WorldWideScience

Sample records for unified electronic phase

  1. Unified Phase Diagram for Iron-Based Superconductors.

    Science.gov (United States)

    Gu, Yanhong; Liu, Zhaoyu; Xie, Tao; Zhang, Wenliang; Gong, Dongliang; Hu, Ding; Ma, Xiaoyan; Li, Chunhong; Zhao, Lingxiao; Lin, Lifang; Xu, Zhuang; Tan, Guotai; Chen, Genfu; Meng, Zi Yang; Yang, Yi-Feng; Luo, Huiqian; Li, Shiliang

    2017-10-13

    High-temperature superconductivity is closely adjacent to a long-range antiferromagnet, which is called a parent compound. In cuprates, all parent compounds are alike and carrier doping leads to superconductivity, so a unified phase diagram can be drawn. However, the properties of parent compounds for iron-based superconductors show significant diversity and both carrier and isovalent dopings can cause superconductivity, which casts doubt on the idea that there exists a unified phase diagram for them. Here we show that the ordered moments in a variety of iron pnictides are inversely proportional to the effective Curie constants of their nematic susceptibility. This unexpected scaling behavior suggests that the magnetic ground states of iron pnictides can be achieved by tuning the strength of nematic fluctuations. Therefore, a unified phase diagram can be established where superconductivity emerges from a hypothetical parent compound with a large ordered moment but weak nematic fluctuations, which suggests that iron-based superconductors are strongly correlated electron systems.

  2. Unified Phase Diagram for Iron-Based Superconductors

    Science.gov (United States)

    Gu, Yanhong; Liu, Zhaoyu; Xie, Tao; Zhang, Wenliang; Gong, Dongliang; Hu, Ding; Ma, Xiaoyan; Li, Chunhong; Zhao, Lingxiao; Lin, Lifang; Xu, Zhuang; Tan, Guotai; Chen, Genfu; Meng, Zi Yang; Yang, Yi-feng; Luo, Huiqian; Li, Shiliang

    2017-10-01

    High-temperature superconductivity is closely adjacent to a long-range antiferromagnet, which is called a parent compound. In cuprates, all parent compounds are alike and carrier doping leads to superconductivity, so a unified phase diagram can be drawn. However, the properties of parent compounds for iron-based superconductors show significant diversity and both carrier and isovalent dopings can cause superconductivity, which casts doubt on the idea that there exists a unified phase diagram for them. Here we show that the ordered moments in a variety of iron pnictides are inversely proportional to the effective Curie constants of their nematic susceptibility. This unexpected scaling behavior suggests that the magnetic ground states of iron pnictides can be achieved by tuning the strength of nematic fluctuations. Therefore, a unified phase diagram can be established where superconductivity emerges from a hypothetical parent compound with a large ordered moment but weak nematic fluctuations, which suggests that iron-based superconductors are strongly correlated electron systems.

  3. designing a framework for a unified electronic identity system

    African Journals Online (AJOL)

    DJFLEX

    In this paper, a Unified Identity System is proposed where single electronic identity (eID) is issued that can be used ... online commerce and public sector organizations. Because ..... SearchUnifiedCommunications.com Definitions, Access date.

  4. Unifying hydrotropy under Gibbs phase rule.

    Science.gov (United States)

    Shimizu, Seishi; Matubayasi, Nobuyuki

    2017-09-13

    The task of elucidating the mechanism of solubility enhancement using hydrotropes has been hampered by the wide variety of phase behaviour that hydrotropes can exhibit, encompassing near-ideal aqueous solution, self-association, micelle formation, and micro-emulsions. Instead of taking a field guide or encyclopedic approach to classify hydrotropes into different molecular classes, we take a rational approach aiming at constructing a unified theory of hydrotropy based upon the first principles of statistical thermodynamics. Achieving this aim can be facilitated by the two key concepts: (1) the Gibbs phase rule as the basis of classifying the hydrotropes in terms of the degrees of freedom and the number of variables to modulate the solvation free energy; (2) the Kirkwood-Buff integrals to quantify the interactions between the species and their relative contributions to the process of solubilization. We demonstrate that the application of the two key concepts can in principle be used to distinguish the different molecular scenarios at work under apparently similar solubility curves observed from experiments. In addition, a generalization of our previous approach to solutes beyond dilution reveals the unified mechanism of hydrotropy, driven by a strong solute-hydrotrope interaction which overcomes the apparent per-hydrotrope inefficiency due to hydrotrope self-clustering.

  5. Unified model of secondary electron cascades in diamond

    International Nuclear Information System (INIS)

    Ziaja, Beata; London, Richard A.; Hajdu, Janos

    2005-01-01

    In this article we present a detailed and unified theoretical treatment of secondary electron cascades that follow the absorption of x-ray photons. A Monte Carlo model has been constructed that treats in detail the evolution of electron cascades induced by photoelectrons and by Auger electrons following inner shell ionizations. Detailed calculations are presented for cascades initiated by electron energies between 0.1 and 10 keV. The present article expands our earlier work [B. Ziaja, D. van der Spoel, A. Szoeke, and J. Hajdu, Phys. Rev. B 64, 214104 (2001), Phys. Rev. B 66, 024116 (2002)] by extending the primary energy range, by improving the treatment of secondary electrons, especially at low electron energies, by including ionization by holes, and by taking into account their coupling to the crystal lattice. The calculations describe the three-dimensional evolution of the electron cloud, and monitor the equivalent instantaneous temperature of the free electron gas as the system cools. The dissipation of the impact energy proceeds predominantly through the production of secondary electrons whose energies are comparable to the binding energies of the valence (40-50 eV) and of the core electrons (300 eV). The electron cloud generated by a 10 keV electron is strongly anisotropic in the early phases of the cascade (t≤1 fs). At later times, the sample is dominated by low energy electrons, and these are scattered more isotropically by atoms in the sample. Our results for the total number of secondary electrons agree with available experimental data, and show that the emission of secondary electrons approaches saturation within about 100 fs following the primary impact

  6. Designing a framework for a unified electronic identity system ...

    African Journals Online (AJOL)

    In this paper, a Unified Identity System is proposed where single electronic identity (eID) is issued that can be used across the various platforms of business transaction. The activity/state diagram of the model is presented, and the means of authentication is based on the Secure Assertion Markup Language (SAML) ...

  7. Phase transitions at finite chemical potential in grand unified theories

    International Nuclear Information System (INIS)

    Bailin, D.; Love, A.

    1984-01-01

    We discuss the circumstances in which non-zero chemical potentials might prevent symmetry restoration in phase transitions in the early universe at grand unification or partial unification scales. The general arguments are illustrated by consideration of SO(10) and SU(5) grand unified theories. (orig.)

  8. Unified Approach to Universal Cloning and Phase-Covariant Cloning

    OpenAIRE

    Hu, Jia-Zhong; Yu, Zong-Wen; Wang, Xiang-Bin

    2008-01-01

    We analyze the problem of approximate quantum cloning when the quantum state is between two latitudes on the Bloch's sphere. We present an analytical formula for the optimized 1-to-2 cloning. The formula unifies the universal quantum cloning (UQCM) and the phase covariant quantum cloning.

  9. Unified pH values of liquid chromatography mobile phases.

    Science.gov (United States)

    Suu, Agnes; Jalukse, Lauri; Liigand, Jaanus; Kruve, Anneli; Himmel, Daniel; Krossing, Ingo; Rosés, Martí; Leito, Ivo

    2015-03-03

    This work introduces a conceptually new approach of measuring pH of mixed-solvent liquid chromatography (LC) mobile phases. Mobile phase pH is very important in LC, but its correct measurement is not straightforward, and all commonly used approaches have deficiencies. The new approach is based on the recently introduced unified pH (pH(abs)) scale, which enables direct comparison of acidities of solutions made in different solvents based on chemical potential of the proton in the solutions. This work represents the first experimental realization of the pH(abs) concept using differential potentiometric measurement for comparison of the chemical potentials of the proton in different solutions (connected by a salt bridge), together with earlier published reference points for obtaining the pH(abs) values (referenced to the gas phase) or pH(abs)(H₂O) values (referenced to the aqueous solution). The liquid junction potentials were estimated in the framework of Izutsu's three-component method. pH(abs) values for a number of common LC and LC-MS mobile phases have been determined. The pH(abs) scale enables for the first time direct comparison of acidities of any LC mobile phases, with different organic additives, different buffer components, etc. A possible experimental protocol of putting this new approach into chromatographic practice has been envisaged and its applicability tested. It has been demonstrated that the ionization behavior of bases (cationic acids) in the mobile phases can be better predicted by using the pH(abs)(H₂O) values and aqueous pKa values than by using the alternative means of expressing mobile phase acidity. Description of the ionization behavior of acids on the basis of pH(abs)(H₂O) values is possible if the change of their pKa values with solvent composition change is taken into account.

  10. Electron microscope phase enhancement

    Science.gov (United States)

    Jin, Jian; Glaeser, Robert M.

    2010-06-15

    A microfabricated electron phase shift element is used for modifying the phase characteristics of an electron beam passing though its center aperture, while not affecting the more divergent portion of an incident beam to selectively provide a ninety-degree phase shift to the unscattered beam in the back focal plan of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. One application of the element is to increase the contrast of an electron microscope for viewing weakly scattering samples while in focus. Typical weakly scattering samples include biological samples such as macromolecules, or perhaps cells. Preliminary experimental images demonstrate that these devices do apply a ninety degree phase shift as expected. Electrostatic calculations have been used to determine that fringing fields in the region of the scattered electron beams will cause a negligible phase shift as long as the ratio of electrode length to the transverse feature-size aperture is about 5:1. Calculations are underway to determine the feasibility of aspect smaller aspect ratios of about 3:1 and about 2:1.

  11. Electron Holography: phases matter.

    Science.gov (United States)

    Lichte, Hannes

    2013-06-01

    Essentially, all optics is wave optics, be it with light, X-rays, neutrons or electrons. The information transfer from the object to the image can only be understood in terms of waves given by amplitude and phase. However, phases are difficult to measure: for slowly oscillating waves such as sound or low-frequency electromagnetic waves, phases can be measured directly; for high frequencies this has to be done by heterodyne detection, i.e. superposition with a reference and averaging over time. In optics, this is called interferometry. Because interference is mostly very difficult to achieve, phases have often been considered 'hidden variables' seemingly pulling the strings from backstage, only visible by their action on the image intensity. This was almost the case in conventional Electron Microscopy with the phase differences introduced by an object. However, in the face of the urgent questions from solid state physics and materials science, these phases have to be determined precisely, because they encode the most dominant object properties, such as charge distributions and electromagnetic fields. After more than six decades of very patient advancement, electron interferometry and holography offer unprecedented analytical facilities down to an atomic scale. Akira Tonomura has prominently contributed to the present state.

  12. Unified Symmetry and Conserved Quantities of Mechanical System in Phase Space

    International Nuclear Information System (INIS)

    Fang Jianhui; Ding Ning; Wang Peng

    2006-01-01

    In this paper, a new symmetry and its conserved quantities of a mechanical system in phase space are studied. The definition of this new symmetry, i.e., a unified one is presented, and the criterion of this symmetry is also given. The Noether, the generalized Hojman and the Mei conserved quantities of the unified symmetry of the system are obtained. The unified symmetry contains the Noether, the Lie and the Mei symmetries, and has more generalized significance.

  13. Electronic phase transitions

    CERN Document Server

    Kopaev, YuV

    1992-01-01

    Electronic Phase Transitions deals with topics, which are presently at the forefront of scientific research in modern solid-state theory. Anderson localization, which has fundamental implications in many areas of solid-state physics as well as spin glasses, with its influence on quite different research activities such as neural networks, are two examples that are reviewed in this book. The ab initio statistical mechanics of structural phase transitions is another prime example, where the interplay and connection of two unrelated disciplines of solid-state theory - first principle ele

  14. Unified Nonlinear Flight Dynamics and Aeroelastic Simulator Tool, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes a R&D effort to develop a Unified Nonlinear Flight Dynamics and Aeroelastic Simulator (UNFDAS) Tool that will combine...

  15. Dark-field electron holography for the measurement of geometric phase

    International Nuclear Information System (INIS)

    Hytch, M.J.; Houdellier, F.; Huee, F.; Snoeck, E.

    2011-01-01

    The genesis, theoretical basis and practical application of the new electron holographic dark-field technique for mapping strain in nanostructures are presented. The development places geometric phase within a unified theoretical framework for phase measurements by electron holography. The total phase of the transmitted and diffracted beams is described as a sum of four contributions: crystalline, electrostatic, magnetic and geometric. Each contribution is outlined briefly and leads to the proposal to measure geometric phase by dark-field electron holography (DFEH). The experimental conditions, phase reconstruction and analysis are detailed for off-axis electron holography using examples from the field of semiconductors. A method for correcting for thickness variations will be proposed and demonstrated using the phase from the corresponding bright-field electron hologram. -- Highlights: → Unified description of phase measurements in electron holography. → Detailed description of dark-field electron holography for geometric phase measurements. → Correction procedure for systematic errors due to thickness variations.

  16. A Unified Impedance Model of Voltage-Source Converters with Phase-Locked Loop Effect

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Harnefors, Lennart; Blaabjerg, Frede

    2016-01-01

    This paper proposes a unified impedance model for analyzing the effect of Phase-Locked Loop (PLL) on the stability of grid-connected voltage-source converters. In the approach, the dq-frame impedance model is transformed into the stationary αβ-frame by means of complex transfer functions...... and complex space vectors, which not only predicts the stability impact of the PLL, but reveals also its frequency coupling effect in the phase domain. Thus, the impedance models previously developed in the different domains can be unified. Moreover, the impedance shaping effects of PLL are structurally...... characterized for the current control in the rotating dq-frame and the stationary αβ-frame. Case studies based on the unified impedance model are presented, which are then verified in the time-domain simulations and experiments. The results closely correlate with the impedance-based analysis....

  17. A unified view on Aharanov–Bohm like phases and some applications

    Indian Academy of Sciences (India)

    physics pp. 321–331. A unified view on Aharanov–Bohm like phases and some ... that flourished in the last century with the success of the general theory of relativity and of ... ical quantities in terms of topological properties of either the real or the ... ical part and a geometrical part has also obscured in some cases certain ...

  18. Self energies of the electron and photon in the unified space field theory

    International Nuclear Information System (INIS)

    Duong Van Phi, Nguyen Mong Giao.

    1981-01-01

    Self energies of the electron and photon are calculated in the second approximation of perturbation theory. The formalism of the field theory of interaction in the unified 8-dimensional space is used. The calculations are free of divergence the unitary condition is fulfilled. It is shown that the ''naked'' and physical masses of a free electron are identical. A similar result is obtained for a free photon. Some other effects are discussed [ru

  19. Phase detection electronics for CLIC

    CERN Document Server

    Andersson, A

    2011-01-01

    The Compact Linear Collider (CLIC) requires very tight RF phase synchronisation in order to preserve high luminosity. The electronics required for processing the signals delivered from the phase pick-ups present a significant challenge. This paper discusses the strategy adopted to achieve a sufficiently accurate measurement of the phase. Performance measurements performed in the lab of some of the sub-systems are also presented.

  20. Electronically soft phases in manganites.

    Science.gov (United States)

    Milward, G C; Calderón, M J; Littlewood, P B

    2005-02-10

    The phenomenon of colossal magnetoresistance in manganites is generally agreed to be a result of competition between crystal phases with different electronic, magnetic and structural order; a competition which can be strong enough to cause phase separation between metallic ferromagnetic and insulating charge-modulated states. Nevertheless, closer inspection of phase diagrams in many manganites reveals complex phases where the two order parameters of magnetism and charge modulation unexpectedly coexist. Here we show that such experiments can be naturally explained within a phenomenological Ginzburg-Landau theory. In contrast to models where phase separation originates from disorder or as a strain-induced kinetic phenomenon, we argue that magnetic and charge modulation coexist in new thermodynamic phases. This leads to a rich diagram of equilibrium phases, qualitatively similar to those seen experimentally. The success of this model argues for a fundamental reinterpretation of the nature of charge modulation in these materials, from a localized to a more extended 'charge-density wave' picture. The same symmetry considerations that favour textured coexistence of charge and magnetic order may apply to many electronic systems with competing phases. The resulting 'electronically soft' phases of matter with incommensurate, inhomogeneous and mixed order may be general phenomena in correlated systems.

  1. Unified electronic unit for miniature radioactivity logging equipment

    International Nuclear Information System (INIS)

    Bragin, A.A.; Goldshtejn, L.M.; Fedorov, R.F.; Shikhman, A.S.

    1981-01-01

    Appropriateness and urgency of the unification of components of radioactivity logging equipment used for the investigation of wells at solid mineral deposits is substantiated. A two-channel electronic unit for miniature equipment for radioactivity logging is described and its basic specifications and performance are given. All functional assemblies of the unit are structurally made in the form of printed circuit boards placed in a pan-shaped chassis 28 mm in diameter. The unit's general design provides for the possibility to attach two probes with detection devices to the unit. The unit is used in the two-channel radioactivity logging instrument ''Kura-2'' and in the two-channel radiometer ''RUR-2''. The outer diameter of these instruments is 48 mm and they ensure the investigation of ore and coal wells with a combination radioactivity methods [ru

  2. 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

  3. ELSI: A unified software interface for Kohn-Sham electronic structure solvers

    Science.gov (United States)

    Yu, Victor Wen-zhe; Corsetti, Fabiano; García, Alberto; Huhn, William P.; Jacquelin, Mathias; Jia, Weile; Lange, Björn; Lin, Lin; Lu, Jianfeng; Mi, Wenhui; Seifitokaldani, Ali; Vázquez-Mayagoitia, Álvaro; Yang, Chao; Yang, Haizhao; Blum, Volker

    2018-01-01

    Solving the electronic structure from a generalized or standard eigenproblem is often the bottleneck in large scale calculations based on Kohn-Sham density-functional theory. This problem must be addressed by essentially all current electronic structure codes, based on similar matrix expressions, and by high-performance computation. We here present a unified software interface, ELSI, to access different strategies that address the Kohn-Sham eigenvalue problem. Currently supported algorithms include the dense generalized eigensolver library ELPA, the orbital minimization method implemented in libOMM, and the pole expansion and selected inversion (PEXSI) approach with lower computational complexity for semilocal density functionals. The ELSI interface aims to simplify the implementation and optimal use of the different strategies, by offering (a) a unified software framework designed for the electronic structure solvers in Kohn-Sham density-functional theory; (b) reasonable default parameters for a chosen solver; (c) automatic conversion between input and internal working matrix formats, and in the future (d) recommendation of the optimal solver depending on the specific problem. Comparative benchmarks are shown for system sizes up to 11,520 atoms (172,800 basis functions) on distributed memory supercomputing architectures.

  4. Modeling of annular two-phase flow using a unified CFD approach

    Energy Technology Data Exchange (ETDEWEB)

    Li, Haipeng, E-mail: haipengl@kth.se; Anglart, Henryk, E-mail: henryk@kth.se

    2016-07-15

    Highlights: • Annular two-phase flow has been modeled using a unified CFD approach. • Liquid film was modeled based on a two-dimensional thin film assumption. • Both Eulerian and Lagrangian methods were employed for the gas core flow modeling. - Abstract: A mechanistic model of annular flow with evaporating liquid film has been developed using computational fluid dynamics (CFD). The model is employing a separate solver with two-dimensional conservation equations to predict propagation of a thin boiling liquid film on solid walls. The liquid film model is coupled to a solver of three-dimensional conservation equations describing the gas core, which is assumed to contain a saturated mixture of vapor and liquid droplets. Both the Eulerian–Eulerian and the Eulerian–Lagrangian approach are used to describe the droplet and vapor motion in the gas core. All the major interaction phenomena between the liquid film and the gas core flow have been accounted for, including the liquid film evaporation as well as the droplet deposition and entrainment. The resultant unified framework for annular flow has been applied to the steam-water flow with conditions typical for a Boiling Water Reactor (BWR). The simulation results for the liquid film flow rate show good agreement with the experimental data, with the potential to predict the dryout occurrence based on criteria of critical film thickness or critical film flow rate.

  5. Modeling of annular two-phase flow using a unified CFD approach

    International Nuclear Information System (INIS)

    Li, Haipeng; Anglart, Henryk

    2016-01-01

    Highlights: • Annular two-phase flow has been modeled using a unified CFD approach. • Liquid film was modeled based on a two-dimensional thin film assumption. • Both Eulerian and Lagrangian methods were employed for the gas core flow modeling. - Abstract: A mechanistic model of annular flow with evaporating liquid film has been developed using computational fluid dynamics (CFD). The model is employing a separate solver with two-dimensional conservation equations to predict propagation of a thin boiling liquid film on solid walls. The liquid film model is coupled to a solver of three-dimensional conservation equations describing the gas core, which is assumed to contain a saturated mixture of vapor and liquid droplets. Both the Eulerian–Eulerian and the Eulerian–Lagrangian approach are used to describe the droplet and vapor motion in the gas core. All the major interaction phenomena between the liquid film and the gas core flow have been accounted for, including the liquid film evaporation as well as the droplet deposition and entrainment. The resultant unified framework for annular flow has been applied to the steam-water flow with conditions typical for a Boiling Water Reactor (BWR). The simulation results for the liquid film flow rate show good agreement with the experimental data, with the potential to predict the dryout occurrence based on criteria of critical film thickness or critical film flow rate.

  6. UNIFIED MODELS OF ELEMENTS OF POWER SUPPLY SYSTEMS BASED ON EQUATIONS IN PHASE COORDINATES

    Directory of Open Access Journals (Sweden)

    Yu.N. Vepryk

    2015-12-01

    Full Text Available Purpose. The models of electrical machines in the phase coordinates, the universal algorithm for the simulation of separate elements in a d-q coordinates system and in a phase-coordinates system are proposed. Methodology. Computer methods of investigation of transients in electrical systems are based on a compilation of systems of differential equations and their numerical integration solution methods. To solve differential equations an implicit method of numerical integration was chosen. Because it provides to complete structural simulation possibility: firstly developing models of separate elements and then forming a model of the complex system. For the mathematical simulation of electromagnetic transients in the elements of the electrical systems has been accepted the implicit Euler-Cauchy method, because it provides a higher precision and stability of the computing processes. Results. In developing the model elements identified two groups of elements: - Static elements and electrical machines in the d-q coordinates; - Rotating electrical machines in phase coordinates. As an example, the paper provides a model of synchronous and asynchronous electric machines in the d-q coordinates system and the phase coordinate system. The generalization algorithm and the unified notation form of equations of elements of an electrical system are obtained. It provides the possibility of using structural methods to develop a mathematical model of power systems under transient conditions. Practical value. In addition, the using of a computer model allows to implement multivariant calculations for research and study of factors affecting the quantitative characteristics of the transients.

  7. Ponderomotive phase plate for transmission electron microscopes

    Science.gov (United States)

    Reed, Bryan W [Livermore, CA

    2012-07-10

    A ponderomotive phase plate system and method for controllably producing highly tunable phase contrast transfer functions in a transmission electron microscope (TEM) for high resolution and biological phase contrast imaging. The system and method includes a laser source and a beam transport system to produce a focused laser crossover as a phase plate, so that a ponderomotive potential of the focused laser crossover produces a scattering-angle-dependent phase shift in the electrons of the post-sample electron beam corresponding to a desired phase contrast transfer function.

  8. A unified picture of energy and electron transfer in primary photosynthesis

    International Nuclear Information System (INIS)

    Barter, Laura M.C.; Klug, David R.

    2005-01-01

    A quantitative structure-function relationship for an enzyme should relate the coordinates of atoms in a protein structure to the rates, equilibria and activation energies of the catalysed reaction. In effect, the calculational tools used for determining a structure-function relationship in an enzyme are linking two sets of experimental data, one data set being the coordinates of the enzymes constituent atoms and the other being measurements of its chemical activity. The ability to compare structure and function in this quantitative manner is an important stage in the ultimate development of engineering design rules for biological catalysts. This paper discusses the determination of parameters, in particular the state energies and the free energy surfaces that control the structure-function relationship, and thus the catalytic function of a photosynthetic enzyme. We discuss two different microscopic descriptions, one using conventional non-adiabatic electron transfer theory and the other a supermolecular description of the system (the Multimer Model), which takes into account the electron-phonon coupling in the system in a consistent manner. We demonstrate that although conventional non-adiabatic theory can be employed to reproduce the rates of electron transfer it cannot be employed to provide a consistent and unified description of all the spectroscopic data available in the literature from studies of this enzyme

  9. A unified picture of energy and electron transfer in primary photosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Barter, Laura M.C. [Molecular Dynamics Group, Room 266, Department of Chemistry, South Kensington Campus, Exhibition Road, Imperial College London, SW7 2AZ (United Kingdom)], E-mail: l.barter@ic.ac.uk; Klug, David R. [Molecular Dynamics Group, Room 266, Department of Chemistry, South Kensington Campus, Exhibition Road, Imperial College London, SW7 2AZ (United Kingdom)

    2005-12-07

    A quantitative structure-function relationship for an enzyme should relate the coordinates of atoms in a protein structure to the rates, equilibria and activation energies of the catalysed reaction. In effect, the calculational tools used for determining a structure-function relationship in an enzyme are linking two sets of experimental data, one data set being the coordinates of the enzymes constituent atoms and the other being measurements of its chemical activity. The ability to compare structure and function in this quantitative manner is an important stage in the ultimate development of engineering design rules for biological catalysts. This paper discusses the determination of parameters, in particular the state energies and the free energy surfaces that control the structure-function relationship, and thus the catalytic function of a photosynthetic enzyme. We discuss two different microscopic descriptions, one using conventional non-adiabatic electron transfer theory and the other a supermolecular description of the system (the Multimer Model), which takes into account the electron-phonon coupling in the system in a consistent manner. We demonstrate that although conventional non-adiabatic theory can be employed to reproduce the rates of electron transfer it cannot be employed to provide a consistent and unified description of all the spectroscopic data available in the literature from studies of this enzyme.

  10. On a unified presentation of the non-equilibrium two-phase flow models

    International Nuclear Information System (INIS)

    Boure, J.A.

    1975-01-01

    If the various existing one-dimensional two-phase flow models are consistent, they must appear as particular cases of more general models. It is shown that such is the case if, and only if, the mathematical form of the laws of the transfers between the phases is sufficiently general. These transfer laws control the non-equilibrium phenomena. A convenient general model is a particular form of the two-fluid model. This particular form involves three equations and three dependent variables characterizing the mixture, and three equations and three dependent variables characterizing the differences between the phases (slip, thermal non-equilibriums). The mathematical expressions of the transfert terms present in the above equations involve first-order partial derivatives of the dependent variables. The other existing models may be deduced from the general model by making assumptions on the fluid evolution. Several examples are given. The resulting unified presentation of the existing model enables a comparison of the implicit assumptions made in these models on the transfer laws. It is therefore, a useful tool for the appraisal of the existing models and for the development of new models [fr

  11. Control strategy for Single-phase Transformerless Three-leg Unified Power Quality Conditioner Based on Space Vector Modulation

    DEFF Research Database (Denmark)

    Lu, Yong; Xiao, Guochun; Wang, Xiongfei

    2016-01-01

    The unified power quality conditioner (UPQC) is known as an effective compensation device to improve PQ for sensitive end-users. This paper investigates the operation and control of a single-phase three-leg UPQC (TL-UPQC), where a novel space vector modulation method is proposed for naturally...

  12. A unified triangle carrier based PWM strategy for three-phase N-level diode clamped inverters

    DEFF Research Database (Denmark)

    Li, Kai; Xie, Chuan; Wei, Min

    2017-01-01

    The triangle carrier based pulse width modulation (TCB-PWM) can be functionally equivalent to space vector base PWM (SVB-PWM). For multi-level inverter, it is very difficult to realize the SVB-PWM because its vector space is very complex. In this paper, a unified TCB-PWM strategy for three-phase ...

  13. Unifying the crystallization behavior of hexagonal and square crystals with the phase-field-crystal model

    International Nuclear Information System (INIS)

    Yang Tao; Chen Zheng; Zhang Jing; Wang Yongxin; Lu Yanli

    2016-01-01

    By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force, both crystals (in the steady-state) transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer (LL) mode while for the apex-bulged polygonal and the dendritic crystals, it first adopts the LL mode and then transits into the multi-layer (ML) mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced. (paper)

  14. Quantum Phase Extraction in Isospectral Electronic Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Christopher

    2010-04-28

    Quantum phase is not a direct observable and is usually determined by interferometric methods. We present a method to map complete electron wave functions, including internal quantum phase information, from measured single-state probability densities. We harness the mathematical discovery of drum-like manifolds bearing different shapes but identical resonances, and construct quantum isospectral nanostructures possessing matching electronic structure but divergent physical structure. Quantum measurement (scanning tunneling microscopy) of these 'quantum drums' [degenerate two-dimensional electron states on the Cu(111) surface confined by individually positioned CO molecules] reveals that isospectrality provides an extra topological degree of freedom enabling robust quantum state transplantation and phase extraction.

  15. Electronic construction collaboration system : phase III.

    Science.gov (United States)

    2011-12-01

    This phase of the electronic collaboration project involved two major efforts: 1) implementation of AEC Sync (formerly known as Attolist), a web-based project management system (WPMS), on the Broadway Viaduct Bridge Project and the Iowa Falls Arch Br...

  16. Airborne electronically steerable phased array

    Science.gov (United States)

    1972-01-01

    The results are presented of the second stage of a program for the design and development of a phased array capable of simultaneous and separate transmission and reception of radio frequency signals at S-band frequencies. The design goals of this stage were the development of three major areas of interest required for the final prototype model. These areas are the construction and testing of the low-weight, full-scale 128-element array of antenna elements, the development of the RF manifold feed system, and the construction and testing of a working module containing diplexer and transmit and receive circuits.

  17. 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.

  18. Unified first principles description from warm dense matter to ideal ionized gas plasma: electron-ion collisions induced friction.

    Science.gov (United States)

    Dai, Jiayu; Hou, Yong; Yuan, Jianmin

    2010-06-18

    Electron-ion interactions are central to numerous phenomena in the warm dense matter (WDM) regime and at higher temperature. The electron-ion collisions induced friction at high temperature is introduced in the procedure of ab initio molecular dynamics using the Langevin equation based on density functional theory. In this framework, as a test for Fe and H up to 1000 eV, the equation of state and the transition of electronic structures of the materials with very wide density and temperature can be described, which covers a full range of WDM up to high energy density physics. A unified first principles description from condensed matter to ideal ionized gas plasma is constructed.

  19. Phase diagram of classical electronic bilayers

    International Nuclear Information System (INIS)

    Ranganathan, S; Johnson, R E

    2006-01-01

    Extensive molecular dynamics calculations have been performed on classical, symmetric electronic bilayers at various values of the coupling strength Γ and interlayer separation d to delineate its phase diagram in the Γ-d plane. We studied the diffusion, the amplitude of the main peak of the intralayer static structure factor and the peak positions of the intralayer pair correlation function with the aim of defining equivalent signatures of freezing and constructing the resulting phase diagram. It is found that for Γ greater than 75, crystalline structures exist for a certain range of interlayer separations, while liquid phases are favoured at smaller and larger d. It is seen that there is good agreement between our phase diagram and previously published ones

  20. Phase diagram of classical electronic bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ranganathan, S [Department of Physics, Royal Military College of Canada, Kingston, Ontario K7K 7B4 (Canada); Johnson, R E [Department of Mathematics and Computer Science, Royal Military College of Canada, Kingston, Ontario K7K 7B4 (Canada)

    2006-04-28

    Extensive molecular dynamics calculations have been performed on classical, symmetric electronic bilayers at various values of the coupling strength {gamma} and interlayer separation d to delineate its phase diagram in the {gamma}-d plane. We studied the diffusion, the amplitude of the main peak of the intralayer static structure factor and the peak positions of the intralayer pair correlation function with the aim of defining equivalent signatures of freezing and constructing the resulting phase diagram. It is found that for {gamma} greater than 75, crystalline structures exist for a certain range of interlayer separations, while liquid phases are favoured at smaller and larger d. It is seen that there is good agreement between our phase diagram and previously published ones.

  1. Unified communications

    OpenAIRE

    Kravos, Urban

    2011-01-01

    In the modern business world, communication are becoming more and more complex. As a solution to this problem unified communications occurred. Using a single communication approach unified communications are the integration of various communication technologies (eg, telephony, unified messaging, audio, video and web conferencing and collaboration tools). Unified Messaging, which represents only part of the unified communications means the integration of different non real time communication t...

  2. Electron-irradiation-induced phase transformation in alumina

    International Nuclear Information System (INIS)

    Chen, C.L.; Arakawa, K.; Lee, J.-G.; Mori, H.

    2010-01-01

    In this study, electron-irradiation-induced phase transformations between alumina polymorphs were investigated by high-resolution transmission electron microscopy. It was found that the electron-irradiation-induced α → κ' phase transformation occurred in the alumina under 100 keV electron irradiation. It is likely that the knock-on collision between incident electrons and Al 3+ cations is responsible for the occurrence of electron-irradiation-induced phase transformation from α-alumina to κ'-alumina.

  3. Unified description of inelastic propensity rules for electron transport through nanoscale junctions

    DEFF Research Database (Denmark)

    Paulsson, Magnus; Frederiksen, Thomas; Ueba, Hiromu

    2008-01-01

    We present a method to analyze the results of first-principles based calculations of electronic currents including inelastic electron-phonon effects. This method allows us to determine the electronic and vibrational symmetries in play, and hence to obtain the so-called propensity rules for the st......We present a method to analyze the results of first-principles based calculations of electronic currents including inelastic electron-phonon effects. This method allows us to determine the electronic and vibrational symmetries in play, and hence to obtain the so-called propensity rules...... for the studied systems. We show that only a few scattering states-namely those belonging to the most transmitting eigenchannels-need to be considered for a complete description of the electron transport. We apply the method on first-principles calculations of four different systems and obtain the propensity...

  4. Electronic phase separation and high temperature superconductors

    International Nuclear Information System (INIS)

    Kivelson, S.A.

    1994-01-01

    The authors review the extensive evidence from model calculations that neutral holes in an antiferromagnet separate into hole-rich and hole-poor phases. All known solvable limits of models of holes in a Heisenberg antiferromagnet exhibit this behavior. The authors show that when the phase separation is frustrated by the introduction of long-range Coulomb interactions, the typical consequence is either a modulated (charge density wave) state or a superconducting phase. The authors then review some of the strong experimental evidence supporting an electronically-driven phase separation of the holes in the cuprate superconductors and the related Ni oxides. Finally, the authors argue that frustrated phase separation in these materials can account for many of the anomalous normal state properties of the high temperature superconductors and provide the mechanism of superconductivity. In particular, it is shown that the T-linear resistivity of the normal state is a paraconductivity associated with a novel composite pairing, although the ordered superconducting state is more conventional

  5. Unified solution of the Boltzmann equation for electron and ion velocity distribution functions and transport coefficients in weakly ionized plasmas

    Science.gov (United States)

    Konovalov, Dmitry A.; Cocks, Daniel G.; White, Ronald D.

    2017-10-01

    The velocity distribution function and transport coefficients for charged particles in weakly ionized plasmas are calculated via a multi-term solution of Boltzmann's equation and benchmarked using a Monte-Carlo simulation. A unified framework for the solution of the original full Boltzmann's equation is presented which is valid for ions and electrons, avoiding any recourse to approximate forms of the collision operator in various limiting mass ratio cases. This direct method using Lebedev quadratures over the velocity and scattering angles avoids the need to represent the ion mass dependence in the collision operator through an expansion in terms of the charged particle to neutral mass ratio. For the two-temperature Burnett function method considered in this study, this amounts to avoiding the need for the complex Talmi-transformation methods and associated mass-ratio expansions. More generally, we highlight the deficiencies in the two-temperature Burnett function method for heavy ions at high electric fields to calculate the ion velocity distribution function, even though the transport coefficients have converged. Contribution to the Topical Issue "Physics of Ionized Gases (SPIG 2016)", edited by Goran Poparic, Bratislav Obradovic, Dragana Maric and Aleksandar Milosavljevic.

  6. Liquid phase exfoliated graphene for electronic applications

    Science.gov (United States)

    Sukumaran, Sheena S.; Jinesh, K. B.; Gopchandran, K. G.

    2017-09-01

    Graphene dispersions were prepared using the liquid phase exfoliation method with three different surfactants. One surfactant was used from each of the surfactant types, anionic, cationic, and non-ionic; those used, were sodium dodecylbenzene sulfonate (SDBS), cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP), respectively. Raman spectroscopy was used to investigate the number of layers and the nature of any defects present in the exfoliated graphene. The yield of graphene was found to be less with the non-ionic surfactant, PVP. The deconvolution of 2D peaks at ~2700 cm-1 indicated that graphene prepared using these surfactants resulted in sheets consisting of few-layer graphene. The ratio of intensity of the D and G bands in the Raman spectra showed that edge defect density is high for samples prepared with SDBS compared to the other two, and is attributed to the smaller size of the graphene sheets, as shown in the electron micrographs. In the case of the dispersion in PVP, it is found that the sizes of the graphene sheets are highly sensitive to the concentration of the surfactant used. Here, we have made an attempt to investigate the local density of states in the graphene sheets by measuring the tunnelling current-voltage characteristics. Graphene layers have shown consistent p-type behaviour when exfoliated with SDBS and n-type behaviour when exfoliated with CTAB, with a larger band gap for graphene exfoliated using CTAB. Hence, in addition to the known advantages of liquid phase exfoliation, we found that by selecting suitable surfactants, to a certain extent it is possible to tune the band gap and determine the type of majority carriers.

  7. Electron spectrometer for gas-phase spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bozek, J.D.; Schlachter, A.S. [Ernest Orlando Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    An electron spectrometer for high-resolution spectroscopy of gaseous samples using synchrotron radiation has been designed and constructed. The spectrometer consists of a gas cell, cylindrical electrostatic lens, spherical-sector electron energy analyzer, position-sensitive detector and associated power supplies, electronics and vacuum pumps. Details of the spectrometer design are presented together with some representative spectra.

  8. Highly efficient electron vortex beams generated by nanofabricated phase holograms

    Energy Technology Data Exchange (ETDEWEB)

    Grillo, Vincenzo, E-mail: vincenzo.grillo@nano.cnr.it [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); CNR-IMEM Parco Area delle Scienze 37/A, I-43124 Parma (Italy); Carlo Gazzadi, Gian [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Karimi, Ebrahim [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada); Mafakheri, Erfan [Dipartimento di Fisica Informatica e Matematica, Università di Modena e Reggio Emilia, via G Campi 213/a, I-41125 Modena (Italy); Boyd, Robert W. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada); Frabboni, Stefano [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Dipartimento di Fisica Informatica e Matematica, Università di Modena e Reggio Emilia, via G Campi 213/a, I-41125 Modena (Italy)

    2014-01-27

    We propose an improved type of holographic-plate suitable for the shaping of electron beams. The plate is fabricated by a focused ion beam on a silicon nitride membrane and introduces a controllable phase shift to the electron wavefunction. We adopted the optimal blazed-profile design for the phase hologram, which results in the generation of highly efficient (25%) electron vortex beams. This approach paves the route towards applications in nano-scale imaging and materials science.

  9. Highly efficient electron vortex beams generated by nanofabricated phase holograms

    International Nuclear Information System (INIS)

    Grillo, Vincenzo; Carlo Gazzadi, Gian; Karimi, Ebrahim; Mafakheri, Erfan; Boyd, Robert W.; Frabboni, Stefano

    2014-01-01

    We propose an improved type of holographic-plate suitable for the shaping of electron beams. The plate is fabricated by a focused ion beam on a silicon nitride membrane and introduces a controllable phase shift to the electron wavefunction. We adopted the optimal blazed-profile design for the phase hologram, which results in the generation of highly efficient (25%) electron vortex beams. This approach paves the route towards applications in nano-scale imaging and materials science

  10. Measurement of electron beam bunch phase length by rectangular cavities

    International Nuclear Information System (INIS)

    Afanas'ev, V.D.; Rudychev, V.G.; Ushakov, V.I.

    1976-01-01

    An analysis of a phase length of electron bunches with the help of crossed rectangular resonators with the Hsub(102) oscillation type has been made. It has been shown that the electron coordinates after the duplex resonator are described by an ellipse equation for a non-modulated beam. An influence of the initial energy spread upon the electron motion has been studied. It has been ascertained that energy modulation of the electron beam results in displacement of each electron with respect to the ellipse which is proportional to modulation energy, i.e. an error in determination of the phase length of an electron bunch is proportional to the beam energy spread. Relations have been obtained which enable to find genuine values of phases of the analyzed electrons with an accuracy up to linear multipliers

  11. Three phase carbon EOS model with electronic excitation

    International Nuclear Information System (INIS)

    van Thiel, M.; Ree, F.H.; Grover, R.

    1987-07-01

    A simple and rapid way for computing EOS data of multiphase solids with a liquid phase is described with emphasis on carbon. The method uses a scaling model for the liquid phase and includes a provision for electronic effects. The free energy minimum determines the stable phase

  12. Simulation of solution phase electron transfer in a compact donor-acceptor dyad.

    Science.gov (United States)

    Kowalczyk, Tim; Wang, Lee-Ping; Van Voorhis, Troy

    2011-10-27

    Charge separation (CS) and charge recombination (CR) rates in photosynthetic architectures are difficult to control, yet their ratio can make or break photon-to-current conversion efficiencies. A rational design approach to the enhancement of CS over CR requires a mechanistic understanding of the underlying electron-transfer (ET) process, including the role of the environment. Toward this goal, we introduce a QM/MM protocol for ET simulations and use it to characterize CR in the formanilide-anthraquinone dyad (FAAQ). Our simulations predict fast recombination of the charge-transfer excited state, in agreement with recent experiments. The computed electronic couplings show an electronic state dependence and are weaker in solution than in the gas phase. We explore the role of cis-trans isomerization on the CR kinetics, and we find strong correlation between the vertical energy gaps of the full simulations and a collective solvent polarization coordinate. Our approach relies on constrained density functional theory to obtain accurate diabatic electronic states on the fly for molecular dynamics simulations, while orientational and electronic polarization of the solvent is captured by a polarizable force field based on a Drude oscillator model. The method offers a unified approach to the characterization of driving forces, reorganization energies, electronic couplings, and nonlinear solvent effects in light-harvesting systems.

  13. Electronic structure of elements and compounds and electronic phases of solids

    International Nuclear Information System (INIS)

    Nadykto, B.A.

    2000-01-01

    The paper reviews technique and computed energies for various electronic states of many-electron multiply charged ions, molecular ions, and electronic phases of solids. The model used allows computation of the state energy for free many-electron multiply charged ions with relative accuracy ∼10 -4 suitable for analysis of spectroscopy data

  14. Intelligent Electronic Speed Controller, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This project intends to design and develop an Intelligent Electronic Speed Controller (IESC) for use on Unmanned Aerial Vehicles (UAVs). The IESC will advance the...

  15. Electronic Procedures for Medical Operations, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Electronic procedures are currently being used to document the steps in performing medical operations for the Space Shuttle and/or the International Space Station...

  16. Tackling the Transition to UC: To Implement Unified Communications on Campus, It Often Pays to Take a Phased Approach

    Science.gov (United States)

    Ramaswami, Rama

    2011-01-01

    In this article, the author talks about the challenges faced by two schools that lie, coincidentally, just 110 miles apart in the vast spaces of North Dakota. Both schools, members of the North Dakota University System, decided to forge ahead with a unified communications (UC) implementation. And while their final solutions differ, how the two…

  17. Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

    Science.gov (United States)

    Phatak, C.; Petford-Long, A. K.; Beleggia, M.; De Graef, M.

    2014-06-01

    Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift computation for a uniformly polarized prolate ellipsoid with varying aspect ratio in the absence of screening charges.

  18. SU-G-JeP2-02: A Unifying Multi-Atlas Approach to Electron Density Mapping Using Multi-Parametric MRI for Radiation Treatment Planning

    Energy Technology Data Exchange (ETDEWEB)

    Ren, S [Stanford University, Stanford, CA (United States); Tianjin University, Tianjin (China); Hara, W; Le, Q; Wang, L; Xing, L; Li, R [Stanford University, Stanford, CA (United States)

    2016-06-15

    Purpose: MRI has a number of advantages over CT as a primary modality for radiation treatment planning (RTP). However, one key bottleneck problem still remains, which is the lack of electron density information in MRI. In the work, a reliable method to map electron density is developed by leveraging the differential contrast of multi-parametric MRI. Methods: We propose a probabilistic Bayesian approach for electron density mapping based on T1 and T2-weighted MRI, using multiple patients as atlases. For each voxel, we compute two conditional probabilities: (1) electron density given its image intensity on T1 and T2-weighted MR images, and (2) electron density given its geometric location in a reference anatomy. The two sources of information (image intensity and spatial location) are combined into a unifying posterior probability density function using the Bayesian formalism. The mean value of the posterior probability density function provides the estimated electron density. Results: We evaluated the method on 10 head and neck patients and performed leave-one-out cross validation (9 patients as atlases and remaining 1 as test). The proposed method significantly reduced the errors in electron density estimation, with a mean absolute HU error of 138, compared with 193 for the T1-weighted intensity approach and 261 without density correction. For bone detection (HU>200), the proposed method had an accuracy of 84% and a sensitivity of 73% at specificity of 90% (AUC = 87%). In comparison, the AUC for bone detection is 73% and 50% using the intensity approach and without density correction, respectively. Conclusion: The proposed unifying method provides accurate electron density estimation and bone detection based on multi-parametric MRI of the head with highly heterogeneous anatomy. This could allow for accurate dose calculation and reference image generation for patient setup in MRI-based radiation treatment planning.

  19. SU-G-JeP2-02: A Unifying Multi-Atlas Approach to Electron Density Mapping Using Multi-Parametric MRI for Radiation Treatment Planning

    International Nuclear Information System (INIS)

    Ren, S; Hara, W; Le, Q; Wang, L; Xing, L; Li, R

    2016-01-01

    Purpose: MRI has a number of advantages over CT as a primary modality for radiation treatment planning (RTP). However, one key bottleneck problem still remains, which is the lack of electron density information in MRI. In the work, a reliable method to map electron density is developed by leveraging the differential contrast of multi-parametric MRI. Methods: We propose a probabilistic Bayesian approach for electron density mapping based on T1 and T2-weighted MRI, using multiple patients as atlases. For each voxel, we compute two conditional probabilities: (1) electron density given its image intensity on T1 and T2-weighted MR images, and (2) electron density given its geometric location in a reference anatomy. The two sources of information (image intensity and spatial location) are combined into a unifying posterior probability density function using the Bayesian formalism. The mean value of the posterior probability density function provides the estimated electron density. Results: We evaluated the method on 10 head and neck patients and performed leave-one-out cross validation (9 patients as atlases and remaining 1 as test). The proposed method significantly reduced the errors in electron density estimation, with a mean absolute HU error of 138, compared with 193 for the T1-weighted intensity approach and 261 without density correction. For bone detection (HU>200), the proposed method had an accuracy of 84% and a sensitivity of 73% at specificity of 90% (AUC = 87%). In comparison, the AUC for bone detection is 73% and 50% using the intensity approach and without density correction, respectively. Conclusion: The proposed unifying method provides accurate electron density estimation and bone detection based on multi-parametric MRI of the head with highly heterogeneous anatomy. This could allow for accurate dose calculation and reference image generation for patient setup in MRI-based radiation treatment planning.

  20. Electronic structure theory of alloy phase stability

    International Nuclear Information System (INIS)

    Turchi, P.E.A.; Sluiter, M.

    1992-01-01

    We present a brief overview of the advanced methodology which has been developed and applied to the study of phase stability properties in substitutional alloys. The approach is based on the real space version of the Generalized Perturbation Method within the Korringa-Kohn-Rostoker multiple scattering formulation of the Coherent Potential Approximation. Temperature effects are taken into account with a generalized meanfield approach, namely the Cluster Variation Method, or with Monte-Carlo simulations. We show that this approach is well suited for studying ground state properties of substitutional alloys, for calculating energies of idealized interfaces and antiphase boundaries, and finally to compute alloy phase diagrams

  1. Electronic construction collaboration system -- final phase.

    Science.gov (United States)

    2014-09-01

    This phase of the research project involved two major efforts: (1) Complete the implementation of AEC-Sync (formerly known as : Attolist) on the Iowa Falls Arch Bridge project and (2) develop a WPMS for projects under $10 million. : For the first maj...

  2. Cromatografia unificada Unified chromatography

    Directory of Open Access Journals (Sweden)

    Carin von Mühlen

    2004-10-01

    Full Text Available The scope of this study encompasses an overview of the principles of unified chromatography as well as the principles of chromatographic techniques as applied to unified systems, which include gas chromatography, liquid chromatography, supercritical fluid chromatography, high temperature and high pressure liquid chromatography, micro-liquid chromatography, enhanced fluidity chromatography, and solvating gas chromatography. Theoretical considerations and individual instrumental parameters such as mobile phase, sample introduction system, columns, and detection system are also discussed. Future applications of this separation approach are discussed.

  3. Biological applications of phase-contrast electron microscopy.

    Science.gov (United States)

    Nagayama, Kuniaki

    2014-01-01

    Here, I review the principles and applications of phase-contrast electron microscopy using phase plates. First, I develop the principle of phase contrast based on a minimal model of microscopy, introducing a double Fourier-transform process to mathematically formulate the image formation. Next, I explain four phase-contrast (PC) schemes, defocus PC, Zernike PC, Hilbert differential contrast, and schlieren optics, as image-filtering processes in the context of the minimal model, with particular emphases on the Zernike PC and corresponding Zernike phase plates. Finally, I review applications of Zernike PC cryo-electron microscopy to biological systems such as protein molecules, virus particles, and cells, including single-particle analysis to delineate three-dimensional (3D) structures of protein and virus particles and cryo-electron tomography to reconstruct 3D images of complex protein systems and cells.

  4. Electron correlation in molecules and condensed phases

    CERN Document Server

    March, N H

    1996-01-01

    This reference describes the latest research on correlation effects in the multicenter problems of atoms, molecules, and solids The author utilizes first- and second-order matrices, including the important observable electron density rho(r), and the Green function for discussing quantum computer simulations With its focus on concepts and theories, this volume will benefit experimental physicists, materials scientists, and physical and inorganic chemists as well as graduate students

  5. Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers.

    Science.gov (United States)

    Kumar, Krishan; Moudgil, R K

    2012-10-17

    We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

  6. Three-phase electric drive with modified electronic smoothing inductor

    DEFF Research Database (Denmark)

    Singh, Yash Veer; Rasmussen, Peter Omand; Andersen, Torben Ole

    2010-01-01

    This paper presents a three-phase electric drive with a modified electronic smoothing inductor (MESI) having reduced size of passive components. The classical electronic smoothing inductor (ESI) is able to control a diode bridge output current and also reduce not only mains current harmonics...

  7. Phase-Space Models of Solitary Electron Hoies

    DEFF Research Database (Denmark)

    Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans

    1985-01-01

    Two different phase-space models of solitary electron holes are investigated and compared with results from computer simulations of an actual laboratory experiment, carried out in a strongly magnetized, cylindrical plasma column. In the two models, the velocity distribution of the electrons...

  8. Effect of electron-electron collisions on the phase transition and kinetics of nonequilibrium superconductors

    International Nuclear Information System (INIS)

    Elesin, V.F.; Kashurnikov, V.A.; Kondrashov, V.E.; Shamraev, B.N.

    1983-01-01

    An explicit expression is obtained for the distribution function of excess quasiparticles, taking into account electron-electron collisions in nonequilibrium superconductors. It is shown that the character of the phase transition may change at a definite ratio of the electron-electron and electron-phonon interaction constants: the dependence of the order parameter on the power of the source becomes single-valued. In addition, diffusion instability and paramagnetism of the superconductors arise. The multiplication factor of the excess quasiparticles due to electron-electron collisions and to reabsorption of phonons is calculated

  9. Analysis of quaternary ammonium and phosphonium ionic liquids by reversed-phase high-performance liquid chromatography with charged aerosol detection and unified calibration.

    Science.gov (United States)

    Stojanovic, Anja; Lämmerhofer, Michael; Kogelnig, Daniel; Schiesel, Simone; Sturm, Martin; Galanski, Markus; Krachler, Regina; Keppler, Bernhard K; Lindner, Wolfgang

    2008-10-31

    Several hydrophobic ionic liquids (ILs) based on long-chain aliphatic ammonium- and phosphonium cations and selected aromatic anions were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) employing trifluoroacetic acid as ion-pairing additive to the acetonitrile-containing mobile phase and adopting a step-gradient elution mode. The coupling of charged aerosol detection (CAD) for the non-chromophoric aliphatic cations with diode array detection (DAD) for the aromatic anions allowed their simultaneous analysis in a set of new ILs derived from either tricaprylmethylammonium chloride (Aliquat 336) and trihexyltetradecylphosphonium chloride as precursors. Aliquat 336 is a mix of ammonium cations with distinct aliphatic chain lengths. In the course of the studies it turned out that CAD generates an identical detection response for all the distinct aliphatic cations. Due to lack of single component standards of the individual Aliquat 336 cation species, a unified calibration function was established for the quantitative analysis of the quaternary ammonium cations of the ILs. The developed method was validated according to ICH guidelines, which confirmed the validity of the unified calibration. The application of the method revealed molar ratios of cation to anion close to 1 indicating a quantitative exchange of the chloride ions of the precursors by the various aromatic anions in the course of the synthesis of new ILs. Anomalies of CAD observed for the detection of some aromatic anions (thiosalicylate and benzoate) are discussed.

  10. Unifying Abstractions

    DEFF Research Database (Denmark)

    Torgersen, Mads

    This thesis presents the RUNE language, a semantic construction of related and tightly coupled programming constructs presented in the shape of a programming language. The major contribution is the succesfull design of a highly unified and general programming model, capable of expressing some of ...... a unified name declaration mechanism. The resulting expressiveness allows for argument covariance, dependent types and module types, plus a solution to the so-called expression problem of two way extensibility in object-oriented languages....... of the most complex type relations put forth in type systems research, without compromising such fundamental qualities as conceptuality, modularity and static typing. While many new constructs and unifications are put forth  to substantiate their conceptual validity, type rules are given to support...

  11. Why unify

    International Nuclear Information System (INIS)

    Georgi, H.

    1980-01-01

    Unified gauge theories such as SU(5) of particle interactions are built on the colour SU(3) and SU(2) x U(1) gauge theories which apparently describe strong and weak and electromagnetic interactions at distances as small as 10 -16 cm. In this article the classical reasons for going beyond SU(3)xSU(2)xU(1) to a fully unified theory such as SU(5) are reviewed, and a new reason formulated. A class of imaginary worlds similar to our own is considered and it is shown that unification is possible only in ours. This suggests that the low-energy interactions are unique in that they are constructed to make unification possible. (author)

  12. Electron concentration and phase stability in NbCr2-based Laves phase alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.H.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Liu, C.T. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-05-12

    Phase stability in NbCr{sub 2}-based transition-metal Laves phases was studied, based on the data reported for binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor, e/a, is the dominating factor in controlling the phase stability of NbCr{sub 2}-based transition-metal Laves phases. The e/a ratios for different Laves polytypes were determined as followed: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88--7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure is stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of Mg-based Laves phases and transition-metal A{sub 3}B intermetallic compounds is also reviewed and compared with the present observations in transition-metal Laves phases. In order to verify the e/a/phase stability relationship experimentally, additions of Cu (with e/a = 11) were selected to replace Cr in the NbCr{sub 2} Laves phase. Experimental results for the ternary Nb-Cr-Cu system are reported and discussed in terms of the correlation between the e/a ratio and phase stability in NbCr{sub 2}-based Laves phases. A new phase was found, which has an average composition of Nb-47Cr-3Cu. Within the solubility limit, the electron concentration and phase stability relationship is obeyed in the Nb-Cr-Cu system.

  13. Superfluid phase stiffness in electron doped superconducting Gd-123

    Science.gov (United States)

    Das, P.; Ghosh, Ajay Kumar

    2018-05-01

    Current-voltage characteristics of Ce substituted Gd-123 superconductor exhibits nonlinearity below a certain temperature below the critical temperature. An exponent is extracted using the nonlinearity of current-voltage relation. Superfluid phase stiffness has been studied as a function of temperature following the Ambegaokar-Halperin-Nelson-Siggia (AHNS) theory. Phase stiffness of the superfluid below the superconducting transition is found to be sensitive to the change in the carrier concentration in superconducting system. There may be a crucial electron density which affects superfluid stiffness strongly. Electron doping is found to be effective even if the coupling of the superconducting planes is changed.

  14. Rational Unified Process

    OpenAIRE

    Kopal, Nils

    2016-01-01

    In this German seminar paper, which was written in the year 2011 at the University of Duisburg for a Bachelor Colloquium in Applied computer science, we show a brief overview of the Rational Unified Process (RUP). Thus, interested students or generally interested people in software development gain a first impression of RUP. The paper includes a survey and overview of the underlying process structure, the phases of the process, its workflows, and describes the always by the RUP developers pos...

  15. Improvement of the accuracy of phase observation by modification of phase-shifting electron holography

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Takahiro; Aizawa, Shinji; Tanigaki, Toshiaki [Advanced Science Institute, RIKEN, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Ota, Keishin, E-mail: ota@microphase.co.jp [Microphase Co., Ltd., Onigakubo 1147-9, Tsukuba, Ibaragi 300-2651 (Japan); Matsuda, Tsuyoshi [Japan Science and Technology Agency, Kawaguchi-shi, Saitama 332-0012 (Japan); Tonomura, Akira [Advanced Science Institute, RIKEN, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Okinawa Institute of Science and Technology, Graduate University, Kunigami, Okinawa 904-0495 (Japan); Central Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama 350-0395 (Japan)

    2012-07-15

    We found that the accuracy of the phase observation in phase-shifting electron holography is strongly restricted by time variations of mean intensity and contrast of the holograms. A modified method was developed for correcting these variations. Experimental results demonstrated that the modification enabled us to acquire a large number of holograms, and as a result, the accuracy of the phase observation has been improved by a factor of 5. -- Highlights: Black-Right-Pointing-Pointer A modified phase-shifting electron holography was proposed. Black-Right-Pointing-Pointer The time variation of mean intensity and contrast of holograms were corrected. Black-Right-Pointing-Pointer These corrections lead to a great improvement of the resultant phase accuracy. Black-Right-Pointing-Pointer A phase accuracy of about 1/4000 rad was achieved from experimental results.

