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Sample records for linear theta pinch devices

  1. Beam heated linear theta-pinch device for producing hot plasmas

    DOEpatents

    Bohachevsky, Ihor O.

    1981-01-01

    A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

  2. New model of calculating the energy transfer efficiency for the spherical theta-pinch device

    SciTech Connect

    Xu, G.; Hock, C.; Loisch, G.; Jacoby, J.; Xiao, G.; Zhao, Y.; Weyrich, K.; Li, Y.

    2015-05-15

    Ion-beam-plasma-interaction plays an important role in the field of warm dense matter and inertial confinement fusion. A spherical theta pinch is proposed to act as a plasma target in various applications including a plasma stripper cell. One key parameter for such applications is the free electron density. A linear dependency of this density to the amount of energy transferred into the plasma from an energy storage was found by Teske. Since the amount of stored energy is known, the energy transfer efficiency is a reliable parameter for the design of a spherical theta pinch device. As the main assumption of a constant reflected plasma resistance is contradictory by the measured data, the traditional two models of energy transfer efficiency will lead to wrong results. From measurements, the parasitic resistance is derived as constant. Based on this key parameter, a new model is proposed. Due to no assumption, the new model is considered as exact. Further, a comparison of these three different models is given at a fixed operation voltage for the full range of working gas pressures. Due to the inappropriate assumptions included in the traditional models, one owns a tendency to overestimate the energy transfer efficiency whereas the other leads to an underestimation. Applying our new model to a wide spread set of operation voltages and gas pressures, an overall picture of the energy transfer efficiency results.

  3. Numerical experiments on the theta pinch

    NASA Technical Reports Server (NTRS)

    Volosevich, P. P.; Zukakishyili, G. G.

    1979-01-01

    Numerical calculation of theta pinch problems are presented. Physical processes in theta pinch systems are considered in a one dimensional, two temperature magnetohydrodynamic, approximation with allowance for end losses by longitudinal heat conductivity. The numerical calculations are compared with results of earlier experiments.

  4. Study of flow and loss processes at the ends of a linear theta pinch. Progress report, June 1, 1979-September 30, 1980

    SciTech Connect

    York, T.M.; Klevans, E.H.

    1980-05-01

    Experimental and analytical studies of particle and energy loss at the ends of a linear theta pinch have been carried out. A study of transients occurring in the formation of reversed trapped fields within the coil, and of transients in the end region of a 25 cm long device was completed. A 1-D code has proven to be highly accurate in describing loss events and defining transport mechanisms in different experiments and is described here. A study of loss along field lines in a 50 cm long device has generated new information on loss velocity, axial and radial temperature gradients, and has established an initial effort in understanding thermal loss to the walls. Rotation and parallel trapped fields have been added to the existing 0-D code. A new technique crowbar switch and magnetic field prediction code have been developed. Direct measurment of electron velocity with Thomson scattering was accomplished experimentally. A Nd-glass laser system, frequency doubled, is being developed for low density diagnostics. Theoretical results that accurately predict confinement in FRX devices are described.

  5. CUSP-PINCH DEVICE

    DOEpatents

    Baker, W.R.; Watteau, J.P.H.

    1962-06-01

    An ion-electron plasma heating device of the pinch tube class is designed with novel means for counteracting the instabilities of an ordinary linear pinch discharge. A plasma-forming discharge is created between two spacedapart coaxial electiodes through a gas such as deuterium. A pair of spaced coaxial magnetic field coils encircle the discharge and carry opposing currents so that a magnetic field having a cuspate configuration is created around the plasma, the field being formed after the plasma has been established but before significant instability arises. Thus, containment time is increased and intensified heating is obtained. In addition to the pinch compression heating additional heating is obtained by high-frequency magnetic field modulation. (AEC)

  6. Analysis of the energetic parameters of a theta pinch

    SciTech Connect

    Cavalcanti, G. H.; Farias, E. E.

    2009-12-15

    This work is devoted to study experimentally the performance of a theta pinch when the number of capacitors and turns of magnetic coil and the diameter of the glass tube are changed. To model the theta pinch a simple RLC circuit is used and the measurement of energy transmission from the bank of capacitors to the plasma is made using few experimental resources. In this work it was analyzed more than 2500 curves with a nonlinear procedure. Our results show that it is possible to design an optimized theta pinch making the appropriated choice of energetic parameters and therefore to reduce the stress of the system.

  7. Theta-Pinch Thruster for Piloted Deep Space Exploration

    NASA Technical Reports Server (NTRS)

    LaPointe, Mike R.; Reddy, Dhanireddy (Technical Monitor)

    2000-01-01

    A new high-power propulsion concept that combines a rapidly pulsed theta-pinch discharge with upstream particle reflection by a magnetic mirror was evaluated under a Phase 1 grant awarded through the NASA Institute for Advanced Concepts. Analytic and numerical models were developed to predict the performance of a theta-pinch thruster operated over a wide range of initial gas pressures and discharge periods. The models indicate that a 1 m radius, 10 m long thruster operated with hydrogen propellant could provide impulse-bits ranging from 1 N-s to 330 N-s with specific impulse values of 7,500 s to 2,500 s, respectively. A pulsed magnetic field strength of 2 T is required to compress and heat the preionized hydrogen over a 10(exp -3) second discharge period, with about 60% of the heated plasma exiting the chamber each period to produce thrust. The unoptimized thruster efficiency is low, peaking at approximately 16% for an initial hydrogen chamber pressure of 100 Torr. The specific impulse and impulse-bit at this operating condition are 3,500 s and 90 N-s, respectively, and the required discharge energy is approximately 9x10(exp 6) J. For a pulse repetition rate of 10 Hz, the engine would produce an average thrust of 900 N at 3,500 s specific impulse. Combined with the electrodeless nature of the device, these performance parameters indicate that theta-pinch thrusters could provide unique, long-life propulsion systems for piloted deep space mission applications.

  8. A model code for the radiative theta pinch

    SciTech Connect

    Lee, S.; Saw, S. H.; Lee, P. C. K.; Akel, M.; Damideh, V.; Khattak, N. A. D.; Mongkolnavin, R.; Paosawatyanyong, B.

    2014-07-15

    A model for the theta pinch is presented with three modelled phases of radial inward shock phase, reflected shock phase, and a final pinch phase. The governing equations for the phases are derived incorporating thermodynamics and radiation and radiation-coupled dynamics in the pinch phase. A code is written incorporating correction for the effects of transit delay of small disturbing speeds and the effects of plasma self-absorption on the radiation. Two model parameters are incorporated into the model, the coupling coefficient f between the primary loop current and the induced plasma current and the mass swept up factor f{sub m}. These values are taken from experiments carried out in the Chulalongkorn theta pinch.

  9. Method for plasma formation for extreme ultraviolet lithography-theta pinch

    DOEpatents

    Hassanein, Ahmed; Konkashbaev, Isak; Rice, Bryan

    2007-02-20

    A device and method for generating extremely short-wave ultraviolet electromagnetic wave, utilizing a theta pinch plasma generator to produce electromagnetic radiation in the range of 10 to 20 nm. The device comprises an axially aligned open-ended pinch chamber defining a plasma zone adapted to contain a plasma generating gas within the plasma zone; a means for generating a magnetic field radially outward of the open-ended pinch chamber to produce a discharge plasma from the plasma generating gas, thereby producing a electromagnetic wave in the extreme ultraviolet range; a collecting means in optical communication with the pinch chamber to collect the electromagnetic radiation; and focusing means in optical communication with the collecting means to concentrate the electromagnetic radiation.

  10. Current halo structures in high-current plasma experiments: {theta}-pinch

    SciTech Connect

    Matveev, Yu. V.

    2007-03-15

    Experimental data elucidating mechanisms for halo formation in {theta}-pinch discharges are presented and discussed. The experiments were performed with different gases (H{sub 2}, D{sub 2}, He, and Ar) in a theta-pinch device with a porcelain vacuum chamber and an excitation coil 15 cm in diameter and 30 cm in length. The stored energy, the current in the excitation coil, and the current half-period were W = 10 kJ, I = 400 kA, and T/2 = 14 {mu}s, respectively. It is found that the plasma rings (halos) surrounding the pinch core arise as a result of coaxial pinch stratification due to both the excitation of closed currents (inductons) inside the pinch and the radial convergence of the plasma current sheaths produced after the explosion of T-layers formed near the wall in the initial stage of the discharge. It is concluded that halo structures observed in pinches, tokamaks, and other high-current devices used in controlled fusion research have the same nature.

  11. Simplified scaling model for the THETA-pinch

    SciTech Connect

    Ewing, K. J.; Thomson, D. B.

    1982-02-01

    A simple ID scaling model for the fast THETA-pinch was developed and written as a code that would be flexible, inexpensive in computer time, and readily available for use with the Los Alamos explosive-driven high-magnetic-field program. The simplified model uses three successive separate stages: (1) a snowplow-like radial implosion, (2) an idealized resistive annihilation of reverse bias field, and (3) an adiabatic compression stage of a BETA = 1 plasma for which ideal pressure balance is assumed to hold. The code uses one adjustable fitting constant whose value was first determined by comparison with results from the Los Alamos Scylla III, Scyllacita, and Scylla IA THETA-pinches.

  12. Hydrogen plasma dynamics in the spherical theta pinch plasma target for heavy ion stripping

    SciTech Connect

    Loisch, G.; Jacoby, J.; Xu, G.; Blazevic, A.; Cihodariu-Ionita, B.

    2015-05-15

    Due to the superior ability of dense and highly ionised plasmas to ionise penetrating heavy ion beams to degrees beyond those reachable by common gas strippers, many experiments have been performed to find suitable plasma generators for this application. In the field of gas discharges, mainly z-pinch devices have been investigated so far, which are known to be limited by the nonlinear focusing effects of the plasma columns sustaining current and by electrode erosion. The spherical theta pinch has therefore been proposed as a substitution for the z-pinch, promising progress by inductive rather than capacitive coupling and displacement of the outer magnetic field by the dense, diamagnetic discharge plasma. As yet mainly experiments with argon/hydrogen mixture gas have been performed, which is not suitable for the application as a plasma stripper, this paper describes the first detailed analysis of the plasma parameters and dynamics of a hydrogen plasma created by the spherical theta pinch. These include the time integrated and time resolved electron density, the dynamics of the plasma in the discharge vessel, the comparison with the argon dominated plasma, and an outlook to reachable characteristics with similar devices.

  13. Hydrogen plasma dynamics in the spherical theta pinch plasma target for heavy ion stripping

    NASA Astrophysics Data System (ADS)

    Loisch, G.; Xu, G.; Blazevic, A.; Cihodariu-Ionita, B.; Jacoby, J.

    2015-05-01

    Due to the superior ability of dense and highly ionised plasmas to ionise penetrating heavy ion beams to degrees beyond those reachable by common gas strippers, many experiments have been performed to find suitable plasma generators for this application. In the field of gas discharges, mainly z-pinch devices have been investigated so far, which are known to be limited by the nonlinear focusing effects of the plasma columns sustaining current and by electrode erosion. The spherical theta pinch has therefore been proposed as a substitution for the z-pinch, promising progress by inductive rather than capacitive coupling and displacement of the outer magnetic field by the dense, diamagnetic discharge plasma. As yet mainly experiments with argon/hydrogen mixture gas have been performed, which is not suitable for the application as a plasma stripper, this paper describes the first detailed analysis of the plasma parameters and dynamics of a hydrogen plasma created by the spherical theta pinch. These include the time integrated and time resolved electron density, the dynamics of the plasma in the discharge vessel, the comparison with the argon dominated plasma, and an outlook to reachable characteristics with similar devices.

  14. Axial laser heating of three meter theta pinch plasma columns

    NASA Astrophysics Data System (ADS)

    Hoffman, A. L.; Lowenthal, D. D.

    1980-10-01

    A 3-m long plasma column formed and confined by a fast rising solenoidal field was irradiated from one end by a powerful pulsed CO2 laser. It was found that beam trapping density minima could be maintained for the length of the laser pulse if the plasma diameter exceeded about 1.5 cm. The erosion of the density minimum was governed by classical diffusion processes. Three meter long plasmas in 2.6 cm bore plasma tubes could be fairly uniformly heated by 3.0 kJ of CO2 laser irradiation. Best results were obtained when heating began before or during the theta pinch implosion phase and the plasma fill pressure exceeded 1.0 torr H2. Plasma line energies of about 1 kJ/m could be obtained in a magnetic field rising to 6 T in 4.7 microseconds.

  15. Necessary stability condition for field-reversed theta pinches

    SciTech Connect

    Cary, J. R.

    1981-03-01

    Toroidal systems of arbitrary cross section without toroidal magnetic field are analyzed via the double adiabatic fluid equations. Such systems are shown to be unstable if there exists one closed field line on which the average of kapparB/sup 2/ is positive, where kappa is the curvature. A similar criterion is derived for linear systems and is applied to a noncircular z-pinch.

  16. Upgrade of a Theta Pinch Plasma Source for Energetic Plasma Flow Generation

    NASA Astrophysics Data System (ADS)

    Jung, Soonwook; Andruczyk, Daniel; Ruzic, David; CenterPlasma-Material Interactions Team

    2011-10-01

    DEVeX is a theta pinch device used to investigate fusion-related material interaction such as vapor shielding and ICRF antenna interactions with plasma-pulses in a laboratory setting. However, recent upgrades of the device indicate that guiding magnet and crowbar operation hinder plasma flow to the target when the magnetic field at the theta coil is reversed from that of the guiding magnet. This reversal occurs mainly due to finite inductance and resistance at the crowbar switch. Therefore, an upgrade for more suitable fusion-related material study is required. In this study, several upgrades to produce higher-temperature plasma have been carried out. Major modification of theta coil is carried out and its effects on plasma parameters are theoretically predicted with simulation. The results will be compared with experiments including voltage/current measurement at the coil, plasma parameter measurement with triple Langmuir probe and time of flight technique, and incident energy measurement with thermocouples. The research reported in this paper was performed in support of Contract number DE-FG02-04ER54765 with the U.S. Department of Energy and Oak Ridge National Laboratory.

  17. Thrust Stand Measurements of the Conical Theta Pinch FARAD Thruster

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.

    2010-01-01

    It is found that the impulse of a pulsed inductive plasma thruster utilizing preionization is maximized for a particular ratio of the stored energy in the capacitor to the injected propellant mass. The fact that the impulse depends on the ratio of the initial stored energy to injected propellant mass agrees with previous current sheet studies, supporting the idea that a Townsend-like breakdown process strongly influences current sheet formation, and in turn, current sheet formation strongly affects the operational efficiency of the device. The optimum in half cone angle of the inductive coil can be explained in terms of a balance between the direct axial acceleration and the radial pinching contribution to thrust. From the trends in these data we conclude that operation at the correct ratio of capacitor energy to propellant mass is essential for efficient operation of pulsed inductive plasma thrusters employing a preionized propellant.

  18. Upgrade of a Theta Pinch Plasma Source for Energetic Plasma Flow Generation and Fusion-Related Material Interaction Study

    NASA Astrophysics Data System (ADS)

    Jung, Soonwook; Surla, Vijay; Ruzic, David

    2010-11-01

    In order to investigate material erosion by exposure to a burst of high density plasma in a laboratory setting, a theta pinch device called the Divertor Erosion and Vapor Shielding eXperiment facility was built at UIUC. It consists of a theta-pinch coil driven by pulse discharge from 32 μF capacitor bank to produce high density plasma. Recent measurements have shown that plasma sustains approximately for 100 μs at each pulse, with 1.0 ± 0.2(10)21 /m^3 plasma density and 12.5 ± 2.5 eV electron temperature. To simulate the extreme condition in magnetic fusion device a higher electron temperature is desired. For this reason, several upgrades have been implemented: (1) the main capacitor bank, for compression and heating was operated in conjunction with RF antenna and a preionization bank. (2) a guide magnetic field was installed to transport the flow minimizing losses in the radial direction and (3) a crow-bar circuit was added to prevent the pinch from ringing and therefore working against the imposed static magnetic field. The results from the upgrades will be presented.

  19. Transient loss of plasma from a theta pinch having an initially reversed magnetic field

    SciTech Connect

    Heidrich, J. E.

    1981-01-01

    The results of an experimental study of the transient loss of plasma from a 25-cm-long theta pinch initially containing a reversed trapped magnetic field are presented. The plasma, amenable to MHD analyses, was a doubly ionized helium plasma characterized by an ion density N/sub i/ = 2 x 10/sup 16/ cm/sup -3/ and an ion temperature T/sub i/ = 15 eV at midcoil and by N/sub i/ = 0.5 x 10/sup 16/ cm/sup -3/ and T/sub i/ = 6 eV at a position 2.5 cm beyond the end of the theta coil.

  20. Sampling and excitation of refractory solids with a theta pinch designed as an atomic emission source

    SciTech Connect

    White, J.S.; Scheeline, A.

    1987-01-15

    Work with a theta pinch designed as an atomic emission source for solids analysis is reported. Argon at 3.5 torr provided the most intense analyte emission compared to several other gases. A study of the effects of sample positioning provides further understanding of the plasma motion and plasma/sample interactions. Application of the new sample positioning knowledge has resulted in significant increases in analyte emission, as is demonstrated by use of samples of tungsten powder, boron nitride, and aluminum oxide ceramics.

  1. Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

    NASA Technical Reports Server (NTRS)

    Hallock, A. K.; Martin, A. K.; Polzin, K. A.; Kimberlin, A. C.; Eskridge, R. H.

    2013-01-01

    Impulse bits produced by conical theta-pinch inductive pulsed plasma thrusters possessing cone angles of 20deg, 38deg, and 60deg, were quantified for 500J/pulse operation by direct measurement using a hanging-pendulum thrust stand. All three cone angles were tested in single-pulse mode, with the 38deg model producing the highest impulse bits at roughly 1 mN-s operating on both argon and xenon propellants. A capacitor charging system, assembled to support repetitively-pulsed thruster operation, permitted testing of the 38deg thruster at a repetition-rate of 5 Hz at power levels of 0.9, 1.6, and 2.5 kW. The average thrust measured during multiple-pulse operation exceeded the value obtained when the single-pulse impulse bit is multiplied by the repetition rate.

  2. Effect of Inductive Coil Geometry and Current Sheet Trajectory of a Conical Theta Pinch Pulsed Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Bonds, Kevin W.; Emsellem, Gregory D.

    2011-01-01

    Results are presented demonstrating the e ect of inductive coil geometry and current sheet trajectory on the exhaust velocity of propellant in conical theta pinch pulsed induc- tive plasma accelerators. The electromagnetic coupling between the inductive coil of the accelerator and a plasma current sheet is simulated, substituting a conical copper frustum for the plasma. The variation of system inductance as a function of plasma position is obtained by displacing the simulated current sheet from the coil while measuring the total inductance of the coil. Four coils of differing geometries were employed, and the total inductance of each coil was measured as a function of the axial displacement of two sep- arate copper frusta both having the same cone angle and length as the coil but with one compressed to a smaller size relative to the coil. The measured relationship between total coil inductance and current sheet position closes a dynamical circuit model that is used to calculate the resulting current sheet velocity for various coil and current sheet con gura- tions. The results of this model, which neglects the pinching contribution to thrust, radial propellant con nement, and plume divergence, indicate that in a conical theta pinch ge- ometry current sheet pinching is detrimental to thruster performance, reducing the kinetic energy of the exhausting propellant by up to 50% (at the upper bound for the parameter range of the study). The decrease in exhaust velocity was larger for coils and simulated current sheets of smaller half cone angles. An upper bound for the pinching contribution to thrust is estimated for typical operating parameters. Measurements of coil inductance for three di erent current sheet pinching conditions are used to estimate the magnetic pressure as a function of current sheet radial compression. The gas-dynamic contribution to axial acceleration is also estimated and shown to not compensate for the decrease in axial electromagnetic acceleration

  3. Computer simulation of plasma behavior in open-ended linear theta machines. Scientific report 81-5

    SciTech Connect

    Stover, E. K.

    1981-04-01

    Zero-dimensional and one-dimensional fluid plasma computer models have been developed to study the behavior of linear theta pinch plasmas. Computer simulation results generated from these codes are compared with data obtained from two theta pinch experiments so that significant machine plasma behavior can be identified. The experiments examined are a collisional experiment, T/sub i/ approx. 50 eV, n/sub e/ approx. 10/sup 17/ cm/sup -3/, where the plasma mean-free-path was significantly less than the plasma column length, and a hot ion species experiment, T/sub i/ approx. 3 keV, n/sub e/ approx. 10/sup 16/ cm/sup -3/, where the ion mean-free-path was on the order of the plasma column length.

  4. Current Sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-frequency Assisted Discharge

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Hallock, Ashley K.; Choueiri, Edgar Y.

    2008-01-01

    Data from an inductive conical theta pinch accelerator are presented to gain insight into the process of inductive current sheet formation in the presence of a preionized background gas produced by a steady-state RF-discharge. The presence of a preionized plasma has been previously shown to allow for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts, leading to greater accelerator efficiencies at lower power levels. Time-resolved magnetic probe measurements are obtained for different background pressures and pulse energies to characterize the effects of these parameters on current sheet formation. Indices are defined that describe time-resolved current sheet characteristics, such as the total current owing in the current sheet, the time-integrated total current ('strength'), and current sheet velocity. It is found that for a given electric field strength, maximums in total current, strength, and velocity occur for one particular background pressure. At other pressures, these current sheet indices are considerably smaller. The trends observed in these indices are explained in terms of the principles behind Townsend breakdown that lead to a dependence on the ratio of the electric field to the background pressure. Time-integrated photographic data are also obtained at the same experimental conditions, and qualitatively they compare quite favorably with the time-resolved magnetic field data.

  5. Energy deposition into heavy gas plasma via pulsed inductive theta-pinch

    NASA Astrophysics Data System (ADS)

    Pahl, Ryan Alan

    The objective of this research is to study the formation processes of a pulsed inductive plasma using heavy gases, specifically the coupling of stored capacitive energy into plasma via formation in a theta pinch coil. To aid in this research, the Missouri Plasmoid Experiment Mk. I (and later Mk. II) was created. In the first paper, the construction of differential magnetic field probes are discussed. The effects of calibration setup on B-dot probes is studied using a Helmholtz coil driven by a vector network analyzer and a pulsed-power system. Calibration in a pulsed-power environment yielded calibration factors at least 9.7% less than the vector network analyzer. In the second paper, energy deposition into various gases using a pulsed inductive test article is investigated. Experimental data are combined with a series RLC model to quantify the energy loss associated with plasma formation in Argon, Hydrogen, and Xenon at pressures from 10-100 mTorr. Plasma resistance is found to vary from 25.8-51.6 mΩ and plasma inductance varies from 41.3--47.0 nH. The greatest amount of initial capacitively stored energy that could be transferred to the plasma was 6.4 J (8.1%) of the initial 79.2 +/- 0.1 J. In the third paper, the effects of a DC preionization source on plasma formation energy is studied. The preionization source radial location is found to have negligible impact on plasma formation repeatability while voltage is found to be critical at low pressures. Without preionization, plasma formation was not possible. At 20 mTorr, 0.20 W of power was sufficient to stabilize plasma formation about the first zero-crossing of the discharge current. Increasing power to 1.49 W increased inductively coupled energy by 39%. At 200 mTorr, 4.3 mW was sufficient to produce repeatable plasma properties.

  6. Current sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-Frequency Assisted Discharge

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Choueiri, Edgar Y.; Polzin, Kurt A.

    2007-01-01

    The inductive formation of current sheets in a conical theta pinch FARAD (Faraday Accelerator with Radio-frequency Assisted Discharge) thruster is investigated experimentally with time-integrated photography. The goal is to help in understanding the mechanisms and conditions controlling the strength and extent of the current sheet, which are two indices important for FARAD as a propulsion concept. The profiles of these two indices along the inside walls of the conical acceleration coil are assumed to be related to the profiles of the strength and extent of the luminosity pattern derived from photographs of the discharge. The variations of these profiles as a function of uniform back-fill neutral pressure (with no background magnetic field and all parameters held constant) provided the first clues on the nature and qualitative dependencies of current sheet formation. It was found that there is an optimal pressure for which both indices reach a maximum and that the rate of change in these indices with pressure differs on either side of this optimal pressure. This allowed the inference that current sheet formation follows a Townsend-like breakdown mechanism modified by the existence of a finite pressure-dependent radio-frequency-generated electron density background. The observation that the effective location of the luminosity pattern favors the exit-half of the conical coil is explained as the result of the tendency of the inductive discharge circuit to operate near its minimal self-inductance. Movement of the peak in the luminosity pattern towards the upstream side of the cone with increasing pressure is believed to result from the need of the circuit to compensate for the increase in background plasma resistivity due to increasing pressure.

  7. Behavior of some singly ionized, heavy-ion impurities during compression in a theta-pinch plasma

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.

    1975-01-01

    The introduction of a small percentage of an impurity gas containing a desired element into a theta-pinch plasma is a standard procedure used to investigate the spectra and atomic processes of the element. This procedure assumes that the mixing ratio of impurity-to-fill gases remains constant during the collapse and heating phase. Spectroscopic investigations of the constant-mixing-ratio assumption for a 2% neon and argon impurity verifies the assumption only for the neon impurity. However, for the 2% argon impurity, only 20 to 25% of the argon is in the high-temperature compressed plasma. It is concluded that the constant-mixing-ratio assumption is not applicable to the argon impurity.

  8. Numerical investigation on the implosion dynamics of wire-array Z-pinches in (r, {theta}) geometry

    SciTech Connect

    Huang Jun; Ding Ning; Ning Cheng; Sun Shunkai; Zhang Yang; Xiao Delong; Xue Chuang

    2012-06-15

    The implosion dynamics of wire-array Z-pinches are investigated numerically in 2D (r, {theta}) geometry by using a resistive MHD code. It is assumed that the wires have expanded to plasmas with diameter d{sub 0}, which is used as the initial condition for the consequent implosion process. In fact, the explosion process of individual wires is not included. By changing d{sub 0}, the effects of the wire expansion degree on the implosion dynamics are analyzed. When d{sub 0} is larger, the current density is more concentrated at the outer side of the wires and the fraction of current flow around the wire plasmas is nearly in proportion to d{sub 0}. As a result, the ablation rate of wires is increased and the implosion phase starts earlier. This conclusion agrees with the simulation works of other authors [Chittenden et al., Phys. Plasmas 11(3), 1118 (2004)]. When the array radius and initial wire plasma diameter are fixed, the increase of wire number leads to the azimuthal merge of wires during implosion. When the wires number exceed a critical value, which is related to d{sub 0}, wire plasmas can merge to a continuous shell with an azimuthal perturbation in density, which depends on the initial wires number.

  9. Linear encoding device

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    1993-01-01

    A Linear Motion Encoding device for measuring the linear motion of a moving object is disclosed in which a light source is mounted on the moving object and a position sensitive detector such as an array photodetector is mounted on a nearby stationary object. The light source emits a light beam directed towards the array photodetector such that a light spot is created on the array. An analog-to-digital converter, connected to the array photodetector is used for reading the position of the spot on the array photodetector. A microprocessor and memory is connected to the analog-to-digital converter to hold and manipulate data provided by the analog-to-digital converter on the position of the spot and to compute the linear displacement of the moving object based upon the data from the analog-to-digital converter.

  10. Linear pinch driven by a moving compact torus

    SciTech Connect

    Hartman, C.W.; Hammer, J.H.; Eddleman, J.L.

    1984-04-25

    In principle, a Z-pinch of sufficiently large aspect ratio can provide arbitrarily high magnetic field intensity for the confinement of plasma. In practice, however, achievable field intensities and timescales are limited by parasitic inductances, pulse driver power, current, voltage, and voltage standoff of nearby insulating surfaces or surrounding gas. Further, instabilities may dominate to prevent high fields (kink mode) or enhance them (sausage mode) but in a nonuniform and uncontrollable way. In this paper we discuss an approach to producing a high-field-intensity pinch using a moving compact torus. The moving torus can serve as a very high power driver and may be used to compress a pre-established pinch field, switch on an accelerating pinch field, or may itself be reconfigured to form an intense pinch. In any case, the high energy, high energy density, and high velocity possible with an accelerated compact torus can provide extremely high power to overcome, by a number of orders of magnitude, the limitations to pinch formation described earlier. In this paper we will consider in detail pinches formed by reconfiguration of the compact torus.

  11. The linear model and experimentally observed resonant field amplification in tokamaks and reversed field pinches

    SciTech Connect

    Pustovitov, V. D.

    2011-01-15

    A review is given of the experimentally observed effects related to the resonant field amplification (RFA) and the Resistive Wall Mode (RWM) instability in tokamaks and reversed field pinches (RFPs). This includes the feedback rotation of RWM in RFX-mod RFP, dependence of the RWM growth rate on the plasma-wall separation observed in JT-60U, appearance of the slowly growing RWM precursors in JT-60U and similar phenomena in other devices. The experimental results are compared with theoretical predictions based on the model comprising the Maxwell equations, Ohm's law for the conducting wall, the boundary conditions and assumption of linear plasma response to the external magnetic perturbations. The model describes the plasma reaction to the error field as essentially depending on two factors: the plasma proximity to the RWM stability threshold and the natural rotation frequency of the plasma mode. The linear response means that these characteristics are determined by the plasma equilibrium parameters only. It is shown that the mentioned effects in different devices under different conditions can be described on a common basis with only assumption that the plasma behaves as a linear system. To extend the range of the model validation, some predictions are derived with proposals for experimental studies of the RFA dynamics.

  12. Linear force device

    NASA Technical Reports Server (NTRS)

    Clancy, John P.

    1988-01-01

    The object of the invention is to provide a mechanical force actuator which is lightweight and manipulatable and utilizes linear motion for push or pull forces while maintaining a constant overall length. The mechanical force producing mechanism comprises a linear actuator mechanism and a linear motion shaft mounted parallel to one another. The linear motion shaft is connected to a stationary or fixed housing and to a movable housing where the movable housing is mechanically actuated through actuator mechanism by either manual means or motor means. The housings are adapted to releasably receive a variety of jaw or pulling elements adapted for clamping or prying action. The stationary housing is adapted to be pivotally mounted to permit an angular position of the housing to allow the tool to adapt to skewed interfaces. The actuator mechanisms is operated by a gear train to obtain linear motion of the actuator mechanism.

  13. Quasi-linear gyrokinetic predictions of the Coriolis momentum pinch in National Spherical Torus Experiment

    DOE PAGESBeta

    Guttenfelder, W.; Kaye, S. M.; Ren, Y.; Solomon, W.; Bell, R. E.; Candy, J.; Gerhardt, S. P.; LeBlanc, B. P.; Yuh, H.

    2016-05-11

    This paper presents quasi-linear gyrokinetic predictions of the Coriolis momentum pinch for low aspect-ratio National Spherical Torus Experiment (NSTX) H-modes where previous experimental measurements were focused. Local, linear calculations predict that in the region of interest (just outside the mid-radius) of these relatively high-beta plasmas, profiles are most unstable to microtearing modes that are only effective in transporting electron energy. However, sub-dominant electromagnetic and electrostaticballooning modes are also unstable, which are effective at transporting energy, particles, and momentum. The quasi-linear prediction of transport from these weaker ballooning modes, assuming they contribute transport in addition to that from microtearing modes inmore » a nonlinear turbulent state, leads to a very small or outward convection of momentum, inconsistent with the experimentally measured inward pinch, and opposite to predictions in conventional aspect ratio tokamaks. Additional predictions of a low beta L-mode plasma, unstable to more traditional electrostatic ion temperature gradient-trapped electron mode instability, show that the Coriolis pinch is inward but remains relatively weak and insensitive to many parameter variations. The weak or outward pinch predicted in NSTX plasmas appears to be at least partially correlated to changes in the parallel mode structure that occur at a finite beta and low aspect ratio, as discussed in previous theories. The only conditions identified where a stronger inward pinch is predicted occur either in the purely electrostatic limit or if the aspect ratio is increased. Lastly, as the Coriolis pinch cannot explain the measured momentum pinch, additional theoretical momentum transport mechanisms are discussed that may be potentially important.« less

  14. Quasi-linear gyrokinetic predictions of the Coriolis momentum pinch in National Spherical Torus Experiment

    NASA Astrophysics Data System (ADS)

    Guttenfelder, W.; Kaye, S. M.; Ren, Y.; Solomon, W.; Bell, R. E.; Candy, J.; Gerhardt, S. P.; LeBlanc, B. P.; Yuh, H.

    2016-05-01

    This paper presents quasi-linear gyrokinetic predictions of the Coriolis momentum pinch for low aspect-ratio National Spherical Torus Experiment (NSTX) H-modes where previous experimental measurements were focused. Local, linear calculations predict that in the region of interest (just outside the mid-radius) of these relatively high-beta plasmas, profiles are most unstable to microtearing modes that are only effective in transporting electron energy. However, sub-dominant electromagnetic and electrostatic ballooning modes are also unstable, which are effective at transporting energy, particles, and momentum. The quasi-linear prediction of transport from these weaker ballooning modes, assuming they contribute transport in addition to that from microtearing modes in a nonlinear turbulent state, leads to a very small or outward convection of momentum, inconsistent with the experimentally measured inward pinch, and opposite to predictions in conventional aspect ratio tokamaks. Additional predictions of a low beta L-mode plasma, unstable to more traditional electrostatic ion temperature gradient-trapped electron mode instability, show that the Coriolis pinch is inward but remains relatively weak and insensitive to many parameter variations. The weak or outward pinch predicted in NSTX plasmas appears to be at least partially correlated to changes in the parallel mode structure that occur at a finite beta and low aspect ratio, as discussed in previous theories. The only conditions identified where a stronger inward pinch is predicted occur either in the purely electrostatic limit or if the aspect ratio is increased. As the Coriolis pinch cannot explain the measured momentum pinch, additional theoretical momentum transport mechanisms are discussed that may be potentially important.

  15. Stability of a diffuse linear pinch with axial boundaries

    NASA Technical Reports Server (NTRS)

    Einaudi, G.; Van Hoven, G.

    1981-01-01

    A formulation of the stability behavior of a finite-length pinch is presented. A general initial perturbation is expressed as a uniformly convergent sum over a complete discrete k set. A variational calculation is then performed, based on the energy principle, in which the end-boundary conditions appear as constraints. The requisite Lagrange multipliers mutually couple the elemental periodic excitations. The resulting extended form of delta-W still admits a proper second-variation treatment so that the minimization and stability considerations of Newcomb remain applicable. Comparison theorems are discussed as is the relevance of this end-effect model to the stability of solar coronal loops.

  16. Aluminum and tungsten X-pinch experiments on 100 kA, 100 ns linear transformer driver stage

    SciTech Connect

    Wu Jian; Sun Tieping; Wu Gang; Wang Liangping; Han Juanjuan; Li Mo; Cong Peitian; Qiu Aici; Lv Min

    2011-05-15

    X-pinch experiments have been carried out on a 100 kA, 100 ns linear transformer driver stage recently built up. The X-pinches exhibited a source size of about 10 {mu}m, a pulse duration of 3 ns, 3-5 keV radiation energy of 3.9 mJ, and a burst time jitter of tens of nanosecond with the 2-wire 8 {mu}m W X-pinch load. The generator output current and the X-pinch characteristics depended on the X-pinch wire materials in the tests. X-ray backlighting images from the insects showed the significant phase-contrast effect.

  17. Aluminum and tungsten X-pinch experiments on 100 kA, 100 ns linear transformer driver stage

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Sun, Tie-Ping; Wu, Gang; Wang, Liang-Ping; Han, Juan-Juan; Li, Mo; Cong, Pei-Tian; Qiu, Ai-Ci; Lv, Min

    2011-05-01

    X-pinch experiments have been carried out on a 100 kA, 100 ns linear transformer driver stage recently built up. The X-pinches exhibited a source size of about 10 μm, a pulse duration of 3 ns, 3-5 keV radiation energy of 3.9 mJ, and a burst time jitter of tens of nanosecond with the 2-wire 8 μm W X-pinch load. The generator output current and the X-pinch characteristics depended on the X-pinch wire materials in the tests. X-ray backlighting images from the insects showed the significant phase-contrast effect.

  18. Progress in Z-pinch research driven by the mega-ampere device SPEED2

    SciTech Connect

    Pavez, Cristian; Soto, Leopoldo; Moreno, Jose; Tarifeno, Ariel; Sylvester, Gustavo

    2008-04-07

    Several pinch configurations have being studied at the Chilean Nuclear Energy Commission using the SPEED2 generator: plasma focus, gas embedded z-pinch and wire arrays. SPEED2 is a generator based on Marx technology (4.1 {mu}F equivalent Marx generator capacity, 300 kV, 4 MA in short circuit, 187 kJ, 400 ns rise time, dI/dt{approx}10{sup 13} A/s). Currently the device is being operated at 70kJ stored energy producing a peak current of 2.4 MA in short circuit. In this work results related to studies in gas embedded z-pinch in deuterium and studies in wire arrays are presented.

  19. 250 kA compact linear transformer driver for wire array z-pinch loads

    NASA Astrophysics Data System (ADS)

    Bott, S. C.; Haas, D. M.; Madden, R. E.; Ueda, U.; Eshaq, Y.; Collins, G., IV; Gunasekera, K.; Mariscal, D.; Peebles, J.; Beg, F. N.; Mazarakis, M.; Struve, K.; Sharpe, R.

    2011-05-01

    We present the application of a short rise (˜150ns) 250 kA linear transformer driver (LTD) to wire array z-pinch loads for the first time. The generator is a modification of a previous driver in which a new conical power feed provides a low inductance coupling to wire loads. Performance of the new design using both short circuit and plasma loads is presented and discussed. The final design delivers ˜200kA to a wire array load which is in good agreement with SCREAMER calculations using a simplified representative circuit. Example results demonstrate successful experiments using cylindrical, conical, and inverse wire arrays as well as previously published work on x-pinch loads.

  20. Reversed-field pinch and screw pinch

    SciTech Connect

    Kito, M.; Yoshimura, H.

    1983-12-01

    The Electrotechnical Laboratory and the College of Science and Technology at Nihon University discuss the results, device parameters, and objectives of reversed-field pinch TPE-1R(M). This device is illustrated and tables are given of machine parameters, as well as plasma parameters and temperature and density scalings. Other reversed-field pinch (RFP) machines are discussed, and tables show the RFP devices of Japan and design parameters of TPE-2, a screw-pinch device with a noncircular cross section. The STP-3 screw-pinch device is also discussed.

  1. Theta phase precession and phase selectivity: a cognitive device description of neural coding

    NASA Astrophysics Data System (ADS)

    Zalay, Osbert C.; Bardakjian, Berj L.

    2009-06-01

    Information in neural systems is carried by way of phase and rate codes. Neuronal signals are processed through transformative biophysical mechanisms at the cellular and network levels. Neural coding transformations can be represented mathematically in a device called the cognitive rhythm generator (CRG). Incoming signals to the CRG are parsed through a bank of neuronal modes that orchestrate proportional, integrative and derivative transformations associated with neural coding. Mode outputs are then mixed through static nonlinearities to encode (spatio) temporal phase relationships. The static nonlinear outputs feed and modulate a ring device (limit cycle) encoding output dynamics. Small coupled CRG networks were created to investigate coding functionality associated with neuronal phase preference and theta precession in the hippocampus. Phase selectivity was found to be dependent on mode shape and polarity, while phase precession was a product of modal mixing (i.e. changes in the relative contribution or amplitude of mode outputs resulted in shifting phase preference). Nonlinear system identification was implemented to help validate the model and explain response characteristics associated with modal mixing; in particular, principal dynamic modes experimentally derived from a hippocampal neuron were inserted into a CRG and the neuron's dynamic response was successfully cloned. From our results, small CRG networks possessing disynaptic feedforward inhibition in combination with feedforward excitation exhibited frequency-dependent inhibitory-to-excitatory and excitatory-to-inhibitory transitions that were similar to transitions seen in a single CRG with quadratic modal mixing. This suggests nonlinear modal mixing to be a coding manifestation of the effect of network connectivity in shaping system dynamic behavior. We hypothesize that circuits containing disynaptic feedforward inhibition in the nervous system may be candidates for interpreting upstream rate codes to

  2. Design of a 5-MA 100-ns linear-transformer-driver accelerator for wire array Z-pinch experiments

    NASA Astrophysics Data System (ADS)

    Zhou, Lin; Li, Zhenghong; Wang, Zhen; Liang, Chuan; Li, Mingjia; Qi, Jianmin; Chu, Yanyun

    2016-03-01

    The linear-transformer-driver (LTD) is a recently developed pulsed-power technology that shows great promise for a number of applications. These include a Z -pinch-driven fission-fusion-hybrid reactor that is being developed by the Chinese Academy of Engineering Physics. In support of the reactor development effort, we are planning to build an LTD-based accelerator that is optimized for driving wire-array Z -pinch loads. The accelerator comprises six modules in parallel, each of which has eight series 0.8-MA LTD cavities in a voltage-adder configuration. Vacuum transmission lines are used from the interior of the adder to the central vacuum chamber where the load is placed. Thus the traditional stack-flashover problem is eliminated. The machine is 3.2 m tall and 12 m in outer diameter including supports. A prototype cavity was built and tested for more than 6000 shots intermittently at a repetition rate of 0.1 Hz. A novel trigger, in which only one input trigger pulse is needed by utilizing an internal trigger brick, was developed and successfully verified in these shots. A full circuit modeling was conducted for the accelerator. The simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%-90%) can be delivered to the wire-array load, which is 1.5 cm in height, 1.2 cm in initial radius, and 1 mg in mass. The maximum implosion velocity of the load is 32 cm /μ s when compressed to 0.1 of the initial radius. The maximum kinetic energy is 78 kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%-30%, providing a high efficient facility for research on the fast Z pinch and technologies for repetition-rate-operated accelerators.

  3. Divertor for a linear fusion device

    NASA Astrophysics Data System (ADS)

    Ryutov, D. D.; Yushmanov, P. N.; Barnes, D. C.; Putvinski, S. V.

    2016-03-01

    Linear fusion devices can use large magnetic flux flaring in the end tanks to reduce the heat load on the end structures. In order to reduce parallel electron heat loss, one has to create conditions where the neutral gas density in the end tanks is low, as otherwise cold electrons produced by the ionization of the neutrals would cool down the core plasma electrons. The processes determining the neutral gas formation and spatial distribution are analysed for the case where neutrals are formed by the surface recombination of the outflowing plasma. The conditions under which the cooling of the core plasma is negligible are formulated.

  4. Pinched Nerve

    MedlinePlus

    ... Enhancing Diversity Find People About NINDS NINDS Pinched Nerve Information Page Table of Contents (click to jump ... being done? Clinical Trials Organizations What is Pinched Nerve? The term "pinched nerve" is a colloquial term ...

  5. An alternative scaling model for neutron production in Z-pinch devices

    NASA Astrophysics Data System (ADS)

    Bures, Brian L.; Krishnan, Mahadevan

    2012-11-01

    The DD neutron yield (Yn) from z-pinches, either dense plasma foci or fast radial pinches, has been fitted for decades to the scaling model Yn ˜ α(Imax)δ, where α is a numerical scaling coefficient, Imax the peak current, and 3 < δ < 5. The data from 12 000 pulses analyzed from eight different z-pinches presented in this paper show that Yn varies by as much as ±15 000% about the best fit value of the conventional scaling model with δ = 4. A revised scaling model derived from the reaction rate equation and a circuit model that includes the time derivative of the current dI/dt (normalized to its initial value) reduces the scatter in data from ±15 000% to ±100%. For the special case of very high normalized dI/dt, the standard deviation between the revised scaling prediction and the measured neutron yields is reduced to just ±30%. Implications of this revised scaling for higher current pinches are discussed.

  6. An alternative scaling model for neutron production in Z-pinch devices

    SciTech Connect

    Bures, Brian L.; Krishnan, Mahadevan

    2012-11-15

    The DD neutron yield (Y{sub n}) from z-pinches, either dense plasma foci or fast radial pinches, has been fitted for decades to the scaling model Y{sub n} {approx} {alpha}(I{sub max}){sup {delta}}, where {alpha} is a numerical scaling coefficient, I{sub max} the peak current, and 3 < {delta} < 5. The data from 12 000 pulses analyzed from eight different z-pinches presented in this paper show that Y{sub n} varies by as much as {+-}15 000% about the best fit value of the conventional scaling model with {delta} = 4. A revised scaling model derived from the reaction rate equation and a circuit model that includes the time derivative of the current dI/dt (normalized to its initial value) reduces the scatter in data from {+-}15 000% to {+-}100%. For the special case of very high normalized dI/dt, the standard deviation between the revised scaling prediction and the measured neutron yields is reduced to just {+-}30%. Implications of this revised scaling for higher current pinches are discussed.

  7. Preliminary Results of Cone Z-Pinch Device with 5 kJ

    NASA Astrophysics Data System (ADS)

    Abdel-kader, M. E.; Abd Al-Halim, M. A.; Shagar, A. M.; Eltayeb, H. A.; Algamal, H. A.; Saudy, A. H.

    2013-10-01

    The Cone Z-Pinch Experiment with 5 kJ is designed, constructed and operated. The electric discharge takes place between an upper ring electrode and a lower pin electrode creating plasma sheath in shape of cone. The preliminary experimental results using Helium gas in discharge show that the discharge period is 35 μs, the total system inductance is 287 nH, and the total system resistance is 15 mΩ. The breakdown curve shows a minimum breakdown value at 0.2 torr pressure. The cone plasma is confined by electromagnetic force and plasma inductance has its maximum value at the pinch. The plasma current has a maximum value of 53 kA at the axis of the discharge tube. The experimental results showed that a time of 2.1 μs at least is required for the pinch to occur and that both the pinch time and the duration time decrease with increasing the charging voltage.

  8. Distributed control using linear momentum exchange devices

    NASA Technical Reports Server (NTRS)

    Sharkey, J. P.; Waites, Henry; Doane, G. B., III

    1987-01-01

    MSFC has successfully employed the use of the Vibrational Control of Space Structures (VCOSS) Linear Momentum Exchange Devices (LMEDs), which was an outgrowth of the Air Force Wright Aeronautical Laboratory (AFWAL) program, in a distributed control experiment. The control experiment was conducted in MSFC's Ground Facility for Large Space Structures Control Verification (GF/LSSCV). The GF/LSSCV's test article was well suited for this experiment in that the LMED could be judiciously placed on the ASTROMAST. The LMED placements were such that vibrational mode information could be extracted from the accelerometers on the LMED. The LMED accelerometer information was processed by the control algorithms so that the LMED masses could be accelerated to produce forces which would dampen the vibrational modes of interest. Experimental results are presented showing the LMED's capabilities.

  9. Non-linear electrohydrodynamics in microfluidic devices.

    PubMed

    Zeng, Jun

    2011-01-01

    Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid and the charged suspensions. Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed over a small distance, from sub-millimeter to a few microns, a very high electric field is easy to obtain. The electric force can be highly localized as its strength rapidly decays away from the peak. This makes the electric force an ideal candidate for precise spatial control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by Micro-Electro-Mechanical Systems (MEMS) fabrication methods. In this paper, we examine several electrically driven liquid handling operations. The emphasis is given to non-linear electrohydrodynamic effects. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications. PMID:21673912

  10. Non-Linear Electrohydrodynamics in Microfluidic Devices

    PubMed Central

    Zeng, Jun

    2011-01-01

    Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid and the charged suspensions. Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed over a small distance, from sub-millimeter to a few microns, a very high electric field is easy to obtain. The electric force can be highly localized as its strength rapidly decays away from the peak. This makes the electric force an ideal candidate for precise spatial control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by Micro-Electro-Mechanical Systems (MEMS) fabrication methods. In this paper, we examine several electrically driven liquid handling operations. The emphasis is given to non-linear electrohydrodynamic effects. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications. PMID:21673912

  11. Design of a 100 J Dense Plasma Focus Z-pinch Device as a Portable Neutron Source

    NASA Astrophysics Data System (ADS)

    Jiang, Sheng; Higginson, Drew; Link, Anthony; Liu, Jason; Schmidt, Andrea

    2015-11-01

    The dense plasma focus (DPF) Z-pinch devices are capable of accelerating ions to high energies through MV/mm-scale electric fields. When deuterium is used as the filling gas, neutrons are generated through beam-target fusion when fast D beams collide with the bulk plasma. The neutron yield on a DPF scales favorably with current, and could be used as portable sources for active interrogation. Past DPF experiments have been optimized empirically. Here we use the particle-in-cell (PIC) code LSP to optimize a portable DPF for high neutron yield prior to building it. In this work, we are designing a DPF device with about 100 J of energy which can generate 106 - 107 neutrons. The simulations are run in the fluid mode for the rundown phase and are switched to kinetic to capture the anomalous resistivity and beam acceleration process during the pinch. A scan of driver parameters, anode geometries and gas pressures are studied to maximize the neutron yield. The optimized design is currently under construction. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by the Laboratory Directed Research and Development Program (15-ERD-034) at LLNL.

  12. Charge-coupled device systems for recording two-dimensional multi-mega-ampere z-pinch data

    NASA Astrophysics Data System (ADS)

    Failor, B. H.; Coleman, P. L.; Levine, J. S.; Song, Y.; Sze, H.; LePell, P. D.; Coverdale, C. A.; Deeney, C.; Pressley, L.; Schneider, R.

    2001-04-01

    Hardware and software have been developed for recording and displaying accurate image and spectral data produced by z-pinch plasma radiation sources at the Double-EAGLE facility at Maxwell Physics International. Desktop computers are used to acquire the data, analyze it, and display and print the results. Of the four charge-coupled device (CCD) image recording systems implemented, two record x rays directly and two record optical light emission from electron-excited phosphors. The CCD systems required careful shielding to allow them to operate in the harsh radio frequency noise environment. During a series of shots at the SATURN facility at Sandia National Laboratories, the quality of a keV x-ray spectrum recorded directly with a CCD compared well with an equivalent spectrum recorded with 2497 film.

  13. Linear optimal control of tokamak fusion devices

    SciTech Connect

    Kessel, C.E.; Firestone, M.A.; Conn, R.W.

    1989-05-01

    The control of plasma position, shape and current in a tokamak fusion reactor is examined using linear optimal control. These advanced tokamaks are characterized by non up-down symmetric coils and structure, thick structure surrounding the plasma, eddy currents, shaped plasmas, superconducting coils, vertically unstable plasmas, and hybrid function coils providing ohmic heating, vertical field, radial field, and shaping field. Models of the electromagnetic environment in a tokamak are derived and used to construct control gains that are tested in nonlinear simulations with initial perturbations. The issues of applying linear optimal control to advanced tokamaks are addressed, including complex equilibrium control, choice of cost functional weights, the coil voltage limit, discrete control, and order reduction. Results indicate that the linear optimal control is a feasible technique for controlling advanced tokamaks where the more common classical control will be severely strained or will not work. 28 refs., 13 figs.

  14. Multispectral linear array multiband selection device

    NASA Technical Reports Server (NTRS)

    Richard, H. L.

    1986-01-01

    An apparatus for detecting multiple spectral bands, individually or concurrently, using linear detector arrays is described. The system employs a beamsplitter to divide the optical source into two or more optical beams which are directed at the linear detector arrays. Filter trays are positioned in the focal planes of the optical beams so that the beams pass through the filter trays prior to impinging upon the detector arrays. Multiple filters are placed on the filter trays. Linear actuators positioned adjacent the filter trays translate the trays across the focal planes of the optical beams so that individual filters are positioned in the path of beams such that those frequencies of the beams that fall within the spectral ranges of the individual bandpass filter through which it passes may be detected by the detector arrays for further examination and analysis.

  15. Embolization of a PORT-A-CATH device in the main pulmonary artery and its percutaneous extraction in a patient with pinch-off syndrome.

    PubMed

    Çilingiroğlu, Mehmet; Akkuş, Nuri lker

    2012-03-01

    Totally implanted port devices play an important role in acute and chronic medical care of patients with various conditions and are widely used for infusion of fluids, medications, blood or other blood products, and for monitoring hemodynamic parameters. Embolization of a part of port devices is a rare but potentially serious complication of port catheter placement. We report distal embolization of a catheter fragment of a PORT-A-CATH device into the main pulmonary artery and right ventricle and its successful percutaneous retrieval in a patient with metastatic lung cancer, who was also found to have thoracic inlet syndrome or pinch-off syndrome. PMID:22710588

  16. Control of a powered prosthetic device via a pinch gesture interface

    NASA Astrophysics Data System (ADS)

    Yetkin, Oguz; Wallace, Kristi; Sanford, Joseph D.; Popa, Dan O.

    2015-06-01

    A novel system is presented to control a powered prosthetic device using a gesture tracking system worn on a user's sound hand in order to detect different grasp patterns. Experiments are presented with two different gesture tracking systems: one comprised of Conductive Thimbles worn on each finger (Conductive Thimble system), and another comprised of a glove which leaves the fingers free (Conductive Glove system). Timing tests were performed on the selection and execution of two grasp patterns using the Conductive Thimble system and the iPhone app provided by the manufacturer. A modified Box and Blocks test was performed using Conductive Glove system and the iPhone app provided by Touch Bionics. The best prosthetic device performance is reported with the developed Conductive Glove system in this test. Results show that these low encumbrance gesture-based wearable systems for selecting grasp patterns may provide a viable alternative to EMG and other prosthetic control modalities, especially for new prosthetic users who are not trained in using EMG signals.

  17. Proceedings of the international workshop on engineering design of next step reversed field pinch devices

    SciTech Connect

    Thomson, D.B.

    1987-11-01

    These Proceedings contain the formal contributed papers, the workshop papers and workshop summaries presented at the International Workshop on Engineering Design of Next Step RFP Devices held at Los Alamos, July 13-17, 1987. Contributed papers were presented at formal sessions on the topics: (1) physics overview (3 papers); (2) general overview (3 papers); (3) front-end (9 papers); (4) computer control and data acquisition (1 paper); (5) magnetics (5 papers); and (6) electrical design (9 papers). Informal topical workshop sessions were held on the topics: (1) RFP physics (9 papers); (2) front-end (7 papers); (3) magnetics (3 papers); and (4) electrical design (1 paper). This volume contains the summaries written by the Chairmen of each of the informal topical workshop sessions. The papers in these Proceedings represent a significant review of the status of the technical base for the engineering design of the next step RFP devices being developed in the US, Europe, and Japan, as of this date.

  18. X-pinch. Part II

    NASA Astrophysics Data System (ADS)

    Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.

    2015-06-01

    Results of experimental studies of the X-pinch since its invention and implementation in 1982 at the Lebedev Physical Institute are presented. The review consists of two parts. The first part briefly outlines the history of creation and studies of X-pinches, describes the diagnostic techniques and devices developed during these studies, and presents the main results obtained in studying the physical processes occurring in the X-pinch. The second part is devoted to the results of detailed studies of the spatial, temporal, and spectral characteristics of the X-pinch hot spot—the region where the highest plasma parameters are achieved and which is a source of X-ray emission with extreme parameters. Some results of X-pinch simulations are also presented.

  19. X-pinch. Part II

    SciTech Connect

    Pikuz, S. A. Shelkovenko, T. A.; Hammer, D. A.

    2015-06-15

    Results of experimental studies of the X-pinch since its invention and implementation in 1982 at the Lebedev Physical Institute are presented. The review consists of two parts. The first part briefly outlines the history of creation and studies of X-pinches, describes the diagnostic techniques and devices developed during these studies, and presents the main results obtained in studying the physical processes occurring in the X-pinch. The second part is devoted to the results of detailed studies of the spatial, temporal, and spectral characteristics of the X-pinch hot spot—the region where the highest plasma parameters are achieved and which is a source of X-ray emission with extreme parameters. Some results of X-pinch simulations are also presented.

  20. Total dose dependency and ELDRS effects on bipolar linear devices

    NASA Technical Reports Server (NTRS)

    Yui, C. C.; McClure, S. S.; Rax, B. G.; Lehman, J. M.; Minto, T. D.; Wiedeman, M.

    2002-01-01

    The use of bipolar linear devices is prevalent in most satellite and some space applications. However, degradation as a result of low dose irradiations known as ELDERS (effects of enhanced low dose rate sensitivity) is a major concern when selecting flight hardware. Many studies and reports have been conducted on this possible phenomenon as well as their responsible physical mechanisms.

  1. High reliability linear drive device for artificial hearts

    NASA Astrophysics Data System (ADS)

    Ji, Jinghua; Zhao, Wenxiang; Liu, Guohai; Shen, Yue; Wang, Fangqun

    2012-04-01

    In this paper, a new high reliability linear drive device, termed as stator-permanent-magnet tubular oscillating actuator (SPM-TOA), is proposed for artificial hearts (AHs). The key is to incorporate the concept of two independent phases into this linear AH device, hence achieving high reliability operation. The fault-tolerant teeth are employed to provide the desired decoupling phases in magnetic circuit. Also, as the magnets and the coils are located in the stator, the proposed SPM-TOA takes the definite advantages of robust mover and direct-drive capability. By using the time-stepping finite element method, the electromagnetic characteristics of the proposed SPM-TOA are analyzed, including magnetic field distributions, flux linkages, back- electromotive forces (back-EMFs) self- and mutual inductances, as well as cogging and thrust forces. The results confirm that the proposed SPM-TOA meets the dimension, weight, and force requirements of the AH drive device.

  2. Analysis of Power Model for Linear Plasma Device

    NASA Astrophysics Data System (ADS)

    Zhang, Weiwei; Deng, Baiquan; Zuo, Haoyi; Zheng, Xianjun; Cao, Xiaogang; Xue, Xiaoyan; Ou, Wei; Cao, Zhi; Gou, Fujun

    2016-08-01

    A single cathode linear plasma device has been designed and constructed to investigate the interactions between plasma and materials at the Sichuan University. In order to further investigate the Ohmic power of the device, the output heat load on the specimen and electric potential difference (between cathode and anode) have been tested under different discharge currents. This special power distribution in the radial direction of the plasma discharge channel has also been discussed and described by some improved integral equations in this paper; it can be further simplified as P ∝ α‑2 in one-parameter. Besides, we have measured the power loss of the channel under different discharge currents by the calorimetric method, calculated the effective power of the device and evaluated the performances of the plasma device through the power efficiency analysis. supported by International Thermonuclear Experimental Reactor (ITER) Program (No. 2013GB114003) and National Natural Science Foundation of China (Nos. 11275135 and 11475122)

  3. X-pinch. Part I

    NASA Astrophysics Data System (ADS)

    Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.

    2015-04-01

    Results of experimental studies of the X-pinch since its invention and implementation in 1982 at the Lebedev Physical Institute are presented. The concept of the X-pinch arose in the course of innovative experiments on studying the generation of hot dense plasma in nanosecond Z-pinches. The main idea was to localize the region occupied by the plasma and stabilize the moment of its formation. This was achieved by using a load in the form of crossed wires. The resulting plasma object turned out to be so interesting that a new scientific direction appeared in plasma physics. At present, studies in this direction are being performed in many laboratories worldwide. The term X-pinch became conventional, and sections devoted to its study are always present at plasma conferences. X-pinch is not only a very interesting scientific object, but also a unique source of X-ray emission with extreme parameters. The use of X-pinches for point-projection X-ray radiography of high-energy-density objects provided many new experimental results. In some cases, the concepts of the processes occurring in matter upon fast energy deposition changed dramatically. The review consists of two parts. The first part briefly outlines the history of creation and studies of X-pinches, describes the diagnostic techniques and devices developed during these studies, and presents the main results obtained in studying the physical processes occurring in the X-pinch. The second part is devoted to the results of detailed studies of the X-pinch hot spot—the region where the highest plasma parameters are achieved and which is a source of X-ray emission with extreme parameters. Some results of X-pinch simulations are also presented.

  4. X-pinch. Part I

    SciTech Connect

    Pikuz, S. A. Shelkovenko, T. A.; Hammer, D. A.

    2015-04-15

    Results of experimental studies of the X-pinch since its invention and implementation in 1982 at the Lebedev Physical Institute are presented. The concept of the X-pinch arose in the course of innovative experiments on studying the generation of hot dense plasma in nanosecond Z-pinches. The main idea was to localize the region occupied by the plasma and stabilize the moment of its formation. This was achieved by using a load in the form of crossed wires. The resulting plasma object turned out to be so interesting that a new scientific direction appeared in plasma physics. At present, studies in this direction are being performed in many laboratories worldwide. The term X-pinch became conventional, and sections devoted to its study are always present at plasma conferences. X-pinch is not only a very interesting scientific object, but also a unique source of X-ray emission with extreme parameters. The use of X-pinches for point-projection X-ray radiography of high-energy-density objects provided many new experimental results. In some cases, the concepts of the processes occurring in matter upon fast energy deposition changed dramatically. The review consists of two parts. The first part briefly outlines the history of creation and studies of X-pinches, describes the diagnostic techniques and devices developed during these studies, and presents the main results obtained in studying the physical processes occurring in the X-pinch. The second part is devoted to the results of detailed studies of the X-pinch hot spot—the region where the highest plasma parameters are achieved and which is a source of X-ray emission with extreme parameters. Some results of X-pinch simulations are also presented.

  5. The magnitude of sawtooth crash events in multiple and quasi-single helicity states in a reversed-field-pinch plasma

    SciTech Connect

    Yagi, Y.; Frassinetti, L.; Hirano, Y.; Koguchi, H.; Sakakita, H.

    2005-08-15

    Factors affecting the magnitude of sawtooth crashes in soft x-ray (SXR) signals (I{sub SXR}) have been studied using data from high-{theta} (pinch parameter) discharges in the toroidal pinch experiment TPE-1RM20 reversed-field pinch device [Y. Yagi et al., J. Plasma Fusion Research 69, 700 (1993)]. In TPE-1RM20, discharges with a high {theta} that are free of large sawteeth (improved high-{theta} mode discharges), spontaneously appeared [Y. Hirano et al., Nucl. Fusion 36, 721 (1996)] among typical conventional discharges exhibiting large sawtooth crashes. The reason for the spontaneous appearance of sawtooth-free discharges has been unclear. It is shown that the normalized magnitude of the SXR crashes, [{delta}(I{sub SXR})/I{sub SXR}], is well correlated with the m (poloidal mode number)=0 mode amplitude in the postcrash phase. It is also shown that {delta}(I{sub SXR})/I{sub SXR} is smaller when the quasi-single helicity state precedes the crash rather than when the multiple-helicity state precedes the crash, and {delta}(I{sub SXR})/I{sub SXR} is smaller when E{sub parallel} (the parallel electric field at the plasma surface) is approximately zero in the precrash phase rather than E{sub parallel} being negative.

  6. Non-linear optical crystal vibration sensing device

    DOEpatents

    Kalibjian, R.

    1994-08-09

    A non-linear optical crystal vibration sensing device including a photorefractive crystal and a laser is disclosed. The laser produces a coherent light beam which is split by a beam splitter into a first laser beam and a second laser beam. After passing through the crystal the first laser beam is counter-propagated back upon itself by a retro-mirror, creating a third laser beam. The laser beams are modulated, due to the mixing effect within the crystal by vibration of the crystal. In the third laser beam, modulation is stable and such modulation is converted by a photodetector into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal. 3 figs.

  7. Non-linear optical crystal vibration sensing device

    DOEpatents

    Kalibjian, Ralph

    1994-01-11

    A non-linear optical crystal vibration sensing device (10) including a photorefractive crystal (26) and a laser (12). The laser (12 ) produces a coherent light beam (14) which is split by a beam splitter (18) into a first laser beam (20) and a second laser beam (22). After passing through the crystal (26) the first laser beam (20) is counter-propagated back upon itself by a retro-mirror (32), creating a third laser beam (30). The laser beams (20, 22, 30) are modulated, due to the mixing effect within the crystal (26) by vibration of the crystal (30). In the third laser beam (30), modulation is stable and such modulation is converted by a photodetector (34) into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal (26).

  8. MEMS Micro-Translation Device with Improved Linear Travel Capability

    NASA Technical Reports Server (NTRS)

    Abushagur, Mustafa A. G. (Inventor); Ferguson, Cynthia K. (Inventor); Nordin, Gregory P. (Inventor); English, Jennifer M. (Inventor)

    2007-01-01

    A microscopic translation device for a microelectromechanical system includes a pair of linear stator assemblies disposed in spaced relation to define an elongate channel. Each assembly is formed by a plurality of stators arranged in a row along the channel. A shuttle member is disposed between the stator assemblies for translating movement along the channel. The shuttle member includes a plurality of rotors extending outwardly from opposite sides. The shuttle is grounded through the stator assemblies and includes a mounting area for an object to be translated. Electrical lines are individually connected to alternate stators of a plurality of groups of the stators. A current supply sequentially supplies current through the electrical lines to the alternate stators so as to effect charging of the stators in a predetermined sequence. This produces a tangential capacitive force that causes translation of the shuttle.

  9. Recyclable transmission line (RTL) and linear transformer driver (LTD) development for Z-pinch inertial fusion energy (Z-IFE) and high yield.

