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Sample records for range boundaries electronic

  1. Electron transmission through a stacking domain boundary in multilayer graphene

    Science.gov (United States)

    Nam, Nguyen N. T.; Koshino, Mikito

    2015-06-01

    We present a theoretical study of the electron transmission through the AB-BA stacking boundary in multilayer graphenes. Using the tight-binding model and the transfer matrix method, we calculate the electron transmission probability through the boundary as a function of electron Fermi energy in multilayers from bilayer to five-layer. We find that the transmission is strongly suppressed particularly near the band touching point, suggesting that the electronic conductivity in general multilayer graphenes is significantly interfered with by stacking fault. The conductivity suppression by stacking fault is the strongest in the bilayer graphene, while it is gradually relaxed as the number of layers increases. At a large carrier density, we observe an even-odd effect where the transmission is relatively lower in trilayer and five-layer than in bilayer and four-layer, and this is related to the existence of a monolayerlike linear band in odd layers. For bilayer graphene, we also study the effect of the perpendicular electric field opening an energy gap, and show that the band deformation enhances the electron transmission at a fixed carrier density.

  2. Short Rayleigh Range Free Electron Laser Amplifiers

    CERN Document Server

    Yu, L H; Murphy, J B; Rose, J; Shaftan, T V; Wang, X J; Watanabe, T

    2005-01-01

    An important requirement for a high average power laser system is a manageable power density on the first optical element. One possibility to achieve this is a single pass amplifier which generates a short Rayleigh range (SRL) light beam. We present design parameters and calculated performances for several SRL configurations. These include a simulation of the optically guided (pinched) MW class FEL [1], the scalloped beam FEL amplifier [2] and high gain TOK amplifiers we propose to explore at our SDL facility.

  3. Plasmon Reflections by Topological Electronic Boundaries in Bilayer Graphene

    Science.gov (United States)

    Jiang, Bor-Yuan; Ni, Guang-Xin; Addison, Zachariah; Shi, Jing K.; Liu, Xiaomeng; Zhao, Shu Yang Frank; Kim, Philip; Mele, Eugene J.; Basov, Dimitri N.; Fogler, Michael M.

    2017-11-01

    Domain walls separating regions of AB and BA interlayer stacking in bilayer graphene have attracted attention as novel examples of structural solitons, topological electronic boundaries, and nanoscale plasmonic scatterers. We show that strong coupling of domain walls to surface plasmons observed in infrared nanoimaging experiments is due to topological chiral modes confined to the walls. The optical transitions among these chiral modes and the band continua enhance the local ac conductivity, which leads to plasmon reflection by the domain walls. The imaging reveals two kinds of plasmonic standing-wave interference patterns, which we attribute to shear and tensile domain walls. We compute the electronic structure of both wall varieties and show that the tensile wall contain additional confined bands which produce a structure-specific contrast of the local conductivity. The calculated plasmonic interference profiles are in quantitative agreement with our experiments.

  4. Efficient electron open boundaries for simulating electrochemical cells

    Science.gov (United States)

    Zauchner, Mario G.; Horsfield, Andrew P.; Todorov, Tchavdar N.

    2018-01-01

    Nonequilibrium electrochemistry raises new challenges for atomistic simulation: we need to perform molecular dynamics for the nuclear degrees of freedom with an explicit description of the electrons, which in turn must be free to enter and leave the computational cell. Here we present a limiting form for electron open boundaries that we expect to apply when the magnitude of the electric current is determined by the drift and diffusion of ions in a solution and which is sufficiently computationally efficient to be used with molecular dynamics. We present tight-binding simulations of a parallel-plate capacitor with nothing, a dimer, or an atomic wire situated in the space between the plates. These simulations demonstrate that this scheme can be used to perform molecular dynamics simulations when there is an applied bias between two metal plates with, at most, weak electronic coupling between them. This simple system captures some of the essential features of an electrochemical cell, suggesting this approach might be suitable for simulations of electrochemical cells out of equilibrium.

  5. Short range correlations in a one dimensional electron gas

    OpenAIRE

    Tas, Murat; Tomak, Mehmet

    2001-01-01

    We use the SSTL (Singwi, Sjolander, Tosi, Land) approximation to investigate the short--range correlations in a one dimensional electron gas, for the first time. Although SSTL is introduced to better satisfy the compressibility sum rule in three dimensions, the widely used STLS (Singwi, Tosi, Land, Sjolander) approximation turns out to be more successful in the case of the one dimensional electron gas.

  6. Boundary Associated Long Noncoding RNA Mediates Long-Range Chromosomal Interactions.

    Directory of Open Access Journals (Sweden)

    Ifeoma Jane Nwigwe

    Full Text Available CCCTC binding factor (CTCF is involved in organizing chromosomes into mega base-sized, topologically associated domains (TADs along with other factors that define sub-TAD organization. CTCF-Cohesin interactions have been shown to be critical for transcription insulation activity as it stabilizes long-range interactions to promote proper gene expression. Previous studies suggest that heterochromatin boundary activity of CTCF may be independent of Cohesin, and there may be additional mechanisms for defining topological domains. Here, we show that a boundary site we previously identified known as CTCF binding site 5 (CBS5 from the homeotic gene cluster A (HOXA locus exhibits robust promoter activity. This promoter activity from the CBS5 boundary element generates a long noncoding RNA that we designate as boundary associated long noncoding RNA-1 (blncRNA1. Functional characterization of this RNA suggests that the transcript stabilizes long-range interactions at the HOXA locus and promotes proper expression of HOXA genes. Additionally, our functional analysis also shows that this RNA is not needed in the stabilization of CTCF-Cohesin interactions however CTCF-Cohesin interactions are critical in the transcription of blncRNA1. Thus, the CTCF-associated boundary element, CBS5, employs both Cohesin and noncoding RNA to establish and maintain topologically associated domains at the HOXA locus.

  7. Characteristic energy range of electron scattering due to plasmaspheric hiss

    Science.gov (United States)

    Ma, Q.; Li, W.; Thorne, R. M.; Bortnik, J.; Reeves, G. D.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Spence, H. E.; Baker, D. N.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Angelopoulos, V.

    2016-12-01

    We investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth's inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth's outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to the first adiabatic invariant μ = 4-200 MeV/G. The electron diffusion coefficients due to hiss scattering are calculated at L = 2-6, and the modeled energy band of effective pitch angle scattering is also well correlated with the constant μ lines and is consistent with the observed energy range of electron decay. Using the previously developed statistical plasmaspheric hiss model during modestly disturbed periods, we perform a 2-D Fokker-Planck simulation of the electron phase space density evolution at L = 3.5 and demonstrate that plasmaspheric hiss causes the significant decay of 100 keV-1 MeV electrons with the largest decay rate occurring at around 340 keV, forming anisotropic pitch angle distributions at lower energies and more flattened distributions at higher energies. Our study provides reasonable estimates of the electron populations that can be most significantly affected by plasmaspheric hiss and the consequent electron decay profiles.

  8. Method for computing short-range forces between solid-liquid interfaces driving grain boundary premelting

    Science.gov (United States)

    Hoyt, J. J.; Olmsted, David; Jindal, Saryu; Asta, Mark; Karma, Alain

    2009-02-01

    We present a molecular dynamics based method for accurately computing short-range structural forces resulting from the overlap of spatially diffuse solid-liquid interfaces at wetted grain boundaries close to the melting point. The method is based on monitoring the fluctuations of the liquid layer width at different temperatures to extract the excess interfacial free energy as a function of this width. The method is illustrated for a high-energy Σ9 twist boundary in pure Ni. The short-range repulsion driving premelting is found to be dominant in comparison to long-range dispersion and entropic forces and consistent with previous experimental findings that nanometer-scale layer widths may be observed only very close to the melting point.

  9. Predicting transition ranges to fully turbulent viscous boundary layers in low Prandtl number convection flows

    Science.gov (United States)

    Scheel, Janet D.; Schumacher, Jörg

    2017-12-01

    We discuss two aspects of turbulent Rayleigh-Bénard convection (RBC) on the basis of high-resolution direct numerical simulations in a unique setting: a closed cylindrical cell of aspect ratio of one. First, we present a comprehensive comparison of statistical quantities such as energy dissipation rates and boundary layer thickness scales. Data are used from three simulation run series at Prandtl numbers Pr that cover two orders of magnitude. In contrast to most previous studies in RBC the focus of the present work is on convective turbulence at very low Prandtl numbers including Pr=0.021 for liquid mercury or gallium and Pr=0.005 for liquid sodium. In this parameter range of RBC, inertial effects cause a dominating turbulent momentum transport that is in line with highly intermittent fluid turbulence both in the bulk and in the boundary layers and thus should be able to trigger a transition to the fully turbulent boundary layers of the ultimate regime of convection for higher Rayleigh number. Second, we predict the ranges of Rayleigh numbers for which the viscous boundary layer will transition to turbulence and the flow as a whole will cross over into the ultimate regime. These transition ranges are obtained by extrapolation from our simulation data. The extrapolation methods are based on the large-scale properties of the velocity profile. Two of the three methods predict similar ranges for the transition to ultimate convection when their uncertainties are taken into account. All three extrapolation methods indicate that the range of critical Rayleigh numbers Rac is shifted to smaller magnitudes as the Prandtl number becomes smaller.

  10. Detection of expansion at large angle grain boundaries using electron diffraction

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    1984-02-01

    Lamarre and Sass (LS) (Scripta Metall. 17: 1141(1983) observed a grain boundary electron diffraction effect from a large angle twist boundary which is used to obtain the volume expansion at the grain boundary in a direction normal to it. The case where the intensity from the grain boundary region, is close to lattice reflections on the same element of the boundary diffraction lattice is considered. Analysis of this complex problem show that the simplified model of LS is misleading in this case.

  11. Detection of expansion at large angle grain boundaries using electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1984-02-01

    Lamarre and Sass (LS) (Scripta Metall. 17: 1141(1983)) observed a grain boundary electron diffraction effect from a large angle twist boundary which they claim can be used to obtain the volume expansion at the grain boundary in a direction normal to it. This paper considers the case where the intensity from the grain boundary region, is close to lattice reflections on the same element of the boundary diffraction lattice. Analysis of this complex problem show that the simplified model of LS is misleading in this case. (DLC)

  12. Characteristics of different frequency ranges in scanning electron microscope images

    Energy Technology Data Exchange (ETDEWEB)

    Sim, K. S., E-mail: kssim@mmu.edu.my; Nia, M. E.; Tan, T. L.; Tso, C. P.; Ee, C. S. [Faculty of Engineering and Technology, Multimedia University, 75450 Melaka (Malaysia)

    2015-07-22

    We demonstrate a new approach to characterize the frequency range in general scanning electron microscope (SEM) images. First, pure frequency images are generated from low frequency to high frequency, and then, the magnification of each type of frequency image is implemented. By comparing the edge percentage of the SEM image to the self-generated frequency images, we can define the frequency ranges of the SEM images. Characterization of frequency ranges of SEM images benefits further processing and analysis of those SEM images, such as in noise filtering and contrast enhancement.

  13. Electronic properties of a grain boundary in Sb-doped ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, J.M.; Hellsing, B. [Experimental Physics, Chalmers and Goeteborg University, Gothenburg (Sweden); Domingos, H.S.; Bristowe, P.D. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge (United Kingdom)]. E-mail: pdb1000@cus.cam.ac.uk

    2001-11-05

    The electronic properties of a {sigma}=13 32.2 deg. [0001] tilt grain boundary in ZnO have been investigated using first-principles calculations. Two atomic models for the boundary have been considered, one of which contains structural units that are consistent with those observed for this orientation using electron microscopy. Doping both the grain boundary models with antimony reveals a strong driving force for segregation. Analysis of the electronic densities of states, bond populations and Mulliken charges shows that antimony creates a localized impurity state in the grain boundary and acts as a donor dopant. The resulting charge accumulation at the grain boundary together with the presence of local bonds that are metallic in character, will influence the mechanism for charge transport across the interface and this is discussed in relation to varistor applications. (author)

  14. Electronic properties of a grain boundary in Sb-doped ZnO

    Science.gov (United States)

    Carlsson, J. M.; Hellsing, B.; Domingos, H. S.; Bristowe, P. D.

    2001-11-01

    The electronic properties of a Σ = 13 32.2° [0001] tilt grain boundary in ZnO have been investigated using first-principles calculations. Two atomic models for the boundary have been considered, one of which contains structural units that are consistent with those observed for this orientation using electron microscopy. Doping both the grain boundary models with antimony reveals a strong driving force for segregation. Analysis of the electronic densities of states, bond populations and Mulliken charges shows that antimony creates a localized impurity state in the grain boundary and acts as a donor dopant. The resulting charge accumulation at the grain boundary together with the presence of local bonds that are metallic in character, will influence the mechanism for charge transport across the interface and this is discussed in relation to varistor applications.

  15. Electron Sheaths: The Outsized Influence of Positive Boundaries on Plasmas

    CERN Document Server

    Yee, Benjamin T; Baalrud, Scott D; Barnat, Edward V; Hopkins, Matthew M

    2015-01-01

    Electron sheaths form near the surface of objects biased more positive than the plasma potential, such as in the electron saturation region of a Langmuir probe trace. They are commonly thought to be local phenomena that collect the random thermal electron current, but do not otherwise perturb a plasma. Here, using experiments, particle-in-cell simulations and theory, it is shown that under low temperature plasma conditions ($T_e \\gg T_i$) electron sheaths are far from local. Instead, a long presheath region extends into the plasma where electrons are accelerated via a pressure gradient to a flow speed exceeding the electron thermal speed at the sheath edge. This fast flow is found to excite instabilities, causing strong fluctuations near the sheath edge.

  16. Atomic structure and electronic properties of MgO grain boundaries in tunnelling magnetoresistive devices

    Science.gov (United States)

    Bean, Jonathan J.; Saito, Mitsuhiro; Fukami, Shunsuke; Sato, Hideo; Ikeda, Shoji; Ohno, Hideo; Ikuhara, Yuichi; McKenna, Keith P.

    2017-04-01

    Polycrystalline metal oxides find diverse applications in areas such as nanoelectronics, photovoltaics and catalysis. Although grain boundary defects are ubiquitous their structure and electronic properties are very poorly understood since it is extremely challenging to probe the structure of buried interfaces directly. In this paper we combine novel plan-view high-resolution transmission electron microscopy and first principles calculations to provide atomic level understanding of the structure and properties of grain boundaries in the barrier layer of a magnetic tunnel junction. We show that the highly [001] textured MgO films contain numerous tilt grain boundaries. First principles calculations reveal how these grain boundaries are associated with locally reduced band gaps (by up to 3 eV). Using a simple model we show how shunting a proportion of the tunnelling current through grain boundaries imposes limits on the maximum magnetoresistance that can be achieved in devices.

  17. Short-Range Correlation Models in Electronic Structure Theory

    Science.gov (United States)

    Goldey, Matthew Bryant

    Correlation methods within electronic structure theory focus on recovering the exact electron-electron interaction from the mean-field reference. For most chemical systems, including dynamic correlation, the correlation of the movement of electrons proves to be sufficient, yet exact methods for capturing dynamic correlation inherently scale polynomially with system size despite the locality of the electron cusp. This work explores a new family of methods for enhancing the locality of dynamic correlation methodologies with an aim toward improving accuracy and scalability. The introduction of range-separation into ab initio wavefunction methods produces short-range correlation methodologies, which can be supplemented with much faster approximate methods for long-range interactions. First, I examine attenuation of second-order Moller-Plesset perturbation theory (MP2) in the aug-cc-pVDZ basis. MP2 treats electron correlation at low computational cost, but suffers from basis set superposition error (BSSE) and fundamental inaccuracies in long-range contributions. The cost differential between complete basis set (CBS) and small basis MP2 restricts system sizes where BSSE can be removed. Range-separation of MP2 could yield more tractable and/or accurate forms for short- and long-range correlation. Retaining only short-range contributions proves to be effective for MP2 in the small aug-cc-pVDZ (aDZ) basis. Using one range-separation parameter within either the complementary error function (erfc) or a sum of two error functions (terfc), superior behavior is obtained versus both MP2/aDZ and MP2/CBS for inter- and intra-molecular test sets. Attenuation of the long-range helps to cancel both BSSE and intrinsic MP2 errors. Direct scaling of the MP2 correlation energy (SMP2) proves useful as well. The resulting SMP2/aDZ, MP2(erfc, aDZ), and MP2(terfc, aDZ) methods perform far better than MP2/aDZ across systems with hydrogen-bonding, dispersion, and mixed interactions at a

  18. Long-range topological insulators and weakened bulk-boundary correspondence

    Science.gov (United States)

    Lepori, L.; Dell’Anna, L.

    2017-10-01

    We investigate the appearance of new types of insulators and superconductors in long-range (LR) fermionic quantum systems. These phases are not included in the famous ‘ten-fold way classification’ (TWC), valid in the short-range (SR) limit. This conclusion is obtained analysing at first specific one-dimensional models, in particular their phase diagrams and entanglement properties. The LR phases are signalled, for instance, by the violation of the area-law for the von Neumann entropy and by a corresponding peculiar entanglement spectrum (ES). Later on, the origin of the deviations from the TWC is investigated from a more general point of view and in any dimension, showing that it is related with the presence of divergences occurring in the spectrum, due to the LR couplings. A satisfying characterization for the LR phases can be achieved, at least for one-dimensional quantum systems, as well as the definition of a nontrivial topology for them, resulting in the presence of massive edge states, provided a careful evaluation of the LR contributions. Our results allows to infer, at least for one-dimensional models, the weakening of the bulk-boundary correspondence, due to the important correlations between bulk and edges, and consequently to clarify the nature of the massive edge states. The emergence of this peculiar edge structure is signalled again by the bulk ES. The stability of the LR phases against local disorder is also discussed, showing notably that this ingredient can even strengthen the effect of the LR couplings. Finally, we analyse the entanglement content of the paradigmatic LR Ising chain, inferring again important deviations from the SR regime, as well as the limitations of bulk-boundary (tensor-network based) approaches to classify LR spin models.

  19. Thermal Relaxation in Titanium Nanowires: Signatures of Inelastic Electron-Boundary Scattering in Heat Transfer

    Science.gov (United States)

    Elo, Teemu; Lähteenmäki, Pasi; Golubev, Dmitri; Savin, Alexander; Arutyunov, Konstantin; Hakonen, Pertti

    2017-11-01

    We have employed noise thermometry for investigations of thermal relaxation between the electrons and the substrate in nanowires patterned from 40-nm-thick titanium film on top of silicon wafers covered by a native oxide. By controlling the electronic temperature T_e by Joule heating at the base temperature of a dilution refrigerator, we probe the electron-phonon coupling and the thermal boundary resistance at temperatures T_e= 0.5-3 K. Using a regular T^5-dependent electron-phonon coupling of clean metals and a T^4-dependent interfacial heat flow, we deduce a small contribution for the direct energy transfer from the titanium electrons to the substrate phonons due to inelastic electron-boundary scattering.

  20. Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements

    Energy Technology Data Exchange (ETDEWEB)

    Basu, I., E-mail: basu@imm.rwth-aachen.de; Chen, M.; Loeck, M.; Al-Samman, T.; Molodov, D.A.

    2016-07-15

    One of the key aspects influencing microstructural design pathways in metallic systems is grain boundary motion. The present work introduces a method by means of which direct measurement of grain boundary mobility vs. misorientation dependence is made possible. The technique utilizes datasets acquired by means of serial electron backscatter diffraction (EBSD) measurements. The experimental EBSD measurements are collectively analyzed, whereby datasets were used to obtain grain boundary mobility and grain aspect ratio with respect to grain boundary misorientation. The proposed method is further validated using cellular automata (CA) simulations. Single crystal aluminium was cold rolled and scratched in order to nucleate random orientations. Subsequent annealing at 300 °C resulted in grains growing, in the direction normal to the scratch, into a single deformed orientation. Growth selection was observed, wherein the boundaries with misorientations close to Σ7 CSL orientation relationship (38° 〈111〉) migrated considerably faster. The obtained boundary mobility distribution exhibited a non-monotonic behavior with a maximum corresponding to misorientation of 38° ± 2° about 〈111〉 axes ± 4°, which was 10–100 times higher than the mobility values of random high angle boundaries. Correlation with the grain aspect ratio values indicated a strong growth anisotropy displayed by the fast growing grains. The observations have been discussed in terms of the influence of grain boundary character on grain boundary motion during recrystallization. - Highlights: • Statistical microstructure method to measure grain boundary mobility during recrystallization • Method implementation independent of material or crystal structure • Mobility of the Σ7 boundaries in 5N Al was calculated as 4.7 × 10{sup –8} m{sup 4}/J ⋅ s. • Pronounced growth selection in the recrystallizing nuclei in Al • Boundary mobility values during recrystallization 2–3 orders of

  1. Electron scattering from neon via effective range theory

    Energy Technology Data Exchange (ETDEWEB)

    Fedus, Kamil, E-mail: kamil@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun (Poland)

    2014-07-01

    Elastic cross-sections for electron scattering on neon from 0 energy up to 16 eV are analyzed by an analytical approach to the modified effective range theory (MERT). It is shown that energy and angular variations of elastic differential, integral and momentum transfer cross sections can be accurately parameterized by six MERT coefficients up to the energy threshold for the first Feshbach resonance. MERT parameters are determined empirically by numerical comparison with large collection of available experimental data of elastic total (integral) cross-sections. The present analysis is validated against numerous electron beams and swarm experiments. The comparison of derived MERT parameters with those found for other noble gases, helium, argon and krypton, is done. The derived scattering length (for the s-partial wave) in neon, 0.227a0, agrees well with recent theories; it is small but, differently from Ar and Kr, still positive. Analogue parameters for the p-wave and the d-wave are negative and positive respectively for all the four gases compared. (author)

  2. Substorm-injected protons and electrons and the injection boundary model

    Science.gov (United States)

    Konradi, A.; Semar, C. L.; Fritz, T. A.

    1975-01-01

    Analysis of observations of substorm-associated enhancements of proton and electron fluxes: (1) makes a strong case for the existence of a boundary limiting the regional particle injection associated with substorms, (2) supports the hypothesis that the injection process is almost instantaneous (less than approximately 5 min), and (3) indicates that the injection takes place within a large region extending at least several earth radii tailward of the injection boundary. The injection boundary model is superior to others in that it simultaneously explains: (1) the drift and energy dispersion of substorm-injected protons between 1 and 30 keV, (2) the relative behavior of protons with 81 deg and 27 deg pitch angles, (3) the absence of observed electrons below 30 keV, and (4) the time dispersion of impulsively injected electrons seen outside the plasmapause.

  3. Profile Monitors for Wide Multiplicity Range Electron Beams

    CERN Document Server

    Buonomo, B; Quintieri, L

    2005-01-01

    The DAFNE Beam Test Facility (BTF) provides electron and positron beams in a wide range of intensity, from single particle up to 1010 particles per pulse, and energy, from a few tens of MeV up to 800 MeV. The pulse time width can be adjusted between 1 and 10 ns and the maximum repetition rate is 50 Hz. The large range of operation of the facility requires the implementation of different beam profile and multiplicity monitors. In the single particle operation mode the beam spot profile and position are measured by a x-y scintillating fiber system with millimetric resolution and multi-anode PMT readout. From a few tens up to 106-107 particles per pulse, a silicon chamber made of two 9.5x9.5 cm2 wide 400μm thick silicon strip detectors organized in a x-y configuration with a pitch of 121μm has been developed. Once calibrated, the system can be used also as an intensity monitor. The description of the devices and the results obtained during the data taking periods of several experiments at the...

  4. Localized electronic states at grain boundaries on the surface of graphene and graphite

    DEFF Research Database (Denmark)

    Luican-Mayer, Adina; Barrios-Vargas, Jose E.; Falkenberg, Jesper Toft

    2016-01-01

    morphology affects the electronic properties is crucial for the development of applications such as flexible electronics, energy harvesting devices or sensors. We here report on atomic scale characterization of several GBs and on the structural-dependence of the localized electronic states in their vicinity......ecent advances in large-scale synthesis of graphene and other 2D materials have underscored the importance of local defects such as dislocations and grain boundaries (GBs), and especially their tendency to alter the electronic properties of the material. Understanding how the polycrystalline...

  5. Habitat Preferences and Growth of Ruditapes bruguieri (Bivalvia: Veneridae at the Northern Boundary of Its Range

    Directory of Open Access Journals (Sweden)

    Alla V. Silina

    2014-01-01

    Full Text Available This work is the first attempt to study growth and some morphological parameters of the clam Ruditapes bruguieri, as well as its habitat preferences. It is found that R. bruguieri lives on bottom sediments including pebble and coarse- and medium-grained sand with a slight admixture of silt. At the study area, this bivalve inhabits sea waters with good aeration, stable oceanic water salinity, and a high oxygen concentration. The annual fluctuations of the water temperature from 13-14°C (in winter to 22–29°C (in summer are close to the threshold temperature values, within which the species can exist. Near the boundary of the species range, along the Jeju Island coasts, south of Republic of Korea, 83.8% of all clams die during the coldest period of the year. Here, annual rings are formed on R. bruguieri shells during winter. The maximum age of R. bruguieri, determined during the study, is 6.5 years, but the clam samples contain mainly individuals at 3.0–3.5 years of age (34%. The largest clam dimensions are 36.0 × 26.5 mm (length × height of shell. At the study area, a usual shell length is 20.0–32.0 mm (75% of all the collected individuals.

  6. In-situ transmission electron microscopy : on moving dislocations and mobile grain boundaries

    NARCIS (Netherlands)

    De Hosson, J. T. M.; Soer, W.

    This paper delineates the possibilities of utilizing in situ transmission electron microscopy to unravel dislocation-g rain boundary interactions. In situ nanoindentation experiments have been conducted in TEM on ultrafine-grained Al and Al-Mg films with varying Mg contents. The observed propagation

  7. Electron scattering at surfaces and grain boundaries in thin Au films

    Energy Technology Data Exchange (ETDEWEB)

    Henriquez, Ricardo [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Casilla 110-V, Valparaíso (Chile); Flores, Marcos; Moraga, Luis [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile); Kremer, German [Bachillerato, Universidad de Chile, Las Palmeras 3425, Santiago 7800024 (Chile); González-Fuentes, Claudio [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Casilla 110-V, Valparaíso (Chile); Munoz, Raul C., E-mail: ramunoz@ing.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile)

    2013-05-15

    The electron scattering at surfaces and grain boundaries is investigated using polycrystalline Au films deposited onto mica substrates. We vary the three length scales associated with: (i) electron scattering in the bulk, that at temperature T is characterized by the electronic mean free path in the bulk ℓ{sub 0}(T); (ii) electron-surface scattering, that is characterized by the film thickness t; (iii) electron-grain boundary scattering, that is characterized by the mean grain diameter D. We varied independently the film thickness from approximately 50 nm to about 100 nm, and the typical grain size making up the samples from 12 nm to 160 nm. We also varied the scale of length associated with electron scattering in the bulk by measuring the resistivity of each specimen at temperatures T, 4 K < T < 300 K. Cooling the samples to 4 K increases ℓ{sub 0}(T) by approximately 2 orders of magnitude. Detailed measurements of the grain size distribution as well as surface roughness of each sample were performed with a Scanning Tunnelling Microscope (STM). We compare, for the first time, theoretical predictions with resistivity data employing the two theories available that incorporate the effect of both electron-surface as well as electron-grain boundary scattering acting simultaneously: the theory of A.F. Mayadas and M. Shatzkes, Phys. Rev. 1 1382 (1970) (MS), and that of G. Palasantzas, Phys. Rev. B 58 9685 (1998). We eliminate adjustable parameters from the resistivity data analysis, by using as input the grain size distribution as well as the surface roughness measured with the STM on each sample. The outcome is that both theories provide a fair representation of both the temperature as well as the thickness dependence of the resistivity data, but yet there are marked differences between the resistivity predicted by these theories. In the case of the MS theory, when the average grain diameter D is significantly smaller than ℓ{sub 0}(300) = 37 nm, the electron mean

  8. How disturbance, competition, and dispersal interact to prevent tree range boundaries from keeping pace with climate change.

    Science.gov (United States)

    Liang, Yu; Duveneck, Matthew J; Gustafson, Eric J; Serra-Diaz, Josep M; Thompson, Jonathan R

    2018-01-01

    Climate change is expected to cause geographic shifts in tree species' ranges, but such shifts may not keep pace with climate changes because seed dispersal distances are often limited and competition-induced changes in community composition can be relatively slow. Disturbances may speed changes in community composition, but the interactions among climate change, disturbance and competitive interactions to produce range shifts are poorly understood. We used a physiologically based mechanistic landscape model to study these interactions in the northeastern United States. We designed a series of disturbance scenarios to represent varied disturbance regimes in terms of both disturbance extent and intensity. We simulated forest succession by incorporating climate change under a high-emissions future, disturbances, seed dispersal, and competition using the landscape model parameterized with forest inventory data. Tree species range boundary shifts in the next century were quantified as the change in the location of the 5th (the trailing edge) and 95th (the leading edge) percentiles of the spatial distribution of simulated species. Simulated tree species range boundary shifts in New England over the next century were far below (usually change (usually more than 110 km over 100 years) under a high-emissions scenario. Simulated species` ranges shifted northward at both the leading edge (northern boundary) and trailing edge (southern boundary). Disturbances may expedite species' recruitment into new sites, but they had little effect on the velocity of simulated range boundary shifts. Range shifts at the trailing edge tended to be associated with photosynthetic capacity, competitive ability for light and seed dispersal ability, whereas shifts at the leading edge were associated only with photosynthetic capacity and competition for light. This study underscores the importance of understanding the role of interspecific competition and disturbance when studying tree range

  9. Impact of Wide-Ranging Nanoscale Chemistry on Band Structure at Cu(In, Ga)Se2 Grain Boundaries.

    Science.gov (United States)

    Stokes, Adam; Al-Jassim, Mowafak; Diercks, David; Clarke, Amy; Gorman, Brian

    2017-10-26

    The relative chemistry from grain interiors to grain boundaries help explain why grain boundaries may be beneficial, detrimental or benign towards device performance. 3D Nanoscale chemical analysis extracted from atom probe tomography (APT) (10's of parts-per-million chemical sensitivity and sub-nanometer spatial resolution) of twenty grain boundaries in a high-efficiency Cu(In, Ga)Se2 solar cell shows the matrix and alkali concentrations are wide-ranging. The concentration profiles are then related to band structure which provide a unique insight into grain boundary electrical performance. Fluctuating Cu, In and Ga concentrations result in a wide distribution of potential barriers at the valence band maximum (VBM) (-10 to -160 meV) and the conduction band minimum (CBM) (-20 to -70 meV). Furthermore, Na and K segregation is not correlated to hampering donors, (In, Ga)Cu and VSe, contrary to what has been previously reported. In addition, Na and K are predicted to be n-type dopants at grain boundaries. An overall band structure at grain boundaries is presented.

  10. Disentangling climatic versus biotic drivers of tree range constraints: Broad scale tradeoffs between climate and competion rarely explain local range boundaries

    Science.gov (United States)

    Anderegg, L. D. L.; Hillerislambers, J.

    2016-12-01

    Accurate prediction of climatically-driven range shifts requires knowledge of the dominant forces constraining species ranges, because climatically controlled range boundaries will likely behave differently from biotically controlled range boundaries in a changing climate. Yet the roles of climatic constraints (due to species physiological tolerance) versus biotic constraints (caused by species interactions) on geographic ranges are largely unknown, infusing large uncertainty into projections of future range shifts. Plant species ranges across strong climatic gradients such as elevation gradients are often assumed to represent a tradeoff between climatic constraints on the harsh side of the range and biotic constraints (often competitive constraints) on the climatically benign side. To test this assumption, we collected tree cores from across the elevational range of the three dominant tree species inhabiting each of three climatically disparate mountain slopes and assessed climatic versus competitive constraints on growth at each species' range margins. Across all species and mountains, we found evidence for a tradeoff between climatic and competitve growth constraints. We also found that some individual species did show an apparent trade-off between a climatic constraint at one range margin and a competitive constraint at the other. However, even these simple elevation gradients resulted in complex interactions between temperature, moisture, and competitive constraints such that a climate-competition tradeoff did not explain range constraints for many species. Our results suggest that tree species can be constrained by a simple trade-off between climate and competition, but that the intricacies of real world climate gradients complicate the application of this theory even in apparently harsh environments, such as near high elevation tree line.

  11. The effect of electron scattering from disordered grain boundaries on the resistivity of metallic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Arenas, Claudio [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile); Synopsys Inc., Avenida Vitacura 5250, Oficina 708, Vitacura, Santiago (Chile); Henriquez, Ricardo [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Casilla 110-V, Valparaíso (Chile); Moraga, Luis [Universidad Central de Chile, Toesca 1783, Santiago (Chile); Muñoz, Enrique [Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 7820436 (Chile); Munoz, Raul C., E-mail: ramunoz@ing.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile)

    2015-02-28

    Highlights: • Quantum theory of the resistivity arising from electron-grain boundary scattering in nanometric metallic structures. • The resistivity is controlled by the collective properties of the grain assembly, by the allowed Kronig-Penney (KP) bands and by the electron transmission probability across successive grains. • When the grain diameter d is larger than the electron mean free path l, the increase in resistivity arises mainly from a decrease of the number of states at the Fermi surface that are allowed KP bands. • When the grain diameter d is smaller than the electron mean free path l, the increase in resistivity arises primarily from Anderson localization caused by electron transmission across successive grains. - Abstract: We calculate the electrical resistivity of a metallic specimen, under the combined effects of electron scattering by impurities, grain boundaries, and rough surfaces limiting the film, using a quantum theory based upon the Kubo formalism. Grain boundaries are represented by a one-dimensional periodic array of Dirac delta functions separated by a distance “d” giving rise to a Kronig–Penney (KP) potential. We use the Green's function built from the wave functions that are solutions of this KP potential; disorder is included by incorporating into the theory the probability that an electron is transmitted through several successive grain boundaries. We apply this new theory to analyze the resistivity of samples S1, S2, S7 and S8 measured between 4 and 300 K reported in Appl. Surf. Science273, 315 (2013). Although both the classical and the quantum theories predict a resistivity that agrees with experimental data to within a few percent or better, the phenomena giving rise to the increase of resistivity over the bulk are remarkably different. Classically, each grain boundary contributes to the electrical resistance by reflecting a certain fraction of the incoming electrons. In the quantum description, there are states

  12. The INTERBALL-Tail ELECTRON experiment: initial results on the low-latitude boundary layer of the dawn magnetosphere

    Directory of Open Access Journals (Sweden)

    J.-A. Sauvaud

    1997-05-01

    Full Text Available The Toulouse electron spectrometer flown on the Russian project INTERBALL-Tail performs electron measurements from 10 to 26 000 eV over a 4 solid angle in a satellite rotation period. The INTERBALL-Tail probe was launched on 3 August 1995 together with a subsatellite into a 65° inclination orbit with an apogee of about 30 RE. The INTERBALL mission also includes a polar spacecraft launched in August 1996 for correlated studies of the outer magnetosphere and of the auroral regions. We present new observations concerning the low-latitude boundary layers (LLBL of the magnetosphere obtained near the dawn magnetic meridian. LLBL are encountered at the interface between two plasma regimes, the magnetosheath and the dayside extension of the plasma sheet. Unexpectedly, the radial extent of the region where LLBL electrons can be sporadically detected as plasma clouds can reach up to 5 RE inside the magnetopause. The LLBL core electrons have an average energy of the order of 100 eV and are systematically field-aligned and counterstreaming. As a trend, the temperature of the LLBL electrons increases with decreasing distance to Earth. Along the satellite orbit, the apparent time of occurrence of LLBL electrons can vary from about 5 to 20 min from one pass to another. An initial first comparison between electron- and magnetic-field measurements indicates that the LLBL clouds coincide with a strong increase in the magnetic field (by up to a factor of 2. The resulting strong magnetic field gradient can explain why the plasma-sheet electron flux in the keV range is strongly depressed in LLBL occurrence regions (up to a factor of \\sim10. We also show that LLBL electron encounters are related to field-aligned current structures and that wide LLBL correspond to northward interplanetary magnetic field. Evidence for LLBL/plasma-sheet electron leakage into the magnetosheath during southward IMF is also presented.

  13. Electronic structure and switching behavior of the metastable silicene domain boundary

    Science.gov (United States)

    Oh, Youngtek; Cho, Yeonchoo; Kwon, Hyeokshin; Lee, Junsu; Jeon, Insu; Ko, Wonhee; Kim, Hyo Won; Ku, JiYeon; Kim, Gunn; Suh, Hwansoo; Hwang, Sung Woo

    2017-06-01

    Silicene, a silicon allotrope with a buckled honeycomb lattice, has been extensively studied in the search for materials with graphene-like properties. Here, we study the domain boundaries of a silicene 4 × 4 superstructure on an Ag(111) surface at the atomic resolution using scanning tunneling microscopy (STM) and spectroscopy (STS) along with density functional theory calculations. The silicene domain boundaries (β-phases) are formed at the interface between misaligned domains (α-phases) and show a bias dependence, forming protrusions or depressions as the sample bias changes. In particular, the STM topographs of the silicene-substrate system at a bias of ˜2.0 V show brightly protruding domain boundaries, which can be explained by an energy state originating from the Si 3s and 3pz orbitals. In addition, the topographs depicting the vicinity of the domain boundaries show that the structure does not follow the buckled geometry of the atomic ball-and-stick model. Inside the domain, STS data showed a step-up at ˜0.4 V, which originated from the Si 3p orbitals. We found this step-up to have shifted, which may be attributed to the strain effect at the interface regions between silver and silicene and between the domain and its boundary upon performing spatially resolved STS measurements. The metastable characteristic of the domain boundary (β-phase) causes changes, such as creation or annihilation, in the buckling structures (switching behavior). The observed low activation energy for the buckling change between distinct states may find applications in the electronic control of properties related to domain boundary structures in silicene.

  14. The range and intensity of backscattered electrons for use in the creation of high fidelity electron beam lithography patterns.

    Science.gov (United States)

    Czaplewski, David A; Holt, Martin V; Ocola, Leonidas E

    2013-08-02

    We present a set of universal curves that predict the range and intensity of backscattered electrons which can be used in conjunction with electron beam lithography to create high fidelity nanoscale patterns. The experimental method combines direct write dose, backscattered dose, and a self-reinforcing pattern geometry to measure the dose provided by backscattered electrons to a nanoscale volume on the substrate surface at various distances from the electron source. Electron beam lithography is used to precisely control the number and position of incident electrons on the surface of the material. Atomic force microscopy is used to measure the height of the negative electron beam lithography resist. Our data shows that the range and the intensity of backscattered electrons can be predicted using the density and the atomic number of any solid material, respectively. The data agrees with two independent Monte Carlo simulations without any fitting parameters. These measurements are the most accurate electron range measurements to date.

  15. The range and intensity of backscattered electrons for use in the creation of high fidelity electron beam lithography patterns

    Science.gov (United States)

    Czaplewski, David A.; Holt, Martin V.; Ocola, Leonidas E.

    2013-08-01

    We present a set of universal curves that predict the range and intensity of backscattered electrons which can be used in conjunction with electron beam lithography to create high fidelity nanoscale patterns. The experimental method combines direct write dose, backscattered dose, and a self-reinforcing pattern geometry to measure the dose provided by backscattered electrons to a nanoscale volume on the substrate surface at various distances from the electron source. Electron beam lithography is used to precisely control the number and position of incident electrons on the surface of the material. Atomic force microscopy is used to measure the height of the negative electron beam lithography resist. Our data shows that the range and the intensity of backscattered electrons can be predicted using the density and the atomic number of any solid material, respectively. The data agrees with two independent Monte Carlo simulations without any fitting parameters. These measurements are the most accurate electron range measurements to date.

  16. Interaction of magnetized electrons with a boundary sheath: investigation of a specular reflection model

    Science.gov (United States)

    Krüger, Dennis; Brinkmann, Ralf Peter

    2017-11-01

    This publication reports analytical and numerical results concerning the interaction of gyrating electrons with a plasma boundary sheath, with focus on partially magnetized technological plasmas. It is assumed that the electron Debye length {λ }{{D}} is much smaller than the electron gyroradius {r}{{L}}, and {r}{{L}} in turn much smaller than the mean free path λ and the gradient length L of the fields. Focusing on the scale of the gyroradius, the sheath is assumed as infinitesimally thin ({λ }{{D}}\\to 0), collisions are neglected (λ \\to ∞ ), the magnetic field is taken as homogeneous, and electric fields (=potential gradients) in the bulk are neglected (L\\to ∞ ). The interaction of an electron with the electric field of the plasma boundary sheath is represented by a specular reflection {v}\\to {v}-2{v}\\cdot {{e}}z {{e}}z of the velocity {v} at the plane z = 0 of a naturally oriented Cartesian coordinate system (x,y,z). The electron trajectory is then given as sequences of helical sections, with the kinetic energy ɛ and the canonical momenta p x and p y conserved, but not the position of the axis (base point {{R}}0), the slope (pitch angle χ), and the phase (gyrophase φ). A ‘virtual interaction’ which directly maps the incoming electrons to the outgoing ones is introduced and studied in dependence of the angle γ between the field and the sheath normal {{e}}z. The corresponding scattering operator is constructed, mathematically characterized, and given as an infinite matrix. An equivalent boundary condition for a transformed kinetic model is derived.

  17. Long-Range Photoinduced Electron Transfer Through a DNA Helix

    Science.gov (United States)

    Murphy, C. J.; Arkin, M. R.; Jenkins, Y.; Ghatlia, N. D.; Bossmann, S. H.; Turro, N. J.; Barton, J. K.

    1993-11-01

    Rapid photoinduced electron transfer is demonstrated over a distance of greater than 40 angstroms between metallointercalators that are tethered to the 5' termini of a 15-base pair DNA duplex. An oligomeric assembly was synthesized in which the donor is Ru(phen)_2dppz^2+ (phen, phenanthroline, and dppz, dipyridophenazine) and the acceptor is Rh(phi)_2phen^3+ (phi, phenanthrenequinone diimine). These metal complexes are intercalated either one or two base steps m from the helix termini. Although the ruthenium-modified oligonucleotide hybridized to an unmodified complement luminesces intensely, the ruthenium-modified oligomer hybridized to the rhodium-modified oligomer shows no detectable luminescence. Time-resolved studies point to a lower limit of 109 per second for the quenching rate. No quenching was observed upon metallation of two complementary octamers by Ru(phen)_32+ and Rh(phen)_33+ under conditions where the phen complexes do not intercalate. The stacked aromatic heterocycles of the DNA duplex therefore serve as an efficient medium for coupling electron donors and acceptors over very long distances.

  18. Long-range photoinduced electron transfer through a DNA helix

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, C.J.; Arkin, M.R.; Jenkins, Y.; Barton, J.K. (California Institute of Technology, Pasadena, CA (United States)); Ghatlia, N.D.; Bossmann, S.H.; Turro, N.J. (Columbia Univ., New York, NY (United States))

    1993-11-12

    Rapid photoinduced electron transfer is demonstrated over a distance of greater than 40 angstroms between metallointercalators that are tethered to the 5' termini of a 15-base pair DNA duplex. An oligomeric assembly was synthesized in which the donor is Ru(phen)[sub 2]dppz[sup 2+] (phen, phenanthroline, and dppz, dipyridophenazine) and the acceptor is Rh(phi)[sub 2]phen[sup 3+] (phi, phenanthrenequinone diimine). These metal complexes are intercalated either one or two base steps in from the helix termini. Although the ruthenium-modified oligonucleotide hybridized to an unmodified complement luminesces intensely, the ruthenium-modified oligomer hybridized to the rhodium-modified oligomer shows no detectable luminescence. Time-resolved studies point to a lower limit of 10[sup 9] per second for the quenching rate. No quenching was observed upon metallation of two complementary octamers by Ru(phen)[sub 3][sup 2+] and Rh(phen)[sub 3][sup 3+] under conditions where the phen complexes do not intercalate. The stacked aromatic heterocycles of the DNA duplex therefore serve as an efficient medium for coupling electron donors and acceptors over very long distances.

  19. Enzymatic cellulose oxidation is linked to lignin by long-range electron transfer

    DEFF Research Database (Denmark)

    Westereng, Bjorge; Cannella, David; Wittrup Agger, Jane

    2015-01-01

    cell walls. Electron transfer was confirmed by electron paramagnetic resonance spectroscopy showing that LPMO activity on cellulose changes the level of unpaired electrons in the lignin. The discovery of a long-range electron transfer mechanism links the biodegradation of cellulose and lignin and sheds...

  20. Pelletron-based MeV-range electron beam recirculation

    CERN Document Server

    Crawford, A C; Sharapa, A N; Shemyakin, A

    1999-01-01

    In this paper we describe the successful recirculation of a DC electron beam at energies 1-1.5 MeV and currents up to 0.7 A with typical relative losses of 5-20x10 sup - sup 6. Currents of 200 mA were maintained for periods of up to five hours without a single breakdown. We found that the aperture-limiting diaphragm in the gun anode significantly increased the stability of the recirculation. We also found that the stability depended strongly on vacuum pressure in the beamline. The performance of the collector with transverse magnetic fields was found to be adequate for beam currents up to 0.6 A, which is in agreement with our low-energy bench test results. (author)

  1. Boundary Electron and Beta Dosimetry-Quantification of the Effects of Dissimilar Media on Absorbed Dose

    Science.gov (United States)

    Nunes, Josane C.

    1991-02-01

    This work quantifies the changes effected in electron absorbed dose to a soft-tissue equivalent medium when part of this medium is replaced by a material that is not soft -tissue equivalent. That is, heterogeneous dosimetry is addressed. Radionuclides which emit beta particles are the electron sources of primary interest. They are used in brachytherapy and in nuclear medicine: for example, beta -ray applicators made with strontium-90 are employed in certain ophthalmic treatments and iodine-131 is used to test thyroid function. More recent medical procedures under development and which involve beta radionuclides include radioimmunotherapy and radiation synovectomy; the first is a cancer modality and the second deals with the treatment of rheumatoid arthritis. In addition, the possibility of skin surface contamination exists whenever there is handling of radioactive material. Determination of absorbed doses in the examples of the preceding paragraph requires considering boundaries of interfaces. Whilst the Monte Carlo method can be applied to boundary calculations, for routine work such as in clinical situations, or in other circumstances where doses need to be determined quickly, analytical dosimetry would be invaluable. Unfortunately, few analytical methods for boundary beta dosimetry exist. Furthermore, the accuracy of results from both Monte Carlo and analytical methods has to be assessed. Although restricted to one radionuclide, phosphorus -32, the experimental data obtained in this work serve several purposes, one of which is to provide standards against which calculated results can be tested. The experimental data also contribute to the relatively sparse set of published boundary dosimetry data. At the same time, they may be useful in developing analytical boundary dosimetry methodology. The first application of the experimental data is demonstrated. Results from two Monte Carlo codes and two analytical methods, which were developed elsewhere, are compared

  2. Stopping-Power and Range Tables for Electrons, Protons, and Helium Ions

    Science.gov (United States)

    SRD 124 Stopping-Power and Range Tables for Electrons, Protons, and Helium Ions (Web, free access)   The databases ESTAR, PSTAR, and ASTAR calculate stopping-power and range tables for electrons, protons, or helium ions. Stopping-power and range tables can be calculated for electrons in any user-specified material and for protons and helium ions in 74 materials.

  3. A Boundary Scattering Strength Extraction Algorithm for the Analysis of Long-Range Reverberation Data

    Science.gov (United States)

    1991-03-29

    range reverberation time series and will enable us to corroborate the scattering strengths deduced from short-range measurements with those from long...System Performance Prediction Model (RASP), which generates reverberation time series that are used in active system performance prediction. Reference 2...strength function is selected, and its parameters are varied to obtain an cptimumn fit to the measured reverberation time series. The critical aspects of

  4. Enzymatic cellulose oxidation is linked to lignin by long-range electron transfer

    Science.gov (United States)

    Westereng, Bjørge; Cannella, David; Wittrup Agger, Jane; Jørgensen, Henning; Larsen Andersen, Mogens; Eijsink, Vincent G.H.; Felby, Claus

    2015-01-01

    Enzymatic oxidation of cell wall polysaccharides by lytic polysaccharide monooxygenases (LPMOs) plays a pivotal role in the degradation of plant biomass. While experiments have shown that LPMOs are copper dependent enzymes requiring an electron donor, the mechanism and origin of the electron supply in biological systems are only partly understood. We show here that insoluble high molecular weight lignin functions as a reservoir of electrons facilitating LPMO activity. The electrons are donated to the enzyme by long-range electron transfer involving soluble low molecular weight lignins present in plant cell walls. Electron transfer was confirmed by electron paramagnetic resonance spectroscopy showing that LPMO activity on cellulose changes the level of unpaired electrons in the lignin. The discovery of a long-range electron transfer mechanism links the biodegradation of cellulose and lignin and sheds new light on how oxidative enzymes present in plant degraders may act in concert. PMID:26686263

  5. Vegetation history across the Permian-Triassic boundary in Pakistan (Amb section, Salt Range)

    NARCIS (Netherlands)

    Schneebeli-Hermann, E.; Kurschner, W.M.|info:eu-repo/dai/nl/14915268X; Kerp, H.; Bomfleur, B.; Hochuli, P.A.; Bucher, H.; Ware, D.; Roohi, G.

    2015-01-01

    Hypotheses about the Permian–Triassic floral turnover range from a catastrophic extinction of terrestrial plant communities to a gradual change in floral composition punctuated by intervals indicating dramatic changes in the plant communities. The shallow marine Permian–Triassic succession in the

  6. The abiotic and biotic factors limiting establishment of predatory fishes at their expanding northern range boundaries in Ontario, Canada.

    Science.gov (United States)

    Alofs, Karen M; Jackson, Donald A

    2015-06-01

    There is a poor understanding of the importance of biotic interactions in determining species distributions with climate change. Theory from invasion biology suggests that the success of species introductions outside of their historical ranges may be either positively (biotic acceptance) or negatively (biotic resistance) related to native biodiversity. Using data on fish community composition from two survey periods separated by approximately 28 years during which climate was warming, we examined the factors influencing the establishment of three predatory centrarchids: Smallmouth Bass (Micropterus dolomieu), Largemouth Bass (M. salmoides), and Rock Bass (Ambloplites rupestris) in lakes at their expanding northern range boundaries in Ontario. Variance partitioning demonstrated that, at a regional scale, abiotic factors play a stronger role in determining the establishment of these species than biotic factors. Pairing lakes within watersheds where each species had established with lakes sharing similar abiotic conditions where the species had not established revealed both positive and negative relationships between the establishment of centrarchids and the historical presence of other predatory species. The establishment of these species near their northern range boundaries is primarily determined by abiotic factors at a regional scale; however, biotic factors become important at the lake-to-lake scale. Studies of exotic species invasions have previously highlighted how spatial scale mediates the importance of abiotic vs. biotic factors on species establishment. Our study demonstrates how concepts from invasion biology can inform our understanding of the factors controlling species distributions with changing climate. © 2014 John Wiley & Sons Ltd.

  7. Species boundaries and host range of tortoise mites (Uropodoidea phoretic on bark beetles (Scolytinae, using morphometric and molecular markers.

    Directory of Open Access Journals (Sweden)

    Wayne Knee

    Full Text Available Understanding the ecology and evolutionary history of symbionts and their hosts requires accurate taxonomic knowledge, including clear species boundaries and phylogenies. Tortoise mites (Mesostigmata: Uropodoidea are among the most diverse arthropod associates of bark beetles (Curculionidae: Scolytinae, but their taxonomy and host associations are largely unstudied. We tested the hypotheses that (1 morphologically defined species are supported by molecular data, and that (2 bark beetle uropodoids with a broad host range comprise cryptic species. To do so, we assessed the species boundaries of uropodoid mites collected from 51 host species, across 11 countries and 103 sites, using morphometric data as well as partial cytochrome oxidase I (COI and nuclear large subunit ribosomal DNA (28S. Overall, morphologically defined species were confirmed by molecular datasets, with a few exceptions. Twenty-nine of the 36 uropodoid species (Trichouropoda, Nenteria and Uroobovella collected in this study had narrow host ranges, while seven species had putative broad host ranges. In all but one species, U. orri, our data supported the existence of these host generalists, which contrasts with the typical finding that widespread generalists are actually complexes of cryptic specialists.

  8. Species boundaries and host range of tortoise mites (Uropodoidea) phoretic on bark beetles (Scolytinae), using morphometric and molecular markers.

    Science.gov (United States)

    Knee, Wayne; Beaulieu, Frédéric; Skevington, Jeffrey H; Kelso, Scott; Cognato, Anthony I; Forbes, Mark R

    2012-01-01

    Understanding the ecology and evolutionary history of symbionts and their hosts requires accurate taxonomic knowledge, including clear species boundaries and phylogenies. Tortoise mites (Mesostigmata: Uropodoidea) are among the most diverse arthropod associates of bark beetles (Curculionidae: Scolytinae), but their taxonomy and host associations are largely unstudied. We tested the hypotheses that (1) morphologically defined species are supported by molecular data, and that (2) bark beetle uropodoids with a broad host range comprise cryptic species. To do so, we assessed the species boundaries of uropodoid mites collected from 51 host species, across 11 countries and 103 sites, using morphometric data as well as partial cytochrome oxidase I (COI) and nuclear large subunit ribosomal DNA (28S). Overall, morphologically defined species were confirmed by molecular datasets, with a few exceptions. Twenty-nine of the 36 uropodoid species (Trichouropoda, Nenteria and Uroobovella) collected in this study had narrow host ranges, while seven species had putative broad host ranges. In all but one species, U. orri, our data supported the existence of these host generalists, which contrasts with the typical finding that widespread generalists are actually complexes of cryptic specialists.

  9. Dynamism in the upstream invasion edge of a freshwater fish exposes range boundary constraints.

    Science.gov (United States)

    Rubenson, Erika S; Olden, Julian D

    2017-06-01

    Studying the dynamics of species' borders can provide insight into the mechanisms limiting or promoting range expansion in response to environmental change. In the John Day River, Oregon (USA), rising stream temperatures are facilitating the upstream expansion of invasive smallmouth bass Micropterus dolomieu. Here, where smallmouth bass occupy the upstream limit of its thermal tolerance, we explore population structure and seasonal movement patterns to elucidate the environmental conditions and individual traits that define front edge (where individuals reside year-round) and leading edge (where individuals colonize, but may not establish) limits to its upstream distribution. Reporting on a multi-year, spatially extensive riverscape survey, our results show dramatic ebbs and flows of seasonal occupancies due to individual movement with an overall trend of upstream expansion. We revealed distinct front and leading edge invasion extents, each constrained by different ecological conditions. The front edge is largely constrained by the ability for juveniles to survive an overwinter starvation period, whereas the leading edge is associated with adult growth potential and seasonal hydrological conditions. We also found key morphological traits associated with more mobile individuals. By providing mechanistic insight into the factors that promote or limit range expansion of an invasive riverine species, our study enhances the ability to predict future range shifts and provides critical information to managers tasked with restricting further expansion.

  10. The INTERBALL-Tail ELECTRON experiment: initial results on the low-latitude boundary layer of the dawn magnetosphere

    Directory of Open Access Journals (Sweden)

    J.-A. Sauvaud

    Full Text Available The Toulouse electron spectrometer flown on the Russian project INTERBALL-Tail performs electron measurements from 10 to 26 000 eV over a 4 solid angle in a satellite rotation period. The INTERBALL-Tail probe was launched on 3 August 1995 together with a subsatellite into a 65° inclination orbit with an apogee of about 30 RE. The INTERBALL mission also includes a polar spacecraft launched in August 1996 for correlated studies of the outer magnetosphere and of the auroral regions. We present new observations concerning the low-latitude boundary layers (LLBL of the magnetosphere obtained near the dawn magnetic meridian. LLBL are encountered at the interface between two plasma regimes, the magnetosheath and the dayside extension of the plasma sheet. Unexpectedly, the radial extent of the region where LLBL electrons can be sporadically detected as plasma clouds can reach up to 5 RE inside the magnetopause. The LLBL core electrons have an average energy of the order of 100 eV and are systematically field-aligned and counterstreaming. As a trend, the temperature of the LLBL electrons increases with decreasing distance to Earth. Along the satellite orbit, the apparent time of occurrence of LLBL electrons can vary from about 5 to 20 min from one pass to another. An initial first comparison between electron- and magnetic-field measurements indicates that the LLBL clouds coincide with a strong increase in the magnetic field (by up to a factor of 2. The resulting strong magnetic field gradient can explain why the plasma-sheet electron flux in the keV range is strongly depressed in LLBL occurrence regions (up to a factor of sim10. We also show that LLBL electron encounters are related to field-aligned current structures and that wide LLBL correspond to northward interplanetary magnetic field. Evidence for LLBL/plasma-sheet electron leakage into the magnetosheath during southward IMF is also presented.

  11. Excitation of the lowest CO2 vibrational states by electrons in hypersonic boundary layers

    Science.gov (United States)

    Armenise, I.

    2017-07-01

    The state-to-state vibrational kinetics of a CO2/O2/CO/C/O/e- mixture in a hypersonic boundary layer under conditions compatible with the Mars re-entry is studied. The model adopted treats three CO2 modes (the two degenerated bending modes are approximated as a unique one) as not independent ones. Vibrational-translational transitions in the bending mode, inter-mode exchanges within CO2 molecule and between molecules of different chemical species as well as dissociation-recombination reactions are considered. Attention is paid to the electron-CO2 collisions that cause transitions from the ground vibrational state, CO2(0,0,0), to the first excited ones, CO2(1,0,0), CO2(0,1,0) and CO2(0,0,1). The corresponding processes rate coefficients are obtained starting from the electron energy distribution function, calculated either as an equilibrium Boltzmann distribution at the local temperature or by solving the Boltzmann equation. Results obtained either neglecting or including in the kinetic scheme the electron-CO2 collisions are compared and explained by analysing the rate coefficients of the electron-CO2 collisions.