  16. Improvement of the accuracy of phase observation by modification of phase-shifting electron holography

    International Nuclear Information System (INIS)

    Suzuki, Takahiro; Aizawa, Shinji; Tanigaki, Toshiaki; Ota, Keishin; Matsuda, Tsuyoshi; Tonomura, Akira

    2012-01-01

    We found that the accuracy of the phase observation in phase-shifting electron holography is strongly restricted by time variations of mean intensity and contrast of the holograms. A modified method was developed for correcting these variations. Experimental results demonstrated that the modification enabled us to acquire a large number of holograms, and as a result, the accuracy of the phase observation has been improved by a factor of 5. -- Highlights: ► A modified phase-shifting electron holography was proposed. ► The time variation of mean intensity and contrast of holograms were corrected. ► These corrections lead to a great improvement of the resultant phase accuracy. ► A phase accuracy of about 1/4000 rad was achieved from experimental results.

  17. Electron-phonon interaction in Chevrel-phase compounds

    International Nuclear Information System (INIS)

    Rainer, D.; Pobell, F.

    1981-03-01

    Experiments on the electron-phonon interaction in Chevrel-phase compounds (CPC) and a theoretical discussion of their results are presented. The authors particularly discuss measurements of the isotope effect of the transition temperature in Mo 6 Se 8 and SnMo 6 S 8 and tunneling spectroscopy experiments on Cu 1 . 8 Mo 6 S 8 and PbMo 6 S 8 . These investigations have been performed to get information about the strength of the electron-phonon interaction in CPC, and about the question whether there are phonon modes which couple particularly strongly to the electrons in these compounds. (orig./GSCH)

  18. Spin delocalization phase transition in a correlated electrons model

    International Nuclear Information System (INIS)

    Huerta, L.

    1990-11-01

    In a simplified one-site model for correlated electrons systems we show the existence of a phase transition corresponding to spin delocalization. The system becomes a solvable model and zero-dimensional functional techniques are used. (author). 7 refs, 3 figs

  19. Ultrafast Hot Electron Induced Phase Transitions in Vanadium Dioxide

    Directory of Open Access Journals (Sweden)

    Haglund R. F.

    2013-03-01

    Full Text Available The Au/Cr/VO2/Si system was investigated in pump–probe experiments. Hot-electrons generated in the Au were found to penetrate into the underlying VO2 and couple with its lattice inducing a semiconductor-to-metal phase transition in ~2 picoseconds.

  20. Sculpturing the electron wave function using nanoscale phase masks

    Energy Technology Data Exchange (ETDEWEB)

    Shiloh, Roy, E-mail: royshilo@post.tau.ac.il; Lereah, Yossi; Lilach, Yigal; Arie, Ady

    2014-09-15

    Electron beams are extensively used in lithography, microscopy, material studies and electronic chip inspection. Today, beams are mainly shaped using magnetic or electric forces, enabling only simple shaping tasks such as focusing or scanning. Recently, binary amplitude gratings achieved complex shapes. These, however, generate multiple diffraction orders, hence the desired shape, appearing only in one order, retains little of the beam energy. Here we demonstrate a method in electron-optics for arbitrarily shaping electron beams into a single desired shape, by precise patterning of a thin-membrane. It is conceptually similar to shaping light beams using refractive or diffractive glass elements such as lenses or holograms – rather than applying electromagnetic forces, the beam is controlled by spatially modulating its wavefront. Our method allows for nearly-maximal energy transference to the designed shape, and may avoid physical damage and charging effects that are the scorn of commonly-used (e.g. Zernike and Hilbert) phase-plates. The experimental demonstrations presented here – on-axis Hermite–Gauss and Laguerre–Gauss (vortex) beams, and computer-generated holograms – are a first example of nearly-arbitrary manipulation of electron beams. Our results herald exciting prospects for microscopic material studies, enables electron lithography with fixed sample and beam and high resolution electronic chip inspection by structured electron illumination. - Highlights: • Nanoscale-patterned membranes are used to shape electron beams. • Designing on-axis phase plates outside the back focal plane is possible. • Computer-generated holograms enable nearly-arbitrary beam shaping. • Applications in microscopy, lithography, chip inspection and material sciences.

  1. Prospects for electron beam aberration correction using sculpted phase masks

    Energy Technology Data Exchange (ETDEWEB)

    Shiloh, Roy, E-mail: royshilo@post.tau.ac.il; Remez, Roei; Arie, Ady

    2016-04-15

    Technological advances in fabrication methods allowed the microscopy community to take incremental steps towards perfecting the electron microscope, and magnetic lens design in particular. Still, state of the art aberration-corrected microscopes are yet 20–30 times shy of the theoretical electron diffraction limit. Moreover, these microscopes consume significant physical space and are very expensive. Here, we show how a thin, sculpted membrane is used as a phase-mask to induce specific aberrations into an electron beam probe in a standard high resolution TEM. In particular, we experimentally demonstrate beam splitting, two-fold astigmatism, three-fold astigmatism, and spherical aberration. - Highlights: • Thin membranes can be used as aberration correctors in electron columns. • We demonstrate tilt, twofold-, threefold-astigmatism, and spherical aberrations. • Experimental and physical-optics simulation results are in good agreement. • Advantages in cost, size, nonmagnetism, and nearly-arbitrary correction.

  2. A unified universe

    DEFF Research Database (Denmark)

    Codello, Alessandro; Jain, Rajeev Kumar

    2018-01-01

    We present a unified evolution of the universe from very early times until the present epoch by including both the leading local correction R2 and the leading non-local term R1□2R to the classical gravitational action. We find that the inflationary phase driven by R2 term gracefully exits...... in a transitory regime characterized by coherent oscillations of the Hubble parameter. The universe then naturally enters into a radiation dominated epoch followed by a matter dominated era. At sufficiently late times after radiation–matter equality, the non-local term starts to dominate inducing an accelerated...... expansion of the universe at the present epoch. We further exhibit the fact that both the leading local and non-local terms can be obtained within the covariant effective field theory of gravity. This scenario thus provides a unified picture of inflation and dark energy in a single framework by means...

  3. Electronic properties and phase transitions in low-dimensional semiconductors

    International Nuclear Information System (INIS)

    Panich, A M

    2008-01-01

    We present the first review of the current state of the literature on electronic properties and phase transitions in TlX and TlMX 2 (M = Ga, In; X = Se, S, Te) compounds. These chalcogenides belong to a family of the low-dimensional semiconductors possessing chain or layered structure. They are of significant interest because of their highly anisotropic properties, semi- and photoconductivity, nonlinear effects in their I-V characteristics (including a region of negative differential resistance), switching and memory effects, second harmonic optical generation, relaxor behavior and potential applications for optoelectronic devices. We review the crystal structure of TlX and TlMX 2 compounds, their transport properties under ambient conditions, experimental and theoretical studies of the electronic structure, transport properties and semiconductor-metal phase transitions under high pressure, and sequences of temperature-induced structural phase transitions with intermediate incommensurate states. The electronic nature of the ferroelectric phase transitions in the above-mentioned compounds, as well as relaxor behavior, nanodomains and possible occurrence of quantum dots in doped and irradiated crystals is discussed. (topical review)

  4. Quantum phase transitions of strongly correlated electron systems

    International Nuclear Information System (INIS)

    Imada, Masatoshi

    1998-01-01

    Interacting electrons in solids undergo various quantum phase transitions driven by quantum fluctuations. The quantum transitions take place at zero temperature by changing a parameter to control quantum fluctuations rather than thermal fluctuations. In contrast to classical phase transitions driven by thermal fluctuations, the quantum transitions have many different features where quantum dynamics introduces a source of intrinsic fluctuations tightly connected with spatial correlations and they have been a subject of recent intensive studies as we see below. Interacting electron systems cannot be fully understood without deep analyses of the quantum phase transitions themselves, because they are widely seen and play essential roles in many phenomena. Typical and important examples of the quantum phase transitions include metal-insulator transitions, (2, 3, 4, 5, 6, 7, 8, 9) metal-superconductor transitions, superconductor-insulator transitions, magnetic transitions to antiferromagnetic or ferromagnetic phases in metals as well as in Mott insulators, and charge ordering transitions. Here, we focus on three different types of transitions

  5. Towards a Unified Understanding of Event-Related Changes in the EEG: The Firefly Model of Synchronization through Cross-Frequency Phase Modulation

    Science.gov (United States)

    Burgess, Adrian P.

    2012-01-01

    Although event-related potentials (ERPs) are widely used to study sensory, perceptual and cognitive processes, it remains unknown whether they are phase-locked signals superimposed upon the ongoing electroencephalogram (EEG) or result from phase-alignment of the EEG. Previous attempts to discriminate between these hypotheses have been unsuccessful but here a new test is presented based on the prediction that ERPs generated by phase-alignment will be associated with event-related changes in frequency whereas evoked-ERPs will not. Using empirical mode decomposition (EMD), which allows measurement of narrow-band changes in the EEG without predefining frequency bands, evidence was found for transient frequency slowing in recognition memory ERPs but not in simulated data derived from the evoked model. Furthermore, the timing of phase-alignment was frequency dependent with the earliest alignment occurring at high frequencies. Based on these findings, the Firefly model was developed, which proposes that both evoked and induced power changes derive from frequency-dependent phase-alignment of the ongoing EEG. Simulated data derived from the Firefly model provided a close match with empirical data and the model was able to account for i) the shape and timing of ERPs at different scalp sites, ii) the event-related desynchronization in alpha and synchronization in theta, and iii) changes in the power density spectrum from the pre-stimulus baseline to the post-stimulus period. The Firefly Model, therefore, provides not only a unifying account of event-related changes in the EEG but also a possible mechanism for cross-frequency information processing. PMID:23049827

  6. An Empirical Analysis of Citizens' Acceptance Decisions of Electronic-Government Services: A Modification of the Unified Theory of Acceptance and Use of Technology (UTAUT) Model to Include Trust as a Basis for Investigation

    Science.gov (United States)

    Awuah, Lawrence J.

    2012-01-01

    Understanding citizens' adoption of electronic-government (e-government) is an important topic, as the use of e-government has become an integral part of governance. Success of such initiatives depends largely on the efficient use of e-government services. The unified theory of acceptance and use of technology (UTAUT) model has provided a…

  7. Crossover between the dense electron-hole phase and the BCS excitonic phase in quantum dots

    International Nuclear Information System (INIS)

    Rodriguez, B.A.; Gonzalez, A.; Quiroga, L.; Capote, R.; Rodriguez, F.J.

    1999-09-01

    Second order perturbation theory and a Lipkin-Nogami scheme combined with an exact Monte Carlo projection after variation are applied to compute the ground-state energy of 6 ≤ N ≤ 210 electron-hole pairs confined in a parabolic two-dimensional quantum dot. The energy shows nice scaling properties as N or the confinement strength is varied. A crossover from the high-density electron-hole phase to the BCS excitonic phase is found at a density which is roughly four times the close-packing density of excitons. (author)

  8. Phase analysis of nano-phase materials using selected area electron diffraction in the TEM

    International Nuclear Information System (INIS)

    Labar, J. L.

    2002-01-01

    In analogy to X-ray power diffraction (XRD), we are developing a method to help phase identification when examining a large number of grains simultaneously by electron diffraction. Although XRD is well established, it can not be used for small quantities of materials (volumes below 1 mm 3 ). Examining a usual TEM sample with thickness of 100 nm and using a selected area of 1 mm in diameter, the selected area electron diffraction pattern (SAED) carries information about several thousands of grains from a material with an average grain size of about 10 nm. The accuracy of XRD can not be attained by electron diffraction (ED). However, simultaneous visual observation of the nanostructure is an additional benefit of TEM (beside the small amount of needed material). The first step of the development project was the development of a computer program ('ProcessDiffraction') that processes digital versions of SAED patterns and presents them in an XRD-like form (intensity vs. scattering vector). In the present version (V2.0.3) phase identification is carried out by comparing the measured distribution to 'Markers', i.e. data of known phases. XRD data cards are used if the detailed structure of a phase is not known. Kinematic electron diffraction intensities are calculated for phases with known atomic positions (Author)

  9. Phase stability and electronic structure of transition-metal aluminides

    International Nuclear Information System (INIS)

    Carlsson, A.E.

    1992-01-01

    This paper will describe the interplay between die electronic structure and structural energetics in simple, complex, and quasicrystalline Al-transition metal (T) intermetallics. The first example is the Ll 2 -DO 22 competition in Al 3 T compounds. Ab-initio electronic total-energy calculations reveal surprisingly large structural-energy differences, and show that the phase stability of both stoichiometric and ternary-substituted compounds correlates closely with a quasigap in the electronic density of states (DOS). Secondly, ab-initio calculations for the structural stability of the icosahedrally based Al 12 W structure reveal similar quasigap effects, and provide a simple physical explanation for the stability of the complex aluminide structures. Finally, parametrized tight-binding model calculations for the Al-Mn quasicrystal reveal a large spread in the local Mn DOS behavior, and support a two-site model for the quasicrystal's magnetic behavior

  10. Fitting phase shifts to electron-ion elastic scattering measurements

    International Nuclear Information System (INIS)

    Per, M.C.; Dickinson, A.S.

    2000-01-01

    We have derived non-Coulomb phase shifts from measured differential cross sections for electron scattering by the ions Na + , Cs + , N 3+ , Ar 8+ and Xe 6+ at energies below the inelastic threshold. Values of the scaled squared deviation between the observed and fitted differential cross sections, χ 2 , for the best-fit phase shifts were typically in the range 3-6 per degree of freedom. Generally good agreement with experiment is obtained, except for wide-angle scattering by Ar 8+ and Xe 6+ . Current measurements do not define phase shifts to better than approx. 0.1 rad even in the most favourable circumstances and uncertainties can be much larger. (author)

  11. Electron band theory predictions and the construction of phase diagrams

    International Nuclear Information System (INIS)

    Watson, R.E.; Bennett, L.H.; Davenport, J.W.; Weinert, M.

    1985-01-01

    The a priori theory of metals is yielding energy results which are relevant to the construction of phase diagrams - to the solution phases as well as to line compounds. There is a wide range in the rigor of the calculations currently being done and this is discussed. Calculations for the structural stabilities (fcc vs bcc vs hcp) of the elemental metals, quantities which are employed in the constructs of the terminal phases, are reviewed and shown to be inconsistent with the values currently employed in such constructs (also see Miodownik elsewhere in this volume). Finally, as an example, the calculated heats of formation are compared with experiment for PtHf, IrTa and OsW, three compounds with the same electron to atom ratio but different bonding properties

  12. Unifying Physics

    Science.gov (United States)

    Goradia, Shantilal

    2013-04-01

    Century old GR fails to unify quantum physics, nuclear force or distinguish between the mass of living bodies from inert mass. Probabilistic gravity [1] explains strong coupling (nuclear force). The natural log of the age of the universe, 10E60 in Planck times, equaling 137 (1/Alpha) extends physics to deeper science, if we stand on the shoulders of giants like Feynman and Gamow. Implications of [1] are that it is not the earth, but M and S numbers of the particles of the earth are remotely interacting with corresponding numbers of the particles of the moon and the sun respectively, neglecting other heavenly bodies in this short draft. This new physics is likely to enable creative scientific minds to throw light on a theoretical basis for an otherwise arbitrary cosmological constant, uniformity of microwave background, further vindication of Boltzmann, quantum informatics, Einstein’s later publicized views and more, eliminating the need to spend money for implicitly nonexistent quantum gravity and graviton.[4pt] [1] Journal of Physical Science and Applications 2 (7) (2012) 265-268.

  13. A Unified Algorithm for Channel Imbalance and Antenna Phase Center Position Calibration of a Single-Pass Multi-Baseline TomoSAR System

    Directory of Open Access Journals (Sweden)

    Yuncheng Bu

    2018-03-01

    Full Text Available The multi-baseline synthetic aperture radar (SAR tomography (TomoSAR system is employed in such applications as disaster remote sensing, urban 3-D reconstruction, and forest carbon storage estimation. This is because of its 3-D imaging capability in a single-pass platform. However, a high 3-D resolution of TomoSAR is based on the premise that the channel imbalance and antenna phase center (APC position are precisely known. If this is not the case, the 3-D resolution performance will be seriously degraded. In this paper, a unified algorithm for channel imbalance and APC position calibration of a single-pass multi-baseline TomoSAR system is proposed. Based on the maximum likelihood method, as well as the least squares and the damped Newton method, we can calibrate the channel imbalance and APC position. The algorithm is suitable for near-field conditions, and no phase unwrapping operation is required. The effectiveness of the proposed algorithm has been verified by simulation and experimental results.

  14. A general unified non-equilibrium model for predicting saturated and subcooled critical two-phase flow rates through short and long tubes

    International Nuclear Information System (INIS)

    Fraser, D.W.H.; Abdelmessih, A.H.

    1995-01-01

    A general unified model is developed to predict one-component critical two-phase pipe flow. Modelling of the two-phase flow is accomplished by describing the evolution of the flow between the location of flashing inception and the exit (critical) plane. The model approximates the nonequilibrium phase change process via thermodynamic equilibrium paths. Included are the relative effects of varying the location of flashing inception, pipe geometry, fluid properties and length to diameter ratio. The model predicts that a range of critical mass fluxes exist and is bound by a maximum and minimum value for a given thermodynamic state. This range is more pronounced at lower subcooled stagnation states and can be attributed to the variation in the location of flashing inception. The model is based on the results of an experimental study of the critical two-phase flow of saturated and subcooled water through long tubes. In that study, the location of flashing inception was accurately controlled and adjusted through the use of a new device. The data obtained revealed that for fixed stagnation conditions, the maximum critical mass flux occurred with flashing inception located near the pipe exit; while minimum critical mass fluxes occurred with the flashing front located further upstream. Available data since 1970 for both short and long tubes over a wide range of conditions are compared with the model predictions. This includes test section L/D ratios from 25 to 300 and covers a temperature and pressure range of 110 to 280 degrees C and 0.16 to 6.9 MPa. respectively. The predicted maximum and minimum critical mass fluxes show an excellent agreement with the range observed in the experimental data

  15. A general unified non-equilibrium model for predicting saturated and subcooled critical two-phase flow rates through short and long tubes

    Energy Technology Data Exchange (ETDEWEB)

    Fraser, D.W.H. [Univ. of British Columbia (Canada); Abdelmessih, A.H. [Univ. of Toronto, Ontario (Canada)

    1995-09-01

    A general unified model is developed to predict one-component critical two-phase pipe flow. Modelling of the two-phase flow is accomplished by describing the evolution of the flow between the location of flashing inception and the exit (critical) plane. The model approximates the nonequilibrium phase change process via thermodynamic equilibrium paths. Included are the relative effects of varying the location of flashing inception, pipe geometry, fluid properties and length to diameter ratio. The model predicts that a range of critical mass fluxes exist and is bound by a maximum and minimum value for a given thermodynamic state. This range is more pronounced at lower subcooled stagnation states and can be attributed to the variation in the location of flashing inception. The model is based on the results of an experimental study of the critical two-phase flow of saturated and subcooled water through long tubes. In that study, the location of flashing inception was accurately controlled and adjusted through the use of a new device. The data obtained revealed that for fixed stagnation conditions, the maximum critical mass flux occurred with flashing inception located near the pipe exit; while minimum critical mass fluxes occurred with the flashing front located further upstream. Available data since 1970 for both short and long tubes over a wide range of conditions are compared with the model predictions. This includes test section L/D ratios from 25 to 300 and covers a temperature and pressure range of 110 to 280{degrees}C and 0.16 to 6.9 MPa. respectively. The predicted maximum and minimum critical mass fluxes show an excellent agreement with the range observed in the experimental data.

  16. Dissociative attachment reactions of electrons with gas phase superacids

    International Nuclear Information System (INIS)

    Liu, X.

    1992-01-01

    Using the flowing afterglow Langmuir probe (FALP) technique, dissociative attachment coefficients β for reactions of electrons with gas phase superacids HCo(PF 3 ) 4 , HRh(PF 3 ) 4 and carbonyl hydride complexes HMn(CO) 5 , HRe(CO) 5 have been determined under thermal conditions over the approximate temperature range 300∼550 K. The superacids react relatively slowly ( max ) with free electrons in a thermal plasma, and the values of β obtained this far do not show a correlation between acidity and β. The pioneer researchers in this field had speculated that any superacid would be a rapid attacher of electrons; it was found that this speculation is not true in general. The product distribution of electron attachment reaction to HCo(PF 3 ) 4 was found to be independent of temperature even though the β[HCo(PF 3 ) 4 ] increases with temperature. This proposes that the electron attachment process occurs well before the excited complex dissociates. In addition, the activation energy of HCo(PF 3 ) 4 for electron attachment has been derived from the Arrhenius plots. The carbonyl hydride complexes, HMn(CO) 5 and HRe(CO) 5 , react relatively rapidly (>1/4 of β max ) with free electrons in thermal plasma. This indicates that these reactions cannot be significantly endothermic. Observation of rapid attachment for these non-superacids shows that the Mn-CO and Re-CO bonds are weaker than the Mn-H and Re-H bonds, respectively. Comparisons between the carbonyl and trifluorophosphine cases implies that fast electron capture is related more to the CO ligand than to the transition-metal species

  17. Electron correlation influenced magnetic phase transitions in f-electron systems

    International Nuclear Information System (INIS)

    Frauenheim, T.; Ropke, G.

    1980-01-01

    The temperature-induced phase transition (on lowering the temperature) antiferromagnet-ferromagnet in the heavy rare earth and some of actinide compounds is qualitatively explained in the scope of a two-band Hubbard model and the more complex RKKY model as the result of electron correlation effects in the conduction bands. (orig.)

  18. General Unified Integral Controller with Zero Steady-State Error for Single-Phase Grid-Connected Inverters

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; Guerrero, Josep M.

    2016-01-01

    Current regulation is crucial for operating single-phase grid-connected inverters. The challenge of the current controller is how to fast and precisely tracks the current with zero steady-state error. This paper proposes a novel feedback mechanism for the conventional PI controller. It allows...... done indicates that the widely used PR (P+Resonant) control is just a special case of the proposed control solution. The time-domain simulation in Matlab/Simulink and experimental results from a TMS320F2812 DSP based laboratory prototypes are in good agreement, which verify the effectiveness...

  19. Unified analytical treatment of multicentre electron attraction, electric field and electric field gradient integrals over Slater orbitals

    International Nuclear Information System (INIS)

    Guseinov, I I

    2004-01-01

    The new central and noncentral potential functions (CPFs and NCPFs) of a molecule depending on the coordinates of the nuclei are introduced. Using complete orthonormal sets of Ψ α -exponential-type orbitals (Ψ α -ETOs) introduced by the author, the series expansion formulae for the multicentre electronic attraction (EA), electric field (EF) and electric field gradient (EFG) integrals over Slater-type orbitals (STOs) in terms of CPFs and NCPFs are derived. The relationships obtained are valid for the arbitrary location, quantum numbers and screening constants of STOs

  20. The happy marriage between electron-phonon superconductivity and Mott physics in Cs3C60: A first-principle phase diagram

    Science.gov (United States)

    Capone, Massimo; Nomura, Yusuke; Sakai, Shiro; Giovannetti, Gianluca; Arita, Ryotaro

    The phase diagram of doped fullerides like Cs3C60 as a function of the spacing between fullerene molecules is characterized by a first-order transition between a Mott insulator and an s-wave superconductor with a dome-shaped behavior of the critical temperature. By means of an ab-initio modeling of the bandstructure, the electron-phonon interaction and the interaction parameter and a Dynamical Mean-Field Theory solution, we reproduce the phase diagram and demonstrate that phonon superconductivity benefits from strong correlations confirming earlier model predictions. The role of correlations is manifest also in infrared measurements carried out by L. Baldassarre. The superconducting phase shares many similarities with ''exotic'' superconductors with electronic pairing, suggesting that the anomalies in the ''normal'' state, rather than the pairing glue, can be the real common element unifying a wide family of strongly correlated superconductors including cuprates and iron superconductors

  1. Phase Diagram and Electronic Structure of Praseodymium and Plutonium

    Directory of Open Access Journals (Sweden)

    Nicola Lanatà

    2015-01-01

    Full Text Available We develop a new implementation of the Gutzwiller approximation in combination with the local density approximation, which enables us to study complex 4f and 5f systems beyond the reach of previous approaches. We calculate from first principles the zero-temperature phase diagram and electronic structure of Pr and Pu, finding good agreement with the experiments. Our study of Pr indicates that its pressure-induced volume-collapse transition would not occur without change of lattice structure—contrarily to Ce. Our study of Pu shows that the most important effect originating the differentiation between the equilibrium densities of its allotropes is the competition between the Peierls effect and the Madelung interaction and not the dependence of the electron correlations on the lattice structure.

  2. Numerical analysis of sawtooth oscillation during electron cyclotron heating phases

    International Nuclear Information System (INIS)

    Wang Shiqing; Jin Yaqiu

    2001-01-01

    By employing two models, namely the reconnection model and the turbulence model, the authors present a transport code simulation of sawtooth discharges in T-10 Tokamak in the electron cyclotron heating phases, and the trigger conditions are also coupled into the transport code. In one discharge, ECRH was located nearly on-axis, and in another ECRH was located well off-axis. The comparison of numerical results and experiment data show that good prediction was obtained with the turbulence model. In contrast, due to some fundamental shortcoming of the reconnection model, no satisfactory fit could be obtained using the latter

  3. Structural phase transition and electronic properties in samarium chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, Y. S., E-mail: yspanwar2011@gmail.com [Department of Physics, Govt. New Science College Dewas-455001 (India); Aynyas, Mahendra [Department of Physics, C.S.A. Govt. P.G. College, Sehore, 466001 (India); Pataiya, J.; Sanyal, Sankar P. [Department of Physics, Barkatullah University, Bhopal, 462026 (India)

    2016-05-06

    The electronic structure and high pressure properties of samarium monochalcogenides SmS, SmSe and SmTe have been reported by using tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). The total energy as a function of volume is evaluated. It is found that these monochalcogenides are stable in NaCl-type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B{sub 1}-phase) structure to CsCl-type (B{sub 2}-type) structure for these compounds. Phase transition pressures were found to be 1.7, 4.4 and 6.6 GPa, for SmS, SmSe and SmTe respectively. Apart from this, the lattice parameter (a{sub 0}), bulk modulus (B{sub 0}), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed that these compounds exhibit metallic character. The calculated values of equilibrium lattice parameter and phase transition pressure are in general good agreement with available data.

  4. A Unified Electronic Tool for CPR and Emergency Treatment Escalation Plans Improves Communication and Early Collaborative Decision Making for Acute Hospital Admissions.

    Science.gov (United States)

    Johnson, Mae; Whyte, Martin; Loveridge, Robert; Yorke, Richard; Naleem, Shairana

    2017-01-01

    The National Confidential Enquiry into Patient Outcomes and Death (NCEPOD) report 'Time to Intervene' (2012) stated that in a substantial number of cases, resuscitation is attempted when it was thought a 'do not attempt cardiopulmonary resuscitation' (DNACPR) decision should have been in place. Early decisions about CPR status and advance planning about limits of care now form part of national recommendations by the UK Resuscitation Council (2016). Treatment escalation plans (TEP) document what level of treatment intervention would be appropriate if a patient were to become acutely unwell and were not previously formally in place at King's College Hospital. A unifying paper based form was successfully piloted in the Acute Medical Unit, introducing the TEP and bringing together decision making around both treatment escalation and CPR status. Subsequently an electronic order-set for CPR status and treatment escalation was launched in April 2015 which led to a highly visible CPR and escalation status banner on the main screen at the top of the patient's electronic record. Ultimately due to further iterations in the electronic process by December 2016, all escalation decisions for acutely admitted patients now have high quality supporting, explanatory documentation with 100% having TEPs in place. There is now widespread multidisciplinary engagement in the process of defining limits of care for acutely admitted medical patients within the first 14 hours of admission and a strategy for rolling this process out across all the divisions of the hospital through our Deteriorating Patient Group (DPG). The collaborative design with acute medical, palliative and intensive care teams and the high visibility provided by the electronic process in the Electronic Patient Record (EPR) has enhanced communication with these teams, patients, nursing staff and the multidisciplinary team by ensuring clarity through a universally understood process about escalation and CPR. Clarity and

  5. Interference electron microscopy of one-dimensional electron-optical phase objects

    International Nuclear Information System (INIS)

    Fazzini, P.F.; Ortolani, L.; Pozzi, G.; Ubaldi, F.

    2006-01-01

    The application of interference electron microscopy to the investigation of electron optical one-dimensional phase objects like reverse biased p-n junctions and ferromagnetic domain walls is considered. In particular the influence of diffraction from the biprism edges on the interference images is analyzed and the range of applicability of the geometric optical equation for the interpretation of the interference fringe shifts assessed by comparing geometric optical images with full wave-optical simulations. Finally, the inclusion of partial spatial coherence effects are discussed

  6. Unified interpretation of exciplex formation and marcus electron transfer on the basis of two-dimensional free energy surfaces.

    Science.gov (United States)

    Murata, Shigeo; Tachiya, M

    2007-09-27

    The mechanism of exciplex formation proposed in a previous paper has been refined to show how exciplex formation and Marcus electron transfer (ET) in fluorescence quenching are related to each other. This was done by making simple calculations of the free energies of the initial (DA*) and final (D+A-) states of ET. First it was shown that the decrease in D-A distance can induce intermolecular ET even in nonpolar solvents where solvent orientational polarization is absent, and that it leads to exciplex formation. This is consistent with experimental results that exciplex is most often observed in nonpolar solvents. The calculation was then extended to ET in polar solvents where the free energies are functions of both D-A distance and solvent orientational polarization. This enabled us to discuss both exciplex formation and Marcus ET in the same D-A pair and solvent on the basis of 2-dimensional free energy surfaces. The surfaces contain more information about the rates of these reactions, the mechanism of fluorescence quenching by ET, etc., than simple reaction schemes. By changing the parameters such as the free energy change of reaction, solvent dielectric constants, etc., one can construct the free energy surfaces for various systems. The effects of free energy change of reaction and of solvent polarity on the mechanism and relative importance of exciplex formation and Marcus ET in fluorescence quenching can be well explained. The free energy surface will also be useful for discussion of other phenomena related to ET reactions.

  7. Electronic structure and phase equilibria in ternary substitutional alloys

    International Nuclear Information System (INIS)

    Traiber, A.J.S.; Allen, S.M.; Waterstrat, R.M.

    1996-01-01

    A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate abinitio calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr 0.5 (Ru, Pd) 0.5

  8. Tomography of the electron beam transverse phase space at PITZ

    Energy Technology Data Exchange (ETDEWEB)

    Asova, Galina

    2013-09-15

    The operation of a Free Elector Laser, FEL, requires high energy, high peak current electron beams with small transverse emittance. In the contemporary FELs, the electron beam is passed through a periodic magnetic structure - an undulator - which modifies the straight beam trajectory into a sinusoidal one, where FEL light is generated at each bend. According to the energy, the transverse emittance and the peak current of the beam and the parameters of the undulator, FEL radiation with wavelength in the range of nano- to micrometers can be generated. Studies and development of FELs are done all over the world. The Free electron LASer in Hamburg, FLASH, and the international European X-ray FEL, XFEL, in Hamburg, Germany, are two leading projects of the Deutsches Elektronen SYnchrotron, DESY. Part of the research program on FELs in DESY is realized in Zeuthen within the project Photo-Injector Test Facility at DESY in Zeuthen, PITZ. PITZ is an international collaboration including Germany, Russia, Italy, France, Bulgaria, Thailand, United Kingdom. The Institute of Nuclear Research and Nuclear Energy, INRNE, at the Bulgarian Academy of Sciences participates from bulgarian side. PITZ studies and optimizes the photo-injectors for FLASH and the XFEL. The research program emphasizes on detailed measurements of the transverse phase-space density distribution. Until 2010 the single slit scan technique has been used to measure the beam transverse distributions. At the end of 2010 a module for tomographic diagnostics has been installed which extends the possibilities of PITZ to measure simultaneously the two transverse planes of a single micropulse with improved signal-to-noise ratio. The difficult conditions of low emittance for high bunch charge and low energy make the operation of the module challenging. This thesis presents the design considerations for the tomography module, a number of reconstruction algorithms and their applicability to limited data sets, the influence

  9. Tomography of the electron beam transverse phase space at PITZ

    International Nuclear Information System (INIS)

    Asova, Galina

    2013-09-01

    The operation of a Free Elector Laser, FEL, requires high energy, high peak current electron beams with small transverse emittance. In the contemporary FELs, the electron beam is passed through a periodic magnetic structure - an undulator - which modifies the straight beam trajectory into a sinusoidal one, where FEL light is generated at each bend. According to the energy, the transverse emittance and the peak current of the beam and the parameters of the undulator, FEL radiation with wavelength in the range of nano- to micrometers can be generated. Studies and development of FELs are done all over the world. The Free electron LASer in Hamburg, FLASH, and the international European X-ray FEL, XFEL, in Hamburg, Germany, are two leading projects of the Deutsches Elektronen SYnchrotron, DESY. Part of the research program on FELs in DESY is realized in Zeuthen within the project Photo-Injector Test Facility at DESY in Zeuthen, PITZ. PITZ is an international collaboration including Germany, Russia, Italy, France, Bulgaria, Thailand, United Kingdom. The Institute of Nuclear Research and Nuclear Energy, INRNE, at the Bulgarian Academy of Sciences participates from bulgarian side. PITZ studies and optimizes the photo-injectors for FLASH and the XFEL. The research program emphasizes on detailed measurements of the transverse phase-space density distribution. Until 2010 the single slit scan technique has been used to measure the beam transverse distributions. At the end of 2010 a module for tomographic diagnostics has been installed which extends the possibilities of PITZ to measure simultaneously the two transverse planes of a single micropulse with improved signal-to-noise ratio. The difficult conditions of low emittance for high bunch charge and low energy make the operation of the module challenging. This thesis presents the design considerations for the tomography module, a number of reconstruction algorithms and their applicability to limited data sets, the influence

  10. Printable Spacecraft: Flexible Electronic Platforms for NASA Missions. Phase One

    Science.gov (United States)

    Short, Kendra (Principal Investigator); Van Buren, David (Principal Investigator)

    2012-01-01

    Atmospheric confetti. Inchworm crawlers. Blankets of ground penetrating radar. These are some of the unique mission concepts which could be enabled by a printable spacecraft. Printed electronics technology offers enormous potential to transform the way NASA builds spacecraft. A printed spacecraft's low mass, volume and cost offer dramatic potential impacts to many missions. Network missions could increase from a few discrete measurements to tens of thousands of platforms improving areal density and system reliability. Printed platforms could be added to any prime mission as a low-cost, minimum resource secondary payload to augment the science return. For a small fraction of the mass and cost of a traditional lander, a Europa flagship mission might carry experimental printed surface platforms. An Enceladus Explorer could carry feather-light printed platforms to release into volcanic plumes to measure composition and impact energies. The ability to print circuits directly onto a variety of surfaces, opens the possibility of multi-functional structures and membranes such as "smart" solar sails and balloons. The inherent flexibility of a printed platform allows for in-situ re-configurability for aerodynamic control or mobility. Engineering telemetry of wheel/soil interactions are possible with a conformal printed sensor tape fit around a rover wheel. Environmental time history within a sample return canister could be recorded with a printed sensor array that fits flush to the interior of the canister. Phase One of the NIAC task entitled "Printable Spacecraft" investigated the viability of printed electronics technologies for creating multi-functional spacecraft platforms. Mission concepts and architectures that could be enhanced or enabled with this technology were explored. This final report captures the results and conclusions of the Phase One study. First, the report presents the approach taken in conducting the study and a mapping of results against the proposed

  11. Electron cryotomography of vitrified cells with a Volta phase plate.

    Science.gov (United States)

    Fukuda, Yoshiyuki; Laugks, Ulrike; Lučić, Vladan; Baumeister, Wolfgang; Danev, Radostin

    2015-05-01

    Electron cryotomography provides a means of studying the three dimensional structure of pleomorphic objects, such as organelles or cells, with a resolution of 1-3nm. A limitation in the study of radiation sensitive biological samples is the low signal-to-noise ratio of the tomograms which may obscure fine details. To overcome this limitation, the recently developed Volta phase plate (VPP) was applied in electron cryotomographic studies of a wide range of cellular structures, from magnetotactic bacteria to primary cultured neurons. The results show that the VPP improves contrast significantly and consequently the signal-to-noise ratio of the tomograms, moreover it avoids disturbing fringing artifacts typical for Zernike phase plates. The contrast improvement provided by the VPP was also confirmed in projection images of relatively thick (∼400nm) samples. In order to investigate the respective contributions of the VPP and the energy filter, images acquired with different combinations of the two were compared. Zero-loss energy filtering reduced the background noise in thicker areas of the sample and improved the contrast of features such as poly-β-hydroxybutyrate granules in magnetotactic bacteria, whereas the VPP provided an overall contrast improvement for all sample areas. After 3D reconstruction, tomograms acquired with the combination of a VPP and an energy filter showed structural features in neuronal processes with outstanding clarity. We also show that the VPP can be combined with focused ion beam milling to examine structures embedded deeply inside cells. Thus, we expect that VPP will become a standard element of the electron cryotomography workflow. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Electronic transport in amorphous phase-change materials

    Energy Technology Data Exchange (ETDEWEB)

    Luckas, Jennifer Maria

    2012-09-14

    Phase change materials combine a pronounced contrast in resistivity and reflectivity between their disordered amorphous and ordered crystalline state with very fast crystallization kinetics. Due to this exceptional combination of properties phase-change materials find broad application in non-volatile optical memories such as CD, DVD or Bluray Disc. Furthermore, this class of materials demonstrates remarkable electrical transport phenomena in their disordered state, which have shown to be crucial for their application in electronic storage devices. The threshold switching phenomenon denotes the sudden decrease in resistivity beyond a critical electrical threshold field. The threshold switching phenomenon facilitates the phase transitions at practical small voltages. Below this threshold the amorphous state resistivity is thermally activated and is observed to increase with time. This effect known as resistance drift seriously hampers the development of multi-level storage devices. Hence, understanding the physical origins of threshold switching and resistance drift phenomena is crucial to improve non-volatile phase-change memories. Even though both phenomena are often attributed to localized defect states in the band gap, the defect state density in amorphous phase-change materials has remained poorly studied. Starting from a brief introduction of the physics of phase-change materials this thesis summarizes the most important models behind electrical switching and resistance drift with the aim to discuss the role of localized defect states. The centerpiece of this thesis is the investigation of defects state densities in different amorphous phase-change materials and electrical switching chalcogenides. On the basis of Modulated Photo Current (MPC) Experiments and Photothermal Deflection Spectroscopy, a sophisticated band model for the disordered phase of the binary phase-change alloy GeTe has been developed. By this direct experimental approach the band-model for a

  13. Electronic transport in amorphous phase-change materials

    International Nuclear Information System (INIS)

    Luckas, Jennifer Maria

    2012-01-01

    Phase change materials combine a pronounced contrast in resistivity and reflectivity between their disordered amorphous and ordered crystalline state with very fast crystallization kinetics. Due to this exceptional combination of properties phase-change materials find broad application in non-volatile optical memories such as CD, DVD or Bluray Disc. Furthermore, this class of materials demonstrates remarkable electrical transport phenomena in their disordered state, which have shown to be crucial for their application in electronic storage devices. The threshold switching phenomenon denotes the sudden decrease in resistivity beyond a critical electrical threshold field. The threshold switching phenomenon facilitates the phase transitions at practical small voltages. Below this threshold the amorphous state resistivity is thermally activated and is observed to increase with time. This effect known as resistance drift seriously hampers the development of multi-level storage devices. Hence, understanding the physical origins of threshold switching and resistance drift phenomena is crucial to improve non-volatile phase-change memories. Even though both phenomena are often attributed to localized defect states in the band gap, the defect state density in amorphous phase-change materials has remained poorly studied. Starting from a brief introduction of the physics of phase-change materials this thesis summarizes the most important models behind electrical switching and resistance drift with the aim to discuss the role of localized defect states. The centerpiece of this thesis is the investigation of defects state densities in different amorphous phase-change materials and electrical switching chalcogenides. On the basis of Modulated Photo Current (MPC) Experiments and Photothermal Deflection Spectroscopy, a sophisticated band model for the disordered phase of the binary phase-change alloy GeTe has been developed. By this direct experimental approach the band-model for a

  14. Unified Internet Messaging

    OpenAIRE

    Healy, Paul; Barber, Declan

    2015-01-01

    As telephony services, mobile services and internet services continue to converge, the prospect of providing Unified Messaging and even Unified Communications becomes increasingly achievable. This paper discusses the growing importance of IP-based networks to Unified Messaging developments and examines some of the key services and protocols that are likely to make Unified Messaging more widely available. In this initial paper, we limit ourselves initially to the unification of text-based mess...

  15. Electronic structure, phase transitions and diffusive properties of elemental plutonium

    Science.gov (United States)

    Setty, Arun; Cooper, B. R.

    2003-03-01

    We present a SIC-LDA-LMTO based study of the electronic structure of the delta, alpha and gamma phases of plutonium, and also of the alpha and gamma phases of elemental cerium. We find excellent agreement with the experimental densities and magnetic properties [1]. Furthermore, detailed studies of the computational densities of states for delta plutonium, and comparison with the experimental photoemission spectrum [2], provide evidence for the existence of an unusual fluctuating valence state. Results regarding the vacancy formation and self-diffusion in delta plutonium will be presented. Furthermore, a study of interface diffusion between plutonium and steel (technologically relevant in the storage of spent fuel) or other technologically relevant alloys will be included. Preliminary results regarding gallium stabilization of delta plutonium, and of plutonium alloys will be presented. [1] M. Dormeval et al., private communication (2001). [2] A. J. Arko, J. J. Joyce, L. Morales, J. Wills, and J. Lashley et. al., Phys. Rev. B, 62, 1773 (2000). [3] B. R. Cooper et al, Phil. Mag. B 79, 683 (1999); B.R. Cooper, Los Alamos Science 26, 106 (2000)); B.R. Cooper, A.K. Setty and D.L.Price, to be published.

  16. ACHP | Unified Federal Review

    Science.gov (United States)

    Search skip specific nav links Home arrow Unified Federal Review Three logos: 1) Executive Office of the Homeland Security. Unified Federal Environmental and Historic Preservation Review Process Please visit the new location for the Unified Federal Review located here: http://www.fema.gov/environmental-historic

  17. Dissociative electron attachment to the gas-phase nucleobase hypoxanthine

    Energy Technology Data Exchange (ETDEWEB)

    Dawley, M. Michele [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Tanzer, Katrin; Denifl, Stephan, E-mail: Stephan.Denifl@uibk.ac.at, E-mail: Sylwia.Ptasinska.1@nd.edu [Institut für Ionenphysik und Angewandte Physik, and Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Carmichael, Ian [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Ptasińska, Sylwia, E-mail: Stephan.Denifl@uibk.ac.at, E-mail: Sylwia.Ptasinska.1@nd.edu [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    2015-06-07

    We present high-resolution measurements of the dissociative electron attachment (DEA) to isolated gas-phase hypoxanthine (C{sub 5}H{sub 4}N{sub 4}O, Hyp), a tRNA purine base. The anion mass spectra and individual ion efficiency curves from Hyp were measured as a function of electron energy below 9 eV. The mass spectra at 1 and 6 eV exhibit the highest anion yields, indicating possible common precursor ions that decay into the detectable anionic fragments. The (Hyp − H) anion (C{sub 5}H{sub 3}N{sub 4}O{sup −}) exhibits a sharp resonant peak at 1 eV, which we tentatively assign to a dipole-bound state of the keto-N1H,N9H tautomer in which dehydrogenation occurs at either the N1 or N9 position based upon our quantum chemical computations (B3LYP/6-311+G(d,p) and U(MP2-aug-cc-pVDZ+)) and prior studies with adenine. This closed-shell dehydrogenated anion is the dominant fragment formed upon electron attachment, as with other nucleobases. Seven other anions were also observed including (Hyp − NH){sup −}, C{sub 4}H{sub 3}N{sub 4}{sup −}/C{sub 4}HN{sub 3}O{sup −}, C{sub 4}H{sub 2}N{sub 3}{sup −}, C{sub 3}NO{sup −}/HC(HCN)CN{sup −}, OCN{sup −}, CN{sup −}, and O{sup −}. Most of these anions exhibit broad but weak resonances between 4 and 8 eV similar to many analogous anions from adenine. The DEA to Hyp involves significant fragmentation, which is relevant to understanding radiation damage of biomolecules.

  18. Peculiarities of laser phase behavior associated with the accelerated electron in a chirped laser pulse

    International Nuclear Information System (INIS)

    Song, Q.; Wu, X. Y.; Wang, J. X.; Kawata, S.; Wang, P. X.

    2014-01-01

    In this paper, we qualitatively analyzed peculiarities of laser phase behavior associated with the accelerated electron in a chirped laser pulse. We unveiled the relationship between the changes in the orientation of the electron trajectory and the cusps in magnitude of the phase velocity of the optical field along the electron trajectory in a chirped laser pulse. We also explained how the chirp effect induced the singular point of the phase velocity. Finally, we discussed the phase velocity and phase witnessed by the electron in the particle's moving instantaneous frame

  19. Electron-beam synthesis of fuel in the gas phase

    International Nuclear Information System (INIS)

    Ponomarev, A.V.; Holodkova, E.M.; Ershov, B.G.

    2011-01-01

    Complete text of publication follows. Tendencies of world development focus attention on a vegetative biomass as on the major raw resource for future chemistry and a fuel industry. The significant potential for perfection of biomass conversion processes is concentrated in the field of radiation-chemical methods. Both the mode of post-radiation distillation and mode of electron-beam distillation of biomass have been investigated as well as the mode of gas-phase synthesis of liquid engine fuel from of biomass distillation products. Synergistic action of radiation and temperature has been analyzed at use of the accelerated electron beams allowing to combine radiolysis with effective radiation heating of a material without use of additional heaters. At dose rate above 1 kGy/s the electron-beam irradiation results in intensive decomposition of a biomass and evaporation of formed fragments with obtaining of a liquid condensate (∼ 60 wt%), CO 2 and Co gases (13-18 wt%) and charcoal in the residue. Biomass distillation at radiation heating allows to increase almost three times an organic liquid yield in comparison with pyrolysis. The majority of liquid products from cellulose is represented by the furan derivatives considered among the very perspective components for alternative engine fuels. Distilled-off gases and vapors are diluted with gaseous C 1 -C 5 alkanes and again are exposed to an irradiation to produce liquid fuel from a biomass. This transformation is based on a method of electron-beam circulation conversion of gaseous C 1 -C 5 alkanes (Ponomarev, A.V., Radiat. Phys. Chem., 78, 48, 2009) which consists in formation and removal of liquid products with high degree of carbon skeleton branching. The isomers ratio in a liquid may be controlled by means of change of an irradiation condition and initial gas composition. The irradiation of gaseous alkanes together with vaporous products of biomass destruction allows to synthesize the fuel enriched by conventional

  20. Unified Digital Periodic Signal Filters for Power Converter Systems

    DEFF Research Database (Denmark)

    Yang, Yongheng; Xin, Zhen; Zhou, Keliang

    2017-01-01

    Periodic signal controllers like repetitive and resonant controllers have demonstrated much potential in the control of power electronic converters, where periodic signals (e.g., ac voltages and currents) can be precisely regulated to follow references. Beyond the control of periodic signals, ac...... signal processing (e.g., in synchronization and pre-filtering) is also very important for power converter systems. Hence, this paper serves to unify digital periodic signal filters so as to maximize their roles in power converter systems (e.g., enhance the control of ac signals). The unified digital...... periodic signal filters behave like a comb filter, but it can also be configured to selectively filter out the harmonics of interest (e.g., the odd-order harmonics in single-phase power converter systems). Moreover, a virtual variable-sampling-frequency unit delay that enables frequency adaptive periodic...

  1. ATLAS LAr Calorimeter Trigger Electronics Phase-1 Upgrade

    CERN Document Server

    Aad, Georges; The ATLAS collaboration

    2017-01-01

    The upgrade of the Large Hadron Collider (LHC) scheduled for a shut-down period of 2019-2020, referred to as the Phase-I upgrade, will increase the instantaneous luminosity to about three times the design value. Since the current ATLAS trigger system does not allow sufficient increase of the trigger rate, an improvement of the trigger system is required. The Liquid Argon (LAr) Calorimeter read-out will therefore be modified to use digital trigger signals with a higher spatial granularity in order to improve the identification efficiencies of electrons, photons, tau, jets and missing energy, at high background rejection rates at the Level-1 trigger. The new trigger signals will be arranged in 34000 so-called Super Cells which achieves 5-10 times better granularity than the trigger towers currently used and allows an improved background rejection. The readout of the trigger signals will process the signal of the Super Cells at every LHC bunch-crossing at 12-bit precision and a frequency of 40 MHz. The data will...

  2. Passive Two-Phase Cooling of Automotive Power Electronics: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, G.; Jeffers, J. R.; Narumanchi, S.; Bennion, K.

    2014-08-01

    Experiments were conducted to evaluate the use of a passive two-phase cooling strategy as a means of cooling automotive power electronics. The proposed cooling approach utilizes an indirect cooling configuration to alleviate some reliability concerns and to allow the use of conventional power modules. An inverter-scale proof-of-concept cooling system was fabricated, and tests were conducted using the refrigerants hydrofluoroolefin HFO-1234yf and hydrofluorocarbon HFC-245fa. Results demonstrated that the system can dissipate at least 3.5 kW of heat with 250 cm3 of HFC-245fa. An advanced evaporator design that incorporates features to improve performance and reduce size was conceived. Simulation results indicate its thermal resistance can be 37% to 48% lower than automotive dual side cooled power modules. Tests were also conducted to measure the thermal performance of two air-cooled condensers--plain and rifled finned tube designs. The results combined with some analysis were then used to estimate the required condenser size per operating conditions and maximum allowable system (i.e., vapor and liquid) temperatures.

  3. Modular, Fault-Tolerant Electronics Supporting Space Exploration, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Modern electronic systems tolerate only as many point failures as there are redundant system copies, using mere macro-scale redundancy. Fault Tolerant Electronics...

  4. Single Electron Transistor Platform for Microgravity Proteomics, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase II program builds from the successful Phase I efforts to demonstrate that Quantum Logic Devices' nanoelectronic platform for biological detection could...

  5. Coherent-phase or random-phase acceleration of electron beams in solar flares

    Science.gov (United States)

    Aschwanden, Markus J.; Benz, Arnold O.; Montello, Maria L.

    1994-01-01

    Time structures of electron beam signatures at radio wavelengths are investigated to probe correlated versus random behavior in solar flares. In particular we address the issue whether acceleration and injection of electron beams is coherently modulated by a single source, or whether the injection is driven by a stochastic (possibly spatially fragmented) process. We analyze a total of approximately = 6000 type III bursts observed by Ikarus (Zurich) in the frequency range of 100-500 MHz, during 359 solar flares with simultaneous greater than or = 25 keV hard X-ray emission, in the years 1890-1983. In 155 flares we find a total of 260 continuous type III groups, with an average number of 13 +/- 9 bursts per group, a mean duration of D = 12 +/- 14 s, a mean period of P = 2.0 +/- 1.2 s, with the highest burst rate at a frequency of nu = 310 +/- 120 MHz. Pulse periods have been measured between 0.5 and 10 s, and can be described by an exponential distribution, i.e., N(P) varies as e (exp -P/1.0s). The period shows a frequency dependence of P(nu)=46(exp-0.6)(sub MHz)s for different flares, but is invariant during a particular flare. We measure the mean period P and its standard deviation sigma (sub p) in each type III group, and quantify the degree of periodicity (or phase-coherence) by the dimensionless parameter sigma (sub p)P. The representative sample of 260 type III burst groups shows a mean periodicity of sigma (sub p/P) = 0.37 +/- 0.12, while Monte Carlo simulations of an equivalent set of truly random time series show a distinctly different value of sigma (sub p)P = 0.93 +/- 0.26. This result indicates that the injection of electron beams is coherently modulated by a particle acceleration source which is either compact or has a global organization on a timescale of seconds, in contrast to an incoherent acceleration source, which is stochastic either in time or space. We discuss the constraints on the size of the acceleration region resulting from electron beam

  6. Overview of Phase Space Manipulations of Relativistic Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Dao; /SLAC

    2012-08-31

    Phase space manipulation is a process to rearrange beam's distribution in 6-D phase space. In this paper, we give an overview of the techniques for tailoring beam distribution in 2D, 4D, and 6D phase space to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and very likely these advanced concepts will open up new opportunities in advanced accelerators and the science enabled by them.

  7. Overview of Phase Space Manipulations of Relativistic Electron Beams

    International Nuclear Information System (INIS)

    Xiang, Dao

    2012-01-01

    Phase space manipulation is a process to rearrange beam's distribution in 6-D phase space. In this paper, we give an overview of the techniques for tailoring beam distribution in 2D, 4D, and 6D phase space to meet the requirements of various applications. These techniques become a new focus of accelerator physics R and D and very likely these advanced concepts will open up new opportunities in advanced accelerators and the science enabled by them.

  8. Ultrafast electronic relaxation of excited state vitamin B12 in the gas phase

    International Nuclear Information System (INIS)

    Shafizadeh, Niloufar; Poisson, Lionel; Soep, Benoit

    2008-01-01

    The time evolution of electronically excited vitamin B 12 (cyanocobalamin) has been observed for the first time in the gas phase. It reveals an ultrafast decay to a state corresponding to metal excitation. This decay is interpreted as resulting from a ring to metal electron transfer. This opens the observation of the excited state of other complex biomimetic systems in the gas phase, the key to the characterisation of their complex evolution through excited electronic states

  9. Phase separation and d-wave superconductivity induced by extended electron-exciton interaction

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Ming [Department of Physics and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204 (United States)], E-mail: cheng896@hotmail.com; Su Wupei [Department of Physics and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204 (United States)

    2008-12-15

    Using an auxiliary-field quantum Monte Carlo (AFQMC) method, we have studied a two-dimensional tight-binding model in which the conduction electrons can polarize an adjacent layer of molecules through electron-electron repulsion. Calculated average conduction electron density as a function of chemical potential exhibits a clear break characteristic of phase separation. Compared to the noninteracting system, the d-wave pair-field correlation function shows significant enhancement. The simultaneous presence of phase separation and d-wave superconductivity suggests that an effective extended pairing force is induced by the electron-exciton coupling.

  10. Phase separation and d-wave superconductivity induced by extended electron-exciton interaction

    International Nuclear Information System (INIS)

    Cheng Ming; Su Wupei

    2008-01-01

    Using an auxiliary-field quantum Monte Carlo (AFQMC) method, we have studied a two-dimensional tight-binding model in which the conduction electrons can polarize an adjacent layer of molecules through electron-electron repulsion. Calculated average conduction electron density as a function of chemical potential exhibits a clear break characteristic of phase separation. Compared to the noninteracting system, the d-wave pair-field correlation function shows significant enhancement. The simultaneous presence of phase separation and d-wave superconductivity suggests that an effective extended pairing force is induced by the electron-exciton coupling

  11. On the supression of electron phase-bunching in gyroresonant interactions in the magnetosphere

    International Nuclear Information System (INIS)

    Serra, F.M.

    1985-01-01

    The gyroresonant interaction between a whistler mode monochromatic wave and energetic electrons may cause a spatial and temporal coherence of resonant electrons. It is shown using a simple test particle model that a perturbing second wave can destroy the coherence by inhibiting phase bunching of the first-wave resonant electron. (R.P.)

  12. Electron impact ionization of the gas-phase sorbitol

    Science.gov (United States)

    Chernyshova, Irina; Markush, Pavlo; Zavilopulo, Anatoly; Shpenik, Otto

    2015-03-01

    Ionization and dissociative ionization of the sorbitol molecule by electron impact have been studied using two different experimental methods. In the mass range of m/ z = 10-190, the mass spectra of sorbitol were recorded at the ionizing electron energies of 70 and 30 eV. The ion yield curves for the fragment ions have been analyzed and the appearance energies of these ions have been determined. The relative total ionization cross section of the sorbitol molecule was measured using monoenergetic electron beam. Possible fragmentation pathways for the sorbitol molecule were proposed.

  13. Electronic Prognostics for Vehicle Health Management, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — All electronic systems are prone to wear-out and eventual failure and this has direct implications for Vehicle Health Management for NASA with its long space...

  14. Electronic Modeling and Design for Extreme Temperatures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop electronics for operation at temperatures that range from -230oC to +130oC. This new technology will minimize the requirements for external...

  15. Extreme Environment Electronics based on Silicon Carbide, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Radiation tolerant, extreme temperature capable electronics are needed for a variety of planned NASA missions. For example, in-situ exploration of Venus and long...

  16. Extreme Environment Electronics based on Silicon Carbide, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Radiation tolerant, extreme temperature capable electronics are needed for a variety of planned NASA missions. For example, in-situ exploration of Venus and long...

  17. SOI MESFETs for Extreme Environment Electronics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We are proposing a new extreme environment electronics (EEE) technology based on silicon-on-insulator (SOI) metal-semiconductor field-effect transistors (MESFETs)....

  18. Charge Dissipating Transparent Conformal Coatings for Spacecraft Electronics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The space environment poses significant challenges to spacecraft electronics in the form of electrostatic discharge (ESD) as a result of exposure to highly charged...

  19. SSVD Extreme Temperature Electronics for Planned Venus Missions, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The purpose of this project is to demonstrate, based on a new class of electronic devices called solid state vacuum devices (SSVD?s), a highly promising enabling...

  20. Pressure induced phase transition behaviour in -electron based ...

    Indian Academy of Sciences (India)

    The present review on the high pressure phase transition behaviour of ... For instance, closing of energy gaps lead to metal–insulator transitions [4], shift in energy ... systematic study of the pressure induced structural sequences has become ...