    SciTech Connect

    Sharpe, Robin Arthur; Kingsep, Alexander S. (Kurchatov Institute, Moscow, Russia); Smith, David Lewis; Olson, Craig Lee; Ottinger, Paul F. (Naval Research Laboratory, Washington, DC); Schumer, Joseph Wade (Naval Research Laboratory, Washington, DC); Welch, Dale Robert (Voss Scientific, Albuquerque, NM); Kim, Alexander (High Currents Institute, Tomsk, Russia); Kulcinski, Gerald L. (University of Wisconsin, Madison, WI); Kammer, Daniel C. (University of Wisconsin, Madison, WI); Rose, David Vincent (Voss Scientific, Albuquerque, NM); Nedoseev, Sergei L. (Kurchatov Institute, Moscow, Russia); Pointon, Timothy David; Smirnov, Valentin P.; Turgeon, Matthew C.; Kalinin, Yuri G. (Kurchatov Institute, Moscow, Russia); Bruner, Nichelle "Nicki" (Voss Scientific, Albuquerque, NM); Barkey, Mark E. (University of Alabama, Tuscaloosa, AL); Guthrie, Michael (University of Wisconsin, Madison, WI); Thoma, Carsten (Voss Scientific, Albuquerque, NM); Genoni, Tom C. (Voss Scientific, Albuquerque, NM); Langston, William L.; Fowler, William E.; Mazarakis, Michael Gerrassimos

    2007-01-01

    Z-Pinch Inertial Fusion Energy (Z-IFE) complements and extends the single-shot z-pinch fusion program on Z to a repetitive, high-yield, power plant scenario that can be used for the production of electricity, transmutation of nuclear waste, and hydrogen production, all with no CO{sub 2} production and no long-lived radioactive nuclear waste. The Z-IFE concept uses a Linear Transformer Driver (LTD) accelerator, and a Recyclable Transmission Line (RTL) to connect the LTD driver to a high-yield fusion target inside a thick-liquid-wall power plant chamber. Results of RTL and LTD research are reported here, that include: (1) The key physics issues for RTLs involve the power flow at the high linear current densities that occur near the target (up to 5 MA/cm). These issues include surface heating, melting, ablation, plasma formation, electron flow, magnetic insulation, conductivity changes, magnetic field diffusion changes, possible ion flow, and RTL mass motion. These issues are studied theoretically, computationally (with the ALEGRA and LSP codes), and will work at 5 MA/cm or higher, with anode-cathode gaps as small as 2 mm. (2) An RTL misalignment sensitivity study has been performed using a 3D circuit model. Results show very small load current variations for significant RTL misalignments. (3) The key structural issues for RTLs involve optimizing the RTL strength (varying shape, ribs, etc.) while minimizing the RTL mass. Optimization studies show RTL mass reductions by factors of three or more. (4) Fabrication and pressure testing of Z-PoP (Proof-of-Principle) size RTLs are successfully reported here. (5) Modeling of the effect of initial RTL imperfections on the buckling pressure has been performed. Results show that the curved RTL offers a much greater buckling pressure as well as less sensitivity to imperfections than three other RTL designs. (6) Repetitive operation of a 0.5 MA, 100 kV, 100 ns, LTD cavity with gas purging between shots and automated operation is

  10. Newly developed ventricular assist device with linear oscillatory actuator.

    PubMed

    Fukunaga, Kazuyoshi; Funakubo, Akio; Fukui, Yasuhiro

    2003-01-01

    The goal of this study was to develop a new direct electromagnetic left ventricular assist device (DEM-LVAD) with a linear oscillatory actuator (LOA). The DEM-LVAD is a pulsatile pump with a pusher plate. The pusher plate is driven directly by the mover of the LOA. The LOA provides reciprocating motion without using any movement converter such as a roller screw or a hydraulic system. It consists of a stator with a single winding excitation coil and a mover with two permanent magnets. The simple structure of the LOA is based on fewer parts to bring about high reliability and smaller size. The mover moves back and forth when forward and backward electric current is supplied to the excitation coil. The pump housings have been designed using three-dimensional computer aided design software and fabricated with the aid of computer aided manufacturing technology. Monostrut valves (Bjork-Shiley #21) were used for the prototype. The DEM-LVAD dimension is 96 mm in diameter and 50 mm thick with a mass of 0.62 kg and a volume of 280 ml. An in vitro test (afterload 100 mm Hg; preload 10 mm Hg; input power 10 W) demonstrated more than 6 L/minute maximum output and 15% maximum efficiency at 130 beats per minute (bpm). Dynamic stroke volume ranged between 40 and 60 ml. The feasibility of the DEM-LVAD was confirmed. PMID:12790386

  11. The study of pinch regimes based on radiation-enhanced compression and anomalous resistivity phenomena and their effects on hard x-ray emission in a Mather type dense plasma focus device (SABALAN2)

    NASA Astrophysics Data System (ADS)

    Piriaei, D.; Mahabadi, T. D.; Javadi, S.; Ghoranneviss, M.; Saw, S. H.; Lee, S.

    2015-12-01

    In this study, by using argon and nitrogen as the filling gases in a Mather type dense plasma focus device at different values of pressure and charging voltage, two different kinds of pinch regimes were observed for each of the gases. The physics of the pinch regimes could be explained by using the two versions of the Lee's computational model which predicted each of the scenarios and clarified their differences between the two gases according to the radiation-enhanced compression and, additionally, predicted the pinch regimes through the anomalous resistivity effect during the pinch time. This was accomplished through the fitting process (simulation) on the current signal. Moreover, the characteristic amplitude and time scales of the anomalous resistances were obtained. The correlations between the features of the plasma current dip and the emitted hard x-ray pulses were observed. The starting time, intensity, duration, and the multiple or single feature of the emitted hard x-ray strongly correlated to the same respective features of the current dip.

  12. The study of pinch regimes based on radiation-enhanced compression and anomalous resistivity phenomena and their effects on hard x-ray emission in a Mather type dense plasma focus device (SABALAN2)

    SciTech Connect

    Piriaei, D.; Javadi, S.; Ghoranneviss, M.; Mahabadi, T. D.; Saw, S. H.; Lee, S.

    2015-12-15

    In this study, by using argon and nitrogen as the filling gases in a Mather type dense plasma focus device at different values of pressure and charging voltage, two different kinds of pinch regimes were observed for each of the gases. The physics of the pinch regimes could be explained by using the two versions of the Lee's computational model which predicted each of the scenarios and clarified their differences between the two gases according to the radiation-enhanced compression and, additionally, predicted the pinch regimes through the anomalous resistivity effect during the pinch time. This was accomplished through the fitting process (simulation) on the current signal. Moreover, the characteristic amplitude and time scales of the anomalous resistances were obtained. The correlations between the features of the plasma current dip and the emitted hard x-ray pulses were observed. The starting time, intensity, duration, and the multiple or single feature of the emitted hard x-ray strongly correlated to the same respective features of the current dip.

  13. Dense-Pinch Photocathode

    NASA Astrophysics Data System (ADS)

    Asmus, John F.; Lovberg, Ralph H.

    1988-05-01

    A promising approach to the generation of low-emittance e-beams for particle beam and FEL application employs a photoelectron cathode. IF such an e-beam source is to be viable at high power, a high-performance hard-UV illuminator is needed. Toward this end, experiments have been performed by illuminating a metal photocathode with the VUV radiation from a laser-guided gas-embedded high-density high-Z pinch. Such a VUV source is interesting because the plasma is created at high density and is optically thick. Thus, it is both a stable and an efficient radiator. Coupled with a copper photocathode it has generated a-beam current densities up to 60 A/sq-cm. The test device has been modified to utilize a pinch formed from a liquid jet in vacuum, rather than the laser-guided discharge in high-pressure gas. This is more suitable for rep-rate operation as it dispenses with the VUV-absorbing interposed gas, the channel-forming laser, and gas transport at high average power. A decane-jet device has been tested at 10 Hz with a peak pulse VUV power of 100 MW.

  14. An empirical scaling law for improved confinement in reversed-field pinch plasmas

    NASA Astrophysics Data System (ADS)

    Yagi, Y.; Koguchi, H.; Hirano, Y.; Sakakita, H.; Frassinetti, L.

    2005-02-01

    A database of the confinement properties of the toroidal pinch experiment (TPE) series reversed-field pinch (RFP) devices was established, and an empirical scaling law for the energy confinement time, τE, was deduced for a consistently selected set of the database (Yagi Y. et al 2003 Nucl. Fusion 43 1787). The scaling for τE [TPE-scaling; \\smash{\\tau _E \\sim a^{1.7} I_p^{0.8} (I_p/N)^{0.3} \\Theta ^{3}} ], in particular, is a power law similar to that predicted on the basis of the tearing modes, as a function of the plasma minor radius (a), plasma current (Ip), and Ip/N, where N is the column density. On the other hand, the TPE-scaling has a strong dependence on the pinch parameter, Θ, namely τE ~ Θ3. Recently, we have investigated the database of the improved confinement in the pulsed poloidal current drive (PPCD). We show that the TPE-scaling agrees well with the improved τE in the PPCD database, because of its strong Θ dependence. Namely, Θ3 is a factor of merit for RFP plasmas. We discuss why this agreement is obtained in spite of the general difference between the underlying transport mechanisms of the standard and PPCD discharges. We also show that this improvement, represented by Θ3, is related to the increase in magnetic shear with Θ.

  15. X-ray Spectroscopy and Imaging of Combined X-pinches with Mo and W wires at Cornell and UNR 1MA Pulsed Power Devices

    SciTech Connect

    Safronova, Alla; Kantsyrev, Victor; Fedin, Dmitry; Yilmaz, Fatih; Hoppe, Travis; Nalajala, Vidya

    2006-01-05

    X-pinch experiments using combined Mo and W wires were implemented on the 1MA Cornell University (CU) COBRA and University of Nevada, Reno (UNR) ZEBRA facilities. Spatially-resolved and integrated x-ray spectral data and time integrated and time-gated pinhole x-ray images accumulated in these X-pinch experiments are analyzed. In particular, x-ray L-shell spectra of Mo ions and M-shell spectra of W ions have been studied. A non-LTE collisional-radiative (CR) atomic kinetic model of Mo, successfully applied before to interpret UNR and CU x-ray spectra from Mo X-pinches, was used here to provide plasma parameters from L-shell Mo radiation from the combined (W/Mo) X-pinches. The recently developed non-LTE CR model of W based on FAC atomic structure code data has been applied to identify and diagnose the spectral features of W ions and to provide parameters of the plasma from M-shell W radiation from W/Mo X-pinches. As a result, the radiative properties of W/Mo X-pinches produced on two 1 MA university-scale pulsed power facilities are analyzed and compared.

  16. Rigid-drift magnetohydrodynamic equilibria for cylindrical screw pinches

    NASA Technical Reports Server (NTRS)

    Turner, L.

    1979-01-01

    The rigid-drift equations of MHD equilibria in cylindrical geometry are solved analytically in terms of an infinite series of hypergeometric functions for the case where the pressure is proportional to the square of number density and the current density is arbitrarily pitched. Solutions are obtained for a pure Z pinch, a pure theta pinch, and a general screw pinch. It is found that the shapes of the pressure and magnetic-field profiles are completely determined by the model once two parameters are specified: the local plasma beta on the axis and a quantity related to the pitch of the current density. A set of profiles that resemble those observed experimentally in reversed-field pinches is presented. The results also indicate that hollow pressure profiles and reversed Bz profiles can occur either simultaneously or independently and that the pressure always falls to zero at a finite value of the radius.

  17. Total dose bias dependency and ELDRS effects in bipolar linear devices

    NASA Technical Reports Server (NTRS)

    Yui, C. C.; McClure, S. S.; Rex, B. G.; Lehman, J. M.; Minto, T. D.; Wiedeman, M.

    2002-01-01

    Total dose tests of several bipolar linear devices show sensitivity to both dose rate and bias during exposure. All devices exhibited Enhanced Low Dose Rate Sensitivity (ELDRS). An accelerated ELDRS test method for three different devices demonstrate results similar to tests at low dose rate. Behavior and critical parameters from these tests are compared and discussed.

  18. Megampere Multi-Wire Z-{theta} Pinch

    SciTech Connect

    Selemir, V.D.; Repin, P.B.; Pikulin, I.V.; Volkov, A.A.; Orlov, A.P.; Tatsenko, O.M.; Markevtsev, I.M.; Moiseenko, A.N.; Selyavsky, V.T.; Dydykin, P.S.; Grebenev, E.V.; Bukharov, V.F.; Ryaslov, E.A.; Kudryavtsev, V.P.; Kotelnikov, D.V.; Duday, P.V.

    2006-01-05

    Experimental results on study of magnetic flux compression efficiency with a plasma shell, formed at electric explosion of a multi-wire cylindrical frame are presented. Liners of 70 mm diameter consisting of 48 tungsten wires of 11 {mu}m diameter were used. The liner was put into longitudinal quasi-stationary magnetic field with induction of 0.45 T and powered with the current having amplitude up to 1.5 MA at rise time of {approx}1 {mu}s. A magneto-optical detector recorded magnetic fields in the center of the liner system, which exceeded initial value of the magnetic field in a factor of 10.

  19. Generation of ultra-high magnetic fields by a degenerate, snow-plow pinch

    NASA Astrophysics Data System (ADS)

    Hartman, C. W.; Eddleman, J. L.; Gee, M.; Harte, J. A.; Zimmerman, G. B.

    1992-12-01

    We discuss 1-D and 2-D LASNEX calculations of a snow-plow pinch in Xenon. The pinch is driven by inductively stored energy, switched by a compact-torus, fast-opening switch, with performance characteristics calculated by the TRACII, 2-D, MHD code. The 10-cm initial radius, 1 cm long Xe pinch, is driven by 50 MA current thatis switched on in 100 ns. The pinch uniquely undergoes radiative collapse during the snow-plow phase, conforming to the original description of the 'snow-plow', to form a high-density, high-kinetic energy Xe shell which dynamically converges to a pinch equilibrium with degenerate electron pressure, high-density high-magnetic field. The described pinch configuration, calculated in 1-D, is expected to be unstable to R-T, sausage, and kink instabilities. A small initial B(sub zo) field (approximately 100 G) is calculated to be compressed to B(sub z) approximately = B (sub theta) at the final, degenerate, pinch equilibrium, thus stabilizing sausage instability. A larger initial B(sub z) field (approximately 10 kG) is calculated to be compressed by the radiatively collapsing plasma in the snow-plow to B(sub z) approximately = B (sub theta) to stabilize R-T instability during the snow-plow phase. Finally, the kink instability (if it occurs) is expected, as observed, to leave intact the tightly pinched plasma column.

  20. Polytropic scaling of a flow Z-pinch

    NASA Astrophysics Data System (ADS)

    Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.; Weed, J. R.

    2015-11-01

    The ZaP Flow Z-Pinch project investigates the use of velocity shear to mitigate MHD instabilities. The ZaP-HD experiment produces 50 cm long pinches of varying radii. The power to the experiment is split between the plasma formation and acceleration process and the pinch assembly and compression process. Once the pinch is formed, low magnetic fluctuations indicate a quiescent, long-lived pinch. The split power supply allows more control of the pinch current than previous machine iterations, with a designed range from 50 to 150 kA. Radial force balance leads to the Bennett relation which indicates that as the pinch compresses due to increasing currents, the plasma pressure and/or linear density must change. Through ion spectroscopy and digital holographic interferometry coupled with magnetic measurements of the pinch current, the components of the Bennett relation can be fully measured. A scaling relation is then assumed to follow a polytrope as the pinch pressure, initially approximately 250 kPa, increases from an initially formed state to much higher values, approaching 100 MPa. A preliminary analysis of pinch scaling is shown corroborating with other diagnostics on the machine along with extrapolations to required currents for an HEDLP machine. This work is supported by grants from the U.S. Department of Energy and the U.S. National Nuclear Security Administration.

  1. A Bi-Frequency Linear Slow Wave Device

    NASA Astrophysics Data System (ADS)

    Simon, David; Zhang, Peng; Lau, Y. Y.; Greening, Geoff; Gilgenbach, Ronald; Hoff, Brad

    2014-10-01

    Bi-frequency sources are of interest to plasma processing, diagnostics, RF heating, and defense electronics. The recirculating planar magnetron has been modified to produce two frequencies using two different slow wave structures in the planar regions. To highlight the coupling in the two frequencies, we consider here a linear TWT driven by a sheet beam inside such a structure. The cold tube dispersion is derived and is compared favorably with HFSS. The hot tube dispersion has also been derived, and is being compared with MAGIC simulations. Various nonlinear effects are explored, such as harmonic generation, parametric amplification, and intermodulation. This work was supported by ONR and AFOSR.

  2. Continuing evaluation of bipolar linear devices for total dose bias dependency and ELDRS effects

    NASA Technical Reports Server (NTRS)

    McClure, Steven S.; Gorelick, Jerry L.; Yui, Candice; Rax, Bernard G.; Wiedeman, Michael D.

    2003-01-01

    We present results of continuing efforts to evaluate total dose bias dependency and ELDRS effects in bipolar linear microcircuits. Several devices were evaluated, each exhibiting moderate to significant bias and/or dose rate dependency.

  3. Heavy Ion and Proton Induced Single Event Transients in Linear Devices

    NASA Technical Reports Server (NTRS)

    Nichols, D. K.; Coss, J. R.; Miyahira, T.; Schwartz, H. R.

    1996-01-01

    This paper presents a display of heavy-ion and proton-induced single event transients for selected linear devices. The transient vital signs are serious; low LET threshold, high voltage amplitude and extended pulse duration (microsecs.).

  4. Symmetric multilayer megampere X-pinch

    SciTech Connect

    Shelkovenko, T. A.; Pikuz, S. A.; McBride, R. D.; Knapp, P. F.; Wilhelm, G.; Sinars, D. B.; Hammer, D. A.; Orlov, N. Yu.

    2010-01-15

    Raising the power of X-ray emission from an X-pinch by increasing the pinch current to the megampere level requires the corresponding increase in the initial linear mass of the load. This can be achieved by increasing either the number of wires or their diameter. In both cases, special measures should be undertaken to prevent the formation of a complicated configuration with an uncontrolled spatial structure in the region of wire crossing, because such a structure breaks the symmetry of the neck formed in the crossing region, destabilizes plasma formation, and degrades X-ray generation. To improve the symmetry of the wire crossing region, X-pinch configurations with a regular multilayer arrangement of wires in this region were proposed and implemented. The results of experiments with various symmetric X-pinch configurations on the COBRA facility at currents of {approx}1MA are presented. It is shown that an X-pinch with a symmetric crossing region consisting of several layers of wires made of different materials can be successfully used in megampere facilities. The most efficient combinations of wires in symmetric multilayer X-pinches are found in which only one hot spot forms and that are characterized by a high and stable soft X-ray yield.

  5. Understanding the theta aurora

    NASA Astrophysics Data System (ADS)

    Fear, Robert; Milan, Steve; Carter, Jennifer; Maggiolo, Romain; Fazakerley, Andrew; Dandouras, Iannis; Mende, Stephen

    2015-04-01

    The theta aurora, first observed by Dynamics Explorer in the 1980s, is a configuration of the Earth's aurora in which auroral emissions extend into and across the polar cap in the form of a transpolar arc. It is well established that the theta aurora occurs predominantly when the interplanetary magnetic field has a northward component, but over the last thirty years various mechanisms have been put forward to explain this intriguing phenomenon. In the last couple of years, a range of evidence has accumulated which strongly suggests that the transpolar arc is formed as proposed by Milan et al. (2005): magnetotail reconnection occurs during intervals of northward IMF, which results in a local "wedge" of closed magnetospheric flux that remains trapped in the magnetotail. Precipitation on these closed field lines results in the transpolar arc analogously to the formation of the aurora in the main oval. Evidence for magnetotail reconnection as the cause of the theta aurora includes the timescales necessary to influence the location at which the transpolar arc forms, and the presence of characteristic ionospheric flows which are excited by magnetotail reconnection and which are statistically associated with transpolar arcs (Fear & Milan, 2012a,b). Most recently, direct observation has been made of a localised wedge of closed magnetic flux, "trapped" in the lobe, which was observed to move back and forth in a manner which (to our knowledge) can only be explained by the magnetotail reconnection mechanism (Fear et al., 2014). In this talk, we summarise the evidence for the formation of the theta aurora by magnetotail reconnection, and discuss the remaining challenges in obtaining a comprehensive understanding of this spectacular phenomenon.

  6. Driven, steady-state RFP computations. [reversed field pinch

    NASA Technical Reports Server (NTRS)

    Dahlburg, J. P.; Montgomery, D.; Doolen, G. D.; Turner, L.

    1988-01-01

    The pseudospectral three-dimensional MHD code of Dahlburg et al. (1986 and 1987) is used to compute the dynamical behavior of a channel of magnetofluid carrying an axial current and magnetic flux. This situation contains the essential MHD behavior of the reversed-field pinch (RFP). An externally imposed electric field is applied to an initially current-free magnetofluid and drives currents that rise and eventually fluctuate about values corresponding to pinch ratios Theta of about 1.3, 2.2, and 4.5. A period of violent turbulence leads to an approximately force-free core, surrounded by an active MHD boundary layer that is not force-free. A steady state is reached that can apparently be sustained indefinitely (for several hundred Alfven transit times or longer). The turbulence level and time variability in the steady state increase with increasing Theta. The average toroidal magnetic field at the wall reverses for Theta = 2.2 and 4.5, but not for Theta = 1.3. Negative toroidal current filaments are observed. The Lundquist numbers are of the order of a few hundred.

  7. Inverse mirror plasma experimental device (IMPED) - a magnetized linear plasma device for wave studies

    NASA Astrophysics Data System (ADS)

    Bose, Sayak; Chattopadhyay, P. K.; Ghosh, J.; Sengupta, S.; Saxena, Y. C.; Pal, R.

    2015-04-01

    In a quasineutral plasma, electrons undergo collective oscillations, known as plasma oscillations, when perturbed locally. The oscillations propagate due to finite temperature effects. However, the wave can lose the phase coherence between constituting oscillators in an inhomogeneous plasma (phase mixing) because of the dependence of plasma oscillation frequency on plasma density. The longitudinal electric field associated with the wave may be used to accelerate electrons to high energies by exciting large amplitude wave. However when the maximum amplitude of the wave is reached that plasma can sustain, the wave breaks. The phenomena of wave breaking and phase mixing have applications in plasma heating and particle acceleration. For detailed experimental investigation of these phenomena a new device, inverse mirror plasma experimental device (IMPED), has been designed and fabricated. The detailed considerations taken before designing the device, so that different aspects of these phenomena can be studied in a controlled manner, are described. Specifications of different components of the IMPED machine and their flexibility aspects in upgrading, if necessary, are discussed. Initial results meeting the prerequisite condition of the plasma for such study, such as a quiescent, collisionless and uniform plasma, are presented. The machine produces δnnoise/n <= 1%, Luniform ~ 120 cm at argon filling pressure of ~10-4 mbar and axial magnetic field of B = 1090 G.

  8. Ramanujan's mock theta functions.

    PubMed

    Griffin, Michael; Ono, Ken; Rolen, Larry

    2013-04-01

    In his famous deathbed letter, Ramanujan introduced the notion of a mock theta function, and he offered some alleged examples. Recent work by Zwegers [Zwegers S (2001) Contemp Math 291:268-277 and Zwegers S (2002) PhD thesis (Univ of Utrecht, Utrecht, The Netherlands)] has elucidated the theory encompassing these examples. They are holomorphic parts of special harmonic weak Maass forms. Despite this understanding, little attention has been given to Ramanujan's original definition. Here, we prove that Ramanujan's examples do indeed satisfy his original definition. PMID:23536292

  9. Non-linear control of the ''clam'' wave energy device. Final report

    SciTech Connect

    Not Available

    1983-09-01

    A promising wave energy device being currently investigated is the ''clam'' device. The clam extracts energy by pumping air through a specially designed (Wells) turbine. Although operation of the Wells turbine does not require a rectified air flow, some additional control will be necessary to optimize the phase of the clam motion for good efficiencies. An examination of the equation of motion in the time domain suggests the possibility of non-linear phase control by mechanical, power take-off, or pneumatic latching. Latching can be shown to increase the efficiency of the device in the longer wavelengths of the wave spectrum, i.e. those of high incident wave power.

  10. Specifications for the Linear Charge Coupled Device for use in transient recording

    SciTech Connect

    Balch, J.W.

    1981-05-28

    Specifications are presented for the Linear Charge Coupled Device (LCCD) developed at the Lawrence Livermore National Laboratory for recording data from transients. This device can be used to record electrical signals at sample rates greater than 10/sup 9/ samples per second. Both electrical and physical specifications of the device are presented. The bias and drive requirements of the device are presented in tables and in timing diagrams. Typical performance data are tabulated and shown in oscilloscope photos. The physical specifications of the device include plane and cross sectional drawings of its various registers and I/O sections. Enlarged photos of the mask set are shown and all critical dimensions of the active regions are given. Finally, the impurity doping profile used for the transfer channels is shown.

  11. The theta aurora

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Craven, J. D.; Gurnett, D. A.; Shawhan, S. D.; Burch, J. L.; Winningham, J. D.; Chappell, C. R.; Waite, J. H.; Maynard, N. C.; Sugiura, M.

    1986-01-01

    A comprehensive review is presented of the characteristics of theta aurora as revealed from four imaging efforts with the DE 1 and 2 satellites. The theta aurora consists of an auroral oval with a sun-aligned arc extending from the dayside to the nightside sectors of the oval. The DE 1 spacecraft provided high altitude simultaneous measurements of the electric and magnetic fields and plasma and the DE 2 collected equivalent low altitude data on the four events. The plasma was found to convect sunward when the transpolar arc appeared, while the convection was antisunward in other regions over the polar cap. The arc plasmas featured field-aligned electron acceleration into the polar atmosphere and field-aligned current sheets, both of which were sparse over the rest of the polar cap. The ions originated in the ionosphere and the solar wind; ions over the rest of the polar cap mainly arrived from the magnetosphere. Further discussions are provided of the dominant electrons and ions and the associated flow directions into and out of the various regions of the pole, similarities between the transpolar arc and the auroral oval, and interactions between the ionosphere and the auroral phenomena.

  12. Characterization of Radiation Hardened Bipolar Linear Devices for High Total Dose Missions

    NASA Technical Reports Server (NTRS)

    McClure, Steven S.; Harris, Richard D.; Rax, Bernard G.; Thorbourn, Dennis O.

    2012-01-01

    Radiation hardened linear devices are characterized for performance in combined total dose and displacement damage environments for a mission scenario with a high radiation level. Performance at low and high dose rate for both biased and unbiased conditions is compared and the impact to hardness assurance methodology is discussed.

  13. Linear motion device and method for inserting and withdrawing control rods

    DOEpatents

    Smith, Jay E.

    1984-01-01

    A linear motion device, more specifically a control rod drive mechanism (CRDM) for inserting and withdrawing control rods into a reactor core, is capable of independently and sequentially positioning two sets of control rods with a single motor stator and rotor. The CRDM disclosed can control more than one control rod lead screw without incurring a substantial increase in the size of the mechanism.

  14. A linear-actuated torsional device to replicate clinically relevant spiral fractures in long bones.

    PubMed

    Edwards, W Brent; Troy, Karen L

    2012-09-01

    To better understand the mechanisms underlying spiral fracture we would like to carry out biomechanical tests of long bones loaded in torsion to failure. A device was fabricated to perform torsional tests of long bones using a single-axis linear actuator. The principal operation of the device was to transform the vertical displacement of a material testing machine's linear actuator into rotational movement using a spur gear and rack system. Accuracy and precision of the device were quantified using cast-acrylic rods with known torque-rotation behavior. Cadaveric experimentation was used to replicate a clinically relevant spiral fracture in eleven human proximal tibiae; strain-gage data were recorded for a single specimen. The device had an experimental error of less than 0.2 Nm and was repeatable to within 0.3%. Strain gage data were in line with those expected from pure torsion and the cadaveric tibiae illustrated spiral fractures at ultimate torque and rotation values of 130.6 +/- 53.2 Nm and 8.3 +/- 1.5 degrees, respectively. Ultimate torque was highly correlated with DXA assessed bone mineral density (r = 0.87; p < 0.00 1). The device presented is applicable to any torsional testing of long bone when only a single-axis linear actuator is available. PMID:23025174

  15. 2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches

    SciTech Connect

    Hammer, J.H.; Eddleman, J.L.; Springer, P.T.

    1995-11-06

    Z-pinch implosions driven by the SATURN device at Sandia National Laboratory are modeled with a 2D radiation magnetohydrodynamic (MHD) code, showing strong growth of magneto-Rayleigh Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time span of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. 2D krypton simulations show an output x-ray power > 80 TW for the peaked profile.

  16. Accuracy and Linearity of Positive Airway Pressure Devices: A Technical Bench Testing Study

    PubMed Central

    Torre-Bouscoulet, Luis; López-Escárcega, Elodia; Carrillo-Alduenda, José Luis; Arredondo-del-Bosque, Fernando; Reyes-Zúñiga, Margarita; Castorena-Maldonado, Armando

    2010-01-01

    Study Objectives: To analyze the accuracy and linearity of different CPAP devices outside of the manufacturers' own quality control environment. Methods: Accuracy (how well readings agree with the gold standard) and linearity were evaluated by comparing programmed pressure to measured CPAP pressure using an instrument established as the gold standard. Comparisons were made centimeter-by-centimeter (linearity) throughout the entire programming spectrum of each device (from 4 to 20 cm H2O). Results: A total of 108 CPAP devices were tested (1836 measurements); mean use of the devices was 956 hours. Twenty-two of them were new. The intra-class correlation coefficient (ICC) decreased from 0.97 at pressures programmed between 4 and 10 cm H2O, to 0.84 at pressures of 16 to 20 cm H2O. Despite this high ICC, the 95% agreement limit oscillated between −1 and 1 cm H2O. This same behavior was observed in relation to hours of use: the ICC for readings taken on devices with < 2,000 hours of use was 0.99, while that of the 50 measurements made on devices with > 6,000 hours was 0.97 (the agreement limit oscillated between −1.3 and 2.5 cm H2O). “Adequate adjustments” were documented in 97% of measurements when the definition was ± 1 cm H2O of the programmed pressure, but this index of adequate adjustment readings decreased to 85% when the ± 0.5 cm H2O criterion was applied. Conclusions: In general, the CPAP devices were accurate and linear throughout the spectrum of programmable pressures; however, strategies to assure short- and long-term equipment reliability are required in conditions of routine use. Citation: Torre-Bouscoulet L; López-Escárcega E; Carrillo-Alduenda JL; Arredondo-del-Bosque F; Reyes-Zúñiga M; Castorena-Maldonado A. Accuracy and linearity of positive airway pressure devices: a technical bench testing study. J Clin Sleep Med 2010;6(4):369-373. PMID:20726286

  17. Theta vocabulary II. Multidimensional case

    NASA Astrophysics Data System (ADS)

    Kharchev, S.; Zabrodin, A.

    2016-06-01

    It is shown that the Jacobi and Riemann identities of degree four for the multidimensional theta functions as well as the Weierstrass identities emerge as algebraic consequences of the fundamental multidimensional binary identities connecting the theta functions with Riemann matrices τ and 2 τ.

  18. Effects of Three-Dimensional Electromagnetic Structures on Resistive-Wall-Mode Stability of Reversed Field Pinches

    SciTech Connect

    Villone, F.

    2008-06-27

    In this Letter, the linear stability of the resistive wall modes (RWMs) in toroidal geometry for a reversed field pinch (RFP) plasma is studied. Three computational models are used: the cylindrical code ETAW, the toroidal MHD code MARS-F, and the CarMa code, able to take fully into account the effects of a three-dimensional conducting structure which mimics the real shell geometry of a reversed field pinch experimental device. The computed mode growth rates generally agree with experimental data. The toroidal effects and the three-dimensional features of the shell, like gaps, allow a novel interpretation of the RWM spectrum in RFP's and remove its degeneracy. This shows the importance of making accurate modeling of conductors for the RWM predictions also in future devices such as ITER.

  19. Linear conversion of pressure into concentration, rapid switching of concentration, and generation of linear ramps of concentration in a microfluidic device

    PubMed Central

    Adler, Micha; Groisman, Alex

    2012-01-01

    Mixing of liquids to produce solutions with different concentrations is one of the basic functionalities of microfluidic devices. Generation of specific temporal patterns of concentration in microfluidic devices is an important technique to study responses of cells and model organisms to variations in the chemical composition of their environment. Here, we present a simple microfluidic network that linearly converts pressure at an inlet into concentration of a soluble reagent in an observation region and also enables independent concurrent linear control of concentrations of two reagents. The microfluidic device has an integrated mixer channel with chaotic three-dimensional flow that facilitates rapid switching of concentrations in a continuous range. A simple pneumatic setup generating linear ramps of pressure is used to produce smooth linear ramps and triangular waves of concentration with different slopes. The use of chaotic vs. laminar mixers is discussed in the context of microfluidic devices providing rapid switching and generating temporal waves of concentration. PMID:22550555

  20. Rapid multi sample DNA amplification using rotary-linear polymerase chain reaction device (PCRDisc).

    PubMed

    Sugumar, D; Kong, L X; Ismail, Asma; Ravichandran, M; Su Yin, Lee

    2012-03-01

    Multiple sample DNA amplification was done by using a novel rotary-linear motion polymerase chain reaction (PCR) device. A simple compact disc was used to create the stationary sample chambers which are individually temperature controlled. The PCR was performed by shuttling the samples to different temperature zones by using a combined rotary-linear movement of the disc. The device was successfully used to amplify up to 12 samples in less than 30 min with a sample volume of 5 μl. A simple spring loaded heater mechanism was introduced to enable good thermal contact between the samples and the heaters. Each of the heater temperatures are controlled by using a simple proportional-integral-derivative pulse width modulation control system. The results show a good improvement in the amplification rate and duration of the samples. The reagent volume used was reduced to nearly 25% of that used in conventional method. PMID:22685508

  1. Rapid multi sample DNA amplification using rotary-linear polymerase chain reaction device (PCRDisc)

    PubMed Central

    Sugumar, D.; Kong, L. X.; Ismail, Asma; Ravichandran, M.; Su Yin, Lee

    2012-01-01

    Multiple sample DNA amplification was done by using a novel rotary-linear motion polymerase chain reaction (PCR) device. A simple compact disc was used to create the stationary sample chambers which are individually temperature controlled. The PCR was performed by shuttling the samples to different temperature zones by using a combined rotary-linear movement of the disc. The device was successfully used to amplify up to 12 samples in less than 30 min with a sample volume of 5 μl. A simple spring loaded heater mechanism was introduced to enable good thermal contact between the samples and the heaters. Each of the heater temperatures are controlled by using a simple proportional–integral–derivative pulse width modulation control system. The results show a good improvement in the amplification rate and duration of the samples. The reagent volume used was reduced to nearly 25% of that used in conventional method. PMID:22685508

  2. Modified hyperspheres algorithm to trace homotopy curves of nonlinear circuits composed by piecewise linear modelled devices.

    PubMed

    Vazquez-Leal, H; Jimenez-Fernandez, V M; Benhammouda, B; Filobello-Nino, U; Sarmiento-Reyes, A; Ramirez-Pinero, A; Marin-Hernandez, A; Huerta-Chua, J

    2014-01-01

    We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157

  3. Modified Hyperspheres Algorithm to Trace Homotopy Curves of Nonlinear Circuits Composed by Piecewise Linear Modelled Devices

    PubMed Central

    Vazquez-Leal, H.; Jimenez-Fernandez, V. M.; Benhammouda, B.; Filobello-Nino, U.; Sarmiento-Reyes, A.; Ramirez-Pinero, A.; Marin-Hernandez, A.; Huerta-Chua, J.

    2014-01-01

    We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157

  4. Parametric Decay of Pump Waves into two Linear Modes in SINP MaPLE Device

    SciTech Connect

    Biswas, Subir; Pal, Rabindranath

    2010-11-23

    Parametric decay of incident waves of ion cyclotron frequency range into linear modes is observed in experiment performed in the SINP MaPLE device where nitrogen plasma produced by ECR discharge. Along with a mode in drift wave frequency range, sideband of the incident waves are observed when amplitude of the exciter signal goes above a threshold value. Sideband of the second harmonic is also seen. Preliminary studies point towards excitation of ion Bernstein wave. Details of the experimental results are presented.

  5. Parametric Decay of Pump Waves into two Linear Modes in SINP MaPLE Device

    NASA Astrophysics Data System (ADS)

    Biswas, Subir; Pal, Rabindranath

    2010-11-01

    Parametric decay of incident waves of ion cyclotron frequency range into linear modes is observed in experiment performed in the SINP MaPLE device where nitrogen plasma produced by ECR discharge. Along with a mode in drift wave frequency range, sideband of the incident waves are observed when amplitude of the exciter signal goes above a threshold value. Sideband of the second harmonic is also seen. Preliminary studies point towards excitation of ion Bernstein wave. Details of the experimental results are presented.

  6. Linear motion device and method for inserting and withdrawing control rods

    DOEpatents

    Smith, J.E.

    Disclosed is a linear motion device and more specifically a control rod drive mechanism (CRDM) for inserting and withdrawing control rods into a reactor core. The CRDM and method disclosed is capable of independently and sequentially positioning two sets of control rods with a single motor stator and rotor. The CRDM disclosed can control more than one control rod lead screw without incurring a substantial increase in the size of the mechanism.

  7. 3D imaging LADAR with linear array devices: laser, detector and ROIC

    NASA Astrophysics Data System (ADS)

    Kameyama, Shumpei; Imaki, Masaharu; Tamagawa, Yasuhisa; Akino, Yosuke; Hirai, Akihito; Ishimura, Eitaro; Hirano, Yoshihito

    2009-07-01

    This paper introduces the recent development of 3D imaging LADAR (LAser Detection And Ranging) in Mitsubishi Electric Corporation. The system consists of in-house-made key devices which are linear array: the laser, the detector and the ROIC (Read-Out Integrated Circuit). The laser transmitter is the high power and compact planar waveguide array laser at the wavelength of 1.5 micron. The detector array consists of the low excess noise Avalanche Photo Diode (APD) using the InAlAs multiplication layer. The analog ROIC array, which is fabricated in the SiGe- BiCMOS process, includes the Trans-Impedance Amplifiers (TIA), the peak intensity detectors, the Time-Of-Flight (TOF) detectors, and the multiplexers for read-out. This device has the feature in its detection ability for the small signal by optimizing the peak intensity detection circuit. By combining these devices with the one dimensional fast scanner, the real-time 3D range image can be obtained. After the explanations about the key devices, some 3D imaging results are demonstrated using the single element key devices. The imaging using the developed array devices is planned in the near future.

  8. In situ azimuthal rotation device for linear dichroism measurements in scanning transmission x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Hernández-Cruz, D.; Hitchcock, A. P.; Tyliszczak, T.; Rousseau, M.-E.; Pézolet, M.

    2007-03-01

    A novel miniature rotation device used in conjunction with a scanning transmission x-ray microscope is described. It provides convenient in situ sample rotation to enable measurements of linear dichroism at high spatial resolution. The design, fabrication, and mechanical characterization are presented. This device has been used to generate quantitative maps of the spatial distribution of the orientation of proteins in several different spider and silkworm silks. Specifically, quantitative maps of the dichroic signal at the C 1s→π*amide transition in longitudinal sections of the silk fibers give information about the spatial orientation, degree of alignment, and spatial distribution of protein peptide bonds. A new approach for analyzing the dichroic signal to extract orientation distributions, in addition to magnitudes of aligned components, is presented and illustrated with results from Nephila clavipes dragline spider silk measured using the in situ rotation device.

  9. Loss of energy dissipation capacity from the deadzone in linear and nonlinear viscous damping devices

    NASA Astrophysics Data System (ADS)

    Tong, Mai; Liebner, Thomas

    2007-03-01

    In a viscous damping device under cyclic loading, after the piston reaches a peak stroke, the reserve movement that follows may sometimes experience a short period of delayed or significantly reduced device force output. A similar delay or reduced device force output may also occur at the damper’s initial stroke as it moves away from its neutral position. This phenomenon is referred to as the effect of “deadzone”. The deadzone can cause a loss of energy dissipation capacity and less efficient vibration control. It is prominent in small amplitude vibrations. Although there are many potential causes of deadzone such as environmental factors, construction, material aging, and manufacture quality, in this paper, its general effect in linear and nonlinear viscous damping devices is analyzed. Based on classical dynamics and damping theory, a simple model is developed to capture the effect of deadzone in terms of the loss of energy dissipation capacity. The model provides several methods to estimate the loss of energy dissipation within the deadzone in linear and sublinear viscous fluid dampers. An empirical equation of loss of energy dissipation capacity versus deadzone size is formulated, and the equivalent reduction of effective damping in SDOF systems has been obtained. A laboratory experimental evaluation is carried out to verify the effect of deadzone and its numerical approximation. Based on the analysis, a modification is suggested to the corresponding formulas in FEMA 356 for calculation of equivalent damping if a deadzone is to be considered.

  10. Linearized superconducting quantum interference device array for high bandwidth frequency-domain readout multiplexing.

    PubMed

    Lanting, T; Dobbs, M; Spieler, H; Lee, A T; Yamamoto, Y

    2009-09-01

    We have designed and demonstrated a superconducting quantum interference device (SQUID) array linearized with cryogenic feedback. To achieve the necessary loop gain, a 300-element series array SQUID is constructed from three monolithic 100-element series arrays. A feedback resistor completes the loop from the SQUID output to the input coil. The short feedback path of this linearized SQUID array (LISA) allows for a substantially larger flux-locked loop bandwidth as compared to a SQUID flux-locked loop that includes a room temperature amplifier. The bandwidth, linearity, noise performance, and 3 Phi(0) dynamic range of the LISA are sufficient for its use in our target application: the multiplexed readout of transition-edge sensor bolometers. PMID:19791952

  11. Anomalous resistivity at the field null of the FRC: a quasi-linear expression based upon flute-type modes

    SciTech Connect

    Gerwin, R.

    1983-10-01

    In the Field-Reversed Theta Pinch (FRC) experiment, the poloidal flux is observed to be lost at a rate several times greater than classical resistivity would allow. Thus, there must be anomalous resistivity at the field null. Assuming that an electromagnetic microinstability of the flute mode type is responsible for this, we derived a general expression for the anomalous resistivity at the field null based upon a quasi-linear model of the microturbulence. This general expression does not depend upon the details of the ion-species model, for example, whether the ions are fluid or kinetic.

  12. Organic Light Emitting Devices with Linearly-Graded Mixed Host Architecture

    NASA Astrophysics Data System (ADS)

    Lee, Sang Min

    Organic Light Emitting Devices (OLEDs) with a linearly-graded mixed (LGM) host architecture in the emissive layer (EML) were studied by the application of a newly-developed thermal deposition boat. A new thermal deposition boat, featuring indirect deposition control and fast rate response, was developed in order to make an evaporation coater of high space utilization and to achieve a real time linearly-graded rate control during the device fabrication process. A new design of dual-hole boat, based on the reduced wall resistance of the side hole toward the vapor flow, enabled the indirect deposition rate control with sufficient control accuracy by using the feature of the stable ratio of rates from top and side holes. Minimizing the thermal mass of the body and designing a direct heat transfer with a coil placed inside the boat resulted in the realization of the linearly-graded deposition rate within acceptable deviation range. Thanks to the feature of fast rate response, it was possible to control the linearly-graded rate of each host material during the process and to apply the architecture to some of the fluorescent and phosphorescent OLED devices. The reported efficiency improvement of a fluorescent OLED, based on step-graded junction in the literature, was well reproduced in an OLED with a LGM architecture, demonstrating that charge balance in the emissive layer can be further improved using the LGM architecture. By minimizing the internal energy barrier in the LGM device, a higher EL efficiency was well demonstrated over the uniformly-mixed (UM) host device, where residual internal interfaces were present as additional quenching sites in the EML. Similar effects were observed in blue phosphorescent OLED devices, where the mobility of the hole transport material (HTM) was usually much higher than that of the electron transport material (ETM) such that the recombination zone was more localized at the EML/ETL interface. It was found that the main effect of the

  13. Optimum pinch grips in the handling of dies.

    PubMed

    Heffernan, C; Freivalds, A

    2000-08-01

    Handling roller-press dies has caused numerous work-related musculoskeletal disorders in the leather industry. The dies are quite large (0.61 x 0.30 m), heavy (3.5 kg) and are difficult to handle because of the large pinch span requirements (up to 16 cm). The purpose of this study was to determine the optimum pinch span and optimum crossbar angulation to minimize die handling forces. Five-finger pulp-pinch forces were measured on five males and five females with a force-sensitive-resistor instrumented glove while handling a simulated adjustable die. Maximum pinch forces occurred at pinch spans between 1.27 and 3.81 cm, with average female strengths being 57% of average male pinch strengths. Minimum pinch forces to hold the die occurred at a 45 degrees angulation and increased linearly as the angle approached 90 degrees or the normal vertical orientation. The simplest solution to redesigning the dies is to: (1) decrease the distance between the braces to less than 4 cm and (2) slant the braces at 45 degrees. PMID:10975667

  14. Hybrid X-pinches

    SciTech Connect

    Shelkovenko, T. A.; Pikuz, S. A.; Mishin, S. A.; Mingaleev, A. R.; Tilikin, I. N.; Knapp, P. F.; Cahill, A. D.; Hoyt, C. L.; Hammer, D. A.

    2012-05-15

    Results from experimental studies of a hybrid X-pinch with an initial configuration in the form of a high-current diode with conical tungsten electrodes spaced by 1-2 mm and connected to one another with 20- to 100-{mu}m-diameter wires are presented. The experiments were carried out at four facilities with a current amplitude from 200 to 1000 kA and front duration from 45 to 200 ns. It is shown that, in spite of their simpler configuration, hybrid X-pinches with a short rise time of the current pulse (50-100 ns) are highly competitive with standard X-pinches in the generated soft X-ray power and the formation of a single hot spot in them is much more stable, while hard X-ray emission is almost absent. The possibility of using hybrid X-pinches as soft X-ray sources for point projection X-ray imaging of plasma objects is considered.

  15. Resonances, and mechanisms of Theta-production

    SciTech Connect

    Ya.I. Azimov; I.I. Strakovsky

    2004-09-01

    After explaining necessity of exotic hadrons, we discuss mechanisms which could determine production of the exotic Theta-baryon. A possible important role of resonances (producing the Theta in real or virtual decays) is emphasized for various processes. Several experimental directions for studies of such resonances, and the Theta itself, are suggested. We briefly discuss also recent negative results on the Theta-baryon.

  16. Timing of x-ray burst from X-pinch

    SciTech Connect

    Zhao, Shen; Zhang, Ran; Zhu, Xinlei; Zou, Xiaobing; Wang, Xinxin

    2015-06-15

    The x-ray burst timings of X-pinches, T{sub XB}, made using eight different wires for different current were measured. The results showed that a higher current makes a shorter T{sub XB} for a given X-pinch wire. In other words, T{sub XB} scales linearly with the line mass density for a given current. Based on the snow-plow model for Z-pinch plasma, it was derived that for a given X-pinch wire the integral of the current over time from zero to T{sub XB} is constant, i.e., ∫{sub 0}{sup T{sub X}{sub B}}i(t)⋅dt=const.. This theoretically derived relation was confirmed by our experiments.

  17. Quantum bounds on multiplayer linear games and device-independent witness of genuine tripartite entanglement

    NASA Astrophysics Data System (ADS)

    Murta, Gláucia; Ramanathan, Ravishankar; Móller, Natália; Terra Cunha, Marcelo

    2016-02-01

    Here we study multiplayer linear games, a natural generalization of xor games to multiple outcomes. We generalize a recently proposed efficiently computable bound, in terms of the norm of a game matrix, on the quantum value of two-player games to linear games with n players. As an example, we bound the quantum value of a generalization of the well-known CHSH game to n players and d outcomes. We also apply the bound to show in a simple manner that any nontrivial functional box, that could lead to trivialization of communication complexity in a multiparty scenario, cannot be realized in quantum mechanics. We then present a systematic method to derive device-independent witnesses of genuine tripartite entanglement.

  18. A 500 A device characterizer utilizing a pulsed-linear amplifier

    NASA Astrophysics Data System (ADS)

    Lacouture, Shelby; Bayne, Stephen

    2016-02-01

    With the advent of modern power semiconductor switching elements, the envelope defining "high power" is an ever increasing quantity. Characterization of these semiconductor power devices generally falls into two categories: switching, or transient characteristics, and static, or DC characteristics. With the increasing native voltage and current levels that modern power devices are capable of handling, characterization equipment meant to extract quasi-static IV curves has not kept pace, often leaving researchers with no other option than to construct ad hoc curve tracers from disparate pieces of equipment. In this paper, a dedicated 10 V, 500 A curve tracer was designed and constructed for use with state of the art high power semiconductor switching and control elements. The characterizer is a physically small, pulsed power system at the heart of which is a relatively high power linear amplifier operating in a switched manner in order to deliver well defined square voltage pulses. These actively shaped pulses are used to obtain device's quasi-static DC characteristics accurately without causing any damage to the device tested. Voltage and current waveforms from each pulse are recorded simultaneously by two separate high-speed analog to digital converters and averaged over a specified interval to obtain points in the reconstructed IV graph.

  19. A 500 A device characterizer utilizing a pulsed-linear amplifier.

    PubMed

    Lacouture, Shelby; Bayne, Stephen

    2016-02-01

    With the advent of modern power semiconductor switching elements, the envelope defining "high power" is an ever increasing quantity. Characterization of these semiconductor power devices generally falls into two categories: switching, or transient characteristics, and static, or DC characteristics. With the increasing native voltage and current levels that modern power devices are capable of handling, characterization equipment meant to extract quasi-static IV curves has not kept pace, often leaving researchers with no other option than to construct ad hoc curve tracers from disparate pieces of equipment. In this paper, a dedicated 10 V, 500 A curve tracer was designed and constructed for use with state of the art high power semiconductor switching and control elements. The characterizer is a physically small, pulsed power system at the heart of which is a relatively high power linear amplifier operating in a switched manner in order to deliver well defined square voltage pulses. These actively shaped pulses are used to obtain device's quasi-static DC characteristics accurately without causing any damage to the device tested. Voltage and current waveforms from each pulse are recorded simultaneously by two separate high-speed analog to digital converters and averaged over a specified interval to obtain points in the reconstructed IV graph. PMID:26931892

  20. Method for linearizing deflection of a MEMS device using binary electrodes and voltage modulation

    DOEpatents

    Horenstein, Mark N [West Roxbury, MA

    2008-06-10

    A micromechanical device comprising one or more electronically movable structure sets comprising for each set a first electrode supported on a substrate and a second electrode supported substantially parallel from said first electrode. Said second electrode is movable with respect to said first electrode whereby an electric potential applied between said first and second electrodes causing said second electrode to move relative to said first electrode a distance X, (X), where X is a nonlinear function of said potential, (V). Means are provided for linearizing the relationship between V and X.

  1. Experimentally validated quantitative linear model for the device physics of elastomeric microfluidic valves

    NASA Astrophysics Data System (ADS)

    Kartalov, Emil P.; Scherer, Axel; Quake, Stephen R.; Taylor, Clive R.; Anderson, W. French

    2007-03-01

    A systematic experimental study and theoretical modeling of the device physics of polydimethylsiloxane "pushdown" microfluidic valves are presented. The phase space is charted by 1587 dimension combinations and encompasses 45-295μm lateral dimensions, 16-39μm membrane thickness, and 1-28psi closing pressure. Three linear models are developed and tested against the empirical data, and then combined into a fourth-power-polynomial superposition. The experimentally validated final model offers a useful quantitative prediction for a valve's properties as a function of its dimensions. Typical valves (80-150μm width) are shown to behave like thin springs.

  2. Design and construction details of the FRX-C/T device: a compact toroid plasma translation experiment

    SciTech Connect

    Rej, D.J.

    1984-08-01

    The engineering design and construction details for the compact toroid plasma translation experiment FRX-C/T are reviewed. A translation region consisting of a 0.4-m-i.d., up to 6-m-long metallic vacuum chamber has been added onto one end of the field-reversed theta-pinch device FRX-C. A 2.5-MW, dc-powered, water-cooled solenoid magnet produces an axial magnetic field of up to 10 kG in this region. A complete directory of all related engineering drawings is also included.

  3. Z-Pinch Fusion Propulsion

    NASA Technical Reports Server (NTRS)

    Miernik, Janie

    2011-01-01

    Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Shorter trips are better for humans in the harmful radiation environment of deep space. Nuclear propulsion and power plants can enable high Ispand payload mass fractions because they require less fuel mass. Fusion energy research has characterized the Z-Pinch dense plasma focus method. (1) Lightning is form of pinched plasma electrical discharge phenomena. (2) Wire array Z-Pinch experiments are commonly studied and nuclear power plant configurations have been proposed. (3) Used in the field of Nuclear Weapons Effects (NWE) testing in the defense industry, nuclear weapon x-rays are simulated through Z-Pinch phenomena.

  4. Segmented flow sampling with push-pull theta pipettes.

    PubMed

    Saha-Shah, Anumita; Green, Curtis M; Abraham, David H; Baker, Lane A

    2016-03-21

    We report development of a mobile and easy-to-fabricate theta pipette microfluidic device for segmented flow sampling. The theta pipettes were also used as electrospray emitters for analysis of sub-nanoliter segments, which resulted in delivery of analyte to the vacuum inlet of the mass spectrometer without multiple transfer steps. Theta pipette probes enable sample collection with high spatial resolution due to micron or smaller sized probe inlets and can be used to manipulate aqueous segments in the range of 200 pL to tens of nanoliters. Optimized conditions can enable sampling with high spatial and temporal resolution, suitable for chemical monitoring in biological samples and studies of sample heterogeneity. Intercellular heterogeneity among Allium cepa cells was studied by collecting cytoplasm from multiple cells using a single probe. Extracted cytoplasm was analyzed in a fast and high throughput manner by direct electrospray mass spectrometry of segmented sample from the probe tip. PMID:26907673

  5. Step-response of a torsional device with multiple discontinuous non-linearities: Formulation of a vibratory experiment

    NASA Astrophysics Data System (ADS)

    Krak, Michael D.; Dreyer, Jason T.; Singh, Rajendra

    2016-03-01

    A vehicle clutch damper is intentionally designed to contain multiple discontinuous non-linearities, such as multi-staged springs, clearances, pre-loads, and multi-staged friction elements. The main purpose of this practical torsional device is to transmit a wide range of torque while isolating torsional vibration between an engine and transmission. Improved understanding of the dynamic behavior of the device could be facilitated by laboratory measurement, and thus a refined vibratory experiment is proposed. The experiment is conceptually described as a single degree of freedom non-linear torsional system that is excited by an external step torque. The single torsional inertia (consisting of a shaft and torsion arm) is coupled to ground through parallel production clutch dampers, which are characterized by quasi-static measurements provided by the manufacturer. Other experimental objectives address physical dimensions, system actuation, flexural modes, instrumentation, and signal processing issues. Typical measurements show that the step response of the device is characterized by three distinct non-linear regimes (double-sided impact, single-sided impact, and no-impact). Each regime is directly related to the non-linear features of the device and can be described by peak angular acceleration values. Predictions of a simplified single degree of freedom non-linear model verify that the experiment performs well and as designed. Accordingly, the benchmark measurements could be utilized to validate non-linear models and simulation codes, as well as characterize dynamic parameters of the device including its dissipative properties.

  6. Plasma flow in peripheral region of detached plasma in linear plasma device

    NASA Astrophysics Data System (ADS)

    Hayashi, Y.; Ohno, N.; Kajita, S.; Tanaka, H.

    2016-01-01

    A plasma flow structure is investigated using a Mach probe under detached plasma condition in a linear plasma device NAGDIS-II. A reverse flow along the magnetic field is observed in a steady-state at far-peripheral region of the plasma column in the upstream side from the recombination front. These experimental results indicate that plasma near the recombination front should strongly diffuse across the magnetic field, and it should be transported along the magnetic field in the reverse flow direction. Furthermore, bursty plasma density fluctuations associated with intermittent convective plasma transport are observed in the far-peripheral region of the plasma column in both upstream and downstream sides from the recombination front. Such a nondiffusive transport can contribute to the intermittent reverse plasma flow, and the experimental results indicate that intermittent transports are frequently produced near the recombination front.

  7. PINCHED PLASMA REACTOR

    DOEpatents

    Phillips, J.A.; Suydam, R.; Tuck, J.L.

    1961-07-01

    BS>A plasma confining and heating reactor is described which has the form of a torus with a B/sub 2/ producing winding on the outside of the torus and a helical winding of insulated overlapping tunns on the inside of the torus. The inner helical winding performs the double function of shielding the plasma from the vitreous container and generating a second B/sub z/ field in the opposite direction to the first B/sub z/ field after the pinch is established.

  8. Staged Z-pinch for Fusion

    NASA Astrophysics Data System (ADS)

    Wessel, Frank; Rahman, Hafiz; Ney, Paul; Darling, Tim; McKee, Erik; Covington, Aaron; Beg, Farhat; Valenzuela, Julio; Narkis, Jeff; Presura, Radu

    2015-11-01

    The Staged Z-pinch (SZP) is configured as a plasma shell imploding onto an uniform, plasma fill (50:50 Deuterium:Tritium); the pinch is pre-magnetized, with an axial Bz field. Gas-puff experiments, at the University of California, Irvine, 1.25 MA, 1.25 μs, and 50 kJ, demonstrated that the implosion was stable, as primary (DD) and secondary (DT) neutrons were produced at peak compression. Subsequent analysis accounts for the stability and neutron yield, indicating that the SZP implosion is magneto-inertial, shock-driven, with magneto-sonic shocks in the liner and ordinary (sonic) shocks in the target. The shock waves preheat the target, as a stable, current-carrying, shock front forms at the interface. Near-term, the SZP team will test pinch loads on the 1 MA, 130 ns, 100 kJ University of Nevada, Reno, Nevada Terawatt, Zebra Facility. This paper details the context and our specific plans for the upcoming experiments, as well as our recent simulations predicting breakeven fusion on existing devices. Funded by the US Department of Energy, ARPA-E, Control Number 1184-1527.

  9. Dynamic cyclotron resonance in relativistic microwave devices with linear electron beams

    SciTech Connect

    Vlasov, A.N.; Kornienko, V.N.; Cherepenin, V.A. |

    1995-12-31

    In the present work the authors analyze theoretically and by numerical simulation dependencies of output radiation versus magnitude of focusing magnetic field when magnetic field magnitude is sufficiently smaller than value corresponding to cyclotron absorption. The high frequency electromagnetic field amplitude is high for optimum regimes with high efficiency level. In this case some electrons are accelerated and different electrons are decelerated during interaction inside device. As a result, cyclotron resonance conditions are different for different electron groups. The authors have found theoretically condition of dynamic cyclotron resonance when it is possible to improve efficiency of interaction in devices with distributed interaction such as TWT, BWO, generator of diffractional radiation by combination of Cherenkov and cyclotron interactions in strong nonlinear regimes with optimum efficiency levels. The numerical simulation of the interaction between initially linear electron beam and electromagnetic field show that there are regions of efficiency improvement up to 50 and amplitude of high-frequency electromagnetic field. One of the important features of such combined interaction is dependence on relativistic factor. They have found optimum region of relativistic factors by numerical simulation. The results of numerical simulation were compared with experimental data refer to relativistic diffractional generators and multiwave Cherenkov generators. Good agreement in value of optimum magnitude of guiding magnetic field was obtained.

  10. Haptic cue control of an MR gear shifting assistance device via Preisach hysteresis linearization

    NASA Astrophysics Data System (ADS)

    Han, Young-Min; Choi, Seung-Bok; Chung, Jye Ung; Kim, Soomin

    2015-04-01

    This paper proposes a driver assistance device to notify vehicle drivers an optimal gear shifting timing considering fuel consumption in manual transmission vehicles. The haptic cue function of the proposed gear shifting assistance device is utilizing magnetorheological (MR) clutch mechanism as haptic interface between driver and vehicle. The shear stress level and hysteretic behavior of the employed MR fluid are experimentally observed and identified with the Preisach model. A rotary type clutch mechanism is designed and manufactured with electromagnetic circuit and its transmission torque level is experimentally evaluated according to the applied current. The manufactured MR clutch is integrated with accelerator pedal on which driver's foot is placed to transmit haptic cue signal. In the meantime, a cue algorithm for gear shifting is formulated by considering vehicle model. The cue algorithm is then integrated with a haptic controller which is a torque model based-compensation strategy regarding Presiach hystersis linearization of the employed MR fluid. In this work, the haptic cue controller is implemented in discrete manner. Control performances are experimentally evaluated such as haptic tracking responses.

  11. Thin silicon layer SOI power device with linearly-distance fixed charge islands

    NASA Astrophysics Data System (ADS)

    Yuan, Zuo; Haiou, Li; Jianghui, Zhai; Ning, Tang; Shuxiang, Song; Qi, Li

    2015-05-01

    A new high-voltage LDMOS with linearly-distanced fixed charge islands is proposed (LFI LDMOS). A lot of linearly-distanced fixed charge islands are introduced by implanting the Cs or I ion into the buried oxide layer and dynamic holes are attracted and accumulated, which is crucial to enhance the electric field of the buried oxide and the vertical breakdown voltage. The surface electric field is improved by increasing the distance between two adjacent fixed charge islands from source to drain, which lead to the higher concentration of the drift region and a lower on-resistance. The numerical results indicate that the breakdown voltage of 500 V with Ld = 45 μm is obtained in the proposed device in comparison to 209 V of conventional LDMOS, while maintaining low on-resistance. Project supported by the Guangxi Natural Science Foundation of China (No. 2013GXNSFAA019335), the Guangxi Department of Education Project (No.201202ZD041), the China Postdoctoral Science Foundation Project (Nos. 2012M521127, 2013T60566), and the National Natural Science Foundation of China (Nos. 61361011, 61274077, 61464003).

  12. Numerical studies of International Linear Collider positron target and optical matching device field effects on beam

    SciTech Connect

    Antipov, Sergey; Spentzouris, Linda; Liu Wanming; Gai Wei

    2007-07-01

    For an International Linear Collider (ILC) undulator-based positron source target configuration, a strong optical matching device (OMD) field is needed inside the target to increase the positron yield (by more than 40%) [Y. K. Batygin, Proceedings of the 2005 ALCPG and ILC Workshops, Snowmas, CO, 14-27 August 2005 (unpublished)] It is also required that the positron target be constantly rotated to reduce thermal and radiation damages. Eddy currents, produced by an OMD field in turn, interact with the magnetic field and produce a drag (stopping) force. This force not only produces heat in the disk but also creates a dipole deflecting field, which affects the beam. Therefore it is important to simulate such a system in detail to design the motor and cooling system and also a correction magnet system. In order to guide the ILC target design, an exact simulation of the spinning disk in a magnetic field is required. In this paper we present a simulation method implemented using COMSOL and compare it with the experimental results recently obtained at Stanford Linear Accelerator Center and Lawrence Livermore National Laboratory. Good agreement between the simulation and the experiment gives confidence in the validity of the method. We give detailed results on the proposed ILC target system, such as parametric studies for reduction of the power required to keep the target spinning. We present simulation results of the induced deflection field and of the reduction of the OMD field effect.

  13. Soft x-ray (0.2pinch plasma radiation sources

    SciTech Connect

    Failor, B.H.; Qi, N.; Levine, J.S.; Sze, H.; Gullickson, E.M.

    2004-10-01

    Z-pinches can produce intense fluxes of argon K-shell (3 keV) radiation, but typically only a fraction of the load mass near the axis of the pinch radiates in this spectral range. The majority of the mass does not get hot or dense enough to radiate efficiently in the K-shell. We have designed, built, and tested an instrument to image pinch emission, specifically the radial emission profile, at energies below the K-shell in order to track the location of the cooler mass. A gold mirror provides a high-energy cut-off at 2 keV while a transmission grating disperses the incoming radiation and provides a low-energy cutoff at 0.1 keV. A vertical slit images the pinch radiation in the radial direction and the emission profile is recorded with either an extreme ultraviolet-sensitive charge-coupled device camera (time-integrated) or a linear photodiode array ({approx}1 ns time resolution). We present results for the mirror, grating, and system characterization obtained at the Advanced Light Source synchrotron located at Lawrence Berkeley National Laboratory (Berkeley, CA)

  14. The reversed-field pinch as a poloidal-field-dominated, compact, high-power-density fusion system

    SciTech Connect

    Krakowski, R.A.

    1988-01-01

    This paper discusses the feasibility of reversed-field pinch devices as future thermonuclear reactors. Safety, cost, ion temperatures, Lawson numbers, and power densities are reviewed for these types of devices. 12 refs., 2 figs., 1 tab. (LSP)

  15. On Ramanujan's definition of mock theta function.

    PubMed

    Rhoades, Robert C

    2013-05-01

    In his famous "deathbed" letter, Ramanujan "defined" the notion of a mock theta function and offered some examples of functions he believed satisfied his definition. Very recently, Griffin et al. established for the first time that Ramanujan's mock theta functions actually satisfy his own definition. On the other hand, Zwegers' 2002 doctoral thesis [Zwegers S (2002) Mock theta functions. PhD thesis (Univ Utrecht, Utrecht, The Netherlands)] showed that all of Ramanujan's examples are holomorphic parts of harmonic Maass forms. This has led to an alternate definition of a mock theta function. This paper shows that Ramanujan's definition of mock theta function is not equivalent to the modern definition. PMID:23625007

  16. What is a Reversed Field Pinch?

    NASA Astrophysics Data System (ADS)

    Escande, D. F.

    2015-12-01

    The following sections are included: * Introduction * Short description * Usefulness of the RFP configuration for fusion science and dynamo physics * Attractivity of the RFP configuration for a reactor * Challenges ahead * Lawson criterion * Intuitive model of magnetic self-reversal * Intuitive description of the dynamo * Necessity of a helical deformation * MHD simulations * From single to multiple helicity * Single helicity * Multiple helicity * Quasi single helicity * Experimental results * Multiple helicity * Quasi single helicity * Upgrade of the RFX device * From double to single magnetic axis * Analytical description of the single helicity RFP * Helical Grad-Shafranov equation * Parallel Ohm's law * Pinch-stellarator equation * Single helicity ohmic RFP states * Calculation of the dynamo * Conclusion * Acknowledgments * References

  17. Architecture of petawatt-class z-pinch accelerators

    NASA Astrophysics Data System (ADS)

    Stygar, W. A.; Cuneo, M. E.; Headley, D. I.; Ives, H. C.; Leeper, R. J.; Mazarakis, M. G.; Olson, C. L.; Porter, J. L.; Wagoner, T. C.; Woodworth, J. R.

    2007-03-01

    We have developed an accelerator architecture that can serve as the basis of the design of petawatt-class z-pinch drivers. The architecture has been applied to the design of two z-pinch accelerators, each of which can be contained within a 104-m-diameter cylindrical tank. One accelerator is driven by slow (˜1μs) Marx generators, which are a mature technology but which necessitate significant pulse compression to achieve the short pulses (≪1μs) required to drive z pinches. The other is powered by linear transformer drivers (LTDs), which are less mature but produce much shorter pulses than conventional Marxes. Consequently, an LTD-driven accelerator promises to be (at a given pinch current and implosion time) more efficient and reliable. The Marx-driven accelerator produces a peak electrical power of 500 TW and includes the following components: (i) 300 Marx generators that comprise a total of 1.8×104 capacitors, store 98 MJ, and erect to 5 MV; (ii) 600 water-dielectric triplate intermediate-store transmission lines, which also serve as pulse-forming lines; (iii) 600 5-MV laser-triggered gas switches; (iv) three monolithic radial-transmission-line impedance transformers, with triplate geometries and exponential impedance profiles; (v) a 6-level 5.5-m-diameter 15-MV vacuum insulator stack; (vi) six magnetically insulated vacuum transmission lines (MITLs); and (vii) a triple-post-hole vacuum convolute that adds the output currents of the six MITLs, and delivers the combined current to a z-pinch load. The accelerator delivers an effective peak current of 52 MA to a 10-mm-length z pinch that implodes in 95 ns, and 57 MA to a pinch that implodes in 120 ns. The LTD-driven accelerator includes monolithic radial transformers and a MITL system similar to those described above, but does not include intermediate-store transmission lines, multimegavolt gas switches, or a laser trigger system. Instead, this accelerator is driven by 210 LTD modules that include a total of 1

  18. Global confinement and discrete dynamo activity in the MST reversed field pinch

    SciTech Connect

    Hokin, S.; Almagri, A.; Assadi, S.; Beckstead, J.; Chartas, G.; Crocker, N.; Cudzinovic, M.; Den Hartog, D.; Dexter, R.; Holly, D.; Prager, S.; Rempel, T.; Sarff, J.; Scime, E.; Shen, W.; Spragins, C.; Sprott, C.; Starr, G.; Stoneking, M.; Watts, C. ); Nebel, R. )

    1991-04-01

    Results obtained on the Madison Symmetric Torus (MST) reversed field pinch after installation of the design poloidal field winding are presented. Values of {beta}{sub {theta}e0} {triple bond} 2{mu}{sub 0}n{sub e0}T{sub e0}/B{sub {theta}}{sup 2}(a) {approximately} 12% are achieved in low-current (I = 220 kA) operation; here n{sub e0} and T{sub e0} are central electron density and temperature, and B{sub {theta}}(a) is the poloidal magnetic field at the plasma edge. An observed decrease in {beta}{sub {theta}e0} with increasing plasma current may be due to inadequate fueling, enhanced wall interaction, and the growth of a radial field error at the vertical cut in the shell at high current. Energy confinement time varies little with plasma current, lying in the range 0.5 {minus} 1.0 ms. Strong discrete dynamo activity is present, characterized by the coupling of m = 1, n = 5 {minus} 7 modes leading to an m = 0, n = 0 crash (m and n are poloidal and toroidal mode numbers). The m = 0 crash generates toroidal flux and produces a small (2.5%) increase in plasma current. 25 refs., 9 figs., 1 tab.

