Science.gov

Sample records for crossed fields

  1. Cross-spectrally pure light, cross-spectrally pure fields and statistical similarity in electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Chen, Jingjing; Lu, RongSheng; Chen, Feinan; Li, Jia

    2014-08-01

    This paper describes the concept of cross-spectrally pure light, implications of statistical similarity of an optical field on its cross-spectral purity and cross-spectrally pure fields. First, the concept of cross-spectral purity of light is analysed in the space-frequency domain by taking into account the vectorial nature of the radiation, and the conditions and reduction formula are obtained. Then, by utilizing statistical similarity, the relationship between cross-spectral purity and spatial coherence is explored in the electromagnetic field. Last, the conditions for cross-spectrally pure fields are discussed, the polychromatic plane wave and the far field produced by a planar, secondary, stochastic electromagnetic source are studied as examples, and moreover, the relationship between cross-spectral purity and spatial coherence, which we have drawn, is verified during the study.

  2. Cross Sections From Scalar Field Theory

    NASA Technical Reports Server (NTRS)

    Norbury, John W.; Dick, Frank; Norman, Ryan B.; Nasto, Rachel

    2008-01-01

    A one pion exchange scalar model is used to calculate differential and total cross sections for pion production through nucleon- nucleon collisions. The collisions involve intermediate delta particle production and decay to nucleons and a pion. The model provides the basic theoretical framework for scalar field theory and can be applied to particle production processes where the effects of spin can be neglected.

  3. Crossed receptive field components and crossed dendrites in cat sacrocaudal dorsal horn.

    PubMed

    Gladfelter, W E; Millecchia, R J; Pubols, L M; Sonty, R V; Ritz, L A; Covalt-Dunning, D; Culberson, J; Brown, P B

    1993-10-01

    The hypothesis that sacrocaudal dorsal horn neurons with crossed receptive field components on the tail have dendrites which cross to the contralateral dorsal horn was tested in a combined electrophysiological and morphological study. Dorsal horn cells in the sacrocaudal spinal cord of anesthetized cats were penetrated with horseradish peroxidase-filled microelectrodes. After mapping their low threshold mechanoreceptive fields, cells were iontophoretically injected with horseradish peroxidase. A sample of 16 well-stained cells was obtained in laminae III and IV. Cells with receptive fields crossing the dorsal midline of the tail (n = 8) had somata in the lateral ipsilateral dorsal horn, and some of these cells (5/8) had dendrites which crossed to the lateral contralateral dorsal horn. Cells with receptive fields spanning the ventral midline (n = 2) were located near the center of the fused dorsal horn, and one of these had bilateral dendrites in this region. Cells with receptive fields on the lateral tail, crossing neither the dorsal nor the ventral midline (n = 6), had cell bodies in the middle of the ipsilateral dorsal horn; half had only ipsilateral dendrites, and half had crossed dendritic branches. Although the relationship between cell receptive field (RF) location (RF center, expressed as distance from tips of toes) and mediolateral location of the cell body was statistically significant, the correlation between crossed RF components and crossed dendritic branches was not significant. PMID:8254116

  4. Role of ions in a crossed-field diode.

    PubMed

    Lau, Y Y; Luginsland, J W; Cartwright, K L; Haworth, M D

    2007-01-01

    The effect of ions in a magnetically insulated crossed-field gap is studied using a single particle orbit model, shear flow model, and particle-in-cell simulation. It is found that, in general, the presence of ions in a crossed-field gap always increases the electrons' excursion toward the anode region, regardless of the location of the ions. Thus, the rate at which the electrons migrate toward the anode, which is a measure of the diode closure rate, is related to the rate at which ions are introduced into the crossed-field gap. This anode migration of electrons is unrelated to crossed-field ambipolar diffusion. The implications of these findings are explored, such as pulse shortening in relativistic magnetrons and bipolar flows in pulsed-power systems. PMID:17358481

  5. Electron transport in argon in crossed electric and magnetic fields

    PubMed

    Ness; Makabe

    2000-09-01

    An investigation of electron transport in argon in the presence of crossed electric and magnetic fields is carried out over a wide range of values of electric and magnetic field strengths. Values of mean energy, ionization rate, drift velocity, and diffusion tensor are reported here. Two unexpected phenomena arise; for certain values of electric and magnetic field we find regions where the swarm mean energy decreases with increasing electric fields for a fixed magnetic field and regions where swarm mean energy increases with increasing magnetic field for a fixed electric field. PMID:11088933

  6. Contrasting characteristics of linear-field and cross-field atmospheric plasma jets

    NASA Astrophysics Data System (ADS)

    Walsh, J. L.; Kong, M. G.

    2008-09-01

    This letter reports an experimental study of two types of atmospheric pressure plasma jets in terms of their fundamental properties and their efficiency in etching polymeric materials. The first plasma jet has a cross-field configuration with its electric field perpendicular to its gas flow field, whereas the second is a linear-field device having parallel electric and flow fields. The linear-field jet is shown to drive electron transportation to the downstream application region, thus facilitating more active plasma chemistry there. This is responsible for its etching rate of polyamide films being 13-fold that of its cross-field counterpart.

  7. Crossed-field divertor for a plasma device

    DOEpatents

    Kerst, Donald W.; Strait, Edward J.

    1981-01-01

    A divertor for removal of unwanted materials from the interior of a magnetic plasma confinement device includes the division of the wall of the device into segments insulated from each other in order to apply an electric field having a component perpendicular to the confining magnetic field. The resulting crossed-field drift causes electrically charged particles to be removed from the outer part of the confinement chamber to a pumping chamber. This method moves the particles quickly past the saddle point in the poloidal magnetic field where they would otherwise tend to stall, and provides external control over the rate of removal by controlling the magnitude of the electric field.

  8. Evolution of Modes in Magnetically Insulated Crossed Field Diodes

    NASA Astrophysics Data System (ADS)

    Takeall, S.; Greenwood, A.; Cartwright, K.; Fleming, T.; Mardahl, P.; Lau, Y. Y.; Roderick, N.

    2006-10-01

    The time-dependent behavior of electron sheaths in a magnetically insulated B>BHull anode-cathode gap with crossed electric and magnetic fields is studied. The crossed-field, space-charge limited diode is modeled for various magnetic fields by means of multidimensional (1d and 2d), self consistent, electromagnetic, particle-in-cell (PIC) simulations in both cylindrical and planar geometries. The transient behavior of the system is examined in detail and is divided into three separate stages: cycloidal flow, collapse of cycloidal flow and sheared (near-Brillouin) flow. Our 2d electromagnetic PIC simulations (both planar and cylindrical) show that cycloidal flow also collapses into a perturbed flow that is dominated by the E cross B drift, but is neither steady nor stable. This observed cycloidal flow instability is a kinetic mode, not a fluid mode such as the magnetron or diocotron instability. The growth of the kinetic mode is faster than that of either of the above mentioned fluid instabilities. After the kinetic mode saturates, the fastest growing fluid mode grows to dominate the system. The SWS is added by three different methods to separate the RF effects from the DC electric field effects created by the SWS. The first method is to add a circuit to the anode that does not effect the DC electric fields, the second is to add the SWS by placing a thin dielectric (with and unphysical large dielectric constant), and last is to add the geometric SWS.

  9. Crossing the termination shock into the heliosheath: magnetic fields.

    PubMed

    Burlaga, L F; Ness, N F; Acuña, M H; Lepping, R P; Connerney, J E P; Stone, E C; McDonald, F B

    2005-09-23

    Magnetic fields measured by Voyager 1 show that the spacecraft crossed or was crossed by the termination shock on about 16 December 2004 at 94.0 astronomical units. An estimate of the compression ratio of the magnetic field strength B (+/- standard error of the mean) across the shock is B2/B1 = 3.05 +/- 0.04, but ratios in the range from 2 to 4 are admissible. The average B in the heliosheath from day 1 through day 110 of 2005 was 0.136 +/- 0.035 nanoteslas, approximately 4.2 times that predicted by Parker's model for B. The magnetic field in the heliosheath from day 361 of 2004 through day 110 of 2005 was pointing away from the Sun along the Parker spiral. The probability distribution of hourly averages of B in the heliosheath is a Gaussian distribution. The cosmic ray intensity increased when B was relatively large in the heliosheath. PMID:16179471

  10. Rapid current transition in a crossed-field diode

    SciTech Connect

    Verboncoeur, J.P.; Birdsall, C.K.

    1996-03-01

    The transmitted current in a crossed-field gap has been characterized analytically by a number of authors. Using a one dimensional PIC simulation, we explore the behavior of the crossed-field diode at {ital B}={ital B}{sub {ital Hull}}. For mono-energetic (cold) emission, a rapid reduction of transmitted current is observed when the injected current exceeds the critical current by just 1{percent}. The addition of a small electron temperature normal to the cathode eliminates the transition, even for {ital kT}/{ital V}{approximately}10{sup {minus}5} ({ital V}=10 kV, gap = 1 cm, {ital B}=337 G, {ital J}=1.69 A/cm{sup 2}), while an isotropic velocity distribution accelerates the transition. {copyright} {ital 1996 American Institute of Physics.}

  11. Cathode driven high gain crossed-field amplifier

    NASA Astrophysics Data System (ADS)

    1983-07-01

    The objective of this three-phase program is to achieve the design of a cathode driven high gain re-entrant Crossed Field Amplifier capable of meeting the parameters of Raytheon Company specification No. 968838 dated 10 May 1978. The effort includes the fabrication and test of three developmental and four final configuration tubes. One final configuration tube will be life tested and two will be delivered to the Navy. The tasks discussed during this report period relate to the cold tests performed on various subassemblies of model no. 4 and on the sealed-in model no. 4 of the S-band high gain cathode driven crossed field amplifier. Based on the performance of model no. 3 certain remedial measures have been implemented in model no. 4 that have resulted in the elimination of key resonances within the tube and an improvement in the isolation between the cathode and anode circuits.

  12. Electromagnetic instabilities attributed to a cross-field ion drift

    NASA Technical Reports Server (NTRS)

    Chang, C. L.; Wong, H. K.; Wu, C. S.

    1990-01-01

    Instabilities due to a cross-field ion flow are reexamined by including the electromagnetic response of the ions, which has been ignored in existing discussions. It is found that this effect can lead to significant enhancement of the growth rate. Among the new results, a purely growing, electromagnetic unstable mode with a wave vector k parallel to the ambient magnetic field is found. The plasma configuration under consideration is similar to that used in the discussion of the well-known modified-two-stream instability. This instability has a growth rate faster than the ion cyclotron frequency, and is not susceptible to high-plasma-beta stabilization.

  13. Evolution of Modes in Magnetically Insulated Crossed-Field Diodes

    NASA Astrophysics Data System (ADS)

    Cartwright, Keith

    2005-10-01

    The time-dependent behavior of electron sheaths in a magnetically insulated B>BHull anode-cathode gap with crossed electric and magnetic fields is studied. The crossed-field, diode is modeled for various magnetic fields by means of multidimensional (1d and 2d), self-consistent, electromagnetic, particle-in-cell (PIC) simulations. The transient behavior of the system is examined in detail and is divided into three separate stages: cycloidal flow, collapse of cycloidal flow and sheared (near-Brillouin) flow. It has been shown in 1d planar geometry that the cycloidal flows collapse into a steady, near-Brillouin flow. Our 2d electromagnetic PIC simulations (both planar and cylindrical) show that cycloidal flows also collapses into a flow that is dominated by the E cross B drift, but is neither steady nor stable. The growth of the kinetic mode is faster than that of either magnetron or diocotron fluid instability. After the kinetic mode saturates, the fastest growing fluid mode grows to dominate the system. A slow wave structure (SWS) is added to the anode that matches the wavelength and frequency of the fastest growing fluid instability. The SWS is then perturbed so that wavelength and/or frequency does not match the smooth bore diode growth rate and the region of `lock-in' to the SWS is found. This work is supported by a grant from AFOSR.

  14. Nonlinear analysis of generalized cross-field current instability

    NASA Technical Reports Server (NTRS)

    Yoon, Peter H.; Lui, Anthony T. Y.

    1993-01-01

    Analysis of the generalized cross-field current instability is carried out in which cross-field drift of both the ions and electrons and their temperatures are permitted to vary in time. The unstable mode under consideration is the electromagnetic generalization of the classical modified-two-stream instability. The generalized instability is made of the modified-two-stream and ion-Weibel modes. The relative importance of the features associated with the ion-Weibel mode and those of the modified-two-stream mode is assessed. Specific applications are made to the Earth's neutral sheet prior to substorm onset and to the Earth's bow shock. The numerical solution indicates that the ion-Weibel mode dominates in the Earth's neutral sheet environment. In contrast, the situation for the bow shock is dominated by the modified-two-stream mode. Notable differences are found between the present calculation and previous results on ion-Weibel mode which restrict the analysis to only parallel propagating waves. However, in the case of Earth's bow shock for which the ion-Weibel mode plays no important role, the inclusion of the electromagnetic ion response is found to differ little from the previous results which treats ions responding only to the electrostatic component of the excited waves.

  15. Influence of oblique magnetic field on electron cross-field transport in a Hall effect thruster

    SciTech Connect

    Miedzik, Jan; Daniłko, Dariusz; Barral, Serge

    2015-04-15

    The effects of the inclination of the magnetic field with respect to the channel walls in a Hall effect thruster are numerically studied with the use of a one-dimensional quasi-neutral Particle-In-Cell model with guiding center approximation of electron motion along magnetic lines. Parametric studies suggest that the incidence angle strongly influences electron transport across the magnetic field. In ion-focusing magnetic topologies, electrons collide predominantly on the side of the magnetic flux tube closer to the anode, thus increasing the electron cross-field drift. The opposite effect is observed in ion-defocussing topology.

  16. Influence of oblique magnetic field on electron cross-field transport in a Hall effect thruster

    NASA Astrophysics Data System (ADS)

    Miedzik, Jan; Barral, Serge; Daniłko, Dariusz

    2015-04-01

    The effects of the inclination of the magnetic field with respect to the channel walls in a Hall effect thruster are numerically studied with the use of a one-dimensional quasi-neutral Particle-In-Cell model with guiding center approximation of electron motion along magnetic lines. Parametric studies suggest that the incidence angle strongly influences electron transport across the magnetic field. In ion-focusing magnetic topologies, electrons collide predominantly on the side of the magnetic flux tube closer to the anode, thus increasing the electron cross-field drift. The opposite effect is observed in ion-defocussing topology.

  17. Lockhart Crossing field: new Wilcox trend in southeastern Louisiana

    SciTech Connect

    Self, G.A.; Breard, S.Q.; Rael, H.P.; Stein, J.A.; Thayer, P.A.; Traugott, M.O.; Eason, W.D.

    1986-05-01

    In 1982, a significant onshore oil discovery in the lower Eocene Wilcox was made at Lockhart Crossing field, illuminating a new oil trend in southeast Louisiana. Twenty-eight producers and nine dry holes were drilled, resulting in development of 3400 productive acres with estimated recoverable reserves of 21 million bbl of oil after secondary recovery. The main field reservoir is a 40 to 80-ft (12 to 24-m) marine sandstone. The dominant facies is an upward-coarsening sequence of very fine to fine-grained glauconitic sandstone deposited as a nearshore marine bar. The associated facies is a younger, upward-fining, channelized sequence of medium to very fine-grained sandstone. Faulting initiated channeling and erosion into the existing nearshore bar facies with subsequent deposition of channel fill. Together these two facies constitute one reservoir. The primary trapping mechanism is structural, in the form of a rollover anticline. This solution gas drive reservoir is normally pressured and displays a concave-downward producing water level that initially masked the true productive limits of the field. 14 figures, 3 tables.

  18. A cross-field current instability for substorm expansions

    SciTech Connect

    Lui, A.T.Y. ); Chang, C.L.; Mankofsky, A. ); Wong, H.K. ); Winske, D. )

    1991-07-01

    The authors investigate a cross-field current instability (CFCI) as a candidate for current disruption during substorm expansions. The numerical solution of the linear dispersion equation indicates that (1) the proposed instability can occur at the inner edge or the midsection of the neutral sheet just prior to the substorm expansion onset although the former environment is found more favorable at the same drift speed scaled to the ion thermal speed, (2) the computed growth time is comparable to the substorm onset time, and (3) the excited waves have a mixed polarization with frequencies near the ion gyrofrequency at the inner edge and near the lower hybrid frequency in the midtail region. On the basis of this analysis, they propose a substorm development scenario in which plasma sheet thinning during the substorm growth phase leads to an enhancement in the relative drift between ions and electrons. This results in the neutral sheet being susceptible to the CHCI and initiates the diversion of the cross-tail current through the ionosphere. Whether or not a substorm current wedge is ultimately formed is regulated by the ionospheric condition. A large number of substorm features can be readily understood with the proposed scheme. These include (1) precursory activities (pseudobreakups) prior to substorm onset, (2) substorm initiation region to be spatially localized, (3) three different solar wind conditions for substorm occurence, (4) skew towards evening local times for substorm onset locations, (5) different acceleration characteristics between ions and electrons, (6) tailward spreading of current disruption region after substorm onset, and (7) local time expansion of substorm current wedge with possible discrete westward jump for the evening expansion.

  19. Solar coronal loop heating by cross-field wave transport

    NASA Technical Reports Server (NTRS)

    Amendt, Peter; Benford, Gregory

    1989-01-01

    Solar coronal arches heated by turbulent ion-cyclotron waves may suffer significant cross-field transport by these waves. Nonlinear processes fix the wave-propagation speed at about a tenth of the ion thermal velocity, which seems sufficient to spread heat from a central core into a large cool surrounding cocoon. Waves heat cocoon ions both through classical ion-electron collisions and by turbulent stochastic ion motions. Plausible cocoon sizes set by wave damping are in roughly kilometers, although the wave-emitting core may be only 100 m wide. Detailed study of nonlinear stabilization and energy-deposition rates predicts that nearby regions can heat to values intermediate between the roughly electron volt foot-point temperatures and the about 100 eV core, which is heated by anomalous Ohmic losses. A volume of 100 times the core volume may be affected. This qualitative result may solve a persistent problem with current-driven coronal heating; that it affects only small volumes and provides no way to produce the extended warm structures perceptible to existing instruments.

  20. High-field electron transport in GaN under crossed electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Kochelap, V. A.; Korotyeyev, V. V.; Syngayivska, G. I.; Varani, L.

    2015-10-01

    High-field electron transport studied in crossed electric and magnetic fields in bulk GaN with doping of 1016 cm-3, compensation around 90% at the low lattice temperature (30 K). It was found the range of the magnetic and electric fields where the non-equilibrium electron distribution function has a complicated topological structure in the momentum space with a tendency to the formation of the inversion population. Field dependences of dissipative and Hall components of the drift velocity were calculated for the samples with short- and open- circuited Hall contacts in wide ranges of applied electric (0 — 20 kV/cm) and magnetic (1 — 10 T) fields. For former sample, field dependences of dissipative and Hall components of the drift velocity have a non-monotonic behavior. The dissipative component has the inflection point which corresponds to the maximum point of the Hall component. For latter sample, the drift velocity demonstrate a usual sub-linear growth without any critical points. We found that GaN samples with controlled resistance of the Hall circuit can be utilized as a electronic high-power switch.

  1. Use of Neutron Benchmark Fields for the Validation of Dosimetry Cross Sections

    NASA Astrophysics Data System (ADS)

    Griffin, Patrick

    2016-02-01

    The evolution of validation metrics for dosimetry cross sections in neutron benchmark fields is explored. The strength of some of the metrics in providing validation evidence is examined by applying them to the 252Cf spontaneous fission standard neutron benchmark field, the 235U thermal neutron fission reference benchmark field, the ACRR pool-type reactor central cavity reference benchmark fields, and the SPR-III fast burst reactor central cavity. The IRDFF dosimetry cross section library is used in the validation study and observations are made on the amount of coverage provided to the library contents by validation data available in these benchmark fields.

  2. Nuclear reaction cross sections of exotic nuclei in the Glauber model for relativistic mean field densities

    SciTech Connect

    Patra, S. K.; Panda, R. N.; Arumugam, P.; Gupta, Raj K.

    2009-12-15

    We have calculated the total nuclear reaction cross sections of exotic nuclei in the framework of the Glauber model, using as inputs the standard relativistic mean field (RMF) densities and the densities obtained from the more recently developed effective-field-theory-motivated RMF (the E-RMF). Both light and heavy nuclei are taken as the representative targets, and the light neutron-rich nuclei as projectiles. We found the total nuclear reaction cross section to increase as a function of the mass number, for both the target and projectile nuclei. The differential nuclear elastic scattering cross sections are evaluated for some selected systems at various incident energies. We found a large dependence of the differential elastic scattering cross section on incident energy. Finally, we have applied the same formalism to calculate both the total nuclear reaction cross section and the differential nuclear elastic scattering cross section for the recently discussed superheavy nucleus with atomic number Z=122.

  3. Current-Free Plasma Thruster Controlling Cross-Field Diffusion under a Magnetic Nozzle

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazunori; Charles, Christine; Boswell, Rod; Ando, Akira

    A current-free helicon plasma thruster is designed to control cross-field diffusion in a magnetic nozzle while maintaining a constant plasma injection into the nozzle for investigation of the cross-field diffusion effect on the thruster performance. When increasing the magnetic field strength, the cross-field diffusion is inhibited and the higher plasma density in the magnetic nozzle downstream of the thruster is observed. Directly measured thrust also increases with an increase in the field strength, as the Lorentz force arising from the radial magnetic field and the electron diamagnetic drift current is enhanced by the higher electron pressure within the magnetic nozzle. Further, the rf power is increased up to 2 kW and the maximum thrust of about 15 mN is obtained for 20 sccm argon propellant.

  4. Cross-Cultural Psychiatry in the Field: Collaborating with Anthropology

    ERIC Educational Resources Information Center

    Folmar, Steven; Palmes, Guy K.

    2009-01-01

    Psychiatric and anthropological collaborations have produced robust literatures on varied topics but there are challenges in the working relation between these two fields. A research into how cultures deal with attention-deficit hyperactivity disorders in Afghanistan is discussed to highlight the challenges in the working relations between…

  5. Cross-field transport in Goldreich-Sridhar magnetohydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    Fraschetti, F.

    2016-01-01

    I derive analytically the temporal dependence of the perpendicular transport coefficient of a charged particle in the three-dimensional anisotropic turbulence conjectured by Goldreich-Sridhar by implementing multispacecraft constraints on the turbulence power spectrum. The particle motion away from the turbulent local field line is assessed as gradient-curvature drift of the guiding center and compared with the magnetic field line random walk. At inertial scales much smaller than the turbulence outer scale, particles decorrelate from field lines in a free-streaming motion, with no diffusion. In the solar wind at 1 AU, for energy sufficiently small (<1 keV protons), the perpendicular average displacement due to field line tangling generally dominates over two decades of turbulent scales. However, for higher energies (≃25 MeV protons) within the range of multispacecraft measurements, the longitudinal spread originating from transport due to gradient-curvature drift reaches up to ≃10∘ -20∘. This result highlights the role of perpendicular transport in the interpretation of interplanetary and interstellar data.

  6. Cross-field transport in Goldreich-Sridhar magnetohydrodynamic turbulence.

    PubMed

    Fraschetti, F

    2016-01-01

    I derive analytically the temporal dependence of the perpendicular transport coefficient of a charged particle in the three-dimensional anisotropic turbulence conjectured by Goldreich-Sridhar by implementing multispacecraft constraints on the turbulence power spectrum. The particle motion away from the turbulent local field line is assessed as gradient-curvature drift of the guiding center and compared with the magnetic field line random walk. At inertial scales much smaller than the turbulence outer scale, particles decorrelate from field lines in a free-streaming motion, with no diffusion. In the solar wind at 1 AU, for energy sufficiently small (<1 keV protons), the perpendicular average displacement due to field line tangling generally dominates over two decades of turbulent scales. However, for higher energies (≃25 MeV protons) within the range of multispacecraft measurements, the longitudinal spread originating from transport due to gradient-curvature drift reaches up to ≃10^{∘}-20^{∘}. This result highlights the role of perpendicular transport in the interpretation of interplanetary and interstellar data. PMID:26871182

  7. Current Filament Merging Driven by Cross-Field Plasma Flows

    NASA Astrophysics Data System (ADS)

    Vincena, S.; Gekelman, W.; Collette, A.; Cooper, C.

    2007-05-01

    The study of the penetration and mixing of plasmas with differing density, temperature, and species composition has wide-ranging applicability to space plasma systems such as coronal mass ejections, magnetic clouds, galactic jets, and super novae. In these laboratory experiments, two high-beta plasmas are created using a pair of 1.5J, 8ns lasers which strike facing solid carbon targets at right angles to the background magnetic field. The targets are immersed within a low-beta, helium plasma and the lasers are aimed to produce head-on, or glancing collisions. The cylindrical background plasma is 17 m long (10 parallel Alfven wavelengths) by 60 cm wide (300 ρi or 175 c/ωpe). The laser-produced plasmas (LPPs) expand as diamagnetic cavities, become polarized, and then E× B drift at speeds of Mach 10 (v/cs) across the field. As they do so, the ambient plasma facilitates charge separation between energetic LPP electrons and relatively unmagnetized 1keV LPP ions. One of the many resulting dynamic features is the release of a continuous stream of electrons from each LPP. Downstream from the LPP merging, the fast electron current filaments come together with reconnection-like X-line field patterns and eventually merge with a broadband spectrum of electromagnetic (whistler wave) fluctuations. Near-miss LPP collisions result in elongated current sheet formations and the shedding of magnetic field eddies. Current sheet thicknesses are a few electron inertial lengths and the width is approximately one ion inertial length. These results will be presented along with 3D measurements of the magnetic fields and the underlying current systems. These experiments are conducted at the Basic Plasma Science Facility, in the upgraded Large Plasma Device (LAPD) located at the University of California, Los Angeles, USA. This work is funded by the United States Department of Energy and the National Science Foundation.

  8. Program to stimulate graduate training in the field of aeroacoustics. [cross correlation of flow fields of a jet-blown flap with far fields

    NASA Technical Reports Server (NTRS)

    Becker, R. S.

    1975-01-01

    An experiment is reported to cross correlate the output of hot film probes located at various points in the flow field of a jet-blown flap with the output of microphones in the acoustic far field. Fluid dynamic measurements of the flow fields of the test configuration are reported.

  9. TURBULENT CROSS-HELICITY IN THE MEAN-FIELD SOLAR DYNAMO PROBLEM

    SciTech Connect

    Pipin, V. V.; Kuzanyan, K. M.; Zhang, H.; Kosovichev, A. G.

    2011-12-20

    We study the dynamical and statistical properties of turbulent cross-helicity (correlation of the aligned fluctuating velocity and magnetic field components). We derive an equation governing generation and evolution of the turbulent cross-helicity and discuss its meaning for the dynamo. Using the symmetry properties of the problem we suggest a general expression for the turbulent cross-helicity. Effects of the density stratification, large-scale magnetic fields, differential rotation, and turbulent convection are taken into account. We investigate the relative contribution of these effects to the cross-helicity evolution for two kinds of dynamo models of the solar cycle: a distributed mean-field model and a flux-transport dynamo model. We show that the contribution from the density stratification follows the evolution of the radial magnetic field, while large-scale electric currents produce a more complicated pattern of the cross-helicity of comparable magnitude. The pattern of the cross-helicity evolution strongly depends on details of the dynamo mechanism. Thus, we anticipate that direct observations of the cross-helicity on the Sun may serve for the diagnostic purpose of the solar dynamo process.

  10. Small Group Dynamics in Cross-Cultural Collaborative Field Research: Voices from the Field

    ERIC Educational Resources Information Center

    Freeman, Karen A.; Gahungu, Athanase

    2013-01-01

    The purpose of this study was to examine (a) factors that influence effective cross-cultural collaboration, and (b) challenges and issues that face researchers in cross-cultural collaboration. During the summer of 2010, 20 researchers and student interns from Ghana Education Service, Chicago State University (CSU-USA), Winneba University of…

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

    SciTech Connect

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

    2006-10-16

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

  12. Cross-field plasma injection into mirror geometry

    NASA Astrophysics Data System (ADS)

    Uzun-Kaymak, I. U.; Messer, S.; Bomgardner, R.; Case, A.; Clary, R.; Ellis, R.; Elton, R.; Teodorescu, C.; Witherspoon, F. D.; Young, W.

    2009-09-01

    The Maryland Centrifugal Experiment (MCX) and HyperV Technologies Corp. are collaborating on a series of experiments to test the use of a plasma gun to inject mass and momentum into a magnetic-confinement device. HyperV has designed, built and installed a prototype coaxial gun to drive rotation in MCX. The gun has been designed to avoid the blow-by instability via a combination of electrode shaping and a tailored plasma armature. Preliminary measurements at HyperV indicate the gun generates plasma jets with a mass of 160 µg, velocities up to 90 km s-1 and plasma density in the high 1014 cm-3. This paper emphasizes characteristics of the plasma gun and penetration of the plasma jet through the MCX magnetic field. Plans for future injection experiments are briefly discussed.

  13. Life on the Reservation: Cross-Cultural Field Experiences and Student Learning

    ERIC Educational Resources Information Center

    Richardson, Belinda Conrad; Dinkins, Elizabeth G.

    2014-01-01

    Twenty-first century classrooms are filled with increasingly diverse student populations. Effective teacher preparation programs must include explicit course work in culturally responsive pedagogies and field experiences that place educators in new sociocultural contexts. Field experiences in cross-cultural, place-based settings have the potential…

  14. Cross-field current instability for auroral bead formation in breakup arcs

    NASA Astrophysics Data System (ADS)

    Lui, A. T. Y.

    2016-06-01

    The physical process responsible for the onset of substorm expansion is still unresolved in spite of decades of research on the topic. Detailed properties of the spatially periodic auroral beads on prebreakup auroral arcs that initiate substorm expansion onset are now available. These auroral bead properties impose severe observational constraints on the onset process. In this work, theoretical predictions of the cross-field current instability are evaluated in terms of these constraints. The growth rates and wavelengths associated with auroral beads in several previously published events are reproduced by the cross-field current instability, implying that the instability can indeed account for the characteristics of auroral beads that eventually lead to substorm onset. The present results differ from the conclusion reached by a previous analysis that the shear flow ballooning instability can account for the growth and spatial scales of auroral beads better than the cross-field current instability.

  15. Azimuthal dependence of the Garton-Tomkins orbit in crossed magnetic and electric fields

    NASA Astrophysics Data System (ADS)

    Bleasdale, C.; Lewis, R. A.; Bruno-Alfonso, A.

    2016-08-01

    Work on classical closed orbits in the diamagnetic Kepler problem is predominately focused on the chaos observed in the polar launch angle as opposed to the azimuthal launch angle. This is due to atomic systems, along with widely studied external-field geometries (parallel magnetic and electric fields or pure magnetic field), being uniform in azimuthal angle, rendering the azimuthal angle unimportant. In the case of crossed magnetic and electric fields, this is no longer the case, and closed orbits do present an azimuthal launch angle dependence. In atomic systems, due to their spherical symmetry, the electric-field orientation in the plane perpendicular to the magnetic field does not affect the spectrum of orbits. However, in shallow n -type donors in anisotropic semiconductors such as silicon, the orientation of the external fields with respect to conduction-band valleys will be important. In this work we examine the Garton-Tomkins orbit in crossed magnetic and electric fields, and analyze how it and its harmonics' azimuthal dependencies behave through variation of the scaled field or scaled energy. At low scaled fields, harmonics have either twofold or fourfold azimuthal dependencies determined by the rotational symmetry of the individual harmonics. As the scaled field or scaled energy is increased, several harmonics undergo significant bifurcations, resulting in large azimuthal angular regions of essentially closed orbits, which will lead to strong resonances in experimental work.

  16. Modeling the effects of anode secondary electron emission on transmitted current in crossed-field diodes

    NASA Astrophysics Data System (ADS)

    Gopinath, Venkatesh; Vanderberg, Bo

    1996-11-01

    Recent experimental measurements of transmitted current in a crossed-field switch by Vanderberg and Eninger ( B. H. Vanderberg and J. E. Eninger, ``Space-charge limited current cut-off in crossed fields,'' presented at IEEE ICOPS'95, Madison, Wi. ) have shown that the measured values of transmitted current are significantly smaller than the theoretically predicted limit. The experiments also showed larger decrease in transmitted current for higher magnetic fields, implying an effect due to the higher angle of incidence of incident electrons (i.e., at values of B closer to B_H). Studies by Verboncoeur and Birdsall ( J. P. Verboncoeur and C. K. Birdsall. ``Rapid current transition in a crossed-field diode,'' Phys. Plasmas 3) 3, March 1996. have shown that even small amount ( < 1%) of over injection in a crossed-field diode near cut-off led to substantial decrease in transmitted current. In our current work, we show that the same effect can be triggered by the presence of secondary electron emission from the anode. This study models the dependence of emission upon incident electron angle and energy. Since the yield of secondary electrons increases with incident angle, this model follows the experimental results as B approaches B_Hull accurately. This work was supported in part by ONR under grant FD-N00014-90-J-1198

  17. CMB power spectra induced by primordial cross-bispectra between metric perturbations and vector fields

    SciTech Connect

    Shiraishi, Maresuke; Saga, Shohei; Yokoyama, Shuichiro E-mail: saga.shohei@nagoya-u.jp

    2012-11-01

    We study temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation sourced from primordial cross-bispectra between metric perturbations and vector fields, which are generated from the inflation model where an inflaton and a vector field are coupled. In case the vector field survives after the reheating, both the primordial scalar and tensor fluctuations can be enhanced by the anisotropic stress composed of the vector fields during radiation dominated era. We show that through this enhancement the primordial cross-bispectra generate not only CMB bispectra but also CMB power spectra. In general, we can expect such cross-bispectra produce the non-trivial mode-coupling signals between the scalar and tensor fluctuations. However, we explicitly show that such mode-coupling signals do not appear in CMB power spectra. Through the numerical analysis of the CMB scalar-mode power spectra, we find that although signals from these cross-bispectra are smaller than primary non-electromagnetic ones, these have some characteristic features such as negative auto-correlations of the temperature and polarization modes, respectively. On the other hand, signals from tensor modes are almost comparable to primary non-electromagnetic ones and hence the shape of observed B-mode spectrum may deviate from the prediction in the non-electromagnetic case. The above imprints may help us to judge the existence of the coupling between the scalar and vector fields in the early Universe.

  18. Trace Distance and Level Crossing in Spin-Bosen Model with Added Classical Driving Fields

    NASA Astrophysics Data System (ADS)

    He, Qi-Liang; Xiao, Yong-Jun; Zhou, Rui-Xue; Zhang, Ye-Qi

    2016-07-01

    By making use of the trace distance as a measure we investigate the influence of classical driving fields on a open quantum system when the system and its environment are initially in a correlated state. It is shown that the amount of trace distance is sensitive to the classical driving fields which implies that the information flowing between open system and its environment can be controlled by the classical driving fields. Furthermore, we also explore the dependence of the trace distance on the initial parameters when the total system is considered in the thermal equilibrium state. We find that the trace distance on the coupling strength can be used to demonstrate the level crossing of the ground state of the system. In particular, the classical driving fields have significant effect on the level crossing of the ground state.

  19. Measurement and interpretation of current transmission in a crossed-field diode below cutoff

    SciTech Connect

    Vanderberg, B.H.; Eninger, J.E.

    1997-02-01

    Measurements on the current-voltage-magnetic field characteristics of a space-charge-limited cylindrical cross-field diode below cutoff are presented. The measured current is found to be lower than predicted by simple cold-fluid theory. This reduction combined with observed oscillations in the current can be explained by secondary electron emission from the anode, leading to an increase of space charge in the diode. {copyright} {ital 1997 American Institute of Physics.}

  20. Measurement and interpretation of current transmission in a crossed-field diode below cutoff

    NASA Astrophysics Data System (ADS)

    Vanderberg, Bo H.; Eninger, Jan E.

    1997-02-01

    Measurements on the current-voltage-magnetic field characteristics of a space-charge-limited cylindrical cross-field diode below cutoff are presented. The measured current is found to be lower than predicted by simple cold-fluid theory. This reduction combined with observed oscillations in the current can be explained by secondary electron emission from the anode, leading to an increase of space charge in the diode.

  1. On Theoretical Broadband Shock-Associated Noise Near-Field Cross-Spectra

    NASA Technical Reports Server (NTRS)

    Miller, Steven A. E.

    2015-01-01

    The cross-spectral acoustic analogy is used to predict auto-spectra and cross-spectra of broadband shock-associated noise in the near-field and far-field from a range of heated and unheated supersonic off-design jets. A single equivalent source model is proposed for the near-field, mid-field, and far-field terms, that contains flow-field statistics of the shock wave shear layer interactions. Flow-field statistics are modeled based upon experimental observation and computational fluid dynamics solutions. An axisymmetric assumption is used to reduce the model to a closed-form equation involving a double summation over the equivalent source at each shock wave shear layer interaction. Predictions are compared with a wide variety of measurements at numerous jet Mach numbers and temperature ratios from multiple facilities. Auto-spectral predictions of broadband shock-associated noise in the near-field and far-field capture trends observed in measurement and other prediction theories. Predictions of spatial coherence of broadband shock-associated noise accurately capture the peak coherent intensity, frequency, and spectral width.

  2. Pressure field in flow through uniform straight pipes with varying wall cross curvature.

    PubMed

    Naili, Salah; Thiriet, Marc

    2005-10-01

    Pressure fields in rigid smooth straight tubes with an axially uniform cross section, in which an incompressible Newtonian fluid flows steadily, have been determined. Five cross section shapes are used. The reference cross section S0 is slightly elliptic (ellipticity of 1.005). Four cross section shapes, which mimic collapsed vessels in an uniformly frozen state, are defined according to the curvature of their opposite faces (the mid-face is located on the minor axis) Sq (parallel faces), St (face folding), Sc (point contact between faces) and Sl (line contact). These four selected cross shapes are characterized by large changes in both the cross sectional shape and area with respect to S0. The cross shapes are obtained from the computation of the deformation under uniform transmural pressures, without extension, of a thin-walled conduit of infinite length and of homogeneous purely elastic walls of constant thickness. The Navier-Stokes equations are solved using the finite element method for the five tubes summation operator0, summation operatorq, summation operatort, summation operatorc and summation operatorl, which are associated with S0,Sq,St,Sc and Sl, respectively. The numerical tests are performed with the same value of the volume flow rate whatever the tube configuration for three Reynolds numbers ( [See text] ). The present work is aimed at studying the pressure field for the design of the flow chamber in which endothelial cells are cultured. This field is used not only to define a new relative pressure index to determine the entry length but also to estimate the wall shear stress when the flow is fully developed. PMID:16124988

  3. Experimental Study of Corona Properties with a Heated Discharge Electrode and Crossed Magnetic Fields Individually

    NASA Astrophysics Data System (ADS)

    Abu-Elabass, Karim

    2015-07-01

    This work involves ac and dc corona in air with heated discharge electrode, and breakdown streamers in corona in a crossed magnetic field. At first, the triggering of the breakdown streamers in positive and ac corona are governed by the temperature of the discharge electrode. In the negative corona, however, the breakdown streamers found to be practically independent of the temperature of the discharge electrode. Then, the transverse magnetic field, applied perpendicularly to the electric field, result in an improvement in pre-breakdown characteristic of the wire-tube gap. The application of the transverse field has the effect of increasing the corona onset voltage and the breakdown voltage. Also the transverse applied field has the effect of decreasing the corona current. It has been observed that triggering of the breakdown streamers in negative corona is affected appreciably by the transverse magnetic field.

  4. Semiconductor crystal growth in crossed electric and magnetic fields: Center Director's Discretionary Fund

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.

    1996-01-01

    A unique growth cell was designed in which crossed electric and magnetic fields could be separately or simultaneously applied during semiconductor crystal growth. A thermocouple was inserted into an InSb melt inside the growth cell to examine the temperature response of the fluid to applied electromagnetic fields. A static magnetic field suppressed time-dependent convection when a destabilizing thermal field was applied. The simultaneous application of electric and magnetic fields resulted in forced convection in the melt. The InSb ingots grown in the cell were polycrystalline. An InGaSb crystal, 0.5 cm in diameter and 23-cm long, was grown without electromagnetic fields applied. The axial composition results indicated that complete mixing in the melt occurred for this large aspect ratio.

  5. Apparent Cross-field Superslow Propagation of Magnetohydrodynamic Waves in Solar Plasmas

    NASA Astrophysics Data System (ADS)

    Kaneko, T.; Goossens, M.; Soler, R.; Terradas, J.; Van Doorsselaere, T.; Yokoyama, T.; Wright, A. N.

    2015-10-01

    In this paper we show that the phase-mixing of continuum Alfvén waves and/or continuum slow waves in the magnetic structures of the solar atmosphere as, e.g., coronal arcades, can create the illusion of wave propagation across the magnetic field. This phenomenon could be erroneously interpreted as fast magnetosonic waves. The cross-field propagation due to the phase-mixing of continuum waves is apparent because there is no real propagation of energy across the magnetic surfaces. We investigate the continuous Alfvén and slow spectra in two-dimensional (2D) Cartesian equilibrium models with a purely poloidal magnetic field. We show that apparent superslow propagation across the magnetic surfaces in solar coronal structures is a consequence of the existence of continuum Alfvén waves and continuum slow waves that naturally live on those structures and phase-mix as time evolves. The apparent cross-field phase velocity is related to the spatial variation of the local Alfvén/slow frequency across the magnetic surfaces and is slower than the Alfvén/sound velocities for typical coronal conditions. Understanding the nature of the apparent cross-field propagation is important for the correct analysis of numerical simulations and the correct interpretation of observations.

  6. Near-Field Fluorescence Cross-Correlation Spectroscopy on Planar Membranes

    PubMed Central

    2015-01-01

    The organization and dynamics of plasma membrane components at the nanometer scale are essential for biological functions such as transmembrane signaling and endocytosis. Planarized nanoscale apertures in a metallic film are demonstrated as a means of confining the excitation light for multicolor fluorescence spectroscopy to a 55 ± 10 nm beam waist. This technique provides simultaneous two-color, subdiffraction-limited fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy on planar membranes. The fabrication and implementation of this technique are demonstrated for both model membranes and live cells. Membrane-bound proteins were observed to cluster upon the addition of a multivalent cross-linker: On supported lipid bilayers, clusters of cholera toxin subunit B were formed upon cross-linking by an antibody specific for this protein; on living cells, immunoglobulin E bound to its receptor (FcεRI) on the plasma membranes of RBL mast cells was observed to form clusters upon exposure to a trivalent antigen. The formation of membrane clusters was quantified via fluorescence intensity vs time and changes in the temporal auto- and cross-correlations above a single nanoscale aperture. The illumination profile from a single aperture is analyzed experimentally and computationally with a rim-dominated illumination profile, yielding no change in the autocorrelation dwell time with changes in aperture diameter from 60 to 250 nm. This near-field fluorescence cross-correlation methodology provides access to nanoscale details of dynamic membrane interactions and motivates further development of near-field optical methods. PMID:25004429

  7. Lobe crossing events observed by the Van Allen Probes as tests of magnetic field line mapping

    NASA Astrophysics Data System (ADS)

    Dixon, P.; MacDonald, E.; Grande, M.; Glocer, A.

    2014-04-01

    In this paper we examine a series of lobe crossing events witnessed by the twin Van Allen Probes spacecraft between 0200 and 0515 on November 14th 2012. The events occurred on the flank between 0400 and 0635 local time and at altitudes between 5.6 and 6.2 RE. During the events Dst was less than 100nT with the IMF being strongly southward (Bz = - 15nT) and eastward (By = 20 nT). Other observations at geosynchronous orbit also show lobe crossings at dawn and dusk flanks. These events provide a chance to examine the magnetic field topology in detail and compare it with models. We will show that the spacecraft were in locations with access to the open field lines by comparison to the CRCM + BATS-RUS models as well as comparing spacecraft encounters with the lobe to the predicted magnetic field topology.

  8. Effect of electron thermal anisotropy on the kinetic cross-field streaming instability

    NASA Technical Reports Server (NTRS)

    Tsai, S. T.; Tanaka, M.; Gaffey, J. D., Jr.; Wu, C. S.; Da Jornada, E. H.; Ziebell, L. F.

    1984-01-01

    The investigation of the kinetic cross-field streaming instability, motivated by the research of collisionless shock waves and previously studied by Wu et al. (1983), is discussed more fully. Since in the ramp region of a quasi-perpendicular shock electrons can be preferentially heated in the direction transverse to the ambient magnetic field, it is both desirable and necessary to include the effect of the thermal anisotropy on the instability associated with a shock. It is found that Te-perpendicular greater than Te-parallel can significantly enhance the peak growth rate of the cross-field streaming instability when the electron beta is sufficiently high. Furthermore, the present analysis also improves the analytical and numerical solutions previously obtained.

  9. Long-Lived States of Positronium in Crossed Electric and Magnetic Fields

    SciTech Connect

    Ackermann, J.; Shertzer, J.; Schmelcher, P.

    1997-01-01

    We show that crossed electric and magnetic fields provide a unique way for stabilizing simple matter-antimatter systems. Theoretical calculations on positronium in crossed fields predict the existence of long-lived states in which the average positron-electron separation is several thousand angstroms.These delocalized states are due to the existence of an outer well in the potential for certain values of the pseudomomentum and field strength. The near zero probability for positron-electron overlap suppresses direct annihilation processes. Transition moments between the ground state in the outer well and the Coulomb states are also extremely small, resulting in lifetimes up to the order of one year. {copyright} {ital 1997} {ital The American Physical Society}

  10. Tuning equilibration of quantum Hall edge states in graphene - Role of crossed electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Dubey, Sudipta; Deshmukh, Mandar M.

    2016-07-01

    We probe quantum Hall effect in a tunable 1-D lateral superlattice (SL) in graphene created using electrostatic gates. Lack of equilibration is observed along edge states formed by electrostatic gates inside the superlattice. We create strong local electric field at the interface of regions of different charge densities. Crossed electric and magnetic fields modify the wavefunction of the Landau Levels (LLs) - a phenomenon unique to graphene. In the region of copropagating electrons and holes at the interface, the electric field is high enough to modify the Landau levels resulting in increased scattering that tunes equilibration of edge states and this results in large longitudinal resistance.

  11. Cross-correlation analysis of the AE index and the interplanetary magnetic field Bz component.

    NASA Technical Reports Server (NTRS)

    Meng, C.-I.; Tsurutani, B.; Kawasaki, K.; Akasofu, S.-I.

    1973-01-01

    A cross-correlation study between magnetospheric activity (the AE index) and the southward-directed component of the interplanetary magnetic field (IMF) is made for a total of 792 hours (33 days) with a time resolution of about 5.5 min. The peak correlation tends to occur when the interplanetary data are shifted approximately 40 min later with respect to the AE index data. Cross-correlation analysis is conducted on some idealized wave forms to illustrate that this delay between southward turning of the IMF and the AE index should not be interpreted as being the duration of the growth phase.

  12. Random walk study of electron motion in helium in crossed electromagnetic fields

    NASA Technical Reports Server (NTRS)

    Englert, G. W.

    1972-01-01

    Random walk theory, previously adapted to electron motion in the presence of an electric field, is extended to include a transverse magnetic field. In principle, the random walk approach avoids mathematical complexity and concomitant simplifying assumptions and permits determination of energy distributions and transport coefficients within the accuracy of available collisional cross section data. Application is made to a weakly ionized helium gas. Time of relaxation of electron energy distribution, determined by the random walk, is described by simple expressions based on energy exchange between the electron and an effective electric field. The restrictive effect of the magnetic field on electron motion, which increases the required number of collisions per walk to reach a terminal steady state condition, as well as the effect of the magnetic field on electron transport coefficients and mean energy can be quite adequately described by expressions involving only the Hall parameter.

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

    NASA Astrophysics Data System (ADS)

    Raitses, Yevgeny

    2014-10-01

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

  14. Cross-field diffusion in Hall thrusters and other plasma thrusters

    NASA Astrophysics Data System (ADS)

    Boeuf, J. P.

    2012-10-01

    Understanding and quantifying electron transport perpendicular to the magnetic field is a challenge in many low temperature plasma applications. Hall effect thrusters (HETs) provide an excellent example of cross-field transport. The HET is a very successful concept that can be considered both as a gridless ion source and an electromagnetic thruster. In HETs, the electric field E accelerating the ions is a consequence of the Lorentz force due to an external magnetic field B acting on the ExB Hall electron current. An essential aspect of HETs is that the ExB drift is closed, i.e. is in the azimuthal direction of a cylindrical channel. In the first part of this presentation we will discuss the physics of cross-field electron transport in HETs, and the current understanding (or non-understanding) of the possible role of turbulence and wall collisions on cross-field diffusion. We will also briefly comment on alternative designs of ion sources based on the same principles as the conventional HET (Anode Layer Thruster, Diverging Cusp Field Thrusters, End-Hall ion sources). In a second part of the presentation we show that the Lorentz force acting on diamagnetic currents (associated with the ∇PexB term in the electron momentum equation) can also provide thrust. This is the case for example in helicon thrusters where the plasma expands in a magnetic nozzle. We will report and discuss recent work on helicon thrusters and other devices where the diamagnetic current is dominant (with some examples where the ∇PexB current is not closed and is directed toward a wall!).

  15. Electron Cross-field Transport in a Low Power Cylindrical Hall Thruster

    SciTech Connect

    A. Smirnov; Y. Raitses; N.J. Fisch

    2004-06-24

    Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. We show that in order to explain the observed discharge current, the electron anomalous collision frequency {nu}{sub B} has to be on the order of the Bohm value, {nu}{sub B} {approx} {omega}{sub c}/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant.

  16. Anomalous cross-B field transport and spokes in HiPIMS plasma

    NASA Astrophysics Data System (ADS)

    Hecimovic, A.

    2016-05-01

    Localized light emission patterns observed during on time of a high power impulse magnetron sputtering (HiPIMS) discharge on a planar magnetron, known as spokes or ionization zones, have been identified as a potential source of anomalous cross-B field diffusion. In this paper experimental evidence is presented that anomalous diffusion is triggered by the appearance of spokes. The Hall parameter {ω\\text{ce}}{τ\\text{c}} , product of the electron cyclotron frequency and the classical collision time, reduces from Bohm diffusion values (∼ 16 and higher) down to the value of 3 as spokes appear, indicating anomalous cross-B field transport. A combination of intensified charge coupled device imaging and electric probe measurements reveals that the ions from the spokes are instantaneously diffusing away from the target. The ion diffusion coefficients calculated from a sideways image of the spoke are six times higher than Bohm diffusion coefficients, which is consistent with the reduction of the Hall parameter.

  17. Computer model of crossed-field devices using moving wavelength codes

    SciTech Connect

    McDowell, H.L.

    1996-12-31

    DECFA and DEMAG are moving wavelength, particle in cell codes for modeling crossed-field amplifiers (CFAs) and magnetrons. The codes model the interaction between a single traveling wave on a smooth anode surface and the space charge in crossed electric and magnetic fields. The detailed anode vane tip geometry is not included in the model. Periodic boundary conditions are imposed on the sides of the moving interaction wavelength thereby imposing the wave periodicity on the solution. In spite of the assumptions involved, the codes successfully model the performance of many existing CFAs and magnetrons. Correlation of computer model and experimental results will be presented for typical devices. The only failures of the codes to correlate with device performance have occurred for small gap anode vane tip geometries which degrade the efficiency of electron collection. To avoid such possibilities, the simulation codes need to be supplemented with trajectory tracing studies of electrons between anode vanes. Results of such studies will be presented.

  18. Anomalous Cross-Field Current and Fluctuating Equilibrium of Magnetized Plasmas

    SciTech Connect

    Rypdal, K.; Garcia, O.E.; Paulsen, J.

    1997-09-01

    It is shown by simple physical arguments and fluid simulations that electrostatic flute-mode fluctuations can sustain a substantial cross-field current in addition to mass and energy transport. The simulations show that this current determines essential features of the fluctuating plasma equilibrium, and explain qualitatively the experimental equilibria and the coherent flute-mode structures observed in a simple magnetized torus. {copyright} {ital 1997} {ital The American Physical Society}

  19. Snorkel-type conical objective lens with E cross B field for detecting secondary electrons

    NASA Astrophysics Data System (ADS)

    Sato, Mitsugu; Todokoro, Hideo; Kageyama, Kaneo

    1993-09-01

    A new optical system has been developed which employs a snorkel type conical objective lens that allows high resolution imaging at high tilt angles, up to 45 degrees. An E cross B field for detecting secondary electrons is utilized in this optical system in order to avoid influence upon the primary beam from the extraction field generated by the usual scintillator secondary electron detector. Spatial resolution of better than 4 nm at an accelerating voltage of 1 kV has been obtained from a secondary electron image, with a working distance of 3 mm.

  20. Simulations of limiting current in a crossed-field gap: Hull diode

    SciTech Connect

    Verboncoeur, J.P.; Birdsall, C.K.

    1994-12-31

    Simulations confirm the Hull cutoff as the limiting stable current for a space charge limited planar crossed-field diode, proposed by Lau. In addition, a current occurs beyond the Hull cutoff, with a near-zero average value plus a high frequency oscillatory component which dies rapidly in time. The diode reacts strongly to small increases in injection current above the current limit and magnetic field above the Hull cutoff, with a rapid reduction of transmitted current. The simulations are performed in 1D3V, using PDP1.

  1. Self-Consistent Field Approach for Cross-Linked Copolymer Materials

    NASA Astrophysics Data System (ADS)

    Schmid, Friederike

    2013-07-01

    A generalized self-consistent field approach for polymer networks with a fixed topology is developed. It is shown that the theory reproduces the localization of cross-links, which is characteristic for gels. The theory is then used to study the order-disorder transition in regular networks of end-linked diblock copolymers. Compared to diblock copolymer melts, the transition is shifted towards lower values of the incompatibility parameter χ (the Flory- Huggins parameter). Moreover, the transition becomes strongly first order already at the mean-field level. If stress is applied, the transition is further shifted and finally vanishes in a critical point.

  2. The ionized electron return phenomenon of Rydberg atom in crossed-fields

    NASA Astrophysics Data System (ADS)

    Dong, Chengwei; Wang, Peijie; Du, Mengli; Uzer, Turgay; Lan, Yueheng

    2016-05-01

    Rydberg atom is highly excited with one valence electron being in a high quantum state, which is very far away from the nucleus. The energy level is similar to that of the hydrogen atom. Introducing externally perpendicular electric and magnetic fields breaks the rotation symmetry and the traditional view is that the ionized electron crosses from the bound into the unbound region and will never return. However, we find that when the field is strong enough, the electron does not move off to infinity and there is a certain possibility of return. Three new periodic orbits are found by the variational method and the physical significance of the phenomenon is also discussed.

  3. Stationary electron velocity distribution function in crossed electric and magnetic fields with collisions

    SciTech Connect

    Shagayda, Andrey

    2012-08-15

    Analytical studies and numerical simulations show that the electron velocity distribution function in a Hall thruster discharge with crossed electric and magnetic fields is not Maxwellian. This is due to the fact that the mean free path between collisions is greater than both the Larmor radius and the characteristic dimensions of the discharge channel. However in numerical models of Hall thrusters, a hydrodynamic approach is often used to describe the electron dynamics, because discharge simulation in a fully kinetic approach requires large computing resources and is time consuming. A more accurate modeling of the electron flow in the hydrodynamic approximation requires taking into account the non-Maxwellian character of the distribution function and finding its moments, an approach that reflects the properties of electrons drifting in crossed electric and magnetic fields better than the commonly used Euler or Navier-Stokes approximations. In the present paper, an expression for the electron velocity distribution function in rarefied spatially homogeneous stationary plasma with crossed electric and magnetic fields and predominance of collisions with heavy particles is derived in the relaxation approximation. The main moments of the distribution function including longitudinal and transversal temperatures, the components of the viscous stress tensor, and of the heat flux vector are calculated. Distinctive features of the hydrodynamic description of electrons with a strongly non-equilibrium distribution function and the prospects for further development of the proposed approach for calculating the distribution function in spatially inhomogeneous plasma are discussed.

  4. Recent horizontal drilling in Lockhart Crossing Field, Livingston Parish, Louisiana: Its impact on geological interpretation

    SciTech Connect

    Johnson, R.J. )

    1993-09-01

    Recent horizontal completions drilled to date by Callon Petroleum Company in the Lockhart Crossing field have optimized production in the lower Eocene First Wilcox sandstone, a 40-45-ft-thick, marine bar composed to very fine- to fine-grained glauconitic sand. The First Wilcox sandstone reservoir has produced a cumulative of 16 MMBO and 17 BCFG from a total of 40 wells on the Lockhart Crossing field since 1982. Well-site geology was a key factor in these successful horizontal completions because mud logs, electric logs, and cores were not taken for these well bores. Over 3000 ft of drilled cuttings, taken at 10-ft intervals, were examined to maintain the drilling well bore near the top of the First Wilcox sandstone, which has the highest degree of permeability and porosity. By drilling horizontally, we encountered First Wilcox sandstone structure that was not previously mapped using existing subsurface well control. Callon's International Paper Company (IPCO) No. 6 well, the first of three horizontal wells drilled in the Lockhart Crossing field, flowed at a rate of 527 BOPD and 400 MCFGD with a final tubing pressure of 650 lb from the First Wilcox Sandstone in March 1992. The IPCO No. 6 horizontal well, located upthrown to a down-to-the-south fault, has produced 147 MBO an should adequately drain this area of the reservoir.

  5. Polarization dependence of plasmonic near-field enhanced photoemission from cross antennas

    NASA Astrophysics Data System (ADS)

    Klaer, P.; Razinskas, G.; Lehr, M.; Wu, X.; Hecht, B.; Schertz, F.; Butt, H.-J.; Schönhense, G.; Elmers, H. J.

    2016-05-01

    The field enhancement of individual cross-shaped nanoantennas for normal incident light has been measured by the relative photoemission yield using a photoemission electron microscope. We not only measured the electron yield in dependence on the intensity of infrared light (800 nm, 100 fs), but also the polarization dependence. In the normal incidence geometry, the electrical field vector of the illuminating light lies in the surface plane of the sample, independent of the polarization state. Strong yield variations due to an out-of-plane field component as well as changes in the polarization state described by the Fresnel laws are avoided. The electron yield is related to the near-field enhancement as a function of the polarization state of the incident light. The polarization dependence is well explained by numerical simulations.

