13 refs

  7. Density functional theory for strongly-interacting electrons: Perspectives for Physics and Chemistry

    NARCIS (Netherlands)

    Gori Giorgi, P.; Seidl, M.

    2010-01-01

    Improving the accuracy and thus broadening the applicability of electronic density functional theory (DFT) is crucial to many research areas, from material science, to theoretical chemistry, biophysics and biochemistry. In the last three years, the mathematical structure of the strong-interaction

  8. Electron density and temperature determination in a Tokamak plasma using light scattering

    International Nuclear Information System (INIS)

    Perez-Navarro Gomez, A.; Zurro Hernandez, B.

    1976-01-01

    A theoretical foundation review for light scattering by plasmas is presented. Furthemore, a review of the experimental methods for electron density and temperature measurements, with spatial and time resolution, is included in a Tokamak plasma using spectral analysis of the scattered radiation. (author) [es

  9. EDMA: a computer program for topological analysis of discrete electron densities

    Czech Academy of Sciences Publication Activity Database

    Palatinus, Lukáš; Prathapa, S.J.; van Smaalen, S.

    2012-01-01

    Roč. 45, Part 3 (2012), 575-580 ISSN 0021-8898 Institutional research plan: CEZ:AV0Z10100521 Keywords : discrete electron density * maximum entropy method * atoms in molecules Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.343, year: 2012

  10. Electron density measurement with dual-energy x-ray CT using synchrotron radiation

    International Nuclear Information System (INIS)

    Torikoshi, Masami; Tsunoo, Takanori; Sasaki, Makoto; Endo, Masahiro; Noda, Yutaka; Ohno, Yumiko; Kohno, Toshiyuki; Hyodo, Kazuyuki; Uesugi, Kentaro; Yagi, Naoto

    2003-01-01

    Monochromatic x-ray computed tomography (CT) at two different energies provides information about electron density of human tissue without ambiguity due to the beam hardening effect. This information makes the treatment planning for proton and heavy-ion radiotherapy more precise. We have started a feasibility study on dual energy x-ray CT by using synchrotron radiation. A translation-rotation scanning CT system was developed for quantitative measurement in order to clarify what precision in the measurement was achieved. Liquid samples of solutions of K 2 HPO 4 and solid samples of tissue equivalent materials were used to simulate human tissue. The experiments were carried out using monochromatic x-rays with energies of 40, 70 and 80 keV produced by monochromatizing synchrotron radiation. The solid samples were also measured in a complementary method using high-energy carbon beams to evaluate the electron densities. The measured electron densities were compared with the theoretical values or the values measured in the complementary method. It was found that these values were in agreement in 0.9% on average. Effective atomic numbers were obtained as well from dual-energy x-ray CT. The tomographic image based on each of the electron densities and the effective atomic number presents a different feature of the material, and its contrast drastically differs from that in a conventional CT image

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

    Indian Academy of Sciences (India)

    II–VI semiconductor alloys; band structure; charge density; empirical pseudopotential method. Abstract. 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 ...

  12. Efficient k⋅p method for the calculation of total energy and electronic density of states

    OpenAIRE

    Iannuzzi, Marcella; Parrinello, Michele

    2001-01-01

    An efficient method for calculating the electronic structure in large systems with a fully converged BZ sampling is presented. The method is based on a k.p-like approximation developed in the framework of the density functional perturbation theory. The reliability and efficiency of the method are demostrated in test calculations on Ar and Si supercells

  13. 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.

  14. Pressure dependence of electron density distribution and d-p-π hybridization in titanate perovskite ferroelectrics

    Science.gov (United States)

    Yamanaka, Takamitsu; Nakamoto, Yuki; Ahart, Muhtar; Mao, Ho-kwang

    2018-04-01

    Electron density distributions of PbTi O3 , BaTi O3 , and SrTi O3 were determined by synchrotron x-ray powder diffraction up to 55 GPa at 300 K and ab initio quantum chemical molecular orbital (MO) calculations, together with a combination of maximum entropy method calculations. The intensity profiles of Bragg peaks reveal split atoms in both ferroelectric PbTi O3 and BaTi O3 , reflecting the two possible positions occupied by the Ti atom. The experimentally obtained atomic structure factor was used for the determination of the deformation in electron density and the d-p-π hybridization between dx z (and dy z) of Ti and px (and py) of O in the Ti-O bond. Ab initio MO calculations proved the change of the molecular orbital coupling and of Mulliken charges with a structure transformation. The Mulliken charge of Ti in the Ti O6 octahedron increased in the ionicity with increasing pressure in the cubic phase. The bonding nature is changed with a decrease in the hybridization of the Ti-O bond and the localization of the electron density with increasing pressure. The hybridization decreases with pressure and disappears in the cubic paraelectric phase, which has a much more localized electron density distribution.

  15. Wormholes in chemical space connecting torus knot and torus link pi-electron density topologies.

    Science.gov (United States)

    Rzepa, Henry S

    2009-03-07

    Möbius aromaticities can be considered as deriving from cyclic delocalized pi-electron densities rho(r)(pi) which have the topological form of either a two-component torus link or a single-component torus knot. These two topological forms are distinguished by their (non-zero) linking number L(k), which describes how many times the two components of a torus link cross each other or the single component of a torus knot crosses with itself. The special case of Hückel or benzenoid aromaticity is associated with a pi-electron density that takes the form of a two-component torus link for which the linking number is zero. A class of molecule has been identified which here is termed a Janus aromatic, and which bears the characteristics of both a two-component torus link and a single-component torus knot in the topology of the pi-electron density. This is achieved by the formation of one (or more) wormholes or throats in the pi-electron density connecting the two torus forms, which can impart a Janus-like dual personality to the aromaticity of the system. The impact of such wormholes on the overall pi-delocalized aromaticity of such molecules is approximately estimated using a NICS(rcp) index, and subdivides into two types; those where the forms of aromaticity associated with a torus link and a torus knot cooperate and those where they oppose.

  16. Construction of New Electronic Density Functionals with Error Estimation Through Fitting

    DEFF Research Database (Denmark)

    Petzold, V.; Bligaard, T.; Jacobsen, K. W.

    2012-01-01

    We investigate the possibilities and limitations for the development of new electronic density functionals through large-scale fitting to databases of binding energies obtained experimentally or through high-quality calculations. We show that databases with up to a few hundred entries allow for up...

  17. Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

    Energy Technology Data Exchange (ETDEWEB)

    Byrd, John; De Santis, Stefano; Sonnad, Kiran; Caspers, Fritz; Kroyer, Tom; Krasnykh, Anatoly; Pivi, Mauro

    2008-06-01

    Clouds of low energy electronsin the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energyelectron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solenoid magnets to control the electrons.

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

    African Journals Online (AJOL)

    empirical basis with the International Reference Ionosphere (IRI-90) and the CCIR models. Electron density profiles are computed using the median values of ionospheric data routinely scaled from ionograms at Ibadan (7.40N, 3.90E) and ...

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

    Indian Academy of Sciences (India)

    Unknown

    structural refinement using JANA 2000, and then the re- fined structure factors have been utilized for MEM re- finements to elucidate the ... the appropriate methods in which the concept of entropy is introduced to handle the uncertainty properly. The principle of MEM is to obtain an electron density distri- bution, which is ...

  20. Measuring Density Profiles of Electrons and Heavy Particles in a Stable Axially Blown Arc

    Science.gov (United States)

    Carstensen, J.; Stoller, P.; Galletti, B.; Doiron, C. B.; Sokolov, A.

    2017-08-01

    Two-color spatial carrier wave interferometry employing pulsed 532- and 671-nm lasers is used to measure the electron-density and heavy-particle-density profiles in the stagnation point of a stable, axially blown arc in argon for currents of 50 to 200 A and stagnation point pressures of 0.2 to 16 bar. This technique takes advantage of the fact that the free-electron contribution to the refractive index depends strongly on the wavelength, while that of the heavy particles does not. The high spatial resolution achieved allows the hot core of the arc to be readily distinguished from the surrounding boundary layer. A custom-built test device is used to ensure flow conditions that lead to a stable, axisymmetric arc; this permits the reconstruction of the density and temperature profiles using a single projection (interferometric image) of the refractive-index distribution through the arc (at two wavelengths). The arc radius determined from the heavy-particle density decreases with increasing stagnation pressure and increases with the current. These measurements are in good agreement with a simple axially blown arc model taking into account Ohmic heating, radiation losses, and enthalpy flow for core temperatures of approximately 16 500 K. The measured electron density at the center of the arc agrees well with a prediction based on local thermodynamic equilibrium.

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

    International Nuclear Information System (INIS)

    Antoniassi, M.; Conceição, A.L.C.; Poletti, M.E.

    2012-01-01

    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: ► Electron density of normal and neoplastic breast tissues was measured using Compton scattering. ► Monochromatic synchrotron radiation was used to obtain the Compton scattering data. ► The area of Compton peaks was used to determine the electron densities of samples. ► Adipose tissue shows the lowest electron density values whereas the malignant tissue the highest. ► Comparison with previous results showed differences smaller than 4%.

  3. Recent activities on nuclear and electron density study by diffraction technique

    International Nuclear Information System (INIS)

    Noda, Yukio

    2005-01-01

    Advanced structure analysis is to know the detail structures in a crystal as atomic and electronic level and also to know the relation between the crystal structure and physical properties of the material. In this talk, I will emphasize the importance of the role of neutron single crystal experiments. As one of the examples, the comparison of electron density observed by x-ray crystal structure analysis and nuclear distribution observed by neutron structure analysis, especially in the hydrogen bond system, will be given. As a result, we found a large electronic polarization in a hydrogen atom, which plays an important role for the antiferroelectric phase transition. Other examples are the direct measurements of d-electron orbital using neutron magnetic structure analyses. MnF 2 (d 5 ) and Nd 2 CuO 4 (d 1 ) are examples. Finally, a π-electron distribution in an organic crystal using the similar technique will be shown

  4. 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...

  5. Solar Type IIIb Radio Bursts as Tracers for Electron Density Fluctuations in the Corona

    Science.gov (United States)

    Mugundhan, V.; Hariharan, K.; Ramesh, R.

    2017-11-01

    We present an estimation of the electron density modulation index (δ{Ne}/Ne) for the first time using solar type IIIb radio burst observations. The mean value of δ{Ne}/Ne is calculated to be ≈ 0.006±0.002 over the heliocentric distance range r ≈1.6 - 2.2 R_{⊙}. The estimated {δ{Ne}}/{Ne} shows a power law dependence on r with a power law index ≈ 0.31±0.10. The wavenumber (k) spectrum for the electron density fluctuation ({δ{Ne}/Ne})2 values shows a Kolmogorov-like behavior. Using δ{Ne}/Ne and the Kolmogorov turbulence index, we estimated the amplitude of density turbulence [Cn2{(r)}] in the aforementioned range of r.

  6. 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.

  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. Bayesian modeling of JET Li-BES for edge electron density profiles using Gaussian processes

    Science.gov (United States)

    Kwak, Sehyun; Svensson, Jakob; Brix, Mathias; Ghim, Young-Chul; JET Contributors Collaboration

    2015-11-01

    A Bayesian model for the JET lithium beam emission spectroscopy (Li-BES) system has been developed to infer edge electron density profiles. The 26 spatial channels measure emission profiles with ~15 ms temporal resolution and ~1 cm spatial resolution. The lithium I (2p-2s) line radiation in an emission spectrum is calculated using a multi-state model, which expresses collisions between the neutral lithium beam atoms and the plasma particles as a set of differential equations. The emission spectrum is described in the model including photon and electronic noise, spectral line shapes, interference filter curves, and relative calibrations. This spectral modeling gets rid of the need of separate background measurements for calculating the intensity of the line radiation. Gaussian processes are applied to model both emission spectrum and edge electron density profile, and the electron temperature to calculate all the rate coefficients is obtained from the JET high resolution Thomson scattering (HRTS) system. The posterior distributions of the edge electron density profile are explored via the numerical technique and the Markov chain Monte Carlo (MCMC) samplings. See the Appendix of F. Romanelli et al., Proceedings of the 25th IAEA Fusion Energy Conference 2014, Saint Petersburg, Russia.

  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. Density functional theory description of electronic properties of wurtzite zinc oxide

    Science.gov (United States)

    Franklin, L.; Ekuma, C. E.; Zhao, G. L.; Bagayoko, D.

    2013-05-01

    We report calculated, electronic properties of wurtzite zinc oxide (w-ZnO). We solved self-consistently the two inherently coupled equations of density functional theory (DFT), following the Bagayoko, Zhao, and Williams (BZW) method as enhanced by the work of Ekuma and Franklin (BZW-EF). We employed a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO). Most of the calculated, electronic properties of w-ZnO are in excellent agreement with experiment, including our zero temperature band gap of 3.39 eV and the electron effective mass. The doubly self-consistent approach utilized in this work points to the ability of theory to predict accurately key properties of semiconductors and hence to inform and to guide the design and fabrication of semiconductor-based devices.

  11. Electronic and structural properties of ultrathin tungsten nanowires and nanotubes by density functional theory calculation

    International Nuclear Information System (INIS)

    Sun, Shih-Jye; Lin, Ken-Huang; Li, Jia-Yun; Ju, Shin-Pon

    2014-01-01

    The simulated annealing basin-hopping method incorporating the penalty function was used to predict the lowest-energy structures for ultrathin tungsten nanowires and nanotubes of different sizes. These predicted structures indicate that tungsten one-dimensional structures at this small scale do not possess B.C.C. configuration as in bulk tungsten material. In order to analyze the relationship between multi-shell geometries and electronic transfer, the electronic and structural properties of tungsten wires and tubes including partial density of state and band structures which were determined and analyzed by quantum chemistry calculations. In addition, in order to understand the application feasibility of these nanowires and tubes on nano-devices such as field emitters or chemical catalysts, the electronic stability of these ultrathin tungsten nanowires was also investigated by density functional theory calculations.

  12. Multiconfiguration Pair-Density Functional Theory Is as Accurate as CASPT2 for Electronic Excitation.

    Science.gov (United States)

    Hoyer, Chad E; Ghosh, Soumen; Truhlar, Donald G; Gagliardi, Laura

    2016-02-04

    A correct description of electronically excited states is critical to the interpretation of visible-ultraviolet spectra, photochemical reactions, and excited-state charge-transfer processes in chemical systems. We have recently proposed a theory called multiconfiguration pair-density functional theory (MC-PDFT), which is based on a combination of multiconfiguration wave function theory and a new kind of density functional called an on-top density functional. Here, we show that MC-PDFT with a first-generation on-top density functional performs as well as CASPT2 for an organic chemistry database including valence, Rydberg, and charge-transfer excitations. The results are very encouraging for practical applications.

  13. Fuzzy electron density fragments in macromolecular quantum chemistry, combinatorial quantum chemistry, functional group analysis, and shape-activity relations.

    Science.gov (United States)

    Mezey, Paul G

    2014-09-16

    Conspectus Just as complete molecules have no boundaries and have "fuzzy" electron density clouds approaching zero density exponentially at large distances from the nearest nucleus, a physically justified choice for electron density fragments exhibits similar behavior. Whereas fuzzy electron densities, just as any fuzzy object, such as a thicker cloud on a foggy day, do not lend themselves to easy visualization, one may partially overcome this by using isocontours. Whereas a faithful representation of the complete fuzzy density would need infinitely many such isocontours, nevertheless, by choosing a selected few, one can still obtain a limited pictorial representation. Clearly, such images are of limited value, and one better relies on more complete mathematical representations, using, for example, density matrices of fuzzy fragment densities. A fuzzy density fragmentation can be obtained in an exactly additive way, using the output from any of the common quantum chemical computational techniques, such as Hartree-Fock, MP2, and various density functional approaches. Such "fuzzy" electron density fragments properly represented have proven to be useful in a rather wide range of applications, for example, (a) using them as additive building blocks leading to efficient linear scaling macromolecular quantum chemistry computational techniques, (b) the study of quantum chemical functional groups, (c) using approximate fuzzy fragment information as allowed by the holographic electron density theorem, (d) the study of correlations between local shape and activity, including through-bond and through-space components of interactions between parts of molecules and relations between local molecular shape and substituent effects, (e) using them as tools of density matrix extrapolation in conformational changes, (f) physically valid averaging and statistical distribution of several local electron densities of common stoichiometry, useful in electron density databank mining, for

  14. Density-functional theory based on the electron distribution on the energy coordinate

    Science.gov (United States)

    Takahashi, Hideaki

    2018-03-01

    We developed an electronic density functional theory utilizing a novel electron distribution n(ɛ) as a basic variable to compute ground state energy of a system. n(ɛ) is obtained by projecting the electron density n({\\boldsymbol{r}}) defined on the space coordinate {\\boldsymbol{r}} onto the energy coordinate ɛ specified with the external potential {\\upsilon }ext}({\\boldsymbol{r}}) of interest. It was demonstrated that the Kohn–Sham equation can also be formulated with the exchange-correlation functional E xc[n(ɛ)] that employs the density n(ɛ) as an argument. It turned out an exchange functional proposed in our preliminary development suffices to describe properly the potential energies of several types of chemical bonds with comparable accuracies to the corresponding functional based on local density approximation. As a remarkable feature of the distribution n(ɛ) it inherently involves the spatially non-local information of the exchange hole at the bond dissociation limit in contrast to conventional approximate functionals. By taking advantage of this property we also developed a prototype of the static correlation functional E sc including no empirical parameters, which showed marked improvements in describing the dissociations of covalent bonds in {{{H}}}2,{{{C}}}2{{{H}}}4 and {CH}}4 molecules.

  15. Analysis of the Effect of Electron Density Perturbations Generated by Gravity Waves on HF Communication Links

    Science.gov (United States)

    Fagre, M.; Elias, A. G.; Chum, J.; Cabrera, M. A.

    2017-12-01

    In the present work, ray tracing of high frequency (HF) signals in ionospheric disturbed conditions is analyzed, particularly in the presence of electron density perturbations generated by gravity waves (GWs). The three-dimensional numerical ray tracing code by Jones and Stephenson, based on Hamilton's equations, which is commonly used to study radio propagation through the ionosphere, is used. An electron density perturbation model is implemented to this code based upon the consideration of atmospheric GWs generated at a height of 150 km in the thermosphere and propagating up into the ionosphere. The motion of the neutral gas at these altitudes induces disturbances in the background plasma which affects HF signals propagation. To obtain a realistic model of GWs in order to analyze the propagation and dispersion characteristics, a GW ray tracing method with kinematic viscosity and thermal diffusivity was applied. The IRI-2012, HWM14 and NRLMSISE-00 models were incorporated to assess electron density, wind velocities, neutral temperature and total mass density needed for the ray tracing codes. Preliminary results of gravity wave effects on ground range and reflection height are presented for low-mid latitude ionosphere.

  16. 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).

  17. High frequency electric field spikes formed by electron beam-plasma interaction in plasma density gradients

    International Nuclear Information System (INIS)

    Gunell, H.; Loefgren, T.

    1997-02-01

    In the electron beam-plasma interaction at an electric double layer the beam density is much higher than in the classical beam-plasma experiments. The wave propagation takes place along the density gradient, that is present at the high potential side of the double layer. Such a case is studied experimentally by injecting the electron beam from a plane cathode, without any grids suppressing the gradient, and by particle simulations. The high frequency field concentrates in a sharp 'spike' with a half width of the order of one wavelength. The spike is found to be a standing wave surrounded by regions dominated by propagating waves. It forms at a position where its frequency is close to the local plasma frequency. The spike forms also when the electric field is well below the threshold for modulational instability, and long before a density cavity is formed in the simulations. Particle simulations reveal that, at the spike, there is a backward travelling wave that, when it is strongly damped, accelerates electrons back towards the cathode. In a simulation of a homogeneous plasma without the density gradient no spike is seen, and the wave is purely travelling instead of standing. 9 refs

  18. Electric field spikes formed by electron beam endash plasma interaction in plasma density gradients

    International Nuclear Information System (INIS)

    Gunell, H.; Loefgren, T.

    1997-01-01

    In the electron beam endash plasma interaction at an electric double layer the beam density is much higher than in the classical beam endash plasma experiments. The wave propagation takes place along the density gradient that is present at the high potential side of the double layer. Such a case is studied experimentally by injecting the electron beam from a plane cathode, without any grids suppressing the gradient, and by particle simulations. The high frequency field concentrates in a sharp open-quotes spikeclose quotes with a half width of the order of one wavelength. The spike is found to be a standing wave surrounded by regions dominated by propagating waves. It forms at a position where its frequency is close to the local plasma frequency. The spike forms also when the electric field is well below the threshold for modulational instability, and long before a density cavity is formed in the simulations. Particle simulations reveal that, at the spike, there is a backward traveling wave that, when it is strongly damped, accelerates electrons back towards the cathode. In a simulation of a homogeneous plasma without the density gradient no spike is seen, and the wave is purely travelling instead of standing. copyright 1997 American Institute of Physics

  19. Real-time electron density measurements from Cotton-Mouton effect in JET machine

    International Nuclear Information System (INIS)

    Brombin, M.; Boboc, A.; Zabeo, L.; Murari, A.

    2008-01-01

    Real-time density profile measurements are essential for advanced fusion tokamak operation and interferometry is a proven method for this task. Nevertheless, as a consequence of edge localized modes, pellet injections, fast density increases, or disruptions, the interferometer is subject to fringe jumps, which produce loss of the signal preventing reliable use of the measured density in a real-time feedback controller. An alternative method to measure the density is polarimetry based on the Cotton-Mouton effect, which is proportional to the line-integrated electron density. A new analysis approach has been implemented and tested to verify the reliability of the Cotton-Mouton measurements for a wide range of plasma parameters and to compare the density evaluated from polarimetry with that from interferometry. The density measurements based on polarimetry are going to be integrated in the real-time control system of JET since the difference with the interferometry is within one fringe for more than 90% of the cases.