  19. Silicon Photonics: All-Optical Devices for Linear and Nonlinear Applications

    NASA Astrophysics Data System (ADS)

    Driscoll, Jeffrey B.

    Silicon photonics has grown rapidly since the first Si electro-optic switch was demonstrated in 1987, and the field has never grown more quickly than it has over the past decade, fueled by milestone achievements in semiconductor processing technologies for low loss waveguides, high-speed Si modulators, Si lasers, Si detectors, and an enormous toolbox of passive and active integrated devices. Silicon photonics is now on the verge of major commercialization breakthroughs, and optical communication links remain the force driving integrated and Si photonics towards the first commercial telecom and datacom transceivers; however other potential and future applications are becoming uncovered and refined as researchers reveal the benefits of manipulating photons on the nanoscale. This thesis documents an exploration into the unique guided-wave and nonlinear properties of deeply-scaled high-index-contrast sub-wavelength Si waveguides. It is found that the tight confinement inherent to single-mode channel waveguides on the silicon-on-insulator platform lead to a rich physics, which can be leveraged for new devices extending well beyond simple passive interconnects and electro-optic devices. The following chapters will concentrate, in detail, on a number of unique physical features of Si waveguides and extend these attributes towards new and interesting devices. Linear optical properties and nonlinear optical properties are investigated, both of which are strongly affected by tight optical confinement of the guided waveguide modes. As will be shown, tight optical confinement directly results in strongly vectoral modal components, where the electric and magnetic fields of the guided modes extend into all spatial dimensions, even along the axis of propagation. In fact, the longitudinal electric and magnetic field components can be just as strong as the transverse fields, directly affecting the modal group velocity and energy transport properties since the longitudinal fields

  20. Characterization of a linear device developed for research on advanced plasma imaging and dynamics.

    PubMed

    Chung, J; Lee, K D; Seo, D C; Nam, Y U; Choi, M C

    2010-10-01

    Within the scope of long term research on imaging diagnostics for steady-state plasmas and understanding of edge plasma physics through diagnostics with conventional spectroscopic methods, we have constructed a linear electron cyclotron resonance (ECR) plasma device named Research on Advanced Plasma Imaging and Dynamics (RAPID). It has a variety of axial magnetic field profiles provided by eight water-cooled magnetic coils and two dc power supplies. The positions of the magnetic coils are freely adjustable along the axial direction and the power supplies can be operated with many combinations of electrical wiring to the coils. Here, a 6 kW 2.45 GHz magnetron is used to produce steady-state hydrogen, helium, and argon plasmas with central magnetic fields of 875 and/or 437.5 G (second harmonic). In order to achieve the highest possible plasma performance within the limited input parameters, wall conditioning experiments were carried out. Chamber bake-out was achieved with heating coils that were wound covering the vessel, and long-pulse electron cyclotron heating discharge cleaning was also followed after 4 days of bake-out. A uniform bake-out temperature (150 °C) was achieved by wrapping the vessel in high temperature thermal insulation textile and by controlling the heating coil current using a digital control system. The partial pressure changes were observed using a residual gas analyzer, and a total system pressure of 5×10(-8) Torr was finally reached. Diagnostic systems including a millimeter-wave interferometer, a high resolution survey spectrometer, a Langmuir probe, and an ultrasoft x-ray detector were used to provide the evidence that the plasma performance was improved as we desired. In this work, we present characterization of the RAPID device for various system conditions and configurations. PMID:21033972

  1. Characterization of a linear device developed for research on advanced plasma imaging and dynamics

    SciTech Connect

    Chung, J.; Lee, K. D.; Seo, D. C.; Nam, Y. U.; Choi, M. C.

    2010-10-15

    Within the scope of long term research on imaging diagnostics for steady-state plasmas and understanding of edge plasma physics through diagnostics with conventional spectroscopic methods, we have constructed a linear electron cyclotron resonance (ECR) plasma device named Research on Advanced Plasma Imaging and Dynamics (RAPID). It has a variety of axial magnetic field profiles provided by eight water-cooled magnetic coils and two dc power supplies. The positions of the magnetic coils are freely adjustable along the axial direction and the power supplies can be operated with many combinations of electrical wiring to the coils. Here, a 6 kW 2.45 GHz magnetron is used to produce steady-state hydrogen, helium, and argon plasmas with central magnetic fields of 875 and/or 437.5 G (second harmonic). In order to achieve the highest possible plasma performance within the limited input parameters, wall conditioning experiments were carried out. Chamber bake-out was achieved with heating coils that were wound covering the vessel, and long-pulse electron cyclotron heating discharge cleaning was also followed after 4 days of bake-out. A uniform bake-out temperature (150 deg. C) was achieved by wrapping the vessel in high temperature thermal insulation textile and by controlling the heating coil current using a digital control system. The partial pressure changes were observed using a residual gas analyzer, and a total system pressure of 5x10{sup -8} Torr was finally reached. Diagnostic systems including a millimeter-wave interferometer, a high resolution survey spectrometer, a Langmuir probe, and an ultrasoft x-ray detector were used to provide the evidence that the plasma performance was improved as we desired. In this work, we present characterization of the RAPID device for various system conditions and configurations.

  2. Device and method for imaging of non-linear and linear properties of formations surrounding a borehole

    DOEpatents

    Johnson, Paul A; Tencate, James A; Le Bas, Pierre-Yves; Guyer, Robert; Vu, Cung Khac; Skelt, Christopher

    2013-11-05

    In some aspects of the disclosure, a method and an apparatus is disclosed for investigating material surrounding the borehole. The method includes generating a first low frequency acoustic wave within the borehole, wherein the first low frequency acoustic wave induces a linear and a nonlinear response in one or more features in the material that are substantially perpendicular to a radius of the borehole; directing a first sequence of high frequency pulses in a direction perpendicularly with respect to the longitudinal axis of the borehole into the material contemporaneously with the first acoustic wave; and receiving one or more second high frequency pulses at one or more receivers positionable in the borehole produced by an interaction between the first sequence of high frequency pulses and the one or more features undergoing linear and nonlinear elastic distortion due to the first low frequency acoustic wave to investigate the material surrounding the borehole.

  3. Scheme for correcting coupling variation induced by insertion devices near linear difference resonance

    NASA Astrophysics Data System (ADS)

    Kaneyasu, T.; Takabayashi, Y.; Iwasaki, Y.; Koda, S.

    2011-06-01

    We have developed a scheme for correcting emittance coupling variations resulting from the operation of insertion devices (IDs) in a storage ring operated near a linear difference resonance. The present scheme corrects for weak skew quadrupole error fields and betatron tune shifts induced by the IDs since the sensitivity of the emittance coupling to the skew error field is enhanced near a difference resonance and betatron tune shifts also contribute to the coupling variation. We applied the coupling correction scheme to the operation of the APPLE-II type variable polarization undulator in the SAGA-LS storage ring. Changes in the gap and phase of the APPLE-II undulator significantly alter the emittance coupling, which modulates the photon beam intensities in the experimental stations. The coupling correction system employs a feedforward scheme by using two-dimensional look-up tables. Correction coil currents are determined by measuring the betatron tune and the vertical beam size. Beam test results suggest that the coupling variation can be well explained by the ID skew error field and the tune shift caused by the intrinsic focusing effect of the APPLE-II undulator. They also demonstrate that the correction system sufficiently suppresses the coupling variation.

  4. MHD simulation studies of z-pinch shear flow stabilization

    NASA Astrophysics Data System (ADS)

    Paraschiv, I.; Bauer, B. S.; Sotnikov, V. I.; Makhin, V.; Siemon, R. E.

    2003-10-01

    The development of the m=0 instability in a z-pinch in the presence of sheared plasma flows is investigated with the aid of a two-dimensional magnetohydrodynamic (MHD) simulation code (MHRDR). The linear growth rates are compared to the results obtained by solving the ideal MHD linearized equations [1] and to the results obtained using a 3D hybrid simulation code [2]. The instability development is followed into the nonlinear regime where its growth and saturation are examined. [1] V.I. Sotnikov, I. Paraschiv, V. Makhin, B.S. Bauer, J.-N. Leboeuf, and J.M. Dawson, "Linear analysis of sheared flow stabilization of global magnetohydrodynamic instabilities based on the Hall fluid mode", Phys. Plasmas 9, 913 (2002). [2] V.I. Sotnikov, V. Makhin, B.S. Bauer, P. Hellinger, P. Travnicek, V. Fiala, J.-N. Leboeuf, "Hybrid Simulations of Current-Carrying Instabilities in Z-pinch Plasmas with Sheared Axial Flow", AIP Conference Proceedings, Volume 651, Dense Z-Pinches: 5th International Conference on Dense Z-Pinches, edited by J. Davis et al., page 396, June 2002.

  5. The MaPLE device: A linear machine for laboratory studies of the magnetized plasma physics phenomena

    NASA Astrophysics Data System (ADS)

    Biswas, Subir; Chowdhury, Satyajit; Pal, Abhik M.; Bhattacharya, Shashwat; Basu, Subhasis; Chattopadhyay, Monobir; Chakrabarti, Nikhil; Pal, Rabindranath

    2015-04-01

    The Magnetized Plasma Linear Experimental (MaPLE) device is developed in the plasma physics laboratory of the Saha Institute of Nuclear Physics for studying basic plasma physics phenomena like waves, instabilities and their nonlinear behavior in magnetized plasma. Details description of the device and its plasma characteristics are presented. The machine provides flexibilities in terms of magnetic configuration and plasma sources. Recently, low frequency drift waves are excited in the weak density gradient region of electron cyclotron resonance (ECR) produced low density plasmas and their nonlinear coupling is studied. Results of this experiment and some more experiments done in the device are summarized. Reasoning behind a possible upgrade plan of the device for studying shear Alfven waves (SAW) and magnetic drift waves in future is also discussed.

  6. Zeeman effect in the X-ray star candidates HD 77581 and theta super 2 Orionis.

    NASA Technical Reports Server (NTRS)

    Kemp, J. C.; Wolstencroft, R. D.

    1973-01-01

    The discovery of Zeeman effects is reported in HD 77581 and theta super 2 Orionis, optical candidates for the X-ray sources Vela XR-1 and 2U 0525-06, respectively. The maximum longitudinal magnetic fields recorded were -10,000 G in HD 77581 and +1500 G in theta super 2 Ori. Various polarimetric data are also given, including evidence for a variable linear polarization in HD 77581.

  7. A non-device-specific approach to display characterization based on linear, nonlinear, and hybrid search algorithms.

    PubMed

    Ban, Hiroshi; Yamamoto, Hiroki

    2013-01-01

    In almost all of the recent vision experiments, stimuli are controlled via computers and presented on display devices such as cathode ray tubes (CRTs). Display characterization is a necessary procedure for such computer-aided vision experiments. The standard display characterization called "gamma correction" and the following linear color transformation procedure are established for CRT displays and widely used in the current vision science field. However, the standard two-step procedure is based on the internal model of CRT display devices, and there is no guarantee as to whether the method is applicable to the other types of display devices such as liquid crystal display and digital light processing. We therefore tested the applicability of the standard method to these kinds of new devices and found that the standard method was not valid for these new devices. To overcome this problem, we provide several novel approaches for vision experiments to characterize display devices, based on linear, nonlinear, and hybrid search algorithms. These approaches never assume any internal models of display devices and will therefore be applicable to any display type. The evaluations and comparisons of chromaticity estimation accuracies based on these new methods with those of the standard procedure proved that our proposed methods largely improved the calibration efficiencies for non-CRT devices. Our proposed methods, together with the standard one, have been implemented in a MATLAB-based integrated graphical user interface software named Mcalibrator2. This software can enhance the accuracy of vision experiments and enable more efficient display characterization procedures. The software is now available publicly for free. PMID:23729771

  8. Influence of electromagnetic interference on implanted cardiac arrhythmia devices in and around a magnetically levitated linear motor car.

    PubMed

    Fukuta, Motoyuki; Mizutani, Noboru; Waseda, Katsuhisa

    2005-01-01

    This study was designed to determine the susceptibility of implanted cardiac arrhythmia devices to electromagnetic interference in and around a magnetically levitated linear motor car [High-Speed Surface Transport (HSST)]. During the study, cardiac devices were connected to a phantom model that had similar characteristics to the human body. Three pacemakers from three manufacturers and one implantable cardioverter-defibrillator (ICD) were evaluated in and around the magnetically levitated vehicle. The system is based on a normal conductive system levitated by the attractive force of magnets and propelled by a linear induction motor without wheels. The magnetic field strength at 40 cm from the vehicle in the nonlevitating state was 0.12 mT and that during levitation was 0.20 mT. The magnetic and electric field strengths on a seat close to the variable voltage/variable frequency inverter while the vehicle was moving and at rest were 0.13 mT, 2.95 V/m and 0.04 mT, 0.36 V/m, respectively. Data recorded on a seat close to the reactor while the vehicle was moving and at rest were 0.09 mT, 2.45 V/m and 0.05 mT, 1.46 V/m, respectively. Measured magnetic and electric field strengths both inside and outside the linear motor car were too low to result in device inactivation. No sensing, pacing, or arrhythmic interactions were noted with any pacemaker or ICD programmed in either bipolar and unipolar configurations. In conclusion, our data suggest that a permanent programming change or a device failure is unlikely to occur and that the linear motor car system is probably safe for patients with one of the four implanted cardiac arrhythmia devices used in this study under the conditions tested. PMID:16235032

  9. Pinch technology improves olefin heat recovery

    SciTech Connect

    Barton, J.

    1989-02-01

    Pyrolysis of naphthas or gas oils to provide ethylene and propylene for polymers is gaining in popularity in many countries. Pyrolysis takes place at the comparatively high temperatures of 800 to 850/sup 0/C. The very common solution of pyrolysis gas heat recovery in an ethylene unit is shown. Pinch technology allows finding the temperature point (the pinch) that divides the temperature scale in a process into two parts. If there is a pinch in a process (not every process has a pinch), heat from external sources must be supplied to the process at temperatures above the pinch, and must be taken from the system by cooling media at temperatures below the pinch only. If minimum consumption of energy for heating and cooling from external sources is desired, matching process streams across the pinch and adding heat to the system from external sources below the pinch temperature is not allowed.

  10. Dynamics of Fluctuations, Flows and Global Stability Under Electrode Biasing in a Linear Plasma Device

    NASA Astrophysics Data System (ADS)

    Desjardins, Tiffany

    2015-11-01

    Various bias electrodes have been inserted into the Helicon-Cathode (HelCat) device at the University of New Mexico, in order to affect intrinsic drift-wave turbulence and flows. The goal of the experiments was to suppress and effect the intrinsic turbulence and with detailed measurements, understand the changes that occur during biasing. The drift-mode in HelCat varies from coherent at low magnetic field (<1kG) to broad-band turbulent at high magnetic fields (>1kG). The first electrode consists of 6 concentric rings set in a ceramic substrate; these rings act as a boundary condition, sitting at the end of the plasma column 2-m away from the source. A negative bias has been found to have no effect on the fluctuations, but a positive bias (Vr>5Te) is required in order to suppress the drift-mode. Two molybdenum grids can also be inserted into the plasma and sit close to the source. Floating or grounding a grid results in suppressing the drift-mode of the system. A negative bias (>-5Te) is found to return the drift-mode, and it is possible to drive a once coherent mode into a broad-band turbulent one. From a bias voltage of -5Te10Te, a new large-scale global mode is excited. This mode exhibits fluctuations in the ion saturation current, as well as in the potential, with a magnitude >50%. This mode has been identified as the potential relaxation instability (PRI). In order to better understand the modes and changes observed in the plasma, a linear stability code, LSS, was employed. As well, a 1D3V-PIC code utilizing Braginskii's equations was also utilized to understand the high-bias instability.

  11. Traveling Theta Waves in the Human Hippocampus.

    PubMed

    Zhang, Honghui; Jacobs, Joshua

    2015-09-01

    The hippocampal theta oscillation is strongly correlated with behaviors such as memory and spatial navigation, but we do not understand its specific functional role. One hint of theta's function came from the discovery in rodents that theta oscillations are traveling waves that allow parts of the hippocampus to simultaneously exhibit separate oscillatory phases. Because hippocampal theta oscillations in humans have different properties compared with rodents, we examined these signals directly using multielectrode recordings from neurosurgical patients. Our findings confirm that human hippocampal theta oscillations are traveling waves, but also show that these oscillations appear at a broader range of frequencies compared with rodents. Human traveling waves showed a distinctive pattern of spatial propagation such that there is a consistent phase spread across the hippocampus regardless of the oscillations' frequency. This suggests that traveling theta oscillations are important functionally in humans because they coordinate phase coding throughout the hippocampus in a consistent manner. Significance statement: We show for the first time in humans that hippocampal theta oscillations are traveling waves, moving along the length of the hippocampus in a posterior-anterior direction. The existence of these traveling theta waves is important for understanding hippocampal neural coding because they cause neurons at separate positions in the hippocampus to experience different theta phases simultaneously. The theta phase that a neuron measures is a key factor in how that cell represents behavioral information. Therefore, the existence of traveling theta waves indicates that, to fully understand how a hippocampal neuron represents information, it is vital to also account for that cell's location in addition to conventional measures of neural activity. PMID:26354915

  12. Scannerless three-dimensional imaging using a pulsed laser and an intensified charge-coupled device with linearly modulated gain

    SciTech Connect

    Jin Chenfei; Zhao Yuan; Zhang Yong; Liu Liping; Sun Xiudong

    2009-07-01

    We have developed a scannerless three-dimensional imaging approach that uses a pulsed laser to illuminate a target and an intensified charge-coupled device as the receiver with linearly modulated gain in gated time. The target range is extracted by processing an intensity image with linearly modulated gain and an intensity image with constant gain. Feasibility of the approach is demonstrated by an indoor experiment. Our prototype system can produce 256x256 pixel range images at a 20 Hz frame rate in an outdoor test. The test results indicate that range accuracy is related to the slope coefficient and initial value of the modulated gain.

  13. The importance of EBIT data for Z-pinch plasma diagnostics

    SciTech Connect

    Safronova, A S; Kantsyrev, V L; Neill, P; Safronova, U I; Fedin, D A; Ouart, N D; Yilmaz, M F; Osborne, G; Shrestha, I; Williamson, K; Hoppe, T; Harris, C; Beiersdorfer, P; Hansen, S

    2007-04-04

    The results from the last six years of x-ray spectroscopy and spectropolarimetry of high energy density Z-pinch plasmas complemented by experiments with the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory (LLNL) are presented. The two topics discussed are the development of M-shell x-ray W spectroscopic diagnostics and K-shell Ti spectropolarimetry of Z-pinch plasmas. The main focus is on radiation from a specific load configuration called an 'X-pinch'. X-pinches are excellent sources for testing new spectral diagnostics and for atomic modelling because of the high density and temperature of the pinch plasmas, which scale from a few {micro}m to several mm in size. They offer a variety of load configurations, which differ in wire connections, number of wires, and wire materials. In this work the study of X-pinches with tungsten wires combined with wires from other, lower-Z materials is reported. Utilizing data produced with the LLNL EBIT at different energies of the electron beam the theoretical prediction of line positions and intensity of M-shell W spectra were tested and calibrated. Polarization-sensitive X-pinch experiments at the University of Nevada, Reno (UNR) provide experimental evidence for the existence of strong electron beams in Ti and Mo X-pinch plasmas and motivate the development of x-ray spectropolarimetry of Z-pinch plasmas. This diagnostic is based on the measurement of spectra recorded simultaneously by two spectrometers with different sensitivity to the linear polarization of the observed lines and compared with theoretical models of polarization-dependent spectra. Polarization-dependent K-shell spectra from Ti X-pinches are presented and compared with model calculations and with spectra generated by a quasi-Maxwellian electron beam at the LLNL EBIT-II electron beam ion trap.

  14. Existence of a return direction for plasma escaping from a pinched column in a plasma focus discharge

    SciTech Connect

    Kubes, P.; Cikhardt, J.; Klir, D.; Kravarik, J.; Rezac, K.; Kortanek, J.; Cikhardtova, B.; Paduch, M.; Zielinska, E.

    2015-05-15

    The use of multi-frame interferometry used on the PF-1000 device with the deuterium filling showed the existence of a return motion of the top of several lobules of the pinched column formed at the pinched plasma column. This phenomenon was observed in the presence of an over-optimal mass in front of the anode, which depressed the intensity of the implosion and the smooth surface of the pinched plasma column. The observed evolution was explored through the use of closed poloidal currents transmitted outside the pinched plasma. This interpretation complements the scenario of the closed currents flowing within the structures inside the pinched column, which has been published recently on the basis of observations from interferometry, neutron, and magnetic probe diagnostics on this device.

  15. High-flux first-wall design for a small reversed-field pinch reactor

    NASA Astrophysics Data System (ADS)

    Cort, G. E.; Graham, A. L.; Christensen, K. E.

    To achieve the goal of a commercially economical fusion power reactor, small physical size and high power density should be combined with simplicity (minimized use of high technology systems). The Reversed-Field Pinch (RFP) is a magnetic confinement device that promises to meet these requirements with power densities comparable to those in existing fission power plants. To establish feasibility of such an RFP reactor, a practical design for a first wall capable of withstanding high levels of cyclic neutron wall loadings is needed. Associated with the neutron flux in the proposed RFP reactor is a time averaged heat flux of 4.5 MW/sq m with a conservatively estimated transient peak approximately twice the average value. The design for a modular first wall made from a high-strength copper alloy that will meet these requirements of cyclic thermal loading is presented. The heat removal from the wall is by subcooled water flowing in straight tubes at high linear velocities.

  16. Sheath broadening in imploding z-pinches due to large-bandwidth Rayleigh-Taylor instability

    SciTech Connect

    Hammer, J.H.; Eddleman, J.L.; Tabak, M.; Toor, A.; Zimmerman, G.B.; De Groot, J.S.

    1996-06-04

    The magnetic Rayleigh-Taylor (RT) instability has been predicted and observed to cause breakup of the plasma sheath in imploding Z-pinches. In this work we show that for the type of density profile encountered in strongly radiating pinches, instability at very short wavelengths grows to the non-linear stage and seeds progressively longer wavelengths. The result is a self-similar broadening of the sheath as found for mix layers in fluid RT unstable systems.

  17. Scaling the Shear-flow Stabilized Z-pinch to Reactor Conditions

    NASA Astrophysics Data System (ADS)

    McLean, H. S.; Schmidt, A.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Cleveau, E.

    2015-11-01

    We present a conceptual design along with scaling calculations for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device, at the University of Washington, have demonstrated stable operation for durations of 20 usec at ~100kA discharge current for pinches that are ~1 cm in diameter and 100 cm long. The inverse of the pinch diameter and plasma energy density scale strongly with pinch current and calculations show that maintaining stabilization durations of ~7 usec for increased discharge current (~15x) in a shortened pinch (10 cm) results in a pinch diameter of ~200 um and plasma conditions that approach those needed to support significant fusion burn and energy gain (Ti ~ 30keV, density ~ 3e26/m3, ntau ~1.4e20 sec/m3). Compelling features of the concept include operation at modest discharge current (1.5 MA) and voltage (40kV) along with direct adoption of liquid metals for at least one electrode--technological capabilities that have been proven in existing, commercial, pulse power devices such as large ignitrons. LLNL-ABS-674920. This work performed under the auspices of the U.S. Department of Energy ARPAe ALPHA Program by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  18. Development of InSb charge-coupled infrared imaging devices: Linear imager

    NASA Technical Reports Server (NTRS)

    Phillips, J. D.

    1976-01-01

    The following results were accomplished in the development of charge coupled infrared imaging devices: (1) a four-phase overlapping gate with 9 transfers (2-bits) and 1.0-mil gate lengths was successfully operated, (2) the measured transfer efficiency of 0.975 for this device is in excellent agreement with predictions for the reduced gate length device, (3) mask revisions of the channel stop metal on the 8582 mask have been carried out with the result being a large increase in the dc yield of the tested devices, (4) partial optical sensitivity to chopped blackbody radiation was observed for an 8582 9-bit imager, (5) analytical consideration of the modulation transfer function degradation caused by transfer inefficiency in the CCD registers was presented, and (6) for larger array lengths or for the insertion of isolated bits between sensors, improvements in InSb fabrication technology with corresponding decrease in the interface state density are required.

  19. The Concept of the Pinch Helicon Magnetoplasma Thruster

    NASA Astrophysics Data System (ADS)

    Ribeiro, Celso

    2015-11-01

    A new concept of a high efficient electrodeless magnetoplasma-based electric thruster using a helicon plasma submitted to a pinch effect is proposed. This concept is intended to have high thrust for a short period, while reducing the plasma-wall contact. This proposal is highly suitable for rocket devices for faster satellites' orbital correction, a feasible way to lead manned missions into deep space, and for a more compact plasma sources for plasma materials for fusion studies. The pinch effect is created by a set of poloidal field coils placed around the insulating cylinder where the helical antenna is mounted. A pulsed current creates the pinch effect, which immediately insulates the plasma to the wall, thus reducing the perpendicular particle and energy losses. As a consequence, the axial flux, thus the thrust, should be increased because of particle balance. This may require an additional magnetic field produced by a single coil placed at the back of the helicon antenna (the gas entrance) to be acted during the pinch phase, leading to an unbalanced magnetic mirror-type configuration, therefore a net flux outwards. The combination with the double helicon structure may also maximize the efficiency. If everything is synchronized, there will be no gas or energy wasted, and the wall heat will be minimal, thus reducing the problems of material fatigue and failures, and making feasible the use of conventional materials.

  20. InSb charge coupled infrared imaging device: The 20 element linear imager

    NASA Technical Reports Server (NTRS)

    Thom, R. D.; Koch, T. L.; Parrish, W. J.; Langan, J. D.; Chase, S. C.

    1980-01-01

    The design and fabrication of the 8585 InSb charge coupled infrared imaging device (CCIRID) chip are reported. The InSb material characteristics are described along with mask and process modifications. Test results for the 2- and 20-element CCIRID's are discussed, including gate oxide characteristics, charge transfer efficiency, optical mode of operation, and development of the surface potential diagram.

  1. The origin of convective structures in the scrape-off layer of linear magnetic fusion devices investigated by fast imaging

    SciTech Connect

    Antar, G. Y.; Yu, J. H.; Tynan, G.

    2007-02-15

    A fast imaging camera is used to unveil the spatio-temporal properties of radially convective events in the CSDX linear plasma device [M. J. Burin et al., Phys. Plasmas, 12, 052320 (2005)]. The exposure time is set to 1 {mu}s and the time between frames to 10 {mu}s. The time series from a Langmuir probe and from a pixel in the 50000-frame movie are compared and cross-correlated. Excellent agreement between the two diagnostics is found for spatial scales greater than 2.5 mm. The fluctuations inside the main plasma column are found to change between different poloidal mode numbers as a function of time. Accordingly, the power spectra determined in these linear devices reflect the sum over these modes. Outside the main plasma column, avaloids are observed to remain attached to the main plasma, hence their behavior does not become independent of the dynamics inside the main plasma column. Avaloid properties, assessed from imaging, agree with Langmuir probes done on various devices, except that the radial length is found to be much larger than previously determined because the blob-shape assumption is not valid. The link between fluctuations inside and outside the main plasma column indicates that the nonlinear evolution of the m=1 poloidal mode number is responsible for the creation of avaloids.

  2. A feedback linearization approach to spacecraft control using momentum exchange devices. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Dzielski, John Edward

    1988-01-01

    Recent developments in the area of nonlinear control theory have shown how coordiante changes in the state and input spaces can be used with nonlinear feedback to transform certain nonlinear ordinary differential equations into equivalent linear equations. These feedback linearization techniques are applied to resolve two problems arising in the control of spacecraft equipped with control moment gyroscopes (CMGs). The first application involves the computation of rate commands for the gimbals that rotate the individual gyroscopes to produce commanded torques on the spacecraft. The second application is to the long-term management of stored momentum in the system of control moment gyroscopes using environmental torques acting on the vehicle. An approach to distributing control effort among a group of redundant actuators is described that uses feedback linearization techniques to parameterize sets of controls which influence a specified subsystem in a desired way. The approach is adapted for use in spacecraft control with double-gimballed gyroscopes to produce an algorithm that avoids problematic gimbal configurations by approximating sets of gimbal rates that drive CMG rotors into desirable configurations. The momentum management problem is stated as a trajectory optimization problem with a nonlinear dynamical constraint. Feedback linearization and collocation are used to transform this problem into an unconstrainted nonlinear program. The approach to trajectory optimization is fast and robust. A number of examples are presented showing applications to the proposed NASA space station.

  3. Device with Functions of Linear Motor and Non-contact Power Collector for Wireless Drive

    NASA Astrophysics Data System (ADS)

    Fujii, Nobuo; Mizuma, Tsuyoshi

    The authors propose a new apparatus with functions of propulsion and non-contact power collection for a future vehicle which can run like an electric vehicle supplied from the onboard battery source in most of the root except near stations. The batteries or power-capacitors are non-contact charged from the winding connected with commercial power on ground in the stations etc. The apparatus has both functions of linear motor and transformer, and the basic configuration is a wound-secondary type linear induction motor (LIM). In the paper, the wound type LIM with the concentrated single-phase winding for the primary member on the ground is dealt from the viewpoint of low cost arrangement. The secondary winding is changed to the single-phase connection for zero thrust in the transformer operation, and the two-phase connection for the linear motor respectively. The change of connection is done by the special converter for charge and linear drive on board. The characteristics are studied analytically.

  4. X-Pinch And Its Applications In X-ray Radiograph

    SciTech Connect

    Zou Xiaobing; Wang Xinxin; Liu Rui; Zhao Tong; Zeng Naigong; Zhao Yongchao; Du Yanqiang

    2009-07-07

    An X-pinch device and the related diagnostics of x-ray emission from X-pinch were briefly described. The time-resolved x-ray measurements with photoconducting diodes show that the x-ray pulse usually consists of two subnanosecond peaks with a time interval of about 0.5 ns. Being consistent with these two peaks of the x-ray pulse, two point x-ray sources of size ranging from 100 mum to 5 mum and depending on cut-off x-ray photon energy were usually observed on the pinhole pictures. The x-pinch was used as x-ray source for backlighting of the electrical explosion of single wire and the evolution of X-pinch, and for phase-contrast imaging of soft biological objects such as a small shrimp and a mosquito.

  5. Adaptive [theta]-methods for pricing American options

    NASA Astrophysics Data System (ADS)

    Khaliq, Abdul Q. M.; Voss, David A.; Kazmi, Kamran

    2008-12-01

    We develop adaptive [theta]-methods for solving the Black-Scholes PDE for American options. By adding a small, continuous term, the Black-Scholes PDE becomes an advection-diffusion-reaction equation on a fixed spatial domain. Standard implementation of [theta]-methods would require a Newton-type iterative procedure at each time step thereby increasing the computational complexity of the methods. Our linearly implicit approach avoids such complications. We establish a general framework under which [theta]-methods satisfy a discrete version of the positivity constraint characteristic of American options, and numerically demonstrate the sensitivity of the constraint. The positivity results are established for the single-asset and independent two-asset models. In addition, we have incorporated and analyzed an adaptive time-step control strategy to increase the computational efficiency. Numerical experiments are presented for one- and two-asset American options, using adaptive exponential splitting for two-asset problems. The approach is compared with an iterative solution of the two-asset problem in terms of computational efficiency.

  6. Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Martin, Adam; Polzin, Kurt; Kimberlin, Adam; Eskridge, Richard

    2013-01-01

    Fabricated and tested CTP IPPTs at cone angles of 20deg, 38deg, and 60deg, and performed direct single-pulse impulse bit measurements with continuous gas flow. Single pulse performance highest for 38deg angle with impulse bit of approx.1 mN-s for both argon and xenon. Estimated efficiencies low, but not unexpectedly so based on historical data trends and the direction of the force vector in the CTP. Capacitor charging system assembled to provide rapid recharging of capacitor bank, permitting repetition-rate operation. IPPT operated at repetition-rate of 5 Hz, at maximum average power of 2.5 kW, representing to our knowledge the highest average power for a repetitively-pulsed thruster. Average thrust in repetition-rate mode (at 5 kV, 75 sccm argon) was greater than simply multiplying the single-pulse impulse bit and the repetition rate.

  7. Power of the pinch: pinch lower lid blepharoplasty.

    PubMed

    Kim, Elizabeth M; Bucky, Louis P

    2008-05-01

    Lower lid blepharoplasty is performed with great variation in technique. Conventional lower lid blepharoplasty with anterior fat removal via the orbital septum has a potential lower lid malposition rate of 15% to 20%. Lower lid malposition and the stigma of obvious lower lid surgery have led plastic surgeons to continue to change their approach to lower lid rejuvenation. In recent years, some surgeons have come to rely on alternative procedures like laser resurfacing alone or in conjunction with transconjunctival fat removal and canthopexy in an effort to avoid such complications. The pinch blepharoplasty technique removes redundant skin without undermining. This allows for more controlled wound healing, predictable recovery, and potential for simultaneous laser resurfacing. The combination of pinch blepharoplasty with transconjunctival fat removal leaves the middle lamella intact and reduces the chance of scleral show or ectropion. The purpose of this series is to demonstrate that pinch excision of redundant lower eyelid skin can be safely performed and that it can be used with laser resurfacing and/or transconjunctival fat removal for optimal treatment of the aging eye. A retrospective review of 46 consecutive patients who underwent pinch blepharoplasty, either in isolation or with other periorbital procedures was performed. Follow-up was at least 4 months (range of 4-24 months). In addition, we performed a prospective study of 25 consecutive patients to quantify the amount of skin removed and evaluate results and complications. An average of 8 mm of skin was resected (range of 4-12 mm) with the pinch blepharoplasty technique. Of these patients, 5.6% also underwent transconjunctival blepharoplasty, laser resurfacing, and/or fat grafting of the nasojugal groove. Despite the addition of simultaneous laser resurfacing, we did not see an increase in lower lid malposition. Three of the 71 patients had temporary scleral show that resolved with lower lid massage. In

  8. Grid cells and theta as oscillatory interference: theory and predictions.

    PubMed

    Burgess, Neil

    2008-01-01

    The oscillatory interference model [Burgess et al. (2007) Hippocampus 17:801-802] of grid cell firing is reviewed as an algorithmic level description of path integration and as an implementation level description of grid cells and their inputs. New analyses concern the relationships between the variables in the model and the theta rhythm, running speed, and the intrinsic firing frequencies of grid cells. New simulations concern the implementation of velocity-controlled oscillators (VCOs) with different preferred directions in different neurons. To summarize the model, the distance traveled along a specific direction is encoded by the phase of a VCO relative to a baseline frequency. Each VCO is an intrinsic membrane potential oscillation whose frequency increases from baseline as a result of depolarization by synaptic input from speed modulated head-direction cells. Grid cell firing is driven by the VCOs whose preferred directions match the current direction of motion. VCOs are phase-reset by location-specific input from place cells to prevent accumulation of error. The baseline frequency is identified with the local average of VCO frequencies, while EEG theta frequency is identified with the global average VCO frequency and comprises two components: the frequency at zero speed and a linear response to running speed. Quantitative predictions are given for the inter-relationships between a grid cell's intrinsic firing frequency and grid scale, the two components of theta frequency, and the running speed of the animal. Qualitative predictions are given for the properties of the VCOs, and the relationship between environmental novelty, the two components of theta, grid scale and place cell remapping. PMID:19021256

  9. Emotional conflict processing induce boosted theta oscillation.

    PubMed

    Ma, Jianling; Liu, Chang; Chen, Xu

    2015-05-19

    Although previous studies have reported the neural correlates and dynamics of emotional conflict processing, the neural oscillatory features of such processing remain unclear. The present study uses time-frequency analysis to determine the event-related spectral perturbation (ERSP) characteristics underlying emotional conflict processing. Our behavioral results replicate previous findings of shorter response times and fewer response errors under the congruent condition relative to the incongruent condition, indicating a robust interference effect. Theta oscillatory activity was larger for the incongruent than for the congruent condition over frontal and frontal-central midline areas, reflecting a greater need for control under conditions of conflict. Moreover, the theta power difference was negatively associated with the RT difference, indicating that greater theta power leads to better behavioral performance. The present findings provide evidence that the theta oscillation is necessary for the control of emotional conflict. PMID:25863173

  10. Note on trigonometric expansions of theta functions

    NASA Astrophysics Data System (ADS)

    Chouikha, A. Raouf

    2003-04-01

    We are interested in properties of coefficients of certain expansions of the classical theta functions. We show that they are solutions of a differential system derived from the heat equation. We plan to explicitly give expressions of these coefficients.

  11. Human hippocampal theta activity during virtual navigation.

    PubMed

    Ekstrom, Arne D; Caplan, Jeremy B; Ho, Emily; Shattuck, Kirk; Fried, Itzhak; Kahana, Michael J

    2005-01-01

    This study examines whether 4-8-Hz theta oscillations can be seen in the human hippocampus, and whether these oscillations increase during virtual movement and searching, as they do in rodents. Recordings from both hippocampal and neocortical depth electrodes were analyzed while six epileptic patients played a virtual taxi-driver game. During the game, the patients alternated between searching for passengers, whose locations were random, and delivering them to stores, whose locations remained constant. In both hippocampus and neocortex, theta increased during virtual movement in all phases of the game. Hippocampal and neocortical theta activity were also significantly correlated with each other, but this correlation did not differ between neocortex and hippocampus and within disparate neocortical electrodes. Our findings demonstrate the existence of movement-related theta oscillations in human hippocampus, and suggest that both cortical and hippocampal oscillations play a role in attention and sensorimotor integration. PMID:16114040

  12. On-line monitoring system for roller wear with axes shift compensation based on laser-linear charge coupled device

    NASA Astrophysics Data System (ADS)

    Wei, Liansuo; Guo, Yuan

    2013-04-01

    Based on the principle of laser-linear array charge-coupled device (CCD) detection technology, a high accuracy nontouch on-line system for monitoring roller wear is brought forward. The principle and composition of the laser-linear array CCD detection system and the operation process were expatiated. Aiming at the errors of the roller's axes shifting during the detection process, compensating steps were adopted from the vertical and the parallel direction to the detection surface. This effectively enhanced the accuracy of the detection system. Experiments proved that the accuracy of the system could reach the demand of the practical production process. It provides a new method for high speed, accuracy, and automatic on-line monitoring of roller wear. r shapegear array CCD detection. A simulation-software program is also compiled based on this principle. By using this program, the I/O signals's data for this system is gained and the detection curves can be drawn automatically.

  13. Magnetic shield for turbomolecular pump of the Magnetized Plasma Linear Experimental device at Saha Institute of Nuclear Physics.

    PubMed

    Biswas, Subir; Chattopadhyay, Monobir; Pal, Rabindranath

    2011-01-01

    The turbo molecular pump of the Magnetized Plasma Linear Experimental device is protected from damage by a magnetic shield. As the pump runs continuously in a magnetic field environment during a plasma physics experiment, it may get damaged owing to eddy current effect. For design and testing of the shield, first we simulate in details various aspects of magnetic shield layouts using a readily available field design code. The performance of the shield made from two half cylinders of soft iron material, is experimentally observed to agree very well with the simulation results. PMID:21280830

  14. Study of a non-equilibrium plasma pinch with application for microwave generation

    NASA Astrophysics Data System (ADS)

    Al Agry, Ahmad Farouk

    The Non-Equilibrium Plasma Pinch (NEPP), also known as the Dense Plasma Focus (DPF) is well known as a source of energetic ions, relativistic electrons and neutrons as well as electromagnetic radiation extending from the infrared to X-ray. In this dissertation, the operation of a 15 kJ, Mather type, NEPP machine is studied in detail. A large number of experiments are carried out to tune the machine parameters for best performance using helium and hydrogen as filling gases. The NEPP machine is modified to be able to extract the copious number of electrons generated at the pinch. A hollow anode with small hole at the flat end, and a mock magnetron without biasing magnetic field are built. The electrons generated at the pinch are very difficult to capture, therefore a novel device is built to capture and transport the electrons from the pinch to the magnetron. The novel cup-rod-needle device successfully serves the purpose to capture and transport electrons to monitor the pinch current. Further, the device has the potential to field emit charges from its needle end acting as a pulsed electron source for other devices such as the magnetron. Diagnostics tools are designed, modeled, built, calibrated, and implemented in the machine to measure the pinch dynamics. A novel, UNLV patented electromagnetic dot sensors are successfully calibrated, and implemented in the machine. A new calibration technique is developed and test stands designed and built to measure the dot's ability to track the impetus signal over its dynamic range starting and ending in the noise region. The patented EM-dot sensor shows superior performance over traditional electromagnetic sensors, such as Rogowski coils. On the other hand, the cup-rod structure, when grounded on the rod side, serves as a diagnostic tool to monitor the pinch current by sampling the actual current, a quantity that has been always very challenging to measure without perturbing the pinch. To the best of our knowledge, this method

  15. Linear response theory for annealing of radiation damage in semiconductor devices

    NASA Technical Reports Server (NTRS)

    Litovchenko, Vitaly

    1988-01-01

    A theoretical study of the radiation/annealing response of MOS ICs is described. Although many experiments have been performed in this field, no comprehensive theory dealing with radiation/annealing response has been proposed. Many attempts have been made to apply linear response theory, but no theoretical foundation has been presented. The linear response theory outlined here is capable of describing a broad area of radiation/annealing response phenomena in MOS ICs, in particular, both simultaneous irradiation and annealing, as well as short- and long-term annealing, including the case when annealing is nearing completion. For the first time, a simple procedure is devised to determine the response function from experimental radiation/annealing data. In addition, this procedure enables us to study the effect of variable temperature and dose rate, effects which are of interest in spaceflight. In the past, the shift in threshold potential due to radiation/annealing has usually been assumed to depend on one variable: the time lapse between an impulse dose and the time of observation. While such a suggestion of uniformity in time is certainly true for a broad range of radiation annealing phenomena, it may not hold for some ranges of the variables of interest (temperature, dose rate, etc.). A response function is projected which is dependent on two variables: the time of observation and the time of the impulse dose. This dependence on two variables allows us to extend the theory to the treatment of a variable dose rate. Finally, the linear theory is generalized to the case in which the response is nonlinear with impulse dose, but is proportional to some impulse function of dose. A method to determine both the impulse and response functions is presented.

  16. Z-Pinch Fusion for Energy Applications

    SciTech Connect

    SPIELMAN,RICK B.

    2000-01-01

    Z pinches, the oldest fusion concept, have recently been revisited in light of significant advances in the fields of plasma physics and pulsed power engineering. The possibility exists for z-pinch fusion to play a role in commercial energy applications. We report on work to develop z-pinch fusion concepts, the result of an extensive literature search, and the output for a congressionally-mandated workshop on fusion energy held in Snowmass, Co July 11-23,1999.

  17. Nested X Pinches on the COBRA Generator

    NASA Astrophysics Data System (ADS)

    Shelkovenko, T. A.; Pikuz, S. A.; McBride, R. D.; Knapp, P. F.; Wilhelm, H.; Hammer, D. A.; Sinars, D. B.

    2009-01-01

    Recent results of X pinch studies on the COBRA generator at Cornell University (peak current up to 1.2 MA and rise time of 100 ns) are presented. Using an initial configuration of wires before their twisting, similar to nested cylindrical wire arrays enables the assembly of a symmetric configuration at the X pinch crossing region. It also enables an investigation of multilayered X pinches. X pinches with different configurations, including with different materials in the inner and outer wire layers, were tested.

  18. Ulnar Nerve Tendon Transfers for Pinch.

    PubMed

    Cook, Shane; Gaston, R Glenn; Lourie, Gary M

    2016-08-01

    Power and tip pinch are an integral part of intrinsic hand function that can be significantly compromised with dysfunction of the ulnar nerve. Loss of power pinch is one component that can significantly affect an individual's ability to perform simple daily tasks. Tip pinch is less affected, as this task has significant contributions from the median nerve. To restore power pinch, the primary focus must be on restoring the action of the adductor pollicis primarily, and if indicated the first dorsal interosseous muscle and flexor pollicis brevis. PMID:27387080

  19. Nested X Pinches on the COBRA Generator

    SciTech Connect

    Shelkovenko, T. A.; Pikuz, S. A.; McBride, R. D.; Knapp, P. F.; Wilhelm, H.; Hammer, D. A.; Sinars, D. B.

    2009-01-21

    Recent results of X pinch studies on the COBRA generator at Cornell University (peak current up to 1.2 MA and rise time of 100 ns) are presented. Using an initial configuration of wires before their twisting, similar to nested cylindrical wire arrays enables the assembly of a symmetric configuration at the X pinch crossing region. It also enables an investigation of multilayered X pinches. X pinches with different configurations, including with different materials in the inner and outer wire layers, were tested.

  20. TPE-1R (M) reversed field pinch experiment

    SciTech Connect

    Shimada, T.; Hirano, Y.; Maejima, Y.; Ogawa, K.

    1981-01-01

    This report describes the engineering aspects of the design, tests, and performances of the toroidal device TPE-1RM with which plasma physics researches on ''Reversed Field Pinch''configurations are carried out and this is an intermediate scale like HBTX-1A, ZT-40M, and ETA-BETA II. In TPE-1RM experiments are being performed in order to obtain an optimum reversed field configurations for MHD stability. The main description in this report is devoted to the metal vacuum vessel and specially contrived electrical circuit for field programming control techniques. The experiments with this device have been successful both from the technical and physcial points of view.

  1. Electron dynamics and energy conversion in O-type linear-beam devices.

    NASA Technical Reports Server (NTRS)

    Detweiler, H. K.; Rowe, J. E.

    1971-01-01

    A general nonlinear interaction theory is used to investigate the effects of transverse fields (i.e., radial circuit fields and radial space-charge fields) in traveling-wave amplifiers for a variety of beam-focusing conditions. Magnetic focusing fields which are periodic or tapered (increased) with distance along the device are considered in addition to uniform magnetic fields. Results are presented for Brillouin flow and near-Brillouin flow, and the minimum magnetic field strength required to effectively constrain the electron beam is determined as a function of the operating parameters for the various focusing systems. Confined flow is also examined for the uniform-field case in order to have a basis of comparison from which the effects of radial motion of the beam electrons can be determined. The results indicate the importance of transverse effects and further yield information on the stability of strongly modulated cylindrical electron beams.-

  2. Dynamics of flows, fluctuations, and global instability under electrode biasing in a linear plasma device

    NASA Astrophysics Data System (ADS)

    Desjardins, T. R.; Gilmore, M.

    2016-05-01

    Grid biasing is utilized in a large-scale helicon plasma to modify an existing instability. It is shown both experimentally and with a linear stability analysis to be a hybrid drift-Kelvin-Helmholtz mode. At low magnetic field strengths, coherent fluctuations are present, while at high magnetic field strengths, the plasma is broad-band turbulent. Grid biasing is used to drive the once-coherent fluctuations to a broad-band turbulent state, as well as to suppress them. There is a corresponding change in the flow shear. When a high positive bias (10Te) is applied to the grid electrode, a large-scale ( n ˜/n ≈50 % ) is excited. This mode has been identified as the potential relaxation instability.

  3. One-dimensional breakdown voltage model of SOI RESURF lateral power device based on lateral linearly graded approximation

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Guo, Yu-Feng; Xu, Yue; Lin, Hong; Yang, Hui; Hong, Yang; Yao, Jia-Fei

    2015-02-01

    A novel one-dimensional (1D) analytical model is proposed for quantifying the breakdown voltage of a reduced surface field (RESURF) lateral power device fabricated on silicon on an insulator (SOI) substrate. We assume that the charges in the depletion region contribute to the lateral PN junctions along the diagonal of the area shared by the lateral and vertical depletion regions. Based on the assumption, the lateral PN junction behaves as a linearly graded junction, thus resulting in a reduced surface electric field and high breakdown voltage. Using the proposed model, the breakdown voltage as a function of device parameters is investigated and compared with the numerical simulation by the TCAD tools. The analytical results are shown to be in fair agreement with the numerical results. Finally, a new RESURF criterion is derived which offers a useful scheme to optimize the structure parameters. This simple 1D model provides a clear physical insight into the RESURF effect and a new explanation on the improvement in breakdown voltage in an SOI RESURF device. Project supported by the National Natural Science Foundation of China (Grant No. 61076073) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20133223110003).

  4. ZaP-HD: High Energy Density Z-Pinch Plasmas using Sheared Flow Stabilization

    NASA Astrophysics Data System (ADS)

    Golingo, R. P.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Hughes, M. C.; Kim, B.; Ross, M. P.; Weed, J. R.

    2015-11-01

    The ZaP-HD flow Z-pinch project investigates scaling the flow Z-pinch to High Energy Density Plasma, HEDP, conditions by using sheared flow stabilization. ZaP used a single power supply to produce 100 cm long Z-pinches that were quiescent for many radial Alfven times and axial flow-through times. The flow Z-pinch concept provides an approach to achieve HED plasmas, which are dimensionally large and persist for extended durations. The ZaP-HD device replaces the single power supply from ZaP with two separate power supplies to independently control the plasma flow and current in the Z-pinch. Equilibrium is determined by diagnostic measurements of the density with interferometry and digital holography, the plasma flow and temperature with passive spectroscopy, the magnetic field with surface magnetic probes, and plasma emission with optical imaging. The diagnostics fully characterize the plasma from its initiation in the coaxial accelerator, through the pinch, and exhaust from the assembly region. The plasma evolution is modeled with high resolution codes: Mach2, WARPX, and NIMROD. Experimental results and scaling analyses are presented. This work is supported by grants from the U.S. Department of Energy and the U.S. National Nuclear Security Administration.

  5. Monte Carlo simulation studies of ring polymers at athermal and theta conditions

    NASA Astrophysics Data System (ADS)

    Fuereder, Ingo; Zifferer, Gerhard

    2011-11-01

    By use of an intramolecular criterion, i.e., the direct proportionality between mean square dimension and chain length, theta conditions for linear chains and ring shaped polymers are evaluated for several types of cubic lattice chains (simple cubic, body centered cubic, and face centered cubic). The properties of the rings are evaluated for the same thermodynamic conditions under which they are prepared thus allowing for a natural amount of knots which have been identified by use of Alexander polynomials. For the limit of infinite chain lengths the same theta parameter is found for linear chains and rings. On the contrary, a significant theta point depression occurs due to an additional excluded volume effect if unknots are exclusively regarded. Parameters characteristic of the shape of rings and chains under theta conditions extrapolated to infinite chain length fairly well coincide with respective data for random walks. Mean square dimensions (characteristic of the size) of theta systems are slightly in excess as compared to nonreversal random walks due to the necessity of avoiding overlaps on a local scale. Furthermore athermal systems are studied as well for comparison; mean square dimensions are described by use of scaling relations with proper short chain corrections, shape parameters are given in the limit of infinite chain length.

  6. A vertically integrated pixel readout device for the Vertex Detector at the International Linear Collider

    SciTech Connect

    Deptuch, Grzegorz; Christian, David; Hoff, James; Lipton, Ronald; Shenai, Alpana; Trimpl, Marcel; Yarema, Raymond; Zimmerman, Tom; /Fermilab

    2008-12-01

    3D-Integrated Circuit technology enables higher densities of electronic circuitry per unit area without the use of nanoscale processes. It is advantageous for mixed mode design with precise analog circuitry because processes with conservative feature sizes typically present lower process dispersions and tolerate higher power supply voltages, resulting in larger separation of a signal from the noise floor. Heterogeneous wafers (different foundries or different process families) may be combined with some 3D integration methods, leading to the optimization of each tier in the 3D stack. Tracking and vertexing in future High-Energy Physics (HEP) experiments involves construction of detectors composed of up to a few billions of channels. Readout electronics must record the position and time of each measurement with the highest achievable precision. This paper reviews a prototype of the first 3D readout chip for HEP, designed for a vertex detector at the International Linear Collider. The prototype features 20 x 20 {micro}m{sup 2} pixels, laid out in an array of 64 x 64 elements and was fabricated in a 3-tier 0.18 {micro}m Fully Depleted SOI CMOS process at MIT-Lincoln Laboratory. The tests showed correct functional operation of the structure. The chip performs a zero-suppressed readout. Successive submissions are planned in a commercial 3D bulk 0.13 {micro}m CMOS process to overcome some of the disadvantages of an FDSOI process.

  7. Three-dimensional linear peeling-ballooning theory in magnetic fusion devices

    SciTech Connect

    Weyens, T. Sánchez, R.; García, L.; Loarte, A.; Huijsmans, G.

    2014-04-15

    Ideal magnetohydrodynamics theory is extended to fully 3D magnetic configurations to investigate the linear stability of intermediate to high n peeling-ballooning modes, with n the toroidal mode number. These are thought to be important for the behavior of edge localized modes and for the limit of the size of the pedestal that governs the high confinement H-mode. The end point of the derivation is a set of coupled second order ordinary differential equations with appropriate boundary conditions that minimize the perturbed energy and that can be solved to find the growth rate of the perturbations. This theory allows of the evaluation of 3D effects on edge plasma stability in tokamaks such as those associated with the toroidal ripple due to the finite number of toroidal field coils, the application of external 3D fields for elm control, local modification of the magnetic field in the vicinity of ferromagnetic components such as the test blanket modules in ITER, etc.

  8. Analysis of matrix cracking and local delamination in (O/theta/-theta)sub s graphite epoxy laminates under tension load

    NASA Technical Reports Server (NTRS)

    Salpekar, S. A.; O'Brien, T. K.

    1991-01-01

    Several 3D finite element analyses of (O/theta/-theta)sub s graphite epoxy laminates, where theta = 15, 20, 25, 30, and 45 deg, subjected to axial tension load were performed. The interlaminar stresses in the theta/-theta interface were calculated with and without a matrix crack in the central -theta plies. The interlaminar normal stress changes from a small compressive stress when no matrix crack is present to a high tensile stress at the intersection of the matrix crack and free edge. The analysis of local delamination from the -theta matrix crack indicates a high strain energy release rate and a localized mode I component near the free edge, within one ply distance from the matrix crack. In order to examine the stress state causing the matrix cracking the maximum principal normal stress in a plane perpendicular to the fiber direction in the -theta ply was calculated in an uncracked laminate. The corresponding shear stress parallel to the fiber was also calculated. The principal normal stress at the laminate edge increases through the ply thickness and reached a very high tensile value at the theta/-theta interface indicating that the crack in the -theta ply may initiate at the theta/-theta interface. Crack profiles on the laminate edge in the -theta ply were constructed from the principal stress directions. The cracks were found to be more curved for layups with smaller theta angles, which is consistent with experimental observations in the literature.

  9. Analysis of matrix cracking and local delamination in (0/theta/-theta)sub s graphite epoxy laminates under tension load

    NASA Technical Reports Server (NTRS)

    Salpekar, S. A.; Obrien, T. K.

    1991-01-01

    Several 3D finite element analyses of (0/theta/-theta)sub s graphite epoxy laminates, where theta=15, 20, 25, 30, and 45 deg, subjected to axial tension load were performed. The interlaminar stresses in the theta/-theta interface were calculated with and without a matrix crack in the central -theta plies. The interlaminar normal stress changes from a small compressive stress when no matrix crack is present to a high tensile stress at the intersection of the matrix crack and free edge. The analysis of local delamination from the -theta matrix crack indicates a high strain energy release rate and a localized mode I component near the free edge, within one ply distance from the matrix crack. In order to examine the stress state causing the matrix cracking the maximum principal normal stress in a plane perpendicular to the fiber direction in the -theta ply was calculated in an uncracked laminate. The corresponding shear stress parallel to the fiber was also calculated. The principal normal stress at the laminate edge increases through the ply thickness and reached a very high tensile value at the theta/-theta interface indicating that the crack in the -theta ply may initiate at the theta/-theta interface. Crack profiles on the laminate edge in the -theta ply were constructed from the principal stress directions. The cracks were found to be more curved for layups with smaller theta angles, which is consistent with experimental observations in the literature.

  10. The Imaging of Z-Pinches Using X-Pinch Backlighting

    SciTech Connect

    Douglass, J.D.; Greenly, J.B.; Hammer, D.A.; McBride, R.D.; Pikuz, S.A.; Shelkovenko, T.A.

    2006-01-05

    Imaging using X-pinch backlighters has been implemented on the COBRA accelerator at Cornell University to study the early stages of wire-array Z-pinches. Two of four return-current posts in the wire-array load region are replaced by X pinches so that two images of one wire in an eight-wire z-pinch are obtained from different angles and at different times. High resolution images have been obtained that show the evolution of wire structure and instabilities. X-pinch wire diameter and other parameters were varied in order to shift the timing of the X pinches relative to the start of the z-pinch current pulse. It was found that XPBL wire diameter (mass per unit length) has the strongest influence on radiation timing.

  11. Measuring Theta_13 at Daya Bay

    SciTech Connect

    Lau, Kwong

    2014-03-14

    We measured the neutrino mixing angle, theta13, presumably related to the preponderance of matter over antimatter in our universe with high precision. We determined theta13 by measuring the disappearance of neutrinos from a group of six nuclear reactors. The target, located inside a mountain at about 2 km from the reactors, is 80 tons of liquid scintillator doped with trace amount of Gadolinium to increase its neutron detection efficiency. The neutrino flux is measured by the inverse beta-decay reaction where the final-state particles are detected by the liquid scintillator. The measured value of theta13, based on data collected over 3 years, is large, around 8 degrees, rendering the measurement of the parameter related to matter-antimatter asymmetry in future long baseline neutrino experiments easier.

  12. Pinch Experiments in a Table Top Generator

    SciTech Connect

    Pavez, Cristian; Moreno, Jose; Soto, Leopoldo; Tarifeno, Ariel

    2009-01-21

    The design and construction of a table top multipurpose capacitor bank of hundred of Joules and hundred of kiloAmperes conceived to be used in small scale Z-pinch experiments is reported. A recent result on a Z-pinch gas embedded discharge using hollow conical electrodes done in a similar table top generator is also presented.

  13. The high density Z-pinch

    NASA Astrophysics Data System (ADS)

    McCall, G. H.

    During the past few years techniques have been developed for producing pinches in solid deuterium. The conditions which exist in these plasmas are different from those produced earlier. The pinch is formed from a fiber of solid deuterium rather than from a low density gas, and the current is driven by a low impedance, high voltage pulse generator. Because of the high initial density, it is not necessary to compress the pinch to reach thermonuclear conditions, and the confinement time required for energy production is much shorter than for a gas. Results, which have been verified by experiments performed at higher current were quite surprising and encouraging. The pinch appeared to be stable for a time much longer than the Alfven radial transit time. It is argued that the pinch is not strictly stable, but it does not appear to disassemble in a catastrophic fashion. It appears that there may be a distinction between stability and confinement in the high density pinch. In the discussion below the status of the high density Z-pinch experiments at laboratories around the world is presented, and some of the calculational and experimental results described. Remarks are confined to recent work on the high density pinch.

  14. A plasma source driven predator-prey like mechanism as a potential cause of spiraling intermittencies in linear plasma devices

    NASA Astrophysics Data System (ADS)

    Reiser, D.; Ohno, N.; Tanaka, H.; Vela, L.

    2014-03-01

    Three-dimensional global drift fluid simulations are carried out to analyze coherent plasma structures appearing in the NAGDIS-II linear device (nagoya divertor plasma Simulator-II). The numerical simulations reproduce several features of the intermittent spiraling structures observed, for instance, statistical properties, rotation frequency, and the frequency of plasma expulsion. The detailed inspection of the three-dimensional plasma dynamics allows to identify the key mechanism behind the formation of these intermittent events. The resistive coupling between electron pressure and parallel electric field in the plasma source region gives rise to a quasilinear predator-prey like dynamics where the axisymmetric mode represents the prey and the spiraling structure with low azimuthal mode number represents the predator. This interpretation is confirmed by a reduced one-dimensional quasilinear model derived on the basis of the findings in the full three-dimensional simulations. The dominant dynamics reveals certain similarities to the classical Lotka-Volterra cycle.

  15. Nested X Pinches on the COBRA Generator

    NASA Astrophysics Data System (ADS)

    Hammer, David; Shelkovenko, Tatiana; Pikuz, Sergei; McBride, Ryan; Knapp, Patrick; Wilhelm, Harold; Sinars, Daniel

    2008-11-01

    Recent results of X pinch studies on the COBRA generator at Cornell University (peak current up to 1.2 MA and rise time of 100 ns) are presented. Increasing of the pulser current requires the use of loads with higher mass per unit length. Such loads can be made by increasing the number of wires or the wire diameters, which leads to increasing the size and complexity of the wire crossing region. Using an initial configuration of wires (before their twisting), similar to nested arrays enables the assembly of a more-nearly symmetric configuration at the X pinch crossing region. It also enables an investigation of multilayered X pinches. We will present experimental results obtained from X pinches with different configurations, including X pinches with different materials in the inner and outer wire layers.

  16. Pinch technology/process optimization

    SciTech Connect

    Not Available

    1992-12-01

    Improved process efficiency is of great importance to electric utilities and their industrial customers. It enhances company profitability, thereby fostering load retention and strategic load growth. Moreover, the technical means of achieving improved efficiency can significantly impact utility load shapes. By understanding the energy use patterns and options in an industrial facility, the utility and industrial user can work together to define mutually beneficial investment and operating decisions and to clarify how the decisions might be impacted by existing or alternative energy prices. Efforts to achieve such understanding are facilitated by using pinch technology, an innovative and highly effective methodology for systematically analyzing total industrial sites. This report documents a series of twelve industrial process optimization case studies. The studies were carried out using pinch technology. '' Each study was cosponsored by the industrial site's local electric utility. The twelve studies are follows: (1) pulp and paper, (2) refinery, (3) refinery, (4) yeast, (5) soups/sauces, (6) cellulose- acetate, (7) refinery, (8) chemicals, (9) gelatin-capsules, (10) refinery, (11) brewery, (12) cereal grains.

  17. Analysis of matrix cracking and local delamination in (0/theta/-theta)s graphite epoxy laminates under tensile load

    NASA Technical Reports Server (NTRS)

    Salpekar, S. A.; O'Brien, T. K.

    1993-01-01

    Three-dimensional element analyses of (0/theta/-theta)s graphite epoxy laminates, where theta = 15, 20, 25, 30, and 45 deg, subjected to axial tensile load, were performed. The interlaminar stresses in the theta/-theta interface were calculated with and without a matrix crack in the central -theta plies. The interlaminar normal stress changes from a small compressive stress when no matrix crack is present to a high tensile stress at the intersection of the matrix crack and the free edge. The analysis of local delamination from the -theta matrix crack indicates a high strain energy release rate and a localized Mode I component near the free edge, within one-ply distance from the matrix crack. To examine the stress state causing the matrix cracking, the maximum principal normal stress in a plane perpendicular to the fiber direction in the -theta ply was calculated in an uncracked laminate. The corresponding shear stress parallel to the fiber was also calculated. The principal normal stress at the laminate edge increased through the ply thickness and reached a very high tensile value at the theta/-theta interface indicating that the crack in the -theta ply may initiate at the theta/-theta interface.

  18. Dynamical processes in the reversed-field pinch

    SciTech Connect

    Caramana, E.; Cayton, T.; Dagazian, R.

    1982-01-01

    This paper presents a review of recent theoretical work on the Reversed-Field Pinch (RFP) at Los Alamos National Laboratory. A wide variety of topics are discussed. These include: nonlinear, two-dimensional, helical, magnetohydrodynamic (MHD) simulations of current-driven modes; a statistical model of plasma turbulence in the RFP; analytic and numerical calculations of resistive ballooning modes in toroidal geometry; work on coherent m = 0 excitations observed in the ZT-40M device; finite Larmor radius effects on the tearing mode; destabilization of MHD modes by kinetic effects; and, possible plasma heating by means of magnetoacoustic oscillations.

  19. Hippocampal theta, gamma, and theta-gamma coupling: effects of aging, environmental change, and cholinergic activation

    PubMed Central

    Jacobson, Tara K.; Howe, Matthew D.; Schmidt, Brandy; Hinman, James R.; Escabí, Monty A.

    2013-01-01

    Hippocampal theta and gamma oscillations coordinate the timing of multiple inputs to hippocampal neurons and have been linked to information processing and the dynamics of encoding and retrieval. One major influence on hippocampal rhythmicity is from cholinergic afferents. In both humans and rodents, aging is linked to impairments in hippocampus-dependent function along with degradation of cholinergic function. Cholinomimetics can reverse some age-related memory impairments and modulate oscillations in the hippocampus. Therefore, one would expect corresponding changes in these oscillations and possible rescue with the cholinomimetic physostigmine. Hippocampal activity was recorded while animals explored a familiar or a novel maze configuration. Reexposure to a familiar situation resulted in minimal aging effects or changes in theta or gamma oscillations. In contrast, exploration of a novel maze configuration increased theta power; this was greater in adult than old animals, although the deficit was reversed with physostigmine. In contrast to the theta results, the effects of novelty, age, and/or physostigmine on gamma were relatively weak. Unrelated to the behavioral situation were an age-related decrease in the degree of theta-gamma coupling and the fact that physostigmine lowered the frequency of theta in both adult and old animals. The results indicate that age-related changes in gamma and theta modulation of gamma, while reflecting aging changes in hippocampal circuitry, seem less related to aging changes in information processing. In contrast, the data support a role for theta and the cholinergic system in encoding and that hippocampal aging is related to impaired encoding of new information. PMID:23303862

  20. D3-instantons, mock theta series and twistors

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sergei; Manschot, Jan; Pioline, Boris

    2013-04-01

    The D-instanton corrected hypermultiplet moduli space of type II string theory compactified on a Calabi-Yau threefold is known in the type IIA picture to be determined in terms of the generalized Donaldson-Thomas invariants, through a twistorial construction. At the same time, in the mirror type IIB picture, and in the limit where only D3-D1-D(-1)-instanton corrections are retained, it should carry an isometric action of the S-duality group SL(2, {Z} ). We prove that this is the case in the one-instanton approximation, by constructing a holomorphic action of SL(2, {Z} ) on the linearized twistor space. Using the modular invariance of the D4-D2-D0 black hole partition function, we show that the standard Darboux coordinates in twistor space have modular anomalies controlled by period integrals of a Siegel-Narain theta series, which can be canceled by a contact transformation generated by a holomorphic mock theta series.