  1. Imaging of soft and hard materials using a Boersch phase plate in a transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Alloyeau, D., E-mail: alloyeau.damien@gmail.com [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, One Cyclotron Road, MS/72, Berkeley, CA 94720 (United States); Hsieh, W.K. [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, One Cyclotron Road, MS/72, Berkeley, CA 94720 (United States); Anderson, E.H.; Hilken, L. [Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley CA 94720 (United States); Benner, G. [Carl Zeiss NTS GmbH, Oberkochen 73447 (Germany); Meng, X. [Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley, CA 94720-1770 (United States); Chen, F.R. [Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan (China); Kisielowski, C. [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, One Cyclotron Road, MS/72, Berkeley, CA 94720 (United States)

    2010-04-15

    Using two levels of electron beam lithography, vapor phase deposition techniques, and FIB etching, we have fabricated an electrostatic Boersch phase plate for contrast enhancement of weak phase objects in a transmission electron microscope. The phase plate has suitable dimensions for the imaging of small biological samples without compromising the high-resolution capabilities of the microscope. A micro-structured electrode allows for phase tuning of the unscattered electron beam, which enables the recording of contrast enhanced in-focus images and in-line holograms. We have demonstrated experimentally that our phase plate improves the contrast of carbon nanotubes while maintaining high-resolution imaging performance, which is demonstrated for the case of an AlGaAs heterostructure. The development opens a new way to study interfaces between soft and hard materials.

  2. Phase engineering of monolayer transition-metal dichalcogenide through coupled electron doping and lattice deformation

    International Nuclear Information System (INIS)

    Ouyang, Bin; Lan, Guoqiang; Song, Jun; Guo, Yinsheng; Mi, Zetian

    2015-01-01

    First-principles calculations were performed to investigate the phase stability and transition within four monolayer transition-metal dichalcogenide (TMD) systems, i.e., MX 2 (M = Mo or W and X = S or Se) under coupled electron doping and lattice deformation. With the lattice distortion and electron doping density treated as state variables, the energy surfaces of different phases were computed, and the diagrams of energetically preferred phases were constructed. These diagrams assess the competition between different phases and predict conditions of phase transitions for the TMDs considered. The interplay between lattice deformation and electron doping was identified as originating from the deformation induced band shifting and band bending. Based on our findings, a potential design strategy combining an efficient electrolytic gating and a lattice straining to achieve controllable phase engineering in TMD monolayers was demonstrated

  3. Characterisation of phases in nanostructured, multilayered titanium alloys by analytical and high-resolution electron microscopy.

    Science.gov (United States)

    Czyrska-Filemonowicz, A; Buffat, P A

    2009-01-01

    Surface processing of a Ti-6Al-4V alloy led to a complex multilayered microstructure containing several phases of the Ni-Ti-P-Al-O system, which improves the mechanical and tribological surface properties. The microstructure, chemical and phase compositions of the hard layer formed on the surface were investigated by LM, XRD, SEM as well as analytical/high-resolution TEM, STEM, EDS, electron diffraction and FIB. Phase identification based on electron diffraction, HRTEM and EDS microanalysis revealed the presence of several binary and ternary phases in the system Ti-Ni-P, sometimes with partial substitution of Ti by Al. However some phases, mainly nanoparticles, still remain not identified satisfactorily. Electron microscopy techniques used for identification of phases present in surface multilayers and some practical limits to their routine application are reminded here.

  4. Quantum coherent optical phase modulation in an ultrafast transmission electron microscope.

    Science.gov (United States)

    Feist, Armin; Echternkamp, Katharina E; Schauss, Jakob; Yalunin, Sergey V; Schäfer, Sascha; Ropers, Claus

    2015-05-14

    Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven 'quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

  5. The electron spectrum of UF6 recorded in the gas phase

    Science.gov (United States)

    Mârtensson, N.; Malmquist, P.-Å.; Svensson, S.; Johansson, B.

    1984-06-01

    Gas phase core and valence electron spectra from UF6, excited by AlKα monochromatized x rays, in the binding energy range 0-1000 eV are presented. It is shown that the AlKα excited valence electron spectrum can be used to reassign the highest occupied molecular orbital (HOMO) in UF6. Many-body effects on the core levels are discussed and core level lifetimes are determined. The shift between solid phase and gas phase electron binding energies for core lines is used to discuss the U5 f population in UF6.

  6. Exotic Quantum Phases and Phase Transitions of Strongly Interacting Electrons in Low-Dimensional Systems

    Science.gov (United States)

    Mishmash, Ryan V.

    Experiments on strongly correlated quasi-two-dimensional electronic materials---for example, the high-temperature cuprate superconductors and the putative quantum spin liquids kappa-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2---routinely reveal highly mysterious quantum behavior which cannot be explained in terms of weakly interacting degrees of freedom. Theoretical progress thus requires the introduction of completely new concepts and machinery beyond the traditional framework of the band theory of solids and its interacting counterpart, Landau's Fermi liquid theory. In full two dimensions, controlled and reliable analytical approaches to such problems are severely lacking, as are numerical simulations of even the simplest of model Hamiltonians due to the infamous fermionic sign problem. Here, we attempt to circumvent some of these difficulties by studying analogous problems in quasi-one dimension. In this lower dimensional setting, theoretical and numerical tractability are on much stronger footing due to the methods of bosonization and the density matrix renormalization group, respectively. Using these techniques, we attack two problems: (1) the Mott transition between a Fermi liquid metal and a quantum spin liquid as potentially directly relevant to the organic compounds kappa-(BEDT-TTF)2Cu 2(CN)3 and EtMe3Sb[Pd(dmit)2] 2 and (2) non-Fermi liquid metals as strongly motivated by the strange metal phase observed in the cuprates. In both cases, we are able to realize highly exotic quantum phases as ground states of reasonable microscopic models. This lends strong credence to respective underlying slave-particle descriptions of the low-energy physics, which are inherently strongly interacting and also unconventional in comparison to weakly interacting alternatives. Finally, working in two dimensions directly, we propose a new slave-particle theory which explains in a universal way many of the intriguing experimental results of the triangular lattice organic spin

  7. Electronic basis of hardness and phase transformations (covalent crystals)

    International Nuclear Information System (INIS)

    Gilman, J J

    2008-01-01

    Several electronic parameters measure the stabilities of covalent crystals, including minimum energy band-gap densities, inverse polarizabilities, plasma frequencies, transverse vibrational frequencies and elastic shear moduli. Convenient is the band-gap density (energy/volume; called the 'bond modulus'). For a given bonding type, the indentation hardness is proportional to the bond modulus. Examples are the group IV elements, III-V compounds; and II-VI compounds. The motion of dislocation kinks requires the excitation of bonding electrons into anti-bonding states. The bond modulus measures this together with the work done by the applied stress when a kink moves. In addition to hardness, the bond modulus measures the compressive strain (pressure) needed to transform an ambient structure into a more dense structure. Activation of such transformations also requires the excitation of bonding electrons into anti-bonding states together with the work done by the compressive stress

  8. An efficient digital phase sensitive detector for use in electron spin resonance spectroscopy

    International Nuclear Information System (INIS)

    Vistnes, A.I; Wormald, D.I.; Isachsen, S.

    1983-10-01

    A digital sensitive detector for a modified Bruker electron spin resonance spectrometer, equipped with an Aspect 2000 minicomputer, is described. Magnetic field modulation is derived from a clock in the computer, which makes it possible to perform the data acquisition fully synchronously with the modulation. The resulting high phase accuracy makes it possible to compress the data to a single modulation period before the Fourier transformation. Both the in-phase and the phase-quadrature signals (of the first or second harmonic) are recorded simultaneously. The system makes the data processing, including the Fourier transformation, approximately 1000 times faster than previously reported digital phase sensitive detector systems for electron spin resonance spectrometers

  9. Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

    DEFF Research Database (Denmark)

    Phatak, C.; Petford-Long, A. K.; Beleggia, Marco

    2014-01-01

    Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We prese...

  10. Structural and electronic phase transitions of ThS2 from first-principles calculations

    International Nuclear Information System (INIS)

    Guo, Yongliang; Wang, Changying; Qiu, Wujie; Ke, Xuezhi

    2016-01-01

    Performed a systematic study using first-principles methods of the pressure-induced structural and electronic phase transitions in ThS_2, which may play an important role in the next generation nuclear energy fuel technology.

  11. Development of Diamond Vacuum Differential Amplifier for Harsh Environment Power Electronics, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — In this proposed Phase II, Scientic and Vanderbilt University will develop a novel vacuum field emission differential amplifier (VFEDA) using low electron affinity...

  12. Electron-phonon interactions and the phonon anomaly in β-phase NiTi

    International Nuclear Information System (INIS)

    Zhao, G.L.; Harmon, B.N.

    1993-01-01

    The electronic structure of β-phase NiTi has been calculated using a first-principles linear-combination-of-atomic-orbitals method. The resulting band structure was fitted with a nonorthogonal tight-binding Hamiltonian from which electron-phonon matrix elements were evaluated. The soft phonon near Q 0 =(2/3, 2) / (3 ,0)π/a, which is responsible for the premartensitic phase transition in β-phase NiTi, is found to arise from the strong electron-phonon coupling of nested electronic states on the Fermi surface. Thermal vibrations and changes in electronic occupation cause a smearing of the nested features, which in turn cause a hardening of the phonon anomaly

  13. Electron-beam-irradiation-induced crystallization of amorphous solid phase change materials

    Science.gov (United States)

    Zhou, Dong; Wu, Liangcai; Wen, Lin; Ma, Liya; Zhang, Xingyao; Li, Yudong; Guo, Qi; Song, Zhitang

    2018-04-01

    The electron-beam-irradiation-induced crystallization of phase change materials in a nano sized area was studied by in situ transmission electron microscopy and selected area electron diffraction. Amorphous phase change materials changed to a polycrystalline state after being irradiated with a 200 kV electron beam for a long time. The results indicate that the crystallization temperature strongly depends on the difference in the heteronuclear bond enthalpy of the phase change materials. The selected area electron diffraction patterns reveal that Ge2Sb2Te5 is a nucleation-dominated material, when Si2Sb2Te3 and Ti0.5Sb2Te3 are growth-dominated materials.

  14. Zernike phase-contrast electron cryotomography applied to marine cyanobacteria infected with cyanophages.

    Science.gov (United States)

    Dai, Wei; Fu, Caroline; Khant, Htet A; Ludtke, Steven J; Schmid, Michael F; Chiu, Wah

    2014-11-01

    Advances in electron cryotomography have provided new opportunities to visualize the internal 3D structures of a bacterium. An electron microscope equipped with Zernike phase-contrast optics produces images with markedly increased contrast compared with images obtained by conventional electron microscopy. Here we describe a protocol to apply Zernike phase plate technology for acquiring electron tomographic tilt series of cyanophage-infected cyanobacterial cells embedded in ice, without staining or chemical fixation. We detail the procedures for aligning and assessing phase plates for data collection, and methods for obtaining 3D structures of cyanophage assembly intermediates in the host by subtomogram alignment, classification and averaging. Acquiring three or four tomographic tilt series takes ∼12 h on a JEM2200FS electron microscope. We expect this time requirement to decrease substantially as the technique matures. The time required for annotation and subtomogram averaging varies widely depending on the project goals and data volume.

  15. Zernike Phase Contrast Electron Cryo-Tomography Applied to Marine Cyanobacteria Infected with Cyanophages

    Science.gov (United States)

    Dai, Wei; Fu, Caroline; Khant, Htet A.; Ludtke, Steven J.; Schmid, Michael F.; Chiu, Wah

    2015-01-01

    Advances in electron cryo-tomography have provided a new opportunity to visualize the internal 3D structures of a bacterium. An electron microscope equipped with Zernike phase contrast optics produces images with dramatically increased contrast compared to images obtained by conventional electron microscopy. Here we describe a protocol to apply Zernike phase plate technology for acquiring electron tomographic tilt series of cyanophage-infected cyanobacterial cells embedded in ice, without staining or chemical fixation. We detail the procedures for aligning and assessing phase plates for data collection, and methods to obtain 3D structures of cyanophage assembly intermediates in the host, by subtomogram alignment, classification and averaging. Acquiring three to four tomographic tilt series takes approximately 12 h on a JEM2200FS electron microscope. We expect this time requirement to decrease substantially as the technique matures. Time required for annotation and subtomogram averaging varies widely depending on the project goals and data volume. PMID:25321408

  16. Ultrafast Phase Transition in Vanadium Dioxide Driven by Hot-Electron Injection

    Directory of Open Access Journals (Sweden)

    Prasankumar R. P.

    2013-03-01

    Full Text Available We present a novel all-optical method of triggering the phase transition in vanadium dioxide by means of ballistic electrons injected across the interface between a mesh of Au nanoparticles coveringd VO2 nanoislands. By performing non-degenerate pump-probe transmission spectroscopy on this hybrid plasmonic/phase-changing nanostructure, structural and electronic dynamics can be retrieved and compared.

  17. Application of phase change materials in thermal management of electronics

    International Nuclear Information System (INIS)

    Kandasamy, Ravi; Wang Xiangqi; Mujumdar, Arun S.

    2007-01-01

    Application of a novel PCM package for thermal management of portable electronic devices was investigated experimentally for effects of various parameters e.g. power input, orientation of package, and various melting/freezing times under cyclic steady conditions. Also, a two-dimensional numerical study was made and compared the experimental results. Results show that increased power inputs increase the melting rate, while orientation of the package to gravity has negligible effect on the thermal performance of the PCM package. The thermal resistance of the device and the power level applied to the PCM package are of critical importance for design of a passive thermal control system. Comparison with numerical results confirms that PCM-based design is an excellent candidate design for transient electronic cooling applications

  18. Enhanced phase contrast transfer using ptychography combined with a pre-specimen phase plate in a scanning transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hao; Ercius, Peter [Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Nellist, Peter D. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Ophus, Colin, E-mail: clophus@lbl.gov [Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2016-12-15

    The ability to image light elements in both crystalline and noncrystalline materials at near atomic resolution with an enhanced contrast is highly advantageous to understand the structure and properties of a wide range of beam sensitive materials including biological specimens and molecular hetero-structures. This requires the imaging system to have an efficient phase contrast transfer at both low and high spatial frequencies. In this work we introduce a new phase contrast imaging method in a scanning transmission electron microscope (STEM) using a pre-specimen phase plate in the probe forming aperture, combined with a fast pixelated detector to record diffraction patterns at every probe position, and phase reconstruction using ptychography. The phase plate significantly enhances the contrast transfer of low spatial frequency information, and ptychography maximizes the extraction of the phase information at all spatial frequencies. In addition, the STEM probe with the presence of the phase plate retains its atomic resolution, allowing simultaneous incoherent Z-contrast imaging to be obtained along with the ptychographic phase image. An experimental image of Au nanoparticles on a carbon support shows high contrast for both materials. Multislice image simulations of a DNA molecule shows the capability of imaging soft matter at low dose conditions, which implies potential applications of low dose imaging of a wide range of beam sensitive materials. - Highlights: • This work demonstrates a phase contrast imaging method by combining a pre-specimen phase plate with ptychogrpahy. • This method is shown to have a high phase contrast transfer efficiency at both low and high spatial frequencies. • Unlike CTEM which uses a heavy defocus to gain contrast, the phase plate gives a linear phase contrast at zero defocus aberrations. • Image simulations of DNA suggest this method is highly attractive for imaging beam sensitive materials at a low dose.

  19. Phase synchronized quasiperiodicity in power electronic inverter systems

    DEFF Research Database (Denmark)

    Zhusubaliyev, Zhanybai T.; Mosekilde, Erik; Andriyanov, Alexey I.

    2014-01-01

    The development of switch-mode operated power electronic converter systems has provided a broad range of new effective approaches to the conversion of electric power. In this paper we describe the transitions from regular periodic operation to quasiperiodicity and high-periodic resonance behavior...... findings are verified through comparison with an experimental inverter system. The results shed light on the transitions to quasiperiodicity and to various forms of three-frequency dynamics in non-smooth systems....

  20. Regional Educational Laboratory Electronic Network Phase 2 System

    Science.gov (United States)

    Cradler, John

    1995-01-01

    The Far West Laboratory in collaboration with the other regional educational laboratories is establishing a regionally coordinated telecommunication network to electronically interconnect each of the ten regional laboratories with educators and education stakeholders from the school to the state level. For the national distributed information database, each lab is working with mid-level networks to establish a common interface for networking throughout the country and include topics of importance to education reform as assessment and technology planning.

  1. In-focus electron microscopy of frozen-hydrated biological samples with a Boersch phase plate

    Energy Technology Data Exchange (ETDEWEB)

    Barton, B.; Rhinow, D.; Walter, A.; Schroeder, R. [Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main (Germany); Benner, G.; Majorovits, E.; Matijevic, M.; Niebel, H. [Carl Zeiss NTS GmbH, D-73447 Oberkochen (Germany); Mueller, H.; Haider, M. [CEOS GmbH, Englerstr. 26, 69126 Heidleberg (Germany); Lacher, M.; Schmitz, S.; Holik, P. [Caesar Research Center, Ludwig-Erhard-Allee 2, D-53175 Bonn (Germany); Kuehlbrandt, W., E-mail: werner.kuehlbrandt@mpibp-frankfurt.mpg.de [Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main (Germany)

    2011-12-15

    We report the implementation of an electrostatic Einzel lens (Boersch) phase plate in a prototype transmission electron microscope dedicated to aberration-corrected cryo-EM. The combination of phase plate, C{sub s} corrector and Diffraction Magnification Unit (DMU) as a new electron-optical element ensures minimal information loss due to obstruction by the phase plate and enables in-focus phase contrast imaging of large macromolecular assemblies. As no defocussing is necessary and the spherical aberration is corrected, maximal, non-oscillating phase contrast transfer can be achieved up to the information limit of the instrument. A microchip produced by a scalable micro-fabrication process has 10 phase plates, which are positioned in a conjugate, magnified diffraction plane generated by the DMU. Phase plates remained fully functional for weeks or months. The large distance between phase plate and the cryo sample permits the use of an effective anti-contaminator, resulting in ice contamination rates of <0.6 nm/h at the specimen. Maximal in-focus phase contrast was obtained by applying voltages between 80 and 700 mV to the phase plate electrode. The phase plate allows for in-focus imaging of biological objects with a signal-to-noise of 5-10 at a resolution of 2-3 nm, as demonstrated for frozen-hydrated virus particles and purple membrane at liquid-nitrogen temperature. -- Highlights: Black-Right-Pointing-Pointer We implement an electrostatic Boersch phase plate into a dedicated prototypical TEM. Black-Right-Pointing-Pointer Phase contrast aberration-corrected electron microscope (PACEM) includes a diffraction magnification unit (DMU). Black-Right-Pointing-Pointer DMU minimizes obstruction of low spatial frequencies by the phase plate. Black-Right-Pointing-Pointer In-focus phase contrast generation is demonstrated for frozen-hydrated biological specimens.

  2. Charging of carbon thin films in scanning and phase-plate transmission electron microscopy

    DEFF Research Database (Denmark)

    Hettler, Simon; Kano, Emi; Dries, Manuel

    2018-01-01

    A systematic study on charging of carbon thin films under intense electron-beam irradiation was performed in a transmission electron microscope to identify the underlying physics for the functionality of hole-free phase plates. Thin amorphous carbon films fabricated by different deposition techni...

  3. Changing electronic density in sites of crystalline lattice under superconducting of phase transition

    International Nuclear Information System (INIS)

    Turaev, N.Yu.; Turaev, E.Yu.; Khuzhakulov, E.S.; Seregin, P.P.

    2006-01-01

    Results of electron density change calculations for sites of the one-dimensional Kronig-Penny lattice at the superconducting phase transition have been presented. The transition from normal state to super conducting one is accompanied by the rise of the electron density at the unit cell centre. It is agreement with Moessbauer spectroscopy data. (author)

  4. Comparative study of runaway electron diffusion in the rise phase of ...

    Indian Academy of Sciences (India)

    The behaviour of runaway electrons in the SINP tokamak, which can be operated in a normal edge safety factor () (NQ) discharge configuration as well as in a low (LQ) configuration, was experimentally investigated, during the initial plasma generation phase. An energy analysis of the runaway electron dynamics in ...

  5. Comparative study of runaway electron diffusion in the rise phase of ...

    Indian Academy of Sciences (India)

    Abstract. The behaviour of runaway electrons in the SINP tokamak, which can be operated in a normal edge safety factor (qa) (NQ) discharge configuration as well as in a low qa (LQ) configuration, was experimentally investigated, during the initial plasma generation phase. An energy analysis of the runaway electron ...

  6. Proposals for the solution of the phase problem in electron microscopy

    International Nuclear Information System (INIS)

    Toorn, P. van.

    1979-01-01

    This thesis discusses the phase problem in electron microscopy, i.e. the determination of the unknown complex wave function in the image plane or in the exit pupil from the measured intensity distributions in both planes. The calculation of the wave function is the first problem to be solved for the determination of the object structure from electron micrographs. (Auth.)

  7. In-situ studies on phase transformations under electron irradiation in ...

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    under 1 MeV electron irradiation at 300 K has been recorded in HVEM experiments. The similarity of the diffuse intensity distribution in these two cases brings out the importance of the lattice collapse mechanism in both the cases. 2. Crystallography of the ordered phases in Ni–Mo system. The equilibrium phase diagram of ...

  8. Geometric phase and quantum interference in photosynthetic reaction center: Regulation of electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuming, E-mail: ymsun@ytu.edu.cn; Su, Yuehua; Dai, Zhenhong; Wang, WeiTian

    2016-10-20

    Photosynthesis is driven by electron transfer in reaction centers in which the functional unit is composed of several simple molecules C{sub 2}-symmetrically arranged into two branches. In view of quantum mechanism, both branches are possible pathways traversed by the transferred electron. Due to different evolution of spin state along two pathways in transmembrane electric potential (TEP), quantum state of the transferred electron at the bridged site acquires a geometric phase difference dependent on TEP, the most efficient electron transport takes place in a specific range of TEP beyond which electron transfer is dramatically suppressed. What’s more, reaction center acts like elaborately designed quantum device preparing polarized spin dependent on TEP for the transferred electron to regulate the reduction potential at bridged site. In brief, electron transfer generates the TEP, reversely, TEP modulates the efficiency of electron transfer. This may be an important approach to maintaining an appreciable pH environment in photosynthesis.

  9. Electron Bernstein wave current drive in the start-up phase of a tokamak discharge

    International Nuclear Information System (INIS)

    Montes, A.; Ludwig, G.O.

    1986-04-01

    Current drive by electron Bernstein waves in the start-up phase of tokamak discharges is studied. A general analytical expression is derived for the figure of merit J/Pd associated with these waves. This is coupled with a ray tracing code, allowing the calculation of the total current generated per unit of incident power in realistic tokamak conditions. The resuts show that the electron Bernstein waves can drive substantial currents even at very low electron temperatures. (Author) [pt

  10. From Relativistic Electrons to X-ray Phase Contrast Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A. H. [Fermilab; Garson, A. B. [Washington U., St. Louis; Anastasio, M. A. [Washington U., St. Louis

    2017-10-09

    We report the initial demonstrations of the use of single crystals in indirect x-ray imaging for x-ray phase contrast imaging at the Washington University in St. Louis Computational Bioimaging Laboratory (CBL). Based on single Gaussian peak fits to the x-ray images, we observed a four times smaller system point spread function (21 μm (FWHM)) with the 25-mm diameter single crystals than the reference polycrystalline phosphor’s 80-μm value. Potential fiber-optic plate depth-of-focus aspects and 33-μm diameter carbon fiber imaging are also addressed.

  11. Deep learning the quantum phase transitions in random two-dimensional electron systems

    International Nuclear Information System (INIS)

    Ohtsuki, Tomoki; Ohtsuki, Tomi

    2016-01-01

    Random electron systems show rich phases such as Anderson insulator, diffusive metal, quantum Hall and quantum anomalous Hall insulators, Weyl semimetal, as well as strong/weak topological insulators. Eigenfunctions of each matter phase have specific features, but owing to the random nature of systems, determining the matter phase from eigenfunctions is difficult. Here, we propose the deep learning algorithm to capture the features of eigenfunctions. Localization-delocalization transition, as well as disordered Chern insulator-Anderson insulator transition, is discussed. (author)

  12. Power Electronic Transformer based Three-Phase PWM AC Drives

    Science.gov (United States)

    Basu, Kaushik

    A Transformer is used to provide galvanic isolation and to connect systems at different voltage levels. It is one of the largest and most expensive component in most of the high voltage and high power systems. Its size is inversely proportional to the operating frequency. The central idea behind a power electronic transformer (PET) also known as solid state transformer is to reduce the size of the transformer by increasing the frequency. Power electronic converters are used to change the frequency of operation. Steady reduction in the cost of the semiconductor switches and the advent of advanced magnetic materials with very low loss density and high saturation flux density implies economic viability and feasibility of a design with high power density. Application of PET is in generation of power from renewable energy sources, especially wind and solar. Other important application include grid tied inverters, UPS e.t.c. In this thesis non-resonant, single stage, bi-directional PET is considered. The main objective of this converter is to generate adjustable speed and magnitude pulse width modulated (PWM) ac waveforms from an ac or dc grid with a high frequency ac link. The windings of a high frequency transformer contains leakage inductance. Any switching transition of the power electronic converter connecting the inductive load and the transformer requires commutation of leakage energy. Commutation by passive means results in power loss, decrease in the frequency of operation, distortion in the output voltage waveform, reduction in reliability and power density. In this work a source based partially loss-less commutation of leakage energy has been proposed. This technique also results in partial soft-switching. A series of converters with novel PWM strategies have been proposed to minimize the frequency of leakage inductance commutation. These PETs achieve most of the important features of modern PWM ac drives including 1) Input power factor correction, 2) Common

  13. Determination of electron bunch shape using transition radiation and phase-energy measurements

    Energy Technology Data Exchange (ETDEWEB)

    Crosson, E.R.; Berryman, K.W.; Richman, B.A. [Stanford Univ., CA (United States)] [and others

    1995-12-31

    We present data comparing microbunch temporal information obtained from electron beam phase-energy measurements with that obtained from transition radiation auto-correlation measurements. The data was taken to resolve some of the ambiguities in previous transition radiation results. By measuring the energy spectrum of the electron beam as a function of its phase relative to the accelerating field, phase-energy information was extracted. This data was analyzed using tomographic techniques to reconstruct the phase-space distribution assuming an electron energy dependence of E({var_phi}) = E{sub o} + E{sub acc}cos({var_phi}), where E{sub o} is the energy of an electron entering the field, E{sub acc} is the peak energy gain, and {var_phi} is the phase between the crest of the RF wave and an electron. Temporal information about the beam was obtained from the phase space distribution by taking the one dimensional projection along the time axis. We discuss the use of this technique to verify other transition radiation analysis methods.

  14. Determination of electron bunch shape using transition radiation and phase-energy measurements

    International Nuclear Information System (INIS)

    Crosson, E.R.; Berryman, K.W.; Richman, B.A.

    1995-01-01

    We present data comparing microbunch temporal information obtained from electron beam phase-energy measurements with that obtained from transition radiation auto-correlation measurements. The data was taken to resolve some of the ambiguities in previous transition radiation results. By measuring the energy spectrum of the electron beam as a function of its phase relative to the accelerating field, phase-energy information was extracted. This data was analyzed using tomographic techniques to reconstruct the phase-space distribution assuming an electron energy dependence of E(var-phi) = E o + E acc cos(var-phi), where E o is the energy of an electron entering the field, E acc is the peak energy gain, and var-phi is the phase between the crest of the RF wave and an electron. Temporal information about the beam was obtained from the phase space distribution by taking the one dimensional projection along the time axis. We discuss the use of this technique to verify other transition radiation analysis methods

  15. Structural and electronic properties of in-plane phase engineered WSe2: A DFT study

    Science.gov (United States)

    Bhart, Ankush; Kapoor, Pooja; Sharma, Munish; Sharma, Raman; Ahluwalia, P. K.

    2018-04-01

    We present first principal investigations on structural and electronic properties of in-plane phase engineered WSe2 with armchair type interface. The 2H and 1T phases of WSe2, joined along x-direction is a natural metal-semiconductor heterostructure and therefore shows potential for applications in 2D electronics and opto-electronics. The electronic properties transit towards metallic 1T region. No inflections across interface shows negligible mismatch strain which is unlike what has been reported for MoS2. Charge density analysis shows charge accumulation on 1T domain. This can lead to reduction of Schottky barrier heights at the metal-semiconductor junction. STM analysis confirms transition of 1T phase towards distorted 1T' structure. The present results provide essential insights for nano-devices using 2D hybrid materials.

  16. Electron Energy Confinement for HHFW Heating and Current Drive Phasing on NSTX

    International Nuclear Information System (INIS)

    Hosea, J.C.; Bernabei, S.; Biewer, T.; LeBlanc, B.; Phillips, C.K.; Wilson, J.R.; Stutman, D.; Ryan, P.; Swain, D.W.

    2005-01-01

    Thomson scattering laser pulses are synchronized relative to modulated HHFW power to permit evaluation of the electron energy confinement time during and following HHFW pulses for both heating and current drive antenna phasing. Profile changes resulting from instabilities require that the total electron stored energy, evaluated by integrating the midplane electron pressure P(sub)e(R) over the magnetic surfaces prescribed by EFIT analysis, be used to derive the electron energy confinement time. Core confinement is reduced during a sawtooth instability but, although the electron energy is distributed outward by the sawtooth, the bulk electron energy confinement time is essentially unaffected. The radial deposition of energy into the electrons is noticeably more peaked for current drive phasing (longer wavelength excitation) relative to that for heating phasing (shorter wavelength excitation) as is expected theoretically. However, the power delivered to the core plasma is reduced consider ably for the current drive phasing, indicating that surface/peripheral damping processes play a more important role for this case

  17. Thermal Peak Management Using Organic Phase Change Materials for Latent Heat Storage in Electronic Applications

    Science.gov (United States)

    Maxa, Jacob; Novikov, Andrej; Nowottnick, Mathias

    2017-01-01

    Modern high power electronics devices consists of a large amount of integrated circuits for switching and supply applications. Beside the benefits, the technology exhibits the problem of an ever increasing power density. Nowadays, heat sinks that are directly mounted on a device, are used to reduce the on-chip temperature and dissipate the thermal energy to the environment. This paper presents a concept of a composite coating for electronic components on printed circuit boards or electronic assemblies that is able to buffer a certain amount of thermal energy, dissipated from a device. The idea is to suppress temperature peaks in electronic components during load peaks or electronic shorts, which otherwise could damage or destroy the device, by using a phase change material to buffer the thermal energy. The phase change material coating could be directly applied on the chip package or the PCB using different mechanical retaining jigs.

  18. Thermal Peak Management Using Organic Phase Change Materials for Latent Heat Storage in Electronic Applications

    Directory of Open Access Journals (Sweden)

    Jacob Maxa

    2017-12-01

    Full Text Available Modern high power electronics devices consists of a large amount of integrated circuits for switching and supply applications. Beside the benefits, the technology exhibits the problem of an ever increasing power density. Nowadays, heat sinks that are directly mounted on a device, are used to reduce the on-chip temperature and dissipate the thermal energy to the environment. This paper presents a concept of a composite coating for electronic components on printed circuit boards or electronic assemblies that is able to buffer a certain amount of thermal energy, dissipated from a device. The idea is to suppress temperature peaks in electronic components during load peaks or electronic shorts, which otherwise could damage or destroy the device, by using a phase change material to buffer the thermal energy. The phase change material coating could be directly applied on the chip package or the PCB using different mechanical retaining jigs.

  19. Grand unified theories

    International Nuclear Information System (INIS)

    Rosner, J.L.

    1987-01-01

    This paper reports on a pedagogical introduction that attempts to unify the strong and electroweak interactions. Unifying groups discussed include SU(5), SO(10), and E 6 . Particular attention is paid to the questions of whether the low-energy gauge group (that accessible at accelerator experiments in the foreseeable future) extends beyond SU(3) x SU(2) L x U(1). Low-energy studies of neutral-current effects, direct production of gauge bosons, and new fermions all can shed light on this question. Brief remarks are made concerning the role of monopoles, cosmic strings, baryogenesis, supersymmetry, and higher dimensions in this program

  20. On the additivity of scattering phases in collisions of electrons on endohedrals

    International Nuclear Information System (INIS)

    Amusia, M Ya; Chernysheva, L V

    2015-01-01

    It is demonstrated that an inner atom, either Ne or Ar, qualitatively affects the electron scattering phases upon an endohedral, in spite of the fact that the fullerene consists of 60 carbon atoms, while the atom staffed inside is only one. Calculations are performed in the one-electron Hartree-Fock (HF) and random phase approximation with exchange (RPAE) for the inner atom while the fullerenes shell is substituted by static potential without and with the polarization potential. The total endohedral scattering phase is a sum of atomic, Ne or Ar, and fullerenes C 60 phases, contrary to the intuitive assumption that the total phases on C 60 and Ne@C 60 or Ar@C 60 has to be the same. (paper)

  1. Unified geometric description of black hole thermodynamics

    International Nuclear Information System (INIS)

    Alvarez, Jose L.; Quevedo, Hernando; Sanchez, Alberto

    2008-01-01

    In the space of thermodynamic equilibrium states we introduce a Legendre invariant metric which contains all the information about the thermodynamics of black holes. The curvature of this thermodynamic metric becomes singular at those points where, according to the analysis of the heat capacities, phase transitions occur. This result is valid for the Kerr-Newman black hole and all its special cases and, therefore, provides a unified description of black hole phase transitions in terms of curvature singularities.

  2. A phase-field and electron microscopy study of phase separation in Fe-Cr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hedstroem, Peter, E-mail: pheds@kth.se [Materials Science and Engineering, KTH (Royal Institute of Technology), SE-100 44 Stockholm (Sweden); Baghsheikhi, Saeed [Materials Science and Engineering, KTH (Royal Institute of Technology), SE-100 44 Stockholm (Sweden); Liu, Ping [Sandvik Materials Technology, R and D Centre, SE-81181 Sandviken (Sweden); Odqvist, Joakim [Materials Science and Engineering, KTH (Royal Institute of Technology), SE-100 44 Stockholm (Sweden); Sandvik Materials Technology, R and D Centre, SE-81181 Sandviken (Sweden)

    2012-02-01

    Highlights: Black-Right-Pointing-Pointer Experimental characterization and Phase-field modeling of phase separation in Fe-Cr. Black-Right-Pointing-Pointer Transition from particle-like to spinodal-like structure observed. Black-Right-Pointing-Pointer Structural evolution generates increased hardness. Black-Right-Pointing-Pointer Results in agreement with recent thermodynamic description. Black-Right-Pointing-Pointer Quantitative kinetic modeling must include thermal noise and improved kinetic data. - Abstract: Phase separation in the binary Fe-Cr system, the basis for the entire stainless steel family, is considered responsible for the low temperature embrittlement in ferritic, martensitic and duplex stainless steels. These steels are often used in load-bearing applications with considerable service time at elevated temperature. Thus, understanding the effect of microstructure on mechanical properties and predicting dynamics of phase separation are key issues. In the present work, experimental evaluation of structure and mechanical properties in binary Fe-Cr alloys as well as phase-field modeling, using a new thermodynamic description of Fe-Cr, is conducted. A significant hardening evolution with time is found for alloys aged between 400 and 550 Degree-Sign C, and it can be attributed to phase separation. The decomposed structure changed with increasing Cr content at 500 Degree-Sign C, with a more particle-like structure at 25 wt% Cr and a more spinodal-like structure at 30 wt% Cr. The observed transition of structure agrees with the thermodynamically predicted spinodal, although the transition is expected to be gradual. The phase-field simulations qualitatively agree with experiments. However, to enable accurate quantitative predictions, the diffusional mobilities must be evaluated further and thermal fluctuations as well as 3D diffusion fields must be properly accounted for.

  3. Single particle analysis based on Zernike phase contrast transmission electron microscopy.

    Science.gov (United States)

    Danev, Radostin; Nagayama, Kuniaki

    2008-02-01

    We present the first application of Zernike phase-contrast transmission electron microscopy to single-particle 3D reconstruction of a protein, using GroEL chaperonin as the test specimen. We evaluated the performance of the technique by comparing 3D models derived from Zernike phase contrast imaging, with models from conventional underfocus phase contrast imaging. The same resolution, about 12A, was achieved by both imaging methods. The reconstruction based on Zernike phase contrast data required about 30% fewer particles. The advantages and prospects of each technique are discussed.

  4. Electron crystallography applied to the structure determination of Nb(Cu,Al,X) Laves phases.

    Science.gov (United States)

    Gigla, M; Lelatko, J; Krzelowski, M; Morawiec, H

    2006-09-01

    The presence of primary precipitates of the Laves phases considerably improves the mechanical properties and the resistance to thermal degradation of the high-temperature shape memory Cu-Al-Nb alloys. The structure analysis of the Laves phases was carried out on particles contained in the ternary and quaternary alloys as well on synthesized compounds related to the composition of the Nb(Cu,Al,X)(2) phase, where X = Ni, Co, Cr, Ti and Zr. The precise structure determination of the Laves phases was carried out by the electron crystallography method using the CRISP software.

  5. Studies of some elementary processes involving electrons in the gas phase by pulse-radiolysis microwave-cavity technique

    International Nuclear Information System (INIS)

    Sunagawa, Takeyoshi; Makita, Takeshi; Musasa, Hirofumi; Tatsumi, Yoshitsugu; Shimamori, Hiroshi

    1995-01-01

    The pulse radiolysis-microwave cavity technique has been employed for detection of free electrons in the gas phase. Presented are results of the observation of electron disappearance by attachment to molecules, the electron thermalization (energy loss) processes in the presence of an electron-attaching compound, and the formation of electrons by Penning ionization. (author)

  6. The unified mechanism of aging effects in both martensite and parent phase for shape-memory alloys: atomic-level simulations

    Science.gov (United States)

    Deng, J.; Ding, X.; Suzuki, T.; Otsuka, K.; Lookman, T.; Saxena, A.; Sun, J.; Ren, X.

    2011-03-01

    Most shape-memory alloys (SMAs) subject to the aging effects not only in the martensite phase but also in the parent phase. These aging effects have been attracted much attention as they strongly affect the practical applications of SMAs. So far, the intrinsic mechanism of them has remained controversial due to the difficulty in visualization of what happens in atomic scale. In the present study, by using a combination of molecular dynamics method and Monte-Carlo method [1], we investigate the aging effects in both martensite and parent phase. We successfully reproduced the thermal behaviors of aging effects for SMAs, i.e., the Af temperature increase with aging time in martensite and the Ms temperature decrease with aging time in parent phase, which keep good agreement with the experimental observations [2]. In addition, quantitative analysis of the atomic configurations during aging reveals that the aging effects are not associated with a change in the average structure.

  7. Invited Review Article: Methods for imaging weak-phase objects in electron microscopy

    International Nuclear Information System (INIS)

    Glaeser, Robert M.

    2013-01-01

    Contrast has traditionally been produced in electron-microscopy of weak phase objects by simply defocusing the objective lens. There now is renewed interest, however, in using devices that apply a uniform quarter-wave phase shift to the scattered electrons relative to the unscattered beam, or that generate in-focus image contrast in some other way. Renewed activity in making an electron-optical equivalent of the familiar “phase-contrast” light microscope is based in part on the improved possibilities that are now available for device microfabrication. There is also a better understanding that it is important to take full advantage of contrast that can be had at low spatial frequency when imaging large, macromolecular objects. In addition, a number of conceptually new phase-plate designs have been proposed, thus increasing the number of options that are available for development. The advantages, disadvantages, and current status of each of these options is now compared and contrasted. Experimental results that are, indeed, superior to what can be accomplished with defocus-based phase contrast have been obtained recently with two different designs of phase-contrast aperture. Nevertheless, extensive work also has shown that fabrication of such devices is inconsistent, and that their working lifetime is short. The main limitation, in fact, appears to be electrostatic charging of any device that is placed into the electron diffraction pattern. The challenge in fabricating phase plates that are practical to use for routine work in electron microscopy thus may be more in the area of materials science than in the area of electron optics

  8. STATISTICAL STUDY ON THE DECAY PHASE OF SOLAR NEAR-RELATIVISTIC ELECTRON EVENTS

    International Nuclear Information System (INIS)

    Lario, D.

    2010-01-01

    We study the decay phase of solar near-relativistic (53-315 keV) electron events as observed by the Advanced Composition Explorer (ACE) and the Ulysses spacecraft during solar cycle 23. By fitting an exponential function (exp - t/τ) to the time-intensity profile in the late phase of selected solar near-relativistic electron events, we examine the dependence of τ on electron energy, electron intensity spectra, event peak intensity, event fluence, and solar wind velocity, as well as heliocentric radial distance, heliolatitude, and heliolongitude of the spacecraft with respect to the parent solar event. The decay rates are found to be either independent or slightly decrease with the electron energy. No clear dependence is found between τ and the heliolongitude of the parent solar event, with the exception of well-connected events for which low values of τ are more commonly observed than for poorly-connected events. For those events concurrently observed by ACE and Ulysses, decay rates increase at distances >3 AU. Events with similar decay rates at ACE and Ulysses were observed mainly when Ulysses was at high heliographic latitudes. We discuss the basic physical mechanisms that control the decay phase of the electron events and conclude that both solar wind convection and adiabatic deceleration effects influence the final shape of the decay phase of solar energetic particle events, but not as expressed by the models based on diffusive transport acting on an isotropic particle population.

  9. Multiscale phase mapping of LiFePO4-based electrodes by transmission electron microscopy and electron forward scattering diffraction.

    Science.gov (United States)

    Robert, Donatien; Douillard, Thierry; Boulineau, Adrien; Brunetti, Guillaume; Nowakowski, Pawel; Venet, Denis; Bayle-Guillemaud, Pascale; Cayron, Cyril

    2013-12-23

    LiFePO4 and FePO4 phase distributions of entire cross-sectioned electrodes with various Li content are investigated from nanoscale to mesoscale, by transmission electron microscopy and by the new electron forward scattering diffraction technique. The distributions of the fully delithiated (FePO4) or lithiated particles (LiFePO4) are mapped on large fields of view (>100 × 100 μm(2)). Heterogeneities in thin and thick electrodes are highlighted at different scales. At the nanoscale, the statistical analysis of 64 000 particles unambiguously shows that the small particles delithiate first. At the mesoscale, the phase maps reveal a core-shell mechanism at the scale of the agglomerates with a preferential pathway along the electrode porosities. At larger scale, lithiation occurs in thick electrodes "stratum by stratum" from the surface in contact with electrolyte toward the current collector.

  10. Unified electricity market

    International Nuclear Information System (INIS)

    Anon

    2011-01-01

    A unified European electricity market means a unification and harmonisation of functioning of the national electricity market into one European Market or into one entity. It gives an opportunity to Slovenske elektrarne to open room for their wider activity within Europe where common rules for cross-boarder trade and markets functioning will apply. (author)

  11. Unified field theory

    International Nuclear Information System (INIS)

    Prasad, R.

    1975-01-01

    Results of researches into Unified Field Theory over the past seven years are presented. The subject is dealt with in chapters entitled: the choice of affine connection, algebraic properties of the vector fields, field laws obtained from the affine connection based on the path integral method, application to quantum theory and cosmology, interpretation of physical theory in terms of geometry. (U.K.)

  12. Finite unified models

    Energy Technology Data Exchange (ETDEWEB)

    Kapetanakis, D. (Technische Univ. Muenchen, Garching (Germany). Physik Dept.); Mondragon, M. (Technische Univ. Muenchen, Garching (Germany). Physik Dept.); Zoupanos, G. (National Technical Univ., Athens (Greece). Physics Dept.)

    1993-09-01

    We present phenomenologically viable SU(5) unified models which are finite to all orders before the spontaneous symmetry breaking. In the case of two models with three families the top quark mass is predicted to be 178.8 GeV. (orig.)

  13. Finite unified models

    International Nuclear Information System (INIS)

    Kapetanakis, D.; Mondragon, M.; Zoupanos, G.

    1993-01-01

    We present phenomenologically viable SU(5) unified models which are finite to all orders before the spontaneous symmetry breaking. In the case of two models with three families the top quark mass is predicted to be 178.8 GeV. (orig.)

  14. Link between the photonic and electronic topological phases in artificial graphene

    Science.gov (United States)

    Lannebère, Sylvain; Silveirinha, Mário G.

    2018-04-01

    In recent years the study of topological phases of matter has emerged as a very exciting field of research, both in photonics and in electronics. However, up to now the electronic and photonic properties have been regarded as totally independent. Here we establish a link between the electronic and the photonic topological phases of the same material system and theoretically demonstrate that they are intimately related. We propose a realization of the Haldane model as a patterned two-dimensional electron gas and determine its optical response using the Kubo formula. It is shown that the electronic and photonic phase diagrams of the patterned electron gas are strictly related. In particular, the system has a trivial photonic topology when the inversion symmetry is the prevalent broken symmetry, whereas it has a nontrivial photonic topology for a dominant broken time-reversal symmetry, similar to the electronic case. To confirm these predictions, we numerically demonstrate the emergence of topologically protected unidirectional electromagnetic edge states at the interface with a trivial photonic material.

  15. Practical aspects of Boersch phase contrast electron microscopy of biological specimens

    Energy Technology Data Exchange (ETDEWEB)

    Walter, Andreas [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany); Muzik, Heiko; Vieker, Henning; Turchanin, Andrey; Beyer, Andre; Goelzhaeuser, Armin [University of Bielefeld, Physics of Supramolecular Systems and Surfaces, Universitaetsstr. 25, D-33615 Bielefeld (Germany); Lacher, Manfred; Steltenkamp, Siegfried; Schmitz, Sam; Holik, Peter [Caesar Research Center, Ludwig-Erhard-Allee 2, D-53175 Bonn (Germany); Kuehlbrandt, Werner [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany); Rhinow, Daniel, E-mail: daniel.rhinow@biophys.mpg.de [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany)

    2012-05-15

    Implementation of physical phase plates into transmission electron microscopes to achieve in-focus contrast for ice-embedded biological specimens poses several technological challenges. During the last decade several phase plates designs have been introduced and tested for electron cryo-microscopy (cryoEM), including thin film (Zernike) phase plates and electrostatic devices. Boersch phase plates (BPPs) are electrostatic einzel lenses shifting the phase of the unscattered beam by an arbitrary angle. Adjusting the phase shift to 90 Degree-Sign achieves the maximum contrast transfer for phase objects such as biomolecules. Recently, we reported the implementation of a BPP into a dedicated phase contrast aberration-corrected electron microscope (PACEM) and demonstrated its use to generate in-focus contrast of frozen-hydrated specimens. However, a number of obstacles need to be overcome before BPPs can be used routinely, mostly related to the phase plate devices themselves. CryoEM with a physical phase plate is affected by electrostatic charging, obliteration of low spatial frequencies, and mechanical drift. Furthermore, BPPs introduce single sideband contrast (SSB), due to the obstruction of Friedel mates in the diffraction pattern. In this study we address the technical obstacles in detail and show how they may be overcome. We use X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to identify contaminants responsible for electrostatic charging, which occurs with most phase plates. We demonstrate that obstruction of low-resolution features is significantly reduced by lowering the acceleration voltage of the microscope. Finally, we present computational approaches to correct BPP images for SSB contrast and to compensate for mechanical drift of the BPP. -- Highlights: Black-Right-Pointing-Pointer Various obstacles need to be overcome before Boersch phase plates can be used routinely. Black-Right-Pointing-Pointer Technical problems include

  16. Practical aspects of Boersch phase contrast electron microscopy of biological specimens

    International Nuclear Information System (INIS)

    Walter, Andreas; Muzik, Heiko; Vieker, Henning; Turchanin, Andrey; Beyer, André; Gölzhäuser, Armin; Lacher, Manfred; Steltenkamp, Siegfried; Schmitz, Sam; Holik, Peter; Kühlbrandt, Werner; Rhinow, Daniel

    2012-01-01

    Implementation of physical phase plates into transmission electron microscopes to achieve in-focus contrast for ice-embedded biological specimens poses several technological challenges. During the last decade several phase plates designs have been introduced and tested for electron cryo-microscopy (cryoEM), including thin film (Zernike) phase plates and electrostatic devices. Boersch phase plates (BPPs) are electrostatic einzel lenses shifting the phase of the unscattered beam by an arbitrary angle. Adjusting the phase shift to 90° achieves the maximum contrast transfer for phase objects such as biomolecules. Recently, we reported the implementation of a BPP into a dedicated phase contrast aberration-corrected electron microscope (PACEM) and demonstrated its use to generate in-focus contrast of frozen–hydrated specimens. However, a number of obstacles need to be overcome before BPPs can be used routinely, mostly related to the phase plate devices themselves. CryoEM with a physical phase plate is affected by electrostatic charging, obliteration of low spatial frequencies, and mechanical drift. Furthermore, BPPs introduce single sideband contrast (SSB), due to the obstruction of Friedel mates in the diffraction pattern. In this study we address the technical obstacles in detail and show how they may be overcome. We use X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to identify contaminants responsible for electrostatic charging, which occurs with most phase plates. We demonstrate that obstruction of low-resolution features is significantly reduced by lowering the acceleration voltage of the microscope. Finally, we present computational approaches to correct BPP images for SSB contrast and to compensate for mechanical drift of the BPP. -- Highlights: ► Various obstacles need to be overcome before Boersch phase plates can be used routinely. ► Technical problems include electrostatic charging, mechanical drift, and image artefacts.

  17. Phase diagram of a symmetric electron-hole bilayer system: a variational Monte Carlo study.

    Science.gov (United States)

    Sharma, Rajesh O; Saini, L K; Bahuguna, Bhagwati Prasad

    2018-05-10

    We study the phase diagram of a symmetric electron-hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater-Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r s , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at [Formula: see text] and the ferromagnetic fluid phase being particularly stable at [Formula: see text]. As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r s   =  20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r s   Wigner crystal is stable over the considered range of r s and d. We also find that as r s increases, the critical layer separations for Wigner crystallization increase.

  18. Free electron laser small signal dynamics and inclusion of electron-beam energy phase correlation

    International Nuclear Information System (INIS)

    Dattoli, G.; Giannessi, L.; Ottaviani, P. L.

    1998-01-01

    In this paper are analyzed the problems associated with the generation of coherent radiation by an e-beam, traversing an undulator magnet, with an initial energy-phase correlation. The mechanism of the process are explained and the role played by the bunching is clarified. The effect of the correlation on the stimulated part of the emission is also discussed [it

  19. The Unified Theory of Physics

    OpenAIRE

    Chung, Ding-Yu

    2002-01-01

    The unified theory of physics unifies various phenomena in our observable universe and other universes. The unified theory is based on the zero-energy universe and the space-object structures. Different universes in different developmental stages are the different expressions of the space-object structures. The unified theory is divided into five parts: the space-object structures, cosmology, the periodic table of elementary particles, the galaxy formation, and the extreme force field. The sp...

  20. Generation of high harmonic free electron laser with phase-merging effect

    Energy Technology Data Exchange (ETDEWEB)

    Li, Heting, E-mail: liheting@ustc.edu.cn; Jia, Qika; Zhao, Zhouyu

    2017-03-01

    An easy-to-implement scheme is proposed to produce the longitudinal electron bunch density modulation with phase-merging phenomenon. In this scheme an electron bunch is firstly transversely dispersed in a modified dogleg to generate the exact dependence of electron energy on the transverse position, then it is modulated in a normal modulator. After travelling through a modified chicane with specially designed transfer matrix elements, the density modulation with phase-merging effect is generated which contains high harmonic components of the seed laser. We present theoretical analysis and numerical simulations for seeded soft x-ray free-electron laser. The results demonstrate that this technique can significantly enhance the frequency up-conversion efficiency and allow a seeded FEL operating at very high harmonics.

  1. Zernike phase contrast cryo-electron tomography of whole bacterial cells.

    Science.gov (United States)

    Guerrero-Ferreira, Ricardo C; Wright, Elizabeth R

    2014-01-01

    Cryo-electron tomography (cryo-ET) provides three-dimensional (3D) structural information of bacteria preserved in a native, frozen-hydrated state. The typical low contrast of tilt-series images, a result of both the need for a low electron dose and the use of conventional defocus phase-contrast imaging, is a challenge for high-quality tomograms. We show that Zernike phase-contrast imaging allows the electron dose to be reduced. This limits movement of gold fiducials during the tilt series, which leads to better alignment and a higher-resolution reconstruction. Contrast is also enhanced, improving visibility of weak features. The reduced electron dose also means that more images at more tilt angles could be recorded, further increasing resolution. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Electronic structure and phase stability during martensitic transformation in Al-doped ZrCu intermetallics

    International Nuclear Information System (INIS)

    Qiu Feng; Shen Ping; Liu Tao; Lin Qiaoli; Jiang Qichuan

    2010-01-01

    Martensitic transformation, phase stability and electronic structure of Al-doped ZrCu intermetallics were investigated by experiments and first-principles calculations using the pseudopotentials plane wave method. The formation energy calculations indicate that the stability of the ZrCu phase increases with the increasing Al content. Al plays a decisive role in controlling the formation and microstructures of the martensite phases in Zr-Cu-Al alloys. The total energy difference between ZrCu (B2) austenite and ZrCu martensite plays an important role in the martensitic transformation. The phase stability is dependent on its electronic structure. The densities of states (DOS) of the intermetallics were discussed in detail.

  3. Infrared spectroscopy of gas-phase clusters using a free-electron laser

    International Nuclear Information System (INIS)

    Heijnsbergen, D. van; Helden, G. von; Meijer, G.

    2002-01-01

    Most clusters produced in the gas phase, especially those containing metals, remain largely uncharaterized, among these are transition metal - carbide, -oxide and -nitride clusters. A method for recording IR spectra of strongly bound gas-phase clusters is presented. It is based on a free-electron laser called Felix, characterized by wide wavelength tuning range, covering almost the full 'molecular finger print' region, high power and fluence which make it suited to excite gas-phase species i.e. gas -phase clusters. Neutral clusters were generated by laser vaporization technique, ions that were created after the interaction with the free-electron laser were analyzed in a flight mass spectrometer. Experiments were run with titanium carbide clusters and their IR spectra given. It was shown that this method is suited to strongly bound clusters with low ionization energies, a condition met for many pure metal clusters and metal compound clusters. (nevyjel)

  4. Plasma phase transition in dense hydrogen and electron-hole plasmas

    CERN Document Server

    Filinov, V S; Levashov, P R; Fortov, V E; Ebeling, W; Schlanges, M; Koch, S W

    2003-01-01

    Plasma phase transitions in dense hydrogen and electron-hole plasmas are investigated by direct path integral Monte Carlo methods. The phase boundary of the electron-hole liquid in germanium is calculated and is found to agree reasonably well with the known experimental results. Analogous behaviour is found for high-density hydrogen. For a temperature of T = 10 000 K it is shown that the internal energy is lowered due to droplet formation for densities between 10 sup 2 sup 3 cm sup - sup 3 and 10 sup 2 sup 4 cm sup - sup 3.

  5. Modeling and control of three phase rectifier with electronic smoothing inductor

    DEFF Research Database (Denmark)

    Singh, Yash Veer; Rasmussen, Peter Omand; Andersen, Torben Ole

    2011-01-01

    This paper presents a simple, direct method for deriving the approximate, small-signal, average model and control strategy for three-phase diode bridge rectifier operating with electronic smoothing technique. Electronic smoothing inductor (ESI) performs the function of an inductor that has...... controlled variable impedance. This increases power factor (PF) and reduces total harmonic distortions (THDs) in mains current. The ESI based rectifier enables compact and cost effective design of three phase electric drive as size of passive components is reduced significantly. In order to carry out...

  6. Magnetic imaging with a Zernike-type phase plate in a transmission electron microscope

    DEFF Research Database (Denmark)

    Pollard, Shawn; Malac, Marek; Beleggia, Marco

    2013-01-01

    We demonstrate the use of a hole-free phase plate (HFPP) for magnetic imaging in transmission electron microscopy by mapping the domain structure in PrDyFeB samples. The HFPP, a Zernike-like imaging method, allows for detecting magnetic signals in-focus to correlate the sample crystal structure...... the reference wave distortion from long-range fields affecting electron holography....

  7. High-pressure electron-resonance studies of electronic, magnetic, and structural phase transitions. Progress report

    International Nuclear Information System (INIS)

    Pifer, J.H.; Croft, M.C.

    1983-01-01

    Research is described in development of a high-pressure electron-resonance probe capable of operating down to 1.5 0 K temperatures. The apparatus has been used to measure the EPR of a sample of DPPH at room temperature and zero pressure. EPR has been used to measure valence field instabilities in alloy systems. Studies have been done on metal-insulator transitions at high pressure, and are briefly described

  8. Molecular structure determination of cyclootane by ab initio and electron diffraction methods in the gas phase

    OpenAIRE

    De Almeida, Wagner B.

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can ma...

  9. Scanning Precession Electron Diffraction Study of 2xxx Series Aluminium Alloys Exhibiting Several Coexisting Strengthening Phases

    OpenAIRE

    Sunde, Jonas Kristoffer

    2016-01-01

    Throughout this thesis, scanning precession electron diffraction is applied to heat-treated Al-Cu-Li and Al-Mg-Cu-Ag alloys, shedding light on the distribution of phases present and the complex interplay between these microstructural features. The employed technique yielded high quality data sets, which through subsequent data processing enabled a detailed phase mapping of these multi-component Al alloys. Among the main results presented, are virtual dark field images highlighting all separat...

  10. Strongly correlated electron systems and neutron scattering. Magnetism, superconductivity, structural phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Katano, Susumu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Neutron scattering experiments in our group on strongly correlated electron systems are reviewed Metal-insulator transitions caused by structural phase transitions in (La{sub 1-x}Sr{sub x}) MnO{sub 3}, a novel magnetic transition in the CeP compound, correlations between antiferromagnetism and superconductivity in UPd{sub 2}Al{sub 3} and so forth are discussed. Here, in this note, the phase transition of Mn-oxides was mainly described. (author)

  11. Cosmology and unified gauge theory

    Science.gov (United States)

    Oraifeartaigh, L.