  20. Experimental Investigation of m=1 Diocotron Mode Growth at Low Electron Densities

    International Nuclear Information System (INIS)

    Paul, Stephen F.; Morrison, Kyle; Davidson, Ronald C.

    2003-01-01

    Previous experiments on the Electron Diffusion Gauge showed that the diocotron mode damping increases with higher neutral gas filling pressure. Yet the energy dissipated from a rotating plasma by collisions with neutrals is predicted to excite the mode. To resolve this, experiments have been conducted to examine the coupling between expansion and the m=1 diocotron mode. Results from recent experiments have shown interesting phenomena: (1) The degree and sensitivity of mode growth is observed to be strongly dependent on filament conditions. Mode growth rates of nearly 20 sec -1 have been observed even with negligible resistive drive. Specifically, at low filament bias voltages (and correspondingly low electron densities ∼1-2 x 10 7 electrons/cm), the mode growth is very sensitive to the heating voltage across the filament, even though changes in filament heating voltage barely affect the plasma expansion, the plasma density profile, the filament emission, or the resulting electron density. (2) At low neutral gas pressure ( -9 Torr), the diocotron mode growth rate increases with neutral pressure. However, the growth rate is several orders of magnitude larger than theoretical predictions

  1. 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

  2. Evaluation of critical current density and residual resistance ratio limits in powder in tube Nb3Sn conductors

    CERN Document Server

    Segal, Christopher; Sung, Zu Hawn; Lee, Peter J; Sailer, Bernd; Thoener, Manfred; Schlenga, Klaud; Ballarino, Amalia; Bottura, Luca; Bordini, Bernardo; Scheuerlein, Christian; Larnalestier, David C

    2016-01-01

    High critical current density ( Jc) Nb3Sn A15 multifilamentary wires require a large volume fraction of small grain (SG), superconducting A15 phase, as well as Cu stabilizer with high Residual Resistance Ratio (RRR) to provide electromagnetic stabilization and protection. In powder-in-tube (PIT) wires the unreacted Nb7.5 wt%Ta outer layer of the tubular filaments acts as a diffusion barrier and protects the interfilamentary Cu stabilizer from Sn contamination. A high RRR requirement generally imposes a restricted A15 reaction heat treatment to prevent localized full reaction of the filament that could allow Sn to reach the Cu. In this study we investigate recent high quality PIT wires that achieve a Jc (12 T, 4.2 K) up to ∼2500 A mm−2 and find that the minimum diffusion barrier thickness decreases as the filament aspect ratio increases from ∼1 in the inner rings of filaments to 1.3 in the outer filament rings. We found that just 2–3 diffusion barrier breaches can degrade RRR from 300 to 150 or less. U...

  3. DAMQT: A package for the analysis of electron density in molecules

    Science.gov (United States)

    López, Rafael; Rico, Jaime Fernández; Ramírez, Guillermo; Ema, Ignacio; Zorrilla, David

    2009-09-01

    DAMQT is a package for the analysis of the electron density in molecules and the fast computation of the density, density deformations, electrostatic potential and field, and Hellmann-Feynman forces. The method is based on the partition of the electron density into atomic fragments by means of a least deformation criterion. Each atomic fragment of the density is expanded in regular spherical harmonics times radial factors, which are piecewise represented in terms of analytical functions. This representation is used for the fast evaluation of the electrostatic potential and field generated by the electron density and nuclei, as well as for the computation of the Hellmann-Feynman forces on the nuclei. An analysis of the atomic and molecular deformations of the density can be also carried out, yielding a picture that connects with several concepts of the empirical structural chemistry. Program summaryProgram title: DAMQT1.0 Catalogue identifier: AEDL_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDL_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPLv3 No. of lines in distributed program, including test data, etc.: 278 356 No. of bytes in distributed program, including test data, etc.: 31 065 317 Distribution format: tar.gz Programming language: Fortran90 and C++ Computer: Any Operating system: Linux, Windows (Xp, Vista) RAM: 190 Mbytes Classification: 16.1 External routines: Trolltech's Qt (4.3 or higher) ( http://www.qtsoftware.com/products), OpenGL (1.1 or higher) ( http://www.opengl.org/), GLUT 3.7 ( http://www.opengl.org/resources/libraries/glut/). Nature of problem: Analysis of the molecular electron density and density deformations, including fast evaluation of electrostatic potential, electric field and Hellmann-Feynman forces on nuclei. Solution method: The method of Deformed Atoms in Molecules, reported elsewhere [1], is used for partitioning the molecular electron density

  4. Recent measurements of electron density profiles of plasmas in PLADIS I, a plasma disruption simulator

    International Nuclear Information System (INIS)

    Bradley, J. III; Sharp, G.; Gahl, J.M. Kuznetsov, V.; Rockett, P.; Hunter, J.

    1995-01-01

    Tokamak disruption simulation experiments are being conducted at the University of New Mexico (UNM) using the PLADIS I plasma gun system. PLADIS I is a high power, high energy coaxial plasma gun configured to produce an intense plasma beam. First wall candidate materials are placed in the beam path to determine their response under disruption relevant energy densities. An optically thick vapor shield plasma has been observed to form above the target surface in PLADIS I. Various diagnostics have been used to determine the characteristics of the incident plasma and the vapor shielding plasma. The cross sectional area of the incident plasma beam is a critical characteristic, as it is used in the calculation of the incident plasma energy density. Recently, a HeNe interferometer in the Mach-Zehnder configuration has been constructed and used to probe the electron density of the incident plasma beam and vapor shield plasma. The object beam of the interferometer is scanned across the plasma beam on successive shots, yielding line integrals of beam density on different chords through the plasma. Data from the interferometer is used to determine the electron density profile of the incident plasma beam as a function of beam radius. This data is then used to calculate the effective beam area. Estimates. of beam area, obtained from other diagnostics such as damage targets, calorimeter arrays and off-axis measurements of surface pressure, will be compared with data from the interferometer to obtain a better estimate of the beam cross sectional area

  5. First principle local density approximation description of the electronic properties of ferroelectric sodium nitrite

    Energy Technology Data Exchange (ETDEWEB)

    Ekuma, C.E., E-mail: panaceamee@yahoo.com [Department of Physics and Astronomy and Center for Computation and Technology, Louisiana State University (LSU) Baton Rouge, Louisiana 70803 (United States); Jarrell, M.; Moreno, J. [Department of Physics and Astronomy and Center for Computation and Technology, Louisiana State University (LSU) Baton Rouge, Louisiana 70803 (United States); Franklin, L.; Zhao, G.L.; Wang, J.T.; Bagayoko, D. [Department of Physics, Southern University and A and M College in Baton Rouge (SUBR) Baton Rouge, Louisiana 70813 (United States)

    2012-10-15

    The electronic structure of the ferroelectric crystal, NaNO{sub 2}, is studied by means of first-principles, local density calculations. Our ab-initio, non-relativistic calculations employed a local density functional approximation (LDA) potential and the linear combination of atomic orbitals (LCAO). Following the Bagayoko, Zhao, Williams, method, as enhanced by Ekuma and Franklin (BZW-EF), we solved self-consistently both the Kohn-Sham equation and the equation giving the ground state charge density in terms of the wave functions of the occupied states. We found an indirect band gap of 2.83 eV, from W to R. Our calculated direct gaps are 2.90, 2.98, 3.02, 3.22, and 3.51 eV at R, W, X, {Gamma}, and T, respectively. The band structure and density of states show high localization, typical of a molecular solid. The partial density of states shows that the valence bands are formed only by complex anionic states. These results are in excellent agreement with experiment. So are the calculated densities of states. Our calculated electron effective masses of 1.18, 0.63, and 0.73 m{sub o} in the {Gamma}-X, {Gamma}-R, and {Gamma}-W directions, respectively, show the highly anisotropic nature of this material. -- Highlights: Black-Right-Pointing-Pointer Ferro-NaNO{sub 2} has been studied using the BZW-EF method. Black-Right-Pointing-Pointer For the valence states, polarization has primacy over spherical symmetry. Black-Right-Pointing-Pointer The optimal basis set is verified to be complete for the ground state of NaNO{sub 2}. Black-Right-Pointing-Pointer Computed electronic and related properties are in agreement with experiment.

  6. Biofiltration of composting gases using different municipal solid waste-pruning residue composts: monitoring by using an electronic nose.

    Science.gov (United States)

    López, R; Cabeza, I O; Giráldez, I; Díaz, M J

    2011-09-01

    The concentration of volatile organic compounds (VOCs) during the composting of kitchen waste and pruning residues, and the abatement of VOCs by different compost biofilters was studied. VOCs removal efficiencies greater than 90% were obtained using composts of municipal solid waste (MSW) or MSW-pruning residue as biofilter material. An electronic nose identified qualitative differences among the biofilter output gases at very low concentrations of VOCs. These differences were related to compost constituents, compost particle size (2-7 or 7-20mm), and a combination of both factors. The total concentration of VOCs determined by a photoionization analyser and inferred from electronic nose data sets were correlated over an ample range of concentrations of VOCs, showing that these techniques could be specially adapted for the monitoring of these processes. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Comparison of Residual Stresses in Inconel 718 Simple Parts Made by Electron Beam Melting and Direct Laser Metal Sintering

    Science.gov (United States)

    Sochalski-Kolbus, L. M.; Payzant, E. A.; Cornwell, P. A.; Watkins, T. R.; Babu, S. S.; Dehoff, R. R.; Lorenz, M.; Ovchinnikova, O.; Duty, C.

    2015-03-01

    Residual stress profiles were mapped using neutron diffraction in two simple prism builds of Inconel 718: one fabricated with electron beam melting (EBM) and the other with direct laser metal sintering. Spatially indexed stress-free cubes were obtained by electrical discharge machining (EDM) equivalent prisms of similar shape. The (311) interplanar spacings from the EDM sectioned sample were compared to the interplanar spacings calculated to fulfill stress and moment balance. We have shown that applying stress and moment balance is a necessary supplement to the measurements for the stress-free cubes with respect to accurate stress calculations in additively manufactured components. In addition, our work has shown that residual stresses in electron beam melted parts are much smaller than that of direct laser metal sintered parts most likely due to the powder preheating step in the EBM process.

  8. 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.

  9. Application of modern electronic balances to measure densities of solids and liquids by a hydrostatic method

    International Nuclear Information System (INIS)

    Prokic, D.

    1983-01-01

    Modern balances (analytical and microanalytical) operate on the electromagnetic principle, i.e. without arms and without the use of weights. Accordingly, this paper presents a method dealing with the application of modern electronic single-plan balances of the accuracy class I to measurements of the density of solids and liquids by a hydrostatic method. The proposed method has some advantages compared with conventional ones for density measurements with corresponding mechanical balances, such as for instance: improved measurement accuracy, automatic establishment of balance equilibrium, ready read-out of measurement results, and the possibility of computer processing and printing thereof. (orig.) [de

  10. 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.

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

    International Nuclear Information System (INIS)

    Thiele, Mark

    2009-01-01

    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.)

  12. 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.)

  13. Fast electron current density profile and diffusion studies during LHCD in PBX-M

    Energy Technology Data Exchange (ETDEWEB)

    Jones, S.E.; Kesner, J.; Luckhardt, S.; Paoletti, F. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center; von Goeler, S.; Bernabei, S.; Kaita, R. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Rimini, F. [JET Joint Undertaking, Abingdon (United Kingdom)

    1993-08-01

    Successful current profile control experiments using lower hybrid current drive (LCHD) clearly require knowledge of (1) the location of the driven fast electrons and (2) the ability to maintain that location from spreading due to radial diffusion. These issues can be addressed by examining the data from the hard x-ray camera on PBX-M, a unique diagnostic producing two-dimensional, time resolved tangential images of fast electron bremsstrahlung. Using modeling, these line-of-sight images are inverted to extract a radial fast electron current density profile. We note that ``hollow`` profiles have been observed, indicative of off-axis current drive. These profiles can then be used to calculate an upper bound for an effective fast electron diffusion constant: assuming an extremely radially narrow lower hybrid absorption profile and a transport model based on Rax and Moreau, a model fast electron current density profile is calculated and compared to the experimentally derived profile. The model diffusion constant is adjusted until a good match is found. Applied to steady-state quiescent modes on PBX-M, we obtain an upper limit for an effective diffusion constant of about D*=1.1 m{sup 2}/sec.

  14. The effect of energetic electron precipitation on the nitric oxide density in the lower thermosphere

    International Nuclear Information System (INIS)

    Saetre, Camilla

    2006-12-01

    The objective of this thesis has been the study of the chemical effects of the electron precipitation in the upper atmosphere, and mainly the increase of thermospheric nitric oxide (NO). NO plays an important role in the temperature balance for the mesosphere and thermosphere.In this project auroral electron precipitation data, derived from the Polar Ionospheric X-ray Imaging Experiment (PIXIE) and the Ultraviolet Imager (UVI) on board the Polar satellite, have been used together with NO density measurements from the Student Nitric Oxide Explorer (SNOE)

  15. Positron study of electron momentum density and Fermi surface in titanium and zirconium

    International Nuclear Information System (INIS)

    Suzuki, Ryoichi; Osawa, Makoto; Tanigawa, Shoichiro; Matsumoto, Makoto; Shiotani, Nobuhiro.

    1989-01-01

    The three dimensional electron-positron momentum densities have been obtained on Ti and Zr from measurements of two dimensional angular correlation of positron annihilation radiation followed by an image reconstruction technique based on direct Fourier transformation. Augmented-plane wave band structure calculations have been carried out and the results are compared with the experiments. Agreement between the experiment and the theory leads to a conclusion that both Ti and Zr have electron surface sheets which are centered at H and hole surface sheets which are running along the Γ-A axis. (author)

  16. The improved DGR analytical model of electron density height profile and total electron content in the ionosphere

    OpenAIRE

    Radicella, S. M.; Zhang, M. L.

    1995-01-01

    Tests of the analytical model of the electron density profile originally proposed by G, Di Giovanni and S.M. Radicella (DGR model) have shown the need to introduce improvements in order to obtain a model able to reproduce the ionosphere in a larger spectrum of geophysical and time conditions. The present paper reviews the steps toward such progress and presents the final formulation of the model. It gives also a brief re- view of tests of the improved model done by different authors.

  17. Subshell fitting of relativistic atomic core electron densities for use in QTAIM analyses of ECP-based wave functions.

    Science.gov (United States)

    Keith, Todd A; Frisch, Michael J

    2011-11-17

    Scalar-relativistic, all-electron density functional theory (DFT) calculations were done for free, neutral atoms of all elements of the periodic table using the universal Gaussian basis set. Each core, closed-subshell contribution to a total atomic electron density distribution was separately fitted to a spherical electron density function: a linear combination of s-type Gaussian functions. The resulting core subshell electron densities are useful for systematically and compactly approximating total core electron densities of atoms in molecules, for any atomic core defined in terms of closed subshells. When used to augment the electron density from a wave function based on a calculation using effective core potentials (ECPs) in the Hamiltonian, the atomic core electron densities are sufficient to restore the otherwise-absent electron density maxima at the nuclear positions and eliminate spurious critical points in the neighborhood of the atom, thus enabling quantum theory of atoms in molecules (QTAIM) analyses to be done in the neighborhoods of atoms for which ECPs were used. Comparison of results from QTAIM analyses with all-electron, relativistic and nonrelativistic molecular wave functions validates the use of the atomic core electron densities for augmenting electron densities from ECP-based wave functions. For an atom in a molecule for which a small-core or medium-core ECPs is used, simply representing the core using a simplistic, tightly localized electron density function is actually sufficient to obtain a correct electron density topology and perform QTAIM analyses to obtain at least semiquantitatively meaningful results, but this is often not true when a large-core ECP is used. Comparison of QTAIM results from augmenting ECP-based molecular wave functions with the realistic atomic core electron densities presented here versus augmenting with the limiting case of tight core densities may be useful for diagnosing the reliability of large-core ECP models in

  18. Determination of Bulk Residual Stresses in Electron Beam Additive-Manufactured Aluminum

    Science.gov (United States)

    Brice, Craig A.; Hofmeister, William H.

    2013-11-01

    Additive-manufactured aluminum alloy deposits were analyzed using neutron diffraction to characterize the effect of intermediate stress relief anneal heat treatment on bulk residual stresses in the final part. Based on measured interplanar spacing, stresses were calculated at various locations along a single bead, stacked wall deposit. A comparison between an uninterrupted deposited wall and an interrupted, stress-relieved, and annealed deposited wall showed a measureable reduction in residual stress magnitude at the interface with a corresponding shift in stress character into the deposit. This shift changes the interface stresses from purely compressive to partially tensile. The residual stress profile varied along the length of the deposit, and the heat-treatment procedure reduced the overall magnitude of the stress at the interface by 10 through 25 MPa. These results are interpreted in terms of thermal gradients inherent to the process and compared with prior residual stress-characterization studies in additive-manufactured metallic structures.

  19. Conceptual density functional theory for electron transfer and transport in mesoscopic systems.

    Science.gov (United States)

    Bueno, Paulo R; Miranda, David A

    2017-02-22

    Molecular and supramolecular systems are essentially mesoscopic in character. The electron self-exchange, in the case of energy fluctuations, or electron transfer/transport, in the case of the presence of an externally driven electrochemical potential, between mesoscopic sites is energetically driven in such a manner where the electrochemical capacitance (C [small mu, Greek, macron] ) is fundamental. Thus, the electron transfer/transport through channels connecting two distinct energetic (ΔE [small mu, Greek, macron] ) and spatially separated mesoscopic sites is capacitively modulated. Remarkably, the relationship between the quantum conductance (G) and the standard electrochemical rate constant (k r ), which is indispensable to understanding the physical and chemical characteristics governing electron exchange in molecular scale systems, was revealed to be related to C [small mu, Greek, macron] , that is, C [small mu, Greek, macron] = G/k r . Accordingly, C [small mu, Greek, macron] is the proportional missing term that controls the electron transfer/transport in mesoscopic systems in a wide-range, and equally it can be understood from first principles density functional quantum mechanical approaches. Indeed the differences in energy between states is calculated (or experimentally accessed) throughout the electrochemical capacitance as ΔE [small mu, Greek, macron] = β/C [small mu, Greek, macron] , and thus constitutes the driving force for G and/or k r , where β is only a proportional constant that includes the square of the unit electron charge times the square of the number of electron particles interchanged.

  20. 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.

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

    Science.gov (United States)

    Tierno, S. P.; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L.

    2016-01-01

    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.

  2. 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.

  3. Distributions of the ion temperature, ion pressure, and electron density over the current sheet surface

    Energy Technology Data Exchange (ETDEWEB)

    Kyrie, N. P., E-mail: kyrie@fpl.gpi.ru; Markov, V. S., E-mail: natalya.kyrie@yandex.ru; Frank, A. G.; Vasilkov, D. G.; Voronova, E. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

    2016-06-15

    The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampère force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampère force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampère force is counterbalanced by the pressure gradient.

  4. Measurements of electron density and temperature profiles in a gas blanket experiment

    International Nuclear Information System (INIS)

    Kuthy, A.

    1979-02-01

    Radial profiles of electron density, temperature and H sub(β) intensity are presented for the rotating plasma device F-1. The hydrogen filling pressure, the average magnetic field strength at the midplane, and the power input to the discharge have been varied in the ranges 10-100 mTorr, 0.25-0.5 Tesla, and 0.1 to 1.5 MW, respectively. These experiments have been performed with the main purpose of studying the gas blanket (cold-mantle) state of the plasma. It is shown, that a simple spectroscopic method can be used to derive the radial distribution of the electron temperature in such plasmas. The observed peak temperatures and densities are in agreement with earlier theoretical estimates. (author)

  5. 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

    inadequate when the molecule has near-degeneracies and/or low-lying double-excited states. To address these issues we have recently proposed multiconfiguration short-range density-functional theory-MC-srDFT-as a new tool in the toolbox. While initial applications for systems with multireference character......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......-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...

  6. Interstellar electron density fluctuations due to cosmic-ray acceleration at supernova remnant shock waves

    International Nuclear Information System (INIS)

    Max, C.E.; Zachary, A.; Arons, J.

    1988-01-01

    We have performed computer simulations to investigate whether sizeable electron density fluctuations might be produced in the process of cosmic-ray acceleration at supernova remnant shock waves. The hypothesis is the following: Cosmic-ray acceleration via a Fermi I mechanism leads to large-amplitude Alfven waves upstream of a supernova remnant shock wave. If the Alfven waves reach a large enough amplitude, they can drive sound waves in the interstellar medium. The fluctuations in the electron density due to these sound waves will then contribute to the observed interstellar scintillation. Our simulations suggest that this mechanism may be a plausible one. Issues remaining to be addressed include the resulting filling factor, and the integrated strength C 2 /sub n/ to be expected for the turbulence

  7. 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.