  1. Human Hippocampal Theta Oscillations during Movement without Visual Cues.

    PubMed

    Qasim, Salman E; Jacobs, Joshua

    2016-03-16

    The hippocampus exhibits theta oscillations when animals navigate. Vass et al. (2016) discovered that theta oscillations are also present when humans are moved through a virtual environment without sensory feedback, indicating that theta oscillations have a general role in spatial cognition beyond sensorimotor processing. PMID:26985718

  2. Gyrokinetic simulations of ion temperature gradient modes in the reversed field pinch

    SciTech Connect

    Predebon, I.; Guo, S. C.; Angioni, C.

    2010-01-15

    Linear gyrokinetic calculations are applied to the reversed field pinch configuration to investigate the occurrence of ion temperature gradient instabilities. The analysis shows this type of instability to be only marginally responsible for particle and energy transport. The required gradients could be reached only in correspondence to the temperature slopes arising at the boundary of the helical structure in the quasisingle helicity states. The dependence of the instability threshold on the relevant macroscopic quantities is considered. A discussion on the main differences in the driving mechanisms existing between the reversed field pinch and the tokamak configuration is addressed.

  3. Study of micro-pinches in wire-array Z pinches

    SciTech Connect

    Ivanov, V. V.; Papp, D.; Anderson, A. A.; Talbot, B. R.; Astanovitskiy, A. L.; Nalajala, V.; Dmitriev, O.; Chittenden, J. P.; Niasse, N.; Pikuz, S. A.; Shelkovenko, T. A.

    2013-11-15

    Bright and hot areas with a high plasma density and temperature are observed in all kinds of Z pinches. We studied bright radiating spots produced by micro-pinches in cylindrical and planar wire-arrays at the 1 MA Zebra pulsed power generator using an x-ray streak camera synchronized with laser diagnostics, x-ray time-gated pinhole camera, and spectroscopy. Hot spots with extremely dense and relatively hot plasma arise during the collapse of the micro-pinches. These hot spots radiate a continuum spectrum with energy >2.5 keV. Typical micro-pinches in Al wire arrays generate x-ray bursts with durations of 0.4–1 ns in the soft x-ray range and 0.1–0.4 ns in the keV range. UV two-frame shadowgraphy shows spatial correlation of hot spots with the collapse and explosion of micro-pinches. Micro-pinches typically occur at the necks of the Z pinch, but can demonstrate a variety of parameters and different dynamics. An analysis of x-ray streak images shows that micro-pinches can generate >20% of the x-ray energy in some types of wire-array Z pinches.

  4. Study of micro-pinches in wire-array Z pinches

    NASA Astrophysics Data System (ADS)

    Ivanov, V. V.; Papp, D.; Anderson, A. A.; Talbot, B. R.; Astanovitskiy, A. L.; Nalajala, V.; Dmitriev, O.; Chittenden, J. P.; Niasse, N.; Pikuz, S. A.; Shelkovenko, T. A.

    2013-11-01

    Bright and hot areas with a high plasma density and temperature are observed in all kinds of Z pinches. We studied bright radiating spots produced by micro-pinches in cylindrical and planar wire-arrays at the 1 MA Zebra pulsed power generator using an x-ray streak camera synchronized with laser diagnostics, x-ray time-gated pinhole camera, and spectroscopy. Hot spots with extremely dense and relatively hot plasma arise during the collapse of the micro-pinches. These hot spots radiate a continuum spectrum with energy >2.5 keV. Typical micro-pinches in Al wire arrays generate x-ray bursts with durations of 0.4-1 ns in the soft x-ray range and 0.1-0.4 ns in the keV range. UV two-frame shadowgraphy shows spatial correlation of hot spots with the collapse and explosion of micro-pinches. Micro-pinches typically occur at the necks of the Z pinch, but can demonstrate a variety of parameters and different dynamics. An analysis of x-ray streak images shows that micro-pinches can generate >20% of the x-ray energy in some types of wire-array Z pinches.

  5. Warm dense matter study and pulsed-power developments for X-pinch equipment in Nagaoka University of Technology

    NASA Astrophysics Data System (ADS)

    Sasaki, Toru; Miki, Yasutoshi; Tachinami, Fumitaka; Saito, Hirotaka; Takahashi, Takuya; Anzai, Nobuyuki; Kikuchi, Takashi; Aso, Tsukasa; Harada, Nob.

    2014-01-01

    In order to explore high energy density physics, we have performed WDM experiment by using several pulsed-power devices. To generate well-defined warm dense state for evaluating electrical conductivity and its properties, we have proposed an isochoric heating of foamed metal by using pulsed-power discharge. The proposed technique yields the electrical conductivity of warm dense matter with a well-defined temperature. To observe the warm dense matter, a pulsed-power generator based on a pulse-forming-network (PFN) was studied toward generating an intense point-spot-like X-ray source from X-pinch technique. From comparison of the designing and the actual inductances of the X-pinch system, the actual inductance of X-pinch system is 3.5 times higher than the designing inductance. To reduce the total inductance of X-pinch system, we will modify the gap switch system such as multi spake gap.

  6. High energy density Z-pinch plasmas using flow stabilization

    SciTech Connect

    Shumlak, U. Golingo, R. P. Nelson, B. A. Bowers, C. A. Doty, S. A. Forbes, E. G. Hughes, M. C. Kim, B. Knecht, S. D. Lambert, K. K. Lowrie, W. Ross, M. P. Weed, J. R.

    2014-12-15

    The ZaP Flow Z-Pinch research project[1] at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Plasma evolution is modeled with high-resolution simulation codes – Mach2, WARPX, NIMROD, and HiFi. Plasma flow profiles are experimentally measured with a multi-chord ion Doppler spectrometer. A sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density[2]; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements[3]; and fast framing photography for global structure. Wall stabilization has been investigated computationally and experimentally by removing 70% of the surrounding conducting wall to demonstrate no change in stability behavior.[4] Experimental evidence suggests that the plasma lifetime is only limited by plasma supply and current waveform. The flow Z-pinch concept provides an approach to achieve high energy density plasmas,[5] which are large, easy to diagnose, and persist for extended durations. A new experiment, ZaP-HD, has been built to investigate this approach by separating the flow Z-pinch formation from the radial compression using a triaxial-electrode configuration. This innovation allows more detailed investigations of the sheared flow stabilizing effect, and it allows compression to much higher densities than previously achieved on ZaP by reducing the linear density and increasing the pinch current. Experimental results and

  7. High energy density Z-pinch plasmas using flow stabilization

    NASA Astrophysics Data System (ADS)

    Shumlak, U.; Golingo, R. P.; Nelson, B. A.; Bowers, C. A.; Doty, S. A.; Forbes, E. G.; Hughes, M. C.; Kim, B.; Knecht, S. D.; Lambert, K. K.; Lowrie, W.; Ross, M. P.; Weed, J. R.

    2014-12-01

    The ZaP Flow Z-Pinch research project[1] at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Plasma evolution is modeled with high-resolution simulation codes - Mach2, WARPX, NIMROD, and HiFi. Plasma flow profiles are experimentally measured with a multi-chord ion Doppler spectrometer. A sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density[2]; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements[3]; and fast framing photography for global structure. Wall stabilization has been investigated computationally and experimentally by removing 70% of the surrounding conducting wall to demonstrate no change in stability behavior.[4] Experimental evidence suggests that the plasma lifetime is only limited by plasma supply and current waveform. The flow Z-pinch concept provides an approach to achieve high energy density plasmas,[5] which are large, easy to diagnose, and persist for extended durations. A new experiment, ZaP-HD, has been built to investigate this approach by separating the flow Z-pinch formation from the radial compression using a triaxial-electrode configuration. This innovation allows more detailed investigations of the sheared flow stabilizing effect, and it allows compression to much higher densities than previously achieved on ZaP by reducing the linear density and increasing the pinch current. Experimental results and scaling

  8. Theory of coupled whistler-electron temperature gradient mode in high beta plasma: Application to linear plasma device

    SciTech Connect

    Singh, S. K.; Awasthi, L. M.; Singh, R.; Kaw, P. K.; Jha, R.; Mattoo, S. K.

    2011-10-15

    This paper presents a theory of coupled whistler (W) and electron temperature gradient (ETG) mode using two-fluid model in high beta plasma. Non-adiabatic ion response, parallel magnetic field perturbation ({delta}B{sub z}), perpendicular magnetic flutter ({delta}B{sub perpendicular}), and electron collisions are included in the treatment of theory. A linear dispersion relation for whistler-electron temperature gradient (W-ETG) mode is derived. The numerical results obtained from this relation are compared with the experimental results observed in large volume plasma device (LVPD) [Awasthi et al., Phys. Plasma 17, 42109 (2010)]. The theory predicts that the instability grows only where the temperature gradient is finite and the density gradient flat. For the parameters of the experiment, theoretically estimated frequency and wave number of W-ETG mode match with the values corresponding to the peak in the power spectrum observed in LVPD. By using simple mixing length argument, estimated level of fluctuations of W-ETG mode is in the range of fluctuation level observed in LVPD.

  9. Axial X Pinch Backlighting on COBRA

    NASA Astrophysics Data System (ADS)

    Blesener, Isaac; Greenly, John; Pikuz, Sergey; Shelkovenko, Tatiania; Hammer, David; Kusse, Bruce

    2008-11-01

    X pinch backlighting is a useful imaging technique whereby two or more wires are crossed at a single point and driven with a high current (300-500 kA). At the crossing point, a micron-scale sub-nanosecond x-ray source is produced that acts as a point source and can be used for point-projection imaging. Axial x pinch backlighting is a new technique that allows an end-on image of Z pinches. New load geometry was developed at Cornell University to allow all standard diagnostics to be used on the same shot as the axial x pinch backlighting diagnostic. High density plasma features have been observed that correlate well with XUV self-emission images previously recorded on COBRA and simulation results from GORGON. Data and images will be presented illustrating the latest results from COBRA. Future applications include the possibility of shockwave imaging in the center of thing foil cylinders.

  10. Modeling the Parker instability in a rotating plasma screw pinch

    NASA Astrophysics Data System (ADS)

    Khalzov, I. V.; Brown, B. P.; Katz, N.; Forest, C. B.

    2012-02-01

    We analytically and numerically study the analogue of the Parker (magnetic buoyancy) instability in a uniformly rotating plasma screw pinch confined in a cylinder. Uniform plasma rotation is imposed to create a centrifugal acceleration, which mimics the gravity required for the classical Parker instability. The goal of this study is to determine how the Parker instability could be unambiguously identified in a weakly magnetized, rapidly rotating screw pinch, in which the rotation provides an effective gravity and a radially varying azimuthal field is controlled to give conditions for which the plasma is magnetically buoyant to inward motion. We show that an axial magnetic field is also required to circumvent conventional current driven magnetohydrodynamic (MHD) instabilities such as the sausage and kink modes that would obscure the Parker instability. These conditions can be realized in the Madison plasma Couette experiment (MPCX). Simulations are performed using the extended MHD code NIMROD for an isothermal compressible plasma model. Both linear and nonlinear regimes of the instability are studied, and the results obtained for the linear regime are compared with analytical results from a slab geometry. Based on this comparison, it is found that in a cylindrical pinch, the magnetic buoyancy mechanism dominates at relatively large Mach numbers (M > 5), while at low Mach numbers (M < 1), the instability is due to the curvature of magnetic field lines. At intermediate values of Mach number (1 < M < 5), the Coriolis force has a strong stabilizing effect on the plasma. A possible scenario for experimental demonstration of the Parker instability in MPCX is discussed.

  11. Formation of a sheared flow Z pinch

    NASA Astrophysics Data System (ADS)

    Golingo, R. P.; Shumlak, U.; Nelson, B. A.

    2005-06-01

    The ZaP Flow Z-Pinch project is experimentally studying the effect of sheared flows on Z-pinch stability. It has been shown theoretically that when dVz/dr exceeds 0.1kVA the kink (m =1) mode is stabilized. [U. Shumlak and C. W. Hartman, Phys. Rev. Lett. 75, 3285 (1995).] Z pinches with an embedded axial flow are formed in ZaP with a coaxial accelerator coupled with a 1m assembly region. Long-lived, quiescent Z pinches are generated throughout the first half cycle of the current. During the initial plasma acceleration phase, the axial motion of the current sheet is consistent with snowplow models. Magnetic probes in the assembly region measure the azimuthal modes of the magnetic field. The amplitude of the m =1 mode is proportional to the radial displacement of the Z-pinch plasma current. The magnetic mode levels show a quiescent period which is over 2000 times the growth time of a static Z pinch. The axial velocity is measured along 20 chords through the plasma and deconvolved to provide a radial profile. Using data from multiple pulses, the time evolution of the velocity profile is measured during formation, throughout the quiescent period, and into the transition to instability. The evolution shows that a sheared plasma flow develops as the Z pinch forms. Throughout the quiescent period, the flow shear is greater than the theoretically required threshold for stability. As the flow shear decreases, the magnetic mode fluctuations increase. The coaxial accelerator provides plasma throughout the quiescent period and may explain the evolution of the velocity profile and the sustainment of the flow Z pinch.

  12. Electromagnetic theta gun and tubular projectiles

    SciTech Connect

    Burgess, T.J.; Cnare, E.C.; Oberkampf, W.L.; Beard, S.G.; Cowan, M.

    1980-12-01

    Unlike the better known rail gun, the theta gun applies the propelling force along the length of its projectile. This is shown to allow much greater acceleration of high fineness ratio projectiles for a given barrel pressure, allowing much shorter barrels for military applications. A computer code which simulates performance of the theta gun is described and experimental results from a few simple, low energy experiments show close agreement with code predictions. Trajectories and aerodynamic heating for three candidate military projectiles are calculated for vertical and horizontal atmospheric launches where initial velocity is as high as 3 km/s. The calculations indicate that in some cases a thin layer of heatshield (ablator) will be required to control projectile heating.

  13. Development of novel techniques to study the magnetic field evolution in wire array Z-pinches and X pinches

    NASA Astrophysics Data System (ADS)

    Syed, Wasif

    Understanding the magnetic field topology in wire-array Z-pinches is of great significance for their ultimate application to stockpile stewardship and inertial confinement fusion. We have developed and tested several novel techniques involving material-based sensors to measure magnetic fields as a function of space and time in high energy density plasmas on pulsed power machines. We first briefly introduce a technique that was used to measure a lower limit of the maximum magnetic field of a sub-microsecond duration pulse using magnetic reversal in CoPt thin films. The time-varying magnetic field was generated by an exploding wire array plasma called an X pinch produced on the 0.5 MA, 100 ns pulse duration, XP pulsed power generator. We then introduce a technique based on Faraday rotation that was used to measure magnetic fields in wire-array Z-pinches produced on the 1 MA, 100 ns rise time, COBRA pulsed power generator as well as on the XP generator. This technique measures magnetic fields as a function of space and time using Faraday rotation of a single longitudinal mode (SLM) laser through a magneto-optically active bulk waveguide, multicomponent terbium borate glass, placed adjacent to, or within, the wire array. We have measured fields > 10 T with 100 ns rise times outside of a wire-array Z-pinch for the entire duration (˜250 ns) of the current pulse and as much as ˜2 T inside a wire-array for ˜40 ns from the start of current. This is the first time that such rapidly varying and large fields have been measured using the terbium borate glass. The third method, also based on Faraday rotation of SLM laser light utilized an integrated optical fiber sensor (a fiber-sensor-fiber assembly) on the XP pulsed power generator that also yielded a measurement of the magnetic field of a wire-array Z-pinch for part of the current pulse. Finally, we repeated the third method by fabricating a "thin film waveguide" of terbium borate glass to increase the spatial resolution

  14. The Physics of Fast Z Pinches

    SciTech Connect

    RYUTOV,D.D.; DERZON,MARK S.; MATZEN,M. KEITH

    1999-10-25

    The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizing the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 36 figures and more than 300 references.

  15. The physics of fast Z pinches

    SciTech Connect

    Ryutov, D.D.; Derzon, M.S.; Matzen, M.K.

    1998-07-01

    The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizes the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z-pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 52 figures and nearly 300 references.

  16. Theta-specific susceptibility in a model of adaptive synaptic plasticity

    PubMed Central

    Albers, Christian; Schmiedt, Joscha T.; Pawelzik, Klaus R.

    2013-01-01

    Learning and memory formation are processes which are still not fully understood. It is widely believed that synaptic plasticity is the most important neural substrate for both. However, it has been observed that large-scale theta band oscillations in the mammalian brain are beneficial for learning, and it is not clear if and how this is linked to synaptic plasticity. Also, the underlying dynamics of synaptic plasticity itself have not been completely uncovered yet, especially for non-linear interactions between multiple spikes. Here, we present a new and simple dynamical model of synaptic plasticity. It incorporates novel contributions to synaptic plasticity including adaptation processes. We test its ability to reproduce non-linear effects on four different data sets of complex spike patterns, and show that the model can be tuned to reproduce the observed synaptic changes in great detail. When subjected to periodically varying firing rates, already linear pair based spike timing dependent plasticity (STDP) predicts a specific susceptibility of synaptic plasticity to pre- and postsynaptic firing rate oscillations in the theta-band. Our model retains this band-pass property, while for high firing rates in the non-linear regime it modifies the specific phase relation required for depression and potentiation. For realistic parameters, maximal synaptic potentiation occurs when the postsynaptic is trailing the presynaptic activity slightly. Anti-phase oscillations tend to depress it. Our results are well in line with experimental findings, providing a straightforward and mechanistic explanation for the importance of theta oscillations for learning. PMID:24312047

  17. Progressive Fracture of [0/90/ + or - Theta]s Composite Structure Under Uniform Pressure Load

    NASA Technical Reports Server (NTRS)

    Gotsis, Pascalis K.; Chamis, Christos C.; Gotsis, Christos K.; Mouratidis, Ericos

    2007-01-01

    S-Glass/epoxy [0/90/plus or minus theta]s for theta =45 deg., 60 deg., and 75 deg. laminated fiber-reinforced composite stiffened plate was simulated to investigated for damage and fracture progression under uniform pressure. An integrated computer code was augmented for the simulation of the damage initiation, growth, accumulation, and propagation to fracture and to structural collapse. Results show in detail the damage progression sequence and structural fracture resistance during different degradation stages. Damage through the thickness of the laminate initiated first at [0/90/plus or minus 45]s at 15.168 MPa (2200 psi), followed by [0/90/plus or minus 60]s at 16.96 MPa (2460 psi) and finally by [0/90/plus or minus 75]s at 19.3 MPa (2800 psi). After damage initiation happened the cracks propagate rapidly to structural fracture.

  18. In vivo analysis of trapeziometacarpal joint kinematics during pinch tasks.

    PubMed

    Kuo, Li-Chieh; Lin, Chien-Ju; Chen, Guan-Po; Jou, I-Ming; Wang, Chien-Kuo; Goryacheva, Irina G; Dosaev, Marat Z; Su, Fong-Chin

    2014-01-01

    This study investigated how the posture of the thumb while performing common pinch movements and the levels of pinch force applied by the thumb affect the arthrokinematics of the trapeziometacarpal joint in vivo. Fifteen subjects performed the pinch tasks at the distal phalange (DP), proximal interphalangeal (PIP) joint, and metacarpophalangeal (MP) joint of the index finger with 0%, 50%, and 80% of maximal pinch forces by a single-axis load cell. 3D images of the thumb were obtained using the computed tomography. The results show that the reference points moved from the central region to the dorsal-radial region when changing from pinching the DP to the MP joint without pinching force being applied. Pinching with 80% of the maximum pinching force resulted in reference points being the closest to the volar-ulnar direction. Significant differences were seen between 0% and 50% of maximum pinch force, as well as between 0% and 80%, when pinching the MP joint in the distal-proximal direction. The effects of posture of the thumb and applied pinch force on the arthrokinematics of the joint were investigated with a 3D model of the trapeziometacarpal joint. Pinching with more than 50% of maximum pinch force might subject this joint to extreme displacement. PMID:24683540

  19. In Vivo Analysis of Trapeziometacarpal Joint Kinematics during Pinch Tasks

    PubMed Central

    Chen, Guan-Po; Jou, I-Ming; Goryacheva, Irina G.; Dosaev, Marat Z.; Su, Fong-Chin

    2014-01-01

    This study investigated how the posture of the thumb while performing common pinch movements and the levels of pinch force applied by the thumb affect the arthrokinematics of the trapeziometacarpal joint in vivo. Fifteen subjects performed the pinch tasks at the distal phalange (DP), proximal interphalangeal (PIP) joint, and metacarpophalangeal (MP) joint of the index finger with 0%, 50%, and 80% of maximal pinch forces by a single-axis load cell. 3D images of the thumb were obtained using the computed tomography. The results show that the reference points moved from the central region to the dorsal-radial region when changing from pinching the DP to the MP joint without pinching force being applied. Pinching with 80% of the maximum pinching force resulted in reference points being the closest to the volar-ulnar direction. Significant differences were seen between 0% and 50% of maximum pinch force, as well as between 0% and 80%, when pinching the MP joint in the distal-proximal direction. The effects of posture of the thumb and applied pinch force on the arthrokinematics of the joint were investigated with a 3D model of the trapeziometacarpal joint. Pinching with more than 50% of maximum pinch force might subject this joint to extreme displacement. PMID:24683540

  20. Long-length, long-lived flow-shear stabilized Z-pinches: Background and Experimental plans for scaling studies

    NASA Astrophysics Data System (ADS)

    Nelson, B. A.; Shumlak, U.; Golingo, R. P.; Claveau, E. L.; McLean, H. S.; Schmidt, A. E.

    2015-11-01

    The ZaP experiment produces long-lived sheared-flow-stabilized Z-pinch plasmas up to 126 cm in length for several flow-through times, and up to thousands of Alfvén times. Experimental measurements of the magnetic structure along the full length of the plasma column show an axially uniform Z-pinch plasma during the observed quiescent period. Interferometry, fast-framing images, and Rogowskii coils corroborate the existence of a pinched plasma during this quiescent period of time. Detailed two-dimensional non-linear magnetohydrodynamic (MHD) calculations have been performed showing the formation and assembly of long-length, long-lived Z-pinches. Experimentally-observed plasma lifetimes and velocity-shear profiles are shown to be consistent with calculations of viscous-damping timescales based on the measured plasma parameters. A newly-funded ARPA-E ALPHA project, the Fusion Z-pinch Experiment ``FuZE'' is being constructed at the University of Washington, in collaboration with the Lawrence Livermore National Laboratory. FuZE will study scaling and stability of the successful ZaP experiment to higher pinch currents. The FuZE experimental design, goals, and plans, based on ZaP experimental results, will be presented.

  1. Development and simulation study of a new inverse-pinch high Coulomb transfer switch

    NASA Technical Reports Server (NTRS)

    Choi, Sang H.

    1989-01-01

    The inverse-pinch plasma switch was studied using a computer simulation code. The code was based on a 2-D, 2-temperature magnetohydrodynamic (MHD) model. The application of this code was limited to the disk-type inverse-pinch plasma switch. The results of the computer analysis appear to be in agreement with the experimental results when the same parameters are used. An inverse-pinch plasma switch for closing has been designed and tested for high-power switching requirements. An azimuthally uniform initiation of breakdown is a key factor in achieving an inverse-pinch current path in the switch. Thus, various types of triggers, such as trigger pins, wire-brush, ring trigger, and hypocycloidal-pinch (HCP) devices have been tested for uniform breakdown. Recently, triggering was achieved by injection of a plasma-ring (plasma puff) that is produced separately with hypocycloidal-pinch electrodes placed under the cathode of the main gap. The current paths at switch closing, initiated by the injection of a plasma-ring from the HCP trigger are azimuthally uniform, and the local current density is significantly reduced, so that damage to the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes is four orders of magnitude less than that of a spark-gap switch for the same switching power. Indeed, a few thousand shots with peak current exceeding a mega-ampere and with hold-off voltage up to 20 kV have been conducted without showing measurable damage to the electrodes and insulators.

  2. Radiative signatures of Z-pinch plasmas at UNR: from X-pinches to wire arrays

    NASA Astrophysics Data System (ADS)

    Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Safronova, U. I.; Shlyaptseva, V. V.; Shrestha, I.; Osborne, G. C.; Weller, M. E.; Stafford, A.; Lorance, M.; Chuvatin, A. S.

    2014-08-01

    University-scale Z-pinch generators are able to produce High Energy Density (HED) plasmas in a broad range of plasma parameters under well-controlled and monitored experimental conditions suitable for radiation studies. The implosion of X-pinch and wire array loads at a 1 MA generator yields short (1-20 nsec) x-ray bursts from one or several bright plasma spots near the wire cross point (for X-pinches) or along and near Z-pinch axis (for wire arrays). Such X- and Z-pinch HED plasma with scales from a few µm to several mm in size emits radiation in a broad range of energies from 10 eV to 0.5 MeV and is subject of our studies during the last ten years. In particular, the substantial number of experiments with very different wire loads was performed on the 1 MA Zebra generator and analyzed: X-pinch, cylindrical, nested, and various types of the novel load, Planar Wire Arrays (PWA). Also, the experiments at an enhanced current of 1.5-1.7 MA on Zebra using Load Current Multiplier (LCM) were performed. This paper highlights radiative signatures of X-pinches and Single and Double PWAs which are illustrated using the new results with combined wire loads from two different materials.

  3. Axial x-ray backlighting of wire-array Z-pinches using X pinches

    NASA Astrophysics Data System (ADS)

    Blesener, I. C.; Greenly, J. B.; Pikuz, S. A.; Shelkovenko, T. A.; Vishniakou, S.; Hammer, D. A.; Kusse, B. R.

    2009-12-01

    For the first time, a geometry has been developed to allow for an axial imaging system for wire-array Z-pinch experiments that produce high-resolution x-ray images. The new geometry required a significant redesign of the electrode hardware. Calibrated areal density measurements of the Z-pinch plasma including wire cores, coronal plasma, streaming plasma, and the precursor were obtained. The system used eight-wire molybdenum (Mo) X pinches in series with and directly below the Z-pinch axis to provide micron-scale x-rays sources for point-projection radiography. The images formed on the x-ray sensitive film had a 15 mm diameter field of view at the center height of the array and a magnification of about 7.5:1. Titanium (Ti) filters in front of the film transmitted radiation in the spectral range of 3-5 keV. For calibration, a separate film with the same thickness Ti filter was placed the same distance from the X pinch. This film had an unobstructed path that bypasses the Z-pinch but included step wedges for calibration of the Z-pinch plasma. The step wedges had thicknesses of tungsten (W) ranging from 0.015 to 1.1 μm to obtain areal density measurements of the W plasma from the wire-array. Images had subnanosecond temporal resolution and about 10 μm spatial resolution.

  4. Breakeven Fusion in Staged Z Pinch

    NASA Astrophysics Data System (ADS)

    Rahman, Hafiz; Ney, Paul; Rostoker, Norman; Wessel, Frank

    2008-03-01

    We are studying the prospect for breakeven thermonuclear fusion considering a Mega joule (MJ) class, 100 ns, impulse generator using a modified version of MACH2, a 2-1/2 D, radiation-code. The load is a cylindrical, xenon plasma shell that implodes radially onto a co-axial, deuterium-tritium plasma target. Optimized plasma density and pinch radius lead to a fusion-energy output that is many times the stored capacitor bank energy. In this ``Staged Z-pinch'' shock fronts form that preheat the DT plasma to several hundred eV, before adiabatic compression. During compression, the Xe liner becomes Rayleigh-Taylor (RT) unstable while the DT target remains stable. Proper selection of the initial pinch radius and plasma density is crucial for optimum implosion efficiency.

  5. Pinch technology experience in plant retrofits

    SciTech Connect

    Kumana, J.D.; Spriggs, H.D.; Ashton, G.

    1987-01-01

    Pinch technology has been applied to retrofit of many plants employing a wide variety of technologies, including continuous and batch processes, and those involving solids processing. This paper reports the authors recent experience in identifying energy savings opportunities in an oil refinery, an ethylene plant, and a corn wet milling plant. The key findings are that: Pinch technology can be successfully applied to retrofits as well as new plant designs; the correct design for retrofits is not the same as that for new designs; pinch technology gives good results even in ''difficult'' processes employing the less common unit operations; and some commonly accepted practices (specifically in solids drying) are fundamentally wrong; multiple-effect drying based on a countercurrent humidity profile offers significant potential for energy savings.

  6. D-D fusion experiments using fast z pinches

    SciTech Connect

    Spielman, R.B.; Baldwin, G.T.; Cooper, G.

    1994-04-01

    The development of high current (I > 10 MA) drivers provides us with a new tool for the study of neutron-producing plasmas in the thermal regime. The imploded deuterium mass (or collisionality) increases as I{sup 2} and the ability of the driver to heat the plasma to relevant fusion temperatures improves as the power of the driver increases. Additionally, fast (< 100 ns) implosions are more stable to the usual MHD instabilities that plagued the traditional slower implosions. We describe experiments in which deuterium gas puffs or CD{sub 2} fiber arrays were imploded in a fast z-pinch configuration on Sandia`s Saturn facility generating up to 3 {times} 10{sup 12} D-D neutrons. These experiments were designed to explore the physics of neutron-generating plasmas in a z-pinch geometry. Specifically, we intended to produce neutrons from a nearly thermal plasma where the electrons and ions have a nearly Maxwellian distribution. This is to be clearly differentiated from the more usual D-D beam-target neutrons generated in many dense plasma focus (DPF) devices.

  7. D-D fusion experiments using fast Z pinches

    SciTech Connect

    Spielman, R.B.; Baldwin, G.T.; Cooper, G.

    1998-03-01

    The development of high current (I > 10 MA) drivers provides the authors with a new tool for the study of neutron-producing plasmas in the thermal regime. The imploded deuterium mass (or collisionality) increases as I{sup 2} and the ability of the driver to heat the plasma to relevant fusion temperatures improves as the power of the driver increases. Additionally, fast (<100 ns) implosions are more stable to the usual MHD instabilities that plagued the traditional slower implosions. The authors describe experiments in which deuterium gas puffs or CD{sub 2} fiber arrays were imploded in a fast z-pinch configuration on Sandia`s Saturn facility generating up to 3 {times} 10{sup 12} D-D neutrons. These experiments were designed to explore the physics of neutron-generating plasmas in a z-pinch geometry. Specifically, the authors intended to produce neutrons from a nearly thermal plasma where the electrons and ions have a nearly Maxwellian distribution. This is to be clearly differentiated from the more usual D-D beam-target neutrons generated in many dense plasma focus (DPF) devices.

  8. Theta oscillations accompanying concurrent auditory stream segregation.

    PubMed

    Tóth, Brigitta; Kocsis, Zsuzsanna; Urbán, Gábor; Winkler, István

    2016-08-01

    The ability to isolate a single sound source among concurrent sources is crucial for veridical auditory perception. The present study investigated the event-related oscillations evoked by complex tones, which could be perceived as a single sound and tonal complexes with cues promoting the perception of two concurrent sounds by inharmonicity, onset asynchrony, and/or perceived source location difference of the components tones. In separate task conditions, participants performed a visual change detection task (visual control), watched a silent movie (passive listening) or reported for each tone whether they perceived one or two concurrent sounds (active listening). In two time windows, the amplitude of theta oscillation was modulated by the presence vs. absence of the cues: 60-350ms/6-8Hz (early) and 350-450ms/4-8Hz (late). The early response appeared both in the passive and the active listening conditions; it did not closely match the task performance; and it had a fronto-central scalp distribution. The late response was only elicited in the active listening condition; it closely matched the task performance; and it had a centro-parietal scalp distribution. The neural processes reflected by these responses are probably involved in the processing of concurrent sound segregation cues, in sound categorization, and response preparation and monitoring. The current results are compatible with the notion that theta oscillations mediate some of the processes involved in concurrent sound segregation. PMID:27170058

  9. Self-pinched transport of an intense proton beam

    SciTech Connect

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

    2000-01-01

    Ion beam self-pinched transport (SPT) experiments have been carried out using a 1.1-MeV, 100-kA proton beam. A Rutherford scattering diagnostic and a LiF nuclear activation diagnostic measured the number of protons within a 5 cm radius at 50 cm into the transport region that was filled with low-pressure helium. Time-integrated signals from both diagnostics indicate self-pinching of the ion beam in a helium pressure window between 35 and 80 mTorr. Signals from these two diagnostics are consistent with ballistic transport at pressures above and below this SPT pressure window. Interferometric measurements of electron densities during beam injection into vacuum are consistent with ballistic transport with co-moving electrons. Interferometric measurements for beam injection into helium show that the electron density increases quadratically with pressure through the SPT window and roughly linearly with pressure above the SPT window. The ionization fraction of the helium plateaus at about 1.5% for pressures above 80 mTorr. In the SPT window, the electron density is 3 to 20 times the beam density. Numerical simulations of these beam transport experiments produce results that are in qualitative agreement with the experimental measurements. (c) 2000 American Institute of Physics.

  10. Absorption of CO2-laser radiation in a hypocycloidal-pinch plasma

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Mcfarland, D. R.

    1976-01-01

    Absorption of a 50-J pulsed CO2 laser beam in the plasma produced in a hypocycloidal-pinch apparatus was studied. The apparatus consists of three disk electrodes with a 5-cm hole on the axis. The current sheets are snow-plowed toward the center of the hole to produce a plasma with a density greater than 10 to the 18th/cu cm and a temperature near 1 keV which emits soft X rays for 5 microsec. IR detectors measured the laser radiation incident onto, transmitted through, and scattered from the plasma as functions of time. For a period up to 70 microsec from the onset of X-ray emission, neither transmitted nor scattered laser radiation was observed above the detector threshold of 0.3% of the incident flux. This indicates effective absorption of the laser beam (greater than 99%) and that the particle confinement time extends far beyond the energy confinement time of 5 microsec. Thus, the plasma in this apparatus appears much more amenable to laser heating than that in a theta pinch.

  11. Fusion in a staged Z-pinch

    NASA Astrophysics Data System (ADS)

    Wessel, F. J.; Rahman, H. U.; Ney, P.; Valenzuela, J.; Beg, F.; McKee, E.; Darling, T.

    2016-03-01

    This paper is dedicated to Norman Rostoker, our (FJW and HUR) mentor and long-term collaborator, who will always be remembered for the incredible inspiration that he has provided us. Norman's illustrious career dealt with a broad range of fundamental-physics problems and we were fortunate to have worked with him on many important topics: intense-charged-particle beams, field-reversed configurations, and Z-pinches. Rostoker 's group at the University of CA, Irvine was well known for having implemented many refinements to the Z-pinch, that make it more stable, scalable, and efficient, including the development of: the gas-puff Z-pinch [1], which provides for the use of an expanded range of pinch-load materials; the gas-mixture Z-pinch [2], which enhances the pinch stability and increases its radiation efficiency; e-beam pre-ionization [3], which enhances the uniformity of the initial-breakdown process in a gas pinch; magnetic-flux-compression [4, 5], which allows for the amplification of an axial-magnetic field Bz; the Z-θ pinch [6], which predicts fusion in a pinch-on-fiber configuration; the Staged Z-pinch (SZP) [7], which allows for the amplification of the pinch self-magnetic field, Bθ , in addition to a Bz, and leads to a stable implosion and high-gain fusion [8, 9, 10]. This paper describes the physical basis for a magneto-inertial compression in a liner-on-target SZP [11]. Initially a high-atomic-number liner implodes under the action of the J →×B → , Lorentz Force. As the implosion becomes super Alfvénic, magnetosonic waves form, transporting current and magnetic field through the liner toward the interface of the low-atomic-number target. The target implosion remains subsonic with its surface bounded by a stable-shock front. Shock waves that pass into the target provide a source of target plasma pre-heat. At peak compression the assembly is compressed by liner inertia, with flux compression producing an intense-magnetic field near the target

  12. If it’s pinched it’s a memristor

    NASA Astrophysics Data System (ADS)

    Chua, Leon

    2014-10-01

    This paper presents an in-depth review of the memristor from a rigorous circuit-theoretic perspective, independent of the material the device is made of. From an experimental perspective, a memristor is best defined as any two-terminal device that exhibits a pinched hysteresis loop in the voltage-current plane when driven by any periodic voltage or current signal that elicits a periodic response of the same frequency. This definition greatly broadens the scope of memristive devices to encompass even non-semiconductor devices, both organic and inorganic, from many unrelated disciplines, including biology, botany, brain science, etc. For pedagogical reasons, the broad terrain of memristors is partitioned into three classes of increasing generality, dubbed Ideal Memristors, Generic Memristors, and Extended Memristors. Each class is distinguished from the others via unique fingerprints and signatures. This paper clarifies many confusing issues, such as non-volatility, dc V-I curves, high-frequency v-i curves, local activity, as well as nonlinear dynamical and bifurcation phenomena that are the hallmarks of memristive devices. Above all, this paper addresses several fundamental issues and questions that many memristor researchers do not comprehend but are afraid to ask.

  13. Further development of an indium antimonide (InSb)Charge-Coupled Infrared Imaging Device (CCIRID), 20-element linear imager

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Problems encountered in the development of an indium antimonide charge coupled device for infrared imaging and real time signal processing on the focal plane are summarized. A new generation chip is described which contains, 2, 4, and 20-element imagers, a 4-element TDI array, a monolithic gated charge integrator, and test devices. A system study of a future LANDSAT sensor system configured around an InSb TDi array is considered.

  14. Pinch technique: Theory and applications

    NASA Astrophysics Data System (ADS)

    Binosi, Daniele; Papavassiliou, Joannis

    2009-08-01

    We review the theoretical foundations and the most important physical applications of the Pinch Technique (PT). This general method allows the construction of off-shell Green’s functions in non-Abelian gauge theories that are independent of the gauge-fixing parameter and satisfy ghost-free Ward identities. We first present the diagrammatic formulation of the technique in QCD, deriving, at one loop, the gauge independent gluon self-energy, quark-gluon vertex, and three-gluon vertex, together with their Abelian Ward identities. The generalization of the PT to theories with spontaneous symmetry breaking is carried out in detail, and the profound connection with the optical theorem and the dispersion relations are explained within the electroweak sector of the Standard Model. The equivalence between the PT and the Feynman gauge of the Background Field Method (BFM) is elaborated, and the crucial differences between the two methods are critically scrutinized. A variety of field theoretic techniques needed for the generalization of the PT to all orders are introduced, with particular emphasis on the Batalin-Vilkovisky quantization method and the general formalism of algebraic renormalization. The main conceptual and technical issues related to the extension of the technique beyond one loop are described, using the two-loop construction as a concrete example. Then the all-order generalization is thoroughly examined, making extensive use of the field theoretic machinery previously introduced; of central importance in this analysis is the demonstration that the PT-BFM correspondence persists to all orders in perturbation theory. The extension of the PT to the non-perturbative domain of the QCD Schwinger-Dyson equations is presented systematically, and the main advantages of the resulting self-consistent truncation scheme are discussed. A plethora of physical applications relying on the PT are finally reviewed, with special emphasis on the definition of gauge

  15. Effects of an axial magnetic field on Z-pinch plasmas for extreme ultraviolet sources

    SciTech Connect

    Katsuki, Sunao; Kimura, Akihiro; Kondo, Yoshihiro; Horita, Hiroyuki; Namihira, Takao; Sakugawa, Takashi; Akiyama, Hidenori

    2006-01-01

    This paper describes the effect of an axial magnetic field (B{sub z}) on plasma pinch dynamics and on the extreme ultraviolet (EUV) emission property of a compact Z-pinch device for EUV sources. The Z-pinch xenon plasma was driven by a pulse current with an amplitude of 27 kA and duration of 150 ns in an alumina tube with a diameter of 5 mm. A quasistatic magnetic field of up to 360 G is applied to the plasma. The EUV emission was evaluated for spectra, spatial distribution of the emission, and light energy at 13.5 nm with 2% bandwidth. A time-resolved interferogram provides the electron line density and pinch dynamics of the plasma. When a magnetic field of 160 G was applied to the plasma, the emission energy was approximately double that without the magnetic field. The spectroscopic measurement shows that the EUV spectrum drastically varies with magnetic-field strength. The time-resolved interferogram indicates that the axial magnetic field contributes by making the plasma compression smooth and by sustaining certain plasma conditions longer. From these experimental results, it was concluded that applying an axial magnetic field can be an effective method to improve EUV emission.

  16. Design of the Fusion Z-Pinch Experiment - FuZE

    NASA Astrophysics Data System (ADS)

    Shumlak, U.; McLean, H. S.; Nelson, B. A.; Golingo, R. P.; Schmidt, A.; Claveau, E. L.

    2015-11-01

    Based on the successful results of the sheared flow stabilized (SFS) Z-pinch from ZaP and ZaP-HD, a new experiment FuZE is designed to scale the plasma performance to fusion conditions. The SFS Z-pinch is immune to the instabilities that plague the conventional Z-pinch yet maintains the same favorable radial scaling. The plasma density and temperature increase rapidly with decreasing plasma radius, which naturally leads to a compact configuration at fusion conditions. The SFS Z-pinch is being investigated as a novel approach to a compact fusion device in a new collaborative ARPA-E ALPHA project with the University of Washington and Lawrence Livermore National Laboratory. The project includes an experimental effort coupled with high-fidelity physics modeling using kinetic and fluid simulations. Along with scaling law analysis, computational and experimental results that have informed the design and development of the FuZE apparatus are presented. This work is supported by an award from US ARPA-E.

  17. Performance of an array of plasma pinches as a new optical pumping source for dye lasers

    SciTech Connect

    Rieger, H.; Kim, K.

    1983-11-01

    A new optical pumping source consisting of an array of plasma pinches in the hypocycloidal-pinch geometry is employed to pump a variety of dye lasers. A dye cuvette is inserted along the symmetry axis of the plasma device such that it may be surrounded by the plasma pinch. The light from the plasma pinch is very intense and rich in ultraviolet, which makes it an attractive optical pumping source for dye lasers, particularly in the blue-green spectral region. Control of the plasma fluorescence is achieved by the choice of gas, its fill pressure, and the capacitor bank voltage and its stored energy. The rise time of this ''plasma flashlamp'' depends mainly on the gas species and the fill pressure. Output energy of approx.2 mJ per cm/sup 3/ of lasing medium, or 2 kW/cm/sup 3/ for a 1-..mu..s laser pulse, is obtained from rhodamine 6G, coumarin 480, LD 490, and coumarin 504 dyes. That both the coumarin 480 and rhodamine 6G lasers have the comparable output power is a direct proof that the present optical pumping source is more efficient than the commercial xenon flashlamps in pumping lasers in the blue-green spectral region.

  18. Multiwire X Pinches on the COBRA Pulsed Power Generator

    SciTech Connect

    Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Douglass, Jonathan D.; McBride, Ryan D.; Hammer, David A.

    2006-01-05

    The rebuilt COBRA pulsed power generator, which has a variable current pulse waveform and amplitude (90-150 ns rise time, 0.6 - 1 MA) has extended the range of current pulse parameters that can be used to study X pinches. X pinches with 2 to 12 wires with diameters from 25 to 75 {mu}m of several different wire materials (from Al to W) have been studied. The influence of different current shapes on X pinch plasma formation and pinch implosion dynamics has been studied using a set of diagnostics with spatial and/or temporal resolution. Multiwire X pinches were placed in the diode center and/or two four wire X pinches were places in one of four parallel return current circuits of the diode. Radiographic images of different test objects, wires in the array and the X pinches, themselves, were obtained with {mu}m scale spatial resolution.

  19. Hippocampo-cerebellar theta band phase synchrony in rabbits.

    PubMed

    Wikgren, J; Nokia, M S; Penttonen, M

    2010-02-17

    Hippocampal functioning, in the form of theta band oscillation, has been shown to modulate and predict cerebellar learning of which rabbit eyeblink conditioning is perhaps the most well-known example. The contribution of hippocampal neural activity to cerebellar learning is only possible if there is a functional connection between the two structures. Here, in the context of trace eyeblink conditioning, we show (1) that, in addition to the hippocampus, prominent theta oscillation also occurs in the cerebellum, and (2) that cerebellar theta oscillation is synchronized with that in the hippocampus. Further, the degree of phase synchrony (PS) increased both as a response to the conditioning stimuli and as a function of the relative power of hippocampal theta oscillation. However, the degree of PS did not change as a function of either training or learning nor did it predict learning rate as the hippocampal theta ratio did. Nevertheless, theta band synchronization might reflect the formation of transient neural assemblies between the hippocampus and the cerebellum. These findings help us understand how hippocampal function can affect eyeblink conditioning, during which the critical plasticity occurs in the cerebellum. Future studies should examine cerebellar unit activity in relation to hippocampal theta oscillations in order to discover the detailed mechanisms of theta-paced neural activity. PMID:19945512

  20. General process improvements through pinch technology

    SciTech Connect

    Linnhoff, B.; Polley, G.T.; Sahdev, V.

    1988-06-01

    Over the last ten years pinch technology has emerged as somewhat of a ''maverick'' development in the process design and energy conservation scene. Running contrary to general trends by taking the computer out of the loop and putting the engineer back in control, it has been questioned by some and welcomed by others. Regardless of persuasion, however, critics and advocates alike have largely failed to notice that pinch technology is more than an energy conservation tool. This is probably because soon after the advent of pinch technology in the 1970s, the process design scene became dominated by the oil crisis. Energy savings became the primary task of process designers and, therefore, the primary focus of the technology. Application during this period typically demonstrated energy cost savings in the range of 20 to 50 percent and payback periods of one year or less. Only recently have the other benefits of the technology reemerged. While it is true that pinch technology is essentially a heat-flow-based technique it is also true that it can be used to address a very diverse range of objectives.

  1. Dynamics of hybrid X-pinches

    SciTech Connect

    Shelkovenko, T. A.; Tilikin, I. N.; Ivanenkov, G. V.; Stepniewski, W.; Mingaleev, A. R.; Romanova, V. M.; Agafonov, A. V.; Cahill, A. D.; Hoyt, C. L.; Gourdain, P. A.; Hammer, D. A.; Pikuz, S. A.

    2015-01-15

    The dynamics of a new type of pinches—hybrid X-pinches (HXPs)—has been studied experimentally and numerically. The initial configuration of an HXP consists of a high-current diode with conical tungsten electrodes separated by a 1- to 3-mm-long gap and shunted with a 20- to 100-μm diameter wire. It was shown earlier that a hot spot (HS) with high plasma parameters also formed in the HXP, although its initial configuration is simpler than that of a standard X-pinch. Although details of the HXP dynamics still remain insufficiently studied, the main factors governing the HXP formation were investigated both experimentally and using magnetohydrodynamic simulations. The formation of a specific pressure profile in the electrode plasma after the wire explosion was investigated both experimentally and theoretically. It is shown that the effect of the pressure profile on the expanding wire plasma is similar for both standard X-pinches and HXPs, which allows one to assign them to the same class of loads of pulsed facilities. It is also established that the final stages of HS formation and the parameters of the HS plasma in standard X-pinches and HXPs are practically identical.

  2. Spectroscopic study in Z-pinch discharge

    SciTech Connect

    Garamoon, A.A.; Saudy, A.H.; Shark, W.

    1995-12-31

    The temporal variation of the emitted line intensity has been investigated, and thus an important information about the dynamic ionization stages in the Z-pinch discharge has been studied. Also the electron temperature Te, has been deduced by using a spectroscopic technique.

  3. The Pinch Pot Technique and Raku.

    ERIC Educational Resources Information Center

    Demery, Marie

    Since the 16th century, the small Japanese raku tea bowl has reflected the merged cultural influences of art, religion, and other countries on the art of Japanese pottery. Artistically, the bowl is a combination of ceramics (pinching) and sculpture (carving). The dictates of the Zen Buddhist tea masters determine its sculptural process and steps,…

  4. Magnetic pinch compression of silica glass

    NASA Technical Reports Server (NTRS)

    Bless, S. J.

    1974-01-01

    SiO2 glass has been irreversibly densified by pressures up to 250 kbar produced in a magnetic pinch apparatus. The threshold for significant densification was about 60 kbar. The recovered densities agree better with published shock wave results than with static results.

  5. Theta Phase Synchrony and Conscious Target Perception

    PubMed Central

    Slagter, Heleen A.; Lutz, Antoine; Greischar, Lawrence L.; Nieuwenhuis, Sander; Davidson, Richard J.

    2008-01-01

    The information processing capacity of the human mind is limited, as is evidenced by the attentional blink—a deficit in identifying the second of two targets (T1 and T2) presented in close succession. This deficit is thought to result from an overinvestment of limited resources in T1 processing. We previously reported that intensive mental training in a style of meditation aimed at reducing elaborate object processing, reduced brain resource allocation to T1, and improved T2 accuracy [Slagter, H. A., Lutz, A., Greisschar, L. L., Frances, A. D., Nieuwenhuis, S., Davis, J., et al. Mental training affects distribution of limited brain resources. PloS Biology, 5, e138, 2007]. Here we report EEG spectral analyses to examine the possibility that this reduction in elaborate T1 processing rendered the system more available to process new target information, as indexed by T2-locked phase variability. Intensive mental training was associated with decreased cross-trial variability in the phase of oscillatory theta activity after successfully detected T2s, in particular, for those individuals who showed the greatest reduction in brain resource allocation to T1. These data implicate theta phase locking in conscious target perception, and suggest that after mental training the cognitive system is more rapidly available to process new target information. Mental training was not associated with changes in the amplitude of T2-induced responses or oscillatory activity before task onset. In combination, these findings illustrate the usefulness of systematic mental training in the study of the human mind by revealing the neural mechanisms that enable the brain to successfully represent target information. PMID:18823234

  6. Neural circuits underlying the generation of theta oscillations.

    PubMed

    Pignatelli, Michele; Beyeler, Anna; Leinekugel, Xavier

    2012-01-01

    Theta oscillations represent the neural network configuration underlying active awake behavior and paradoxical sleep. This major EEG pattern has been extensively studied, from physiological to anatomical levels, for more than half a century. Nevertheless the cellular and network mechanisms accountable for the theta generation are still not fully understood. This review synthesizes the current knowledge on the circuitry involved in the generation of theta oscillations, from the hippocampus to extra hippocampal structures such as septal complex, entorhinal cortex and pedunculopontine tegmentum, a main trigger of theta state through direct and indirect projections to the septal complex. We conclude with a short overview of the perspectives offered by technical advances for deciphering more precisely the different neural components underlying the emergence of theta oscillations. PMID:21964249

  7. Dense plasma in Z-pinches and the plasma focus

    NASA Astrophysics Data System (ADS)

    Haines, M. G.

    1981-04-01

    Studies of the plasma focus, which after its three-dimensional compression closely resembles a Z-pinch, have shown that an electron temperature of 1 keV can be achieved in a narrow filament. Of great interest is the very high neutron yield, up to one trillion neutrons per discharge, which greatly exceeds that of any other fusion device. The origin of the neutrons is still a matter for research, as under different conditions there is evidence of intense electron and ion beams, instabilities, turbulence, and filamentations. All of these phenomena seem to be closely correlated to the neutron production which may not be thermonuclear in origin at all. An investigation is conducted of the physical processes that could be playing an important role in this case. A simplified interpretation of the phenomena could be that at a high line density the plasma focus is violently MHD unstable, but can form reconnecting bubbles.

  8. On the Riemann theta function of a trigonal curve and solutions of the Boussinesq and KP equations

    NASA Astrophysics Data System (ADS)

    Matveev, V. B.; Smirnov, A. O.

    1987-07-01

    Recently, considerable progress has been made in understanding the nature of the algebro-geometrical superposition principles for the solutions of nonlinear completely integrable evolution equations, and mainly for the equations related to hyperelliptic Riemann surfaces. Here we find such a superposition formula for particular real solutions of the KP and Boussinesq equations related to the nonhyperelliptic curve ω4 = (λ - E 1) (λ - E 2) (λ - E 3) (λ - E 4). It is shown that the associated Riemann theta function may be decomposed into a sum containing two terms, each term being the product of three one-dimensional theta functions. The space and time variables of the KP and Boussinesq equations enter into the arguments of these one-dimensional theta functions in a linear way.

  9. Conceptual Design of a Z-Pinch Fusion Propulsion System

    NASA Technical Reports Server (NTRS)

    Adams, Robert; Polsgrove, Tara; Fincher, Sharon; Fabinski, Leo; Maples, Charlotte; Miernik, Janie; Stratham, Geoffrey; Cassibry, Jason; Cortez, Ross; Turner, Matthew; Santarius, John; Percy, Thomas

    2010-01-01

    This slide presentation reviews a project that aims to develop a conceptual design for a Z-pinch thruster, that could be applied to develop advanced thruster designs which promise high thrust/high specific impulse propulsion. Overviews shows the concept of the design, which use annular nozzles with deuterium-tritium (D-T) fuel and a Lithium mixture as a cathode, Charts show the engine performance as a function of linear mass, nozzle performance (i.e., plasma segment trajectories), and mission analysis for possible Mars and Jupiter missions using this concept for propulsion. Slides show views of the concepts for the vehicle configuration, thrust coil configuration, the power management system, the structural analysis of the magnetic nozzle, the thermal management system, and the avionics suite,

  10. Large linear magnetoresistance in a GaAs/AlGaAs heterostructure

    SciTech Connect

    Aamir, Mohammed Ali Goswami, Srijit Ghosh, Arindam; Baenninger, Matthias; Farrer, Ian; Ritchie, David A.; Tripathi, Vikram; Pepper, Michael

    2013-12-04

    We report non-saturating linear magnetoresistance (MR) in a two-dimensional electron system (2DES) at a GaAs/AlGaAs heterointerface in the strongly insulating regime. We achieve this by driving the gate voltage below the pinch-off point of the device and operating it in the non-equilibrium regime with high source-drain bias. Remarkably, the magnitude of MR is as large as 500% per Tesla with respect to resistance at zero magnetic field, thus dwarfing most non-magnetic materials which exhibit this linearity. Its primary advantage over most other materials is that both linearity and the enormous magnitude are retained over a broad temperature range (0.3 K to 10 K), thus making it an attractive candidate for cryogenic sensor applications.

  11. An investigation of transient pressures and plasma properties in a pinched plasma column. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Stover, E. K.; York, T. M.

    1971-01-01

    The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with several plasma diagnostics; they were: a rapid response pressure transducer, a magnetic field probe, a voltage probe, and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior: (1) strong axial pressure asymmetry noted early in plasma column lifetime, (2) followed by plasma heating in which there is a rapid rise in static pressure, and (3) a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating could be attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity.

  12. Theta synchronizes the activity of medial prefrontal neurons during learning.

    PubMed

    Paz, Rony; Bauer, Elizabeth P; Paré, Denis

    2008-07-01

    Memory consolidation is thought to involve the gradual transfer of transient hippocampal-dependent traces to distributed neocortical sites via the rhinal cortices. Recently, medial prefrontal (mPFC) neurons were shown to facilitate this process when their activity becomes synchronized. However, the mechanisms underlying this enhanced synchrony remain unclear. Because the hippocampus projects to the mPFC, we tested whether theta oscillations contribute to synchronize mPFC neurons during learning. Thus, we obtained field (LFP) and unit recordings from multiple mPFC sites during the acquisition of a trace-conditioning task, where a visual conditioned stimulus (CS) predicted reward delivery. In quiet waking, the activity of mPFC neurons was modulated by theta oscillations. During conditioning, CS presentation caused an increase in mPFC theta power that augmented as the CS gained predictive value for reward delivery. This increased theta power coincided with a transient theta phase locking at distributed mPFC sites, an effect that was also manifest in the timing of mPFC unit activity. Overall, these results show that theta oscillations contribute to synchronize neuronal activity at distributed mPFC sites, suggesting that the hippocampus, by generating a stronger theta source during learning, can synchronize mPFC activity, in turn facilitating rhinal transfer of its activity to the neocortex. PMID:18612069

  13. Note: high frequency vibration rejection using a linear shaft actuator-based image stabilizing device via vestibulo-ocular reflex adaptation control method.

    PubMed

    Koh, Doo-Yeol; Kim, Young-Kook; Kim, Kyung-Soo; Kim, Soohyun

    2013-08-01

    In mobile robotics, obtaining stable image of a mounted camera is crucial for operating a mobile system to complete given tasks. This note presents the development of a high-speed image stabilizing device using linear shaft actuator, and a new image stabilization method inspired by human gaze stabilization process known as vestibulo-ocular reflex (VOR). In the proposed control, the reference is adaptively adjusted by the VOR adaptation control to reject residual vibration of a camera as the VOR gain converges to optimal state. Through experiments on a pneumatic vibrator, it will be shown that the proposed system is capable of stabilizing 10 Hz platform vibration, which shows potential applicability of the device to a high-speed mobile robot. PMID:24007125

  14. Note: High frequency vibration rejection using a linear shaft actuator-based image stabilizing device via vestibulo-ocular reflex adaptation control method

    NASA Astrophysics Data System (ADS)

    Koh, Doo-Yeol; Kim, Young-Kook; Kim, Kyung-Soo; Kim, Soohyun

    2013-08-01

    In mobile robotics, obtaining stable image of a mounted camera is crucial for operating a mobile system to complete given tasks. This note presents the development of a high-speed image stabilizing device using linear shaft actuator, and a new image stabilization method inspired by human gaze stabilization process known as vestibulo-ocular reflex (VOR). In the proposed control, the reference is adaptively adjusted by the VOR adaptation control to reject residual vibration of a camera as the VOR gain converges to optimal state. Through experiments on a pneumatic vibrator, it will be shown that the proposed system is capable of stabilizing 10 Hz platform vibration, which shows potential applicability of the device to a high-speed mobile robot.

  15. The Study of a Fibre Z-Pinch

    NASA Astrophysics Data System (ADS)

    Klir, Daniel

    2007-03-01

    This thesis presents the results of fibre Z-pinch experiments carried out on the Z-150 device at the CTU in Prague. The generator that was used to drive the experiments consisted of one capacitor of 3e-6 F capacitance. In the case of 20 kV charging voltage, the current was peaking at 80 kA with a 850 ns quarter period. The Z-pinch was formed from carbon fibres of 15 micrometer diameter and 1 cm length. The discharge was observed by a large number of diagnostic tools. This comprehensive set of diagnostics enabled us to describe the gross dynamics of the Z-pinch. It was found out that after the breakdown a low density coronal plasma was formed while the fibre diameter remained almost unchanged. This low density corona was carrying almost all the current of the order of 10 kA. When the current had built up, the implosion of the corona onto the central fibre occurred. The implosion velocity approached the value of 2e5 m/s. When the imploded corona had reached the fibre, the dip in dI/dt, voltage peak up to 10 kV, and XUV pulse of a 10-30 ns width were observed. XUV radiation was emitted from several bright spots which corresponded to the interaction of m=0 instability necks with the dense core. The electron temperature and density were approximately 80 eV and 10e25 per cubic meter, respectively. Although the presence of a fibre did not significantly suppress MHD instabilities, they were not disruptive. After the fibre ablation, i.e. after 500 ns, material evaporated from electrodes started to play a dominant role. The observed plasma column seemed to be MHD unstable and when m=0 instabilities had developed, X-ray pulses were emitted from several hot spots, particularly near the anode. At that time the voltage peak of up to 30 kV was detected.

  16. Fracture Fabrication of a Multi-scale, Channel Device that Efficiently Captures and Linearizes DNA from Dilute Solutions

    PubMed Central

    Kim, Byoung Choul; Weerappuli, Priyan; Thouless; Takayama, Shuichi

    2015-01-01

    This paper describes a simple technique for patterning channels on elastomeric substrates, at two distinct scales of depth, through the use of controlled fracture. Control of channel depth is achieved by the careful use of different layers of PDMS, where the thickness and material properties of each layer, and the position of layers relative to one another, dictate the depth of the channels formed. The system created in this work consists of a single ‘deep’ channel, whose width can be adjusted between the micron- and nano-scale by the controlled application or removal of a uniaxial strain, and an array of ‘shallow’ nano-scale channels oriented perpendicular to the ‘deep’ channel. The utility of this system is demonstrated through the successful capture and linearization of DNA from a dilute solution, by executing a two-step ‘concentrate-then-linearize’ procedure. When the ‘deep’ channel is in its open state, and a voltage is applied across the channel network, an overlapping electric double layer forms within the ‘shallow’ channel array. This overlapping electric double layer is used to prevent passage of DNA into the ‘shallow’ channels when the DNA molecules migrate into the junctional region by electrophoresis. Release of the applied strain then allows the ‘deep’ channel to return to its closed state, reducing the cross-sectional area of this channel from the micro- to the nano-scale. The resulting hydrodynamic flow and nano-confinement effects then combine to efficiently uncoil and trap the DNA in its linearized form. By adopting this strategy, we were able to overcome the entropic barriers associated with capturing and linearizing DNA derived from a dilute solution. PMID:25589471

  17. Network mechanisms of responsiveness to continuous theta-burst stimulation.

    PubMed

    Rizk, Sviatlana; Ptak, Radek; Nyffeler, Thomas; Schnider, Armin; Guggisberg, Adrian G

    2013-10-01

    Continuous theta-burst stimulation (cTBS) can modify behavior, but effects are inconsistent and their mechanisms insufficiently understood. As coherence in resting-state networks influences human behavior, we hypothesized that cTBS may act via modulation of neural oscillation coherence. This study used electroencephalography (EEG) to investigate whether behavioral effects of cTBS on visuospatial attention are associated with coherence changes in the attention network. In healthy human subjects, cTBS of the right posterior parietal cortex (PPC) and the right frontal eye field was compared with sham stimulation. Effects on visuospatial attention were quantified with a visual exploration task, and network effects were assessed from surface EEG with inverse solutions and source coherence analyses. Before stimulation, left visual exploration was linearly correlated with alpha-band coherence between the right temporo-parietal cortex and the rest of the brain. Posterior parietal cortex stimulation induced neglect-like visual exploration behavior in the majority, but not all, subjects. It reduced alpha-band coherence between the stimulation site and the rest of the brain but also enhanced it between the contralateral left parietal cortex and the rest of the brain. The contralateral increase correlated with the induced reduction in left visual attention. The behavioral response of individual participants to cTBS could be predicted by coherence in the right temporo-parietal junction before stimulation. Behavioral effects of cTBS therefore depend on network states before stimulation and are linearly associated with changes in network interactions. In particular, cTBS modulates an interhemispheric competition in alpha-band coherence. EEG network imaging might help to optimize therapeutic cTBS in the future. PMID:23941616

  18. Confocal reflectance theta line-scanner for imaging tissues in vivo

    NASA Astrophysics Data System (ADS)

    Dwyer, Peter J.; DiMarzio, Charles A.; Fox, William J.; Zavislan, James M.; Rajadhyaksha, Milind

    2005-03-01

    A confocal reflectance theta line-scanner is being developed for imaging human tissues in vivo. The theta line scanner design potentially offers a newer alternative to current point scanners that may simplify the optics, electronics and mechanics and lead to smaller, inexpensive confocal microscopes. An oscillating galvanometric mirror directly scans in the pupil of a cylindrical lens and one-half of an objective lens, to produce a focused, scanned line in the object plane within tissue. Backscattered light is collected by the other half of the objective lens and focused onto a linear CMOS detector. The illumination is with a diode laser at 830 nm and imaging with a 10X, 0.8 NA water immersion lens. The illumination and detection paths are thus oriented at an angle (theta) to each other, and are separate everywhere except in the confocal plane. This configuration eliminates back-scattered light from optical components and enhances contrast. Optical design analysis has been verified with experimental results, demonstrating lateral resolution on the order of 1 um and optical sectioning (axial resolution) better than 5 um within living human skin. A Fourier optics-based analytical model is in progress to evaluate line spread functions versus illumination and detection pupil conditions. Nuclear and cellular detail is imaged in the epidermis of human skin in vivo and ex vivo (freshly excised specimens). Such a scanner may prove useful for imaging human tissues in clinical and intra-operative settings.

  19. Intrinsic Cornu Ammonis Area 1 Theta-Nested Gamma Oscillations Induced by Optogenetic Theta Frequency Stimulation

    PubMed Central

    Butler, James L.; Mendonça, Philipe R. F.; Robinson, Hugh P. C.

    2016-01-01

    Gamma oscillations (30–120 Hz) are thought to be important for various cognitive functions, including perception and working memory, and disruption of these oscillations has been implicated in brain disorders, such as schizophrenia and Alzheimer's disease. The cornu ammonis area 1 (CA1) of the hippocampus receives gamma frequency inputs from upstream regions (cornu ammonis area 3 and medial entorhinal cortex) and generates itself a faster gamma oscillation. The exact nature and origin of the intrinsic CA1 gamma oscillation is still under debate. Here, we expressed channelrhodopsin-2 under the CaMKIIα promoter in mice and prepared hippocampal slices to produce a model of intrinsic CA1 gamma oscillations. Sinusoidal optical stimulation of CA1 at theta frequency was found to induce robust theta-nested gamma oscillations with a temporal and spatial profile similar to CA1 gamma in vivo. The results suggest the presence of a single gamma rhythm generator with a frequency range of 65–75 Hz at 32°C. Pharmacological analysis found that the oscillations depended on both AMPA and GABAA receptors. Cell-attached and whole-cell recordings revealed that excitatory neuron firing slightly preceded interneuron firing within each gamma cycle, suggesting that this intrinsic CA1 gamma oscillation is generated with a pyramidal–interneuron circuit mechanism. SIGNIFICANCE STATEMENT This study demonstrates that the cornu ammonis area 1 (CA1) is capable of generating intrinsic gamma oscillations in response to theta input. This gamma generator is independent of activity in the upstream regions, highlighting that CA1 can produce its own gamma oscillation in addition to inheriting activity from the upstream regions. This supports the theory that gamma oscillations predominantly function to achieve local synchrony, and that a local gamma generated in each area conducts the signal to the downstream region. PMID:27076416

  20. An ICF system based on Z-pinch radiation produced by an explosive magnetic generator

    NASA Astrophysics Data System (ADS)

    Garanin, S. G.; Ivanovsky, A. V.; Mkhitariyan, L. S.

    2011-10-01

    It is known that a thermonuclear target can be ignited by an implosion accomplished with X-radiation generated by means of laser radiation conversion or by a Z pinch formed by a high-power current pulse. For these purposes laser facility NIF has been constructed in the USA, 'Megajoule' is being constructed in France and there is a project of laser facility UFL in Russia. The project of stationary facility X has been developed in SNL USA to produce a Z pinch capable of generating an x-ray pulse with parameters close to the ignition threshold. There is a great chance, however, that the already tested technologies, including disc explosive magnetic generators (DEMG), systems of current peaking based on electrically exploded foil opening switches and high-voltage switching devices, allow the intriguing problem of the ignition feasibility to be solved and the quickest and cheapest way to accomplish this to be provided. To explore this possibility, the paper will sequentially analyse the ignition conditions. The required parameters of Z pinch X-radiation and the size of the DEMG-based facility to obtain these parameters will be evaluated. Capabilities of the new current sources based on the DEMG and of the devices shaping a current pulse will be presented and compared with those required for the ignition.

