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Sample records for high-frequency recoil spectrometer

  1. Time-of-flight direct recoil ion scattering spectrometer

    DOEpatents

    Krauss, A.R.; Gruen, D.M.; Lamich, G.J.

    1994-09-13

    A time-of-flight direct recoil and ion scattering spectrometer beam line is disclosed. The beam line includes an ion source which injects ions into pulse deflection regions and separated by a drift space. A final optics stage includes an ion lens and deflection plate assembly. The ion pulse length and pulse interval are determined by computerized adjustment of the timing between the voltage pulses applied to the pulsed deflection regions. 23 figs.

  2. Time-of-flight direct recoil ion scattering spectrometer

    DOEpatents

    Krauss, Alan R.; Gruen, Dieter M.; Lamich, George J.

    1994-01-01

    A time of flight direct recoil and ion scattering spectrometer beam line (10). The beam line (10) includes an ion source (12) which injects ions into pulse deflection regions (14) and (16) separated by a drift space (18). A final optics stage includes an ion lens and deflection plate assembly (22). The ion pulse length and pulse interval are determined by computerized adjustment of the timing between the voltage pulses applied to the pulsed deflection regions (14) and (16).

  3. Calibration of a compact magnetic proton recoil neutron spectrometer

    NASA Astrophysics Data System (ADS)

    Zhang, Jianfu; Ouyang, Xiaoping; Zhang, Xianpeng; Ruan, Jinlu; Zhang, Guoguang; Zhang, Xiaodong; Qiu, Suizheng; Chen, Liang; Liu, Jinliang; Song, Jiwen; Liu, Linyue; Yang, Shaohua

    2016-04-01

    Magnetic proton recoil (MPR) neutron spectrometer is considered as a powerful instrument to measure deuterium-tritium (DT) neutron spectrum, as it is currently used in inertial confinement fusion facilities and large Tokamak devices. The energy resolution (ER) and neutron detection efficiency (NDE) are the two most important parameters to characterize a neutron spectrometer. In this work, the ER calibration for the MPR spectrometer was performed by using the HI-13 tandem accelerator at China Institute of Atomic Energy (CIAE), and the NDE calibration was performed by using the neutron generator at CIAE. The specific calibration techniques used in this work and the associated accuracies were discussed in details in this paper. The calibration results were presented along with Monte Carlo simulation results.

  4. A telescope proton recoil spectrometer for fast neutron beam-lines

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Rebai, M.; Tardocchi, M.; Croci, G.; Nocente, M.; Ansell, S.; Frost, C. D.; Gorini, G.

    2015-07-01

    Fast neutron measurements were performed on the VESUVIO beam-line at the ISIS spallation source using a new telescope proton recoil spectrometer. Neutrons interact on a plastic target. Proton production is mainly due to elastic scattering on hydrogen nuclei and secondly due to interaction with carbon nuclei. Recoil protons are measured by a proton spectrometer, which uses in coincidence a 2.54 cm thick YAP scintillator and a 500μm thick silicon detector, measuring the full proton recoil energy and the partial deposited energy in transmission, respectively. Recoil proton spectroscopy measurements (up to Ep = 60MeV) have been interpreted by using Monte Carlo simulations of the beam-line. This instrument is of particular interest for the characterization of the ChipIr beam-line at ISIS, which was designed to feature an atmospheric-like neutron spectrum for the irradiation of micro-electronics.

  5. A Spectrometer for Dynamic Nuclear Polarization and Electron Paramagnetic Resonance at High Frequencies

    NASA Astrophysics Data System (ADS)

    Becerra, L. R.; Gerfen, G. J.; Bellew, B. F.; Bryant, J. A.; Hall, D. A.; Inati, S. J.; Weber, R. T.; Un, S.; Prisner, T. F.; McDermott, A. E.; Fishbein, K. W.; Kreischer, K. E.; Temkin, R. J.; Singel, D. J.; Griffin, R. G.

    A high-frequency dynamic nuclear polarization (DNP)/electron paramagnetic resonance spectrometer operating at 211 MHz for 1H and 140 GHz for g= 2 paramagnetic centers (5 T static field) is described. The salient feature of the instrument is a cyclotron-resonance maser (gyrotron) which generates high-frequency, high-power microwave radiation. This gyrotron, which under conventional operation produces millisecond pulses at kilowatt powers, has been adapted to operate at ˜100 W for 1 to 20 s pulses and in the continuous wave mode at the 10 W power level. Experiments combining DNP with magic-angle spinning (MAS) nuclear magnetic resonance were performed on samples consisting of 2% by weight of the free radical BDPA doped into polystyrene. Room-temperature DNP enhancement factors of 10 for 1H and 40 for 13C were obtained in the NMR-MAS spectra. Static DNP NMR has also been performed on samples containing nitroxides dissolved in water:glycerol solvent mixtures. Enhancements of approximately 200 have been obtained for low-temperature (14 K) 1H NMR. A pulsed/CW EPR spectrometer operating at 140 GHz has been developed in conjunction with the DNP spectrometer. Microwave sources include Gunn-diode oscillators which provide low-power (20 mW) radiation, and the gyrotron, which has been used to deliver higher power levels in pulsed experiments. Results using this spectrometer are presented for continuous-wave and echo-detected EPR, electron spin-echo-envelope modulation (ESEEM), and Fourier-transform EPR.

  6. Initial results of the commissioning of the HRIBF recoil mass spectrometer

    SciTech Connect

    Gross, C.J.; Akovali, Y.A.; Brinkman, M.J.; Mas, J.; McConnell, J.W.; Milner, W.T.; Shapira, D.; Ginter, T.N.; James, A.N.

    1996-10-01

    The recoil mass spectrometer at the Holifield Radioactive Ion Beam Facility is currently undergoing commissioning tests. This new spectrometer is designed to transmit ions with rigidities of K = 100 resulting from fusion-evaporation reactions using inverse-kinematics. The device consists of two sections: a momentum separator to provide beam rejection and a mass separator for product identification. Using normal-kinematic and symmetric reactions, the commissioning tests have shown that the A/Q acceptance is almost {+-}5%, the energy acceptance is approximately {+-}12%, and there has been little, if any, primary beam observed on the focal plane. Commissioning tests are presently underway with reactions using inverse-kinematics.

  7. Development of a compact magnetic proton recoil spectrometer for measurement of deuterium-tritium neutrons

    SciTech Connect

    Zhang, Jianfu Ouyang, Xiaoping; Zhang, Xianpeng; Qiu, Suizheng; Zhang, Guoguang; Ruan, Jinlu; Zhang, Xiaodong; Yang, Shaohua; Song, Jiwen; Liu, Linyue; Li, Hongyun

    2015-12-15

    A new compact magnetic proton recoil (MPR) neutron spectrometer has been designed for precise measurement of deuterium-tritium (DT) neutrons. This design is presented emphasizing the magnetic analyzing system, which is based on a compact quadrupole-dipole (QD) electromagnet. The focal plane detector (FPD) is also discussed with respect to application for the next step. The characteristics of the MPR spectrometer were calculated by using Monte Carlo simulation. A preliminary experiment was performed to test the magnetic analyzing system and the proton images of the FPD. Since the QD electromagnet design allows for a larger foil thickness and solid angle to be utilized, the MPR spectrometer defined in this paper can achieve neutron detection efficiency more than 5 × 10{sup −7} at an energy resolution of 1.5% for measuring DT neutrons.

  8. Development of a compact magnetic proton recoil spectrometer for measurement of deuterium-tritium neutrons.

    PubMed

    Zhang, Jianfu; Ouyang, Xiaoping; Qiu, Suizheng; Zhang, Guoguang; Ruan, Jinlu; Zhang, Xiaodong; Zhang, Xianpeng; Yang, Shaohua; Song, Jiwen; Liu, Linyue; Li, Hongyun

    2015-12-01

    A new compact magnetic proton recoil (MPR) neutron spectrometer has been designed for precise measurement of deuterium-tritium (DT) neutrons. This design is presented emphasizing the magnetic analyzing system, which is based on a compact quadrupole-dipole (QD) electromagnet. The focal plane detector (FPD) is also discussed with respect to application for the next step. The characteristics of the MPR spectrometer were calculated by using Monte Carlo simulation. A preliminary experiment was performed to test the magnetic analyzing system and the proton images of the FPD. Since the QD electromagnet design allows for a larger foil thickness and solid angle to be utilized, the MPR spectrometer defined in this paper can achieve neutron detection efficiency more than 5 × 10(-7) at an energy resolution of 1.5% for measuring DT neutrons.

  9. Development of a compact magnetic proton recoil spectrometer for measurement of deuterium-tritium neutrons.

    PubMed

    Zhang, Jianfu; Ouyang, Xiaoping; Qiu, Suizheng; Zhang, Guoguang; Ruan, Jinlu; Zhang, Xiaodong; Zhang, Xianpeng; Yang, Shaohua; Song, Jiwen; Liu, Linyue; Li, Hongyun

    2015-12-01

    A new compact magnetic proton recoil (MPR) neutron spectrometer has been designed for precise measurement of deuterium-tritium (DT) neutrons. This design is presented emphasizing the magnetic analyzing system, which is based on a compact quadrupole-dipole (QD) electromagnet. The focal plane detector (FPD) is also discussed with respect to application for the next step. The characteristics of the MPR spectrometer were calculated by using Monte Carlo simulation. A preliminary experiment was performed to test the magnetic analyzing system and the proton images of the FPD. Since the QD electromagnet design allows for a larger foil thickness and solid angle to be utilized, the MPR spectrometer defined in this paper can achieve neutron detection efficiency more than 5 × 10(-7) at an energy resolution of 1.5% for measuring DT neutrons. PMID:26724081

  10. First measurements of the absolute neutron spectrum using the Magnetic Recoil Spectrometer (MRS) at the NIF

    NASA Astrophysics Data System (ADS)

    Frenje, J.; Casey, D.; Li, C.; Seguin, F.; Petrasso, R.; Bionta, R.; Cerjan, C.; Eckart, M.; Haan, S.; Hatchett, S.; Khater, H.; Landen, O.; MacKinnon, A.; Moran, M.; Rygg, J.; Kilkenny, J.; Glebov, V.; Sangster, T.; Meyerhofer, D.; Magoon, J.; Fletcher, K.; Leeper, R.

    2010-11-01

    Proper assembly of capsule mass, as manifested through evolution of fuel areal density (ρR), is fundamentally important for achieving hot-spot ignition planned at the National Ignition Facility (NIF). Experimental information about ρR and ρR asymmetries, Ti and yield is therefore essential for understanding how this assembly occurs. To obtain this information, a neutron spectrometer, called the Magnetic-Recoil Spectrometer (MRS) has been implemented on the NIF. Its primary objective is to measure the absolute neutron spectrum in the range 5 to 30 MeV, from which ρR, Ti and yield can be directly inferred for both low-yield tritium-hydrogen-deuterium (THD) and high-yield DT implosions. In this talk, the results from the first measurements of the absolute neutron spectrum produced in exploding pusher and THD implosions will be presented. This work was supported in part by the U.S. DOE, LLNL and LLE.

  11. The magnetic recoil spectrometer for measurements of the absolute neutron spectrum at OMEGA and the NIF

    SciTech Connect

    Casey, D. T.; Frenje, J. A.; Gatu Johnson, M.; Seguin, F. H.; Li, C. K.; Petrasso, R. D.; Glebov, V. Yu.; Katz, J.; Magoon, J.; Meyerhofer, D. D.; Sangster, T. C.; Shoup, M.; Ulreich, J.; Ashabranner, R. C.; Bionta, R. M.; Carpenter, A. C.; Felker, B.; Khater, H. Y.; LePape, S.; MacKinnon, A.; McKernan, M. A.; Moran, M.; Rygg, J. R.; Yeoman, M. F.; Zacharias, R.; Leeper, R. J.; Fletcher, K.; Farrell, M.; Jasion, D.; Kilkenny, J.; Paguio, R.

    2013-04-18

    The neutron spectrum produced by deuterium-tritium (DT) inertial confinement fusion implosions contains a wealth of information about implosion performance including the DT yield, iontemperature, and areal-density. The Magnetic Recoil Spectrometer (MRS) has been used at both the OMEGA laser facility and the National Ignition Facility (NIF) to measure the absolute neutron spectrum from 3 to 30 MeV at OMEGA and 3 to 36 MeV at the NIF. These measurements have been used to diagnose the performance of cryogenic target implosions to unprecedented accuracy. Interpretation of MRS data requires a detailed understanding of the MRS response and background. This paper describes ab initio characterization of the system involving Monte Carlo simulations of the MRS response in addition to the commission experiments for in situ calibration of the systems on OMEGA and the NIF.

  12. Measuring the absolute DT neutron yield using the Magnetic Recoil Spectrometer at OMEGA and the NIF

    SciTech Connect

    Mackinnon, A; Casey, D; Frenje, J A; Johnson, M G; Seguin, F H; Li, C K; Petrasso, R D; Glebov, V Y; Katz, J; Knauer, J; Meyerhofer, D; Sangster, T; Bionta, R; Bleuel, D; Hachett, S P; Hartouni, E; Lepape, S; Mckernan, M; Moran, M; Yeamans, C

    2012-05-03

    A Magnetic Recoil Spectrometer (MRS) has been installed and extensively used on OMEGA and the National Ignition Facility (NIF) for measurements of the absolute neutron spectrum from inertial confinement fusion (ICF) implosions. From the neutron spectrum measured with the MRS, many critical implosion parameters are determined including the primary DT neutron yield, the ion temperature, and the down-scattered neutron yield. As the MRS detection efficiency is determined from first principles, the absolute DT neutron yield is obtained without cross-calibration to other techniques. The MRS primary DT neutron measurements at OMEGA and the NIF are shown to be in excellent agreement with previously established yield diagnostics on OMEGA, and with the newly commissioned nuclear activation diagnostics on the NIF.

  13. The magnetic recoil spectrometer for measurements of the absolute neutron spectrum at OMEGA and the NIF.

    PubMed

    Casey, D T; Frenje, J A; Johnson, M Gatu; Séguin, F H; Li, C K; Petrasso, R D; Glebov, V Yu; Katz, J; Magoon, J; Meyerhofer, D D; Sangster, T C; Shoup, M; Ulreich, J; Ashabranner, R C; Bionta, R M; Carpenter, A C; Felker, B; Khater, H Y; LePape, S; MacKinnon, A; McKernan, M A; Moran, M; Rygg, J R; Yeoman, M F; Zacharias, R; Leeper, R J; Fletcher, K; Farrell, M; Jasion, D; Kilkenny, J; Paguio, R

    2013-04-01

    The neutron spectrum produced by deuterium-tritium (DT) inertial confinement fusion implosions contains a wealth of information about implosion performance including the DT yield, ion-temperature, and areal-density. The Magnetic Recoil Spectrometer (MRS) has been used at both the OMEGA laser facility and the National Ignition Facility (NIF) to measure the absolute neutron spectrum from 3 to 30 MeV at OMEGA and 3 to 36 MeV at the NIF. These measurements have been used to diagnose the performance of cryogenic target implosions to unprecedented accuracy. Interpretation of MRS data requires a detailed understanding of the MRS response and background. This paper describes ab initio characterization of the system involving Monte Carlo simulations of the MRS response in addition to the commission experiments for in situ calibration of the systems on OMEGA and the NIF.

  14. The magnetic recoil spectrometer for measurements of the absolute neutron spectrum at OMEGA and the NIF

    SciTech Connect

    Casey, D. T.; Frenje, J. A.; Gatu Johnson, M.; Seguin, F. H.; Li, C. K.; Petrasso, R. D.; Glebov, V. Yu.; Katz, J.; Magoon, J.; Meyerhofer, D. D.; Sangster, T. C.; Shoup, M.; Ulreich, J.; Ashabranner, R. C.; Bionta, R. M.; Carpenter, A. C.; Felker, B.; Khater, H. Y.; LePape, S.; MacKinnon, A.; and others

    2013-04-15

    The neutron spectrum produced by deuterium-tritium (DT) inertial confinement fusion implosions contains a wealth of information about implosion performance including the DT yield, ion-temperature, and areal-density. The Magnetic Recoil Spectrometer (MRS) has been used at both the OMEGA laser facility and the National Ignition Facility (NIF) to measure the absolute neutron spectrum from 3 to 30 MeV at OMEGA and 3 to 36 MeV at the NIF. These measurements have been used to diagnose the performance of cryogenic target implosions to unprecedented accuracy. Interpretation of MRS data requires a detailed understanding of the MRS response and background. This paper describes ab initio characterization of the system involving Monte Carlo simulations of the MRS response in addition to the commission experiments for in situ calibration of the systems on OMEGA and the NIF.

  15. Shielding design for the Magnetic Recoil Spectrometer (MRS) at OMEGA and the NIF using TART2002

    NASA Astrophysics Data System (ADS)

    Casey, D. T.; Glebov, V. Yu.; Haan, S.; Wilson, D. C.; Leeper, R.

    2005-10-01

    A Magnetic Recoil Spectrometer (MRS) is currently being developed, at both OMEGA and the NIF, for measurements of down-scattered neutrons from which ρR of cryogenic DT implosions can be inferred. As is the case for complementary methods to measure ρR,ootnotetextC. K. Li et al, Phys. Plasmas 8, 4902 (2001) minimizing the effect of the background is critical for successful implementation. The established minimum S/B of 20, folded with CR-39 neutron response, determines the tolerable neutron fluence. The transport code TART2002 was used to calculate the neutron fluence at the MRS detector and provided input for design of the shielding for the MRS. This poster will present the current status of this project. This work was supported in part by LLE, LLNL, the U.S. DoE, the Univ. of Rochester, and the N.Y. State Energy Research and Development Authority.

  16. The magnetic recoil spectrometer for measurements of the absolute neutron spectrum at OMEGA and the NIF

    DOE PAGESBeta

    Casey, D. T.; Frenje, J. A.; Gatu Johnson, M.; Seguin, F. H.; Li, C. K.; Petrasso, R. D.; Glebov, V. Yu.; Katz, J.; Magoon, J.; Meyerhofer, D. D.; et al

    2013-04-18

    The neutron spectrum produced by deuterium-tritium (DT) inertial confinement fusion implosions contains a wealth of information about implosion performance including the DT yield, iontemperature, and areal-density. The Magnetic Recoil Spectrometer (MRS) has been used at both the OMEGA laser facility and the National Ignition Facility (NIF) to measure the absolute neutron spectrum from 3 to 30 MeV at OMEGA and 3 to 36 MeV at the NIF. These measurements have been used to diagnose the performance of cryogenic target implosions to unprecedented accuracy. Interpretation of MRS data requires a detailed understanding of the MRS response and background. This paper describesmore » ab initio characterization of the system involving Monte Carlo simulations of the MRS response in addition to the commission experiments for in situ calibration of the systems on OMEGA and the NIF.« less

  17. The magnetic recoil spectrometer for measurements of the absolute neutron spectrum at OMEGA and the NIF

    NASA Astrophysics Data System (ADS)

    Casey, D. T.; Frenje, J. A.; Gatu Johnson, M.; Séguin, F. H.; Li, C. K.; Petrasso, R. D.; Glebov, V. Yu.; Katz, J.; Magoon, J.; Meyerhofer, D. D.; Sangster, T. C.; Shoup, M.; Ulreich, J.; Ashabranner, R. C.; Bionta, R. M.; Carpenter, A. C.; Felker, B.; Khater, H. Y.; LePape, S.; MacKinnon, A.; McKernan, M. A.; Moran, M.; Rygg, J. R.; Yeoman, M. F.; Zacharias, R.; Leeper, R. J.; Fletcher, K.; Farrell, M.; Jasion, D.; Kilkenny, J.; Paguio, R.

    2013-04-01

    The neutron spectrum produced by deuterium-tritium (DT) inertial confinement fusion implosions contains a wealth of information about implosion performance including the DT yield, ion-temperature, and areal-density. The Magnetic Recoil Spectrometer (MRS) has been used at both the OMEGA laser facility and the National Ignition Facility (NIF) to measure the absolute neutron spectrum from 3 to 30 MeV at OMEGA and 3 to 36 MeV at the NIF. These measurements have been used to diagnose the performance of cryogenic target implosions to unprecedented accuracy. Interpretation of MRS data requires a detailed understanding of the MRS response and background. This paper describes ab initio characterization of the system involving Monte Carlo simulations of the MRS response in addition to the commission experiments for in situ calibration of the systems on OMEGA and the NIF.

  18. A recoil ion momentum spectrometer for molecular and atomic fragmentation studies.

    PubMed

    Khan, Arnab; Tribedi, Lokesh C; Misra, Deepankar

    2015-04-01

    We report the development and performance studies of a newly built recoil ion momentum spectrometer for the study of atomic and molecular fragmentation dynamics in gas phase upon the impact of charged particles and photons. The present design is a two-stage Wiley-McLaren type spectrometer which satisfies both time and velocity focusing conditions and is capable of measuring singly charged ionic fragments up-to 13 eV in all directions. An electrostatic lens has been introduced in order to achieve velocity imaging. Effects of the lens on time-of-flight as well as on the position have been investigated in detail, both, by simulation and in experiment. We have used 120 keV proton beam on molecular nitrogen gas target. Complete momentum distributions and kinetic energy release distributions have been derived from the measured position and time-of-flight spectra. Along with this, the kinetic energy release spectra of fragmentation of doubly ionized nitrogen molecule upon various projectile impacts are presented.

  19. A recoil ion momentum spectrometer for molecular and atomic fragmentation studies

    SciTech Connect

    Khan, Arnab; Tribedi, Lokesh C.; Misra, Deepankar

    2015-04-15

    We report the development and performance studies of a newly built recoil ion momentum spectrometer for the study of atomic and molecular fragmentation dynamics in gas phase upon the impact of charged particles and photons. The present design is a two-stage Wiley-McLaren type spectrometer which satisfies both time and velocity focusing conditions and is capable of measuring singly charged ionic fragments up-to 13 eV in all directions. An electrostatic lens has been introduced in order to achieve velocity imaging. Effects of the lens on time-of-flight as well as on the position have been investigated in detail, both, by simulation and in experiment. We have used 120 keV proton beam on molecular nitrogen gas target. Complete momentum distributions and kinetic energy release distributions have been derived from the measured position and time-of-flight spectra. Along with this, the kinetic energy release spectra of fragmentation of doubly ionized nitrogen molecule upon various projectile impacts are presented.

  20. Recent Results from the Commissioning of the HRIBF Recoil Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Ginter, T. N.; Hamilton, J. H.; Ramayya, A. V.; Gross, C. J.; Johnson, J. W.; Shapira, D.; Akovali, Y. A.; Brinkman, M. J.; Mas, J.; McConnell, J. W.; Milner, W. T.; James, A. N.

    1997-04-01

    The Recoil Mass Spectrometer (RMS) at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory (Managed by Lockheed Martin Energy Research Corporation for the U.S. Department of Energy.) is designed (Cole, J. D., et al.) al., Nucl. Instrum. Methods B70 (1992), 343. to transmit ions with rigidities of up to K = 100 resulting from fusion-evaporation and other nuclear reactions. Commissioning tests (We would like to acknowledge the work performed by P. F. Mantica, J. J. Das, and R. L. Auble on the installation of the RMS.) have been under way on the RMS and auxiliary detectors at its target position and focal plane. These tests, performed using normal and symmetric kinematic reactions, have shown that the RMS has an A/Q acceptance of ± 5% and an energy acceptance of ± 10%. A mass resolution M/ΔM of 470 was obtained using a ^58Ni beam on a ^60Ni target, with little primary beam observed at the focal plane. Recent results from these tests will be presented.

  1. A stretch/compress scheme for a high temporal resolution detector for the magnetic recoil spectrometer time (MRSt)

    DOE PAGESBeta

    Hilsabeck, T. J.; Frenje, J. A.; Hares, J. D.; Wink, C. W.

    2016-08-02

    Here we present a time-resolved detector concept for the magnetic recoil spectrometer for time-resolved measurements of the NIF neutron spectrum. The measurement is challenging due to the time spreading of the recoil protons (or deuterons) as they transit an energy dispersing magnet system. Ions arrive at the focal plane of the magnetic spectrometer over an interval of tens of nanoseconds. We seek to measure the time-resolved neutron spectrum with 20 ps precision by manipulating an electron signal derived from the ions. A stretch-compress scheme is employed to remove transit time skewing while simultaneously reducing the bandwidth requirements for signal recording.more » Simulation results are presented along with design concepts for structures capable of establishing the required electromagnetic fields.« less

  2. A stretch/compress scheme for a high temporal resolution detector for the magnetic recoil spectrometer time (MRSt)

    NASA Astrophysics Data System (ADS)

    Hilsabeck, T. J.; Frenje, J. A.; Hares, J. D.; Wink, C. W.

    2016-11-01

    A time-resolved detector concept for the magnetic recoil spectrometer for time-resolved measurements of the NIF neutron spectrum is presented. The measurement is challenging due to the time spreading of the recoil protons (or deuterons) as they transit an energy dispersing magnet system. Ions arrive at the focal plane of the magnetic spectrometer over an interval of tens of nanoseconds. We seek to measure the time-resolved neutron spectrum with 20 ps precision by manipulating an electron signal derived from the ions. A stretch-compress scheme is employed to remove transit time skewing while simultaneously reducing the bandwidth requirements for signal recording. Simulation results are presented along with design concepts for structures capable of establishing the required electromagnetic fields.

  3. Upgrading a high-throughput spectrometer for high-frequency (<400 kHz) measurements

    NASA Astrophysics Data System (ADS)

    Nishizawa, T.; Nornberg, M. D.; Den Hartog, D. J.; Craig, D.

    2016-11-01

    The upgraded spectrometer used for charge exchange recombination spectroscopy on the Madison Symmetric Torus resolves emission fluctuations up to 400 kHz. The transimpedance amplifier's cutoff frequency was increased based upon simulations comparing the change in the measured photon counts for time-dynamic signals. We modeled each signal-processing stage of the diagnostic and scanned the filtering frequency to quantify the uncertainty in the photon counting rate. This modeling showed that uncertainties can be calculated based on assuming each amplification stage is a Poisson process and by calibrating the photon counting rate with a DC light source to address additional variation.

  4. First high-statistics and high-resolution recoil-ion data from the WITCH retardation spectrometer

    NASA Astrophysics Data System (ADS)

    Finlay, P.; Breitenfeldt, M.; Porobić, T.; Wursten, E.; Ban, G.; Beck, M.; Couratin, C.; Fabian, X.; Fléchard, X.; Friedag, P.; Glück, F.; Herlert, A.; Knecht, A.; Kozlov, V. Y.; Liénard, E.; Soti, G.; Tandecki, M.; Traykov, E.; Van Gorp, S.; Weinheimer, Ch.; Zákoucký, D.; Severijns, N.

    2016-07-01

    The first high-statistics and high-resolution data set for the integrated recoil-ion energy spectrum following the β^+ decay of 35Ar has been collected with the WITCH retardation spectrometer located at CERN-ISOLDE. Over 25 million recoil-ion events were recorded on a large-area multichannel plate (MCP) detector with a time-stamp precision of 2ns and position resolution of 0.1mm due to the newly upgraded data acquisition based on the LPC Caen FASTER protocol. The number of recoil ions was measured for more than 15 different settings of the retardation potential, complemented by dedicated background and half-life measurements. Previously unidentified systematic effects, including an energy-dependent efficiency of the main MCP and a radiation-induced time-dependent background, have been identified and incorporated into the analysis. However, further understanding and treatment of the radiation-induced background requires additional dedicated measurements and remains the current limiting factor in extracting a beta-neutrino angular correlation coefficient for 35Ar decay using the WITCH spectrometer.

  5. In situ high-frequency UV-Vis spectrometer probes for investigating runoff processes and end member stability.

    NASA Astrophysics Data System (ADS)

    Schwab, Michael; Weiler, Markus; Pfister, Laurent; Klaus, Julian

    2014-05-01

    In recent years, several limitations as to the application of end member mixing analysis with isotope and geochemical tracers have been revealed: unstable end member solutions, inputs varying in space and time, and unrealistic mixing assumptions. In addition, the necessary high-frequency sampling using conventional methods is time and resources consuming, and hence most sampling rates are not suitable for capturing the response times of the majority of observed headwater catchments. However, high-frequency observations are considered fundamental for gaining new insights into hydrological systems. In our study, we have used two portable, in situ, high-frequency UV-Vis spectrometers (spectro::lyser; scan Messtechnik GmbH) to investigate the variability of several signatures in streamflow and end member stability. The spectro::lyser measures TOC, DOC, nitrate and the light absorption spectrum from 220 to 720 nm with 2.5 nm increment. The Weierbach catchment (0.45 km2) in the Attert basin (297 km2) in Luxemburg is a small headwater research catchment (operated by the CRP Gabriel Lippmann), which is completely forested and underlain by schist bedrock. The catchment is equipped with a dense network of hydrological instruments and for this study, the outlet of the Weierbach catchment was equipped with one spectro::lyser, permanently sensing stream water at a 15 minutes time step over several months. Hydrometric and meteorologic data was compared with the high-frequency spectro::lyser time series of TOC, DOC, nitrate and the light absorption spectrum, to get a first insight into the behaviour of the catchment under different environmental conditions. As a preliminary step for a successful end member mixing analysis, the stability of rainfall, soil water, and groundwater was tested with one spectro::lyser, both temporally and spatially. Thereby, we focused on the investigation of changes and patterns of the light absorption spectrum of the different end members and the

  6. Improvements in Fabrication of Elastic Scattering Foils Used to Measure Neutron Yield by the Magnetic Recoil Spectrometer

    DOE PAGESBeta

    Reynolds, H. G.; Schoff, M. E.; Farrell, M. P.; Gatu Johnson, M.; Bionta, R. M.; Frenje, J. A.

    2016-08-01

    The magnetic recoil spectrometer uses a deuterated polyethylene polymer (CD2) foil to measure neutron yield in inertial confinement fusion experiments. Higher neutron yields in recent experiments have resulted in primary signal saturation in the detector CR-39 foils, necessitating the fabrication of thinner CD2 foils than established methods could provide. A novel method of fabricating deuterated polymer foils is described. The resulting foils are thinner, smoother, and more uniform in thickness than the foils produced by previous methods. Here, these new foils have successfully been deployed at the National Ignition Facility, enabling higher neutron yield measurements than previous foils, with nomore » primary signal saturation.« less

  7. The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

    DOE PAGESBeta

    Frenje, J. A.; Hilsabeck, T. J.; Wink, C. W.; Bell, P.; Bionta, R.; Cerjan, C.; Gatu Johnson, M.; Kilkenny, J. D.; Li, C. K.; Séguin, F. H.; et al

    2016-08-02

    The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (Ti), yield (Yn), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate data with amore » time resolution of ~20 ps and energy resolution of ~100 keV for total neutron yields above ~1016. Lastly, at lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ~20 ps.« less

  8. The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

    NASA Astrophysics Data System (ADS)

    Frenje, J. A.; Hilsabeck, T. J.; Wink, C. W.; Bell, P.; Bionta, R.; Cerjan, C.; Gatu Johnson, M.; Kilkenny, J. D.; Li, C. K.; Séguin, F. H.; Petrasso, R. D.

    2016-11-01

    The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (Ti), yield (Yn), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate data with a time resolution of ˜20 ps and energy resolution of ˜100 keV for total neutron yields above ˜1016. At lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ˜20 ps.

  9. A recoil-proton spectrometer based on a p-i-n diode implementing pulse-shape discrimination.

    PubMed

    Agosteo, S; D'Angelo, G; Fazzi, A; Foglio Para, A; Pola, A; Ventura, L; Zotto, P

    2004-01-01

    A recoil-proton spectrometer was created by coupling a p-i-n diode with a polyethylene converter. The maximum detectable energy, imposed by the thickness of the totally depleted layer, is approximately 6 MeV. The minimum detectable energy is limited by the contribution of secondary electrons generated by photons in the detector assembly. This limit is approximately 1.5 MeV at full-depletion voltage and was decreased using pulse-shape discrimination. The diode was set up in the 'reverse-injection' configuration (i.e. with the N+ layer adjacent to the converter). This configuration provides longer collection times for the electron-hole pairs generated by the recoil-protons. The pulse-shape discrimination was based on the zero-crossing time of bipolar signals from a (CR)2-(RC)2 filter. The detector was characterised using monoenergetic neutrons generated in the Van De Graaff CN accelerator at the INFN-Laboratori Nazionali di Legnaro. The energy limit for discrimination proved to be approximately 900 keV. PMID:15353700

  10. Measuring the absolute deuterium-tritium neutron yield using the magnetic recoil spectrometer at OMEGA and the NIF.

    PubMed

    Casey, D T; Frenje, J A; Gatu Johnson, M; Séguin, F H; Li, C K; Petrasso, R D; Glebov, V Yu; Katz, J; Knauer, J P; Meyerhofer, D D; Sangster, T C; Bionta, R M; Bleuel, D L; Döppner, T; Glenzer, S; Hartouni, E; Hatchett, S P; Le Pape, S; Ma, T; MacKinnon, A; McKernan, M A; Moran, M; Moses, E; Park, H-S; Ralph, J; Remington, B A; Smalyuk, V; Yeamans, C B; Kline, J; Kyrala, G; Chandler, G A; Leeper, R J; Ruiz, C L; Cooper, G W; Nelson, A J; Fletcher, K; Kilkenny, J; Farrell, M; Jasion, D; Paguio, R

    2012-10-01

    A magnetic recoil spectrometer (MRS) has been installed and extensively used on OMEGA and the National Ignition Facility (NIF) for measurements of the absolute neutron spectrum from inertial confinement fusion implosions. From the neutron spectrum measured with the MRS, many critical implosion parameters are determined including the primary DT neutron yield, the ion temperature, and the down-scattered neutron yield. As the MRS detection efficiency is determined from first principles, the absolute DT neutron yield is obtained without cross-calibration to other techniques. The MRS primary DT neutron measurements at OMEGA and the NIF are shown to be in excellent agreement with previously established yield diagnostics on OMEGA, and with the newly commissioned nuclear activation diagnostics on the NIF.

  11. Real time high frequency monitoring of water quality in river streams using a UV-visible spectrometer: interest, limits and consequences for monitoring strategies

    NASA Astrophysics Data System (ADS)

    Faucheux, Mikaël; Fovet, Ophélie; Gruau, Gérard; Jaffrézic, Anne; Petitjean, Patrice; Gascuel-Odoux, Chantal; Ruiz, Laurent

    2013-04-01

    Stream water chemistry is highly variable in space and time, therefore high frequency water quality measurement methods are likely to lead to conceptual advances in the hydrological sciences. Sub-daily data on water quality improve the characterization of pollutant sources and pathways during flood events as well as during long-term periods [1]. However, real time, high frequency monitoring devices needs to be properly calibrated and validated in real streams. This study analyses data from in situ monitoring of a stream water quality. During two hydrological years (2010-11, 2011-12), a submersible UV-visible spectrometer (Scan Spectrolyser) was used for surface water quality measurement at the outlet of a headwater catchment located at Kervidy-Naizin, Western France (AgrHys long-term hydrological observatory, http://www.inra.fr/ore_agrhys/). The spectrometer is reagentless and equipped with an auto-cleaning system. It allows real time, in situ and high frequency (20 min) measurements and uses a multiwavelengt spectral (200-750 nm) for simultaneous measurement of nitrate, dissolved organic carbon (DOC) and total suspended solids (TSS). A global calibration based on a PLS (Partial Least Squares) regression is provided by the manufacturer as default configuration of the UV-visible spectrometer. We carried out a local calibration of the spectrometer based on nitrates and DOC concentrations analysed in the laboratory from daily manual sampling and sub-daily automatic sampling of flood events. TSS results are compared with 15 min turbidity records from a continuous turdidimeter (Ponsel). The results show a good correlation between laboratory data and spectrometer data both during basis flows periods and flood events. However, the local calibration gives better results than the global one. Nutrient fluxes estimates based on high and different low frequency time series (daily to monthly) are compared to discuss the implication for environmental monitoring strategies. Such

  12. High-resolution measurements of the DT neutron spectrum using new CD foils in the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Gatu Johnson, M.; Frenje, J. A.; Bionta, R. M.; Casey, D. T.; Eckart, M. J.; Farrell, M. P.; Grim, G. P.; Hartouni, E. P.; Hatarik, R.; Hoppe, M.; Kilkenny, J. D.; Li, C. K.; Petrasso, R. D.; Reynolds, H. G.; Sayre, D. B.; Schoff, M. E.; Séguin, F. H.; Skulina, K.; Yeamans, C. B.

    2016-11-01

    The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility measures the DT neutron spectrum from cryogenically layered inertial confinement fusion implosions. Yield, areal density, apparent ion temperature, and directional fluid flow are inferred from the MRS data. This paper describes recent advances in MRS measurements of the primary peak using new, thinner, reduced-area deuterated plastic (CD) conversion foils. The new foils allow operation of MRS at yields 2 orders of magnitude higher than previously possible, at a resolution down to ˜200 keV FWHM.

  13. High-resolution measurements of the DT neutron spectrum using new CD foils in the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility

    DOE PAGESBeta

    Gatu Johnson, M.; Frenje, J. A.; Bionta, R. M.; Casey, D. T.; Eckart, M. J.; Farrell, M. P.; Grim, G. P.; Hartouni, E. P.; Hatarik, R.; Hoppe, M.; et al

    2016-08-09

    The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility measures the DT neutron spectrum from cryogenically layered inertial confinement fusion implosions. Yield, areal density, apparent ion temperature, and directional fluid flow are inferred from the MRS data. Here, this paper describes recent advances in MRS measurements of the primary peak using new, thinner, reduced-area deuterated plastic (CD) conversion foils. The new foils allow operation of MRS at yields 2 orders of magnitude higher than previously possible, at a resolution down to ~200 keV FWHM.

  14. A high-frequency electron paramagnetic resonance spectrometer for multi-dimensional, multi-frequency, and multi-phase pulsed measurements.

    PubMed

    Cho, F H; Stepanov, V; Takahashi, S

    2014-07-01

    We describe instrumentation for a high-frequency electron paramagnetic resonance (EPR) and pulsed electron-electron double resonance (PELDOR) spectroscopy. The instrumentation is operated in the frequency range of 107-120 GHz and 215-240 GHz and in the magnetic field range of 0-12.1 T. The spectrometer consisting of a high-frequency high-power solid-state source, a quasioptical system, a phase-sensitive detection system, a cryogenic-free superconducting magnet, and a (4)He cryostat enables multi-frequency continuous-wave EPR spectroscopy as well as pulsed EPR measurements with a few hundred nanosecond pulses. Here we discuss the details of the design and the pulsed EPR sensitivity of the instrumentation. We also present performance of the instrumentation in unique experiments including PELDOR spectroscopy to probe correlations in an insulating electronic spin system and application of dynamical decoupling techniques to extend spin coherence of electron spins in an insulating solid-state system. PMID:25085176

  15. A high-frequency electron paramagnetic resonance spectrometer for multi-dimensional, multi-frequency, and multi-phase pulsed measurements

    SciTech Connect

    Cho, F. H.; Stepanov, V.; Takahashi, S.

    2014-07-15

    We describe instrumentation for a high-frequency electron paramagnetic resonance (EPR) and pulsed electron-electron double resonance (PELDOR) spectroscopy. The instrumentation is operated in the frequency range of 107−120 GHz and 215−240 GHz and in the magnetic field range of 0−12.1 T. The spectrometer consisting of a high-frequency high-power solid-state source, a quasioptical system, a phase-sensitive detection system, a cryogenic-free superconducting magnet, and a {sup 4}He cryostat enables multi-frequency continuous-wave EPR spectroscopy as well as pulsed EPR measurements with a few hundred nanosecond pulses. Here we discuss the details of the design and the pulsed EPR sensitivity of the instrumentation. We also present performance of the instrumentation in unique experiments including PELDOR spectroscopy to probe correlations in an insulating electronic spin system and application of dynamical decoupling techniques to extend spin coherence of electron spins in an insulating solid-state system.

  16. Measurements of fuel and ablator ρR in Symmetry-Capsule implosions with the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility

    SciTech Connect

    Gatu Johnson, M. Frenje, J. A.; Li, C. K.; Séguin, F. H.; Petrasso, R. D.; Bionta, R. M.; Casey, D. T.; Caggiano, J. A.; Hatarik, R.; Khater, H. Y.; Sayre, D. B.; Knauer, J. P.; Sangster, T. C.; Herrmann, H. W.; Kilkenny, J. D.

    2014-11-15

    The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility (NIF) measures the neutron spectrum in the energy range of 4–20 MeV. This paper describes MRS measurements of DT-fuel and CH-ablator ρR in DT gas-filled symmetry-capsule implosions at the NIF. DT-fuel ρR's of 80–140 mg/cm{sup 2} and CH-ablator ρR's of 400–680 mg/cm{sup 2} are inferred from MRS data. The measurements were facilitated by an improved correction of neutron-induced background in the low-energy part of the MRS spectrum. This work demonstrates the accurate utilization of the complete MRS-measured neutron spectrum for diagnosing NIF DT implosions.

  17. Measurements of fuel and ablator ρR in Symmetry-Capsule implosions with the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility.

    PubMed

    Gatu Johnson, M; Frenje, J A; Li, C K; Séguin, F H; Petrasso, R D; Bionta, R M; Casey, D T; Caggiano, J A; Hatarik, R; Khater, H Y; Sayre, D B; Knauer, J P; Sangster, T C; Herrmann, H W; Kilkenny, J D

    2014-11-01

    The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility (NIF) measures the neutron spectrum in the energy range of 4-20 MeV. This paper describes MRS measurements of DT-fuel and CH-ablator ρR in DT gas-filled symmetry-capsule implosions at the NIF. DT-fuel ρR's of 80-140 mg/cm(2) and CH-ablator ρR's of 400-680 mg/cm(2) are inferred from MRS data. The measurements were facilitated by an improved correction of neutron-induced background in the low-energy part of the MRS spectrum. This work demonstrates the accurate utilization of the complete MRS-measured neutron spectrum for diagnosing NIF DT implosions. PMID:25430283

  18. The coincidence counting technique for orders of magnitude background reduction in data obtained with the magnetic recoil spectrometer at OMEGA and the NIF.

    PubMed

    Casey, D T; Frenje, J A; Séguin, F H; Li, C K; Rosenberg, M J; Rinderknecht, H; Manuel, M J-E; Gatu Johnson, M; Schaeffer, J C; Frankel, R; Sinenian, N; Childs, R A; Petrasso, R D; Glebov, V Yu; Sangster, T C; Burke, M; Roberts, S

    2011-07-01

    A magnetic recoil spectrometer (MRS) has been built and successfully used at OMEGA for measurements of down-scattered neutrons (DS-n), from which an areal density in both warm-capsule and cryogenic-DT implosions have been inferred. Another MRS is currently being commissioned on the National Ignition Facility (NIF) for diagnosing low-yield tritium-hydrogen-deuterium implosions and high-yield DT implosions. As CR-39 detectors are used in the MRS, the principal sources of background are neutron-induced tracks and intrinsic tracks (defects in the CR-39). The coincidence counting technique was developed to reduce these types of background tracks to the required level for the DS-n measurements at OMEGA and the NIF. Using this technique, it has been demonstrated that the number of background tracks is reduced by a couple of orders of magnitude, which exceeds the requirement for the DS-n measurements at both facilities.

  19. FieldSpec: A field portable mass spectrometer prototype for high frequency measurements of δ (2) H and δ (18) O ratios in water

    NASA Astrophysics Data System (ADS)

    López Días, Veneranda; Quang Hoang, Hung; Martínez-Carreras, Núria; Barnich, François; Wirtz, Tom; Pfister, Laurent; McDonnell, Jeffrey

    2016-04-01

    Hydrological studies relying on stable water isotopes to better understand water sources, flowpaths and transit times are currently limited by the coarse temporal resolution of sampling and analysis protocols. At present, two kinds of lab-based instruments are used : (i) the standard isotope ratio mass spectrometers (IRMS) [1] and (ii) the laser-based instruments [2, 3]. In both cases, samples need to be collected in the field and then transferred to the laboratory for the water isotopic ratio measurements (even further complex sample preparation is required for the IRMS). Hence, past and ongoing research targets the development of field deployable instruments for measuring stable water isotopes at high temporal frequencies. While recent studies have demonstrated that laser-based instruments may be taken to the field [4, 5], their size and power consumption still restrict their use to sites equipped with mains power or generators. Here, we present progress on the development of a field portable mass spectrometer (FieldSpec) for direct high frequency measurements of δ2H and δ18O ratios in water. The FieldSpec instrument is based upon the use of a double focusing magnetic sector mass spectrometer in combination with an electron impact ion source and a membrane dual inlet system. The instrument directly collects liquid water samples in the field, which are then converted into water vapour before being injected into the mass spectrometer for the stable isotope analysis. δ2H and δ18O are derived from the measured mass spectra. All the components are arranged in a vacuum case having a suit case type dimension with portable electronics and battery. Proof-of-concept experiments have been carried out to characterize the instrument. The results show that the FieldSpec instrument has good linearity (R2 = 0.99). The reproducibility of the instrument ranges between 1 and 4 ‰ for δ2H and between 0.1 and 0.4 ‰ for δ18O isotopic ratio measurements. A measurement

  20. A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements.

    PubMed

    Sigaud, L; de Jesus, V L B; Ferreira, Natalia; Montenegro, E C

    2016-08-01

    In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell-to study ionization of atoms and molecules by electron impact-is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed. PMID:27587105

  1. A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements.

    PubMed

    Sigaud, L; de Jesus, V L B; Ferreira, Natalia; Montenegro, E C

    2016-08-01

    In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell-to study ionization of atoms and molecules by electron impact-is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed.

  2. A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements

    NASA Astrophysics Data System (ADS)

    Sigaud, L.; de Jesus, V. L. B.; Ferreira, Natalia; Montenegro, E. C.

    2016-08-01

    In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell—to study ionization of atoms and molecules by electron impact—is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed.

  3. Light response of YAP:Ce and LaBr3:Ce scintillators to 4-30 MeV protons for applications to Telescope Proton Recoil neutron spectrometers

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Cremona, A.; Nocente, M.; Rebai, M.; Rigamonti, D.; Tardocchi, M.; Croci, G.; Ericsson, G.; Fazzi, A.; Hjalmarsson, A.; Mazzocco, M.; Strano, E.; Gorini, G.

    2016-06-01

    The light response of two thin inorganic scintillators based on YAP:Ce and LaBr3:Ce crystals has been measured with protons in the 4-8 MeV energy range at the Uppsala tandem accelerator and in the 8-26 MeV energy range at the Legnaro tandem accelerator. The crystals have been calibrated in situ with 137Cs and 60Co γ-ray sources. The relative light yields of protons with respect to gammas have been measured and are here reported to be (96±2)% and (80±2)% for YAP:Ce and LaBr3:Ce, respectively. The results open up to the development of a Telescope Proton Recoil spectrometer based on either of the two crystals as alternative to a silicon based spectrometer for applications to high neutron fluxes.

  4. High Frequency Design Considerations for the Large Detector Number and Small Form Factor Dual Electron Spectrometer of the Fast Plasma Investigation on NASA's Magnetospheric Multiscale Mission

    NASA Technical Reports Server (NTRS)

    Kujawski, Joseph T.; Gliese, Ulrik B.; Cao, N. T.; Zeuch, M. A.; White, D.; Chornay, D. J; Lobell, J. V.; Avanov, L. A.; Barrie, A. C.; Mariano, A. J.; Tucker, C. J.; Piepgrass, B.; Auletti, C.; Weidner, S.; Jacques, A. D.; Pollock, C. J.

    2015-01-01

    Each half of the Dual Electron Spectrometer (DES) of the Fast Plasma Investigation (FPI) on NASA's Magnetospheric MultiScale (MMS) mission utilizes a microchannel plate Chevron stack feeding 16 separate detection channels each with a dedicated anode and amplifier/discriminator chip. The desire to detect events on a single channel with a temporal spacing of 100 ns and a fixed dead-time drove our decision to use an amplifier/discriminator with a very fast (GHz class) front end. Since the inherent frequency response of each pulse in the output of the DES microchannel plate system also has frequency components above a GHz, this produced a number of design constraints not normally expected in electronic systems operating at peak speeds of 10 MHz. Additional constraints are imposed by the geometry of the instrument requiring all 16 channels along with each anode and amplifier/discriminator to be packaged in a relatively small space. We developed an electrical model for board level interactions between the detector channels to allow us to design a board topology which gave us the best detection sensitivity and lowest channel to channel crosstalk. The amplifier/discriminator output was designed to prevent the outputs from one channel from producing triggers on the inputs of other channels. A number of Radio Frequency design techniques were then applied to prevent signals from other subsystems (e.g. the high voltage power supply, command and data handling board, and Ultraviolet stimulation for the MCP) from generating false events. These techniques enabled us to operate the board at its highest sensitivity when operated in isolation and at very high sensitivity when placed into the overall system.

  5. Forward fitting of experimental data from a NE213 neutron detector installed with the magnetic proton recoil upgraded spectrometer at JET

    SciTech Connect

    Binda, F. Ericsson, G.; Eriksson, J.; Hellesen, C.; Conroy, S.; Sundén, E. Andersson; Collaboration: JET-EFDA Team

    2014-11-15

    In this paper, we present the results obtained from the data analysis of neutron spectra measured with a NE213 liquid scintillator at JET. We calculated the neutron response matrix of the instrument combining MCNPX simulations, a generic proton light output function measured with another detector and the fit of data from ohmic pulses. For the analysis, we selected a set of pulses with neutral beam injection heating (NBI) only and we applied a forward fitting procedure of modeled spectral components to extract the fraction of thermal neutron emission. The results showed the same trend of the ones obtained with the dedicated spectrometer TOFOR, even though the values from the NE213 analysis were systematically higher. This discrepancy is probably due to the different lines of sight of the two spectrometers (tangential for the NE213, vertical for TOFOR). The uncertainties on the thermal fraction estimates were from 4 to 7 times higher than the ones from the TOFOR analysis.

  6. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique. PMID:25636803

  7. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  8. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  9. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique.

  10. A magnetic recoil spectrometer (MRS) for ρR_fuel and Ti measurements of warm, fizzle and ignited implosions at OMEGA and the NIF

    NASA Astrophysics Data System (ADS)

    Frenje, J. A.; Petrasso, R. D.; Li, C. K.; Séguin, F. H.; Deciantis, J. L.; Kurebayashi, S.; Rygg, J. R.; Glebov, V. Yu.; Meyerhofer, D. D.; Sangster, T. C.; Soures, J. M.; Hatchett, S. P.; Hann, S. W.; Schmid, G. J.; Landen, O. L.; Izumi, N.

    2003-10-01

    A method for determining ρR_fuel of cryogenic deuterium-tritium plasmas involves measurement of the energy spectrum of elastically-scattered, primary neutrons. A spectrometer has been designed for doing this at OMEGA and the NIF, using scattered neutrons in the energy range 7-10 MeV to determine ρR_fuel and primary neutrons to measure T_i. The instrument utilizes a magnet and a conversion foil for production of charged particles. A large dynamic range (>10^6) will allow operation at yields as low as 10^12. This will allow ρR_fuel and Ti measurements of warm and cryogenic DT targets at OMEGA, and fizzle and ignited cryogenic DT targets at the NIF. This work was supported in part by the US DoE (contract W-7405-ENG-48 with LLNL, grant DE-FG03-99DP00300 and Cooperative Agreement DE-FC03-92SF19460), LLE (subcontract P0410025G), and LLNL (subcontract B313975).

  11. High-frequency ECG

    NASA Technical Reports Server (NTRS)

    Tragardh, Elin; Schlegel, Todd T.

    2006-01-01

    The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal. With high-resolution technology, it is possible to record and analyze these higher frequencies. The highest amplitudes of the high-frequency components are found within the QRS complex. In past years, the term "high frequency", "high fidelity", and "wideband electrocardiography" have been used by several investigators to refer to the process of recording ECGs with an extended bandwidth of up to 1000 Hz. Several investigators have tried to analyze HF-QRS with the hope that additional features seen in the QRS complex would provide information enhancing the diagnostic value of the ECG. The development of computerized ECG-recording devices that made it possible to record ECG signals with high resolution in both time and amplitude, as well as better possibilities to store and process the signals digitally, offered new methods for analysis. Different techniques to extract the HF-QRS have been described. Several bandwidths and filter types have been applied for the extraction as well as different signal-averaging techniques for noise reduction. There is no standard method for acquiring and quantifying HF-QRS. The physiological mechanisms underlying HF-QRS are still not fully understood. One theory is that HF-QRS are related to the conduction velocity and the fragmentation of the depolarization wave in the myocardium. In a three-dimensional model of the ventricles with a fractal conduction system it was shown that high numbers of splitting branches are associated with HF-QRS. In this experiment, it was also shown that the changes seen in HF-QRS in patients with myocardial ischemia might be due to the slowing of the conduction velocity in the region of ischemia. This mechanism has been tested by Watanabe et al by infusing sodium channel blockers into the left anterior descending artery in dogs. In their study, 60 unipolar ECGs were recorded from the entire

  12. The SAGE spectrometer

    NASA Astrophysics Data System (ADS)

    Pakarinen, J.; Papadakis, P.; Sorri, J.; Herzberg, R.-D.; Greenlees, P. T.; Butler, P. A.; Coleman-Smith, P. J.; Cox, D. M.; Cresswell, J. R.; Jones, P.; Julin, R.; Konki, J.; Lazarus, I. H.; Letts, S. C.; Mistry, A.; Page, R. D.; Parr, E.; Pucknell, V. F. E.; Rahkila, P.; Sampson, J.; Sandzelius, M.; Seddon, D. A.; Simpson, J.; Thornhill, J.; Wells, D.

    2014-03-01

    The SAGE spectrometer has been constructed for in-beam nuclear structure studies. SAGE combines a Ge-detector array and an electron spectrometer for detection of -rays and internal conversion electrons, respectively, and allows simultaneous observation of both electrons and -rays emitted from excited nuclei. SAGE is set up in the Accelerator Laboratory of the University of Jyväskylä and works in conjunction with the RITU gas-filled recoil separator and the GREAT focal-plane spectrometer allowing the use of the recoil-decay tagging method.

  13. FAST NEUTRON SPECTROMETER

    DOEpatents

    Davis, F.J.; Hurst, G.S.; Reinhardt, P.W.

    1959-08-18

    An improved proton recoil spectrometer for determining the energy spectrum of a fast neutron beam is described. Instead of discriminating against and thereby"throwing away" the many recoil protons other than those traveling parallel to the neutron beam axis as do conventional spectrometers, this device utilizes protons scattered over a very wide solid angle. An ovoidal gas-filled recoil chamber is coated on the inside with a scintillator. The ovoidal shape of the sensitive portion of the wall defining the chamber conforms to the envelope of the range of the proton recoils from the radiator disposed within the chamber. A photomultiplier monitors the output of the scintillator, and a counter counts the pulses caused by protons of energy just sufficient to reach the scintillator.

  14. Elastic recoil detection

    NASA Astrophysics Data System (ADS)

    Bik, W. M. A.; Habraken, F. H. P. M.

    1993-07-01

    In elastic recoil detection (ERD) one determines the yield and energy of particles ejected out of the surface region of samples under MeV ion bombardment. By application of this surface and thin film analysis technique one can obtain quantitative information concerning the depth distribution of light elements in a sample to be analysed. The quantitativity and the depth resolving power are based on knowledge of the recoil cross section and the stopping power of high-energy ions in matter. This paper reviews the fundamentals of this technique and the various experimental methods for recoil identification. Furthermore, important features for material analysis, such as detection limits, depth resolution and elemental range are discussed. Some emphasis is put on the conversion of the spectral contribution of the elements to atomic concentrations in the films for several representative cases. Throughout the review numerous examples are given to illustrate the features of ERD and to demonstrate empirically the accuracy of the quantification method.

  15. High acceptance recoil polarimeter

    SciTech Connect

    The HARP Collaboration

    1992-12-05

    In order to detect neutrons and protons in the 50 to 600 MeV energy range and measure their polarization, an efficient, low-noise, self-calibrating device is being designed. This detector, known as the High Acceptance Recoil Polarimeter (HARP), is based on the recoil principle of proton detection from np[r arrow]n[prime]p[prime] or pp[r arrow]p[prime]p[prime] scattering (detected particles are underlined) which intrinsically yields polarization information on the incoming particle. HARP will be commissioned to carry out experiments in 1994.

  16. High frequency integrated MOS filters

    NASA Technical Reports Server (NTRS)

    Peterson, C.

    1990-01-01

    Several techniques exist for implementing integrated MOS filters. These techniques fit into the general categories of sampled and tuned continuous-time filters. Advantages and limitations of each approach are discussed. This paper focuses primarily on the high frequency capabilities of MOS integrated filters.

  17. Interpreting Recoil for Undergraduate Students

    ERIC Educational Resources Information Center

    Elsayed, Tarek A.

    2012-01-01

    The phenomenon of recoil is usually explained to students in the context of Newton's third law. Typically, when a projectile is fired, the recoil of the launch mechanism is interpreted as a reaction to the ejection of the smaller projectile. The same phenomenon is also interpreted in the context of the conservation of linear momentum, which is…

  18. Interpreting Recoil for Undergraduate Students

    NASA Astrophysics Data System (ADS)

    Elsayed, Tarek A.

    2012-04-01

    The phenomenon of recoil is usually explained to students in the context of Newton's third law. Typically, when a projectile is fired, the recoil of the launch mechanism is interpreted as a reaction to the ejection of the smaller projectile. The same phenomenon is also interpreted in the context of the conservation of linear momentum, which is closely related to Newton's third law. Since the actual microscopic causes of recoil differ from one problem to another, some students (and teachers) may not be satisfied with understanding recoil through the principles of conservation of linear momentum and Newton's third law. For these students, the origin of the recoil motion should be presented in more depth.

  19. High frequency power distribution system

    NASA Technical Reports Server (NTRS)

    Patel, Mikund R.

    1986-01-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  20. Special Aspects in Designing High - Frequency Betatron

    NASA Astrophysics Data System (ADS)

    Filimonov, A. A.; Kasyanov, S. V.; Kasyanov, V. A.

    2016-01-01

    The article is devoted to designing the high - frequency betatron. In high - frequency betatron most important problem is overheating of the elements of the body radiator unit. In an article some directions of solving this problem are shown.

  1. High frequency-heated air turbojet

    NASA Technical Reports Server (NTRS)

    Miron, J. H. D.

    1986-01-01

    A description is given of a method to heat air coming from a turbojet compressor to a temperature necessary to produce required expansion without requiring fuel. This is done by high frequency heating, which heats the walls corresponding to the combustion chamber in existing jets, by mounting high frequency coils in them. The current transformer and high frequency generator to be used are discussed.

  2. High Frequency Chandler Wobble Excitation

    NASA Astrophysics Data System (ADS)

    Seitz, F.; Stuck, J.; Thomas, M.

    2003-04-01

    and OMCT forcing fields give no hint for increased excitation power in the Chandler band. Thus it is assumed, that continuous high frequency excitation due to stochastic weather phenomena is responsible for the perpetuation of the Chandler wobble.

  3. 75 FR 81284 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Draft...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-27

    ... SECURITY Coast Guard Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology... of High Frequency (HF) and Ultra High Frequency (UHF) Sound Navigation and Ranging (SONAR) Technology... in the January 17, 2008, issue of the Federal Register (73 FR 3316). Background and Purpose...