  8. Neutron Diffraction Measurement of Residual Stresses, Dislocation Density and Texture in Zr-bonded U-10Mo ''Mini'' Fuel Foils and Plates

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Donald W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Okuniewski, M. A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sisneros, Thomas A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Clausen, Bjorn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moore, G. A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Balogh, L [Queen' s Univ., Kingston, ON (Canada)

    2014-08-07

    Aluminum clad monolithic uranium 10 weight percent molybdenum (U-10Mo) fuel plates are being considered for conversion of several research and test nuclear reactors from high-enriched to low-enriched uranium fuel due to the inherently high density of fissile material. Comprehensive neutron diffraction measurements of the evolution of the textures, residual phase stresses, and dislocation densities in the individual phases of the mini-foils throughout several processing steps and following hot-isostatic pressing to the Al cladding, have been completed. Recovery and recrystallization of the bare U-10Mo fuel foil, as indicated by the dislocation density and texture, are observed depending on the state of the material prior to annealing and the duration and temperature of the annealing process. In general, the HIP procedure significantly reduces the dislocation density, but the final state of the clad plate, both texture and dislocation density, depends strongly on the final processing step of the fuel foil. In contrast, the residual stresses in the clad fuel plate do not depend strongly on the final processing step of the bare foil prior to HIP bonding. Rather, the residual stresses are dominated by the thermal expansion mismatch of the constituent materials of the fuel plate.

  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...

  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. Study of the electron density variability at fixed heights over San Juan and Tucuman

    International Nuclear Information System (INIS)

    Ezquer, R.G.; Mosert, M.; Radicella, S.M.; Jadur, C.A.

    2002-01-01

    The electron density (N) variability at fixed heights in the bottomside N profile over two Argentinean stations is presented. In this first study different solar conditions and some seasons are considered. The NHPC and CARP programs were used. The results show that, in general, for nighttime conditions the variability increases above 250 km. By noon the variability decreases with increasing the solar activity. At fixed heights, in general, the variability is larger by night than by day above 220 km. (author)

  12. Characteristics and sources of the electron density irregularities in the mid latitude E and Fregions

    Science.gov (United States)

    2017-05-10

    such irregularities, to understand the onset conditions of such irregularities, and to predict or avoid the impact of these irregularities on society ...impact of these irregularities on society . Such electron density irregularities in the ionosphere exhibit an anisotropic distribution with respect to...with QP echoes, mapped upward along the geomagnetic field, and played an important role in determining the structures of the whole ionospheric E region

  13. Application of seamless vertical profiles for use in the topside electron density modeling

    Czech Academy of Sciences Publication Activity Database

    Třísková, Ludmila; Galkin, I.; Truhlík, Vladimír; Reinisch, B. W.

    2007-01-01

    Roč. 39, č. 5 (2007), s. 774-778 ISSN 0273-1177 R&D Projects: GA AV ČR IAA300420603; GA MŠk ME 651 Grant - others:US National Science Foundation(US) 0245457 Institutional research plan: CEZ:AV0Z30420517 Keywords : Topside ionosphere * Electron density * Ionospheric model * Altitude profile Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.774, year: 2007

  14. 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 ...

  15. Structural and electronic properties of ZnO nanotubes from density functional calculations

    International Nuclear Information System (INIS)

    Xu Hu; Zhang, R Q; Zhang Xiaohong; Rosa, A L; Frauenheim, Th

    2007-01-01

    The structural and electronic properties of armchair and zigzag ZnO nanotubes were studied using density functional theory with the generalized gradient approximation. It was found that the strain energy required for rolling a ZnO graphitic sheet into a tube is lower than those for BN and GaN nanotubes. Both the armchair and zigzag ZnO nanotubes were found to be direct gap semiconductors with the gaps decreasing with the diameter increase

  16. Density induced crossover of electron mobilities in fluid C3 hydrocarbons; liquid phase behavior

    International Nuclear Information System (INIS)

    Gee, N.; Freeman, G.R.

    1980-01-01

    At n = 2 x 10 20 mol/cm 3 in the saturated vapors, the density normalized mobility (μn) of electrons equalled 2.4 x 10 23 mol/cmVs in cyclopropane, 1.5 x 10 23 in propane and 5.4 x 10 22 in propene. In cyclopropane and propene μn decreased due to quasilocalization at n > 4 x 10 20 mol/cm 3 . In propane quasilocalization occurred at n > 8 x 10 20 mol/cm 3 . The more extensive quasilocalization in cyclopropane caused mobilities to be lower than those in propane at the same density when the densities were greater than 1.3 x 10 21 mol/cm 3 . In propylene, μn remained below those in the other compounds at all gas densities. In the liquid phase the mobilities were affected more by the changes of temperature than by those of density. The mobilities at a given temperature decreased in the order propane > propene > cyclopropane. It is curious that the electron traps are deeper in cyclopropane than in propene. The energies of both thermal and optical excitation of solvated electrons may be expressed by equations of the form E 0 = E(0) - aT over considerable ranges of temperature T. The thermal value of a/E(0) is 1.7 x 10 -3 K -1 in many hydrocarbons, estimated from the mobilities. The equivalent ratio of the optical parameters also equals 1.7 x 10 -3 K -1 in ethers and in ammonia. (author)

  17. A study of fast electron energy transport in relativistically intense laser-plasma interactions with large density scalelengths

    Energy Technology Data Exchange (ETDEWEB)

    Scott, R. H. H.; Norreys, P. A. [Department of Physics, Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom); Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxford OX11 0QX (United Kingdom); Perez, F.; Baton, S. D. [LULI, Ecole Polytechnique, UMR 7605, CNRS/CEA/UPMC, Route de Saclay, 91128 Palaiseau (France); Santos, J. J.; Nicolai, Ph.; Hulin, S. [Univ. Bordeaux/CNRS/CEA, CELIA, UMR 5107, 33405 Talence (France); Ridgers, C. P. [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Department of Physics, Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom); Davies, J. R. [GoLP, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Lancaster, K. L.; Trines, R. M. G. M. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxford OX11 0QX (United Kingdom); Bell, A. R.; Tzoufras, M. [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxford OX11 0QX (United Kingdom); Rose, S. J. [Department of Physics, Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom)

    2012-05-15

    A systematic experimental and computational investigation of the effects of three well characterized density scalelengths on fast electron energy transport in ultra-intense laser-solid interactions has been performed. Experimental evidence is presented which shows that, when the density scalelength is sufficiently large, the fast electron beam entering the solid-density plasma is best described by two distinct populations: those accelerated within the coronal plasma (the fast electron pre-beam) and those accelerated near or at the critical density surface (the fast electron main-beam). The former has considerably lower divergence and higher temperature than that of the main-beam with a half-angle of {approx}20 Degree-Sign . It contains up to 30% of the total fast electron energy absorbed into the target. The number, kinetic energy, and total energy of the fast electrons in the pre-beam are increased by an increase in density scalelength. With larger density scalelengths, the fast electrons heat a smaller cross sectional area of the target, causing the thinnest targets to reach significantly higher rear surface temperatures. Modelling indicates that the enhanced fast electron pre-beam associated with the large density scalelength interaction generates a magnetic field within the target of sufficient magnitude to partially collimate the subsequent, more divergent, fast electron main-beam.

  18. Carrier density independent scattering rate in SrTiO3-based electron liquids.

    Science.gov (United States)

    Mikheev, Evgeny; Raghavan, Santosh; Zhang, Jack Y; Marshall, Patrick B; Kajdos, Adam P; Balents, Leon; Stemmer, Susanne

    2016-02-10

    We examine the carrier density dependence of the scattering rate in two- and three-dimensional electron liquids in SrTiO3 in the regime where it scales with T(n) (T is the temperature and n ≤ 2) in the cases when it is varied by electrostatic control and chemical doping, respectively. It is shown that the scattering rate is independent of the carrier density. This is contrary to the expectations from Landau Fermi liquid theory, where the scattering rate scales inversely with the Fermi energy (EF). We discuss that the behavior is very similar to systems traditionally identified as non-Fermi liquids (n density-independent scattering rates have been observed. The results indicate that the applicability of Fermi liquid theory should be questioned for a much broader range of correlated materials and point to the need for a unified theory.

  19. Electron density modification in ionospheric E layer by inserting fine dust particles

    International Nuclear Information System (INIS)

    Misra, Shikha; Mishra, S. K.

    2015-01-01

    In this paper, we have developed the kinetics of E-region ionospheric plasma comprising of fine dust grains and shown that the electron density in E-layer can purposely be reduced/enhanced up to desired level by inserting fine dust particles of appropriate physical/material properties; this may certainly be promising for preferred rf-signal processing through these layers. The analytical formulation is based on average charge theory and includes the number and energy balance of the plasma constituents along with charge balance over dust particles. The effect of varying number density, work function, and photo-efficiency of dust particles on ionospheric plasma density at different altitude in E-layer has been critically examined and presented graphically

  20. A high density two-dimensional electron gas in an oxide heterostructure on Si (001)

    Energy Technology Data Exchange (ETDEWEB)

    Jin, E. N.; Kornblum, L.; Kumah, D. P.; Zou, K.; Walker, F. J. [Center for Research on Interface Structures and Phenomena and Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States); Broadbridge, C. C. [Center for Research on Interface Structures and Phenomena and Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States); Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, Connecticut 06515 (United States); Ngai, J. H. [Department of Physics, The University of Texas at Arlington, Arlington, Texas 76019 (United States); Ahn, C. H. [Center for Research on Interface Structures and Phenomena and Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511 (United States)

    2014-11-01

    We present the growth and characterization of layered heterostructures comprised of LaTiO{sub 3} and SrTiO{sub 3} epitaxially grown on Si (001). Magnetotransport measurements show that the sheet carrier densities of the heterostructures scale with the number of LaTiO{sub 3}/SrTiO{sub 3} interfaces, consistent with the presence of an interfacial 2-dimensional electron gas (2DEG) at each interface. Sheet carrier densities of 8.9 × 10{sup 14} cm{sup −2} per interface are observed. Integration of such high density oxide 2DEGs on silicon provides a bridge between the exceptional properties and functionalities of oxide 2DEGs and microelectronic technologies.

  1. Electron density analysis of 1-butyl-3-methylimidazolium chloride ionic liquid.

    Science.gov (United States)

    del Olmo, Lourdes; Morera-Boado, Cercis; López, Rafael; García de la Vega, José M

    2014-06-01

    An analysis of the electron density of different conformers of the 1-butyl-3-methylimidazolium chloride (bmimCl) ionic liquid by using DFT through the BVP86 density functional has been obtained within the framework of Bader's atom in molecules (AIM), localized orbital locator (LOL), natural bond orbital (NBO), and deformed atoms in molecules (DAM). We also present an analysis of the reduced density gradients that deliver the non-covalent interaction regions and allow to understand the nature of intermolecular interactions. The most polar conformer can be characterized as ionic by AIM, LOL, and DAM methods while the most stable and the least polar shows shared-type interactions. The NBO method allows to comprehend what causes the stabilization of the most stable conformer based on analysis of the second-order perturbative energy and the charge transferred among the natural orbitals involved in the interaction.

  2. Electronic properties and momentum densities of tin chalcogenides: Validation of PBEsol exchange-correlation potential

    Energy Technology Data Exchange (ETDEWEB)

    Ahuja, B.L., E-mail: blahuja@yahoo.ik [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Raykar, Veera; Joshi, Ritu [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Tiwari, Shailja [Department of Physics, Govt. Women Engineering College, Ajmer 305001, Rajasthan (India); Talreja, Sonal [Department of Computer Science, M.L. Sukhadia University, Udaipur 313001 (India); Choudhary, Gopal [Department of Physics, Techno India NJR Institute of Technology, Udaipur 313001, Rajasthan (India)

    2015-05-15

    We report Compton profiles of SnS and SnTe at a momentum resolution of 0.34 a.u. using a 20 Ci {sup 137}Cs Compton spectrometer. To compare our experimental data, we have also computed the theoretical Compton profiles using density functional theory within linear combination of atomic orbitals (LCAO) method. To interpret the relative nature of bonding in these compounds, we have scaled the experimental and theoretical Compton profiles on equal-valence-electron-density (EVED). On the basis of EVED profiles, it is seen that SnTe shows more covalent character than SnS. To rectify the substantial disagreement between experimental and theoretical band gaps, we have also presented the energy bands and density of states of both the compounds using full-potential linearized augmented plane wave method (FP-LAPW) including spin–orbit interaction within the PBEsol exchange-correlation potential.

  3. Electronic properties and momentum densities of tin chalcogenides: Validation of PBEsol exchange-correlation potential

    Science.gov (United States)

    Ahuja, B. L.; Raykar, Veera; Joshi, Ritu; Tiwari, Shailja; Talreja, Sonal; Choudhary, Gopal

    2015-05-01

    We report Compton profiles of SnS and SnTe at a momentum resolution of 0.34 a.u. using a 20 Ci 137Cs Compton spectrometer. To compare our experimental data, we have also computed the theoretical Compton profiles using density functional theory within linear combination of atomic orbitals (LCAO) method. To interpret the relative nature of bonding in these compounds, we have scaled the experimental and theoretical Compton profiles on equal-valence-electron-density (EVED). On the basis of EVED profiles, it is seen that SnTe shows more covalent character than SnS. To rectify the substantial disagreement between experimental and theoretical band gaps, we have also presented the energy bands and density of states of both the compounds using full-potential linearized augmented plane wave method (FP-LAPW) including spin-orbit interaction within the PBEsol exchange-correlation potential.

  4. Electronic density measurement in the TB R-1 tokamak using Faraday rotation

    International Nuclear Information System (INIS)

    Elizondo, Juan Iraburu

    1996-01-01

    In this work, the experimental results of electronic density measurements in the TBR-1 tokamak, obtained by Faraday rotation of a microwave beam, are presented, The beam (65 GHz, 500 MW) is generated by a Klystron and crosses the plasma in the horizontal plane. The density values obtained are in agreement with the measurements of a conventional microwave interferometer. As a result of numerical simulations and measurements, it can be concluded that it would be advisable the use of lower wavelengths, to minimize the beam refraction when it crosses the plasma. The results show the feasibility of the Faraday rotation method for density measurement, in the first experiment performed in a tokamak, for the geometry considered. (author)

  5. Unbiased reduced density matrices and electronic properties from full configuration interaction quantum Monte Carlo

    International Nuclear Information System (INIS)

    Overy, Catherine; Blunt, N. S.; Shepherd, James J.; Booth, George H.; Cleland, Deidre; Alavi, Ali

    2014-01-01

    Properties that are necessarily formulated within pure (symmetric) expectation values are difficult to calculate for projector quantum Monte Carlo approaches, but are critical in order to compute many of the important observable properties of electronic systems. Here, we investigate an approach for the sampling of unbiased reduced density matrices within the full configuration interaction quantum Monte Carlo dynamic, which requires only small computational overheads. This is achieved via an independent replica population of walkers in the dynamic, sampled alongside the original population. The resulting reduced density matrices are free from systematic error (beyond those present via constraints on the dynamic itself) and can be used to compute a variety of expectation values and properties, with rapid convergence to an exact limit. A quasi-variational energy estimate derived from these density matrices is proposed as an accurate alternative to the projected estimator for multiconfigurational wavefunctions, while its variational property could potentially lend itself to accurate extrapolation approaches in larger systems

  6. 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.

  7. Study of thermal and suprathermal electron density fluctuations in a plasma Focus

    International Nuclear Information System (INIS)

    Jolas, Alain.

    1982-02-01

    Thomson scattering of ruby laser light is used to study electron density fluctuations in a plasma Focus. One measures frequency and wavenumber spectra as well as angular distribution of fluctuations at given wavenumber. During the implosion phase, plasma layers with different characteristics are evidenced: a dense plasma layer where density fluctuations are isotropic with a thermal level, and a tenuous plasma layer where fluctuations are clearly anisotropic with a suprathermal level. The suprathermal fluctuations are attributed to microscopic instabilities due to the large electrical current which flows in the transition zone where the magnetic field mixes into the plasma. Thermal fluctuation measurements allow the determination of electron density and electron and ion temperatures of the dense layer plasma. One compares the observed characteristics of spectral components of suprathermal fluctuations with various types of known micro-instabilities. Relying on a simplified shock wave model it is deduced an average electrical resistivity greater than the classical Spitzer relation by two order of magnitudes. The lower hybrid drift instability appears to be dominant at the beginning of the implosion phase [fr

  8. 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

    2017-11-02

    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.

  9. Advances in electric field and atomic surface derived properties from experimental electron densities.

    Science.gov (United States)

    Bouhmaida, Nouzha; Ghermani, Nour Eddine

    2008-07-14

    The present study is devoted to a general use of the Gauss law. This is applied to the atomic surfaces derived from the topological analysis of the electron density. The method proposed here is entirely numerical, robust and does not necessitate any specific parametrization of the atomic surfaces. We focus on two fundamental properties: the atomic charges and the electrostatic forces acting on atoms in molecules. Application is made on experimental electron densities modelized by the Hansen-Coppens model from which the electric field is derived for a heterogenic set of compounds: water molecule, NO(3) anion, bis-triazine molecule and MgO cluster. Charges and electrostatic forces are estimated by the atomic surface flux of the electric field and the Maxwell stress tensor, respectively. The charges obtained from the present method are in good agreement with those issued from the conventional volume integration. Both Feynman and Ehrenfest forces as well as the electrostatic potential at the nuclei (EPN) are here estimated from the experimental electron densities. The values found for the molecular compounds are presented and discussed in the scope of the mechanics of atomic interactions.

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

    International Nuclear Information System (INIS)

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

    2017-01-01

    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. Lastly, 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.

  11. 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.

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

    Science.gov (United States)

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

    2017-03-21

    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.

  13. Electron momentum density, band structure, and structural properties of SrS

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, G., E-mail: gsphysics@gmail.com [University of Kota, Department of Pure and Applied Physics (India); Munjal, N.; Vyas, V. [Banasthali University, Department of Physics (India); Kumar, R.; Sharma, B. K. [University of Rajasthan, Department of Physics (India); Joshi, K. B. [MLS University, Department of Physics (India)

    2013-10-15

    The electron momentum density, the electronic band structure, and the structural properties of SrS are presented in this paper. The isotropic Compton profile, anisotropies in the directional Compton profiles, the electronic band structure and density of states are calculated using the ab initio periodic linear combination of atomic orbitals method with the CRYSTAL06 code. Structural parameters of SrS-lattice constants and bulk moduli in the B1 and B2 phases-are computed together with the transition pressure. The computed parameters are well in agreement with earlier investigations. To compare the calculated isotropic Compton profile, measurement on polycrystalline SrS is performed using 5Ci-{sup 241}Am Compton spectrometer. Additionally, charge transfer is studied by means of the Compton profiles computed from the ionic model. The nature of bonding in the isovalent SrS and SrO compounds is compared on the basis of equal-valenceelectron-density profiles and the bonding in SrS is found to be more covalent than in SrO.

  14. Beam-deflection technique for the measurement of electron density in laser-produced plasmas

    International Nuclear Information System (INIS)

    Faris, G.W.; Bergstrom, H.

    1988-01-01

    Beam-deflection techniques have been shown to perform well for measurements in fluid flows and flames. Because of the growing interest in laser-produced plasmas, the authors have investigated the capability of beam-deflection techniques for plasma measurement. While other techniques including interferometry and schlieren techniques are well established for measuring electron density in laser-produced plasmas, they show that a beam-deflection technique is simple to implement and has advantages over current techniques. They describe a two-wavelength beam-deflection technique for temporally and spatially resolved electron density measurements in a laser-produced plasma. Deflection of a laser beam in a plasma or other system arises from gradients in the index of refraction. Measurement of beam deflections is quantitative in that the deflection angle is proportional to the integrated transverse gradient of the index of refraction. Techniques such as Abel inversion or tomography may be applied to such measurements to reconstruct spatially resolved values of the index of refraction. From measurements of the index of refraction at two wave-lengths, the electron density may be calculated

  15. Human METTL20 methylates lysine residues adjacent to the recognition loop of the electron transfer flavoprotein in mitochondria.

    Science.gov (United States)

    Rhein, Virginie F; Carroll, Joe; He, Jiuya; Ding, Shujing; Fearnley, Ian M; Walker, John E

    2014-08-29

    In mammalian mitochondria, protein methylation is a relatively uncommon post-transcriptional modification, and the extent of the mitochondrial protein methylome, the modifying methyltransferases, and their substrates have been little studied. As shown here, the β-subunit of the electron transfer flavoprotein (ETF) is one such methylated protein. The ETF is a heterodimer of α- and β-subunits. Lysine residues 199 and 202 of mature ETFβ are almost completely trimethylated in bovine heart mitochondria, whereas ETFα is not methylated. The enzyme responsible for the modifications was identified as methyltransferase-like protein 20 (METTL20). In human 143B cells, the methylation of ETFβ is less extensive and is diminished further by suppression of METTL20. Tagged METTL20 expressed in HEK293T cells specifically associates with the ETF and promotes the trimethylation of ETFβ lysine residues 199 and 202. ETF serves as a mobile electron carrier linking dehydrogenases involved in fatty acid oxidation and one-carbon metabolism to the membrane-associated ubiquinone pool. The methylated residues in ETFβ are immediately adjacent to a protein loop that recognizes and binds to the dehydrogenases. Suppression of trimethylation of ETFβ in mouse C2C12 cells oxidizing palmitate as an energy source reduced the consumption of oxygen by the cells. These experiments suggest that the oxidation of fatty acids in mitochondria and the passage of electrons via the ETF may be controlled by modulating the protein-protein interactions between the reduced dehydrogenases and the β-subunit of the ETF by trimethylation of lysine residues. METTL20 is the first lysine methyltransferase to be found to be associated with mitochondria. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. 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.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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 S 0 state and the doubly-excited S 2 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

  18. 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.