  6. Cross-Field Electron Heat Transport in a Magnetoplasma, in the Presence of Ion Turbulence

    NASA Astrophysics Data System (ADS)

    Needelman, David Dore

    Cross-field heat transport through a cylindrical pulsed argon afterglow magnetoplasma, (B_0 = 48-300G, rm T_{e} ~ 0.5-7 eV, n_{e} ~ 10^{11} cm^{ -3}, Phi_{s } ~ 2V, radius = 5 cm), is investigated. The study of heat flow is relevant to the fields of fusion engineering and space physics. A BaO-coated dispenser cathode is used to produce a pulsed electron beam, (V_{b}=750 V, I_{b} = 1A, radius = 1.27 cm, tau_{b} = 5 - 10mus, fired 300 mus into the afterglow), propagating down the central axis of the plasma. The beam heats the background electrons within some centimeters of the beam launching point (Whe85); heat diffuses along field lines, forming a "flux tube" of hot plasma. Biased grids, (radius = 5 cm, V_{g} = -200V), are used to retard the axial heat flow through the tube. A radially inserted Langmuir probe is used to map T_{e}, n_ {e}, and Phi_{s } as a function of position and time. There profiles are used to deduce the electron cross-field thermal conductivity coefficient, kappa_| . Anomalous heat transport is found for all cases studied; kappa_| is found to be up to two orders of magnitude above classical predictions. Such transport is attributed to quasilinear effects; collisions of the background electrons with radial ion acoustic waves created indirectly by the beam, through action of the beam/plasma and oscillating two-stream instabilities (Whe85), and with azimuthal ion acoustic waves, created by the pressure-gradient instability(All74). An enhanced collision frequency leads to faster cross-field particle and heat diffusion. Measurements of wave amplitudes are presented, as are correlation measurements proving the waves are ion acoustic. Comparisons of experimental measurements with quasilinear theory predictions (Man78) are shown to be quite close.

  7. Whistler mode waves and Hall fields detected by MMS during a dayside magnetopause crossing

    NASA Astrophysics Data System (ADS)

    Contel, O. Le; Retinò, A.; Breuillard, H.; Mirioni, L.; Robert, P.; Chasapis, A.; Lavraud, B.; Chust, T.; Rezeau, L.; Wilder, F. D.; Graham, D. B.; Argall, M. R.; Gershman, D. J.; Lindqvist, P.-A.; Khotyaintsev, Y. V.; Marklund, G.; Ergun, R. E.; Goodrich, K. A.; Burch, J. L.; Torbert, R. B.; Needell, J.; Chutter, M.; Rau, D.; Dors, I.; Russell, C. T.; Magnes, W.; Strangeway, R. J.; Bromund, K. R.; Leinweber, H. K.; Plaschke, F.; Fischer, D.; Anderson, B. J.; Le, G.; Moore, T. E.; Pollock, C. J.; Giles, B. L.; Dorelli, J. C.; Avanov, L.; Saito, Y.

    2016-06-01

    We present Magnetospheric Multiscale (MMS) mission measurements during a full magnetopause crossing associated with an enhanced southward ion flow. A quasi-steady magnetospheric whistler mode wave emission propagating toward the reconnection region with quasi-parallel and oblique wave angles is detected just before the opening of the magnetic field lines and the detection of escaping energetic electrons. Its source is likely the perpendicular temperature anisotropy of magnetospheric energetic electrons. In this region, perpendicular and parallel currents as well as the Hall electric field are calculated and found to be consistent with the decoupling of ions from the magnetic field and the crossing of a magnetospheric separatrix region. On the magnetosheath side, Hall electric fields are found smaller as the density is larger but still consistent with the decoupling of ions. Intense quasi-parallel whistler wave emissions are detected propagating both toward and away from the reconnection region in association with a perpendicular anisotropy of the high-energy part of the magnetosheath electron population and a strong perpendicular current, which suggests that in addition to the electron diffusion region, magnetosheath separatrices could be a source region for whistler waves.

  8. Generalized crossing states in the interacting case: The uniform gravitational field

    SciTech Connect

    Villanueva, Anthony D.; Galapon, Eric A.

    2010-11-15

    We reconsider Baute et al.'s free crossing states [Phys. Rev. A 61, 022118 (2000)] and show that if we require a generalization in the interacting case that goes in complete parallel with the free-particle case, then this generalized crossing state cannot be arbitrary but is determined by the null space of the particle's quantum time-of-arrival operator. Nonetheless, the free crossing states appear as the leading term in the asymptotic expansion of our generalized crossing state in the limit of large momentum. We then examine the quantum time-of-arrival problem of a spinless particle in a uniform gravitational field. Mass-dependent time-of-arrival probability distributions emerge, signifying quantum departures from the weak equivalence principle. However, in the classical limit of large mass and vanishing uncertainty in position, the mass dependence of the quantum time-of-arrival distribution becomes exponentially small and the mean quantum time of arrival reduces to the classical time of arrival.

  9. A new method for calculating the scattered field by an arbitrary cross-sectional conducting cylinder

    NASA Astrophysics Data System (ADS)

    Ragheb, Hassan A.

    2011-04-01

    Scattering of a plane electromagnetic wave by an arbitrary cross-sectional perfectly conducting cylinder must be performed numerically. This article aims to present a new approach for addressing this problem, which is based on simulating the arbitrary cross-sectional perfectly conducting cylinder by perfectly conducting strips of narrow width. The problem is then turned out to calculate the scattered electromagnetic field from N conducting strips. The technique of solving such a problem uses an asymptotic method. This method is based on an approximate technique introduced by Karp and Russek (Karp, S.N., and Russek, A. (1956), 'Diffraction by a Wide Slit', Journal of Applied Physics, 27, 886-894.) for solving scattering by wide slit. The method is applied here for calculating the scattered field in the far zone for E-polarised incident waves (transverse magnetic (TM) with respect to z-axis) on a perfectly conducting cylinder with arbitrary cross-section. Numerical examples are introduced first for comparison to show the accuracy of the method. Other examples for well-known scattering by conducting cylinders are then introduced followed by new examples which can only be solved by numerical methods.

  10. Compton scattering S matrix and cross section in strong magnetic field

    NASA Astrophysics Data System (ADS)

    Mushtukov, Alexander A.; Nagirner, Dmitrij I.; Poutanen, Juri

    2016-05-01

    Compton scattering of polarized radiation in a strong magnetic field is considered. The recipe for calculation of the scattering matrix elements, the differential and total cross sections based on quantum electrodynamic second-order perturbation theory is presented for the case of arbitrary initial and final Landau level, electron momentum along the field and photon momentum. Photon polarization and electron spin state are taken into account. The correct dependence of natural Landau level width on the electron spin state is taken into account in a general case of arbitrary initial photon momentum for the first time. A number of steps in the calculations were simplified analytically making the presented recipe easy to use. The redistribution functions over the photon energy, momentum and polarization states are presented and discussed. The paper generalizes already known results and offers a basis for the accurate calculation of radiation transfer in a strong B field, for example, in strongly magnetized neutron stars.

  11. Plasma heating at collisionless shocks due to the kinetic cross-field streaming instability

    NASA Technical Reports Server (NTRS)

    Winske, D.; Quest, K. B.; Tanaka, M.; Wu, C. S.

    1985-01-01

    Heating at collisionless shocks due to the kinetic cross-field streaming instability, which is the finite beta (ratio of plasma to magnetic pressure) extension of the modified two stream instability, is studied. Heating rates are derived from quasi-linear theory and compared with results from particle simulations to show that electron heating relative to ion heating and heating parallel to the magnetic field relative to perpendicular heating for both the electrons and ions increase with beta. The simulations suggest that electron dynamics determine the saturation level of the instability, which is manifested by the formation of a flattop electron distribution parallel to the magnetic field. As a result, both the saturation levels of the fluctuations and the heating rates decrease sharply with beta. Applications of these results to plasma heating in simulations of shocks and the earth's bow shock are described.

  12. Local and global effects of the cross-field current instability

    NASA Technical Reports Server (NTRS)

    Lui, A. T. Y.

    1996-01-01

    The cross-field current instability (CCI) was proposed elsewhere as a plausible mechanism for the initiation and intensification of substorm expansions. This instability encompasses the modified two stream, the ion-Weibel and the lower hybrid drift modes. The work carried out in relation to this instability and its local and global effects is reviewed. Predicted local effects include current reduction, particle acceleration, the excitation of oblique whistlers and lower hybrid drift waves, and the breakdown of the frozen-in-field condition through anomalous dissipation. The predicted global effects of CCI include the offset of force equilibrium and the generation of field aligned currents at the disruption site, which allow the efficient large scale transportation of mass, momentum and energy within the magnetosphere.

  13. Evidence for enhanced cross-field transport mechanisms in the TCV Snowflake divertor

    NASA Astrophysics Data System (ADS)

    Vijvers, Wouter

    2015-11-01

    TCV experiments demonstrate that cross-field plasma transport is enhanced in the Snowflake divertor (SFD) compared to a standard single-null divertor (SND). This enhanced cross-field transport spreads the exhaust power over a larger surface area than can be achieved by magnetic geometry alone and, thereby, reduces the peak heat flux. Comparison of the experiments with modelling identifies steepened radial gradients, ExB drift effects, and βp-driven instabilities as the responsible transport mechanisms. The uncovered physics is also relevant to the SND and may help improve predictive models for the target profiles in ITER and DEMO. In SFD variants with an X-point in the scrape-off layer (SOL), part of the heat flux profile is split off and redirected to an additional target. The resulting steepened radial gradients enhance cross-field diffusion. This is confirmed by EMC3-Eirene simulations, which show a factor two reduction of the parallel heat flux, even if diffusivities remain constant. Theoretical analysis predicts enhanced ExB drifts in the SFD by increased poloidal gradients of the temperature and density. The predictions are confirmed by target heat and particle flux measurements in dedicated experiments with both toroidal field directions. Cross-field convection by curvature-driven modes at high βp (``churning modes'') explains the large fluxes into the private flux region of the SFD. This activates the extra targets and reduces the peak power to the primary targets up to a factor four. This mechanism is expected to be most effective when the divertor conditions are most severe: near the separatrix of a narrow, high-pressure SOL of a large tokamak. These and other alternative divertor configurations thus provide potential solutions to the power exhaust challenge, as well as laboratories to study SOL transport, one of the most important topics in tokamak research. This project was carried out with financial support from NWO. The work was carried out within

  14. Crossed-magnetic-field experiments on stacked second generation superconducting tapes: Reduction of the demagnetization effects

    NASA Astrophysics Data System (ADS)

    Baghdadi, M.; Ruiz, H. S.; Coombs, T. A.

    2014-06-01

    The crossed-magnetic-field effect on the demagnetization factor of stacked second generation (2G) high temperature superconducting tapes is presented. The superconducting sample was initially magnetized along the c-axis by the field cooling magnetization method and after achieving the magnetic relaxation of the sample, an extensive set of experimental measurements for different amplitudes of an applied ac magnetic field parallel to the ab-plane was performed. On the one hand, a striking reduction of the demagnetization factor compared with the reported values for superconducting bulks is reported. On the other hand, the demagnetization factor increases linearly with the amplitude of the ac transverse magnetic field confirming the universal linear behavior for the magnetic susceptibility predicted by Brandt [Phys. Rev. B 54, 4246 (1996)]. The study has been also pursued at different frequencies of the ac transverse magnetic field in order to determine the influence of this parameter on the demagnetization factor measurements. We report an even lower demagnetization factor as long as the frequency of the transverse magnetic field increases. Thus, the significant reduction on the demagnetization factor that we have found by using stacked 2G-superconducting tapes, with higher mechanical strength compared with the one of superconducting bulks, makes to this configuration a highly attractive candidate for the future development of more efficient high-power density rotating machines and strong magnet applications.

  15. Variable-effective-field cross polarization. An approach to broadband Hartmann-Hahn matching in MAS NMR

    NASA Astrophysics Data System (ADS)

    Kolbert, Andrew C.; Gann, Sheryl L.

    1994-07-01

    A method for broadening the Hartmann-Hahn matching condition for cross polarization under magic angle spinning is presented. Variable-effective-field cross polarization (VEFCP) employs different effective raido-frequency (rf) fields on the 1H channel during mixing, while the 13C rf field remains constant. VEFCP is shown to result in both a broader matching condition, and a more rapid polarization transfer than ordinary cross polarization at the Hartmann-Hahn match. Experimental results on both adamantane and polycarbonate are discussed.

  16. Evidence of stochastic diffusion across a cross-field sheath due to Kelvin-Helmholtz vortices

    SciTech Connect

    Parker, S.E.; Xu, X.Q.; Lichtenberg, A.J.; Birdsall, C.K. )

    1992-03-15

    We identify mechanisms for particle transport across a cross-field sheath. We present a study of {bold E}{times}{bold B} drift motion in a vortex in which the ion drifts are perturbed by their finite gyroradii and electron drifts are perturbed by one or more traveling waves. Large-scale vortices, which are the result of nonlinear saturation of the Kelvin-Helmholtz instability resulting from shear in the {bold E}{times}{bold B} drift velocity, have been observed in plasma simulations of the cross-field sheath (K. Theilhaber and C. K. Birdsall, Phys. Rev. Lett. 62, 772 (1989); Phys. Fluids B 1, 2241 (1989); 1, 2260 (1989)). Small-scale turbulence is also present, and ions and electrons are transported across the sheath. A vortex alone does not allow for the observed electron transport because the electron drift orbits simply circulate. On the other hand, the ion motion can be stochastic from resonant interaction between harmonics of the drift motion and the gyromotion, independent of the background turbulence. The fluctuations in the ion density would then give rise to a small-amplitude wave spectrum. The combined action of the vortex fields and traveling-wave fields on the electron motion can then lead to stochastic electron diffusion. We study these effects, showing that the values of vortex fields observed in the simulation are sufficient to lead to both ion and electron stochasticity. Furthermore, the rate of the resulting diffusion is sufficient to account for the diffusion observed in the simulation.

  17. Near Noise Field of a Jet-engine Exhaust II : Cross Correlation of Sound Pressures

    NASA Technical Reports Server (NTRS)

    Callaghan, Edmund E; Howes, Walton L; Coles, Willard D

    1956-01-01

    Pressure cross correlations were obtained over a range of jet velocities both longitudinally and laterally for the overall sound pressure and for several frequency bands. The region of positive correlation was found to increase with distance downstream of the nozzle exit and was greater for lateral than for longitudinal correlations. In general, little change in the correlation curves was found as a function of jet velocity or frequency band width. Measurements made with a fixed and a movable microphone in a plate showed correlations similar to the free-field results. The results are interpreted in terms of pressure loads on surfaces.

  18. Similarity of stability characteristics of planar and coaxial crossed-field diodes

    SciTech Connect

    Gopinath, V.P.; Verboncoeur, J.P.; Birdsall, C.K.

    1996-07-01

    Simulations of cylindrical crossed-field diodes for anode/cathode radius ratios of 2 and 5 indicate that the limiting current curve in the region {ital B}{lt}{ital B}{sub {ital H}} in coaxial diodes follows the planar theory and simulations very closely. Coaxial diodes also follow planar theory predicting transition to turbulence in the region {ital B}{approx_gt}{ital B}{sub {ital H}}. Larger radius ratio (10, 20) diodes show somewhat larger limits. These results show little variation with respect to operating voltage or cathode radius. A possible explanation for this behavior is also examined. {copyright} {ital 1996 American Institute of Physics.}

  19. On the source of cross-grain lineations in the central Pacific gravity field

    NASA Technical Reports Server (NTRS)

    Mcadoo, David C.; Sandwell, David T.

    1989-01-01

    The source of cross-grain lineations in marine gravity field observed in central Pacific was investigated by comparing multiple collinear gravity profiles from Geosat data with coincident bathymetry profiles, in the Fourier transform domain. Bathymetric data were collected by multibeam sonar systems operating from two research vessels, one in June-August 1985, the other in February and March 1987. The results of this analysis indicate that the lineations are superficial features that appear to result from a combination of subsurface and surface loads supported by a thin (2 km to 5 km) lithosphere.

  20. Magnetic helicity signature produced by cross-field 2D turbulence

    SciTech Connect

    Markovskii, S. A.; Vasquez, Bernard J.

    2013-06-13

    Hybrid numerical simulations of freely decaying 2D turbulence are presented. The background magnetic field is perpendicular to the simulation plane, which eliminates linear kinetic Alfven waves from the system. The normalized magnetic helicity of the initial large-scale fluctuations is zero, while the normalized cross-helicity is not. As the turbulence evolves, it develops nonzero magnetic helicity at smaller scales, in the proton kinetic range. In the quasi-steady state of evolution, the magnetic helicity spectrum has a peak consistent with the solar wind observations.

  1. Detection of Two Buried Cross Pipelines by Observation of the Scattered Electromagnetic Field

    NASA Astrophysics Data System (ADS)

    Mangini, Fabio; Di Gregorio, Pietro Paolo; Frezza, Fabrizio; Muzi, Marco; Tedeschi, Nicola

    2015-04-01

    In this work we present a numerical study on the effects that can be observed in the electromagnetic scattering of a plane wave due to the presence of two crossed pipelines buried in a half-space occupied by cement. The pipeline, supposed to be used for water conveyance, is modeled as a cylindrical shell made of metallic or poly-vinyl chloride (PVC) material. In order to make the model simpler, the pipelines are supposed running parallel to the air-cement interface on two different parallel planes; moreover, initially we suppose that the two tubes make an angle of 90 degrees. We consider a circularly-polarized plane wave impinging normally to the interface between air and the previously-mentioned medium, which excites the structure in order to determine the most useful configuration in terms of scattered-field sensitivity. To perform the study, a commercially available simulator which implements the Finite Element Method was adopted. A preliminary frequency sweep allows us to choose the most suitable operating frequency depending on the dimensions of the commercial pipeline cross-section. We monitor the three components of the scattered electric field along a line just above the interface between the two media. The electromagnetic properties of the materials employed in this study are taken from the literature and, since a frequency-domain technique is adopted, no further approximation is needed. Once the ideal problem has been studied, i.e. having considered orthogonal and tangential scenario, we further complicate the model by considering different crossing angles and distances between the tubes, in two cases of PVC and metallic material. The results obtained in these cases are compared with those of the initial problem with the goal of determining the scattered field dependence on the geometrical characteristics of the cross between two pipelines. One of the practical applications in the field of Civil Engineering of this study may be the use of ground

  2. Coincidence measurement of the fully differential cross section for atomic-field bremsstrahlung

    NASA Technical Reports Server (NTRS)

    Faulk, J. D.; Quarles, C. A.

    1974-01-01

    A coincidence measurement was made of the absolute cross section for electron-atomic-field bremsstrahlung, differential in photon energy, photon-emission angle, and electron scattering angle. The incident electron energy was 140 keV and the scattering materials were thin films of aluminum and gold. The data are compared to the theoretical calculations of Elwert and Haug and of Bethe and Heitler. Both theories give generally satisfactory agreement for aluminum. The Elwert-Haug theory is somewhat more accurate for gold.

  3. One-dimensional modulational instability in a crossed-field gap

    NASA Astrophysics Data System (ADS)

    Christenson, Peggy J.; Lau, Y. Y.

    1996-04-01

    Cycloidal electron flows in a gap with crossed electric and magnetic fields are found to be violently unstable when a small ac voltage is imposed across the gap. This instability is electrostatic and one dimensional. It occurs over a wide band of frequencies and is insensitive to the precise level of the injected current density. The physical origin of this instability is the formation of a virtual cathode right in front of the cathode. An analytic theory is presented which accurately predicts the onset of the instability in the low-frequency limit.

  4. Fluctuations in the cross-correlation for fields lacking full diffusivity: The statistics of spurious features.

    PubMed

    Yoritomo, John Y; Weaver, Richard L

    2016-07-01

    Inasmuch as ambient noise fields are often not fully diffuse the question arises as to how, or whether, noise cross-correlations converge to Green's function in practice. Well-known theoretical estimates suggest that the quality of convergence scales with the square root of the product of integration time and bandwidth. However, correlations from natural environments often show random features too large to be consistent with fluctuations from insufficient integration time. Here it is argued that empirical seismic correlations suffer in practice from spurious arrivals due to scatterers, and not from insufficient integration time. Estimates are sought for differences by considering a related problem consisting of waves from a finite density of point sources. The resulting cross-correlations are analyzed for their mean and variance. The mean is, as expected, Green's function with amplitude dependent on noise strength. The variance is found to have support for all times up to its maximum at the main arrival. The signal-to-noise ratio there scales with the square root of source density. Numerical simulations support the theoretical estimates. The result permits estimates of spurious arrivals' impact on identification of cross-correlations with Green's function and indicates that spurious arrivals may affect estimates of amplitudes, complicating efforts to infer attenuation. PMID:27475191

  5. Non-Markovian work fluctuation theorem in crossed electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Jiménez-Aquino, J. I.

    2015-08-01

    The validity of the transient work fluctuation theorem for a charged Brownian harmonic oscillator embedded in a non-Markovian heat bath and under the action of crossed electric and magnetic fields is investigated. The aforementioned theorem is verified to be valid within the context of the generalized Langevin equation with an arbitrary memory kernel and arbitrary dragging in the potential minimum. The fluctuation-dissipation relation of the second kind is assumed to be valid and shows that the non-Markovian stochastic dynamics associated with the particle, in the absence of the external time-dependent electric field, reaches an equilibrium state, as is precisely demanded by such a relation. The Jarzynski equality in this problem is also analyzed.

  6. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    SciTech Connect

    Mance, Deni; Baldus, Marc; Gast, Peter; Huber, Martina; Ivanov, Konstantin L.

    2015-06-21

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between “bulk” and “core” nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.

  7. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    NASA Astrophysics Data System (ADS)

    Mance, Deni; Gast, Peter; Huber, Martina; Baldus, Marc; Ivanov, Konstantin L.

    2015-06-01

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between "bulk" and "core" nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.

  8. Numerical studies on flow fields around buildings in an Urban street canyon and cross-road

    NASA Astrophysics Data System (ADS)

    Cheng, Xueling; Hu, Fei

    2005-03-01

    The questions on how vortices are constructed and on the relationship between the flow patterns and concentration distributions in real street canyons are the most pressing questions in pollution control studies. In this paper, the very large eddy simulation (VLES) and large eddy simulation (LES) are applied to calculate the flow and pollutant concentration fields in an urban street canyon and a cross-road respectively. It is found that the flow separations are not only related to the canyon aspect ratios, but also with the flow velocities and wall temperatures. And the turbulent dispersions are so strongly affected by the flow fields that the pollutant concentration distributions can be distinguished from the different aspect ratios, flow velocities and wall temperatures.

  9. Cross-tail current, field-aligned current, and B(y)

    NASA Technical Reports Server (NTRS)

    Kaufmann, Richard L.; Lu, Chen; Larson, Douglas J.

    1994-01-01

    Orbits of individual charged particles were traced in a one-dimensional magnetic field model that included a uniform cross-tail component B(sub yo). The effects of B(sub yo) on the cross-tail current distribution j(sub y)(z), the average cross-tail drift velocity(nu(sub y)z), and the average pitch angle change(delta alpha) experienced during current sheet encounters were calculated. The addition of a B(sub yo) that exceeded several tenths of one nanotesla completely eliminated all resonance effects for odd-N orbits. An odd-N resonance involves ions that enter and exit the current sheet on the same side. Pitch angles of nearly all such ions changed substantially during a typical current sheet interaction, and there was no region of large cross-tail drift velocity in the presence of a modest B(sub yo). the addition of a very large B(sub yo) guide field in the direction that enhances the natural drift produces a large j(y) and small (Delta alpha) for ions with all energies. The addition of a modest B(sub yo) had less effect near even-N resonances. In this case, ions in a small energy range were found to undergo so little change in pitch angle that particles which originated in the ionosphere would pass through the current sheet and return to the conjugate ionosphere. Finally, the cross-tail drift of ions from regions dominated by stochastic orbits to regions dominated by either resonant or guiding center orbits was considered. The ion drift speed changed substantially during such transitions. The accompanying electrons obey the guiding center equations, so electron drift is more uniform. Any difference between gradients in the fluxes associated with electron and ion drifts requires the presence of a Birkeland current in order to maintain charge neutrality. This plasma sheet region therefore serves as a current generator. The analysis predicts that the resulting Birkeland current connects to the lowest altitude equatorial regions in which ions drift to or from a point

  10. Acoustic propagation through anisotropic internal wave fields: transmission loss, cross-range coherence, and horizontal refraction.

    PubMed

    Oba, Roger; Finette, Steven

    2002-02-01

    Results of a computer simulation study are presented for acoustic propagation in a shallow water, anisotropic ocean environment. The water column is characterized by random volume fluctuations in the sound speed field that are induced by internal gravity waves, and this variability is superimposed on a dominant summer thermocline. Both the internal wave field and resulting sound speed perturbations are represented in three-dimensional (3D) space and evolve in time. The isopycnal displacements consist of two components: a spatially diffuse, horizontally isotropic component and a spatially localized contribution from an undular bore (i.e., a solitary wave packet or solibore) that exhibits horizontal (azimuthal) anisotropy. An acoustic field is propagated through this waveguide using a 3D parabolic equation code based on differential operators representing wide-angle coverage in elevation and narrow-angle coverage in azimuth. Transmission loss is evaluated both for fixed time snapshots of the environment and as a function of time over an ordered set of snapshots which represent the time-evolving sound speed distribution. Horizontal acoustic coherence, also known as transverse or cross-range coherence, is estimated for horizontally separated points in the direction normal to the source-receiver orientation. Both transmission loss and spatial coherence are computed at acoustic frequencies 200 and 400 Hz for ranges extending to 10 km, a cross-range of 1 km, and a water depth of 68 m. Azimuthal filtering of the propagated field occurs for this environment, with the strongest variations appearing when propagation is parallel to the solitary wave depressions of the thermocline. A large anisotropic degradation in horizontal coherence occurs under the same conditions. Horizontal refraction of the acoustic wave front is responsible for the degradation, as demonstrated by an energy gradient analysis of in-plane and out-of-plane energy transfer. The solitary wave packet is

  11. Acoustic propagation through anisotropic internal wave fields: Transmission loss, cross-range coherence, and horizontal refraction

    NASA Astrophysics Data System (ADS)

    Oba, Roger; Finette, Steven

    2002-02-01

    Results of a computer simulation study are presented for acoustic propagation in a shallow water, anisotropic ocean environment. The water column is characterized by random volume fluctuations in the sound speed field that are induced by internal gravity waves, and this variability is superimposed on a dominant summer thermocline. Both the internal wave field and resulting sound speed perturbations are represented in three-dimensional (3D) space and evolve in time. The isopycnal displacements consist of two components: a spatially diffuse, horizontally isotropic component and a spatially localized contribution from an undular bore (i.e., a solitary wave packet or solibore) that exhibits horizontal (azimuthal) anisotropy. An acoustic field is propagated through this waveguide using a 3D parabolic equation code based on differential operators representing wide-angle coverage in elevation and narrow-angle coverage in azimuth. Transmission loss is evaluated both for fixed time snapshots of the environment and as a function of time over an ordered set of snapshots which represent the time-evolving sound speed distribution. Horizontal acoustic coherence, also known as transverse or cross-range coherence, is estimated for horizontally separated points in the direction normal to the source-receiver orientation. Both transmission loss and spatial coherence are computed at acoustic frequencies 200 and 400 Hz for ranges extending to 10 km, a cross-range of 1 km, and a water depth of 68 m. Azimuthal filtering of the propagated field occurs for this environment, with the strongest variations appearing when propagation is parallel to the solitary wave depressions of the thermocline. A large anisotropic degradation in horizontal coherence occurs under the same conditions. Horizontal refraction of the acoustic wave front is responsible for the degradation, as demonstrated by an energy gradient analysis of in-plane and out-of-plane energy transfer. The solitary wave packet is

  12. Field Tests of a NaI(Tl)-Based Vehicle Portal Monitor at Border Crossings

    SciTech Connect

    Stromswold, David C.; Darkoch, Justin; Ely, James H.; Hansen, Randy R.; Kouzes, Richard T.; Milbrath, Brian D.; Runkle, Robert C.; Sliger, William A.; Smart, John E.; Stephens, Daniel L.; Todd, Lindsay C.; Woodring, Mitchell L.

    2004-10-01

    Radiation portal monitors are commonly used at international border crossings to detect illicit transport of radioactive material. Most monitors use plastic scintillators to detect gamma rays, but next-generation monitors may contain NaI(Tl). In order to directly compare the performance of the two types of detectors, a prototype NaI(Tl) monitor was tested at two international border crossings adjacent to a comparable plastic scintillator monitor. The NaI(Tl) monitor housed four large detectors, each 10.2 cm x 10.2 cm x 41 cm. The empirical data set from the two field tests contains approximately 3800 passages with known cargo loads for each vehicle For a small subset of the vehicles, high purity germanium detector spectra were also collected. During the survey period several vehicles containing commercial products with naturally occurring radioactive material (NORM) passed through the monitor. Typical NORM cargo included pottery, large granite slabs, rock-based floor tiles, construction stone blocks, abrasive material, and fertilizer. Non-NORM sources encountered during the field tests included a large source of 60Co (200,000 GBq) and a shipment of uranium oxide, both items being legally transported. The information obtained during the tests provides a good empirical data set to compare the effectiveness of NaI(Tl) and plastic-scintillator portal monitors. The capability to be sensitive to illicit materials, but not alarm on NORM, is a key figure of merit for portal monitors. (PIET-43741-TM-210)

  13. Effect of Secondary Electron Emission on Electron Cross-Field Current in E×B Discharges

    SciTech Connect

    Yevgeny Raitses, Igor D. Kaganovich, Alexander Khrabrov, Dmytro Sydorenko, Nathaniel J. Fisch and Andrei Smolyakov

    2011-02-10

    This paper reviews and discusses recent experimental, theoretical, and numerical studies of plasma-wall interaction in a weakly collisional magnetized plasma bounded with channel walls made from different materials. A lowpressure ExB plasma discharge of the Hall thruster was used to characterize the electron current across the magnetic field and its dependence on the applied voltage and electron-induced secondary electron emission (SEE) from the channel wall. The presence of a depleted, anisotropic electron energy distribution function with beams of secondary electrons was predicted to explain the enhancement of the electron cross-field current observed in experiments. Without the SEE, the electron crossfield transport can be reduced from anomalously high to nearly classical collisional level. The suppression of SEE was achieved using an engineered carbon velvet material for the channel walls. Both theoretically and experimentally, it is shown that the electron emission from the walls can limit the maximum achievable electric field in the magnetized plasma. With nonemitting walls, the maximum electric field in the thruster can approach a fundamental limit for a quasineutral plasma.

  14. Thin film deposition by electric and magnetic crossed-field diode sputtering. [Patent application

    DOEpatents

    Welch, K.M.

    1975-04-04

    Applying a coating of titanium nitride to a klystron window by means of a cross-field diode sputtering array is described. The array is comprised of a cohesive group of numerous small hollow electrically conducting cylinders and is mounted so that the open ends of the cylinders on one side of the group are adjacent to a titanium cathode plate. The workpiece is mounted so as to face the open ends of the other side of the group. A magnetic field is applied to the array so as to be coaxial with the cylinders and a potential is applied across the cylinders and the cathode plate, the cylinders as an anode being positive with respect to the cathode plate. The cylinders, the cathode plate, and the workpiece are situated in an atmosphere of nitrogen which becomes ionized such as by field emission because of the electric field between the cylinders and cathode plate, thereby establishing an anode-cathode discharge that results in sputtering of the titanium plate. The sputtered titanium coats the workpiece and chemically combines with the nitrogen to form a titanium nitride coating on the workpiece. Gas pressure, gas mixtures, cathode material composition, voltages applied to the cathode and anode, the magnetic field, cathode, anode and workpiece spacing, and the aspect ratio (ratio of length to inner diameter) of the anode cylinders, all may be controlled to provide consistent optimum thin film coatings of various compositions and thickness. Another facet of the disclosure is the coating of microwave components per se with titanium nitride to reduce multifactoring under operating conditions of the components.

  15. Thin film deposition by electric and magnetic crossed-field diode sputtering

    DOEpatents

    Welch, Kimo M.

    1977-01-01

    Applying a thin film coating to the surface of a workpiece, in particular, applying a coating of titanium nitride to a klystron window by means of a crossed-field diode sputtering array. The array is comprised of a cohesive group of numerous small hollow electrically conducting cylinders and is mounted so that the open ends of the cylinders on one side of the group are adjacent a titanium cathode plate. The workpiece is mounted so as to face the open ends of the other side of the group. A magnetic field is applied to the array so as to be coaxial with the cylinders and a potential is applied across the cylinders and the cathode plate, the cylinders as an anode being positive with respect to the cathode plate. The cylinders, the cathode plate and the workpiece are situated in an atmosphere of nitrogen which becomes ionized such as by field emission because of the electric field between the cylinders and cathode plate, thereby establishing an anode-cathode discharge that results in sputtering of the titanium plate. The sputtered titanium coats the workpiece and chemically combines with the nitrogen to form a titanium nitride coating on the workpiece. Gas pressure, gas mixtures, cathode material composition, voltages applied to the cathode and anode, the magnetic field, cathode, anode and workpiece spacing, and the aspect ratio (ratio of length to inner diameter) of the anode cylinders, all may be controlled to provide consistent optimum thin film coatings of various compositions and thicknesses. Another facet of the disclosure is the coating of microwave components per se with titanium nitride to reduce multipactoring under operating conditions of the components.

  16. Thin film deposition by electric and magnetic crossed-field diode sputtering

    DOEpatents

    Welch, Kimo M.

    1980-01-01

    Applying a thin film coating to the surface of a workpiece, in particular, applying a coating of titanium nitride to a klystron window by means of a crossed-field diode sputtering array. The array is comprised of a cohesive group of numerous small hollow electrically conducting cylinders and is mounted so that the open ends of the cylinders on one side of the group are adjacent a titanium cathode plate. The workpiece is mounted so as to face the open ends of the other side of the group. A magnetic field is applied to the array so as to be coaxial with the cylinders and a potential is applied across the cylinders and the cathode plate, the cylinders as an anode being positive with respect to the cathode plate. The cylinders, the cathode plate and the workpiece are situated in an atmosphere of nitrogen which becomes ionized such as by field emission because of the electric field between the cylinders and cathode plate, thereby establishing an anode-cathode discharge that results in sputtering of the titanium plate. The sputtered titanium coats the workpiece and chemically combines with the nitrogen to form a titanium nitride coating on the workpiece. Gas pressure, gas mixtures, cathode material composition, voltages applied to the cathode and anode, the magnetic field, cathode, anode and workpiece spacing, and the aspect ratio (ratio of length to inner diameter) of the anode cylinders, all may be controlled to provide consistent optimum thin film coatings of various compositions and thicknesses. Another facet of the disclosure is the coating of microwave components per se with titanium nitride to reduce multipactoring under operating conditions of the components.

  17. Cross-field electron transport induced by a rotating spoke in a cylindrical Hall thruster

    SciTech Connect

    Ellison, C. L.; Raitses, Y.; Fisch, N. J.

    2012-01-15

    Rotating spoke phenomena have been observed in a variety of Hall thruster and other E x B devices. It has been suggested that the spoke may be associated with the enhancement of the electron cross-field transport. In this paper, the current conducted across the magnetic field via a rotating spoke has been directly measured for the first time in the E x B discharge of a cylindrical Hall thruster. The spoke current was measured using a segmented anode. Synchronized measurements with a high speed camera and a four-segment anode allow observation of the current as a function of time and azimuthal position. Upwards of 50% of the total current is conducted through the spoke, which occupies a quarter of the Hall thruster channel area. To determine the transport mechanism, emissive and Langmuir probes were installed to measure fluctuating plasma potential, electron density, and temperature. A perturbed, azimuthal electric field and density are observed to oscillate in-phase with the rotating spoke. The resulting drift current is found to enhance electron transport with a magnitude equal to the spoke current to within margins of error.

  18. Suppression of current fluctuations in a crossed E×B field system for low-voltage plasma immersion treatment

    NASA Astrophysics Data System (ADS)

    Levchenko, I.; Keidar, M.; Ostrikov, K.; Yu, M. Y.

    2006-01-01

    Plasma transport in a hybrid dc vacuum arc plasma source for ion deposition and plasma immersion treatment is considered. It is found that external crossed electric and magnetic fields near the substrate can significantly reduce the relative amplitude of ion current fluctuations If at the substrate surface. In particular, If decreases with the applied magnetic field when the bias voltage exceeds 300 V, thus allowing one to reduce the deviations from the rated process parameters. This phenomenon can be attributed to an interaction between the metal-plasma jet from the arc source and the discharge plasma in the crossed fields.

  19. Electron Cross-field Transport in a Miniaturized Cylindrical Hall Thruster

    SciTech Connect

    Smirnov Artem, Raitses Yevgeny, Fisch Nathaniel J

    2005-10-14

    Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. The present paper gives a review of the experimental and numerical investigations of electron crossfield transport in the 2.6 cm miniaturized cylindrical Hall thruster (100 W power level). We show that, in order to explain the discharge current observed for the typical operating conditions, the electron anomalous collision frequency {nu}{sub b} has to be on the order of the Bohm value, {nu}{sub B} {approx} {omega}{sub c}/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant. The optimal regimes of thruster operation at low background pressure (below 10{sup -5} Torr) in the vacuum tank appear to be different from those at higher pressure ({approx} 10{sup -4} Torr).

  20. Quantum capacitance oscillations in graphene under crossed magnetic and electric fields

    NASA Astrophysics Data System (ADS)

    Alisultanov, Z. Z.; Reis, M. S.

    2016-01-01

    Quantum oscillations of metallic systems at low temperatures are one of the key rules to experimentally access their electronic properties, such as energy spectrum, scattering mechanisms, geometry of Fermi surface and many other features. The importance of these knowledge is enormous, since from these a thorough understanding of the anomalous Hall effect, thermopower and Nernst coefficients, just to name a few, is possible; and from those knowledge, plenty of applications arise as emerging technologies. In this direction, the present contribution focuses on a complete description of quantum capacitance oscillations of monolayer and bilayer graphene under crossed electric and magnetic fields, considering to this purpose the Lifshitz-Onsager quantization condition. We found a closed theoretical expression for the quantum capacitance and highlight their amplitude, period and phase —important parameters to access the electronic properties of graphene. These results open doors for further experimental studies.

  1. Kelvin-Helmholtz vortex formation and particle transport in a cross-field plasma sheath

    SciTech Connect

    Theilhaber, K.; Birdsall, C.K.

    1989-02-13

    The time-dependent behavior of a magnetized, two-dimensional plasma-wall sheath has been studied through particle simulations, whcih have shown that the cross-field sheath develops into a turbulent boundary layer, driven by the Kelvin-Helmholtz instability. The sheath acquires an equilibrium thickness l/sub x/approx.5rho/sub i/, and maintains long-lived vortices, with amplitudes deltaphiapprox.-2T/sub i//e, which drift parallel to the wall at half the ion thermal velocity. A central simulation result is that for ..omega../sub ..pi../greater than or equal to2..omega../sub ci/, the anomalous particle transport in the sheath scales like Bohn diffusion.

  2. Thermal effects and space-charge limited transition in crossed-field devices

    SciTech Connect

    Marini, Samuel; Rizzato, Felipe B.; Pakter, Renato

    2014-08-15

    A fully kinetic model for the electron flow in a crossed field device is derived and used to determine the system stationary states. It is found that for low injection temperatures, there is a simultaneous presence of distinct stationary solutions and an abrupt transition between accelerating and space-charge limited regimes. On the other hand, for high injection temperatures, there is only a single stationary solution branch and the change between the regimes becomes continuous. For intermediate temperatures, it is then identified a critical point that separates the abrupt and continuous behaviors. It is also investigated how intrinsic space-charge oscillations may drive stationary states unstable in certain parameter regimes. The results are verified with N-particle self-consistent simulations.

  3. Austin Chalk: cross-link gel water, slick water fracs common in Giddings field

    SciTech Connect

    Mickey, V.

    1981-05-01

    Of the approx. 600 wells drilled in the Giddings field, Austin Chalk trend in the last year, most were probably completed by cross-link gel fracs or slick water fracs. Although open hole completions are not uncommon in the chalk, they are not really practical in most situations, given the 600 to 800 ft of gross pay usually encountered in the Austin Chalk trend. Most of the open hole completions occur when an operator takes a kick while drilling and decides to drop a mud pill over the zone, run casing above it, cement it in and produce the interval open hole. Chalk wells are subject to kick at any time during drilling because of natural fracturing systems throughout the trend. Mud weights are generally fairly light for faster drilling, approx. 9.4 to 9.8 lb, depending on the particular area.

  4. A New One-Dimensional Modulational Instability in a Crossed-Field Gap

    NASA Astrophysics Data System (ADS)

    Christenson, P. J.; Lau, Y. Y.

    1996-11-01

    Cycloidal electron flows in a gap with a crossed electric and magnetic field are found to be violently unstable when a small AC voltage is imposed across the gap footnote P. J. Christenson and Y. Y. Lau, Phys. Rev. Lett. 76, 3324 (1996). This instability is electrostatic, one dimensional and, therefore, it has nothing to do with the diocotron or magnetron instability. It occurs over a wide band of frequencies, possibly from 1/10 to a few times of the electron cyclotron frequency. Its excitation is insensitive to the precise values of the electron current density, and may occur even if the AC voltage is less than one per cent of the DC voltage. This instability is quite violent. In the low frequency regime, breakdown of the flow may occur in less than one rf cycle of the AC voltage. The physical origin of this instability is the formation of a virtual cathode right in front of the cathode.

  5. Optimal Magnetic Field for Crossing Super-Para-Magnetic Nanoparticles through the Brain Blood Barrier: A Computational Approach

    PubMed Central

    Pedram, Maysam Z.; Shamloo, Amir; Alasty, Aria; Ghafar-Zadeh, Ebrahim

    2016-01-01

    This paper scrutinizes the magnetic field effect to deliver the superparamagnetic nanoparticles (SPMNs) through the Blood Brain Barrier (BBB). Herein we study the interaction between the nanoparticle (NP) and BBB membrane using Molecular Dynamic (MD) techniques. The MD model is used to enhance our understanding of the dynamic behavior of SPMNs crossing the endothelial cells in the presence of a gradient magnetic field. Actuation of NPs under weak magnetic field offers the great advantage of a non-invasive drug delivery without the risk of causing injury to the brain. Furthermore, a weak magnetic portable stimulator can be developed using low complexity prototyping techniques. Based on MD simulation results in this paper, SPMNs can cross the cell membrane while experiencing very weak mechanical forces in the range of pN. This study also derives guidelines for the design of the SPMNs dedicated to crossing the BBB using external magnetic fields. PMID:27314396

  6. Optimal Magnetic Field for Crossing Super-Para-Magnetic Nanoparticles through the Brain Blood Barrier: A Computational Approach.

    PubMed

    Pedram, Maysam Z; Shamloo, Amir; Alasty, Aria; Ghafar-Zadeh, Ebrahim

    2016-01-01

    This paper scrutinizes the magnetic field effect to deliver the superparamagnetic nanoparticles (SPMNs) through the Blood Brain Barrier (BBB). Herein we study the interaction between the nanoparticle (NP) and BBB membrane using Molecular Dynamic (MD) techniques. The MD model is used to enhance our understanding of the dynamic behavior of SPMNs crossing the endothelial cells in the presence of a gradient magnetic field. Actuation of NPs under weak magnetic field offers the great advantage of a non-invasive drug delivery without the risk of causing injury to the brain. Furthermore, a weak magnetic portable stimulator can be developed using low complexity prototyping techniques. Based on MD simulation results in this paper, SPMNs can cross the cell membrane while experiencing very weak mechanical forces in the range of pN. This study also derives guidelines for the design of the SPMNs dedicated to crossing the BBB using external magnetic fields. PMID:27314396

  7. DEEPER BY THE DOZEN: UNDERSTANDING THE CROSS-FIELD TEMPERATURE DISTRIBUTIONS OF CORONAL LOOPS

    SciTech Connect

    Schmelz, J. T.; Pathak, S.; Jenkins, B. S.; Worley, B. T.

    2013-02-10

    Spectroscopic analysis of coronal loops has revealed a variety of cross-field temperature distributions. Some loops appear to be isothermal while others require multithermal plasma. The EUV Imaging Spectrometer on Hinode has the spatial resolution and temperature coverage required for differential emission measure (DEM) analysis of coronal loops. Our results also use data from the X-Ray Telescope on Hinode as a high-temperature constraint. Of our 12 loops, two were post-flare loops with broad temperature distributions, two were narrow but not quite isothermal, and the remaining eight were in the mid range. We consider our DEM methods to be a significant advance over previous work, and it is also reassuring to learn that our findings are consistent with results available in the literature. For the quiescent loops analyzed here, 10 MK plasma, a signature of nanoflares, appears to be absent at a level of approximately two orders of magnitude down from the DEM peak. We find some evidence that warmer loops require broader DEMs. The cross-field temperatures obtained here cannot be modeled as single flux tubes. Rather, the observed loop must be composed of several or many unresolved strands. The plasma contained in each of these strands could be cooling at different rates, contributing to the multithermal nature of the observed loop pixels. An important implication of our DEM results involves observations from future instruments. Once solar telescopes can truly resolve X-ray and EUV coronal structures, these images would have to reveal the loop substructure implied by our multithermal results.

  8. Quasi-TEM electromagnetic modes of a plasma waveguide with a nonsimply connected cross section in an external magnetic field

    SciTech Connect

    Kartashov, I. N. Kuzelev, M. V.

    2014-12-15

    Electromagnetic modes of a plasma waveguide with a nonsimply connected cross section in an external magnetic field are investigated. The existence of quasi-TEM modes in a finite-strength magnetic field is demonstrated. It is shown that, in the limits of infinitely strong and zero magnetic fields, this mode transforms into a true TEM mode. The possibility of excitation of such modes by an electron beam in the regime of the anomalous Doppler effect is analyzed.

  9. Auditory-evoked magnetic fields in relation to the interaural cross correlation

    NASA Astrophysics Data System (ADS)

    Soeta, Yoshiharu; Nakagawa, Seiji; Tonoike, Mitsuo; Hotehama, Takuya; Ando, Yoichi

    2001-05-01

    Noninvasive measurements utilizing magnetoencephalography (MEG) have been used to study how sound stimulus features are represented in the human brain. These measurements have successfully revealed how, for example, tone frequency, periodicity, and intensity are encoded. Here, the auditory-evoked magnetic fields in change of the magnitude of the interaural cross correlation (IACC) were analyzed. The IACC of the stimuli was controlled by mixing two independent bandpass noises in appropriate ratios. The auditory stimuli were binaurally delivered through silicon tubes and earpieces inserted into the ear canals. All source signals had the same sound-pressure level. Nine volunteers with normal hearing took part in this study. The auditory-evoked fields were recorded using a neuromagnetometer in a magnetically shielded room. Combinations of a reference stimulus (IACC=1.0) and test stimuli (IACC=0.2,0.6,0.85) were presented alternately at a constant 0.5-s interstimulus interval, and the MEGs were recorded and averaged more than 50 times. The results showed that the peak amplitude of N1m, which was found above left and right temporal lobes around 100 ms after the stimulus onset, significantly decreased with increasing IACC. The N1m latencies were not affected by IACC.

  10. A high power cross-field amplifier at X-Band

    SciTech Connect

    Eppley, K.; Feinstein, J.; Ko, K.; Kroll, N.; Lee, T.; Nelson, E.

    1991-05-01

    A high power cross-field amplifier is under development at SLAC with the objective of providing sufficient peak power to feed a section of an X-Band (11.424 GHz) accelerator without the need for pulse compression. The CFA being designed employs a conventional distributed secondary emission cathode but a novel anode structure which consists of an array of vane resonators alternatively coupled to a rectangular waveguide. The waveguide impedance (width) is tapered linearly from input to output so as to provide a constant RF voltage at the vane tips, leading to uniform power generation along the structure. Nominal design for this tube calls for 300 MW output power, 20 dB gain, DC voltage 142 KV, magnetic field 5 KG, anode-cathode gap 3.6 mm and total interaction length of about 60 cm. These specifications have been supported by computer simulations of both the RF slow wave structure as well as the electron space charge wave interaction. We have used ARGUS to model the cold circuit properties and CONDOR to model the electronic power conversion. An efficiency of 60 percent can be expected. We will discuss the details of the design effort. 5 refs., 6 figs.

  11. Kr II and Xe II axial velocity distribution functions in a cross-field ion source

    SciTech Connect

    Lejeune, A.; Bourgeois, G.; Mazouffre, S.

    2012-07-15

    Laser induced fluorescence measurements were carried out in a cross-field ion source to examine the behaviour of the axial ion velocity distribution functions (VDFs) in the expanding plasma. In the present paper, we focus on the axial VDFs of Kr II and Xe II ions. We examine the contourplots in a 1D-phase space (x,v{sub x}) representation in front of the exhaust channel and along the centerline of the ion source. The main ion beam, whose momentum corresponds to the ions that are accelerated through the whole potential drop, is observed. A secondary structure reveals the ions coming from the opposite side of the channel. We show that the formation of the neutralized ion flow is governed by the annular geometry. The assumption of a collisionless shock or a double layer due to supersonic beam interaction is not necessary. A non-negligible fraction of slow ions originates in local ionization or charge-exchange collision events between ions of the expanding plasma and atoms of the background residual gas. Slow ions that are produced near the centerline in the vicinity of the exit plane are accelerated toward the source body with a negative velocity leading to a high sputtering of front face. On the contrary, the ions that are produced in the vicinity of the channel exit plane are partially accelerated by the extended electric field.

  12. Kr II and Xe II axial velocity distribution functions in a cross-field ion source

    NASA Astrophysics Data System (ADS)

    Lejeune, A.; Bourgeois, G.; Mazouffre, S.

    2012-07-01

    Laser induced fluorescence measurements were carried out in a cross-field ion source to examine the behaviour of the axial ion velocity distribution functions (VDFs) in the expanding plasma. In the present paper, we focus on the axial VDFs of Kr II and Xe II ions. We examine the contourplots in a 1D-phase space (x,vx) representation in front of the exhaust channel and along the centerline of the ion source. The main ion beam, whose momentum corresponds to the ions that are accelerated through the whole potential drop, is observed. A secondary structure reveals the ions coming from the opposite side of the channel. We show that the formation of the neutralized ion flow is governed by the annular geometry. The assumption of a collisionless shock or a double layer due to supersonic beam interaction is not necessary. A non-negligible fraction of slow ions originates in local ionization or charge-exchange collision events between ions of the expanding plasma and atoms of the background residual gas. Slow ions that are produced near the centerline in the vicinity of the exit plane are accelerated toward the source body with a negative velocity leading to a high sputtering of front face. On the contrary, the ions that are produced in the vicinity of the channel exit plane are partially accelerated by the extended electric field.

  13. Influence of crossed fields in structures combining large grain, bulk (RE)BCO superconductors and soft ferromagnetic discs

    NASA Astrophysics Data System (ADS)

    Philippe, M. P.; Fagnard, J. F.; Wéra, L.; Morita, M.; Nariki, S.; Teshima, H.; Caps, H.; Vanderheyden, B.; Vanderbemden, P.

    2016-03-01

    Bulk (RE)BCO superconductors are able to trap record magnetic fields and can be used as powerful permanent magnets in various engineering applications such as rotating machines and magnetic bearings. When such superconducting (SC) “trapped field magnets” are combined to a ferromagnetic (FM) disc, the total magnetic moment is increased with respect to that of the superconductor alone. In the present work, we study experimentally the magnetic behaviour of such hybrid FM/SC structures when they are subjected to cycles of applied field that are orthogonal to their permanent magnetization, i.e. a “crossed-field” configuration. Experimental results show that the usual “crossed-field demagnetization” caused by the cycles of transverse field is strongly reduced in the presence of the ferromagnet.

  14. A cross-platform solution for light field based 3D telemedicine.

    PubMed

    Wang, Gengkun; Xiang, Wei; Pickering, Mark

    2016-03-01

    Current telehealth services are dominated by conventional 2D video conferencing systems, which are limited in their capabilities in providing a satisfactory communication experience due to the lack of realism. The "immersiveness" provided by 3D technologies has the potential to promote telehealth services to a wider range of applications. However, conventional stereoscopic 3D technologies are deficient in many aspects, including low resolution and the requirement for complicated multi-camera setup and calibration, and special glasses. The advent of light field (LF) photography enables us to record light rays in a single shot and provide glasses-free 3D display with continuous motion parallax in a wide viewing zone, which is ideally suited for 3D telehealth applications. As far as our literature review suggests, there have been no reports of 3D telemedicine systems using LF technology. In this paper, we propose a cross-platform solution for a LF-based 3D telemedicine system. Firstly, a novel system architecture based on LF technology is established, which is able to capture the LF of a patient, and provide an immersive 3D display at the doctor site. For 3D modeling, we further propose an algorithm which is able to convert the captured LF to a 3D model with a high level of detail. For the software implementation on different platforms (i.e., desktop, web-based and mobile phone platforms), a cross-platform solution is proposed. Demo applications have been developed for 2D/3D video conferencing, 3D model display and edit, blood pressure and heart rate monitoring, and patient data viewing functions. The demo software can be extended to multi-discipline telehealth applications, such as tele-dentistry, tele-wound and tele-psychiatry. The proposed 3D telemedicine solution has the potential to revolutionize next-generation telemedicine technologies by providing a high quality immersive tele-consultation experience. PMID:26689324

  15. Simulation of Large Parallel Plasma Flows in the Tokamak SOL Driven by Cross-Field Transport Asymmetries

    SciTech Connect

    Pigarov, A Y; Krasheninnikov, S I; LaBombard, B; Rognlien, T D

    2006-06-06

    Large-Mach-number parallel plasma flows in the single-null SOL of different tokamaks are simulated with multi-fluid transport code UEDGE. The key role of poloidal asymmetry of cross-field plasma transport as the driving mechanism for such flows is discussed. The impact of ballooning-like diffusive and convective transport and plasma flows on divertor detachment, material migration, impurity flows, and erosion/deposition profiles is studied. The results on well-balanced double null plasma modeling that are indicative of strong asymmetry of cross-field transport are presented.

  16. Quantitative Eatimation of Ground Water Recharge Process in Vadose Zone Beneath a Rice Paddy Field Using Cross-Borehole Radar

    NASA Astrophysics Data System (ADS)

    Kuroda, S.; Shiina, Y.; Okuyama, T.; Takeutch, M.

    2005-12-01

    Wet Rice Paddy field is one of most important components of land uses in monsoon Asia. It is known to have some other beneficial functions than food production, for example ground water recharge, purification of surface and subsurface water, and alleviation of flood. Though ground water recharge process of paddy field is essential for those functions, the actual conditions of ground water recharge process beneath paddy field has not been clarified besides in the zone of about 1m depth from soil surface. Recently cross borehole radar is recognized as one of usefull methods for measurement of soil water distribution and its change. We applied cross borehole radar for monitoring of soil water in vadose zone beneath a paddy field to clarify the ground water recharge process. Cross borehole radar monitoring clarified the infiltration process into the vadose zone and shallow ground water aquifer beneath the paddy field. We estimated the increment of soil volumetric water content from CRIME model, the descent velocity of wetting front, and infiltration rate from cross borehole radar data quantitatively. They were almost coincident with the directly measured results. Using these results,we tried to estimate permeability based on some hypothesis of infiltration process.

  17. Normalized gradient fields cross-correlation for automated detection of prostate in magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Fotin, Sergei V.; Yin, Yin; Periaswamy, Senthil; Kunz, Justin; Haldankar, Hrishikesh; Muradyan, Naira; Cornud, François; Turkbey, Baris; Choyke, Peter L.

    2012-02-01

    Fully automated prostate segmentation helps to address several problems in prostate cancer diagnosis and treatment: it can assist in objective evaluation of multiparametric MR imagery, provides a prostate contour for MR-ultrasound (or CT) image fusion for computer-assisted image-guided biopsy or therapy planning, may facilitate reporting and enables direct prostate volume calculation. Among the challenges in automated analysis of MR images of the prostate are the variations of overall image intensities across scanners, the presence of nonuniform multiplicative bias field within scans and differences in acquisition setup. Furthermore, images acquired with the presence of an endorectal coil suffer from localized high-intensity artifacts at the posterior part of the prostate. In this work, a three-dimensional method for fast automated prostate detection based on normalized gradient fields cross-correlation, insensitive to intensity variations and coil-induced artifacts, is presented and evaluated. The components of the method, offline template learning and the localization algorithm, are described in detail. The method was validated on a dataset of 522 T2-weighted MR images acquired at the National Cancer Institute, USA that was split in two halves for development and testing. In addition, second dataset of 29 MR exams from Centre d'Imagerie Médicale Tourville, France were used to test the algorithm. The 95% confidence intervals for the mean Euclidean distance between automatically and manually identified prostate centroids were 4.06 +/- 0.33 mm and 3.10 +/- 0.43 mm for the first and second test datasets respectively. Moreover, the algorithm provided the centroid within the true prostate volume in 100% of images from both datasets. Obtained results demonstrate high utility of the detection method for a fully automated prostate segmentation.

  18. Occupational Electromagnetic Field Exposures Associated with Sleep Quality: A Cross-Sectional Study

    PubMed Central

    Liu, Hui; Chen, Guangdi; Pan, Yifeng; Chen, Zexin; Jin, Wen; Sun, Chuan; Chen, Chunjing; Dong, Xuanjun; Chen, Kun; Xu, Zhengping; Zhang, Shanchun; Yu, Yunxian

    2014-01-01

    Background Exposure to electromagnetic field (EMF) emitted by mobile phone and other machineries concerns half the world’s population and raises the problem of their impact on human health. The present study aims to explore the effects of electromagnetic field exposures on sleep quality and sleep duration among workers from electric power plant. Methods A cross-sectional study was conducted in an electric power plant of Zhejiang Province, China. A total of 854 participants were included in the final analysis. The detailed information of participants was obtained by trained investigators using a structured questionnaire, which including socio-demographic characteristics, lifestyle variables, sleep variables and electromagnetic exposures. Physical examination and venous blood collection were also carried out for every study subject. Results After grouping daily occupational electromagnetic exposure into three categories, subjects with long daily exposure time had a significantly higher risk of poor sleep quality in comparison to those with short daily exposure time. The adjusted odds ratios were 1.68 (95%CI: 1.18, 2.39) and 1.57 (95%CI: 1.10, 2.24) across tertiles. Additionally, among the subjects with long-term occupational exposure, the longer daily occupational exposure time apparently increased the risk of poor sleep quality (OR (95%CI): 2.12 (1.23∼3.66) in the second tertile; 1.83 (1.07∼3.15) in the third tertile). There was no significant association of long-term occupational exposure duration, monthly electric fee or years of mobile-phone use with sleep quality or sleep duration. Conclusions The findings showed that daily occupational EMF exposure was positively associated with poor sleep quality. It implies EMF exposure may damage human sleep quality rather than sleep duration. PMID:25340654

  19. ^129Xe-Rb spin-exchange cross section measurement at high magnetic field

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu; Kuzma, N. N.; Walter, D. K.; Griffith, W. M.; Happer, W.

    2002-05-01

    We report NMR measurements of the velocity-averaged ^129Xe-Rb spin-exchange cross section <σ_exv> using isotopically enriched xenon gas in a sealed aluminosilicate cell. At 9.4 T, it is possible to detect Boltzmann polarization of xenon gas nuclei without optical pumping. Over the temperature range from 160 to 200^rcC, binary collisions with Rb atoms dominate the ^129Xe spin-relaxation rate (1/T_1) through spin-exchange. Our data show that the spin-exchange contribution of van der Waals RbXe molecules at high magnetic field is very small compared to the contribition of binary collisions. From the observed linear dependence of 1/T1 on Rb density, we extract the value <σ_exv>=1.720.29× 10-16 cm^3/sec at 180^rcC and 9.4 T, where we deduce the Rb number density from our Faraday rotation measurements. In addition, we discuss a theoretical prediction of <σ_exv> based on our numerical computations and compare it to the experimental result.

  20. Relaxation of virtual cathode oscillations due to transverse effects in a crossed-field diode

    SciTech Connect

    Cartwright, K.L.; Verboncoeur, J.P.; Gopinath, V.P.; Birdsall, C.K.