  12. Characteristic dielectric behaviour of the wide temperature range twist grain boundary phases of unsymmetrical liquid crystal dimers

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, M B [Physics Department, University of Allahabad, Allahabad-211 002 (India); Dhar, R [Physics Department, University of Allahabad, Allahabad-211 002 (India); Achalkumar, A S [Centre for Liquid Crystal Research, Jalahalli, Bangalore-560 103 (India); Yelamaggad, C V [Centre for Liquid Crystal Research, Jalahalli, Bangalore-560 103 (India)

    2007-10-31

    The investigated optically active dimeric compound, 4-n-undecyloxy-4{sup '}-(cholesteryloxycarbonyl-1-butyloxy)chalcone, shows wide temperature ranges of two twist grain boundary (TGB) phases, TGBA and TGBC*. Comprehensive dielectric studies have been carried out for this compound in the frequency range 1 Hz-10 MHz for different conditions of molecular anchoring. This compound shows negative dielectric anisotropy ({delta}{epsilon}'={epsilon}{sub parallel}'-{epsilon}{sub perpendicul=} a{sub r}'<0). Various electrical parameters, namely the dielectric permittivity, dielectric anisotropy, DC conductivity and activation energy, have been determined for these TGB phases. Weak relaxation processes have been detected in the TGBA and TGBC* phases, presumably due to amplitude (soft mode) and phase (Goldstone mode) fluctuations.

  13. Ozone sonde measurements aboard long-range boundary-layer pressurized balloons over the western Mediterranean basin

    Science.gov (United States)

    Gheusi, François; Barret, Brice; Verdier, Nicolas; Dulac, François; Durand, Pierre; Jambert, Corinne

    Since few years, the French space agency CNES has developed boundary-layer pressurized balloons (BLPBs) with the capability to transport scientific payloads at isopicnic level over very long distances and durations (up to several weeks in absence of navigation limits). However, the autonomy of conventional electro-chemical cell (ECC) ozone sondes, that are widely used for tropospheric and stratospheric soundings, is limited to few hours due to power consumption and electrolyte evaporation (due to air bubbling in the cathode solution). In collaboration with the French research community, CNES has developed a new ozone payload suited for long duration flights aboard BLPBs. The mechanical elements (Teflon pump and motor) and the electro-chemical cell of conventional ECC sondes have been kept but the electronic implementation is entirely new. The main feature is the possibility of programming periodic measurement sequences -- with possible remote control during the flight. To increase the ozone sonde autonomy, the strategy has been adopted of short measurement sequences (typically 3 min) regularly spaced in time (e.g. every 15 min, which is usually sufficient for air quality studies). The rest of the time, the sonde is left at rest (pump motor off). The response time of an ECC sonde to an ozone concentration step is below one minute. Therefore, the typical measurement sequence is composed of a one-minute spin-up period after the pump has been turned on, followed by a two-minute acquisition period. (Note that the time intervals given here are indicative. All can be adjusted before and during the flight.) Results of a preliminary ground-based test in spring 2012 will be first presented. The sonde provided correct ozone concentrations against a reference UV analyzer every 15 minutes during 4 days. Then, we will illustrate results from 16 BLBP flights launched in the low troposphere over the Mediterranean during the three summer field campaings of the coordinated project

  14. Evolutionary dynamics of a rapidly receding southern range boundary in the threatened California red-legged frog (Rana draytonii)

    Science.gov (United States)

    Richmond, Jonathan Q.; Barr, Kelly R.; Backlin, Adam R.; Vandergast, Amy G.; Fisher, Robert N.

    2013-01-01

    Populations forming the edge of a species range are often imperiled by isolation and low genetic diversity, with proximity to human population centers being a major determinant of edge stability in modern landscapes. Since the 1960s, the California red-legged frog (Rana draytonii) has undergone extensive declines in heavily urbanized southern California, where the range edge has rapidly contracted northward while shifting its cardinal orientation to an east-west trending axis. We studied the genetic structure and diversity of these frontline populations, tested for signatures of contemporary disturbance, specifically fire, and attempted to disentangle these signals from demographic events extending deeper into the past. Consistent with the genetic expectations of the ‘abundant-center’ model, we found that diversity, admixture, and opportunity for random mating increases in populations sampled successively further away from the range boundary. Demographic simulations indicate that bottlenecks in peripheral isolates are associated with processes extending tens to a few hundred generations in the past, despite the demographic collapse of some due to recent fire-flood events. While the effects of recent disturbance have left little genetic imprint on these populations, they likely contribute to an extinction debt that will lead to continued range contraction unless management intervenes to stall or reverse the process.

  15. High dynamic range isotope ratio measurements using an analog electron multiplier

    Czech Academy of Sciences Publication Activity Database

    Williams, P.; Lorinčík, Jan; Franzreb, K.; Herwig, R.

    2013-01-01

    Roč. 45, č. 1 (2013), s. 549-552 ISSN 0142-2421 R&D Projects: GA MŠk ME 894 Institutional support: RVO:67985882 Keywords : Isotope ratios * electron multiplier * dynamic range Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.393, year: 2013

  16. Incorporation of planetary boundary layer dynamics in a numerical model of long-range air-pollutant transport

    Science.gov (United States)

    Syrakov, D.; Djolov, G.; Yordanov, D.

    1983-05-01

    A numerical model of long-range air-pollutant transport is developed, in which a simple planetary boundary layer (PBL) is incorporated. The pollution field results from the superposition of discrete ‘puffs’ of pollutants which are emitted periodically in different regions. The instantaneous sources in the different cells are approximated by rotational ellipsoids with Gaussian concentration distributions. The puff movement due to the external flow is followed by the displacement of the centroid. The expansion of the puff is modelled by nonisotropic Fickian diffusion. A simple barotropic PBL model is used to study the PBL influence. This model gives the flow velocity and the vertical turbulent exchange coefficient, which depend on the external parameters Ro and S — Rossby number and stratification parameter. The model performance is investigated by special test runs. The dependence of the pollution field on source height, stability conditions and vertical motions is shown.

  17. The effect of entrainment through atmospheric boundary layer growth on observed and modeled surface ozone in the Colorado Front Range

    Science.gov (United States)

    Kaser, L.; Patton, E. G.; Pfister, G. G.; Weinheimer, A. J.; Montzka, D. D.; Flocke, F.; Thompson, A. M.; Stauffer, R. M.; Halliday, H. S.

    2017-06-01

    Ozone concentrations at the Earth's surface are controlled by meteorological and chemical processes and are a function of advection, entrainment, deposition, and net chemical production/loss. The relative contributions of these processes vary in time and space. Understanding the relative importance of these processes controlling surface ozone concentrations is an essential component for designing effective regulatory strategies. Here we focus on the diurnal cycle of entrainment through atmospheric boundary layer (ABL) growth in the Colorado Front Range. Aircraft soundings and surface observations collected in July/August 2014 during the DISCOVER-AQ/FRAPPÉ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality/Front Range Air Pollution and Photochemistry Éxperiment) campaigns and equivalent data simulated by a regional chemical transport model are analyzed. Entrainment through ABL growth is most important in the early morning, fumigating the surface at a rate of 5 ppbv/h. The fumigation effect weakens near noon and changes sign to become a small dilution effect in the afternoon on the order of -1 ppbv/h. The chemical transport model WRF-Chem (Weather Research and Forecasting Model with chemistry) underestimates ozone at all altitudes during this study on the order of 10-15 ppbv. The entrainment through ABL growth is overestimated by the model in the order of 0.6-0.8 ppbv/h. This results from differences in boundary layer growth in the morning and ozone concentration jump across the ABL top in the afternoon. This implicates stronger modeled fumigation in the morning and weaker modeled dilution after 11:00 LT.

  18. The Range of 1-3 keV Electrons in Solid Oxygen and Carbon Monoxide

    DEFF Research Database (Denmark)

    Oehlenschlæger, M.; Andersen, H.H.; Schou, Jørgen

    1985-01-01

    The range of 1-3 keV electrons in films of solid oxygen and carbon monoxide has been measured by a mirror substrate method. The technique used here is identical to the one previously used for range measurements in solid hydrogen and nitrogen. The range in oxygen is slightly shorter than that in n......The range of 1-3 keV electrons in films of solid oxygen and carbon monoxide has been measured by a mirror substrate method. The technique used here is identical to the one previously used for range measurements in solid hydrogen and nitrogen. The range in oxygen is slightly shorter than...... that in nitrogen whereas the range in carbon monoxide is about 20% larger than that in the nitrogen....

  19. Electronic grain boundary properties in polycrystalline Cu(In,Ga)Se{sub 2} semiconductors for thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Baier, Robert

    2012-06-25

    Solar cells based on polycrystalline Cu(In,Ga)Se{sub 2} (CIGSe) thin film absorbers reach the highest energy conversion efficiency among all thin film solar cells. The record efficiency is at least partly attributed to benign electronic properties of grain boundaries (GBs) in the CIGSe layers. However, despite a high amount of research on this phenomenon the underlying physics is not sufficiently understood. This thesis presents an elaborate study on the electronic properties of GBs in CIGSe thin films. Kelvin probe force microscopy (KPFM) was employed to investigate the electronic properties of GBs in dependence of the Ga-content. Five CIGSe thin lms with various Ga-contents were grown by means of similar three stage co-evaporation processes. Both as grown as well as chemically treated (KCN etched) thin films were analyzed. The chemical treatment was employed to remove surface oxides. No difference in electronic GB properties was found with or without the chemical treatment. Therefore, we conclude that a moderate surface oxidation does not alter the electronic properties of GBs. In general, one can observe significant variations of electronic potential barriers at GBs. Under consideration of the averaging effect of the work function signal of nanoscale potential distributions in KPFM measurements which was quantified in the course of this thesis both positive and negative potential barriers in a range between ∼-350 mV and ∼+450 mV were detected. Additionally, variations in the defect densities at GBs between ∼3.1 x 10{sup 11} cm{sup -2} and ∼2.1 x 10{sup 12} cm{sup -2} were found. However, no correlation between the electronic properties of GBs and the Ga-content of CIGSe thin films was discovered. Consequently, one cannot explain the drop in device efficiency observed for CIGSe thin film solar cells with a high Ga-content by a change of the electronic properties of GBs. Combined KPFM and electron backscatter diffraction measurements were employed for the

  20. Enrichment of boron at grain boundaries of platinum-based alloys determined by electron energy loss spectroscopy in a transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Preussner, Johannes [Fraunhofer Institute for Mechanics of Materials (IWM), Freiburg (Germany); Karlsruhe Institue of Technology, Karlsruhe (DE). Inst. for Reliability of Components and Systems (izbs); Fleischmann, Ernst; Voelkl, Rainer; Glatzel, Uwe [Bayreuth Univ. (Germany). Metals and Alloys

    2010-05-15

    Polycrystalline platinum-based alloys show very good creep properties at high temperatures. Small amounts of boron (less than 1 at.%) considerably increase the creep strength. Transmission electron microscopy measurements were conducted to localize the element boron in the samples. With image electron energy loss spectroscopy spectra were extracted revealing an enrichment of B at grain boundaries. The boron distribution was plotted with the three window method. (orig.)

  1. Valence electronic structure of cobalt phthalocyanine from an optimally tuned range-separated hybrid functional

    Science.gov (United States)

    Brumboiu, Iulia Emilia; Prokopiou, Georgia; Kronik, Leeor; Brena, Barbara

    2017-07-01

    We analyse the valence electronic structure of cobalt phthalocyanine (CoPc) by means of optimally tuning a range-separated hybrid functional. The tuning is performed by modifying both the amount of short-range exact exchange (α ) included in the hybrid functional and the range-separation parameter (γ ), with two strategies employed for finding the optimal γ for each α . The influence of these two parameters on the structural, electronic, and magnetic properties of CoPc is thoroughly investigated. The electronic structure is found to be very sensitive to the amount and range in which the exact exchange is included. The electronic structure obtained using the optimal parameters is compared to gas-phase photo-electron data and GW calculations, with the unoccupied states additionally compared with inverse photo-electron spectroscopy measurements. The calculated spectrum with tuned γ , determined for the optimal value of α = 0.1 , yields a very good agreement with both experimental results and with GW calculations that well-reproduce the experimental data.

  2. Applying shot boundary detection for automated crystal growth analysis during in situ transmission electron microscope experiments

    Energy Technology Data Exchange (ETDEWEB)

    Moeglein, W. A.; Griswold, R.; Mehdi, B. L.; Browning, N. D.; Teuton, J.

    2017-01-03

    In-situ (scanning) transmission electron microscopy (S/TEM) is being developed for numerous applications in the study of nucleation and growth under electrochemical driving forces. For this type of experiment, one of the key parameters is to identify when nucleation initiates. Typically the process of identifying the moment that crystals begin to form is a manual process requiring the user to perform an observation and respond accordingly (adjust focus, magnification, translate the stage etc.). However, as the speed of the cameras being used to perform these observations increases, the ability of a user to “catch” the important initial stage of nucleation decreases (there is more information that is available in the first few milliseconds of the process). Here we show that video shot boundary detection (SBD) can automatically detect frames where a change in the image occurs. We show that this method can be applied to quickly and accurately identify points of change during crystal growth. This technique allows for automated segmentation of a digital stream for further analysis and the assignment of arbitrary time stamps for the initiation of processes that are independent of the user’s ability to observe and react.

  3. Time-of-flight electron spectrometer for a broad range of kinetic energies

    Energy Technology Data Exchange (ETDEWEB)

    Kothe, Alexander; Metje, Jan; Wilke, Martin; Moguilevski, Alexandre; Engel, Nicholas; Al-Obaidi, Ruba; Richter, Clemens; Golnak, Ronny; Kiyan, Igor Yu.; Aziz, Emad F. [Joint Ultrafast Dynamics Lab in Solutions and at Interfaces (JULiq), Helmholtz-Zentrum Berlin fuer Materialien und Energie (HZB), Albert-Einstein-Str. 15, 12489 Berlin (Germany) and Freie Universitaet Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin (Germany)

    2013-02-15

    A newly constructed time-of-flight electron spectrometer of the magnetic bottle type is characterized for electron detection in a broad range of kinetic energies. The instrument is designed to measure the energy spectra of electrons generated from liquids excited by strong laser fields and photons in the range of extreme ultra violet and soft X-rays. Argon inner shell electrons were recorded to calibrate the spectrometer and investigate its characteristics, such as energy resolution and collection efficiency. Its energy resolution {Delta}E/E of 1.6% allows resolving the Ar 2p spin orbit structure at kinetic energies higher than 100 eV. The collection efficiency is determined and compared to that of the spectrometer in its field-free configuration.

  4. Ground boundaries

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    The present document is a progress report describing the work accomplished on the study of grain boundaries in Ag, Au, Ni, Si, and Ge. Research was focused on the following four major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; grain boundary migration; short-circuit diffusion along grain boundaries; and development of Thin-Film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  5. Nanocompositional Electron Microscopic Analysis and Role of Grain Boundary Phase of Isotropically Oriented Nd-Fe-B Magnets

    Directory of Open Access Journals (Sweden)

    Gregor A. Zickler

    2017-01-01

    Full Text Available Nanoanalytical TEM characterization in combination with finite element micromagnetic modelling clarifies the impact of the grain misalignment and grain boundary nanocomposition on the coercive field and gives guidelines how to improve coercivity in Nd-Fe-B based magnets. The nanoprobe electron energy loss spectroscopy measurements obtained an asymmetric composition profile of the Fe-content across the grain boundary phase in isotropically oriented melt-spun magnets and showed an enrichment of iron up to 60 at% in the Nd-containing grain boundaries close to Nd2Fe14B grain surfaces parallel to the c-axis and a reduced iron content up to 35% close to grain surfaces perpendicular to the c-axis. The numerical micromagnetic simulations on isotropically oriented magnets using realistic model structures from the TEM results reveal a complex magnetization reversal starting at the grain boundary phase and show that the coercive field increases compared to directly coupled grains with no grain boundary phase independently of the grain boundary thickness. This behaviour is contrary to the one in aligned anisotropic magnets, where the coercive field decreases compared to directly coupled grains with an increasing grain boundary thickness, if Js value is > 0.2 T, and the magnetization reversal and expansion of reversed magnetic domains primarily start as Bloch domain wall at grain boundaries at the prismatic planes parallel to the c-axis and secondly as Néel domain wall at the basal planes perpendicular to the c-axis. In summary our study shows an increase of coercive field in isotropically oriented Nd-Fe-B magnets for GB layer thickness > 5 nm and an average Js value of the GB layer < 0.8 T compared to the magnet with perfectly aligned grains.

  6. Engineering Mixed Ionic Electronic Conduction in La 0.8 Sr 0.2 MnO 3+ δ Nanostructures through Fast Grain Boundary Oxygen Diffusivity

    KAUST Repository

    Saranya, Aruppukottai M.

    2015-04-09

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Nanoionics has become an increasingly promising field for the future development of advanced energy conversion and storage devices, such as batteries, fuel cells, and supercapacitors. Particularly, nanostructured materials offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. However, the enhancement of the mass transport properties at the nanoscale has often been found to be difficult to implement in nanostructures. Here, an artificial mixed ionic electronic conducting oxide is fabricated by grain boundary (GB) engineering thin films of La0.8Sr0.2MnO3+δ. This electronic conductor is converted into a good mixed ionic electronic conductor by synthesizing a nanostructure with high density of vertically aligned GBs with high concentration of strain-induced defects. Since this type of GBs present a remarkable enhancement of their oxide-ion mass transport properties (of up to six orders of magnitude at 773 K), it is possible to tailor the electrical nature of the whole material by nanoengineering, especially at low temperatures. The presented results lead to fundamental insights into oxygen diffusion along GBs and to the application of these engineered nanomaterials in new advanced solid state ionics devices such are micro-solid oxide fuel cells or resistive switching memories. An electronic conductor such as La0.8Sr0.2MnO3+δ is converted into a good mixed ionic electronic conductor by synthesizing a nanostructure with excellent electronic and oxygen mass transport properties. Oxygen diffusion highways are created by promoting a high concentration of strain-induced defects in the grain boundary region. This novel strategy opens the way for synthesizing new families of artificial mixed ionic-electronic conductors by design.

  7. Spatially-resolved studies on the role of defects and boundaries in electronic behavior of 2D materials

    Science.gov (United States)

    Hus, Saban M.; Li, An-Ping

    2017-08-01

    Two-dimensional (2D) materials are intrinsically heterogeneous. Both localized defects, such as vacancies and dopants, and mesoscopic boundaries, such as surfaces and interfaces, give rise to compositional or structural heterogeneities. The presence of defects and boundaries can break lattice symmetry, modify the energy landscape, and create quantum confinement, leading to fascinating electronic properties different from the ;ideal; 2D sheets. This review summarizes recent progress in understanding the roles of defects and boundaries in electronic, magnetic, thermoelectric, and transport properties of 2D layered materials. The focus is on the understanding of correlation of atomic-scale structural information with electronic functions by interrogating heterogeneities individually. The materials concerned are graphene, transition metal dichalcogenides (TMDs), hexagonal boron nitride (hBN), and topological insulators (TIs). The experimental investigations benefit from new methodologies and techniques in scanning tunneling microscopy (STM), including spin-polarized STM, scanning tunneling potentiometry (STP), scanning tunneling thermopower microscopy, and multi-probe STM. The experimental effort is complemented by the computational and theoretical approaches, capable of discriminating between closely competing states and achieving the length scales necessary to bridge across features such as local defects and complex heterostructures. The goal is to provide a general view of current understanding and challenges in studying the heterogeneities in 2D materials and to evaluate the potential of controlling and exploiting these heterogeneities for novel functionalities and electron devices.

  8. Ranges and limits of the electron-phonon coupling constant of ...

    African Journals Online (AJOL)

    A simplified study of the effect of including self energy and vertex corrections to the BCS critical temperature Tc expression is carried out her to identify the possible ranges and limits of the electron-phonon coupling constant λ in superconductivity. The results show that the inclusion of the self energy will reduce the BCS Tc to ...

  9. Magnetic Skyrmion Formation at Lattice Defects and Grain Boundaries Studied by Quantitative Off-Axis Electron Holography.

    Science.gov (United States)

    Li, Zi-An; Zheng, Fengshan; Tavabi, Amir Hossein; Caron, Jan; Jin, Chiming; Du, Haifeng; Kovács, András; Tian, Mingliang; Farle, Michael; Dunin-Borkowski, Rafal E

    2017-03-08

    We use in situ Lorentz microscopy and off-axis electron holography to investigate the formation and characteristics of skyrmion lattice defects and their relationship to the underlying crystallographic structure of a B20 FeGe thin film. We obtain experimental measurements of spin configurations at grain boundaries, which reveal inversions of crystallographic and magnetic chirality across adjacent grains, resulting in the formation of interface spin stripes at the grain boundaries. In the absence of material defects, we observe that skyrmions lattices possess dislocations and domain boundaries, in analogy to atomic crystals. Moreover, the distorted skyrmions can flexibly change their size and shape to accommodate local geometry, especially at sites of dislocations in the skyrmion lattice. Our findings provide a detailed understanding of the elasticity of topologically protected skyrmions and their correlation with underlying material defects.

  10. Surface treatment by the ion flow from electron beam generated plasma in the forevacuum pressure range

    Directory of Open Access Journals (Sweden)

    Klimov Aleksandr

    2018-01-01

    Full Text Available The paper presents research results of peculiarities of gas ion flows usage and their generation from large plasma formation (>50 sq.cm obtained by electron beam ionization of gas in the forevacuum pressure range. An upgraded source was used for electron beam generation, which allowed obtaining ribbon electron beam with no transmitting magnetic field. Absence of magnetic field in the area of ion flow formation enables to obtain directed ion flows without distorting their trajectories. In this case, independent control of current and ion energy is possible. The influence of electron beam parameters on the parameters of beam plasma and ion flow – current energy and density – was determined. The results of alumina ceramics treatment with a beam plasma ions flow are given.

  11. Prototype system for proton beam range measurement based on gamma electron vertex imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Han Rim [Neutron Utilization Technology Division, Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057 (Korea, Republic of); Kim, Sung Hun; Park, Jong Hoon [Department of Nuclear Engineering, Hanyang University, Seongdong-gu, Seoul 04763 (Korea, Republic of); Jung, Won Gyun [Heavy-ion Clinical Research Division, Korean Institute of Radiological & Medical Sciences, Seoul 01812 (Korea, Republic of); Lim, Hansang [Department of Electronics Convergence Engineering, Kwangwoon University, Seoul 01897 (Korea, Republic of); Kim, Chan Hyeong, E-mail: chkim@hanyang.ac.kr [Department of Nuclear Engineering, Hanyang University, Seongdong-gu, Seoul 04763 (Korea, Republic of)

    2017-06-11

    In proton therapy, for both therapeutic effectiveness and patient safety, it is very important to accurately measure the proton dose distribution, especially the range of the proton beam. For this purpose, recently we proposed a new imaging method named gamma electron vertex imaging (GEVI), in which the prompt gammas emitting from the nuclear reactions of the proton beam in the patient are converted to electrons, and then the converted electrons are tracked to determine the vertices of the prompt gammas, thereby producing a 2D image of the vertices. In the present study, we developed a prototype GEVI system, including dedicated signal processing and data acquisition systems, which consists of a beryllium plate (= electron converter) to convert the prompt gammas to electrons, two double-sided silicon strip detectors (= hodoscopes) to determine the trajectories of those converted electrons, and a plastic scintillation detector (= calorimeter) to measure their kinetic energies. The system uses triple coincidence logic and multiple energy windows to select only the events from prompt gammas. The detectors of the prototype GEVI system were evaluated for electronic noise level, energy resolution, and time resolution. Finally, the imaging capability of the GEVI system was tested by imaging a {sup 90}Sr beta source, a {sup 60}Co gamma source, and a 45-MeV proton beam in a PMMA phantom. The overall results of the present study generally show that the prototype GEVI system can image the vertices of the prompt gammas produced by the proton nuclear interactions.

  12. Characterization and Evaluation of 600 V Range Devices for Active Power Factor Correction in Boundary and Continuous Conduction Modes

    DEFF Research Database (Denmark)

    Hernandez Botella, Juan Carlos; Petersen, Lars Press; Andersen, Michael A. E.

    2015-01-01

    Traditional characterization of semiconductors switching dynamics is performed based on clamped inductive load measurements using the double pulse tester (DPT) configuration. This approach is valid for converters operating in continuous conduction mode (CCM), however in boundary conduction mode (...

  13. On the detection of expansion at large angle grain boundaries using electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1984-06-01

    A model of the type shown by Brokman and Balluffi in this article, should hold for grain boundary reflections from twist boundaries occurring at positions in reciprocal space on elements of the ''boundary diffraction lattice'' (BDL) which do not contain lattice reflections. In such cases, the intensities scattered by the boundary region and the two unperturbed lattices can be separated to a good approximation, and the scattering from the boundary region can be considered independently. However, in the present case, where the intensity from the grain boundary region, considered separately, would appear close to lattice reflections on the same element of the BDL, it is not clear that this is the case. It may be necessary to perform a more complicated analysis taking account of the total scattering from the grain boundary region and the two adjoining lattices. The purpose of this article is to present such an analysis. The results show that the more complicated analysis is required and a more realistic explanation of the observed result is discussed.

  14. Atomic configuration and electronic structure of extended defects from the point of view of positron annihilation: a grain boundary example

    Energy Technology Data Exchange (ETDEWEB)

    Sob, M.; Turek, I. [Akademie Ved Ceske Republiky, Brno (Czech Republic). Ustav Fyzikalni Metalurgie; Vitek, V. [Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science and Engineering

    1997-10-01

    A quantum-mechanical approach for determining the electronic structure and atomic configuration of extended defects in metals is described and importance of theoretical methods for interpretation of positron annihilation spectroscopy data is stressed. As an example, atomic configuration of the {Sigma} = 5(210)/[001] tilt grain boundary in tungsten is determined and local densities of states at atoms in defect region are discussed. (author). 19 refs, 3 figs.

  15. High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy.

    Science.gov (United States)

    Tate, Mark W; Purohit, Prafull; Chamberlain, Darol; Nguyen, Kayla X; Hovden, Robert; Chang, Celesta S; Deb, Pratiti; Turgut, Emrah; Heron, John T; Schlom, Darrell G; Ralph, Daniel C; Fuchs, Gregory D; Shanks, Katherine S; Philipp, Hugh T; Muller, David A; Gruner, Sol M

    2016-02-01

    We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80-200 keV electron beams.

  16. Interaction of a relativistic electron beam with radiation in the THz frequency range

    Science.gov (United States)

    Sung, Chieh

    The ability to generate a train of microbunches that are only typically tens of femtosecond wide and are separated by a picosecond is a topic of contemporary interest in the field of free electron lasers and plasma based accelerators. Moreover the usefulness of the high gradients present in plasma accelerators will depend on the ability to obtain mono-energetic relativistic electrons. This means that in addition to being prebunched on a scale shorter than the plasma wavelength the externally injected electron beam must be phase-locked to the accelerating plasma wave structure. In this thesis we investigate two techniques, Free Electron Laser interaction (FEL) and the Inverse Free Electron Laser interaction (IFEL), by which a medium energy electron beam can be prebunched into a series of microbunches with the same periodicity as a plasma wave and is phase locked to it. Using full-scale, 3-D simulations we show in this thesis that when a relativistic electron beam and an electromagnetic wave propagate collinearly through a magnetic undulator, FEL and IFEL interactions have the capability to form electron microbunches with periodicity 300-100 mum (1-3 THz range), which contain 50% of electrons within a small fraction of the ponderomotive buckets. Such a bunched beam is suitable for injection into plasma densities in the range 1016-1017 cm-3, respectively. Microbunching using the FEL mechanism requires a narrowband THz radiation source to act as a seed whereas the IFEL mechanism requires, in addition, such a source to be high power. In this thesis the generation of THz radiation in the Neptune Laboratory by mixing of two CO2 laser lines in a non-collinearly phase matched GaAs at room temperature is described A high-power THz pulse with up to 2 MW of peak power in a 250 ps pulse was generated using a TW class CO2 laser pulse. Such high power THz radiation is needed for the IFEL approach to microbunching. We also produced a high repetition rate THz source tunable in the

  17. Electrical, optical, and electronic properties of Al:ZnO films in a wide doping range

    Energy Technology Data Exchange (ETDEWEB)

    Valenti, Ilaria; Valeri, Sergio [CNR, Istituto Nanoscienze, S3, Via G. Campi 213/a, 41125 Modena (Italy); Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via G. Campi 213/a, 41125 Modena (Italy); Benedetti, Stefania, E-mail: stefania.benedetti@unimore.it; Bona, Alessandro di [CNR, Istituto Nanoscienze, S3, Via G. Campi 213/a, 41125 Modena (Italy); Lollobrigida, Valerio [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome, Italy and Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Perucchi, Andrea; Di Pietro, Paola [INSTM Udr Trieste-ST and Elettra-Sincrotrone Trieste S.C.p.A., Area Science Park, I-34012 Trieste (Italy); Lupi, Stefano [CNR-IOM and Dipartimento di Fisica, Università di Roma Sapienza, P.le Aldo Moro 2, I-00185 Roma (Italy); Torelli, Piero [Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, I-34149 Trieste (Italy)

    2015-10-28

    The combination of photoemission spectroscopies, infrared and UV-VIS absorption, and electric measurements has allowed to clarify the mechanisms governing the conductivity and the electronic properties of Al-doped ZnO (AZO) films in a wide doping range. The contribution of defect-related in-gap states to conduction has been excluded in optimally doped films (around 4 at. %). The appearance of gap states at high doping, the disappearance of occupied DOS at Fermi level, and the bands evolution complete the picture of electronic structure in AZO when doped above 4 at. %. In this situation, compensating defects deplete the conduction band and increase the electronic bandgap of the material. Electrical measurements and figure of merit determination confirm the high quality of the films obtained by magnetron sputtering, and thus allow to extend their properties to AZO films in general.

  18. Variability of the planktonic foraminifera community across the Eocene/Oligocene boundary, Fuente Caldera Section, Baetic Ranges (Spain)

    Science.gov (United States)

    Legarda-Lisarri, A.

    2013-12-01

    During the Eocene/Oligocene transition, in a massive extinction event that took place about 33.7 million years ago, the current high resolution study analyzes qualitatively and quantitatively the community structure of the planktonic foraminifera that were preserved in the hemipelagic sediments of the Tethys Sea. The sampled section of the Fuente Caldera column, located in the Baetic mountain ranges, spans a register of 396,551.7 years. Based in the identification of 27 species, that belong to 13 genera and 2 families of foraminifera, there have been found three biozones of Gonzalvo Zonation (Gonzalvo, 2002) in the studied stratigraphic interval: Turborotalia cocoaensis and Cribrohantkenina lazzarii Biozones (Rupelian), and Paragloborotalia increbescens (Priabonian). The planktonic foraminifera associations variability patterns are defined by paleoecologic indexes (diversity index, high and low latitude species index and planktonic and benthic foraminifera index), by geochemical proxies: δ18O and δ13C and by 'Q' Mode Factor Analysis. They prove that the deposition environment is outer platform and also, they suggest that the studied area in the Tethys Sea underwent many thermal pulses, during which some species extinct or appear. In the first extinction event the species Turborotalia cocoaensis and Turborotalia cunialensis became extinct. In the second one, Hantkenina alabamensis, Hantkenina brevispina, Cribrohantkenina lazzarii and Pseudohastigerina micra became extinct while a succession occured; Globigerina officinalis, Globoturborotalita anguliofficinalis and Tenuitellinata angustiumbilicata appeared. The cooling event that finished in the Lower Oligocene was the biggest of these pulses, which was extremely abrupt and corresponds to the Oi-1 event that was described by Miller (Miller, 1991). All this evidences that the planktonic foraminifera extinction in the Upper Eocene was a gradual and fast event, what is supported by the Factor Analysis application. Key

  19. Lithosphere-Asthenosphere Boundary Beneath Regions of Recent Volcanism in the Basin and Range Province and Mojave Desert

    Science.gov (United States)

    Forsyth, D. W.; Rau, C. J.; Plank, T.; Gazel, E.; Bendersky, C.

    2010-12-01

    Melt in the asthenosphere may contribute strongly to the development of the lithosphere-asthenosphere boundary (LAB) in some settings. We have compiled a set of vertical shear-velocity profiles beneath centers of recent (Hill and Amboy in the southern Mojave, the lithospheric lid extends to a depth of ~ 90 km. Minimum velocities in the LVZs beneath the higher velocity lids typically are 4.00-4.05 km/s, similar to that beneath the East Pacific Rise and too low to be caused by temperature alone without unreasonably high attenuation. Beneath other centers, like Big Pine, Lathrop Wells and Tahoe, there is no resolvable lid. The lid is either missing or too thin to resolve, but the absence of the lid/LVZ pattern seems to be due to a combination of lower velocities immediately beneath the Moho and higher velocities in the LVZ. Petrological indicators of temperature and depth of melting from basalt composition are in general agreement with the seismological observations, with the depth of last equilibration typically occurring near the top of the LVZ. Beneath Big Pine, for example, the equilibration temperatures are unusually low and the equilibration depth is 40 to 50 km, just below the Moho, in agreement with the lack of a distinct lid. Beneath Cima, equilibration depths are 60-70 km. Beneath Coso, equilibration depths are only slightly deeper than Big Pine, but the temperatures are higher, in agreement with the more pronounced LVZ and the presence of a thin lid. Beneath the Tabernacle Hill/Black Rock volcanic field in west-central Utah, there is a well-developed lid/LVZ structure, but the "high" velocity lid is only ~ 4.10 km/s while the underlying LVZ reaches as low as 3.90 km/s. This observation points to the importance of melt concentration or distribution controlling the velocities. Lid velocities are often relatively low (4.2-4.4 km/s) in the Basin and Range, indicating high temperatures, but here there is probably melt within the lid as well, with higher

  20. Evaluation of simulated climatological diurnal temperature range in CMIP5 models from the perspective of planetary boundary layer turbulent mixing

    Science.gov (United States)

    Wei, Nan; Zhou, Liming; Dai, Yongjiu

    2017-07-01

    This study examines the effects of modeled planetary boundary layer (PBL) mixing on the simulated temperature diurnal cycle climatology over land in 20 CMIP5 models with AMIP simulations. When compared with observations, the magnitude of diurnal temperature range (DTR) is systematically underestimated over almost all land areas due to a widespread warm bias of daily minimum temperature (Tmin) and mostly a cold bias of daily maximum temperature (Tmax). Analyses of the CMIP5 multi-model ensemble means suggest that the biases of the simulated PBL mixing could very likely contribute to the temperature biases. For the regions with the cold bias in Tmax, the daytime PBL mixing is generally underestimated. The consequent more dry air entrainment from the free atmosphere could help maintain the surface humidity gradient, and thus produce more surface evaporation and potentially lower the Tmax. The opposite situation holds true for the regions with the warm bias of Tmax. This mechanism could be particularly applicable to the regions with moderate and wet climate conditions where surface evaporation depends more on the surface humidity gradient, but less on the available soil moisture. For the widespread warm bias of Tmin, the widely-recognized overestimated PBL mixing at nighttime should play a dominant role by transferring more heat from the atmosphere to the near-surface to warm the Tmin. Further analyses using the high resolution CFMIP2 output also support the CMIP5 results about the connections of the biases between the simulated turbulent mixing and the temperature diurnal cycle. The large inter-model variations of the simulated temperature diurnal cycle primarily appear over the arid and semi-arid regions and boreal arctic regions where the model differences in the PBL turbulence mixing could make equally significant contributions to the inter-model variations of DTR, Tmax and Tmin compared to the model differences in surface radiative processes. These results

  1. 100 keV electron backscattered range and coefficient for silicon.

    Energy Technology Data Exchange (ETDEWEB)

    Czaplewski, D.A.; Ocola, L.E. (Center for Nanoscale Materials)

    2012-01-01

    The authors have measured the range and intensity of backscattered electrons in silicon from a 100 keV source using a process independent method. Backscattered electrons contributed to the total dose of features written in a negative tone electron beam resist. Instead of measuring the height of the resist and using a contrast curve to convert the resist height to dose, the heights of the features were made equal by adjusting the backscattered contribution through dose assignments. Creating features of equal height eliminated the need to use a contrast curve to convert from resist height to total dose. Also, it allowed for measurements of the backscattered contribution from larger distances. Using a circularly symmetric torus pattern, the three-dimensional backscatter problem was reduced to a 1-dimensional Gaussian form. The authors measured the range of the backscattered electrons, {beta}, to be 31.08 {+-} 0.06 {micro}m. By varying the writing dose of the pattern, we determined the backscatter coefficient, {eta}, to be 0.63 {+-} 0.03.

  2. Short Range Correlations in Nuclei at Large xbj through Inclusive Quasi-Elastic Electron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Zhihong [Univ. of Virginia, Charlottesville, VA (United States)

    2013-12-01

    The experiment, E08-014, in Hall-A at Jefferson Lab aims to study the short-range correlations (SRC) which are necessary to explain the nuclear strength absent in the mean field theory. The cross sections for 2H, 3He, 4He, 12C, 40Ca and 48Ca, were measured via inclusive quasi-elastic electron scattering from these nuclei in a Q2 range between 0.8 and 2.8 (GeV/c)2 for x>1. The cross section ratios of heavy nuclei to 2H were extracted to study two-nucleon SRC for 1

  3. Electron scattering on the short-range potential of crystal lattice defects in gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Malyk, Orest [Semiconductor Electronics Department, Lviv Polytechnic National University, Bandera Street 12, 79013 Lviv (Ukraine)

    2012-03-15

    The processes of the charge carrier scattering on the short-range potential caused by interaction with polar and nonpolar optical phonons, piezoelectric and acoustic phonons, static strain, neutral and ionized impurities in wurtzite n-GaN with impurity concentration 4 x 10{sup 16}-2 x 10{sup 19} cm{sup -3} are considered. The temperature dependences of electron mobility in the range 40-500 K are calculated. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Configurable Electronics with Low Noise and 14-bit Dynamic Range for Photodiode-based Photon Detectors

    CERN Document Server

    Müller, H; Yin, Z; Zhou, D; Cao, X; Li, Q; Liu, Y; Zou, F; Skaali, B; Awes, T C

    2006-01-01

    We describe the principles and measured performance characteristics of custom configurable 32-channel shaper/digitizer Front End Electronics (FEE) cards with 14-bit dynamic range for use with gain-adjustable photon detectors. The electronics has been designed for the PHOS calorimeter of ALICE with avalanche photodiode (APD) readout operated at -25 C ambient temperature and a signal shaping time of $1 {\\mu}s$. The electronics has also been adopted by the EMCal detector of ALICE with the same APD readout, but operated at an ambient temperature of +20 C and with a shaping time of 100ns. The CR-RC2 signal shapers on the FEE cards are implemented in discrete logic on a 10-layer board with two shaper sections for each input channel. The two shaper sections with gain ratio of 16:1 are digitized by 10-bit ADCs and provide an effective dynamic range of 14 bits. Gain adjustment for each individual APD is available through 32 bias voltage control registers of 10-bit range. The fixed gains and shaping times of the pole-z...

  5. A Comparison between Boundary and Continuous Conduction Modes in Single Phase PFC Using 600V Range Devices

    DEFF Research Database (Denmark)

    Hernandez Botella, Juan Carlos; Petersen, Lars Press; Andersen, Michael A. E.

    2015-01-01

    This paper presents an analysis and comparison of boundary conduction mode (BCM) and continuous conduction mode (CCM) in single phase power factor correction (PFC) applications. The comparison is based on double pulse tester (DPT) characterization results of state-of-the-art superjunction devices...

  6. Seeded free-electron and inverse free-electron laser techniques for radiation amplification and electron microbunching in the terahertz range

    Directory of Open Access Journals (Sweden)

    C. Sung

    2006-12-01

    Full Text Available A comprehensive analysis is presented that describes amplification of a seed THz pulse in a single-pass free-electron laser (FEL driven by a photoinjector. The dynamics of the radiation pulse and the modulated electron beam are modeled using the time-dependent FEL code, GENESIS 1.3. A 10-ps (FWHM electron beam with a peak current of 50–100 A allows amplification of a ∼1  kW seed pulse in the frequency range 0.5–3 THz up to 10–100 MW power in a relatively compact 2-m long planar undulator. The electron beam driving the FEL is strongly modulated, with some inhomogeneity due to the slippage effect. It is shown that THz microbunching of the electron beam is homogeneous over the entire electron pulse when saturated FEL amplification is utilized at the very entrance of an undulator. This requires seeding of a 30-cm long undulator buncher with a 1–3 MW of pump power with radiation at the resonant frequency. A narrow-band seed pulse in the THz range needed for these experiments can be generated by frequency mixing of CO_{2} laser lines in a GaAs nonlinear crystal. Two schemes for producing MW power pulses in seeded FELs are considered in some detail for the beam parameters achievable at the Neptune Laboratory at UCLA: the first uses a waveguide to transport radiation in the 0.5–3 THz range through a 2-m long FEL amplifier and the second employs high-gain third harmonic generation using the FEL process at 3–9 THz.

  7. Precipitation of subrelativistic-energy electrons near the polar boundary of the Earth radiation belt according to the data of measurements on the Vernov and Lomonosov satellites

    Science.gov (United States)

    Bogomolov, A. V.; Myagkova, I. N.; Kalegaev, V. V.; Svertilov, S. I.; Bogomolov, V. V.; Panasyuk, M. I.; Petrov, V. L.; Yashin, I. V.

    2017-11-01

    The work is devoted to observations of sharp growths of magnetospheric electron fluxes in the vicinity of the polar boundary of the outer radiation belt of the Earth according to the data of measurements on the Vernov and Lomonosov satellites. This precipitation was observed at the high-latitude boundary of the outer radiation belt toward the equator from the isotropization boundary, and can be caused by scattering waves of various physical natures, including electromagnetic and electrostatic waves.

  8. Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

    Directory of Open Access Journals (Sweden)

    K. Schäfer

    2012-07-01

    Full Text Available Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2 are needed to assess the spatial distribution of emissions. This can be readily done using spatial-integrating micro-meteorological methods like flux-gradient methods which were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Non-intrusive path-integrating measurements are utilized. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind, and in the applicability of boundary-layer turbulence theory; consequently the procedures to qualify measurements that can be used to determine the flux is critical. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s−1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study of N2O emissions of flat grassland and NH3 emissions from a cattle lagoon involves quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that following the Monin-Obukhov similarity theory (MOST flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus flux in the stable boundary layer. An alternative approach is considered on the basis of turbulent diffusivity, i.e. the measured friction velocity as well as height gradients of horizontal wind speeds and concentrations without MOST correction for stability. It is shown that this is the most accurate of the flux-gradient methods under stable conditions.

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

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  10. Measurements of low-energy electron reflection at a plasma boundary

    Energy Technology Data Exchange (ETDEWEB)

    Demidov, V. I., E-mail: vladimir.demidov@mail.wvu.edu [Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States); Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506 (United States); Adams, S. F. [Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States); Kaganovich, I. D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Koepke, M. E. [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506 (United States); Kurlyandskaya, I. P. [Department of Optics and Spectroscopy, St. Petersburg State University, St. Petersburg 199034 (Russian Federation); International Laboratory “Nonlocal Plasma in Nanotechnology and Medicine,” ITMO University, St. Petersburg 197101 (Russian Federation)

    2015-10-15

    It is demonstrated that low-energy (<3 eV) electron reflection from a solid surface in contact with a low-temperature plasma can have significant variation with time. An uncontaminated, i.e., “clean,” metallic surface (just after heating up to glow) in a plasma environment may have practically no reflection of low-energy incident electrons. However, a contaminated, i.e., “dirty,” surface (in some time after cleaning by heating) that has a few monolayers of absorbent can reflect low-energy incident electrons and therefore significantly affect the net electron current collected by the surface. This effect may significantly change plasma properties and should be taken into account in plasma experiments and models. A diagnostic method is demonstrated for measurements of low-energy electron absorption coefficient in plasmas with a mono-energetic electron group.

  11. Ground boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1990-01-01

    The present document is a progress report describing the work accomplished on the study of grain boundaries in Ag, Au, Ni, Si, and Ge. Research was focused on the following four major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; grain boundary migration; short-circuit diffusion along grain boundaries; and development of Thin-Film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals. 10 refs., 1 fig.

  12. Broad-scale latitudinal variation in female reproductive success contributes to the maintenance of a geographic range boundary in bagworms (Lepidoptera: Psychidae.

    Directory of Open Access Journals (Sweden)

    Marc Rhainds

    Full Text Available BACKGROUND: Geographic range limits and the factors structuring them are of great interest to biologists, in part because of concerns about how global change may shift range boundaries. However, scientists lack strong mechanistic understanding of the factors that set geographic range limits in empirical systems, especially in animals. METHODOLOGY/PRINCIPAL FINDINGS: Across dozens of populations spread over six degrees of latitude in the American Midwest, female mating success of the evergreen bagworm Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae declines from ∼100% to ∼0% near the edge of the species range. When coupled with additional latitudinal declines in fecundity and in egg and pupal survivorship, a spatial gradient of bagworm reproductive success emerges. This gradient is associated with a progressive decline in local abundance and an increased risk of local population extinction, up to a latitudinal threshold where extremely low female fitness meshes spatially with the species' geographic range boundary. CONCLUSIONS/SIGNIFICANCE: The reduction in fitness of female bagworms near the geographic range limit, which concords with the abundant centre hypothesis from biogeography, provides a concrete, empirical example of how an Allee effect (increased pre-reproductive mortality of females in sparsely populated areas may interact with other demographic factors to induce a geographic range limit.

  13. Long-range protein electron transfer observed at the single-molecule level

    DEFF Research Database (Denmark)

    Chi, Qijin; Farver, Ole; Ulstrup, Jens

    2005-01-01

    potential. Maximum resonance appears around the equilibrium redox potential of azurin with an on/off current ratio of approximately 9. Simulation analyses, based on a two-step interfacial ET model for the scanning tunneling microscopy redox process, were performed and provide quantitative information......A biomimetic long-range electron transfer (ET) system consisting of the blue copper protein azurin, a tunneling barrier bridge, and a gold single-crystal electrode was designed on the basis of molecular wiring self-assembly principles. This system is sufficiently stable and sensitive in a quasi...

  14. Broadening of Plasmonic Resonance Due to Electron Collisions with Nanoparticle Boundary: а Quantum Mechanical Consideration

    DEFF Research Database (Denmark)

    Uskov, Alexander; Protsenko, Igor E.; Mortensen, N. Asger

    2014-01-01

    We present a quantum mechanical approach to calculate broadening of plasmonic resonances in metallic nanostructures due to collisions of electrons with the surface of the structure. The approach is applicable if the characteristic size of the structure is much larger than the de Broglie electron...

  15. Variable range hopping in TiO2 insulating layers for oxide electronic devices

    Directory of Open Access Journals (Sweden)

    Y. L. Zhao

    2012-03-01

    Full Text Available TiO2 thin films are of importance in oxide electronics, e.g., Pt/TiO2/Pt for memristors and Co-TiO2/TiO2/Co-TiO2 for spin tunneling devices. When such structures are deposited at a variety of oxygen pressures, how does TiO2 behave as an insulator? We report the discovery of an anomalous resistivity minimum in a TiO2 film at low pressure (not strongly dependent on deposition temperature. Hall measurements rule out band transport and in most of the pressure range the transport is variable range hopping (VRH though below 20 K it was difficult to differentiate between Mott and Efros-Shklovskii's (ES mechanism. Magnetoresistance (MR of the sample with lowest resistivity was positive at low temperature (for VRH but negative above 10 K indicating quantum interference effects.

  16. Timing of Deformation in the Central Metasedimentary Belt Boundary Thrust Zone (CMBbtz), southern Ontario, Canada, from Electron Microprobe Dating of Monazite

    Science.gov (United States)

    Markley, M. J.; Dunn, S. R.; Peck, W. H.; Jercinovic, M. J.; Williams, M. L.

    2015-12-01

    In the Grenville Province of Southern Ontario, the Central Metasedimentary Belt boundary thrust zone (CMBbtz) is a crustal-scale tectonic boundary between the older, granulite-facies Central Gneiss Belt to the NW and the younger, amphibolite-facies Central Metasedimentary Belt to the SE. Although there are a range of tectonic models for the CMBbtz, most workers agree it is a major tectonic boundary that accommodated ductile thrusting and crustal shortening during the Ottawan phase of the Grenville Orogeny (~1080-1020 Ma). Some studies suggest that ductile thrusting in the CMBbtz was roughly synchronous with synorogenic extensional collapse below an orogenic lid. Previous geochronological studies also provide evidence of earlier deformation and/or metamorphic events in the CMBbtz, although the relation between deformation in the CMBbtz to the Elzeviran (~1230 Ma) and Shawinigan (~1180 Ma) orogenies is unclear. Our study is the first to report in situ electron microprobe monazite (mnz) dates from amphibolite-grade ortho- and para-gneisses of the CMBbtz. Our results are broadly consistent with other chronometers. We present dates from 132 age-domains within 83 mnz grains in 14 samples. Although our data provide strong evidence for deformation and metamorphism along the length of the CMBbtz during the Ottawan (1080-1020 Ma), we also report two other clusters of ages: 1140-1110 Ma and 1230-1170 Ma. The latter cluster falls between the widely accepted ranges for the Elzeviran and Shawinigan orogenies. In addition, some individual outcrops, particularly those in Killaloe and Minden, show mnz ages spanning over 200 m.y., and the setting and compositions of individual monazite domains allow us to link mnz growth to episodes of garnet growth during multiple events. Together these data indicate an unexpectedly continuous and long-lived period of deformation and metamorphism in the CMBbtz.

  17. Overpotential-induced lability of the electronic overlap factor in long-range electrochemical electron transfer: charge and distance dependence

    DEFF Research Database (Denmark)

    Kornyshev, A. A.; Kuznetsov, A. M.; Nielsen, Jens Ulrik

    2000-01-01

    Long-distance electrochemical electron transfer exhibits approximately exponential dependence on the electron transfer distance. On the basis of a jellium model of the metal surface we show that the slope of the logarithm of the current vs. the transfer distance also depends strongly...... on the electrode charge. The slope is smaller the more negative the charge density due to enhanced extension of the surface electronic density profile on the solution side, and thereby better electronic overlap with the reacting molecule. The effect is sensitive to the bulk electron density of the metal...... and the localization of the electronic state at the molecular reactant site. Effects similar to these have been observed experimentally and could be common for electronically light metals....

  18. Tyrosine oxidation in heme oxygenase: examination of long-range proton-coupled electron transfer.

    Science.gov (United States)

    Smirnov, Valeriy V; Roth, Justine P

    2014-10-01

    Heme oxygenase is responsible for the degradation of a histidine-ligated ferric protoporphyrin IX (Por) to biliverdin, CO, and the free ferrous ion. Described here are studies of tyrosyl radical formation reactions that occur after oxidizing Fe(III)(Por) to Fe(IV)=O(Por(·+)) in human heme oxygenase isoform-1 (hHO-1) and the structurally homologous protein from Corynebacterium diphtheriae (cdHO). Site-directed mutagenesis on hHO-1 probes the reduction of Fe(IV)=O(Por(·+)) by tyrosine residues within 11 Å of the prosthetic group. In hHO-1, Y58· is implicated as the most likely site of oxidation, based on the pH and pD dependent kinetics. The absence of solvent deuterium isotope effects in basic solutions of hHO-1 and cdHO contrasts with the behavior of these proteins in the acidic solution, suggesting that long-range proton-coupled electron transfer predominates over electron transfer.

  19. Ceramic Translations. Volume 41. Grain Boundaries and Interfacial Phenomena in Electronic Ceramics

    Science.gov (United States)

    1994-01-01

    10. J.P. Coutures, P. Odier and C. Proust , "Barium Titanate Formation by Organic Resins Formed with Mixed Citrate", J. Mater. Sci., 27 [7] 1849-56...Technology," Chapter 8 in Electronic Ceramics. Editor L M. Levinson, Marcel Dekker, New York, 1988. Hodgkins, C. E., "Delaminations in Multilayer Ceramic...Processing and Applications) 2nd Edition, Editor: R. C. Buchanan, Marcel and Dekker, New York, 1990. Table 1. PSID of the buoifrn nowders tsed In make the

  20. Statistical study of the location and size of the electron edge of the Low-Latitude Boundary Layer as observed by Cluster at mid-altitudes

    Directory of Open Access Journals (Sweden)

    Y. V. Bogdanova

    2006-10-01

    Full Text Available The nature of particle precipitations at dayside mid-altitudes can be interpreted in terms of the evolution of reconnected field lines. Due to the difference between electron and ion parallel velocities, two distinct boundary layers should be observed at mid-altitudes between the boundary between open and closed field lines and the injections in the cusp proper. At lowest latitudes, the electron-dominated boundary layer, named the "electron edge" of the Low-Latitude Boundary Layer (LLBL, contains soft-magnetosheath electrons but only high-energy ions of plasma sheet origin. A second layer, the LLBL proper, is a mixture of both ions and electrons with characteristic magnetosheath energies. The Cluster spacecraft frequently observe these two boundary layers. We present an illustrative example of a Cluster mid-altitude cusp crossing with an extended electron edge of the LLBL. This electron edge contains 10–200 eV, low-density, isotropic electrons, presumably originating from the solar wind halo population. These are occasionally observed with bursts of parallel and/or anti-parallel-directed electron beams with higher fluxes, which are possibly accelerated near the magnetopause X-line. We then use 3 years of data from mid-altitude cusp crossings (327 events to carry out a statistical study of the location and size of the electron edge of the LLBL. We find that the equatorward boundary of the LLBL electron edge is observed at 10:00–17:00 magnetic local time (MLT and is located typically between 68° and 80° invariant latitude (ILAT. The location of the electron edge shows a weak, but significant, dependence on some of the external parameters (solar wind pressure, and IMF BZ- component, in agreement with expectations from previous studies of the cusp location. The latitudinal extent of the electron edge has been estimated using new multi-spacecraft techniques. The Cluster tetrahedron crosses the electron and ion boundaries of the LLBL/cusp with

  1. Statistical study of the location and size of the electron edge of the Low-Latitude Boundary Layer as observed by Cluster at mid-altitudes

    Directory of Open Access Journals (Sweden)

    Y. V. Bogdanova

    2006-10-01

    Full Text Available The nature of particle precipitations at dayside mid-altitudes can be interpreted in terms of the evolution of reconnected field lines. Due to the difference between electron and ion parallel velocities, two distinct boundary layers should be observed at mid-altitudes between the boundary between open and closed field lines and the injections in the cusp proper. At lowest latitudes, the electron-dominated boundary layer, named the "electron edge" of the Low-Latitude Boundary Layer (LLBL, contains soft-magnetosheath electrons but only high-energy ions of plasma sheet origin. A second layer, the LLBL proper, is a mixture of both ions and electrons with characteristic magnetosheath energies. The Cluster spacecraft frequently observe these two boundary layers. We present an illustrative example of a Cluster mid-altitude cusp crossing with an extended electron edge of the LLBL. This electron edge contains 10–200 eV, low-density, isotropic electrons, presumably originating from the solar wind halo population. These are occasionally observed with bursts of parallel and/or anti-parallel-directed electron beams with higher fluxes, which are possibly accelerated near the magnetopause X-line. We then use 3 years of data from mid-altitude cusp crossings (327 events to carry out a statistical study of the location and size of the electron edge of the LLBL. We find that the equatorward boundary of the LLBL electron edge is observed at 10:00–17:00 magnetic local time (MLT and is located typically between 68° and 80° invariant latitude (ILAT. The location of the electron edge shows a weak, but significant, dependence on some of the external parameters (solar wind pressure, and IMF BZ- component, in agreement with expectations from previous studies of the cusp location. The latitudinal extent of the electron edge has been estimated using new multi-spacecraft techniques. The Cluster tetrahedron crosses the electron and ion boundaries of

  2. [The data on helminth infestation of the Siberian tree frog (Rana amurensis Boulenger, 1886) in the western boundary of the range].

    Science.gov (United States)

    Zhigileva, O N; Kirina, I Iu

    2014-01-01

    Helminth species composition and infection rates of the Siberian tree frog Rana amurensis in Western Siberia were studied. Four species of helminthes--nematodes Rhabdias bufonis, Oswaldocruzia filiformis, Cosmocerca ornata and the trematode Haplometra cylindracea were found. Prevalence of helminths in the Siberian tree frog is 100%, and mean abundance is 27.5 +/- 4.8. Helminth species richness in the Siberian tree frog in the western periphery of their distribution area is lower than in the center of the range, in Yakutia and Transbaikalia, and is approximately equal to that in the northeastern boundary of the range, in Magadan Province. R. bufonis, a highly pathogenic nematode species, dominates in prevalence and abundance in the Siberian tree frog in Western Siberia as well as in other parts of the geographical range of this species.

  3. Grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1991-01-01

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990--February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: Study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  4. Grain boundaries

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990 to February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  5. Jointed magnetic skyrmion lattices at a small-angle grain boundary directly visualized by advanced electron microscopy.

    Science.gov (United States)

    Matsumoto, Takao; So, Yeong-Gi; Kohno, Yuji; Sawada, Hidetaka; Ishikawa, Ryo; Ikuhara, Yuichi; Shibata, Naoya

    2016-10-24

    The interactions between magnetic skyrmions and structural defects, such as edges, dislocations, and grain boundaries (GBs), which are all considered as topological defects, will be important issues when magnetic skyrmions are utilized for future memory device applications. To investigate such interactions, simultaneous visualization of magnetic skyrmions and structural defects at high spatial resolution, which is not feasible by conventional techniques, is essential. Here, taking advantages of aberration-corrected differential phase-contrast scanning transmission electron microscopy, we investigate the interaction of magnetic skyrmions with a small-angle GB in a thin film of FeGe 1-x Si x . We found that the magnetic skyrmions and the small-angle GB can coexist each other, but a domain boundary (DB) was formed in the skyrmion lattice along the small-angle GB. At the core of the DB, unexpectedly deformed magnetic skrymions, which appear to be created by joining two portions of magnetic skyrmions in the adjacent lattices, were formed to effectively compensate misorientations between the two adjacent magnetic skyrmion lattices. These observations strongly suggest the flexible nature of individual magnetic skyrmions, and also the significance of defect engineering for future device applications.

  6. Improved Models and Tools for Prediction of Radiation Effects on Space Electronics in Wide Temperature Range Project

    Data.gov (United States)

    National Aeronautics and Space Administration — All NASA exploration systems operate in the extreme environments of space and require reliable electronics capable of handling a wide temperature range (-180:C to...

  7. High resolution electron microscopy studies of twin boundary structures in B19{prime} martensite in the Ti-Ni shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, M.; Itai, I.; Ohgi, H.; Chiba, A. [Kumamoto Univ. (Japan). Dept. of Materials Science and Resource Engineering; Yamauchi, K. [Tokin Corp., Sendai (Japan). Materials Science and Development Lab.