  19. Uniform electron gases. III. Low-density gases on three-dimensional spheres

    International Nuclear Information System (INIS)

    Agboola, Davids; Knol, Anneke L.; Gill, Peter M. W.; Loos, Pierre-François

    2015-01-01

    By combining variational Monte Carlo (VMC) and complete-basis-set limit Hartree-Fock (HF) calculations, we have obtained near-exact correlation energies for low-density same-spin electrons on a three-dimensional sphere (3-sphere), i.e., the surface of a four-dimensional ball. In the VMC calculations, we compare the efficacies of two types of one-electron basis functions for these strongly correlated systems and analyze the energy convergence with respect to the quality of the Jastrow factor. The HF calculations employ spherical Gaussian functions (SGFs) which are the curved-space analogs of Cartesian Gaussian functions. At low densities, the electrons become relatively localized into Wigner crystals, and the natural SGF centers are found by solving the Thomson problem (i.e., the minimum-energy arrangement of n point charges) on the 3-sphere for various values of n. We have found 11 special values of n whose Thomson sites are equivalent. Three of these are the vertices of four-dimensional Platonic solids — the hyper-tetrahedron (n = 5), the hyper-octahedron (n = 8), and the 24-cell (n = 24) — and a fourth is a highly symmetric structure (n = 13) which has not previously been reported. By calculating the harmonic frequencies of the electrons around their equilibrium positions, we also find the first-order vibrational corrections to the Thomson energy

  20. 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.

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

    International Nuclear Information System (INIS)

    Dale, Stephen G.; Johnson, Erin R.

    2015-01-01

    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

  2. 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.

  3. Electronic-structure calculations of praseodymium metal by means of modified density-functional theory

    International Nuclear Information System (INIS)

    Svane, A.; Trygg, J.; Johansson, B.; Eriksson, O.

    1997-01-01

    Electronic-structure calculations of elemental praseodymium are presented. Several approximations are used to describe the Pr f electrons. It is found that the low-pressure, trivalent phase is well described using either the self-interaction corrected (SIC) local-spin-density (LSD) approximation or the generalized-gradient approximation (GGA) with spin and orbital polarization (OP). In the SIC-LSD approach the Pr f electrons are treated explicitly as localized with a localization energy given by the self-interaction of the f orbital. In the GGA+OP scheme the f-electron localization is described by the onset of spin and orbital polarization, the energetics of which is described by spin-moment formation energy and a term proportional to the total orbital moment, L z 2 . The high-pressure phase is well described with the f electrons treated as band electrons, in either the LSD or the GGA approximations, of which the latter describes more accurately the experimental equation of state. The calculated pressure of the transition from localized to delocalized behavior is 280 kbar in the SIC-LSD approximation and 156 kbar in the GGA+OP approach, both comparing favorably with the experimentally observed transition pressure of 210 kbar. copyright 1997 The American Physical Society

  4. 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

  5. Electronic and vibrational properties of graphene monolayers with iron adatoms: A density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Dimakis, Nicholas, E-mail: dimakis@utpa.edu [Department of Physics and Geology, University of Texas-Pan American, Edinburg, TX (United States); Navarro, Nestor E. [Department of Chemistry, University of Texas-Pan American, Edinburg, TX (United States); Velazquez, Julian; Salgado, Andres [Department of Physics and Geology, University of Texas-Pan American, Edinburg, TX (United States)

    2015-04-15

    Highlights: • Periodic density functional calculations were performed on graphene monolayers with and without an iron adatom. • Densities of states, charge transfers, and overlap populations were used to elucidate the effects of weak iron adsorption on graphene compared to CO adsorption on Pt. • Infrared intensities and normal mode analysis verify weak iron adsorption on graphene by studying the shift in prominent vibrational modes and changes in lattice dynamics. - Abstract: Periodic density functional calculations on graphene monolayers with and without an iron adatom have been used to elucidate iron-graphene adsorption and its effects on graphene electronic and vibrational properties. Density-of-states calculations and charge density contour plots reveal charge transfer from the iron s orbitals to the d orbitals, in agreement with past reports. Adsorbed iron atoms covalently bind to the graphene substrate, verified by the strong hybridization of iron d-states with the graphene bands in the energy region just below the Fermi level. This adsorption is weak and compared to the well-analyzed CO adsorption on Pt: It is indicated by its small adsorption energy and the minimal change of the substrate geometry due to the presence of the iron adatoms. Graphene vibrational spectra are analyzed though a systematic variation of the graphene supercell size. The shifts of graphene most prominent infrared active vibrational modes due to iron adsorption are explored using normal mode eigenvectors.

  6. Exploiting the spatial locality of electron correlation within the parametric two-electron reduced-density-matrix method

    Science.gov (United States)

    DePrince, A. Eugene; Mazziotti, David A.

    2010-01-01

    The parametric variational two-electron reduced-density-matrix (2-RDM) method is applied to computing electronic correlation energies of medium-to-large molecular systems by exploiting the spatial locality of electron correlation within the framework of the cluster-in-molecule (CIM) approximation [S. Li et al., J. Comput. Chem. 23, 238 (2002); J. Chem. Phys. 125, 074109 (2006)]. The 2-RDMs of individual molecular fragments within a molecule are determined, and selected portions of these 2-RDMs are recombined to yield an accurate approximation to the correlation energy of the entire molecule. In addition to extending CIM to the parametric 2-RDM method, we (i) suggest a more systematic selection of atomic-orbital domains than that presented in previous CIM studies and (ii) generalize the CIM method for open-shell quantum systems. The resulting method is tested with a series of polyacetylene molecules, water clusters, and diazobenzene derivatives in minimal and nonminimal basis sets. Calculations show that the computational cost of the method scales linearly with system size. We also compute hydrogen-abstraction energies for a series of hydroxyurea derivatives. Abstraction of hydrogen from hydroxyurea is thought to be a key step in its treatment of sickle cell anemia; the design of hydroxyurea derivatives that oxidize more rapidly is one approach to devising more effective treatments.

  7. A new electron density model of the plasmasphere for operational applications and services

    Science.gov (United States)

    Jakowski, Norbert; Hoque, Mohammed Mainul

    2018-03-01

    The Earth's plasmasphere contributes essentially to total electron content (TEC) measurements from ground or satellite platforms. Furthermore, as an integral part of space weather, associated plasmaspheric phenomena must be addressed in conjunction with ionosphere weather monitoring by operational space weather services. For supporting space weather services and mitigation of propagation errors in Global Navigation Satellite Systems (GNSS) applications we have developed the empirical Neustrelitz plasmasphere model (NPSM). The model consists of an upper L shell dependent part and a lower altitude dependent part, both described by specific exponential decays. Here the McIllwain parameter L defines the geomagnetic field lines in a centered dipole model for the geomagnetic field. The coefficients of the developed approaches are successfully fitted to numerous electron density data derived from dual frequency GPS measurements on-board the CHAMP satellite mission from 2000 to 2005. The data are utilized for fitting up to the L shell L = 3 because a previous validation has shown a good agreement with IMAGE/RPI measurements up to this value. Using the solar radio flux index F10.7 as the only external parameter, the operation of the model is robust, with 40 coefficients fast and sufficiently accurate to be used as a background model for estimating TEC or electron density profiles in near real time GNSS applications and services. In addition to this, the model approach is sensitive to ionospheric coupling resulting in anomalies such as the Nighttime Winter Anomaly and the related Mid-Summer Nighttime Anomaly and even shows a slight plasmasphere compression of the dayside plasmasphere due to solar wind pressure. Modelled electron density and TEC values agree with estimates reported in the literature in similar cases.

  8. 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.

  9. Comparison of the activation energy barrier for succinimide formation from α- and β-aspartic acid residues obtained from density functional theory calculations.

    Science.gov (United States)

    Nakayoshi, Tomoki; Kato, Koichi; Fukuyoshi, Shuichi; Takahashi, Ohgi; Kurimoto, Eiji; Oda, Akifumi

    2018-01-03

    The l-α-Asp residues in peptides or proteins are prone to undergo nonenzymatic reactions to form l-β-Asp, d-α-Asp, and d-β-Asp residues via a succinimide five-membered ring intermediate. From these three types of isomerized aspartic acid residues, particularly d-β-Asp has been widely detected in aging tissue. In this study, we computationally investigated the cyclization of α- and β-Asp residues to form succinimide with dihydrogen phosphate ion as a catalyst (H 2 PO 4 - ). We performed the study using B3LYP/6-31+G(d,p) density functional theory calculations. The comparison of the activation barriers of both residues is discussed. All the calculations were performed using model compounds in which an α/β-Asp-Gly sequence is capped with acetyl and methylamino groups on the N- and C-termini, respectively. Moreover, H 2 PO 4 - catalyzes all the steps of the succinimide formation (cyclization-dehydration) acting as a proton-relay mediator. The calculated activation energy barriers for succinimide formation of α- and β-Asp residues are 26.9 and 26.0kcalmol -1 , respectively. Although it was experimentally confirmed that β-Asp has higher stability than α-Asp, there was no clear difference between the activation barriers. Therefore, the higher stability of β-Asp residue than α-Asp residue may be caused by an entropic effect associated with the succinimide formation. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. 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.

  11. 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.

  12. Molstack-Interactive visualization tool for presentation, interpretation, and validation of macromolecules and electron density maps.

    Science.gov (United States)

    Porebski, Przemyslaw J; Sroka, Piotr; Zheng, Heping; Cooper, David R; Minor, Wladek

    2018-01-01

    Our understanding of the world of biomolecular structures is based upon the interpretation of macromolecular models, of which ∼90% are an interpretation of electron density maps. This structural information guides scientific progress and exploration in many biomedical disciplines. The Protein Data Bank's web portals have made these structures available for mass scientific consumption and greatly broaden the scope of information presented in scientific publications. The portals provide numerous quality metrics; however, the portion of the structure that is most vital for interpretation of the function may have the most difficult to interpret electron density and this ambiguity is not reflected by any single metric. The possible consequences of basing research on suboptimal models make it imperative to inspect the agreement of a model with its experimental evidence. Molstack, a web-based interactive publishing platform for structural data, allows users to present density maps and structural models by displaying a collection of maps and models, including different interpretation of one's own data, re-refinements, and corrections of existing structures. Molstack organizes the sharing and dissemination of these structural models along with their experimental evidence as an interactive session. Molstack was designed with three groups of users in mind; researchers can present the evidence of their interpretation, reviewers and readers can independently judge the experimental evidence of the authors' conclusions, and other researchers can present or even publish their new hypotheses in the context of prior results. The server is available at http://molstack.bioreproducibility.org. © 2017 The Protein Society.

  13. Electronic structures and large spectrum shifts in hydrogenated fullerenes: Density functional theory study

    International Nuclear Information System (INIS)

    Tachikawa, Hiroto; Iyama, Tetsuji

    2014-01-01

    Electronic structures and band gaps of hydrogenated fullerenes have been investigated by means of density functional theory method. The mechanism of hydrogen addition reaction to the fullerene (C 60 ) surface was also investigated. Addition of one and two hydrogen atoms was examined in the calculations. The binding energies of the second hydrogen atom to C 60 H were widely distributed in the range 1.5–3.6 eV. It was found that the bonding energy is strongly dependent on the spin density of carbon atom of C 60 H. The second hydrogen atom preferentially binds to the neighbor site of the first addition site. The electronic states and excitation energies of C 60 -H were discussed on the basis of theoretical results. - Highlights: • Hydrogen atom addition to C60 was investigated. • First hydrogen atom addition proceeded with very low activation barrier. • Second hydrogen addition was dependent on the binding site. • Addition site of second atom was correlated with spin density

  14. The effect of disorder on the local density of electronic states at an interface

    International Nuclear Information System (INIS)

    Mata, G.J.; Noguera, A.

    1995-04-01

    We have studied the effect of disorder on the local electronic structure in a model interface. In particular we follow the evolution of the local density of states with increasing disorder. To model the disorder we use a supercell approach in which a relatively large and disordered cluster is periodically repeated in two dimensions so as to form the interface. The degree of disorder within a given cluster is parametrized by the order parameter of a nearest neighbor lattice-gas model, in such a way as to interpolate between a perfectly ordered an a completely disordered interface. Cell configurations are sampled by means of Monte Carlo simulation of the lattice-gas model. For a given configuration, the local electronic structure is obtained by means of a Green function technique. An average over the sample configurations is then performed to obtain the average density of states for a set of values of the order parameter. We find that as the interface disorder increases there appears a new and characteristic feature in the local density of states. The relative weight of this feature grows with increasing disorder. For large band offsets the form of this feature is similar to that of a two-dimensional band, a fact which suggests that it might be due to that appearance of interface states. (author). 7 refs, 10 figs

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

    Science.gov (United States)

    Farzaneh, Saeed; Forootan, Ehsan

    2018-03-01

    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).

  16. MAVEN Observations of the Effects of Crustal Magnetic Fields on Electron Density and Temperature in the Martian Dayside Ionosphere

    Science.gov (United States)

    Flynn, Casey L.; Vogt, Marissa F.; Withers, Paul; Andersson, Laila; England, Scott; Liu, Guiping

    2017-11-01

    Mars lacks a global magnetic field but possesses concentrated regions of crustal magnetic field that influence the planet's interaction with the solar wind and the structure of the Martian ionosphere. In this study we survey 17 months of MAVEN Langmuir Probe and Waves dayside electron density and temperature measurements to study how these quantities are affected in regions with strong crustal magnetic fields. Above 200 km altitude, we find that regions of strong crustal magnetic fields feature cooler electron temperatures and enhanced electron densities compared to regions with little or no crustal magnetic field. Neutral densities and temperatures are not significantly affected. Closed field lines on which electrons can be trapped are more prevalent in strong crustal field regions than elsewhere. Trapped on closed field lines, electrons are protected against loss processes involving the solar wind. This would lead to longer plasma lifetimes, higher densities, and lower temperatures.

  17. Measurement of electron density of the plasma in the Tokamak TCABR, through Thomson scattering diagnostic

    International Nuclear Information System (INIS)

    Jeronimo, Leonardo Cunha

    2013-01-01

    Over the last few years is remarkable, so increasingly evident the need for a new source of energy for mankind. One promising option is through nuclear fusion, where the plasma produced in the reactor can be converted into electrical energy. Therefore, knowing the characteristics of this plasma is very important to control it and understand it so desirable. One of the diagnostic options is called Thomson scattering . This is considered the most reliable method for the determination of important plasma parameters such as temperature and electron density, and may also help in the study and explanation of various internal mechanisms. The great advantage lies in the tact that they consist of a direct measurement and nonperturbative. But it is a diagnosis whose installation and execution is admittedly complex, limiting it only a few laboratories in the fíeld of fusion for the world. Among the main difficulties, wc can highlight the fact that the scattered signal is very small, thus requiring a large increase of the incident power. Moreover, the external physical conditions can cause mechanical vibrations that eliminate or minimize them as much as possible, is a great challenge, considering the optical micrometrically very sensitive and needs involved in the system. This work describes the entire process of installation and operation of Thomson scattering diagnostic in tokamak TCABR and through this diagnosis, we work on results of electron temperature, to finally be able to calculate the electron density of the plasma. (author)

  18. 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.

  19. 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.

  20. 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.

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

    Science.gov (United States)

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

    2013-01-01

    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. PMID:25995522

  2. 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

  3. Interaction of an intense relativistic electron beam with full density air

    International Nuclear Information System (INIS)

    Murphy, D.P.; Pechacek, R.E.; Raleigh, M.; Oliphant, W.F.; Meger, R.A.

    1987-01-01

    The authors report on a study of plasma generation by direct deposition of energy from an intense relativistic electron beam (REB) into full density air. It has been postulated that a sufficiently intense REB can fully ionize the air and produce a 2 eV plasma with Spitzer conductivity. The REB is produced from a field emission diode driven by either the Gamble I or Gamble II generator. Gamble I can produce a 0.60 MV, 300 kA, 50 ns REB and Gamble II can produce a 2.0 MV, 1.0 MA, 50 ns REB. The REB was injected into a short diagnostic cell containing full density air and up to a 14 kG solenoidal magnetic field. The diagnostics include beam and net current measurements, x-ray and visible photography and visible light spectroscopy

  4. 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).

  5. 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.)

  6. Synaptic Ribbons Require Ribeye for Electron Density, Proper Synaptic Localization, and Recruitment of Calcium Channels

    Directory of Open Access Journals (Sweden)

    Caixia Lv

    2016-06-01

    Full Text Available Synaptic ribbons are structures made largely of the protein Ribeye that hold synaptic vesicles near release sites in non-spiking cells in some sensory systems. Here, we introduce frameshift mutations in the two zebrafish genes encoding for Ribeye and thus remove Ribeye protein from neuromast hair cells. Despite Ribeye depletion, vesicles collect around ribbon-like structures that lack electron density, which we term “ghost ribbons.” Ghost ribbons are smaller in size but possess a similar number of smaller vesicles and are poorly localized to synapses and calcium channels. These hair cells exhibit enhanced exocytosis, as measured by capacitance, and recordings from afferent neurons post-synaptic to hair cells show no significant difference in spike rates. Our results suggest that Ribeye makes up most of the synaptic ribbon density in neuromast hair cells and is necessary for proper localization of calcium channels and synaptic ribbons.

  7. 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.

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

    International Nuclear Information System (INIS)

    Skrzynski, Witold; Slusarczyk-Kacprzyk, Wioletta; Bulski, Wojciech; Zielinska-Dabrowska, Sylwia; Wachowicz, Marta; Kukolowicz, Pawel F.

    2010-01-01

    Purpose: to evaluate the performance of computed tomography (CT) systems of various designs as a source of electron density (ρ el ) data for treatment planning of radiation therapy. Material and methods: dependence of CT numbers on relative electron density of tissue-equivalent materials (HU-ρ 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-ρ el relationships predefined in two commercial treatment-planning systems (TPS). Results: the HU-ρ 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 ρ 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-ρ 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.)

  9. Curly arrows meet electron density transfers in chemical reaction mechanisms: from electron localization function (ELF) analysis to valence-shell electron-pair repulsion (VSEPR) inspired interpretation.

    Science.gov (United States)

    Andrés, Juan; Berski, Sławomir; Silvi, Bernard

    2016-07-07

    Probing the electron density transfers during a chemical reaction can provide important insights, making possible to understand and control chemical reactions. This aim has required extensions of the relationships between the traditional chemical concepts and the quantum mechanical ones. The present work examines the detailed chemical insights that have been generated through 100 years of work worldwide on G. N. Lewis's ground breaking paper on The Atom and the Molecule (Lewis, G. N. The Atom and the Molecule, J. Am. Chem. Soc. 1916, 38, 762-785), with a focus on how the determination of reaction mechanisms can be reached applying the bonding evolution theory (BET), emphasizing how curly arrows meet electron density transfers in chemical reaction mechanisms and how the Lewis structure can be recovered. BET that combines the topological analysis of the electron localization function (ELF) and Thom's catastrophe theory (CT) provides a powerful tool providing insight into molecular mechanisms of chemical rearrangements. In agreement with physical laws and quantum theoretical insights, BET can be considered as an appropriate tool to tackle chemical reactivity with a wide range of possible applications. Likewise, the present approach retrieves the classical curly arrows used to describe the rearrangements of chemical bonds for a given reaction mechanism, providing detailed physical grounds for this type of representation. The ideas underlying the valence-shell-electron pair-repulsion (VSEPR) model applied to non-equilibrium geometries provide simple chemical explanations of density transfers. For a given geometry around a central atom, the arrangement of the electronic domain may comply or not with the VSEPR rules according with the valence shell population of the considered atom. A deformation yields arrangements which are either VSEPR defective (at least a domain is missing to match the VSEPR arrangement corresponding to the geometry of the ligands), VSEPR compliant

  10. Estimation of cluster stability using the theory of electron density functional

    International Nuclear Information System (INIS)

    Borisov, Yu.A.

    1985-01-01

    Prospects of using simple versions of the electron density functional for studying the energy characteristics of cluster compounds Was discussed. These types of cluster compounds were considered: clusters of Cs, Be, B, Sr, Cd, Sc, In, V, Tl, I elements as intermediate form between molecule and solid body, metalloorganic Mo, W, Tc, Re, Rn clusters and elementoorganic compounds of nido-cluster type. The problem concerning changes in the binding energy of homoatomic clusters depending on their size and three-dimensional structure was analysed

  11. Data description and quality assessment of ionospheric electron density profiles for ARPA modeling project. Technical report

    International Nuclear Information System (INIS)

    Conkright, R.O.

    1977-03-01

    This report presents a description of the automated method used to produce electron density (N(h)) profiles from ionograms recorded on 35mm film and an assessment of the resulting data base. A large data base of about 30,000 profiles was required for an ionospheric modeling project. This motivated a search for an automated method of producing profiles. The automated method used is fully described, the resulting data are given a quality grade, and the noon and midnight profiles are presented. Selected portions of this data base are compared with profiles produced by the standard profiling method in use by the Environmental Data Service at Boulder, Colorado

  12. Evaluating of electronic structure of Lanthanum chromite under doping of divalent ion using density functional theory

    International Nuclear Information System (INIS)

    Saievar, E.; Gharleghi, A.

    2006-01-01

    Doping Calcium in Lanthanum site of LaCrO 3 compound increasing the density of states in valance band and decreasing the band gap width because of increases of S electrons in valance band and variety of interaction energies from Cr +3 -Cr +4 couple in valance band. We have used Wien2k software for evaluating this mechanisms. Using of 0.25 percent of dopant and a kind of the space group of cell, let us to use one cell in calculations. We have used GGA approximation in this calculations.