    1996-12-31

    Recent studies of cylindrical and planar cross-field diodes indicate the transverse dimension plays a role in delaying the onset of virtual cathode oscillations for currents injected above the theoretical limiting current. For 1d and 2d planar devices, the limiting current for the magnetized and unmagnetized diodes is examined for cold and thermal injection. A significant difference between the 1d and 2d smooth diodes is that the transverse direction gives an extra degree of freedom which is found to warm the electrons rapidly. The mechanism of this warming appears to be an instability in the transverse direction. The simulations show three different states; laminar flow, virtual cathode oscillation and warm flow. Warm flow occurs when the electron has a spread of energy, either due to an instability or by thermal injection, when they pas through the potential minimum. Birdsall and Bridges showed that a small thermal spread of injected electrons damps virtual cathode oscillations. This warming effect allows warm flow to exist on the 2d state diagram which is not found on the 1d state diagram for cold emission. Parameter space is explored on these state diagrams for B = 0 and B = B{sub Hull} for J near state transitions (J {approx_equal} J{sub C}).

  1. Genesis of two-dimensional patterns in cross-gradient fields

    NASA Astrophysics Data System (ADS)

    Pismen, L. M.; Simakov, D. S. A.

    2011-12-01

    Tissue morphogenesis is controlled by the two-dimensional patterning of gene expression in epithelial layers, that determines cell fates. The mechanisms of pattern formation involve intracellular regulatory networks controlled by paracrine and autocrine signaling. We develop a general logical scheme to deduce the morphology of two-dimensional patterns in the field of two crossed morphogen gradients enriched by the action of autocrine signaling that may subdivide expression domains in nontrivial ways. A variety of persistent patterns, either stationary or oscillatory, are generated using the various interaction schemes, some of which have been generated by a special algorithm including random inputs and selected according to suitable criteria. We give the full classification of a variety of stationary and oscillatory expression patterns in the presence of a single autocrine signal based on logical arguments. These results are further confirmed by numerical computations based on reaction-diffusion equations for morphogens and ligands and the discrete (cell-level) description of intracellular dynamics. Model simulations also elucidate transient processes, in particular interaction schemes. Different internal schemes may lead to identical persistent patterns, although relaxation may proceed in distinct ways. As an illustration of the general method, we test a particular scheme suggested by genetic studies of dynamic gene expression patterns in the follicular epithelium of the Drosophila eggshell.

  2. Internal feedback and its effect on phase linearity in a forward wave crossed-field amplifier

    SciTech Connect

    Chernin, D.

    1995-12-31

    Two sources of internal feedback couple the input and output of crossed-field amplifiers (CFA`s). Direct rf feedback occurs because the ends of the slow wave circuit radiate energy into the drift space connecting the output and input; the magnitude of this type of feedback may be measured at cold test. Electronic feedback, on the other hand, occurs only when the tube is operating, and is much harder to measure. It is due to the residual coherency retained by the beam after its passage through the drift space. As the input signal frequency of the amplifier is varied, the difference in electrical path length around the tube leads to a periodic variation of the total feedback signal relative to that of the input signal, resulting in a variation in phase of the effective drive signal, which in turn produces a periodic variation in phase of the output signal. This variation can have significant consequences for the system in which the CFA is used. The magnitude of this variation is very difficult to estimate other than by the use of a simulation code. The authors have applied their CFA simulation code, MASK, to this problem and have produced very good agreement with measurements of output phase versus frequency for a high power, forward wave S-band tube.

  3. Cross-Field Current Instabilities in Thin Ionization Layers and the Enhanced Aurora

    SciTech Connect

    Jay R. Johnson and Hideo Okuda

    2008-05-20

    Nearly half of the time, auroral displays exhibit thin, bright layers known as \\enhanced aurora." There is a substantial body of evidence that connects these displays with thin, dense, heavy ion layers in the E-region. Based on the spectral characteristics of the enhanced layers, it is believed that they result when wave-particle interaction heats ambient electrons to energies at or just above the 17 eV ionization energy of N2. While there are several possible instabilities that could produce suprathermal electrons in thin layers, there has been no clear theoretical investigation which examines in detail how wave instabilities in the thin ionization layers could develop and produce the suprathermal electrons. We examine instabilities which would occur in thin, dense, heavy ion layers using extensive analytical analysis combined with particle simulations. We analyze a cross field current instability that is found to be strongly unstable in the heavy ion layers. Electrostatic simulations show that substantial heating of the ambient electrons occurs with energization at or above the N2 ionization energy.

  4. ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF CORONAL LOOPS: CROSS-FIELD TEMPERATURE DISTRIBUTIONS

    SciTech Connect

    Schmelz, J. T.; Jenkins, B. S.; Pathak, S.

    2013-06-10

    We construct revised response functions for the Atmospheric Imaging Assembly (AIA) using the new atomic data, ionization equilibria, and coronal abundances available in CHIANTI 7.1. We then use these response functions in multithermal analysis of coronal loops, which allows us to determine a specific cross-field temperature distribution without ad hoc assumptions. Our method uses data from the six coronal filters and the Monte Carlo solutions available from our differential emission measure (DEM) analysis. The resulting temperature distributions are not consistent with isothermal plasma. Therefore, the observed loops cannot be modeled as single flux tubes and must be composed of a collection of magnetic strands. This result is now supported by observations from the High-resolution Coronal Imager, which show fine-scale braiding of coronal strands that are reconnecting and releasing energy. Multithermal analysis is one of the major scientific goals of AIA, and these results represent an important step toward the successful achievement of that goal. As AIA DEM analysis becomes more straightforward, the solar community will be able to take full advantage of the state-of-the-art spatial, temporal, and temperature resolution of the instrument.

  5. Cross-border collaboration in the field of highly contagious livestock diseases: a general framework for policy support.

    PubMed

    Hop, G E; Mourits, M C M; Oude Lansink, A G J M; Saatkamp, H W

    2014-08-01

    This paper analyses the potential gains and the main challenges for increased cross-border collaboration in the control of highly contagious livestock diseases in regions with cross-border reliance on production and consumption of livestock commodities. The aim of this intensification of cross-border collaboration is to retain the economic advantages of cross-border trade in livestock and livestock commodities while maintaining a low risk of highly contagious livestock diseases. From these two foci, possibilities for future policy making with respect to highly contagious livestock diseases are discussed: peacetime cross-border cooperation to improve the cost-effectiveness of routine veterinary measures and crisis time cross-border harmonization of current disease control strategies. A general disease management framework was used to describe the way in which these two fields are related to and affect the epidemiological system and, consequently, how they impact the stakeholders. In addition to this framework, the importance of a good understanding of influencing factors, that is, the production structure of livestock, was stressed because these factors are important determinants of the frequency and magnitude of highly contagious livestock diseases and their economic impact. The use of the suggested integrated approach was illustrated for the extended cross-border region of the Netherlands and Germany, that is, North Rhine Westphalia and Lower Saxony. For this region, current difficulties in cross-border trade in livestock and livestock commodities and possibilities for future cross-border collaboration were examined. The concepts and ideas presented in this paper should foster future development of cross-border collaboration in animal health control. PMID:23066698

  6. Diamond nitrogen vacancy electronic and nuclear spin-state anti-crossings under weak transverse magnetic fields

    NASA Astrophysics Data System (ADS)

    Clevenson, Hannah; Chen, Edward; Dolde, Florian; Teale, Carson; Englund, Dirk; Braje, Danielle

    2016-05-01

    We report on detailed studies of electronic and nuclear spin states in the diamond nitrogen vacancy (NV) center under moderate transverse magnetic fields. We numerically predict and experimentally verify a previously unobserved NV ground state hyperfine anti-crossing occurring at magnetic bias fields as low as tens of Gauss - two orders of magnitude lower than previously reported hyperfine anti-crossings at ~ 510 G and ~ 1000 G axial magnetic fields. We then discuss how this regime can be optimized for magnetometry and other sensing applications and propose a method for how the nitrogen-vacancy ground state Hamiltonian can be manipulated by small transverse magnetic fields to polarize the nuclear spin state. Acknowlegement: The Lincoln Laboratory portion of this work is sponsored by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract #FA8721-05-C-0002. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the United States Government.

  7. Shannon entropy as an indicator of atomic avoided crossings for Rydberg potassium atoms interacting with a static electric field

    NASA Astrophysics Data System (ADS)

    He, Yong Lin; Chen, Yan; Han, Jiu Ning; Zhu, Zhi Bin; Xiang, Geng Xiang; Liu, Huai Dong; Ma, Bao Hong; He, De Chun

    2015-12-01

    We propose a method to calculate the positions of avoided crossings for Rydberg potassium in a static electric field by using Shannon entropy. Our method can be divided into two steps. At first we made a rough estimate of the range of the static electric field strength at which the given avoided crossings occur through strength dependence of the Shannon entropies for all the related states. Next, we obtained the position of the given avoided crossing by calculating the Shannon entropies intersection field strength for the two involved states. The Shannon entropies are calculated by using the one-electron wave functions derived from a well-established diagonalization method which is based on B-spline expansion technique and a parametric one-electron model potential. We have used this method to calculate a number of positions of both s and p states of avoided crossings for Rydberg potassium. The results are in excellent agreement with observed and other calculated results by using the ionization energies. Our study proves that Shannon entropy is an efficient information-theoretic parameter for characterization and prediction of avoided crossings of Rydberg potassium in the l-mixing region.

  8. WE-G-18C-05: Characterization of Cross-Vendor, Cross-Field Strength MR Image Intensity Variations

    SciTech Connect

    Paulson, E; Prah, D

    2014-06-15

    Purpose: Variations in MR image intensity and image intensity nonuniformity (IINU) can challenge the accuracy of intensity-based image segmentation and registration algorithms commonly applied in radiotherapy. The goal of this work was to characterize MR image intensity variations across scanner vendors and field strengths commonly used in radiotherapy. Methods: ACR-MRI phantom images were acquired at 1.5T and 3.0T on GE (450w and 750, 23.1), Siemens (Espree and Verio, VB17B), and Philips (Ingenia, 4.1.3) scanners using commercial spin-echo sequences with matched parameters (TE/TR: 20/500 ms, rBW: 62.5 kHz, TH/skip: 5/5mm). Two radiofrequency (RF) coil combinations were used for each scanner: body coil alone, and combined body and phased-array head coils. Vendorspecific B1- corrections (PURE/Pre-Scan Normalize/CLEAR) were applied in all head coil cases. Images were transferred offline, corrected for IINU using the MNI N3 algorithm, and normalized. Coefficients of variation (CV=σ/μ) and peak image uniformity (PIU = 1−(Smax−Smin)/(Smax+Smin)) estimates were calculated for one homogeneous phantom slice. Kruskal-Wallis and Wilcoxon matched-pairs tests compared mean MR signal intensities and differences between original and N3 image CV and PIU. Results: Wide variations in both MR image intensity and IINU were observed across scanner vendors, field strengths, and RF coil configurations. Applying the MNI N3 correction for IINU resulted in significant improvements in both CV and PIU (p=0.0115, p=0.0235). However, wide variations in overall image intensity persisted, requiring image normalization to improve consistency across vendors, field strengths, and RF coils. These results indicate that B1- correction routines alone may be insufficient in compensating for IINU and image scaling, warranting additional corrections prior to use of MR images in radiotherapy. Conclusions: MR image intensities and IINU vary as a function of scanner vendor, field strength, and RF coil

  9. Power-Factor Calculation under Consideration of Cross Saturation of the Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation

    SciTech Connect

    Lee, Seong T; Burress, Timothy A; Hsu, John S

    2009-01-01

    This paper introduces a new method for calculating the power factor with consideration of the cross saturation between the direct-axis (d-axis) and the quadrature-axis (q-axis) of an interior permanent magnet synchronous motor (IPMSM). The conventional two-axis IPMSM model is modified to include the cross-saturation effect by adding the cross-coupled inductance terms. This paper also contains the new method of calculating the cross-coupled inductance values as well as self-inductance values in d- and q-axes. The analyzed motor is a high-speed brushless field excitation machine that offers high torque per ampere per core length at low speed and weakened flux at high speed, which was developed for the traction motor of a hybrid electric vehicle.

  10. Evidence for Cross-Adaptation between s-triazine herbicides resulting in reduced efficacy under field conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soils exhibiting enhanced atrazine degradation may be cross-adapted with other triazine herbicides resulting in reduced residual weed control. The objectives of this study were to 1) determine field persistence of simazine in atrazine adapted and non-adapted soils; 2) compare mineralization of ring...

  11. Sea surface Ka-band radar cross-section from field observations in the Black Sea

    NASA Astrophysics Data System (ADS)

    Yurovsky, Yury; Kudryavtsev, Vladimir; Grodsky, Semyon; Chapron, Bertrand

    2016-04-01

    An interest in Ka-band radar backscattering from the ocean surface is growing due to better spatial resolution and more accurate Doppler anomaly estimate. But, available empirical models of Ka-band cross-section are quite scarce and sometime controversial. Here we present multi-year (2009-2015) field measurements of Ka-band co-polarized (VV and HH) sea surface normalized radar cross-section (NRCS) from research platform in the Black sea collected in a wide range of observation and sea state conditions. The data are fitted by polynomial function of incidence angle, azimuth and wind speed with accounting for measured radar antenna pattern. This empirical NRCS is compared with published Ka- and Ku-band data. Our Ka-band NRCS is close to Ku-band, but is 5-7 dB higher than 'pioneer' measurements by Masuko et al. (1986). Following the two-scale Bragg paradigm, the NRCS is split into polarized (Bragg) and non-polarized components and analyzed in terms of polarization ratio (VV/HH) and polarization difference (VV-HH) to estimate wave spectra at the Bragg wave number. Non-polarized component dominates at low incidence angles <30° due to specular reflection from regular surface. At larger incidence angles, the relative non-polarized contribution decreases, but grows again at HH-polarization approaching 0.7-0.8 at 65° for 10 m/s wind speed, suggesting that backscattering from breaking waves dominates HH NRCS at low grazing angles. At high incidence angles (>60°) NRCS azimuth dependency is unimodal (upwind peak) for HH and bimodal (with up- and downwind peaks) for VV polarization. This again can be attributed to different backscattering mechanisms for VV and HH polarizations. With decreasing of incidence angle, up- to downwind ratio tends to 1, and under light wind conditions (4-6 m/s) can be less than 1. The same situation is observed for polarization difference, which reflects Bragg backscattering properties only. This effect can be explained by enhanced roughness on

  12. Identification of Field Line Resonances in the Magnetosphere Using the Super Dual Auroral Radar Network (superdarn): New ``CROSS-POWER and Cross-Phase Technique

    NASA Astrophysics Data System (ADS)

    Mazzino, L.; Fenrich, F. R.

    2010-12-01

    Field Line Resonances (FLRs) are Ultra Low Frequency (ULF) standing waves that appear in discrete frequencies and occur in Earth’s Magnetic Field as a result of wave coupling of MHD compressional and Shear Alfvén waves. The main purpose of the new ‘cross-power and cross-phase’ technique, presented in this analysis, is to systematically identify FLR occurrence using data from the Super Dual Auroral Radar Network (SuperDARN), a radar network that detects coherent echoes from plasma irregularities that are aligned with the field lines. SuperDARN data has been successfully used for more than 17 years to identify FLRs, due to its large coverage over the polar cap and auroral region. Specifications of the instrument as well as the algorithm used by this new technique will be explained in detail. As an example we will apply the technique to a known 1.9 mHz FLR that occurred on November 20th 2003 at 22:30-23:00 UT detected by the Prince George station. Discussion of the application of this technique to automatically detect other events, and the future statistical analysis of all events identified will be presented.

  13. Computational studies of suppression of microwave gas breakdown by crossed dc magnetic field using electron fluid model

    NASA Astrophysics Data System (ADS)

    Zhao, Pengcheng; Guo, Lixin; Shu, Panpan

    2016-08-01

    The gas breakdown induced by a square microwave pulse with a crossed dc magnetic field is investigated using the electron fluid model, in which the accurate electron energy distribution functions are adopted. Simulation results show that at low gas pressures the dc magnetic field of a few tenths of a tesla can prolong the breakdown formation time by reducing the mean electron energy. With the gas pressure increasing, the higher dc magnetic field is required to suppress the microwave breakdown. The electric field along the microwave propagation direction generated due to the motion of electrons obviously increases with the dc magnetic field, but it is much less than the incident electric field. The breakdown predictions of the electron fluid model agree very well with the particle-in-cell-Monte Carlo collision simulations as well as the scaling law for the microwave gas breakdown.

  14. Assessment of health status of adolescent burn victims undergoing rehabilitation: a cross-sectional field study.

    PubMed

    Nicolosi, Júlia Teixeira; de Carvalho, Viviane Fernandes; Sabatés, Ana Llonch; Paggiaro, André Oliveira

    2013-01-01

    Teenagers may experience physiological and psychological changes when they suffer from a severe burn. The aim of this study was to assess the state of health of teenagers who were undergoing a rehabilitation process following a severe burn. A cross-sectional field study was carried out with 63 teenagers and young adults who had suffered burns. The tests applied were social, demographic, and clinical instruments. The specific tests included the Burn Specific Health Scale-Revised, Beck Depression Inventory, Rosenberg's Self-Esteem Scale, and Functional Independence Measurement. The results were analyzed by using descriptive statistics, multivariate analysis of variance, variance analysis, and Cronbach's reliability analysis. The social and demographic analysis of the population has shown a prevalence of female (60.3%), single subjects (93.7%), and ages between 12 and 20 years (mean age of 15.95 years). The mean total body surface area burn was 23.84%, with accidents as the main causative factor (92.10%). More than half (52.4%) reported functional and aesthetic effects after the burn, with 81% concerned about the visible scar. Cronbach's reliability analysis has shown statistically confident results for all the instruments as applied. The multivariate analysis showed a correlation between the work domain and marital status, whereas there was no evidence to show a correlation between sex, age, physical or aesthetic sequelae or visibility of burns, and depression, self-esteem, functional independence, or current state of health. The results obtained prove the reliability of the instruments applied, making it possible to assess the state of teenagers and young adults health during the rehabilitation process. PMID:24297081

  15. Two-dimensional compressed sensing using the cross-sampling approach for low-field MRI systems.

    PubMed

    Tamada, Daiki; Kose, Katsumi

    2014-09-01

    A compressed sensing method using a cross sampling and self-calibrated off-resonance correction is proposed. Estimation of the magnetic field inhomogeneity based on image registration enables the off-resonance correction with no additional radio-frequency pulses or acquisitions. In addition to this advantage, a fast and straightforward calculation was achieved by using the first-order components of the magnetic field inhomogeneity. Imaging experiments using a phantom and a chemically fixed mouse demonstrated practical benefits in improving blurring and artifacts in magnetic resonance images in low field magnetic resonance imaging systems. PMID:24879645

  16. Field-induced superconducting phase of FeSe in the BCS-BEC cross-over.

    PubMed

    Kasahara, Shigeru; Watashige, Tatsuya; Hanaguri, Tetsuo; Kohsaka, Yuhki; Yamashita, Takuya; Shimoyama, Yusuke; Mizukami, Yuta; Endo, Ryota; Ikeda, Hiroaki; Aoyama, Kazushi; Terashima, Taichi; Uji, Shinya; Wolf, Thomas; von Löhneysen, Hilbert; Shibauchi, Takasada; Matsuda, Yuji

    2014-11-18

    Fermi systems in the cross-over regime between weakly coupled Bardeen-Cooper-Schrieffer (BCS) and strongly coupled Bose-Einstein-condensate (BEC) limits are among the most fascinating objects to study the behavior of an assembly of strongly interacting particles. The physics of this cross-over has been of considerable interest both in the fields of condensed matter and ultracold atoms. One of the most challenging issues in this regime is the effect of large spin imbalance on a Fermi system under magnetic fields. Although several exotic physical properties have been predicted theoretically, the experimental realization of such an unusual superconducting state has not been achieved so far. Here we show that pure single crystals of superconducting FeSe offer the possibility to enter the previously unexplored realm where the three energies, Fermi energy εF, superconducting gap Δ, and Zeeman energy, become comparable. Through the superfluid response, transport, thermoelectric response, and spectroscopic-imaging scanning tunneling microscopy, we demonstrate that εF of FeSe is extremely small, with the ratio Δ/εF ~ 1(~0.3) in the electron (hole) band. Moreover, thermal-conductivity measurements give evidence of a distinct phase line below the upper critical field, where the Zeeman energy becomes comparable to εF and Δ. The observation of this field-induced phase provides insights into previously poorly understood aspects of the highly spin-polarized Fermi liquid in the BCS-BEC cross-over regime. PMID:25378706

  17. THE HYDROMAGNETIC INTERIOR OF A SOLAR QUIESCENT PROMINENCE. II. MAGNETIC DISCONTINUITIES AND CROSS-FIELD MASS TRANSPORT

    SciTech Connect

    Low, B. C.; Casini, R.; Liu, W.; Berger, T.

    2012-09-20

    This second paper of the series investigates the transverse response of a magnetic field to the independent relaxation of its flux tubes of fluid seeking hydrostatic and energy balance, under the frozen-in condition and suppression of cross-field thermal conduction. The temperature, density, and pressure naturally develop discontinuities across the magnetic flux surfaces separating the tubes, requiring the finite pressure jumps to be compensated by magnetic-pressure jumps in cross-field force balance. The tangentially discontinuous fields are due to discrete currents in these surfaces, {delta}-function singularities in the current density that are fully admissible under the rigorous frozen-in condition but must dissipate resistively if the electrical conductivity is high but finite. The magnetic field and fluid must thus endlessly evolve by this spontaneous formation and resistive dissipation of discrete currents taking place intermittently in spacetime, even in a low-{beta} environment. This is a multi-dimensional effect in which the field plays a central role suppressed in the one-dimensional (1D) slab model of the first paper. The study begins with an order-of-magnitude demonstration that of the weak resistive and cross-field thermal diffusivities in the corona, the latter is significantly weaker for small {beta}. This case for spontaneous discrete currents, as an important example of the general theory of Parker, is illustrated with an analysis of singularity formation in three families of two-dimensional generalizations of the 1D slab model. The physical picture emerging completes the hypothesis formulated in Paper I that this intermittent process is the origin of the dynamic interiors of a class of quiescent prominences revealed by recent Hinode/SOT and SDO/AIA high-resolution observations.

  18. Nuclear spin-lattice relaxation at field-induced level crossings in a Cr8F8 pivalate single crystal

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shoji

    2016-01-01

    We construct a microscopic theory for the proton spin-lattice relaxation-rate 1 / T1 measurements around field-induced level crossings in a single crystal of the trivalent chromium ion wheel complex [Cr8F8(OOCtBu)16] at sufficiently low temperatures [E. Micotti et al., Phys. Rev. B 72 (2005) 020405(R)]. Exactly diagonalizing a well-equipped spin Hamiltonian for the individual clusters and giving further consideration to their possible interactions, we reveal the mechanism of 1 / T1 being single-peaked normally at the first level crossing but double-peaked intriguingly around the second level crossing. We wipe out the doubt about poor crystallization and find out a solution-intramolecular alternating Dzyaloshinsky-Moriya interaction combined with intermolecular coupling of antiferromagnetic character, each of which is so weak as several tens of mK in magnitude.

  19. Memory-bit selection and recording by rotating fields in vortex-core cross-point architecture

    SciTech Connect

    Yu, Y. -S.; Jung, H.; Lee, K. -S.; Fischer, P.; Kim, S. -K.

    2010-10-21

    In one of our earlier studies [Appl. Phys. Lett. 92, 022509 (2008)], we proposed a concept of robust information storage, recording and readout, which can be implementaed in nonvolatile magnetic random-access memories and is based on the energetically degenerated twofold ground states of vortex-core magnetizations. In the present study, we experimentally demonstrate reliable memory-bit selection and information recording in vortex-core cross-point architecture, specifically using a two-by-two vortex-state disk array. In order to efficiently switch a vortex core positioned at the intersection of crossed electrodes, two orthogonal addressing electrodes are selected, and then two Gaussian pulse currents of optimal pulse width and time delay are applied. Such tailored pulse-type rotating magnetic fields which occurs only at the selected intersection is prerequisite for a reliable memory-bit selection and low-power-consumption recording of information in the existing cross-point architecture.

  20. Cross-Field Differences in Creative Problem-Solving Skills: A Comparison of Health, Biological, and Social Sciences

    PubMed Central

    Mumford, Michael D.; Antes, Alison L.; Caughron, Jared J.; Connelly, Shane; Beeler, Cheryl

    2010-01-01

    In the present study, 258 doctoral students working in the health, biological, and social sciences were asked to solve a series of field-relevant problems calling for creative thought. Proposed solutions to these problems were scored with respect to critical creative thinking skills such as problem definition, conceptual combination, and idea generation. Results indicated that health, biological, and social scientists differed with respect to their skill in executing various operations, or processes, involved in creative thought. Interestingly, no differences were observed as a function of the students’ level of experience. The implications of these findings for understanding cross-field, and cross-experience level, differences in creative thought are discussed. PMID:20936085

  1. Cross-Field Differences in Creative Problem-Solving Skills: A Comparison of Health, Biological, and Social Sciences.

    PubMed

    Mumford, Michael D; Antes, Alison L; Caughron, Jared J; Connelly, Shane; Beeler, Cheryl

    2010-02-01

    In the present study, 258 doctoral students working in the health, biological, and social sciences were asked to solve a series of field-relevant problems calling for creative thought. Proposed solutions to these problems were scored with respect to critical creative thinking skills such as problem definition, conceptual combination, and idea generation. Results indicated that health, biological, and social scientists differed with respect to their skill in executing various operations, or processes, involved in creative thought. Interestingly, no differences were observed as a function of the students' level of experience. The implications of these findings for understanding cross-field, and cross-experience level, differences in creative thought are discussed. PMID:20936085

  2. Finite Element Analysis of Cross Rolling on AISI 304 Stainless Steel: Prediction of Stress and Strain Fields

    NASA Astrophysics Data System (ADS)

    Rout, Matruprasad; Pal, Surjya Kanta; Singh, Shiv Brat

    2016-05-01

    Studies on the effect of strain path during rolling has been carried out for a long time, but the same has not been done using Finite Element Analysis (FEA). Change in strain path affects the state variables in the rolled plate like stress, strain, temperature etc. In the current work, Finite Element Analysis for cross rolling of AISI 304 austenitic stainless steel has been carried out by rotating the plate by 90° in between the passes. To analyze stress and strain fields in the material for cross rolling, a full 3D model of work-roll and plate has been developed using rigid-viscoplastic finite element method. The stress and strain fields, considering von-Mises yield criteria, are calculated by using updated Lagrangian method. In addition to these, the model also calculates the normal pressure and strain rate distribution in the plate during cross rolling. The nature of the variations of stress and strain fields in the plate, predicted by the model, is in good agreement with the previously published works for unidirectional rolling.

  3. Cross-field diffusion of energetic (100 keV to 2 MeV) protons in interplanetary space

    SciTech Connect

    Costa Jr, Edio da; Tsurutani, Bruce T.; Alves, Maria Virgínia; Echer, Ezequiel; Lakhina, Gurbax S. E-mail: costajr.e@gmail.com

    2013-12-01

    Magnetic field magnitude decreases (MDs) are observed in several regions of the interplanetary medium. In this paper, we characterize MDs observed by the Ulysses spacecraft instrumentation over the solar south pole by using magnetic field data to obtain the empirical size, magnetic field MD, and frequency of occurrence distribution functions. The interaction of energetic (100 keV to 2 MeV) protons with these MDs is investigated. Charged particle and MD interactions can be described by a geometrical model allowing the calculation of the guiding center shift after each interaction. Using the distribution functions for the MD characteristics, Monte Carlo simulations are used to obtain the cross-field diffusion coefficients as a function of particle kinetic energy. It is found that the protons under consideration cross-field diffuse at a rate of up to ≈11% of the Bohm rate. The same method used in this paper can be applied to other space regions where MDs are observed, once their local features are well known.

  4. Negative index of refraction in a four-level system with magnetoelectric cross coupling and local field corrections

    SciTech Connect

    Bello, F.

    2011-07-15

    This research focuses on a coherently driven four-level atomic medium with the aim of inducing a negative index of refraction while taking into consideration local field corrections as well as magnetoelectric cross coupling (i.e.,chirality) within the material's response functions. Two control fields are used to render the medium transparent for a probe field which simultaneously couples to an electric and a magnetic dipole transition, thus allowing one to test the permittivity and permeability of the material at the same time. Numerical simulations show that a negative index of refraction with low absorption can be obtained for a range of probe detunings while depending on number density and the ratio between the intensities of the control fields.

  5. Method of sustaining a radial electric field and poloidal plasma rotation over most of the cross-section of a tokamak

    DOEpatents

    Darrow, Douglass S.; Ono, Masayuki

    1990-03-06

    A radial electric field of a desired magnitude and configuration is created throughout a substantial portion of the cross-section of the plasma of a tokamak. The radial electric field is created by injection of a unidirectional electron beam. The magnitude and configuration of the radial electric field may be controlled by the strength of the toroidal magnetic field of the tokamak.

  6. Method of sustaining a radial electric field and poloidal plasma rotation over most of the cross-section of a tokamak

    DOEpatents

    Darrow, Douglass S.; Ono, Masayuki

    1990-01-01

    A radial electric field of a desired magnitude and configuration is created hroughout a substantial portion of the cross-section of the plasma of a tokamak. The radial electric field is created by injection of a unidirectional electron beam. The magnitude and configuration of the radial electric field may be controlled by the strength of the toroidal magnetic field of the tokamak.

  7. Model and field studies of the degradation of cross-linked polyacrylamide gels used during the revegetation of slate waste.

    PubMed

    Holliman, Peter J; Clark, Jennifer A; Williamson, Julie C; Jones, Davey L

    2005-01-01

    Cross-linked polyacrylamide gels are increasingly being used in environmental restoration schemes and horticulture as a means of enhancing water supply to plants. However, the environmental impact of cross-linked polyacrylamide gel deployment in soil remains poorly understood. This study assessed the chemical, physical and biological properties of new and field-conditioned cross-linked polyacrylamide gels. Both monomeric acrylamide (11 microg l(-1)) and acrylic acid (285 microg l(-1)) were observed in new gel; however, the levels of monomers in field-conditioned gels (1-6 years old) were very low (acrylamide <1 microg l(-1); acrylic acid <7 microg l(-1)). Generally, freeze-thaw processes and exposure to UV radiation had little effect on gel acrylic acid and acrylamide concentrations. However, elevated temperatures (35 degrees C) caused a significant release of up to 144 mug l(-1) of acrylamide and 453 microg l(-1) of acrylic acid in new gel and up to 25 microg l(-1) of acrylamide and 157 microg l(-1) of acrylic acid in field-conditioned gels. In contrast, gel water holding capacity was highly dependent upon environmental conditions (UV exposure and freeze/thaw cycles produced the greatest loss of water holding in new gels) and gel age. Optical microscopy revealed that after placement in the field the gels became increasingly colonised over time by fungi and bacteria. In enrichment cultures, we were unable, however, to demonstrate microbial growth when cross-linked polyacrylamide was used as the sole nitrogen source. In summary, under a range of conditions cross-linked polyacrylamide did not release acrylamide above legally permitted limits, with the exception of gel subjected to elevated temperatures. However, their capacity for holding water decreased sharply within 18 months. We therefore conclude that cross-linked polyacrylamide placed in soil is relatively stable with respect to the production of potentially toxic acrylamide, a species with a short half

  8. Effects of crossed electric and magnetic fields on the interband optical absorption spectra of variably spaced semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Zuleta, J. N.; Reyes-Gómez, E.

    2016-05-01

    The interband optical absorption spectra of a GaAs-Ga1-xAlxAs variably spaced semiconductor superlattice under crossed in-plane magnetic and growth-direction applied electric fields are theoretically investigated. The electronic structure, transition strengths and interband absorption coefficients are analyzed within the weak and strong magnetic-field regimes. A dramatic quenching of the absorption coefficient is observed, in the weak magnetic-field regime, as the applied electric field is increased, in good agreement with previous experimental measurements performed in a similar system under growth-direction applied electric fields. A decrease of the resonant tunneling in the superlattice is also theoretically obtained in the strong magnetic-field regime. Moreover, in this case, we found an interband absorption coefficient weakly dependent on the applied electric field. Present theoretical results suggest that an in-plane magnetic field may be used to tune the optical properties of variably spaced semiconductor superlattices, with possible future applications in solar cells and magneto-optical devices.

  9. Near-field effects in Green's function retrieval from cross-correlation of elastic fields: experimental study with application to elastography.

    PubMed

    Benech, N; Brum, J; Catheline, S; Gallot, T; Negreira, C

    2013-05-01

    In a lossless system, the causal and acausal Green's function for elastic waves can be retrieved by cross-correlating the elastic field at two positions. This field, composed of converging and diverging waves, is interpreted in the frame of a time-reversal process. In this work, the near-field effects on the spatio-temporal focusing of elastic waves are analyzed through the elastodynamic Green's function. Contrary to the scalar field case, the spatial focusing is not symmetric preserving the directivity pattern of a simple source. One important feature of the spatial asymmetry is its dependency on the Poisson ratio of the solid. Additionally, it is shown that the retrieval of the bulk wave speed values is affected by diffraction. The correction factor depends on the relative direction between the source and the observed field. Experimental verification of the analysis is carried out on the volume of a soft-solid. A low-frequency diffuse-like field is generated by random impacts at the sample's free surface. The displacement field is imaged using ultrasound by a standard speckle tracking technique. One important application of this work is in the estimation of the shear elastic modulus in soft biological tissues, whose quantification can be useful in non-invasive diagnosis of various diseases. PMID:23654383

  10. Benchmark calculations of nonconservative charged-particle swarms in dc electric and magnetic fields crossed at arbitrary angles.

    PubMed

    Dujko, S; White, R D; Petrović, Z Lj; Robson, R E

    2010-04-01

    A multiterm solution of the Boltzmann equation has been developed and used to calculate transport coefficients of charged-particle swarms in gases under the influence of electric and magnetic fields crossed at arbitrary angles when nonconservative collisions are present. The hierarchy resulting from a spherical-harmonic decomposition of the Boltzmann equation in the hydrodynamic regime is solved numerically by representing the speed dependence of the phase-space distribution function in terms of an expansion in Sonine polynomials about a Maxwellian velocity distribution at an internally determined temperature. Results are given for electron swarms in certain collisional models for ionization and attachment over a range of angles between the fields and field strengths. The implicit and explicit effects of ionization and attachment on the electron-transport coefficients are considered using physical arguments. It is found that the difference between the two sets of transport coefficients, bulk and flux, resulting from the explicit effects of nonconservative collisions, can be controlled either by the variation in the magnetic field strengths or by the angles between the fields. In addition, it is shown that the phenomena of ionization cooling and/or attachment cooling/heating previously reported for dc electric fields carry over directly to the crossed electric and magnetic fields. The results of the Boltzmann equation analysis are compared with those obtained by a Monte Carlo simulation technique. The comparison confirms the theoretical basis and numerical integrity of the moment method for solving the Boltzmann equation and gives a set of well-established data that can be used to test future codes and plasma models. PMID:20481843

  11. Long lifetimes of high molecular Rydberg states in crossed magnetic and electric fields: An experimental and classical computational study

    NASA Astrophysics Data System (ADS)

    Mühlpfordt, Annette; Even, U.; Rabani, Eran; Levine, R. D.

    1995-05-01

    Crossed magnetic and electric fields are observed to extend the lifetime of high molecular Rydberg states of DABCO (1,4-Diazabicyclo[2.2.2]octane) well into the microsecond range. The experimental and computational (using classical mechanics and for a diatomic polar core) results agree both on the magnitude of the effect and on its decrease with increasing electrical field. Theoretical considerations suggest that this time-stretching effect is only present for high Rydberg states and/or for not too weak fields. The computed lifetime increases as the magnetic-field strength is decreased but it requires a finite magnetic field for the onset of the effect. The experimental technique of detection of the surviving Rydberg states via their ionization in a delayed field pulse (known as ZEKE spectroscopy) is most easily implemented for high (say, n>100) but not too high (n<400) Rydberg states. In this regime, the magnetic field required for the additional time stretching is larger than that due to the earth but can be significantly weaker than that required to induce extensive chaotic behavior. The results of the numerically exact classical simulations are interpreted using equations of motion, cast in the form of a mapping, which retain terms up to second order in the fields. (The first-order terms are qualitatively and quantitatively not, by themselves, sufficient.) As is to be expected on physical grounds, the origin of the effect is the slow, periodic modulation of the magnitude of the magnetic quantum number ml of the electron due to terms second order in the magnetic field. Since the angular momentum l of the electron is bounded from below by ml, and since it requires a low l for the electron to couple effectively to the molecular core, the presence of the magnetic field provides for an elongation of the time scale which is over and above that made possible due to the periodic motion of l due to the dc electric field.

  12. Experimental investigation of the flow in the near-field of a cross-shaped orifice jet

    NASA Astrophysics Data System (ADS)

    El Hassan, Mouhammad; Meslem, Amina; Abed-Meraim, Kamel

    2011-04-01

    The flow in the near-field of a cross-shaped orifice jet is investigated experimentally in the present study. The three components of the velocity field are obtained at different longitudinal locations using time-resolved stereoscopic particle-image velocimetry measurements. The mean and the instantaneous entrainment rates are calculated to study the entrainment mechanism. The distribution of momentum thicknesses is also inspected in the region of the axis switching. It is found that both the instantaneous entrainment rate and the net volume flux are strongly dependent on the vortical structures present in the flow and particularly at different parts of the Kelvin-Helmholtz vortex ring. Hence, different phases of the flow are investigated in the region of the axis switching. The contribution of the turbulent normal and shear stresses to the streamwise vorticity generation is also studied in the near-field of the cross jet. The momentum flux and its streamwise evolution are obtained from the mean velocity field. The contribution of different turbulent intensities to the momentum flux is given. The proper orthogonal decomposition (POD) is then applied to show the streamwise evolution of energy content of the most energetic POD modes.

  13. Theory and simulation of oscillations on near-steady state in crossed-field electron flow and the resulting transport

    NASA Astrophysics Data System (ADS)

    Cartwright, Keith Lewis

    The purpose of this study is to understand the oscillatory steady-state behavior of crossed-field electron flow in diodes for magnetic fields greater than the Hull field (B > BH) by the means of theory and self-consistent, electrostatic particle-in-cell (PIC) simulations. Many prior analytic studies of diode-like problems have been time-independent, which leaves the stability and time-dependence of these models unresolved. We investigate fluctuations through the system, including virtual cathode oscillations, and compare results for various cathode injection models. The dominant oscillations in magnetically insulated crossed-field diodes are found to be a series resonance, Z(ω s) = 0, between the pure electron plasma and vacuum impedance of the diode. The series resonance in crossed-field electron flow is shown to be the ky --> 0 (one-dimensional) limit of the diocotron/magnetron eigenmode equation. The wavenumber, ky, is perpendicular to the direction across the diode and magnetic field. The series resonance is derived theoretically and verified with self-consistent, electrostatic, PIC simulations. Electron transport across the magnetic field in a cutoff planar smooth-bore magnetron is described on the basis of surface waves (formed by the shear flow instability) perpendicular to the magnetic field and along the cathode. A self-consistent, 2d3v (two spatial dimensions and three velocity components), electrostatic PIC simulation of a crossed-field diode produces a near- Brillouin flow which slowly expands across the diode, punctuated by sudden transport across the diode. The theory of slow transport across the diode is explained by the addition of perturbed orbits to the Brillouin shear flow motion of the plasma in the diode. A slow drift compared to the shear flow is described which results from the fields caused by the surface wave inducing an electrostatic ponderomotive-like force in a dc external magnetic field. In order to perform the above

  14. Effect of the variable cross-section channel on performance of a cusped field thruster at low power

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Chen, Pengbo; Mao, Wei; Yu, Daren; Wang, Chunsheng

    2015-09-01

    The cusped field thruster has drawn much attention from many institutions due to its wide thrust range, high impulse, and long lifetime. However, lots of experimental results reveal that the cusped field thruster at low power has a poor performance. A cusped field thruster with a variable cross-section channel by putting a ceramic spacer in the channel is introduced in this paper, aimed at improving the thruster performance at low power. The DSMC results validate that the upstream atom density can be increased by a spacer, especially near the wall. Based on simulated results, spacers are put into different positions of the channel. The experimental results show that a suitable spacer can enhance thruster performance at low power, which can be confirmed by the results that the anode efficiency can achieve 40% at 400 V anode voltage and 20 sccm gas flow rate by contrast to 35% without a spacer under the same condition.

  15. Resistance oscillations of two-dimensional electrons in crossed electric and tilted magnetic fields

    NASA Astrophysics Data System (ADS)

    Mayer, William; Vitkalov, Sergey; Bykov, A. A.

    2016-06-01

    The effect of dc electric field on transport of highly mobile two-dimensional electrons is studied in wide GaAs single quantum wells placed in titled magnetic fields. The study shows that in perpendicular magnetic field resistance oscillates due to electric-field induced Landau-Zener transitions between quantum levels that correspond to geometric resonances between cyclotron orbits and periodic modulation of electron density of states. Magnetic field tilt inverts these oscillations. Surprisingly the strongest inverted oscillations are observed at a tilt corresponding to nearly absent modulation of the electron density of states in regime of magnetic breakdown of semiclassical electron orbits. This phenomenon establishes an example of quantum resistance oscillations due to Landau quantization, which occur in electron systems with a constant density of states.

  16. Results of design calculations for the modulator of the crossed field undulator device

    SciTech Connect

    Sovay, R.

    1990-08-01

    The modulator is a five pole wiggler with a fixed 5 cm gap. In the current design, the modulator is oriented so that the magnetic field in the device is parallel to the field in one of the undulators. The two end poles have no coil and are only half as thick as the inner poles. The end poles serve as field clamps that reduce the stray field of the modulator and the sextupole coefficient of the field integral. The center pole and the two side poles can be energized with coils. As long as the permeability is large enough within the steel the current in the center coil should be twice the current in a side coil to avoid steering the electron beam. Therefore, if the center coil has twice as many turns as the side coil, the magnet can be driven by one power supply.

  17. Spatiotemporal splitting of global eigenmodes due to cross-field coupling via vortex dynamics in drift wave turbulence.

    PubMed

    Brandt, C; Thakur, S C; Light, A D; Negrete, J; Tynan, G R

    2014-12-31

    Spatiotemporal splitting events of drift wave (DW) eigenmodes due to nonlinear coupling are investigated in a cylindrical helicon plasma device. DW eigenmodes in the radial-azimuthal cross section have been experimentally observed to split at radial locations and recombine into the global eigenmode with a time shorter than the typical DW period (t≪fDW(-1)). The number of splits correlates with the increase of turbulence. The observed dynamics can be theoretically reproduced by a Kuramoto-type model of a network of radially coupled azimuthal eigenmodes. Coupling by E×B-vortex convection cell dynamics and ion gyro radii motion leads to cross-field synchronization and occasional mode splitting events. PMID:25615346

  18. Volume moiré tomography based on double cross gratings for real three-dimensional flow field diagnosis.

    PubMed

    Sun, Nan; Song, Yang; Wang, Jia; Li, Zhen-Hua; He, An-Zhi

    2012-12-01

    Since the advantages of noncontact, strong antidisturbing capability and wide measurement range, moiré tomography has been considered a powerful diagnostic tool for flow fields. In this paper, the volume computerized tomography is introduced to obtain the real three-dimensional reconstruction based on moiré deflectometry. In order to realize volume moiré tomography (VMT), double cross gratings are applied in the moiré deflected system to gain the shearing phase distribution of the moiré deflected projection in two mutually perpendicular directions simultaneously. Thus, the scalar diffraction theory is used for analyzing the imaging process of VMT based on double cross gratings to achieve the explicit form of shearing phase. Finally, the real temperature distribution of a propane flame is reconstructed, which can confirm the VMT method. PMID:23207377

  19. Single-unit activity, threshold crossings, and local field potentials in motor cortex differentially encode reach kinematics.

    PubMed

    Perel, Sagi; Sadtler, Patrick T; Oby, Emily R; Ryu, Stephen I; Tyler-Kabara, Elizabeth C; Batista, Aaron P; Chase, Steven M

    2015-09-01

    A diversity of signals can be recorded with extracellular electrodes. It remains unclear whether different signal types convey similar or different information and whether they capture the same or different underlying neural phenomena. Some researchers focus on spiking activity, while others examine local field potentials, and still others posit that these are fundamentally the same signals. We examined the similarities and differences in the information contained in four signal types recorded simultaneously from multielectrode arrays implanted in primary motor cortex: well-isolated action potentials from putative single units, multiunit threshold crossings, and local field potentials (LFPs) at two distinct frequency bands. We quantified the tuning of these signal types to kinematic parameters of reaching movements. We found 1) threshold crossing activity is not a proxy for single-unit activity; 2) when examined on individual electrodes, threshold crossing activity more closely resembles LFP activity at frequencies between 100 and 300 Hz than it does single-unit activity; 3) when examined across multiple electrodes, threshold crossing activity and LFP integrate neural activity at different spatial scales; and 4) LFP power in the "beta band" (between 10 and 40 Hz) is a reliable indicator of movement onset but does not encode kinematic features on an instant-by-instant basis. These results show that the diverse signals recorded from extracellular electrodes provide somewhat distinct and complementary information. It may be that these signal types arise from biological phenomena that are partially distinct. These results also have practical implications for harnessing richer signals to improve brain-machine interface control. PMID:26133797

  20. Kelvin--Helmholtz vortex formation and particle transport in a cross-field plasma sheath. I. Transient behavior

    SciTech Connect

    Theilhaber, K.; Birdsall, C.K. )

    1989-11-01

    The time-dependent behavior of a transversely magnetized, two-dimensional plasma--wall sheath has been studied through particle simulations, with the aim of modeling plasma behavior in the vicinity of the limiters and walls of magnetized plasma devices. The model assumes a magnetic field perfectly parallel to the confining surfaces. The simulations have shown that the cross-field sheath between a wall and a plasma is a self-sustaining turbulent boundary layer, with strong potential fluctuations and anomalous particle transport. The driving mechanism for this turbulence is the Kelvin--Helmholtz instability, which arises from the sheared particle drifts created near the wall. In this paper, the transient behavior leading to the turbulent steady state is presented, and the processes of linear growth, vortex saturation, and vortex coalescence are examined. An analytic model for the boundary Kelvin--Helmholtz instability is derived and shown to correctly predict the growth rates of the long-wavelength modes. In a companion paper, the steady-state structure and behavior of the cross-field sheath will be discussed in detail.

  1. A cross-case analysis of three Native Science Field Centers

    NASA Astrophysics Data System (ADS)

    Augare, Helen J.; Davíd-Chavez, Dominique M.; Groenke, Frederick I.; Little Plume-Weatherwax, Melissa; Lone Fight, Lisa; Meier, Gene; Quiver-Gaddie, Helene; Returns From Scout, Elvin; Sachatello-Sawyer, Bonnie; St. Pierre, Nate; Valdez, Shelly; Wippert, Rachel

    2015-12-01

    Native Science Field Centers (NSFCs) were created to engage youth and adults in environmental science activities through the integration of traditional Native ways of knowing (understanding about the natural world based on centuries of observation including philosophy, worldview, cosmology, and belief systems of Indigenous peoples), Native languages, and Western science concepts. This paper focuses on the Blackfeet Native Science Field Center, the Lakota Native Science Field Center, and the Wind River Native Science Field Center. One of the long-term, overarching goals of these NSFCs was to stimulate the interest of Native American students in ways that encouraged them to pursue academic and career paths in science, technology, engineering, and mathematics (STEM) fields. A great deal can be learned from the experiences of the NSFCs in terms of effective educational strategies, as well as advantages and challenges in blending Native ways of knowing and Western scientific knowledge in an informal science education setting. Hopa Mountain—a Bozeman, Montana-based nonprofit—partnered with the Blackfeet Community College on the Blackfeet Reservation, Fremont County School District #21 on the Wind River Reservation, and Oglala Lakota College on the Pine Ridge Reservation to cooperatively establish the Native Science Field Centers. This paper presents a profile of each NSFC and highlights their program components and accomplishments.

  2. Background-free imaging of plasmonic structures with cross-polarized apertureless scanning near-field optical microscopy.

    PubMed

    Esslinger, M; Dorfmüller, J; Khunsin, W; Vogelgesang, R; Kern, K

    2012-03-01

    We present advances in experimental techniques of apertureless scanning near-field optical microscopy (aSNOM). The rational alignment procedure we outline is based upon a phase singularity that occurs while scanning polarizers around the nominal cross-polarized configuration of s-polarized excitation and p-polarized detection. We discuss the theoretical origin of this topological feature of the setup, which is robust against small deviations, such as minor tip misalignment or shape variations. Setting the polarizers to this singular configuration point eliminates all background signal, allowing for reproducible plasmonic eigenmode mapping with optimal signal-to-noise ratio. PMID:22462926

  3. Planar near-field scanning for compact range bistatic radar cross-section measurement. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Tuhela-Reuning, S. R.; Walton, E. K.

    1991-01-01

    The design, construction, and testing of a low cost, planar scanning system to be used in a compact range environment for bistatic radar cross-section (bistatic RCS) measurement data are discussed. This scanning system is similar to structures used for measuring near-field antenna patterns. A synthetic aperture technique is used for plane wave reception. System testing entailed comparison of measured and theoretical bistatic RCS of a sphere and a right circular cylinder. Bistatic scattering analysis of the ogival target support, target and pedestal interactions, and compact range room was necessary to determine measurement validity.

  4. Effects of electric field component representation on estimated cross polar cap potential - Implications for interhemispheric asymmetries

    NASA Astrophysics Data System (ADS)

    Magnus Laundal, Karl; Förster, Matthias; Haaland, Stein; Snekvik, Kristian; Østgaard, Nikolai; Tenfjord, Paul; Reistad, Jone; Milan, Steve

    2015-04-01

    Ionospheric electrodynamics is well organized with respect to the Earth's magnetic field. The most commonly used coordinate systems which take this field into account are the apex (Richmond, 1995) and Altitude Adjusted Corrected Geomagnetic (AACGM) coordinate systems (Baker and Wing, 1989). Both coordinate systems are based on magnetic field line tracing using the International Geomagnetic Reference Field (IGRF), which resolves structures in the Earth's magnetic field at approximately 3000 km resolution. Seen in a geographic grid, both coordinate systems are non-orthogonal and non-uniform. Despite the widespread use in the space physics community, the conversion of electrodynamic vector components are often handled in an approximate fashion, treating the coordinate system as orthogonal. In this study we investigate how such approximations affect the estimated electric potential. We show that an electric potential which is symmetrical between hemispheres can appear asymmetrical when vector component conversion is not exact. We investigate how these errors depend on longitude and universal time bias in a data set. We also apply the technique to measurements from the Electron Drift Instruments on the Cluster spacecrafts mapped to the ionosphere, and compare the results to previously reported inter-hemispheric asymmetries.

  5. An Analysis of the Relationship between Educational Aspiration, Cross-Cultural Sensitivity, and Field of Study of Chinese Student-Teachers at the University of Macau.

    ERIC Educational Resources Information Center

    Koo, Ramsey D.

    This study examined the relationship among educational aspiration, cross-cultural sensitivity, and field of study of 196 Chinese student teachers enrolled in the Faculty of Education for Fall 1994 and Spring 1995 at the University of Macau (China). The study investigated other patterns of cross-cultural experience and activities, including average…

  6. Orientational dynamics of ferrofluids with finite magnetic anisotropy of the particles: relaxation of magneto-birefringence in crossed fields.

    PubMed

    Raikher, Yu L; Stepanov, V I; Bacri, J-C; Perzynski, R

    2002-08-01

    Dynamic birefringence in a ferrofluid subjected to crossed bias (constant) and probing (pulse or ac) fields is considered, assuming that the nanoparticles have finite magnetic anisotropy. This is done on the basis of the general Fokker-Planck equation that takes into account both internal magnetic and external mechanical degrees of freedom of the particle. We describe the orientation dynamics in terms of the integral relaxation time of the macroscopic orientation order parameter. To account for an arbitrary relation between the bias (external) and anisotropy (internal) fields, an interpolation expression for the integral relaxation time is proposed and justified. A developed description is used to interpret the measurements of birefringence relaxation in magnetic fluids with nanoparticles of high (cobalt ferrite) and low (maghemite) anisotropy. The proposed theory appears to be in full qualitative agreement with all the experimental data available. PMID:12241160

  7. Absorption enhancement by matching the cross-section of plasmonic nanowires to the field structure of tightly focused beams.

    PubMed

    Normatov, Alexander; Spektor, Boris; Leviatan, Yehuda; Shamir, Joseph

    2011-04-25

    Nanostructured materials, designed for enhanced light absorption, are receiving increased scientific and technological interest. In this paper we propose a physical criterion for designing the cross-sectional shape of plasmonic nanowires for improved absorption of a given tightly focused illumination. The idea is to design a shape which increases the matching between the nanowire plasmon resonance field and the incident field. As examples, we design nanowire shapes for two illumination cases: a tightly focused plane wave and a tightly focused beam containing a line singularity. We show that properly shaped and positioned silver nanowires that occupy a relatively small portion of the beam-waist area can absorb up to 65% of the total power of the incident beam. PMID:21643100

  8. Regional geomagnetic main field and secular variation modelling using ground, satellite and marine cross-over data

    NASA Astrophysics Data System (ADS)

    Talarn, Àngela; Pavón-Carrasco, F. Javier; Miquel Torta, J.; Qamili, Enkelejda

    2014-05-01

    After the good results obtained from an attempt to generate a regional model for the secular variation of the total geomagnetic field for gaining a better knowledge of the field over oceanic regions, we now present a new regional model for the full vector main field and its secular variation from 1960.0 to 2000.0 over the North Atlantic Ocean. The distinct facts of our approach with respect to previous existing global models arise from the new information afforded by a collection and selection of marine cross-over data, along with the techniques that we propose for constructing the regional model, which include uncertainty estimates of the results. The marine data offer the possibility to gain better and robust knowledge of the field over large areas lacked of observatories over periods of time without satellite information. In addition to the marine data, we used observatory and repeat station data in the peripheral areas and satellite data from OERSTED, MAGSAT and the OGO series. All the data passed a rigorous selection in order to reject suspicious data and different random selections of satellite data were applied to reduce the effect of the satellite tracks. Due to the use of different altitude data, we obtained our model using the Revised Spherical Cap Harmonic Analysis (R-SCHA) in space and the penalized cubic B-splines in time. Taking advantage of the orthogonality of the basis functions, being particularly important in the inverse problem approach, we introduced two temporal and spatial regularization matrices with appropriate damping parameters, which are adjusted to assess the best compromise between the data fit and the model roughness. The obtained results show an improvement in terms of root mean square error when the regional model is compared with other global models for those epochs, such as the CM4, highlighting the importance of the use of the cross-over marine data in the oceanic regions.

  9. Mapping a New Field: Cross-Border Professional Development for Teachers

    ERIC Educational Resources Information Center

    Johnson, Janelle M.

    2011-01-01

    Many of the international, supranational, national, and grassroots development organizations working in the field of education channel their efforts into capacity-building for teachers. My research examines the nexus of such international development by US-based organizations with national schooling systems by naming and theorizing this process as…

  10. To Be Transformed: Emotions in Cross-Cultural, Field-Based Learning in Northern Australia

    ERIC Educational Resources Information Center

    Wright, Sarah; Hodge, Paul

    2012-01-01

    Students undertaking field-based learning, in which they work with Indigenous people in Northern Australia, describe a profound learning experience redolent with emotion. Inspired, challenged and transformed, the students are compelled in ways that require them to interrogate their own selves and taken-for-granted beliefs. In this paper, we draw…

  11. Teaching "Out-of-Field" as a Boundary-Crossing Event: Factors Shaping Teacher Identity

    ERIC Educational Resources Information Center

    Hobbs, Linda

    2013-01-01

    Teaching "out-of-field" occurs when teachers teach a subject for which they are not qualified. The issues around this increasingly common practice are not widely researched and are under-theorised. A qualitative pilot study using teacher interviews in 3 rural schools examined meanings, support mechanisms and teacher identities associated with…

  12. Comparison of site calibration and cross calibration of Gao Fen (GF)-1 Wide Field of View (WFV)

    NASA Astrophysics Data System (ADS)

    Liu, Li; Xu, Wen; Lu, Shuning; Fu, Qiaoyan; Pan, Zhiqiang; Shi, Tingting

    2015-10-01

    The Wide Field of View (WFV) is one of the key instruments for China's high resolution earth observing system, operating on the Gao Fen-1 (GF-1) satellite which was launched on April 26, 2013. WFV has 4 typical reflective solar bands from 0.45-0.89 μm with 16m nadir spatial resolution. Because of GF-1's lacking in onboard calibrators, on-orbit radiometric calibration is mainly relies on site calibration. The reflectance-based method of site calibration has been used for the absolute radiometric calibration of the GF-1 WFV on June 26th, 2013 and August 3rd, 2014. The reflectance-based method relies on ground-based measurements of the surface reflectance and atmospheric conditions at Dunhuang test site nearly coincident with the imaging of the test site by the WFV. Site calibration is a time consuming and hard sledding method, which is also difficult to reveal or adequately correct for the deficiency of instrument calibration by its own calibration subsystem. Cross-calibration can be a powerful method to remedy the insufficient of the site calibration. Terra Moderate Resolution Imaging Spectroradiometer (MODIS) with its high accuracy onboard calibration system has been selected as reference sensor. Cross calibration between GF-1/WFV and Terra/MODIS are based on the near-simultaneous and cloud-free image pairs over Dunhuang test site on the same day with site calibration. Spectral band adjustment factors (SBAF) for the cross calibration are determined by SRF, solar zenith and azimuth angle, sensors' zenith and azimuth angle and a typical reflectance spectrum over the Dunhuang test site obtained by in-situ measurements. The percentage difference between the site calibrations is within 5% which reflects that the GF-1/WFV is stable after the launch and the reflectance-based method itself is reliable. The comparison of site calibration and cross calibration shows that site calibration has higher accuracy than the cross calibration, the cross calibration is affected by

  13. CROSS SECTIONS AND FIELD MAPS: CHEROKEE AND BUG FIELDS, SAN JUAN COUNTY, UTAH, AND LITTLE UTE AND SLEEPING UTE FIELDS, MONTEZUMA COUNTY, COLORADO

    SciTech Connect

    Thomas C. Chidsey Jr; Craig D. Morgan; Kevin McClure; David E. Eby; Laura L. Wray

    2003-12-01

    Over 400 million barrels (64 million m{sup 3}) of oil have been produced from the shallow-shelf carbonate reservoirs in the Pennsylvanian (Desmoinesian) Paradox Formation in the Paradox Basin, Utah and Colorado. With the exception of the giant Greater Aneth field, the other 100 plus oil fields in the basin typically contain 2 to 10 million barrels (0.3-1.6 million m{sup 3}) of original oil in place. Most of these fields are characterized by high initial production rates followed by a very short productive life (primary), and hence premature abandonment. Only 15 to 25 percent of the original oil in place is recoverable during primary production from conventional vertical wells. An extensive and successful horizontal drilling program has been conducted in the giant Greater Aneth field. However, to date, only two horizontal wells have been drilled in small Ismay and Desert Creek fields. The results from these wells were disappointing due to poor understanding of the carbonate facies and diagenetic fabrics that create reservoir heterogeneity. These small fields, and similar fields in the basin, are at high risk of premature abandonment. At least 200 million barrels (31.8 million m{sup 3}) of oil will be left behind in these small fields because current development practices leave compartments of the heterogeneous reservoirs undrained. Through proper geological evaluation of the reservoirs, production may be increased by 20 to 50 percent through the drilling of low-cost single or multilateral horizontal legs from existing vertical development wells. In addition, horizontal drilling from existing wells minimizes surface disturbances and costs for field development, particularly in the environmentally sensitive areas of southeastern Utah and southwestern Colorado.