  4. Imaging Observations of a Very High Frequency Type II Burst

    NASA Astrophysics Data System (ADS)

    White, S. M.; Mercier, C.; Bradley, R.; Bastian, T.; Kerdraon, A.; Pick, M.

    2006-05-01

    A remarkable Type II burst was detected by the high-frequency system of the Green Bank Solar Radio Burst Spectrometer on 2005 November 14. The harmonic branch of the Type II extended up to 800 MHz, making it one of the highest frequency Type II bursts ever detected, but it failed to propagate to heights corresponding to frequencies below 100 MHz. At such high frequencies, it implies the formation of a shock relatively low in the corona. No coronal mass ejection was evident in the LASCO data for this east limb event. It is one of the few Type II bursts to be observable at every frequency of observation of the Nancay Radio Heliograph (164-432 MHz). Here we present analysis of images of the event, including simultaneous imaging of the fundamental and harmonic branches.

  5. Lightning protection devices for high frequencies equipments

    SciTech Connect

    Pierre, J.

    1983-01-01

    Contents: Mechanism of a Lightning Stroke from Antenna to Ground; Principles of Protection Devices for Feeders; Electrical Characteristics of H.F. Protection Devices; Calculation of H.F. Protection Devices; Catalogue Devices for High Frequency Protection; Some Measurement Results for Tees; Measurement Results for Decoupling Line Devices; Installation of High Frequency Devices.

  6. Force optimized recoil control system

    NASA Astrophysics Data System (ADS)

    Townsend, P. E.; Radkiewicz, R. J.; Gartner, R. F.

    1982-05-01

    Reduction of the recoil force of high rate of fire automatic guns was proven effective. This system will allow consideration of more powerful guns for use in both helicopter and armored personnel carrier applications. By substituting the large shock loads of firing guns with a nearly constant force, both vibration and fatigue problems that prevent mounting of powerful automatic guns is eliminated.

  7. Recoil Separators for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Blackmon, J. C.

    2004-10-01

    Hydrogen and helium capture reactions are important in many astrophysical environments. Measurements in inverse kinematics using recoil separators have demonstrated a particularly sensitive technique for studying low-yield capture reactions.(M. S. Smith, C. E. Rolfs, and C. A. Barnes, Nucl. Instrum. Meth. Phys. Res. A306) (1991) 233. This approach allows a low background rate to be achieved with a high detection efficiency (about 50%) for the particles of interest using a device with only modest acceptance. Recoil separators using a variety of ion-optic configurations have been installed at numerous accelerator facilities in the past decade and have been used to measure, for example, alpha capture reactions using stable beams(D. Rogalla et al.), Eur. Phys. J. 6 (1999) 471. and proton capture reactions using radioactive ion beams.(S. Bishop et al.), Phys. Rev. Lett. 90 (2003) 162501. Measurements in inverse kinematics are the only viable means for studying reactions on short-lived nuclei that are crucial for understanding stellar explosions, and a recoil separator optimized for the measurement of capture reactions with radioactive ion beams figures prominently into the design of the low energy experimental area at the Rare Isotope Accelerator (RIA). The operational requirements for such a device will be outlined, and recoil separator designs and characteristics will be presented.

  8. A gas ionisation detector in the axial (Bragg) geometry used for the time-of-flight elastic recoil detection analysis.

    PubMed

    Siketić, Zdravko; Skukan, Natko; Bogdanović Radović, Iva

    2015-08-01

    In this paper, time-of-flight elastic recoil detection analysis spectrometer with a newly constructed gas ionization detector for energy detection is presented. The detector is designed in the axial (Bragg) geometry with a 3 × 3 array of 50 nm thick Si3N4 membranes as an entrance window. 40 mbar isobutane gas was sufficient to stop a 30 MeV primary iodine beam as well as all recoils in the detector volume. Spectrometer and detector performances were determined showing significant improvement in the mass and energy resolution, respectively, comparing to the spectrometer with a standard silicon particle detector for an energy measurement.

  9. A gas ionisation detector in the axial (Bragg) geometry used for the time-of-flight elastic recoil detection analysis

    SciTech Connect

    Siketić, Zdravko; Skukan, Natko; Bogdanović Radović, Iva

    2015-08-15

    In this paper, time-of-flight elastic recoil detection analysis spectrometer with a newly constructed gas ionization detector for energy detection is presented. The detector is designed in the axial (Bragg) geometry with a 3 × 3 array of 50 nm thick Si{sub 3}N{sub 4} membranes as an entrance window. 40 mbar isobutane gas was sufficient to stop a 30 MeV primary iodine beam as well as all recoils in the detector volume. Spectrometer and detector performances were determined showing significant improvement in the mass and energy resolution, respectively, comparing to the spectrometer with a standard silicon particle detector for an energy measurement.

  10. A gas ionisation detector in the axial (Bragg) geometry used for the time-of-flight elastic recoil detection analysis

    NASA Astrophysics Data System (ADS)

    Siketić, Zdravko; Skukan, Natko; Bogdanović Radović, Iva

    2015-08-01

    In this paper, time-of-flight elastic recoil detection analysis spectrometer with a newly constructed gas ionization detector for energy detection is presented. The detector is designed in the axial (Bragg) geometry with a 3 × 3 array of 50 nm thick Si3N4 membranes as an entrance window. 40 mbar isobutane gas was sufficient to stop a 30 MeV primary iodine beam as well as all recoils in the detector volume. Spectrometer and detector performances were determined showing significant improvement in the mass and energy resolution, respectively, comparing to the spectrometer with a standard silicon particle detector for an energy measurement.

  11. 78 FR 70567 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-26

    ... SECURITY Coast Guard Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology...) and Ultra High Frequency (UHF) Sound Navigation and Ranging (SONAR) Technology and Finding of No... less than two weeks; however, for environmental disasters such as the Deepwater Horizon oil...

  12. Propagation of high frequencies in Scandinavia

    SciTech Connect

    Bame, D.

    1989-04-01

    To determine if seismic signals at frequencies up to 50 Hz are useful for detecting events and discriminating between earthquakes and explosions, approximately 180 events from the three-component high-frequency seismic element (HFSE) installed at the center of the Norwegian Regional Seismic Array (NRSA) have been analyzed. The attenuation of high-frequency signals in Scandinavia varies with distance, azimuth, magnitude, and source effects. Most of the events were detected with HFSE, although detections were better on the NRSA where signal processing techniques were used. Based on a preliminary analysis, high-frequency data do not appear to be a useful discriminant in Scandinavia. 21 refs., 29 figs., 3 tabs.

  13. A detector for filtering γ-ray spectra from weak fusion evaporation reactions out of strong background and for Doppler correction: The recoil filter detector, RFD

    NASA Astrophysics Data System (ADS)

    Męczyński, W.; Bednarczyk, P.; Grębosz, J.; Heese, J.; Janicki, M.; Maier, K. H.; Merdinger, J. C.; Spohr, K.; Ziębliński, M.; Styczeń, J.

    2007-10-01

    A detector has been designed and built to assist in-beam γ-ray spectroscopy with fusion-evaporation reactions. It measures with high efficiency the evaporation residues that recoil out of a thin target into the angular interval from 1.8° to 9.0° at an adjustable distance of 1000-1350 mm from a target, in coincidence with γ-rays detected in a Ge-detector array. This permits filtering of such γ-rays out of a much stronger background of other reaction products and scattered beam. Evaporation residues are identified by their time-of-flight and the pulse height using a pulsed beam. The velocity vector of the γ-emitting recoil is also measured in the event-by-event mode, facilitating to correct the registered γ-ray energy for the Doppler shift, with the resulting significant improvement of the energy resolution. The heavy-ion detection scheme uses emission of secondary electrons caused by the recoiling ions when hitting a thin foil. These electrons are then electrostatically accelerated and focused onto a small scintillator that measures the summed electron energy, which is proportional to the number of electrons. The detector is able to operate at high frequency of the order of 1 MHz and detect very heavy nuclei with as low kinetic energy as 5 MeV. The paper describes the properties of the detector and gives examples of measurements with the OSIRIS, GAREL+ and EUROBALL IV γ-ray spectrometers. The usefulness of the technique for spectroscopic investigations of nuclei with a continuous beam is also discussed.

  14. Neural coding of high-frequency tones

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1976-01-01

    Available evidence was presented indicating that neural discharges in the auditory nerve display characteristic periodicities in response to any tonal stimulus including high-frequency stimuli, and that this periodicity corresponds to the subjective pitch.

  15. Overview of the Advanced High Frequency Branch

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    2015-01-01

    This presentation provides an overview of the competencies, selected areas of research and technology development activities, and current external collaborative efforts of the NASA Glenn Research Center's Advanced High Frequency Branch.

  16. High power, high frequency component test facility

    NASA Technical Reports Server (NTRS)

    Roth, Mary Ellen; Krawczonek, Walter

    1990-01-01

    The NASA Lewis Research Center has available a high frequency, high power laboratory facility for testing various components of aerospace and/or terrestrial power systems. This facility is described here. All of its capabilities and potential applications are detailed.

  17. Real-time, high frequency QRS electrocardiograph

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

    2006-01-01

    Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as RAZs. RAZs are displayed as go, no-go signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

  18. The recoil proton polarization in. pi. p elastic scattering

    SciTech Connect

    Seftor, C.J.

    1988-09-01

    The polarization of the recoil proton for ..pi../sup +/p and ..pi../sup -/p elastic scattering has been measured for various angles at 547 MeV/c and 625 MeV/c by a collaboration involving The George Washington University; the University of California, Los Angeles; and Abilene Christian University. The experiment was performed at the P/sup 3/ East experimental area of the Los Alamos Meson Physics Facility. Beam intensities varied from 0.4 to 1.0 x 10/sup 7/ ..pi../sup -/'s/sec and from 3.0 to 10.0 x 10/sup 7/ ..pi../sup +/'s/sec. The beam spot size at the target was 1 cm in the horizontal direction by 2.5 cm in the vertical direction. A liquid-hydrogen target was used in a flask 5.7 cm in diameter and 10 cm high. The scattered pion and recoil proton were detected in coincidence using the Large Acceptance Spectrometer (LAS) to detect and momentum analyze the pions and the JANUS recoil proton polarimeter to detect and measure the polarization of the protons. Results from this experiment are compared with previous measurements of the polarization, with analyzing power data previously taken by this group, and to partial-wave analysis predictions. 12 refs., 53 figs., 18 tabs.

  19. Metrology For High-Frequency Nanoelectronics

    SciTech Connect

    Wallis, T. Mitch; Imtiaz, Atif; Nembach, Hans T.; Rice, Paul; Kabos, Pavel

    2007-09-26

    Two metrological tools for high-frequency measurements of nanoscale systems are described: (i) two/N-port analysis of nanoscale devices as well as (ii) near-field scanning microwave microscopy (NSMM) for materials characterization. Calibrated two/N-port measurements were made on multiwalled carbon nanotubes (MWNT) welded to a coplanar waveguide. Significant changes in the extracted high-frequency electrical response of the welded MWNT were measured when the contacts to the MWNT were modified. Additionally, NSMM was used to characterize films of nanotube soot deposited on copper and sapphire substrates. The material properties of the films showed a strong dependence on the substrate material.

  20. High frequency III–V nanowire MOSFETs

    NASA Astrophysics Data System (ADS)

    Lind, Erik

    2016-09-01

    III–V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  1. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

    For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

  2. Transponder System for High-Frequency Ranging

    NASA Technical Reports Server (NTRS)

    Lichtenberg, C. L.; Shores, P. W.; Kobayashi, H. S.

    1986-01-01

    Transponder system uses phase difference between transmitted and reflected high-frequency radio waves to measure distance to target. To suppress spurious measurements of reflections from objects near target at transmitted frequency and its harmonics, transponder at target generates return signal at half transmitted frequency. System useful in such applications as surveying, docking of ships, and short-range navigation.

  3. High frequency pressure oscillator for microcryocoolers

    NASA Astrophysics Data System (ADS)

    Vanapalli, S.; ter Brake, H. J. M.; Jansen, H. V.; Zhao, Y.; Holland, H. J.; Burger, J. F.; Elwenspoek, M. C.

    2008-04-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80K, delivering a cooling power of 10mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5MPa and compression volume of about 22.6mm3 when operating the actuator with a peak-to-peak sinusoidal voltage of 100V at a frequency of 1kHz. The electrical power input was 2.73W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

  4. High frequency pressure oscillator for microcryocoolers.

    PubMed

    Vanapalli, S; ter Brake, H J M; Jansen, H V; Zhao, Y; Holland, H J; Burger, J F; Elwenspoek, M C

    2008-04-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80 K, delivering a cooling power of 10 mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5 MPa and compression volume of about 22.6 mm(3) when operating the actuator with a peak-to-peak sinusoidal voltage of 100 V at a frequency of 1 kHz. The electrical power input was 2.73 W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

  5. High frequency III-V nanowire MOSFETs

    NASA Astrophysics Data System (ADS)

    Lind, Erik

    2016-09-01

    III-V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  6. Navy Applications of High-Frequency Acoustics

    NASA Astrophysics Data System (ADS)

    Cox, Henry

    2004-11-01

    Although the emphasis in underwater acoustics for the last few decades has been in low-frequency acoustics, motivated by long range detection of submarines, there has been a continuing use of high-frequency acoustics in traditional specialized applications such as bottom mapping, mine hunting, torpedo homing and under ice navigation. The attractive characteristics of high-frequency sonar, high spatial resolution, wide bandwidth, small size and relatively low cost must be balanced against the severe range limitation imposed by attenuation that increases approximately as frequency-squared. Many commercial applications of acoustics are ideally served by high-frequency active systems. The small size and low cost, coupled with the revolution in small powerful signal processing hardware has led to the consideration of more sophisticated systems. Driven by commercial applications, there are currently available several commercial-off-the-shelf products including acoustic modems for underwater communication, multi-beam fathometers, side scan sonars for bottom mapping, and even synthetic aperture side scan sonar. Much of the work in high frequency sonar today continues to be focused on specialized applications in which the application is emphasized over the underlying acoustics. Today's vision for the Navy of the future involves Autonomous Undersea Vehicles (AUVs) and off-board ASW sensors. High-frequency acoustics will play a central role in the fulfillment of this vision as a means of communication and as a sensor. The acoustic communication problems for moving AUVs and deep sensors are discussed. Explicit relationships are derived between the communication theoretic description of channel parameters in terms of time and Doppler spreads and ocean acoustic parameters, group velocities, phase velocities and horizontal wavenumbers. Finally the application of synthetic aperture sonar to the mine hunting problems is described.

  7. A recoil separator for nuclear astrophysics SECAR

    NASA Astrophysics Data System (ADS)

    Berg, G. P. A.; Bardayan, D. W.; Blackmon, J. C.; Chipps, K. A.; Couder, M.; Greife, U.; Hager, U.; Montes, F.; Rehm, K. E.; Schatz, H.; Smith, M. S.; Wiescher, M.; Wrede, C.; Zeller, A.

    2016-06-01

    A recoil separator SECAR has been designed to study radiative capture reactions relevant for the astrophysical rp-process in inverse kinematics for the Facility for Rare Isotope Beams (FRIB). We describe the design, layout, and ion optics of the recoil separator and present the status of the project.

  8. High-current, high-frequency capacitors

    NASA Technical Reports Server (NTRS)

    Renz, D. D.

    1983-01-01

    The NASA Lewis high-current, high-frequency capacitor development program was conducted under a contract with Maxwell Laboratories, Inc., San Diego, California. The program was started to develop power components for space power systems. One of the components lacking was a high-power, high-frequency capacitor. Some of the technology developed in this program may be directly usable in an all-electric airplane. The materials used in the capacitor included the following: the film is polypropylene, the impregnant is monoisopropyl biphenyl, the conductive epoxy is Emerson and Cuming Stycast 2850 KT, the foil is aluminum, the case is stainless steel (304), and the electrode is a modified copper-ceramic.

  9. Apparatus for measuring high frequency currents

    NASA Technical Reports Server (NTRS)

    Hagmann, Mark J. (Inventor); Sutton, John F. (Inventor)

    2003-01-01

    An apparatus for measuring high frequency currents includes a non-ferrous core current probe that is coupled to a wide-band transimpedance amplifier. The current probe has a secondary winding with a winding resistance that is substantially smaller than the reactance of the winding. The sensitivity of the current probe is substantially flat over a wide band of frequencies. The apparatus is particularly useful for measuring exposure of humans to radio frequency currents.

  10. Radome structures for high frequency applications

    NASA Astrophysics Data System (ADS)

    Hager, W.

    The optimization of radome structures for high-frequency applications is examined for the cases of thin-walled radomes, thick-walled radomes, sandwich radomes, and multilayer radomes. Examples of applications are briefly described, including radomes in an ECM-pod of a Tornado aircraft, a radome for a mobile two-dimensional radar installation, and a radome for a millimeter wave search radar.

  11. Ionospheric modifications in high frequency heating experiments

    SciTech Connect

    Kuo, Spencer P.

    2015-01-15

    Featured observations in high-frequency (HF) heating experiments conducted at Arecibo, EISCAT, and high frequency active auroral research program are discussed. These phenomena appearing in the F region of the ionosphere include high-frequency heater enhanced plasma lines, airglow enhancement, energetic electron flux, artificial ionization layers, artificial spread-F, ionization enhancement, artificial cusp, wideband absorption, short-scale (meters) density irregularities, and stimulated electromagnetic emissions, which were observed when the O-mode HF heater waves with frequencies below foF2 were applied. The implication and associated physical mechanism of each observation are discussed and explained. It is shown that these phenomena caused by the HF heating are all ascribed directly or indirectly to the excitation of parametric instabilities which instigate anomalous heating. Formulation and analysis of parametric instabilities are presented. The results show that oscillating two stream instability and parametric decay instability can be excited by the O-mode HF heater waves, transmitted from all three heating facilities, in the regions near the HF reflection height and near the upper hybrid resonance layer. The excited Langmuir waves, upper hybrid waves, ion acoustic waves, lower hybrid waves, and field-aligned density irregularities set off subsequent wave-wave and wave-electron interactions, giving rise to the observed phenomena.

  12. Extremely high frequency RF effects on electronics.

    SciTech Connect

    Loubriel, Guillermo Manuel; Vigliano, David; Coleman, Phillip Dale; Williams, Jeffery Thomas; Wouters, Gregg A.; Bacon, Larry Donald; Mar, Alan

    2012-01-01

    The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of effects as frequency increases into the millimeter-wave regime. Our purpose was to answer the questions, 'What are the tradeoffs between coupling, transmission losses, and device responses as frequency increases?', and, 'How high in frequency do effects on electronic systems continue to occur?' Using full wave electromagnetics codes and a transmission-line/circuit code, we investigated how extremely high-frequency RF propagates on wires and printed circuit board traces. We investigated both field-to-wire coupling and direct illumination of printed circuit boards to determine the significant mechanisms for inducing currents at device terminals. We measured coupling to wires and attenuation along wires for comparison to the simulations, looking at plane-wave coupling as it launches modes onto single and multiconductor structures. We simulated the response of discrete and integrated circuit semiconductor devices to those high-frequency currents and voltages, using SGFramework, the open-source General-purpose Semiconductor Simulator (gss), and Sandia's Charon semiconductor device physics codes. This report documents our findings.

  13. 1987 calibration of the TFTR neutron spectrometers

    SciTech Connect

    Barnes, C.W.; Strachan, J.D.; Princeton Univ., NJ . Plasma Physics Lab.)

    1989-12-01

    The {sup 3}He neutron spectrometer used for measuring ion temperatures and the NE213 proton recoil spectrometer used for triton burnup measurements were absolutely calibrated with DT and DD neutron generators placed inside the TFTR vacuum vessel. The details of the detector response and calibration are presented. Comparisons are made to the neutron source strengths measured from other calibrated systems. 23 refs., 19 figs., 6 tabs.

  14. Gas powered fluid gun with recoil mitigation

    DOEpatents

    Grubelich, Mark C; Yonas, Gerold

    2013-11-12

    A gas powered fluid gun for propelling a stream or slug of a fluid at high velocity toward a target. Recoil mitigation is provided that reduces or eliminates the associated recoil forces, with minimal or no backwash. By launching a quantity of water in the opposite direction, net momentum forces are reduced or eliminated. Examples of recoil mitigation devices include a cone for making a conical fluid sheet, a device forming multiple impinging streams of fluid, a cavitating venturi, one or more spinning vanes, or an annular tangential entry/exit.

  15. Gas powered fluid gun with recoil mitigation

    DOEpatents

    Grubelich, Mark C.; Yonas, Gerold

    2016-03-01

    A gas powered fluid gun for propelling a stream or slug of a fluid at high velocity toward a target. Recoil mitigation is provided that reduces or eliminates the associated recoil forces, with minimal or no backwash. By launching a quantity of water in the opposite direction, net momentum forces are reduced or eliminated. Examples of recoil mitigation devices include a cone for making a conical fluid sheet, a device forming multiple impinging streams of fluid, a cavitating venturi, one or more spinning vanes, or an annular tangential entry/exit.

  16. Photon Recoil Momentum in Dispersive Media

    SciTech Connect

    Campbell, Gretchen K.; Leanhardt, Aaron E.; Mun, Jongchul; Boyd, Micah; Streed, Erik W.; Ketterle, Wolfgang; Pritchard, David E.

    2005-05-06

    A systematic shift of the photon recoil momentum due to the index of refraction of a dilute gas of atoms has been observed. The recoil frequency was determined with a two-pulse light grating interferometer using near-resonant laser light. The results show that the recoil momentum of atoms caused by the absorption of a photon is n({Dirac_h}/2{pi})k, where n is the index of refraction of the gas and k is the vacuum wave vector of the photon. This systematic effect must be accounted for in high-precision atom interferometry with light gratings.

  17. High-frequency Rayleigh-wave method

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

    2009-01-01

    High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  18. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-10-01

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  19. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-12-31

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  20. High frequency inductive lamp and power oscillator

    DOEpatents

    MacLennan, Donald A.; Turner, Brian P.; Dolan, James T.; Kirkpatrick, Douglas A.; Leng, Yongzhang

    2000-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.

  1. High frequency inductive lamp and power oscillator

    DOEpatents

    MacLennan, Donald A.; Dymond, Jr., Lauren E.; Gitsevich, Aleksandr; Grimm, William G.; Kipling, Kent; Kirkpatrick, Douglas A.; Ola, Samuel A.; Simpson, James E.; Trimble, William C.; Tsai, Peter; Turner, Brian P.

    2001-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and I or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to adjust the driving frequency of the oscillator.

  2. High Frequency Plasma Generators for Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Divergilio, W. F.; Goede, H.; Fosnight, V. V.

    1981-01-01

    The results of a one year program to experimentally adapt two new types of high frequency plasma generators to Argon ion thrusters and to analytically study a third high frequency source concept are presented. Conventional 30 cm two grid ion extraction was utilized or proposed for all three sources. The two plasma generating methods selected for experimental study were a radio frequency induction (RFI) source, operating at about 1 MHz, and an electron cyclotron heated (ECH) plasma source operating at about 5 GHz. Both sources utilize multi-linecusp permanent magnet configurations for plasma confinement. The plasma characteristics, plasma loading of the rf antenna, and the rf frequency dependence of source efficiency and antenna circuit efficiency are described for the RFI Multi-cusp source. In a series of tests of this source at Lewis Research Center, minimum discharge losses of 220+/-10 eV/ion were obtained with propellant utilization of .45 at a beam current of 3 amperes. Possible improvement modifications are discussed.

  3. Optical generation of narrowband high frequency ultrasound

    NASA Astrophysics Data System (ADS)

    Hung, Shi-Yao; Hsieh, Bao-Yu; Li, Pai-Chi

    2014-03-01

    We propose a multilayer film structure to generate high frequency and narrowband ultrasound. It consists of three light-absorbing layers and two light-transmittance layers. The amplitude is tunable by adjusting the optical absorption coefficient of light-absorbing layers. The delay can be adjusted by changing thicknesses of light-transmittance layers. In one example, the generated high frequency narrowband ultrasound signal has a center frequency of 18.4MHz and 32.6% fractional bandwidth using the proposed multilayer structure. Compared with this result, the single layer structure produces a center frequency of 20.2MHz and 125.7% fractional bandwidth. In addition, a single laser pulse was employed to generate US on the multilayer film as an US source and PA signals of the high optical absorption region of the phantom at the same time. Because the spectral characteristics of the ultrasound signals generated by the multi-layer film are tunable, it can be designed such that the US echo and PA echo are spectrally separable, thus enabling simultaneous US/PA imaging using only a single laser pulse. Feasibility of this proposed method was demonstrated by imaging of a cyst-like phantom.

  4. Investigating Sonothrombolysis with High Frequency Ultrasound

    NASA Astrophysics Data System (ADS)

    Wright, Cameron; Hynynen, Kullervo; Goertz, David

    2009-04-01

    Despite a significant body of work establishing the feasibility of ultrasound mediated thrombolysis in vitro, in vivo, and in clinical settings, there remains considerable uncertainty about the specific mechanisms involved in this process. This motivates further work to elucidate these mechanisms, which will be central to optimizing safe and effective operating conditions, and to guide the development of novel approaches and instrumentation. In this study, we investigate the use of high frequency ultrasound as a means of gaining mechanistic insight into sonothrombolysis. A high frequency ultrasound (20-50 MHz) instrument is employed which provides the ability to conduct volumetric clot imaging as well as pulsed-wave Doppler to monitor hemodynamics within vessels and clots. With modifications, it is enabled to perform the acquisition of RF data to assess the displacement of clots and vessel walls subjected to therapeutic pulses. Additional modifications were made to perform nonlinear imaging of micron to submicron sized bubbles, which are of interest in enhancing clot lysis. Experiments were performed on in vitro clots, and in vivo using a rabbit femoral artery clot model initiated by the injection of thrombin. Therapeutic pulses are provided by a single element spherically focused air backed transducer with transmit frequencies of 1.68 MHz. Clear visualization of the clots, displacements, and presence or absence of flow within these vessels is shown to be feasible, indicating the potential of this approach as a tool for providing insight into sonothrombolysis.

  5. Noise temperature in graphene at high frequencies

    NASA Astrophysics Data System (ADS)

    Rengel, Raúl; Iglesias, José M.; Pascual, Elena; Martín, María J.

    2016-07-01

    A numerical method for obtaining the frequency-dependent noise temperature in monolayer graphene is presented. From the mobility and diffusion coefficient values provided by Monte Carlo simulation, the noise temperature in graphene is studied up to the THz range, considering also the influence of different substrate types. The influence of the applied electric field is investigated: the noise temperature is found to increase with the applied field, dropping down at high frequencies (in the sub-THz range). The results show that the low-frequency value of the noise temperature in graphene on a substrate tends to be reduced as compared to the case of suspended graphene due to the important effect of remote polar phonon interactions, thus indicating a reduced emitted noise power; however, at very high frequencies the influence of the substrate tends to be significantly reduced, and the differences between the suspended and on-substrate cases tend to be minimized. The values obtained are comparable to those observed in GaAs and semiconductor nitrides.

  6. High frequency ultrasonic scattering by biological tissues

    NASA Astrophysics Data System (ADS)

    Shung, K. Kirk; Maruvada, Subha

    2002-05-01

    High frequency (HF) diagnostic ultrasonic imaging devices at frequencies higher than 20 MHz have found applications in ophthalmology, dermatology, and vascular surgery. To be able to interpret these images and to further the development of these devices, a better understanding of ultrasonic scattering in biological tissues such as blood, liver, myocardium in the high frequency range is crucial. This work has previously been hampered by the lack of suitable transducers. With the availability of HF transducers going to 90 MHz, HF attenuation and backscatter experiments have been made on porcine red blood cell (RBC) suspensions, for which much data on attenuation and backscatter can be found in the literature in the lower frequency range for frequencies, from 30 to 90 MHz and on bovine tissues for frequencies from 10 to 30 MHz using a modified substitution method that allow the utilization of focused transducers. These results will be reviewed in this talk along with relevant theoretical models that could be applied to interpreting them. The relevance of the parameter that has been frequently used in the biomedical ultrasound literature to describe backscattering, the backscattering coefficient, will be critically examined.

  7. High-Frequency Fluctuations During Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Jara-Almonte, J.; Ji, H.; Daughton, W. S.; Roytershteyn, V.; Yamada, M.; Yoo, J.; Fox, W. R., II

    2014-12-01

    During collisionless reconnection, the decoupling of the field from the plasma is known to occur only within the localized ion and electron diffusion regions, however predictions from fully kinetic simulations do not agree with experimental observations on the size of the electron diffusion region, implying differing reconnection mechanisms. Previous experiments, along with 2D and 3D simulations, have conclusively shown that this discrepancy cannot be explained by either classical collisions or Lower-Hybrid Drift Instability (Roytershtyn 2010, 2013). Due to computational limitations, however, previous simulations were constrained to have minimal scale separation between the electron skin depth and the Debye length (de/λD ~ 10), much smaller than in experiments (de/λD ~ 300). This lack of scale-separation can drastically modify the electrostatic microphysics within the diffusion layer. Using 3D, fully explicit kinetic simulations with a realistic and unprecedentedly large separation between the Debye length and the electron skin depth, de/λD = 64, we show that high frequency electrostatic waves (ω >> ωLH) can exist within the electron diffusion region. These waves generate small-scale turbulence within the electron diffusion region which acts to broaden the layer. Anomalous resistivity is also generated by the turbulence and significantly modifies the force balance. In addition to simulation results, initial experimental measurements of high frequency fluctuations (electrostatic and electromagnetic, f ≤ 1 GHz) in the Magnetic Reconnection Experiment (MRX) will be presented.

  8. Transport of Radioactive Material by Alpha Recoil

    SciTech Connect

    Icenhour, A.S.

    2005-05-19

    The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and results of a number of the studies.

  9. Recoil by Auger electrons: Theory and application

    SciTech Connect

    Demekhin, Ph. V.; Scheit, S.; Cederbaum, L. S.

    2009-10-28

    General equations accounting for the molecular dynamics induced by the recoil of a fast Auger electron are presented. The implications of the degree of localization of the molecular orbitals of diatomic molecules involved in the Auger decay are analyzed. It is shown that the direct and exchange terms of the Auger transition matrix element may give rise to opposite signs and hence to opposite directions of the recoil momenta transferred to the nuclear vibrational motion. Consequently, these terms have a different impact on the recoil-induced nuclear dynamics in the final Auger decay state. The developed theory is applied to study the influence of the recoil on the interatomic Coulombic decay (ICD) following the K-LL Auger decay of the Ne dimer. Our calculations illustrate a significant effect of the recoil of nuclei on the computed wave packets propagating on the potential energy curve populated by the Auger decay. The corresponding final states of the Auger process decay further by ICD. We show that the recoil momentum imparted onto the nuclei modifies the computed ICD spectra considerably.

  10. A Measurement of the Recoil Polarization of Electroproduced {Lambda}(1116)

    SciTech Connect

    Simeon McAleer

    2002-01-01

    The CEBAF Large Acceptance Spectrometer at the Thomas Jefferson National Laboratory was used to study the reaction e + p {yields} e{prime} + K{sup +} + {Lambda}(1116) for events where {Lambda}(1116) subsequently decayed via the channel {Lambda}(1116) {yields} p + {pi}{sup -}. Data were taken at incident electron beam energies of 2.5, 4.0, and 4.2 GeV during the 1999 E1C run period. They hyperon production spectra span the Q{sup 2} range from 0.5 to 2.8 GeV{sup 2} and nearly the entire range in the center of mass angles. The proton angular distribution in the {Lambda}(1116) rest frame is used to deduce the recoil polarization of the hyperon, and the W and cos {theta}{sub cm}{sup K+} dependence of the recoil polarization will be presented. The data show sizeable negative polarizations for the {Lambda}(1116) as a function of both cos {theta}{sub cm}{sup K+} and W.

  11. Lifetimes in neutron-rich fission fragments using the differential recoil distance method

    SciTech Connect

    Kruecken, R.; Chou, W.-T.; Cooper, J. R.; Beausang, C. W.; Barton, C. J.; Caprio, M. A.; Casten, R. F.; Hecht, A. A.; Novak, J. R.; Pietralla, N.

    2001-07-01

    Lifetimes in the neutron-rich nuclei {sup 104}Mo, {sup 110}Ru, and {sup 144}Ba were measured using the differential recoil distance method. The experiment was performed with a {sup 252}Cf fission source inside the New Yale Plunger Device. {gamma} rays were detected by the SPEctrometer for Experiments with Doppler shifts at Yale (SPEEDY) while fission fragments with the appropriate kinematics were detected by an array of photocells.

  12. Parametric nanomechanical amplification at very high frequency.

    PubMed

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach. PMID:19736969

  13. High-frequency ultrasonic wire bonding systems

    PubMed

    Tsujino; Yoshihara; Sano; Ihara

    2000-03-01

    The vibration characteristics of longitudinal-complex transverse vibration systems with multiple resonance frequencies of 350-980 kHz for ultrasonic wire bonding of IC, LSI or electronic devices were studied. The complex vibration systems can be applied for direct welding of semiconductor tips (face-down bonding, flip-chip bonding) and packaging of electronic devices. A longitudinal-complex transverse vibration bonding system consists of a complex transverse vibration rod, two driving longitudinal transducers 7.0 mm in diameter and a transverse vibration welding tip. The vibration distributions along ceramic and stainless-steel welding tips were measured at up to 980 kHz. A high-frequency vibration system with a height of 20.7 mm and a weight of less than 15 g was obtained.

  14. High-frequency micromechanical columnar resonators

    NASA Astrophysics Data System (ADS)

    Kehrbusch, Jenny; Ilin, Elena A.; Bozek, Peter; Radzio, Bernhard; Oesterschulze, Egbert

    2009-06-01

    High-frequency silicon columnar microresonators are fabricated using a simple but effective technological scheme. An optimized fabrication scheme was invented to obtain mechanically protected microcolumns with lateral dimensions controlled on a scale of at least 1 μm. In this paper, we investigate the influence of the environmental conditions on the mechanical resonator properties. At ambient conditions, we observed a frequency stability δf/f of less than 10-6 during 5 h of operation at almost constant temperature. However, varying the temperature shifts the frequency by approximately -173 Hz °C- 1. In accordance with a viscous damping model of the ambient gas, we perceived that the quality factor of the first flexural mode decreased with the inverse of the square root of pressure. However, in the low-pressure regime, a linear dependence was observed. We also investigated the influence of the type of the immersing gas on the resonant frequency.

  15. High-frequency resonant-tunneling oscillators

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Parker, C. D.; Calawa, A. R.; Manfra, M. J.; Chen, C. L.

    1991-01-01

    Advances in high-frequency resonant-tunneling-diode (RTD) oscillators are described. Oscillations up to a frequency of 420 GHz have been achieved in the GaAs/AlAs system. Recent results obtained with In0.53Ga0.47As/AlAs and InAs/AlSb RTDs show a greatly increased power density and indicate the potential for fundamental oscillations up to about 1 THz. These results are consistent with a lumped-element equivalent circuit model of the RTD. The model shows that the maximum oscillation frequency of the GaAs/AlAs RTDs is limited primarily by series resistance, and that the power density is limited by low peak-to-valley current ratio.

  16. Parametric nanomechanical amplification at very high frequency.

    PubMed

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  17. Fundamentals of bipolar high-frequency surgery.

    PubMed

    Reidenbach, H D

    1993-04-01

    In endoscopic surgery a very precise surgical dissection technique and an efficient hemostasis are of decisive importance. The bipolar technique may be regarded as a method which satisfies both requirements, especially regarding a high safety standard in application. In this context the biophysical and technical fundamentals of this method, which have been known in principle for a long time, are described with regard to the special demands of a newly developed field of modern surgery. After classification of this method into a general and a quasi-bipolar mode, various technological solutions of specific bipolar probes, in a strict and in a generalized sense, are characterized in terms of indication. Experimental results obtained with different bipolar instruments and probes are given. The application of modern microprocessor-controlled high-frequency surgery equipment and, wherever necessary, the integration of additional ancillary technology into the specialized bipolar instruments may result in most useful and efficient tools of a key technology in endoscopic surgery.

  18. A Double Scattering Analytical Model For Elastic Recoil Detection Analysis

    SciTech Connect

    Barradas, N. P.; Lorenz, K.; Alves, E.; Darakchieva, V.

    2011-06-01

    We present an analytical model for calculation of double scattering in elastic recoil detection measurements. Only events involving the beam particle and the recoil are considered, i.e. 1) an ion scatters off a target element and then produces a recoil, and 2) an ion produces a recoil which then scatters off a target element. Events involving intermediate recoils are not considered, i.e. when the primary ion produces a recoil which then produces a second recoil. If the recoil element is also present in the stopping foil, recoil events in the stopping foil are also calculated. We included the model in the standard code for IBA data analysis NDF, and applied it to the measurement of hydrogen in Si.

  19. High frequency, high power capacitor development

    NASA Technical Reports Server (NTRS)

    White, C. W.; Hoffman, P. S.

    1983-01-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  20. High-frequency plasma-heating apparatus

    DOEpatents

    Brambilla, Marco; Lallia, Pascal

    1978-01-01

    An array of adjacent wave guides feed high-frequency energy into a vacuum chamber in which a toroidal plasma is confined by a magnetic field, the wave guide array being located between two toroidal current windings. Waves are excited in the wave guide at a frequency substantially equal to the lower frequency hybrid wave of the plasma and a substantially equal phase shift is provided from one guide to the next between the waves therein. For plasmas of low peripheral density gradient, the guides are excited in the TE.sub.01 mode and the output electric field is parallel to the direction of the toroidal magnetic field. For exciting waves in plasmas of high peripheral density gradient, the guides are excited in the TM.sub.01 mode and the magnetic field at the wave guide outlets is parallel to the direction of the toroidal magnetic field. The wave excited at the outlet of the wave guide array is a progressive wave propagating in the direction opposite to that of the toroidal current and is, therefore, not absorbed by so-called "runaway" electrons.

  1. High frequency, high power capacitor development

    NASA Astrophysics Data System (ADS)

    White, C. W.; Hoffman, P. S.

    1983-03-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  2. Radio spectra of High Frequency Peakers

    NASA Astrophysics Data System (ADS)

    Dallacasa, D.; Orienti, M.

    2016-02-01

    New radio spectra of High Frequency Peakers (HFP) obtained from the Jansky Very Large Array (JVLA) show that variability is common among this class of sources. A subsample of sources have been observed with a nearly continuous spectral sampling between 1 and 10 GHz. The observed HFP sources were previously classified as F (flat), H (HFP profile with little or no flux density variability) and V (variable, but preserving a peaked spectrum). In general, sources classified as V and H show a decrease of the flux density measured in the optically thin part of the spectrum, while there is a moderate increment in the optically thick region, resulting into a progressive shift of the spectral peak to lower frequencies. This is consistent with the idea of an expanding bubble of radio plasma. The sources with an F classification instead show substantial variability, both in spectral shape and in time evolution. In these HFP sources an irregular production of energy is best observed since the radio emission is dominated by recently generated relativistic plasma, and the contribution of mini lobes, in which old plasma accumulates, is marginal if not absent at all, given the short radiative life of electrons in strong magnetic fields (tens of mG) found in these objects.

  3. A High Frequency Model of Cascade Noise

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    1998-01-01

    Closed form asymptotic expressions for computing high frequency noise generated by an annular cascade in an infinite duct containing a uniform flow are presented. There are two new elements in this work. First, the annular duct mode representation does not rely on the often-used Bessel function expansion resulting in simpler expressions for both the radial eigenvalues and eigenfunctions of the duct. In particular, the new representation provides an explicit approximate formula for the radial eigenvalues obviating the need for solutions of the transcendental annular duct eigenvalue equation. Also, the radial eigenfunctions are represented in terms of exponentials eliminating the numerical problems associated with generating the Bessel functions on a computer. The second new element is the construction of an unsteady response model for an annular cascade. The new construction satisfies the boundary conditions on both the cascade and duct walls simultaneously adding a new level of realism to the noise calculations. Preliminary results which demonstrate the effectiveness of the new elements are presented. A discussion of the utility of the asymptotic formulas for calculating cascade discrete tone as well as broadband noise is also included.

  4. Plant Responses to High Frequency Electromagnetic Fields

    PubMed Central

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre

    2016-01-01

    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  5. Aerodynamics of high frequency flapping wings

    NASA Astrophysics Data System (ADS)

    Hu, Zheng; Roll, Jesse; Cheng, Bo; Deng, Xinyan

    2010-11-01

    We investigated the aerodynamic performance of high frequency flapping wings using a 2.5 gram robotic insect mechanism developed in our lab. The mechanism flaps up to 65Hz with a pair of man-made wing mounted with 10cm wingtip-to-wingtip span. The mean aerodynamic lift force was measured by a lever platform, and the flow velocity and vorticity were measured using a stereo DPIV system in the frontal, parasagittal, and horizontal planes. Both near field (leading edge vortex) and far field flow (induced flow) were measured with instantaneous and phase-averaged results. Systematic experiments were performed on the man-made wings, cicada and hawk moth wings due to their similar size, frequency and Reynolds number. For insect wings, we used both dry and freshly-cut wings. The aerodynamic force increase with flapping frequency and the man-made wing generates more than 4 grams of lift at 35Hz with 3 volt input. Here we present the experimental results and the major differences in their aerodynamic performances.

  6. Plant Responses to High Frequency Electromagnetic Fields.

    PubMed

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre

    2016-01-01

    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  7. A high frequency electromagnetic impedance imaging system

    SciTech Connect

    Tseng, Hung-Wen; Lee, Ki Ha; Becker, Alex

    2003-01-15

    Non-invasive, high resolution geophysical mapping of the shallow subsurface is necessary for delineation of buried hazardous wastes, detecting unexploded ordinance, verifying and monitoring of containment or moisture contents, and other environmental applications. Electromagnetic (EM) techniques can be used for this purpose since electrical conductivity and dielectric permittivity are representative of the subsurface media. Measurements in the EM frequency band between 1 and 100 MHz are very important for such applications, because the induction number of many targets is small and the ability to determine the subsurface distribution of both electrical properties is required. Earlier workers were successful in developing systems for detecting anomalous areas, but quantitative interpretation of the data was difficult. Accurate measurements are necessary, but difficult to achieve for high-resolution imaging of the subsurface. We are developing a broadband non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using an EM impedance approach similar to the MT exploration technique. Electric and magnetic sensors were tested to ensure that stray EM scattering is minimized and the quality of the data collected with the high-frequency impedance (HFI) system is good enough to allow high-resolution, multi-dimensional imaging of hidden targets. Additional efforts are being made to modify and further develop existing sensors and transmitters to improve the imaging capability and data acquisition efficiency.

  8. Performance of annular high frequency thermoacoustic engines

    NASA Astrophysics Data System (ADS)

    Rodriguez, Ivan A.

    This thesis presents studies of the behavior of miniature annular thermoacoustic prime movers and the imaging of the complex sound fields using PIV inside the small acoustic wave guides when driven by a temperature gradient. Thermoacoustic engines operating in the standing wave mode are limited in their acoustic efficiency by a high degree of irreversibility that is inherent in how they work. Better performance can be achieved by using traveling waves in the thermoacoustic devices. This has led to the development of an annular high frequency thermoacoustic prime mover consisting of a regenerator, which is a random stack in-between a hot and cold heat exchanger, inside an annular waveguide. Miniature devices were developed and studied with operating frequencies in the range of 2-4 kHz. This corresponds to an average ring circumference of 11 cm for the 3 kHz device, the resonator bore being 6 mm. A similar device of 11 mm bore, length of 18 cm was also investigated; its resonant frequency was 2 kHz. Sound intensities as high as 166.8 dB were generated with limited heat input. Sound power was extracted from the annular structure by an impedance-matching side arm. The nature of the acoustic wave generated by heat was investigated using a high speed PIV instrument. Although the acoustic device appears symmetric, its performance is characterized by a broken symmetry and by perturbations that exist in its structure. Effects of these are observed in the PIV imaging; images show axial and radial components. Moreover, PIV studies show effects of streaming and instabilities which affect the devices' acoustic efficiency. The acoustic efficiency is high, being of 40% of Carnot. This type of device shows much promise as a high efficiency energy converter; it can be reduced in size for microcircuit applications.

  9. High frequency stimulation can block axonal conduction.

    PubMed

    Jensen, Alicia L; Durand, Dominique M

    2009-11-01

    High frequency stimulation (HFS) is used to control abnormal neuronal activity associated with movement, seizure, and psychiatric disorders. Yet, the mechanisms of its therapeutic action are not known. Although experimental results have shown that HFS suppresses somatic activity, other data has suggested that HFS could generate excitation of axons. Moreover it is unclear what effect the stimulation has on tissue surrounding the stimulation electrode. Electrophysiological and computational modeling literature suggests that HFS can drive axons at the stimulus frequency. Therefore, we tested the hypothesis that unlike cell bodies, axons are driven by pulse train HFS. This hypothesis was tested in fibers of the hippocampus both in-vivo and in-vitro. Our results indicate that although electrical stimulation could activate and drive axons at low frequencies (0.5-25 Hz), as the stimulus frequency increased, electrical stimulation failed to continuously excite axonal activity. Fiber tracts were unable to follow extracellular pulse trains above 50 Hz in-vitro and above 125 Hz in-vivo. The number of cycles required for failure was frequency dependent but independent of stimulus amplitude. A novel in-vitro preparation was developed, in which, the alveus was isolated from the remainder of the hippocampus slice. The isolated fiber tract was unable to follow pulse trains above 75 Hz. Reversible conduction block occurred at much higher stimulus amplitudes, with pulse train HFS (>150 Hz) preventing propagation through the site of stimulation. This study shows that pulse train HFS affects axonal activity by: (1) disrupting HFS evoked excitation leading to partial conduction block of activity through the site of HFS; and (2) generating complete conduction block of secondary evoked activity, as HFS amplitude is increased. These results are relevant for the interpretation of the effects of HFS for the control of abnormal neural activity such as epilepsy and Parkinson's disease. PMID

  10. High-frequency furnace. Final technical report

    SciTech Connect

    Zumbrunnen, A.D.

    1985-04-30

    An experimental furnace has been built for the purpose of evaluating a new technique for the high purity melting of certain metals and semiconductors. The melt is contained in a solidified skull of the same material being melted, thus avoiding crucible reactions that are a problem in conventional processing. A number of commercial applications of the invention are discussed, assuming that feasibility can be etablished. These include the melting and crystal growth of silicon, where the avoidance of crucible contamination would improve the energy conversion efficiency of solar cells; and the consolidation of titanium sponge and scrap, where energy savings and other process advantages would be realized. The production of ferrous and non-ferrous, specialty alloys is also discussed. Heating power is derived from the electrical, proximity effect which is used to concentrate a high-frequency (9.6 kHz) current in the melt zone. The power source is a conventional, 50 kW, solid-state inverter of the type used in induction heating practice. All heats were conducted on a cast iron workpiece in argon at atmospheric pressure. The melt temperature of the casting (2100/sup 0/F) was not achieved in any test run; however, the ability of proximity effect to generate localized heating was clearly demonstrated. A maximum temperature of about 1600/sup 0/F was reached at an inverter power output of approximately seventy-five percent. Full power was not obtained because of a poor impedance match between the furnace and power supply. Temperature was further limited because of the absence of heat shielding and other factors which resulted in excessive heat loss from the workpiece. These results are considered to be only preliminary since no attempt has been made to optimize either the electrical or thermal characteristics of the system.

  11. Elastic recoil detection analysis for large recoil angles (LA-ERDA)

    NASA Astrophysics Data System (ADS)

    Bogdanović Radović, I.; Steinbauer, E.; Benka, O.

    2000-09-01

    In this paper, elastic recoil detection (ERD) measurements at recoil angle of 60° using ion-induced electron emission (IEE) for particle identification are presented. In our IEE system for particle identification, recoiled target atoms and scattered projectiles penetrate a set of thin carbon foils before their energy is analyzed in a solid state detector. Particle identification is based on the fact that the total number of electrons emitted from the foils depends on the particle nuclear charge. This method is characterized by its low minimum detectable energy, which stimulated us to study ERDA at 60°. Due to collision kinematics and due to the angular dependence of the scattering cross-sections, it is expected that the sensitivity can be significantly improved. In this work, the detection efficiency of the IEE particle identification system for H recoils at energies below 1 MeV was determined. LA-ERDA measurements were performed with 4He and 12C projectiles using two different types of samples with a well-known amount and depth distribution of H atoms near the surface. Sample 1 consisted of a 50 μg/cm 2 melamine layer evaporated on a flat Si substrate, sample 2 was a Si wafer with implanted H. Sensitivity and depth resolution were measured using LA-ERDA with a recoil angle of 60° and ERDA with recoil angles of 30° and 45°. The results for different recoil geometries and projectiles are discussed and compared with theoretical predictions.

  12. Monolithic spectrometer

    DOEpatents

    Rajic, S.; Egert, C.M.; Kahl, W.K.; Snyder, W.B. Jr.; Evans, B.M. III; Marlar, T.A.; Cunningham, J.P.

    1998-05-19

    A monolithic spectrometer is disclosed for use in spectroscopy. The spectrometer is a single body of translucent material with positioned surfaces for the transmission, reflection and spectral analysis of light rays. 6 figs.

  13. Monolithic spectrometer

    DOEpatents

    Rajic, Slobodan; Egert, Charles M.; Kahl, William K.; Snyder, Jr., William B.; Evans, III, Boyd M.; Marlar, Troy A.; Cunningham, Joseph P.

    1998-01-01

    A monolithic spectrometer is disclosed for use in spectroscopy. The spectrometer is a single body of translucent material with positioned surfaces for the transmission, reflection and spectral analysis of light rays.

  14. High Frequency QRS ECG Accurately Detects Cardiomyopathy

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds

    2005-01-01

    High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing

  15. Recoil separator ERNA: ion beam specifications

    NASA Astrophysics Data System (ADS)

    Rogalla, D.; Aliotta, M.; Barnes, C. A.; Campajola, L.; D'Onofrio, A.; Fritz, E.; Gialanella, L.; Greife, U.; Imbriani, G.; Ordine, A.; Ossmann, J.; Roca, V.; Rolfs, C.; Romano, M.; Sabbarese, C.; Schürmann, D.; Schümann, F.; Strieder, F.; Theis, S.; Terrasi, F.; Trautvetter, H. P.

    For improved measurements of the key astrophysical reaction 12C(α,γ)16O in inverted kinematics, a recoil separator ERNA is being developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with about 50% efficiency. Calculations of the ion beam optics including all filtering and focusing elements of ERNA are presented. Since the 12C projectiles and the 16O recoils have essentially the same momentum, and since the 12C ion beam emerging from the accelerator passes through a momentum filter (analysing magnet), the 12C ion beam must be as free as possible from 16O contamination for ERNA to succeed. In the present work, the 16O contamination was reduced from a level of 1 × 10-11 to a level below 2 × 10-29 by the installation of Wien filters both before and after the analysing magnet. The measurement of these and other beam specifications involved other parts of the final ERNA layout - sequentially a Wien filter, a 60˚ dipole magnet, another Wien filter, and a ΔE-E telescope. The setup led to a measured suppression factor of 5 × 10-18 for the 12C ion beam. The experiments also indicate that an almost free choice of the charge state for the 16O recoils is possible in the separator.

  16. Proton recoil scintillator neutron rem meter

    DOEpatents

    Olsher, Richard H.; Seagraves, David T.

    2003-01-01

    A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

  17. Effects of interelectrode gap on high frequency and very high frequency capacitively coupled plasmas

    SciTech Connect

    Bera, Kallol; Rauf, Shahid; Ramaswamy, Kartik; Collins, Ken

    2009-07-15

    Capacitively coupled plasma (CCP) discharges using high frequency (HF) and very high frequency (VHF) sources are widely used for dielectric etching in the semiconductor industry. A two-dimensional fluid plasma model is used to investigate the effects of interelectrode gap on plasma spatial characteristics of both HF and VHF CCPs. The plasma model includes the full set of Maxwell's equations in their potential formulation. The peak in plasma density is close to the electrode edge at 13.5 MHz for a small interelectrode gap. This is due to electric field enhancement at the electrode edge. As the gap is increased, the plasma produced at the electrode edge diffuses to the chamber center and the plasma becomes more uniform. At 180 MHz, where electromagnetic standing wave effects are strong, the plasma density peaks at the chamber center at large interelectrode gap. As the interelectrode gap is decreased, the electron density increases near the electrode edge due to inductive heating and electrostatic electron heating, which makes the plasma more uniform in the interelectrode region.

  18. On-clip high frequency reliability and failure test structures

    DOEpatents

    Snyder, Eric S.; Campbell, David V.

    1997-01-01

    Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer.

  19. On-clip high frequency reliability and failure test structures

    DOEpatents

    Snyder, E.S.; Campbell, D.V.

    1997-04-29

    Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer. 22 figs.

  20. Recoil Based Fuel Breeding Fuel Structure

    SciTech Connect

    Popa-Simil, Liviu

    2008-07-01

    Nuclear transmutation reactions are based on the absorption of a smaller particle as neutron, proton, deuteron, alpha, etc. The resulting compound nucleus gets out of its initial lattice mainly by taking the recoil, also with help from its sudden change in chemical properties. The recoil implantation is used in correlation with thin and ultra thin materials mainly for producing radiopharmaceuticals and ultra-thin layer radioactive tracers. In nuclear reactors, the use of nano-particulate pellets could facilitate the recoil implantation for breeding, transmutation and partitioning purposes. Using enriched {sup 238}U or {sup 232}Th leads to {sup 239}Pu and {sup 233}U production while using other actinides as {sup 240}Pu, {sup 241}Am etc. leads to actinide burning. When such a lattice is immersed into a radiation resistant fluid (water, methanol, etc.), the recoiled product is transferred into the flowing fluid and removed from the hot area using a concentrator/purifier, preventing the occurrence of secondary transmutation reactions. The simulation of nuclear collision and energy transfer shows that the impacted nucleus recoils in the interstitial space creating a defect or lives small lattices. The defect diffuses, and if no recombination occurs it stops at the lattices boundaries. The nano-grains are coated in thin layer to get a hydrophilic shell to be washed by the collection liquid the particle is immersed in. The efficiency of collection depends on particle magnitude and nuclear reaction channel parameters. For {sup 239}Pu the direct recoil extraction rate is about 70% for {sup 238}UO{sub 2} grains of 5 nm diameters and is brought up to 95% by diffusion due to {sup 239}Neptunium incompatibility with Uranium dioxide lattice. Particles of 5 nm are hard to produce so a structure using particles of 100 nm have been tested. The particles were obtained by plasma sputtering in oxygen atmosphere. A novel effect as nano-cluster radiation damage robustness and cluster

  1. Correlation spectrometer

    DOEpatents

    Sinclair, Michael B.; Pfeifer, Kent B.; Flemming, Jeb H.; Jones, Gary D.; Tigges, Chris P.

    2010-04-13

    A correlation spectrometer can detect a large number of gaseous compounds, or chemical species, with a species-specific mask wheel. In this mode, the spectrometer is optimized for the direct measurement of individual target compounds. Additionally, the spectrometer can measure the transmission spectrum from a given sample of gas. In this mode, infrared light is passed through a gas sample and the infrared transmission signature of the gasses present is recorded and measured using Hadamard encoding techniques. The spectrometer can detect the transmission or emission spectra in any system where multiple species are present in a generally known volume.

  2. RELATIVISTIC SUPPRESSION OF BLACK HOLE RECOILS

    SciTech Connect

    Kesden, Michael; Sperhake, Ulrich; Berti, Emanuele

    2010-06-01

    Numerical-relativity simulations indicate that the black hole produced in a binary merger can recoil with a velocity up to v {sub max} {approx_equal} 4000 km s{sup -1} with respect to the center of mass of the initial binary. This challenges the paradigm that most galaxies form through hierarchical mergers, yet retain supermassive black holes (SBHs) at their centers despite having escape velocities much less than v {sub max}. Interaction with a circumbinary disk can align the binary black hole spins with their orbital angular momentum, reducing the recoil velocity of the final black hole produced in the subsequent merger. However, the effectiveness of this alignment depends on highly uncertain accretion flows near the binary black holes. In this paper, we show that if the spin S {sub 1} of the more massive binary black hole is even partially aligned with the orbital angular momentum L, relativistic spin precession on sub-parsec scales can align the binary black hole spins with each other. This alignment significantly reduces the recoil velocity even in the absence of gas. For example, if the angle between S {sub 1} and L at large separations is 10{sup 0} while the second spin S {sub 2} is isotropically distributed, the spin alignment discussed in this paper reduces the median recoil from 864 km s{sup -1} to 273 km s{sup -1} for maximally spinning black holes with a mass ratio of 9/11. This reduction will greatly increase the fraction of galaxies retaining their SBHs.

  3. Effects of high frequency current in welding aluminum alloy 6061

    NASA Technical Reports Server (NTRS)

    Fish, R. E.

    1968-01-01

    Uncontrolled high frequency current causes cracking in the heat-affected zone of aluminum alloy 6061 weldments during tungsten inert gas ac welding. Cracking developed when an improperly adjusted superimposed high frequency current was agitating the semimolten metal in the areas of grain boundary.

  4. 140 GHz pulsed Fourier transform microwave spectrometer

    DOEpatents

    Kolbe, W.F.; Leskovar, B.

    1985-07-29

    A high frequency energy pulsing system suitable for use in a pulsed microwave spectrometer, including means for generating a high frequency carrier signal, and means for generating a low frequency modulating signal. The carrier signal is continuously fed to a modulator and the modulating signal is fed through a pulse switch to the modulator. When the pulse switch is on, the modulator will produce sideband signals above and below the carrier signal frequency. A frequency-responsive device is tuned to one of the sideband signals and sway from the carrier frequency so that the high frequency energization of the frequency-responsive device is controlled by the pulse switch.

  5. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, Howard D.

    1996-01-01

    A method and apparatus for monitoring an electrical-motor-driven device by injecting a high frequency carrier signal onto the power line current. The method is accomplished by injecting a high frequency carrier signal onto an AC power line current. The AC power line current supplies the electrical-motor-driven device with electrical energy. As a result, electrical and mechanical characteristics of the electrical-motor-driven device modulate the high frequency carrier signal and the AC power line current. The high frequency carrier signal is then monitored, conditioned and demodulated. Finally, the modulated high frequency carrier signal is analyzed to ascertain the operating condition of the electrical-motor-driven device.

  6. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, H.D.

    1996-04-30

    A method and apparatus for monitoring an electrical-motor-driven device by injecting a high frequency carrier signal onto the power line current. The method is accomplished by injecting a high frequency carrier signal onto an AC power line current. The AC power line current supplies the electrical-motor-driven device with electrical energy. As a result, electrical and mechanical characteristics of the electrical-motor-driven device modulate the high frequency carrier signal and the AC power line current. The high frequency carrier signal is then monitored, conditioned and demodulated. Finally, the modulated high frequency carrier signal is analyzed to ascertain the operating condition of the electrical-motor-driven device. 6 figs.

  7. Haemodynamic changes during high frequency oscillation for respiratory distress syndrome.

    PubMed Central

    Laubscher, B.; van Melle, G.; Fawer, C. L.; Sekarski, N.; Calame, A.

    1996-01-01

    In a crossover trial left ventricular output (LVO), cerebral blood flow velocity (CBFV), and resistance index (RI) of the anterior cerebral artery were compared using Doppler ultrasonography, in eight preterm infants with respiratory distress syndrome (RDS) during conventional mechanical ventilation and high frequency oscillation. LVO was 14% to 18% lower with high frequency oscillation. There were no significant changes in CBFV. On the first day of life there was a trend towards lower RI on high frequency oscillation; the fall in LVO on high frequency oscillation was not related to lung hyperinflation. Changes in ventilation type (from conventional mechanical ventilation to high frequency oscillation, or vice versa) can induce significant LVO changes in preterm infants with RDS. PMID:8777679

  8. Bulk and integrated acousto-optic spectrometers for molecular astronomy with heterodyne spectrometers

    NASA Technical Reports Server (NTRS)

    Chin, G.; Buhl, D.; Florez, J. M.

    1981-01-01

    A survey of acousto-optic spectrometers for molecular astronomy is presented, noting a technique of combining the acoustic bending of a collimated coherent light beam with a Bragg cell followed by an array of sensitive photodetectors. This acousto-optic spectrometer has a large bandwidth, a large number of channels, high resolution, and is energy efficient. Receiver development has concentrated on high-frequency heterodyne systems for the study of the chemical composition of the interstellar medium. RF spectrometers employing acousto-optic diffraction cells are described. Acousto-optic techniques have been suggested for applications to electronic warfare, electronic countermeasures and electronic support systems. Plans to use integrated optics for the further miniaturization of acousto-optic spectrometers are described. Bulk acousto-optic spectrometers with 300 MHz and 1 GHz bandwidths are being developed for use in the back-end of high-frequency heterodyne receivers for astronomical research.

  9. Multidimensional spectrometer

    DOEpatents

    Zanni, Martin Thomas; Damrauer, Niels H.

    2010-07-20

    A multidimensional spectrometer for the infrared, visible, and ultraviolet regions of the electromagnetic spectrum, and a method for making multidimensional spectroscopic measurements in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum. The multidimensional spectrometer facilitates measurements of inter- and intra-molecular interactions.

  10. High-frequency energy in singing and speech

    NASA Astrophysics Data System (ADS)

    Monson, Brian Bruce

    While human speech and the human voice generate acoustical energy up to (and beyond) 20 kHz, the energy above approximately 5 kHz has been largely neglected. Evidence is accruing that this high-frequency energy contains perceptual information relevant to speech and voice, including percepts of quality, localization, and intelligibility. The present research was an initial step in the long-range goal of characterizing high-frequency energy in singing voice and speech, with particular regard for its perceptual role and its potential for modification during voice and speech production. In this study, a database of high-fidelity recordings of talkers was created and used for a broad acoustical analysis and general characterization of high-frequency energy, as well as specific characterization of phoneme category, voice and speech intensity level, and mode of production (speech versus singing) by high-frequency energy content. Directionality of radiation of high-frequency energy from the mouth was also examined. The recordings were used for perceptual experiments wherein listeners were asked to discriminate between speech and voice samples that differed only in high-frequency energy content. Listeners were also subjected to gender discrimination tasks, mode-of-production discrimination tasks, and transcription tasks with samples of speech and singing that contained only high-frequency content. The combination of these experiments has revealed that (1) human listeners are able to detect very subtle level changes in high-frequency energy, and (2) human listeners are able to extract significant perceptual information from high-frequency energy.

  11. An inkjet vision measurement technique for high-frequency jetting

    SciTech Connect

    Kwon, Kye-Si Jang, Min-Hyuck; Park, Ha Yeong; Ko, Hyun-Seok

    2014-06-15

    Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance.

  12. Quantum inductance and high frequency oscillators in graphene nanoribbons.

    PubMed

    Begliarbekov, Milan; Strauf, Stefan; Search, Christopher P

    2011-04-22

    Here we investigate high frequency AC transport through narrow graphene nanoribbons with top-gate potentials that form a localized quantum dot. We show that as a consequence of the finite dwell time of an electron inside the quantum dot (QD), the QD behaves like a classical inductor at sufficiently high frequencies ω ≥ GHz. When the geometric capacitance of the top-gate and the quantum capacitance of the nanoribbon are accounted for, the admittance of the device behaves like a classical serial RLC circuit with resonant frequencies ω ∼ 100-900 GHz and Q-factors greater than 10(6). These results indicate that graphene nanoribbons can serve as all-electronic ultra-high frequency oscillators and filters, thereby extending the reach of high frequency electronics into new domains.

  13. High-frequency matrix converter with square wave input

    DOEpatents

    Carr, Joseph Alexander; Balda, Juan Carlos

    2015-03-31

    A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

  14. Neutron electric form factor via recoil polarimetry

    SciTech Connect

    Madey, Richard; Semenov, Andrei; Taylor, Simon; Aghalaryan, Aram; Crouse, Erick; MacLachlan, Glen; Plaster, Bradley; Tajima, Shigeyuki; Tireman, William; Yan, Chenyu; Ahmidouch, Abdellah; Anderson, Brian; Asaturyan, Razmik; Baker, O; Baldwin, Alan; Breuer, Herbert; Carlini, Roger; Christy, Michael; Churchwell, Steve; Cole, Leon; Danagoulian, Samuel; Day, Donal; Elaasar, Mostafa; Ent, Rolf; Farkhondeh, Manouchehr; Fenker, Howard; Finn, John; Gan, Liping; Garrow, Kenneth; Gueye, Paul; Howell, Calvin; Hu, Bitao; Jones, Mark; Kelly, James; Keppel, Cynthia; Khandaker, Mahbubul; Kim, Wooyoung; Kowalski, Stanley; Lung, Allison; Mack, David; Manley, D; Markowitz, Pete; Mitchell, Joseph; Mkrtchyan, Hamlet; Opper, Allena; Perdrisat, Charles; Punjabi, Vina; Raue, Brian; Reichelt, Tilmann; Reinhold, Joerg; Roche, Julie; Sato, Yoshinori; Seo, Wonick; Simicevic, Neven; Smith, Gregory; Stepanyan, Samuel; Tadevosyan, Vardan; Tang, Liguang; Ulmer, Paul; Vulcan, William; Watson, John; Wells, Steven; Wesselmann, Frank; Wood, Stephen; Yan, Chen; Yang, Seunghoon; Yuan, Lulin; Zhang, Wei-Ming; Zhu, Hong Guo; Zhu, Xiaofeng

    2003-05-01

    The ratio of the electric to the magnetic form factor of the neutron, G_En/G_Mn, was measured via recoil polarimetry from the quasielastic d({pol-e},e'{pol-n)p reaction at three values of Q^2 [viz., 0.45, 1.15 and 1.47 (GeV/c)^2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that G_En follows the Galster parameterization up to Q^2 = 1.15 (GeV/c)^2 and appears to rise above the Galster parameterization at Q^2 = 1.47 (GeV/c)^2.

  15. High frequency ultrasound with color Doppler in dermatology*

    PubMed Central

    Barcaui, Elisa de Oliveira; Carvalho, Antonio Carlos Pires; Lopes, Flavia Paiva Proença Lobo; Piñeiro-Maceira, Juan; Barcaui, Carlos Baptista

    2016-01-01

    Ultrasonography is a method of imaging that classically is used in dermatology to study changes in the hypoderma, as nodules and infectious and inflammatory processes. The introduction of high frequency and resolution equipments enabled the observation of superficial structures, allowing differentiation between skin layers and providing details for the analysis of the skin and its appendages. This paper aims to review the basic principles of high frequency ultrasound and its applications in different areas of dermatology. PMID:27438191

  16. High frequency single mode traveling wave structure for particle acceleration

    NASA Astrophysics Data System (ADS)

    Ivanyan, M. I.; Danielyan, V. A.; Grigoryan, B. A.; Grigoryan, A. H.; Tsakanian, A. V.; Tsakanov, V. M.; Vardanyan, A. S.; Zakaryan, S. V.

    2016-09-01

    The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM01 mode in a metallic tube with internally coated low conductive thin layer are examined.

  17. High frequency, small signal MH loops of ferromagnetic thin films

    NASA Technical Reports Server (NTRS)

    Grimes, C. A.; Ong, K. G.

    2000-01-01

    A method is presented for transforming the high frequency bias susceptibility measurements of ferromagnetic thin films into the form of a MH loop with, depending upon the measurement geometry, the y-axis zero crossing giving a measure of the coercive force or anisotropy field. The loops provide a measure of the quantitative and qualitative high frequency switching properties of ferromagnetic thin films. c2000 American Institute of Physics.

  18. Recoil separator ERNA: gas target and beam suppression

    NASA Astrophysics Data System (ADS)

    Gialanella, L.; Schürmann, D.; Strieder, F.; Di Leva, A.; De Cesare, N.; D'Onofrio, A.; Imbriani, G.; Klug, J.; Lubritto, C.; Ordine, A.; Roca, V.; Röcken, H.; Rolfs, C.; Rogalla, D.; Romano, M.; Schümann, F.; Terrasi, F.; Trautvetter, H. P.

    2004-04-01

    For improved cross-section measurements of the reaction 12C(α,γ) 16O in inverted kinematics, a recoil separator ERNA is developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with high efficiency. The 16O recoils are produced by the 12C projectiles in a windowless 4He gas target. We report on the pressure profile of the gas target, the beam suppression by the separator, and the first observation of the 16O recoils at selected energies.

  19. Thermal recoil force, telemetry, and the Pioneer anomaly

    SciTech Connect

    Toth, Viktor T.; Turyshev, Slava G.

    2009-02-15

    Precision navigation of spacecraft requires accurate knowledge of small forces, including the recoil force due to anisotropies of thermal radiation emitted by spacecraft systems. We develop a formalism to derive the thermal recoil force from the basic principles of radiative heat exchange and energy-momentum conservation. The thermal power emitted by the spacecraft can be computed from engineering data obtained from flight telemetry, which yields a practical approach to incorporate the thermal recoil force into precision spacecraft navigation. Alternatively, orbit determination can be used to estimate the contribution of the thermal recoil force. We apply this approach to the Pioneer anomaly using a simulated Pioneer 10 Doppler data set.

  20. Precision Determination of Electron Scattering Angle by Differential Nuclear Recoil Energy Method

    SciTech Connect

    Liyanage, Nilanga; Saenboonruang, Kiadtisak

    2015-09-01

    The accurate determination of the scattered electron angle is crucial to electron scattering experiments, both with open-geometry large-acceptance spectrometers and ones with dipole-type magnetic spectrometers for electron detection. In particular, for small central-angle experiments using dipole-type magnetic spectrometers, in which surveys are used to measure the spectrometer angle with respect to the primary electron beam, the importance of the scattering angle determination is emphasized. However, given the complexities of large experiments and spectrometers, the accuracy of such surveys is limited and insufficient to meet demands of some experiments. In this article, we present a new technique for determination of the electron scattering angle based on an accurate measurement of the primary beam energy and the principle of differential nuclear recoil. This technique was used to determine the scattering angle for several experiments carried out at the Experimental Hall A, Jefferson Lab. Results have shown that the new technique greatly improved the accuracy of the angle determination compared to surveys.

  1. Precision determination of electron scattering angle by differential nuclear recoil energy method

    SciTech Connect

    Liyanage, N.; Saenboonruang, K.

    2015-12-01

    The accurate determination of the scattered electron angle is crucial to electron scattering experiments, both with open-geometry large-acceptance spectrometers and ones with dipole-type magnetic spectrometers for electron detection. In particular, for small central-angle experiments using dipole-type magnetic spectrometers, in which surveys are used to measure the spectrometer angle with respect to the primary electron beam, the importance of the scattering angle determination is emphasized. However, given the complexities of large experiments and spectrometers, the accuracy of such surveys is limited and insufficient to meet demands of some experiments. In this article, we present a new technique for determination of the electron scattering angle based on an accurate measurement of the primary beam energy and the principle of differential nuclear recoil. This technique was used to determine the scattering angle for several experiments carried out at the Experimental Hall A, Jefferson Lab. Results have shown that the new technique greatly improved the accuracy of the angle determination compared to surveys.

  2. SCINTILLATION SPECTROMETER

    DOEpatents

    Bell, P.R.; Francis, J.E.

    1960-06-21

    A portable scintillation spectrometer is described which is especially useful in radio-biological studies for determining the uptake and distribution of gamma -emitting substances in tissue. The spectrometer includes a collimator having a plurality of apertures that are hexagonal in cross section. Two crystals are provided: one is activated to respond to incident rays from the collimator; the other is not activated and shields the first from external radiation.

  3. A pair spectrometer for nuclear astrophysics experiments

    NASA Astrophysics Data System (ADS)

    Guerro, L.; Di Leva, A.; Gialanella, L.; Saltarelli, A.; Schürmann, D.; Tabassam, U.; Busso, M.; De Cesare, N.; D'Onofrio, A.; Romoli, M.; Terrasi, F.

    2014-11-01

    Non-radiative transitions in nuclear capture reactions between light nuclei play a relevant role in stellar nuclear astrophysics, where nuclear processes occur at typical energies from tens to hundreds of keV. At higher energies, instead, the E0 contributions may be shadowed by more intense transitions. The experimental study of E0 transitions requires a specific detection setup, able to uniquely identify events where an electron-positron pair is produced. A compact ΔE- E charged-particle spectrometer based on two silicon detectors has been designed to be installed in the jet gas target chamber of the recoil mass separator ERNA (European Recoil separator for Nuclear Astrophysics) at the CIRCE laboratory of Caserta, Italy. The detector design, its performances and the first foreseen applications are described.

  4. Solution of high frequency variations of ERP from VLBI observations

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Li, J. L.; Wang, G. L.; Zhao, M.

    2005-01-01

    In the astrometric and geodetic VLBI data analysis software CALC/SOLVE, the high frequency variations of the Earth Rotation Parameters (ERP) are determined by a constrained continuous piecewise linear model. The ERP rate within two epoch nodes is constrained to be smaller than a limitation setting, and the ERP is forced to be continuous at epoch nodes. Observation analysis shows that when the data points are not very dense the constraint and the continuation requirement are helpful to the improvement in the stability of the solution, but degrade the independence of ERP solutions at epoch nodes as well. By using the Userpartial entry of CALC/SOLVE a direct solution module of the high frequency variations of ERP is realized without any constraint on the rate nor the requirement of continuation at nodes. It is shown from real observation reduction that the direct solution mode is feasible. In the solution of high frequency variations of ERP from VLBI observations with long period coverage, the model errors of the precession and nutation (celestial pole offset) should be taken into consideration. A corresponding module is realized and global solutions of the high frequency variation of ERP are successfully performed on the VLBI observations from 1979 to 2003. Comparison of the solutions shows that with the consideration of the pole offsets the precision of parameters could be improved obviously. In the solution of high frequency variation of ERP from VLBI observations, the direct solution mode with the consideration of the pole offsets is accordingly recommended.

  5. A digital multigate Doppler method for high frequency ultrasound.

    PubMed

    Qiu, Weibao; Ye, Zongying; Yu, Yanyan; Chen, Yan; Chi, Liyang; Mu, Peitian; Li, Guofeng; Wang, Congzhi; Xiao, Yang; Dai, Jiyan; Sun, Lei; Zheng, Hairong

    2014-01-01

    Noninvasive visualization of blood flow with high frequency Doppler ultrasound has been extensively used to assess the morphology and hemodynamics of the microcirculation. A completely digital implementation of multigate pulsed-wave (PW) Doppler method was proposed in this paper for high frequency ultrasound applications. Analog mixer was eliminated by a digital demodulator and the same data acquisition path was shared with traditional B-mode imaging which made the design compact and flexible. Hilbert transform based quadrature demodulation scheme was employed to achieve the multigate Doppler acquisition. A programmable high frequency ultrasound platform was also proposed to facilitate the multigate flow visualization. Experimental results showed good performance of the proposed method. Parabolic velocity gradient inside the vessel and velocity profile with different time slots were acquired to demonstrate the functionality of the multigate Doppler. Slow wall motion was also recorded by the proposed method.

  6. Switch over to the high frequency rf systems near transition

    SciTech Connect

    Brennan, J.M.; Wei, J.

    1988-01-01

    The purpose of this note is to point out that since bunch narrowing naturally occurs in the acceleration process in the vicinity of transition, it should be possible to switch over to the high frequency system close to transition when the bunch has narrowed enough to fit directly into the high frequency bucket. The advantage of this approach is the simplicity, no extra components or gymnastics are required of the low frequency system. The disadvantage, of course, is for protons which do not go through transition. But on the other hand, there is no shortage of intensity for protons and so it should be possible to keep the phase space area low for protons, and then matching to the high frequency bucket should be easily accomplished by adiabatic compression. 3 refs., 7 figs.

  7. The SAGE spectrometer: A tool for combined in-beam γ-ray and conversion electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Papadakis, P.; Herzberg, R.-D.; Pakarinen, J.; Greenlees, P. T.; Sorri, J.; Butler, P. A.; Coleman-Smith, P. J.; Cox, D.; Cresswell, J. R.; Hauschild, K.; Jones, P.; Julin, R.; Lazarus, I. H.; Letts, S. C.; Parr, E.; Peura, P.; Pucknell, V. F. E.; Rahkila, P.; Sampson, J.; Sandzelius, M.; Seddon, D. A.; Simpson, J.; Thornhill, J.; Wells, D.

    2011-09-01

    The SAGE spectrometer allows simultaneous in-beam γ-ray and internal conversion electron measurements, by combining a germanium detector array with a highly segmented silicon detector and an electron transport system. SAGE is coupled with the ritu gas-filled recoil separator and the great focal-plane spectrometer for recoil-decay tagging studies. Digital electronics are used both for the γ ray and the electron parts of the spectrometer. SAGE was commissioned in the Accelerator Laboratory of the University of Jyväskylä in the beginning of 2010.

  8. High Frequency Haplotypes are Expected Events, not Historical Figures.

    PubMed

    Guillot, Elsa G; Cox, Murray P

    2015-01-01

    Cultural transmission of reproductive success states that successful men have more children and pass this raised fecundity to their offspring. Balaresque and colleagues found high frequency haplotypes in a Central Asian Y chromosome dataset, which they attribute to cultural transmission of reproductive success by prominent historical men, including Genghis Khan. Using coalescent simulation, we show that these high frequency haplotypes are consistent with a neutral model, where they commonly appear simply by chance. Hence, explanations invoking cultural transmission of reproductive success are statistically unnecessary.

  9. High Frequency Haplotypes are Expected Events, not Historical Figures

    PubMed Central

    Guillot, Elsa G.; Cox, Murray P.

    2016-01-01

    Cultural transmission of reproductive success states that successful men have more children and pass this raised fecundity to their offspring. Balaresque and colleagues found high frequency haplotypes in a Central Asian Y chromosome dataset, which they attribute to cultural transmission of reproductive success by prominent historical men, including Genghis Khan. Using coalescent simulation, we show that these high frequency haplotypes are consistent with a neutral model, where they commonly appear simply by chance. Hence, explanations invoking cultural transmission of reproductive success are statistically unnecessary. PMID:26834987

  10. Real-Time, High-Frequency QRS Electrocardiograph

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; DePalma, Jude L.; Moradi, Saeed

    2003-01-01

    An electronic system that performs real-time analysis of the low-amplitude, high-frequency, ordinarily invisible components of the QRS portion of an electrocardiographic signal in real time has been developed. Whereas the signals readily visible on a conventional electrocardiogram (ECG) have amplitudes of the order of a millivolt and are characterized by frequencies <100 Hz, the ordinarily invisible components have amplitudes in the microvolt range and are characterized by frequencies from about 150 to about 250 Hz. Deviations of these high-frequency components from a normal pattern can be indicative of myocardial ischemia or myocardial infarction

  11. A MEMS-based high frequency x-ray chopper.

    PubMed

    Siria, A; Dhez, O; Schwartz, W; Torricelli, G; Comin, F; Chevrier, J

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  12. Induced and Form Birefringence in High-Frequency Polarization Gratings

    NASA Astrophysics Data System (ADS)

    Martinez-Ponce, Geminiano; Solano, Cristina

    2001-08-01

    High-frequency phase polarization gratings are fabricated holographically in dichromated gelatin dyed with malachite green. It is observed that the intensity of the -1 diffracted beam is a sinusoidal function of the incident polarization angle. In addition, we analyze the dependence of the diffracted order polarization on grating frequency. It is evident from our results that form birefringence becomes significant when the grating period is smaller than the illumination wavelength, thus modifying the optically induced birefringence. Then, in polarization hologram reconstruction, it is not possible to obtain the polarization distribution at the recording step for high-frequency objects.

  13. Spectrometer gun

    DOEpatents

    Waechter, D.A.; Wolf, M.A.; Umbarger, C.J.

    1981-11-03

    A hand-holdable, battery-operated, microprocessor-based spectrometer gun is described that includes a low-power matrix display and sufficient memory to permit both real-time observation and extended analysis of detected radiation pulses. Universality of the incorporated signal processing circuitry permits operation with various detectors having differing pulse detection and sensitivity parameters.

  14. Spectrometer gun

    DOEpatents

    Waechter, David A.; Wolf, Michael A.; Umbarger, C. John

    1985-01-01

    A hand-holdable, battery-operated, microprocessor-based spectrometer gun includes a low-power matrix display and sufficient memory to permit both real-time observation and extended analysis of detected radiation pulses. Universality of the incorporated signal processing circuitry permits operation with various detectors having differing pulse detection and sensitivity parameters.

  15. HISS spectrometer

    SciTech Connect

    Greiner, D.E.

    1984-11-01

    This talk describes the Heavy Ion Spectrometer System (HISS) facility at the Lawrence Berkeley Laboratory's Bevalac. Three completed experiments and their results are illustrated. The second half of the talk is a detailed discussion of the response of drift chambers to heavy ions. The limitations of trajectory measurement over a large range in incident particle charge are presented.

  16. High-frequency hearing in seals and sea lions.

    PubMed

    Cunningham, Kane A; Reichmuth, Colleen

    2016-01-01

    Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism. PMID:26519092

  17. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications.

    PubMed

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K Kirk

    2011-02-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol-gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed.

  18. Factors Affecting the Benefits of High-Frequency Amplification

    ERIC Educational Resources Information Center

    Horwitz, Amy R.; Ahlstrom, Jayne B.; Dubno, Judy R.

    2008-01-01

    Purpose: This study was designed to determine the extent to which high-frequency amplification helped or hindered speech recognition as a function of hearing loss, gain-frequency response, and background noise. Method: Speech recognition was measured monaurally under headphones for nonsense syllables low-pass filtered in one-third-octave steps…

  19. Disappearance of high frequency modes in polymer dilute solution viscoelasticity

    NASA Astrophysics Data System (ADS)

    Larson, Ronald; Jain, Semant

    2009-03-01

    We address the problem of the ``missing modes'' in the high frequency rheology of dilute polymer solutions. According to the Rouse-Zimm theory, the slow viscoelastic response of dilute polymers is dominated by the collective motion of the chain, as described by a bead-spring model. However, one expects this description to break down at high frequencies at which chain motion on scales too small to be represented by beads and springs should be evident; this motion should be controlled by rotations of individual backbone bonds of the polymer. The viscoelastic response produced by these ``local modes'' is observable in polymer melts; however, for dilute polymer solutions, the ``local modes'' are absent from viscoelastic spectra, as shown by Schrag and coworkers (Peterson, et al., J. Polym. Sci. B, 39:2860 (2001)). Here we address this problem by directly simulating single polymer chains using Brownian dynamics simulations, with realistic bending and torsional potentials. We show using these simulations that the ``missing modes'' result from barriers to bond rotation that make the chain ``dynamically rigid'' at high frequencies. As a result, the ``dynamical Kuhn length'' of the chain exceeds the static one, and the chain at high frequencies is not able to explore local conformations as fast as would be needed for their relaxation to contribute to the mechanical relaxation spectrum.

  20. Pulsating fireballs with high-frequency sheath-plasma instabilities

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Gruenwald, J.; Ionita, C.; Schrittwieser, R.

    2011-08-01

    High-frequency instabilities are observed in connection with unstable fireballs. Fireballs are discharge phenomena near positively biased electrodes in discharge plasmas. They are bounded by a double layer whose potential is of order of the ionization potential. Fireballs become unstable when plasma losses and plasma production are not in balance, resulting in periodic fireball pulses. High-frequency instabilities in the range of the electron plasma frequency have been observed. These occur between fireball pulses, hence are not due to electron beam-plasma instabilities since there are no beams without double layers. The instability has been identified as a sheath-plasma instability. Electron inertia creates a phase shift between high-frequency current and electric fields which destabilizes the sheath-plasma resonance. High-frequency signals are observed in the current to the electrode and on probes near the sheath of the electrode. Waveforms and spectra are presented, showing bursty emissions, phase shifts, frequency jumps, beat phenomena between two sheaths, and nonlinear effects such as amplitude clipping. These reveal many interesting properties of sheaths with periodic ionization phenomena.

  1. Collocations of High Frequency Noun Keywords in Prescribed Science Textbooks

    ERIC Educational Resources Information Center

    Menon, Sujatha; Mukundan, Jayakaran

    2012-01-01

    This paper analyses the discourse of science through the study of collocational patterns of high frequency noun keywords in science textbooks used by upper secondary students in Malaysia. Research has shown that one of the areas of difficulty in science discourse concerns lexis, especially that of collocations. This paper describes a corpus-based…

  2. High frequency excitation of Earth rotation parameters (ERP) from atmosphere.

    NASA Astrophysics Data System (ADS)

    Xie, Boquan; Zheng, Dawei

    1996-06-01

    The data sets of Earth rotation parameters measured by space geodetic techniques and atmospheric angular momentum reduced by the global meteorological data from 1983 through 1992 are used to analyze and study the high frequency excitations of Earth rotation parameters for the length of day and polar motion up to the monthly time scale from the atmosphere. The main results are given.

  3. High-frequency hearing in seals and sea lions.

    PubMed

    Cunningham, Kane A; Reichmuth, Colleen

    2016-01-01

    Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism.

  4. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications

    PubMed Central

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K. Kirk

    2011-01-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol–gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed. PMID:21720451

  5. High-Frequency Oscillations and Seizure Generation in Neocortical Epilepsy

    ERIC Educational Resources Information Center

    Worrell, Greg A.; Parish, Landi; Cranstoun, Stephen D.; Jonas, Rachel; Baltuch, Gordon; Litt, Brian

    2004-01-01

    Neocortical seizures are often poorly localized, explosive and widespread at onset, making them poorly amenable to epilepsy surgery in the absence of associated focal brain lesions. We describe, for the first time in an unselected group of patients with neocortical epilepsy, the finding that high-frequency (60--100 Hz) epileptiform oscillations…

  6. A novel probe head for high-field, high-frequency electron paramagnetic resonance

    NASA Astrophysics Data System (ADS)

    Annino, G.; Cassettari, M.; Longo, I.; Martinelli, M.; Van Bentum, P. J. M.; Van der Horst, E.

    1999-03-01

    A probe head especially useful for electron paramagnetic resonance (EPR) spectrometers working at high field—high frequency is presented. The probe head is based on the whispering gallery mode dielectric resonators that proved very effective in the ultrahigh frequency range. The excitation network uses a properly shaped dielectric waveguide sharing its external field pattern with the field of the resonators. Very simple resonators made with polyethylene in both single and doubly stacked disk configurations are used. The experimental characterization by a submillimeter network analyzer shows for the resonances studied in a wide range of frequencies up to ≈400 GHz high loaded merit factor QL values and good coupling factors. Resonators also maintain their general characteristics when large quantities of low loss samples for EPR measurements are properly inserted. Preliminary EPR spectra of diphenylpicrylhyldrazyl at 7 and 10 T obtained with the novel apparatus are finally presented.

  7. A gun recoil system employing a magnetorheological fluid damper

    NASA Astrophysics Data System (ADS)

    Li, Z. C.; Wang, J.

    2012-10-01

    This research aims to design and control a full scale gun recoil buffering system which works under real firing impact loading conditions. A conventional gun recoil absorber is replaced with a controllable magnetorheological (MR) fluid damper. Through dynamic analysis of the gun recoil system, a theoretical model for optimal design and control of the MR fluid damper for impact loadings is derived. The optimal displacement, velocity and optimal design rules are obtained. By applying the optimal design theory to protect against impact loadings, an MR fluid damper for a full scale gun recoil system is designed and manufactured. An experimental study is carried out on a firing test rig which consists of a 30 mm caliber, multi-action automatic gun with an MR damper mounted to the fixed base through a sliding guide. Experimental buffering results under passive control and optimal control are obtained. By comparison, optimal control is better than passive control, because it produces smaller variation in the recoil force while achieving less displacement of the recoil body. The optimal control strategy presented in this paper is open-loop with no feedback system needed. This means that the control process is sensor-free. This is a great benefit for a buffering system under impact loading, especially for a gun recoil system which usually works in a harsh environment.

  8. Modeling the Observability of Recoiling Black Holes as Offset Quasars

    NASA Astrophysics Data System (ADS)

    Blecha, Laura; Torrey, Paul; Vogelsberger, Mark; Genel, Shy; Springel, Volker; Sijacki, Debora; Snyder, Gregory; Bird, Simeon; Nelson, Dylan; Xu, Dandan; Hernquist, Lars

    2015-08-01

    The merger of two supermassive black holes (SMBHs) imparts a gravitational-wave (GW) recoil kick to the remnant SMBH. In extreme cases these kicks may be thousands of km/s -- enough to easily eject them from their host galaxies. Moderate recoil kicks may also cause substantial displacements of the SMBH, however. An actively-accreting, recoiling SMBH may be observable as an offset quasar. Prior to the advent of a space-based GW observatory, detections of these offset quasars may offer the best chance for identifying recent SMBH mergers. Indeed, observational searches for recoiling quasars have already identified several promising candidates. However, systematic searches for recoils are currently hampered by large uncertainties regarding how often offset quasars should be observable, where they are most likely to be found, and whether BH spin alignment prior to merger is efficient at suppressing large recoils. Motivated by this, we have developed a model for the observable population of recoiling quasars in a cosmological framework, utilizing detailed information about the progenitor galaxies from state-of-the-art cosmological hydrodynamic simulations (the Illustris Project). The model for offset quasar lifetimes includes a physically-motivated, time-dependent model for accretion onto kicked SMBHs, and results are analyzed for a range of possible BH spin alignment models. We find that the observability of offset quasars depends strongly on the efficiency of pre-merger spin alignment, with promising indications that observations of recoils could distinguish between at least the extreme limits of spin alignment models. Our results also suggest that observable offset quasars should inhabit preferred types of host galaxies, where again these populations depend on the degree of pre-merger spin alignment. These findings will be valuable for planned and future dedicated searches for recoiling quasars, and they indicate that such objects might be used to place indirect

  9. Spectrometers for fast neutrons from solar flares.

    PubMed

    Slobodrian, R J; Potvin, L; Rioux, C

    1994-10-01

    Neutrons with energies exceeding 1 GeV are emitted in the course of solar flares. Suitable dedicated neutron spectrometers with directional characteristics are necessary for a systematic spectroscopy of solar neutrons. We report here a study of instruments based on the detection of proton recoils from hydrogenous media, with double scattering in order to provide directional information, and also a novel scheme based on the detection of radiation from the neutron magnetic dipole moment, permitting also directional detection of neutrons. Specific designs and detection systems are discussed.

  10. Difference between a Photon's Momentum and an Atom's Recoil

    SciTech Connect

    Gibble, Kurt

    2006-08-18

    When an atom absorbs a photon from a laser beam that is not an infinite plane wave, the atom's recoil is less than ({Dirac_h}/2{pi})k in the propagation direction. We show that the recoils in the transverse directions produce a lensing of the atomic wave functions, which leads to a frequency shift that is not discrete but varies linearly with the field amplitude and strongly depends on the atomic state detection. The same lensing effect is also important for microwave atomic clocks. The frequency shifts are of the order of the naive recoil shift for the transverse wave vector of the photons.

  11. The Spectrometer

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2012-03-01

    In the fall of 1999 I was shown an Ocean Optics spectrometer-in-the-computer at St. Patricks College at Maynooth, Ireland, and thought that I had seen heaven. Of course, it could not resolve the sodium D-lines (I had done that many years before with a homemade wire diffraction grating ), and I began to realize that inside was some familiar old technology. In this paper I would like to discuss its ancestors.

  12. The Spectrometer

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    2012-01-01

    In the fall of 1999 I was shown an Ocean Optics spectrometer-in-the-computer at St. Patricks College at Maynooth, Ireland, and thought that I had seen heaven. Of course, it could not resolve the sodium D-lines (I had done that many years before with a homemade wire diffraction grating), and I began to realize that inside was some familiar old…

  13. How High Frequency Trading Affects a Market Index

    PubMed Central

    Kenett, Dror Y.; Ben-Jacob, Eshel; Stanley, H. Eugene; gur-Gershgoren, Gitit

    2013-01-01

    The relationship between a market index and its constituent stocks is complicated. While an index is a weighted average of its constituent stocks, when the investigated time scale is one day or longer the index has been found to have a stronger effect on the stocks than vice versa. We explore how this interaction changes in short time scales using high frequency data. Using a correlation-based analysis approach, we find that in short time scales stocks have a stronger influence on the index. These findings have implications for high frequency trading and suggest that the price of an index should be published on shorter time scales, as close as possible to those of the actual transaction time scale. PMID:23817553

  14. Transformation ray method: controlling high frequency elastic waves (L).

    PubMed

    Chang, Zheng; Liu, Xiaoning; Hu, Gengkai; Hu, Jin

    2012-10-01

    Elastic ray theory is a high frequency asymptotic approximation of solution of elastodynamic equation, and is widely used in seismology. In this paper, the form invariance under a general spatial mapping and high frequency wave control have been examined by transformation method. It is showed that with the constraint of major and minor symmetry of the transformed elastic tensor, the eikonal equation keeps its form under a general mapping, however, the transport equation loses its form except for conformal mapping. Therefore, the elastic ray path can be controlled in an exact manner by a transformation method, whereas energy distribution along the ray is only approximately controlled. An elastic rotator based on ray tracing method is also provided to illustrate the method and to access the approximation. PMID:23039561

  15. Clustered Desynchronization from High-Frequency Deep Brain Stimulation.

    PubMed

    Wilson, Dan; Moehlis, Jeff

    2015-12-01

    While high-frequency deep brain stimulation is a well established treatment for Parkinson's disease, its underlying mechanisms remain elusive. Here, we show that two competing hypotheses, desynchronization and entrainment in a population of model neurons, may not be mutually exclusive. We find that in a noisy group of phase oscillators, high frequency perturbations can separate the population into multiple clusters, each with a nearly identical proportion of the overall population. This phenomenon can be understood by studying maps of the underlying deterministic system and is guaranteed to be observed for small noise strengths. When we apply this framework to populations of Type I and Type II neurons, we observe clustered desynchronization at many pulsing frequencies. PMID:26713619

  16. High-frequency oscillations and the neurobiology of schizophrenia.

    PubMed

    Uhlhaas, Peter J; Singer, Wolf

    2013-09-01

    Neural oscillations at low- and high-frequency ranges are a fundamental feature of large-scale networks. Recent evidence has indicated that schizophrenia is associated with abnormal amplitude and synchrony of oscillatory activity, in particular, at high (beta/gamma) frequencies. These abnormalities are observed during task-related and spontaneous neuronal activity which may be important for understanding the pathophysiology of the syndrome. In this paper, we shall review the current evidence for impaired beta/gamma-band oscillations and their involvement in cognitive functions and certain symptoms of the disorder. In the first part, we will provide an update on neural oscillations during normal brain functions and discuss underlying mechanisms. This will be followed by a review of studies that have examined high-frequency oscillatory activity in schizophrenia and discuss evidence that relates abnormalities of oscillatory activity to disturbed excitatory/inhibitory (E/I) balance. Finally, we shall identify critical issues for future research in this area.

  17. High-Frequency Power Gain in the Mammalian Cochlea

    NASA Astrophysics Data System (ADS)

    Maoiléidigh, Dáibhid Ó.; Hudspeth, A. J.

    2011-11-01

    Amplification in the mammalian inner ear is thought to result from a nonlinear active process known as the cochlear amplifier. Although there is much evidence that outer hair cells (OHCs) play a central role in the cochlear amplifier, the mechanism of amplification remains uncertain. In non-mammalian ears hair bundles can perform mechanical work and account for the active process in vitro, yet in the mammalian cochlea membrane-based electromotility is required for amplification in vivo. A key issue is how OHCs conduct mechanical power amplification at high frequencies. We present a physical model of a segment of the mammalian cochlea that can amplify the power of external signals. In this representation both electromotility and active hair-bundle motility are required for mechanical power gain at high frequencies. We demonstrate how the endocochlear potential, the OHC resting potential, Ca2+ gradients, and ATP-fueled myosin motors serve as the energy sources underlying mechanical power gain in the cochlear amplifier.

  18. High Frequency Amplitude Detector for GMI Magnetic Sensors

    PubMed Central

    Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul

    2014-01-01

    A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted. PMID:25536003

  19. Clustered Desynchronization from High-Frequency Deep Brain Stimulation

    PubMed Central

    Wilson, Dan; Moehlis, Jeff

    2015-01-01

    While high-frequency deep brain stimulation is a well established treatment for Parkinson’s disease, its underlying mechanisms remain elusive. Here, we show that two competing hypotheses, desynchronization and entrainment in a population of model neurons, may not be mutually exclusive. We find that in a noisy group of phase oscillators, high frequency perturbations can separate the population into multiple clusters, each with a nearly identical proportion of the overall population. This phenomenon can be understood by studying maps of the underlying deterministic system and is guaranteed to be observed for small noise strengths. When we apply this framework to populations of Type I and Type II neurons, we observe clustered desynchronization at many pulsing frequencies. PMID:26713619

  20. Parametric Study of High Frequency Pulse Detonation Tubes

    NASA Technical Reports Server (NTRS)

    Cutler, Anderw D.

    2008-01-01

    This paper describes development of high frequency pulse detonation tubes similar to a small pulse detonation engine (PDE). A high-speed valve injects a charge of a mixture of fuel and air at rates of up to 1000 Hz into a constant area tube closed at one end. The reactants detonate in the tube and the products exit as a pulsed jet. High frequency pressure transducers are used to monitor the pressure fluctuations in the device and thrust is measured with a balance. The effects of injection frequency, fuel and air flow rates, tube length, and injection location are considered. Both H2 and C2H4 fuels are considered. Optimum (maximum specific thrust) fuel-air compositions and resonant frequencies are identified. Results are compared to PDE calculations. Design rules are postulated and applications to aerodynamic flow control and propulsion are discussed.

  1. High frequency vibration analysis by the complex envelope vectorization.

    PubMed

    Giannini, O; Carcaterra, A; Sestieri, A

    2007-06-01

    The complex envelope displacement analysis (CEDA) is a procedure to solve high frequency vibration and vibro-acoustic problems, providing the envelope of the physical solution. CEDA is based on a variable transformation mapping the high frequency oscillations into signals of low frequency content and has been successfully applied to one-dimensional systems. However, the extension to plates and vibro-acoustic fields met serious difficulties so that a general revision of the theory was carried out, leading finally to a new method, the complex envelope vectorization (CEV). In this paper the CEV method is described, underlying merits and limits of the procedure, and a set of applications to vibration and vibro-acoustic problems of increasing complexity are presented.

  2. Missing Mass Recoiling Against the Charged D

    SciTech Connect

    Cain, Hillary

    2003-09-05

    This paper chronicles the investigation of a peak in the BaBar mass data set of mass recoiling against charged D*s. Our hypothesis is that the peak at 2620 MeV is a reflection of the D{sub s}* and {pi} system. Specifically, we explored the idea that the peak might be a reflection from the decay B {yields} D**{sup -} D*{sub s}{sup +} with the D**{sup -} {yields} D*{sup -} {pi}. Theoretically, when the D**{sup -} decays, the trajectory of the resulting {pi} will form an angle with the D*{sub s}{sup +}, and different angles impart difference masses to the system over a range of a GeV or so. If quantum mechanics dictates that their paths will form a particular angle more often than others, a peak would appear in the histogram of their collective mass. Using the Monte Carlo model of particle collision events, Anders Ryd's EVTGEN program, C++ code derived from GeneratorsQA, and PAW, we tested the hypothesis that the peak might be a reflection of the system, but found that this possible explanation could not account for the peak. No 2620 MeV peak appears in the histogram of the system mass. We therefore discount the hypothesis and conclude that some other reflection, statistical fluctuation, or particle is causing the peak.

  3. Microstrip antenna modeling and measurement at high frequencies

    SciTech Connect

    Bevensee, R.M.

    1986-04-30

    This report addresses the task C(i) of the Proposal for Microstrip Antenna Modeling and Measurement at High Frequencies by the writer, July 1985. The task is: Assess the advantages and disadvantages of the three computational approaches outlined in the Proposal, including any difficulties to be resolved and an estimate of the time required to implement each approach. The three approaches are (1) Finite Difference, (2) Sommerfeld-GTD-MOM, and (3) Surface Intergral Equations - MOM. These are discussed in turn.

  4. High-frequency audibility: benefits for hearing-impaired listeners.

    PubMed

    Hogan, C A; Turner, C W

    1998-07-01

    The present study was a systematic investigation of the benefit of providing hearing-impaired listeners with audible high-frequency speech information. Five normal-hearing and nine high-frequency hearing-impaired listeners identified nonsense syllables that were low-pass filtered at a number of cutoff frequencies. As a means of quantifying audibility for each condition, Articulation Index (AI) was calculated for each condition for each listener. Most hearing-impaired listeners demonstrated an improvement in speech recognition as additional audible high-frequency information was provided. In some cases for more severely impaired listeners, increasing the audibility of high-frequency speech information resulted in no further improvement in speech recognition, or even decreases in speech recognition. A new measure of how well hearing-impaired listeners used information within specific frequency bands called "efficiency" was devised. This measure compared the benefit of providing a given increase in speech audibility to a hearing-impaired listener to the benefit observed in normal-hearing listeners for the same increase in speech audibility. Efficiencies were calculated using the old AI method and the new AI method (which takes into account the effects of high speech presentation levels). There was a clear pattern in the results suggesting that as the degree of hearing loss at a given frequency increased beyond 55 dB HL, the efficacy of providing additional audibility to that frequency region was diminished, especially when this degree of hearing loss was present at frequencies of 4000 Hz and above. A comparison of analyses from the "old" and "new" AI procedures suggests that some, but not all, of the deficiencies of speech recognition in these listeners was due to high presentation levels.

  5. High frequency resolution terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Sangala, Bagvanth Reddy

    2013-12-01

    A new method for the high frequency resolution terahertz time-domain spectroscopy is developed based on the characteristic matrix method. This method is useful for studying planar samples or stack of planar samples. The terahertz radiation was generated by optical rectification in a ZnTe crystal and detected by another ZnTe crystal via electro-optic sampling method. In this new characteristic matrix based method, the spectra of the sample and reference waveforms will be modeled by using characteristic matrices. We applied this new method to measure the optical constants of air. The terahertz transmission through the layered systems air-Teflon-air-Quartz-air and Nitrogen gas-Teflon-Nitrogen gas-Quartz-Nitrogen gas was modeled by the characteristic matrix method. A transmission coefficient is derived from these models which was optimized to fit the experimental transmission coefficient to extract the optical constants of air. The optimization of an error function involving the experimental complex transmission coefficient and the theoretical transmission coefficient was performed using patternsearch algorithm of MATLAB. Since this method takes account of the echo waveforms due to reflections in the layered samples, this method allows analysis of longer time-domain waveforms giving rise to very high frequency resolution in the frequency-domain. We have presented the high frequency resolution terahertz time-domain spectroscopy of air and compared the results with the literature values. We have also fitted the complex susceptibility of air to the Lorentzian and Gaussian functions to extract the linewidths.

  6. Nonlocal theory for heat transport at high frequencies

    NASA Astrophysics Data System (ADS)

    Koh, Yee Kan; Cahill, David G.; Sun, Bo

    2014-11-01

    We develop a nonlocal theory for heat conduction under high-frequency temperature fields and apply the theory to explain reductions of the apparent thermal conductivity observed in recent experiments. Our nonlocal theory is an analytical solution of the Boltzmann transport equation for phonons in a semi-infinite solid, similar to a prior nonlocal theory for heat conduction under a high-temperature gradient but subjected to periodic heating at the surface. The boundary condition of periodic heating, as opposed to prior calculations of heating by a single laser pulse, better mimics time-domain thermoreflectance (TDTR) and broadband frequency-domain thermoreflectance (BB-FDTR) measurements. We find that, except for pure crystals at high frequencies, the effective thermal conductivity derived using the nonlocal theory compares well with calculations of a modified Callaway model that includes an upper limit on the phonon mean-free path at twice the thermal penetration depth. For pure crystals, however, the effective thermal conductivity derived from the out-of-phase calculations are independent of frequency, in agreement with prior TDTR measurements, due to the countereffect of reduced heat flux and diminished relative phase between the heat flux and temperature oscillations at high frequencies. Our results suggest that empirical interpretation of ballistic phonons not contributing to heat conduction is not general and can only be applied to measurements on alloys and not pure crystals, even when a large laser spot size is used in the experiments and the interfacial thermal resistance is negligible.

  7. The Origin of High-Frequency Hearing in Whales.

    PubMed

    Churchill, Morgan; Martinez-Caceres, Manuel; de Muizon, Christian; Mnieckowski, Jessica; Geisler, Jonathan H

    2016-08-22

    Odontocetes (toothed whales) rely upon echoes of their own vocalizations to navigate and find prey underwater [1]. This sensory adaptation, known as echolocation, operates most effectively when using high frequencies, and odontocetes are rivaled only by bats in their ability to perceive ultrasonic sound greater than 100 kHz [2]. Although features indicative of ultrasonic hearing are present in the oldest known odontocetes [3], the significance of this finding is limited by the methods employed and taxa sampled. In this report, we describe a new xenorophid whale (Echovenator sandersi, gen. et sp. nov.) from the Oligocene of South Carolina that, as a member of the most basal clade of odontocetes, sheds considerable light on the evolution of ultrasonic hearing. By placing high-resolution CT data from Echovenator sandersi, 2 hippos, and 23 fossil and extant whales in a phylogenetic context, we conclude that ultrasonic hearing, albeit in a less specialized form, evolved at the base of the odontocete radiation. Contrary to the hypothesis that odontocetes evolved from low-frequency specialists [4], we find evidence that stem cetaceans, the archaeocetes, were more sensitive to high-frequency sound than their terrestrial ancestors. This indicates that selection for high-frequency hearing predates the emergence of Odontoceti and the evolution of echolocation. PMID:27498568

  8. High-frequency hearing loss among mobile phone users.

    PubMed

    Velayutham, P; Govindasamy, Gopala Krishnan; Raman, R; Prepageran, N; Ng, K H

    2014-01-01

    The objective of this study is to assess high frequency hearing (above 8 kHz) loss among prolonged mobile phone users is a tertiary Referral Center. Prospective single blinded study. This is the first study that used high-frequency audiometry. The wide usage of mobile phone is so profound that we were unable to find enough non-users as a control group. Therefore we compared the non-dominant ear to the dominant ear using audiometric measurements. The study was a blinded study wherein the audiologist did not know which was the dominant ear. A total of 100 subjects were studied. Of the subjects studied 53% were males and 47% females. Mean age was 27. The left ear was dominant in 63%, 22% were dominant in the right ear and 15% did not have a preference. This study showed that there is significant loss in the dominant ear compared to the non-dominant ear (P < 0.05). Chronic usage mobile phone revealed high frequency hearing loss in the dominant ear (mobile phone used) compared to the non dominant ear.

  9. Source of high-frequency oscillations in oblique saccade trajectory.

    PubMed

    Ghasia, Fatema F; Shaikh, Aasef G

    2014-04-01

    Most common eye movements, oblique saccades, feature rapid velocity, precise amplitude, but curved trajectory that is variable from trial-to-trial. In addition to curvature and inter-trial variability, the oblique saccade trajectory also features high-frequency oscillations. A number of studies proposed the physiological basis of the curvature and inter-trial variability of the oblique saccade trajectory, but kinematic characteristics of high-frequency oscillations are yet to be examined. We measured such oscillations and compared their properties with orthogonal pure horizontal and pure vertical oscillations generated during pure vertical and pure horizontal saccades, respectively. We found that the frequency of oscillations during oblique saccades ranged between 15 and 40 Hz, consistent with the frequency of orthogonal saccadic oscillations during pure horizontal or pure vertical saccades. We also found that the amplitude of oblique saccade oscillations was larger than pure horizontal and pure vertical saccadic oscillations. These results suggest that the superimposed high-frequency sinusoidal oscillations upon the oblique saccade trajectory represent reverberations of disinhibited circuit of reciprocally innervated horizontal and vertical burst generators.

  10. Neuronal morphology generates high-frequency firing resonance.

    PubMed

    Ostojic, Srdjan; Szapiro, Germán; Schwartz, Eric; Barbour, Boris; Brunel, Nicolas; Hakim, Vincent

    2015-05-01

    The attenuation of neuronal voltage responses to high-frequency current inputs by the membrane capacitance is believed to limit single-cell bandwidth. However, neuronal populations subject to stochastic fluctuations can follow inputs beyond this limit. We investigated this apparent paradox theoretically and experimentally using Purkinje cells in the cerebellum, a motor structure that benefits from rapid information transfer. We analyzed the modulation of firing in response to the somatic injection of sinusoidal currents. Computational modeling suggested that, instead of decreasing with frequency, modulation amplitude can increase up to high frequencies because of cellular morphology. Electrophysiological measurements in adult rat slices confirmed this prediction and displayed a marked resonance at 200 Hz. We elucidated the underlying mechanism, showing that the two-compartment morphology of the Purkinje cell, interacting with a simple spiking mechanism and dendritic fluctuations, is sufficient to create high-frequency signal amplification. This mechanism, which we term morphology-induced resonance, is selective for somatic inputs, which in the Purkinje cell are exclusively inhibitory. The resonance sensitizes Purkinje cells in the frequency range of population oscillations observed in vivo. PMID:25948257

  11. High-frequency ultrasound in parotid gland disease.

    PubMed

    Onkar, Prashant Madhukar; Ratnaparkhi, Chetana; Mitra, Kajal

    2013-12-01

    Parotid gland is involved in many inflammatory and neoplastic conditions. Many a times, it is difficult to ascertain the type of swelling by clinical examination. The anatomy and various abnormalities of the glands are very easily visualized by high-frequency ultrasound. Ultrasound can confirm the presence of the mass with sensitivity up to 100%. It can demonstrate whether a lesion is located in the parotid gland or outside. It can help in differentiating benign from malignant neoplasms and local staging of the mass in malignant lesions. In addition, ultrasound can identify those entities that may not need surgical intervention. The glands appear enlarged and show altered echopattern in acute inflammation and may be normal or reduce in size in chronic inflammation. Other pathologies that involve salivary glands are sialolithiasis and various benign and malignant neoplasms. Ultrasound many times suggests final diagnosis or supplies important differential diagnosis. In this article, the use of high-frequency ultrasound in parotid disease is discussed, and sonographic features of different parotid pathologies are reviewed with examples illustrated. High-frequency ultrasound is the first and many a times the only imaging investigation done for evaluation of parotid glands.

  12. Recoil splitting of x-ray-induced optical fluorescence

    SciTech Connect

    Gavrilyuk, S.; Aagren, H.; Gel'mukhanov, F.; Sun, Y.-P.; Levin, S.

    2010-03-15

    We show that the anisotropy of the recoil velocity distribution of x-ray-ionized atoms or molecules leads to observable splittings in subsequent optical fluorescence or absorption when the polarization vector of the x rays is parallel to the momentum of the fluorescent photons. The order of the magnitude of the recoil-induced splitting is about 10 {mu}eV, which can be observed using Fourier or laser-absorption spectroscopic techniques.

  13. RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES

    SciTech Connect

    Liu, F. K.; Wang Dong; Chen Xian

    2012-02-20

    Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q {approx}> 0.3 with a minimum possible value q{sub min} {approx_equal} 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s{sup -1} in the direction within an angle {approx}< 40 Degree-Sign relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

  14. Characteristics of high-frequency consumers of prescription psychoactive drugs.

    PubMed

    Chambers, C D; White, O Z

    1980-01-01

    Two cohorts of white middle-class housewives who reported themselves as high-frequency consumers of prescription sedatives, tranquilizers, and stimulants have been studied and their characteristics have been reported. One group of these women are residents of a Midwestern state, and the other in a Southern state. These women can best be described as follows: Most reported their primary physician as being a general practitioner (60%), and most reported they had consulted two or more separate physicians during the last year (78%). More than a third (36%) had seen at least three different physicians. Interestingly, while most of these women were consulting general practitioners and/or internists, almost a third were presenting them with general psychological complaints. The self-reported high-frequency users most frequently used the relaxants/minor tranquilizers (64%), followed by sedatives (41%), stimulants (31%), and major tranquilizers (7%). Almost half of all these high-frequency medicine consumers were also regular drinkers (47%), and some 13 to 17% could be considered as heavy drinkers. The majority of the relaxant/minor tranquilizer users had been taking the medications daily or several times a week for at least six months. Less than half of these users, however, felt their "condition" had gotten "better." The majority of the sedative users had also been taking the medications daily or several times a week for at least six months. Less than a third of these users felt the condition that precipitated the prescription had improved during this period of use. Of major importance, only a minority of these long-term high-frequency users of sedatives and relaxants/minor tranquilizers believe these drugs to be habit-forming or to have any potential for physical or psychological harm. Although the stimulant-users were also found to be high-frequency consumers, stimulant-users were found to have been using these drugs for a shorter period of time. There also appears to

  15. Phosphorus geochemical cycling inferences from high frequency lake monitoring

    NASA Astrophysics Data System (ADS)

    Crockford, Lucy; Jordan, Philip; Taylor, David

    2013-04-01

    Freshwater bodies in Europe are required to return to good water quality status under the Water Framework Directive by 2015. A small inter-drumlin lake in the northeast of Ireland has been susceptible to eutrophic episodes and the presence of algal blooms during summer since annual monitoring began in 2002. While agricultural practice has been controlled by the implementation of the Nitrates Directive in 2006, the lake is failing to recover to good water quality status to meet with the Water Framework Directive objectives. Freshwaters in Ireland are regarded, in the main, as phosphorus (P) limited so identifying the sources of P possibly fuelling the algal blooms may provide an insight into how to improve water quality conditions. In a lake, these sources are divided between external catchment driven loads, as a result of farming and point sources, and P released from sediments made available to photic waters through internal lake mechanisms. High frequency sensors on data-sondes, installed on the lake in three locations, have provided chlorophyll a, redox potential, dissolved oxygen, temperature, pH, conductivity and turbidity data since March 2010. A data-sonde was installed in the hypolimnion to observe the change in lake conditions as P is released from lake sediments as a result of geochemical cycling with iron during anoxic periods. As compact high frequency sampling equipment for P analysis is still in its infancy for freshwaters, a proxy measurement of geochemical cycling in lakes would be useful to determine fully the extent of P contribution from sediments to the overall P load. Phosphorus was analysed once per month along with a number of other parameters and initial analysis of the high frequency data has shown changes in readings when known P release from lake sediments has occurred. Importantly, these data have shown when these P enriched hypolimnetic waters may be re-introduced to shallower waters in the photic zone, by changes in dissolved oxygen

  16. High frequency seismic waves and slab structures beneath Italy

    NASA Astrophysics Data System (ADS)

    Sun, Daoyuan; Miller, Meghan S.; Piana Agostinetti, Nicola; Asimow, Paul D.; Li, Dunzhu

    2014-04-01

    Tomographic images indicate a complicated subducted slab structure beneath the central Mediterranean where gaps in fast velocity anomalies in the upper mantle are interpreted as slab tears. The detailed shape and location of these tears are important for kinematic reconstructions and understanding the evolution of the subduction system. However, tomographic images, which are produced by smoothed, damped inversions, will underestimate the sharpness of the structures. Here, we use the records from the Italian National Seismic Network (IV) to study the detailed slab structure. The waveform records for stations in Calabria show large amplitude, high frequency (f>5 Hz) late arrivals with long coda after a relatively low-frequency onset for both P and S waves. In contrast, the stations in the southern and central Apennines lack such high frequency arrivals, which correlate spatially with the central Apennines slab window inferred from tomography and receiver function studies. Thus, studying the high frequency arrivals provides an effective way to investigate the structure of slab and detect possible slab tears. The observed high frequency arrivals in the southern Italy are the strongest for events from 300 km depth and greater whose hypocenters are located within the slab inferred from fast P-wave velocity perturbations. This characteristic behavior agrees with previous studies from other tectonic regions, suggesting the high frequency energy is generated by small scale heterogeneities within the slab which act as scatterers. Furthermore, using a 2-D finite difference (FD) code, we calculate synthetic seismograms to search for the scale, shape and velocity perturbations of the heterogeneities that may explain features observed in the data. Our preferred model of the slab heterogeneities beneath the Tyrrhenian Sea has laminar structure parallel to the slab dip and can be described by a von Kármán function with a down-dip correlation length of 10 km and 0.5 km in

  17. High-Frequency Excitation of a Plane Wake

    NASA Technical Reports Server (NTRS)

    Cain, Alan B.; Rogers, Michael M.

    2000-01-01

    In the early 1990's, Glezer and his co-workers at Georgia Tech made a startling discovery. They found that forcing at frequencies too high to directly affect the production scales led to a dramatic alteration in the development of a turbulent shear layer. An experimental study of this phenomenon is presented in Wiltse and Glezer. They used piezoelectric actuators located near the jet exit plane to force the shear layers of a square low-speed jet. The actuators were driven at a high frequency in the Kolmogorov inertial subrange, much higher than the frequencies associated with the large-scale motion (where the turbulent energy is produced and located) but much lower than those associated with the Kolmogorov scale (where the turbulent energy is dissipated). Measurements of the shear-layer turbulence showed that direct excitation of small-scale motion by high-frequency forcing led to an increase in the turbulent dissipation of more than an order of magnitude in the initial region of the shear layer! The turbulent dissipation gradually decreased with downstream distance but remained above the corresponding level for the unforced flow at all locations examined. The high-frequency forcing increased the turbulent kinetic energy in the initial region near the actuators, but the kinetic energy decreased quite rapidly with downstream distance, dropping to levels that were a small fraction of the level for the unforced case. Perhaps most importantly from the present standpoint, the high-frequency forcing significantly decreased the energy in the large-scale motion, increasingly so with downstream distance. Wiltse and Glezer interpreted this behavior as an enhanced transfer of energy from the large scales to the small scales. The initial work by Wiltse and Glezer has expanded into other applications. To explore the potential of high-frequency forcing for active acoustic suppression, in 1998 the first author proposed a set of experiments involving an edge tone shear layer and

  18. Photophoretic spectrometer

    SciTech Connect

    Arnold, S.; Amani, Y.; Orenstein, A.

    1980-09-01

    An instrument is described which measures the spectral dependence of the radiometric (photophoretic) force on a micron-sized particle in a static configuration. This spectrometer consists of a servo-stabilized Millikan chamber which can be used as a photophoretic balance over the spectral range from 200 nm to 1000 nm. Spectra may be taken in a vacuum as small as 10/sup -4/ torr. The action spectrum of the photophoretic force on a crystallite of CdS is used as an example. The pressure dependence of the force at 500 nm is consistant with a radiometric mechanism.

  19. MASS SPECTROMETER

    DOEpatents

    White, F.A.

    1960-08-23

    A mass spectrometer is designed with a first adjustable magnetic field for resolving an ion beam into beams of selected masses, a second adjustable magnetic field for further resolving the ion beam from the first field into beams of selected masses, a thin foil disposed in the path of the beam between the first and second magnets to dissociate molecular ions incident thereon, an electrostatic field for further resolving the ion beam from the second field into beams of selected masses, and a detector disposed adjacent to the electrostatic field to receive the ion beam.

  20. Lifetime measurement of 2+- state in 74Zn by recoil-distance Doppler-shift method

    NASA Astrophysics Data System (ADS)

    Niikura, M.; Mouginot, B.; Azaiez, F.; Franchoo, S.; Matea, I.; Stefan, I.; Verney, D.; Assie, M.; Bednarczyk, P.; Borcea, C.; Burger, A.; Burgunder, G.; Buta, A.; Cáceres, L.; Cléement, E.; Coquard, L.; de Angelis, G.; de France, G.; de Oliveira Santos, F.; Dewald, A.; Dijon, A.; Dombradi, Z.; Fiori, E.; Fransen, C.; Friessner, G.; Gaudefroy, L.; Georgiev, G.; Grévy, S.; Hackstein, M.; Harakeh, M. N.; Ibrahim, F.; Kamalou, O.; Kmiecik, M.; Lozeva, R.; Maj, A.; Mihai, C.; Möller, O.; Myalski, S.; Negoita, F.; Pantelica, D.; Perrot, L.; Pissulla, Th.; Rotaru, F.; Rother, W.; Scarpaci, J. A.; Stodel, C.; Thomas, J. C.; Ujic, P.

    2013-09-01

    We have performed the first direct lifetime measurement of the 2+- state in 74Zn. The neutron-rich 74Zn beam was produced by in-flight fragmentation of 76Ge at the Grand Accélérateur National d'Ions Lourds and separated with the LISE spectrometer. The lifetime of the 2+- state was measured by the recoil-distance Doppler-shift method with the Cologne plunger device combined with the EXOGAM detectors. The lifetime of the 2+- state in 74Zn was determined to be 27.0(24) ps, which corresponds to a reduced transition probability B(E2; 2+- -> 0+) = 370(33) e2fm4.

  1. Development of a new Recoil Distance Technique using Coulomb Excitation in Inverse Kinematics

    SciTech Connect

    Rother, Wolfram; Dewald, Alfred; Ilie, Gabriela; Pissulla, Thomas; Melon, Barbara; Jolie, Jan; Pascovici, Gheorghe; Iwasaki, Hironori; Hackstein, Matthias; Zell, Karl-Oskar; Julin, Rauno; Jones, Peter; Greenlees, Paul; Rahkila, Panu; Uusitalo, Juha; Scholey, Cath; Harissopulos, Sotirios; Lagoyannis, Anastasios; Konstantinopoulos, Theodore; Grahn, Tuomas

    2009-01-28

    We report on an experiment using Coulomb excitation in inverse kinematics in combination with the plunger technique for measuring lifetimes of excited states of the projectiles. Aside from the investigation of E(5) features in {sup 128}Xe, the aim was to explore the special features of such experiments which are also suited to be used with radioactive beams. The measurement was performed at the JYFL with the Koeln coincidence plunger device and the JUROGAM spectrometer using a {sup 128}Xe beam impinging on a {sup nat}Fe target at a beam energy of 525 MeV. Recoils were detected by means of 32 solar cells placed at extreme forward angles. Particle-gated {gamma}-singles and {gamma}{gamma}-coincidences were measured at different target-degrader distances. Details of the experiment and first results are presented.

  2. Recoil-α-fission and recoil-α-α-fission events observed in the reaction 48Ca + 243Am

    NASA Astrophysics Data System (ADS)

    Forsberg, U.; Rudolph, D.; Andersson, L.-L.; Di Nitto, A.; Düllmann, Ch. E.; Fahlander, C.; Gates, J. M.; Golubev, P.; Gregorich, K. E.; Gross, C. J.; Herzberg, R.-D.; Heßberger, F. P.; Khuyagbaatar, J.; Kratz, J. V.; Rykaczewski, K.; Sarmiento, L. G.; Schädel, M.; Yakushev, A.; Åberg, S.; Ackermann, D.; Block, M.; Brand, H.; Carlsson, B. G.; Cox, D.; Derkx, X.; Dobaczewski, J.; Eberhardt, K.; Even, J.; Gerl, J.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nazarewicz, W.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Ragnarsson, I.; Runke, J.; Schaffner, H.; Schausten, B.; Shi, Yue; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Ward, D. E.; Wiehl, N.

    2016-09-01

    Products of the fusion-evaporation reaction 48Ca + 243Am were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. Amongst the detected thirty correlated α-decay chains associated with the production of element Z = 115, two recoil-α-fission and five recoil- α- α-fission events were observed. The latter five chains are similar to four such events reported from experiments performed at the Dubna gas-filled separator, and three such events reported from an experiment at the Berkeley gas-filled separator. The four chains observed at the Dubna gas-filled separator were assigned to start from the 2n-evaporation channel 289115 due to the fact that these recoil- α- α-fission events were observed only at low excitation energies. Contrary to this interpretation, we suggest that some of these recoil- α- α-fission decay chains, as well as some of the recoil- α- α-fission and recoil-α-fission decay chains reported from Berkeley and in this article, start from the 3n-evaporation channel 288115.

  3. 140 GHz pulsed Fourier transform microwave spectrometer

    DOEpatents

    Kolbe, W.F.; Leskovar, B.

    1987-10-27

    A high frequency energy pulsing system suitable for use in a pulsed microwave spectrometer, including means for generating a high frequency carrier signal, and means for generating a low frequency modulating signal is disclosed. The carrier signal is continuously fed to a modulator and the modulating signal is fed through a pulse switch to the modulator. When the pulse switch is on, the modulator will produce sideband signals above and below the carrier signal frequency. A frequency-responsive device is tuned to one of the sideband signals and away from the carrier frequency so that the high frequency energization of the frequency-responsive device is controlled by the pulse switch. 5 figs.

  4. 140 GHz pulsed fourier transform microwave spectrometer

    DOEpatents

    Kolbe, William F.; Leskovar, Branko

    1987-01-01

    A high frequency energy pulsing system suitable for use in a pulsed microwave spectrometer (10), including means (11, 19) for generating a high frequency carrier signal, and means (12) for generating a low frequency modulating signal. The carrier signal is continuously fed to a modulator (20) and the modulating signal is fed through a pulse switch (23) to the modulator. When the pulse switch (23) is on, the modulator (20) will produce sideband signals above and below the carrier signal frequency. A frequency-responsive device (31) is tuned to one of the sideband signals and away from the carrier frequency so that the high frequency energization of the frequency-responsive device (31) is controlled by the pulse switch (23).

  5. Study of switching transients in high frequency converters

    NASA Technical Reports Server (NTRS)

    Zinger, Donald S.; Elbuluk, Malik E.; Lee, Tony

    1993-01-01

    As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented. A current regulated ac/ac PDM converter built using MCT's and IGBT's is

  6. High-frequency P wave spectra from explosions and earthquakes

    NASA Astrophysics Data System (ADS)

    Walter, William R.; Priestley, Keith F.

    Two explosion P wave spectral models [Sharpe, 1942; Mueller-Murphy, 1971] and two earthquake P wave spectral models [Archambeau, 1968, 1972; modified Brune 1970, 1971] are reviewed to assess their implications for high-frequency (>1 Hz) seismic discrimination between earthquakes and explosions. The importance of the corner frequency scaling, particularly for models with the same high-frequency spectral decay rate, is demonstrated by calculating source spectral ratios (a potentially important regional discriminant) for these models. We compare North American events and a limited data set of Central Asian events with these spectral models. We find North American earthquakes are consistent with a constant stress drop modified Brune model between 10 and 30 Hz. Shallow (<700 m depth) Pahute Mesa explosions at the Nevada Test Site have a high-frequency spectral decay between 10 and 30 Hz greater than the ω-2 predicted by the explosion models. Near regional recordings of the Soviet Joint Verification Experiment (JVE) explosion show a higher corner frequency and lower 1 to 4 Hz spectral ratios than predicted by either explosion model. The higher corner frequency of the Soviet JVE appears not to be due to attenuation, or receiver effects, and may represent a need for different corner frequency scaling, or result from source complications such as spall and tectonic release. A regional recording of the Soviet JVE (NEIC mb = 6.1) is shown to have a lower 1 to 4 Hz spectral ratio than a smaller earthquake (NEIC mb = 4.6) recorded on a nearly reciprocal path.

  7. Engineering Graphene Conductivity for Flexible and High-Frequency Applications.

    PubMed

    Samuels, Alexander J; Carey, J David

    2015-10-14

    Advances in lightweight, flexible, and conformal electronic devices depend on materials that exhibit high electrical conductivity coupled with high mechanical strength. Defect-free graphene is one such material that satisfies both these requirements and which offers a range of attractive and tunable electrical, optoelectronic, and plasmonic characteristics for devices that operate at microwave, terahertz, infrared, or optical frequencies. Essential to the future success of such devices is therefore the ability to control the frequency-dependent conductivity of graphene. Looking to accelerate the development of high-frequency applications of graphene, here we demonstrate how readily accessible and processable organic and organometallic molecules can efficiently dope graphene to carrier densities in excess of 10(13) cm(-2) with conductivities at gigahertz frequencies in excess of 60 mS. In using the molecule 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane (F2-HCNQ), a high charge transfer (CT) of 0.5 electrons per adsorbed molecule is calculated, resulting in p-type doping of graphene. n-Type doping is achieved using cobaltocene and the sulfur-containing molecule tetrathiafulvalene (TTF) with a CT of 0.41 and 0.24 electrons donated per adsorbed molecule, respectively. Efficient CT is associated with the interaction between the π electrons present in the molecule and in graphene. Calculation of the high-frequency conductivity shows dispersion-less behavior of the real component of the conductivity over a wide range of gigahertz frequencies. Potential high-frequency applications in graphene antennas and communications that can exploit these properties and the broader impacts of using molecular doping to modify functional materials that possess a low-energy Dirac cone are also discussed.

  8. Engineering Graphene Conductivity for Flexible and High-Frequency Applications.

    PubMed

    Samuels, Alexander J; Carey, J David

    2015-10-14

    Advances in lightweight, flexible, and conformal electronic devices depend on materials that exhibit high electrical conductivity coupled with high mechanical strength. Defect-free graphene is one such material that satisfies both these requirements and which offers a range of attractive and tunable electrical, optoelectronic, and plasmonic characteristics for devices that operate at microwave, terahertz, infrared, or optical frequencies. Essential to the future success of such devices is therefore the ability to control the frequency-dependent conductivity of graphene. Looking to accelerate the development of high-frequency applications of graphene, here we demonstrate how readily accessible and processable organic and organometallic molecules can efficiently dope graphene to carrier densities in excess of 10(13) cm(-2) with conductivities at gigahertz frequencies in excess of 60 mS. In using the molecule 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane (F2-HCNQ), a high charge transfer (CT) of 0.5 electrons per adsorbed molecule is calculated, resulting in p-type doping of graphene. n-Type doping is achieved using cobaltocene and the sulfur-containing molecule tetrathiafulvalene (TTF) with a CT of 0.41 and 0.24 electrons donated per adsorbed molecule, respectively. Efficient CT is associated with the interaction between the π electrons present in the molecule and in graphene. Calculation of the high-frequency conductivity shows dispersion-less behavior of the real component of the conductivity over a wide range of gigahertz frequencies. Potential high-frequency applications in graphene antennas and communications that can exploit these properties and the broader impacts of using molecular doping to modify functional materials that possess a low-energy Dirac cone are also discussed. PMID:26387636

  9. High frequency columnar silicon microresonators for mass detection

    SciTech Connect

    Kehrbusch, J.; Ilin, E. A.; Hullin, M.; Oesterschulze, E.

    2008-07-14

    A simple but effective technological scheme for the fabrication of high frequency silicon columnar microresonators is presented. With the proposed technique the dimensions of the microresonators are controlled on a scale of at least 1 {mu}m. Characterization of the mechanical properties of silicon columns gave resonant frequencies of the lowest flexural mode of 3-7 MHz with quality factors of up to 2500 in air and {approx}8800 under vacuum condition. Columnar microresonators were operated as mass balance with a sensitivity of 1 Hz/fg. A mass detection limit of 25 fg was deduced from experiments.

  10. External high-frequency control of combustion instability

    NASA Astrophysics Data System (ADS)

    Larionov, V. M.; Mitrofanov, G. A.; Kozar, A. N.

    2016-01-01

    The article presents the results of experimental studies of combustion instability in the pulse combustor. Propane-air mixture is burned in the chamber with the flame holder. It was experimentally found that feeding high-frequency sound vibrations into the combustion chamber causes the suppression of pulsating combustion. The oscillation frequency ranges in 870 to 1400 Hz. This corresponds to 9-12 resonance frequencies of oscillations in the combustor. The physical mechanism of the observed phenomenon consists in changing the conditions of formation and destruction of fuel jets in the vortex zone behind the flame holder.

  11. Dynamics and sensitivity analysis of high-frequency conduction block

    NASA Astrophysics Data System (ADS)

    Ackermann, D. Michael; Bhadra, Niloy; Gerges, Meana; Thomas, Peter J.

    2011-10-01

    The local delivery of extracellular high-frequency stimulation (HFS) has been shown to be a fast acting and quickly reversible method of blocking neural conduction and is currently being pursued for several clinical indications. However, the mechanism for this type of nerve block remains unclear. In this study, we investigate two hypotheses: (1) depolarizing currents promote conduction block via inactivation of sodium channels and (2) the gating dynamics of the fast sodium channel are the primary determinate of minimal blocking frequency. Hypothesis 1 was investigated using a combined modeling and experimental study to investigate the effect of depolarizing and hyperpolarizing currents on high-frequency block. The results of the modeling study show that both depolarizing and hyperpolarizing currents play an important role in conduction block and that the conductance to each of three ionic currents increases relative to resting values during HFS. However, depolarizing currents were found to promote the blocking effect, and hyperpolarizing currents were found to diminish the blocking effect. Inward sodium currents were larger than the sum of the outward currents, resulting in a net depolarization of the nodal membrane. Our experimental results support these findings and closely match results from the equivalent modeling scenario: intra-peritoneal administration of the persistent sodium channel blocker ranolazine resulted in an increase in the amplitude of HFS required to produce conduction block in rats, confirming that depolarizing currents promote the conduction block phenomenon. Hypothesis 2 was investigated using a spectral analysis of the channel gating variables in a single-fiber axon model. The results of this study suggested a relationship between the dynamical properties of specific ion channel gating elements and the contributions of corresponding conductances to block onset. Specifically, we show that the dynamics of the fast sodium inactivation gate are

  12. Motor monitoring method and apparatus using high frequency current components

    DOEpatents

    Casada, D.A.

    1996-05-21

    A motor current analysis method and apparatus for monitoring electrical-motor-driven devices are disclosed. The method and apparatus utilize high frequency portions of the motor current spectra to evaluate the condition of the electric motor and the device driven by the electric motor. The motor current signal produced as a result of an electric motor is monitored and the low frequency components of the signal are removed by a high-pass filter. The signal is then analyzed to determine the condition of the electrical motor and the driven device. 16 figs.

  13. High-frequency nonreciprocal reflection from magnetic films with overlayers

    SciTech Connect

    Wang, Ying; Nie, Yan; Camley, R. E.

    2013-11-14

    We perform a theoretical study of the nonreciprocal reflection of high-frequency microwave radiation from ferromagnetic films with thin overlayers. Reflection from metallic ferromagnetic films is always near unity and shows no nonreciprocity. In contrast, reflection from a structure which has a dielectric overlayer on top of a film composed of insulated ferromagnetic nanoparticles or nanostructures can show significant nonreciprocity in the 75–80 GHz frequency range, a very high value. This can be important for devices such as isolators or circulators.

  14. HIGH FREQUENCY ULTRASOUND OF ARMOR-GRADE ALUMINA CERAMICS

    SciTech Connect

    Bottiglieri, S.; Haber, R. A.

    2009-03-03

    Different lots of high density, commercial, armor-grade alumina (Al{sub 2}O{sub 3}) were tested using high frequency ultrasound in order to determine any correlation between measured properties and ballistic performance. C-scan images were taken using a 15 MHz ultrasonic transducer in order to form attenuation coefficient and elastic property maps. These samples were further characterized by using quantitative analysis. The results indicate that attenuation coefficient values appear to have the strongest correlation, of every property measured, to ballistic classifications.

  15. ZCS High Frequency Inverter for Aluminum Vessel Induction Heating

    NASA Astrophysics Data System (ADS)

    Ogiwara, Hiroyuki; Nakaoka, Mutsuo

    Recent induction cooking apparatus are utilized for induction heating of ferromagnetic materials at 20-50kHz with a high efficiency. They can not, however, be applied for non-magnetic materials such as aluminum vessels. Here, we present a voltage-clamp reverse conducting ZCS high frequency inverter of half bridge type for induction heating of an aluminum vessel. The switching devices utilized for this inverter are SITs and its operating frequency is determined as 200kHz. This paper describes its circuit constitution and the obtained experimental results from a practical point of view.

  16. Acoustic trapping with a high frequency linear phased array

    NASA Astrophysics Data System (ADS)

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K. Kirk

    2012-11-01

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  17. Kapitza thermal resistance studied by high-frequency photothermal radiometry

    NASA Astrophysics Data System (ADS)

    Horny, Nicolas; Chirtoc, Mihai; Fleming, Austin; Hamaoui, Georges; Ban, Heng

    2016-07-01

    Kapitza thermal resistance is determined using high-frequency photothermal radiometry (PTR) extended for modulation up to 10 MHz. Interfaces between 50 nm thick titanium coatings and silicon or stainless steel substrates are studied. In the used configuration, the PTR signal is not sensitive to the thermal conductivity of the film nor to its optical absorption coefficient, thus the Kapitza resistance is directly determined from single thermal parameter fits. Results of thermal resistances show the significant influence of the nature of the substrate, as well as of the presence of free electrons at the interface.

  18. A fast directional algorithm for high-frequency electromagnetic scattering

    SciTech Connect

    Tsuji, Paul; Ying Lexing

    2011-06-20

    This paper is concerned with the fast solution of high-frequency electromagnetic scattering problems using the boundary integral formulation. We extend the O(N log N) directional multilevel algorithm previously proposed for the acoustic scattering case to the vector electromagnetic case. We also detail how to incorporate the curl operator of the magnetic field integral equation into the algorithm. When combined with a standard iterative method, this results in an almost linear complexity solver for the combined field integral equations. In addition, the butterfly algorithm is utilized to compute the far field pattern and radar cross section with O(N log N) complexity.

  19. [A new method of high-frequency electrosurgery (coblation technology)].

    PubMed

    Sergeev, V N; Belov, S V

    2003-01-01

    A new method of electrosurgical intervention, i.e. a high-frequency cold-plasma ablation or coblation-technology, is presented in the article. The method is based on an ionic "bombardment" of the biological tissue at the intervention site, which leads to ruptures of intermolecular cohesions. The method has been widely used in arthrosurgery, cardiosurgery, otorhinolaryngology, spinal surgery and cosmetology. The "ArthroCare" Company (USA) was the first to start developing the discussed method. As for Russia, the Research Institute for Medical Instrument-Making of the Russian Academy of Medical Sciences and Stavropol State Medical Academy are the leaders in promoting the technology in question.

  20. Generation of sheet currents by high frequency fast MHD waves

    NASA Astrophysics Data System (ADS)

    Núñez, Manuel

    2016-07-01

    The evolution of fast magnetosonic waves of high frequency propagating into an axisymmetric equilibrium plasma is studied. By using the methods of weakly nonlinear geometrical optics, it is shown that the perturbation travels in the equatorial plane while satisfying a transport equation which enables us to predict the time and location of formation of shock waves. For plasmas of large magnetic Prandtl number, this would result into the creation of sheet currents which may give rise to magnetic reconnection and destruction of the original equilibrium.

  1. Acoustic trapping with a high frequency linear phased array.

    PubMed

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K Kirk

    2012-11-19

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  2. Explanation of persistent high frequency density structure in coalesced bunches

    SciTech Connect

    Jackson, Gerald P.

    1988-07-01

    It has been observed that after the Main Ring rf manipulation of coalescing (where 5 to 13 primary bunches are transferred into a single rf bucket) the new secondary bunch displays evidence of high frequency density structure superimposed on the approximately Gaussian longitudinal bunch length distribution. This structure is persistent over a period of many seconds (hundreds of synchrotron oscillation periods). With the help of multiparticle simulation programs, an explanation of this phenomenon is given in terms of single particle longitudinal phase space dynamics. No coherent effects need be taken into account. 6 refs., 10 figs.

  3. Motor monitoring method and apparatus using high frequency current components

    DOEpatents

    Casada, Donald A.

    1996-01-01

    A motor current analysis method and apparatus for monitoring electrical-motor-driven devices. The method and apparatus utilize high frequency portions of the motor current spectra to evaluate the condition of the electric motor and the device driven by the electric motor. The motor current signal produced as a result of an electric motor is monitored and the low frequency components of the signal are removed by a high-pass filter. The signal is then analyzed to determine the condition of the electrical motor and the driven device.

  4. High frequency chest compression therapy: a case study.

    PubMed

    Butler, S; O'Neill, B

    1995-01-01

    A new device, the ThAIRapy Bronchial Drainage System, enables patients with cystic fibrosis to self-administer the technique of high frequency chest compression (HFCC) to assist with mucociliary clearance. We review the literature on HFCC and outline a case study of a patient currently using the ThAIRapy Bronchial Drainage System. While mucociliary clearance and lung function may be enhanced by HFCC therapy, more research is needed to determine its efficacy, cost benefits, and optimum treatment guidelines. Although our initial experience with the patient using this device has been positive, we were unable to accurately evaluate the ThAIRapy Bronchial Drainage System.

  5. Fluctuation patterns in high-frequency financial asset returns

    NASA Astrophysics Data System (ADS)

    Preis, T.; Paul, W.; Schneider, J. J.

    2008-06-01

    We introduce a new method for quantifying pattern-based complex short-time correlations of a time series. Our correlation measure is 1 for a perfectly correlated and 0 for a random walk time series. When we apply this method to high-frequency time series data of the German DAX future, we find clear correlations on short time scales. In order to subtract trivial autocorrelation parts from the pattern conformity, we introduce a simple model for reproducing the antipersistent regime and use alternatively level 1 quotes. When we remove the pattern conformity of this stochastic process from the original data, remaining pattern-based correlations can be observed.

  6. High Frequency PIN-Diode Switches for Radiometer Applications

    NASA Technical Reports Server (NTRS)

    Montes, Oliver; Dawson, Douglas E.; Kangaslahti, Pekka; Reising, Steven C.

    2011-01-01

    Internally calibrated radiometers are needed for ocean topography and other missions. Typically internal calibration is achieved with Dicke switching as one of the techniques. We have developed high frequency single-pole double-throw (SPDT) switches in the form of monolithic microwave integrated circuits (MMIC) that can be easily integrated into Dicke switched radiometers that utilize microstrip technology. In particular, the switches we developed can be used for a radiometer such as the one proposed for the Surface Water and Ocean Topography (SWOT) Satellite Mission whose three channels at 92, 130, and 166 GHz would allow for wet-tropospheric path delay correction near coastal zones and over land. This feat is not possible with the current Jason-class radiometers due to their lower frequency signal measurement and thus lower resolution. The MMIC chips were fabricated at NGST using their InP PIN diode process and measured at JPL using high frequency test equipment. Measurement and simulation results will be presented.

  7. Corrosion monitoring using high-frequency guided ultrasonic waves

    NASA Astrophysics Data System (ADS)

    Fromme, Paul

    2014-02-01

    Corrosion develops due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Both pitting corrosion and generalized corrosion leading to wall thickness loss can cause the degradation of the structural integrity. The nondestructive detection and monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic transducers with single sided access to the structure, guided wave modes were generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted and the wall thickness reduced by consecutive milling of the steel structure. Further measurements were conducted using accelerated corrosion in a salt water bath and the damage severity monitored. From the measured signal change due to the wave mode interference the wall thickness reduction was monitored. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

  8. High-frequency wave normals in the solar wind

    SciTech Connect

    Herbert, F.; Smith, L.D.; Sonett, C.P.

    1984-05-01

    High-frequency (0.01--0.04 Hz) magnetic fluctuations in 506 ten-minute intervals of contemporaneous Explorer 35 and Apollo 12 measurements made in the solar wind near the morning side of the Earth's bow shock show the presence of a large population of disturbances resembling Alfven waves. Each wavefront normal n is systematically aligned (median deviation = 35/sup 0/) with , the associated ten-minute average of the magnetic field. Because of variability in the direction of from one interval to another, the coupled distribution of n is nearly isotropic in solar ecliptic coordinates, in contrast with the results of other studies of waves at much lower frequency indicating outward propagation from the sun. Presumably the high frequency waves discussed here are stirred into isotropy (in solar ecliptic coordinates) by following the low frequency fluctuations. As these waves maintain their alignement of n with despite the great variation of , a strong physical alignment constraint is inferred.

  9. High frequency dielectrophoretic response of microalgae over time

    PubMed Central

    Hadady, Hanieh; Wong, Johnson J.; Hiibel, Sage R.; Redelman, Doug; Geiger, Emil J.

    2015-01-01

    The high frequency dielectrophoresis (>20 MHz) response of microalgae cells with different lipid content was monitored over time. Chlamydomonas reinhardtii was cultured in regular medium and under nitrogen-depleted conditions in order to produce populations of cells with low and high lipid content, respectively. The electrical conductivity (EC) of the culture media was also monitored over the same time. The upper crossover frequency (UCOF) decreased for high-lipid cells over time. The single-shell model predicts that the upper crossover frequency is dictated primarily by the dielectric properties of the cytoplasm. The high frequency DEP response of the high-lipid cells’ cytoplasm was changed by lipid accumulation. DEP response of the low-lipid cells also varied with the conductivity of the culture media due to nutrient consumption. Relative lipid content was estimated with BODIPY 505/515 dye by calculating the area-weighted intensity average of fluorescent images. Finally, microalgae cells were successfully separated based on lipid content at 41 MHz and DEP media conductivity 106 ± 1 µS/cm. PMID:25229637

  10. 10 K high frequency pulse tube cryocooler with precooling

    NASA Astrophysics Data System (ADS)

    Liu, Sixue; Chen, Liubiao; Wu, Xianlin; Zhou, Yuan; Wang, Junjie

    2016-07-01

    A high frequency pulse tube cryocooler with precooling (HPTCP) has been developed and tested to meet the requirement of weak magnetic signals measurement, and the performance characteristics are presented in this article. The HPTCP is a two-stage pulse tube cryocooler with the precooling-stage replaced by liquid nitrogen. Two regenerators completely filled with stainless steel (SS) meshes are used in the cooler. Together with cold inertance tubes and cold gas reservoir, a cold double-inlet configuration is used to control the phase relationship of the HPTCP. The experimental result shows that the cold double-inlet configuration has improved the performance of the cooler obviously. The effects of operation parameters on the performance of the cooler are also studied. With a precooling temperature of 78.5 K, the maximum refrigeration capacity is 0.26 W at 15 K and 0.92 W at 20 K when the input electric power are 174 W and 248 W respectively, and the minimum no-load temperature obtained is 10.3 K, which is a new record on refrigeration temperature for high frequency pulse tube cryocooler reported with SS completely used as regenerative matrix.

  11. High-frequency ultrasound imaging for breast cancer biopsy guidance.

    PubMed

    Cummins, Thomas; Yoon, Changhan; Choi, Hojong; Eliahoo, Payam; Kim, Hyung Ham; Yamashita, Mary W; Hovanessian-Larsen, Linda J; Lang, Julie E; Sener, Stephen F; Vallone, John; Martin, Sue E; Kirk Shung, K

    2015-10-01

    Image-guided core needle biopsy is the current gold standard for breast cancer diagnosis. Microcalcifications, an important radiographic finding on mammography suggestive of early breast cancer such as ductal carcinoma in situ, are usually biopsied under stereotactic guidance. This procedure, however, is uncomfortable for patients and requires the use of ionizing radiation. It would be preferable to biopsy microcalcifications under ultrasound guidance since it is a faster procedure, more comfortable for the patient, and requires no radiation. However, microcalcifications cannot reliably be detected with the current standard ultrasound imaging systems. This study is motivated by the clinical need for real-time high-resolution ultrasound imaging of microcalcifications, so that biopsies can be accurately performed under ultrasound guidance. We have investigated how high-frequency ultrasound imaging can enable visualization of microstructures in ex vivo breast tissue biopsy samples. We generated B-mode images of breast tissue and applied the Nakagami filtering technique to help refine image output so that microcalcifications could be better assessed during ultrasound-guided core biopsies. We describe the preliminary clinical results of high-frequency ultrasound imaging of ex vivo breast biopsy tissue with microcalcifications and without Nakagami filtering and the correlation of these images with the pathology examination by hematoxylin and eosin stain and whole slide digital scanning. PMID:26693167

  12. Corrosion monitoring using high-frequency guided waves

    NASA Astrophysics Data System (ADS)

    Fromme, P.

    2016-04-01

    Corrosion can develop due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Generalized corrosion leading to wall thickness loss can cause the reduction of the strength and thus degradation of the structural integrity. The monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic wedge transducers with single sided access to the structure, guided wave modes were selectively generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted for wall thickness reduction due to milling of the steel structure. From the measured signal changes due to the wave mode interference the reduced wall thickness was monitored. Good agreement with theoretical predictions was achieved. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

  13. Very High Frequency (Beyond 100 MHz) PZT Kerfless Linear Arrays

    PubMed Central

    Wu, Da-Wei; Zhou, Qifa; Geng, Xuecang; Liu, Chang-Geng; Djuth, Frank; Shung, K. Kirk

    2010-01-01

    This paper presents the design, fabrication, and measurements of very high frequency kerfless linear arrays prepared from PZT film and PZT bulk material. A 12-µm PZT thick film fabricated from PZT-5H powder/solution composite and a piece of 15-µm PZT-5H sheet were used to fabricate 32-element kerfless high-frequency linear arrays with photolithography. The PZT thick film was prepared by spin-coating of PZT sol-gel composite solution. The thin PZT-5H sheet sample was prepared by lapping a PZT-5H ceramic with a precision lapping machine. The measured results of the 2 arrays were compared. The PZT film array had a center frequency of 120 MHz, a bandwidth of 60% with a parylene matching layer, and an insertion loss of 41 dB. The PZT ceramic sheet array was found to have a center frequency of 128 MHz with a poorer bandwidth (40% with a parylene matching layer) but a better sensitivity (28 dB insertion loss). PMID:19942516

  14. High-Frequency Oscillations as a New Biomarker in Epilepsy

    PubMed Central

    Zijlmans, Maeike; Jiruska, Premysl; Zelmann, Rina; Leijten, Frans S.S.; Jefferys, John G.R.; Gotman, Jean

    2013-01-01

    The discovery that electroencephalography (EEG) contains useful information at frequencies above the traditional 80Hz limit has had a profound impact on our understanding of brain function. In epilepsy, high-frequency oscillations (HFOs, >80Hz) have proven particularly important and useful. This literature review describes the morphology, clinical meaning, and pathophysiology of epileptic HFOs. To record HFOs, the intracranial EEG needs to be sampled at least at 2,000Hz. The oscillatory events can be visualized by applying a high-pass filter and increasing the time and amplitude scales, or EEG time-frequency maps can show the amount of high-frequency activity. HFOs appear excellent markers for the epileptogenic zone. In patients with focal epilepsy who can benefit from surgery, invasive EEG is often required to identify the epileptic cortex, but current information is sometimes inadequate. Removal of brain tissue generating HFOs has been related to better postsurgical outcome than removing the seizure onset zone, indicating that HFOs may mark cortex that needs to be removed to achieve seizure control. The pathophysiology of epileptic HFOs is challenging, probably involving populations of neurons firing asynchronously. They differ from physiological HFOs in not being paced by rhythmic inhibitory activity and in their possible origin from population spikes. Their link to the epileptogenic zone argues that their study will teach us much about the pathophysiology of epileptogenesis and ictogenesis. HFOs show promise for improving surgical outcome and accelerating intracranial EEG investigations. Their potential needs to be assessed by future research. PMID:22367988

  15. High-Frequency Dynamics of Ultrasound Contrast Agents

    PubMed Central

    Sun, Yang; Kruse, Dustin E.; Dayton, Paul A.; Ferrara, Katherine W.

    2006-01-01

    Ultrasound contrast agents enhance echoes from the microvasculature and enable the visualization of flow in smaller vessels. Here, we optically and acoustically investigate microbubble oscillation and echoes following insonation with a 10 MHz center frequency pulse. A high-speed camera system with a temporal resolution of 10 ns, which provides two-dimensional (2-D) frame images and streak images, is used in optical experiments. Two confocally aligned transducers, transmitting at 10 MHz and receiving at 5 MHz, are used in acoustical experiments in order to detect subharmonic components. Results of a numerical evaluation of the modified Rayleigh-Plesset equation are used to predict the dynamics of a microbubble and are compared to results of in vitro experiments. From the optical observations of a single microbubble, nonlinear oscillation, destruction, and radiation force are observed. The maximum bubble expansion, resulting from insonation with a 20-cycle, 10-MHz linear chirp with a peak negative pressure of 3.5 MPa, has been evaluated. For an initial diameter ranging from 1.5 to 5 μm, a maximum diameter less than 8 μm is produced during insonation. Optical and acoustical experiments provide insight into the mechanisms of destruction, including fragmentation and active diffusion. High-frequency pulse transmission may provide the opportunity to detect contrast echoes resulting from a single pulse, may be robust in the presence of tissue motion, and may provide the opportunity to incorporate high-frequency ultrasound into destruction-replenishment techniques. PMID:16422410

  16. Optoacoustics for high-frequency ultrasonic imaging and manipulation

    NASA Astrophysics Data System (ADS)

    O'Donnell, Matthew; Buma, Takashi

    2001-05-01

    Pulsed lasers can generate ultrasound through thermoelastic expansion of a thin optical absorber. By carefully designing the optical absorbing structure, efficient transduction is possible for a number of biomedical applications including high-frequency imaging, microfluidics, and sensing. The major key for efficient optoacoustic transduction in biomedical applications is to engineer a nearly perfect optical absorber possessing a large coefficient of thermal expansion with acoustic properties well matched to a water medium. We have obtained an optoacoustic efficiency increase of over 20 dB compared to conventional approaches using a thin, optically absorbing layer consisting of polydimethylsiloxane (PDMS) and carbon black spin coated onto a clear PDMS substrate. This structure has been extensively analyzed both experimentally and analytically and seems to provide opportunities for a wide range of optoacoustic devices. In this talk we show how PDMS-based optoacoustic transduction can be used for high-frequency imaging using longitudinal waves and acoustic tweezing using Lamb waves. The basic mechanism of optoacoustic transduction will be described, and specific devices will be presented.

  17. High-frequency-link based power electronics in power systems

    NASA Astrophysics Data System (ADS)

    Sree, Hari

    Power quality has become a serious concern to many utility customers in recent times. Among the many power quality problems, voltage sags are one of the most common and most mischievous, affecting industrial and commercial customers. They are primarily caused by power system faults at the transmission and distribution level, and thus, are mostly unavoidable. Their effect depends on the equipment sensitivities to the magnitude and duration of these sags and each can cost an industry up to few million dollars. To counter these limitations, many solutions at the customer end have been proposed which include Constant Voltage Transformers (CVT's), UPS and line frequency transformer based Dynamic Voltage Restorer (DVR). These approaches have their respective limitations with regard to capabilities, size and cost. This research proposes a new approach to mitigating these voltage sags involving the use of high frequency transformer link. Suitable switching logic and control strategies have been implemented. The proposed approach in a one-phase application is verified with computer simulations and by a hardware proof-of-concept prototype. Application to three-phase system is verified through simulations. Application of high frequency transformers in other utility applications such as active filters and static compensators is also looked at.

  18. Carbon nanotube transistor based high-frequency electronics

    NASA Astrophysics Data System (ADS)

    Schroter, Michael

    At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks. Carbon nanotube transistor based high-frequency electronics.

  19. High-Frequency Normal Mode Propagation in Aluminum Cylinders

    USGS Publications Warehouse

    Lee, Myung W.; Waite, William F.

    2009-01-01

    Acoustic measurements made using compressional-wave (P-wave) and shear-wave (S-wave) transducers in aluminum cylinders reveal waveform features with high amplitudes and with velocities that depend on the feature's dominant frequency. In a given waveform, high-frequency features generally arrive earlier than low-frequency features, typical for normal mode propagation. To analyze these waveforms, the elastic equation is solved in a cylindrical coordinate system for the high-frequency case in which the acoustic wavelength is small compared to the cylinder geometry, and the surrounding medium is air. Dispersive P- and S-wave normal mode propagations are predicted to exist, but owing to complex interference patterns inside a cylinder, the phase and group velocities are not smooth functions of frequency. To assess the normal mode group velocities and relative amplitudes, approximate dispersion relations are derived using Bessel functions. The utility of the normal mode theory and approximations from a theoretical and experimental standpoint are demonstrated by showing how the sequence of P- and S-wave normal mode arrivals can vary between samples of different size, and how fundamental normal modes can be mistaken for the faster, but significantly smaller amplitude, P- and S-body waves from which P- and S-wave speeds are calculated.

  20. Advantages of polymer transducers in high frequency inspections

    SciTech Connect

    Samari, S.; Stanton, M.

    1993-12-31

    Since the discovery of piezoelectricity in PVDF in 1969 the polymer transducers have now emerged as a significant tool in many ultrasonic inspections that otherwise would have been very difficult or impossible for conventional ceramic transducers. The major advantage, of Polymer transducers is in their inherent broadband characteristics in immersion applications which leads to their superior resolution and improved signal to noise ration over conventional ceramic transducers. This paper will show empirical results of high frequency polymer transducer in inspection of different materials including engineering materials such as ceramics. Other advantages of the polymer transducers are their low acoustic impedance as well as the compliance of the plastic material during construction. The compliance of the plastic PVDF film allows the manufacture of the high frequency polymer transducers without the use of permanent delays which can interfere with ultrasonic measurements. This paper will also give experimental results that will show how polymer transducers are instrument dependent, and how an operator can achieve optimum results by using an impedance matching network between the instrument and the polymer transducer.

  1. High-frequency filtering of strong-motion records

    USGS Publications Warehouse

    Douglas, J.; Boore, D.M.

    2011-01-01

    The influence of noise in strong-motion records is most problematic at low and high frequencies where the signal to noise ratio is commonly low compared to that in the mid-spectrum. The impact of low-frequency noise (5 Hz) on computed pseudo-absolute response spectral accelerations (PSAs). In contrast to the case of low-frequency noise our analysis shows that filtering to remove high-frequency noise is only necessary in certain situations and that PSAs can often be used up to 100 Hz even if much lower high-cut corner frequencies are required to remove the noise. This apparent contradiction can be explained by the fact that PSAs are often controlled by ground accelerations associated with much lower frequencies than the natural frequency of the oscillator because path and site attenuation (often modelled by Q and κ, respectively) have removed the highest frequencies. We demonstrate that if high-cut filters are to be used, then their corner frequencies should be selected on an individual basis, as has been done in a few recent studies.

  2. Median recoil direction as a WIMP directional detection signal

    SciTech Connect

    Green, Anne M.; Morgan, Ben

    2010-03-15

    Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP 'smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of {approx}2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

  3. Stimulated Rayleigh resonances and recoil-induced effects

    SciTech Connect

    Courtois, J.Y.; Grynberg, G.

    1996-12-31

    The organization of this paper is as follows. We present in Section II the basic ideas about stimulated Rayleigh scattering by considering more particularly the situation where it arises from a relaxation process going on in the material system, and we describe a few experimental observations made in atomic and molecular physics. We then consider the case of nonstationary two-level atoms, and we derive the shape and characteristics of the recoil-induced resonances (Section III). In particular, we show that these resonances can be interpreted either as originating from a stimulated Rayleigh effect or as a stimulated Raman phenomena between atomic energy-momentum states having different momenta. Finally, to make a clear distinction between the physical phenomena that pertain directly to recoil-induced processes (i.e., that actually permit the measurement of the photon recoil) and those for which the introduction of the recoil constitutes a mere physical convenience, we review in Section IV some indisputable manifestations of the photon recoil in atomic and molecular physics. 92 refs., 22 figs.

  4. Calculation of recoil implantation profiles using known range statistics

    NASA Technical Reports Server (NTRS)

    Fung, C. D.; Avila, R. E.

    1985-01-01

    A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.

  5. Inaudible high-frequency sounds affect brain activity: hypersonic effect.

    PubMed

    Oohashi, T; Nishina, E; Honda, M; Yonekura, Y; Fuwamoto, Y; Kawai, N; Maekawa, T; Nakamura, S; Fukuyama, H; Shibasaki, H

    2000-06-01

    Although it is generally accepted that humans cannot perceive sounds in the frequency range above 20 kHz, the question of whether the existence of such "inaudible" high-frequency components may affect the acoustic perception of audible sounds remains unanswered. In this study, we used noninvasive physiological measurements of brain responses to provide evidence that sounds containing high-frequency components (HFCs) above the audible range significantly affect the brain activity of listeners. We used the gamelan music of Bali, which is extremely rich in HFCs with a nonstationary structure, as a natural sound source, dividing it into two components: an audible low-frequency component (LFC) below 22 kHz and an HFC above 22 kHz. Brain electrical activity and regional cerebral blood flow (rCBF) were measured as markers of neuronal activity while subjects were exposed to sounds with various combinations of LFCs and HFCs. None of the subjects recognized the HFC as sound when it was presented alone. Nevertheless, the power spectra of the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) recorded from the occipital region increased with statistical significance when the subjects were exposed to sound containing both an HFC and an LFC, compared with an otherwise identical sound from which the HFC was removed (i.e., LFC alone). In contrast, compared with the baseline, no enhancement of alpha-EEG was evident when either an HFC or an LFC was presented separately. Positron emission tomography measurements revealed that, when an HFC and an LFC were presented together, the rCBF in the brain stem and the left thalamus increased significantly compared with a sound lacking the HFC above 22 kHz but that was otherwise identical. Simultaneous EEG measurements showed that the power of occipital alpha-EEGs correlated significantly with the rCBF in the left thalamus. Psychological evaluation indicated that the subjects felt the sound containing an HFC to be more

  6. Recoil separator ERNA: acceptances in angle and energy

    NASA Astrophysics Data System (ADS)

    Rogalla, D.; Schürmann, D.; Strieder, F.; Aliotta, M.; DeCesare, N.; DiLeva, A.; Lubritto, C.; D'Onofrio, A.; Gialanella, L.; Imbriani, G.; Kluge, J.; Ordine, A.; Roca, V.; Röcken, H.; Rolfs, C.; Romano, M.; Schümann, F.; Terrasi, F.; Trautvetter, H. P.

    2003-11-01

    For improved cross-section measurements of the reaction 12C(α,γ) 16O in inverted kinematics, a recoil separator ERNA is developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with high efficiency. Due to the emission of the capture γ-rays, the kinematically forward directed 16O recoils are described by an angle and energy spread. Thus, the acceptances in angle and energy of ERNA must cover these spreads in order to extract reliable cross-section values. We report on such acceptance measurements over the energy range Ecm=0.7-5.0 MeV, using an 16O pilot beam.

  7. Accounting for Recoil Effects in Geochronometers: A New Model Approach

    NASA Astrophysics Data System (ADS)

    Lee, V. E.; Huber, C.

    2012-12-01

    A number of geologically important chronometers are affected by, or owe their utility to, the "recoil effect". This effect describes the physical displacement of a nuclide due to energetic nuclear processes such as radioactive alpha decay (as in the case of various parent-daughter pairs in the uranium-series decay chains, and Sm-Nd), as well as neutron irradiation (in the case of the methodology for the 40Ar/39Ar dating method). The broad range of affected geochronometers means that the recoil effect can impact a wide range of dating method applications in the geosciences, including but not limited to: Earth surface processes, paleoclimate, volcanic processes, and cosmochemistry and planetary evolution. In particular, the recoil effect can have a notable impact on the use of fine grains (silt- and clay-sized particles) for geochronometric dating purposes. This is because recoil-induced loss of a nuclide from the surfaces of a grain can create an isotopically-depleted outer rind, and for small grains, this depleted rind can be volumetrically significant. When this recoil loss is measurable and occurs in a known time-dependent fashion, it can usefully serve as the basis for chronometers (such as the U-series comminution age method); in other cases recoil loss from fine particles creates an unwanted deviation from expected isotope values (such as for the Ar-Ar method). To improve both the accuracy and precision of ages inferred from geochronometric systems that involve the recoil of a key nuclide from small domains, it is necessary to quantify the magnitude of the recoil loss of that particular nuclide. It is also necessary to quantitatively describe the effect of geological processes that can alter the outer surface of grains, and hence the isotopically-depleted rind. Here we present a new mathematical and numerical model that includes two main features that enable enhanced accuracy and precision of ages determined from geochronometers. Since the surface area of the

  8. Nuclear Recoil Calibration of DarkSide-50

    NASA Astrophysics Data System (ADS)

    Edkins, Erin; DarkSide Collaboration

    2016-03-01

    DarkSide-50 dark matter experiment is a liquid argon time projection chamber (TPC) surrounded by a liquid scintillator active neutron veto, designed for the direct detection of Weakly Interacting Massive Particles (WIMPs). The success of such an experiment is dependent upon a detailed understanding of both the expected signal and backgrounds, achieved using radioactive calibration sources of known energies. Nuclear recoils provide a measurement of both the expected signal and the most dangerous background, as nuclear recoils from neutrons cannot be distinguished from a dark matter signal on an event-by-event basis in the TPC. In this talk, I will present the DS-50 calibration system, and analysis of the results of the calibration of DarkSide-50 to nuclear recoils using radioactive neutron sources. See also the DS-50 presentations by X. Xiang and G. Koh.

  9. Rupture and recoil of bent-core liquid crystal filaments.

    PubMed

    Salili, S M; Ostapenko, T; Kress, O; Bailey, C; Weissflog, W; Harth, K; Eremin, A; Stannarius, R; Jákli, A

    2016-05-25

    The recoil process of free-standing liquid crystal filaments is investigated experimentally and theoretically. We focus on two aspects, the contraction speed of the filament and a spontaneously formed undulation instability. At the moment of rupture, the filaments buckle similarly to the classical Euler buckling of elastic rods. The tip velocity decays with decreasing filament length. The wavelength of buckling affinely decreases with the retracting filament tip. The energy gain related to the decrease of the total length and surface area of the filaments is mainly dissipated by layer rearrangements during thickening of the fibre. A flow back into the meniscus is relevant only in the final stage of the recoil process. We introduce a model for the quantitative description of the filament retraction speed. The dynamics of this recoil behaviour may find relevance as a model for biology-related filaments. PMID:27140824

  10. ICD lead failure detection through high frequency impedance.

    PubMed

    Kollmann, Daniel T; Swerdlow, Charles D; Kroll, Mark W; Seifert, Gregory J; Lichter, Patrick A

    2014-01-01

    Abrasion-induced insulation breach is a common failure mode of silicone-body, transvenous, implantable cardioverter defibrillator leads. It is caused either by external compression or internal motion of conducting cables. The present method of monitoring lead integrity measures low frequency conductor impedance. It cannot detect insulation failures until both the silicone lead body and inner fluoropolymer insulation have been breached completely, exposing conductors directly to blood or tissue. Thus the first clinical presentation may be either failure to deliver a life-saving shock or painful, inappropriate shocks in normal rhythm. We present a new method for identifying lead failure based on high frequency impedance measurements. This method was evaluated in 3D electromagnetic simulation and bench testing to identify insulation defects in the St. Jude Medical Riata® lead, which is prone to insulation breach.

  11. Development of high frequency and wide bandwidth Johnson noise thermometry

    SciTech Connect

    Crossno, Jesse; Liu, Xiaomeng; Kim, Philip; Ohki, Thomas A.; Fong, Kin Chung

    2015-01-12

    We develop a high frequency, wide bandwidth radiometer operating at room temperature, which augments the traditional technique of Johnson noise thermometry for nanoscale thermal transport studies. Employing low noise amplifiers and an analog multiplier operating at 2 GHz, auto- and cross-correlated Johnson noise measurements are performed in the temperature range of 3 to 300 K, achieving a sensitivity of 5.5 mK (110 ppm) in 1 s of integration time. This setup allows us to measure the thermal conductance of a boron nitride encapsulated monolayer graphene device over a wide temperature range. Our data show a high power law (T ∼ 4) deviation from the Wiedemann-Franz law above T ∼ 100 K.

  12. High-frequency radar observations of ocean surface currents.

    PubMed

    Paduan, Jeffrey D; Washburn, Libe

    2013-01-01

    This article reviews the discovery, development, and use of high-frequency (HF) radio wave backscatter in oceanography. HF radars, as the instruments are commonly called, remotely measure ocean surface currents by exploiting a Bragg resonant backscatter phenomenon. Electromagnetic waves in the HF band (3-30 MHz) have wavelengths that are commensurate with wind-driven gravity waves on the ocean surface; the ocean waves whose wavelengths are exactly half as long as those of the broadcast radio waves are responsible for the resonant backscatter. Networks of HF radar systems are capable of mapping surface currents hourly out to ranges approaching 200 km with a horizontal resolution of a few kilometers. Such information has many uses, including search and rescue support and oil-spill mitigation in real time and larval population connectivity assessment when viewed over many years. Today, HF radar networks form the backbone of many ocean observing systems, and the data are assimilated into ocean circulation models.

  13. High-Frequency Wave Propagation by the Segment Projection Method

    NASA Astrophysics Data System (ADS)

    Engquist, Björn; Runborg, Olof; Tornberg, Anna-Karin

    2002-05-01

    Geometrical optics is a standard technique used for the approximation of high-frequency wave propagation. Computational methods based on partial differential equations instead of the traditional ray tracing have recently been applied to geometrical optics. These new methods have a number of advantages but typically exhibit difficulties with linear superposition of waves. In this paper we introduce a new partial differential technique based on the segment projection method in phase space. The superposition problem is perfectly resolved and so is the problem of computing amplitudes in the neighborhood of caustics. The computational complexity is of the same order as that of ray tracing. The new algorithm is described and a number of computational examples are given, including a simulation of waveguides.

  14. Toward a High-Frequency Pulsed-Detonation Actuator

    NASA Technical Reports Server (NTRS)

    Cutler, Andrew D.; Drummond, J. Philip

    2006-01-01

    This paper describes the continued development of an actuator, energized by pulsed detonations, that provides a pulsed jet suitable for flow control in high-speed applications. A high-speed valve, capable of delivering a pulsed stream of reactants a mixture of H2 and air at rates of up to 1500 pulses per second, has been constructed. The reactants burn in a resonant tube and the products exit the tube as a pulsed jet. High frequency pressure transducers have been used to monitor the pressure fluctuations in the device at various reactant injection frequencies, including both resonant and off-resonant conditions. Pulsed detonations have been demonstrated in the lambda/4 mode of an 8 inch long tube at approximately 600 Hz. The pulsed jet at the exit of the device has been observed using shadowgraph and an infrared camera.

  15. Toward a High-Frequency Pulsed-Detonation Actuator

    NASA Technical Reports Server (NTRS)

    Cutler, Andrew D.; Drummond, J. Philip

    2006-01-01

    This paper describes the continued development of an actuator, energized by pulsed detonations, that provides a pulsed jet suitable for flow control in high-speed applications. A high-speed valve, capable of delivering a pulsed stream of reactants a mixture of H2 and air at rates of up to 1500 pulses per second, has been constructed. The reactants burn in a resonant tube and the products exit the tube as a pulsed jet. High frequency pressure transducers have been used to monitor the pressure fluctuations in the device at various reactant injection frequencies, including both resonant and off-resonant conditions. Pulsed detonations have been demonstrated in the lambda/4 mode of an 8 inch long tube at approx. 600 Hz. The pulsed jet at the exit of the device has been observed using shadowgraph and an infrared camera.

  16. High frequency properties of YBCO bridges fabricated by MOCVD

    SciTech Connect

    Chen, J.; Yamoshita, T. ); Suzuki, H.; Kurosawa, H. ); Yamane, H.; Hirai, T. . Inst. for Materials Research)

    1991-03-01

    This paper reports on the high frequency properties of YBCO bridges at 4.2% and 77K. The YBCO films were prepared by MOCVD. For small bridges with the width(w) of about 1 {mu}m and thickness(t) of less than 0.5{mu}m, the constant voltage steps at integral multiples of {phi}{sub 0}fr = 20 {mu}V were observed up to 1 mV, which is much higher than the IcR{sub N} ({lt}0.13 mV) product of these bridges at 77K. The magnitudes of the current steps as functions of the rf current at 4.2K and 77K were in quantitative agreement with the theoretical results based on the RSJ model.

  17. High frequency activity correlates of robust movement in humans.

    PubMed

    Kerr, Matthew S D; Kahn, Kevin; Hyun-Joo Park; Thompson, Susan; Hao, Stephanie; Bulacio, Juan; Gonzalez-Martinez, Jorge A; Gale, John; Sarma, Sridevi V

    2014-01-01

    The neural circuitry underlying fast robust human motor control is not well understood. In this study we record neural activity from multiple stereotactic encephalograph (SEEG) depth electrodes in a human subject while he/she performs a center-out reaching task holding a robotic manipulandum that occasionally introduces an interfering force field. Collecting neural data from humans during motor tasks is rare, and SEEG provides an unusual opportunity to examine neural correlates of movement at a millisecond time scale in multiple brain regions. Time-frequency analysis shows that high frequency activity (50-150 Hz) increases significantly in the left precuneus and left hippocampus when the subject is compensating for a perturbation to their movement. These increases in activity occur with different durations indicating differing roles in the motor control process.

  18. Convective mixing mechanisms in high frequency intermittent jet ventilation.

    PubMed

    Scherer, P W; Muller, W J; Raub, J B; Haselton, F R

    1989-01-01

    A liquid flow visualization technique was used to identify the location of neutrally buoyant bead clouds injected into airway models during flows simulating high frequency intermittent jet ventilation (HFIJV) in neonatal lungs. The motions of these bead clouds show that the convective or bulk mixing that occurs during HFIJV is made up of two parts; a turbulent convective exchange with the atmosphere caused by the jet in the trachea and a streaming motion along the airways driven by an interaction between the jet and the expansion and contraction of the airways due to their compliance. These convective streaming motions combine with molecular diffusion to produce augmented diffusion which transports O2 and CO2 between the trachea and the peripheral alveoli. Optimizing HFIJV (as well as other forms of HFV) depends on maximizing these airway convective streaming flows which depend on many more lung and fluid mechanical parameters than are necessary to describe conventional mechanical ventilation.

  19. High-frequency extensions of magnetorotational instability in astrophysical plasmas

    SciTech Connect

    Mikhailovskii, A. B.; Lominadze, J. G.; Churikov, A. P.; Pustovitov, V. D.; Erokhin, N. N.; Tsypin, V. S.; Galvao, R. M. O.

    2008-08-15

    High-frequency extensions of magnetorotational instability driven by the Velikhov effect beyond the standard magnetohydrodynamic (MHD) regime are studied. The existence of the well-known Hall regime and a new electron inertia regime is demonstrated. The electron inertia regime is realized for a lesser plasma magnetization of rotating plasma than that in the Hall regime. It includes the subregime of nonmagnetized electrons. It is shown that, in contrast to the standard MHD regime and the Hall regime, magnetorotational instability in this subregime can be driven only at positive values of dln{Omega}/dlnr, where {Omega} is the plasma rotation frequency and r is the radial coordinate. The permittivity of rotating plasma beyond the standard MHD regime, including both the Hall regime and the electron inertia regime, is calculated.

  20. High Frequency Monitoring Reveals Aftershocks in Subcritical Crack Growth

    NASA Astrophysics Data System (ADS)

    Stojanova, M.; Santucci, S.; Vanel, L.; Ramos, O.

    2014-03-01

    By combining direct imaging and acoustic emission measurements, the subcritical propagation of a crack in a heterogeneous material is analyzed. Both methods show that the fracture proceeds through a succession of discrete events. However, the macroscopic opening of the fracture captured by the images results from the accumulation of more-elementary events detected by the acoustics. When the acoustic energy is cumulated over large time scales corresponding to the image acquisition rate, a similar statistics is recovered. High frequency acoustic monitoring reveals aftershocks responsible for a time scale dependent exponent of the power law energy distributions. On the contrary, direct imaging, which is unable to resolve these aftershocks, delivers a misleading exponent value.

  1. Recording and analysis techniques for high-frequency oscillations

    PubMed Central

    Worrell, G.A.; Jerbi, K.; Kobayashi, K.; Lina, J.M.; Zelmann, R.; Le Van Quyen, M.

    2013-01-01

    In recent years, new recording technologies have advanced such that, at high temporal and spatial resolutions, high-frequency oscillations (HFO) can be recorded in human partial epilepsy. However, because of the deluge of multichannel data generated by these experiments, achieving the full potential of parallel neuronal recordings depends on the development of new data mining techniques to extract meaningful information relating to time, frequency and space. Here, we aim to bridge this gap by focusing on up-to-date recording techniques for measurement of HFO and new analysis tools for their quantitative assessment. In particular, we emphasize how these methods can be applied, what property might be inferred from neuronal signals, and potentially productive future directions. PMID:22420981

  2. Disruption of microalgal cells using high-frequency focused ultrasound.

    PubMed

    Wang, Meng; Yuan, Wenqiao; Jiang, Xiaoning; Jing, Yun; Wang, Zhuochen

    2014-02-01

    The objective of this study was to evaluate the effectiveness of high-frequency focused ultrasound (HFFU) in microalgal cell disruption. Two microalgal species including Scenedesmus dimorphus and Nannochloropsis oculata were treated by a 3.2-MHz, 40-W focused ultrasound and a 100-W, low-frequency (20kHz) non-focused ultrasound (LFNFU). The results demonstrated that HFFU was effective in the disruption of microalgal cells, indicated by significantly increased lipid fluorescence density, the decrease of cell sizes, and the increase of chlorophyll a fluorescence density after treatments. Compared with LFNFU, HFFU treatment was more energy efficient. The combination of high and low frequency treatments was found to be even more effective than single frequency treatment at the same processing time, indicating that frequency played a critical role in cell disruption. In both HFFU and LFNFU treatments, the effectiveness of cell disruption was found to be dependent on the cell treated. PMID:24374364

  3. High-Frequency Cutoff in Type III Bursts

    NASA Astrophysics Data System (ADS)

    Stanislavsky, A. A.; Konovalenko, A. A.; Volvach, Ya. S.; Koval, A. A.

    In this article we report about a group of solar bursts with high-frequency cutoff, observed on 19 August of 2012 near 8:23 UT, simultaneously by three different radio telescopes: the Ukrainian decameter radio telescope (8-33 MHz), the French Nancay Decametric Array (10-70 MHz) and the Italian San Vito Solar Observatory of RSTN (25-180 MHz). Morphologically the bursts are very similar to the type III bursts. The solar activity is connected with the emergency of a new group of solar spots on the far side of the Sun with respect to observers on Earth. The solar bursts accompany many moderate flares over eastern limb. The refraction of the behind-limb radio bursts towards the Earth is favorable, if CMEs generate low-density cavities in solar corona.

  4. Graphene Quantum Capacitors for High Frequency Tunable Analog Applications.

    PubMed

    Moldovan, Clara F; Vitale, Wolfgang A; Sharma, Pankaj; Tamagnone, Michele; Mosig, Juan R; Ionescu, Adrian M

    2016-08-10

    Graphene quantum capacitors (GQC) are demonstrated to be enablers of radio-frequency (RF) functions through voltage-tuning of their capacitance. We show that GQC complements MEMS and MOSFETs in terms of performance for high frequency analog applications and tunability. We propose a CMOS compatible fabrication process and report the first experimental assessment of their performance at microwaves frequencies (up to 10 GHz), demonstrating experimental GQCs in the pF range with a tuning ratio of 1.34:1 within 1.25 V, and Q-factors up to 12 at 1 GHz. The figures of merit of graphene variable capacitors are studied in detail from 150 to 350 K. Furthermore, we describe a systematic, graphene specific approach to optimize their performance and predict the figures of merit achieved if such a methodology is applied.

  5. High-frequency electric field measurement using a toroidal antenna

    DOEpatents

    Lee, Ki Ha

    2002-01-01

    A simple and compact method and apparatus for detecting high frequency electric fields, particularly in the frequency range of 1 MHz to 100 MHz, uses a compact toroidal antenna. For typical geophysical applications the sensor will be used to detect electric fields for a wide range of spectrum starting from about 1 MHz, in particular in the frequency range between 1 to 100 MHz, to detect small objects in the upper few meters of the ground. Time-varying magnetic fields associated with time-varying electric fields induce an emf (voltage) in a toroidal coil. The electric field at the center of (and perpendicular to the plane of) the toroid is shown to be linearly related to this induced voltage. By measuring the voltage across a toroidal coil one can easily and accurately determine the electric field.

  6. High-frequency shear-horizontal surface acoustic wave sensor

    SciTech Connect

    Branch, Darren W

    2013-05-07

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  7. Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies.

    PubMed

    Wang, Zenghui; Jia, Hao; Zheng, Xuqian; Yang, Rui; Wang, Zefang; Ye, G J; Chen, X H; Shan, Jie; Feng, Philip X-L

    2015-01-21

    We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ∼100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ∼200 nm down to ∼20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory devices and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus.

  8. Graphene Quantum Capacitors for High Frequency Tunable Analog Applications.

    PubMed

    Moldovan, Clara F; Vitale, Wolfgang A; Sharma, Pankaj; Tamagnone, Michele; Mosig, Juan R; Ionescu, Adrian M

    2016-08-10

    Graphene quantum capacitors (GQC) are demonstrated to be enablers of radio-frequency (RF) functions through voltage-tuning of their capacitance. We show that GQC complements MEMS and MOSFETs in terms of performance for high frequency analog applications and tunability. We propose a CMOS compatible fabrication process and report the first experimental assessment of their performance at microwaves frequencies (up to 10 GHz), demonstrating experimental GQCs in the pF range with a tuning ratio of 1.34:1 within 1.25 V, and Q-factors up to 12 at 1 GHz. The figures of merit of graphene variable capacitors are studied in detail from 150 to 350 K. Furthermore, we describe a systematic, graphene specific approach to optimize their performance and predict the figures of merit achieved if such a methodology is applied. PMID:27387370

  9. Spectroscopic measurements of high frequency plasma in supercritical carbon dioxide

    SciTech Connect

    Maehara, T.; Mukasa, S.; Takemori, T.; Watanabe, T.; Kurokawa, K.; Toyota, H.; Nomura, S.; Kawashima, A.; Iwamae, A.

    2009-03-15

    Spectroscopic measurements of high frequency (hf) plasma were performed under high pressure conditions (5 and 7 MPa) and supercritical (sc) CO{sub 2} conditions (8-20 MPa). Temperature evaluated from C{sub 2} Swan bands (d {sup 3}{pi}{sub g}{yields}a {sup 3}{pi}{sub u}) increased from 3600 to 4600 K with an increase in pressure. The first observation of broadening and shifting of the O I line profile (3p {sup 5} P{sub 3,2,1}{yields}3s {sup 5} S{sub 2}{sup 0}) of hf plasma under sc CO{sub 2} conditions was carried out. However, the origin of broadening and the shifting cannot be understood because the present theory explaining them is not valid for such high pressure conditions.

  10. High frequency ultrasonic characterization of sintered SiC

    NASA Technical Reports Server (NTRS)

    Baaklini, George Y.; Generazio, Edward R.; Kiser, James D.

    1987-01-01

    High frequency (60 to 160 MHz) ultrasonic nondestructive evaluation was used to characterize variations in density and microstructural constituents of sintered SiC bars. Ultrasonic characterization methods included longitudinal velocity, reflection coefficient, and precise attenuation measurements. The SiC bars were tailored to provide bulk densities ranging from 90 to 98 percent of theoretical, average grain sizes ranging from 3.0 to 12.0 microns, and average pore sizes ranging from 1.5 to 4.0 microns. Velocity correlated with specimen bulk density irrespective of specimen average grain size, average pore size, and average pore orientation. Attenuation coefficient was found to be sensitive to both density and average pore size variations, but was not affected by large differences in average grain size.

  11. High-Frequency, High-Temperature Fretting Experiments

    NASA Technical Reports Server (NTRS)

    Matlik, J. F.; Farris, T. N.; Haake, F. K.; Swanson, G. R.; Duke, G. C.

    2005-01-01

    Fretting is a structural damage mechanism observed when two nominally clamped surfaces are subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high-temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact. These contact stresses drive crack nucleation and propagation in fretting and are very sensitive to the geometry of the contacting bodies, the contact loads, materials, temperature, and contact surface tribology (friction). To diagnose the threat that small and relatively undetectable fretting cracks pose to damage tolerance and structural integrity of in-service components, the objective of this work is to develop a well-characterized experimental fretting rig capable of investigating fretting behavior of advanced aerospace alloys subjected to load and temperature conditions representative of such turbomachinery components.

  12. Improve predictive maintenance with HFE monitoring. [High Frequency Envelope

    SciTech Connect

    Page, E.A. ); Berggren, C. )

    1994-01-01

    New on-line machine vibration monitoring systems are offering substantially lower costs and simpler installation requirement. By incorporating high-frequency envelope (HFE) spectrum analysis, these systems can provide earlier and more reliable fault detection. These new capabilities are spurring a transition to on-line predictive monitoring of even noncritical machinery. These condition-monitoring systems automatically perform both conventional vibration analysis and HFE spectrum analysis. Conventional low-frequency spectrum analysis, between 0 to 10 kHz, is widely acknowledged as the most effective means of detecting imbalance, misalignment, mechanical resonances and looseness on machinery. HFE spectrum analysis, above 15 kHz, is now accepted as the most effective method for detecting machine faults, such as pitting or cracking in bearings and gears, insufficient lubrication, shaft rubbing and pump cavitation. The performance and economics of this method is discussed.

  13. High-frequency health data and spline functions.

    PubMed

    Martín-Rodríguez, Gloria; Murillo-Fort, Carlos

    2005-03-30

    Seasonal variations are highly relevant for health service organization. In general, short run movements of medical magnitudes are important features for managers in this field to make adequate decisions. Thus, the analysis of the seasonal pattern in high-frequency health data is an appealing task. The aim of this paper is to propose procedures that allow the analysis of the seasonal component in this kind of data by means of spline functions embedded into a structural model. In the proposed method, useful adaptions of the traditional spline formulation are developed, and the resulting procedures are capable of capturing periodic variations, whether deterministic or stochastic, in a parsimonious way. Finally, these methodological tools are applied to a series of daily emergency service demand in order to capture simultaneous seasonal variations in which periods are different.

  14. High-frequency shear-horizontal surface acoustic wave sensor

    SciTech Connect

    Branch, Darren W

    2014-03-11

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  15. Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies.

    PubMed

    Wang, Zenghui; Jia, Hao; Zheng, Xuqian; Yang, Rui; Wang, Zefang; Ye, G J; Chen, X H; Shan, Jie; Feng, Philip X-L

    2015-01-21

    We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ∼100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ∼200 nm down to ∼20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory devices and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus. PMID:25385657

  16. Electrokinetic particle-electrode interactions at high frequencies

    NASA Astrophysics Data System (ADS)

    Yariv, Ehud; Schnitzer, Ory

    2013-01-01

    We provide a macroscale description of electrokinetic particle-electrode interactions at high frequencies, where chemical reactions at the electrodes are negligible. Using a thin-double-layer approximation, our starting point is the set of macroscale equations governing the “bounded” configuration comprising of a particle suspended between two electrodes, wherein the electrodes are governed by a capacitive charging condition and the imposed voltage is expressed as an integral constraint. In the large-cell limit the bounded model is transformed into an effectively equivalent “unbounded” model describing the interaction between the particle and a single electrode, where the imposed-voltage condition is manifested in a uniform field at infinity together with a Robin-type condition applying at the electrode. This condition, together with the standard no-flux condition applying at the particle surface, leads to a linear problem governing the electric potential in the fluid domain in which the dimensionless frequency ω of the applied voltage appears as a governing parameter. In the high-frequency limit ω≫1 the flow is dominated by electro-osmotic slip at the particle surface, the contribution of electrode electro-osmosis being O(ω-2) small. That simplification allows for a convenient analytical investigation of the prevailing case where the clearance between the particle and the adjacent electrode is small. Use of tangent-sphere coordinates allows to calculate the electric and flows fields as integral Hankel transforms. At large distances from the particle, along the electrode, both fields decay with the fourth power of distance.

  17. The Influence of High-Frequency Gravitational Waves Upon Muscles

    SciTech Connect

    Moy, Lawrence S.; Baker, Robert M. L. Jr

    2007-01-30

    The objective of this paper is to present a theory for the possible influence of high-frequency gravitational waves or HFGWs and pulsed micro-current electromagnetic waves or EMs on biological matter specifically on muscle cells and myofibroblasts. The theory involves consideration of the natural frequency of contractions and relaxations of muscles, especially underlying facial skin, and the possible influence of HFGWs on that process. GWs pass without attenuation through all material thus conventional wisdom would dictate that GWs would have no influence on biological matter. On the other hand, GWs can temporarily modify a gravitational field in some locality if they are of high frequency and such a modification might have an influence in changing the skin muscles' natural frequency. Prior to the actual laboratory generation of HFGWs their influence can be emulated by micro-current EM pulses to the skin and some evidence presented here on that effect may predict the influence of HFGWs. We believe that the HFGW pulsations lead to increased muscle activity and may serve to reverse the aging process. A novel theoretical framework concerning these relaxation phenomena is one result of the paper. Another result is the analysis of the possible delivery system of the FBAR-generated HFGWs, the actual power of the generated HFGWs, and the system's application to nanostructural modification of the skin or muscle cells. It is concluded that a series of non-evasive experiments, which are identified, will have the potential to test theory by detecting and analyzing the possible HFGWs change in polarization, refraction, etc. after their interaction with the muscle cells.

  18. Sensitivity of high-frequency Rayleigh-wave data revisited

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Ivanov, J.

    2007-01-01

    Rayleigh-wave phase velocity of a layered earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity (Vs), density, and thickness of layers. Analysis of the Jacobian matrix (or the difference method) provides a measure of dispersion curve sensitivity to earth properties. Vs is the dominant influence for the fundamental mode (Xia et al., 1999) and higher modes (Xia et al., 2003) of dispersion curves in a high frequency range (>2 Hz) followed by layer thickness. These characteristics are the foundation of determining S-wave velocities by inversion of Rayleigh-wave data. More applications of surface-wave techniques show an anomalous velocity layer such as a high-velocity layer (HVL) or a low-velocity layer (LVL) commonly exists in near-surface materials. Spatial location (depth) of an anomalous layer is usually the most important information that surface-wave techniques are asked to provide. Understanding and correctly defining the sensitivity of high-frequency Rayleigh-wave data due to depth of an anomalous velocity layer are crucial in applying surface-wave techniques to obtain a Vs profile and/or determine the depth of an anomalous layer. Because depth is not a direct earth property of a layered model, changes in depth will result in changes in other properties. Modeling results show that sensitivity at a given depth calculated by the difference method is dependent on the Vs difference (contrast) between an anomalous layer and surrounding layers. The larger the contrast is, the higher the sensitivity due to depth of the layer. Therefore, the Vs contrast is a dominant contributor to sensitivity of Rayleigh-wave data due to depth of an anomalous layer. Modeling results also suggest that the most sensitive depth for an HVL is at about the middle of the depth to the half-space, but for an LVL it is near the ground surface. ?? 2007 Society of Exploration Geophysicists.

  19. Development of a Multi-Channel, High Frequency QRS Electrocardiograph

    NASA Technical Reports Server (NTRS)

    DePalma, Jude L.

    2003-01-01

    With the advent of the ISS era and the potential requirement for increased cardiovascular monitoring of crewmembers during extended EVAs, NASA flight surgeons would stand to benefit from an evolving technology that allows for a more rapid diagnosis of myocardial ischemia compared to standard electrocardiography. Similarly, during the astronaut selection process, NASA flight surgeons and other physicians would also stand to benefit from a completely noninvasive technology that, either at rest or during maximal exercise tests, is more sensitive than standard ECG in identifying the presence of ischemia. Perhaps most importantly, practicing cardiologists and emergency medicine physicians could greatly benefit from such a device as it could augment (or even replace) standard electrocardiography in settings where the rapid diagnosis of myocardial ischemia (or the lack thereof) is required for proper clinical decision-making. A multi-channel, high-frequency QRS electrocardiograph is currently under development in the Life Sciences Research Laboratories at JSC. Specifically the project consisted of writing software code, some of which contained specially-designed digital filters, which will be incorporated into an existing commercial software program that is already designed to collect, plot and analyze conventional 12-lead ECG signals on a desktop, portable or palm PC. The software will derive the high-frequency QRS signals, which will be analyzed (in numerous ways) and plotted alongside of the conventional ECG signals, giving the PC-viewing clinician advanced diagnostic information that has never been available previously in all 12 ECG leads simultaneously. After the hardware and software for the advanced digital ECG monitor have been fully integrated, plans are to use the monitor to begin clinical studies both on healthy subjects and on patients with known coronary artery disease in both the outpatient and hospital settings. The ultimate goal is to get the technology

  20. Electrokinetic particle-electrode interactions at high frequencies.

    PubMed

    Yariv, Ehud; Schnitzer, Ory

    2013-01-01

    We provide a macroscale description of electrokinetic particle-electrode interactions at high frequencies, where chemical reactions at the electrodes are negligible. Using a thin-double-layer approximation, our starting point is the set of macroscale equations governing the "bounded" configuration comprising of a particle suspended between two electrodes, wherein the electrodes are governed by a capacitive charging condition and the imposed voltage is expressed as an integral constraint. In the large-cell limit the bounded model is transformed into an effectively equivalent "unbounded" model describing the interaction between the particle and a single electrode, where the imposed-voltage condition is manifested in a uniform field at infinity together with a Robin-type condition applying at the electrode. This condition, together with the standard no-flux condition applying at the particle surface, leads to a linear problem governing the electric potential in the fluid domain in which the dimensionless frequency ω of the applied voltage appears as a governing parameter. In the high-frequency limit ω>1 the flow is dominated by electro-osmotic slip at the particle surface, the contribution of electrode electro-osmosis being O(ω(-2)) small. That simplification allows for a convenient analytical investigation of the prevailing case where the clearance between the particle and the adjacent electrode is small. Use of tangent-sphere coordinates allows to calculate the electric and flows fields as integral Hankel transforms. At large distances from the particle, along the electrode, both fields decay with the fourth power of distance.

  1. Trans-Ionospheric High Frequency Signal Ray Tracing

    NASA Astrophysics Data System (ADS)

    Wright, S.; Gillespie, R. J.

    2012-09-01

    All electromagnetic radiation undergoes refraction as it propagates through the atmosphere. Tropospheric refraction is largely governed by interaction of the radiation with bounded electrons; ionospheric refraction is primarily governed by free electron interactions. The latter phenomenon is important for propagation and refraction of High Frequency (HF) through Extremely High Frequency (EHF) signals. The degree to which HF to EHF signals are bent is dependent upon the integrated refractive effect of the ionosphere: a result of the signal's angle of incidence with the boundaries between adjacent ionospheric regions, the magnitude of change in electron density between two regions, as well as the frequency of the signal. In the case of HF signals, the ionosphere may bend the signal so much that it is directed back down towards the Earth, making over-the-horizon HF radio communication possible. Ionospheric refraction is a major challenge for space-based geolocation applications, where the ionosphere is typically the biggest contributor to geolocation error. Accurate geolocation requires an algorithm that accurately reflects the physical process of a signal transiting the ionosphere, and an accurate specification of the ionosphere at the time of the signal transit. Currently implemented solutions are limited by both the algorithm chosen to perform the ray trace and by the accuracy of the ionospheric data used in the calculations. This paper describes a technique for adapting a ray tracing algorithm to run on a General-Purpose Graphics Processing Unit (GPGPU or GPU), and using a physics-based model specifying the ionosphere at the time of signal transit. This technique allows simultaneous geolocation of significantly more signals than an equivalently priced Central Processing Unit (CPU) based system. Additionally, because this technique makes use of the most widely accepted numeric algorithm for ionospheric ray tracing and a timely physics-based model of the ionosphere

  2. Accurate hydrogen depth profiling by reflection elastic recoil detection analysis

    SciTech Connect

    Verda, R. D.; Tesmer, Joseph R.; Nastasi, Michael Anthony,; Bower, R. W.

    2001-01-01

    A technique to convert reflection elastic recoil detection analysis spectra to depth profiles, the channel-depth conversion, was introduced by Verda, et al [1]. But the channel-depth conversion does not correct for energy spread, the unwanted broadening in the energy of the spectra, which can lead to errors in depth profiling. A work in progress introduces a technique that corrects for energy spread in elastic recoil detection analysis spectra, the energy spread correction [2]. Together, the energy spread correction and the channel-depth conversion comprise an accurate and convenient hydrogen depth profiling method.

  3. Evaluation of neutron spectrometer techniques for ITER using synthetic data

    NASA Astrophysics Data System (ADS)

    Andersson Sundén, E.; Ballabio, L.; Cecconello, M.; Conroy, S.; Ericsson, G.; Johnson, M. Gatu; Gorini, G.; Hellesen, C.; Ognissanto, F.; Ronchi, E.; Sjöstrand, H.; Tardocchi, M.; Weiszflog, M.

    2013-02-01

    A neutron spectrometer at ITER is expected to provide estimates of plasma parameters such as ion temperature, Ti, fuel ion ratio, nt/nd, and Qthermal/Qtot, with 10-20% precision at a time resolution, Δt, of at least 100 ms. The present paper describes a method for evaluating different neutron spectroscopy techniques based on their instrumental response functions and synthetic measurement data. We include five different neutron spectrometric techniques with realistic response functions, based on simulations and measurements where available. The techniques are magnetic proton recoil, thin-foil proton recoil, gamma discriminating organic scintillator, diamond and time-of-flight. The reference position and line of sight of a high resolution neutron spectrometer on ITER are used in the study. ITER plasma conditions are simulated for realistic operating scenarios. The ITER conditions evaluated are beam and radio frequency heated and thermal deuterium-tritium plasmas. Results are given for each technique in terms of the estimated time resolution at which the parameter determination can be made within the required precision (here 10% for Ti and the relative intensities of NB and RF emission components). It is shown that under the assumptions made, the thin-foil techniques out-perform the other spectroscopy techniques in practically all measurement situations. For thermal conditions, the range of achieved Δt in the determination of Ti varies in time scales from ms (for the magnetic and thin-foil proton recoil) to s (for gamma discriminating organic scintillator).

  4. Feasibility of High Frequency Acoustic Imaging for Inspection of Containments

    SciTech Connect

    C.N. Corrado; J.E. Bondaryk; V. Godino

    1998-08-01

    The Nuclear Regulatory Commission has a program at the Oak Ridge National Laboratory to provide assistance in their assessment of the effects of potential degradation on the structural integrity and Ieaktightness of metal containment vessels and steel liners of concrete containment in nuclear power plants. One of the program objectives is to identify a technique(s) for inspection of inaccessible portions of the containment pressure boundary. Acoustic imaging has been identified as one of these potential techniques. A numerical feasibility study investigated the use of high-frequency bistatic acoustic imaging techniques for inspection of inaccessible portions of the metallic pressure boundary of nuclear power plant containment. The range-dependent version of the OASES Code developed at the Massachusetts Institute of Technology was utilized to perform a series of numerical simulations. OASES is a well developed and extensively tested code for evaluation of the acoustic field in a system of stratified fluid and/or elastic layers. Using the code, an arbitrary number of fluid or solid elastic layers are interleaved, with the outer layers modeled as halfspaces. High frequency vibrational sources were modeled to simulate elastic waves in the steel. The received field due to an arbitrary source array can be calculated at arbitrary depth and range positions. In this numerical study, waves that reflect and scatter from surface roughness caused by modeled degradations (e.g., corrosion) are detected and used to identify and map the steel degradation. Variables in the numerical study included frequency, flaw size, interrogation distance, and sensor incident angle.Based on these analytical simulations, it is considered unlikely that acoustic imaging technology can be used to investigate embedded steel liners of reinforced concrete containment. The thin steel liner and high signal losses to the concrete make this application difficult. Results for portions of steel containment

  5. Novel high frequency devices with graphene and GaN

    NASA Astrophysics Data System (ADS)

    Zhao, Pei

    This work focuses on exploring new materials and new device structures to develop novel devices that can operate at very high speed. In chapter 2, the high frequency performance limitations of graphene transistor with channel length less than 100 nm are explored. The simulated results predict that intrinsic cutoff frequency fT of graphene transistor can be close to 2 THz at 15 nm channel length. In chapter 3, we explored the possibility of developing a 2D materials based vertical tunneling device. An analytical model to calculate the channel potentials and current-voltage characteristics in a Symmetric tunneling Field-Effect-Transistor (SymFET) is presented. The symmetric resonant peak in SymFET is a good candidate for high-speed analog applications. Rest of the work focuses on Gallium Nitride (GaN), several novel device concepts based on GaN heterostructure have been proposed for high frequency and high power applications. In chapter 4, we compared the performance of GaN Schottky diodes on bulk GaN substrates and GaN-on-sapphire substrates. In addition, we also discussed the lateral GaN Schottky diode between metal/2DEGs. The advantage of lateral GaN Schottky diodes is the intrinsic cutoff frequency is in the THz range. In chapter 5, a GaN Heterostructure barrier diode (HBD) is designed using the polarization charge and band offset at the AlGaN/GaN heterojunction. The polarization charge at AlGaN/GaN interface behaves as a delta-doping which induces a barrier without any chemical doping. The IV characteristics can be explained by the barrier controlled thermionic emission current. GaN HBDs can be directly integrated with GaN HEMTs, and serve as frequency multipliers or mixers for RF applications. In chapter 6, a GaN based negative effective mass oscillator (NEMO) is proposed. The current in NEMO is estimated under the ballistic limits. Negative differential resistances (NDRs) can be observed with more than 50% of the injected electrons occupied the negative

  6. The comparison of three high-frequency chest compression devices.

    PubMed

    Lee, Yong W; Lee, Jongwon; Warwick, Warren J

    2008-01-01

    High-frequency chest compression (HFCC) is shown to enhance clearance of pulmonary airway secretions. Several HFCC devices have been designed to provide this therapy. Standard equipment consists of an air pulse generator attached by lengths of tubing to an adjustable, inflatable vest/jacket (V/J) garment. In this study, the V/Js were fitted over a mannequin. The three device air pulse generators produced characteristic waveform patterns. The variations in the frequency and pressure setting of devices were consistent with specific device design features. These studies suggest that a better understanding of the effects of different waveform, frequency, and pressure combinations may improve HFCC therapeutic efficacy of three different HFCC machines. The V/J component of HFCC devices delivers the compressive pulses to the chest wall to produce both airflow through and oscillatory effects in the airways. The V/J pressures of three HFCC machines were measured and analyzed to characterize the frequency, pressure, and waveform patterns generated by each of three device models. The dimensions of all V/Js were adjusted to a circumference of approximately 110% of the chest circumference. The V/J pressures were measured, and maximum, minimum, and mean pressure, pulse pressure, and root mean square of three pulse generators were calculated. Jacket pressures ranged between 2 and 34 mmHg. The 103 and 104 models' pulse pressures increased with the increase in HFCC frequency at constant dial pressure. With the ICS the pulse pressure decreased when the frequency increased. The waveforms of models 103 and 104 were symmetric sine wave and asymmetric sine wave patterns, respectively. The ICS had a triangular waveform. At 20 Hz, both the 103 and 104 were symmetric sine waveform but the ICS remained triangular. Maximum crest factors emerged in low-frequency and high-pressure settings for the ICS and in the high-frequency and low-pressure settings for models 103 and 104. Recognizing the

  7. Towards in situ and high frequency estimates of suspended sediment properties

    NASA Astrophysics Data System (ADS)

    Martínez-Carreras, Núria; Schwab, Michael Peter; Klaus, Julian; Hissler, Christophe

    2016-04-01

    Sediment properties, including sediment-associated chemical constituents and sediment physical properties (as colour), can exhibit significant variations within and between storm runoff events. However, the number of samples included in suspended sediment studies is often limited by the time consuming and expensive laboratory procedures for suspended sediment analysis after stream water sampling. This, in turn, restricts high frequency sampling campaigns to a limited number of events and reduces accuracy when aiming to estimate fluxes and loads of sediment-associated chemical constituents. Our contribution addresses the potential for portable ultraviolet-visible (UV-VIS) light spectrometers (220-730 nm) to estimate suspended sediment properties in situ and at high temporal resolution. As far as we know, these instruments have primarily been developed and used to quantify solute concentrations (e.g. DOC and NO3-N), total concentrations of dissolved and particulate forms (e.g. TOC) and turbidity. Here we argue that light absorbance values can be calibrated to estimate solely sediment properties. For our proof-of-concept experiment, we measured light absorbance at 15-min intervals at the Weierbach catchment (NW Luxembourg, 0.46 km2) from December 2013 to January 2015. We then performed a local calibration using suspended sediment loss-on-ignition (LOI) measurements (n=34). We assessed the performance of several regression models that relate light absorbance measurements with the percentage weight LOI. The robust regression method presented the lowest standard error of prediction (0.48{%}) and was selected for calibration (adjusted r2 = 0.76 between observed and predicted values). This study demonstrates that spectrometers can be used to estimate suspended sediment properties at high temporal resolution and for long time spans in a simple, non-destructive and affordable manner. The advantages and disadvantages of the method compared to traditional approaches will be

  8. Direct Measurement of Photon Recoil from a Levitated Nanoparticle

    NASA Astrophysics Data System (ADS)

    Jain, Vijay; Gieseler, Jan; Moritz, Clemens; Dellago, Christoph; Quidant, Romain; Novotny, Lukas

    2016-06-01

    The momentum transfer between a photon and an object defines a fundamental limit for the precision with which the object can be measured. If the object oscillates at a frequency Ω0 , this measurement backaction adds quanta ℏΩ0 to the oscillator's energy at a rate Γrecoil, a process called photon recoil heating, and sets bounds to coherence times in cavity optomechanical systems. Here, we use an optically levitated nanoparticle in ultrahigh vacuum to directly measure Γrecoil. By means of a phase-sensitive feedback scheme, we cool the harmonic motion of the nanoparticle from ambient to microkelvin temperatures and measure its reheating rate under the influence of the radiation field. The recoil heating rate is measured for different particle sizes and for different excitation powers, without the need for cavity optics or cryogenic environments. The measurements are in quantitative agreement with theoretical predictions and provide valuable guidance for the realization of quantum ground-state cooling protocols and the measurement of ultrasmall forces.

  9. Epitaxial silicide formation on recoil-implanted substrates

    SciTech Connect

    Hashimoto, Shin; Egashira, Kyoko; Tanaka, Tomoya; Etoh, Ryuji; Hata, Yoshifumi; Tung, R. T.

    2005-01-15

    An epitaxy-on-recoil-implanted-substrate (ERIS) technique is presented. A disordered surface layer, generated by forward recoil implantation of {approx}0.7-3x10{sup 15} cm{sup -2} of oxygen during Ar plasma etching of surface oxide, is shown to facilitate the subsequent epitaxial growth of {approx}25-35-nm-thick CoSi{sub 2} layers on Si(100). The dependence of the epitaxial fraction of the silicide on the recoil-implantation parameters is studied in detail. A reduction in the silicide reaction rate due to recoil-implanted oxygen is shown to be responsible for the observed epitaxial formation, similar to mechanisms previously observed for interlayer-mediated growth techniques. Oxygen is found to remain inside the fully reacted CoSi{sub 2} layer, likely in the form of oxide precipitates. The presence of these oxide precipitates, with only a minor effect on the sheet resistance of the silicide layer, has a surprisingly beneficial effect on the thermal stability of the silicide layers. The agglomeration of ERIS-grown silicide layers on polycrystalline Si is significantly suppressed, likely from a reduced diffusivity due to oxygen in the grain boundaries. The implications of the present technique for the processing of deep submicron devices are discussed.

  10. Direct Measurement of Photon Recoil from a Levitated Nanoparticle.

    PubMed

    Jain, Vijay; Gieseler, Jan; Moritz, Clemens; Dellago, Christoph; Quidant, Romain; Novotny, Lukas

    2016-06-17

    The momentum transfer between a photon and an object defines a fundamental limit for the precision with which the object can be measured. If the object oscillates at a frequency Ω_{0}, this measurement backaction adds quanta ℏΩ_{0} to the oscillator's energy at a rate Γ_{recoil}, a process called photon recoil heating, and sets bounds to coherence times in cavity optomechanical systems. Here, we use an optically levitated nanoparticle in ultrahigh vacuum to directly measure Γ_{recoil}. By means of a phase-sensitive feedback scheme, we cool the harmonic motion of the nanoparticle from ambient to microkelvin temperatures and measure its reheating rate under the influence of the radiation field. The recoil heating rate is measured for different particle sizes and for different excitation powers, without the need for cavity optics or cryogenic environments. The measurements are in quantitative agreement with theoretical predictions and provide valuable guidance for the realization of quantum ground-state cooling protocols and the measurement of ultrasmall forces. PMID:27367388

  11. High frequency electrical conduction block of the pudendal nerve

    NASA Astrophysics Data System (ADS)

    Bhadra, Narendra; Bhadra, Niloy; Kilgore, Kevin; Gustafson, Kenneth J.

    2006-06-01

    A reversible electrical block of the pudendal nerves may provide a valuable method for restoration of urinary voiding in individuals with bladder-sphincter dyssynergia. This study quantified the stimulus parameters and effectiveness of high frequency (HFAC) sinusoidal waveforms on the pudendal nerves to produce block of the external urethral sphincter (EUS). A proximal electrode on the pudendal nerve after its exit from the sciatic notch was used to apply low frequency stimuli to evoke EUS contractions. HFAC at frequencies from 1 to 30 kHz with amplitudes from 1 to 10 V were applied through a conforming tripolar nerve cuff electrode implanted distally. Sphincter responses were recorded with a catheter mounted micro-transducer. A fast onset and reversible motor block was obtained over this range of frequencies. The HFAC block showed three phases: a high onset response, often a period of repetitive firing and usually a steady state of complete or partial block. A complete EUS block was obtained in all animals. The block thresholds showed a linear relationship with frequency. HFAC pudendal nerve stimulation effectively produced a quickly reversible block of evoked urethral sphincter contractions. The HFAC pudendal block could be a valuable tool in the rehabilitation of bladder-sphincter dyssynergia.

  12. [Use of high frequency jet ventilation in extracorporeal shockwave lithotripsy].

    PubMed

    Schulte am Esch, J; Kochs, E; Meyer, W H

    1985-06-01

    High frequency jet ventilation (HFJV) was used in 68 patients which were treated with extracorporal shock wave lithotripsy (ESWL) because of stone diseases in the upper urinary tract. The question was whether HFJV in combination with a semiclosed conventional circle system offered a practicable and safe technique to minimize the oscillations which are proportional to the applied tidal volume and to the diaphragmatic movements. With IPPV the mean distance of the stone movement was 32 mm, whereas with the application of HFJV the stones oscillated around their resting position within limits of 2 to 3 mm (ventilation frequency: 200-300/min, driving pressure: 0.6-1.1 bar, tidal volume: 3-8 1/min). The effectiveness of HFJV was monitored by the end-tidal carbon dioxide tension (PeCO2) during intermittently conventional ventilation with "adequate" tidal volumes (TV 15 ml/kg bw). The correlation between PeCO2 and simultaneous measured PaCO2 was r = 0,91. The application of HFJV enhances the efficiency of ESWL. So the treatment of stones of the upper urinary tract can be varied by more subtle dosage of the incoming shock wave energy and by stabilisation of the stones in the underlying ellipsoid of the energy focus.

  13. High-Frequency Stimulation of Excitable Cells and Networks

    PubMed Central

    Weinberg, Seth H.

    2013-01-01

    High-frequency (HF) stimulation has been shown to block conduction in excitable cells including neurons and cardiac myocytes. However, the precise mechanisms underlying conduction block are unclear. Using a multi-scale method, the influence of HF stimulation is investigated in the simplified FitzhHugh-Nagumo and biophysically-detailed Hodgkin-Huxley models. In both models, HF stimulation alters the amplitude and frequency of repetitive firing in response to a constant applied current and increases the threshold to evoke a single action potential in response to a brief applied current pulse. Further, the excitable cells cannot evoke a single action potential or fire repetitively above critical values for the HF stimulation amplitude. Analytical expressions for the critical values and thresholds are determined in the FitzHugh-Nagumo model. In the Hodgkin-Huxley model, it is shown that HF stimulation alters the dynamics of ionic current gating, shifting the steady-state activation, inactivation, and time constant curves, suggesting several possible mechanisms for conduction block. Finally, we demonstrate that HF stimulation of a network of neurons reduces the electrical activity firing rate, increases network synchronization, and for a sufficiently large HF stimulation, leads to complete electrical quiescence. In this study, we demonstrate a novel approach to investigate HF stimulation in biophysically-detailed ionic models of excitable cells, demonstrate possible mechanisms for HF stimulation conduction block in neurons, and provide insight into the influence of HF stimulation on neural networks. PMID:24278435

  14. High frequency MoS2 nanomechanical resonators.

    PubMed

    Lee, Jaesung; Wang, Zenghui; He, Keliang; Shan, Jie; Feng, Philip X-L

    2013-07-23

    Molybdenum disulfide (MoS2), a layered semiconducting material in transition metal dichalcogenides (TMDCs), as thin as a monolayer (consisting of a hexagonal plane of Mo atoms covalently bonded and sandwiched between two planes of S atoms, in a trigonal prismatic structure), has demonstrated unique properties and strong promises for emerging two-dimensional (2D) nanodevices. Here we report on the demonstration of movable and vibrating MoS2 nanodevices, where MoS2 diaphragms as thin as 6 nm (a stack of 9 monolayers) exhibit fundamental-mode nanomechanical resonances up to f0 ~ 60 MHz in the very high frequency (VHF) band, and frequency-quality (Q) factor products up to f0 × Q ~ 2 × 10(10)Hz, all at room temperature. The experimental results from many devices with a wide range of thicknesses and lateral sizes, in combination with theoretical analysis, quantitatively elucidate the elastic transition regimes in these ultrathin MoS2 nanomechanical resonators. We further delineate a roadmap for scaling MoS2 2D resonators and transducers toward microwave frequencies. This study also opens up possibilities for new classes of vibratory devices to exploit strain- and dynamics-engineered ultrathin semiconducting 2D crystals.

  15. Challenges in graphene integration for high-frequency electronics

    NASA Astrophysics Data System (ADS)

    Giannazzo, F.; Fisichella, G.; Greco, G.; Roccaforte, F.

    2016-06-01

    This paper provides an overview of the state-of-the-art research on graphene (Gr) for high-frequency (RF) devices. After discussing current limitations of lateral Gr RF transistors, novel vertical devices concepts such as the Gr Base Hot Electron Transistor (GBHET) will be introduced and the main challenges in Gr integration within these architectures will be discussed. In particular, a GBHET device based on Gr/AlGaN/GaN heterostructure will be considered. An approach to the fabrication of this heterostructure by transfer of CVD grown Gr on copper to the AlGaN surface will be presented. The morphological and electrical properties of this system have been investigated at nanoscale by atomic force microscopy (AFM) and conductive atomic force microscopy (CAFM). In particular, local current-voltage measurements by the CAFM probe revealed the formation of a Schottky contact with low barrier height (˜0.41 eV) and excellent lateral uniformity between Gr and AlGaN. Basing on the electrical parameters extracted from this characterization, the theoretical performances of a GBHET formed by a metal/Al2O3/Gr/AlGaN/GaN stack have been evaluated.

  16. Spatial characterization of interictal high frequency oscillations in epileptic neocortex

    PubMed Central

    Trevelyan, A. J.; Schroeder, C. E.; Goodman, R. R.; McKhann, G.; Emerson, R. G.

    2009-01-01

    Interictal high frequency oscillations (HFOs), in particular those with frequency components in excess of 200 Hz, have been proposed as important biomarkers of epileptic cortex as well as the genesis of seizures. We investigated the spatial extent, classification and distribution of HFOs using a dense 4 × 4 mm2 two dimensional microelectrode array implanted in the neocortex of four patients undergoing epilepsy surgery. The majority (97%) of oscillations detected included fast ripples and were concentrated in relatively few recording sites. While most HFOs were limited to single channels, ∼10% occurred on a larger spatial scale with simultaneous but morphologically distinct detections in multiple channels. Eighty per cent of these large-scale events were associated with interictal epileptiform discharges. We propose that large-scale HFOs, rather than the more frequent highly focal events, are the substrates of the HFOs detected by clinical depth electrodes. This feature was prominent in three patients but rarely seen in only one patient recorded outside epileptogenic cortex. Additionally, we found that HFOs were commonly associated with widespread interictal epileptiform discharges but not with locally generated ‘microdischarges’. Our observations raise the possibility that, rather than being initiators of epileptiform activity, fast ripples may be markers of a secondary local response. PMID:19745024

  17. Resting high frequency heart rate variability selectively predicts cooperative behavior.

    PubMed

    Beffara, Brice; Bret, Amélie G; Vermeulen, Nicolas; Mermillod, Martial

    2016-10-01

    This study explores whether the vagal connection between the heart and the brain is involved in prosocial behaviors. The Polyvagal Theory postulates that vagal activity underlies prosocial tendencies. Even if several results suggest that vagal activity is associated with prosocial behaviors, none of them used behavioral measures of prosociality to establish this relationship. We recorded the resting state vagal activity (reflected by High Frequency Heart Rate Variability, HF-HRV) of 48 (42 suitale for analysis) healthy human adults and measured their level of cooperation during a hawk-dove game. We also manipulated the consequence of mutual defection in the hawk-dove game (severe vs. moderate). Results show that HF-HRV is positively and linearly related to cooperation level, but only when the consequence of mutual defection is severe (compared to moderate). This supports that i) prosocial behaviors are likely to be underpinned by vagal functioning ii) physiological disposition to cooperate interacts with environmental context. We discuss these results within the theoretical framework of the Polyvagal Theory. PMID:27343804

  18. High frequency dynamic engine simulation. [TF-30 engine

    NASA Technical Reports Server (NTRS)

    Schuerman, J. A.; Fischer, K. E.; Mclaughlin, P. W.

    1977-01-01

    A digital computer simulation of a mixed flow, twin spool turbofan engine was assembled to evaluate and improve the dynamic characteristics of the engine simulation to disturbance frequencies of at least 100 Hz. One dimensional forms of the dynamic mass, momentum and energy equations were used to model the engine. A TF30 engine was simulated so that dynamic characteristics could be evaluated against results obtained from testing of the TF30 engine at the NASA Lewis Research Center. Dynamic characteristics of the engine simulation were improved by modifying the compression system model. Modifications to the compression system model were established by investigating the influence of size and number of finite dynamic elements. Based on the results of this program, high frequency engine simulations using finite dynamic elements can be assembled so that the engine dynamic configuration is optimum with respect to dynamic characteristics and computer execution time. Resizing of the compression systems finite elements improved the dynamic characteristics of the engine simulation but showed that additional refinements are required to obtain close agreement simulation and actual engine dynamic characteristics.

  19. Theory of High Frequency Rectification by Silicon Crystals

    DOE R&D Accomplishments Database

    Bethe, H. A.

    1942-10-29

    The excellent performance of British "red dot" crystals is explained as due to the knife edge contact against a polished surface. High frequency rectification depends critically on the capacity of the rectifying boundary layer of the crystal, C. For high conversion efficiency, the product of this capacity and of the "forward" (bulk) resistance R {sub b} of the crystal must be small. For a knife edge, this product depends primarily on the breadth of the knife edge and very little upon its length. The contact can therefore have a rather large area which prevents burn-out. For a wavelength of 10 cm. the computations show that the breadth of the knife edge should be less than about 10 {sup -3} cm. For a point contact the radius must be less than 1.5 x 10 {sup -3} cm. and the resulting small area is conducive to burn-out. The effect of "tapping" is probably to reduce the area of contact. (auth)

  20. Why high-frequency pulse tubes can be tipped

    SciTech Connect

    Swift, Gregory W092710; Backhaus, Scott N

    2010-01-01

    The typical low-frequency pulse-tube refrigerator loses significant cooling power when it is tipped with the pulse tube's cold end above its hot end, because natural convection in the pulse tube loads the cold heat exchanger. Yet most high-frequency pulse-tube refrigerators work well in any orientation with respect to gravity. In such a refrigerator, natural convection is suppressed by sufficiently fast velocity oscil1ations, via a nonlinear hydrodynamic effect that tends to align the density gradients in the pulse tube parallel to the oscillation direction. Since gravity's tendency to cause convection is only linear in the pulse tube's end-to-end temperature difference while the oscillation's tendency to align density gradients with oscillating velocity is nonlinear, it is easiest to suppress convection when the end-to-end temperature difference is largest. Simple experiments demonstrate this temperature dependence, the strong dependence on the oscillating velocity, and little dependence on the magnitude or phase of the oscillating pressure. In some circumstances in this apparatus, the suppression of convection is a hysteretic function of oscillating velocity. In some other circumstances, a time-dependent convective state seems more difficult to suppress.

  1. High frequency strain measurements with fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Koch, J.; Angelmahr, M.; Schade, W.

    2015-05-01

    In recent years fiber Bragg grating sensors gained interest in structural health monitoring and concepts for smart structures. They are small, lightweight, and immune to electromagnetic interference. Using multiplexing techniques, several sensors can be addressed by a single fiber. Therefore, well-established structures and materials in industrial applications can be easily equipped with fiber optical sensors with marginal influence on their mechanical properties. In return, critical components can be monitored in real-time, leading to reduced maintenance intervals and a great reduction of costs. Beside of generally condition monitoring, the localization of failures in a structure is a desired feature of the condition monitoring system. Detecting the acoustic emission of a sudden event, its place of origin can be determined by analyzing the delay time of distributed sensor signals. To achieve high localization accuracies for the detection of cracks, breaks, and impacts high sampling rates combined with the simultaneous interrogation of several fiber Bragg grating sensors are required. In this article a fiber Bragg grating interrogator for high frequency measurements up to the megahertz range is presented. The interrogator is based on a passive wavelength to intensity conversion applying arrayed waveguide gratings. Light power fluctuations are suppressed by a differential data evaluation, leading to a reduced signal-to-noise ratio and a low strain detection limit. The measurement system is used to detect, inter alia, wire breaks in steel wire ropes for dockside cranes.

  2. Turbofan Noise Propagation and Radiation at High Frequencies

    NASA Technical Reports Server (NTRS)

    Koch, Danielle (Technical Monitor); Eversman, Walter

    2003-01-01

    This report summarizes progress on NASA Glenn Research Center Grant NAG3-2718 to the University of Missouri at Rolla This grant was awarded on February 22, 2002 and this report covers the performance period to September 30, 2002. There is considerable overlap in research effort with previous NASA Glenn Grant NAG3-2340, as the current effort represents a continuation and extension of this previous grant, which with a no cost supplement terminated on January 31, 2002. This report outlines progress on each task in the original proposal. In addition to progress on several of the specifically proposed tasks, considerable progress has been made in FEM algorithm development with the intent of introducing computational efficiencies required to model high frequency propagation and radiation and to open the possibility of expanding the scope of the modeling capability to three dimensional duct and nacelle geometries. Appended to this document is a paper presented at the 8th AIAA/CEAS Aeroacoustics Conference in June 2002. This paper overlaps the present grant and the previous grant identified above, and it is noted that this paper has also been appended to the final report for NAG3-2304.

  3. Design, analysis, and testing of high frequency passively damped struts

    NASA Technical Reports Server (NTRS)

    Yiu, Y. C.; Davis, L. Porter; Napolitano, Kevin; Ninneman, R. Rory

    1993-01-01

    Objectives of the research are: (1) to develop design requirements for damped struts to stabilize control system in the high frequency cross-over and spill-over range; (2) to design, fabricate and test viscously damped strut and viscoelastically damped strut; (3) to verify accuracy of design and analysis methodology of damped struts; and (4) to design and build test apparatus, and develop data reduction algorithm to measure strut complex stiffness. In order to meet the stringent performance requirements of the SPICE experiment, the active control system is used to suppress the dynamic responses of the low order structural modes. However, the control system also inadvertently drives some of the higher order modes unstable in the cross-over and spill-over frequency range. Passive damping is a reliable and effective way to provide damping to stabilize the control system. It also improves the robustness of the control system. Damping is designed into the SPICE testbed as an integral part of the control-structure technology.

  4. High-frequency electrostatic waves in the magnetosphere.

    NASA Technical Reports Server (NTRS)

    Young, T. S. T.

    1973-01-01

    High-frequency electrostatic microinstabilities in magnetospheric plasmas are considered in detail. Rather special plasma parameters are found to be required to match the theoretical wave spectrum with satellite observations in the magnetosphere. In particular, it is necessary to have a cold and a warm species of electrons such that (1) the warm component has an anomalous velocity distribution function that is nonmonotonic in the perpendicular component of velocity and is the source of free energy driving the instabilities, (2) the density ratio of the cold component to the hot component is greater than about 0.01, and (3) the temperature ratio of the two components for cases of high particle density is no less than 0.1. These requirements and the corresponding instability criteria are satisfied only in the trapping region; this is also the region in which the waves are most frequently observed. The range of unstable wavelengths and an estimate of the diffusion coefficient are also obtained. The wave are found to induce strong diffusion in velocity space for low-energy electrons during periods of moderate wave amplitude.

  5. High Frequency Scattering from Arbitrarily Oriented Dielectric Disks

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Meneghini, R.; Lang, R. H.; Seker, S. S.

    1982-01-01

    Calculations have been made of electromagnetic wave scattering from dielectric disks of arbitrary shape and orientation in the high frequency (physical optics) regime. The solution is obtained by approximating the fields inside the disk with the fields induced inside an identically oriented slab (i.e. infinite parallel planes) with the same thickness and dielectric properties. The fields inside the disk excite conduction and polarization currents which are used to calculate the scattered fields by integrating the radiation from these sources over the volume of the disk. This computation has been executed for observers in the far field of the disk in the case of disks with arbitrary orientation and for arbitrary polarization of the incident radiation. The results have been expressed in the form of a dyadic scattering amplitude for the disk. The results apply to disks whose diameter is large compared to wavelength and whose thickness is small compared to diameter, but the thickness need not be small compared to wavelength. Examples of the dependence of the scattering amplitude on frequency, dielectric properties of the disk and disk orientation are presented for disks of circular cross section.

  6. HIGH FREQUENCY POWER TRANSMISSION LINE FOR CYCLOTRONS AND THE LIKE

    DOEpatents

    Armstrong, W.J.

    1954-04-20

    High-frequency power transmission systems, particularly a stacked capacitance alternating power current transmission line wherein maximum utilization of the effective conductios skin of the line conductors is achieved while enabling a low impedance to be obtained are reported. The transmission line consists of a number of flat metal strips with interleaved dielectric strips. The metal dielectric strips are coiled spirally with the axis of the spiral extending along the length of the strips, and the alternating metal strips at the output end have outwardly extending aligned lugs which are directly strapped together and connected to the respective terminals on the load. At the input end of the transmission line, similarly, the alternate metal strips are directly strapped together and connected to an altereating current source. With the arrangement described each metal strip conducts on both sides, so that the metal strips are designed to have a thickness corresponding to twice the depth of the "skin effect" conducting lamina of each conductor at the source frequency.

  7. Very high frequency plasma reactant for atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Oh, Il-Kwon; Yoo, Gilsang; Yoon, Chang Mo; Kim, Tae Hyung; Yeom, Geun Young; Kim, Kangsik; Lee, Zonghoon; Jung, Hanearl; Lee, Chang Wan; Kim, Hyungjun; Lee, Han-Bo-Ram

    2016-11-01

    Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al2O3 were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al2O3 shows superior physical and electrical properties over RF PE-ALD Al2O3, including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al2O3 on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.

  8. Extremely high-frequency micro-Doppler measurements of humans

    NASA Astrophysics Data System (ADS)

    Hedden, Abigail S.; Silvious, Jerry L.; Dietlein, Charles R.; Green, Jeremy A.; Wikner, David A.

    2014-05-01

    The development of sensors that are capable of penetrating smoke, dust, fog, clouds, and rain is critical for maintaining situational awareness in degraded visual environments and for providing support to the Warfighter. Atmospheric penetration properties, the ability to form high-resolution imagery with modest apertures, and available source power make the extremely high-frequency (EHF) portion of the spectrum promising for the development of radio frequency (RF) sensors capable of penetrating visual obscurants. Comprehensive phenomenology studies including polarization and backscatter properties of relevant targets are lacking at these frequencies. The Army Research Laboratory (ARL) is developing a fully-polarimetric frequency-modulated continuous-wave (FMCW) instrumentation radar to explore polarization and backscatter properties of in-situ rain, scattering from natural and man-made surfaces, and the radar cross section and micro-Doppler signatures of humans at EHF frequencies, specifically, around the 220 GHz atmospheric window. This work presents an overview of the design and construction of the radar system, hardware performance, data acquisition software, and initial results including an analysis of human micro-Doppler signatures.

  9. High-Frequency Gravitational Wave Induced Nuclear Fusion

    NASA Astrophysics Data System (ADS)

    Fontana, Giorgio; Baker, Robert M. L.

    2007-01-01

    Nuclear fusion is a process in which nuclei, having a total initial mass, combine to produce a single nucleus, having a final mass less than the total initial mass. Below a given atomic number the process is exothermic; that is, since the final mass is less than the combined initial mass and the mass deficit is converted into energy by the nuclear fusion. On Earth nuclear fusion does not happen spontaneously because electrostatic barriers prevent the phenomenon. To induce controlled, industrial scale, nuclear fusion, only a few methods have been discovered that look promising, but net positive energy production is not yet possible because of low overall efficiency of the systems. In this paper we propose that an intense burst of High Frequency Gravitational Waves (HFGWs) could be focused or beamed to a target mass composed of appropriate fuel or target material to efficiently rearrange the atomic or nuclear structure of the target material with consequent nuclear fusion. Provided that efficient generation of HFGW can be technically achieved, the proposed fusion reactor could become a viable solution for the energy needs of mankind and alternatively a process for beaming energy to produce a source of fusion energy remotely — even inside solid materials.

  10. High-frequency Ultrasound Imaging of Mouse Cervical Lymph Nodes

    PubMed Central

    Weed, Scott A.

    2015-01-01

    High-frequency ultrasound (HFUS) is widely employed as a non-invasive method for imaging internal anatomic structures in experimental small animal systems. HFUS has the ability to detect structures as small as 30 µm, a property that has been utilized for visualizing superficial lymph nodes in rodents in brightness (B)-mode. Combining power Doppler with B-mode imaging allows for measuring circulatory blood flow within lymph nodes and other organs. While HFUS has been utilized for lymph node imaging in a number of mouse  model systems, a detailed protocol describing HFUS imaging and characterization of the cervical lymph nodes in mice has not been reported. Here, we show that HFUS can be adapted to detect and characterize cervical lymph nodes in mice. Combined B-mode and power Doppler imaging can be used to detect increases in blood flow in immunologically-enlarged cervical nodes. We also describe the use of B-mode imaging to conduct fine needle biopsies of cervical lymph nodes to retrieve lymph tissue for histological  analysis. Finally, software-aided steps are described to calculate changes in lymph node volume and to visualize changes in lymph node morphology following image reconstruction. The ability to visually monitor changes in cervical lymph node biology over time provides a simple and powerful technique for the non-invasive monitoring of cervical lymph node alterations in preclinical mouse models of oral cavity disease. PMID:26274059

  11. High frequency flow-structural interaction in dense subsonic fluids

    NASA Technical Reports Server (NTRS)

    Liu, Baw-Lin; Ofarrell, J. M.

    1995-01-01

    Prediction of the detailed dynamic behavior in rocket propellant feed systems and engines and other such high-energy fluid systems requires precise analysis to assure structural performance. Designs sometimes require placement of bluff bodies in a flow passage. Additionally, there are flexibilities in ducts, liners, and piping systems. A design handbook and interactive data base have been developed for assessing flow/structural interactions to be used as a tool in design and development, to evaluate applicable geometries before problems develop, or to eliminate or minimize problems with existing hardware. This is a compilation of analytical/empirical data and techniques to evaluate detailed dynamic characteristics of both the fluid and structures. These techniques have direct applicability to rocket engine internal flow passages, hot gas drive systems, and vehicle propellant feed systems. Organization of the handbook is by basic geometries for estimating Strouhal numbers, added mass effects, mode shapes for various end constraints, critical onset flow conditions, and possible structural response amplitudes. Emphasis is on dense fluids and high structural loading potential for fatigue at low subsonic flow speeds where high-frequency excitations are possible. Avoidance and corrective measure illustrations are presented together with analytical curve fits for predictions compiled from a comprehensive data base.

  12. High-frequency ultrasonic arrays for ocular imaging

    NASA Astrophysics Data System (ADS)

    Jaeger, M. D.; Kline-Schoder, R. J.; Douville, G. M.; Gagne, J. R.; Morrison, K. T.; Audette, W. E.; Kynor, D. B.

    2007-03-01

    High-resolution ultrasound imaging of the anterior portion of the eye has been shown to provide important information for sizing of intraocular lens implants, diagnosis of pathological conditions, and creation of detailed maps of corneal topography to guide refractive surgery. Current ultrasound imaging systems rely on mechanical scanning of a single acoustic element over the surface of the eye to create the three-dimensional information needed by clinicians. This mechanical scanning process is time-consuming and subject to errors caused by eye movement during the scanning period. This paper describes development of linear ultrasound imaging arrays intended to increase the speed of image acquisition and reduce problems associated with ocular motion. The arrays consist of a linear arrangement of high-frequency transducer elements designed to operate in the 50 - 75 MHz frequency range. The arrays are produced using single-crystal lithium niobate piezoelectric material, thin film electrodes, and epoxy-based acoustic layers. The array elements have been used to image steel test structures and bovine cornea.

  13. High-frequency techniques for RCS prediction of plate geometries

    NASA Technical Reports Server (NTRS)

    Balanis, Constantine A.; Polka, Lesley A.

    1991-01-01

    Radar cross section (RCS) prediction of several rectangular plate geometries is discussed using high-frequency techniques such as the Uniform Theory of Diffraction (UTD) for perfectly conducting and impedance wedges and the Method of Equivalent Currents (MEC). Previous reports have presented detailed solutions to the principal-plane scattering by a perfectly conducting and a coated rectangular plate and nonprincipal-plane scattering by a perfectly conducting plate. These solutions are briefly reviewed and a modified model is presented for the coated plate. Theoretical and experimental data are presented for the perfectly conducting geometries. Agreement between theory and experiment is very good near and at normal incidence. In regions near and at grazing incidence, the disagreement between the data vary according to diffraction distances and angles involved. It is these areas of disagreement which are of extreme interest as an explanation for the disagreement will yield invaluable insight into scattering mechanisms which are not yet identified as major contributors near and at grazing incidence. Areas of disagreement between theory and experiment are identified and examined in an attempt to better understand and predict near-grazing incidence, grazing incidence, and nonprincipal-plane diffractions.

  14. High temperature pressurized high frequency testing rig and test method

    DOEpatents

    De La Cruz, Jose; Lacey, Paul

    2003-04-15

    An apparatus is described which permits the lubricity of fuel compositions at or near temperatures and pressures experienced by compression ignition fuel injector components during operation in a running engine. The apparatus consists of means to apply a measured force between two surfaces and oscillate them at high frequency while wetted with a sample of the fuel composition heated to an operator selected temperature. Provision is made to permit operation at or near the flash point of the fuel compositions. Additionally a method of using the subject apparatus to simulate ASTM Testing Method D6079 is disclosed, said method involving using the disclosed apparatus to contact the faces of prepared workpieces under a measured load, sealing the workface contact point into the disclosed apparatus while immersing said contact point between said workfaces in a lubricating media to be tested, pressurizing and heating the chamber and thereby the fluid and workfaces therewithin, using the disclosed apparatus to impart a differential linear motion between the workpieces at their contact point until a measurable scar is imparted to at least one workpiece workface, and then evaluating the workface scar.

  15. High frequency alternating current chip nano calorimeter with laser heating

    SciTech Connect

    Shoifet, E.; Schick, C.; Chua, Y. Z.; Huth, H.

    2013-07-15

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (∼1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm{sup 2}). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10{sup −3} Hz and 10{sup 6} Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  16. Carbon nanotube transistor based high-frequency electronics

    NASA Astrophysics Data System (ADS)

    Schroter, Michael

    At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks.

  17. High-Frequency Gravitational Wave Induced Nuclear Fusion

    SciTech Connect

    Fontana, Giorgio; Baker, Robert M. L. Jr.

    2007-01-30

    Nuclear fusion is a process in which nuclei, having a total initial mass, combine to produce a single nucleus, having a final mass less than the total initial mass. Below a given atomic number the process is exothermic; that is, since the final mass is less than the combined initial mass and the mass deficit is converted into energy by the nuclear fusion. On Earth nuclear fusion does not happen spontaneously because electrostatic barriers prevent the phenomenon. To induce controlled, industrial scale, nuclear fusion, only a few methods have been discovered that look promising, but net positive energy production is not yet possible because of low overall efficiency of the systems. In this paper we propose that an intense burst of High Frequency Gravitational Waves (HFGWs) could be focused or beamed to a target mass composed of appropriate fuel or target material to efficiently rearrange the atomic or nuclear structure of the target material with consequent nuclear fusion. Provided that efficient generation of HFGW can be technically achieved, the proposed fusion reactor could become a viable solution for the energy needs of mankind and alternatively a process for beaming energy to produce a source of fusion energy remotely - even inside solid materials.

  18. High-frequency nano-optomechanical disk resonators in liquids.

    PubMed

    Gil-Santos, E; Baker, C; Nguyen, D T; Hease, W; Gomez, C; Lemaître, A; Ducci, S; Leo, G; Favero, I

    2015-09-01

    Nano- and micromechanical resonators are the subject of research that aims to develop ultrasensitive mass sensors for spectrometry, chemical analysis and biomedical diagnosis. Unfortunately, their merits generally diminish in liquids because of an increased dissipation. The development of faster and lighter miniaturized devices would enable improved performances, provided the dissipation was controlled and novel techniques were available to drive and readout their minute displacement. Here we report a nano-optomechanical approach to this problem using miniature semiconductor disks. These devices combine a mechanical motion at high frequencies (gigahertz and above) with an ultralow mass (picograms) and a moderate dissipation in liquids. We show that high-sensitivity optical measurements allow their Brownian vibrations to be resolved directly, even in the most-dissipative liquids. We investigate their interaction with liquids of arbitrary properties, and analyse measurements in light of new models. Nano-optomechanical disks emerge as probes of rheological information of unprecedented sensitivity and speed, which opens up applications in sensing and fundamental science.

  19. Protection Circuits for Very High Frequency Ultrasound Systems

    PubMed Central

    Shung, K. Kirk

    2014-01-01

    The purpose of protection circuits in ultrasound applications is to block noise signals from the transmitter from reaching the transducer and also to prevent unwanted high voltage signals from reaching the receiver. The protection circuit using a resistor and diode pair is widely used due to its simple architecture, however, it may not be suitable for very high frequency (VHF) ultrasound transducer applications (>100 MHz) because of its limited bandwidth. Therefore, a protection circuit using MOSFET devices with unique structure is proposed in this paper. The performance of the designed protection circuit was compared with that of other traditional protection schemes. The performance characteristics measured were the insertion loss (IL), total harmonic distortion (THD) and transient response time (TRT). The new protection scheme offers the lowest IL (−1.0 dB), THD (−69.8 dB) and TRT (78 ns) at 120 MHz. The pulse-echo response using a 120 MHz LiNbO3 transducer with each protection circuit was measured to validate the feasibility of the protection circuits in VHF ultrasound applications. The sensitivity and bandwidth of the transducer using the new protection circuit improved by 252.1 and 50.9 %, respectively with respect to the protection circuit using a resistor and diode pair. These results demonstrated that the new protection circuit design minimizes the IL, THD and TRT for VHF ultrasound transducer applications. PMID:24682684

  20. Refraction of high frequency noise in an arbitrary jet flow

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Krejsa, Eugene A.

    1994-01-01

    Refraction of high frequency noise by mean flow gradients in a jet is studied using the ray-tracing methods of geometrical acoustics. Both the two-dimensional (2D) and three-dimensional (3D) formulations are considered. In the former case, the mean flow is assumed parallel and the governing propagation equations are described by a system of four first order ordinary differential equations. The 3D formulation, on the other hand, accounts for the jet spreading as well as the axial flow development. In this case, a system of six first order differential equations are solved to trace a ray from its source location to an observer in the far field. For subsonic jets with a small spreading angle both methods lead to similar results outside the zone of silence. However, with increasing jet speed the two prediction models diverge to the point where the parallel flow assumption is no longer justified. The Doppler factor of supersonic jets as influenced by the refraction effects is discussed and compared with the conventional modified Doppler factor.

  1. Advances to Dynamic Mechanical Analysis: High Frequencies and Environmental Applications

    NASA Astrophysics Data System (ADS)

    Foreman, Jonathon

    2002-03-01

    In dynamic mechanical analysis (DMA) the sample is deformed and released sinusoidally providing information about the modulus and damping behaviors with respect to temperature, time, oscillation frequency and amplitude of motion. It offers exceptional sensitivity to glass transitions and secondary relaxations. Recent developments have increased the frequency range up to 1000 Hz, which allow properties measurements under actual end-use conditions. Furthermore high frequencies enhance the ability to determine the kinetics of viscoelastic relaxations. Another recent development allows DMA measurements while samples are immersed in fluids or enveloped in gases. Most significant is the ability to alter the furnace control parameters to account for the thermal properties of the environment used. This configuration allows temperature-controlled measurements (both heating and isothermal profiles) on a wide range of sample shapes and sizes. Environmental DMA is easier to interpret than standard DMA (in air or inert gas) on preconditioned samples because such samples often lose the conditioning solvent or gas during the measurement. Examples will show real-time property changes from the interaction of unconditioned materials with conditioning environments and experiments on pre-conditioned materials that are heated while immersed in conditioning environments. -------------------------------------------------------------

  2. High frequency chest compression effects heart rate variability.

    PubMed

    Lee, Jongwon; Lee, Yong W; Warwick, Warren J

    2007-01-01

    High frequency chest compression (HFCC) supplies a sequence of air pulses through a jacket worn by a patient to remove excessive mucus for the treatment or prevention of lung disease patients. The air pulses produced from the pulse generator propagates over the thorax delivering the vibration and compression energy. A number of studies have demonstrated that the HFCC system increases the ability to clear mucus and improves lung function. Few studies have examined the change in instantaneous heart rate (iHR) and heart rate variability (HRV) during the HFCC therapy. The purpose of this study is to measure the change of HRV with four experimental protocols: (a) without HFCC, (b) during Inflated, (c)HFCC at 6Hz, and (d) HFCC at 21Hz. The nonlinearity and regularity of HRV was assessed by approximate entropy (ApEn), a method used to quantify the complexities and randomness. To compute the ApEn, we sectioned with a total of eight epochs and displayed the ApEn over the each epoch. Our results show significant differences in the both the iHR and HRV between the experimental protocols. The iHR was elevated at both the (c) 6Hz and (d) 21Hz condition from without HFCC (10%, 16%, respectively). We also found that the HFCC system tends to increase the HRV. Our study suggests that monitoring iHR and HRV are very important physiological indexes during HFCC therapy.

  3. High-frequency chest compression: a summary of the literature.

    PubMed

    Dosman, Cara F; Jones, Richard L

    2005-01-01

    The purpose of the present literature summary is to describe high-frequency chest compression (HFCC), summarize its history and outline study results on its effect on mucolysis, mucus transport, pulmonary function and quality of life. HFCC is a mechanical method of self-administered chest physiotherapy, which induces rapid air movement in and out of the lungs. This mean oscillated volume is an effective method of mucolysis and mucus clearance. HFCC can increase independence. Some studies have shown that HFCC leads to more mucus clearance and better lung function compared with conventional chest physiotherapy. However, HFCC also decreases end-expiratory lung volume, which can lead to increased airway resistance and a decreased oscillated volume. Adding positive end-expiratory pressure to HFCC has been shown to prevent this decrease in end-expiratory lung volume and to increase the oscillated volume. It is possible that the HFCC-induced decrease in end-expiratory lung volume may result in more mucus clearance in airways that remain open by reducing airway size. Adjunctive methods, such as positive end-expiratory pressure, may not always be needed to make HFCC more effective.

  4. High-frequency Ultrasound Imaging of Mouse Cervical Lymph Nodes.

    PubMed

    Walk, Elyse L; McLaughlin, Sarah L; Weed, Scott A

    2015-01-01

    High-frequency ultrasound (HFUS) is widely employed as a non-invasive method for imaging internal anatomic structures in experimental small animal systems. HFUS has the ability to detect structures as small as 30 µm, a property that has been utilized for visualizing superficial lymph nodes in rodents in brightness (B)-mode. Combining power Doppler with B-mode imaging allows for measuring circulatory blood flow within lymph nodes and other organs. While HFUS has been utilized for lymph node imaging in a number of mouse  model systems, a detailed protocol describing HFUS imaging and characterization of the cervical lymph nodes in mice has not been reported. Here, we show that HFUS can be adapted to detect and characterize cervical lymph nodes in mice. Combined B-mode and power Doppler imaging can be used to detect increases in blood flow in immunologically-enlarged cervical nodes. We also describe the use of B-mode imaging to conduct fine needle biopsies of cervical lymph nodes to retrieve lymph tissue for histological  analysis. Finally, software-aided steps are described to calculate changes in lymph node volume and to visualize changes in lymph node morphology following image reconstruction. The ability to visually monitor changes in cervical lymph node biology over time provides a simple and powerful technique for the non-invasive monitoring of cervical lymph node alterations in preclinical mouse models of oral cavity disease. PMID:26274059

  5. Resting high frequency heart rate variability selectively predicts cooperative behavior.

    PubMed

    Beffara, Brice; Bret, Amélie G; Vermeulen, Nicolas; Mermillod, Martial

    2016-10-01

    This study explores whether the vagal connection between the heart and the brain is involved in prosocial behaviors. The Polyvagal Theory postulates that vagal activity underlies prosocial tendencies. Even if several results suggest that vagal activity is associated with prosocial behaviors, none of them used behavioral measures of prosociality to establish this relationship. We recorded the resting state vagal activity (reflected by High Frequency Heart Rate Variability, HF-HRV) of 48 (42 suitale for analysis) healthy human adults and measured their level of cooperation during a hawk-dove game. We also manipulated the consequence of mutual defection in the hawk-dove game (severe vs. moderate). Results show that HF-HRV is positively and linearly related to cooperation level, but only when the consequence of mutual defection is severe (compared to moderate). This supports that i) prosocial behaviors are likely to be underpinned by vagal functioning ii) physiological disposition to cooperate interacts with environmental context. We discuss these results within the theoretical framework of the Polyvagal Theory.

  6. High Frequency Mechanical Pyroshock Simulations for Payload Systems

    SciTech Connect

    BATEMAN,VESTA I.; BROWN,FREDERICK A.; CAP,JEROME S.; NUSSER,MICHAEL A.

    1999-12-15

    Sandia National Laboratories (SNL) designs mechanical systems with components that must survive high frequency shock environments including pyrotechnic shock. These environments have not been simulated very well in the past at the payload system level because of weight limitations of traditional pyroshock mechanical simulations using resonant beams and plates. A new concept utilizing tuned resonators attached to the payload system and driven with the impact of an airgun projectile allow these simulations to be performed in the laboratory with high precision and repeatability without the use of explosives. A tuned resonator has been designed and constructed for a particular payload system. Comparison of laboratory responses with measurements made at the component locations during actual pyrotechnic events show excellent agreement for a bandwidth of DC to 4 kHz. The bases of comparison are shock spectra. This simple concept applies the mechanical pyroshock simulation simultaneously to all components with the correct boundary conditions in the payload system and is a considerable improvement over previous experimental techniques and simulations.

  7. Photodetachment of H- from intense, short, high-frequency pulses

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Robicheaux, F.

    2016-05-01

    We study the photodetachment of an electron from the hydrogen anion due to short, high-frequency laser pulses by numerically solving the time-dependent Schrödinger equation. Simulations are performed to investigate the dependence of the photoelectron spectra on the duration, chirp, and intensity of the pulses. Specifically, we concentrate on the low-energy distributions in the spectra that result from the Raman transitions of the broadband pulses. Contrary to the one-photon ionization, the low-energy distribution maintains a similar width as the laser bandwidth is expanded by chirping the pulses. In addition, we study the transitions of the ionization dynamics from the perturbative to strong-field regime. At high intensities, the positions of the net one- and two-photon absorption peaks in the spectrum shifts and the peaks split to multiple subpeaks because of the multiphoton effects. Moreover, although the one- and two-photon peaks and low-energy distribution exhibit saturation of the ionization yields, the latter shows relatively mild saturation. This work has been supported by DOE under Award No. DE-SC0012193.

  8. Low temperature high frequency coaxial pulse tube for space application

    SciTech Connect

    Charrier, Aurelia; Charles, Ivan; Rousset, Bernard; Duval, Jean-Marc

    2014-01-29

    The 4K stage is a critical step for space missions. The Hershel mission is using a helium bath, which is consumed day by day (after depletion, the space mission is over) while the Plank mission is equipped with one He4 Joule-Thomson cooler. Cryogenic chain without helium bath is a challenge for space missions and 4.2K Pulse-Tube working at high frequency (around 30Hz) is one option to take it up. A low temperature Pulse-Tube would be suitable for the ESA space mission EChO (Exoplanet Characterisation Observatory, expected launch in 2022), which requires around 30mW cooling power at 6K; and for the ESA space mission ATHENA (Advanced Telescope for High ENergy Astrophysics), to pre-cool the sub-kelvin cooler (few hundreds of mW at 15K). The test bench described in this paper combines a Gifford-McMahon with a coaxial Pulse-Tube. A thermal link is joining the intercept of the Pulse-Tube and the second stage of the Gifford-McMahon. This intercept is a separator between the hot and the cold regenerators of the Pulse-Tube. The work has been focused on the cold part of this cold finger. Coupled with an active phase shifter, this Pulse-Tube has been tested and optimized and temperatures as low as 6K have been obtained at 30Hz with an intercept temperature at 20K.

  9. Three-Dimensional Electromagnetic High Frequency Axisymmetric Cavity Scars.

    SciTech Connect

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt

    2014-10-01

    This report examines the localization of high frequency electromagnetic fi elds in three-dimensional axisymmetric cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This report treats both the case where the opposing sides, or mirrors, are convex, where there are no interior foci, and the case where they are concave, leading to interior foci. The scalar problem is treated fi rst but the approximations required to treat the vector fi eld components are also examined. Particular att ention is focused on the normalization through the electromagnetic energy theorem. Both projections of the fi eld along the scarred orbit as well as point statistics are examined. Statistical comparisons are m ade with a numerical calculation of the scars run with an axisymmetric simulation. This axisymmetric cas eformstheoppositeextreme(wherethetwomirror radii at each end of the ray orbit are equal) from the two -dimensional solution examined previously (where one mirror radius is vastly di ff erent from the other). The enhancement of the fi eldontheorbitaxiscanbe larger here than in the two-dimensional case. Intentionally Left Blank

  10. Cobalt Nanoparticle Inks for Printed High Frequency Applications on Polycarbonate

    NASA Astrophysics Data System (ADS)

    Nelo, Mikko; Myllymäki, Sami; Juuti, Jari; Uusimäki, Antti; Jantunen, Heli

    2015-12-01

    In this work the high frequency properties of low curing temperature cobalt nanoparticle inks printed on polycarbonate substrates were investigated. The inks consisted of 30-70 vol.% metallic cobalt nanoparticles and poly (methylene methacrylate) polymer, having excellent adhesion on polycarbonate and a curing temperature of 110°C. The influence of binder material content on the electromagnetic properties of the ink was investigated using the shorted microstrip transmission-line perturbation method. Changes in mechanical properties were evaluated with adhesion tests using the pull-out strength test and the ASTM D 3359-B cross-hatch tape peel test. The microstructure of the printed patterns was investigated with field emission scanning electron microscopy (FESEM). The inks remained mechanically durable with metal contents up to 60 vol.%, achieving pull-off strength of up to 5.2 MPa and the highest marks in adhesion of the tape peel test. The inks obtained a relative permeability of 1.5-3 in the 45 MHz-10 GHz band with a magnetic loss tangent of 0.01-0.06. The developed inks can be utilized in various printed electronics applications such as antenna miniaturization, antenna substrates and magnetic sensors or sensing.

  11. High frequency nanomechanical resonators in ultraclean suspended graphene pn junctions

    NASA Astrophysics Data System (ADS)

    Jung, Minkyung; Rickhaus, Peter; Zihmann, Simon; Makk, Peter; Eichler, Alexander; Weiss, Markus; Schönenberger, Christian; Department of Physics, University of Basel Team; Department of Physics, ETH Zurich Team

    2015-03-01

    Here, we demonstrate high frequency nanomechanical resonators in ultraclean suspended graphene pn junctions. The suspended graphene resonators are fabricated on two bottom gates (left and right) covered with lift-off resist (LOR) by using a mechanical transfer technique. After current annealing, the device exhibits a clear charge neutrality point around zero gate voltage. Depending on the left and right bottom gate voltages, the device shows four different conductance regimes: pp, nn, np and pn corresponding to two different carrier types in the two sides of the sample. At pn and np regimes, the clear Fabry-Perot interference pattern is observed, indicating ballistic transport behavior over 1 μm-long channel. Then, the mechanical resonance is measured in the same device with a frequency modulation (FM) mixing technique at 4.2 K in the vacuum chamber. The resonance frequency is about 405 MHz. By fitting resonance frequency, we deduce both the mass density and the built-in tension in the graphene sheet. In a similar device structure with different strain environment, we observe a resonance frequency as high as 1.17 GHz for the fundamental mode.

  12. Software for Displaying High-Frequency Test Data

    NASA Technical Reports Server (NTRS)

    Elmore, Jason L.

    2003-01-01

    An easy-to-use, intuitive computer program was written to satisfy a need of test operators and data requestors to quickly view and manipulate high-frequency test data recorded at the East and West Test Areas at Marshall Space Flight Center. By enabling rapid analysis, this program makes it possible to reduce times between test runs, thereby potentially reducing the overall cost of test operations. The program can be used to perform quick frequency analysis, using multiple fast- Fourier-transform windowing and amplitude options. The program can generate amplitude-versus-time plots with full zoom capabilities, frequency-component plots at specified time intervals, and waterfall plots (plots of spectral intensity versus frequency at successive small time intervals, showing the changing frequency components over time). There are options for printing of the plots and saving plot data as text files that can be imported into other application programs. The program can perform all of the aforementioned plotting and plot-data-handling functions on a relatively inexpensive computer; other software that performs the same functions requires computers with large amounts of power and memory.

  13. High-frequency synthetic ultrasound array incorporating an actuator

    NASA Astrophysics Data System (ADS)

    Ritter, Timothy A.; Shrout, Thomas R.; Shung, K. Kirk

    2001-05-01

    Ultrasound imaging at frequencies above 20 MHz relies almost exclusively on single-element transducers. IN order to apply array technology at these frequencies, several practical problems must be solved, including spatial scale and fabrication limitations, low device capacitance, and lack of a hardware beamformer. One method of circumventing these problems is to combine an array, an actuator, and a synthetic aperture software beamformer. The array can use relatively wide elements spaced on a coarse pitch. The actuator is used to move the array in short steps (less than the element pitch), and pulse-echo data is acquired at intermediate sample positions. The synthetic aperture beamformer reconstructs the image from the pulse-echo data. A 50 MHz example is analyzed in detail. Estimates of signal-to-noise reveal performance comparable to a standard phased array; furthermore, the actuated array requires half the number of elements, the elements are 8x wider, and only one channel is required. Simulated three-dimensional point spread functions demonstrate side lobe levels approaching - 40dB and main beam widths of 50 to 100 microns. A 50 MHz piezo-composite array design has been tested which displays experimental bandwidth of 70% while maintaining high sensitivity. Individual composite sub-elements are 18 microns wide. Once this array is integrated with a suitable actuator, it is anticipated that a tractable method of imaging with high frequency arrays will result.

  14. Gas transport in branched airways during high-frequency ventilation.

    PubMed

    Scherer, P W; Haselton, F R; Seybert, J R

    1984-01-01

    A theoretical model of high-frequency ventilation (HFV) is presented based on the physical convective exchange process that occurs due to the irreversibility of gas velocity profiles in oscillatory flow through the bronchial airways. Mass transport during the convective exchange process can be characterized by a convective exchange length, LE, which depends only on the irreversibility of bronchial velocity profiles and can be measured by the experimental technique of photographic flow visualization in bronchial tree models. Using the exchange length and the molecular diffusivity, a simple model of overall bronchial mass transfer is developed. The model allows a prediction of the mean gas concentration profiles along the airways, the site of maximum mass transfer resistance, and overall flow rate of the gas of interest in or out of the lung as functions of the parameters of HFV. The results predicted by the model agree with the limited experimental data available for animals and humans. For normal unassisted ventilation, total bronchial cross-sectional area around the 15th Weibel bronchial generation is predicted to be the single most important parameter in controlling the total gas transport rate along the airways. For the breathing of room air, values of the respiratory quotient around 0.78 are predicted, which are insensitive to VT and f. The model represents a fruitful combination of fluid mechanical theory and experiment with physiologic data to yield new and deeper insight into the operation of the human respiratory system during HFV and normal breathing.

  15. High-frequency ultrasonic imaging of thickly sliced specimens

    NASA Astrophysics Data System (ADS)

    Miyasaka, Chiaki; Tittmann, Bernhard R.; Chandraratna, Premindra A. N.

    2003-07-01

    It has been reported that a mechanical scanning reflection acoustic microscope (hereinafter called simply "SAM"), using high frequency ultrasonic tone-burst waves, can form a horizontal cross-sectional image (i.e., c-scan image) showing a highly resolved cellular structure of biological tissue. However, the tissue prepared for the SAM has been mostly a thinly sectioned specimen. In this study, the SAM images of specimens thickly sectioned from the tissue were analyzed. Optical and scanning acoustic microscopies were used to evaluate tissues of human small intestine and esophagus. For preparing thin specimens, the tissue was embedded in paraffin, and substantially sectioned at 5-10μm by the microtome. For optical microscopy, the tissue was stained with hematoxylin and eosin, and affixed onto glass substrates. For scanning acoustic microscopy, two types of specimens were prepared: thinly sectioned specimens affixed on the glass substrate, wherein the specimens were deparaffinized in xylene, but not stained, and thickely sectioned specimens. Images of the thick specimens obtained with frequency at 200 MHz revealed cellular structures. The morphology was very similar to that seen in the thinly sectioned specimens with optical and scanning acoustic microscopy. In addition, scanning electron microscopy was used to compare the images of biological tissue. An acoustic lens with frequency at 200 MHz permitted the imaging of surface and/or subsurface of microstructures in the thick sections of small intestine and esophagus.

  16. High-frequency nano-optomechanical disk resonators in liquids

    NASA Astrophysics Data System (ADS)

    Gil-Santos, E.; Baker, C.; Nguyen, D. T.; Hease, W.; Gomez, C.; Lemaître, A.; Ducci, S.; Leo, G.; Favero, I.

    2015-09-01

    Nano- and micromechanical resonators are the subject of research that aims to develop ultrasensitive mass sensors for spectrometry, chemical analysis and biomedical diagnosis. Unfortunately, their merits generally diminish in liquids because of an increased dissipation. The development of faster and lighter miniaturized devices would enable improved performances, provided the dissipation was controlled and novel techniques were available to drive and readout their minute displacement. Here we report a nano-optomechanical approach to this problem using miniature semiconductor disks. These devices combine a mechanical motion at high frequencies (gigahertz and above) with an ultralow mass (picograms) and a moderate dissipation in liquids. We show that high-sensitivity optical measurements allow their Brownian vibrations to be resolved directly, even in the most-dissipative liquids. We investigate their interaction with liquids of arbitrary properties, and analyse measurements in light of new models. Nano-optomechanical disks emerge as probes of rheological information of unprecedented sensitivity and speed, which opens up applications in sensing and fundamental science.

  17. The mechanics of elastic loading and recoil in anuran jumping.

    PubMed

    Astley, Henry C; Roberts, Thomas J

    2014-12-15

    Many animals use catapult mechanisms to produce extremely rapid movements for escape or prey capture, resulting in power outputs far beyond the limits of muscle. In these catapults, muscle contraction loads elastic structures, which then recoil to release the stored energy extremely rapidly. Many arthropods employ anatomical 'catch mechanisms' to lock the joint in place during the loading period, which can then be released to allow joint motion via elastic recoil. Jumping vertebrates lack a clear anatomical catch, yet face the same requirement to load the elastic structure prior to movement. There are several potential mechanisms to allow loading of vertebrate elastic structures, including the gravitational load of the body, a variable mechanical advantage, and moments generated by the musculature of proximal joints. To test these hypothesized mechanisms, we collected simultaneous 3D kinematics via X-ray Reconstruction of Moving Morphology (XROMM) and single-foot forces during the jumps of three Rana pipiens. We calculated joint mechanical advantage, moment and power using inverse dynamics at the ankle, knee, hip and ilio-sacral joints. We found that the increasing proximal joint moments early in the jump allowed for high ankle muscle forces and elastic pre-loading, and the subsequent reduction in these moments allowed the ankle to extend using elastic recoil. Mechanical advantage also changed throughout the jump, with the muscle contracting against a poor mechanical advantage early in the jump during loading and a higher mechanical advantage late in the jump during recoil. These 'dynamic catch mechanisms' serve to resist joint motion during elastic loading, then allow it during elastic recoil, functioning as a catch mechanism based on the balance and orientation of forces throughout the limb rather than an anatomical catch. PMID:25520385

  18. The mechanics of elastic loading and recoil in anuran jumping.

    PubMed

    Astley, Henry C; Roberts, Thomas J

    2014-12-15

    Many animals use catapult mechanisms to produce extremely rapid movements for escape or prey capture, resulting in power outputs far beyond the limits of muscle. In these catapults, muscle contraction loads elastic structures, which then recoil to release the stored energy extremely rapidly. Many arthropods employ anatomical 'catch mechanisms' to lock the joint in place during the loading period, which can then be released to allow joint motion via elastic recoil. Jumping vertebrates lack a clear anatomical catch, yet face the same requirement to load the elastic structure prior to movement. There are several potential mechanisms to allow loading of vertebrate elastic structures, including the gravitational load of the body, a variable mechanical advantage, and moments generated by the musculature of proximal joints. To test these hypothesized mechanisms, we collected simultaneous 3D kinematics via X-ray Reconstruction of Moving Morphology (XROMM) and single-foot forces during the jumps of three Rana pipiens. We calculated joint mechanical advantage, moment and power using inverse dynamics at the ankle, knee, hip and ilio-sacral joints. We found that the increasing proximal joint moments early in the jump allowed for high ankle muscle forces and elastic pre-loading, and the subsequent reduction in these moments allowed the ankle to extend using elastic recoil. Mechanical advantage also changed throughout the jump, with the muscle contracting against a poor mechanical advantage early in the jump during loading and a higher mechanical advantage late in the jump during recoil. These 'dynamic catch mechanisms' serve to resist joint motion during elastic loading, then allow it during elastic recoil, functioning as a catch mechanism based on the balance and orientation of forces throughout the limb rather than an anatomical catch.

  19. Prompt and delayed spectroscopy of {sup 142}Tb using recoil-isomer tagging

    SciTech Connect

    Mason, P. J. R.; Cullen, D. M.; Kishada, A. M.; Rigby, S. V.; Varley, B. J.; Scholey, C.; Eeckhaudt, S.; Grahn, T.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Leppaenen, A.-P.; Maentyniemi, K.; Nieminen, P.; Nyman, M.; Pakarinen, J.

    2009-02-15

    Recoil-isomer tagging has been used to characterize the states built upon an I{sup {pi}}=8{sup +} isomer in {sup 142}Tb. High-spin states of the neutron-deficient nucleus {sup 142}Tb were populated using an {sup 54}Fe beam, accelerated onto a {sup 92}Mo target of thickness {approx}500 {mu}g/cm{sup 2} at energies of 245, 252, and 265 MeV using the K130 cyclotron at the University of Jyvaeskylae, Finland. Use of the JUROGAM target-position Ge-detector array coupled with the GREAT focal-plane spectrometer at the RITU gas-filled recoil separator has significantly increased the efficiency of the isomer-tagging technique. The rotational band built upon the I{sup {pi}}=8{sup +} isomeric state was established with isomer-tagged {gamma}-{gamma} coincidence data and angular distributions were measured for some of the more intensely populated states. Two previously unobserved bands that bypass the isomer were also established. The new data have been interpreted within the framework of the cranked-shell model. The data show good agreement with the calculated triaxial nuclear shape with {gamma}=-30 deg. for the {sup 142m2}Tb isomeric state. The B(M1)/B(E2) branching ratios, nuclear alignment, signature splitting, and reduced transition probability, B(E1), of the isomeric state have been systematically compared with those of the neighboring nuclei. These comparisons give further evidence for the {pi}h{sub 11/2} x {nu}h{sub 11/2} configuration of the isomer.

  20. Development of neutron spectrometer toward deuterium plasma diagnostics in LHD

    SciTech Connect

    Tomita, H.; Iwai, H.; Iguchi, T.; Kawarabayashi, J.; Isobe, M.; Konno, C.

    2010-10-15

    Neutron spectrometer based on coincident counting of associated particles has been developed for deuterium plasma diagnostics on Large Helical Device (LHD) at the National Institute for Fusion Science. Efficient detection of 2.5 MeV neutron with high energy resolution would be achievable by coincident detection of a scattered neutron and a recoiled proton associated with an elastic scattering of incident neutron in a plastic scintillator as a radiator. The calculated neutron spectra from deuterium plasma heated by neutral beam injection indicate that the energy resolution of better than 7% is required for the spectrometer to evaluate energetic deuterium confinement. By using a prototype of the proposed spectrometer, the energy resolution of 6.3% and the detection efficiency of 3.3x10{sup -7} count/neutron were experimentally demonstrated for 2.5 MeV monoenergetic neutron, respectively.

  1. Robust Optimization Design Algorithm for High-Frequency TWTs

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Chevalier, Christine T.

    2010-01-01

    Traveling-wave tubes (TWTs), such as the Ka-band (26-GHz) model recently developed for the Lunar Reconnaissance Orbiter, are essential as communication amplifiers in spacecraft for virtually all near- and deep-space missions. This innovation is a computational design algorithm that, for the first time, optimizes the efficiency and output power of a TWT while taking into account the effects of dimensional tolerance variations. Because they are primary power consumers and power generation is very expensive in space, much effort has been exerted over the last 30 years to increase the power efficiency of TWTs. However, at frequencies higher than about 60 GHz, efficiencies of TWTs are still quite low. A major reason is that at higher frequencies, dimensional tolerance variations from conventional micromachining techniques become relatively large with respect to the circuit dimensions. When this is the case, conventional design- optimization procedures, which ignore dimensional variations, provide inaccurate designs for which the actual amplifier performance substantially under-performs that of the design. Thus, this new, robust TWT optimization design algorithm was created to take account of and ameliorate the deleterious effects of dimensional variations and to increase efficiency, power, and yield of high-frequency TWTs. This design algorithm can help extend the use of TWTs into the terahertz frequency regime of 300-3000 GHz. Currently, these frequencies are under-utilized because of the lack of efficient amplifiers, thus this regime is known as the "terahertz gap." The development of an efficient terahertz TWT amplifier could enable breakthrough applications in space science molecular spectroscopy, remote sensing, nondestructive testing, high-resolution "through-the-wall" imaging, biomedical imaging, and detection of explosives and toxic biochemical agents.

  2. High frequency noise studies at the Hartousov mofette area (CZE)

    NASA Astrophysics Data System (ADS)

    Schmidt, Andreas; Flores-Estrella, Hortencia; Pommerencke, Julia; Umlauft, Josefine

    2014-05-01

    Ambient noise analysis has been used as a reliable tool to investigate sub-surface structures at seismological quiet regions with none or less specific seismic events. Here, we consider the acoustic signals from a single mofette at the Hartoušov area (CZE) as a noise-like high frequency source caused by multiple near surface degassing processes in a restricted location. From this assumption we have used different array geometries for recording at least one hour of continuous noise. We installed triangular arrays with 3 component geophones: the first deployment consisted on two co-centric triangles with side length of 30 and 50 m with the mofette in the center; the second deployment consisted on two triangular arrays, both with side length of 30 m, co-directional to the mofette. Furthermore, we also installed profiles with 24 channels and vertical geophones locating them in different positions with respect to the mofette. In this work, we present preliminary results from the data analysis dependent on the geometry, to show the characteristics of the noise wave-field referring to frequency content and propagation features, such as directionality and surface wave velocity. The spectral analysis shows that the energy is concentrated in a frequency band among 10 and 40 Hz. However, in this interval there is no evidence of any exclusive fundamental frequencies. From this, man-induced influences can be identified as intermittent signal peaks in narrow frequency bands and can be separated to receive the revised mofette wave-field record. The inversion of dispersive surface waves, that were detected by interferometric methods, provides a velocity model down to 12 m with an S-wave velocity between 160 and 180 m/s on the uppermost layer. Furthermore, the interferometric signal properties indicate that it is not possible to characterize the mofette as a punctual source, but rather as a conglomerate of multiple sources with time and location variations.

  3. Observations of High Frequency Harmonics of the Ionospheric Alfven Resonator

    NASA Astrophysics Data System (ADS)

    Mann, Ian; Usanova, Maria; Bortnik, Jacob; Milling, David; Kale, Andy; Shao, Leo; Miles, David; Rae, I. Jonathan

    We present observations of high frequency harmonics of the ionospheric Alfven Resonator (IAR). These are seen in the form of spectral resonance structures (SRS) recorded by a ground-based search coil magnetometer sampling at 100 samples/s at the Ministik Lake station at L=4.2 within the expanded CARISMA magnetometer array. Previous observational studies have indicated that such SRS are typically confined to frequencies <~5 Hz with only several SRS harmonics being observed. We report the first observations of clear and discrete SRS, which we believe are harmonics of the IAR, and which extend to around 20 Hz in at least 10-12 clear SRS harmonics. We additionally demonstrate the utility of the Bortnik et al. (2007) auto-detection algorithm, designed for Pc1 wavepackets, for characterising the properties of the IAR. Our results also indicate that the cavity supporting SRS in the IAR at this time must be structured to support and trap much higher frequency IAR harmonics than previously assumed. This impacts the potential importance of the IAR for magnetosphere-ionosphere coupling, especially in relation to the impacts of incident Alfven waves on the ionosphere including Alfvenic aurora. Our observations also highlight the potential value of IAR observations for diagnosing the structure of the topside ionosphere, not least using the observed structure of the SRS. These are the first mid-latitude observations demonstrating that the IAR can extend to frequencies beyond those of the lowest few harmonics of the Schumann resonances - significantly suggesting the possibility that the Schumann resonance modes and the IAR may be coupled. The in-situ structure of the IAR is also examined by combining satellite data with conjugate measurements from the ground, and the impacts of the IAR for magnetosphere-ionosphere-thermosphere coupling examined.

  4. High-frequency dynamics of hybrid oxide Josephson heterostructures

    NASA Astrophysics Data System (ADS)

    Komissinskiy, P.; Ovsyannikov, G. A.; Constantinian, K. Y.; Kislinski, Y. V.; Borisenko, I. V.; Soloviev, I. I.; Kornev, V. K.; Goldobin, E.; Winkler, D.

    2008-07-01

    We summarize our results on Josephson heterostructures Nb/Au/YBa2Cu3Ox that combine conventional (S) and oxide high- Tc superconductors with a dominant d -wave symmetry of the superconducting order parameter (D). The heterostructures were fabricated on (001) and (1 1 20) YBa2Cu3Ox films grown by pulsed laser deposition. The structural and surface studies of the (1 1 20) YBa2Cu3Ox thin films reveal nanofaceted surface structure with two facet domain orientations, which are attributed as (001) and (110)-oriented surfaces of YBa2Cu3Ox and result in S/D(001) and S/D(110) nanojunctions formed on the facets. Electrophysical properties of the Nb/Au/YBa2Cu3Ox heterostructures are investigated by the electrical and magnetic measurements at low temperatures and analyzed within the faceting scenario. The superconducting current-phase relation (CPR) of the heterostructures with finite first and second harmonics is derived from the Shapiro steps, which appear in the I-V curves of the heterostructures irradiated at frequencies up to 100 GHz. The experimental positions and amplitudes of the Shapiro steps are explained within the modified resistive Josephson junction model, where the second harmonic of the CPR and capacitance of the Josephson junctions are taken into account. We experimentally observe a crossover from a lumped to a distributed Josephson junction limit for the size of the heterostructures smaller than Josephson penetration depth. The effect is attributed to the variations of the harmonics of the superconducting CPR across the heterojunction, which may give rise to splintered vortices of magnetic flux quantum. Our investigations of parameters and phenomena that are specific for superconductors having d -wave symmetry of the superconducting order parameter may be of importance for applications such as high-frequency detectors and novel elements of a possible quantum computer.

  5. Catchment Very-High Frequency Hydrochemistry: the Critex Chemical House

    NASA Astrophysics Data System (ADS)

    Floury, P.; Gaillardet, J.; Tallec, G.; Blanchouin, A.; Ansart, P.

    2015-12-01

    Exploring the variations of river quality at very high frequency is still a big challenge that has fundamental implications both for understanding catchment ecosystems and for water quality monitoring. Within the French Critical Zone program CRITEX, we have proposed to develop a prototype called "Chemical House", applying the "lab on field" concept to one of the stream of the Orgeval Critical Zone Observatory. The Orgeval catchment (45 km2) is part of the Critical Zone RBV ("Réseau des bassins versants") network. It is a typical temperate agricultural catchment that has been intensively monitored for the last 50 years for hydrology and nutrient chemistry. Agricultural inputs and land use are also finely monitored making Orgeval an ideal basin to test the response of the Critical Zone to agricultural forcing. Geology consists of a typical sedimentary basin of Cenozoic age with horizontal layers of limestones, silcrete and marls, covered by a thin loamy layer. Two main aquifers are present within the catchment: the Brie and the Champigny aquifers. Mean runoff is 780 mm/yr. The Chemical House is a fully automated lab and installed directly along the river, which performs measurement of all major dissolved elements such as Na, Cl, Mg, Ca, NO3, SO4 and K every half hour. It also records all physical parameters (Temperature, pH, conductivity, O2 dissolved, Turbidity) of the water every minute. Orgeval Chemical House started to measure river chemistry on June 12, 2015 and has successfully now recorded several months of data. We will present the architecture of the Chemical House and the first reproducibility and accuracy tests made during the summer drought 2015 period. Preliminary results show that the chemical house is recoding significant nychtemeral (day/night) cycles for each element. We also observe that each element has its own behaviour along a day. First results open great prospects.

  6. Piezoelectric Shaker Development for High Frequency Calibration of Accelerometers

    SciTech Connect

    Payne, Bev; Harper, Kari K.; Vogl, Gregory W.

    2010-05-28

    Calibration of vibration transducers requires sinusoidal motion over a wide frequency range with low distortion and low cross-axial motion. Piezoelectric shakers are well suited to generate such motion and are suitable for use with laser interferometric methods at frequencies of 3 kHz and above. An advantage of piezoelectric shakers is the higher achievable accelerations and displacement amplitudes as compared to electro-dynamic (ED) shakers. Typical commercial ED calibration shakers produce maximum accelerations from 100 m/s{sup 2} to 500 m/s{sup 2}. Very large ED shakers may produce somewhat higher accelerations but require large amplifiers and expensive cooling systems to dissipate heat. Due to the limitations in maximum accelerations by ED shakers at frequencies above 5 kHz, the amplitudes of the generated sinusoidal displacement are frequently below the resolution of laser interferometers used in primary calibration methods. This limits the usefulness of ED shakers in interferometric based calibrations at higher frequencies.Small piezoelectric shakers provide much higher acceleration and displacement amplitudes for frequencies above 5 kHz, making these shakers very useful for accelerometer calibrations employing laser interferometric measurements, as will be shown in this paper. These piezoelectric shakers have been developed and used at NIST for many years for high frequency calibration of accelerometers. This paper documents the construction and performance of a new version of these shakers developed at NIST for the calibration of accelerometers over the range of 3 kHz to 30 kHz and possibly higher. Examples of typical calibration results are also given.

  7. High-frequency voltage oscillations in cultured astrocytes

    PubMed Central

    Fleischer, Wiebke; Theiss, Stephan; Slotta, Johannes; Holland, Christine; Schnitzler, Alfons

    2015-01-01

    Because of their close interaction with neuronal physiology, astrocytes can modulate brain function in multiple ways. Here, we demonstrate a yet unknown astrocytic phenomenon: Astrocytes cultured on microelectrode arrays (MEAs) exhibited extracellular voltage fluctuations in a broad frequency spectrum (100–600 Hz) after electrical stimulation. These aperiodic high-frequency oscillations (HFOs) could last several seconds and did not spread across the MEA. The voltage-gated calcium channel antagonist cilnidipine dose-dependently decreased the power of the oscillations. While intracellular calcium was pivotal, incubation with bafilomycin A1 showed that vesicular release of transmitters played only a minor role in the emergence of HFOs. Gap junctions and volume-regulated anionic channels had just as little functional impact, which was demonstrated by the addition of carbenoxolone (100 μmol/L) and NPPB (100 μmol/L). Hyperpolarization with low potassium in the extracellular solution (2 mmol/L) dramatically raised oscillation power. A similar effect was seen when we added extra sodium (+50 mmol/L) or if we replaced it with NMDG+ (50 mmol/L). The purinergic receptor antagonist PPADS suppressed the oscillation power, while the agonist ATP (100 μmol/L) had only an increasing effect when the bath solution pH was slightly lowered to pH 7.2. From these observations, we conclude that astrocytic voltage oscillations are triggered by activation of voltage-gated calcium channels and driven by a downstream influx of cations through channels that are permeable for large ions such as NMDG+. Most likely candidates are subtypes of pore-forming P2X channels with a low affinity for ATP. PMID:25969464

  8. High-frequency homogenization for travelling waves in periodic media

    NASA Astrophysics Data System (ADS)

    Harutyunyan, Davit; Milton, Graeme W.; Craster, Richard V.

    2016-07-01

    We consider high-frequency homogenization in periodic media for travelling waves of several different equations: the wave equation for scalar-valued waves such as acoustics; the wave equation for vector-valued waves such as electromagnetism and elasticity; and a system that encompasses the Schrödinger equation. This homogenization applies when the wavelength is of the order of the size of the medium periodicity cell. The travelling wave is assumed to be the sum of two waves: a modulated Bloch carrier wave having crystal wavevector k and frequency ω1 plus a modulated Bloch carrier wave having crystal wavevector m and frequency ω2. We derive effective equations for the modulating functions, and then prove that there is no coupling in the effective equations between the two different waves both in the scalar and the system cases. To be precise, we prove that there is no coupling unless ω1=ω2 and (k -m )⊙Λ ∈2 π Zd, where Λ=(λ1λ2…λd) is the periodicity cell of the medium and for any two vectors a =(a1,a2,…,ad),b =(b1,b2,…,bd)∈Rd, the product a⊙b is defined to be the vector (a1b1,a2b2,…,adbd). This last condition forces the carrier waves to be equivalent Bloch waves meaning that the coupling constants in the system of effective equations vanish. We use two-scale analysis and some new weak-convergence type lemmas. The analysis is not at the same level of rigour as that of Allaire and co-workers who use two-scale convergence theory to treat the problem, but has the advantage of simplicity which will allow it to be easily extended to the case where there is degeneracy of the Bloch eigenvalue.

  9. Achieving High-Frequency Optical Control of Synaptic Transmission

    PubMed Central

    Jackman, Skyler L.; Beneduce, Brandon M.; Drew, Iain R.

    2014-01-01

    The optogenetic tool channelrhodopsin-2 (ChR2) is widely used to excite neurons to study neural circuits. Previous optogenetic studies of synapses suggest that light-evoked synaptic responses often exhibit artificial synaptic depression, which has been attributed to either the inability of ChR2 to reliably fire presynaptic axons or to ChR2 elevating the probability of release by depolarizing presynaptic boutons. Here, we compare light-evoked and electrically evoked synaptic responses for high-frequency stimulation at three synapses in the mouse brain. At synapses from Purkinje cells to deep cerebellar nuclei neurons (PC→DCN), light- and electrically evoked synaptic currents were remarkably similar for ChR2 expressed transgenically or with adeno-associated virus (AAV) expression vectors. For hippocampal CA3→CA1 synapses, AAV expression vectors of serotype 1, 5, and 8 led to light-evoked synaptic currents that depressed much more than electrically evoked currents, even though ChR2 could fire axons reliably at up to 50 Hz. The disparity between optical and electrical stimulation was eliminated when ChR2 was expressed transgenically or with AAV9. For cerebellar granule cell to stellate cell (grc→SC) synapses, AAV1 also led to artificial synaptic depression and AAV9 provided superior performance. Artificial synaptic depression also occurred when stimulating over presynaptic boutons, rather than axons, at CA3→CA1 synapses, but not at PC→DCN synapses. These findings indicate that ChR2 expression methods and light stimulation techniques influence synaptic responses in a neuron-specific manner. They also identify pitfalls associated with using ChR2 to study synapses and suggest an approach that allows optogenetics to be applied in a manner that helps to avoid potential complications. PMID:24872574

  10. Gravitational Wave Astronomy:The High Frequency Window

    NASA Astrophysics Data System (ADS)

    Andersson, Nils; Kokkotas, Kostas D.

    As several large scale interferometers are beginning to take data at sensitivities where astrophysical sources are predicted, the direct detection of gravitational waves may well be imminent. This would (finally) open the long anticipated gravitational-wave window to our Universe, and should lead to a much improved understanding of the most violent processes imaginable; the formation of black holes and neutron stars following core collapse supernovae and the merger of compact objects at the end of binary inspiral. Over the next decade we can hope to learn much about the extreme physics associated with, in particular, neutron stars. This contribution is divided in two parts. The first part provides a text-book level introduction to gravitational radiation. The key concepts required for a discussion of gravitational-wave physics are introduced. In particular, the quadrupole formula is applied to the anticipated bread-and-butter source for detectors like LIGO, GEO600, EGO and TAMA300: inspiralling compact binaries. The second part provides a brief review of high frequency gravitational waves. In the frequency range above (say) 100 Hz, gravitational collapse, rotational instabilities and oscillations of the remnant compact objects are potentially important sources of gravitational waves. Significant and unique information concerning the various stages of collapse, the evolution of protoneutron stars and the details of the supranuclear equation of state of such objects can be drawn from careful study of the gravitational-wave signal. As the amount of exciting physics one may be able to study via the detections of gravitational waves from these sources is truly inspiring, there is strong motivation for the development of future generations of ground based detectors sensitive in the range from hundreds of Hz to several kHz.

  11. A recoil resilient lumen support, design, fabrication and mechanical evaluation

    NASA Astrophysics Data System (ADS)

    Mehdizadeh, Arash; Ali, Mohamed Sultan Mohamed; Takahata, Kenichi; Al-Sarawi, Said; Abbott, Derek

    2013-06-01

    Stents are artificial implants that provide scaffolding to a cavity inside the body. This paper presents a new luminal device for reducing the mechanical failure of stents due to recoil, which is one of the most important issues in stenting. This device, which we call a recoil-resilient ring (RRR), is utilized standalone or potentially integrated with existing stents to address the problem of recoil. The proposed structure aims to minimize the need for high-pressure overexpansion that can induce intra-luminal trauma and excess growth of vascular tissue causing later restenosis. The RRR is an overlapped open ring with asymmetrical sawtooth structures that are intermeshed. These teeth can slide on top of each other, while the ring is radially expanded, but interlock step-by-step so as to keep the final expanded state against compressional forces that normally cause recoil. The RRRs thus deliver balloon expandability and, when integrated with a stent, bring both radial rigidity and longitudinal flexibility to the stent. The design of the RRR is investigated through finite element analysis (FEA), and then the devices are fabricated using micro-electro-discharge machining of 200-µm-thick Nitinol sheet. The standalone RRR is balloon expandable in vitro by 5-7 Atm in pressure, which is well within the recommended in vivo pressure ranges for stenting procedures. FEA compression tests indicate 13× less reduction of the cross-sectional area of the RRR compared with a typical stainless steel stent. These results also show perfect elastic recovery of the RRR after removal of the pressure compared to the remaining plastic deformations of the stainless steel stent. On the other hand, experimental loading tests show that the fabricated RRRs have 2.8× radial stiffness compared to a two-column section of a commercial stent while exhibiting comparable elastic recovery. Furthermore, testing of in vitro expansion in a mock artery tube shows around 2.9% recoil, approximately 5-11

  12. High Frequency Measurements of Methane Concentrations and Carbon Isotopes at a Marsh and Landfill

    NASA Astrophysics Data System (ADS)

    Mortazavi, B.; Wilson, B.; Chanton, J.; Eller, K.; Dong, F.; Baer, D. S.; Gupta, M.; Dzwonkowski, B.

    2012-12-01

    High frequency measurements of methane concentrations and carbon isotopes can help constrain the source strengths of methane emitted to the atmosphere. We report here methane concentrations and 13C values measured at 0.5 Hz with cavity enhanced laser absorption spectrometers (Los Gatos Research) deployed at a saltmarsh in Alabama and a landfill in Florida. Methane concentrations and 13C at the saltmarsh were monitored over a 2.5 day time period at 2 m, 0.5 m above the ground as well as from the outflow of a flow-through (2 L) chamber placed on the Spartina alterniflora dominated marsh. A typical measurement cycle included regular samples from two tanks of known methane concentrations and isotopic values and from ambient air samples. Over the 2.5-day measurement period methane concentrations and isotopic ratios at 2 m averaged 1.85 ppm and -43.57‰ (±0.34, 1 SE), respectively. The concentration and isotopic values from the chamber outflow varied from 1.92 to 5.81 ppm and -38.5 to -59.3‰, respectively. Methane flux from the marsh ranged from undetectable to 3.6 mgC m-2hr-1, with high fluxes measured during low tide. The 13δCH4 of the emitted CH4 from the marsh, determined from a mass balance equation using the chamber inflow and outflow concentration and isotopic values ranged from -62.1 to -93.9‰ and averaged -77‰ (±1.25, 1SE). At the landfill ambient methane concentrations and 13C ratios measured over multiple days varied from 4.25 to 11.91 ppm and from -58.81 to -45.12‰, respectively. At higher methane concentrations the δ13C of CH4 was more depleted consistent with previously observed relationship at this site made by more traditional techniques. Over a 30-minute measurement period CH4 concentrations at the landfill could vary by as much as 15 ppm. The high frequency continuous optical measurements with field-deployed instruments provide us with an unprecedented temporal resolution of CH4 concentrations and isotopic ratios. These measurements will

  13. A Compton scatter attenuation gamma ray spectrometer

    NASA Technical Reports Server (NTRS)

    Austin, W. E.

    1972-01-01

    A Compton scatter attenuation gamma ray spectrometer conceptual design is discussed for performing gamma spectral measurements in monodirectional gamma fields from 100 R per hour to 1,000,000 R per hour. Selectable Compton targets are used to scatter gamma photons onto an otherwise heavily shielded detector with changeable scattering efficiencies such that the count rate is maintained between 500 and 10,000 per second. Use of two sum-Compton coincident detectors, one for energies up to 1.5 MeV and the other for 600 keV to 10 MeV, will allow good peak to tail pulse height ratios to be obtained over the entire spectrum and reduces the neutron recoil background rate.

  14. Sensing with High-Frequency Ultrasound in Air

    NASA Astrophysics Data System (ADS)

    Fox, John David

    This thesis explores the excitation and detection of extremely high-frequency (300 kHz to 10 MHz) acoustic waves in air and the use of these ultrasonic waves for measurement purposes. Focused and unfocused transducers and electronic systems are developed for the measurement of the distance from a sensor to an object. Such rangefinder systems have applications to robotics and automated manufacturing. The physics of the propagation and attenuation of ultrasonic waves in air is reviewed, and techniques for impedance matching into low-impedance materials are discussed. Theoretical models are developed to estimate the performance of piezoelectric air transducers using single or multiple quarter wavelength matching layers of lossy materials. Experimental results are presented for three pulse -echo rangefinder systems. Two of these systems operate at 780 kHz and have a distance measurement range of 2-40 cm, with a measurement accuracy of 0.5 mm. The third rangefinder operates at 8.4 MHz and utilizes a novel transducer design. Experimental results are presented which show that the distance measurement resolution of this system is 0.2 x 10('-6) m over air paths of 0-0.8 mm. The experimental work is extended with the development of a focused air acoustic imaging system that operates at 2 MHz. Experimental results are presented which show the transverse resolution of the imaging system to be 390 x 10('-6) m, and the vertical resolution (as determined with a phase-based measurement) to be 0.5 x 10('-6) m. Applications of this imaging system to noncontacting inspection, surface profiling and quantitative film thickness measurements are discussed. The final experimental section presents a transducer design and operational technique that is quite different from the techniques used in the three rangefinders and the focused system. A narrowband resonant transducer and instrument system are discussed and theoretical models are developed to describe the operation of the resonant

  15. High-frequency incremental methods for electromagnetic complex source points

    NASA Astrophysics Data System (ADS)

    Canta, Stefano Mihai

    This dissertation advances knowledge in field-based High-Frequency (HF) incremental methods for electromagnetic Complex Source Points (CSP), and its most immediate impact is a significantly faster analysis and design of reflector antennas. HF incremental methods overcome many difficulties encountered in other ray-tracing techniques, mostly when crossing shadow boundaries in the electromagnetic (EM) field predictions. The combination of HF methods with CSPs allows to speed up EM computations. CSPs are obtained by locating real electric or magnetic dipole sources in complex space. EM field patterns are derived through analytical continuation of the geometrical quantities associated with the source position; the continuation provides an exact Maxwellian description of a Gaussian Beam. When CSPs are used as basis functions, they can represent any radiated field pattern. Then, by truncating negligible beams in the direction of observation, computations are sped up compared to a plane- or spherical-wave based expansion. Because of these facts, CSPs can be used with Physical Optics (PO) based HF methods for the efficient analysis of electrically large reflectors. However, PO does not always provide accurate field predictions, especially in regions of greatest shadowing or at grazing incidence. Therefore, I developed a HF Incremental Fringe Formulation (IFF) for CSPs to provide a correction term for PO that, when added to the total PO field, recovers an accurate estimate of the scattered field at the first asymptotic order. In addition, since PO does not have caustic problems, the new fringe asymptotic recovery is free of caustics for any geometrical configuration, too. Moreover, I also introduced a double diffraction formulation for CSPs, using the Incremental Theory of Diffraction, yielding simulation results very close to those obtained with a Method of Moments (MoM) approach. Unlike ray-based methods, no tracing in complex space is necessary, and no caustics are

  16. REVIEW ARTICLE: The high-frequency dynamics of liquid water

    NASA Astrophysics Data System (ADS)

    Ruocco, Giancarlo; Sette, Francesco

    1999-06-01

    This article is dedicated to reviewing the recent inelastic x-ray scattering (IXS) work on the high-frequency collective dynamics in liquid water. The results obtained with the IXS technique are directly compared with existing ones from inelastic neutron scattering (INS) and molecular dynamics simulation investigations that were carried out with the aim of achieving an understanding of the collective properties of water at the microscopic level. The IXS work has made it possible to demonstrate experimentally the existence, in the range of exchange momentum (Q) examined (1-10 nm-1), of two branches of collective modes: one linearly dispersing with Q (with the apparent sound velocity of icons/Journals/Common/approx" ALT="approx" ALIGN="TOP"/>3200 m s-1) and the other at almost constant energy (5-7 meV). It has been possible to show that the dispersing branch originates from an upwards bend of the ordinary sound branch observed in low-frequency measurements. The study of this sound velocity dispersion, marking a transition from the ordinary sound, co, to the `fast' sound, cicons/Journals/Common/infty" ALT="infty" ALIGN="MIDDLE"/>, as a function of temperature, has made it possible to relate the origin of this phenomenon to a structural relaxation process, which presents many analogies with those observed for glass-forming systems. The possibility of estimating from the IXS data the value of the relaxation time, icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/>, as a function of temperature leads to a relating of the relaxation process to the structural rearrangements induced by the making and breaking of hydrogen bonds. In this framework, it is then possible to recognize a hydrodynamical `normal' regime, i.e. one for which the density fluctuations have a period of oscillation that is on a timescale that is long with respect to icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/>, and a solid-like regime in the opposite limit. In the latter regime, the density

  17. Variable Temperature High-Frequency Response of Heterostructure Transistors

    NASA Astrophysics Data System (ADS)

    Laskar, Joy

    1992-01-01

    The development of high performance heterostructure transistors is essential for emerging opto-electronic integrated circuits (OEICs) and monolithic microwave integrated circuits (MMICs). Applications for OEICs and MMICs include the rapidly growing telecommunications and personal communications markets. The key to successful OEIC and MMIC chip sets is the development of high performance, cost-effective technologies. In this work, several different transistor structures are investigated to determine the potential for high speed performance and the physical mechanisms controlling the ultimate device operation. A cryogenic vacuum microwave measurement system has been developed to study the high speed operation of modulation doped field-effect transistors (MODFETs), doped channel metal insulator field-effect transistors (MISFETs), and metal semiconductor field-effect transistors (MESFETs). This study has concluded that the high field velocity and not the low field mobility is what controls high frequency operation of GaAs based field-effect transistors. Both Al_{rm x} Ga_{rm 1-x}As/GaAs and InP/In_{rm y}Ga _{rm 1-y}As heterostructure bipolar transistors (HBTs) have also been studied at reduced lattice temperatures to understand the role of diffusive transport in the Al_{rm x} Ga_{rm 1-x}As/GaAs HBT and nonequilibrium transport in the InP/In _{rm y}Ga_ {rm 1-y}As HBT. It is shown that drift/diffusion formulation must be modified to accurately estimate the base delay time in the conventional Al _{rm x}Ga_ {rm 1-x}As/GaAs HBT. The reduced lattice temperature operation of the InP/In_ {rm y}Ga_{rm 1-y}As HBT demonstrates extreme nonequilibrium transport in the neutral base and collector space charge region with current gain cut-off frequency exceeding 300 GHz, which is the fastest reported transistor to date. Finally, the MODFET has been investigated as a three-terminal negative differential resistance (NDR) transistor. The existence of real space transfer is confirmed by

  18. Tropospheric Emission Spectrometer and Airborne Emission Spectrometer

    NASA Technical Reports Server (NTRS)

    Glavich, T.; Beer, R.

    1996-01-01

    The Tropospheric Emission Spectrometer (TES) is an instrument being developed for the NASA Earth Observing System Chemistry Platform. TES will measure the distribution of ozone and its precursors in the lower atmosphere. The Airborne Emission Spectrometer (AES) is an aircraft precursor to TES. Applicable descriptions are given of instrument design, technology challenges, implementation and operations for both.

  19. Performance of a neutron spectrometer based on a PIN diode.

    PubMed

    Agosteo, S; D'Angelo, G; Fazzi, A; Para, A Foglio; Pola, A; Ventura, L; Zotto, P

    2005-01-01

    The neutron spectrometer discussed in this work consists of a PIN diode coupled with a polyethylene converter. Neutrons are detected through the energy deposited by recoil-protons in silicon. The maximum detectable energy is -6 MeV and is imposed by the thickness of the fully depleted layer (300 microm for the present device). The minimum detectable energy which can be assessed with pulse-shape discrimination (PSD) is -0.9 MeV. PSD is performed with a crossover method and setting the diode in the 'reverse-injection' configuration (i.e. with the N+ layer adjacent to the converter). This configuration provides longer collection times for the electron-hole pairs generated by the recoil-protons. The limited interval of detectable energies restricts the application of this spectrometer to low-energy neutron fields, such as the ones which can be produced at facilities hosting low-energy ion accelerators. The capacity to reproduce continuous neutron spectra was investigated by optimising the electronic chain for pulse-shape discrimination. In particular, the spectrometer was irradiated with neutrons that were generated by striking a thick beryllium target with protons of several energies and the measured spectra were compared with data taken from the literature. PMID:16604623

  20. High-resolution inelastic x-ray scattering to study the high-frequency atomic dynamics of disordered systems

    NASA Astrophysics Data System (ADS)

    Monaco, Giulio

    2008-06-01

    The use of momentum-resolved inelastic x-ray scattering with meV energy resolution to study the high-frequency atomic dynamics in disordered systems is here reviewed. The typical realization of this experiment is described together with some common models used to interpret the measured spectra and to extract parameters of interest for the investigation of disordered systems. With the help of some selected examples, the present status of the field is discussed. Particular attention is given to those results which are still open for discussion or controversial, and which will require further development of the technique to be fully solved. Such an instrumental development seems nowadays possible at the light of recently proposed schemes for advanced inelastic x-ray scattering spectrometers. To cite this article: G. Monaco, C. R. Physique 9 (2008).

  1. Ionization efficiency study for low energy nuclear recoils in germanium

    NASA Astrophysics Data System (ADS)

    Barker, D.; Wei, W.-Z.; Mei, D.-M.; Zhang, C.

    2013-08-01

    We used the internal conversion (E0 transition) of germanium-72 to indirectly measure the low energy nuclear recoils of germanium. Together with a reliable Monte Carlo package, in which we implement the internal conversion process, the data was compared to the Lindhard (k = 0.159) and Barker-Mei models. A shape analysis indicates that both models agree well with data in the region of interest within 4%. The most probable value (MPV) of the nuclear recoils obtained from the shape analysis is 17.5 ± 0.12 (sys) ±0.035 (stat) keV with an average path-length of 0.014 μm.

  2. Characterization of the CRESST detectors by neutron induced nuclear recoils

    NASA Astrophysics Data System (ADS)

    Coppi, C.; Ciemniak, C.; von Feilitzsch, F.; Gütlein, A.; Hagn, H.; Isaila, C.; Jochum, J.; Kimmerle, M.; Lanfranchi, J.-C.; Pfister, S.; Potzel, W.; Rau, W.; Roth, S.; Rottler, K.; Sailer, C.; Scholl, S.; Usherov, I.; Westphal, W.

    CRESST is an experiment for the direct detection of dark matter particles via nuclear recoils. The CRESST detectors, based on CaWO4 scintillating crystals, are able to discriminate γ and β background by simultaneously measuring the light and phonon signals produced by particle interactions. The discrimination of the background is possible because of the different light output (Quenching Factor, QF) for nuclear and electron recoils. In this article a measurement is shown, aimed at the determination of the QFs of the different nuclei (O, Ca, W) of the detector crystal at 40-60 mK using an 11 MeV neutron beam produced at the Maier-Leibnitz-Laboratorium in Garching (MLL).

  3. Dynamical formation of horizons in recoiling D-branes

    SciTech Connect

    Ellis, John; Mavromatos, N. E.; Nanopoulos, D. V.

    2000-10-15

    A toy calculation of string or D-particle interactions within a world-sheet approach indicates that quantum recoil effects -- reflecting the gravitational back reaction on space-time foam due to the propagation of energetic particles -- induces the appearance of a microscopic event horizon, or ''bubble,'' inside which stable matter can exist. The scattering event causes this horizon to expand, but we expect quantum effects to cause it to contract again, in a ''bounce'' solution. Within such ''bubbles,'' massless matter propagates with an effective velocity that is less than the velocity of light in vacuo, which may lead to observable violations of Lorentz symmetry that may be tested experimentally. The conformal invariance conditions in the interior geometry of the bubbles select preferentially 3 for the number of the spatial dimensions, corresponding to a consistent formulation of the interaction of D3-branes with recoiling D particles, which are allowed to fluctuate independently only on the D3-brane hypersurface.

  4. Dynamical formation of horizons in recoiling D-branes

    NASA Astrophysics Data System (ADS)

    Ellis, John; Mavromatos, N. E.; Nanopoulos, D. V.

    2000-10-01

    A toy calculation of string or D-particle interactions within a world-sheet approach indicates that quantum recoil effects-reflecting the gravitational back reaction on space-time foam due to the propagation of energetic particles-induces the appearance of a microscopic event horizon, or ``bubble,'' inside which stable matter can exist. The scattering event causes this horizon to expand, but we expect quantum effects to cause it to contract again, in a ``bounce'' solution. Within such ``bubbles,'' massless matter propagates with an effective velocity that is less than the velocity of light in vacuo, which may lead to observable violations of Lorentz symmetry that may be tested experimentally. The conformal invariance conditions in the interior geometry of the bubbles select preferentially 3 for the number of the spatial dimensions, corresponding to a consistent formulation of the interaction of D3-branes with recoiling D particles, which are allowed to fluctuate independently only on the D3-brane hypersurface.

  5. Recoil-induced subradiance in an ultracold atomic gas

    SciTech Connect

    Cola, M. M.; Bigerni, D.; Piovella, N.

    2009-05-15

    Subradiance, i.e., the cooperative inhibition of spontaneous emission by destructive interatomic interference, can be realized in a cold atomic sample confined in a ring cavity and lightened by a two-frequency laser. The atoms, scattering the photons of the two laser fields into the cavity mode, recoil and change their momentum. Under proper conditions the atomic initial momentum state and the first two momentum recoil states form a three-level degenerate cascade. A stationary subradiant state is obtained after the scattered photons have left the cavity, leaving the atoms in a coherent superposition of the three collective momentum states. Both a semiclassical description of the process and the quantum subradiant state with its Wigner function are given. Antibunching, quantum correlations, and entanglement between the atomic modes of the subradiant state are demonstrated.

  6. Recoiling supermassive black holes: a search in the nearby universe

    SciTech Connect

    Lena, D.; Robinson, A.; Axon, D. J.; Merritt, D.; Marconi, A.; Capetti, A.; Batcheldor, D.

    2014-11-10

    The coalescence of a binary black hole can be accompanied by a large gravitational recoil due to anisotropic emission of gravitational waves. A recoiling supermassive black hole (SBH) can subsequently undergo long-lived oscillations in the potential well of its host galaxy, suggesting that offset SBHs may be common in the cores of massive ellipticals. We have analyzed Hubble Space Telescope archival images of 14 nearby core ellipticals, finding evidence for small (≲ 10 pc) displacements between the active galactic nucleus (AGN; the location of the SBH) and the center of the galaxy (the mean photocenter) in 10 of them. Excluding objects that may be affected by large-scale isophotal asymmetries, we consider six galaxies to have detected displacements, including M87, where a displacement was previously reported by Batcheldor et al. In individual objects, these displacements can be attributed to residual gravitational recoil oscillations following a major or minor merger within the last few gigayears. For plausible merger rates, however, there is a high probability of larger displacements than those observed, if SBH coalescence took place in these galaxies. Remarkably, the AGN-photocenter displacements are approximately aligned with the radio source axis in four of the six galaxies with displacements, including three of the four having relatively powerful kiloparsec-scale jets. This suggests intrinsic asymmetries in radio jet power as a possible displacement mechanism, although approximate alignments are also expected for gravitational recoil. Orbital motion in SBH binaries and interactions with massive perturbers can produce the observed displacement amplitudes but do not offer a ready explanation for the alignments.

  7. Spallation recoil and age of presolar grains in meteorites

    NASA Astrophysics Data System (ADS)

    Ott, U.; Begemann, F.

    2000-01-01

    We have determined the recoil losses from silicon carbide grain size fractions of spallation neon produced by irradiation with 1.6 GeV protons. During the irradiation the SiC grains were dispersed in paraffin wax in order to avoid re-implantation into neighboring grains. Analysis for spallogenic 21Ne of grain size separates in the size range 0.3 μm to 6 μm and comparison with the 22Na activity of the SiC+paraffin mixture indicates an effective recoil range of 2-3 μm with no apparent effect from acid treatments such as routinely used in the isolation of meteoritic SiC grains. Our results indicate that the majority of presolar SiC grains in primitive meteorites, which are ~μm-sized, will have lost essentially all spallogenic Ne produced by cosmic ray interaction in the interstellar medium. This argues against the validity of previously published presolar ages of Murchison SiC (~10 to ~130 Ma; increasing with grain size; Lewis et al., 1994), where recoil losses had been based on calculated recoil energies. It is argued that the observed variations in meteoritic SiC grain size fractions of 21Ne/22Ne ratios are more likely due to the effects of nucleosynthesis in the He burning shell of the parent AGB stars which imposes new boundary conditions on nuclear parameters and stellar models. It is suggested that spallation-Xe produced on the abundant Ba and REE in presolar SiC, rather than spallogenic Ne, may be a promising approach to the presolar age problem. There is a hint in the currently available Xe data (Lewis et al., 1994) that the large (>1 μm) grains may be younger than the smaller (<1 μm) ones.

  8. Recoil Polarization for Neutral Pion Electroproduction near the Delta Resonance

    SciTech Connect

    Kelly, James J

    2003-10-01

    We have measured angular distributions for recoil polarization in the p(e,e'p)p0 reaction at Q2»1(GeV/c)2 with 1.16 |lte| W |lte|1.36 GeV across the D resonance. The data are compared with representative models and a truncated Legendre analysis is compared with a more general multipole analysis.

  9. Compact Infrared Spectrometers

    NASA Technical Reports Server (NTRS)

    Mouroulis, Pantazis

    2009-01-01

    Concentric spectrometer forms are advantageous for constructing a variety of systems spanning the entire visible to infrared range. Spectrometer examples are given, including broadband or high resolution forms. Some issues associated with the Dyson catadioptric type are also discussed.

  10. Mars Airborne Prospecting Spectrometer

    NASA Astrophysics Data System (ADS)

    Steinkraus, J. M.; Wright, M. W.; Rheingans, B. E.; Steinkraus, D. E.; George, W. P.; Aljabri, A.; Hall, J. L.; Scott, D. C.

    2012-06-01

    One novel approach towards addressing the need for innovative instrumentation and investigation approaches is the integration of a suite of four spectrometer systems to form the Mars Airborne Prospecting Spectrometers (MAPS) for prospecting on Mars.

  11. The velocity and recoil of DNA bands during gel electrophoresis

    NASA Astrophysics Data System (ADS)

    Keiner, Louis E.; Holzwarth, G.

    1992-09-01

    The velocity and recoil of bands of DNA containing 48.5 to 4800 kilobasepairs (kb) were measured during pulsed-field gel electrophoresis by a video imaging and analysis system. When a 10 V/cm electric field was first applied, the velocity showed an initial sharp peak after approximately 1 s whose amplitude depended on the molecular weight of the DNA and the rest time and polarity of the previous pulse. For example, G DNA (670 kb) exhibited an initial velocity peak of 13 μm/s. The velocity then oscillated through a shallow minimum and small maximum before reaching a 5.0 μm/s plateau. After the field was turned off, the bands moved backward (recoiled). The band position obeyed a stretched-exponential relation, x = x0 exp[ - (t/τ)β] with amplitude x0 equal to approximately 1/10th of the DNA contour length and β≊0.6; for S. pombe DNA, x0 was a remarkable 165 μm. Both the initial velocity spike and the recoil arise from the presence of a significant fraction of U-shaped molecules with low configurational entropy. The initial velocity spike is exploited in field-inversion gel electrophoresis to generate the ``antiresonance,'' which is the basis of size-dependent mobility. Recent computer simulations which include tube-length fluctuations and tube leakage are in excellent accord with the measured velocities.

  12. Anatomy of the Binary Black Hole Recoil: A Multipolar Analysis

    NASA Technical Reports Server (NTRS)

    Schnittman, Jeremy; Buonanno, Alessandra; vanMeter, James R.; Baker, John G.; Boggs, William D.; Centrella, Joan; Kelly, Bernard J.; McWilliams, Sean T.

    2007-01-01

    We present a multipolar analysis of the recoil velocity computed in recent numerical simulations of binary black hole coalescence, for both unequal masses and non-zero, non-precessing spins. We show that multipole moments up to and including 1 = 4 are sufficient to accurately reproduce the final recoil velocity (= 98%) and that only a few dominant modes contribute significantly to it (2 95%). We describe how the relative amplitude, and more importantly, the relative phase, of these few modes control the way in which the recoil builds up throughout the inspiral, merger, and ring-down phases. We also find that the numerical results can be reproduced, to a high level of accuracy, by an effective Newtonian formula for the multipole moments obtained by replacing in the Newtonian formula the radial separation with an effective radius computed from the numerical data. Beyond the merger, the numerical results are reproduced by a superposition of three Kerr quasi-normal modes. Analytic formulae, obtained by expressing the multipole moments in terms of the fundamental QNMs of a Kerr BH, are able to explain the onset and amount of '.anti-kick" for each of the simulations. Lastly, we apply this multipolar analysis to understand the remarkable difference between the amplitudes of planar and non-planar kicks for equal-mass spinning black holes.

  13. Recoiling from a Kick in the Head-On Case

    NASA Technical Reports Server (NTRS)

    Choi, Dae-Il; Kelly, Bernard J.; Boggs, William D.; Baker, John G.; Centrella, Joan; Van Meter, James

    2007-01-01

    Recoil "kicks" induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin; adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian (PN) theory, even though the kick is generated in the nonlinear merger interaction, where PN theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin-kicks.

  14. Excitation and Ionisation dynamics in high-frequency plasmas

    NASA Astrophysics Data System (ADS)

    O'Connell, D.

    2008-07-01

    excitation and sustainment of the discharge. As the pressure decreases the discharge operates in so-called 'alpha-mode' where the sheath expansion is responsible for discharge sustainment. Decreasing the pressure towards the limit of operation (below 1 Pa) the discharge operates in a regime where kinetic effects dominate plasma sustainment. Wave particle interactions resulting from the flux of highly energetic electrons interacting with thermal bulk electrons give rise to a series of oscillations in the electron excitation phase space at the sheath edge. This instability is responsible for a significant energy deposit in the plasma when so-called 'ohmic heating' is no longer efficient. In addition to this an interesting electron acceleration mechanism occurs during the sheath collapse. The large sheath width, due to low plasma densities at the lower pressure, and electron inertia allows the build up of a local electric field accelerating electrons towards the electrode. Multi-frequency plasmas, provide additional process control for technological applications, and through investigating the excitation dynamics in such discharges the limitations of functional separation is observed. Non-linear frequency coupling is observed in plasma boundary sheaths governed by two frequencies simultaneously. In an alpha-operated discharge the sheath edge velocity governs the excitation and ionisation within the plasma, and it will be shown that this is determined by the time varying sheath width. The nature of the coupling effects strongly depends on the ratio of the applied voltages. Under technologically relevant conditions (low frequency voltage >> high frequency voltage) interesting phenomena depending on the phase relation of the voltages are also observed and will be discussed.

  15. High frequency magnetization dynamics of ferromagnetic nano-structures

    NASA Astrophysics Data System (ADS)

    Zohar, Sioan

    The development of smaller high frequency magnetic devices with new functionalities requires a more thorough understanding of magnetization dynamics. This thesis documents research into ultrafast magnetization dynamics in ferromagnetic nanoscale materials and summarizes the theoretical foundations and measurement techniques. We present our investigation into the microwave properties of monodisperse, superparamagnetic Fe2O3 nanoparticle arrays using broadband ferromagnetic resonance. We identified a novel field-for resonance relationship in the films. Compared with ferromagnetic films of equal magnetization, resonance frequencies are decreased for in-plane magnetization and increased for out-of-plane magnetization, over the range 0--8 Ghz. The behavior identified is that of a superparamagnetic thin film, where thin-film dipolar fields act on a gradually saturating magnetization described by the Langevin function. Resonance linewidths can be described by the natural dispersion in properties of the system. The second section addresses magnetization dynamics in metalic heterostructures, where the component ultrathin films have nanometer scale dimensions. We have searched for a signature of nonlocal magnetization dynamics, or magnetization dynamics driven by pure spin currents ("spin pumping"), in magnetically soft, polycrystalline Ni81Fe19/Cu/Co93Zr7 tri-layers using ferromagnetic resonance. An interface-related enhancement of damping is expected for each ferromagnetic layer when incorporated in a tri-layer; the enhancement should be absent where layer resonances overlap. While size effects in Gilbert damping have been identified, we note that expectations specific to spin pumping are not confirmed. We have also observed this effect in Ni81Fe19/Cu/Ni81Fe19/Mn 50Fe50 exchange biased spin valves with clearly defined giant magneto-resistance (GMR). Finally, we have investigated the dynamic effects in these films using a novel time-resolved x-ray technique. The reciprocal

  16. Magnetoencephalography Detection of High-Frequency Oscillations in the Developing Brain

    PubMed Central

    Leiken, Kimberly; Xiang, Jing; Zhang, Fawen; Shi, Jingping; Tang, Lu; Liu, Hongxing; Wang, Xiaoshan

    2014-01-01

    Increasing evidence from invasive intracranial recordings suggests that the matured brain generates both physiological and pathological high-frequency signals. The present study was designed to detect high-frequency brain signals in the developing brain using newly developed magnetoencephalography (MEG) methods. Twenty healthy children were studied with a high-sampling rate MEG system. Functional high-frequency brain signals were evoked by electrical stimulation applied to the index fingers. To determine if the high-frequency neuromagnetic signals are true brain responses in high-frequency range, we analyzed the MEG data using the conventional averaging as well as newly developed time-frequency analysis along with beamforming. The data of healthy children showed that very high-frequency brain signals (>1000 Hz) in the somatosensory cortex in the developing brain could be detected and localized using MEG. The amplitude of very high-frequency brain signals was significantly weaker than that of the low-frequency brain signals. Very high-frequency brain signals showed a much earlier latency than those of a low-frequency. Magnetic source imaging (MSI) revealed that a portion of the high-frequency signals was from the somatosensory cortex, another portion of the high-frequency signals was probably from the thalamus. Our results provide evidence that the developing brain generates high-frequency signals that can be detected with the non-invasive technique of MEG. MEG detection of high-frequency brain signals may open a new window for the study of developing brain function. PMID:25566015

  17. Measurement of the beam-recoil polarization in low-energy virtual Compton scattering from the proton

    NASA Astrophysics Data System (ADS)

    Doria, L.; Janssens, P.; Achenbach, P.; Ayerbe Gayoso, C.; Baumann, D.; Bensafa, I.; Benali, M.; Beričič, J.; Bernauer, J. C.; Böhm, R.; Bosnar, D.; Correa, L.; D'Hose, N.; Defaÿ, X.; Ding, M.; Distler, M. O.; Fonvieille, H.; Friedrich, J.; Friedrich, J. M.; Laveissière, G.; Makek, M.; Marroncle, J.; Merkel, H.; Mihovilovič, M.; Müller, U.; Nungesser, L.; Pasquini, B.; Pochodzalla, J.; Postavaru, O.; Potokar, M.; Ryckbosch, D.; Sánchez Majos, S.; Schlimme, B. S.; Seimetz, M.; Širca, S.; Tamas, G.; Van de Vyver, R.; Van Hoorebeke, L.; Van Overloop, A.; Walcher, Th.; Weinriefer, M.; A1 Collaboration

    2015-11-01

    Double-polarization observables in the reaction e ⃗p →e'p ⃗'γ have been measured at Q2=0.33 (GeV/c ) 2 . The experiment was performed at the spectrometer setup of the A1 Collaboration using the 855 MeV polarized electron beam provided by the Mainz Microtron (MAMI) and a recoil proton polarimeter. From the double-polarization observables the structure function PLT ⊥ is extracted for the first time, with the value (-15.4 ±3 .3(stat .)-2.4+1.5(syst.)) GeV-2 , using the low-energy theorem for virtual Compton scattering. This structure function provides a hitherto unmeasured linear combination of the generalized polarizabilities of the proton.

  18. Spherical grating spectrometers

    NASA Astrophysics Data System (ADS)

    O'Donoghue, Darragh; Clemens, J. Christopher

    2014-07-01

    We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

  19. Recoil ion charge state distribution following the beta(sup +) decay of {sup 21}Na

    SciTech Connect

    Scielzo, Nicholas D.; Freedman, Stuart J.; Fujikawa, Brian K.; Vetter, Paul A.

    2003-01-03

    The charge state distribution following the positron decay of 21Na has been measured, with a larger than expected fraction of the daughter 21Ne in positive charge states. No dependence on either the positron or recoil nucleus energy is observed. The data is compared to a simple model based on the sudden approximation. Calculations suggest a small but important contribution from recoil ionization has important consequences for precision beta decay correlation experiments detecting recoil ions.

  20. Revealing compressed stops using high-momentum recoils

    DOE PAGESBeta

    Macaluso, Sebastian; Park, Michael; Shih, David; Tweedie, Brock

    2016-03-22

    In this study, searches for supersymmetric top quarks at the LHC have been making great progress in pushing sensitivity out to higher mass, but are famously plagued by gaps in coverage around lower-mass regions where the decay phase space is closing off. Within the common stop-NLSP/neutralino-LSP simplified model, the line in the mass plane where there is just enough phase space to produce an on-shell top quark remains almost completely unconstrained. Here, we show that is possible to define searches capable of probing a large patch of this difficult region, with S/B ~ 1 and significances often well beyond 5σ.more » The basic strategy is to leverage the large energy gain of LHC Run 2, leading to a sizable population of stop pair events recoiling against a hard jet. The recoil not only re-establishes a ET, but also leads to a distinctive anti-correlation between the ET and the recoil jet transverse vectors when the stops decay all-hadronically. Accounting for jet combinatorics, backgrounds, and imperfections in ET measurements, we estimate that Run 2 will already start to close the gap in exclusion sensitivity with the first few 10s of fb–1. By 300 fb–1, exclusion sensitivity may extend from stop masses of 550 GeV on the high side down to below 200 GeV on the low side, approaching the “stealth” point at mt¯ = mt and potentially overlapping with limits from tt¯ cross section and spin correlation measurements.« less

  1. Revealing compressed stops using high-momentum recoils

    NASA Astrophysics Data System (ADS)

    Macaluso, Sebastian; Park, Michael; Shih, David; Tweedie, Brock

    2016-03-01

    Searches for supersymmetric top quarks at the LHC have been making great progress in pushing sensitivity out to higher mass, but are famously plagued by gaps in coverage around lower-mass regions where the decay phase space is closing off. Within the common stop-NLSP/neutralino-LSP simplified model, the line in the mass plane where there is just enough phase space to produce an on-shell top quark remains almost completely unconstrained. Here, we show that is possible to define searches capable of probing a large patch of this difficult region, with S/B ˜ 1 and significances often well beyond 5 σ. The basic strategy is to leverage the large energy gain of LHC Run 2, leading to a sizable population of stop pair events recoiling against a hard jet. The recoil not only re-establishes a [InlineMediaObject not available: see fulltext.] signature, but also leads to a distinctive anti-correlation between the [InlineMediaObject not available: see fulltext.] and the recoil jet transverse vectors when the stops decay all-hadronically. Accounting for jet combinatorics, backgrounds, and imperfections in [InlineMediaObject not available: see fulltext.] measurements, we estimate that Run 2 will already start to close the gap in exclusion sensitivity with the first few 10s of fb-1. By 300 fb-1, exclusion sensitivity may extend from stop masses of 550 GeV on the high side down to below 200 GeV on the low side, approaching the "stealth" point at {m}_{overline{t}}={m}_t and potentially overlapping with limits from toverline{t} cross section and spin correlation measurements.

  2. B -> D* l nu at zero recoil: an update

    SciTech Connect

    Bailey, Jon A.; Bazavov, A.; Bernard, C.; Bouchard, C.M.; DeTar, C.; El-Khadra, A.X.; Freeland, E.D.; Gamiz, E.; Gottlieb, Steven; Heller, U.M.; Hetrick, J.E.

    2010-11-01

    We present an update of our calculation of the form factor for {bar B} {yields} D*{ell}{bar {nu}} at zero recoil, with higher statistics and finer lattices. As before, we use the Fermilab action for b and c quarks, the asqtad staggered action for light valence quarks, and the MILC ensembles for gluons and light quarks (Luescher-Weisz married to 2+1 rooted staggered sea quarks). In this update, we have reduced the total uncertainty on F(1) from 2.6% to 1.7%.

  3. Projectile paths corrected for recoil and air resistance

    NASA Astrophysics Data System (ADS)

    Kemp, H. R.

    1986-01-01

    The angle of projection of a bullet is not the same as the angle of the bore of the firearm just before firing. This is because recoil alters the direction of the barrel as the bullet moves along the barrel. Neither is the angle of projection of an arrow the same as the direction of the arrow just before it is projected. The difficulty in obtaining the angle of projection limits the value of the standard equation for trajectories relative to a horizontal plane. Furthermore, air resistance makes this equation unrealistic for all but short ranges.

  4. Precision lifetime measurements using the recoil distance method

    SciTech Connect

    Kruecken, R.

    2000-02-01

    The recoil distance method (RDM) for the measurements of lifetimes of excited nuclear levels in the range from about 1 ps to 1,000 ps is reviewed. The New Yale Plunger Device for RDM experiments is introduced and the Differential Decay Curve Method for their analysis is reviewed. Results from recent RDM experiments on SD bands in the mass-190 region, shears bands in the neutron deficient lead isotopes, and ground state bands in the mass-130 region are presented. Perspectives for the use of RDM measurements in the study of neutron-rich nuclei are discussed.

  5. Bulk and integrated acousto-optic spectrometers for radio astronomy

    NASA Technical Reports Server (NTRS)

    Chin, G.; Buhl, D.; Florez, J. M.

    1981-01-01

    The development of sensitive heterodyne receivers (front end) in the centimeter and millimeter range, and the construction of sensitive RF spectrometers (back end) enable the spectral lines of interstellar molecules to be detected and identified. A technique was developed which combines acoustic bending of a collimated coherent light beam by a Bragg cell followed by detection by a sensitive array of photodetectors (thus forming an RF acousto-optic spectrometer (AOS). An AOS has wide bandwidth, large number of channels, and high resolution, and is compact, lightweight, and energy efficient. The thrust of receiver development is towards high frequency heterodyne systems, particularly in the millimeter, submillimeter, far infrared, and 10 micron spectral ranges.

  6. Demonstration of An Image Rejection Mixer for High Frequency Applications (26-36 GHz)

    NASA Technical Reports Server (NTRS)

    Bankston, Cheryl D.; Carlstrom, John E.

    1999-01-01

    A new high frequency image-rejection mixer was successfully tested in a 26-36 GHz band receiver. This paper briefly describes the motivation for implementation of an image rejection mixer in a receiver system, the basic operation of an image rejection mixer, and the development and testing of an image rejection mixer for a high frequency, cryogenic receiver system.

  7. Does Phonology Play a Role When Skilled Readers Read High-Frequency Words? Evidence from ERPs

    ERIC Educational Resources Information Center

    Newman, Randy Lynn; Jared, Debra; Haigh, Corinne A.

    2012-01-01

    We used event-related brain potentials to clarify the role of phonology in activating the meanings of high-frequency words during skilled silent reading. Target homophones ("meet") in sentences such as "The students arranged to meet in the library to study" were replaced on some trials by either a high-frequency homophone mate ("meat") or a…

  8. Recoil separator ERNA: charge state distribution, target density, beam heating, and longitudinal acceptance

    NASA Astrophysics Data System (ADS)

    Schürmann, D.; Strieder, F.; Di Leva, A.; Gialanella, L.; De Cesare, N.; D'Onofrio, A.; Imbriani, G.; Klug, J.; Lubritto, C.; Ordine, A.; Roca, V.; Röcken, H.; Rolfs, C.; Rogalla, D.; Romano, M.; Schümann, F.; Terrasi, F.; Trautvetter, H. P.

    2004-10-01

    For improved cross section measurements of the reaction 12C(α,γ)16O in inverted kinematics, a recoil separator ERNA is developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the 16O recoils with high efficiency. The 16O recoils are produced by the 12C projectiles in a windowless 4He gas target. We report on the charge state distribution of the 16O recoils, the gas target density, the beam heating of the gas target, and the acceptance of the separator along the extended gas target.

  9. Silicon shallow doping by erbium and oxygen recoils implantation

    NASA Astrophysics Data System (ADS)

    Feklistov, K. V.; Cherkov, A. G.; Popov, V. P.

    2016-09-01

    In order to get shallow high doping of Si with optically active complexes ErOn, Er followed by O recoils implantation was realized by means of subsequent Ar+ 250-290 keV implantation with doses 2×1015-1×1016 cm-2 through 50-nm deposited films of Er and then SiO2, accordingly. High Er concentration up to 5×1020 cm-3 to the depth of 10 nm was obtained after implantation. However, about a half of the Er implanted atoms become part of surface SiO2 during post-implantation annealing at 950 °C for 1 h in the N2 ambient under a SiO2 cap. The mechanism of Er segregation into the cap oxide following the moving amorphous-crystalline interface during recrystallization was rejected by the transmission electron microscopy (TEM) analysis. Instead, the other mechanism of immobile Er atoms and redistribution of recoil-implanted O atoms toward cap oxide was proposed. It explains the observed formation of two Er containing phases: Er-Si-O phase with a high O content adjacent to the cap oxide and deeper O depleted Er-Si phase. The correction of heat treatments is proposed in order to avoid the above-mentioned problems.

  10. Decay data measurements on 213Bi using recoil atoms.

    PubMed

    Marouli, M; Suliman, G; Pommé, S; Ammel, R Van; Jobbágy, V; Stroh, H; Dikmen, H; Paepen, J; Dirican, A; Bruchertseifer, F; Apostolidis, C; Morgenstern, A

    2013-04-01

    In this work, (213)Bi has been separated from an open (225)Ac source by collecting recoil atoms onto a glass plate in vacuum. The activity of such recoil sources has been measured as a function of time, using an ion-implanted planar Si detector in quasi-2π geometry. From these measurements, a new half-life value of T1/2((213)Bi)=45.62 (6)min was derived. Additionally, high-resolution alpha-spectrometry measurements were performed at a solid angle of 0.4% of 4πsr, to verify the energies and emission probabilities of the α-emissions from (213)Bi. Using (225)Ac, (221)Fr, (217)At and (213)Po peaks as reference peaks, the measured (213)Bi α-peak energies at Eα,0=5878 (4)keV and Eα,1=5560 (4)keV were about 10keV higher than validated data. The relative α-particle emission probabilities of (213)Bi, Pα,0=0.9155 (11) and Pα,1=0.0845 (11), and the (213)Bi alpha branching factor, Pα=1-Pβ=2.140 (10)%, are compatible with recommended values, but have a higher accuracy.

  11. The Quadrupole Mass Spectrometer

    ERIC Educational Resources Information Center

    Matheson, E.; Harris, T. J.

    1969-01-01

    Describes the construction and operation of a quadrupole mass spectrometer for experiments in an advanced-teaching laboratory. Discusses the theory of operation of the spectrometer and the factors affecting the resolution. Some examples of mass spectra obtained with this instrument are presented and discussed. (LC)

  12. The Effects of High-Frequency Amplification on the Objective and Subjective Performance of Hearing Instrument Users with Varying Degrees of High-Frequency Hearing Loss

    ERIC Educational Resources Information Center

    Plyler, Patrick N.; Fleck, Erica L.

    2006-01-01

    Purpose: The purpose of the present study was to determine if amplifying beyond 2 kHz affected the objective and subjective performance of hearing instrument users with varying degrees of mild-to-severe high-frequency sensorineural hearing loss. Method: Twenty participants were fitted binaurally with digital completely-in-the-canal devices with…

  13. Unprecedentedly strong and narrow electromagnetic emissions stimulated by high-frequency radio waves in the ionosphere.

    PubMed

    Norin, L; Leyser, T B; Nordblad, E; Thidé, B; McCarrick, M

    2009-02-13

    Experimental results of secondary electromagnetic radiation, stimulated by high-frequency radio waves irradiating the ionosphere, are reported. We have observed emission peaks, shifted in frequency up to a few tens of Hertz from radio waves transmitted at several megahertz. These emission peaks are by far the strongest spectral features of secondary radiation that have been reported. The emissions are attributed to stimulated Brillouin scattering, long predicted but hitherto never unambiguously identified in high-frequency ionospheric interaction experiments. The experiments were performed at the High-Frequency Active Auroral Research Program (HAARP), Alaska, USA. PMID:19257596

  14. Killer whale (Orcinus orca) whistles from the western South Atlantic Ocean include high frequency signals.

    PubMed

    Andriolo, Artur; Reis, Sarah S; Amorim, Thiago O S; Sucunza, Federico; de Castro, Franciele R; Maia, Ygor Geyer; Zerbini, Alexandre N; Bortolotto, Guilherme A; Dalla Rosa, Luciano

    2015-09-01

    Acoustic parameters of killer whale (Orcinus orca) whistles were described for the western South Atlantic Ocean and highlight the occurrence of high frequency whistles. Killer whale signals were recorded on December of 2012, when a pod of four individuals was observed harassing a group of sperm whales. The high frequency whistles were highly stereotyped and were modulated mostly at ultrasonic frequencies. Compared to other contour types, the high frequency whistles are characterized by higher bandwidths, shorter durations, fewer harmonics, and higher sweep rates. The results add to the knowledge of vocal behavior of this species.

  15. Unprecedentedly Strong and Narrow Electromagnetic Emissions Stimulated by High-Frequency Radio Waves in the Ionosphere

    SciTech Connect

    Norin, L.; Leyser, T. B.; Nordblad, E.; Thide, B.; McCarrick, M.

    2009-02-13

    Experimental results of secondary electromagnetic radiation, stimulated by high-frequency radio waves irradiating the ionosphere, are reported. We have observed emission peaks, shifted in frequency up to a few tens of Hertz from radio waves transmitted at several megahertz. These emission peaks are by far the strongest spectral features of secondary radiation that have been reported. The emissions are attributed to stimulated Brillouin scattering, long predicted but hitherto never unambiguously identified in high-frequency ionospheric interaction experiments. The experiments were performed at the High-Frequency Active Auroral Research Program (HAARP), Alaska, USA.

  16. A critical review of liquid helium temperature high frequency pulse tube cryocoolers for space applications

    NASA Astrophysics Data System (ADS)

    Wang, B.; Gan, Z. H.

    2013-08-01

    The importance of liquid helium temperature cooling technology in the aerospace field is discussed, and the results indicate that improving the efficiency of liquid helium cooling technologies, especially the liquid helium high frequency pulse tube cryocoolers, is the principal difficulty to be solved. The state of the art and recent developments of liquid helium high frequency pulse tube cryocoolers are summarized. The main scientific challenges for high frequency pulse tube cryocoolers to efficiently reach liquid helium temperatures are outlined, and the research progress addressing those challenges are reviewed. Additionally some possible solutions to the challenges are pointed out and discussed.

  17. Killer whale (Orcinus orca) whistles from the western South Atlantic Ocean include high frequency signals.

    PubMed

    Andriolo, Artur; Reis, Sarah S; Amorim, Thiago O S; Sucunza, Federico; de Castro, Franciele R; Maia, Ygor Geyer; Zerbini, Alexandre N; Bortolotto, Guilherme A; Dalla Rosa, Luciano

    2015-09-01

    Acoustic parameters of killer whale (Orcinus orca) whistles were described for the western South Atlantic Ocean and highlight the occurrence of high frequency whistles. Killer whale signals were recorded on December of 2012, when a pod of four individuals was observed harassing a group of sperm whales. The high frequency whistles were highly stereotyped and were modulated mostly at ultrasonic frequencies. Compared to other contour types, the high frequency whistles are characterized by higher bandwidths, shorter durations, fewer harmonics, and higher sweep rates. The results add to the knowledge of vocal behavior of this species. PMID:26428807

  18. Prediction of high frequency core loss for electrical steel using the data provided by manufacturer

    NASA Astrophysics Data System (ADS)

    Roy, Rakesh; Dalal, Ankit; Kumar, Praveen

    2016-07-01

    This paper describes a technique to determine the core loss data, at high frequencies, using the loss data provided by the lamination manufacturer. Steinmetz equation is used in this proposed method to determine core loss at high frequency. This Steinmetz equation consists of static hysteresis and eddy current loss. The presented technique considers the coefficients of Steinmetz equation as variable with frequency and peak magnetic flux density. The high frequency core loss data, predicted using this model is compared with the catalogue data given by manufacturer and very good accuracy has been obtained for a wide range of frequency.

  19. Use of a laser doppler vibrometer for high frequency accelerometer characterizations

    SciTech Connect

    Bateman, V.I.; Hansche, B.D.; Solomon, O.M.

    1995-12-31

    A laser doppler vibrometer (LDV) is being used for high frequency characterizations of accelerometers at Sandia National Laboratories (SNL). A LDV with high frequency (up to 1.5 MHz) and high velocity (10 M/s) capability was purchased from a commercial source and has been certified by the Primary Electrical Standards Department at SNL. The method used for this certification and the certification results are presented. Use of the LDV for characterization of accelerometers at high frequencies and of accelerometer sensitivity to cross-axis shocks on a Hopkinson bar apparatus is discussed.

  20. Beam suppression of the DRAGON recoil separator for 3He(α,γ)7Be

    NASA Astrophysics Data System (ADS)

    Sjue, S. K. L.; Nara Singh, B. S.; Adsley, P.; Buchmann, L.; Carmona-Gallardo, M.; Davids, B.; Fallis, J.; Fulton, B. R.; Galinski, N.; Hager, U.; Hass, M.; Howell, D.; Hutcheon, D. A.; Laird, A. M.; Martin, L.; Ottewell, D.; Reeve, S.; Ruiz, C.; Ruprecht, G.; Triambak, S.

    2013-02-01

    Preliminary studies in preparation for an absolute cross-section measurement of the radiative capture reaction 3He(α,γ)7Be with the DRAGON recoil separator have demonstrated beam suppression >1014 at the 90% confidence level. A measurement of this cross section by observation of 7Be recoils at the focal plane of the separator should be virtually background free.

  1. Analytical calculation of radiative-recoil corrections to muonium hyperfine splitting: Muon-line contribution

    SciTech Connect

    Eides, M.I.; Karshenboim, S.G.; Shelyuto, V.A. )

    1991-02-01

    Analytic expression for radiative-recoil corrections to muonium ground-state hyperfine splitting induced by muon-line radiative insertions is obtained. This result completes the program of analytic calculation of all radiative-recoil corrections. The perspectives of further muonium hyperfine splitting investigations are also discussed.

  2. Optimal control of gun recoil in direct fire using magnetorheological absorbers

    NASA Astrophysics Data System (ADS)

    Singh, Harinder J.; Wereley, Norman M.

    2014-05-01

    Optimal control of a gun recoil absorber is investigated for minimizing recoil loads and maximizing rate of fire. A multi-objective optimization problem was formulated by considering the mechanical model of the recoil absorber employing a spring and a magnetorheological (MR) damper. The damper forces are predicted by evaluating pressure drops using a nonlinear Bingham-plastic model. The optimization methodology provides multiple optimal design configurations with a trade-off between recoil load minimization and increased rate of fire. The configurations with low or high recoil loads imply low or high rate of fire, respectively. The gun recoil absorber performance is also analyzed for perturbations in the firing forces. The adaptive control of the MR damper for varying gun firing forces provides a smooth operation by returning the recoil mass to its battery position (ready to reload and fire) without incurring an end-stop impact. Furthermore, constant load transmissions are observed with respect to the recoil stroke by implementing optimal control during the simulated firing events.

  3. Exact calculations of nuclear-recoil energies from prompt gamma decays resulting from neutron capture

    SciTech Connect

    Kinney, J.H.

    1981-07-20

    The results of an accurate determination of the recoil spectrum from (n, ..gamma..) reactions in molybdenum are presented. The recoil spectrum has been calculated from nuclear level structure data and measured branching ratios. Angular correlations between successive gammas have been accounted for using the standard theoretical techniques of Racah algebra and the density matrix formalism.

  4. Fluence measurement of fast neutron fields with a highly efficient recoil proton telescope using active pixel sensors.

    PubMed

    Taforeau, J; Higueret, S; Husson, D; Kachel, M; Lebreton, L

    2014-10-01

    The spectrometer ATHENA (Accurate Telescope for High-Energy Neutron metrology Applications) is being developed at the LNE-IRSN and aims at characterising energy and fluence of fast neutron fields. The detector is a recoil proton telescope and measures neutron fields in the range of 5-20 MeV. This telescope is intended to become a primary standard for both energy and fluence measurements. The neutron detection is achieved by a polyethylene radiator for n-p conversion, three 50-µm-thick silicon sensors that use CMOS technology for proton tracking and a 3-mm-thick silicon diode to measure the residual proton energy. The use of CMOS sensors and silicon diode, owing to a large detection solid angle, increases the intrinsic efficiency of the detector by a factor of 10 compared with conventional designs. The ability of the spectrometer to determine the neutron energy was demonstrated and reported elsewhere. This paper focuses on the fluence measurement of monoenergetic neutron fields in the range of 5-20 MeV. Experimental investigations, performed at the AMANDE facility, indicate a good estimation of neutron fluence at various energies. In addition, a complete description of uncertainties budget is presented in this paper and a Monte Carlo propagation of uncertainty sources leads to a fluence measurement with a precision ∼3-5 % depending on the neutron energy.

  5. Deconvoluting nonaxial recoil in Coulomb explosion measurements of molecular axis alignment

    NASA Astrophysics Data System (ADS)

    Christensen, Lauge; Christiansen, Lars; Shepperson, Benjamin; Stapelfeldt, Henrik

    2016-08-01

    We report a quantitative study of the effect of nonaxial recoil during Coulomb explosion of laser-aligned molecules and introduce a method to remove the blurring caused by nonaxial recoil in the fragment-ion angular distributions. Simulations show that nonaxial recoil affects correlations between the emission directions of fragment ions differently from the effect caused by imperfect molecular alignment. The method, based on analysis of the correlation between the emission directions of the fragment ions from Coulomb explosion, is used to deconvolute the effect of nonaxial recoil from experimental fragment angular distributions. The deconvolution method is then applied to a number of experimental data sets to correct the degree of alignment for nonaxial recoil, to select optimal Coulomb explosion channels for probing molecular alignment, and to estimate the highest degree of alignment that can be observed from selected Coulomb explosion channels.

  6. COSY Simulations to Guide Commissioning of the St. George Recoil Mass Separator

    NASA Astrophysics Data System (ADS)

    Schmitt, Jaclyn; Moran, Michael; Seymour, Christopher; Gilardy, Gwenaelle; Meisel, Zach; Couder, Manoel

    2015-10-01

    The goal of St. George (STrong Gradient Electromagnetic Online Recoil separator for capture Gamma ray Experiments) is to measure (α, γ) cross sections relevant to stellar helium burning. Recoil separators such as St. George are able to more closely approach the low astrophysical energies of interest because they collect reaction recoils rather than γ-rays, and thus are not limited by room background. In order to obtain an accurate cross section measurement, a recoil separator must be able to collect all recoils over their full range of expected energy and angular spread. The energy acceptance of St. George is currently being measured, and the angular acceptance will be measured soon. Here we present the results of COSY ion optics simulations and magnetic field analyses which were performed to help guide the commissioning measurements and diagnostic upgrades required to complete those measurements. National Science Foundation Research Experiences for Undergraduates program.

  7. High-frequency acoustic waves are not sufficient to heat the solar chromosphere.

    PubMed

    Fossum, Astrid; Carlsson, Mats

    2005-06-16

    One of the main unanswered questions in solar physics is why the Sun's outer atmosphere is hotter than its surface. Theory predicts abundant production of high-frequency (10-50 mHz) acoustic waves in subsurface layers of the Sun, and such waves are believed by many to constitute the dominant heating mechanism of the chromosphere (the lower part of the outer solar atmosphere) in non-magnetic regions. Such high-frequency waves are difficult to detect because of high-frequency disturbances in Earth's atmosphere (seeing) and other factors. Here we report the detection of high-frequency waves, and we use numerical simulations to show that the acoustic energy flux of these waves is too low, by a factor of at least ten, to balance the radiative losses in the solar chromosphere. Acoustic waves therefore cannot constitute the dominant heating mechanism of the solar chromosphere. PMID:15959510

  8. High-frequency brain activity and muscle artifacts in MEG/EEG: a review and recommendations

    PubMed Central

    Muthukumaraswamy, Suresh D.

    2013-01-01

    In recent years high-frequency brain activity in the gamma-frequency band (30–80 Hz) and above has become the focus of a growing body of work in MEG/EEG research. Unfortunately, high-frequency neural activity overlaps entirely with the spectral bandwidth of muscle activity (~20–300 Hz). It is becoming appreciated that artifacts of muscle activity may contaminate a number of non-invasive reports of high-frequency activity. In this review, the spectral, spatial, and temporal characteristics of muscle artifacts are compared with those described (so far) for high-frequency neural activity. In addition, several of the techniques that are being developed to help suppress muscle artifacts in MEG/EEG are reviewed. Suggestions are made for the collection, analysis, and presentation of experimental data with the aim of reducing the number of publications in the future that may contain muscle artifacts. PMID:23596409

  9. Real-time, high frequency QRS electrocardiograph with reduced amplitude zone detection

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

    2009-01-01

    Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as ''RAZs''. RAZs are displayed as ''go, no-go'' signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

  10. High-Frequency Electrocardiography: Optimizing the Diagnosis of the Acute Myocardial Infarct with ST-Elevation

    NASA Astrophysics Data System (ADS)

    Naydenov, S.; Donova, T.; Matveev, M.; Gegova, A.; Popdimitrova, N.; Zlateva, G.; Vladimirova, D.

    2007-04-01

    The analysis of the received digital signal by computer microprocessor in high-frequency electrocardiography, used in our research, makes possible synthesis of vectorcardiographic images and loops, allowing improved qualitative and quantitative diagnosing of the myocardial injury.

  11. High frequency wide-band transformer uses coax to achieve high turn ratio and flat response

    NASA Technical Reports Server (NTRS)

    De Parry, T.

    1966-01-01

    Center-tap push-pull transformer with toroidal core helically wound with a single coaxial cable creates a high frequency wideband transformer. This transformer has a high-turn ratio, a high coupling coefficient, and a flat broadband response.

  12. Automated Classification of Vowel Category and Speaker Type in the High-Frequency Spectrum.

    PubMed

    Donai, Jeremy J; Motiian, Saeid; Doretto, Gianfranco

    2016-04-20

    The high-frequency region of vowel signals (above the third formant or F3) has received little research attention. Recent evidence, however, has documented the perceptual utility of high-frequency information in the speech signal above the traditional frequency bandwidth known to contain important cues for speech and speaker recognition. The purpose of this study was to determine if high-pass filtered vowels could be separated by vowel category and speaker type in a supervised learning framework. Mel frequency cepstral coefficients (MFCCs) were extracted from productions of six vowel categories produced by two male, two female, and two child speakers. Results revealed that the filtered vowels were well separated by vowel category and speaker type using MFCCs from the high-frequency spectrum. This demonstrates the presence of useful information for automated classification from the high-frequency region and is the first study to report findings of this nature in a supervised learning framework. PMID:27588160

  13. An Investigation of High Frequency Motions in the Tropical Tropopause Layer near Convection

    NASA Technical Reports Server (NTRS)

    Pfister, Leonhard; Bui, T. P.; Dean-Day, Jon; Lim, Boon; Lawson, Paul

    2016-01-01

    Indirect evidence indicates a role for vertical mixing in the Tropical Tropopause Layer (TTL). In the past 20 years, high altitude NASA aircraft such as the ER-2, WB-57, and GLobal Hawk have been making 20hz measurements of vertical velocity and other meteorological parameters in the Upper Tropospere-Lower Stratosphere region, many in the tropics, most recently in connection with the Airborne Tropical TRopopause EXperiment (ATTREX). In the stable environment of the UTLS, high frequency activity occurs in bursts, presumably in connection with nearby convection or strong vertical shear associated with larger scale gravity waves. This paper examines tropical high frequency aircraft data to obtain some basic information about the distribution and character of high frequency activity in vertical velocity in the TTL. In particular, we focus on relating the high frequency activity to nearby tropical convection.

  14. Automated Classification of Vowel Category and Speaker Type in the High-Frequency Spectrum.

    PubMed

    Donai, Jeremy J; Motiian, Saeid; Doretto, Gianfranco

    2016-04-20

    The high-frequency region of vowel signals (above the third formant or F3) has received little research attention. Recent evidence, however, has documented the perceptual utility of high-frequency information in the speech signal above the traditional frequency bandwidth known to contain important cues for speech and speaker recognition. The purpose of this study was to determine if high-pass filtered vowels could be separated by vowel category and speaker type in a supervised learning framework. Mel frequency cepstral coefficients (MFCCs) were extracted from productions of six vowel categories produced by two male, two female, and two child speakers. Results revealed that the filtered vowels were well separated by vowel category and speaker type using MFCCs from the high-frequency spectrum. This demonstrates the presence of useful information for automated classification from the high-frequency region and is the first study to report findings of this nature in a supervised learning framework.

  15. Laser and high-frequency cauthery gingivectomy in nonperiodontal indications: assessment and comparison of techniques

    NASA Astrophysics Data System (ADS)

    Bartak, Petr; Smucler, Roman

    2003-06-01

    The authors have verified the efficiency and safety of laser and high-frequency gingivectomy in non-periodontal indications. Within a prospective, non-selective study, they treated and monitored 357 dental areas in 139 teeth.Out of the total number, 248 areas were treated wtih a diode laser, 980nm; 109 areas with high-frequency electrocautery. The following parameters were monitored: a) regeneration of the marginal gingiva; b) generation of iatrogenic recessions or periodontal pockets; c) bleeding from gingival sulcus during probing; d) changes in tooth vitality; e) patient's subjective evaluation. The authors identified a high degree of safety in both laser and high-frequency gingivectomy, with no significant difference between these two methods. Laser gingivectomy appears to have a wider indication range, while high-frequency gingivectomy requires lower financial expenses.

  16. Automated Classification of Vowel Category and Speaker Type in the High-Frequency Spectrum

    PubMed Central

    Donai, Jeremy J.; Motiian, Saeid; Doretto, Gianfranco

    2016-01-01

    The high-frequency region of vowel signals (above the third formant or F3) has received little research attention. Recent evidence, however, has documented the perceptual utility of high-frequency information in the speech signal above the traditional frequency bandwidth known to contain important cues for speech and speaker recognition. The purpose of this study was to determine if high-pass filtered vowels could be separated by vowel category and speaker type in a supervised learning framework. Mel frequency cepstral coefficients (MFCCs) were extracted from productions of six vowel categories produced by two male, two female, and two child speakers. Results revealed that the filtered vowels were well separated by vowel category and speaker type using MFCCs from the high-frequency spectrum. This demonstrates the presence of useful information for automated classification from the high-frequency region and is the first study to report findings of this nature in a supervised learning framework. PMID:27588160

  17. Dielectric barrier structure with hollow electrodes and its recoil effect

    SciTech Connect

    Yu, Shuang; Chen, Qunzhi; Liu, Jiahui; Wang, Kaile; Jiang, Zhe; Sun, Zhili; Zhang, Jue; Fang, Jing

    2015-06-15

    A dielectric barrier structure with hollow electrodes (HEDBS), in which gas flow oriented parallel to the electric field, was proposed. Results showed that with this structure, air can be effectively ignited, forming atmospheric low temperature plasma, and the proposed HEDBS could achieve much higher electron density (5 × 10{sup 15}/cm{sup 3}). It was also found that the flow condition, including outlet diameter and flow rate, played a key role in the evolution of electron density. Optical emission spectroscopy diagnostic results showed that the concentration of reactive species had the same variation trend as the electron density. The simulated distribution of discharge gas flow indicated that the HEDBS had a strong recoil effect on discharge gas, and could efficiently promote generating electron density as well as reactive species.

  18. Spectroscopy of {sup 144}Ho using recoil-isomer tagging

    SciTech Connect

    Mason, P. J. R; Cullen, D. M.; Scholey, C.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Peura, P.; Puurunen, A.; Rahkila, P.; Ruotsalainen, P.; Sorri, J.; Saren, J.; Uusitalo, J.; Xu, F. R.

    2010-02-15

    Excited states in the proton-unbound odd-odd nucleus {sup 144}Ho have been populated using the {sup 92}Mo({sup 54}Fe,pn){sup 144}Ho reaction and studied using the recoil-isomer-tagging technique. The alignment properties and signature splitting of the rotational band above the I{sup p}i=(8{sup +}){sup 144m}Ho isomer have been analyzed and the isomer confirmed to have a pih{sub 11/2} x nuh{sub 11/2} two-quasiparticle configuration. The configuration-constrained blocking method has been used to calculate the shapes of the ground and isomeric states, which are both predicted to have triaxial nuclear shapes with |gamma|approx =24 deg.

  19. Molecular Dynamics Simulation of Energetic Uranium Recoil Damage in Zircon

    SciTech Connect

    Devanathan, Ram; Corrales, Louis R.; Weber, William J.; Chartier, Alain; Meis, Constantin

    2006-10-11

    Defect production and amorphization due to energetic uranium recoils in zircon (ZrSiO4), which is a promising ceramic nuclear waste form, is studied using molecular dynamics simulations with a partial charge model. An algorithm that distinguishes between undamaged crystal, crystalline defects and amorphous regions is used to develop a fundamental understanding of the primary damage state. The amorphous cascade core is separated from the surrounding crystal by a defect-rich region. Small, chemically inhomogeneous amorphous clusters are also produced around the core. The amorphous regions consist of under-coordinated Zr and polymerized Si leading to amorphization and phase separation on a nanometer scale into Zr- and Si-rich regions. This separation could play an important role in the experimentally observed formation of nanoscale ZrO2 in ZrSiO4 irradiated at elevated temperatures.

  20. Neutron absorbed dose determination by calculations of recoil energy.

    PubMed

    Wrobel, F; Benabdesselam, M; Iacconi, P; Lapraz, D

    2004-01-01

    The aim of this work is to calculate the absorbed dose to matter due to neutrons in the 5-150 MeV energy range. Materials involved in the calculations are Al2O3, CaSO4 and CaS, which may be used as dosemeters and have already been studied for their luminescent properties. The absorbed dose is assumed to be mainly due to the energy deposited by the recoils. Elastic reactions are treated with the ECIS code while for the non-elastic ones, a Monte Carlo code has been developed and allowed to follow the nucleus decay and to determine its characteristics (nature and energy). Finally, the calculations show that the absorbed dose is mainly due to non-elastic process and that above 20 MeV this dose decreases slightly with the neutron energy. PMID:15353750

  1. Recoil Polarization for Delta Excitation in Pion Electroproduction

    SciTech Connect

    J. J. Kelly; R. E. Roche; Z. Chai; M. K. Jones; O. Gayou; A. J. Sarty; S. Frullani; K. Aniol; E. J. Beise; F. Benmokhtar; W. Bertozzi; W. U. Boeglin; T. Botto; E. J. Brash; H. Breuer; E. Brown; E. Burtin; J. R. Calarco; C. Cavata; C. C. Chang; N. S. Chant; J.-P. Chen; M. Coman; D. Crovelli; R. De Leo; S. Dieterich; S. Escoffier; K. G. Fissum; V. Garde; F. Garibaldi; S. Georgakopoulus; S. Gilad; R. Gilman; C. Glashausser; J.-O. Hansen; D. W. Higinbotham; A. Hotta; G. M. Huber; H. Ibrahim; M. Iodice; C. W. de Jager; X. Jiang; A. Klimenko; A. Kozlov; G. Kumbartzki; M. Kuss; L. Lagamba; G. Laveissiere; J. J. LeRose; R. A. Lindgren; N. Liyanage; G. J. Lolos; R. W. Lourie; D. J. Margaziotis; F. Marie; P. Markowitz; S. McAleer; D. Meekins; R. Michaels; B. D. Milbrath; J. Mitchell; J. Nappa; D. Neyret; C. F. Perdrisat; M. Potokar; V. A. Punjabi; T. Pussieux; R. D. Ransome; P. G. Roos; M. Rvachev; A. Saha; S. Sirca; R. Suleiman; S. Strauch; J. A. Templon; L. Todor; P. E. Ulmer; G. M. Urciuoli; L. B. Weinstein; K. Wijesooriya; B. Wojtsekhowski; X. Zheng; and L. Zhu

    2005-08-01

    We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q{sup 2}=1.0 (GeV/c){sup 2}, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re(S1+/M1+)=-(6.84+/-0.15)% and Re(E1+/M1+)=-(2.91+/-0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and sp truncation.

  2. Study of nuclear recoils in liquid argon with monoenergetic neutrons

    NASA Astrophysics Data System (ADS)

    Regenfus, C.; Allkofer, Y.; Amsler, C.; Creus, W.; Ferella, A.; Rochet, J.; Walter, M.

    2012-07-01

    In the framework of developments for liquid argon dark matter detectors we assembled a laboratory setup to scatter neutrons on a small liquid argon target. The neutrons are produced mono-energetically (Ekin = 2.45 MeV) by nuclear fusion in a deuterium plasma and are collimated onto a 3" liquid argon cell operating in single-phase mode (zero electric field). Organic liquid scintillators are used to tag scattered neutrons and to provide a time-of-flight measurement. The setup is designed to study light pulse shapes and scintillation yields from nuclear and electronic recoils as well as from alpha particles at working points relevant for dark matter searches. Liquid argon offers the possibility to scrutinise scintillation yields in noble liquids with respect to the population strength of the two fundamental excimer states. Here we present experimental methods and first results from recent data towards such studies.

  3. B{yields}D* at zero recoil revisited

    SciTech Connect

    Gambino, Paolo; Mannel, Thomas; Uraltsev, Nikolai

    2010-06-01

    We examine the B{yields}D* form factor at zero recoil using a continuum QCD approach rooted in the heavy quark sum rules framework. A refined evaluation of the radiative corrections as well as the most recent estimates of higher-order power terms together with more careful continuum calculation are included. An upper bound on the form factor of F(1) < or approx. 0.93 is derived, based on just the positivity of inelastic contributions. A model-independent estimate of the inelastic contributions shows they are quite significant, lowering the form factor by about 6% or more. This results in an unbiased estimate F(1){approx_equal}0.86 with about 3% uncertainty in the central value.

  4. High frequency ultrasound study of skin tumors in dermatological and aesthetic practice.

    PubMed

    Bezugly, Artur

    2015-12-01

    The accurate measurement of skin tumors and the precise delimitation of its borders are important tools for tumor diagnosis and treatment. In this paper we summarized our practical experience in `the examination of different skin tumors using high frequency ultrasound (HFU). High-frequency transducers 22 MHz and 75 MHz with resolution of 72 and 21 μm were used for the examination. HFU characteristics of the most important non-melanoma skin tumors are depicted. PMID:26649352

  5. High-overtone self-focusing acoustic transducers for high-frequency ultrasonic Doppler.

    PubMed

    Zhu, Jie; Lee, Chuangyuan; Kim, Eun Sok; Wu, Dawei; Hu, Changhong; Zhou, Qifa; Shung, K Kirk; Wang, Gaofeng; Yu, Hongyu

    2010-05-01

    This work reports the potential use of high-overtone self-focusing acoustic transducers for high-frequency ultrasonic Doppler. By using harmonic frequencies of a thick bulk Lead Zirconate Titanate (PZT) transducer with a novel air-reflector Fresnel lens, we obtained strong ultrasound signals at 60 MHz (3rd harmonic) and 100 MHz (5th harmonic). Both experimental and theoretical analysis has demonstrated that the transducers can be applied to Doppler systems with high frequencies up to 100 MHz.

  6. High frequency graphene transistors: can a beauty become a cash cow?

    NASA Astrophysics Data System (ADS)

    Neumaier, Daniel; Zirath, Herbert

    2015-09-01

    This is a specially commissioned editorial from the Graphene Flagship Work Package on High Frequency Electronics. This editorial is part of the 2D Materials focus collection on ‘Progress on the science and applications of two-dimensional materials’, published in association with the Graphene Flagship. It provides an overview of key, recent advances from the ‘High Frequency Electronics’ work package and is not intended as a comprehensive review of this field.

  7. Metronidazole as a protector of cells from electromagnetic radiation of extremely high frequencies

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Pavel E.; Malinina, Ulia A.; Popyhova, Era B.; Rogacheva, Svetlana M.; Somov, Alexander U.

    2006-08-01

    It is well known that weak electromagnetic fields of extremely high frequencies cause significant modification of the functional status of biological objects of different levels of organization. The aim of the work was to study the combinatory effect of metronidazole - the drug form of 1-(2'hydroxiethil)-2-methil-5-nitroimidazole - and electromagnetic radiation of extremely high frequencies (52...75 GHz) on the hemolytic stability of erythrocytes and hemotaxis activity of Infusoria Paramecium caudatum.

  8. Effect of high-frequency driving current on magnetization reversal in Co-rich amorphous microwires

    SciTech Connect

    Chizhik, A.; Zhukov, A.; Gonzalez, J.; Blanco, J.M.

    2004-09-20

    Influence of high frequency electric current on the magnetization reversal in Co-rich glass covered amorphous microwires has been studied. The strong correlation between the coercivity and the circular magnetization in the outer shell of the wire has been found. The change of the mechanism of magnetization reversal in the presence of high-frequency circular magnetic field, which is related with the impedance properties, is presented.

  9. Measurements of neutron energy spectra from 7Li(p,n)7Be reaction with Bonner sphere spectrometer, Nested Neutron Spectrometer and ROSPEC.

    PubMed

    Atanackovic, J; Matysiak, W; Witharana, S; Dubeau, J; Waker, A J

    2014-10-01

    Neutron spectrometry measurements were carried out at the McMaster Accelerator Laboratory (MAL), which is equipped with a 3-MV Van de Graaff-type accelerator. Protons were accelerated onto a thick natural lithium target inducing the (7)Li(p,n)(7)Be threshold reaction. Depending on the proton energy, slightly different poly-energetic neutron fields were produced. Neutron spectra were measured at two incident proton energies: 2.15 and 2.24 MeV, which produced poly-energetic neutrons with maximum kinetic energies of 401 and 511 keV, respectively. Measurements were performed at a distance of 1.5 m from the target in the forward direction with three different instruments: Bonner sphere spectrometer, Nested Neutron Spectrometer and ROtational proton recoil SPECtrometer.

  10. Sub-barrier reactions measured using a recoil mass separator

    SciTech Connect

    Betts, R.R.

    1988-01-01

    Few data exist in the sub-barrier region for reaction channels other than fusion. In particular, our experimental knowledge of quasi-elastic transfer reactions is sparse, despite the belief that this particular channel may be dominant in determining some features of the sub-barrier fusion enhancement. Transfer reactions are governed primarily by the closet approach of the colliding nuclei which, at low energies, results in a strong backward peaking of the angular distribution in the center-of-mass frame. For situations where the projectile has a significant fraction of the target mass, as is so in most cases of interest, the backscattered projectile-like fragment has such low energy that the usual techniques of measurement and identification become invalid. Here, we report on a solution to this problem which allows a systematic study of many aspects of transfer reactions in the energy regime of interest. We exploit the fact that associated with the low-energy backscattered projectile-like fragment is a complementary target-like fragment which recoils to forward angles with a large fraction of the incident beam energy. These target-like fragments were detected and identified using the Daresbury Recoil Mass Separator thus allowing the measurement of quasi-elastic transfer over hitherto inaccessible energy range from the vicinity of the barrier to several tens of MeV below. The experiments described here used VYNi beams of energies ranging from 180 to 260 MeV provided by the Daresbury Laboratory Nuclear Structure Facility tandem accelerator. Data on sub-barrier transfer for targets of /sup 116,118,120,122,124/Sn and /sup 144,148,150,152,154/Sm were obtained. 16 refs., 10 figs., 2 tabs.

  11. α -decay chains of recoiled superheavy nuclei: A theoretical study

    NASA Astrophysics Data System (ADS)

    Niyti, Sawhney, Gudveen; Sharma, Manoj K.; Gupta, Raj K.

    2015-05-01

    A systematic theoretical study of α -decay half-lives in the superheavy mass region of the periodic table of elements is carried out by extending the quantum-mechanical fragmentation theory based on the preformed cluster model (PCM) to include temperature (T ) dependence in its built-in preformation and penetration probabilities of decay fragments. Earlier, the α -decay chains of the isotopes of Z =115 were investigated by using the standard PCM for spontaneous decays, with"hot-optimum" orientation effects included, which required a constant scaling factor of 104 to approach the available experimental data. In the present approach of the PCM (T ≠0 ), the temperature effects are included via the recoil energy of the residual superheavy nucleus (SHN) left after x -neutron emission from the superheavy compound nucleus. The important result is that the α -decay half-lives calculated by the PCM (T ≠0 ) match the experimental data nearly exactly, without using any scaling factor of the type used in the PCM. Note that the PCM (T ≠0 ) is an equivalent of the dynamical cluster-decay model for heavy-ion collisions at angular momentum ℓ =0 . The only parameter of model is the neck-length parameter Δ R , which for the calculated half-lives of α -decay chains of various isotopes of Z =113 to 118 nuclei formed in "hot-fusion" reactions is found to be nearly constant, i.e., Δ R ≈0.95 ±0.05 fm for all the α -decay chains studied. The use of recoiled residue nucleus as a secondary heavy-ion beam for nuclear reactions has also been suggested in the past.

  12. A Study of Nuclear Recoils in Liquid Argon Time Projection Chamber for the Direct Detection of WIMP Dark Matter

    SciTech Connect

    Cao, Huajie

    2014-11-01

    Robust results of WIMP direct detection experiments depend on rm understandings of nuclear recoils in the detector media. This thesis documents the most comprehensive study to date on nuclear recoils in liquid argon - a strong candidate for the next generation multi-ton scale WIMP detectors. This study investigates both the energy partition from nuclear recoil energy to secondary modes (scintillation and ionization) and the pulse shape characteristics of scintillation from nuclear recoils.

  13. Study on the dynamic characteristics of a high frequency brake based on giant magnetostrictive material

    NASA Astrophysics Data System (ADS)

    Xu, Ai Qun

    2016-06-01

    In order to meet the requirements of rapid and smooth braking, high-frequency braking using a giant magnetostrictive actuator is proposed, which can solve the problems in hydraulic braking, such as, it leaks easily, catches fire easily, is difficult to find failures, high cost on maintenance and repairing, etc. The main factors affecting the force of a high-frequency braking actuator are emphatically analyzed, the brakes dynamic model is established and a performance testing device for high frequency braking is constructed based on LabVIEW. The output force of the actuator increases with the excitation current of the driving coil increasing, and the increased multiple of the output force is greater than that of the excitation current; the range of the actuator force amplitude is 121.63 N ∼ 158.14 N, which changes little, while excitation frequency changes between 200 Hz ∼ 1000 Hz. In a minor range of pre-stress, the output force decreases with an increase in the axial pre-stress of the giant magnetostrictive rod, but is not obvious. It is known by finite element simulation analysis that high-frequency braking shortens the braking displacement and time effectively, which proves the feasibility and effectiveness of high frequency braking. Theoretical analysis and experimental results indicate that the output force of the actuator changes at the same frequency with excitation current; it is controllable and its mechanical properties meet the requirements of high frequency braking.

  14. High-Frequency Transcranial Random Noise Stimulation Enhances Perception of Facial Identity.

    PubMed

    Romanska, Aleksandra; Rezlescu, Constantin; Susilo, Tirta; Duchaine, Bradley; Banissy, Michael J

    2015-11-01

    Recently, a number of studies have demonstrated the utility of transcranial current stimulation as a tool to facilitate a variety of cognitive and perceptual abilities. Few studies, though, have examined the utility of this approach for the processing of social information. Here, we conducted 2 experiments to explore whether a single session of high-frequency transcranial random noise stimulation (tRNS) targeted at lateral occipitotemporal cortices would enhance facial identity perception. In Experiment 1, participants received 20 min of active high-frequency tRNS or sham stimulation prior to completing the tasks examining facial identity perception or trustworthiness perception. Active high-frequency tRNS facilitated facial identity perception, but not trustworthiness perception. Experiment 2 assessed the spatial specificity of this effect by delivering 20 min of active high-frequency tRNS to lateral occipitotemporal cortices or sensorimotor cortices prior to participants completing the same facial identity perception task used in Experiment 1. High-frequency tRNS targeted at lateral occipitotemporal cortices enhanced performance relative to motor cortex stimulation. These findings show that high-frequency tRNS to lateral occipitotemporal cortices produces task-specific and site-specific enhancements in face perception.

  15. High-Frequency Transcranial Random Noise Stimulation Enhances Perception of Facial Identity

    PubMed Central

    Romanska, Aleksandra; Rezlescu, Constantin; Susilo, Tirta; Duchaine, Bradley; Banissy, Michael J.

    2015-01-01

    Recently, a number of studies have demonstrated the utility of transcranial current stimulation as a tool to facilitate a variety of cognitive and perceptual abilities. Few studies, though, have examined the utility of this approach for the processing of social information. Here, we conducted 2 experiments to explore whether a single session of high-frequency transcranial random noise stimulation (tRNS) targeted at lateral occipitotemporal cortices would enhance facial identity perception. In Experiment 1, participants received 20 min of active high-frequency tRNS or sham stimulation prior to completing the tasks examining facial identity perception or trustworthiness perception. Active high-frequency tRNS facilitated facial identity perception, but not trustworthiness perception. Experiment 2 assessed the spatial specificity of this effect by delivering 20 min of active high-frequency tRNS to lateral occipitotemporal cortices or sensorimotor cortices prior to participants completing the same facial identity perception task used in Experiment 1. High-frequency tRNS targeted at lateral occipitotemporal cortices enhanced performance relative to motor cortex stimulation. These findings show that high-frequency tRNS to lateral occipitotemporal cortices produces task-specific and site-specific enhancements in face perception. PMID:25662714

  16. Imaging Fourier transform spectrometer

    SciTech Connect

    Bennett, C.L.

    1993-09-13

    This invention is comprised of an imaging Fourier transform spectrometer having a Fourier transform infrared spectrometer providing a series of images to a focal plane array camera. The focal plane array camera is clocked to a multiple of zero crossing occurrences as caused by a moving mirror of the Fourier transform infrared spectrometer and as detected by a laser detector such that the frame capture rate of the focal plane array camera corresponds to a multiple of the zero crossing rate of the Fourier transform infrared spectrometer. The images are transmitted to a computer for processing such that representations of the images as viewed in the light of an arbitrary spectral ``fingerprint`` pattern can be displayed on a monitor or otherwise stored and manipulated by the computer.

  17. Composite Spectrometer Prisms

    NASA Technical Reports Server (NTRS)

    Breckinridge, J. B.; Page, N. A.; Rodgers, J. M.

    1985-01-01

    Efficient linear dispersive element for spectrometer instruments achieved using several different glasses in multiple-element prism. Good results obtained in both two-and three-element prisms using variety of different glass materials.

  18. AUTOMATIC MASS SPECTROMETER

    DOEpatents

    Hanson, M.L.; Tabor, C.D. Jr.

    1961-12-01

    A mass spectrometer for analyzing the components of a gas is designed which is capable of continuous automatic operation such as analysis of samples of process gas from a continuous production system where the gas content may be changing. (AEC)

  19. A Simple Raman Spectrometer.

    ERIC Educational Resources Information Center

    Blond, J. P.; Boggett, D. M.

    1980-01-01

    Discusses some basic physical ideas about light scattering and describes a simple Raman spectrometer, a single prism monochromator and a multiplier detector. This discussion is intended for British undergraduate physics students. (HM)

  20. Fourier Transform Spectrometer System

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F. (Inventor)

    2014-01-01

    A Fourier transform spectrometer (FTS) data acquisition system includes an FTS spectrometer that receives a spectral signal and a laser signal. The system further includes a wideband detector, which is in communication with the FTS spectrometer and receives the spectral signal and laser signal from the FTS spectrometer. The wideband detector produces a composite signal comprising the laser signal and the spectral signal. The system further comprises a converter in communication with the wideband detector to receive and digitize the composite signal. The system further includes a signal processing unit that receives the composite signal from the converter. The signal processing unit further filters the laser signal and the spectral signal from the composite signal and demodulates the laser signal, to produce velocity corrected spectral data.

  1. High-Frequency Observation of Water Spectrum and Its Application in Monitoring of Dynamic Variation of Suspended Materials in the Hangzhou Bay.

    PubMed

    Dai, Qian; Pan, De-lu; He, Xian-qiang; Zhu, Qian-kun; Gong, Fang; Huang, Hai-qing

    2015-11-01

    In situ measurement of water spectrum is the basis of the validation of the ocean color remote sensing. The traditional method to obtain the water spectrum is based on the shipboard measurement at limited stations, which is difficult to meet the requirement of validation of ocean color remote sensing in the highly dynamic coastal waters. To overcome this shortage, continuously observing systems of water spectrum have been developed in the world. However, so far, there are still few high-frequency observation systems of the water spectrum in coastal waters, especially in the highly turbid and high-dynamic waters. Here, we established a high-frequency water-spectrum observing system based on tower in the Hangzhou Bay. The system measures the water spectrum at a step of 3 minutes, which can fully match the satellite observation. In this paper, we primarily developed a data processing method for the tower-based high-frequency water spectrum data, to realize automatic judgment of clear sky, sun glint, platform shadow, and weak illumination, etc. , and verified the processing results. The results show that the normalized water-leaving radiance spectra obtained through tower observation have relatively high consistency with the shipboard measurement results, with correlation coefficient of more than 0. 99, and average relative error of 9.96%. In addition, the long-term observation capability of the tower-based high-frequency water-spectrum observing system was evaluated, and the results show that although the system has run for one year, the normalized water-leaving radiance obtained by this system have good consistency with the synchronously measurement by Portable spectrometer ASD in respect of spectral shape and value, with correlation coefficient of more than 0.90 and average relative error of 6.48%. Moreover, the water spectra from high-frequency observation by the system can be used to effectively monitor the rapid dynamic variation in concentration of suspended

  2. High-Frequency Observation of Water Spectrum and Its Application in Monitoring of Dynamic Variation of Suspended Materials in the Hangzhou Bay.

    PubMed

    Dai, Qian; Pan, De-lu; He, Xian-qiang; Zhu, Qian-kun; Gong, Fang; Huang, Hai-qing

    2015-11-01

    In situ measurement of water spectrum is the basis of the validation of the ocean color remote sensing. The traditional method to obtain the water spectrum is based on the shipboard measurement at limited stations, which is difficult to meet the requirement of validation of ocean color remote sensing in the highly dynamic coastal waters. To overcome this shortage, continuously observing systems of water spectrum have been developed in the world. However, so far, there are still few high-frequency observation systems of the water spectrum in coastal waters, especially in the highly turbid and high-dynamic waters. Here, we established a high-frequency water-spectrum observing system based on tower in the Hangzhou Bay. The system measures the water spectrum at a step of 3 minutes, which can fully match the satellite observation. In this paper, we primarily developed a data processing method for the tower-based high-frequency water spectrum data, to realize automatic judgment of clear sky, sun glint, platform shadow, and weak illumination, etc. , and verified the processing results. The results show that the normalized water-leaving radiance spectra obtained through tower observation have relatively high consistency with the shipboard measurement results, with correlation coefficient of more than 0. 99, and average relative error of 9.96%. In addition, the long-term observation capability of the tower-based high-frequency water-spectrum observing system was evaluated, and the results show that although the system has run for one year, the normalized water-leaving radiance obtained by this system have good consistency with the synchronously measurement by Portable spectrometer ASD in respect of spectral shape and value, with correlation coefficient of more than 0.90 and average relative error of 6.48%. Moreover, the water spectra from high-frequency observation by the system can be used to effectively monitor the rapid dynamic variation in concentration of suspended

  3. [111]-oriented PIN-PMN-PT crystals with ultrahigh dielectric permittivity and high frequency constant for high-frequency transducer applications

    NASA Astrophysics Data System (ADS)

    Li, Fei; Zhang, Shujun; Luo, Jun; Geng, Xuecang; Xu, Zhuo; Shrout, Thomas R.

    2016-08-01

    The electromechanical properties of [111]-oriented tetragonal Pb(In1/2Nb1/2O3)-Pb(Mg1/3Nb2/3O3)-PbTiO3 (PIN-PMN-PT) crystals were investigated for potential high frequency ultrasonic transducers. The domain-engineered tetragonal crystals exhibit an ultrahigh free dielectric permittivity ɛ33T > 10 000 with a moderate electromechanical coupling factor k33 ˜ 0.79, leading to a high clamped dielectric permittivity ɛ33S of 2800, significantly higher than those of the rhombohedral relaxor-PT crystals and high-K (dielectric permittivity) piezoelectric ceramics. Of particular significance is that the [111]-oriented tetragonal crystals were found to possess high elastic stiffness, with frequency constant N33 of ˜2400 Hz m, allowing relatively easy fabrication of high-frequency transducers. In addition, no scaling effect of piezoelectric and dielectric properties was observed down to thickness of 0.1 mm, corresponding to an operational frequency of ˜24 MHz. These advantages of [111]-oriented tetragonal PIN-PMN-PT crystals will benefit high-frequency ultrasonic array transducers, allowing for high sensitivity, broad bandwidth, and reduced noise/crosstalk.

  4. New Seasonal Shift in In-Stream Diurnal Nitrate Cycles Identified by Mining High-Frequency Data.

    PubMed

    Aubert, Alice H; Breuer, Lutz

    2016-01-01

    The recent development of in-situ monitoring devices, such as UV-spectrometers, makes the study of short-term stream chemistry variation relevant, especially the study of diurnal cycles, which are not yet fully understood. Our study is based on high-frequency data from an agricultural catchment (Studienlandschaft Schwingbachtal, Germany). We propose a novel approach, i.e. the combination of cluster analysis and Linear Discriminant Analysis, to mine from these data nitrate behavior patterns. As a result, we observe a seasonality of nitrate diurnal cycles, that differs from the most common cycle seasonality described in the literature, i.e. pre-dawn peaks in spring. Our cycles appear in summer and the maximum and minimum shift to a later time in late summer/autumn. This is observed both for water- and energy-limited years, thus potentially stressing the role of evapotranspiration. This concluding hypothesis on the role of evapotranspiration on nitrate stream concentration, which was obtained through data mining, broadens the perspective on the diurnal cycling of stream nitrate concentrations. PMID:27073838

  5. New Seasonal Shift in In-Stream Diurnal Nitrate Cycles Identified by Mining High-Frequency Data

    PubMed Central

    2016-01-01

    The recent development of in-situ monitoring devices, such as UV-spectrometers, makes the study of short-term stream chemistry variation relevant, especially the study of diurnal cycles, which are not yet fully understood. Our study is based on high-frequency data from an agricultural catchment (Studienlandschaft Schwingbachtal, Germany). We propose a novel approach, i.e. the combination of cluster analysis and Linear Discriminant Analysis, to mine from these data nitrate behavior patterns. As a result, we observe a seasonality of nitrate diurnal cycles, that differs from the most common cycle seasonality described in the literature, i.e. pre-dawn peaks in spring. Our cycles appear in summer and the maximum and minimum shift to a later time in late summer/autumn. This is observed both for water- and energy-limited years, thus potentially stressing the role of evapotranspiration. This concluding hypothesis on the role of evapotranspiration on nitrate stream concentration, which was obtained through data mining, broadens the perspective on the diurnal cycling of stream nitrate concentrations. PMID:27073838

  6. A Novel method for modeling the recoil in W boson events at hadron collider

    SciTech Connect

    Abazov, Victor Mukhamedovich; Abbott, Braden Keim; Abolins, Maris A.; Acharya, Bannanje Sripath; Adams, Mark Raymond; Adams, Todd; Aguilo, Ernest; Ahsan, Mahsana; Alexeev, Guennadi D.; Alkhazov, Georgiy D.; Alton, Andrew K.; /Michigan U. /Augustana Coll., Sioux Falls /Northeastern U.

    2009-07-01

    We present a new method for modeling the hadronic recoil in W {yields} {ell}{nu} events produced at hadron colliders. The recoil is chosen from a library of recoils in Z {yields} {ell}{ell} data events and overlaid on a simulated W {yields} {ell}{nu} event. Implementation of this method requires that the data recoil library describe the properties of the measured recoil as a function of the true, rather than the measured, transverse momentum of the boson. We address this issue using a multidimensional Bayesian unfolding technique. We estimate the statistical and systematic uncertainties from this method for the W boson mass and width measurements assuming 1 fb{sup -1} of data from the Fermilab Tevatron. The uncertainties are found to be small and comparable to those of a more traditional parameterized recoil model. For the high precision measurements that will be possible with data from Run II of the Fermilab Tevatron and from the CERN LHC, the method presented in this paper may be advantageous, since it does not require an understanding of the measured recoil from first principles.

  7. Perception and coding of high-frequency spectral notches: potential implications for sound localization.

    PubMed

    Alves-Pinto, Ana; Palmer, Alan R; Lopez-Poveda, Enrique A

    2014-01-01

    The interaction of sound waves with the human pinna introduces high-frequency notches (5-10 kHz) in the stimulus spectrum that are thought to be useful for vertical sound localization. A common view is that these notches are encoded as rate profiles in the auditory nerve (AN). Here, we review previously published psychoacoustical evidence in humans and computer-model simulations of inner hair cell responses to noises with and without high-frequency spectral notches that dispute this view. We also present new recordings from guinea pig AN and "ideal observer" analyses of these recordings that suggest that discrimination between noises with and without high-frequency spectral notches is probably based on the information carried in the temporal pattern of AN discharges. The exact nature of the neural code involved remains nevertheless uncertain: computer model simulations suggest that high-frequency spectral notches are encoded in spike timing patterns that may be operant in the 4-7 kHz frequency regime, while "ideal observer" analysis of experimental neural responses suggest that an effective cue for high-frequency spectral discrimination may be based on sampling rates of spike arrivals of AN fibers using non-overlapping time binwidths of between 4 and 9 ms. Neural responses show that sensitivity to high-frequency notches is greatest for fibers with low and medium spontaneous rates than for fibers with high spontaneous rates. Based on this evidence, we conjecture that inter-subject variability at high-frequency spectral notch detection and, consequently, at vertical sound localization may partly reflect individual differences in the available number of functional medium- and low-spontaneous-rate fibers. PMID:24904258

  8. Spreading and recoil of a surfactant-containing water drop on glass-supported alcohol films.

    PubMed

    Chowdhury, Devasish; Sarkar, Surya Protim; Kalita, Dipankar; Sarma, Tridib Kumar; Paul, Anumita; Chattopadhyay, Arun

    2004-02-17

    In this paper we report the experimental observation of spreading and recoil of surfactant-containing water drops on various alcohol films supported on glass slides. The time evolution of spreading and recoil behavior was recorded by placing a web camera above the drop. We observed that the drop spread the fastest on CH3OH, followed by C2H5OH, and the slowest on i-PrOH. On the other hand, the recoil behavior was just the opposite. The drop recoiled the slowest on CH3OH and fastest on i-PrOH, while it recoiled in an intermediate time on C2H5OH. In addition, concentration of surfactant in the drop played a prominent role in the spreading and recoil time of the drop, with higher surfactant concentration making the drop spread and recoil faster. The time evolution of spreading velocity of the drop on different alcohol films at various surfactant concentrations occurred with a Gaussian distribution and the peak velocity was reached earliest on CH3OH followed by C2H5OH, while on i-PrOH it took the longest time. The recoil behavior was similar. The variation of velocity as a function of radius exhibited oscillatory behavior, indicating the existence of an interfacial phenomenon. We also report the observation that spreading of the drop occurred without observable fingering instability. Further, we observed by Fourier transform infrared (FTIR) spectroscopic measurements that the drop had mixed with the alcohol films as it spread. Miscibility of the alcohol in the film with the drop, alcohol evaporation cooling-induced temperature gradient, and Marangoni effect probably play important roles in the spreading and recoil behavior of the drop.

  9. Effect of near-surface topography on high-frequency Rayleigh-wave propagation

    NASA Astrophysics Data System (ADS)

    Wang, Limin; Xu, Yixian; Xia, Jianghai; Luo, Yinhe

    2015-05-01

    Rayleigh waves, which are formed due to interference of P- and Sv-waves near the free surface, propagate along the free surface and vanish exponentially in the vertical direction. Their propagation is strongly influenced by surface topography. Due to the high resolution and precision requirements of near-surface investigations, the high-frequency Rayleigh waves are usually used for near-surface structural detecting. Although there are some numerical studies on high-frequency Rayleigh-wave propagation on topographic free surface, detailed analysis of characters of high-frequency Rayleigh-wave propagation on topographic free surface remains untouched. Hence, research of propagation of Rayleigh waves on complex topographic surface becomes critical for Rayleigh-wave methods in near-surface applications. To study the propagation of high-frequency Rayleigh waves on topographic free surface, two main topographic models are designed in this study. One of the models contains a depressed topographic surface, and another contains an uplifted topographic surface. We numerically simulate the propagation of high-frequency Rayleigh waves on these two topographic surfaces by finite-difference method. Soon afterwards, we analyze the propagation character of high-frequency Rayleigh waves on such topographic models, and compare the variations on its energy and frequency before and after passing the topographic region. At last, we discuss the relationship between the variations and topographical steepness of each model. Our numerical results indicate that influence of depressed topography for high-frequency Rayleigh waves is more distinct than influence of uplifted topography. Rayleigh waves produce new scattering body waves during passing the depressed topography with reduction of amplitude and loss of high-frequency components. Moreover, the steeper the depressed topography is, the more energy of Rayleigh waves is lost. The uplifted topography with gentle slope produces similar

  10. Far-Infrared Heterodyne Spectrometer for Sofia

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1998-01-01

    The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band.

  11. Far-Infrared Heterodyne Spectrometer for SOFIA

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Boreiko, R. T.

    1998-01-01

    This report summarizes work done under NASA Grant NAG2-1062 awarded to the University of Colorado. The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant (USRA 8500-98-010) to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band.

  12. Retention studies of recoiling daughter nuclides of 225Ac in polymer vesicles.

    PubMed

    Wang, G; de Kruijff, R M; Rol, A; Thijssen, L; Mendes, E; Morgenstern, A; Bruchertseifer, F; Stuart, M C A; Wolterbeek, H T; Denkova, A G

    2014-02-01

    Alpha radionuclide therapy is steadily gaining importance and a large number of pre-clinical and clinical studies have been carried out. However, due to the recoil effects the daughter recoil atoms, most of which are alpha emitters as well, receive energies that are much higher than the energies of chemical bonds resulting in decoupling of the radionuclide from common targeting agents. Here, we demonstrate that polymer vesicles (i.e. polymersomes) can retain recoiling daughter nuclei based on an experimental study examining the retention of (221)Fr and (213)Bi when encapsulating (225)Ac. PMID:24374072

  13. Retention studies of recoiling daughter nuclides of 225Ac in polymer vesicles.

    PubMed

    Wang, G; de Kruijff, R M; Rol, A; Thijssen, L; Mendes, E; Morgenstern, A; Bruchertseifer, F; Stuart, M C A; Wolterbeek, H T; Denkova, A G

    2014-02-01

    Alpha radionuclide therapy is steadily gaining importance and a large number of pre-clinical and clinical studies have been carried out. However, due to the recoil effects the daughter recoil atoms, most of which are alpha emitters as well, receive energies that are much higher than the energies of chemical bonds resulting in decoupling of the radionuclide from common targeting agents. Here, we demonstrate that polymer vesicles (i.e. polymersomes) can retain recoiling daughter nuclei based on an experimental study examining the retention of (221)Fr and (213)Bi when encapsulating (225)Ac.

  14. Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter

    NASA Astrophysics Data System (ADS)

    Sorensen, Peter; Dahl, Carl Eric

    2011-03-01

    We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

  15. Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter

    SciTech Connect

    Sorensen, P; Dahl, C E

    2011-02-14

    We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al.. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

  16. The high frequency characteristics of laser reflection and visible light during solid state disk laser welding

    NASA Astrophysics Data System (ADS)

    Gao, Xiangdong; You, Deyong; Katayama, Seiji

    2015-07-01

    Optical properties are related to weld quality during laser welding. Visible light radiation generated from optical-induced plasma and laser reflection is considered a key element reflecting weld quality. An in-depth analysis of the high-frequency component of optical signals is conducted. A combination of a photoelectric sensor and an optical filter helped to obtain visible light reflection and laser reflection in the welding process. Two groups of optical signals were sampled at a high sampling rate (250 kHz) using an oscilloscope. Frequencies in the ranges 1-10 kHz and 10-125 kHz were investigated respectively. Experimental results showed that there was an obvious correlation between the high-frequency signal and the laser power, while the high-frequency signal was not sensitive to changes in welding speed. In particular, when the defocus position was changed, only a high frequency of the visible light signal was observed, while the high frequency of the laser reflection signal remained unchanged. The basic correlation between optical features and welding status during the laser welding process is specified, which helps to provide a new research focus for investigating the stability of welding status.

  17. The apparent immunity of high-frequency ``transposed'' stimuli to low-frequency binaural interference

    NASA Astrophysics Data System (ADS)

    Bernstein, Leslie R.; Trahiotis, Constantine

    2004-11-01

    Discrimination of interaural temporal disparities (ITDs) was measured with either conventional or transposed ``targets'' centered at 4 kHz. The targets were presented either in the presence or absence of a simultaneously gated diotic noise centered at 500 Hz, the interferer. As expected, the presence of the low-frequency interferer resulted in substantially elevated threshold-ITDs for the conventional high-frequency stimuli. In contrast, these interference effects were absent for ITDs conveyed by the high-frequency transposed targets. The binaural interference effects observed with the conventional high-frequency stimuli were well accounted for, quantitatively, by the model described by Heller and Trahiotis [L. M. Heller and C. Trahiotis, J. Acoust. Soc. Am. 99, 3632-3637 (1996)]. The lack of binaural interference effects observed with the high-frequency transposed stimuli was not predicted by that model. It is suggested that transposed stimuli may be one of a class of stimuli that do not foster an obligatory combination of binaural information between low- and high-frequency regions. Under those conditions that do foster such an obligatory combination, one could still consider models of binaural interference, such as the one described in Heller and Trahiotis, to be valid descriptors of binaural processing. .

  18. Measures of extents of laterality for high-frequency ``transposed'' stimuli under conditions of binaural interference

    NASA Astrophysics Data System (ADS)

    Bernstein, Leslie R.; Trahiotis, Constantine

    2005-09-01

    Our purpose in this study was to determine whether across-frequency binaural interference would occur if ITD-based extents of laterality were measured using high-frequency transposed stimuli as targets. The results of an earlier study [L. R. Bernstein and C. Trahiotis, J. Acoust. Soc. Am. 116, 3062-3069 (2004)], which focused on threshold-ITDs, rather than extents of laterality, suggested that high-frequency transposed stimuli might be ``immune'' to binaural interference effects resulting from the addition of a spectrally remote, low-frequency interferer. In contrast to the earlier findings, the data from this study indicate that high-frequency transposed targets are susceptible to binaural interference. Nevertheless, high-frequency transposed targets, even when presented along with an interferer, yielded greater extents of ITD-based laterality than did high-frequency Gaussian noise targets presented in isolation. That is, the ``enhanced potency'' of ITDs conveyed by transposed stimuli persisted, even in the presence of a low-frequency interferer. Predictions made using an extension of the model of Heller and Trahiotis [L. M. Heller and C. Trahiotis, J. Acoust. Soc. Am. 99, 3632-3637 (1996)] accounted well for across-frequency binaural interference obtained with conventional Gaussian noise targets but, in all but one case, overpredicted the amounts of interference found with the transposed targets.

  19. Conventional Audiometry, Extended High-Frequency Audiometry, and DPOAE for Early Diagnosis of NIHL

    PubMed Central

    Mehrparvar, Amir Houshang; Mirmohammadi, Seyyed Jalil; Davari, Mohammad Hossein; Mostaghaci, Mehrdad; Mollasadeghi, Abolfazl; Bahaloo, Maryam; Hashemi, Seyyed Hesam

    2014-01-01

    Background: Noise most frequently affects hearing system, as it may typically cause a bilateral, progressive sensorineural hearing loss at high frequencies. Objectives: This study was designed to compare three different methods to evaluate noise-induced hearing loss (conventional audiometry, high-frequency audiometry, and distortion product otoacoustic emission). Material and Methods: This was a cross-sectional study. Data was analyzed by SPSS (ver. 19) using chi square, T test and repeated measures analysis. Study samples were workers from tile and ceramic industry. Results: We found that conventional audiometry, extended high-frequency audiometry, low-tone distortion product otoacoustic emission and high-tone distortion product otoacoustic emission had abnormal findings in 29 %, 69 %, 22 %, and 52 % of participants. Most frequently affected frequencies were 4000 and 6000Hz in conventional audiometry, and 14000 and 16000 in extended high-frequency audiometry. Conclusions: Extended high-frequency audiometry was the most sensitive test for detection of hearing loss in workers exposed to hazardous noise compared with conventional audiometry and distortion product otoacoustic. PMID:24719719

  20. Research for the jamming mechanism of high-frequency laser to the laser seeker

    NASA Astrophysics Data System (ADS)

    Zheng, Xingyuan; Zhang, Haiyang; Wang, Yunping; Feng, Shuang; Zhao, Changming

    2013-08-01

    High-frequency laser will be able to enter the enemy laser signal processing systems without encoded identification and a copy. That makes it one of the research directions of new interference sources. In order to study the interference mechanism of high-frequency laser to laser guided weapons. According to the principle of high-frequency laser interference, a series of related theoretical models such as a semi-active laser seeker coded identification model, a time door model, multi-signal processing model and a interference signal modulation processing model are established. Then seeker interfere with effective 3σ criterion is proposed. Based on this, the study of the effect of multi-source interference and signal characteristics of the effect of high repetition frequency laser interference are key research. According to the simulation system testing, the results show that the multi-source interference and interference signal frequency modulation can effectively enhance the interference effect. While the interference effect of the interference signal amplitude modulation is not obvious. The research results will provide the evaluation of high-frequency laser interference effect and provide theoretical references for high-frequency laser interference system application.

  1. The nonreciprocal effect under low- and high-frequency collinear acousto-optic interactions

    NASA Astrophysics Data System (ADS)

    Dyakonov, E. A.; Voloshinov, V. B.; Nikitin, P. A.

    2012-12-01

    The nonreciprocal effect under collinear acousto-optic interaction in the low- and high-frequency regimes is studied theoretically. The magnitudes of nonreciprocity determined from the ultrasonic frequency and from the wavelength of light are shown to be quantitatively identical. An expression that governs the magnitude of the nonreciprocity and that is valid for both low- and high-frequency regimes of the collinear acousto-optic interaction is obtained. The shape and width of the frequency characteristic of the collinear acousto-optic interaction calculated in the low diffraction efficiency approximation are shown to be the same in the low- and high-frequency regimes. The dependence of the frequency bandwidth of the collinear acousto-optic interaction on the ultrasonic-wave attenuation and diffraction efficiency is obtained. The magnitude of the nonreciprocal effect in some of the crystals used in acousto-optics is estimated numerically. The nonreciprocity of the collinear interaction is shown to be substantially stronger in the high-frequency regime relative to the low-frequency regime. Sapphire is proved to be an optimal material for experimental realization of the nonreciprocal effect in the high-frequency regime.

  2. NEPTUN-A spectrometer for measuring the Spin Analyzing Power in p-p elastic scattering at large P2⊥ at 400 GeV (and 3 TeV) at UNK

    NASA Astrophysics Data System (ADS)

    Lin, Ali M. T.

    1995-09-01

    We are constructing the NEPTUN-A spectrometer for measuring the Spin Analyzing Power in p+p↑→p+p at P2⊥=2 to 10 (GeV/c)2 at 400 GeV (or at 3 TeV) when the UNK accelerator in Protvino, Russia, becomes operational. The spectrometer consists of a 55 m long recoil arm with 3 horizontally bending magnets to guide the recoil protons onto a fixed 37° line. Then two vertical dipole magnets bend the protons up by 12° for momentum analysis. The momentum will be measured to an accuracy of 0.1% using chambers. In order to accept a large solid angle, the spectrometer contains a strong-focusing pair of quadrupoles looking at the polarized proton jet target. The forward arm consists of scintillator hodoscopes for measurement of the forward vertical angle. Acceptances and event rates are calculated. The status of the spectrometer is reported.

  3. Myoneural necrosis following high-frequency electrical stimulation of the cast-immobilized rabbit hindlimb

    NASA Technical Reports Server (NTRS)

    Friden, J.; Lieber, R. L.; Myers, R. R.; Powell, H. C.; Hargens, A. R.

    1989-01-01

    The morphological and physiological effects of 4 weeks of high-frequency electrical stimulation (1 h/day, 5 days/week) on cast-immobilized rabbit hindlimbs were investigated in the tibialis anterior muscle and peroneal nerve. In 2 out of 6 animals, high-frequency stimulation with immobilization caused muscle fiber death, internalization of muscle fiber nuclei, connective tissue proliferation, inflammatory response, altered fiber size distribution and variable staining intensities. The fast-twitch fibers were predominantly affected. Two of six peripheral nerves subjected to immobilization and stimulation showed severe damage. Tetanic forces were significantly reduced in the affected muscles. Therefore, the immobilization and high-frequency stimulation may be detrimental to myoneural structure and function and, thus, this combination of therapies should be applied conservatively.

  4. Fourier Spot Volatility Estimator: Asymptotic Normality and Efficiency with Liquid and Illiquid High-Frequency Data

    PubMed Central

    2015-01-01

    The recent availability of high frequency data has permitted more efficient ways of computing volatility. However, estimation of volatility from asset price observations is challenging because observed high frequency data are generally affected by noise-microstructure effects. We address this issue by using the Fourier estimator of instantaneous volatility introduced in Malliavin and Mancino 2002. We prove a central limit theorem for this estimator with optimal rate and asymptotic variance. An extensive simulation study shows the accuracy of the spot volatility estimates obtained using the Fourier estimator and its robustness even in the presence of different microstructure noise specifications. An empirical analysis on high frequency data (U.S. S&P500 and FIB 30 indices) illustrates how the Fourier spot volatility estimates can be successfully used to study intraday variations of volatility and to predict intraday Value at Risk. PMID:26421617

  5. High-frequency neural oscillations and visual processing deficits in schizophrenia

    PubMed Central

    Tan, Heng-Ru May; Lana, Luiz; Uhlhaas, Peter J.

    2013-01-01

    Visual information is fundamental to how we understand our environment, make predictions, and interact with others. Recent research has underscored the importance of visuo-perceptual dysfunctions for cognitive deficits and pathophysiological processes in schizophrenia. In the current paper, we review evidence for the relevance of high frequency (beta/gamma) oscillations towards visuo-perceptual dysfunctions in schizophrenia. In the first part of the paper, we examine the relationship between beta/gamma band oscillations and visual processing during normal brain functioning. We then summarize EEG/MEG-studies which demonstrate reduced amplitude and synchrony of high-frequency activity during visual stimulation in schizophrenia. In the final part of the paper, we identify neurobiological correlates as well as offer perspectives for future research to stimulate further inquiry into the role of high-frequency oscillations in visual processing impairments in the disorder. PMID:24130535

  6. Chromatic and high-frequency cVEP-based BCI paradigm.

    PubMed

    Aminaka, Daiki; Makino, Shoji; Rutkowski, Tomasz M

    2015-01-01

    We present results of an approach to a code-modulated visual evoked potential (cVEP) based brain-computer interface (BCI) paradigm using four high-frequency flashing stimuli. To generate higher frequency stimulation compared to the state-of-the-art cVEP-based BCIs, we propose to use the light-emitting diodes (LEDs) driven from a small micro-controller board hardware generator designed by our team. The high-frequency and green-blue chromatic flashing stimuli are used in the study in order to minimize a danger of a photosensitive epilepsy (PSE). We compare the the green-blue chromatic cVEP-based BCI accuracies with the conventional white-black flicker based interface. The high-frequency cVEP responses are identified using a canonical correlation analysis (CCA) method.

  7. Short-interval intracortical inhibition is modulated by high-frequency peripheral mixed nerve stimulation.

    PubMed

    Murakami, Takenobu; Sakuma, Kenji; Nomura, Takashi; Nakashima, Kenji

    2007-06-01

    Cortical excitability can be modulated by manipulation of afferent input. We investigated the influence of peripheral mixed nerve stimulation on the excitability of the motor cortex. Motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the right abductor pollicis brevis (APB), extensor carpi radialis (ECR) and first dorsal interosseous (FDI) muscles were evaluated using paired-pulse transcranial magnetic stimulation (TMS) before and after high-frequency peripheral mixed nerve stimulation (150 Hz, 30 min) over the right median nerve at the wrist. The MEP amplitude and SICI of the APB muscle decreased transiently 0-10 min after the intervention, whereas the ICF did not change. High-frequency peripheral mixed nerve stimulation reduced the excitability of the motor cortex. The decrement in the SICI, which reflects the function of GABA(A)ergic inhibitory interneurons, might compensate for the reduced motor cortical excitability after high-frequency peripheral mixed nerve stimulation.

  8. High frequency electromagnetic resistive instability in a Hall thruster under the effect of ionization

    SciTech Connect

    Singh, Sukhmander; Malik, Hitendra K.; Nishida, Yasushi

    2013-10-15

    Two types of high frequency electromagnetic resistive instabilities are found to occur in a Hall thruster plasma in the presence of collisions and ionization, out of which one of lower growth rate (called lower magnitude high frequency instability (LMHFI)) is sensitive to the axial component of the wave vector. The effects of ionization, collisions, and electron drift velocity on the growth rates of these instabilities are studied in greater details. The LMHFI grows faster in the presence of ionization but shows weaker dependence on the electrons' E(vector sign)×B(vector sign) drift, contrary to the case of other instability (called higher magnitude high frequency instability) which is sensitive to the azimuthal wave number and collisions.

  9. Fourier Spot Volatility Estimator: Asymptotic Normality and Efficiency with Liquid and Illiquid High-Frequency Data.

    PubMed

    Mancino, Maria Elvira; Recchioni, Maria Cristina

    2015-01-01

    The recent availability of high frequency data has permitted more efficient ways of computing volatility. However, estimation of volatility from asset price observations is challenging because observed high frequency data are generally affected by noise-microstructure effects. We address this issue by using the Fourier estimator of instantaneous volatility introduced in Malliavin and Mancino 2002. We prove a central limit theorem for this estimator with optimal rate and asymptotic variance. An extensive simulation study shows the accuracy of the spot volatility estimates obtained using the Fourier estimator and its robustness even in the presence of different microstructure noise specifications. An empirical analysis on high frequency data (U.S. S&P500 and FIB 30 indices) illustrates how the Fourier spot volatility estimates can be successfully used to study intraday variations of volatility and to predict intraday Value at Risk. PMID:26421617

  10. [Endoscopic hemostasis using high-frequency hemostatic forceps for hemorrhagic gastric ulcer].

    PubMed

    Enomoto, Shotaro; Yahagi, Naohisa; Fujishiro, Mitsuhiro; Iguchi, Mikitaka; Ichinose, Masao

    2004-03-01

    Gastric ulcer is a major responsible lesion for upper gastrointestinal bleeding. Several methods for endoscopic hemostasis are widely used throughout Japan to treat the ulcerative lesion. High-frequency hemostatic forceps is one of the endoscopic coagulation devices developed solely for hemostasis. Unlike biopsy forceps, it has narrow opening angle, a small cup and a dull edge to make pinpoint holding of the target lesion possible. We applied high-frequency hemostatic forceps for eleven cases of hemorrhagic gastric ulcer with exposed vessels. All of the cases were treated by endoscopic hemostasis with the device. Initial hemostasis obtained in all of the cases(100%), and no rebleeding was observed. Additional treatment, however, was necessary in four cases(36%). No serious complication, like perforation, was observed. We concluded that endoscopic hemostasis using high-frequency hemostatic forceps for hemorrhagic gastric ulcer is safe and effective method.

  11. High-frequency excitation of earth rotation parameters by the atmosphere

    NASA Astrophysics Data System (ADS)

    Xie, Bo-Quan; Zheng, Da-Wei

    1996-02-01

    Using the ERP series from space geodetic measurement in the period 1983-1992 and the AAM series from global meteorological data we analyzed the high-frequency (timescales below one month) excitation of LOD and polar drift by the atmosphere. We found: 1) The atmosphere has an effect on the estimated value of the high-frequency tides of the LOD component, whereas the variation of the tidal distortion parameter k/c is caused by non-atmospheric factors. 2) The atmosphere can account for most part of the non-tidal variation of LOD below 30 d. 3) The high-frequency variations below 30 d of the polar drift are mainly excited by the atmosphere. The atmosphere can contribute as much as 70% to the 27 d-variation in the x-component.

  12. Advanced waveforms and frequency with spinal cord stimulation: burst and high-frequency energy delivery.

    PubMed

    Pope, Jason E; Falowski, Steven; Deer, Tim R

    2015-07-01

    In recent years, software development has been key to the next generation of neuromodulation devices. In this review, we will describe the new strategies for electrical waveform delivery for spinal cord stimulation. A systematic literature review was performed using bibliographic databases, limited to the English language and human data, between 2010 and 2014. The literature search yielded three articles on burst stimulation and four articles on high-frequency stimulation. High-frequency and burst stimulation may offer advantages over tonic stimulation, as data suggest improved patient tolerance, comparable increase in function and possible success with a subset of patients refractory to tonic spinal cord stimulation. High-frequency and burst stimulation are new ways to deliver energy to the spinal cord that may offer advantages over tonic stimulation. These may offer new salvage strategies to mitigate spinal cord stimulation failure and improve cost-effectiveness by reducing explant rate.

  13. A compact neutron spectrometer for characterizing inertial confinement fusion implosions at OMEGA and the NIF

    SciTech Connect

    Zylstra, A. B.; Gatu Johnson, M.; Frenje, J. A.; Séguin, F. H.; Rinderknecht, H. G.; Rosenberg, M. J.; Sio, H. W.; Li, C. K.; Petrasso, R. D.; McCluskey, M.; Mastrosimone, D.; Glebov, V. Yu.; Forrest, C.; Stoeckl, C.; Sangster, T. C.

    2014-06-04

    A compact spectrometer for measurements of the primary deuterium-tritium neutron spectrum has been designed and implemented on the OMEGA laser facility. This instrument uses the recoil spectrometry technique, where neutrons produced in an implosion elastically scatter protons in a plastic foil, which are subsequently detected by a proton spectrometer. This diagnostic is capable of measuring the yield to ~±10% accuracy, and mean neutron energy to ~±50 keV precision. As these compact spectrometers can be readily placed at several locations around an implosion, effects of residual fuel bulk flows during burn can be measured. Future improvements to reduce the neutron energy uncertainty to ±15-20 keV are discussed, which will enable measurements of fuel velocities to an accuracy of ~±25-40 km/s.

  14. A compact neutron spectrometer for characterizing inertial confinement fusion implosions at OMEGA and the NIF.

    PubMed

    Zylstra, A B; Gatu Johnson, M; Frenje, J A; Séguin, F H; Rinderknecht, H G; Rosenberg, M J; Sio, H W; Li, C K; Petrasso, R D; McCluskey, M; Mastrosimone, D; Glebov, V Yu; Forrest, C; Stoeckl, C; Sangster, T C

    2014-06-01

    A compact spectrometer for measurements of the primary deuterium-tritium neutron spectrum has been designed and implemented on the OMEGA laser facility [T. Boehly et al., Opt. Commun. 133, 495 (1997)]. This instrument uses the recoil spectrometry technique, where neutrons produced in an implosion elastically scatter protons in a plastic foil, which are subsequently detected by a proton spectrometer. This diagnostic is currently capable of measuring the yield to ~±10% accuracy, and mean neutron energy to ~±50 keV precision. As these compact spectrometers can be readily placed at several locations around an implosion, effects of residual fuel bulk flows during burn can be measured. Future improvements to reduce the neutron energy uncertainty to ±15-20 keV are discussed, which will enable measurements of fuel velocities to an accuracy of ~±25-40 km/s.

  15. A compact neutron spectrometer for characterizing inertial confinement fusion implosions at OMEGA and the NIF

    DOE PAGESBeta

    Zylstra, A. B.; Gatu Johnson, M.; Frenje, J. A.; Séguin, F. H.; Rinderknecht, H. G.; Rosenberg, M. J.; Sio, H. W.; Li, C. K.; Petrasso, R. D.; McCluskey, M.; et al

    2014-06-04

    A compact spectrometer for measurements of the primary deuterium-tritium neutron spectrum has been designed and implemented on the OMEGA laser facility. This instrument uses the recoil spectrometry technique, where neutrons produced in an implosion elastically scatter protons in a plastic foil, which are subsequently detected by a proton spectrometer. This diagnostic is capable of measuring the yield to ~±10% accuracy, and mean neutron energy to ~±50 keV precision. As these compact spectrometers can be readily placed at several locations around an implosion, effects of residual fuel bulk flows during burn can be measured. Future improvements to reduce the neutron energymore » uncertainty to ±15-20 keV are discussed, which will enable measurements of fuel velocities to an accuracy of ~±25-40 km/s.« less

  16. A compact neutron spectrometer for characterizing inertial confinement fusion implosions at OMEGA and the NIF

    SciTech Connect

    Zylstra, A. B. Gatu Johnson, M.; Frenje, J. A.; Séguin, F. H.; Rinderknecht, H. G.; Rosenberg, M. J.; Sio, H. W.; Li, C. K.; Petrasso, R. D.; McCluskey, M.; Mastrosimone, D.; Glebov, V. Yu.; Forrest, C.; Stoeckl, C.; Sangster, T. C.

    2014-06-15

    A compact spectrometer for measurements of the primary deuterium-tritium neutron spectrum has been designed and implemented on the OMEGA laser facility [T. Boehly et al., Opt. Commun. 133, 495 (1997)]. This instrument uses the recoil spectrometry technique, where neutrons produced in an implosion elastically scatter protons in a plastic foil, which are subsequently detected by a proton spectrometer. This diagnostic is currently capable of measuring the yield to ∼±10% accuracy, and mean neutron energy to ∼±50 keV precision. As these compact spectrometers can be readily placed at several locations around an implosion, effects of residual fuel bulk flows during burn can be measured. Future improvements to reduce the neutron energy uncertainty to ±15−20 keV are discussed, which will enable measurements of fuel velocities to an accuracy of ∼±25−40 km/s.

  17. Factors Associated with High-Frequency Illicit Methadone Use among Rural Appalachian Drug Users

    PubMed Central

    Hall, Martin T.; Leukefeld, Carl G.; Havens, Jennifer R.

    2013-01-01

    Background In recent years there has been a sharp increase in the use of illicit methadone as well as methadone-related overdose deaths. Objective The purpose of this study is to describe factors associated low- and high-frequency methadone use in a cohort of rural Appalachian drug users. Methods Interviews assessing sociodemographics, illicit drug use and drug treatment, psychiatric disorders, health, and sociometric drug network characteristics were conducted with 503 rural drug users between 2008 and 2010. A two-level mixed effects regression model was utilized to differentiate low- (one use per month or less in the past 6 months) versus high-frequency (daily or weekly use in the past 6 months) illicit methadone users. Results The lifetime prevalence of illicit methadone use in this population was 94.7% (n=476) and slightly less than half (46.3%) were high-frequency users. In the mixed effects regression model, initiating illicit methadone use at a younger age was associated with high-frequency illicit methadone use. Whereas taking a prescribed medication for a physical problem, undergoing additional weeks of outpatient drug free treatment, daily OxyContin® use in the past month, and having fewer ties and second order connections in the drug network reduced the odds of high-frequency illicit methadone use. Conclusions Rates of illicit methadone use and high-frequency illicit methadone use among this sample of rural drug users were considerably higher than those previously reported in the literature. Health practitioners in rural areas should routinely screen for illicit opioid use, including methadone. PMID:23841864

  18. Accumulated source imaging of brain activity with both low and high-frequency neuromagnetic signals

    PubMed Central

    Xiang, Jing; Luo, Qian; Kotecha, Rupesh; Korman, Abraham; Zhang, Fawen; Luo, Huan; Fujiwara, Hisako; Hemasilpin, Nat; Rose, Douglas F.

    2014-01-01

    Recent studies have revealed the importance of high-frequency brain signals (>70 Hz). One challenge of high-frequency signal analysis is that the size of time-frequency representation of high-frequency brain signals could be larger than 1 terabytes (TB), which is beyond the upper limits of a typical computer workstation's memory (<196 GB). The aim of the present study is to develop a new method to provide greater sensitivity in detecting high-frequency magnetoencephalography (MEG) signals in a single automated and versatile interface, rather than the more traditional, time-intensive visual inspection methods, which may take up to several days. To address the aim, we developed a new method, accumulated source imaging, defined as the volumetric summation of source activity over a period of time. This method analyzes signals in both low- (1~70 Hz) and high-frequency (70~200 Hz) ranges at source levels. To extract meaningful information from MEG signals at sensor space, the signals were decomposed to channel-cross-channel matrix (CxC) representing the spatiotemporal patterns of every possible sensor-pair. A new algorithm was developed and tested by calculating the optimal CxC and source location-orientation weights for volumetric source imaging, thereby minimizing multi-source interference and reducing computational cost. The new method was implemented in C/C++ and tested with MEG data recorded from clinical epilepsy patients. The results of experimental data demonstrated that accumulated source imaging could effectively summarize and visualize MEG recordings within 12.7 h by using approximately 10 GB of computer memory. In contrast to the conventional method of visually identifying multi-frequency epileptic activities that traditionally took 2–3 days and used 1–2 TB storage, the new approach can quantify epileptic abnormalities in both low- and high-frequency ranges at source levels, using much less time and computer memory. PMID:24904402

  19. Fast thermometry for trapped atoms using recoil-induced resonance

    NASA Astrophysics Data System (ADS)

    Zhao, Yan-Ting; Su, Dian-Qiang; Ji, Zhong-Hua; Zhang, Hong-Shan; Xiao, Lian-Tuan; Jia, Suo-Tang

    2015-09-01

    We have employed recoil-induced resonance (RIR) with linewidth on the order of 10 kHz to demonstrate the fast thermometry for ultracold atoms. We theoretically calculate the absorption spectrum of RIR which agrees well with the experimental results. The temperature of the ultracold sample derived from the RIR spectrum is T = 84±4.5 μK, which is close to 85 μK that measured by the method of time-of-flight absorption imaging. To exhibit the fast measurement advantage in applying RIR to the ultracold atom thermometry, we study the dependence of ultracold sample temperature on the trapping beam frequency detuning. This method can be applied to determine the translational temperature of molecules in photoassociation dynamics. Project supported by the National Basic Research Development Program of China (Grant No. 2012CB921603), the National High Technology Research and Development Program of China (Grant No. 2011AA010801), the National Natural Science Foundation of China (Grant Nos. 61275209, 11304189, 61378015, and 11434007), and Program for Changjiang Scholars and Innovative Research Team in Universities of China (Grant No. IRT13076).

  20. First Measurement of Beam-Recoil Observables Cx and Cz

    SciTech Connect

    R. Bradford; R.A. Schumacher; G. Adams; M.J. Amaryan; P. Ambrozewicz; E. Anciant; M. Anghinolfi; B. Asavapibhop; G. Asryan; G. Audit; H. Avakian; H. Bagdasaryan; N. Baillie; J.P. Ball; N.A. Baltzell; S. Barrow; V. Batourine; M. Battaglieri; K. Beard; I. Bedlinskiy; M. Bektasoglu; M. Bellis; N. Benmouna; B.L. Berman; N. Bianchi; A.S. Biselli; B.E. Bonner; S. Bouchigny; S. Boiarinov; D. Branford; W.J. Briscoe; W.K. Brooks; S. B¨ultmann; V.D. Burkert; C. Butuceanu; J.R. Calarco; S.L. Careccia; D.S. Carman; B. Carnahan; S. Chen; P.L. Cole; A. Coleman; P. Collins; P. Coltharp; D. Cords; † P. Corvisiero; D. Crabb; H. Crannell; V. Crede; J.P. Cummings; R. De Masi; E. De Sanctis; R. De Vita; P.V. Degtyarenko; H. Denizli; L. Dennis; A. Deur; K.V. Dharmawardane; R. Dickson; C. Djalali; G.E. Dodge; J. Donnelly; D. Doughty; P. Dragovitsch; M. Dugger; S. Dytman; O.P. Dzyubak; H. Egiyan; K.S. Egiyan; L. El Fassi; L. Elouadrhiri; A. Empl; P. Eugenio; R. Fatemi; G. Fedotov; G. Feldman; R.J. Feuerbach; T.A. Forest; H. Funsten; M. Garcon; G. Gavalian; G.P. Gilfoyle; K.L. Giovanetti; F.X. Girod; J.T. Goetz; A. Gonenc; R.W. Gothe; K.A. Griffioen; M. Guidal; M. Guillo; N. Guler; L. Guo; V. Gyurjyan; C. Hadjidakis; K. Hafidi; H. Hakobyan; R.S. Hakobyan; J. Hardie; D. Heddle; F.W. Hersman; K. Hicks; I. Hleiqawi; M. Holtrop; J. Hu; M. Huertas; C.E. Hyde-Wright; Y. Ilieva; D.G. Ireland; B.S. Ishkhanov; E.L. Isupov; M.M. Ito; D. Jenkins; H.S. Jo; K. Joo; H.G. Juengst; N. Kalantarians; J.D. Kellie; M. Khandaker; K.Y. Kim; K. Kim; W. Kim; A. Klein; F.J. Klein; M. Klusman; M. Kossov; L.H. Kramer; V. Kubarovsky; J. Kuhn; S.E. Kuhn; S.V. Kuleshov; J. Lachniet; J.M. Laget; J. Langheinrich; D. Lawrence; A.C.S. Lima; K. Livingston; H.Y. Lu; K. Lukashin; M. MacCormick; J.J. Manak; C. Marchand; N. Markov; S. McAleer; B. McKinnon; J.W.C. McNabb; B.A. Mecking; M.D. Mestayer; C.A. Meyer; T. Mibe; K. Mikhailov; M. Mirazita; R. Miskimen; V. Mokeev; K. Moriya; S.A. Morrow; M. Moteabbed; V. Muccifora; J. Mueller; G.S. Mutchler; P. Nadel-Turonski; J. Napolitano; R. Nasseripour; N. Natasha; S. Niccolai; G. Niculescu; I. Niculescu; B.B. Niczyporuk; M.R. Niroula; R.A. Niyazov; M. Nozar; G.V. O’Rielly; M. Osipenko; A.I. Ostrovidov; K. Park; E. Pasyuk; C. Paterson; S.A. Philips; J. Pierce; N. Pivnyuk; D. Pocanic; O. Pogorelko; E. Polli; I. Popa; S. Pozdniakov; B.M. Preedom; J.W. Price; Y. Prok; D. Protopopescu; L.M. Qin; B.P. Quinn; B.A. Raue; G. Riccardi; G. Ricco; M. Ripani; B.G. Ritchie; F. Ronchetti; G. Rosner; P. Rossi; D. Rowntree; P.D. Rubin; F. Sabatie; J. Salamanca; C. Salgado; J.P. Santoro; V. Sapunenko; V.S. Serov; A. Shafi; Y.G. Sharabian; J. Shaw; N.V. Shvedunov; S. Simionatto; A.V. Skabelin; E.S. Smith; L.C. Smith; D.I. Sober; D. Sokhan; M. Spraker; A. Stavinsky; S.S. Stepanyan; S. Stepanyan; B.E. Stokes; P. Stoler; I.I. Strakovsky; S. Strauch; M. Taiuti; S. Taylor; D.J. Tedeschi; U. Thoma; R. Thompson; A. Tkabladze; S. Tkachenko; L. Todor; C. Tur; M. Ungaro; M.F. Vineyard; A.V. Vlassov; K. Wang; D.P. Watts; L.B. Weinstein; H. Weller; D.P. Weygand; M. Williams; E. Wolin; M.H. Wood; A. Yegneswaran; J. Yun; L. Zana; J. Zhang; B. Zhao; and Z.W. Zhao

    2007-03-01

    Spin transfer from circularly polarized real photons to recoiling hyperons has been measured for the reactions $\\vec\\gamma + p \\to K^+ + \\vec\\Lambda$ and $\\vec\\gamma + p \\to K^+ + \\vec\\Sigma^0$. The data were obtained using the CLAS detector at Jefferson Lab for center-of-mass energies $W$ between 1.6 and 2.53 GeV, and for $-0.85<\\cos\\theta_{K^+}^{c.m.}< +0.95$. For the $\\Lambda$, the polarization transfer coefficient along the photon momentum axis, $C_z$, was found to be near unity for a wide range of energy and kaon production angles. The associated transverse polarization coefficient, $C_x$, is smaller than $C_z$ by a roughly constant difference of unity. Most significantly, the {\\it total} $\\Lambda$ polarization vector, including the induced polarization $P$, has magnitude consistent with unity at all measured energies and production angles when the beam is fully polarized. For the $\\Sigma^0$ this simple phenomenology does not hold. All existing hadrodynamic models are in poor agreement with these results.