  13. Extending the random-phase approximation for electronic correlation energies: the renormalized adiabatic local density approximation

    DEFF Research Database (Denmark)

    Olsen, Thomas; Thygesen, Kristian S.

    2012-01-01

    while chemical bond strengths and absolute correlation energies are systematically underestimated. In this work we extend the RPA by including a parameter-free renormalized version of the adiabatic local-density (ALDA) exchange-correlation kernel. The renormalization consists of a (local) truncation...... of the ALDA kernel for wave vectors q > 2kF, which is found to yield excellent results for the homogeneous electron gas. In addition, the kernel significantly improves both the absolute correlation energies and atomization energies of small molecules over RPA and ALDA. The renormalization can...... be straightforwardly applied to other adiabatic local kernels....

  14. Orbital energies and negative electron affinities from density functional theory: Insight from the integer discontinuity

    Science.gov (United States)

    Teale, Andrew M.; de Proft, Frank; Tozer, David J.

    2008-07-01

    Orbital energies in Kohn-Sham density functional theory (DFT) are investigated, paying attention to the role of the integer discontinuity in the exact exchange-correlation potential. A series of closed-shell molecules are considered, comprising some that vertically bind an excess electron and others that do not. High-level ab initio electron densities are used to calculate accurate orbital energy differences, Δɛ, between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), using the same potential for both. They are combined with accurate vertical ionization potentials, I0, and electron affinities, A0, to determine accurate ``average'' orbital energies. These are the orbital energies associated with an exchange-correlation potential that averages over a constant jump in the accurate potential, of magnitude ΔXC=(I0-A0)-Δɛ, as given by the discontinuity analysis. Local functional HOMO energies are shown to be almost an order of magnitude closer to these average values than to -I0, with typical discrepancies of just 0.02 a.u. For systems that do not bind an excess electron, this level of agreement is only achieved when A0 is set equal to the negative experimental affinity from electron transmission spectroscopy (ETS); it degrades notably when the zero ground state affinity is instead used. Analogous observations are made for the local functional LUMO energies, although the need to use the ETS affinities is less pronounced for systems where the ETS values are very negative. The application of an asymptotic correction recovers the preference, leading to positive LUMO energies (but bound orbitals) for these systems, consistent with the behavior of the average energies. The asymptotically corrected LUMO energies typically agree with the average values to within 0.02 a.u., comparable to that observed with the HOMOs. The study provides numerical support for the view that local functionals exhibit a near-average behavior

  15. A massively-parallel electronic-structure calculations based on real-space density functional theory

    International Nuclear Information System (INIS)

    Iwata, Jun-Ichi; Takahashi, Daisuke; Oshiyama, Atsushi; Boku, Taisuke; Shiraishi, Kenji; Okada, Susumu; Yabana, Kazuhiro

    2010-01-01

    Based on the real-space finite-difference method, we have developed a first-principles density functional program that efficiently performs large-scale calculations on massively-parallel computers. In addition to efficient parallel implementation, we also implemented several computational improvements, substantially reducing the computational costs of O(N 3 ) operations such as the Gram-Schmidt procedure and subspace diagonalization. Using the program on a massively-parallel computer cluster with a theoretical peak performance of several TFLOPS, we perform electronic-structure calculations for a system consisting of over 10,000 Si atoms, and obtain a self-consistent electronic-structure in a few hundred hours. We analyze in detail the costs of the program in terms of computation and of inter-node communications to clarify the efficiency, the applicability, and the possibility for further improvements.

  16. Using tomography of GPS TEC to routinely determine ionospheric average electron density profiles

    Science.gov (United States)

    Yizengaw, E.; Moldwin, M. B.; Dyson, P. L.; Essex, E. A.

    2007-03-01

    This paper introduces a technique that calculates average electron density (Ne) profiles over a wide geographic area of coverage, using tomographic ionospheric Ne profiles. These Ne profiles, which can provide information of the Ne distribution up to global positioning system (GPS) orbiting altitude (with the coordination of space-based GPS tomographic profiles), can be incorporated into the next generation of the international reference ionosphere (IRI) model. An additional advantage of tomography is that it enables accurate modeling of the topside ionosphere. By applying the tomographic reconstruction approach to ground-based GPS slant total electron content (STEC), we calculate 3-h average Ne profiles over a wide region. Since it uses real measurement data, tomographic average Ne profiles describe the ionosphere during quiet and disturbed periods. The computed average Ne profiles are compared with IRI model profiles and average Ne profiles obtained from ground-based ionosondes.

  17. The behavior of the electron density and temperature at Millstone Hill during the equinox transition study September 1984

    Science.gov (United States)

    Richards, P. G.; Torr, D. G.; Buonsanto, M. J.; Miller, K. L.

    1989-01-01

    The ionospheric electron density and temperature variations is simulated during the equinox transition study in September 1984 and the results are compared with measurements made at Millstone Hill. The agreement between the modeled and measured electron density and temperature for the quiet day (18 September) is very good but there are large differences on the day of the storm (19 September). On the storm day, the measured electron density decreases by a factor of 1.7 over the previous day, while the model density actually increases slightly. The model failure is attributed to an inadequate increase in the ratio of atomic oxygen to molecular neutral densities in the MSIS neutral atmosphere model, for this particular storm. A factor of 3 to 5 increase in the molecular to atomic oxygen density ratio at 300 km is needed to explain the observed decrease in electron density. The effect of vibrationally excited N sub 2 on the electron density were studied and found to be small.

  18. The behavior of the electron density and temperatue at Millstone Hill during the equinox transition study September 1984

    Science.gov (United States)

    Richards, P. G.; Torr, D. G.; Buonsanto, M. J.; Miller, K. L.

    1989-01-01

    The ionospheric electron density and temperature variations is simulated during the equinox transition study in September 1984 and the results are compared with measurements made at Millstone Hill. The agreement between the modeled and measured electron density and temperature for the quiet day (18 September) is very good but there are large differences on the day of the storm (19 September). On the storm day, the measured electron density decreases by a factor of 1.7 over the previous day, while the model density actually increases slightly. The model failure is attributed to an inadequate increase in the ratio of atomic oxygen to molecular neutral densities in the MSIS neutral atmosphere model, for this particular storm. A factor of 3 to 5 increase in the molecular to atomic oxygen density ratio at 300 km is needed to explain the observed decrease in electron density. The effect of vibrationally excited N sub 2 on the electron density were studied and found to be small.

  19. Configurational forces in electronic structure calculations using Kohn-Sham density functional theory

    Science.gov (United States)

    Motamarri, Phani; Gavini, Vikram

    2018-04-01

    We derive the expressions for configurational forces in Kohn-Sham density functional theory, which correspond to the generalized variational force computed as the derivative of the Kohn-Sham energy functional with respect to the position of a material point x . These configurational forces that result from the inner variations of the Kohn-Sham energy functional provide a unified framework to compute atomic forces as well as stress tensor for geometry optimization. Importantly, owing to the variational nature of the formulation, these configurational forces inherently account for the Pulay corrections. The formulation presented in this work treats both pseudopotential and all-electron calculations in a single framework, and employs a local variational real-space formulation of Kohn-Sham density functional theory (DFT) expressed in terms of the nonorthogonal wave functions that is amenable to reduced-order scaling techniques. We demonstrate the accuracy and performance of the proposed configurational force approach on benchmark all-electron and pseudopotential calculations conducted using higher-order finite-element discretization. To this end, we examine the rates of convergence of the finite-element discretization in the computed forces and stresses for various materials systems, and, further, verify the accuracy from finite differencing the energy. Wherever applicable, we also compare the forces and stresses with those obtained from Kohn-Sham DFT calculations employing plane-wave basis (pseudopotential calculations) and Gaussian basis (all-electron calculations). Finally, we verify the accuracy of the forces on large materials systems involving a metallic aluminum nanocluster containing 666 atoms and an alkane chain containing 902 atoms, where the Kohn-Sham electronic ground state is computed using a reduced-order scaling subspace projection technique [P. Motamarri and V. Gavini, Phys. Rev. B 90, 115127 (2014), 10.1103/PhysRevB.90.115127].

  20. Electron density distribution in ferromagnetic nickel: A γ -ray diffraction study

    Science.gov (United States)

    Jauch, W.; Reehuis, M.

    2008-12-01

    High-accuracy single-crystal structure factors, complete up to sinθ/λ=1.9Å-1 , have been measured from ferromagnetic nickel at 295 K using 316.5-keV gamma radiation. The experimental uncertainty of the structure factors is of the order of 10 millielectrons per atom for all data. A detailed description of the electron density distribution is presented in terms of a multipolar atomic deformation model. Achievement of a reliable Debye-Waller factor is of vital importance in this context. The charge asphericity is due to an excess eg orbital occupancy of 43.4(2)%. The 3d shell in the metal is contracted by 2.07(5)% relative to the free atom. The results are discussed and compared with earlier experimental and theoretical works. In contrast to bcc Cr and Fe, solid-state effects are less pronounced in fcc Ni. Clear disentanglement between the 3d and 4s valence electrons could be accomplished for the first time. The general expectation that the number of 3d electrons in the metal should be increased as compared to the atom was confirmed in the case of iron by combining spin and charge-density data. In the case of nickel, it is rejected as revealed by the γ -ray data alone. Only with the d8 configuration, consistency is achieved between observed and refined mosaic widths of the sample crystal. A 3d8 configuration implies that the majority-spin d band cannot be full. Strong support is lent to a localized atomic character of the valence electrons.

  1. Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

    Science.gov (United States)

    Parker, James A. D.; Eleri Pryse, S.; Jackson-Booth, Natasha; Buckland, Rachel A.

    2018-01-01

    The main ionospheric trough is a large-scale spatial depletion in the electron density distribution at the interface between the high- and mid-latitude ionosphere. In western Europe it appears in early evening, progresses equatorward during the night, and retreats rapidly poleward at dawn. It exhibits substantial day-to-day variability and under conditions of increased geomagnetic activity it moves progressively to lower latitudes. Steep gradients on the trough-walls on either side of the trough minimum, and their variability, can cause problems for radio applications. Numerous studies have sought to characterize and quantify the trough behaviour. The Electron Density Assimilative Model (EDAM) models the ionosphere on a global scale. It assimilates observations into a background ionosphere, the International Reference Ionosphere 2007 (IRI2007), to provide a full 3-D representation of the ionospheric plasma distribution at specified times and days. This current investigation studied the capability of EDAM to model the ionosphere in the region of the main trough. Total electron content (TEC) measurements from 46 GPS stations in western Europe from September to December 2002 were assimilated into EDAM to provide a model of the ionosphere in the trough region. Vertical electron content profiles through the model revealed the trough and the detail of its structure. Statistical results are presented of the latitude of the trough minimum, TEC at the minimum and of other defined parameters that characterize the trough structure. The results are compared with previous observations made with the Navy Ionospheric Monitoring System (NIMS), and reveal the potential of EDAM to model the large-scale structure of the ionosphere.

  2. Electronic transport properties of one dimensional lithium nanowire using density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Anil, E-mail: anil-t2001@yahoo.com [Department of Physics, Govt. P.G. College Solan, Himachal Pradesh, India 173212 (India); Kumar, Arun [Department of Physics, Govt. P.G. College Banjar, Himachal Pradesh (India); Chandel, Surjeet [Department of Physics, Govt. P.G. College Bilaspur, Himachal Pradesh (India); Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University Shimla, Himachal Pradesh, India 171005 (India)

    2015-05-15

    Single nanowire electrode devices are a unique platform for studying as energy storage devices. Lithium nanowire is of much importance in lithium ion batteries and therefore has received a great deal of attention in past few years. In this paper we investigated structural and electronic transport properties of Li nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Li nanowire are investigated theoretically. The calculations are performed in two steps: first an optimized geometry for Li nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations correspondingly. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Agreement of bulk properties of Li with experimental values make the study of electronic and transport properties in lithium nanowires interesting because they are promising candidates as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Li nano wire indicates that Li nanowire can be used as an electrode device.

  3. 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.

  4. The influence of solder mask and hygroscopic flux residues on water layer formation on PCBA surface and corrosion reliability of electronics

    DEFF Research Database (Denmark)

    Piotrowska, Kamila; Jellesen, Morten Stendahl; Ambat, Rajan

    2017-01-01

    The presence of solder flux residue on the Printed Circuit Board Assembly (PCBA) surface compromises the corrosion reliability of electronics under humid conditions and can lead to degradation of the device’s lifetime. In this work, the effect of solder mask morphology and hygroscopic residues were...... studied towards assessment of their influence on the water film formation on the PCBA surface. The in-situ observations of water layer build-up was studied on the solder mask substrates as a function of surface finish and residue type (adipic and glutaric acids). The effect of solder flux residues...

  5. 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.

  6. 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.

  7. Residual stress measurements by neutron diffraction in laser and electron beam welded joints in 9Cr-1Mo(V, Nb) steel plates

    International Nuclear Information System (INIS)

    Kumar, Santosh; Viswanadham, C.S.; Bhanumurthy, K.; Dey, G.K.; Kundu, Amrita; Bouchard, P.J.

    2014-01-01

    Residual stresses are invariably associated with welded joints and have serious implications for integrity of welded components in service conditions. Laser and electron beam welding produces weld joints with narrow fusion zone and heat affected zone. Therefore, there exists very high spatial gradient of residual stresses across the weld joints; measurement of which is indeed a challenging task. Residual stress measurements in laser and electron beam welded 9Cr-1Mo (V, Nb) steel plates were carried out by neutron diffraction. Measurements for laser welded plates were carried out using monochromatic neutron beam at ILL, France and that for electron beam welded plates were carried out using white neutron beam at ISIS, UK. Measurements were made across the weld joints as well as along the weld centre-line for the three orthogonal components-longitudinal, transverse and normal of the residual stress. The cross-weld residual stress profile showed a low tensile/compressive trough in the fusion zone and a high tensile peak on the either side of the joint in the parent metal just outside of metallurgical HAZ. Besides, longitudinal and normal components of the residual stress are significant while the transverse component is the least significant. Residual stress profiles showed very similar characteristics in the weld joints made by laser and electron beam welding processes. These results are presented in this paper and discussed in the context of the metallurgical attributes of the material

  8. 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.

  9. 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.

  10. 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...

  11. Feasibility study of the plasma electron density measurement by electromagnetic radiation from the laser-driven plasma wave

    International Nuclear Information System (INIS)

    Jang, D G; Kim, J J; Suk, H; Hur, M S

    2012-01-01

    When an intense laser beam is focused in a plasma, a plasma wake wave is generated and the oscillatary motion of the plasma electrons produces a strong electromagnetic wave by a Cherenkov-like process. Spectrum of the genetated electromagnetic wave has dependence on the plasma density. In this paper, we propose to use the emitted electromagnetic radiation for plasma diagnostic, which may provide an accurate information for local electron densities of the plasma and will be very useful for three-dimensional plasma density profiles by changing the focal point location of the laser beam. Two-dimensional (2-D) particle-in-cell (PIC) simulation is used to study the correlation between the spectrum of the emitted radiation and plasma density, and the results demonstrate that this method is promising for the electron density measurement in the plasma.

  12. 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

  13. Status of electron temperature and density measurement with beam emission spectroscopy on thermal helium at TEXTOR

    International Nuclear Information System (INIS)

    Schmitz, O; Schweer, B; Pospieszczyk, A; Lehnen, M; Samm, U; Unterberg, B; Beigman, I L; Vainshtein, L A; Kantor, M; Xu, Y; Krychowiak, M

    2008-01-01

    Beam emission spectroscopy on thermal helium is used at the TEXTOR tokamak as a reliable method to obtain radial profiles of electron temperature T e (r, t) and electron density n e (r, t). In this paper the experimental realization of this method at TEXTOR and the status of the atomic physics employed as well as the major factors for the measurement's accuracy are evaluated. On the experimental side, the hardware specifications are described and the impact of the beam atoms on the local plasma parameters is shown to be negligible. On the modeling side the collisional-radiative model (CRM) applied to infer n e and T e from the measured He line intensities is evaluated. The role of proton and deuteron collisions and of charge exchange processes is studied with a new CRM and the impact of these so far neglected processes appears to be of minor importance. Direct comparison to Thomson scattering and fast triple probe data showed that for high densities n e > 3.5 x 10 19 m -3 the T e values deduced with the established CRM are too low. However, the new atomic data set implemented in the new CRM leads in general to higher T e values. This allows us to specify the range of reliable application of BES on thermal helium to a range of 2.0 x 10 18 e 19 m -3 and 10 eV e < 250 eV which can be extended by routine application of the new CRM.

  14. Pulse compression radar reflectometry to measure electron density in plasma with parasitic reflections.

    Science.gov (United States)

    Li, Bin; Li, Hong; Chen, Zhipeng; Luo, Chen; Wang, Huihui; Geng, Song; Feng, Lei; Liu, Qiuyan; Liu, Wandong

    2008-07-01

    Pulse compression radar reflectometry is used to obtain electron density profile in plasma with parasitic reflections in this article. The pulse compression radar relies on the relation between the temporal width of a pulse and the frequency bandwidth of this pulse: Deltat proportional, variant1Deltaf. So a set of sweep-frequency microwaves within a bandwidth Deltaf can be introduced sequentially into the plasma to obtain the same information as the one obtained by a real pulse. By applying a Fourier transform to the data of reflectivity array in the frequency domain, the temporal response in the time domain is obtained. The limitation of the parasitic reflections on measurement can be eliminated from the temporal response by the method of time gate. This is a prominent advantage when this method is compared to the traditional reflectometry. For this method, an appropriate compromise between the spatial resolution and the electron density resolution is important. Experimental results show that the profile obtained from pulse compression radar reflectometry is similar to that from a double Langmuir probe.

  15. 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.

  16. Difficulties in applying pure Kohn-Sham density functional theory electronic structure methods to protein molecules

    Science.gov (United States)

    Rudberg, Elias

    2012-02-01

    Self-consistency-based Kohn-Sham density functional theory (KS-DFT) electronic structure calculations with Gaussian basis sets are reported for a set of 17 protein-like molecules with geometries obtained from the Protein Data Bank. It is found that in many cases such calculations do not converge due to vanishing HOMO-LUMO gaps. A sequence of polyproline I helix molecules is also studied and it is found that self-consistency calculations using pure functionals fail to converge for helices longer than six proline units. Since the computed gap is strongly correlated to the fraction of Hartree-Fock exchange, test calculations using both pure and hybrid density functionals are reported. The tested methods include the pure functionals BLYP, PBE and LDA, as well as Hartree-Fock and the hybrid functionals BHandHLYP, B3LYP and PBE0. The effect of including solvent molecules in the calculations is studied, and it is found that the inclusion of explicit solvent molecules around the protein fragment in many cases gives a larger gap, but that convergence problems due to vanishing gaps still occur in calculations with pure functionals. In order to achieve converged results, some modeling of the charge distribution of solvent water molecules outside the electronic structure calculation is needed. Representing solvent water molecules by a simple point charge distribution is found to give non-vanishing HOMO-LUMO gaps for the tested protein-like systems also for pure functionals.

  17. Effective atomic numbers and electron densities of bioactive glasses for photon interaction

    Science.gov (United States)

    Shantappa, Anil; Hanagodimath, S. M.

    2015-08-01

    This work was carried out to study the nature of mass attenuation coefficient of bioactive glasses for gamma rays. Bioactive glasses are a group of synthetic silica-based bioactive materials with unique bone bonding properties. In the present study, we have calculated the effective atomic number, electron density for photon interaction of some selected bioactive glasses viz., SiO2-Na2O, SiO2-Na2O-CaO and SiO2-Na2O-P2O5 in the energy range 1 keV to 100 MeV. We have also computed the single valued effective atomic number by using XMuDat program. It is observed that variation in effective atomic number (ZPI, eff) depends also upon the weight fractions of selected bioactive glasses and range of atomic numbers of the elements. The results shown here on effective atomic number, electron density will be more useful in the medical dosimetry for the calculation of absorbed dose and dose rate.

  18. 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.

  19. Electronic properties of B and Al doped graphane: A hybrid density functional study

    Science.gov (United States)

    Mapasha, R. E.; Igumbor, E.; Andriambelaza, N. F.; Chetty, N.

    2018-04-01

    Using a hybrid density functional theory approach parametrized by Heyd, Scuseria and Ernzerhof (HSE06 hybrid functional), we study the energetics, structural and electronic properties of a graphane monolayer substitutionally doped with the B (BCH) and Al (AlCH) atoms. The BCH defect can be integrated within a graphane monolayer at a relative low formation energy, without major structural distortions and symmetry breaking. The AlCH defect relaxes outward of the monolayer and breaks the symmetry. The density of states plots indicate that BCH doped graphane monolayer is a wide band gap semiconductor, whereas the AlCH defect introduces the spin dependent mid gap states at the vicinity of the Fermi level, revealing a metallic character with the pronounced magnetic features. We further examine the response of the Al dependent spin states on the multiple charge states doping. We find that the defect formation energy, structural and electronic properties can be altered via charge state modulation. The +1 charge doping opens an energy band gap of 1.75 eV. This value corresponds to the wavelength in the visible spectrum, suggesting an ideal material for solar cell absorbers. Our study fine tunes the graphane band gap through the foreign atom doping as well as via defect charge state modulation.

  20. Electron-density critical points analysis and catastrophe theory to forecast structure instability in periodic solids.