  14. Model Stacking (MOST) technique applied in cross-hole ERT field data for the detection of Thessaloniki ancient walls' depth

    NASA Astrophysics Data System (ADS)

    Leontarakis, Konstantinos; Apostolopoulos, George V.

    2013-06-01

    A cross-hole Electrical Resistivity Tomography (ERT) study was undertaken near the center of Thessaloniki in order to detect the depth of the existing city walls in the planned route of the new city underground train. This cross-hole setup was used for a study of measurements with various electrode arrays in real urban field conditions to evaluate the resolution of the models which is produced by each array and the reliability of the models which is produced by the newly published "MOST" technique. The pole-tripole array (C2-C1P1P2) produces high resolution models, even when only borehole electrodes are used. The bipole-bipole C1C2-P1P2 array, when used for cross-hole measurements only, produces higher resolution models compared to the C1P1-C2P2 array, even with a lower signal-to-noise ratio, which can result in extremely high RMS error, when noise, systematic or not, must be faced. The models of both arrays are greatly improved by the use of surface electrodes. The pole-bipole array (C1-P1P2) is proved to be less accurate in imaging and quite unstable to the noisy urban environment and to systematic errors. Furthermore, the Model Stacking (MOST) interpretation technique leads to better results with models of greater resolution and fewer artifacts compared even with the combined data inversion. Finally, the ERT cross-hole analysis has been reliable in detecting the city walls.

  15. Kelvin--Helmholtz vortex formation and particle transport in a cross-field plasma sheath. II. Steady state

    SciTech Connect

    Theilhaber, K.; Birdsall, C.K. )

    1989-11-01

    The steady-state behavior of the magnetized plasma--wall sheath has been studied through two-dimensional particle simulations, which have shown that the sheath maintains itself in a strongly nonlinear, turbulent equilibrium, continuously driven by the edge Kelvin--Helmholtz instability. The sheath assumes a thickness of order {ital l}{sub {ital x}}{similar to}5{rho}{sub {ital i}}, and maintains large, long-lived vortices, with amplitudes {delta}{phi}{similar to}2.5{ital T}{sub {ital i}}/{ital e}, which drift parallel to the wall at half the ion thermal velocity. The sheath also maintains a large, spatially averaged potential drop from the wall to the plasma with {Delta}{phi}{approx}{minus}2{ital T}{sub {ital i}}/{ital e}, opposite in sign to that of the unmagnetized sheath. Accompanying the long-wavelength vortices are shorter-wavelength fluctuations, which induce an anomalous cross-field transport, scaling in accordance to Bohm diffusion when {omega}{sub {ital pi}}{ge}2{omega}{sub {ital ci}}. At lower densities, {omega}{sub {ital pi}}{lt}2{omega}{sub {ital ci}}, the diffusion coefficient has an additional factor, proportional to the density. These results permit the modeling of the cross-field sheath by a simple effective boundary condition.

  16. Wide-Field-of-View Millimeter-Wave Telescope Design with Ultra-Low Cross-Polarization

    SciTech Connect

    Bernacki, Bruce E.; Kelly, James F.; Sheen, David M.; Hatchell, Brian K.; Valdez, Patrick LJ; Tedeschi, Jonathan R.; Hall, Thomas E.; McMakin, Douglas L.

    2012-05-01

    As millimeter-wave arrays become available, off-axis imaging performance of the fore optics increases in importance due to the relatively large physical extent of the arrays. Typically, simple optical telescope designs are adapted to millimeter-wave imaging but single-mirror spherical or classic conic designs cannot deliver adequate image quality except near the optical axis. Since most millimeter-wave designs are quasi-optical, optical ray tracing and commercial design software can be used to optimize designs to improve off-axis imaging as well as minimize cross-polarization. Methods that obey the Dragone-Mizuguchi condition for the design of reflective millimeter-wave telescopes with low cross-polarization also provide additional degrees of freedom that offer larger fields of view than possible with single-reflector designs. Dragone’s graphical design method does not lend itself readily to computer-based optical design approaches, but subsequent authors expanded on Dragone’s geometric design approach with analytic expressions that describe the location, shape, off-axis height and tilt of the telescope elements that satisfy Dragone’s design rules and can be used as a first-order design for subsequent computer-based design and optimization. We investigate two design variants that obey the Dragone-Mizuguchi conditions that exhibit ultra-low polarization crosstalk and a large diffraction-limited field of view well suited to millimeter-wave imaging arrays.

  17. The cross correlation between the 21-cm radiation and the CMB lensing field: a new cosmological signal

    SciTech Connect

    Vallinotto, Alberto

    2011-01-01

    The measurement of Baryon Acoustic Oscillations through the 21-cm intensity mapping technique at redshift z {<=} 4 has the potential to tightly constrain the evolution of dark energy. Crucial to this experimental effort is the determination of the biasing relation connecting fluctuations in the density of neutral hydrogen (HI) with the ones of the underlying dark matter field. In this work I show how the HI bias relevant to these 21-cm intensity mapping experiments can successfully be measured by cross-correlating their signal with the lensing signal obtained from CMB observations. In particular I show that combining CMB lensing maps from Planck with 21-cm field measurements carried out with an instrument similar to the Cylindrical Radio Telescope, this cross-correlation signal can be detected with a signal-to-noise (S/N) ratio of more than 5. Breaking down the signal arising from different redshift bins of thickness {Delta}z = 0.1, this signal leads to constraining the large scale neutral hydrogen bias and its evolution to 4{sigma} level.

  18. Hamiltonian description of ion motion in crossed electric and magnetic fields with cylindrical symmetry

    NASA Astrophysics Data System (ADS)

    Botman, J. I. M.; Hagedoorn, H. L.

    1992-02-01

    A Hamiltonian description is given of charged particle motion around a circular design trajectory in static electromagnetic systems possessing cylindrical symmetry. In particular the ion motion in a constant magnetic field in the z-direction and a hyperboloid electric potential, V(x,y,z) = {1}/{2}k 2z 2 - {1}/{4}k 2(x 2 + y 2) , where k2 is the potential strength parameter, is considered in Cartesian coordinates, to provide an exact solution to the Hamiltonian problem. The Wien filter can be considered as a special application of the system described. For a general electric field shape an expansion of the potential around the design orbit is required and a treatment in cylindrical coordinates seems more appropriate. Applications of these systems can be found in inflectors and deflectors in circular ion accelerators as well as in Wien filters or ion separators in various ion optical devices.

  19. Charging and the cross-field discharge during electron accelerator operation on a rocket

    NASA Technical Reports Server (NTRS)

    Kellogg, Paul J.; Monson, Steven J.

    1988-01-01

    Preliminary results are presented from experiments to study the neutralization processes around an electron beam emitting rocket. The rocket, SCEX II, was flown on January 31, 1987 from Alaska, with a payload consisting of two independent electron accelerators and two arms with conducting elements to act as Langmuir probes and to measure floating potentials. It was expected that electrons in the strong electric fields around the charged rocket would gain sufficient energy to ionize neutrals, producing ions which would be hurled outward at energies up to the rocket potential. Three hemispherical retarding potential analyzers were ejected from the main payload to measure these ions. The measurements show that fields sufficient to accelerate electrons to ionizing energies were present around the rocket.

  20. VELOCITY POWER SPECTRA FROM CROSS-FIELD TURBULENCE IN THE PROTON KINETIC REGIME

    SciTech Connect

    Vasquez, Bernard J.; Markovskii, Sergei A. E-mail: sergei.markovskii@unh.edu

    2012-03-01

    Numerical hybrid simulations with particle protons and fluid electrons are conducted for turbulent fluctuations with spatial variations in a plane perpendicular to the background magnetic field. In the turbulent phase, the proton bulk velocity spectrum has a dissipation range starting at a smaller wavenumber than the magnetic spectrum dissipation range. The steepened portion of the proton bulk velocity spectrum is constrained to a smaller wavenumber with an increasing ratio of background proton plasma to magnetic pressure {beta}{sub p}. The form of the magnetic spectrum does not depend on {beta}{sub p}. The collisionless proton and fluctuation interaction which heats protons mainly across the magnetic field is deemed to be the result of a viscous-like interaction based, in part, on the dependence of the velocity spectrum on {beta}{sub p}.

  1. Conceptual Schematic Geologic Cross-Sections of the Geysers Steam Field

    SciTech Connect

    Hebein, Jeffrey J.

    1986-01-21

    While formerly studied in terms of ancient Franciscan stratigraphy, The Geysers Steam Field now offers new views and interpretations on the deeper structure and importance of the lithocap, main metagraywacke, and felsic intrusive basement units with respect to the huge fractured reservoir. The Big Sulphur Creek enhanced tectonic disruption area provides the best situation for shallow felsite injection, shallow reservoir top, metasomatism transformation, and profound fracture permeability. Steam cells commonly extend to great depths and laterally drop off sharply, with relatively flat lateral continuance in some resource areas. Injectate ponding may offer a third fluid interface for reservoir steam reserves. A possible boiled down residuum of complex evaporates and hematite has been viewed in one area of the field where the reservoir (proper) bottom was encountered. Such a deposit may exist along all reservoir cell(s) bottoms, where in numerous cases the reservoir proper has been seen to pass into a somewhat mysterious ultra-superheated reservoir.

  2. Co thickness dependence of structural and magnetic properties in spin quantum cross devices utilizing stray magnetic fields

    SciTech Connect

    Kaiju, H. Kasa, H.; Mori, S.; Misawa, T.; Abe, T.; Nishii, J.; Komine, T.

    2015-05-07

    We investigate the Co thickness dependence of the structural and magnetic properties of Co thin-film electrodes sandwiched between borate glasses in spin quantum cross (SQC) devices that utilize stray magnetic fields. We also calculate the Co thickness dependence of the stray field between the two edges of Co thin-film electrodes in SQC devices using micromagnetic simulation. The surface roughness of Co thin films with a thickness of less than 20 nm on borate glasses is shown to be as small as 0.18 nm, at the same scanning scale as the Co film thickness, and the squareness of the hysteresis loop is shown to be as large as 0.96–1.0. As a result of the establishment of polishing techniques for Co thin-film electrodes sandwiched between borate glasses, we successfully demonstrate the formation of smooth Co edges and the generation of stray magnetic fields from Co edges. Theoretical calculation reveals that a strong stray field beyond 6 kOe is generated when the Co thickness is greater than 10 nm at a junction gap distance of 5 nm. From these experimental and calculation results, it can be concluded that SQC devices with a Co thickness of 10–20 nm can be expected to function as spin-filter devices.

  3. Cross-field transport of less than 1 MeV protons in energetic particle events

    NASA Technical Reports Server (NTRS)

    Zwickl, R. D.; Roelof, E. C.; Gold, R. E.

    1980-01-01

    A systematic analysis of hourly averaged low-energy anisotropy data (0.3-0.5 MeV) has been carried out with the JHU/APL detectors onboard the IMP-7 and 8 spacecraft from 1972-1975. The energetic particle events were divided into two major groups: flare-associated or nonimpulsive. Resolving the anistropy vectors into components parallel and perpendicular to the measured magnetic field leads directly to the following model-independent conclusions: (1) the average perpendicular anisotropy component is entirely accounted for in terms of the ExB drift, and hence transverse diffusion is negligible at these energies; application of the diffusion model to the nonimpulsive data set implies a ratio of the diffusion mean free paths parallel and perpendicular to the magnetic field much less than 0.051; (2) the parallel anisotropy component averages nearly to zero in the nonimpulsive data set, indicating virtually no net streaming along the field at 1 AU, averaged over all events.

  4. Some experimental observations on circulating currents in a crossed field plasma accelerator

    NASA Technical Reports Server (NTRS)

    Jedlicka, J.; Haacker, J.

    1971-01-01

    Experiments on a thermally ionized argon plasma suggest that applying a Lorentz force by means of orthogonal electric and magnetic fields to an electrically conducting fluid flow imposes necessary but not sufficient conditions for acceleration. There are, in fact, many combinations of current and magnetic field which cause decelerations of the fluid. The deceleration arises from a retarding force which may be larger than the applied Lorentz force. The retarding force causing the deceleration is a consequence of currents circulating completely within the fluid. These currents arise from differences in velocity between the central and wall regions of the duct which interact with the imposed magnetic field to produce differences in induced voltages. The observed physical effects of the circulating currents cause a loss in velocity in the central region of the duct, an increase in thermal energy in the sidewall region, and little change in thermal energy near the electrode wall region. For similar velocity profiles, the adverse effects appear to be related to the product of electrical conductivity and velocity, and performance as an accelerator appears to be controlled by the Hoffman loading parameter (i.e., the ratio of the applied to the induced currents).

  5. A uniform field ion mobility study of melittin and implications of low-field mobility for resolving fine cross-sectional detail in peptide and protein experiments.

    PubMed

    May, Jody C; McLean, John A

    2015-08-01

    An experimental investigation of protonated melittin was undertaken using uniform field ion mobility-mass spectrometry (IM-MS) to measure helium-based collision cross sections (CCS). Upon varying the electrospray solvent from aqueous to methanol, the [M + 2H](2+) species was observed to shift from a compact to an extended CCS, suggesting a gas-phase structural transition which depends on initial solvent conditions. The [M + 3H](3+), [M + 4H](4+), and [M + 5H](5+) species exhibited peak broadening in response to the organic solvent, but retained their CCS, suggesting these are locked into a stable gas-phase structure. The CCS of the stable [M + 3H](3+) and [M + 4H](4+) species were found to be similar, suggesting these ions adopt structurally similar features in the gas phase, which, based on previous studies, likely retains α-helical characteristics. We also report on the resolution of additional low-abundance ion mobility peak features which are sensitive to the magnitude of the drift field. We observe a loss in the peptide ion mobility resolution above ca. eight Townsends, suggesting that the ability to resolve subtle structural details is inherently related to conducting ion mobility measurements at low field and under conditions which minimize ion heating. PMID:25884242

  6. Empirical electron cross-field mobility in a Hall effect thruster

    SciTech Connect

    Garrigues, L.; Perez-Luna, J.; Lo, J.; Hagelaar, G. J. M.; Boeuf, J. P.; Mazouffre, S.

    2009-10-05

    Electron transport across the magnetic field in Hall effect thrusters is still an open question. Models have so far assumed 1/B{sup 2} or 1/B scaling laws for the 'anomalous' electron mobility, adjusted to reproduce the integrated performance parameters of the thruster. We show that models based on such mobility laws predict very different ion velocity distribution functions (IVDF) than measured by laser induced fluorescence (LIF). A fixed spatial mobility profile, obtained by analysis of improved LIF measurements, leads to much better model predictions of thruster performance and IVDF than 1/B{sup 2} or 1/B mobility laws for discharge voltages in the 500-700 V range.

  7. Analytical solutions and particle simulations of cross-field plasma sheaths

    SciTech Connect

    Gerver, M.J. . Plasma Fusion Center); Parker, S.E.; Theilhaber, K. . Electronics Research Lab.)

    1989-08-30

    Particles simulations have been made of an infinite plasma slab, bounded by absorbing conducting walls, with a magnetic field parallel to the walls. The simulations have been either 1-D, or 2-D, with the magnetic field normal to the simulation plane. Initially, the plasma has a uniform density between the walls, and there is a uniform source of ions and electrons to replace particles lost to the walls. In the 1-D case, there is no diffusion of the particle guiding centers, and the plasma remains uniform in density and potential over most of the slab, with sheaths about a Debye length wide where the potential rises to the wall potential. In the 2-D case, the density profile becomes parabolic, going almost to zero at the walls, and there is a quasineutral presheath in the bulk of the plasma, in addition to sheaths near the walls. Analytic expressions are found for the density and potential profiles in both cases, including, in the 2-D case, the magnetic presheath due to finite ion Larmor radius, and the effects of the guiding center diffusion rate being either much less than or much grater than the energy diffusion rate. These analytic expressions are shown to agree with the simulations. A 1-D simulation with Monte Carlo guiding center diffusion included gives results that are good agreement with the much more expensive 2-D simulation. 17 refs., 10 figs.

  8. Single-shot spatiotemporal measurements of ultrashort THz waveforms using temporal electric-field cross correlation

    SciTech Connect

    Matlis, Nicholas; Plateau, Guillaume; van Tilborg, Jeroen; Leemans, Wim

    2011-06-17

    A new single-shot technique based on linear spectral interferometry between a temporally short reader pulse and a temporally long probe pulse is demonstrated for measuring the spatiotemporal phase and amplitude of an optical probe for use as an ultrafast diagnostic. The probe spatiotemporal field information is recovered, with a resolution set by the duration of the reader pulse, by applying a single Fourier transform operation to the interferogram image, without need of any reference data. The technique was used in conjunction with electro-optic sampling to measure waveforms of coherent, ultrashort THz pulses emitted by electron bunches from a laser-plasma accelerator with sub-50fs resolution. The presence of strong spatiotemporal coupling in the THz waveforms and of complex temporal electron-bunch structure was determined.

  9. Energization in regions of CIRs unconnected to shocks are probably not the result of cross-field transport

    NASA Technical Reports Server (NTRS)

    Intriligator, Devrie S.; Siscoe, George

    1995-01-01

    Corotating energetic ion populations (CEIPs) associated with the forward and reverse shocks of corotating interaction regions (CIRs) are observed in CIRs at places where models say are magnetically unconnected to either shock. Such disconnections between CEIPs and shocks are common and have been documented with data from Pioneers 10 and 11 and confirmed with data from Ulysses. They pose a problem for models that account for these CEIPs in terms of ion energization at the shocks followed by ion propagation along field lines. Two possible resolutions to this problem have been suggested: diffusion of the ions across field lines and extension of the ion energization process to regions beyond the shock waves. Here we quantitatively examine the first of these possibilities. We give the Green's function solution to the convection-diffusion equation applied to idealized CIR geometry, with a source at the reverse shock -- the main producer of CEIPs. Two kinds of diffusion are considered: resonant diffusion and stochastic field line diffusion. We find that for resonant diffusion the computed ratio is many orders of magnitudes below the observed ratio. For stochastic field line diffusion, the computed ratio approximately equals the observed ratio if a diffusion coefficient appropriate to the free solar wind is used. It is several orders of magnitude below the observed ratio, however, if a diffusion coefficient appropriate to CIRs is used. We conclude that cross-field diffusion probably does not account for the presence of energetic ions in regions of CIRs that are magnetically unconnected to its shock waves. We suggest that the alternative possibility -- the energetic ions in regions magnetically unconnected to shocks result from an acceleration process that is independent of shocks -- be pursued to the point where quantitative tests can be performed.

  10. How International Field Experiences Promote Cross-Cultural Awareness in Preservice Teachers through Experiential Learning: Findings from a Six-Year Collective Case Study

    ERIC Educational Resources Information Center

    Malewski, Erik; Sharma, Suniti; Phillion, JoAnn

    2012-01-01

    Background/Context: The article examines how international field experiences promote cross-cultural awareness in U.S. American preservice teachers through experiential learning. The findings presented here are based on a 6-year study of a short-term study abroad program in Honduras that included an international field experience component and took…

  11. The effect of external magnetic fields on the catalytic activity of Pd nanoparticles in Suzuki cross-coupling reactions.

    PubMed

    Gao, Lei; Wang, Changlai; Li, Ren; Li, Ran; Chen, Qianwang

    2016-04-14

    Pd nanoparticles supported on Co3[Co(CN)6]2 nanoparticles (marked as Pd@Co3[Co(CN)6]2 nanoparticles) were prepared as catalysts for the Suzuki cross-coupling reaction under external magnetic fields (MFs). It is shown that a weak external MF can increase the rate of the Suzuki cross-coupling reaction at room temperature, and with the increase of the strength of external MFs the reaction rate also increased. At 30 °C, the yield was increased by nearly 50% under a 0.5 T external MF after 24 hours compared to that without a MF applied. Theoretical calculations revealed that the adsorption energy changed from -1.07 to -1.12 eV in the presence of MFs, which increased by 5% compared with the absence of MFs, leading to a lower total energy of the adsorption system, which is beneficial to the reaction. From the analysis of the partial density states, it could be seen that the 2p orbital of the carbon atom in bromobenzene and the 4d orbital of the Pd atom overlap more closely in the presence of MFs, which is beneficial for the electron transfer from the Pd substrate to the bromobenzene molecule. This study is helpful in understanding the interaction between MFs and catalysts and regulating the process of catalytic reactions via MFs. PMID:27043428

  12. Spatial cross modulation method using a random diffuser and phase-only spatial light modulator for constructing arbitrary complex fields.

    PubMed

    Shibukawa, Atsushi; Okamoto, Atsushi; Takabayashi, Masanori; Tomita, Akihisa

    2014-02-24

    We propose a spatial cross modulation method using a random diffuser and a phase-only spatial light modulator (SLM), by which arbitrary complex-amplitude fields can be generated with higher spatial resolution and diffraction efficiency than off-axis and double-phase computer-generated holograms. Our method encodes the original complex object as a phase-only diffusion image by scattering the complex object using a random diffuser. In addition, all incoming light to the SLM is consumed for a single diffraction order, making a diffraction efficiency of more than 90% possible. This method can be applied for holographic data storage, three-dimensional displays, and other such applications. PMID:24663718

  13. Modeling cross-field transport of solar energetic particles including solar wind effects

    NASA Astrophysics Data System (ADS)

    Lampa, Florian; Kallenrode, May-Britt

    Under consideration of solar wind effects, we have extended the Ruffolo's equation of focused transport for solar energetic particles to accommodate perpendicular transport in the ecliptic plane, and made a different approach concerning the reference frame. Numerically, the additional transport term is solved with the implicit and stable Laasonen scheme. In parameter studies and fits to observations for typical ratios κ⊥ /κ ranging between 0.02 and 0.1 at 1 AU as suggested in numerous studies (e.g. non-linear guiding-center theory) and a scaling of κ⊥ with r2 as suggested from the random walk of field lines as well as from numerical simulations, we find that azimuthal spread as well as the variation of maximum intensities with longitude is comparable to the ones inferred from multi-spacecraft observations. Implications for the interpretation of the observed intensity and anisotropy time profiles and consequences for our understanding of particle propagation and acceleration in space will be discussed.

  14. Cross-field dynamics of the homogenization of the pellet deposited material in Tore Supra

    NASA Astrophysics Data System (ADS)

    Sakamoto, R.; Pégourié, B.; Clairet, F.; Géraud, A.; Gil, C.; Hacquin, S.; Köchl, F.

    2013-06-01

    For investigating the damping effect of low-order rational surfaces on the drift of pellet deposited plasmoids, a safety factor (q) profile scan experiment was performed in Tore Supra, on a series of discharges with identical temperature and density profiles. Fast time-resolved density measurements show that the position of the deposition peak does not move smoothly during the ablation/homogenization phase but changes step by step, each step being located close to an integer or half-integer q value. This behaviour is well reproduced by time-dependent simulations with the pellet ablation/deposition code HPI2, which takes into account the braking of the plasmoid drift by external currents flowing along field lines in the background plasma. The key feature of this damping mechanism is a modulation as a function of the local safety factor, the braking being more effective in the vicinity of simple rational q values. The overall agreement between measurements and code predictions for a significant range of edge safety factors is fully consistent with the fact that the limitation of the plasmoid polarization by parallel currents is the dominant damping process of the ∇B-induced drift in tokamaks.

  15. A Cross-Polarization Based Rotating-Frame Separated-Local-Field NMR Experiment Under Ultrafast MAS Conditions

    PubMed Central

    Zhang, Rongchun; Damron, Joshua; Vosegaard, Thomas

    2014-01-01

    Rotating-frame separated-local-field solid-state NMR experiments measure highly resolved heteronuclear dipolar couplings which, in turn, provide valuable interatomic distances for structural and dynamic studies of molecules in the solid-state. Though many different rotating-frame SLF sequences have been put forth, recent gains in ultrafast MAS technology have considerably simplified pulse sequence requirements due to the suppression of proton-proton dipolar interactions. In this study we revisit a simple two-dimensional 1H-13C dipolar coupling/chemical shift correlation experiment using 13C detected Cross-Polarization with a Variable Contact time (CPVC) and systematically study the conditions for its optimal performance at 60 kHz MAS. In addition, we demonstrate the feasibility of a proton-detected version of the CPVC experiment. The theoretical analysis of the CPVC pulse sequence under different Hartmann-Hahn matching conditions confirms that it performs optimally under the ZQ (w1H-w1C=±wr) condition for polarization transfer. The limits of the cross polarization process are explored and precisely defined as a function of offset and Hartmann-Hahn mismatch via spin dynamics simulation and experiments on a powder sample of uniformly 13C-labeled L-isoleucine. Our results show that the performance of the CPVC sequence and subsequent determination of 1H-13C dipolar couplings are insensitive to 1H/13C frequency offset frequency when high RF fields are used on both RF channels. Conversely, the CPVC sequence is quite sensitive to the Hartmann-Hahn mismatch, particularly for systems with weak heteronuclear dipolar couplings. We demonstrate the use of the CPVC based SLF experiment as a tool to identify different carbon groups, and hope to motivate the exploration of more sophisticated 1H detected avenues for ultrafast MAS. PMID:25486635

  16. Vortex dynamics and transport to the wall in a crossed-field plasma sheath

    SciTech Connect

    Theilhaber, K.; Birdsall, C.K.

    1987-04-10

    Results of numerical simulations of the time-dependent behavior of a transversely magnetized plasma-wall sheath are presented. These simulations have been conducted with the aim of modelling plasma behavior in the vicinity of the limiters and walls of a fusion device. The two-dimensional, bounded particle simulation code ''ES2'' has been used as a tool for the investigation of these edge effects, in an idealized geometry which retains, however, the essential features of the physics of the edge plasma. The simulations have revealed that the bounded plasma is subject to the so-called ''Kelvin-Helmholtz'' instability, an instability maintained by the non-uniform electric field which is induced by the presence of the material walls. This instability is seen to saturate into large and stable vortices, with e phi/T/sub i/ approx. 1, which exist in the vicinity of the walls, and drift parallel to their surfaces. An important feature of these structures is that they continuously convect particles to the walls, at an ''anomalous'' rate much greater than that induced by collisional diffusion, a feature which seems tied to the mutual interaction of the vortices. In the code ''ES2'', volume ionization of neutrals has been modelled by a uniform electron-ion pair creation in the simulation region, and this results in a steady state, in which the linear edge instability, the nonlinear fluid dynamics of the vortices, and the nonlinear dynamics of the particles scattered by the vortices all balance each other. This steady-state but non-equilibrium configuration, which is a first model of the edge behavior induced by the boundaries, is conceptually analogous to Rayleigh-Benard convection.

  17. Ultra-sensitive magnetic field sensor with resolved temperature cross-sensitivity employing microfiber-assisted modal interferometer integrated with magnetic fluids

    NASA Astrophysics Data System (ADS)

    Liu, Haifeng; Zhang, Hao; Liu, Bo; Song, Binbin; Wu, Jixuan; Lin, Lie

    2016-07-01

    A compact and ultra-sensitive magnetic field sensor has been proposed by exploiting a microfiber-assisted Mach-Zehnder interferometer functionalized by magnetic fluids. We have experimentally investigated the transmission spectral responses of the proposed sensor to the variation of applied magnetic field intensity and environmental temperature. The interference dips exhibit a magnetic field sensitivity as large as -1.193 nm/Oe for a low magnetic field intensity range of 3 Oe to 21 Oe. By using the sensing matrix containing the magnetic field as well as temperature sensitivities for different interference dips, the temperature cross-sensitivity issue could be effectively resolved. Our proposed sensor is anticipated to find potential applications in weak magnetic field detection, and moreover, the immunity to temperature cross-sensitivity effect ensures its applicability in temperature-fluctuated environments.

  18. Communication: Transition state trajectory stability determines barrier crossing rates in chemical reactions induced by time-dependent oscillating fields

    NASA Astrophysics Data System (ADS)

    Craven, Galen T.; Bartsch, Thomas; Hernandez, Rigoberto

    2014-07-01

    When a chemical reaction is driven by an external field, the transition state that the system must pass through as it changes from reactant to product—for example, an energy barrier—becomes time-dependent. We show that for periodic forcing the rate of barrier crossing can be determined through stability analysis of the non-autonomous transition state. Specifically, strong agreement is observed between the difference in the Floquet exponents describing stability of the transition state trajectory, which defines a recrossing-free dividing surface [G. T. Craven, T. Bartsch, and R. Hernandez, "Persistence of transition state structure in chemical reactions driven by fields oscillating in time," Phys. Rev. E 89, 040801(R) (2014)], and the rates calculated by simulation of ensembles of trajectories. This result opens the possibility to extract rates directly from the intrinsic stability of the transition state, even when it is time-dependent, without requiring a numerically expensive simulation of the long-time dynamics of a large ensemble of trajectories.

  19. Aligned magnetic field and cross-diffusion effects of a nanofluid over an exponentially stretching surface in porous medium

    NASA Astrophysics Data System (ADS)

    Sulochana, C.; Sandeep, N.; Sugunamma, V.; Rushi Kumar, B.

    2016-06-01

    In this paper, we investigated the effects of aligned magnetic field, thermal radiation, heat generation/absorption, cross-diffusion, viscous dissipation, heat source and chemical reaction on the flow of a nanofluid past an exponentially stretching sheet in porous medium. The governing partial differential equations are transformed to set of ordinary differential equations using self-similarity transformation, which are then solved numerically using bvp4c Matlab package. Finally the effects of various non-dimensional parameters on velocity, temperature, concentration, skin friction, local Nusselt and Sherwood numbers are thoroughly investigated and presented through graphs and tables. We observed that an increase in the aligned angle strengthens the applied magnetic field and decreases the velocity profiles of the flow. Soret and Dufour numbers are helpful to enhance the heat transfer rate. An increase in the heat source parameter, radiation parameter and Eckert number increases the mass transfer rate. Mixed convection parameter has tendency to enhance the friction factor along with the heat and mass transfer rate.

  20. Aligned magnetic field and cross-diffusion effects of a nanofluid over an exponentially stretching surface in porous medium

    NASA Astrophysics Data System (ADS)

    Sulochana, C.; Sandeep, N.; Sugunamma, V.; Rushi Kumar, B.

    2015-07-01

    In this paper, we investigated the effects of aligned magnetic field, thermal radiation, heat generation/absorption, cross-diffusion, viscous dissipation, heat source and chemical reaction on the flow of a nanofluid past an exponentially stretching sheet in porous medium. The governing partial differential equations are transformed to set of ordinary differential equations using self-similarity transformation, which are then solved numerically using bvp4c Matlab package. Finally the effects of various non-dimensional parameters on velocity, temperature, concentration, skin friction, local Nusselt and Sherwood numbers are thoroughly investigated and presented through graphs and tables. We observed that an increase in the aligned angle strengthens the applied magnetic field and decreases the velocity profiles of the flow. Soret and Dufour numbers are helpful to enhance the heat transfer rate. An increase in the heat source parameter, radiation parameter and Eckert number increases the mass transfer rate. Mixed convection parameter has tendency to enhance the friction factor along with the heat and mass transfer rate.

  1. The effect of external magnetic fields on the catalytic activity of Pd nanoparticles in Suzuki cross-coupling reactions

    NASA Astrophysics Data System (ADS)

    Gao, Lei; Wang, Changlai; Li, Ren; Li, Ran; Chen, Qianwang

    2016-04-01

    Pd nanoparticles supported on Co3[Co(CN)6]2 nanoparticles (marked as Pd@Co3[Co(CN)6]2 nanoparticles) were prepared as catalysts for the Suzuki cross-coupling reaction under external magnetic fields (MFs). It is shown that a weak external MF can increase the rate of the Suzuki cross-coupling reaction at room temperature, and with the increase of the strength of external MFs the reaction rate also increased. At 30 °C, the yield was increased by nearly 50% under a 0.5 T external MF after 24 hours compared to that without a MF applied. Theoretical calculations revealed that the adsorption energy changed from -1.07 to -1.12 eV in the presence of MFs, which increased by 5% compared with the absence of MFs, leading to a lower total energy of the adsorption system, which is beneficial to the reaction. From the analysis of the partial density states, it could be seen that the 2p orbital of the carbon atom in bromobenzene and the 4d orbital of the Pd atom overlap more closely in the presence of MFs, which is beneficial for the electron transfer from the Pd substrate to the bromobenzene molecule. This study is helpful in understanding the interaction between MFs and catalysts and regulating the process of catalytic reactions via MFs.Pd nanoparticles supported on Co3[Co(CN)6]2 nanoparticles (marked as Pd@Co3[Co(CN)6]2 nanoparticles) were prepared as catalysts for the Suzuki cross-coupling reaction under external magnetic fields (MFs). It is shown that a weak external MF can increase the rate of the Suzuki cross-coupling reaction at room temperature, and with the increase of the strength of external MFs the reaction rate also increased. At 30 °C, the yield was increased by nearly 50% under a 0.5 T external MF after 24 hours compared to that without a MF applied. Theoretical calculations revealed that the adsorption energy changed from -1.07 to -1.12 eV in the presence of MFs, which increased by 5% compared with the absence of MFs, leading to a lower total energy of the

  2. Level crossings and zero-field splitting in the {Cr8}-cubane spin-cluster studied using inelastic neutron scattering and magnetization

    SciTech Connect

    Vaknin, D.; Garlea, Vasile O; Demmel, F.; Mamontov, Eugene; Nojiri, H; Martin, Catalin; Chiorescu, Irinel; Qiu, Y.; Luban, M.; Kogerler, P.; Fielden, J.; Engelhardt, L; Rainey, C

    2010-01-01

    Inelastic neutron scattering (INS) in variable magnetic field and high-field magnetization measurements in the millikelvin temperature range were performed to gain insight into the low-energy magnetic excitation spectrum and the field-induced level crossings in the molecular spin cluster {Cr8}-cubane. These complementary techniques provide consistent estimates of the lowest level-crossing field. The overall features of the experimental data are explained using an isotropic Heisenberg model, based on three distinct exchange interactions linking the eight CrIII paramagnetic centers (spins s = 3/2), that is supplemented with a relatively large molecular magnetic anisotropy term for the lowest S = 1 multiplet. It is noted that the existence of the anisotropy is clearly evident from the magnetic field dependence of the excitations in the INS measurements, while the magnetization measurements are not sensitive to its effects.

  3. Impacts of field of view configuration of Cross-track Infrared Sounder on clear-sky observations.

    PubMed

    Wang, Likun; Chen, Yong; Han, Yong

    2016-09-01

    Hyperspectral infrared radiance measurements from satellite sensors contain valuable information on atmospheric temperature and humidity profiles and greenhouse gases, and therefore are directly assimilated into numerical weather prediction (NWP) models as inputs for weather forecasting. However, data assimilations in current operational NWP models still mainly rely on cloud-free observations due to the challenge of simulating cloud-contaminated radiances when using hyperspectral radiances. The limited spatial coverage of the 3×3 field of views (FOVs) in one field of regard (FOR) (i.e., spatial gap among FOVs) as well as relatively large footprint size (14 km) in current Cross-track Infrared Sounder (CrIS) instruments limits the amount of clear-sky observations. This study explores the potential impacts of future CrIS FOV configuration (including FOV size and spatial coverage) on the amount of clear-sky observations by simulation experiments. The radiance measurements and cloud mask products (VCM) from the Visible Infrared Imager Radiometer Suite (VIIRS) are used to simulate CrIS clear-sky observation under different FOV configurations. The results indicate that, given the same FOV coverage (e.g., 3×3), the percentage of clear-sky FOVs and the percentage of clear-sky FORs (that contain at least one clear-sky FOV) both increase as the FOV size decreases. In particular, if the CrIS FOV size were reduced from 14 km to 7 km, the percentage of clear-sky FOVs increases from 9.02% to 13.51% and the percentage of clear-sky FORs increases from 18.24% to 27.51%. Given the same FOV size but with increasing FOV coverage in each FOR, the clear-sky FOV observations increases proportionally with the increasing sampling FOVs. Both reducing FOV size and increasing FOV coverage can result in more clear-sky FORs, which benefit data utilization of NWP data assimilation. PMID:27607289

  4. Fully automated prostate segmentation in 3D MR based on normalized gradient fields cross-correlation initialization and LOGISMOS refinement

    NASA Astrophysics Data System (ADS)

    Yin, Yin; Fotin, Sergei V.; Periaswamy, Senthil; Kunz, Justin; Haldankar, Hrishikesh; Muradyan, Naira; Cornud, François; Turkbey, Baris; Choyke, Peter

    2012-02-01

    Manual delineation of the prostate is a challenging task for a clinician due to its complex and irregular shape. Furthermore, the need for precisely targeting the prostate boundary continues to grow. Planning for radiation therapy, MR-ultrasound fusion for image-guided biopsy, multi-parametric MRI tissue characterization, and context-based organ retrieval are examples where accurate prostate delineation can play a critical role in a successful patient outcome. Therefore, a robust automated full prostate segmentation system is desired. In this paper, we present an automated prostate segmentation system for 3D MR images. In this system, the prostate is segmented in two steps: the prostate displacement and size are first detected, and then the boundary is refined by a shape model. The detection approach is based on normalized gradient fields cross-correlation. This approach is fast, robust to intensity variation and provides good accuracy to initialize a prostate mean shape model. The refinement model is based on a graph-search based framework, which contains both shape and topology information during deformation. We generated the graph cost using trained classifiers and used coarse-to-fine search and region-specific classifier training. The proposed algorithm was developed using 261 training images and tested on another 290 cases. The segmentation performance using mean DSC ranging from 0.89 to 0.91 depending on the evaluation subset demonstrates state of the art performance. Running time for the system is about 20 to 40 seconds depending on image size and resolution.

  5. An experimental study of the flow field surrounding a subsonic jet in a cross flow. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Dennis, Robert Foster

    1993-01-01

    An experimental investigation of the flow interaction of a 5.08 cm (2.00 in.) diameter round subsonic jet exhausting perpendicularly to a flat plate in a subsonic cross flow was conducted in the NASA Ames 7x1O ft. Wind Tunnel Number One. Flat plate surface pressures were measured at 400 locations in a 30.48 cm (12.0 in.) concentric circular array surrounding the jet exit. Results from these measurements are provided in tabular and graphical form for jet-to-crossflow velocity ratios ranging from 4 to 12, and for jet exit Mach numbers ranging from 0.50 to 0.93. Laser doppler velocimeter (LDV) three component velocity measurements were made in selected regions in the developed jet plume and near the flat plate surface, at a jet Mach number of 0.50 and jet-to-crossflow velocity ratios of 6 and 8. The results of both pressure and LDV measurements are compared with the results of previous experiments. In addition, pictures of the jet plume shape at jet velocity ratios ranging from 4 to 12 were obtained using schleiren photography. The LDV measurements are consistent with previous work, but more extensive measurements will be necessary to provide a detailed picture of the flow field. The surface pressure results compare closely with previous work and provide a useful characterization of jet induced surface pressures. The results demonstrate the primary influence of jet velocity ratio and the secondary influence of jet Mach number in determining such surface pressures.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  8. On a moving four-level N-type atom interacting with two-mode cavity field in the presence of the cross-Kerr medium

    NASA Astrophysics Data System (ADS)

    Abdel-Wahab, N. H.; Thabet, Lamia E.

    2016-01-01

    In this paper, some properties through the moving four-level N-type atom interacting with a two-mode radiation field are presented. We study this system in the presence of the nonlinearity. The exact solution of this model is given by using the Schrödinger equation when the atom and the field are initially in an excited state and a squeezed state, respectively. We employed the results to perform a careful investigation of the temporal evolution of the cross-correlation function, the momentum increment, the difference mean photon numbers and the normal squeezing. The influence of the Kerr and the cross-Kerr medium parameters on these aspects is examined. It is found that the atom-field properties are affected by the changing of these parameters.

  9. Power-Factor and Torque Calculation under Consideration of Cross Saturation of the Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation

    SciTech Connect

    Lee, Seong T; Burress, Timothy A; Tolbert, Leon M

    2009-01-01

    This paper introduces a new method for calculating the power factor and output torque by considering the cross saturation between direct-axis (d-axis) and quadrature-axis (q-axis) of an interior permanent magnet synchronous motor (IPMSM). The conventional two-axis IPMSM model is modified to include the cross saturation effect by adding the cross-coupled inductance terms. This paper also contains the new method of calculating the cross-coupled inductance values as well as self-inductance values in d- and q-axes. The analyzed motor is a high-speed brushless field excitation machine that offers high torque per ampere per core length at low speed and weakened flux at high speed, which was developed for the traction motor of a hybrid electric vehicle. The conventional two-axis IPMSM model was modified to include the cross-saturation effect by adding the cross-coupled inductance terms Ldq and Lqd. By the advantage of the excited structure of the experimental IPMSM, the analyzing works were performed under two conditions, the highest and lowest excited conditions. Therefore, it is possible to investigate the cross-saturation effect when a machine has higher magnetic flux from its rotor. The following is a summary of conclusions that may be drawn from this work: (1) Considering cross saturation of an IPMSM offers more accurate expected values of motor parameters in output torque calculation, especially when negative d-axis current is high; (2) A less saturated synchronous machine could be more affected by the cross-coupled saturation effect; (3) Both cross-coupled inductances, L{sub qd} and L{sub dq}, are mainly governed by d-axis current rather than q-axis current; (4) The modified torque equation, can be used for the dynamic model of an IPMSM for developing a better control model or control strategy; and (5) It is possible that the brushless field excitation structure has a common magnetic flux path on both d- and q-axis, and as a result, the reluctance torque of the

  10. Ion collision cross sections and transport coefficients extended to intermediate energies and reduced electric fields for He(2)(+) ions colliding with He.

    PubMed

    Chicheportiche, A; Benhenni, M; Yousfi, M; Lepetit, B; Kalus, R; Gadea, F X

    2013-10-01

    This work is devoted to the calculation of transport coefficients for He(2)(+) ions in gaseous He at intermediate reduced electric fields. These swarm data are of great interest for a better understanding of the mechanisms of formation and propagation of the fast plasma bullets or ionization waves observed in dielectric barrier plasma jet devices. For transport data, the collision cross sections required are determined from several theoretical methods based on quantum, semiclassical, and hybrid approaches and a diatomics-in-molecules model for the potential energy surfaces of He(2)(+). The corresponding collision cross sections are then used in an optimized Monte Carlo code to calculate the ion transport coefficients over a wide range of reduced electric fields extending over the experimental range. Calculated transport coefficients are compared with available experimental data at low electric fields. Moreover, an extrapolation method is used in order to determine the reduced mobility for stronger fields. A critical discussion has been performed on the pertinence and the reliability of these different methods of determination of collision cross sections needed for the calculation of ion transport data. Such ion data will be used in electrohydrodynamic and chemical kinetic models of the low-temperature plasma jet to quantify and to tune the active species production for a better use in biomedical applications. PMID:24229290

  11. An Effective Field Theory Calculation of n(p, d)gamma Cross-section for Big Bang Nucleo-synthesis

    NASA Astrophysics Data System (ADS)

    Kamand, Rasha Adnan

    Studying the nuclear reaction n(p, d)gamma and calculating its cross-section is not only a matter of interest from theoretical particle physics point of view but also from the viewpoint of cosmology. We now know that the universe is made up of only ≈ 5% baryonic matter. So, computing the density of baryons is of particular importance to physicists in general and cosmologists in particular. Deuterium production during Big Bang Nucleo-synthesis (BBN) is very sensitive to the density of baryons, thus baryon density can be inferred from the abundance of deuterium. In order to calculate deuterium abundance one needs to use the cross-section of np --> dgamma reaction as one of the inputs; hence the importance of this cross-section calculation. In this document, a leading-order (LO) calculation of n( p, d)gamma cross-section is presented using the framework of pion-less effective field theory with dibaryon fields. The computation yielded a numerical value of sigmaLO = 494 mb which is then compared to the experimental value.

  12. Dust particles under the influence of crossed electric and magnetic fields in the sheath of an rf discharge

    SciTech Connect

    Puttscher, M. Melzer, A.

    2014-12-15

    Experimental studies on the interaction of micron-sized dust particles in plasmas with external magnetic fields are presented. The particles are levitated in the sheath region of an rf discharge by gravity and electric field force under the presence of a horizontal magnetic field of up to 50 mT. It is observed that the dust particles are pushed either in the E{sup →}×B{sup →}- or in the opposite direction depending on magnetic field strength, particle properties, and discharge conditions. This transport behavior is described by a competition between horizontal ambipolar electric field force and ion and neutral drag.

  13. Effect of Cross-Field Drifts and Core Rotation on Flows in the Main Scrape-Off Layer of DIII-D L-mode Plasmas

    SciTech Connect

    Groth, M; Boedo, J A; Brooks, N H; Isler, R C; Leonard, A W; Porter, G D; Watkins, J G; West, W P; Bray, B D; Fenstermacher, M E; Groebner, R J; Moyer, R A; Rudakov, D L; Yu, J H; Zeng, L

    2008-10-13

    The flow velocities of deuterons and low charge-state carbon ions have been measured simultaneously for the first time at the crown of the main SOL for low-density plasmas in DIII-D. The dependences of the flow fields on the direction of the cross-field drifts (E x B and B x {del}B) and core plasma rotation were investigated. The measurements indicate that the carbon ion flow direction and magnitude along the magnetic field lines are not necessarily determined by the deuteron flow field, but other physics must also play a role. The deuteron velocities at the plasma crown are high (20-30 km/s) in configurations with the ion B x {del}B drift toward the divertor X-point, while nearly zero in configurations with the opposite B x {del}B drift direction. The flow velocities of doubly charged carbon ions are independent of the ion B x {del}B drift direction, and the measurements suggest a stagnation point in the flow field at the crown of the plasma. Both deuteron and carbon ion flow velocities in the SOL were found to be independent of the direction of core plasma rotation. Simulations with the UEDGE code have been carried out to better understand the underlying physics processes. Including the cross-field drifts in the simulations produced divertor solutions that are in significantly closer agreement with the measurements. They do not, however, reproduce the measured flow fields at the crown for the configuration with the ion B x {del}B drift toward the divertor X-point.

  14. Self-consistent particle modeling of radio frequency discharge in Ar/O{sub 2} mixtures: Effects of crossed electric and magnetic fields and partial pressure

    SciTech Connect

    Benyoucef, Djilali; Yousfi, Mohammed; Belmadani, Bachir

    2011-04-15

    A particle-in-cell/Monte Carlo model is developed to study and analyze the electrical characteristics of the nonequilibrium plasma created by radio frequency (RF) discharge in Ar/O{sub 2} mixtures in the presence of crossed electric and magnetic fields. The method of collision treatment is based on an optimized estimation of the free time flight. The needed basic data--more specifically, the ion-neutral cross sections--are determined first. The simulation conditions are 50 mTorr for the total gas pressure and 200 V for the peak of the RF voltage at a frequency of 13.56 MHz. The magnetic field is varied from 0 to 50 G. The effect of the partial pressure ratio of O{sub 2} in the mixture and the effect of the magnitude of the magnetic field are discussed. In particular, the results show an increase of the plasma density that is ten times higher in the presence of a magnetic field.

  15. Experimental study on the effect of applying a crossed magnetic field on the insulator flashover behavior in high vacuum

    NASA Astrophysics Data System (ADS)

    Abu-Elabass, K.

    2015-09-01

    In this study, a possible method of reducing the flashover stress is achieved by the effect of an additional magnetic field in the transverse direction on the main applied electric field. The degree of vacuum used in this study was 5×10-5 Pa. The magnetic flux density B employed in this study extends from 4×10-3 to 24×10-3 T. From the results obtained throughout this work, the transverse magnetic field increases the flashover voltage and decreases the leakage current. The effect of the transverse magnetic field on the surface flashover of the dielectric solid in vacuum shows a marked dependence on the material and the thickness of the test specimen, the vacuum degree, the type of electric field (AC or DC) as well as the type of magnetic field (AC or DC).

  16. Low-temperature cross-talk magnetic-field sensor based on tapered all-solid waveguide-array fiber and magnetic fluids.

    PubMed

    Miao, Yinping; Ma, Xixi; Wu, Jixuan; Song, Binbin; Zhang, Hao; Zhang, Kailiang; Liu, Bo; Yao, Jianquan

    2015-08-15

    A compact fiber-optic magnetic-field sensor based on tapered all-solid waveguide-array fiber (WAF) and magnetic fluid (MF) has been proposed and experimentally demonstrated. The tapered all-solid WAF is fabricated by using a fusion splicer, and the sensor is formed by immersing the tapered all-solid WAF into the MF. The transmission spectra have been measured and analyzed under different magnetic-field intensities. Experimental results show that the acquired magnetic-field sensitivity is 44.57 pm/Oe for a linear magnetic-field intensity range from 50 to 200 Oe. All-solid WAF has very similar thermal expansion coefficient for high- and low-refractive-index glasses, so mode profile is not affected by thermal drifts. Also, magnetically induced refractive-index changes into the ferrofluid are of the order of ∼5×10(-2), while the corresponding thermally induced refractive-index changes into the ferrofluid are expected to be lower. The temperature response has also been detected, and the temperature-induced wavelength shift perturbation is less than 0.3 nm from temperature of 26.9°C-44°C. The proposed magnetic-field sensor has such advantages as low temperature sensitivity, simple structure, and ease of fabrication. It also indicates that the magnetic-field sensor based on tapered all-solid WAF and MF is helpful to reduce temperature cross-sensitivity for the measurement of magnetic field. PMID:26274690

  17. POROSITY/PERMEABILITY CROSS-PLOTS: CHEROKEE AND BUG FIELDS, SAN JUAN COUNTY, UTAH, AND LITTLE UTE AND SLEEPING UTE FIELDS, MONTEZUMA COUNTY, COLORADO

    SciTech Connect

    Thomas C. Chidsey Jr; David E. Eby; Laura L. Wray

    2003-12-01

    Over 400 million barrels (64 million m{sup 3}) of oil have been produced from the shallow-shelf carbonate reservoirs in the Pennsylvanian (Desmoinesian) Paradox Formation in the Paradox Basin, Utah and Colorado. With the exception of the giant Greater Aneth field, the other 100 plus oil fields in the basin typically contain 2 to 10 million barrels (0.3-1.6 million m{sup 3}) of original oil in place. Most of these fields are characterized by high initial production rates followed by a very short productive life (primary), and hence premature abandonment. Only 15 to 25 percent of the original oil in place is recoverable during primary production from conventional vertical wells. An extensive and successful horizontal drilling program has been conducted in the giant Greater Aneth field. However, to date, only two horizontal wells have been drilled in small Ismay and Desert Creek fields. The results from these wells were disappointing due to poor understanding of the carbonate facies and diagenetic fabrics that create reservoir heterogeneity. These small fields, and similar fields in the basin, are at high risk of premature abandonment. At least 200 million barrels (31.8 million m{sup 3}) of oil will be left behind in these small fields because current development practices leave compartments of the heterogeneous reservoirs undrained. Through proper geological evaluation of the reservoirs, production may be increased by 20 to 50 percent through the drilling of low-cost single or multilateral horizontal legs from existing vertical development wells. In addition, horizontal drilling from existing wells minimizes surface disturbances and costs for field development, particularly in the environmentally sensitive areas of southeastern Utah and southwestern Colorado.

  18. High-Frequency Alternating-Crossed-Field Gel Electrophoresis WithNeutral or Slightly Charged Interpenetrating Networks to Improve DNASeparation

    SciTech Connect

    Boyd, B.; Prausnitz, J.; Blanch, H.

    1998-07-01

    Toward improving DNA separations, this work reports theeffects of high-frequency square-wave AC fields superimposedperpendicular to the direct current (DC) separation field on DNAmigration in both polyacrylamide-based interpenetrating networks (IPNs)and in agarose networks. Compared to standard polyacrylamide gels, IPNsallow the separation of larger DNA (9000 bp vs. 5000 bp at 5 V/cm). Innovel polyacrylamide-based IPNs, an alternating current (AC) field of 5Hz increased the maximum DNA size separable. This effect was extended tolarger DNA sizes with increasing electric-field strength up to andapparently beyond the power supply-limited maximum electric-fieldstrength of 48 V/cm. The orthogonal AC field also increased mobility.These two results combine to yield a reduction in separation time of upto a factor of 20 in novel polyacrylamide-based IPNs. When negativelycharged acrylic-acid groups were incorporated into the IPNs, the use ofthe AC field changed the DNA-network interaction, which altered the sizedependence of DNA mobility. In agarose gels, an AC field of 50 Hzincreased the size range separable; however, there was no increase in DNAmobility. There was no change in size dependence of mobility in an ACfield when the number of charged groups in the agarose network wasincreased. Based on results in the literature, possible mechanisms wereexamined for the effects of the AC field on DNA separation.

  19. Spin dependent electronic structure and level crossings as a function of magnetic field in InAs nanowire

    NASA Astrophysics Data System (ADS)

    Jin, S. Q.; Waugh, J.; Matsuura, T.; Faniel, S.; Wu, H. Z.; Koga, Takaaki

    2010-01-01

    We point out that the electric field formed in the surface inversion layer in InAs nanowires leads to effective magnetic fields, due to the Rashba effect, that are mostly aligned along the wire axis, i.e., parallel to the external magnetic field B. While this situation leads to some similarities in spin splitting between the Zeeman and Rashba effects, extensive theoretical simulations revealed that large and small spin splittings should take place alternately at Fermi energies with increasing magnetic field B, as a result of the competition between the Rashba and Zeeman spin splittings. We suggest that an experimental detection of such characteristics should bring up quantitative insights into the relative strengths between the Rashba and Zeeman magnetic fields.

  20. Effect of cross-field drifts on flows in the main scrape-off-layer of DIII-D L-mode plasmas

    SciTech Connect

    Groth, M.; Boedo, J.A.; Brooks, N. H.; Isler, R. C.; Leonard, A. W.; Porter, G. D.; Watkins, J. G.; West, W. P.; Bray, Brad D; Fenstermacher, M. E.; Groebner, R.; Moyer, R.A.; Rudakov, D.L.; Yu, J.H.; Zeng, L.

    2009-01-01

    The flow velocities of deuterons and low charge-state carbon ions have been measured simultaneously in the main scrape-off-layer (SOL) in low-density plasmas in DIII-D, and the dependences of these flow fields on the direction of the cross-field drifts (E x B and B x del B) have been investigated. These measurements were taken poloidally localized in the SOL region vertically opposite the divertor X-point. The carbon ion flows do not necessarily match those of the deuterons either in the direction with respect to the magnetic field lines or in magnitude, suggesting that physics effects apart from entrainment play a significant role in the impurity response. In configurations with the ion B x del B drift towards the divertor X-point, the parallel-B deuteron velocities at the plasma crown are high (-20 to -30 km s(-1) in the direction of the high field side (HFS) divertor), while they are nearly zero in configurations with the opposite B x del B drift direction. The flow direction of singly and doubly charged carbon ions is independent of the ion B x del B drift direction, and the ions flow at approximately -5 to -10 km s(-1) towards the HFS divertor. Simulations with the UEDGE code have been carried out to better understand the underlying physics processes. Inclusion of cross-field drifts in the simulations produced divertor solutions for density and temperature that agree significantly better with measured divertor parameters. These simulations do not, however, reproduce the measured flow fields at the crown for the configuration with the ion B x del B drift towards the divertor X-point. The UEDGE code has also been used to understand the influence of pumping at the HFS divertor plate, and a poloidal dependence in the radial transport coefficient.

  1. Braneworld models with a non-minimally coupled phantom bulk field: a simple way to obtain the -1-crossing at late times

    SciTech Connect

    Setare, M.R.; Saridakis, E.N. E-mail: msaridak@phys.uoa.gr

    2009-03-15

    We investigate general braneworld models, with a non-minimally coupled phantom bulk field and arbitrary brane and bulk matter contents. We show that the effective dark energy of the brane-universe acquires a dynamical nature, as a result of the non-minimal coupling which provides a mechanism for an indirect ''bulk-brane interaction'' through gravity. For late-time cosmological evolution and without resorting to special ansatzes or to specific areas of the parameter space, we show that the -1-crossing of its equation-of-state parameter is general and can be easily achieved. As an example we provide a simple, but sufficiently general, approximate analytical solution, that presents the crossing behavior.

  2. Two-Dimensional (z-θ) Hybrid Fluid-PIC Simulation of Enhanced Cross-field Electron Transport in an Annular ExB Discharge

    NASA Astrophysics Data System (ADS)

    Lam, Cheryl; Fernandez, Eduardo; Cappelli, Mark

    2012-10-01

    We use a numerical model to study quasi-coherent plasma fluctuations and their impact on cross-field electron transport. We consider the case of an annular discharge, subject to a radial magnetic field and an axial electric field. Motivated by experimental evidence of anomalously high electron mobility across the magnetic field in Hall thruster discharges, we choose a two-dimensional axial-azimuthal (z-θ) simulation geometry. The model includes a continuously-replenished heavy (Xe) neutral background, with an imposed radial magnetic field and an applied axial electric potential. We use a hybrid fluid-Particle-In-Cell treatment; the ion and neutral species are treated as collisionless particles, while the electrons are treated as a fluid continuum. Using numerical simulations to resolve the azimuthal electron dynamics, we focus on understanding the role played by fluctuations, particularly those that propagate with components perpendicular to both the applied electric and magnetic fields. Preliminary simulations predict dispersive ``tilted'' wave fluctuations in the plasma density and electron velocities. These fluctuations appear to contribute to an enhanced overall electron mobility, which is significantly higher than that based on classical scattering.

  3. Direct measurements of classical and enhanced gradient-aligned cross-field ion flows in a helicon plasma source using laser-induced fluorescence

    SciTech Connect

    Siddiqui, M. Umair Thompson, Derek S.; McIlvain, Julianne M.; Short, Zachary D.; Scime, Earl E.

    2015-12-15

    Direct laser induced fluorescence measurements are shown of cross-field ion flows normal to an absorbing boundary that is aligned parallel to the axial magnetic field in a helicon plasma. We show Langmuir and emissive probe measurements of local density and plasma potential in the same region, as well as floating probe spectra near the boundary. With these measurements, we investigate the influence of ion-neutral collisionality on radial ion transport by varying the ratio of the ion gyro-radius, ρ{sub i}, to the ion-neutral collision length, λ, over the range 0.34 ≤ ρ{sub i}λ{sup −1} ≤ 1.60. Classical drift-diffusion transport along density and potential gradients is sufficient to describe flow profiles for most cases. For two parameter regimes (ρ{sub i}λ{sup −1} = 0.65 and 0.44), low-frequency electrostatic fluctuations (f < 10 kHz) and enhanced cross-field bulk ion flow to the boundary are observed.

  4. On the photoemission from 3-D quantum well boxes of nonlinear optical materials in the presence of crossed electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Ghatak, Kamakhya P.