    1981-09-01

    Theoretical points in common between cosmology and unified gauge theory (UGT) are reviewed, with attention given to areas of one which have proven useful for the other. The underlying principles for both theoretical frameworks are described, noting the differences in scale, i.e., 10 to the 25th cm in cosmology and 10 to the -15th cm for UGT. Cosmology has produced bounds on the number of existing neutrino species, and also on the mass of neutrinos, two factors of interest in particle physics. Electrons, protons, and neutrinos, having been spawned from the same massive leptons, each composed of three quarks, have been predicted to be present in equal numbers in the Universe by UGT, in line with necessities of cosmology. The Grand UGT also suggests specific time scales for proton decay, thus accounting for the observed baryon assymmetry.

  12. Limit on the radiative neutrinoless double electron capture of {sup 36}Ar from GERDA Phase I

    Energy Technology Data Exchange (ETDEWEB)

    Agostini, M.; Balata, M.; D' Andrea, V.; Di Vacri, A.; Junker, M.; Laubenstein, M. [INFN Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, Assergi (Italy); Allardt, M.; Domula, A.; Lehnert, B.; Schneider, B.; Wester, T.; Wilsenach, H.; Zuber, K. [Technische Universitaet Dresden, Institut fuer Kern- und Teilchenphysik, Dresden (Germany); Bakalyarov, A.M.; Belyaev, S.T.; Lebedev, V.I.; Zhukov, S.V. [National Research Centre ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Barabanov, I.; Bezrukov, L.; Doroshkevich, E.; Fedorova, O.; Gurentsov, V.; Kazalov, V.; Kuzminov, V.V.; Lubsandorzhiev, B.; Moseev, P.; Selivanenko, O.; Veresnikova, A.; Yanovich, E. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow (Russian Federation); Barros, N. [Technische Universitaet Dresden, Institut fuer Kern- und Teilchenphysik, Dresden (Germany); University of Pennsylvania, Philadelphia, PA (United States); Baudis, L.; Benato, G.; Kish, A.; Miloradovic, M.; Mingazheva, R.; Walter, M. [Physik Institut der Universitaet Zuerich, Zurich (Switzerland); Bauer, C.; Hakenmueller, J.; Heisel, M.; Heusser, G.; Hofmann, W.; Kihm, T.; Kirsch, A.; Knoepfle, K.T.; Lindner, M.; Maneschg, W.; Salathe, M.; Schreiner, J.; Schwingenheuer, B.; Simgen, H.; Smolnikov, A.; Stepaniuk, M.; Wagner, V.; Wegmann, A. [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Bellotti, E. [Universita Milano Bicocca, Dipartimento di Fisica, Milan (Italy); INFN Milano Bicocca, Milan (Italy); Belogurov, S.; Kornoukhov, V.N. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow (Russian Federation); Institute for Theoretical and Experimental Physics NRC ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Bettini, A.; Brugnera, R.; Garfagnini, A.; Medinaceli, E.; Sada, C.; Sturm, K. von [Dipartimento di Fisica e Astronomia dell' Universita di Padova, Padua (Italy); INFN Padova, Padua (Italy); Bode, T.; Csathy, J.J.; Lazzaro, A.; Schoenert, S.; Wiesinger, C. [Technische Universitaet Muenchen, Physik Department and Excellence Cluster Universe, Munich (Germany); Borowicz, D. [Jagiellonian University, Institute of Physics, Krakow (Poland); Joint Institute for Nuclear Research, Dubna (Russian Federation); Brudanin, V.; Egorov, V.; Kochetov, O.; Nemchenok, I.; Rumyantseva, N.; Zhitnikov, I.; Zinatulina, D. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Caldwell, A.; Gooch, C.; Kneissl, R.; Liao, H.Y.; Majorovits, B.; Palioselitis, D.; Schulz, O.; Vanhoefer, L. [Max-Planck-Institut fuer Physik, Munich (Germany); Cattadori, C.; Salamida, F. [INFN Milano Bicocca, Milan (Italy); Chernogorov, A.; Demidova, E.V.; Kirpichnikov, I.V.; Vasenko, A.A. [Institute for Theoretical and Experimental Physics NRC ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Falkenstein, R.; Freund, K.; Grabmayr, P.; Hegai, A.; Jochum, J.; Schmitt, C.; Schuetz, A.K. [Eberhard Karls Universitaet Tuebingen, Physikalisches Institut, Tuebingen (Germany); Frodyma, N.; Misiaszek, M.; Panas, K.; Pelczar, K.; Wojcik, M.; Zuzel, G. [Jagiellonian University, Institute of Physics, Krakow (Poland); Gangapshev, A. [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Institute for Nuclear Research of the Russian Academy of Sciences, Moscow (Russian Federation); Gusev, K. [Joint Institute for Nuclear Research, Dubna (Russian Federation); National Research Centre ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Technische Universitaet Muenchen, Physik Department and Excellence Cluster Universe, Munich (Germany); Hemmer, S.; Lippi, I.; Stanco, L. [INFN Padova, Padua (Italy); Hult, M.; Lutter, G. [European Commission, JRC-Geel, Geel (Belgium); Inzhechik, L.V. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow (Russian Federation); Moscow Institute of Physics and Technology, Moscow (Russian Federation); Klimenko, A. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); International University for Nature, Society and Man ' ' Dubna' ' , Dubna (Russian Federation); Lubashevskiy, A. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Macolino, C. [INFN Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, Assergi (Italy); LAL, CNRS/IN2P3, Universite Paris-Saclay, Orsay (France); Pandola, L. [INFN Laboratori Nazionali del Sud, Catania (Italy); Pullia, A.; Riboldi, S. [Universita degli Studi di Milano, Dipartimento di Fisica, Milan (Italy); INFN Milano (Italy); Shirchenko, M. [Joint Institute for Nuclear Research, Dubna (Russian Federation); National Research Centre ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Collaboration: GERDA collaboration

    2016-12-15

    Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron capture of {sup 36}Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array (Gerda) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of {sup 36}Ar was established: T{sub 1/2} > 3.6 x 10{sup 21} years at 90% CI. (orig.)

  13. Limit on the radiative neutrinoless double electron capture of ^{36}Ar from GERDA Phase I

    Science.gov (United States)

    Agostini, M.; Allardt, M.; Bakalyarov, A. M.; Balata, M.; Barabanov, I.; Barros, N.; Baudis, L.; Bauer, C.; Bellotti, E.; Belogurov, S.; Belyaev, S. T.; Benato, G.; Bettini, A.; Bezrukov, L.; Bode, T.; Borowicz, D.; Brudanin, V.; Brugnera, R.; Caldwell, A.; Cattadori, C.; Chernogorov, A.; D'Andrea, V.; Demidova, E. V.; di Vacri, A.; Domula, A.; Doroshkevich, E.; Egorov, V.; Falkenstein, R.; Fedorova, O.; Freund, K.; Frodyma, N.; Gangapshev, A.; Garfagnini, A.; Gooch, C.; Grabmayr, P.; Gurentsov, V.; Gusev, K.; Hakenmüller, J.; Hegai, A.; Heisel, M.; Hemmer, S.; Heusser, G.; Hofmann, W.; Hult, M.; Inzhechik, L. V.; Csáthy, J. Janicskó; Jochum, J.; Junker, M.; Kazalov, V.; Kihm, T.; Kirpichnikov, I. V.; Kirsch, A.; Kish, A.; Klimenko, A.; Kneißl, R.; Knöpfle, K. T.; Kochetov, O.; Kornoukhov, V. N.; Kuzminov, V. V.; Laubenstein, M.; Lazzaro, A.; Lebedev, V. I.; Lehnert, B.; Liao, H. Y.; Lindner, M.; Lippi, I.; Lubashevskiy, A.; Lubsandorzhiev, B.; Lutter, G.; Macolino, C.; Majorovits, B.; Maneschg, W.; Medinaceli, E.; Miloradovic, M.; Mingazheva, R.; Misiaszek, M.; Moseev, P.; Nemchenok, I.; Palioselitis, D.; Panas, K.; Pandola, L.; Pelczar, K.; Pullia, A.; Riboldi, S.; Rumyantseva, N.; Sada, C.; Salamida, F.; Salathe, M.; Schmitt, C.; Schneider, B.; Schönert, S.; Schreiner, J.; Schütz, A.-K.; Schulz, O.; Schwingenheuer, B.; Selivanenko, O.; Shirchenko, M.; Simgen, H.; Smolnikov, A.; Stanco, L.; Stepaniuk, M.; Vanhoefer, L.; Vasenko, A. A.; Veresnikova, A.; von Sturm, K.; Wagner, V.; Walter, M.; Wegmann, A.; Wester, T.; Wiesinger, C.; Wilsenach, H.; Wojcik, M.; Yanovich, E.; Zhitnikov, I.; Zhukov, S. V.; Zinatulina, D.; Zuber, K.; Zuzel, G.

    2016-12-01

    Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron capture of ^{36}Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array ( Gerda) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of ^{36}Ar was established: T_{1/2} > 3.6 × 10^{21} years at 90% CI.

  14. Linking the gaseous and the condensed phases of matter: The slow electron and its interactions

    International Nuclear Information System (INIS)

    Christophorou, L.G.

    1993-01-01

    The interfacing of the gaseous and the condensed phases of matter as effected by interphase and cluster studies on the behavior of key reactions involving slow electrons either as reacting initial particles or as products of the reactions themselves is discussed. Emphasis is placed on the measurement of both the cross sections and the energetics involved, although most of the available information to date is on the latter. The discussion is selectively focussed on electron scattering (especially the role of negative ion states in gases, clusters, and dense matter), ionization, electron attachment and photodetachment. The dominant role of the electric polarization of the medium is emphasized

  15. Langmuir wave phase-mixing in warm electron-positron-dusty plasmas

    Science.gov (United States)

    Pramanik, Sourav; Maity, Chandan

    2018-04-01

    An analytical study on nonlinear evolution of Langmuir waves in warm electron-positron-dusty plasmas is presented. The massive dust grains of either positively or negatively charged are assumed to form a fixed charge neutralizing background. A perturbative analysis of the fluid-Maxwell's equations confirms that the excited Langmuir waves phase-mix and eventually break, even at arbitrarily low amplitudes. It is shown that the nature of the dust-charge as well as the amount of dust grains can significantly influence the Langmuir wave phase-mixing process. The phase-mixing time is also found to increase with the temperature.

  16. Grand unified theories

    International Nuclear Information System (INIS)

    Langacker, P.

    1981-01-01

    In this talk I discuss the present status of these theories and of their observational and experimental implications. In section II, I briefly review the standard SU 3 sup(c) x SU 2 x U 1 model of the strong and electroweak interactions. Although phenomenologically successful, the standard model leaves many questions unanswered. Some of these questions are addressed by grand unified theories, which are defined and discussed in Section III. The Georgi-Glashow SU 5 model is described, as are theories based on larger groups such as SO 10 , E 6 , or SO 16 . It is emphasized that there are many possible grand unified theories and that it is an experimental problem not only to test the basic ideas but to discriminate between models. (orig./HSI)

  17. Observations of electron phase-space holes driven during magnetic reconnection in a laboratory plasma

    Science.gov (United States)

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

    2012-03-01

    This work presents detailed experimental observations of electron phase-space holes driven during magnetic reconnection events on the Versatile Toroidal Facility. The holes are observed to travel on the order of or faster than the electron thermal speed, and are of large size scale, with diameter of order 60 Debye lengths. In addition, they have 3D spheroidal structure with approximately unity aspect ratio. We estimate the direct anomalous resistivity due to ion interaction with the holes and find it to be too small to affect the reconnection rate; however, the holes may play a role in reining in a tail of accelerated electrons and they indicate the presence of other processes in the reconnection layer, such as electron energization and electron beam formation.

  18. Femtosecond single electron bunch generation by rotating longitudinal bunch phase space in magnetic field

    International Nuclear Information System (INIS)

    Yang, J.; Kondoh, T.; Kan, K.; Kozawa, T.; Yoshida, Y.; Tagawa, S.

    2006-01-01

    A femtosecond (fs) electron bunching was observed in a photoinjector with a magnetic compressor by rotating the bunch in longitudinal phase space. The bunch length was obtained by measuring Cherenkov radiation of the electron beam with a femtosecond streak camera technique. A single electron bunch with rms bunch length of 98 fs was observed for a 32 MeV electron beam at a charge of 0.17 nC. The relative energy spread and the normalized transverse emittance of the electron beam were 0.2% and 3.8 mm-mrad, respectively. The effect of space charge on the bunch compression was investigated experimentally for charges from 0.17 to 1.25 nC. The dependences of the relative energy spread and the normalized beam transverse emittance on the bunch charge were measured

  19. Identification of phases in zinc alloy powders using electron backscatter diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Martin G. [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States); Kenik, Edward A. [Oak Ridge National Laboratory, 100 Bethel Valley Rd., Bldg. 4515, MS-6064, P.O. Box 2008, Oak Ridge, TN 37831 (United States); O' Keefe, Matthew J. [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States)]. E-mail: mjokeefe@umr.edu; Miller, F. Scott [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States); Johnson, Benedict [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States)

    2006-05-25

    Scanning electron microscopy and electron backscatter diffraction (EBSD) were used for the structural characterization of phases in Zn alloy powders. Commercial Zn alloy powders contained additions of <1000 ppm of Bi, In, Al or Mg. Bismuth and In have extremely low solubility in Zn and form intermetallic Bi-In compounds which segregate to the Zn grain boundaries. The Bi-In phases were <0.3 {mu}m in size, had low melting points, and were not abundant enough for EBSD analysis. Increasing the alloying additions 20-40-fold resulted in Bi-In phases >1 {mu}m that could be used for EBSD analysis for phase characterization. Deformation-free microstructures were obtained by mechanical polishing and ion milling. The Zn matrix was characterized as Zn via EBSD. A BiIn{sub 2} phase was identified in the powder microstructures via EBSD. An In phase with 8-9 wt.% Bi was identified using low voltage energy dispersive spectroscopy and closely matched the composition predicted by the Bi-In phase diagram.

  20. The relationship between optical guiding and the relative phase in free-electron lasers

    International Nuclear Information System (INIS)

    Freund, H.P.; Antonsen, T.M. Jr.

    1991-01-01

    In this paper the relationship between the relative phase and optical guiding in the free-electron laser is studied. The relative phase in this case is defined as the shift in the wavenumber from the vacuum value integrated over the interaction length. In terms of the optical guiding of the signal in free-electron lasers, the relative phase must be positive in order for refractive guiding of the signal to occur. The relative phase is studied from the standpoint of the linear stability analysis in both the high- and low-gain regimes, and the qualitative implications in each of these regimes of the relative phase on the refractive guiding of the signal are identical. Specifically, the relative phase is found to be negative at the low-frequency over this band until it turns positive at a frequency approximately 10% below the frequency of peak gain. Thus optical guiding is indicated over a large portion, but not all, of the gain band. A quantitative measure of the optical guiding of the signal is obtained by an analytic formulation of the guiding of the signal. This formulation is based upon a separable beam approximation in which the evolution of the signal is determined by a Green's function analysis. The specific example of interest involves the low-gain regime prior to saturation. In this case, it is shown that the analytic result is in substantial agreement with the calculation of the relative phase

  1. Operation Unified Protector

    DEFF Research Database (Denmark)

    Buhl, Kenneth Øhlenschlæger

    2012-01-01

    Formålet med denne artikel er at se nærmere på erfaringerne fra den maritime kampagne under den militære indsats i konflikten i Libyen i 2011, som i NATO regi blev kendt som Operation Unified Protector (OUP). Dækningen i de danske medier fokuserede primært på luftkampagnen, hvilket må tilskrives,...

  2. Unified Engineering Software System

    Science.gov (United States)

    Purves, L. R.; Gordon, S.; Peltzman, A.; Dube, M.

    1989-01-01

    Collection of computer programs performs diverse functions in prototype engineering. NEXUS, NASA Engineering Extendible Unified Software system, is research set of computer programs designed to support full sequence of activities encountered in NASA engineering projects. Sequence spans preliminary design, design analysis, detailed design, manufacturing, assembly, and testing. Primarily addresses process of prototype engineering, task of getting single or small number of copies of product to work. Written in FORTRAN 77 and PROLOG.

  3. Electron microscopy and phase analysis of fly ash from pressurized fluidized bed combustion

    International Nuclear Information System (INIS)

    Maenami, Hiroki; Isu, Norifumi; Ishida, Emile H.; Mitsuda, Takeshi

    2004-01-01

    The characterization of the typical fly ashes from pressurized fluidized bed combustion system (PFBC) in Japan and Europe was carried out by electron microscopy and phase analysis using energy-dispersive X-ray spectroscopy (EDX). The purity of limestone as in-bed sulfur removal sorbent influences the desulfurization reaction. The high-purity limestone yielded both hydroxyl ellestadite and anhydrite in Japanese PFBC ashes, while dolomite-rich limestone yielded anhydrite in European PFBC ashes. When the high-purity limestone was used, hydroxyl ellestadite particles were observed as the independent particles or the rim around limestone particles. The Al 2 O 3 content in the glassy phase was inversely proportional to the CaO content in the glassy phase, suggesting that the glassy phases were formed from metakaoline and calcite as end members. Since hydroxyl ellestadite, glassy phase and metakaoline are reactive under hydrothermal conditions, PFBC ashes are expected to be used as raw materials for autoclaved products

  4. Deep Learning the Quantum Phase Transitions in Random Electron Systems: Applications to Three Dimensions

    Science.gov (United States)

    Ohtsuki, Tomi; Ohtsuki, Tomoki

    2017-04-01

    Three-dimensional random electron systems undergo quantum phase transitions and show rich phase diagrams. Examples of the phases are the band gap insulator, Anderson insulator, strong and weak topological insulators, Weyl semimetal, and diffusive metal. As in the previous paper on two-dimensional quantum phase transitions [J. Phys. Soc. Jpn. 85, 123706 (2016)], we use an image recognition algorithm based on a multilayered convolutional neural network to identify which phase the eigenfunction belongs to. The Anderson model for localization-delocalization transition, the Wilson-Dirac model for topological insulators, and the layered Chern insulator model for Weyl semimetal are studied. The situation where the standard transfer matrix approach is not applicable is also treated by this method.

  5. Electronic structure of the antiferromagnetic phase of Sr2Co2O5

    International Nuclear Information System (INIS)

    Pardo, V.; Botta, P.M.; Baldomir, D.; Rivas, J.; Pineiro, A.; Calle, C. de la; Alonso, J.A.; Arias, J.E.

    2008-01-01

    Ab initio calculations analyze the properties of the G-type antiferromagnetic Sr 2 Co 2 O 5 as a high-spin system. The description of the electronic structure is given; all the Co atoms are in a high-spin state with a small unquenched orbital angular momentum. Thermal analysis on a polycrystalline sample shows a magnetic phase transition at high temperatures

  6. Large scale electronic structure calculations in the study of the condensed phase

    NARCIS (Netherlands)

    van Dam, H.J.J.; Guest, M.F.; Sherwood, P.; Thomas, J.M.H.; van Lenthe, J.H.; van Lingen, J.N.J.; Bailey, C.L.; Bush, I.J.

    2006-01-01

    We consider the role that large-scale electronic structure computations can now play in the modelling of the condensed phase. To structure our analysis, we consider four distict ways in which today's scientific targets can be re-scoped to take advantage of advances in computing resources: 1. time to

  7. Gas-phase synthesis of magnesium nanoparticles : A high-resolution transmission electron microscopy study

    NARCIS (Netherlands)

    Kooi, B.J.; Palasantzas, G.; de Hosson, J.T.M.

    2006-01-01

    Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg{1010} facets. Oxidation of Mg yields a MgO shell (similar to 3 nm

  8. Application of ab initio electronic structure calculations for prediction of phase equilibria in superaustenitic steels

    Czech Academy of Sciences Publication Activity Database

    Vřešťál, J.; Kroupa, Aleš; Šob, Mojmír

    2006-01-01

    Roč. 38, č. 11 (2006), s. 298-302 ISSN 0927-0256 R&D Projects: GA ČR(CZ) GA106/03/1354; GA AV ČR(CZ) IBS2041105 Institutional research plan: CEZ:AV0Z20410507 Keywords : electronic structure * Phase diagrams * Steel Subject RIV: BJ - Thermodynamics Impact factor: 1.104, year: 2006

  9. Differential phase-contrast dark-field electron holography for strain mapping

    Energy Technology Data Exchange (ETDEWEB)

    Denneulin, Thibaud, E-mail: thibaud.denneulin@cemes.fr; Houdellier, Florent, E-mail: florent.houdellier@cemes.fr; Hÿtch, Martin, E-mail: martin.hytch@cemes.fr

    2016-01-15

    Strain mapping is an active area of research in transmission electron microscopy. Here we introduce a dark-field electron holographic technique that shares several aspects in common with both off-axis and in-line holography. Two incident and convergent plane waves are produced in front of the specimen thanks to an electrostatic biprism in the condenser system of a transmission electron microscope. The interference of electron beams diffracted by the illuminated crystal is then recorded in a defocused plane. The differential phase recovered from the hologram is directly proportional to the strain in the sample. The strain can be quantified if the separation of the images due to the defocus is precisely determined. The present technique has the advantage that the derivative of the phase is measured directly which allows us to avoid numerical differentiation. The distribution of the noise in the reconstructed strain maps is isotropic and more homogeneous. This technique was used to investigate different samples: a Si/SiGe superlattice, transistors with SiGe source/drain and epitaxial PZT thin films. - Highlights: • DPC dark-field electron holography is set up with a condenser biprism. • The DPC phase is directly proportional to the lattice deformation. • The technique is illustrated with epitaxial SiGe and Pb(Zr,Ti)O{sub 3} samples. • The defocus allows us to control the strain sensitivity and the spatial resolution. • A solution is proposed to setup this technique with a post-specimen biprism.

  10. An integrated electron and optical metallographic procedure for the identification of precipitate phases in type 316 stainless steel

    International Nuclear Information System (INIS)

    Slattery, G.F.; O'Riordan, P.; Lambert, M.E.; Green, S.M.

    1981-01-01

    A sequential and integrated metallographic procedure has been developed and successfully employed to differentiate between carbide, sigma, chi, Laves and ferrite phases which are commonly encountered in type 316 austenitic steel. The experimental techniques of optical and electron microscopy to identify these phases have been outlined and provide a rapid and convenient method of characterizing the microstructure of the steel. The techniques sequence involves selective metallographic etching, Nomarski interference microscopy, scanning electron microscopy, energy dispersive microanalysis, transmission electron microscopy and electron diffraction. (author)

  11. Stability of Sarma phases in density imbalanced electron-hole bilayer systems

    International Nuclear Information System (INIS)

    Subasi, A. L.; Tanatar, B.; Pieri, P.; Senatore, G.

    2010-01-01

    We study excitonic condensation in an electron-hole bilayer system with unequal layer densities at zero temperature. Using mean-field theory we solve the Bardeen-Cooper-Schrieffer (BCS) gap equations numerically and investigate the effects of intralayer interactions. The electron-hole system evolves from BCS in the weak coupling limit to Bose-Einstein condensation (BEC) in the strong coupling limit. We analyze the stability of the Sarma phase with k,-k pairing by calculating the superfluid mass density and also by checking the compressibility matrix. We find that with bare Coulomb interactions the superfluid density is always positive in the Sarma phase, due to a peculiar momentum structure of the gap function originating from the singular behavior of the Coulomb potential at zero momentum and the presence of a sharp Fermi surface. Introducing a simple model for screening, we find that the superfluid density becomes negative in some regions of the phase diagram, corresponding to an instability toward a Fulde-Ferrel-Larkin-Ovchinnikov-type superfluid phase. Thus, intralayer interaction and screening together can lead to a rich phase diagram in the BCS-BEC crossover regime in electron-hole bilayer systems.

  12. An enhanced electronic topology aimed at improving the phase sensitivity of GMI sensors

    International Nuclear Information System (INIS)

    Costa Silva, E; Gusmão, L A P; Hall Barbosa, C R; Costa Monteiro, E

    2014-01-01

    The giant magnetoimpedance effect (GMI) is used in the most recent technologies developed for the detection of magnetic fields, showing potential to be applied in the measurement of ultra-weak fields. GMI samples exhibit a huge dependency of their electrical impedance on the magnetic field, which makes them excellent magnetic sensors. In spite of GMI magnetometers being mostly based on magnitude impedance characteristics, it was previously verified that sensitivity could be significantly increased by reading the impedance phase. Pursuing this idea, a phase-based GMI magnetometer has been already developed as well as an electronic configuration capable of improving the phase sensitivity of GMI samples. However, when using this topology, it was noted that the sensitivity improvement comes at the cost of reduced voltage levels in the reading terminal, degrading the signal-to-noise ratio. Another drawback of the electronic configuration was that it was not capable of enforcing a linear behavior of the impedance phase in the function of the magnetic field in a given operation region. Aiming at overcoming those issues and then optimizing the behavior of the circuit developed to improve the phase sensitivity, this paper mathematically describes a completely new methodology, presents an enhanced newly developed electronic topology and exemplifies its application. (paper)

  13. Electronic structure and high pressure phase transition in LaSb and CeSb

    International Nuclear Information System (INIS)

    Mathi Jaya, S.; Sanyal, S.P.

    1992-09-01

    The electronic structure and high pressure structural phase transition in cerium and lanthanum antimonides have been investigated using the tight binding LMTO method. The calculation of total energy reveals that the simple tetragonal structure is found to be stable at high pressures for both the compounds. In the case of LaSb, the calculated value of the equilibrium cell volume and the cell volume at which phase transition occurs are found to have a fairly good agreement with the experimental results. However, in the case of CeSb, the agreement is not as good as in LaSb. We also predicted the most favoured c/a value in the high pressure phase (simple tetragonal) for these compounds. Further we present the calculated results on the electronic structure of these systems at the equilibrium as well as at the reduced cell volumes. (author). 8 refs, 11 figs, 1 tab

  14. Molecular structure determination of cyclooctane by Ab Initio and electron diffraction methods in the gas phase

    International Nuclear Information System (INIS)

    Almeida, Wagner B. de

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can make a significant contribution for an unambiguous determination of the geometrical parameters. In this article the determination for an unambiguous determination of the geometrical parameters. In this article the determination of the molecular structure of the cyclooctane molecule by electron diffraction in the gas phase an initio calculations will be addressed, providing an example of a comparative analysis of theoretical and experimental predictions. (author)

  15. Field electron emission characteristics of chemical vapour deposition diamond films with controlled sp2 phase concentration

    International Nuclear Information System (INIS)

    Lu, X.; Yang, Q.; Xiao, C.; Hirose, A.

    2008-01-01

    Diamond films were synthesized in a microwave plasma-enhanced chemical vapour deposition reactor. The microstructure and surface morphology of deposited films were characterized by Raman spectroscope and scanning electron microscope. The sp 2 phase concentration in diamond films was varied and its effect on the field electron emission (FEE) properties was investigated. Diamond films deposited under higher methane concentration exhibit better FEE property including lower turn-on electric field and larger emission current. The predominating factor modifying the FEE property is presumed to be the increase of sp 2 phase concentration. The influence of bias voltage on the FEE property of diamond films is not monotonic. Postgrowth acid treatment reduces the sp 2 phase content in diamond films without changing diamond grain sizes. The corresponding FEE property was degraded

  16. Omega phase in materials

    International Nuclear Information System (INIS)

    Sikka, S.K.; Vohra, Y.K.; Chidambaram, R.

    1982-01-01

    The subject is covered in sections, entitled: introduction; occurrence and some systematics of omega phase (omega phase in Ti, Zr and Hf under high pressures; omega phase in Group IV transition metal alloys; omega in other systems; omega embryos at high temperatures); crystallography (omega structure; relationship of ω-structure to bcc (β) and hcp (α) structures); physical properties; kinetics of formation, synthesis and metastability of omega phase (kinetics of α-ω transformation under high pressures; kinetics of β-ω transformation; synthesis and metastability studies); electronic structure of omega phase (electronic structure models; band structure calculations; theoretical results and experimental studies); electronic basis for omega phase stability (unified phase diagram; stability of omega phase); omega phase formation under combined thermal and pressure treatment in alloys (Ti-V alloys under pressure - a prototype case study; P-X phase diagrams for alloys; transformation mechanisms and models for diffuse omega phase (is omega structure a charge density distortion of the bcc phase; nature of incommensurate ω-structure and models for diffuse scattering); conclusion. (U.K.)

  17. Quasi-phase-matched acceleration of electrons in a corrugated plasma channel

    Directory of Open Access Journals (Sweden)

    S. J. Yoon

    2012-08-01

    Full Text Available A laser pulse propagating in a corrugated plasma channel is composed of spatial harmonics whose phase velocities can be subluminal. The phase velocity of a spatial harmonic can be matched to the speed of a relativistic electron resulting in direct acceleration by the guided laser field in a plasma waveguide and linear energy gain over the interaction length. Here we examine the fully self-consistent interaction of the laser pulse and electron beam using particle-in-cell (PIC simulations. For low electron beam densities, we find that the ponderomotive force of the laser pulse pushes plasma channel electrons towards the propagation axis, which deflects the beam electrons. When the beam density is high, the space charge force of the beam drives the channel electrons off axis, providing collimation of the beam. In addition, we consider a ramped density profile for lowering the threshold energy for trapping in a subluminal spatial harmonic. By using a density ramp, the trapping energy for a normalized vector potential of a_{0}=0.1 is reduced from a relativistic factor γ_{0}=170 to γ_{0}=20.

  18. Effect of isotopic substitution upon the gas phase and solution electron affinities of nitrobenzene

    International Nuclear Information System (INIS)

    Stevenson, G.R.; Reiter, R.C.; Espe, M.E.; Bartmess, J.E.

    1987-01-01

    Ion cyclotron resonance and electron spin resonance have been utilized to determine the equilibrium constant for the electron transfer from the nitrobenzene anion radical to 15 N labeled nitrobenzene (Ph 14 NO 2 - + Ph 15 NO 2 ↔ Ph 14 NO 2 + Ph 15 NO 2 9 . It was found that the equilibrium constant is within experimental error of unity at 305 K. Molecular orbital calculations indicate that this might be accounted for by the shortening of the C-N bond and a counterbalancing lengthening of the N-O bonds upon electron attachment to nitrobenzene. An equilibrium constant that is much larger than unity can be observed in liquid ammonia at 208 K when K + serves as the gegenion (K/sub eq/ = 2.1). However, when Na + serves as the gegenion, the solution electron affinity of Ph 14 NO 2 is greater than that of Ph 15 NO 2 (K/sub eq/ = 0.4). These results are explained in terms of ion association. When the hydrogen atoms are replaced with deuteriums, the gas phase electron affinity is decreased. A similar decrease is observed in liquid ammonia. In the gas phase this is attributed to the slight lengthening of all the C-H bonds upon electron attachment

  19. Electronic motion in the pre-oscillation phase of a smooth bore magnetron

    International Nuclear Information System (INIS)

    Garelis, E.; Hickman, R.B.

    1979-01-01

    The calculation of the electronic motion in the pre-oscillation phase of a smooth bore magnetron is the problem of calculating the electronic motion in the region between two concentric cylinders with an applied radial electric field and a constant axial B/sub z/ magnetic field. The inner cylinder represents the electron emitting cathode and the outer cylinder represents the anode. The emission is assumed to be space charge limited. This results in an electronic cloud surrounding the cathode. The radial velocity of the electrons is limited by the space charge and in addition the axial magnetic field tends to curve the path of the electrons so that they return to the cathode. Consequently, the electronic orbit extends to some distance r 0 from the cathode and for values of the radius r > r 0 exists a charge free region. The model assumes relativistic electronic motion with self-consistent magnetic fields. The magnetic flux is assumed to be conserved; i.e., conducting cylindrical walls

  20. Unified explanation for optical and electron paramagnetic resonance spectra of Cr sup 3 sup + ions in LiNbO sub 3 crystals

    CERN Document Server

    Zhao, M G

    1997-01-01

    An approximately microscopic model is developed for the Cr sup 3 sup + -6O sup 2 sup - cluster and applied to study the optical data and electron paramagnetic resonance (EPR) g-factors and the zero-field splitting D-value in LiNbO sub 3 :Cr sup 3 sup +. Analysis of the optical and EPR data indicate that Cr sup 3 sup + ions substitute at Nb sites and Nb-vacancy (Li) sites simultaneously. The results are in good agreement with the experimental findings. This means that the optical and EPR data and the substitution site of Cr sup 3 sup + ions in LiNbO sub 3 can be interpreted uniformly. (author)

  1. Electron backscatter diffraction studies of focused ion beam induced phase transformation in cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Jones, H.G., E-mail: helen.jones@npl.co.uk [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Day, A.P. [Aunt Daisy Scientific Ltd, Claremont House, High St, Lydney GL15 5DX (United Kingdom); Cox, D.C. [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2016-10-15

    A focused ion beam microscope was used to induce cubic to hexagonal phase transformation in a cobalt alloy, of similar composition to that of the binder phase in a hardmetal, in a controlled manner at 0°, 45° and 80° ion incident angles. The cobalt had an average grain size of ~ 20 μm, allowing multiple orientations to be studied, exposed to a range of doses between 6 × 10{sup 7} and 2 × 10{sup 10} ions/μm{sup 2}. Electron backscatter diffraction (EBSD) was used to determine the original and induced phase orientations, and area fractions, before and after the ion beam exposure. On average, less phase transformation was observed at higher incident angles and after lower ion doses. However there was an orientation effect where grains with an orientation close to (111) planes were most susceptible to phase transformation, and (101) the least, where grains partially and fully transformed at varying ion doses. - Highlights: •Ion-induced phase change in FCC cobalt was observed at multiple incidence angles. •EBSD was used to study the relationship between grain orientation and transformation. •Custom software analysed ion dose and phase change with respect to grain orientation. •A predictive capability of ion-induced phase change in cobalt was enabled.

  2. High resolution electron microscopy of the triply incommensurate phase of 2H-TaSe2

    Science.gov (United States)

    Onozuka, Takashi; Otsuka, Nobuo; Sato, Hiroshi

    1986-09-01

    The triply incommensurate phase of 2H-TaSe2 obtained by cooling from the normal phase was investigated by transmission electron microscopy between 87 and 113 K with the resolution of 3 Å, one order of magnitude better than earlier experiments. Moirélike patterns observed in this phase were confirmed to be interference fringes due to the first- and second-order diffraction beams (with small separation and possibly with higher-order diffraction beams) from the incommensurate structure and were not due to the dark-field diffraction contrast of domains of the commensurate structure as interpreted earlier. Lattice fringes (~9 Å) of this modulated phase do not show any discontinuity across the boundaries of regions of different contrasts of the moirélike fringes which is expected from domain boundaries. Instead, a periodic change in the spacing of the lattice fringes (phase-slip region) expected from the superposition of split superlattice spots in forming the lattice image is observed. This is what is believed to be the first direct observation of the existence of the phase-slip region which is also expected from the discommensuration theory. A series of observations presented here thus shows that the triply incommensurate phase is intrinsically incommensurate and suggests the need for a modification of interpretations of this phase in terms of the double honeycomb discommensuration model.

  3. Electronic Identification of the Parental Phases and Mesoscopic Phase Separation of K_{x}Fe_{2-y}Se_{2} Superconductors

    Directory of Open Access Journals (Sweden)

    F. Chen

    2011-12-01

    Full Text Available The nature of the parent compound of a high-temperature superconductor (HTS often plays a pivotal role in determining its superconductivity. The parent compounds of the cuprate HTSs are antiferromagnetically ordered Mott insulators, while those of the iron-pnictide HTSs are metals with spin-density-wave order. Here we report the electronic identification of two insulating parental phases and one semiconducting parental phase of the newly discovered family of K_{x}Fe_{2-y}Se_{2} superconductors. The two insulating phases exhibit Mott-insulator-like signatures, and one of the insulating phases is even present in the superconducting and semiconducting K_{x}Fe_{2-y}Se_{2} compounds. However, it is mesoscopically phase-separated from the superconducting or semiconducting phase. Moreover, we find that both the superconducting and semiconducting phases are free of the magnetic and vacancy orders present in the insulating phases, and that the electronic structure of the superconducting phase could be developed by doping the semiconducting phase with electrons. The rich electronic properties discovered in these parental phases of the K_{x}Fe_{2-y}Se_{2} superconductors provide the foundation for studying the anomalous behavior in this new class of iron-based superconductors.

  4. NIST/Sandia/ICDD Electron Diffraction Database: A Database for Phase Identification by Electron Diffraction.

    Science.gov (United States)

    Carr, M J; Chambers, W F; Melgaard, D; Himes, V L; Stalick, J K; Mighell, A D

    1989-01-01

    A new database containing crystallographic and chemical information designed especially for application to electron diffraction search/match and related problems has been developed. The new database was derived from two well-established x-ray diffraction databases, the JCPDS Powder Diffraction File and NBS CRYSTAL DATA, and incorporates 2 years of experience with an earlier version. It contains 71,142 entries, with space group and unit cell data for 59,612 of those. Unit cell and space group information were used, where available, to calculate patterns consisting of all allowed reflections with d -spacings greater than 0.8 A for ~ 59,000 of the entries. Calculated patterns are used in the database in preference to experimental x-ray data when both are available, since experimental x-ray data sometimes omits high d -spacing data which falls at low diffraction angles. Intensity data are not given when calculated spacings are used. A search scheme using chemistry and r -spacing (reciprocal d -spacing) has been developed. Other potentially searchable data in this new database include space group, Pearson symbol, unit cell edge lengths, reduced cell edge length, and reduced cell volume. Compound and/or mineral names, formulas, and journal references are included in the output, as well as pointers to corresponding entries in NBS CRYSTAL DATA and the Powder Diffraction File where more complete information may be obtained. Atom positions are not given. Rudimentary search software has been written to implement a chemistry and r -spacing bit map search. With typical data, a full search through ~ 71,000 compounds takes 10~20 seconds on a PDP 11/23-RL02 system.

  5. Parallel power electronics filters in three-phase four-wire systems principle, control and design

    CERN Document Server

    Wong, Man-Chung; Lam, Chi-Seng

    2016-01-01

    This book describes parallel power electronic filters for 3-phase 4-wire systems, focusing on the control, design and system operation. It presents the basics of power-electronics techniques applied in power systems as well as the advanced techniques in controlling, implementing and designing parallel power electronics converters. The power-quality compensation has been achieved using active filters and hybrid filters, and circuit models, control principles and operational practice problems have been verified by principle study, simulation and experimental results. The state-of-the-art research findings were mainly developed by a team at the University of Macau. Offering background information and related novel techniques, this book is a valuable resource for electrical engineers and researchers wanting to work on energy saving using power-quality compensators or renewable energy power electronics systems. .

  6. Communication: Predictive partial linearized path integral simulation of condensed phase electron transfer dynamics

    International Nuclear Information System (INIS)

    Huo, Pengfei; Miller, Thomas F. III; Coker, David F.

    2013-01-01

    A partial linearized path integral approach is used to calculate the condensed phase electron transfer (ET) rate by directly evaluating the flux-flux/flux-side quantum time correlation functions. We demonstrate for a simple ET model that this approach can reliably capture the transition between non-adiabatic and adiabatic regimes as the electronic coupling is varied, while other commonly used semi-classical methods are less accurate over the broad range of electronic couplings considered. Further, we show that the approach reliably recovers the Marcus turnover as a function of thermodynamic driving force, giving highly accurate rates over four orders of magnitude from the normal to the inverted regimes. We also demonstrate that the approach yields accurate rate estimates over five orders of magnitude of inverse temperature. Finally, the approach outlined here accurately captures the electronic coherence in the flux-flux correlation function that is responsible for the decreased rate in the inverted regime

  7. Laboratory Observation of Electron Phase-Space Holes during Magnetic Reconnection

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  8. 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%.

  9. Phase mapping of iron-based rapidly quenched alloys using precession electron diffraction

    International Nuclear Information System (INIS)

    Svec, P.; Janotova, I.; Hosko, J.; Matko, I.; Janickovic, D.; Svec, P. Sr.; Kepaptsoglou, D. M.

    2013-01-01

    The present contribution is focused on application of PED and phase/orientation mapping of nanocrystals of bcc-Fe formed during the first crystallization stage of amorphous Fe-Co-Si-B ribbon. Using precession electron diffraction and phase/orientation mapping the formation of primary crystalline phase, bcc-Fe, from amorphous Fe-Co-Si-B has been analyzed. Important information about mutual orientation of the phase in individual submicron grains as well as against the sample surface has been obtained. This information contributes to the understanding of micromechanisms controlling crystallization from amorphous rapidly quenched structure and of the structure of the original amorphous state. The presented technique due to its high spatial resolution, speed and information content provided complements well classical techniques, especially in nanocrystalline materials. (authors)

  10. Crystal growth and electronic structure of low-temperature phase SrMgF{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Atuchin, Victor V. [Laboratory of Optical Materials and Structures, Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Functional Electronics Laboratory, Tomsk State University, Tomsk 634050 (Russian Federation); Laboratory of Semiconductor and Dielectric Materials, Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Goloshumova, Alina A. [Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Isaenko, Ludmila I. [Laboratory of Semiconductor and Dielectric Materials, Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Jiang, Xingxing [BCCRD, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lobanov, Sergey I. [Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Zhang, Zhaoming [Australian Nuclear Science & Technology Organisation, Lucas Heights, NSW 2234 (Australia); Lin, Zheshuai, E-mail: zslin@mail.ipc.ac.cn [BCCRD, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2016-04-15

    Using the vertical Bridgman method, the single crystal of low temperature phase SrMgF{sub 4} is obtained. The crystal is in a very good optical quality with the size of 10×7×5 mm{sup 3}. Detailed photoemission spectra of the element core levels are determined by a monochromatic AlKa (1486.6 eV) X-ray source. Moreover, the first-principles calculations are performed to investigate the electronic structure of SrMgF{sub 4}. A good agreement between experimental and calculated results is achieved. It is demonstrated that almost all the electronic orbitals are strongly localized and the hybridization with the others is very small, but the Mg–F bonds covalency is relatively stronger than that of Sr–F bonds. - Graphical abstract: Large size of low-temperature phase SrMgF{sub 4} crystal was obtained (right) and its electronic structure was investigated by X-ray photoelectron spectroscopy and first-principles calculation (left). - Highlights: • Large size single crystal of low-temperature phase SrMgF{sub 4} is obtained. • Electronic structure of SrMgF{sub 4} is measured by X-ray photoelectron spectroscopy. • Partial densities of states are determined by first-principles calculation. • Good agreement between experimental and calculated results is achieved. • Strong ionic characteristics of chemical bonds are exhibited in SrMgF{sub 4}.

  11. On the inward drift of runaway electrons during the plateau phase of runaway current

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Di, E-mail: hudi-2@pku.edu.cn [School of Physics, Peking University, Beijing 100871 (China); Qin, Hong [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08540 (United States); School of Nuclear Science and Technology and Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)

    2016-03-15

    The well observed inward drift of current carrying runaway electrons during runaway plateau phase after disruption is studied by considering the phase space dynamic of runaways in a large aspect ratio toroidal system. We consider the case where the toroidal field is unperturbed and the toroidal symmetry of the system is preserved. The balance between the change in canonical angular momentum and the input of mechanical angular momentum in such a system requires runaways to drift horizontally in configuration space for any given change in momentum space. The dynamic of this drift can be obtained by integrating the modified Euler-Lagrange equation over one bounce time. It is then found that runaway electrons will always drift inward as long as they are decelerating. This drift motion is essentially non-linear, since the current is carried by runaways themselves, and any runaway drift relative to the magnetic axis will cause further displacement of the axis itself. A simplified analytical model is constructed to describe such inward drift both in the ideal wall case and no wall case, and the runaway current center displacement as a function of parallel momentum variation is obtained. The time scale of such displacement is estimated by considering effective radiation drag, which shows reasonable agreement with the observed displacement time scale. This indicates that the phase space dynamic studied here plays a major role in the horizontal displacement of runaway electrons during plateau phase.

  12. Electronic structure of the cuprate superconducting and pseudogap phases from spectroscopic imaging STM

    Science.gov (United States)

    Schmidt, A. R.; Fujita, K.; Kim, E.-A.; Lawler, M. J.; Eisaki, H.; Uchida, S.; Lee, D.-H.; Davis, J. C.

    2011-06-01

    We survey the use of spectroscopic imaging scanning tunneling microscopy (SI-STM) to probe the electronic structure of underdoped cuprates. Two distinct classes of electronic states are observed in both the d-wave superconducting (dSC) and the pseudogap (PG) phases. The first class consists of the dispersive Bogoliubov quasiparticle excitations of a homogeneous d-wave superconductor, existing below a lower energy scale E=Δ0. We find that the Bogoliubov quasiparticle interference (QPI) signatures of delocalized Cooper pairing are restricted to a k-space arc, which terminates near the lines connecting k=±(π/a0,0) to k=±(0,π/a0). This arc shrinks continuously with decreasing hole density such that Luttinger's theorem could be satisfied if it represents the front side of a hole-pocket that is bounded behind by the lines between k=±(π/a0,0) and k=±(0,π/a0). In both phases, the only broken symmetries detected for the |E|modulations, locally breaking both rotational and translational symmetries, coexist with this intra-unit-cell electronic symmetry breaking at E=Δ1. Their characteristic wavevector Q is determined by the k-space points where Bogoliubov QPI terminates and therefore changes continuously with doping. The distinct broken electronic symmetry states (intra-unit-cell and finite Q) coexisting at E~Δ1 are found to be indistinguishable in the dSC and PG phases. The next challenge for SI-STM studies is to determine the relationship of the E~Δ1 broken symmetry electronic states with the PG phase, and with the E<Δ0 states associated with Cooper pairing.

  13. Ab initio calculations of indium arsenide in the wurtzite phase: structural, electronic and optical properties

    International Nuclear Information System (INIS)

    Dacal, Luis C O; Cantarero, A

    2014-01-01

    Most III–V semiconductors, which acquire the zinc-blende phase as bulk materials, adopt the metastable wurtzite phase when grown in the form of nanowires. These are new semiconductors with new optical properties, in particular, a different electronic band gap when compared with that grown in the zinc-blende phase. The electronic gap of wurtzite InAs at the Γ–point of the Brillouin zone (E 0 gap) has been recently measured, E 0 =0.46 eV at low temperature. The electronic gap at the A–point of the Brillouin zone (equivalent to the L–point in the zinc-blende structure, E 1 ) has also been obtained recently based on a resonant Raman scattering experiment. In this work, we calculate the band structure of InAs in the zinc-blende and wurtzite phases, using the full potential linearized augmented plane wave method, including spin-orbit interaction. The electronic band gap has been improved through the modified Becke–Johnson exchange-correlation potential. Both the E 0 and E 1 gaps agree very well with the experiment. From the calculations, a crystal field splitting of 0.122 eV and a spin-orbit splitting of 0.312 eV (the experimental value in zinc-blende InAs is 0.4 eV) has been obtained. Finally, we calculate the dielectric function of InAs in both the zinc-blende and wurtzite phases and a comparative discussion is given. (paper)

  14. Ab initio calculations of indium arsenide in the wurtzite phase: structural, electronic and optical properties

    Science.gov (United States)

    Dacal, Luis C. O.; Cantarero, A.

    2014-03-01

    Most III-V semiconductors, which acquire the zinc-blende phase as bulk materials, adopt the metastable wurtzite phase when grown in the form of nanowires. These are new semiconductors with new optical properties, in particular, a different electronic band gap when compared with that grown in the zinc-blende phase. The electronic gap of wurtzite InAs at the \\Gamma -point of the Brillouin zone ({{E}_{0}} gap) has been recently measured, {{E}_{0}}=0.46 eV at low temperature. The electronic gap at the A-point of the Brillouin zone (equivalent to the L-point in the zinc-blende structure, {{E}_{1}}) has also been obtained recently based on a resonant Raman scattering experiment. In this work, we calculate the band structure of InAs in the zinc-blende and wurtzite phases, using the full potential linearized augmented plane wave method, including spin-orbit interaction. The electronic band gap has been improved through the modified Becke-Johnson exchange-correlation potential. Both the {{E}_{0}} and {{E}_{1}} gaps agree very well with the experiment. From the calculations, a crystal field splitting of 0.122 eV and a spin-orbit splitting of 0.312 eV (the experimental value in zinc-blende InAs is 0.4 eV) has been obtained. Finally, we calculate the dielectric function of InAs in both the zinc-blende and wurtzite phases and a comparative discussion is given.

  15. Existing and emerging detection technologies for DNA (Deoxyribonucleic Acid) finger printing, sequencing, bio- and analytical chips: a multidisciplinary development unifying molecular biology, chemical and electronics engineering.

    Science.gov (United States)

    Kumar Khanna, Vinod

    2007-01-01

    The current status and research trends of detection techniques for DNA-based analysis such as DNA finger printing, sequencing, biochips and allied fields are examined. An overview of main detectors is presented vis-à-vis these DNA operations. The biochip method is explained, the role of micro- and nanoelectronic technologies in biochip realization is highlighted, various optical and electrical detection principles employed in biochips are indicated, and the operational mechanisms of these detection devices are described. Although a diversity of biochips for diagnostic and therapeutic applications has been demonstrated in research laboratories worldwide, only some of these chips have entered the clinical market, and more chips are awaiting commercialization. The necessity of tagging is eliminated in refractive-index change based devices, but the basic flaw of indirect nature of most detection methodologies can only be overcome by generic and/or reagentless DNA sensors such as the conductance-based approach and the DNA-single electron transistor (DNA-SET) structure. Devices of the electrical detection-based category are expected to pave the pathway for the next-generation DNA chips. The review provides a comprehensive coverage of the detection technologies for DNA finger printing, sequencing and related techniques, encompassing a variety of methods from the primitive art to the state-of-the-art scenario as well as promising methods for the future.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  17. Phasor power electronics

    CERN Document Server

    Rim, Chun T

    2016-01-01

    This book presents a comprehensive introduction to the principles of power electronics, focusing on the switched transformer concept and phasor transformation techniques as employed in the analysis and design of power electronic circuits. Phasor transformations, as introduced in this book, make the time-varying nature of a switching converter simple and easy to handle, transforming it into an equivalent time-invariant circuit. The book starts with an introduction to the philosophy and fundamental principles of power electronics. The switched transformer concept, which is applicable to any switching converter, is introduced, and it is shown how DC-DC converters analyses are then so straightforward that very little equational manipulation is needed. Then the phasor transformation techniques are comprehensively explained over three parts. Single phase and multi-phase AC systems are dealt with through the single phase phasor transformation and circuit DQ transformation, respectively. A general unified phasor tran...

  18. Electron microscopy analyses and electrical properties of the layered Bi2WO6 phase

    International Nuclear Information System (INIS)

    Taoufyq, A.; Ait Ahsaine, H.; Patout, L.; Benlhachemi, A.; Ezahri, M.

    2013-01-01

    The bismuth tungstate Bi 2 WO 6 was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2 1 non centrosymmetric space group previously proposed for this phase. The layers Bi 2 O 2 2+ and WO 4 2− have been directly evidenced from the HRTEM images. The electrical properties of Bi 2 WO 6 compacted pellets systems were determined from electrical impedance spectrometry (EIS) and direct current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi 2 WO 6 phase, with a representation of the cell dimensions (b and c vectors). The Bi 2 O 2 2+ and WO 4 2− sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi 2 WO 6 . • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification

  19. Low magnification differential phase contrast imaging of electric fields in crystals with fine electron probes

    Energy Technology Data Exchange (ETDEWEB)

    Taplin, D.J. [School of Physics and Astronomy, Monash University, Clayton, Victoria 3800 (Australia); Shibata, N. [Institute of Engineering Innovation, School of Engineering, University of Tokyo, Tokyo 113-8656 (Japan); Weyland, M. [Monash Centre for Electron Microscopy, Monash University, Clayton, Victoria 3800 (Australia); Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800 (Australia); Findlay, S.D., E-mail: scott.findlay@monash.edu [School of Physics and Astronomy, Monash University, Clayton, Victoria 3800 (Australia)

    2016-10-15

    To correlate atomistic structure with longer range electric field distribution within materials, it is necessary to use atomically fine electron probes and specimens in on-axis orientation. However, electric field mapping via low magnification differential phase contrast imaging under these conditions raises challenges: electron scattering tends to reduce the beam deflection due to the electric field strength from what simple models predict, and other effects, most notably crystal mistilt, can lead to asymmetric intensity redistribution in the diffraction pattern which is difficult to distinguish from that produced by long range electric fields. Using electron scattering simulations, we explore the effects of such factors on the reliable interpretation and measurement of electric field distributions. In addition to these limitations of principle, some limitations of practice when seeking to perform such measurements using segmented detector systems are also discussed. - Highlights: • Measuring electric fields by on-axis electron diffraction is explored by simulation. • Electron channelling reduces deflection predicted by the phase object approximation. • First moment measurements cannot distinguish electric fields from specimen mistilt. • Segmented detector estimates are fairly insensitive to camera length and orientation.

  20. Effect of electron correlations on the electronic structure and phase stability of FeSe upon lattice expansion

    Science.gov (United States)

    Skornyakov, S. L.; Anisimov, V. I.; Vollhardt, D.; Leonov, I.

    2017-07-01

    We present results of a detailed theoretical study of the electronic, magnetic, and structural properties of the chalcogenide parent system FeSe using a fully charge-self-consistent implementation of the density functional theory plus dynamical mean-field theory (DFT+DMFT) method. In particular, we predict a remarkable change of the electronic structure of FeSe which is accompanied by a complete reconstruction of the Fermi surface topology (Lifshitz transition) upon a moderate expansion of the lattice volume. The phase transition results in a change of the in-plane magnetic nesting wave vector from (π ,π ) to (π ,0 ) and is associated with a transition from itinerant to orbital-selective localized magnetic moments. We attribute this behavior to a correlation-induced shift of the Van Hove singularity of the Fe t2 bands at the M point across the Fermi level. Our results reveal a strong orbital-selective renormalization of the effective mass m*/m of the Fe 3 d electrons upon expansion. The largest effect occurs in the Fe x y orbital, which gives rise to a non-Fermi-liquid-like behavior above the transition. The behavior of the momentum-resolved magnetic susceptibility χ (q ) demonstrates that magnetic correlations are also characterized by a pronounced orbital selectivity, suggesting a spin-fluctuation origin of the nematic phase of paramagnetic FeSe. We conjecture that the anomalous behavior of FeSe upon expansion is associated with the proximity of the Fe t2 Van Hove singularity to the Fermi level and the sensitive dependence of its position on external conditions.

  1. Structural, electronic and elastic properties of heavy fermion YbRh2 Laves phase compound

    Science.gov (United States)

    Pawar, Harsha; Shugani, Mani; Aynyas, Mahendra; Sanyal, Sankar P.

    2018-05-01

    The structural, electronic and elastic properties of YbRh2 Laves phase intermetallic compound which crystallize in cubic (MgCu2-type) structure have been investigated using ab-initio full potential linearized augmented plane wave (FP- LAPW) method with LDA and LDA+U approximation. The calculated ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B') are in good agreement with available experimental and theoretical data. The electronic properties are analyzed from band structures and density of states. Elastic constants are predicted first time for this compound which obeys the stability criteria for cubic system.

  2. Gas-phase synthesis of magnesium nanoparticles: A high-resolution transmission electron microscopy study

    International Nuclear Information System (INIS)

    Kooi, B. J.; Palasantzas, G.; De Hosson, J. Th. M.

    2006-01-01

    Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg(1010) facets. Oxidation of Mg yields a MgO shell (∼3 nm thick), which has an orientation relation with the Mg. Inhomogeneous facet oxidation influences their growth kinetics resulting in a relatively broad size and shape distribution. Faceted voids between Mg and MgO shells indicate a fast outward diffusion of Mg and vacancy rearrangement into voids. The faceting of polar (220) planes is assisted by electron irradiation

  3. Phase and amplitude feedback control system for the Los Alamos free-electron laser

    International Nuclear Information System (INIS)

    Lynch, M.T.; Tallerico, P.J.; Higgins, E.F.

    1985-01-01

    Phase and amplitude feedback control systems for the Los Alamos free-electron laser (FEL) are described. Beam-driven voltages are very high in the buncher cavity because the electron gun is pulsed at the fifth subharmonic of the buncher resonant frequency. The high beam loading necessitated a novel feedback and drive configuration for the buncher. A compensation cirucit has been added to the gun/driver system to reduce observed drift. Extremely small variations in the accelerator gradients had dramatic effects on the laser output power. These problems and how they were solved are described and plans for improvements in the feedback control system are discussed. 5 refs., 7 figs

  4. Development strategy and process models for phased automation of design and digital manufacturing electronics

    Science.gov (United States)

    Korshunov, G. I.; Petrushevskaya, A. A.; Lipatnikov, V. A.; Smirnova, M. S.

    2018-03-01

    The strategy of quality of electronics insurance is represented as most important. To provide quality, the processes sequence is considered and modeled by Markov chain. The improvement is distinguished by simple database means of design for manufacturing for future step-by-step development. Phased automation of design and digital manufacturing electronics is supposed. The MatLab modelling results showed effectiveness increase. New tools and software should be more effective. The primary digital model is proposed to represent product in the processes sequence from several processes till the whole life circle.

  5. Energy efficient power electronic controller for a capacitor-run single-phase induction motor

    International Nuclear Information System (INIS)

    Saravana Ilango, G.; Samidurai, K.; Roykumar, M.; Thanushkodi, K.

    2009-01-01

    At present the speed control of a capacitor-run single-phase induction motor is being achieved by using triac based voltage regulators. This paper proposes a new scheme; an electronic transformer acts as a voltage regulator. Performance comparison is made between these two schemes in this paper. It is found that the proposed scheme has superior operating and performance characteristics. Experimental results show that apart from improvement in performance with respect to power factor and total harmonic distortion an appreciable amount of energy saving is also obtained in the electronic transformer based scheme.