    Science.gov (United States)

    Merli, Marcello; Pavese, Alessandro

    2018-03-01

    The critical points analysis of electron density, i.e. ρ(x), from ab initio calculations is used in combination with the catastrophe theory to show a correlation between ρ(x) topology and the appearance of instability that may lead to transformations of crystal structures, as a function of pressure/temperature. In particular, this study focuses on the evolution of coalescing non-degenerate critical points, i.e. such that ∇ρ(x c ) = 0 and λ 1 , λ 2 , λ 3 ≠ 0 [λ being the eigenvalues of the Hessian of ρ(x) at x c ], towards degenerate critical points, i.e. ∇ρ(x c ) = 0 and at least one λ equal to zero. The catastrophe theory formalism provides a mathematical tool to model ρ(x) in the neighbourhood of x c and allows one to rationalize the occurrence of instability in terms of electron-density topology and Gibbs energy. The phase/state transitions that TiO 2 (rutile structure), MgO (periclase structure) and Al 2 O 3 (corundum structure) undergo because of pressure and/or temperature are here discussed. An agreement of 3-5% is observed between the theoretical model and experimental pressure/temperature of transformation.

  1. Evaluation of gas chromatography – electron ionization – full scan high resolution Orbitrap mass spectrometry for pesticide residue analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mol, Hans G.J., E-mail: hans.mol@wur.nl; Tienstra, Marc; Zomer, Paul

    2016-09-07

    Gas chromatography with electron ionization and full scan high resolution mass spectrometry with an Orbitrap mass analyzer (GC-EI-full scan Orbitrap HRMS) was evaluated for residue analysis. Pesticides in fruit and vegetables were taken as an example application. The relevant aspects for GC-MS based residue analysis, including the resolving power (15,000 to 120,000 FWHM at m/z 200), scan rate, dynamic range, selectivity, sensitivity, analyte identification, and utility of existing EI-libraries, are assessed and discussed in detail. The optimum acquisition conditions in full scan mode (m/z 50–500) were a resolving power of 60,000 and an automatic-gain-control target value of 3E6. These conditions provided (i) an optimum mass accuracy: within 2 ppm over a wide concentration range, with/without matrix, enabling the use of ±5 ppm mass extraction windows (ii) adequate scan speed: minimum 12 scans/peak, (iii) an intra-scan dynamic range sufficient to achieve LOD/LOQs ≤0.5 pg in fruit/vegetable matrices (corresponding to ≤0.5 μg kg{sup −1}) for most pesticides. EI-Orbitrap spectra were consistent over a very wide concentration range (5 orders) with good match values against NIST (EI-quadrupole) spectra. The applicability for quantitative residue analysis was verified by validation of 54 pesticides in three matrices (tomato, leek, orange) at 10 and 50 μg/kg. The method involved a QuEChERS-based extraction with a solvent switch into iso-octane, and 1 μL hot splitless injection into the GC-HRMS system. A recovery between 70 and 120% and a repeatability RSD <10% was obtained in most cases. Linearity was demonstrated for the range ≤5–250 μg kg{sup −1}. The pesticides could be identified according to the applicable EU criteria for GC-HRMS (SANTE/11945/2015). GC-EI-full scan Orbitrap HRMS was found to be highly suited for quantitative pesticide residue analysis. The potential of qualitative screening to extend the scope makes it an attractive

  2. Simultaneous analysis of residual stress and stress intensity factor in a resist after UV-nanoimprint lithography based on electron moiré fringes

    International Nuclear Information System (INIS)

    Wang, Qinghua; Kishimoto, Satoshi

    2012-01-01

    In this study, the residual stress in a resist (PAK01) film and the stress intensity factor (SIF) of an induced crack are simultaneously estimated during ultraviolet nanoimprint lithography (UV-NIL) based on electron moiré fringes. A micro grid in a triangular arrangement on the resist film fabricated by UV-NIL is directly used as the model grid. Electron moiré fringes formed by the interference between the fabricated grid and the electron scan beam are used to measure the displacement distribution around the tip of a crack induced by the residual stress in the resist. The SIF of the crack is estimated using a displacement extrapolation method. The residual strain fields and the corresponding residual stress in the resist film far from the crack are determined and analyzed. This method is effective for evaluating the grid quality fabricated by the UV-NIL technique. (paper)

  3. 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

  4. Reconstructive approaches to one- and two-electron density matrix theory

    Science.gov (United States)

    Herbert, John Michael

    Novel computational methods for electronic structure theory are explored, in which the fundamental variable is either the one- or the two-electron reduced density matrix (1- or 2-RDM), rather than the electronic wavefunction. A unifying theme among these methods is density matrix reconstruction, that is, decoupling approximations that express higher-order density matrices as functionals of lower-order ones. On the 2-RDM side, a connected (extensive) version of the Contracted Schrodinger Equation (CSE) is developed, in which the basic unknowns are the RDM cumulants through order four. Reconstruction functionals that neglect the 3- and 4-RDM cumulants are examined and revealed to be significantly less accurate than suggested by previous minimal-basis results. Exact 3-RDM cumulants for some four-electron systems are calculated and found to be comparable in importance to unconnected products of lower-order cumulants. Decoupling approximations for the 3- and 4-RDM cumulants are developed based upon a renormalized, diagrammatic perturbation theory for the three- and four-particle Green's functions, in which the effective, pairwise interaction is extracted from the two-particle cumulant. Diagram rules suitable for both the time-dependent and time-independent versions of this perturbation theory are derived. Reconstructive approaches to natural orbital (1-RDM) functional theory are also examined, wherein the 2-RDM is parametrized in terms of the natural orbitals and their (generally fractional) occupancies. It is demonstrated, at the theorem level, that proposed "corrected Hartree" and "corrected Hartree-Fock" natural orbital functionals necessarily violate positivity of the 2-RDM, which is closely related to their failure to respect antisymmetry. Calculations demonstrate that negative eigenvalues of the 2-RDM are associated with a large, stabilizing (but ultimately spurious) contribution to the energy. Nevertheless, a partially self-interaction-corrected version of the

  5. Spacecraft radio scattering observations of the power spectrum of electron density fluctuations in the solar wind

    International Nuclear Information System (INIS)

    Woo, R.; Armstrong, J.W.

    1979-01-01

    Solar wind electron density power spectra in the solar equatorial region are inferred from observations of phase scintillations and spectral broadening made with the Viking, Helios, and Pioneer spacecraft. The heliocentric distance range covered is 2--215 R/sub S/, and for some observations close to the sun the spectra extend to fluctuation frequencies as high as 100 Hz. For heliocentric distances > or approx. =20 R/sub S/ the equivalent spacecraft-measured one-dimensional density spectrym V/sub n/e is well modeled by a single power law (f/sup -alpha/) in the frequency range 10 -4 -5 x 10 -2 Hz. The mean spectral index α is 1.65, very close to the Kolmogorov value of 5/3. Under the assumption of constant solar wind speed, V/sub n/e varies as R/sup -3.45/, where R is heliocentric distance. Within 20 R/sub S/, V/sub n/e can still be modeled by a single power law over the frequency range 10 -3 -10 1 Hz, but the spectral index becomes smaller, αapprox.1.1. The flattening of the density spectrum with 20 R/sub S/ is presumably associated with energy deposition in the near-sun region and acceleration of the solar wind

  6. Measurements of transient electron density distributions by femtosecond X-ray diffraction

    International Nuclear Information System (INIS)

    Freyer, Benjamin

    2013-01-01

    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.

  7. 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%.

  8. General filtering method for electronic speckle pattern interferometry fringe images with various densities based on variational image decomposition.

    Science.gov (United States)

    Li, Biyuan; Tang, Chen; Gao, Guannan; Chen, Mingming; Tang, Shuwei; Lei, Zhenkun

    2017-06-01

    Filtering off speckle noise from a fringe image is one of the key tasks in electronic speckle pattern interferometry (ESPI). In general, ESPI fringe images can be divided into three categories: low-density fringe images, high-density fringe images, and variable-density fringe images. In this paper, we first present a general filtering method based on variational image decomposition that can filter speckle noise for ESPI fringe images with various densities. In our method, a variable-density ESPI fringe image is decomposed into low-density fringes, high-density fringes, and noise. A low-density fringe image is decomposed into low-density fringes and noise. A high-density fringe image is decomposed into high-density fringes and noise. We give some suitable function spaces to describe low-density fringes, high-density fringes, and noise, respectively. Then we construct several models and numerical algorithms for ESPI fringe images with various densities. And we investigate the performance of these models via our extensive experiments. Finally, we compare our proposed models with the windowed Fourier transform method and coherence enhancing diffusion partial differential equation filter. These two methods may be the most effective filtering methods at present. Furthermore, we use the proposed method to filter a collection of the experimentally obtained ESPI fringe images with poor quality. The experimental results demonstrate the performance of our proposed method.

  9. Beam energy distribution influences on density modulation efficiency in seeded free-electron lasers

    Directory of Open Access Journals (Sweden)

    Guanglei Wang

    2015-06-01

    Full Text Available The beam energy spread at the entrance of an undulator system is of paramount importance for efficient density modulation in high-gain seeded free-electron lasers (FELs. In this paper, the dependences of high harmonic bunching efficiency in high-gain harmonic generation (HGHG, echo-enabled harmonic generation (EEHG and phase-merging enhanced harmonic generation (PEHG schemes on the electron beam energy spread distribution are studied. Theoretical investigations and multidimensional numerical simulations are applied to the cases of uniform and saddle beam energy distributions and compared to a traditional Gaussian distribution. It shows that the uniform and saddle electron energy distributions significantly enhance the bunching performance of HGHG FELs, while they almost have no influence on EEHG and PEHG schemes. A further start-to-end simulation example demonstrated that, with the saddle distribution of sliced beam energy spread controlled by a laser heater, the 30th harmonic can be directly generated by a single-stage HGHG scheme for a soft x-ray FEL facility.

  10. 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.

  11. 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|.

  12. Analytical thermal modelling of multilayered active embedded chips into high density electronic board

    Directory of Open Access Journals (Sweden)

    Monier-Vinard Eric

    2013-01-01

    Full Text Available The recent Printed Wiring Board embedding technology is an attractive packaging alternative that allows a very high degree of miniaturization by stacking multiple layers of embedded chips. This disruptive technology will further increase the thermal management challenges by concentrating heat dissipation at the heart of the organic substrate structure. In order to allow the electronic designer to early analyze the limits of the power dissipation, depending on the embedded chip location inside the board, as well as the thermal interactions with other buried chips or surface mounted electronic components, an analytical thermal modelling approach was established. The presented work describes the comparison of the analytical model results with the numerical models of various embedded chips configurations. The thermal behaviour predictions of the analytical model, found to be within ±10% of relative error, demonstrate its relevance for modelling high density electronic board. Besides the approach promotes a practical solution to study the potential gain to conduct a part of heat flow from the components towards a set of localized cooled board pads.

  13. Electron Density Dropout Near Enceladus in the Context of Water-Vapor and Water-Ice

    Science.gov (United States)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Johnson, R. E.; Kaiser, M. L.; Wahlund, J.-E.; Waite, J. H., Jr.

    2009-01-01

    On 12 March 2008, the Cassini spacecraft made a close encounter with the Saturnian moon Enceladus, passing within 52 km of the moon. The spacecraft trajectory was intentionally-oriented in a southerly direction to create a close alignment with the intense water-dominated plumes emitted from the south polar region. During the passage, the Cassini Radio and Plasma Wave System (RPWS) detected two distinct radio signatures: 1) Impulses associated with small water-ice dust grain impacts and 2) an upper hybrid (UH) resonance emission that both intensified and displayed a sharp frequency decrease in the near-vicinity of the moon. The frequency decrease of the UH emission is associated with an unexpectedly sharp decrease in electron density from approximately 90 el/cubic cm to below 20 el/cubic cm that occurs on a time scale of a minute near the closest encounter with the moon. In this work, we consider a number of scenarios to explain this sharp electron dropout, but surmise that electron absorption by ice grains is the most likely process.

  14. Temporal evolutions of electron temperature and density with edge localized mode in the JT-60U divertor plasma

    International Nuclear Information System (INIS)

    Nakano, T; Kubo, H; Asakura, N

    2010-01-01

    From the intensity ratios of the three He I lines measured at 20 kHz, the temporal evolutions of the electron temperature and density during and after the power and the particle flow into the divertor plasma caused by edge localized modes are determined. The electron temperature increases from 70 eV to 80 eV with increasing D α intensity. Then, at the peak of D α intensity, the electron temperature starts decreasing down to 60 eV. The electron density increases from 0.1 x 10 19 m -3 to 0.3 x 10 19 m -3 with increasing D α intensity, and then starts to decrease more gradually compared with the electron temperature after the peak of D α intensity. It is interpreted that the increase of the electron temperature is ascribed to the power and the particle flow into the divertor plasma, and that the decrease of the electron temperature and the increase of the electron density are ascribed to the ionization of the recycled neutrals, which consumes the electron energy and produces electrons.

  15. Simulation of the Plasma Density Evolution during Electron Cyclotron Resonance Heating at the T-10 Tokamak

    Science.gov (United States)

    Dnestrovskij, Yu. N.; Vershkov, V. A.; Danilov, A. V.; Dnestrovskij, A. Yu.; Zenin, V. N.; Lysenko, S. E.; Melnikov, A. V.; Shelukhin, D. A.; Subbotin, G. F.; Cherkasov, S. V.

    2018-01-01

    In ohmically heated (OH) plasma with low recycling, an improved particle confinement (IPC) mode is established during gas puffing. However, after gas puffing is switched off, this mode is retained only for about 100 ms, after which an abrupt phase transition into the low particle confinement (LPC) mode occurs in the entire plasma cross section. During such a transition, energy transport due to heat conduction does not change. The phase transition in OH plasma is similar to the effect of density pump-out from the plasma core, which occurs after electron cyclotron heating (ECH) is switched on. Analysis of the measured plasma pressure profiles in the T-10 tokamak shows that, after gas puffing in the OH mode is switched off, the plasma pressure profile in the IPC stage becomes more peaked and, after the peakedness exceeds a certain critical value, the IPC-LPC transition occurs. Similar processes are also observed during ECH. If the pressure profile is insufficiently peaked during ECH, then the density pump-out effect comes into play only after the critical peakedness of the pressure profile is reached. In the plasma core, the density and pressure profiles are close to the corresponding canonical profiles. This allows one to derive an expression for the particle flux within the canonical profile model and formulate a criterion for the IPC-LPC transition. The time evolution of the plasma density profile during phase transitions was simulated for a number of T-10 shots with ECH and high recycling. The particle transport coefficients in the IPC and LPC phases, as well as the dependences of these coefficients on the ECH power, are determined.

  16. 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.

  17. An open-source framework for analyzing N-electron dynamics. II. Hybrid density functional theory/configuration interaction methodology.

    Science.gov (United States)

    Hermann, Gunter; Pohl, Vincent; Tremblay, Jean Christophe

    2017-10-30

    In this contribution, we extend our framework for analyzing and visualizing correlated many-electron dynamics to non-variational, highly scalable electronic structure method. Specifically, an explicitly time-dependent electronic wave packet is written as a linear combination of N-electron wave functions at the configuration interaction singles (CIS) level, which are obtained from a reference time-dependent density functional theory (TDDFT) calculation. The procedure is implemented in the open-source Python program detCI@ORBKIT, which extends the capabilities of our recently published post-processing toolbox (Hermann et al., J. Comput. Chem. 2016, 37, 1511). From the output of standard quantum chemistry packages using atom-centered Gaussian-type basis functions, the framework exploits the multideterminental structure of the hybrid TDDFT/CIS wave packet to compute fundamental one-electron quantities such as difference electronic densities, transient electronic flux densities, and transition dipole moments. The hybrid scheme is benchmarked against wave function data for the laser-driven state selective excitation in LiH. It is shown that all features of the electron dynamics are in good quantitative agreement with the higher-level method provided a judicious choice of functional is made. Broadband excitation of a medium-sized organic chromophore further demonstrates the scalability of the method. In addition, the time-dependent flux densities unravel the mechanistic details of the simulated charge migration process at a glance. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  18. A quantum molecular similarity analysis of changes in molecular electron density caused by basis set flotation and electric field application

    Science.gov (United States)

    Simon, Sílvia; Duran, Miquel

    1997-08-01

    Quantum molecular similarity (QMS) techniques are used to assess the response of the electron density of various small molecules to application of a static, uniform electric field. Likewise, QMS is used to analyze the changes in electron density generated by the process of floating a basis set. The results obtained show an interrelation between the floating process, the optimum geometry, and the presence of an external field. Cases involving the Le Chatelier principle are discussed, and an insight on the changes of bond critical point properties, self-similarity values and density differences is performed.

  19. Low-energy effective Hamiltonians for correlated electron systems beyond density functional theory

    Science.gov (United States)

    Hirayama, Motoaki; Miyake, Takashi; Imada, Masatoshi; Biermann, Silke

    2017-08-01

    We propose a refined scheme of deriving an effective low-energy Hamiltonian for materials with strong electronic Coulomb correlations beyond density functional theory (DFT). By tracing out the electronic states away from the target degrees of freedom in a controlled way by a perturbative scheme, we construct an effective Hamiltonian for a restricted low-energy target space incorporating the effects of high-energy degrees of freedom in an effective manner. The resulting effective Hamiltonian can afterwards be solved by accurate many-body solvers. We improve this "multiscale ab initio scheme for correlated electrons" (MACE) primarily in two directions by elaborating and combining two frameworks developed by Hirayama et al. [M. Hirayama, T. Miyake, and M. Imada, Phys. Rev. B 87, 195144 (2013), 10.1103/PhysRevB.87.195144] and Casula et al. [M. Casula, P. Werner, L. Vaugier, F. Aryasetiawan, T. Miyake, A. J. Millis, and S. Biermann, Phys. Rev. Lett. 109, 126408 (2012), 10.1103/PhysRevLett.109.126408]: (1) Double counting of electronic correlations between the DFT and the low-energy solver is avoided by using the constrained G W scheme; and (2) the frequency dependent interactions emerging from the partial trace summation are successfully separated into a nonlocal part that is treated following ideas by Hirayama et al. and a local part treated nonperturbatively in the spirit of Casula et al. and are incorporated into the renormalization of the low-energy dispersion. The scheme is favorably tested on the example of SrVO3.

  20. Distinguishing of Ile/Leu amino acid residues in the PP3 protein by (hot) electron capture dissociation in Fourier transform ion cyclotron resonance mass spectrometry

    DEFF Research Database (Denmark)

    Kjeldsen, Frank; Haselmann, Kim F; Sørensen, Esben Skipper

    2003-01-01

    In hot electron capture dissociation (HECD), multiply protonated polypeptides fragment upon capturing approximately 11-eV electrons. The excess of energy upon the primary c, z* cleavage induces secondary fragmentation in z* fragments. The resultant w ions allow one to distinguish between the isom......In hot electron capture dissociation (HECD), multiply protonated polypeptides fragment upon capturing approximately 11-eV electrons. The excess of energy upon the primary c, z* cleavage induces secondary fragmentation in z* fragments. The resultant w ions allow one to distinguish between...... the isomeric Ile and Leu residues. The analytical utility of HECD is evaluated using tryptic peptides from the bovine milk protein PP3 containing totally 135 amino acid residues. Using a formal procedure for Ile/Leu (Xle) residue assignment, the identities of 20 out of 25 Xle residues (80%) were determined....... The identity of an additional two residues could be correctly guessed from the absence of the alternative w ions, and only two residues, for which neither expected nor alternative w ions were observed, remained unassigned. Reinspection of conventional ECD spectra also revealed the presence of Xle w ions...

  1. Experimental evidence of excited electron number density and temperature effects on electron-phonon coupling in gold films

    International Nuclear Information System (INIS)

    Giri, Ashutosh; Gaskins, John T.; Foley, Brian M.; Cheaito, Ramez; Hopkins, Patrick E.

    2015-01-01

    The electronic transport properties of metals with weak electron-phonon coupling can be influenced by non-thermal electrons. Relaxation processes involving non-thermal electrons competing with the thermalized electron system have led to inconsistencies in the understanding of how electrons scatter and relax with the less energetic lattice. Recent theoretical and computational works have shown that the rate of energy relaxation with the metallic lattice will change depending on the thermalization state of the electrons. Even though 20 years of experimental works have focused on understanding and isolating these electronic relaxation mechanisms with short pulsed irradiation, discrepancies between these existing works have not clearly answered the fundamental question of the competing effects between non-thermal and thermal electrons losing energy to the lattice. In this work, we demonstrate the ability to measure the electron relaxation for varying degrees of both electron-electron and electron-phonon thermalization. This series of measurements of electronic relaxation over a predicted effective electron temperature range up to ∼3500 K and minimum lattice temperatures of 77 K validate recent computational and theoretical works that theorize how a nonequilibrium distribution of electrons transfers energy to the lattice. Utilizing this wide temperature range during pump-probe measurements of electron-phonon relaxation, we explain discrepancies in the past two decades of literature of electronic relaxation rates. We experimentally demonstrate that the electron-phonon coupling factor in gold increases with increasing lattice temperature and laser fluences. Specifically, we show that at low laser fluences corresponding to small electron perturbations, energy relaxation between electrons and phonons is mainly governed by non-thermal electrons, while at higher laser fluences, non-thermal electron scattering with the lattice is less influential on the energy relaxation

  2. 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.

  3. Density of the unoccupied electronic states of the ultrathin films of the aziridinylphenylpyrrol substituted fullerene

    International Nuclear Information System (INIS)

    Komolov, A.S.; Lazneva, E.F.; Gerasimova, N.B.; Panina, Yu.A.; Zashikhin, G.D.; Baramygin, A.V.; Si, P.; Akhremtchik, S.N.; Gavrikov, A.A.