    1990-08-01

    An attempt is made to study the photoemission :eron 3D quantum well boxes (QWBs) of nonlinear optical materials in the presence of crossed electric and magnetic fields, taking ternary chalcopyrite semiconductors as an example. Consi3ering the anisotropic crystal potential in the Harniltonian, we have formulated the generalized electron energy spectrum taking into account the anisotropies of the 0ther energy band par arne ter s, within the fr sine work of theory. We have then derlved.the photoernission from 3D QWBs of ternary chalCopyrite compounds by using the modified dispersion law under cross field configuration in the said material. It is found, taking 3D QWBs of n-CdGeAs2 as an example, that the photoernission exhibits ladder like dependence with incident photon energy as found in quanturn Hall effect and the corresponding results for three and two-band Kane models together with that of parabolic energy bands have been obtained from the present generalized exjressions as special cases. The photoeinission decreases with increasing magnetic field and decreasing electron concentration respectively. The oscillations in accordance with the present generalized model show up much more significantly and are in agreement with the experimental results as given elsewhere.

  5. Direct measurements of classical and enhanced gradient-aligned cross-field ion flows in a helicon plasma source using laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Siddiqui, M. Umair; Thompson, Derek S.; McIlvain, Julianne M.; Short, Zachary D.; Scime, Earl E.

    2015-12-01

    Direct laser induced fluorescence measurements are shown of cross-field ion flows normal to an absorbing boundary that is aligned parallel to the axial magnetic field in a helicon plasma. We show Langmuir and emissive probe measurements of local density and plasma potential in the same region, as well as floating probe spectra near the boundary. With these measurements, we investigate the influence of ion-neutral collisionality on radial ion transport by varying the ratio of the ion gyro-radius, ρi, to the ion-neutral collision length, λ, over the range 0.34 ≤ ρiλ-1 ≤ 1.60. Classical drift-diffusion transport along density and potential gradients is sufficient to describe flow profiles for most cases. For two parameter regimes (ρiλ-1 = 0.65 and 0.44), low-frequency electrostatic fluctuations (f < 10 kHz) and enhanced cross-field bulk ion flow to the boundary are observed.

  6. ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and its Implication to the Cross-Polar Cap Pedersen Currents

    NASA Technical Reports Server (NTRS)

    Le, Guan; Slavin, J. A.; Strangeway, Robert

    2010-01-01

    In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar windmagnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approximately 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  7. ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and Its Implication to the Cross-Polar Cap Pedersen Currents

    NASA Technical Reports Server (NTRS)

    Le, Guan; Slavin, J. A.; Strangeway, Robert

    2011-01-01

    In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  8. A mechanism for the dynamo terms to sustain closed-flux current, including helicity balance, by driving current which crosses the magnetic field

    SciTech Connect

    Jarboe, T. R.; Nelson, B. A.; Sutherland, D. A.

    2015-07-15

    An analysis of imposed dynamo current drive (IDCD) [T.R. Jarboe et al., Nucl. Fusion 52 083017 (2012)] reveals: (a) current drive on closed flux surfaces seems possible without relaxation, reconnection, or other flux-surface-breaking large events; (b) the scale size of the key physics may be smaller than is often computationally resolved; (c) helicity can be sustained across closed flux; and (d) IDCD current drive is parallel to the current which crosses the magnetic field to produce the current driving force. In addition to agreeing with spheromak data, IDCD agrees with selected tokamak data.

  9. Linear stability analysis of the Vlasov-Poisson equations in high density plasmas in the presence of crossed fields and density gradients

    NASA Technical Reports Server (NTRS)

    Kaup, D. J.; Hansen, P. J.; Choudhury, S. Roy; Thomas, Gary E.

    1986-01-01

    The equations for the single-particle orbits in a nonneutral high density plasma in the presence of inhomogeneous crossed fields are obtained. Using these orbits, the linearized Vlasov equation is solved as an expansion in the orbital radii in the presence of inhomogeneities and density gradients. A model distribution function is introduced whose cold-fluid limit is exactly the same as that used in many previous studies of the cold-fluid equations. This model function is used to reduce the linearized Vlasov-Poisson equations to a second-order ordinary differential equation for the linearized electrostatic potential whose eigenvalue is the perturbation frequency.

  10. Two-dimensional strain fields on the cross-section of the bovine humeral head under contact loading.

    PubMed

    Canal, Clare E; Hung, Clark T; Ateshian, Gerard A

    2008-11-14

    The objective of this study was to provide a detailed experimental assessment of the two-dimensional cartilage strain distribution on the cross-section of immature and mature bovine humeral heads subjected to contact loading at a relatively rapid physiological loading rate. Six immature and six mature humeral head specimens were loaded against glass and strains were measured at the end of a 5s loading ramp on the textured articular cross-section using digital image correlation analysis. The primary findings indicate that elevated tensile and compressive strains occur near the articular surface, around the center of the contact region. Few qualitative or quantitative differences were observed between mature and immature joints. Under an average contact stress of approximately 1.7 MPa, the peak compressive strains averaged -0.131+/-0.048, which was significantly less than the relative change in cartilage thickness, -0.104+/-0.032 (p<0.05). The peak tensile strains were significantly smaller in magnitude, at 0.0325+/-0.013. These experimental findings differ from a previous finite element analysis of articular contact, which predicted peak strains at the cartilage-bone interface even when accounting for the porous-hydrated nature of the tissue, its depth-dependent inhomogeneity, and the disparity between its tensile and compressive properties. These experimental results yield new insights into the local mechanical environment of the tissue and cells, and suggest that further refinements are needed in the modeling of contacting articular layers. PMID:18952212

  11. La Crosse Encephalitis Virus Infection in Field-Collected Aedes albopictus, Aedes japonicus, and Aedes triseriatus in Tennessee.

    PubMed

    Westby, Katie M; Fritzen, Charissa; Paulsen, Dave; Poindexter, Stephanie; Moncayo, Abelardo C

    2015-09-01

    La Crosse virus (LACV) is a mosquito-borne virus and a major cause of pediatric encephalitis in the USA. La Crosse virus emerged in Tennessee and other states in the Appalachian region in 1997. We investigated LACV infection rates and seasonal abundances of the native mosquito vector, Aedes triseriatus, and 2 recently introduced mosquito species, Ae. albopictus and Ae. japonicus, in an emerging disease focus in Tennessee. Mosquitoes were collected using multiple trapping methods specific for Aedes mosquitoes at recent human case sites. Mosquito pools were tested via reverse transcriptase-polymerase chain reaction (RT-PCR) of the S segment to detect multiple Bunyamwera and California serogroup viruses, including LACV, as well as real-time RT-PCR of the M segment. A total of 54 mosquito pools were positive, including wild-caught adult females and laboratory-reared adults, demonstrating transovarial transmission in all 3 species. Maximum likelihood estimates (per 1,000 mosquitoes) were 2.72 for Ae. triseriatus, 3.01 for Ae. albopictus, and 0.63 for Ae. japonicus. We conclude that Ae. triseriatus and Ae. albopictus are important LACV vectors and that Ae. japonicus also may be involved in virus maintenance and transmission. PMID:26375904

  12. Nonlinear and three-dimensional theory for cross-magnetic field propagation of short-pulse lasers in underdense plasmas

    NASA Astrophysics Data System (ADS)

    Ren, C.; Mori, W. B.

    2004-05-01

    The nonlinear and finite spot size effects for short laser pulses propagating in a plasma across a constant magnetic field (ordinary and extraordinary modes) have been studied. Starting from a fluid Lagrangian for magnetized plasmas with immobile ions, we derive the envelope equation for the laser and also the equation for the plasma wake in a three-dimensional geometry. The derived equations reveal that the external magnetic field reduces the strength of ponderomotive self-focusing, causes astigmatic self-focusing, and leads to the possibility of deflecting a short and narrow laser pulse in a magnetized plasma.

  13. Cross-field motion of plasma blob-filaments and related particle flux in an open magnetic field line configuration on QUEST

    NASA Astrophysics Data System (ADS)

    Liu, H. Q.; Hanada, K.; Nishino, N.; Ogata, R.; Ishiguro, M.; Gao, X.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Quest Group

    2013-07-01

    Blob-filaments have been observed by combined measurement with a fast camera and a movable Langmuir probe in an open magnetic field line configuration of electron cyclotron resonance (ECR) heating plasma in QUEST. Blob-filaments extended along field lines do correspond to over-dense plasma structures and propagated across the field lines to the outer wall. The radial velocity of the blob structure, Vb, was obtained by three methods and was dominantly driven by the E × B force. The radial velocity, size of the blob showed good agreements with the results obtained by sheath-connected interchange theoretical model. Vb corresponds to roughly 0.02-0.07 of the local sound speed (Cs) in QUEST. The higher moments (skewness S and kurtosis K) representing the shape of PDF of density fluctuation are studied. Their least squares fitting with quadratic polynomial is K = (1.60 ± 0.27)S2 - (0.46 ± 0.20). The larger blob structures, occurring only 10% of the time, can carry more than 60% loss of the entire radial particle flux.

  14. Design and analysis of Cross-Appalachian Tracer Experiment (CAPTEX) field trials. Second annual progress report. [CAPTEX

    SciTech Connect

    Baer, F.; Holland, J.Z.

    1985-01-01

    Procedures for testing atmospheric transport and dispersion models for distances of several hundred to 1000 km from sources of pollutants are reviewed. The approach is to use both simulated tracer distributions and actual tracer measurements on the US-Canada multi-agency Cross-Appalachian Tracer Experiment CAPTEX '83 surface sampling domain to estimate the accuracy with which the parameters describing the location and distribution of the tracer cloud can be determined from experimental data. In CAPTEX '83, five perfluorocarbon tracer releases were made from Dayton, Ohio, and two releases from Sudbury, Ontario. Surface air samples were collected at 84 locations in northeastern United States and eastern Canada. Three simulation experiments have been conducted with a Gaussian plume model simulating time-integrated surface-layer concentration (i.e., dosage) distributions of tracer clouds from a surface source.

  15. Evaluation of Cross-Protection of a Lineage 1 West Nile Virus Inactivated Vaccine against Natural Infections from a Virulent Lineage 2 Strain in Horses, under Field Conditions

    PubMed Central

    Chaintoutis, Serafeim C.; Diakakis, Nikolaos; Papanastassopoulou, Maria; Banos, Georgios

    2015-01-01

    Although experimental data regarding cross-protection of horse West Nile virus (WNV) vaccines against lineage 2 infections exist, the cross-protective efficacy of these vaccines under field conditions has not been demonstrated. This study was conducted to evaluate the capability of an inactivated lineage 1 vaccine (Equip WNV) to protect against natural infections from the Nea Santa-Greece-2010 lineage 2 strain. In total, 185 WNV-seronegative horses in Thessaloniki, Greece, were selected during 2 consecutive years (2011 and 2012); 140 were immunized, and 45 were used as controls. Horses were examined for signs compatible with WNV infection. Neutralizing antibody titers against the Greek strain and the PaAn001/France lineage 1 strain were determined in immunized horses. WNV circulation was detected during both years in the study area. It was estimated that 37% and 27% of the horses were infected during 2011 and 2012, respectively. Three control animals developed clinical signs, and the WNV diagnosis was confirmed. Signs related to WNV infection were not observed in the vaccinated animals. The nonvaccinated animals had a 7.58% ± 1.82% higher chance of exhibiting signs than immunized animals (P < 0.05). Neutralizing antibodies raised against both strains in all immunized horses were detectable 1 month after the initial vaccination course. The cross-protective capacity of the lowest titer (1:40) was evident in 19 animals which were subsequently infected and did not exhibit signs. Neutralizing antibodies were detectable until the annual booster, when strong anamnestic responses were observed (geometrical mean titer ratio [GMTR] for lineage 1 of 30.2; GMTR for lineage 2 of 27.5). The results indicate that Equip WNV is capable of inducing cross-protection against natural infections from a virulent lineage 2 WNV strain in horses. PMID:26178384

  16. Immediately and with all available means: the Dutch Red Cross and the field hospital on behalf of the Netherlands Voluntary Legion in WWII.

    PubMed

    van Bergen, Leo

    2009-01-01

    Medical neutrality is one of the main principles of medical-humanitarian aid, and certainly of Red Cross aid. But how does this work in times of foreign occupation? Is it even possible then, or does it almost automatically lead to collaboration? The Dutch example of 1940-1945 gives some insight into this problem. Abandoning its post would end the aid the Dutch Red Cross (DRC) gave, so it was decided to stay in business. This, however, led to adherence to German orders, given not for humanitarian, but for military-political reasons. Amongst other things, the DRC helped to equip a field hospital for Dutch volunteers to the Waffen-SS on the eastern front, so directly strengthening the German war effort. It was clear that the doctors and nurses of this field hospital would do next to nothing to help save Russian sick or wounded, and that, if necessary, they would have to fight alongside German and Dutch soldiers. PMID:19413158

  17. Polarized Scattering of Light for Arbitrary Magnetic Fields with Level-crossings from the Combination of Hyperfine and Fine Structure Splittings

    NASA Astrophysics Data System (ADS)

    Sowmya, K.; Nagendra, K. N.; Sampoorna, M.; Stenflo, J. O.

    2015-12-01

    Interference between magnetic substates of the hyperfine structure states belonging to different fine structure states of the same term influences the polarization for some of the diagnostically important lines of the Sun's spectrum, like the sodium and lithium doublets. The polarization signatures of this combined interference contain information on the properties of the solar magnetic fields. Motivated by this, in the present paper, we study the problem of polarized scattering on a two-term atom with hyperfine structure by accounting for the partial redistribution in the photon frequencies arising due to the Doppler motions of the atoms. We consider the scattering atoms to be under the influence of a magnetic field of arbitrary strength and develop a formalism based on the Kramers-Heisenberg approach to calculate the scattering cross section for this process. We explore the rich polarization effects that arise from various level-crossings in the Paschen-Back regime in a single scattering case using the lithium atomic system as a concrete example that is relevant to the Sun.

  18. A Modified Alderman-Grant Coil makes possible an efficient cross-coil probe for high field solid-state NMR of lossy biological samples

    NASA Astrophysics Data System (ADS)

    Grant, Christopher V.; Yang, Yuan; Glibowicka, Mira; Wu, Chin H.; Park, Sang Ho; Deber, Charles M.; Opella, Stanley J.

    2009-11-01

    The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the 1H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B 1 field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the 1H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194-241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed.

  19. Dynamic vehicle-track interaction in switches and crossings and the influence of rail pad stiffness - field measurements and validation of a simulation model

    NASA Astrophysics Data System (ADS)

    Pålsson, Björn A.; Nielsen, Jens C. O.

    2015-06-01

    A model for simulation of dynamic interaction between a railway vehicle and a turnout (switch and crossing, S&C) is validated versus field measurements. In particular, the implementation and accuracy of viscously damped track models with different complexities are assessed. The validation data come from full-scale field measurements of dynamic track stiffness and wheel-rail contact forces in a demonstrator turnout that was installed as part of the INNOTRACK project with funding from the European Union Sixth Framework Programme. Vertical track stiffness at nominal wheel loads, in the frequency range up to 20 Hz, was measured using a rolling stiffness measurement vehicle (RSMV). Vertical and lateral wheel-rail contact forces were measured by an instrumented wheel set mounted in a freight car featuring Y25 bogies. The measurements were performed for traffic in both the through and diverging routes, and in the facing and trailing moves. The full set of test runs was repeated with different types of rail pad to investigate the influence of rail pad stiffness on track stiffness and contact forces. It is concluded that impact loads on the crossing can be reduced by using more resilient rail pads. To allow for vehicle dynamics simulations at low computational cost, the track models are discretised space-variant mass-spring-damper models that are moving with each wheel set of the vehicle model. Acceptable agreement between simulated and measured vertical contact forces at the crossing can be obtained when the standard GENSYS track model is extended with one ballast/subgrade mass under each rail. This model can be tuned to capture the large phase delay in dynamic track stiffness at low frequencies, as measured by the RSMV, while remaining sufficiently resilient at higher frequencies.

  20. The prevalence and severity of injuries in field hockey drag flickers: a retrospective cross-sectional study.

    PubMed

    Ng, Leo; Sherry, Dorianne; Loh, Wei Bing; Sjurseth, Andreas Myhre; Iyengar, Shrikant; Wild, Catherine; Rosalie, Simon

    2016-09-01

    The drag flick is the preferred method of scoring during a penalty corner in field hockey. Performing the drag flick requires a combination of strength, coordination and timing, which may increase susceptibility to injuries. However, injury prevalence in drag flickers has not previously been investigated. Therefore, this study compared the injury prevalence and severity of lower limb and lower back injuries between drag flickers and non-drag flickers in field hockey. A total of 432 local, national and international adult field hockey players (242 males, 188 females) completed an online questionnaire to retrospectively determine the 3-month prevalence and severity of ankle, knee, hip and lower back injuries. Of this group, 140 self-identified as drag flickers and 292 as non-drag flickers. The results showed that drag flickers had significantly higher prevalence of hip (OR: 1.541; 95% CI: 1.014, 2.343) and lower back injury (OR: 1.564; 95% CI: 1.034, 2.365) compared to non-drag flickers. No significant differences were observed between drag flickers and non-drag flickers in injury prevalence at the ankle and knee. There were no significant between-group differences in injury severity scores. Overall, the prevalence of hip and lower back injuries was significantly higher in drag flickers compared to non-drag flickers. PMID:26760078

  1. Classical dynamics and localization of resonances in the high-energy region of the hydrogen atom in crossed fields.

    PubMed

    Schweiner, Frank; Main, Jörg; Cartarius, Holger; Wunner, Günter

    2015-01-01

    When superimposing the potentials of external fields on the Coulomb potential of the hydrogen atom, a saddle point (called the Stark saddle point) appears. For energies slightly above the saddle point energy, one can find classical orbits that are located in the vicinity of this point. We follow those so-called quasi-Penning orbits to high energies and field strengths, observing structural changes and uncovering their bifurcation behavior. By plotting the stability behavior of those orbits against energy and field strength, the appearance of a stability apex is reported. A cusp bifurcation, located in the vicinity of the apex, will be investigated in detail. In this cusp bifurcation, another orbit of similar shape is found. This orbit becomes completely stable in the observed region of positive energy, i.e., in a region of parameter space, where the Kepler-like orbits located around the nucleus are already unstable. By quantum mechanically exact calculations, we prove the existence of signatures in quantum spectra belonging to those orbits. Husimi distributions are used to compare quantum-Poincaré sections with the extension of the classical torus structure around the orbits. Since periodic orbit theory predicts that each classical periodic orbit contributes an oscillating term to photoabsorption spectra, we finally give an estimation for future experiments, which could verify the existence of the stable orbits. PMID:25679690

  2. Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles.

    PubMed

    Koroloff, Sophie N; Nevzorov, Alexander A

    2015-07-01

    Solid-state NMR (ssNMR) of oriented membrane proteins (MPs) is capable of providing structural and dynamic information at nearly physiological conditions. However, NMR experiments performed on oriented membrane proteins generally suffer from low sensitivity. Moreover, utilization of high-power radiofrequency (RF) irradiations for magnetization transfer may give rise to sample heating, thereby decreasing the efficiency of conventional cross-polarization schemes. Here we have optimized the recently developed repetitive cross-polarization (REP-CP) sequence (Tang et al., 2011) to further increase the magnetization transfer efficiency for membrane proteins reconstituted in magnetically aligned bicelles and compared its performance to single-contact Hartmann-Hahn cross-polarization (CP), CP-MOIST and the adiabatic transfer. It has been found that employing the REP-CP sequence at RF amplitudes of 19kHz instead of the commonly used higher RF fields (>45kHz) enhances the efficiency of REP-CP. An additional 30% signal can be obtained as compared to the previously published REP-CP, and 20% when compared to the re-optimized REP-CP at 50kHz RF fields. Moreover, the (15)N signal gain of low-power REP-CP was found to be 40% over the adiabatic CP and up to 80% over CP-MOIST. Thus, the low-power REP-CP sequence surpasses all of the previous CP schemes in addition of having the tremendous advantage of reducing the RF powers by a factor of seven, thereby preserving the liquid-like bicelle sample. By contrast, in purely static (NAL crystal) and semi-rigid systems (Pf1 phage), the adiabatic CP was found to be more effective. Periodic oscillations of the intensity profile (distinct from the transient oscillations) as a function of the CP contact time and B1 RF field strengths were observed during the REP-CP optimization with the oscillations becoming more pronounced with lower RF fields. Many-spin simulations were performed to explain the oscillations and their periodicity. PMID

  3. Cross-linking high-k fluoropolymer gate dielectrics enhances the charge mobility in rubrene field effect transistors

    NASA Astrophysics Data System (ADS)

    Adhikari, Jwala; Gadinski, Matthew; Wang, Qing; Gomez, Enrique

    2015-03-01

    Polymer dielectrics are promising materials where the chemical flexibility enables gate insulators with desired properties. For example, polar groups can be introduced to enhance the dielectric constant, although fluctuations in chain conformations at the semiconductor-dielectric interface can introduce energetic disorder and limit charge mobilities in thin-film transistors. Here, we demonstrate a photopatternable high-K fluoropolymer, poly(vinylidene fluoride-bromotrifluoroethylene) P(VDF-BTFE), with a dielectric constant between 8 and 11. The bromotrifluoroethylene moiety enables photo-crosslinking and stabilization of gate insulator films while also significantly enhancing the population of trans torsional conformations of the chains. Using rubrene single crystals as the active layer, charge mobilities exceeding 10 cm2/Vs are achieved in thin film transistors with cross-linked P(VDF-BTFE) gate dielectrics. We hypothesize that crosslinking reduces energetic disorder at the dielectric-semiconductor interface by suppressing segmental motion and controlling chain conformations of P(VDF-BTFE), thereby leading to approximately a three-fold enhancement in the charge mobility of rubrene thin-film transistors over devices incorporating uncross-linked dielectrics or silicon oxide. Center for Flexible Electronic, Penn State; The Dow Chemical Company.

  4. Retrieving both phase and amplitude information of Green's functions by ambient seismic wave field cross-correlation: A case study with a limestone mine induced seismic event

    NASA Astrophysics Data System (ADS)

    Kwak, S.; Song, S. G.; Kim, G.; Shin, J. S.

    2015-12-01

    Recently many seismologists have paid attention to ambient seismic field, which is no more referred as noise and called as Earth's hum, but as useful signal to understand subsurface seismic velocity structure. It has also been demonstrated that empirical Green's functions can be constructed by retrieving both phase and amplitude information from ambient seismic field (Prieto and Beroza 2008). The constructed empirical Green's functions can be used to predict strong ground motions after focal depth and double-couple mechanism corrections (Denolle et al. 2013). They do not require detailed subsurface velocity model and intensive computation for ground motion simulation. In this study, we investigate the capability of predicting long period surface waves by the ambient seismic wave field with a seismic event of Mw 4.0, which occurred with a limestone mine collapse in South Korea on January 31, 2015. This limestone-mine event provides an excellent opportunity to test the efficiency of the ambient seismic wave field in retrieving both phase and amplitude information of Green's functions due to the single force mechanism of the collapse event. In other words, both focal depth and double-couple mechanism corrections are not required for this event. A broadband seismic station, which is about 5.4 km away from the mine event, is selected as a source station. Then surface waves retrieved from the ambient seismic wave field cross-correlation are compared with those generated by the event. Our preliminary results show some potential of the ambient seismic wave field in retrieving both phase and amplitude of Green's functions from a single force impulse source at the Earth's surface. More comprehensive analysis by increasing the time length of stacking may improve the results in further studies. We also aim to investigate the efficiency of retrieving the full empirical Green's functions with the 2007 Mw 4.6 Odaesan earthquake, which is one of the strongest earthquakes occurred

  5. Geophysical investigation of the pressure field produced by water guns at a pond site in La Crosse, Wisconsin

    USGS Publications Warehouse

    Adams, Ryan F.; Morrow, William S.

    2015-01-01

    The July 2013 study consisted of three scenarios: fish behavior, single gun assessment, and experimental barrier evaluation. The fish behavior scenario simulated the pond conditions from previous studies. Two 80-in3 water guns were fired in the south end of the testing pond. Pressures essentially doubled from the testing of the single 80-in3 water gun. The single gun assessment scenario sought to replicate the setup of the 80-in3 scenario in September 2012, but with additional sensors to better define the pressure field. The 5-lb/in2 target pressure field continued to show a radius ranging from 40 to 45 feet, dependent on the pressure of the input air. The final scenario, the experimental barrier evaluation, showed that a two-dimensional continuous plane of 5 lb/in2 can be created between two 80-in3 water guns to a separation of 99 feet and a depth of 6.5 feet with 1,500 lb/in2 of input air.

  6. Near-field scanning optical microscopy cross-sectional measurements of crystalline GaAs solar cells

    SciTech Connect

    Herndon, M. K.; Bradford, W. C.; Collins, R. T.; Hawkins, B. E.; Kuech, T. F.; Friedman, D. J.; Kurtz, S. R.

    2000-07-03

    Near-field scanning optical microscopy (NSOM) was used to study cleaved edges of GaAs solar cell devices. Using visible light for excitation, the NSOM acquired spatially resolved traces of the photocurrent response across the various layers in the device. For excitation energies well above the band gap, carrier recombination at the cleaved surface had a strong influence on the photocurrent signal. Decreasing the excitation energy, which increased the optical penetration depth, allowed the effects of surface recombination to be separated from collection by the pn junction. Using this approach, the NSOM measurements directly observed the effects of a buried minority carrier reflector/passivation layer. (c) 2000 American Institute of Physics.

  7. An experimental study of the structure and acoustic field of a jet in a cross stream. [Ames 7-ft by 10-ft wind tunnel tests

    NASA Technical Reports Server (NTRS)

    Camelier, I.; Karamcheti, K.

    1976-01-01

    The plane of symmetry of a high speed circular jet was surveyed to measure the mean and turbulent velocity fields by using constant temperature hot wire anemometry. The intensity of the noise radiated from the jet was determined in the tunnel test section by utilizing the cross-correlation at a particular time delay between the signals of two microphones suitably located along a given direction. Experimental results indicate that the turbulent intensity inside the crossflow jet increases by a factor of (1 + 1/2) as compared to the turbulent intensity of the same jet under free conditions, with r indicating the ratio of the jet velocity by the cross stream velocity. The peak observed in the turbulence spectra obtained inside the potential core of the jet has a frequency that increases by the same factor with respect to the corresponding frequency measured in the case of the free jet. The noise radiated by the jet becomes more intense as the crossflow velocity increases. The measured acoustic intensity of the crossflow jet is higher than the value which would be expected from the increase of the turbulent intensity only.

  8. A TIPS-TPDO-tetraCN-Based n-Type Organic Field-Effect Transistor with a Cross-linked PMMA Polymer Gate Dielectric.

    PubMed

    Jung, Sungyeop; Albariqi, Mohammed; Gruntz, Guillaume; Al-Hathal, Thamer; Peinado, Alba; Garcia-Caurel, Enric; Nicolas, Yohann; Toupance, Thierry; Bonnassieux, Yvan; Horowitz, Gilles

    2016-06-15

    Recent improvement in the performance of the n-type organic semiconductors as well as thin gate dielectrics based on cross-linked polymers offers new opportunities to develop high-performance low-voltage n-type OFETs suitable for organic complementary circuits. Using TIPS-tetracyanotriphenodioxazine (TIPS-TPDO-tetraCN) and cross-linked poly(methyl methacrylate) (c-PMMA), respectively as n-type organic semiconductor and gate dielectric, linear regime field-effect mobility (1.8 ± 0.2) × 10(-2) cm(2) V(-1)s(-1), small spatial standard deviation of threshold voltage (∼0.1 V), and operating voltage less than 3 V are attainable with the same device structure and contact materials used commonly for p-type OFETs. Through comparative static and dynamic characterizations of c-PMMA and PMMA gate dielectrics, it is shown that both smaller thickness and larger relative permittivity of c-PMMA contributes to reduced operating voltage. Furthermore, negligible hysteresis brings evidence to small trap states in the semiconductor near gate dielectric of the n-type OFETs with c-PMMA. The use of TIPS-TPDO-tetraCN and c-PMMA is fully compatible with polyethylene terephthalate substrate, giving promise to various flexible applications. PMID:27188403

  9. Influence Of Secondary Electrons Produced From Plasma Material Interaction In Presence Of Crossed Electric And Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Sawlani, Kapil; Herzog, Joshua M.; Kwak, Joowon; Foster, John

    2012-10-01

    The electron energy distribution function (EEDF) plays a very important role in determining thruster efficiency as it determines various gas phase reaction rates. In Hall thrusters, secondary electron emission derived from the interaction of energetic electrons with ceramic channel surfaces influence the overall shape of the EEDF as well as determine the potential difference between the plasma and wall. The role of secondary electrons on the discharge operation of Hall thrusters is poorly understood. Experimentally, determining this effect is even more taxing as the secondary electron yield (SEY) varies drastically based on many parameters such as incident electron energies, flux and impact angle, and also on the surface properties such as temperature and roughness. The electron transport is also affected by the profile of the magnetic field, which is not uniform across the length of the accelerating channel. The goal of this work is to map out the variation of the EEDF and potential profile in response to the controlled introduction of secondary electrons. This data is expected to serve as a tool to validate and improve existing numerical models by providing boundary conditions and SEY for various situations that are encountered in Hall thrusters.

  10. Challenging the holy grail of hospital accreditation: A cross sectional study of inpatient satisfaction in the field of cardiology

    PubMed Central

    2010-01-01

    Background Subjective parameters such as quality of life or patient satisfaction gain importance as outcome parameters and benchmarks in health care. In many countries hospitals are now undergoing accreditation as mandatory or voluntary measures. It is believed but unproven that accreditations positively influence quality of care and patient satisfaction. The present study aims to assess in a defined specialty (cardiology) the relationship between patient satisfaction (as measured by the recommendation rate) and accreditation status. Methods Consecutive patients discharged from 25 cardiology units received a validated patient satisfaction questionnaire. Data from 3,037 patients (response rate > 55%) became available for analysis. Recommendation rate was used as primary endpoint. Different control variables such as staffing level were considered. Results The 15 accredited units did not differ significantly from the 10 non-accredited units regarding main hospital (i.e. staffing levels, no. of beds) and patient (age, gender) characteristics. The primary endpoint "recommendation rate of a given hospital" for accredited hospitals (65.6%, 95% Confidence Interval (CI) 63.4 - 67.8%) and hospitals without accreditation (65.8%, 95% CI 63.1 - 68.5%) was not significantly different. Conclusion Our results support the notion that - at least in the field of cardiology - successful accreditation is not linked with measurable better quality of care as perceived by the patient and reflected by the recommendation rate of a given institution. Hospital accreditation may represent a step towards quality management, but does not seem to improve overall patient satisfaction. PMID:20459873

  11. The Application of a Car Confidence Feature for the Classification of Cross-Roads Using Conditional Random Fields

    NASA Astrophysics Data System (ADS)

    Kosov, S.; Rottensteiner, F.; Heipke, C.; Leitloff, J.; Hinz, S.

    2013-10-01

    The precise classification and reconstruction of crossroads from multiple aerial images is a challenging problem in remote sensing. We apply the Conditional Random Fields (CRF) approach to this problem, a probabilistic model that can be used to consider context in classification. A simple appearance-based model is combined with a probabilistic model of the co-occurrence of class label at neighbouring image sites to distinguish classes that are relevant for scenes containing crossroads. The parameters of these models are learnt from training data. We use multiple overlap aerial images to derive a digital surface model (DSM) and a true orthophoto without moving cars. From the DSM and the orthophoto we derive feature vectors that are used in the classification. Within our framework we make use of a car detector based on support vector machines (SVM), which delivers car probability values. These values are used as additional feature to support the classification when the road surface is occluded by static cars. Our approach is evaluated on a dataset of airborne photos of an urban area by a comparison of the results to reference data. The evaluation is performed for images of different resolution. The method is shown to produce promising results when using the car probability values and higher image resolution.

  12. Risk assessment, cross-resistance potential, and biochemical mechanism of resistance to emamectin benzoate in a field strain of house fly (Musca domestica Linnaeus).

    PubMed

    Khan, Hafiz Azhar Ali; Akram, Waseem; Khan, Tiyyabah; Haider, Muhammad Saleem; Iqbal, Naeem; Zubair, Muhammad

    2016-05-01

    Reduced sensitivity to insecticides in insect pests often results in control failures and increases in the dose and frequency of applications, ultimately polluting the environment. Reduced sensitivity to emamectin benzoate, a broad-spectrum agrochemical belonging to the avermectin group of pesticides, was reported in house flies (Musca domestica L.) collected from Punjab, Pakistan, in 2013. The aim of the present study was to investigate the risk for resistance development, biochemical mechanism, and cross-resistance potential to other insecticides in an emamectin benzoate selected (EB-SEL) strain of house flies. A field-collected strain showing reduced sensitivity to emamectin was re-selected in the laboratory for five consecutive generations and compared with a laboratory susceptible (Lab-Susceptible) reference strain, using bioassays. The field strain showed rapid development of resistance to emamectin (resistance ratio (RR) increased from 35.15 to 149.26-fold) as a result of selection experiments; however, resistance declined when the selection pressure uplifted. The EB-SEL strain showed reduction in resistance to abamectin, indoxacarb, and thiamethoxam. The results of synergism experiments using piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) enzyme inhibitors and biochemical analyses revealed that the metabolic resistance mechanism was not responsible in developing emamectin resistance in the EB-SEL strain. In conclusion, the risk for the rapid development of emamectin resistance under continuous selection pressure suggests using a multifaceted integrated pest management approach for house flies. Moreover, the instable nature of emamectin resistance in the EB-SEL strain and lack of cross-resistance to other insecticides provide windows for the rotational use of insecticides with different modes of action. This will ultimately reduce emamectin selection pressure and help improving management programs for house flies without polluting the

  13. Balancing cross-sections combining field work and remote sensing data using LithoTect software in the Zagros fold-and-thrust belt, N Iraq.

    NASA Astrophysics Data System (ADS)

    Reif, Daniel; Grasemann, Bernhard; Lockhart, Duncan

    2010-05-01

    The Zagros fold-and-thrust belt has formed in detached Phanerozoic sedimentary cover rocks above a shortened crystalline Precambrian basement and evolved through the Late Cretaceous to Miocene collision between the Arabian and Eurasian plate, during which the Neotethys oceanic basin was closed. Deformation is partitioned in SW directed folding and thrusting of the sediments and NW-SE to N-S trending dextral strike slip faults. The sub-cylindrical doubly-plunging fold trains with wavelengths of 5 - 10 km host more than half of the world's hydrocarbon reserves in mostly anticlinal traps. Generally the Zagros is divided into three NW-SE striking tectonic units: the Zagros Imbricate Zone, the Zagros Simply Folded Belt and the Zagros Foredeep. This work presents a balanced cross-section through the Simply Folded Belt, NE of the city of Erbil (Kurdistan, Iraq). The regional stratigraphy comprises mainly Cretaceous to Cenozoic folded sediments consisting of massive, carbonate rocks (limestones, dolomites), reacting as competent layers during folding compared to the incompetent behavior of interlayered siltstones, claystones and marls. Although the overall security situation in Kurdistan is much better than in the rest of Iraq, structural field mapping was restricted to asphalt streets, mainly because of the contamination of the area with landmines and unexploded ordnance. In order to extend the structural measurements statistically over the investigated area, we used a newly developed software tool (www.terramath.com) for interactive structural mapping of spatial orientations (i.e. dip direction and dip angles) of the sedimentary beddings from digital elevation models. Structural field data and computed measurements where integrated and projected in NE-SW striking balanced cross-sections perpendicular to the regional trend of the fold axes. We used the software LithoTect (www.geologicsystems.com) for the restoration of the cross-sections. Depending on the interpretation

  14. South-to-North, cross-disciplinary training in global health practice: ten years of lessons learned from an infectious disease field course in Jamaica.

    PubMed

    Scarlett, Henroy P; Nisbett, Richard A; Stoler, Justin; Bain, Brendan C; Bhatta, Madhav P; Castle, Trevor; Harbertson, Judith; Brodine, Stephanie K; Vermund, Sten H

    2011-09-01

    Global commerce, travel, and emerging and resurging infectious diseases have increased awareness of global health threats and opportunities for collaborative and service learning. We review course materials, knowledge archives, data management archives, and student evaluations for the first 10 years of an intensive summer field course in infectious disease epidemiology and surveillance offered in Jamaica. We have trained 300 students from 28 countries through collaboration between the University of the West Indies and U.S. partner universities. Participants were primarily graduate students in public health, but also included health professionals with terminal degrees, and public health nurses and inspectors. Strong institutional synergies, committed faculty, an emphasis on scientific and cultural competencies, and use of team-based field research projects culminate in a unique training environment that provides participants with career-developing experiences. We share lessons learned over the past decade, and conclude that South-to-North leadership is critical in shaping transdisciplinary, cross-cultural, global health practice. PMID:21896794

  15. [Shaping the future of vocational rehabilitation of adults: eight fields of action as starting points for a cross-actor innovation process].

    PubMed

    Riedel, H-P; Ellger-Rüttgardt, S; Karbe, H; Niehaus, M; Rauch, A; Schian, H-M; Schmidt, C; Schott, T; Schröder, H; Spijkers, W; Wittwer, U

    2009-12-01

    Established by the Federal Ministry of Labour and Social Affairs (BMAS) in October 2007, the Scientific Expert Group RehaFutur had been commissioned to elaborate cornerstones for the medium- and long-term development of vocational rehabilitation of adults with disabilities (re-integration). Initial questions inter alia were as follows: Which function should vocational rehabilitation have in a service- and knowledge-oriented working world that will increasingly be affected by demographic change? How can disabled persons' right to occupational participation by way of vocational rehabilitation, a right stipulated both under the German constitution and in German law, be realized as needed also in the future? Various fields of action have been derived on the basis, for one, of an investigation of the factors, social law, social and education policy as well as European, influencing vocational rehabilitation and, for the other, of an evaluation of current labour market and demographic developments. Dealt with in the fields of action outlined are the aspects: equitable opportunities of access, developmental and needs orientation, closeness to the real occupational and working world, as well as the role of self-determination and self-responsibility. The fields of action are to be understood as framework concept for shaping a cross-actor innovation process. Sustainable vocational rehabilitation is characterized in particular by the fact that it is specifically targeted at promoting disabled persons' self-determination and self-responsibility actively using these in the process and that it strengthens an independent lifestyle, ensures social participation by inclusive structures; also, it facilitates continued participation in working life by ongoing education involving holistic development of professional and personal competencies oriented towards the individual's resources and potentials, safeguarding it by systematic networking with companies. The concept presented for

  16. Evaluation of the Cross-Protective Efficacy of a Chimeric Porcine Reproductive and Respiratory Syndrome Virus Constructed Based on Two Field Strains.

    PubMed

    Shabir, Nadeem; Khatun, Amina; Nazki, Salik; Kim, Bumseok; Choi, Eun-Jin; Sun, Dong; Yoon, Kyoung-Jin; Kim, Won-Il

    2016-01-01

    One of the major hurdles to porcine reproductive and respiratory syndrome (PRRS) vaccinology is the limited or no cross-protection conferred by current vaccines. To overcome this challenge, a PRRS chimeric virus (CV) was constructed using an FL12-based cDNA infectious clone in which open reading frames (ORFs) 3-4 and ORFs 5-6 were replaced with the two Korean field isolates K08-1054 and K07-2273,respectively. This virus was evaluated as a vaccine candidate to provide simultaneous protection against two genetically distinct PRRS virus (PRRSV) strains. Thirty PRRS-negative three-week-old pigs were divided into five groups and vaccinated with CV, K08-1054, K07-2273, VR-2332, or a mock inoculum. At 25 days post-vaccination (dpv), the pigs in each group were divided further into two groups and challenged with either K08-1054 or K07-2273. All of the pigs were observed until 42 dpv and were euthanized for pathological evaluation. Overall, the CV-vaccinated group exhibited higher levels of tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), and interleukin-12 (IL-12) expression and of serum virus-neutralizing antibodies compared with the other groups after vaccination and also demonstrated better protection levels against both viruses compared with the challenge control group. Based on these results, it was concluded that CV might be an effective vaccine model that can confer a broader range of cross-protection to various PRRSV strains. PMID:27556483

  17. Evaluation of the Cross-Protective Efficacy of a Chimeric Porcine Reproductive and Respiratory Syndrome Virus Constructed Based on Two Field Strains

    PubMed Central

    Shabir, Nadeem; Khatun, Amina; Nazki, Salik; Kim, Bumseok; Choi, Eun-Jin; Sun, Dong; Yoon, Kyoung-Jin; Kim, Won-Il

    2016-01-01

    One of the major hurdles to porcine reproductive and respiratory syndrome (PRRS) vaccinology is the limited or no cross-protection conferred by current vaccines. To overcome this challenge, a PRRS chimeric virus (CV) was constructed using an FL12-based cDNA infectious clone in which open reading frames (ORFs) 3–4 and ORFs 5–6 were replaced with the two Korean field isolates K08-1054 and K07-2273,respectively. This virus was evaluated as a vaccine candidate to provide simultaneous protection against two genetically distinct PRRS virus (PRRSV) strains. Thirty PRRS-negative three-week-old pigs were divided into five groups and vaccinated with CV, K08-1054, K07-2273, VR-2332, or a mock inoculum. At 25 days post-vaccination (dpv), the pigs in each group were divided further into two groups and challenged with either K08-1054 or K07-2273. All of the pigs were observed until 42 dpv and were euthanized for pathological evaluation. Overall, the CV-vaccinated group exhibited higher levels of tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), and interleukin-12 (IL-12) expression and of serum virus-neutralizing antibodies compared with the other groups after vaccination and also demonstrated better protection levels against both viruses compared with the challenge control group. Based on these results, it was concluded that CV might be an effective vaccine model that can confer a broader range of cross-protection to various PRRSV strains. PMID:27556483

  18. Tracking and understanding volcanic emissions through cross-disciplinary integration of field, textural, geochemical and geophysical data: A textural working group. (Invited)

    NASA Astrophysics Data System (ADS)

    gurioli, L.

    2013-12-01

    Relating magma ascent to eruption style using information preserved in pyroclastic deposits is a major challenge in modern volcanology. Because magma ascent and fragmentation are inaccessible to direct observation, one way to obtain quantitative information for conduit dynamics is through textural quantification of the sampled products (i.e., full definition of the rock vesicle and crystal properties). Many workers have shown that quantification of vesicle and crystal size distributions yields valuable insights into the processes that created the pyroclasts. However, the physical characteristics of individual pyroclasts must not be considered in isolation from information regarding: (i) the deposits from which they are taken; (ii) their chemistry; (iii) geophysical signatures of the related explosive events; and (iv) results from petrological and/or analogue experiments. As a result, attempts to understand eruption dynamics have increasingly involved the coupling of traditional field and sample-return analyses with geophysical measurements made synchronous with sample collection. In spite of this progress, we remain far from developing a definitive methods that allows us to sample, correlate and/or compare the multitude of parameters that can be measured at an actively building field deposits. As a result, no study has yet been able to correlate all derivable textural parameters with the full range of available multidisciplinary data. To discuss these issues, a working group met during 6-7 November 2012 at the Maison International of the Université Blaise Pascal (Clermont-Ferrand, France). The workshop was supported by the European Science Foundation and was held under the title: 'Tracking and understanding volcanic emissions through cross-disciplinary integration: A textural working group'. Our main objective was to gather an advisory group to define measurements, methods, formats and standards to be applied to integration of geophysical and physical

  19. Cross-Cultural Psychology.

    ERIC Educational Resources Information Center

    Triandis, Harry C.; Brislin, Richard W.

    1984-01-01

    Provides references to the work of cross-cultural psychologists that can be integrated into regular undergraduate psychology courses. Discusses methodological problems, benefits, and difficulties of cross-cultural research. Reviews contributions of this field to the study of perception, cognition, motivation, interpersonal interaction, and group…

  20. Cross-Permeability of the Semisolid Region in Directional Solidification: A Combined Phase-Field and Lattice-Boltzmann Simulation Approach

    NASA Astrophysics Data System (ADS)

    Böttger, B.; Haberstroh, C.; Giesselmann, N.

    2016-01-01

    Based on the results of microstructure simulations, fluid flow through the semisolid region during directional solidification of the technical Ni-base alloy 718 has been studied. Three-dimensional microstructures at different positions in the semisolid region were obtained by using a multicomponent multiphase-field model that was online coupled to a commercial thermodynamic database. For the range of five different primary dendrite distances λ 1 between 50 µm and 250 µm, the flow velocity and the permeability perpendicular to the dendrite growth direction was evaluated by using a proprietary Lattice-Boltzmann model. The commercial CFD software ANSYS FLUENT was alternatively applied for reference. Consistent values of the average flow velocity along the dendrites were obtained for both methods. From the results of the fluid flow simulations, the cross-permeability was evaluated as a function of temperature and fraction liquid for each of the five different primary dendrite distances λ 1. The obtained permeability values can be approximated by a single analytical function of the fraction liquid and λ 1 and are discussed and compared with known relations from the literature.

  1. Cross-arc geochemical variations in volcanic fields in Honduras C.A.: progressive changes in source with distance from the volcanic front

    NASA Astrophysics Data System (ADS)

    Patino, Lina C.; Carr, Michael J.; Feigenson, Mark D.

    A geochemical traverse across Honduras reveals the heterogeneity of the mantle underneath Central America. Alkali basalts from Lake Yojoa (170km behind the front) have low 87Sr/86Sr but high La/Yb, and elevated incompatible trace element abundances, consistent with derivation from a normal mid-ocean ridge basalt source mantle via low degrees of melting. These lavas lack evidence for an enriched source thought to be intermingled with normal mid-ocean ridge basalt source mantle beneath most of Central America. The amplitude of the subducted slab signature decreases smoothly with distance from the volcanic front. Lavas from Zacate Grande, the area nearest to the volcanic front (17 km behind the arc), display large ion lithophile element enrichment and high field strength element depletion indicating the involvement of subducted material in magma genesis. Components of subducted material are not evident in lavas from Lake Yojoa, the area furthest from the arc. Basalts and basaltic andesites from Tegucigalpa, 102 km behind the volcanic front, are geochemically intermediate between those of Lake Yojoa and Zacate Grande. The lavas from Tegucigalpa show a decreased influence of the subduction component, and are affected by assimilation-fractional crystallization processes at shallow depths. The gradual decrease in the subducted component from the volcanic front to Zacate Grande, Tegucigalpa and finally Lake Yojoa contrasts with the abrupt decrease documented for southeast Guatemala, the only other area in Central America where a cross-arc transect has been studied.

  2. Breaking The Quasar L-z Degeneracy Using PDF-weighted Quasar-galaxy Cross-correlations In Deep, Wide NASA Fields

    NASA Astrophysics Data System (ADS)

    Ball, Nicholas M.; Myers, A. D.; White, M.; Hickox, R. C.; Brunner, R. J.

    2010-01-01

    We present a new method for measuring the two-point correlation function, as described by Myers, White, and Ball (2009). The method is an augmentation of previous techniques that use a heterogeneous set of spectroscopic objects to anchor the distance scale, and a well-controlled set of photometric detections to reduce noise. Our new approach weights by the information present in the full photometric redshift probability density function (PDF) to dramatically improve the clustering signal. For instance, an initial test yielded a factor of 5 improvement for quasar clustering in the Sloan Digital Sky Survey. The extra signal arises because we neither express the photometric redshift as a single value nor assign a simplified PDF functional form such as a single Gaussian. Our technique is generally applicable and should be particularly useful where complex spectroscopic data sets (e.g., BOSS) are overlapped by deep photometry (e.g., Pan-STARRS, DES, or LSST). Our method depends only on photometric detections in a single survey, but additional multi-wavelength data can be used to refine the information in the PDF weighting. This makes our approach also highly suited to regions of the sky where deep, multiwavelength space surveys overlap ground-based spectroscopy (e.g., COSMOS or the Bootes Survey). We assign photometric redshift PDFs to photometrically classified galaxies detected in the optical component of COSMOS, and use PDF weights to cross-correlate them against a spectroscopically confirmed AGN sample. We also report on similar results in the Bootes Survey. The deep spectroscopy and photometry in fields such as COSMOS and Bootes will allow new investigations of how AGN cluster as a function of luminosity and type, potentially breaking the so-called L-z degeneracy. Finally, we address the often computationally intensive requirements of utilizing full PDFs. This research was funded in part by NASA ADP grant NNX08AJ28G.

  3. Comparison of LFP-based and spike-based spectro-temporal receptive fields and cross-correlation in cat primary auditory cortex.

    PubMed

    Eggermont, Jos J; Munguia, Raymundo; Pienkowski, Martin; Shaw, Greg

    2011-01-01

    Multi-electrode array recordings of spike and local field potential (LFP) activity were made from primary auditory cortex of 12 normal hearing, ketamine-anesthetized cats. We evaluated 259 spectro-temporal receptive fields (STRFs) and 492 frequency-tuning curves (FTCs) based on LFPs and spikes simultaneously recorded on the same electrode. We compared their characteristic frequency (CF) gradients and their cross-correlation distances. The CF gradient for spike-based FTCs was about twice that for 2-40 Hz-filtered LFP-based FTCs, indicating greatly reduced frequency selectivity for LFPs. We also present comparisons for LFPs band-pass filtered between 4-8 Hz, 8-16 Hz and 16-40 Hz, with spike-based STRFs, on the basis of their marginal frequency distributions. We find on average a significantly larger correlation between the spike based marginal frequency distributions and those based on the 16-40 Hz filtered LFP, compared to those based on the 4-8 Hz, 8-16 Hz and 2-40 Hz filtered LFP. This suggests greater frequency specificity for the 16-40 Hz LFPs compared to those of lower frequency content. For spontaneous LFP and spike activity we evaluated 1373 pair correlations for pairs with >200 spikes in 900 s per electrode. Peak correlation-coefficient space constants were similar for the 2-40 Hz filtered LFP (5.5 mm) and the 16-40 Hz LFP (7.4 mm), whereas for spike-pair correlations it was about half that, at 3.2 mm. Comparing spike-pairs with 2-40 Hz (and 16-40 Hz) LFP-pair correlations showed that about 16% (9%) of the variance in the spike-pair correlations could be explained from LFP-pair correlations recorded on the same electrodes within the same electrode array. This larger correlation distance combined with the reduced CF gradient and much broader frequency selectivity suggests that LFPs are not a substitute for spike activity in primary auditory cortex. PMID:21625385

  4. Velocity field of a round jet in a cross flow for various jet injection angles and velocity ratios. [Langley V/STOL tunnel

    NASA Technical Reports Server (NTRS)

    Fearn, R. L.; Weston, R. P.

    1979-01-01

    A subsonic round jet injected from a flat plate into a subsonic crosswind of the same temperature was investigated. Velocity and pressure measurements in planes perpendicular to the path of the jet were made for nominal jet injection angles of 45 deg, 60 deg, 75 deg, 90 deg, and 105 deg and for jet/cross flow velocity ratios of four and eight. The velocity measurements were obtained to infer the properties of the vortex pair associated with a jet in a cross flow. Jet centerline and vortex trajectories were determined and fit with an empirical equation that includes the effects of jet injection angle, jet core length, and jet/cross flow velocity ratios.

  5. Validation Analyses of IEAF-2001 Activation Cross-Section Data for SS-316 and F82H Steels Irradiated in a White d-Li Neutron Field

    NASA Astrophysics Data System (ADS)

    Simakov, S. P.; Fischer, U.; v. Möllendorff, U.; Schmuck, I.; Tsige-Tamirat, H.; Wilson, P. P. H.

    2005-05-01

    The evaluated intermediate-energy activation cross-section library IEAF-2001 has been tested against integral experiments with SS-316 and F82H steels exposed to a white neutron flux spectrum extending up to 55 MeV. By making use of the ALARA inventory code the expected γ-active product nuclide inventories were calculated and compared with the measured one. It was found that IEAF-2001 reasonably agrees with experimental data for most of the detected radioisotopes. The reasons for some larger disagreements were found to be the uncertainty of the sample elemental composition, non-validated neutron activation reaction cross sections, and sequential charge particle reactions.

  6. False Cross

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The asterism formed by the four stars δ and κ Velorum, and ɛ and ι Carinae, all of the second magnitude, which make up a cross of about 10°×6°. It is so named because it is sometimes mistaken for the Southern Cross (Crux) by observers unfamiliar with the southern sky. There is a superficial resemblance, but Crux is more compact (about 7°×5°) and comprises rather brighter stars. The two crosses ca...

  7. Track and Field Guide including Cross Country, Pentathlon Scoring Tables and Rules for Intercollegiate Meets and Championships with Official Rules. Janauary 1974-January 1976.

    ERIC Educational Resources Information Center

    Thompson, Donnis H., Ed.

    This guide includes information on cross country running, pentathlon scoring tables, and rules for intercollegiate meets and championships, following an introductory portion on the organization's credo and standards. The first section covers track activities for children, coaching techniques, the benefits of weight training, and some practical…

  8. Is Authentic Cross-Cultural Collaboration Possible between Universities and Public Schools within a Professional Development School Model? Perceptions from the Field

    ERIC Educational Resources Information Center

    Parkinson, Debra D.; Muir Welsh, Kate

    2009-01-01

    In 2003, a state in the Rocky Mountain region combined the concept of partner schools (Goodlad, 1993) and the model of a professional development school (Holmes Group, 1986, 1995) to develop four university public school partnerships. This study asked two guiding questions: Is authentic cross-cultural collaboration possible between a university…

  9. Properties of the static NMR response of a confined thin nematic film of 5CB-d2 under crossed electric and magnetic fields: theory and experiments.

    PubMed

    Véron, A; Sugimura, A; Luckhurst, G R; Martins, A F

    2012-11-01

    This work describes an investigation of the static (or quasistatic) nuclear magnetic resonance (NMR) response in a nematic liquid crystal confined between two planar conducting plates and subject to a magnetic field and an electric field produced by a difference of voltage applied on the plates. Deuterium NMR spectroscopy of 4-pentyl-d(2)-4'-cyanobiphenyl (5CB-d(2)) under these conditions has revealed a voltage dependent inhomogeneous director distribution for a particular narrow range of voltages and for a fixed magnetic field (that of the spectrometer). In the ideal setup the two plates are assumed to be rigorously parallel, so that a difference of voltage applied on the plates leads to a constant electric field normal to them. When the magnetic field is parallel to the plates (orthogonal geometry) there exists a threshold value of the electric field for which the effect of both fields exactly compensate; moreover, for stronger electric field the director aligns with the electric field while for weaker electric field the director aligns with the magnetic field. If there is a lack of parallelism between the two plates, the electric field becomes inhomogeneous so that it may be larger than the threshold value in some region of the sample and smaller in the remaining part of the sample. In that case the director will adopt essentially two orientations within the sample, namely, parallel or perpendicular to the magnetic field, and the position of the frontier between the two domains depends on the voltage. This feature is clearly shown by deuterium NMR spectra that exhibit a transfer of intensity between two quadrupolar doublets with increase in the applied voltage. The coexistence of two director populations occurs for a range of voltages that depends on the degree of nonparallelism; accordingly, an estimation of this range by NMR yields an experimental estimation of the lack of parallelism. A tiny tilt of the magnetic field (nonorthogonal geometry) entrains a

  10. Properties of the static NMR response of a confined thin nematic film of 5CB-d2 under crossed electric and magnetic fields: Theory and experiments

    NASA Astrophysics Data System (ADS)

    Véron, A.; Sugimura, A.; Luckhurst, G. R.; Martins, A. F.

    2012-11-01

    This work describes an investigation of the static (or quasistatic) nuclear magnetic resonance (NMR) response in a nematic liquid crystal confined between two planar conducting plates and subject to a magnetic field and an electric field produced by a difference of voltage applied on the plates. Deuterium NMR spectroscopy of 4-pentyl-d2-4'-cyanobiphenyl (5CB-d2) under these conditions has revealed a voltage dependent inhomogeneous director distribution for a particular narrow range of voltages and for a fixed magnetic field (that of the spectrometer). In the ideal setup the two plates are assumed to be rigorously parallel, so that a difference of voltage applied on the plates leads to a constant electric field normal to them. When the magnetic field is parallel to the plates (orthogonal geometry) there exists a threshold value of the electric field for which the effect of both fields exactly compensate; moreover, for stronger electric field the director aligns with the electric field while for weaker electric field the director aligns with the magnetic field. If there is a lack of parallelism between the two plates, the electric field becomes inhomogeneous so that it may be larger than the threshold value in some region of the sample and smaller in the remaining part of the sample. In that case the director will adopt essentially two orientations within the sample, namely, parallel or perpendicular to the magnetic field, and the position of the frontier between the two domains depends on the voltage. This feature is clearly shown by deuterium NMR spectra that exhibit a transfer of intensity between two quadrupolar doublets with increase in the applied voltage. The coexistence of two director populations occurs for a range of voltages that depends on the degree of nonparallelism; accordingly, an estimation of this range by NMR yields an experimental estimation of the lack of parallelism. A tiny tilt of the magnetic field (nonorthogonal geometry) entrains a notably

  11. Vertically aligned dust particles under the influence of crossed electric and magnetic fields in the sheath of a radio frequency discharge

    NASA Astrophysics Data System (ADS)

    Puttscher, M.; Melzer, A.

    2015-07-01

    We present experiments on two dust particles with a size of a few microns that are levitated in the sheath region of an rf discharge in the presence of an external magnetic field transverse to the sheath electric field. The two particles are vertically aligned due to the ion focusing effect. First, it is observed that the magnetic field causes a displacement of the dust particles either in the E → × B → - or in the opposite direction. Second, at a sufficiently large neutral gas pressure, the vertical alignment breaks up when the magnetic field strength is increased. The occurrence of this dissociation is described by the horizontal force balance on the two particles.

  12. Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross ...

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

    Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross Bracing Joint, Vertical Cross Bracing End Detail - Ceylon Covered Bridge, Limberlost Park, spanning Wabash River at County Road 900 South, Geneva, Adams County, IN

  13. Factory-based permethrin impregnation of uniforms: residual activity against Aedes aegypti and Ixodes ricinus in battle dress uniforms worn under field conditions, and cross-contamination during the laundering and storage process.

    PubMed

    Faulde, Michael K; Uedelhoven, Waltraud M; Malerius, Miriam; Robbins, Richard G

    2006-06-01

    The factory-based permethrin coating technique has only recently been developed. Consequently, no data are available on residual activity, laundering, and weathering resistance in impregnated battle dress uniforms (BDUs) worn under military deployment conditions, or on the cross-contamination potential of such uniforms. Herein, factory-impregnated BDUs worn-out during military deployment to Afghanistan were investigated for residual permethrin concentration, residual efficacy against arthropod vectors, and cross-contamination during laundering and storage. When compared with BDUs subjected to 50 defined washings using the U.S. Insect/Arthropod Repellent Fabric Treatment method, no significant differences in efficacy were observed against Aedes mosquitoes, but remaining knockdown activity in Ixodes ticks was significantly better in polymer-coated BDUs. BDUs impregnated by the polymer-coating method were found to be effective for the life of the uniform, ensuring protection of soldiers in the field from arthropod vectors, while causing less cross-contamination than those treated by the Insect/Arthropod Repellent Fabric Treatment method. PMID:16808123

  14. Complement-mediated neutralization of canine distemper virus in vitro: cross-reaction between vaccine Onderstepoort and field KDK-1 strains with different hemagglutinin gene characteristics.