  1. Turbulent Equipartition Theory of Toroidal Momentum Pinch

    SciTech Connect

    T.S. Hahm, P.H. Diamond, O.D. Gurcan, and G. Rewaldt

    2008-01-31

    The mode-independet part of magnetic curvature driven turbulent convective (TuroCo) pinch of the angular momentum density [Hahm et al., Phys. Plasmas 14,072302 (2007)] which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of "magnetically weighted angular momentum density," nmi U|| R/B2, and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustratd that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms which exist in a simpler geometry.

  2. Turbulent equipartition theory of toroidal momentum pinch

    SciTech Connect

    Hahm, T. S.; Rewoldt, G.; Diamond, P. H.; Gurcan, O. D.

    2008-05-15

    The mode-independent part of the magnetic curvature driven turbulent convective (TurCo) pinch of the angular momentum density [Hahm et al., Phys. Plasmas 14, 072302 (2007)], which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of 'magnetically weighted angular momentum density', nm{sub i}U{sub parallel}R/B{sup 2}, and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustrated that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms that exist in a simpler geometry.

  3. A Robotic Pinch-Off System for the Sealing of Neutron Tube Assemblies

    SciTech Connect

    Ney, R.J.; Schmale, D.T.

    1999-01-01

    The process of manufacturing the MC4277 Neutron Tube requires the evacuation of the device through a 4.76 mm (.1875 in.) OD copper tube. Eight tubes are simultaneously evacuated and then baked out. When the process is completed, the tubes must be separated from the system without compromising the ultra-high vacuum in the tube and the system. Previously, a manual pinch-off tool was used. This procedure required up to 3 operators with a high probability of creating defective seals or destroyed tubes. Two new identical robotic systems were built to allow a single operator to consistently produce good tubes with perfect seals. These systems have the added capability of partially pinching off tubes at jaw displacements repeatable to *0.05 mm (kO.002 in.). Both systems have operated flawlessly since their installation in January and March, 1998. A detailed description of these systems is given in this report.

  4. Z-pinch X-ray spectra obtained with a polarization splitting crystal

    NASA Astrophysics Data System (ADS)

    Presura, R.; Wallace, M. S.; Pereira, N. R.

    2014-10-01

    Anisotropy in a plasma may cause polarization of the spectral lines emitted. For example, the X-rays emitted by Z-pinch plasmas may be polarized if electron beams are present. To detect the polarization, we developed an X-ray spectropolarimeter using a single polarization-splitting crystal. Reflections on intersecting internal planes of the crystal select lines with mutually orthogonal linear polarization. The (10-10) internal planes of a quartz crystal can be used to split several lines of the Al K-shell spectrum according to polarization. We applied this technique to several types of Al wire arrays (cylindrical, conical, and X-pinches), expected to produce increasing beam contributions to the electron population. Peculiarities of the instrument set-up and of the spectra analysis will be presented. This work was supported by DOE, NNSA Grant DE-NA0001834 and cooperative Agreement DE-FC52-06NA27616.

  5. Microturbulence studies of pulsed poloidal current drive discharges in the reversed field pinch

    NASA Astrophysics Data System (ADS)

    Carmody, D.; Pueschel, M. J.; Anderson, J. K.; Terry, P. W.

    2015-01-01

    Experimental discharges with pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed field pinch are investigated using a semi-analytic equilibrium model in the gyrokinetic turbulence code Gene. PPCD cases, with plasma currents of 500 kA and 200 kA, exhibit a density-gradient-driven trapped electron mode (TEM) and an ion temperature gradient mode, respectively. Relative to expectations of tokamak core plasmas, the critical gradients for the onset of these instabilities are found to be greater by roughly a factor of the aspect ratio. A significant upshift in the nonlinear TEM transport threshold, previously found for tokamaks, is confirmed in nonlinear reversed field pinch simulations and is roughly three times the threshold for linear instability. The simulated heat fluxes can be brought in agreement with measured diffusivities by introducing a small, resonant magnetic perturbation, thus modeling the residual fluctuations from tearing modes. These fluctuations significantly enhance transport.

  6. Microturbulence studies of pulsed poloidal current drive discharges in the reversed field pinch

    SciTech Connect

    Carmody, D. Pueschel, M. J.; Anderson, J. K.; Terry, P. W.

    2015-01-15

    Experimental discharges with pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed field pinch are investigated using a semi-analytic equilibrium model in the gyrokinetic turbulence code GENE. PPCD cases, with plasma currents of 500 kA and 200 kA, exhibit a density-gradient-driven trapped electron mode (TEM) and an ion temperature gradient mode, respectively. Relative to expectations of tokamak core plasmas, the critical gradients for the onset of these instabilities are found to be greater by roughly a factor of the aspect ratio. A significant upshift in the nonlinear TEM transport threshold, previously found for tokamaks, is confirmed in nonlinear reversed field pinch simulations and is roughly three times the threshold for linear instability. The simulated heat fluxes can be brought in agreement with measured diffusivities by introducing a small, resonant magnetic perturbation, thus modeling the residual fluctuations from tearing modes. These fluctuations significantly enhance transport.

  7. Hippocampal-Prefrontal Theta Oscillations Support Memory Integration.

    PubMed

    Backus, Alexander R; Schoffelen, Jan-Mathijs; Szebényi, Szabolcs; Hanslmayr, Simon; Doeller, Christian F

    2016-02-22

    Integration of separate memories forms the basis of inferential reasoning--an essential cognitive process that enables complex behavior. Considerable evidence suggests that both hippocampus and medial prefrontal cortex (mPFC) play a crucial role in memory integration. Although previous studies indicate that theta oscillations facilitate memory processes, the electrophysiological mechanisms underlying memory integration remain elusive. To bridge this gap, we recorded magnetoencephalography data while participants performed an inference task and employed novel source reconstruction techniques to estimate oscillatory signals from the hippocampus. We found that hippocampal theta power during encoding predicts subsequent memory integration. Moreover, we observed increased theta coherence between hippocampus and mPFC. Our results suggest that integrated memory representations arise through hippocampal theta oscillations, possibly reflecting dynamic switching between encoding and retrieval states, and facilitating communication with mPFC. These findings have important implications for our understanding of memory-based decision making and knowledge acquisition. PMID:26832442

  8. Reversed theta sequences of hippocampal cell assemblies during backward travel.

    PubMed

    Cei, Anne; Girardeau, Gabrielle; Drieu, Céline; Kanbi, Karim El; Zugaro, Michaël

    2014-05-01

    Hippocampal cell assemblies coding for past, present and future events form theta-timescale (~100 ms) sequences that represent spatio-temporal episodes. However, the underlying mechanisms remain largely unknown. We recorded hippocampal and entorhinal cortical activity as rats experienced backward travel on a model train. Although the firing fields of place cells remained stable, the order in which they were activated in the theta sequence was reversed during backward travel. Thus, hippocampal cell assemblies coordinated their relative timing to correctly predict the sequential traversal of place fields in reverse order. At the single-cell level, theta phase represented distance traveled through the field, even though the head of the rat was oriented opposite to travel direction and entorhinal head-direction cells maintained their preferred firing direction. Our results challenge most theoretical models of theta sequence generation in the hippocampus. PMID:24667574

  9. Simultaneous observations of a theta aurora and associated magnetotail plasmas

    SciTech Connect

    Huang, C.Y.; Craven, J.D.; Frank, L.A.

    1989-08-01

    Observations of a transpolar arc and simultaneous measurements of associated plasmas in the magnetotail lobe on March 25, 1982, are presented. The auroral imager on board Dynamics Explorer 1 observes a theta aurora in the northern polar cap for more than 2 hours, between 0502 and 0720 UT. ISEE 1 is located in the southern lobe of the geomagnetic tail at a distance of 22.2 RE during this time. The plasma and particle detectors measure intermittent bursts of particle fluxes between 0530 and 0705 UT. The observations suggest that these particle fluxes represent the high-altitude signature of a theta aurora in the southern polar cap. The relatively dense and energetic plasmas are organized into several filamentary structures. Magnetic mapping between the two polar regions indicates that the theta aurora in the southern hemisphere is a mirror reflection about the noon-midnight meridional plane of the theta aurora in the northern hemisphere.

  10. Neutrino mass hierarchy determination for theta{sub 13} = 0

    SciTech Connect

    Gandhi, Raj; Ghoshal, Pomita; Goswami, Srubabati; Sankar, S. Uma

    2010-03-30

    We examine the possibility of determining the neutrino mass hierarchy in the limit theta{sub 13} = 0 using atmospheric neutrinos as the source. In this limit, theta{sub 13} driven matter effects are absent so independent measurements of DELTA{sub 31} and DELTA{sub 32} can, in principle, lead to hierarchy determination. Since their difference is DELTA{sub 21}, one needs an experimental arrangement where DELTA{sub 21}L/E > or approx. 1 can be achieved. This can be satisfied by atmospheric neutrinos which have a large range of L and E. Still, we find that hierarchy determination in the theta{sub 13} = 0 limit with atmospheric neutrinos is not a realistic possibility, even in conjunction with a beam experiment like T2K or NOnuA. We discuss why, and also reiterate the general conditions for hierarchy determination if theta{sub 13} = 0.

  11. Probing {theta}{sub 23} in neutrino telescopes

    SciTech Connect

    Choubey, Sandhya; Niro, Viviana; Rodejohann, Werner

    2008-06-01

    Among all neutrino mixing parameters, the atmospheric neutrino mixing angle {theta}{sub 23} introduces the strongest variation on the flux ratios of ultrahigh-energy neutrinos. We investigate the potential of these flux ratio measurements at neutrino telescopes to constrain {theta}{sub 23}. We consider astrophysical neutrinos originating from pion, muon-damped, and neutron sources and make a comparative study of their sensitivity reach to {theta}{sub 23}. It is found that neutron sources are most favorable for testing deviations from maximal {theta}{sub 23}. Using a {chi}{sup 2} analysis, we show, in particular, the power of combining (i) different flux ratios from the same type of source, and also (ii) combining flux ratios from different astrophysical sources. We include in our analysis 'impure' sources, i.e., deviations from the usually assumed initial (1 ratio 2 ratio 0), (0 ratio 1 ratio 0), or (1 ratio 0 ratio 0) flux compositions.

  12. The cos-theta coil re-re-visited

    NASA Astrophysics Data System (ADS)

    Crawford, Christopher

    2013-10-01

    Precision measurement of symmetry violating effects such the electric dipole moment (EDM) of fundamental particles requires extremely uniform fields. The cos-theta coil is the standard workhorse for generating uniform transverse magnetic fields in these experiments. Limitations in field uniformity include fringe effects (finite length), discretization (finite number of wires), and construction tolerance (finite resources). The field can be isolated from its environment by superposition of two coaxial cos-theta coils of different radii and opposite magnetic moment (double-cos-theta coil), or by shielding the coil inside a permeable or superconducting cylinder. I will discuss methods for optimizing the field uniformity of a compact cos-theta coil, and compare the ultimate limit on errors due to each source described above. Within the context of the scalar potential, I will show a straightforward generalization to non-circular coils with z- or ϕ-symmetry. Supported in part by DOE contract DE-SC0008107.

  13. Simultaneous observations of a theta aurora and associated magnetotail plasmas

    NASA Technical Reports Server (NTRS)

    Huang, C. Y.; Craven, J. D.; Frank, L. A.

    1989-01-01

    Observations of a transpolar arc and simultaneous measurements of associated plasmas in the magnetotail lobe on March 25, 1982, are presented. The auroral imager on board Dynamics Explorer 1 observes a theta aurora in the northern polar cap for more than two hours, between 0502 and 0720 UT. ISEE 1 is located in the southern lobe of the geomagnetic tail at a distance of 22.2 R(E) during this time. The plasma and particle detectors measure intermittent bursts of particle fluxes between 0530 and 0705 UT. The observations suggest that these particle fluxes represent the high-altitude signature of a theta aurora in the southern polar cap. The relatively dense and energetic plasmas are organized into several filamentary structures. Magnetic mapping between the two polar regions indicates that the theta aurora in the Southern Hemisphere is a mirror reflection about the noon-midnight meridional plane of the theta aurora in the Northern Hemisphere.

  14. The quantum pinch effect in semiconducting quantum wires: A bird’s-eye view

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2016-01-01

    Those who measure success with culmination do not seem to be aware that life is a journey not a destination. This spirit is best reflected in the unceasing failures in efforts for solving the problem of controlled thermonuclear fusion for even the simplest pinches for over decades; and the nature keeps us challenging with examples. However, these efforts have permitted researchers the obtention of a dense plasma with a lifetime that, albeit short, is sufficient to study the physics of the pinch effect, to create methods of plasma diagnostics, and to develop a modern theory of plasma processes. Most importantly, they have impregnated the solid state plasmas, particularly the electron-hole plasmas in semiconductors, which do not suffer from the issues related with the confinement and which have demonstrated their potential not only for the fundamental physics but also for the device physics. Here, we report on a two-component, cylindrical, quasi-one-dimensional quantum plasma subjected to a radial confining harmonic potential and an applied magnetic field in the symmetric gauge. It is demonstrated that such a system, as can be realized in semiconducting quantum wires, offers an excellent medium for observing the quantum pinch effect at low temperatures. An exact analytical solution of the problem allows us to make significant observations: Surprisingly, in contrast to the classical pinch effect, the particle density as well as the current density display a determinable maximum before attaining a minimum at the surface of the quantum wire. The effect will persist as long as the equilibrium pair density is sustained. Therefore, the technological promise that emerges is the route to the precise electronic devices that will control the particle beams at the nanoscale.

  15. Medial prefrontal theta phase coupling during spatial memory retrieval.

    PubMed

    Kaplan, Raphael; Bush, Daniel; Bonnefond, Mathilde; Bandettini, Peter A; Barnes, Gareth R; Doeller, Christian F; Burgess, Neil

    2014-06-01

    Memory retrieval is believed to involve a disparate network of areas, including medial prefrontal and medial temporal cortices, but the mechanisms underlying their coordination remain elusive. One suggestion is that oscillatory coherence mediates inter-regional communication, implicating theta phase and theta-gamma phase-amplitude coupling in mnemonic function across species. To examine this hypothesis, we used non-invasive whole-head magnetoencephalography (MEG) as participants retrieved the location of objects encountered within a virtual environment. We demonstrate that, when participants are cued with the image of an object whose location they must subsequently navigate to, there is a significant increase in 4-8 Hz theta power in medial prefrontal cortex (mPFC), and the phase of this oscillation is coupled both with ongoing theta phase in the medial temporal lobe (MTL) and perceptually induced 65-85 Hz gamma amplitude in medial parietal cortex. These results suggest that theta phase coupling between mPFC and MTL and theta-gamma phase-amplitude coupling between mPFC and neocortical regions may play a role in human spatial memory retrieval. PMID:24497013

  16. Analytical Insights on Theta-Gamma Coupled Neural Oscillators

    PubMed Central

    2013-01-01

    In this paper, we study the dynamics of a quadratic integrate-and-fire neuron, spiking in the gamma (30–100 Hz) range, coupled to a delta/theta frequency (1–8 Hz) neural oscillator. Using analytical and semianalytical methods, we were able to derive characteristic spiking times for the system in two distinct regimes (depending on parameter values): one regime where the gamma neuron is intrinsically oscillating in the absence of theta input, and a second one in which gamma spiking is directly gated by theta input, i.e., windows of gamma activity alternate with silence periods depending on the underlying theta phase. In the former case, we transform the equations such that the system becomes analogous to the Mathieu differential equation. By solving this equation, we can compute numerically the time to the first gamma spike, and then use singular perturbation theory to find successive spike times. On the other hand, in the excitable condition, we make direct use of singular perturbation theory to obtain an approximation of the time to first gamma spike, and then extend the result to calculate ensuing gamma spikes in a recursive fashion. We thereby give explicit formulas for the onset and offset of gamma spike burst during a theta cycle, and provide an estimation of the total number of spikes per theta cycle both for excitable and oscillator regimes. PMID:23945442

  17. Bent Crystal Monochromator with Constant Crystal Center Position and 2-theta Arm for a Dispersive Beamline

    SciTech Connect

    Neuenschwander, Regis T.; Tolentino, Helio C.N.

    2004-05-12

    For the new LNLS dispersive beam line it was designed a single-crystal monochromator and a 2-theta arm. The monochromator uses a new bender design assembled on the top of an in-vacuum HUBER goniometer. This bender is able to apply independent torque on each extremity of the crystal in a way that changes in the curvature radius do not affect the position of the center of the crystal. It also has a twist mechanism, based on eccentric bearings and elastic components. The crystal extremities are clamped to the bender using two water-cooled copper blocks, for thermal stabilization. All the bender's movements are done with vacuum compatible stepping-motors. The vacuum chamber was built with enough space to allow future installation of another bender for crystals with different Bragg planes. The internal mechanics is isolated from the vacuum chamber and can move up and down with three high precision jacks. The design of the 2-theta arm is based on two linear translation stages and some special bearings. The two stages are equipped with linear encoders, ball screws end linear bearings. With a proper alignment procedure, it is possible to find the equations that controls each translation stage in order to get a virtual rotation referenced to the monochromator center. The main arm is composed of a steel frame, a 3m long granite block, a central aluminum optical rail and two auxiliary side rails.

  18. Application of linear response theory to experimental data of simultaneous radiation and annealing response of a CMOS device. Quarterly report No. 3, 8 June-8 September 1988

    SciTech Connect

    Litovchenko, V.

    1988-01-01

    Results from the application of linear response theory are compared to experimental data from simultaneous radiation and annealing response of a CMOS device. In particular, a method is applied which was developed earlier to determine the characteristic time, t(0), as well as the parameters A and C in the 1n(t) dependence of the linear response function R(t) = -C + A1n(1-t/t(0)). The method is based on a study of the linear response for t being much less than t(0), when R(t) can be expanded in a power series of t: R(t) = R(0) + R'(0)t + 1/2R''(0)t-squared + 1/3R'''(0)t-cubed + ..., where R'(0) and R''(0) are, respectively, the first and second derivatives of R with respect to t. To find the linear response, R(t-t') is substituted in the form of this power series equation into a general equation for the shift of the threshold potential. To test the method, irradiation experiments were conducted on RCA 10(6) rad-hard CMOS IC's. A dose rate of approximately 130 rads/min was used. An IC was irradiated with Co-60 gamma rays for several hours, taking measurements of the threshold potential for one n-channel and one p-channel transistor every ten minutes. For the p-channel transistor, t(0) was found to be approximately 110 min and for the n-channel, t(0) was approximately 70 min. For the p-channel, the theoretical curve deviates from the experimental points only after 70 min; for the n-channel, the deviation takes place after 45 min. Additional findings are discussed and the application of the method to pure annealing is described.

  19. A Experimental Study of the Dynamics of X-Pinch and Z-Pinch Plasmas

    NASA Astrophysics Data System (ADS)

    Kalantar, Daniel Husayn

    X-pinch experiments have been carried out using 12 to 100 μm diameter Al wires with peak currents of 330 to 380 kA. Two wires were placed between the output electrodes of a low inductance pulser so as to cross and touch at a single point, resulting in intense K-shell soft x-ray radiation from a sub-millimeter high temperature (300 to 700 eV) and density (2 times 10^{19} to 1 times 10^{21 } cm^{-3}) plasma at the cross point. Single wire z-pinch experiments were conducted for comparison. Additional x-pinch experiments were carried out using up to eight wires at peak currents from 280 kA to 1.0 MA. Intense soft x-ray emission from the cross region occurs in short bursts. Filtered GaAs:Cr photoconducting diodes and streaked x-ray pinhole images show individual bursts lasting <=1 ns. Time-integrated K-shell spectra obtained with a curved KAP crystal spectrograph were used to determine the electron temperature and density for individual bright spots. A sub-ns pulsed nitrogen laser was used for time -resolved schlieren and interferometry measurements of the unstable expansion of a coronal plasma that develops around the wires. The implosion and re-expansion of the corona at the x-pinch cross region was observed immediately prior to x-ray emission. Jets of plasma were ejected along the axis, as recorded in schlieren images and visible light frame images. Late in the pulse, gaps formed along the axis with electron density <=5 times 10^{17} cm^{-3}. Spectra indicated the presence of electron beams carrying the current in these gaps. Interferometry measurements provided the electron density profile late in the current pulse. Individual bursts of x-ray emission from one x -pinch were used to record a shadow of the dense core plasma at the initial wire position of a parallel x-pinch or z -pinch. This core expanded uniformly within the corona, surviving until it was disrupted by the implosion of the corona prior to soft x-ray emission. The Bennett relation is used to estimate

  20. Investigation on the pinch point position in heat exchangers

    NASA Astrophysics Data System (ADS)

    Pan, Lisheng; Shi, Weixiu

    2016-06-01

    The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out by theoretical method. The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties. In most cases, the pinch point locates at the bubble point for the evaporator and the dew point for the condenser. However, the pinch point shifts to the supercooled liquid state in the near critical conditions for the evaporator. Similarly, it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser. It even can shift to the working fluid entrance of the evaporator or the supercritical heater when the heat source fluid temperature is very high compared with the absorbing heat temperature. A wrong position for the pinch point may generate serious mistake. In brief, the pinch point should be founded by the iterative method in all conditions rather than taking for granted.

  1. Optical design and performance of F-Theta lenses for high-power and high-precision applications

    NASA Astrophysics Data System (ADS)

    Yurevich, V. I.; Grimm, V. A.; Afonyushkin, A. A.; Yudin, K. V.; Gorny, S. G.

    2015-09-01

    F-Theta lenses are widely used in remote laser processing. Nowadays, a large variety of scanning systems utilizing these devices are commercially available. In this paper, we demonstrate that all practical issues lose their triviality in designing high-performance F-Theta scanning systems. Laser power scaling requires attention to thermally-induced phenomena and ghost reflections. This requirement considerably complicates optimization of the optical configuration of the system and primary aberration correction, even during preliminary design. Obtaining high positioning accuracy requires taking into consideration all probable reasons for processing field distortion. We briefly describe the key engineering relationships and invariants as well as the typical design of a scanner lens and the main field-flattening techniques. Specific emphasis is directed to consideration of the fundamental nonlinearity of two-mirror scanners. To the best of our knowledge, this issue has not been yet studied. We also demonstrate the benefits of our F-Theta lens optimization technique, which uses a plurality of entrance pupils. The problems of eliminating focused ghost reflections and the effects of thermally-induced processes in high-power F-Theta lenses are considered. A set of multi-path 3D processing and laser cutting experiments were conducted and are presented herein to demonstrate the impact of laser beam degradation on the process performance. A selection of our non-standard optical designs is presented.

  2. Nonlocal Transport in the Reversed Field Pinch

    SciTech Connect

    Spizzo, G.; White, R. B.; Cappello, S.; Marrelli, L.

    2009-09-21

    Several heuristic models for nonlocal transport in plasmas have been developed, but they have had a limited possibility of detailed comparision with experimental data. Nonlocal aspects introduced by the existence of a known spectrum of relatively stable saturated tearing modes in a low current reversed field pinch offers a unique possibility for such a study. A numerical modelling of the magnetic structure and associated particle transport is carried out for the reversed-field pinch experiment at the Consorzio RFX, Padova, Italy. A reproduction of the tearing mode spectrum with a guiding center code1 reliably reproduces the observed soft X-ray tomography. Following particle trajectories in the stochastic magnetic field shows the transport across the unperturbed flux surfaces to be due to a spectrum of Levy flights, with the details of the spectrum position dependent. The resulting transport is subdiffusive, and cannot be described by Rechester-Rosenbluth diffusion, which depends on a random phase approximation. If one attempts to fit the local transport phenomenologically, the subdiffusion can be fit with a combination of diffusion and inward pinch2. It is found that whereas passing particles explore the stochastic field and hence participate in Levy flights, the trapped particles experience normal neoclassical diffusion. A two fluid nonlocal Montroll equation is used to model this transport, with a Levy flight defined as the motion of an ion during the period that the pitch has one sign. The necessary input to the Montroll equation consists of a time distribution for the Levy flights, given by the pitch angle scattering operator, and a distribution of the flight distances, determined numerically using a guiding center code. Results are compared to experiment. The relation of this formulation to fractional kinetics is also described.

  3. Parallel X pinches on the 1 MA COBRA pulser

    NASA Astrophysics Data System (ADS)

    Pikuz, S. A.; Shelkovenko, T. A.; Knapp, P. F.; Hoyt, C. L.; Greenly, J. B.; Wilhelm, H.; Hammer, D. A.

    2009-11-01

    Two standard and nested X pinches have been tested in parallel as the load on the 1MA, 100 ns risetime COBRA pulsed power generator at Cornell University. The spatial, temporal, and spectral parameters of the X pinches were studied using laser-based imaging, time gated XUV-sensitive cameras, a slit-step-wedge and pinhole cameras, X-ray spectroscopy and x-ray radiography. The latter includes testing a new method of point-projection quasi-monochromatic radiography. Electrical cross-talk of the X pinches was studied using very small B-dot probes placed in the space between X-pinches. The experiments show that the parallel nested x-pinches produce smaller, brighter and more stable x-ray source points than the standard configuration.

  4. Effect of transcranial magnetic stimulation on force of finger pinch

    NASA Astrophysics Data System (ADS)

    Odagaki, Masato; Fukuda, Hiroshi; Hiwaki, Osamu

    2009-04-01

    Transcranial magnetic stimulation (TMS) is used to explore many aspects of brain function, and to treat neurological disorders. Cortical motor neuronal activation by TMS over the primary motor cortex (M1) produces efferent signals that pass through the corticospinal tracts. Motor-evoked potentials (MEPs) are observed in muscles innervated by the stimulated motor cortex. TMS can cause a silent period (SP) following MEP in voluntary electromyography (EMG). The present study examined the effects of TMS eliciting MEP and SP on the force of pinching using two fingers. Subjects pinched a wooden block with the thumb and index finger. TMS was applied to M1 during the pinch task. EMG of first dorsal interosseous muscles and pinch forces were measured. Force output increased after the TMS, and then oscillated. The results indicated that the motor control system to keep isotonic forces of the muscles participated in the finger pinch was disrupted by the TMS.

  5. Thermal Runaway Risk Evaluation of Li-Ion Cells Using a Pinch-Torsion Test

    SciTech Connect

    Ren, Fei; Cox, Thomas S; Wang, Hsin

    2014-01-01

    Internal short circuit (ISCr) can lead to failure of Li-ion cells and sometimes result in thermal runaway. Understanding the behavior of Li-ion cells in ISCr condition is thus critical to evaluate the safety of these energy storage devices. In the current work, a pinch-torsion test is developed to simulate ISCr in a controlled manner. It is demonstrated that the torsional component superimposed on compression loading can reduce the axial load required to induce ISCr with smaller short spot size. Using this pinch-torsion test, two commercial Li-ion pouch cells were tested under different state of charge (SOC). Based on the severity of the cell damage, a series of thermal runaway risk scores were used to rate the thermal stability of these cells. One of the cell types showed significantly increased hazard as the SOC increased while the other type exhibited relative uniform behavior among different SOC. Therefore this novel pinch-torsion test seems to be an attractive candidate for safety testing of Li-ion cells due to its abilities to consistently create small ISCr spots and to differentiate cell stability in a wide range of SOC.

  6. Thermal runaway risk evaluation of Li-ion cells using a pinch-torsion test

    NASA Astrophysics Data System (ADS)

    Ren, Fei; Cox, Thomas; Wang, Hsin

    2014-03-01

    Internal short circuit (ISCr) can lead to failure of Li-ion cells and sometimes result in thermal runaway. Understanding the behavior of Li-ion cells in ISCr condition is thus critical to evaluate the safety of these energy storage devices. In the current work, a pinch-torsion test is developed to simulate ISCr in a controlled manner. It is demonstrated that the torsional component superimposed on compression loading can reduce the axial load required to induce ISCr with smaller short spot size. Using this pinch-torsion test, two types of commercial Li-ion pouch cells were tested under different state of charge (SOC). Based on the severity of the cell damage, a series of thermal runaway risk scores were used to rate the thermal stability of these cells. One of the cell types showed significantly increased hazard as the SOC increased while the other type exhibited relative uniform behavior among different SOC. Therefore, this novel pinch-torsion test seems to be an attractive candidate for safety testing of Li-ion cells due to its abilities to consistently create small ISCr spots and to differentiate cell stability in a wide range of SOC.

  7. Dynamics and Stability of Self-similar Pinch-off via Surface Diffusion

    NASA Astrophysics Data System (ADS)

    Bernoff, Andrew J.; Bertozzi, Andrea L.; Witelski, Thomas P.

    1998-11-01

    The motion of an interface via surface diffusion is a well-known model in the study of thin solid filaments with application to such fields as integrated circuit technology. The interface moves with a normal velocity proportional to minus the surface Laplacian of its mean curvature. This flow conserves the volume enclosed inside the surface while minimizing its surface area. A cylindrical surface is unstable to long-wave perturbations, analogous to the Rayleigh instability in fluid dynamics. The initial instability leads to a conical pinch-off of the cylinder to form isolated spheres. We examine the structure of the pinch-off, showing it has self-similar structure, using asymptotic, numerical and analytical methods. In addition to a previously known solution(Wong et al. Scripta Mater.) 39(1):55, 1998, we find a countable set of similarity solutions, each with a different cone angle. We develop a stability theory in similarity variables that selects the original similarity solution as the only linearly stable one and consequently the only observable one. We confirm this theory via numerical simulations, using self-similar adaptive mesh refinement, of the pinch-off.

  8. Structural Basis of Competition Between PINCH1 and PINCH2 for Binding to the Ankyrin Repeat Domain of Integrin-linked Kinase

    SciTech Connect

    Chiswell, B.; Steigler, A; Razinia, Z; Nalibotski, E; Boggon, T; Calderwood, D

    2010-01-01

    Formation of a heterotrimeric IPP complex composed of integrin-linked kinase (ILK), the LIM domain protein PINCH, and parvin is important for signaling through integrin adhesion receptors. Mammals possess two PINCH genes that are expressed simultaneously in many tissues. PINCH1 and PINCH2 have overlapping functions and can compensate for one another in many settings; however, isoform-specific functions have been reported and it is proposed that association with a PINCH1- or PINCH2-containing IPP complex may provide a bifurcation point in integrin signaling promoting different cellular responses. Here we report that the LIM1 domains of PINCH1 and PINCH2 directly compete for the same binding site on the ankyrin repeat domain (ARD) of ILK. We determined the 1.9 {angstrom} crystal structure of the PINCH2 LIM1 domain complexed with the ARD of ILK, and show that disruption of this interface by point mutagenesis reduces binding in vitro and alters localization of PINCH2 in cells. These studies provide further evidence for the role of the PINCH LIM1 domain in association with ILK and highlight direct competition as one mechanism for regulating which PINCH isoform predominates in IPP complexes. Differential regulation of PINCH1 and PINCH2 expression may therefore provide a means for altering cellular integrin signaling pathways.

  9. Quantum modular forms, mock modular forms, and partial theta functions

    NASA Astrophysics Data System (ADS)

    Kimport, Susanna

    Defined by Zagier in 2010, quantum modular forms have been the subject of an explosion of recent research. Many of these results are aimed at discovering examples of these functions, which are defined on the rational numbers and have "nice" modularity properties. Though the subject is in its early stages, numerous results (including Zagier's original examples) show these objects naturally arising from many areas of mathematics as limits of other modular-like functions. One such family of examples is due to Folsom, Ono, and Rhoades, who connected these new objects to partial theta functions (introduced by Rogers in 1917) and mock modular forms (about which there is a rich theory, whose origins date back to Ramanujan in 1920). In this thesis, we build off of the work of Folsom, Ono, and Rhoades by providing an infinite family of quantum modular forms of arbitrary positive half-integral weight. Further, this family of quantum modular forms "glues" mock modular forms to partial theta functions and is constructed from a so-called "universal" mock theta function by extending a method of Eichler and Zagier (originally defined for holomorphic Jacobi forms) into a non-holomorphic setting. In addition to the infinite family, we explore the weight 1/2 and 3/2 functions in more depth. For both of these weights, we are able to explicitly write down the quantum modular form, as well as the corresponding "errors to modularity," which can be shown to be Mordell integrals of specific theta functions and, as a consequence, are real-analytic functions. Finally, we turn our attention to the partial theta functions associated with these low weight examples. Berndt and Kim provide asymptotic expansions for a certain class of partial theta functions as q approaches 1 radially within the unit disk. Here, we extend this work to not only obtain asymptotic expansions for this class of functions as q approaches any root of unity, but also for a certain class of derivatives of these functions

  10. Comprehensive behavioral model of dual-gate high voltage JFET and pinch resistor

    NASA Astrophysics Data System (ADS)

    Banáš, Stanislav; Paňko, Václav; Dobeš, Josef; Hanyš, Petr; Divín, Jan

    2016-09-01

    Many analog technologies operate in large voltage range and therefore include at least one or more high voltage devices built from low doped layers. Such devices exhibit effects not covered by standard compact models, namely pinching (depletion) effects, in high voltage FETs often called quasisaturation. For example, the conventional compact JFET model is insufficient and oversimplified. Its scalability is controlled by the area factor, which only multiplies currents and capacitances but does not take into account existing 3-D effects. Also the optional second independent gate is missing. Therefore, the customized four terminal (4T) model written in Verilog-A (FitzPatrick and Miller, 2007; Sagdeo, 2007) was developed. It converges very well, its simulation speed is comparable with conventional compact models, and contains all required phenomena, including parasitic effects as, for example, impact ionization. This model has universal usage for many types of devices in various high voltage technologies such as stand-alone voltage dependent resistor, pinch resistor, drift area of power FET, part of special high side or start-up devices, and dual-gate JFET.

  11. Harnessing the power of theta: natural manipulations of cognitive performance during hippocampal theta-contingent eyeblink conditioning.

    PubMed

    Hoffmann, Loren C; Cicchese, Joseph J; Berry, Stephen D

    2015-01-01

    Neurobiological oscillations are regarded as essential to normal information processing, including coordination and timing of cells and assemblies within structures as well as in long feedback loops of distributed neural systems. The hippocampal theta rhythm is a 3-12 Hz oscillatory potential observed during cognitive processes ranging from spatial navigation to associative learning. The lower range, 3-7 Hz, can occur during immobility and depends upon the integrity of cholinergic forebrain systems. Several studies have shown that the amount of pre-training theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning. Our lab has used a brain-computer interface (BCI) that delivers eyeblink conditioning trials contingent upon the explicit presence or absence of hippocampal theta. A behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to four-fold increase in learning speed. This behavioral effect is accompanied by enhanced amplitude and synchrony of hippocampal local field potential (LFP)s, multi-unit excitation, and single-unit response patterns that depend on theta state. Additionally, training in the presence of hippocampal theta has led to increases in the salience of tone-induced unit firing patterns in the medial prefrontal cortex, followed by persistent multi-unit activity during the trace interval. In cerebellum, rhythmicity and precise synchrony of stimulus time-locked LFPs with those of hippocampus occur preferentially under the theta condition. Here we review these findings, integrate them into current models of hippocampal-dependent learning and suggest how improvement in our understanding of neurobiological oscillations is critical for theories of medial temporal lobe processes underlying intact and pathological learning. PMID:25918501

  12. Harnessing the power of theta: natural manipulations of cognitive performance during hippocampal theta-contingent eyeblink conditioning

    PubMed Central

    Hoffmann, Loren C.; Cicchese, Joseph J.; Berry, Stephen D.

    2015-01-01

    Neurobiological oscillations are regarded as essential to normal information processing, including coordination and timing of cells and assemblies within structures as well as in long feedback loops of distributed neural systems. The hippocampal theta rhythm is a 3–12 Hz oscillatory potential observed during cognitive processes ranging from spatial navigation to associative learning. The lower range, 3–7 Hz, can occur during immobility and depends upon the integrity of cholinergic forebrain systems. Several studies have shown that the amount of pre-training theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning. Our lab has used a brain-computer interface (BCI) that delivers eyeblink conditioning trials contingent upon the explicit presence or absence of hippocampal theta. A behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to four-fold increase in learning speed. This behavioral effect is accompanied by enhanced amplitude and synchrony of hippocampal local field potential (LFP)s, multi-unit excitation, and single-unit response patterns that depend on theta state. Additionally, training in the presence of hippocampal theta has led to increases in the salience of tone-induced unit firing patterns in the medial prefrontal cortex, followed by persistent multi-unit activity during the trace interval. In cerebellum, rhythmicity and precise synchrony of stimulus time-locked LFPs with those of hippocampus occur preferentially under the theta condition. Here we review these findings, integrate them into current models of hippocampal-dependent learning and suggest how improvement in our understanding of neurobiological oscillations is critical for theories of medial temporal lobe processes underlying intact and pathological learning. PMID:25918501

  13. Theta EEG neurofeedback benefits early consolidation of motor sequence learning.

    PubMed

    Rozengurt, Roman; Barnea, Anat; Uchida, Sunao; Levy, Daniel A

    2016-07-01

    Procedural learning is subject to consolidation processes believed to depend on the modulation of functional connections involved in representing the acquired skill. While sleep provides the most commonly studied framework for such consolidation processes, posttraining modulation of oscillatory brain activity may also impact on plasticity processes. Under the hypothesis that consolidation of motor learning is associated with theta band activity, we used EEG neurofeedback (NFB) to enable participants to selectively increase either theta or beta power in their EEG spectra following the acquisition phase of motor sequence learning. We tested performance on a motor task before and after training, right after the NFB session to assess immediate NFB effects, 1 day after NFB to assess interaction between NFB effects and overnight sleep-dependent stabilization, and 1 week after the initial session, to assess the effects of NFB on long-term stabilization of motor training. We also explored the extent of the influence of single-electrode NFB on EEG recorded across the scalp. Results revealed a significantly greater improvement in performance immediately after NFB in the theta group than in the beta group. This effect continued for testing up to 1 week following training. Across participants, post-NFB improvement correlated positively with theta/beta ratio change achieved during NFB. Additionally, NFB was found to cause widespread band-power modulation beyond the electrode used for feedback. Thus, upregulating postlearning theta power may yield contributions to the immediate performance and subsequent consolidation of an acquired motor skill. PMID:27080752

  14. Theta oscillations and human navigation: a magnetoencephalography study.

    PubMed

    de Araújo, Dráulio B; Baffa, Oswaldo; Wakai, Ronald T

    2002-01-01

    Magnetoencephalography (MEG) was used to study alpha and theta activity while subjects navigated through a computer-generated virtual reality town. The subjects were first allowed to explore the environment freely. They then had to navigate from a starting point to a destination, knowing that an obstruction would appear at one of several possible locations along the main route and force them to take a detour. Spatiotemporal analysis of the theta and alpha bands were performed (1) prior to the start of navigation, (2) from the start of navigation until the obstruction was encountered, (3) during the time subjects were contemplating a detour and were not navigating, and (4) from the resumption of navigation until the destination was reached. In all subjects, theta power was strongest during the two periods of navigation. The peak frequency of the oscillations was approximately 3.7 Hz. Control studies consisted of a motor task similar to that required for navigation, passive viewing of a tour through the same virtual reality town, and a mental concentration task. No consistent increases in theta power were seen in the MEG during any of the control tasks. The results suggest an association between theta rhythm and the performance of navigational tasks in humans. PMID:11798388

  15. A circular equilibrium model for local gyrokinetic simulations of ion temperature gradient fluctuations in reversed field pinches

    SciTech Connect

    Tangri, Varun; Terry, P. W.; Waltz, R. E.

    2011-05-15

    A simple large-aspect-ratio (R{sub 0}/r) circular equilibrium model is developed for low-beta reversed field pinch (RFP) geometry. The model is suitable for treating small scale instability and turbulent transport driven by ion temperature gradient (ITG) and related electron drift modes in gyrokinetic simulations. The equilibrium model is an RFP generalization of the common tokamak s-{alpha} model to small safety factor (q), where the poloidal field dominates the toroidal field. The model accommodates the RFP toroidal field reversal (where q vanishes) by generalizing the cylindrical force-free Bessel function model (BFM) [J. B. Taylor, Phys. Rev. Lett. 33, 1139 (1974)] to toroidal geometry. The global equilibrium can be described in terms of the RFP field reversal and pinch parameters [F,{Theta}]. This new toroidal Bessel function model (TBFM) has been incorporated into the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J.Comput. Phys. 186, 545 (2003)] and used here to explore local electrostatic ITG adiabatic electron instability rates for typical low-q RFP parameters.

  16. Age-Related and Sex-Related Differences in Hand and Pinch Grip Strength in Adults

    ERIC Educational Resources Information Center

    Puh, Urska

    2010-01-01

    The purpose of the study was to quantify age-related changes in hand grip strength and three types of pinch grip strength (key pinch, tip pinch, and palmar pinch) among male and female participants. The study included 199 healthy participants (100 females, 99 males) aged 20-79 years, who were divided into four age groups. The Baseline Hydraulic…

  17. Fusion Propulsion Z-Pinch Engine Concept

    NASA Technical Reports Server (NTRS)

    Miernik, J.; Statham, G.; Fabisinski, L.; Maples, C. D.; Adams, R.; Polsgrove, T.; Fincher, S.; Cassibry, J.; Cortez, R.; Turner, M.; Percy, T.

    2011-01-01

    Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Due to the great distances between the planets of our solar system and the harmful radiation environment of interplanetary space, high specific impulse (Isp) propulsion in vehicles with high payload mass fractions must be developed to provide practical and safe vehicles for human spaceflight missions. The Z-Pinch dense plasma focus method is a Magneto-Inertial Fusion (MIF) approach that may potentially lead to a small, low cost fusion reactor/engine assembly1. Recent advancements in experimental and theoretical understanding of this concept suggest favorable scaling of fusion power output yield 2. The magnetic field resulting from the large current compresses the plasma to fusion conditions, and this process can be pulsed over short timescales (10(exp -6 sec). This type of plasma formation is widely used in the field of Nuclear Weapons Effects testing in the defense industry, as well as in fusion energy research. A Decade Module 2 (DM2), approx.500 KJ pulsed-power is coming to the RSA Aerophysics Lab managed by UAHuntsville in January, 2012. A Z-Pinch propulsion concept was designed for a vehicle based on a previous fusion vehicle study called "Human Outer Planet Exploration" (HOPE), which used Magnetized Target Fusion (MTF) 3 propulsion. The reference mission is the transport of crew and cargo to Mars and back, with a reusable vehicle.

  18. Theta oscillations regulate the speed of locomotion via a hippocampus to lateral septum pathway

    PubMed Central

    Bender, Franziska; Gorbati, Maria; Cadavieco, Marta Carus; Denisova, Natalia; Gao, Xiaojie; Holman, Constance; Korotkova, Tatiana; Ponomarenko, Alexey

    2015-01-01

    Hippocampal theta oscillations support encoding of an animal's position during spatial navigation, yet longstanding questions about their impact on locomotion remain unanswered. Combining optogenetic control of hippocampal theta oscillations with electrophysiological recordings in mice, we show that hippocampal theta oscillations regulate locomotion. In particular, we demonstrate that their regularity underlies more stable and slower running speeds during exploration. More regular theta oscillations are accompanied by more regular theta-rhythmic spiking output of pyramidal cells. Theta oscillations are coordinated between the hippocampus and its main subcortical output, the lateral septum (LS). Chemo- or optogenetic inhibition of this pathway reveals its necessity for the hippocampal regulation of running speed. Moreover, theta-rhythmic stimulation of LS projections to the lateral hypothalamus replicates the reduction of running speed induced by more regular hippocampal theta oscillations. These results suggest that changes in hippocampal theta synchronization are translated into rapid adjustment of running speed via the LS. PMID:26455912

  19. Theta oscillations regulate the speed of locomotion via a hippocampus to lateral septum pathway.

    PubMed

    Bender, Franziska; Gorbati, Maria; Cadavieco, Marta Carus; Denisova, Natalia; Gao, Xiaojie; Holman, Constance; Korotkova, Tatiana; Ponomarenko, Alexey

    2015-01-01

    Hippocampal theta oscillations support encoding of an animal's position during spatial navigation, yet longstanding questions about their impact on locomotion remain unanswered. Combining optogenetic control of hippocampal theta oscillations with electrophysiological recordings in mice, we show that hippocampal theta oscillations regulate locomotion. In particular, we demonstrate that their regularity underlies more stable and slower running speeds during exploration. More regular theta oscillations are accompanied by more regular theta-rhythmic spiking output of pyramidal cells. Theta oscillations are coordinated between the hippocampus and its main subcortical output, the lateral septum (LS). Chemo- or optogenetic inhibition of this pathway reveals its necessity for the hippocampal regulation of running speed. Moreover, theta-rhythmic stimulation of LS projections to the lateral hypothalamus replicates the reduction of running speed induced by more regular hippocampal theta oscillations. These results suggest that changes in hippocampal theta synchronization are translated into rapid adjustment of running speed via the LS. PMID:26455912

  20. Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

    SciTech Connect

    Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J.P.; Chittenden, J.P.; Lebedev, S.V.; Jennings, C.A.; Bland, S.N.

    2006-01-05

    Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1{mu}s rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-{theta} simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

  1. Geometrical model for non-zero {theta}{sub 13}

    SciTech Connect

    Chen Junmou; Wang Bin; Li Xueqian

    2011-10-01

    Based on Friedberg and Lee's geometric picture by which the tribimaximal Pontecorvo-Maki-Nakawaga-Sakata leptonic mixing matrix is constructed, namely, corresponding mixing angles correspond to the geometric angles among the sides of a cube. We suggest that the three realistic mixing angles, which slightly deviate from the values determined for the cube, are due to a viable deformation from the perfectly cubic shape. Taking the best-fitted results of {theta}{sub 12} and {theta}{sub 23} as inputs, we determine the central value of sin{sup 2}2{theta}{sub 13} should be 0.0238, with a relatively large error tolerance; this value lies in the range of measurement precision of the Daya Bay experiment and is consistent with recent results from the T2K Collaboration.

  2. Frontal theta as a mechanism for cognitive control

    PubMed Central

    Cavanagh, James F.; Frank, Michael J.

    2014-01-01

    Recent advancements in cognitive neuroscience have afforded a description of neural responses in terms of latent algorithmic operations. However, the adoption of this approach to human scalp EEG has been more limited, despite the ability of this methodology to quantify canonical neuronal processes. Here we provide evidence that theta band activities over the mid-frontal cortex appear to reflect a common computation used for realizing the need for cognitive control. Moreover, by virtue of inherent properties of field oscillations, these theta band processes may be used to communicate this need and subsequently implement such control across disparate brain regions. Frontal theta is thus a compelling candidate mechanism by which emergent processes such as ‘cognitive control’ may be biophysically realized. PMID:24835663

  3. The correlation of x-ray emission with pinch energy in a 1.5 kJ plasma focus

    NASA Astrophysics Data System (ADS)

    Hussain, S. S.; Ahmad, S.; Lee, S.; Zakaullah, M.

    2007-08-01

    Correlation of x-ray emission with pinch energy from a 1.5 kJ Mather-type plasma focus device for Ag and Sn inserts at the Cu tapered anode tip is reported. The space and time resolved x-ray emission characteristics are investigated by using a simple pinhole camera with appropriate filters and a multichannel pin-diode spectrometer. High voltage probe and Rogowski coil signals are used to estimate the pinch energy. At optimum conditions, the maximum x-ray yield in 4π-geometry is found to be 9 and 8 J/shot with efficiency of 0.6% and 0.5% for Sn and Ag inserted anodes. This is despite the fact that input energy converted to pinch energy is lower at 8% for Sn insert compared with 15% for the Ag insert. An increase in x-ray yield with an increase in pinch energy is observed for Sn as well as Ag. Pinhole images reveal that x-rays of energy less than 5 keV are emitted from the focus region and the high-energy x-rays are emanated from the anode tip.

  4. Pre-stimulus thalamic theta power predicts human memory formation.

    PubMed

    Sweeney-Reed, Catherine M; Zaehle, Tino; Voges, Jürgen; Schmitt, Friedhelm C; Buentjen, Lars; Kopitzki, Klaus; Richardson-Klavehn, Alan; Hinrichs, Hermann; Heinze, Hans-Jochen; Knight, Robert T; Rugg, Michael D

    2016-09-01

    Pre-stimulus theta (4-8Hz) power in the hippocampus and neocortex predicts whether a memory for a subsequent event will be formed. Anatomical studies reveal thalamus-hippocampal connectivity, and lesion, neuroimaging, and electrophysiological studies show that memory processing involves the dorsomedial (DMTN) and anterior thalamic nuclei (ATN). The small size and deep location of these nuclei have limited real-time study of their activity, however, and it is unknown whether pre-stimulus theta power predictive of successful memory formation is also found in these subcortical structures. We recorded human electrophysiological data from the DMTN and ATN of 7 patients receiving deep brain stimulation for refractory epilepsy. We found that greater pre-stimulus theta power in the right DMTN was associated with successful memory encoding, predicting both behavioral outcome and post-stimulus correlates of successful memory formation. In particular, significant correlations were observed between right DMTN theta power and both frontal theta and right ATN gamma (32-50Hz) phase alignment, and frontal-ATN theta-gamma cross-frequency coupling. We draw the following primary conclusions. Our results provide direct electrophysiological evidence in humans of a role for the DMTN as well as the ATN in memory formation. Furthermore, prediction of subsequent memory performance by pre-stimulus thalamic oscillations provides evidence that post-stimulus differences in thalamic activity that index successful and unsuccessful encoding reflect brain processes specifically underpinning memory formation. Finally, the findings broaden the understanding of brain states that facilitate memory encoding to include subcortical as well as cortical structures. PMID:27208861

  5. Differential geometry of the Fermat quartic and theta functions

    NASA Astrophysics Data System (ADS)

    Hadnot, Jason

    2012-02-01

    The universal curve over a finite cover of the moduli space of elliptic curves with level four structure is embedded in C as the Fermat quartic and is parametrized via the four Jacobi theta functions. Constructions from completely integrable systems have shown the importance of looking at the curvature of certain spaces and here we compute sectional curvatures. For our computations, we choose the ambient Fubini-Study metric of C. We also derive several theta identities which arise from the quartic's holomorphic two-form.

  6. Progress in Z-pinch inertial fusion energy.

    SciTech Connect

    Weed, John Woodruff

    2010-03-01

    The goal of z-pinch inertial fusion energy (IFE) is to extend the single-shot z-pinch inertial confinement fusion (ICF) results on Z to a repetitive-shot z-pinch power plant concept for the economical production of electricity. Z produces up to 1.8 MJ of x-rays at powers as high as 230 TW. Recent target experiments on Z have demonstrated capsule implosion convergence ratios of 14-21 with a double-pinch driven target, and DD neutron yields up to 8x10exp10 with a dynamic hohlraum target. For z-pinch IFE, a power plant concept is discussed that uses high-yield IFE targets (3 GJ) with a low rep-rate per chamber (0.1 Hz). The concept includes a repetitive driver at 0.1 Hz, a Recyclable Transmission Line (RTL) to connect the driver to the target, high-yield targets, and a thick-liquid wall chamber. Recent funding by a U.S. Congressional initiative for $4M for FY04 is supporting research on RTLs, repetitive pulsed power drivers, shock mitigation, full RTL cycle planned experiments, high-yield IFE targets, and z-pinch power plant technologies. Recent results of research in all of these areas are discussed, and a Road Map for Z-Pinch IFE is presented.

  7. ROTATING PLASMA DEVICE

    DOEpatents

    Boyer, K.; Hammel, J.E.; Longmire, C.L.; Nagle, D.E.; Ribe, F.L.; Tuck, J.L.

    1961-10-24

    ABS>A method and device are described for obtaining fusion reactions. The basic concept is that of using crossed electric and magnetic fields to induce a plasma rotation in which the ionized particles follow a circumferential drift orbit on wldch a cyclotron mode of motion is superimposed, the net result being a cycloidal motion about the axis of symmetry. The discharge tube has a radial electric field and a longitudinal magnetic field. Mirror machine geometry is utilized. The device avoids reliance on the pinch effect and its associated instability problems. (AEC)

  8. Spectroscopic Observation of Fluctuation-Induced Dynamo in the Edge of the Reversed-Field Pinch

    SciTech Connect

    Fontana, P. W.; Den Hartog, D. J.; Fiksel, G.; Prager, S. C.

    2000-07-17

    The fluctuation-induced dynamo has been investigated by direct measurement of v(tilde sign) and b(tilde sign) in the edge of a reversed-field pinch and is found to be significant in balancing Ohm's law. The velocity fluctuations producing the dynamo emf have poloidal mode number m=0 , consistent with MHD calculations and in contrast with the core m=1 dynamo. The velocity fluctuations exhibit the parity relative to their resonant surface predicted by linear MHD theory. (c) 2000 The American Physical Society.

  9. Radio frequency wave experiments on the MST reversed field pinch

    SciTech Connect

    Forest, C.B.; Chattopadhyay, P.K.; Nornberg, M.D.; Prager, S.C.; Thomas, M.A.; Uchimoto, E.; Smirnov, A.P.; Harvey, R.W.; Ram, A.K.

    1999-04-01

    Experiments, simulations, and theory all indicate that the magnetic fluctuations responsible for the poor confinement in the reversed field pinch (RFP) can be controlled by altering the radial profile of the current density. The magnetic fluctuations in the RFP are due to resistive MHD instabilities caused by current profile peaking; thus confinement in the RFP is ultimately the result of a misalignment between inductively driven current profiles and the stable current profiles characteristic of the Taylor state. If a technique such as rf current drive can be developed to non-inductively sustain a Taylor state (a current profile linearly stable to all tearing modes), the confinement of the RFP and its potential as a reactor concept are likely to increase. Whether there is a self-consistent path from poor confinement to greatly improved confinement through current profile modification is an issue for future experiments to address if and only if near term experiments can demonstrate: (1) coupling to and the propagation of rf waves in RFP plasmas, (2) efficient current drive, and (3) control of the power deposition which will make it possible to control the current profile. In this paper, modeling results and experimental plans are presented for two rf experiments which have the potential of satisfying these three goals: high-n{sub {parallel}} lower hybrid (LH) waves and electron Bernstein waves (EBWs).

  10. Pinch-off of threads of nonhomogeneous Polymer solutions

    NASA Astrophysics Data System (ADS)

    Garg, Vishrut; Thete, Sumeet; Appathurai, Santosh; Bhat, Pradeep; Basaran, Osman

    2014-11-01

    Motivated by applications involving inkjet printing of complex fluids, we analyze the nonlinear dynamics of the deformation and breakup of polymeric liquid threads. Virtually all previous such studies have been restricted to situations in which the polymer concentration is uniform within the threads. Recently, Eggers (2014) has proposed that non-uniform polymer concentration can account for the blistering pattern that is sometimes seen during breakup of polymeric threads where at the incipience of pinch-off, the thread has the morphology of small drops that are separated by threads of highly concentrated polymer solution. Following Eggers's approach but one in which he restricted his study to a linear stability analysis, we analyze the full nonlinear dynamics by solving simultaneously Cauchy's momentum equation, the continuity equation, a convection-diffusion equation for the number density of polymers, and a constitutive equation for stress. The latter two equations account for the coupling between polymer concentration and the flow. As the thread profiles seen in experiments are typically quite slender, we expedite the analysis by solving these equations in the slender-jet limit by an approach based on the finite element method.

  11. Evaluation of Internal Brushing on Pinch Weld Quality

    SciTech Connect

    Korinko, P

    2005-12-01

    Post machining operations such as borescope inspection can cause linear indications down the length of the bore of fill stems. Often these indications are removed or obscured using rotary wire brushing. This study evaluated the effect this mechanical operation may have on pinch weld quality when relatively cold welds were made. A total of four stems with two levels of brushing of both Type 304L and 21-6-9 stainless steels were tested. In addition, two each of the Type 304L stems were Nitradd cleaned and the other two were aqueously cleaned; all four 21-6-9 stems were aqueously cleaned. All of the brushed stem areas exhibited more surface anomalies based on borescope evaluation. On average, the bond rating was a higher value (worse) for the brushed areas than the unadulterated areas for both Type 304L and 21-6-9 stems. The test method used may have biased the results towards a lesser quality bond for the brushed areas so additional testing is recommended.

  12. Linear pocket energy exchange device

    SciTech Connect

    Harvey, A.C.; Harding, J.C.

    1983-10-18

    An hydraulic energy recovery system is disclosed for sea water desalinization reverse osmosis processes wherein a tube receives salt water at low pressure and a conveyor in the tube transports the low pressure liquid to a first station where the salt water is pressurized and fed to the desalinization process. The brine from the process is conveyed under pressure to a second station along the tube from which it is conveyed to a discharge. The first and second stations are maintained at high pressure, and the salt water at the inlet end and the brine at the outlet end cooperate with the conveyor to form labyrinth seals at each end of the tube so as to maintain the pressure at the first and second stations.

  13. Refueling and density control in the ZT-40M reversed field pinch

    SciTech Connect

    Wurden, G.A.; Weber, P.G.; Watt, R.G.; Munson, C.P.; Cayton, T.E.; Buechl, K.

    1987-01-01

    The effects of pellet injection and gas puff refueling have been studied in the ZT-40M Reversed Field Pinch. Multiple deuterium pellets (less than or equal to 6 x 10/sup 19/D atoms/pellet) with velocities ranging from 300 to 700 m/sec have been injected into plasmas with n-bar/sub e/ approx.1 to 5 X 10/sup 19/m/sup -3/, I/sub phi/ approx.100 to 250 kA, T/sub e/(0) approx.150 to 300 eV and discharge durations of less than or equal to 20 msec. Photographs and an array D/sub ..cap alpha../ detectors show substantial deflection of the pellet trajectory in both the poloidal and toroidal planes, due to asymmetric ablation of the pellet by electrons streaming along field lines. To compensate for the poloidal deflection, the injector was moved up +14 cm off-axis, allowing the pellets to curve down to the midplane. In this fashion, central peaking of the pellet density deposition profile can be obtained. Both electron and ion temperatures fall in response to the density rise, such that ..beta../sub theta/(..beta../sub theta/ identical to n-bar/sub e/(T/sub e/(0) + T/sub i/)/(B/sub theta/(a))/sup 2/) remains roughly constant. Energy confinement is momentarily degraded, and typically a decrease in F (F identical to B/sub phi/(a)/(B/sub phi/)) is seen as magnetic energy is converted to plasma energy when the pellet ablates. As a result of pellet injection at I/sub phi/ = 150 kA we observe T/sub e/(0) ..cap alpha.. n-bar/sub e//sup -.9 +- .1/, while the helicity based resistivity eta/sub k/ transiently varies as n-bar/sub e//sup .7 +- .1/. While the achievement of center-peaked density profiles is possible with pellet injection, gas puffing at rates strong enough to show a 50% increase in n-bar/sub e/ over a period of 10 msec (approx.150 torr-litres/sec) leads to hollow density profiles. The refueling requirements for parameters expected in the next generation RFPs (ZTH, RFX) can be extrapolated from these data using modified tokamak pellet ablation codes.

  14. Pinching solutions of slender cylindrical jets

    NASA Technical Reports Server (NTRS)

    Papageorgiou, Demetrios T.; Orellana, Oscar

    1993-01-01

    Simplified equations for slender jets are derived for a circular jet of one fluid flowing into an ambient second fluid, the flow being confined in a circular tank. Inviscid flows are studied which include both surface tension effects and Kelvin-Helmholtz instability. For slender jets a coupled nonlinear system of equations is found for the jet shape and the axial velocity jump across it. The equations can break down after a finite time and similarity solutions are constructed, and studied analytically and numerically. The break-ups found pertain to the jet pinching after a finite time, without violation of the slender jet ansatz. The system is conservative and admissible singular solutions are those which conserve the total energy, mass, and momentum. Such solutions are constructed analytically and numerically, and in the case of vortex sheets with no surface tension certain solutions are given in closed form.

  15. A Low energy neutrino factory for large theta(13)

    SciTech Connect

    Geer, Steve; Mena, Olga; Pascoli, Silvia; /Durham U., IPPP

    2007-01-01

    If the value of {theta}{sub 13} is within the reach of the upcoming generation of long-baseline experiments, T2K and NOvA, they show that a low-energy neutrino factory, with peak energy in the few GeV range, would provide a sensitive tool to explore CP-violation and the neutrino mass hierarchy. They consider baselines with typical length 1000-1500 km. The unique performance of the low energy neutrino factory is due to the rich neutrino oscillation pattern at energies between 1 and 4 GeV at baselines {Omicron}(1000) km. They perform both a semi-analytical study of the sensitivities and a numerical analysis to explore how well this setup can measure {theta}{sub 13}, CP-violation, and determine the type of mass hierarchy and the {theta}{sub 23} quadrant. A low energy neutrino factory provides a powerful tool to resolve ambiguities and make precise parameter determinations, for both large and fairly small values of the mixing parameter {theta}{sub 13}.

  16. Holomorphic projections and Ramanujan’s mock theta functions

    PubMed Central

    Imamoğlu, Özlem; Raum, Martin; Richter, Olav K.

    2014-01-01

    We use spectral methods of automorphic forms to establish a holomorphic projection operator for tensor products of vector-valued harmonic weak Maass forms and vector-valued modular forms. We apply this operator to discover simple recursions for Fourier series coefficients of Ramanujan’s mock theta functions. PMID:24591582

  17. Presence of state transitions in the cryptophyte alga Guillardia theta

    PubMed Central

    Cheregi, Otilia; Kotabová, Eva; Prášil, Ondřej; Schröder, Wolfgang P.; Kaňa, Radek; Funk, Christiane

    2015-01-01

    Plants and algae have developed various regulatory mechanisms for optimal delivery of excitation energy to the photosystems even during fluctuating light conditions; these include state transitions as well as non-photochemical quenching. The former process maintains the balance by redistributing antennae excitation between the photosystems, meanwhile the latter by dissipating excessive excitation inside the antennae. In the present study, these mechanisms have been analysed in the cryptophyte alga Guillardia theta. Photoprotective non-photochemical quenching was observed in cultures only after they had entered the stationary growth phase. These cells displayed a diminished overall photosynthetic efficiency, measured as CO2 assimilation rate and electron transport rate. However, in the logarithmic growth phase G. theta cells redistributed excitation energy via a mechanism similar to state transitions. These state transitions were triggered by blue light absorbed by the membrane integrated chlorophyll a/c antennae, and green light absorbed by the lumenal biliproteins was ineffective. It is proposed that state transitions in G. theta are induced by small re-arrangements of the intrinsic antennae proteins, resulting in their coupling/uncoupling to the photosystems in state 1 or state 2, respectively. G. theta therefore represents a chromalveolate algae able to perform state transitions. PMID:26254328

  18. Presence of state transitions in the cryptophyte alga Guillardia theta.

    PubMed

    Cheregi, Otilia; Kotabová, Eva; Prášil, Ondřej; Schröder, Wolfgang P; Kaňa, Radek; Funk, Christiane

    2015-10-01

    Plants and algae have developed various regulatory mechanisms for optimal delivery of excitation energy to the photosystems even during fluctuating light conditions; these include state transitions as well as non-photochemical quenching. The former process maintains the balance by redistributing antennae excitation between the photosystems, meanwhile the latter by dissipating excessive excitation inside the antennae. In the present study, these mechanisms have been analysed in the cryptophyte alga Guillardia theta. Photoprotective non-photochemical quenching was observed in cultures only after they had entered the stationary growth phase. These cells displayed a diminished overall photosynthetic efficiency, measured as CO2 assimilation rate and electron transport rate. However, in the logarithmic growth phase G. theta cells redistributed excitation energy via a mechanism similar to state transitions. These state transitions were triggered by blue light absorbed by the membrane integrated chlorophyll a/c antennae, and green light absorbed by the lumenal biliproteins was ineffective. It is proposed that state transitions in G. theta are induced by small re-arrangements of the intrinsic antennae proteins, resulting in their coupling/uncoupling to the photosystems in state 1 or state 2, respectively. G. theta therefore represents a chromalveolate algae able to perform state transitions. PMID:26254328

  19. Interindividual Differences in Alpha and Theta Power Reflect Memory Performance.

    ERIC Educational Resources Information Center

    Klimesch, W.; Vogt, F.; Doppelmayr, M.

    1999-01-01

    Tested whether tonic EEG power is related to memory performance by analyzing ongoing EEG for 60 subjects in 5 experimental conditions. Subjects with good memory performance had significantly larger upper alpha power, but less theta and lower alpha power. Also discusses findings for subjects good at calculation. (SLD)

  20. Violations of parity and charge conjugation in the {theta} vacuum with imaginary chemical potential

    SciTech Connect

    Kouno, Hiroaki; Sakai, Yuji; Sasaki, Takahiro; Kashiwa, Kouji; Yahiro, Masanobu

    2011-04-01

    Charge conjugation (C) and parity (P) are exact symmetries at {theta}={pi} and {Theta}{identical_to}{mu}/(iT)={pi}, where {theta} is the parameter of the so-called {theta} vacuum, {mu} is the imaginary quark-number chemical potential and T is the temperature. Spontaneous breakings of these discrete symmetries are investigated by the Polyakov-loop extended Nambu-Jona-Lasinio model. At zero T, P symmetry is spontaneously broken while C symmetry is conserved. As T increases, P symmetry is restored just after C symmetry is spontaneously broken, so that either P or C symmetry or both the symmetries are spontaneously broken for any T. The chiral-symmetry restoration and the deconfinement transition at {theta}={Theta}=0 are remnants of the P restoration and the C breaking at {theta}={Theta}={pi}, respectively.

  1. Hard X-rays from hybrid X pinches

    SciTech Connect

    Shelkovenko, T. A. Pikuz, S. A.; Hoyt, C. L.; Cahill, A. D.; Hammer, D. A.; Tilikin, I. N.; Mingaleev, A. R.; Agafonov, A. V.

    2014-12-15

    X pinches are well known to produce very small, dense plasma pinches (“hot spots”) that emit short bursts of 1.5–8 keV radiation. Hard X-ray radiation in the 8–100 keV range is also emitted, only a small portion of which is associated with the X-pinch hot spot. In hybrid X-pinches, the “long” X-ray pulse is terminated by fast closure of the gap between the two conical electrodes by rapidly expanding electrode plasmas. The temporal, spectral, and spatial properties of this higher energy radiation, 10 – 60 keV, have been studied. This radiation was used for point-projection imaging with magnification between 1.5 and 3, and spatial resolution less than100 micrometers was demonstrated.

  2. A Z-Pinch Driven Fusion Reactor Concept

    NASA Astrophysics Data System (ADS)

    Derzon, Mark; Rochau, Gregory; Spielman, Rick; Slutz, Stephen; Rochau, G. E.; Peterson, R. R.; Peterson, P. F.

    1999-11-01

    Recent z-pinch target physics progress has encouraged us to consider how a power reactor could be configured based on a fast z-pinch driver. Initial cost estimates show that recyclable transmission lines (RTLs) are economically viable. Providing 'standoff' between the primary power supply and the target, which is what disposable RTLs provide, has historically been the main obstacle to the consideration of pinches as fusion drivers. We will be introducing basic reactor scaling in terms of shot rate, yield, tritium breeding and neutron flux, etc. This concept has advantages in that z-pinches provide a robust mechanical environment, as well as a chamber which does not require low-pressure pumping between shots and the wall lifetime is expected to be limited factors other than neutron damage. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

  3. Turbulent equipartition pinch of toroidal momentum in spherical torus

    NASA Astrophysics Data System (ADS)

    Hahm, T. S.; Lee, J.; Wang, W. X.; Diamond, P. H.; Choi, G. J.; Na, D. H.; Na, Y. S.; Chung, K. J.; Hwang, Y. S.

    2014-12-01

    We present a new analytic expression for turbulent equipartition (TEP) pinch of toroidal angular momentum originating from magnetic field inhomogeneity of spherical torus (ST) plasmas. Starting from a conservative modern nonlinear gyrokinetic equation (Hahm et al 1988 Phys. Fluids 31 2670), we derive an expression for pinch to momentum diffusivity ratio without using a usual tokamak approximation of B ∝ 1/R which has been previously employed for TEP momentum pinch derivation in tokamaks (Hahm et al 2007 Phys. Plasmas 14 072302). Our new formula is evaluated for model equilibria of National Spherical Torus eXperiment (NSTX) (Ono et al 2001 Nucl. Fusion 41 1435) and Versatile Experiment Spherical Torus (VEST) (Chung et al 2013 Plasma Sci. Technol. 15 244) plasmas. Our result predicts stronger inward pinch for both cases, as compared to the prediction based on the tokamak formula.

  4. The TITAN reversed-field-pinch fusion reactor study

    SciTech Connect

    Not Available

    1990-01-01

    This paper on titan plasma engineering contains papers on the following topics: reversed-field pinch as a fusion reactor; parametric systems studies; magnetics; burning-plasma simulations; plasma transient operations; current drive; and physics issues for compact RFP reactors.

  5. About plasma points' generation in Z-pinch

    SciTech Connect

    Afonin, V. I.; Potapov, A. V.; Lazarchuk, V. P.; Murugov, V. M.; Senik, A. V.

    1997-05-05

    The streak tube study results (at visible and x-ray ranges) of dynamics of fast Z-pinch formed at explosion of metal wire in diode of high current generator are presented. Amplitude of current in the load reached {approx}180 kA at increase time {approx}50 ns. The results' analysis points to capability of controlling hot plasma points generation process in Z-pinch.

  6. Tuning the theta temperature and critical micellization temperature of polymers in ionic liquids

    NASA Astrophysics Data System (ADS)

    Lodge, Timothy; Hoarfrost, Megan

    2014-03-01

    Ionic liquids feature a combination of properties that make them very interesting solvents for polymers, but questions remain regarding the thermodynamics of polymer/ionic liquid solutions. In this work, the lower-critical-solution-temperature (LCST) phase behavior of poly(n-butyl methacrylate) (PnBMA) in mixtures of the ionic liquids 1-butyl-3-methylimidazolium: bis(trifluoromethylsulfonyl)imide ([BMIm][TFSI]) and 1-ethyl-3-methylimidazolium:TFSI ([EMIm][TFSI]) is characterized by transmittance, light scattering, and small-angle neutron scattering measurements. Relevant thermodynamic parameters are readily tuned by varying the ionic liquid composition. In particular, the cloud point, spinodal, and theta temperatures are all found to increase linearly with [BMIm] content. The interaction parameters are determined as a function of temperature and concentration using three different methods, and the results from each method are compared. The theta temperatures are then compared quantitatively to the critical micellization temperatures (CMTs) for PnBMA-poly(ethylene oxide) diblocks, to test the proposition that the CMT corresponds to a fixed value of chi.

  7. Pinch-off Scaling Law of Soap Bubbles

    NASA Astrophysics Data System (ADS)

    Davidson, John; Ryu, Sangjin

    2014-11-01

    Three common interfacial phenomena that occur daily are liquid drops in gas, gas bubbles in liquid and thin-film bubbles. One aspect that has been studied for these phenomena is the formation or pinch-off of the drop/bubble from the liquid/gas threads. In contrast to the formation of liquid drops in gas and gas bubbles in liquid, thin-film bubble pinch-off has not been well documented. Having thin-film interfaces may alter the pinch-off process due to the limiting factor of the film thickness. We observed the pinch-off of one common thin-film bubble, soap bubbles, in order to characterize its pinch-off behavior. We achieved this by constructing an experimental model replicating the process of a human producing soap bubbles. Using high-speed videography and image processing, we determined that the minimal neck radius scaled with the time left till pinch-off, and that the scaling law exponent was 2/3, similar to that of liquid drops in gas.

  8. Learner Acquisition of Dialect Variation in a Study Abroad Context: The Case of the Spanish [Theta

    ERIC Educational Resources Information Center

    Ringer-Hilfinger, Kathryn

    2012-01-01

    The present study aims at analyzing the acquisition of dialect variation by native English-speaking university students who study Spanish for a semester in Spain. The selected variable is the phoneme /[theta]/ (theta). The goal is to assess learner awareness, opinion, and use of [theta]. Data were elicited through a set of oral and written tasks…

  9. Modulation of Hippocampal Theta Oscillations and Spatial Memory by Relaxin-3 Neurons of the Nucleus Incertus

    ERIC Educational Resources Information Center

    Ma, Sherie; Olucha-Bordonau, Francisco E.; Hossain, M. Akhter; Lin, Feng; Kuei, Chester; Liu, Changlu; Wade, John D.; Sutton, Steven W.; Nunez, Angel; Gundlach, Andrew L.

    2009-01-01

    Hippocampal theta rhythm is thought to underlie learning and memory, and it is well established that "pacemaker" neurons in medial septum (MS) modulate theta activity. Recent studies in the rat demonstrated that brainstem-generated theta rhythm occurs through a multisynaptic pathway via the nucleus incertus (NI), which is the primary source of the…

  10. Short-lived radioisotopes scaling with energy in plasma focus device

    NASA Astrophysics Data System (ADS)

    Kakavandi, Javad A.; Roshan, Mahmood V.; Habibi, Morteza

    2016-03-01

    The computational investigation of the correlation between the achievable reaction yield and discharge energy for a plasma focus device (PFD) is presented. Radioisotope production in PFDs with applicable activities is highly dependent on establishing the related scaling law. Carbon target is bombarded by high energy deuterons and short-lived radioisotope of 13N is produced through 12C(d,n)13N in which the threshold energy is not very high. Both computed and measured ion energy spectra are used to estimate and optimize the scaling law. It is shown that the number of ions emitted from the pinch region for a device operating under optimized conditions is linearly proportional to the discharge energy of the PFD.

  11. Theoretical z -pinch scaling relations for thermonuclear-fusion experiments.

    PubMed

    Stygar, W A; Cuneo, M E; Vesey, R A; Ives, H C; Mazarakis, M G; Chandler, G A; Fehl, D L; Leeper, R J; Matzen, M K; McDaniel, D H; McGurn, J S; McKenney, J L; Muron, D J; Olson, C L; Porter, J L; Ramirez, J J; Seamen, J F; Speas, C S; Spielman, R B; Struve, K W; Torres, J A; Waisman, E M; Wagoner, T C; Gilliland, T L

    2005-08-01

    We have developed wire-array z -pinch scaling relations for plasma-physics and inertial-confinement-fusion (ICF) experiments. The relations can be applied to the design of z -pinch accelerators for high-fusion-yield (approximately 0.4 GJ/shot) and inertial-fusion-energy (approximately 3 GJ/shot) research. We find that (delta(a)/delta(RT)) proportional (m/l)1/4 (Rgamma)(-1/2), where delta(a) is the imploding-sheath thickness of a wire-ablation-dominated pinch, delta(RT) is the sheath thickness of a Rayleigh-Taylor-dominated pinch, m is the total wire-array mass, l is the axial length of the array, R is the initial array radius, and gamma is a dimensionless functional of the shape of the current pulse that drives the pinch implosion. When the product Rgamma is held constant the sheath thickness is, at sufficiently large values of m/l, determined primarily by wire ablation. For an ablation-dominated pinch, we estimate that the peak radiated x-ray power P(r) proportional (I/tau(i))(3/2)Rlphigamma, where I is the peak pinch current, tau(i) is the pinch implosion time, and phi is a dimensionless functional of the current-pulse shape. This scaling relation is consistent with experiment when 13 MA < or = I < or = 20 MA, 93 ns < or = tau(i) < or = 169 ns, 10 mm < or = R < or = 20 mm, 10 mm < or = l < or = 20 mm, and 2.0 mg/cm < or = m/l < or = 7.3 mg/cm. Assuming an ablation-dominated pinch and that Rlphigamma is held constant, we find that the x-ray-power efficiency eta(x) congruent to P(r)/P(a) of a coupled pinch-accelerator system is proportional to (tau(i)P(r)(7/9 ))(-1), where P(a) is the peak accelerator power. The pinch current and accelerator power required to achieve a given value of P(r) are proportional to tau(i), and the requisite accelerator energy E(a) is proportional to tau2(i). These results suggest that the performance of an ablation-dominated pinch, and the efficiency of a coupled pinch-accelerator system, can be improved substantially by decreasing the

  12. A short-pulse mode for the SPHINX LTD Z-pinch driver

    NASA Astrophysics Data System (ADS)

    D'Almeida, Thierry; Lassalle, Francis; Zucchini, Frederic; Loyen, Arnaud; Morell, Alain; Chuvatin, Alexander

    2015-11-01

    The SPHINX machine is a 6MA, 1 μs, LTD Z-pinch driver at CEA Gramat (France) and primarily used for studying radiation effects. Different power amplification concepts were examined in order to reduce the current rise time without modifying the generator discharge scheme, including the Dynamic Load Current Multiplier (DLCM) proposed by Chuvatin. A DLCM device, capable of shaping the current pulse without reducing the rise time, was developed at CEA. This device proved valuable for isentropic compression experiments in cylindrical geometry. Recently, we achieved a short pulse operation mode by inserting a vacuum closing switch between the DLCM and the load. The current rise time was reduced to ~300 ns. We explored the use of a reduced-height wire array for the Dynamic Flux Extruder in order to improve the wire array compression rate and increase the efficiency of the current transfer to the load. These developments are presented. Potential benefits of these developments for future Z pinch experiments are discussed.

  13. Tensor analyzing powers T/sub 20/(theta) and T/sub 22/(theta) in the /sup 2/H(darrow,. gamma. ) /sup 4/He reaction

    SciTech Connect

    Seyler, R.G.; Weller, H.R.

    1985-05-01

    Reaction theory expressions are used to prove that the tensor analyzing powers T/sub 20/(theta) and T/sub 22/(theta) for the /sup 2/H(darrow,..gamma..) /sup 4/He reaction are isotropic if the reaction is pure E2 and terms quadratic in channel-spin-2 matrix elements are neglected. Experimental departures from isotropy can be expected near theta-0/sup 0/, 90/sup 0/, and 189/sup 0/.

  14. Z-Pinch Pulsed Plasma Propulsion Technology Development

    NASA Technical Reports Server (NTRS)

    Polsgrove, Tara; Adams, Robert B.; Fabisinski, Leo; Fincher, Sharon; Maples, C. Dauphne; Miernik, Janie; Percy, Tom; Statham, Geoff; Turner, Matt; Cassibry, Jason; Cortez, Ross; Santarius, John

    2010-01-01

    Fusion-based propulsion can enable fast interplanetary transportation. Magneto-inertial fusion (MIF) is an approach which has been shown to potentially lead to a low cost, small reactor for fusion break even. The Z-Pinch/dense plasma focus method is an MIF concept in which a column of gas is compressed to thermonuclear conditions by an axial current (I approximates 100 MA). Recent advancements in experiments and the theoretical understanding of this concept suggest favorable scaling of fusion power output yield as I(sup 4). This document presents a conceptual design of a Z-Pinch fusion propulsion system and a vehicle for human exploration. The purpose of this study is to apply Z-Pinch fusion principles to the design of a propulsion system for an interplanetary spacecraft. This study took four steps in service of that objective; these steps are identified below. 1. Z-Pinch Modeling and Analysis: There is a wealth of literature characterizing Z-Pinch physics and existing Z-Pinch physics models. In order to be useful in engineering analysis, simplified Z-Pinch fusion thermodynamic models are required to give propulsion engineers the quantity of plasma, plasma temperature, rate of expansion, etc. The study team developed these models in this study. 2. Propulsion Modeling and Analysis: While the Z-Pinch models characterize the fusion process itself, propulsion models calculate the parameters that characterize the propulsion system (thrust, specific impulse, etc.) The study team developed a Z-Pinch propulsion model and used it to determine the best values for pulse rate, amount of propellant per pulse, and mixture ratio of the D-T and liner materials as well as the resulting thrust and specific impulse of the system. 3. Mission Analysis: Several potential missions were studied. Trajectory analysis using data from the propulsion model was used to determine the duration of the propulsion burns, the amount of propellant expended to complete each mission considered. 4

  15. Event-related desynchronization of frontal-midline theta rhythm during preconscious auditory oddball processing.

    PubMed

    Kawamata, Masaru; Kirino, Eiji; Inoue, Reiichi; Arai, Heii

    2007-10-01

    The goal of this study was to explore the frontal-midline theta rhythm (Fm theta) generation mechanism employing event-related desynchronization/synchronization (ERD/ERS) analysis in relation to task-irrelevant external stimuli. A dual paradigm was employed: a videogame and the simultaneous presentation of passive auditory oddball stimuli. We analyzed the data concerning ERD/ERS using both Fast Fourier Transformation (FFT) and wavelet transform (WT). In the FFT data, during the periods with appearance of Fm theta, apparent ERD of the theta band was observed at Fz and Cz. ERD when Fm theta was present was much more prominent than when Fm theta was absent. In the WT data, as in the FFT data, ERD was seen again, but in this case the ERD was preceded by ERS during both the periods with and without Fm theta. Furthermore, the WT analysis indicated that ERD was followed by ERS during the periods without Fm theta. However, during Fm theta, no apparent ERS following ERD was seen. In our study, Fm theta was desynchronized by the auditory stimuli that were independent of the video game task used to evoke the Fm theta. The ERD of Fm theta might be reflecting the mechanism of "positive suppression" to process external auditory stimuli automatically and preventing attentional resources from being unnecessarily allocated to those stimuli. Another possibility is that Fm theta induced by our dual paradigm may reflect information processing modeled by multi-item working memory requirements for playing the videogame and the simultaneous auditory processing using a memory trace. ERS in the WT data without Fm theta might indicate further processing of the auditory information free from "positive suppression" control reflected by Fm theta. PMID:17993201

  16. Measurement of the spatial neutral deuterium temperature distribution in the HBTX1B reversed-field pinch by fluorescence scattering

    SciTech Connect

    Forrest, M.J.; Trotman, D.L.; Bamford, R.; Lazaros, A.

    1988-08-01

    The spatial neutral deuterium temperature distribution has been made in the HBTX1B reversed-field pinch plasma device by Balmer-beta fluorescence scattering. This measurement is based on tuning a dye laser to the n = 2--4 transition of deuterium and passing it through the deuterium plasma with sufficient power to saturate the selected transition. The technique, hitherto used to determine neutral densities and energies, has been extended by means of an optimized two-channel narrow-band interference-filter arrangement to analyze the scattered spectrum. Spatial resolution is achieved by a scanning Risley prism arrangement. Neutral temperatures in the range 20--150 eV have been measured and the spatial distribution is consistent with neutral particle analyzer results and an ion power balance model proposed for the reversed-field pinch.

  17. Application of the focusing x-ray spectrograph with crossed dispersion to investigations of X pinch plasmas

    SciTech Connect

    Pikuz, S.A.; Song, B.M.; Shelkovenko, T.A.; Chandler, K.M.; Mitchell, M.D.; Hammer, D.A.

    2004-10-01

    A new focusing spectrograph configuration with crossed dispersion (FSCD) has been developed for use in X pinch experiments. This device solves the problem in a crystal spectrograph of the overlapping of reflected radiation in many orders. The x-ray radiation from a small source is dispersed by a transmission grating before it reaches the Bragg reflector (mica crystal). A large aperture (10 mmx10 mm), 0.5 {mu}m period gold transmission grating was made on a 0.5 {mu}m thick Si{sub 3}N{sub 4} substrate and combined with spherically bent mica crystals with radii of curvature of 100 mm or 186 mm. Results of FSCD application to plasma experiments with X pinch x-ray sources is presented.

  18. Cold iron cos THETA magnet option for the SSC

    SciTech Connect

    Reardon, P.

    1985-01-01

    We review first the evolution over the past several years of a cold iron, high field cos THETA magnet design option for the SSC. We note the collaborative approach pursued by BNL and LBL on the 2-in-1 option, and the culmination of this effort in the tests of the BNL 4.5 m model magnets. Next, we discuss the subsequent 1-in-1 option being pursued jointly by BNL, Fermilab and LBL.

  19. The role of REM sleep theta activity in emotional memory

    PubMed Central

    Hutchison, Isabel C.; Rathore, Shailendra

    2015-01-01

    While non-REM (NREM) sleep has been strongly implicated in the reactivation and consolidation of memory traces, the role of rapid-eye movement (REM) sleep remains unclear. A growing body of research on humans and animals provide behavioral evidence for a role of REM sleep in the strengthening and modulation of emotional memories. Theta activity—which describes low frequency oscillations in the local field potential within the hippocampus, amygdala and neocortex—is a prominent feature of both wake and REM sleep in humans and rodents. Theta coherence between the hippocampus and amygdala drives large-scale pontine-geniculo-occipital (PGO) waves, the density of which predicts increases in plasticity-related gene expression. This could potentially facilitate the processing of emotional memory traces within the hippocampus during REM sleep. Further, the timing of hippocampal activity in relation to theta phase is vital in determining subsequent potentiation of neuronal activity. This could allow the emotionally modulated strengthening of novel and gradual weakening of consolidated hippocampal memory traces during REM sleep. Hippocampal theta activity is also correlated with REM sleep levels of achetylcholine - which is thought to reduce hippocampal inputs in the neocortex. The additional low levels of noradrenaline during REM sleep, which facilitate feedback within the neocortex, could allow the integration of novel memory traces previously consolidated during NREM sleep. We therefore propose that REM sleep mediates the prioritized processing of emotional memories within the hippocampus, the integration of previously consolidated memory traces within the neocortex, as well as the disengagement of consolidated neocortical memory traces from the hippocampus. PMID:26483709

  20. Correlation of hippocampal theta rhythm with changes in cutaneous temperature

    NASA Technical Reports Server (NTRS)

    Horowitz, J. M.; Saleh, M. A.; Karem, R. D.

    1974-01-01

    Investigation of the possibility that the hippocampus performs the function of alerting an animal to changes in cutaneous temperature, using unanesthetized, loosely restrained rabbits. The results indicate that the hippocampal theta rhythm, which appears to be evoked by changes in cutaneous temperature, can be related to a specific type of hyppocampal neuron which is, in turn, connected with other areas of the brain involved in temperature regulation.

  1. The role of REM sleep theta activity in emotional memory.

    PubMed

    Hutchison, Isabel C; Rathore, Shailendra

    2015-01-01

    While non-REM (NREM) sleep has been strongly implicated in the reactivation and consolidation of memory traces, the role of rapid-eye movement (REM) sleep remains unclear. A growing body of research on humans and animals provide behavioral evidence for a role of REM sleep in the strengthening and modulation of emotional memories. Theta activity-which describes low frequency oscillations in the local field potential within the hippocampus, amygdala and neocortex-is a prominent feature of both wake and REM sleep in humans and rodents. Theta coherence between the hippocampus and amygdala drives large-scale pontine-geniculo-occipital (PGO) waves, the density of which predicts increases in plasticity-related gene expression. This could potentially facilitate the processing of emotional memory traces within the hippocampus during REM sleep. Further, the timing of hippocampal activity in relation to theta phase is vital in determining subsequent potentiation of neuronal activity. This could allow the emotionally modulated strengthening of novel and gradual weakening of consolidated hippocampal memory traces during REM sleep. Hippocampal theta activity is also correlated with REM sleep levels of achetylcholine - which is thought to reduce hippocampal inputs in the neocortex. The additional low levels of noradrenaline during REM sleep, which facilitate feedback within the neocortex, could allow the integration of novel memory traces previously consolidated during NREM sleep. We therefore propose that REM sleep mediates the prioritized processing of emotional memories within the hippocampus, the integration of previously consolidated memory traces within the neocortex, as well as the disengagement of consolidated neocortical memory traces from the hippocampus. PMID:26483709

  2. Cell discharge correlates of posterior hypothalamic theta rhythm. Recipe for success in recording stable field potential.

    PubMed

    Bocian, Renata; Kłos-Wojtczak, Paulina; Konopacki, Jan

    2016-09-01

    The theta rhythm discovered in the posterior hypothalamus area (PHa) differs from theta observed in the hippocampal formation. In comparison to hippocampal spontaneous theta, the theta recorded in the PHa is rarely registered, has lower amplitude, often disappears, and sometimes returns after a few minutes. These features indicate that spontaneous theta recorded in the PHa is not an appropriate experimental model to search for the correlation between PHa cell discharges and local field potential. In this paper we present standard experimental conditions necessary to record theta-related cells in the PHa in anesthetized rats. Three pharmacological agents were used in the experiments to induce PHa theta rhythm in urethanized rats: carbachol (CCH), carbenoxolone and kainic acid, which are potent enough to induce well-synchronized PHa theta. However, CCH was found to be the best pharmacological tool to induce PHa theta oscillations, due to its longest duration of action and lack of preliminary epileptogenic effects. It seems that CCH-induced theta can be the most suitable pharmacological model for experiments with the use of protocol of long-lasting recordings of PHa theta-related cell discharges. PMID:27353451

  3. A Modified Theta Projection Model for Creep Behavior of Metals and Alloys

    NASA Astrophysics Data System (ADS)

    Kumar, Manish; Singh, I. V.; Mishra, B. K.; Ahmad, S.; Venugopal Rao, A.; Kumar, Vikas

    2016-06-01

    In this work, a modified theta projection model is proposed for the constitutive modeling of creep behavior of metals and alloys. In the conventional theta projection model, strain hardening exponent is a function of time and theta, whereas in the modified theta projection model, the exponent is taken as a function of time, theta, and applied stress. The results obtained by the modified theta projection model for Al 2124 T851 alloy at constant uniaxial tensile stress are compared with the experimental results and with the predictions of the conventional theta projection method. The creep behavior of Al 7075 T651 alloy is also predicted using modified and conventional theta projection model and compared with the available experimental data. It is observed that the modified theta projection model captures the creep behavior more accurately as compared to the conventional theta projection model. The modified theta projection model can be used to predict the creep strain of pure metals and class M alloys (similar creep behavior to pure metals) for intermediate range of stress and temperature.

  4. Theta Series, Wall-Crossing and Quantum Dilogarithm Identities

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sergei; Pioline, Boris

    2016-05-01

    Motivated by mathematical structures which arise in string vacua and gauge theories with {{{N}=2}} supersymmetry, we study the properties of certain generalized theta series which appear as Fourier coefficients of functions on a twisted torus. In Calabi-Yau string vacua, such theta series encode instanton corrections from k Neveu-Schwarz five-branes. The theta series are determined by vector-valued wave-functions, and in this work we obtain the transformation of these wave-functions induced by Kontsevich-Soibelman symplectomorphisms. This effectively provides a quantum version of these transformations, where the quantization parameter is inversely proportional to the five-brane charge k. Consistency with wall-crossing implies a new five-term relation for Faddeev's quantum dilogarithm {Φ_b} at b = 1, which we prove. By allowing the torus to be non-commutative, we obtain a more general five-term relation valid for arbitrary b and k, which may be relevant for the physics of five-branes at finite chemical potential for angular momentum.

  5. Theta Series, Wall-Crossing and Quantum Dilogarithm Identities

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sergei; Pioline, Boris

    2016-08-01

    Motivated by mathematical structures which arise in string vacua and gauge theories with N=2 supersymmetry, we study the properties of certain generalized theta series which appear as Fourier coefficients of functions on a twisted torus. In Calabi-Yau string vacua, such theta series encode instanton corrections from k Neveu-Schwarz five-branes. The theta series are determined by vector-valued wave-functions, and in this work we obtain the transformation of these wave-functions induced by Kontsevich-Soibelman symplectomorphisms. This effectively provides a quantum version of these transformations, where the quantization parameter is inversely proportional to the five-brane charge k. Consistency with wall-crossing implies a new five-term relation for Faddeev's quantum dilogarithm {Φ_b} at b = 1, which we prove. By allowing the torus to be non-commutative, we obtain a more general five-term relation valid for arbitrary b and k, which may be relevant for the physics of five-branes at finite chemical potential for angular momentum.

  6. Speech encoding by coupled cortical theta and gamma oscillations.

    PubMed

    Hyafil, Alexandre; Fontolan, Lorenzo; Kabdebon, Claire; Gutkin, Boris; Giraud, Anne-Lise

    2015-01-01

    Many environmental stimuli present a quasi-rhythmic structure at different timescales that the brain needs to decompose and integrate. Cortical oscillations have been proposed as instruments of sensory de-multiplexing, i.e., the parallel processing of different frequency streams in sensory signals. Yet their causal role in such a process has never been demonstrated. Here, we used a neural microcircuit model to address whether coupled theta-gamma oscillations, as observed in human auditory cortex, could underpin the multiscale sensory analysis of speech. We show that, in continuous speech, theta oscillations can flexibly track the syllabic rhythm and temporally organize the phoneme-level response of gamma neurons into a code that enables syllable identification. The tracking of slow speech fluctuations by theta oscillations, and its coupling to gamma-spiking activity both appeared as critical features for accurate speech encoding. These results demonstrate that cortical oscillations can be a key instrument of speech de-multiplexing, parsing, and encoding. PMID:26023831

  7. Impaired theta-gamma coupling in APP-deficient mice

    PubMed Central

    Zhang, Xiaomin; Zhong, Wewei; Brankačk, Jurij; Weyer, Sascha W.; Müller, Ulrike C.; Tort, Adriano B. L.; Draguhn, Andreas

    2016-01-01

    Amyloid precursor protein (APP) is critically involved in the pathophysiology of Alzheimer’s disease, but its physiological functions remain elusive. Importantly, APP knockout (APP-KO) mice exhibit cognitive deficits, suggesting that APP plays a role at the neuronal network level. To investigate this possibility, we recorded local field potentials (LFPs) from the posterior parietal cortex, dorsal hippocampus and lateral prefrontal cortex of freely moving APP-KO mice. Spectral analyses showed that network oscillations within the theta- and gamma-frequency bands were not different between APP-KO and wild-type mice. Surprisingly, however, while gamma amplitude coupled to theta phase in all recorded regions of wild-type animals, in APP-KO mice theta-gamma coupling was strongly diminished in recordings from the parietal cortex and hippocampus, but not in LFPs recorded from the prefrontal cortex. Thus, lack of APP reduces oscillatory coupling in LFP recordings from specific brain regions, despite not affecting the amplitude of the oscillations. Together, our findings reveal reduced cross-frequency coupling as a functional marker of APP deficiency at the network level. PMID:26905287

  8. Distinct representations and theta dynamics in dorsal and ventral hippocampus

    PubMed Central

    Royer, Sébastien; Sirota, Anton; Patel, Jagdish; Buzsáki, György

    2010-01-01

    Although anatomical, lesion and imaging studies of the hippocampus indicate qualitatively different information processing along its septo-temporal axis, physiological mechanisms supporting such distinction are missing. We found fundamental differences between the dorsal (dCA3) and the ventral-most parts (vCA3) of the hippocampus in both environmental representation and temporal dynamics. Discrete place fields of dCA3 neurons evenly covered all parts of the testing environments. In contrast, vCA3 neurons i) rarely showed continuous two-dimensional place fields, ii) differentiated open and closed arms of a radial maze, and iii) discharged similar firing patterns with respect to the goals, both on multiple arms of a radial maze and during opposite journeys in a zig-zag maze. In addition, theta power and the fraction of theta-rhythmic neurons were substantially reduced in the ventral as compared to dorsal hippocampus. We hypothesize that the spatial representation in the septo-temporal axis of the hippocampus is progressively decreased. This change is paralleled with a reduction of theta rhythm and an increased representation of non-spatial information. PMID:20130187

  9. Pinch Me - I'm Fusing!

    SciTech Connect

    DERZON,MARK S.

    2000-07-19

    The process of combining nuclei (the protons and neutrons inside an atomic nucleus) together with a release of kinetic energy is called fusion. This process powers the Sun, it contributes to the world stockpile of weapons of mass destruction and may one day generate safe, clean electrical power. Understanding the intricacies of fusion power, promised for 50 years, ,is sometimes difficult because there are a number of ways of doing it. There is hot fusion, cold fusion and con-fusion. Hot fusion is what powers suns through the conversion of mass energy to kinetic energy. Cold fusion generates con-fusion and nobody really knows what it is. Honestly - this is true. There does seem to be something going on here; I just don't know what. Apparently some experimenters get energy out of a process many call cold fission but no one seems to know what it is, or how to do it reliably. It is not getting much attention from the mainline physics community. Even so, no one is generating electrical power for you and me with either method. In this article 1 will point out some basic features of the mainstream approaches taken to hot fusion power, as well as describe why z pinches are worth pursuing as a driver for a power reactor and may one day generate electrical power for mankind.

  10. Circuit model for the inverse Z-pinch wire array switch.

    SciTech Connect

    Waisman, Eduardo Mario; Cuneo, Michael Edward; Harvey-Thompson, A.; Lebedev, Sergey V.

    2010-06-01

    A 0D circuit code is introduced to study the wire array switch concept introduced in. It has been implemented and researched at Imperial College. An exploding wire array, the switch, is in parallel with the load, an imploding wire array. Most of the current flows in the exploding array until it expands and becomes highly resistive. The 0D code contains simple models of Joule energy deposition and plasma expansion for W and Al wires. The purpose of the device is to produce fast Z-pinch implosion, below 100ns on MAGPIE and the Sandia Z machine. Self and mutual inductances are taken into consideration as well as the rocket model for wire ablation. The switch characteristics of the exploding array are prescribed and tuned up to agree with MAGPIE shots. The dependence of the device on the configuration of the arrays is studied and scaling to ZR conditions is explored.

  11. INPIStron switched pulsed power for dense plasma pinches

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Lee, Ja H.

    1993-01-01

    The inverse plasma switch INPIStron was employed for 10kJ/40kV capacitor bank discharge system to produce focused dense plasmas in hypocycloidal-pinch (HCP) devices. A single unit and an array of multiple HCP's were coupled as the load of the pulsed power circuit. The geometry and switching plasma dynamics were found advantageous and convenient for commutating the large current pulse from the low impedance transmission line to the low impedance plasma load. The pulse power system with a single unit HCP, the system A, was used for production of high temperature plasma focus and its diagnostics. The radially running down plasma dynamics, revealed in image converter photographs, could be simulated by a simple snow-plow model with a correction for plasma resistivity. The system B with an array of 8-HCP units which forms a long coaxial discharge chamber was used for pumping a Ti-sapphire laser. The intense UV emission from the plasma was frequency shifted with dye-solution jacket to match the absorption band of the Ti crystal laser near 500 nm. An untuned laser pulse energy of 0.6 J/pulse was obtained for 6.4 kJ/40 kV discharge, or near 103 times of the explosion limit of conventional flash lamps. For both systems the advantages of the INPIStron were well demonstrated: a single unit is sufficient for a large current (greater than 50 kA) without increasing the system impedance, highly reliable and long life operation and implied scalability for the high power ranges above I(sub peak) = 1 MA and V(sub hold) = 100 kV.

  12. The Dense Z-Pinch Programme at Imperial College

    NASA Astrophysics Data System (ADS)

    Haines, M. G.

    1994-03-01

    An extensive programme of research, both experimental and theoretical, into the stability and dynamics of Z-pinches has led to the funding of the DZP Project to study both radiative collapse of Z-pinch plasmas and pinches close to thermonuclear fusion conditions. The MAGPIE (Mega-Ampere Generator for Plasma Implosion Experiments) generator (2.4MV, 336kJ, 200ns) is now being commissioned ready for Z-pinch experiments commencing this summer. The design of the generator has been determined by the perceived requirements demanded by consideration of (a) fusion conditions with end losses to electrodes, (b) radiative collapse at currents well above the Pease-Braginskii limit, and (c) stability studies particularly under large ion Larmor radius conditions. As a result, and in contrast to other generators in the >1TW class this has a long pulse length (200ns) and a final line impedance of 1.25 ohm. The stability regimes together with theoretical and experimental results are reviewed in the framework of the I4a-N diagram. Our understanding (albeit incomplete) of other phenomena characteristic of Z-pinches, namely the formation of electron beams, dense spots of intense X-ray emission, ion beams and filaments will be summarised.

  13. Scaling of X pinches from 1 MA to 6 MA.

    SciTech Connect

    Bland, Simon Nicholas; McBride, Ryan D.; Wenger, David Franklin; Sinars, Daniel Brian; Chittenden, Jeremy Paul; Pikuz, Sergei A.; Harding, Eric; Jennings, Christopher A.; Ampleford, David J.; Yu, Edmund P.; Cuneo, Michael Edward; Shelkovenko, Tatiana A.; Hansen, Stephanie B.

    2010-09-01

    This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parameters at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).

  14. Comparison of numerical techniques for the evaluation of the Doppler broadening functions psi(x,theta) and chi(x,theta)

    NASA Technical Reports Server (NTRS)

    Canright, R. B., Jr.; Semler, T. T.

    1972-01-01

    Several approximations to the Doppler broadening functions psi(x, theta) and chi(x, theta) are compared with respect to accuracy and speed of evaluation. A technique, due to A. M. Turning (1943), is shown to be at least as accurate as direct numerical quadrature and somewhat faster than Gaussian quadrature. FORTRAN 4 listings are included.

  15. Applicability/evaluation of flux based representations for linear/higher order elements for heat transfer in structures - Generalized gamma(T)-family

    NASA Technical Reports Server (NTRS)

    Namburu, R. R.; Tamma, K. K.

    1991-01-01

    The applicability and evaluation of a generalized gamma(T) family of flux-based representations are examined for two different thermal analysis formulations for structures and materials which exhibit no phase change effects. The so-called H-theta and theta forms are demonstrated for numerous test models and linear and higher-order elements. The results show that the theta form with flux-based representations is generally superior to traditional approaches.

  16. Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

    SciTech Connect

    Etchessahar, Bertrand; Bicrel, Beatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hebert, David; Bernigaud, Virgile; Magnin, Laurent; Nicolas, Remi; Poulet, Frederic; Tailleur, Yaeel; Caron, Michel; Cartier, Frederic; Cartier, Stephanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle; and others

    2012-09-15

    The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., 'Considerations of rod-pinch diode operation in negative polarity for radiography,' in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975-978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., 'Theoretical modeling and experimental characterization of a rod-pinch diode,' Phys. Plasmas 8(10), 4618-4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., 'Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,' IEEE Trans. Plasma Sci. 32(5), 2004-2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., 'ASTERIX, a high intensity X-ray generator,' in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567-570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., 'Negative polarity rod pinch diode experiments on the ASTERIX generator,' in Conference Records-Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most comprehensive characterization of the

  17. Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

    NASA Astrophysics Data System (ADS)

    Etchessahar, Bertrand; Bernigaud, Virgile; Caron, Michel; Cartier, Frédéric; Cartier, Stéphanie; Hourdin, Laurent; Magnin, Laurent; Nicolas, Rémi; Poulet, Frédéric; Rosol, Rodolphe; Tailleur, Yaël; Toury, Martial; Compant La Fontaine, Antoine; Bicrel, Béatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hébert, David; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle

    2012-09-01

    The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., "Considerations of rod-pinch diode operation in negative polarity for radiography," in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975-978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., "Theoretical modeling and experimental characterization of a rod-pinch diode," Phys. Plasmas 8(10), 4618-4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., "Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources," IEEE Trans. Plasma Sci. 32(5), 2004-2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., "ASTERIX, a high intensity X-ray generator," in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567-570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., "Negative polarity rod pinch diode experiments on the ASTERIX generator," in Conference Records-Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most comprehensive characterization of the

  18. Distinguishing Linear vs. Non-Linear Integration in CA1 Radial Oblique Dendrites: It’s about Time

    PubMed Central

    Gómez González, José Francisco; Mel, Bartlett W.; Poirazi, Panayiota

    2011-01-01

    It was recently shown that multiple excitatory inputs to CA1 pyramidal neuron dendrites must be activated nearly simultaneously to generate local dendritic spikes and supralinear responses at the soma; even slight input desynchronization prevented local spike initiation (Gasparini and Magee, 2006; Losonczy and Magee, 2006). This led to the conjecture that CA1 pyramidal neurons may only express their non-linear integrative capabilities during the highly synchronized sharp waves and ripples that occur during slow wave sleep and resting/consummatory behavior, whereas during active exploration and REM sleep (theta rhythm), inadequate synchronization of excitation would lead CA1 pyramidal cells to function as essentially linear devices. Using a detailed single neuron model, we replicated the experimentally observed synchronization effect for brief inputs mimicking single synaptic release events. When synapses were driven instead by double pulses, more representative of the bursty inputs that occur in vivo, we found that the tolerance for input desynchronization was increased by more than an order of magnitude. The effect depended mainly on paired-pulse facilitation of NMDA receptor-mediated responses at Schaffer collateral synapses. Our results suggest that CA1 pyramidal cells could function as non-linear integrative units in all major hippocampal states. PMID:22171217

  19. Experimental study of self magnetic pinch diode as flash radiography source at 4 megavolt

    NASA Astrophysics Data System (ADS)

    Etchessahar, Bertrand; Maisonny, Rémi; Toury, Martial; Hourdin, Laurent; Bicrel, Béatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Cartier, Frédéric; Cartier, Stéphanie; D'Almeida, Thierry; Delbos, Christophe; Garrigues, Alain; Plouhinec, Damien; Ritter, Sandra; Sol, David; Zucchini, Frédéric; Caron, Michel

    2013-10-01

    The Self Magnetic Pinch (SMP) diode is a potential high-brightness X-ray source for high voltage generators (2-10 MV) that has shown good reliability for flash radiography applications [D. D. Hinchelwood et al., "High power self-pinch diode experiments for radiographic applications" IEEE Trans. Plasma Sci. 35(3), 565-572 (2007)]. We have studied this diode at about 4 MV, driven by the ASTERIX generator operated at the CEA/GRAMAT [G. Raboisson et al., "ASTERIX, a high intensity X-ray generator," in Proceedings of the 7th IEEE Pulsed Power Conference (1989), pp. 567-570]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode is modified in order to set up flash radiographic diodes. A previous set of radiographic experiments was carried out on ASTERIX with a Negative Polarity Rod Pinch (NPRP) diode [B. Etchessahar et al., "Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV," Phys. Plasmas 19(9), 093104 (2012)]. The SMP diode which is examined in the present study provides an alternative operating point on the same generator and a different radiographic performance: 142 ± 11 rad at 1 m dose (Al) for a 3.46 ± 0.42 mm spot size (1.4× FWHM of the LSF). This performance is obtained in a reproducible and robust nominal configuration. However, several parametric variations were also tested, such as cathode diameter and anode/cathode gap. They showed that an even better performance is accessible after optimization, in particular, a smaller spot size (<3 mm). Numbers of electrical, optical, and X-ray diagnostics have been implemented in order to gain more insight in the diode physics and to optimize it further. For the first time in France, visible and laser imaging of the SMP diode has been realized, from a radial point of view, thus, providing key information on the electrode plasmas evolution

  20. Experimental study of self magnetic pinch diode as flash radiography source at 4 megavolt

    SciTech Connect

    Etchessahar, Bertrand; Bicrel, Béatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Maisonny, Rémi; Toury, Martial; Hourdin, Laurent; Cartier, Frédéric; Cartier, Stéphanie; D'Almeida, Thierry; Delbos, Christophe; Garrigues, Alain; Plouhinec, Damien; Ritter, Sandra; Sol, David; Zucchini, Frédéric; Caron, Michel

    2013-10-15

    The Self Magnetic Pinch (SMP) diode is a potential high-brightness X-ray source for high voltage generators (2–10 MV) that has shown good reliability for flash radiography applications [D. D. Hinchelwood et al., “High power self-pinch diode experiments for radiographic applications” IEEE Trans. Plasma Sci. 35(3), 565–572 (2007)]. We have studied this diode at about 4 MV, driven by the ASTERIX generator operated at the CEA/GRAMAT [G. Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference (1989), pp. 567–570]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode is modified in order to set up flash radiographic diodes. A previous set of radiographic experiments was carried out on ASTERIX with a Negative Polarity Rod Pinch (NPRP) diode [B. Etchessahar et al., “Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV,” Phys. Plasmas 19(9), 093104 (2012)]. The SMP diode which is examined in the present study provides an alternative operating point on the same generator and a different radiographic performance: 142 ± 11 rad at 1 m dose (Al) for a 3.46 ± 0.42 mm spot size (1.4× FWHM of the LSF). This performance is obtained in a reproducible and robust nominal configuration. However, several parametric variations were also tested, such as cathode diameter and anode/cathode gap. They showed that an even better performance is accessible after optimization, in particular, a smaller spot size (<3 mm). Numbers of electrical, optical, and X-ray diagnostics have been implemented in order to gain more insight in the diode physics and to optimize it further. For the first time in France, visible and laser imaging of the SMP diode has been realized, from a radial point of view, thus, providing key information on the electrode

  1. Approach to universality in axisymmetric bubble pinch-off

    NASA Astrophysics Data System (ADS)

    Gekle, Stephan; Snoeijer, Jacco H.; Lohse, Detlef; van der Meer, Devaraj

    2009-09-01

    The pinch-off of an axisymmetric air bubble surrounded by an inviscid fluid is compared in four physical realizations: (i) cavity collapse in the wake of an impacting disk, (ii) gas bubbles injected through a small orifice, (iii) bubble rupture in a straining flow, and (iv) a bubble with an initially necked shape. Our boundary-integral simulations suggest that all systems eventually follow the universal behavior characterized by slowly varying exponents predicted by J. Eggers [Phys. Rev. Lett. 98, 094502 (2007)]. However, the time scale for the onset of this final regime is found to vary by orders of magnitude depending on the system in question. While for the impacting disk it is well in the millisecond range, for the gas injection needle universal behavior sets in only a few microseconds before pinch-off. These findings reconcile the different views expressed in recent literature about the universal nature of bubble pinch-off.

  2. First results from the Madison Symmetric Torus reversed field pinch

    SciTech Connect

    Prager, S.C.; Almagri, A.F.; Assadi, S.; Beckstead, J.A.; Dexter, R.N.; Den Hartog, D.J.; Chartas, G.; Hokin, S.A.; Lovell, T.W.; Rempel, T.D.; Sarff, J.S.; Shen, W.; Spragins, C.W.; Sprott, J.C. )

    1990-06-01

    The first period of physics operation of the Madison Symmetric Torus (MST) reversed field pinch ({ital Plasma} {ital Physics} {ital and} {ital Controlled} {ital Nuclear} {ital Fusion} {ital Research} 1988 (IAEA, Vienna, 1989), Vol 2, p. 757) has produced information on sawtooth oscillations, edge magnetic and electrostatic fluctuations, and equilibrium parameters at large plasma size. Sawtooth oscillations are prevalent at all values of pinch parameter and might constitute discrete dynamo events. Both electrostatic and magnetic fluctuations are of sufficient magnitude to be relevant to transport in the reversed field pinch. In the plasmas studied to date (up to a plasma current of 0.5 MA) the poloidal beta value is about 10% or greater.

  3. Resolving microstructures in Z pinches with intensity interferometry

    SciTech Connect

    Apruzese, J. P.; Kroupp, E.; Maron, Y.; Giuliani, J. L.; Thornhill, J. W.

    2014-03-15

    Nearly 60 years ago, Hanbury Brown and Twiss [R. Hanbury Brown and R. Q. Twiss, Nature 178, 1046 (1956)] succeeded in measuring the 30 nrad angular diameter of Sirius using a new type of interferometry that exploited the interference of photons independently emitted from different regions of the stellar disk. Its basis was the measurement of intensity correlations as a function of detector spacing, with no beam splitting or preservation of phase information needed. Applied to Z pinches, X pinches, or laser-produced plasmas, this method could potentially provide spatial resolution under one micron. A quantitative analysis based on the work of Purcell [E. M. Purcell, Nature 178, 1449 (1956)] reveals that obtaining adequate statistics from x-ray interferometry of a Z-pinch microstructure would require using the highest-current generators available. However, using visible light interferometry would reduce the needed photon count and could enable its use on sub-MA machines.

  4. MHD Simulation of the Inverse Pinch Plasma Discharge

    SciTech Connect

    Esaulov, A; Bauer, B; Lindemuth, I; Makhin, V; Presura, R; Ryutov, D

    2004-07-01

    A wall confined plasma in an inverse pinch configuration holds potential as a plasma target for Magnetized Target Fusion (MTF) as well as the simple geometry to study wall-confined plasma. An experiment is planned to study the inverse pinch configuration using the Nevada Terawatt Facility (NTF) at the University of Nevada, Reno (UNR). The dynamics of the discharge formation have been analyzed using analytic models and numerical methods. Strong heating occurs by thermalization of directed energy when an outward moving current sheet (the inverse pinch effect) collides with the outer wall of the experimental chamber. Two dimensional MHD simulations show Rayleigh-Taylor and Richtmyer-Meshkov -like modes of instability, as expected because of the shock acceleration during plasma formation phase. The instabilities are not disruptive, but give rise to a mild level of turbulence. The conclusion from this work is that an interesting experiment relevant to wall confinement for MTF could be done using existing equipment at UNR.

  5. X-pinch dynamics: Neck formation and implosion

    SciTech Connect

    Oreshkin, V. I.; Chaikovsky, S. A.; Artyomov, A. P.; Labetskaya, N. A.; Fedunin, A. V.; Rousskikh, A. G.; Zhigalin, A. S.

    2014-10-15

    We propose a model that describes the neck formation and implosion in an X-pinch. The process is simulated to go in two stages. The first stage is neck formation. This stage begins with an electrical explosion of the wires forming the X-pinch, and at the end of the stage, a micropinch (neck) is formed in the region where the wires are crossed. The second stage is neck implosion. The implosion is accompanied by outflow of matter from the neck region, resulting in the formation of a “hot spot”. Analytical estimates obtained in the study under consideration indicate that these stages are approximately equal in duration. Having analyzed the neck implosion dynamics, we have verified a scaling which makes it possible to explain the observed dependences of the time of occurrence of an x-ray pulse on the X-pinch current and mass.

  6. Suppression of Rayleigh-Taylor instabilities in Z-pinches

    NASA Astrophysics Data System (ADS)

    Zhigalin, A. S.; Rousskikh, A. G.; Baksht, R. B.; Chaikovsky, S. A.; Labetskaya, N. A.; Oreshkin, V. I.

    2015-06-01

    Experiments on studying the stability of Z-pinch compression were carried out at a current of 450 kA with a build-up time of 450 ns. The plasma shell of the pinches was formed by evaporating the electrode material in the process of vacuum arc burning. The Rayleigh-Taylor (RT) instabilities were suppressed using the regime of arc combustion on the surface of one of the electrodes in the high-voltage gap in which the pinch was positioned. As a result of free plasma discharge, the radial density distribution was formed such that the plasma concentration increased from the outer boundary to the shell axis. The experiments demonstrated that such an initial radial density distribution almost completely suppresses of the RT instability.

  7. Canards and curvature: nonsmooth approximation by pinching

    NASA Astrophysics Data System (ADS)

    Desroches, M.; Jeffrey, M. R.

    2011-05-01

    In multiple time-scale (singularly perturbed) dynamical systems, canards are counterintuitive solutions that evolve along both attracting and repelling invariant manifolds. In two dimensions, canards result in periodic oscillations whose amplitude and period grow in a highly nonlinear way: they are slowly varying with respect to a control parameter, except for an exponentially small range of values where they grow extremely rapidly. This sudden growth, called a canard explosion, has been encountered in many applications ranging from chemistry to neuronal dynamics, aerospace engineering and ecology. Canards were initially studied using nonstandard analysis, and later the same results were proved by standard techniques such as matched asymptotics, invariant manifold theory and parameter blow-up. More recently, canard-like behaviour has been linked to surfaces of discontinuity in piecewise-smooth dynamical systems. This paper provides a new perspective on the canard phenomenon by showing that the nonstandard analysis of canard explosions can be recast into the framework of piecewise-smooth dynamical systems. An exponential coordinate scaling is applied to a singularly perturbed system of ordinary differential equations. The scaling acts as a lens that resolves dynamics across all time-scales. The changes of local curvature that are responsible for canard explosions are then analysed. Regions where different time-scales dominate are separated by hypersurfaces, and these are pinched together to obtain a piecewise-smooth system, in which curvature changes manifest as discontinuity-induced bifurcations. The method is used to classify canards in arbitrary dimensions, and to derive the parameter values over which canards form either small cycles (canards without head) or large cycles (canards with head).

  8. Peak frequency in the theta and alpha bands correlates with human working memory capacity.

    PubMed

    Moran, Rosalyn J; Campo, Pablo; Maestu, Fernando; Reilly, Richard B; Dolan, Raymond J; Strange, Bryan A

    2010-01-01

    Theta oscillations in the local field potential of neural ensembles are considered key mediators of human working memory. Theoretical accounts arising from animal hippocampal recordings propose that the phase of theta oscillations serves to instantiate sequential neuronal firing to form discrete representations of items held online. Human evidence of phase relationships in visual working memory has enhanced this theory, implicating long theta cycles in supporting greater memory capacity. Here we use human magnetoencephalographic recordings to examine a novel, alternative principle of theta functionality. The principle we hypothesize is derived from information theory and predicts that rather than long (low frequency) theta cycles, short (high frequency) theta cycles are best suited to support high information capacity. From oscillatory activity recorded during the maintenance period of a visual working memory task we show that a network of brain regions displays an increase in peak 4-12 Hz frequency with increasing memory load. Source localization techniques reveal that this network comprises bilateral prefrontal and right parietal cortices. Further, the peak of oscillation along this theta-alpha frequency axis is significantly higher in high capacity individuals compared to low capacity individuals. Importantly while we observe the adherence of cortical neuronal oscillations to our novel principle of theta functioning, we also observe the traditional inverse effect of low frequency theta maintaining high loads, where critically this was located in medial temporal regions suggesting parallel, dissociable hippocampal-centric, and prefrontal-centric theta mechanisms. PMID:21206531

  9. Sex differences in human EEG theta oscillations during spatial navigation in virtual reality.

    PubMed

    Kober, Silvia Erika; Neuper, Christa

    2011-03-01

    The present study examines theta oscillations (electroencephalographic (EEG) activity with a frequency of 4-8 Hz) in male and female young adults during spatial navigation in virtual environments. Twenty-seven participants (13 males and 14 females) performed a spatial navigation task in a virtual maze where they had to find the shortest ways between landmarks. Absolute theta band power and event-related desynchronisation/synchronisation (ERD/ERS) in the theta frequency band was used to analyze the EEG data. Processing of spatial cues or landmarks induced cortical theta activity compared to a baseline condition, confirming the hypothesis that theta oscillations reflect sensorimotor integration. The sensorimotor integration hypothesis proposes that theta oscillations coordinate sensory information with a motor plan to direct wayfinding behaviour to known goal locations. No sex differences were found in spatial performance. However, female participants showed a stronger increase in theta oscillations during processing of landmarks as navigational aids compared to a baseline condition than men. Additionally, a higher theta power was associated with an increased navigation performance in women, whereas an increase in theta power was associated with a decreased navigation performance in men. These results might indicate a stronger sensorimotor integration in females than in males. Possible explanations for the emerged sex differences in cortical theta activity are discussed. PMID:21146566

  10. Aged rats show dominant modulation of lower frequency hippocampal theta rhythm during running.

    PubMed

    Li, Jia-Yi; Kuo, Terry B J; Yang, Cheryl C H

    2016-10-01

    Aging causes considerable decline in both physiological and mental functions, particularly cognitive function. The hippocampal theta rhythm (4-12Hz) is related to both cognition and locomotion. Aging-related findings of the frequency and amplitude of hippocampal theta oscillations are inconsistent and occasionally contradictory. This inconsistency may be due to the effects of the sleep/wake state and different frequency subbands being overlooked. We assumed that aged rats have lower responses of the hippocampal theta rhythm during running, which is mainly due to the dominant modulation of theta frequency subbands related to cognition. By simultaneously recording electroencephalography, physical activity (PA), and the heart rate (HR), this experiment explored the theta oscillations before, during, and after treadmill running at a constant speed in 8-week-old (adult) and 60-week-old (middle-aged) rats. Compared with adult rats, the middle-aged rats exhibited lower theta activity in all frequency ranges before running. Running increased the theta frequency (Frq, 4-12Hz), total activity of the whole theta band (total power, TP), activity of the middle theta frequency (MT, 6.5-9.5Hz), and PA in both age groups. However, the middle-aged rats still showed fewer changes in these parameters during the whole running process. After the waking baseline values were substracted, middle-aged rats showed significantly fewer differences in ΔFrq, ΔTP, and ΔMT but significantly more differences in low-frequency theta activity (4.0-6.5Hz) and HR than the adult rats did. Therefore, the decreasing activity and response of the whole theta band in the middle-aged rats resulted in dominant modulation of the middle to lower frequency (4.0-9.5Hz) theta rhythm. The different alterations in the theta rhythm during treadmill running in the two groups may reflect that learning decline with age. PMID:27496645

  11. Magnetic Field Measurements in Wire-Array Z-Pinches using Magneto-Optically Active Waveguides

    SciTech Connect

    Syed, Wasif; Blesener, Isaac; Hammer, David A.; Lipson, Michal

    2009-01-21

    Understanding the magnetic field topology in wire-array Z-pinches as a function of time is of great significance to understanding these high-energy density plasmas especially for their ultimate application to stockpile stewardship and inertial confinement fusion. We are developing techniques to measure magnetic fields as a function of space and time using Faraday rotation of a single longitudinal mode (SLM) laser through a magneto-optically active bulk waveguide (multicomponent terbium borate glass) placed adjacent to, or within, the wire array in 1 MA experiments. We have measured fields >10 T with 100 ns rise times outside of a wire-array for the entire duration of the current pulse and as much as {approx}2 T inside a wire-array for {approx}40 ns from the start of current. This is the first time that such rapidly varying and large fields have been measured using these materials. In a dense Z-pinch, these sensing devices may not survive for long but may provide the magnetic field at the position of the sensor that can be used to corroborate magnetic probes, with which we compare our results.

  12. Evaluating the Usability of Pinchigator, a system for Navigating Virtual Worlds using Pinch Gloves

    NASA Technical Reports Server (NTRS)

    Hamilton, George S.; Brookman, Stephen; Dumas, Joseph D. II; Tilghman, Neal

    2003-01-01

    Appropriate design of two dimensional user interfaces (2D U/I) utilizing the well known WIMP (Window, Icon, Menu, Pointing device) environment for computer software is well studied and guidance can be found in several standards. Three-dimensional U/I design is not nearly so mature as 2D U/I, and standards bodies have not reached consensus on what makes a usable interface. This is especially true when the tools for interacting with the virtual environment may include stereo viewing, real time trackers and pinch gloves instead of just a mouse & keyboard. Over the last several years the authors have created a 3D U/I system dubbed Pinchigator for navigating virtual worlds based on the dVise dV/Mockup visualization software, Fakespace Pinch Gloves and Pohlemus trackers. The current work is to test the usability of the system on several virtual worlds, suggest improvements to increase Pinchigator s usability, and then to generalize about what was learned and how those lessons might be applied to improve other 3D U/I systems.

  13. Magnetic Field Measurements in Wire-Array Z-Pinches using Magneto-Optically Active Waveguides

    NASA Astrophysics Data System (ADS)

    Syed, Wasif; Blesener, Isaac; Hammer, David A.; Lipson, Michal

    2009-01-01

    Understanding the magnetic field topology in wire-array Z-pinches as a function of time is of great significance to understanding these high-energy density plasmas especially for their ultimate application to stockpile stewardship and inertial confinement fusion. We are developing techniques to measure magnetic fields as a function of space and time using Faraday rotation of a single longitudinal mode (SLM) laser through a magneto-optically active bulk waveguide (multicomponent terbium borate glass) placed adjacent to, or within, the wire array in 1 MA experiments. We have measured fields >10 T with 100 ns rise times outside of a wire-array for the entire duration of the current pulse and as much as ˜2 T inside a wire-array for ˜40 ns from the start of current. This is the first time that such rapidly varying and large fields have been measured using these materials. In a dense Z-pinch, these sensing devices may not survive for long but may provide the magnetic field at the position of the sensor that can be used to corroborate magnetic probes, with which we compare our results.

  14. Linking natural microstructures with numerical modeling of pinch-and-swell structures

    NASA Astrophysics Data System (ADS)

    Peters, Max; Berger, Alfons; Herwegh, Marco; Regenauer-Lieb, Klaus

    2016-04-01

    dominated deformation at relatively high extensional strains in the pinches. The numerical simulations indicate that viscosity weakening due to dissipated heat from grain size reduction marks the onset of localization, resulting in continuous necking of the layer. Interestingly, there exist multiple steady states, i.e. a first homogeneous state out of which localization arises, steady states of the stable end-member structure, expressed by homogeneous conditions in both pinches and swells, and in the surrounding matrix, the latter obeying a linear rheology. Based on our microstructural and numerical results, we suggest that the onset of localization represents a fundamental material bifurcation. This implies that the studied structures can be described as ductile instabilities. Finally, we discuss the profound role of the energy theory of localization described here, which allows deriving the paleo-deformation conditions, as well as fundamental material properties in a self-consistent manner. REFERENCES Herwegh, M., Poulet, T., Karrech, A. and Regenauer-Lieb, K. (2014): Journal of Geophysical Research 119, doi:10.1002/2013JB010701 Peters, M., Veveakis, M., Poulet, T., Karrech, A., Herwegh, M. and Regenauer-Lieb, K. (2015): Journal of Structural Geology 78, doi:10.1016/j.jsg.2015.06.005

  15. Measurement of Radiation Symmetry in Z-Pinch Driven Hohlraums

    NASA Astrophysics Data System (ADS)

    Hanson, David L.

    2001-10-01

    The z-pinch driven hohlraum (ZPDH) is a promising approach to high yield inertial confinement fusion currently being characterized in experiments on the Sandia Z accelerator [1]. In this concept [2], x rays are produced by an axial z-pinch in a primary hohlraum at each end of a secondary hohlraum. A fusion capsule in the secondary is imploded by a symmetric x-ray flux distribution, effectively smoothed by wall reemission during transport to the capsule position. Capsule radiation symmetry, a critical issue in the design of such a system, is influenced by hohlraum geometry, wall motion and time-dependent albedo, as well as power balance and pinch timing between the two z-pinch x-ray sources. In initial symmetry studies on Z, we used solid low density burnthrough spheres to diagnose highly asymmetric, single-sided-drive hohlraum geometries. We then applied this technique to the more symmetric double z-pinch geometry [3]. As a result of design improvements, radiation flux symmetry in Z double-pinch wire array experiments now exceeds the measurement sensitivity of this self-backlit foam ball symmetry diagnostic (15% max-min flux asymmetry). To diagnose radiation symmetry at the 2 - 5% level attainable with our present ZPDH designs, we are using high-energy x rays produced by the recently-completed Z-Beamlet laser backlighter for point-projection imaging of thin-wall implosion and symmetry capsules. We will present the results of polar flux symmetry measuremets on Z for several ZPDH capsule geometries together with radiosity and radiation-hydrodynamics simulations for comparison. [1] M. E. Cuneo et al., Phys. Plasmas 8,2257(2001); [2] J. H. Hammer et al., Phys. Plasmas 6,2129(1999); [3] D. L. Hanson et al., Bull. Am. Phys. Soc. 45,360(2000).

  16. An investigation of transient pressure and plasma properties in a pinched plasma column. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Stover, E. K.; York, T. M.

    1971-01-01

    The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with the following plasma diagnostics: a special rapid response pressure transducer, a magnetic field probe, a voltage probe and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior; they were in temporal sequence: strong axial pressure asymmetry noted early in plasma column lifetime followed by plasma heating in which there is a rapid rise in static pressure and a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating is attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity. Turbulent heating arising from discharge current excitation of the ion acoustic wave instability is also considered a possible heating mechanism.

  17. Polycrystalline diamond based detector for Z-pinch plasma diagnosis

    SciTech Connect

    Liu Linyue; Zhao Jizhen; Chen Liang; Ouyang Xiaoping; Wang Lan

    2010-08-15

    A detector setup based on polycrystalline chemical-vapor-deposition diamond film is developed with great characteristics: low dark current (lower than 60 pA within 3 V/{mu}m), fast pulsed response time (rise time: 2-3 ns), flat spectral response (3-5 keV), easy acquisition, low cost, and relative large sensitive area. The characterizing data on Qiangguang-I accelerator show that this detector can satisfy the practical requirements in Z-pinch plasma diagnosis very well, which offers a promising prototype for the x-ray detection in Z-pinch diagnosis.

  18. Seeded perturbations in wire array Z-Pinches.

    SciTech Connect

    Robinson, Allen Conrad; Fedin, Dmitry; Kantsyrev, Victor Leonidovich; Wunsch, Scott Edward; Oliver, Bryan Velten; Lebedev, Sergey V.; Coverdale, Christine Anne; Ouart, Nicholas D.; LePell, Paul David; Safronova, Alla S.; Shrestha, I.; McKenney, John Lee; Ampleford, David J.; Rapley, J.; Bott, S. C.; Palmer, J. B. A.; Sotnikov, Vladimir Isaakovich; Bland, Simon Nicholas; Ivanov, Vladimir V.; Chittenden, Jeremy Paul; Jones, B.; Garasi, Christopher Joseph; Hall, Gareth Neville; Yilmaz, M. Faith; Mehlhorn, Thomas Alan; Deeney, Christopher; Pokala, S.; Nalajala, V.

    2005-07-01

    Controlled seeding of perturbations is employed to study the evolution of wire array z-pinch implosion instabilities which strongly impact x-ray production when the 3D plasma stagnates on axis. Wires modulated in radius exhibit locally enhanced magnetic field and imploding bubble formation at discontinuities in wire radius due to the perturbed current path. Wires coated with localized spectroscopic dopants are used to track turbulent material flow. Experiments and MHD modeling offer insight into the behavior of z-pinch instabilities.

  19. Rotating plasma disks in dense Z-pinch experiments

    SciTech Connect

    Bennett, M. J. E-mail: s.lebedev@imperial.ac.uk; Lebedev, S. V. E-mail: s.lebedev@imperial.ac.uk; Suttle, L.; Burdiak, G.; Suzuki-Vidal, F.; Hare, J.; Swadling, G.; Patankar, S.; Bocchi, M.; Chittenden, J. P.; Smith, R.; Hall, G. N.; Frank, A.; Blackman, E.; Drake, R. P.; Ciardi, A.

    2014-12-15

    We present data from the first z-pinch experiments aiming to simulate aspects of accretion disk physics in the laboratory. Using off axis ablation flows from a wire array z-pinch we demonstrate the formation of a hollow disk structure that rotates at 60 kms{sup −1} for 150 ns. By analysing the Thomson scattered spectrum we make estimates for the ion and electron temperatures as T{sub i} ∼ 60 eV and ZT{sub e} ∼ 150 to 200 eV.

  20. A compact, coaxial shunt current diagnostic for X pinches

    NASA Astrophysics Data System (ADS)

    Wang, Liangping; Zhang, Jinhai; Li, Mo; Zhang, Xinjun; Zhao, Chen; Zhang, Shaoguo

    2015-08-01

    A compact coaxial shunt was applied in X-pinches experiments on Qiangguang pulsed power generator. The coaxial shunt was designed to have a compact construction for smaller inductance and more, for conveniently assembling upon the X pinch load structure. The coaxial shunt is also a cheap current probe and was easily built by research groups. The shunt can monitor a 100 kA high current with a 100 ns rise time. The calibration results showed that the probe used in the experiments has a resistance of 3.2 mΩ with an uncertainty of 3%, and its response time to the step signal is less than 7 ns.

  1. {alpha} Heating in a Stagnated Z-pinch

    SciTech Connect

    Appelbe, Brian; Chittenden, Jeremy

    2009-01-21

    A computational investigation of a scheme for magneto-inertial confinement fusion in a Z-pinch is carried out. In the scheme implosion of a deuterium-tritium fuel mass is preceded by formation of a hotspot containing warm, dense plasma on axis. The presence of the hotspot increases energy yield. Compression of the hotspot by the main fuel mass initiates thermonuclear burn. There is significant heating of the plasma by thermonuclear {alpha} particles which are confined by the strong magnetic field of the Z-pinch.

  2. ELECTROSTATIC MODE ASSOCIATED WITH PINCH VELOCITY IN RFPS

    SciTech Connect

    DELZANNO, GIAN LUCA; FINN, JOHN M.; CHACON, LUIS

    2007-02-08

    The existence of a new electrostatic instability is shown for RFP (reversed field pinch) equilibria. This mode arises due to the non-zero equilibrium radial flow (pinch flow). In RFP simulations with no-stress boundary conditions on the tangential velocity at the radial wall, this electrostatic mode is unstable and dominates the nonlinear dynamics, even in the presence of the MHD modes typically responsible for the reversal of the axial magnetic field at edge. Nonlinearly, this mode leads to two beams moving azimuthally towards each other, which eventually collide. The electrostatic mode can be controlled by using Dirichlet (no-slip) boundary conditions on the azimuthal velocity at the radial wall.

  3. Reversed field pinch current drive with oscillating helical fields

    SciTech Connect

    Farengo, Ricardo; Clemente, Roberto Antonio

    2006-04-15

    The use of oscillating helical magnetic fields to produce and sustain the toroidal and poloidal currents in a reversed field pinch (RFP) is investigated. A simple physical model that assumes fixed ions, massless electrons, and uniform density and resistivity is employed. Thermal effects are neglected in Ohm's law and helical coordinates are introduced to reduce the number of coupled nonlinear equations that must be advanced in time. The results show that it is possible to produce RFP-like magnetic field profiles with pinch parameters close to the experimental values. The efficiencies obtained for moderate resistivity, and the observed scaling, indicate that this could be a very attractive method for high temperature plasmas.

  4. On equilibrium parameters of a radiation-compression model pinch

    SciTech Connect

    Afonin, V.I.

    1994-12-31

    Up to date, the micropinch effect in high-current axially symmetric electric discharges was the subject of extensive theoretical and experimental research. The radiation compression mechanism proved to fit the experimental data better than any other model. It assumes the pinch equilibrium to occur when the surface radiation emission replaces the surface emission mode. The aim of the present work is to show that a quasi-stationary pinch state can exist in the case of an optically thin plasma as well. 8 figs.

  5. Linear Accelerator (LINAC)

    MedlinePlus

    ... is the device most commonly used for external beam radiation treatments for patients with cancer. The linear ... shape of the patient's tumor and the customized beam is directed to the patient's tumor. The beam ...

  6. Use of EEG Beta-1 Power and Theta/Beta Ratio Over Broca's Area to confirm Diagnosis of Attention Deficit/Hyperactivity Disorder in Children.

    PubMed

    Sangal, R Bart; Sangal, JoAnne M

    2015-07-01

    The Food and Drug Administration has approved a medical device using the electroencephalogram (EEG) theta/beta ratio (tbr) to help assess pediatric attention deficit/hyperactivity disorder (ADHD). Tbr is reported to be higher in ADHD, with increased theta and decreased beta. This study examined theta and beta-1 power differences between ADHD and normal children, during tasks of selective attention, and elucidated topographical differences. EEGs were collected from 28 normal and 58 ADHD children, aged 6 to 14 years, using 31 scalp electrodes during auditory and visual tasks requiring selective attention. Spectral analysis was performed. Tbr was higher in ADHD than in normal children (2.60 vs 2.25, P = .007), with lower beta-1 (3.66 vs 4.22, P = .01), but no difference in theta power. There was lower beta-1 (P < .001) and higher tbr (P = .002) over Broca's area (electrode locations F7 and FC5). Beta-1 power over Broca's area was the best diagnostic test, with sensitivity 0.86 and specificity 0.57. Tbr is higher and beta-1 power lower in ADHD than in normal children, especially over Broca's area. Beta-1 power and tbr assist in confirming the diagnosis of ADHD in a sample with moderate pretest probability of ADHD. PMID:24973230

  7. Theta brain rhythms index perceptual narrowing in infant speech perception

    PubMed Central

    Bosseler, Alexis N.; Taulu, Samu; Pihko, Elina; Mäkelä, Jyrki P.; Imada, Toshiaki; Ahonen, Antti; Kuhl, Patricia K.

    2013-01-01

    The development of speech perception shows a dramatic transition between infancy and adulthood. Between 6 and 12 months, infants' initial ability to discriminate all phonetic units across the world's languages narrows—native discrimination increases while non-native discrimination shows a steep decline. We used magnetoencephalography (MEG) to examine whether brain oscillations in the theta band (4–8 Hz), reflecting increases in attention and cognitive effort, would provide a neural measure of the perceptual narrowing phenomenon in speech. Using an oddball paradigm, we varied speech stimuli in two dimensions, stimulus frequency (frequent vs. infrequent) and language (native vs. non-native speech syllables) and tested 6-month-old infants, 12-month-old infants, and adults. We hypothesized that 6-month-old infants would show increased relative theta power (RTP) for frequent syllables, regardless of their status as native or non-native syllables, reflecting young infants' attention and cognitive effort in response to highly frequent stimuli (“statistical learning”). In adults, we hypothesized increased RTP for non-native stimuli, regardless of their presentation frequency, reflecting increased cognitive effort for non-native phonetic categories. The 12-month-old infants were expected to show a pattern in transition, but one more similar to adults than to 6-month-old infants. The MEG brain rhythm results supported these hypotheses. We suggest that perceptual narrowing in speech perception is governed by an implicit learning process. This learning process involves an implicit shift in attention from frequent events (infants) to learned categories (adults). Theta brain oscillatory activity may provide an index of perceptual narrowing beyond speech, and would offer a test of whether the early speech learning process is governed by domain-general or domain-specific processes. PMID:24130536

  8. Interinstrument reliability of the Jamar electronic dynamometer and pinch gauge compared with the Jamar hydraulic dynamometer and B&L Engineering mechanical pinch gauge.

    PubMed

    King, Theodore I

    2013-01-01

    OBJECTIVE. This study sought to determine interinstrument reliability of the Jamar electronic dynamometer and pinch gauge compared with the commonly used Jamar hydraulic dynamometer and B&L Engineering mechanical pinch gauge. METHOD. Twenty men and 20 women were tested for grip strength with the two different dynamometers, and 17 men and 25 women were tested for lateral pinch strength with the two different pinch gauges. RESULTS. Grip strength measurements were approximately 10% higher with the hydraulic dynamometer, and lateral pinch strength measurements were approximately 18% higher with the mechanical pinch gauge. Paired t tests and intraclass correlation coefficients (ICCs) were used for statistical analyses. The two-tailed p value was <.0001, and the ICC indicated poor to moderate reliability. CONCLUSION. When retesting patients, it is recommended that occupational therapists use the same instrument to measure hand strength because interinstrument reliability may be lacking. PMID:23791323

  9. The effective chiral Lagrangian from the theta term

    SciTech Connect

    Mereghetti, E.; Hockings, W.H.; Kolck, U. van

    2010-11-15

    We construct the effective chiral Lagrangian involving hadronic and electromagnetic interactions originating from the QCD {theta}-bar term. We impose vacuum alignment at both quark and hadronic levels, including field redefinitions to eliminate pion tadpoles. We show that leading time-reversal-violating (TV) hadronic interactions are related to isospin-violating interactions that can in principle be determined from charge-symmetry-breaking experiments. We discuss the complications that arise from TV electromagnetic interactions. Some implications of the expected sizes of various pion-nucleon TV interactions are presented, and the pion-nucleon form factor is used as an example.

  10. Chiral symmetry breaking and {theta} vacuum structure in QCD

    SciTech Connect

    Morchio, G. Strocchi, F.

    2009-10-15

    The solution of the axial U(1) problem, the role of the topology of the gauge group in forcing the breaking of axial symmetry in any irreducible representation of the observable algebra and the {theta} vacua structure are revisited in the temporal gauge with attention to the mathematical consistency of the derivations. Both realizations with strong and weak Gauss law are discussed; the control of the general mechanisms and structures is obtained on the basis of the localization of the (large) gauge transformations and the local generation of the chiral symmetry. The Schwinger model in the temporal gauge exactly reproduces the general results.

  11. Associative Memory Storage and Retrieval: Involvement of Theta Oscillations in Hippocampal Information Processing

    PubMed Central

    Stella, Federico; Treves, Alessandro

    2011-01-01

    Theta oscillations are thought to play a critical role in neuronal information processing, especially in the hippocampal region, where their presence is particularly salient. A detailed description of theta dynamics in this region has revealed not only a consortium of layer-specific theta dipoles, but also within-layer differences in the expression of theta. This complex and articulated arrangement of current flows is reflected in the way neuronal firing is modulated in time. Several models have proposed that these different theta modulators flexibly coordinate hippocampal regions, to support associative memory formation and retrieval. Here, we summarily review different approaches related to this issue and we describe a mechanism, based on experimental and simulation results, for memory retrieval in CA3 involving theta modulation. PMID:21961072

  12. Numerical studies of ablated-plasma dynamics and precursor current of wire-array Z-pinches

    SciTech Connect

    Huang Jun; Sun Shunkai; Ding Ning; Ning Cheng; Xiao Delong; Zhang Yang; Xue Chuang

    2011-04-15

    The dynamics of ablated plasmas of wire-array Z-pinches are studied numerically in (r,{theta}) geometry by using the magnetohydrodynamic (MHD) simulation model in which the mass injection boundary conditions are presented, and two-dimensional spatio-temporal distributions of magnetic field and precursor current during the ablation phase are obtained. The ablated-plasma dynamics contains four processes: drifting toward the axis, arriving at the axis and forming the precursor column, and contraction and expansion of the precursor column. The relationship among the maximum inward velocity of ablated plasma streams and the initial wire array parameters is analyzed and it is found that this velocity is relatively sensitive to the change of inter-wire separation but weakly depends on the original array radius. The results are in reasonable agreement with the experiments on MAGPIE facility. The origin of the current flow in the precursor plasmas is analyzed from the point of view of the B-field convection in (r,{theta}) plane. The dynamics of ablation streams determine the distribution of magnetic field and the current density J{sub z} inside the wire array. The precursor current can be approximately calculated by the integral of J{sub z} inside the region of a radius near to the column. In this model, the fraction of precursor current is less than 10% of the total current, which is close to the experimental results. When the current waveform is fixed, the increase of the inter-wire gap or decrease of the initial radius will lead to the increase of the precursor current.

  13. Immediate effects of Alpha/theta and Sensory-Motor Rhythm feedback on music performance.

    PubMed

    Gruzelier, J H; Hirst, L; Holmes, P; Leach, J

    2014-07-01

    This is one of a series of investigations comparing two EEG-neurofeedback protocols - Alpha/theta (A/T) and Sensory-Motor Rhythm (SMR) - for performance enhancement in the Arts, here with the focus on music. The original report (Egner and Gruzelier, 2003) established a beneficial outcome for elite conservatoire musicians following A/T training in two investigations. Subsequently this A/T advantage was replicated for both advanced instrumental and novice singing abilities, including improvisation, while SMR training benefited novice performance only (Gruzelier, Holmes et al., 2014). Here we report a replication of the latter study in university instrumentalists who as before were novice singers with one design change - post-training performances were conducted within the tenth final session instead of on a subsequent occasion. As before expert judges rated the domains of Creativity/Musicality, Communication/Presentation and Technique. The proximity to training of the music performances within the last session likely compromised gains from A/T learning, but perhaps reinforced the impact of SMR training efficacy. In support of validation there was evidence of strong within- and across-session A/T learning and positive linear trends for across-session SMR/theta and SMR/beta-2 ratio learning. In support of mediation learning correlated with music performance. The A/T outcome was markedly discrepant from previous studies and should dispel any impression that the hypnogogic state itself is transferred to the performance context. The effects of SMR ratio training are consistent with an impact on lower-order abilities required in novice performance such as sustained attention and memory, and benefiting all three domains of music assessment. PMID:24681246

  14. Theta and gamma coherence across the septotemporal axis during distinct behavioral states.

    PubMed

    Penley, Stephanie C; Hinman, James R; Sabolek, Helen R; Escabí, Monty A; Markus, Etan J; Chrobak, James J

    2012-05-01

    Theta (4-12 Hz) and gamma (40-100 Hz) field potentials represent the interaction of synchronized synaptic input onto distinct neuronal populations within the hippocampal formation. Theta is quite prominent during exploratory activity, locomotion, and REM sleep. Although it is generally acknowledged that theta is coherent throughout most of the hippocampus, there is significant variability in theta, as well as gamma, coherence across lamina at any particular septotemporal level of the hippocampus. Larger differences in theta coherence are observed across the septotemporal (long) axis. We have reported that during REM sleep there is a decrease in theta coherence across the long axis that varies with the topography of CA3/mossy cell input rather than the topography of the prominent entorhinal input. On the basis of differences in the rat's behavior as well as the activity of neuromodulatory inputs (e.g., noradrenergic and serotonergic), we hypothesized that theta coherence across the long axis would be greater during locomotion than REM sleep and exhibit a pattern more consistent with the topography of entorhinal inputs. We examined theta and gamma coherence indices at different septotemporal and laminar sites during distinct theta states: locomotion during maze running, REM sleep, following acute treatment with a θ-inducing cholinomimetic (physostigmine) and for comparison during slow-wave sleep. The results demonstrate a generally consistent pattern of theta and gamma coherence across the septotemporal axis of the hippocampus that is quite indifferent to sensory input and overt behavior. These results are discussed with regards to the neurobiological mechanisms that generate theta and gamma and the growing body of evidence linking theta and gamma indices to memory and other cognitive functions. PMID:21748821

  15. Correlation of the Hippocampal theta rhythm to changes in hypothalamic temperature

    NASA Technical Reports Server (NTRS)

    Saleh, M. A.; Horowitz, J. M.; Hsieh, A. C. L.

    1974-01-01

    Warming and cooling the preoptic anterior hypothalamic area in awake, loosely restrained rabbits was found to evoke theta rhythm. This is consistent with previous studies indicating that theta rhythm is a nonspecific response evoked by stimulation of several sensory modalities. Several studies have correlated theta rhythm with alertness. A neural pathway involving the hypothalamus, the hippocampus, the septal area, and the reticular formation is proposed. Thus, a role of this pathway may be to alert the animal to changes in its body temperature.

  16. Light-front description for the theta dependence of meson masses in the massive Schwinger model

    SciTech Connect

    Burkardt, M.; Harada, K.

    1998-05-01

    We present a continuum formulation for {theta} vacua in the massive Schwinger model on the light front, where {theta} enters as a background electric field. The effective coupling of the external field is partially screened due to vacuum polarization processes. For small fermion masses and small {theta}, we calculate the mass of the meson and find agreement with results from bosonization. {copyright} {ital 1998} {ital The American Physical Society}

  17. Pentaquark {Theta}{sup +} production from the reaction {gamma}p {yields} {pi}{sup +} K{sup -} {Theta}{sup +}

    SciTech Connect

    W. Liu; C. M. Ko; V. Kubarovsky

    2004-02-01

    The cross section for {Theta}{sup +} production from the reaction {gamma}p {yields} {pi}{sup +} K{sup -} {Theta}{sup +}, which was observed in the CLAS experiment at the Jefferson National Laboratory, is evaluated in a hadronic model that includes couplings of {Theta}{sup +} to both KN and K*N. With their coupling constants determined from the empirical {pi} NN(1710) and {rho} NN(1710) coupling constants using the SU(3) symmetry, the cross section for this reaction has been evaluated by taking {Theta}{sup +} to have spin 1/2 and isospin 0 but either positive or negative parity. We find that the cross section is 10-15 nb if {Theta}{sup +} has positive parity as predicted by the chiral soliton model. The cross section is reduced by more than a factor of 10 if {Theta}{sup +} has negative parity as given by lattice QCD studies. For both parities, the differential distribution peaks at small negative four momentum transfer as expected from the dominating t-channel kaon-exchange diagram that involves only the coupling of {Theta}{sup +} to KN.

  18. The use of cubic Nd-Ba-Cu-O seeds to create {theta}[100], 90{degree}-{theta}[100], and {theta}[001] tilt Y-Ba-Cu-O grain boundaries.

    SciTech Connect

    Field, M. B.

    1998-10-20

    Using seeding techniques to control the orientation of grains, we have been able to create a wide variety of YBa{sub 2}Cu{sub 3}O{sub 6+x}, grain boundaries. In addition to five domain samples with 90{degree}[100] twist and tilt grain boundaries, we have now developed a method to produce grain boundaries in the same sample that have the misorientations {theta}[001] tilt, {theta}[100] tilt, and 90{degree} {approximately} {theta}[100], where the disorientation angle {theta} is fully controllable. We will demonstrate how these boundaries can be synthesized, give experimental evidence via polarized light microscopy and electron backscatter patterns (EBSP) that the intended grain boundaries were indeed formed, and discuss the importance of these boundaries in future grain boundary studies.

  19. Effect of particle pinch on the fusion performance and profile features of an international thermonuclear experimental reactor-like fusion reactor

    NASA Astrophysics Data System (ADS)

    Wang, Shijia; Wang, Shaojie

    2015-04-01

    The evolution of the plasma temperature and density in an international thermonuclear experimental reactor (ITER)-like fusion device has been studied by numerically solving the energy transport equation coupled with the particle transport equation. The effect of particle pinch, which depends on the magnetic curvature and the safety factor, has been taken into account. The plasma is primarily heated by the alpha particles which are produced by the deuterium-tritium fusion reactions. A semi-empirical method, which adopts the ITERH-98P(y,2) scaling law, has been used to evaluate the transport coefficients. The fusion performances (the fusion energy gain factor, Q) similar to the ITER inductive scenario and non-inductive scenario (with reversed magnetic shear) are obtained. It is shown that the particle pinch has significant effects on the fusion performance and profiles of a fusion reactor. When the volume-averaged density is fixed, particle pinch can lower the pedestal density by ˜30 % , with the Q value and the central pressure almost unchanged. When the particle source or the pedestal density is fixed, the particle pinch can significantly enhance the Q value by 60 % , with the central pressure also significantly raised.

  20. Effect of particle pinch on the fusion performance and profile features of an international thermonuclear experimental reactor-like fusion reactor

    SciTech Connect

    Wang, Shijia Wang, Shaojie

    2015-04-15

    The evolution of the plasma temperature and density in an international thermonuclear experimental reactor (ITER)-like fusion device has been studied by numerically solving the energy transport equation coupled with the particle transport equation. The effect of particle pinch, which depends on the magnetic curvature and the safety factor, has been taken into account. The plasma is primarily heated by the alpha particles which are produced by the deuterium-tritium fusion reactions. A semi-empirical method, which adopts the ITERH-98P(y,2) scaling law, has been used to evaluate the transport coefficients. The fusion performances (the fusion energy gain factor, Q) similar to the ITER inductive scenario and non-inductive scenario (with reversed magnetic shear) are obtained. It is shown that the particle pinch has significant effects on the fusion performance and profiles of a fusion reactor. When the volume-averaged density is fixed, particle pinch can lower the pedestal density by ∼30%, with the Q value and the central pressure almost unchanged. When the particle source or the pedestal density is fixed, the particle pinch can significantly enhance the Q value by  60%, with the central pressure also significantly raised.

  1. Cholinergic Blockade Reduces Theta-Gamma Phase Amplitude Coupling and Speed Modulation of Theta Frequency Consistent with Behavioral Effects on Encoding

    PubMed Central

    Gillet, Shea N.; Climer, Jason R.; Hasselmo, Michael E.

    2013-01-01

    Large-scale neural activation dynamics in the hippocampal-entorhinal circuit local field potential, observable as theta and gamma rhythms and coupling between these rhythms, is predictive of encoding success. Behavioral studies show that systemic administration of muscarinic acetylcholine receptor antagonists selectively impairs encoding, suggesting that they may also disrupt the coupling between the theta and gamma bands. Here, we tested the hypothesis that muscarinic antagonists selectively disrupt coupling between theta and gamma. Specifically, we characterized the effects of systemically administered scopolamine on movement-induced theta and gamma rhythms recorded in the superficial layers of the medial entorhinal cortex (MEC) of freely moving rats. We report the novel result that gamma power at the peak of theta was most reduced following muscarinic blockade, significantly shifting the phase of maximal gamma power to occur at later phases of theta. We also characterize the existence of multiple distinct gamma bands in the superficial layers of the MEC. Further, we observed that theta frequency was significantly less modulated by movement speed following muscarinic blockade. Finally, the slope relating speed to theta frequency, a correlate of familiarity with a testing enclosure, increased significantly less between the preinjection and recovery trials when scopolamine was administered during the intervening injection session than when saline was administered, suggesting that scopolamine reduced encoding of the testing enclosure. These data are consistent with computational models suggesting that encoding and retrieval occur during the peak and trough of theta, respectively, and support the theory that acetylcholine regulates the balance between encoding versus retrieval. PMID:24336727

  2. Acceleration of Hydrogen Ions up to 30 MeV and Generation of 3 × 1012 Neutrons in Megaampere Deuterium Gas-Puff Z-Pinch

    NASA Astrophysics Data System (ADS)

    Klir, D.; Cikhardt, J.; Kravarik, J.; Kubes, P.; Rezac, K.; Sila, O.; Shishlov, A.; Cherdizov, R.; Fursov, F.; Kokshenev, V.; Kovalchuk, B.; Kurmaev, N.; Labetsky, A.; Ratakhin, N.; Orcikova, H.; Turek, K.

    2013-10-01

    Fusion neutrons were produced with a deuterium gas-puff z-pinch on the GIT-12 generator at the Institute of High Current Electronics in Tomsk. The peak neutron yield from DD reactions reached Yn = (2 . 9 +/- 0 . 3) ×1012 at 100 μg/cm linear mass density of deuterium, 700 ns implosion time and 2.7 MA current. Such a neutron yield means that the scaling law of deuterium z-pinches Yn ~I4 was extended to 3 MA currents. The further increase of neutron yields up to (3 . 7 +/- 0 . 4) ×1012 was achieved by placing a deuterated polyethylene catcher onto the axis. Maximum neutron energies of 15 and 22 MeV were observed by radial and axial nToF detectors, respectively. A stack of CR-39 track detectors showed up to 40 MeV deuterons (or 30 MeV protons) on the z-pinch axis. Since the energy input into plasmas was 70 kJ, the number of DD neutrons per one joule of stored plasma energy exceeded the value of 5 ×107 . This value implies that deuterium gas-puff z-pinches belong to the most efficient plasma-based sources of DD neutrons. This work was partially supported by the GACR grant No. P205/12/0454 and by the RFBR research project No. 13-08-00479-a.

  3. Resting state theta band source distribution and functional connectivity in remitted schizophrenia.

    PubMed

    Shreekantiah Umesh, D; Tikka, Sai Krishna; Goyal, Nishant; Nizamie, S Haque; Sinha, Vinod Kumar

    2016-09-01

    Increased resting theta activity is one consistent observation occurring during all the phases of schizophrenia. However, the resting theta oscillations during the remission phase are yet unclear. We studied resting theta current source density and functional connectivity in remitted schizophrenia and compared with healthy controls. Significantly increased current source density was found in the dominant anterior cingulate cortex. Increased connectivity between the inferior parietal lobe bilaterally and between the left inferior parietal lobe and right middle frontal gyrus was also found. It may be concluded that schizophrenia patients have aberrant regional theta band current source density and functional connectivity even during remission. PMID:27484634

  4. Theta variation and spatiotemporal scaling along the septotemporal axis of the hippocampus

    PubMed Central

    Long, Lauren L.; Bunce, Jamie G.; Chrobak, James J.

    2015-01-01

    Hippocampal theta has been related to locomotor speed, attention, anxiety, sensorimotor integration and memory among other emergent phenomena. One difficulty in understanding the function of theta is that the hippocampus (HPC) modulates voluntary behavior at the same time that it processes sensory input. Both functions are correlated with characteristic changes in theta indices. The current review highlights a series of studies examining theta local field potential (LFP) signals across the septotemporal or longitudinal axis of the HPC. While the theta signal is coherent throughout the entirety of the HPC, the amplitude, but not the frequency, of theta varies significantly across its three-dimensional expanse. We suggest that the theta signal offers a rich vein of information about how distributed neuronal ensembles support emergent function. Further, we speculate that emergent function across the long axis varies with respect to spatiotemporal scale. Thus, septal HPC processes details of the proximal spatiotemporal environment while more temporal aspects process larger spaces and wider time-scales. The degree to which emergent functions are supported by the synchronization of theta across the septotemporal axis is an open question. Our working model is that theta synchrony serves to bind ensembles representing varying resolutions of spatiotemporal information at interdependent septotemporal areas of the HPC. Such synchrony and cooperative interactions along the septotemporal axis likely support memory formation and subsequent consolidation and retrieval. PMID:25852496

  5. Increased oscillatory theta activation evoked by violent digital game events.

    PubMed

    Salminen, Mikko; Ravaja, Niklas

    2008-04-11

    The authors examined electroencephalographic (EEG) oscillatory responses to two violent events, the player character wounding and killing an opponent character with a gun, in the digital game James Bond 007: NightFire. EEG was recorded from 25 (16 male) right-handed healthy young adults. EEG data were segmented into one 1-s baseline epoch before each event and two 1-s epochs after event onset. Power estimates (microV(2)) were derived with the fast Fourier transform (FFT) for each artefact free event. Both of the studied events evoked increased occipital theta (4-6Hz) responses as compared to the pre-event baseline. The wounding event evoked also increased occipital high theta (6-8Hz) response and the killing event evoked low alpha (8-10Hz) asymmetry over the central electrodes, both relative to the pre-event baseline. The results are discussed in light of facial electromyographic and electrodermal activity responses evoked by these same events, and it is suggested that the reported EEG responses may be attributable to affective processes related to these violent game events. PMID:18325669

  6. Speech encoding by coupled cortical theta and gamma oscillations

    PubMed Central

    Hyafil, Alexandre; Fontolan, Lorenzo; Kabdebon, Claire; Gutkin, Boris; Giraud, Anne-Lise

    2015-01-01

    Many environmental stimuli present a quasi-rhythmic structure at different timescales that the brain needs to decompose and integrate. Cortical oscillations have been proposed as instruments of sensory de-multiplexing, i.e., the parallel processing of different frequency streams in sensory signals. Yet their causal role in such a process has never been demonstrated. Here, we used a neural microcircuit model to address whether coupled theta–gamma oscillations, as observed in human auditory cortex, could underpin the multiscale sensory analysis of speech. We show that, in continuous speech, theta oscillations can flexibly track the syllabic rhythm and temporally organize the phoneme-level response of gamma neurons into a code that enables syllable identification. The tracking of slow speech fluctuations by theta oscillations, and its coupling to gamma-spiking activity both appeared as critical features for accurate speech encoding. These results demonstrate that cortical oscillations can be a key instrument of speech de-multiplexing, parsing, and encoding. DOI: http://dx.doi.org/10.7554/eLife.06213.001 PMID:26023831

  7. X-rays from a microsecond X-pinch

    SciTech Connect

    Appartaim, R. K.

    2013-08-28

    The characteristics of x-rays emitted by X-pinches driven by discharging a current of ∼320 kA with a quarter period of 1 μs in crossed 25 μm wires have been investigated. The x-ray emissions are studied using filtered silicon photodiodes, diamond radiation detectors, and pinhole cameras. The results show that predominantly x-rays from the microsecond X-pinch tend to be emitted in two distinct sets of bursts. The first is predominantly “soft,” i.e., with photon energy hν < 5 keV, followed by a second set of bursts beginning up to 100 ns following the initial bursts, and usually consisting of higher photon energies. Our results show, however, that the x-ray emissions do not contain a significant component with hν > 10 keV as might be expected from electron beam activity within the plasma or from the X-pinch diode. High-resolution images obtained with the observed x-rays suggest a well-defined small source of soft x-rays that demonstrates the potential of the microsecond X-pinch.

  8. Comment on Turbulent Equipartition Theory of Toroidal Momentum Pinch

    SciTech Connect

    Hahm, T. S.; Diamond, P. H.; Gurcan, O. D.; Rewoldt, G.

    2009-03-12

    This response demonstrates that the comment by Peeters et al. contains an incorrect and misleading interpretation of our paper [Hahm et al., Phys. Plasmas 15, 055902 (2008)] regarding the density gradient dependence of momentum pinch and the turbulent equipartition (TEP) theory.

  9. Z-pinch experiments on Saturn at 30 TW

    NASA Astrophysics Data System (ADS)

    Spielman, R. B.; Dukart, R. J.; Hanson, D. L.; Hammel, B. A.; Hsing, W. W.; Matzen, M. K.; Porter, J. L.

    1989-12-01

    We have recently completed the first gas-puff Z-pinch experiments on Saturn (32 TW, 1.4 MJ, 1.9 MV, 40-ns FWHM, and 0.11 Ω). These experiments used the most powerful driver to date for fast Z-pinch experiments. Saturn, a 36 module accelerator, uses a double post-hole vacuum convolute to deliver the total machine current to the load. The 10-nH Saturn Z-pinch diode is capable of delivering a peak current of 10.5 MA. We diagnosed the current using segmented Rogowski coils at the insulator, resistive shunts in the vacuum transmission lines, and B-dot loops and piezoelectric pressure gauges near the load. On most shots electrical losses in the vacuum convolute were minimal with nearly complete current delivery to the Z-pinch load. We have conducted experiments with deuterium, neon, argon, krypton, and xenon gas puffs. A maximum total radiation yield of 505+/-25 kJ was obtained with xenon. The peak keV x-ray yields were 100+/-5 kJ for neon L-shell radiation, 30+/-4 kJ for krypton l-shell radiation, and 39+/-4 kJ for argon K-shell radiation.

  10. Z-pinch experiments on Saturn at 30 TW

    NASA Astrophysics Data System (ADS)

    Spielman, R. B.; Dukart, R. J.; Hanson, D. L.; Hammel, B. A.; Hsing, W. W.; Matzen, M. K.; Porter, J. L.

    We have recently completed the first gas-puff z-pinch on Saturn (32 TW, 1.4 MJ, 1.9 MV, 40-ns FWHM, and 0.11 ohm). These experiments used the most powerful driver to date for fast z-pinch experiments. Saturn, a 36 module accelerator, uses a double post-hole vacuum convolute to deliver the total machine current to the load. The 10-nH Saturn z-pinch diode is capable of delivering a peak current of 10.5 MA. We diagnosed the current using segmented Rogowski coils at the insulator, resistive shunts in the vacuum transmission lines, and B-dot loops and piezoelectric pressure gauges near the load. On most shots electrical losses in the vacuum convolute were minimal with nearly complete current delivery to the z-pinch load. We have conducted experiments with deuterium, neon, argon, krypton, and xenon gas puffs. A maximum total radiation yield of 505 + or - 25 kJ was obtained with xenon. The peak keV X-ray yields were 100 + or - 5 kJ for neon K-shell radiation, 30 + or - 4 kJ for krypton L-shell radiation, and 39 + or - 4 kJ for argon K-shell radiation.

  11. Pinch-off Dynamics of Non-Newtonian Fluids

    NASA Astrophysics Data System (ADS)

    Huisman, F. M.; Gutman, S. R.; Taborek, P.

    2010-11-01

    The pinch-off dynamics of a variety of shear-thinning fluids (foams, concentrated emulsions, and slurries) were studied using high speed videography. The pinch was characterized by the variation of the minimum neck radius rmin as a function of the time to pinch t, with rmin prop to t^α. The rheology of shear thinning fluids can be characterized by an exponent τ = k γ^n, with n < 1. We found that for a variety of shear-thinning fluids including mayonnaise and acrylic paint, rmin scales with t to a power α equal to the flow index for the particular fluid. The flow index was measured using a TA instruments AR-G2 rheometer. The flow index for acrylic paint was 0.440 +/- 0.014 and rmin scales with t to the 0.41 +/- 0.03; for mayonnaise the flow index was 0.355 +/- 0.014; and rmin scales with t to the 0.35+/- 0.02. To study the transition from conventional Newtonian pinch, we systematically varied the concentration of a water-Xanthan gum mixture.

  12. Stabilization in the ZaP Flow Z-Pinch

    NASA Astrophysics Data System (ADS)

    Shumlak, U.; Blakely, J. M.; Chan, B.-J.; Golingo, R. P.; Knecht, S. D.; Nelson, B. A.; Oberto, R. J.; Sybouts, M. R.; Vogman, G. V.; Den Hartog, D. J.

    2009-06-01

    The ZaP flow Z-pinch experiment at the University of Washington investigates the innovative plasma confinement concept of using sheared flows to stabilize an otherwise unstable configuration. The ZaP experiment generates an axially flowing Z-pinch that is 1 m long with a 1 cm radius with a coaxial accelerator coupled to a pinch assembly chamber. Magnetic probes measure the fluctuation levels of the azimuthal modes m = 1, 2, and 3. After assembly, the plasma is magnetically confined for an extended quiescent period where the mode activity is significantly reduced. Experimental measurements show a sheared flow profile that is coincident with the low magnetic fluctuations during the quiescent period. Recent experimental modifications produce more energetic Z-pinch plasmas that exhibit the same general behavior. The plasma equilibrium is characterized with a suite of diagnostics that measure the plasma density, magnetic field, ion and electron temperatures, in addition to plasma flow. The equilibrium is shown to satisfy radial force balance.

  13. Pinch technique and the Batalin-Vilkovisky formalism

    NASA Astrophysics Data System (ADS)

    Binosi, Daniele; Papavassiliou, Joannis

    2002-07-01

    In this paper we take the first step towards a nondiagrammatic formulation of the pinch technique. In particular we proceed into a systematic identification of the parts of the one-loop and two-loop Feynman diagrams that are exchanged during the pinching process in terms of unphysical ghost Green's functions; the latter appear in the standard Slavnov-Taylor identity satisfied by the tree-level and one-loop three-gluon vertex. This identification allows for the consistent generalization of the intrinsic pinch technique to two loops, through the collective treatment of entire sets of diagrams, instead of the laborious algebraic manipulation of individual graphs, and sets up the stage for the generalization of the method to all orders. We show that the task of comparing the effective Green's functions obtained by the pinch technique with those computed in the background field method Feynman gauge is significantly facilitated when employing the powerful quantization framework of Batalin and Vilkovisky. This formalism allows for the derivation of a set of useful nonlinear identities, which express the background field method Green's functions in terms of the conventional (quantum) ones and auxiliary Green's functions involving the background source and the gluonic antifield; these latter Green's functions are subsequently related by means of a Schwinger-Dyson type of equation to the ghost Green's functions appearing in the aforementioned Slavnov-Taylor identity.

  14. Advances in reversed field pinch theory and computation

    SciTech Connect

    Schnack, D.D.; Ho, Y.L.; Carreras, B.A.; Sidikman, K.; Craddock, G.G.; Mattor, N.; Nebel, R.A.; Prager, S.C.; Terry, P.W.; Zita, E.J.

    1992-12-31

    Advances in theory and computations related to the reversed field pinch (RFP) are presented. These are: (1) the effect of the dynamo on thermal transport; (2) a theory of ion heating due to dynamo fluctuations; (3) studies of active and passive feedback schemes for controlling dynamo fluctuations; and (4) an analytic model for coupled g-mode and rippling turbulence in the RFP edge.

  15. Theta responses are abnormal in mild cognitive impairment: evidence from analysis of theta event-related synchronization during a temporal expectancy task.

    PubMed

    Caravaglios, Giuseppe; Muscoso, Emma Gabriella; Di Maria, Giulia; Costanzo, Erminio

    2013-07-01

    We examined the hypothesis that the attention/executive deficits in mild cognitive impairment (MCI) due to Alzheimer's disease is associated to an abnormal cortical activation, revealed by the method of event-related synchronization/desynchronization (ERS/ERD) in the theta band during a paradigm of temporal orienting of attention. MCI patients (n = 25) and healthy elderly (HE) matched controls (n = 15) performed a task in which periodically omitted tones had to be predicted and their virtual onset time had to be marked by pressing a button. Single-trial theta responses were measured, respectively, before and after the motor response. Then, theta responses were compared to theta power during eyes closed resting state (ERD/ERS method).The temporal course of the task was characterized by two different behavioural conditions: (1) a pre-event epoch, in which the subject awaited the virtual onset of the omitted tone, (2) a post-event (after button pressing) epoch, in which the subject was in a post-motor response condition. The most important findings are summarized as follows: (1) in both groups, the pre-event epoch was characterized by theta ERS on temporal electrodes, but HE had a greater theta ERS compared to that of MCI group; (2) in both groups, during the post-motor condition, there was a theta ERS on prefrontal regions, and, also in this case, HE showed a greater theta enhancement compared to that of MCI patients; (3) HE showed evidence of lateralization: during the waiting epoch, theta ERS was dominant on the right posterior temporal lead (T6), whilst, during the post-motor epoch, theta ERS was greater on the left, as well as the midline prefrontal leads. Compared to the traditional neuropsychological measures for the episodic memory, these theta ERS indicators were less accurate in differentiating MCI patients from healthy elderly. The clinical relevance of these findings is that the weaker theta reactivity in MCI would indicate an early impairment in the

  16. SLAC linear collider conceptual design report

    SciTech Connect

    Not Available

    1980-06-01

    The linear collider system is described in detail, including the transport system, the collider lattice, final focusing system, positron production, beam damping and compression, high current electron source, instrumentation and control, and the beam luminosity. The experimental facilities and the experimental uses are discussed along with the construction schedule and estimated costs. Appendices include a discussion of space charge effects in the linear accelerator, emittance growth in the collider, the final focus system, beam-beam instabilities and pinch effects, and detector backgrounds. (GHT)

  17. Microparticles manipulation and enhancement of their separation in pinched flow fractionation by insulator-based dielectrophoresis.

    PubMed

    Khashei, Hesamodin; Latifi, Hamid; Seresht, Mohsen Jamshidi; Ghasemi, Amir Hossein Baradaran

    2016-03-01

    The separation and manipulation of microparticles in lab on a chip devices have importance in point of care diagnostic tools and analytical applications. The separation and sorting of particles from biological and clinical samples can be performed using active and passive techniques. In passive techniques, no external force is applied while in active techniques by applying external force (e.g. electrical), higher separation efficiency is obtained. In this article, passive (pinched flow fractionation) and active (insulator-based dielectrophoresis) methods were combined to increase the separation efficiency at lower voltages. First by simulation, appropriate values of geometry and applied voltages for better focusing, separation, and lower Joule heating were obtained. Separation of 1.5 and 6 μm polystyrene microparticles was experimentally obtained at optimized geometry and low total applied voltage (25 V). Also, the trajectory of 1.5 μm microparticles was controlled by adjusting the total applied voltage. PMID:26685118

  18. Linear integrated circuits

    NASA Astrophysics Data System (ADS)

    Young, T.

    This book is intended to be used as a textbook in a one-semester course at a variety of levels. Because of self-study features incorporated, it may also be used by practicing electronic engineers as a formal and thorough introduction to the subject. The distinction between linear and digital integrated circuits is discussed, taking into account digital and linear signal characteristics, linear and digital integrated circuit characteristics, the definitions for linear and digital circuits, applications of digital and linear integrated circuits, aspects of fabrication, packaging, and classification and numbering. Operational amplifiers are considered along with linear integrated circuit (LIC) power requirements and power supplies, voltage and current regulators, linear amplifiers, linear integrated circuit oscillators, wave-shaping circuits, active filters, DA and AD converters, demodulators, comparators, instrument amplifiers, current difference amplifiers, analog circuits and devices, and aspects of troubleshooting.

  19. Enhanced keV peak power and yield using twisted pair 'cables' in a z-pinch

    SciTech Connect

    Hoyt, C. L.; Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Cahill, A. D.; Gourdain, P.-A.; Greenly, J. B.; Kusse, B. R.; Hammer, D. A.

    2012-06-11

    Individual wires in a z-pinch were replaced with twisted pair 'cables' of similar linear mass on the COBRA pulsed power generator, resulting in peak power and yield increases in radiation above 1 keV. A cable is defined here as two or more fine wires twisted together to form a continuous strand with a wavelength ({lambda}{sub t}) dependent on the twists per unit length. The magnitude of {lambda}{sub t} appears to play a strong role in these increases, with the largest gains found for a {lambda}{sub t} of Almost-Equal-To 0.75 mm.

  20. Magnetohydrodynamic simulations of noninductive helicity injection in the reversed-field pinch and tokamak

    SciTech Connect

    Sovinec, C.R.

    1995-12-31

    Numerical computation is used to investigate resistive magnetohydrodynamic (MHD) fluctuations in the reversed-field pinch (RFP) and in tokamak-like configurations driven solely by direct current (DC) helicity injection. A Lundquist number (S) scan of RFP turbulence without plasma pressure produces the weak scaling of S{sup -0.18} for the root-mean-square magnetic fluctuation level for 2.5x10{sup 3}{le}S{le}4x10{sup 4}. The temporal behavior of fluctuations and the reversal parameter becomes more regular as S is increased, acquiring a {open_quotes}sawtooth{close_quotes} shape at the largest value of S. Simulations with plasma pressure and anisotropic thermal conduction demonstrate energy transport resulting from parallel heat fluctuations. To investigate means of improving RFP energy confinement, three forms of current profile modification are tested. Radio frequency (RF) current drive is modeled with an auxiliary electron force, and linear stability calculations are used.

  1. High-Beta, Improved Confinement Reversed-Field Pinch Plasmas at High Density

    SciTech Connect

    Wyman, M.; Chapman, B. E.; Ahn, J. W.; Almagri, A.; Anderson, J.; Bonomo, F.; Brower, D. L.; Combs, Stephen Kirk; Craig, D.; Hartog, D. J. Den; Deng, B.; Ding, W. X.; Ebrahimi, F.; Ennis, D.; Fiksel, G.; Foust, Charles R; Franz, P.; Goetz, J.; O'Connell, R,; Oliva, S.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Yates, T.

    2008-01-01

    In Madison Symmetric Torus Dexter et al., Fusion Technol. 19, 131 1991 discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching ne=41019 m 3. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

  2. High-{beta}, improved confinement reversed-field pinch plasmas at high density

    SciTech Connect

    Wyman, M. D.; Chapman, B. E.; Ahn, J. W.; Almagri, A. F.; Anderson, J. K.; Den Hartog, D. J.; Ebrahimi, F.; Ennis, D. A.; Fiksel, G.; Gangadhara, S.; Goetz, J. A.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Bonomo, F.; Franz, P.; Brower, D. L.

    2008-01-15

    In Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching n{sub e}=4x10{sup 19} m{sup -3}. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

  3. MAIZE: a 1 MA LTD-Driven Z-Pinch at The University of Michigan

    SciTech Connect

    Gilgenbach, R. M.; Gomez, M. R.; Zier, J. C.; Tang, W. W.; French, D. M.; Lau, Y. Y.; Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Oliver, B. V.; Mehlhorn, T. A.; Kim, A. A.; Sinebryukhov, V. A.

    2009-01-21

    Researchers at The University of Michigan have constructed and tested a 1-MA Linear Transformer Driver (LTD), the first of its type to reach the USA. The Michigan Accelerator for Inductive Z-pinch Experiments, (MAIZE), is based on the LTD developed at the Institute of High Current Electronics in collaboration with Sandia National Labs and UM. This LTD utilizes 80 capacitors and 40 spark gap switches, arranged in 40 'bricks,' to deliver a 1 MA, 100 kV pulse with 100 ns risetime into a matched resistive load. Preliminary resistive-load test results are presented for the LTD facility.Planned experimental research programs at UM include: a) Studies of Magneto-Raleigh-Taylor instability of planar foils, and b) Vacuum convolute studies including cathode and anode plasma.

  4. Confinement studies of reversed field pinch plasma on TPE-1RM20

    SciTech Connect

    Yagi, Yasuyuki; Hirano, Yoichi; Maejima, Yoshiki; Shimada, Toshio; Hirota, Isao

    1995-04-01

    Confinement properties of a reversed field pinch (RFP), TPE-1RM20, are intensively presented. Plasma current, I{sub p}, dependencies of confinement properties are particularly shown in comparison with the forerunner machine, TPE-1RM15. The results without any active density controls are presented in this paper. It is shown that both machines have almost the same, relatively high, I/N values (<= 12 x 10{sup -14} Am) and the poloidal beta, {Beta}{sub p} (= 0.1) and they do not change very much with I{sub p}, where N is the column density. The energy confinement time, {tau}{sub E}, linearly increases with I{sub p} and the behavior of the resistive part of the loop voltage has an important role to the I{sub p} dependence of {tau}{sub E}. 8 refs., 3 figs.

  5. Nonlinear thermoelectricity in point contacts at pinch off: A catastrophe aids cooling

    NASA Astrophysics Data System (ADS)

    Whitney, Robert S.

    2013-08-01

    I consider refrigeration and heat engine circuits based on the nonlinear thermoelectric response of point contacts at pinch off, allowing for electrostatic interaction effects. I show that a refrigerator can cool to much lower temperatures than predicted by the thermoelectric figure of merit ZT (which is based on linear-response arguments). The lowest achievable temperature has a discontinuity, called a fold catastrophe in mathematics, at a critical driving current I=Ic. For I>Ic one can in principle cool to absolute zero, when for I

  6. Stability threshold of ion temperature gradient driven mode in reversed field pinch plasmas

    SciTech Connect

    Guo, S. C.

    2008-12-15

    For the first time in the reversed field pinch (RFP) configuration, the stability threshold of the ion temperature gradient driven (ITG) mode is studied by linear gyrokinetic theory. In comparison with tokamaks, the RFP configuration has a shorter connection length and stronger magnetic curvature drift. These effects result in a stronger instability driving mechanism and a larger growth rate in the fluid limit. However, the kinetic theory shows that the temperature slopes required for the excitation of ITG instability are much steeper than the tokamak ones. This is because the effect of Landau damping also becomes stronger due to the shorter connection length, which is dominant and ultimately determines the stability threshold. The required temperature slope for the instability may only be found in the very edge of the plasma and/or near the border of the dominant magnetic island during the quasi-single helicity state of discharge.

  7. Collisional tearing in a field-reversed sheet pinch assuming nonparallel propagation

    NASA Technical Reports Server (NTRS)

    Quest, K. B.; Coroniti, F. V.

    1985-01-01

    Linear tearing in a collisional reversed-field sheet pinch is examined assuming that the wave vector k is not parallel to the equilibrium magnetic field. Equilibrium and magnetic geometry are defined, and a set of perturbed moment equations is derived assuming quasi-parallel propagation. It is shown that the usual expression for collisional growth is recovered, assuming that k sub y = 0. It is shown that the y component of momentum balance requires the generation of nonzero dJ sub x well away from the null, and an interial coupling when z not equal to 0. The effects of k sub y not equal to 0 on the growth rate are discussed.

  8. Digit mechanics in relation to endpoint compliance during precision pinch

    PubMed Central

    Nataraj, Raviraj; Audu, Musa L.; Li, Zong-Ming

    2015-01-01

    This study investigates the mechanics of the thumb and index finger in relation to compliant endpoint forces during precision pinch. The objective was to gain insight into how individuals modulate motor output at the digit endpoints and joints according to compliance-related sensory feedback across the digits. Thirteen able-bodied subjects performed precision pinch upon elastic resistance bands of a customized apparatus instrumented with six degree-of-freedom load-cells. Compliance levels were discretely adjusted according to the number of bands connected. Subjects were provided visual feedback to control the rate of force application. Fifteen repetitions of low-to-moderate force (<20 N) pinches were analyzed at each of five compliance levels, during which force and motion data were collected. Joint angles and moments normalized by pinch force magnitude were computed. Second-order polynomials were used to characterize joint mechanics as a function of compliance. The joint degrees-of-freedom (DOFs) at the finger showed greater dependence on compliance for angular position while the thumb joint DOFs demonstrated greater dependence for normalized joint moment. The digits also adjusted coordination of their endpoint forces according to compliance. Overall, the finger may be altering its position to increase load to the joints of the thumb with changing compliance. These findings describe naturally emergent changes in digit mechanics for compliant precision pinch, which involves motor execution in response to endpoint sensory feedback. Identifying and understanding these motor patterns may provide theoretical basis for restoring and rehabilitating sensorimotor pathologies of the hand. PMID:25596633

  9. Hysteretic pinching of human secondary osteons subjected to torsion.

    PubMed

    Ascenzi, Maria-Grazia; Di Comite, Mariasevera; Mitov, Plamen; Kabo, John Michael

    2007-01-01

    The mechanical behavior of bone tissue's ultra- and micro- structure is fundamental to assessment of macroscopic bone mechanics. This paper explores the ultra-structural characteristics of human femoral tissue responsible for energy absorption of secondary osteons under mechanical loading. A novel mathematical interpretation of single osteon mechanics elucidates the behavior of the collagen-apatite interface. Fully calcified single osteon specimens were mechanically tested quasi-statically under cyclic torsional loading about their longitudinal axis. On each hysteretic diagram, all cycles after the initial monotonic cycle appear pinched and share two points. Stiffness degradation and pinching degradation were investigated on the torque versus deflection-angle-per-unit-length diagrams as the number of cycles increases, in relation to the appearance of osteons in cross-section under circularly polarized light microscopy. Material science's Bauschinger effect, originally defined for metals and later extended to structures reinforced with metal bars, is adapted to describe pinching. Material science's prying effect, defined as amplification of eccentric tensile load through lever action, is employed to explain pinching. The presence of the two points shared by all complete cycles is analyzed in terms of the mathematical fixed point theorem. The results allow formulation of the following conjectures: (1) the prying of carbonated apatite crystallites at the interface with the 40 nm long bands of non-calcified collagen fibrils causes pinching; (2) the prying effect increases with the increasing percentage of collagen-apatite elements that form a larger angle with the osteon axis; and (3) micro-cracks increase more in number than in length as the number of cycles increases. PMID:17399724

  10. A real-time pinch-to-zoom motion detection by means of a surface EMG-based human-computer interface.

    PubMed

    Kim, Jongin; Cho, Dongrae; Lee, Kwang Jin; Lee, Boreom

    2015-01-01

    In this paper, we propose a system for inferring the pinch-to-zoom gesture using surface EMG (Electromyography) signals in real time. Pinch-to-zoom, which is a common gesture in smart devices such as an iPhone or an Android phone, is used to control the size of images or web pages according to the distance between the thumb and index finger. To infer the finger motion, we recorded EMG signals obtained from the first dorsal interosseous muscle, which is highly related to the pinch-to-zoom gesture, and used a support vector machine for classification between four finger motion distances. The powers which are estimated by Welch's method were used as feature vectors. In order to solve the multiclass classification problem, we applied a one-versus-one strategy, since a support vector machine is basically a binary classifier. As a result, our system yields 93.38% classification accuracy averaged over six subjects. The classification accuracy was estimated using 10-fold cross validation. Through our system, we expect to not only develop practical prosthetic devices but to also construct a novel user experience (UX) for smart devices. PMID:25551482

  11. A Real-Time Pinch-to-Zoom Motion Detection by Means of a Surface EMG-Based Human-Computer Interface

    PubMed Central

    Kim, Jongin; Cho, Dongrae; Lee, Kwang Jin; Lee, Boreom

    2015-01-01

    In this paper, we propose a system for inferring the pinch-to-zoom gesture using surface EMG (Electromyography) signals in real time. Pinch-to-zoom, which is a common gesture in smart devices such as an iPhone or an Android phone, is used to control the size of images or web pages according to the distance between the thumb and index finger. To infer the finger motion, we recorded EMG signals obtained from the first dorsal interosseous muscle, which is highly related to the pinch-to-zoom gesture, and used a support vector machine for classification between four finger motion distances. The powers which are estimated by Welch's method were used as feature vectors. In order to solve the multiclass classification problem, we applied a one-versus-one strategy, since a support vector machine is basically a binary classifier. As a result, our system yields 93.38% classification accuracy averaged over six subjects. The classification accuracy was estimated using 10-fold cross validation. Through our system, we expect to not only develop practical prosthetic devices but to also construct a novel user experience (UX) for smart devices. PMID:25551482

  12. Formation of a pinched electron beam and an intense x-ray source in radial foil rod-pinch diodes

    NASA Astrophysics Data System (ADS)

    Sorokin, S. A.

    2016-04-01

    Low-impedance rod-pinch diode experiments were performed on the MIG generator at Institute of High Current Electronics using an aluminum foil placed between concentric electrodes of a rod-pinch diode. The J × B force accelerates the foil plasma in the axial and radial directions. After the foil plasma is pushed beyond the tip of the rod, a vacuum gap and a pinched electron beam form. The anode and cathode plasmas expansion and the following plasmas sweeping up by the J × B force can result in repetitive gap formations and closures, which are evident in the several successive intense x-ray pulses. A 0.7-mm-size point-like x-ray source was realized using a 1-mm-diameter tungsten rod, tapered to a point over the last 10 mm. The results of experiments show that the foil-shorted rod-pinch diode configuration has the potential to form low-impedance diodes, to shorten x-ray pulse duration and to realize submillimeter spot-size x-ray sources.

  13. Research on pinching characteristics of electron beams emitted from different cathode surfaces of a rod-pinch diode

    NASA Astrophysics Data System (ADS)

    Gao, Yi; Qiu, Aici; Zhang, Zhong; Zhang, Pengfei; Wang, Zhiguo; Yang, Hailiang

    2010-07-01

    The particle-in-cell code UNIPIC is used to simulate the working process of a rod-pinch diode and investigate the pinching characteristics of electron beams emitted from different cathode surfaces. The simulation results indicate that the electron beam emitted from the upstream surface pinches better than from other surfaces when all the three surfaces emit electrons. The charge-density deposition on the anode surface peaks at the rod tip while the deposited charge density is approximately uniform over the first 15 mm of the rod before rapidly increasing over the last 3 mm, indicating a large axial extent of electron deposition. For the case of single-surface emission, the pinching quality of the electron beam emitted from the downstream surface is better than those from other surfaces. The charge-density deposition peaks at the rod tip and decreases rapidly off the tip. Based on the relationship of Larmor radius, beam's self-magnetic field, and the spatial current distribution, the above simulation results are analyzed theoretically. The experiments are performed on the inductive voltage adder to examine the simulations. By comparing the axial distribution of the radiation on the anode rod measured with the pinhole camera and the on-axis forward x-ray dose measured with the LiF thermoluminescent detectors, the simulation results are verified. The electron emission suppression method and the impedance change for each case are investigated or discussed in this paper.

  14. Neutron spectra from beam-target reactions in dense Z-pinches

    SciTech Connect

    Appelbe, B. Chittenden, J.

    2015-10-15

    The energy spectrum of neutrons emitted by a range of deuterium and deuterium-tritium Z-pinch devices is investigated computationally using a hybrid kinetic-MHD model. 3D MHD simulations are used to model the implosion, stagnation, and break-up of dense plasma focus devices at currents of 70 kA, 500 kA, and 2 MA and also a 15 MA gas puff. Instabilities in the MHD simulations generate large electric and magnetic fields, which accelerate ions during the stagnation and break-up phases. A kinetic model is used to calculate the trajectories of these ions and the neutron spectra produced due to the interaction of these ions with the background plasma. It is found that these beam-target neutron spectra are sensitive to the electric and magnetic fields at stagnation resulting in significant differences in the spectra emitted by each device. Most notably, magnetization of the accelerated ions causes the beam-target spectra to be isotropic for the gas puff simulations. It is also shown that beam-target spectra can have a peak intensity located at a lower energy than the peak intensity of a thermonuclear spectrum. A number of other differences in the shapes of beam-target and thermonuclear spectra are also observed for each device. Finally, significant differences between the shapes of beam-target DD and DT neutron spectra, due to differences in the reaction cross-sections, are illustrated.

  15. Spontaneous quasi single helicity regimes in EXTRAP T2R reversed-field pinch

    SciTech Connect

    Frassinetti, L.; Brunsell, P. R.; Drake, J. R.; Menmuir, S.; Cecconello, M.

    2007-11-15

    In recent years, good progress toward a better understanding and control of the plasma performance in reversed-field pinch devices has been made. These improvements consist both of the discovery of spontaneous plasma regimes, termed the quasi single helicity (QSH) regime, in which part of the plasma core is no longer stochastic, and of the development of techniques for active control of plasma instabilities. In this paper, a systematic study of spontaneous QSH in the EXTRAP T2R device [P. R. Brunsell, H. Bergsaker, M. Cecconello et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] is presented. In this device, QSH states can occur spontaneously and it is associated with magnetic and thermal structures. A statistical analysis to determine the most favorable experimental conditions to have a transition to the QSH regime will be presented. The results described here are useful to understand the underlying properties of QSH regimes in view of future applications of the QSH active control in EXTRAP T2R; they are also important to have a comparison with the QSH studied in other devices.

  16. Neutron spectra from beam-target reactions in dense Z-pinches

    NASA Astrophysics Data System (ADS)

    Appelbe, B.; Chittenden, J.

    2015-10-01

    The energy spectrum of neutrons emitted by a range of deuterium and deuterium-tritium Z-pinch devices is investigated computationally using a hybrid kinetic-MHD model. 3D MHD simulations are used to model the implosion, stagnation, and break-up of dense plasma focus devices at currents of 70 kA, 500 kA, and 2 MA and also a 15 MA gas puff. Instabilities in the MHD simulations generate large electric and magnetic fields, which accelerate ions during the stagnation and break-up phases. A kinetic model is used to calculate the trajectories of these ions and the neutron spectra produced due to the interaction of these ions with the background plasma. It is found that these beam-target neutron spectra are sensitive to the electric and magnetic fields at stagnation resulting in significant differences in the spectra emitted by each device. Most notably, magnetization of the accelerated ions causes the beam-target spectra to be isotropic for the gas puff simulations. It is also shown that beam-target spectra can have a peak intensity located at a lower energy than the peak intensity of a thermonuclear spectrum. A number of other differences in the shapes of beam-target and thermonuclear spectra are also observed for each device. Finally, significant differences between the shapes of beam-target DD and DT neutron spectra, due to differences in the reaction cross-sections, are illustrated.

  17. Theta Burst Stimulation in the Rehabilitation of the Upper Limb: A Semirandomized, Placebo-Controlled Trial in Chronic Stroke Patients

    PubMed Central

    Talelli, Penelope; Wallace, Amanda; Dileone, Michelle; Hoad, Damon; Cheeran, Binith; Oliver, Rupert; VandenBos, Mehdi; Hammerbeck, Ulrike; Barratt, Karen; Gillini, Cecilia; Musumeci, Gabriella; Boudrias, Marie-Hélène; Cloud, Geoffrey C.; Ball, Joanna; Marsden, Jonathan F.; Ward, Nicholas S.; Di Lazzaro, Vincenzo; Greenwood, Richard G.; Rothwell, John C.

    2013-01-01

    Background Noninvasive cortical stimulation could represent an add-on treatment to enhance motor recovery after stroke. However, its clinical value, including anticipated size and duration of the treatment effects, remains largely unknown. Objective The authors designed a small semi-randomized clinical trial to explore whether long-lasting clinically important gains can be achieved by adding theta burst stimulation (TBS), a form of repetitive transcranial magnetic stimulation (TMS), to a rehabilitation program for the hand. Methods A total of 41 chronic stroke patients received excitatory TBS to the ipsilesional hemisphere or inhibitory TBS to the contralesional hemisphere in 2 centers; each active group was compared with a group receiving sham TBS. TBS was followed by physical therapy for 10 working days. Patients and therapists were blinded to the type of TBS. Primary outcome measures (9-hole Peg Test [9HPT], Jebsen Taylor Test [JTT], and grip and pinch-grip dynamometry) were assessed 4, 30, and 90 days post treatment. The clinically important difference was defined as 10% of the maximum score. Results There were no differences between the active treatment and sham groups in any of the outcome measures. All patients achieved small sustainable improvements—9HPT, 5% of maximum (confidence interval [CI] = 3%-7%); JTT, 5.7% (CI = 3%-8%); and grip strength, 6% (CI = 2%-10%)—all below the defined clinically important level. Conclusions Cortical stimulation did not augment the gains from a late rehabilitation program. The effect size anticipated by the authors was overestimated. These results can improve the design of future work on therapeutic uses of TMS. PMID:22412171

  18. The focal adhesion protein PINCH-1 associates with EPLIN at integrin adhesion sites

    PubMed Central

    Karaköse, Esra; Geiger, Tamar; Flynn, Kevin; Lorenz-Baath, Katrin; Zent, Roy; Mann, Matthias; Fässler, Reinhard

    2015-01-01

    ABSTRACT PINCH-1 is a LIM-only domain protein that forms a ternary complex with integrin-linked kinase (ILK) and parvin (to form the IPP complex) downstream of integrins. Here, we demonstrate that PINCH-1 (also known as Lims1) gene ablation in the epidermis of mice caused epidermal detachment from the basement membrane, epidermal hyperthickening and progressive hair loss. PINCH-1-deficient keratinocytes also displayed profound adhesion, spreading and migration defects in vitro that were substantially more severe than those of ILK-deficient keratinocytes indicating that PINCH-1 also exerts functions in an ILK-independent manner. By isolating the PINCH-1 interactome, the LIM-domain-containing and actin-binding protein epithelial protein lost in neoplasm (EPLIN, also known as LIMA1) was identified as a new PINCH-1-associated protein. EPLIN localized, in a PINCH-1-dependent manner, to integrin adhesion sites of keratinocytes in vivo and in vitro and its depletion severely attenuated keratinocyte spreading and migration on collagen and fibronectin without affecting PINCH-1 levels in focal adhesions. Given that the low PINCH-1 levels in ILK-deficient keratinocytes were sufficient to recruit EPLIN to integrin adhesions, our findings suggest that PINCH-1 regulates integrin-mediated adhesion of keratinocytes through the interactions with ILK as well as EPLIN. PMID:25609703

  19. The synchronous activity of lateral habenular neurons is essential for regulating hippocampal theta oscillation.

    PubMed

    Aizawa, Hidenori; Yanagihara, Shin; Kobayashi, Megumi; Niisato, Kazue; Takekawa, Takashi; Harukuni, Rie; McHugh, Thomas J; Fukai, Tomoki; Isomura, Yoshikazu; Okamoto, Hitoshi

    2013-05-15

    Lateral habenula (LHb) has attracted growing interest as a regulator of serotonergic and dopaminergic neurons in the CNS. However, it remains unclear how the LHb modulates brain states in animals. To identify the neural substrates that are under the influence of LHb regulation, we examined the effects of rat LHb lesions on the hippocampal oscillatory activity associated with the transition of brain states. Our results showed that the LHb lesion shortened the theta activity duration both in anesthetized and sleeping rats. Furthermore, this inhibitory effect of LHb lesion on theta maintenance depended upon an intact serotonergic median raphe, suggesting that LHb activity plays an essential role in maintaining hippocampal theta oscillation via the serotonergic raphe. Multiunit recording of sleeping rats further revealed that firing of LHb neurons showed significant phase-locking activity at each theta oscillation cycle in the hippocampus. LHb neurons showing activity that was coordinated with that of the hippocampal theta were localized in the medial LHb division, which receives afferents from the diagonal band of Broca (DBB), a pacemaker region for the hippocampal theta oscillation. Thus, our findings indicate that the DBB may pace not only the hippocampus, but also the LHb, during rapid eye movement sleep. Since serotonin is known to negatively regulate theta oscillation in the hippocampus, phase-locking activity of the LHb neurons may act, under the influence of the DBB, to maintain the hippocampal theta oscillation by modulating the activity of serotonergic neurons. PMID:23678132

  20. Ketamine disrupts theta modulation of gamma in a computer model of hippocampus

    PubMed Central

    Neymotin, Samuel A.; Lazarewicz, Maciej T.; Sherif, Mohamed; Contreras, Diego; Finkel, Leif H.; Lytton, William W.

    2011-01-01

    Abnormalities in oscillations have been suggested to play a role in schizophrenia. We studied theta-modulated gamma oscillations in a computer model of hippocampal CA3 in vivo with and without simulated application of ketamine, an NMDA receptor antagonist and psychotomimetic. Networks of 1200 multi-compartment neurons (pyramidal, basket and oriens-lacunosum moleculare, OLM, cells) generated theta and gamma oscillations from intrinsic network dynamics: basket cells primarily generated gamma and amplified theta, while OLM cells strongly contributed to theta. Extrinsic medial septal inputs paced theta and amplified both theta and gamma oscillations. Exploration of NMDA receptor reduction across all location combinations demonstrated that the experimentally-observed ketamine effect occurred only with isolated reduction of NMDA receptors on OLMs. In the ketamine simulations, lower OLM activity reduced theta power and disinhibited pyramidal cells, resulting in increased basket cell activation and gamma power. Our simulations predict: ketamine increases firing rates;oscillations can be generated by intrinsic hippocampal circuits;medial septum inputs pace and augment oscillations;pyramidal cells lead basket cells at the gamma peak but lag at trough;basket cells amplify theta rhythms;ketamine alters oscillations due to primary blockade at OLM NMDA receptors;ketamine alters phase relationships of cell firing;ketamine reduces network responsivity to the environmentketamine effect could be reversed by providing a continuous inward current to OLM cells. We suggest that this last prediction has implications for a possible novel treatment for cognitive deficits of schizophrenia by targeting OLM cells. PMID:21832203

  1. Decrease of theta response in euthymic bipolar patients during an oddball paradigm.

    PubMed

    Atagün, M İ; Güntekin, B; Ozerdem, A; Tülay, E; Başar, E

    2013-06-01

    Theta oscillations are related to cognitive functions and reflect functional integration of frontal and medial temporal structures into coherent neurocognitive networks. This study assessed event-related theta oscillations in medication-free, euthymic patients with bipolar disorder upon auditory oddball paradigm. Twenty-two DSM-IV euthymic bipolar I (n = 19) and II (n = 3) patients and twenty-two healthy subjects were included. Patients were euthymic for at least 6 months, and psychotropic-free for at least 2 weeks. EEG was recorded at 30 electrode sites. Auditory oddball paradigm and sensory stimuli were used. Event-related Oscillations were analyzed using adaptive filtering in two different theta frequency bands (4-6 Hz, 6-8 Hz). In healthy subjects, slow theta (4-6 Hz) responses were significantly higher than those of euthymic patients upon target, non-target and sensory stimuli (p < 0.05). Fast theta (6-8 Hz) responses of healthy subjects were significantly higher than those of euthymic patients upon target-only stimuli (p < 0.05). Reduced theta oscillations during auditory processing provide strong quantitative evidence of activation deficits in related networks in bipolar disorder. Fast theta responses are related to cognitive functions, whereas slow theta responses are related to sensory processes more than cognitive processes. PMID:24427202

  2. Spike-timing error backpropagation in theta neuron networks.

    PubMed

    McKennoch, Sam; Voegtlin, Thomas; Bushnell, Linda

    2009-01-01

    The main contribution of this letter is the derivation of a steepest gradient descent learning rule for a multilayer network of theta neurons, a one-dimensional nonlinear neuron model. Central to our model is the assumption that the intrinsic neuron dynamics are sufficient to achieve consistent time coding, with no need to involve the precise shape of postsynaptic currents; this assumption departs from other related models such as SpikeProp and Tempotron learning. Our results clearly show that it is possible to perform complex computations by applying supervised learning techniques to the spike times and time response properties of nonlinear integrate and fire neurons. Networks trained with our multilayer training rule are shown to have similar generalization abilities for spike latency pattern classification as Tempotron learning. The rule is also able to train networks to perform complex regression tasks that neither SpikeProp or Tempotron learning appears to be capable of. PMID:19431278

  3. Public Kepler Data on the Bright Star Theta Cygni

    NASA Astrophysics Data System (ADS)

    Haas, Michael Robert; Bryson, S. T.; Rowe, J. F.; Still, M. D.

    2011-01-01

    The bright star Theta Cygni (Kepler ID 11918630) has been observed by Kepler in both short (59 sec) and long (29.4 min) cadence for a period of approximately 50 days starting on MJD 55410. These observations were made at the request of the Kepler Guest Observer Office and are intended for immediate public release. The purpose is to demonstrate Kepler's exquisite photometric precision on bright, highly saturated targets. Theta Cygni is a F3V/M3V binary with a visual magnitude of 4.9/13.0. The short-cadence data show evidence of granulation (i.e., convection) out to about 1 mHz ( 100 c/d) and clear detection of numerous p-modes with a peak near 1.8 mHz ( 150 c/d). The high-frequency noise floor has a 3-sigma upper envelope of 0.4 ppm. The amplitude of the p-modes agrees with the stellar effective temperature, indicating that the star has a thin convective layer. Since a custom aperture was employed, the light curves will be constructed manually and placed on the Guest Observer website (http://keplergo.arc.nasa.gov/). The corresponding pixel-level data will be available from the Kepler archive (http://archive.stsci.edu/kepler/). The Kepler mission can accommodate a small number of such bright targets every quarter. Observing proposals can be submitted annually to the peer-reviewed Guest Observer Program, or much less formally on a quarterly basis for Director's Discretionary Time (see http://keplergo.arc.nasa.gov/GOprogramDDT.shtml). Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA, Science Mission Directorate.

  4. An Inertial-Fusion Z-Pinch Power Plant Concept

    SciTech Connect

    DERZON,MARK S.; ROCHAU,GARY E.; DEGROOT,J.; OLSON,CRAIG L.; PETERSON,P.; PETERSON,R.R.; SLUTZ,STEPHEN A.; ZAMORA,ANTONIO J.

    2000-12-15

    With the promising new results of fast z-pinch technology developed at Sandia National Laboratories, we are investigating using z-pinch driven high-yield Inertial Confinement Fusion (ICF) as a fusion power plant energy source. These investigations have led to a novel fusion system concept based on an attempt to separate many of the difficult fusion engineering issues and a strict reliance on existing technology, or a reasonable extrapolation of existing technology, wherever possible. In this paper, we describe the main components of such a system with a focus on the fusion chamber dynamics. The concept works with all of the electrically-coupled ICF proposed fusion designs. It is proposed that a z-pinch driven ICF power system can be feasibly operated at high yields (1 to 30 GJ) with a relatively low pulse rate (0.01-0.1 Hz). To deliver the required current from the rep-rated pulse power driver to the z-pinch diode, a Recyclable Transmission Line (RTL) and the integrated target hardware are fabricated, vacuum pumped, and aligned prior to loading for each power pulse. In this z-pinch driven system, no laser or ion beams propagate in the chamber such that the portion of the chamber outside the RTL does not need to be under vacuum. Additionally, by utilizing a graded-density solid lithium or fluorine/lithium/beryllium eutectic (FLiBe) blanket between the source and the first-wall the system can breed its own fuel absorb a large majority of the fusion energy released from each capsule and shield the first-wall from a damaging neutron flux. This neutron shielding significantly reduces the neutron energy fluence at the first-wall such that radiation damage should be minimal and will not limit the first-wall lifetime. Assuming a 4 m radius, 8 m tall cylindrical chamber design with an 80 cm thick spherical FLiBe blanket, our calculations suggest that a 20 cm thick 6061-T6 Al chamber wall will reach the equivalent uranium ore radioactivity level within 100 years after a 30

  5. Age-related oscillatory theta modulation of multisensory integration in frontocentral regions.

    PubMed

    Yan, Tianyi; Bi, Xiaoshan; Zhang, Mengmeng; Wang, Wenhui; Yao, Zhiqi; Yang, Weiping; Wu, Jinglong

    2016-08-01

    This study used electroencephalogram measurements to investigate the effects of aging on oscillatory theta modulation during an audiovisual discrimination task. By a wavelet-based time-frequency analysis, age-related theta oscillation response differences were observed within a relatively restricted time range (0-500 ms) over frontal-central regions. Older adults showed stronger theta spectral power during visual and audiovisual stimuli in the left frontal regions; however, young adults showed stronger theta spectral power during auditory and audiovisual stimuli in the central regions. These findings suggest that multisensory oscillatory theta responses differ according to age, which further proves that the left frontal regions play an important role in audiovisual integration. PMID:27272690

  6. Can induced theta vacua be created in heavy-Ion collisions?

    PubMed

    Buckley; Fugleberg; Zhitnitsky

    2000-05-22

    We discuss a phenomenon important to the development of the early Universe which may be experimentally testable in heavy-ion collisions. An arbitrary induced straight theta vacuum state should be created in heavy-ion collisions, similar to the creation of the disoriented chiral condensate. It should be a large domain with a wrong straight theta(ind) not equal0 orientation which will mimic the physics of the early Universe when it is believed that the fundamental parameter straight theta(fund) not equal0. We test this idea numerically in a simple model where we study the evolution of the phases of the chiral condensates in QCD with two quark flavors with nonzero straight theta(ind) parameter. We see the formation of a nonzero straight theta(ind) vacuum on a time scale of 10(-23) s. PMID:10990805

  7. Theta lingua franca: a common mid-frontal substrate for action monitoring processes.

    PubMed

    Cavanagh, James F; Zambrano-Vazquez, Laura; Allen, John J B

    2012-02-01

    We present evidence that a multitude of mid-frontal event-related potential (ERP) components partially reflect a common theta band oscillatory process. Specifically, mid-frontal ERP components in the N2 time range and error-related negativity time range are parsimoniously characterized as reflections of theta band activities. Forty participants completed three different tasks with varying stimulus-response demands. Permutation tests were used to identify the dominant time-frequency responses of stimulus- and response-locked conditions as well as the enhanced responses to novelty, conflict, punishment, and error. A dominant theta band feature was found in all conditions, and both ERP component amplitudes and theta power measures were similarly modulated by novelty, conflict, punishment, and error. The findings support the hypothesis that generic and reactive medial prefrontal cortex processes are parsimoniously reflected by theta band activities. PMID:22091878

  8. Effects of thienodiazepine derivatives, etizolam and clotiazepam on the appearance of Fm theta.

    PubMed

    Nakamura, J; Mukasa, H

    1992-12-01

    The effects of new thienodiazepine anxiolytics, etizolam and clotiazepam, on the appearance of frontal midline theta activity (Fm theta) were studied by the double-blind crossover method. The results were as follows; 1) Both clotiazepam and placebo tended to increase the Fm theta appearance in all subjects, but etizolam showed no such tendency. 2) Clotiazepam significantly increased the Fm theta appearance as compared with placebo in subjects with a high neurotic tendency (N-scale of MPI above 19). 3) Clotiazepam tended to increase the Fm theta appearance as compared with placebo and etizolam in subjects with a high anxiety level (MAS score above 14). 4) Apparently more subjects complained of drowsiness after the administration of etizolam than after clotiazepam or placebo. PMID:1363923

  9. Loss of hippocampal theta rhythm results in spatial memory deficit in the rat.

    PubMed

    Winson, J

    1978-07-14

    Rats learned, using distal room cues, to run to a goal on an elevated, circular track starting from any position on the track. The goal was one of eight equidistant, recessed cups set around the track, the goal cup being distinguished from the others solely by its position in the room. After learning, electrolytic lesions were made in the medial septal nucleus eliminating hippocampal theta rhythm in some animals but not in others. Rats without theta rhythm were no longer able to perform the spatial task, whereas rats with undisturbed theta rhythm retrained normal performance. Although rats without theta rhythm could not find their way directly to the goal, they recognized its location when they came upon it by chance. This type of spatial deficit appears similar to that shown by hippocampally lesioned patient H.M. Subsequent tests demonstrated that rats deprived of theta rhythm before training could nevertheless learn the task. PMID:663646

  10. Radiative generation of {theta}{sub 13} with the seesaw threshold effect

    SciTech Connect

    Mei Jianwei; Xing Zhizhong

    2004-09-01

    We examine whether an appreciable value of the lepton flavor mixing angle {theta}{sub 13} at the electroweak scale {lambda}{sub EW} can be radiatively generated from {theta}{sub 13}=0 deg. at the grand unified theory (GUT) scale {lambda}{sub GUT}. It is found that the renormalization-group running and seesaw threshold effects may lead to {theta}{sub 13}{approx}5 deg. at low energies for two simple large-maximal mixing patterns of the Maki-Nakagawa-Sakata matrix in the minimal supersymmetric standard model. If {theta}{sub 12} is sufficiently large at {lambda}{sub GUT}, it will be possible to radiatively produce {theta}{sub 13}{approx}5 deg. at {lambda}{sub EW} both in the standard model and in its supersymmetric extensions. The mass spectrum of three heavy right-handed Majorana neutrinos and the cosmological baryon number asymmetry via leptogenesis are also calculated.

  11. Effects of controlled-release fertilizer on leaf area index and fruit yield in high-density soilless tomato culture using low node-order pinching.

    PubMed

    Kinoshita, Takafumi; Yano, Takayoshi; Sugiura, Makoto; Nagasaki, Yuji

    2014-01-01

    To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m(2) · m(-2); the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32-46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method. PMID:25402478

  12. Effects of Controlled-Release Fertilizer on Leaf Area Index and Fruit Yield in High-Density Soilless Tomato Culture Using Low Node-Order Pinching

    PubMed Central

    Kinoshita, Takafumi; Yano, Takayoshi; Sugiura, Makoto; Nagasaki, Yuji

    2014-01-01

    To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m2·m−2; the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32−46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method. PMID:25402478

  13. The presence of pacemaker HCN channels identifies theta rhythmic GABAergic neurons in the medial septum

    PubMed Central

    Varga, Viktor; Hangya, Balázs; Kránitz, Kinga; Ludányi, Anikó; Zemankovics, Rita; Katona, István; Shigemoto, Ryuichi; Freund, Tamás F; Borhegyi, Zsolt

    2008-01-01

    The medial septum (MS) is an indispensable component of the subcortical network which synchronizes the hippocampus at theta frequency during specific stages of information processing. GABAergic neurons exhibiting highly regular firing coupled to the hippocampal theta rhythm are thought to form the core of the MS rhythm-generating network. In recent studies the hyperpolarization-activated, cyclic nucleotide-gated non-selective cation (HCN) channel was shown to participate in theta synchronization of the medial septum. Here, we tested the hypothesis that HCN channel expression correlates with theta modulated firing behaviour of MS neurons by a combined anatomical and electrophysiological approach. HCN-expressing neurons represented a subpopulation of GABAergic cells in the MS partly overlapping with parvalbumin (PV)-containing neurons. Rhythmic firing in the theta frequency range was characteristic of all HCN-expressing neurons. In contrast, only a minority of HCN-negative cells displayed theta related activity. All HCN cells had tight phase coupling to hippocampal theta waves. As a group, PV-expressing HCN neurons had a marked bimodal phase distribution, whereas PV-immunonegative HCN neurons did not show group-level phase preference despite significant individual phase coupling. Microiontophoretic blockade of HCN channels resulted in the reduction of discharge frequency, but theta rhythmic firing was perturbed only in a few cases. Our data imply that HCN-expressing GABAergic neurons provide rhythmic drive in all phases of the hippocampal theta activity. In most MS theta cells rhythm genesis is apparently determined by interactions at the level of the network rather than by the pacemaking property of HCN channels alone. PMID:18565991

  14. Movement-Related Theta Rhythm in Humans: Coordinating Self-Directed Hippocampal Learning

    PubMed Central

    Kaplan, Raphael; Doeller, Christian F.; Barnes, Gareth R.; Litvak, Vladimir; Düzel, Emrah; Bandettini, Peter A.; Burgess, Neil

    2012-01-01

    The hippocampus is crucial for episodic or declarative memory and the theta rhythm has been implicated in mnemonic processing, but the functional contribution of theta to memory remains the subject of intense speculation. Recent evidence suggests that the hippocampus might function as a network hub for volitional learning. In contrast to human experiments, electrophysiological recordings in the hippocampus of behaving rodents are dominated by theta oscillations reflecting volitional movement, which has been linked to spatial exploration and encoding. This literature makes the surprising cross-species prediction that the human hippocampal theta rhythm supports memory by coordinating exploratory movements in the service of self-directed learning. We examined the links between theta, spatial exploration, and memory encoding by designing an interactive human spatial navigation paradigm combined with multimodal neuroimaging. We used both non-invasive whole-head Magnetoencephalography (MEG) to look at theta oscillations and Functional Magnetic Resonance Imaging (fMRI) to look at brain regions associated with volitional movement and learning. We found that theta power increases during the self-initiation of virtual movement, additionally correlating with subsequent memory performance and environmental familiarity. Performance-related hippocampal theta increases were observed during a static pre-navigation retrieval phase, where planning for subsequent navigation occurred. Furthermore, periods of the task showing movement-related theta increases showed decreased fMRI activity in the parahippocampus and increased activity in the hippocampus and other brain regions that strikingly overlap with the previously observed volitional learning network (the reverse pattern was seen for stationary periods). These fMRI changes also correlated with participant's performance. Our findings suggest that the human hippocampal theta rhythm supports memory by coordinating exploratory

  15. Experimental search for radiative decays of the pentaquark baryon {Theta}{sup +}(1540)

    SciTech Connect

    Barmin, V. V.; Asratyan, A. E.; Borisov, V. S.; Curceanu, C.; Davidenko, G. V.; Dolgolenko, A. G.; Guaraldo, C.; Kubantsev, M. A.; Larin, I. F.; Matveev, V. A.; Shebanov, V. A.; Shishov, N. N.; Sokolov, L. I.; Tumanov, G. K.; Verebryusov, V. S.

    2010-07-15

    The data on the reactions K{sup +}Xe {sup {yields}}K{sup 0{gamma}}X and K{sup +}Xe {sup {yields}}K{sup +{gamma}}X, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the {Theta}{sup +}(1540) baryon: {Theta}{sup +} {sup {yields}}K{sup 0}p{gamma} and {Theta}{sup +} {sup {yields}}K{sup +}n{gamma}. No signals have been observed, and we derive the upper limits {Gamma}({Theta}{sup +} {sup {yields}}K{sup 0}p{gamma})/{Gamma}({Theta}{sup +} {sup {yields}}K{sup 0}p) < 0.032 and {Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma})/{Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma}) < 0.041 which, using our previous measurement of {Gamma}({Theta}{sup +} {sup {yields}}KN) = 0.39 {+-} 0.10 MeV, translate to {Gamma}({Theta}{sup +} {sup {yields}}K{sup 0}p{gamma}) < 8 keV and {Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma}) < 11 keV at 90% confidence level. We have also measured the cross sections of K{sup +}-induced reactions involving emission of a neutral pion: {sigma}(K{sup +}n {sup {yields}}K{sup 0}p{pi}{sup 0}) = 68 {+-} 18 {mu}b and {sigma}(K{sup +}N {sup {yields}}K{sup +}N{pi}{sup 0}) = 30 {+-} 8 {mu}b for incident K{sup +} momentum of 640 MeV.

  16. Evidence that the recently discovered theta 1-globin gene is functional in higher primates.

    PubMed

    Shaw, J P; Marks, J; Shen, C K

    A new subfamily of the alpha-globin-like family has recently been identified in higher primates, rabbit, galago and possibly the horse. One member of this subfamily, theta 1, is downstream from the adult alpha 1-globin gene. In orang-utan, but not in rabbit or galago, the theta 1-gene appears to be structurally intact, suggesting that it may be functional in this species. The orang-utan theta 1-gene possesses initiation and termination codons, and the predicted polypeptide differs from the orang-utan alpha 1-globin by 55 amino acids. The upstream promoter boxes CCAAT and ATA are present, although approximately 150 base pairs (bp) farther upstream than in the alpha 1-gene. This structural difference in the promoter between the orang-utan theta 1- and alpha 1-genes has led Proudfoot to speculate that the theta 1-gene may be inactive. We have now cloned the theta 1- and alpha 1-globin genes from the olive baboon, and have compared their sequences with those of orang-utan. The unique promoter structure of the orang-utan theta 1-gene is highly conserved in baboon, although the orang-utan and baboon diverged nearly 30 million years ago. The coding sequences of the two theta 1-genes differ by only 6.3% with 22 out of 27 nucleotide substitutions being codon third position silent changes. These data support the view that the theta 1-gene has been functional in the baboon, orang-utan, and by implication, in man. We also estimate that the duplication event generating the theta 1- and alpha-globin-like subfamilies may have occurred as much as 260 million years ago. PMID:3561513

  17. Frontal and rostral anterior cingulate (rACC) theta EEG in depression: implications for treatment outcome?

    PubMed

    Arns, Martijn; Etkin, Amit; Hegerl, Ulrich; Williams, Leanne M; DeBattista, Charles; Palmer, Donna M; Fitzgerald, Paul B; Harris, Anthony; deBeuss, Roger; Gordon, Evian

    2015-08-01

    In major depressive disorder (MDD), elevated theta current density in the rostral anterior cingulate (rACC), as estimated by source localization of scalp-recorded electroencenphalogram (EEG), has been associated with response to antidepressant treatments, whereas elevated frontal theta has been linked to non-response. This study used source localization to attempt to integrate these apparently opposite results and test, whether antidepressant response is associated with elevated rACC theta and non-response with elevated frontal theta and whether theta activity is a differential predictor of response to different types of commonly used antidepressants. In the international Study to Predict Optimized Treatment in Depression (iSPOT-D), a multi-center, international, randomized, prospective practical trial, 1008 MDD participants were randomized to escitalopram, sertraline or venlafaxine-XR. The study also recruited 336 healthy controls. Treatment response and remission were established after eight weeks using the 17-item Hamilton Rating Scale for Depression (HRSD17). The resting-state EEG was assessed at baseline with eyes closed and source localization (eLORETA) was employed to extract theta from the rACC and frontal cortex. Patients with MDD had elevated theta in both frontal cortex and rACC, with small effect sizes. High frontal and rACC theta were associated with treatment non-response, but not with non-remission, and this effect was most pronounced in a subgroup with previous treatment failures. Low theta in frontal cortex and rACC are found in responders to antidepressant treatments with a small effect size. Future studies should investigate in more detail the role of previous treatment (failure) in the association between theta and treatment outcome. PMID:25936227

  18. MiRNA let-7g regulates skeletal myoblast motility via Pinch-2.

    PubMed

    Boudoukha, S; Rivera Vargas, T; Dang, I; Kropp, J; Cuvellier, S; Gautreau, A; Polesskaya, A

    2014-05-01

    Post-transcriptional regulation of gene expression by RNA-binding proteins and by small non-coding RNAs plays an important role in cell biology. Our previous results show that in murine skeletal myoblasts, the expression of Pinch-2, a focal adhesion remodeling factor that regulates cell motility, is repressed by an RNA-binding protein IMP-2/Igf2bp2. We now show that the expression of Pinch-2 is also regulated by the miRNA let-7g. Let-7g and IMP-2 repress Pinch-2 expression independently of each other. A knock-down of let-7g leads to an increase in Pinch-2 expression, and to a decrease of cell motility, which can be reversed by a simultaneous knock-down of Pinch-2. We conclude that let-7g controls the motility of mouse myoblasts in cell culture by post-transcriptionally regulating the expression of Pinch-2. PMID:24613920

  19. Transport and Measurements of High-Current Electron Beams from X pinches

    NASA Astrophysics Data System (ADS)

    Agafonov, Alexey V.; Mingaleev, Albert R.; Romanova, Vera M.; Tarakanov, Vladimir P.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Blesener, Isaac C.; Kusse, Bruce R.; Hammer, David A.

    2009-01-01

    Generation of electron beams is an unavoidable property of X-pinches and other pulsed-power-driven pinches of different geometry. Some issues concerning high-current electron beam transport from the X pinch to the diagnostic system and measurements of the beam current by Faraday cups with different geometry's are discussed. Of particular interest is the partially neutralized nature of the beam propagating from the X-pinch to a diagnostic system. Two scenarios of electron beam propagation from X-pinch to Faraday cup are analyzed by means of computer simulation using the PIC-code KARAT. The first is longitudinal neutralization by ions extracted from plasma at an output window of the X-pinch diode; the second is the beam transport through a plasma background between the diode and a diagnostic system.

  20. Transport and Measurements of High-Current Electron Beams from X pinches

    SciTech Connect

    Agafonov, Alexey V.; Mingaleev, Albert R.; Romanova, Vera M.; Tarakanov, Vladimir P.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Blesener, Isaac C.; Kusse, Bruce R.; Hammer, David A.

    2009-01-21

    Generation of electron beams is an unavoidable property of X-pinches and other pulsed-power-driven pinches of different geometry. Some issues concerning high-current electron beam transport from the X pinch to the diagnostic system and measurements of the beam current by Faraday cups with different geometry's are discussed. Of particular interest is the partially neutralized nature of the beam propagating from the X-pinch to a diagnostic system. Two scenarios of electron beam propagation from X-pinch to Faraday cup are analyzed by means of computer simulation using the PIC-code KARAT. The first is longitudinal neutralization by ions extracted from plasma at an output window of the X-pinch diode; the second is the beam transport through a plasma background between the diode and a diagnostic system.

  1. Kinetic simulation of neutron production in a deuterium z-pinch.

    SciTech Connect

    Mostrom, C.; Stygar, William A.; Thoma, Carsten; Welch, Dale Robert; Clark, R. E.; Leeper, Ramon Joe; Rose, David V.

    2010-11-01

    We have found computationally that, at sufficiently high currents, half of the neutrons produced by a deuterium z pinch are thermonuclear in origin. Early experiments below 1-MA current found that essentially all of the neutrons produced by a deuterium pinch are not thermonuclear, but are initiated by an instability that creates beam-target neutrons. Many subsequent authors have supported this result while others have claimed that pinch neutrons are thermonuclear. To resolve this issue, we have conducted fully kinetic, collisional, and electromagnetic simulations of the complete time evolution of a deuterium pinch. We find that at 1-MA pinch currents, most of the neutrons are, indeed, beam-target in origin. At much higher current, half of the neutrons are thermonuclear and half are beam-target driven by instabilities that produce a power law fall off in the ion energy distribution function at large energy. The implications for fusion energy production with such pinches are discussed.

  2. Light detonation wave in a cylindrical Z-pinch

    NASA Astrophysics Data System (ADS)

    Yusupaliev, U.; Sysoev, N. N.; Shuteev, S. A.; Elenskii, V. G.

    2015-09-01

    A secondary compression wave previously observed by other researchers in a cylindrical Z-pinch has been identified in this work as a light detonation wave. It appears on the inner surface of a discharge chamber under the action of the intense ultraviolet radiation from a plasma pinch at the stage of its maximum compression. The condition of the light detonation wave has been determined experimentally. The dependence of its Mach number on a generalized dimensionless variable has been determined taking into account the conservation laws for the light detonation wave including the pressure of the gas, expenses on the formation of the surface plasma, and the energy of ionization of the gas involved in the wave. An analogy with the laser-supported detonation wave created by intense laser radiation has been revealed. The indicated dependence is within the error of measurement in agreement with the experimental data for light detonation waves created by both methods.

  3. Terahertz pinch harmonics enabled by single nano rods.

    PubMed

    Park, Hyeong-Ryeol; Bahk, Young-Mi; Choe, Jong Ho; Han, Sanghoon; Choi, Seong Soo; Ahn, Kwang Jun; Park, Namkyoo; Park, Q-Han; Kim, Dai-Sik

    2011-11-21

    A pinch harmonic (or guitar harmonic) is a musical note produced by lightly pressing the thumb of the picking hand upon the string immediately after it is picked [J. Chem. Educ. 84, 1287 (2007)]. This technique turns off the fundamental and all overtones except those with a node at that location. Here we present a terahertz analogue of pinch harmonics, whereby a metallic nano rod placed at a harmonic node on a terahertz nanoresonator suppresses the fundamental mode, making the higher harmonics dominant. Strikingly, a skin depth-wide nano rod placed at the mid-point turns off all resonances. Our work demonstrates that terahertz electromagnetic waves can be tailored by nanoparticles strategically positioned, paving important path towards terahertz switching and detection applications. PMID:22109504

  4. Tungsten Z-Pinch Long Implosions on the Saturn Generator

    SciTech Connect

    DOUGLAS,MELISSA R.; DEENEY,CHRISTOPHER; SPIELMAN,RICK B.; COVERDALE,CHRISTINE A.; RODERICK,N.F.; HAINES,M.G.

    1999-11-05

    Recent success on the Saturn and Z accelerators at Sandia National Laboratories have demonstrated the ability to scale z-pinch parameters to increasingly larger current pulsed power facilities. Next generation machines will require even larger currents (>20 MA), placing further demands on pulsed power technology. To this end, experiments have been carried out on Saturn operating in a long pulse mode, investigating the potential of lower voltages and longer implosion times while still maintaining pinch fidelity. High wire number, 25 mm diameter tungsten arrays were imploded with implosion times ranging from 130 to 240 ns. The results were comparable to those observed in the Saturn short pulse mode, with risetimes on the order of 4.5 to 6.5 ns. Experimental data will be presented, along with two dimensional radiation magnetohydrodynamic simulations used to explain and reproduce the experiment.

  5. Modeling Z-Pinch implosions in two dimensions

    SciTech Connect

    Peterson, D.; Bowers, R.; Brownell, J.

    1997-12-31

    Ideally, simulations of Z-Pinch implosions should provide useful information about important physics processes underlying observed experimental results and provide design capabilities for future experiments. With this goal the authors have developed a methodology for simulating hollow Z-Pinches in two dimensions and applied it to experiments conducted on the Pegasus I and Pegasus II capacitor banks, the Procyon explosion generator system, and the Saturn and PBFA-Z accelerators. In comparisons with experimental results the simulations have reproduced important features of the current drive, spectrum, radiation pulse shape, peak power and total radiated energy. Comparison of the instability development in the simulations with visible light framing camera photos has shown a close correlation with the observed instability wavelengths and amplitudes. Using this methodology the authors are analyzing recent Saturn and PBFA-Z experiments and applying the 2-D modeling in developing applications such as the dynamic hohlraum.

  6. High gain fusion in a Staged Z-pinch

    NASA Astrophysics Data System (ADS)

    Ney, Paul; Rahman, Hafiz; Wessel, Frank; Presura, Radu

    2013-10-01

    The implosion of a Staged Z-pinch is simulated for the Sandia National Laboratories, ZR accelerator. The pinch is comprised of a silver (Ag) plasma shell, 3-mm outer radius, 0.01-cm thick, imploding onto a uniform fill (target) of deuterium-tritium (DT); the Z-R parameters are: 130 ns, 27 MA, 22 MJ; the 2-1/2 D, radiation-MHD code is MACH2. Magnetosonic shock waves generated during implosion propagate at different speeds in the liner and target, producing a shock front at the interface, and a conduction channel ahead of the liner. The interface remains stable even as the outer-surface of the liner is RT unstable. At peak compression target plasma hot spots trigger ignition with a fusion yield of 200 MJ and a net-energy gain approaching 10. The stability remains robust and the gain is unaffected for perturbations ranging from 2-5%.

  7. Optimization of Capsule Symmetry in Z-Pinch Driven Hohlraums

    NASA Astrophysics Data System (ADS)

    Vesey, R. A.; Cuneo, M.; Hanson, D.; Porter, J.; Mehlhorn, T.; Ruggles, L.; Simpson, W.; Vargas, M.; Hammer, J.; Landen, O.

    1999-11-01

    The uniformity of the radiation flux incident on the capsule is a critical issue for indirect drive fusion using the z-pinch driven hohlraum high-yield concept(J.H. Hammer et al., Phys. Plas. 6), 2129 (1999).. Experiments on the Z accelerator at Sandia have demonstrated the ability to diagnose the uniformity of the flux striking a foam ball (surrogate capsule)(P.A. Amendt et al., Phys. Plas. 4), 1862 (1997); S.G. Glendinning et al. Rev. Sci. Instrum. 70, 536 (1999).. These single-sided drive experiments have been modeled using radiosity and radiation-hydrodynamics codes, yielding agreement with the measured ablation rate vs. angle on the foam ball. Flux uniformity at the 1-2% level needed for high-convergence capsule implosions requires a 2-sided drive (top and bottom z-pinch) configuration. Constrained optimization methods have identified hohlraum geometries with improved symmetry.

  8. Final Technical Report, DOE Grant DE-FG02-98ER54496, Physics of High-Energy-Density X Pinch Plasmas

    SciTech Connect

    David Hammer

    2008-12-03

    be as short as 30 trillionths of a second. Additional experiments have demonstrated that a spherical shell of plasma expands away from the cross point region after the x-ray burst. It reaches millimeter scale in a few billionths of a second, leaving a small (less than 0.1 millimeter) gap in the middle that enables energetic electrons to be accelerated to 10 or a few 10’s of kilovolts of energy. In addition to gaining an understanding of the physics of the X pinch plasmas, we have had to develop several new X-ray diagnostic devices in order to obtain and verify the above results. On the non-technical side, 4 students have completed Ph.D.s working under the auspices of this project, including one woman, and another woman has begun her Ph.D. research under this project. In addition, several undergraduate students have worked with us on the X-pinch experiments, including one who is now a graduate student in plasma physics at Princeton University.

  9. Density peaking and turbulent pinch in DIII-D discharges

    SciTech Connect

    Estrada-Mila, C.; Candy, J.; Waltz, R. E.

    2006-07-15

    A study of density peaking and particle flow in low confinement (L-mode) DIII-D discharges [G. R. McKee, C. C. Petty, R. E. Waltz et al., Nucl. Fusion 41, 1235 (2001)], using global gyrokinetic simulations, is presented. It is found that under experimental conditions, in particular when realistic collisionality is included, a turbulent pinch driven by electron temperature and density gradients can occur.

  10. Sausage mode of a pinched charged particle beam

    SciTech Connect

    Lee, E.P.

    1981-02-10

    The axisymmetric oscillations of a self-pinched charged particle beam are analyzed using a dispersion relation derived from a 3/2 dimensional model. This calculation includes the effects of rounded profiles, finite conductivity, a steady return current, and phase mix damping among particle orbits. However, only the lowest order radial mode of distortion is treated, and this is done in an approximate fashion.

  11. Cu spectroscopy from a z-pinch plasma

    NASA Astrophysics Data System (ADS)

    Dasgupta, Arati; Clark, Robert W.; Ouart, Nicholas D.; Giuliani, John L.

    2014-11-01

    Recent improvements in diagnostic techniques at the Sandia Laboratories Z accelerator have facilitated the production of very detailed x-ray spectral data in the range of 1-20 keV. The high energy density plasma produced in a z-pinch is inherently in non-local thermodynamic equilibrium (NLTE). We therefore employ a NLTE collisional equilibrium model in a 1D radiation-magnetohydrodynamics code to simulate the dynamics of the pinch and to generate synthetic emission spectra. We will discuss the effects on radiation spectra and the yields of using simplifying assumptions in the atomic model and/or the radiation transport. X-ray emission from moderately high atomic number plasmas such as Fe and Cu wire array implosions often include substantial 2p-1s K-α radiation. In a z-pinch plasma, K-shell vacancies can be produced by e-beams, hot electrons at the tail of a Maxwellian and also by photopumping from energetic photons emitted near the pinch axis. In the Z-1975 Cu wire implosion, K-α lines from various ionization stages of Cu as well as from minor constituents including Ni, Fe and Cr are observed. We have calculated K-α production within a full simulation of a Cu implosion, including contributions from energetic electrons and photons. Photo-pumped K-α emission can be distinguished from that produced by e-beams; K-shell vacancies will be produced near the axis for a beam, and near the outer edge of the plasma for energetic photons. Spectroscopic modeling of these K-α lines as well as K- and L-shell emission from valence electrons can provide quantitative diagnostics of plasma parameters. This methodology can also be used to investigate K-α emission from other laboratory experiments such as EBIT and astrophysical plasmas.

  12. Characteristics of switching plasma in an inverse-pinch switch

    NASA Technical Reports Server (NTRS)

    Lee, Ja H.; Choi, Sang H.; Venable, Demetrius D.; Han, Kwang S.; Nam, Sang H.

    1993-01-01

    Characteristics of the plasma that switches on tens of giga volt-ampere in an inverse-pinch plasma switch (INPIStron) have been made. Through optical and spectroscopic diagnostics of the current carrying plasma, the current density, the motion of current paths, dominant ionic species have been determined in order to access their effects on circuit parameters and material erosion. Also the optimum operational condition of the plasma-puff triggering method required for azimuthally uniform conduction in the INPIStron has been determined.

  13. Quasi-steady operation of reversed field pinches

    SciTech Connect

    Nebel, R.A.

    1980-01-01

    A three fluid, Lagrangian mesh, transport and stability code (RFPBRN) has been developed and applied to the Reversed Field Pinch reactor concept. Using a circular cylinder, quasi-static approximation, RFPBRN follows the time evolution of the temperature, density, and magnetic field profiles for the RFP while simultaneously monitoring ideal MHD stability. Local stability is monitored for Suydam modes while global stability is monitored using a Rayleigh-Ritz expansion of the energy principle.

  14. Diagnostics for Z-pinch implosion experiments on PTS

    SciTech Connect

    Ren, X. D. Huang, X. B. Zhou, S. T. Zhang, S. Q. Dan, J. K. Li, J. Cai, H. C. Wang, K. L. Ouyang, K. Xu, Q. Duan, S. C. Chen, G. H. Wang, M. Feng, S. P. Yang, L. B. Xie, W. P. Deng, J. J.

    2014-12-15

    The preliminary experiments of wire array implosion were performed on PTS, a 10 MA z-pinch driver with a 70 ns rise time. A set of diagnostics have been developed and fielded on PTS to study pinch physics and implosion dynamics of wire array. Radiated power measurement for soft x-rays was performed by multichannel filtered x-ray diode array, and flat spectral responses x-ray diode detector. Total x-ray yield was measured by a calibrated, unfiltered nickel bolometer which was also used to obtain pinch power. Multiple time-gated pinhole cameras were used to produce spatial-resolved images of x-ray self-emission from plasmas. Two time-integrated pinhole cameras were used respectively with 20-μm Be filter and with multilayer mirrors to record images produced by >1-keV and 277±5 eV self-emission. An optical streak camera was used to produce radial implosion trajectories, and an x-ray streak camera paired with a horizontal slit was used to record a continuous time-history of emission with one-dimensional spatial resolution. A frequency-doubled Nd:YAG laser (532 nm) was used to produce four frame laser shadowgraph images with 6 ns time interval. We will briefly describe each of these diagnostics and present some typical results from them.

  15. Fluid Closure, Theory, Relations to Particle Pinches, Fluid Resonances

    SciTech Connect

    Weiland, Jan; Zagorodny, Anatoly

    2011-10-03

    The fluid closure in a toroidal plasma is discussed. In particular the relation to particle and temperature pinches is considered. Implications for the radial growth of transport coefficients are given. A particularly significant effect of dissipative kinetic resonances is that they reduce particle pinches. This is shown both for a gyrofluid and a quasilinear kinetic model. In particular the fact that the ITG and Trapped electron modes are resonant modes and that the effect of dissipative kinetic resonanses is ignorable for impurities but not for main ions shows that the closure aspect in a fluid description and strongly nonlinear effects in a kinetic description are instrumental for a proper description of particle pinches. We assume here that only the ITG mode due to main ions is unstable. The ITG mode due to impurities would, of course, be sensitive to the resonance with impurities. This also addresses the question of sources in the Fokker-Planck equation. The point is that we need only to worry about resonant sources for the wave dynamics, since RF heating with phase velocity or NBI heating with beam velocity far from the drift waves will appear only as ideal heat sources. The difference in phase velocity between drift waves and RF waves is much larger than the difference in thermal velocity of main ions and typical impurity ions.

  16. Dynamics of conical wire array Z-pinch implosions

    SciTech Connect

    Ampleford, D. J.; Lebedev, S. V.; Bland, S. N.; Bott, S. C.; Chittenden, J. P.; Jennings, C. A.; Kantsyrev, V. L.; Safronova, A. S.; Ivanov, V. V.; Fedin, D. A.; Laca, P. J.; Yilmaz, M. F.; Nalajala, V.; Shrestha, I.; Williamson, K.; Osborne, G.; Haboub, A.; Ciardi, A.

    2007-10-15

    A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generators--the MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility's Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P. Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.

  17. Effects of EVA spacesuit glove on grasping and pinching tasks

    NASA Astrophysics Data System (ADS)

    Appendino, Silvia; Battezzato, Alessandro; Chen Chen, Fai; Favetto, Alain; Mousavi, Mehdi; Pescarmona, Francesco

    2014-03-01

    The human hand has a wide range of degrees of freedom, allowing a great variety of movements, and is also one of the most sensitive parts of the human body. Due to these characteristics, it is the most important tool for astronauts to perform extravehicular activities (EVA). However, astronauts must wear mandatory EVA equipment to be protected from the harsh conditions in space and this strongly reduces hand performance, in particular as regards dexterity, tactile perception, mobility and fatigue. Several studies have been conducted to determine the influence of the EVA glove on manual capabilities, both in the past and more recently. This study presents experimental data regarding the performance decline occurring in terms of force and fatigue in the execution of grasping and pinching tasks when wearing an EVA glove, in pressurized and unpressurized conditions, compared with barehanded potential. Results show that wearing the unpressurized EVA glove hinders grip and lateral pinch performances, dropping exerted forces to about 50-70%, while it barely affects two- and three-finger pinch performances. On the other hand, wearing the pressurized glove worsens performances in all cases, reducing forces to about 10-30% of barehanded potential. The results are presented and compared with the previous literature.

  18. Hybrid X Pinches at 1.2 MA

    NASA Astrophysics Data System (ADS)

    Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Cahill, Adam D.; Hoyt, Cad L.; Hammer, David A.; Tilikin, Ivan N.; Mishin, Sergey N.; Mingaleev, Albert R.

    2012-10-01

    A hybrid X-pinch (HXP) configuration consisting of solid conical electrodes connected by a wire as a central load has been tested on four different generators with currents varying from 200 kA to 1.2 MA and risetimes ranging from 50 ns to 170 ns. It was possible to optimize the wire material, length and diameter so that most of these HXPs generated an intense single burst of soft x-rays with energy yield comparable with that produced by standard X pinches. This configuration is useful primarily for pulsers with MA current level and was suggested to simplify standard wire X-pinch configurations with many wires. Wires as well as hollow and filled tubes made of Al, Ni and polyethylene were tested as a load on the COBRA pulser (1.2 MA, 100 ns rise time). The filled tubes expand the range of materials that can be studied under extreme conditions. Electron beams generation in HXPs has also been studied.

  19. Kolmogorov and trigonometric widths of the Besov classes B^r_{p,\\theta} of multivariate periodic functions

    NASA Astrophysics Data System (ADS)

    Romanyuk, A. S.

    2006-02-01

    Precise (in order) estimates of the Kolmogorov widths in the space L_q, 1, of the classes B^r_{1,\\theta} and B^r_{\\infty,\\theta} and also of the trigonometric widths of the classes B^r_{p,\\theta} in L_q for p and q satisfying certain relations are obtained.

  20. Developing models for simulation of pinched-beam dynamics in heavy ion fusion. Revision 1

    SciTech Connect

    Boyd, J.K.; Mark, J.W.K.; Sharp, W.M.; Yu, S.S.

    1984-02-22

    For heavy-ion fusion energy applications, Mark and Yu have derived hydrodynamic models for numerical simulation of energetic pinched-beams including self-pinches and external-current pinches. These pinched-beams are applicable to beam propagation in fusion chambers and to the US High Temperature Experiment. The closure of the Mark-Yu model is obtained with adiabatic assumptions mathematically analogous to those of Chew, Goldberger, and Low for MHD. Features of this hydrodynamic beam model are compared with a kinetic treatment.

  1. Use of spherically bent crystals to diagnose wire array z pinches

    SciTech Connect

    Shelkovenko, T.A.; Pikuz, S.A.; Hammer, D.A.; Ampleford, D.J.; Bland, S.N.; Bott, S.C.; Chittenden, J.P.; Lebedev, S.V.

    2004-10-01

    Spherically bent mica and quartz crystals have provided time-integrated spectra and monochromatic images in self-radiation of wire array z-pinch implosions on the MAGPIE generator (1 MA, 240 ns) at Imperial College. Diagnostics based on spherically bent crystals offer higher efficiencies than those based on flat or convex dispersion elements, allowing positioning far from the pinch with good debris shielding. A mica crystal spectrometer produced an image of the pinch in each emission line with about 100 {mu}m axial resolution. Combining the results of monochromatic imaging and spectra confirmed the presence of bright spots, probably generated by energetic electrons inside the pinch.

  2. Study of soft X-ray emission from Z-pinches with a complex atomic composition

    SciTech Connect

    Volkov, G. S.; Zaitsev, V. I.; Grabovski, E. V.; Fedulov, M. V.; Aleksandrov, V. V.; Lakhtyushko, N. I.

    2010-03-15

    Results are presented from experimental studies of Z-pinches produced by implosion of aluminum and tungsten cylindrical wire arrays in the Angara-5-1 facility. The electron temperature T{sub e} and density n{sub e} of the high-temperature pinch plasma have been determined by analyzing line emission from multicharged ions. For the same mass and radius of the array and the same number of wires in it, the intensity of line emission of H- and He-like Al ions from an imploded Al + W wire array containing even a small amount of tungsten (7 wt %) is one order of magnitude lower than that from an Al array. As the W content increases, the total soft X-ray (SXR) yield increases, while the duration of the SXR pulse decreases. For the 30% W content in the array, the power and duration of the SXR pulse are nearly the same as those recorded during the implosion of a W array with the same linear mass and radius and the same number of wires. Results are also presented from experiments with nested wire arrays in which the outer and inner shells were made of Al and W wires, respectively. It is found that, in this case, the effect of tungsten on the line emission of aluminum is much weaker than that in experiments with arrays in which tungsten and aluminum wires were placed in the same shell, even if the mass of the inner (tungsten) shell was larger than that of the outer (aluminum) one. At the same time, the inner W shell plays a significant role in the implosion dynamics of a nested wire array, reducing the duration of the SXR pulse and increasing the SXR power.

  3. Study of soft X-ray emission from Z-pinches with a complex atomic composition

    NASA Astrophysics Data System (ADS)

    Volkov, G. S.; Zaitsev, V. I.; Grabovski, E. V.; Fedulov, M. V.; Aleksandrov, V. V.; Lakhtyushko, N. I.

    2010-03-01

    Results are presented from experimental studies of Z-pinches produced by implosion of aluminum and tungsten cylindrical wire arrays in the Angara-5-1 facility. The electron temperature T e and density n e of the high-temperature pinch plasma have been determined by analyzing line emission from multicharged ions. For the same mass and radius of the array and the same number of wires in it, the intensity of line emission of H- and He-like Al ions from an imploded Al + W wire array containing even a small amount of tungsten (7 wt %) is one order of magnitude lower than that from an Al array. As the W content increases, the total soft X-ray (SXR) yield increases, while the duration of the SXR pulse decreases. For the 30% W content in the array, the power and duration of the SXR pulse are nearly the same as those recorded during the implosion of a W array with the same linear mass and radius and the same number of wires. Results are also presented from experiments with nested wire arrays in which the outer and inner shells were made of Al and W wires, respectively. It is found that, in this case, the effect of tungsten on the line emission of aluminum is much weaker than that in experiments with arrays in which tungsten and aluminum wires were placed in the same shell, even if the mass of the inner (tungsten) shell was larger than that of the outer (aluminum) one. At the same time, the inner W shell plays a significant role in the implosion dynamics of a nested wire array, reducing the duration of the SXR pulse and increasing the SXR power.

  4. Spin asymmetries in {gamma} N {yields} {bar K}* {Theta}{sup +}

    SciTech Connect

    Yongseok Oh; Hungchong Kim; Su Houng Lee

    2004-11-01

    The photoproduction processes of the exotic {Theta}{sup +}(1540) baryon and the K* meson from the nucleon targets, i.e., {gamma}n {yields} K*{sup -} {Theta}{sup +} and {gamma}p {yields} {bar K}*{sup 0}{Theta}{sup +} are investigated in a hadronic model. We consider K and K* exchanges as well as the s and u channel nucleon and {Theta} terms. Various spin asymmetries together with cross sections are first computed in order to study the production mechanisms and the parity of the {Theta}{sup +}(1540) baryon. Within the uncertainties arising from the model-dependence of the production mechanisms and several coupling constants, we find that some target-recoil double spin asymmetries, C{sub xx{prime}}{sup TR} and C{sub xx{prime}}{sup TR} are sensitive to the parity of {Theta}{sup +}. In addition, the parity asymmetry of this reaction on the neutron target, which can be obtained by analyzing K* decay distribution, is found to be useful to estimate the K* N{Theta} coupling.

  5. Someone has to give in: theta oscillations correlate with adaptive behavior in social bargaining

    PubMed Central

    Zamorano, Francisco; López, Tamara; Rodriguez, Carlos; Cosmelli, Diego; Aboitiz, Francisco

    2014-01-01

    During social bargain, one has to both figure out the others’ intentions and behave strategically in such a way that the others’ behaviors will be consistent with one’s expectations. To understand the neurobiological mechanisms underlying these behaviors, we used electroencephalography while subjects played as proposers in a repeated ultimatum game. We found that subjects adapted their offers to obtain more acceptances in the last round and that this adaptation correlated negatively with prefrontal theta oscillations. People with higher prefrontal theta activity related to a rejection did not adapt their offers along the game to maximize their earning. Moreover, between-subject variation in posterior theta oscillations correlated positively with how individual theta activity influenced the change of offer after a rejection, reflecting a process of behavioral adaptation to the others’ demands. Interestingly, people adapted better their offers when they knew that they where playing against a computer, although the behavioral adaptation did not correlate with prefrontal theta oscillation. Behavioral changes between human and computer games correlated with prefrontal theta activity, suggesting that low adaptation in human games could be a strategy. Taken together, these results provide evidence for specific roles of prefrontal and posterior theta oscillations in social bargaining. PMID:24493841

  6. Photoproduction of the \\Theta^+ resonance on the nucleon in a Regge model

    SciTech Connect

    H. Kwee; M. Guidal; M. Polyakov; M. Vanderhaeghen

    2005-09-15

    We estimate the reaction mechanisms for the photoproduction of the {Theta}{sup +}(1540) resonance on the nucleon, through K and K* Regge exchanges. We compare the size of the cross sections for the {gamma}n {yields} K{sup -} {Theta}{sup +} and {gamma}p {yields} {bar K}{sup 0} {Theta}{sup +} reactions, and investigate their sensitivity to the spin-parity assignments J{sup P} = (1/2){sup {+-}}, (3/2){sup {+-}} for the {Theta}{sup +} resonance. The model allows to estimate the cross sections corresponding with a given upper bound on the width of the {Theta}{sup +}. Within this model, the cross sections on the neutron are found to be around a factor 5 larger than the ones on the proton, due to the presence of charged K exchange for the reaction on a neutron target. Furthermore, the photon asymmetry is found to display a pronounced sensitivity to the parity of the {Theta}{sup +}, making it a very promising observable to help determining the quantum numbers of the {Theta}{sup +} resonance.

  7. Developmental change in EEG theta activity in the medial prefrontal cortex during response control.

    PubMed

    Liu, Zhong-Xu; Woltering, Steven; Lewis, Marc D

    2014-01-15

    Cognitive control functions continue to improve from infancy until early adulthood, allowing flexible adaptation to a complex environment. However, it remains controversial how this development in cognitive capabilities is mediated by changes in cortical activity: both age-related increases and decreases of mediofrontal neural activity have been observed and interpreted as neural underpinnings of this functional development. To better understand this developmental process, we examined EEG theta activity in the mediofrontal region using a Go/No-go response control task. We found that both pre-stimulus baseline theta-power and theta-power during the response control task, without baseline-correction, decreased with age. Conversely, when task-related theta-power was baseline corrected (using a ratio method), it exhibited a positive developmental trajectory. The age-related theta-power increase was source-localized to the anterior cingulate cortex. This increase in theta activity also partially mediated age-related improvements in response control and was greatest in a condition that demanded greater effort. Theta activity in older children also showed greater temporal reliability across trials as measured by inter-trial phase-coherence. Interestingly, directly subtracting baseline activity from task-related activity did not yield significant developmental effects, which highlights the necessity of separating and contrasting the pre-stimulus baseline with task-related processing in the understanding of neurodevelopmental changes. PMID:24007804

  8. Hippocampal Non-Theta-Contingent Eyeblink Classical Conditioning: A Model System for Neurobiological Dysfunction

    PubMed Central

    Cicchese, Joseph J.; Berry, Stephen D.

    2016-01-01

    Typical information processing is thought to depend on the integrity of neurobiological oscillations that may underlie coordination and timing of cells and assemblies within and between structures. The 3–7 Hz bandwidth of hippocampal theta rhythm is associated with cognitive processes essential to learning and depends on the integrity of cholinergic, GABAergic, and glutamatergic forebrain systems. Since several significant psychiatric disorders appear to result from dysfunction of medial temporal lobe (MTL) neurochemical systems, preclinical studies on animal models may be an important step in defining and treating such syndromes. Many studies have shown that the amount of hippocampal theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning and attainment of asymptotic performance. Our lab has developed a brain–computer interface that makes eyeblink training trials contingent upon the explicit presence or absence of hippocampal theta. The behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to fourfold increase in learning speed over non-theta states. The non-theta behavioral impairment is accompanied by disruption of the amplitude and synchrony of hippocampal local field potentials, multiple-unit excitation, and single-unit response patterns dependent on theta state. Our findings indicate a significant electrophysiological and behavioral impact of the pretrial state of the hippocampus that suggests an important role for this MTL system in associative learning and a significant deleterious impact in the absence of theta. Here, we focus on the impairments in the non-theta state, integrate them into current models of psychiatric disorders, and suggest how improvement in our understanding of neurobiological oscillations is critical for theories and treatment of psychiatric

  9. A critical test of the hippocampal theta model of anxiolytic drug action.

    PubMed

    Yeung, Michelle; Treit, Dallas; Dickson, Clayton T

    2012-01-01

    Hippocampal theta rhythms have been associated with a number of behavioural processes, including learning, memory and arousal. Recently it has been argued that the suppression of hippocampal theta is a valid indicator of anxiolytic drug action. Like all such models, however, it has relied almost exclusively on the experimental effects of well-known, clinically proven anxiolytic compounds for validation. The actual predictive validity of putative models of anxiolytic drug action, however, cannot be rigorously tested with this approach alone. The present study provides a stringent test of the predictive validity of the theta suppression model, using the drug phenytoin (50 mg/kg and 10 mg/kg), and a positive comparison compound, diazepam (2 mg/kg). Phenytoin has two important properties that are advantageous for assessing the validity of the theta suppression model: 1) it is a standard antiepileptic drug with no known anxiolytic effects, and 2) its primary mechanism of action is through suppression of the persistent sodium current, an effect that should also suppress hippocampal theta. Because of the latter property, we also directly compared the effects of phenytoin in the theta suppression model with its effects in the most widely tested behavioural model of anxiolytic drug action, the elevated plus-maze. While an anxiolytic-like effect of phenytoin in the theta suppression model might be expected simply due to its suppressive effects on sodium channel currents, anxiolytic effects in both tests would provide strong support for the predictive validity of the theta suppression model. Surprisingly, phenytoin produced clear anxiolytic-like effects in both neurophysiological and behavioural models, thus providing strong evidence of the predictive validity of the theta suppression model. This article is part of a Special Issue entitled 'Anxiety and Depression'. PMID:21723303

  10. Theta oscillations during the processing of monetary loss and gain: A perspective on gender and impulsivity

    PubMed Central

    Kamarajan, Chella; Rangaswamy, Madhavi; Chorlian, David B.; Manz, Niklas; Tang, Yongqiang; Pandey, Ashwini K.; Roopesh, Bangalore N.; Stimus, Arthur T.; Porjesz, Bernice

    2008-01-01

    Event-related oscillations (EROs) have proved to be very useful in the understanding of a variety of neurocognitive processes including reward/outcome processing. In the present study, theta power (4.0–7.0 Hz) following outcome stimuli in the time window of the N2-P3 complex (200–500 ms) was analyzed in healthy normals (20 males and 20 females) while performing a gambling task that involved monetary loss and gain. The main aim was to analyze outcome processing in terms of event-related theta power in the context of valence, amount, gender, and impulsivity. The S-transform was used for the signal processing of the ERO data in terms of time-frequency-power. Results from filtered waveforms showed a partially consistent phase-alignment of the increased theta activity corresponding to N2 and P3 components following the outcome stimuli. Gain conditions produced more theta power than loss conditions. While there was anterior involvement in both gain and loss, posterior activation was stronger during gain conditions than during loss conditions. Females exhibited posterior maxima during gain conditions while males had an anterior maxima during both loss and gain conditions. The current source density of theta activity in females involved larger areas of the scalp including a bilateral frontal activity while males predominantly had a frontal midline activity. Theta power was significantly higher in females than males across all conditions. Low theta (4.0–5.5 Hz) predominantly contributed to the posterior activity during gain conditions. High theta (5.5–7.0 Hz) was more associated with impulsivity measures than low theta activity. These findings may offer valuable clues to understand outcome processing, impulsivity, and gender differences. PMID:18616934

  11. Hippocampal Non-Theta-Contingent Eyeblink Classical Conditioning: A Model System for Neurobiological Dysfunction.

    PubMed

    Cicchese, Joseph J; Berry, Stephen D

    2016-01-01

    Typical information processing is thought to depend on the integrity of neurobiological oscillations that may underlie coordination and timing of cells and assemblies within and between structures. The 3-7 Hz bandwidth of hippocampal theta rhythm is associated with cognitive processes essential to learning and depends on the integrity of cholinergic, GABAergic, and glutamatergic forebrain systems. Since several significant psychiatric disorders appear to result from dysfunction of medial temporal lobe (MTL) neurochemical systems, preclinical studies on animal models may be an important step in defining and treating such syndromes. Many studies have shown that the amount of hippocampal theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning and attainment of asymptotic performance. Our lab has developed a brain-computer interface that makes eyeblink training trials contingent upon the explicit presence or absence of hippocampal theta. The behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to fourfold increase in learning speed over non-theta states. The non-theta behavioral impairment is accompanied by disruption of the amplitude and synchrony of hippocampal local field potentials, multiple-unit excitation, and single-unit response patterns dependent on theta state. Our findings indicate a significant electrophysiological and behavioral impact of the pretrial state of the hippocampus that suggests an important role for this MTL system in associative learning and a significant deleterious impact in the absence of theta. Here, we focus on the impairments in the non-theta state, integrate them into current models of psychiatric disorders, and suggest how improvement in our understanding of neurobiological oscillations is critical for theories and treatment of psychiatric

  12. Theta-rhythmic drive between medial septum and hippocampus in slow-wave sleep and microarousal: a Granger causality analysis.

    PubMed

    Kang, D; Ding, M; Topchiy, I; Shifflett, L; Kocsis, B

    2015-11-01

    Medial septum (MS) plays a critical role in controlling the electrical activity of the hippocampus (HIPP). In particular, theta-rhythmic burst firing of MS neurons is thought to drive lasting HIPP theta oscillations in rats during waking motor activity and REM sleep. Less is known about MS-HIPP interactions in nontheta states such as non-REM sleep, in which HIPP theta oscillations are absent but theta-rhythmic burst firing in subsets of MS neurons is preserved. The present study used Granger causality (GC) to examine the interaction patterns between MS and HIPP in slow-wave sleep (SWS, a nontheta state) and during its short interruptions called microarousals (a transient theta state). We found that during SWS, while GC revealed a unidirectional MS→HIPP influence over a wide frequency band (2-12 Hz, maximum: ∼8 Hz), there was no theta peak in the hippocampal power spectra, indicating a lack of theta activity in HIPP. In contrast, during microarousals, theta peaks were seen in both MS and HIPP power spectra and were accompanied by bidirectional GC with MS→HIPP and HIPP→MS theta drives being of equal magnitude. Thus GC in a nontheta state (SWS) vs. a theta state (microarousal) primarily differed in the level of HIPP→MS. The present findings suggest a modification of our understanding of the role of MS as the theta generator in two regards. First, a MS→HIPP theta drive does not necessarily induce theta field oscillations in the hippocampus, as found in SWS. Second, HIPP theta oscillations entail bidirectional theta-rhythmic interactions between MS and HIPP. PMID:26354315

  13. Effects of intermittent theta burst stimulation on spasticity after stroke.

    PubMed

    Kim, Dae Hyun; Shin, Ji Cheol; Jung, Seungsoo; Jung, Tae-Min; Kim, Deog Young

    2015-07-01

    Spasticity is a common cause of long-term disability in poststroke hemiplegic patients. We investigated whether intermittent theta burst stimulation (iTBS) could reduce upper-limb spasticity after a stroke. Fifteen hemiplegic stroke patients were recruited for a double-blind sham-controlled cross-over design study. A single session of iTBS or sham stimulation was delivered on the motor hotspot of the affected flexor carpi radialis muscle in a random and counterbalanced order with a 1-week interval. Modified Ashworth scale (MAS), modified Tardieu scale (MTS), H-wave/M-wave amplitude ratio, peak torque (PT), peak torque angle (PTA), work of affected wrist flexor, and rectified integrated electromyographic activity of the flexor carpi radialis muscle were measured before, immediately after, 30 min after, and 1 week after iTBS or sham stimulation. Repeated-measures analysis of variance showed a significant interaction between time and intervention for the MAS, MTS, PT, PTA, and rectified integrated electromyographic activity (P<0.05), indicating that these parameters were significantly improved by iTBS compared with sham stimulation. However, the H-wave/M-wave amplitude ratio and work were not affected. MAS and MTS significantly improved for at least 30 min after iTBS, but the other parameters only improved immediately after iTBS (P<0.05). In conclusion, iTBS on the affected hemisphere may help to reduce poststroke spasticity transiently. PMID:26011507

  14. Mammalian Polymerase Theta Promotes Alternative-NHEJ and Suppresses Recombination

    PubMed Central

    Mateos-Gomez, Pedro A.; Gong, Fade; Nair, Nidhi; Miller, Kyle M.; Lazzerini-Denchi, Eros; Sfeir, Agnel

    2016-01-01

    The alternative nonhomologous end-joining (alt-NHEJ) machinery facilitates a number of genomic rearrangements, some of which can lead to cellular transformation. This error-prone repair pathway is triggered upon telomere de-protection to promote the formation of deleterious chromosome end-to-end fusions1,2,3. Using next-generation sequencing technology, we found that repair by alt-NHEJ yields non-TTAGGG nucleotide insertions at fusion breakpoints of dysfunctional telomeres. Investigating the enzymatic activity responsible for the random insertions enabled us to identify Polymerase theta (Polθ; encoded by PolQ) as a critical alt-NHEJ factor in mammalian cells. PolQ inhibition suppresses alt-NHEJ at dysfunctional telomeres, and hinders chromosomal translocations at non-telomeric loci. In addition, we found that PolQ loss results in increased rates of homology directed repair (HDR), evident by recombination of dysfunctional telomeres and accumulation of Rad51 at double stranded breaks. Lastly, we show that depletion of PolQ has a synergistic impact on cell survival in the absence of BRCA genes, suggesting that the inhibition of this mutagenic polymerase represents a valid therapeutic avenue for tumors carrying mutations in HDR genes. PMID:25642960

  15. ''Theta gun,'' a multistage, coaxial, magnetic induction projectile accelerator

    SciTech Connect

    Burgess, T.J.; Duggin, B.W.; Cowan, M. Jr.

    1985-11-01

    We experimentally and theoretically studied a multistage coaxial magnetic induction projectile accelerator. We call this system a ''theta gun'' to differentiate it from other coaxial accelerator concepts such as the mass driver. We conclude that this system can theoretically attain railgun performance only for large caliber or very high injection velocity and, even then, only for long coil geometry. Our experiments with a three-stage, capactor bank-driven accelerator are described. The experiments are modeled with a 1-1/2 dimensional equivalent circuit-hydrodynamics code which is also described. We derive an expression for the conditions of coaxial accelerator-railgun ''velocity breakeven'' in the absence of ohmic and hydrodynamic effects. This, in conjunction with an expression for the magnetic coupling coefficient, defines a set of geometric relations which the coaxial system must simultaneously satisfy. Conclusions concerning both the existence and configuration of a breakeven coaxial system follow from this requirement. The relative advantages and disadvantages of the coaxial induction projectile accelerator, previously cited in the literature, are critiqued from the viewpoint of our analysis and experimental results. We find that the advantages vis-a-vis the railgun have been overstated. 13 refs., 17 figs.

  16. Modulation of EEG Theta Band Signal Complexity by Music Therapy

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Joydeep; Lee, Eun-Jeong

    The primary goal of this study was to investigate the impact of monochord (MC) sounds, a type of archaic sounds used in music therapy, on the neural complexity of EEG signals obtained from patients undergoing chemotherapy. The secondary goal was to compare the EEG signal complexity values for monochords with those for progressive muscle relaxation (PMR), an alternative therapy for relaxation. Forty cancer patients were randomly allocated to one of the two relaxation groups, MC and PMR, over a period of six months; continuous EEG signals were recorded during the first and last sessions. EEG signals were analyzed by applying signal mode complexity, a measure of complexity of neuronal oscillations. Across sessions, both groups showed a modulation of complexity of beta-2 band (20-29Hz) at midfrontal regions, but only MC group showed a modulation of complexity of theta band (3.5-7.5Hz) at posterior regions. Therefore, the neuronal complexity patterns showed different changes in EEG frequency band specific complexity resulting in two different types of interventions. Moreover, the different neural responses to listening to monochords and PMR were observed after regular relaxation interventions over a short time span.

  17. Magnetic Reconnection in the MST Reversed Field Pinch

    SciTech Connect

    Crocker, N.E.

    2001-06-01

    Magnetic field line reconnection is a process whereby magnetic field lines which are otherwise topologically preserved by, and frozen into, a plasma can break and reconnect to form field lines with different topologies. It plays a significant role in a wide variety of plasmas, including stellar, space and laboratory plasmas. The focus of this dissertation is the underlying dynamics of reconnection in one particular kind of laboratory plasma: the Reversed Field Pinch (RFP). Specifically, this dissertation reports measurements, made using a pair of insertable diagnostics in conjunction with arrays of magnetic sensing coils positioned near the plasma surface, of the spatial structure of the magnetic and parallel current density fluctuations associated with reconnection in the edge of MST. At least 4 significant results are obtained form such measurements. First we observe direct evidence of reconnection which takes the form of tearing modes in an RFP. Specifically we measure a (radial) magnetic field fluctuation that causes reconnection in the so-called reversal surface, or q = 0 surface, in the edge of MST. Notably this evidence of reconnection at the reversal surface is the first of its kind in an RFP. Second, we measure the radial width of the associated current sheet, or fluctuation in the component of the current density parallel to the equilibrium magnetic field. Such current sheets are a characteristic feature of the reconnection process but their radial widths are sensitive to the specific effects that allow reconnection to occur sometimes call non-ideal effects because reconnection is forbidden by ideal MHD. We compare the observed width to those expected from models of reconnection that incorporate different non-ideal effects in Ohm's law. In particular we see that the observed width is significantly larger than those expected form resistivity in the context of linearly unstable tearing modes and electron inertia. It is a factor of a few larger than the

  18. Photon beam quality variations of a flattening filter free linear accelerator

    SciTech Connect

    Georg, Dietmar; Kragl, Gabriele; Wetterstedt, Sacha af; McCavana, Patrick; McClean, Brendan; Knoeoes, Tommy

    2010-01-15

    Purpose: Recently, there has been an increasing interest in operating conventional linear accelerators without a flattening filter. The aim of this study was to determine beam quality variations as a function of off-axis ray angle for unflattened beams. In addition, a comparison was made with the off-axis energy variation in flattened beams. Methods: Two Elekta Precise linear accelerators were modified in order to enable radiation delivery with and without the flattening filter in the beam line. At the Medical University Vienna (Vienna, Austria), half value layer (HVL) measurements were performed for 6 and 10 MV with an in-house developed device that can be easily mounted on the gantry. At St. Luke's Hospital (Dublin, Ireland), measurements were performed at 6 MV in narrow beam geometry with the gantry tilted around 270 deg. with pinhole collimators, an attenuator, and the chamber positioned on the table. All attenuation measurements were performed with ionization chambers and a buildup cap (2 mm brass) or a PMMA mini phantom (diameter 3 cm, measurement depth 2.5 cm). Results: For flattened 6 and 10 MV photon beams from the Elekta linac the relative HVL({theta}) varies by about 11% for an off-axis ray angle {theta}=10 deg. These results agree within {+-}2% with a previously proposed generic off-axis energy correction. For unflattened beams, the variation was less than 5% in the whole range of off-axis ray angles up to 10 deg. The difference in relative HVL data was less than 1% for unflattened beams at 6 and 10 MV. Conclusions: Off-axis energy variation is rather small in unflattened beams and less than half the one for flattened beams. Thus, ignoring the effect of off-axis energy variation for dose calculations in unflattened beams can be clinically justified.

  19. Two-dimensional linear elasticity theory of magneto-electro-elastic plates considering surface and nonlocal effects for nanoscale device applications

    NASA Astrophysics Data System (ADS)

    Wang, Wenjun; Li, Peng; Jin, Feng

    2016-09-01

    A novel two-dimensional linear elastic theory of magneto-electro-elastic (MEE) plates, considering both surface and nonlocal effects, is established for the first time based on Hamilton’s principle and the Lee plate theory. The equations derived are more general, suitable for static and dynamic analyses, and can also be reduced to the piezoelectric, piezomagnetic, and elastic cases. As a specific application example, the influences of the surface and nonlocal effects, poling directions, piezoelectric phase materials, volume fraction, damping, and applied magnetic field (i.e., constant applied magnetic field and time-harmonic applied magnetic field) on the magnetoelectric (ME) coupling effects are first investigated based on the established two-dimensional plate theory. The results show that the ME coupling coefficient has an obvious size-dependent characteristic owing to the surface effects, and the surface effects increase the ME coupling effects significantly when the plate thickness decreases to its critical thickness. Below this critical thickness, the size-dependent effect is obvious and must be considered. In addition, the output power density of a magnetic energy nanoharvester is also evaluated using the two-dimensional plate theory obtained, with the results showing that a relatively larger output power density can be achieved at the nanoscale. This study provides a mathematical tool which can be used to analyze the mechanical properties of nanostructures theoretically and numerically, as well as evaluating the size effect qualitatively and quantitatively.

  20. Characterisation of the current switch mechanism in two-stage wire array Z-pinches

    NASA Astrophysics Data System (ADS)

    Burdiak, G. C.; Lebedev, S. V.; Harvey-Thompson, A. J.; Hall, G. N.; Swadling, G. F.; Suzuki-Vidal, F.; Khoory, E.; Bland, S. N.; Pickworth, L.; de Grouchy, P.; Skidmore, J.; Suttle, L.; Waisman, E. M.

    2015-11-01

    In this paper, we describe the operation of a two-stage wire array z-pinch driven by the 1.4 MA, 240 ns rise-time Magpie pulsed-power device at Imperial College London. In this setup, an inverse wire array acts as a fast current switch, delivering a current pre-pulse into a cylindrical load wire array, before rapidly switching the majority of the generator current into the load after a 100-150 ns dwell time. A detailed analysis of the evolution of the load array during the pre-pulse is presented. Measurements of the load resistivity and energy deposition suggest significant bulk heating of the array mass occurs. The ˜5 kA pre-pulse delivers ˜0.8 J of energy to the load, leaving it in a mixed, predominantly liquid-vapour state. The main current switch occurs as the inverse array begins to explode and plasma expands into the load region. Electrical and imaging diagnostics indicate that the main current switch may evolve in part as a plasma flow switch, driven by the expansion of a magnetic cavity and plasma bubble along the length of the load array. Analysis of implosion trajectories suggests that approximately 1 MA switches into the load in 100 ns, corresponding to a doubling of the generator dI/dt. Potential scaling of the device to higher current machines is discussed.