    2015-01-01

    Graphical abstract: - Highlights: • DOUS of the ultrathin films of the aziridinylphenylpyrrol substituted C 60 was determined by using the transmission of the low-energy electrons technique and by the DFT calculations. • The introduction of the APP substituent to C 60 molecule was accompanied by the modifications of DOUS in the energy range from 2 eV to 9 eV above E F . • The major DOUS bands were assigned π* and σ* - type character using the spatial distribution of the relevant orbitals obtained from the DFT calculation results. - Abstract: The ultrathin films of aziridinylphenylpyrrol-C 60 (APP-C 60 ) and of the unsubstituted C 60 thermally deposited in UHV on an oxidized silicon substrate (SiO 2 )n-Si were studied experimentally using the very low energy electron diffraction (VLEED) method and the total current spectroscopy (TCS) measurement scheme. The density of the unoccupied electronic states (DOUS) located 2-20 eV above the Fermi level (E F ) of the films under study was determined using the TCS results and using the results of the density functional theory (DFT) calculations of the vacant electronic orbitals of the APP-C 60 and C 60 molecules. The DOUS peak structure obtained on the basis of the calculation results corresponds well to the structure of the major DOUS bands obtained from the TCS experiment. The comparison of the DOUS spectra of the APP-C 60 and C 60 films under study showed that the introduction of the APP substituent to the C 60 molecule was accompanied by the pronounced changes of the π* DOUS bands in the energy range from 2 eV to 5 eV above E F and of the DOUS band composed from both π* and σ* - type orbitals in the energy range from 5 eV to 9 eV above E F . The formation of the low-lying σ* DOUS band in the APP-C 60 film in the energy range from 8 eV to 13 eV above E F can be explained by the superposition of the relevant DOUS maxima from the C 60 film and from the APP fragment.

  4. Characterising electron beam welded dissimilar metal joints to study residual stress relaxation from specimen extraction

    OpenAIRE

    Abburi Venkata, Kiranmayi; Truman, Christopher E; Smith, David J; Bhaduri, Arun K

    2016-01-01

    Nuclear power plants require dissimilar metal weld joints to connect the primary steam generator made from ferritic steel to the intermediate heat exchanger made from austenitic steel. Such joints are complex because of the mismatch in the thermal and the mechanical properties of the materials used in the joint. Electron Beam (EB) welding is emerging as a promising technique to manufacture dissimilar joints providing a great many advantages over conventional welding techniques, in terms of lo...

  5. 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.

  6. The determination of electron momentum densities by inelastic scattering gamma-ray-electron coincidence measurements: The (γ,eγ)-experiment

    International Nuclear Information System (INIS)

    Rollason, A.J.; Bell, F.; Schneider, J.R.

    1989-09-01

    Measurements have been made of the recoiling electron in 320 keV gamma ray inelastic scattering collisions in thin aluminium targets. The angular correlation of these electrons detected in coincidence with the scattered photon is in agreement with the kinematic requirements of the Compton effect and is correctly predicted by Monte Carlo simulations based on the impulse approximation. Further simulations of ideal-geometry experiments indicate that information about the initial electron momenta is available from an examination of those electron-photon events originating in a surface layer of one electronic mean free path depth and that elastic scattering of the recoil electrons from greater depths produces a nearly flat background to this signal. The results clearly demonstrate the feasibility of the (γ,eγ) experiment for studying electron momentum densities with synchrotron radiation. (orig.) With 23 refs., 17 figs

  7. 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.

  8. Model representation of the ambient electron density distribution in the middle atmosphere

    Science.gov (United States)

    Ramanamurty, Y. V.

    1989-01-01

    While the Langmuir probe controlled by rocket propagation experiments by the University of Illinois at midlatitude revealed the existence of a permanent D region turning point (DTP), similar measurements over the Thumba equatorial station did not clearly bring out the above daytime feature. Moreover, the calibration constant (ratio of electron density to the current drawn by the Langmuir probe) increased with height (in the 70 to 100 km region) in the case of the midlatitude observations whereas the recent measurements over Thumba showed a decrease up to about 90 km followed by an increase above 90 km. Secondly, there is the problem of reconciling the station oriented observations from the COSPAR family with the ground based radio propagation measurements from the URSI family. Thirdly, new information on Winter in Northern Europe (WINE) and in USSR is available by asking for its incorporation into any global model such as the IRI. The results of investigation of the above aspects are presented.

  9. 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.

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

    International Nuclear Information System (INIS)

    Cardoso, Jessica R.; Gabriel, Leandro; Geraldo, Aurea B.C.; Moura, Eduardo

    2015-01-01

    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)

  11. 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.

  12. 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.

  13. Ultra-High Density Electron Beams for Beam Radiation and Beam Plasma Interaction

    CERN Document Server

    Anderson, Scott; Frigola, Pedro; Gibson, David J; Hartemann, Fred V; Jacob, Jeremy S; Lim, Jae; Musumeci, Pietro; Rosenzweig, James E; Travish, Gil; Tremaine, Aaron M

    2005-01-01

    Current and future applications of high brightness electron beams, which include advanced accelerators such as the plasma wake-field accelerator (PWFA) and beam-radiation interactions such as inverse-Compton scattering (ICS), require both transverse and longitudinal beam sizes on the order of tens of microns. Ultra-high density beams may be produced at moderate energy (50 MeV) by compression and subsequent strong focusing of low emittance, photoinjector sources. We describe the implementation of this method used at LLNL's PLEIADES ICS x-ray source in which the photoinjector-generated beam has been compressed to 300 fsec duration using the velocity bunching technique and focused to 20 μm rms size using an extremely high gradient, permanent magnet quadrupole (PMQ) focusing system.

  14. Electronic and Optical Properties of Sodium Niobate: A Density Functional Theory Study

    Directory of Open Access Journals (Sweden)

    Daniel Fritsch

    2018-01-01

    Full Text Available In recent years, much effort has been devoted to replace the most commonly used piezoelectric ceramic lead zirconate titanate Pb[ZrxTi1−x]O3 (PZT with a suitable lead-free alternative for memory or piezoelectric applications. One possible alternative to PZT is sodium niobate as it exhibits electrical and mechanical properties that make it an interesting material for technological applications. The high-temperature simple cubic perovskite structure undergoes a series of structural phase transitions with decreasing temperature. However, particularly the phases at room temperature and below are not yet fully characterised and understood. Here, we perform density functional theory calculations for the possible phases at room temperature and below and report on the structural, electronic, and optical properties of the different phases in comparison to experimental findings.

  15. Cancer therapy using non-thermal atmospheric pressure plasma with ultra-high electron density

    International Nuclear Information System (INIS)

    Tanaka, Hiromasa; Mizuno, Masaaki; Toyokuni, Shinya; Maruyama, Shoichi; Kodera, Yasuhiro; Terasaki, Hiroko; Adachi, Tetsuo; Kato, Masashi; Kikkawa, Fumitaka; Hori, Masaru

    2015-01-01

    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

  16. Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration

    International Nuclear Information System (INIS)

    Awad, Wael; Svensson Birkedal, Gabriel; Thunnissen, Marjolein M. G. M.; Mani, Katrin; Logan, Derek T.

    2013-01-01

    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 inc . Of these, the most important was shown to be T 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

  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 Win......XCom program. The significant variation of Z(eff) and N-el is due to the variations in the dominance of different interaction processes in different energy regions. The maximum values of Z(eff) and N-el are found in the low-energy range, where photoelectric absorption is the main interaction process....... The minimum values of Z(eff) and N-el are found at intermediate energies, typically 0.05 MeV atomic number of the bio-molecule. Wherever possible, the calculations are compared with experimental results. A comparison...

  18. Ab initio density functional theory investigation of structural and electronic properties of silicon carbide nanotube bundles

    International Nuclear Information System (INIS)

    Moradian, Rostam; Behzad, Somayeh; Chegel, Raad

    2008-01-01

    By using ab initio density functional theory the structural and electronic properties of isolated and bundled (8,0) and (6,6) silicon carbide nanotubes (SiCNTs) are investigated. Our results show that for such small diameter nanotubes the inter-tube interaction causes a very small radial deformation, while band splitting and reduction of the semiconducting energy band gap are significant. We compared the equilibrium interaction energy and inter-tube separation distance of (8,0) SiCNT bundle with (10,0) carbon nanotube (CNT) bundle where they have the same radius. We found that there is a larger inter-tube separation and weaker inter-tube interaction in the (8,0) SiCNT bundle with respect to (10,0) CNT bundle, although they have the same radius

  19. Optical thickness and electron density in the flare August 4, 1972

    International Nuclear Information System (INIS)

    Mitropol'skaya, O.N.

    1975-01-01

    Optical thicknesses tau(Δ lambda) are obtained by the Shvestky method from measurements of metal lines absorbtion in the wings of the Hsub(β) and Hsub(γ) lines, by the flash in the photosphere. The linear dependence of lgtau on the logarithm of the distance from the absorption line to the center of the hydrogen line lg Δ lambda is obtained by the least squares method. It is found to be close to the dependence expected for the Stark broadening. Electron density in the flare nsub(e) and the number of hydrogen atoms in the second state n 2 are determined using the Stark mechanism theory for the wings of Hsub(β) and Hsub(γ) lines

  20. 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

  1. Experimental Electron Density Distribution in Two Cocrystals of Betaines with p-Hydroxybenzoic Acid

    Directory of Open Access Journals (Sweden)

    Agata Owczarzak

    2018-03-01

    Full Text Available Experimental determination of electron density distribution in crystals by means of high-resolution X-ray diffraction allows, among others, for studying the details of intra- and inter-molecular interactions. In case of co-crystals, this method may help in finding the conditions of creating such species. The results of such analysis for two co-crystals containing betaines, namely trigonelline (TRG: nicotinic acid N-methylbetaine, IUPAC name: 1-methylpyridinium-3-carboxylate and N-methylpiperidine betaine (MPB: 1-methylpiperidinium-1-yl-carboxylate with p-hydroxybenzoic acid (HBA are reported. TRG-HBA crystallizes as a hydrate. For both of the co-crystals, high-quality diffraction data were collected up to sinθ/λ = 1.13 Å−1. Hansen-Coppens multipolar model was then applied for modelling the electron density distribution and Atoms-In-Molecules approach was used for detailed analysis of interactions in crystals. A number of intermolecular interactions was identified, ranging from strong O-H···O hydrogen bonds through C-H···O to C-H···π and π···π interactions. Correlations between the geometrical characteristics of the contacts and the features of their critical points were analyzed in detail. Atomic charges show that in zwitterionic species there are regions of opposite charges, rather than charges that are localized on certain atoms. In case of MPB-HBA, a significant charge transfer between the components of co-crystal (0.5 e was found, as opposed to TRG-HBA, where all of the components are almost neutral.

  2. Quantum hydrodynamic theory for plasmonics: Impact of the electron density tail

    Science.gov (United States)

    Ciracı, Cristian; Della Sala, Fabio

    2016-05-01

    Multiscale plasmonic systems (e.g., extended metallic nanostructures with subnanometer inter-distances) play a key role in the development of next-generation nanophotonic devices. An accurate modeling of the optical interactions in these systems requires an accurate description of both quantum effects and far-field properties. Classical electromagnetism can only describe the latter, while time-dependent density functional theory (TD-DFT) can provide a full first-principles quantum treatment. However, TD-DFT becomes computationally prohibitive for sizes that exceed few nanometers, which are instead very important for most applications. In this article, we introduce a method based on the quantum hydrodynamic theory (QHT) that includes nonlocal contributions of the kinetic energy and the correct asymptotic description of the electron density. We show that our QHT method can predict both plasmon energy and spill-out effects in metal nanoparticles in excellent agreement with TD-DFT predictions, thus allowing reliable and efficient calculations of both quantum and far-field properties in multiscale plasmonic systems.

  3. 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.

  4. The Inversion of Ionospheric/plasmaspheric Electron Density From GPS Beacon Observations

    Science.gov (United States)

    Zou, Y. H.; Xu, J. S.; Ma, S. Y.

    It is a space-time 4-D tomography to reconstruct ionospheric/ plasmaspheric elec- tron density, Ne, from ground-based GPS beacon measurements. The mathematical foundation of such inversion is studied in this paper and some simulation results of reconstruction for GPS network observation are presented. Assuming reasonably a power law dependence of NE on time with an index number of 1-3 during one ob- servational time of GPS (60-90min.), 4-D inversion in consideration is reduced to a 3-D cone-beam tomography with incomplete projections. To see clearly the effects of the incompleteness on the quality of reconstruction for 3-D condition, we deduced theoretically the formulae of 3-D parallel-beam tomography. After establishing the mathematical basis, we adopt linear temporal dependence of NE and voxel elemental functions to perform simulation of NE reconstruction with the help of IRI90 model. Reasonable time-dependent 3-D images of ionosphere/ plasmasphere electron density distributions are obtained when taking proper layout of the GPS network and allowing variable resolutions in vertical.

  5. Diagrammatic expansion for positive density-response spectra: Application to the electron gas

    Science.gov (United States)

    Uimonen, A.-M.; Stefanucci, G.; Pavlyukh, Y.; van Leeuwen, R.

    2015-03-01

    In a recent paper [Phys. Rev. B 90, 115134 (2014), 10.1103/PhysRevB.90.115134] we put forward a diagrammatic expansion for the self-energy which guarantees the positivity of the spectral function. In this work we extend the theory to the density-response function. We write the generic diagram for the density-response spectrum as the sum of "partitions." In a partition the original diagram is evaluated using time-ordered Green's functions on the left half of the diagram, antitime-ordered Green's functions on the right half of the diagram, and lesser or greater Green's function gluing the two halves. As there exists more than one way to cut a diagram in two halves, to every diagram corresponds more than one partition. We recognize that the most convenient diagrammatic objects for constructing a theory of positive spectra are the half-diagrams. Diagrammatic approximations obtained by summing the squares of half-diagrams do indeed correspond to a combination of partitions which, by construction, yield a positive spectrum. We develop the theory using bare Green's functions and subsequently extend it to dressed Green's functions. We further prove a connection between the positivity of the spectral function and the analytic properties of the polarizability. The general theory is illustrated with several examples and then applied to solve the long-standing problem of including vertex corrections without altering the positivity of the spectrum. In fact already the first-order vertex diagram, relevant to the study of gradient expansion, Friedel oscillations, etc., leads to spectra which are negative in certain frequency domain. We find that the simplest approximation to cure this deficiency is given by the sum of the zeroth-order bubble diagram, the first-order vertex diagram, and a partition of the second-order ladder diagram. We evaluate this approximation in the three-dimensional homogeneous electron gas and show the positivity of the spectrum for all frequencies and

  6. Electron transfer dissociation facilitates the measurement of deuterium incorporation into selectively labeled peptides with single residue resolution

    DEFF Research Database (Denmark)

    Zehl, Martin; Rand, Kasper D; Jensen, Ole N

    2008-01-01

    Mass spectrometry is routinely applied to measure the incorporation of deuterium into proteins and peptides. The exchange of labile, heteroatom-bound hydrogens is mainly used to probe the structural dynamics of proteins in solution, e.g., by hydrogen-exchange mass spectrometry, but also to study...... the gas-phase structure and fragmentation mechanisms of polypeptide ions. Despite considerable effort in recent years, there is no widely established mass spectrometric method to localize the incorporated deuterium to single amino acid residues, and typically, only the overall deuterium content...... of peptides or proteins is obtained. The main reason for this is that CID and related techniques induce intramolecular migration of hydrogens ("hydrogen scrambling") upon vibrational excitation of the even-electron precursor ion, thus randomizing the positional distribution of the incorporated deuterium atoms...

  7. Neutron diffraction study of residual strains across electron beam welds in AISI 316L stainless steel

    International Nuclear Information System (INIS)

    Braham, C.; Ceretti, M.; Coppola, R.; Lodini, A.; Rustichelli, F.; Tosto, S.

    1995-01-01

    The results of neutron diffraction investigation of the strains produced across an electron-beam (EB) weld in SA AISI 316L reference steel for NET are presented. The sample size was 10 x 5 x 3 cm 3 and the measurements have been carried out at different distances from the weld plane with a spatial resolution of approximately 8 mm 3 in the bulk of the material. Grain size and crystallographic texture effects were investigated, on the same sample, by means of X-ray diffraction and metallography. A method to determine the stress field from the neutron diffraction data even in the presence of strong texture is discussed. (orig.)

  8. A study of electron momentum density distribution in Al2O3 ceramic

    Science.gov (United States)

    Vyas, V.; Kumar, R.; Mishra, M. C.; Sharma, G.; Sharma, B. K.

    2011-08-01

    A study of electron momentum density distribution in α-Al2O3 ceramic using Compton spectroscopy is presented in this work. Measurements have been carried out using 59.54 keV gamma-rays emanating from an Am241 source. Calculations have been performed on the basis of the ab-initio linear combination of atomic orbitals (LCAO) method embodied in the CRYSTAL code. The correlation scheme proposed by Perdew-Burke-Ernzerhof was adopted. The exchange was treated following the Becke scheme. The Hartree-Fock and hybrid schemes were also applied to the compound. All the schemes yielded results that are in good agreement with the measurements. The agreement with experiment is, however, better with the hybrid B3LYP (Lee-Yang-Parr) scheme. Ionic model calculations for a number of configurations of (Al+x)2(O-2x/3)3 (2.75<=x<=3 in steps of 0.125) were also performed utilizing free atom profiles. The ionic model suggests transfer of 2.875 electrons from the valence sp state of Al to the p state of O.

  9. 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.

  10. 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.

  11. Strong electron-lattice coupling as the mechanism behind charge density wave transformations in transition-metal dichalcogenides

    Science.gov (United States)

    Gor'kov, Lev P.

    2012-04-01

    We consider a single band of conduction electrons interacting with displacements of the transitional ions. In the classical regime strong enough coupling transforms the harmonic elastic energy for an ion to the one of the well with two deep minima, so that the system is described in terms of Ising spins. Intersite interactions order spins at lower temperatures. Extension to the quantum regime is discussed. Below the charge density wave (CDW) transition the energy spectrum of electrons remains metallic because the structural vector Q and the Fermi surface sizes are not related. Large values of the CDW gap seen in the tunneling experiments correspond to the energy of the minima in the electron-ion two-well complex. The gap is defined through the density of states inside the electronic bands below the CDW transition. We focus mainly on electronic properties of transition-metal dichalcogenides.

  12. Accurate Electron Affinities and Orbital Energies of Anions from a Nonempirically Tuned Range-Separated Density Functional Theory Approach.

    Science.gov (United States)

    Anderson, Lindsey N; Oviedo, M Belén; Wong, Bryan M

    2017-04-11

    The treatment of atomic anions with Kohn-Sham density functional theory (DFT) has long been controversial because the highest occupied molecular orbital (HOMO) energy, E HOMO , is often calculated to be positive with most approximate density functionals. We assess the accuracy of orbital energies and electron affinities for all three rows of elements in the periodic table (H-Ar) using a variety of theoretical approaches and customized basis sets. Among all of the theoretical methods studied here, we find that a nonempirically tuned range-separated approach (constructed to satisfy DFT-Koopmans' theorem for the anionic electron system) provides the best accuracy for a variety of basis sets, even for small basis sets where most functionals typically fail. Previous approaches to solve this conundrum of positive E HOMO values have utilized non-self-consistent methods; however, electronic properties, such as electronic couplings/gradients (which require a self-consistent potential and energy), become ill-defined with these approaches. In contrast, the nonempirically tuned range-separated procedure used here yields well-defined electronic couplings/gradients and correct E HOMO values because both the potential and resulting electronic energy are computed self-consistently. Orbital energies and electron affinities are further analyzed in the context of the electronic energy as a function of electronic number (including fractional numbers of electrons) to provide a stringent assessment of self-interaction errors for these complex anion systems.

  13. Density functional theory of electron transfer beyond the Born-Oppenheimer approximation: Case study of LiF.

    Science.gov (United States)

    Li, Chen; Requist, Ryan; Gross, E K U

    2018-02-28

    We perform model calculations for a stretched LiF molecule, demonstrating that nonadiabatic charge transfer effects can be accurately and seamlessly described within a density functional framework. In alkali halides like LiF, there is an abrupt change in the ground state electronic distribution due to an electron transfer at a critical bond length R = R c , where an avoided crossing of the lowest adiabatic potential energy surfaces calls the validity of the Born-Oppenheimer approximation into doubt. Modeling the R-dependent electronic structure of LiF within a two-site Hubbard model, we find that nonadiabatic electron-nuclear coupling produces a sizable elongation of the critical R c by 0.5 bohr. This effect is very accurately captured by a simple and rigorously derived correction, with an M -1 prefactor, to the exchange-correlation potential in density functional theory, M = reduced nuclear mass. Since this nonadiabatic term depends on gradients of the nuclear wave function and conditional electronic density, ∇ R χ(R) and ∇ R n(r, R), it couples the Kohn-Sham equations at neighboring R points. Motivated by an observed localization of nonadiabatic effects in nuclear configuration space, we propose a local conditional density approximation-an approximation that reduces the search for nonadiabatic density functionals to the search for a single function y(n).

  14. 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.

  15. 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.

  16. 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)

  17. Prediction of hot electron production by ultraintense KrF laser-plasma interactions on solid-density targets

    International Nuclear Information System (INIS)

    Kato, Susumu; Takahashi, Eiichi; Miura, Eisuke; Owadano, Yoshiro; Nakamura, Tatsufumi; Kato, Tomokazu

    2002-01-01

    The scaling of hot electron temperature and the spectrum of electron energy by intense laser plasma interactions are reexamined from a viewpoint of the difference in laser wavelength. Laser plasma interaction such as parametric instabilities is usually determined by the Iλ2 scaling, where I and λ is the laser intensity and wavelength, respectively. However, the hot electron temperature is proportional to (ncr/ne0)1/2 [(1 + a 0 2 ) 1/2 - 1] rather than [(1 + a 0 2 ) 1/2 - 1] at the interaction with overdense plasmas, where ne0 is a electron density of overdense plasmas and a0 is a normalized laser intensity

  18. 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.

  19. 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

  20. Influence of lubricant oil residual fraction on recycled high density polyethylene properties and plastic packaging reverse logistics proposal

    Directory of Open Access Journals (Sweden)

    Harley Moraes Martins

    2015-10-01

    Full Text Available Abstract To recycle post-consumer HDPE contaminated with waste lubricating oils, companies include prior washing and drying in the process. This consumes large amounts of water and energy, generates significant effluent requiring treatment. This study assesses lubricating oil influence on HDPE properties to evaluate the feasibility of its direct mechanical recycling without washing. The current lubricating oil packaging reverse logistics in Rio de Janeiro municipality is also analyzed. HDPE bottle samples were processed with seven oil contents ranging from 1.6-29.4 (wt%. The results indicated the possibility to reprocess the polymer with oily residue not exceeding 3.2%. At higher levels, the external oil lubricating action affects the plastic matrix processing in the extruder and injection, and the recycled material has a burnt oil odor and free oil on the surface. Small residual oil amounts retain the plastic properties comparable to the washed recycled polymer and exhibited benefits associated with the oil plasticizer action. However, oil presence above 7.7% significantly changes the properties and reduces the elasticity and flexural modulus and the plastic matrix crystallinity.

  1. Nondestructive Testing of Residual Stress on the Welded Part of Butt-welded A36 Plates Using Electronic Speckle Pattern Interferometry

    Directory of Open Access Journals (Sweden)

    Kyeongsuk Kim

    2016-02-01

    Full Text Available Most manufacturing processes, including welding, create residual stresses. Residual stresses can reduce material strength and cause fractures. For estimating the reliability and aging of a welded structure, residual stresses should be evaluated as precisely as possible. Optical techniques such as holographic interferometry, electronic speckle pattern interferometry (ESPI, Moire interferometry, and shearography are noncontact means of measuring residual stresses. Among optical techniques, ESPI is typically used as a nondestructive measurement technique of in-plane displacement, such as stress and strain, and out-of-plane displacement, such as vibration and bending. In this study, ESPI was used to measure the residual stress on the welded part of butt-welded American Society for Testing and Materials (ASTM A36 specimens with CO2 welding. Four types of specimens, base metal specimen (BSP, tensile specimen including welded part (TSP, compression specimen including welded part (CSP, and annealed tensile specimen including welded part (ATSP, were tested. BSP was used to obtain the elastic modulus of a base metal. TSP and CSP were used to compare residual stresses under tensile and compressive loading conditions. ATSP was used to confirm the effect of heat treatment. Residual stresses on the welded parts of specimens were obtained from the phase map images obtained by ESPI. The results confirmed that residual stresses of welded parts can be measured by ESPI.

  2. A far-infrared Michelson interferometer for tokamak electron density measurements using computer-generated reference fringes

    International Nuclear Information System (INIS)

    Krug, P.A.; Stimson, P.A.; Falconer, I.S.

    1986-01-01

    A simple far-infrared interferometer which uses the 394 μm laser line from optically-pumped formic acid vapour to measure tokamak electron density is described. This interferometer is unusual in requiring only one detector and a single probing beam since reference fringes during the plasma shot are obtained by computer interpolation between the fringes observed immediately before and after the shot. Electron density has been measured with a phase resolution corresponding to + - 1/20 wavelength fringe shift, which is equivalent to a central density resolution of + - 0.1 x 10 19 m -3 for an assumed parabolic density distribution in a plasma of diameter of 0.2 m, and with a time resolution of 0.2 ms. (author)

  3. Ab-initio local density approximation description of the electronic properties of zinc blende cadmium sulfide (zb-CdS)

    Energy Technology Data Exchange (ETDEWEB)

    Ekuma, E.C., E-mail: panaceamee@yahoo.co [Department of Physics, Southern University and A and M College, Baton Rouge, LA 70813 (United States); Franklin, L.; Zhao, G.L.; Wang, J.T. [Department of Physics, Southern University and A and M College, Baton Rouge, LA 70813 (United States); Bagayoko, D., E-mail: bagayoko@aol.co [Department of Physics, Southern University and A and M College, Baton Rouge, LA 70813 (United States)

    2011-04-01

    Ab-initio, self-consistent electronic energy bands of zinc blende CdS are reported within the local density functional approximation (LDA). Our first principle, non-relativistic and ground state calculations employed a local density potential and the linear combination of atomic orbitals (LCAO). Within the framework of the Bagayoko, Zhao, and Williams (BZW) method, we solved self-consistently both the Kohn-Sham equation and the equation giving the ground state density in terms of the wavefunctions of the occupied states. Our calculated, direct band gap of 2.39 eV, at the {Gamma} point, is in accord with the experiment. Our calculation reproduced the peaks in the conduction and valence bands density of states, within experimental uncertainties. The calculated electron effective mass agrees with experimental findings.

  4. Effect of age-dependent bone electron density on the calculated dose distribution from kilovoltage and megavoltage photon and electron radiotherapy in paediatric MRI-only treatment planning.

    Science.gov (United States)

    Zeinali-Rafsanjani, B; Faghihi, R; Mosleh-Shirazi, M A; Saeedi-Moghadam, M; Jalli, R; Sina, S

    2018-01-01

    MRI-only treatment planning (TP) can be advantageous in paediatric radiotherapy. However, electron density extraction is necessary for dose calculation. Normally, after bone segmentation, a bulk density is assigned. However, the variation of bone bulk density in patients makes the creation of pseudo CTs challenging. This study aims to assess the effects of bone density variations in children on radiation attenuation and dose calculation for MRI-only TP. Bone contents of dose and beam profile of 150 kVp and 6 MV photon and 6 MeV electron beams were then calculated using Xcom, MCNPX (Monte Carlo N-particle version X) and ORLN phantoms. Using 150 kVp X-rays, the difference in attenuation coefficient was almost 5% between an 11-year-old child and a newborn, and ~8% between an adult and a newborn. With megavoltage radiation, the differences were smaller but still important. For an 18 MV photon beam, the difference of radiation attenuation between an 11-year-old child and a newborn was 4% and ~7.4% between an adult and a newborn. For 6 MeV electrons, dose differences were observed up to the 2 cm depth. The percentage depth dose difference between 1 and 10-year-olds was 18.5%, and between 10 and 15-year-olds was 24%. The results suggest that for MRI-only TP of photon- or electron-beam radiotherapy, the bone densities of each age group should be defined separately for accurate dose calculation. Advances in knowledge: This study highlights the need for more age-specific determination of bone electron density for accurate dose calculations in paediatric MRI-only radiotherapy TP.

  5. Non-Born-Oppenheimer electronic and nuclear densities for a Hooke-Calogero three-particle model: non-uniqueness of density-derived molecular structure.

    Science.gov (United States)

    Ludeña, E V; Echevarría, L; Lopez, X; Ugalde, J M

    2012-02-28

    We consider the calculation of non-Born-Oppenheimer, nBO, one-particle densities for both electrons and nuclei. We show that the nBO one-particle densities evaluated in terms of translationally invariant coordinates are independent of the wavefunction describing the motion of center of mass of the whole system. We show that they depend, however, on an arbitrary reference point from which the positions of the vectors labeling the particles are determined. We examine the effect that this arbitrary choice has on the topology of the one-particle density by selecting the Hooke-Calogero model of a three-body system for which expressions for the one-particle densities can be readily obtained in analytic form. We extend this analysis to the one-particle densities obtained from full Coulomb interaction wavefunctions for three-body systems. We conclude, in view of the fact that there is a close link between the choice of the reference point and the topology of one-particle densities that the molecular structure inferred from the topology of these densities is not unique. We analyze the behavior of one-particle densities for the Hooke-Calogero Born-Oppenheimer, BO, wavefunction and show that topological transitions are also present in this case for a particular mass value of the light particles even though in the BO regime the nuclear masses are infinite. In this vein, we argue that the change in topology caused by variation of the mass ratio between light and heavy particles does not constitute a true indication in the nBO regime of the emergence of molecular structure.

  6. Two-pulse Thomson scattering system for measurements of fast fluctuations of electron density in multimirror trap GOL-3

    Science.gov (United States)

    Popov, S. S.; Burdakov, A. V.; Ivantsivskiy, M. V.; Kasatov, A. A.; Polosatkin, S. V.; Postupaev, V. V.; Vyacheslavov, L. N.

    2013-08-01

    Two-pulse modification of the Thomson scattering system that is used at GOL-3 for studies of fast large-amplitude local density fluctuations is described. Two 1054 nm 20 J pulses are generated with two master oscillators that share the same power amplification chain. First experiments indicate existence of shots with a significant change of electron density at adjacent radial locations at ˜100 ns time scale.

  7. Study of the effect of electron irradiation on the density of the activated sludge in aqueous solution

    Science.gov (United States)

    Kupchishin, A. I.; Niyazov, M. N.; Taipova, B. G.; Voronova, N. A.; Khodarina, N. N.

    2018-01-01

    Complex experimental studies on the effect of electron irradiation on the deposition rate of active sludge in aqueous systems by the optical method have been carried out. The obtained dependences of density (ρ) on time (t) are of the same nature for different radiation sources. The experimental curves of the dependence of the active sludge density on time are satisfactorily described by an exponential model.

  8. The MOSDEF Survey: Electron Density and Ionization Parameter at z ~ 2.3

    Science.gov (United States)

    Sanders, Ryan L.; Shapley, Alice E.; Kriek, Mariska; Reddy, Naveen A.; Freeman, William R.; Coil, Alison L.; Siana, Brian; Mobasher, Bahram; Shivaei, Irene; Price, Sedona H.; de Groot, Laura

    2016-01-01

    Using observations from the MOSFIRE Deep Evolution Field survey, we investigate the physical conditions of star-forming regions in z ˜ 2.3 galaxies, specifically the electron density and ionization state. From measurements of the [O II]λλ3726,3729 and [S II]λλ6716,6731 doublets, we find a median electron density of ˜250 cm-3 at z ˜ 2.3, an increase of an order of magnitude compared to measurements of galaxies at z ˜ 0. While z ˜ 2.3 galaxies are offset toward significantly higher O32 values relative to local galaxies at fixed stellar mass, we find that the high-redshift sample follows a similar distribution to the low-metallicity tail of the local distribution in the O32 versus R23 and O3N2 diagrams. Based on these results, we propose that z ˜ 2.3 star-forming galaxies have the same ionization parameter as local galaxies at fixed metallicity. In combination with simple photoionization models, the position of local and z ˜ 2.3 galaxies in excitation diagrams suggests that there is no significant change in the hardness of the ionizing spectrum at fixed metallicity from z ˜ 0 to z ˜ 2.3. We find that z ˜ 2.3 galaxies show no offset compared to low-metallicity local galaxies in emission line ratio diagrams involving only lines of hydrogen, oxygen, and sulfur, but show a systematic offset in diagrams involving [N II]λ6584. We conclude that the offset of z ˜ 2.3 galaxies from the local star-forming sequence in the [N II] BPT diagram is primarily driven by elevated N/O at fixed O/H compared to local galaxies. These results suggest that the local gas-phase and stellar metallicity sets the ionization state of star-forming regions at z ˜ 0 and z ˜ 2. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

  9. The effect of electron density fluctuations on critical temperature in layered superconductors with arbitrary thickness of conducting layer

    Science.gov (United States)

    Askerzade, I. N.

    2018-04-01

    In this work, we analyse the effect of electron density fluctuations of in layered superconductors on the transition temperature Tc. Primarily, we consider the effect of thickness of conducting layer in modelling of superconducting compounds. It is observed that increasing the thickness of conducting layers increases the transition temperature Tc. Also it is shown that, the fluctuations of electron density has negligible character in the case layers with highly different dielectric constants. Obtained results are applicable to Bi2 Sr2 Can - 1 CunO2 n + 4 + δ compounds with n = 1,2,3.

  10. Direct Imaging of Charge Density Modulation in Switchable Two-Dimensional Electron Gas at the Oxide Hetero-Interfaces by Using Electron Bean Inline Holography

    Science.gov (United States)

    2015-08-16

    Switchable Two-Dimensional Electron Gas at the Oxide Hetero-Interfaces by Using Electron Bean Inline Holography 5a. CONTRACT NUMBER FA2386-13-1-4136...directly imaged the charge carrier densities and spatial distributions at the (001) LaAlO3/SrTiO3 heterointerfaces by in-situ TEM holography . The new...Hetero-Interfaces by Using Electron Bean Inline Holography 5a. CONTRACT NUMBER FA2386-13-1-4136 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F

  11. Method for making 2-electron response reduced density matrices approximately N-representable

    Science.gov (United States)

    Lanssens, Caitlin; Ayers, Paul W.; Van Neck, Dimitri; De Baerdemacker, Stijn; Gunst, Klaas; Bultinck, Patrick

    2018-02-01

    In methods like geminal-based approaches or coupled cluster that are solved using the projected Schrödinger equation, direct computation of the 2-electron reduced density matrix (2-RDM) is impractical and one falls back to a 2-RDM based on response theory. However, the 2-RDMs from response theory are not N-representable. That is, the response 2-RDM does not correspond to an actual physical N-electron wave function. We present a new algorithm for making these non-N-representable 2-RDMs approximately N-representable, i.e., it has the right symmetry and normalization and it fulfills the P-, Q-, and G-conditions. Next to an algorithm which can be applied to any 2-RDM, we have also developed a 2-RDM optimization procedure specifically for seniority-zero 2-RDMs. We aim to find the 2-RDM with the right properties which is the closest (in the sense of the Frobenius norm) to the non-N-representable 2-RDM by minimizing the square norm of the difference between this initial response 2-RDM and the targeted 2-RDM under the constraint that the trace is normalized and the 2-RDM, Q-matrix, and G-matrix are positive semidefinite, i.e., their eigenvalues are non-negative. Our method is suitable for fixing non-N-representable 2-RDMs which are close to being N-representable. Through the N-representability optimization algorithm we add a small correction to the initial 2-RDM such that it fulfills the most important N-representability conditions.

  12. Semiconducting iron silicide thin films on silicon (111) with large Hall mobility and low residual electron concentration

    Science.gov (United States)

    Muret, P.; Ali, I.; Brunel, M.

    1998-10-01

    Unprecedented Hall mobility, electron concentration and photoconductivity are demonstrated in semiconducting 0268-1242/13/10/020/img6-0268-1242/13/10/020/img7 thin films prepared on Si(111) surfaces by co-sputtering of iron and silicon followed by post-anneal. Characterization of the silicide as a function of the initial temperature and post-treatment shows that annealing temperatures above 0268-1242/13/10/020/img8C are needed to obtain single phase 0268-1242/13/10/020/img6-0268-1242/13/10/020/img7. Reactive deposition on substrates heated at 0268-1242/13/10/020/img11C leads to textured films. Majority carriers are electrons in all these unintentionally doped films. Hall concentrations between 0268-1242/13/10/020/img12 and 0268-1242/13/10/020/img13 electrons 0268-1242/13/10/020/img14 and respective Hall mobilities from 290 to 0268-1242/13/10/020/img15 are measured at room temperature, involving two different conduction band minima in these two extreme cases. Only deep centres exist in the samples having the lower carrier concentration. In such a situation, raw data must be corrected for the substrate contribution to extract values which are relevant for the 0268-1242/13/10/020/img6-0268-1242/13/10/020/img7 film alone. Photoconductivity also takes place in these samples: at 80 K, it shows a maximum value at the direct band gap of 0268-1242/13/10/020/img6-0268-1242/13/10/020/img7 while at 296 K a step still appears at the same energy. Such results are a consequence of the important decrease of the residual impurity concentration in comparison to values previously published.

  13. 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.

  14. Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, Thomas M., E-mail: baumannt@nscl.msu.edu; Lapierre, Alain, E-mail: lapierre@nscl.msu.edu; Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg [National Superconducting Cyclotron Laboratory (NSCL), Michigan State University (MSU), 640 S. Shaw Lane, East Lansing, Michigan, 48824 (United States)

    2014-07-15

    The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r{sub 80%}=(212±19)μm in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm{sup 2} is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments.

  15. Residue analysis of organophosphorus and organochlorine pesticides in fatty matrices by gas chromatography coupled with electron-capture detection.

    Science.gov (United States)

    Park, Jae-Woo; Abd El-Aty, A M; Lee, Myoung-Heon; Song, Sung-Ok; Shim, Jae-Han

    2006-01-01

    A multiresidue method for the simultaneous determination of 22 organochlorine (OCs) and organophosphorus (Ops) pesticides (including isomers and metabolites), representing a wide range of physicochemical properties, was developed in fatty matrices extracted from meat. Pesticides were extracted from samples with acetonitrile/n-hexane (v:v, 1:1). The analytical screening was performed by gas chromatography coupled with electron-capture detection (ECD). The identification of compounds was based on their retention time and on comparison of the primary and secondary ions. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of samples fortified at 38 to 300 ng/g levels. Correlation coefficients for the 22 extracted pesticide standard curves (linear regression analysis, n = 3) ranged from 0.998 to 1.000. Recovery studies from 2 g samples fortified at 3 levels demonstrated that the GC-ECD method provides 64.4-96.0% recovery for all pesticides except 2,4'-DDE (44.6-50.4%), 4,4'-DDE (51.1-57.5%) and 2,4'-DDT (50.0-51.2%). Both repeatability and reproducibility relative standard deviation values were < 20% for all residues. Detection limits ranged from 0.31 to 1.27 ng/g and quantification limits were between 1.04 and 4.25 ng/g. The proposed analytical method may be used as a simple procedure in routine determinations of OCs and Ops in meat. It can also be applied to the determination of pesticide multi-residues in other animal products such as butter and milk.

  16. High-frequency emissions during the propagation of an electron beam in a high-density plasma

    International Nuclear Information System (INIS)

    Lalita and Tripathi, V.K.

    1988-01-01

    A relativistic annular electron beam passing through a high-density plasma excites Langmuir waves via Cerenkov interaction. The Langmuir waves are backscattered off ions via nonlinear ion Landau damping. At moderately high amplitudes these waves are parametrically up-converted by the beam into high-frequency electromagnetic radiation, as observed in some recent experiments. A nonlocal theory of this process is developed in a cylindrical geometry. It is seen that the growth rate of the Langmuir wave scales as one-third power of beam density. The growth rate of parametric instability scales as one-fourth power of beam density and the square root of beam thickness

  17. 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.

  18. Plasma core electron density and temperature measurements using CVI line emissions in TCABR Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, F. do, E-mail: fellypen@ifi.unicamp.br [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Centro de Componentes Semicondutores; Machida, M. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Instituto de Fisica Gleb Wataghin; Severo, J.H.F.; Sanada, E.; Ronchi, G. [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Fisica

    2015-08-15

    In this work, we present results of electron temperature (T{sub e} ) and density (n {sub e} ) measurements obtained in Tokamak Chauffage Alfven Bresilien (TCABR) tokamak using visible spectroscopy from CVI line emissions which occurs mainly near the center of the plasma column. The presented method is based on a well-known relationship between the particle flux (Γ {sub ion}) and the photon flux (ø {sub ion}) emitted by an ion species combined with ionizations per photon atomic data provided by the atomic data and analysis structure (ADAS) database. In the experiment, we measured the photon fluxes of three different CVI spectral line emissions, 4685.2, 5290.5, and 6200.6 Å (one line per shot). Using this method it was possible to find out the temporal evolution of T{sub e} and n{sub e} in the plasma. The results achieved are in good agreement with T{sub e} and n{sub e} measurements made using other diagnostic tools. (author)

  19. 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.

  20. A quantum Monte Carlo and density functional theory study of the electronic structure of peroxynitrite anion

    Science.gov (United States)

    Harkless, J. A. W.; Rodriguez, J. H.; Mitas, L.; Lester, W. A.

    2003-03-01

    Single point calculations of the ground state electronic structure of peroxynitrite anion have been performed at the optimized cis geometry using the restricted Hartree-Fock (RHF), Møller Plesset second order perturbation theory (MP2), generalized gradient approximation density functional theory (GGA DFT) in the B3LYP form and two quantum Monte Carlo (QMC) methods, variational Monte Carlo (VMC) and diffusion Monte Carlo (DMC). These calculations reveal differences in atomization energies estimated by B3LYP (287.03 kcal/mol), MP2 (290.84 kcal/mol), and DMC, 307.4(1.9) kcal/mol, as compared to experiment, 313(1) kcal/mol. The error associated with MP2 and B3LYP methods is attributed largely to differential recovery of correlation energies for neutral nitrogen and oxygen atoms relative to the oxygen and peroxynitrite anions. In addition, basis set studies were carried out to determine potential sources of error in MP2 and B3LYP valence energy values. Our studies indicate that MP2 and B3LYP valence energies are strongly dependent on the presence of diffuse functions for the negative ions O- and ONOO-.