    PubMed

    Mochizuki, Masami; Motoyoshi, Megumi; Maeda, Ken; Kai, Kazunari

    2002-07-01

    The properties of neutralization of antigens of canine distemper virus Onderstepoort and a recent field isolate, KDK-1, were investigated with strain-specific dog sera. A conventional neutralization assay indicated antigenic dissimilarity between the strains; however, when guinea pig complement was included in the reaction mixture, the strains were neutralized with not only the homologous but also the heterologous antibodies. PMID:12093697

  15. Non-perturbative measurement of cross-field thermal diffusivity reduction at the O-point of 2/1 neoclassical tearing mode islands in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Bardóczi, L.; Rhodes, T. L.; Carter, T. A.; Crocker, N. A.; Peebles, W. A.; Grierson, B. A.

    2016-05-01

    Neoclassical tearing modes (NTMs) often lead to the decrease of plasma performance and can lead to disruptions, which makes them a major impediment in the development of operating scenarios in present toroidal fusion devices. Recent gyrokinetic simulations predict a decrease of plasma turbulence and cross-field transport at the O-point of the islands, which in turn affects the NTM dynamics. In this paper, a heat transport model of magnetic islands employing spatially non-uniform cross-field thermal diffusivity (χ⊥) is presented. This model is used to derive χ⊥ at the O-point from electron temperature data measured across 2/1 NTM islands in DIII-D. It was found that χ⊥ at the O-point is 1 to 2 orders of magnitude smaller than the background plasma transport, in qualitative agreement with gyrokinetic predictions. As the anomalously large values of χ⊥ are often attributed to turbulence driven transport, the reduction of the O-point χ⊥ is consistent with turbulence reduction found in recent experiments. Finally, the implication of reduced χ⊥ at the O-point on NTM dynamics was investigated using the modified Rutherford equation that predicts a significant effect of reduced χ⊥ at the O-point on NTM saturation.

  16. Physical analysis on improving the recovery accuracy of the Earth's gravity field by a combination of satellite observations in along-track and cross-track directions

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Hsu, Hou-Tse; Zhong, Min; Yun, Mei-Juan

    2014-10-01

    The physical investigations on the accuracy improvement to the measurement of the Earth's gravity field recovery are carried out based on the next-generation Pendulum-A/B out-of-plane twin-satellite formation in this paper. Firstly, the Earth's gravity field complete up to degree and order 100 is, respectively, recovered by the collinear and pendulum satellite formations using the orbital parameters of the satellite and the matching accuracies of key payloads from the twin GRACE satellites. The research results show that the accuracy of the Earth's gravity field model from the Pendulum-A/B satellite formation is about two times higher than from the collinear satellite formation, and the further improvement of the determination accuracy of the Earth's gravity field model is feasible by the next-generation Pendulum-A/B out-of-plane twin-satellite formation. Secondly, the Earth's gravity field from Pendulum-A/B complete up to degree and order 100 is accurately recovered based on the orbital parameters of the satellite (e.g., an orbital altitude of 400 km, an intersatellite range of 100 km, an orbital inclination of 89° and an orbital eccentricity of 0.001), the matching accuracies of space-borne instruments (e.g. 10-6 m in the intersatellite range, 10-3 m in the orbital position, 10-6 m/s in orbital velocity, and 10-11 m/s2 in non-conservative force), an observation time of 30 days and a sampling interval of 10 s. The measurement accuracy of the Earth's gravity field from the next-generation Pendulum-A/B out-of-plane twin-satellite formation is full of promise for being improved by about 10 times compared with that from the current GRACE satellite formation. Finally, the physical requirements for the next-generation Pendulum-A/B out-of-plane twin-satellite formation are analyzed, and it is proposed that the satellite orbital altitude be preferably designed to be close to 400±50 km and the matching precision of key sensors from the Pendulum-A/B mission be about one

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  18. Co-propagation of two optical fields in a semiconductor doped dispersion decreasing fiber and modulational instability induced by cross-phase modulation

    NASA Astrophysics Data System (ADS)

    Nithyanandan, K.; Porsezian, K.

    2016-01-01

    A theoretical study of cross phase modulation (XPM) induced modulational instability (MI) in a semiconductor doped dispersion decreasing fiber (SD-DDF) is presented. The equation is suitably modeled to account for the saturable nonlinearity and dispersion decreasing nature of the fiber. Using linear stability analysis, the exact dispersion relation is obtained and MI analysis is performed. We exclusively analyze the influence of the walk-off effect in the instability spectra of an SD-DDF and an optimum walk-off parameter is identified. The contrasting nature of action of decreasing dispersion and saturating nonlinearity is emphasized, such that the former enhances and the latter suppresses bandwidth. Thus, a suitable combination of the two physical effects can enable one to realize the desired bandwidth profile. MI analysis in the normal dispersion regime is compared with the anomalous counterpart as well as the conventional single pump case and the results are tabulated. Also, our analytical results are compared through direct numerical simulation and the results are documented. Thus, we present a comprehensive study of XPM-MI in an SD-DDF and the influence of various physical effects on the MI dynamics.

  19. Anti-Kibble-Zurek Behavior in Crossing the Quantum Critical Point of a Thermally Isolated System Driven by a Noisy Control Field.

    PubMed

    Dutta, Anirban; Rahmani, Armin; Del Campo, Adolfo

    2016-08-19

    We show that a thermally isolated system driven across a quantum phase transition by a noisy control field exhibits anti-Kibble-Zurek behavior, whereby slower driving results in higher excitations. We characterize the density of excitations as a function of the ramping rate and the noise strength. The optimal driving time to minimize excitations is shown to scale as a universal power law of the noise strength. Our findings reveal the limitations of adiabatic protocols such as quantum annealing and demonstrate the universality of the optimal ramping rate. PMID:27588838

  20. The Cenozoic fold-and-thrust belt of Eastern Sardinia: Evidences from the integration of field data with numerically balanced geological cross section

    NASA Astrophysics Data System (ADS)

    Arragoni, S.; Maggi, M.; Cianfarra, P.; Salvini, F.

    2016-06-01

    Newly collected structural data in Eastern Sardinia (Italy) integrated with numerical techniques led to the reconstruction of a 2-D admissible and balanced model revealing the presence of a widespread Cenozoic fold-and-thrust belt. The model was achieved with the FORC software, obtaining a 3-D (2-D + time) numerical reconstruction of the continuous evolution of the structure through time. The Mesozoic carbonate units of Eastern Sardinia and their basement present a fold-and-thrust tectonic setting, with a westward direction of tectonic transport (referred to the present-day coordinates). The tectonic style of the upper levels is thin skinned, with flat sectors prevailing over ramps and younger-on-older thrusts. Three regional tectonic units are present, bounded by two regional thrusts. Strike-slip faults overprint the fold-and-thrust belt and developed during the Sardinia-Corsica Block rotation along the strike of the preexisting fault ramps, not affecting the numerical section balancing. This fold-and-thrust belt represents the southward prosecution of the Alpine Corsica collisional chain and the missing link between the Alpine Chain and the Calabria-Peloritani Block. Relative ages relate its evolution to the meso-Alpine event (Eocene-Oligocene times), prior to the opening of the Tyrrhenian Sea (Tortonian). Results fill a gap of information about the geodynamic evolution of the European margin in Central Mediterranean, between Corsica and the Calabria-Peloritani Block, and imply the presence of remnants of this double-verging belt, missing in the Southern Tyrrhenian basin, within the Southern Apennine chain. The used methodology proved effective for constraining balanced cross sections also for areas lacking exposures of the large-scale structures, as the case of Eastern Sardinia.

  1. Permanent monitoring of the high-atmosphere wind field over Europe - Height-time cross sections of the upper mesopause wind fields (prevailing and semidiurnal tidal components) obtained from LF D1 measurements in 1991 at the Collm Geophysical Observator

    NASA Astrophysics Data System (ADS)

    Schminder, R.; Kuerschner, D.

    Recordings of the upper mesopause wind field over Central Europe during 1991 using daily D1 radio measurements in the LF range are reviewed. Emphasis is given to wind measurements made at the Collm Geophysical Observatory. The regression model used to evaluate the observations is described.

  2. Impact of development of population-based study in biomedical field on laws and regulations: a cross-strait experience on biobank development.

    PubMed

    Fan, Chien Te; Wu, Chunyan; Shi, Zhiyuan

    2008-12-01

    scenario crossing the Taiwan Strait. Also, mainly following the realm of comparative policy or legal approaches, the paper, learning from the fruits of this comparative study, tries to propose some recommendations for future legislative consideration by both mainland China & Taiwan. It's been this author's wish that, when establishing a large scale population based Biobank, the promotion of public trust shall be placed as the primary goal together with the emphasis on the supporting publicity and transparency on the administrative practices, so as to encourage the public participation in observing the principle of altruism and, in turns, benefit the future biomedicine development. PMID:19492726

  3. The impact of development of population-based study in the biomedical field on laws and regulations: a cross-strait experience on biobank development.

    PubMed

    Te, Fan Chien; Chunyan, Wu; Zhiyuan, Shi

    2012-06-01

    development scenario crossing the Taiwan Strait. Also, mainly following the realm of comparative policy or legal approaches, the paper learning from the fruits of this comparative study, tries to propose some recommendations for future legislative consideration by both mainland China and Taiwan. It's been this author's wish that, when establishing a large scale population based Biobank, the promotion of public trust shall be placed as the primary goal together with the emphasis on supporting publicity and transparency on the administrative practices, so as to encourage the public participation in observing the principle of altruism and, in turn, benefit the future biomedicine development. PMID:22924199

  4. Enhancing University Courses and Field Schools through Cross-cultural Exchange: Joint US-Bangladeshi Trips to the Ganges-Brahmaputra and Mississippi Deltas

    NASA Astrophysics Data System (ADS)

    Steckler, M. S.; Goodbred, S. L., Jr.; Lowes, S.; Gilligan, J. M.; Ackerly, B.; Ahmed, K. M.; Akhter, S. H.; Sousa, D.; Wilson, C.; Datta, D. K.; Roy, K.; Mondal, D. R.

    2014-12-01

    As part of an NSF PIRE grant, we have led four field trips for undergraduate, MS and PhD students to large deltaic systems. Three trips took US students to the Ganges-Brahmaputra (GB) delta in Bangladesh and one brought Bangladeshi faculty and students to the Mississippi (Miss.) delta in the US. An essential component in the learning process and overall experience of each trip was that ~2/5 of the participants were students and professors from Bangladesh. In all cases, the involvement of a substantial international cohort greatly broadened perspectives on the topics being covered. For example, in GBD the local geologic and cultural knowledge of the Bangladeshis deepened the learning and engagement of the US students, an outcome that was almost universally noted in student reviews. The trips received similar feedback from Bangladeshi participants, as they had an enthusiastic and engaged audience of peers from the US. Even for the Miss. delta trip, the Bangladeshis added a unique perspective from a nation that faces similar environmental issues. These overwhelmingly positive contributions have been experienced in several different contexts. Three trips were associated with US courses and run over Spring Break. One matched sustainable development undergrads at Columbia U. with geology undergrads from Dhaka U., and two others matched a mixed group of graduate and undergrad students from Vanderbilt U. with cohorts from Bangladesh. The fourth trip was a stand-alone Field School for PhD students from 14 US universities and mostly MS students from 4 Bangladeshi universities. The focus of each trip ranged from broader surveys of tectonic, fluvial and coastal processes to investigations of geology and people affected by tropical storms. Of particular interest was the success of mixing undergrad and graduate students in the Vanderbilt course, which centered on the intersection of social sciences, physical sciences, and engineering. In this case, undergrads engaged in a

  5. Interfacial insertion of a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) layer between the poly(3-hexyl thiophene) semiconductor and cross-linked poly(vinyl alcohol) insulator layer in organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Cruz-Cruz, Isidro; Tavares, Ana C. B.; Reyes-Reyes, Marisol; López-Sandoval, Román; Hümmelgen, Ivo A.

    2014-02-01

    The role of a thin layer of conductive poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT : PSS), inserted between the gate dielectric and the active layer in poly(3-hexylthiophene)-based transistors was investigated. The devices were fabricated in the bottom-gate top-contact geometry by using cross-linked poly(vinyl alcohol) as the dielectric, whereas the PEDOT : PSS layer was prepared by using an aged aqueous dispersion with addition of different amounts of dimethyl sulfoxide (DMSO) as a secondary dopant. Under these conditions, both a significant reduction in the number of electrically active traps at the interface with the semiconductor and an improvement in the field-effect mobility were obtained, whereas the low power consumption was preserved. The threshold voltage was also displaced by approximately -1 V.

  6. Perception of health risks of electromagnetic fields by MRI radiographers and airport security officers compared to the general Dutch working population: a cross sectional analysis

    PubMed Central

    2011-01-01

    Background The amount of exposure to electromagnetic fields (EMF) at work is mainly determined by an individual's occupation and may differ from exposure at home. It is, however, unknown how different occupational groups perceive possible adverse health effects of EMF. Methods Three occupational groups, the general Dutch working population (n = 567), airport security officers who work with metal detectors (n = 106), and MRI radiographers who work with MRI (n = 193), were compared on perceived risk of and positive and negative feelings towards EMF in general and of different EMF sources, and health concerns by using analyses of variances. Data were collected via an internet survey. Results Overall, MRI radiographers had a lower perceived risk, felt less negative, and more positive towards EMF and different sources of EMF than the general working population and the security officers. For security officers, feeling more positive about EMF was not significantly related to perceived risk of EMF in general or EMF of domestic sources. Feeling positive about a source did not generalize to a lower perceived risk, while negative feelings were stronger related to perceived risk. MRI radiographers had fewer health concerns regarding EMF than the other two groups, although they considered it more likely that EMF could cause physical complaints. Conclusions These data show that although differences in occupation appear to be reflected in different perceptions of EMF, the level of occupational exposure to EMF as such does not predict the perceived health risk of EMF. PMID:22070906

  7. A zero-equation turbulent electron transport model for cross-field migration and its implementation in a 2-D hybrid plasma Hall thruster simulation

    NASA Astrophysics Data System (ADS)

    Cappelli, Mark; Young, Chris; Cha, Eusnun; Fernandez, Eduardo; Stanford Plasma Physics Laboratory Collaboration; Eckerd College Collaboration

    2015-09-01

    We present a simple, zero-equation turbulence model for electron transport across the magnetic field of a plasma Hall thruster and integrate this model into 2-D hybrid particle-in-cell simulations of a 72 mm diameter laboratory thruster operating at 400 W. The turbulent transport model is based on the assumption that the primary means of electron energy dissipation is the turbulent eddy cascade in the electron fluid to smaller scales. Implementing the model into 2-D hybrid simulations is relatively straightforward and leverages the existing framework for solving the electron fluid equations. We find that the model captures the strong axial variation in the mobility seen in experiments. In particular, it predicts the existence of a strong transport barrier which anchors the region of plasma acceleration. The model also captures the time-averaged experimental discharge current and its fluctuations due to ionization instabilities. We observe quantitative agreement with recent laser induced fluorescence measurements of time-averaged xenon ion and neutral velocities along the channel centerline. This work was supported by the Air Force Office of Scientific Research.

  8. The impact of exposure to radio frequency electromagnetic fields on chronic well-being in young people--a cross-sectional study based on personal dosimetry.

    PubMed

    Heinrich, Sabine; Thomas, Silke; Heumann, Christian; von Kries, Rüdiger; Radon, Katja

    2011-01-01

    A possible influence of radio frequency electromagnetic field (RF EMF) exposure on health outcomes was investigated in various studies. The main problem of previous studies was exposure assessment. The aim of our study was the investigation of a possible association between RF EMF and chronic well-being in young persons using personal dosimetry. 3022 children and adolescents were randomly selected from the population registries of four Bavarian cities in Germany (participation 52%). Personal interview data on chronic symptoms, socio-demographic characteristics and potential confounders were collected. A 24-h radio frequency exposure profile was generated using a personal dosimeter. Exposure levels over waking hours were expressed as mean percentage of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference level. Half of the children and nearly every adolescent owned a mobile phone which was used only for short durations per day. Measured exposure was far below the current ICNIRP reference levels. The most reported chronic symptom in children and adolescents was fatigue. No statistically significant association between measured exposure and chronic symptoms was observed. Our results do not indicate an association between measured exposure to RF EMF and chronic well-being in children and adolescents. Prospective studies investigating potential long-term effects of RF EMF are necessary to confirm our results. PMID:20619895

  9. In-situ experimental investigations of electron space-charge instabilities and noise mechanisms in a reentrant crossed-field amplifier via distributed-cathode emission and gated-beam injection

    SciTech Connect

    Ye, J.Z.; MacGregor, R.; Chan, C.; Ruden, T.E.

    1995-12-31

    Experimental investigations of the true physical conditions inside the crossed-field devices are of fundamental importance for the understanding of the operation of these devices and may lead to eventual improvement of the present tubes. At Northeastern University, tube research has taken up a combined approach of in situ plasma diagnostics and computer simulation using two frequency scaled CFA`s as test vehicles. A collection of temporal and time-averaged diagnostic techniques have been developed through the research. Probe measurements as well as device performance of the linear CFA and the beam-injected, reentrant CFA have been directly compared with computer simulation results from MASK and NEAMP codes. The authors have recently incorporated in their reentrant CFA a secondary emission cathode for the purpose of gaining insight on improving the noise performance of both military and commercial devices. It has long been speculated, and appears more so as a result of the improved diagnostic techniques, that the instabilities in the space charge cloud are the major source of noise in crossed-field devices. Long electron transit time facilitates large-scale energy exchanges between hub electrons and eliminates the condition for the classical Brillouin flow. Their time-averaged density measurements confirmed that electron cloud extends beyond that predicted by the classical theory; preliminary observations showed organized space charge oscillations for static operating regimes. These oscillations can interact with the applied RF drive signal at different levels resulting in noise on the RF circuit. Other instabilities associated with the cathode secondary emission and due to reentrant electrons are, among other factors, evaluated in terms of their contribution to the turbulent behavior via spatial probes that monitor the anode current, back bombardment current and space charge fluctuation.

  10. Association of Myopic Optic Disc Deformation with Visual Field Defects in Paired Eyes with Open-Angle Glaucoma: A Cross-Sectional Study

    PubMed Central

    Sawada, Yu; Hangai, Masanori; Ishikawa, Makoto; Yoshitomi, Takeshi

    2016-01-01

    Purpose To examine the association of myopia with the visual field (VF) defects in open-angle glaucoma (OAG) using paired eyes to eliminate the effect of unknown confounding factors that are diverse among individuals. Methods One hundred eighteen eyes of 59 subjects with myopia (spherical equivalent [SE] ≥ -2 diopter [D] and axial length ≥ 24.0 mm) whose intra-ocular pressure between paired eyes was similar and the mean deviation (MD) of the Humphrey VF test differed by more than 6 dB were included. Refractive errors (SE, axial length) and parameters associated with the papillary and parapapillary myopic deformation (tilt ratio, torsion angle, and β-zone parapapillary atrophy [PPA] area without Bruch’s membrane) were measured in each eye. The paired eyes were divided into worse and better eyes according to the MD of the VF, and parameters were compared between them. Further, multiple linear regression analysis was performed to examine the correlation of the difference in various parameters with the MD difference between paired eyes. Results The SE of all eyes was -6.39 ± 2.15 D (mean ± standard deviation) and axial length was 26.42 ± 1.07 mm. MD of the worse and better VF eyes were -13.56 ± 6.65 dB and -4.87 ± 5.32 dB, respectively. Eyes with worse VFs had significantly greater SE, axial length, tilt ratio, and PPA area without Bruch’s membrane than those with better VFs (all P < 0.05). In multiple linear regression analysis, the difference of the MD between paired eyes was significantly correlated with the difference in the tilt ratio and PPA area without Bruch’s membrane. Conclusion The myopic papillary and parapapillary deformations, but not refractive error itself, were related to the worse VF in paired eyes with OAG. This suggests that myopia influences the severity of the glaucomatous VF defects via structural deformation. PMID:27571303

  11. Low-field magnetic resonance imaging or combined ultrasonography and anti-cyclic citrullinated peptide antibody improve correct classification of individuals as established rheumatoid arthritis: results of a population-based, cross-sectional study

    PubMed Central

    2014-01-01

    Background The aim of the present study was to evaluate the accuracy of two approaches using magnetic resonance imaging (MRI) or combined ultrasonography (US) and anti-cyclic citrullinated peptide antibody (ACPA) for diagnosis and classification of individuals with established rheumatoid arthritis (RA). Methods In 53 individuals from a population-based, cross-sectional study, historic fulfilment of the American College of Rheumatology (ACR) 1987 criteria (“classification”) or RA diagnosed by a rheumatologist (“diagnosis”) were used as standard references. The sensitivity, specificity and Area under Curve for Receiver Operating Characteristics curves (ROC-area: (sensitivity + specificity)/2) were calculated for “current fulfilment of the ACR 1987 criteria” (list format), “adapted ACR 1987 criteria” (list format, substituting IgM rheumatoid factor with ACPA and clinical joint swelling and erosions on radiography with synovitis and erosions detected by US on a semi-quantitative scale), and RA MRI scoring System (RAMRIS) scores on low-field MRI in the unilateral hand. Results For the ACR 1987 criteria the ROC-area was 75% (sensitivity/specificity = 50%/100%) (with “classification” as standard reference) and 69% (44%/94%) (with “diagnosis” as standard reference), while for the adapted ACR 1987 criteria it was 86% (75%/97%) (classification) and 82% (72%/91%) (diagnosis). For RAMRIS synovitis score in metacarpophalangeal (MCP) joints only (cut-off ≥5), the ROC-area (sensitivity/specificity) was 78% (62%/94%) (classification) and 85% (69%/100%) (diagnosis), while for the total synovitis score of MCP joints plus wrist (cut-off ≥10) it was 78% (62%/94%) (both classification and diagnosis). Conclusions Compared with the ACR 1987 criteria, low-field MRI alone or adapted criteria incorporating US and ACPA increased the correct classification and diagnosis of RA. PMID:25103610

  12. Direct measurement and characterization of n+ superhalo implants in a 120 nm gate-length Si metal-oxide-semiconductor field-effect transistor using cross-sectional scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Rosenthal, P. A.; Taur, Y.; Yu, E. T.

    2002-11-01

    We have directly measured nanoscale electronic features associated with a 120 nm physical gate length p-channel silicon metal-oxide-semiconductor field-effect transistor device structure including n+ superhalo implants using cross-sectional scanning capacitance microscopy (SCM). A dc bias-dependent voltage series of SCM images representing nine bias conditions from 2 to -2 V in 0.5 V steps was obtained. The SCM contrast observed varies with the ac and dc bias applied to the sample and allows delineation of the device features, including the p+ source and drain contacts, p+ source and drain extensions, p+ polycrystalline silicon gate, electrical p-n junction, n-well, and n+ superhalo implants. It is demonstrated that the superhalo implant features are imaged only under specific SCM bias conditions. Detailed analysis of the resulting SCM contrast indicates an apparent channel length of 73±11 nm, and reveals clear asymmetry in the individual lobes of the n+ superhalo implant features.

  13. Intercultural Sourcebook: Cross-Cultural Training Methods. Volume 2.

    ERIC Educational Resources Information Center

    Fowler, Sandra M., Ed.; Mumford, Monica G., Ed.

    This comprehensive collection of training methods and exercises used by top trainers in the cross-cultural field contains resources essential for cross-cultural learning. This second volume of the collection includes articles by 34 leading cross-cultural trainers and covers new or divergent training methods for cross-cultural skill development and…

  14. Curriculum Integration and Cross-Cultural Psychology.

    ERIC Educational Resources Information Center

    Goldstein, Susan B.

    While many undergraduate disciplines are revising curricula to address issues of diversity more effectively, it is commonly assumed that courses in cross-cultural psychology are less in need of revision due to their inherent multi-cultural focus. The field of cross-cultural psychology, however, is not immune to Eurocentric and androcentric biases.…

  15. Creating Cross-disciplinary Courses

    PubMed Central

    Reynolds, Elaine R.

    2012-01-01

    Because of its focus on the biological underpinnings of action and behavior, neuroscience intersects with many fields of human endeavor. Some of these cross-disciplinary intersections have been long standing, while others, such as neurotheology or neuroeconomics, are more recently formed fields. Many undergraduate institutions have sought to include cross-disciplinary courses in their curriculum because this style of pedagogy is often seen as applicable to real world problems. However, it can be difficult for faculty with specialized training within their discipline to expand beyond their own fields to offer cross-disciplinary courses. I have been creating a series of multi- or cross-disciplinary courses and have found some strategies that have helped me successfully teach these classes. I will discuss general strategies and tools in developing these types of courses including: 1) creating mixed experience classrooms of students and contributing faculty 2) finding the right tools that will allow you to teach to a mixed population without prerequisites 3) examining the topic using multiple disciplinary perspectives 4) feeding off student experience and interest 5) assessing the impact of these courses on student outcomes and your neuroscience program. This last tool in particular is important in establishing the validity of this type of teaching for neuroscience students and the general student population. PMID:23494491

  16. The radar cross section of dielectric disks

    NASA Technical Reports Server (NTRS)

    Levine, D. M.

    1982-01-01

    A solution is presented for the backscatter (nonstatic) radar cross section of dielectric disks of arbitrary shape, thickness and dielectric constant. The result is obtained by employing a Kirchhoff type approximation to obtain the fields inside the disk. The internal fields induce polarization and conduction currents from which the scattered fields and the radar cross section can be computed. The solution for the radar cross section obtained in this manner is shown to agree with known results in the special cases of normal incidence, thin disks and perfect conductivity. The solution can also be written as a product of the reflection coefficient of an identically oriented slab times the physical optics solution for the backscatter cross section of a perfectly conducting disk of the same shape. This result follows directly from the Kirchhoff type approximation without additional assumptions.

  17. The ground vortex flow field associated with a jet in a cross flow impinging on a ground plane for uniform and annular turbulent axisymmetric jets. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Cavage, William M.; Kuhlman, John M.

    1993-01-01

    An experimental study was conducted of the impingement of a single circular jet on a ground plane in a cross flow. This geometry is a simplified model of the interaction of propulsive jet exhaust from a V/STOL aircraft with the ground in forward flight. Jets were oriented normal to the cross flow and ground plane. Jet size, cross flow-to-jet velocity ratio, ground plane-to-jet board spacing, and jet exit turbulence level and mean velocity profile shape were all varied to determine their effects on the size of the ground vortex interaction region which forms on the ground plane, using smoke injection into the jet. Three component laser Doppler velocimeter measurements were made with a commercial three color system for the case of a uniform jet with exit spacing equal to 5.5 diameters and cross flow-to-jet velocity ratio equal to 0.11. The flow visualization data compared well for equivalent runs of the same nondimensional jet exit spacing and the same velocity ratio for different diameter nozzles, except at very low velocity ratios and for the larger nozzle, where tunnel blockage became significant. Variation of observed ground vortex size with cross flow-to-jet velocity ratio was consistent with previous studies. Observed effects of jet size and ground plane-to-jet board spacing were relatively small. Jet exit turbulence level effects were also small. However, an annular jet with a low velocity central core was found to have a significantly smaller ground vortex than an equivalent uniform jet at the same values of cross flow-to-jet velocity ratio and jet exit-to-ground plane spacing. This may suggest a means of altering ground vortex behavior somewhat, and points out the importance of proper simulation of jet exit velocity conditions. LV data indicated unsteady turbulence levels in the ground vortex in excess of 70 percent.

  18. Cross-Cultural Psychology Newsletter. Volume 7, Number 2.

    ERIC Educational Resources Information Center

    Dawson, John, Ed.

    The Cross-Cultural Psychology Newsletter, an official publication of the International Association for Cross-Cultural Psychology, reports on recent publications and research in cross-cultural psychology. Notes on international conferences in the field are followed by annotations of new publications. In addition, recent research projects are…

  19. Virtual Field Trips.

    ERIC Educational Resources Information Center

    Cooper, Gail; Cooper, Garry

    The Internet field trips in this directory allow teachers to take students almost anywhere--without the usual ordeals associated with field trips. Organized by subject and cross-referenced for quick and easy access, this book leads educators and students to the most exciting, educational, and innovative Web sites on the Internet. Chapters cover…

  20. Cross-Validation.

    ERIC Educational Resources Information Center

    Langmuir, Charles R.

    1954-01-01

    Cross-validation in relation to choosing the best tests and selecting the best items in tests is discussed. Cross-validation demonstrated whether a decision derived from one set of data is truly effective when this decision is applied to another independent, but relevant, sample of people. Cross-validation is particularly important after…

  1. Delta wings with shock-free cross flow

    NASA Technical Reports Server (NTRS)

    Sritharan, S. S.

    1984-01-01

    In order to have a high level of maneuverability, supersonic delta wings should have a cross flow that is free of embedded shock waves. The conical cross flow sonic surface differs from that of plane transonic flow in many aspects. Well-known properties such as the monotone law are not true for conical cross flow sonic surfaces. By using a local analysis of the cross flow sonic line, relevant conditions for smooth cross flow are obtained. A technique to artificially construct a smooth sonic surface and an efficient numerical method to calculate the flow field are used to obtain cones with smooth cross flow.

  2. Cross-functional systems

    NASA Technical Reports Server (NTRS)

    Lee, Mark

    1991-01-01

    Many companies, including Xerox and Texas Instruments, are using cross functional systems to deal with the increasingly complex and competitive business environment. However, few firms within the aerospace industry appear to be aware of the significant benefits that cross functional systems can provide. Those benefits are examined and a flexible methodology is discussed that companies can use to identify and develop cross functional systems that will help improve organizational performance. In addition, some of the managerial issues are addressed that cross functional systems may raise and specific examples are used to explore networking's contributions to cross functional systems.

  3. Planet-crossing asteroid survey

    NASA Technical Reports Server (NTRS)

    Wilder, P. D.

    1984-01-01

    The planet-crossing asteroid survey was begun in 1973 in order to study those asteroids which may intersect the orbits of the inner planets. Throughout the history of the survey, many of the various classes of asteroids were investigated. The near-Earth objects including the Apollo, Amor, and Aten families were studied in addition to asteroids whose orbits cross that of Mars, and some objects which are generally confined to the main belt. Observing was done on the 18 inch Schmidt telescope at the Palomar Mtn. Observatory. Typically, two consecutive photographs of a favorable field are taken. The exposure times of the films are usually twenty minutes and ten minutes, respectively. The telescope is guided at sidereal rate, so that asteroids will leave short trailed images. The films are then scanned for trails. By comparing the two films, the direction and approximate rate of motion of an asteroid may be determined.

  4. Modeling jets in cross flow

    NASA Technical Reports Server (NTRS)

    Demuren, A. O.

    1994-01-01

    Various approaches to the modeling of jets in cross flow are reviewed. These are grouped into four classes, namely: empirical models, integral models, perturbation models, and numerical models. Empirical models depend largely on the correlation of experimental data and are mostly useful for first-order estimates of global properties such as jet trajectory and velocity and temperature decay rates. Integral models are based on some ordinary-differential form of the conservation laws, but require substantial empirical calibration. They allow more details of the flow field to be obtained; simpler versions have to assume similarity of velocity and temperature profiles, but more sophisticated ones can actually calculate these profiles. Perturbation models require little empirical input, but the need for small parameters to ensure convergent expansions limits their application to either the near-field or the far-field. Therefore, they are mostly useful for the study of flow physics. Numerical models are based on conservation laws in partial-differential form. They require little empirical input and have the widest range of applicability. They also require the most computational resources. Although many qualitative and quantitative features of jets in cross flow have been predicted with numerical models, many issues affecting accuracy such as grid resolution and turbulence model are not completely resolved.

  5. Revised cross section for RHIC dipole magnets

    SciTech Connect

    Thompson, P.A.; Gupta, R.C.; Kahn, S.A.; Hahn, H.; Morgan, G.H.; Wanderer, P.J.; Willen, E.

    1991-01-01

    Using the experience gained in designing and building Relativistic Heavy Ion Collider (RHIC) dipole prototype magnets an improved cross section has been developed. Significant features of this design include the use of only three wedges for field shaping and wedge cross sections which are sectors of an annulus. To aid in the understanding of the actual magnets, one has been sectioned, and detailed mechanical and photographic measurements made of the wire positions. The comparison of these measurements with the magnetic field measurements will is presented. 2 refs, 3 figs., 2 tabs.

  6. Numerical calculations of flow fields

    NASA Technical Reports Server (NTRS)

    Anderson, D.; Vogel, J. M.

    1973-01-01

    Numerical calculations were made of flow fields generated by various aerodynamic configurations. Data cover flow fields generated by a finitely thick lifting three dimensional wing with subsonic tips moving at supersonic speeds, cross flow instability associated with lifting delta wing configurations such as space shuttles, and flow fields produced by a lifting elliptic cone. Finite difference techniques were used to determine elliptic cone flow.

  7. Cross-Generational Storytelling

    ERIC Educational Resources Information Center

    Smith, Cindy; Thurston, Judy Kay

    2007-01-01

    What happens when you combine senior citizens, pre-service art teachers, and elementary students? Cross-generational connections based on sharing memories, ideas, skills, laughter, tears, and creativity. The authors describe the cross-generational book exchange project. This project was initiated when a group of Central Michigan University (CMU)…

  8. Jet inclusive cross sections

    SciTech Connect

    Del Duca, V.

    1992-11-01

    Minijet production in jet inclusive cross sections at hadron colliders, with large rapidity intervals between the tagged jets, is evaluated by using the BFKL pomeron. We describe the jet inclusive cross section for an arbitrary number of tagged jets, and show that it behaves like a system of coupled pomerons.

  9. Cross-Shelf Exchange.

    PubMed

    Brink, K H

    2016-01-01

    Cross-shelf exchange dominates the pathways and rates by which nutrients, biota, and materials on the continental shelf are delivered and removed. This follows because cross-shelf gradients of most properties are usually far greater than those in the alongshore direction. The resulting transports are limited by Earth's rotation, which inhibits flow from crossing isobaths. Thus, cross-shelf flows are generally weak compared with alongshore flows, and this leads to interesting observational issues. Cross-shelf flows are enabled by turbulent mixing processes, nonlinear processes (such as momentum advection), and time dependence. Thus, there is a wide range of possible effects that can allow these critical transports, and different natural settings are often governed by different combinations of processes. This review discusses examples of representative transport mechanisms and explores possible observational and theoretical paths to future progress. PMID:26747520

  10. Literacy and Access to the Written Culture by Youth and Adults Excluded from the School System: A Cross-Country Field Study in Nine Countries in Latin America and the Caribbean

    ERIC Educational Resources Information Center

    Torres, Rosa-Maria

    2008-01-01

    The title of this article refers to a field study carried out in 2006-2007 in nine countries in Latin America and the Caribbean. The article summarizes the basic concepts, aims, methodology and findings of the study. In conclusion, the author points out a number of important policy changes that are called for in this domain. While the study itself…

  11. "We Cross Night": Some Reflections on the Role of the ESKOM Expo for Young Scientists as a Means of Accommodating Disadvantaged Learners into the Field of Science and Technology

    ERIC Educational Resources Information Center

    Alant, Busisiwe P.

    2010-01-01

    This article critiques the role of the ESKOM Expo for Young Scientists as a particularly salient node in the constitution of young learners' identity as prospective participants in the field of science and technology. The ESKOM Expo is seen as a particularly exciting means of providing access to the niche area of science and technology. Yet this…

  12. Research Trends with Cross Tabulation Search Engine

    ERIC Educational Resources Information Center

    Yin, Chengjiu; Hirokawa, Sachio; Yau, Jane Yin-Kim; Hashimoto, Kiyota; Tabata, Yoshiyuki; Nakatoh, Tetsuya

    2013-01-01

    To help researchers in building a knowledge foundation of their research fields which could be a time-consuming process, the authors have developed a Cross Tabulation Search Engine (CTSE). Its purpose is to assist researchers in 1) conducting research surveys, 2) efficiently and effectively retrieving information (such as important researchers,…

  13. Corneal cross-linking.

    PubMed

    Randleman, J Bradley; Khandelwal, Sumitra S; Hafezi, Farhad

    2015-01-01

    Since its inception in the late 1990s, corneal cross-linking has grown from an interesting concept to a primary treatment for corneal ectatic disease worldwide. Using a combination of ultraviolet-A light and a chromophore (vitamin B2, riboflavin), the cornea can be stiffened, usually with a single application, and progressive thinning diseases such as keratoconus arrested. Despite being in clinical use for many years, some of the underlying processes, such as the role of oxygen and the optimal treatment times, are still being worked out. More than a treatment technique, corneal cross-links represent a physiological principle of connective tissue, which may explain the enormous versatility of the method. We highlight the history of corneal cross-linking, the scientific underpinnings of current techniques, evolving clinical treatment parameters, and the use of cross-linking in combination with refractive surgery and for the treatment of infectious keratitis. PMID:25980780

  14. A cross-sectional study assessing the residual bio-efficacy and durability of field-distributed long-lasting insecticidal nets in malaria endemic ethnic communities of Assam, Northeast India.

    PubMed

    Dev, Vas; Barman, Keshab; Khound, Kamal

    2016-01-01

    Long-lasting insecticidal nets (LLINs) are being promoted for malaria vector control in the northeastern Indian state of Assam. A cross-sectional study was conducted to assess the current residual bio-efficacy and durability of both the Olyset(®) and PermaNet(®)2.0 LLINs that were distributed earlier in 2009, 2011 and 2013 to help formulate informed policy regarding net procurement, supplies and replacement. The study was undertaken in three different malaria endemic blocks of Assam during the period of June to October of 2014. The residual bio-efficacies were ascertained using the WHO cone-bioassay method for mosquito mortality post-exposure and corroborated with the ring-net assay for the median knockdown times of both types of LLINs in use by these communities. Cross-sectional community surveys were distributed to assess net ownership, utilization, community practices and the physical conditions of the nets in terms of being torn and the numbers of holes per position. Both the Olyset(®) and PermaNet(®)2.0 LLINs that were distributed in 2009 (i.e., nearly after five years of community usage) were completely torn, worn out and obsolete. However, the LLINs distributed in 2011 (i.e., three years of community usage) retained their residual bio-efficacies in susceptibility ranges that varied from 57% to 79%. However, for the LLINs that were distributed in 2013, the observed residual efficacy was adequate and resulted in a mosquito mortality rate >80 percent. Of the two types of LLINs inspected, the Olyset(®)nets were more durable and robust in terms of being torn less frequently (37.1%, 39/105) compared with the PermaNet(®)2.0 nets (51.8%, 204/394). Regarding the LLINs that were distributed in 2013, all were physically intact and in good condition. The majority of the distributed LLINs (99.2%, 639/644) were still in the possession of the householders of the surveyed populations. This study revealed that the serviceable life of the nets was slightly less than

  15. Avoided Crossing and Synchronization

    NASA Astrophysics Data System (ADS)

    Sekii, T.; Shibahashi, H.

    2013-12-01

    We examine avoided crossing of stellar pulsations in the nonlinear regime, where synchronization may occur, based on a simple model of weakly coupled van der Pol oscillators with close frequencies. For this simple case, avoided crossing is unaffected in the sense that there is a frequency difference between the symmetric and antisymmetric modes, but as a result of synchronization, unlike the linear oscillations case, the system can vibrate in only one of the modes.

  16. Anticrossproducts and cross divisions.

    PubMed

    de Leva, Paolo

    2008-01-01

    This paper defines, in the context of conventional vector algebra, the concept of anticrossproduct and a family of simple operations called cross or vector divisions. It is impossible to solve for a or b the equation axb=c, where a and b are three-dimensional space vectors, and axb is their cross product. However, the problem becomes solvable if some "knowledge about the unknown" (a or b) is available, consisting of one of its components, or the angle it forms with the other operand of the cross product. Independently of the selected reference frame orientation, the known component of a may be parallel to b, or vice versa. The cross divisions provide a compact and insightful symbolic representation of a family of algorithms specifically designed to solve problems of such kind. A generalized algorithm was also defined, incorporating the rules for selecting the appropriate kind of cross division, based on the type of input data. Four examples of practical application were provided, including the computation of the point of application of a force and the angular velocity of a rigid body. The definition and geometrical interpretation of the cross divisions stemmed from the concept of anticrossproduct. The "anticrossproducts of axb" were defined as the infinitely many vectors x(i) such that x(i)xb=axb. PMID:18423647

  17. Literacy and Access to the Written Culture by Youth and Adults Excluded from the School System . A cross-country field study in nine countries in Latin America and the Caribbean

    NASA Astrophysics Data System (ADS)

    Torres, Rosa-Maria

    2008-11-01

    LITERACY AND ACCESS TO THE WRITTEN CULTURE BY YOUTH AND ADULTS EXCLUDED FROM THE SCHOOL SYSTEM - The title of this article refers to a field study carried out in 2006-2007 in nine countries in Latin America and the Caribbean. The article summarizes the basic concepts, aims, methodology and findings of the study. In conclusion, the author points out a number of important policy changes that are called for in this domain. While the study itself was carried out in a particular region, the findings have implications for a wider international audience.

  18. Impact of a trace element supplementation programme on health and performance of cross-breed (Bos indicus x Bos taurus) dairy cattle under tropical farming conditions: a double-blinded randomized field trial.

    PubMed

    Dermauw, V; Dierenfeld, E; Du Laing, G; Buyse, J; Brochier, B; Van Gucht, S; Duchateau, L; Janssens, G P J

    2015-06-01

    Small-scale urban dairy farms (n = 16) in and around Jimma, Ethiopia with cross-bred (Bos indicus × Bos taurus) cows were enrolled in a double-blinded intervention study to investigate the effect of a trace element supplementation programme on trace element status and milk concentrations as well as performance [body condition score (BCS), milk yield, leptin], milk composition, antioxidant status (ferric-reducing ability of plasma (FRAP), thiobarbituric acid-reactive substances (TBARS)], blood biochemistry, serum proteins and immune response (antibody titre upon rabies vaccination). The farms were allocated to a (1) placebo or (2) Cu, Zn, Se, Co and I supplementation treatment for 150 d. On days 0 and 120, four lactating cows per farm were sampled for milk and plasma, and on day 150 for serum, following primo-vaccination. Cu deficiency was present in 17% and marginal Se deficiency in 30% of initially sampled cows, while no Zn shortage was detected. Over 120 days, trace element supplementation caused a bigger increase in plasma Se and Cu concentrations, but also a larger decrease of plasma Fe concentrations. A larger increase in milk Se concentrations was observed in the supplemented group, whereas none of the other elements were affected. BCS decreased more over time in the supplemented group. None of the other parameters of performance and antioxidant status nor milk composition or blood biochemistry was affected by treatment. Antibody response to rabies vaccination did not differ between groups, whereas α1-globulins tended to be lower and β-globulins tended to be higher in the supplemented group. In conclusion, despite improved Cu and Se status and Se concentrations in milk, cows on tropical urban dairy farms did not seem to benefit from trace element supplementation, with respect to the parameters investigated. PMID:24990384

  19. Challenges and Opportunities in Cross-Cultural Geographic Inquiry

    ERIC Educational Resources Information Center

    Wesche, Sonia; Huynh, Niem Tu; Nelson, Erin; Ramachandran, Leela

    2010-01-01

    While qualitative fieldwork in cross-cultural settings is central to human geography, there has been limited focus in the literature on the expectations and skills required to succeed as a field researcher in this area. Some practical advice is available for researchers who are new to cross-cultural fieldwork (e.g. graduate students, junior…

  20. Chris Christiansen and the Chris Cross

    NASA Astrophysics Data System (ADS)

    Orchiston, Wayne; Mathewson, Don

    2009-03-01

    The Chris Cross was the world's first crossed-grating interferometer, and was the brainchild of orte of Australia's foremost radio astronomers, W.N. (Chris) Christiansen, from the CSIRO's Division of Radiophysics in Sydney. Inspired by the innovative and highly-successful E-W and N-S solar grating arrays that he constructed at Potts Hill (Sydney) in the early 1950s, Christiansen sited the Chris Cross at the Division's Fleurs field station near Sydney, and from 1957 to 1988 it provided two-dimensional maps of solar radio emission at 1423 MHz. In 1960 an 18m parabolic antenna was installed adjacent to the Chris Cross array, and when used with the Chris Cross formed the Southern Hemisphere's first high-resolution compound interferometer. A survey of discrete radio sources was carried out with this radio telescope. The Division of Radiophysics handed the Fleurs field station over to the School of Engineering at the University of Sydney in 1963, and Christiansen and his colleagues from the Department of Electrical Engineering proceeded to develop the Chris Cross into the Fleurs Synthesis Telescope (FST) by adding six stand-alone 13.7m parabolic antennas. The FST was used for detailed studies of large radio galaxies, supernova remnants and emission nebulae. The FST was closed down in 1988, and antennas in the original Chris Cross array quickly began to deteriorate. A number of individual antennas in the central part of the array received a new lease of life in 1991 when they were refurbished by staff and students from the Department of Electrical Engineering at the Universityy of Western Sydney, but this only proved to be a temporary reprieve as even these aerials were bulldozed by the landowner in 2004, bringing to an untimely end one of the world's most remarkable radio telescopes.

  1. QuickSite Cross Section Processing

    Energy Science and Technology Software Center (ESTSC)

    2003-05-27

    This AGEM-developed system produces cross sections by inputting data in both standard and custom file formats and outputting a graphic file that can be printed or further modified in a commercial graphic program. The system has evolved over several years in order to combine and visualize a changing set of field data more rapidly than was possible with commercially available cross section software packages. It uses some commercial packages to produce the input and tomore » modify the output files. Flexibility is provided by a dynamic set of programs that are customized to accept varying input and accomodate varying output requirements. There are two basic types of routines: conversion routines and cross section generation routines. The conversion routines convery various data files to logger file format which is compatible with a standard file format for LogPlot 98, a commonly used commercial log plotting program. The cross section routines generate cross sections and apply topography to these cross sections. All of the generation routines produce a standard graphic DXF file, which is the format used in AutoCAD and can then be modified in a number of available graphics programs.« less

  2. Cross-linked informofers.

    PubMed Central

    Prosvirnin, V V; Ruzidic, S; Samarina, O P

    1979-01-01

    The proteins of 30S RNP particles containing pre-mRNA (hnRNA) were cross-linked with bifunctional reagents (dimethyl-suberimidate and dimethyl-3,3'-dithiobispropionimidate). Further treatment with 1 or 2 M NaCl dissociates all RNA from protein. However, a significant part of protein particles--informofers being cross-linked survived high salt treatment. Their sedimentation coefficients were close to those of original particles. No RNA could be detected in the informofers even after labeling the cells with a precursor for a long period of time. Sodium dodecylsulfate or urea dissociated cross-linked informofers into oligomeric polypeptides. They could be dissociated by beta-mercaptoethanol treatment if a reversible cross-linked reagent had been used. The resulting polypeptides were represented by informatin. RNP particles (30S RNP or poly-particles) were reconstituted upon mixing of cross-linked informofers with pre-mRNA and removal of 2 M NaCl. PMID:503864

  3. Path forward for dosimetry cross sections

    SciTech Connect

    Griffin, P.J.; Peters, C.D.

    2011-07-01

    In the 1980's the dosimetry community embraced the need for a high fidelity quantification of uncertainty in nuclear data used for dosimetry applications. This led to the adoption of energy-dependent covariance matrices as the accepted manner of quantifying the uncertainty data. The trend for the dosimetry community to require high fidelity treatment of uncertainty estimates has continued to the current time where requirements on nuclear data are codified in standards such as ASTM E 1018. This paper surveys the current state of the dosimetry cross sections and investigates the quality of the current dosimetry cross section evaluations by examining calculated-to-experimental ratios in neutron benchmark fields. In recent years more nuclear-related technical areas are placing an emphasis on uncertainty quantification. With the availability of model-based cross sections and covariance matrices produced by nuclear data codes, some nuclear-related communities are considering the role these covariance matrices should play. While funding within the dosimetry community for cross section evaluations has been very meager, other areas, such as the solar-related astrophysics community and the US Nuclear Criticality Safety Program, have been supporting research in the area of neutron cross sections. The Cross Section Evaluation Working Group (CSEWG) is responsible for the creation and maintenance of the ENDF/B library which has been the mainstay for the reactor dosimetry community. Given the new trends in cross section evaluations, this paper explores the path forward for the US nuclear reactor dosimetry community and its use of the ENDF/B cross-sections. The major concern is maintenance of the sufficiency and accuracy of the uncertainty estimate when used for dosimetry applications. The two major areas of deficiency in the proposed ENDF/B approach are: 1) the use of unrelated covariance matrices in ENDF/B evaluations and 2) the lack of 'due consideration' of experimental data

  4. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

    Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

    2008-01-01

    A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

  5. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

    Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

    2011-01-01

    A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

  6. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

    Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

    2013-01-01

    A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

  7. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

    Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

    2010-01-01

    A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

  8. Cross delay line sensor characterization

    SciTech Connect

    Owens, Israel J; Remelius, Dennis K; Tiee, Joe J; Buck, Steven E; Whittemore, Stephen R; Thompson, David C; Shirey, Robert

    2010-01-01

    There exists a wealth of information in the scientific literature on the physical properties and device characterization procedures for complementary metal oxide semiconductor (CMOS), charge coupled device (CCD) and avalanche photodiode (APD) format detectors. Numerous papers and books have also treated photocathode operation in the context of photomultiplier tube (PMT) operation for either non imaging applications or limited night vision capability. However, much less information has been reported in the literature about the characterization procedures and properties of photocathode detectors with novel cross delay line (XDL) anode structures. These allow one to detect single photons and create images by recording space and time coordinate (X, Y & T) information. In this paper, we report on the physical characteristics and performance of a cross delay line anode sensor with an enhanced near infrared wavelength response photocathode and high dynamic range micro channel plate (MCP) gain (> 10{sup 6}) multiplier stage. Measurement procedures and results including the device dark event rate (DER), pulse height distribution, quantum and electronic device efficiency (QE & DQE) and spatial resolution per effective pixel region in a 25 mm sensor array are presented. The overall knowledge and information obtained from XDL sensor characterization allow us to optimize device performance and assess capability. These device performance properties and capabilities make XDL detectors ideal for remote sensing field applications that require single photon detection, imaging, sub nano-second timing response, high spatial resolution (10's of microns) and large effective image format.

  9. Cross delay line sensor characterization

    NASA Astrophysics Data System (ADS)

    Owens, Israel J.; Remelius, Dennis K.; Tiee, Joe J.; Buck, Steven E.; Whittemore, Stephen R.; Thompson, David C.; Shirey, Robert

    2010-04-01

    There exists a wealth of information in the scientific literature on the physical properties and device characterization procedures for complementary metal oxide semiconductor (CMOS), charge coupled device (CCD) and avalanche photodiode (APD) format detectors. Numerous papers and books have also treated photocathode operation in the context of photomultiplier tube (PMT) operation for either non imaging applications or limited night vision capability. However, much less information has been reported in the literature about the characterization procedures and properties of photocathode detectors with novel cross delay line (XDL) anode structures. These allow one to detect single photons and create images by recording space and time coordinate (X, Y & T) information. In this paper, we report on the physical characteristics and performance of a cross delay line anode sensor with an enhanced near infrared wavelength response photocathode and high dynamic range micro channel plate (MCP) gain (> 106 ) multiplier stage. Measurement procedures and results including the device dark event rate (DER), pulse height distribution, quantum and electronic device efficiency (QE & DQE) and spatial resolution per effective pixel region in a 25 mm sensor array are presented. The overall knowledge and information obtained from XDL sensor characterization allow us to optimize device performance and assess capability. These device performance properties and capabilities make XDL detectors ideal for remote sensing field applications that require single photon detection, imaging, sub nano-second timing response, high spatial resolution (10's of microns) and large effective image format.ÿ

  10. Deionization shocks in cross flows

    NASA Astrophysics Data System (ADS)

    Mani, Ali

    2011-11-01

    Recent experimental and theoretical studies have shown that surface conduction in supported electrolytes, such as in micro/nanochannels or porous media, can lead to nonlinear modes of transport and formation of sharp concentration fronts analogous to shock waves in gas dynamics. Propagation of these shocks leaves behind a region of ultra pure fluid, acting to deionize the bulk solution. In this work we present the analysis of salt transport in a porous medium next to a membrane with an electric field applied normal to the interface and cross flow in tangential direction. We show that two distinct boundary layers grow near the membrane: an inner (shocked) region with almost deionized solution dominated by surface conduction, and an outer layer with diffuse dynamics. Under certain conditions both regions collapse into a similarity solution with the same scaling. We will discuss advantages of such systems for desalination and water purification. Research performed in collaboration with Martin Bazant (MIT).

  11. How the structure of a continental margin affects the development of a fold and thrust belt. 3: evidences from field mapping and geological cross-sections in south-central Taiwan

    NASA Astrophysics Data System (ADS)

    Alvarez-Marron, Joaquina; Biete, Cristina; Brown, Dennis; Camanni, Giovanni; Kuo-Chen, Hao; Ho, Chun-Wei

    2016-04-01

    The Eurasian Margin is obliquely colliding with the Luzon Arc to form the Taiwan orogen. This configuration is particularly apparent in south-central part of the island providing a case example to investigate the effects of structural inheritance in the development of the thrust and fold belt. The Eurasian Margin evolved from a pre-Cenozoic continental basement that underwent rifting in the Early Eocene and subsequent sea-floor spreading to form the South China Sea during the late Early Oligocene. The margin underwent localized extension in the Middle Miocene, before the initiation of collision with the Luzon Arc by the Early Miocene. The important along-strike changes in structure and topography of south-central Taiwan thrust and fold belt are evidenced in the detailed geological map and 3 balanced geological cross sections. A 3D tomography model is integrated in this study to help constrain the structure at depth. Major along-strike changes seem to be related to structures oriented at a high angle to the thrust system. These include changes in strike of thrusts and fold traces, the changing elevation of thrusts and stratigraphic contacts, and the growing importance of Middle Miocene sediments within the thrust system that take place from north to south. Horizontal slices of the tomography model illustrate that N-S changes in velocity have the orientation of the inherited structural grain of the Eurasian margin. In particular, the inherited location of the Mesozoic margin's shelf-slope transition affects the distribution of seismicity and the location of lateral stratigraphic and structural changes. Also, it appears to be associated with the inversion of Eocene- and Miocene-age extensional faults, deeply rooted in the pre-Cenozoic basement that trend oblique to the thrust belt. The inversion of inherited structures affects the uplift of Miocene syn-extensional and syn-tectonic Plio-Pleistocene foreland basin sediments, and of the pre-Cenozoic basement. Section A

  12. Visual field

    MedlinePlus

    Perimetry; Tangent screen exam; Automated perimetry exam; Goldmann visual field exam; Humphrey visual field exam ... Confrontation visual field exam : This is a quick and basic check of the visual field. The health care provider ...

  13. Visual field

    MedlinePlus

    Perimetry; Tangent screen exam; Automated perimetry exam; Goldmann visual field exam; Humphrey visual field exam ... Confrontation visual field exam : This is a quick and basic check of the visual field. The health care provider sits directly in front ...

  14. Red Cross Swimming Update.

    ERIC Educational Resources Information Center

    Vlasich, Cynthia

    1989-01-01

    Six new aquatic courses, developed by the Red Cross, are described. They are: Infant and Preschool Aquatics, Longfellow's Whale Tales (classroom water safety lessons for K-Six), Basic Water Safety, Emergency Water Safety, Lifeguard Training, and Safety Training for Swim Coaches. (IAH)

  15. Cross-Cultural HRD.

    ERIC Educational Resources Information Center

    1996

    This document consists of three papers presented at a symposium on cross-cultural human resource development (HRD) moderated by Connie Fletcher at the 1996 conference of the Academy of Human Resource Development. "Intercultural Adjustment of U.S. Expatriates in the People's Republic of China" (Hallett G. Hullinger, Robert E. Nolan) presents…

  16. Analyzing crossings under roads

    SciTech Connect

    Ingraffea, A.R.; Barry, A. )

    1989-10-01

    Current design procedures for cased and uncased crossings under highways and railroads are generated from semi-empirical methods. The authors describe the results of a GRI/Cornell University study to develop a three-dimensional finite element modeling to address some of the previous design shortcomings.

  17. Canadian Red Cross.

    PubMed

    Lavender, Colleen

    2008-01-01

    The Canadian Red Cross is guided by its Fundamental Principles--humanity, impartiality, neutrality, independence, voluntary service, unity, and universality--and organized in a traditional geographic hierarchical structure. Among the characteristics that have contributed to its success are a budgeting process that starts at the local level, measurement of program outcomes, and coordinated fundraising activities at the regional level. PMID:18551842

  18. Cross-Cultural Psychology.

    ERIC Educational Resources Information Center

    Triandis, Harry C.; Brislin, Richard W.

    Cross-Cultural psychology refers to the collective efforts of researchers who work among people who live in different societies, with different languages and different forms of government. There are a number of benefits to the study of human behavior which can be accrued by carrying out research in various cultures, largely concerned with better…

  19. Cross-Cultural HRD.

    ERIC Educational Resources Information Center

    1995

    These five papers are from a symposium that was facilitated by David C. Bjorkquist on cross-cultural human resource development (HRD) at the 1995 Academy of Human Resource Development conference. "Developing Managers for Overseas Assignments in the Pacific Rim: A Study of International HRD Issues in Singapore" (A. Ahad M. Osman-Gani, Thian-Ser…

  20. CRESS-CROSS, 1976.

    ERIC Educational Resources Information Center

    Calderon, Margarita, Ed.

    Three issues of the "CRESS-CROSS" newsletter published during 1976 are compiled in this publication. These issues include information on: how to contribute to the ERIC system, the computer search services at the ERIC Clearinghouse on Rural Education and Small Schools, the Rural/Regional Education Association's research award for meritorious…

  1. Has Voyager 1 really crossed the heliopause?

    NASA Astrophysics Data System (ADS)

    Gloeckler, G.; Fisk, L. A.

    2015-01-01

    The Voyager 1 spacecraft is currently in the vicinity of the heliopause, which separates the heliosphere from the local interstellar medium. There has been a precipitous decrease in particles accelerated in the heliosphere, and a substantial increase in galactic cosmic rays (GCRs). The evidence is unclear, however, as to whether Voyager 1 has crossed the heliopause into the local interstellar medium, or remains within the heliosheath. In this paper we propose a test that will determine whether Voyager 1 has crossed the heliopause: If Voyager 1 remains in the heliosheath, the high plasma densities must be due to compressed solar wind, with the consequence that Voyager 1 will encounter another current sheet, where the polarity of the magnetic field reverses. Voyager 1 observations can be used to predict that the next current sheet crossing is likely to occur during 2015. A prediction is also provided as to what the Voyager 2 plasma detector will measure in the next few years.

  2. Algorithmic analysis of quantum radar cross sections

    NASA Astrophysics Data System (ADS)

    Lanzagorta, Marco; Venegas-Andraca, Salvador

    2015-05-01

    Sidelobe structures on classical radar cross section graphs are a consequence of discontinuities in the surface currents. In contrast, quantum radar theory states that sidelobe structures on quantum radar cross section graphs are due to quantum interference. Moreover, it is conjectured that quantum sidelobe structures may be used to detect targets oriented off the specular direction. Because of the high data bandwidth expected from quantum radar, it may be necessary to use sophisticated quantum signal analysis algorithms to determine the presence of stealth targets through the sidelobe structures. In this paper we introduce three potential quantum algorithmic techniques to compute classical and quantum radar cross sections. It is our purpose to develop a computer science-oriented tool for further physical analysis of quantum radar models as well as applications of quantum radar technology in various fields.