  6. Unified Symmetry of Hamilton Systems

    International Nuclear Information System (INIS)

    Xu Xuejun; Qin Maochang; Mei Fengxiang

    2005-01-01

    The definition and the criterion of a unified symmetry for a Hamilton system are presented. The sufficient condition under which the Noether symmetry is a unified symmetry for the system is given. A new conserved quantity, as well as the Noether conserved quantity and the Hojman conserved quantity, deduced from the unified symmetry, is obtained. An example is finally given to illustrate the application of the results.

  7. Influence of molybdenum impurity on the electronic properties of refractory phases

    International Nuclear Information System (INIS)

    Ivanovskij, A.L.

    1992-01-01

    Results of calculations of electronic structure modification of refractory phases - TiC, TiN - during dissolution in their volume of molybdenum as the element, dominating in the processes of formation of ring transition area (K-phase) are presented. It is shown that reconstruction of local state density (LSD) of Mo in the system Ni:Mo reflects the effects of impurity state and nickel valency area hybridization. LSD of Mo in MoC, MoN acquires quite a new form

  8. Transmission electron microscopy studies on nanometer-sized ω phase produced in Gum Metal

    International Nuclear Information System (INIS)

    Yano, Takaaki; Murakami, Yasukazu; Shindo, Daisuke; Hayasaka, Yuichiro; Kuramoto, Shigeru

    2010-01-01

    The morphology, numerical density and average spacing of the ω phase formed in Gum Metal, a Ti-based alloy showing unique mechanical properties, were studied by transmission electron microscopy. Based on dark-field image observations and precise thickness measurements using a thin-foil specimen, the average spacing of the nanometer-sized ω phase was determined to be 6 nm. This spacing appeared to be sufficiently small for trapping dislocations. The results are discussed in conjunction with the dislocation-free deformation mechanism proposed for Gum Metal.

  9. A study of phase control in the FEL [free electron laser] two-beam accelerator

    International Nuclear Information System (INIS)

    Sessler, A.M.; Whittum, D.H.; Wurtele, J.S.

    1989-08-01

    A formalism is developed for the analysis of a steady-state free electron laser (FEL) and is applied to the two-beam accelerator (TBA). Conditions are derived for the design of a FEL TBA with rf output power and phase insensitive to errors in both beam current and energy. An example is presented of a suitably phase insensitive TBA design with 100 reaccelerations employing untapered FEL sections and with low power rf input to each section. The theoretical analysis is confirmed by a single particle FEL simulations. 9 refs., 2 tabs

  10. Probing Protein Structure and Folding in the Gas Phase by Electron Capture Dissociation

    Science.gov (United States)

    Schennach, Moritz; Breuker, Kathrin

    2015-07-01

    The established methods for the study of atom-detailed protein structure in the condensed phases, X-ray crystallography and nuclear magnetic resonance spectroscopy, have recently been complemented by new techniques by which nearly or fully desolvated protein structures are probed in gas-phase experiments. Electron capture dissociation (ECD) is unique among these as it provides residue-specific, although indirect, structural information. In this Critical Insight article, we discuss the development of ECD for the structural probing of gaseous protein ions, its potential, and limitations.

  11. Unified Bohm criterion

    Energy Technology Data Exchange (ETDEWEB)

    Kos, L. [LECAD Laboratory, Faculty of Mechanical Engineering, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Tskhakaya, D. D.; Jelić, N. [Institute for Theoretical Physics, Fusion@ÖAW, University of Innsbruck, A-6020 Innsbruck (Austria)

    2015-09-15

    Recent decades have seen research into the conditions necessary for the formation of the monotonic potential shape in the sheath, appearing at the plasma boundaries like walls, in fluid, and kinetic approximations separately. Although either of these approaches yields a formulation commonly known as the much-acclaimed Bohm criterion (BC), the respective results involve essentially different physical quantities that describe the ion gas behavior. In the fluid approach, such a quantity is clearly identified as the ion directional velocity. In the kinetic approach, the ion behavior is formulated via a quantity (the squared inverse velocity averaged by the ion distribution function) without any clear physical significance, which is, moreover, impractical. In the present paper, we try to explain this difference by deriving a condition called here the Unified Bohm Criterion, which combines an advanced fluid model with an upgraded explicit kinetic formula in a new form of the BC. By introducing a generalized polytropic coefficient function, the unified BC can be interpreted in a form that holds, irrespective of whether the ions are described kinetically or in the fluid approximation.

  12. Beyond the Unified Model

    Science.gov (United States)

    Frauendorf, S.

    2018-04-01

    The key elements of the Unified Model are reviewed. The microscopic derivation of the Bohr Hamiltonian by means of adiabatic time-dependent mean field theory is presented. By checking against experimental data the limitations of the Unified Model are delineated. The description of the strong coupling between the rotational and intrinsic degrees of freedom in framework of the rotating mean field is presented from a conceptual point of view. The classification of rotational bands as configurations of rotating quasiparticles is introduced. The occurrence of uniform rotation about an axis that differs from the principle axes of the nuclear density distribution is discussed. The physics behind this tilted-axis rotation, unknown in molecular physics, is explained on a basic level. The new symmetries of the rotating mean field that arise from the various orientations of the angular momentum vector with respect to the triaxial nuclear density distribution and their manifestation by the level sequence of rotational bands are discussed. Resulting phenomena, as transverse wobbling, rotational chirality, magnetic rotation and band termination are discussed. Using the concept of spontaneous symmetry breaking the microscopic underpinning of the rotational degrees is refined.

  13. Analytical electron microscope study of the omega phase transformation in a zirconium--niobium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zaluzec, N.J.

    1979-06-01

    An in-situ study of the as-quenched omega phase transformation in Zr--15% Nb was conducted between the temperatures of 77 and 300/sup 0/K using analytical electron microscopy. The domain size of the omega regions observed in this investigation was on the order of 30 A, consistent with previous observations in this system. No alignment of omega domains along <222> directions of the bcc lattice was observed and in-situ thermal cycling experiments failed to produce a long period structure of alternating ..beta.. and ..omega.. phase regions as predicted by one theory of this transformation. Several techniques of microstructural analysis were developed, refined, and standardized. Grouped under the general classification of Analytical Electron Microscopy (AEM) they provide the experimentalist with a unique tool for the microcharacterization of solids, allowing semiquantitative to quantitative analysis of the morphology, crystallography, elemental composition, and electronic structure of regions as small as 20 A in diameter. These techniques have complications, and it was necessary to study the AEM system used in this work so that instrumental artifacts which invalidate the information produced in the microscope environment might be eliminated. Once these factors had been corrected, it was possible to obtain a wealth of information about the microvolume of material under investigation. The microanalytical techniques employed during this research include: energy dispersive x-ray spectroscopy (EDS) using both conventional and scanning transmission electron microscopy (CTEM, STEM), transmission scanning electron diffraction (TSED), the stationary diffraction pattern technique, and electron energy loss spectroscopy (ELS) using a dedicated scanning transmission electron microscope (DSTEM).

  14. Analytical electron microscope study of the omega phase transformation in a zirconium--niobium alloy

    International Nuclear Information System (INIS)

    Zaluzec, N.J.

    1979-06-01

    An in-situ study of the as-quenched omega phase transformation in Zr--15% Nb was conducted between the temperatures of 77 and 300 0 K using analytical electron microscopy. The domain size of the omega regions observed in this investigation was on the order of 30 A, consistent with previous observations in this system. No alignment of omega domains along directions of the bcc lattice was observed and in-situ thermal cycling experiments failed to produce a long period structure of alternating β and ω phase regions as predicted by one theory of this transformation. Several techniques of microstructural analysis were developed, refined, and standardized. Grouped under the general classification of Analytical Electron Microscopy (AEM) they provide the experimentalist with a unique tool for the microcharacterization of solids, allowing semiquantitative to quantitative analysis of the morphology, crystallography, elemental composition, and electronic structure of regions as small as 20 A in diameter. These techniques have complications, and it was necessary to study the AEM system used in this work so that instrumental artifacts which invalidate the information produced in the microscope environment might be eliminated. Once these factors had been corrected, it was possible to obtain a wealth of information about the microvolume of material under investigation. The microanalytical techniques employed during this research include: energy dispersive x-ray spectroscopy (EDS) using both conventional and scanning transmission electron microscopy (CTEM, STEM), transmission scanning electron diffraction (TSED), the stationary diffraction pattern technique, and electron energy loss spectroscopy (ELS) using a dedicated scanning transmission electron microscope

  15. Beyond the Random Phase Approximation for the Electron Correlation Energy: The Importance of Single Excitations

    OpenAIRE

    Ren, Xinguo; Rinke, Patrick; Tkatchenko, Alexandre; Scheffler, Matthias

    2010-01-01

    The random-phase approximation (RPA) for the electron correlation energy, combined with the exact-exchange (EX) energy, represents the state-of-the-art exchange-correlation functional within density-functional theory. However, the standard RPA practice-evaluating both the EX and the RPA correlation energies using Kohn-Sham (KS) orbitals from local or semilocal exchange-correlation functionals-leads to a systematic underbinding of molecules and solids. Here we demonstrate that this behavior ca...

  16. Electronic structure and elasticity of Z-phases in the Cr–Nb–V–N system

    Czech Academy of Sciences Publication Activity Database

    Legut, D.; Pavlů, Jana

    2012-01-01

    Roč. 24, č. 19 (2012), s. 195502-195509 ISSN 0953-8984 R&D Projects: GA ČR(CZ) GAP108/10/1908; GA MŠk(CZ) ED1.1.00/02.0068 Institutional research plan: CEZ:AV0Z20410507 Keywords : ab initio calculations * Z-phase * Cr-Nb-V-N * electronic structure * elasticity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.355, year: 2012

  17. Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction

    Energy Technology Data Exchange (ETDEWEB)

    Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H. [Department of Physics and Astronomy, UCLA, Los Angeles California, 90095 (United States)

    2012-12-21

    A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.

  18. Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction

    International Nuclear Information System (INIS)

    Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H.

    2012-01-01

    A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.

  19. Topological Phase Transitions in Zinc-Blende Semimetals Driven Exclusively by Electronic Temperature

    Science.gov (United States)

    Trushin, Egor; Görling, Andreas

    2018-04-01

    We show that electronic phase transitions in zinc-blende semimetals with quadratic band touching (QBT) at the center of the Brillouin zone, like GaBi, InBi, or HgTe, can occur exclusively due to a change of the electronic temperature without the need to involve structural transformations or electron-phonon coupling. The commonly used Kohn-Sham density-functional methods based on local and semilocal density functionals employing the local density approximation (LDA) or generalized gradient approximations (GGAs), however, are not capable of describing such phenomena because they lack an intrinsic temperature dependence and account for temperature only via the occupation of bands, which essentially leads only to a shift of the Fermi level without changing the shape or topology of bands. Kohn-Sham methods using the exact temperature-dependent exchange potential, not to be confused with the Hartree-Fock exchange potential, on the other hand, describe such phase transitions. A simple modeling of correlation effects can be achieved by screening of the exchange. In the considered zinc-blende compounds the QBT is unstable at low temperatures and a transition to electronic states without QBT takes place. In the case of HgTe and GaBi Weyl points of type I and type II, respectively, emerge during the transitions. This demonstrates that Kohn-Sham methods can describe such topological phase transitions provided they are based on functionals more accurate than those within the LDA or GGA. Moreover, the electronic temperature is identified as a handle to tune topological materials.

  20. Phase-mixing of Langmuir oscillations in cold electron-positron-ion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Maity, Chandan [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2014-07-15

    Space-time evolution of Langmuir oscillations in a cold homogeneous electron-positron-ion plasma has been analyzed by employing a straightforward perturbation expansion method, showing phase-mixing and, thus, wave-breaking of excited oscillations at arbitrary amplitudes. Within an assumption of infinitely massive ions, an approximate phase-mixing time is found to scale as ω{sub pe}t{sub mix}∼[(6/δ{sup 2})((2−α){sup 5/2}/(1−α))]{sup 1/3}, where “δ” and “α” (= n{sub 0i}/n{sub 0e}) are the amplitude of perturbation and the ratio of equilibrium ion density to equilibrium electron density, respectively, and ω{sub pe}∼√(4πn{sub 0e}e{sup 2}/m) is the electron plasma frequency. The results presented on phase-mixing of Langmuir modes in multispecies plasmas are expected to be relevant to laboratory and astrophysical environments.

  1. A model to determine the initial phase space of a clinical electron beam from measured beam data.

    NARCIS (Netherlands)

    Janssen, J.J.M.; Korevaar, E.W.; Battum, L.J. van; Storchi, P.R.; Huizenga, H.

    2001-01-01

    Advanced electron beam dose calculation models for radiation oncology require as input an initial phase space (IPS) that describes a clinical electron beam. The IPS is a distribution in position, energy and direction of electrons and photons in a plane in front of the patient. A method is presented

  2. Hydride vapor phase GaN films with reduced density of residual electrons and deep traps

    International Nuclear Information System (INIS)

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Yugova, T. G.; Cox, H.; Helava, H.; Makarov, Yu.; Usikov, A. S.

    2014-01-01

    Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ∼10 17  cm −3 to (2–5) × 10 14  cm −3 . The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ∼5 × 10 13  cm −3 versus 2.9 × 10 16  cm −3 in the standard samples, with a similar decrease in the electron traps concentration

  3. Longitudinal phase space manipulation in energy recovering linac-driven free-electron lasers

    Directory of Open Access Journals (Sweden)

    P. Piot

    2003-03-01

    Full Text Available Energy recovering an electron beam after it has participated in a free-electron laser (FEL interaction can be quite challenging because of the substantial FEL-induced energy spread and the energy antidamping that occurs during deceleration. In the Jefferson Lab infrared FEL driver accelerator, such an energy recovery scheme was implemented by properly matching the longitudinal phase space throughout the recirculation transport by employing the so-called energy compression scheme. In the present paper, after presenting a single-particle dynamics approach of the method used to energy recover the electron beam, we report on experimental validation of the method obtained by measurements of the so-called “compression efficiency” and “momentum compaction” lattice transfer maps at different locations in the recirculation transport line. We also compare these measurements with numerical tracking simulations.

  4. Strain-induced phase transition and electron spin-polarization in graphene spirals.

    Science.gov (United States)

    Zhang, Xiaoming; Zhao, Mingwen

    2014-07-16

    Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices.

  5. Note: An improved calibration system with phase correction for electronic transformers with digital output.

    Science.gov (United States)

    Cheng, Han-miao; Li, Hong-bin

    2015-08-01

    The existing electronic transformer calibration systems employing data acquisition cards cannot satisfy some practical applications, because the calibration systems have phase measurement errors when they work in the mode of receiving external synchronization signals. This paper proposes an improved calibration system scheme with phase correction to improve the phase measurement accuracy. We employ NI PCI-4474 to design a calibration system, and the system has the potential to receive external synchronization signals and reach extremely high accuracy classes. Accuracy verification has been carried out in the China Electric Power Research Institute, and results demonstrate that the system surpasses the accuracy class 0.05. Furthermore, this system has been used to test the harmonics measurement accuracy of all-fiber optical current transformers. In the same process, we have used an existing calibration system, and a comparison of the test results is presented. The system after improvement is suitable for the intended applications.

  6. Note: An improved calibration system with phase correction for electronic transformers with digital output

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Han-miao, E-mail: chenghanmiao@hust.edu.cn; Li, Hong-bin, E-mail: lihongbin@hust.edu.cn [CEEE of Huazhong University of Science and Technology, Wuhan 430074 (China); State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Wuhan 430074 (China)

    2015-08-15

    The existing electronic transformer calibration systems employing data acquisition cards cannot satisfy some practical applications, because the calibration systems have phase measurement errors when they work in the mode of receiving external synchronization signals. This paper proposes an improved calibration system scheme with phase correction to improve the phase measurement accuracy. We employ NI PCI-4474 to design a calibration system, and the system has the potential to receive external synchronization signals and reach extremely high accuracy classes. Accuracy verification has been carried out in the China Electric Power Research Institute, and results demonstrate that the system surpasses the accuracy class 0.05. Furthermore, this system has been used to test the harmonics measurement accuracy of all-fiber optical current transformers. In the same process, we have used an existing calibration system, and a comparison of the test results is presented. The system after improvement is suitable for the intended applications.

  7. Direction: unified theory of interactions

    International Nuclear Information System (INIS)

    Valko, P.

    1987-01-01

    Briefly characterized are the individual theories, namely, the general relativity theory, the Kaluza-Klein theory, the Weyl theory, the unified theory of electromagnetic and weak interactions, the supergravity theory, and the superstring theory. The history is recalled of efforts aimed at creating a unified theory of interactions, and future prospects are outlined. (M.D.). 2 figs

  8. Grand unified theories. Pt. 2

    International Nuclear Information System (INIS)

    Ellis, J.

    1982-01-01

    The author gives an introduction to the construction of grand unified theories on the base of the SU(3)xSU(2)xU(1) model of the strong, weak, and electromagnetic interactions. Especially he discusses the proton decay, neutrino masses and oscillations, and cosmological implications in connection with grand unified theories. (orig./HSI)

  9. High resolution transmission electron microscopy studies of {sigma} phase in Ni-based single crystal superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Sun Fei [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Zhang Jianxin, E-mail: jianxin@sdu.edu.cn [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Liu Pan [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Feng Qiang [National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Han Xiaodong; Mao Shengcheng [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)

    2012-09-25

    Graphical abstract: (a) TEM micrograph of {sigma} phase; (b) HRTEM image of {sigma}/{gamma} interface corresponding to the area of the white frame in (a); (c) an enlarged image of area from the white frame in (b). The combination of {sigma}/{gamma} interface appears very well, and a two-atomic-layer step is shown on the {sigma}/{gamma} interface. In addition, {sigma} phase has the orientation relationship of [0 0 1]{sub {gamma}}//[1 1 2{sup Macron }]{sub {sigma}}, (2{sup Macron} 2 0){sub {gamma}}//(1{sup Macron} 1 0){sub {sigma}}, (2{sup Macron }2{sup Macron} 0){sub {gamma}}//(1 1 1){sub {sigma}}; [0 1 1]{sub {gamma}}//[1 1 0]{sub {sigma}}, (1 1{sup Macron} 1){sub {gamma}}//(0 0 1{sup Macron }){sub {sigma}} with the {gamma} phase. Highlights: Black-Right-Pointing-Pointer Elemental characteristic of {sigma} phase is studied by HAADF techniques and EDS analysis. Black-Right-Pointing-Pointer Interfacial characteristics of {sigma}/{gamma} interface are revealed by HRTEM. Black-Right-Pointing-Pointer An atomic structural {sigma}/{gamma} interface with a two-atomic-layer step has been proposed. - Abstract: By means of high resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field image technique (HAADF), morphological of plate-shaped {sigma} phase and interfacial characteristics between plate-shaped {sigma} phase and {gamma} phase in Ni-based single crystal superalloys have been studied. On the basis of HRTEM observations, an atomic structural interface between {sigma} phase and {gamma} phase with a step has been proposed. {sigma} Phase has the relationship of [0 0 1]{sub {gamma}}//[1 1 2{sup Macron }]{sub {sigma}}, (2{sup Macron} 2 0){sub {gamma}}//(1{sup Macron} 1 0){sub {sigma},} (2{sup Macron }2{sup Macron} 0){sub {gamma}}//(1 1 1){sub {sigma}}; [0 1 1]{sub {gamma}}//[1 1 0]{sub {sigma}}, (1 1{sup Macron} 1){sub {gamma}}//(0 0 1{sup Macron }){sub {sigma}} with the {gamma} phase. The compositional characteristics of the {sigma} phase which

  10. Time-resolved electron beam phase space tomography at a soft x-ray free-electron laser

    Directory of Open Access Journals (Sweden)

    Michael Röhrs

    2009-05-01

    Full Text Available High-gain free-electron lasers (FELs in the ultraviolet and x-ray regime put stringent demands on the peak current, transverse emittance, and energy spread of the driving electron beam. At the soft x-ray FEL FLASH, a transverse deflecting microwave structure (TDS has been installed to determine these parameters for the longitudinally compressed bunches, which are characterized by a narrow leading peak of high charge density and a long tail. The rapidly varying electromagnetic field in the TDS deflects the electrons vertically and transforms the time profile into a streak on an observation screen. The bunch current profile was measured single shot with an unprecedented resolution of 27 fs under FEL operating conditions. A precise single-shot measurement of the energy distribution along a bunch was accomplished by using the TDS in combination with an energy spectrometer. Variation of quadrupole strengths allowed for a determination of the horizontal emittance as a function of the longitudinal position within a bunch, the so-called slice emittance. In the bunch tail, a normalized slice emittance of about 2  μm was found, in agreement with expectations. In the leading spike, however, surprisingly large emittance values were observed, in apparent contradiction with the low emittance deduced from the measured FEL gain. By applying three-dimensional phase space tomography, we were able to show that the bunch head contains a central core of low emittance and high local current density, which is presumably the lasing part of the bunch.

  11. Quantitative study of substorm-associated VLF phase anomalies and precipitating energetic electrons on November 13, 1979

    International Nuclear Information System (INIS)

    Kikuchi, T.; Evans, D.S.

    1983-01-01

    The phase anomalies associated with substorms are observed on VLF signals propagating on transauroral paths (transmitters at OMEGA-ALDRA (13.6 kHz), GBR (16.0 kHz), and OMEGA--NORTH DAKOTA (13.6 kHz)) which were continually received at Inubo, Japan, during the events on November 13, 1979. Detailed comparisons are made between these phase anomalies and geomagnetic bays, and quantitative relations are obtained with precipitating energetic electrons (E>30, E>100, and E>300 keV) detected on board the TIROS-N and NOAA 6 satellites. It is concluded that two types of VLF phase anomalies exist which, in turn, are associated with two phases in the history of energetic electron precipitation into the atmosphere. The first type of phase anomaly is associated with direct injection of energetic electrons into the outer magnetosphere and atmosphere which, in turn, is completely correlated in time with development of the auroral electrojet current system. The second type arises from energetic electrons which subsequently precipitate from a trapped electron population and has a delayed onset and prolonged duration. An excellent quantitative correlation is obtained between the logarithm of the electron flux and the magnitude of the phase anomaly on the OMEGA-ALDRA signal. From the local time characteristics of this quantitative relation it is deduced that the electrons with E>300 keV are the main source of D region ionization responsible for the VLF phase anomaly

  12. Steering Charge Kinetics of Tin Niobate Photocatalysts: Key Roles of Phase Structure and Electronic Structure.

    Science.gov (United States)

    Huang, Shushu; Wang, Chunyan; Sun, Hao; Wang, Xiaojing; Su, Yiguo

    2018-05-23

    Tin niobate photocatalysts with the phase structures of froodite (SnNb 2 O 6 ) and pyrochlore (Sn 2 Nb 2 O 7 ) were obtained by a facile solvothermal method in order to explore the impact of phase structure and electronic structure on the charge kinetics and photocatalytic performance. By employing tin niobate as a model compound, the effects of phase structure over electronic structure, photocatalytic activity toward methyl orange solution and hydrogen evolution were systematically investigated. It is found that the variation of phase structure from SnNb 2 O 6 to Sn 2 Nb 2 O 7 accompanied with modulation of particle size and band edge potentials that has great consequences on photocatalytic performance. In combination with the electrochemical impedance spectroscopy (EIS), transient photocurrent responses, transient absorption spectroscopy (TAS), and the analysis of the charge-carrier dynamics suggested that variation of electronic structure has great impacts on the charge separation and transfer rate of tin niobate photocatalysts and the subsequent photocatalytic performance. Moreover, the results of the X-ray photoelectron spectroscopy (XPS) indicated that the existent of Sn 4+ species in Sn 2 Nb 2 O 7 could result in a decrease in photocatalytic activity. Photocatalytic test demonstrated that the SnNb 2 O 6 (froodite) catalyst possesses a higher photocatalytic activity toward MO degradation and H 2 evolution compared with the sample of Sn 2 Nb 2 O 7 (pyrochlore). On the basis of spin resonance measurement and trapping experiment, it is expected that photogenerated holes, O 2 -• , and OH • active species dominate the photodegradation of methyl orange.

  13. Structure-phase states evolution in Al-Si alloy under electron-beam treatment and high-cycle fatigue

    International Nuclear Information System (INIS)

    Konovalov, Sergey; Alsaraeva, Krestina; Gromov, Victor; Semina, Olga; Ivanov, Yurii

    2015-01-01

    By methods of scanning and transmission electron diffraction microscopy the analysis of structure-phase states and defect substructure of silumin subjected to high-intensity electron beam irradiation in various regimes and subsequent fatigue loading up to failure was carried out. It is revealed that the sources of fatigue microcracks are silicon plates of micron and submicron size are not soluble in electron beam processing. The possible reasons of the silumin fatigue life increase under electron-beam treatment are discussed

  14. Energetic electron propagation in the decay phase of non-thermal flare emission

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jing; Yan, Yihua [Key Laboratory of Solar Activities, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Tsap, Yuri T., E-mail: huangj@nao.cas.cn [Crimean Astrophysical Observatory of Kyiv National Taras Shevchenko University, 98409 Crimea, Nauchny (Ukraine)

    2014-06-01

    On the basis of the trap-plus-precipitation model, the peculiarities of non-thermal emission in the decay phase of solar flares have been considered. The calculation formulas for the escape rate of trapped electrons into the loss cone in terms of time profiles of hard X-ray (HXR) and microwave (MW) emission have been obtained. It has been found that the evolution of the spectral indices of non-thermal emission depend on the regimes of the pitch angle diffusion of trapped particles into the loss cone. The properties of non-thermal electrons related to the HXR and MW emission of the solar flare on 2004 November 3 are studied with Nobeyama Radioheliograph, Nobeyama Radio Polarimeters, RHESSI, and Geostationary Operational Environmental Satellite observations. The spectral indices of non-thermal electrons related to MW and HXR emission remained constant or decreased, while the MW escape rate as distinguished from that of the HXRs increased. This may be associated with different diffusion regimes of trapped electrons into the loss cone. New arguments in favor of an important role of the superstrong diffusion for high-energy electrons in flare coronal loops have been obtained.

  15. Structural phase transition and opto-electronic properties of NaZnAs

    International Nuclear Information System (INIS)

    Djied, A.; Seddik, T.; Merabiha, O.; Murtaza, G.; Khenata, R.; Ahmed, R.; Bin-Omran, S.; Uğur, Ş.; Bouhemadou, A.

    2015-01-01

    Highlights: • First competent characterizations of NaZnAs at the level of FP-LAPW+lo. • NaZnAs, a potential alternative candidate to III-V for photovoltaic applications. • NaZnAs, a cheaper and abundantly available direct band gap semiconductor. • Potential material for solar radiation absorber from infrared to ultraviolet. - Abstract: In this study, we predict the structural phase transitions as well as opto-electronic properties of the filled-tetrahedral (Nowotny-Juza) NaZnAs compound. Calculations employ the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme. The exchange-correlation potential is treated within the generalized gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). In addition, Tran and Blaha (TB) modified Becke-Johnson (mBJ) potential is also used to obtain more accurate optoelectronic properties. Geometry optimization is performed to obtain reliable total energies and other structural parameters for each NaZnAs phase. In our study, the sequence of the structural phase transition on compression is Cu 2 Sb-type → β → α phase. NaZnAs is a direct (Γ-Γ) band gap semiconductor for all the structural phases. However, compared to PBE-GGA, the mBJ approximation reproduces better fundamental band gaps. Moreover, for insight into its potential for photovoltaic applications, different optical parameters are studied

  16. Competing Phases of 2D Electrons at ν = 5/2 and 7/3

    Science.gov (United States)

    Xia, Jing

    2011-03-01

    The N=1 Landau level (LL) exhibits collective electronic phenomena characteristic of both fractional quantum Hall (FQHE) states seen in the lowest LL and anisotropic nematic states in the higher LLs. A modest in-plane magnetic field B| | is sufficient to destroy the fractional quantized Hall states at ν = 5 / 2 (and 7/2) and replace them with anisotropic compressible nematic phases, revealing the close competition between the two. We find that at larger B| | these anisotropic phases ν = 5 / 2 can themselves be replaced by a new isotropic state, dubbed re-entrant isotropic compressible (RIC) phase. We present strong evidence that this transition is a consequence of the mixing of Landau levels from different electric subbands in the confinement potential. In addition, we find that with B| | , the normally isotropic ν = 7 / 3 FQHE state can transform into an anisotropic phase with an accurately quantized Hall plateau but an anisotropic longitudinal resistivities. As temperature is lowered towards zero, ρxx diminishes while ρyy tends to diverge, reminiscent of the anisotropic nematic states, while surprisingly ρxy and ρyx remain quantized at 3 h / 7e2 , indicating a completely new quantum phase. This work represents a collaboration with J.P. Eisenstein (Caltech) and L.N. Pfeiffer and K.W West (Princeton), and is supported by Microsoft Project Q.

  17. FPGA based phase detection technique for electron density measurement in SST-1 tokamak

    International Nuclear Information System (INIS)

    Pramila; Mandaliya, Hitesh; Rajpal, Rachana; Kaur, Rajwinder

    2016-01-01

    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.

  18. Structural phase transition and opto-electronic properties of NaZnAs

    Energy Technology Data Exchange (ETDEWEB)

    Djied, A.; Seddik, T.; Merabiha, O. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 (Algeria); Murtaza, G. [Materials Modeling Lab, Department of Physics, Islamia College University, Peshawar (Pakistan); Khenata, R. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 (Algeria); Ahmed, R., E-mail: rashidahmed@utm.my [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor (Malaysia); Bin-Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Uğur, Ş. [Department of Physics, Faculty of Sciences, Gazi University, 06500 Teknikokullar, Ankara (Turkey); Bouhemadou, A. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, University Setif 1, 19000 Setif (Algeria)

    2015-02-15

    Highlights: • First competent characterizations of NaZnAs at the level of FP-LAPW+lo. • NaZnAs, a potential alternative candidate to III-V for photovoltaic applications. • NaZnAs, a cheaper and abundantly available direct band gap semiconductor. • Potential material for solar radiation absorber from infrared to ultraviolet. - Abstract: In this study, we predict the structural phase transitions as well as opto-electronic properties of the filled-tetrahedral (Nowotny-Juza) NaZnAs compound. Calculations employ the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme. The exchange-correlation potential is treated within the generalized gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). In addition, Tran and Blaha (TB) modified Becke-Johnson (mBJ) potential is also used to obtain more accurate optoelectronic properties. Geometry optimization is performed to obtain reliable total energies and other structural parameters for each NaZnAs phase. In our study, the sequence of the structural phase transition on compression is Cu{sub 2}Sb-type → β → α phase. NaZnAs is a direct (Γ-Γ) band gap semiconductor for all the structural phases. However, compared to PBE-GGA, the mBJ approximation reproduces better fundamental band gaps. Moreover, for insight into its potential for photovoltaic applications, different optical parameters are studied.

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

    Science.gov (United States)

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

    2014-09-01

    Optimization of the initial phasing has been a decisive factor in the success of the subsequent electron-density modification, model building and structure determination of biological macromolecules using the single-wavelength anomalous dispersion (SAD) method. Two possible phase solutions (φ1 and φ2) generated from two symmetric phase triangles in the Harker construction for the SAD method cause the well known phase ambiguity. A novel direct phase-selection method utilizing the θ(DS) list as a criterion to select optimized phases φ(am) from φ1 or φ2 of a subset of reflections with a high percentage of correct phases to replace the corresponding initial SAD phases φ(SAD) has been developed. Based on this work, reflections with an angle θ(DS) in the range 35-145° are selected for an optimized improvement, where θ(DS) is the angle between the initial phase φ(SAD) and a preliminary density-modification (DM) phase φ(DM)(NHL). The results show that utilizing the additional direct phase-selection step prior to simple solvent flattening without phase combination using existing DM programs, such as RESOLVE or DM from CCP4, significantly improves the final phases in terms of increased correlation coefficients of electron-density maps and diminished mean phase errors. With the improved phases and density maps from the direct phase-selection method, the completeness of residues of protein molecules built with main chains and side chains is enhanced for efficient structure determination.

  1. Electron microscopy and microanalysis of uranium phases in primary ores, Eocene and Miocene of south Texas

    International Nuclear Information System (INIS)

    Liang, L.C.; Price, J.G.; Bobeck, P.

    1984-01-01

    Two contrasting types of roll-front uranium deposits occur in south Texas. In the barrier-bar sands of the Eocene Jackson Group, organic matter was essential to uranium reduction, whereas in the fluvial sands of the Miocene Oakville Formation, epigenetic pyrite was the reductant. In a sample of reduced Oakville ore, a uranium phase with grains ranging in diameter from < 1 to 20μm was recognized by SEM backscattered-electron imaging and wavelength-dispersive spectrometer (WDS) elemental-dot mapping. Quantitative microprobe analyses indicated that the phase is a uranium-calcium silicate-phosphate with molar Ca/P approximately equal to 1.0, U/P equal to 2.8 +/- 0.4 (n = 27), and U/Si approaching 1.0 in samples uncontaminated with quartz, feldspar, or clay minerals. Highest uranium content is 59%. Oakville ore is typically easy to leach by in-situ methods. Jackson ore contains 2 uranium phases. Sulfur-rich organic matter contains 4.1 +/- 1.6% uranium (n = 27). Although individual grains of a possible uranium mineral within the organic matter are too small to be resolved by electron imaging, a consistent molar U/Fe (0.5 +/- 0.1) suggests a uranium-iron oxide phase. Alternatively, uranium is adsorbed by or otherwise bound to the organic matter. The second phase is a uranium-calcium silicate-phosphate that differs from the Oakville ore. Molar Ca/P equals 0.8 +/- 0.2 (n = 13), and U/P equals 4.7 +/- 0.4. Small grain size (generally less than 1 μm) prevented analysis of samples uncontaminated with quartz and pyrite. The grain with highest uranium content (43%) has U/Si equal to 0.34. Jackson ore is less favorable for in-situ leaching than Oakville ore in part because the organic-associated uranium is difficult to extract

  2. Transverse phase space mapping of relativistic electron beams using optical transition radiation

    Directory of Open Access Journals (Sweden)

    G. P. Le Sage

    1999-12-01

    Full Text Available Optical transition radiation (OTR has proven to be a versatile and effective diagnostic for measuring the profile, divergence, and emittance of relativistic electron beams with a wide range of parameters. Diagnosis of the divergence of modern high brightness beams is especially well suited to OTR interference (OTRI techniques, where multiple dielectric or metal foils are used to generate a spatially coherent interference pattern. Theoretical analysis of measured OTR and OTRI patterns allows precise measurement of electron beam emittance characteristics. Here we describe an extension of this technique to allow mapping of divergence characteristics as a function of transverse coordinates within a measured beam. We present the first experimental analysis of the transverse phase space of an electron beam using all optical techniques. Comparing an optically masked portion of the beam to the entire beam, we measure different angular spread and average direction of the particles. Direct measurement of the phase-space ellipse tilt angle has been demonstrated using this optical masking technique.

  3. Solid-phase characterization in flammable-gas-tank sludges by electron microscopy

    International Nuclear Information System (INIS)

    Liu, J.; Pederson, L.R.; Qang, L.Q.

    1995-09-01

    The crystallinity, morphology, chemical composition, and crystalline phases of several Tank 241-SY-101 (hereinafter referred to as SY-101) and Tank 241-SY-103 (hereinafter referred to as SY-103) solid samples were studied by transmission electron microscopy (TEM), electron energy dispersive spectroscopy (EDS), and electron diffraction. The main focus is on the identification of aluminum hydroxide thought to be present in these tank samples. Aluminum hydroxide was found in SY-103, but not in SY-101. This difference can be explained by the different OH/Al ratios found in the two tank samples: a high OH/Al ratio in SY-101 favors the formation of sodium aluminate, but a low OH/Al ratio in SY-103 favors aluminum hydroxide. These results were confirmed by a magnetic resonance study on SY-101 and SY-103 simulant. The transition from aluminum hydroxide to sodium aluminate occurs at an OH/Al molar ratio of 3.6. It is believed that the study of Al(OH) 3 was not affected by sample preparation because all Al(OH) 3 is in the solid form according to the NMR experiments. There is no Al(OH) 3 in the liquid. It is, therefore, most likely that the observation of Al(OH) 3 is representative of the real sludge sample, and is not affected by drying. Similar conclusions also apply to other insoluble phases such as iron and chromium

  4. Phase and amplitude perturbations on the NWC signal at Dunedin from lightning-induced electron precipitation

    International Nuclear Information System (INIS)

    Dowden, R.L.; Adams, C.D.D.

    1989-01-01

    Localized ionospheric depressions near the NWC-Dunedin great circle path diffract echoes which interfere with the direct signal at the Dunedin receiver to produce perturbations in phase and amplitude. The statistics both of these perturbations and of the echo phasors (echo magnitude and echo phase) which can be deduced from them are studied here. From these statistics it is deduced that echo paths must be frequently more than a wavelength (14 km) longer than the direct path so that many of the diffracting centers (electron precipitation beams) must be laterally displaced up to 200 km from the direct path. Since echo signals from these must be diffracted through angles of ∼10 0 , ionization enhancements produced by electron precipitation must frequently have lateral (cross-path) dimensions of less than 50 km, with some as narrow as 25 km. The largest perturbation magnitudes seem to require ionization enhancement of longitudinal (parallel to path) dimensions of ∼300 km. Electron precipitation confined to thin L-shells could produce such enhancements for the NWC-Dunedin path. copyright American Geophysical Union 1989

  5. Thermal management of electronics using phase change material based pin fin heat sinks

    International Nuclear Information System (INIS)

    Baby, R; Balaji, C

    2012-01-01

    This paper reports the results of an experimental study carried out to explore the thermal characteristics of phase change material based heat sinks for electronic equipment cooling. The phase change material (PCM) used in this study is n – eicosane. All heat sinks used in the present study are made of aluminium with dimensions of 80 × 62 mm 2 base with a height of 25 mm. Pin fins acts as the thermal conductivity enhancer (TCE) to improve the distribution of heat more uniformly as the thermal conductivity of the PCM is very low. A total of three different pin fin heat sink geometries with 33, 72 and 120 pin fins filled with phase change materials giving rise to 4%, 9% and 15% volume fractions of the TCE respectively were experimentally investigated. Baseline comparisons are done with a heat sink filled with PCM, without any fin. Studies are conducted for heat sinks on which a uniform heat load is applied at the bottom for the finned and unfinned cases. The effect of pin fins of different volume fractions with power levels ranging from 4 to 8 W corresponding to a heat flux range of 1. 59 to 3.17 kW/m 2 , was explored in this paper. The volume fraction of the PCM (PCM volume / (Total volume – fin volume)) is also varied as 0. 3, 0.6 and 1 to determine the effect of PCM volume on the overall performance of the electronic equipment.

  6. Electron diffraction analysis of an AB{sub 2}-type Laves phase for hydrogen battery applications

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Z.; Chumbley, S.; Laabs, F.C. [Iowa State Univ., Ames, IA (United States). Ames Lab.

    2000-11-16

    A multicomponent AB{sub 2} type nickel-metal hydride (Ni-MH) battery alloy prepared by high-pressure gas atomization (HPGA) was investigated by transmission electron microscopy (TEM) in both the as-atomized and heat treated condition. TEM examination showed a heavily faulted dendritic growth structure in as-atomized powder. Selected area diffraction (SAD) showed that this region consisted of both a cubic C15 structure with lattice constant a=7.03 A and an hexagonal C14 structure with lattice parameter a=4.97 A, c=8.11 A. The orientation relationship (OR) between the C14 and C15 structures was determined to be (111)[1 anti 10]{sub C15}//(0001)[11 anti 20]C{sub 14}. An interdendritic phase possessing the C14 structure was also seen. There was also a very fine grain region consisting of the C14 structure. Upon heat treatment, the faulted structure became more defined and appeared as intercalation layers within the grains. Spherical particles rich in Zr and Ni appeared scattered at the grain boundries instead of the C14 interdendritic phase. The polycrystalline region also changed to a mixture of C14 and C15 structures. The phase stability of the C15 and C14 structures based on a consideration of atomic size factor and the average electron concentration is discussed. (orig.)

  7. Sub-nanometre resolution of atomic motion during electronic excitation in phase-change materials.

    Science.gov (United States)

    Mitrofanov, Kirill V; Fons, Paul; Makino, Kotaro; Terashima, Ryo; Shimada, Toru; Kolobov, Alexander V; Tominaga, Junji; Bragaglia, Valeria; Giussani, Alessandro; Calarco, Raffaella; Riechert, Henning; Sato, Takahiro; Katayama, Tetsuo; Ogawa, Kanade; Togashi, Tadashi; Yabashi, Makina; Wall, Simon; Brewe, Dale; Hase, Muneaki

    2016-02-12

    Phase-change materials based on Ge-Sb-Te alloys are widely used in industrial applications such as nonvolatile memories, but reaction pathways for crystalline-to-amorphous phase-change on picosecond timescales remain unknown. Femtosecond laser excitation and an ultrashort x-ray probe is used to show the temporal separation of electronic and thermal effects in a long-lived (>100 ps) transient metastable state of Ge2Sb2Te5 with muted interatomic interaction induced by a weakening of resonant bonding. Due to a specific electronic state, the lattice undergoes a reversible nondestructive modification over a nanoscale region, remaining cold for 4 ps. An independent time-resolved x-ray absorption fine structure experiment confirms the existence of an intermediate state with disordered bonds. This newly unveiled effect allows the utilization of non-thermal ultra-fast pathways enabling artificial manipulation of the switching process, ultimately leading to a redefined speed limit, and improved energy efficiency and reliability of phase-change memory technologies.

  8. Electronic, ductile, phase transition and mechanical properties of Lu-monopnictides under high pressures.

    Science.gov (United States)

    Gupta, Dinesh C; Bhat, Idris Hamid

    2013-12-01

    The structural, elastic and electronic properties of lutatium-pnictides (LuN, LuP, LuAs, LuSb, and LuBi) were analyzed by using full-potential linearized augmented plane wave within generalized gradient approximation in the stable rock-salt structure (B1 phase) with space group Fm-3m and high-pressure CsCl structure (B2 phase) with space group Pm-3m. Hubbard-U and spin-orbit coupling were included to predict correctly the semiconducting band gap of LuN. Under compression, these materials undergo first-order structural transitions from B1 to B2 phases at 241, 98, 56.82, 25.2 and 32.3 GPa, respectively. The computed elastic properties show that LuBi is ductile by nature. The electronic structure calculations show that LuN is semiconductor at ambient conditions with an indirect band gap of 1.55 eV while other Lu-pnictides are metallic. It was observed that LuN shows metallization at high pressures. The structural properties, viz, equilibrium lattice constant, bulk modulus and its pressure derivative, transition pressure, equation of state, volume collapse, band gap and elastic moduli, show good agreement with available data.

  9. The effect of laser pulse parameters and initial phase on the acceleration of electrons in a vacuum

    International Nuclear Information System (INIS)

    Singh, Kunwar Pal; Gupta, Devki Nandan; Malik, Hitendra K

    2008-01-01

    Laser driven acceleration of electrons lying along the axis of the laser has been studied. We have considered a linearly polarized laser pulse. The quiver amplitude causes electrons to escape from the pulse. The energy gained by the electrons peaks for a suitable value of laser spot size. The value of a suitable laser spot size increases with laser intensity and initial electron energy. The energy gained by the electron depends upon its initial position with respect to the laser pulse. The electrons close to the pulse peak with initial phase π/2 are scattered least and gain higher energy. The electrons close to the leading edge of the pulse gain sufficient energy for a short laser pulse and the effect of initial phase is not important. A suitable value of laser spot size can be estimated from this study

  10. Atomic structure and electronic properties of the SixSb100-x phase-change memory material

    DEFF Research Database (Denmark)

    Verma, Ashok K.; Modak, Paritosh; Svane, Axel

    2011-01-01

    The electronic and structural properties of SixSb100-x (x∼16) materials are investigated using first-principles molecular dynamics simulations. Crystalline-liquid-amorphous phase transitions are examined and remarkable changes in the local structure around the Si atoms are found. The average Si...... coordination number 6 (3 long + 3 short Si-Sb bonds) of the crystalline phase changes to 4 (3 long Si-Sb + 1 short Si-Si bonds) by preserving three Si-Sb bonds in both the liquid and the amorphous phases. In the amorphous phase ∼90% of the Si atoms are fourfold coordinated compared to 40% in the liquid....... The electronic density of states is metal-like in both the crystalline and the liquid phases, but it exhibits a pseudogap at the Fermi level in the amorphous phase, reflecting the strong abundance of fourfold coordinated Si in the amorphous phase....

  11. UPS and DFT investigation of the electronic structure of gas-phase trimesic acid

    Energy Technology Data Exchange (ETDEWEB)

    Reisberg, L., E-mail: rebban@ut.ee [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Pärna, R. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); MAX IV Laboratory, Lund University, Fotongatan 2, 225 94 Lund (Sweden); Kikas, A.; Kuusik, I.; Kisand, V. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Hirsimäki, M.; Valden, M. [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, FIN-33101 Tampere (Finland); Nõmmiste, E. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia)

    2016-11-15

    Highlights: • In the current study outer valence band electronic structure of benzene-1,3,5-tricarboxylic acid was interpreted. • Experimental and calculated trimesic acid (TMA) spectrum were compared to ones of benzene and benzoic acid. • It is shown that similarities between MO energies and shapes for benzene and TMA exists. • Addition of carboxyl groups to the benzene ring clearly correlates with increasing binding energy of HOMO. - Abstract: Benzene-1,3,5-tricarboxylic acid (trimesic acid, TMA) molecules in gas-phase have been investigated by using valence band photoemission. The photoelectron spectrum in the binding energy region from 9 to 22 eV is interpreted by using density functional theory calculations. The electronic structure of TMA is compared with benzene and benzoic acid in order to demonstrate changes in molecular orbital energies induced by addition of carboxyl groups to benzene ring.

  12. Runaway electron damage to the Tore Supra Phase III outboard pump limiter

    International Nuclear Information System (INIS)

    Nygren, R.; Lutz, T.; Walsh, D.; Martin, G.; Chatelier, M.; Loarer, T.; Guilhem, D.

    1996-01-01

    Operation of the Phase III outboard pump limiter (OPL) in Tore Supra in 1994 was terminated prematurely when runaway electrons during the current decay following a disruption pierced leading edge tube on the electron side and caused a water leak. The location, about 20 mm outside the last closed flux surface during normal operation, and the infrared (IR) images of the limiter indicate that the runaways moved in large outward steps, i.e. tens of millimeters, in one toroidal revolution. For plasma (runaway) currents in the range of 155 to 250 kA, the drift orbits open to the outside. Basic trajectory computations suggest that such motion is possible under the conditions present for this experiment. Activation measurements made on sections of the tube to indicate the area of local damage are presented here. An understanding of this event may provide important guidance regarding the potential damage from runaways in future tokamaks

  13. Phase-space description of wave packet approach to electronic transport in nanoscale systems

    International Nuclear Information System (INIS)

    Szydłowski, D; Wołoszyn, M; Spisak, B J

    2013-01-01

    The dynamics of conduction electrons in resonant tunnelling nanosystems is studied within the phase-space approach based on the Wigner distribution function. The time evolution of the distribution function is calculated from the time-dependent quantum kinetic equation for which an effective numerical method is presented. Calculations of the transport properties of a double-barrier resonant tunnelling diode are performed to illustrate the proposed techniques. Additionally, analysis of the transient effects in the nanosystem is carried out and it is shown that for some range of the bias voltage the temporal variations of electronic current can take negative values. The explanation of this effect is based on the analysis of the time changes of the Wigner distribution function. The decay time of the temporal current oscillations in the nanosystem as a function of the bias voltage is determined. (paper)

  14. Seven Deadliest Unified Communications Attacks

    CERN Document Server

    York, Dan

    2010-01-01

    Do you need to keep up with the latest hacks, attacks, and exploits effecting Unified Communications technology? Then you need Seven Deadliest Unified Communication Attacks. This book pinpoints the most dangerous hacks and exploits specific to Unified Communications, laying out the anatomy of these attacks including how to make your system more secure. You will discover the best ways to defend against these vicious hacks with step-by-step instruction and learn techniques to make your computer and network impenetrable. Attacks featured in this book include: UC Ecosystem Attacks Insecure Endpo

  15. Electron attachment to DNA single strands: gas phase and aqueous solution.

    Science.gov (United States)

    Gu, Jiande; Xie, Yaoming; Schaefer, Henry F

    2007-01-01

    The 2'-deoxyguanosine-3',5'-diphosphate, 2'-deoxyadenosine-3',5'-diphosphate, 2'-deoxycytidine-3',5'-diphosphate and 2'-deoxythymidine-3',5'-diphosphate systems are the smallest units of a DNA single strand. Exploring these comprehensive subunits with reliable density functional methods enables one to approach reasonable predictions of the properties of DNA single strands. With these models, DNA single strands are found to have a strong tendency to capture low-energy electrons. The vertical attachment energies (VEAs) predicted for 3',5'-dTDP (0.17 eV) and 3',5'-dGDP (0.14 eV) indicate that both the thymine-rich and the guanine-rich DNA single strands have the ability to capture electrons. The adiabatic electron affinities (AEAs) of the nucleotides considered here range from 0.22 to 0.52 eV and follow the order 3',5'-dTDP > 3',5'-dCDP > 3',5'-dGDP > 3',5'-dADP. A substantial increase in the AEA is observed compared to that of the corresponding nucleic acid bases and the corresponding nucleosides. Furthermore, aqueous solution simulations dramatically increase the electron attracting properties of the DNA single strands. The present investigation illustrates that in the gas phase, the excess electron is situated both on the nucleobase and on the phosphate moiety for DNA single strands. However, the distribution of the extra negative charge is uneven. The attached electron favors the base moiety for the pyrimidine, while it prefers the 3'-phosphate subunit for the purine DNA single strands. In contrast, the attached electron is tightly bound to the base fragment for the cytidine, thymidine and adenosine nucleotides, while it almost exclusively resides in the vicinity of the 3'-phosphate group for the guanosine nucleotides due to the solvent effects. The comparatively low vertical detachment energies (VDEs) predicted for 3',5'-dADP(-) (0.26 eV) and 3',5'-dGDP(-) (0.32 eV) indicate that electron detachment might compete with reactions having high activation barriers

  16. Tricritical behaviour in the phase transition induced by electron-hole pairing

    International Nuclear Information System (INIS)

    Crisan, M.

    1980-01-01

    The electron-hole pairing, which is possible in metals or semiconductors, can give condensed phases with two order parameters. If the coupling between the two order parameters is considered, the free energy functional is similar with the free energy of a n-component spin system with cubic anisotropy. Using the Wagner hypothesis (tricritical scaling) the non-linear scaling fields have been calculated. In order to perform the calculation of the nonlinear fields we used the method given by Rudnick and Nelson to solve the recursion relations for the 4-epsilon-dimensional system with n=6 components. The present calculation in the frame-work of the renormalization-group approach confirms the result obtained in the mean-field theory that the coupling of the two order parameters induces a first order phase transition. (author)

  17. Dual-comb spectroscopy of molecular electronic transitions in condensed phases

    Science.gov (United States)

    Cho, Byungmoon; Yoon, Tai Hyun; Cho, Minhaeng

    2018-03-01

    Dual-comb spectroscopy (DCS) utilizes two phase-locked optical frequency combs to allow scanless acquisition of spectra using only a single point detector. Although recent DCS measurements demonstrate rapid acquisition of absolutely calibrated spectral lines with unprecedented precision and accuracy, complex phase-locking schemes and multiple coherent averaging present significant challenges for widespread adoption of DCS. Here, we demonstrate Global Positioning System (GPS) disciplined DCS of a molecular electronic transition in solution at around 800 nm, where the absorption spectrum is recovered by using a single time-domain interferogram. We anticipate that this simplified dual-comb technique with absolute time interval measurement and ultrabroad bandwidth will allow adoption of DCS to tackle molecular dynamics investigation through its implementation in time-resolved nonlinear spectroscopic studies and coherent multidimensional spectroscopy of coupled chromophore systems.

  18. Phase-selective staining of metal salt for scanning electron microscopy imaging of block copolymer film

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jing Ze, E-mail: Lijinge@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Microelectronic and Solid-state Electronic, University of Electronic Science and Technology of China, Chengdu 610054 (China); State Key Laboratory of Polymer Materials Engineering (Sichuan University), Chengdu 610054 (China); Xinjiang Key Laboratory of Electronic Information Materials and Devices, Urumuqi 830011 (China); Wang, Ying; Hong Wang, Zhi; Mei, Di; Zou, Wei [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Microelectronic and Solid-state Electronic, University of Electronic Science and Technology of China, Chengdu 610054 (China); Min Chang, Ai [State Key Laboratory of Polymer Materials Engineering (Sichuan University), Chengdu 610054 (China); Wang, Qi [Xinjiang Key Laboratory of Electronic Information Materials and Devices, Urumuqi 830011 (China); Komura, Motonori; Ito, Kaori [Division of Integrated Molecular Engineering, Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Iyoda, Tomokazu, E-mail: Iyoda.t.aa@m.titech.ac.jp [Division of Integrated Molecular Engineering, Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan)

    2010-09-15

    Three metal salts, i.e., AgNO{sub 3}, HAuCl{sub 4}, and KCl, were proposed as novel staining reagents instead of traditional RuO{sub 4} and OsO{sub 4} labeled with expensive price and extreme toxicity for scanning electron microscopy (SEM) imaging of microphase separated block copolymer film. A simple and costless aqueous solution immersion procedure could ensure selective staining of the metal slat in specific phase of the nanostructured copolymer film, leading to a clear phase contrasted SEM image. The heavy metal salt has better staining effect, demonstrating stable and high signal-to-noise SEM image even at an acceleration voltage as high as 30 kV and magnification up to 250,000 times.

  19. Transmission electron microscopy investigation of interfaces in a two-phase TiAl alloy

    Science.gov (United States)

    Mahon, G. J.; Howe, J. M.

    1990-06-01

    The atomic structures of the γ/α2 and γ/γT interfaces in a TiAl alloy were investigated using conventional and high-resolution transmission electron microscopy (TEM) in order to understand the growth mechanisms and deformation behavior of the two-phase alloy. The results show that the α2 plates grow from the γ phase by the migration of a/6 partial dislocation ledges across the faces and that the γ/α2 interface usually contains closely spaced arrays of interfacial dislocations. Deformation twins cut through both γ twin boundaries and α2 plates during deformation, although slip of twinning c slocations through α2 appears to be a difficult process. Both the γ/α2 and γ/γT interfaces can be imaged and modeled at the atomic level, although slight crystal and/or beam tilt can complicate image interpretation.

  20. Phase transitions in trajectories of a superconducting single-electron transistor coupled to a resonator.

    Science.gov (United States)

    Genway, Sam; Garrahan, Juan P; Lesanovsky, Igor; Armour, Andrew D

    2012-05-01

    Recent progress in the study of dynamical phase transitions has been made with a large-deviation approach to study trajectories of stochastic jumps using a thermodynamic formalism. We study this method applied to an open quantum system consisting of a superconducting single-electron transistor, near the Josephson quasiparticle resonance, coupled to a resonator. We find that the dynamical behavior shown in rare trajectories can be rich even when the mean dynamical activity is small, and thus the formalism gives insights into the form of fluctuations. The structure of the dynamical phase diagram found from the quantum-jump trajectories of the resonator is studied, and we see that sharp transitions in the dynamical activity may be related to the appearance and disappearance of bistabilities in the state of the resonator as system parameters are changed. We also demonstrate that for a fast resonator, the trajectories of quasiparticles are similar to the resonator trajectories.

  1. Electron holes in phase space: What they are and why they matter

    Science.gov (United States)

    Hutchinson, I. H.

    2017-05-01

    This is a tutorial and selective review explaining the fundamental concepts and some currently open questions concerning the plasma phenomenon of the electron hole. The widespread occurrence of electron holes in numerical simulations, space-craft observations, and laboratory experiments is illustrated. The elementary underlying theory is developed of a one-dimensional electron hole as a localized potential maximum, self-consistently sustained by a deficit of trapped electron phase-space density. The spatial extent of a hole is typically a few Debye lengths; what determines the minimum and maximum possible lengths is explained, addressing the key aspects of the as yet unsettled dispute between the integral and differential approaches to hole structure. In multiple dimensions, holes tend to form less readily; they generally require a magnetic field and distribution-function anisotropy. The mechanisms by which they break up are explained, noting that this transverse instability is not fully understood. Examples are given of plasma circumstances where holes play an important role, and of recent progress on understanding their holistic kinematics and self-acceleration.

  2. Controlling the thermoelectric effect by mechanical manipulation of the electron's quantum phase in atomic junctions.

    Science.gov (United States)

    Aiba, Akira; Demir, Firuz; Kaneko, Satoshi; Fujii, Shintaro; Nishino, Tomoaki; Tsukagoshi, Kazuhito; Saffarzadeh, Alireza; Kirczenow, George; Kiguchi, Manabu

    2017-08-11

    The thermoelectric voltage developed across an atomic metal junction (i.e., a nanostructure in which one or a few atoms connect two metal electrodes) in response to a temperature difference between the electrodes, results from the quantum interference of electrons that pass through the junction multiple times after being scattered by the surrounding defects. Here we report successfully tuning this quantum interference and thus controlling the magnitude and sign of the thermoelectric voltage by applying a mechanical force that deforms the junction. The observed switching of the thermoelectric voltage is reversible and can be cycled many times. Our ab initio and semi-empirical calculations elucidate the detailed mechanism by which the quantum interference is tuned. We show that the applied strain alters the quantum phases of electrons passing through the narrowest part of the junction and hence modifies the electronic quantum interference in the device. Tuning the quantum interference causes the energies of electronic transport resonances to shift, which affects the thermoelectric voltage. These experimental and theoretical studies reveal that Au atomic junctions can be made to exhibit both positive and negative thermoelectric voltages on demand, and demonstrate the importance and tunability of the quantum interference effect in the atomic-scale metal nanostructures.

  3. The Phase-I Trigger Readout Electronics Upgrade for the ATLAS Liquid-Argon Calorimeters

    CERN Document Server

    Ochoa, Ines; The ATLAS collaboration

    2017-01-01

    Electronics developments are pursued for the trigger readout of the ATLAS Liquid-Argon Calorimeter towards the Phase-I upgrade scheduled in the LHC shut-down period of 2019-2020. The LAr Trigger Digitizer system will digitize 34000 channels at a 40 MHz sampling with 12 bit precision after the bipolar shaper at the front-end system, and transmit to the LAr Digital Processing system in the back-end to extract the transverse energies. Results of ASIC developments including QA and radiation hardness evaluations, and performances on prototypes will presented with the overall system design.