    1995-03-01

    The boundary structure of the <011> Type II, {l_brace}11{bar 1}{r_brace} Type I, {l_brace}011{r_brace} Type I, (100) compound and (001) compound twins in the B19{prime} martensite in the Ti-Ni shape memory alloy was observed in the edge-on state by high resolution electron microscopy (HREM). The lattice images of the Type I and the compound twins exhibit the well-defined crystallographic features of those boundaries. Lattice image of the <011> Type II twin taken from the unique {eta}{sub 1} axis suggests that neither ledge nor step structures are present at the irrational boundary.

  8. Assessment of oscillator strengths with multiconfigurational short-range density functional theory for electronic excitations in organic molecules

    DEFF Research Database (Denmark)

    Hedegård, Erik Donovan

    2017-01-01

    considered the large collection of organic molecules whose excited states were investigated with a range of electronic structure methods by Thiel et al. As a by-product of our calculations of oscillator strengths, we also obtain electronic excitation energies, which enable us to compare the performance......We have in a series of recent papers investigated electronic excited states with a hybrid between a complete active space self-consistent field (CASSCF) wave function and density functional theory (DFT). This method has been dubbed the CAS short-range DFT method (CAS–srDFT). The previous papers...

  9. Phase Boundary Propagation in Li-Alloying Battery Electrodes Revealed by Liquid-Cell Transmission Electron Microscopy.

    Science.gov (United States)

    Leenheer, Andrew J; Jungjohann, Katherine L; Zavadil, Kevin R; Harris, Charles T

    2016-06-28

    Battery cycle life is directly influenced by the microstructural changes occurring in the electrodes during charge and discharge cycles. Here, we image in situ the nanoscale phase evolution in negative electrode materials for Li-ion batteries using a fully enclosed liquid cell in a transmission electron microscope (TEM) to reveal early degradation that is not evident in the charge-discharge curves. To compare the electrochemical phase transformation behavior between three model materials, thin films of amorphous Si, crystalline Al, and crystalline Au were lithiated and delithiated at controlled rates while immersed in a commercial liquid electrolyte. This method allowed for the direct observation of lithiation mechanisms in nanoscale negative electrodes, revealing that a simplistic model of a surface-to-interior lithiation front is insufficient. For the crystalline films, a lithiation front spread laterally from a few initial nucleation points, with continued grain nucleation along the growing interface. The intermediate lithiated phases were identified using electron diffraction, and high-resolution postmortem imaging revealed the details of the final microstructure. Our results show that electrochemically induced solid-solid phase transformations can lead to highly concentrated stresses at the laterally propagating phase boundary which should be considered for future designs of nanostructured electrodes for Li-ion batteries.

  10. "Feathered" fractal surfaces to minimize secondary electron emission for a wide range of incident angles

    Science.gov (United States)

    Swanson, Charles; Kaganovich, Igor D.

    2017-07-01

    Complex structures on a material surface can significantly reduce the total secondary electron emission from that surface. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at one point of the structure and intersecting another. We performed Monte Carlo calculations to demonstrate that fractal surfaces can reduce net secondary electron emission produced by the surface as compared to the flat surface. Specifically, we describe one surface, a "feathered" surface, which reduces the secondary electron emission yield more effectively than other previously considered configurations. Specifically, feathers grown onto a surface suppress secondary electron emission from shallow angles of incidence more effectively than velvet. We find that, for the surface simulated, secondary electron emission yield remains below 20% of its un-suppressed value, even for shallow incident angles, where the velvet-only surface gives reduction factor of only 50%.

  11. Medium-Range Order in Amorphous Silicon Measured by Fluctuation Electron Microscopy: Final Report, 23 June 1999--23 August 2002

    Energy Technology Data Exchange (ETDEWEB)

    Voyles, P. M.; Abelson, J. R.

    2003-10-01

    Despite occasional experimental hints, medium-range structural order in covalently bonded amorphous semiconductors had largely escaped detection until the advent of fluctuation electron microscopy (FEM) in 1996. Using FEM, we find that every sample of amorphous silicon and germanium we have investigated, regardless of deposition method or hydrogen content, is rich in medium-range order. The paracrystalline structural model, which consists of small, topologically ordered grains in an amorphous matrix, is consistent with the FEM data; but due to strain effects, materials with a paracrystalline structure appear to be amorphous in diffraction measurements. We present measurements on hydrogenated amorphous silicon deposited by different methods, some of which are reported to have greater stability against the Staebler-Wronski effect. FEM reveals that the matrix material of these samples is relatively similar, but the order changes in different ways upon both light soaking and thermal annealing. Some materials are inhomogeneous, with either nanocrystalline inclusions or large area-to-area variation in the medium-range order. We cite recent calculations that electronic states in the conduction band tail are preferentially located around the boundaries of the nm-scale paracrystalline regions that we have identified. This is new evidence in support of spatially inhomogeneous conduction mechanisms in a-Si. The key discovery in our work is that all samples of amorphous silicon must be described as having nm-scale topological crystalline order. This strongly modifies the long-standing model of a covalent random network. Our new understanding of medium-range order must be considered in all future models of electronic properties and the Staebler-Wronski effect.

  12. Improved superconducting hot-electron bolometer devices for the THz range

    NARCIS (Netherlands)

    Klapwijk, T.M.; Barends, R.; Gao, J.R.; Hajenius, M.; Baselmans, J.J.A.

    2004-01-01

    Improved and reproducible heterodyne mixing (noise temperatures of 950 K at 2.5 THz) has been realized with NbN based hot-electron superconducting devices with low contact resistances. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature,

  13. Enzymatic cellulose oxidation is linked to lignin by long-range electron transfer

    DEFF Research Database (Denmark)

    Westereng, Bjorge; Cannella, David; Wittrup Agger, Jane

    2015-01-01

    Enzymatic oxidation of cell wall polysaccharides by lytic polysaccharide monooxygenases (LPMOs) plays a pivotal role in the degradation of plant biomass. While experiments have shown that LPMOs are copper dependent enzymes requiring an electron donor, the mechanism and origin of the electron supp...

  14. Long-range interactions and the sign of natural amplitudes in two-electron systems

    NARCIS (Netherlands)

    Giesbertz, K.J.H.; Van Leeuwen, R.

    In singlet two-electron systems, the natural occupation numbers of the one-particle reduced density matrix are given as squares of the natural amplitudes which are defined as the expansion coefficients of the two-electron wave function in a natural orbital basis. In this work, we relate the sign of

  15. Effects of long-range disorder and electronic interactions on the optical properties of graphene quantum dots

    Science.gov (United States)

    Altıntaş, A.; ćakmak, K. E.; Güçlü, A. D.

    2017-01-01

    We theoretically investigate the effects of long-range disorder and electron-electron interactions on the optical properties of hexagonal armchair graphene quantum dots consisting of up to 10 806 atoms. The numerical calculations are performed using a combination of tight-binding, mean-field Hubbard, and configuration interaction methods. Imperfections in the graphene quantum dots are modeled as a long-range random potential landscape, giving rise to electron-hole puddles. We show that, when the electron-hole puddles are present, the tight-binding method gives a poor description of the low-energy absorption spectra compared to mean-field and configuration interaction calculation results. As the size of the graphene quantum dot is increased, the universal optical conductivity limit can be observed in the absorption spectrum. When disorder is present, the calculated absorption spectrum approaches the experimental results for isolated monolayers of graphene sheets.

  16. Grain boundaries: Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1988-02-01

    Quantitative measurements of grain boundary structure factors using x-ray diffraction have been performed on low angle (001) twist boundaries in gold. Also, a computer atomistic simulation program is being implemented to examine the equilibrium properties of a series of boundaries in gold. Simulation of boundaries at room temperature have been performed. Electron microscopy of grain boundary melting in aluminum was also performed. Results indicated an absence of melting. (CBS)

  17. Dynamic response of a two-dimensional electron gas: Effect of short-range correlations in the ladder approximation

    Science.gov (United States)

    Takayanagi, K.; Lipparini, E.

    1996-09-01

    The Dyson equation for the particle-hole Green's function, including exchange matrix elements, has been solved exactly for the effective interaction between two electrons in a two-dimensional electron gas. The effective interaction is obtained numerically by solving the Bethe-Goldstone integral equation in a two-dimensional electron gas. The effect of short-range correlations on static and dynamic dielectric functions is studied. Results are compared with the normal random-phase approximation, local-field theories, and recent quantum Monte Carlo results.

  18. Role of ligand substitution on long-range electron transfer in azurins

    DEFF Research Database (Denmark)

    Farver, O; Jeuken, L J; Canters, G W

    2000-01-01

    Azurin contains two potential redox sites, a copper centre and, at the opposite end of the molecule, a cystine disulfide (RSSR). Intramolecular electron transfer between a pulse radiolytically produced RSSR- radical anion and the blue Cu(II) ion was studied in a series of azurins in which single......-site mutations were introduced into the copper ligand sphere. In the Met121His mutant, the rate constant for intramolecular electron transfer is half that of the corresponding wild-type azurin. In the His46Gly and His117Gly mutants, a water molecule is co-ordinated to the copper ion when no external ligands...... are added. Both these mutants also exhibit slower intramolecular electron transfer than the corresponding wild-type azurin. However, for the His117Gly mutant in the presence of excess imidazole, an azurin-imidazole complex is formed and the intramolecular electron-transfer rate increases considerably...

  19. Electronic Properties of Grain Boundaries in GaAs: A Study of Oriented Bicrystals Prepared by Epitaxial Lateral Overgrowth.

    Science.gov (United States)

    1984-05-10

    adequately described by arrays of dislocations, termed grain boundary dislocations ( GBDs ), formed in the crystallographic lattice appropriate for the...In this limit the structure can no longer be assumed to be based on discrete GBDs and it becomes necessary to adopt other formalisms to describe the...unique "crystallography" associated with a grain boundary.(7 9) In contrast to the limited applicability of the GBD model, this grain boundary

  20. Long-range coupling of electron-hole pairs in spatially separated organic donor-acceptor layers

    Science.gov (United States)

    Nakanotani, Hajime; Furukawa, Taro; Morimoto, Kei; Adachi, Chihaya

    2016-01-01

    Understanding exciton behavior in organic semiconductor molecules is crucial for the development of organic semiconductor-based excitonic devices such as organic light-emitting diodes and organic solar cells, and the tightly bound electron-hole pair forming an exciton is normally assumed to be localized on an organic semiconducting molecule. We report the observation of long-range coupling of electron-hole pairs in spatially separated electron-donating and electron-accepting molecules across a 10-nanometers-thick spacer layer. We found that the exciton energy can be tuned over 100 megaelectron volts and the fraction of delayed fluorescence can be increased by adjusting the spacer-layer thickness. Furthermore, increasing the spacer-layer thickness produced an organic light-emitting diode with an electroluminescence efficiency nearly eight times higher than that of a device without a spacer layer. Our results demonstrate the first example of a long-range coupled charge-transfer state between electron-donating and electron-accepting molecules in a working device. PMID:26933691

  1. Thermoluminescence response of sodalime glass irradiated with photon and electron beams in the 1-20 Gy range

    Energy Technology Data Exchange (ETDEWEB)

    Bartolotta, A., E-mail: antonio.bartolotta@unipa.it [Dipartimento Farmacochimico, Tossicologico e Biologico, via Archirafi 32, 90123 Palermo (Italy); Brai, M. [Dipartimento di Fisica e Tecnologie Relative, Universita di Palermo, Viale delle Scienze, Ed. 18, 90128 Palermo (Italy); Gruppo V, INFN, Sezione di Catania, Catania (Italy); Caputo, V. [Unita Operativa Complessa Fisica Sanitaria, ARNAS, Palermo (Italy); D' Oca, M.C. [Dipartimento Farmacochimico, Tossicologico e Biologico, via Archirafi 32, 90123 Palermo (Italy); Longo, A.; Marrale, M. [Dipartimento di Fisica e Tecnologie Relative, Universita di Palermo, Viale delle Scienze, Ed. 18, 90128 Palermo (Italy); Gruppo V, INFN, Sezione di Catania, Catania (Italy)

    2011-09-15

    The thermoluminescence response of a watch commercial glass was studied after irradiation with photons and electrons, in the range 1-20 Gy, of interest in accidental dosimetry; a linear response was obtained with both beams. This result, together with the satisfactory time stability of the thermoluminescence signal, indicates this glass as a potential material for retrospective dosimetry applications.

  2. A measurement of auroral electrons in the 1–10 MeV range

    NARCIS (Netherlands)

    Gils, J.N. van; Beek, H.F. van; Fetter, L.D. de; Hendrickx, R.V.

    Particle fluxes have been measured by means of shielded Geiger-Müller telescopes mounted m a rocket, which was launched from ESRANGE(Kiruna) into a diffuse aurora. The analysis of the dependence of the counting rates on altitude indicates that a weak flux of energetic electrons, 1–10 MeV, has been

  3. Single-molecule Mapping of Long-range Electron Transfer for a Cytochrome b562 Variant

    DEFF Research Database (Denmark)

    Della Pia, Eduardo Antonio; Chi, Qijin; Jones, D. Dafydd

    2011-01-01

    Cytochrome b562 was engineered to introduce a cysteine residue at a surface-exposed position to facilitate direct self-assembly on a Au(111) surface. The confined protein exhibited reversible and fast electron exchange with a gold substrate over a distance of 20 Å between the heme redox center an...

  4. Unconventional superconductivity in two-dimensional electron systems with long-range correlations

    Energy Technology Data Exchange (ETDEWEB)

    Clark, J.W.; Khodel, V.A.; Zverev, M.V.; Yakovenko, V.M

    2004-03-01

    We explore salient features of high-T{sub c} superconductivity in two-dimensional electron liquid, that are triggered by critical fluctuations enhanced in the vicinity of an impending second order phase transition. A simple theoretical explanation for the transition from d-wave to another type of superconducting pairing that has recently observed in the electron-doped cuprates is offered. The d{sub x{sup 2}}{sub -y{sup 2}} pairing potential {delta}, which has maximal magnitude at the hot spots on the Fermi surface, becomes suppressed under increase of electron doping, because the hot spots approach the Brillouin zone diagonals where the respective gap value vanishes, and pairing with d{sub x{sup 2}}{sub -y{sup 2}} symmetry is then replaced by either singlet s-wave or triplet p-wave pairing. We argue in favor of p-wave pairing and propose experiments to verify this assertion. The phenomenon of flattening of electron spectra in high-T{sub c} superconductors is discussed. We suggest that this phenomenon can be explained on the basis of the Fermi liquid approach, involving unconventional solutions emerging beyond the point where stability conditions for the traditional Landau state are violated. The problem of pairing in anisotropic electron systems possessing patches of fermion condensate in the vicinity of the van Hove points is analyzed. Attention is directed to opportunities for the occurrence of non-BCS pairing correlations between the states belonging to the fermion condensate. It is shown that the physical emergence of such pairing correlations would drastically alter the behavior of the single-particle Green function, the canonical pole of Fermi-liquid theory being replaced by a branch point.

  5. Electron-phonon interaction and thermal boundary resistance at the crystal-amorphous interface of the phase change compound GeTe

    Energy Technology Data Exchange (ETDEWEB)

    Campi, Davide; Bernasconi, Marco, E-mail: marco.bernasconi@mater.unimib.it [Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi 55, I-20125, Milano (Italy); Donadio, Davide [Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany); Sosso, Gabriele C. [Computational Science, Department of Chemistry and Applied Biosciences, ETH Zurich, USI Campus, via Giuseppe Buffi 13, CH-6900 Lugano (Switzerland); Behler, Jörg [Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Universitätsstrasse 150, D-44780 Bochum (Germany)

    2015-01-07

    Phonon dispersion relations and electron-phonon coupling of hole-doped trigonal GeTe have been computed by density functional perturbation theory. This compound is a prototypical phase change material of interest for applications in phase change non-volatile memories. The calculations allowed us to estimate the electron-phonon contribution to the thermal boundary resistance at the interface between the crystalline and amorphous phases present in the device. The lattice contribution to the thermal boundary resistance has been computed by non-equilibrium molecular dynamics simulations with an interatomic potential based on a neural network scheme. We find that the electron-phonon term contributes to the thermal boundary resistance to an extent which is strongly dependent on the concentration and mobility of the holes. Further, for measured values of the holes concentration and electrical conductivity, the electron-phonon term is larger than the contribution from the lattice. It is also shown that the presence of Ge vacancies, responsible for the p-type degenerate character of the semiconductor, strongly affects the lattice thermal conductivity of the crystal.

  6. Electron-phonon interaction and thermal boundary resistance at the crystal-amorphous interface of the phase change compound GeTe

    Science.gov (United States)

    Campi, Davide; Donadio, Davide; Sosso, Gabriele C.; Behler, Jörg; Bernasconi, Marco

    2015-01-01

    Phonon dispersion relations and electron-phonon coupling of hole-doped trigonal GeTe have been computed by density functional perturbation theory. This compound is a prototypical phase change material of interest for applications in phase change non-volatile memories. The calculations allowed us to estimate the electron-phonon contribution to the thermal boundary resistance at the interface between the crystalline and amorphous phases present in the device. The lattice contribution to the thermal boundary resistance has been computed by non-equilibrium molecular dynamics simulations with an interatomic potential based on a neural network scheme. We find that the electron-phonon term contributes to the thermal boundary resistance to an extent which is strongly dependent on the concentration and mobility of the holes. Further, for measured values of the holes concentration and electrical conductivity, the electron-phonon term is larger than the contribution from the lattice. It is also shown that the presence of Ge vacancies, responsible for the p-type degenerate character of the semiconductor, strongly affects the lattice thermal conductivity of the crystal.

  7. Wide Temperature Range DC-DC Boost Converters for Command/Control/Drive Electronics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We shall develop wide temperature range DC-DC boost converters that can be fabricated using commercial CMOS foundries. The boost converters will increase the low...

  8. Parametric decay instability of an obliquely propagating ordinary wave in the electron cyclotron frequency range

    Science.gov (United States)

    Gusakov, E. Z.; Popov, A. Yu.

    2018-01-01

    The possibility of the low-power-threshold parametric decay of an obliquely propagating ordinary wave to an upper hybrid wave and a low-hybrid wave is analysed under conditions of nonmonotonic plasma density profile in a magnetic trap. The instability threshold and growth rate are derived explicitly. The analytical results are illustrated under the conditions typical of the ordinary mode fundamental electron cyclotron resonance heating harmonic experiments at the FTU tokamak.

  9. Testing and Comparison of Imaging Detectors for Electrons in the Energy Range 10–20 keV

    Science.gov (United States)

    Matheson, J.; Moldovan, G.; Kirkland, A.; Allinson, N.; Abrahams, J. P.

    2017-11-01

    Interest in direct detectors for low-energy electrons has increased markedly in recent years. Detection of electrons in the energy range up to low tens of keV is important in techniques such as photoelectron emission microscopy (PEEM) and electron backscatter diffraction (EBSD) on scanning electron microscopes (SEMs). The PEEM technique is used both in the laboratory and on synchrotron light sources worldwide. The ubiquity of SEMs means that there is a very large market for EBSD detectors for materials studies. Currently, the most widely used detectors in these applications are based on indirect detection of incident electrons. Examples include scintillators or microchannel plates (MCPs), coupled to CCD cameras. Such approaches result in blurring in scintillators/phosphors, distortions in optical systems, and inefficiencies due the limited active area of MCPs. In principle, these difficulties can be overcome using direct detection in a semiconductor device. Growing out of a feasibility study into the use of a direct detector for use on an XPEEM, we have built at Rutherford Appleton Laboratory a system to illuminate detectors with an electron beam of energy up to 20 keV . We describe this system in detail. It has been used to measure the performance of a custom back-thinned monolithic active pixel sensor (MAPS), a detector based on the Medipix2 chip, and a commercial detector based on MCPs. We present a selection of the results from these measurements and compare and contrast different detector types.

  10. Electron probe microanalysis (EPMA) measurement of thin-film thickness in the nanometre range.

    Science.gov (United States)

    Procop, M; Radtke, M; Krumrey, M; Hasche, K; Schädlich, S; Frank, W

    2002-10-01

    The thickness of thin films of platinum and nickel on fused silica and silicon substrates has been determined by EPMA using the commercial software STRATAGEM for calculation of film thickness. Film thickness ranged in the order 10 nm. An attempt was made to estimate the confidence range of the method by comparison with results from other methods of analysis. The data show that in addition to the uncertainty of the spectral intensity measurement and the complicated fitting routine, systematic deviation caused by the underlying model should be added. The scattering in the results from other methods does not enable specification of a range of uncertainty, but deviations from the real thickness are estimated to be less than 20%.

  11. Crop and field boundary influences on the activity of a wide range of beneficial invertebrate groups on a split conventional/organic farm in northern England.

    Science.gov (United States)

    Eyre, M D; Leifert, C

    2011-04-01

    Activity of 12 beneficial invertebrate groups was assessed in 2005 and 2006 on a farm in northern England split into conventional and organic management halves, using pitfall and pan traps set in both crops and field boundaries. Management, crop and boundary structure influences on invertebrate activity were assessed, as was the relationship between crop and boundary type. Classification of crop and boundary assemblages produced three and two groups, respectively, in both years. Organic arable crops had well-defined assemblages in both years; and, while grass and grass/clover fields were separated from conventional arable fields in 2005, there was mixing in 2006. One boundary group, in both years, was dominated by conventional arable fields with tall herbaceous boundary vegetation. The other group had more organic arable and grassy fields with shorter boundary vegetation. Redundancy analyses showed that a number of groups (Cantharidae, Coccinellidae, Syrphidae, Ichneumonidae, Braconidae, Proctotrupoidea, Lycosidae) were more active in organic arable fields with more Staphylinidae in conventional arable crops and no obvious trend with Carabidae, Hemiptera, Neuroptera and Linyphiidae. Activity of some groups, especially Coccinellidae, Syrphidae and parasitic wasps, was strongly related to weed cover. Staphylinidae were most active in tall herbaceous boundaries by conventional arable crops with more of a number of groups (Cantharidae, Coccinellidae, parasitic wasps) in short herbaceous boundaries by organic arable crops. Organic management produced most differences in aerially-dispersed invertebrates, and management had a profound effect on activity in field boundaries. Possible management prescriptions to increase invertebrate activity include changing sowing times, weed cover manipulation and field boundary and margin management.

  12. Solid-state pulsed microwave bridge for electron spin echo spectrometers of 8-mm wavelength range

    Directory of Open Access Journals (Sweden)

    Kalabukhova E. N.

    2012-12-01

    Full Text Available The article presents a construction of a coherent pulsed microwave bridge with an output power up to 10 Wt with a time resolution of 10–8 seconds at a pulse repetition rate of 1 kHz designed for electron spin echo spectrometers. The bridge is built on a homodyne scheme based on IMPATT diodes, which are used for modulation and amplification of microwave power coming from the reference Gunn diode oscillator. The advantages of the bridge are optimal power and minimum pulse width, simple operation, low cost.

  13. Geochemical evidences for palaeoclimatic fluctuations at the Triassic-Jurassic boundary: southwestern margin of the Neotethys in the Salt Range, Pakistan

    Science.gov (United States)

    Iqbal, Shahid; Wagreich, Michael; Jan, Irfanullah; Kürschner, Wolfram Michael; Gier, Susanne

    2017-04-01

    The Triassic-Jurassic boundary interval reveals a change from warm-arid to a warm and humid climate in the Tethyan domain. Sea-level reconstruction records across the European basins during this interval reveal an end-Triassic global regression event and is linked to the Central Atlantic Magmatic Province (CAMP) activity and Pangaea breakup. In the Tethyan Salt Range of Pakistan a succession of Upper Triassic dolomites/green-black mudstones (Kingriali Formation), overlying quartzose sandstone, mudstones, laterites and Lower Jurassic conglomerates/pebbly sandstones (Datta Formation) provides information on the palaeoclimatic evolution of the area. Preliminary palynological results from the mudstones indicate a Rhaetian age for the Kingriali Formation and a Hettangian age for the Datta Formation. X-ray diffraction (XRD) analysis of the mudstones (upper part of the Kingriali Formation) indicates the presence of mainly illite while kaolinite is a minor component. The kaolinite content, a reflection of the advanced stage of chemical weathering and hence warm-humid conditions, increases up-section in the overlying sandstone-mudstone succession. The overlying laterite-bauxite horizons lack illite/smectite and are entirely composed of kaolinite, boehmite and haematite. At places these kaolinite rich horizons are mined in the area (Western Salt Range). The bulk rock geochemistry of the succession confirms a similar trend. The Chemical Index of Alteration (CIA) displays an increasing trend from the Upper Triassic shales (CIA 75-80) through the overlying sandstones/mudstones-laterites to the overlying quartz rich sandstones and mudstones (CIA 90-97). The overall results for the succession reveal an increasing chemical maturity trend (increase in the intensity of chemical weathering) from Rhaetian to Hettangian thereby supporting a change from warm-arid to a warm-humid palaeoclimate, probably extreme greenhouse conditions.

  14. Characterisation of a detector based on microchannel plates for electrons in the energy range 10 20 keV

    Science.gov (United States)

    Moldovan, G.; Matheson, J.; Derbyshire, G.; Kirkland, A.

    2008-11-01

    As part of a feasibility study into the use of novel electron detectors for an X-ray photoelectron emission microscope (XPEEM), we have characterised a detector based on microchannel plates (MCPs), a phosphor screen and a CCD camera. For XPEEM, an imaging detector is required for electrons in the energy range 10-20 keV. This type of detector is a standard fitment on commercial instruments and we have studied its performance in some detail in order to provide a baseline against which to evaluate future detector technologies. We present detective quantum efficiency (DQE), noise power spectrum (NPS) and modulation transfer function (MTF) measurements of a commercial detector, in the energy range of interest, as a function of the detector bias voltage.

  15. Modular Power Electronic Converters in the Power Range 1 to 10 kW

    DEFF Research Database (Denmark)

    Klimczak, Pawel

    Thanks to CO2 emission reduction policies and increasing prices of fossil fuels a significant growth in field of sustainable energy sources (SES) is being observed during last decade. A government support and take-off projects in Europe and US shall ensure an increasing trend in future too. Some...... of SES based plants , like hydro-, geothermal-, biofuel-plants, use synchronous generators directly connected to the grid. But some other SES technologies, like fuel cell or photovoltaic, require a power electronic converter between the energy source and the load or the grid. Work presented...... in this thesis concentrates on dc-dc non-isolated converters suitable for high voltage gain applications, like uninterruptible power supply (UPS) and some of sustainable energy sources. A special attention is on reduction of power losses and efficiency improvements in non-isolated dc-dc step-up converters...

  16. Variable-range electron hopping, conductivity cross-over and space-charge relaxation in C60Br6

    OpenAIRE

    Manesh, Zachariah; Romanini, Michela; Zygouri, Panagiota; Gournis, Dimitrios; Tamarit Mur, José Luis; Barrio Casado, María del; Macovez, Roberto

    2016-01-01

    Dielectric spectroscopy is employed to probe the frequency-dependent conductivity and dipolar dielectric response of solid C60Br6. Below approximately 215 K, charge conduction is electronic and well described by Mott's variable-range polaron hopping model, with effective hopping activation energy Ea varying between 0.12 eV at 125 K and 0.16 eV at 220 K, and most probable hopping range varying between 100 and 125% of the decay length of the localized polaron's wavefunction. Above 215 K a new c...

  17. Determination of Chromium Valence Over the Range Cr(0)-Cr(VI) by Electron Energy Loss Spectroscopy

    Science.gov (United States)

    2006-01-01

    be of Cr (VI): Cr (V) [14,40-45] and Cr (IV) [46]. To fully altered by microbes [11-13], green algae [14], higher plants understand the geochemistry of Cr ... Cr (III) by bacteria [42,44,45] and Further, nearly all mineralized Cr in the terrestrial crust is green algae [14], reacts with diphenylcarbazide to...Determination of chromium valence over the range Cr (O)- Cr (VI) by electron energy loss spectroscopy Tyrone L. Daultona , Brenda J. Littleb ’Marine

  18. Acceleration of Long-Range Photoinduced Electron Transfer through DNA by Hydroxyquinolines as Artificial Base Pairs.

    Science.gov (United States)

    Bätzner, Effi; Liang, Yu; Schweigert, Caroline; Unterreiner, Andreas-Neil; Wagenknecht, Hans-Achim

    2015-06-08

    The C-nucleoside based on the hydroxyquinoline ligand (Hq) is complementary to itself and forms stable Hq-Hq pairs in double-stranded DNA. These artificial Hq-Hq pairs may serve as artificial electron carriers for long-range photoinduced electron transfer in DNA, as elucidated by a combination of gel electrophoretic analysis of irradiated samples and time-resolved transient absorption spectroscopy. For this study, the Hq-Hq pair was combined with a DNA-based donor-acceptor system consisting of 6-N,N-dimethylaminopyrene conjugated to 2'-deoxyuridine as photoinducible electron donor, and methyl viologen attached to the 2'-position of uridine as electron acceptor. The Hq radical anion was identified in the time-resolved measurements and strand cleavage products support its role as an intermediate charge carrier. Hence, the Hq-Hq pair significantly enhances the electron hopping capability of DNA compared to natural DNA bases over long distances while keeping the self-assembly properties as the most attractive feature of DNA as a supramolecular architecture. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Gold nanoparticle assisted assembly of a heme protein for enhancement of long-range interfacial electron transfer

    DEFF Research Database (Denmark)

    Jensen, Palle Skovhus; Chi, Qijin; Grumsen, Flemming Bjerg

    2007-01-01

    -defined stoichiometry. The systems were investigated in homogeneous solution and at liquid/solid interface. Conjugation of cyt c results in a small but consistent broadening of the nanoparticle plasmon band. This phenomenon can be explained in terms of long-range electronic interactions between the gold nanoparticle...... and characterization of water-soluble gold nanoparticles (AuNPs) with core diameter 3-4 nm and their application for the enhancement of long-range interfacial ET of a heme protein. Gold nanoparticles were electrostatically conjugated with cyt c to form nanoparticle-protein hybrid ET systems with well...... and the protein molecule. When the nanoparticle-protein conjugates are assembled on Au(111) surfaces, long-range interfacial ET across a physical distance of over 50 A via the nanoparticle becomes feasible. Moreover, significant enhancement of the interfacial ET rate by more than an order of magnitude compared...

  20. A wide dynamic range BF{sub 3} neutron monitor with front-end electronics based on a logarithmic amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Ferrarini, M., E-mail: michele.ferrarini@polimi.i [Politecnico di Milano, Dipartimento Energia, via G. Ponzio 34/3, I-20133 Milano (Italy); Fondazione CNAO, via Caminadella 16, 20123 Milano (Italy); Varoli, V. [Politecnico di Milano, Dipartimento Energia, via G. Ponzio 34/3, I-20133 Milano (Italy); Favalli, A. [European Commission, Joint Research Centre, Institute for the Protection and Security of Citizen, TP 800, Via E. Fermi, 21027 Ispra (Vatican City State, Holy See) (Italy); Caresana, M. [Politecnico di Milano, Dipartimento Energia, via G. Ponzio 34/3, I-20133 Milano (Italy); Pedersen, B. [European Commission, Joint Research Centre, Institute for the Protection and Security of Citizen, TP 800, Via E. Fermi, 21027 Ispra (Italy)

    2010-02-01

    This paper describes a wide dynamic range neutron monitor based on a BF{sub 3} neutron detector. The detector is used in current mode, and front-end electronics based on a logarithmic amplifier are used in order to have a measurement capability ranging over many orders of magnitude. The system has been calibrated at the Polytechnic of Milan, CESNEF, with an AmBe neutron source, and has been tested in a pulsed field at the PUNITA facility at JRC, Ispra. The detector has achieved a dynamic range of over 6 orders of magnitude, being able to measure single neutron pulses and showing saturation-free response for a reaction rate up to 10{sup 6} s{sup -1}. It has also proved effective in measuring the PUNITA facility pulse integral fluence.

  1. Aromatic amino acids required for pili conductivity and long-range extracellular electron transport in Geobacter sulfurreducens.

    Science.gov (United States)

    Vargas, Madeline; Malvankar, Nikhil S; Tremblay, Pier-Luc; Leang, Ching; Smith, Jessica A; Patel, Pranav; Snoeyenbos-West, Oona; Synoeyenbos-West, Oona; Nevin, Kelly P; Lovley, Derek R

    2013-03-12

    It has been proposed that Geobacter sulfurreducens requires conductive pili for long-range electron transport to Fe(III) oxides and for high-density current production in microbial fuel cells. In order to investigate this further, we constructed a strain of G. sulfurreducens, designated Aro-5, which produced pili with diminished conductivity. This was accomplished by modifying the amino acid sequence of PilA, the structural pilin protein. An alanine was substituted for each of the five aromatic amino acids in the carboxyl terminus of PilA, the region in which G. sulfurreducens PilA differs most significantly from the PilAs of microorganisms incapable of long-range extracellular electron transport. Strain Aro-5 produced pili that were properly decorated with the multiheme c-type cytochrome OmcS, which is essential for Fe(III) oxide reduction. However, pili preparations of the Aro-5 strain had greatly diminished conductivity and Aro-5 cultures were severely limited in their capacity to reduce Fe(III) compared to the control strain. Current production of the Aro-5 strain, with a graphite anode serving as the electron acceptor, was less than 10% of that of the control strain. The conductivity of the Aro-5 biofilms was 10-fold lower than the control strain's. These results demonstrate that the pili of G. sulfurreducens must be conductive in order for the cells to be effective in extracellular long-range electron transport. Extracellular electron transfer by Geobacter species plays an important role in the biogeochemistry of soils and sediments and has a number of bioenergy applications. For example, microbial reduction of Fe(III) oxide is one of the most geochemically significant processes in anaerobic soils, aquatic sediments, and aquifers, and Geobacter organisms are often abundant in such environments. Geobacter sulfurreducens produces the highest current densities of any known pure culture, and close relatives are often the most abundant organisms colonizing anodes

  2. Transmission electron microscopy and electron diffraction study of the short-range ordering structure of alpha-LiFeO2.

    Science.gov (United States)

    Mitome, Masanori; Kohiki, Shigemi; Murakawa, Yusuke; Hori, Kyoko; Kurashima, Keiji; Bando, Yoshio

    2004-12-01

    The basic structure of alpha-LiFeO2, lithium iron oxide, is a cubic NaCl-type structure with a lattice constant of 0.42 nm; some short-range ordering characterized by octahedral clusters exists. The local structure of the short-range ordering was investigated by transmission electron microscopy and electron diffraction. A new short-range ordering structure was found in local areas. The local structure has a cubic lattice with a doubled lattice constant. The occupation factors of cations on Wyckoff sites 4(a) and 4(b) are different from those on 24(d) sites, but the stoichiometric composition in cubic clusters is the same as the macroscopic composition. The number of pairs in which iron cations exist in nearest-neighbor sites and next nearest-neighbor sites is reduced in the structure. This means that a magnetic interaction between the iron cations is reduced by cation ordering even without spin ordering at room temperature.

  3. Size effects and charge transport in metals: Quantum theory of the resistivity of nanometric metallic structures arising from electron scattering by grain boundaries and by rough surfaces

    Science.gov (United States)

    Munoz, Raul C.; Arenas, Claudio

    2017-03-01

    We discuss recent progress regarding size effects and their incidence upon the coefficients describing charge transport (resistivity, magnetoresistance, and Hall effect) induced by electron scattering from disordered grain boundaries and from rough surfaces on metallic nanostructures; we review recent measurements of the magneto transport coefficients that elucidate the electron scattering mechanisms at work. We review as well theoretical developments regarding quantum transport theories that allow calculating the increase in resistivity induced by electron-rough surface scattering (in the absence of grain boundaries) from first principles—from the parameters that describe the surface roughness that can be measured with a Scanning Tunnelling Microscope (STM). We evaluate the predicting power of the quantum version of the Fuchs-Sondheimer theory and of the model proposed by Calecki, abandoning the method of parameter fitting used for decades, but comparing instead theoretical predictions with resistivity measured in thin films where surface roughness has also been measured with a STM, and where electron-grain boundary scattering can be neglected. We also review the theory of Mayadas and Shatzkes (MS) [Phys. Rev. B 1, 1382 (1970)] used for decades, and discuss its severe conceptual difficulties that arise out of the fact that: (i) MS employed plane waves to describe the electronic states within the metal sample having periodic grain boundaries, rather than the Bloch states known since the thirties to be the solutions of the Schrödinger equation describing electrons propagating through a Krönig-Penney [Proc. R. Soc. London Ser. A 130, 499 (1931)] periodic potential; (ii) MS ignored the fact that the wave functions describing electrons propagating through a 1-D disordered potential are expected to decay exponentially with increasing distance, a fact known since the work of Anderson [Phys. Rev. 109, 1492 (1958)] in 1958 for which he was awarded the Nobel Prize in

  4. Effect of Long-Range Coulomb Interaction on NMR Shift in Massless Dirac Electrons of Organic Conductor

    Science.gov (United States)

    Suzumura, Yoshikazu

    2018-02-01

    The nuclear magnetic resonance (NMR) shift, χα, at low temperatures is examined for massless Dirac electrons in the organic conductor, α-(BEDT-TTF)2I3, where α [= A (= A'), B, and C] denotes the sites of the four molecules in the unit cell. The Dirac cone exists within an energy of 0.01 eV between the conduction and valence bands. The magnetic response function is calculated by taking account of the long-range Coulomb interaction and electron doping. Calculating the interaction within the first order in the perturbation, the chemical potential is determined self-consistently, and the self-energy and vertex corrections are taken to satisfy the Ward identity. The site-dependent χα is calculated at low temperatures of 0.0002 χ B. The relevance of the shift to the experiment is discussed.

  5. Coherent diffraction and Cherenkov radiation of relativistic electrons from a dielectric target in the millimeter wavelength range

    Energy Technology Data Exchange (ETDEWEB)

    Bleko, V.V., E-mail: bleko_vitold@mail.ru; Konkov, A.S., E-mail: Ekwinus@tpu.ru; Soboleva, V.V.

    2015-07-15

    The coherent diffraction radiation (DR) and Cherenkov radiation (ChR) emitted by bunched electron beam of 6.1 MeV passing near a flat dielectric target have been observed in the millimeter wavelength range. The simple geometry of experiment allows testing different theoretical approaches, which consider the process of simultaneous emission of DR and ChR from dielectric targets. Properties of the radiation have been experimentally investigated in far-field zone. The angular distribution of the observed radiation at various tilt angles of the target in respect to the electron beam have shown the effect of interference between DR and ChR. The comparison of experimental results with the theoretical calculations based on the approach of polarization currents has been done.

  6. Review of Historic Parishes of England and Wales: An Electronic Map of Boundaries before 1850 with a Gazetteer and Metadata.

    Directory of Open Access Journals (Sweden)

    Thomas Pickles

    2002-11-01

    Full Text Available According to the authors, Historic Parishes of England and Wales aims to provide one possible solution to 'a major lacuna militating against the effective exploitation of many post-medieval to mid-Victorian historical sources collected by local administrative areas.' That is 'the lack of information on the boundaries of those administrative areas: the so-called "historic" or "ancient" parishes of England and Wales.' There is no doubt that this is indeed a problem, and that such information will find a wide potential audience. As they admirably illustrate in the accompanying book, parish boundaries have been some of the most enduring and stable organising units, certainly formed by the thirteenth century and largely unchanged until the nineteenth. However, a series of Victorian parliamentary acts sought to rationalise the parochial pattern, and no national sources exist that record the status quo preceding these changes. Kain and Oliver point to an impressive number of historians of locally compiled sources who would benefit from reliable information on these pre-Victorian boundaries, and their list is by no means exhaustive. The core of the package is a database of 'metadata', intended for use with either Acrobat Reader or Microsoft Excel, which records the character of each administrative unit mapped, and the origins of the evidence for its boundaries. Three CDs contain this database in addition to maps of the 'historic' parish boundaries of England that can be read using Acrobat Reader, with the necessary reader software supplied. A further six CDs contain those same maps saved as three separate interactive layers, to be viewed using Adobe Illustrator but this software is not included.

  7. Total projectile electron loss cross sections of U^{28+} ions in collisions with gaseous targets ranging from hydrogen to krypton

    Directory of Open Access Journals (Sweden)

    G. Weber

    2015-03-01

    Full Text Available Beam lifetimes of stored U^{28+} ions with kinetic energies of 30 and 50  MeV/u, respectively, were measured in the experimental storage ring of the GSI accelerator facility. By using the internal gas target station of the experimental storage ring, it was possible to obtain total projectile electron loss cross sections for collisions with several gaseous targets ranging from hydrogen to krypton from the beam lifetime data. The resulting experimental cross sections are compared to predictions by two theoretical approaches, namely the CTMC method and a combination of the DEPOSIT code and the RICODE program.

  8. Ranges, Reflection and Secondary Electron Emission for keV Hydrogen Ions Incident on Solid N2

    DEFF Research Database (Denmark)

    Børgesen, P.; Sørensen, H.; Hao-Ming, Chen

    1983-01-01

    Ranges were measured for 0.67–3.3 keV/amu hydrogen and deuterium ions in solid N2. Comparisons with similar results for N2-gas confirm the previously observed large phase effect in the stopping cross section. Measurements of the secondary electron emission coefficient for bulk solid N2 bombarded...... by 0.67–9 keV/amu ions also seem to support such a phase effect. It is argued that we may also extract information about the charge state of reflected projectiles....

  9. Progress report on grain boundaries

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    1989-06-01

    The research was focused on the following three major areas: (1) study of the atomic structure of grain boundaries by means of X-ray diffraction, transmission electron microscopy and computer modeling; (2) study of grain boundary phase transitions by electron microscopy and computer modeling; (3) investigation of the mechanism of high angle grain boundary migration. Results are briefly discussed.

  10. Progress report on grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1989-06-01

    The research was focused on the following three major areas: (1) study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; (2) study of grain boundary phase transitions by electron microscopy and computer modeling; (3) investigation of the mechanism of high angle grain boundary migration. Results are briefly discussed. 20 refs.

  11. Observation of ferri-nonmagnetic boundary in CrPt{sub 3} line-and-space patterned media using a dark-field transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Oshima, Daiki [Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Suharyadi, Edi [Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Japan Society for the Promotion of Science (JSPS), Sumitomo-Ichibancho Bldg. 2F, 6 Ichibancho, Chiyoda-ku, Tokyo 102-8471 (Japan); Kato, Takeshi, E-mail: takeshik@nuee.nagoya-u.ac.jp [Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Iwata, Satoshi [Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan)

    2012-04-15

    Ion beam patterned CrPt{sub 3} films were prepared by Kr{sup +} ion irradiation at a dose of 2 Multiplication-Sign 10{sup 14} ions/cm{sup 2} onto L1{sub 2}-ordered CrPt{sub 3} whose surface was partially masked by electron beam patterned resists. Cross-sectional observation using transmission electron microscopy was carried out to study the patterning boundary of the CrPt{sub 3} film. Dark-field imaging showed a distinct contrast between non-irradiated (L1{sub 2} phase) and irradiated (A1 phase) regions. The transition width between the two phases was estimated to be about 5 nm, which agreed well with the value simulated by a transport ion in matter (TRIM) code simulation. - Highlights: Black-Right-Pointing-Pointer Dark field transmission electron microscope observation to study the bit boundary of the ion beam patterned CrPt{sub 3} film. Black-Right-Pointing-Pointer Clear contrast between non-irradiated (L1{sub 2} phase CrPt{sub 3}) and irradiated (A1 phase CrPt{sub 3}) regions in the image. Black-Right-Pointing-Pointer The transition width between the two phases is about 5 nm. Black-Right-Pointing-Pointer The estimated width agrees well with the simulation.

  12. Measurement of cervical range of motion (CROM) by electronic CROM goniometer: a test of reliability and validity.

    Science.gov (United States)

    Law, Ellis Yuk Hung; Chiu, Thomas Tai-Wing

    2013-01-01

    To investigate the reliability and validity of the Electronic Cervical Range of Motion (CROM) Goniometer in measurement of cervical spine mobility in adults with and without neck pain. A cross-sectional reliability study was conducted on 54 subjects (26 neck pain and 26 non-neck pain) aged from 20-70 years old. The Numerical Pain Rating Scale and Chinese version of Northwick Park Neck Pain Questionnaire were used to assess neck pain severity and disability respectively. The CROM was measured in sitting position except left to right rotation was measured in supine lying. All the cervical active movements were measured by using the Electronic CROM Goniometer from ARCON TM Functional Capacity Evaluation (FCE) systems. The intra-tester and inter-tester reliability were high in both normal and chronic neck pain groups with ICC coefficients ranged from 0.75-*0.92. There was significant difference in the total CROM between the normal (374.7°) and chronic neck pain group (292.6°). The ACRON cervical goniometer was found to be reliable for measuring cervical mobility in 3 planes for both normal and patient subjects. Construct validity of the goniometer was supported as the test's result documented significant difference in CROM between the control and the neck pain groups.

  13. Boundary-corrected four-body continuum-intermediate-state method: Single-electron capture from heliumlike atomic systems by fast nuclei

    Science.gov (United States)

    Mančev, Ivan; Milojević, Nenad; Belkić, Dževad

    2015-06-01

    Single charge exchange in collisions between bare projectiles and heliumlike atomic systems at intermediate and high incident energies is examined by using the four-body formalism of the first- and second-order theories. The main purpose of the present study is to investigate the relative importance of the intermediate ionization continua of the captured electron compared to the usual direct path of the single electron transfer from a target to a projectile. In order to achieve this goal, comprehensive comparisons are made between the four-body boundary-corrected continuum-intermediate-states (BCIS-4B) method and the four-body boundary-corrected first Born (CB1-4B) method. The perturbation potential is the same in the CB1-4B and BCIS-4B methods. Both methods satisfy the correct boundary conditions in the entrance and exit channels. However, unlike the CB1-4B method, the second-order BCIS-4B method takes into account the electronic Coulomb continuum-intermediate states in either the entrance or the exit channel depending on whether the post or the prior version of the transition amplitude is used. Hence, by comparing the results from these two theories, the relative importance of the intermediate ionization electronic continua can be assessed within the four-body formalism of scattering theory. The BCIS-4B method predicts the usual second-order effect through double scattering of the captured electron on two nuclei as a quantum-mechanical counterpart of the Thomas classical two-step, billiard-type collision. The physical mechanism for this effect in the BCIS-4B method is also comprised of two steps such that ionization occurs first. This is followed by capture of the electron by the projectile with both processes taking place on the energy shell. Moreover, the role of the second, noncaptured electron in a heliumlike target is revisited. To this end, the BCIS-4B method describes the effect of capture of one electron by the interaction of the projectile nucleus with

  14. Optimal all-optical switching of a microcavity resonance in the telecom range using the electronic Kerr effect.

    Science.gov (United States)

    Yüce, Emre; Ctistis, Georgios; Claudon, Julien; Gérard, Jean-Michel; Vos, Willem L

    2016-01-11

    We have switched GaAs/AlAs and AlGaAs/AlAs planar microcavities that operate in the "Original" (O) telecom band by exploiting the instantaneous electronic Kerr effect. We observe that the resonance frequency reversibly shifts within one picosecond when the nanostructure is pumped with low-energy photons. We investigate experimentally and theoretically the role of several parameters: the material backbone and its electronic bandgap, the quality factor, and the duration of the switch pulse. The magnitude of the frequency shift is reduced when the backbone of the central λ-layer has a greater electronic bandgap compared to the cavity resonance frequency and the frequency of the pump. This observation is caused by the fact that pumping with photon energies near the bandgap resonantly enhances the switched magnitude. We thus find that cavities operating in the telecom O-band are more amenable to ultrafast Kerr switching than those operating at lower frequencies, such as the C-band. Our results indicate that the large bandgap of AlGaAs/AlAs cavity allows to tune both the pump and the probe to the telecom range to perform Kerr switching without detrimental two-photon absorption. We observe that the magnitude of the resonance frequency shift decreases with increasing quality factor of the cavity. Our model shows that the magnitude of the resonance frequency shift depends on the pump pulse duration and is maximized when the duration matches the cavity storage time to within a factor two. In our experiments, we obtain a maximum shift of the cavity resonance relative to the cavity linewidth of 20%. We project that the shift of the cavity resonance can be increased twofold with a pump pulse duration that better matches the cavity storage time. We provide the essential parameter settings for different materials so that the frequency shift of the cavity resonance can be maximized using the electronic Kerr effect.

  15. Laser acceleration of electrons in two-dimensionally inhomogeneous plasma at the boundary of a metal foil

    Energy Technology Data Exchange (ETDEWEB)

    Pugachev, L. P., E-mail: pugachev@ihed.ras.ru; Andreev, N. E., E-mail: andreev@ras.ru; Levashov, P. R., E-mail: pasha@ihed.ras.ru [Russian Academy of Sciences, Joint Institute for High Temperature (Russian Federation); Malkov, Yu. A., E-mail: yurymalkov@mail.ru; Stepanov, A. N., E-mail: step@ufp.appl.sci-nnov.ru; Yashunin, D. A., E-mail: yashuninda@yandex.ru [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

    2015-07-15

    The electron acceleration mechanism associated with the generation of a plasma wave due to self-modulation instability of laser radiation in a subcritical plasma produced by a laser prepulse coming 10 ns before the arrival of the main intense femtosecond pulse is considered. Three-dimensional particle-in-cell simulations of the interaction of laser radiation with two-dimensionally inhomogeneous subcritical plasma have shown that, for a sufficiently strong plasma inhomogeneity and a sharp front of the laser pulse, efficient plasma wave excitation, electron trapping, and generation of collimated electron beams with energies on the order of 0.2–0.5 MeV can occur. The simulation results agree with experiments on the generation of collimated beams of accelerated electrons from metal targets irradiated by intense femtosecond laser pulses.

  16. Opto-electronic device for frequency standard generation and terahertz-range optical demodulation based on quantum interference

    Science.gov (United States)

    Georgiades, Nikos P.; Polzik, Eugene S.; Kimble, H. Jeff

    1999-02-02

    An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100's THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 .mu.m to 1.66 .mu.m for fiber optics can be accomplished with a nearly continuous frequency coverage.

  17. Tilt-pair analysis of images from a range of different specimens in single-particle electron cryomicroscopy.

    Science.gov (United States)

    Henderson, Richard; Chen, Shaoxia; Chen, James Z; Grigorieff, Nikolaus; Passmore, Lori A; Ciccarelli, Luciano; Rubinstein, John L; Crowther, R Anthony; Stewart, Phoebe L; Rosenthal, Peter B

    2011-11-11

    The comparison of a pair of electron microscope images recorded at different specimen tilt angles provides a powerful approach for evaluating the quality of images, image-processing procedures, or three-dimensional structures. Here, we analyze tilt-pair images recorded from a range of specimens with different symmetries and molecular masses and show how the analysis can produce valuable information not easily obtained otherwise. We show that the accuracy of orientation determination of individual single particles depends on molecular mass, as expected theoretically since the information in each particle image increases with molecular mass. The angular uncertainty is less than 1° for particles of high molecular mass (~50 MDa), several degrees for particles in the range 1-5 MDa, and tens of degrees for particles below 1 MDa. Orientational uncertainty may be the major contributor to the effective temperature factor (B-factor) describing contrast loss and therefore the maximum resolution of a structure determination. We also made two unexpected observations. Single particles that are known to be flexible showed a wider spread in orientation accuracy, and the orientations of the largest particles examined changed by several degrees during typical low-dose exposures. Smaller particles presumably also reorient during the exposure; hence, specimen movement is a second major factor that limits resolution. Tilt pairs thus enable assessment of orientation accuracy, map quality, specimen motion, and conformational heterogeneity. A convincing tilt-pair parameter plot, where 60% of the particles show a single cluster around the expected tilt axis and tilt angle, provides confidence in a structure determined using electron cryomicroscopy. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. Cross sections for electron scattering by methylfluoride (CH{sub 3}F) in the low- and intermediate-energy ranges

    Energy Technology Data Exchange (ETDEWEB)

    Ferraz, J.R.; Santos, A.S. dos [Departamento de Física, UFSCar, 13565-905 São Carlos, SP (Brazil); Souza, G.L.C. de; Lee, M.-T. [Departamento de Química, UFSCar, 13565-905 São Carlos, SP (Brazil); Brescansin, L.M. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-970 Campinas, SP (Brazil); Lucchese, R.R. [Department of Chemistry, Texas A and M University, College Station, TX 7784-3255 (United States); Machado, L.E., E-mail: dlem@df.ufscar.br [Departamento de Física, UFSCar, 13565-905 São Carlos, SP (Brazil)

    2014-03-01

    Highlights: • Theoretical investigation on e{sup −}–CH{sub 3}F collisions. • Complex optical potential is used to evaluate elastic, total, and total absorption cross sections. • Single-center expansion, combined with the Padé approximant technique, is used to solve the scattering equations. • Calculated results are in good agreement with existing theoretical and experimental data. - Abstract: We report a theoretical study on electron scattering by methylfluoride (CH{sub 3}F) in the intermediate-energy range. Calculated elastic differential, integral, and momentum-transfer, as well as grand-total (elastic + inelastic) and total absorption cross sections are reported for impact energies ranging from 15 to 500 eV. A complex optical potential is used to represent the electron–molecule interaction dynamics. A theoretical method based on the single-center-expansion close-coupling framework and corrected by the Padé approximant technique is used to solve the scattering equations. The comparison of our calculated results with experimental and other available theoretical data is encouraging.

  19. Radiation-Hardening of Best-in-Class SiGe Mixed-Signal and RF Electronics for Ultra-Wide Temperature Range Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Innovative, reliable, low-power, and low-noise electronics that can operate over a wide temperature range and high radiation are critical for future NASA missions....

  20. Structure and properties of grain boundaries

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    1984-03-01

    Results were obtained in the following areas: determination of relative grain boundary energies by the rotating crystallite method; simple structural unit model for core dependent properties of tilt boundaries; twist boundary energies for metals with long ranged pairwise interatomic potentials; structural unit/grain boundary dislocation model for grain boundary structure; detection of expansion of boundaries using diffraction; effect of secondary relaxations on diffraction from high-(SIGMA) 001 twist boundaries; and mechanism of grain boundary migration.

  1. Electron scattering on the short-range potential in narrow gap Cd {sub x}Hg{sub 1-x}Te

    Energy Technology Data Exchange (ETDEWEB)

    Malyk, O.P. [Lviv Polytechnic National University, Semiconductor Electronics Department, Bandera Street 12, 79013 Lviv (Ukraine)]. E-mail: omalyk@mail.lviv.ua

    2006-04-15

    Models of electron scattering on the short-range potential caused by the interaction with polar and nonpolar optical phonons, piezoelectric and acoustic phonons, ionized and neutral impurities in the narrow gap solid solution Cd {sub x}Hg{sub 1-x}Te (x = 0, 0.08, 0.17, 0.26 and 0.36) are proposed. The temperature dependences of electron mobility in temperature range 4.2-300 K are calculated.

  2. Spatially resolved analytical electron microscopy at grain boundaries of {alpha}-Al{sub 2}O{sub 3}; Ortsaufgeloeste analytische Elektronenmikroskopie an Korngrenzen in {alpha}Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Nufer, S.

    2001-10-01

    Aluminum oxide, {alpha}-Al{sub 2}O{sub 3}, is a common structural ceramic material. The most technologically important properties are either determined or strongly influenced by the polycrystalline microstructure. For instance, the grain boundaries control the mechanical behavior (e.g. plasticity, creep, and fracture) or various transport phenomena (e.g. ion diffusion, segregation, and electrical resistivity). In order to understand the structure-properties relationships, it is therefore important to characterize the structure and chemistry of grain boundaries, both experimentally and theoretically. In this work the electronic structure of the basal and rhombohedral twin grain boundaries and the impurity excess at different tilt grain boundaries in bicrystals were investigated, using electron energy-loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS). The electronic structure of the rhombohedral twin grain boundary was determined by comparing spatially resolved EELS measurements of the O-K ionisation edge with the theoretical density of states (DOS), obtained from local density functional theory (LDFT) calculations. The interface excess of impurities was quantitatively analysed at grain boundaries with and without Y-doping. (orig.)

  3. Slow dynamics of electrons at a metal–Mott insulator boundary in an organic system with disorder

    Science.gov (United States)

    Itou, Tetsuaki; Watanabe, Eri; Maegawa, Satoru; Tajima, Akiko; Tajima, Naoya; Kubo, Kazuya; Kato, Reizo; Kanoda, Kazushi

    2017-01-01

    The Mott transition—a metal-insulator transition caused by repulsive Coulomb interactions between electrons—is a central issue in condensed matter physics because it is the mother earth of various attractive phenomena. Outstanding examples are high–Tc (critical temperature) cuprates and manganites exhibiting colossal magnetoresistance. Furthermore, spin liquid states, which are quantum-fluctuation–driven disordered ground states in antiferromagnets, have recently been found in magnetic systems very near the Mott transition. To date, intensive studies on the Mott transition have been conducted and appear to have established a nearly complete framework for understanding the Mott transition. We found an unknown type of Mott transition in an organic spin liquid material with a slightly disordered lattice. Around the Mott transition region of this material under pressure, nuclear magnetic resonance experiments capture the emergence of slow electronic fluctuations of the order of kilohertz or lower, which is not expected in the conventional Mott transition that appears as a clear first-order transition at low temperatures. We suggest that they are due to the unconventional metal-insulator fluctuations emerging around the disordered Mott transition in analogy to the slowly fluctuating spin phase, or Griffiths phase, realized in Ising spin systems with disordered lattices. PMID:28819640

  4. On the Monte Carlo simulation of electron transport in the sub-1 keV energy range.

    Science.gov (United States)

    Thomson, Rowan M; Kawrakow, Iwan

    2011-08-01

    The validity of "classic" Monte Carlo (MC) simulations of electron and positron transport at sub-1 keV energies is investigated in the context of quantum theory. Quantum theory dictates that uncertainties on the position and energy-momentum four-vectors of radiation quanta obey Heisenberg's uncertainty relation; however, these uncertainties are neglected in "classical" MC simulations of radiation transport in which position and momentum are known precisely. Using the quantum uncertainty relation and electron mean free path, the magnitudes of uncertainties on electron position and momentum are calculated for different kinetic energies; a validity bound on the classical simulation of electron transport is derived. In order to satisfy the Heisenberg uncertainty principle, uncertainties of 5% must be assigned to position and momentum for 1 keV electrons in water; at 100 eV, these uncertainties are 17 to 20% and are even larger at lower energies. In gaseous media such as air, these uncertainties are much smaller (less than 1% for electrons with energy 20 eV or greater). The classical Monte Carlo transport treatment is questionable for sub-1 keV electrons in condensed water as uncertainties on position and momentum must be large (relative to electron momentum and mean free path) to satisfy the quantum uncertainty principle. Simulations which do not account for these uncertainties are not faithful representations of the physical processes, calling into question the results of MC track structure codes simulating sub-1 keV electron transport. Further, the large difference in the scale at which quantum effects are important in gaseous and condensed media suggests that track structure measurements in gases are not necessarily representative of track structure in condensed materials on a micrometer or a nanometer scale.