  3. Standard model cross-over on the lattice

    NASA Astrophysics Data System (ADS)

    D'Onofrio, Michela; Rummukainen, Kari

    2016-01-01

    With the physical Higgs mass the standard model symmetry restoration phase transition is a smooth cross-over. We study the thermodynamics of the cross-over using numerical lattice Monte Carlo simulations of an effective SU (2 )×U (1 ) gauge+Higgs theory, significantly improving on previously published results. We measure the Higgs field expectation value, thermodynamic quantities like pressure, energy density, speed of sound and heat capacity, and screening masses associated with the Higgs and Z fields. While the cross-over is smooth, it is very well defined with a width of only ˜5 GeV . We measure the cross-over temperature from the maximum of the susceptibility of the Higgs condensate, with the result Tc=159.5 ±1.5 GeV . Outside of the narrow cross-over region the perturbative results agree well with nonperturbative ones.

  4. Application of Fresnel Zone to Cross Talk

    NASA Technical Reports Server (NTRS)

    Javan, Hank

    1998-01-01

    Unintentional radiation results in cross coupling to nearby cables. As frequency increases, the amount of this coupling becomes significant especially in high speed data transmission and space lab experiments. There has been a considerable amount of research to model this radiation and design the electronic equipment accordingly so that operation of space lab instruments will be immune to unwanted radiation. Here at MSFC, the Electromagnetics and Aerospace Environment Branch has the responsibility to analyze, test, and make the necessary recommendation as to the safe operation of instruments used in the space program. Rules, regulation, and limits as set by this group are published in Electromagnetic Compatibility Design and Interference Control (MEDIC) Handbook. This document contains both conducted and radiate emission rules and limits are set by NASA. However cross coupling have not been included. At the time of assigning the research task for the author, the Group decided that a more in-depth investigation of Near Field is needed before establishing a set of rules and limits for cross coupling. Thus this task was assigned to the author with hope that his work will be more beneficial to NASA's Space mission experiments. The model and the method which will be described shortly is intended to improve the present approach of this Group and suggests a method for measuring the cross field coupling capacitance.

  5. Constraints on gauge field production during inflation

    SciTech Connect

    Nurmi, Sami; Sloth, Martin S. E-mail: sloth@cp3.dias.sdu.dk

    2014-07-01

    In order to gain new insights into the gauge field couplings in the early universe, we consider the constraints on gauge field production during inflation imposed by requiring that their effect on the CMB anisotropies are subdominant. In particular, we calculate systematically the bispectrum of the primordial curvature perturbation induced by the presence of vector gauge fields during inflation. Using a model independent parametrization in terms of magnetic non-linearity parameters, we calculate for the first time the contribution to the bispectrum from the cross correlation between the inflaton and the magnetic field defined by the gauge field. We then demonstrate that in a very general class of models, the bispectrum induced by the cross correlation between the inflaton and the magnetic field can be dominating compared with the non-Gaussianity induced by magnetic fields when the cross correlation between the magnetic field and the inflaton is ignored.

  6. Cross-helicity in rotating homogeneous shear-stratified turbulence.

    PubMed

    Pieri, A B; Godeferd, F S; Cambon, C; Dubrulle, B; Thalabard, S

    2014-03-21

    We consider homogeneous shear-stratified turbulence in a rotating frame, that exhibits complex nonlinear dynamics. Since the analysis of relative orientation between coupled fluctuating fields helps us to understand turbulence dynamics, we focus on the alignment properties of both the velocity and gravity fields with the potential vorticity gradient. With the help of statistical mechanics, we define a vector field which plays a role in the analogous so-called cross-helicity in magnetohydrodynamics. High-resolution direct numerical simulations of developed homogeneous baroclinic turbulence are performed, and a detailed analysis of probability density functions for cross-helicity is provided. A net preference for positive cross-helicity is shown to be related to a new alignment mechanism. We argue that the analysis of cross-helicity is crucial for understanding the dynamics of buoyancy driven flows. PMID:24702376

  7. Actinide cross section program at ORELA

    SciTech Connect

    Dabbs, J.W.T.

    1980-01-01

    The actinide cross section program at ORELA, the Oak Ridge Electron Linear Accelerator, is aimed at obtaining accurate neutron cross sections (primarily fission, capture, and total) for actinide nuclides which occur in fission reactors. Such cross sections, measured as a function of neutron energy over as wide a range of energies as feasible, comprise a data base that permits calculated predictions of the formation and removal of these nuclides in reactors. The present program is funded by the Division of Basic Energy Sciences of DOE, and has components in several divisions at ORNL. For intensively ..cap alpha..-active nuclides, many of the existing fission cross section data have been provided by underground explosions. New measurement techniques, developed at ORELA, now permit linac measurements on fissionable nuclides with alpha half-lives as short as 28 years. Capture and capture-plus-fission measurements utilize scintillation detectors (of capture ..gamma.. rays and fission neutrons) in which pulse shape discrimination plays an important role. Total cross sections can be measured at ORELA on samples of only a few milligrams. A simultaneous program of chemical and isotopic analyses of samples irradiated in EBR-II is in progress to provide benchmarks for the existing differential measurements. These analyses are being studied with updated versions of ORIGEN and with sensitivity determinations. Calculations of the sensitivity to cross section changes of various aspects of the nuclear fuel cycle are also being made. Even in this relatively mature field, many cross sections still require improvements to provide an adequate data base. Examples of recent techniques and measurements are presented. 12 figures, 3 tables.

  8. Global reinforcement training of CrossNets

    NASA Astrophysics Data System (ADS)

    Ma, Xiaolong

    2007-10-01

    Hybrid "CMOL" integrated circuits, incorporating advanced CMOS devices for neural cell bodies, nanowires as axons and dendrites, and latching switches as synapses, may be used for the hardware implementation of extremely dense (107 cells and 1012 synapses per cm2) neuromorphic networks, operating up to 10 6 times faster than their biological prototypes. We are exploring several "Cross- Net" architectures that accommodate the limitations imposed by CMOL hardware and should allow effective training of the networks without a direct external access to individual synapses. Our studies have show that CrossNets based on simple (two-terminal) crosspoint devices can work well in at least two modes: as Hop-field networks for associative memory and multilayer perceptrons for classification tasks. For more intelligent tasks (such as robot motion control or complex games), which do not have "examples" for supervised learning, more advanced training methods such as the global reinforcement learning are necessary. For application of global reinforcement training algorithms to CrossNets, we have extended Williams's REINFORCE learning principle to a more general framework and derived several learning rules that are more suitable for CrossNet hardware implementation. The results of numerical experiments have shown that these new learning rules can work well for both classification tasks and reinforcement tasks such as the cartpole balancing control problem. Some limitations imposed by the CMOL hardware need to be carefully addressed for the the successful application of in situ reinforcement training to CrossNets.

  9. Universal enveloping crossed module of Leibniz crossed modules and representations

    NASA Astrophysics Data System (ADS)

    Casado, Rafael F.; García-Martínez, Xabier; Ladra, Manuel

    2016-03-01

    The universal enveloping algebra functor UL: Lb → Alg, defined by Loday and Pirashvili [1], is extended to crossed modules. Then we construct an isomorphism between the category of representations of a Leibniz crossed module and the category of left modules over its universal enveloping crossed module of algebras. Note that the procedure followed in the proof for the Lie case cannot be adapted, since the actor in the category of Leibniz crossed modules does not always exist.

  10. [Apples with oranges? Comparison of scientometric indicators between fields].

    PubMed

    Schubert, András

    2016-04-17

    It is well known that all scientometric indicators strongly depend on research fields. Therefore, there is a certain reluctance to make any cross-field comparison of these indicators. The paper reviews the possibilities to normalize the most important scientometric indicators: publication counts, citation rate or h-index, thus making them suitable for cross-field comparison. PMID:27063431

  11. SFD-261 crossed-field amplifier manufacturing technology program

    NASA Astrophysics Data System (ADS)

    Laplante, R. A.; Trojan, F. E.

    1980-09-01

    The objective of the MT program is to demonstrate improved production techniques by a pilot production run of ten (10) tubes to meet performance specification and system compatibility criteria under production line conditions. The SFD-261 is a microwave amplifier used to increase the power level of pulses of energy by a factor of 20. It is used in the Aegis AN/SPY-1 radar transmitter. A single ship's complement without spares is seventy-six. Its internal parts are made from high purity copper and many are complex and involve high precision. Most of the fabrication is by precious metal brazing in hydrogen or in vacuum. Modest production rates (10 to 30 units per month) presently restrict the amount of automation which can be effectively applied. Nearly 30 design changes were made without altering performance significantly. Self-jigging techniques permitted assembly by lower skill levels. A 'one-shot' vacuum braze for the cathode produced significant cost and equipment reduction. If the selling price of the standard design is normalized at 100, the price of the MT design is now 57.

  12. Electromagnetic fields in axial symmetric waveguides with variable cross section

    SciTech Connect

    Kheifets, S.

    1980-02-15

    A new class of separable variables is found which allows one to find an approximate analytical solution of the Maxwell equations for axial symmetric waveguides with slow (but not necessarily small) varying boundary surfaces. An example of the solution is given. Possible applications and limitations of this approach are discussed. 6 refs., 10 figs.

  13. The Magnetospheric Sash and the Cross-Tail S

    NASA Astrophysics Data System (ADS)

    White, Willard W.; Siscoe, George L.; Erickson, Gary M.; Kaymaz, Zerefsan; Maynard, Nelson C.; Siebert, Keith D.; Sonnerup, Bengt U. Ö.; Weimer, Daniel R.

    As revealed in MHD simulation, the magnetospheric sash is a band of weak magnetic field that, for the usual case in which the IMF is approximately perpendicular to the geomagnetic dipole, runs tailward along the high-latitude magnetopause flanks from one dayside cusp to the other, closing via the cross-tail neutral sheet. On the magnetopause flanks, it contains the magnetic separator line, at which all three topological types of field lines meet. Seen in a cross-sectional plane through the near-Earth tail, the magnetospheric sash takes the form of the cross-tail S, a weak-field feature comprised of the tail neutral sheet with diagonally symmetric extensions along the magnetopause flanks connecting it to the separator line. The cross-tail S is evident in the MHD results and in cross-sectional maps based on IMP 8 data. The magnetopause expression of the sash is latent in prior works that described the geometry of antiparallel fields across the magnetopause and the consequent cancellation of the fields within the magnetopause layer. The sash picture bears a strong resemblance to antiparallel merging geometry.

  14. Modeling Saturn's Magnetospheric Field

    NASA Astrophysics Data System (ADS)

    Khurana, K. K.; Leinweber, H. K.; Russell, C. T.; Dougherty, M. K.

    2015-12-01

    The Cassini spacecraft has now provided an excellent coverage of radial distances, local times and latitudes in Saturn's magnetosphere. The magnetic field observations from Cassini continue to provide deep insights on the structure and dynamics of Saturn's magnetosphere. Two of the unexpected findings from Saturn's magnetosphere are that the current sheet of Saturn assumes a shallow saucer like shape from the forcing of the solar wind on the magnetosphere and that rotational diurnal periodicities are ubiquitous in a magnetosphere formed by an axisymmetric internal field from Saturn. We have used the comprehensive magnetic field data from Cassini to construct a versatile new model of Saturn's magnetospheric field for use in current and future data analysis. Our model consists of fully shielded modules that specify the internal spherical harmonic field of Saturn, the ring current and the magnetotail current systems and the interconnection magnetic field from the solar wind IMF. The tilt and hinging of the current sheet is introduced by using the general deformation technique [Tsyganenko, 1998]. In the new model, Saturn's current sheet field is based on Tsyganenko and Peredo [1994] formalism for disk-shaped current sheets. The shielding field from the magnetopause for the equatorial current sheet and the internal field is specified by Cartesian and cylindrical harmonics, respectively. To derive the shielding fields we use a model of the magnetopause constructed from magnetopause crossings observed by both Cassini and Voyager (Arridge et al. 2006). The model uses observations from Pioneer, Voyager and Cassini. A comparison of model field with the observations will be presented. Finally, we discuss both the applications of the new model and its further generalization using data from the proximal orbit phase of Cassini.

  15. The Effect of Cross Flow on Slat Noise

    NASA Technical Reports Server (NTRS)

    Lockard, David P.; Choudhari, Meelan M.

    2010-01-01

    This paper continues the computational examination (AIAA Journal, Vol. 45, No. 9, 2007, pp. 2174-2186) of the unsteady flow within the slat cove region of a multi-element high-lift airfoil configuration. Two simulations have been performed to examine the effect of cross flow on the near-field fluctuations and far-field acoustics. The cross flow was imposed by changing the free-stream velocity vector and modifying the Reynolds number. The cross flow does appear to alter the dynamics in the cove region, but the impact on the noise seems to be more dependent on the flow conditions. However, separating out the true effects of the cross flow from those of the Mach and Reynolds number would require additional calculations to isolate those effects.

  16. Visual monitoring of railroad grade crossing

    NASA Astrophysics Data System (ADS)

    Sheikh, Yaser A.; Zhai, Yun; Shafique, Khurram; Shah, Mubarak A.

    2004-09-01

    There are approximately 261,000 rail crossings in the United States according to the studies by the National Highway Traffic Safety Administration (NHTSA) and Federal Railroad Administration (FRA). From 1993 to 1998, there were over 25,000 highway-rail crossing incidents involving motor vehicles - averaging 4,167 incidents a year. In this paper, we present a real-time computer vision system for the monitoring of the movement of pedestrians, bikers, animals and vehicles at railroad intersections. The video is processed for the detection of uncharacteristic events, triggering an immediate warning system. In order to recognize the events, the system first performs robust object detection and tracking. Next, a classification algorithm is used to determine whether the detected object is a pedestrian, biker, group or a vehicle, allowing inferences on whether the behavior of the object is characteristic or not. Due to the ubiquity of low cost, low power, and high quality video cameras, increased computing power and memory capacity, the proposed approach provides a cost effective and scalable solution to this important problem. Furthermore, the system has the potential to significantly decrease the number of accidents and therefore the resulting deaths and injuries that occur at railroad crossings. We have field tested our system at two sites, a rail-highway grade crossing, and a trestle located in Central Florida, and we present results on six hours of collected data.

  17. Perceptual crossing: the simplest online paradigm

    PubMed Central

    Auvray, Malika; Rohde, Marieke

    2012-01-01

    Researchers in social cognition increasingly realize that many phenomena cannot be understood by investigating offline situations only, focusing on individual mechanisms and an observer perspective. There are processes of dynamic emergence specific to online situations, when two or more persons are engaged in a real-time interaction that are more than just the sum of the individual capacities or behaviors, and these require the study of online social interaction. Auvray et al.'s (2009) perceptual crossing paradigm offers possibly the simplest paradigm for studying such online interactions: two persons, a one-dimensional space, one bit of information, and a yes/no answer. This study has provoked a lot of resonance in different areas of research, including experimental psychology, computer/robot modeling, philosophy, psychopathology, and even in the field of design. In this article, we review and critically assess this body of literature. We give an overview of both behavioral experimental research and simulated agent modeling done using the perceptual crossing paradigm. We discuss different contexts in which work on perceptual crossing has been cited. This includes the controversy about the possible constitutive role of perceptual crossing for social cognition. We conclude with an outlook on future research possibilities, in particular those that could elucidate the link between online interaction dynamics and individual social cognition. PMID:22723776

  18. Cross-Connections of Chemistry

    NASA Astrophysics Data System (ADS)

    Mason, Diana S.

    2002-02-01

    We are in desperate need of qualified chemistry teachers. Are the teachers who have biology, physics, or some psychology degrees qualified to teach chemistry? Have they taken enough chemistry to be prepared to teach outside their degree field? If remediation is necessary, what courses should be required? Attracting pre-service science teachers to the study of pure chemistry is not an easy task when more attractive course offerings are available. Maybe we should concentrate on cross-training in-service teachers by providing appropriate graduate courses to encourage them and bring them into the family. Many teachers with degrees outside the traditional discipline of chemistry have adequate backgrounds in the applications of chemistry. Requiring hours of undergraduate education before they enter the hallowed halls of the chemistry building as graduate students only serves to discourage a large segment of in-service teachers who wish to broaden their perspective. The National Science Education Standards make a compelling argument for connecting and integrating science courses for practicing teachers (3). We are at the crossroads. At a time when we so desperately need qualified chemistry teachers, shouldn't we be more open in our graduate teaching programs, inviting those with degrees in other disciplines to start on a graduate degree without insisting on undergraduate or survey coursework first? Many potential chemical education graduate students have a background in chemistry--it is just known by another name.

  19. Crossing the Next Frontier

    NASA Astrophysics Data System (ADS)

    Goldston, R.; Menard, J.; Brooks, J.; Doerner, R.; Gates, D.; Fu, G.-Y.; Gorelenkov, N.; Kaita, R.; Kaye, S.; Kramer, G.; Kugel, H.; Majeski, R.; Ono, M.; Skinner, C.; Strachan, J.; Harris, J.; Maingi, R.; Kotschenreuther, M.; Mahajan, S.; Valanju, P.; Nygren, R.; Ulrickson, M.; Ruzic, D.; Sabbagh, S.; Soukhanovskii, V.

    2007-11-01

    The plasma-material interface is the next frontier in fusion science. ITER's approaches to heat flux and tritium retention do not extrapolate to Demo. Defining questions at this frontier include: Can extremely high radiated-power fraction be consistent with high confinement and low Zeff? Can magnetic flux expansion or edge ergodization reduce heat loads sufficiently? Can tungsten survive with acceptable core radiation and tritium retention? Can liquid metals more effectively handle high heat flux, off-normal loads and tritium exhaust? Answers must be integrated with high-performance, fully steady state plasma operation, avoiding ELMs and eliminating disruptions. The vehicle to cross this frontier is a high-power-density plasma with long pulses, excellent diagnostic access, flexible first wall, divertor, heating, current drive and plasma control systems, extensive deuterium and trace tritium operation, and the ability to test a range of plasma-facing materials at reactor-relevant temperature.

  20. Caution -- Beam Crossing Ahead

    SciTech Connect

    Barat, Kenneth L.

    2008-04-02

    There are times when a laser beam needs to cross between tables or even go from one room to another. This presents an interesting traffic-flow and safety challenge to both the laser safety officer and laser user. Fortunately it is a challenge that has several solutions But the simplest solution may not be the best one. For example, the simplest way to get a beam from one optical table to another is just to put a sturdy tube around it. That's a permanent solution, and it completely contains the laser beam. While this is laser safe, there can be egress issues if it blocks a walkway. One comment this author often hears is, 'We can just duck under the tube.' The fire marshal, as well as the laser safety officer, might have issues with this. Especially in the case of a darkened lab, a blocked walkway can present a hazard of its own. One good solution is to transport the beam from Point A to Point B through a fiberoptic cable, when that is possible. One should easily be able to run the fiber up and over any walkway or down through a conduit on the floor. An important concern often overlooked with fibers is a label at the termination end indicating disconnection may expose one to laser radiation. Suppose there's an experiment that is usually confined to a single optical table, but sometimes needs to expand to a second table. It's inconvenient to install a permanent tube between the tables, so some sort of temporary arrangement is desirable. I have often seen people casually lay a beam tube across support arms, and remove it when it's not needed. The problem with this approach is that there's no mechanism to prevent the beam from crossing if somebody's forgotten the tube, or if the tube gets knocked out of place. A better solution is a mechanism that only allows the beam to cross when the beam protection is in place. A swing shutter, or a guillotine and swing arm, are examples (Figures 1 and 2). Another alternative is a sensor, maybe a little microswitch, that activates a

  1. Mojave remote sensing field experiment

    NASA Technical Reports Server (NTRS)

    Arvidson, Raymond E.; Petroy, S. B.; Plaut, J. J.; Shepard, Michael K.; Evans, D.; Farr, T.; Greeley, Ronald; Gaddis, L.; Lancaster, N.

    1991-01-01

    The Mojave Remote Sensing Field Experiment (MFE), conducted in June 1988, involved acquisition of Thermal Infrared Multispectral Scanner (TIMS); C, L, and P-band polarimetric radar (AIRSAR) data; and simultaneous field observations at the Pisgah and Cima volcanic fields, and Lavic and Silver Lake Playas, Mojave Desert, California. A LANDSAT Thematic Mapper (TM) scene is also included in the MFE archive. TM-based reflectance and TIMS-based emissivity surface spectra were extracted for selected surfaces. Radiative transfer procedures were used to model the atmosphere and surface simultaneously, with the constraint that the spectra must be consistent with field-based spectral observations. AIRSAR data were calibrated to backscatter cross sections using corner reflectors deployed at target sites. Analyses of MFE data focus on extraction of reflectance, emissivity, and cross section for lava flows of various ages and degradation states. Results have relevance for the evolution of volcanic plains on Venus and Mars.

  2. Cross-Linked Nanotube Materials with Variable Stiffness Tethers

    NASA Technical Reports Server (NTRS)

    Frankland, Sarah-Jane V.; Odegard, Gregory M.; Herzog, Matthew N.; Gates, Thomas S.; Fay, Catherine C.

    2004-01-01

    The constitutive properties of a cross-linked single-walled carbon nanotube material are predicted with a multi-scale model. The material is modeled as a transversely isotropic solid using concepts from equivalent-continuum modeling. The elastic constants are determined using molecular dynamics simulation. Some parameters of the molecular force field are determined specifically for the cross-linker from ab initio calculations. A demonstration of how the cross-linked nanotubes may affect the properties of a nanotube/polyimide composite is included using a micromechanical analysis.

  3. Crossed responses of spin and orbital magnetism in topological insulators

    NASA Astrophysics Data System (ADS)

    Nakai, Ryota; Nomura, Kentaro

    2016-06-01

    Crossed magnetic responses between spin and orbital angular momentum are studied in time-reversal-symmetric topological insulators. Due to spin-orbit coupling in the quantum spin Hall systems and three-dimensional topological insulators, the magnetic susceptibility has crossed (intersectional) components between the spin and orbital parts of magnetism. In this study, the crossed susceptibility for the orbital magnetization is studied in two- and three-dimensional topological insulator models, in which an external magnetic field interacts with the electron spin by Zeeman coupling via distinct g factors for conduction and valence energy bands. The crossed susceptibility in two-dimensional quantum spin Hall insulators shows a quantized signature of the Z2 topological phase in response to Zeeman coupling via an averaged g factor, and the quantization persists even when σz conservation of electrons is broken by a tilted magnetic field. The bulk orbital magnetization is interpreted by the persistent edge current attributed to the chiral anomaly at the (1+1)-dimensional boundary. In three-dimensional topological insulators, we found that the crossed susceptibility is proportional to the difference of g factors of conduction and valence electrons, which is qualitatively different from the two-dimensional case. Steep changes of the crossed susceptibility in three dimensions at the phase transition points are explained by the surface Dirac fermion theory. Finally, dependence of the crossed susceptibility on g factors in two- and three-dimensional cases is discussed from the viewpoint of time-reversal and particle-hole symmetries.

  4. Horizon crossing and inflation with large {eta}

    SciTech Connect

    Kinney, William H.

    2005-07-15

    I examine the standard formalism of calculating curvature perturbations in inflation at horizon crossing, and derive a general relation which must be satisfied for the horizon-crossing formalism to be valid. This relation is satisfied for the usual cases of power-law and slow-roll inflation. I then consider a model for which the relation is strongly violated, and the curvature perturbation evolves rapidly on superhorizon scales. This model has Hubble slow-roll parameter {eta}=3, but predicts a scale-invariant spectrum of density perturbations. I consider the case of hybrid inflation with large {eta}, and show that such solutions do not solve the '{eta} problem' in supergravity. These solutions correspond to field evolution which has not yet relaxed to the inflationary attractor solution, and may make possible new, more natural models on the string landscape.

  5. Cross sections required for FMIT dosimetry

    SciTech Connect

    Gold, R.; McElroy, W.N.; Lippincott, E.P.; Mann, F.M.; Oberg, D.L.; Roberts, J.H.; Ruddy, F.H.

    1980-05-02

    The Fusion Materials Irradiation Test (FMIT) facility, currently under construction, is designed to produce a high flux of high energy neutrons for irradiation effects experiments on fusion reactor materials. Characterization of the flux-fluence-spectrum in this rapidly varying neutron field requires adaptation and extension of currently available dosimetry techniques. This characterization will be carried out by a combination of active, passive, and calculational dosimetry. The goal is to provide the experimenter with accurate neutron flux-fluence-spectra at all positions in the test cell. Plans have been completed for a number of experimental dosimetry stations and provision for these facilities has been incorporated into the FMIT design. Overall needs of the FMIT irradiation damage program delineate goal accuracies for dosimetry that, in turn, create new requirements for high energy neutron cross section data. Recommendations based on these needs have been derived for required cross section data and accuracies.

  6. Circular-harmonic vector analysis of a dielectric waveguide with a cross-cut-circle cross section.

    PubMed

    Yang, S C; Kim, H S; Lee, H J

    1995-11-20

    Vector-wave solutions of dielectric waveguides with cross-cut-circle cross sections, which are commonly produced by reflow of the waveguide core on a planar substrate at high temperature, are rigorously analyzed by the use of the point-matching method. As a numerical example, the propagation constant, electromagnetic-field distribution, and convergence of mode solutions for a semicircular waveguide are presented, and the properties of these modes are discussed. PMID:21060651

  7. Absence of significant cross-correlation between WMAP and SDSS

    NASA Astrophysics Data System (ADS)

    López-Corredoira, M.; Sylos Labini, F.; Betancort-Rijo, J.

    2010-04-01

    Aims: Several authors have claimed to detect a significant cross-correlation between microwave WMAP anisotropies and the SDSS galaxy distribution. We repeat these analyses to determine the different cross-correlation uncertainties caused by re-sampling errors and field-to-field fluctuations. The first type of error concerns overlapping sky regions, while the second type concerns non-overlapping sky regions. Methods: To measure the re-sampling errors, we use bootstrap and jack-knife techniques. For the field-to-field fluctuations, we use three methods: 1) evaluation of the dispersion in the cross-correlation when correlating separated regions of WMAP with the original region of SDSS; 2) use of mock Monte Carlo WMAP maps; 3) a new method (developed in this article), which measures the error as a function of the integral of the product of the self-correlations for each map. Results: The average cross-correlation for b > 30 deg is significantly stronger than the re-sampling errors - both the jack-knife and bootstrap techniques provide similar results - but it is of the order of the field-to-field fluctuations. This is confirmed by the cross-correlation between anisotropies and galaxies in more than the half of the sample being null within re-sampling errors. Conclusions: Re-sampling methods underestimate the errors. Field-to-field fluctuations dominate the detected signals. The ratio of signal to re-sampling errors is larger than unity in a way that strongly depends on the selected sky region. We therefore conclude that there is no evidence yet of a significant detection of the integrated Sachs-Wolfe (ISW) effect. Hence, the value of Ω_Λ ≈ 0.8 obtained by the authors who assumed they were observing the ISW effect would appear to have originated from noise analysis.

  8. Link invariants of electromagnetic fields.

    PubMed

    von Bodecker, Hanno; Hornig, Gunnar

    2004-01-23

    The cross-helicity integral is known in fluid dynamics and plasma physics as a topological invariant which measures the mutual linkage of two divergence-free vector fields, e.g., magnetic fields, on a three-dimensional domain. Generalizing this concept, a new topological invariant is found which measures the mutual linkage of three closed two-forms, e.g., electromagnetic fields, on a four-dimensional domain. The integral is shown to detect a separation of the cross helicity between two of the fields with the help of the third field. It can be related to the triple linking number known in knot theory. Furthermore, it is shown that the well-known three-dimensional cross helicity and the new four-dimensional invariant are the first two examples of a series of topological invariants which are defined by n-1 field strengths F=dA on a simply connected n-dimensional manifold M(n). PMID:14753856

  9. Radar cross section of insects

    NASA Astrophysics Data System (ADS)

    Riley, J. R.

    1985-02-01

    X-band measurements of radar cross section as a function of the angle between insect body axis and the plane of polarization are presented. A finding of particular interest is that in larger insects, maximum cross section occurs when the E-vector is perpendicular to the body axis. A new range of measurements on small insects (aphids, and planthoppers) is also described, and a comprehensive summary of insect cross-section data at X-band is given.

  10. Prototype security system for Mexico City's light train crossings

    NASA Astrophysics Data System (ADS)

    Rodriguez-Juarez, Mauricio; Lopez-Meyer, Paulo; Gonzalez-Serrano, Edson; Acosta-Mendoza, Luis; Silva-Lopez, Mario; Serrania, Florencia; Hernandez-Cordero, Juan

    2004-03-01

    Mexico City"s Light Train, one of the electrical transportation systems belonging to the government of Mexico City, services 40,000 passengers daily in the southern sector of the city. Along its trajectory, the Train has to go through several crossings in which safety for vehicles and pedestrians is of paramount importance. We have developed a prototype security system for these crossings based on infrared (IR) detection systems and laser barriers. All the subsystems used in the prototype are controlled by a PC/104 CPU board via the serial communications port and an A/D card. An IR transmitter installed in the train constantly sends information to several receivers deployed at different locations within the crossing. Once the train is detected, the computer activates a set of alarms and barriers in a logical sequence in order to clear the crossing for the train. The laser barrier, formed by a set of eight transmitters and receivers located at different heights within the crossing, is activated as well and is used as a means to detect other emergency situations such as vehicles or pedestrians stranded in the crossing. Discrimination between real and false alarm situations is achieved by encoding both the IR transmitters and the laser beams. In this paper we will discuss experimental and field trials of the prototype system which will be installed in one crossing this year. Once in place, the Light Train of Mexico City will have its first automated crossing.

  11. Chao Formalism & Kondratenko Crossing Tests

    NASA Astrophysics Data System (ADS)

    Raymond, R. S.; Chao, A. W.; Krisch, A. D.; Leonova, M. A.; Morozov, V. S.; Sivers, D. W.; Wong, V. K.; Gebel, R.; Lehrach, A.; Lorentz, B.; Maier, R.; Prasuhn, D.; Schnase, A.; Stockhorst, H.; Hinterberger, F.; Ulbrich, K.; Kondratenko, A. M.

    2007-06-01

    We recently started testing Chao's proposed new matrix formalism for describing the spin dynamics due to a single spin resonance; this seems to be the first generalization of the Froissart-Stora equation since it was published in 1960. The Chao matrix formalism allows one to calculate analytically the polarization's behavior inside a resonance, which is not possible using the Froissart-Stora equation. We recently tested some Chao formalism predictions using a 1.85 GeV/c polarized deuteron beam stored in COSY. We swept an rf dipole's frequency through 200 Hz while varying the distance from the sweep's end frequency to an rf-induced spin resonance's central frequency. While the Froissart-Stora formula can make no prediction in this case, the data seem to support the Chao formalism. We also started investigating the new Kondratenko method to preserve beam polarization during a spin resonance crossing; the method uses 3 rapid changes of the crossing rate near the resonance. With a proper choice of crossing parameters, Kondratenko Crossing may better preserve the polarization than simple fast crossing. We tested Kondratenko's idea using 2.1 GeV/c polarized protons stored in COSY; the frequency of a ferrite rf dipole was swept though an rf-induced spin resonance using Kondratenko's crossing shape. We have not yet observed a significant advantage of Kondratenko Crossing over simple fast crossing. We plan to study it further by choosing better crossing parameters and a smaller momentum spread.

  12. (abstract) Cross with Your Spectra? Cross-Correlate Instead!

    NASA Technical Reports Server (NTRS)

    Beer, Reinhard

    1994-01-01

    The use of cross-correlation for certain types of spectral analysis is discussed. Under certain circumstances, the use of cross-correlation between a real spectrum and either a model or another spectrum can provide a very powerful tool for spectral analysis. The method (and its limitations) will be described with concrete examples using ATMOS data.

  13. Electron acceleration using two crossed Bessel beams in vacuum

    NASA Astrophysics Data System (ADS)

    Zhao, Zhiguo; Lü, Baida

    2007-09-01

    The direct acceleration of electrons by using two crossed linearly polarized Bessel beams with equal frequency and amplitude in vacuum is studied and compared with the case of single linearly polarized Bessel beam. It is found that two zeroth- and first-order Bessel beams with π-rad phase difference have a nonvanishing longitudinal electric field on the z-axis, which can be maximized under certain conditions and used to accelerate electrons. Two crossed zeroth- and first-order Bessel beams have a larger maximum longitudinal electric field on the z-axis than that of a single first-order Bessel beam, and are suited for laser electron acceleration.

  14. Crab Crossing Consideration for MEIC 2

    SciTech Connect

    S. Ahmed, Y.S. Derbenev, G.A. Krafft, Y. Zhang, A. Castilla, J.R. Delayen, S.D. Silva

    2011-03-01

    Crab crossing of colliding electron and ion beams is essential for accommodating the ultra high bunch repetition frequency in the conceptual design of MEIC – a high luminosity polarized electron-ion collider at Jefferson Lab. The scheme eliminates parasitic beam-beam interactions and avoids luminosity reduction by restoring head-on collisions at interaction points. In this paper, we report simulation studies of beam dynamics with crab cavities for MEIC design. The detailed study involves full 3-D simulations of particle tracking through the various configurations of crab cavities for evaluating the performance. To gain insight, beam and RF dominated fields with other parametric studies will be presented in the paper.

  15. High-energy electroproduction in an atomic field

    NASA Astrophysics Data System (ADS)

    Krachkov, P. A.; Milstein, A. I.

    2016-06-01

    The differential cross section of high-energy electroproduction in the electric field of heavy atoms is derived. The results are obtained with the exact account for the atomic field. We use the quasiclassical approximation to the wave functions in the external field. For heavy atoms, the Coulomb corrections substantially modify the differential cross section as compared with the Born result. They lead to the azimuth asymmetry in the differential cross section for the polarized incoming electron. The Coulomb corrections to the total cross section are obtained in the leading logarithmic approximation.

  16. XCOM: Photon Cross Sections Database

    National Institute of Standards and Technology Data Gateway

    SRD 8 XCOM: Photon Cross Sections Database (Web, free access)   A web database is provided which can be used to calculate photon cross sections for scattering, photoelectric absorption and pair production, as well as total attenuation coefficients, for any element, compound or mixture (Z <= 100) at energies from 1 keV to 100 GeV.

  17. Cross-Country Skiing Today.

    ERIC Educational Resources Information Center

    Caldwell, John

    This book presents changes in cross country skiing which have taken place in the last several years and is directed toward both beginning and seasoned tour skiers. Discussed are the following topics: (1) the cross-country revolution (new fiberglass skis); (2) equipment (how to choose from the new waxless touring skis); (3) care of equipment; (4)…

  18. The total charm cross section

    SciTech Connect

    Vogt, R

    2007-09-14

    We assess the theoretical uncertainties on the total charm cross section. We discuss the importance of the quark mass, the scale choice and the parton densities on the estimate of the uncertainty. We conclude that the uncertainty on the total charm cross section is difficult to quantify.

  19. Housatonic crossing tests the technology

    SciTech Connect

    Garrett, L.D. )

    1992-06-01

    One of the early problems facing engineers planning the construction of the Iroquois Gas Transmission System, from the Canadian border through six Northeastern states, was how and where to cross the major rivers and Long Island Sound. The Housatonic River, a major waterway near Shelton, Conn., had been crossed earlier during a previous pipeline project. The earlier crossing had been installed by conventional open cutting. However, the state of Connecticut and its environmental agencies insisted that the Iroquois crossing must be installed by horizontal directional drilling. This paper reports that prior to completing the design of the Housatonic River crossing, Iroquois Gas engineers took several deep soil borings at three possible crossing sites. Each site showed the same thing: a hard schist rock with compression strengths from 2,760 psi to 16,500 psi, overlain by either recent fill or alluvial till. Although most of the river crossing would be drilled through the hard rock formation, the drilled path would certainly have to cross the transition zones of fill or till on both sides of the river.

  20. Evaluating Cross-Lingual Equating.

    ERIC Educational Resources Information Center

    Rapp, Joel; Allalouf, Avi

    This study examined the cross-lingual equating process adopted by a large scale testing system in which target language (TL) forms are equated to the source language (SL) forms using a set of translated items. The focus was on evaluating the degree of error inherent in the routine cross-lingual equating of the Verbal Reasoning subtest of the…

  1. Boundary Crossing and Boundary Objects

    ERIC Educational Resources Information Center

    Akkerman, Sanne F.; Bakker, Arthur

    2011-01-01

    Diversity and mobility in education and work present a paramount challenge that needs better conceptualization in educational theory. This challenge has been addressed by educational scholars with the notion of "boundaries", particularly by the concepts of "boundary crossing" and "boundary objects". Although studies on boundary crossing and…

  2. Thermoelastic damping in microrings with circular cross-section

    NASA Astrophysics Data System (ADS)

    Li, Pu; Fang, Yuming; Zhang, Jianrun

    2016-01-01

    Predicting thermoelastic damping (TED) is crucial in the design of high Q micro-resonators. Microrings are often critical components in many micro-resonators. Some analytical models for TED in microrings have already been developed in the past. However, the previous works are limited to the microrings with rectangular cross-section. The temperature field in the rectangular cross-section is one-dimensional. This paper deals with TED in the microrings with circular cross-section. The temperature field in the circular cross-section is two-dimensional. This paper first presents a 2-D analytical model for TED in the microrings with circular cross-section. Only the two-dimensional heat conduction in the circular cross-section is considered. The heat conduction along the circumferential direction of the microring is neglected in the 2-D model. Then the 2-D model has been extended to cover the circumferential heat conduction, and a 3-D analytical model for TED has been developed. The analytical results from the present 2-D and 3-D models show good agreement with the numerical results of FEM model. The limitations of the present 2-D analytical model are assessed.

  3. abo-cross: Hydrogen broadening cross-section calculator

    NASA Astrophysics Data System (ADS)

    Barklem, P. S.; Anstee, S. D.; O'Mara, B. J.

    2015-07-01

    Line broadening cross sections for the broadening of spectral lines by collisions with neutral hydrogen atoms have been tabulated by Anstee & O'Mara (1995), Barklem & O'Mara (1997) and Barklem, O'Mara & Ross (1998) for s-p, p-s, p-d, d-p, d-f and f-d transitions. abo-cross, written in Fortran, interpolates in these tabulations to make these data more accessible to the end user. This code can be incorporated into existing spectrum synthesis programs or used it in a stand-alone mode to compute line broadening cross sections for specific transitions.

  4. Unstable avoided crossing in coupled spinor condensates.

    PubMed

    Bernier, Nathan R; Dalla Torre, Emanuele G; Demler, Eugene

    2014-08-01

    We consider the dynamics of a Bose-Einstein condensate with two internal states, coupled through a coherent drive. We focus on a specific quench protocol, in which the sign of the coupling field is suddenly changed. At a mean-field level, the system is transferred from a minimum to a maximum of the coupling energy and can remain dynamically stable, in spite of the development of negative-frequency modes. In the presence of a nonzero detuning between the two states, the "charge" and "spin" modes couple, giving rise to an unstable avoided crossing. This phenomenon is generic to systems with two dispersing modes away from equilibrium and constitutes an example of class-I(o) nonequilibrium pattern formation in quantum systems. PMID:25148334

  5. To Cross or Not to Cross: Objective Timing Methods of Assessing Street Crossings without Traffic Controls.

    ERIC Educational Resources Information Center

    Sauerburger, Dona

    1989-01-01

    This paper presents methods for visually impaired pedestrians assessing safety of street crossings in the absence of traffic controls, considering both limited detection ability and the difficulty of judging when approaching traffic is distant or slow enough to allow crossing. Alternatives for "uncrossable" streets and teaching methods are…

  6. Cross flow filter development for advanced fossil power generation

    SciTech Connect

    Lippert, T.E.; Alvin, M.A.; Bachovchin, D.M.; Haldipur, G.B.; Newby, R.A.; Smeltzer, E.E. )

    1990-01-01

    The porous ceramic cross flow filter has been under development at Westinghouse in conjunction with the U.S. Department of Energy, Morgantown Energy Technology Center (DOE/METC) for advanced fossil power generation. The ceramic cross flow filter is capable of high temperature operation, and is basically an absolute filter on ash. The cross flow filter can be operated at high flow capacity, while simultaneously exhibiting relatively low pressure drop flow characteristics. This paper describes the cross flow filter development at Westinghouse, and reviews the results of many in-house and field test programs. Testing has included operation of the filter in subpilot pressurized fluidized-bed combustion and coal gasification applications. Testing is also being conducted at Westinghouse to evaluate filter characteristics over long-term operation (3,000 hours) utilizing dedicated test facilities.

  7. Analog computation of auto and cross-correlation functions

    NASA Technical Reports Server (NTRS)

    1974-01-01

    For analysis of the data obtained from the cross beam systems it was deemed desirable to compute the auto- and cross-correlation functions by both digital and analog methods to provide a cross-check of the analysis methods and an indication as to which of the two methods would be most suitable for routine use in the analysis of such data. It is the purpose of this appendix to provide a concise description of the equipment and procedures used for the electronic analog analysis of the cross beam data. A block diagram showing the signal processing and computation set-up used for most of the analog data analysis is provided. The data obtained at the field test sites were recorded on magnetic tape using wide-band FM recording techniques. The data as recorded were band-pass filtered by electronic signal processing in the data acquisition systems.

  8. Transient scattering from dielectric cylinders - E-field, H-field, and combined field solutions

    NASA Astrophysics Data System (ADS)

    Vechinski, Douglas A.; Rao, Sadasiva M.

    1992-10-01

    In this work, the problem of transient scattering by arbitrarily shaped two-dimensional dielectric cylinders is solved using the marching-on-in-time technique. The dielectric problem is approached via the equivalence principle. Three different formulations, namely, the electric field integral equation formulation, the magnetic field integral equation formulation, and the combined field integral equation formulation are considered. Numerical results are presented for two cross sections, namely, a circle and a square, and compared with inverse discrete Fourier transform (IDFT) techniques. In each case, good agreement is obtained with the IDFT solution.

  9. Transient scattering from dielectric cylinders - E-field, H-field, and combined field solutions

    NASA Technical Reports Server (NTRS)

    Vechinski, Douglas A.; Rao, Sadasiva M.

    1992-01-01

    In this work, the problem of transient scattering by arbitrarily shaped two-dimensional dielectric cylinders is solved using the marching-on-in-time technique. The dielectric problem is approached via the equivalence principle. Three different formulations, namely, the electric field integral equation formulation, the magnetic field integral equation formulation, and the combined field integral equation formulation are considered. Numerical results are presented for two cross sections, namely, a circle and a square, and compared with inverse discrete Fourier transform (IDFT) techniques. In each case, good agreement is obtained with the IDFT solution.

  10. Modeling elastic momentum transfer cross-sections from mobility data

    NASA Astrophysics Data System (ADS)

    Nikitović, Ž. D.; Stojanović, V. D.; Raspopović, Z. M.

    2016-04-01

    In this letter we present a new method to simply obtain the elastic momentum transfer cross-section which predicts a maximum of reduced mobility and its sensitivity to the temperature variation at low energies. We first determined the transport cross-section which resembles mobility data for similar closed-shell systems by using the Monte Carlo method. Second, we selected the most probable reactive processes and compiled cross-sections from experimental and theoretical data. At the end, an elastic momentum transfer cross-section is obtained by subtracting the compiled cross-sections from the momentum transfer cross-section, taking into account the effects of the angular scattering distributions. Finally, the cross-section set determined in such a way is used as an input in a final Monte Carlo code run, to calculate the flux and bulk reduced mobility for Ne+ + CF4 which were discussed as functions of the reduced electric field E/N (N is the gas density) for the temperature T = 300 K.

  11. Level crossings in a cavity QED model

    SciTech Connect

    Larson, J.

    2006-01-15

    In this paper I study the dynamics of a two-level atom interacting with a standing-wave field. When the atom is subjected to a weak linear force, the problem can be turned into a time-dependent one, and the evolution is understood from the band structure of the spectrum. The presence of level crossings in the spectrum gives rise to Bloch oscillations of the atomic motion. Here I investigate the effects of the atom-field detuning parameter. A variety of different level crossings are obtained by changing the magnitude of the detuning, and the behavior of the atomic motion is strongly affected due to this. I also consider the situation in which the detuning is oscillating in time, and its impact on the atomic motion. Wave-packet simulations of the full problem are treated numerically and the results are compared with analytical solutions given by the standard Landau-Zener and the three-level Landau-Zener models.

  12. Cross-Sectional Transport Imaging in a Multijunction Solar Cell

    SciTech Connect

    Haegel, Nancy M.; Ke, Chi-Wen; Taha, Hesham; Guthrey, Harvey; Fetzer, C. M.; King, Richard

    2015-06-14

    Combining highly localized electron-beam excitation at a point with the spatial resolution capability of optical near-field imaging, we have imaged carrier transport in a cross-sectioned multijunction (GaInP/GaInAs/Ge) solar cell. We image energy transport associated with carrier diffusion throughout the full width of the middle (GaInAs) cell and luminescent coupling from point excitation in the top cell GaInP to the middle cell. Supporting cathodoluminescence and near-field photoluminescence measurements demonstrate excitation-dependent Fermi level splitting effects that influence cross-sectioned spectroscopy results as well as transport limitations on the spatial resolution of cross-sectional measurements.

  13. Cross polarization with long delayed contact in rotating solids

    NASA Astrophysics Data System (ADS)

    Ding, Shangwu; McDowell, Charles A.

    1996-06-01

    The cross polarization NMR spectra and cross relaxation rates of polycrystalline hexamethylbenzene and adamantane were obtained by employing a long delay before contact for samples spinning at, and off, the magic angle with respect to the static magnetic field. The results are compared with those obtained by using the conventional cross polarization pulse sequence. The results support the memory effect explanation of origin of the SPEDA spectra in contrast with the assumptions that the high resolution SPEDA spectra arising either, from the nearly isotropic motion of a very small fraction, or a pool of highly thermo-activated molecules, or from special spin pairs within the crystallites which are orientated at the magic angle with respect to the static magnetic field.

  14. Chemical Dependency and Violence: Working with Dually Affected Families. A Cross-Training Program Manual for Counselors and Advocates.

    ERIC Educational Resources Information Center

    Wright, Janet M.

    This manual is designed as a cross-training program guide for counselors working in the fields of woman abuse and chemical dependency. (A cross-training program is a system for one (or more) agency personnel to train each other in their respective areas of expertise.) Chapter 1 discusses the rationale and goals of a cross-training program; issues…

  15. EPIC: E-field Parallel Imaging Correlator

    NASA Astrophysics Data System (ADS)

    Thyagarajan, Nithyanandan; Beardsley, Adam P.; Bowman, Judd D.; Morales, Miguel F.

    2015-11-01

    E-field Parallel Imaging Correlator (EPIC), a highly parallelized Object Oriented Python package, implements the Modular Optimal Frequency Fourier (MOFF) imaging technique. It also includes visibility-based imaging using the software holography technique and a simulator for generating electric fields from a sky model. EPIC can accept dual-polarization inputs and produce images of all four instrumental cross-polarizations.

  16. Hill crossing during preheating after hilltop inflation

    NASA Astrophysics Data System (ADS)

    Antusch, Stefan; Nolde, David; Orani, Stefano

    2015-06-01

    In ``hilltop inflation'', inflation takes place when the inflaton field slowly rolls from close to a maximum of its potential (i.e. the ``hilltop'') towards its minimum. When the inflaton potential is associated with a phase transition, possible topological defects produced during this phase transition, such as domain walls, are efficiently diluted during inflation. It is typically assumed that they also do not reform after inflation, i.e. that the inflaton field stays on its side of the ``hill'', finally performing damped oscillations around the minimum of the potential. In this paper we study the linear and the non-linear phases of preheating after hilltop inflation. We find that the fluctuations of the inflaton field during the tachyonic oscillation phase grow strong enough to allow the inflaton field to form regions in position space where it crosses ``over the top of the hill'' towards the ``wrong vacuum''. We investigate the formation and behaviour of these overshooting regions using lattice simulations: rather than durable domain walls, these regions form oscillon-like structures (i.e. localized bubbles that oscillate between the two vacua) which should be included in a careful study of preheating in hilltop inflation.

  17. Cross-Cultural Counseling Concerns.

    ERIC Educational Resources Information Center

    Ahia, Chikezie Emmanuel

    1984-01-01

    Examines problems and concerns of cross cultural counseling and psychotherapy. Raises specific questions concerning research designs and approaches, differences in cosmology, epistemology, differences in nosology, and problems of evaluation or testing. (JAC)

  18. Oculocerebral hypopigmentation syndrome (Cross syndrome).

    PubMed

    Ozkan, H; Unsal, E; Köse, G

    1991-01-01

    A typical case of Cross syndrome with hypopigmentation, mental and psychomotor retardation, spasticity, bilateral optic atrophy and dental defects in a three-year-old boy is presented. The clinical features of this rare syndrome are discussed. PMID:1814043

  19. Cross-Referencing Program Participation.

    ERIC Educational Resources Information Center

    Siegel, Donald

    1981-01-01

    In an attempt to ascertain student involvement in physical education programs, a cross-referencing participation scale was conducted to determine which activities were most popular, the extent of participation, and budget justifications. (JN)

  20. Cross sections at hadron colliders

    SciTech Connect

    Paige, F.E.

    1982-01-01

    The predicted cross sections are given for new Z'/sup 0/ bosons, for the Drell-Yan continuum of ..mu../sup +/..mu../sup -/ pairs, for high p/sub T/ hadron jets, for high p/sub T/ single photons, and for the associated production of heavy quarks. These processes have been selected not to cover the most interesting physics, but to provide a representative selection of cross sections for which to compare various energies and luminosities.

  1. Multivalued Fields

    SciTech Connect

    Kleinert, Hagen

    2008-01-03

    The lecture gives a short introduction to the theory of multivalued fields which are important for understanding the behavior and phase transitions of many physical systems, such as superfluids, superconductors, crystals, and confined charges.

  2. Cross-Validated Bagged Learning

    PubMed Central

    Petersen, Maya L.; Molinaro, Annette M.; Sinisi, Sandra E.; van der Laan, Mark J.

    2007-01-01

    Many applications aim to learn a high dimensional parameter of a data generating distribution based on a sample of independent and identically distributed observations. For example, the goal might be to estimate the conditional mean of an outcome given a list of input variables. In this prediction context, bootstrap aggregating (bagging) has been introduced as a method to reduce the variance of a given estimator at little cost to bias. Bagging involves applying an estimator to multiple bootstrap samples, and averaging the result across bootstrap samples. In order to address the curse of dimensionality, a common practice has been to apply bagging to estimators which themselves use cross-validation, thereby using cross-validation within a bootstrap sample to select fine-tuning parameters trading off bias and variance of the bootstrap sample-specific candidate estimators. In this article we point out that in order to achieve the correct bias variance trade-off for the parameter of interest, one should apply the cross-validation selector externally to candidate bagged estimators indexed by these fine-tuning parameters. We use three simulations to compare the new cross-validated bagging method with bagging of cross-validated estimators and bagging of non-cross-validated estimators. PMID:19255599

  3. A set of cross sections and transport coefficients for electrons in HBr

    NASA Astrophysics Data System (ADS)

    Šašić, O.; Dujko, S.; Makabe, T.; Petrović, Z. Lj.

    2012-04-01

    We have compiled a set of electron collision cross sections for HBr. It will be useful for a fluid modeling of HBr plasmas together with transport coefficients in both DC and RF, E and E × B fields. The calculation made use of a Monte Carlo technique. The transport coefficients are rather unstructured because the total cross section resembles that of a constant collisonal frequency model. Additional measurements of swarm parameters are required in order to obtain more acurate set of cross sections.

  4. 242Amm fission cross section

    NASA Astrophysics Data System (ADS)

    Browne, J. C.; White, R. M.; Howe, R. E.; Landrum, J. H.; Dougan, R. J.; Dupzyk, R. J.

    1984-06-01

    The neutron-induced fission cross section of 242Amm has been measured over the energy region from 10-3 eV to ~20 MeV in a series of experiments utilizing a linac-produced "white" neutron source and a monoenergetic source of 14.1 MeV neutrons. The cross section was measured relative to that of 235U in the thermal (0.001 to ~3 eV) and high energy (1 keV to ~20 MeV) regions and normalized to the ENDF/B-V 235U(n,f) evaluated cross section. In the resonance energy region (0.5 eV to 10 keV) the neutron flux was measured using thin lithium glass scintillators and the relative cross section thus obtained was normalized to the thermal energy measurement. This procedure allowed a consistency check between the thermal and high energy data. The cross section data have a statistical accuracy of ~0.5% at thermal energies and in the 1-MeV energy region, and a systematic uncertainty of ~5%. We confirmed that 242Amm has the largest thermal fission cross section known with a 2200 m/sec value of 6328 b. Results of a Breit-Wigner sum-of-single-levels analysis of 48 fission resonances up to 20 eV are presented and the connection of these resonance properties to the large thermal cross section is discussed. Our measurements are compared with previously reported results.

  5. A Concept of Cross-Ferroic Plasma Turbulence

    PubMed Central

    Inagaki, S.; Kobayashi, T.; Kosuga, Y.; Itoh, S.-I.; Mitsuzono, T.; Nagashima, Y.; Arakawa, H.; Yamada, T.; Miwa, Y.; Kasuya, N.; Sasaki, M.; Lesur, M.; Fujisawa, A.; Itoh, K.

    2016-01-01

    The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux. PMID:26917218

  6. A Concept of Cross-Ferroic Plasma Turbulence.

    PubMed

    Inagaki, S; Kobayashi, T; Kosuga, Y; Itoh, S-I; Mitsuzono, T; Nagashima, Y; Arakawa, H; Yamada, T; Miwa, Y; Kasuya, N; Sasaki, M; Lesur, M; Fujisawa, A; Itoh, K

    2016-01-01

    The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux. PMID:26917218

  7. Probing magnetic microstructures with quasi-ballistic Hall crosses

    NASA Astrophysics Data System (ADS)

    Fasbender, S.; Schluck, J.; Cerchez, M.; Heinzel, T.; Sievers, S.; Pierz, K.; Schumacher, H. W.

    2016-03-01

    Hall sensing is performed on a localized magnetic field pattern using a quasi-ballistic Hall cross device. The Hall resistance shows a pronounced peak as a function of the magnetic field amplitude which is absent in the magnetization hysteresis loop. This non-monotonic response exemplifies qualitatively the failure of conventional Hall sensing. It is demonstrated how, by using a numerical simulation based on the Landauer-Büttiker model, the amplitude of the magnetic field profile can be determined from such measurements.

  8. The World of Cross-Cultural Research: Insights for Gifted Education

    ERIC Educational Resources Information Center

    VanTassel-Baska, Joyce

    2013-01-01

    As the world becomes smaller in a small field like gifted education, cross-cultural research gives us a unique opportunity to understand top students and academic interventions in a deeper way. In this article, the author describes the importance of cross-cultural research as a way to serve gifted children globally. A description of a…

  9. Crossing of the phantom divide using tachyon-Gauss-Bonnet gravity

    SciTech Connect

    Sadeghi, J.; Banijamali, A.; Milani, F.; Setare, M. R.

    2009-06-15

    In this paper we consider two models. First, we study tachyon-Gauss-Bonnet gravity and obtain the condition of the equation of state crossing -1. Second, we discuss the modified Gauss-Bonnet gravity with the tachyon field and show the condition of {omega} crossing -1. Also, we plot figures for {omega} numerically in special potential and coupling function.

  10. Radar cross section visualization using sample buffer progressive refinement volume rendering

    NASA Astrophysics Data System (ADS)

    Jones, Alain L.

    1993-12-01

    This thesis explores how to interactively examine the radar cross section characteristics of an object. As such, this research encompasses two rapidly burgeoning fields: scientific visualization and low-observables technology.

  11. Screening bean germplasm for cross-resistance to candidate begomoviruses and Beet mild curly top virus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Candidate cultivars of selected Phaselous vulgaris L. in a core collection (Americas) were screened for geminivirus cross-resistance by inoculating seedlings with candidate viruses from phylogenetically divergent genera Begomovirus and Curtovirus (family Geminiviridae). Field trials under natural v...

  12. Antisymmetric galaxy cross-correlations as a cosmological probe

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Kamionkowski, Marc; Kovetz, Ely D.; Raccanelli, Alvise; Shiraishi, Maresuke

    2016-01-01

    The autocorrelation between two members of a galaxy population is symmetric under the interchange of the two galaxies being correlated. The cross-correlation between two different types of galaxies, separated by a vector r , is not necessarily the same as that for a pair separated by -r . Local anisotropies in the two-point cross-correlation function may thus indicate a specific direction which when mapped as a function of position trace out a vector field. This vector field can then be decomposed into longitudinal and transverse components, and those transverse components written as positive- and negative-helicity components. A locally asymmetric cross-correlation of the longitudinal type arises naturally in halo clustering, even with Gaussian initial conditions, and could be enhanced with local-type non-Gaussianity. Early-Universe scenarios that introduce a vector field may also give rise to such effects. These antisymmetric cross-correlations also provide a new possibility to seek a preferred cosmic direction correlated with the hemispherical power asymmetry in the cosmic microwave background and to seek a preferred location associated with the cosmic microwave background cold spot. New ways to seek cosmic parity breaking are also possible.

  13. Cross-cultural organizational behavior.

    PubMed

    Gelfand, Michele J; Erez, Miriam; Aycan, Zeynep

    2007-01-01

    This article reviews research on cross-cultural organizational behavior (OB). After a brief review of the history of cross-cultural OB, we review research on work motivation, or the factors that energize, direct, and sustain effort across cultures. We next consider the relationship between the individual and the organization, and review research on culture and organizational commitment, psychological contracts, justice, citizenship behavior, and person-environment fit. Thereafter, we consider how individuals manage their interdependence in organizations, and review research on culture and negotiation and disputing, teams, and leadership, followed by research on managing across borders and expatriation. The review shows that developmentally, cross-cultural research in OB is coming of age. Yet we also highlight critical challenges for future research, including moving beyond values to explain cultural differences, attending to levels of analysis issues, incorporating social and organizational context factors into cross-cultural research, taking indigenous perspectives seriously, and moving beyond intracultural comparisons to understand the dynamics of cross-cultural interfaces. PMID:17044797

  14. Weak lensing corrections to tSZ-lensing cross correlation

    NASA Astrophysics Data System (ADS)

    Tröster, Tilman; Van Waerbeke, Ludovic

    2014-11-01

    The cross correlation between the thermal Sunyaev-Zeldovich (tSZ) effect and gravitational lensing in wide field has recently been measured. It can be used to probe the distribution of the diffuse gas in large scale structure, as well as inform us about the missing baryons. As for any lensing-based quantity, higher order lensing effects can potentially affect the signal. Here, we extend previous higher order lensing calculations to the case of tSZ-lensing cross correlations. We derive terms analogous to corrections due to the Born approximation, lens-lens coupling, and reduced shear up to order l gtrsim 3000.