  4. Rocket measurements of electric fields, electron density and temperature during the three phases of auroral substorms

    International Nuclear Information System (INIS)

    Marklund, G.; Block, L.; Lindqvist, P.-A.

    1979-12-01

    On Jan. 27, 1979, three rocket payloads were launched from Kiruna, Sweden, into different phases of two successive auroral substorms. Among other experiments, the payloads carried the RIT double probe electric field experiments, providing electric field, electron density and temperature data, which are presented here. These are discussed in association with observations of particles, ionospheric drifts (STARE) and electric fields in the equatorial plane (GEOS). The motions of the auroral forms, as obtained from auroral pictures are compared with the E x B/B 2 drifts and the currents calculated from the rocket electric field and density measurements with the equivalent current system deduced from ground based magnetometer data (SMA). (Auth.)

  5. Phase-I Trigger Readout Electronics Upgrade for the ATLAS Liquid-Argon Calorimeters

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00452211; The ATLAS collaboration

    2017-01-01

    The upgrade of the Large Hadron Collider (LHC) scheduled for the Long Shut-down period of 2019-2020 (LS2), referred to as Phase-I upgrade, will increase the instantaneous luminosity to about three times the design value. Since the current ATLAS trigger system does not allow sucient increase of the trigger rate, an improvement of the trigger system is required. The Liquid Argon (LAr) Calorimeter read-out will therefore be modi ed to use digital trigger signals with a higher spatial granularity in order to improve the identi cation effciencies of electrons, photons, tau, jets and missing energy, at high background rejection rates at the Level-1 trigger.

  6. The Phase-I Trigger Readout Electronics Upgrade of the ATLAS Liquid Argon Calorimeters

    CERN Document Server

    Enari, Yuji; The ATLAS collaboration

    2018-01-01

    Electronics developments are pursued for the trigger readout of the ATLAS Liquid-Argon Calorimeter towards the Phase-I upgrade scheduled in the LHC shut-down period of 2019-2020. The LAr Trigger Digitizer system will digitize 34000 channels at a 40 MHz sampling with 12 bit precision after the bipolar shaper at the front-end system, and transmit to the LAr Digital Processing system in the back-end to extract the transverse energies. Results of ASIC developments including QA and radiation hardness evaluations, performances of the final prototypes and results of the system integration tests will presented along with the overall system design.

  7. Transient cooling of electronics using phase change material (PCM)-based heat sinks

    International Nuclear Information System (INIS)

    Kandasamy, Ravi; Wang Xiangqi; Mujumdar, Arun S.

    2008-01-01

    Use of a phase change material (PCM)-based heat sink in transient thermal management of plastic quad flat package (QFP) electronic devices was investigated experimentally and numerically. Results show that increased power inputs enhance the melting rate as well as the thermal performance of the PCM-based heat sinks until the PCM is fully melted. A three-dimensional computational fluid dynamics model was proposed to simulate the problem and demonstrated good agreement with experimental data. Results indicate the potential for PCM-based heat sinks for use in intermittent-use devices

  8. Berry phase dependent quantum trajectories of electron-hole pairs in semiconductors under intense terahertz fields

    Science.gov (United States)

    Yang, Fan; Liu, Ren-Bao

    2013-03-01

    Quantum evolution of particles under strong fields can be approximated by the quantum trajectories that satisfy the stationary phase condition in the Dirac-Feynmann path integrals. The quantum trajectories are the key concept to understand strong-field optics phenomena, such as high-order harmonic generation (HHG), above-threshold ionization (ATI), and high-order terahertz siedeband generation (HSG). The HSG in semiconductors may have a wealth of physics due to the possible nontrivial ``vacuum'' states of band materials. We find that in a spin-orbit-coupled semiconductor, the cyclic quantum trajectories of an electron-hole pair under a strong terahertz field accumulates nontrivial Berry phases. We study the monolayer MoS2 as a model system and find that the Berry phases are given by the Faraday rotation angles of the pulse emission from the material under short-pulse excitation. This result demonstrates an interesting Berry phase dependent effect in the extremely nonlinear optics of semiconductors. This work is supported by Hong Kong RGC/GRF 401512 and the CUHK Focused Investments Scheme.

  9. Phase separation in strongly correlated electron systems with two types of charge carriers

    International Nuclear Information System (INIS)

    Kugel, K.I.; Rakhmanov, A.L.; Sboychakov, A.O.

    2007-01-01

    Full text: A competition between the localization of the charge carriers due to Jahn-Teller distortions and the energy gain due to their delocalization in doped manganite and related magnetic oxides is analyzed based on a Kondo-lattice type model. The resulting effective Hamiltonian is, in fact, a generalization of the Falicov-Kimball model. We find that the number of itinerant charge carriers can be significantly lower than that implied by the doping level x. The phase diagram of the model in the T plane is constructed. The system exhibits magnetic ordered (antiferromagnetic, ferromagnetic, or canted) states as well the paramagnetic states with zero and nonzero density of the itinerant electrons. It is shown that a phase-separation is favorable in energy for a wide doping range. The characteristic size of inhomogeneities in a phase-separated state is of the order of several lattice constants. We also analyzed the two-band Hubbard model in the limit of strong on-site Coulomb repulsion. It was shown that such a system has a tendency to phase separation into the regions with different charge densities even in the absence of magnetic or any other ordering, if the ratio of the bandwidths is large enough. The work was supported by the European project CoMePhS and by the Russian Foundation for Basic Research, project no. 05-02-17600. (authors)

  10. Trajectories of electrons with large longitudinal momenta in the phase plane during surfatron acceleration by an electromagnetic wave

    Energy Technology Data Exchange (ETDEWEB)

    Mkrtichyan, G. S., E-mail: hay-13@mail.ru [Peoples’ Friendship University of Russia (Russian Federation)

    2015-07-15

    The trajectories of electrons with large longitudinal momenta in the phase plane in the course of their surfatron acceleration by an electromagnetic wave propagating in space plasma across the external magnetic field are analyzed. Electrons with large longitudinal momenta are trapped immediately if the initial wave phase Ψ(0) on the particle trajectory is positive. For negative values of Ψ(0), no electrons trapping by the wave is observed over the available computational times. According to numerical calculations, the trajectories of trapped particles in the phase plane have a singular point of the stable focus type and the behavior of the trajectory corresponds to the motion in a complex nonstationary effective potential well. For some initial phases, electrons are confined in the region of the accelerating electric field for relatively short time, the energy gain being about 50–130% and more.

  11. Electronic structures and superconductivity in LuTE2Si2 phases (TE = d-electron transition metal)

    Science.gov (United States)

    Samsel-Czekała, M.; Chajewski, G.; Wiśniewski, P.; Romanova, T.; Hackemer, A.; Gorzelniak, R.; Pikul, A. P.; Kaczorowski, D.

    2018-05-01

    In the course of our search for unconventional superconductors amidst the 1:2:2 phases, we have re-investigated the LuTE2Si2 compounds with TE = Fe, Co, Ni, Ru, Pd and Pt. In this paper, we present the results of our fully relativistic ab initio calculations of the band structures, performed using the full-potential local-orbital code. The theoretical data are supplemented by the results of low-temperature electrical transport and specific heat measurements performed down to 0.35 K. All the materials studied but LuPt2Si2 crystallize with the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm). Their Fermi surfaces exhibit a three-dimensional multi-band character. In turn, the Pt-bearing compound adopts the primitive tetragonal CaBe2Ge2-type structure (space group P4/nmm), and its Fermi surface consists of predominantly quasi-two-dimensional sheets. Bulk superconductivity was found only in LuPd2Si2 and LuPt2Si2 (independent of the structure type and dimensionality of the Fermi surface). The key superconducting characteristics indicate a fully-gapped BCS type character. Though the electronic structure of LuFe2Si2 closely resembles that of the unconventional superconductor YFe2Ge2, this Lu-based silicide exhibits neither superconductivity nor spin fluctuations at least down to 0.35 K.

  12. UPQC (Unified power Quality Conditioner)

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. UPQC (Unified power Quality Conditioner). Hybrid of Shunt and Series compensator. Compensate both Current Quality and Voltage Quality. Costlier Solution as it involves two set of Inverters.

  13. Study of nanometer-level precise phase-shift system used in electronic speckle shearography and phase-shift pattern interferometry

    Science.gov (United States)

    Jing, Chao; Liu, Zhongling; Zhou, Ge; Zhang, Yimo

    2011-11-01

    The nanometer-level precise phase-shift system is designed to realize the phase-shift interferometry in electronic speckle shearography pattern interferometry. The PZT is used as driving component of phase-shift system and translation component of flexure hinge is developed to realize micro displacement of non-friction and non-clearance. Closed-loop control system is designed for high-precision micro displacement, in which embedded digital control system is developed for completing control algorithm and capacitive sensor is used as feedback part for measuring micro displacement in real time. Dynamic model and control model of the nanometer-level precise phase-shift system is analyzed, and high-precision micro displacement is realized with digital PID control algorithm on this basis. It is proved with experiments that the location precision of the precise phase-shift system to step signal of displacement is less than 2nm and the location precision to continuous signal of displacement is less than 5nm, which is satisfied with the request of the electronic speckle shearography and phase-shift pattern interferometry. The stripe images of four-step phase-shift interferometry and the final phase distributed image correlated with distortion of objects are listed in this paper to prove the validity of nanometer-level precise phase-shift system.

  14. Leading gravitational corrections and a unified universe

    DEFF Research Database (Denmark)

    Codello, Alessandro; Jain, Rajeev Kumar

    2016-01-01

    Leading order gravitational corrections to the Einstein-Hilbert action can lead to a consistent picture of the universe by unifying the epochs of inflation and dark energy in a single framework. While the leading local correction induces an inflationary phase in the early universe, the leading...... nonlocal term leads to an accelerated expansion of the universe at the present epoch. We argue that both the leading UV and IR terms can be obtained within the framework of a covariant effective field theory of gravity. The perturbative gravitational corrections therefore provide a fundamental basis...

  15. Model of unified gauge fields

    International Nuclear Information System (INIS)

    Leite Lopes, J.

    1998-04-01

    In this work, we discuss the physical ideas which represents the basis for the unified gauge field model. Despite of the difficulties that we presently have for embodying in a natural manner muons and hadrons in that model, we have the feeling that we are on the way which seems to lead to the construction of a theory in which the Maxwell electromagnetic field and the Fermi weak interaction field are manifestations of a unique subjacent physical entity - the unified gauge fields. (author)

  16. Analysis of the factors influencing healthcare professionals' adoption of mobile electronic medical record (EMR) using the unified theory of acceptance and use of technology (UTAUT) in a tertiary hospital.

    Science.gov (United States)

    Kim, Seok; Lee, Kee-Hyuck; Hwang, Hee; Yoo, Sooyoung

    2016-01-30

    Although the factors that affect the end-user's intention to use a new system and technology have been researched, the previous studies have been theoretical and do not verify the factors that affected the adoption of a new system. Thus, this study aimed to confirm the factors that influence users' intentions to utilize a mobile electronic health records (EMR) system using both a questionnaire survey and a log file analysis that represented the real use of the system. After observing the operation of a mobile EMR system in a tertiary university hospital for seven months, we performed an offline survey regarding the user acceptance of the system based on the Unified Theory of Acceptance and Use of Technology (UTAUT) and the Technology Acceptance Model (TAM). We surveyed 942 healthcare professionals over two weeks and performed a structural equation modeling (SEM) analysis to identify the intention to use the system among the participants. Next, we compared the results of the SEM analysis with the results of the analyses of the actual log files for two years to identify further insights into the factors that affected the intention of use. For these analyses, we used SAS 9.0 and AMOS 21. Of the 942 surveyed end-users, 48.3 % (23.2 % doctors and 68.3 % nurses) responded. After eliminating six subjects who completed the survey insincerely, we conducted the SEM analyses on the data from 449 subjects (65 doctors and 385 nurses). The newly suggested model satisfied the standards of model fitness, and the intention to use it was especially high due to the influences of Performance Expectancy on Attitude and Attitude. Based on the actual usage log analyses, both the doctors and nurses used the menus to view the inpatient lists, alerts, and patients' clinical data with high frequency. Specifically, the doctors frequently retrieved laboratory results, and the nurses frequently retrieved nursing notes and used the menu to assume the responsibilities of nursing work. In this

  17. Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

    International Nuclear Information System (INIS)

    Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

    2017-01-01

    We describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We then observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wave trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.

  18. Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

    Science.gov (United States)

    Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

    2017-12-01

    Here, we describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wave trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.

  19. Thermal entanglement between π-electrons in silicene and photons; occurrence of phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Rastgoo, S., E-mail: rastgooo@gmail.com [Mathematics and Computer Science Department, Sirjan University of Technology, Sirjan 78137 (Iran, Islamic Republic of); Golshan, M.M., E-mail: golshan@susc.ac.ir [Physics Department, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

    2017-03-18

    In this article, the thermal entanglement between π-electronic states in a monolayer silicene sheet and a single mode quantized electromagnetic field is investigated. We assume that the system is in thermal equilibrium with the environment at a temperature T, so that the whole system is described by the Boltzmann distribution. Using the states of total Hamiltonian, the thermal density matrix and, consequently, its partially transposed one is computed, giving rise to the determination of negativity. Our analytical calculations, along with representative figures, show that the system is separable at zero temperature, exhibits a maximum, at a specific temperature, and asymptotically vanishes. Along these lines we also report the effects of electron–photon coupling, as well as the silicene buckling, on the entanglement. Specifically, we demonstrate that the maximal value of entanglement is larger for stronger electron–photon coupling, while it decreases for larger buckling effect. Moreover, we show that the gap in the total energy spectrum remains intact for any value of the buckling parameter. There is, however, one state whose energy changes sign, at a specific buckling, indicating a change of phase. - Highlights: • Thermal entanglement between π-electrons and photons in silicene is reported. • Intrinsic spin-orbit coupling and buckling effect are taken into account. • The ground state of the system is shown to be separable. • Thermal entanglement exhibits a maximum at a certain controllable temperature. • A rapid increase in the negativity for small temperature and buckling indicates a phase transition.

  20. Electron Number-Based Phase Diagram of Pr1 -xLaCex CuO4 -δ and Possible Absence of Disparity between Electron- and Hole-Doped Cuprate Phase Diagrams

    Science.gov (United States)

    Song, Dongjoon; Han, Garam; Kyung, Wonshik; Seo, Jeongjin; Cho, Soohyun; Kim, Beom Seo; Arita, Masashi; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki; Yoshida, Y.; Eisaki, H.; Park, Seung Ryong; Kim, C.

    2017-03-01

    We performed annealing and angle resolved photoemission spectroscopy studies on electron-doped cuprate Pr1 -xLaCex CuO4 -δ (PLCCO). It is found that the optimal annealing condition is dependent on the Ce content x . The electron number (n ) is estimated from the experimentally obtained Fermi surface volume for x =0.10 , 0.15 and 0.18 samples. It clearly shows a significant and annealing dependent deviation from the nominal x . In addition, we observe that the pseudo-gap at hot spots is also closely correlated with n ; the pseudogap gradually closes as n increases. We established a new phase diagram of PLCCO as a function of n . Different from the x -based one, the new phase diagram shows similar antiferromagnetic and superconducting phases to those of hole doped ones. Our results raise a possibility for absence of disparity between the phase diagrams of electron- and hole-doped cuprates

  1. Modification of electronic structure, magnetic structure, and topological phase of bismuthene by point defects

    Science.gov (United States)

    Kadioglu, Yelda; Kilic, Sevket Berkay; Demirci, Salih; Aktürk, O. Üzengi; Aktürk, Ethem; Ciraci, Salim

    2017-12-01

    This paper reveals how the electronic structure, magnetic structure, and topological phase of two-dimensional (2D), single-layer structures of bismuth are modified by point defects. We first showed that a free-standing, single-layer, hexagonal structure of bismuth, named h-bismuthene, exhibits nontrivial band topology. We then investigated interactions between single foreign adatoms and bismuthene structures, which comprise stability, bonding, electronic structure, and magnetic structures. Localized states in diverse locations of the band gap and resonant states in band continua of bismuthene are induced upon the adsorption of different adatoms, which modify electronic and magnetic properties. Specific adatoms result in reconstruction around the adsorption site. Single vacancies and divacancies can form readily in bismuthene structures and remain stable at high temperatures. Through rebondings, Stone-Whales-type defects are constructed by divacancies, which transform into a large hole at high temperature. Like adsorbed adatoms, vacancies induce also localized gap states, which can be eliminated through rebondings in divacancies. We also showed that not only the optical and magnetic properties, but also the topological features of pristine h-bismuthene can be modified by point defects. The modification of the topological features depends on the energies of localized states and also on the strength of coupling between point defects.

  2. First principles study of structural and electronic properties of different phases of boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Rashid [Centre for High Energy Physics, University of the Punjab, Lahore 54590 (Pakistan)], E-mail: rasofi@hotmail.com; Fazal-e-Aleem [Centre for High Energy Physics, University of the Punjab, Lahore 54590 (Pakistan); Hashemifar, S. Javad; Akbarzadeh, Hadi [Department of Physics, Isfahan University of Technology, 84156 Isfahan (Iran, Islamic Republic of)

    2007-11-15

    A theoretical study of structural and electronic properties of the four phases of BN (zincblende, wurtzite, hexagonal and rhombohedral) is presented. The calculations are done by full potential (linear) augmented plane wave plus local orbitals (APW+lo) method based on the density functional theory (DFT) as employed in WIEN2k code. Using the local density approximation (LDA) and generalized gradient approximation (GGA-PBE) for the exchange correlation energy functional, we have calculated lattice parameters, bulk modulus, its pressure derivative and cohesive energy. In order to calculate electronic band structure, another form of the generalized gradient approximation proposed by Engel and Vosko (GGA-EV) has been employed along with LDA and GGA-PBE. It is found that all the three approximations exhibit similar band structure qualitatively. However, GGA-EV gives energy band gap values closer to the measured data. Our results for structural and electronic properties are compared with the experimental and other theoretical results wherever these are available.

  3. "Diffusion" region of magnetic reconnection: electron orbits and the phase space mixing

    Science.gov (United States)

    Kropotkin, Alexey P.

    2018-05-01

    The nonlinear dynamics of electrons in the vicinity of magnetic field neutral lines during magnetic reconnection, deep inside the diffusion region where the electron motion is nonadiabatic, has been numerically analyzed. Test particle orbits are examined in that vicinity, for a prescribed planar two-dimensional magnetic field configuration and with a prescribed uniform electric field in the neutral line direction. On electron orbits, a strong particle acceleration occurs due to the reconnection electric field. Local instability of orbits in the neighborhood of the neutral line is pointed out. It combines with finiteness of orbits due to particle trapping by the magnetic field, and this should lead to the effect of mixing in the phase space, and the appearance of dynamical chaos. The latter may presumably be viewed as a mechanism producing finite conductivity in collisionless plasma near the neutral line. That conductivity is necessary to provide violation of the magnetic field frozen-in condition, i.e., for magnetic reconnection to occur in that region.

  4. The effect of relativity on stability of Copernicium phases, their electronic structure and mechanical properties

    Science.gov (United States)

    Čenčariková, Hana; Legut, Dominik

    2018-05-01

    The phase stability of the various crystalline structures of the super-heavy element Copernicium was determined based on the first-principles calculations with different levels of the relativistic effects. We utilized the Darwin term, mass-velocity, and spin-orbit interaction with the single electron framework of the density functional theory while treating the exchange and correlation effects using local density approximations. It is found that the spin-orbit coupling is the key component to stabilize the body-centered cubic (bcc) structure over the hexagonal closed packed (hcp) structure, which is in accord with Sol. Stat. Comm. 152 (2012) 530, but in contrast to Atta-Fynn and Ray (2015) [11], Gaston et al. (2007) [10], Papaconstantopoulos (2015) [9]. It seems that the main role here is the correct description of the semi-core relativistic 6p1/2 orbitals. The all other investigated structures, i.e. face-centered cubic (fcc) , simple cubic (sc) as well as rhombohedral (rh) structures are higher in energy. The criteria of mechanical stability were investigated based on the calculated elastic constants, identifying the phase instability of fcc and rh structures, but surprisingly confirm the stability of the energetically higher sc structure. In addition, the pressure-induced structural transition between two stable sc and bcc phases has been detected. The ground-state bcc structure exhibits the highest elastic anisotropy from single elements of the Periodic table. At last, we support the experimental findings that Copernicium is a metal.

  5. Preparation and thermal conductivity enhancement of composite phase change materials for electronic thermal management

    International Nuclear Information System (INIS)

    Wu, Weixiong; Zhang, Guoqing; Ke, Xiufang; Yang, Xiaoqing; Wang, Ziyuan; Liu, Chenzhen

    2015-01-01

    Highlights: • A kind of composite phase change material board (PCMB) is prepared and tested. • PCMB presents a large thermal storage capacity and enhanced thermal conductivity. • PCMB displays much better cooling effect in comparison to natural air cooling. • PCMB presents different cooling characteristics in comparison to ribbed radiator. - Abstract: A kind of phase change material board (PCMB) was prepared for use in the thermal management of electronics, with paraffin and expanded graphite as the phase change material and matrix, respectively. The as-prepared PCMB presented a large thermal storage capacity of 141.74 J/g and enhanced thermal conductivity of 7.654 W/(m K). As a result, PCMB displayed much better cooling effect in comparison to natural air cooling, i.e., much lower heating rate and better uniformity of temperature distribution. On the other hand, compared with ribbed radiator technology, PCMB also presented different cooling characteristics, demonstrating that they were suitable for different practical application

  6. Electronic structure and quantum spin fluctuations at the magnetic phase transition in MnSi

    Science.gov (United States)

    Povzner, A. A.; Volkov, A. G.; Nogovitsyna, T. A.

    2018-05-01

    The effect of spin fluctuations on the heat capacity and homogeneous magnetic susceptibility of the chiral magnetic MnSi in the vicinity of magnetic transition has been investigated by using the free energy functional of the coupled electron and spin subsystems and taking into account the Dzyaloshinsky-Moriya interaction. For helical ferromagnetic ordering, we found that zero-point fluctuations of the spin density are large and comparable with fluctuations of the non-uniform magnetization. The amplitude of zero-point spin fluctuations shows a sharp decrease in the region of the magnetic phase transition. It is shown that sharp decrease of the amplitude of the quantum spin fluctuations results in the lambda-like maxima of the heat capacity and the homogeneous magnetic susceptibility. Above the temperature of the lambda anomaly, the spin correlation radius becomes less than the period of the helical structure and chiral fluctuations of the local magnetization appear. It is shown that formation of a "shoulder" on the temperature dependence of the heat capacity is due to disappearance of the local magnetization. Our finding allows to explain the experimentally observed features of the magnetic phase transition of MnSi as a result of the crossover of quantum and thermodynamic phase transitions.

  7. Phase-coherent electron transport in (Zn, Al)Ox thin films grown by atomic layer deposition

    Science.gov (United States)

    Saha, D.; Misra, P.; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M.

    2014-11-01

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)Ox thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al2O3 sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length ( l φ ∝ T - 3 / 4 ), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  8. Phase-coherent electron transport in (Zn, Al)O{sub x} thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Saha, D., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Misra, P., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

    2014-11-24

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)O{sub x} thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al{sub 2}O{sub 3} sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length (l{sub φ}∝T{sup −3/4}), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  9. Density-functional theory for f-electron systems. The α-γ phase transition in cerium

    International Nuclear Information System (INIS)

    Casadei, Marco

    2013-01-01

    Rare earths are technologically important and scientifically highly interesting elements. The description of the volume collapse exhibited by some rare earth metals poses a great challenge to density-functional theory (DFT) since local/semi-local functionals (LDA/GGA) only partially capture the associated phase transitions. In this work this problem is approached by treating all electrons at the same quantum mechanical level, using both hybrid functionals (e.g. PBE0 and HSE06) and exact-exchange plus correlation in the random-phase approximation (EX+cRPA). The performance of recently developed beyond RPA schemes is also assessed. The isostructural α-γ phase transition in cerium is the most studied. The exact exchange contribution in PBE0 and HSE06 is crucial to produce two distinct solutions that can be associated with the α and γ phases. The two solutions emerge in bulk as well as in cluster calculations. Most notable is their presence in the cerium dimer. However, quantitative agreement with the extrapolated phase diagram requires EX+cRPA. So far the EX+cRPA correction can only be applied to cerium clusters and not to the bulk. A cluster of 19 atoms cut from the fcc crystal structure (the same that characterizes the α and γ phases) was therefore determined as representative. (EX+cRPA) rate at PBE0 for Ce 19 provides good agreement with the extrapolated transition pressure to zero temperature. We predict that a pressure induced phase transition should exist at or close to zero. A finite temperature phase diagram can be drawn in reasonable agreement with experiment by adding entropic effects. The cerium neighbors are also studied: lanthanum, which has no f electrons, praseodymium, with three f electrons and a volume collapse, and neodymium, with four f electrons and no volume collapse. Multiple solutions are also present for these f electron elements, confirming the importance of exact-exchange for f electron systems.

  10. Phase-space holes due to electron and ion beams accelerated by a current-driven potential ramp

    Directory of Open Access Journals (Sweden)

    M. V. Goldman

    2003-01-01

    Full Text Available One-dimensional open-boundary simulations have been carried out in a current-carrying plasma seeded with a neutral density depression and with no initial electric field. These simulations show the development of a variety of nonlinear localized electric field structures: double layers (unipolar localized fields, fast electron phase-space holes (bipolar fields moving in the direction of electrons accelerated by the double layer and trains of slow alternating electron and ion phase-space holes (wave-like fields moving in the direction of ions accelerated by the double layer. The principal new result in this paper is to show by means of a linear stability analysis that the slow-moving trains of electron and ion holes are likely to be the result of saturation via trapping of a kinetic-Buneman instability driven by the interaction of accelerated ions with unaccelerated electrons.

  11. The Kubo-Greenwood formula as a result of the random phase approximation for the electrons of the metal

    Science.gov (United States)

    Ivliev, S. V.

    2017-12-01

    For calculation of short laser pulse absorption in metal the imaginary part of permittivity, which is simply related to the conductivity, is required. Currently to find the static and dynamic conductivity the Kubo-Greenwood formula is most commonly used. It describes the electromagnetic energy absorption in the one-electron approach. In the present study, this formula is derived directly from the expression for the permittivity expression in the random phase approximation, which in fact is equivalent to the method of the mean field. The detailed analysis of the role of electron-electron interaction in the calculation of the matrix elements of the velocity operator is given. It is shown that in the one-electron random phase approximation the single-particle conductive electron wave functions in the field of fixed ions should be used. The possibility of considering the exchange and correlation effects by means of an amendment to a local function field is discussed.

  12. Modeling of hydrodynamic cavitation reactors: a unified approach

    NARCIS (Netherlands)

    Moholkar, V.S.; Pandit, A.B.

    2001-01-01

    An attempt has been made to present a unified theoretical model for the cavitating flow in a hydrodynamic cavitation reactor using the nonlinear continuum mixture model for two-phase flow as the basis. This model has been used to describe the radial motion of bubble in the cavitating flow in two

  13. Characterization of Isomeric Glycans by Reversed Phase Liquid Chromatography-Electronic Excitation Dissociation Tandem Mass Spectrometry

    Science.gov (United States)

    Tang, Yang; Wei, Juan; Costello, Catherine E.; Lin, Cheng

    2018-04-01

    The occurrence of numerous structural isomers in glycans from biological sources presents a severe challenge for structural glycomics. The subtle differences among isomeric structures demand analytical methods that can provide structural details while working efficiently with on-line glycan separation methods. Although liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a powerful tool for mixture analysis, the commonly utilized collision-induced dissociation (CID) method often does not generate a sufficient number of fragments at the MS2 level for comprehensive structural characterization. Here, we studied the electronic excitation dissociation (EED) behaviors of metal-adducted, permethylated glycans, and identified key spectral features that could facilitate both topology and linkage determinations. We developed an EED-based, nanoscale, reversed phase (RP)LC-MS/MS platform, and demonstrated its ability to achieve complete structural elucidation of up to five structural isomers in a single LC-MS/MS analysis. [Figure not available: see fulltext.

  14. Beyond the random-phase approximation for the electron correlation energy: the importance of single excitations.

    Science.gov (United States)

    Ren, Xinguo; Tkatchenko, Alexandre; Rinke, Patrick; Scheffler, Matthias

    2011-04-15

    The random-phase approximation (RPA) for the electron correlation energy, combined with the exact-exchange (EX) energy, represents the state-of-the-art exchange-correlation functional within density-functional theory. However, the standard RPA practice--evaluating both the EX and the RPA correlation energies using Kohn-Sham (KS) orbitals from local or semilocal exchange-correlation functionals--leads to a systematic underbinding of molecules and solids. Here we demonstrate that this behavior can be corrected by adding a "single excitation" contribution, so far not included in the standard RPA scheme. A similar improvement can also be achieved by replacing the non-self-consistent EX total energy by the corresponding self-consistent Hartree-Fock total energy, while retaining the RPA correlation energy evaluated using KS orbitals. Both schemes achieve chemical accuracy for a standard benchmark set of noncovalent intermolecular interactions.

  15. 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

    The adiabatic connection fluctuation-dissipation theorem with the random phase approximation (RPA) has recently been applied with success to obtain correlation energies of a variety of chemical and solid state systems. The main merit of this approach is the improved description of dispersive forces...... 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...

  16. Crystalline phases and electronic structures in superconducting Bi endash Sr endash Ca endash Cu oxides

    International Nuclear Information System (INIS)

    Giardina, M.D.; Feduzi, R.; Inzaghi, D.; Manara, A.; Giori, C.; Sora, I.N.; Dallacasa, V.

    1997-01-01

    Two classes of samples, designated A and B, of layered Bi endash Sr endash Ca endash Cu oxides having the same nominal composition 4:3:3:4, but different thermal histories, were investigated by using field modulated microwave absorption (ESR), powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and x-ray absorption near the edge structure (XANES). Previous electrical resistivity measurements showed that the B samples only presented two superconducting phases with midpoints of the transition temperatures at ∼80K and ∼105K. The microwave absorption technique indicated instead the presence of islands which became superconducting at the above-mentioned temperatures also in the A samples. The crystalline and electronic structures of the two types of samples are illustrated and discussed. A plausible theoretical interpretation of the experimental results, based on a quantum percolation model with Coulomb interaction, is also given. copyright 1997 Materials Research Society

  17. Combined effect of dopant and electron beam-irradiation on phase transition in lithium potassium sulphate

    Science.gov (United States)

    Kassem, M. E.; Gaafar, M.; Abdel Gawad, M. M. H.; El-Muraikhi, M.; Ragab, I. M.

    2004-02-01

    Thermodynamic studies of polycrystalline ruthenium (Ru) doped LiKSO 4 have been made for different concentrations of Ru in the range 0%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3% by weight. The thermal behaviour has been investigated using a differential scanning calorimeter in the vicinity of high temperature phases. From this, the effect of electron beam-irradiation on the thermal properties of these polycrystalline samples has been studied. The results showed a change in the transition temperature Tc, as well as the value of specific heat CPmax at the transition temperature due to the change in Ru content and irradiation energies. The change of enthalpy and entropy of the polycrystalline have been estimated numerically.

  18. Combined effect of dopant and electron beam-irradiation on phase transition in lithium potassium sulphate

    International Nuclear Information System (INIS)

    Kassem, M.E.; Gaafar, M.; Abdel Gawad, M.M.H.; El-Muraikhi, M.; Ragab, I.M.

    2004-01-01

    Thermodynamic studies of polycrystalline ruthenium (Ru) doped LiKSO 4 have been made for different concentrations of Ru in the range 0%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3% by weight. The thermal behaviour has been investigated using a differential scanning calorimeter in the vicinity of high temperature phases. From this, the effect of electron beam-irradiation on the thermal properties of these polycrystalline samples has been studied. The results showed a change in the transition temperature T c , as well as the value of specific heat C P max at the transition temperature due to the change in Ru content and irradiation energies. The change of enthalpy and entropy of the polycrystalline have been estimated numerically

  19. In Situ Transmission Electron Microscopy Observation of Nanostructural Changes in Phase-Change Memory

    KAUST Repository

    Meister, Stefan

    2011-04-26

    Phase-change memory (PCM) has been researched extensively as a promising alternative to flash memory. Important studies have focused on its scalability, switching speed, endurance, and new materials. Still, reliability issues and inconsistent switching in PCM devices motivate the need to further study its fundamental properties. However, many investigations treat PCM cells as black boxes; nanostructural changes inside the devices remain hidden. Here, using in situ transmission electron microscopy, we observe real-time nanostructural changes in lateral Ge2Sb2Te5 (GST) PCM bridges during switching. We find that PCM devices with similar resistances can exhibit distinct threshold switching behaviors due to the different initial distribution of nanocrystalline and amorphous domains, explaining variability of switching behaviors of PCM cells in the literature. Our findings show a direct correlation between nanostructure and switching behavior, providing important guidelines in the design and operation of future PCM devices with improved endurance and lower variability. © 2011 American Chemical Society.

  20. Phasing of the Triatoma virus diffraction data using a cryo-electron microscopy reconstruction

    International Nuclear Information System (INIS)

    Estrozi, L.F.; Neumann, E.; Squires, G.; Rozas-Dennis, G.; Costabel, M.; Rey, F.A.; Guerin, D.M.A.; Navaza, J.

    2008-01-01

    The blood-sucking reduviid bug Triatoma infestans, one of the most important vector of American human trypanosomiasis (Chagas disease) is infected by the Triatoma virus (TrV). TrV has been classified as a member of the Cripavirus genus (type cricket paralysis virus) in the Dicistroviridae family. This work presents the three-dimensional cryo-electron microscopy (cryo-EM) reconstruction of the TrV capsid at about 25 A resolution and its use as a template for phasing the available crystallographic data by the molecular replacement method. The main structural differences between the cryo-EM reconstruction of TrV and other two viruses, one from the same family, the cricket paralysis virus (CrPV) and the human rhinovirus 16 from the Picornaviridae family are presented and discussed

  1. Electron-irradiation induced changes in the phases and photocatalytic activity of TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Sapnar, K.B.; Dhole, S.D. [Department of Physics, University of Pune, Pune 411007 (India); Bhoraskar, V.N., E-mail: vnb@physics.unipune.ac.in [Department of Physics, University of Pune, Pune 411007 (India)

    2012-04-01

    Highlights: Black-Right-Pointing-Pointer The phases of TiO{sub 2} nanoparticles have been changed by electron irradiation. Black-Right-Pointing-Pointer The photocatalytic activity of TiO{sub 2} gets enhanced after electron irradiation. Black-Right-Pointing-Pointer The brookite phase has appeared in TiO{sub 2} after electron irradiation. - Abstract: Samples of TiO{sub 2} nanoparticles, with mixed anatase and rutile phases, were irradiated with 6.5 MeV electrons at fluences, 1.5, 2.0, 2.5, 3.0, and 3.5 Multiplication-Sign 10{sup 15} e cm{sup -2} and characterized by several methods. With increasing electron fluence, a continuous decrease in the average particle size from {approx}80 nm to around 30 nm were observed along with a decrease in the rutile and the anatase phases of TiO{sub 2}, but at different rates, and growth of the TiO{sub 2} brookite phase at slow rate. The photocatalytic activities of different electron irradiated TiO{sub 2} samples, in the photodegradation of methylene blue, were studied by recording UV-Vis absorption spectra of the respective solutions. On electron irradiation, even though the rutile phase in the TiO{sub 2} was decreasing, the photocatalytic activity of the nanoparticles increased continuously with fluence up to {approx}3.0 Multiplication-Sign 10{sup 15} e cm{sup -2}, but decreased at 3.5 Multiplication-Sign 10{sup 15} e cm{sup -2}. The energy levels introduced by the brookite phase and the electron induced defects in TiO{sub 2} could have effectively reduced the electron-hole recombination rate in the absence of the rutile phase. The observed enhancement in the photocatalytic activity of the irradiated TiO{sub 2} is attributed to the formation of small size particles, the introduction of the oxygen related vacancies and other defects, the growth of the brookite phase, and increased absorption of radiation over the ultraviolet and visible range.

  2. Phase-locking of a terahertz solid-state source using a superconducting hot-electron bolometer mixer

    International Nuclear Information System (INIS)

    Miao, W; Zhang, W; Zhou, K M; Li, S L; Zhang, K; Duan, W Y; Yao, Q J; Shi, S C

    2013-01-01

    We report on a scheme whereby the local-oscillator (LO) of a THz heterodyne receiver can be phase-locked by the mixer of the heterodyne receiver. This scheme is demonstrated for the phase-locking of an 847.6 GHz Gunn oscillator and multiplier chain combined source with a superconducting hot-electron bolometer (HEB) mixer. We show that with this technique the phase-locked beat signal can reach a signal-to-noise ratio higher than 70 dB in a resolution bandwidth (RBW) of 1 Hz. This phase-locking scheme should find good use in THz heterodyne spectrometers. (paper)

  3. In situ observation of electron beam-induced phase transformation of CaCO3 to CaO via ELNES at low electron beam energies.

    Science.gov (United States)

    Golla-Schindler, Ute; Benner, Gerd; Orchowski, Alexander; Kaiser, Ute

    2014-06-01

    It is demonstrated that energy-filtered transmission electron microscope enables following of in situ changes of the Ca-L2,3 edge which can originate from variations in both local symmetry and bond lengths. Low accelerating voltages of 20 and 40 kV slow down radiation damage effects and enable study of the start and finish of phase transformations. We observed electron beam-induced phase transformation of single crystalline calcite (CaCO3) to polycrystalline calcium oxide (CaO) which occurs in different stages. The coordination of Ca in calcite is close to an octahedral one streched along the direction. Changes during phase transformation to an octahedral coordination of Ca in CaO go along with a bond length increase by 5 pm, where oxygen is preserved as a binding partner. Electron loss near-edge structure of the Ca-L2,3 edge show four separated peaks, which all shift toward lower energies during phase transformation at the same time the energy level splitting increases. We suggest that these changes can be mainly addressed to the change of the bond length on the order of picometers. An important pre-condition for such studies is stability of the energy drift in the range of meV over at least 1 h, which is achieved with the sub-Ångström low-voltage transmission electron microscope I prototype microscope.

  4. Observation of superconducting fluxons by transmission electron microscopy: A Fourier space approach to calculate the electron optical phase shifts and images

    International Nuclear Information System (INIS)

    Beleggia, M.; Pozzi, G.

    2001-01-01

    An approach is presented for the calculation of the electron optical phase shift experienced by high-energy electrons in a transmission electron microscope, when they interact with the magnetic field associated with superconducting fluxons in a thin specimen tilted with respect to the beam. It is shown that by decomposing the vector potential in its Fourier components and by calculating the phase shift of each component separately, it is possible to obtain the Fourier transform of the electron optical phase shift, which can be inverted either analytically or numerically. It will be shown how this method can be used to recover the result, previously obtained by the real-space approach, relative to the case of a straight flux tube perpendicular to the specimen surfaces. Then the method is applied to the case of a London fluxon in a thin film, where the bending and the broadening of the magnetic-field lines due to the finite specimen thickness are now correctly taken into account and not treated approximately by means of a parabolic fit. Finally, it will be shown how simple models for the pancake structure of the fluxon can be analyzed within this framework and the main features of electron transmission images predicted

  5. S-Matrix theory of laser-induced nonsequential double ionization: from electron-electron dynamics to absolute-phase diagnosis

    International Nuclear Information System (INIS)

    Figueira de Morisson Faria, C.; Sanpera, A.; Lewenstein, M.; Schomerus, H.; Liu, X.; Becker, W.

    2005-01-01

    studies, in which a systematic analysis of the influence of the initial bound states of both electrons, and of the spatial extension of the electronic wave function, on the NSDI momentum distributions, has been performed. Such studies have shown that the best agreement with experiments should occur for highly localized bound states and an effective short-range interaction. In the above-stated studies, the external laser field has been approximated by a monochromatic wave. This is a reasonable assumption if the laser pulses in question are relatively long. For few-cycle pulses, however, one expects a very different behavior and, in particular, that the so-called absolute phase, i.e., the phase difference between the pulse envelope and its carrier oscillation, influences the momentum distributions in question. Within this context, we have shown that the differential momentum distributions are highly asymmetric and either concentrated in the first or the third quadrant of the (p 1II , p 2II ) plane. Around a critical value of the absolute phase, the distributions shift from one region to the other. Such a behavior can be explained in terms of the trajectories of an electron recombining inelastically with its parent ion, and the critical phase can be traced to a change in the dominant set of trajectories. This effect is present both in a classical and a quantum-mechanical framework, with the difference that, in the quantum-mechanical case, the distributions start to shift at a slightly smaller phase. This is due to the fact that, if NSDI is classically forbidden, the quantum mechanical distributions are exponentially decaying, whereas their classical counterparts vanish. This behavior is more extreme than those observed for other high-intensity phenomena, such as above-threshold ionization or high-harmonic generation, so that NSDI is an efficient tool for absolute-phase measurements. Refs. 3 (author)

  6. Direct observation of dopant distribution in GaAs compound semiconductors using phase-shifting electron holography and Lorentz microscopy.

    Science.gov (United States)

    Sasaki, Hirokazu; Otomo, Shinya; Minato, Ryuichiro; Yamamoto, Kazuo; Hirayama, Tsukasa

    2014-06-01

    Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in GaAs compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p-n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10(19) cm(-3) and 1 × 10(18) cm(-3) regions were clearly observed by using phase-shifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image. © The Author 2014. 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.

  7. The Phase-I Trigger Readout Electronics Upgrade of the ATLAS Liquid Argon Calorimeters

    CERN Document Server

    Yang, Yi-lin; The ATLAS collaboration

    2018-01-01

    The Super Cell has been proposed in the Phase-I LAr upgrade to replace the existing trigger system "Trigger Tower" due to higher luminosity environments in Run 3 at LHC. The higher granularity of the Super Cell trigger systems requires higher data transmission and processing rate. The new system is also needed to be compatible with the existing trigger system. To fulfill these requirements, the new electronics including frond end and back end are developed. In the front-end part, the new LSB sums the LAr cell signals into Super Cell signals. The new baseplane distributes analog signals among FEBs, LTDB and TBB. The LTDB sums Super Cell signals to Trigger Tower signals and redirected the signals to TBB. The Analog signals are also digitized in LTDB and then sent to back end electronics. In the back-end part, the architecture is based on ATCA. The LAr carrier is used for monitoring and controlling. The LATOMEs inserted into the LAr carrier provide energy calculation from the digitized signals. So far, the demon...

  8. Proposal for a study of laser acceleration of electrons using micrograting structures at ATF (Phase 1)

    International Nuclear Information System (INIS)

    Chen, W.; Claus, J.; Fernow, R.C.

    1989-01-01

    We propose to investigate new methods of particle acceleration using a short-pulse CO 2 laser as the power source and grating-like structures as accelerator ''cavities''. Phase I of this program is intended to demonstrate the principle of the method. We will focus the laser light to a 3 mm line on the surface of the microstructure. The structure is used to transform the electric field pattern of the incoming transversely polarized laser beam to a mode which has a component along the electron beam direction in the vicinity of the surface. With 6 mJ of laser energy and a 6 ps pulse length, the electric field in the spot will be around 1 GV/m. The electron beam from the Brookhaven Accelerator Test Facility (ATF) will be focused transversely within the few micron transverse dimension of the microstructure. The maximum expected acceleration for a 1 GV/m field and a 3 mm acceleration length is 3 MeV. 17 refs., 11 figs., 2 tabs

  9. Constructal design of phase change material enclosures used for cooling electronic devices

    International Nuclear Information System (INIS)

    Kalbasi, Rasool; Salimpour, Mohammad Reza

    2015-01-01

    Recent developments in cooling methods for portable electronic devices have heightened the need for using the large latent heat capacity of phase change materials (PCM). The aim of the present study is to evaluate the thermal characteristics of a PCM-based heat sink with high conductive materials. The solution is acquired as a procession of optimization stages which starts with the elemental area and proceeds toward the first assembly. Every optimization stage is the result of maximizing the safe operation time without allowing the electronics to reach the critical temperature. Primarily, the degrees of freedom and constrains were defined and then by changing the geometrical parameters, the target function which is the maximization of operation time, was optimized. Results show that the melting process in rectangular enclosures with vertical fins attached to the heated bottom surface can be affected by the contact surface between the fin and PCM and the convection of the melted PCM. For a rectangular enclosure with a constant area, it is better to use wider enclosure than the square and thin one. Also results indicate that the ratio of the vertical fin thickness to the horizontal one does not have a considerable effect on performance. By increasing the number of enclosures, the contact surface is raised, but the performance is not necessarily improved. - Highlights: • Thermal characteristics of a finned PCM-based heat sink are studied. • Constructal theory was used to optimize the PCM enclosures. • By increasing the number of enclosures, the performance is not necessarily improved

  10. Correlated structural and electronic phase transformations in transition metal chalcogenide under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chunyu, E-mail: licy@hpstar.ac.cn, E-mail: yanhao@hpstar.ac.cn; Ke, Feng; Yu, Zhenhai; Chen, Zhiqiang; Yan, Hao, E-mail: licy@hpstar.ac.cn, E-mail: yanhao@hpstar.ac.cn [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 (China); Hu, Qingyang [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 (China); Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States); Zhao, Jinggeng [Natural Science Research Center, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080 (China)

    2016-04-07

    Here, we report comprehensive studies on the high-pressure structural and electrical transport properties of the layered transition metal chalcogenide (Cr{sub 2}S{sub 3}) up to 36.3 GPa. A structural phase transition was observed in the rhombohedral Cr{sub 2}S{sub 3} near 16.5 GPa by the synchrotron angle dispersive X-ray diffraction measurement using a diamond anvil cell. Through in situ resistance measurement, the electric resistance value was detected to decrease by an order of three over the pressure range of 7–15 GPa coincided with the structural phase transition. Measurements on the temperature dependence of resistivity indicate that it is a semiconductor-to-metal transition in nature. The results were also confirmed by the electronic energy band calculations. Above results may shed a light on optimizing the performance of Cr{sub 2}S{sub 3} based applications under extreme conditions.

  11. Electroluminescence pulse shape and electron diffusion in liquid argon measured in a dual-phase TPC

    Energy Technology Data Exchange (ETDEWEB)

    Agnes, P.; et al.

    2018-02-05

    We report the measurement of the longitudinal diffusion constant in liquid argon with the DarkSide-50 dual-phase time projection chamber. The measurement is performed at drift electric fields of 100 V/cm, 150 V/cm, and 200 V/cm using high statistics $^{39}$Ar decays from atmospheric argon. We derive an expression to describe the pulse shape of the electroluminescence signal (S2) in dual-phase TPCs. The derived S2 pulse shape is fit to events from the uppermost portion of the TPC in order to characterize the radial dependence of the signal. The results are provided as inputs to the measurement of the longitudinal diffusion constant DL, which we find to be (4.12 $\\pm$ 0.04) cm$^2$/s for a selection of 140keV electron recoil events in 200V/cm drift field and 2.8kV/cm extraction field. To study the systematics of our measurement we examine datasets of varying event energy, field strength, and detector volume yielding a weighted average value for the diffusion constant of (4.09 $\\pm$ 0.09) cm$^2$ /s. The measured longitudinal diffusion constant is observed to have an energy dependence, and within the studied energy range the result is systematically lower than other results in the literature.

  12. Transmission electron microscopy characterization of the interfacial structure of a galvanized dual-phase steel

    Energy Technology Data Exchange (ETDEWEB)

    Aslam, I., E-mail: ia31@msstate.edu [Center for Advanced Vehicular Systems, Mississippi State University, MS 39759 (United States); Department of Mechanical Engineering, Mississippi State University, MS 39762 (United States); Li, B. [Center for Advanced Vehicular Systems, Mississippi State University, MS 39759 (United States); Department of Chemical and Materials Engineering, University of Nevada, Reno, NV 89557 (United States); Martens, R.L.; Goodwin, J.R. [Central Analytical Facility, the University of Alabama, Tuscaloosa, AL 35487 (United States); Rhee, H.J. [Center for Advanced Vehicular Systems, Mississippi State University, MS 39759 (United States); Department of Mechanical Engineering, Mississippi State University, MS 39762 (United States); Goodwin, F. [International Zinc Association, Durham, NC 27713 (United States)

    2016-10-15

    Site-specific studies were carried out to characterize the interface of a galvanized dual-phase (DP) steel. Focused ion beam (FIB) was used to prepare specimens in the interface region (~ 100 nm thick) between the coating and the substrate. Transmission electron microscopy (TEM), scanning TEM (STEM), and high resolution TEM (HRTEM) were performed to resolve the phases and the structures at the interface between the zinc (Zn) coating and the steel substrate. The STEM and TEM results showed that a continuous manganese oxide (MnO) film with a thickness of ~ 20 nm was present on the surface of the substrate while no silicon (Si) oxides were resolved. Internal oxide particles were observed as well in the sub-surface region. Despite the presence of the continuous oxide film, a well-developed inhibition layer was observed right on top of the oxide film. The inhibition layer has a thickness of ~ 100 nm. Possible mechanisms for the growth of the inhibition layer were discussed. - Highlights: •Site-specific examinations were performed on the Zn/steel interface. •Continuous external MnO oxides (20 nm) were observed at the interface. •No Si oxides were observed at the interface. •Internal oxide particles were distributed in the subsurface. •A continuous inhibition layer grew on top of the external oxides.

  13. Phased-array antenna system for electron Bernstein wave heating and current drive experiments in QUEST

    International Nuclear Information System (INIS)

    Idei, H.; Sakaguchi, M.; Kalinnikova, E.I.

    2010-11-01

    The phased-array antenna system for Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments has been developed in the QUEST. The antenna was designed to excite a pure O-mode wave in the oblique injection for the EBWH/CD experiments, and was tested at a low power level. The measured two orthogonal fields were in excellent agreements with the fields evaluated by a developed Kirchhoff code. The heat load and thermal stress in CW 200 kW operation were analyzed with finite element codes. The phased array has been fast scanned [∼10 4 degree/s] to control the incident polarization and angle to follow time evolutions of the plasma current and density. The RF startup and sustainment experiments were conducted using the developed antenna system. The plasma current (< ∼15 kA) with an aspect ratio of 1.5 was started up and sustained by only RF injection. The long pulse discharge of 10 kA was attained for 40 s with the 30 kW injection. (author)

  14. Mechanism of Pseudogap Detected by Electronic Raman Scattering: Phase Fluctuation or Hidden Order?

    International Nuclear Information System (INIS)

    Hong-Yan, Lu; Yuan, Wan; Xiang-Mei, He; Qiang-Hua, Wang

    2009-01-01

    We study the electronic Raman scattering in the cuprates to distinguish the two possible scenarios of the pseudo-gap normal state. In one scenario, the pseudogap is assumed to be caused by phase fluctuations of the preformed Cooper pairs. We find that pair-breaking peaks appear in both the B 1g and B 2g Raman channels, and they are smeared and tend to shift to the same energy with the increasing strength of phase fluctuations. Thus both channels reflect the same pairing energy scale, irrespectively of the doping level. In another scenario, the pseudogap is assumed to be caused by a hidden order that competes with the superconducting order. As an example, we assume that the hidden order is the d-density-wave (DDW) order. We find analytically and numerically that in the DDW normal state there is no Raman peak in the B 2g channel in a tight-binding model up to the second nearest-neighbor hopping, while the Raman peak in the B 1g channel reflects the energy gap caused by the DDW order. This behavior is in agreement with experiments in the pseudogap normal state. To gain further insights, we also calculate the Raman spectra in the DDW+SC state. We study the doping and temperature dependence of the peak energy in both channels and find a two-gap behavior, which is in agreement with recent Raman experiments. Therefore, our results shed light on the hidden order scenario for the pseudogap

  15. 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)

  16. Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

    Science.gov (United States)

    Wienkes, Lee Raymond

    Interest in mixed-phase silicon thin film materials, composed of an amorphous semiconductor matrix in which nanocrystalline inclusions are embedded, stems in part from potential technological applications, including photovoltaic and thin film transistor technologies. Conventional mixed-phase silicon films are produced in a single plasma reactor, where the conditions of the plasma must be precisely tuned, limiting the ability to adjust the film and nanoparticle parameters independently. The films presented in this thesis are deposited using a novel dual-plasma co-deposition approach in which the nanoparticles are produced separately in an upstream reactor and then injected into a secondary reactor where an amorphous silicon film is being grown. The degree of crystallinity and grain sizes of the films are evaluated using Raman spectroscopy and X-ray diffraction respectively. I describe detailed electronic measurements which reveal three distinct conduction mechanisms in n-type doped mixed-phase amorphous/nanocrystalline silicon thin films over a range of nanocrystallite concentrations and temperatures, covering the transition from fully amorphous to ~30% nanocrystalline. As the temperature is varied from 470 to 10 K, we observe activated conduction, multiphonon hopping (MPH) and Mott variable range hopping (VRH) as the nanocrystal content is increased. The transition from MPH to Mott-VRH hopping around 100K is ascribed to the freeze out of the phonon modes. A conduction model involving the parallel contributions of these three distinct conduction mechanisms is shown to describe both the conductivity and the reduced activation energy data to a high accuracy. Additional support is provided by measurements of thermal equilibration effects and noise spectroscopy, both done above room temperature (>300 K). This thesis provides a clear link between measurement and theory in these complex materials.

  17. Visualization of phase evolution in model organic photovoltaic structures via energy-filtered transmission electron microscopy.

    Science.gov (United States)

    Herzing, Andrew A; Ro, Hyun Wook; Soles, Christopher L; DeLongchamp, Dean M

    2013-09-24

    The morphology of the active layer in an organic photovoltaic bulk-heterojunction device is controlled by the extent and nature of phase separation during processing. We have studied the effects of fullerene crystallinity during heat treatment in model structures consisting of a layer of poly(3-hexylthiophene) (P3HT) sandwiched between two layers of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Utilizing a combination of focused ion-beam milling and energy-filtered transmission electron microscopy, we monitored the local changes in phase distribution as a function of annealing time at 140 °C. In both cases, dissolution of PCBM within the surrounding P3HT was directly visualized and quantitatively described. In the absence of crystalline PCBM, the overall phase distribution remained stable after intermediate annealing times up to 60 s, whereas microscale PCBM aggregates were observed after annealing for 300 s. Aggregate growth proceeded vertically from the substrate interface via uptake of PCBM from the surrounding region, resulting in a large PCBM-depleted region in their vicinity. When precrystallized PCBM was present, amorphous PCBM was observed to segregate from the intermediate P3HT layer and ripen the crystalline PCBM underneath, owing to the far lower solubility of crystalline PCBM within P3HT. This process occurred rapidly, with segregation already evident after annealing for 10 s and with uptake of nearly all of the amorphous PCBM by the crystalline layer after 60 s. No microscale aggregates were observed in the precrystallized system, even after annealing for 300 s.

  18. Local probe investigations of the electronic phase diagrams of iron pnictides and chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Materne, Philipp

    2015-09-24

    In this work, the electronic phase diagrams of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} and Fe{sub 1+y}Te were investigated using muon spin relaxation and Moessbauer spectroscopy. Single crystals of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} with x = 0.00, 0.35, 0.50, and 0.67 were examined. The undoped 122 parent compound CaFe{sub 2}As{sub 2} is a semi metal and shows antiferromagnetic commensurate spin density wave order below 167 K. By hole doping via Na substitution, the magnetic order is suppressed and superconductivity emerges including a Na-substitution level region, where both phases coexist. Upon Na substitution, a tilting of the magnetic moments out of the ab-plane is found. The interaction of the magnetic and superconducting order parameter in this coexistence region was studied and a nanoscopic coexistence of both order parameters is found. This is proven by a reduction of the magnetic order parameter of 7 % in x = 0.50 below the superconducting transition temperature. This reduction was analysed using Landau theory and a systematic correlation between the reduction of the magnetic order parameter and the ratio of the transition temperatures, T{sub c}/T{sub N}, for the 122 family of the iron pnictides is presented. The magnetic phase transition is accompanied by a tetragonal-to-orthorhombic phase transition. The lattice dynamics at temperatures above and below this magneto-structural phase transition were studied and no change in the lattice dynamics were found. However, the lattice for finite x is softer than for the undoped compound. For x = 0.67, diluted magnetic order is found. Therefore, the magnetism in Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} is persistent even at optimal doping. The superconducting state is investigated by measuring the temperature dependence of the magnetic penetration depth, where two superconducting gaps with a weighting of nearly 50:50 are obtained. A temperature independent anisotropy of the magnetic penetration depth γ{sub

  19. Local probe investigations of the electronic phase diagrams of iron pnictides and chalcogenides

    International Nuclear Information System (INIS)

    Materne, Philipp

    2015-01-01

    In this work, the electronic phase diagrams of Ca 1-x Na x Fe 2 As 2 and Fe 1+y Te were investigated using muon spin relaxation and Moessbauer spectroscopy. Single crystals of Ca 1-x Na x Fe 2 As 2 with x = 0.00, 0.35, 0.50, and 0.67 were examined. The undoped 122 parent compound CaFe 2 As 2 is a semi metal and shows antiferromagnetic commensurate spin density wave order below 167 K. By hole doping via Na substitution, the magnetic order is suppressed and superconductivity emerges including a Na-substitution level region, where both phases coexist. Upon Na substitution, a tilting of the magnetic moments out of the ab-plane is found. The interaction of the magnetic and superconducting order parameter in this coexistence region was studied and a nanoscopic coexistence of both order parameters is found. This is proven by a reduction of the magnetic order parameter of 7 % in x = 0.50 below the superconducting transition temperature. This reduction was analysed using Landau theory and a systematic correlation between the reduction of the magnetic order parameter and the ratio of the transition temperatures, T c /T N , for the 122 family of the iron pnictides is presented. The magnetic phase transition is accompanied by a tetragonal-to-orthorhombic phase transition. The lattice dynamics at temperatures above and below this magneto-structural phase transition were studied and no change in the lattice dynamics were found. However, the lattice for finite x is softer than for the undoped compound. For x = 0.67, diluted magnetic order is found. Therefore, the magnetism in Ca 1-x Na x Fe 2 As 2 is persistent even at optimal doping. The superconducting state is investigated by measuring the temperature dependence of the magnetic penetration depth, where two superconducting gaps with a weighting of nearly 50:50 are obtained. A temperature independent anisotropy of the magnetic penetration depth γ λ = 1.5(4) is obtained, which is much smaller compared to other 122 compounds

  20. The inversion layer of electric fields and electron phase-space-hole structure during two-dimensional collisionless magnetic reconnection

    International Nuclear Information System (INIS)

    Chen Lijen; Lefebvre, Bertrand; Torbert, Roy B.; Daughton, William S.