  5. Boundary issues

    Science.gov (United States)

    Townsend, Alan R.; Porder, Stephen

    2011-03-01

    -centric boundary (Filippelli 2008, Handoh and Lenton 2003). However, human alteration of the P cycle has multiple potential boundaries (figure 1), including P-driven freshwater eutrophication (Smith and Schindler 2009), the potential for world P supply to place an ultimate limit on food production (Smil 2000, Childers et al 2011), and depletion of soil P stocks in some world regions (MacDonald et al 2011). Carpenter and Bennett revisit the P boundary from the freshwater eutrophication perspective. Given the extraordinary variation in freshwater ecosystems across the globe, this is a challenging task, but the authors strengthen their analysis by using three different boundaries with relevance to eutrophication, along with two water quality targets and a range of estimates of P flow to the sea. In doing so, they make a compelling case that if freshwater eutrophication is indeed a Rubicon, we have already crossed it. Importantly, Carpenter and Bennett go beyond the calculation of new boundaries to make broader points about humanity's relationship with the P cycle. Disruptions of both the P and N cycles are mostly about our need for food (Galloway et al 2008, Cordell et al 2009), but unlike N, P supplies are finite and irreplaceable. Environmental concerns aside, we can fix all the N2 from the atmosphere we want—but deplete our economically viable P reserves and we're in trouble. Figure 1 Figure 1. Human alteration of the global P cycle has multiple possible boundaries. These include the environmental risks posed by freshwater eutrophication and marine anoxic events, and the food security risks that come from depletion of soil P stocks in some world regions, as well as finite global supplies of high-value mineral P reserves. Photo credits beyond authors: upper left, Shelby Riskin; upper right, Pedro Sanchez. In effect, Carpenter and Bennett argue that among P's multiple boundaries, the one for freshwaters is less forgiving of our current activities (but no less important) than is

  6. REVIEW ARTICLE: From single photons to milliwatt radiant power—electron storage rings as radiation sources with a high dynamic range

    Science.gov (United States)

    Klein, Roman; Thornagel, Reiner; Ulm, Gerhard

    2010-10-01

    The spectral radiant intensity of synchrotron radiation from electron storage rings can be calculated from basic electrodynamic relations (Schwinger equation) and it is directly proportional to the stored electron beam current, i.e. the number of stored electrons. With the necessary equipment installed to measure and control the electron beam current over a wide dynamic range, the radiant intensity of the synchrotron radiation can be adjusted accordingly without changing the spectrum. This is done, e.g., at the Metrology Light Source (MLS), the dedicated electron storage ring of the Physikalisch-Technische Bundesanstalt. The MLS is operated as a primary radiation source standard from the near IR up to the soft x-ray region and its operational parameters can be adjusted and accurately measured in a wide range: the electron beam current can be varied from 1 pA (one stored electron) up to 200 mA and thus the radiant intensity can be changed by more than 11 decades. The photon flux or radiant power for typical angular acceptances can thus be varied from single photons to milliwatts. This is a very powerful tool, e.g., for the characterization of the linearity of the response of radiation detectors or for the calibration of photon counting detectors. In this article we present an overview of past, current and possible future activities exploiting this feature.

  7. First-Principles Calculations of Electronic States and Self-Doping Effects at a 45° Grain Boundary in the High Temperature YBa2Cu3O7 Superconductor

    KAUST Repository

    Schwingenschlögl, Udo

    2009-06-03

    The charge redistribution at grain boundaries determines the applicability of high-Tc superconductors in electronic devices because the transport across the grains can be hindered considerably. We investigate the local charge transfer and the modification of the electronic states in the vicinity of the grain-grain interface by ab initio calculations for a (normal-state) 45°-tilted [001] grain boundary in YBa2Cu3O7. Our results explain the suppressed interface transport and the influence of grain boundary doping in a quantitative manner, in accordance with the experimental situation. The charge redistribution is found to be strongly inhomogeneous, which has a substantial effect on transport properties since it gives rise to a self-doping of 0.10±0.02 holes per Cu atom.

  8. Improved Models and Tools for Prediction of Radiation Effects on Space Electronics in Wide Temperature Range Project

    Data.gov (United States)

    National Aeronautics and Space Administration — All NASA exploration systems operate in the extreme environments of space (Moon, Mars, etc.) and require reliable electronics capable of handling a wide temperature...

  9. Electron-trapping polycrystalline materials with negative electron affinity.

    Science.gov (United States)

    McKenna, Keith P; Shluger, Alexander L

    2008-11-01

    The trapping of electrons by grain boundaries in semiconducting and insulating materials is important for a wide range of physical problems, for example, relating to: electroceramic materials with applications as sensors, varistors and fuel cells, reliability issues for solar cell and semiconductor technologies and electromagnetic seismic phenomena in the Earth's crust. Surprisingly, considering their relevance for applications and abundance in the environment, there have been few experimental or theoretical studies of the electron trapping properties of grain boundaries in highly ionic materials such as the alkaline earth metal oxides and alkali halides. Here we demonstrate, by first-principles calculations on MgO, LiF and NaCl, a qualitatively new type of electron trapping at grain boundaries. This trapping is associated with the negative electron affinity of these materials and is unusual as the electron is confined in the empty space inside the dislocation cores.

  10. Minnesota Pheasant Range

    Data.gov (United States)

    Minnesota Department of Natural Resources — This dataset delineates the spatial range of wild pheasant populations in Minnesota as of 2002 by dividing the MN state boundary into 2 units: pheasant range and...

  11. Calorimetry for dose measurement at electron accelerators in the 80-120 keV energy range

    DEFF Research Database (Denmark)

    Helt-Hansen, J.; Miller, A.; Duane, S.

    2005-01-01

    Calorimeters for dose measurement at low-energy electron accelerator energies (80-120 keV) are described. Three calorimeters with different characteristics were designed and their dose response and measurement uncertainties were characterized. The heated air between the beam exit window and the c...

  12. Optimal all-optical switching of a microcavity resonance in the telecom range using the electronic Kerr effect

    CERN Document Server

    Yüce, Emre; Claudon, Julien; Gérard, Jean-Michel; Vos, Willem L

    2015-01-01

    We have switched GaAs/AlAs and AlGaAs/AlAs planar microcavities operating in the "original" telecom band by exploiting the instantaneous electronic Kerr effect. We demonstrate that resonance frequency reversibly shifts within a picosecond and the magnitude of the shift is affected by the backbone of the $\\lambda-$layer. We investigate experimentally and theoretically the role of the quality factor in terms of its effect on resonance frequency shift. Our model shows that the magnitude of the resonance frequency shift depends on the pump pulse duration and is maximized when the cavity cavity storage time is matched. Our experiments and our calculations indicate that the resonance frequency shift induced via the electronic Kerr effect can be maximized by judicious tuning of the pump frequency, pump power and pump pulse duration relative to the storage time of the cavity.

  13. Research Investigation Directed Toward Extending the Useful Range of the Electromagnetic Spectrum. [atomic spectra and electronic structure of alkali metals

    Science.gov (United States)

    Hartmann, S. R.; Happer, W.

    1974-01-01

    The report discusses completed and proposed research in atomic and molecular physics conducted at the Columbia Radiation Laboratory from July 1972 to June 1973. Central topics described include the atomic spectra and electronic structure of alkali metals and helium, molecular microwave spectroscopy, the resonance physics of photon echoes in some solid state systems (including Raman echoes, superradiance, and two photon absorption), and liquid helium superfluidity.

  14. Accurate transport simulation of electron tracks in the energy range 1 keV-4 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Cobut, V. E-mail: vincent.cobut@chim.u-cergy.fr; Cirioni, L.; Patau, J.P

    2004-01-01

    Multipurpose electron transport simulation codes are widely used in the fields of radiation protection and dosimetry. Broadly based on multiple scattering theories and continuous energy loss stopping powers with some mechanism taking straggling into account, they give reliable answers to many problems. However they may be unsuitable in some specific situations. In fact, many of them are not able to accurately describe particle transport through very thin slabs and/or in high atomic number materials, or also when knowledge of high-resolution depth dose distributions is required. To circumvent these deficiencies, we developed a Monte Carlo code simulating each interaction along electron tracks. Gas phase elastic cross sections are corrected to take into account solid state effects. Inelastic interactions are described within the framework of the Martinez et al. [J. Appl. Phys. 67 (1990) 2955] theory intended to deal with energy deposition in both condensed insulators and conductors. The model described in this paper is validated for some materials as aluminium and silicon, encountered in spectrometric and dosimetric devices. Comparisons with experimental, theoretical and other simulation results are made for angular distributions and energy spectra of transmitted electrons through slabs of different thicknesses and for depth energy distributions in semi-infinite media. These comparisons are quite satisfactory.

  15. Two-band electronic metal and neighboring spin Bose-metal on a zigzag strip with longer-ranged repulsion

    Science.gov (United States)

    Lai, Hsin-Hua; Motrunich, Olexei I.

    2010-01-01

    We consider an electronic model for realizing the spin Bose-metal (SBM) phase on a two-leg triangular strip—a spin liquid phase found by Sheng [Phys. Rev. B 79, 205112 (2009)] in a spin-1/2 model with ring exchanges. The SBM can be viewed as a “C1S2” Mott insulator of electrons where the overall charge transporting mode is gapped out. We start from a two-band “C2S2” metal and consider extended repulsion motivated by recent ab initio derivation of electronic model for κ-ET spin liquid material [K. Nakamura , J. Phys. Soc. Jpn. 78, 083710 (2009)]. Using weak coupling renormalization group analysis, we find that the extended interactions allow much wider C2S2 metallic phase than in the Hubbard model with on-site repulsion only. An eight-fermion umklapp term plays a crucial role in producing a Mott insulator but cannot be treated in weak coupling. We use bosonization to extend the analysis to intermediate coupling and study phases obtained out of the C2S2 metal upon increasing overall repulsion strength, finding that the SBM phase is a natural outcome for extended interactions.

  16. Grain Boundary Energies in Copper.

    Science.gov (United States)

    Omar, Ramli

    Available from UMI in association with The British Library. Requires signed TDF. The dependence of grain boundary energy on boundary orientation was studied in copper annealed at 1000 ^circC. Grain boundary orientations and the disorientations across the boundaries were measured. A rotation matrix notation is used to interpret selected area electron channelling patterns observed in a scanning electron microscope. The Herring and Shewmon torque terms were investigated using wire specimens having a "bamboo" structure. The Herring torque terms were determined using the Hess relation. The (110) section of the Sigma 11 gamma-plot (i.e. the variation of grain boundary energy with boundary orientation) was evaluated. In this plot, minima in energies were found at the (311) and (332) mirror planes. Sigma 3 and Sigma9 boundaries were investigated in sheet specimens. The (110) and (111) sections of the Sigma3 gamma -plot were evaluated. In addition to the sharp cusps occurring at the Sigma3 {111} planes, the further shallower cusps occur at the incoherent Sigma 3 boundaries with the interfacial planes approximately parallel to {322} in one crystal and {11.44} in the other crystal. Flat and curved Sigma9 boundaries were investigated. The break up of Sigma9 boundaries into two Sigma3 boundaries and the relation between the Sigma3 and Sigma 9 gamma-plots was also examined. The (110) section of the Sigma9 gamma-plot was constructed.

  17. Interplanetary transport of solar near-relativistic electrons on 2014 August 1 over a narrow range of heliolongitudes

    Directory of Open Access Journals (Sweden)

    Pacheco Daniel

    2017-01-01

    Full Text Available We study two consecutive solar near-relativistic (>50 keV electron events observed on 2014 August 1 by both STEREO spacecraft with a longitudinal separation of only about 35°. The events were unambiguously associated with a solar source location and not accompanied by type II radio bursts or coronal mass ejections. Despite their close location, the two spacecraft were embedded in different solar wind streams and the electron intensities observed by the two STEREOs showed clear differences in onset times, peak intensities and pitch-angle distributions. The apparently better connected spacecraft, STEREO B, observed a smaller and more isotropic intensity increase and a later event onset time than STEREO A. Since the interplanetary transport conditions of solar energetic particles (SEPs have a direct influence on the characteristics of the observed temporal profiles and the particle anisotropies at the spacecraft location, our aim is to understand if the observations on 2014 August 1 could be explained by different interplanetary transport conditions along each flux tube connecting the spacecraft with the solar source. For that purpose, we use a Monte Carlo interplanetary transport model combined with an inversion procedure to fit the in-situ observations of the two near-relativistic multi-spacecraft electron events. This allows us to obtain the injection profiles at the Sun and infer the transport conditions, which are characterized by the electron radial mean free path, λr. We obtain an almost simultaneous release of electrons for both spacecraft in both events. The release is consistent with the timing and duration of the type III radio burst emission and it is larger for STEREO B, the better connected spacecraft. In addition, we obtain different transport conditions in different solar wind streams. We find that the stream in which STEREO B was embedded was more diffusive (λr = 0.1AU for Event I and λr = 0.06AU for Event II than the

  18. Interplanetary transport of solar near-relativistic electrons on 2014 August 1 over a narrow range of heliolongitudes

    Science.gov (United States)

    Pacheco, Daniel; Agueda, Neus; Gómez-Herrero, Raúl; Aran, Angels

    2017-11-01

    We study two consecutive solar near-relativistic (>50 keV) electron events observed on 2014 August 1 by both STEREO spacecraft with a longitudinal separation of only about 35°. The events were unambiguously associated with a solar source location and not accompanied by type II radio bursts or coronal mass ejections. Despite their close location, the two spacecraft were embedded in different solar wind streams and the electron intensities observed by the two STEREOs showed clear differences in onset times, peak intensities and pitch-angle distributions. The apparently better connected spacecraft, STEREO B, observed a smaller and more isotropic intensity increase and a later event onset time than STEREO A. Since the interplanetary transport conditions of solar energetic particles (SEPs) have a direct influence on the characteristics of the observed temporal profiles and the particle anisotropies at the spacecraft location, our aim is to understand if the observations on 2014 August 1 could be explained by different interplanetary transport conditions along each flux tube connecting the spacecraft with the solar source. For that purpose, we use a Monte Carlo interplanetary transport model combined with an inversion procedure to fit the in-situ observations of the two near-relativistic multi-spacecraft electron events. This allows us to obtain the injection profiles at the Sun and infer the transport conditions, which are characterized by the electron radial mean free path, λr. We obtain an almost simultaneous release of electrons for both spacecraft in both events. The release is consistent with the timing and duration of the type III radio burst emission and it is larger for STEREO B, the better connected spacecraft. In addition, we obtain different transport conditions in different solar wind streams. We find that the stream in which STEREO B was embedded was more diffusive (λr = 0.1AU for Event I and λr = 0.06AU for Event II) than the stream in which STEREO A

  19. Negotiating boundaries

    DEFF Research Database (Denmark)

    Aarhus, Rikke; Ballegaard, Stinne Aaløkke

    2010-01-01

    to maintain the order of the home when managing disease and adopting new healthcare technology. In our analysis we relate this boundary work to two continuums of visibility-invisibility and integration-segmentation in disease management. We explore five factors that affect the boundary work: objects......To move treatment successfully from the hospital to that of technology assisted self-care at home, it is vital in the design of such technologies to understand the setting in which the health IT should be used. Based on qualitative studies we find that people engage in elaborate boundary work......, activities, places, character of disease, and collaboration. Furthermore, the processes are explored of how boundary objects move between social worlds pushing and shaping boundaries. From this we discuss design implications for future healthcare technologies for the home....

  20. Boundary Spanning

    DEFF Research Database (Denmark)

    Zølner, Mette

    The paper explores how locals span boundaries between corporate and local levels. The aim is to better comprehend potentialities and challenges when MNCs draws on locals’ culture specific knowledge. The study is based on an in-depth, interpretive case study of boundary spanning by local actors...... in the period of post-acquisition when their organization is being integrated into the acquiring MNC. The paper contributes to the literature on boundary spanning in three ways: First, by illustrating that boundary spanning is performed by numerous organizational actors in a variety of positions in MNCs......, inclusively by locals in subsidiaries. Second, by showing that boundary spanning is ‘situated’ in the sense that its result depends on the kind of knowledge to be transmitted and the attitude of the receivers. A third contribution is methodological. The study illustrates that combining bottom-up grounded...

  1. Total cross sections for electron scattering by CO{sub 2} molecules in the energy range 400{endash}5000 eV

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, G.; Manero, F. [Direccion de Tecnologia, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Avenida Complutense 22, 28040 Madrid (Spain)]|[Instituto de Investigacion Basica, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Avenida Complutense 22, 28040 Madrid (Spain)

    1996-01-01

    Total cross sections for electron scattering by CO{sub 2} molecules in the energy range 400{endash}5000 eV have been measured with experimental errors of {approximately}3{percent}. The present results have been compared with available experimental and theoretical data. The dependence of the total cross sections on electron energy shows an asymptotic behavior with increasing energies, in agreement with the Born-Bethe approximation. In addition, an analytical formula is provided to extrapolate total cross sections to higher energies. {copyright} {ital 1996 The American Physical Society.}

  2. The physical limits of metal reduction by long-range extracellular electron transfer, and the role of cytochrome-bound flavins

    Science.gov (United States)

    Michelson, K.; Sanford, R. A.; Valocchi, A. J.; Werth, C. J.

    2015-12-01

    Microbial reduction of metals and radionuclides in the subsurface plays an essential role in the biogeochemical cycling of micronutrients and the remediation of contaminated groundwater. While recent advances in the field have improved our ability to understand and predict bioreduction in these environments, the contribution of long-range extracellular electron transfer (EET) by electron shuttling or reduction along conductive pili remains elusive. Long-range EET is implicated in the reduction of radionuclides like uranium that are reversibly sorbed in clay nanopores and exist as persistant sources of contamination. In regions of low hydraulic conductivity, electron shuttles and conductive pili may increase physical mixing beyond what is possible by advection and diffusion, resulting in reduction over a larger area than predicted by current models. We present a novel microfluidic platform that allows us to study long-range EET to the exclusion of other mechanisms, directly observe these phenomena under a controlled environment representative of groundwater conditions, monitor the metabolic activity and redox state of bacteria, and determine the presence of reduced products in-situ. Using Geobacter sulfurreducens as a model metal-reducing bacteria, insoluble manganese dioxide as an electron acceptor, and Escherichia coli K-12 as a reductant and redox buffer, we demonstate that 1) long-range EET by conductive pili requires the presence of flavins 2) Reduction by direct contact only requires the presence of a lowered electric potential 3) The limit of reduction by conductive pili is on the order of 15-20 microns. We are actively exploring the influence of hydrological conditions on the expression of different mechanisms of long-range EET, and the importance of extracellular cytochromes and pili conductivity on metal reduction.

  3. On the effect of impurities on resistivity recovery, short-range ordering, and defect migration in electron-irradiated concentrated Fe-Cr alloys

    CERN Document Server

    Nikolaev, A L; Davletshin, A E

    1997-01-01

    The resistivity recovery of pure and impurity-doped (0.2-1.5% Si, 0.15% C+N) concentrated ferritic Fe-Cr alloys after electron irradiation at 50-60 K has been investigated over the temperature range 110-390 K. A fine recovery spectrum structure consisting of five peaks has been observed over the range 135-230 K. Short-range ordering starts with the onset of vacancy long-range migration. Doping with both types of impurity suppresses the recovery spectrum structure over the range 160-220 K in a similar manner. Additional effects of impurity doping on the resistivity recovery caused by deviation from Matthiessen's rule have been analysed. A stage III peak is found at 210 K, and two peaks - at 175 K and 195 K - are interpreted as being due to the vacancy short-range migration. It is supposed that such a manifestation of short-range vacancy migration is due to a strong immobilization of self-interstitial atoms, and suppression of short-range and long-range defect annealing processes in stage I, according to a conf...

  4. Long-range organization of bacteriochlorophyll in chlorosomes of Chlorobium tepidum investigated by cryo-electron microscopy

    NARCIS (Netherlands)

    Oostergetel, Gert T.; Reus, Michael; Chew, Aline Gomez Maqueo; Bryant, Donald A.; Boekema, Egbert J.; Holzwarth, Alfred R.

    2007-01-01

    Intact chlorosomes of Chlorobium tepidum were embedded in amorphous ice layers and examined by cryoelectron microscopy to study the long-range organization of bacteriochlorophyll ( BChl) layers. End-on views reveal that chlorosomes are composed of several multi-layer tubules of variable diameter

  5. Ionization Energies, Electron Affinities, and Polarization Energies of Organic Molecular Crystals: Quantitative Estimations from a Polarizable Continuum Model (PCM)–Tuned Range-Separated Density Functional Approach

    KAUST Repository

    Sun, Haitao

    2016-05-16

    We propose a new methodology for the first-principles description of the electronic properties relevant for charge transport in organic molecular crystals. This methodology, which is based on the combination of a non-empirical, optimally tuned range-separated hybrid functional with the polarizable continuum model, is applied to a series of eight representative molecular semiconductor crystals. We show that it provides ionization energies, electron affinities, and transport gaps in very good agreement with experimental values as well as with the results of many-body perturbation theory within the GW approximation at a fraction of the computational costs. Hence, this approach represents an easily applicable and computationally efficient tool to estimate the gas-to-crystal-phase shifts of the frontier-orbital quasiparticle energies in organic electronic materials.

  6. The Au-S bond and SAM-protein contact in long-range electron transfer of pure and biomimetic metalloproteins via functionalized alkanethiol linkers

    DEFF Research Database (Denmark)

    Chi, Qijin; Ford, Michael J.; Halder, Arnab

    functionalized alkanethiols have emerged as core linkers. We have studied molecular linking in the long-range ET (LRET) processes in detail using electrochemistry, in situ STM and AFM, and electronic structure computations. A focus is the electronic structure of the Au-S link and the SAM packing. We have...... illustrate this by high-resolution in situ STM of straight, branched, and chiral alkanethiols on Au(111)-electrode surfaces. We discuss next LRET of two SAM immobilized multi-copper enzymes, nitrite reductase and laccase, mapped to single-molecule resolution by in situ STM and AFM. The voltammetry...... degree of electronic structure sophistication. At the molecular scale this requirement is met by NPs of the renownedmixed-valence Prussian Blue (PB) assembled on Au(111)-electrode surfaces via functionalized alkanethiols. PBNP SAMs show LRET comparable to metalloproteins. Alkanethiols with different...

  7. Ion cyclotron range of frequencies mode conversion electron heating in deuterium-hydrogen plasmas in the Alcator C-Mod tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Y [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wukitch, S J [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Bonoli, P T [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Marmar, E [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Mossessian, D [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Nelson-Melby, E [Centre de Recherches en Physique des Plasmas, Association EURATOM - Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Phillips, P [Fusion Research Center, University of Texas, Austin, Texas 78712 (United States); Porkolab, M [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Schilling, G [Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Wolfe, S [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wright, J [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2003-06-01

    Localized direct electron heating (EH) by mode-converted (MC) ion cyclotron range of frequencies (ICRF) waves in D(H) tokamak plasmas has been clearly observed for the first time in Alcator C-Mod. Both on- and off-axis (high field side) mode conversion EH (MCEH) have been observed. The MCEH profile was obtained from a break-in-slope analysis of electron temperature signals in the presence of radio frequency shut-off. The temperature was measured by a 32-channel high spatial resolution ({<=}7 mm) 2nd harmonic heterodyne electron cyclotron emission system. The experimental profiles were compared with the predictions from a toroidal full-wave ICRF code TORIC. Using the hydrogen concentration measured by a high-resolution optical spectrometer, TORIC predictions were shown qualitatively in agreement with the experimental results for both on- and off-axis MC cases. From the simulations, the EH from MC ion cyclotron wave and ion Bernstein wave is examined.

  8. Organic electronic materials: Recent advances in the dft description of the ground and excited states using tuned range-separated hybrid functionals

    KAUST Repository

    Körzdörfer, Thomas

    2014-11-18

    Density functional theory (DFT) and its time-dependent extension (TD-DFT) are powerful tools enabling the theoretical prediction of the ground- and excited-state properties of organic electronic materials with reasonable accuracy at affordable computational costs. Due to their excellent accuracy-to-numerical-costs ratio, semilocal and global hybrid functionals such as B3LYP have become the workhorse for geometry optimizations and the prediction of vibrational spectra in modern theoretical organic chemistry. Despite the overwhelming success of these out-of-the-box functionals for such applications, the computational treatment of electronic and structural properties that are of particular interest in organic electronic materials sometimes reveals severe and qualitative failures of such functionals. Important examples include the overestimation of conjugation, torsional barriers, and electronic coupling as well as the underestimation of bond-length alternations or excited-state energies in low-band-gap polymers.In this Account, we highlight how these failures can be traced back to the delocalization error inherent to semilocal and global hybrid functionals, which leads to the spurious delocalization of electron densities and an overestimation of conjugation. The delocalization error for systems and functionals of interest can be quantified by allowing for fractional occupation of the highest occupied molecular orbital. It can be minimized by using long-range corrected hybrid functionals and a nonempirical tuning procedure for the range-separation parameter.We then review the benefits and drawbacks of using tuned long-range corrected hybrid functionals for the description of the ground and excited states of π-conjugated systems. In particular, we show that this approach provides for robust and efficient means of characterizing the electronic couplings in organic mixed-valence systems, for the calculation of accurate torsional barriers at the polymer limit, and for the

  9. Simulation of electron transport in GaAs/AlAs superlattices with a small number of periods for the THz frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Pavelyev, D. G., E-mail: pavelev@rf.unn.ru, E-mail: obolensk@rf.unn.ru [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Vasilev, A. P., E-mail: vasiljev@mail.ioffe.ru [Russian Academy of Sciences, Submicron Heterostructures for Microelectronics, Research and Engineering Center (Russian Federation); Kozlov, V. A., E-mail: kozlov@ipm.sci-nnov.ru; Koschurinov, Yu. I.; Obolenskaya, E. S.; Obolensky, S. V. [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Ustinov, V. M., E-mail: vmust@beam.ioffe.ru [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2016-11-15

    The electron transport in superlattices based on GaAs/AlAs heterostructures with a small number of periods (6 periods) is calculated by the Monte Carlo method. These superlattices are used in terahertz diodes for the frequency stabilization of quantum cascade lasers in the range up to 4.7 THz. The band structure of superlattices with different numbers of AlAs monolayers is considered and their current–voltage characteristics are calculated. The calculated current–voltage characteristics are compared with the experimental data. The possibility of the efficient application of these superlattices in the THz frequency range is established both theoretically and experimentally.

  10. The Noble Gas Dimers as a Probe of the Energetic Contributions of Dispersion and Short-Range Electron Correlation in Weakly-Bound Systems

    OpenAIRE

    Housden, Michael Philip; Pyper, Nicholas Charles

    2008-01-01

    Abstract The binding of the noble gas dimers is examined using a theory in which the Hartree-Fock interaction energy is augmented with both a short-range correlation term derived from the theory of a uniform electron-gas plus a dispersion energy damped according to the theory of Jabobi and Csanak. The good agreement between the predicted and experimental binding energies and equilibrium inter-nuclear separations confirms that this approach captures the essential physics of the int...

  11. Local boundary migration during recrystallization in pure aluminium

    DEFF Research Database (Denmark)

    Zhang, Yubin; Godfrey, Andrew; Juul Jensen, Dorte

    2011-01-01

    Boundary migration during recrystallization has been followed by an ex situ electron channelling contrast technique, and protrusions/retrusions formed locally on recrystallization boundaries have been quantified. The results show that the motion of recrystallization boundaries is much more comple...

  12. A classification of ecological boundaries

    Science.gov (United States)

    Strayer, D.L.; Power, M.E.; Fagan, W.F.; Pickett, S.T.A.; Belnap, J.

    2003-01-01

    Ecologists use the term boundary to refer to a wide range of real and conceptual structures. Because imprecise terminology may impede the search for general patterns and theories about ecological boundaries, we present a classification of the attributes of ecological boundaries to aid in communication and theory development. Ecological boundaries may differ in their origin and maintenance, their spatial structure, their function, and their temporal dynamics. A classification system based on these attributes should help ecologists determine whether boundaries are truly comparable. This system can be applied when comparing empirical studies, comparing theories, and testing theoretical predictions against empirical results.

  13. Heterogeneous Boundary Layers through the Diurnal Cycle: Evaluation of the WRF Wind Farm Parameterization using Scanning Lidar Observations and Wind Turbine Power Measurements during a Range of Stability Conditions

    Science.gov (United States)

    Lundquist, J. K.

    2015-12-01

    As wind energy deployment increases, questions arise regarding impacts on local climates and how these impacts evolve with the diurnal cycle of the boundary layer. Satellite observations suggest nocturnal increases of surface temperatures, and measurements of turbine wakes document stronger and more persistent reductions of wind speed and increases in turbulence downwind of turbines during stable conditions. Validations of mesoscale parameterizations of these effects have been constrained to idealized conditions defined by neutrally-stratified conditions and/or limited wind directions and wind speeds, or by comparison to idealized large-eddy simulations. Synthesis of conventional meteorological measurements and unconventional measurements can offer unique insights for validating models over a large heterogeneous domain. The CWEX-13 field experiment provides an extensive dataset for such validation at spatial scales on the order of 10 km in a range of atmospheric stability and wind conditions. CWEX-13 took place within a 300 MW wind farm in central Iowa during summer 2013 and featured strong diurnal cycles. The wind turbines are sited irregularly, creating a heterogenous "canopy". Three profiling lidars, numerous surface flux stations, and a scanning lidar sampled wakes from multiple turbines. Further, the wind farm owner/operator has provided access to turbine power production and wind speed measurement data for model validation, providing ~ 200 measurements of proxies that integrate the wind profile over the rotor disk, from 40 m to 120 m above the surface. Building on previous work that identified optimal physics options, grid configurations, and boundary condition data sets by comparison to lidar wind profile measurements, we execute simulations with the WRF Wind Farm Parameterization for a ten-day period featuring moderate winds and strong diurnal cycles. We evaluate simulations with different modeling choices (e.g., vertical resolution, approaches to

  14. The impact of long-range electron-hole interaction on the charge separation yield of molecular photocells

    Science.gov (United States)

    Nemati Aram, Tahereh; Ernzerhof, Matthias; Asgari, Asghar; Mayou, Didier

    2017-01-01

    We discuss the effects of charge carrier interaction and recombination on the operation of molecular photocells. Molecular photocells are devices where the energy conversion process takes place in a single molecular donor-acceptor complex attached to electrodes. Our investigation is based on the quantum scattering theory, in particular on the Lippmann-Schwinger equation; this minimizes the complexity of the problem while providing useful and non-trivial insight into the mechanism governing photocell operation. In this study, both exciton pair creation and dissociation are treated in the energy domain, and therefore there is access to detailed spectral information, which can be used as a framework to interpret the charge separation yield. We demonstrate that the charge carrier separation is a complex process that is affected by different parameters, such as the strength of the electron-hole interaction and the non-radiative recombination rate. Our analysis helps to optimize the charge separation process and the energy transfer in organic solar cells and in molecular photocells.

  15. Proposal and verification numerical simulation for a microwave forward scattering technique at upper hybrid resonance for the measurement of electron gyroscale density fluctuations in the electron cyclotron frequency range in magnetized plasmas

    Science.gov (United States)

    Kawamori, E.; Igami, H.

    2017-11-01

    A diagnostic technique for detecting the wave numbers of electron density fluctuations at electron gyro-scales in an electron cyclotron frequency range is proposed, and the validity of the idea is checked by means of a particle-in-cell (PIC) numerical simulation. The technique is a modified version of the scattering technique invented by Novik et al. [Plasma Phys. Controlled Fusion 36, 357-381 (1994)] and Gusakov et al., [Plasma Phys. Controlled Fusion 41, 899-912 (1999)]. The novel method adopts forward scattering of injected extraordinary probe waves at the upper hybrid resonance layer instead of the backward-scattering adopted by the original method, enabling the measurement of the wave-numbers of the fine scale density fluctuations in the electron-cyclotron frequency band by means of phase measurement of the scattered waves. The verification numerical simulation with the PIC method shows that the technique has a potential to be applicable to the detection of electron gyro-scale fluctuations in laboratory plasmas if the upper-hybrid resonance layer is accessible to the probe wave. The technique is a suitable means to detect electron Bernstein waves excited via linear mode conversion from electromagnetic waves in torus plasma experiments. Through the numerical simulations, some problems that remain to be resolved are revealed, which include the influence of nonlinear processes such as the parametric decay instability of the probe wave in the scattering process, and so on.

  16. Boundary Transgressions: An Issue In Psychotherapeutic Encounter ...

    African Journals Online (AJOL)

    Boundary transgressions tend to be conceptualized on a continuum ranging from boundary crossings to boundary violations. Boundary crossings (e.g. accepting an inexpensive holiday gift from a client, unintentionally encountering a client in public, or attending a client's special event) are described in the literature as ...

  17. Polymers in waste electric and electronic equipment (WEEE) contain PBDD/F in the ppb-range

    Energy Technology Data Exchange (ETDEWEB)

    Schlummer, M.; Brandl, F.; Maeurer, A.; Gruber, L.; Wolz, G. [Fraunhofer-Institut fuer Verfahrenstechnik und Verpackung (IVV), Freising (Germany)

    2004-09-15

    Waste electric and electronic equipment (WEEE) consists of metals (60%), polymers (20%) and residual materials as wood or glass (20%). Whereas state-of the art-technologies are able to recover most of the metals present, recovery rates for polymers and residuals are negligible low. Primarily, this is due to low disposal costs, which refers to landfill or incineration depending on geographic circumstances. The European WEEE directive, which assesses material recovery rates above 70%, and changes in the German disposal regulation, which will prohibit the landfill of organic materials starting 2005, currently alter the legislative conditions. This leads to an increased interest in polymer recovery strategies. Approaches discussed include polymer recycling and pyrolysis-based material recovery, both characterised by temperatures below 240 C or 600 C, respectively. Polybrominated biphenyls (PBB) and/or diphenyl ethers (PBDE) in these waste streams complicate waste treatment techniques, since they are known to form brominated dioxins and furans (PBDD/F) under thermal stress, either in polymer recyclates or in pyrolysis products. Additionally, polymer recycling is affected by European directive 2003/11/EC, restricting the distribution of products containing more than 0.1% of octa- or pentabrominated diphenyl ethers, respectively. Aim of this study was to determine concentration levels of polybrominated compounds including PBDD/F and brominated flame retardants in polymers from WEEE. Both, mixed polymer waste and pre-sorted polymer fractions consisting mainly of monitors, TV-sets or telecommunication housings, were examined. Furthermore, the dependency of PBDD/F concentrations on waste source, pre-treatment and flame retardant system was investigated, implication on waste treatment alternatives are discussed.

  18. Distance-including rigorous upper bounds and tight estimates for two-electron integrals over long- and short-range operators

    Science.gov (United States)

    Thompson, Travis H.; Ochsenfeld, Christian

    2017-10-01

    We introduce both rigorous and non-rigorous distance-dependent integral estimates for four-center two-electron integrals derived from a distance-including Schwarz-type inequality. The estimates are even easier to implement than our so far most efficient distance-dependent estimates [S. A. Maurer et al., J. Chem. Phys. 136, 144107 (2012)] and, in addition, do not require well-separated charge-distributions. They are also applicable to a wide range of two-electron operators such as those found in explicitly correlated theories and in short-range hybrid density functionals. For two such operators with exponential distance decay [e-r12 and erfc (0.11 ṡr12 ) /r12], the rigorous bound is shown to be much tighter than the standard Schwarz estimate with virtually no error penalty. The non-rigorous estimate gives results very close to an exact screening for these operators and for the long-range 1/r12 operator, with errors that are completely controllable through the integral screening threshold. In addition, we present an alternative form of our non-rigorous bound that is particularly well-suited for improving the PreLinK method [J. Kussmann and C. Ochsenfeld, J. Chem. Phys. 138, 134114 (2013)] in the context of short-range exchange calculations.

  19. Ab initio electronic transport and thermoelectric properties of solids from full and range-separated hybrid functionals

    Science.gov (United States)

    Sansone, Giuseppe; Ferretti, Andrea; Maschio, Lorenzo

    2017-09-01

    Within the semiclassical Boltzmann transport theory in the constant relaxation-time approximation, we perform an ab initio study of the transport properties of selected systems, including crystalline solids and nanostructures. A local (Gaussian) basis set is adopted and exploited to analytically evaluate band velocities as well as to access full and range-separated hybrid functionals (such as B3LYP, PBE0, or HSE06) at a moderate computational cost. As a consequence of the analytical derivative, our approach is computationally efficient and does not suffer from problems related to band crossings. We investigate and compare the performance of a variety of hybrid functionals in evaluating Boltzmann conductivity. Demonstrative examples include silicon and aluminum bulk crystals as well as two thermoelectric materials (CoSb3, Bi2Te3). We observe that hybrid functionals other than providing more realistic bandgaps—as expected—lead to larger bandwidths and hence allow for a better estimate of transport properties, also in metallic systems. As a nanostructure prototype, we also investigate conductivity in boron-nitride (BN) substituted graphene, in which nanoribbons (nanoroads) alternate with BN ones.

  20. Numerical study of the atomic and electronic structure of some silicon grain boundaries; Etude numerique de la structure atomique et electronique de quelques joints de grains du silicium

    Energy Technology Data Exchange (ETDEWEB)

    Torrent, M

    1996-07-01

    This work contributes to the theoretical study of extended defects in covalent materials. The study is especially devoted to the tilt grain boundaries in silicon as a model material. The theoretical model is based on the self-consistent tight-binding approximation and is applied within two numerical techniques: the fast 'order N' density-matrix method and the diagonalization technique which allows the sampling of the reciprocal space. Total energy parameters of the model have been fitted in order to reproduce the silicon band structure (with a correct gap value) and the transferability of crystalline and mechanical properties of this material. A new type of boundary conditions is proposed and tested. These conditions, named 'ante-periodic' or 'Moebius', allow only one grain boundary per box instead of two and decrease the CPU time by a factor of two. The model is then applied to the study of the {sigma}=25 [001] (710) grain boundary. The results show the possible presence in this boundary of low energy non-reconstructed atomic structures which are electrically active. This confirms what had been suggested by some experimental observations. The same study is also performed for the {sigma}=13 [001] (510) grain boundary. In order to compare the intrinsic electrical activity in the previous grain boundaries with the one induced by impurities, a total energy parametrization for the silicon-nickel bond is achieved and used in preliminary calculations. Finally the two variants of the {sigma}=11 [011] (2-33) interface are studied, especially their respective interfacial energies. The result disagrees with previous calculations using phenomenological potentials. (author)

  1. Semi empirical formula to calculate MSP of relativistic electrons in the range of 940 keV–1020 keV

    Directory of Open Access Journals (Sweden)

    S. Ramesh Babu

    2016-01-01

    Full Text Available A semi empirical formula has been obtained to calculate the Mass stopping power (MSP of relativistic electrons in the energy range of 950 keV–1050 keV, for any material of atomic number or Zeff ranging from 10–82. The MSP of 942 keV and 1016 keV internal conversion electrons of Bi207 are obtained by allowing them to pass through the targets of atomic numbers 13, 29, 47, 50, 79 and 82. The energies of the incident and transmitted electrons are measured using a Si(Li detector coupled to 8 K multi channel analyzer and the MSP has been determined from the measured incident and transmitted energies. The resultant variation of MSP with the atomic number of the material is plotted and best fitted to a first order exponential equation. The results predicted by this semi empirical formula are compared with the NIST-ESTAR database & Batra's formula and found to be in good agreement. Application of this formula to calculate the MSP and effective atomic number of any biological sample or compound is discussed.

  2. Blurring Boundaries

    DEFF Research Database (Denmark)

    Neergaard, Ulla; Nielsen, Ruth

    2010-01-01

    This article builds on the results obtained in the so-called Blurring Boundaries project which was undertaken at the Law Department, Copenhagen Business School, in the period from 2007 to 2009. It looks at the sustainability of the Danish welfare state in an EU law context and on the integration...... of welfare functions into EU law both from an internal market law and a constitutional law perspective. The main problem areas covered by the Blurring Boundaries project were studied in sub-projects on: 1) Internal market law and welfare services; 2) Fundamental rights and non-discrimination law aspects......; and 3) Services of general interest. In the Blurring Boundaries project, three aspects of the European Social Model have been particularly highlighted: the constitutionalisation of the European Social Model, its multi-level legal character, and the clash between market access justice at EU level...

  3. Polar observations of ion/electron bursts at the pre-dawn polar cap boundary: evidence for internal reconnection of overdraped lobe flux

    Directory of Open Access Journals (Sweden)

    P. E. Sandholt

    2008-08-01

    Full Text Available Observations made by Polar of ion-electron bursts on the dawn side of the polar cap are presented. They occurred when conditions external to the magnetosphere corresponded to that of the sheath region of a magnetic cloud, which was characterized by very high densities/dynamic pressure and a magnetic field which was strong in all components and which was tilted antisunward (Bx<0 and northward (Bz>0 with its clock angle lying between 20 and 90° (By: 8–15 nT. A clear temporal development in the energy range spanned by the individual ion bursts (from 0.2–2 keV to 1–10 keV was present. We relate this to a corresponding temporal evolution in the cloud sheath field and plasma. We analyze the solar wind-magnetosphere aspects of the observations using the concepts of (i (i overdraped lobe flux, (ii Bx- and By-regulated sequential reconnections in opposite hemispheres (magnetopause and internal modes, and (iii newly-closed magnetic flux. In particular, we find that the most energetic ion bursts (accompanied by bi-directionally streaming electrons at 1–10 keV and intense magnetosheath-origin fluxes are located on newly closed field lines generated by internal reconnection occurring between overdraped lobe field lines and the closed geomagnetic field. This result corroborates a topology of lobe reconnection under conditions of dipole tilt and/or nonzero IMF Bx component advanced by Watanabe et al. (2006, which in our case is adapted to nonzero IMF By conditions.

  4. A closed-form formulation for the build-up factor and absorbed energy for photons and electrons in the Compton energy range in Cartesian geometry

    Energy Technology Data Exchange (ETDEWEB)

    Borges, Volnei; Vilhena, Marco Tullio, E-mail: borges@ufrgs.b, E-mail: vilhena@pq.cnpq.b [Universidade Federal do Rio Grande do Sul (PROMEC/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica; Fernandes, Julio Cesar Lombaldo, E-mail: julio.lombaldo@ufrgs.b [Universidade Federal do Rio Grande do Sul (DMPA/UFRGS), Porto Alegre, RS (Brazil). Dept. de Matematica Pura e Aplicada. Programa de Pos Graduacao em Matematica Aplicada

    2011-07-01

    In this work, we report on a closed-form formulation for the build-up factor and absorbed energy, in one and two dimensional Cartesian geometry for photons and electrons, in the Compton energy range. For the one-dimensional case we use the LTS{sub N} method, assuming the Klein-Nishina scattering kernel for the determination of the angular radiation intensity for photons. We apply the two-dimensional LTS{sub N} nodal solution for the averaged angular radiation evaluation for the two-dimensional case, using the Klein-Nishina kernel for photons and the Compton kernel for electrons. From the angular radiation intensity we construct a closed-form solution for the build-up factor and evaluate the absorbed energy. We present numerical simulations and comparisons against results from the literature. (author)

  5. The analysis of bainitic ferrite microstructure in microalloyed plate steels through quantitative characterization of intervariant boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Singon, E-mail: sikang@mines.edu [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Speer, John G.; Regier, Ryan W. [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Nako, Hidenori [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Materials Research Laboratory, Kobe Steel Ltd., Kobe, Hyogo 651-2271 (Japan); Kennett, Shane C. [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Exponent Failure Analysis Associates, Menlo Park, CA 94025 (United States); Findley, Kip O. [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States)

    2016-07-04

    Electron backscatter diffraction (EBSD) measurements were performed to investigate the bainitic ferrite microstructure in low-carbon, microalloyed steels with varying C and Mn contents. Fully austenitized samples were isothermally heat treated at temperatures ranging from 450 to 550 °C to form bainitic ferrite. The bainitic ferrite microstructures and boundary characteristics obtained from the EBSD measurements were analyzed based on an inferred Kurdjumov-Sachs (K-S) orientation relationship. The heat treated samples exhibit a microstructure composed of laths and the lath aspect ratio tends to increase at lower isothermal heat treatment temperatures. High fractions of boundary misorientation angles below 5° are observed, which are due to lath boundaries in the microstructure. Additionally, misorientations of approximately 7°, 53° and 60° are observed, which are related to the sub-block, packet, and block boundaries, respectively. With decreasing isothermal heat treatment temperature, there is an increase of block boundaries; these boundaries are intervariant boundaries between different blocks within a packet, most of which have the misorientation angle of 60°. The specimens with a higher carbon level contained increased length of block boundaries, whereas the addition of Mn moderated the dependence of block boundary length on the heat treatment temperature within the experimental temperature range. Meanwhile, the length of intervariant boundaries of both packet and sub-block character did not vary much with heat treatment temperature and alloy composition.

  6. Grain boundary melting in ice

    OpenAIRE

    Thomson, E. S.; Hansen-Goos, Hendrik; Wilen, L. A.; Wettlaufer, J. S.

    2012-01-01

    We describe an optical scattering study of grain boundary premelting in water ice. Ubiquitous long ranged attractive polarization forces act to suppress grain boundary melting whereas repulsive forces originating in screened Coulomb interactions and classical colligative effects enhance it. The liquid enhancing effects can be manipulated by adding dopant ions to the system. For all measured grain boundaries this leads to increasing premelted film thickness with increasing electrolyte concentr...

  7. Development of a low-energy x-ray camera for the imaging of secondary electron bremsstrahlung x-ray emitted during proton irradiation for range estimation

    Science.gov (United States)

    Ando, Koki; Yamaguchi, Mitsutaka; Yamamoto, Seiichi; Toshito, Toshiyuki; Kawachi, Naoki

    2017-06-01

    Imaging of secondary electron bremsstrahlung x-ray emitted during proton irradiation is a possible method for measurement of the proton beam distribution in phantom. However, it is not clear that the method is used for range estimation of protons. For this purpose, we developed a low-energy x-ray camera and conducted imaging of the bremsstrahlung x-ray produced during irradiation of proton beams. We used a 20 mm  ×  20 mm  ×  1 mm finely grooved GAGG scintillator that was optically coupled to a one-inch square high quantum efficiency (HQE)-type position-sensitive photomultiplier tube to form an imaging detector. The imaging detector was encased in a 2 cm-thick tungsten container, and a pinhole collimator was attached to its camera head. After performance of the camera was evaluated, secondary electron bremsstrahlung x-ray imaging was conducted during irradiation of the proton beams for three different proton energies, and the results were compared with Monte Carlo simulation as well as calculated value. The system spatial resolution and sensitivity of the developed x-ray camera with 1.5 mm-diameter pinhole collimator were estimated to be 32 mm FWHM and 5.2  ×  10-7 for ~35 keV x-ray photons at 100 cm from the collimator surface, respectively. We could image the proton beam tracks by measuring the secondary electron bremsstrahlung x-ray during irradiation of the proton beams, and the ranges for different proton energies could be estimated from the images. The measured ranges from the images were well matched with the Monte Carlo simulation, and slightly smaller than the calculated values. We confirmed that the imaging of the secondary electron bremsstrahlung x-ray emitted during proton irradiation with the developed x-ray camera has the potential to be a new tool for proton range estimations.

  8. Long-range protein electron transfer observed at the single-molecule level: In situ mapping of redox-gated tunneling resonance

    DEFF Research Database (Denmark)

    Chi, Qijin; Farver, O; Ulstrup, Jens

    2005-01-01

    on the redox potential. Maximum resonance appears around the equilibrium redox potential of azurin with an on/off current ratio of approximate to 9. Simulation analyses, based on a two-step interfacial ET model for the scanning tunneling microscopy redox process, were performed and provide quantitative......A biomimetic long-range electron transfer (ET) system consisting of the blue copper protein azurin, a tunneling barrier bridge, and a gold single-crystal electrode was designed on the basis of molecular wiring self-assembly principles. This system is sufficiently stable and sensitive in a quasi...

  9. Determination of grain boundary geometry using TEM

    NARCIS (Netherlands)

    Jang, H.; Farkas, D.; Hosson, J.T.M. De

    An experimental method to obtain the grain boundary geometry using the transmission electron microscope is presented. The method allows Σ determination including grain boundary plane orientation. In order to determine the specialness of the grain boundary, three different criteria for maximum

  10. Geochemistry and geochronology of the Late Permian mafic intrusions along the boundary area of Jiamusi and Songnen-Zhangguangcai Range massifs and adjacent regions, northeastern China: Petrogenesis and implications for the tectonic evolution of the Mudanjiang Ocean

    Science.gov (United States)

    Dong, Yu; Ge, Wen-chun; Yang, Hao; Xu, Wen-liang; Bi, Jun-hui; Wang, Zhi-hui

    2017-01-01

    This paper presents zircon U-Pb ages, whole-rock major and trace element data, and Hf isotope data for the metagabbros from the Zhushan pluton and gabbros from the Taiping pluton along the boundary area of Jiamusi and Songnen-Zhangguangcai Range massifs and adjacent regions, which will not only place important constraints on the rock-forming ages, source characteristics and tectonic setting of these gabbros, but will also provide insights into understanding the Permian tectonic evolution between the Jiamusi Massif and the Songnen-Zhangguangcai Range Massif. Zircon U-Pb dating, determined using laser ablation-inductively coupled plasma-mass spectrometry and secondary-ion mass spectrometry, indicates that the magmatic zircons from the Zhushan and Taiping plutons yield 206Pb/238U ages of 256 ± 2 Ma and 259 ± 3 Ma, respectively, interpreted as the emplacement ages of the intrusions. The metagabbros from the Zhushan pluton display the geochemical characteristics of calc-alkaline series rocks, and are enriched in light rare earth and large ion lithophile elements, and depleted in Nb, Ta, P, Zr and Hf. The εHf(t) values of magmatic zircons in these metagabbros vary from - 5.47 to + 0.74. All these geochemical features indicate that the primary magma of the Zhushan pluton was derived from an enriched lithospheric mantle source that was metasomatized by subducted slab-derived fluids. The gabbros from the Taiping pluton are also enriched in large ion lithophile elements (e.g., Rb, Ba and U) relative to high field strength elements, and have negative Nb-Ta-P anomalies, with εHf(t) values of - 4.02 to - 1.70. It is inferred that they also formed from a primary magma generated by the partial melting of enriched lithospheric mantle that was metasomatized by subducted slab-derived fluids. The rocks from the Zhushan and Taiping plutons have similar petrogenetic processes, but their primary magmas are likely to be derived from two distinct magma sources based on geochemical and

  11. Soft x-ray free-electron laser imaging by LiF crystal and film detectors over a wide range of fluences.

    Science.gov (United States)

    Pikuz, Tatiana A; Faenov, Anatoly Ya; Fukuda, Yuji; Kando, Masaki; Bolton, Paul; Mitrofanov, Alexander; Vinogradov, Alexander V; Nagasono, Mitsuru; Ohashi, Haruhiko; Yabashi, Makina; Tono, Kensuke; Senba, Yasunori; Togashi, Tadashi; Ishikawa, Tetsuya

    2013-01-20

    LiF crystal and film detectors were used to measure the far-field fluence profile of a self-amplified spontaneous-emission free-electron laser beam and diffraction imaging with high spatial resolution. In these measurements the photoluminescence (PL) response of LiF crystal and film was compared over a wide range of soft x-ray fluences. It was found that the soft x-ray fluence dependences of LiF crystal and film differ. At low fluence, the LiF crystal shows higher PL response compared to LiF film, while this comparison is the opposite at higher fluence. Accurate measurement of LiF crystal and film PL response is important for precise characterization of the spatial, spectral, and coherence features of x-ray beams across the full profile and in localized areas. For such measurements, crucial LiF detector attributes are high spatial resolution and high dynamic range.

  12. Effective atomic numbers and electron densities of bacteriorhodopsin and its comprising amino acids in the energy range 1 keV–100 GeV

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadi, Morteza; Lunscher, Nolan [Waterloo Institute for Nanotechnology and Department of Systems Design Engineering, University of Waterloo, 200 University Ave., W., Waterloo, Ontario, Canada N2L 3G1 (Canada); Yeow, John T.W., E-mail: jyeow@uwaterloo.ca [Waterloo Institute for Nanotechnology and Department of Systems Design Engineering, University of Waterloo, 200 University Ave., W., Waterloo, Ontario, Canada N2L 3G1 (Canada)

    2013-04-01

    Recently, there has been an interest in fabrication of X-ray sensors based on bacteriorhodopsin, a proton pump protein in cell membrane of Halobacterium salinarium. Therefore, a better understanding of interaction of X-ray photons with bacteriorhodopsin is required. We use WinXCom program to calculate the mass attenuation coefficient of bacteriorhodopsin and its comprising amino acids for photon energies from 1 keV to 100 GeV. These amino acids include alanine, arginine, asparagine, aspartic acid, glutamine, glutamic acid, glycine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, Asx1, Asx2, Glx1 and Glx2. We then use that data to calculate effective atomic number and electron densities for the same range of energy. We also emphasize on two ranges of energies (10–200 keV and 1–20 MeV) in which X-ray imaging and radiotherapy machines work.

  13. New analytical model for the ozone electronic ground state potential surface and accurate ab initio vibrational predictions at high energy range.

    Science.gov (United States)

    Tyuterev, Vladimir G; Kochanov, Roman V; Tashkun, Sergey A; Holka, Filip; Szalay, Péter G

    2013-10-07

    An accurate description of the complicated shape of the potential energy surface (PES) and that of the highly excited vibration states is of crucial importance for various unsolved issues in the spectroscopy and dynamics of ozone and remains a challenge for the theory. In this work a new analytical representation is proposed for the PES of the ground electronic state of the ozone molecule in the range covering the main potential well and the transition state towards the dissociation. This model accounts for particular features specific to the ozone PES for large variations of nuclear displacements along the minimum energy path. The impact of the shape of the PES near the transition state (existence of the "reef structure") on vibration energy levels was studied for the first time. The major purpose of this work was to provide accurate theoretical predictions for ozone vibrational band centres at the energy range near the dissociation threshold, which would be helpful for understanding the very complicated high-resolution spectra and its analyses currently in progress. Extended ab initio electronic structure calculations were carried out enabling the determination of the parameters of a minimum energy path PES model resulting in a new set of theoretical vibrational levels of ozone. A comparison with recent high-resolution spectroscopic data on the vibrational levels gives the root-mean-square deviations below 1 cm(-1) for ozone band centres up to 90% of the dissociation energy. New ab initio vibrational predictions represent a significant improvement with respect to all previously available calculations.

  14. Discontinuity of the exchange-correlation potential and the functional derivative of the noninteracting kinetic energy as the number of electrons crosses integer boundaries in Li, Be, and B.

    Science.gov (United States)

    Morrison, Robert C

    2015-01-07

    Accurate densities were determined from configuration interaction wave functions for atoms and ions of Li, Be, and B with up to four electrons. Exchange-correlation potentials, Vxc(r), and functional derivatives of the noninteracting kinetic energy, δK[ρ]/δρ(r), obtained from these densities were used to examine their discontinuities as the number of electrons N increases across integer boundaries for N = 1, N = 2, and N = 3. These numerical results are consistent with conclusions that the discontinuities are characterized by a jump in the chemical potential while the shape of Vxc(r) varies continuously as an integer boundary is crossed. The discontinuity of the Vxc(r) is positive, depends on the ionization potential, electron affinity, and orbital energy differences, and the discontinuity in δK[ρ]/δρ(r) depends on the difference between the energies of the highest occupied and lowest unoccupied orbitals. The noninteracting kinetic energy and the exchange correlation energy have been computed for integer and noninteger values of N between 1 and 4.

  15. Albedo Boundary

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-510, 11 October 2003The sharp, nearly straight line that runs diagonally across the center of this April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is an albedo boundary. Albedois a term that refers to reflectance of sunlight. A surface with a low albedo is one that appears dark because it reflects less light than a high albedo (bright) surface. On Mars, albedo boundaries occur between two materials of differing texture, particle size, or composition, or some combination of these three factors. The boundary shown here is remarkable because it is so sharp and straight. This is caused by wind. Most likely, the entire surface was once covered with the lower-albedo (darker) material that is now seen in the upper half of the image. At some later time, wind stripped away this darker material from the surfaces in the lower half of the image. The difference in albedo here might be related to composition, and possibly particle size. This picture is located near the southwest rim of Schiaparelli Basin at 5.5oS, 345.9oW. The picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  16. PLSS Townships and Sections, Sections-The data set is a polygon feature consisting of 221 polygons representing section boundaries. It was created to maintain the location of township and range sections., Published in 1995, Davis County Government.

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — PLSS Townships and Sections dataset current as of 1995. Sections-The data set is a polygon feature consisting of 221 polygons representing section boundaries. It was...

  17. boundary dissipation

    Directory of Open Access Journals (Sweden)

    Mehmet Camurdan

    1998-01-01

    are coupled by appropriate trace operators. This overall model differs from those previously studied in the literature in that the elastic chamber floor is here more realistically modeled by a hyperbolic Kirchoff equation, rather than by a parabolic Euler-Bernoulli equation with Kelvin-Voight structural damping, as in past literature. Thus, the hyperbolic/parabolic coupled system of past literature is replaced here by a hyperbolic/hyperbolic coupled model. The main result of this paper is a uniform stabilization of the coupled PDE system by a (physically appealing boundary dissipation.

  18. Frequency-resolved optical gating system with a tellurium crystal for characterizing free-electron lasers in the wavelength range of 10-30 microm.

    Science.gov (United States)

    Iijima, Hokuto; Nagai, Ryoji; Nishimori, Nobuyuki; Hajima, Ryoichi; Minehara, Eisuke J

    2009-12-01

    A second-harmonic generation frequency-resolved optical gating (SHG-FROG) system has been developed for the complete characterization of laser pulses in the wavelength range of 10-30 microm. A tellurium crystal is used so that spectrally resolved autocorrelation signals with a good signal-to-noise ratio are obtained. Pulses (wavelength approximately 22 microm) generated from a free-electron laser are measured by the SHG-FROG system. The SHG intensity profile and the spectrum obtained by FROG measurements are well consistent with those of independent measurements of the pulse length and spectrum. The pulse duration and spectral width determined from the FROG trace are 0.6 ps and 5.2 THz at full width half maximum, respectively.

  19. Z-contrast imaging and grain boundaries in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chisholm, M.F.; Pennycook, S.J.

    1996-03-01

    Interest in grain boundaries in semiconductors is linked to the application of polycrystalline semiconductors as photovoltaic and interconnect materials. In real devices such as solar cells and MOS structures as well as future devices such as flat-panel displays, the intergranular regions of the polycrystalline solid have a significant effect on the flow of electronic current. These grain boundary barriers exist because the chemical potential of the boundary atoms are shifted from the bulk value by the change in local symmetry. The chemical potential is also changed by impurities, other structural defects, and other phases in the boundary. The lack of knowledge on the atomic structure of grain boundaries is, at present, the greatest barrier to advancements in the understanding of the electrical properties of these defects. The advances of the last few years have provided the tools with which to probe these interfaces at the true atomic scale. One such tool is the high-resolution scanning transmission electron microscope installed at Oak Ridge National Laboratory (VG Microscopes HB603) that can form a 1.27 {Angstrom} electron probe. Images are formed by scanning the probe across a thin sample and using an annular detector to collect electrons scattered to high angles. Because the annular detector collects electrons scattered over a wide range of angles, phase correlation and dynamical diffraction effects are averaged by this annular integration. Thus, an image with incoherent characteristics is produced and retained to relatively large specimen thickness. The key advantage of incoherent imaging is that when the microscope is focused to produce maximum image contrast, the bright image features directly correspond to the positions of the atomic columns.

  20. A study of gunshot residue distribution for close-range shots with a silenced gun using optical and scanning electron microscopy, X-ray microanalysis and infrared spectroscopy.

    Science.gov (United States)

    Brożek-Mucha, Zuzanna

    2017-03-01

    Detailed physical and chemical analysis of gunshot residue deposited in the nearest vicinity of a submachine gun alone and with a sound suppressor was performed. The studies were inspired by recent shooting cases with the use of a firearm with a silencer and the need to estimate the shooting distance to human body naked and covered with clothing. A series of experiments were performed in the shooting range using a machine pistol and the appropriate ammunition cal. 7.65mm Browning. Targets were placed in the range of 0-30cm from the gun and covered either with white cotton fabric or a porcine skin that mocked people's clothing and the naked skin. Both the organic and inorganic residue were examined by means of optical microscopy, infrared spectrometry as well as scanning electron microscopy and energy dispersive X-ray spectrometry. The influence of factors, such as sound suppressor, shooting distance and the substrate type on the mechanism of particles spread and their availability for research was established and discussed. Copyright © 2016 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.

  1. Electronic sideband locking of 318.6nm UV laser to an ultrastable optical cavity with a wide continuously tunable range

    CERN Document Server

    Bai, Jiandong; He, Jun; Wang, Junmin

    2016-01-01

    We have demonstrated a frequency-stabilized tunable 318.6 nm ultraviolet (UV) laser system for the single-photon 6S1/2 - nP (n = 70 ~ 100) Rydberg excitation of cesium atoms. The 637.2 nm laser produced by single-pass sum frequency generation from two infrared fiber lasers is offset locked to a high-finesse ultra-low expansion (ULE) optical cavity placed in ultra-high vacuum using the electronic sideband locking technique. The generated 318.6 nm UV laser via cavity-enhanced second-harmonic generation can be continuously tuned over 4 GHz by indirectly changing modulation frequency on the electro-optic phase modulator while the whole laser system remains locked. We analyze the tuning range mainly depends on the modulator bandwidth and the tunable range of the seed laser. The locking scheme offers a method to compensate the frequency difference between the reference frequency and the goal frequency to a desired excited state, and has huge potential in precision spectroscopic experiments of cold atoms.

  2. Breaking Boundaries

    DEFF Research Database (Denmark)

    produce desperate attempts to maintain old or create new differences. Political and sociological research into these complex processes has been mainly guided by structural and normative concerns. Faced with growing evidence about the instability of world order and domestic social structures alike, policy....... As a fundamental human experience, liminality transmits cultural practices, codes, rituals, and meanings in-between aggregate structures and uncertain outcomes. As a methodological tool it is well placed to overcome disciplinary boundaries, which often direct attention to specific structures or sectors of society....... Its capacity to provide explanatory accounts of seemingly unstructured situations provides an opportunity to link experience-based and culture-oriented approaches not only to contemporary problems but also to undertake comparisons across historical periods. From a perspective of liminality...

  3. Electron Transport in a Dioxygenase-Ferredoxin Complex: Long Range Charge Coupling between the Rieske and Non-Heme Iron Center.

    Directory of Open Access Journals (Sweden)

    Wayne K Dawson

    Full Text Available Dioxygenase (dOx utilizes stereospecific oxidation on aromatic molecules; consequently, dOx has potential applications in bioremediation and stereospecific oxidation synthesis. The reactive components of dOx comprise a Rieske structure Cys2[2Fe-2S]His2 and a non-heme reactive oxygen center (ROC. Between the Rieske structure and the ROC, a universally conserved Asp residue appears to bridge the two structures forming a Rieske-Asp-ROC triad, where the Asp is known to be essential for electron transfer processes. The Rieske and ROC share hydrogen bonds with Asp through their His ligands; suggesting an ideal network for electron transfer via the carboxyl side chain of Asp. Associated with the dOx is an itinerant charge carrying protein Ferredoxin (Fdx. Depending on the specific cognate, Fdx may also possess either the Rieske structure or a related structure known as 4-Cys-[2Fe-2S] (4-Cys. In this study, we extensively explore, at different levels of theory, the behavior of the individual components (Rieske and ROC and their interaction together via the Asp using a variety of density function methods, basis sets, and a method known as Generalized Ionic Fragment Approach (GIFA that permits setting up spin configurations manually. We also report results on the 4-Cys structure for comparison. The individual optimized structures are compared with observed spectroscopic data from the Rieske, 4-Cys and ROC structures (where information is available. The separate pieces are then combined together into a large Rieske-Asp-ROC (donor/bridge/acceptor complex to estimate the overall coupling between individual components, based on changes to the partial charges. The results suggest that the partial charges are significantly altered when Asp bridges the Rieske and the ROC; hence, long range coupling through hydrogen bonding effects via the intercalated Asp bridge can drastically affect the partial charge distributions compared to the individual isolated

  4. Electron-Impact Ionization Cross Sections of H, He, N, O, Ar, Xe, Au, Pb Atoms and Their Ions in the Electron Energy Range from the Threshold up to 200 keV

    CERN Document Server

    Povyshev, V M; Shevelko, V P; Shirkov, G D; Vasina, E G; Vatulin, V V

    2001-01-01

    Single electron-impact ionization cross sections of H, He, N, O, Ar, Xe, Au, Pb atoms and their positive ions (i.e. all ionization stages) are presented in the electron energy range from the threshold up to 200 keV. The data-set for the cross sections has been created on the basis of available experimental data and calculations performed by the computer code ATOM. Consistent data for the ionization cross sections have been fitted by seven parameters using the LSM method. The accuracy of the calculated data presented is within a factor of 2 that in many cases is sufficient to solve the plasma kinetics problems. Contributions from excitation-autoionization and resonant-ionization processes as well as ionization of atoms and ions are not considered here. The results of the numerical calculations are compared with the well-known Lotz formulae for ionization of neutral atoms and positive ions. The material is illustrated by figures and includes tables of ionization cross sections, binding energies and fitting para...

  5. Mechanically induced grain boundary motion in Al-bicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Gorkaya, Tatiana; Molodov, Dmitri A.; Gottstein, Guenter [Institut fuer Metallkunde und Metallphysik der RWTH Aachen (Germany)

    2010-07-01

    The mechanically induced migration of planar grain boundaries in Al-bicrystals was experimentally measured. The novel tensile/compression module for scanning electron microscope was utilized for in-situ measurements of grain boundary motion at elevated temperatures. From the measured temperature dependence of boundary mobility the migration activation parameters for investigated boundaries were determined. Normal boundary motion was observed to be coupled to a shear of the crystal in the region traversed by the grain boundary during its motion. The measured ratios of the normal grain boundary motion to the lateral translation of grains were compared with geometrical models of stress induced boundary migration.

  6. VUV photoionization of acetamide studied by electron/ion coincidence spectroscopy in the 8-24 eV photon energy range

    Energy Technology Data Exchange (ETDEWEB)

    Schwell, Martin, E-mail: Martin.Schwell@lisa.u-pec.fr [LISA UMR CNRS 7583, Universite Paris Est Creteil and Universite Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du General de Gaulle, 94010 Creteil (France); Benilan, Yves; Fray, Nicolas; Gazeau, Marie-Claire; Es-Sebbar, Et. [LISA UMR CNRS 7583, Universite Paris Est Creteil and Universite Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du General de Gaulle, 94010 Creteil (France); Garcia, Gustavo A.; Nahon, Laurent [Synchrotron SOLEIL, L' Orme des Merisiers, St. Aubin, B.P. 48, 91192 Gif-sur-Yvette Cedex (France); Champion, Norbert [LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon (France); Leach, Sydney, E-mail: Sydney.Leach@obspm.fr [LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon (France)

    2012-01-17

    Highlights: Black-Right-Pointing-Pointer We study the VUV photoionization of acetamide in the 8-24 eV photon energy range. Black-Right-Pointing-Pointer Electron/ion coincidence measurements are performed using synchrotron radiation. Black-Right-Pointing-Pointer The adiabatic ionization energy of acetamide is determined by TPEPICO measurements. Black-Right-Pointing-Pointer VUV induced fragmentation pathways of acetamide are assigned and discussed. - Abstract: A VUV photoionization study of acetamide was carried out over the 8-24 eV photon energy range using synchrotron radiation and photoelectron/photoion coincidence (PEPICO) spectroscopy. Threshold photoelectron photoion coincidence (TPEPICO) measurements were also made. Photoion yield curves and branching ratios were measured for the parent ion and six fragment ions. The adiabatic ionization energy of acetamide was determined as I.E. (1{sup 2}A Prime ) = (9.71 {+-} 0.02) eV, in agreement with an earlier reported photoionization mass spectrometry (PIMS) value. The adiabatic energy of the first excited state of the ion, 1{sup 2}A Double-Prime , was determined to be Almost-Equal-To 10.1 eV. Assignments of the fragment ions and the pathways of their formation by dissociative photoionization were made. The neutral species lost in the principal dissociative photoionization processes are CH{sub 3}, NH{sub 2}, NH{sub 3}, CO, HCCO and NH{sub 2}CO. Heats of formation are derived for all ions detected and are compared with literature values. Some astrophysical implications of these results are discussed.

  7. Electron spin resonance studies of Bi1-xScxFeO3 nanoparticulates: Observation of an enhanced spin canting over a large temperature range

    Science.gov (United States)

    Titus, S.; Balakumar, S.; Sakar, M.; Das, J.; Srinivasu, V. V.

    2017-12-01

    Bi1-xScxFeO3 (x = 0.0, 0.1, 0.15, 0.25) nano particles were synthesized by sol gel method. We then probed the spin system in these nano particles using electron spin resonance technique. Our ESR results strongly suggest the scenario of modified spin canted structures. Spin canting parameter Δg/g as a function of temperature for Scandium doped BFO is qualitatively different from undoped BFO. A broad peak is observed for all the Scandium doped BFO samples and an enhanced spin canting over a large temperature range (75-210 K) in the case of x = 0.15 doping. We also showed that the asymmetry parameter and thereby the magneto-crystalline anisotropy in these BSFO nanoparticles show peaks around 230 K for (x = 0.10 and 0.15) and beyond 300 K for x = 0.25 system. Thus, we established that the Sc doping significantly modifies the spin canting and magneto crystalline anisotropy in the BFO system.

  8. Calibration of the Modulation Transfer Function of Surface Profilometers with Binary Pseudorandom Test Standards: Expanding the Application Range to Fizeau Interferometers and Electron Microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Yashchuk, V.V.; Takacs, P.; Anderson, E.H.; Barber, S.K.; Bouet, N.; Cambie, R.; Conley, R.; McKinney, W.R.; Voronov, D.L.

    2011-09-16

    A modulation transfer function (MTF) calibration method based on binary pseudorandom (BPR) gratings and arrays has been proven to be an effective MTF calibration method for interferometric microscopes and a scatterometer. Here we report on a further expansion of the application range of the method. We describe the MTF calibration of a 6 in. phase shifting Fizeau interferometer. Beyond providing a direct measurement of the interferometer's MTF, tests with a BPR array surface have revealed an asymmetry in the instrument's data processing algorithm that fundamentally limits its bandwidth. Moreover, the tests have illustrated the effects of the instrument's detrending and filtering procedures on power spectral density measurements. The details of the development of a BPR test sample suitable for calibration of scanning and transmission electron microscopes are also presented. Such a test sample is realized as a multilayer structure with the layer thicknesses of two materials corresponding to the BPR sequence. The investigations confirm the universal character of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.

  9. Origin of the low grain boundary conductivity in lithium ion conducting perovskites: Li3xLa0.67-xTiO3.

    Science.gov (United States)

    Wu, Jian-Fang; Guo, Xin

    2017-02-22

    Although the bulk conductivity of lithium ion conducting Li3xLa0.67-xTiO3 electrolytes reaches the level of 10-3 S cm-1, the grain boundary conductivity is orders of magnitude lower; the origin of the low grain boundary conductivity should be thoroughly understood as a prerequisite to improve the overall conductivity. Samples with grain sizes ranging from 25 nm to 3.11 μm were prepared. According to SEM and TEM investigations, the grain boundaries are free of any second phase; however, the grain boundary conductivity is still ∼4 orders of magnitude lower than the bulk conductivity. The grain boundary conductivity decreases with decreasing grain size, indicating that the low grain boundary conductivity is not dominated only by the crystallographic grain boundary. Since electrons are attracted to the grain boundaries, as reflected by the dramatically enhanced grain boundary conductivity when electrons are introduced, the grain boundary core in Li3xLa0.67-xTiO3 should be positively charged, causing the depletion of lithium ions in the adjacent space-charge layers. The very low grain boundary conductivity can be accounted for by the lithium ion depletion in the space-charge layer.

  10. Technology for Boundaries

    DEFF Research Database (Denmark)

    Bødker, Susanne; Kristensen, Jannie Friis; Nielsen, Christina

    2003-01-01

    This paper presents a study of an organisation, which is undergoing a process transforming organisational and technological boundaries. In particular, we shall look at three kinds of boundaries: the work to maintain and change the boundary between the organisation and its customers; boundaries.......After analysing the history and the current boundary work, the paper will propose new technological support for boundary work. In particular the paper will suggest means of supporting boundaries when these are productive and for changing boundaries when this seems more appropriate. In total, flexible technologies...... seem a core issue when dealing with technology for boundaries....

  11. Quantitative Characterization of Boundary Roughness in Metals

    DEFF Research Database (Denmark)

    Sun, Jun

    The boundary migration during recrystallization is by nature a heterogeneous process and local structural variations form on recrystallization boundaries, as revealed from modern techniques such as synchrotron X-rays and advanced electron microscopy. The local structural variations, in the form...... of protrusions and retrusions, can provide a dragging/driving force due to the local boundary curvature and affect the further migration of recrystallization boundaries through the deformed matrix. In order to develop new understandings and models for boundary migration that take the heterogeneous local...... structural aspects into account, a detailed characterization is essential of partly recrystallized microstructures focusing on the local shapes of the boundaries, in particular on whether protrusions and retrusions are formed or not. Quantification of the “amount” of boundary roughness in the form...

  12. Grain boundaries in high temperature superconductors

    NARCIS (Netherlands)

    Hilgenkamp, Johannes W.M.; Mannhart, J.

    2002-01-01

    Since the first days of high-Tc superconductivity, the materials science and the physics of grain boundaries in superconducting compounds have developed into fascinating fields of research. Unique electronic properties, different from those of the grain boundaries in conventional metallic

  13. Plasma boundaries at Mars: a 3-D simulation study

    Directory of Open Access Journals (Sweden)

    A. Bößwetter

    2004-12-01

    Full Text Available The interaction of the solar wind with the ionosphere of planet Mars is studied using a three-dimensional hybrid model. Mars has only a weak intrinsic magnetic field, and consequently its ionosphere is directly affected by the solar wind. The gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the interaction region. Different boundaries emerge from the interaction of the solar wind with the continuously produced ionospheric heavy-ion plasma, which could be identified as a bow shock (BS, ion composition boundary (ICB and magnetic pile up boundary (MPB, where the latter both turn out to coincide. The simulation results regarding the shape and position of these boundaries are in good agreement with the measurements made by Phobos-2 and MGS spacecraft. It is shown that the positions of these boundaries depend essentially on the ionospheric production rate, the solar wind ram pressure, and the often unconsidered electron temperature of the ionospheric heavy ion plasma. Other consequences are rays of planetary plasma in the tail and heavy ion plasma clouds, which are stripped off from the dayside ICB region by some instability.

    Key words. Magnetospheric physics (solar wind interactions with unmagnetized bodies – Space plasma physics (discontinuities; numerical simulation studies

  14. Plasma boundaries at Mars: a 3-D simulation study

    Directory of Open Access Journals (Sweden)

    A. Bößwetter

    2004-12-01

    Full Text Available The interaction of the solar wind with the ionosphere of planet Mars is studied using a three-dimensional hybrid model. Mars has only a weak intrinsic magnetic field, and consequently its ionosphere is directly affected by the solar wind. The gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the interaction region. Different boundaries emerge from the interaction of the solar wind with the continuously produced ionospheric heavy-ion plasma, which could be identified as a bow shock (BS, ion composition boundary (ICB and magnetic pile up boundary (MPB, where the latter both turn out to coincide. The simulation results regarding the shape and position of these boundaries are in good agreement with the measurements made by Phobos-2 and MGS spacecraft. It is shown that the positions of these boundaries depend essentially on the ionospheric production rate, the solar wind ram pressure, and the often unconsidered electron temperature of the ionospheric heavy ion plasma. Other consequences are rays of planetary plasma in the tail and heavy ion plasma clouds, which are stripped off from the dayside ICB region by some instability. Key words. Magnetospheric physics (solar wind interactions with unmagnetized bodies – Space plasma physics (discontinuities; numerical simulation studies

  15. Grain boundary melting in ice

    Science.gov (United States)

    Thomson, E. S.; Hansen-Goos, Hendrik; Wettlaufer, J. S.; Wilen, L. A.

    2013-03-01

    We describe an optical scattering study of grain boundary premelting in water ice. Ubiquitous long ranged attractive polarization forces act to suppress grain boundary melting whereas repulsive forces originating in screened Coulomb interactions and classical colligative effects enhance it. The liquid enhancing effects can be manipulated by adding dopant ions to the system. For all measured grain boundaries this leads to increasing premelted film thickness with increasing electrolyte concentration. Although we understand that the interfacial surface charge densities qs and solute concentrations can potentially dominate the film thickness, we cannot directly measure them within a given grain boundary. Therefore, as a framework for interpreting the data we consider two appropriate qs dependent limits; one is dominated by the colligative effect and other is dominated by electrostatic interactions.

  16. Total electron scattering cross sections of molecules containing H, C, N, O and F in the energy range 0.2–6.0 keV

    Energy Technology Data Exchange (ETDEWEB)

    Gurung, Meera Devi; Ariyasinghe, W.M., E-mail: wickram_ariyasinghe@baylor.edu

    2017-03-15

    Based on the effective atomic total electron scattering cross sections (EATCS) of atoms in a molecular environment, a simple model is proposed to predict the total electron scattering cross sections (TCS) of H, C, N, O, and F containing molecules. The EATCS for these five atoms are reported for 0.2–6.0 keV energies. The predicted TCS by this model are compared with experimental TCS in the literature. The experimental TCS of CHF{sub 3}, C{sub 2}F{sub 4}, C{sub 2}F{sub 2}H{sub 2}, C{sub 4}F{sub 6}, and c-C{sub 4}F{sub 8} have been obtained for 0.2–4.5 keV electrons by measuring the attenuation of the electron beam through a gas cell.

  17. Structure and properties of grain boundaries. Progress report, 15 July 1983-14 July 1984

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1984-03-01

    Results were obtained in the following areas: determination of relative grain boundary energies by the rotating crystallite method; simple structural unit model for core-dependent properties of tilt boundaries; twist boundary energies for metals with long-ranged pairwise interatomic potentials; structural unit/grain boundary dislocation model for grain boundary structure; detection of expansion of boundaries using diffraction; effect of secondary relaxations on diffraction from high-..sigma.. (001) twist boundaries; and mechanism of grain boundary migration.

  18. Attempts to improve the fatigue characteristics of the austenitic steel X5CrNi18-10 in the temperature range of 25-600 C by mechanical boundary layer hardening; Zur Verbesserung des Ermuedungsverhaltens des austenitischen Stahls X5CrNi18-10 im Temperaturbereich 25-600 C durch mechanische Randschichtverfestigungsverfahren

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, Ivan

    2007-01-31

    Pieces of the austenitic steel X5CrNi18-10 whose boundary layers had been hardened by different methods were investigated with a view to their fatigue deformation characteristics in the temperature range of 25-600 degC. Parallel to this, microstructural and X-ray analyses provided deeper understanding of fatigue deformation. The microstructure was characterized, among others, by TEM. Boundary layers were solidified by rolling, by a combination of mechanical and thermal processes, by high-temperature rolling, and by laser shock solidification. The analyses focused on microstructural processes and on the intrinsic stress stability and provided important information on the fabrication of structural components with optimised life. (orig.)

  19. Electron transport simulation in the range 1 keV-4 MeV for the purpose of high-resolution dosimetric application

    Energy Technology Data Exchange (ETDEWEB)

    Cobut, V. [Univ. de Cergy-Pontoise, Neuville/Oise (France). Lab. Pharmacophores Redox, Phytochimie et Radiobiologie; Cirioni, L.; Patau, J.P. [Univ. Paul Sabatier, Toulouse (France). Faculte de Pharmacie

    2001-07-01

    Experimental spectrometry and dosimetry can offer some reliable answers. However, they are not easy to implement in some specific situations. Furthermore, information on dose distributions cannot always be obtained with the desirable geometrical resolution. A way to get rid of these disadvantages consist in simulating every successive individual interactions suffered by electrons and photons along their path. We applied this principle to simulate the response of a detector placed in the field of beta-gamma sources, which maximum energy does not exceed 4 MeV. A part of this work is presented here, which concerns Monte Carlo simulation of electron transport in materials encountered in experimental dosimetric devices. Electrons were followed down to a cutoff energy of 1 keV. (orig.)

  20. Total cross sections for electron scattering by 1-propanol at impact energies in the range 40-500 eV

    Science.gov (United States)

    da Silva, D. G. M.; Gomes, M.; Ghosh, S.; Silva, I. F. L.; Pires, W. A. D.; Jones, D. B.; Blanco, F.; Garcia, G.; Buckman, S. J.; Brunger, M. J.; Lopes, M. C. A.

    2017-11-01

    Absolute total cross section (TCS) measurements for electron scattering from 1-propanol molecules are reported for impact energies from 40 to 500 eV. These measurements were obtained using a new apparatus developed at Juiz de Fora Federal University—Brazil, which is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the molecules to be studied at a given pressure. Besides these experimental measurements, we have also calculated TCS using the Independent-Atom Model with Screening Corrected Additivity Rule and Interference (IAM-SCAR+I) approach with the level of agreement between them being typically found to be very good.

  1. On Boundaries in Linguistic Continua.

    Science.gov (United States)

    Jorgensen, J. Normann; Kristensen, Kjeld

    1995-01-01

    Discusses the notion of regional standards of a language with regard to modern Danish. Regional and national standards of a language as well as local dialect are defined. The article shows that, for a geographical entity, a statistically determined boundary can be established in the range between the extremes of a regional dialect and national…

  2. The boundary-scan handbook

    CERN Document Server

    Parker, Kenneth P

    2016-01-01

    Aimed at electronics industry professionals, this 4th edition of the Boundary Scan Handbook describes recent changes to the IEEE1149.1 Standard Test Access Port and Boundary-Scan Architecture. This updated edition features new chapters on the possible effects of the changes on the work of the practicing test engineers and the new 1149.8.1 standard. Anyone needing to understand the basics of boundary scan and its practical industrial implementation will need this book. Provides an overview of the recent changes to the 1149.1 standard and the effect of the changes on the work of test engineers;   Explains the new IEEE 1149.8.1 subsidiary standard and applications;   Describes the latest updates on the supplementary IEEE testing standards. In particular, addresses: IEEE Std 1149.1                      Digital Boundary-Scan IEEE Std 1149.4                      Analog Boundary-Scan IEEE Std 1149.6                      Advanced I/O Testing IEEE Std 1149.8.1           �...

  3. About the creation of proton-antiproton pair at electron-positron collider in the energy range of ψ(3770) mass

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadov, A.I., E-mail: ahmadov@theor.jinr.ru [Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation); Institute of Physics, Azerbaijan National Academy of Science, Baku (Azerbaijan); Bystritskiy, Yu.M., E-mail: bystr@theor.jinr.ru [Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation); Kuraev, E.A. [Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation); Wang, P., E-mail: wangp@ihep.ac.cn [Institute of High Energy Physic, Chinese Academy of Science (China)

    2014-11-15

    The process of electron-positron annihilation into proton-antiproton pair is considered within the vicinity of ψ(3770) resonance. The interference between the pure electromagnetic intermediate state and the ψ(3770) state is evaluated. It is shown that this interference is destructive and the relative phase between these two contributions is large (ϕ{sub 0}≈250°)

  4. Reticle level compensation for long range effects

    Science.gov (United States)

    Figueiro, Thiago; Browning, Clyde; Thornton, Martin J.; Vannufel, Cyril; Schiavone, Patrick

    2013-03-01

    Proximity Effects in electron beam lithography impact feature dimensions, pattern fidelity and uniformity. Electron scattering effects are commonly addressed using a mathematical model representing the radial exposure intensity distribution induced by a point electron source, commonly named Point Spread Function (PSF). PSF models are usually employed for correcting "short-range" and "long-range" backscattering effects up to 10μm to 15μm. It is well known that there are also some process related phenomena impacting pattern uniformity that have a wider range (fogging, chemical mechanical polishing -CMP- effects, etc.) which impacts up to a few millimeters or more. There are a number of commercial strategies for mitigating such long range effects based on data density. However, those traditional ones are usually performed within a single chip on a reticle field and ignore the presence of adjacent fields, neglecting their influence. Full field reticles can contain several different designs or arrayed chips in a multitude of layout placements. Reticle level jobdeck placing each design at specific sites, independent of each other can be used to account for the density of each pattern that has a relative impact on its neighbors, even if they are several millimeters away from offending data. Therefore, full field density analysis accounting for scribe frames and all neighboring patterns is required for reaching fidelity control requirements such as critical dimension (CD) and line end shortening (LES) on the full plate. This paper describes a technique to compensate long range effects going across chip boundaries to the full reticle exposure field. The extreme long range effects are also represented with a model that is calibrated according to the characteristics of the user's process. Data correction can be based on dose and geometry modulation. Uniform pattern dimensional control matching the user's specific process long range variability can be achieved with the

  5. Boundary layer thickness effect on boattail drag

    Science.gov (United States)

    Blaha, B. J.; Chamberlain, R.; Bober, L. J.

    1976-01-01

    A combined experimental and analytical program was conducted to investigate the effects of boundary layer changes on the flow over high angle boattail nozzles. The tests were run on an isolated axisymmetric sting mounted model. Various boattail geometries were investigated at high subsonic speeds over a range of boundary layer thicknesses. In general, boundary layer effects were small at speeds up to Mach 0.8. However, at higher speeds significant regions of separated flow were present on the boattail. When separation was present large reductions in boattail drag resulted with increasing boundary layer thickness. The analysis predicts both of these trends.

  6. Dimension of Fractal Basin Boundaries.

    Science.gov (United States)

    Park, Bae-Sig

    In many dynamical systems, multiple attractors coexist for certain parameter ranges. The set of initial conditions that asymptotically approach each attractor is its basin of attraction. These basins can be intertwined on arbitrary small scales. Basin boundary can be either smooth or fractal. Dynamical systems that have fractal basin boundary show "final state sensitivity" of the initial conditions. A measure of this sensitivity (uncertainty exponent alpha) is related to the dimension of the basin boundary d = D - alpha , where D is the dimension of the phase space and d is the dimension of the basin boundary. At metamorphosis values of the parameter, there might happen a conversion from smooth to fractal basin boundary (smooth-fractal metamorphosis) or a conversion from fractal to another fractal basin boundary characteristically different from the previous fractal one (fractal-fractal metamorphosis). The dimension changes continuously with the parameter except at the metamorphosis values where the dimension of the basin boundary jumps discontinuously. We chose the Henon map and the forced damped pendulum to investigate this. Scaling of the basin volumes near the metamorphosis values of the parameter is also being studied for the Henon map. Observations are explained analytically by using low dimensional model map. We look for universal scalings of the dimension of fractal basin boundaries near type I and type III intermittency transitions to chaos. Type I intermittency can occur as the system experiences a saddle-node (tangent) bifurcation and type III intermittency can occur as the system experiences an inverted period doubling bifurcation. At these bifurcations, multiple attractors with fractal basin boundaries can be created. It is found the dimension scales, with the parameter, according to the power law d = d_{o } - k| p - p_{c}| ^{beta} with beta = 1/2, where p is the system parameter, p _{c} is the bifurcation value, k is a scaling constant, and d_{o} is

  7. State Agency Administrative Boundaries

    Data.gov (United States)

    Kansas Data Access and Support Center — This database comprises 28 State agency boundaries and point of contact. The Kansas Geological Survey collected legal descriptions of the boundaries for various...

  8. Allegheny County Municipal Boundaries

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset demarcates the municipal boundaries in Allegheny County. Data was created to portray the boundaries of the 130 Municipalities in Allegheny County the...

  9. HUD GIS Boundary Files

    Data.gov (United States)

    Department of Housing and Urban Development — The HUD GIS Boundary Files are intended to supplement boundary files available from the U.S. Census Bureau. The files are for community planners interested in...

  10. Political State Boundary (National)

    Data.gov (United States)

    Department of Transportation — State boundaries with political limit - boundaries extending into the ocean (NTAD). The TIGER/Line Files are shapefiles and related database files (.dbf) that are an...

  11. Experimental investigation of wave boundary layer

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu

    2003-01-01

    A review is presented of experimental investigation of wave boundary layer. The review is organized in six main sections. The first section describes the wave boundary layer in a real-life environment and its simulation in the laboratory in an oscillating water tunnel and in a water tank...... with an oscillating seabed. A brief account is given of measured quantities, measurement techniques (LDA, PIV, flow visualization) and limitations/constraints in the experimental investigation of the wave boundary layer in the laboratory. The second section concentrates on uniform oscillating boundary layers...... with a smooth bed. The boundary layer process is described over the entire range of the Reynolds number (Re from practically nil to Re = O(107)), from the laminar regime to the transitional regime and to the fully developed turbulent regime. The third section focuses on the effect of the boundary roughness...

  12. Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions. Part I: recombination and {delta}-electrons

    Energy Technology Data Exchange (ETDEWEB)

    Parlog, M.; Borderie, B. E-mail: borderie@ipno.in2p3.fr; Rivet, M.F.; Tabacaru, G.; Chbihi, A.; Elouardi, M.; Le Neindre, N.; Lopez, O.; Plagnol, E.; Tassan-Got, L.; Auger, G.; Bacri, Ch.O.; Bellaize, N.; Bocage, F.; Bougault, R.; Bouriquet, B.; Brou, R.; Buchet, P.; Charvet, J.L.; Colin, J.; Cussol, D.; Dayras, R.; Demeyer, A.; Dore, D.; Durand, D.; Frankland, J.D.; Galichet, E.; Genouin-Duhamel, E.; Gerlic, E.; Hudan, S.; Guinet, D.; Lautesse, P.; Lavaud, F.; Laville, J.L.; Lecolley, J.F.; Leduc, C.; Legrain, R.; Louvel, M.; Maskay, A.M.; Nalpas, L.; Normand, J.; Peter, J.; Rosato, E.; Saint-Laurent, F.; Steckmeyer, J.C.; Tamain, B.; Tirel, O.; Vient, E.; Volant, C.; Wieleczko, J.P

    2002-04-21

    A simple formalism describing the light response of CsI(Tl) to heavy ions, which quantifies the luminescence and the quenching in terms of the competition between radiative transitions following the carrier trapping at the Tl activator sites and the electron-hole recombination, is proposed. The effect of the {delta}-rays on the scintillation efficiency is for the first time quantitatively included in a fully consistent way. The light output expression depends on four parameters determined by a procedure of global fit to experimental data.

  13. Long-range interfacial electron transfer and electrocatalysis of molecular scale Prussian Blue nanoparticles linked to Au(111)-electrode surfaces by different chemical contacting groups

    DEFF Research Database (Denmark)

    Zhu, Nan; Ulstrup, Jens; Chi, Qijin

    2017-01-01

    We have explored interfacial electrochemical electron transfer (ET) and electrocatalysis of 5–6 nm Prussian Blue nanoparticles (PBNPs) immobilized on Au(111)-electrode surfaces via molecular wiring with variable-length, and differently functionalized thiol-based self-assembled molecular monolayers...... forming linker molecules. The interfacial ET rate constants were found to depend exponentially on the ET distance for distances longer than a few methylene groups in the chain, with decay factors (β) of 0.9, 1.1, and 1.3 per CH2, for SAMs terminated by −NH3+,–COO–, and–CH3, respectively. This feature...

  14. The peculiarity of the construction of an optical-electronic system for measurement of geometrical parameters of objects in the micrometer range

    Science.gov (United States)

    Markina, Olga M.; Markin, Maksym O.; Filippova, Maryna V.; Harasim, Damian; Mussabekov, Kanat; Annabayev, Azamat

    2017-08-01

    The optical-electronic system for measuring of geometrical parameters of micrometrical objects is a difficult process that requires the observance of certain features designing or improvement. The observance of that will provide a higher measurement accuracy compared with the accuracy metrics of measurement that were developed without compliance with these design features. Every feature of the design reduces the error of the functioning of individual nodes of the system or errors in nodes under the influence of various internal or external factors. When reducing or eliminating each factor of occurrence of the error, respectively, will increase the overall measurement accuracy. In this work, the result of introducing measurement error for each factor is determined experimentally and proved the correctness of such actions. Experimental researches of the measurement error to the stage of compliance with subtleties in the improvement of the opto-electronic system was 10 ± 1.5 μm, and after improvement with considering of the specifics of the design measurement error of geometrical parameters was 10 ± 0,33 μm.

  15. Two-band electronic metal and neighboring spin liquid (spin Bose-metal) on a zigzag strip with longer-ranged repulsion

    Science.gov (United States)

    Lai, Hsin-Hua; Motrunich, Olexei I.

    2010-03-01

    We consider an electronic model for realizing the Spin Bose-metal (SBM) phase on a 2-leg triangular strip -- a spin liquid phase found by D. N. Sheng et al. [Phys. Rev. B 79, 205112 (2009)] in a spin-1/2 model with ring exchanges. Starting from a two-band ``C2S2'' metal, the SBM can be viewed as a ``C1S2'' Mott insulator with gapped overall conducting charge mode. We consider extended repulsive interactions motivated by the ab initio derivation of an electronic model for κ-ET spin liquid material [K. Nakamura et al., J. Phys. Soc. Jpn. 78, 083710(2009)]. Using weak coupling renormalization group analysis, we find that such interactions allow much wider C2S2 metallic phase than in the Hubbard model with on-site repulsion only. We identify a valid eight-fermion Umklapp term that is crucial for producing a Mott insulator and use Bosonization to study phases obtained out of the C2S2 metal upon increasing overall repulsion strength, finding that the SBM phase is a natural outcome for extended interactions.

  16. Studies on effective atomic numbers for photon energy absorption and electron density of some narcotic drugs in the energy range 1 keV-20 MeV

    Science.gov (United States)

    Gounhalli, Shivraj G.; Shantappa, Anil; Hanagodimath, S. M.

    2013-04-01

    Effective atomic numbers for photon energy absorption ZPEA,eff, photon interaction ZPI,eff and for electron density Nel, have been calculated by a direct method in the photon-energy region from 1 keV to 20 MeV for narcotic drugs, such as Heroin (H), Cocaine (CO), Caffeine (CA), Tetrahydrocannabinol (THC), Cannabinol (CBD), Tetrahydrocannabivarin (THCV). The ZPEA,eff, ZPI,eff and Nel values have been found to change with energy and composition of the narcotic drugs. The energy dependence ZPEA,eff, ZPI,eff and Nel is shown graphically. The maximum difference between the values of ZPEA,eff, and ZPI,eff occurs at 30 keV and the significant difference of 2 to 33% for the energy region 5-100 keV for all drugs. The reason for these differences is discussed.

  17. Design of High Dynamic Range Digital to Analog Converters for the Calibration of the CALICE Si-W Ecal readout electronics

    CERN Document Server

    Gallin-Martel, L; Hostachy, J Y; Rarbi, F; Rossetto, O

    2009-01-01

    The ILC ECAL front-end chip will integrate many functions of the readout electronics including a DAC dedicated to calibration. We present two versions of DAC with respectively 12 and 14 bits, designed in a CMOS 0.35μm process. Both are based on segmented arrays of switched capacitors controlled by a Dynamic Element Matching (DEM) algorithm. A full differential architecture is used, and the amplifiers can be turned into a standby mode reducing the power dissipation. The 12 bit DAC features an INL lower than 0.3 LSB at 5MHz, and dissipates less than 7mW. The 14 bit DAC is an improved version of the 12 bit design.

  18. The electron spectro-microscopy beamline at National Synchrotron Light Source II: a wide photon energy range, micro-focusing beamline for photoelectron spectro-microscopies.

    Science.gov (United States)

    Reininger, R; Hulbert, S L; Johnson, P D; Sadowski, J T; Starr, D E; Chubar, O; Valla, T; Vescovo, E

    2012-02-01

    A comprehensive optical design for a high-resolution, high-flux, wide-energy range, micro-focused beamline working in the vacuum ultraviolet and soft x-ray photon energy range is proposed. The beamline is to provide monochromatic radiation to three photoelectron microscopes: a full-field x-ray photoelectron emission microscope and two scanning instruments, one dedicated to angle resolved photoemission spectroscopy (μ-ARPES) and one for ambient pressure x-ray photoelectron spectroscopy and scanning photoelectron microscopy (AP-XPS/SPEM). Microfocusing is achieved with state of the art elliptical cylinders, obtaining a spot size of 1 μm for ARPES and 0.5 μm for AP-XPS/SPEM. A detailed ray tracing analysis quantitatively evaluates the overall beamline performances.

  19. Twin boundaries in d-wave superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Feder, D.L.; Beardsall, A.; Berlinsky, A.J.; Kallin, C. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)

    1997-09-01

    Twin boundaries in orthorhombic d-wave superconductors are investigated numerically using the Bogoliubov{endash}deGennes formalism within the context of an extended Hubbard model. The twin boundaries are represented by tetragonal regions of variable width, with a reduced chemical potential. For sufficiently large twin boundary width and change in chemical potential, an induced s-wave component may break time-reversal symmetry at a low temperature T{sup {asterisk}}. The temperature T{sup {asterisk}}, and the magnitude of the imaginary component, are found to depend strongly on electron density. The results are compared with recent tunneling measurements. {copyright} {ital 1997} {ital The American Physical Society}

  20. SNOWY RANGE WILDERNESS, WYOMING.

    Science.gov (United States)

    Houston, Robert S.; Bigsby, Philip R.

    1984-01-01

    A mineral survey of the Snowy Range Wilderness in Wyoming was undertaken and was followed up with more detailed geologic and geochemical surveys, culminating in diamond drilling of one hole in the Snowy Range Wilderness. No mineral deposits were identified in the Snowy Range Wilderness, but inasmuch as low-grade uranium and associated gold resources were identified in rocks similar to those of the northern Snowy Range Wilderness in an area about 5 mi northeast of the wilderness boundary, the authors conclude that the northern half of the wilderness has a probable-resource potential for uranium and gold. Closely spaced drilling would be required to completely evaluate this mineral potential. The geologic terrane precludes the occurrence of fossil fuels.

  1. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.

  2. Electronic spectrum in the visible frequency range of UF/sub 4/ molecules isolated in solid neon, and its interpretation in the crystal-field approximation

    Energy Technology Data Exchange (ETDEWEB)

    Belyaeva, A.A.; Golubev, Y.M.

    1987-09-01

    The matrix isolation method is used to obtain the spectra of molecules in solid neon in the 1000--400-nm range. All the recorded bands are referred to transitions within the 5f /sup 2/ configuration of U/sup 4 +/ ion in the field of four fluorine ions. The interpretation assumes the case of a weak crystal field in which the terms of U/sup 4 +/ ion with different J are not mixed up. It is concluded that the UF/sub 3/ molecule has the structure of either a tetrahedron or a slightly distorted tetrahedron.

  3. Detonation Shock Dynamics Modelling with Arbitrary Boundaries

    Science.gov (United States)

    Hodgson, Alexander

    2017-06-01

    The Detonation Shock Dynamics (DSD) model can be used to predict detonation wave propagation in a high explosive (HE). The detonation wave is prescribed a velocity that depends on its curvature. Additionally, the angle between the wave and the HE boundary may not exceed a specified ``boundary angle'', the value of which depends on the HE and its confining material(s). The level-set method is commonly used to drive DSD computation. Boundary conditions are applied to the level-set field at the charge edges to maintain the explosive boundary angle criteria. The position of the boundary must be accurate and continuous across adjacent cells to achieve accurate and robust results. This is mainly an issue for mixed material meshes where the boundary does not coincide with the cell boundaries. For such meshes, a set of volume fractions defines the amount of material in each cell. The boundary is defined implicitly by the volume fractions, and must be reconstructed to an explicit form for use in DSD. This work describes a novel synthesis of the level-set method and simulated annealing, an optimisation method used to reconstruct the boundary. The accuracy and robustness of the resulting DSD calculation are evaluated with a range of test problems.

  4. Characterizations of boundary pluripolar hulls

    NARCIS (Netherlands)

    Djire, I.K.; Wiegerinck, J.

    2016-01-01

    We present some basic properties of the so-called boundary relative extremal function and discuss boundary pluripolar sets and boundary pluripolar hulls. We show that for B-regular domains the boundary pluripolar hull is always trivial on the boundary of the domain and present a “boundary version”

  5. Surface and grain boundary scattering in nanometric Cu thin films: A quantitative analysis including twin boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Barmak, Katayun [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 and Department of Materials Science and Engineering and Materials Research Science and Engineering Center, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Darbal, Amith [Department of Materials Science and Engineering and Materials Research Science and Engineering Center, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Ganesh, Kameswaran J.; Ferreira, Paulo J. [Materials Science and Engineering, The University of Texas at Austin, 1 University Station, Austin, Texas 78712 (United States); Rickman, Jeffrey M. [Department of Materials Science and Engineering and Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015 (United States); Sun, Tik; Yao, Bo; Warren, Andrew P.; Coffey, Kevin R., E-mail: kb2612@columbia.edu [Department of Materials Science and Engineering, University of Central Florida, 4000 Central Florida Boulevard, Orlando, Florida 32816 (United States)

    2014-11-01

    The relative contributions of various defects to the measured resistivity in nanocrystalline Cu were investigated, including a quantitative account of twin-boundary scattering. It has been difficult to quantitatively assess the impact twin boundary scattering has on the classical size effect of electrical resistivity, due to limitations in characterizing twin boundaries in nanocrystalline Cu. In this study, crystal orientation maps of nanocrystalline Cu films were obtained via precession-assisted electron diffraction in the transmission electron microscope. These orientation images were used to characterize grain boundaries and to measure the average grain size of a microstructure, with and without considering twin boundaries. The results of these studies indicate that the contribution from grain-boundary scattering is the dominant factor (as compared to surface scattering) leading to enhanced resistivity. The resistivity data can be well-described by the combined Fuchs–Sondheimer surface scattering model and Mayadas–Shatzkes grain-boundary scattering model using Matthiessen's rule with a surface specularity coefficient of p = 0.48 and a grain-boundary reflection coefficient of R = 0.26.

  6. Grain Boundary Complexions

    Science.gov (United States)

    2014-05-01

    deter- mine bulk materials behavior and properties such as superplasticity, creep, fatigue, corrosion , strength and conductivity [2]. Grain boundary...interface (i.e. lattice mismatch accommodated by interface dislocations ), wetting transitions will not occur. A wetting transition is possible in the case...melting only starts around dislocations at low- angle grain boundaries; the grain boundary structure con- sists of isolated liquid pools separated by

  7. Stable Boundary Layer Issues

    OpenAIRE

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The development of robust stable boundary layer parameterizations for use in NWP and climate models is hampered by the multiplicity of processes and their unknown interactions. As a result, these models suffer ...

  8. VUV photoionization of acetamide studied by electron/ion coincidence spectroscopy in the 8-24 eV photon energy range

    KAUST Repository

    Schwell, Martin

    2012-01-01

    A VUV photoionization study of acetamide was carried out over the 8-24 eV photon energy range using synchrotron radiation and photoelectron/photoion coincidence (PEPICO) spectroscopy. Threshold photoelectron photoion coincidence (TPEPICO) measurements were also made. Photoion yield curves and branching ratios were measured for the parent ion and six fragment ions. The adiabatic ionization energy of acetamide was determined as I.E. (1 2A′) = (9.71 ± 0.02) eV, in agreement with an earlier reported photoionization mass spectrometry (PIMS) value. The adiabatic energy of the first excited state of the ion, 1 2A″, was determined to be ≈10.1 eV. Assignments of the fragment ions and the pathways of their formation by dissociative photoionization were made. The neutral species lost in the principal dissociative photoionization processes are CH 3, NH 2, NH 3, CO, HCCO and NH 2CO. Heats of formation are derived for all ions detected and are compared with literature values. Some astrophysical implications of these results are discussed. © 2011 Elsevier B.V. All rights reserved.

  9. Energy loss, range, and bremsstrahlung yield for 10-keV to 100-MeV electrons in various elements and chemical compounds

    Science.gov (United States)

    Pages, Lucien; Bertel, Evelyne; Joffre, Henri; Sklavenitis, Laodamas

    2012-12-01

    Even though the United States lacks a national climate policy, significant action has occurred at the local and regional levels. Some of the most aggressive climate change policies have occurred at the state and local levels and in interagency cooperation on specific management issues. While there is a long history of partnerships in dealing with a wide variety of policy issues, the uncertainty and the political debate surrounding climate change has generated new challenges to establishing effective policy networks. This paper investigates the formation of climate policy networks in the State of Nevada. It presents a methodology based on social network analysis for assessing the structure and function of local policy networks across a range of substantive climate impacted resources (water, landscape management, conservation, forestry and others). It draws from an emerging literature on federalism and climate policy, public sector innovation, and institutional analysis in socio-ecological systems. Comparisons across different policy issue networks in the state are used to highlight the influence of network structure, connectivity, bridging across vertical and horizontal organizational units, organizational diversity, and flows between organizational nodes.

  10. Electron-impact rotationally elastic total cross sections for H{sub 2}CO and HCOOH over a wide range of incident energy (0.01-2000 eV)

    Energy Technology Data Exchange (ETDEWEB)

    Vinodkumar, Minaxi [V P and R P T P Science College, Vallabh Vidyanagar 388 120, Gujarat (India); Bhutadia, Harshad [Government Engineering College, Patan 384265, Gujarat (India); Antony, Bobby [Department of Applied Physics, Indian School of Mines, Dhanbad JH-826004 (India); Mason, Nigel [Department of Physics and Astronomy, Open University, Milton Keynes MK7 6AA (United Kingdom)

    2011-11-15

    This paper reports computational results of the total cross sections for electron impact on H{sub 2}CO and HCOOH over a wide range of electron impact energies from 0.01 eV to 2 keV. The total cross section is presented as sum of the elastic and electronic excitation cross sections for incident energies. The calculation uses two different methodologies, below the ionization threshold of the target the cross section is calculated using the UK molecular R-matrix code through the Quantemol-N software package while cross sections at higher energies are evaluated using the spherical complex optical potential formalism. The two methods are found to be consistent at the transition energy ({approx}15 eV). The present results are, in general, found to be in good agreement with previous experimental and theoretical results (wherever available) and, thus, the present results can serve as a benchmark for the cross section over a wide range of energy.

  11. Oxygen boundary crossing probabilities.

    Science.gov (United States)

    Busch, N A; Silver, I A

    1987-01-01

    The probability that an oxygen particle will reach a time dependent boundary is required in oxygen transport studies involving solution methods based on probability considerations. A Volterra integral equation is presented, the solution of which gives directly the boundary crossing probability density function. The boundary crossing probability is the probability that the oxygen particle will reach a boundary within a specified time interval. When the motion of the oxygen particle may be described as strongly Markovian, then the Volterra integral equation can be rewritten as a generalized Abel equation, the solution of which has been widely studied.

  12. The turbulent plasmasphere boundary layer and the outer radiation belt boundary

    Science.gov (United States)

    Mishin, Evgeny; Sotnikov, Vladimir

    2017-12-01

    We report on observations of enhanced plasma turbulence and hot particle distributions in the plasmasphere boundary layer formed by reconnection-injected hot plasma jets entering the plasmasphere. The data confirm that the electron pressure peak is formed just outward of the plasmapause in the premidnight sector. Free energy for plasma wave excitation comes from diamagnetic ion currents near the inner edge of the boundary layer due to the ion pressure gradient, electron diamagnetic currents in the entry layer near the electron plasma sheet boundary, and anisotropic (sometimes ring-like) ion distributions revealed inside, and further inward of, the inner boundary. We also show that nonlinear parametric coupling between lower oblique resonance and fast magnetosonic waves significantly contributes to the VLF whistler wave spectrum in the plasmasphere boundary layer. These emissions represent a distinctive subset of substorm/storm-related VLF activity in the region devoid of substorm injected tens keV electrons and could be responsible for the alteration of the outer radiation belt boundary during (sub)storms.

  13. Dislocation structures in high angle 001 twist boundaries in magnesium oxide

    Science.gov (United States)

    Sun, C. P.

    1980-12-01

    A systematic transmission electron microscope (TEM) investigation of possible secondary grain boundary dislocation (GBD) structures in 001 high angle twist boundaries in MgO was carried out using bicrystals of controlled geometry. Techniques were developed to fabricate an extensive series of MgO bicrystals containing 001 twist boundaries with twist angle, theta, covering the entire possible range, 0 theta less than or equal to 45 deg. Tables of MgO single crystals with cleaved 100 faces were welded together by hot pressing. The TEM specimens were prepared by a combination of mechanical and chemical jet polishing using phosphoric acid. Weak beam microscopy was used extensively since this technique is capable of producing a characteristic narrow defect image width, and hence allows complicated GBD networks to be resolved more readily than by use of conventional microscopy.

  14. Energy-dispersed ions in the plasma sheet boundary layer and associated phenomena: Ion heating, electron acceleration, Alfvén waves, broadband waves, perpendicular electric field spikes, and auroral emissions

    Directory of Open Access Journals (Sweden)

    A. Keiling

    2006-10-01

    Full Text Available Recent Cluster studies reported properties of multiple energy-dispersed ion structures in the plasma sheet boundary layer (PSBL that showed substructure with several well separated ion beamlets, covering energies from 3 keV up to 100 keV (Keiling et al., 2004a, b. Here we report observations from two PSBL crossings, which show a number of identified one-to-one correlations between this beamlet substructure and several plasma-field characteristics: (a bimodal ion conics (<1 keV, (b field-aligned electron flow (<1 keV, (c perpendicular electric field spikes (~20 mV/m, (d broadband electrostatic ELF wave packets (<12.5 Hz, and (e enhanced broadband electromagnetic waves (<4 kHz. The one-to-one correlations strongly suggest that these phenomena were energetically driven by the ion beamlets, also noting that the energy flux of the ion beamlets was 1–2 orders of magnitude larger than, for example, the energy flux of the ion outflow. In addition, several more loosely associated correspondences were observed within the extended region containing the beamlets: (f electrostatic waves (BEN (up to 4 kHz, (g traveling and standing ULF Alfvén waves, (h field-aligned currents (FAC, and (i auroral emissions on conjugate magnetic field lines. Possible generation scenarios for these phenomena are discussed. In conclusion, it is argued that the free energy of magnetotail ion beamlets drove a variety of phenomena and that the spatial fine structure of the beamlets dictated the locations of where some of these phenomena occurred. This emphasizes the notion that PSBL ion beams are important for magnetosphere-ionosphere coupling. However, it is also shown that the dissipation of electromagnetic energy flux (at altitudes below Cluster of the simultaneously occurring Alfvén waves and FAC was larger (FAC being the largest than the dissipation of beam kinetic energy flux, and thus these two energy carriers contributed more to the energy transport on PSBL field lines

  15. On the structural unit/grain boundary dislocation model for grain boundary structure

    Science.gov (United States)

    Balluffi, R. W.; Bristowe, P. D.

    1984-08-01

    The applicability of the structural unit/grain boundary dislocation (GBD) model to the atomistic structures of [001] and [011] tilt boundary series recently calculated by Sutton, Vitek and Wang is studied in detail. It is found that a hierarchy of structural unit/GBD descriptions exists which may be used to describe such boundaries. Each description corresponds to a different choice of "delimiting boundary" structural units which are mixed together to make up all boundaries in the series. In all cases the structural units exhibit systematic distortions as the tilt angle changes. As the number of delimiting boundaries in a series is increased, and the range of structures is "quantized" on a finer scale, the distortions of the structural units decreases, but the amount of information regarding the GBD structure is decreased. It is pointed out that different members of the hierarchy of descriptions can be used advantageously for different purposes.

  16. Stable Boundary Layer Issues

    NARCIS (Netherlands)

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

  17. Boundary value problems and partial differential equations

    CERN Document Server

    Powers, David L

    2005-01-01

    Boundary Value Problems is the leading text on boundary value problems and Fourier series. The author, David Powers, (Clarkson) has written a thorough, theoretical overview of solving boundary value problems involving partial differential equations by the methods of separation of variables. Professors and students agree that the author is a master at creating linear problems that adroitly illustrate the techniques of separation of variables used to solve science and engineering.* CD with animations and graphics of solutions, additional exercises and chapter review questions* Nearly 900 exercises ranging in difficulty* Many fully worked examples

  18. Martian Electron Foreshock: New Results from MAVEN

    Science.gov (United States)

    Mazelle, C. X.; Meziane, K.; Mitchell, D. L.; Romanelli, N. J.; McFadden, J. P.; Espley, J. R.; Connerney, J. E. P.; Halekas, J. S.; Jakosky, B. M.; Hamza, A. M.

    2016-12-01

    Observations upstream from the Martian bow shock obtained by the MAVEN Solar Wind Electron Analyzer (SWEA) experiment are presented. Significant flux enhancements associated with electrons in the energies 50-400 eV range are always observed when MAVEN spacecraft is magnetically connected to the shock. The electron flux reaches a maximum near the shock surface. In addition, electron spikes with energies up to 1.5 keV are also observed near the Martian foreshock boundary. A detailed examination of the pitch angle distribution shows that the enhanced fluxes correspond to electrons moving sunward away from Mars. Also, the full 3-D angular distributions show that the phase space density values are peaked at a non-zero pitch angle and that the electrons appear in a ring centered along the IMF direction. The gyrotropic feature is observed over a large range of the shock geometry from quasi-parallel to quasi-perpendicular. These signatures in the electron distribution function strongly suggest that the reflection off the shock is the main mechanism for the production of Martian foreshock electrons. Although striking differences exist between the Earth and Mars shock structures, these observations show strong similarities in both the Terrestrial and Martian electronic foreshocks.

  19. Nanodiamonds in the Younger Dryas boundary sediment layer.

    Science.gov (United States)

    Kennett, D J; Kennett, J P; West, A; Mercer, C; Hee, S S Que; Bement, L; Bunch, T E; Sellers, M; Wolbach, W S

    2009-01-02

    We report abundant nanodiamonds in sediments dating to 12.9 +/- 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from approximately 10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.

  20. Secondary electron emission of thin carbon foils under the impact of hydrogen atoms, ions and molecular ions, under energies within the MeV range; Multiplicite des electrons secondaires emis par des cibles minces de carbone sous l'impact de projectiles H0, H2+, H3+ d'energie de l'ordre du MeV

    Energy Technology Data Exchange (ETDEWEB)

    Vidovic, Z

    1997-06-15

    This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H{sup 0}, H{sub 2}{sup +} and H{sub 3}{sup +} projectiles in the 0.25-2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. The phenomenological and theoretical descriptions, as well as a summary of the main theoretical models are the subject of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of a thin carbon foil traversed by an energetic projectile is described in the chapter two. In this chapter are also presented the method and algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with the emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H{sub 2}{sup +} and H{sub 3}{sup +} polyatomic ions. The results are interpreted in terms of collective effects in the interactions of these ions with solids. The role of the proximity of the protons, molecular ion fragments, upon the amplitude of these collective effects is evidenced from the study of the statistics of forward emission. These experiences allowed us to shed light on various aspects of atom and polyatomic ion inter-actions with solid surfaces. (author)

  1. 3D Characterization of Recrystallization Boundaries

    DEFF Research Database (Denmark)

    Zhang, Yubin; Godfrey, Andrew William; MacDonald, A. Nicole

    2016-01-01

    A three-dimensional (3D) volume containing a recrystallizing grain and a deformed matrix in a partially recrystallized pure aluminum was characterized using the 3D electron backscattering diffraction technique. The 3D shape of a recrystallizing boundary, separating the recrystallizing grain and d...

  2. Study of grain boundary segregation using the Auger electron emission technique. Annual technical progress report VI, January 1, 1976--December 31, 1976. [Summary of research activities at Michigan Tech

    Energy Technology Data Exchange (ETDEWEB)

    Stein, D.F.; Heldt, L.A.; Lee, J.K.; Pinchback, T.R.

    1976-01-01

    Studies of admirality brass stress corrosion in copper sulfate and copper nitrate have provided information on environmental contributions to SCC in acid systems. SCC susceptibility is a function of bulk corrosion rate, and is maximized when conditions favor localized attack. At a given pH and stress, solution composition determines crack initiation rates, but the crack crevice environment is not characteristic of the bulk salt solution. Crack propagation appears to be strongly related to anodic dissolution; however, contributions from thin film rupture and hydrogen embrittlement must be considered. The brittle tarnish rupture mechanism is not operative during the stress corrosion of copper alloys in any of a wide variety of environments. Theoretical models have been developed that are providing a basic understanding of segregation to grain boundaries. The statistical thermodynamic approach using a distribution of energy sites at the grain boundary has extended the McLean model and the results are consistent with sulfur segregation in Ni/sub 3/Al and Ni/sub 3/(Al,Ti). A model based on the interatomic potentials of Cu-Cu, Cu-Bi, and Bi-Bi shows the segregation of Bi should occur at grain boundaries and that the segregation should be more extensive at asymmetrical grain boundaries. This is in agreement with earlier measurements made in this program. Grain boundary diffusion experiments continue. The Mo-S-Cr system is still the most desirable one for this purpose but difficulty has been encountered in controlling the sulfur additions and keeping the Cr plate on the surface. A new closed system has been designed that appears to have solved the problem. Experiments using the Cu-Bi-Ni system have been successful so it is clear that the general approach to studying grain boundary diffusion and the effect of impurity segregation on this diffusion will be successful.

  3. Seeking the boundary of boundary extension.

    Science.gov (United States)

    McDunn, Benjamin A; Siddiqui, Aisha P; Brown, James M

    2014-04-01

    Boundary extension (BE) is a remarkably consistent visual memory error in which participants remember seeing a more wide-angle image of a scene than was actually viewed (Intraub & Richardson, Journal of Experimental Psychology: Learning, Memory, and Cognition 15:179-187, 1989). Multiple stimulus factors are thought to contribute to the occurrence of BE, including object recognition, conceptual knowledge of scenes, and amodal perception at the view boundaries (Intraub, Wiley Interdisciplinary Reviews: Cognitive Science 3:117-127, 2012). In the present study, we used abstract scenes instead of images of the real world, in order to remove expectations based on semantic associations with objects and the schematic context of the view. Close-angle and wide-angle scenes were created using irregular geometric shapes rated by independent observers as lacking any easily recognizable structure. The abstract objects were tested on either a random-dot or a blank background in order to assess the influence of implied continuation of the image beyond its boundaries. The random-dot background conditions had background occlusion cues either present or absent at the image border, in order to test their influence on BE in the absence of high-level information about the scenes. The results indicate that high-level information about objects and schematic context is unnecessary for BE to occur, and that occlusion information at the image boundary also has little influence on BE. Contrary to previous studies, we also found clear BE for all conditions, despite using scenes depicting undetailed objects on a blank white background. The results highlighted the ubiquitous nature of BE and the adaptability of scene perception processes.

  4. Symmetries and Boundary Conditions with a Twist

    Science.gov (United States)

    Zawadzki, Krissia; D'Amico, Irene; Oliveira, Luiz N.

    2017-10-01

    Interest in finite-size systems has risen in the last decades, due to the focus on nanotechnological applications and because they are convenient for numerical treatment that can subsequently be extrapolated to infinite lattices. Independently of the envisioned application, special attention must be given to boundary condition, which may or may not preserve the symmetry of the infinite lattice. Here, we present a detailed study of the compatibility between boundary conditions and conservation laws. The conflict between open boundary conditions and momentum conservation is well understood, but we examine other symmetries, as well: we discuss gauge invariance, inversion, spin, and particle-hole symmetry and their compatibility with open, periodic, and twisted boundary conditions. In the interest of clarity, we develop the reasoning in the framework of the one-dimensional half-filled Hubbard model, whose Hamiltonian displays a variety of symmetries. Our discussion includes analytical and numerical results. Our analytical survey shows that, as a rule, boundary conditions break one or more symmetries of the infinite-lattice Hamiltonian. The exception is twisted boundary condition with the special torsion Θ = πL/2, where L is the lattice size. Our numerical results for the ground-state energy at half-filling and the energy gap for L = 2-7 show how the breaking of symmetry affects the convergence to the L → ∞ limit. We compare the computed energies and gaps with the exact results for the infinite lattice drawn from the Bethe-Ansatz solution. The deviations are boundary-condition dependent. The special torsion yields more rapid convergence than open or periodic boundary conditions. For sizes as small as L = 7, the numerical results for twisted condition are very close to the L → ∞ limit. We also discuss the ground-state electronic density and magnetization at half filling under the three boundary conditions.

  5. Administrative Area Boundaries 2 (State Boundaries), Region 9, 2010, NAVTEQ

    Data.gov (United States)

    U.S. Environmental Protection Agency — NAVTEQ Administrative Area Boundaries 2 (State Boundaries) for Region 9. There are five Administrative Area Boundaries layers (1, 2, 3, 4, 5). These layers contain...

  6. Administrative Area Boundaries 4 (City Boundaries), Region 9, 2010, NAVTEQ

    Data.gov (United States)

    U.S. Environmental Protection Agency — NAVTEQ Administrative Area Boundaries 4 (City Boundaries) for Region 9. There are five Administrative Area Boundaries layers (1, 2, 3, 4, 5). These layers contain...

  7. Inverse boundary spectral problems

    CERN Document Server

    Kachalov, Alexander; Lassas, Matti

    2001-01-01

    Inverse boundary problems are a rapidly developing area of applied mathematics with applications throughout physics and the engineering sciences. However, the mathematical theory of inverse problems remains incomplete and needs further development to aid in the solution of many important practical problems.Inverse Boundary Spectral Problems develop a rigorous theory for solving several types of inverse problems exactly. In it, the authors consider the following: ""Can the unknown coefficients of an elliptic partial differential equation be determined from the eigenvalues and the boundary value

  8. Beyond the Boundary

    DEFF Research Database (Denmark)

    Gorm Hansen, Birgitte

    2011-01-01

    Whether celebratory or critical, STS research on science-industry relations has focused on the blurring of boundaries and hybridization of codes and practices. However, the vocabulary of boundary and hybrid tends to reify science and industry as separate in the attempt to map their relation...... as the negotiation of a preexisting science-industry boundary. Rather, viability is obtained through a strategy of "circumventing" the science-industry food chain and "sequestering" biotech components within the research center. Symbiosis allows academic scientists to do biology while at the same time demonstrating...

  9. Beyond the Boundary

    DEFF Research Database (Denmark)

    Gorm Hansen, Birgitte

    2012-01-01

    Whether celebratory or critical, STS research on science-industry relations has focused on the blurring of boundaries and hybridization of codes and practices. However, the vocabulary of boundary and hybrid tends to reify science and industry as separate in the attempt to map their relation...... as the negotiation of a preexisting science-industry boundary. Rather, viability is obtained through a strategy of circumventing the science-industry food chain and sequestering biotech components within the research center. Symbiosis allows academic scientists to do biology while at the same time demonstrating...

  10. International boundary experiences by the United Nations

    Science.gov (United States)

    Kagawa, A.

    2013-12-01

    Over the last few decades, the United Nations (UN) has been approached by Security Council and Member States on international boundary issues. The United Nations regards the adequate delimitation and demarcation of international boundaries as a very important element for the maintenance of peace and security in fragile post-conflict situations, establishment of friendly relationships and cross-border cooperation between States. This paper will present the main principles and framework the United Nations applies to support the process of international boundary delimitation and demarcation activities. The United Nations is involved in international boundary issues following the principle of impartiality and neutrality and its role as mediator. Since international boundary issues are multi-faceted, a range of expertise is required and the United Nations Secretariat is in a good position to provide diverse expertise within the multiple departments. Expertise in different departments ranging from legal, political, technical, administrative and logistical are mobilised in different ways to provide support to Member States depending on their specific needs. This presentation aims to highlight some of the international boundary projects that the United Nations Cartographic Section has been involved in order to provide the technical support to different boundary requirements as each international boundary issue requires specific focus and attention whether it be in preparation, delimitation, demarcation or management. Increasingly, the United Nations is leveraging geospatial technology to facilitate boundary delimitation and demarcation process between Member States. Through the presentation of the various case studies ranging from Iraq - Kuwait, Israel - Lebanon (Blue Line), Eritrea - Ethiopia, Cyprus (Green Line), Cameroon - Nigeria, Sudan - South Sudan, it will illustrate how geospatial technology is increasingly used to carry out the support. In having applied a range

  11. HUC 8 Boundaries

    Data.gov (United States)

    Kansas Data Access and Support Center — This data set is a digital hydrologic unit boundary that is at the 4-digit, 6-digit, 8-digit, and 11-digit level. The data set was developed by delineating the...

  12. FWS Approved Acquisition Boundaries

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This data layer depicts the external boundaries of lands and waters that are approved for acquisition by the U.S. Fish and Wildlife Service (USFWS) in North America,...

  13. National Forest Boundaries

    Data.gov (United States)

    Minnesota Department of Natural Resources — This theme shows the USFS national forest boundaries in the state. This data was acquired from the GIS coordinators at both the Chippewa National Forest and the...

  14. VT Telephone Exchange Boundaries

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The UtilityTelecom_EXCHANGE represents Vermont Telephone Exchange boundaries as defined by the VT Public Service Board. The original data was...

  15. State Park Statutory Boundaries

    Data.gov (United States)

    Minnesota Department of Natural Resources — Legislative statutory boundaries for sixty six state parks, six state recreation areas, and eight state waysides. These data are derived principally from DNR's...

  16. 500 Cities: City Boundaries

    Data.gov (United States)

    U.S. Department of Health & Human Services — This city boundary shapefile was extracted from Esri Data and Maps for ArcGIS 2014 - U.S. Populated Place Areas. This shapefile can be joined to 500 Cities...

  17. Allegheny County Parcel Boundaries

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset contains parcel boundaries attributed with county block and lot number. Use the Property Information Extractor for more control downloading a filtered...

  18. Watershed Boundary Areas

    Data.gov (United States)

    Department of Homeland Security — This map layer contains hydrologic unit boundaries and codes for the United States, Puerto Rico, and the U.S. Virgin Islands. It was revised for inclusion in the...

  19. NM School District Boundaries

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — The dataset represents the boundaries of all public school districts in the state of New Mexico. The source for the data layer is the New Mexico Public Education...

  20. Allegheny County Boundary

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset contains the Allegheny County boundary. If viewing this description on the Western Pennsylvania Regional Data Center’s open data portal...

  1. Boundary representation modelling techniques

    CERN Document Server

    2006-01-01

    Provides the most complete presentation of boundary representation solid modelling yet publishedOffers basic reference information for software developers, application developers and users Includes a historical perspective as well as giving a background for modern research.

  2. Site Area Boundaries

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset consists of site boundaries from multiple Superfund sites in U.S. EPA Region 8. These data were acquired from multiple sources at different times and...

  3. Tax Unit Boundaries

    Data.gov (United States)

    Kansas Data Access and Support Center — The Statewide GIS Tax Unit boundary file was created through a collaborative partnership between the State of Kansas Department of Revenue Property Valuation...

  4. VT Federal Aid Urban Boundaries

    Data.gov (United States)

    Vermont Center for Geographic Information — Federal Aid Urban boundaries are defined based on US Census data. The roadways within these boundaries have urban classifications. These FAU boundaries were updated...

  5. Confronting unknown planetary boundary threats from chemical pollution.

    Science.gov (United States)

    Persson, Linn M; Breitholtz, Magnus; Cousins, Ian T; de Wit, Cynthia A; MacLeod, Matthew; McLachlan, Michael S

    2013-11-19

    Rockström et al. proposed a set of planetary boundaries that delimitate a "safe operating space for humanity". One of the planetary boundaries is determined by "chemical pollution", however no clear definition was provided. Here, we propose that there is no single chemical pollution planetary boundary, but rather that many planetary boundary issues governed by chemical pollution exist. We identify three conditions that must be simultaneously met for chemical pollution to pose a planetary boundary threat. We then discuss approaches to identify chemicals that could fulfill those conditions, and outline a proactive hazard identification strategy that considers long-range transport and the reversibility of chemical pollution.

  6. Boundary layer polarization and voltage in the 14 MLT region

    Science.gov (United States)

    Lundin, R.; Yamauchi, M.; Woch, J.; Marklund, G.

    1995-05-01

    Viking midlatitude observations of ions and electrons in the postnoon auroral region show that field-aligned acceleration of electrons and ions with energies up to a few kiloelectron volts takes place. The characteristics of the upgoing ion beams and the local transverse electric field observed by Viking indicate that parallel ion acceleration is primarily due to a quasi-electrostatic field-aligned acceleration process below Viking altitudes, i.e., below 10,000-13,500 km. A good correlation is found between the maximum upgoing ion beam energy and the depth of the local potential well determined by the Viking electric field experiment within dayside 'ion inverted Vs.' The total transverse potential throughout the entire region near the ion inverted Vs. is generally much higher than the field-aligned potential and may reach well above 10 kV. However, the detailed mapping of the transverse potential out to the boundary layer, a fundamental issue which remains controversial, was not attempted here. An important finding in this study is the strong correlation between the maximum up going ion beam energy of dayside ion inverted Vs and the solar wind velocity. This suggests a direct coupling of the solar wind plasma dynamo/voltage generator to the region of field-aligned particle acceleration. The fact that the center of dayside ion inverted Vs coincide with convection reversals/flow stagnation and upward Birkeland currents on what appears to be closed field lines (Woch et al., 1993), suggests that field-aligned potential structures connect to the inner part of an MHD dyanmo in the low-latitude boundary layer. Thus the Viking observations substantiate the idea of a solar wind induced boundary layer polarization where negatively charged perturbations in the postnoon sector persistently develops along the magnetic field lines, establishing accelerating potential drops along the geomagnetic field lines in the 0.5-10 kV range.

  7. Grain boundaries: Annual technical progress report

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1988-04-28

    The present document is a progress report describing the work accomplished on the study of grain of gold. The research that was proposed initially for this period consisted of studies of the atomistics structure of grain boundaries by means of combined x-ray diffraction and computer modeling and of grain boundary phase transitions by electron microscopy and computer modeling. Progress has been made on both of these areas which is described in more detail. A list of reports describing the research completely during the first year is presented.

  8. Evolution of the dispersionless injection boundary associated with substorms

    Directory of Open Access Journals (Sweden)

    T. Sarris

    2005-03-01

    Full Text Available One manifestation of energetic particle acceleration during magnetospheric substorms is the sudden appearance of particle injections into the inner magnetosphere, often observed near geosynchronous orbit. Injections that show simultaneous flux increases in all energy ranges of a detector are called dispersionless injections, and are most often observed in a narrow region around local midnight. In these events it is assumed that the satellite is located close to or inside the region where acceleration and/or transport processes are taking place, called the injection region. We present a study of the location, extent and temporal evolution of the injection region, based on simulation results of a model of the expansion of the electric and magnetic fields associated with a substorm. The model simulates the fields during a substorm onset with an electric field and consistent magnetic field pulse that propagates towards the Earth with a decreasing speed. Our simulation shows that the dispersionless injection boundary can be considered coincident with the leading edge of the pulse field, which transports particles toward the Earth across a certain range of local time. Under the same model field, the dispersionless injection boundary shifts eastward for electrons and westward for protons, consistent with the observation results deduced from statistical analysis of multiple spacecraft measurements.

  9. Home range and travels

    Science.gov (United States)

    Stickel, L.F.; King, John A.

    1968-01-01

    The concept of home range was expressed by Seton (1909) in the term 'home region,' which Burr (1940, 1943) clarified with a definition of home range and exemplified in a definitive study of Peromyscus in the field. Burt pointed out the ever-changing characteristics of home-range area and the consequent absence of boundaries in the usual sense--a finding verified by investigators thereafter. In the studies summarized in this paper, sizes of home ranges of Peromyscus varied within two magnitudes, approximately from 0.1 acre to ten acres, in 34 studies conducted in a variety of habitats from the seaside dunes of Florida to the Alaskan forests. Variation in sizes of home ranges was correlated with both environmental and physiological factors; with habitat it was conspicuous, both in the same and different regions. Food supply also was related to size of home range, both seasonally and in relation to habitat. Home ranges generally were smallest in winter and largest in spring, at the onset of the breeding season. Activity and size also were affected by changes in weather. Activity was least when temperatures were low and nights were bright. Effects of rainfall were variable. Sizes varied according to sex and age; young mice remained in the parents' range until they approached maturity, when they began to travel more widely. Adult males commonly had larger home ranges than females, although there were a number of exceptions. An inverse relationship between population density and size of home range was shown in several studies and probably is the usual relationship. A basic need for activity and exploration also appeared to influence size of home range. Behavior within the home range was discussed in terms of travel patterns, travels in relation to home sites and refuges, territory, and stability of size of home range. Travels within the home range consisted of repeated use of well-worn trails to sites of food, shelter, and refuge, plus more random exploratory travels

  10. Wide-range high-resolution transmission electron microscopy reveals morphological and distributional changes of endomembrane compartments during log to stationary transition of growth phase in tobacco BY-2 cells.

    Science.gov (United States)

    Toyooka, Kiminori; Sato, Mayuko; Kutsuna, Natsumaro; Higaki, Takumi; Sawaki, Fumie; Wakazaki, Mayumi; Goto, Yumi; Hasezawa, Seiichiro; Nagata, Noriko; Matsuoka, Ken

    2014-09-01

    Rapid growth of plant cells by cell division and expansion requires an endomembrane trafficking system. The endomembrane compartments, such as the Golgi stacks, endosome and vesicles, are important in the synthesis and trafficking of cell wall materials during cell elongation. However, changes in the morphology, distribution and number of these compartments during the different stages of cell proliferation and differentiation have not yet been clarified. In this study, we examined these changes at the ultrastructural level in tobacco Bright yellow 2 (BY-2) cells during the log and stationary phases of growth. We analyzed images of the BY-2 cells prepared by the high-pressure freezing/freeze substitution technique with the aid of an auto-acquisition transmission electron microscope system. We quantified the distribution of secretory and endosomal compartments in longitudinal sections of whole cells by using wide-range gigapixel-class images obtained by merging thousands of transmission electron micrographs. During the log phase, all Golgi stacks were composed of several thick cisternae. Approximately 20 vesicle clusters (VCs), including the trans-Golgi network and secretory vesicle cluster, were observed throughout the cell. In the stationary-phase cells, Golgi stacks were thin with small cisternae, and only a few VCs were observed. Nearly the same number of multivesicular body and small high-density vesicles were observed in both the stationary and log phases. Results from electron microscopy and live fluorescence imaging indicate that the morphology and distribution of secretory-related compartments dramatically change when cells transition from log to stationary phases of growth. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  11. Dynamical simulation of structural multiplicity in grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Majid, I.; Bristowe, P.D.

    1987-06-01

    Work on a computer simulation study of a low-energy high-angle boundary structure which is not periodic have been recently reported. This result is of interest since grain boundary structures are usually assumed to have a periodicity corresponding to the appropriate coincidence site lattice (CSL) and many experimental observations of the structure of grain boundaries performed using conventional and high-resolution electron microscopy, electron diffraction and x-ray diffraction appear to support this work. However, this work, using empirical interatomic pair potentials and the relaxation method of molecular statics, have simulated a ..sigma.. = 5 36.87/sup 0/ (001) twist boundary and found a low energy structure having a larger repeat cell than the CSL and is composed of two different types of structural unit that are randomly distributed in the boundary plane. This result, which has been termed the multiplicity of grain boundary structures, has also been found in the simulation of tilt boundaries. The multiplicity phenomenon is of special interest in twist boundaries since it is used as a structural model to explain the x-ray scattering from a ..sigma.. = 5 boundary in gold. These scattering patterns had previously remained unexplained using stable structures that had simple CSL periodicity. Also, the effect of having a multiple number of low energy structural units coexisting in the grain boundary is of more general interest since it implies that the boundary structures may be quasi-periodic and, in some circumstances, may even result in a roughening of the boundary plane. This paper extends this work by showing, using molecular dynamics, that a multiplicity of structural units can actually nucleate spontaneously in a high-angle grain boundary at finite temperatures.

  12. Dynamical simulation of structural multiplicity in grain boundaries

    Science.gov (United States)

    Majid, I.; Bristowe, P. D.

    1987-06-01

    Work on a computer simulation study of a low-energy high-angle boundary structure which is not periodic have been recently reported. This result is of interest since grain boundary structures are usually assumed to have a periodicity corresponding to the appropriate coincidence site lattice (CSL) and many experimental observations of the structure of grain boundaries performed using conventional and high-resolution electron microscopy, electron diffraction and X-ray diffraction appear to support this work. However, this work, using empirical interatomic pair potentials and the relaxation method of molecular statics, have simulated a Sigma=5 (36.87 deg)(001) twist boundary and found a low energy structure having a larger repeat cell than the CSL and is composed of two different types of structural unit randomly distributed in the boundary plane. This result, termed the multiplicity of grain boundary structures, has also been found in the simulation of tilt boundaries. The multiplicity phenomenon is of special interest in twist boundaries since it is used as a structural model to explain the X-ray scattering from a Sigma=5 boundary in gold. These scattering patterns had previously remained unexplained using stable structures that had simple CSL periodicity. Also, the effect of having a multiple number of low energy structural units coexisting in the grain boundary is of more general interest since it implies that the boundary structures may be quasi-periodic and, in some circumstances, may even result in a roughening of the boundary plane. This work is extended by showing, using molecular dynamics, that a multiplicity of structural units can actually nucleate spontaneously in a high-angle grain boundary at finite temperatures.

  13. Grain boundary engineering to enhance thermal stability of electrodeposited nickel

    DEFF Research Database (Denmark)

    Alimadadi, Hossein

    by miniaturization of the grains down to nano-meter scale. However, this augments the total grain boundary energy stored in the material, hence, making the material less thermally stable. Coherent twin boundaries are of very low energy and mobility compared to all other boundaries in a FCC material. Accordingly......, grain boundary engineering of electrodeposited nickel to achieve high population of coherent twin boundaries and, hence, higher thermal stability is a promising method to achieve simultaneous improvement in mechanical properties and thermal stability. This is of particular scientific and practical...... interest. The evolution of microstructure in as-deposited and annealed condition was investigated with a combination of complementary microscopic techniques, electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI), ion channelling contrast imaging (ICCI), and, for the as...

  14. Adaptive Sentence Boundary Disambiguation

    CERN Document Server

    Palmer, D D; Palmer, David D.; Hearst, Marti A.

    1994-01-01

    Labeling of sentence boundaries is a necessary prerequisite for many natural language processing tasks, including part-of-speech tagging and sentence alignment. End-of-sentence punctuation marks are ambiguous; to disambiguate them most systems use brittle, special-purpose regular expression grammars and exception rules. As an alternative, we have developed an efficient, trainable algorithm that uses a lexicon with part-of-speech probabilities and a feed-forward neural network. After training for less than one minute, the method correctly labels over 98.5\\% of sentence boundaries in a corpus of over 27,000 sentence-boundary marks. We show the method to be efficient and easily adaptable to different text genres, including single-case texts.

  15. The Bottom Boundary Layer.

    Science.gov (United States)

    Trowbridge, John H; Lentz, Steven J

    2018-01-03

    The oceanic bottom boundary layer extracts energy and momentum from the overlying flow, mediates the fate of near-bottom substances, and generates bedforms that retard the flow and affect benthic processes. The bottom boundary layer is forced by winds, waves, tides, and buoyancy and is influenced by surface waves, internal waves, and stratification by heat, salt, and suspended sediments. This review focuses on the coastal ocean. The main points are that (a) classical turbulence concepts and modern turbulence parameterizations provide accurate representations of the structure and turbulent fluxes under conditions in which the underlying assumptions hold, (b) modern sensors and analyses enable high-quality direct or near-direct measurements of the turbulent fluxes and dissipation rates, and (c) the remaining challenges include the interaction of waves and currents with the erodible seabed, the impact of layer-scale two- and three-dimensional instabilities, and the role of the bottom boundary layer in shelf-slope exchange.

  16. A statistical comparison of SuperDARN spectral width boundaries and DMSP particle precipitation boundaries in the morning sector ionosphere

    Directory of Open Access Journals (Sweden)

    G. Chisham

    2005-03-01

    Full Text Available Determining reliable proxies for the ionospheric signature of the open-closed field line boundary (OCB is crucial for making accurate ionospheric measurements of many magnetospheric processes (e.g. magnetic reconnection. This study compares the latitudes of Spectral Width Boundaries (SWBs, identified in the morning sector ionosphere using the Super Dual Auroral Radar Network (SuperDARN, with Particle Precipitation Boundaries (PPBs determined using the low-altitude Defense Meteorological Satellite Program (DMSP spacecraft, in order to determine whether the SWB represents a good proxy for the ionospheric projection of the OCB. The latitudes of SWBs and PPBs were identified using automated algorithms applied to 5 years (1997-2001 of data measured in the 00:00-12:00 Magnetic Local Time (MLT range. A latitudinal difference was measured between each PPB and the nearest SWB within a ±10min Universal Time (UT window and within a ±1h MLT window. The results show that the SWB represents a good proxy for the OCB close to midnight (~00:00-02:00 MLT and noon (~08:00-12:00 MLT, but is located some distance (~2°-4° equatorward of the OCB across much of the morning sector ionosphere (~02:00-08:00 MLT. On the basis of this and other studies we deduce that the SWB is correlated with the poleward boundary of auroral emissions in the Lyman-Birge-Hopfield ``Long" (LBHL UV emission range and hence, that spectral width is inversely correlated with the energy flux of precipitating electrons. We further conclude that the combination of two factors may explain the spatial distribution of spectral width values in the polar ionospheres. The small-scale structure of the convection electric field leads to an enhancement in spectral width in regions close to the OCB, whereas increases in ionospheric conductivity (relating to the level of incident electron energy flux lead to a reduction in spectral width in regions just equatorward of the OCB.

  17. Structure of grain boundaries in hexagonal materials

    CERN Document Server

    Sarrazit, F

    1998-01-01

    which allows the behaviour of line-defects to be studied in complex interfacial processes. The work presented in this thesis describes experimental and theoretical aspects associated with the structure of grain boundaries in hexagonal materials. It has been found useful to classify grain boundaries as low-angle, special or general on the basis of their structure. High-angle grain boundaries were investigated in tungsten carbide (WC) using conventional electron microscopy techniques, and three examples characteristic of the interfaces observed in this material were studied extensively. Three-dimensionally periodic patterns are proposed as plausible reference configurations, and the Burgers vectors of observed interfacial dislocations were predicted using a theory developed recently. The comparison of experimental observations with theoretical predictions proved to be difficult as contrast simulation techniques require further development for analysis to be completed confidently. Another part of this work invol...

  18. Simulations of Boundary Turbulence in Tokamak Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Nevins, W M; Xu, X Q; Carlstrom, T N; Cohen, R H; Groebner, R; Jennings, T; LaBombard, B; Maqueda, R A; Mazurenko, A; McKee, G R; Moyer, R; Mossessian, D; Porkolab, M; Porter, G D; Rensink, M E; Rhodes, T L; Rognlien, T D; Rost, C; Snipes, J; Stotler, D P; Terry, J; Zweben, S

    2002-10-11

    Comparisons between the boundary plasma turbulence observed in the BOUT code and experiments on C-Mod, NSTX, and DIII-D are presented. BOUT is a 3D non-local electromagnetic turbulence simulation code which models boundary-plasma turbulence in a realistic divertor geometry using the modified Braginskii equations for plasma vorticity, density, the electron and ion temperatures and parallel momenta. Many features of the Quasi-Coherent (QC) mode, observed at high densities during enhanced D-alpha (EDA) H-Mode in Alcator C-Mod, are reproduced in BOUT simulations. The spatial structure of boundary plasma turbulence as observed by gas puff imaging (GPI) from discharges on NSTX and C-Mod are in general (NSTX) to good (CMod) agreement with BOUT simulations. Finally, BOUT simulations of DIII-D L-mode experiments near the Hmode transition threshold are in broad agreement with the experimental results.

  19. Solar wind- and EUV-dependent models for the shapes of the Martian plasma boundaries based on Mars Express measurements

    Science.gov (United States)

    Ramstad, Robin; Barabash, Stas; Futaana, Yoshifumi; Holmström, Mats

    2017-07-01

    The long operational life (2003-present) of Mars Express (MEX) has allowed the spacecraft to make plasma measurements in the Martian environment over a wide range of upstream conditions. We have analyzed ˜7000 MEX orbits, covering three orders of magnitude in solar wind dynamic pressure, with data from the on board Analyzer of Space Plasmas and Energetic Particles (ASPERA-3) package, mapping the locations where MEX crosses the main plasma boundaries, induced magnetosphere boundary (IMB), ionosphere boundary (IB), and bow shock (BS). A coincidence scheme was employed, where data from the Ion Mass Analyzer (IMA) and the Electron Spectrometer (ELS) had to agree for a positive boundary identification, which resulted in crossings from 1083 orbit segments that were used to create dynamic two-parameter (solar wind density, nsw, and velocity vsw) dependent global dynamic models for the IMB, IB, and BS. The modeled response is found to be individual to each boundary. The IMB scales mainly dependent on solar wind dynamic pressure and EUV intensity. The BS location closely follows the location of the IMB at the subsolar point, though under extremely low nsw and vsw the BS assumes a more oblique shape. The IB closely follows the IMB on the dayside and changes its nightside morphology with different trends for nsw and vsw. We also investigate the influence of extreme ultraviolet (EUV) radiation on the IMB and BS, finding that increased EUV intensity expands both boundaries.

  20. Structural complexity in grain boundaries with covalent bonding

    Energy Technology Data Exchange (ETDEWEB)

    Tarnow, E.; Dallot, P.; Bristowe, P.D.; Joannopoulos, J.D. (Massachusetts Institute of Technology, Cambridge, MA (USA)); Francis, G.P.; Payne, M.C. (Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom))

    1990-08-15

    The structural properties of two short-period twist boundaries in germanium are explored using a state-of-the-art total-energy calculation. The structures of these boundaries are found to be very complex, with boundary bonds that are distorted and weak. These systems are found to exhibit a large degeneracy in the number of local energy minima. Thus the boundaries have difficulty in arriving at a locally ordered state. The situation may be unique to the {ital semiconducting} {ital twist} grain boundaries due to the inherent frustration present between the tendency to form directional bonds and the imposed twist geometry which makes the bond formation improbable. This study focuses on the energy, coordination, volume change, and electronic states characteristic of the local minima. A trend towards dimerization is found especially in the highest-angle twist boundary.

  1. Structural complexity in grain boundaries with covalent bonding

    Science.gov (United States)

    Tarnow, E.; Dallot, P.; Bristowe, P. D.; Joannopoulos, J. D.; Francis, G. P.; Payne, M. C.

    1990-08-01

    The structural properties of two short-period twist boundaries in germanium are explored using a state-of-the-art total-energy calculation. The structures of these boundaries are found to be very complex, with boundary bonds that are distorted and weak. These systems are found to exhibit a large degeneracy in the number of local energy minima. Thus the boundaries have difficulty in arriving at a locally ordered state. The situation may be unique to the semiconducting twist grain boundaries due to the inherent frustration present between the tendency to form directional bonds and the imposed twist geometry which makes the bond formation improbable. This study focuses on the energy, coordination, volume change, and electronic states characteristic of the local minima. A trend towards dimerization is found especially in the highest-angle twist boundary.

  2. Effect of Trace Levels of Si on Microstructure and Grain Boundary Segregation in DOP-26 Iridium Alloy

    Science.gov (United States)

    Pierce, Dean; Muralidharan, Govindarajan; Heatherly, Lee; Fox, Ethan

    2017-10-01

    The thermodynamics and kinetics of Silicon (Si) segregation to grain boundaries in Iridium alloy DOP-26 with added trace levels of Si of 6, 11, 29, and 36 wppm was studied by Auger Electron Spectroscopy. The four alloys were annealed at 1500 or 1535 °C for 19 or 76 hours followed by cooling at three different rates. Si enrichment at the grain boundaries (GB) increased with increasing bulk Si content, with the grain boundary Si enrichment factors ranging from 62 to 344, depending on the bulk Si content and the cooling rate. Grain boundary Si contents increased with decreasing cooling rate in all alloys, indicating that Si GB segregation is influenced by both thermodynamic and kinetic factors in the alloys and temperature ranges of the study. A Langmuir-McLean isotherm-based model was successfully used to predict the temperature dependence of GB Si segregation in DOP-26 alloys with Si additions and estimate the temperature independent free energy of Si segregation to grain boundaries in DOP-26.

  3. Minnesota County Boundaries - lines

    Data.gov (United States)

    Minnesota Department of Natural Resources — Minnesota county boundaries derived from a combination of 1:24,000 scale PLS lines, 1:100,000 scale TIGER, 1:100,000 scale DLG, and 1:24,000 scale hydrography lines....

  4. Knowledge production at boundaries

    NARCIS (Netherlands)

    Stange, Kari

    2017-01-01

    This thesis addresses how knowledge is used and produced in stakeholder-led collaborations to make long-term management plans for European fishery management. Boundary object theory is applied and developed to explain how stakeholders from the fishing industry interact with each other, and with

  5. Environmentalists without Boundaries

    African Journals Online (AJOL)

    GREGORY

    2009-03-16

    Mar 16, 2009 ... African Journal of Environmental Science and Technology Vol. ... The most fruitful scientific endeavors invariably cross boundaries – across ... The White Man's Burden: Why the West's Efforts to Aid the Rest Have Done So Much ... cooperation and capacity (7)stimulating economic development and growth, ...

  6. Environmentalists without Boundaries

    African Journals Online (AJOL)

    GREGORY

    2009-03-16

    Mar 16, 2009 ... Hence, this is a laudable project, but Coca Cola should also be cognizant of the growing African environmental pollution problems associated with plastics disposal as they market bottled water and other juices on the continent. This is an example of a challenge associated with advertent boundary crossing ...

  7. Minnesota County Boundaries

    Data.gov (United States)

    Minnesota Department of Natural Resources — Minnesota county boundaries derived from a combination of 1:24,000 scale PLS lines, 1:100,000 scale TIGER, 1:100,000 scale DLG, and 1:24,000 scale hydrography lines....

  8. Boundaries of the universe

    CERN Document Server

    Glasby, John S

    2013-01-01

    The boundaries of space exploration are being pushed back constantly, but the realm of the partially understood and the totally unknown is as great as ever. Among other things this book deals with astronomical instruments and their application, recent discoveries in the solar system, stellar evolution, the exploding starts, the galaxies, quasars, pulsars, the possibilities of extraterrestrial life and relativity.

  9. Dual boundary spanning

    DEFF Research Database (Denmark)

    Li-Ying, Jason

    2016-01-01

    The extant literature runs short in understanding openness of innovation regarding and the different pathways along which internal and external knowledge resources can be combined. This study proposes a unique typology for outside-in innovations based on two distinct ways of boundary spanning...

  10. Environmentalists without Boundaries

    African Journals Online (AJOL)

    GREGORY

    2009-03-16

    Mar 16, 2009 ... idea that development and environmental sustainability require poverty eradication is not a shocking one, but many scholars remain skeptical about the ... in developing countries has potentially solved this boundary problem by asking for donations through the purchase of bottled water at a price that will ...

  11. Towards realistic molecular dynamics simulations of grain boundary mobility

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J., E-mail: zhou@imm.rwth-aachen.de [Institut fuer Metallkunde und Metallphysik, Rheinisch-Westfaelische Technische Hochschule (RWTH), Aachen (Germany); Mohles, V. [Institut fuer Metallkunde und Metallphysik, Rheinisch-Westfaelische Technische Hochschule (RWTH), Aachen (Germany)

    2011-09-15

    In order to investigate grain boundary migration by molecular dynamics (MD) simulations a new approach involving a crystal orientation-dependent driving force has been developed by imposing an appropriate driving force on grain boundary atoms and enlarging the effective range of driving force. The new approach has been validated by the work of the driving force associated with the motion of grain boundaries. With the new approach the relation between boundary migration velocity and driving force is found to be nonlinear, as was expected from rate theory for large driving forces applied in MD simulations. By evaluating grain boundary mobility nonlinearly for a set of symmetrical <1 1 1> tilt boundaries in aluminum at high temperature, high-angle grain boundaries were shown to move much faster than low-angle grain boundaries. This agrees well with experimental findings for recrystallization and grain growth. In comparison with the available data the simulated mobility of a 38.21{sup o{Sigma}}7 boundary was found to be significantly lower than other MD simulation results and comparable with the experimental values. Furthermore, the average volume involved during atomic jumps for boundary migration is determined in MD simulations for the first time. The large magnitude of the volume indicates that grain boundary migration is accomplished by the correlated motion of atom groups.

  12. In-Situ Investigation of Local Boundary Migration During Recrystallization

    DEFF Research Database (Denmark)

    Zhang, Yubin; Godfrey, Andy; Juul Jensen, Dorte

    2014-01-01

    A combination of electron channeling contrast (ECC) and electron backscatter diffraction pattern (EBSP) techniques has been used to follow in situ the migration during annealing at 323 K (50 A degrees C) of a recrystallizing boundary through the deformed matrix of high-purity aluminum rolled to 8...

  13. PLSS Townships and Sections, Public Land Survey square-mile section boundaries within Sedgwick County. Layer was developed interactively by GIS staff. Primary attribues include section, township, and range identifiers, and x-y coordinates, and Public Safety (ortho) map numbers., Published in 2008, 1:1200 (1in=100ft) scale, Sedgwick County Government.

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — PLSS Townships and Sections dataset current as of 2008. Public Land Survey square-mile section boundaries within Sedgwick County. Layer was developed interactively...

  14. Cities, Towns and Villages, Public Land Survey township boundaries within Sedgwick County. Layer was developed interactively by GIS staff. Primary attribues include township, and range identifiers, and x-y coordinates., Published in 2008, 1:1200 (1in=100ft) scale, Sedgwick County Government.

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — Cities, Towns and Villages dataset current as of 2008. Public Land Survey township boundaries within Sedgwick County. Layer was developed interactively by GIS staff....

  15. The turning of the wind in the atmospheric boundary layer

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Gryning, Sven-Erik; Floors, Rogier Ralph

    2014-01-01

    Here we use accurate observations of the wind speed vector to analyze the behavior with height of the wind direction. The observations are a combination of tall meteorological mast and long-range wind lidar measurements covering the entire atmospheric boundary layer. The observations were performed...... winds underpredict the turning of the wind and the boundary-layer winds in general....

  16. Global environmental governance and planetary boundaries: An introduction

    NARCIS (Netherlands)

    Galaz, V.; Biermann, F.; Folke, C.; Nilsson, M.; Olsson, P.

    2012-01-01

    The notion of 'planetary boundaries' is rapidly diffusing into a range of policy arenas and has clearly stimulated a discussion on the need to reform international environmental governance. This article summarizes the special section "Global Environmental Governance and Planetary Boundaries". The

  17. Grain Boundary Segregation in Metals

    CERN Document Server

    Lejcek, Pavel

    2010-01-01

    Grain boundaries are important structural components of polycrystalline materials used in the vast majority of technical applications. Because grain boundaries form a continuous network throughout such materials, their properties may limit their practical use. One of the serious phenomena which evoke these limitations is the grain boundary segregation of impurities. It results in the loss of grain boundary cohesion and consequently, in brittle fracture of the materials. The current book deals with fundamentals of grain boundary segregation in metallic materials and its relationship to the grain boundary structure, classification and other materials properties.

  18. Grain boundary sliding mechanism during high temperature deformation of AZ31 Magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Roodposhti, Peiman Shahbeigi, E-mail: pshahbe@ncsu.edu [North Carolina State University (United States); University of Connecticut (United States); Sarkar, Apu; Murty, Korukonda Linga [North Carolina State University (United States); Brody, Harold [University of Connecticut (United States); Scattergood, Ronald [North Carolina State University (United States)

    2016-07-04

    High temperature tensile creep tests were conducted on AZ31 Magnesium alloy at low stress range of 1–13 MPa to clarify the existence of grain boundary sliding (GBS) mechanism during creep deformation. Experimental data within the GBS regime shows the stress exponent is ~2 and the activation energy value is close to that for grain boundary diffusion. Analyses of the fracture surface of the sample revealed that the GBS provides many stress concentrated sites for diffusional cavities formation and leads to premature failure. Scanning electron microscopy images show the appearances of both ductile and brittle type fracture mechanism. X-ray diffraction line profile analysis (based on Williamson-Hall technique) shows a reduction in dislocation density due to dynamic recovery (DRV). A correlation between experimental data and Langdon's model for GBS was also demonstrated.

  19. Student Solutions Manual to Boundary Value Problems and Partial Differential Equations

    CERN Document Server

    Powers, David L

    2005-01-01

    This student solutions manual accompanies the text, Boundary Value Problems and Partial Differential Equations, 5e. The SSM is available in print via PDF or electronically, and provides the student with the detailed solutions of the odd-numbered problems contained throughout the book.Provides students with exercises that skillfully illustrate the techniques used in the text to solve science and engineering problemsNearly 900 exercises ranging in difficulty from basic drills to advanced problem-solving exercisesMany exercises based on current engineering applications

  20. Boundary-layer theory

    CERN Document Server

    Schlichting (Deceased), Hermann

    2017-01-01

    This new edition of the near-legendary textbook by Schlichting and revised by Gersten presents a comprehensive overview of boundary-layer theory and its application to all areas of fluid mechanics, with particular emphasis on the flow past bodies (e.g. aircraft aerodynamics). The new edition features an updated reference list and over 100 additional changes throughout the book, reflecting the latest advances on the subject.

  1. Measuring the Substellar Boundary

    Science.gov (United States)

    Cancino, Adolfo Andrew; Dupuy, Trent

    2018-01-01

    Brown dwarfs are not massive enough to undergo hydrogen fusion and therefore constantly lose heat and change luminosity over their lifetime. Because of this, brown dwarfs do not follow the same pattern that stars on the main sequence follow. Brown dwarfs can have similar luminosities but widely differing masses, or vice versa, while stars follow a tight relationship between mass and luminosity. In principle, mass and luminosity measurements straddling the boundary between stars and brown dwarfs could be used to directly measure this dividing line in mass. We present a method for determining this boundary accurately given a limited sample size. We tested our method with Monte Carlo simulated samples of brown dwarfs and stars with randomly drawn masses and ages, using evolutionary models to infer luminosities. In our simulation designed to mimic the largest current sample of such mass measurements (37 objects; Dupuy & Liu 2017), we find that the uncertainty in the dividing line that can be inferred from the data is ± 4 MJup. This implies that distinguishing between competing evolutionary model predictions for the boundary (~70-80 MJup) will be difficult given the current sample size of mass measurements.

  2. A statistical comparison of SuperDARN spectral width boundaries and DMSP particle precipitation boundaries in the afternoon sector ionosphere

    Directory of Open Access Journals (Sweden)

    G. Chisham

    2005-12-01

    Full Text Available The open-closed magnetic field line boundary (OCB is best measured at the foot points of the boundary in the Earth's ionosphere where continuous and extensive spatiotemporal measurements can be made. The ability to make routine observations of this type is crucial if accurate global measurements of energy transfer processes occurring at the boundary, such as magnetic reconnection, are to become a reality. The spectral width boundary (SWB measured by the Super Dual Auroral Radar Network (SuperDARN has been shown to be a reliable ionospheric proxy for the OCB at certain magnetic local times (MLTs. However, the reliability of the SWB proxy in the afternoon sector ionosphere (12:00-18:00 MLT has been questionable. In this paper we undertake a statistical comparison of the latitudinal locations of SWBs measured by SuperDARN and particle precipitation boundaries (PPBs measured by the Defense Meteorological Satellite Program (DMSP spacecraft, concentrating on the PPB which best approximates the location of the OCB. The latitudes of SWBs and PPBs were identified using automated algorithms applied to 5 years (1997-2001 of data measured in the 12:00-18:00 MLT range. A latitudinal difference was measured between each PPB and the nearest SWB within a ±10 min universal time (UT window and within a ±1 h MLT window. The results show that when the SWB is identified at higher geomagnetic latitudes (poleward of ~74, it is a good proxy for the OCB, with 76% of SWBs lying within 3 of the OCB. At lower geomagnetic latitudes (equatorward of ~74, the correlation is poor and the results suggest that most of the SWBs being identified represent ionospheric variations unassociated with the OCB, with only 32% of SWBs lying within 3 of the OCB. We propose that the low level of precipitating electron energy flux, typical of latitudes well equatorward of the OCB in the afternoon sector, may be a factor in enhancing spectral width values at these lower latitudes. A

  3. Seismic Detectability of the Postperovskite Boundary (Invited)

    Science.gov (United States)

    Shim, S.; Catalli, K.; Prakapenka, V.

    2009-12-01

    The depth range where both perovskite (Pv) and postperovskite (PPv) phases exist (mixed phase region or boundary thickness) strongly influence the seismic detectability of the PPv boundary and convection in the D" layer. We measured the thickness of the postperovskite (PPv) boundary in (Mg0.91Fe0.09)SiO3, (Mg0.9Fe0.1)(Al0.1Si0.9)O3, and (Mg0.91Fe0.09)(Fe0.09Si0.91)O3 in the laser-heated diamond-anvil cell at in situ high pressure-temperature conditions up to 3000 K and 145 GPa. Both Fe2+ and Fe3++Al increase the PPv boundary thickness to 400~600±100 km which is substantially larger than the thickness of the D" discontinuity (<30 km) [Lay 2008], while Fe3+ alone does not increase the thickness. Calculations using our PPv boundary results and recent element partitioning studies show that the Fe2+ buffering effect of ferropericlase (Fp) may increase the PPv transition pressure and decrease the PPv boundary thickness in an Al-free system. However, the magnitude of the buffering effect is not sufficient to fit the PPv boundary thickness to the thickness of the D" discontinuity for pyrolite. Furthermore, Al increases the PPv boundary thickness, and the rapid temperature increase in the D" layer suppresses the nonlinearity in the PPv phase fraction profile and prevents the completion of the PPv transition in Earth's mantle. The PPv boundary will be particularly thick in regions with elevated Al content and/or low Mg/Si ratio (such as basaltic materials), reducing the effects of the large positive Clapeyron slope of the PPv boundary on the buoyancy of thermal anomalies and stabilizing the compositional heterogeneities at the lowermost mantle. If the PPv transition is the source of the D" discontinuity, regions with sharp discontinuities require distinct compositions, such as a higher Mg/Si ratio or low Al content.

  4. Boundary issues and personality disorders.

    Science.gov (United States)

    Gutheil, Thomas G

    2005-03-01

    The author first presents an overview of the basic elements of boundary theory and clarifies the distinction between boundary crossings and boundary violations. The concepts of context dependence, power asymmetry, and fiduciary duty as they relate to boundary problems are also discussed. The intrinsic and extrinsic consequences of boundary problems are reviewed. The extrinsic consequences fall into three major categories: civil lawsuits, complaints to the board of registration, and complaints to professional societies. The author then reviews types of boundary issues that arise in relation to histrionic, dependent, antisocial, and borderline personality disorders. Countertransference issues that arise in working with patients with personality disorders are discussed, as well as cultural differences that may affect the perception of boundary problems. The article ends with a list of risk management principles and recommendations for avoiding boundary problems in the therapeutic relationship.

  5. Allegheny County Zip Code Boundaries

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset demarcates the zip code boundaries that lie within Allegheny County. These are not clipped to the Allgeheny County boundary. If viewing this...

  6. An Optical Study of Ice Grain Boundaries

    Science.gov (United States)

    Thomson, Erik S.

    The equilibrium phase geometry and evolution of polycrystals underlies the nature of materials. In particular, grain boundaries dominate the total interfacial area within polycrystalline materials. Our experimental studies are motivated by the importance of the structure, evolution, and thermodynamic behavior of grain boundaries near bulk melting temperatures. Ice is singled out as a material of interest due to its geophysical importance and its advantageous optical properties. An experimental apparatus and light reflection technique is designed to measure grain boundary melting in ice bicrystals, in thermodynamic equilibrium The technique allows continuous monitoring of reflected light intensity from the grain boundary as the temperature and solutal composition are systematically varied. For each sample the individual crystal orientations are also measured. The type and concentration of impurity in the liquid is controlled and the temperature is continuously recorded and controlled over a range near the melting point. An optical model of the interface is developed in order to convert experimental reflection data into a physical measurement of the liquidity of the grain boundary. Solutions are found for reflection and transmission amplitude coefficients for waves propagating from an arbitrarily oriented uniaxial anisotropic material into an isotropic material. This general model is used to determine solutions for three layer, ice/water/ice, systems with crystals of arbitrary orientation, and is broadly applicable to layered materials. Experimental results show thicker grain boundary liquid layers than expected from classical colligative effects. A physically realistic model of intermolecular interactions succeeds in bounding the measurements. These measurements may have important implications for understanding a wide range of effects in polycrystalline materials. Likewise, the experimental techniques and optical theory may be applied to other systems of broad

  7. An analysis of Mn-Zn ferrite microstructure by impedance spectroscopy, scanning transmission electron microscopy and energy dispersion spectrometry characterizations

    Science.gov (United States)

    Loyau, V.; Wang, G.-Y.; Bue, M. Lo; Mazaleyrat, F.

    2012-03-01

    AC (alternative current) resistivity measurement results on Mn-Zn sintered ferrite were analyzed in the 0.1-500 MHz range. From electrical point of view, the material could be represented by an equivalent circuit of parallel resistance-capacitance cells connected in series corresponding to the contributions from bulk grains in one hand, and grain boundary layers in the other hand. The experimental resistivity curves were fitted with the model. The as obtained parameters give information on dielectric properties and conductivity of both bulk grains and boundary layers. For the studied material, it appears that the resistivity at low frequencies is increased 27 times due to the boundary layers effects. Scanning transmission electron microscopy and energy dispersion spectrometry characterization where performed in order to detect impurities at a grain boundary layer which can explain those wide differences between bulk grains and boundary layers electrical properties. It appears that the two components have close chemical compositions, but some calcium impurities segregate at the boundary which increases dramatically the resistivity of these layers. Furthermore, the bulk grains show relative permittivity around 350 at low frequency which is much smaller than the one measured for the whole material which is in the 50,000-100,000 range. This giant-dielectric behavior can be explained by an internal barrier layer at the grain boundaries. At last, the components of classical eddy current losses including losses due to ohmic effects and (true) dielectric losses on both bulk grain and boundary layers are distinguished.

  8. Report to Congress on Sustainable Ranges, 2015

    Science.gov (United States)

    2015-03-01

    no organic capability. HQ NTTR continues to work with JIOR to provide a mobile service which can be deployed at the Urban Operations Complex ( UOC ...NTTR continues to work with JIOR to provide a mobile service which can be deployed at the Urban Operations Complex ( UOC ) on Range 62. Electronic... UOC ) on Range 62. Electronic Combat Support h The range lacks a complete electronic target set. EA platforms do not get real-time feedback on their

  9. Atomistic studies of grain boundaries in alloys and compounds

    Energy Technology Data Exchange (ETDEWEB)

    Vitek, V.

    1992-02-01

    In this research project we carry out theoretical, computer modeling, studies of the atomic structure of grain boundaries in binary alloys. Both ordered and disordered alloys are investigated. The goal is to analyze those structural, chemical and electronic features that distinguish alloys from pure metals and are responsible for remarkably different intergranular fracture behavior of alloys when compared with pure metals. The most important phenomenon is, of course, segregation and related structural changes in the boundary region. When studying segregation phenomena copper-bismuth is a very suitable model system since bismuth segregation occurs readily, leads to boundary faceting and thus to remarkable changes in the boundary structure, as well as to a very strong embrittlement. Our recent research concentrated on the investigation of the structure of {Sigma} = 3 (111)/(11{bar 1}) facets formed during segregation from boundaries which were originally curved.

  10. Boundaries and Boundary Marks - Substantive Cultural Heritage of Extensive Importance

    Science.gov (United States)

    Waldhaeusl, P.; Koenig, H.; Mansberger, R.

    2015-08-01

    The Austrian Society for surveying and Geoinformation (ASG) has proposed to submit "Boundaries and Boundary Marks" for the UNESCO World Heritage title. It was time that boundaries, borders and limits of all types as well as ownership rights would find the proper attention in the global public. Landmarks symbolize the real property and the associated rights and obligations, in a figurative sense, the property generally and all legal limits. A democratic state of law is impossible at today's population density without a functioning land administration system with surveying and jurisdiction. As monumental World Heritage representatives of the geodetic artwork "Boundaries and Boundary Marks" are specifically proposed: remaining monuments of the original cadastral geodetic network, the first pan-Austrian surveying headquarters in Vienna, and a specific selection of outstanding boundary monuments. Landmarks are monuments to the boundaries which separate rights and obligations, but also connect the neighbors peacefully after written agreement. "And cursed be he who does not respect the boundaries" you wrote already 3000 years ago. Boundaries and Boundary Marks are a real thing; they all belong to the tangible or material heritage of human history. In this context also the intangible heritage is discussed. This refers to oral tradition and expressions, performing arts; social practices, rituals and festive events; as well as to knowledge and practices handling nature and the universe. "Boundaries and Boundary Marks" do not belong to it, but clearly to the material cultural world heritage. "Boundary and Boundary Marks" is proposed to be listed according to the criteria (ii),(iv),(vi).

  11. Managing collaboration across boundaries in health information technology projects.

    Science.gov (United States)

    Garrety, Karin; Dalley, Andrew; McLoughlin, Ian; Wilson, Rob; Yu, Ping

    2012-01-01

    One reason that it is so difficult to build electronic systems for collecting and sharing health information is that their design and implementation requires clear goals and a great deal of collaboration among people from diverse social and occupational worlds. This paper uses empirical examples from two Australian health informatics projects to illustrate the importance of boundary objects and boundary spanning activities in facilitating the high degree of collaboration required for the design and implementation of workable systems.

  12. Solar wind dependent models for the shapes of the Martian plasma boundaries based on Mars Express measurements

    Science.gov (United States)

    Ramstad, Robin; Barabash, Stas; Futaana, Yoshifumi; Holmstrom, Mats

    2016-10-01

    The long operational life (2003-) of Mars Express (MEX) has allowed the spacecraft to make plasma measurements in the Martian environment over a wide range of upstream conditions. We have analyzed ~5000 MEX orbits, covering three orders of magnitude in solar wind dynamic pressure, with data from the on-board Analyzer of Space Plasmas and Energetic Particles (ASPERA-3) package, mapping the locations where MEX crosses the main plasma boundaries; induced magnetosphere boundary (IMB), ionosphere boundary (IB) and bow shock (BS). A coincidence scheme was employed, where data from the Ion Mass Analyzer (IMA) and the Electron Spectrometer (ELS) had to agree for a positive boundary identification, which resulted in crossings from 882 orbit segments that were used to create dynamic 2-parameter (solar wind density, nsw, and velocity vsw dependent global dynamic models for the IMB, IB and BS. The modeled response is found to be individual to each boundary; the BS is stationary for all but extremely thin and slow solar wind, the IMB scales solely dependent on dynamic pressure and the IB changes morphology with different trends for nsw and vsw. We find no significant trend in IMB location with changing EUV intensities when the upstream solar wind is constrained to nominal conditions. Finally, the IMB model is used to extrapolate the solar wind stand-off distance in the ancient (0.7 Ga old) solar wind.

  13. Transcending Organizational Boundaries

    DEFF Research Database (Denmark)

    Kringelum, Louise Tina Brøns

    This thesis explores how processes of business model innovation can unfold in a port authority by transcending organizational boundaries through inter-organizational collaboration. The findings contribute to two fields of academic inquiry: the study of business model innovation and the study of how...... by applying the engaged scholarship approach, thereby providing a methodological contribution to both port and business model research. Emphasizing the interplay of intra- and inter-organizational business model innovation, the thesis adds insight into the roles of port authorities, business model trends...

  14. Grain boundaries: Progress report, June 15, 1988--June 14, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1989-02-01

    The present document is a progress report describing the work accomplished during the second year (June 15, 1988-June 14, 1989) of our three-year grant to study grain boundaries which started 15 June 1987. The research that was proposed initially for this period consisted of the following: (1) study of the atomistic structure of grain boundaries by means by combined x-ray diffraction and computer modeling; (2) study of grain boundary phase transitions by electron microscopy and computer modeling. 12 refs.

  15. Grain boundaries. Progress report, February 15, 1991--October 15, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1991-12-31

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990--February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: Study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  16. Electronic plants.

    Science.gov (United States)

    Stavrinidou, Eleni; Gabrielsson, Roger; Gomez, Eliot; Crispin, Xavier; Nilsson, Ove; Simon, Daniel T; Berggren, Magnus

    2015-11-01

    The roots, stems, leaves, and vascular circuitry of higher plants are responsible for conveying the chemical signals that regulate growth and functions. From a certain perspective, these features are analogous to the contacts, interconnections, devices, and wires of discrete and integrated electronic circuits. Although many attempts have been made to augment plant function with electroactive materials, plants' "circuitry" has never been directly merged with electronics. We report analog and digital organic electronic circuits and devices manufactured in living plants. The four key components of a circuit have been achieved using the xylem, leaves, veins, and signals of the plant as the template and integral part of the circuit elements and functions. With integrated and distributed electronics in plants, one can envisage a range of applications including precision recording and regulation of physiology, energy harvesting from photosynthesis, and alternatives to genetic modification for plant optimization.

  17. Reweighting twisted boundary conditions

    CERN Document Server

    Bussone, Andrea; Hansen, Martin; Pica, Claudio

    2015-01-01

    Imposing twisted boundary conditions on the fermionic fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour and only in the valence, and this causes a breaking of unitarity. In this work we explore the possibility of restoring unitarity through the reweighting method. We first study some properties of the approach at tree level and then we stochastically evaluate ratios of fermionic determinants for different boundary conditions in order to include them in the gauge averages, avoiding in this way the expensive generation of new configurations for each choice of the twisting angle, $\\theta$. As expected the effect of reweighting is negligible in the case of large volumes but it is important when the volumes are small and the twisting angles are large. In particular we find a measurable effect for the plaquette and the pion correlation function in the case of $\\theta=\\pi/2$ in a volume $16\\times 8^3$, and we observe a syst...

  18. Boundary Plasma Turbulence Simulations for Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Xu, X; Umansky, M; Dudson, B; Snyder, P

    2008-05-15

    The boundary plasma turbulence code BOUT models tokamak boundary-plasma turbulence in a realistic divertor geometry using modified Braginskii equations for plasma vorticity, density (ni), electron and ion temperature (T{sub e}; T{sub i}) and parallel momenta. The BOUT code solves for the plasma fluid equations in a three dimensional (3D) toroidal segment (or a toroidal wedge), including the region somewhat inside the separatrix and extending into the scrape-off layer; the private flux region is also included. In this paper, a description is given of the sophisticated physical models, innovative numerical algorithms, and modern software design used to simulate edge-plasmas in magnetic fusion energy devices. The BOUT code's unique capabilities and functionality are exemplified via simulations of the impact of plasma density on tokamak edge turbulence and blob dynamics.

  19. Electronics and electronic systems

    CERN Document Server

    Olsen, George H

    1987-01-01

    Electronics and Electronic Systems explores the significant developments in the field of electronics and electronic devices. This book is organized into three parts encompassing 11 chapters that discuss the fundamental circuit theory and the principles of analog and digital electronics. This book deals first with the passive components of electronic systems, such as resistors, capacitors, and inductors. These topics are followed by a discussion on the analysis of electronic circuits, which involves three ways, namely, the actual circuit, graphical techniques, and rule of thumb. The remaining p

  20. Grain boundaries: Final report, June 16, 1984-June 15, 1987

    Energy Technology Data Exchange (ETDEWEB)

    Balluffi, R.W.; Bristowe, P.D.

    1987-01-01

    During the three-year period coming to a close on June 15, 1987, we have conducted a relatively broad investigation of the structure and properties of grain boundaries on a basic level. The work mainly consisted of a combined experimental and computer simulation attack on the problem of determining the atomic structure and corresponding properties of high-angle grain boundaries in metals. The experimental work has relied heavily on techniques developed for producing thin film specimens containing planar grain boundaries of predetermined and controlled geometry. Studies of the atomistic and dislocation structures of these boundaries have been carried out using electron microscopy in the diffraction, diffraction contrast and lattice imaging modes. Of particular interest have been experiments aimed at deciding questions such as ''to what extent are grain boundaries ordered structures.'' and ''to what extent can grain boundary structures be described by dislocation and structural unit models.''. Efforts have been made to measure relative grain boundary energies. The computer simulation work has involved both molecular statics and molecular dynamics calculations using pair potentials and more sophisticated ab initio methods. Emphasis has been on calculating boundary structures and energies in situations where the results can be compared with experiments. Efforts have been made to determine whether the calculated results fit dislocation and structural unit models.

  1. Valley Chern numbers and boundary modes in gapped bilayer graphene.

    Science.gov (United States)

    Zhang, Fan; MacDonald, Allan H; Mele, Eugene J

    2013-06-25

    Electronic states at domain walls in bilayer graphene are studied by analyzing their four- and two-band continuum models, by performing numerical calculations on the lattice, and by using quantum geometric arguments. The continuum theories explain the distinct electronic properties of boundary modes localized near domain walls formed by interlayer electric field reversal, by interlayer stacking reversal, and by simultaneous reversal of both quantities. Boundary mode properties are related to topological transitions and gap closures, which occur in the bulk Hamiltonian parameter space. The important role played by intervalley coupling effects not directly captured by the continuum model is addressed using lattice calculations for specific domain wall structures.

  2. Negotiating Cluster Boundaries

    DEFF Research Database (Denmark)

    Giacomin, Valeria

    2017-01-01

    Palm oil was introduced to Malay(si)a as an alternative to natural rubber, inheriting its cluster organizational structure. In the late 1960s, Malaysia became the world’s largest palm oil exporter. Based on archival material from British colonial institutions and agency houses, this paper focuses...... on the governance dynamics that drove institutional change within this cluster during decolonization. The analysis presents three main findings: (i) cluster boundaries are defined by continuous tug-of-war style negotiations between public and private actors; (ii) this interaction produces institutional change...... within the cluster, in the form of cumulative ‘institutional rounds’ – the correction or disruption of existing institutions or the creation of new ones; and (iii) this process leads to a broader inclusion of local actors in the original cluster configuration. The paper challenges the prevalent argument...

  3. Repeated judgment sampling: Boundaries

    Directory of Open Access Journals (Sweden)

    Johannes Muller-Trede

    2011-06-01

    Full Text Available This paper investigates the boundaries of the recent result that eliciting more than one estimate from the same person and averaging these can lead to accuracy gains in judgment tasks. It first examines its generality, analysing whether the kind of question being asked has an effect on the size of potential gains. Experimental results show that the question type matters. Previous results reporting potential accuracy gains are reproduced for year-estimation questions, and extended to questions about percentage shares. On the other hand, no gains are found for general numerical questions. The second part of the paper tests repeated judgment sampling's practical applicability by asking judges to provide a third and final answer on the basis of their first two estimates. In an experiment, the majority of judges do not consistently average their first two answers. As a result, they do not realise the potential accuracy gains from averaging.

  4. Superfluid Boundary Layer.

    Science.gov (United States)

    Stagg, G W; Parker, N G; Barenghi, C F

    2017-03-31

    We model the superfluid flow of liquid helium over the rough surface of a wire (used to experimentally generate turbulence) profiled by atomic force microscopy. Numerical simulations of the Gross-Pitaevskii equation reveal that the sharpest features in the surface induce vortex nucleation both intrinsically (due to the raised local fluid velocity) and extrinsically (providing pinning sites to vortex lines aligned with the flow). Vortex interactions and reconnections contribute to form a dense turbulent layer of vortices with a nonclassical average velocity profile which continually sheds small vortex rings into the bulk. We characterize this layer for various imposed flows. As boundary layers conventionally arise from viscous forces, this result opens up new insight into the nature of superflows.

  5. Public Computation & Boundary Play

    CERN Document Server

    Sengupta, Pratim

    2016-01-01

    In this paper, we introduce 'public computation' as a genre of learning environments that can be used to radically broaden public participation in authentic, computation-enabled STEM disciplinary practices. Our paradigmatic approach utilizes open source software designed for professional scientists, engineers and digital artists, and situates them in an undiluted form, alongside live and archived expert support, in a public space. We present a case study of DigiPlay, a prototypical public computation space we designed at the University of Calgary, where users can interact directly with scientific simulations as well as the underlying open source code using an array of massive multi- touch screens. We argue that in such a space, public interactions with the code can be thought of as boundary work and play, through which public participation becomes legitimate scientific act, as the public engages in scientific creation through truly open-ended explorations with the code.

  6. Challenging the Boundaries

    DEFF Research Database (Denmark)

    Nørgaard, Nina

    2004-01-01

    to explore in the study and teaching of foreign languages. Not only may linguistics and literature be employed to shed light on each other, the insights gained may furthermore prove useful in a broader context in our foreign language studies. The article begins with a brief introduction to literary...... linguistics in general and to Hallidayan linguistics in particular. The theoretical framework thus laid out, it is exemplified how Halliday's theory of language may be employed in the analysis of literature. The article concludes by considering the possible status of literary linguistics in a broader......To many people, challenging the boundaries between the traditional disciplines in foreign language studies means doing cultural studies. The aim of this article is to pull in a different direction by suggesting how the interface between linguistics and literature may be another fertile field...

  7. The electronic band structure of Ge1-x Sn x in the full composition range: indirect, direct, and inverted gaps regimes, band offsets, and the Burstein-Moss effect

    Science.gov (United States)

    Polak, M. P.; Scharoch, P.; Kudrawiec, R.

    2017-05-01

    A comprehensive and detailed study of the composition dependence of lattice constants, band gaps and band offsets has been performed for bulk Ge1-x Sn x alloy in the full composition range using state-of-the-art density functional theory methods. A spectral weight approach to band unfolding has been applied as a means of distinguishing the indirect and direct band gaps from folded supercell band structures. In this way, four characteristic regions of the band gap character have been identified for Ge1-x Sn x alloy: an indirect band gap (x    25%) with inverse spin-orbit split-off for 45%  text{C{{\\text{B}} Γ }}}   =  2.43  ±  0.06 eV, {{b}\\text{C{{\\text{B}}L}}}   =  0.64  ±  0.04 eV, {{b}\\text{VB}}   =  -0.59  ±  0.04 eV, and {{b}\\text{SO}}   =  -0.49  ±  0.05 eV). This indicates that Ge1-x Sn x behaves like a highly mismatched group IV alloy. The composition dependence of lattice constant shows negligible bowing (b a   =  -0.083 Å). Obtained results have been compared with available experimental data. The origin of band gap reduction and large bowing has been analyzed and conclusions have been drawn regarding the relationship between experimental and theoretical results. It is shown that due to the low DOS at the Γ-point, a significant filling of CB by electrons in the direct gap regime may easily take place. Therefore, the Burstein-Moss effect should be considered when comparing experimental data with theoretical predictions as has already been shown for other intrinsic n-type narrow gap semiconductors (e.g. InN).

  8. The Plasmasphere Boundary Layer

    Directory of Open Access Journals (Sweden)

    D. L. Carpenter

    2004-12-01

    Full Text Available As an inner magnetospheric phenomenon the plasmapause region is of interest for a number of reasons, one being the occurrence there of geophysically important interactions between the plasmas of the hot plasma sheet and of the cool plasmasphere. There is a need for a conceptual framework within which to examine and discuss these interactions and their consequences, and we therefore suggest that the plasmapause region be called the Plasmasphere Boundary Layer, or PBL. Such a term has been slow to emerge because of the complexity and variability of the plasma populations that can exist near the plasmapause and because of the variety of criteria used to identify the plasmapause in experimental data. Furthermore, and quite importantly in our view, a substantial obstacle to the consideration of the plasmapause region as a boundary layer has been the longstanding tendency of textbooks on space physics to limit introductory material on the plasmapause phenomenon to zeroth order descriptions in terms of ideal MHD theory, thus implying that the plasmasphere is relatively well understood. A textbook may introduce the concept of shielding of the inner magnetosphere from perturbing convection electric fields, but attention is not usually paid to the variety of physical processes reported to occur in the PBL, such as heating, instabilities, and fast longitudinal flows, processes which must play roles in plasmasphere dynamics in concert with the flow regimes associated with the major dynamo sources of electric fields. We believe that through the use of the PBL concept in future textbook discussions of the plasmasphere and in scientific communications, much progress can be made on longstanding questions about the physics involved in the formation of the plasmapause and in the cycles of erosion and recovery of the plasmasphere. Key words. Magnetospheric physics (plasmasphere; plasma convection; MHD waves and instabilities

  9. The Plasmasphere Boundary Layer

    Directory of Open Access Journals (Sweden)

    D. L. Carpenter

    2004-12-01

    Full Text Available As an inner magnetospheric phenomenon the plasmapause region is of interest for a number of reasons, one being the occurrence there of geophysically important interactions between the plasmas of the hot plasma sheet and of the cool plasmasphere. There is a need for a conceptual framework within which to examine and discuss these interactions and their consequences, and we therefore suggest that the plasmapause region be called the Plasmasphere Boundary Layer, or PBL. Such a term has been slow to emerge because of the complexity and variability of the plasma populations that can exist near the plasmapause and because of the variety of criteria used to identify the plasmapause in experimental data. Furthermore, and quite importantly in our view, a substantial obstacle to the consideration of the plasmapause region as a boundary layer has been the longstanding tendency of textbooks on space physics to limit introductory material on the plasmapause phenomenon to zeroth order descriptions in terms of ideal MHD theory, thus implying that the plasmasphere is relatively well understood. A textbook may introduce the concept of shielding of the inner magnetosphere from perturbing convection electric fields, but attention is not usually paid to the variety of physical processes reported to occur in the PBL, such as heating, instabilities, and fast longitudinal flows, processes which must play roles in plasmasphere dynamics in concert with the flow regimes associated with the major dynamo sources of electric fields. We believe that through the use of the PBL concept in future textbook discussions of the plasmasphere and in scientific communications, much progress can be made on longstanding questions about the physics involved in the formation of the plasmapause and in the cycles of erosion and recovery of the plasmasphere.

    Key words. Magnetospheric physics (plasmasphere; plasma convection; MHD waves and instabilities

  10. Conformal boundaries of warped products

    DEFF Research Database (Denmark)

    Kokkendorff, Simon Lyngby

    2006-01-01

    In this note we prove a result on how to determine the conformal boundary of a type of warped product of two length spaces in terms of the individual conformal boundaries. In the situation, that we treat, the warping and conformal distortion functions are functions of distance to a base point....... The result is applied to produce examples of CAT(0)-spaces, where the conformal and ideal boundaries differ in interesting ways....

  11. Electronics engineer's reference book

    CERN Document Server

    Turner, L W

    1976-01-01

    Electronics Engineer's Reference Book, 4th Edition is a reference book for electronic engineers that reviews the knowledge and techniques in electronics engineering and covers topics ranging from basics to materials and components, devices, circuits, measurements, and applications. This edition is comprised of 27 chapters; the first of which presents general information on electronics engineering, including terminology, mathematical equations, mathematical signs and symbols, and Greek alphabet and symbols. Attention then turns to the history of electronics; electromagnetic and nuclear radiatio

  12. The Boundary Function Method. Fundamentals

    Science.gov (United States)

    Kot, V. A.

    2017-03-01

    The boundary function method is proposed for solving applied problems of mathematical physics in the region defined by a partial differential equation of the general form involving constant or variable coefficients with a Dirichlet, Neumann, or Robin boundary condition. In this method, the desired function is defined by a power polynomial, and a boundary function represented in the form of the desired function or its derivative at one of the boundary points is introduced. Different sequences of boundary equations have been set up with the use of differential operators. Systems of linear algebraic equations constructed on the basis of these sequences allow one to determine the coefficients of a power polynomial. Constitutive equations have been derived for initial boundary-value problems of all the main types. With these equations, an initial boundary-value problem is transformed into the Cauchy problem for the boundary function. The determination of the boundary function by its derivative with respect to the time coordinate completes the solution of the problem.

  13. Analysis of turbulent boundary layers

    CERN Document Server

    Cebeci, Tuncer

    1974-01-01

    Analysis of Turbulent Boundary Layers focuses on turbulent flows meeting the requirements for the boundary-layer or thin-shear-layer approximations. Its approach is devising relatively fundamental, and often subtle, empirical engineering correlations, which are then introduced into various forms of describing equations for final solution. After introducing the topic on turbulence, the book examines the conservation equations for compressible turbulent flows, boundary-layer equations, and general behavior of turbulent boundary layers. The latter chapters describe the CS method for calculati

  14. The Pinning by Particles of Low and High Angle Grain Boundaries during Grain Growth

    DEFF Research Database (Denmark)

    Tweed, C.J.; Ralph, B.; Hansen, Niels

    1984-01-01

    and coworkers. These estimates of local driving pressures have shown that they are similar for both the low and the high angle boundaries encountered in the samples. The pinning effects by particles at high angle boundaries are in general accord with the model due to Zener whilst those at low angle boundaries......A study has been made using transmission electron microscopy of the pinning of grain boundaries in aluminium during grain growth by fine dispersions of alumina particles. The boundary parameters have been determined with precision and the pinning effects measured using an approach due to Ashby...

  15. Electronic detectors for electron microscopy.

    Science.gov (United States)

    Faruqi, A R; McMullan, G

    2011-08-01

    Electron microscopy (EM) is an important tool for high-resolution structure determination in applications ranging from condensed matter to biology. Electronic detectors are now used in most applications in EM as they offer convenience and immediate feedback that is not possible with film or image plates. The earliest forms of electronic detector used routinely in transmission electron microscopy (TEM) were charge coupled devices (CCDs) and for many applications these remain perfectly adequate. There are however applications, such as the study of radiation-sensitive biological samples, where film is still used and improved detectors would be of great value. The emphasis in this review is therefore on detectors for use in such applications. Two of the most promising candidates for improved detection are: monolithic active pixel sensors (MAPS) and hybrid pixel detectors (of which Medipix2 was chosen for this study). From the studies described in this review, a back-thinned MAPS detector appears well suited to replace film in for the study of radiation-sensitive samples at 300 keV, while Medipix2 is suited to use at lower energies and especially in situations with very low count rates. The performance of a detector depends on the energy of electrons to be recorded, which in turn is dependent on the application it is being used for; results are described for a wide range of electron energies ranging from 40 to 300 keV. The basic properties of detectors are discussed in terms of their modulation transfer function (MTF) and detective quantum efficiency (DQE) as a function of spatial frequency.

  16. Symbolic Boundary Work in Schools: Demarcating and Denying Ethnic Boundaries

    Science.gov (United States)

    Tabib-Calif, Yosepha; Lomsky-Feder, Edna

    2014-01-01

    This article examines the symbolic boundary work that is carried out at a school whose student population is heterogeneous in terms of ethnicity and class. Based on ethnography, the article demonstrates how the school's staff seeks to neutralize ethnic boundaries and their accompanying discourse, while the pupils try to bring ethnic…

  17. Collaboration in Healthcare Through Boundary Work and Boundary Objects

    DEFF Research Database (Denmark)

    Meier, Ninna

    2015-01-01

    This article contributes to our understanding of how boundary work is practiced in healthcare settings. Previous studies have shown how boundaries are constantly changing, multiple, and co-existing, and can also be relatively stable cognitive and social distinctions between individuals and groups....... In highly specialized, knowledge-intensive organizations such as healthcare organizations, organizational, professional, and disciplinary boundaries mark the formal structure and division of work. Collaboration and coordination across these boundaries are essential to minimizing gaps in patient care......, but also may be challenging to achieve in practice. By drawing on data from an ethnographic study of two hospital wards, this article investigates practices of cross-disciplinary and professional collaboration and adds to our knowledge of how this kind of boundary work is produced in context. Moreover...

  18. Boundary-Layer & health

    Science.gov (United States)

    Costigliola, V.

    2010-09-01

    It has long been known that specific atmospheric processes, such as weather and longer-term climatic fluctuations, affect human health. The biometeorological literature refers to this relationship as meteorotropism, defined as a change in an organism that is correlated with a change in atmospheric conditions. Plenty of (patho)physiological functions are affected by those conditions - like the respiratory diseases - and currently it is difficult to put any limits for pathologies developed in reply. Nowadays the importance of atmospheric boundary layer and health is increasingly recognised. A number of epidemiologic studies have reported associations between ambient concentrations of air pollution, specifically particulate pollution, and adverse health effects, even at the relatively low concentrations of pollution found. Since 1995 there have been over twenty-one studies from four continents that have explicitly examined the association between ambient air pollutant mixes and daily mortality. Statistically significant and positive associations have been reported in data from various locations around the world, all with varying air pollutant concentrations, weather conditions, population characteristics and public health policies. Particular role has been given to atmospheric boundary layer processes, the impact of which for specific patient-cohort is, however, not well understood till now. Assessing and monitoring air quality are thus fundamental to improve Europe's welfare. One of current projects run by the "European Medical Association" - PASODOBLE will develop and demonstrate user-driven downstream information services for the regional and local air quality sectors by combining space-based and in-situ data with models in 4 thematic service lines: - Health community support for hospitals, pharmacies, doctors and people at risk - Public information for regions, cities, tourist industry and sporting event organizers - Compliance monitoring support on particulate

  19. Grain boundary tunnel spectroscopy of the electron-doped cuprate superconductor La{sub 2-x}Ce{sub x}CuO{sub 4}; Korngrenzen-Tunnelspektroskopie am elektronendotierten Kupratsupraleiter La{sub 2-x}Ce{sub x}CuO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Wagenknecht, Michael

    2008-07-01

    The electron doped superconductor La{sub 2-x}Ce{sub x}CuO{sub 4} (LCCO) has been investigated by electric transport measurements at low temperatures T down to 5 K and high magnetic fields up to 16 T. For this purpose LCCO thin film tunnel junctions have been prepared on bicrystal substrates by molecular beam epitaxy and micro structuring. The samples were characterised by measuring the thin film resistivity and the tunnel conductance of quasi particles across the grain boundary. By these measurements an unconventional symmetry of the order parameter could be revealed for La{sub 2-x}Ce{sub x}CuO{sub 4}. Furthermore it was shown, that the tunnel conductance can be used as a probe for the upper critical field B{sub c2}(T). By using this method a value of B{sub c2}{proportional_to}24 T has been found for La{sub 2-x}Ce{sub x}CuO{sub 4}, a value roughly three times bigger than previously known. By this observation it was shown that the superconducting phase covers a larger region in the B-T-phase diagram. In addition it was concluded, that the pseudogap phase in La{sub 2-x}Ce{sub x}CuO{sub 4} is either not existent at all or covers only a small temperature region. Besides quasiparticle tunneling also the tunneling of Cooper pairs in small magnetic fields has been investigated. It was shown that the critical current across the grain boundary depends on the supplier of the bicrystal substrate. (orig.)

  20. Revealing the Microscopic Real-Space Excursion of a Laser-Driven Electron

    Directory of Open Access Journals (Sweden)

    Heiko G. Kurz

    2016-08-01

    Full Text Available High-order harmonic spectroscopy allows one to extract information on fundamental quantum processes, such as the exit time in the tunneling of an electron through a barrier with attosecond time resolution and molecular structure with angstrom spatial resolution. Here, we study the spatial motion of the electron during high-order harmonic generation in an in situ pump-probe measurement using high-density liquid water droplets as a target. We show that molecules adjacent to the emitting electron-ion pair can disrupt the electron’s trajectory when positioned within the range of the maximum electronic excursion distance. This allows us to use the parent ion and the neighboring molecules as boundaries for the electronic motion to measure the maximum electronic excursion distance during the high-order harmonic generation process. Our analysis of the process is relevant for optimizing high-harmonic yields in dense media.

  1. Seismic link at plate boundary

    Indian Academy of Sciences (India)

    transfer between two major faults, and parallel to the geothermal area extension. 1. Introduction. Plate boundaries are the zones where most earth dynamics are focussed. The complexity of tectonic boundaries draws attention to them as the largest earthquakes are felt in these areas and they elicit the natural hazard of ...

  2. Exclusion Process with Slow Boundary

    Science.gov (United States)

    Baldasso, Rangel; Menezes, Otávio; Neumann, Adriana; Souza, Rafael R.

    2017-06-01

    We study the hydrodynamic and the hydrostatic behavior of the simple symmetric exclusion process with slow boundary. The term slow boundary means that particles can be born or die at the boundary sites, at a rate proportional to N^{-θ }, where θ > 0 and N is the scaling parameter. In the bulk, the particles exchange rate is equal to 1. In the hydrostatic scenario, we obtain three different linear profiles, depending on the value of the parameter θ ; in the hydrodynamic scenario, we obtain that the time evolution of the spatial density of particles, in the diffusive scaling, is given by the weak solution of the heat equation, with boundary conditions that depend on θ . If θ \\in (0,1), we get Dirichlet boundary conditions, (which is the same behavior if θ =0, see Farfán in Hydrostatics, statical and dynamical large deviations of boundary driven gradient symmetric exclusion processes, 2008); if θ =1, we get Robin boundary conditions; and, if θ \\in (1,∞), we get Neumann boundary conditions.

  3. Fuzzy Boundary and Fuzzy Semiboundary

    OpenAIRE

    Athar, M.; Ahmad, B.

    2008-01-01

    We present several properties of fuzzy boundary and fuzzy semiboundary which have been supported by examples. Properties of fuzzy semi-interior, fuzzy semiclosure, fuzzy boundary, and fuzzy semiboundary have been obtained in product-related spaces. We give necessary conditions for fuzzy continuous (resp., fuzzy semicontinuous, fuzzy irresolute) functions. Moreover, fuzzy continuous (resp., fuzzy semicontinuous, fuzzy irresolute) functions have been characterized via fuzzy...

  4. Nucleation of small angle boundaries

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1996-12-01

    Full Text Available The internal stresses induced by the strain gradients in an array of lattice cells delineated by low-angle dislocation boundaries are partially relieved by the creation of new low-angle boundaries. This is shown to be a first-order transition...

  5. How Firms Make Boundary Decisions

    DEFF Research Database (Denmark)

    Dobrajska, Magdalena; Billinger, Stephan; Becker, Markus

    2014-01-01

    We report findings from an analysis of 234 firm boundary decisions that a manufacturing firm has made during a 10 year period. Extensive interviews with all major decision makers located both at the headquarters and subsidiaries allow us to examine (a) who was involved in each boundary decision...

  6. Studies of Grain Boundaries in Materials Subjected to Diffusional Creep

    DEFF Research Database (Denmark)

    Nørbygaard, Thomas

    Grain boundaries in crystalline Cu(2%Ni) creep specimens have been studied by use of scanning and transmission electron microscopy in order to establish the mechanism of deformation. Creep rate measurements and dependencies were found to fit reasonably well with the model for diffusional creep......) with the activity displayed during diffusional creep testing. It was found that boundaries with low deviation from perfect Σ did not contribute macroscopically to the creep strain. A resist deposition procedure was examined to improve the reference surface grid so as to allow determination of the grain boundary...... plane by use of simple stereomicroscopy directly on the surface. The etched pattern deteriorated heav-ily during creep testing, supposedly because of dislocation creep, due to exces-sive creep stress. Grain boundaries have been studied and characterised by TEM providing an insight into the diversity...

  7. Interactive Prosodic Marking of Focus, Boundary and Newness in Mandarin.

    Science.gov (United States)

    Wang, Bei; Xu, Yi; Ding, Qifan

    2017-06-09

    The current study investigates whether and how focus, phrase boundary and newness can be simultaneously marked in speech prosody in Mandarin Chinese. Homophones were used to construct three syntactic structures that differed only in boundary condition, focus was elicited by preceding questions, while newness of postboundary words was manipulated as whether they had occurred in the previous text. Systematic analysis of F0 and duration showed that (1) duration was a reliable correlate of boundary strength regardless of focus location, while involvement of F0 was only in terms of lowering of phrase-final F0 minima and raising of phrase-initial F0 minima at a relatively strong boundary, (2) postfocus compression (PFC) of F0 was applied across all boundaries, including those with long silent pauses (over 200 ms), and postfocus F0 was lowered to almost the same degree in all boundary conditions, and (3) newness of postfocus words had no systematic effect on F0 or duration. These results indicate that not only functionally focus is independent of prosodic structure and newness, but also phonetically its realization is separate from boundary marking. Focus is signaled mainly through pitch range adjustments, which can occur even across phrase breaks, whereas boundaries are mostly signaled by duration adjustments. © 2017 S. Karger AG, Basel.

  8. Diffusive boundary layers over varying topography

    KAUST Repository

    Dell, R. W.

    2015-03-25

    Diffusive bottom boundary layers can produce upslope flows in a stratified fluid. Accumulating observations suggest that these boundary layers may drive upwelling and mixing in mid-ocean ridge flank canyons. However, most studies of diffusive bottom boundary layers to date have concentrated on constant bottom slopes. We present a study of how diffusive boundary layers interact with various idealized topography, such as changes in bottom slope, slopes with corrugations and isolated sills. We use linear theory and numerical simulations in the regional ocean modeling system (ROMS) model to show changes in bottom slope can cause convergences and divergences within the boundary layer, in turn causing fluid exchanges that reach far into the overlying fluid and alter stratification far from the bottom. We also identify several different regimes of boundary-layer behaviour for topography with oceanographically relevant size and shape, including reversing flows and overflows, and we develop a simple theory that predicts the regime boundaries, including what topographies will generate overflows. As observations also suggest there may be overflows in deep canyons where the flow passes over isolated bumps and sills, this parameter range may be particularly significant for understanding the role of boundary layers in the deep ocean.

  9. The Future of Boundary Plasma and Material Science

    Science.gov (United States)

    Whyte, Dennis

    2012-03-01

    The boundary of magnetic confinement devices, from the pedestal through to the surrounding surfaces, encompasses an enormous range of plasma and material physics, and their integrated coupling. It is becoming clear that due to fundamental limits of plasma stability and material response the boundary will largely define the viability of an MFE reactor. However we face an enormous knowledge deficit in stepping from present devices and ITER towards a demonstration power plant. We outline the future of boundary research required to address this deficit. The boundary should be considered a multi-scale system of coupled plasma and material science regulated through the non-linear interface of the sheath. Measurement, theory and modeling across these scales are assessed. Dimensionless parameters, often used to organized core plasma transport on similarity arguments, can be extended to the boundary plasma, plasma-surface interactions and material response. This methodology suggests an intriguing way forward to prescribe and understand the boundary issues of an eventual reactor in intermediate devices. A particularly critical issue is that the physical chemistry of the material, which is mostly determined by the material temperature, has been too neglected; pointing to the requirement for boundary plasma experiments at appropriate material temperatures. Finally the boundary plasma requirements for quiescent heat exhaust and control of transient events, such as ELMs, will be examined.

  10. Science at the interface : grain boundaries in nanocrystalline metals.

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Mark Andrew; Follstaedt, David Martin; Knapp, James Arthur; Brewer, Luke N.; Holm, Elizabeth Ann; Foiles, Stephen Martin; Hattar, Khalid M.; Clark, Blythe B.; Olmsted, David L.; Medlin, Douglas L.

    2009-09-01

    Interfaces are a critical determinant of the full range of materials properties, especially at the nanoscale. Computational and experimental methods developed a comprehensive understanding of nanograin evolution based on a fundamental understanding of internal interfaces in nanocrystalline nickel. It has recently been shown that nanocrystals with a bi-modal grain-size distribution possess a unique combination of high-strength, ductility and wear-resistance. We performed a combined experimental and theoretical investigation of the structure and motion of internal interfaces in nanograined metal and the resulting grain evolution. The properties of grain boundaries are computed for an unprecedented range of boundaries. The presence of roughening transitions in grain boundaries is explored and related to dramatic changes in boundary mobility. Experimental observations show that abnormal grain growth in nanograined materials is unlike conventional scale material in both the level of defects and the formation of unfavored phases. Molecular dynamics simulations address the origins of some of these phenomena.

  11. Prediction of dislocation boundary characteristics

    DEFF Research Database (Denmark)

    Winther, Grethe

    Plastic deformation of both fcc and bcc metals of medium to high stacking fault energy is known to result in dislocation patterning in the form of cells and extended planar dislocation boundaries. The latter align with specific crystallographic planes, which depend on the crystallographic....... Crystal plasticity calculations combined with the hypothesis that these boundaries separate domains with local differences in the slip system activity are introduced to address precise prediction of the experimentally observed boundaries. The presentation will focus on two cases from fcc metals...... orientation of the grain [1]. For selected boundaries it has been experimentally verified that the boundaries consist of fairly regular networks of dislocations, which come from the active slip systems [2]. The networks have been analyzed within the framework of Low-Energy-Dislocation-Structures (LEDS...

  12. Boundary Drawing in Clinical Work

    DEFF Research Database (Denmark)

    Meier, Ninna

    The aim of this paper is to show how health care professionals temporarily dissolve and redraw boundaries in their everyday work, in order to coordinate clinical work and facilitate collaboration in patient pathways. Boundaries are social constructions that help us make sense of our complex, social...... world. In health care, formal boundaries are important distinctions that separate health care practitioners into medical specialties, professions and organizational departments. But clinical work also relies on the ability of health care practitioners to collaborate around patients in formal...... arrangements or emergent, temporary teams. Focusing on the cognitive and social boundaries we draw to establish identity and connection (to a profession, team or person) the paper shows how health care professionals can use inter-personal relationships to temporarily dismiss formal boundaries. By redrawing...

  13. Distributed Tuning of Boundary Resources

    DEFF Research Database (Denmark)

    Eaton, Ben; Elaluf-Calderwood, Silvia; Sørensen, Carsten

    2015-01-01

    in the context of a paradoxical tension between the logic of generative and democratic innovations and the logic of infrastructural control. Boundary resources play a critical role in managing the tension as a firm that owns the infrastructure can secure its control over the service system while independent...... firms can participate in the service system. In this study, we explore the evolution of boundary resources. Drawing on Pickering’s (1993) and Barrett et al.’s (2012) conceptualizations of tuning, the paper seeks to forward our understanding of how heterogeneous actors engage in the tuning of boundary...... resources within Apple’s iOS service system. We conduct an embedded case study of Apple’s iOS service system with an in-depth analysis of 4,664 blog articles concerned with 30 boundary resources covering 6 distinct themes. Our analysis reveals that boundary resources of service systems enabled by digital...

  14. Brain response to prosodic boundary cues depends on boundary position

    Directory of Open Access Journals (Sweden)

    Julia eHolzgrefe

    2013-07-01

    Full Text Available Prosodic information is crucial for spoken language comprehension and especially for syntactic parsing, because prosodic cues guide the hearer’s syntactic analysis. The time course and mechanisms of this interplay of prosody and syntax are not yet well understood. In particular, there is an ongoing debate whether local prosodic cues are taken into account automatically or whether they are processed in relation to the global prosodic context in which they appear. The present study explores whether the perception of a prosodic boundary is affected by its position within an utterance. In an event-related potential (ERP study we tested if the brain response evoked by the prosodic boundary differs when the boundary occurs early in a list of three names connected by conjunctions (i.e., after the first name as compared to later in the utterance (i.e., after the second name. A closure positive shift (CPS — marking the processing of a prosodic phrase boundary — was elicited only for stimuli with a late boundary, but not for stimuli with an early boundary. This result is further evidence for an immediate integration of prosodic information into the parsing of an utterance. In addition, it shows that the processing of prosodic boundary cues depends on the previously processed information from the preceding prosodic context.

  15. A finite difference method for free boundary problems

    KAUST Repository

    Fornberg, Bengt

    2010-04-01

    Fornberg and Meyer-Spasche proposed some time ago a simple strategy to correct finite difference schemes in the presence of a free boundary that cuts across a Cartesian grid. We show here how this procedure can be combined with a minimax-based optimization procedure to rapidly solve a wide range of elliptic-type free boundary value problems. © 2009 Elsevier B.V. All rights reserved.

  16. Porosity of free boundaries in the obstacle problem for quasilinear ...

    Indian Academy of Sciences (India)

    Indian Acad. Sci. (Math. Sci.) Vol. 123, No. 3, August 2013, pp. 373–382. c Indian Academy of Sciences. Porosity of free boundaries in the obstacle problem ... 2School of Mathematical Sciences, University of Electronic Science and Technology of China, Chengdu ... conditions for some positive constants γ0,γ1, namely. N. ∑.

  17. Colloidal Plasmas: Electrostatic sheath at the boundary of a ...

    Indian Academy of Sciences (India)

    Considering the Boltzmann response of the ions and electrons in plasma dynamics and inertial dynamics of the dust charged grains in a highly collisional dusty plasma, the nature of the electrostatic potential near a boundary is investigated. Based on the fluid approximation, the formation as well as the characteristic ...

  18. Effect of Grain Orientation and Boundary Distributions on Hydrogen-Induced Cracking in Low-Carbon-Content Steels

    Science.gov (United States)

    Masoumi, Mohammad; Coelho, Hana Livia Frota; Tavares, Sérgio Souto Maior; Silva, Cleiton Carvalho; de Abreu, Hamilton Ferreira Gomes

    2017-08-01

    Hydrogen-induced cracking (HIC) causes considerable economic losses in a wide range of steels exposed to corrosive environments. The effect of crystallographic texture and grain boundary distributions tailored by rolling at 850 °C in three different steels with a body-centered cube structure was investigated on HIC resistance. The x-ray and electron backscattered diffraction techniques were used to characterize texture evolutions during the rolling process. The findings revealed a significant improvement against HIC based on texture engineering. In addition, increasing the number of {111} and {110} grains, associated with minimizing the number of {001} grains in warm-rolled samples, reduced HIC susceptibility. Moreover, the results showed that boundaries associated with low {hkl} indexing and denser packing planes had more resistance against crack propagation.

  19. Boundaries of dreams, boundaries of dreamers: thin and thick boundaries as a new personality measure.

    Science.gov (United States)

    Hartmann, E

    1989-11-01

    Previous work by the author and his collaborators on frequent nightmare sufferers demonstrated that these people had striking personality characteristics which could be called "thin boundaries" in a number of different senses. In order to measure thin and thick boundaries, a 145-item questionnaire, the Boundary Questionnaire, has been developed which has now been taken by over 1,000 persons. Preliminary results are presented indicating that, as predicted a priori, several new groups of nightmare sufferers and groups of art students scored usually "thin," whereas a group of naval officers had usually "thick" boundaries. Overall, thinness on the Boundary Questionnaire correlated highly positively (r = .40) with frequency of dream recall and also significantly (r = .16) with length of sleep.

  20. Optimal boundary control and boundary stabilization of hyperbolic systems

    CERN Document Server

    Gugat, Martin

    2015-01-01

    This brief considers recent results on optimal control and stabilization of systems governed by hyperbolic partial differential equations, specifically those in which the control action takes place at the boundary.  The wave equation is used as a typical example of a linear system, through which the author explores initial boundary value problems, concepts of exact controllability, optimal exact control, and boundary stabilization.  Nonlinear systems are also covered, with the Korteweg-de Vries and Burgers Equations serving as standard examples.  To keep the presentation as accessible as possible, the author uses the case of a system with a state that is defined on a finite space interval, so that there are only two boundary points where the system can be controlled.  Graduate and post-graduate students as well as researchers in the field will find this to be an accessible introduction to problems of optimal control and stabilization.

  1. Precipitates and boundaries interaction in ferritic ODS steels

    Energy Technology Data Exchange (ETDEWEB)

    Sallez, Nicolas, E-mail: nicolas.sallez@simap.grenoble-inp.fr [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); Hatzoglou, Constantinos [Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634, Normandie Université (France); Delabrouille, Fredéric [EDF–EDF R& D, Les Renardières, 77818 Moret-sur-Loing (France); Sornin, Denis; Chaffron, Laurent [CEA, DEN, Service de Recherches Métallurgiques Appliqué, 91191 Gif-sur-Yvette (France); Blat-Yrieix, Martine [EDF–EDF R& D, Les Renardières, 77818 Moret-sur-Loing (France); Radiguet, Bertrand; Pareige, Philippe [Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634, Normandie Université (France); Donnadieu, Patricia; Bréchet, Yves [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France)

    2016-04-15

    In the course of a recrystallization study of Oxide Dispersion Strengthened (ODS) ferritic steels during extrusion, particular interest was paid to the (GB) Grain Boundaries interaction with precipitates. Complementary and corresponding characterization experiments using Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX) and Atom Probe Tomography (APT) have been carried out on a voluntarily interrupted extrusion or extruded samples. Microscopic observations of Precipitate Free Zones (PFZ) and precipitates alignments suggest precipitate interaction with migrating GB involving dissolution and Oswald ripening of the precipitates. This is consistent with the local chemical information gathered by EDX and APT. This original mechanism for ODS steels is similar to what had been proposed in the late 80s for similar observation made on Ti alloys reinforced by nanosized yttrium oxides: An interaction mechanism between grain boundaries and precipitates involving a diffusion controlled process of precipitates dissolution at grain boundaries. It is believed that this mechanism can be of primary importance to explain the mechanical behaviour of such steels. - Highlights: • To study the microstructural evolution of a ferritic ODS steel during its extrusion, observations have been carried on samples resulting from a voluntarily interrupted extrusion and extruded materials. • A highly heterogeneous precipitate population have been observed. Nanosized coherent precipitates (2–5 nm) on both sides of the grain boundaries despite grain boundary migration after precipitation due to further thermo-mechanical processing as well as coarse precipitates (10–40 nm) alignments are observed on the grain boundaries and within the grains, parallel to the grain boundaries. • Asymmetrical PFZs can be observed around precipitates alignments and grain boundaries. Using TEM with EDX and APT we have been able to ensure that the PFZs are chemically depleted.

  2. Grain boundary structure and solute segregation in titanium-doped sapphire bicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Seth Thomas [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    Solute segregation to ceramic grain boundaries governs material processing and microstructure evolution, and can strongly influence material properties critical to engineering performance. Understanding the evolution and implications of grain boundary chemistry is a vital component in the greater effort to engineer ceramics with controlled microstructures. This study examines solute segregation to engineered grain boundaries in titanium-doped sapphire (Al2O3) bicrystals, and explores relationships between grain boundary structure and chemistry at the nanometer scale using spectroscopic and imaging techniques in the transmission electron microscope (TEM). Results demonstrate dramatic changes in solute segregation stemming from small fluctuations in grain boundary plane and structure. Titanium and silicon solute species exhibit strong tendencies to segregate to non-basal and basal grain boundary planes, respectively. Evidence suggests that grain boundary faceting occurs in low-angle twis t boundaries to accommodate nonequilibrium solute segregation related to slow specimen cooling rates, while faceting of tilt grain boundaries often occurs to expose special planes of the coincidence site lattice (CSL). Moreover, quantitative analysis of grain boundary chemistry indicates preferential segregation of charged defects to grain boundary dislocations. These results offer direct proof that static dislocations in ionic materials can assume a net charge, and emphasize the importance of interactions between charged point, line, and planar defects in ionic materials. Efforts to understand grain boundary chemistry in terms of space charge theory, elastic misfit and nonequilibrium segregation are discussed for the Al2O3 system.

  3. Cavity Formation in Aluminium Irradiated with a Pulsating Beam of 225 MeV Electrons

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Bilde-Sørensen, Jørgen; Leffers, Torben

    1984-01-01

    High-purity aluminium was irradiated with a pulsating beam of 225 MeV electrons to a maximum dose of 0.035 dpa with a helium generation rate of up to 17 appm/dpa. The irradiated samples contained cavities in the size range 5 to 70 nm. In a zone of up to 14 μm from the grain boundaries cavity size...

  4. Boundary-Object Trimming

    DEFF Research Database (Denmark)

    Bossen, Claus; Jensen, Lotte Groth; Udsen, Flemming Witt

    2014-01-01

    As health care IT gradually develops from being stand-alone systems towards integrated infrastructures, the work of various groups, occupations and units is likely to become more tightly integrated and dependent upon each other. Hitherto, the focus within health care has been upon the two most...... prominent professions, physicians and nurses, but most likely other non-clinical occupations will become relevant for the design and implementation of health care IT. In this paper, we describe the cooperative work of medical secretaries at two hospital departments, based on a study evaluating...... a comprehensive electronic health record (EHR) shortly after implementation. The subset of data on medical secretaries includes observation (eleven hours), interviews (three individual and one group) and survey data (thirty one of two hundred and fifty respondents were medical secretaries). We depict medical...

  5. Computer simulations of the structure and properties of grain boundary dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Bristowe, P.D.

    1985-10-01

    The core structure of intrinsic grain boundary dislocations embedded in (001) twist grain boundaries has been modelled using conventional atomistic techniques and a variety of empirical and pseudo-potentials representing fcc metals. In particular the width of the dislocation core region in the boundary plane has been studied as a function of the periodicity of the boundary ..sigma.. and interatomic potential. Generally, the core width increases with increasing ..sigma.. and is wider than that of lattice dislocations. Also the core width of twist grain boundary dislocations can be wider than that of tilt grain boundary dislocations. The presence of resolvable cusps on the computed energy/misorientation curve is related to the degree of core localization and the formation of domains of relatively low energy structure. The results are compared to transmission electron microscope observations, previous calculations, and the structural unit/grain boundary dislocation model.

  6. The path for long range conduction in high J{sub c} TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+x} spray-pyrolyzed deposits

    Energy Technology Data Exchange (ETDEWEB)

    Kroeger, D.M.; Goyal, A.; Specht, E.D.; Wang, Z.L. [Oak Ridge National Lab., TN (United States); Tkaczyk, J.E.; Sutliff, J.A.; DeLuca, J.A. [General Electric Co., Schenectady, NY (United States). Corporate Research and Development Center

    1993-12-31

    Grain boundary misorientations and local texture in polycrystalline TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+x} deposits prepared by thallination of spray-pyrolyzed precursor deposits on yttria-stabilized zirconia have been determined from transmission electron microscopy, electron backscatter diffraction patterns and x-ray diffraction. The deposits were polycrystalline, had small grains, and excellent c-axis alignment The deposits contained colonies of grains with similar but not identical a-axis orientations. Most grain boundaries within a colony have small misorientation angles and should not be weak links. It is proposed that long range current flow occurs through a percolative network of small angle grain boundaries at colony intersections.

  7. Extreme environment electronics

    CERN Document Server

    Cressler, John D

    2012-01-01

    Unfriendly to conventional electronic devices, circuits, and systems, extreme environments represent a serious challenge to designers and mission architects. The first truly comprehensive guide to this specialized field, Extreme Environment Electronics explains the essential aspects of designing and using devices, circuits, and electronic systems intended to operate in extreme environments, including across wide temperature ranges and in radiation-intense scenarios such as space. The Definitive Guide to Extreme Environment Electronics Featuring contributions by some of the world's foremost exp

  8. Allegheny County School District Boundaries

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset demarcates the school district boundaries within Allegheny County If viewing this description on the Western Pennsylvania Regional Data Center’s open...

  9. Boundary Layer Control on Airfoils.

    Science.gov (United States)

    Gerhab, George; Eastlake, Charles

    1991-01-01

    A phenomena, boundary layer control (BLC), produced when visualizing the fluidlike flow of air is described. The use of BLC in modifying aerodynamic characteristics of airfoils, race cars, and boats is discussed. (KR)

  10. County Boundaries with Shorelines (National)

    Data.gov (United States)

    Department of Transportation — County boundaries with shorelines cut in (NTAD). The TIGER/Line Files are shapefiles and related database files (.dbf) that are an extract of selected geographic and...

  11. HUC 8-11 Boundaries

    Data.gov (United States)

    Kansas Data Access and Support Center — This data set is a digital hydrologic unit boundary that is at the 4-digit, 6-digit, 8-digit, and 11-digit level. The data set was developed by delineating the...

  12. The laminar boundary layer equations

    CERN Document Server

    Curle, N

    2017-01-01

    Thorough introduction to boundary layer problems offers an ordered, logical presentation accessible to undergraduates. The text's careful expositions of the limitations and accuracy of various methods will also benefit professionals. 1962 edition.

  13. State Highway District Boundaries - 2004

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — This data represents the NM Department of Transportation District boundaries as legislatively defined (i.e. these are not maintenance defined districts).

  14. Boundary Spanners in Global Partnerships

    DEFF Research Database (Denmark)

    Søderberg, Anne-Marie; Romani, Laurence

    2017-01-01

    client relationships and coordinating highly complex projects. We analyze vendor managers’ narratives of their collaboration with a European client in a long-term project, which is presented as a strategic partnership in an outsourcing 3.0 mode. The study offers a rich and conceptualized account of those...... technology (IT) development projects from the rare perspective of Indian vendor managers in one of the world’s largest IT service companies. It draws on a qualitative study of a collaborative partnership and focuses on the key boundary spanners who are responsible for developing trustful and sustainable...... managers’ boundary-spanning activities and a context-sensitive understanding of their boundary work. The study applies Bourdieu’s concept of capital (economic, cultural, social, and symbolic) not only in its analysis of the two powerful partners but also in its discussion of the boundary...

  15. Recognition of boundary feedback systems

    DEFF Research Database (Denmark)

    Pedersen, Michael

    1989-01-01

    A system that has been the object of intense research is outlined. In view of that and recent progress of the theory of pseudodifferential boundary operator calculus, the author describes some features that could prove to be interesting in connection with the problems of boundary feedback...... stabilizability. It is shown that it is possible to use the calculus to consider more general feedback systems in a variational setup....

  16. Searching for the nanoscopic–macroscopic boundary

    Energy Technology Data Exchange (ETDEWEB)

    Velásquez, E.A. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Grupo de Investigación en Modelamiento y Simulación Computacional, Universidad de San Buenaventura Sec. Medellín, A.A. 5222, Medellín (Colombia); Altbir, D. [Departamento de Física, Universidad de Santiago de Chile (USACH), CEDENNA, Santiago (Chile); Mazo-Zuluaga, J. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Duque, L.F. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Grupo de Física Teórica, Aplicada y Didáctica, Facultad de Ciencias Exactas y Aplicadas Instituto Tecnológico Metropolitano, Medellín (Colombia); Mejía-López, J., E-mail: jmejia@puc.cl [Facultad de Física, Pontificia Universidad Católica de Chile, CEDENNA, Santiago (Chile)

    2013-12-15

    Several studies have focused on the size-dependent properties of elements, looking for a unique definition of the nanoscopic–macroscopic boundary. By using a novel approach consisting of an energy variational method combined with a quantum Heisenberg model, here we address the size at which the ordering temperature of a magnetic nanoparticle reaches its bulk value. We consider samples with sizes in the range 1–500 nm, as well as several geometries and crystalline lattices and observe that, contrarily to what is commonly argued, the nanoscopic-microscopic boundary depends on both factors: shape and crystalline structure. This suggests that the surface-to-volume ratio is not the unique parameter that defines the behavior of a nanometric sample whenever its size increases reaching the bulk dimension. Comparisons reveal very good agreement with experimental evidence with differences less than 2%. Our results have broad implications for practical issues in measurements on systems at the nanometric scale. - Highlights: • A novel quantum-Heisenberg variational energy method is implemented. • The asymptotic behavior toward the thermodynamic limit is explored. • An important dependence of the nano-bulk boundary on the geometry is found. • And also an important dependence on the crystalline lattice. • We obtain a very good agreement with experimental evidence with differences <2%.

  17. Phase boundary of hot dense fluid hydrogen.

    Science.gov (United States)

    Ohta, Kenji; Ichimaru, Kota; Einaga, Mari; Kawaguchi, Sho; Shimizu, Katsuya; Matsuoka, Takahiro; Hirao, Naohisa; Ohishi, Yasuo

    2015-11-09

    We investigated the phase transformation of hot dense fluid hydrogen using static high-pressure laser-heating experiments in a laser-heated diamond anvil cell. The results show anomalies in the heating efficiency that are likely to be attributed to the phase transition from a diatomic to monoatomic fluid hydrogen (plasma phase transition) in the pressure range between 82 and 106 GPa. This study imposes tighter constraints on the location of the hydrogen plasma phase transition boundary and suggests higher critical point than that predicted by the theoretical calculations.

  18. Scalar boundary conditions in hyperscaling violating geometry

    Directory of Open Access Journals (Sweden)

    Jian-Pin Wu

    2016-02-01

    Full Text Available We study the possible boundary conditions of scalar field modes in a hyperscaling violation (HV geometry with Lifshitz dynamical exponent z (z≥1 and hyperscaling violation exponent θ (θ≠0. For the case with θ>0, we show that in the parameter range 1≤z≤2, −z+d−12, −z+d−10, which has been addressed in Ref. [1]. Meanwhile, we also carry out the parallel investigation in the case with θ0, only one type is available.

  19. Structural and electronic properties of dense liquid and amorphous nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Boates, B; Bonev, S A

    2011-02-11

    We present first-principles calculations of the structural and electronic properties of liquid nitrogen in the pressure-temperature range of 0-200 GPa and 2000-6000 K. The molecular-polymerization and molecular-atomic liquid phase boundaries have been mapped over this region. We find the polymeric liquid to be metallic, similar to what has been reported for the higher-temperature atomic fluid. An explanation of the electronic properties is given based on the structure and bonding character of the transformed liquids. We discuss the structural and bonding differences between the polymeric liquid and insulating solid cubic-gauche nitrogen to explain the differences in their electronic properties. Furthermore, we discuss the mechanism responsible for charge transport in polymeric nitrogen systems to explain the conductivity of the polymeric fluid and the semi-conducting nature of low-temperature amorphous nitrogen.

  20. Ellipsometric and reflectometric characterization of thin films exhibiting thickness non-uniformity and boundary roughness

    Science.gov (United States)

    Ohlídal, Ivan; Franta, Daniel; Nečas, David

    2017-11-01

    In this paper epitaxial ZnSe thin films prepared by molecular beam epitaxy onto GaAs single crystal substrates exhibiting two defects, i.e. boundary roughness and thickness non-uniformity, are optically characterized using a combination of spectroscopic ellipsometry and near-normal spectroscopic reflectometry. The influence of boundary roughness is included into optical quantity formulae by the combination of the scalar diffraction theory and Rayleigh-Rice theory. Very thin overalyers modelled by rough thin films with identically rough boundaries are taken into account on the upper boundaries of the ZnSe thin films. Two approximations are used to express the local reflection coefficient of the rough ZnSe thin films covered with the overlayers within combination of both the theories. Thickness non-uniformity is incorporated by means of averaging the elements of the unnormalized Mueller matrices. The universal dispersion model of the optical constants of the ZnSe thin films based on parametrization of the joint density of electronic states is used. The spectral dependencies of the optical constants of the ZnSe thin films are determined within the wide spectral range (0.12-8.7 eV). Moreover, the mean thickness of the ZnSe thin films and thickness of overlayers are determined together with the other structural parameters characterizing the defects. The values of roughness parameters, determined by the optical method, are verified by a comparison with results achieved by atomic force microscopy. It is also shown that the approximations of the local reflection coefficient presented are usable for processing the experimental data.

  1. Formation of Boundary Film from Ionic Liquids Enhanced by Additives

    Directory of Open Access Journals (Sweden)

    Erik Nyberg

    2017-04-01

    Full Text Available Room temperature ionic liquids (RTILs have several properties that make them interesting candidates as base fluids for extreme conditions. However, a lack of compatibility with tribo-improving additives combined with an often overly aggressive nature is limiting their use as base fluids. To overcome these drawbacks, hydrocarbon-imitating RTIL base fluids have recently been developed. In this study, the effects of several common additives in the novel RTIL (P-SiSO were examined by laboratory tribotesting. A reciprocating steel-steel ball-on-flat setup in an air atmosphere was used, where the lubricant performance was evaluated over a range of loads and temperatures. Surface analyses after testing were carried out using optical profilometry, scanning electron microscopy (SEM, and energy dispersive X-ray spectroscopy (EDS. Neat P-SiSO displayed high performance in the tribotests. At an elevated load and temperature, a shift in lubrication mode was observed with an accompanying increase in friction and wear. Surface analysis revealed a boundary film rich in Si and O in the primary lubrication mode, while P was detected after a shift to the secondary lubrication mode. An amine additive was effective in reducing wear and friction under harsh conditions. The amine was determined to increase formation of the protective Si–O film, presumably by enhancing the anion activity.

  2. Lifestyle Journalism: Blurring boundaries

    DEFF Research Database (Denmark)

    From, Unni

    2013-01-01

    Lifestyle journalism has experienced enormous growth in the media over the past two decades, but scholars in the fields of journalism and communication studies have so far paid relatively little attention to a field that is still sometimes seen as "not real journalism". There is now an urgent need...... for in-depth exploration and contextualisation of this field, with its increasing relevance for 21st century consumer cultures. For the first time, this book presents a wide range of studies which have engaged with the field of lifestyle journalism in order to outline the various political, economic......, social and cultural tensions within it. Taking a comparative view, the collection includes studies covering four continents, including countries such as Australia, China, Norway, Denmark, Singapore, the UK and the USA. While keeping the broader lifestyle field in mind, the chapters focus on a variety...

  3. A computational study of twist boundary structures in strontium titanate

    Energy Technology Data Exchange (ETDEWEB)

    Astala, R; Bristowe, P D [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge (United Kingdom)

    2002-12-16

    A density functional plane-wave pseudopotential method is used to study various {sigma} = 5 (001) twist boundary models for strontium titanate. Results concerning the atom-level geometries and electronic structures are reported. The structures have varying SrO/TiO{sub 2} ratios and their relative stabilities are discussed in terms of the SrO chemical potential. A twist boundary containing a Sr-O pair of vacancies is found to be exceptionally stable and have a low volume expansion and is a possible candidate for showing impurity segregation.

  4. A computational study of twist boundary structures in strontium titanate

    Science.gov (United States)

    Astala, R.; Bristowe, P. D.

    2002-12-01

    A density functional plane-wave pseudopotential method is used to study various Sigma = 5 (001) twist boundary models for strontium titanate. Results concerning the atom-level geometries and electronic structures are reported. The structures have varying SrO/TiO2 ratios and their relative stabilities are discussed in terms of the SrO chemical potential. A twist boundary containing a Sr-O pair of vacancies is found to be exceptionally stable and have a low volume expansion and is a possible candidate for showing impurity segregation.

  5. Electron Backscatter Diffraction Analysis of Inconel 718 Parts Fabricated by Selective Laser Melting Additive Manufacturing

    Science.gov (United States)

    Wang, Xiaoqing; Chou, Kevin

    2017-02-01

    In this study, the crystallographic texture of an Inconel 718 part fabricated by selective laser melting was investigated. The front surface (X-Z plane) microstructure is characterized by the columnar grains growing along the build direction, and the width of columnar grains is in the range of about 75-150 µm, with the bottom layers having narrower grains as a result of a higher cooling rate. In addition to equiaxed grains, the top surface (X-Y plane) has a feature of patch patterns resulting from the laser scanning strategy. Based on the electron backscatter diffraction results, there appears only weak crystallographic texture in both the X-Z plane and the X-Y plane of the part. From the grain boundary map, the microstructures are composed of high-angle boundaries with a larger fraction of subgrain boundaries.

  6. Boundary slip from the immersed boundary lattice Boltzmann models.

    Science.gov (United States)

    Le, Guigao; Zhang, Junfeng

    2009-02-01

    We report an interesting and important observation of the velocity fields from immersed boundary lattice Boltzmann methods (IB-LBM). The computed velocity profiles can deviate from theoretical predictions greatly even for very simple flow situations, both in the immersed boundary layer and the bulk region. A rigorous analysis of the IB-LBM simulated velocity for a symmetric shear flow is carried out, and the analytical solutions indicate a strong dependence of velocity on the relaxation parameter (kinetic viscosity). Also our simulations demonstrate that simply increasing the immersed boundary layer thickness is not an efficient approach to reduce such velocity discrepancy. We hope this work will bring the awareness of this essential issue to people using IB-LBM for various flow situations.

  7. Metallographic screening of grain boundary engineered type 304 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Hanning, F., E-mail: Fabian.Hanning@googlemail.com; Engelberg, D.L., E-mail: Dirk.engelberg@manchester.ac.uk

    2014-08-15

    An electrochemical etching method for the identification of grain boundary engineered type 304 austenitic stainless steel microstructures is described. The method can be applied for rapid microstructure screening to complement electron backscatter diffraction analysis. A threshold parameter to identify grain boundary engineered microstructure is proposed, and the application of metallographic etching for characterising the degree of grain boundary engineering discussed. - Highlights: • As-received (annealed) and grain boundary engineered microstructures were compared. • Electro-chemical polarisation in nitric acid solutions was carried out. • A metallographic screening method has been developed. • The screening method complements EBSD analysis for microstructure identification.

  8. Imaging magnetospheric boundaries at ionospheric heights

    Science.gov (United States)

    Mendillo, Michael; Baumgardner, Jeffrey; Wroten, Joei; Martinis, Carlos; Smith, Steven; Merenda, Kevin-Druis; Fritz, Theodore; Hairston, Marc; Heelis, Rod; Barbieri, Cesare

    2013-11-01

    all-sky imager (ASI) records atmospheric emissions from zenith to low on the horizon at all azimuths, a region typically spanning millions of square kilometers. Each pixel (with its unique elevation, azimuth, and emission height) can be mapped along B-field lines to the equatorial plane of the magnetosphere. Auroral and subauroral structures and boundaries seen in emission within the ionosphere-thermosphere (I-T) system can thus be related to source regions. For a midlatitude site, this I-T to inner magnetosphere connection typically falls within the L = 2-5 earth radii domain. In this study, we present the first case of a stable auroral red (SAR) arc observed from three widely spaced ASI sites (Europe, North America, New Zealand). SAR arcs are produced during the main and recovery phases of a geomagnetic storm, with emission driven by heat conduction from a very specific location in the magnetosphere—the L value where the plasmapause and the inner edge of the ring current overlap. Using three-site observations, we show that this boundary can be followed for 24 consecutive hours. Simultaneous observations made by three satellites in the Defense Meteorological Satellite Program (DMSP) show that the lowest latitude peak in electron temperature can be used to map the same boundary. A key structure of the inner magnetosphere that cannot be observed continuously from sensors orbiting within the magnetosphere is made continuously visible to ground-based optical systems via effects caused by the drainage of small amounts of ring current energy into the I-T system.

  9. Undulatory microswimming near solid boundaries

    Science.gov (United States)

    Schulman, R. D.; Backholm, M.; Ryu, W. S.; Dalnoki-Veress, K.

    2014-10-01

    The hydrodynamic forces involved in the undulatory microswimming of the model organism C. elegans are studied in proximity to solid boundaries. Using a micropipette deflection technique, we attain direct and time-resolved force measurements of the viscous forces acting on the worm near a single planar boundary as well as confined between two planar boundaries. We observe a monotonic increase in the lateral and propulsive forces with increasing proximity to the solid interface. We determine normal and tangential drag coefficients for the worm, and find these to increase with confinement. The measured drag coefficients are compared to existing theoretical models. The ratio of normal to tangential drag coefficients is found to assume a constant value of 1.5 ± 0.1(5) at all distances from a single boundary, but increases significantly as the worm is confined between two boundaries. In response to the increased drag due to confinement, we observe a gait modulation of the nematode, which is primarily characterized by a decrease in the swimming amplitude.

  10. Copper segregation to the Sigma5 (310)/[001] symmetric tilt grain boundary in aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Geoffrey H.; Plitzko, Jurgen M.; King, Wayne E.; Foiles, Stephen M.; Kisielowski, Christian; Duscher, Gerd J.M.

    2003-01-01

    New insight into the atomic segregation of copper to an aluminum grain boundary has been obtained using multiple, complementary atomic resolution electron microscopy techniques coupled with ab-initio electronic structure calculations. The copper segregation is site specific and changes the structure of the boundary by occupying interstitial sites. Minor elemental constituents in materials can have profound effects on their engineering performance. This change in structure can be associated with these strong effects. The observed structural change will alter the mass transport behavior of the boundary and has implications for the understanding of electromigration mechanisms.

  11. Characterization of the structure and polarity of twin boundaries in GaP

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, D. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science]|[Sandia National Labs., Livermore, CA (United States); Medlin, D.L. [Sandia National Labs., Livermore, CA (United States); Carter, C.B. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science

    1998-04-01

    The structure of planar defects in GaP films grown by MBE on Si (110) was investigated by transmission electron microscopy. Growth of GaP films on the (110) surface produced numerous microtwins which formed both first and second order twin boundaries. Using high-resolution transmission electron microscopy, the atomic structure of {Sigma} = 3 and {Sigma} = 9 twin boundaries were studied. Both the {Sigma} = 3 and {Sigma} = 9 interfaces were observed to facet along specific crystallographic planes. Geometric models of the {Sigma} = 9 {l_brace}221{r_brace} twin boundary accounting for different polar bonding configurations were proposed and compared with experimental observations.

  12. First-principles study of a tilt grain boundary in rutile

    Science.gov (United States)

    Dawson, I.; Bristowe, P. D.; Lee, M.-H.; Payne, M. C.; Segall, M. D.; White, J. A.

    1996-11-01

    The atomic and electronic structure of a tilt grain boundary in rutile TiO2 has been calculated in an ab initio manner. The method employs a plane-wave basis set and optimized pseudopotentials and is carried out within the local-density approximation of density-functional theory. The study focuses on the structure and energy of the ∑=15 36.9° (210)[001] tilt boundary, which is relaxed to equilibrium using a conjugate gradients iterative minimization technique. The calculations confirm the stability of a proposed atomic model for the boundary and provide some insight into its electronic structure.

  13. An ab initio investigation of a grain boundary in a transition metal oxide

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, I.; Bristowe, P.D. [Univ. of Cambridge (United Kingdom). Dept. of Materials Science and Metallurgy; Payne, M.C.; Lee, M.H. [Univ. of Cambridge (United Kingdom). Cavendish Lab.

    1996-12-31

    The authors have used ab initio total energy plane wave pseudopotential methods to perform the first completely ab initio investigation of the atomic and electronic structure of a grain boundary in a transition metal oxide. The {Sigma} = 15 (210)[001] tilt boundary in rutile TiO{sub 2} is studied using the conjugate gradients iterative minimization technique for performing total energy calculations within the LDA and pseudopotential approximations. The stability of the experimentally observed translation state of the boundary is confirmed, and some insight is gained into its electronic structure.

  14. Grain boundaries in Cu(In,Ga)(Se,S){sub 2} thin-film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Rau, Uwe [Forschungszentrum Juelich, IEF5-Photovoltaik, Juelich (Germany); Taretto, Kurt [Universidad Nacional del Comahue, Dto. de Electrotecnia, Buenos Aires, Neuquen (Argentina); Siebentritt, Susanne [Universite du Luxembourg, Luxembourg (Luxembourg)

    2009-07-15

    The paper reviews the current status of the research on grain boundaries in polycrystalline Cu(In,Ga)(S,Se){sub 2} alloys used as absorber materials for thin-film solar cells. We discuss the different concepts that are available to explain the relatively low electronic activity of grain boundaries in these materials. Numerical simulations that have been undergone so far to model the polycrystalline solar cells are briefly summarized. In addition, we give an overview on the experiments that have been conducted so far to elucidate the structural, defect-chemical, and electronic properties of grain boundaries in Cu(In,Ga)(S,Se){sub 2} thin-films. (orig.)

  15. Range management visual impacts

    Science.gov (United States)

    Bruce R. Brown; David Kissel

    1979-01-01

    Historical overgrazing of western public rangelands has resulted in the passage of the Public Rangeland Improvement Act of 1978. The main purpose of this Act is to improve unsatisfactory range conditions. A contributing factor to unfavorable range conditions is adverse visual impacts. These visual impacts can be identified in three categories of range management: range...

  16. Electron-electron correlations in liquid s-p metals

    CERN Document Server

    Leys, F E

    2003-01-01

    We present calculations for the valence electron-electron structure factor in liquid Mg near freezing, assuming knowledge of the jellium result. On the basis of this, we predict significant corrections to jellium short-range correlations in liquid s-p metals and in particular an increase in the electron-electron contact probability.

  17. A study of chromium carbide precipitation at interphase boundaries in stainless steel welds

    Energy Technology Data Exchange (ETDEWEB)

    Willis, C.F.

    1990-04-01

    Sensitization is a deleterious process which can occur in stainless steels. It is caused by grain boundary or phase boundary precipitation of chromium carbides and the resulting formation of a chromium depleted zone adjacent to these boundaries. The carbides in question actually have the composition (Cr,Fe){sub 23}C{sub 6} (usually written M{sub 23}C{sub 6}), and precipitate in the temperature range 450--900{degree}C. Since a minimum chromium content is required to maintain the passive film necessary for resistance to electrochemical attack, the result of chromium depletion is that the steel becomes sensitized'' to possible intergranular corrosion. Sensitization often occurs as a result of welding operations. The material close to the fusion line reaches temperatures within the sensitization range. This region is called the heat affected zone (HAZ). Since many welds are multi-pass welds, the actual weld bead of one pass may lie in the heat affected zone of the next pass. The weld bead of the first pass might therefore be sensitized. Furthermore there are applications where welds will be exposed to sensitizing temperatures for very long periods of time, such as welded labels on retrievable nuclear waste containers. For these reasons the sensitization behavior of the actual weld-bead microstructures must be understood. It has been known for many years that duplex stainless steels (steels with both ferrite and austenite phases present at room temperature) have superior resistance to intergranular corrosion. A model has been proposed to explain the sensitization behavior of these alloys. This work will be concerned with testing the validity of aspects of this model using transmission electron microscopy and further understanding of the sensitization process in duplex stainless steel welds. 52 refs., 23 figs.

  18. SILICON CARBIDE GRAIN BOUNDARY DISTRIBUTIONS, IRRADIATION CONDITIONS, AND SILVER RETENTION IN IRRADIATED AGR-1 TRISO FUEL PARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    Lillo, T. M.; Rooyen, I. J.; Aguiar, J. A.

    2016-11-01

    Precession electron diffraction in the transmission electron microscope was used to map grain orientation and ultimately determine grain boundary misorientation angle distributions, relative fractions of grain boundary types (random high angle, low angle or coincident site lattice (CSL)-related boundaries) and the distributions of CSL-related grain boundaries in the SiC layer of irradiated TRISO-coated fuel particles. Two particles from the AGR-1 experiment exhibiting high Ag-110m retention (>80%) were compared to a particle exhibiting low Ag-110m retention (<19%). Irradiated particles with high Ag-110m retention exhibited a lower fraction of random, high angle grain boundaries compared to the low Ag-110m retention particle. An inverse relationship between the random, high angle grain boundary fraction and Ag-110m retention is found and is consistent with grain boundary percolation theory. Also, comparison of the grain boundary distributions with previously reported unirradiated grain boundary distributions, based on SEM-based EBSD for similarly fabricated particles, showed only small differences, i.e. a greater low angle grain boundary fraction in unirradiated SiC. It was, thus, concluded that SiC layers with grain boundary distributions susceptible to Ag-110m release were present prior to irradiation. Finally, irradiation parameters were found to have little effect on the association of fission product precipitates with specific grain boundary types.

  19. ELECTRONS IN NONPOLAR LIQUIDS.

    Energy Technology Data Exchange (ETDEWEB)

    HOLROYD,R.A.

    2002-10-22

    Excess electrons can be introduced into liquids by absorption of high energy radiation, by photoionization, or by photoinjection from metal surfaces. The electron's chemical and physical properties can then be measured, but this requires that the electrons remain free. That is, the liquid must be sufficiently free of electron attaching impurities for these studies. The drift mobility as well as other transport properties of the electron are discussed here as well as electron reactions, free-ion yields and energy levels, Ionization processes typically produce electrons with excess kinetic energy. In liquids during thermalization, where this excess energy is lost to bath molecules, the electrons travel some distance from their geminate positive ions. In general the electrons at this point are still within the coulombic field of their geminate ions and a large fraction of the electrons recombine. However, some electrons escape recombination and the yield that escapes to become free electrons and ions is termed G{sub fi}. Reported values of G{sub fi} for molecular liquids range from 0.05 to 1.1 per 100 eV of energy absorbed. The reasons for this 20-fold range of yields are discussed here.

  20. The Electron

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, George

    1972-01-01

    Electrons are elementary particles of atoms that revolve around and outside the nucleus and have a negative charge. This booklet discusses how electrons relate to electricity, some applications of electrons, electrons as waves, electrons in atoms and solids, the electron microscope, among other things.

  1. Asymptotic analysis and boundary layers

    CERN Document Server

    Cousteix, Jean

    2007-01-01

    This book presents a new method of asymptotic analysis of boundary-layer problems, the Successive Complementary Expansion Method (SCEM). The first part is devoted to a general comprehensive presentation of the tools of asymptotic analysis. It gives the keys to understand a boundary-layer problem and explains the methods to construct an approximation. The second part is devoted to SCEM and its applications in fluid mechanics, including external and internal flows. The advantages of SCEM are discussed in comparison with the standard Method of Matched Asymptotic Expansions. In particular, for the first time, the theory of Interactive Boundary Layer is fully justified. With its chapter summaries, detailed derivations of results, discussed examples and fully worked out problems and solutions, the book is self-contained. It is written on a mathematical level accessible to graduate and post-graduate students of engineering and physics with a good knowledge in fluid mechanics. Researchers and practitioners will estee...

  2. Free boundary ballooning mode representation

    Science.gov (United States)

    Zheng, Linjin

    2012-03-01

    Considerable efforts have been made in this field to develop a free boundary ballooning mode representation, which can incorporate the peeling mode stability criterion. Those efforts have not succeeded, simply because the so-called ballooning mode invariance is broken toward plasma edge. This makes 1D description of high n modes at plasma edge become impossible, where n is toroidal mode number. Nevertheless, we prove that the existence of ``half" ballooning mode invariance toward plasma core enables an 1.δ-dimentional representation of the modes, where δ˜O(1/n). This considerably reduces the complicity in investigating high n modes at plasma edge and can be used to study peeling-ballooning modes. This technique can also be useful to extend the 1D calculation of fixed boundary ballooning modes for free boundary ballooning modes. Numerical example will also be presented together with the topological symmetry analysis.

  3. Boundary Value Problems and Approximate Solutions ...

    African Journals Online (AJOL)

    In this paper, we discuss about some basic things of boundary value problems. Secondly, we study boundary conditions involving derivatives and obtain finite difference approximations of partial derivatives of boundary value problems. The last section is devoted to determine an approximate solution for boundary value ...

  4. Boundary Spanners as supports of social capital

    DEFF Research Database (Denmark)

    Vincenti, Gordon

    2016-01-01

    Boundary Spanners are important agenets of supporting the capacity building of local neighbourhoods and of sustainable social captial the article focuses on the skills and competnces adn role of Boundary Spanners.......Boundary Spanners are important agenets of supporting the capacity building of local neighbourhoods and of sustainable social captial the article focuses on the skills and competnces adn role of Boundary Spanners....

  5. Drawing boundaries : boundary arrangements of the IPCC working groups

    NARCIS (Netherlands)

    Christel van Eck

    2016-01-01

    The present research investigates how the IPCC’s Working Groups safeguard their scientific character while communicating with policymakers. Due to the different nature of Working Groups’ assessments, all Working Groups make different boundary arrangements of how science is defined; what is

  6. Boundary works of Grindr research

    DEFF Research Database (Denmark)

    Jørgensen, Kristian Møller

    . It can be understood as arising from boundary works (Jamieson 2005, [Auhor of this paper] forthcoming) and thus be ontologically entangled with the meeting of the prospect of boundary transgression that marks the end of intimacy. Lauren Berlant on the other hand sees intimacy as: …the processes by which....... Communications, 36(1), 91–111. Lundby, K. (ed.) (2014). Mediatization of Communication: Handbooks of Communication Science, vol. 21. Berlin: De Gruyter Mouton. Marwick, A., & Boyd, D. (2014). Networked privacy: How teenagers negotiate context in social media. New Media & Society. Markham, A., & Buchanan, E...

  7. Boundary effect in electrorheological fluids.

    Science.gov (United States)

    Gong, X L; Yang, F; Xuan, S H; Zong, L H; Zhu, W; Jiang, W Q

    2011-12-01

    The effect of the boundary friction coefficient on the rheological properties of the electrorheological (ER) fluids in quasistatic and dynamic states is investigated by computer simulation. The relation between the shear stress and the boundary friction coefficient in quasistatic and dynamic states is discussed qualitatively and quantitatively, and the trend matches the previously reported experimental results well. The flow curves of ER fluids, under different friction coefficients, are calculated, and it is found that the friction coefficient affects the flow curves. In two dimensions, the transitions in structure corresponding to the shear stress variations are presented to understand the mechanism of ER fluids.

  8. Information dynamics of boundary perception

    DEFF Research Database (Denmark)

    Kragness, Haley; Hansen, Niels Christian; Vuust, Peter

    It has long been noted that expert musicians lengthen notes at phrase boundaries in expressive performance. Recently, we have extended research on this phenomenon by showing that undergraduates with no formal musical training and children as young as 3 years lengthen phrase boundaries during self......-paced listening to chord sequences in a lab setting (the musical dwell-time effect). However, the origin of the musical dwell-time effect is still unknown. Recent work has demonstrated that musicians and non-musicians are sensitive to entropy in musical sequences, experiencing high-entropy contexts as more...

  9. Tropical cyclone boundary layer shocks

    OpenAIRE

    Slocum, Christopher J.; Williams, Gabriel J.; Taft, Richard K.; Wayne H. Schubert

    2014-01-01

    This paper presents numerical solutions and idealized analytical solutions of axisymmetric, $f$-plane models of the tropical cyclone boundary layer. In the numerical model, the boundary layer radial and tangential flow is forced by a specified pressure field, which can also be interpreted as a specified gradient balanced tangential wind field $v_{\\rm gr}(r)$ or vorticity field $\\zeta_{\\rm gr}(r)$. When the specified $\\zeta_{\\rm gr}(r)$ field is changed from one that is radially concentrated i...

  10. Discovering the Role of Grain Boundary Complexions in Materials

    Energy Technology Data Exchange (ETDEWEB)

    Harmer, Martin P. [Lehigh Univ., Bethlehem, PA (United States)

    2015-03-19

    Grain boundaries are inherently an area of disorder in polycrystalline materials which define the transport and various other material properties. The relationship between the interfacial chemistry, structure and the material properties is not well understood. Among the various taxonomies for grain boundaries, Grain Boundary Complexion is a relatively new conceptual scheme that relates the structure and kinetic properties of grain boundaries. In this classification scheme, grain boundaries are considered to be distinct three dimensional (the thickness being considerably smaller as compared to the other two dimensions but nonetheless discernible) equilibrium thermodynamic phases abutted between two crystalline phases. The stability and structure of these interfacial phases are dictated by various thermodynamic variables such as temperature, stress (pressure), interfacial chemistry (chemical potential) and most importantly by the energies of the adjoining crystal surfaces. These phases are only stable within the constraint of the adjoining grains. Although these interfacial phases are not stable in bulk form, they can transform from one complexion to another as a function of various thermodynamic variables analogous to the behavior of bulk phases. Examples of different complexions have been reported in various publications. However, a systematic investigation exploring the existence of grain boundary complexions in material systems other than alumina remains to be done. Although the role of interfacial chemistry on grain boundary complexions in alumina has been addressed, a clear understanding of the underlying thermodynamics governing complexion formation is lacking. Finally, the effects of grain boundary complexions in bulk material properties are widely unknown. Factors above urge a thorough exploration of grain boundary complexions in a range of different materials systems The purpose of the current program is to verify the existence of grain boundary complexion

  11. Electron radiography

    Science.gov (United States)

    Merrill, Frank E.; Morris, Christopher

    2005-05-17

    A system capable of performing radiography using a beam of electrons. Diffuser means receive a beam of electrons and diffuse the electrons before they enter first matching quadrupoles where the diffused electrons are focused prior to the diffused electrons entering an object. First imaging quadrupoles receive the focused diffused electrons after the focused diffused electrons have been scattered by the object for focusing the scattered electrons. Collimator means receive the scattered electrons and remove scattered electrons that have scattered to large angles. Second imaging quadrupoles receive the collimated scattered electrons and refocus the collimated scattered electrons and map the focused collimated scattered electrons to transverse locations on an image plane representative of the electrons' positions in the object.

  12. Thermal flux limited electron Kapitza conductance in copper-niobium multilayers

    Science.gov (United States)

    Cheaito, Ramez; Hattar, Khalid; Gaskins, John T.; Yadav, Ajay K.; Duda, John C.; Beechem, Thomas E.; Ihlefeld, Jon F.; Piekos, Edward S.; Baldwin, Jon K.; Misra, Amit; Hopkins, Patrick E.

    2015-03-01

    We study the interplay between the contributions of electron thermal flux and interface scattering to the Kapitza conductance across metal-metal interfaces through measurements of thermal conductivity of copper-niobium multilayers. Thermal conductivities of copper-niobium multilayer films of period thicknesses ranging from 5.4 to 96.2 nm and sample thicknesses ranging from 962 to 2677 nm are measured by time-domain thermoreflectance over a range of temperatures from 78 to 500 K. The Kapitza conductances between the Cu and Nb interfaces in multilayer films are determined from the thermal conductivities using a series resistor model and are in good agreement with the electron diffuse mismatch model. Our results for the thermal boundary conductance between Cu and Nb are compared to literature values for the thermal boundary conductance across Al-Cu and Pd-Ir interfaces, and demonstrate that the interface conductance in metallic systems is dictated by the temperature derivative of the electron energy flux in the metallic layers, rather than electron mean free path or scattering processes at the interface.

  13. Thermal flux limited electron Kapitza conductance in copper-niobium multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cheaito, Ramez; Gaskins, John T.; Duda, John C.; Hopkins, Patrick E., E-mail: phopkins@virginia.edu [Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Hattar, Khalid; Beechem, Thomas E.; Ihlefeld, Jon F.; Piekos, Edward S. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Yadav, Ajay K. [Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Baldwin, Jon K. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Misra, Amit [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2015-03-02

    We study the interplay between the contributions of electron thermal flux and interface scattering to the Kapitza conductance across metal-metal interfaces through measurements of thermal conductivity of copper-niobium multilayers. Thermal conductivities of copper-niobium multilayer films of period thicknesses ranging from 5.4 to 96.2 nm and sample thicknesses ranging from 962 to 2677 nm are measured by time-domain thermoreflectance over a range of temperatures from 78 to 500 K. The Kapitza conductances between the Cu and Nb interfaces in multilayer films are determined from the thermal conductivities using a series resistor model and are in good agreement with the electron diffuse mismatch model. Our results for the thermal boundary conductance between Cu and Nb are compared to literature values for the thermal boundary conductance across Al-Cu and Pd-Ir interfaces, and demonstrate that the interface conductance in metallic systems is dictated by the temperature derivative of the electron energy flux in the metallic layers, rather than electron mean free path or scattering processes at the interface.

  14. Substring Range Reporting

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li

    2014-01-01

    We revisit various string indexing problems with range reporting features, namely, position-restricted substring searching, indexing substrings with gaps, and indexing substrings with intervals. We obtain the following main results. We give efficient reductions for each of the above problems...... to a new problem, which we call substring range reporting. Hence, we unify the previous work by showing that we may restrict our attention to a single problem rather than studying each of the above problems individually. We show how to solve substring range reporting with optimal query time and little...... for substring range reporting generalize to substring range counting and substring range emptiness variants. We also obtain non-trivial time-space trade-offs for these problems. Our bounds for substring range reporting are based on a novel combination of suffix trees and range reporting data structures...

  15. Communication accross territory boundaries: distance dependent responses in nightingale

    NARCIS (Netherlands)

    Sprau, P.; Roth, T.; Schmidt, Rouven; Amrhein, V.; Naguib, M.

    2010-01-01

    In communication, vocal signals are often used for long-range signaling. Yet, little experimental evidence is available on the role of territorial signals across territory boundaries and their effectiveness at different propagation distances. In many songbird species, song overlapping and rapid

  16. The Anglophone Cameroon-Nigeria boundary : opportunities and conflicts

    NARCIS (Netherlands)

    Konings, P.J.J.

    2005-01-01

    Recent studies of African boundaries have tended to focus either on the growing number of border disputes between States or on frontier regions that are said to offer local inhabitants a wide range of economic opportunities. This article combines both approaches and demonstrates the ambiguous nature

  17. Phase-field crystal study of grain-boundary premelting

    Science.gov (United States)

    Mellenthin, Jesper; Karma, Alain; Plapp, Mathis

    2008-11-01

    We study the phenomenon of grain-boundary premelting for temperatures below the melting point in the phase-field crystal model of a pure material with hexagonal ordering in two dimensions. We investigate the structures of symmetric tilt boundaries as a function of misorientation θ for two different inclinations and compute in the grand canonical ensemble the “disjoining potential” V(w) that describes the fundamental interaction between crystal-melt interfaces as a function of the premelted layer width w , which is defined here in terms of the excess mass of the grain boundary via a Gibbs construction. The results reveal qualitatively different behaviors for high-angle grain boundaries that are uniformly wetted, with w diverging logarithmically as the melting point is approached from below, and low-angle boundaries that are punctuated by liquid pools surrounding dislocations, separated by solid bridges. The latter persist over a superheated range of temperature. This qualitative difference between high- and low-angle boundaries is reflected in the w dependence of the disjoining potential that is purely repulsive [ V'(w)<0 for all w ] for misorientations larger than a critical angle θc , but switches from repulsive at small w to attractive at large w for θ<θc . In the latter case, V(w) has a minimum that corresponds to a premelted boundary of finite width at the melting point. Furthermore, we find that the standard wetting condition γgb(θc)=2γsl gives a much too low estimate of θc when a low-temperature value of the grain-boundary energy γgb is used. In contrast, a reasonable lower-bound estimate can be obtained if γgb is extrapolated to the melting point, taking into account both the elastic softening of the material at high homologous temperature and local melting around dislocations.

  18. Radiative charge transfer in He{sup +}+ H{sub 2} collisions in the milli- to nano-electron-volt range: A theoretical study within state-to-state and optical potential approaches

    Energy Technology Data Exchange (ETDEWEB)

    Mrugala, Felicja [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, PL 87-100 Torun (Poland); Kraemer, Wolfgang P. [Max-Planck-Institute of Astrophysics, Postfach 1317, D-85741 Garching (Germany)

    2013-03-14

    The paper presents a theoretical study of the low-energy dynamics of the radiative charge transfer (RCT) reaction He{sup +}({sup 2}S)+H{sub 2}(X{sup 1}{Sigma}{sub g}{sup +}){yields}He({sup 1}S)+H{sub 2}{sup +}(X{sup 2}{Sigma}{sub g}{sup +})+h{nu} extending our previous studies on radiative association of HeH{sub 2}{sup +} [F. Mrugala, V. Spirko, and W. P. Kraemer, J. Chem. Phys. 118, 10547 (2003); F. Mrugala and W. P. Kraemer, ibid. 122, 224321 (2005)]. The calculations account for the vibrational and rotational motions of the H{sub 2}/H{sub 2}{sup +} diatomics and for the atom-diatom complex formation in the reactant and the product channels of the RCT reaction. Continuum states of He{sup +}+ H{sub 2}(v= 0, j= 0) in the collision energy range {approx}10{sup -7}-18.6 meV and all quasi-bound states of the He{sup +}- H{sub 2}(para;v= 0) complex formed in this range are taken into account. Close-coupling calculations are performed to determine rates of radiative transitions from these states to the continuum and quasi-bound states of the He +H{sub 2}{sup +} system in the energy range extending up to {approx}0.16 eV above the opening of the HeH{sup +}+ H arrangement channel. From the detailed state-to-state calculated characteristics global functions of the RCT reaction, such as cross-section {sigma}(E), emission intensity I({nu}, T), and rate constant k(T) are derived, and are presented together with their counterparts for the radiative association (RA) reaction He{sup +}({sup 2}S) +H{sub 2}(X{sup 1}{Sigma}{sub g}{sup +}){yields} HeH{sub 2}{sup +}(X{sup 2}A{sup Prime })+h{nu}. The rate constant k{sup RCT} is approximately 20 times larger than k{sup RA} at the considered temperatures, 0.1 {mu}K-50 K. Formation of rotational Feshbach resonances in the reactant channel plays an important role in both reactions. Transitions mediated by these resonances contribute more than 70% to the respective rates. An extension of the one-dimensional optical potential model is

  19. Seismic link at plate boundary

    Indian Academy of Sciences (India)

    ... tested using the coherence of time series to determine the causality and related orientation. The resulting link orientations at the plate boundary conditions indicate that causal triggering seems to be localized along a major fault, as a stress transfer between two major faults, and parallel to the geothermal area extension.

  20. Current Sinkhole Boundaries in Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This dataset is a polygon coverage of the sinkhole boundaries as determined by using LiDAR data. The polygons relate to the point coverage using the KPolyID field in...

  1. Humor styles and symbolic boundaries

    NARCIS (Netherlands)

    Kuipers, G.

    2009-01-01

    Humor is strongly related to group boundaries. Jokes and other humorous utterances often draw on implicit references and inside knowledge; they tend to refer to sensitive topics which may offend people; and they ideally incite laughter, one of the strongest markers of social solidarity and emotional

  2. Boundaries of flat compact surfaces

    DEFF Research Database (Denmark)

    Røgen, Peter

    1999-01-01

    type. The number of $3$-singular points (points of zero curvature or if not then of zero torsion) on the boundary of a flat immersed compact surface is greater than or equal to twice the absolute value of the Euler characteristic of the surface. A set of necessary and, in a weakened sense, sufficient...

  3. 'Regime shopping' across (blurring) boundaries

    NARCIS (Netherlands)

    Houwerzijl, M.S.; Evju, Stein

    2014-01-01

    This book chapter identifies and explores the (blurring) boundaries between the legal regimes for labour mobility across the EU. In the context of - what is sometimes called - 'regime shopping' a close look is taken into the law on freedom of movement within the EU. Several categories of

  4. the Martian atmospheric boundary layer

    DEFF Research Database (Denmark)

    Petrosyan, A.; Galperin, B.; Larsen, Søren Ejling

    2011-01-01

    The planetary boundary layer (PBL) represents the part of the atmosphere that is strongly influenced by the presence of the underlying surface and mediates the key interactions between the atmosphere and the surface. On Mars, this represents the lowest 10 km of the atmosphere during the daytime...

  5. BRIDGES ACROSS AFRICA'S INTERNATIONAL BOUNDARIES ...

    African Journals Online (AJOL)

    The empirical data for this paper is drawn from the ethnic minorities divided along and astride the Cross River borderlands with southern Cameroon. Scholars who have studied the Nigeria Cameroon Boundary tend to lay more emphasis on the state centric perspective that continues to operate largely within the framework ...

  6. Editorial: Environmentalists without Boundaries | Ogunseitan ...

    African Journals Online (AJOL)

    African Journal of Environmental Science and Technology. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 3, No 3 (2009) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. Editorial: Environmentalists without Boundaries.

  7. Transmission Electron Microscopy Characterization of Nanocrystalline Copper

    Energy Technology Data Exchange (ETDEWEB)

    Kung, H.; Sanders, P.G.; Weertman, J.R.

    1999-11-01

    The microstructure and grain boundary structure of nanocrystalline Cu powders and a compact prepared by the inert-gas condensation technique have been characterized by transmission electron microscopy. The as-prepared particles are round in shape and have no distinct surface facets. Annealing twins (coherent {Sigma}3 boundaries) have been observed in the as-prepared Cu particles as well as in the compact. Pores are commonly found at grain boundaries, triple grain junctions and some in the interior of grains in the compact. In addition to twin boundaries, a number of special grain boundaries have been observed. These special grain boundaries have low-index interface planes, and sometimes have misorientation angles close to coincidence site lattice (CSL) orientations.

  8. Exact and Optimal Quantum Mechanics/Molecular Mechanics Boundaries.

    Science.gov (United States)

    Sun, Qiming; Chan, Garnet Kin-Lic

    2014-09-09

    Motivated by recent work in density matrix embedding theory, we define exact link orbitals that capture all quantum mechanical (QM) effects across arbitrary quantum mechanics/molecular mechanics (QM/MM) boundaries. Exact link orbitals are rigorously defined from the full QM solution, and their number is equal to the number of orbitals in the primary QM region. Truncating the exact set yields a smaller set of link orbitals optimal with respect to reproducing the primary region density matrix. We use the optimal link orbitals to obtain insight into the limits of QM/MM boundary treatments. We further analyze the popular general hybrid orbital (GHO) QM/MM boundary across a test suite of molecules. We find that GHOs are often good proxies for the most important optimal link orbital, although there is little detailed correlation between the detailed GHO composition and optimal link orbital valence weights. The optimal theory shows that anions and cations cannot be described by a single link orbital. However, expanding to include the second most important optimal link orbital in the boundary recovers an accurate description. The second optimal link orbital takes the chemically intuitive form of a donor or acceptor orbital for charge redistribution, suggesting that optimal link orbitals can be used as interpretative tools for electron transfer. We further find that two optimal link orbitals are also sufficient for boundaries that cut across double bonds. Finally, we suggest how to construct "approximately" optimal link orbitals for practical QM/MM calculations.

  9. Cross-sectional measurement of grain boundary segregation using WDS

    Energy Technology Data Exchange (ETDEWEB)

    Christien, F., E-mail: frederic.christien@emse.fr [Laboratoire Georges Friedel, CNRS, Ecole des Mines de Saint-Etienne, 158 Cours Fauriel, 42023 Saint-Etienne (France); Risch, P. [Institut des Matériaux Jean Rouxel (IMN), CNRS, Université de Nantes, Rue Christian Pauc, 44306 Nantes (France)

    2016-11-15

    A new method is proposed for the quantification of grain boundary segregation using Wavelength Dispersive Spectroscopy (WDS) in a Scanning Electron Microscope (SEM). Analyses are undertaken on a simple metallographically polished section of material. The method is demonstrated for the model system of sulphur segregation to nickel grain boundaries. Quantification was carried out from sulphur concentration profiles acquired across 11 grain boundaries of a nickel specimen containing 5.4 wt ppm of sulphur in the bulk and equilibrated at 550 °C. The average sulphur grain boundary concentration determined is µ=35.2 ng cm{sup −2}=6.6×10{sup 14} atoms cm{sup −2}≈0.5 monolayer, which is in good agreement with a previous quantification obtained from SIMS (Secondary Ion Mass Spectrometry) on the same material. However this is lower by a factor of two than the quantification obtained using “surface” techniques on fractured specimens of the same material. With the conditions of analysis used in this study, the limit of detection of the method developed is found to be better than 10% of a sulphur monolayer. - Highlights: • Impurity grain boundary segregation can be measured using WDS in a SEM. • The method proposed is quantitative. • The specimen preparation is simple: metallographical section.

  10. Influence of Ion Streaming Instabilities on Transport Near Plasma Boundaries

    CERN Document Server

    Baalrud, Scott D

    2015-01-01

    Plasma boundary layers are susceptible to electrostatic instabilities driven by ion flows in presheaths and, when present, these instabilities can influence transport. In plasmas with a single species of positive ion, ion-acoustic instabilities are expected under conditions of low pressure and large electron-to-ion temperature ratio ($T_e/T_i \\gg 1$). In plasmas with two species of positive ions, ion-ion two-stream instabilities can also be excited. The stability phase-space is characterized using the Penrose criterion and approximate linear dispersion relations. Predictions for how these instabilities affect ion and electron transport in presheaths, including rapid thermalization due to instability-enhanced collisions and an instability-enhanced ion-ion friction force, are also briefly reviewed. Recent experimental tests of these predictions are discussed along with research needs required for further validation. The calculated stability boundaries provide a guide to determine the experimental conditions at ...

  11. Charging of small two-dimensional electron puddles

    Science.gov (United States)

    Brodsky, Misha

    We study electron additions in 2D quantum dots of varying sizes and over a wide range of electron densities using Single Electron Capacitance Spectroscopy. For high electron densities in dots of any size, we observe a conventional pattern of nearly periodic Coulomb blockade. However, the addition spectra of electron droplets larger than 0.2 μm in diameter and below a critical electron density (n0 = 1 × 1011cm-2 in all of our dots) are highly nonperiodic and contain pairs and bunches: two or more successive electrons can enter the dot at nearly the same energy; they show almost no sign of repelling each other. Application of high perpendicular magnetic field increases n0, creating a sharp boundary between periodic and ``paired'' parts of the addition spectrum. Previously, we hypothesized that disorder and electron interactions within the low-density dot split it into two spatially separate droplets, and pairing arises once this localization occurs. We have produced experiments to study this transition in a controlled fashion. One probes the spatial extent of electronic wavefunctions by investigating the dependence of these energies on changes in the dot confining potential. We find that for low electron densities, electrons occupy distinct spatial sites localized within the dot. At higher densities, the electrons become delocalized, and all wavefunctions are spread over the full dot area. The transition occurs around the critical electron density n 0 = 1 × 1011cm-2 . For densities just below the critical density our data establish the existence of electronic states localized at the dot's periphery. We also create a dot with a potential profile containing two minima separated by a barrier. Our studies conclusively demonstrate that under precisely the same conditions for observation of the paired electron additions, a low-density electron droplet inside the dot indeed splits up into smaller fragments, each residing in a disorder minimum. We find that the two

  12. Electronic collection management

    CERN Document Server

    Mcginnis, Suzan D

    2013-01-01

    Build and manage your collection of digital resources with these successful strategies! This comprehensive volume is a practical guide to the art and science of acquiring and organizing electronic resources. The collections discussed here range in size from small college libraries to large research libraries, but all are facing similar problems: shrinking budgets, increasing demands, and rapidly shifting formats. Electronic Collection Management offers new ideas for coping with these issues. Bringing together diverse aspects of collection development, Electronic Collection

  13. Scanning Auger Electron Microscope

    Data.gov (United States)

    Federal Laboratory Consortium — A JEOL model 7830F field emission source, scanning Auger microscope.Specifications / Capabilities:Ultra-high vacuum (UHV), electron gun range from 0.1 kV to 25 kV,...

  14. Grain Boundary Engineering of Electrodeposited Thin Films

    DEFF Research Database (Denmark)

    Alimadadi, Hossein

    of the favorable boundaries that break the network of general grain boundaries. Successful dedicated synthesis of a textured nickel film fulfilling the requirements of grain boundary engineered materials, suggests improved boundary specific properties. However, the textured nickel film shows fairly low......Grain boundary engineering aims for a deliberate manipulation of the grain boundary characteristics to improve the properties of polycrystalline materials. Despite the emergence of some successful industrial applications, the mechanism(s) by which the boundary specific properties can be improved...... to engineer new materials. In this study, one of the most widely used electrolytes for electrodeposition is chosen for the synthesis of nickel films and based on thorough characterization of the boundaries the potentials in grain boundary engineering are outlined. The internal structure of the nickel films...

  15. Solid State Theory of Photovoltaic Materials: Nanoscale Grain Boundaries and Doping CIGS

    Energy Technology Data Exchange (ETDEWEB)

    Zunger, A

    2005-01-01

    We use modern first-principles electronic structure theory to investigate (1) why are grain boundaries in chalcopyrites passive; (2) can chalcopyrites be doped by transition metals, and; (3) can hot electrons and carrier multiplication be efficient in quantum-dot solar cells.

  16. Morphological Instability of Grain Boundaries in Two-Phase Coherent Solids

    Science.gov (United States)

    Geslin, Pierre-Antoine; Xu, Yechuan; Karma, Alain

    2015-03-01

    We show both computationally and analytically that grain boundaries that exhibit shear-coupled motion become morphologically unstable in solid alloys that phase separate into coherent domains of distinct chemical compositions. We carry out simulations of continuum models demonstrating that this instability is mediated by long-range elastic interaction between compositional domains and grain boundaries. In addition, we perform a linear stability analysis that predicts the range of unstable wavelengths in good quantitative agreement with simulations. In nonlinear stages, this pattern-forming instability leads to the breakup of low-angle grain boundaries, thereby strongly impacting microstructural evolution in a wide range of phase-separating materials.

  17. Report to Congress on Sustainable Ranges, 2010

    Science.gov (United States)

    2010-05-01

    Continuing to work with JIOR to provide a mobile service which can be deployed at the Urban Operations Complex ( UOC ) on Range 62. Electronic Combat...range; some means of facilitating IO play but no organic capability. NTTR continuing to work with JIOR to provide a mobile service to deploy at UOC ...no organic capability. Continuing to work with JIOR to provide a mobile service which can be deployed at the UOC . Collective Ranges Information

  18. Controlling electromagnetic fields at boundaries of arbitrary geometries

    Science.gov (United States)

    Teo, Jonathon Yi Han; Wong, Liang Jie; Molardi, Carlo; Genevet, Patrice

    2016-08-01

    Rapid developments in the emerging field of stretchable and conformable photonics necessitate analytical expressions for boundary conditions at metasurfaces of arbitrary geometries. Here, we introduce the concept of conformal boundary optics: a design theory that determines the optical response for designer input and output fields at such interfaces. Given any object, we can realize coatings to achieve exotic effects like optical illusions and anomalous diffraction behavior. This approach is relevant to a broad range of applications from conventional refractive optics to the design of the next-generation of wearable optical components. This concept can be generalized to other fields of research where designer interfaces with nontrivial geometries are encountered.

  19. Marine boundary layer investigations in the False Bay, supported by optical refraction and scintillation measurements

    NARCIS (Netherlands)

    Jong, A.N. de; Eijk, A.M.J. van; Benoist, K.W.; Gunter, W.H.; Vrahimis, G.; October, F.J.

    2011-01-01

    Knowledge on the marine boundary layer is of importance for the prediction of the optical image quality obtained from long range targets. One property of the boundary layer, that can be studied rather easily by means of optical refraction measurements, is the vertical temperature profile. This

  20. Simulation of high-energy radiation belt electron fluxes using NARMAX-VERB coupled codes.

    Science.gov (United States)

    Pakhotin, I P; Drozdov, A Y; Shprits, Y Y; Boynton, R J; Subbotin, D A; Balikhin, M A

    2014-10-01

    This study presents a fusion of data-driven and physics-driven methodologies of energetic electron flux forecasting in the outer radiation belt. Data-driven NARMAX (Nonlinear AutoRegressive Moving Averages with eXogenous inputs) model predictions for geosynchronous orbit fluxes have been used as an outer boundary condition to drive the physics-based Versatile Electron Radiation Belt (VERB) code, to simulate energetic electron fluxes in the outer radiation belt environment. The coupled system has been tested for three extended time periods totalling several weeks of observations. The time periods involved periods of quiet, moderate, and strong geomagnetic activity and captured a range of dynamics typical of the radiation belts. The model has successfully simulated energetic electron fluxes for various magnetospheric conditions. Physical mechanisms that may be responsible for the discrepancies between the model results and observations are discussed.

  1. Substring Range Reporting

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li

    2011-01-01

    We revisit various string indexing problems with range reporting features, namely, position-restricted substring searching, indexing substrings with gaps, and indexing substrings with intervals. We obtain the following main results. – We give efficient reductions for each of the above problems...... to a new problem, which we call substring range reporting. Hence, we unify the previous work by showing that we may restrict our attention to a single problem rather than studying each of the above problems individually. – We show how to solve substring range reporting with optimal query time and little...... range reporting are based on a novel combination of suffix trees and range reporting data structures. The reductions are simple and general and may apply to other combinations of string indexing with range reporting....

  2. Compact Antenna Range

    Data.gov (United States)

    Federal Laboratory Consortium — Facility consists of a folded compact antenna range including a computer controlled three axis position table, parabolic reflector and RF sources for the measurement...

  3. Dryden Aeronautical Test Range

    Data.gov (United States)

    Federal Laboratory Consortium — Recently redesignated to honor Dr. Hugh L. Dryden, NASA's Dryden Aeronautical Test Range (DATR) supports aerospace flight research and technology integration, space...

  4. Nanodiamonds and Carbon Spherules from Tunguska, the K/T Boundary, and the Younger Dryas Boundary Layer

    Science.gov (United States)

    Wittke, J. H.; Bunch, T. E.; West, A.; Kennett, J.; Kennett, D. J.; Howard, G. A.

    2009-12-01

    More than a dozen markers, including nanodiamonds (NDs) and carbon spherules (CS), occur in a sedimentary layer marking the onset of the Younger Dryas (YD) cooling episode at ~12.9 ka. This boundary layer, called the YDB, has been found at nearly forty locations across North America, Europe, and Asia, although not all markers are present at any given site. Firestone et al. (2007) and Kennett et al. (2008, 2009) proposed that these markers resulted from a cosmic impact/airburst and impact-related biomass burning. Here we report features common to the YDB event, the Cretaceous-Tertiary (K/T) impact, and the Tunguska airburst of 1908. In sediments attributed to each event, we and other researchers have recovered NDs either inside or closely associated with CS, which appear to be the high-temperature by-products of biomass burning. CS range in diameter from about 500 nanometers to 4 millimeters with a mean of ~100 microns, and they typically contain NDs, including lonsdaleite (hexagonal diamonds), in the interior matrix and in the crust. To date, CS and NDs have been found in the K/T layer in the United States, Spain, and New Zealand. Similarly, CS and NDs have been found in the YDB layer in the United States, Canada, United Kingdom, Belgium, the Netherlands, Germany, and France. Thus far, every site examined contains NDs and/or CS in the K/T and YDB layers; conversely, we have yet to detect CS associated with NDs in any non-YDB sediments tested. Five allotropes of NDs have been identified in association with CS: cubic diamonds, lonsdaleite, n-diamonds, p-diamonds, and i-carbon, which are differentiated by slight variations in their crystalline structure. All allotropes have been identified using scanning electron microscopy (SEM), high-resolution electron microscopy (HREM), and transmission electron microscopy (TEM) with confirmation by selected area diffraction (SAED). Lonsdaleite is found on Earth only in three instances: (1) in the laboratory, where it is produced

  5. Power electronics substrate for direct substrate cooling

    Science.gov (United States)

    Le, Khiet [Mission Viejo, CA; Ward, Terence G [Redondo Beach, CA; Mann, Brooks S [Redondo Beach, CA; Yankoski, Edward P [Corona, CA; Smith, Gregory S [Woodland Hills, CA

    2012-05-01

    Systems and apparatus are provided for power electronics substrates adapted for direct substrate cooling. A power electronics substrate comprises a first surface configured to have electrical circuitry disposed thereon, a second surface, and a plurality of physical features on the second surface. The physical features are configured to promote a turbulent boundary layer in a coolant impinged upon the second surface.

  6. Plasma Waves Observed in the Cusp Turbulent Boundary Layer: An Analysis of High Time Resolution Wave and Particle Measurements from the Polar Spacecraft

    Science.gov (United States)

    Pickett, J. S.; Franz, J. R.; Scudder, J. D.; Menietti, J. D.; Gurnett, D. A.; Hospodarsky, G. B.; Braunger, R. M.; Kintner, P. M.; Kurth, W. S.

    2001-01-01

    The boundary layer located in the cusp and adjacent to the magnetopause is a region that is quite turbulent and abundant with waves. The Polar spacecraft's orbit and sophisticated instrumentation are ideal for studying this region of space. Our analysis of the waveform data obtained in this turbulent boundary layer shows broadband magnetic noise extending up to a few kilohertz (but less than the electron cyclotron frequency); sinusoidal bursts (a few tenths of a second) of whistler mode waves at around a few tens of hertz, a few hundreds of hertz, and just below the electron cyclotron frequency; and bipolar pulses, interpreted as electron phase-space holes. In addition, bursts of electron cyclotron harmonic waves are occasionally observed with magnetic components. We show evidence of broadband electrostatic bursts covering a range of approx. 3 to approx. 25 kHz (near but less than the plasma frequency) occurring in packets modulated at the frequency of some of the whistler mode waves. On the basis of high time resolution particle data from the Polar HYDRA instrument, we show that these bursts are consistent with generation by the resistive medium instability. The most likely source of the whistler mode waves is the magnetic reconnection site closest to the spacecraft, since the waves are observed propagating both toward and away from the Earth, are bursty, which is often the case with reconnection, and do not fit on the theoretical cold plasma dispersion relation curve.

  7. Evolution of microstructure and grain boundary character distribution of a tin bronze annealed at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Weijiu [College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Chongqing Municipal Key Laboratory of Institutions of Higher Education for Mould Technology, Chongqing University of Technology, Chongqing 400054 (China); Chai, Linjiang, E-mail: chailinjiang@cqut.edu.cn [College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Chongqing Municipal Key Laboratory of Institutions of Higher Education for Mould Technology, Chongqing University of Technology, Chongqing 400054 (China); Li, Zhijun; Yang, Xusheng [College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Guo, Ning; Song, Bo [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China)

    2016-04-15

    Specimens cut from a rolled tin bronze sheet were annealed at 400–800 °C for 1 h and evolution of their microstructures was then characterized in details by electron channeling contrast imaging and electron backscatter diffraction techniques. Particularly, statistics on special boundaries (SBs) with Σ ≤ 29 and network connectivity of random high angle boundaries (HABs) in the annealed specimens were examined to probe optimization potentials of grain boundary character distribution (GBCD) for this material. Results show that the deformed microstructure in the as-received material begins to be recrystallized when the annealing temperature increase to 500 °C and average grain sizes surge with further increasing temperatures. As a result of the recrystallization, a large number of annealing twins (with Σ3 misorientation) are produced, leading to remarkably increased fractions of SBs (f{sub SBs}). Thanks to preexisting dense low angle boundaries, the majority of SBs in the 500 °C specimen with only partial recrystallization are Σ3{sub ic} (incoherent) boundaries, which effectively disrupt connectivity of random HABs network. Although the f{sub SBs} can be further increased (up to 72.5%) in specimens with full recrystallization (at higher temperatures), the Σ3{sub ic} boundaries would be replaced to some extent by Σ3{sub c} (coherent) boundaries which do not contribute directly to optimizing the GBCD. This work should be able to provide clear suggestions on applying the concept of grain boundary engineering to tin bronze alloys. - Highlights: • The rolled tin bronze begins to be recrystallized as temperature increases to 500 °C. • A lot of SBs are produced after recrystallization and the highest f{sub SBs} is 72.5%. • Partially recrystallized specimen has the optimum GBCD due to more Σ3{sub ic} boundaries. • The Σ3{sub ic} boundaries are replaced by Σ3{sub c} boundaries after full recrystallization.

  8. Free boundary ballooning mode representation

    Science.gov (United States)

    Zheng, L. J.

    2012-10-01

    A new type of ballooning mode invariance is found in this paper. Application of this invariance is shown to be able to reduce the two-dimensional problem of free boundary high n modes, such as the peeling-ballooning modes, to a one-dimensional problem. Here, n is toroidal mode number. In contrast to the conventional ballooning representation, which requires the translational invariance of the Fourier components of the perturbations, the new invariance reflects that the independent solutions of the high n mode equations are translationally invariant from one radial interval surrounding a single singular surface to the other intervals. The conventional ballooning mode invariance breaks down at the vicinity of plasma edge, since the Fourier components with rational surfaces in vacuum region are completely different from those with rational surfaces in plasma region. But, the new type of invariance remains valid. This overcomes the limitation of the conventional ballooning mode representation for studying free boundary modes.

  9. Social Entrepreneurship: Definition and Boundaries

    Directory of Open Access Journals (Sweden)

    Samer Abu-Saifan

    2012-02-01

    Full Text Available While individuals may be publicly recognized as social entrepreneurs for their contributions to improve the welfare of communities, the field of social entrepreneurship continues to struggle to gain academic legitimacy. Social entrepreneurship is a term in search of a good definition. The current use of the term seems vague and limitless; it needs boundaries to demarcate its function. The lack of a common definition hinders research and raises questions about which social or profit-making activities fall within the spectrum of social entrepreneurship. To become an important stream in the entrepreneurship literature, social entrepreneurship needs to be properly defined and it requires a theoretical framework that links it to the theory of entrepreneurship. This article builds on the literature to define social entrepreneurship, discusses the boundaries of socially-oriented entrepreneurial activities, and positions the social entrepreneur in the spectrum of entrepreneurship.

  10. Helmholtz bright and boundary solitons

    Energy Technology Data Exchange (ETDEWEB)

    Christian, J M [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); McDonald, G S [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); Chamorro-Posada, P [Departmento de TeorIa de la Senal y Comunicaciones e IngenierIa Telematica, Universidad de Valladolid, ETSI Telecomunicacion, Campus Miguel Delibes s/n, 47011 Valladolid (Spain)

    2007-02-16

    We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic nonlinear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently derived Helmholtz bright solitons, for this type of polynomial nonlinearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterparts.

  11. New trend in electron holography

    Science.gov (United States)

    Tanigaki, Toshiaki; Harada, Ken; Murakami, Yasukazu; Niitsu, Kodai; Akashi, Tetsuya; Takahashi, Yoshio; Sugawara, Akira; Shindo, Daisuke

    2016-06-01

    Electron holography using a coherent electron wave is a promising technique for high-resolution visualization of electromagnetic fields in and around objects. The capability of electron holography has been enhanced by the development of new technologies and has thus become an even more powerful tool for exploring scientific frontiers. This review introduces these technologies including split-illumination electron holography and vector-field electron tomography. Split-illumination electron holography, which uses separated coherent waves, overcomes the limits imposed by the lateral coherence requirement for electron waves in electron holography. Areas that are difficult to observe using conventional electron holography are now observable. Exemplified applications include observing a singular magnetic domain wall in electrical steel sheets, local magnetizations at anti-phase boundaries, and electrostatic potentials in metal-oxide-semiconductor field-effect transistors. Vector-field electron tomography can be used to visualize magnetic vectors in three dimensions. Two components of the vectors are reconstructed using dual-axis tomography, and the remaining one is calculated using div B   =  0. A high-voltage electron microscope can be used to achieve precise magnetic reconstruction. For example, magnetic vortices have been visualized using a 1 MV holography electron microscope.

  12. Defining Our National Cyberspace Boundaries

    Science.gov (United States)

    2010-02-17

    took place within our national cyberspace boundaries. 14. ABSTRACT Cyber Borders, Cyberspace National Policy, Convention On The Law Of Cyberspace... The Law Of Cyberspace, Cyberspace Law, Cyberspace Theory CLASSIFICATION: Unclassified In February 2009, the Obama Administration...Justinian” to the more recent United Nations “Convention on the Law of the Sea” approved in 1982 by 150 12 countries.22 Risk is an area that is not as

  13. Equilibrium composition of interphase boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Wynblatt, P.

    1990-01-01

    Two modeling approaches have been used to investigate segregation effects at interphase boundaries. The first approach is based on the nearest neighbor bond model, used in conjunction with the regular solution approximation, and is an extension of an earlier framework developed to address segregation phenomena at free surfaces. In order to model a semicoherent interphase boundary, we have employed a second modeling approach, based on Monte Carol simulation, in conjunction with the embedded atom method (EAM). The EAM is a powerful new method for describing interatomic interactions in metallic systems. It includes certain many-body interactions that depend on the local environment of an atom. The Monte Carol approach has been applied to semicoherent interphase boundaries in Cu-Ag-Au alloys dilute in Au. These alloys consist of coexisting Cu-rich and Ag-rich phases, which differ in lattice constant by about 12%, such that good matching across in interface occurs when nine structural units of the Cu-rich phase are opposed to eight structural units of the Ag-rich phase. Thus far, interfaces with two different orientations have been studied: {l brace}001{r brace}-Cu//{l brace}001{r brace}-Ag, {l angle}110{r angle}-Cu//{l angle}110{r angle}-Ag; and {l brace}111{r brace}-Cu//{l brace}111{r brace}-Ag, {l angle}110{r angle}-Cu//{l angle}110{r angle}-Ag. These two interfaces will be referred to as the (001) and (111) interphase boundaries, for short. 18 refs.

  14. Bridging boundaries: CORBA in perspective.

    OpenAIRE

    Cahill, Vinny; Baker, Sean; Nixon, Paddy

    1997-01-01

    peer-reviewed peer-reviewed applications that cross the boundaries of different computing machines, operating systems, and programming languages are increasingly the norm. As a result, the need for what might be called ???bridging technologies??? to develop software that works across heterogeneous environments has become more compelling. The Common Object Request Broker Architecture is one such technology that is both robust and commercially available. CORBA essentially describes...

  15. Bridging boundaries: CORBA in perspective.

    OpenAIRE

    Cahill, Vinny

    1997-01-01

    PUBLISHED pplications that cross the boundaries of different computing machines, operating systems, and programming languages are increasingly the norm. As a result, the need for what might be called ?bridging technologies? to develop software that works across heterogeneous environments has become more compelling. The Common Object Request Broker Architecture is one such technology that is both robust and commercially available. CORBA essentially describes how client app...

  16. Working across Boundaries in Design

    DEFF Research Database (Denmark)

    Clausen, Christian; Yoshinaka, Yutaka

    The paper addresses how insights from the social shaping tradition and political process theory may contribute to an understanding of design as staging of sociotechnical relations and processes cutting across boundaries of diverse organisational, political and knowledge domains. This idea is purs...... organisational practices. One implication of this approach includes an attention towards what (and how) ar-eas may be rendered open to negotiation and transformation in technological design, implementation, and change processes....

  17. Teacher professional boundaries: online & offline

    OpenAIRE

    Morris, Zoe Anna

    2017-01-01

    The 21st century has emerged as an era of accountability and standardisation for the teaching profession (Mikulec & Miller, 2012). The current research is comprised of 4 interrelated empirical studies which measure and explore individual differences in perceptions of teacher-student boundaries in the secondary school context from an ethical perspective. This research is timely given it has been 8 years since the Teacher Code of Conduct was introduced in Victoria (The Institute, 2008). While t...

  18. A quenched study of the Schroedinger functional with chirally rotated boundary conditions. Non-preturbative tuning

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, J. Gonzalez [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Renner, D.B. [Jefferson Lab, Newport News, VA (United States); Shindler, A. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik

    2012-08-23

    The use of chirally rotated boundary conditions provides a formulation of the Schroedinger functional that is compatible with automatic O(a) improvement of Wilson fermions up to O(a) boundary contributions. The elimination of bulk O(a) effects requires the non-perturbative tuning of the critical mass and one additional boundary counterterm. We present the results of such a tuning in a quenched setup for several values of the renormalized gauge coupling, from perturbative to nonperturbative regimes, and for a range of lattice spacings. We also check that the correct boundary conditions and symmetries are restored in the continuum limit. (orig.)

  19. Boundary layer thickness effect on boattail drag. [wind tunnel tests for drag reduction

    Science.gov (United States)

    Blaha, B. J.; Chamberlin, R.; Bober, L. J.

    1976-01-01

    A combined experimental and analytical program has been conducted at the NASA Lewis Research Center, to investigate the effects of boundary layer changes on the flow over high angle boattail nozzles. The tests were run on an isolated axisymmetric sting mounted model. Various boattail geometries were investigated at high subsonic speeds over a range of boundary layer thicknesses. In general, boundary layer effects were small at speeds up to Mach 0.8. However, at higher speeds significant regions of separated flow were present on the boattail. When separation was present large reductions in boattail drag resulted with increasing boundary layer thickness. The analysis predicts both of these trends.

  20. Borders, boundaries and desirable wishes

    Directory of Open Access Journals (Sweden)

    Luca Pinciaroli

    2015-05-01

    Full Text Available “Borders, boundaries and desirable wishes” is the title of the residential workshop offered to a group of young adults (aged 18-25 of the Centro di Salute Mentale (Mental Health Center of the DSM Basaglia of ASL TO2 in Turin. The idea of the workshop, the definition of the objectives and the topics, which are clearly expressed in the title, come from the work of the team dedicated to group psychotherapies, which has been offering group psychodrama sessions to young adults of this age since 2008. In the delicate move to the adult age, these young adults are lost and stuck in static realities where it is not possible to open up to the dimension of desire nor to the transforming encounter with the Other, since they didn’t have the experience of boundaries and lack. These two elements are necessary to acquire the ability to make projects for oneself. During the workshop the following instruments were used: group, psychodrama and art therapy. The group, as a paternal function, ensured the presence of safe boundaries enabling individuals to experiment; psychodrama and art therapy enabled the bodies to experience encounters and transformations, using doing as a metaphor for the movement against the inhibition of doing and as a way to show oneself to the Other and be able to see the Other.