  15. Fe-Catalyzed Cross-Dehydrogenative Coupling Reactions.

    PubMed

    Lv, Leiyang; Li, Zhiping

    2016-08-01

    Cross-dehydrogenative coupling (CDC), which enables the formation of carbon-carbon (C-C) and C-heteroatom bonds from the direct coupling of two C-H bonds or C-H/X-H bonds, represents a new state of the art in the field of organic chemistry. Iron, a prominent metal, has already shown its versatile application in chemical synthesis. This review attempts to provide a comprehensive understanding of the evolution of cross-dehydrogenative coupling via iron catalysis, as well as its application in synthetic chemistry. PMID:27573390

  16. Differential Cross Sections for Proton-Proton Elastic Scattering

    NASA Technical Reports Server (NTRS)

    Norman, Ryan B.; Dick, Frank; Norbury, John W.; Blattnig, Steve R.

    2009-01-01

    Proton-proton elastic scattering is investigated within the framework of the one pion exchange model in an attempt to model nucleon-nucleon interactions spanning the large range of energies important to cosmic ray shielding. A quantum field theoretic calculation is used to compute both differential and total cross sections. A scalar theory is then presented and compared to the one pion exchange model. The theoretical cross sections are compared to proton-proton scattering data to determine the validity of the models.

  17. Method and apparatus for controlling cross contamination of microfluid channels

    DOEpatents

    Hasselbrink, Jr., Ernest F.; Rehm, Jason E.; Paul, Phillip H.; Arnold, Don W.

    2006-02-07

    A method for controlling fluid flow at junctions in microchannel systems. Control of fluid flow is accomplished generally by providing increased resistance to electric-field and pressure-driven flow in the form of regions of reduced effective cross-sectional area within the microchannels and proximate a channel junction. By controlling these flows in the region of a microchannel junction it is possible to eliminate sample dispersion and cross contamination and inject well-defined volumes of fluid from one channel to another.

  18. Holden Crater Dune Field

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    A common location for dune fields on Mars is in the basin of large craters. This dune field is located in Holden Crater at 25 degrees South atitude.

    Image information: VIS instrument. Latitude -25.5, Longitude 326.8 East (33.2 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  19. Regenerator cross arm seal assembly

    DOEpatents

    Jackman, Anthony V.

    1988-01-01

    A seal assembly for disposition between a cross arm on a gas turbine engine block and a regenerator disc, the seal assembly including a platform coextensive with the cross arm, a seal and wear layer sealingly and slidingly engaging the regenerator disc, a porous and compliant support layer between the platform and the seal and wear layer porous enough to permit flow of cooling air therethrough and compliant to accommodate relative thermal growth and distortion, a dike between the seal and wear layer and the platform for preventing cross flow through the support layer between engine exhaust and pressurized air passages, and air diversion passages for directing unregenerated pressurized air through the support layer to cool the seal and wear layer and then back into the flow of regenerated pressurized air.

  20. Accurate Cross Sections for Microanalysis

    PubMed Central

    Rez, Peter

    2002-01-01

    To calculate the intensity of x-ray emission in electron beam microanalysis requires a knowledge of the energy distribution of the electrons in the solid, the energy variation of the ionization cross section of the relevant subshell, the fraction of ionizations events producing x rays of interest and the absorption coefficient of the x rays on the path to the detector. The theoretical predictions and experimental data available for ionization cross sections are limited mainly to K shells of a few elements. Results of systematic plane wave Born approximation calculations with exchange for K, L, and M shell ionization cross sections over the range of electron energies used in microanalysis are presented. Comparisons are made with experimental measurement for selected K shells and it is shown that the plane wave theory is not appropriate for overvoltages less than 2.5 V. PMID:27446747

  1. Analyzing cross-sector interdependencies.

    SciTech Connect

    Peerenboom, J. P.; Fisher, R. E.; Decision and Information Sciences

    2007-01-01

    This paper discusses cross-sector infrastructure interdependencies and key risk considerations, analysis approaches, research and development needs, and the range of interdisciplinary skills required for comprehensive cross-sector analysis. Traditional analysis of interdependencies involves characterization of infrastructure-to-infrastructure linkages to identify the key infrastructure components that, if lost or degraded, could adversely affect the performance of other infrastructures. Such analysis is motivated by the recognition that a series of incidents could interact (cascade) across critical infrastructures to degrade the service upon which all depend. From a risk perspective, cross-sector analysis also must involve identifying and characterizing a wide range of threats (natural and accidental, systems related, and intentional), vulnerabilities (physical and cyber), and consequences of loss (e.g., health and safety, economic, national security, environmental, sociopolitical). Such information provides a foundation for making defensible, cost-effective infrastructure protection and operation decisions to ensure the security and reliability of our interdependent systems.

  2. Arun field

    SciTech Connect

    Jordan, C.F. Jr.; Abdullah, M.

    1988-01-01

    The Arun field is a giant gas-condensate field operated by Mobil and Pertamina with over 20,000 acres of closure at the top of the Arun reservoir. A middle-shelf patch reef complex of early to middle Miocene age is the producing facies at the Arun field. About 1,100 ft of porous limestones, encased in shales, create a stratigraphic trap for overpressure hydrocarbons. Three main carbonate lithologies were encountered during the examination of over 4,300 ft of core; (1) a reef facies consisting of vuggy, coral encrusting, red-algal boundstones, (2) a near-reef facies consisting of foraminiferal, mixed-skeletal packstones with gravel-size coral fragments, and (3) an interreef lagoonal facies consisting of benthonic-foram packstones. Twenty-two species of corals have been identified from Arun reef facies; major reef-forming coals, listed in order of decreasing abundance, are Porites cf P. Lutes, Cyphastrea microphthalma, Astreopora myriophthalma, Styloconiella gunetheri, Porites solida, and Acropora ssp. The Arun reef is comprised of limestones (with minor amounts of dolomite). No shale beds occur in the sequence, and all carbonate facies are in communication. A pervasive microporosity, occurring throughout the Arun Limestone, results from meteoric alteration of original carbonate mud to form a microrhombic porosity that accounts for about three-fourths of the field's total porosity.

  3. Cross-Cultural Interpretations of Curricular Contextual Crossings

    ERIC Educational Resources Information Center

    Schlein, Candace; Garii, Barbara

    2011-01-01

    Teachers--who are generally representatives of the cultural mainstream--are expected to use global experiences to become culturally enhanced and to bring these enhancements back to their classrooms. In this article, the authors discuss a cross-cultural exploration of investigations into the experiences of Canadian and U.S. educators with…

  4. The pecked cross symbol in ancient mesoamerica.

    PubMed

    Aveni, A F; Hartung, H; Buckingham, B

    1978-10-20

    Attention is directed to a design, possibly of Teotihuacan origin, carved both in rock and in the floors of ceremonial buildings throughout ancient Mesoamerica. Consisting generally of a double circular pattern centered on a set of orthogonal axes, the so-called pecked cross or quartered circle figure is shown to exhibit a remarkable consistency in appearance throughout its 29 reported locations, thus suggesting that it was not perfunctory. The metric properties of the symbols gleaned from field surveys are delineated, and several interpretations of their possible functions are discussed. These symbols may have been intended as astronomical orientational devices, surveyor's bench marks, calendars, or ritual games. Evidence is presented which implies that more than one and perhaps all of these functions were employed simultaneously, a view which is shown to be consistent with the cosmological attitude of the pre-Columbian people. PMID:17817633

  5. Geophysical Fluid Flow Cell (GFFC) Cross Section

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This drawing shows a cross-section view of the test cell at the heart of the Geophysical Fluid Flow Cell (GFFC) that flew on two Spacelab missions. The middle and lower drawings depict the volume of the silicone oil layer that served as the atmosphere as the steel ball rotated and an electrostatic field pulled the oil inward to mimic gravity's effects during the experiments. The GFFC thus produced flow patterns that simulated conditions inside the atmospheres of Jupiter and the Sun and other stars. The principal investigator was John Hart of the University of Colorado at Boulder. It was managed by NASA's Marshall Space Flight Center (MSFC). An Acrobat PDF copy of this drawing is available at http://microgravity.nasa.gov/gallery. (Credit: NASA/Marshall Space Flight Center)

  6. Origins of the Field-Dependent and Field Independent Cognitive Styles.

    ERIC Educational Resources Information Center

    Goodenough, Donald R.; Witkin, Herman A.

    The literature on sources of individual differences in field dependence-independence is reviewed, and findings on ontogenetic development and cross-cultural differences are incorporated into the theory of psychological differentiation. During the growth years, individuals develop toward greater field independence. Hormonal and X-linked genetic…

  7. Influence of grid bar shape on field cleaner performance - field testing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A test was conducted to evaluate the influence of grid bar cross sectional shape on cotton stripper field cleaner performance in terms of cleaning efficiency, seed cotton loss, and fiber and yarn quality. Three field cleaner configurations were tested on a cotton stripper harvester operating under f...

  8. 39 CFR 259.2 - Red Cross.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Red Cross. 259.2 Section 259.2 Postal Service....2 Red Cross. (a) General. The Postal Service and the Red Cross cooperate to maintain communication... those caused by enemy action. (b) Role of Postal Service. The Postal Service and the Red Cross...

  9. 39 CFR 259.2 - Red Cross.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 39 Postal Service 1 2013-07-01 2013-07-01 false Red Cross. 259.2 Section 259.2 Postal Service....2 Red Cross. (a) General. The Postal Service and the Red Cross cooperate to maintain communication... those caused by enemy action. (b) Role of Postal Service. The Postal Service and the Red Cross...

  10. 39 CFR 259.2 - Red Cross.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 39 Postal Service 1 2014-07-01 2014-07-01 false Red Cross. 259.2 Section 259.2 Postal Service....2 Red Cross. (a) General. The Postal Service and the Red Cross cooperate to maintain communication... those caused by enemy action. (b) Role of Postal Service. The Postal Service and the Red Cross...

  11. 39 CFR 259.2 - Red Cross.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 39 Postal Service 1 2012-07-01 2012-07-01 false Red Cross. 259.2 Section 259.2 Postal Service....2 Red Cross. (a) General. The Postal Service and the Red Cross cooperate to maintain communication... those caused by enemy action. (b) Role of Postal Service. The Postal Service and the Red Cross...

  12. Yoshizawa's cross-helicity effect and its quenching

    NASA Astrophysics Data System (ADS)

    Brandenburg, A.; Rädler, K.-H.

    2013-02-01

    A central quantity in mean-field magnetohydrodynamics is the mean electromotive force EMF, which in general depends on the mean magnetic field. It may however have a part independent of the mean magnetic field. Here we study an example of a rotating conducting body of turbulent fluid with non-zero cross-helicity, in which a contribution to the EMF proportional to the angular velocity occurs (Yoshizawa 1990). If the forcing is helical, it also leads to an alpha effect, and large-scale magnetic fields can be generated. For not too rapid rotation, the field configuration is such that Yoshizawa's contribution to the EMF is considerably reduced compared to the case without alpha effect. In that case, large-scale flows are also found to be generated.

  13. Redressing Cross-Dressed Shakespeare

    ERIC Educational Resources Information Center

    Martin, Thomas L.; Pesta, Duke

    2003-01-01

    Gender critics obsess over the boy actors who played female roles on the Elizabethan stage. But, in their far-fetched interpretation of Shakespearean drama as a spectacle of cross dressing, these new historicists lose sight of a fundamental principle of theater. Thomas Martin and Duke Pesta argue that with their prurient chatter of "the…

  14. Neutrino cross-sections: Experiments

    SciTech Connect

    Sánchez, F.

    2015-07-15

    Neutrino-nucleus cross-sections are as of today the main source of systematic errors for oscillation experiments together with neutrino flux uncertainties. Despite recent experimental and theoretical developments, future experiments require even higher precisions in their search of CP violation. We will review the experimental status and explore possible future developments required by next generation of experiments.

  15. Cross-Language Information Retrieval.

    ERIC Educational Resources Information Center

    Oard, Douglas W.; Diekema, Anne R.

    1998-01-01

    Reviews research and practice in cross-language information retrieval (CLIR) that seeks to support the process of finding documents written in one natural language with automated systems that can accept queries expressed in other languages. Addresses user needs, document preprocessing, query formulation, matching strategies, sources of translation…

  16. Crossing Thresholds in Academic Reading

    ERIC Educational Resources Information Center

    Abbott, Rob

    2013-01-01

    This paper looks at the conceptual thresholds in relation to academic reading which might be crossed by undergraduate English Literature students. It is part of a wider study following 16 students through three years of undergraduate study. It uses theoretical ideas from Bakhtin and Foucault to analyse interviews with English lecturers. It…

  17. Cross-Cultural HRD. Symposium.

    ERIC Educational Resources Information Center

    2002

    The first of three papers from this symposium on cross-cultural human resource development (HRD), "Determinants of Supply of Technical Training Opportunities for Human Capital Development in Kenya" (Moses Waithanji Ngware, Fredrick Muyia Nafukho) reports findings from interviews of technical training institute department heads in Kenya who…

  18. Improved Zero-Crossing Detector

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Kuhnle, Paul F.

    1992-01-01

    Improved zero-crossing-detector circuit designed for precisely measuring difference between frequencies of two frequency-standard signal sources. Contains low-bandwidth first-stage amplifier and three limiting amplifiers, each "squares" signal bit more. Crosstalk eliminated and jitter reduced to about 10 to the negative 7th power microseconds.

  19. Demonstration of using crossed dipole GPR antennae for site characterization

    NASA Astrophysics Data System (ADS)

    Guy, Erich D.; Daniels, Jeffrey J.; Radzevicius, Stanley J.; Vendl, Mark A.

    Crossed dipole (cross-pole) and parallel dipole (co-pole) GPR data were acquired at an industrial site that formerly operated as a creosote wood treating facility in order to locate buried pipes and tanks or other possible contaminant-filled subsurface structures. Cross-pole data are not typically considered during GPR field studies, but proved essential for accurate site characterization at this location, as images produced using co-pole data had a poor signal to noise ratio. Data interpretations were confirmed through exploratory trenching conducted subsequent to this study. The GPR data proved successful in locating back-filled trenches that contained creosote-filled drainage tile, as well as vaults and a pit filled with pure creosote product at the site.

  20. What can cross-bedding tell us?

    NASA Astrophysics Data System (ADS)

    Douillet, G.; Kueppers, U.; Dingwell, D. B.

    2014-12-01

    Pyroclastic density currents (PDCs) are a common transport mechanism associated with explosive eruptions. They behave as particulate density current (flows of particles and fluid, whose driving force is the excess density compared to the ambient fluid). The particles thus are the defining part of the flow acting as the agent of momentum and the resultant deposits, making PDC sedimentology fundamental. We combine wind tunnel measurements with nontraditional field techniques to consider cross-bedding from dilute PDCs from the mm to the km scale. Each deposited particle requires 1) momentum to reach its final location, but 2) sufficiently low shearing to halt at this place. A range of shearing is constrained from wind tunnel measurements. The results are combined with field data from lacquer peel sampling (an outcrop is impregnated with a solidifying glue, preserving the primary organization of the grains). This enables quantification of the grain size of mm-scale laminae, giving an order of magnitude of turbulence during deposition. The lacquer peel technique also imaged cm-scale, soft sediment deformation patterns producing overturned beds. These are interpreted as related to Kelvin-Helmholtz shear instabilities between a granular-based flow and the bed. Dune bedform (DBs) cross-stratification at the m scale generally have an overall stoss-aggrading stacking pattern. Often interpreted as indicating supercritical flows, the wind-tunnel results and DBs' geometry rather suggest they are a specificity of particulate density currents with high deposition rates. Ground penetrating radar (GPR) reveals the 3D stability in location of a DB over several m depth, although stacking patterns vary with time and laterally. This emphasizes the primary influence of the basal boundary layer in the depositional dynamics. At the 100 m scale, DBs' shape evolves in dimensions and form, calling for 3D datasets. Terrestrial laser scanner and photogrammetry enable quantification of the

  1. Magnetic fields at neptune.

    PubMed

    Ness, N F; Acuña, M H; Burlaga, L F; Connerney, J E; Lepping, R P; Neubauer, F M

    1989-12-15

    The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. The detached bow shock wave in the supersonic solar wind flow was detected upstream at 34.9 Neptune radii (R(N)), and the magnetopause boundary was tentatively identified at 26.5 R(N) near the planet-sun line (1 R(N) = 24,765 kilometers). A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10(-5) gauss) was observed near closest approach, at a distance of 1.18 R(N). The planetary magnetic field between 4 and 15 R(N) can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R(N) and inclined by 47 degrees with respect to the rotation axis. The OTD dipole moment is 0.133 gauss-R(N)(3). Within 4 R(N), the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. The obliquity of Neptune and the phase of its rotation at encounter combined serendipitously so that the spacecraft entered the magnetosphere at a time when the polar cusp region was directed almost precisely sunward. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes

  2. Nili Patera Dune Field

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    This VIS image shows a dune field within Nili Patera, the northern caldera of a large volcanic complex in Syrtis Major.

    Image information: VIS instrument. Latitude 9, Longitude 67 East (293 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  3. Crater Floor Dune Field

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    Our final dune image shows a small dune field inside an unnamed crater south of Nili Fossae.

    Image information: VIS instrument. Latitude 20.6, Longitude 79 East (281 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  4. Reaction cross sections of carbon isotopes incident on a proton

    SciTech Connect

    Abu-Ibrahim, B.; Horiuchi, W.; Kohama, A.; Suzuki, Y.

    2008-03-15

    We systematically study total reaction cross sections of carbon isotopes with N=6-16 on a proton target for wide range of incident energies. An emphasis is put on the difference from the case of a carbon target. The calculations include the reaction cross sections of {sup 19,20,22}C at 40A MeV, the data of which have recently been measured at RIKEN. The Glauber theory is used to calculate the reaction cross sections. To describe the intrinsic structure of the carbon isotopes, we use a Slater determinant generated from a phenomenological mean-field potential, and construct the density distributions. To go beyond the simple mean-field model, we adopt two types of dynamical models: One is a core+n model for odd-neutron nuclei, and the other is a core+n+n model for {sup 16}C and {sup 22}C. We propose empirical formulas which are useful in predicting unknown cross sections.

  5. Cross presentation of antigen by dendritic cells: mechanisms and implications for immunotherapy.

    PubMed

    Sachamitr, Patty; Fairchild, Paul J

    2012-08-01

    Dendritic cells (DCs) possess the specialized potential to present exogenously derived antigen to cytotoxic T lymphocytes to elicit an immune response. This process, termed cross presentation, is crucial in the generation of immune response to viruses, tumors and in autoimmune disease. The ability of DCs to cross-present exogenous antigen to cytotoxic T lymphocytes makes them an attractive target for exploitation in immunotherapy. In recent years, significant advances have been made in understanding the mechanism of cross-presentation and the DC subsets involved. The recent discovery of the human cross presenting DC has given this field a new lease of life. In this report, the authors provide an overview of cross-presentation of antigen by DCs, focusing on the current understanding of the molecular mechanisms of the process. The authors also discuss the DC subsets involved in cross presentation and its role in health and disease. PMID:22992149

  6. Elastic and total cross sections for simple biomolecules in the intermediate energy range

    NASA Astrophysics Data System (ADS)

    Gupta, Dhanoj; Naghma, Rahla; Antony, Bobby

    2015-09-01

    The elastic and total cross sections for formaldehyde, acetaldehyde, acetone, 2-butanone and formamide are calculated using the spherical complex optical potential formalism in the intermediate energy range from 50 eV to 10 keV. These cross sections find application to various fields like radiation damage and biological sciences. The present results are compared with the available experimental and theoretical data and are found to give excellent agreement. The elastic cross sections reported for most of the targets in the present energy range are done for the first time. The energy dependence of the contribution of ionization and elastic cross section with respect to the total cross section and the correlation of total cross section with polarizability of the molecules are also studied.

  7. Elastic and total cross sections for simple biomolecules in the intermediate energy range

    SciTech Connect

    Gupta, Dhanoj; Naghma, Rahla; Antony, Bobby

    2015-09-15

    The elastic and total cross sections for formaldehyde, acetaldehyde, acetone, 2-butanone and formamide are calculated using the spherical complex optical potential formalism in the intermediate energy range from 50 eV to 10 keV. These cross sections find application to various fields like radiation damage and biological sciences. The present results are compared with the available experimental and theoretical data and are found to give excellent agreement. The elastic cross sections reported for most of the targets in the present energy range are done for the first time. The energy dependence of the contribution of ionization and elastic cross section with respect to the total cross section and the correlation of total cross section with polarizability of the molecules are also studied.

  8. Monoenergetic fast neutron reference fields: II. Field characterization

    NASA Astrophysics Data System (ADS)

    Nolte, Ralf; Thomas, David J.

    2011-12-01

    Monoenergetic neutron reference fields are required for the calibration of neutron detectors and dosemeters for various applications ranging from nuclear physics and nuclear data measurements to radiation protection. In a series of two separate publications the metrological aspects of the production and measurement of fast neutrons are reviewed. In the first part, requirements for the nuclear reactions used to produce neutron fields as well as methods for target characterization and the general layout of reference facilities were discussed. This second part focuses on the most important techniques for field characterization and includes the determination of the neutron fluence as well as the spectral neutron distribution and the determination of the fluence of contaminating photons. The measurements are usually carried out relative to reference cross sections which are reviewed in a separate contribution, but for certain conditions 'absolute' methods for neutron measurements can be used which are directly traceable to the international system of units (SI).

  9. Improved multimodal admittance method in varying cross section waveguides.

    PubMed

    Maurel, Agnès; Mercier, Jean-François; Pagneux, Vincent

    2014-04-01

    An improved version of the multimodal admittance method in acoustic waveguides with varying cross sections is presented. This method aims at a better convergence with respect to the number of transverse modes that are taken into account. It is based on an enriched modal expansion of the pressure: the N first modes are the local transverse modes and a supplementary (N+1)th mode, called boundary mode, is a well-chosen transverse function orthogonal to the N first modes. This expansion leads to the classical form of the coupled mode equations where the component of the boundary mode is of evanescent character. Under this form, the multimodal admittance method based on the Riccati equation on the admittance matrix (the Dirichlet-to-Neumann operator) is straightforwardly implemented. With this supplementary mode, in addition to the improvement of the convergence of the pressure field, results show a superconvergence of the scattered field outside of the varying cross sections region. PMID:24711716

  10. Cross-tail ion drift in a realistic model magnetotail

    NASA Technical Reports Server (NTRS)

    Propp, K.; Beard, D. B.

    1984-01-01

    By integrating the exact equations of motion, particle orbits have been followed in a good model magnetospheric field consisting of a planetary dipole, forward magnetosphere, and magnetotail current system. Proton energies from 2 eV to 20 keV were used for the full range of equatorial pitch angles and phase. Despite considerable pitch angle scattering in the equatorial plane crossings, it is found, first, that the bounce-averaged cross-tail drift velocity is approximately independent of pitch angle. Second, it is found that, averaged over initial gyrophase, the drift velocity (due to field curvature and gradient) is proportional to proton energy and is given to good approximation by adiabatic approximations, even up to 20 keV, despite the extreme lack of meeting the adiabatic criteria.

  11. Is Mild Dementia Related to Unsafe Street-Crossing Decisions?

    PubMed

    Dommes, Aurélie; Wu, Ya-Huei; Aquino, Jean-Pierre; Pitti-Ferrandi, Hélène; Soleille, Martine; Martineau-Fleury, Sophie; Samson, Michel; Rigaud, Anne-Sophie

    2015-01-01

    The overrepresentation of very old people (75 or older) in pedestrian crash statistics raises the issue of the effects of normal and pathologic ageing on gap-selection difficulties during street crossing. The present study focused on Alzheimer disease, a condition commonly associated with cognitive declines detrimental to daily life activities such as crossing the street. Twenty-five participants with mild dementia and 33 controls carried out a street-crossing task in a simulated environment. They also took a battery of cognitive tests. The mild-dementia group was more likely than the control group to make decisions that led to collisions with approaching cars, especially when the traffic was coming from 2 directions and they were in the far lane. Regression analyses demonstrated that the increased likelihood of collisions in the dementia group was associated with impairments in processing-speed and visual-attention abilities assessed on the Useful Field of View test. This test has already proven useful for predicting driving outcomes, falls, and street-crossing difficulties in healthy old adults, and among drivers with Alzheimer disease. Clinicians are encouraged to use it to help estimate whether a patient can drive, walk, and cross a street safely. PMID:25494367

  12. Updated compilation of electron-Cl2 scattering cross sections

    NASA Astrophysics Data System (ADS)

    Gregório, J.; Pitchford, L. C.

    2012-06-01

    We present a set of cross sections for electron scattering from ground state neutral chlorine molecules in the energy range from 0.01 to 100 eV. This cross section set is based on the recommendations in the review paper by Christophorou and Olthoff (1999 J. Phys. Chem. Ref. Data 28 131) and on more recently published theoretical and experimental results. These cross sections are used as input to a Boltzmann equation solver to yield the electron energy distribution as a function of E/N, the ratio of the electric field strength to neutral density, from which electron transport and rate coefficients (swarm parameters) in gas mixtures containing Cl2 are obtained. Reasonable agreement with the more reliable of the measured swarm parameters is obtained after slightly adjusting the magnitudes of some of the cross sections. While this agreement validates to some extent the cross section set, it is important to note that swarm data in Cl2-containing mixtures are limited and that there is a critical need for further measurements.

  13. Cross resistances in spinosad-resistant Culex quinquefasciatus (Diptera: Culicidae).

    PubMed

    Su, Tianyun; Cheng, Min-Lee

    2014-03-01

    A Culex quinquefasciatus Say colony was selected for 45 generations at LC70-90 levels using Natular XRG, a granular formulation of 2.5% spinosad for induction of spinosad resistance. Resistance to spinosad was noticed in early generations (F1-F9). Resistance levels increased gradually from generations F11-F35, and elevated significantly from generation F37 through F47, when resistance ratios reached 2,845-2,907-fold at LC50 and 11,948-22,928-fold at LC90 The spinosad-resistant Cx. quinquefasciatus colony was found not to be cross-resistant to Bacillus thuringiensis israelensis (Bti), a combination of Bti and Bacillus sphaericus, methoprene, pyriproxyfen, diflubenzuron, novaluron, temephos, or imidacloprid. However, it showed various levels of cross-resistance to B. sphaericus, spinetoram, abamectin, and fipronil. Conversely, a laboratory colony of Cx. quinquefasciatus that is highly resistant to B. sphaericus did not show cross-resistance to spinosad and spinetoram. Field-collected and laboratory-selected Cx. quinquefasciatus that showed low to moderate resistance to methoprene did not show cross-resistance to spinosad and spinetoram. Mechanisms of cross-resistance among several biorational pesticides were discussed according to their modes of actions. PMID:24724293

  14. Systematic analysis of reaction cross sections of carbon isotopes

    SciTech Connect

    Horiuchi, W.; Suzuki, Y.; Abu-Ibrahim, B.; Kohama, A.

    2007-04-15

    We systematically analyze total reaction cross sections of carbon isotopes with N= 6-16 on a {sup 12}C target for wide range of incident energy. The intrinsic structure of the carbon isotope is described by a Slater determinant generated from a phenomenological mean-field potential, which reasonably well reproduces the ground-state properties for most of the even N isotopes. We need separate studies not only for odd nuclei but also for {sup 16}C and {sup 22}C to improve their wave functions. The density of the carbon isotope is constructed by eliminating the effect of the center-of-mass motion. For the calculations of the cross sections, we take two schemes, the Glauber approximation and the eikonal model using a global optical potential. Both the reaction models successfully reproduce low and high incident energy data on the cross sections of {sup 12}C, {sup 13}C, and {sup 16}C on {sup 12}C. The calculated reaction cross sections of {sup 15}C are found to be considerably smaller than the empirical values observed at low energy. We find a consistent parametrization of the nucleon-nucleon scattering amplitude, differently from previous ones. Finally, we predict the total reaction cross section of {sup 22}C on {sup 12}C.

  15. The American Red Cross disaster mental health services: development of a cooperative, single function, multidisciplinary service model.

    PubMed

    Weaver, J D; Dingman, R L; Morgan, J; Hong, B A; North, C S

    2000-08-01

    Not until 1989 did the Red Cross officially recognize a need for a systematic and organized plan for the mental health needs of disaster survivors. Over the next decade, the Red Cross Disaster Mental Health Services program has developed and evolved to assist both disaster victims and the Red Cross workers who serve them to cope with the overwhelming stresses encountered by both groups in the aftermath of disasters. The Red Cross now coordinates a large and diverse group of mental health professionals from fields of psychology, psychiatry, nursing, social work, marriage and family therapy, and counseling who work together cooperatively. Cross-disciplinary conflicts are minimized by the Red Cross' generic approach to the various mental health professional specialties as functionally interchangeable in performing Red Cross duties. This article reviews the development of this process and describes one local Red Cross chapter's early experience as part of this effort. PMID:10932444

  16. Crossing Total Occlusions: Navigating Towards Recanalization.

    PubMed

    Sakes, Aimée; Regar, Evelyn; Dankelman, Jenny; Breedveld, Paul

    2016-06-01

    Chronic total occlusions (CTOs) represent the "last frontier" of percutaneous interventions. The main technical challenges lies in crossing the guidewire into the distal true lumen, which is primarily due to three problems: device buckling during initial puncture, inadequate visualization, and the inability to actively navigate through the CTO. To improve the success rate and to identify future research pathways, this study systematically reviews the state-of-the-art of all existing and invented devices for crossing occlusions. The literature search was executed in the databases of Scopus and Espacenet using medical and instrument-related keyword combinations. The search yielded over 840 patents and 69 articles. After scanning for relevancy, 45 patents and 16 articles were included. The identified crossing devices were subdivided based on the determinant for the crossing path through the occlusion, which is either the device (straight and angled crossing), the environment (least resistance, tissue selective, centerline, and subintimal crossing) or the user (directly steered and sensor enhanced crossing). It was found that each crossing path is characterized by specific advantages and disadvantages. For a future crossing device, a combination of crossing paths is suggested were the interventionist is able to exert high forces on the CTO (as seen in the device approach) and actively steer through the CTO (user: directly steered crossing) aided by intravascular imaging (user: sensor enhanced crossing) or an intrinsically safe device following the centerline or path of least resistance (environment: centerline crossing or least resistance crossing) to reach the distal true lumen. PMID:26831298

  17. APPARATUS FOR MEASURING TOTAL NEUTRON CROSS SECTIONS

    DOEpatents

    Cranberg, L.

    1959-10-13

    An apparatus is described for measuring high-resolution total neutron cross sections at high counting rate in the range above 50-kev neutron energy. The pulsed-beam time-of-flight technique is used to identify the neutrons of interest which are produced in the target of an electrostatic accelerator. Energy modulation of the accelerator . makes it possible to make observations at 100 energy points simultaneously. 761O An apparatus is described for monitoring the proton resonance of a liquid which is particulariy useful in the continuous purity analysis of heavy water. A hollow shell with parallel sides defines a meander chamber positioned within a uniform magnetic fieid. The liquid passes through an inlet at the outer edge of the chamber and through a spiral channel to the central region of the chamber where an outlet tube extends into the chamber perpendicular to the magnetic field. The radiofrequency energy for the monitor is coupled to a coil positioned coaxially with the outlet tube at its entrance point within the chamber. The improvement lies in the compact mechanical arrangement of the monitor unit whereby the liquid under analysis is subjected to the same magnetic field in the storage and sensing areas, and the entire unit is shielded from external electrostatic influences.

  18. Gauge fields

    SciTech Connect

    Mills, R.

    1989-06-01

    This article is a survey of the history and ideas of gauge theory. Described here are the gradual emergence of symmetry as a driving force in the shaping of physical theory; the elevation of Noether's theorem, relating symmetries to conservation laws, to a fundamental principle of nature; and the force of the idea (''the gauge principle'') that the symmetries of nature, like the interactions themselves, should be local in character. The fundamental role of gauge fields in mediating the interactions of physics springs from Noether's theorem and the gauge principle in a remarkably clean and elegant way, leaving, however, some tantalizing loose ends that might prove to be the clue to a future deeper level of understanding. The example of the electromagnetic field as the prototype gauge theory is discussed in some detail and serves as the basis for examining the similarities and differences that emerge in generalizing to non-Abelian gauge theories. The article concludes with a brief examination of the dream of total unification: all the forces of nature in a single unified gauge theory, with the differences among the forces due to the specific way in which the fundamental symmetries are broken in the local environment.

  19. Cross well seismic reservoir characterization

    SciTech Connect

    Sheline, H.E.

    1995-08-01

    A striking example of how Cross Well Seismic reflection data can help characterize a reservoir, has resulted from an ongoing Multi-Discipline study of the carbonate Mishrif reservoir offshore Dubai, U.A.E. Because the study objectives include a more detailed description of intra reservoir structure and layering, Dubai Petroleum Company (DPC) analyzed the feasibility of Cross Well Seismic (CWS) and decided to acquire two surveys between three wells 337 to 523 feet apart. DPC has concluded that CWS can be cost effectively acquired offshore, in a Carbonate reservoir; as well as processed and interpreted. However, generally it is not often easy to acquire cross well seismic when and where it will be most useful. A CWS survey can provide multiple images such as a velocity Tomogram, P-wave reflections, and S-wave reflections. To date, Tomograms and P-wave reflections have been produced, and the reflection data has proven to be the most useful for reservoir characterization. Cross Well Seismic Reflection data have provided a level of vertical seismic reflection resolution of around 2 feet, which is more than 10 times better than surface seismic data (2D or 3D). The increase in vertical resolution has provided important detailed information about the reservoir, it`s continuity/heterogeneity; it`s detailed structure, stratigraphy and layering; and definition of any faults with more than 2 feet of offset. The CWS has shown detailed intra Mishrif reflectors. These reflectors have verified or changed detailed correlations between well bores, and show significant intra Mishrif thinning. These reflectors imply time stratigraphic layering which is consistent with tracer study results and regional sequence stratigraphy. This new data will be used to improve the reservoir model description.

  20. Geometry of operator cross ratio

    SciTech Connect

    Zelikin, M I

    2006-02-28

    The operator cross ratio, which is meaningful, in particular, for the infinite-dimensional Sato Grassmannian is defined and investigated. Its homological interpretation is presented. A matrix and operator analogue of the Schwartzian differential operator is introduced and its relation to linear Hamiltonian systems and Riccati's equation is established. The aim of these constructions is application to the KP-hierarchy (the Kadomtsev-Petviashvili hierarchy)

  1. Transmission through crossed polaroid filters

    NASA Astrophysics Data System (ADS)

    Easton, Don

    2001-04-01

    A modification to a digital lux meter is described. A Malus' law experiment performed with the meter gives unexpected results. The modified meter is used to show that the unexpected findings result from the inability of Polaroid filters to polarize radiation that is outside the range of visible light. With the use of a diffraction grating and the modified meter crossed Polaroids are shown to transmit infrared radiation.

  2. Electron-Impact Ionization Cross Section Database

    National Institute of Standards and Technology Data Gateway

    SRD 107 Electron-Impact Ionization Cross Section Database (Web, free access)   This is a database primarily of total ionization cross sections of molecules by electron impact. The database also includes cross sections for a small number of atoms and energy distributions of ejected electrons for H, He, and H2. The cross sections were calculated using the Binary-Encounter-Bethe (BEB) model, which combines the Mott cross section with the high-incident energy behavior of the Bethe cross section. Selected experimental data are included.

  3. Cross-border reprogenetic services.

    PubMed

    Couture, V; Drouin, R; Tan, S-L; Moutquin, J-M; Bouffard, C

    2015-01-01

    The purpose of this review is to synthesize the current knowledge on the international movement of patients and biopsied embryo cells for pre-implantation genetic diagnosis and its different applications. Thus far, few attempts have been made to identify the specific nature of this phenomenon called 'cross-border reprogenetic services'. There is scattered evidence, both empirical and speculative, suggesting that these services raise major issues in terms of service provision, risks for patients and the children-to-come, the legal liabilities of physicians, as well as social justice. To compile this evidence, this review uses the narrative overview protocol combined with thematic analysis. Five major themes have emerged from the literature at the conjunction of cross-border treatments and reprogenetics: 'scope', 'scale', 'motivations', 'concerns', and 'governance'. Similar themes have already been observed in the case of other medical tourism activities, but this review highlights their singularity with reprogenetic services. It emphasizes the diagnostic and autologous feature of reprogenetics, the constant risk of misdiagnosis, the restriction on certain tests for medically controversial conditions, and the uncertain accessibility of genetic counseling in cross-border settings. PMID:24798608

  4. First oil pipeline to Norway crosses Norwegian trench

    SciTech Connect

    Johsrud, P.

    1988-05-02

    Norsk Hydro AS laid the first oil pipeline from North Sea fields to Norway last summer as part of the Oseberg transportation system. The line was hydrostatically tested last fall in preparation for start-up next year. After several appraisal wells and extensive evaluation work, the operator for the field, Norsk Hydro, presented a development plan which was approved by the Norwegian parliament in the spring of 1984. This article describes the development phases, the transportation system, and how the trench crossing was done.

  5. Simulation of beams or plasmas crossing at relativistic velocity

    SciTech Connect

    Vay, J.-L.

    2008-05-15

    This paper addresses the numerical issues related to the modeling of beams or plasmas crossing at relativistic velocity using the particle-in-cell method. Issues related to the use of the standard Boris particle pusher are identified and a novel pusher which circumvents them is proposed, whose effectiveness is demonstrated on single particle tests. A procedure for solving the fields is proposed, which retains electrostatic, magnetostatic, and inductive field effects in the direction of the mean velocity of the species, is fully explicit and simpler than the full Darwin approximation. Finally, results are given, from a calculation using the novel features, of an ultrarelativistic beam interacting with a background of electrons.

  6. A study of radar cross section measurement techniques

    NASA Astrophysics Data System (ADS)

    McDonald, Malcolm W.

    1986-11-01

    Past, present, and proposed future technologies for the measurement of radar cross section were studied. The purpose was to determine which method(s) could most advantageously be implemented in the large microwave anechoic chamber facility which is operated at the antenna test range site. The progression toward performing radar cross section measurements of space vehicles with which the Orbital Maneuvering Vehicle will be called upon to rendezvous and dock is a natural outgrowth of previous work conducted in recent years of developing a high accuracy range and velocity sensing radar system. The radar system was designed to support the rendezvous and docking of the Orbital Maneuvering Vehicle with various other space vehicles. The measurement of radar cross sections of space vehicles will be necessary in order to plan properly for Orbital Maneuvering Vehicle rendezvous and docking assignments. The methods which were studied include: standard far-field measurements; reflector-type compact range measurements; lens-type compact range measurement; near field/far field transformations; and computer predictive modeling. The feasibility of each approach is examined.

  7. Summary of the Workshop on Neutron Cross Section Covariances

    SciTech Connect

    Smith, Donald L.

    2008-12-15

    A Workshop on Neutron Cross Section Covariances was held from June 24-27, 2008, in Port Jefferson, New York. This Workshop was organized by the National Nuclear Data Center, Brookhaven National Laboratory, to provide a forum for reporting on the status of the growing field of neutron cross section covariances for applications and for discussing future directions of the work in this field. The Workshop focused on the following four major topical areas: covariance methodology, recent covariance evaluations, covariance applications, and user perspectives. Attention was given to the entire spectrum of neutron cross section covariance concerns ranging from light nuclei to the actinides, and from the thermal energy region to 20 MeV. The papers presented at this conference explored topics ranging from fundamental nuclear physics concerns to very specific applications in advanced reactor design and nuclear criticality safety. This paper provides a summary of this workshop. Brief comments on the highlights of each Workshop contribution are provided. In addition, a perspective on the achievements and shortcomings of the Workshop as well as on the future direction of research in this field is offered.

  8. A study of radar cross section measurement techniques

    NASA Technical Reports Server (NTRS)

    Mcdonald, Malcolm W.

    1986-01-01

    Past, present, and proposed future technologies for the measurement of radar cross section were studied. The purpose was to determine which method(s) could most advantageously be implemented in the large microwave anechoic chamber facility which is operated at the antenna test range site. The progression toward performing radar cross section measurements of space vehicles with which the Orbital Maneuvering Vehicle will be called upon to rendezvous and dock is a natural outgrowth of previous work conducted in recent years of developing a high accuracy range and velocity sensing radar system. The radar system was designed to support the rendezvous and docking of the Orbital Maneuvering Vehicle with various other space vehicles. The measurement of radar cross sections of space vehicles will be necessary in order to plan properly for Orbital Maneuvering Vehicle rendezvous and docking assignments. The methods which were studied include: standard far-field measurements; reflector-type compact range measurements; lens-type compact range measurement; near field/far field transformations; and computer predictive modeling. The feasibility of each approach is examined.

  9. Cavity Femtochemistry: Manipulating Nonadiabatic Dynamics at Avoided Crossings.

    PubMed

    Kowalewski, Markus; Bennett, Kochise; Mukamel, Shaul

    2016-06-01

    Molecular potential energy surfaces can be actively manipulated by light. This is usually done by strong classical laser light but was recently demonstrated for the quantum field in an optical cavity. The photonic vacuum state of a localized cavity mode can be strongly mixed with the molecular degrees of freedom to create hybrid field-matter states known as polaritons. We simulate the avoided crossing of sodium iodide in a cavity by incorporating the quantized cavity field into the nuclear wave packet dynamics calculation. The quantized field is represented on a numerical grid in quadrature space, thus avoiding the limitations set by the rotating wave approximation (RWA) when the field is expanded in Fock space. This approach allows the investigation of cavity couplings in the vicinity of naturally occurring avoided crossings and conical intersections, which is too expensive in the fock space expansion when the RWA does not apply. Numerical results show how the branching ratio between the covalent and ionic dissociation channels can be strongly manipulated by the optical cavity. PMID:27186666

  10. Magnetic field structure evolution in rotating magnetic field plasmas

    SciTech Connect

    Petrov, Yuri; Yang Xiaokang; Huang, T.-S.

    2008-07-15

    A study of magnetic field structure evolution during 40-ms plasma discharge has been performed in a new device with 80 cm long/40 cm diameter cylindrical chamber, in which a plasma current I{sub p}{approx_equal}2 kA was driven and sustained by a rotating magnetic field. The main focus of the experiments is on how the changes in externally applied magnetic field affect the current profile and magnetic field in plasma. During plasma discharge, a pulse current was briefly fed to a magnetic coil located at the midplane (middle coil). The magnetic field in cross section of plasma was scanned with pickup probes. Two regimes were studied: without and with an external toroidal field (TF) produced by axial I{sub z} current. With a relatively small current (I{sub m} {<=} 600 A) in the middle coil, the plasma current is boosted up to 5 kA. The magnetic flux surfaces become extended along the axial Z direction, sometimes with the formation of doublet shape plasma. The regime without TF appears to be less stable, presumably due to the reversal of plasma current in central area of plasma column.

  11. Toroidal linear force-free magnetic fields with axial symmetry

    NASA Astrophysics Data System (ADS)

    Vandas, M.; Romashets, E.

    2016-01-01

    Aims: Interplanetary magnetic flux ropes are often described as linear force-free fields. To account for their curvature, toroidal configurations must be used. The aim is to find an analytic description of a linear force-free magnetic field of the toroidal geometry in which the cross section of flux ropes can be controlled. Methods: The solution is found as a superposition of fields given by linear force-free cylinders tangential to a generating toroid. The cylindrical field is expressed in a series of terms that are not all cylindrically symmetric. Results: We found the general form of a toroidal linear force-free magnetic field. The field is azimuthally symmetric with respect to the torus axis. It depends on a set of coefficients that enables controlling the flux rope shape (cross section) to some extent. By varying the coefficients, flux ropes with circular and elliptic cross sections were constructed. Numerical comparison suggests that the simple analytic formula for calculating the helicity in toroidal flux ropes of the circular cross section can be used for flux ropes with elliptic cross sections if the minor radius in the formula is set to the geometric mean of the semi-axes of the elliptic cross section.

  12. Photoproduction total cross section and shower development

    NASA Astrophysics Data System (ADS)

    Cornet, F.; García Canal, C. A.; Grau, A.; Pancheri, G.; Sciutto, S. J.

    2015-12-01

    The total photoproduction cross section at ultrahigh energies is obtained using a model based on QCD minijets and soft-gluon resummation and the ansatz that infrared gluons limit the rise of total cross sections. This cross section is introduced into the Monte Carlo system AIRES to simulate extended air showers initiated by cosmic ray photons. The impact of the new photoproduction cross section on common shower observables, especially those related to muon production, is compared with previous results.

  13. Current-wave spectra coupling project. Volume I. Hurricane fields and cross sections, surface winds and currents, significant waves and wave spectra for potential OTEC sites: (A) Keahole Point, Hawaii, 100 year hurricane; (B) Punta Tuna, Puerto Rico, 100 year hurricane; (C) New Orleans, Louisiana, 100 year hurricane; (D) West Coast of Florida, 100 year hurricane; and for (E) Hurricane Camille (1969) off Louisiana Coast

    SciTech Connect

    Bretschneider, C.L.

    1980-06-01

    This volume is an extension of and consists of several modifications to the earlier report by Bretschneider (April 1979) on the subject of hurricane design wind, wave and current criteria for the four potential OTEC sites. The 100-year hurricane criteria for the design of OTEC plants is included. The criteria, in addition to the maximum conditions of winds, waves and surface current, include: hurricane fields for wind speed U/sub s/ and significant wave height H/sub s/; hurricane fields for modal wave period f/sub 0//sup -1/ and maximum energy density S/sub max/ of the wave spectrum; the corresponding Ekman wind-driven surface current V/sub s/; tabulated cross-sections for U/sub s/, H/sub s/, f/sub 0//sup -1/ and S/sub max/ through max U/sub s/ and through max H/sub s/ along traverses at right angles to and along traverses parallel to the forward movement of the hurricane; most probable maximum wave height and the expected corresponding wave period, based on statistical analysis of maximum wave heights from five hurricanes; design wave spectra for maximum U/sub s/ and also maximum H/sub s/, since maximum U/sub s/ and maximum H/sub s/ do not occur simultaneously; the envelope of wave spectra through maximum U/sub s/ and through maximum H/sub s/ along traverses parallel to the forward movement of the hurricane; the above same determinations for Hurricane Camille (1969) as for the four OTEC locations; and alternative methods (suggested) for obtaining design wave spectra from the joint probability distribution functions for wave height and period given by Longuet-Higgins (1975) and C.N.E.X.O. after Arhan, et al (1976).

  14. Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: The importance of level crossings

    PubMed Central

    Thurber, Kent R.; Tycko, Robert

    2012-01-01

    We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T1e is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

  15. Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: the importance of level crossings.

    PubMed

    Thurber, Kent R; Tycko, Robert

    2012-08-28

    We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

  16. A Study of Cross-Referencing.

    ERIC Educational Resources Information Center

    Kochen, Manfred; Tagliacozzo, Renata

    The problem of determining the optimal cross-reference structure for a given index and for a given community of users is discussed. A cross-reference structure is represented as a graph in which the nodes are index terms and the links are relations between index terms. In order to clarify the concept of 'level of cross-referencing' the…

  17. Geneticists and the Biology of Race Crossing

    ERIC Educational Resources Information Center

    Provine, William B.

    1973-01-01

    Examines historically the attitudes of United States and British geneticists on the topic of race crossing. Between 1930 and 1950 the attitudes changed from a condemnation of wide race crosses because of deleterious effects to a belief that such inter-racial crosses were at worst biologically harmless. (JR)

  18. Laser cross-flow gas system

    DOEpatents

    Duncan, David B.

    1992-01-01

    A method and laser apparatus are disclosed which provide for a cross-flow of gas near one end of a laser discharge tube. The cross-flow of gas causes a concentration gradient which affects diffusion of contaminants in the discharge tube towards the cross-flow of the gas, which contaminants are then withdrawn from the discharge tube.

  19. Electrospinning formaldehyde cross-linked zein solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as the cross-linking reagent before spinning. The cross-linking reaction was carried out in either acetic acid or ethanolic-HCl where the amount of cross-linking reagent was between 1 and...

  20. 30 CFR 57.9104 - Railroad crossings.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Railroad crossings. 57.9104 Section 57.9104... SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling, and Dumping Traffic Safety § 57.9104 Railroad crossings. Designated railroad crossings shall be posted...

  1. 30 CFR 57.9104 - Railroad crossings.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Railroad crossings. 57.9104 Section 57.9104... SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling, and Dumping Traffic Safety § 57.9104 Railroad crossings. Designated railroad crossings shall be posted...

  2. 30 CFR 57.9104 - Railroad crossings.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Railroad crossings. 57.9104 Section 57.9104... SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling, and Dumping Traffic Safety § 57.9104 Railroad crossings. Designated railroad crossings shall be posted...

  3. 30 CFR 57.9104 - Railroad crossings.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Railroad crossings. 57.9104 Section 57.9104... SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling, and Dumping Traffic Safety § 57.9104 Railroad crossings. Designated railroad crossings shall be posted...

  4. 30 CFR 57.9104 - Railroad crossings.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Railroad crossings. 57.9104 Section 57.9104... SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling, and Dumping Traffic Safety § 57.9104 Railroad crossings. Designated railroad crossings shall be posted...

  5. 30 CFR 56.9104 - Railroad crossings.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Railroad crossings. 56.9104 Section 56.9104 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9104 Railroad crossings. Designated railroad crossings shall be posted...

  6. 30 CFR 56.9104 - Railroad crossings.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Railroad crossings. 56.9104 Section 56.9104 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9104 Railroad crossings. Designated railroad crossings shall be posted...

  7. 30 CFR 56.9104 - Railroad crossings.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Railroad crossings. 56.9104 Section 56.9104 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9104 Railroad crossings. Designated railroad crossings shall be posted...

  8. 30 CFR 56.9104 - Railroad crossings.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Railroad crossings. 56.9104 Section 56.9104 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9104 Railroad crossings. Designated railroad crossings shall be posted...

  9. 30 CFR 56.9104 - Railroad crossings.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Railroad crossings. 56.9104 Section 56.9104 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9104 Railroad crossings. Designated railroad crossings shall be posted...

  10. Absorption of massless scalar field by rotating black holes

    NASA Astrophysics Data System (ADS)

    Leite, Luiz C. S.; Crispino, Luís C. B.; de Oliveira, Ednilton S.; Macedo, Caio F. B.; Dolan, Sam R.

    2016-07-01

    We compute the absorption cross-section of the Kerr black holes (BH) for the massless scalar field, and present a selection of numerical results, to complement the results of Ref.[C. F. B. Macedo, L. C. S. Leite, E. S. Oliveria, S. R. Dolan and L. C. B. Crispino, Phys. Rev. D 88 (2013) 064033.] We show that, in the high-frequency regime, the cross-section approaches the geodesic capture cross-section. We split the absorption cross-section into corotating and counterrotating contributions, and we show that the counterrotating contribution exceeds the corotating one.

  11. Deimos Crosses Face of Sun

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This animation shows the passing, or transit, of the martian moon Deimos over the Sun. This event is similar solar eclipse seen on Earth in which our Moon crosses in front of the Sun. The animation is made up of images taken by the Mars Exploration Rover Opportunity on sol 39 of its mission. Deimos passed slightly closer to the center of the Sun than expected, and arrived about 30 seconds early. This observation will help refine our knowledge of the orbit and position of Deimos.

  12. Petascale cross correlation in software

    NASA Astrophysics Data System (ADS)

    Barsdell, Benjamin R.; Clark, M. A.; Greenhill, L. J.

    2014-04-01

    The exascale computational demands of back-end processing in the era of the SKA and HERA, headlined by the needs of cross-correlation, are likely to require solutions that differ significantly from traditional approaches on smaller arrays. The rapid growth of massively-parallel general-purpose computing hardware presents an alternative to ASIC- or FPGA-based designs and promises several advantages. In this talk we present strong scaling results for an FX correlator that runs entirely in software on GPU-based off-the-shelf HPC clusters.

  13. Recommended Dosimetry Cross Section Compendium.

    Energy Science and Technology Software Center (ESTSC)

    1994-07-11

    Version 00 The data is recommended for spectrum determination applications and for the prediction of neutron activation of typical radiation sensor materials. The library has been tested for consistency of the cross sections in a wide variety of neutron environments. The results and cautions from this testing have been documented. The data has been interfaced with radiation transport codes, such as TWODANT-SYS (CCC-547) and MCNP (CCC-200), in order to compare calculated and measured activities formore » benchmark reactor experiments.« less

  14. Oil and Gas Field Code Master List 1990

    SciTech Connect

    Not Available

    1991-01-04

    This is the ninth annual edition of the Energy Information Administration's (EIA) Oil and Gas Field Code Master List. It reflects data collected through October 1990 and provides standardized field name spellings and codes for all identified oil and/or gas fields in the United States. There are 54,963 field records in this year's Oil and Gas Field Code Master List (FCML). This amounts to 467 more than in last year's report. As it is maintained by EIA, the Master List includes: Field records for each state and county in which a field resides; field records for each offshore area block in the Gulf of Mexico in which a field resides;field records for each alias field name; fields crossing state boundaries that may be assigned different names by the respective state naming authorities.

  15. Fracture Flow Channel Imaging Using Cross-Polarized GPR Signals

    NASA Astrophysics Data System (ADS)

    Tsoflias, G. P.; Perll, C.; Baker, M.; Becker, M.

    2014-12-01

    Fractures control the flow of fluids in rocks with important implications for groundwater resources, contaminant transport, geothermal resources, sequestration of carbon dioxide, and the development of unconventional hydrocarbon resources. Ground penetrating radar (GPR) can be used to image fractured rock and monitor the flow of fluids in the subsurface. Conventional GPR imaging uses single-polarization, co-polarized signals. Changes in reflected signal amplitude result from changes in fracture aperture and changes in fluid electrical properties introduced by tracers or contaminants. Recent research has also shown changes in radar reflected signal phase resulting from changes in fluid electrical conductivity. However, the radar response is dependent on the polarization of EM waves. This study investigates the use of cross-polarized GPR signals for imaging flow channeling at a discrete horizontal fracture. Numerical modeling demonstrated that cross-polarized GPR data are able to image fracture channels when the axis of the channel is oriented obliquely to the EM wavefield orientation. Summation of the cross-polarized and co-polarized components results in an accurate representation of the total scattered energy from the channel. Multipolarization, time-lapse 3D GPR field data were used investigate GPR imaging of flow channeling in a discrete subhorizontal fracture. The GPR surveys were conducted during background fresh fracture water conditions and during six varying orientation dipole flow saline tracer tests. The cross-polarized data revealed flow channeling which is in agreement with the co-polarized GPR data and with independent hydraulic tests. In addition, the cross-polarized components showed changes in flow channeling as a result of changing dipole flow orientation and position. This study demonstrates that cross-polarized GPR signals can be used to enhance imaging of flow in fractured rock.

  16. Acoustic source location in a jet-blown flap using a cross-correlation technique

    NASA Technical Reports Server (NTRS)

    Becker, R. S.; Maus, J. R.

    1977-01-01

    The acoustic source strength distribution in a turbulent flow field was measured for two far field microphones at 45 deg above and below the plane of the flap surface. A processed signal from an inclined hot-film anemometry probe was cross correlated with the signal from the appropriate far field microphone. The contribution made by the sources associated with the fluctuating pressure on the flap surface to the sound received at far field microphone was estimated by cross correlating the processed signals of microphones which were embedded in the flap surface with the far field microphone signals. In addition, detailed fluid dynamic measurements were made in the flow field of the jet flap using dual sensor hot-film anemometry probes.

  17. Cross-language treatment generalisation

    PubMed Central

    Goral, Mira; Levy, Erika S.; Kastl, Rebecca

    2009-01-01

    Background Recent investigations of language gains following treatment in bilingual individuals with chronic aphasia appear to confirm early reports that not only the treated language but also the non-treated language(s) benefit from treatment. The evidence, however, is still suggestive, and the variables that may mitigate generalisation across languages warrant further investigation. Aims We set out to examine cross-language generalisation of language treatment in a trilingual speaker with mild chronic aphasia. Methods & Procedures Language treatment was administered in English, the participant’s second language (L2). The first treatment block focused on morphosyntactic skills and the second on language production rate. Measurements were collected in the treated language (English, L2) as well as the two non-treated languages: Hebrew (the participant’s first language, L1) and French (the participant’s third language, L3). Outcomes & Results The participant showed improvement in his production of selected morphosyntactic elements, such as pronoun gender agreement, in the treated language (L2) as well as in the non-treated French (L3) following the treatment block that focused on morphosyntactic skills. Speech rate also improved in English (L2) and French (L3) following that treatment block. No changes were observed in Hebrew, the participant’s L1. Conclusions Selective cross-language generalisation of treatment benefit was found for morphosyntactic abilities from the participant’s second language to his third language. PMID:20221311

  18. The CrossGrid project

    NASA Astrophysics Data System (ADS)

    Kunze, M.; CrossGrid Collaboration

    2003-04-01

    There are many large-scale problems that require new approaches to computing, such as earth observation, environmental management, biomedicine, industrial and scientific modeling. The CrossGrid project addresses realistic problems in medicine, environmental protection, flood prediction, and physics analysis and is oriented towards specific end-users: Medical doctors, who could obtain new tools to help them to obtain correct diagnoses and to guide them during operations; industries, that could be advised on the best timing for some critical operations involving risk of pollution; flood crisis teams, that could predict the risk of a flood on the basis of historical records and actual hydrological and meteorological data; physicists, who could optimize the analysis of massive volumes of data distributed across countries and continents. Corresponding applications will be based on Grid technology and could be complex and difficult to use: the CrossGrid project aims at developing several tools that will make the Grid more friendly for average users. Portals for specific applications will be designed, that should allow for easy connection to the Grid, create a customized work environment, and provide users with all necessary information to get their job done.

  19. Dentists and cross-infection.

    PubMed

    Naidoo, S

    1997-03-01

    A structured questionnaire was administered to a random sample of general dental practitioners in Natal, South Africa in 1994, to ascertain the precautions they use against cross-infection and to gauge the attitudes and behaviour towards the treatment of HIV-infected individuals. An interview was conducted covering 5 broad topics: demographic details, personal barrier protection, instrument sterilization and disinfection, sharps disposal and incidence of needlestick injuries and the extent of the knowledge, attitude and behaviour of the practitioners toward the treatment of HIV-infected individuals. The key findings were: routine glove wearing, for all patients, was practised by 87 per cent. The most common heat sterilization method was by autoclave (68 per cent), although a dry heat sterilizer and water boiler were used by 22 per cent of the respondents. Of the 18 respondents reporting a needlestick injury in the past 6 months only one sought after-care. 42 per cent of the respondents would continue to treat carriers of HIV in their practices. This survey shows that a significant number of dentists are using unacceptable cross-infection control procedures. Educational efforts should be made to improve their knowledge and to alleviate anxiety of health workers to treat HIV-infected patients. PMID:9461908

  20. Recent fission cross section standards measurements

    SciTech Connect

    Wasson, O.A.

    1985-01-01

    The /sup 235/U(n,f) reaction is the standard by which most neutron induced fission cross sections are determined. Most of these cross sections are derived from relatively easy ratio measurements to /sup 235/U. However, the more difficult /sup 235/U(n,f) cross section measurements require the use of advanced neutron detectors for the determination of the incident neutron fluence. Examples of recent standard cross section measurements are discussed, various neutron detectors are described, and the status of the /sup 235/U(n,f) cross section standard is assessed. 23 refs., 8 figs., 4 tabs.