    2011-01-01

    Based on two-dimensional fully kinetic simulations that resolve the electron diffusion layer in undriven collisionless magnetic reconnection with zero guide field, this paper reports the existence and evolution of an inversion layer of bipolar electric fields, its corresponding phase-space structure (an electron-hole layer), and the implication to collisionless dissipation. The inversion electric field layer is embedded in the layer of bipolar Hall electric field and extends throughout the entire length of the electron diffusion layer. The electron phase-space hole structure spontaneously arises during the explosive growth phase when there exist significant inflows into the reconnection layer, and electrons perform meandering orbits across the layer while being cyclotron-turned toward the outflow directions. The cyclotron turning of meandering electrons by the magnetic field normal to the reconnection layer is shown to be a primary factor limiting the current density in the region where the reconnection electric field is balanced by the gradient (along the current sheet normal) of the off-diagonal electron pressure-tensor.

  1. Experimental status of unified theories

    International Nuclear Information System (INIS)

    Bilen'kij, S.M.

    1979-01-01

    A standard SU(2)xU(1) theory is discussed. It is based on an assumption that the left components of fields form doublets, and the rignt ones - singlets. From the weak interaction lagrangian an expression is obtained for the effective hamiltonian describing neutrino-lepton processes. The results of discussing the experimental status of the unified theories of weak and electromagnetic interactions are in agreement with the simplest version of the unified theories - the Weinberg-Salam theory. It has been noted that the accuracy of the experiments (not exceeding 20%) is insufficient and no information is available on diagonal terms of the hamiltonian

  2. The Simplest Unified Growth Theory

    DEFF Research Database (Denmark)

    Strulik, Holger; Weisdorf, Jacob Louis

    This paper provides a unified growth theory, i.e. a model that explains the very long-run economic and demographic development path of industrialized economies, stretching from the pre-industrial era to present-day and beyond. Making strict use of Malthus' (1798) so-called preventive check...... hypothesis - that fertility rates vary inversely with the price of food - the current study offers a new and straightforward explanation for the demographic transition and the break with the Malthusian era. The current framework lends support to existing unified growth theories and is well in tune...

  3. Hybridization approach to in-line and off-axis (electron) holography for superior resolution and phase sensitivity

    Science.gov (United States)

    Ozsoy-Keskinbora, C.; Boothroyd, C. B.; Dunin-Borkowski, R. E.; van Aken, P. A.; Koch, C. T.

    2014-01-01

    Holography - originally developed for correcting spherical aberration in transmission electron microscopes - is now used in a wide range of disciplines that involve the propagation of waves, including light optics, electron microscopy, acoustics and seismology. In electron microscopy, the two primary modes of holography are Gabor's original in-line setup and an off-axis approach that was developed subsequently. These two techniques are highly complementary, offering superior phase sensitivity at high and low spatial resolution, respectively. All previous investigations have focused on improving each method individually. Here, we show how the two approaches can be combined in a synergetic fashion to provide phase information with excellent sensitivity across all spatial frequencies, low noise and an efficient use of electron dose. The principle is also expected to be widely to applications of holography in light optics, X-ray optics, acoustics, ultra-sound, terahertz imaging, etc. PMID:25387480

  4. Phase mixing of transverse oscillations in the linear and nonlinear regimes for IFR relativistic electron beam propagation

    International Nuclear Information System (INIS)

    Shokair, I.R.

    1991-01-01

    Phase mixing of transverse oscillations changes the nature of the ion hose instability from an absolute to a convective instability. The stronger the phase mixing, the faster an electron beam reaches equilibrium with the guiding ion channel. This is important for long distance propagation of relativistic electron beams where it is desired that transverse oscillations phase mix within a few betatron wavelengths of injection and subsequently an equilibrium is reached with no further beam emittance growth. In the linear regime phase mixing is well understood and results in asymptotic decay of transverse oscillations as 1/Z 2 for a Gaussian beam and channel system, Z being the axial distance measured in betatron wavelengths. In the nonlinear regime (which is likely mode of propagation for long pulse beams) results of the spread mass model indicate that phase mixing is considerably weaker than in the regime. In this paper we consider this problem of phase mixing in the nonlinear regime. Results of the spread mass model will be shown along with a simple analysis of phase mixing for multiple oscillator models. Particle simulations also indicate that phase mixing is weaker in nonlinear regime than in the linear regime. These results will also be shown. 3 refs., 4 figs

  5. Investigations on the electron bunch distribution in the longitudinal phase space at a laser driven RF electron source for the European X-FEL

    Energy Technology Data Exchange (ETDEWEB)

    Roensch, Juliane

    2010-01-15

    The Photoinjector Test facility at DESY, Zeuthen site, (PITZ) is aiming for the optimization of electron guns for SAS-FELs. For this it is necessary to investigate the characteristics of the six dimensional phase space of the bunch produced by a photoinjector. This thesis is focused on the analysis of the longitudinal properties of the electron bunch distribution, this means the temporal current distribution and the momentum distribution as well as the correlation of both properties. The complete distribution of the electron bunch in longitudinal phase space of a photoinjector was measured directly for the first time at a beam momentum of about 5 MeV/c, using an existing apparatus. This system had been designed for an accelerating gradient of 40 MV/m. Its subcomponents were analysed to understand sources of uncertainties of the measurement system. The usage of higher accelerating gradients in the gun (60 MV/m, resulting in a beam momentum of about 6.8 MeV/c) demands major modifications of the existing measurement system for the longitudinal phase space distribution. An upgrade of the facility by an additional accelerating cavity required the design of further longitudinal diagnostics systems for the analysis at higher momenta (up to 40 MeV/c). Measurements of the longitudinal beam properties to determine the influence of different operation parameters, like RF launch phase, charge, accelerating field gradient and laser distribution were performed and compared to simulations. (orig.)

  6. Investigations on the electron bunch distribution in the longitudinal phase space at a laser driven RF electron source for the European X-FEL

    International Nuclear Information System (INIS)

    Roensch, Juliane

    2010-01-01

    The Photoinjector Test facility at DESY, Zeuthen site, (PITZ) is aiming for the optimization of electron guns for SAS-FELs. For this it is necessary to investigate the characteristics of the six dimensional phase space of the bunch produced by a photoinjector. This thesis is focused on the analysis of the longitudinal properties of the electron bunch distribution, this means the temporal current distribution and the momentum distribution as well as the correlation of both properties. The complete distribution of the electron bunch in longitudinal phase space of a photoinjector was measured directly for the first time at a beam momentum of about 5 MeV/c, using an existing apparatus. This system had been designed for an accelerating gradient of 40 MV/m. Its subcomponents were analysed to understand sources of uncertainties of the measurement system. The usage of higher accelerating gradients in the gun (60 MV/m, resulting in a beam momentum of about 6.8 MeV/c) demands major modifications of the existing measurement system for the longitudinal phase space distribution. An upgrade of the facility by an additional accelerating cavity required the design of further longitudinal diagnostics systems for the analysis at higher momenta (up to 40 MeV/c). Measurements of the longitudinal beam properties to determine the influence of different operation parameters, like RF launch phase, charge, accelerating field gradient and laser distribution were performed and compared to simulations. (orig.)

  7. Electronic structure and physical properties of the spinel-type phase of BeP2N4 from all-electron density functional calculations

    International Nuclear Information System (INIS)

    Ching, W. Y.; Aryal, Sitram; Rulis, Paul; Schnick, Wolfgang

    2011-01-01

    Using density-functional-theory-based ab initio methods, the electronic structure and physical properties of the newly synthesized nitride BeP 2 N 4 with a phenakite-type structure and the predicted high-pressure spinel phase of BeP 2 N 4 are studied in detail. It is shown that both polymorphs are wide band-gap semiconductors with relatively small electron effective masses at the conduction-band minima. The spinel-type phase is more covalently bonded due to the increased number of P-N bonds for P at the octahedral sites. Calculations of mechanical properties indicate that the spinel-type polymorph is a promising superhard material with notably large bulk, shear, and Young's moduli. Also calculated are the Be K, P K, P L 3 , and N K edges of the electron energy-loss near-edge structure for both phases. They show marked differences because of the different local environments of the atoms in the two crystalline polymorphs. These differences will be very useful for the experimental identification of the products of high-pressure syntheses targeting the predicted spinel-type phase of BeP 2 N 4 .

  8. Toward a Unified Communication Theory.

    Science.gov (United States)

    McMillan, Saundra

    After discussing the nature of theory itself, the author explains her concept of the Unified Communication Theory, which rests on the assumption that there exists in all living structures a potential communication factor which is delimited by species and ontogeny. An organism develops "symbol fixation" at the level where its perceptual abilities…

  9. A model unified field equation

    International Nuclear Information System (INIS)

    Perring, J.K.; Skyrme, T.H.R.

    1994-01-01

    The classical solutions of a unified field theory in a two-dimensional space-time are considered. This system, a model of a interacting mesons and baryons, illustrates how the particle can be built from a wave-packet of mesons and how reciprocally the meson appears as a tightly bound combination of particle and antiparticle. (author). 6 refs

  10. Electronic Structure Properties and a Bonding Model of Thermoelectric Half-Heusler and Boride Phases

    Science.gov (United States)

    Simonson, Jack William

    Half-Heusler alloys MNiSn and MCoSb (M = Ti, Zr, Hf) and layered boride intermetallics with structure types YCrB4 and Er 3CrB7 were designed, synthesized, and characterized. The thermoelectric properties of these two classes of alloys were measured from room temperature to 1100 K with the intent of indirectly studying their electronic structure properties and gauging not only their suitability but that of related alloys for high temperature thermoelectric power generation. In the case of the half-Heusler alloys, transition metals were substituted to both the M and Ni/Co sites to study the resultant modifications of the d-orbital-rich portion of the electronic structure near the Fermi energy. This modification and subsequent pinning of the Fermi energy within the gap is discussed herein in terms of first principles electronic structure calculations from the literature. In the half-Heusler alloys, it was found that substitution of transition metals invariably led to a decrease in the thermopower, while the resistivity typically maintained its semiconducting trend. On the other hand, Sn doping in MCoSb type alloys -- a dopant that has been known for some time to be efficient -- was shown to result in high ZT at temperatures in excess of 1000 K. Moreover, the band gaps of the transition metal-doped alloys measured in this work offer insight into the discrepancy between the predicted and measured band gaps in the undoped parent compositions. In the case of the layered boride alloys, on the other hand, few electronic calculations have been published, thus prompting the generalization of a well-known electron counting rule -- which is typically used to study molecular organometallics, boranes, and metallocenes -- to predict the trends in the densities of states of crystalline solids that possess the requisite deltahedral bonding geometry. In accordance with these generalized electronic counting rules, alloys of the form RMB4 (R = Y, Gd, Ho; M = Cr, Mo, W) were measured to

  11. Hydrogen-Induced Phase Transformation and Microstructure Evolution for Ti-6Al-4V Parts Produced by Electron Beam Melting

    Directory of Open Access Journals (Sweden)

    Natalia Pushilina

    2018-04-01

    Full Text Available In this paper, phase transitions and microstructure evolution in titanium Ti-6Al-4V alloy parts produced by electron beam melting (EBM under hydrogenation was investigated. Hydrogenation was carried out at the temperature of 650 °C to the absolute hydrogen concentrations in the samples of 0.29, 0.58, and 0.90 wt. %. Comparative analysis of microstructure changes in Ti-6Al-4V alloy parts was performed using scanning electron microscopy (SEM, transmission electron microscopy (TEM, and X-ray diffraction (XRD. Furthermore, in-situ XRD was used to investigate the phase transitions in the samples during hydrogenation. The structure of Ti-6Al-4V parts produced by EBM is represented by the α phase plates with the transverse length of 0.2 μm, the β phase both in the form of plates and globular grains, and metastable α″ and ω phases. Hydrogenation to the concentration of 0.29 wt. % leads to the formation of intermetallic Ti3Al phase. The dimensions of intermetallic Ti3Al plates and their volume fraction increase significantly with hydrogen concentration up to 0.58 wt. % along with precipitation of nano-sized crystals of titanium δ hydrides. Individual Ti3Al plates decay into nanocrystals with increasing hydrogen concentration up to 0.9 wt. % accompanied by the increase of proportion and size of hydride plates. Hardness of EBM Ti-6Al-4V alloy decreases with hydrogen content.

  12. Application of Ab Initio Electronic Structure Calculations in Construction of Phase Diagrams of Metallic Systems with Complex Phases

    Czech Academy of Sciences Publication Activity Database

    Šob, Mojmír; Kroupa, Aleš; Pavlů, Jana; Vřešťál, Jan

    2009-01-01

    Roč. 150, č. 1 (2009), s. 1-28 ISSN 1012-0394 R&D Projects: GA MŠk OC 147; GA ČR GA106/07/1078 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ab initio calculations * CALPHAD method * Laves phases * sigma phase * ternary systems * super-austenitic steels Subject RIV: BM - Solid Matter Physics ; Magnetism

  13. A novel, flat, electronically-steered phased array transducer for tissue ablation: preliminary results

    International Nuclear Information System (INIS)

    Ellens, Nicholas P K; Lucht, Benjamin B C; Gunaseelan, Samuel T; Hudson, John M; Hynynen, Kullervo H

    2015-01-01

    Flat, λ/2-spaced phased arrays for therapeutic ultrasound were examined in silico and in vitro. All arrays were made by combining modules made of 64 square elements with 1.5 mm inter-element spacing along both major axes. The arrays were designed to accommodate integrated, co-aligned diagnostic transducers for targeting and monitoring. Six arrays of 1024 elements (16 modules) and four arrays of 6144 elements (96 modules) were modelled and compared according to metrics such as peak pressure amplitude, focal size, ability to be electronically-steered far off-axis and grating lobe amplitude. Two 1024 element prototypes were built and measured in vitro, producing over 100 W of acoustic power. In both cases, the simulation model of the pressure amplitude field was in good agreement with values measured by hydrophone. Using one of the arrays, it was shown that the peak pressure amplitude dropped by only 24% and 25% of the on-axis peak pressure amplitude when steered to the edge of the array (40 mm) at depths of 30 mm and 50 mm. For the 6144 element arrays studied in in silico only, similarly high steerability was found: even when steered 100 mm off-axis, the pressure amplitude decrease at the focus was less than 20%, while the maximum pressure grating lobe was only 20%. Thermal simulations indicate that the modules produce more than enough acoustic power to perform rapid ablations at physiologically relevant depths and steering angles. Arrays such as proposed and tested in this study have enormous potential: their high electronic steerability suggests that they will be able to perform ablations of large volumes without the need for any mechanical translation. (paper)

  14. Electron Scattering Studies of Gas Phase Molecular Structure at High Temperature

    Science.gov (United States)

    Mawhorter, Richard J., Jr.

    A high precision counting electron diffraction study of the structure of gaseous sulfur dioxide as a function of temperature from 300(DEGREES) to 1000(DEGREES)K is presented. The results agree well with current theory, and yield insight into the effects of anharmonicity on molecular structure. Another aspect of molecular structure is the molecular charge density distribution. The difference (DELTA)(sigma) is between the electron scattering cross sections for the actual molecule and independent atom model (IAM) are a sensitive measure of the change in this distribution due to bond formation. These difference cross sections have been calculated using ab initio methods, and the results for a wide range of simple polyatomic molecules are presented. Such calculations are routinely done for a single, fixed molecular geometry, an approach which neglects the effects of the vibrational motion of real molecules. The effect of vibrational averaging is studied in detail for the three normal vibrational modes of H(,2)O in the ground state. The effects are small, lending credence to the practice of comparing cross sections calculated at a fixed geometry with inherently averaged experimental data. The efficacy of the standard formula used to account for vibrational averaging in the IAM is also examined. Finally, the nature of the ionic bond is probed with an experimental study of the structure of alkali chlorides, NaCl, KCl, RbCl, and CsCl, in the gas phase. Temperatures from 840-960(DEGREES)K were required to achieve the necessary vapor pressures of approximately 0.01 torr. A planar rhombic structure for the dimer molecule is confirmed, with a fairly uniform decrease of the chlorine-alkali-chlorine angle as the alkalis increase in size. The experiment also yields information on the amount of dimer present in the vapor, and these results are compared with thermodynamic values.

  15. A unified dynamics for micro and macrosystems

    International Nuclear Information System (INIS)

    Ghirardi, G.C.; Rimini, A.; Weber, T.

    1985-12-01

    An explicit model allowing a unified description of micro and macrosystems is exhibited. Firstly, a modified quantum dynamics for the description of macroobjects is constructed and it is shown that it forbids the occurrence of linear superpositions of states localized in far away spatial regions and induces an evolution agreeing with classical mechanics. This dynamics also allows a description of the evolution in terms of trajectories. To set up a unified description of all physical phenomena, a modification of the dynamics, with respect to the standard Hamiltonian one, is then postulated also for microscopic systems. It is shown that one can consistently deduce from it the previously considered dynamics for the centre of mass of macroscopic systems. Choosing in an appropriate way the parameters of the so obtained model one can show that the standard quantum theory for microobjects, the quantum mechanical wave packet reduction with fixed pointer positions, and the classical behaviour for macroobjects can be all derived in a consistent way. Moreover, in the case of a macroscopic system one can obtain, by means of appropriate approximations, a description of the evolution in terms of a phase-space density distribution obeying a Fokker-Planck diffusion equation. (author)

  16. Limit on the radiative neutrinoless double electron capture of "3"6Ar from GERDA Phase I

    International Nuclear Information System (INIS)

    Agostini, M.; Balata, M.; D'Andrea, V.; Di Vacri, A.; Junker, M.; Laubenstein, M.; Allardt, M.; Domula, A.; Lehnert, B.; Schneider, B.; Wester, T.; Wilsenach, H.; Zuber, K.; Bakalyarov, A.M.; Belyaev, S.T.; Lebedev, V.I.; Zhukov, S.V.; Barabanov, I.; Bezrukov, L.; Doroshkevich, E.; Fedorova, O.; Gurentsov, V.; Kazalov, V.; Kuzminov, V.V.; Lubsandorzhiev, B.; Moseev, P.; Selivanenko, O.; Veresnikova, A.; Yanovich, E.; Barros, N.; Baudis, L.; Benato, G.; Kish, A.; Miloradovic, M.; Mingazheva, R.; Walter, M.; Bauer, C.; Hakenmueller, J.; Heisel, M.; Heusser, G.; Hofmann, W.; Kihm, T.; Kirsch, A.; Knoepfle, K.T.; Lindner, M.; Maneschg, W.; Salathe, M.; Schreiner, J.; Schwingenheuer, B.; Simgen, H.; Smolnikov, A.; Stepaniuk, M.; Wagner, V.; Wegmann, A.; Bellotti, E.; Belogurov, S.; Kornoukhov, V.N.; Bettini, A.; Brugnera, R.; Garfagnini, A.; Medinaceli, E.; Sada, C.; Sturm, K. von; Bode, T.; Csathy, J.J.; Lazzaro, A.; Schoenert, S.; Wiesinger, C.; Borowicz, D.; Brudanin, V.; Egorov, V.; Kochetov, O.; Nemchenok, I.; Rumyantseva, N.; Zhitnikov, I.; Zinatulina, D.; Caldwell, A.; Gooch, C.; Kneissl, R.; Liao, H.Y.; Majorovits, B.; Palioselitis, D.; Schulz, O.; Vanhoefer, L.; Cattadori, C.; Salamida, F.; Chernogorov, A.; Demidova, E.V.; Kirpichnikov, I.V.; Vasenko, A.A.; Falkenstein, R.; Freund, K.; Grabmayr, P.; Hegai, A.; Jochum, J.; Schmitt, C.; Schuetz, A.K.; Frodyma, N.; Misiaszek, M.; Panas, K.; Pelczar, K.; Wojcik, M.; Zuzel, G.; Gangapshev, A.; Gusev, K.; Hemmer, S.; Lippi, I.; Stanco, L.; Hult, M.; Lutter, G.; Inzhechik, L.V.; Klimenko, A.; Lubashevskiy, A.; Macolino, C.; Pandola, L.; Pullia, A.; Riboldi, S.; Shirchenko, M.

    2016-01-01

    Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron capture of "3"6Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array (Gerda) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of "3"6Ar was established: T_1_/_2 > 3.6 x 10"2"1 years at 90% CI. (orig.)

  17. Phase-Space Density Analyses of the AE-8 Trapped Electron and the AP-8 Trapped Proton Model Environments

    International Nuclear Information System (INIS)

    Cayton, Thomas E.

    2005-01-01

    The AE-8 trapped electron and the AP-8 trapped proton models are used to examine the L-shell variation of phase-space densities for sets of transverse (or 1st) invariants, μ, and geometrical invariants, K (related to the first two adiabatic invariants). The motivation for this study is twofold: first, to discover the functional dependence of the phase-space density upon the invariants; and, second, to explore the global structure of the radiation belts within this context. Variation due to particle rest mass is considered as well. The overall goal of this work is to provide a framework for analyzing energetic particle data collected by instruments on Global Positioning System (GPS) spacecraft that fly through the most intense region of the radiation belt. For all considered values of μ and K, and for 3.5 R E E , the AE-8 electron phase-space density increases with increasing L; this trend--the expected one for a population diffusing inward from an external source--continues to L = 7.5 R E for both small and large values of K but reverses slightly for intermediate values of K. The AP-8 proton phase-space density exhibits μ-dependent local minima around L = 5 R E . Both AE-8 and AP-8 exhibit critical or cutoff values for the invariants beyond which the flux and therefore the phase-space density vanish. For both electrons and protons, these cutoff values vary systematically with magnetic moment and L-shell and are smaller than those estimated for the atmospheric loss cone. For large magnetic moments, for both electrons and protons, the K-dependence of the phase-space density is exponential, with maxima at the magnetic equator (K = 0) and vanishing beyond a cutoff value, K c . Such features suggest that momentum-dependent trapping boundaries, perhaps drift-type loss cones, serve as boundary conditions for trapped electrons as well as trapped protons

  18. Bias voltage effect on electron tunneling across a junction with a ferroelectric–ferromagnetic two-phase composite barrier

    International Nuclear Information System (INIS)

    Wang Jian; Ju Sheng; Li, Z.Y.

    2012-01-01

    The effect of bias voltage on electron tunneling across a junction with a ferroelectric–ferromagnetic composite barrier is investigated theoretically. Because of the inversion symmetry breaking of the spontaneous ferroelectric polarization, bias voltage dependence of the electron tunneling shows significant differences between the positive bias and the negative one. The differences of spin filtering or tunnel magnetoresistance increase with the increasing absolute value of bias voltage. Such direction preferred electron tunneling is found intimately related with the unusual asymmetry of the electrical potential profile in two-phase composite barrier and provides a unique change to realize rectifying functions in spintronics. - Highlights: ► Electron tunneling across a ferroelectric–ferromagnetic composite barrier junction. ► TMR effect is different under the same value but opposite direction bias voltage. ► This directionality of the electron tunneling enhances with increasing bias voltage.

  19. A Statistical Test of the Relationship Between Chorus Wave Activation and Anisotropy of Electron Phase Space Density

    Directory of Open Access Journals (Sweden)

    Dong-Hee Lee

    2014-12-01

    Full Text Available Whistler mode chorus wave is considered to play a critical role in accelerating and precipitating the electrons in the outer radiation belt. In this paper we test a conventional scenario of triggering chorus using THEMIS satellite observations of waves and particles. Specifically, we test if the chorus onset is consistent with development of anisotropy in the electron phase space density (PSD. After analyzing electron PSD for 73 chorus events, we find that, for ~80 % of them, their onsets are indeed associated with development of the positive anisotropy in PSD where the pitch angle distribution of electron velocity peaks at 90 degrees. This PSD anisotropy is prominent mainly at the electron energy range of ≤ ~20 keV. Interestingly, we further find that there is sometimes a time delay among energies in the increases of the anisotropy: A development of the positive anisotropy occurs earlier by several minutes for lower energy than for an adjacent higher energy.

  20. Electronic properties of in-plane phase engineered 1T'/2H/1T' MoS2

    Science.gov (United States)

    Thakur, Rajesh; Sharma, Munish; Ahluwalia, P. K.; Sharma, Raman

    2018-04-01

    We present the first principles studies of semi-infinite phase engineered MoS2 along zigzag direction. The semiconducting (2H) and semi-metallic (1T') phases are known to be stable in thin-film MoS2. We described the electronic and structural properties of the infinite array of 1T'/2H/1T'. It has been found that 1T'phase induced semi-metallic character in 2H phase beyond interface but, only Mo atoms in 2H phase domain contribute to the semi-metallic nature and S atoms towards semiconducting state. 1T'/2H/1T' system can act as a typical n-p-n structure. Also high holes concentration at the interface of Mo layer provides further positive potential barriers.

  1. Phase space determination from measured dose data for intraoperative electron radiation therapy.

    Science.gov (United States)

    Herranz, E; Herraiz, J L; Ibáñez, P; Pérez-Liva, M; Puebla, R; Cal-González, J; Guerra, P; Rodríguez, R; Illana, C; Udías, J M

    2015-01-07

    A procedure to characterize beams of a medical linear accelerator for their use in Monte Carlo (MC) dose calculations for intraoperative electron radiation therapy (IOERT) is presented. The procedure relies on dose measurements in homogeneous media as input, avoiding the need for detailed simulations of the accelerator head. An iterative algorithm (EM-ML) has been employed to extract the relevant details of the phase space (PHSP) of the particles coming from the accelerator, such as energy spectra, spatial distribution and angle of emission of particles. The algorithm can use pre-computed dose volumes in water and/or air, so that the machine-specific tuning with actual data can be performed in a few minutes. To test the procedure, MC simulations of a linear accelerator with typical IOERT applicators and energies, have been performed and taken as reference. A solution PHSP derived from the dose produced by the simulated accelerator has been compared to the reference PHSP. Further, dose delivered by the simulated accelerator for setups not included in the fit of the PHSP were compared to the ones derived from the solution PHSP. The results show that it is possible to derive from dose measurements PHSP accurate for IOERT MC dose estimations.

  2. The Trigger Readout Electronics for the Phase-1 Upgrade of the ATLAS Liquid-Argon Calorimeters

    CERN Document Server

    Wolff, Robert; The ATLAS collaboration

    2017-01-01

    The upgrade of the Large Hadron Collider (LHC) scheduled for the shut-down period of 2018-2019 (Phase-I upgrade), will increase the instantaneous luminosity to about three times the design value. Since the current ATLAS trigger system does not allow a corresponding increase of the trigger rate, an improvement of the trigger system is required. The new trigger signals from the ATLAS Liquid Argon Calorimeter will be arranged in 34000 so-called Super Cells which achieve 5-10 times better granularity than the current system; this improves the background rejection capabilities through more precise energy measurements, and the use of shower shapes to discriminate electrons and photons from jets. The new system will process the signal of the Super Cells at every LHC bunch-crossing at 12-bit precision and a frequency of 40 MHz. The data will be transmitted to the back-end using a custom serializer and optical converter with 5.12 Gb/s. To verify the full functionality, a demonstrator set-up has been installed on the A...

  3. Phase - I Trigger Readout Electronics upgrade for the ATLAS Liquid Argon Calorimeters

    CERN Document Server

    Dinkespiler, Bernard; The ATLAS collaboration

    2017-01-01

    The upgrade of the Large Hadron Collider (LHC) scheduled for shut-down period of 2018-2019, referred to as Phase-I upgrade, will increase the instantaneous luminosity to about three times the design value. Since the current ATLAS trigger system does not allow sufficient increase of the trigger rate, an improvement of the trigger system is required. The Liquid Argon (LAr) Calorimeter read-out will therefore be modified to use digital trigger signals with a higher spatial granularity in order to improve the identification efficiencies of electrons, photons, tau, jets and missing energy, at high background rejection rates at the Level-1 trigger. The new trigger signals will be arranged in 34000 so-called Super Cells which achieves 5-10 times better granularity than the trigger towers currently used and allows an improved background rejection. The readout of the trigger signals will process the signal of the Super Cells at every LHC bunch-crossing at 12-bit precision and a frequency of 40 MHz. The data will be tr...

  4. Phase-I Trigger Readout Electronics Upgrade for the ATLAS Liquid-Argon Calorimeters

    CERN Document Server

    Camplani, Alessandra; The ATLAS collaboration

    2017-01-01

    The upgrade of the Large Hadron Collider (LHC) scheduled for shut-down period of 2018-2019, referred to as Phase-I upgrade, will increase the instantaneous luminosity to about three times the design value. Since the current ATLAS trigger system does not allow sufficient increase of the trigger rate, an improvement of the trigger system is required. The Liquid Argon (LAr) Calorimeter read-out will therefore be modified to use digital trigger signals with a higher spatial granularity in order to improve the identification efficiencies of electrons, photons, tau, jets and missing energy, at high background rejection rates at the Level-1 trigger. The new trigger signals will be arranged in 34000 so-called Super Cells which achieves 5-10 times better granularity than the trigger towers currently used and allows an improved background rejection. The readout of the trigger signals will process the signal of the Super Cells at every LHC bunch-crossing at 12-bit precision and a frequency of 40 MHz. The data will be tr...

  5. Decomposition of gas-phase diphenylether at 473 K by electron beam generated plasma

    CERN Document Server

    Kim, H H; Kojima, T

    2003-01-01

    Decomposition of gas-phase diphenylether (DPE) in the order of several parts per million by volume (ppmv) was studied as a model compound of dioxin using a flow-type electron-beam reactor at an elevated temperature of 473 K. The ground state oxygen ( sup 3 P) atoms played an important role in the decomposition of DPE resulting in the formation of 1,4-hydroquinone (HQ) as a major ring retaining product. The high yield of hydroquinone indicated that the breakage of ether bond (C-O) is important in the initial step of DPE decomposition. Ring cleavage products were CO and CO sub 2 , and NO sub 2 was also produced from background N sub 2 -O sub 2. The sum of the yields of HQ, CO sub 2 and CO accounts for over 90% of the removed DPE. Hydroxyl radicals (OH) were less important in the dilute DPE decomposition at a high water content, and were mostly consumed by recombination reactions to form hydrogen peroxide. The smaller the initial DPE concentrations, the higher the decomposition efficiency and the lower the yield...

  6. EPR policies for electronics in developing Asia: an adapted phase-in approach.

    Science.gov (United States)

    Akenji, Lewis; Hotta, Yasuhiko; Bengtsson, Magnus; Hayashi, Shiko

    2011-09-01

    The amount of e-waste is growing rapidly in developing countries, and the health and environmental problems resulting from poor management of this waste have become a concern for policy makers. In response to these challenges, a number of Asian developing countries have been inspired by policy developments in OECD countries, and have drafted legislations based on the principle of extended producer responsibility (EPR). However, the experiences from developed countries show that a successful implementation of EPR policies requires adequate institutions and sufficient administrative capacity. Even advanced countries are thus facing difficulties. This paper concludes from existing literature and from the authors' own observations that there seems to be a mismatch between the typical policy responses to e-waste problems in developing Asia and the capacity for successful implementation of such policies. It also notes that the e-waste situation in developing Asian countries is further complicated by a number of additional factors, such as difficulties in identifying producers, import of used electronic products and e-waste (sometimes illegal), and the existence of a strong informal waste sector. Given these challenges, the authors conclude that comprehensive EPR policy schemes of the kind that have been implemented in some advanced countries are not likely to be effective. The paper therefore proposes an alternative phase-in approach whereby developing Asian countries are able to move gradually towards EPR systems. It argues that this approach would be more feasible, and discusses what could be the key building blocks of each implementation stage.

  7. Reentrant behavior in the superconducting phase-dependent resistance of a disordered two-dimensional electron gas

    NARCIS (Netherlands)

    den Hartog, S.G.; Wees, B.J.van; Klapwijk, T.M; Nazarov, Y.V.; Borghs, G.

    1997-01-01

    We have investigated the bias-voltage dependence of the phase-dependent differential resistance of a disordered T-shaped two-dimensional electron gas coupled to two superconducting terminals. The resistance oscillations first increase upon lowering the energy. For bias voltages below the Thouless

  8. A Modular Active Front-End Rectifier with Electronic Phase-Shifting for Harmonic Mitigation in Motor Drive Applications

    DEFF Research Database (Denmark)

    Zare, Firuz; Davari, Pooya; Blaabjerg, Frede

    2017-01-01

    In this paper, an electronic phase-shifting strategy has been optimized for a multi-parallel configuration of line-commutated rectifiers with a common dc-bus voltage used in motor drive application. This feature makes the performance of the system independent of the load profile and maximizes its...

  9. Deleterious phases precipitation on superduplex stainless steel UNS S32750: characterization by light optical and scanning electron microscopy

    Directory of Open Access Journals (Sweden)

    Juan Manuel Pardal

    2010-09-01

    Full Text Available Deleterious phases precipitation in superduplex stainless steels is the main concern in fabrication by welding and hot forming of this class of material. Sigma, chi and secondary austenite phases are considered deleterious phases because they produce negative effects on corrosion resistance. Besides, sigma and chi phases also promote strong decrease of toughness. In the present work, the precipitations of sigma, chi and secondary austenite under aging in the 800-950 °C interval were studied in two UNS S32750 steels with different grain sizes. The deleterious phases could be quantified by light optical microscopy, with no distinction between them. Scanning electron microscopy was used to distinguish the individual phases in various aging conditions. The results elucidate the influence of the aging temperature and grain size on the kinetics precipitation and morphology of deleterious phases. The kinetics of deleterious phases is higher in the fine grained material in the initial stage of aging, but the maximum amount of deleterious phases is higher in the coarse grained steel.

  10. Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase

    International Nuclear Information System (INIS)

    Mineo, H.; Lin, S. H.; Fujimura, Y.; Xu, J.; Xu, R. X.; Yan, Y. J.

    2013-01-01

    Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2 ′ -biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified

  11. First-principle study of pressure-induced phase transitions and electronic properties of electride Y2C

    Science.gov (United States)

    Feng, Caihui; Shan, Jingfeng; Xu, Aoshu; Xu, Yang; Zhang, Meiguang; Lin, Tingting

    2017-10-01

    Trigonal yttrium hypocarbide (Y2C), crystallizing in a layered hR3 structure, is an intriguing quasi-two-dimensional electride metal with potential application for the next generation of electronics. By using an efficient structure search method in combination with first-principles calculations, we have extensively explored the phase transitions and electronic properties of Y2C in a wide pressure range of 0-200 GPa. Three structural transformations were predicted, as hR3 → oP12 → tI12 → mC12. Calculated pressures of phase transition are 20, 118, and 126 GPa, respectively. The high-pressure oP12 phase exhibits a three-dimensional extended C-Y network built up from face- and edge-sharing CY8 hendecahedrons, whereas both the tI12 and mC12 phases are featured by the presence of C2 units. No anionic electrons confined to interstitial spaces have been found in the three predicted high-pressure phases, indicating that they are not electrides. Moreover, Y2C is dynamically stable and also energetically stable relative to the decomposition into its elemental solids.

  12. Electronic, optical and transport properties of {alpha}-, {beta}- and {gamma}-phases of spinel indium sulphide: An ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Yamini, E-mail: sharma.yamini62@gmail.com [Department of Physics, Feroze Gandhi College, Rae Bareli 229001, U.P. (India); Srivastava, Pankaj [Department of Physics, Feroze Gandhi College, Rae Bareli 229001, U.P. (India)

    2012-08-15

    Spinel indium sulphide exists in three phases. The tetragonal {beta}-phase transforms to the cubic {alpha}-phase at 420 Degree-Sign C which further transforms to the trigonal {gamma}-phase at 754 Degree-Sign C. Due to wide energy bandgap, the phases of indium sulphide have possibilities of applications in photo-electrochemical solar cell devices as a replacement of toxic CdS. The electronic, optical and transport properties of the three phases have therefore been investigated using full potential linear augmented plane wave (FP-LAPW) + local orbitals (lo) scheme, in the framework of density functional theory (DFT) with generalized gradient approximation (GGA) for the purpose of exchange-correlation energy functional. We present the structure, energy bands and density of states (DOS) for {alpha}-, {beta}- and {gamma}-phases. The partial density of states (PDOS) of {beta}-In{sub 2}S{sub 3} is in good agreement with experiment and earlier ab initio calculations. To obtain the fundamental characteristics of these phases we have analysed their linear optical properties such as the dynamic dielectric function in the energy range of 0-15 eV. From the dynamic dielectric function it is seen that there is no directional anisotropy for {alpha}-phase since the longitudinal and transverse components are almost identical, however the {beta} and {gamma}-phases show birefringence. The optical absorption profiles clearly indicate that {beta}-phase has possibility of greater multiple direct and indirect interband transitions in the visible regions compared to the other phases. To study the existence of interesting thermoelectric properties, transport properties like electrical and thermal conductivities, Seebeck and Hall coefficients etc. are also calculated. Good agreements are found with the available experimental results. -- Highlights: Black-Right-Pointing-Pointer The electronic properties of phases of In{sub 2}S{sub 3} have been investigated. Black-Right-Pointing-Pointer The

  13. Preface to a GUT (Grand Unified Theory)

    International Nuclear Information System (INIS)

    Honig, W.

    1982-01-01

    A Grand Unified Theory (GUT) is proposed exhibiting relativistic invariance and based on a physical model for vacuum space consisting of the superposition of oppositely charged continuous fluids. Models for the photon, electron, neutrino, proton, etc., consist of separate unique variations in the relative densities of the fluids and their flow patterns. This GUT is also based on the use of transfinite axiomatic number forms and on a concept of metrical relativity which hopefully reconciles the many logical dichotomies in and between Special Relativity and Quantum Mechanics. These ideas result in a number of experimental proposals and predicted results which appear to be underivable from present paradigms, first among which is a physical model for the hidden variable of Quantum Mechanics. It is on these features that attention should rest. (Auth.)

  14. Electron spin echo studies of the internal motion of radicals in crystals: Phase memory vs correlation time

    International Nuclear Information System (INIS)

    Kispert, L.D.; Bowman, M.K.; Norris, J.R.; Brown, M.S.

    1982-01-01

    An electron spin echo (ESE) study of the internal motion of the CH 2 protons in irradiated zinc acetate dihydrate crystals shows that quantitative measurements of the motional correlation time can be obtained quite directly from pulsed measurements. In the slow motional limit, the motional correlation time is equal to the phase memory time determined by ESE. In the fast motional limit, the motional correlation time is proportional to the no motion spectral second moment divided by the ESE phase memory time. ESE offers a convenient method of studying motion, electron transfer, conductivity, etc. in a variety of systems too complicated for study by ordinary EPR. New systems for study by ESE include biological samples, organic polymers, liquid solutions of radicals with unresolved hyperfine, etc. When motion modulates large anisotropic hyperfine couplings, ESE measurements of the phase memory time are sensitive to modulation of pseudosecular hyperfine interactions

  15. Phase stability, electronic structure and equation of state of cubic TcN from first-principles calculations

    International Nuclear Information System (INIS)

    Song, T.; Ma, Q.; Sun, X.W.; Liu, Z.J.; Fu, Z.J.; Wei, X.P.; Wang, T.; Tian, J.H.

    2016-01-01

    The phase transition, electronic band structure, and equation of state (EOS) of cubic TcN are investigated by first-principles pseudopotential method based on density-functional theory. The calculated enthalpies show that TcN has a transformation between zincblende and rocksalt phases and the pressure determined by the relative enthalpy is 32 GPa. The calculated band structure indicates the metallic feature and it might make cubic TcN a better candidate for hard materials. Particular attention is paid to the predictions of volume, bulk modulus and its pressure derivative which play a central role in the formulation of approximate EOSs using the quasi-harmonic Debye model. - Highlights: • The phase transition pressure and electronic band structure for cubic TcN are determined. • Particular attention is paid to investigate the equation of state parameters for cubic TcN. • The thermodynamic properties up to 80 GPa and 3000 K are successfully predicted.

  16. Ultra-Short Electron Beam Compression and Phase Locking Using an Inverse Free Electron Laser Interaction in the THz Regime

    International Nuclear Information System (INIS)

    Moody, J. T.; Musumeci, P.; Scoby, C. M.; To, H.; Marcoux, C.

    2010-01-01

    The concept of a THz-based IFEL compressor at the UCLA Pegasus photoinjector laboratory is explored. A 3.5 MeV sub-picosecond electron beam generated in the photoinjector blowout regime can be compressed to femtosecond timescales by a THz IFEL interaction.

  17. A unified grand tour of theoretical physics

    CERN Document Server

    Lawrie, Ian D

    2013-01-01

    A Unified Grand Tour of Theoretical Physics invites its readers to a guided exploration of the theoretical ideas that shape our contemporary understanding of the physical world at the fundamental level. Its central themes, comprising space-time geometry and the general relativistic account of gravity, quantum field theory and the gauge theories of fundamental forces, and statistical mechanics and the theory of phase transitions, are developed in explicit mathematical detail, with an emphasis on conceptual understanding. Straightforward treatments of the standard models of particle physics and cosmology are supplemented with introductory accounts of more speculative theories, including supersymmetry and string theory. This third edition of the Tour includes a new chapter on quantum gravity, focusing on the approach known as Loop Quantum Gravity, while new sections provide extended discussions of topics that have become prominent in recent years, such as the Higgs boson, massive neutrinos, cosmological perturba...

  18. Introduction to Grand Unified Theories. 12

    International Nuclear Information System (INIS)

    Wali, K.C.

    1989-01-01

    This chapter presents an introduction into Grand Unified Theories. After a discussion of the general features to be expected in any such theory, and of the motivations for them, a detailed presentation of SU(5) theory is given. The group structures, particle multiplets, gauge and Higgs bosons are explained. The two stages of spontaneous symmetry breaking via the Higgs model, are calculated individually and in combination. Fermion mass matrices and relations between quark and lepton masses are derived. predictions of SU(5) theory, calculated using renormalization group methods, are derived. The chapter ends with discussions that bring together particle physics and cosmology, including the baryon asymmetry problem, phase transitions in the very early universe, and singularities like domain walls, vortex lines and monopoles. (author). 9 refs.; 4 figs.; 5 tabs

  19. Supersymmetric grand unified theories and cosmology

    International Nuclear Information System (INIS)

    Lazarides, G.; Shafi, Q.

    1983-01-01

    By examining the behavior of supersymmetric grand unified theories (GUT's) in the very early universe we find two classes of realistic models. In one of them supersymmetry is broken at or near superheavy GUT scale. The cosmological implications of such models are expected to be similar to those of nonsupersymmetric GUT's. In the second class of models, the superheavy GUT scale is related to the supersymmetry-breaking scale in the manner of Witten. Two types of cosmological scenarios appear possible in this case, either with or without an intermediate (new) inflationary phase. They can be experimentally distinguished, since the former predicts an absence and the latter an observable number density of superheavy monopoles. A mechanism for generating baryon asymmetry in such models is pointed out

  20. Energetic electron precipitation and VLF phase disturbances at middle latitudes following the magnetic storm of December 6, 1971

    International Nuclear Information System (INIS)

    Larsen, T.R.; Potemra, T.A.; Imhof, W.L.; Reagan, J.B.

    1977-01-01

    Enhanced fluxes of electrons precipitating over middle latitudes (L approx. 3--4) were detected by the polar-orbiting satellite 1971-089A following a period of magnetic activity starting on December 16, 1971. The electron fluxes measured in 256 differential channels between 130 and 2800 keV have been coordinated with phase observations of VLF radio waves propagating in the earth-ionosphere waveguide. The VLF paths in question, NLK (near Seattle, Washington) and GBR (at Rugby, England) to APL (near Washington, D. C.), cover approx. =120 0 in longitude and range from L approx. 2.5 to L approx. 4.0 in invariant latitude. These paths showed marked daytime and nighttime phase advances from 1650 UT on December 17 (in excess of 10 μs during maximum disturbance). The phase values did not return to prestorm levels before December 22--23. The unusual presence of these daytime VLF disturbances is offered as evidence for the widespread precipitation at low L shell vales of nearly relativistic electrons (E/sub e/> approx.200 keV) which would be required to penetrate below approx.70-km altitude to affect the daytime VLF transmissions. Wave guide mode calculations using D region electron density profiles deduced from the satellite particle data predict phase advances which agree reasonably well with the observed values. It is concluded that the observed long-lived VLF phase disturbances can be explained by excess D region ionization caused by energetic electrons precipitating from the earth's radiation belt following their injection deep into the magnetosphere during the magnetic storm

  1. Simultaneous assessment of phase chemistry, phase abundance and bulk chemistry with statistical electron probe micro-analyses: Application to cement clinkers

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, William; Krakowiak, Konrad J.; Ulm, Franz-Josef, E-mail: ulm@mit.edu

    2014-01-15

    According to recent developments in cement clinker engineering, the optimization of chemical substitutions in the main clinker phases offers a promising approach to improve both reactivity and grindability of clinkers. Thus, monitoring the chemistry of the phases may become part of the quality control at the cement plants, along with the usual measurements of the abundance of the mineralogical phases (quantitative X-ray diffraction) and the bulk chemistry (X-ray fluorescence). This paper presents a new method to assess these three complementary quantities with a single experiment. The method is based on electron microprobe spot analyses, performed over a grid located on a representative surface of the sample and interpreted with advanced statistical tools. This paper describes the method and the experimental program performed on industrial clinkers to establish the accuracy in comparison to conventional methods. -- Highlights: •A new method of clinker characterization •Combination of electron probe technique with cluster analysis •Simultaneous assessment of phase abundance, composition and bulk chemistry •Experimental validation performed on industrial clinkers.

  2. Simultaneous assessment of phase chemistry, phase abundance and bulk chemistry with statistical electron probe micro-analyses: Application to cement clinkers

    International Nuclear Information System (INIS)

    Wilson, William; Krakowiak, Konrad J.; Ulm, Franz-Josef

    2014-01-01

    According to recent developments in cement clinker engineering, the optimization of chemical substitutions in the main clinker phases offers a promising approach to improve both reactivity and grindability of clinkers. Thus, monitoring the chemistry of the phases may become part of the quality control at the cement plants, along with the usual measurements of the abundance of the mineralogical phases (quantitative X-ray diffraction) and the bulk chemistry (X-ray fluorescence). This paper presents a new method to assess these three complementary quantities with a single experiment. The method is based on electron microprobe spot analyses, performed over a grid located on a representative surface of the sample and interpreted with advanced statistical tools. This paper describes the method and the experimental program performed on industrial clinkers to establish the accuracy in comparison to conventional methods. -- Highlights: •A new method of clinker characterization •Combination of electron probe technique with cluster analysis •Simultaneous assessment of phase abundance, composition and bulk chemistry •Experimental validation performed on industrial clinkers

  3. Unified theory of effective interaction

    Energy Technology Data Exchange (ETDEWEB)

    Takayanagi, Kazuo, E-mail: k-takaya@sophia.ac.jp

    2016-09-15

    We present a unified description of effective interaction theories in both algebraic and graphic representations. In our previous work, we have presented the Rayleigh–Schrödinger and Bloch perturbation theories in a unified fashion by introducing the main frame expansion of the effective interaction. In this work, we start also from the main frame expansion, and present various nonperturbative theories in a coherent manner, which include generalizations of the Brandow, Brillouin–Wigner, and Bloch–Horowitz theories on the formal side, and the extended Krenciglowa–Kuo and the extended Lee–Suzuki methods on the practical side. We thus establish a coherent and comprehensive description of both perturbative and nonperturbative theories on the basis of the main frame expansion.

  4. Split supersymmetry in unified models

    International Nuclear Information System (INIS)

    Dutta, Bhaskar; Mimura, Yukihiro

    2005-01-01

    In the context of split supersymmetry, the gaugino mass spectrum seems to be very important to satisfy the dark matter content of the universe and the gauge coupling unification. In this Letter, we have considered various sources of gaugino masses in the context of unified models. We show that the gaugino mass spectrum varies in different unification pictures. In the context of SU(5), we have found that the bino/wino mass ratio can be close to one at the weak scale which is helpful to satisfy the WMAP data. The gluino/wino mass ratio is also different from the usual scenario of unified gaugino masses. The gaugino masses can be around one TeV and m SUSY is chosen so that the gluino mass does not create any cosmological problem. In the context of the Pati-Salam model, we show that the gluino mass can be made very heavy even after maintaining the unification of the gauge couplings

  5. Unified theory of the nucleus

    International Nuclear Information System (INIS)

    Wildermuth, K.; Tang, Y.C.

    1977-01-01

    The purpose of this monograph is to describe a microscopic nuclear theory which can be used to consider all low-energy nuclear phenomena from a unified viewpoint. In this theory, the Pauli principle is completely taken into account and translationally invariant wave functions are always employed. It can be utilized to study reactions initiated not only by nucleons but also by arbitrary composite particles

  6. A class of P,T-invariant topological phases of interacting electrons

    International Nuclear Information System (INIS)

    Freedman, Michael; Nayak, Chetan; Shtengel, Kirill; Walker, Kevin; Wang Zhenghan

    2004-01-01

    We describe a class of parity- and time-reversal-invariant topological states of matter which can arise in correlated electron systems in 2+1-dimensions. These states are characterized by particle-like excitations exhibiting exotic braiding statistics. P and T invariance are maintained by a 'doubling' of the low-energy degrees of freedom which occurs naturally without doubling the underlying microscopic degrees of freedom. The simplest examples have been the subject of considerable interest as proposed mechanisms for high-T c superconductivity. One is the 'doubled' version of the chiral spin liquid. The chiral spin liquid gives rise to anyon superconductivity at finite doping and the corresponding field theory is U(1) Chern-Simons theory at coupling constant m=2. The 'doubled' theory is two copies of this theory, one with m=2 the other with m=-2. The second example corresponds to Z 2 gauge theory, which describes a scenario for spin-charge separation. Our main concern, with an eye towards applications to quantum computation, are richer models which support non-Abelian statistics. All of these models, richer or poorer, lie in a tightly organized discrete family indexed by the Baraha numbers, 2cos(π/(k+2)), for positive integer k. The physical inference is that a material manifesting the Z 2 gauge theory or a doubled chiral spin liquid might be easily altered to one capable of universal quantum computation. These phases of matter have a field-theoretic description in terms of gauge theories which, in their infrared limits, are topological field theories. We motivate these gauge theories using a parton model or slave-fermion construction and show how they can be solved exactly. The structure of the resulting Hilbert spaces can be understood in purely combinatorial terms. The highly constrained nature of this combinatorial construction, phrased in the language of the topology of curves on surfaces, lays the groundwork for a strategy for constructing microscopic

  7. Coupled Electronic and Magnetic Phase Transition in the Infinite-Layer Phase LaSrNiRuO4.

    Science.gov (United States)

    Patino, Midori Amano; Zeng, Dihao; Bower, Ryan; McGrady, John E; Hayward, Michael A

    2016-09-06

    Topochemical reduction of the ordered double perovskite LaSrNiRuO6 with CaH2 yields LaSrNiRuO4, an extended oxide phase containing infinite sheets of apex-linked, square-planar Ni(1+)O4 and Ru(2+)O4 units ordered in a checkerboard arrangement. At room temperature the localized Ni(1+) (d(9), S = (1)/2) and Ru(2+) (d(6), S = 1) centers behave paramagnetically. However, on cooling below 250 K the system undergoes a cooperative phase transition in which the nickel spins align ferromagnetically, while the ruthenium cations appear to undergo a change in spin configuration to a diamagnetic spin state. Features of the low-temperature crystal structure suggest a symmetry lowering Jahn-Teller distortion could be responsible for the observed diamagnetism of the ruthenium centers.

  8. Phase behaviors of binary mixtures composed of electron-rich and electron-poor triphenylene discotic liquid crystals

    International Nuclear Information System (INIS)

    An Lingling; Jing Min; Xiao Bo; Bai Xiao-Yan; Zhao Ke-Qing; Zeng Qing-Dao

    2016-01-01

    Disk-like liquid crystals (DLCs) can self-assemble to ordered columnar mesophases and are intriguing one-dimensional organic semiconductors with high charge carrier mobility. To improve their applicable property of mesomorphic temperature ranges, we exploit the binary mixtures of electronic donor-acceptor DLC materials. The electron-rich 2,3,6,7,10,11-hexakis(alkoxy)triphenylenes (C4, C6, C8, C10, C12) and an electron-deficient tetrapentyl triphenylene-2,3,6,10-tetracarboxylate have been prepared and their binary mixtures have been investigated. The mesomorphism of the 1:1 (molar ratio) mixtures has been characterized by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and small angel x-ray scattering (SAXS). The self-assembled monolayer structure of a discogen on a solid-liquid interface has been imaged by the high resolution scanning tunneling microscopy (STM). The match of peripheral chain length has important influence on the mesomorphism of the binary mixtures. (special topic)

  9. Phase equilibria, crystal chemistry, electronic structure and physical properties of Ag-Ba-Ge clathrates

    Energy Technology Data Exchange (ETDEWEB)

    Zeiringer, I.; Chen Mingxing [Institute of Physical Chemistry, University of Vienna, Waehringerstr. 42, 1090 Wien (Austria); Bednar, I.; Royanian, E.; Bauer, E. [Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, 1040 Wien (Austria); Podloucky, R.; Grytsiv, A. [Institute of Physical Chemistry, University of Vienna, Waehringerstr. 42, 1090 Wien (Austria); Rogl, P., E-mail: peter.franz.rogl@univie.ac.at [Institute of Physical Chemistry, University of Vienna, Waehringerstr. 42, 1090 Wien (Austria); Effenberger, H. [Institute of Mineralogy and Crystallography, University of Vienna, A-1090 Wien (Austria)

    2011-04-15

    In the Ag-Ba-Ge system the clathrate type-{Iota} solid solution, Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y}, extends at 800 deg. C from binary Ba{sub 8}Ge{sub 43{open_square}3} ({open_square} is a vacancy) to Ba{sub 8}Ag{sub 5.3}Ge{sub 40.7}. For the clathrate phase (1 {<=} x {<=} 5.3) the cubic space group Pm3-bar n was established by X-ray powder diffraction and confirmed by X-ray single-crystal analyses of the samples Ba{sub 8}Ag{sub 2.3}Ge{sub 41.9{open_square}1.8} and Ba{sub 8}Ag{sub 4.4}Ge{sub 41.3{open_square}0.3}. Increasing the concentration of Ag causes the lattice parameters of the solid solution to increase linearly from a value of a = 1.0656 (x = 0, y = 3) to a = 1.0842 (x = 4.8, y = 0) nm. Site preference determination using X-ray refinement reveals that Ag atoms preferentially occupy the 6d site randomly mixed with Ge and vacancies, which become filled in the compound Ba{sub 8}Ag{sub 4.8}Ge{sub 41.2} when the Ag content increases. At 600 {sup o}C the phase region of the clathrate solution Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y} becomes separated from the Ba-Ge boundary and extends from 6.6 to 9.8 at.% Ag. The compound Ba{sub 6}Ge{sub 25} (clathrate type-{Iota}X) dissolves at 800 {sup o}C a maximum of 1.5 at.% Ag. The homogeneity regions of the two ternary compounds BaAg{sub 2-x}Ge{sub 2+x} (ThCr{sub 2}Si{sub 2}-type, 0.2 {<=} x {<=} 0.7) and Ba(Ag{sub 1-x}Ge{sub x}){sub 2} (AlB{sub 2}-type, 0.65 {<=} x {<=} 0.75) were established at 800 deg. C. Studies of transport properties for the series of Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y} compounds evidenced that electrons are the predominant charge carriers with the Fermi energy close to a gap. Its position can be fine-tuned by the substitution of Ge by Ag atoms and by mechanical processing of the starting material, Ba{sub 8}Ge{sub 43}. The proximity of the electronic structure at Fermi energy of Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y} to a gap is also corroborated by density

  10. Electron induced formation and stability of molecular and cluster ions in gas phase and superfluid helium nanodroplets

    International Nuclear Information System (INIS)

    Aleem, M. A.

    2010-01-01

    The present PhD thesis represents a broad range study of electron induced formation and stability of positive and negative ions in gas phase and superfluid helium nanodroplets. The molecules studied are of industrial, environmental, plasma and biological relevance. The knowledge obtained from the study provides new insight for the proper understanding and control on energetics and dynamics of the reactions involved in the formation and fragmentation processes of the studied molecules and clusters. The experiments are accomplished and investigated using mass spectrometric techniques for the formation of molecular and cluster ions using different mass spectrometers available in our laboratory. One part of the work is focused on electron-induced reactions of the molecules in gas phase. Especially focus is laid to electron attachment to the isomers of mononitrotolouene used as an additive to explosives. The fragile nature and high internal energy of these molecules has lead to extensive fragmentation following the ionisation process. Dissociative electron attachment to the three different isomers has shown different resonances and therefore this process can be utilized to explicitly distinguish these isomers. Anion efficiency curves of the isomers have been studied using effusive molecular beam source in combination with a hemispherical electron monochromator as well as a Nier-type ion source attached to a sector field mass spectrometer. The outcome of the experiment is a reliable and effective detection method highly desirable for environmental and security reasons. Secondly, dissociative electron ionization of acetylene and propene is studied and their data is directly related to the plasma modelling for plasma fusion and processing reactors. Temperature effects for dissociative electron attachment to halo-hydrocarbons are also measured using a trochoidal electron monochromator. The second part of the work is concerned with the investigation of electron

  11. Longitudinal phase-space manipulation of ellipsoidal electron bunches in realistic fields

    Directory of Open Access Journals (Sweden)

    S. B. van der Geer

    2006-04-01

    Full Text Available Since the recent publication of a practical recipe to create “pancake” electron bunches which evolve into uniformly filled ellipsoids, a number of papers have addressed both an alternative method to create such ellipsoids as well as their behavior in realistic fields. So far, the focus has been on the possibilities to preserve the initial “thermal” transverse emittance. This paper addresses the linear longitudinal phase space of ellipsoidal bunches. It is shown that ellipsoidal bunches allow ballistic compression at subrelativistic energies, without the detrimental effects of nonlinear space-charge forces. This in turn eliminates the need for the large correlated energy spread normally required for longitudinal compression of relativistic particle beams, while simultaneously avoiding all problems related to magnetic compression. Furthermore, the linear space-charge forces of ellipsoidal bunches can be used to reduce the remaining energy spread even further, by carefully choosing the beam transverse size, in a process that is essentially the time-reversed process of the creation of an ellipsoid at the cathode. The feasibility of compression of ellipsoidal bunches is illustrated with a relatively simple setup, consisting of a half-cell S-band photogun and a two-cell booster compressor. Detailed GPT simulations in realistic fields predict that 100 pC ellipsoidal bunches can be ballistically compressed to 100 fs, at a transverse emittance of 0.7   μm, with a final energy of 3.7 MeV and an energy spread of only 50 keV.

  12. Influence of electron beam exposure on crystallization of phase-change materials

    NARCIS (Netherlands)

    Pandian, Ramanathaswamy; Kooi, Bart J.; De Hosson, Jeff Th. M.; Pauza, Andrew

    2007-01-01

    Isothermal crystallization of amorphous SbxTe films capped with ZnS-SiO2 or GeCrN layers was performed using in situ heating within a transmission electron microscope. The effect of the electron beam of the microscope on the crystallization process was investigated. It was found that electron

  13. Electron irradiation effect on the reverse phase transformation temperatures in TiNi shape memory alloy thin films

    International Nuclear Information System (INIS)

    Wang, Z.G.; Zu, X.T.; Fu, Y.Q.; Zhu, S.; Wang, L.M.

    2005-01-01

    In this work, Ti-Ni shape memory alloy thin films were irradiated by 1.7 MeV electron with three types of fluences: 4 x 10 20 , 7 x 10 20 and 1 x 10 21 /m 2 . The influence of electron irradiation on the transformation behavior of the TiNi thin films were investigated by differential scanning calorimetry. The transformation temperatures A s and A f shifted to higher temperature after electron irradiation, the martensite was stabilized. The electron irradiation effect can be easily eliminated by one thermal cycle. The shifts of the transformation temperatures can be explained from the change of potential energy barrier and coherency energy between parent phase and martensite after irradiation

  14. Neural network prediction of relativistic electrons at geosynchronous orbit during the storm recovery phase: effects of recurring substorms

    Directory of Open Access Journals (Sweden)

    M. Fukata

    2002-07-01

    Full Text Available During the recovery phase of geomagnetic storms, the flux of relativistic (>2 MeV electrons at geosynchronous orbits is enhanced. This enhancement reaches a level that can cause devastating damage to instruments on satellites. To predict these temporal variations, we have developed neural network models that predict the flux for the period 1–12 h ahead. The electron-flux data obtained during storms, from the Space Environment Monitor on board a Geostationary Meteorological Satellite, were used to construct the model. Various combinations of the input parameters AL, SAL, Dst and SDst were tested (where S denotes the summation from the time of the minimum Dst. It was found that the model, including SAL as one of the input parameters, can provide some measure of relativistic electron-flux prediction at geosynchronous orbit during the recovery phase. We suggest from this result that the relativistic electron-flux enhancement during the recovery phase is associated with recurring substorms after Dst minimum and their accumulation effect.Key words. Magnetospheric physics (energetic particles, trapped; magnetospheric configuration and dynamics; storms and substorms

  15. Effect of calcination routes on phase formation of BaTiO3 and their electronic and magnetic properties

    Science.gov (United States)

    Majumder, Supriyo; Choudhary, R. J.; Tripathi, M.; Phase, D. M.

    2018-05-01

    We have investigated the phase formation and correlation between electronic and magnetic properties of oxygen deficient BaTiO3 ceramics, synthesized by solid state reaction method, following different calcination paths. The phase analysis divulge that a higher calcination temperature above 1000° C is favored for tetragonal phase formation than the cubic phase. The core level X-ray photo electron spectroscopy measurements confirm the presence of oxygen vacancies and oxygen vacancy mediated Ti3+ states. As the calcination temperature and calcination time increases these oxygen vacancies and hence Ti3+ concentrations reduce in the sample. The temperature dependent magnetization curves suggest unexpected magnetic ordering, which may be due to the presence of unpaired electron at the t2g state (d1) of nearest-neighbor Ti atoms. In magnetization vs magnetic field isotherms, the regular decrease of saturation moment value with increasing calcination temperature and calcination time, can be discussed considering the amount of oxygen deficiency induced Ti3+ concentrations, present in the sample.

  16. Equivalence of electronic and mechanical stresses in structural phase stabilization: A case study of indium wires on Si(111)

    Science.gov (United States)

    Kim, Sun-Woo; Kim, Hyun-Jung; Ming, Fangfei; Jia, Yu; Zeng, Changgan; Cho, Jun-Hyung; Zhang, Zhenyu

    2015-05-01

    It was recently proposed that the stress state of a material can also be altered via electron or hole doping, a concept termed electronic stress (ES), which is different from the traditional mechanical stress (MS) due to lattice contraction or expansion. Here we demonstrate the equivalence of ES and MS in structural stabilization, using In wires on Si(111) as a prototypical example. Our systematic density-functional theory calculations reveal that, first, for the same degrees of carrier doping into the In wires, the ES of the high-temperature metallic 4 ×1 structure is only slightly compressive, while that of the low-temperature insulating 8 ×2 structure is much larger and highly anisotropic. As a consequence, the intrinsic energy difference between the two phases is significantly reduced towards electronically phase-separated ground states. Our calculations further demonstrate quantitatively that such intriguing phase tunabilities can be achieved equivalently via lattice-contraction induced MS in the absence of charge doping. We also validate the equivalence through our detailed scanning tunneling microscopy experiments. The present findings have important implications for understanding the underlying driving forces involved in various phase transitions of simple and complex systems alike.

  17. Electronically excited and ionized states in condensed phase: Theory and applications

    Science.gov (United States)

    Sadybekov, Arman

    Predictive modeling of chemical processes in silico is a goal of XXI century. While robust and accurate methods exist for ground-state properties, reliable methods for excited states are still lacking and require further development. Electronically exited states are formed by interactions of matter with light and are responsible for key processes in solar energy harvesting, vision, artificial sensors, and photovoltaic applications. The greatest challenge to overcome on our way to a quantitative description of light-induced processes is accurate inclusion of the effect of the environment on excited states. All above mentioned processes occur in solution or solid state. Yet, there are few methodologies to study excited states in condensed phase. Application of highly accurate and robust methods, such as equation-of-motion coupled-cluster theory EOM-CC, is limited by a high computational cost and scaling precluding full quantum mechanical treatment of the entire system. In this thesis we present successful application of the EOM-CC family of methods to studies of excited states in liquid phase and build hierarchy of models for inclusion of the solvent effects. In the first part of the thesis we show that a simple gasphase model is sufficient to quantitatively analyze excited states in liquid benzene, while the latter part emphasizes the importance of explicit treatment of the solvent molecules in the case of glycine in water solution. In chapter 2, we use a simple dimer model to describe exciton formation in liquid and solid benzene. We show that sampling of dimer structures extracted from the liquid benzene is sufficient to correctly predict exited-state properties of the liquid. Our calculations explain experimentally observed features, which helped to understand the mechanism of the excimer formation in liquid benzene. Furthermore, we shed light on the difference between dimer configurations in the first solvation shell of liquid benzene and in unit cell of solid

  18. A first-principle study on the phase transition, electronic structure, and mechanical properties of three-phase ZrTi2 alloy under high pressure*

    Science.gov (United States)

    Yuan, Xiao-Li; Xue, Mi-An; Chen, Wen; An, Tian-Qing

    2016-11-01

    We employed density-functional theory (DFT) within the generalized gradient approximation (GGA) to investigate the ZrTi2 alloy, and obtained its structural phase transition, mechanical behavior, Gibbs free energy as a function of pressure, P-V equation of state, electronic and Mulliken population analysis results. The lattice parameters and P-V EOS for α, β and ω phases revealed by our calculations are consistent with other experimental and computational values. The elastic constants obtained suggest that ω-ZrTi2 and α-ZrTi2 are mechanically stable, and that β-ZrTi2 is mechanically unstable at 0 GPa, but becomes more stable with increasing pressure. Our calculated results indicate a phase transition sequence of α → ω → β for ZrTi2. Both the bulk modulus B and shear modulus G increase linearly with increasing pressure for three phases. The G/B values illustrated good ductility of ZrTi2 alloy for three phases, with ωJournal web page at http://dx.doi.org/10.1140/epjb/e2016-70218-0

  19. SU-F-T-84: Measurement and Monte-Carlo Simulation of Electron Phase Spaces Using a Wide Angle Magnetic Electron Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Englbrecht, F; Lindner, F; Bin, J; Wislsperger, A; Reiner, M; Kamp, F; Belka, C; Dedes, G; Schreiber, J; Parodi, K [LMU Munich, Munich, Bavaria (Germany)

    2016-06-15

    Purpose: To measure and simulate well-defined electron spectra using a linear accelerator and a permanent-magnetic wide-angle spectrometer to test the performance of a novel reconstruction algorithm for retrieval of unknown electron-sources, in view of application to diagnostics of laser-driven particle acceleration. Methods: Six electron energies (6, 9, 12, 15, 18 and 21 MeV, 40cm × 40cm field-size) delivered by a Siemens Oncor linear accelerator were recorded using a permanent-magnetic wide-angle electron spectrometer (150mT) with a one dimensional slit (0.2mm × 5cm). Two dimensional maps representing beam-energy and entrance-position along the slit were measured using different scintillating screens, read by an online CMOS detector of high resolution (0.048mm × 0.048mm pixels) and large field of view (5cm × 10cm). Measured energy-slit position maps were compared to forward FLUKA simulations of electron transport through the spectrometer, starting from IAEA phase-spaces of the accelerator. The latter ones were validated against measured depth-dose and lateral profiles in water. Agreement of forward simulation and measurement was quantified in terms of position and shape of the signal distribution on the detector. Results: Measured depth-dose distributions and lateral profiles in the water phantom showed good agreement with forward simulations of IAEA phase-spaces, thus supporting usage of this simulation source in the study. Measured energy-slit position maps and those obtained by forward Monte-Carlo simulations showed satisfactory agreement in shape and position. Conclusion: Well-defined electron beams of known energy and shape will provide an ideal scenario to study the performance of a novel reconstruction algorithm using measured and simulated signal. Future work will increase the stability and convergence of the reconstruction-algorithm for unknown electron sources, towards final application to the electrons which drive the interaction of TW-class laser

  20. Electron microscopy analyses and electrical properties of the layered Bi{sub 2}WO{sub 6} phase

    Energy Technology Data Exchange (ETDEWEB)

    Taoufyq, A. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université du Sud Toulon-Var, BP 20132, 83957, La Garde Cedex (France); Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); Département d‘Études des Réacteurs, Laboratoire Dosimétrie Capteurs Instrumentation, CEA Cadarache (France); Société CESIGMA—Signals and Systems, 1576 Chemin de La Planquette, F 83 130 LA GARDE (France); Ait Ahsaine, H. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); Patout, L. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université du Sud Toulon-Var, BP 20132, 83957, La Garde Cedex (France); Benlhachemi, A.; Ezahri, M. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); and others

    2013-07-15

    The bismuth tungstate Bi{sub 2}WO{sub 6} was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2{sub 1} non centrosymmetric space group previously proposed for this phase. The layers Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} have been directly evidenced from the HRTEM images. The electrical properties of Bi{sub 2}WO{sub 6} compacted pellets systems were determined from electrical impedance spectrometry (EIS) and direct current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi{sub 2}WO{sub 6} phase, with a representation of the cell dimensions (b and c vectors). The Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi{sub 2}WO{sub 6}. • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification.

  1. Structural, Electronic and Elastic Properties of Heavy Fermion YbTM2 (TM= Ir and Pt) Laves Phase Compounds

    Science.gov (United States)

    Pawar, H.; Shugani, M.; Aynyas, M.; Sanyal, S. P.

    2018-02-01

    The structural, electronic and elastic properties of YbTM2 (TM = Ir and Pt) Laves phase intermetallic compounds which crystallize in cubic (MgCu2-type) structure, have been investigated using ab-initio full potential linearized augmented plane wave (FP-LAPW) method with LDA and LDA+U approximation. The calculated ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B‧) are in good agreement with available experimental and theoretical data. The electronic properties are analyzed from band structures and density of states. Elastic constants are predicted first time for these compounds which obey the stability criteria for cubic system.

  2. Strain at a semiconductor nanowire-substrate interface studied using geometric phase analysis, convergent beam electron diffraction and nanobeam diffraction

    DEFF Research Database (Denmark)

    Persson, Johan Mikael; Wagner, Jakob Birkedal; Dunin-Borkowski, Rafal E.

    2011-01-01

    Semiconductor nanowires have been studied using electron microscopy since the early days of nanowire growth, e.g. [1]. A common approach for analysing nanowires using transmission electron microscopy (TEM) involves removing them from their substrate and subsequently transferring them onto carbon...... with CBED and NBED [4,5] have shown a high degree of consistency. Strain has previously only been measured in nanowires removed from their substrate [6], or only using GPA [7]. The sample used for the present investigation was an InP nanowire grown on a Si substrate using metal organic vapor phase...

  3. A first principles study of phase stability, bonding, electronic and lattice dynamical properties of beryllium chalcogenides at high pressure

    International Nuclear Information System (INIS)

    Dabhi, Shweta; Mankad, Venu; Jha, Prafulla K.

    2014-01-01

    Highlights: • First principles calculations are performed for BeS, BeSe and BeTe in B3, B8 and B1 phases. • They are indirect wide band gap semiconductors stable in B3 phase at ambient condition. • Phonon calculations at ambient and high pressure are reported. • The NiAs phase is dynamically stable at high pressure. - Abstract: The present paper reports a detailed and systematic theoretical study of structural, mechanical, electronic, vibrational and thermodynamical properties of three beryllium chalcogenides BeS, BeSe and BeTe in zinc blende, NiAs and rock salt phases by performing ab initio calculations based on density-functional theory. The calculated value of lattice constants and bulk modulus are compared with the available experimental and other theoretical data and found to agree reasonably well. These compounds are indirect wide band gap semiconductors with a partially ionic contribution in all considered three phases. The zinc blende phase of these chalcogenides is found stable at ambient condition and phase transition from zinc blende to NiAs structure is found to occur. The bulk modulus, its pressure derivative, anisotropic factor, Poission’s ratio, Young’s modulus for these are also calculated and discussed. The phonon dispersion curves of these beryllium chalcogenides in zinc blende phase depict their dynamical stability in this phase at ambient condition. We have also estimated the temperature variation of specific heat at constant volume, entropy and Debye temperature for these compounds in zinc blende phase. The variation of lattice-specific heat with temperature obeys the classical Dulong–Petit’s law at high temperature, while at low-temperature it obeys the Debye’s T 3 law

  4. A technique for measuring an electron beam close-quote s longitudinal phase space with sub-picosecond resolution

    International Nuclear Information System (INIS)

    Crosson, E.R.; Berryman, K.W.; Richman, B.A.; Smith, T.I.; Swent, R.L.

    1996-01-01

    We have developed a technique for measuring the longitudinal phase space distribution of the Stanford Superconducting Accelerator close-quote s (SCA) electron beam which involves applying tomographic techniques to energy spectra taken as a function of the relative phase between the beam and the accelerating field, and optionally, as a function of the strength of a variable dispersion section in the system. The temporal profile of the beam obtained by projecting the inferred distribution onto the time axis is compared with that obtained from interferometric transition radiation measurements. copyright 1996 American Institute of Physics

  5. Electron spin echo study of the E'-center phase relaxation in γ-irradiated quartz glass

    International Nuclear Information System (INIS)

    Dudkin, V.I.; Petrun'kin, V.Yu.; Rubinov, S.V.; Uspenskij, L.I.

    1986-01-01

    Experimental studies of phase relaxation of E'-centres in γ-irradiated quartz glass are conducted by the method of electron spin echo (ESE) for different concentrations of paramagnetic centres. Contribution of mechanisms of spectral and prompt diffusion to kinetics of amplitude drop of echo signal is proved to reduce with growth of delay time between exciting microwave pulse that results in increase of phase memory time at large delays. The mentioned property can be used in electric controlled delay lines on the base of ESE

  6. The stability of the martensitic phases in Cu-Zn-Al at an electron concentration of 1534

    International Nuclear Information System (INIS)

    Pelegrina, J.L.; Ahlers, Manfred.

    1989-01-01

    The β phase to martensite and the martensite to martensite transformations in Cu-Zn-Al single crystals of a high electron concentration have been studied as a function of the temperature. A stress temperature diagram, similar to that proposed in the Cu-Al-Ni system, is constructed and the stability of the different martensites is analyzed from thermodynamic considerations. The results for the 18R, the 6R and the 2H phase are compared with those obtained from other alloy compositions. (Author) [es

  7. Manifestations of the 2.5-th order phase transition in electronic properties of ω-uranium and cadmium

    International Nuclear Information System (INIS)

    Makarov, V.I.; Kle ner, V.Z.; Ignat'eva, T.A.

    1979-01-01

    It is shown that nonlinear temperature dependence of α-uranium superconducting transformation on the pressure P is a result of two-phase transformations of 2.5-th order. By means of parameters characterizing these transformations calculated is the coefficient of temperature expansion being in agreement with the experimental data. Explained is the influence of molybdenum addition on the electronic specific heat and Tsub(k)(p) dependence. Basing on the representation of the 2.5-th order phase transformation analyzed is a nonlinear change of cadmium Tsub(k) in case of uniaxial deformation

  8. A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs.

    Science.gov (United States)

    Rodrigues, Anna; Sawkey, Daren; Yin, Fang-Fang; Wu, Qiuwen

    2015-05-01

    To develop a framework for accurate electron Monte Carlo dose calculation. In this study, comprehensive validations of vendor provided electron beam phase space files for Varian TrueBeam Linacs against measurement data are presented. In this framework, the Monte Carlo generated phase space files were provided by the vendor and used as input to the downstream plan-specific simulations including jaws, electron applicators, and water phantom computed in the EGSnrc environment. The phase space files were generated based on open field commissioning data. A subset of electron energies of 6, 9, 12, 16, and 20 MeV and open and collimated field sizes 3 × 3, 4 × 4, 5 × 5, 6 × 6, 10 × 10, 15 × 15, 20 × 20, and 25 × 25 cm(2) were evaluated. Measurements acquired with a CC13 cylindrical ionization chamber and electron diode detector and simulations from this framework were compared for a water phantom geometry. The evaluation metrics include percent depth dose, orthogonal and diagonal profiles at depths R100, R50, Rp, and Rp+ for standard and extended source-to-surface distances (SSD), as well as cone and cut-out output factors. Agreement for the percent depth dose and orthogonal profiles between measurement and Monte Carlo was generally within 2% or 1 mm. The largest discrepancies were observed within depths of 5 mm from phantom surface. Differences in field size, penumbra, and flatness for the orthogonal profiles at depths R100, R50, and Rp were within 1 mm, 1 mm, and 2%, respectively. Orthogonal profiles at SSDs of 100 and 120 cm showed the same level of agreement. Cone and cut-out output factors agreed well with maximum differences within 2.5% for 6 MeV and 1% for all other energies. Cone output factors at extended SSDs of 105, 110, 115, and 120 cm exhibited similar levels of agreement. We have presented a Monte Carlo simulation framework for electron beam dose calculations for Varian TrueBeam Linacs. Electron beam energies of 6 to 20 MeV for open and collimated

  9. Structural, electronic and elastic properties of REIr{sub 2} (RE=La and Ce) Laves phase compounds

    Energy Technology Data Exchange (ETDEWEB)

    Shrivastava, Deepika, E-mail: deepika89shrivastava@gmail.com; Fatima, Bushra; Sanyal, Sankar P. [Department of Physics, Barkatullah University, Bhopal, 462026 (India)

    2016-05-23

    REIr{sub 2} (RE = La and Ce) Laves phase intermetallic compounds were investigated with respect to their structural, electronic and elastic properties using full potential linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation (GGA) as implemented in WIEN2k code. The ground state properties such as lattice constants (a{sub 0}), bulk modulus (B), pressure derivative of bulk modulus (B′) and density of state at Fermi level N(E{sub F}) have been obtained by optimization method. The electronic structure (BS, TDOS and PDOS) reveals that these Laves phase compounds are metallic in nature. The calculated elastic constants indicate that these compounds are mechanically stable at ambient pressure and found to be ductile in nature.

  10. Miniaturized Spacecraft Platform for Command, Data Handling and Electronics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Microelectronics Research Development Corporation (Micro RDC) proposes to develop a platform of low mass/volume/power, reliable miniaturized electronic modules that...

  11. Development of Diamond Vacuum Differential Amplifier for Harsh Environment Power Electronics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Scientic, Inc., in collaboration with Vanderbilt University, proposes to develop a novel vacuum field emission differential amplifier (VFEDA) using low electron...

  12. Electronically Steerable Antennas with Panoramic Scan Field of View, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Electronically steerable antennas are key to effective radio transmission at millimeter-wave frequencies. To enable communication with rovers, robots, EVA...

  13. Thermal Management of Transient Power Spikes in Electronics - Phase Change Energy Storage or Copper Heat Sinks?

    OpenAIRE

    Krishnan, S.; Garimella, S V

    2004-01-01

    A transient thermal analysis is performed to investigate thermal control of power semiconductors using phase change materials, and to compare the performance of this approach to that of copper heat sinks. Both the melting of the phase change material under a transient power spike input, as well as the resolidification process, are considered. Phase change materials of different kinds (paraffin waxes and metallic alloys) are considered, with and without the use of thermal conductivity enhancer...

  14. Phase-Space Density Analyses of the AE-8 Trapped Electron and the AP-8 Trapped Proton Model Environments

    Energy Technology Data Exchange (ETDEWEB)

    T.E. Cayton

    2005-08-12

    The AE-8 trapped electron and the AP-8 trapped proton models are used to examine the L-shell variation of phase-space densities for sets of transverse (or 1st) invariants, {mu}, and geometrical invariants, K (related to the first two adiabatic invariants). The motivation for this study is twofold: first, to discover the functional dependence of the phase-space density upon the invariants; and, second, to explore the global structure of the radiation belts within this context. Variation due to particle rest mass is considered as well. The overall goal of this work is to provide a framework for analyzing energetic particle data collected by instruments on Global Positioning System (GPS) spacecraft that fly through the most intense region of the radiation belt. For all considered values of {mu} and K, and for 3.5 R{sub E} < L < 6.5 R{sub E}, the AE-8 electron phase-space density increases with increasing L; this trend--the expected one for a population diffusing inward from an external source--continues to L = 7.5 R{sub E} for both small and large values of K but reverses slightly for intermediate values of K. The AP-8 proton phase-space density exhibits {mu}-dependent local minima around L = 5 R{sub E}. Both AE-8 and AP-8 exhibit critical or cutoff values for the invariants beyond which the flux and therefore the phase-space density vanish. For both electrons and protons, these cutoff values vary systematically with magnetic moment and L-shell and are smaller than those estimated for the atmospheric loss cone. For large magnetic moments, for both electrons and protons, the K-dependence of the phase-space density is exponential, with maxima at the magnetic equator (K = 0) and vanishing beyond a cutoff value, K{sub c}. Such features suggest that momentum-dependent trapping boundaries, perhaps drift-type loss cones, serve as boundary conditions for trapped electrons as well as trapped protons.

  15. Phase-Space Density Analysis of the AE-8 Traped Electron and the AP-8 Trapped Proton Model Environments

    Energy Technology Data Exchange (ETDEWEB)

    Thomas E. Cayton

    2005-08-01

    The AE-8 trapped electron and the AP-8 trapped proton models are used to examine the L-shell variation of phase-space densities for sets of transverse (or 1st) invariants, {mu}, and geometrical invariants, K (related to the first two adiabatic invariants). The motivation for this study is twofold: first, to discover the functional dependence of the phase-space density upon the invariants; and, second, to explore the global structure of the radiation belts within this context. Variation due to particle rest mass is considered as well. The overall goal of this work is to provide a framework for analyzing energetic particle data collected by instruments on Global Positioning System (GPS) spacecraft that fly through the most intense region of the radiation belt. For all considered values of {mu} and K, and for 3.5 R{sub E} < L < 6.5 R{sub E}, the AE-8 electron phase-space density increases with increasing L; this trend--the expected one for a population diffusing inward from an external source--continues to L = 7.5 R{sub E} for both small and large values of K but reverses slightly for intermediate values of K. The AP-8 proton phase-space density exhibits {mu}-dependent local minima around L = 5 R{sub E}. Both AE-8 and AP-8 exhibit critical or cutoff values for the invariants beyond which the flux and therefore the phase-space density vanish. For both electrons and protons, these cutoff values vary systematically with magnetic moment and L-shell and are smaller than those estimated for the atmospheric loss cone. For large magnetic moments, for both electrons and protons, the K-dependence of the phase-space density is exponential, with maxima at the magnetic equator (K = 0) and vanishing beyond a cutoff value, K{sub c}. Such features suggest that momentum-dependent trapping boundaries, perhaps drift-type loss cones, serve as boundary conditions for trapped electrons as well as trapped protons.

  16. Primary processes of the electron-protic species coupling in pure aqueous phases: - femtosecond laser spectroscopy study; - quantum approach of the electron-water interaction

    International Nuclear Information System (INIS)

    Pommeret, Stanislas

    1991-01-01

    This thesis work deals with the coupling mechanisms between an electron, water molecules or protic species (hydronium ion, hydroxyl radical). Two complementary studies have been carry out in pure aqueous phases. The first one is concerned with the structural aspect of the hydrated electron which is studied via a semi-quantum approach Splitting Operator Method. The results indicates the importance of the second hydration shell in the localisation of an electron at 77 and 300 Kelvin. The second part of this work relates to the dynamic of the primary processes in light or heavy water at room temperature: the ion-molecule reaction, radical pair formation, geminate recombination of the hydrated electron with the hydronium ion and the hydroxyl radical. The dynamic of these reactions is studied by time resolved absorption spectroscopy from the near infrared to the near ultraviolet with a few tens femto-seconds temporal precision. The analysis of the primary processes takes into account the protic properties of water molecules. (author) [fr

  17. Unified approach to dense matter

    International Nuclear Information System (INIS)

    Park, Byung-Yoon; Lee, Hee-Jung; Vento, Vicente; Kim, Joon-Il; Min, Dong-Pil; Rho, Mannque

    2005-01-01

    We apply the Skyrme model to dense hadronic matter, which provides a unified approach to high density, valid in the large N c limit. In our picture, dense hadronic matter is described by the classical soliton configuration with minimum energy for the given baryon number density. By incorporating the meson fluctuations on such ground state we obtain an effective Lagrangian for meson dynamics in a dense medium. Our starting point has been the Skyrme model defined in terms of pions, thereafter we have extended and improved the model by incorporating other degrees of freedom such as dilaton, kaons and vector mesons

  18. Einstein's theory of unified fields

    CERN Document Server

    Tonnelat, Marie Antoinette

    2014-01-01

    First published in1966, here is presented a comprehensive overview of one of the most elusive scientific speculations by the pre-eminent genius of the 20th century. The theory is viewed by some scientists with deep suspicion, by others with optimism, but all agree that it represents an extreme challenge. As the author herself affirms, this work is not intended to be a complete treatise or 'didactic exposition' of the theory of unified fields, but rather a tool for further study, both by students and professional physicists. Dealing with all the major areas of research whic

  19. Reversibility of magnetic field driven transition from electronic phase separation state to single-phase state in manganites: A microscopic view

    Science.gov (United States)

    Liu, Hao; Lin, Lingfang; Yu, Yang; Lin, Hanxuan; Zhu, Yinyan; Miao, Tian; Bai, Yu; Shi, Qian; Cai, Peng; Kou, Yunfang; Lan, Fanli; Wang, Wenbin; Zhou, Xiaodong; Dong, Shuai; Yin, Lifeng; Shen, Jian

    2017-11-01

    Electronic phase separation (EPS) is a common phenomenon in strongly correlated oxides. For colossal magnetoresistive (CMR) manganites, the EPS is so pronounced that not only does it govern the CMR behavior, but also raises a question whether EPS exists as a ground state for systems or a metastable state. While it has been well known that a magnetic field can drive the transition of the EPS state into a single-phase state in manganites, the reversibility of this transition is not well studied. In this work we use magnetic force microscopy (MFM) to directly visualize the reversibility of the field driven transition between the EPS state and the single-phase state at different temperatures. The MFM images correspond well with the global magnetic and transport property measurements, uncovering the underlying mechanism of the field driven transition between the EPS state and the single-phase state. We argue that EPS state is a consequence of system quenching whose response to an external magnetic field is governed by a local energy landscape.

  20. Solving structure in the CP29 light harvesting complex with polarization-phased 2D electronic spectroscopy

    Science.gov (United States)

    Ginsberg, Naomi S.; Davis, Jeffrey A.; Ballottari, Matteo; Cheng, Yuan-Chung; Bassi, Roberto; Fleming, Graham R.

    2011-01-01

    The CP29 light harvesting complex from green plants is a pigment-protein complex believed to collect, conduct, and quench electronic excitation energy in photosynthesis. We have spectroscopically determined the relative angle between electronic transition dipole moments of its chlorophyll excitation energy transfer pairs in their local protein environments without relying on simulations or an X-ray crystal structure. To do so, we measure a basis set of polarized 2D electronic spectra and isolate their absorptive components on account of the tensor relation between the light polarization sequences used to obtain them. This broadly applicable advance further enhances the acuity of polarized 2D electronic spectroscopy and provides a general means to initiate or feed back on the structural modeling of electronically-coupled chromophores in condensed phase systems, tightening the inferred relations between the spatial and electronic landscapes of ultrafast energy flow. We also discuss the pigment composition of CP29 in the context of light harvesting, energy channeling, and photoprotection within photosystem II. PMID:21321222

  1. Towards a Unified Business Model Vocabulary: A Proposition of Key Constructs

    OpenAIRE

    Mettler, Tobias

    2014-01-01

    The design of business models is of decisive importance and as such it has been a major research theme in service and particularly electronic markets. Today, different definitions of the term and ideas of core constructs of business models exist. In this paper we present a unified vocabulary for business models that builds upon the elementary perception of three existing, yet very dissimilar ontologies for modeling the essence of a business. The resulting unified business model vocabulary not...

  2. In situ transmission electron microscope studies of ion irradiation-induced and irradiation-enhanced phase changes

    International Nuclear Information System (INIS)

    Allen, C.W.

    1992-01-01

    Motivated at least initially by materials needs for nuclear reactor development, extensive irradiation effects studies employing transmission electron microscopes (TEM) have been performed for several decades, involving irradiation-induced and irradiation-enhanced microstructural changes, including phase transformations such as precipitation, dissolution, crystallization, amorphization, and order-disorder phenomena. From the introduction of commercial high voltage electron microscopes (HVEM) in the mid-1960s, studies of electron irradiation effects have constituted a major aspect of HVEM application in materials science. For irradiation effects studies two additional developments have had particularly significant impact; the development of TEM specimen holder sin which specimen temperature can be controlled in the range 10-2200 K and the interfacing of ion accelerators which allows in situ TEM studies of irradiation effects and the ion beam modification of materials within this broad temperature range. This paper treats several aspects of in situ studies of electron and ion beam-induced and enhanced phase changes and presents two case studies involving in situ experiments performed in an HVEM to illustrate the strategies of such an approach of the materials research of irradiation effects

  3. Pressure-induced change of the electronic state in the tetragonal phase of CaFe2As2

    International Nuclear Information System (INIS)

    Sakaguchi, Yui; Ikeda, Shugo; Kuse, Tetsuji; Kobayashi, Hisao

    2014-01-01

    We have investigated the electronic states of single-crystal CaFe 2 As 2 under hydrostatic pressure using 57 Fe Mössbauer spectroscopy and magnetization measurements. The center shift and the quadrupole splitting were refined from observed 57 Fe Mössbauer spectra using the single-crystalline sample under pressure at room temperature. A discontinuous decrease in the pressure dependence of the refined center shift was observed at 0.33 GPa without any anomaly in the pressure dependence of the refined quadrupole splitting, indicating a purely electronic state change in CaFe 2 As 2 with a tetragonal structure. Such a change is shown to be reflected in the peak-like anomalies observed in the pressure dependences of the magnetic susceptibility at 0.26 GPa above 150 K. Our results reveal that this pressure-induced electronic state change suppresses the tetragonal-to-orthorhombic structural phase transition accompanied by an antiferromagnetic ordering. We further observed superconductivity in CaFe 2 As 2 below ∼8 K around 0.33 GPa although our sample was not in a single phase at this pressure. These findings suggest that the electronic state change observed in CaFe 2 As 2 with the tetragonal structure is relevant to the appearance of the pressure-induced superconductivity in AFe 2 As 2 . (paper)

  4. Estimation of visibility of phase contrast with extraction voltages for field emission gun electron microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Xing, E-mail: xmeng101@gmail.com

    2017-02-15

    Estimation was made for visibility of phase contrast with varying extraction voltages. The resulting decay rates of visibility show that images with low image contrast from cryo EM will be seriously impacted with high extraction voltages. - Highlights: • Cryo EM • Phase contrast • Extraction votage.

  5. Liquid-solid phase transition of Ge-Sb-Te alloy observed by in-situ transmission electron microscopy

    International Nuclear Information System (INIS)

    Berlin, Katja; Trampert, Achim

    2017-01-01

    Melting and crystallization dynamics of the multi-component Ge-Sb-Te alloy have been investigated by in-situ transmission electron microscopy (TEM). Starting point of the phase transition study is an ordered hexagonal Ge 1 Sb 2 Te 4 thin film on Si(111) where the crystal structure and the chemical composition are verified by scanning TEM and electron energy-loss spectroscopy, respectively. The in-situ observation of the liquid phase at 600°C including the liquid-solid and liquid-vacuum interfaces and their movements was made possible due to an encapsulation of the TEM sample. The solid-liquid interface during melting displays a broad and diffuse transition zone characterized by a vacancy induced disordered state. Although the velocities of interface movements are measured to be in the nanometer per second scale, both, for crystallization and solidification, the underlying dynamic processes are considerably different. Melting reveals linear dependence on time, whereas crystallization exhibits a non-linear time-dependency featuring a superimposed start-stop motion. Our results may provide valuable insight into the atomic mechanisms at interfaces during the liquid-solid phase transition of Ge-Sb-Te alloys. - Highlights: • In-situ TEM observation of liquid Ge-Sb-Te phase transition due to encapsulation. • During melting: Observation of non-ordered interface transition due to premelting. • During solidification: Observation of non-linear time-dependent crystallization.

  6. Comparison of the layer structure of vapor phase and leached SRL glass by use of AEM [analytical electron microscopy

    International Nuclear Information System (INIS)

    Biwer, B.M.; Bates, J.K.; Abrajano, T.A. Jr.; Bradley, J.P.

    1989-01-01

    Test samples of 131 type glass that have been reacted for extended time periods in water vapor atmospheres of different relative humidities and in static leaching solution have been examined to characterize the reaction products. Analytical electron microscopy (AEM) was used to characterize the leached samples, and a complicated layer structure was revealed, consisting of phases that precipitate from solution and also form within the residual glass layer. The precipitated phases include birnes-site, saponite, and an iron species, while the intralayer phases include the U-Ti containing phase brannerite distributed within a matrix consisting of bands of an Fe rich montmorillonite clay. Comparison is made between samples leached at 40 degrees C for 4 years with those leached at 90 degrees C for 3-1/2 years. The samples reacted in water vapor were examined with scanning electron microscopy and show increasing reaction as both the relative humidity and time of reaction increases. These samples also contain a layered structure with reaction products on the glass surface. 15 refs., 5 figs

  7. Liquid-solid phase transition of Ge-Sb-Te alloy observed by in-situ transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Berlin, Katja, E-mail: katja.berlin@pdi-berlin.de; Trampert, Achim

    2017-07-15

    Melting and crystallization dynamics of the multi-component Ge-Sb-Te alloy have been investigated by in-situ transmission electron microscopy (TEM). Starting point of the phase transition study is an ordered hexagonal Ge{sub 1}Sb{sub 2}Te{sub 4} thin film on Si(111) where the crystal structure and the chemical composition are verified by scanning TEM and electron energy-loss spectroscopy, respectively. The in-situ observation of the liquid phase at 600°C including the liquid-solid and liquid-vacuum interfaces and their movements was made possible due to an encapsulation of the TEM sample. The solid-liquid interface during melting displays a broad and diffuse transition zone characterized by a vacancy induced disordered state. Although the velocities of interface movements are measured to be in the nanometer per second scale, both, for crystallization and solidification, the underlying dynamic processes are considerably different. Melting reveals linear dependence on time, whereas crystallization exhibits a non-linear time-dependency featuring a superimposed start-stop motion. Our results may provide valuable insight into the atomic mechanisms at interfaces during the liquid-solid phase transition of Ge-Sb-Te alloys. - Highlights: • In-situ TEM observation of liquid Ge-Sb-Te phase transition due to encapsulation. • During melting: Observation of non-ordered interface transition due to premelting. • During solidification: Observation of non-linear time-dependent crystallization.

  8. Imaging of phase change materials below a capping layer using correlative infrared near-field microscopy and electron microscopy

    Science.gov (United States)

    Lewin, M.; Hauer, B.; Bornhöfft, M.; Jung, L.; Benke, J.; Michel, A.-K. U.; Mayer, J.; Wuttig, M.; Taubner, T.

    2015-10-01

    Phase Change Materials (PCM) show two stable states in the solid phase with significantly different optical and electronic properties. They can be switched reversibly between those two states and are promising candidates for future non-volatile memory applications. The development of phase change devices demands characterization tools, yielding information about the switching process at high spatial resolution. Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) allows for spectroscopic analyses of the different optical properties of the PCMs on the nm-scale. By correlating the optical s-SNOM images with transmission electron microscopy images of the same sample, we unambiguously demonstrate the correlation of the infrared optical contrast with the structural state of the phase change material. The investigated sample consists of sandwiched amorphous and crystalline regions of Ag 4 In 3 Sb 67 Te 26 below a 100 nm thick ( ZnS ) 80 - ( SiO2 ) 20 capping layer. Our results demonstrate the sensitivity of s-SNOM to small dielectric near-field contrasts even below a comparably thick capping layer ( 100 nm ).

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

    Directory of Open Access Journals (Sweden)

    Karol Nass

    2016-05-01

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

  10. Microstructures and phase formations in the surface layer of an AISI D2 steel treated with pulsed electron beam

    International Nuclear Information System (INIS)

    Zou, J.X.; Grosdidier, T.; Zhang, K.M.; Gao, B.; Hao, S.Z.; Dong, C.

    2007-01-01

    The nanostructures and metastable phase transformations in the surface layer of an AISI D2 steel treated with high current pulsed electron beam (HCPEB) were investigated. The surface structure is marked by two distinct features, i.e. the formation of sub-micrometer fine austenite γ grains (50-150 nm), and the disappearance of carbides via dissolution and crater eruption. The γ phase directly grows from the melt and is retained down to room temperature. Although the cooling rate is as high as 10 7 K/s in our case, the martensitic transformation could completely be suppressed. Such an effect is due to the increased stability of the austenite phase through grain refinement and chemistry modification

  11. Unified theory of the exciplex formation/dissipation.

    Science.gov (United States)

    Khokhlova, Svetlana S; Burshtein, Anatoly I

    2010-11-04

    The natural extension and reformulation of the unified theory (UT) proposed here makes it integro-differential and capable of describing the distant quenching of excitation by electron transfer, accompanied with contact but reversible exciplex formation. The numerical solution of the new UT equations allows specifying the kinetics of the fluorescence quenching and exciplex association/dissociation as well as those reactions' quantum yields. It was demonstrated that the distant electron transfer in either the normal or inverted Marcus regions screens the contact reaction of exciplex formation, especially at slow diffusion.

  12. Radiation and High Temperature Tolerant GaN Power Electronics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Power electronic components with high operating voltages are desirable in NASA Power Management and Distribution (PMAD) systems since they can lead to reduced mass...

  13. Co-simulation of heavy truck tire dynamics and electronic stability control systems (phase B).

    Science.gov (United States)

    2010-07-01

    In the past decade, electronic stability controls (ESC) have become increasingly common on vehicles operating in the United States. The acceptance of this technology has progressed to the point where all new passenger vehicles sold in the US are requ...

  14. Co-simulation of heavy truck tire dynamics and electronic stability control systems (phase A).

    Science.gov (United States)

    2009-07-01

    Electronic stability control (ESC) systems have been proven to be an effective means of preventing instability and loss of control on both passenger vehicles and heavy trucks. In addition, roll stability algorithms are an effective means of reducing ...

  15. Ka-Band Electronically Steered CubeSat Antenna, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Kymeta Government Solutions (KGS) designed, analyzed, built, tested, and delivered a small, lightweight, low-cost, low-power electronically steered Ka-band prototype...

  16. Software and Tools for Electronics Printing in Space(STEPS), Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We are proposing an to develop a direct write electronics and avionics printing capability within the Techshot BioFabrication Facility currently funded and...

  17. Electronics Modeling and Design for Cryogenic and Radiation Hard Applications, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — We are developing CAD tools, models and methodologies for electronics design for circuit operation in extreme environments with a focus on very low temperature and...

  18. A Low Power Rad-Hard ADC for the KID Readout Electronics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposal aims to develop a radiation hardened analog-to-digital converter (ADC) required for the Kinetic Inductance Detector (KID) readout electronics. KIDs are...

  19. Ionic Polymer-Based Removable and Charge-Dissipative Coatings for Space Electronic Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Protection of critical electronic systems in spacecraft and satellites is imperative for NASA's future missions to high-energy, outer-planet environments. The...

  20. Electronic band structure of TiFese2 in ferromagnetic phase

    International Nuclear Information System (INIS)

    Jahangirli, Z.A.; Mimura, K.; Shim, Y.; Mamedov, N.T.; Wakita, K.; Orudzhev, G.S.; Jahangirli, Z.A.

    2011-01-01

    Electronic band structure of crystalline TiFeSe 2 has been calculated using full-potential method of Linear Augmented Plane Wave (LAPW) in density-functional approach with exchange-correlation potential taken in Generalized Gradient Approximation (GGA). The chemical bond in TiFeSe 2 is shown to be metallic because energies of 3d-electrons localized at iron atoms are close to Fermi energy level

  1. Finite Element Models for Electron Beam Freeform Fabrication Process, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase II proposal offers to develop a comprehensive computer simulation methodology based on the finite element method for...

  2. In Situ Transmission Electron Microscopy Observation of Nanostructural Changes in Phase-Change Memory

    KAUST Repository

    Meister, Stefan; Kim, SangBum; Cha, Judy J.; Wong, H.-S. Philip; Cui, Yi

    2011-01-01

    Phase-change memory (PCM) has been researched extensively as a promising alternative to flash memory. Important studies have focused on its scalability, switching speed, endurance, and new materials. Still, reliability issues and inconsistent

  3. Ultra-Lightweight, High Efficiency Silicon-Carbide (SIC) Based Power Electronic Converters, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business of Innovation Research Phase I proposal seeks to investigate and prove the feasibility of developing highly efficient, ultra-lightweight SiC...

  4. Efficient Computation of Coherent Synchrotron Radiation Taking into Account 6D Phase Space Distribution of Emitting Electrons

    International Nuclear Information System (INIS)

    Chubar, O.; Couprie, M.-E.

    2007-01-01

    CPU-efficient method for calculation of the frequency domain electric field of Coherent Synchrotron Radiation (CSR) taking into account 6D phase space distribution of electrons in a bunch is proposed. As an application example, calculation results of the CSR emitted by an electron bunch with small longitudinal and large transverse sizes are presented. Such situation can be realized in storage rings or ERLs by transverse deflection of the electron bunches in special crab-type RF cavities, i.e. using the technique proposed for the generation of femtosecond X-ray pulses (A. Zholents et. al., 1999). The computation, performed for the parameters of the SOLEIL storage ring, shows that if the transverse size of electron bunch is larger than the diffraction limit for single-electron SR at a given wavelength -- this affects the angular distribution of the CSR at this wavelength and reduces the coherent flux. Nevertheless, for transverse bunch dimensions up to several millimeters and a longitudinal bunch size smaller than hundred micrometers, the resulting CSR flux in the far infrared spectral range is still many orders of magnitude higher than the flux of incoherent SR, and therefore can be considered for practical use

  5. Analytical electron microscope study of the omega phase transformation in a zirconium-niobium alloy

    International Nuclear Information System (INIS)

    Zaluzec, N.J.

    1979-01-01

    The study of the as-quenched omega phase morphology shows that the domain size of Zr-15% Nb is on the order of 30 A. No alignment of omega domains along β directions was observed and samples having undergone thermal cycling in thin foil form, did not develop a long-period structure of alternating β and ω phases below the omega transformation temperature

  6. Constructal Law and the Unifying Principle of Design

    CERN Document Server

    Lorente, Sylvie; Bejan, Adrian

    2013-01-01

    Design happens everywhere, whether in animate objects (e.g., dendritic lung structures, bacterial colonies, and corals), inanimate patterns (river basins, beach slope, and dendritic crystals), social dynamics (pedestrian traffic flows), or engineered systems (heat dissipation in electronic circuitry). This “design in nature” often takes on remarkably similar patterns, which can be explained under one unifying Constructal Law. This book explores the unifying power of the Constructal Law and its applications in all domains of design generation and evolution, ranging from biology and geophysics to globalization, energy, sustainability, and security.  The Constructal Law accounts for the universal tendency of flow systems to morph into evolving configurations that provide greater and easier access over time. The Constructal Law resolves the many and contradictory ad hoc statements of “optimality”, end design, and destiny in nature, such as minimum and maximum entropy production and minimum and maximum fl...

  7. Rational Unified Process jako metodika vývoje softwaru

    OpenAIRE

    Rytíř, Vladimír

    2008-01-01

    Cílem této práce je seznámit se s procesem vývoje softwaru dle vybraných metodik s hlavním zaměřením na metodiku Rational Unified Process od firmy IBM. Incepční a elaborační fáze této metody také aplikuji na praktickém  příkladě. Goal of my work is to introduce software development process metods specialized to Rational Unified Process metod from IBM. I aplicate inception and elaboration phases of RUP on practical example. B

  8. Unified dark fluid in Brans-Dicke theory

    International Nuclear Information System (INIS)

    Tripathy, Sunil K.; Behera, Dipanjali; Mishra, Bivudutta

    2015-01-01

    Anisotropic dark energy cosmological models are constructed in the frame work of generalised Brans-Dicke theory with a self-interacting potential. A unified dark fluid characterised by a linear equation of state is considered as the source of dark energy. The shear scalar is considered to be proportional to the expansion scalar simulating an anisotropic relationship among the directional expansion rates. The dynamics of the universe in the presence of a unified dark fluid in anisotropic background have been discussed. The presence of an evolving scalar field makes it possible to get an accelerating phase of expansion even for a linear relationship among the directional Hubble rates. It is found that the anisotropy in expansion rates does not affect the scalar field, the self-interacting potential, but it controls the non-evolving part of the Brans-Dicke parameter. (orig.)

  9. Water-soluble phosphine-protected Au9 clusters: Electronic structures and nuclearity conversion via phase transfer

    Science.gov (United States)

    Yao, Hiroshi; Tsubota, Shuhei

    2017-08-01

    In this article, isolation, exploration of electronic structures, and nuclearity conversion of water-soluble triphenylphosphine monosulfonate (TPPS)-protected nonagold (Au9) clusters are outlined. The Au9 clusters are obtained by the reduction of solutions containing TPPS and HAuCl4 and subsequent electrophoretic fractionation. Mass spectrometry and elemental analysis reveal the formation of [Au9(TPPS)8]5- nonagold cluster. UV-vis absorption and magnetic circular dichroism (MCD) spectra of aqueous [Au9(TPPS)8]5- are quite similar to those of [Au9(PPh3)8]3+ in organic solvent, so the solution-phase structures are likely similar for both systems. Simultaneous deconvolution analysis of absorption and MCD spectra demonstrates the presence of some weak electronic transitions that are essentially unresolved in the UV-vis absorption. Quantum chemical calculations for a model compound [Au9(pH3)8]3+ show that the possible (solution-phase) skeletal structure of the nonagold cluster has D2h core symmetry rather than C4-symmetrical centered crown conformation, which is known as the crystal form of the Au9 compound. Moreover, we find a new nuclearity conversion route from Au9 to Au8; that is, phase transfer of aqueous [Au9(TPPS)8]5- into chloroform using tetraoctylammonium bromide yields [Au8(TPPS)8]6- clusters in the absence of excess phosphine.

  10. Towards a Unified Programming Language

    DEFF Research Database (Denmark)

    Madsen, Ole Lehrmann

    2000-01-01

    The goal of research in programming languages should be to develop languages that integrates the best of concepts and constructs from the various programming paradigms. We do not argue for a multi-paradigm language, where the programmer alternates between the different paradigms/styles. Instead, we...... find that the languages of the future should integrate the best available concepts and constructs in such a way that the programmer does not think of multiple paradigms when using a given language. In this paper, we describe to what extent the BETA language has been successful in obtaining a unified...... style and where more research is needed. In addition to traditional paradigms such as object-oriented-, imperative-functional- and logic programming, we also discuss concurrent programming and prototype-based programming. We discuss language features such as the BETA pattern construct, virtual...

  11. A unified plant information network

    International Nuclear Information System (INIS)

    Niederauer, G.F.

    1986-01-01

    Technology is bringing power plants fully into the age of computerization. Microcomputers, data base managers, networking, and friendly, expert software are principal technology factors. Monitoring will improve, and the number and power of computers is increasing. The huge information flow will cause computers to be integrated into a communication network. The total plant operating triangle includes process, engineering, and management systems. The total network will integrate all of these into a Total Unified Plant Information Network (TUPIN). Software will take the type of information beyond monitored data. Analysis will improve through direct access to logical, physical, and procedural models by end users. Information management will improve through widespread use of hierarchical, relational, and expert data base managers. Expert systems will aid in diagnostics and interpretation. The goal is to automate plant operations to enhance safety and performance and to reduce cost by making both the plants and the personnel more expert

  12. Unifying physical concepts of reality

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, T.L.

    1983-08-01

    Physics may be characterized as the science of matter and energy. It anchors the two ends of the frontiers of science: the frontier of the very small and the frontier of the very large. All of the phenomena that we observe and study at the frontiers of science - all external experiences - are manifestations of matter and energy. One may, therefore, use physics to exemplify both the diversity and unity of science. This theme will be developed in two separate examples: first by sketching, very briefly, the historical origins of frontiers of the very small and very large and the converging unity of these two frontiers; and then by describing certain unifying concepts that play a central role in physics and provide a framework for relating developments in different sciences.

  13. Phenomenology of unified gauge theories

    International Nuclear Information System (INIS)

    Ellis, J.

    1983-01-01

    Part I of these lectures treats the standard Glashow-Weinberg-Salam model of weak and electromagnetic interactions, discussing in turn its basic structure and weak neutral currents, charged currents, mixing angles and CP violation, and the phenomenology of weak vector and Higgs bosons. Part II of the lectures discusses the structure of theories of dynamical symmetry breaking such as technicolour, phenomenological consequences, frustrations and alternatives. The third part of these lectures offers the standard menu of grand unified theories (GUTs) of the strong, weak and electromagnetic interactions, including an hors d'oeuvre of constraints on the parameters of the standard model, a main course of baryon number violating processes, and desserts which violate lepton number and CP. The fourth and final part goes through different attempts to remedy the inadequacies of previous theories by invoking supersymmetry and reaching out towards gravitation. (orig./HSI)

  14. Unifying physical concepts of reality

    International Nuclear Information System (INIS)

    Gilbert, T.L.

    1983-01-01

    Physics may be characterized as the science of matter and energy. It anchors the two ends of the frontiers of science: the frontier of the very small and the frontier of the very large. All of the phenomena that we observe and study at the frontiers of science - all external experiences - are manifestations of matter and energy. One may, therefore, use physics to exemplify both the diversity and unity of science. This theme will be developed in two separate examples: first by sketching, very briefly, the historical origins of frontiers of the very small and very large and the converging unity of these two frontiers; and then by describing certain unifying concepts that play a central role in physics and provide a framework for relating developments in different sciences

  15. Unified gauge theories with spontaneous symmetry breaking

    International Nuclear Information System (INIS)

    MacDowell, S.W.

    1975-01-01

    Unified gauge theories with spontaneous symmetry breaking are studied with a view to renormalize quantum field theory. Georgi-Glashow and Weinberg-Salam models to unify weak and electromagnetic interactions are discussed in detail. Gauge theories of strong interactions are also considered [pt

  16. Crystal structure of the martensite phase in the ferromagnetic shape memory compound Ni2MnGa studied by electron diffraction

    International Nuclear Information System (INIS)

    Fukuda, Takashi; Kushida, Hiroaki; Todai, Mitsuharu; Kakeshita, Tomoyuki; Mori, Hirotaro

    2009-01-01

    The electron diffraction patterns of Ni 2 MnGa show six satellites at ±q M , ±2q M and ±3q M , with q M = 0.427(5) g 22 -bar 0 between fundamental reflections in the martensite phase, and two satellites at ±q I , with q I = 0.340(5) g 22 -bar 0 in the intermediate phase, meaning that these phases have incommensurate structures. In addition, the diffraction pattern of the intermediate phase continuously changes to that of the parent phase via the X-phase, suggesting the existence of a multicritical phenomenon.

  17. A unifying philosophy of governance

    Directory of Open Access Journals (Sweden)

    Sankarshan Acharya

    2012-09-01

    Full Text Available Bertrand Russell won Nobel Prize for arguing that science has triumphed over religion. Since religions are based on god, Russell’s argument implies that science has triumphed over both religion and god. But neither Russell nor anyone else has ever defined religion and god, rationally. The assertion about triumph of science (which is founded on rationality over concepts such as religion and god (which are not defined rationally or scientifically in the extant literature cannot be rational. This paper offers a novel rational philosophical foundation for the concepts of god, religion and science in which the claim that science triumphs over religion is redundant. This paper also presents substantial new insights about epistemic truths to help resolve current problems facing humanity like financial moral hazard and terrorism which have unnerved nations worldwide. The humanity now begs to answer a fundamental question of how we can govern ourselves. This paper offers a coherent set of credible answers. In particular, it offers a coherent unified philosophy about how humans have universally formed beliefs to govern themselves and how this philosophy could help resolve current problems. The universal rendering of beliefs articulated here subsumes the extant characterization of probability beliefs in mathematics, science, engineering, economics, religion and philosophy. The universal beliefs so articulated in this paper obviate the currently prevalent philosophical conflicts between religion and science or between theism and atheism and paves the way for optimal governance for prosperity amid stability. This philosophy also offers a rational characterization of the spiritual notion of Nirvana or salvation of the soul and the notion of epistemic truth. The unifying philosophy can help humanity achieve unity, stability and prosperity, sans financial moral hazard, antagonism, wars, nuclear proliferation, global warming and atmospheric pollution.

  18. Toward a Unified AGN Structure

    Science.gov (United States)

    Kazanas, Demosthenes; Fukumura, Keigo; Shrader, Chris; Behar, Ehud; Contopoulosa, Ioannis

    2012-01-01

    We present a unified model for the structure and appearance of accretion powered sources across their entire luminosity range from galactic X-ray binaries (XRB) to luminous quasars, with emphasis on AG N and their phenomenology. Central to this model is the notion of MHD winds launched by the accretion disks that power these objects. These winds provide the matter that manifests as blueshifted absorption features in the UV and X-ray spectra of a large fraction of these sources; furthermore, their density distribution in the poloidal plane determines their "appearance" (i.e. the column and velocity structure of these absorption features and the obscuration of the continuum source) as a function of the observer inclination angle (a feature to which INTEGRAL has made significant contributions). This work focuses on just the broadest characteristics of these objects; nonetheless, it provides scaling laws that allow one to reproduce within this model the properties of objects extending in luminosity from luminous quasars to XRBs. Our general conclusion is that the AGN phenomenology can be accounted for in terms of three parameters: The wind maSS flux in units of the Eddington value, m(dot), the observers' inclination angle Theta and the logarithmic slope between the 0/UV and X-ray fluxes alpha(sub ox); however because of a correlation between alpha(sub ox) and UV luminosity the number of significant parameters is two. The AGN correlations implied by this model appear to extend to and consistent with the XRB phenomenology, suggesting the presence of a truly unified underlying structure for accretion powered sources.

  19. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, Celia L. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Depablos-Rivera, Osmary, E-mail: osmarydep@yahoo.com [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Silva-Bermudez, Phaedra [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Instituto Nacional de Rehabilitación, Calz. México Xochimilco No. 289 Col. Arenal de Guadalupe, C.P.14389, Ciudad de México, D.F. (Mexico); Muhl, Stephen [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre [Laboratoire de Physique de la Matière Condensée, Université de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex 1 (France); Camps, Enrique [Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, kilómetro 36.5. La Marquesa, Municipio de Ocoyoacac, CP 52750, Estado de México (Mexico); Rodil, Sandra E. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico)

    2015-03-02

    The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi{sub 2}O{sub 3} thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi{sub 2}O{sub 3} phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi{sub 2}O{sub 3} thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV.

  20. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

    International Nuclear Information System (INIS)

    Gomez, Celia L.; Depablos-Rivera, Osmary; Silva-Bermudez, Phaedra; Muhl, Stephen; Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre; Camps, Enrique; Rodil, Sandra E.

    2015-01-01

    The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi 2 O 3 thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi 2 O 3 phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi 2 O 3 thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV