WorldWideScience

Sample records for high amplitude oscillations

  1. Frequencies and amplitudes of high-degree solar oscillations

    Science.gov (United States)

    Kaufman, James Morris

    Measurements of some of the properties of high-degree solar p- and f-mode oscillations are presented. Using high-resolution velocity images from Big Bear Solar Observatory, we have measured mode frequencies, which provide information about the composition and internal structure of the Sun, and mode velocity amplitudes (corrected for the effects of atmospheric seeing), which tell us about the oscillation excitation and damping mechanisms. We present a new and more accurate table of the Sun's acoustic vibration frequencies, nunl, as a function of radial order n and spherical harmonic degree l. These frequencies are averages over azimuthal order m and approximate the normal mode frequencies of a nonrotating spherically symmetric Sun near solar minimum. The frequencies presented here are for solar p- and f-modes with 180 less than or = l less than or = 1920, 0 less than or = n less than or = 8, and 1.7 mHz less than or = nunl less than or = 5.3 mHz. The uncertainties, sigmanl, in the frequencies areas are as low as 3.1 micro-Hz. The theoretically expected f-mode frequencies are given by omega squared = gkh approx. = gl/R, where g is the gravitational acceleration at the surface, kh is the horizontal component of the wave vector, and R is the radius of the Sun. We find that the observed frequencies are significantly less than expected for l greater than 1000, for which we have no explanation. Observations of high-degree oscillations, which have very small spatial features, suffer from the effects of atmospheric image blurring and image motion (or 'seeing'), thereby reducing the amplitudes of their spatial-frequency components. In an attempt to correct the velocity amplitudes for these effects, we simultaneously measured the atmospheric modulation transfer function (MTF) by looking at the effects of seeing on the solar limb. We are able to correct the velocity amplitudes using the MTF out to l approx. = 1200. We find that the frequency of the peak velocity power (as a

  2. External Drive to Inhibitory Cells Induces Alternating Episodes of High- and Low-Amplitude Oscillations

    NARCIS (Netherlands)

    Gonzalez, Oscar J. Avella; van Aerde, Karlijn I.; van Elburg, Ronald A. J.; Poil, Simon-Shlomo; Mansvelder, Huibert D.; Linkenkaer-Hansen, Klaus; van Pelt, Jaap; van Ooyen, Arjen

    2012-01-01

    Electrical oscillations in neuronal network activity are ubiquitous in the brain and have been associated with cognition and behavior. Intriguingly, the amplitude of ongoing oscillations, such as measured in EEG recordings, fluctuates irregularly, with episodes of high amplitude alternating with epi

  3. The analysis of high amplitude of potential oscillations near the hollow cathode of ion thruster

    Science.gov (United States)

    Qin, Yu; Xie, Kan; Guo, Ning; Zhang, Zun; Zhang, Cen; Gu, Zengjie; Zhang, Yu; Jiang, Zhaorui; Ouyang, Jiting

    2017-05-01

    The influence of gas flow, current level, and different shapes of anode on the oscillation amplitude and the characteristics of the hollow cathode discharge were investigated. The average plasma potential, temporal measurements of plasma potential, ion density, the electron temperature, as well as waveforms of plasma potential for test conditions were measured. At the same time, the time-resolved images of the plasma plume were also recorded. The results show that the potential oscillations appear at high discharge current or low flow rate. The potential oscillation boundaries, the position of maximum amplitude of plasma potential, and the position where the highest ion density was observed, were found. Both of the positions are affected by different shapes of anode configurations. This high amplitude of potential oscillations is ionization-like instabilities. The xenon ions ionized in space was analyzed for the fast potential rise and spatial dissipation of the space xenon ions was the reason for the gradual potential delay.

  4. Non-Linear High Amplitude Oscillations in Wave-shaped Resonators

    Science.gov (United States)

    Antao, Dion; Farouk, Bakhtier

    2011-11-01

    A numerical and experimental study of non-linear, high amplitude standing waves in ``wave-shaped'' resonators is reported here. These waves are shock-less and can generate peak acoustic overpressures that can exceed the ambient pressure by three/four times its nominal value. A high fidelity compressible axisymmetric computational fluid dynamic model is used to simulate the phenomena in cylindrical and arbitrarily shaped axisymmetric resonators. Working fluids (Helium, Nitrogen and R-134a) at various operating pressures are studied. The experiments are performed in a constant cross-section cylindrical resonator in atmospheric pressure nitrogen and helium to provide model validation. The high amplitude non-linear oscillations demonstrated can be used as a prime mover in a variety of applications including thermoacoustic cryocooling. The work reported is supported by the US National Science Foundation under grant CBET-0853959.

  5. [High-frequency ventilation. I. Distribution of alveolar pressure amplitudes during high frequency oscillation in the lung model].

    Science.gov (United States)

    Theissen, J; Lunkenheimer, P P; Niederer, P; Bush, E; Frieling, G; Lawin, P

    1987-09-01

    The pattern of intrapulmonary pressure distribution was studied during high-frequency ventilation in order to explain the inconsistent results reported in the literature. Methods. Pressure and flow velocity (hot-wire anemometry) were measured in different lung compartments: 1. In transalveolar chambers sealed to the perforated pleural surfaces of dried pig lungs; 2. In emphysema-simulating airbags sealed to the isolated bronchial trees of dried pig lungs; and 3. In transalveolar chambers sealed to the perforated pleural surfaces of freshly excised pig lungs. Results. 1. The pressure amplitudes change from one area to another and depending on the exciting frequency. 2. High-frequency oscillation is associated with an increase in pressure amplitude when the exciting frequency rises, whereas with conventional high-frequency jet ventilation the pressure amplitude is more likely to decrease with frequency. 3. During high-frequency jet ventilation the local pressure amplitude changes with the position of the tube in the trachea rather than with the exciting frequency. 4. When the volume of the measuring chamber is doubled the resulting pressure amplitude falls to half the control value. 5. The pressure amplitude and mean pressure measured in the transalveolar chamber vary more or less independently from the peak flow velocity. High-frequency ventilation is thus seen to be a frequency-dependant, inhomogeneous mode of ventilation that can essentially be homogenized by systematically changing the exciting frequency. The frequency-dependant response to different lung areas to excitation is likely to result from an intrabronchially-localized aerodynamic effect rather than the mechanical properties of the lung parenchyma.

  6. Amplitude envelope synchronization in coupled chaotic oscillators.

    Science.gov (United States)

    Gonzalez-Miranda, J M

    2002-03-01

    A peculiar type of synchronization has been found when two Van der Pol-Duffing oscillators, evolving in different chaotic attractors, are coupled. As the coupling increases, the frequencies of the two oscillators remain different, while a synchronized modulation of the amplitudes of a signal of each system develops, and a null Lyapunov exponent of the uncoupled systems becomes negative and gradually larger in absolute value. This phenomenon is characterized by an appropriate correlation function between the returns of the signals, and interpreted in terms of the mutual excitation of new frequencies in the oscillators power spectra. This form of synchronization also occurs in other systems, but it shows up mixed with or screened by other forms of synchronization, as illustrated in this paper by means of the examples of the dynamic behavior observed for three other different models of chaotic oscillators.

  7. High Amplitude Secondary Mass Drive

    Energy Technology Data Exchange (ETDEWEB)

    DYCK,CHRISTOPHER WILLIAM; ALLEN,JAMES J.; HUBER,ROBERT JOHN; SNIEGOWSKI,JEFFRY J.

    2000-07-06

    In this paper we describe a high amplitude electrostatic drive for surface micromachined mechanical oscillators that may be suitable for vibratory gyroscopes. It is an advanced design of a previously reported dual mass oscillator (Dyck, et. al., 1999). The structure is a 2 degree-of-freedom, parallel-plate driven motion amplifier, termed the secondary mass drive oscillator (SMD oscillator). During each cycle the device contacts the drive plates, generating large electrostatic forces. Peak-to-peak amplitudes of 54 {micro}m have been obtained by operating the structure in air with an applied voltage of 11 V. We describe the structure, present the analysis and design equations, and show recent results that have been obtained, including frequency response data, power dissipation, and out-of- plane motion.

  8. Thermodynamic constraints on the amplitude of quantum oscillations

    Science.gov (United States)

    Shekhter, Arkady; Modic, K. A.; McDonald, R. D.; Ramshaw, B. J.

    2017-03-01

    Magneto-quantum oscillation experiments in high-temperature superconductors show a strong thermally induced suppression of the oscillation amplitude approaching the critical dopings [B. J. Ramshaw et al., Science 348, 317 (2014), 10.1126/science.aaa4990; H. Shishido et al., Phys. Rev. Lett. 104, 057008 (2010), 10.1103/PhysRevLett.104.057008; P. Walmsley et al., Phys. Rev. Lett. 110, 257002 (2013), 10.1103/PhysRevLett.110.257002]—in support of a quantum-critical origin of their phase diagrams. We suggest that, in addition to a thermodynamic mass enhancement, these experiments may directly indicate the increasing role of quantum fluctuations that suppress the quantum oscillation amplitude through inelastic scattering. We show that the traditional theoretical approaches beyond Lifshitz-Kosevich to calculate the oscillation amplitude in correlated metals result in a contradiction with the third law of thermodynamics and suggest a way to rectify this problem.

  9. The accretion rate dependence of burst oscillation amplitude

    CERN Document Server

    Ootes, Laura S; Galloway, Duncan K; Wijnands, Rudy

    2016-01-01

    Neutron stars in low mass X-ray binaries exhibit oscillations during thermonuclear bursts, attributed to asymmetric brightness patterns on the burning surfaces. All models that have been proposed to explain the origin of these asymmetries (spreading hotspots, surface waves, and cooling wakes) depend on the accretion rate. By analysis of archival RXTE data of six oscillation sources, we investigate the accretion rate dependence of the amplitude of burst oscillations. This more than doubles the size of the sample analysed previously by Muno et al. (2004), who found indications for a relationship between accretion rate and oscillation amplitudes. We find that burst oscillation signals can be detected at all observed accretion rates. Moreover, oscillations at low accretion rates are found to have relatively small amplitudes ($A_\\text{rms}\\leq0.10$) while oscillations detected in bursts observed at high accretion rates cover a broad spread in amplitudes ($0.05\\leq A_\\text{rms}\\leq0.20$). In this paper we present t...

  10. Oscillations in the hadron scattering amplitude at high energy and small momentum transfer; Oscillations dans l`amplitude de diffusion hadronique a haute energie et petites moments de transfer

    Energy Technology Data Exchange (ETDEWEB)

    Gauron, Pierre; Basarab Nicolescu [Theoretical Physics Division, Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France); Selyugin, O.V. [Lab. of Theoretical Physics, Joint Inst. for Nuclear Research, Dubna (Russian Federation)

    1999-10-01

    We show that the high precision dN/dt UA4/2 data at {radical} = 541 GeV are compatible with the presence of Auberson-Kinoshita-Martin (AKM) type of oscillations at very small momentum transfer. These oscillations seem to be periodic in {radical}|t|, the corresponding period being {approx_equal} 2 {center_dot}10{sup -2} GeV. The existence of such visible oscillations suggests a general mechanism of saturation of axiomatic bounds. As an illustration the consequences for extracting the parameter {rho} = ReF/ImF from dN/dt data are also discussed. (authors) 1 ref., 2 figs.

  11. The effect of airway pressure and oscillation amplitude on ventilation in pre-term infants

    NARCIS (Netherlands)

    Miedema, M.; de Jongh, Franciscus H.C.; Frerichs, I.; van Veenendaal, M.B.; van Kaam, A.H.

    2012-01-01

    We determined the effect of lung recruitment and oscillation amplitude on regional oscillation volume and functional residual capacity (FRC) in high-frequency oscillatory ventilation (HFOV) used in pre-term infants with respiratory distress syndrome (RDS). Changes in lung volume, oscillation volume

  12. High-amplitude, centennial-scale climate oscillations during the last glacial in the western Third Pole as recorded in the Guliya ice cap

    Science.gov (United States)

    Thompson, L. G.; Yao, T.; Mosley-Thompson, E.; Wu, G.; Davis, M. E.; Tian, L.; Lin, P. N.

    2015-12-01

    The Guliya ice cap, located in the Kunlun Mountains in the western Third Pole (TP) region near the northern limit of the southwest monsoon influence, may be the only non-polar ice field that provides detailed histories of climate and environment over the last glacial cycle. A continuous climate record from an ice core drilled in 1992 contains Eemian ice, and basal temperatures measured that year confirmed that the record was not being removed from the bottom. The δ18O record throughout Marine Isotope Stage 2 (MIS2) displays the occurrence of high-amplitude (~20‰) episodes of ~200-year periodicity, and the aerosol records suggest snow cover, regional vegetation and fire frequency that vary in synchrony. These oscillations might reflect the movement of the northernmost penetration of the monsoon precipitation through the Late Glacial Stage, which is restricted by the topographic barrier posed by the Kunlun range, and might also reflect solar-driven nonlinearities in the climate system such as sudden shifts in the jet stream. Recent model simulations suggest that glacial cooling over China was significantly amplified by stationary waves, and the Guliya MIS2 oscillations could reflect cyclical variability in these waves. These results are supported by clumped isotope thermometry of carbonates from the Chinese Loess Plateau, which indicate a 6 to 7oC decrease in Last Glacial Maximum summer temperatures. These studies will lead to a better understanding of the mechanisms driving such high-frequency, high-amplitude oscillations. A review of the 2015 Sino-American cooperative ice core drilling program on Guliya is presented. This program will serve as a flagship for the TP Environment Program, an international, multidisciplinary collaboration among professionals and students in 14 countries designed to investigate environmental changes across the TP. The rapidly warming TP contains ~46,000 glaciers that collectively hold one of Earth's largest stores of fresh water that

  13. Amplitude death, oscillation death, wave, and multistability in identical Stuart-Landau oscillators with conjugate coupling

    Science.gov (United States)

    Han, Wenchen; Cheng, Hongyan; Dai, Qionglin; Li, Haihong; Ju, Ping; Yang, Junzhong

    2016-10-01

    In this work, we investigate the dynamics in a ring of identical Stuart-Landau oscillators with conjugate coupling systematically. We analyze the stability of the amplitude death and find the stability independent of the number of oscillators. When the amplitude death state is unstable, a large number of states such as homogeneous oscillation death, heterogeneous oscillation death, homogeneous oscillation, and wave propagations are found and they may coexist. We also find that all of these states are related to the unstable spatial modes to the amplitude death state.

  14. Amplitudes of stellar oscillations the implications for asteroseismology

    CERN Document Server

    Kjeldsen, H

    1994-01-01

    There are no good predictions for the amplitudes expected from solar-like oscillations in other stars. In the absence of a definitive model for convection, which is thought to be the mechanism that excites these oscillations, the amplitudes for both velocity and luminosity measurements must be estimated by scaling from the Sun. In the case of luminosity measurements, even this is difficult because of disagreement over the solar amplitude. This last point has lead us to investigate whether the luminosity amplitude of oscillations (dL/L) can be derived from the velocity amplitude v_osc. Using linear theory and observational data, we show that p-mode oscillations in a large sample of pulsating stars satisfy (dL/L)_bol proportional to v_osc/T_eff. Using this relationship, together with the best estimate of v_osc(Sun) = (23.4 +/- 1.4) cm/s, we estimate the luminosity amplitude of solar oscillations at 550 nm to be dL/L = (4.7 +/- 0.3) ppm. Next we discuss how to scale the amplitude of solar-like (i.e., convectivel...

  15. Oscillations of a Simple Pendulum with Extremely Large Amplitudes

    Science.gov (United States)

    Butikov, Eugene I.

    2012-01-01

    Large oscillations of a simple rigid pendulum with amplitudes close to 180[degrees] are treated on the basis of a physically justified approach in which the cycle of oscillation is divided into several stages. The major part of the almost closed circular path of the pendulum is approximated by the limiting motion, while the motion in the vicinity…

  16. Phase Synchronization of Coupled Rossler Oscillators: Amplitude Effect

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-Wen; ZHENG Zhi-Gang

    2007-01-01

    Phase synchronization of two linearly coupled Rossler oscillators with parameter misfits is explored.It is found that depending on parameter mismatches,the synchronization of phases exhibits different manners.The synchronization regime can be divided into three regimes.For small mismatches,the amplitude-insensitive regime gives the phase-dominant synchronization; When the parameter misfit increases,the amplitudes and phases of oscillators are correlated,and the amplitudes will dominate the synchronous dynamics for very large mismatches.The lag time among phases exhibits a power law when phase synchronization is achieved.

  17. Oscillator death induced by amplitude-dependent coupling in repulsively coupled oscillators

    Science.gov (United States)

    Liu, Weiqing; Xiao, Guibao; Zhu, Yun; Zhan, Meng; Xiao, Jinghua; Kurths, Jürgen

    2015-05-01

    The effects of amplitude-dependent coupling on oscillator death (OD) are investigated for two repulsively coupled Lorenz oscillators. Based on numerical simulations, it is shown that as constraint strengths on the amplitude-dependent coupling change, an oscillatory state may undergo a transition to an OD state. The parameter regimes of the OD domain are theoretically determined, which coincide well with the numerical results. An electronic circuit is set up to exhibit the transition process to the OD state with an amplitude-dependent coupling. These findings may have practical importance on chaos control and oscillation depression.

  18. Frequency and amplitude stabilization in MEMS and NEMS oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Changyao; Lopez, Omar Daniel; Czaplewski, David A.

    2017-06-14

    This invention comprises a nonlinear micro- and nano-mechanical resonator that can maintain frequency of operation and amplitude of operation for a period of time after all external power has been removed from the device. Utilizing specific nonlinear dynamics of the micromechanical resonator, mechanical energy at low frequencies can be input and stored in higher frequencies modes, thus using the multiple degrees of freedom of the resonator to extend its energy storage capacity. Furthermore, the energy stored in multiple vibrational modes can be used to maintain the resonator oscillating for a fixed period of time, even without an external power supply. This is the first demonstration of an "autonomous" frequency source that can maintain a constant frequency and vibrating amplitude when no external power is provided, making it ideal for applications requiring an oscillator in low power, or limited and intermittent power supplies.

  19. Amplitude death and resurgence of oscillation in networks of mobile oscillators

    Science.gov (United States)

    Majhi, Soumen; Ghosh, Dibakar

    2017-05-01

    The phenomenon of amplitude death has been explored using a variety of different coupling strategies in the last two decades. In most of the works, the basic coupling arrangement is considered to be static over time, although many realistic systems exhibit significant changes in the interaction pattern as time varies. In this article, we study the emergence of amplitude death in a dynamical network composed of time-varying interaction amidst a collection of random walkers in a finite region of three-dimensional space. We consider an oscillator for each walker and demonstrate that depending upon the network parameters and hence the interaction between them, the global oscillation in the network gets suppressed. In this framework, the vision range of each oscillator decides the number of oscillators with which it interacts. In addition, with the use of an appropriate feedback parameter in the coupling strategy, we articulate how the suppressed oscillation can be resurrected in the systems' parameter space. The phenomenon of amplitude death and the resurgence of oscillation is investigated taking limit cycle and chaotic oscillators for broad ranges of the parameters, like the interaction strength k between the entities, the vision range r and the speed of movement v.

  20. The energetics of flow through a rapidly oscillating tube with slowly varying amplitude.

    Science.gov (United States)

    Whittaker, Robert J; Heil, Matthias; Waters, Sarah L

    2011-07-28

    Motivated by the problem of self-excited oscillations in fluid-filled collapsible tubes, we examine the flow structure and energy budget of flow through an elastic-walled tube. Specifically, we consider the case in which a background axial flow is perturbed by prescribed small-amplitude high-frequency long-wavelength oscillations of the tube wall, with a slowly growing or decaying amplitude. We use a multiple-scale analysis to show that, at leading order, we recover the constant-amplitude equations derived by Whittaker et al. (Whittaker et al. 2010 J. Fluid Mech. 648, 83-121. (doi:10.1017/S0022112009992904)) with the effects of growth or decay entering only at first order. We also quantify the effects on the flow structure and energy budget. Finally, we discuss how our results are needed to understand and predict an instability that can lead to self-excited oscillations in collapsible-tube systems.

  1. Revoking amplitude and oscillation deaths by low-pass filter in coupled oscillators

    Science.gov (United States)

    Zou, Wei; Zhan, Meng; Kurths, Jürgen

    2017-06-01

    When in an ensemble of oscillatory units the interaction occurs through a diffusion-like manner, the intrinsic oscillations can be quenched through two structurally different scenarios: amplitude death (AD) and oscillation death (OD). Unveiling the underlying principles of stable rhythmic activity against AD and OD is a challenging issue of substantial practical significance. Here, by developing a low-pass filter (LPF) to track the output signals of the local system in the coupling, we show that it can revoke both AD and OD, and even the AD to OD transition, thereby giving rise to oscillations in coupled nonlinear oscillators under diverse death scenarios. The effectiveness of the local LPF is proven to be valid in an arbitrary network of coupled oscillators with distributed propagation delays. The constructive role of the local LPF in revoking deaths provides a potential dynamic mechanism of sustaining a reliable rhythmicity in real-world systems.

  2. Numerical investigation of amplitude-dependent dynamic response in acoustic metamaterials with nonlinear oscillators.

    Science.gov (United States)

    Manimala, James M; Sun, C T

    2016-06-01

    The amplitude-dependent dynamic response in acoustic metamaterials having nonlinear local oscillator microstructures is studied using numerical simulations on representative discrete mass-spring models. Both cubically nonlinear hardening and softening local oscillator cases are considered. Single frequency, bi-frequency, and wave packet excitations at low and high amplitude levels were used to interrogate the models. The propagation and attenuation characteristics of harmonic waves in a tunable frequency range is found to correspond to the amplitude and nonlinearity-dependent shifts in the local resonance bandgap for such nonlinear acoustic metamaterials. A predominant shift in the propagated wave spectrum towards lower frequencies is observed. Moreover, the feasibility of amplitude and frequency-dependent selective filtering of composite signals consisting of individual frequency components which fall within propagating or attenuating regimes is demonstrated. Further enrichment of these wave manipulation mechanisms in acoustic metamaterials using different combinations of nonlinear microstructures presents device implications for acoustic filters and waveguides.

  3. Streaming vorticity flux from oscillating walls with finite amplitude

    Science.gov (United States)

    Wu, J. Z.; Wu, X. H.; Wu, J. M.

    1993-01-01

    How to describe vorticity creation from a moving wall is a long standing problem. This paper discusses relevant issues at the fundamental level. First, it is shown that the concept of 'vorticity flux due to wall acceleration' can be best understood by following fluid particles on the wall rather than observing the flow at fixed spatial points. This is of crucial importance when the time-averaged flux is to be considered. The averaged flux has to be estimated in a wall-fixed frame of reference (in which there is no flux due to wall acceleration at all); or, if an inertial frame of reference is used, the generalized Lagrangian mean (GLM) also gives the same result. Then, for some simple but typical configurations, the time-averaged vorticity flux from a harmonically oscillating wall with finite amplitude is analyzed, without appealing to small perturbation. The main conclusion is that the wall oscillation will produce an additional mean vorticity flux (a fully nonlinear streaming effect), which is partially responsible for the mechanism of vortex flow control by waves. The results provide qualitative explanation for some experimentally and/or computationally observed phenomena.

  4. Streaming vorticity flux from oscillating walls with finite amplitude

    Science.gov (United States)

    Wu, J. Z.; Wu, X. H.; Wu, J. M.

    1993-01-01

    How to describe vorticity creation from a moving wall is a long standing problem. This paper discusses relevant issues at the fundamental level. First, it is shown that the concept of 'vorticity flux due to wall acceleration' can be best understood by following fluid particles on the wall rather than observing the flow at fixed spatial points. This is of crucial importance when the time-averaged flux is to be considered. The averaged flux has to be estimated in a wall-fixed frame of reference (in which there is no flux due to wall acceleration at all); or, if an inertial frame of reference is used, the generalized Lagrangian mean (GLM) also gives the same result. Then, for some simple but typical configurations, the time-averaged vorticity flux from a harmonically oscillating wall with finite amplitude is analyzed, without appealing to small perturbation. The main conclusion is that the wall oscillation will produce an additional mean vorticity flux (a fully nonlinear streaming effect), which is partially responsible for the mechanism of vortex flow control by waves. The results provide qualitative explanation for some experimentally and/or computationally observed phenomena.

  5. Transition to Amplitude Death in Coupled System with Small Number of Nonlinear Oscillators

    Institute of Scientific and Technical Information of China (English)

    CHEN Hai-Ling; YANG Jun-Zhong

    2009-01-01

    In this work, we investigate the amplitude death in coupled system with small number of nonlinear oscillators. We show how the transitions to the partial and the complete amplitude deathes happen. We also show that the partial amplitude death can be found in globally coupled oscillators either.

  6. Quantifying phase-amplitude coupling in neuronal network oscillations.

    Science.gov (United States)

    Onslow, Angela C E; Bogacz, Rafal; Jones, Matthew W

    2011-03-01

    Neuroscience time series data from a range of techniques and species reveal complex, non-linear interactions between different frequencies of neuronal network oscillations within and across brain regions. Here, we briefly review the evidence that these nested, cross-frequency interactions act in concert with linearly covariant (within-frequency) activity to dynamically coordinate functionally related neuronal ensembles during behaviour. Such studies depend upon reliable quantification of cross-frequency coordination, and we compare the properties of three techniques used to measure phase-amplitude coupling (PAC)--Envelope-to-Signal Correlation (ESC), the Modulation Index (MI) and Cross-Frequency Coherence (CFC)--by standardizing their filtering algorithms and systematically assessing their robustness to noise and signal amplitude using artificial signals. Importantly, we also introduce a freely-downloadable method for estimating statistical significance of PAC, a step overlooked in the majority of published studies. We find that varying data length and noise levels leads to the three measures differentially detecting false positives or correctly identifying frequency bands of interaction; these conditions should therefore be taken into careful consideration when selecting PAC analyses. Finally, we demonstrate the utility of the three measures in quantifying PAC in local field potential data simultaneously recorded from rat hippocampus and prefrontal cortex, revealing a novel finding of prefrontal cortical theta phase modulating hippocampal gamma power. Future adaptations that allow detection of time-variant PAC should prove essential in deciphering the roles of cross-frequency coupling in mediating or reflecting nervous system function.

  7. Detection of a 1258 Hz high-amplitude kilohertz quasi-periodic oscillation in the ultra-compact X-ray binary 1A 1246-588

    CERN Document Server

    Jonker, P G; Méndez, M; Van der Klis, M

    2007-01-01

    We have observed the ultra-compact low-mass X-ray binary (LMXB) 1A 1246-588 with the Rossi X-ray Timing Explorer (RXTE). In this manuscript we report the discovery of a kilohertz quasi-periodic oscillation (QPO) in 1A 1246-588. The kilohertz QPO was only detected when the source was in a soft high-flux state reminiscent of the lower banana branch in atoll sources. Only one kilohertz QPO peak is detected at a relatively high frequency of 1258+-2 Hz and at a single trial significance of more than 7 sigma. Kilohertz QPOs with a higher frequency have only been found on two occasions in 4U 0614+09. Furthermore, the frequency is higher than that found for the lower kilohertz QPO in any source, strongly suggesting that the QPO is the upper of the kilohertz QPO pair often found in LMXBs. The full-width at half maximum is 25+-4 Hz, making the coherence the highest found for an upper kilohertz QPO. From a distance estimate of ~6 kpc from a radius expansion burst we derive that 1A 1246-588 is at a persistent flux of ~0....

  8. Ketamine Dysregulates the Amplitude and Connectivity of High-Frequency Oscillations in Cortical-Subcortical Networks in Humans: Evidence From Resting-State Magnetoencephalography-Recordings.

    Science.gov (United States)

    Rivolta, Davide; Heidegger, Tonio; Scheller, Bertram; Sauer, Andreas; Schaum, Michael; Birkner, Katharina; Singer, Wolf; Wibral, Michael; Uhlhaas, Peter J

    2015-09-01

    Hypofunctioning of the N-methyl-D-aspartate receptor (NMDA-R) has been prominently implicated in the pathophysiology of schizophrenia (ScZ). The current study tested the effects of ketamine, a dissociative anesthetic and NMDA-R antagonist, on resting-state activity recorded with magnetoencephalography (MEG) in healthy volunteers. In a single-blind cross-over design, each participant (n = 12) received, on 2 different sessions, a subanesthetic dose of S-ketamine (0.006 mg/Kg) and saline injection. MEG-data were analyzed at sensor- and source-level in the beta (13-30 Hz) and gamma (30-90 Hz) frequency ranges. In addition, connectivity analysis at source-level was performed using transfer entropy (TE). Ketamine increased gamma-power while beta-band activity was decreased. Specifically, elevated 30-90 Hz activity was pronounced in subcortical (thalamus and hippocampus) and cortical (frontal and temporal cortex) regions, whilst reductions in beta-band power were localized to the precuneus, cerebellum, anterior cingulate, temporal and visual cortex. TE analysis demonstrated increased information transfer in a thalamo-cortical network after ketamine administration. The findings are consistent with the pronounced dysregulation of high-frequency oscillations following the inhibition of NMDA-R in animal models of ScZ as well as with evidence from electroencephalogram-data in ScZ-patients and increased functional connectivity during early illness stages. Moreover, our data highlight the potential contribution of thalamo-cortical connectivity patterns towards ketamine-induced neuronal dysregulation, which may be relevant for the understanding of ScZ as a disorder of disinhibition of neural circuits.

  9. Ketamine Dysregulates the Amplitude and Connectivity of High-Frequency Oscillations in Cortical–Subcortical Networks in Humans: Evidence From Resting-State Magnetoencephalography-Recordings

    Science.gov (United States)

    Rivolta, Davide; Heidegger, Tonio; Scheller, Bertram; Sauer, Andreas; Schaum, Michael; Birkner, Katharina; Singer, Wolf; Wibral, Michael; Uhlhaas, Peter J.

    2015-01-01

    Hypofunctioning of the N-methyl-D-aspartate receptor (NMDA-R) has been prominently implicated in the pathophysiology of schizophrenia (ScZ). The current study tested the effects of ketamine, a dissociative anesthetic and NMDA-R antagonist, on resting-state activity recorded with magnetoencephalography (MEG) in healthy volunteers. In a single-blind cross-over design, each participant (n = 12) received, on 2 different sessions, a subanesthetic dose of S-ketamine (0.006mg/Kg) and saline injection. MEG-data were analyzed at sensor- and source-level in the beta (13–30 Hz) and gamma (30–90 Hz) frequency ranges. In addition, connectivity analysis at source-level was performed using transfer entropy (TE). Ketamine increased gamma-power while beta-band activity was decreased. Specifically, elevated 30–90 Hz activity was pronounced in subcortical (thalamus and hippocampus) and cortical (frontal and temporal cortex) regions, whilst reductions in beta-band power were localized to the precuneus, cerebellum, anterior cingulate, temporal and visual cortex. TE analysis demonstrated increased information transfer in a thalamo-cortical network after ketamine administration. The findings are consistent with the pronounced dysregulation of high-frequency oscillations following the inhibition of NMDA-R in animal models of ScZ as well as with evidence from electroencephalogram-data in ScZ-patients and increased functional connectivity during early illness stages. Moreover, our data highlight the potential contribution of thalamo-cortical connectivity patterns towards ketamine-induced neuronal dysregulation, which may be relevant for the understanding of ScZ as a disorder of disinhibition of neural circuits. PMID:25987642

  10. Time-varying interaction leads to amplitude death in coupled nonlinear oscillators

    Indian Academy of Sciences (India)

    Awadhesh Prasad

    2013-09-01

    A new form of time-varying interaction in coupled oscillators is introduced. In this interaction, each individual oscillator has always time-independent self-feedback while its interaction with other oscillators are modulated with time-varying function. This interaction gives rise to a phenomenon called amplitude death even in diffusively coupled identical oscillators. The nonlinear variation of the locus of bifurcation point is shown. Results are illustrated with Landau–Stuart (LS) and Rössler oscillators.

  11. Nonlinear Vibration of Oscillation Systems using Frequency-Amplitude Formulation

    Directory of Open Access Journals (Sweden)

    A. Fereidoon

    2012-01-01

    Full Text Available In this paper we study the periodic solutions of free vibration of mechanical systems with third and fifth-order nonlinearity for two examples using He's Frequency-Amplitude Formulation (HFAF.The effectiveness and convenience of the method is illustrated in these examples. It will be shown that the solutions obtained with current method have a fabulous conformity with those achieved from time marching solution. HFAF is easy with powerful concepts and the high accuracy, so it can be found widely applicable in vibrations, especially strong nonlinearity oscillatory problems.

  12. Electronically Tunable Quadrature Sinusoidal Oscillator with Equal Output Amplitudes during Frequency Tuning Process

    Directory of Open Access Journals (Sweden)

    Den Satipar

    2017-01-01

    Full Text Available A new configuration of voltage-mode quadrature sinusoidal oscillator is proposed. The proposed oscillator employs two voltage differencing current conveyors (VDCCs, two resistors, and two grounded capacitors. In this design, the use of multiple/dual output terminal active building block is not required. The tuning of frequency of oscillation (FO can be done electronically by adjusting the bias current of active device without affecting condition of oscillation (CO. The electronic tuning can be done by controlling the bias current using a digital circuit. The amplitude of two sinusoidal outputs is equal when the frequency of oscillation is tuned. This makes the sinusoidal output voltages meet good total harmonic distortions (THD. Moreover, the proposed circuit can provide the sinusoidal output current with high impedance which is connected to external load or to another circuit without the use of buffer device. To confirm that the oscillator can generate the quadrature sinusoidal output signal, the experimental results using VDCC constructed from commercially available ICs are also included. The experimental results agree well with theoretical anticipation.

  13. Output-Feedback Control of a Chaotic MEMS Resonator for Oscillation Amplitude Enhancement

    Directory of Open Access Journals (Sweden)

    Alexander Jimenez-Triana

    2014-01-01

    Full Text Available The present work addresses the problem of chaos control in an electrostatic MEMS resonator by using an output-feedback control scheme. One of the unstable orbits immersed in the chaotic attractor is stabilized in order to produce a sustained oscillation of the movable plate composing the microstructure. The orbit is carefully chosen so as to produce a high amplitude oscillation. This approach allows the enhancement of oscillation amplitude of the resonator at a reduced control effort, since the unstable orbit already exists in the system and it is not necessary to spend energy to create it. Realistic operational conditions of the MEMS are considered including parametric uncertainties in the model and constraints due to the difficulty in measuring the speed of the plates of the microstructure. A control law is constructed recursively by using the technique of backstepping. Finally, numerical simulations are carried out to confirm the validity of the developed control scheme and to demonstrate the effect of controlling orbits immersed in the chaotic attractor.

  14. Experimental observation of partial amplitude death in coupled chaotic oscillators

    Institute of Scientific and Technical Information of China (English)

    Liu Wei-Qing; Yang Jun-Zhong; Xiao Jing-Hua

    2006-01-01

    The dynamics of coupled Lorenz circuits is investigated experimentally. The partial amplitude death reported in Phys. Rev. E 72, 057201 (2005) is verified by physical experiments with electronic circuits. With the increase of coupling constant, the coupled circuits undergo the transition from the breakdown of both the reflection symmetry and the translational symmetry to the partial amplitude death. Its stability is also confirmed by analysing the effects of noise.

  15. Decayless low-amplitude kink oscillations: a common phenomenon in the solar corona?

    CERN Document Server

    Anfinogentov, S A; Nisticò, G

    2015-01-01

    We investigate the decayless regime of coronal kink oscillations recently discovered in the Solar Dynamics Observatory (SDO)/AIA data. In contrast to decaying kink oscillations that are excited by impulsive dynamical processes, this type of transverse oscillations is not connected to any external impulsive impact, such as a flare or CME, and does not show any significant decay. Moreover the amplitude of these decayless oscillations is typically lower than that of decaying oscillations. The aim of this research is to estimate the prevalence of this phenomenon and its characteristic signatures. We analysed 21 active regions (NOAA 11637--11657) observed in January 2013 in the 171 A channel of SDO/AIA. For each active region we inspected six hours of observations, constructing time-distance plots for the slits positioned across pronounced bright loops. The oscillatory patterns in time-distance plots were visually identified and the oscillation periods and amplitudes were measured. We also estimated the length of ...

  16. Observational Study of Large Amplitude Longitudinal Oscillations in a Solar Filament

    CERN Document Server

    Knizhnik, K; Muglach, K; Gilbert, H; Kucera, T; Karpen, J

    2013-01-01

    On 20 August 2010 an energetic disturbance triggered damped large-amplitude longitudinal (LAL) oscillations in almost an entire filament. In the present work we analyze this periodic motion in the filament to characterize the damping and restoring mechanism of the oscillation. Our method involves placing slits along the axis of the filament at different angles with respect to the spine of the filament, finding the angle at which the oscillation is clearest, and fitting the resulting oscillation pattern to decaying sinusoidal and Bessel functions. These functions represent the equations of motion of a pendulum damped by mass accretion. With this method we determine the period and the decaying time of the oscillation. Our preliminary results support the theory presented by Luna and Karpen (2012) that the restoring force of LAL oscillations is solar gravity in the tubes where the threads oscillate, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Following an earlier pa...

  17. Self-tuning bistable parametric feedback oscillator: Near-optimal amplitude maximization without model information

    Science.gov (United States)

    Braun, David J.; Sutas, Andrius; Vijayakumar, Sethu

    2017-01-01

    Theory predicts that parametrically excited oscillators, tuned to operate under resonant condition, are capable of large-amplitude oscillation useful in diverse applications, such as signal amplification, communication, and analog computation. However, due to amplitude saturation caused by nonlinearity, lack of robustness to model uncertainty, and limited sensitivity to parameter modulation, these oscillators require fine-tuning and strong modulation to generate robust large-amplitude oscillation. Here we present a principle of self-tuning parametric feedback excitation that alleviates the above-mentioned limitations. This is achieved using a minimalistic control implementation that performs (i) self-tuning (slow parameter adaptation) and (ii) feedback pumping (fast parameter modulation), without sophisticated signal processing past observations. The proposed approach provides near-optimal amplitude maximization without requiring model-based control computation, previously perceived inevitable to implement optimal control principles in practical application. Experimental implementation of the theory shows that the oscillator self-tunes itself near to the onset of dynamic bifurcation to achieve extreme sensitivity to small resonant parametric perturbations. As a result, it achieves large-amplitude oscillations by capitalizing on the effect of nonlinearity, despite substantial model uncertainties and strong unforeseen external perturbations. We envision the present finding to provide an effective and robust approach to parametric excitation when it comes to real-world application.

  18. Dependence of oscillational instabilities on the amplitude of the acoustic wave in single-axis levitators

    DEFF Research Database (Denmark)

    Orozco-Santillán, Arturo; Ruiz-Boullosa, Ricardo; Cutanda Henríquez, Vicente

    2007-01-01

    published on the topic predicts that these instabilities appear when the levitator is driven with a frequency above the resonant frequency of the empty device. The theory also shows that the instabilities can either saturate to a state with constant amplitude, or they can grow without limit until the object...... pressure amplitude in the cavity because of the presence of the sample. The theory predicts that the phase difference depends on the speed of the oscillating object. In this paper, we give for the first time experimental evidence that shows the existence of the phase difference, and that it is negatively...... proportional to the oscillation frequency of the levitated sample. We also present experimental results that show that the oscillational instabilities can be reduced if the amplitude of the acoustic wave is increased; as a result, stable conditions can be obtained where the oscillations of the sphere...

  19. High frequency nanotube oscillator

    Science.gov (United States)

    Peng, Haibing [Houston, TX; Zettl, Alexander K [Kensington, TX

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  20. Basins of attraction changes by amplitude constraining of oscillators with limited power supply

    Energy Technology Data Exchange (ETDEWEB)

    Souza, S.L.T. de [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970 Sao Paulo, SP (Brazil); Caldas, I.L. [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970 Sao Paulo, SP (Brazil); Viana, R.L. [Departamento de Fisica, Universidade Federal do Parana, CP 19081, 81531-990 Curitiba, Parana (Brazil)] e-mail: viana@fisica.ufpr.br; Balthazar, J.M. [Departamento de Estatistica, Matematica Aplicada e Computacional, Instituto de Geociencias e Ciencias Exatas, Universidade Estadual Paulista, CP 178, 13500-230 Rio Claro, SP (Brazil); Brasil, R.M.L.R.F. [Departamento de Engenharia Estrutural e de Fundacoes, Escola Politecnica, Universidade de Sao Paulo, 05424-930 Sao Paulo, SP (Brazil)

    2005-11-01

    We investigate the dynamics of a Duffing oscillator driven by a limited power supply, such that the source of forcing is considered to be another oscillator, coupled to the first one. The resulting dynamics come from the interaction between both systems. Moreover, the Duffing oscillator is subjected to collisions with a rigid wall (amplitude constraint). Newtonian laws of impact are combined with the equations of motion of the two coupled oscillators. Their solutions in phase space display periodic (and chaotic) attractors, whose amplitudes, especially when they are too large, can be controlled by choosing the wall position in suitable ways. Moreover, their basins of attraction are significantly modified, with effects on the final state system sensitivity.

  1. The amplitude of pulse-synchronous oscillations varies with the level of intramuscular pressure in simulated compartment syndrome.

    Science.gov (United States)

    Nilsson, Andreas; Zhang, Qiuxia; Styf, Jorma

    2015-12-01

    Patients with compartment syndromes have elevated intramuscular pressure (IMP) due to increased volume in the affected muscle. However, the accuracy of IMP as a parameter in diagnosing chronic compartment syndrome has been questioned. It has been observed that arterial pulsations create oscillations in the IMP in patients with abnormally elevated IMP. The amplitude of the IMP oscillations appears to be related to a pathogenic mechanism of elevated IMP. Therefore, the purpose of the present study was to investigate the relation between the amplitude of pulse-synchronous IMP oscillations and the absolute level of IMP with a high-end fiber-optic system in a human experimental model of abnormally elevated IMP (simulated compartment syndrome) of the leg. The hypothesis that the amplitude of the IMP oscillations is correlated to the absolute level of IMP was tested. IMP was measured at rest in the anterior tibial muscle in 12 legs of 7 healthy subjects (4 females and 3 males) with a mean age of 28 (range 23-38) years. The subject lay supine with his/her heel placed in a footrest. The foot was kept in a neutral position to avoid biased IMP readings. Measurements were performed at baseline and during 10 minutes with a model of abnormally elevated IMP (simulated compartment syndrome) applied. The abnormally elevated IMP was created by venous obstruction induced by a thigh tourniquet (65 mmHg) of a casted leg. Placement of the pressure-recording catheter was verified by sonography. The IMP increased from 4.7 (SD = 1.8) mmHg at baseline to 48.6 (SD = 7.1) mmHg when the model of elevated IMP was applied. The amplitude of the pulse-synchronous oscillations was undetectable at baseline. It increased to 3.9 (SD = 1.4) mmHg with increasing IMP when the model was applied. The amplitude of the oscillations showed a positive correlation (r = 0.59) with the absolute level of IMP. The amplitude of the pulse-synchronous IMP oscillations is correlated with the absolute

  2. The role of amplitude-to-phase conversion in the generation of oscillator flicker phase noise

    Science.gov (United States)

    Hearn, C. P.

    1985-01-01

    The role of amplitude-to-phase conversion as a factor in feedback oscillator flicker phase noise is examined. A limiting stage consisting of parallel-connected opposite polarity diodes operating in a circuit environment contining reactance is shown to exhibit amplitude-to-phase conversion. This mechanism coupled with resistive upconversion provides an indirect route for very low frequency flicker noise to be transferred into the phase of an oscillator signal. It is concluded that this effect is more significant in the lower frequency regimes where the onlinear reactances associated with active devices are overwhelmed by linear reactive elements.

  3. The effects of dual-channel coupling on the transition from amplitude death to oscillation death

    Science.gov (United States)

    Chen, Jiangnan; Liu, Weiqing; Zhu, Yun; Xiao, Jinghua

    2016-07-01

    Oscillation quenching including amplitude death (AD) and oscillation death (OD) in addition to the transition processes between them have been hot topics in aspect of chaos control, physical and biological applications. The effects of dual-channel coupling on the AD and OD dynamics regimes, and their transition processes in coupled nonidentical oscillators are explored numerically and theoretically. Our results indicate that an additional repulsive coupling tends to shrink the AD domain while it enlarges the OD domain, however, an additional attractive coupling acts inversely. As a result, the transitions from AD to OD are replaced by transitions from oscillation state (OS) to AD or from OS to OD in the dual-channel coupled oscillators with different frequency mismatches. Our results are helpful to better understand the control of AD and OD and their transition processes.

  4. On the amplitude and phase errors of quadrature LC-tank CMOS oscillators

    DEFF Research Database (Denmark)

    Mazzanti, Andrea; Svelto, Francesco; Andreani, Pietro

    2006-01-01

    An analytic approach for the estimation of the phase and amplitude imbalances caused by component mismatches and parasitic magnetic fields in two popular quadrature LC oscillators is presented. Very simple and closed-form equations are derived, proving that, although the two topologies share...

  5. Damped large amplitude oscillations in a solar prominence and a bundle of coronal loops

    CERN Document Server

    Zhang, Quanhao; Liu, Rui; Shen, Chenglong; Zhang, Min; Gou, Tingyu; Liu, Jiajia; Liu, Kai; Zhou, Zhenjun; Wang, Shui

    2016-01-01

    We investigate the evolutions of two prominences (P1,P2) and two bundles of coronal loops (L1,L2), observed with SDO/AIA near the east solar limb on 2012 September 22. It is found that there were large-amplitude oscillations in P1 and L1, but no detectable motions in P2 and L2. These transverse oscillations were triggered by a large-scale coronal wave, originating from a large flare in a remote active region behind the solar limb. By carefully comparing the locations and heights of these oscillating and non-oscillating structures, we conclude that the propagating height of the wave is between 50 Mm and 130 Mm. The wave energy deposited in the oscillating prominence and coronal loops is at least of the order of $10^{28}$ erg. Furthermore, local magnetic field strength and Alfv\\'{e}n speeds are derived from the oscillating periods and damping time scales, which are extracted from the time series of the oscillations. It is demonstrated that oscillations can be used in not only coronal seismology, but also reveal...

  6. Observational Study of Large Amplitude Longitudinal Oscillations in a Solar Filament

    Science.gov (United States)

    Knizhnik, Kalman; Luna, Manuel; Muglach, Karin; Gilbert, Holly; Kucera, Therese; Karpen, Judith

    2014-01-01

    On 20 August 2010 an energetic disturbance triggered damped large-amplitude longitudinal (LAL) oscillations in almost an entire filament. In the present work we analyze this periodic motion in the filament to characterize the damping and restoring mechanism of the oscillation. Our method involves placing slits along the axis of the filament at different angles with respect to the spine of the filament, finding the angle at which the oscillation is clearest, and fitting the resulting oscillation pattern to decaying sinusoidal and Bessel functions. These functions represent the equations of motion of a pendulum damped by mass accretion. With this method we determine the period and the decaying time of the oscillation. Our preliminary results support the theory presented by Luna and Karpen (2012) that the restoring force of LAL oscillations is solar gravity in the tubes where the threads oscillate, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Following an earlier paper, we have determined the magnitude and radius of curvature of the dipped magnetic flux tubes hosting a thread along the filament, as well as the mass accretion rate of the filament threads, via the fitted parameters.

  7. Large amplitude oscillation of magnetization in spin-torque oscillator stabilized by field-like torque

    Energy Technology Data Exchange (ETDEWEB)

    Taniguchi, Tomohiro, E-mail: tomohiro-taniguchi@aist.go.jp; Kubota, Hitoshi; Imamura, Hiroshi [National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba 305-8568 (Japan); Tsunegi, Sumito [Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Ave. A. Fresnel, Palaiseau (France)

    2015-05-07

    Oscillation frequency of spin torque oscillator with a perpendicularly magnetized free layer and an in-plane magnetized pinned layer is theoretically investigated by taking into account the field-like torque. It is shown that the field-like torque plays an important role in finding the balance between the energy supplied by the spin torque and the dissipation due to the damping, which results in a steady precession. The validity of the developed theory is confirmed by performing numerical simulations based on the Landau-Lifshitz-Gilbert equation.

  8. A Closed Form Solution for Nonlinear Oscillators Frequencies Using Amplitude-Frequency Formulation

    Directory of Open Access Journals (Sweden)

    A. Barari

    2012-01-01

    Full Text Available Many nonlinear systems in industry including oscillators can be simulated as a mass-spring system. In reality, all kinds of oscillators are nonlinear due to the nonlinear nature of springs. Due to this nonlinearity, most of the studies on oscillation systems are numerically carried out while an analytical approach with a closed form expression for system response would be very useful in different applications. Some analytical techniques have been presented in the literature for the solution of strong nonlinear oscillators as well as approximate and numerical solutions. In this paper, Amplitude-Frequency Formulation (AFF approach is applied to analyze some periodic problems arising in classical dynamics. Results are compared with another approximate analytical technique called Energy Balance Method developed by the authors (EBM and also numerical solutions. Close agreement of the obtained results reveal the accuracy of the employed method for several practical problems in engineering.

  9. Amplitude and phase noises of a spin-transfer nano-oscillator synchronized by a phase-lock loop

    Science.gov (United States)

    Mitrofanov, A. A.; Safin, A. R.; Udalov, N. N.

    2015-08-01

    We have studied the amplitude and phase noises of a spin-transfer nano-oscillator (STNO) with a phase synchronization system (phase-lock loop, PLL). Spectral characteristics of the amplitude and phase noises of the isochronous and nonisochronous STNO are obtained and compared to the analogous characteristics of an autonomous (nonsynchronized) oscillator. The PLL bandwidth is determined.

  10. Analytical approximations for the amplitude and period of a relaxation oscillator

    Directory of Open Access Journals (Sweden)

    Golkhou Vahid

    2009-01-01

    Full Text Available Abstract Background Analysis and design of complex systems benefit from mathematically tractable models, which are often derived by approximating a nonlinear system with an effective equivalent linear system. Biological oscillators with coupled positive and negative feedback loops, termed hysteresis or relaxation oscillators, are an important class of nonlinear systems and have been the subject of comprehensive computational studies. Analytical approximations have identified criteria for sustained oscillations, but have not linked the observed period and phase to compact formulas involving underlying molecular parameters. Results We present, to our knowledge, the first analytical expressions for the period and amplitude of a classic model for the animal circadian clock oscillator. These compact expressions are in good agreement with numerical solutions of corresponding continuous ODEs and for stochastic simulations executed at literature parameter values. The formulas are shown to be useful by permitting quick comparisons relative to a negative-feedback represillator oscillator for noise (10× less sensitive to protein decay rates, efficiency (2× more efficient, and dynamic range (30 to 60 decibel increase. The dynamic range is enhanced at its lower end by a new concentration scale defined by the crossing point of the activator and repressor, rather than from a steady-state expression level. Conclusion Analytical expressions for oscillator dynamics provide a physical understanding for the observations from numerical simulations and suggest additional properties not readily apparent or as yet unexplored. The methods described here may be applied to other nonlinear oscillator designs and biological circuits.

  11. Large-Amplitude, Pair-Creating Oscillations in Pulsar and Black Hole Magnetospheres

    CERN Document Server

    Levinson, A; Judge, A; Luo, Q; Levinson, Amir; Melrose, Don; Judge, Alex; Luo, Qinghuan

    2005-01-01

    A time-dependent model for pair creation in a pulsar magnetosphere is developed. It is argued that the parallel electric field that develops in a charge-starved region (a gap) of a pulsar magnetosphere oscillates with large amplitude. Electrons and positrons are accelerated periodically and the amplitude of the oscillations is assumed large enough to cause creation of upgoing and downgoing pairs at different phases of the oscillation. With a charge-starved initial condition, we find that the oscillations result in bursts of pair creation in which the pair density rises exponentially with time. The pair density saturates at $N_\\pm\\simeq E_{0}^2/(8\\pi m_ec^2\\Gamma_{\\rm thr})$, where $E_0$ is the parallel electric field in the charge-starved initial state, and $\\Gamma_{\\rm thr}$ is the Lorentz factor for effec tive pair creation. The frequency of oscillations following the pair creation burst is given roughly by $\\omega_{\\rm osc}=eE_0/(8m_ec\\Gamma_{\\rm thr})$. A positive feedback keeps the system stable, such th...

  12. Metabolic pathways reconstruction by frequency and amplitude response to forced glycolytic oscillations in yeast.

    Science.gov (United States)

    Zimmerman, William B

    2005-10-05

    The hypothesis that frequency and amplitude response can be used in a complicated metabolic pathway kinetics model for optimal parameter estimation, as speculated by its successful prior usage for a mechanical oscillator and a heterogeneous chemical system, is tested here. Given the complexity of the glycolysis model of yeast chosen, this question is limited to three kinetics parameters of the 87 in the in vitro model developed in the literature. The direct application of the approach, used with the uninformed selection of operating conditions for the oscillation of external glucose concentration, led to miring the data assimilation process in local minima. Application of linear systems theory, however, identified two natural resonant frequencies that, when excited by external forced oscillations of the same frequency, result in the expression of many harmonics in the Fourier spectra, that is, information-rich experiments. A single such information-rich experiment at one of the resonant frequencies was sufficient to break away from the local minima to find the optimum kinetics parameter estimates. The resonant frequencies themselves represent oscillation modes in glycolysis akin to those previously observed. Furthermore, operation of the bioreactor with large amplitude oscillations of glucose feed (25%) leads to enhanced ethanol average yield by 1.6% at the resonant frequency.

  13. Derivation of amplitude equations for nonlinear oscillators subject to arbitrary forcing.

    Science.gov (United States)

    Mayol, Catalina; Toral, Raúl; Mirasso, Claudio R

    2004-06-01

    By using a generalization of the multiple scales technique we develop a method to derive amplitude equations for zero-dimensional forced systems. The method allows to consider either additive or multiplicative forcing terms and can be straightforwardly applied to the case that the forcing is white noise. We give examples of the use of this method to the case of the van der Pol-Duffing oscillator. The writing of the amplitude equations in terms of a Lyapunov potential allow us to obtain an analytical expression for the probability distribution function which reproduces reasonably well the numerical simulation results.

  14. Amplitudes of solar-like oscillations: constraints from red giants in open clusters observed by Kepler

    CERN Document Server

    Stello, D; Kallinger, T; Basu, S; Mosser, B; Hekker, S; Mathur, S; Garcia, R A; Bedding, T R; Kjeldsen, H; Gilliland, R L; Verner, G A; Chaplin, W J; Benomar, O; Meibom, S; Grundahl, F; Elsworth, Y P; Molenda-Zakowicz, J; Szabó, R; Christensen-Dalsgaard, J; Tenenbaum, P; Twicken, J D; Uddin, K

    2011-01-01

    Scaling relations that link asteroseismic quantities to global stellar properties are important for gaining understanding of the intricate physics that underpins stellar pulsation. The common notion that all stars in an open cluster have essentially the same distance, age, and initial composition, implies that the stellar parameters can be measured to much higher precision than what is usually achievable for single stars. This makes clusters ideal for exploring the relation between the mode amplitude of solar-like oscillations and the global stellar properties. We have analyzed data obtained with NASA's Kepler space telescope to study solar-like oscillations in 100 red giant stars located in either of the three open clusters, NGC 6791, NGC 6819, and NGC 6811. By fitting the measured amplitudes to predictions from simple scaling relations that depend on luminosity, mass, and effective temperature, we find that the data cannot be described by any power of the luminosity-to-mass ratio as previously assumed. As a...

  15. Measurements of wall heat transfer in the presence of large-amplitude combustion-driven oscillations

    Science.gov (United States)

    Perry, E. H.; Culick, F. E. C.

    1974-01-01

    In the studies reported use was made of the T-burner to obtain a correlation between the average heat transfer coefficient along the burner and the amplitude of the flow oscillations. The T-burner used consists of a centrally-vented cylindrical chamber with disks of solid propellant bonded in each end. The obtained data provide a basis for predicting heat transfer rates in other combustion chambers containing oscillatory flows.

  16. Spin interference controlled by electric field: Ensemble average effect on AAS and AB oscillation amplitudes

    Science.gov (United States)

    Nitta, Junsaku; Bergsten, Tobias

    2008-03-01

    Time reversal symmetric Al’tshuler-Aronov-Spivak (AAS) oscillations are measured in an array of InGaAs mesoscopic loops. We confirm that gate voltage dependence of h/2 e period oscillations is due to spin interference from the effect of ensemble average on the AAS and Aharonov-Bohm (AB) amplitudes. This spin interference is based on the time reversal Aharonov-Casher (AC) effect. The AC interference oscillations are controlled over several periods. This result shows evidence for electrical manipulation of the spin precession angle in an InGaAs two-dimensional electron gas channel. We control the precession rate in a precise and predictable way with an electrostatic gate.

  17. Large-amplitude ULF waves at high latitudes

    Science.gov (United States)

    Guido, T.; Tulegenov, B.; Streltsov, A. V.

    2014-11-01

    We present results from the statistical study of ULF waves detected by the fluxgate magnetometer in Gakona, Alaska during several experimental campaigns conducted at the High Frequency Active Auroral Research Program (HAARP) facility in years 2011-2013. We analyzed frequencies of ULF waves recorded during 26 strongly disturbed geomagnetic events (substorms) and compared them with frequencies of ULF waves detected during magnetically quiet times. Our analysis demonstrates that the frequency of the waves carrying most of the power in almost all these events is less than 1 mHz. We also analyzed data from the ACE satellite, measuring parameters of the solar wind in the L1 Lagrangian point between Earth and Sun, and found that in several occasions there is a strong correlation between oscillations of the magnetic field in the solar wind and oscillations detected on the ground. We also found several cases when there is no correlation between signals detected on ACE and on the ground. This finding suggests that these frequencies correspond to the fundamental eigenfrequency of the coupled magnetosphere-ionosphere system, and the amplitude of these waves can reach significant magnitude when the system is driven by the external driver (for example, the solar wind) with this particular frequency. When the frequency of the driver does not match the frequency of the system, the waves still are observed, but their amplitudes are much smaller.

  18. Alpha and gamma oscillation amplitudes synergistically predict the perception of forthcoming nociceptive stimuli.

    Science.gov (United States)

    Tu, Yiheng; Zhang, Zhiguo; Tan, Ao; Peng, Weiwei; Hung, Yeung Sam; Moayedi, Massieh; Iannetti, Gian Domenico; Hu, Li

    2016-02-01

    Ongoing fluctuations of intrinsic cortical networks determine the dynamic state of the brain, and influence the perception of forthcoming sensory inputs. The functional state of these networks is defined by the amplitude and phase of ongoing oscillations of neuronal populations at different frequencies. The contribution of functionally different cortical networks has yet to be elucidated, and only a clear dependence of sensory perception on prestimulus alpha oscillations has been clearly identified. Here, we combined electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) in a large sample of healthy participants to investigate how ongoing fluctuations in the activity of different cortical networks affect the perception of subsequent nociceptive stimuli. We observed that prestimulus EEG oscillations in the alpha (at bilateral central regions) and gamma (at parietal regions) bands negatively modulated the perception of subsequent stimuli. Combining information about alpha and gamma oscillations predicted subsequent perception significantly more accurately than either measure alone. In a parallel experiment, we found that prestimulus fMRI activity also modulated the perception of subsequent stimuli: perceptual ratings were higher when the BOLD signal was higher in nodes of the sensorimotor network and lower in nodes of the default mode network. Similar to what observed in the EEG data, prediction accuracy was improved when the amplitude of prestimulus BOLD signals in both networks was combined. These findings provide a comprehensive physiological basis to the idea that dynamic changes in brain state determine forthcoming behavioral outcomes. Hum Brain Mapp 37:501-514, 2016. © 2015 Wiley Periodicals, Inc.

  19. Amplitude model for beam oscillations in the main Linac of CLIC

    CERN Document Server

    Pfingstner, Jürgen; Schmickler, Hermann; Hofbaur, Michael

    2010-01-01

    To achieve the challenging goal of ultra-low emittance preservation in the main linac of CLIC, different techniques are used. The according algorithms often rely on an accurate, fast and efficient to compute model of the amplitude behavior of the beam oscillations in the beam line. In this paper such a model is developed, considering the accelerator design as well as the effect of filamentation. Filamentation is especially important, due to the high energy spread of the according beam and the large total phase advance of the lattice. Therefore a general model to describe filamentation is adapted to the properties of the beam in the main linac of CLIC. At the beginning of the linac, where made assumptions are not valid, this basic model is supported by a fit to simulation data. An accuracy evaluation of the produced data shows that the quadratic error is around 4 %. Therefore, the developed model delivers a fast and efficient procedure, to precisely predict the beam envelope behavior in the main linac of CLIC.

  20. Analysis and modeling of time-variant amplitude-frequency couplings of and between oscillations of EEG bursts.

    Science.gov (United States)

    Witte, Herbert; Putsche, Peter; Hemmelmann, Claudia; Schelenz, Christoph; Leistritz, Lutz

    2008-08-01

    Low-frequency (0.5-2.5 Hz) and individually defined high-frequency (7-11 or 8-12 Hz; 11-15 or 14-18 Hz) oscillatory components of the electroencephalogram (EEG) burst activity derived from thiopental-induced burst-suppression patterns (BSP) were investigated in seven sedated patients (17-26 years old) with severe head injury. The predominant high-frequency burst oscillations (>7 Hz) were detected for each patient by means of time-variant amplitude spectrum analysis. Thereafter, the instantaneous envelope (IE) and the instantaneous frequency (IF) were computed for these low- and high-frequency bands to quantify amplitude-frequency dependencies (envelope-envelope, envelope-frequency, and frequency-frequency correlations). Time-variant phase-locking, phase synchronization, and quadratic phase couplings are associated with the observed amplitude-frequency characteristics. Additionally, these time-variant analyses were carried out for modeled burst patterns. Coupled Duffing oscillators were adapted to each EEG burst and by means of these models data-based burst simulations were generated. Results are: (1) strong envelope-envelope correlations (IE courses) can be demonstrated; (2) it can be shown that a rise of the IE is associated with an increase of the IF (only for the frequency bands 0.5-2.5 and 7-11 or 8-12 Hz); (3) the rise characteristics of all individually averaged envelope-frequency courses (IE-IF) are strongly correlated; (4) for the 7-11 or 8-12 Hz oscillation these associations are weaker and the variation between the time courses of the patients is higher; (5) for both frequency ranges a quantitative amplitude-frequency dependency can be shown because higher IE peak maxima are accompanied by stronger IF changes; (6) the time range of significant phase-locking within the 7-11 or 8-12 Hz frequency bands and of the strongest quadratic phase couplings (between 0.5-2.5 and 7-11 or 8-12 Hz) is between 0 and 1,000 ms; (7) all phase coupling characteristics of the

  1. Amplitude and Frequency Control: Stability of Limit Cycles in Phase-Shift and Twin-T Oscillators

    Directory of Open Access Journals (Sweden)

    J. P. Dada

    2008-01-01

    Full Text Available We show a technique for external direct current (DC control of the amplitudes of limit cycles both in the Phase-shift and Twin-T oscillators. We have found that amplitudes of the oscillator output voltage depend on the DC control voltage. By varying the total impedance of each oscillator oscillatory network, frequencies of oscillations are controlled using potentiometers. The main advantage of the proposed circuits is that both the amplitude and frequency of the waveforms generated can be independently controlled. Analytical, numerical, and experimental methods are used to determine the boundaries of the states of the oscillators. Equilibrium points, stable limit cycles, and divergent states are found. Analytical results are compared with the numerical and experimental solutions, and a good agreement is obtained.

  2. Amplitudes of solar-like oscillations in red giants: Departures from the quasi-adiabatic approximation

    Directory of Open Access Journals (Sweden)

    Barban C.

    2013-03-01

    Full Text Available CoRoT and Kepler measurements reveal us that the amplitudes of solar-like oscillations detected in red giant stars scale from stars to stars in a characteristic way. This observed scaling relation is not yet fully understood but constitutes potentially a powerful diagnostic about mode physics. Quasi-adiabatic theoretical scaling relations in terms of mode amplitudes result in systematic and large differences with the measurements performed for red giant stars. The use of a non-adiabatic intensity-velocity relation derived from a non-adiabatic pulsation code significantly reduces the discrepancy with the CoRoT measurements. The origin of the remaining difference is still unknown. Departure from adiabatic eigenfunction is a very likely explanation that is investigated in the present work using a 3D hydrodynamical model of the surface layers of a representative red giant star.

  3. Amplitude Expansions for Instabilities in Populations of Globally-Coupled Oscillators

    CERN Document Server

    Crawford, J D

    1994-01-01

    We analyze the nonlinear dynamics near the incoherent state in a mean-field model of coupled oscillators. The population is described by a Fokker-Planck equation for the distribution of phases, and we apply center-manifold reduction to obtain the amplitude equations for steady-state and Hopf bifurcation from the equilibrium state with a uniform phase distribution. When the population is described by a native frequency distribution that is reflection-symmetric about zero, the problem has circular symmetry. In the limit of zero extrinsic noise, although the critical eigenvalues are embedded in the continuous spectrum, the nonlinear coefficients in the amplitude equation remain finite in contrast to the singular behavior found in similar instabilities described by the Vlasov-Poisson equation. For a bimodal reflection-symmetric distribution, both types of bifurcation are possible and they coincide at a codimension-two Takens Bogdanov point. The steady-state bifurcation may be supercritical or subcritical and prod...

  4. Neuronal Oscillations with Non-sinusoidal Morphology Produce Spurious Phase-to-Amplitude Coupling and Directionality

    Science.gov (United States)

    Lozano-Soldevilla, Diego; ter Huurne, Niels; Oostenveld, Robert

    2016-01-01

    Neuronal oscillations support cognitive processing. Modern views suggest that neuronal oscillations do not only reflect coordinated activity in spatially distributed networks, but also that there is interaction between the oscillations at different frequencies. For example, invasive recordings in animals and humans have found that the amplitude of fast oscillations (>40 Hz) occur non-uniformly within the phase of slower oscillations, forming the so-called cross-frequency coupling (CFC). However, the CFC patterns might be influenced by features in the signal that do not relate to underlying physiological interactions. For example, CFC estimates may be sensitive to spectral correlations due to non-sinusoidal properties of the alpha band wave morphology. To investigate this issue, we performed CFC analysis using experimental and synthetic data. The former consisted in a double-blind magnetoencephalography pharmacological study in which participants received either placebo, 0.5 or 1.5 mg of lorazepam (LZP; GABAergic enhancer) in different experimental sessions. By recording oscillatory brain activity with during rest and working memory (WM), we were able to demonstrate that posterior alpha (8–12 Hz) phase was coupled to beta-low gamma band (20–45 Hz) amplitude envelope during all sessions. Importantly, bicoherence values around the harmonics of the alpha frequency were similar both in magnitude and topographic distribution to the cross-frequency coherence (CFCoh) values observed in the alpha-phase to beta-low gamma coupling. In addition, despite the large CFCoh we found no significant cross-frequency directionality (CFD). Critically, simulations demonstrated that a sizable part of our empirical CFCoh between alpha and beta-low gamma coupling and the lack of CFD could be explained by two-three harmonics aligned in zero phase-lag produced by the physiologically characteristic alpha asymmetry in the amplitude of the peaks relative to the troughs. Furthermore, we

  5. Neuronal oscillations with non-sinusoidal morphology produce spurious phase-to-amplitude coupling and directionality.

    Directory of Open Access Journals (Sweden)

    Diego Lozano-Soldevilla

    2016-08-01

    Full Text Available Neuronal oscillations support cognitive processing. Modern views suggest that neuronal oscillations do not only reflect coordinated activity in spatially distributed networks, but also that there is interaction between the oscillations at different frequencies. For example, invasive recordings in animals and humans have found that the amplitude of fast oscillations (> 40 Hz occur non-uniformly within the phase of slower oscillations, forming the so-called cross-frequency coupling (CFC. However, the CFC patterns be influenced by features in the signal that do not relate to underlying physiological interactions. For example, CFC estimates may be sensitive to spectral correlations due to non-sinusoidal properties of the alpha band wave morphology. To investigate this issue, we performed CFC analysis using experimental and synthetic data. The former consisted in a double-blind magnetoencephalography pharmacological study in which participants received either placebo, 0.5 mg or 1.5 mg of lorazepam (LZP; GABAergic enhancer in different experimental sessions. By recording oscillatory brain activity with during rest and working memory (WM, we were able to demonstrate that posterior alpha (8 – 12 Hz phase was coupled to beta-low gamma band (20 – 45 Hz amplitude envelope during all sessions. Importantly, bicoherence values around the harmonics of the alpha frequency were similar both in magnitude and topographic distribution to the cross-frequency coherence (CFCoh values observed in the alpha-phase to beta-low gamma coupling. In addition, despite the large CFCoh we found no significant cross-frequency directionality (CFD. Critically, simulations demonstrated that a sizable part of our empirical CFCoh between alpha and beta-low gamma coupling and the lack of CFD could be explained by two-three harmonics aligned in zero phase-lag produced by the physiologically characteristic alpha asymmetry in the amplitude of the peaks relative to the troughs

  6. Injection coupling with high amplitude transverse modes: Experimentation and simulation

    Science.gov (United States)

    Mery, Yoann; Ducruix, Sébastien; Scouflaire, Philippe; Candel, Sébastien

    2009-06-01

    High frequency combustion instabilities have technical importance in the design of liquid rocket engines. These phenomena involve a strong coupling between transverse acoustic modes and combustion. They are currently being investigated by combining experimentation and numerical simulations. On the experimental level, the coupling is examined in a model scale system featuring a multiple injector combustor (MIC) comprising five coaxial injectors fed with liquid oxygen and gaseous methane. This system is equipped with a novel VHAM actuator (Very High Amplitude Modulator) which comprises two nozzles and a rotating toothed wheel blocking the nozzles in an alternate fashion. This device was designed to obtain the highest possible levels of transverse oscillation in the MIC. After a brief review of the VHAM, this article reports cold flow experiments using this modulator. Velocity maps obtained under resonant conditions using the VHAM are examined at different instants during a cycle of oscillation. Experimental data are compared with numerical pressure and velocity fields obtained from an acoustic solver. The good agreement observed in the nozzle vicinity indicates that numerical simulations can be used to analyze the complex flow field generated by the VHAM. To cite this article: Y. Mery et al., C. R. Mecanique 337 (2009).

  7. Facilitation of epileptic activity during sleep is mediated by high amplitude slow waves.

    Science.gov (United States)

    Frauscher, Birgit; von Ellenrieder, Nicolás; Ferrari-Marinho, Taissa; Avoli, Massimo; Dubeau, François; Gotman, Jean

    2015-06-01

    Epileptic discharges in focal epilepsy are frequently activated during non-rapid eye movement sleep. Sleep slow waves are present during this stage and have been shown to include a deactivated ('down', hyperpolarized) and an activated state ('up', depolarized). The 'up' state enhances physiological rhythms, and we hypothesize that sleep slow waves and particularly the 'up' state are the specific components of non-rapid eye movement sleep that mediate the activation of epileptic activity. We investigated eight patients with pharmaco-resistant focal epilepsies who underwent combined scalp-intracerebral electroencephalography for diagnostic evaluation. We analysed 259 frontal electroencephalographic channels, and manually marked 442 epileptic spikes and 8487 high frequency oscillations during high amplitude widespread slow waves, and during matched control segments with low amplitude widespread slow waves, non-widespread slow waves or no slow waves selected during the same sleep stages (total duration of slow wave and control segments: 49 min each). During the slow waves, spikes and high frequency oscillations were more frequent than during control segments (79% of spikes during slow waves and 65% of high frequency oscillations, both P ∼ 0). The spike and high frequency oscillation density also increased for higher amplitude slow waves. We compared the density of spikes and high frequency oscillations between the 'up' and 'down' states. Spike and high frequency oscillation density was highest during the transition from the 'up' to the 'down' state. Interestingly, high frequency oscillations in channels with normal activity expressed a different peak at the transition from the 'down' to the 'up' state. These results show that the apparent activation of epileptic discharges by non-rapid eye movement sleep is not a state-dependent phenomenon but is predominantly associated with specific events, the high amplitude widespread slow waves that are frequent, but not

  8. Generalization of experimental data on amplitude and frequency of oscillations induced by steam injection into a subcooled pool

    Energy Technology Data Exchange (ETDEWEB)

    Villanueva, Walter; Li, Hua [Division of Nuclear Power Safety, Royal Institute of Technology (KTH), Roslagstullsbacken 21, SE-10691 Stockholm (Sweden); Puustinen, Markku [Nuclear Engineering, LUT School of Energy Systems, Lappeenranta University of Technology (LUT), FIN-53851 Lappeenranta (Finland); Kudinov, Pavel, E-mail: pavel@safety.sci.kth.se [Division of Nuclear Power Safety, Royal Institute of Technology (KTH), Roslagstullsbacken 21, SE-10691 Stockholm (Sweden)

    2015-12-15

    Highlights: • Available data on steam injection into subcooled pool is generalized. • Scaling approach is proposed on amplitude and frequency of chugging oscillations. • The scaled amplitude has a maximum at Froude number Fr ≈ 2.8. • The scaled frequency has a minimum at Fr ≈ 6. • Both amplitude and frequency has a strong dependence on pool bulk temperature. - Abstract: Steam venting and condensation into a subcooled pool of water through a blowdown pipe can undergo a phenomenon called chugging, which is an oscillation of the steam–water interface inside the blowdown pipe. The momentum that is generated by the oscillations is directly proportional to the oscillations’ amplitude and frequency, according to the synthetic jet theory. Higher momentum can enhance pool mixing and positively affect the pool's pressure suppression capacity by reducing thermal stratification. In this paper, we present a generalization of available experimental data on the amplitude and frequency of oscillations during chugging. We use experimental data obtained in different facilities at different scales to suggest a scaling approach for non-dimensional amplitude and frequency of the oscillations. We demonstrate that the Froude number Fr (which relates the inertial forces to gravitational forces) can be used as a scaling criterion in this case. The amplitude has maximum at Fr ≈ 2.8. There is also a strong dependence of the amplitude on temperature; the lower the bulk temperature is the higher the scaled amplitude. A known analytical theory can only capture the decreasing trend in amplitude for Fr > 2.8 and fails to capture the increasing trend and the temperature dependence. Similarly, there is a minimum of the non-dimensional frequency at Fr ≈ 6. A strong dependence on temperature is also observed for Fr > 6; the lower the bulk temperature is the higher the scaled frequency. The known analytical theory is able to capture qualitatively the general trend in

  9. Two generalized algorithms measuring phase-amplitude cross-frequency coupling in neuronal oscillations network.

    Science.gov (United States)

    Li, Qun; Zheng, Chen-Guang; Cheng, Ning; Wang, Yi-Yi; Yin, Tao; Zhang, Tao

    2016-06-01

    An increasing number of studies pays attention to cross-frequency coupling in neuronal oscillations network, as it is considered to play an important role in exchanging and integrating of information. In this study, two generalized algorithms, phase-amplitude coupling-evolution map approach and phase-amplitude coupling-conditional mutual information which have been developed and applied originally in an identical rhythm, are generalized to measure cross-frequency coupling. The effectiveness of quantitatively distinguishing the changes of coupling strength from the measurement of phase-amplitude coupling (PAC) is demonstrated based on simulation data. The data suggest that the generalized algorithms are able to effectively evaluate the strength of PAC, which are consistent with those traditional approaches, such as PAC-PLV and PAC-MI. Experimental data, which are local field potentials obtained from anaesthetized SD rats, have also been analyzed by these two generalized approaches. The data show that the theta-low gamma PAC in the hippocampal CA3-CA1 network is significantly decreased in the glioma group compared to that in the control group. The results, obtained from either simulation data or real experimental signals, are consistent with that of those traditional approaches PAC-MI and PAC-PLV. It may be considered as a proper indicator for the cross frequency coupling in sub-network, such as the hippocampal CA3 and CA1.

  10. Large amplitude oscillation of a boiling bubble growing at a wall in stagnation flow

    Energy Technology Data Exchange (ETDEWEB)

    Geld, C.W.M. van der; Berg, R. van de; Peukert, P. [Eindhoven University of Technology, Eindhoven (Netherlands). Faculty of Mechanical Engineering], e-mail: C.W.M._v.d.Geld@tue.nl

    2009-07-01

    A boiling bubble is created on an artificial site that is part of a bubble generator that is mounted at the center of a pipe. Downflow of water impinges on the bubble generator and creates a stagnation flow above the artificial cavity. Stable axisymmetric elongation in the direction away from the wall and multiple shape oscillation cycles are observed. The time of growth and attachment is typically of the order of 250 ms. Amongst the length scales that characterize the bubble shape is the radius of curvature of the upper part of the bubble, R. The period of oscillation, T, is strongly dependent on time, as is R. The parameters C and m in the defining equation T = C R{sup m} {radical}({rho}L/{sigma}) have been determined by fitting to data of more than 100 bubbles. For each operating condition, the same values of C and m have been found. The value of m is 1.49 {+-} 0.02, which is explained from the continuous growth of the bubble and from the relation to the period of oscillation of a free bubble deforming in the fundamental mode corresponding to the third Legendre Polynomial. For the latter, R is the radius of the volume-equivalent sphere, R{sub 0}, and C is {radical}12, while for attached boiling bubbles C is found to amount 1.9{radical}12. The difference is easily explained from the continuous growth, difference in definition, finite amplitude oscillation and proximity of the wall. (author)

  11. A novel oscillation control for MEMS vibratory gyroscopes using a modified electromechanical amplitude modulation technique

    Science.gov (United States)

    Ma, Wei; Lin, Yiyu; Liu, Siqi; Zheng, Xudong; Jin, Zhonghe

    2017-02-01

    This paper reports a novel oscillation control algorithm for MEMS vibratory gyroscopes using a modified electromechanical amplitude modulation (MEAM) technique, which enhances the robustness against the frequency variation of the driving mode, compared to the conventional EAM (CEAM) scheme. In this approach, the carrier voltage exerted on the proof mass is frequency-modulated by the drive resonant frequency. Accordingly, the pick-up signal from the interface circuit involves a constant-frequency component that contains the amplitude and phase information of the vibration displacement. In other words, this informational detection signal is independent of the mechanical resonant frequency, which varies due to different batches, imprecise micro-fabrication and changing environmental temperature. In this paper, the automatic gain control loop together with the phase-locked loop are simultaneously analyzed using the averaging method and Routh-Hurwitz criterion, deriving the stability condition and the parameter optimization rules of the transient response. Then, a simulation model based on the real system is set up to evaluate the control algorithm. Further, the proposed MEAM method is tested using a field-programmable-gate-array based digital platform on a capacitive vibratory gyroscope. By optimizing the control parameters, the transient response of the drive amplitude reveals a settling time of 45.2 ms without overshoot, according well with the theoretical prediction and simulation results. The first measurement results show that the amplitude variance of the drive displacement is 12 ppm in an hour while the phase standard deviation is as low as 0.0004°. The mode-split gyroscope operating under atmospheric pressure demonstrates an outstanding performance. By virtue of the proposed MEAM method, the bias instability and angle random walk are measured to be 0.9° h-1 (improved by 2.4 times compared to the CEAM method) and 0.068° (√h)-1 (improved by 1.4 times

  12. Noninvasive Focused Ultrasound Stimulation Can Modulate Phase-Amplitude Coupling between Neuronal Oscillations in the Rat Hippocampus

    Science.gov (United States)

    Yuan, Yi; Yan, Jiaqing; Ma, Zhitao; Li, Xiaoli

    2016-01-01

    Noninvasive focused ultrasound stimulation (FUS) can be used to modulate neural activity with high spatial resolution. Phase-amplitude coupling (PAC) between neuronal oscillations is tightly associated with cognitive processes, including learning, attention, and memory. In this study, we investigated the effect of FUS on PAC between neuronal oscillations and established the relationship between the PAC index and ultrasonic intensity. The rat hippocampus was stimulated using focused ultrasound at different spatial-average pulse-average ultrasonic intensities (3.9, 9.6, and 19.2 W/cm2). The local field potentials (LFPs) in the rat hippocampus were recorded before and after FUS. Then, we analyzed PAC between neuronal oscillations using a PAC calculation algorithm. Our results showed that FUS significantly modulated PAC between the theta (4–8 Hz) and gamma (30–80 Hz) bands and between the alpha (9–13 Hz) and ripple (81–200 Hz) bands in the rat hippocampus, and PAC increased with incremental increases in ultrasonic intensity. PMID:27499733

  13. Noninvasive focused ultrasound stimulation can modulate phase-amplitude coupling between neuronal oscillations in the rat hippocampus

    Directory of Open Access Journals (Sweden)

    Yi Yuan

    2016-07-01

    Full Text Available Noninvasive focused ultrasound stimulation (FUS can be used to modulate neural activity with high spatial resolution. Phase-amplitude coupling (PAC between neuronal oscillations is tightly associated with cognitive processes, including learning, attention and memory. In this study, we investigated the effect of FUS on PAC between neuronal oscillations and established the relationship between the PAC index and ultrasonic intensity. The rat hippocampus was stimulated using focused ultrasound at different spatial-average pulse-average ultrasonic intensities (3.9 W/cm2, 9.6 W/cm2, and 19.2 W/cm2. The local field potentials (LFPs in the rat hippocampus were recorded before and after FUS. Then, we analyzed PAC between neuronal oscillations using a PAC calculation algorithm. Our results showed that FUS significantly modulated PAC between the theta (4-8 Hz and gamma (30-80 Hz bands and between the alpha (9-13 Hz and ripple (81-200 Hz bands in the rat hippocampus, and PAC increased with incremental increases in ultrasonic intensity.

  14. On the robustness of the pendulum model for large-amplitude longitudinal oscillations in prominences

    CERN Document Server

    Luna, M; Khomenko, E; Collados, M; de Vicente, A

    2015-01-01

    Large-amplitude longitudinal oscillations (LALOs) in prominences are spectacular manifestations of the solar activity. In such events nearby energetic disturbances induce periodic motions on filaments with displacements comparable to the size of the filaments themselves and with velocities larger than 20 km/s. The pendulum model, in which the gravity projected along a rigid magnetic field is the restoring force, was proposed to explain these events. However, it can be objected that in a realistic situation where the magnetic field reacts to the mass motion of the heavy prominence, the simplified pendulum model could be no longer valid. We have performed non-linear time-dependent numerical simulations of LALOs considering a dipped magnetic field line structure. In this work we demonstrate that for even relatively weak magnetic fields the pendulum model works very well. We therefore validate the pendulum model and show its robustness, with important implications for prominence seismology purposes. With this mod...

  15. Amplitudes of solar-like oscillations: Constraints from red giants in open clusters observed by Kepler

    DEFF Research Database (Denmark)

    Stello, Dennis; Huber, Daniel; Kallinger, Thomas;

    2011-01-01

    with NASA's Kepler space telescope to study solar-like oscillations in 100 red giant stars located in either of the three open clusters, NGC 6791, NGC 6819, and NGC 6811. By fitting the measured amplitudes to predictions from simple scaling relations that depend on luminosity, mass, and effective...... temperature, we find that the data cannot be described by any power of the luminosity-to-mass ratio as previously assumed. As a result we provide a new improved empirical relation which treats luminosity and mass separately. This relation turns out to also work remarkably well for main-sequence and subgiant......Scaling relations that link asteroseismic quantities to global stellar properties are important for gaining understanding of the intricate physics that underpins stellar pulsations. The common notion that all stars in an open cluster have essentially the same distance, age, and initial composition...

  16. The amplitude of the cross-covariance function of solar oscillations as a diagnostic tool for wave attenuation and geometrical spreading

    Science.gov (United States)

    Nagashima, Kaori; Fournier, Damien; Birch, Aaron C.; Gizon, Laurent

    2017-03-01

    Context. In time-distance helioseismology, wave travel times are measured from the two-point cross-covariance function of solar oscillations and are used to image the solar convection zone in three dimensions. There is, however, also information in the amplitude of the cross-covariance function, for example, about seismic wave attenuation. Aims: We develop a convenient procedure to measure the amplitude of the cross-covariance function of solar oscillations. Methods: In this procedure, the amplitude of the cross-covariance function is linearly related to the cross-covariance function and can be measured even for high levels of noise. Results: As an example application, we measure the amplitude perturbations of the seismic waves that propagate through the sunspot in active region NOAA 9787. We can recover the amplitude variations due to the scattering and attenuation of the waves by the sunspot and associated finite-wavelength effects. Conclusions: The proposed definition of cross-covariance amplitude is robust to noise, can be used to relate measured amplitudes to 3D perturbations in the solar interior under the Born approximation, and provides independent information from the travel times.

  17. Amplitudes and lifetimes of solar-like oscillations observed by CoRoT* Red-giant versus main-sequence stars

    CERN Document Server

    Baudin, F; Belkacem, K; Hekker, S; Morel, T; Samadi, R; Benomar, O; Goupil, M -J; Carrier, F; Ballot, J; Deheuvels, S; De Ridder, J; Hatzes, A P; Kallinger, T; Weiss, W W

    2011-01-01

    Context. The advent of space-borne missions such as CoRoT or Kepler providing photometric data has brought new possibilities for asteroseismology across the H-R diagram. Solar-like oscillations are now observed in many stars, including red giants and main- sequence stars. Aims. Based on several hundred identified pulsating red giants, we aim to characterize their oscillation amplitudes and widths. These observables are compared with those of main-sequence stars in order to test trends and scaling laws for these parameters for both main-sequence stars and red giants. Methods. An automated fitting procedure is used to analyze several hundred Fourier spectra. For each star, a modeled spectrum is fitted to the observed oscillation spectrum, and mode parameters are derived. Results. Amplitudes and widths of red-giant solar-like oscillations are estimated for several hundred modes of oscillation. Amplitudes are relatively high (several hundred ppm) and widths relatively small (very few tenths of a {\\mu}Hz). Conclus...

  18. Remote synchronization of amplitudes across an experimental ring of non-linear oscillators

    Science.gov (United States)

    Minati, Ludovico

    2015-12-01

    In this paper, the emergence of remote synchronization in a ring of 32 unidirectionally coupled non-linear oscillators is reported. Each oscillator consists of 3 negative voltage gain stages connected in a loop to which two integrators are superimposed and receives input from its preceding neighbour via a "mixing" stage whose gains form the main system control parameters. Collective behaviour of the network is investigated numerically and experimentally, based on a custom-designed circuit board featuring 32 field-programmable analog arrays. A diverse set of synchronization patterns is observed depending on the control parameters. While phase synchronization ensues globally, albeit imperfectly, for certain control parameter values, amplitudes delineate subsets of non-adjacent but preferentially synchronized nodes; this cannot be trivially explained by synchronization paths along sequences of structurally connected nodes and is therefore interpreted as representing a form of remote synchronization. Complex topology of functional synchronization thus emerges from underlying elementary structural connectivity. In addition to the Kuramoto order parameter and cross-correlation coefficient, other synchronization measures are considered, and preliminary findings suggest that generalized synchronization may identify functional relationships across nodes otherwise not visible. Further work elucidating the mechanism underlying this observation of remote synchronization is necessary, to support which experimental data and board design materials have been made freely downloadable.

  19. Multi-frequency excitation of stiffened triangular plates for large amplitude oscillations

    Science.gov (United States)

    Askari, H.; Saadatnia, Z.; Esmailzadeh, E.; Younesian, D.

    2014-10-01

    Free and forced vibrations of triangular plate are investigated. Diverse types of stiffeners were attached onto the plate to suppress the undesirable large-amplitude oscillations. The governing equation of motion for a triangular plate, based on the von Kármán theory, is developed and the nonlinear ordinary differential equation of the system using Galerkin approach is obtained. Closed-form expressions for the free undamped and large-amplitude vibration of an orthotropic triangular elastic plate are presented using the two well-known analytical methods, namely, the energy balance method and the variational approach. The frequency responses in the closed-form are presented and their sensitivities with respect to the initial amplitudes are studied. An error analysis is performed and the vibration behavior, as well as the accuracy of the solution methods, is evaluated. Different types of the stiffened triangular plates are considered in order to cover a wide range of practical applications. Numerical simulations are carried out and the validity of the solution procedure is explored. It is demonstrated that the two methods of energy balance and variational approach have been quite straightforward and reliable techniques to solve those nonlinear differential equations. Subsequently, due to the importance of multiple resonant responses in engineering design, multi-frequency excitations are considered. It is assumed that three periodic forces are applied to the plate in three specific positions. The multiple time scaling method is utilized to obtain approximate solutions for the frequency resonance cases. Influences of different parameters, namely, the position of applied forces, geometry and the number of stiffeners on the frequency response of the triangular plates are examined.

  20. Quasi-periodic bifurcations and “amplitude death” in low-dimensional ensemble of van der Pol oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Emelianova, Yu.P., E-mail: yuliaem@gmail.com [Department of Electronics and Instrumentation, Saratov State Technical University, Polytechnicheskaya 77, Saratov 410054 (Russian Federation); Kuznetsov, A.P., E-mail: apkuz@rambler.ru [Kotel' nikov' s Institute of Radio-Engineering and Electronics of RAS, Saratov Branch, Zelyenaya 38, Saratov 410019 (Russian Federation); Turukina, L.V., E-mail: lvtur@rambler.ru [Kotel' nikov' s Institute of Radio-Engineering and Electronics of RAS, Saratov Branch, Zelyenaya 38, Saratov 410019 (Russian Federation); Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany)

    2014-01-10

    The dynamics of the four dissipatively coupled van der Pol oscillators is considered. Lyapunov chart is presented in the parameter plane. Its arrangement is discussed. We discuss the bifurcations of tori in the system at large frequency detuning of the oscillators. Here are quasi-periodic saddle-node, Hopf and Neimark–Sacker bifurcations. The effect of increase of the threshold for the “amplitude death” regime and the possibilities of complete and partial broadband synchronization are revealed.

  1. Neuronal Oscillations with Non-sinusoidal Morphology Produce Spurious Phase-to-Amplitude Coupling and Directionality

    NARCIS (Netherlands)

    Lozano Soldevilla, D.; Huurne, N.P. ter; Oostenveld, R.

    2016-01-01

    Neuronal oscillations support cognitive processing. Modern views suggest that neuronal oscillations do not only reflect coordinated activity in spatially distributed networks, but also that there is interaction between the oscillations at different frequencies. For example, invasive recordings in an

  2. High Frequency Amplitude Detector for GMI Magnetic Sensors

    Directory of Open Access Journals (Sweden)

    Aktham Asfour

    2014-12-01

    Full Text Available 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.

  3. Surface activity and oscillation amplitudes of red giants in eclipsing binaries

    Energy Technology Data Exchange (ETDEWEB)

    Gaulme, P.; Jackiewicz, J. [Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003-8001 (United States); Appourchaux, T. [Institut d' Astrophysique Spatiale, Université Paris-Sud 11 and CNRS (UMR 8617), Bâtiment 121, F-91405 Orsay cedex (France); Mosser, B., E-mail: gaulme@nmsu.edu [LESIA, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, F-92195 Meudon cedex (France)

    2014-04-10

    Among the 19 red-giant stars belonging to eclipsing binary systems that have been identified in Kepler data, 15 display solar-like oscillations. We study whether the absence of mode detection in the remaining 4 is an observational bias or possibly evidence of mode damping that originates from tidal interactions. A careful analysis of the corresponding Kepler light curves shows that modes with amplitudes that are usually observed in red giants would have been detected if they were present. We observe that mode depletion is strongly associated with short-period systems, in which stellar radii account for 16%-24% of the semi-major axis, and where red-giant surface activity is detected. We suggest that when the rotational and orbital periods synchronize in close binaries, the red-giant component is spun up, so that a dynamo mechanism starts and generates a magnetic field, leading to observable stellar activity. Pressure modes would then be damped as acoustic waves dissipate in these fields.

  4. Reduction of the 1/f Noise Induced Phase Noise in a CMOS Ring Oscillator by Increasing the Amplitude of Oscillation

    NARCIS (Netherlands)

    Gierkink, S.L.J.; Wel, van der A.P.; Hoogzaad, G.; Klumperink, E.A.M.; Tuijl, van A.J.M.

    1998-01-01

    Spectrum measurement results of a CMOS ring oscillator are presented that show a 10 dB decrease in 1/f noise induced phase noise at a 2 dB increase in carrier power. Simple ring oscillator theory predicts that the 1/f noise induced phase noise is independent of carrier power. It is shown that an inc

  5. Non-linear Vibration of Oscillation Systems using Frequency-Amplitude Formulation

    DEFF Research Database (Denmark)

    Fereidoon, A.; Ghadimi, M.; Barari, Amin

    2012-01-01

    In this paper we study the periodic solutions of free vibration of mechanical systems with third and fifthorder nonlinearity for two examples using He’s Frequency Amplitude Formulation (HFAF).The effectiveness and convenience of the method is illustrated in these examples. It will be shown...... that the solutions obtained with current method have a fabulous conformity with those achieved from time marching solution. HFAF is easy with powerful concepts and the high accuracy, so it can be found widely applicable in vibrations, especially strong nonlinearity oscillatory problems....

  6. Subharmonic and fundamental high amplitude excitation of an axisymmetric jet

    Science.gov (United States)

    Raman, Ganesh; Rice, Edward J.

    1989-01-01

    The effect of simultaneous excitation at the fundamental and subharmonic frequencies on the behavior of a circular jet shear layer is studied. Attention is given to the effect of the initial phase difference, the Strouhal number pair, and amplitudes of the fundamental and subharmonic tones. High-amplitude excitation devices which can provide a wide range of forcing conditions when used in conjunction with equipment that produces complex waveforms are used.

  7. High Amplitude (delta)-Scutis in the Large Magellanic Cloud

    Energy Technology Data Exchange (ETDEWEB)

    Garg, A; Cook, K H; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M

    2010-01-25

    The authors present 2323 High-Amplitude {delta}-Scutis (HADS) candidates discovered in the Large Magellanic Cloud (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F) mode and 19 whose largest amplitude of pulsation is in the first overtone (FO) mode. Using Fourier decomposition of the HADS light curves, they find that the period-luminosity (PL) relation defined by the FO pulsators does not show a clear separation from the PL-relation defined by the F pulsators. This differs from other instability strip pulsators such as type c RR Lyrae. They also present evidence for a larger amplitude, subluminous population of HADS similar to that observed in Fornax (Poretti et al. 2008).

  8. High Amplitude \\delta-Scutis in the Large Magellanic Cloud

    CERN Document Server

    Garg, A; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M

    2010-01-01

    We present 2323 High-Amplitude \\delta-Scuti (HADS) candidates discovered in the Large Magellanic Cloud (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F) mode and 19 whose largest amplitude of pulsation is in the first overtone (FO) mode. Using Fourier decomposition of the HADS light curves, we find that the period-luminosity (PL) relation defined by the FO pulsators does not show a clear separation from the PL-relation defined by the F pulsators. This differs from other instability strip pulsators such as type c RR Lyrae. We also present evidence for a larger amplitude, subluminous population of HADS similar to that observed in Fornax (Poretti et al. 2008).

  9. Experience Drives Synchronization: The phase and Amplitude Dynamics of Neural Oscillations to Musical Chords Are Differentially Modulated by Musical Expertise.

    Science.gov (United States)

    Pallesen, Karen Johanne; Bailey, Christopher J; Brattico, Elvira; Gjedde, Albert; Palva, J Matias; Palva, Satu

    2015-01-01

    Musical expertise is associated with structural and functional changes in the brain that underlie facilitated auditory perception. We investigated whether the phase locking (PL) and amplitude modulations (AM) of neuronal oscillations in response to musical chords are correlated with musical expertise and whether they reflect the prototypicality of chords in Western tonal music. To this aim, we recorded magnetoencephalography (MEG) while musicians and non-musicians were presented with common prototypical major and minor chords, and with uncommon, non-prototypical dissonant and mistuned chords, while watching a silenced movie. We then analyzed the PL and AM of ongoing oscillations in the theta (4-8 Hz) alpha (8-14 Hz), beta- (14-30 Hz) and gamma- (30-80 Hz) bands to these chords. We found that musical expertise was associated with strengthened PL of ongoing oscillations to chords over a wide frequency range during the first 300 ms from stimulus onset, as opposed to increased alpha-band AM to chords over temporal MEG channels. In musicians, the gamma-band PL was strongest to non-prototypical compared to other chords, while in non-musicians PL was strongest to minor chords. In both musicians and non-musicians the long-latency (> 200 ms) gamma-band PL was also sensitive to chord identity, and particularly to the amplitude modulations (beats) of the dissonant chord. These findings suggest that musical expertise modulates oscillation PL to musical chords and that the strength of these modulations is dependent on chord prototypicality.

  10. Convective moisture adjustment time scale as a key factor in regulating model amplitude of the Madden-Julian Oscillation

    Science.gov (United States)

    Jiang, Xianan; Zhao, Ming; Maloney, Eric D.; Waliser, Duane E.

    2016-10-01

    Despite its pronounced impacts on weather extremes worldwide, the Madden-Julian Oscillation (MJO) remains poorly represented in climate models. Here we present findings that point to some necessary ingredients to produce a strong MJO amplitude in a large set of model simulations from a recent model intercomparison project. While surface flux and radiative heating anomalies are considered important for amplifying the MJO, their strength per unit MJO precipitation anomaly is found to be negatively correlated to MJO amplitude across these multimodel simulations. However, model MJO amplitude is found to be closely tied to a model's convective moisture adjustment time scale, a measure of how rapidly precipitation must increase to remove excess column water vapor, or alternately the efficiency of surface precipitation generation per unit column water vapor anomaly. These findings provide critical insights into key model processes for the MJO and pinpoint a direction for improved model representation of the MJO.

  11. Restoring oscillatory behavior from amplitude death with anti-phase synchronization patterns in networks of electrochemical oscillations

    Science.gov (United States)

    Nagao, Raphael; Zou, Wei; Kurths, Jürgen; Kiss, István Z.

    2016-09-01

    The dynamical behavior of delay-coupled networks of electrochemical reactions is investigated to explore the formation of amplitude death (AD) and the synchronization states in a parameter region around the amplitude death region. It is shown that difference coupling with odd and even numbered ring and random networks can produce the AD phenomenon. Furthermore, this AD can be restored by changing the coupling type from difference to direct coupling. The restored oscillations tend to create synchronization patterns in which neighboring elements are in nearly anti-phase configuration. The ring networks produce frozen and rotating phase waves, while the random network exhibits a complex synchronization pattern with interwoven frozen and propagating phase waves. The experimental results are interpreted with a coupled Stuart-Landau oscillator model. The experimental and theoretical results reveal that AD behavior is a robust feature of delayed coupled networks of chemical units; if an oscillatory behavior is required again, even a small amount of direct coupling could be sufficient to restore the oscillations. The restored nearly anti-phase oscillatory patterns, which, to a certain extent, reflect the symmetry of the network, represent an effective means to overcome the AD phenomenon.

  12. Radial convection of finite ion temperature, high amplitude plasma blobs

    DEFF Research Database (Denmark)

    Wiesenberger, M.; Madsen, Jens; Kendl, Alexander

    2014-01-01

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line...... with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very...

  13. Role of the Ionosphere in the Generation of Large-Amplitude Ulf Waves at High Latitudes

    Science.gov (United States)

    Tulegenov, B.; Guido, T.; Streltsov, A. V.

    2014-12-01

    We present results from the statistical study of ULF waves detected by the fluxgate magnetometer in Gakona, Alaska during several experimental campaigns conducted at the High Frequency Active Auroral Research Program (HAARP) facility in years 2011-2013. We analyzed frequencies of ULF waves recorded during 26 strongly disturbed geomagnetic events (substorms) and compared them with frequencies of ULF waves detected during magnetically quite times. Our analysis demonstrates that the frequency of the waves carrying most of the power almost in all these events is less than 1 mHz. We also analyzed data from the ACE satellite, measuring parameters of the solar wind in the L1 Lagrangian point between Earth and Sun, and found that in several occasions there is a strong correlation between oscillations of the magnetic field in the solar wind and oscillations detected on the ground. We also found several cases when there is no correlation between signals detected on ACE and on the ground. This finding suggests that these frequencies correspond to the fundamental eigenfrequency of the coupled magnetosphere-ionosphere system. The low frequency of the oscillations is explained by the effect of the ionosphere, where the current is carried by ions through highly collisional media. The amplitude of these waves can reach significant magnitude when the system is driven by the external driver (for example, the solar wind) with this particular frequency. When the frequency of the driver does not match the frequency of the system, the waves still are observed, but their amplitudes are much smaller.

  14. Simulation of transients of high amplitude in pipe systems

    NARCIS (Netherlands)

    Boersma, J.M.; Looijmans, K.N.H.

    1999-01-01

    Fast high-amplitude transients ask for a non-linear modelling approach in which large density variations and heat exchange can be considered. Operation of safety-valves, relief valves, the occurrence of valve failure and the start-up or shutdown of rotating equipment in industrial pipe systems can l

  15. New edge magnetoplasmon interference like photovoltage oscillations and their amplitude enhancement in the presence of an antidot lattice

    Energy Technology Data Exchange (ETDEWEB)

    Bisotto, I., E-mail: isabelle.bisotto@lncmi.cnrs.fr [LNCMI, UPR 3228, CNRS–INSA–UJF–UPS, BP 166, 38042 Grenoble, Cedex 9 (France); Portal, J.-C. [LNCMI, UPR 3228, CNRS–INSA–UJF–UPS, BP 166, 38042 Grenoble, Cedex 9 (France); Institut National des Sciences Appliquées, 31077 Toulouse Cedex 4 (France); Institut Universitaire de France, 75005 Paris (France); Brown, D. [Microelectronics Research Center Georgia Institute of Technology, 791 Atlantic Drive NW, Atlanta, GA 30332 (United States); Wieck, A. D. [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

    2015-11-15

    We present new photovoltage oscillation in a pure two dimensional electron gas (2DEG) and in the presence of circular or semicircular antidot lattices. Results were interpreted as EMPs-like photovoltage oscillations. We observed and explained the photovoltage oscillation amplitude enhancement in the presence of an antidot lattice with regard to the pure 2DEG. The microwave frequency excitation range is 139 – 350 GHz. The cyclotron and magnetoplasmon resonances take place in the magnetic field range 0.4 – 0.8 T. This original experimental condition allows edge magnetoplasmons EMPs interference like observation at low magnetic field, typically B < B{sub c} where B{sub c} is the magnetic field at which the cyclotron resonance takes place. The different oscillation periods observed and their microwave frequency dependence were discussed. For 139 and 158 GHz microwave excitation frequencies, a unique EMPs-like interference period was found in the presence of antidots whereas two periods were extracted for 295 or 350 GHz. An explanation of this effect is given taking account of strong electron interaction with antidot at low magnetic field. Indeed, electrons involved in EMPs like phenomenon interact strongly with antidots when electron cyclotron orbits are larger than or comparable to the antidot diameter.

  16. New edge magnetoplasmon interference like photovoltage oscillations and their amplitude enhancement in the presence of an antidot lattice

    Directory of Open Access Journals (Sweden)

    I. Bisotto

    2015-11-01

    Full Text Available We present new photovoltage oscillation in a pure two dimensional electron gas (2DEG and in the presence of circular or semicircular antidot lattices. Results were interpreted as EMPs-like photovoltage oscillations. We observed and explained the photovoltage oscillation amplitude enhancement in the presence of an antidot lattice with regard to the pure 2DEG. The microwave frequency excitation range is 139 – 350 GHz. The cyclotron and magnetoplasmon resonances take place in the magnetic field range 0.4 – 0.8 T. This original experimental condition allows edge magnetoplasmons EMPs interference like observation at low magnetic field, typically B < Bc where Bc is the magnetic field at which the cyclotron resonance takes place. The different oscillation periods observed and their microwave frequency dependence were discussed. For 139 and 158 GHz microwave excitation frequencies, a unique EMPs-like interference period was found in the presence of antidots whereas two periods were extracted for 295 or 350 GHz. An explanation of this effect is given taking account of strong electron interaction with antidot at low magnetic field. Indeed, electrons involved in EMPs like phenomenon interact strongly with antidots when electron cyclotron orbits are larger than or comparable to the antidot diameter.

  17. Experience Drives Synchronization: The phase and Amplitude Dynamics of Neural Oscillations to Musical Chords Are Differentially Modulated by Musical Expertise.

    Directory of Open Access Journals (Sweden)

    Karen Johanne Pallesen

    Full Text Available Musical expertise is associated with structural and functional changes in the brain that underlie facilitated auditory perception. We investigated whether the phase locking (PL and amplitude modulations (AM of neuronal oscillations in response to musical chords are correlated with musical expertise and whether they reflect the prototypicality of chords in Western tonal music. To this aim, we recorded magnetoencephalography (MEG while musicians and non-musicians were presented with common prototypical major and minor chords, and with uncommon, non-prototypical dissonant and mistuned chords, while watching a silenced movie. We then analyzed the PL and AM of ongoing oscillations in the theta (4-8 Hz alpha (8-14 Hz, beta- (14-30 Hz and gamma- (30-80 Hz bands to these chords. We found that musical expertise was associated with strengthened PL of ongoing oscillations to chords over a wide frequency range during the first 300 ms from stimulus onset, as opposed to increased alpha-band AM to chords over temporal MEG channels. In musicians, the gamma-band PL was strongest to non-prototypical compared to other chords, while in non-musicians PL was strongest to minor chords. In both musicians and non-musicians the long-latency (> 200 ms gamma-band PL was also sensitive to chord identity, and particularly to the amplitude modulations (beats of the dissonant chord. These findings suggest that musical expertise modulates oscillation PL to musical chords and that the strength of these modulations is dependent on chord prototypicality.

  18. Specific frequency bands of amplitude low-frequency oscillation encodes personality.

    Science.gov (United States)

    Wei, Luqing; Duan, Xujun; Zheng, Chunyan; Wang, Shanshan; Gao, Qing; Zhang, Zhiqiang; Lu, Guangming; Chen, Huafu

    2014-01-01

    The biological model of extraversion and neuroticism identified by Eysenck has stimulated increasing interest in uncovering neurobiological substrate of the two fundamental dimensions. Here we aim to explore brain disturbances underlying extraversion and neuroticism in 87 healthy individuals using fractional amplitude of low-frequency fluctuations (LFF) on resting-state functional magnetic resonance imaging. Two different frequency bands, Slow-5 (0.01-0.027 Hz) exhibiting higher power and involving larger brain regions, and Slow-4 (0.027-0.073 Hz) exhibiting less power and emerging locally, were analyzed. Our results showed a positive correlation between LFF amplitude at Slow-5 and extraversion in medial prefrontal cortex and precuneus, important portions of the default mode network, thus suggesting a link between default network activity and personality traits. LFF amplitude at Slow-5 was correlated positively with neuroticism in right posterior portion of the frontal lobe, further validating neuroticism with frontal lateralization. In addition, LFF amplitude at Slow-4 was negatively associated with extraversion and neuroticism in left hippocampus (HIP) and bilateral superior temporal cortex (STC) respectively, supporting the hypothesized (inverse) relationship between extraversion and resting arousal, also implying neural circuit underlying emotional process influencing on personality. Overall, these findings suggest the important relationships, between personality and LFF amplitude dynamic, depend on specific frequency bands.

  19. Hyperbolic chaotic attractor in amplitude dynamics of coupled self-oscillators with periodic parameter modulation

    DEFF Research Database (Denmark)

    Isaeva, Olga B.; Kuznetsov, Sergey P.; Mosekilde, Erik

    2011-01-01

    The paper proposes an approach to constructing feasible examples of dynamical systems with hyperbolic chaotic attractors based on the successive transfer of excitation between two pairs of self-oscillators that are alternately active. An angular variable that measures the relations of the current...

  20. A novel analytical approximation technique for highly nonlinear oscillators based on the energy balance method

    Science.gov (United States)

    Hosen, Md. Alal; Chowdhury, M. S. H.; Ali, Mohammad Yeakub; Ismail, Ahmad Faris

    In the present paper, a novel analytical approximation technique has been proposed based on the energy balance method (EBM) to obtain approximate periodic solutions for the focus generalized highly nonlinear oscillators. The expressions of the natural frequency-amplitude relationship are obtained using a novel analytical way. The accuracy of the proposed method is investigated on three benchmark oscillatory problems, namely, the simple relativistic oscillator, the stretched elastic wire oscillator (with a mass attached to its midpoint) and the Duffing-relativistic oscillator. For an initial oscillation amplitude A0 = 100, the maximal relative errors of natural frequency found in three oscillators are 2.1637%, 0.0001% and 1.201%, respectively, which are much lower than the errors found using the existing methods. It is highly remarkable that an excellent accuracy of the approximate natural frequency has been found which is valid for the whole range of large values of oscillation amplitude as compared with the exact ones. Very simple solution procedure and high accuracy that is found in three benchmark problems reveal the novelty, reliability and wider applicability of the proposed analytical approximation technique.

  1. Twin-peak quasi-periodic oscillations in X-ray binaries: clues from their amplitude and coherence

    Science.gov (United States)

    Germanà, C.; Casana, R.; Ferreira, M. M., Jr.; Gomes, A. R.

    2014-10-01

    Low-mass X-ray binaries (LMXBs) with either a black hole or a neutron star show power spectra characterized by several enhanced fractions of power at given frequencies, such as quasi-periodic oscillations (QPOs). Twin-peak high-frequency QPOs (HF QPOs) are typical of the orbital motion time-scale for matter orbiting within 10 r_{g} from the compact object (r_{g}=GM/c^{2} is the gravitational radius of the compact object). Thus, such modulations could arise from the energy released by accreting clumps of matter interacting with the strong gravitational field of the compact object. Twin-peak HF QPOs are characterized by their central frequency ν, root mean square amplitude (rms) and coherence Q=νΔν, where Δν is the width of the peak. Here we investigate on the characteristic behavior of the rms observed in several LMXBs. We highlight the work done by the strong tidal force as root source of the energy (rms) released by a QPO. By means of the Schwarzschild potential we estimate the maximum allowed radius of clumps of matter that can survive to tides in the inner part of the accretion disk. It turns to be R˜ 40 m for matter in an accretion disk around a 2 M_{odot} neutron star and R˜ 150 m for matter around a 10 M_{odot } black hole. The work loaded by tides on the clump of matter depends on the Schwarzschild potential shape for the given orbit. We highlight that for orbits approaching to the inner most stable circular orbit (ISCO) the changing Schwarzschild potential shape may account for the observed behavior of the energy (rms) carried by the twin-peak HF QPOs.

  2. Mean-field dispersion-induced spatial synchrony, oscillation and amplitude death, and temporal stability in an ecological model.

    Science.gov (United States)

    Banerjee, Tanmoy; Dutta, Partha Sharathi; Gupta, Anubhav

    2015-05-01

    One of the most important issues in spatial ecology is to understand how spatial synchrony and dispersal-induced stability interact. In the existing studies it is shown that dispersion among identical patches results in spatial synchrony; on the other hand, the combination of spatial heterogeneity and dispersion is necessary for dispersal-induced stability (or temporal stability). Population synchrony and temporal stability are thus often thought of as conflicting outcomes of dispersion. In contrast to the general belief, in this present study we show that mean-field dispersion is conducive to both spatial synchrony and dispersal-induced stability even in identical patches. This simultaneous occurrence of rather conflicting phenomena is governed by the suppression of oscillation states, namely amplitude death (AD) and oscillation death (OD). These states emerge through spatial synchrony of the oscillating patches in the strong-coupling strength. We present an interpretation of the mean-field diffusive coupling in the context of ecology and identify that, with increasing mean-field density, an open ecosystem transforms into a closed ecosystem. We report on the occurrence of OD in an ecological model and explain its significance. Using a detailed bifurcation analysis we show that, depending on the mortality rate and carrying capacity, the system shows either AD or both AD and OD. We also show that the results remain qualitatively the same for a network of oscillators. We identify a new transition scenario between the same type of oscillation suppression states whose geneses differ. In the parameter-mismatched case, we further report on the direct transition from OD to AD through a transcritical bifurcation. We believe that this study will lead to a proper interpretation of AD and OD in ecology, which may be important for the conservation and management of several communities in ecosystems.

  3. Amplitude-squared squeezing of the generalized odd-even coherent states of the anharmonic oscillator in a finite-dimensional Hilbert space

    Institute of Scientific and Technical Information of China (English)

    Muhammad Ashfaq Ahmad; Lin Jie; Qian Yan; Ma Zhi-Min; Ma Ai-Qun; Liu Shu-Tian

    2007-01-01

    This paper discusses the properties of amplitude-squared squeezing of the generalized odd-even coherent states of anharmonic oscillator in finite-dimensional Hilbert space. It demonstrates that the generalized odd coherent states do exhibit strong amplitude-squared squeezing effects in comparison with the generalized even coherent states.

  4. Large amplitude spin torque vortex oscillations at zero external field using a perpendicular spin polarizer

    Energy Technology Data Exchange (ETDEWEB)

    Dussaux, A.; Rache Salles, B.; Jenkins, A. S.; Bortolotti, P.; Grollier, J.; Cros, V.; Fert, A. [Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); Grimaldi, E., E-mail: eva.grimaldi@thalesgroup.com [Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); CNES, 1 Avenue Edouard Belin, 31400 Toulouse (France); Khvalkovskiy, A. V. [Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); A.M. Prokhorov General Physics Institute of RAS, Vavilova Str. 38, 119991 Moscow (Russian Federation); Kubota, H.; Fukushima, A.; Yakushiji, K.; Yuasa, S. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)

    2014-07-14

    We investigate the microwave response of a spin transfer vortex based oscillator in a magnetic tunnel junction with an in-plane reference layer combined with a spin valve with an out-of-plane magnetization spin polarizing layer. The main advantage of this perpendicular spin polarizer is to induce a large spin transfer force even at zero magnetic field, thus leading to a record emitted power (up to 0.6 μW) associated to a very narrow spectral linewidth of a few hundreds of kHz. The characteristics of this hybrid vortex based spin transfer nano-oscillator obtained at zero field and room temperature are of great importance for applications based on rf spintronic devices as integrated and tunable microwave source and/or microwave detector.

  5. Phase-amplitude investigation of spontaneous low-frequency oscillations of cerebral hemodynamics with near-infrared spectroscopy: A sleep study in human subjects

    Science.gov (United States)

    Pierro, Michele; Sassaroli, Angelo; Bergethon, Peter R.; Ehrenberg, Bruce L.; Fantini, Sergio

    2012-01-01

    We have investigated the amplitude and phase of spontaneous low-frequency oscillations (LFOs) of the cerebral deoxy- and oxy-hemoglobin concentrations ([Hb] and [HbO]) in a human sleep study using near-infrared spectroscopy (NIRS). Amplitude and phase analysis was based on the analytic signal method, and phasor algebra was used to decompose measured [Hb] and [HbO] oscillations into cerebral blood volume (CBV) and flow velocity (CBFV) oscillations. We have found a greater phase lead of [Hb] vs. [HbO] LFOs during non-REM sleep with respect to the awake and REM sleep states (maximum increase in [Hb] phase lead: ~π/2). Furthermore, during non-REM sleep, the amplitudes of [Hb] and [HbO] LFOs are suppressed with respect to the awake and REM sleep states (maximum amplitude decrease: 87%). The associated cerebral blood volume and flow velocity oscillations are found to maintain their relative phase difference during sleep, whereas their amplitudes are attenuated during non-REM sleep. These results show the potential of phase-amplitude analysis of [Hb] and [HbO] oscillations measured by NIRS in the investigation of hemodynamics associated with cerebral physiology, activation, and pathological conditions. PMID:22820416

  6. Radial convection of finite ion temperature, high amplitude plasma blobs

    CERN Document Server

    Wiesenberger, M; Kendl, A

    2014-01-01

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in ...

  7. The phase of ongoing EEG oscillations predicts the amplitude of peri-saccadic mislocalization

    Science.gov (United States)

    McLelland, Douglas; Lavergne, Louisa; VanRullen, Rufin

    2016-01-01

    Our constant eye movements mean that updating processes, such as saccadic remapping, are essential for the maintenance of a stable spatial representation of the world around us. It has been proposed that, rather than continually update a full spatiotopic map, only the location of a few key objects is updated, suggesting that the process is linked to attention. At the same time, mounting evidence links attention to oscillatory neuronal processes. We therefore hypothesized that updating processes should themselves show oscillatory characteristics, inherited from underlying attentional processes. To test this, we carried out a combined psychophysics and EEG experiment in human participants, using a saccadic mislocalization task as a behaviourally measureable proxy for spatial updating, and simultaneously recording 64-channel EEG. We then used a time-frequency analysis to test for a correlation between oscillation phase and perceptual outcome. We found a significant phase-dependence of mislocalization in a time-frequency region from around 400 ms prior to saccade initiation and peaking at around 7 Hz, principally apparent over occipital electrodes. Thus the degree of perceived mislocalization is correlated with the phase of a theta-frequency oscillation prior to saccade onset. We conclude that spatial updating processes are indeed linked to rhythmic processes in the brain. PMID:27403937

  8. Single Microbubble Measurements of Lipid Monolayer Viscoelastic Properties for Small-Amplitude Oscillations.

    Science.gov (United States)

    Lum, Jordan S; Dove, Jacob D; Murray, Todd W; Borden, Mark A

    2016-09-20

    Lipid monolayer rheology plays an important role in a variety of interfacial phenomena, the physics of biological membranes, and the dynamic response of acoustic bubbles and drops. We show here measurements of lipid monolayer elasticity and viscosity for very small strains at megahertz frequency. Individual plasmonic microbubbles of 2-6 μm radius were photothermally activated with a short laser pulse, and the subsequent nanometer-scale radial oscillations during ring-down were monitored by optical scatter. This method provided average dynamic response measurements of single microbubbles. Each microbubble was modeled as an underdamped linear oscillator to determine the damping ratio and eigenfrequency, and thus the lipid monolayer viscosity and elasticity. Our nonisothermal measurement technique revealed viscoelastic trends for different lipid shell compositions. We observed a significant increase in surface elasticity with the lipid acyl chain length for 16 to 20 carbons, and this effect was explained by an intermolecular forces model that accounts for the lipid composition, packing, and hydration. The surface viscosity was found to be equivalent for these lipid shells. We also observed an anomalous decrease in elasticity and an increase in viscosity when increasing the acyl chain length from 20 to 22 carbons. These results illustrate the use of a novel nondestructive optical technique to investigate lipid monolayer rheology in new regimes of frequency and strain, possibly elucidating the phase behavior, as well as how the dynamic response of a microbubble can be tuned by the lipid intermolecular forces.

  9. High amplitude nonlinear acoustic wave driven flow fields in cylindrical and conical resonators.

    Science.gov (United States)

    Antao, Dion Savio; Farouk, Bakhtier

    2013-08-01

    A high fidelity computational fluid dynamic model is used to simulate the flow, pressure, and density fields generated in a cylindrical and a conical resonator by a vibrating end wall/piston producing high-amplitude standing waves. The waves in the conical resonator are found to be shock-less and can generate peak acoustic overpressures that exceed the initial undisturbed pressure by two to three times. A cylindrical (consonant) acoustic resonator has limitations to the output response observed at one end when the opposite end is acoustically excited. In the conical geometry (dissonant acoustic resonator) the linear acoustic input is converted to high energy un-shocked nonlinear acoustic output. The model is validated using past numerical results of standing waves in cylindrical resonators. The nonlinear nature of the harmonic response in the conical resonator system is further investigated for two different working fluids (carbon dioxide and argon) operating at various values of piston amplitude. The high amplitude nonlinear oscillations observed in the conical resonator can potentially enhance the performance of pulse tube thermoacoustic refrigerators and these conical resonators can be used as efficient mixers.

  10. Suppressing high-frequency temperature oscillations in microchannels with surface structures

    Science.gov (United States)

    Zhu, Yangying; Antao, Dion S.; Bian, David W.; Rao, Sameer R.; Sircar, Jay D.; Zhang, Tiejun; Wang, Evelyn N.

    2017-01-01

    Two-phase microchannel heat sinks are attractive for thermal management of high heat flux electronic devices, yet flow instability which can lead to thermal and mechanical fatigue remains a significant challenge. Much work has focused on long-timescale (˜seconds) flow oscillations which are usually related to the compressible volume in the loop. The rapid growth of vapor bubbles which can also cause flow reversal, however, occurs on a much shorter timescale (˜tens of milliseconds). While this high-frequency oscillation has often been visualized with high-speed imaging, its effect on the instantaneous temperature has not been fully investigated due to the typical low sampling rates of the sensors. Here, we investigate the temperature response as a result of the high-frequency flow oscillation in microchannels and the effect of surface microstructures on this temperature oscillation with a measurement data acquisition rate of 1000 Hz. For smooth surface microchannels, fluid flow oscillated between complete dry-out and rewetting annular flow due to the short-timescale flow instability, which caused high-frequency and large amplitude temperature oscillations (10 °C in 25 ms). In comparison, hydrophilic surface structures on the microchannel promoted capillary flow which delayed and suppressed dry-out in each oscillation cycle, and thus significantly reduced the temperature oscillation at high heat fluxes. This work suggests that promoting capillary wicking via surface structures is a promising technique to reduce thermal fatigue in high heat flux two-phase microchannel thermal management devices.

  11. Experimental synchronization of chaos in a large ring of mutually coupled single-transistor oscillators: Phase, amplitude, and clustering effects

    Energy Technology Data Exchange (ETDEWEB)

    Minati, Ludovico, E-mail: lminati@ieee.org, E-mail: ludovico.minati@unitn.it [MR-Lab, Center for Mind/Brain Science, University of Trento, Italy and Scientific Department, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan (Italy)

    2014-12-01

    In this paper, experimental evidence of multiple synchronization phenomena in a large (n = 30) ring of chaotic oscillators is presented. Each node consists of an elementary circuit, generating spikes of irregular amplitude and comprising one bipolar junction transistor, one capacitor, two inductors, and one biasing resistor. The nodes are mutually coupled to their neighbours via additional variable resistors. As coupling resistance is decreased, phase synchronization followed by complete synchronization is observed, and onset of synchronization is associated with partial synchronization, i.e., emergence of communities (clusters). While component tolerances affect community structure, the general synchronization properties are maintained across three prototypes and in numerical simulations. The clusters are destroyed by adding long distance connections with distant notes, but are otherwise relatively stable with respect to structural connectivity changes. The study provides evidence that several fundamental synchronization phenomena can be reliably observed in a network of elementary single-transistor oscillators, demonstrating their generative potential and opening way to potential applications of this undemanding setup in experimental modelling of the relationship between network structure, synchronization, and dynamical properties.

  12. Detecting phase-amplitude coupling with high frequency resolution using adaptive decompositions.

    Science.gov (United States)

    Pittman-Polletta, Benjamin; Hsieh, Wan-Hsin; Kaur, Satvinder; Lo, Men-Tzung; Hu, Kun

    2014-04-15

    Phase-amplitude coupling (PAC)--the dependence of the amplitude of one rhythm on the phase of another, lower-frequency rhythm - has recently been used to illuminate cross-frequency coordination in neurophysiological activity. An essential step in measuring PAC is decomposing data to obtain rhythmic components of interest. Current methods of PAC assessment employ narrowband Fourier-based filters, which assume that biological rhythms are stationary, harmonic oscillations. However, biological signals frequently contain irregular and nonstationary features, which may contaminate rhythms of interest and complicate comodulogram interpretation, especially when frequency resolution is limited by short data segments. To better account for nonstationarities while maintaining sharp frequency resolution in PAC measurement, even for short data segments, we introduce a new method of PAC assessment which utilizes adaptive and more generally broadband decomposition techniques - such as the empirical mode decomposition (EMD). To obtain high frequency resolution PAC measurements, our method distributes the PAC associated with pairs of broadband oscillations over frequency space according to the time-local frequencies of these oscillations. We compare our novel adaptive approach to a narrowband comodulogram approach on a variety of simulated signals of short duration, studying systematically how different types of nonstationarities affect these methods, as well as on EEG data. Our results show: (1) narrowband filtering can lead to poor PAC frequency resolution, and inaccuracy and false negatives in PAC assessment; (2) our adaptive approach attains better PAC frequency resolution and is more resistant to nonstationarities and artifacts than traditional comodulograms. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Amplitude modulated, by M1, Earth's oscillating (T = 1 day) electric field triggered by K1 tidal waves. Its relation to the occurrence time of large EQs

    CERN Document Server

    Thanassoulas, C; Verveniotis, G

    2010-01-01

    Starting from the observation that quite often the Earth's oscillating electric field varies in amplitude, a mechanism is postulated that accounts for these observations. That mechanism is the piezoelectric one driven by the M1 and K1 tidal components. It is demonstrated how the system: piezoelectricity triggered in the lithosphere - M1 and K1 tidal components is activated and produces the amplitude modulated Earth's oscillating electric field. This procedure is linked to the strain load conditions met in the seismogenic area before the occurrence of a large EQ. Peaks of the oscillating Earth's electric field are tightly connected to the M1 peak tidal component and to the timing of the occurrence of large EQs. Typical examples from real recordings of the Earth's oscillating electric field, recorded by the ATH (Greece) monitoring site, are given in order to verify the postulated detailed piezoelectric mechanism.

  14. Taylor-Couette flow control by amplitude variation of the inner cylinder cross-section oscillation

    Science.gov (United States)

    Oualli, Hamid; Mekadem, Mahmoud; Lebbi, Mohamed; Bouabdallah, Ahcene

    2015-07-01

    The hydrodynamic stability of a viscous fluid flow evolving in an annular space between a rotating inner cylinder with a periodically variable radius and an outer fixed cylinder is considered. The basic flow is axis-symmetric with two counter-rotating vortices each wavelength along the whole filled system length. The numerical simulations are implemented on the commercial Fluent software package, a finite-volume CFD code. It is aimed to make investigation of the early flow transition with assessment of the flow response to radial pulsatile motion superimposed to the inner cylinder cross-section as an extension of a previous developed work in Oualli et al. [H. Oualli, A. Lalaoua, S. Hanchi, A. Bouabdallah, Eur. Phys. J. Appl. Phys. 61, 11102 (2013)] where a comparative controlling strategy is applied to the outer cylinder. The same basic system is considered with similar calculating parameters and procedure. In Oualli et al. [H. Oualli, A. Lalaoua, S. Hanchi, A. Bouabdallah, Eur. Phys. J. Appl. Phys. 61, 11102 (2013)], it is concluded that for the actuated outer cylinder and relatively to the non-controlled case, the critical Taylor number, Tac1, characterizing the first instability onset illustrated by the piled Taylor vortices along the gap, increases substantially to reach a growing rate of 70% when the deforming amplitude is ɛ = 15%. Interestingly, when this controlling strategy is applied to the inner cylinder cross-section with a slight modification of the actuating law, this tendency completely inverts and the critical Taylor number decreases sharply from Tac1 = 41.33 to Tac1 = 17.66 for ɛ = 5%, corresponding to a reduction rate of 57%. Fundamentally, this result is interesting and can be interpreted by prematurely triggering instabilities resulting in rapid development of flow turbulence. Practically, important applicative aspects can be met in several industry areas where substantial intensification of transport phenomena (mass, momentum and heat) is

  15. Determining the true polarity and amplitude of synaptic currents underlying gamma oscillations of local field potentials.

    Directory of Open Access Journals (Sweden)

    Gonzalo Martín-Vázquez

    Full Text Available Fluctuations in successive waves of oscillatory local field potentials (LFPs reflect the ongoing processing of neuron populations. However, their amplitude, polarity and synaptic origin are uncertain due to the blending of electric fields produced by multiple converging inputs, and the lack of a baseline in standard AC-coupled recordings. Consequently, the estimation of underlying currents by laminar analysis yields spurious sequences of inward and outward currents. We devised a combined analytical/experimental approach that is suitable to study laminated structures. The approach was essayed on an experimental oscillatory LFP as the Schaffer-CA1 gamma input in anesthetized rats, and it was verified by parallel processing of model LFPs obtained through a realistic CA1 aggregate of compartmental units. This approach requires laminar LFP recordings and the isolation of the oscillatory input from other converging pathways, which was achieved through an independent component analysis. It also allows the spatial and temporal components of pathway-specific LFPs to be separated. While reconstructed Schaffer-specific LFPs still show spurious inward/outward current sequences, these were clearly stratified into distinct subcellular domains. These spatial bands guided the localized delivery of neurotransmitter blockers in experiments. As expected, only Glutamate but not GABA blockers abolished Schaffer LFPs when applied to the active but not passive subcellular domains of pyramidal cells. The known chemical nature of the oscillatory LFP allowed an empirical offset of the temporal component of Schaffer LFPs, such that following reconstruction they yield only sinks or sources at the appropriate sites. In terms of number and polarity, some waves increased and others decreased proportional to the concomitant inputs in native multisynaptic LFPs. Interestingly, the processing also retrieved the initiation time for each wave, which can be used to discriminate

  16. Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field

    Science.gov (United States)

    Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team

    2016-11-01

    The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).

  17. Efficient Ultra-High Speed Communication with Simultaneous Phase and Amplitude Regenerative Sampling (SPARS)

    Science.gov (United States)

    Carlowitz, Christian; Girg, Thomas; Ghaleb, Hatem; Du, Xuan-Quang

    2017-08-01

    For ultra-high speed communication systems at high center frequencies above 100 GHz, we propose a disruptive change in system architecture to address major issues regarding amplifier chains with a large number of amplifier stages. They cause a high noise figure and high power consumption when operating close to the frequency limits of the underlying semiconductor technologies. Instead of scaling a classic homodyne transceiver system, we employ repeated amplification in single-stage amplifiers through positive feedback as well as synthesizer-free self-mixing demodulation at the receiver to simplify the system architecture notably. Since the amplitude and phase information for the emerging oscillation is defined by the input signal and the oscillator is only turned on for a very short time, it can be left unstabilized and thus come without a PLL. As soon as gain is no longer the most prominent issue, relaxed requirements for all the other major components allow reconsidering their implementation concepts to achieve further improvements compared to classic systems. This paper provides the first comprehensive overview of all major design aspects that need to be addressed upon realizing a SPARS-based transceiver. At system level, we show how to achieve high data rates and a noise performance comparable to classic systems, backed by scaled demonstrator experiments. Regarding the transmitter, design considerations for efficient quadrature modulation are discussed. For the frontend components that replace PA and LNA amplifier chains, implementation techniques for regenerative sampling circuits based on super-regenerative oscillators are presented. Finally, an analog-to-digital converter with outstanding performance and complete interfaces both to the analog baseband as well as to the digital side completes the set of building blocks for efficient ultra-high speed communication.

  18. Reactions of Standing Bipeds on Moving Platforms to Keep Their Balance May Increase the Amplitude of Oscillations of Platforms Satisfying Hooke's Law.

    Directory of Open Access Journals (Sweden)

    Guillermo H Goldsztein

    Full Text Available Consider a person standing on a platform that oscillates laterally, i.e. to the right and left of the person. Assume the platform satisfies Hooke's law. As the platform moves, the person reacts and moves its body attempting to keep its balance. We develop a simple model to study this phenomenon and show that the person, while attempting to keep its balance, may do positive work on the platform and increase the amplitude of its oscillations. The studies in this article are motivated by the oscillations in pedestrian bridges that are sometimes observed when large crowds cross them.

  19. Increased low-frequency oscillation amplitude of sensorimotor cortex associated with the severity of structural impairment in cervical myelopathy.

    Directory of Open Access Journals (Sweden)

    Fuqing Zhou

    Full Text Available Decreases in metabolites and increased motor-related, but decreased sensory-related activation of the sensorimotor cortex (SMC have been observed in patients with cervical myelopathy (CM using advanced MRI techniques. However, the nature of intrinsic neuronal activity in the SMC, and the relationship between cerebral function and structural damage of the spinal cord in patients with CM are not fully understood. The purpose of this study was to assess intrinsic neuronal activity by calculating the regional amplitude of low frequency fluctuations (ALFF using resting-state functional MRI (rs-fMRI, and correlations with clinical and imaging indices. Nineteen patients and 19 age- and sex-matched healthy subjects underwent rs-fMRI scans. ALFF measurements were performed in the SMC, a key brain network likely to impaired or reorganized patients with CM. Compared with healthy subjects, increased amplitude of cortical low-frequency oscillations (LFO was observed in the right precentral gyrus, right postcentral gyrus, and left supplementary motor area. Furthermore, increased z-ALFF values in the right precentral gyrus and right postcentral gyrus correlated with decreased fractional anisotropy values at the C2 level, which indicated increased intrinsic neuronal activity in the SMC corresponding to the structural impairment in the spinal cord of patients with CM. These findings suggest a complex and diverging relationship of cortical functional reorganization and distal spinal anatomical compression in patients with CM and, thus, add important information in understanding how spinal cord integrity may be a factor in the intrinsic covariance of spontaneous low-frequency fluctuations of BOLD signals involved in cortical plasticity.

  20. High frequency oscillations after median nerve stimulations in healthy children and adolescents.

    Science.gov (United States)

    Zanini, Sergio; Del Piero, Ivana; Martucci, Lucia; Restuccia, Domenico

    2017-10-01

    The aim of the present research was to address somatosensory high frequency oscillations (400-800Hz) in healthy children and adolescents in comparison with healthy adults. We recorded somatosensory evoked potentials following median nerve stimulation in nineteen resting healthy children/adolescents and in nineteen resting healthy adults with eyes closed. We administered six consecutive stimulation blocks (500 sweeps each). The presynaptic component of high frequency oscillations amplitudes was smaller in healthy children/adolescents than in healthy adults (no difference between groups was found as far as the postsynaptic component was concerned). Healthy children/adolescents had smaller presynaptic component than the postsynaptic one (the postsynaptic component amplitude was 145% of the presynaptic one), while healthy adults showed the opposite (reduction of the postsynaptic component to 80% of the presynaptic one). No habituation phenomena concerning high frequency oscillation amplitudes were registered in neither healthy children/adolescents nor healthy adults. These findings suggest that healthy children/adolescents present with significantly different pattern of somatosensory high frequency oscillations compared with healthy adults' ones. This different pattern is reasonably expression of higher cortical excitability of the developing brain cortex. Copyright © 2017 ISDN. Published by Elsevier Ltd. All rights reserved.

  1. Thalamic gap junctions control local neuronal synchrony and influence macroscopic oscillation amplitude during EEG alpha rhythms

    Directory of Open Access Journals (Sweden)

    Stuart eHughes

    2011-08-01

    Full Text Available Although EEG alpha ( (8-13 Hz rhythms are often considered to reflect an ‘idling’ brain state, numerous studies indicate that they are also related to many aspects of perception. Recently, we outlined a potential cellular substrate by which such aspects of perception might be linked to basic  rhythm mechanisms. This scheme relies on a specialized subset of rhythmically bursting thalamocortical (TC neurons (high-threshold bursting cells in the lateral geniculate nucleus (LGN which are interconnected by gap junctions (GJs. By engaging GABAergic interneurons, that in turn inhibit conventional relay-mode TC neurons, these cells can lead to an effective temporal framing of thalamic relay-mode output. Although the role of GJs is pivotal in this scheme, evidence for their involvement in thalamic  rhythms has thus far mainly derived from experiments in in vitro slice preparations. In addition, direct anatomical evidence of neuronal GJs in the LGN is currently lacking. To address the first of these issues we tested the effects of the GJ inhibitors, carbenoxolone (CBX and 18-glycyrrhetinic acid (18-GA, given directly to the LGN via reverse microdialysis, on spontaneous LGN and EEG  rhythms in behaving cats. We also examined the effect of CBX on  rhythm-related LGN unit activity. Indicative of a role for thalamic GJs in these activities, 18-GA and CBX reversibly suppressed both LGN and EEG  rhythms, with CBX also decreasing neuronal synchrony. To address the second point, we used electron microscopy to obtain definitive ultrastructural evidence for the presence of GJs between neurons in the cat LGN. As interneurons show no phenotypic evidence of GJ coupling (i.e. dye-coupling and spikelets we conclude that these GJs must belong to TC neurons. The potential significance of these findings for relating macroscopic changes in  rhythms to basic cellular processes is discussed.

  2. High Amplitude (delta)-Scutis in the Large Magellanic Cloud

    National Research Council Canada - National Science Library

    Garg, A; Cook, K H; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M

    2010-01-01

    ... (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F...

  3. High Reliability Oscillators for Terahertz Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Terahertz sources based on lower frequency oscillators and amplifiers plus a chain of frequency multipliers are the workhorse technology for NASA's terahertz...

  4. The High Amplitude delta Scuti Star AD Canis Minoris

    Science.gov (United States)

    Axelsen, R. A.; Napier-Munn, T.

    2016-12-01

    The high amplitude delta Scuti star AD Canis Minoris was studied by photoelectric photometry (PEP) during one night in in February 2011 and by digital single lens reflex (DSLR) photometry during seven nights in January and February 2016. Nine light curve peaks were captured, eight of them by DSLR photometry. A review of the literature enabled us to tabulate 109 times of maximum since 1959, to which we added 9 times of maximum from our data, thus creating the largest dataset to date for this star. Assuming a linear ephemeris, the period of AD CMi was calculated to be 0.122974511 (+/- 0.000000004) d, almost identical to that quoted in earlier literature. We constructed an observed minus computed (O-C) diagram which exhibited a quasi-sinusoidal shape, and fitted a weighted model characterised by combined quadratic and trigonometric functions. The fit indicates that the shape of the O-C diagram is attributable to the effects of a slow increase in the pulsation period of AD CMi at a constant rate, and the light time effect of a binary pair, confirming the results from previous authors, and updating most of the coefficients of the equation for the fitted model. The values of all of the coefficients in the function are statistically significant. The rate of increase in the pulsation period of AD CMi was calculated from the entire dataset to be dP/dt = 6.17 (+/- 0.75) x 10-9 d yr-1 or dP/Pdt = 5.01 (+/- 0.61) x 10-8 yr-1.

  5. SEMICONDUCTOR PHYSICS: Phonon-induced magnetoresistance oscillations in a high-mobility quantum well

    Science.gov (United States)

    Qisheng, Zhou; Juncheng, Cao; Ming, Qi; Xiaolin, Lei

    2010-09-01

    We examine the temperature dependence of acoustic-phonon-induced magnetoresistance oscillations in a high-mobility GaAs-based quantum well with conventional transverse and longitudinal phonon modes, using a model in which the temperature increase of the Landau level broadening or the single-particle scattering rate 1/τs is attributed to the enhancement of electron-phonon scattering with rising temperature. The non-monotonic temperature behavior, showing an optimal temperature at which a given order of oscillation amplitude exhibits a maximum and the shift of the main resistance peak to higher magnetic field with rising temperature, is produced, in agreement with recent experimental findings.

  6. High intensity neutrino oscillation facilities in Europe

    CERN Document Server

    Edgecock, T R; Davenne, T; Densham, C; Fitton, M; Kelliher, D; Loveridge, P; Machida, S; Prior, C; Rogers, C; Rooney, M; Thomason, J; Wilcox, D; Wildner, E; Efthymiopoulos, I; Garoby, R; Gilardoni, S; Hansen, C; Benedetto, E; Jensen, E; Kosmicki, A; Martini, M; Osborne, J; Prior, G; Stora, T; Melo-Mendonca, T; Vlachoudis, V; Waaijer, C; Cupial, P; Chancé, A; Longhin, A; Payet, J; Zito, M; Baussan, E; Bobeth, C; Bouquerel, E; Dracos, M; Gaudiot, G; Lepers, B; Osswald, F; Poussot, P; Vassilopoulos, N; Wurtz, J; Zeter, V; Bielski, J; Kozien, M; Lacny, L; Skoczen, B; Szybinski, B; Ustrycka, A; Wroblewski, A; Marie-Jeanne, M; Balint, P; Fourel, C; Giraud, J; Jacob, J; Lamy, T; Latrasse, L; Sortais, P; Thuillier, T; Mitrofanov, S; Loiselet, M; Keutgen, Th; Delbar, Th; Debray, F; Trophine, C; Veys, S; Daversin, C; Zorin, V; Izotov, I; Skalyga, V; Burt, G; Dexter, A C; Kravchuk, V L; Marchi, T; Cinausero, M; Gramegna, F; De Angelis, G; Prete, G; Collazuol, G; Laveder, M; Mazzocco, M; Mezzetto, M; Signorini, C; Vardaci, E; Di Nitto, A; Brondi, A; La Rana, G; Migliozzi, P; Moro, R; Palladino, V; Gelli, N; Berkovits, D; Hass, M; Hirsh, T Y; Schaumann, M; Stahl, A; Wehner, J; Bross, A; Kopp, J; Neuffer, D; Wands, R; Bayes, R; Laing, A; Soler, P; Agarwalla, S K; Villanueva, A Cervera; Donini, A; Ghosh, T; Cadenas, J J Gómez; Hernández, P; Martín-Albo, J; Mena, O; Burguet-Castell, J; Agostino, L; Buizza-Avanzini, M; Marafini, M; Patzak, T; Tonazzo, A; Duchesneau, D; Mosca, L; Bogomilov, M; Karadzhov, Y; Matev, R; Tsenov, R; Akhmedov, E; Blennow, M; Lindner, M; Schwetz, T; Martinez, E Fernández; Maltoni, M; Menéndez, J; Giunti, C; García, M C González; Salvado, J; Coloma, P; Huber, P; Li, T; López-Pavón, J; Orme, C; Pascoli, S; Meloni, D; Tang, J; Winter, W; Ohlsson, T; Zhang, H; Scotto-Lavina, L; Terranova, F; Bonesini, M; Tortora, L; Alekou, A; Aslaninejad, M; Bontoiu, C; Kurup, A; Jenner, L J; Long, K; Pasternak, J; Pozimski, J; Back, J J; Harrison, P; Beard, K; Bogacz, A; Berg, J S; Stratakis, D; Witte, H; Snopok, P; Bliss, N; Cordwell, M; Moss, A; Pattalwar, S; Apollonio, M

    2013-01-01

    The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fr\\'ejus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of {\\mu}+ and {\\mu}- beams in a storage ring. The far detector in this case is a 100 kt Magnetised Iron Neutrino Detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular 6He and 18Ne, also stored in a ring. The far detector is also the MEMPHYS detector in the Fr\\'ejus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the ph...

  7. High intensity neutrino oscillation facilities in Europe

    CERN Document Server

    Edgecock, T.R.; Davenne, T.; Densham, C.; Fitton, M.; Kelliher, D.; Loveridge, P.; Machida, S.; Prior, C.; Rogers, C.; Rooney, M.; Thomason, J.; Wilcox, D.; Wildner, E.; Efthymiopoulos, I.; Garoby, R.; Gilardoni, S.; Hansen, C.; Benedetto, E.; Jensen, E.; Kosmicki, A.; Martini, M.; Osborne, J.; Prior, G.; Stora, T.; Melo-Mendonca, T.; Vlachoudis, V.; Waaijer, C.; Cupial, P.; Chancé, A.; Longhin, A.; Payet, J.; Zito, M.; Baussan, E.; Bobeth, C.; Bouquerel, E.; Dracos, M.; Gaudiot, G.; Lepers, B.; Osswald, F.; Poussot, P.; Vassilopoulos, N.; Wurtz, J.; Zeter, V.; Bielski, J.; Kozien, M.; Lacny, L.; Skoczen, B.; Szybinski, B.; Ustrzycka, A.; Wroblewski, A.; Marie-Jeanne, M.; Balint, P.; Fourel, C.; Giraud, J.; Jacob, J.; Lamy, T.; Latrasse, L.; Sortais, P.; Thuillier, T.; Mitrofanov, S.; Loiselet, M.; Keutgen, Th.; Delbar, Th.; Debray, F.; Trophine, C.; Veys, S.; Daversin, C.; Zorin, V.; Izotov, I.; Skalyga, V.; Burt, G.; Dexter, A.C.; Kravchuk, V.L.; Marchi, T.; Cinausero, M.; Gramegna, F.; De Angelis, G.; Prete, G.; Collazuol, G.; Laveder, M.; Mazzocco, M.; Mezzetto, M.; Signorini, C.; Vardaci, E.; Di Nitto, A.; Brondi, A.; La Rana, G.; Migliozzi, P.; Moro, R.; Palladino, V.; Gelli, N.; Berkovits, D.; Hass, M.; Hirsh, T.Y.; Schaumann, M.; Stahl, A.; Wehner, J.; Bross, A.; Kopp, J.; Neuffer, D.; Wands, R.; Bayes, R.; Laing, A.; Soler, P.; Agarwalla, S.K.; Cervera Villanueva, A.; Donini, A.; Ghosh, T.; Gómez Cadenas, J.J.; Hernández, P.; Martín-Albo, J.; Mena, O.; Burguet-Castell, J.; Agostino, L.; Buizza-Avanzini, M.; Marafini, M.; Patzak, T.; Tonazzo, A.; Duchesneau, D.; Mosca, L.; Bogomilov, M.; Karadzhov, Y.; Matev, R.; Tsenov, R.; Akhmedov, E.; Blennow, M.; Lindner, M.; Schwetz, T.; Fernández Martinez, E.; Maltoni, M.; Menéndez, J.; Giunti, C.; González García, M. C.; Salvado, J.; Coloma, P.; Huber, P.; Li, T.; López-Pavón, J.; Orme, C.; Pascoli, S.; Meloni, D.; Tang, J.; Winter, W.; Ohlsson, T.; Zhang, H.; Scotto-Lavina, L.; Terranova, F.; Bonesini, M.; Tortora, L.; Alekou, A.; Aslaninejad, M.; Bontoiu, C.; Kurup, A.; Jenner, L.J.; Long, K.; Pasternak, J.; Pozimski, J.; Back, J.J.; Harrison, P.; Beard, K.; Bogacz, A.; Berg, J.S.; Stratakis, D.; Witte, H.; Snopok, P.; Bliss, N.; Cordwell, M.; Moss, A.; Pattalwar, S.; Apollonio, M.

    2013-02-20

    The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fr\\'ejus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of {\\mu}+ and {\\mu}- beams in a storage ring. The far detector in this case is a 100 kt Magnetised Iron Neutrino Detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular 6He and 18Ne, also stored in a ring. The far detector is also the MEMPHYS detector in the Fr\\'ejus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the ph...

  8. High intensity neutrino oscillation facilities in Europe

    Energy Technology Data Exchange (ETDEWEB)

    Edgecock, T. R.; Caretta, O.; Davenne, T.; Densam, C.; Fitton, M.; Kelliher, D.; Loveridge, P.; Machida, S.; Prior, C.; Rogers, C.; Rooney, M.; Thomason, J.; Wilcox, D.; Wildner, E.; Efthymiopoulos, I.; Garoby, R.; Gilardoni, S.; Hansen, C.; Benedetto, E.; Jensen, E.; Kosmicki, A.; Martini, M.; Osborne, J.; Prior, G.; Stora, T.; Melo Mendonca, T.; Vlachoudis, V.; Waaijer, C.; Cupial, P.; Chancé, A.; Longhin, A.; Payet, J.; Zito, M.; Baussan, E.; Bobeth, C.; Bouquerel, E.; Dracos, M.; Gaudiot, G.; Lepers, B.; Osswald, F.; Poussot, P.; Vassilopoulos, N.; Wurtz, J.; Zeter, V.; Bielski, J.; Kozien, M.; Lacny, L.; Skoczen, B.; Szybinski, B.; Ustrycka, A.; Wroblewski, A.; Marie-Jeanne, M.; Balint, P.; Fourel, C.; Giraud, J.; Jacob, J.; Lamy, T.; Latrasse, L.; Sortais, P.; Thuillier, T.; Mitrofanov, S.; Loiselet, M.; Keutgen, Th.; Delbar, Th.; Debray, F.; Trophine, C.; Veys, S.; Daversin, C.; Zorin, V.; Izotov, I.; Skalyga, V.; Burt, G.; Dexter, A. C.; Kravchuk, V. L.; Marchi, T.; Cinausero, M.; Gramegna, F.; De Angelis, G.; Prete, G.; Collazuol, G.; Laveder, M.; Mazzocco, M.; Mezzetto, M.; Signorini, C.; Vardaci, E.; Di Nitto, A.; Brondi, A.; La Rana, G.; Migliozzi, P.; Moro, R.; Palladino, V.; Gelli, N.; Berkovits, D.; Hass, M.; Hirsh, T. Y.; Schaumann, M.; Stahl, A.; Wehner, J.; Bross, A.; Kopp, J.; Neuffer, D.; Wands, R.; Bayes, R.; Laing, A.; Soler, P.; Agarwalla, S. K.; Cervera Villanueva, A.; Donini, A.; Ghosh, T.; Gómez Cadenas, J. J.; Hernández, P.; Martín-Albo, J.; Mena, O.; Burguet-Castell, J.; Agostino, L.; Buizza-Avanzini, M.; Marafini, M.; Patzak, T.; Tonazzo, A.; Duchesneau, D.; Mosca, L.; Bogomilov, M.; Karadzhov, Y.; Matev, R.; Tsenov, R.; Akhmedov, E.; Blennow, M.; Lindner, M.; Schwetz, T.; Fernández Martinez, E.; Maltoni, M.; Menéndez, J.; Giunti, C.; González García, M. C.; Salvado, J.; Coloma, P.; Huber, P.; Li, T.; López Pavón, J.; Orme, C.; Pascoli, S.; Meloni, D.; Tang, J.; Winter, W.; Ohlsson, T.; Zhang, H.; Scotto-Lavina, L.; Terranova, F.; Bonesini, M.; Tortora, L.; Alekou, A.; Aslaninejad, M.; Bontoiu, C.; Kurup, A.; Jenner, L. J.; Long, K.; Pasternak, J.; Pozimski, J.; Back, J. J.; Harrison, P.; Beard, K.; Bogacz, A.; Berg, J. S.; Stratakis, D.; Witte, H.; Snopok, P.; Bliss, N.; Cordwell, M.; Moss, A.; Pattalwar, S.; Apollonio, M.

    2013-02-01

    The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fr\\'ejus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of {\\mu}+ and {\\mu}- beams in a storage ring. The far detector in this case is a 100 kt Magnetised Iron Neutrino Detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular 6He and 18Ne, also stored in a ring. The far detector is also the MEMPHYS detector in the Fr\\'ejus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of CP violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive.

  9. Bubble Formation at a Submerged Orifice in High-Speed Horizontal Oscillation

    Science.gov (United States)

    Wang, Ningzhen; Chen, Xiang; Yuan, Jianyu; Wang, Guiquan; Li, Yanxiang; Zhang, Huawei; Liu, Yuan

    2016-12-01

    Reducing the cell size of aluminum foams is always a hot and difficult topic in the fabrication of aluminum foams by gas injection route. There lacks theoretical guidance for the bubble size reduction when foaming by the dynamic gas injection method. For the convenience of observation, the aqueous bubbles from small-sized orifice in the high-speed horizontal oscillation were investigated in this paper. A bubble formation and detachment model in the high-speed horizontal oscillation system was proposed. The high-speed system with horizontal simple harmonic oscillation could reduce the average bubble size of aqueous foam effectively. The regularity of bubble formation and the influence of experimental parameters on average bubble size can be predicted by the theoretical model, and the experimental results agree well with the theoretical calculation. The results have shown that bubbles generally detach from the orifice at deceleration periods of the simple harmonic oscillation, and there exist several fixed sizes of bubbles with the fixed experimental parameters due to the effects of periodic forces. The average bubble size decreases with the increase of oscillation frequency and amplitude, and it roughly increases with the increase of gas flow rate. Using the high-speed horizontal oscillation method to prepare aluminum foams, the cell size can be reduced to about 1 mm. Moreover, the cell sizes of aluminum foam can be well predicted by this theoretical model.

  10. Stiffness of sphere–plate contacts at MHz frequencies: dependence on normal load, oscillation amplitude, and ambient medium

    Directory of Open Access Journals (Sweden)

    Jana Vlachová

    2015-03-01

    Full Text Available The stiffness of micron-sized sphere–plate contacts was studied by employing high frequency, tangential excitation of variable amplitude (0–20 nm. The contacts were established between glass spheres and the surface of a quartz crystal microbalance (QCM, where the resonator surface had been coated with either sputtered SiO2 or a spin-cast layer of poly(methyl methacrylate (PMMA. The results from experiments undertaken in the dry state and in water are compared. Building on the shifts in the resonance frequency and resonance bandwidth, the instrument determines the real and the imaginary part of the contact stiffness, where the imaginary part quantifies dissipative processes. The method is closely analogous to related procedures in AFM-based metrology. The real part of the contact stiffness as a function of normal load can be fitted with the Johnson–Kendall–Roberts (JKR model. The contact stiffness was found to increase in the presence of liquid water. This finding is tentatively explained by the rocking motion of the spheres, which couples to a squeeze flow of the water close to the contact. The loss tangent of the contact stiffness is on the order of 0.1, where the energy losses are associated with interfacial processes. At high amplitudes partial slip was found to occur. The apparent contact stiffness at large amplitude depends linearly on the amplitude, as predicted by the Cattaneo–Mindlin model. This finding is remarkable insofar, as the Cattaneo–Mindlin model assumes Coulomb friction inside the sliding region. Coulomb friction is typically viewed as a macroscopic concept, related to surface roughness. An alternative model (formulated by Savkoor, which assumes a constant frictional stress in the sliding zone independent of the normal pressure, is inconsistent with the experimental data. The apparent friction coefficients slightly increase with normal force, which can be explained by nanoroughness. In other words, contact splitting

  11. High-Order Energy Balance Method to Nonlinear Oscillators

    Directory of Open Access Journals (Sweden)

    Seher Durmaz

    2012-01-01

    Full Text Available Energy balance method (EBM is extended for high-order nonlinear oscillators. To illustrate the effectiveness of the method, a cubic-quintic Duffing oscillator was chosen. The maximum relative errors of the frequencies of the oscillator read 1.25% and 0.6% for the first- and second-order approximation, respectively. The third-order approximation has an accuracy as high as 0.008%. Excellent agreement of the approximated frequencies and periodic solutions with the exact ones is demonstrated for several values of parameters of the oscillator.

  12. The active-bridge oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Wessendorf, K.O.

    1998-07-01

    This paper describes the Active-Bridge Oscillator (ABO), a new concept in high-stability oscillator design. The ABO is ab ridge-type oscillator design that is easly to design and overcomes many of the operational and design difficulties associated with standard bridge oscillator designs. The ABO will oscillate with a very stable output amplitude over a wide range of operating conditions without the use of an automatic-level-control (ALC). A standard bridge oscillator design requires an ALC to maintain the desired amplitude of oscillation. for this and other reasons, bridge oscilaltors are not used in mainstream designs. Bridge oscillators are generally relegated to relatively low-volume, high-performance applications. The Colpitts and Pierce designs are the most popular oscillators but are typically less stable than a bridge-type oscillator.

  13. High intensity neutrino oscillation facilities in Europe

    Directory of Open Access Journals (Sweden)

    T. R. Edgecock

    2013-02-01

    Full Text Available The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fréjus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of μ^{+} and μ^{-} beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular ^{6}He and ^{18}Ne, also stored in a ring. The far detector is also the MEMPHYS detector in the Fréjus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of CP violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive.

  14. Noninvasive respiratory support of juvenile rabbits by high-amplitude bubble continuous positive airway pressure.

    Science.gov (United States)

    Diblasi, Robert M; Zignego, Jay C; Tang, Dennis M; Hildebrandt, Jack; Smith, Charles V; Hansen, Thomas N; Richardson, C Peter

    2010-06-01

    Bubble continuous positive airway pressure (B-CPAP) applies small-amplitude, high-frequency oscillations in airway pressure (DeltaPaw) that may improve gas exchange in infants with respiratory disease. We developed a device, high-amplitude B-CPAP (HAB-CPAP), which provides greater DeltaPaw than B-CPAP provides. We studied the effects of different operational parameters on DeltaPaw and volumes of gas delivered to a mechanical infant lung model. In vivo studies tested the hypothesis that HAB-CPAP provides noninvasive respiratory support greater than that provided by B-CPAP. Lavaged juvenile rabbits were stabilized on ventilator nasal CPAP. The animals were then supported at the same mean airway pressure, bias flow, and fraction of inspired oxygen (FiO2) required for stabilization, whereas the bubbler angle was varied in a randomized crossover design at exit angles, relative to vertical, of 0 (HAB-CPAP0; equivalent to conventional B-CPAP), 90 (HAB-CPAP90), and 135 degrees (HAB-CPAP135). Arterial blood gases and pressure-rate product (PRP) were measured after 15 min at each bubbler angle. Pao2 levels were higher (p<0.007) with HAB-CPAP135 than with conventional B-CPAP. PaCO2 levels did not differ (p=0.073) among the three bubbler configurations. PRP with HAB-CPAP135 were half of the PRP with HAB-CPAP0 or HAB-CPAP90 (p=0.001). These results indicate that HAB-CPAP135 provides greater respiratory support than conventional B-CPAP does.

  15. Application of modern time series analysis to high stability oscillators

    Science.gov (United States)

    Farrell, B. F.; Mattison, W. M.; Vessot, R. F. C.

    1980-01-01

    Techniques of modern time series analysis useful for investigating the characteristics of high-stability oscillators and identifying systematic perturbations are discussed with reference to an experiment in which the frequencies of superconducting cavity-stabilized oscillators and hydrogen masers were compared. The techniques examined include transformation to stationarity, autocorrelation and cross-correlation, superresolution, and transfer function determination.

  16. Observable $N-\\bar{N}$ oscillation, high-scale see-saw and origin of matter

    Indian Academy of Sciences (India)

    R N Mohapatra

    2006-11-01

    See-saw mechanism has been a dominant paradigm in the discussion of neutrino masses. We discuss how this idea can be tested via a baryon number violating process such as $N-\\bar{N}$ oscillation. Since the expected see-saw scale is high and the $N-\\bar{N}$ amplitude goes like $M_{R}^{-5}$, one might think that this process is not observable in realistic see-saw models for neutrino masses. In this talk I show that in supersymmetric models, the above conclusion is circumvented leading to an enhanced and observable rate for $N-\\bar{N}$ oscillation. I also discuss a new mechanism for baryogenesis in generic models for neutron-anti-neutron oscillation.

  17. Periodic Solutions for Highly Nonlinear Oscillation Systems

    DEFF Research Database (Denmark)

    Ghadimi, M; Barari, Amin; Kaliji, H.D

    2012-01-01

    In this paper, Frequency-Amplitude Formulation is used to analyze the periodic behavior of tapered beam as well as two complex nonlinear systems. Many engineering structures, such as offshore foundations, oil platform supports, tower structures and moving arms, are modeled as tapered beams...

  18. High amplitude phase resetting in rev-erbalpha/per1 double mutant mice.

    Directory of Open Access Journals (Sweden)

    Corinne Jud

    Full Text Available Over time, organisms developed various strategies to adapt to their environment. Circadian clocks are thought to have evolved to adjust to the predictable rhythms of the light-dark cycle caused by the rotation of the Earth around its own axis. The rhythms these clocks generate persist even in the absence of environmental cues with a period of about 24 hours. To tick in time, they continuously synchronize themselves to the prevailing photoperiod by appropriate phase shifts. In this study, we disrupted two molecular components of the mammalian circadian oscillator, Rev-Erbalpha and Period1 (Per1. We found that mice lacking these genes displayed robust circadian rhythms with significantly shorter periods under constant darkness conditions. Strikingly, they showed high amplitude resetting in response to a brief light pulse at the end of their subjective night phase, which is rare in mammals. Surprisingly, Cry1, a clock component not inducible by light in mammals, became slightly inducible in these mice. Taken together, Rev-Erbalpha and Per1 may be part of a mechanism preventing drastic phase shifts in mammals.

  19. Research on High Frequency Amplitude Attenuation of Electric Fast Transient Generator

    Directory of Open Access Journals (Sweden)

    Huafu Zhang

    2013-01-01

    Full Text Available In order to solve the amplitude attenuation of electric fast transient (EFT generator operating in high frequency, the charging and discharging process of energy storage capacitor in EFT generator are analyzed, the main circuit voltage variation mathematical model is established, the parameters of main loop circuit and the parameters of switch driving waveform which affect burst amplitude are discussed. Through the simulation, this paper puts forward effective methods to overcome burst amplitude attenuation in high frequency. The simulation results show that when the frequency is low, the duty ratio of drive signal have little effect on energy storage capacitor voltage amplitude attenuation. when the charging resistance is less than 500 Ω, the duty ratio of drive signal is less than 0.125, the repetition frequency of burst reaches 1.2 MHz, the amplitude attenuation of energy storage capacitor voltage is less than 9%, the amplitude of burst satisfies IEC61000-4-4 standards.

  20. Ictal high frequency oscillations distinguish two types of seizure territories in humans.

    Science.gov (United States)

    Weiss, Shennan A; Banks, Garrett P; McKhann, Guy M; Goodman, Robert R; Emerson, Ronald G; Trevelyan, Andrew J; Schevon, Catherine A

    2013-12-01

    High frequency oscillations have been proposed as a clinically useful biomarker of seizure generating sites. We used a unique set of human microelectrode array recordings (four patients, 10 seizures), in which propagating seizure wavefronts could be readily identified, to investigate the basis of ictal high frequency activity at the cortical (subdural) surface. Sustained, repetitive transient increases in high gamma (80-150 Hz) amplitude, phase-locked to the low-frequency (1-25 Hz) ictal rhythm, correlated with strong multi-unit firing bursts synchronized across the core territory of the seizure. These repetitive high frequency oscillations were seen in recordings from subdural electrodes adjacent to the microelectrode array several seconds after seizure onset, following ictal wavefront passage. Conversely, microelectrode recordings demonstrating only low-level, heterogeneous neural firing correlated with a lack of high frequency oscillations in adjacent subdural recording sites, despite the presence of a strong low-frequency signature. Previously, we reported that this pattern indicates a failure of the seizure to invade the area, because of a feedforward inhibitory veto mechanism. Because multi-unit firing rate and high gamma amplitude are closely related, high frequency oscillations can be used as a surrogate marker to distinguish the core seizure territory from the surrounding penumbra. We developed an efficient measure to detect delayed-onset, sustained ictal high frequency oscillations based on cross-frequency coupling between high gamma amplitude and the low-frequency (1-25 Hz) ictal rhythm. When applied to the broader subdural recording, this measure consistently predicted the timing or failure of ictal invasion, and revealed a surprisingly small and slowly spreading seizure core surrounded by a far larger penumbral territory. Our findings thus establish an underlying neural mechanism for delayed-onset, sustained ictal high frequency oscillations, and

  1. DESIGN NOTE: A fast high-voltage pulse generator with variable amplitude and duration

    Science.gov (United States)

    Upadhyay, Jankee; Navathe, C. P.

    2006-07-01

    A high-voltage pulse generator based on a self-matched transmission line with variable pulse amplitude and duration is developed. Two avalanche transistor stacks are used as switches. The pulse width is varied by adjusting the delay in triggering two switches whereas amplitude is adjusted by adjusting load resistance. A pulse with amplitude of 800 V to 3.8 kV and width of 5 ns to 38 ns can be obtained using this circuit.

  2. High-Order Energy Balance Method to Nonlinear Oscillators

    OpenAIRE

    Seher Durmaz; Metin Orhan Kaya

    2012-01-01

    Energy balance method (EBM) is extended for high-order nonlinear oscillators. To illustrate the effectiveness of the method, a cubic-quintic Duffing oscillator was chosen. The maximum relative errors of the frequencies of the oscillator read 1.25% and 0.6% for the first- and second-order approximation, respectively. The third-order approximation has an accuracy as high as 0.008%. Excellent agreement of the approximated frequencies and periodic solutions with the exact ones is demonstrated fo...

  3. High Power Room Temperature Terahertz Local Oscillator Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build a high-power, room temperature compact continuous wave terahertz local oscillator for driving heterodyne receivers in the 1-5 THz frequency...

  4. High-frequency Oscillations in Eyewalls of Tropical Cyclones

    Science.gov (United States)

    Li, Weibiao; Chen, Shumin

    2017-04-01

    High-frequency oscillations, with periods of about 2 hours, are first identified by applying wavelet analysis to observed minutely wind speeds around the eye and eyewall of tropical cyclones (TCs). Analysis of a model simulation of Typhoon Hagupit (2008) shows that the oscillations also occur in the intensity of TC, vertical motion, convergence activity and air density around the eyewall. Sequences of oscillations in these variables follow a certain order. In a typical cycle, the drop of density in the planetary boundary layer (PBL) is followed by an increase in the inward radial wind; this enhanced frictional convergence causes increase in density, followed by a decrease in the inward radial wind. The increase in convergence in the PBL causes increase of updraft at the top of the PBL, followed by high vertical velocity at high altitude of 8-10 km, then the increase of the maximum wind speed, and vice versa. Key words: tropical cyclone, high-frequency oscillations, eyewall, intensity

  5. SPoC: a novel framework for relating the amplitude of neuronal oscillations to behaviorally relevant parameters.

    Science.gov (United States)

    Dähne, Sven; Meinecke, Frank C; Haufe, Stefan; Höhne, Johannes; Tangermann, Michael; Müller, Klaus-Robert; Nikulin, Vadim V

    2014-02-01

    Previously, modulations in power of neuronal oscillations have been functionally linked to sensory, motor and cognitive operations. Such links are commonly established by relating the power modulations to specific target variables such as reaction times or task ratings. Consequently, the resulting spatio-spectral representation is subjected to neurophysiological interpretation. As an alternative, independent component analysis (ICA) or alternative decomposition methods can be applied and the power of the components may be related to the target variable. In this paper we show that these standard approaches are suboptimal as the first does not take into account the superposition of many sources due to volume conduction, while the second is unable to exploit available information about the target variable. To improve upon these approaches we introduce a novel (supervised) source separation framework called Source Power Comodulation (SPoC). SPoC makes use of the target variable in the decomposition process in order to give preference to components whose power comodulates with the target variable. We present two algorithms that implement the SPoC approach. Using simulations with a realistic head model, we show that the SPoC algorithms are able extract neuronal components exhibiting high correlation of power with the target variable. In this task, the SPoC algorithms outperform other commonly used techniques that are based on the sensor data or ICA approaches. Furthermore, using real electroencephalography (EEG) recordings during an auditory steady state paradigm, we demonstrate the utility of the SPoC algorithms by extracting neuronal components exhibiting high correlation of power with the intensity of the auditory input. Taking into account the results of the simulations and real EEG recordings, we conclude that SPoC represents an adequate approach for the optimal extraction of neuronal components showing coupling of power with continuously changing behaviorally

  6. Periodic mass loss episodes due to an oscillation mode with variable amplitude in the hot supergiant HD50064

    CERN Document Server

    Aerts, C; Baglin, A; Degroote, P; Oreiro, R; Vuckovic, M; Smolders, K; Acke, B; Verhoelst, T; Desmet, M; Godart, M; Noels, A; Dupret, M -A; Auvergne, M; Baudin, F; Catala, C; Michel, E; Samadi, R

    2010-01-01

    We aim to interpret the photometric and spectroscopic variability of the luminous blue variable supergiant HD\\,50064 ($V=8.21$).CoRoT space photometry and follow-up high-resolution spectroscopy, with a time base of 137\\,d and 169\\,d, respectively, was gathered, analysed and interpreted using standard time series analysis and light curve modelling methods as well as spectral line diagnostics.The space photometry reveals one period of 37\\,d, which undergoes a sudden amplitude change with a factor 1.6. The pulsation period is confirmed in the spectroscopy, which additionally reveals metal line radial velocity values differing by $\\sim 30\\,$km\\,s$^{-1}$ depending on the spectral line and on the epoch. We estimate \\teff$\\sim$13\\,500\\,K, \\logg$\\sim$1.5 from the equivalent width of Si lines. The Balmer lines reveal that the star undergoes episodes of changing mass loss on a time scale similar to the changes in the photometric and spectroscopic variability, with an average value of $\\log\\dot{\\rm M}\\simeq-5$ (in M$_\\o...

  7. The dynamics of high-frequency DC RSQUID oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Pegrum, C M [Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)], E-mail: colin@phys.strath.ac.uk

    2009-06-15

    Josephson circuit simulation software has been used to study the properties of a range of two-junction DC RSQUIDs configured as current-controlled heterodyne oscillators. We find that, if the loop inductance is small, their current-voltage curves are modified substantially due to self-induced Shapiro steps. When the heterodyne frequency is comparable with the Josephson frequency of the junctions the step amplitude becomes very large and additional features are seen, including sub-harmonic steps and step tails. We point out that conventional DC RSQUIDs generally have too large a loop inductance for some of these effects to be seen in the I-V curves, and we suggest that nanofabrication techniques could be used to make novel low-inductance RSQUIDs. We have also demonstrated that by applying a sinusoidally varying RF flux to a DC RSQUID it is possible to phase-modulate the heterodyne oscillation, which could have useful practical applications.

  8. Brh V128 is a Double-Mode High-Amplitude delta Scuti Star

    Science.gov (United States)

    Bernhard, K.; Pejcha, O.; Proksch, W.; Quester, W.; van Cauteren, P.; Wils, P.

    2004-08-01

    CCD-V and unfiltered photometric data show that Brh V128 = GSC 1893-89 is a new high-amplitude double-mode Delta Scuti variable with a fundamental period of 0.1534 days and a period ratio of 0.767. The amplitude of the first overtone pulsation is slightly larger than that of the fundamental mode.

  9. Protostring scattering amplitudes

    Science.gov (United States)

    Thorn, Charles B.

    2016-11-01

    We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.

  10. Degraded Frequency-Tuning Range and Oscillation Amplitude of LC-VCOs due to the Nonquasi-Static Effect in MOS Varactors

    Science.gov (United States)

    Miyake, Masataka; Hori, Daisuke; Sadachika, Norio; Feldmann, Uwe; Miura-Mattausch, Mitiko; Mattausch, Hans Jürgen; Ohguro, Tatsuya; Iizuka, Takahiro; Taguchi, Masahiko; Miyamoto, Shunsuke

    Frequency dependent properties of accumulation-mode MOS varactors, which are key elements in many RF circuits, are dominated by Non-Quasi-Static (NQS) effects in the carrier transport. The circuit performances containing MOS varactors can hardly be reproduced without considering the NQS effect in MOS-varactor models. For the LC-VCO circuit as an example it is verified that frequency-tuning range and oscillation amplitude can be overestimated by over 20% and more than a factor 2, respectively, without inclusion of the NQS effect.

  11. High-frequency capillary waves excited by oscillating microbubbles

    CERN Document Server

    Pommella, Angelo; Poulichet, Vincent; Garbin, Valeria

    2013-01-01

    This fluid dynamics video shows high-frequency capillary waves excited by the volumetric oscillations of microbubbles near a free surface. The frequency of the capillary waves is controlled by the oscillation frequency of the microbubbles, which are driven by an ultrasound field. Radial capillary waves produced by single bubbles and interference patterns generated by the superposition of capillary waves from multiple bubbles are shown.

  12. Off-shell helicity amplitudes in high-energy factorization

    CERN Document Server

    van Hameren, Andreas; Kutak, Krzysztof

    2013-01-01

    In the Catani-Ciafaloni-Hautmann high-energy factorization approach a cross section is expressed as a convolution of unintegrated gluon densities and a gauge-invariant hard process, in which two incoming gluons are off-shell with momenta satisfying certain high-energy kinematics. We present two methods of evaluating the tree-level hard process with multiple final states. The first one assumes that only one of the gluons is off-shell and relies on the Slavnov-Taylor identities. Such asymmetric configuration of incoming gluons is phenomenologically important in small x probing by forward processes. The second method deals also with two off-shell gluons and is based on the analytic continuation of the off-shell gluons momenta to the complex space. The methods were implemented into Monte Carlo computer programs and used in phenomenological applications. The results of both methods are straightforwardly related to Lipatov's effective vertices in quasi-multi-regge kinematics.

  13. High extinction amplitude modulation in ultrashort pulse shaping

    CERN Document Server

    Lin, Yen-Wei

    2016-01-01

    We explored the issues related to the resolution and the modulation extinction when filtering the spectrum of a UV femtosecond laser with a standard ultrashort pulse shaper. We have learned that a higher pulse shaping resolution often requires a larger working beam size or a higher density grating for greater dispersion. However, these approaches also introduce more optical errors and degrade the extinction. In this work, we examined specifics of each component to determine the best configuration of our spectral filtering setup. As a proof-of-concept demonstration, we utilized elements available as standard products and achieved 100 GHz filtering resolution with high extinction at the UV-A wavelength, which is superb in this wavelength range. The high extinction spectral filtering is especially important while modifying a broadband laser for the optical control of molecule's internal state.

  14. Freeform high-speed large-amplitude deformable Piezo Mirrors

    CERN Document Server

    Wapler, Matthias C; Wallrabe, Ulrike

    2013-01-01

    We present a new type of tunable mirror with sharply-featured freeform displacement profiles, large displacements of several 100\\mu m and high operating frequencies close to the kHz range at 15mm diameter. The actuation principle is based on a recently explored "topological" displacement mode of piezo sheets. The prototypes presented here include a rotationally symmetric axicon, a hyperbolic sech-icon and a non-symmetric pyram-icon and are scalable to smaller dimensions. The fabrication process is economic and cleanroom-free, and the optical quality is sufficient to demonstrate the diffraction patterns of the optical elements.

  15. Low frequency modulation of transionospheric radio wave amplitude at low-latitudes: possible role of field line oscillations

    Directory of Open Access Journals (Sweden)

    A. K. Sinha

    Full Text Available Ionospheric scintillations of radio waves at low-latitudes are associated with electron density irregularities. These irregularities are field-aligned and can provide excitation energy all along the field line to non-local field-aligned oscillations, such as the local field line oscillations. Eigen-periods of toroidal field line oscillations at low-latitudes, computed by using the dipole magnetic field and ion distributions obtained from the International Reference Ionosphere (IRI for typical nighttime conditions, fall in the range of 20–25 s. When subjected to spectral analysis, signal strength of the radio waves recorded on the 250 MHz beacon at Pondicherry (4.5° N dip, Mumbai (13.4° N dip and Ujjain (18.6° N dip exhibit periodicities in the same range. For the single event for which simultaneous ground magnetic data were available, the geomagnetic field also oscillated at the same periodicity. The systematic presence of a significant peak in the 20–25 s range during periods of strong radio wave scintillations, and its absence otherwise suggests the possibility that field line oscillations are endogenously excited by the irregularities, and the oscillations associated with the excited field line generate the modulation characteristics of the radio waves received on the ground. The frequency of modulation is found to be much lower than the characteristic frequencies that define the main body of scintillations, and they probably correspond to scales that are much larger than the typical Fresnel scale. It is possible that the refractive mechanism associated with larger scale long-lived irregularities could be responsible for the observed phenomenon. Results of a preliminary numerical experiment that uses a sinusoidal phase irregularity in the ionosphere as a refracting media are presented. The results show that phase variations which are large enough to produce a focal plane close to the ground can reproduce features that are not

  16. Torsional oscillations of neutron stars with highly tangled magnetic fields

    CERN Document Server

    Sotani, Hajime

    2015-01-01

    To determine the frequencies of magnetic oscillations in the neutron stars with highly tangled magnetic fields, we derive the perturbation equations. We assume that the field strength of the global magnetic structure is so small that such fields are negligible compared with the tangled fields, which may still be far from a realistic configuration. Then, we systematically examine the spectra of the magnetic oscillations, as varying the magnetic field strength and stellar mass. The frequencies without crust elasticity are completely proportional to the strength of magnetic field, whose proportionality constant depends strongly on the stellar mass. On the other hand, the oscillation spectra with crust elasticity become more complicated, where the frequencies even for weak magnetic fields are different from the crustal torsional oscillations without magnetic fields. For discussing the spectra, the critical field strength can play an important role, which is determined in such a way that the shear velocity is equi...

  17. High-Energy String Scattering Amplitudes and Signless Stirling Number Identity

    Directory of Open Access Journals (Sweden)

    Jen-Chi Lee

    2012-07-01

    Full Text Available We give a complete proof of a set of identities (7 proposed recently from calculation of high-energy string scattering amplitudes. These identities allow one to extract ratios among high-energy string scattering amplitudes in the fixed angle regime from high-energy amplitudes in the Regge regime. The proof is based on a signless Stirling number identity in combinatorial theory. The results are valid for arbitrary real values L rather than only for L=0,1 proved previously. The identities for non-integer real value L were recently shown to be realized in high-energy compactified string scattering amplitudes [He S., Lee J.C., Yang Y., arXiv:1012.3158]. The parameter L is related to the mass level of an excited string state and can take non-integer values for Kaluza-Klein modes.

  18. Amplitude limits and nonlinear damping of shear-Alfvén waves in high-beta low-collisionality plasmas

    Science.gov (United States)

    Squire, J.; Schekochihin, A. A.; Quataert, E.

    2017-05-01

    This work, which extends Squire et al (Astrophys. J. Lett. 2016 830 L25), explores the effect of self-generated pressure anisotropy on linearly polarized shear-Alfvén fluctuations in low-collisionality plasmas. Such anisotropies lead to stringent limits on the amplitude of magnetic perturbations in high-β plasmas, above which a fluctuation can destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, ‘interrupting’ the wave and stopping its oscillation. These effects are explored in detail in the collisionless and weakly collisional ‘Braginskii’ regime, for both standing and traveling waves. The focus is on simplified models in one dimension, on scales much larger than the ion gyroradius. The effect has interesting implications for the physics of magnetized turbulence in the high-β conditions that are prevalent in many astrophysical plasmas.

  19. Rapid high-amplitude circumferential slow wave propagation during normal gastric pacemaking and dysrhythmias.

    Science.gov (United States)

    O'Grady, G; Du, P; Paskaranandavadivel, N; Angeli, T R; Lammers, W J E P; Asirvatham, S J; Windsor, J A; Farrugia, G; Pullan, A J; Cheng, L K

    2012-07-01

    Gastric slow waves propagate aborally as rings of excitation. Circumferential propagation does not normally occur, except at the pacemaker region. We hypothesized that (i) the unexplained high-velocity, high-amplitude activity associated with the pacemaker region is a consequence of circumferential propagation; (ii) rapid, high-amplitude circumferential propagation emerges during gastric dysrhythmias; (iii) the driving network conductance might switch between interstitial cells of Cajal myenteric plexus (ICC-MP) and circular interstitial cells of Cajal intramuscular (ICC-IM) during circumferential propagation; and (iv) extracellular amplitudes and velocities are correlated. An experimental-theoretical study was performed. High-resolution gastric mapping was performed in pigs during normal activation, pacing, and dysrhythmia. Activation profiles, velocities, and amplitudes were quantified. ICC pathways were theoretically evaluated in a bidomain model. Extracellular potentials were modeled as a function of membrane potentials. High-velocity, high-amplitude activation was only recorded in the pacemaker region when circumferential conduction occurred. Circumferential propagation accompanied dysrhythmia in 8/8 experiments was faster than longitudinal propagation (8.9 vs 6.9 mm s(-1) ; P = 0.004) and of higher amplitude (739 vs 528 μV; P = 0.007). Simulations predicted that ICC-MP could be the driving network during longitudinal propagation, whereas during ectopic pacemaking, ICC-IM could outpace and activate ICC-MP in the circumferential axis. Experimental and modeling data demonstrated a linear relationship between velocities and amplitudes (P propagation. Rapid circumferential propagation also emerges during a range of gastric dysrhythmias, elevating extracellular amplitudes and organizing transverse wavefronts. One possible explanation for these findings is bidirectional coupling between ICC-MP and circular ICC-IM networks. © 2012 Blackwell Publishing Ltd.

  20. High Reliability Oscillators for Terahertz Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To develop reliable THz sources with high power and high DC-RF efficiency, Virginia Diodes, Inc. will develop a thorough understanding of the complex interactions...

  1. VizieR Online Data Catalog: VVV high amplitude NIR variable stars (Contreras Pena+, 2017)

    Science.gov (United States)

    Contreras Pena, C.; Lucas, P. W.; Minniti, D.; Kurtev, R.; Stimson, W.; Navarro Molina, C.; Borissova, J.; Kumar, M. S. N.; Thompson, M. A.; Gledhill, T.; Terzi, R.; Froebrich, D.; Caratti o Garatti, A.

    2017-08-01

    We present the single epoch ZYJHKs photometry obtained from VVV catalogues for 816 high-amplitude variables. We also present the amplitude of the Ks light curve of the objects derived from 2010-2015 photometry. For each object we also provide a provisional classification derived from the shape of the light curve. For objects found to be likely associated with SFRs we present an spectral index derived from the object's spectral energy distribution. (2 data files).

  2. Kepler observations of the high-amplitude δ Scuti star V2367 Cyg

    DEFF Research Database (Denmark)

    Balona, L. A.; Lenz, P.; Antoci, V.

    2012-01-01

    We analyse Kepler observations of the high-amplitude δ Scuti (HADS) star V2367 Cyg (KIC 9408694). The variations are dominated by a mode with frequency f1= 5.6611 d−1. Two other independent modes with f2= 7.1490 d−1 and f3= 7.7756 d−1 have amplitudes an order of magnitude smaller than f1. Nearly ...

  3. Development of high-voltage pulse generator with variable amplitude and duration

    Science.gov (United States)

    Upadhyay, J.; Sharma, M. L.; Ahuja, Aakash B.; Navathe, C. P.

    2014-06-01

    A high voltage pulse generator with variable amplitude (100-3000 V) and duration (100-2000 μs) has been designed and developed. The variable duration pulse has been generated by adopting a simple and novel technique of varying the turn off delay time of a high voltage Metal Oxide Semiconductor Field Effect Transistor (MOSFET) based switch by varying external gate resistance. The pulse amplitude is made variable by adjusting biasing supply of the high voltage switch. The high voltage switch has been developed using a MOSFET based stack of 3 kV rating with switching time of 7 ns.

  4. Hilbert spectrum and intrinsic oscillation mode of dynamic response of a bilinear SDOF system: influence of harmonic excitation amplitude

    Institute of Scientific and Technical Information of China (English)

    Zhang Yushan; Liang Jianwen; Hu Yuxian

    2005-01-01

    Under harmonic wave excitation, the dynamic response of a bilinear SDOF system can be expressed by the Hilbert spectrum. The Hilbert spectrum can be formulated by (1) the inter-wave combination mechanism between the steady response and the transient response when the system behaves linearly, or (2) the intra-wave modulation mechanism embedded in one intrinsic mode function (IMF) component when the system behaves nonlinearly. The temporal variation of the instantaneous frequency of the IMF component is consistent with the system nonlinear behavior of yielding and unloading. As a thorough study of this fundamental structural dynamics problem, this article investigates the influence of the amplitude of the harmonic wave excitation on the Hilbert spectrum and the intrinsic oscillatory mode of the dynamic response of a bilinear SDOF system.

  5. Coordinated ground-based and Cluster observations of large amplitude global magnetospheric oscillations during a fast solar wind speed interval

    Directory of Open Access Journals (Sweden)

    I. R. Mann

    Full Text Available We present magnetospheric observations of very large amplitude global scale ULF waves, from 9 and 10 December 2000 when the upstream solar wind speed exceeded 600 km/s. We characterise these ULF waves using ground-based magnetometer, radar and optical instrumentation on both the dawn and dusk flanks; we find evidence to support the hypothesis that discrete frequency field line resonances (FLRs were being driven by magnetospheric waveguide modes. During the early part of this interval, Cluster was on an outbound pass from the northern dusk side magnetospheric lobe into the magnetosheath, local-time conjugate to the Canadian sector. In situ magnetic fluctuations, observed by Cluster FGM, show evidence of quasi-periodic motion of the magnetosheath boundary layer with the same period as the ULF waves seen on the ground. Our observations represent the first simultaneous magnetometer, radar and optical observations of the characteristics of FLRs, and confirm the potential importance of ULF waves for magnetosphere-ionosphere coupling, particularly via the generation and modulation of electron precipitation into the ionosphere. The in situ Cluster measurements support the hypothesis that, during intervals of fast solar wind speed, the Kelvin-Helmholtz instability (KHI can excite magnetospheric waveguide modes which bathe the flank magnetosphere with discrete frequency ULF wave power and drive large amplitude FLRs. 

    Paper submitted to the special issue devoted to "Cluster: First scientific results", Ann. Geophysicae, 19, 10/11/12, 2001.

    Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; MHD waves and instabilities; solar wind-magnetosphere interactions

  6. Very High Frequency Interleaved Self-Oscillating Resonant SEPIC Converter

    DEFF Research Database (Denmark)

    Kovacevic, Milovan; Knott, Arnold; Andersen, Michael A. E.

    2013-01-01

    This paper describes analysis and design procedure of an interleaved, self-oscillating resonant SEPIC converter, suitable for operation at very high frequencies (VHF) ranging from 30 MHz to 300 MHz. The presented circuit consists of two resonant SEPIC DC-DC converters, and a capacitive...

  7. High frequency pressure oscillator for microcryocoolers

    NARCIS (Netherlands)

    Vanapalli, Srinivas; ter Brake, Hermanus J.M.; Jansen, Henricus V.; Zhao, Yiping; Holland, Herman J.; Burger, Johannes Faas; Elwenspoek, Michael Curt

    2008-01-01

    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

  8. High frequency pressure oscillator for microcryocoolers

    NARCIS (Netherlands)

    Vanapalli, Srinivas; ter Brake, Hermanus J.M.; Jansen, Henricus V.; Zhao, Yiping; Holland, Herman J.; Burger, Johannes Faas; Elwenspoek, Michael Curt

    2008-01-01

    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 pre

  9. High frequency pressure oscillator for microcryocoolers

    NARCIS (Netherlands)

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

    2008-01-01

    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 pre

  10. Effects of high-frequency chest wall oscillation on pleural pressure and oscillated flow.

    Science.gov (United States)

    Zucker, Tal; Skjodt, Neil M; Jones, Richard L

    2008-01-01

    The effectiveness of high-frequency chest wall oscillation (HF-CWO) is directly related to the level of oscillated flow (osc) in the airways. We used the Vest system to investigate the effects of HFCWO on chest wall and pleural pressures and we correlated these pressures to the resultant osc. We also compared the latest HFCWO device with it predecessor. Different combinations of vest inflation pressure (background pressure) and oscillation frequency were randomly applied to 10 healthy volunteers. Chest wall pressure was determined using an air-filled bag under the vest and pleural pressure was estimated using an esophageal balloon. Reverse plethysmography was used to measure osc at the mouth and a spirometer was used to measure changes in end-expired lung volume. We found a significant correlation between chest wall and pleural pressure with approximately one-third of the chest wall pressure transmitted into the pleural space. Mean esophageal pressure remained negative at all background pressure/frequency combinations. There was a significant correlation (pHFCWO and since osc is dependent on esophageal pulse pressure, which in turn is dependent on chest wall pulse pressure, it follows that the effectiveness of HFCWO is influenced by the ability to generate an effective chest wall pulse pressure.

  11. Simple method for measuring vibration amplitude of high power airborne ultrasonic transducer: using thermo-couple.

    Science.gov (United States)

    Saffar, Saber; Abdullah, Amir

    2014-03-01

    Vibration amplitude of transducer's elements is the influential parameters in the performance of high power airborne ultrasonic transducers to control the optimum vibration without material yielding. The vibration amplitude of elements of provided high power airborne transducer was determined by measuring temperature of the provided high power airborne transducer transducer's elements. The results showed that simple thermocouples can be used both to measure the vibration amplitude of transducer's element and an indicator to power transmission to the air. To verify our approach, the power transmission to the air has been investigated by other common method experimentally. The experimental results displayed good agreement with presented approach. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Oscillations of a highly discrete breather with a critical regime

    Science.gov (United States)

    Coquet; Remoissenet; Dinda

    2000-10-01

    We analyze carefully the essential features of the dynamics of a stationary discrete breather in the ultimate degree of energy localization in a nonlinear Klein-Gordon lattice with an on-site double-well potential. We demonstrate the existence of three different regimes of oscillatory motion in the breather dynamics, which are closely related to the motion of the central particle in an effective potential having two nondegenerate wells. In given parameter regions, we observe an untrapped regime, in which the central particle executes large-amplitude oscillations from one to the other side of the potential barrier. In other parameter regions, we find the trapped regime, in which the central particle oscillates in one of the two wells of the effective potential. Between these two regimes we find a critical regime in which the central particle undergoes several temporary trappings within an untrapped regime. Importantly, our study reveals that in the presence of purely anharmonic coupling forces, the breather compactifies, i.e., the energy becomes abruptly localized within the breather.

  13. Amplitudes of solar-like oscillations in red-giant stars: Evidences for non-adiabatic effects using CoRoT observations

    CERN Document Server

    Samadi, R; Dupret, M -A; Ludwig, H -G; Baudin, F; Caffau, E; Goupil, M -J; Barban, C

    2012-01-01

    A growing number of solar-like oscillations has been detected in red-giant stars thanks to CoRoT and Kepler space-crafts. The seismic data gathered by CoRoT on red-giant stars allow us to test mode driving theory in different physical conditions than main-sequence stars. Using a set of 3D hydrodynamical models representative of the upper layers of sub- and red-giant stars, we compute the acoustic modes energy supply rate (Pmax). Assuming adiabatic pulsations and using global stellar models where the surface stratification comes from the 3D hydrodynamical models, mode amplitude is computed in terms of surface velocity. The latter is then converted into intensity fluctuations using either a simplified adiabatic scaling relation or a non-adiabatic one. Given L and M (the luminosity and mass respectively), the energy supply rate Pmax is found to scale as (L/M)^(2.6) for both main-sequence and red-giant stars, extending previous results by Samadi et al. (2007). The theoretical amplitudes in velocity under-estimate...

  14. Internal friction mechanism of Fe-19Mn alloy at low and high strain amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Shuke, E-mail: huangshuke@163.com [Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Huang, Wenrong; Liu, Jianhui [Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Teng, Jin; Li, Ning; Wen, Yuhua [School of Manufacturing Science and Engineering, Sichuan University, Chengdu, Sichuan 610065 (China)

    2013-01-10

    Fe-Mn damping alloy, which can decrease the vibrating and noise effectively, will be widely applied to household appliances, automobiles, industrial facilities, etc. In this paper, the internal friction mechanism of Fe-19Mn alloy at low strain amplitude (10{sup -5} range) and high strain amplitude (10{sup -4} range) was investigated. The internal friction was measured using multifunction internal friction equipment and reversal torsion pendulum. The microstructure was observed using scanning electron microscopy. The phase transformation temperatures were determined using differential scanning calorimetry. The results indicated that the internal friction of Fe-19Mn alloy after solution treating was related to strain amplitude. The internal friction mechanism was believed to the movements of four damping sources ({epsilon}-martensite variant boundaries, stacking fault boundaries in {epsilon}-martensite and {gamma}-austenite, {gamma}/{epsilon} interfaces), which could be explained using the interactive movements of Shockley partial dislocations and point defects. At low strain amplitude (10{sup -5} range), the bowing out movements of Shockley partial dislocations are the main moving mode of generating internal friction. At high strain amplitude (10{sup -4} range), however, the breaking away movements of Shockley partial dislocations are the high internal friction mechanism of Fe-19Mn alloy.

  15. Clinical Implications High Frequency Chest Wall Oscillation (HFCWO)

    OpenAIRE

    Mantellini E.; Perrero L.; Petrozzino S.; Gatta A.; Bona S.

    2012-01-01

    Purpose: patients with neuromuscular diseases presents an high incidence of respiratory infections favoured by stagnation of deep bronchial secretions and deficit of cough. The aim of the study is to evaluate the correct treatment of this condition and the role of High Frequency Chest Wall Oscillation (HFCWO) in helping the removal of bronchial secretions and reduce the incidence of infections in patients with neuromuscular disease.Methods: analysis of the current bibliography related to resp...

  16. High performance single-error-correcting quantum codes for amplitude damping

    CERN Document Server

    Shor, Peter W; Smolin, John A; Zeng, Bei

    2009-01-01

    We construct families of high performance quantum amplitude damping codes. All of our codes are nonadditive and most modestly outperform the best possible additive codes in terms of encoded dimension. One family is built from nonlinear error-correcting codes for classical asymmetric channels, with which we systematically construct quantum amplitude damping codes with parameters better than any prior construction known for any block length n > 7 except n=2^r-1. We generalize this construction to employ classical codes over GF(3) with which we numerically obtain better performing codes up to length 14. Because the resulting codes are of the codeword stabilized (CWS) type, easy encoding and decoding circuits are available.

  17. Multiband carrierless amplitude/phase modulation for ultra-wideband high data rate wireless communications

    DEFF Research Database (Denmark)

    Puerta Ramírez, Rafael; Rommel, Simon; Altabas, Jose A.

    2016-01-01

    We report on the first experimental demonstration of carrierless amplitude/phase modulation in a flexible multiband approach for ultrawideband high-data-rate wireless communications. An effective bitrate of 2 GB/s is achieved while complying with the restrictions on the effective radiated power e...

  18. In search of objective manometric criteria for colonic high-amplitude propagated pressure waves

    NARCIS (Netherlands)

    De Schryver, AMP; Samsom, M; Smout, AJPM

    2002-01-01

    The aims of this study were to explore all characteristics of high-amplitude propagated contractions (HAPCs) that would allow them to be distinguished from nonHAPC colonic pressure waves, and to develop computer algorithms for automated HAPC detection. Colonic manometry recordings obtained from 24 h

  19. Numerical modeling of dune progression in a high amplitude meandering channel

    Science.gov (United States)

    Laboratory experiments carried out by Abad and Garcia (2009) in a high-amplitude Kinoshita meandering channel show bed morphodynamics to comprise steady (local scour and deposition) and unsteady (migrating bedforms) components. The experiments are replicated with a numerical model. The sediment tran...

  20. Clinical Implications High Frequency Chest Wall Oscillation (HFCWO

    Directory of Open Access Journals (Sweden)

    Mantellini E.

    2012-01-01

    Full Text Available Purpose: patients with neuromuscular diseases presents an high incidence of respiratory infections favoured by stagnation of deep bronchial secretions and deficit of cough. The aim of the study is to evaluate the correct treatment of this condition and the role of High Frequency Chest Wall Oscillation (HFCWO in helping the removal of bronchial secretions and reduce the incidence of infections in patients with neuromuscular disease.Methods: analysis of the current bibliography related to respiratory infections and neuromuscular disease. PCEF (Peak Cough Expiratory Flow is used as a standardized indicator of efficiency of cough.Results: the High Frequency Chest Wall Oscillation (HFCWO is useful, in cases of increased production of mucus and impairment of muco-ciliary clearance, to remove the tracheobronchial secretions and reduce the incidence of infections.Conclusions: the correct approach to patients with neuromuscular disease and frequent respiratory infections is focused on treatment of cough ineffective and management of bronchial secretions. High Frequency Chest Wall Oscillation (HFCWO (VEST has a central role in treatment of cough ineffective and management of bronchial secretions reducing respiratory infections.

  1. Some comments on high precision study of neutrino oscillations

    Science.gov (United States)

    Bilenky, S. M.

    2015-07-01

    I discuss here some problems connected with the high precision study of neutrino oscillations. In the general case of n-neutrino mixing I derive a convenient expression for transition probability in which only independent terms (and mass-squared differences) enter. For three-neutrino mixing I discuss a problem of a definition of a large (atmospheric) neutrino mass-squared difference. I comment also possibilities to reveal the character of neutrino mass spectrum in future reactor neutrino experiments.

  2. High-Q cavity-induced synchronization in oscillator arrays

    DEFF Research Database (Denmark)

    Filatrella, Giovanni; Pedersen, Niels Falsig; Wiesenfeld, Kurt

    2000-01-01

    A model for a large number of Josephson junctions coupled to a cavity is presented. The system displays synchronization behavior very similar to that reported in recent experiments [P. Barbara ct al., Phys. Rev. Lett. 82, 1963 (1999)]. The essential dynamical mechanism responsible for coherence...... should be generic in nonlinear oscillator systems where the interactions are mediated by a highly resonant cavity, in analogy with gas lasers....

  3. High initial amplitude and high Mach number effects on the evolution of the single-mode Richtmyer-Meshkov instability.

    Science.gov (United States)

    Rikanati, A; Oron, D; Sadot, O; Shvarts, D

    2003-02-01

    Effects of high-Mach numbers and high initial amplitudes on the evolution of the single-mode Richtmyer-Meshkov shock-wave induced hydrodynamic instability are studied using theoretical models, experiments, and numerical simulations. Two regimes in which there is a significant deviation from the linear dependence of the initial velocity on the initial perturbation amplitude are defined and characterized. In one, the observed reduction of the initial velocity is primarily due to large initial amplitudes. This effect is accurately modeled by a vorticity deposition model, quantifying both the effect of the initial perturbation amplitude and the exact shape of the interface. In the other, the reduction is dominated by the proximity of the shock wave to the interface. This effect is modeled by a modified incompressible model where the shock wave is mimicked by a moving bounding wall. These results are supplemented with high initial amplitude Mach 1.2 shock-tube experiments, enabling separation of the two effects. It is shown that in most of the previous experiments, the observed reduction is predominantly due to the effect of high initial amplitudes.

  4. Completely monolithic linearly polarized high-power fiber laser oscillator

    Science.gov (United States)

    Belke, Steffen; Becker, Frank; Neumann, Benjamin; Ruppik, Stefan; Hefter, Ulrich

    2014-03-01

    We have demonstrated a linearly polarized cw all-in-fiber oscillator providing 1 kW of output power and a polarization extinction ratio (PER) of up to 21.7 dB. The design of the laser oscillator is simple and consists of an Ytterbium-doped polarization maintaining large mode area (PLMA) fiber and suitable fiber Bragg gratings (FBG) in matching PLMA fibers. The oscillator has nearly diffraction-limited beam quality (M² high power 6+1:1 pump coupler. The slope efficiency of the laser is 75 %. The electro/optical efficiency of the complete laser system is ~30 % and hence in the range of Rofin's cw non-polarized fiber lasers. Choosing an adequate bending diameter for the Yb-doped PLMA fiber, one polarization mode as well as higher order modes are sufficiently supressed1. Resulting in a compact and robust linearly polarized high power single mode laser without external polarizing components. Linearly polarized lasers are well established for one dimensional cutting or welding applications. Using beam shaping optics radially polarized laser light can be generated to be independent from the angle of incident to the processing surface. Furthermore, high power linearly polarized laser light is fundamental for nonlinear frequency conversion of nonlinear materials.

  5. Nonlinear reflection of high-amplitude laser pulses from relativistic electron mirrors

    Science.gov (United States)

    Kulagin, V. V.; Kornienko, V. N.; Cherepenin, V. A.

    2016-04-01

    A coherent X-ray pulse of attosecond duration can be formed in the reflection of a counterpropagating laser pulse from a relativistic electron mirror. The reflection of a high-amplitude laser pulse from the relativistic electron mirror located in the field of an accelerating laser pulse is investigated by means of two-dimensional (2D) numerical simulation. It is shown that provided the amplitude of the counterpropagating laser pulse is several times greater than the amplitude of the accelerating laser pulse, the reflection process is highly nonlinear, which causes a significant change in the X-ray pulse shape and its shortening up to generation of quasi-unipolar pulses and single-cycle pulses. A physical mechanism responsible for this nonlinearity of the reflection process is explained, and the parameters of the reflected X-ray pulses are determined. It is shown that the duration of these pulses may constitute 50 - 60 as, while their amplitude may be sub-relativistic.

  6. Pulsed high harmonic generation of light due to pumped Bloch oscillations in noninteracting metals

    CERN Document Server

    Freericks, J K; Kemper, A F; Devereaux, T P; 10.1088/0031-8949/2012/T151/014062

    2012-01-01

    We derive a simple theory for high-order harmonic generation due to pumping a noninteracting metal with a large amplitude oscillating electric field. The model assumes that the radiated light field arises from the acceleration of electrons due to the time-varying current generated by the pump, and also assumes that the system has a constant density of photoexcited carriers, hence it ignores the dipole excitation between bands (which would create carriers in semiconductors). We examine the circumstances under which odd harmonic frequencies would be expected to dominate the spectrum of radiated light, and we also apply the model to real materials like ZnO, for which high-order harmonic generation has already been demonstrated in experiments.

  7. Cutting-Edge High-Power Ultrafast Thin Disk Oscillators

    Directory of Open Access Journals (Sweden)

    Thomas Südmeyer

    2013-04-01

    Full Text Available A growing number of applications in science and industry are currently pushing the development of ultrafast laser technologies that enable high average powers. SESAM modelocked thin disk lasers (TDLs currently achieve higher pulse energies and average powers than any other ultrafast oscillator technology, making them excellent candidates in this goal. Recently, 275 W of average power with a pulse duration of 583 fs were demonstrated, which represents the highest average power so far demonstrated from an ultrafast oscillator. In terms of pulse energy, TDLs reach more than 40 μJ pulses directly from the oscillator. In addition, another major milestone was recently achieved, with the demonstration of a TDL with nearly bandwidth-limited 96-fs long pulses. The progress achieved in terms of pulse duration of such sources enabled the first measurement of the carrier-envelope offset frequency of a modelocked TDL, which is the first key step towards full stabilization of such a source. We will present the key elements that enabled these latest results, as well as an outlook towards the next scaling steps in average power, pulse energy and pulse duration of such sources. These cutting-edge sources will enable exciting new applications, and open the door to further extending the current performance milestones.

  8. Novel method of high-accuracy wavefront-phase and amplitude correction for coronagraphy

    Science.gov (United States)

    Bowers, Charles W.; Woodgate, Bruce E.; Lyon, Richard G.

    2003-11-01

    Detection of extra-solar, and especially terrestrial-like planets, using coronagraphy requires an extremely high level of wavefront correction. For example, the study of Woodruff et al. (2002) has shown that phase uniformity of order 10-4λ(rms) must be achieved over the critical range of spatial frequencies to produce the ~1010 contrast needed for the Terrestrial Planet Finder (TPF) mission. Correction of wavefront phase errors to this level may be accomplished by using a very high precision deformable mirror (DM). However, not only phase but also amplitude uniformity of the same scale (~10-4) and over the same spatial frequency range must be simultaneously obtained to remove all residual speckle in the image plane. We present a design for producing simultaneous wavefront phase and amplitude uniformity to high levels from an input wavefront of lower quality. The design uses a dual Michelson interferometer arrangement incorporating two DM and a single, fixed mirror (all at pupils) and two beamsplitters: one with unequal (asymmetric) beam splitting and one with symmetric beam splitting. This design allows high precision correction of both phase and amplitude using DM with relatively coarse steps and permits a simple correction algorithm.

  9. Dynamics of self-generated, large amplitude magnetic fields following high-intensity laser matter interaction

    CERN Document Server

    Sarri, G; Cecchetti, C A; Kar, S; Liseykina, T V; Yang, X H; Dieckmann, M E; Fuchs, J; Galimberti, M; Gizzi, L A; Jung, R; Kourakis, I; Osterholz, J; Pegoraro, F; Robinson, A P L; Romagnani, L; Willi, O; Borghesi, M

    2012-01-01

    The dynamics of magnetic fields with amplitude of several tens of Megagauss, generated at both sides of a solid target irradiated with a high intensity (? 1019W/cm2) picosecond laser pulse, has been spatially and temporally resolved using a proton imaging technique. The amplitude of the magnetic fields is sufficiently large to have a constraining effect on the radial expansion of the plasma sheath at the target surfaces. These results, supported by numerical simulations and simple analytical modeling, may have implications for ion acceleration driven by the plasma sheath at the rear side of the target as well as for the laboratory study of self-collimated high-energy plasma jets.

  10. Analysis of the Petersen Diagram of Double-Mode High-Amplitude {\\delta} Scuti Stars

    CERN Document Server

    Furgoni, Riccardo

    2016-01-01

    I created the Petersen diagram relative to all the Double Mode High Amplitude {\\delta} Scuti stars listed in the AAVSO's International Variable Star Index up to date December 29, 2015. For the first time I noticed that the ratio between the two periods P1/P0 seems in evident linear relation with the duration of the period P0, a finding never explicitly described in literature regarding this topic.

  11. Variable amplitude corrosion fatigue and fracture mechanics of weldable high strength jack-up steels

    OpenAIRE

    Etube, L. S.

    1998-01-01

    The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to 70OMPa. These steels are thought to exhib...

  12. High-frequency sarcomeric auto-oscillations induced by heating in living neonatal cardiomyocytes of the rat

    Energy Technology Data Exchange (ETDEWEB)

    Shintani, Seine A.; Oyama, Kotaro [Department of Pure and Applied Physics, School of Advanced Science and Engineering, Waseda University, Tokyo (Japan); Fukuda, Norio, E-mail: noriof@jikei.ac.jp [Department of Cell Physiology, The Jikei University School of Medicine, Tokyo (Japan); Ishiwata, Shin’ichi, E-mail: ishiwata@waseda.jp [Department of Pure and Applied Physics, School of Advanced Science and Engineering, Waseda University, Tokyo (Japan); WASEDA Bioscience Research Institute in Singapore (WABIOS) (Singapore)

    2015-02-06

    Highlights: • We tested the effects of infra-red laser irradiation on cardiac sarcomere dynamics. • A rise in temperature (>∼38 °C) induced high-frequency sarcomeric auto-oscillations. • These oscillations occurred with and without blockade of intracellular Ca{sup 2+} stores. • Cardiac sarcomeres can play a role as a temperature-dependent rhythm generator. - Abstract: In the present study, we investigated the effects of infra-red laser irradiation on sarcomere dynamics in living neonatal cardiomyocytes of the rat. A rapid increase in temperature to >∼38 °C induced [Ca{sup 2+}]{sub i}-independent high-frequency (∼5–10 Hz) sarcomeric auto-oscillations (Hyperthermal Sarcomeric Oscillations; HSOs). In myocytes with the intact sarcoplasmic reticular functions, HSOs coexisted with [Ca{sup 2+}]{sub i}-dependent spontaneous beating in the same sarcomeres, with markedly varying frequencies (∼10 and ∼1 Hz for the former and latter, respectively). HSOs likewise occurred following blockade of the sarcoplasmic reticular functions, with the amplitude becoming larger and the frequency lower in a time-dependent manner. The present findings suggest that in the mammalian heart, sarcomeres spontaneously oscillate at higher frequencies than the sinus rhythm at temperatures slightly above the physiologically relevant levels.

  13. High-resolution, high-reflectivity operation of lamellar multilayer amplitude gratings: identification of the single-order regime

    NARCIS (Netherlands)

    Kozhevnikov, I. V.; van der Meer, R.; Bastiaens, H. M. J.; Boller, K. J.; F. Bijkerk,

    2010-01-01

    High resolution while maintaining high peak reflectivities can be achieved for Lamellar Multilayer Amplitude Gratings (LMAG) in the soft-x-ray (SXR) region. Using the coupled waves approach (CWA), it is derived that for small lamellar widths only the zeroth diffraction order needs to be considered f

  14. A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements

    Science.gov (United States)

    Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland

    2016-07-01

    Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.

  15. WEATHER ON OTHER WORLDS. III. A SURVEY FOR T DWARFS WITH HIGH-AMPLITUDE OPTICAL VARIABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Heinze, Aren N.; Metchev, Stanimir [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Kellogg, Kendra, E-mail: aren.heinze@stonybrook.edu, E-mail: smetchev@uwo.ca [Department of Physics and Astronomy, The University of Western Ontario, 1151 Richmond St, London, ON N6A 3K7 (Canada)

    2015-03-10

    We have monitored 12 T dwarfs with the Kitt Peak 2.1 m telescope using an F814W filter (0.7-0.95 μm) to place in context the remarkable 10%-20% variability exhibited by the nearby T dwarf Luhman 16B in this wavelength regime. The motivation was the poorly known red optical behavior of T dwarfs, which have been monitored almost exclusively at infrared wavelengths, where variability amplitudes greater than 10% have been found to be very rare. We detect highly significant variability in two T dwarfs. The T2.5 dwarf 2MASS 13243559+6358284 shows consistent ∼17% variability on two consecutive nights. The T2 dwarf 2MASS J16291840+0335371 exhibits ∼10% variability that may evolve from night to night, similarly to Luhman 16B. Both objects were previously known to be variable in the infrared, but with considerably lower amplitudes. We also find evidence for variability in the T6 dwarf J162414.37+002915.6, but since it has lower significance, we conservatively refrain from claiming this object as a variable. We explore and rule out various telluric effects, demonstrating that the variations we detect are astrophysically real. We suggest that high-amplitude photometric variability for T dwarfs is likely more common in the red optical than at longer wavelengths. The two new members of the growing class of high-amplitude variable T dwarfs offer excellent prospects for further study of cloud structures and their evolution.

  16. High Power Local Oscillator Sources for 1-2 THz

    Science.gov (United States)

    Mehdi, Imran; Thomas, Bertrand; Lin, Robert; Maestrini, Alain; Ward, John; Schlecht, Erich; Gill, John; Lee, Choonsup; Chattopadhyay, Goutam; Maiwald, Frank

    2010-01-01

    Recent results from the Heterodyne Instrument for Far-Infrared (HIFI) on the Herschel Space Telescope have confirmed the usefulness of high resolution spectroscopic data for a better understanding of our Universe. This paper will explore the current status of tunable local oscillator sources beyond HIFI and provide demonstration of how power combining of GaAs Schottky diodes can be used to increase both power and upper operating frequency for heterodyne receivers. Availability of power levels greater than 1 watt in the W-band now makes it possible to design a 1900 GHz source with more than 100 microwatts of expected output power.

  17. Speckle interferometric sensor to measure low-amplitude high frequency Ocular Microtremor (OMT)

    Science.gov (United States)

    Ryle, James P.; Al-Kalbani, Mohammed; Gopinathan, Unnikrishnan; Boyle, Gerard; Coakley, Davis; Sheridan, John T.

    2009-08-01

    Ocular microtremor (OMT) is a physiological high frequency (up to 150Hz) low amplitude (150-2500nm) involuntary tremor of the human eye. It is one of the three fixational ocular motions described by Adler and Fliegelman in 1934 as well as microsaccades and drift. Clinical OMT investigations to date have used eye-contacting piezoelectric probes or piezoelectric strain gauges. Before contact can be made, the eye must first be anaesthetised. In some cases, this induces eyelid spasms (blepharospasm) making it impossible to measure OMT. Using the contact probe method, the eye motion is mechanically damped. In addition to this, it is not possible to obtain exact information about the displacement. Results from clinical studies to date have given electrical signal amplitudes from the probe. Recent studies suggest a number of clinical applications for OMT, these include monitoring the depth of anaesthesia of a patient in surgery, prediction of outcome in coma, diagnosis of brainstem death. In addition to this, abnormal OMT frequency content is present in patients with neurological disorders such as Multiple sclerosis and Parkinson's disease. However for ongoing clinical investigations the contact probe method falls short of a non-contact accurate measurement solution. In this paper, we design a compact non contact phase modulating optical fiber speckle interferometer to measure eye motions. We present our calibration results using a calibrated piezoelectric vibration simulator. Digital signal processing is then performed to extract the low amplitude high frequency displacement information.

  18. Tip radius preservation for high resolution imaging in amplitude modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Jorge R., E-mail: jorge.rr@cea.cu [Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz 3, Canto Blanco, 28049 Madrid, España (Spain)

    2014-07-28

    The acquisition of high resolution images in atomic force microscopy (AFM) is correlated to the cantilever's tip shape, size, and imaging conditions. In this work, relative tip wear is quantified based on the evolution of a direct experimental observable in amplitude modulation atomic force microscopy, i.e., the critical amplitude. We further show that the scanning parameters required to guarantee a maximum compressive stress that is lower than the yield/fracture stress of the tip can be estimated via experimental observables. In both counts, the optimized parameters to acquire AFM images while preserving the tip are discussed. The results are validated experimentally by employing IgG antibodies as a model system.

  19. High CW power, phase and amplitude modulatorrealized with fast ferrite phase-shifters

    CERN Document Server

    Valuch, D

    2004-01-01

    Superconducting cavity resonators are suffering from detuning effects caused by high internal electromagnetic fields (Lorentz force detuning). For classical resonators working with continuous wave signals, this detuning is static and compensated by the slow mechanical tuning system. However, pulsing of superconducting cavities, an operational mode only recently considered, results in dynamic detuning effects. New ways to handle this effect have to be found and worked out. A way to supply several superconducting cavities in the particle accelerator by one large transmitter while keeping the possibility of controlling the field in each individual cavity is shown. By introducing a fast phase and amplitude modulator into each cavity feeder line, the individual deviations of each cavity with respect to the average can be compensated in order to equalize their behaviour for the main control loop, which will compensate the global detuning of all cavities. Several types of phase and amplitude modulators suitable for ...

  20. Sub-cycle control of terahertz high-harmonic generation by dynamical Bloch oscillations

    CERN Document Server

    Schubert, O; Langer, F; Urbanek, B; Lange, C; Huttner, U; Golde, D; Meier, T; Kira, M; Koch, S W; Huber, R

    2016-01-01

    Ultrafast charge transport in strongly biased semiconductors is at the heart of highspeed electronics, electro-optics, and fundamental solid-state physics. Intense light pulses in the terahertz (THz) spectral range have opened fascinating vistas: Since THz photon energies are far below typical electronic interband resonances, a stable electromagnetic waveform may serve as a precisely adjustable bias. Novel quantum phenomena have been anticipated for THz amplitudes reaching atomic field strengths. We exploit controlled THz waveforms with peak fields of 72 MV/cm to drive coherent interband polarization combined with dynamical Bloch oscillations in semiconducting gallium selenide. These dynamics entail the emission of phase-stable high-harmonic transients, covering the entire THz-to-visible spectral domain between 0.1 and 675 THz. Quantum interference of different ionization paths of accelerated charge carriers is controlled via the waveform of the driving field and explained by a quantum theory of inter- and in...

  1. Large amplitude oscillatory elongation flow

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Laillé, Philippe; Yu, Kaijia

    2008-01-01

    A filament stretching rheometer (FSR) was used for measuring the elongation flow with a large amplitude oscillative elongation imposed upon the flow. The large amplitude oscillation imposed upon the elongational flow as a function of the time t was defined as epsilon(t) =(epsilon) over dot(0)t + ...

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

    Science.gov (United States)

    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.

  3. Evidences of an innermost stable bound orbit predicted by general relativity from the amplitude of the twin-peak quasiperiodic oscillations

    Science.gov (United States)

    Germanà, C.; Casana, R.

    2015-04-01

    The twin-peak high-frequency quasiperiodic oscillations (HFQPOs), observed in the power spectra of low-mass x-ray binaries, might carry relevant clues about the physics laws reigning close to a compact object. Their frequencies are typical of the orbital motion time scales a few gravitational radii away from the compact object. The aim of the manuscript is to propose an intuitive model explaining that the energy carried by the lower high-frequency quasiperiodic oscillation can be related to differences of potential energy released by clumps of plasma spiraling in a curved space-time. Our model provides estimates on both the size of clumps of matter that can survive to the strong tidal force and energy loaded by tides on the clump. We also have obtained some constrains on the mechanical properties of the plasma orbiting into the accretion disk. We note that the systematic behavior of the emitted energy as a function of the central frequency of the lower HFQPO, observed in several sources with a neutron star, might give clues related to an innermost stable bound orbit predicted by the general relativity theory in strong field regime.

  4. High load vortex oscillations developed in Francis turbines

    Science.gov (United States)

    Rodriguez, D.; Rivetti, A.; Lucino, C.

    2016-11-01

    Francis turbines operating at high load conditions produce a typical flow pattern in the draft tube cone characterized by the presence of an axisymmetric central vortex. This central cavity could become unstable, generating synchronic pressure pulsations, usually called self-excited oscillations, which propagate into the whole machine. The on-set and size of the central vortex cavity depend on the geometry of the runner and draft tube and on the operating point as well. Numerical flow simulations and model tests allow for the characterization of the different flow patterns induced by each particular Francis turbine design and, when studied in combination with the hydraulic system, including the intake and penstock, could predict the prototype hydraulic behavior for the complete operation zone. The present work focuses the CFD simulation on the development and dynamic behavior of the central axisymmetric vortex for a medium-head Francis turbine operating at high load conditions. The CFD simulations are based in two-phase transient calculations. Oscillation frequencies against its cavity volume development were obtained and good correlation was found with experimental results.

  5. Design Challenges in High Power Free-Electron Laser Oscillators

    CERN Document Server

    Benson, S V

    2005-01-01

    Several FELs have now demonstrated high power lasing and several projects are under construction to deliver higher power or shorter wavelengths. This presentation will summarize progress in upgrading FEL oscillators towards higher power and will discuss some of the challenges these projects face. The challenges fall into three categories: 1. energy recovery with large exhaust energy spread, 2. output coupling and maintaining mirror figure in the presence of high intracavity power loading, and 3. high current operation in an energy recovery linac (ERL). Progress in all three of these areas has been made in the last year. Energy recovery of over 12% of exhaust energy spread has been demonstrated and designs capable of accepting even larger energy spreads have been proposed. Cryogenic transmissive output couplers for narrow band operation and both hole and scraper output coupling have been developed. Investigation of short Rayleigh range operation has started as well. Energy recovery of over 20 mA CW has been de...

  6. Investigation of non-uniform airflow signal oscillation during high frequency chest compression

    Directory of Open Access Journals (Sweden)

    Lee Jongwon

    2005-05-01

    Full Text Available Abstract Background High frequency chest compression (HFCC is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. Methods The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations. Results and discussion We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system. Conclusion We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

  7. Effects of thrust amplitude and duration of high velocity low amplitude spinal manipulation on lumbar muscle spindle responses to vertebral position and movement

    Science.gov (United States)

    Cao, Dong-Yuan; Reed, William R.; Long, Cynthia R.; Kawchuk, Gregory N.; Pickar, Joel G.

    2013-01-01

    OBJECTIVE Mechanical characteristics of high velocity low amplitude spinal manipulations (HVLA-SM) can be variable. Sustained changes in peripheral neuronal signaling due to altered load transmission to a sensory receptor’s local mechanical environment are often considered a mechanism contributing to the therapeutic effects of spinal manipulation. The purpose of this study was to determine whether an HVLA-SM’s thrust amplitude or duration altered neural responsiveness of lumbar muscle spindles to either vertebral movement or position. METHODS Anesthetized cats (n=112) received L6 HVLA-SMs delivered to the spinous process. Cats were divided into 6 cohorts depending upon the peak thrust force (25%, 55%, 85% body weight) or thrust displacement (1, 2, 3mm) they received. Cats in each cohort received 8 thrust durations (0–250ms). Afferent discharge from 112 spindles was recorded in response to ramp and hold vertebral movement before and after the manipulation. Changes in mean instantaneous frequency (MIF) during the baseline period preceding the ramps (ΔMIFresting), during ramp movements (ΔMIFmovement), and with the vertebra held in the new position (ΔMIFposition) were compared. RESULTS Thrust duration had a small but statistically significant effect on ΔMIFresting at all six thrust amplitudes compared to control (0ms thrust duration). The lowest amplitude thrust displacement (1mm) increased ΔMIFresting at all thrust durations. For all the other thrust displacements and forces, the direction of change in ΔMIFresting was not consistent and the pattern of change was not systematically related to thrust duration. Regardless of thrust force, displacement, or duration, ΔMIFmovement and ΔMIFposition were not significantly different from control. Conclusion Relatively low amplitude thrust displacements applied during an HVLA-SM produced sustained increases in the resting discharge of paraspinal muscle spindles regardless of the duration over which the thrust was

  8. Effects of thrust amplitude and duration of high-velocity, low-amplitude spinal manipulation on lumbar muscle spindle responses to vertebral position and movement.

    Science.gov (United States)

    Cao, Dong-Yuan; Reed, William R; Long, Cynthia R; Kawchuk, Gregory N; Pickar, Joel G

    2013-02-01

    Mechanical characteristics of high-velocity, low-amplitude spinal manipulations (HVLA-SMs) can vary. Sustained changes in peripheral neuronal signaling due to altered load transmission to a sensory receptor's local mechanical environment are often considered a mechanism contributing to the therapeutic effects of spinal manipulation. The purpose of this study was to determine whether variation in an HVLA-SM's thrust amplitude and duration alters the neural responsiveness of lumbar muscle spindles to either vertebral movement or position. Anesthetized cats (n = 112) received L6 HVLA-SMs delivered to the spinous process. Cats were divided into 6 cohorts depending upon the peak thrust force (25%, 55%, 85% body weight) or thrust displacement (1, 2, 3 mm) they received. Cats in each cohort received 8 thrust durations (0-250 milliseconds). Afferent discharge from 112 spindles was recorded in response to ramp and hold vertebral movement before and after the manipulation. Changes in mean instantaneous frequency (∆MIF) during the baseline period preceding the ramps (∆MIFresting), during ramp movement (∆MIFmovement), and with the vertebra held in the new position (∆MIFposition) were compared. Thrust duration had a small but statistically significant effect on ∆MIFresting at all 6 thrust amplitudes compared with control (0-millisecond thrust duration). The lowest amplitude thrust displacement (1 mm) increased ∆MIFresting at all thrust durations. For all the other thrust displacements and forces, the direction of change in ∆MIFresting was not consistent, and the pattern of change was not systematically related to thrust duration. Regardless of thrust force, displacement, or duration, ∆MIFmovement and ∆MIFposition were not significantly different from control. Relatively low-amplitude thrust displacements applied during an HVLA-SM produced sustained increases in the resting discharge of paraspinal muscle spindles regardless of the duration over which the thrust

  9. Acoustic minor losses in high amplitude resonators with single-sided junctions

    Science.gov (United States)

    Doller, Andrew J.

    Steady flow engineering handbooks like Idelchik20 do not exist for investigators interested in acoustic (oscillating) fluid flows in complex resonators. Measurements of acoustic minor loss coefficients are presented in this dissertation for a limited number of resonator configurations having single-sided junctions. While these results may be useful, the greater purpose of this work is to provide a set of controlled measurements that can be used to benchmark computational models of acoustic flows used for more complicated resonator structures. The experiments are designed around a driver operating at 150 Hz enabling acoustic pressures in excess of 10k Pa in liquid cooled, temperature controlled resonators with 90°, 45° and 25° junctions. These junctions join a common 109 cm long 4.7 cm diameter section to a section of 8.4 mm diameter tube making two sets of resonators: one set with a small diameter length approximately a quarter-wavelength (45 cm), the other approximately a half-wavelength (112 cm). The long resonators have a velocity node at the junction; the short resonators have a velocity anti-node generating the greatest minor losses. Input power is measured by an accelerometer and a pressure transducer at the driver. A pressure sensor at the rigid termination measures radiation pressure from the driver and static junction pressure, as well as the acoustic pressure used to calculate linear thermal and viscous resonator wall losses. At the largest amplitudes, the 90° junction was found to dissipate as much as 0.3 Watt, 1/3 the power of linear losses alone. For each junction, the power dissipation depends on acoustic pressure differently: pressure cubed for the 90°, pressure to the 3.76 for the 45° and pressure to the 4.48 for the 25°. Common among all resonators, blowing acoustic half-cycle minor losses (KB) are excited at lower amplitudes than the suction half-cycle (KS) minor losses. Data collected for the 90° junction shows KB reaches an asymptotic

  10. First Results with a Fast Phase and Amplitude Modulator for High Power RF Application

    CERN Document Server

    Frischholz, Hans; Valuch, D; Weil, C

    2004-01-01

    In a high energy and high power superconducting proton linac, it is more economical to drive several cavities with a single high power transmitter rather than to use one transmitter per cavity. However, this option has the disadvantage of not permitting individual control for each cavity, which potentially leads to instabilities. Provided that it can be built at a reasonable cost, a fast phase and amplitude modulator inserted into each cavity feeder line can provide the necessary control capability. A prototype of such a device has been built, based on two fast and compact high power RF phase-shifters, magnetically biased by external coils. The design is described, together with the results obtained at high and low power levels.

  11. High frequency oscillations mirror disease activity in patients with focal cortical dysplasia.

    Science.gov (United States)

    Kerber, Karolin; LeVan, Pierre; Dümpelmann, Matthias; Fauser, Susanne; Korinthenberg, Rudolf; Schulze-Bonhage, Andreas; Jacobs, Julia

    2013-08-01

    The study analyzes the occurrence of high frequency oscillations in different types of focal cortical dysplasia in 22 patients with refractory epilepsy. High frequency oscillations are biomarkers for epileptic tissue, but it is unknown whether they can reflect increasingly dysplastic tissue changes as well as epileptic disease activity. High frequency oscillations (80-450 Hz) were visually marked by two independent reviewers in all channels of intracranial implanted grid, strips, and depth electrodes in patients with focal cortical dysplasia and refractory epilepsy. Rates of high frequency oscillations in patients with pathologically confirmed focal cortical dysplasia of Palmini type 1a and b were compared with those in type 2a and b. Patients with focal cortical dysplasia type 2 had significantly more seizures than those with type 1 (p high frequency oscillations were significantly higher in patients with focal cortical dysplasia type 2 versus type 1 (p high frequency oscillations were significantly higher in presumed epileptogenic areas than outside (p high frequency oscillations mirrors the higher epileptogenicity of focal cortical dysplasia type 2 lesions compared to type 1 lesions. Therefore, rates of high frequency oscillations can reflect disease activity of a lesion. This has implications for the use of high frequency oscillations as biomarkers for epileptogenic areas, because a detailed analysis of their rates may be necessary to use high frequency oscillations as a predictive tool in epilepsy surgery. Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.

  12. SPH simulation of turbulent flow past a high-frequency in-line oscillating cylinder near free-surface

    Science.gov (United States)

    Ghazanfarian, Jafar; Saghatchi, Roozbeh; Gorji-Bandpy, Mofid

    2016-08-01

    This paper studies a two-dimensional incompressible viscous flow past a circular cylinder with in-line oscillation close to a free-surface. The sub-particle scale (SPS) turbulence model of a Lagrangian particle-based smoothed-particle hydrodynamics (SPH) method has been used to solve the full Navier-Stokes equations together with the continuity equation. The accuracy of numerical code has been verified using two cases consisting of an oscillating cylinder placed in the stationary fluid, and flow over a fixed cylinder close to a free-surface. Simulations are conducted for the Froude number of 0.3, the Reynolds numbers of 40 and 80, various gap ratios for fully-submerged and half-submerge cylinders. The dimensionless frequency and amplitude of oscillating have been chosen as 0.5, 0.8 and 10, 15, respectively. The selection of such a high oscillating frequency causes the flow regime to become turbulent. It is seen that the gap ratio defined as the ratio of cylinder distance from free-surface and its diameter, strongly affects the flow pattern and the magnitude of the drag and lift coefficients. The jet-like flow (the region above the cylinder and beneath the free-surface) creation is discussed in detail and showed that the strength of this jet-like flow is weakened when the gap ratio shrinks. It is seen that by decreasing the gap ratio, the lift and drag coefficients increase and decrease, respectively. It is found that the Reynolds number has an inverse effect on the drag and lift coefficients. Also, it is concluded that by increasing the amplitude of oscillation the drag coefficient increases.

  13. High-Frequency QPOs and Overstable Oscillations of Black-Hole Accretion Disks

    CERN Document Server

    Lai, Dong; Tsang, David; Horak, Jiri; Yu, Cong

    2012-01-01

    The physical origin of high-frequency QPOs (HFQPOs) in black-hole X-ray binaries remains an enigma despite many years of detailed observational studies. Although there exists a number of models for HFQPOs, many of these are simply "notions" or "concepts" without actual calculation derived from fluid or disk physics. Future progress requires a combination of numerical simulations and semi-analytic studies to extract physical insights. We review recent works on global oscillation modes in black-hole accretion disks, and explain how, with the help of general relativistic effects, the energy stored in the disk differential rotation can be pumped into global spiral density modes in the disk, making these modes grow to large amplitudes under certain conditions ("corotational instability"). These modes are robust in the presence of disk magnetic fields and turbulence. The computed oscillation mode frequencies are largely consistent with the observed values for HFQPOs in BH X-ray binaries. The approximate 2:3 frequen...

  14. Semi-blind Adaptive Beamforming for High-throughput Quadrature Amplitude Modulation Systems

    Institute of Scientific and Technical Information of China (English)

    Sheng Chen; Wang Yao; Lajos Hanzo

    2010-01-01

    A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna array's elements, are first utilised to provide a rough initial least squares estimate of the beamformer's weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.

  15. Real-time, high frequency QRS electrocardiograph with reduced amplitude zone detection

    Science.gov (United States)

    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.

  16. Numerical simulation of transonic limit cycle oscillations using high-order low-diffusion schemes

    Science.gov (United States)

    Wang, Baoyuan; Zha, Ge-Cheng

    2010-05-01

    This paper simulates the NLR7301 airfoil limit cycle oscillation (LCO) caused by fluid-structure interaction (FSI) using Reynolds averaged Navier-Stokes equations (RANS) coupled with Spalart-Allmaras (S-A) one-equation turbulence model. A low diffusion E-CUSP (LDE) scheme with 5th order weighted essentially nonoscillatory scheme (WENO) is employed to calculate the inviscid fluxes. A fully conservative 4th order central differencing is used for the viscous terms. A fully coupled fluid-structural interaction model is employed. For the case computed in this paper, the predicted LCO frequency, amplitudes, averaged lift and moment, all agree excellently with the experiment performed by Schewe et al. The solutions appear to have bifurcation and are dependent on the initial fields or initial perturbation. The developed computational fluid dynamics (CFD)/computational structure dynamics (CSD) simulation is able to capture the LCO with very small amplitudes measured in the experiment. This is attributed to the high order low diffusion schemes, fully coupled FSI model, and the turbulence model used. This research appears to be the first time that a numerical simulation of LCO matches the experiment. The simulation confirms several observations of the experiment.

  17. Adhesive bond strength evaluation in composite materials by laser-generated high amplitude ultrasound

    Science.gov (United States)

    Perton, M.; Blouin, A.; Monchalin, J.-P.

    2011-01-01

    Adhesive bonding of composites laminates is highly efficient but is not used for joining primary aircraft structures, since there is presently no nondestructive inspection technique to ensure the quality of the bond. We are developing a technique based on the propagation of high amplitude ultrasonic waves to evaluate the adhesive bond strength. Large amplitude compression waves are generated by a short pulse powerful laser under water confinement and are converted after reflection by the assembly back surface into tensile waves. The resulting tensile stresses can cause a delamination inside the laminates or at the bond interfaces. The adhesion strength is evaluated by increasing the laser pulse energy until disbond. A good bond is unaffected by a certain level of stress whereas a weaker one is damaged. The method is shown completely non invasive throughout the whole composite assembly. The sample back surface velocity is measured by an optical interferometer and used to estimate stress history inside the sample. The depth and size of the disbonds are revealed by a post-test inspection by the well established laser-ultrasonic technique. Experimental results show that the proposed method is able to differentiate weak bond from strong bonds and to estimate quantitatively their bond strength.

  18. Thermal effects on seeded finite ion temperature, high amplitude plasma blobs

    CERN Document Server

    Held, M; Madsen, J; Kendl, A

    2016-01-01

    Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic finite Larmor radius effects. We find that a temperature perturbation increases the maximal blob velocity and that a finite Larmor radius contributes to highly compact blob structures with finite poloidal motion. An extensive parameter study reveals that a smooth transition to this compact blob regime occurs when the finite Larmor radius effect strength, defined by the ratio of the ion diamagnetic to the perpendicular vorticity, exceeds unity. The maximal blob velocities excellently agree with the inertial velocity scaling law over more than an order of magnitude. We show that the finite Larmor radius effect strength affects the radial transport and verify the here presented empirical scaling law for the maximal radia...

  19. An output amplitude configurable wideband automatic gain control with high gain step accuracy

    Institute of Scientific and Technical Information of China (English)

    何晓丰; 莫太山; 马成炎; 叶甜春

    2012-01-01

    An output amplitude configurable wideband automatic gain control (AGC) with high gain step accuracy for the GNSS receiver is presented.The amplitude of an AGC is configurable in order to cooperate with baseband chips to achieve interference suppression and be compatible with different full range ADCs.And what's more,the gain-boosting technology is introduced and the circuit is improved to increase the step accuracy.A zero,which is composed by the source feedback resistance and the source capacity,is introduced to compensate for the pole.The AGC is fabricated in a 0.18 μm CMOS process.The AGC shows a 62 dB gain control range by 1 dB each step with a gain error of less than 0.2 dB.The AGC provides 3 dB bandwidth larger than 80 MHz and the overall power consumption is less than 1.8 mA,and the die area is 800 × 300μm2.

  20. Relativistic electron scattering by magnetosonic waves: Effects of discrete wave emission and high wave amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Artemyev, A. V., E-mail: ante0226@gmail.com [Space Research Institute, RAS, Moscow (Russian Federation); Mourenas, D.; Krasnoselskikh, V. V. [LPC2E/CNRS - University of Orleans, Orleans (France); Agapitov, O. V. [Space Sciences Laboratory, University of California, Berkeley, California 94720 (United States)

    2015-06-15

    In this paper, we study relativistic electron scattering by fast magnetosonic waves. We compare results of test particle simulations and the quasi-linear theory for different spectra of waves to investigate how a fine structure of the wave emission can influence electron resonant scattering. We show that for a realistically wide distribution of wave normal angles θ (i.e., when the dispersion δθ≥0.5{sup °}), relativistic electron scattering is similar for a wide wave spectrum and for a spectrum consisting in well-separated ion cyclotron harmonics. Comparisons of test particle simulations with quasi-linear theory show that for δθ>0.5{sup °}, the quasi-linear approximation describes resonant scattering correctly for a large enough plasma frequency. For a very narrow θ distribution (when δθ∼0.05{sup °}), however, the effect of a fine structure in the wave spectrum becomes important. In this case, quasi-linear theory clearly fails in describing accurately electron scattering by fast magnetosonic waves. We also study the effect of high wave amplitudes on relativistic electron scattering. For typical conditions in the earth's radiation belts, the quasi-linear approximation cannot accurately describe electron scattering for waves with averaged amplitudes >300 pT. We discuss various applications of the obtained results for modeling electron dynamics in the radiation belts and in the Earth's magnetotail.

  1. Squeeze Film Dampers Executing Small Amplitude Circular-Centered Orbits in High-Speed Turbomachinery

    Directory of Open Access Journals (Sweden)

    Sina Hamzehlouia

    2016-01-01

    Full Text Available This work represents a pressure distribution model for finite length squeeze film dampers (SFDs executing small amplitude circular-centered orbits (CCOs with application in high-speed turbomachinery design. The proposed pressure distribution model only accounts for unsteady (temporal inertia terms, since based on order of magnitude analysis, for small amplitude motions of the journal center, the effect of convective inertia is negligible relative to unsteady (temporal inertia. In this work, the continuity equation and the momentum transport equations for incompressible lubricants are reduced by assuming that the shapes of the fluid velocity profiles are not strongly influenced by the inertia forces, obtaining an extended form of Reynolds equation for the hydrodynamic pressure distribution that accounts for fluid inertia effects. Furthermore, a numerical procedure is represented to discretize the model equations by applying finite difference approximation (FDA and to numerically determine the pressure distribution and fluid film reaction forces in SFDs with significant accuracy. Finally, the proposed model is incorporated into a simulation model and the results are compared against existing SFD models. Based on the simulation results, the pressure distribution and fluid film reaction forces are significantly influenced by fluid inertia effects even at small and moderate Reynolds numbers.

  2. Real-time weak signal detecting using FPGA-based Duffing oscillator with auto-damping and high speed ADC

    Science.gov (United States)

    Shen, Zhongtao; Feng, Changqing

    2017-05-01

    In this paper, a hardware real-time weak signal detection method using Field-Programmable Gate Array (FPGA) Duffing Oscillator (DUOS) and high speed Analog-to-Digital Converter (ADC) is presented. In the design, the Xilinx Kintex-7 FPGA is chosen as the controller and the DUOS weak signal detecting algorithm is implemented in it with single floating precision. The ADS5409, a dual-channel, 12-bit, 900 MSPS ADC of TI, is used for data acquisition. Besides, to guarantee the same detection Signal-Noise Ratio (SNR) for signals of different amplitudes, a signal auto-damping strategy is adopted in the FPGA, which can adjust the amplitudes of the input signals automatically. The method introduced in this paper achieves not only the ability of efficient weak signal detection in noisy environment but also the advantages of hardware processing such as real-time, low power and so on.

  3. Variable amplitude corrosion fatigue and fracture mechanics of weldable high strength jack-up steels

    Science.gov (United States)

    Etube, Linus Sone

    The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to TOOMPa. These steels are thought to exhibit fatigue resistance properties which are different when compared with conventional fixed platform steels such as BS 4360 50D and BS 7191 355D. The difference in their behaviour was heightened by the discovery, in the late 80s and early 90s, of extensive cracking around the spud can regions of several Jack-ups operating in the North Sea. It was thought that these steels may be more susceptible to hydrogen cracking and embrittlement. There was the additional requirement to study their behaviour under realistic loading conditions typical of the North Sea environment. This thesis contains results of an investigation undertaken to assess the performance of a typical high strength weldable Jack-up steel under realistic loading and environmental conditions. Details of the methodology employed to develop a typical Jack-up Offshore Standard load History (JOSH) are presented. The factors which influence fatigue resistance of structural steels used in the construction of Jack-up structures are highlighted. The methods used to model the relevant factors for inclusion in JOSH are presented with particular emphasis on loading and structural response interaction. Results and details of experimental variable amplitude corrosion fatigue (VACF) tests conducted using JOSH are reported and discussed with respect to crack growth mechanisms in high strength weldable Jack-up steels. Different fracture mechanics models for VACF crack growth prediction are compared and an improved generalised methodology for fast

  4. Phase-locking phenomena and excitation of damped and driven nonlinear oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Shagalov, A G [Institute of Metal Physics, Ekaterinburg 620041 (Russian Federation); Rasmussen, J Juul; Naulin, V [Risoe-DTU, Building 128, PO Box 49, DK-4000 Roskilde (Denmark)], E-mail: shagalov@imp.uran.ru, E-mail: jens.juul.rasmussen@risoe.dk, E-mail: volker.naulin@risoe.dk

    2009-01-30

    Resonant phase-locking phenomena ('autoresonance') in the van der Pol-Duffing oscillator forced by a small amplitude periodic driving with slowly varying frequency have been studied. We show that autoresonance occurs for oscillators with sufficiently small damping, when the system may have bi-stable states. We find the range of parameters of the oscillator, the thresholds and the appropriate control paths where autoresonant excitation of high amplitude oscillations is possible.

  5. Phase-locking phenomena and excitation of damped and driven nonlinear oscillators

    DEFF Research Database (Denmark)

    Shagalov, A.G.; Juul Rasmussen, Jens; Naulin, Volker

    2009-01-01

    Resonant phase-locking phenomena ('autoresonance') in the van der Pol Duffing oscillator forced by a small amplitude periodic driving with slowly varying frequency have been studied. We show that autoresonance occurs for oscillators with sufficiently small damping, when the system may have bi......-stable states. We find the range of parameters of the oscillator, the thresholds and the appropriate control paths where autoresonant excitation of high amplitude oscillations is possible....

  6. Giant-amplitude, high-work density microactuators with phase transition activated nanolayer bimorphs.

    Science.gov (United States)

    Liu, Kai; Cheng, Chun; Cheng, Zhenting; Wang, Kevin; Ramesh, Ramamoorthy; Wu, Junqiao

    2012-12-12

    Various mechanisms are currently exploited to transduce a wide range of stimulating sources into mechanical motion. At the microscale, simultaneously high amplitude, high work output, and high speed in actuation are hindered by limitations of these actuation mechanisms. Here we demonstrate a set of microactuators fabricated by a simple microfabrication process, showing simultaneously high performance by these metrics, operated on the structural phase transition in vanadium dioxide responding to diverse stimuli of heat, electric current, and light. In both ambient and aqueous conditions, the actuators bend with exceedingly high displacement-to-length ratios up to 1 in the sub-100 μm length scale, work densities over 0.63 J/cm(3), and at frequencies up to 6 kHz. The functionalities of actuation can be further enriched with integrated designs of planar as well as three-dimensional geometries. Combining the superior performance, high durability, diversity in responsive stimuli, versatile working environments, and microscale manufacturability, these actuators offer potential applications in microelectromechanical systems, microfluidics, robotics, drug delivery, and artificial muscles.

  7. High-frequency oscillations in human and monkey neocortex during the wake-sleep cycle.

    Science.gov (United States)

    Le Van Quyen, Michel; Muller, Lyle E; Telenczuk, Bartosz; Halgren, Eric; Cash, Sydney; Hatsopoulos, Nicholas G; Dehghani, Nima; Destexhe, Alain

    2016-08-16

    Beta (β)- and gamma (γ)-oscillations are present in different cortical areas and are thought to be inhibition-driven, but it is not known if these properties also apply to γ-oscillations in humans. Here, we analyze such oscillations in high-density microelectrode array recordings in human and monkey during the wake-sleep cycle. In these recordings, units were classified as excitatory and inhibitory cells. We find that γ-oscillations in human and β-oscillations in monkey are characterized by a strong implication of inhibitory neurons, both in terms of their firing rate and their phasic firing with the oscillation cycle. The β- and γ-waves systematically propagate across the array, with similar velocities, during both wake and sleep. However, only in slow-wave sleep (SWS) β- and γ-oscillations are associated with highly coherent and functional interactions across several millimeters of the neocortex. This interaction is specifically pronounced between inhibitory cells. These results suggest that inhibitory cells are dominantly involved in the genesis of β- and γ-oscillations, as well as in the organization of their large-scale coherence in the awake and sleeping brain. The highest oscillation coherence found during SWS suggests that fast oscillations implement a highly coherent reactivation of wake patterns that may support memory consolidation during SWS.

  8. Stimulus induced high frequency oscillations are present in neuronal networks on microelectrode arrays.

    Directory of Open Access Journals (Sweden)

    Chadwick M Hales

    2012-05-01

    Full Text Available Pathological high frequency oscillations (250-600Hz are present in the brains of epileptic animals and humans. The etiology of these oscillations and how they contribute to the diseased state remains unclear. This work identifies the presence of microstimulation-evoked high frequency oscillations (250-400Hz in dissociated neuronal networks cultured on microelectrode arrays (MEAs. Oscillations are more apparent with higher stimulus voltages. As with in vivo studies, activity is isolated to a single electrode, however the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200µm away. Oscillations develop across 4 weeks in vitro. Oscillations still occur in the presence of tetrodotoxin and synaptic blockers, and they cause no apparent disruption in the ability of oscillation-presenting electrodes to elicit directly evoked action potentials (dAPs or promote the spread of synaptic activity throughout the culture. Chelating calcium with ethylene glycol tetraacetic acid (EGTA causes a temporal prolongation of the oscillation. Finally, carbenoxolone significantly reduces or eliminates the high frequency oscillations. Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies. This is the first demonstration of stimulus evoked high frequency oscillations in dissociated cultures. Unlike current models that rely on complex in vivo recording conditions, this work presents a simple controllable model in neuronal cultures on MEAs to further investigate how the oscillations occur at the molecular level and how they may contribute to the pathophysiology of disease.

  9. High efficiency processing for reduced amplitude zones detection in the HRECG signal

    Science.gov (United States)

    Dugarte, N.; Álvarez, A.; Balacco, J.; Mercado, G.; Gonzalez, A.; Dugarte, E.; Olivares, A.

    2016-04-01

    Summary - This article presents part of a more detailed research proposed in the medium to long term, with the intention of establishing a new philosophy of electrocardiogram surface analysis. This research aims to find indicators of cardiovascular disease in its early stage that may go unnoticed with conventional electrocardiography. This paper reports the development of a software processing which collect some existing techniques and incorporates novel methods for detection of reduced amplitude zones (RAZ) in high resolution electrocardiographic signal (HRECG).The algorithm consists of three stages, an efficient processing for QRS detection, averaging filter using correlation techniques and a step for RAZ detecting. Preliminary results show the efficiency of system and point to incorporation of techniques new using signal analysis with involving 12 leads.

  10. High Capacity Phase/Amplitude Modulated Optical Communication Systems and Nonlinear Inter-Channel Impairments

    Science.gov (United States)

    Tavassoli, Vahid

    This thesis studies and mathematically models nonlinear interactions among channels of modern high bit rate (amplitude/) phase modulated optical systems. First, phase modulated analogue systems are studied and a differential receiving method is suggested with experimental validation. The main focus of the rest of the thesis is on digital advanced modulation format systems. Cross-talk due to fiber Kerr nonlinearity in two-format hybrid systems as well as 16-QAM systems is mathematically modelled and verified by simulation for different system parameters. A comparative study of differential receivers and coherent receivers is also given for hybrid systems. The model is based on mathematically proven assumptions and provides an intuitive analytical understanding of nonlinear cross-talk in such systems.

  11. Pulsation analysis of the high amplitude δ Scuti star CW Serpentis

    Science.gov (United States)

    Niu, Jia-Shu; Fu, Jian-Ning; Zong, Wei-Kai

    2013-10-01

    Time-series photometric observations were made for the high amplitude δ Scuti star CW Ser between 2011 and 2012 at the Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences. After performing the frequency analysis of the light curves, we confirmed the fundamental frequency of f = 5.28677 c d-1, together with seven harmonics of the fundamental frequency, which are newly detected. No additional frequencies were detected. The O — C diagram, produced with the 21 newly determined times of maximum light combined with those provided in the literature, helps to obtain a new ephemeris formula of the times of maximum light with the pulsation period of 0.189150355 ± 0.000000003 d.

  12. Measuring the Energy Release of Low Amplitude Impact of High Explosive Events

    Science.gov (United States)

    Straight, J. W.; Idar, D. J.; Smith, L.; Osborn, M. A.; Viramontes, L. E.; Chavez, P. J.

    2004-07-01

    Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable for risk assessments and a goal for computational models. Historically, different types of low amplitude impact tests on HE specimens have been performed to determine the critical impact-velocity threshold for high explosive violent reactions (HEVR). Additionally, the energy release relative to a steady-state detonation is also desirable for assessing the potential outcome of an accidental event. Traditionally, blast gauge measurements have been used to measure the overpressure of the HEVR event at a defined distance. This paper summarizes the use of this active technique coupled with a passive technique to derive average energy release curves for Modified Steven tests. A classic ballistic pendulum design was employed with the traditional blast gauge method. Calibration of the ballistic pendulum involved three elements. First, two mechanical measurements were related to the actual peak swing of the pendulum. Second, the general nature of the swing versus energy release curve was estimated. Two different approaches were used to estimate the momenta as a function of HE energy release using the Gurney relationships for an unsymmetrical sandwich. Finally, both techniques were simultaneously benchmarked with PBX 9501 calibration charges. Test results demonstrate the utility of using coupled diagnostic methods for low amplitude insult testing. Each set of data was fit to derive a working curve for the determination of the average energy release for HEVR event based on mass relative to a steady-state detonation. These tests results and working curve derivations are presented.

  13. High-frequency oscillations and mesial temporal lobe epilepsy.

    Science.gov (United States)

    Lévesque, Maxime; Shiri, Zahra; Chen, Li-Yuan; Avoli, Massimo

    2017-01-20

    The interest of epileptologists has recently shifted from the macroscopic analysis of interictal spikes and seizures to the microscopic analysis of short events in the EEG that are not visible to the naked eye but are observed once the signal has been filtered in specific frequency bands. With the use of new technologies that allow multichannel recordings at high sampling rates and the development of computer algorithms that permit the automated analysis of extensive amounts of data, it is now possible to extract high-frequency oscillations (HFOs) between 80 and 500Hz from the EEG; HFOs have been further categorised as ripples (80-200Hz) and fast ripples (250-500Hz). Within the context of epileptic disorders, HFOs should reflect the pathological activity of neural networks that sustain seizure generation, and could serve as biomarkers of epileptogenesis and ictogenesis. We review here the presumptive cellular mechanisms of ripples and fast ripples in mesial temporal lobe epilepsy. We also focus on recent findings regarding the occurrence of HFOs during epileptiform activity observed in in vitro models of epileptiform synchronization, in in vivo models of mesial temporal lobe epilepsy and in epileptic patients. Finally, we address the effects of anti-epileptic drugs on HFOs and raise some questions and issues related to the definition of HFOs.

  14. Beam divergence effects on high power optical parametric oscillation

    Institute of Scientific and Technical Information of China (English)

    Li Hui-Qing; Geng Ai-Cong; Bo Yong; Wu Ling-An; Cui Da-Fu; Xu Zu-Yan

    2005-01-01

    The beam divergence effects of the input pump laser on a high power nanosecond optical parametric oscillator (OPO) have been numerically simulated. The OPO conversion efficiency is affected due to the angular deviation of real laser beams from ideal phase matching conditions. Our theoretical model is based on the decomposition of the Gaussian beam and assumes each component has a single deviation angle and thus a Particular wave vector mismatch. We take into account the variable intensity profile in the spatial and temporal domains of the Gaussian beam, the pump depletion effects for large-signal processes as well as the oscillatory effects of the three waves. Two nonlinear crystals β-BaB2O4 (BBO) and LiB3O5 (LBO) have been investigated in detail. The results indicate that the degree of beam divergence strongly influences the maximum pump intensity, optimum crystal length and OPO conversion efficiency.The impact of beam divergence is much more severe in the case of critical phase-matching for BBO than in the case of non-critical phase-matching for LBO. The results provide a way to choose the optimum parameters for a high power ns OPO such as the nonlinear material, the crystal length and the pump intensity, etc. Good agreement is obtained with our experimental results.

  15. A compact, low jitter, nanosecond rise time, high voltage pulse generator with variable amplitude

    Science.gov (United States)

    Mao, Jiubing; Wang, Xin; Tang, Dan; Lv, Huayi; Li, Chengxin; Shao, Yanhua; Qin, Lan

    2012-07-01

    In this paper, a compact, low jitter, nanosecond rise time, command triggered, high peak power, gas-switch pulse generator system is developed for high energy physics experiment. The main components of the system are a high voltage capacitor, the spark gap switch and R = 50 Ω load resistance built into a structure to obtain a fast high power pulse. The pulse drive unit, comprised of a vacuum planar triode and a stack of avalanche transistors, is command triggered by a single or multiple TTL (transistor-transistor logic) level pulses generated by a trigger pulse control unit implemented using the 555 timer circuit. The control unit also accepts user input TTL trigger signal. The vacuum planar triode in the pulse driving unit that close the first stage switches is applied to drive the spark gap reducing jitter. By adjusting the charge voltage of a high voltage capacitor charging power supply, the pulse amplitude varies from 5 kV to 10 kV, with a rise time of gas-switch and available capacitor recovery time.

  16. High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy

    NARCIS (Netherlands)

    Zweiphenning, W. J E M; van 't Klooster, M. A.; van Diessen, E.; van Klink, N. E C; Huiskamp, G. J M|info:eu-repo/dai/nl/074463640; Gebbink, T. A.; Leijten, F. S S|info:eu-repo/dai/nl/152243054; Gosselaar, P. H.|info:eu-repo/dai/nl/304813990; Otte, W. M.|info:eu-repo/dai/nl/168455706; Stam, C. J.; Braun, K. P J|info:eu-repo/dai/nl/207237239; Zijlmans, G. J M|info:eu-repo/dai/nl/304819581

    2016-01-01

    OBJECTIVE: High frequency oscillations (HFOs; > 80 Hz), especially fast ripples (FRs, 250-500 Hz), are novel biomarkers for epileptogenic tissue. The pathophysiology suggests enhanced functional connectivity within FR generating tissue. Our aim was to determine the relation between brain areas

  17. Probing Neutrino Oscillation Parameters using High Power Superbeam from ESS

    CERN Document Server

    Agarwalla, Sanjib Kumar; Prakash, Suprabh

    2014-01-01

    A high-power neutrino superbeam experiment at the ESS facility has been proposed such that the source-detector distance falls at the second oscillation maximum, giving very good sensitivity to the measurement of CP violation. In this work, we explore the comparative physics reach of the experiment in terms of leptonic CP-violation, precision on atmospheric parameters, non-maximal theta23, and its octant for a variety of choices for the baselines. We also vary the neutrino vs. the anti-neutrino running time for the beam, and study its impact on the physics goals of the experiment. We find that for the determination of CP violation, 540 km baseline with 7 years of neutrino and 3 years of anti-neutrino (7nu+3nubar) run-plan performs the best and one expects a 4sigma sensitivity to CP violation for 59% of true values of deltaCP. The projected reach for the 200 km baseline with 7nu+3nubar run-plan is somewhat worse with 4sigma sensitivity for 51% of true values of deltaCP. On the other hand, for the discovery of a...

  18. Experimental investigation of a reacting transverse jet in a high pressure oscillating vitiated crossflow

    Science.gov (United States)

    Fugger, Christopher A.

    Staged combustion is one design approach in a gas turbine engine to reduce pollutant emission levels. In axially staged combustion, portions of the air and fuel are injected downstream of a lean premixed low NOx primary combustion zone. The gas residence time at elevated temperatures is decreased resulting in lower thermal NOx, and the reduced oxygen and high temperature vitiated primary zone flow further help to reduce pollutant emissions and quickly complete combustion. One implementation of axially staged combustion is transverse fuel jet injection. An important consideration for staged combustion systems, though, is how the primary and secondary combustion zones can couple through the acoustic resonances of the chamber. These couplings can lead to additional source terms that pump energy into the resonant acoustic field and help sustain the high-amplitude combustor pressure oscillations. An understanding of these couplings is important so that it may be possible to design a secondary combustion system that provides inherent damping to the combustor system. To systematically characterize the coupling of a reacting jet in unsteady crossflow in detail, the effects of an an unsteady pressure flowfield and an unsteady velocity flowfield are separately investigated. An optically accessible resonant combustion chamber was designed and built as part of this work to generate a standing wave unsteady vitiated crossflow at a chamber pressure of 0.9 MPa. The location of transverse jet injection corresponds to one of two locations, where one location is the pressure node and the other location the pressure anti-node of the resonant chamber acoustic mode. The injection location is optically accessible, and the dynamic interactions between the transverse jet flow and the 1st and 2nd axial combustor modes are measured using 10 kHz OH-PLIF and 2D PIV. This document analyzes five test cases: two non-reacting jets and three reacting jets. All cases correspond to jet injection

  19. Nuclear Jacobi and Poincaré transitions at high spins and temperatures: Account of dynamic effects and large-amplitude motion

    Science.gov (United States)

    Mazurek, K.; Dudek, J.; Maj, A.; Rouvel, D.

    2015-03-01

    We present a theoretical analysis of the competition between the so-called nuclear Jacobi and Poincaré shape transitions as a function of spin at high temperatures. The latter condition implies the method of choice, a realistic version of the nuclear liquid drop model, here the Lublin-Strasbourg drop model. We address specifically the fact that the Jacobi and Poincaré shape transitions are accompanied by the flattening of the total nuclear energy landscape as a function of the relevant deformation parameters, which enforces large-amplitude oscillation modes that need to be taken into account. For that purpose we introduce an approximate form of the collective Schrödinger equation whose solutions are used to calculate the most probable deformations associated with the nuclear Jacobi and Poincaré transitions. We discuss selected aspects of the new description focusing on the critical-spin values for both types of these transitions.

  20. Nuclear Jacobi and Poincar\\'e Transitions at High Spins and Temperatures: Account~of~Dynamic~Effects~and~Large-Amplitude Motion

    CERN Document Server

    Mazurek, K; Maj, A; Rouvel, D

    2013-01-01

    We present a theoretical analysis of the competition between so-called nuclear Jacobi and Poincar\\'e shape transitions in function of spin - at high temperatures. The latter condition implies the method of choice - a realistic version of the nuclear Liquid Drop Model (LDM), here: the Lublin-Strasbourg Drop (LSD) model. We address specifically the fact that the Jacobi and Poincar\\'e shape transitions are accompanied by the flattening of total nuclear energy landscape as function of the relevant deformation parameters what enforces large amplitude oscillation modes that need to be taken into account. For that purpose we introduce an approximate form of the collective Schr\\"odinger equation whose solutions are used to calculate the most probable deformations associated with both types of transitions and discuss the physical consequences in terms of the associated critical-spin values and transitions themselves.

  1. Protostring Scattering Amplitudes

    CERN Document Server

    Thorn, Charles B

    2016-01-01

    We calculate some tree level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a lightcone worldsheet which supports $s$ integer moded Grassmann fields. In the generalization we supplement this Grassmann worldsheet system with $d=24-s$ transverse coordinate worldsheet fields. The protostring corresponds to $s=24$ and the bosonic string to $s=0$. The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that $s$ is even we calculate the multi-string scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of $s/2$ compactified and $d$ uncompactified bosonic worldsheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then ...

  2. Paradoxical stabilization of forced oscillations by strong nonlinear friction

    Science.gov (United States)

    Esirkepov, Timur Zh.; Bulanov, Sergei V.

    2017-08-01

    In a dissipative dynamic system driven by an oscillating force, a strong nonlinear highly oscillatory friction force can create a quasi-steady tug, which is always directed opposite to the ponderomotive force induced due to a spatial inhomogeneity of oscillations. When the friction-induced tug exceeds the ponderomotive force, the friction stabilizes the system oscillations near the maxima of the oscillation spatial amplitude of the driving force.

  3. A study of daily variation in cosmic ray intensity during high/low amplitude days

    Indian Academy of Sciences (India)

    Rajesh K Mishra; Rekha Agarwal Mishra

    2007-03-01

    A detailed study has been conducted on the long-term changes in the diurnal, semi-diurnal and tri-diurnal anisotropies of cosmic rays in terms of the high/low amplitude anisotropic wave train events (HAE/LAE) during the period 1981-94 using the neutron monitor data from Deep River Neutron Monitoring Station. In all, 38 HAE and 28 LAE cases have been studied. An inter-comparison of the first three harmonics during these events has been made so as to understand the basic reason for the occurrence of these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs and it shifts towards earlier hour as compared to 18-h direction for LAEs. For semi-diurnal anisotropy, phase remains statistically the same for both HAE and LAE. In the case of tri-diurnal anisotropy, phase is evenly distributed for both types of events. The interplanetary magnetic field (IMF) and solar wind plasma (SWP) parameters during these events are also investigated. It has also been observed that HAE/LAEs are weakly dependent on high-speed solar wind velocity. The two types of solar wind streams (corotating streams and flare-generated streams) produce significant deviations in cosmic ray intensity during HAE/LAE.

  4. Spline-based high-accuracy piecewise-polynomial phase-to-sinusoid amplitude converters.

    Science.gov (United States)

    Petrinović, Davor; Brezović, Marko

    2011-04-01

    We propose a method for direct digital frequency synthesis (DDS) using a cubic spline piecewise-polynomial model for a phase-to-sinusoid amplitude converter (PSAC). This method offers maximum smoothness of the output signal. Closed-form expressions for the cubic polynomial coefficients are derived in the spectral domain and the performance analysis of the model is given in the time and frequency domains. We derive the closed-form performance bounds of such DDS using conventional metrics: rms and maximum absolute errors (MAE) and maximum spurious free dynamic range (SFDR) measured in the discrete time domain. The main advantages of the proposed PSAC are its simplicity, analytical tractability, and inherent numerical stability for high table resolutions. Detailed guidelines for a fixed-point implementation are given, based on the algebraic analysis of all quantization effects. The results are verified on 81 PSAC configurations with the output resolutions from 5 to 41 bits by using a bit-exact simulation. The VHDL implementation of a high-accuracy DDS based on the proposed PSAC with 28-bit input phase word and 32-bit output value achieves SFDR of its digital output signal between 180 and 207 dB, with a signal-to-noise ratio of 192 dB. Its implementation requires only one 18 kB block RAM and three 18-bit embedded multipliers in a typical field-programmable gate array (FPGA) device.

  5. High-frequency oscillations in Parkinson's disease: spatial distribution and clinical relevance.

    Science.gov (United States)

    Wang, Jing; Hirschmann, Jan; Elben, Saskia; Hartmann, Christian J; Vesper, Jan; Wojtecki, Lars; Schnitzler, Alfons

    2014-09-01

    The pathophysiology of Parkinson's disease (PD) has been related to excessive beta band oscillations in the basal ganglia. Recent recordings from the subthalamic nucleus of PD patients showed that beta oscillations show strong cross-frequency coupling with high-frequency oscillations (>200 Hz). However, little is known about the characteristics and functional properties of these oscillations. We studied the spatial distribution of high-frequency oscillations and their relation to PD motor symptoms. We included 10 PD patients in medication OFF who underwent implantation of deep brain stimulation (DBS) electrodes. Intraoperative five-channel microelectrode recordings were performed at 9 to 10 recording sites within the subthalamic nucleus and its immediate surroundings. We found a focal spatial distribution of high-frequency oscillations with highest power 2 mm below the dorsolateral border of the subthalamic nucleus. Within the subthalamic nucleus, power peaked slightly anterior to the DBS target site. In addition, contralateral akinesia/rigidity scores were negatively correlated with high-frequency oscillation power. Our results demonstrate a focal origin of high-frequency oscillations within the subthalamic nucleus and provide further evidence for their functional association with motor state. © 2014 International Parkinson and Movement Disorder Society.

  6. High spectral purity Kerr frequency comb radio frequency photonic oscillator.

    Science.gov (United States)

    Liang, W; Eliyahu, D; Ilchenko, V S; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L

    2015-08-11

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz(-1) at 10 Hz, -90 dBc Hz(-1) at 100 Hz and -170 dBc Hz(-1) at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10(-10) at 1-100 s integration time-orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption.

  7. High-power Čerenkov microwave oscillators utilizing High-Current nanosecond Electron beams

    Science.gov (United States)

    Korovin, S. D.; Polevin, S. D.; Rostov, V. V.

    1996-12-01

    A short review is given of results obtained at the Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences on generating high-power microwave radiation. Most of the research was devoted to a study of stimulated Čerenkov radiation from relativistic electron beams. It is shown that the efficiency of a relativistic 3-cm backward wave tube with a nonuniform coupling resistance can reach 35%. High-frequency radiation was discovered in the emission spectrum of the Čerenkov oscillators and it was shown that the nature of the radiation was associated with the stimulated scattering of low-frequency radiation by the relativistic electrons. Radiation with a power of 500 MW was obtained in the 8-mm wavelength range using a two-beam Čerenkov oscillator. High-current pulse-periodic nanosecond accelerators with a charging device utilizing a Tesla transformer were used in the experiments. The possibility was demonstrated of generating high-power microwave radiation with a pulse-repetition frequency of up to 100 Hz. An average power of ˜500 W was achieved from the relativistic oscillators. A relativistic backward wave tube with a high-current electron beam was used to make a prototype nanosecond radar device. Some of the results presented were obtained jointly with the Russian Academy of Sciences Institute of Applied Physics. Questions concerning multiwave Čerenkov interaction are not considered in this paper.

  8. Short-lived high-amplitude cooling on Svalbard during the Dark Ages

    Science.gov (United States)

    van der Bilt, Willem; D`Andrea, William; Bakke, Jostein; Balascio, Nicholas; Werner, Johannes; Hoek, Wim

    2016-04-01

    As the paradigm of a stable Holocene climate has shifted, an increasing number of high-resolution proxy timeseries reveal dynamic conditions, characterized by high-amplitude climate shifts. Some of these events occurred during historical times and allow us to study the interaction between environmental and cultural change, providing valuable lessons for the near future. These include the Dark Ages Cold Period (DACP) between 300 and 800 AD, a period marked by political upheaval and climate instability that remains poorly investigated. Here, we present two temperature reconstructions from the High Arctic Svalbard Archipelago. To this end, we applied the established alkenone-based UK37 paleothermometer on sediments from two lakes on western Spitsbergen, Lake Hajeren and Lake Hakluyt. The Arctic is presently warming twice as fast as the global average and proxy data as well as model simulations suggest that this amplified response is characteristic for regional climate. The Arctic therefore provides a uniquely sensitive environment to study relatively modest climate shifts, like the DACP, that may not be adequately captured at lower-latitude sites. Owing to undisturbed sediments, a high sampling resolution and robust chronological control, the presented reconstructions resolve the attendant sub-centennial-scale climate shifts. Our findings suggest that the DACP marks a cold spell within the cool Neoglacial period, which started some 4 ka BP on Svalbard. Close investigation reveals a distinct temperature minimum around 500 AD that is reproduced in another alkenone-based temperature reconstruction from a nearby lake. At ± 1.75 °C, cooling underlines the sensitivity of Arctic climate as well as the magnitude of the DACP.

  9. Data mining neocortical high-frequency oscillations in epilepsy and controls.

    Science.gov (United States)

    Blanco, Justin A; Stead, Matt; Krieger, Abba; Stacey, William; Maus, Douglas; Marsh, Eric; Viventi, Jonathan; Lee, Kendall H; Marsh, Richard; Litt, Brian; Worrell, Gregory A

    2011-10-01

    Transient high-frequency (100-500 Hz) oscillations of the local field potential have been studied extensively in human mesial temporal lobe. Previous studies report that both ripple (100-250 Hz) and fast ripple (250-500 Hz) oscillations are increased in the seizure-onset zone of patients with mesial temporal lobe epilepsy. Comparatively little is known, however, about their spatial distribution with respect to seizure-onset zone in neocortical epilepsy, or their prevalence in normal brain. We present a quantitative analysis of high-frequency oscillations and their rates of occurrence in a group of nine patients with neocortical epilepsy and two control patients with no history of seizures. Oscillations were automatically detected and classified using an unsupervised approach in a data set of unprecedented volume in epilepsy research, over 12 terabytes of continuous long-term micro- and macro-electrode intracranial recordings, without human preprocessing, enabling selection-bias-free estimates of oscillation rates. There are three main results: (i) a cluster of ripple frequency oscillations with median spectral centroid = 137 Hz is increased in the seizure-onset zone more frequently than a cluster of fast ripple frequency oscillations (median spectral centroid = 305 Hz); (ii) we found no difference in the rates of high frequency oscillations in control neocortex and the non-seizure-onset zone neocortex of patients with epilepsy, despite the possibility of different underlying mechanisms of generation; and (iii) while previous studies have demonstrated that oscillations recorded by parenchyma-penetrating micro-electrodes have higher peak 100-500 Hz frequencies than penetrating macro-electrodes, this was not found for the epipial electrodes used here to record from the neocortical surface. We conclude that the relative rate of ripple frequency oscillations is a potential biomarker for epileptic neocortex, but that larger prospective studies correlating high

  10. Probing neutrino oscillation parameters using high power superbeam from ESS

    Science.gov (United States)

    Agarwalla, Sanjib Kumar; Choubey, Sandhya; Prakash, Suprabh

    2014-12-01

    A high-power neutrino superbeam experiment at the ESS facility has been proposed such that the source-detector distance falls at the second oscillation maximum, giving very good sensitivity towards establishing CP violation. In this work, we explore the comparative physics reach of the experiment in terms of leptonic CP-violation, precision on atmospheric parameters, non-maximal θ 23, and its octant for a variety of choices for the baselines. We also vary the neutrino vs. the anti-neutrino running time for the beam, and study its impact on the physics goals of the experiment. We find that for the determination of CP violation, 540 km baseline with 7 years of ν and 3 years of run-plan performs the best and one expects a 5 σ sensitivity to CP violation for 48% of true values of δ CP. The projected reach for the 200 km baseline with run-plan is somewhat worse with 5 σ sensitivity for 34% of true values of δ CP. On the other hand, for the discovery of a non-maximal θ 23 and its octant, the 200 km baseline option with run-plan performs significantly better than the other baselines. A 5σ determination of a non-maximal θ 23 can be made if the true value of sin2 θ 23 ≲ 0.45 or sin2 θ 23 ≳ 0.57. The octant of θ 23 could be resolved at 5 σ if the true value of sin2 θ 23 ≲ 0.43 or ≳ 0.59, irrespective of δ CP.

  11. Automated force controller for amplitude modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Miyagi, Atsushi, E-mail: atsushi.miyagi@inserm.fr, E-mail: simon.scheuring@inserm.fr; Scheuring, Simon, E-mail: atsushi.miyagi@inserm.fr, E-mail: simon.scheuring@inserm.fr [U1006 INSERM, Université Aix-Marseille, Parc Scientifique et Technologique de Luminy, 163 Avenue de Luminy, 13009 Marseille (France)

    2016-05-15

    Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed.

  12. Amplitude Modulations of Acoustic Communication Signals

    Science.gov (United States)

    Turesson, Hjalmar K.

    2011-12-01

    In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a

  13. All-optical Photonic Oscillator with High-Q Whispering Gallery Mode Resonators

    Science.gov (United States)

    Savchenkov, Anatoliy A.; Matsko, Andrey B.; Strekalov, Dmitry; Mohageg, Makan; Iltchenko, Vladimir S.; Maleki, Lute

    2004-01-01

    We demonstrated low threshold optical photonic hyper-parametric oscillator in a high-Q 10(exp 10) CaF2 whispering gallery mode resonator which generates stable 8.5 GHz signal. The oscillations result from the resonantly enhanced four wave mixing occurring due to Kerr nonlinearity of the material.

  14. High-amplitude electrical stimulation can reduce elicited neuronal activity in visual prosthesis

    Science.gov (United States)

    Barriga-Rivera, Alejandro; Guo, Tianruo; Yang, Chih-Yu; Abed, Amr Al; Dokos, Socrates; Lovell, Nigel H.; Morley, John W.; Suaning, Gregg J.

    2017-01-01

    Retinal electrostimulation is promising a successful therapy to restore functional vision. However, a narrow stimulating current range exists between retinal neuron excitation and inhibition which may lead to misperformance of visual prostheses. As the conveyance of representation of complex visual scenes may require neighbouring electrodes to be activated simultaneously, electric field summation may contribute to reach this inhibitory threshold. This study used three approaches to assess the implications of relatively high stimulating conditions in visual prostheses: (1) in vivo, using a suprachoroidal prosthesis implanted in a feline model, (2) in vitro through electrostimulation of murine retinal preparations, and (3) in silico by computing the response of a population of retinal ganglion cells. Inhibitory stimulating conditions led to diminished cortical activity in the cat. Stimulus-response relationships showed non-monotonic profiles to increasing stimulating current. This was observed in vitro and in silico as the combined response of groups of neurons (close to the stimulating electrode) being inhibited at certain stimulating amplitudes, whilst other groups (far from the stimulating electrode) being recruited. These findings may explain the halo-like phosphene shapes reported in clinical trials and suggest that simultaneous stimulation in retinal prostheses is limited by the inhibitory threshold of the retinal ganglion cells. PMID:28209965

  15. High amplitude theta wave bursts: a novel electroencephalographic feature of rem sleep and cataplexy.

    Science.gov (United States)

    Lo Martire, Viviana Carmen; Bastianini, Stefano; Berteotti, Chiara; Silvani, Alessandro; Zoccoli, Giovanna

    2015-01-01

    High amplitude theta wave bursts (HATs) were originally described during REMS and cataplexy in ORX-deficient mice as a novel neurophysiological correlate of narcolepsy (Bastianini et al., 2012). This finding was replicated the following year by Vassalli et al. in both ORX-deficient narcoleptic mice and narcoleptic children during cataplexy episodes (Vassalli et al., 2013). The relationship between HATs and narcolepsy-cataplexy in mice and patients indicates that the lack of ORX peptides is responsible for this abnormal EEG activity, the physiological meaning of which is still unknown. This review aimed to explore different phasic EEG events previously described in the published literature in order to find analogies and differences with HATs observed in narcoleptic mice and patients. We found similarities in terms of morphology, frequency and duration between HATs and several physiological (mu and wicket rhythms, sleep spindles, saw-tooth waves) or pathological (SWDs, HVSs, bursts of polyphasic complexes EEG complexes reported in a mouse model of CJD, and BSEs) EEG events. However, each of these events also shows significant differences from HATs, and thus cannot be equaled to them. The available evidence thus suggests that HATs are a novel neurophysiological phenomenon. Further investigations on HATs are required in order to investigate their physiological meaning, to individuate their brain structure(s) of origin, and to clarify the neural circuits involved in their manifestation.

  16. Skeletal bone morphology is resistant to the high amplitude seasonal leptin cycle in the Siberian hamster.

    Science.gov (United States)

    Rousseau, K; Atcha, Z; Denton, J; Cagampang, F R A; Ennos, A R; Freemont, A J; Loudon, A S I

    2005-09-01

    Recent studies have suggested that the adipocyte-derived hormone, leptin, plays a role in the regulation of metabolism. Here, we tested this hypothesis in the seasonally breeding Siberian hamster, as this species exhibits profound seasonal changes in adiposity and circulating leptin concentrations driven by the annual photoperiodic cycle. Male hamsters were kept in either long (LD) or short (SD) photoperiods. Following exposure to short photoperiods for 8 weeks animals exhibited a significant weight-loss and a 16-fold reduction of serum leptin concentrations. At Week 9, animals in both photoperiods were infused with leptin or PBS via osmotic mini-pump for 14 days. Chronic leptin infusion mimicked LD-like concentrations in SD-housed animals and caused a further decline in body weight and adipose tissue. In LD-housed animals, leptin infusion resulted in a significant elevation of serum concentrations above natural LD-like levels, but had no discernable effect on body weight or overall adiposity. Both bending and compression characteristics and histomorphometric measurements of trabecular bone mass were unaltered by leptin treatment or photoperiod. Our data therefore show that despite a high natural amplitude cycle of leptin, this hormone has no apparent role in the regulation of bone metabolism, and therefore do not support recent propositions that this hormone is an important component in the metabolism of bone tissue.

  17. The precise determination of mass through the oscillations of a very high-Q superconductor oscillating system

    CERN Document Server

    Schilling, Osvaldo F

    2013-01-01

    The present paper is based upon the fact that if an object is part of a highly stable oscillating system, it is possible to obtain an extremely precise measure for its mass in terms of the energy trapped in this resonance. The subject is timely since there is great interest in Metrology on the establishment of a new electronic standard for the kilogram. Our contribution to such effort includes both the proposal of an alternative definition for mass in terms of energy, as well as the description of a realistic experimental system in which this definition might actually be applied. The setup consists of an oscillating type-II superconducting loop (the SEO system) subjected to the gravity and magnetic fields. The system is shown to be able to reach a dynamic equilibrium by trapping energy up to the point it levitates against the surrounding magnetic and gravitational fields, behaving as an extremely high-Q spring-load system. The proposed energy-mass equation applied to the electromechanical oscillating system e...

  18. A Resonantly-Excited Disk-Oscillation Model of High-Frequency QPOs of Microquasars

    CERN Document Server

    Kato, Shoji

    2012-01-01

    A possible model of twin high-frequency QPOs (HF QPOs) of microquasars is examined. The disk is assumed to have global magnetic fields and to be deformed with a two-armed pattern. In this deformed disk, set of a two-armed ($m=2$) vertical p-mode oscillation and an axisymmetric ($m=0$) g-mode oscillation are considered. They resonantly interact through the disk deformation when their frequencies are the same. This resonant interaction amplifies the set of the above oscillations in the case where these two oscillations have wave energies of opposite signs. These oscillations are assumed to be excited most efficiently in the case where the radial group velocities of these two waves vanish at the same place. The above set of oscillations is not unique, depending on the node number, $n$, of oscillations in the vertical direction. We consider that the basic two sets of oscillations correspond to the twin QPOs. The frequencies of these oscillations depend on disk parameters such as strength of magnetic fields. For o...

  19. Relaxation oscillation SQUIDs with high dV/dfi

    NARCIS (Netherlands)

    Adelerhof, Derk Jan; Adelerhof, D.J.; Nijstad, H.; Nijstad, H.; Flokstra, Jakob; Rogalla, Horst

    1993-01-01

    Relaxation oscillation SQUIDs (ROSs) based on Nb/Al, AlOx /Al/Nb Josephson tunnel junctions have been designed and fabricated. The hysteretic SQUIDs (superconducting quantum interference devices) have a maximum critical current of about 130 μA and an inductance of 20 pH. A voltage modulation of 40

  20. High-power, high repetition-rate, green-pumped, picosecond LBO optical parametric oscillator.

    Science.gov (United States)

    Kienle, Florian; Teh, Peh Siong; Lin, Dejiao; Alam, Shaif-Ul; Price, Jonathan H V; Hanna, D C; Richardson, David J; Shepherd, David P

    2012-03-26

    We report on a picosecond, green-pumped, lithium triborate optical parametric oscillator with record-high output power. It was synchronously pumped by a frequency-doubled (530 nm), pulse-compressed (4.4 ps), high-repetition-rate (230 MHz), fiber-amplified gain-switched laser diode. For a pump power of 17 W, a maximum signal and idler power of 3.7 W and 1.8 W was obtained from the optical parametric oscillator. A signal pulse duration of ~3.2 ps was measured and wide tunability from 651 nm to 1040 nm for the signal and from 1081 nm to 2851 nm for the idler was achieved.

  1. The Spectral Amplitude of Stellar Convection and Its Scaling in the High-Rayleigh-number Regime

    Science.gov (United States)

    Featherstone, Nicholas A.; Hindman, Bradley W.

    2016-02-01

    Convection plays a central role in the dynamics of any stellar interior, and yet its operation remains largely hidden from direct observation. As a result, much of our understanding concerning stellar convection necessarily derives from theoretical and computational models. The Sun is, however, exceptional in that regard. The wealth of observational data afforded by its proximity provides a unique test bed for comparing convection models against observations. When such comparisons are carried out, surprising inconsistencies between those models and observations become apparent. Both photospheric and helioseismic measurements suggest that convection simulations may overestimate convective flow speeds on large spatial scales. Moreover, many solar convection simulations have difficulty reproducing the observed solar differential rotation owing to this apparent overestimation. We present a series of three-dimensional stellar convection simulations designed to examine how the amplitude and spectral distribution of convective flows are established within a star’s interior. While these simulations are nonmagnetic and nonrotating in nature, they demonstrate two robust phenomena. When run with sufficiently high Rayleigh number, the integrated kinetic energy of the convection becomes effectively independent of thermal diffusion, but the spectral distribution of that kinetic energy remains sensitive to both of these quantities. A simulation that has converged to a diffusion-independent value of kinetic energy will divide that energy between spatial scales such that low-wavenumber power is overestimated and high-wavenumber power is underestimated relative to a comparable system possessing higher Rayleigh number. We discuss the implications of these results in light of the current inconsistencies between models and observations.

  2. Simultaneous Unbalanced Shared Local Oscillator Heterodyne Interferometry (SUSHI) for high SNR, minimally destructive dispersive detection of time-dependent atomic spins

    CERN Document Server

    Locke, Mary

    2013-01-01

    We demonstrate "Simultaneous Unbalanced Shared Local Oscillator Heterodyne Interferometry (SUSHI)," a new method for minimally destructive, high SNR dispersive detection of atomic spins. In SUSHI a dual-frequency probe laser interacts with atoms in one arm of a Mach-Zehnder interferometer, then beats against a bright local oscillator beam traversing the other arm, resulting in two simultaneous, independent heterodyne measurements of the atom-induced phase shift. Measurement noise due to mechanical disturbances of beam paths is strongly rejected by the technique of \\emph{active subtraction} in which anti-noise is actively written onto the local oscillator beam via an optical phase-locked-loop. In SUSHI, technical noise due to phase, amplitude, and frequency fluctuations of the various laser fields is strongly rejected (i) for any mean phase bias between the interferometer arms, (ii) without the use of piezo actuated mirrors, and (iii) without signal balancing. We experimentally demonstrate an ultra-low technic...

  3. Gravitational Wave - Gauge Field Oscillations

    CERN Document Server

    Caldwell, R R; Maksimova, N A

    2016-01-01

    Gravitational waves propagating through a stationary gauge field transform into gauge field waves and back again. When multiple families of flavor-space locked gauge fields are present, the gravitational and gauge field waves exhibit novel dynamics. At high frequencies, the system behaves like coupled oscillators in which the gravitational wave is the central pacemaker. Due to energy conservation and exchange among the oscillators, the wave amplitudes lie on a multi-dimensional sphere, reminiscent of neutrino flavor oscillations. This phenomenon has implications for cosmological scenarios based on flavor-space locked gauge fields.

  4. Quantifying the high-velocity, low-amplitude spinal manipulative thrust: a systematic review.

    Science.gov (United States)

    Downie, Aron S; Vemulpad, Subramanyam; Bull, Peter W

    2010-09-01

    The purpose of this study was to systematically review studies that quantify the high-velocity, low-amplitude (HVLA) spinal thrust, to qualitatively compare the apparatus used and the force-time profiles generated, and to critically appraise studies involving the quantification of thrust as an augmented feedback tool in psychomotor learning. A search of the literature was conducted to identify the sources that reported quantification of the HVLA spinal thrust. MEDLINE-OVID (1966-present), MANTIS-OVID (1950-present), and CINAHL-EBSCO host (1981-present) were searched. Eligibility criteria included that thrust subjects were human, animal, or manikin and that the thrust type was a hand-delivered HVLA spinal thrust. Data recorded were single force, force-time, or displacement-time histories. Publications were in English language and after 1980. The relatively small number of studies, combined with the diversity of method and data interpretation, did not enable meta-analysis. Twenty-seven studies met eligibility criteria: 17 studies measured thrust as a primary outcome (13 human, 2 cadaver, and 2 porcine). Ten studies demonstrated changes in psychomotor learning related to quantified thrust data on human, manikin, or other device. Quantifiable parameters of the HVLA spinal thrust exist and have been described. There remain a number of variables in recording that prevent a standardized kinematic description of HVLA spinal manipulative therapy. Despite differences in data between studies, a relationship between preload, peak force, and thrust duration was evident. Psychomotor learning outcomes were enhanced by the application of thrust data as an augmented feedback tool. Copyright © 2010 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  5. High and low frequency relaxation oscillations in a capacitive discharge plasma

    Institute of Scientific and Technical Information of China (English)

    Zhou Zhu-Wen; Sungjin Kim; Ji Shi-Yin; Sun Guang-Yu; Deng Ming-Sen

    2008-01-01

    Both high and low frequency relaxation oscillations have been observed in an argon capacitive discharge connected to a peripheral grounded chamber through a slot with dielectric spacers.The oscillations,observed from time-varying optical emission of the main discharge chamber,show,for example,a high frequency(46 kHz)relaxation oscillation at 100 mTorr,with an absorbed power near the peripheral breakdown,and a low frequency(2.7-3.7 Hz)oscillation,at a higher absorbed power.The high frequency oscillation is found to ignite a plasma in the slot,but usually not in the periphery.The high frequency oscillation is interpreted by using an electromagnetic model of the slot impedance,combined with the circuit analysis of the system including a matching network.The model is further developed by using a parallel connection of variable peripheral capacitance to analyse the low frequency oscillation.The results obtained from the model are in agreement with the experimental observations and indicate that a variety of behaviours are dependent on the matching conditions.

  6. Analytical solution of the second Stokes problem with variable amplitude on behaviour of gas over oscillation surface. Part I: eigenvalues and eigensolutions

    CERN Document Server

    Latyshev, A V

    2016-01-01

    In the present work the second Stokes problem about behaviour of the rarefied gas filling half-space is formulated. A plane limiting half-space makes harmonious fluctuations with variable amplitude in the plane. The amplitude changes on the exponential law. The kinetic equation with model integral of collisions in the form $\\tau$-model is used. The case of diffusion reflexions of gas molecules from a wall is considered. Eigen solutions (continuous modes) of the initial kinetic equation corresponding to the continuous spectrum are searched. Properties of dispersion function are studied. It is investigated the discrete spectrum of the problem consisting of zero of the dispersion functions in the complex plane. It is shown, that number of zero of dispersion function to equally doubled index of problem coefficient. The problem coefficient is understood as the relation of boundary values of dispersion function from above and from below on the real axis. Further are eigen solutions (discrete modes) of the initial k...

  7. Amplitude-integrated electroencephalographic activity is suppressed in preterm infants with high scores on illness severity

    NARCIS (Netherlands)

    ter Horst, Hendrik J.; Jongbloed-Pereboom, Marjolein; van Eykern, Leo A.; Bos, Arend F.

    2011-01-01

    Background: The neonatal acute physiology score. SNAP-II, reflects the severity of illness in newborns. In term newborns, amplitude integrated EEG (aEEG), is depressed following asphyxia. In preterm infants aEEG is discontinuous, and therefore more difficult to assess compared to term infants. Aims:

  8. Neutrino oscillations: what is magic about the "magic" baseline?

    CERN Document Server

    Smirnov, A Yu

    2006-01-01

    Physics interpretation of the ``magic'' baseline that can play important role in future oscillation experiments is given. The ``magic'' baseline coincides with the refraction length, $l_0$. The latter, in turn, approximately equals the oscillation length in matter at high energies. Therefore at the baseline $L = l_0$ the oscillation phase is $2\\pi$, and consequently, the ``solar'' amplitude of oscillations driven by the mixing angle $\\theta_{12}$ and mass splitting $\\Delta m^2_{21}$ vanishes. As a result, in the lowest order (i) the interference of amplitudes in the $\

  9. Subthalamic nucleus phase-amplitude coupling correlates with motor impairment in Parkinson's disease

    NARCIS (Netherlands)

    van Wijk, Bernadette C. M.; Beudel, Martijn; Jha, Ashwani; Oswal, Ashwini; Foltynie, Tom; Hariz, Marwan I.; Limousin, Patricia; Zrinzo, Ludvic; Aziz, Tipu Z.; Green, Alexander L.; Brown, Peter; Litvak, Vladimir

    2016-01-01

    Objective: High-amplitude beta band oscillations within the subthalamic nucleus are frequently associated with Parkinson's disease but it is unclear how they might lead to motor impairments. Here we investigate a likely pathological coupling between the phase of beta band oscillations and the amplit

  10. Inspiratory high frequency airway oscillation attenuates resistive loaded dyspnea and modulates respiratory function in young healthy individuals.

    Directory of Open Access Journals (Sweden)

    Theresa Morris

    Full Text Available Direct chest-wall percussion can reduce breathlessness in Chronic Obstructive Pulmonary Disease and respiratory function may be improved, in health and disease, by respiratory muscle training (RMT. We tested whether high-frequency airway oscillation (HFAO, a novel form of airflow oscillation generation can modulate induced dyspnoea and respiratory strength and/or patterns following 5 weeks of HFAO training (n = 20 compared to a SHAM-RMT (conventional flow-resistive RMT device (n = 15 in healthy volunteers (13 males; aged 20-36 yrs. HFAO causes oscillations with peak-to-peak amplitude of 1 cm H2O, whereas the SHAM-RMT device was identical but created no pressure oscillation. Respiratory function, dyspnoea and ventilation during 3 minutes of spontaneous resting ventilation, 1 minute of maximal voluntary hyperventilation and 1 minute breathing against a moderate inspiratory resistance, were compared PRE and POST 5-weeks of training (2 × 30 breaths at 70% peak flow, 5 days a week. Training significantly reduced NRS dyspnoea scores during resistive loaded ventilation, both in the HFAO (p = 0.003 and SHAM-RMT (p = 0.005 groups. Maximum inspiratory static pressure (cm H2O was significantly increased by HFAO training (vs. PRE; p<0.001. Maximum inspiratory dynamic pressure was increased by training in both the HFAO (vs. PRE; p<0.001 and SHAM-RMT (vs. PRE; p = 0.021 groups. Peak inspiratory flow rate (L.s(-1 achieved during the maximum inspiratory dynamic pressure manoeuvre increased significantly POST (vs. PRE; p = 0.001 in the HFAO group only. HFAO reduced inspiratory resistive loading-induced dyspnoea and augments static and dynamic maximal respiratory manoeuvre performance in excess of flow-resistive IMT (SHAM-RMT in healthy individuals without the respiratory discomfort associated with RMT.

  11. Inspiratory high frequency airway oscillation attenuates resistive loaded dyspnea and modulates respiratory function in young healthy individuals.

    Science.gov (United States)

    Morris, Theresa; Sumners, David Paul; Green, David Andrew

    2014-01-01

    Direct chest-wall percussion can reduce breathlessness in Chronic Obstructive Pulmonary Disease and respiratory function may be improved, in health and disease, by respiratory muscle training (RMT). We tested whether high-frequency airway oscillation (HFAO), a novel form of airflow oscillation generation can modulate induced dyspnoea and respiratory strength and/or patterns following 5 weeks of HFAO training (n = 20) compared to a SHAM-RMT (conventional flow-resistive RMT) device (n = 15) in healthy volunteers (13 males; aged 20-36 yrs). HFAO causes oscillations with peak-to-peak amplitude of 1 cm H2O, whereas the SHAM-RMT device was identical but created no pressure oscillation. Respiratory function, dyspnoea and ventilation during 3 minutes of spontaneous resting ventilation, 1 minute of maximal voluntary hyperventilation and 1 minute breathing against a moderate inspiratory resistance, were compared PRE and POST 5-weeks of training (2 × 30 breaths at 70% peak flow, 5 days a week). Training significantly reduced NRS dyspnoea scores during resistive loaded ventilation, both in the HFAO (p = 0.003) and SHAM-RMT (p = 0.005) groups. Maximum inspiratory static pressure (cm H2O) was significantly increased by HFAO training (vs. PRE; pRMT (vs. PRE; p = 0.021) groups. Peak inspiratory flow rate (L.s(-1)) achieved during the maximum inspiratory dynamic pressure manoeuvre increased significantly POST (vs. PRE; p = 0.001) in the HFAO group only. HFAO reduced inspiratory resistive loading-induced dyspnoea and augments static and dynamic maximal respiratory manoeuvre performance in excess of flow-resistive IMT (SHAM-RMT) in healthy individuals without the respiratory discomfort associated with RMT.

  12. A novel smart rotor support with shape memory alloy metal rubber for high temperatures and variable amplitude vibrations

    Science.gov (United States)

    Ma, Yanhong; Zhang, Qicheng; Zhang, Dayi; Scarpa, Fabrizio; Liu, Baolong; Hong, Jie

    2014-12-01

    The work describes the design, manufacturing and testing of a smart rotor support with shape memory alloy metal rubber (SMA-MR) elements, able to provide variable stiffness and damping characteristics with temperature, motion amplitude and excitation frequency. Differences in damping behavior and nonlinear stiffness between SMA-MR and more traditional metal rubber supports are discussed. The mechanical performance shown by the prototype demonstrates the feasibility of using the SMA-MR concept for active vibration control in rotordynamics, in particular at high temperatures and large amplitude vibrations.

  13. The influence of temperature dynamics and dynamic finite ion Larmor radius effects on seeded high amplitude plasma blobs

    DEFF Research Database (Denmark)

    Held, Magnus; Wiesenberger, M.; Madsen, Jens

    2016-01-01

    Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic...

  14. Parkinsonian Rest Tremor Is Associated With Modulations of Subthalamic High-Frequency Oscillations.

    Science.gov (United States)

    Hirschmann, Jan; Butz, Markus; Hartmann, Christian J; Hoogenboom, Nienke; Özkurt, Tolga E; Vesper, Jan; Wojtecki, Lars; Schnitzler, Alfons

    2016-10-01

    High frequency oscillations (>200 Hz) have been observed in the basal ganglia of PD patients and were shown to be modulated by the administration of levodopa and voluntary movement. The objective of this study was to test whether the power of high-frequency oscillations in the STN is associated with spontaneous manifestation of parkinsonian rest tremor. The electromyogram of both forearms and local field potentials from the STN were recorded in 11 PD patients (10 men, age 58 [9.4] years, disease duration 9.2 [6.3] years). Patients were recorded at rest and while performing repetitive hand movements before and after levodopa intake. High-frequency oscillation power was compared across epochs containing rest tremor, tremor-free rest, or voluntary movement and related to the tremor cycle. We observed prominent slow (200-300 Hz) and fast (300-400 Hz) high-frequency oscillations. The ratio between slow and fast high-frequency oscillation power increased when tremor became manifest. This increase was consistent across nuclei (94%) and occurred in medication ON and OFF. The ratio outperformed other potential markers of tremor, such as power at individual tremor frequency, beta power, or low gamma power. For voluntary movement, we did not observe a significant difference when compared with rest or rest tremor. Finally, rhythmic modulations of high-frequency oscillation power occurred within the tremor cycle. Subthalamic high-frequency oscillation power is closely linked to the occurrence of parkinsonian rest tremor. The balance between slow and fast high-frequency oscillation power combines information on motor and medication state. © 2016 International Parkinson and Movement Disorder Society. © 2016 International Parkinson and Movement Disorder Society.

  15. A single high dose of escitalopram increases mismatch negativity without affecting processing negativity or P300 amplitude in healthy volunteers

    DEFF Research Database (Denmark)

    Wienberg, M; Glenthøj, Birte Yding; Jensen, K S

    2009-01-01

    processing. The present study was designed to replicate and further extent the results of our initial study on the effects of a low dose of escitalopram (10 mg) on MMN, PN and P300 amplitude. In a randomised, double-blind, cross-over experiment, 20 healthy male volunteers received either a single, orally...... administered dose of 15 mg escitalopram (a highly selective serotonin reuptake inhibitor (SSRI)) or placebo, after which their PN, MMN and P300 amplitude were assessed. Similar to our initial study with 10 mg escitalopram, 15 mg escitalopram significantly increased MMN, while it did not affect P300 amplitude....... In contrast to our initial study, however, the currently higher dose of escitalopram did not increase PN. Results support the view that a broad range of increased serotonergic activity enhances MMN, while the relationship between serotonin and PN seems more complex. The current study does not support...

  16. The detection and characterization of high frequency and high wavenumber solar oscillations. Ph.D. Thesis

    Science.gov (United States)

    Fernandes, David Neil

    1992-01-01

    Doppler shift measurements of the Na D(sub 1) absorption line have revealed solar oscillations in a new regime of frequency and wavenumber. Oscillations of vertical velocities in the temperature minimum and low chromosphere of the Sun are observed with frequencies ranging up to 9.5 mHz. There is no evidence for chromospheric modes of 3 minute period. This indicates that the chromosphere does not form a good cavity for acoustic waves. The fundamental-modes appear with wavenumbers up to 5.57 M per m (equivalent spherical harmonic degree, 3877). The frequencies lie below the predicted values at wavenumbers above 1 M per m. The values are in agreement with previous measurements that exist for wavenumbers up to 2.67 M per m. Spatial maps of velocity power show that high wavenumber oscillations are suppressed in active regions. The shape of the power depression indicates that wave motion is affected in the layer of atmosphere where the measurement is made. The f-modes are suppressed in the same way as p-modes, indicating that the mechanism for wave suppression affects velocity fluctuations. Mode frequencies are not affected by the magnetic fields by more than 50 micro Hz, the precision of the measurement.

  17. Stochastically sustained population oscillations in high-beta nanolasers

    CERN Document Server

    Lebreton, A; Takemura, N; Kuwata-Gonokami, M; Robert-Philip, I; Beveratos, A

    2012-01-01

    Non-linear dynamical systems involving small populations of individuals may sustain oscillations in the population densities arising from the discrete changes in population numbers due to random events. By applying these ideas to nanolasers operating with small numbers of emitting dipoles and photons at threshold, we show that such lasers should display photon and dipole population cycles above threshold, which should be observable as a periodic modulation in the second-order correlation function of the nanolaser output. Such a modulation was recently reported in a single-mode vertical-cavity surface-emitting semiconductor laser.

  18. High-codimensional static bifurcations of strongly nonlinear oscillator

    Institute of Scientific and Technical Information of China (English)

    Zhang Qi-Chang; Wang Wei; Liu Fu-Hao

    2008-01-01

    The static bifurcation of the parametrically excited strongly nonlinear oscillator is studied.We consider the averaged equations of a system subject to Duffing-van der Pol and quintic strong nonlinearity by introducing the undetermined fundamental frequency into the computation in the complex normal form.To discuss the static bifurcation,the bifurcation problem is described as a 3-codimensional unfolding with Z2 symmetry on the basis of singularity theory.The transition set and bifurcation diagrams for the singularity are presented,while the stability of the zero solution is studied by using the eigenvalues in various parameter regions.

  19. Quantized amplitudes in a nonlinear resonant electrical circuit

    CERN Document Server

    Cretin, B

    2008-01-01

    We present a simple nonlinear resonant analog circuit which demonstrates quantization of resonating amplitudes, for a given excitation level. The system is a simple RLC resonator where C is an active capacitor whose value is related to the current in the circuit. This variation is energetically equivalent to a variation of the potential energy and the circuit acts as a pendulum in the gravitational field. The excitation voltage, synchronously switched at the current frequency, enables electrical supply and keeping the oscillation of the system. The excitation frequency has been set to high harmonic of the fundamental oscillation so that anisochronicity can keep constant the amplitude of the circuit voltage and current. The behavior of the circuit is unusual: different stable amplitudes have been measured depending on initial conditions and excitation frequency, for the same amplitude of the excitation. The excitation frequency is naturally divided by the circuit and the ratio is kept constant without external...

  20. Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Gaskell, J.; Fromhold, T. M.; Greenaway, M. T. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Eaves, L. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Novoselov, K. S.; Mishchenko, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Geim, A. K. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-09-07

    We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable.

  1. Effect of High-k Oxide on Double Gate Transistor Embedded in RF Colpitts Oscillator

    Directory of Open Access Journals (Sweden)

    M. Bella

    2016-11-01

    Full Text Available The Linear Time Variant (LTV model of phase noise is considered. It is based on the Impulse Sensitivity Function (ISF which describes carefully the sensitivity of an oscillator to a parasite impulse current injection in different nodes of the circuit. The obtained results pointed out that the ISF function is sinusoidal and its period is nearly the same of the oscillator output signal for different dielectric oxide. It also states that the phase noise of a Colpitts oscillator is not affected by the use of the high-k materials. Finally this method, if extended, is a good tool to investigate a perturbation response on such circuits.

  2. Resection of ictal high-frequency oscillations leads to favorable surgical outcome in pediatric epilepsy

    Science.gov (United States)

    Fujiwara, Hisako; Greiner, Hansel M.; Lee, Ki Hyeong; Holland-Bouley, Katherine D.; Seo, Joo Hee; Arthur, Todd; Mangano, Francesco T.; Leach, James L.; Rose, Douglas F.

    2012-01-01

    Summary Purpose Intracranial electroencephalography (EEG) is performed as part of an epilepsy surgery evaluation when noninvasive tests are incongruent or the putative seizure-onset zone is near eloquent cortex. Determining the seizure-onset zone using intracranial EEG has been conventionally based on identification of specific ictal patterns with visual inspection. High-frequency oscillations (HFOs, >80 Hz) have been recognized recently as highly correlated with the epileptogenic zone. However, HFOs can be difficult to detect because of their low amplitude. Therefore, the prevalence of ictal HFOs and their role in localization of epileptogenic zone on intracranial EEG are unknown. Methods We identified 48 patients who underwent surgical treatment after the surgical evaluation with intracranial EEG, and 44 patients met criteria for this retrospective study. Results were not used in surgical decision making. Intracranial EEG recordings were collected with a sampling rate of 2,000 Hz. Recordings were first inspected visually to determine ictal onset and then analyzed further with time-frequency analysis. Forty-one (93%) of 44 patients had ictal HFOs determined with time-frequency analysis of intracranial EEG. Key Findings Twenty-two (54%) of the 41 patients with ictal HFOs had complete resection of HFO regions, regardless of frequency bands. Complete resection of HFOs (n = 22) resulted in a seizure-free outcome in 18 (82%) of 22 patients, significantly higher than the seizure-free outcome with incomplete HFO resection (4/19, 21%). Significance Our study shows that ictal HFOs are commonly found with intracranial EEG in our population largely of children with cortical dysplasia, and have localizing value. The use of ictal HFOs may add more promising information compared to interictal HFOs because of the evidence of ictal propagation and followed by clinical aspect of seizures. Complete resection of HFOs is a favorable prognostic indicator for surgical outcome. PMID

  3. An unusual very low-mass high-amplitude pre-main sequence periodic variable

    CERN Document Server

    Rodriguez-Ledesma, Maria V; Ibrahimov, Mansur; Messina, Sergio; Parihar, Padmakar; Hessman, Frederic; de Oliveira, Catarina Alves; Herbst, William

    2012-01-01

    We have investigated the nature of the variability of CHS7797, an unusual periodic variable in the Orion Nebula Cluster. An extensive I-band photometric data set of CHS7797 was compiled between 2004-2010 using various telescopes. Further optical data have been collected in R and z' bands. In addition, simultaneous observations of the ONC region including CHS7797 were performed in the I, J, Ks and IRAC [3.6] and [4.5] bands over a time interval of about 40d. CHS7797 shows an unusual large-amplitude variation of about 1.7 mag in the R, I, and z' bands with a period 17.786. The amplitude of the brightness modulation decreases only slightly at longer wavelengths. The star is faint during 2/3 of the period and the shape of the phased light-curves for seven different observing seasons shows minor changes and small-amplitude variations. Interestingly, there are no significant colour-flux correlations for wavelengths smaller than 2microns, while the object becomes redder when fainter at longer wavelengths. CHS7797 ha...

  4. Vortex oscillations around a hemisphere-cylinder body with a high fineness ratio

    CERN Document Server

    Ma, Bao-Feng

    2016-01-01

    The vortex unsteadiness around a hemisphere-cylinder body at AOAs of 10 to 80 deg was studied using Large Eddy Simulation (LES) and Dynamic Mode Decomposition (DMD). The Reynolds number (Re) based on the cylinder diameter of the body is 22000. The results show that vortex oscillations exist over the forebody at the whole range of AOAs. The oscillation is characterized by alternate oscillations of a forebody leeward vortex pair up and down and in-phase swings from side to side. The vortex shedding can be found at the afterbody as AOAs more than 20o, and the shedding region moves forwards gradually with AOAs increasing, and accordingly the region of vortex oscillations contracts and eventually only exists near the nose as AOAs sufficiently high. The vortex oscillation and shedding all induce fluctuating side forces along the body, but the ones from vortex oscillations are larger. The frequencies of vortex oscillations are similar to the ones of vortex shedding at the AOAs of 10o-40o with St=0.085-0.12, in which...

  5. Intracranial EEG seizure onset-patterns correlate with high-frequency oscillations in patients with drug-resistant epilepsy.

    Science.gov (United States)

    Ferrari-Marinho, Taissa; Perucca, Piero; Dubeau, Francois; Gotman, Jean

    2016-11-01

    High-frequency oscillations (80-500Hz; HFOs) have been shown to be a specific biomarker of the seizure-onset zone. The relationship of HFOs with seizures having different intracranial electroencephalography (iEEG) morphological onsets, however, has shown significant relationships in experimental animals but has not been studied in humans. We investigated how interictal and ictal HFOs relate to different seizure-onset morphological patterns. We analyzed the most representative seizure type of 37 patients with drug-resistant focal epilepsy who underwent iEEG for diagnostic evaluation. According to the morphology, 211 seizure-onset zone channels were classified in six patterns (low-voltage fast activity; sharp activity at ≤13Hz; low-frequency high-amplitude periodic spikes; burst of high-amplitude polyspikes; spike-and-wave activity; and delta brush). Interictal and ictal HFOs were compared between the six seizure-onset patterns. Interictal ripple and fast ripple rates differed significantly across seizure-onset patterns (ppatterns (ppattern is more likely to be generated in a region of seizure spread. Regarding the difference in HFO density between pre-ictal baseline and seizure-onset section across the six patterns, burst of high-amplitude polyspikes and delta brushes had the highest densities of both ripples and fast ripples (ppatterns correlate specific interictal and ictal HFO profiles confirming that seizures with different morphological patterns likely have different mechanisms of generation. This study emphazises that, in clinical practice, seizure-onset patterns should be distinguished and specified when analyzing HFOs, particularly if they are used in presurgical evaluation to better localize the seizure-onset zone. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Detection of High Frequency Oscillations by Hybrid Depth Electrodes in Standard Clinical Intracranial EEG Recordings

    Directory of Open Access Journals (Sweden)

    Efstathios D Kondylis

    2014-08-01

    Full Text Available High frequency oscillations (HFOs have been proposed as a novel marker for epileptogenic tissue, spurring tremendous research interest into the characterization of these transient events. A wealth of continuously recorded intracranial electroencephalographic (iEEG data is currently available from patients undergoing invasive monitoring for the surgical treatment of epilepsy. In contrast to data recorded on research-customized recording systems, data from clinical acquisition systems remain an underutilized resource for HFO detection in most centers. The effective and reliable use of this clinically obtained data would be an important advance in the ongoing study of HFOs and their relationship to ictogenesis. The diagnostic utility of HFOs ultimately will be limited by the ability of clinicians to detect these brief, sporadic, and low amplitude events in an electrically noisy clinical environment. Indeed, one of the most significant factors limiting the use of such clinical recordings for research purposes is their low signal to noise ratio, especially in the higher frequency bands. In order to investigate the presence of HFOs in clinical data, we first obtained continuous intracranial recordings in a typical clinical environment using a commercially available, commonly utilized data acquisition system and off the shelf hybrid macro/micro depth electrodes. This data was then inspected for the presence of HFOs using semi-automated methods and expert manual review. With targeted removal of noise frequency content, HFOs were detected on both macro- and micro-contacts, and preferentially localized to seizure onset zones. HFOs detected by the offline, semi-automated method were also validated in the clinical viewer, demonstrating that 1 this clinical system allows for the visualization of HFOs, and 2 with effective signal processing, clinical recordings can yield valuable information for offline analysis.

  7. High Performance of Space Vector Modulation Direct Torque Control SVM-DTC Based on Amplitude Voltage and Stator Flux Angle

    Directory of Open Access Journals (Sweden)

    Hassan Farhan Rashag

    2013-04-01

    Full Text Available Various aspects related to controlling induction motor are investigated. Direct torque control is an original high performance control strategy in the field of AC drive. In this proposed method, the control system is based on Space Vector Modulation (SVM, amplitude of voltage in direct- quadrature reference frame (d-q reference and angle of stator flux. Amplitude of stator voltage is controlled by PI torque and PI flux controller. The stator flux angle is adjusted by rotor angular frequency and slip angular frequency. Then, the reference torque and the estimated torque is applied to the input of PI torque controller and the control quadrature axis voltage is determined. The control d-axis voltage is determined from the flux calculator. These q and d axis voltage are converted into amplitude voltage. By applying polar to Cartesian on amplitude voltage and stator flux angle, direct voltage and quadratures voltage are generated. The reference stator voltages in d-q are calculated based on forcing the stator voltage error to zero at next sampling period. By applying inverse park transformation on d-q voltages, the stator voltages in &alpha and &beta frame are generated and apply to SVM. From the output of SVM, the motor control signal is generated and the speed of the induction motor regulated toward the rated speed. The simulation Results have demonstrated exceptional performance in steady and transient states and shows that decrease of torque and flux ripples is achieved in a complete speed range.

  8. Frequency tuning of polarization oscillations: Toward high-speed spin-lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lindemann, Markus, E-mail: markus.lindemann@rub.de; Gerhardt, Nils C.; Hofmann, Martin R. [Photonics and Terahertz Technology, Ruhr-University Bochum, 44780 Bochum (Germany); Pusch, Tobias; Michalzik, Rainer [Institute of Optoelectronics, Ulm University, 89081 Ulm (Germany)

    2016-01-25

    Spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) offer a high potential to overcome several limitations of conventional purely charged-based laser devices. Presumably, the highest potential of spin-VCSELs lies in their ultrafast spin and polarization dynamics, which can be significantly faster than the intensity dynamics in conventional devices. Here, we experimentally demonstrate polarization oscillations in spin-VCSELs with frequencies up to 44 GHz. The results show that the oscillation frequency mainly depends on the cavity birefringence, which can be tuned by applying mechanical strain to the VCSEL structure. A tuning range of about 34 GHz is demonstrated. By measuring the polarization oscillation frequency and the birefringence governed mode splitting as a function of the applied strain simultaneously, we are able to investigate the correlation between birefringence and polarization oscillations in detail. The experimental findings are compared to numerical calculations based on the spin-flip model.

  9. High- T_c superconducting thin film/GaAs MESFET hybrid microwave oscillator

    Institute of Scientific and Technical Information of China (English)

    金飚兵; 康琳; 伍瑞新; 张健羽; 程其恒; 吴培亨; 经东; 焦刚; 邵凯; 蒋明明; 张家宗; 孙敏松; 王蕴仪; 周岳亮; 吕惠宾; 许世发; 何萌; 王小平; 杨秉川; 卢剑; 张其邵

    1997-01-01

    A high- Tc superconducting (HTSC) thin film/GaAs MESFET hybrid microwave oscillator operated at 10 6 GHz has been designed, fabricated and characterized. Microstrip line structures were used throughout the circuit with superconducting thin film YBaiCuiO7 8(YBCO) as the conductor material. The YBCO thin films were deposited on 15 mm×10 mm×0. 5 mm LaAlO3 substrates. The oscillator was common-source, series feedback type using a GaAs-MESFET (NE72084) as the active device and a superconducting microstrip resonator as the frequency stabilizing element. By improving the unloaded quality factor Q0 of the superconducting microstrip resonator and adjusting the coupling coefficient between the resonator and the gate of the MESFET, the phase noise of the oscillator was decreased At 77 K, the phase noise of the oscillator at 10 kHz offset from carrier was - 87 dBc/Hz.

  10. Evaluation of a Hopkinson bar fly-away technique for high amplitude shock accelerometer calibration

    Energy Technology Data Exchange (ETDEWEB)

    Togami, T.C.; Bateman, V.I.; Brown, F.A.

    1997-11-01

    A split Hopkinson bar technique has been developed to evaluate the performance of accelerometers that measure large amplitude pulses. An evaluation of this technique has been conducted in the Mechanical Shock Laboratory at Sandia National Laboratories (SNL) to determine its use in the practical calibration of accelerometers. This evaluation consisted of three tasks. First, the quartz crystal was evaluated in a split Hopkinson bar configuration to evaluate the quartz gage`s sensitivity and frequency response at force levels of 18,000, 35,000 and 53,000 N at ambient temperature, {minus}48 C and +74 C. Secondly, the fly away technique was evaluated at shock amplitudes of 50,000, 100,000, 150,000 and 200,000 G (1 G = 9.81 m/s{sup 2}) at ambient temperature, {minus}48 C and +74 C. Lastly, the technique was performed using a NIST calibrated reference accelerometer. Comparisons of accelerations calculated from the quartz gage data and the measured acceleration data have shown very good agreement. Based on this evaluation, the authors expect this split Hopkinson fly away technique to be certified by the SNL Primary Standards Laboratory.

  11. Implications of high amplitude atmospheric CO2 fluctuations on past millennium climate change

    Science.gov (United States)

    van Hoof, Thomas; Kouwenberg, Lenny; Wagner-Cremer, Friederike; Visscher, Henk

    2010-05-01

    Stomatal frequency analysis of leaves of land plants preserved in peat and lake deposits can provide a proxy record of pre-industrial atmospheric CO2 concentration complementary to measurements in Antarctic ice cores. Stomatal frequency based CO2 trends from the USA and NW European support the presence of significant CO2 variability during the first half of the last millennium (Kouwenberg et al., 2005; Wagner et al., 2004; van Hoof et al., 2008). The timing of the most significant perturbation in the stomata records (1200 AD) is in agreement with an observed CO2 fluctuation in the D47 Antarctic ice-core record (Barnola et al., 1995; van Hoof et al., 2005). The amplitude of the stomatal frequency based CO2 changes (> 34ppmv) exceeds the maximum amplitude of CO2 variability in the D47 ice core (Proceedings of the National Academy of Sciences of the USA, v. 105, no. 41, pp. 15815-15818 Wagner F., L.L.R. Kouwenberg, T.B. van Hoof and H. Visscher 2004. Reproducibility of Holocene atmospheric CO2 records based on stomatal frequency. Quartenary Science Reviews. V. 23, pp. 1947-1954

  12. Atomic fountain clock with very high frequency stability employing a pulse-tube-cryocooled sapphire oscillator.

    Science.gov (United States)

    Takamizawa, Akifumi; Yanagimachi, Shinya; Tanabe, Takehiko; Hagimoto, Ken; Hirano, Iku; Watabe, Ken-ichi; Ikegami, Takeshi; Hartnett, John G

    2014-09-01

    The frequency stability of an atomic fountain clock was significantly improved by employing an ultra-stable local oscillator and increasing the number of atoms detected after the Ramsey interrogation, resulting in a measured Allan deviation of 8.3 × 10(-14)τ(-1/2)). A cryogenic sapphire oscillator using an ultra-low-vibration pulse-tube cryocooler and cryostat, without the need for refilling with liquid helium, was applied as a local oscillator and a frequency reference. High atom number was achieved by the high power of the cooling laser beams and optical pumping to the Zeeman sublevel m(F) = 0 employed for a frequency measurement, although vapor-loaded optical molasses with the simple (001) configuration was used for the atomic fountain clock. The resulting stability is not limited by the Dick effect as it is when a BVA quartz oscillator is used as the local oscillator. The stability reached the quantum projection noise limit to within 11%. Using a combination of a cryocooled sapphire oscillator and techniques to enhance the atom number, the frequency stability of any atomic fountain clock, already established as primary frequency standard, may be improved without opening its vacuum chamber.

  13. Investigating riparian groundwater flow close to a losing river using diurnal temperature oscillations at high vertical resolution

    Directory of Open Access Journals (Sweden)

    T. Vogt

    2012-02-01

    Full Text Available River-water infiltration is of high relevance for hyporheic and riparian groundwater ecology as well as for drinking water supply by river-bank filtration. Heat has become a popular natural tracer to estimate exchange rates between rivers and groundwater. However, quantifying flow patterns and velocities is impeded by spatial and temporal variations of exchange fluxes, insufficient sensors spacing during field investigations, or simplifying assumptions for analysis or modeling such as uniform flow. The objective of this study is to investigate lateral shallow groundwater flow upon river-water infiltration at the shoreline of the riverbed and in the adjacent riparian zone of the River Thur in northeast Switzerland. Here we have applied distributed temperature sensing (DTS along optical fibers wrapped around tubes to measure high-resolution vertical temperature profiles of the unsaturated zone and shallow riparian groundwater. Diurnal temperature oscillations were tracked in the subsurface and analyzed by means of dynamic harmonic regression to extract amplitudes and phase angles. Subsequent calculations of amplitude attenuation and time shift relative to the river signal show in detail vertical and temporal variations of heat transport in shallow riparian groundwater. In addition, we apply a numerical two-dimensional heat transport model for the unsaturated zone and shallow groundwater to obtain a better understanding of the observed heat transport processes in shallow riparian groundwater and to estimate the groundwater flow velocity. Our results show that the observed riparian groundwater temperature distribution cannot be described by uniform flow, but rather by horizontal groundwater flow velocities varying over depth. In addition, heat transfer of diurnal temperature oscillations from the losing river through shallow groundwater is influenced by thermal exchange with the unsaturated zone. Neglecting the influence of the unsaturated zone

  14. Measurement of high-degree solar oscillation frequencies

    Science.gov (United States)

    Bachmann, K. T.; Duvall, T. L., Jr.; Harvey, J. W.; Hill, F.

    1995-01-01

    We present m-averaged solar p- and f-mode oscillation frequencies over the frequency range nu greater than 1.8 and less than 5.0 mHz and the spherical harmonic degree range l greater than or equal to 100 and less than or equal to 1200 from full-disk, 1000 x 1024 pixel, Ca II intensity images collected 1993 June 22-25 with a temporal cadence of 60 s. We itemize the sources and magnitudes of statistical and systematic uncertainties and of small frequency corrections, and we show that our frequencies represent an improvement in accuracy and coverage over previous measurements. Our frequencies agree at the 2 micro Hz level with Mount Wilson frequencies determined for l less than or equal to 600 from full-disk images, and we find systematic offsets of 10-20 micro Hz with respect to frequencies measured from Big Bear and La Palma observations. We give evidence that these latter offsets are indicative of spatial scaling uncertainties associated with the analysis of partial-disk images. In comparison with theory, our p-mode frequencies agree within 10 micro Hz of frequencies predicted by the Los Alamos model but are as much as 100 micro Hz smaller than frequencies predicted by the Denmark and Yale models at degrees near 1000. We also find systematic differences between our n = 0 frequencies and the frequencies closely agreed upon by all three models.

  15. Neutrino Oscillation Parameters After High Statistics KamLAND Results

    CERN Document Server

    Bandyopadhyay, Abhijit; Goswami, Srubabati; Petcov, S T; Roy, D P

    2008-01-01

    We do a re-analysis to asses the impact of the results of the Borexino experiment and the recent 2.8 KTy KamLAND data on the solar neutrino oscillation parameters. The current Borexino results are found to have no impact on the allowed solar neutrino parameter space. The new KamLAND data causes a significant reduction of the allowed range of $\\Delta m^2_{21}$, determining it with an unprecedented precision of 8.3% at 3$\\sigma$. The precision of $\\Delta m^2_{21}$ is controlled practically by the KamLAND data alone. Inclusion of new KamLAND results also improves the upper bound on $\\sin^2\\theta_{12}$, but the precision of this parameter continues to be controlled by the solar data. The third mixing angle is constrained to be $\\sin^2\\theta_{13} < 0.063$ at $3\\sigma$ from a combined fit to the solar, KamLAND, atmospheric and CHOOZ results. We also address the issue of how much further reduction of allowed range of $\\Delta m^2_{21}$ and $\\sin^2\\theta_{12}$ is possible with increased statistics from KamLAND. We ...

  16. Quantum oscillations in non-Fermi liquids: Implications for high-temperature superconductors

    Science.gov (United States)

    Scherpelz, Peter; He, Yan; Levin, K.

    2013-12-01

    We address quantum oscillation experiments in high-Tc superconductors and the evidence from these experiments for a pseudogap versus a Fermi liquid phase at high magnetic fields. As a concrete alternative to a Fermi liquid phase, the pseudogap state we consider derives from earlier work within a Gor'kov-based Landau level approach. Here the normal state pairing gap in the presence of high fields is spatially nonuniform, incorporating small gap values. These, in addition to d-wave gap nodes, are responsible for the persistence of quantum oscillations. Important here are methodologies for distinguishing different scenarios. To this end we examine the temperature dependence of the oscillations. Detailed quantitative analysis of this temperature dependence demonstrates that a high-field pseudogap state in the cuprates may well "masquerade" as a Fermi liquid.

  17. Short duration high amplitude flares detected on the M dwarf star KIC 5474065

    CERN Document Server

    Ramsay, Gavin; Hakala, Pasi; Garcia-Alvarez, David; Brooks, Adam; Barclay, Thomas; Still, Martin

    2013-01-01

    Using data obtained during the RATS-Kepler project we identified one short duration flare in a 1 hour sequence of ground based photometry of the dwarf star KIC 5474065. Observations made using GTC show it is a star with a M4 V spectral type. Kepler observations made using 1 min sampling show that KIC 5474065 exhibits large amplitude (deltaF/F>0.4) optical flares which have a duration as short as 10 mins. We compare the energy distribution of flares from KIC 5474065 with that of KIC 9726699, which has also been observed using 1 min sampling, and ground based observations of other M dwarf stars in the literature. We discuss the possible implications of these short duration, relatively low energy flares would have on the atmosphere of exo-planets orbiting in the habitable zone of these flare stars.

  18. Multiband Carrierless Amplitude Phase Modulation for High Capacity Optical Data Links

    DEFF Research Database (Denmark)

    Iglesias Olmedo, Miguel; Zuo, Tianjian; Jensen, Jesper Bevensee

    2014-01-01

    packaging. Therefore, increasing effort is now put into the possibility of exploiting higher order modulation formats with increased spectral efficiency and reduced optical transceiver complexity. As these type of links are based on intensity modulation and direct detection, modulation formats relying...... on optical coherent detection can not be straight forwardly employed. As an alternative and more viable solution, this paper proposes the use of carrierless amplitude phase (CAP) in a novel multiband approach (MultiCAP) that achieves record spectral efficiency, increases tolerance towards dispersion......Short range optical data links are experiencing bandwidth limitations making it very challenging to cope with the growing data transmission capacity demands. Parallel optics appears as a valid short-term solution. It is, however, not a viable solution in the long-term because of its complex optical...

  19. Using domain walls to perform non-local measurements with high spin signal amplitudes

    Science.gov (United States)

    Savero Torres, W.; Pham, V.-T.; Zahnd, G.; Laczkowski, P.; Nguyen, V.-D.; Beigné, C.; Notin, L.; Jamet, M.; Marty, A.; Vila, L.; Attané, J.-P.

    2016-07-01

    Standard non-local measurements require lateral spin-valves with two different ferromagnetic electrodes, to create and to detect the spin accumulation. Here we show that non-local measurements can also be performed in a cross-shaped nanostructure, made of a single ferromagnetic wire connected to an orthogonal non-magnetic wire. A magnetic domain wall located underneath the ferromagnetic/non-magnetic interface is used to control the magnetizations of the injection and detection zones. As these zones can be very close, our results display spin signals possessing amplitudes larger than those obtained in conventional non-local measurements. We also show that this method can be used as a domain wall detection technique.

  20. The Spectral Amplitude of Stellar Convection and its Scaling in the High-Rayleigh-Number Regime

    CERN Document Server

    Featherstone, Nicholas A

    2015-01-01

    Convection plays a central role in the dynamics of any stellar interior, and yet its operation remains largely-hidden from direct observation. As a result, much of our understanding concerning stellar convection necessarily derives from theoretical and computational models. The Sun is, however, exceptional in that regard. The wealth of observational data afforded by its proximity provides a unique testbed for comparing convection models against observations. When such comparisons are carried out, surprising inconsistencies between those models and observations become apparent. Both photospheric and helioseismic measurements suggest that convection simulations may overestimate convective flow speeds on large spatial scales. Moreover, many solar convection simulations have difficulty reproducing the observed solar differential rotation due to this apparent overestimation. We present a series of 3-dimensional (3-D) stellar convection simulations designed to examine how the amplitude and spectral distribution of ...

  1. Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media

    Science.gov (United States)

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume

    2017-03-01

    The presence of neutral species in a plasma has been shown to greatly affect the properties of magnetohydrodynamic waves. For instance, the interaction between ions and neutrals through momentum transfer collisions causes the damping of Alfvén waves and alters their oscillation frequency and phase speed. When the collision frequencies are larger than the frequency of the waves, single-fluid magnetohydrodynamic approximations can accurately describe the effects of partial ionization, since there is a strong coupling between the various species. However, at higher frequencies, the single-fluid models are not applicable and more complex approaches are required. Here, we use a five-fluid model with three ionized and two neutral components, which takes into consideration Hall’s current and Ohm’s diffusion in addition to the friction due to collisions between different species. We apply our model to plasmas composed of hydrogen and helium, and allow the ionization degree to be arbitrary. By analyzing the corresponding dispersion relation and numerical simulations, we study the properties of small-amplitude perturbations. We discuss the effect of momentum transfer collisions on the ion-cyclotron resonances and compare the importance of magnetic resistivity, and ion–neutral and ion–ion collisions on the wave damping at various frequency ranges. Applications to partially ionized plasmas of the solar atmosphere are performed.

  2. The effects of photobiomodulation and low-amplitude high-frequency vibration on bone healing process: a comparative study.

    Science.gov (United States)

    Rajaei Jafarabadi, M; Rouhi, G; Kaka, G; Sadraie, S H; Arum, J

    2016-12-01

    This study aimed at investigating the effects of photobiomodulation (PBM) and low-amplitude high-frequency (LAHF) whole body mechanical vibration on bone fracture healing process when metallic plates are implanted in rats' femurs. Forty male rats weighing between 250 and 350 g, 12 weeks old, were employed in this study. A transverse critical size defect (CSD) was made in their right femurs that were fixed by stainless steel plates. After the surgery, the rats were divided equally into four groups: low-level laser therapy group (GaAlAs laser, 830 nm, 40 mW, 4 J/cm(2), 0.35 cm beam diameter, LLLT), whole body vibration group (60 Hz, 0.1 mm amplitude, 1.5 g, WBV), a combination of laser and vibration group (LV), and the control group (C). Each group was divided into two subgroups based on sacrifice dates. The rats were sacrificed at intervals of 3 and 6 weeks after the surgery to extract their right femurs for radiography and biomechanical and histological analyses, and the results were analyzed using standard statistical methods. Radiographic analyses showed greater callus formation in the LLLT and WBV groups than in control group at both 3 (P low-amplitude high-frequency WBV both had a positive impact on bone healing process, for critical size defects in the presence of a stainless steel implant. But their combination, i.e., low-level laser therapy and low-amplitude high-frequency whole body vibration (LV), interestingly did not accelerate the fractured bone healing process.

  3. Oscillation death in coupled oscillators

    Institute of Scientific and Technical Information of China (English)

    Wei ZOU; Xin-gang WANG; Qi ZHAO; Meng ZHAN

    2009-01-01

    We study dynamical behaviors in coupled nonlinear oscillators and find that under certain condi- tions, a whole coupled oscillator system can cease oscil- lation and transfer to a globally nonuniform stationary state [I.e., the so-called oscillation death (OD) state], and this phenomenon can be generally observed. This OD state depends on coupling strengths and is clearly differ- ent from previously studied amplitude death (AD) state, which refers to the phenomenon where the whole system is trapped into homogeneously steady state of a fixed point, which already exists but is unstable in the ab- sence of coupling. For larger systems, very rich pattern structures of global death states are observed. These Turing-like patterns may share some essential features with the classical Turing pattern.

  4. The MACHO Project Sample of Galactic Bulge High-Amplitude Scuti Stars: Pulsation Behavior and Stellar Properties

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, D.P.; Cook, K.H.; Freeman, K.C.; Geha, M.; Griest, K.; Lehner, M.J.; Marshall, S.L.; McNamara, B.J.; Minniti, D.; Nelson, C.; Peterson, B.A.; Popowski, P.; Pratt, M.R.; Quinn, P.J.; Rodgers, A.W.; Sutherland, W.; Templeton, M.R.; Vandehei, T.; Welch, D.L.

    1999-11-16

    We have detected 90 objects with periods and lightcurve structure similar to those of field {delta} Scuti stars, using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude {delta} Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground {delta} Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population {delta} Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field {delta} Scuti stars and the {delta} Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude {delta} Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles d{sup -1}) and the observed period ratios of {approx}0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.

  5. Stability analysis of amplitude death in delay-coupled high-dimensional map networks and their design procedure

    Science.gov (United States)

    Watanabe, Tomohiko; Sugitani, Yoshiki; Konishi, Keiji; Hara, Naoyuki

    2017-01-01

    The present paper studies amplitude death in high-dimensional maps coupled by time-delay connections. A linear stability analysis provides several sufficient conditions for an amplitude death state to be unstable, i.e., an odd number property and its extended properties. Furthermore, necessary conditions for stability are provided. These conditions, which reduce trial-and-error tasks for design, and the convex direction, which is a popular concept in the field of robust control, allow us to propose a design procedure for system parameters, such as coupling strength, connection delay, and input-output matrices, for a given network topology. These analytical results are confirmed numerically using delayed logistic maps, generalized Henon maps, and piecewise linear maps.

  6. Plasma oscillations in two-dimensional semiconductor superstructures in the presence of a high electric field

    CERN Document Server

    Glazov, S Y

    2001-01-01

    The effect of the high permanent electric field on plasma oscillations in the two-dimensional electron gas with the superstructure and taking into account the transfer processes is investigated. The dispersions omega(k) is obtained for the case of high temperature T (DELTA << T, where DELTA is the width of the conductivity miniband). It is shown that the frequency of plasmons in the high electric field depends on the value of the electric field intensity and the wave number k as the oscillating function. The spectrum is periodic with the period equal to 2 pi/d for arbitrary values of k. The numerical estimation shown that the oscillations can be manifested at the electric field intensity more than 3 x 10 sup 3 V/cm

  7. Automatic detection of high frequency oscillations during epilepsy surgery predicts seizure outcome

    NARCIS (Netherlands)

    Fedele, Tommaso; van 't Klooster, Maryse; Burnos, Sergey; Zweiphenning, Willemiek; van Klink, Nicole; Leijten, Frans; Zijlmans, Maeike; Sarnthein, Johannes

    2016-01-01

    OBJECTIVE: High frequency oscillations (HFOs) and in particular fast ripples (FRs) in the post-resection electrocorticogram (ECoG) have recently been shown to be highly specific predictors of outcome of epilepsy surgery. FR visual marking is time consuming and prone to observer bias. We validate her

  8. Amplitude of Low-frequency Oscillations in Parkinson′s Disease: A 2-year Longitudinal Resting-state Functional Magnetic Resonance Imaging Study

    Directory of Open Access Journals (Sweden)

    Xiao-Fei Hu

    2015-01-01

    Full Text Available Background: Neuroimaging studies have found that functional changes exist in patients with Parkinson′s disease (PD. However, the majority of functional magnetic resonance imaging (fMRI studies in patients with PD are task-related and cross-sectional. This study investigated the functional changes observed in patients with PD, at both baseline and after 2 years, using resting-state fMRI. It further investigated the relationship between whole-brain spontaneous neural activity of patients with PD and their clinical characteristics. Methods: Seventeen patients with PD underwent an MRI procedure at both baseline and after 2 years using resting-state fMRI that was derived from the same 3T MRI. In addition, 20 age- and sex-matched, healthy controls were examined using resting-state fMRI. The fractional amplitude of low-frequency fluctuation (fALFF approach was used to analyze the fMRI data. Nonlinear registration was used to model within-subject changes over the scanning interval, as well as changes between the patients with PD and the healthy controls. A correlative analysis between the fALFF values and clinical characteristics was performed in the regions showing fALFF differences. Results: Compared to the control subjects, the patients with PD showed increased fALFF values in the left inferior temporal gyrus, right inferior parietal lobule (IPL and right middle frontal gyrus. Compared to the baseline in the 2 years follow-up, the patients with PD presented with increased fALFF values in the right middle temporal gyrus and right middle occipital gyrus while also having decreased fALFF values in the right cerebellum, right thalamus, right striatum, left superior parietal lobule, left IPL, left precentral gyrus, and left postcentral gyrus (P < 0.01, after correction with AlphaSim. In addition, the fALFF values in the right cerebellum were positively correlated with the Unified PD Rating Scale (UPDRS motor scores (r = 0.51, P < 0.05, uncorrected and

  9. High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out

    Science.gov (United States)

    Cardani, L.; Casali, N.; Colantoni, I.; Cruciani, A.; Bellini, F.; Castellano, M. G.; Cosmelli, C.; D'Addabbo, A.; Di Domizio, S.; Martinez, M.; Tomei, C.; Vignati, M.

    2017-01-01

    Developing wide-area cryogenic light detectors with baseline resolution better than 20 eV is one of the priorities of next generation bolometric experiments searching for rare interactions, as the simultaneous read-out of the light and heat signals enables background suppression through particle identification. Among the proposed technological approaches for the phonon sensor, the naturally multiplexed Kinetic Inductance Detectors (KIDs) stand out for their excellent intrinsic energy resolution and reproducibility. The potential of this technique was proved by the CALDER project that reached a baseline resolution of 154 ± 7 eV RMS by sampling a 2 × 2 cm2 Silicon substrate with 4 Aluminum KIDs. In this paper, we present a prototype of Aluminum KID with improved geometry and quality factor. The design improvement, as well as the combined analysis of amplitude and phase signals, allowed to reach a baseline resolution of 82 ± 4 eV by sampling the same substrate with a single Aluminum KID.

  10. Generation of high energy and good beam quality pulses with a master oscillator power amplifier

    Institute of Scientific and Technical Information of China (English)

    Zhigang Li(李志刚); Z.Xiong; Nicholas Moore; Chen Tao; G.C.Lim; Weiling Huang(黄维玲); Dexiu Huang(黄德修)

    2004-01-01

    A high efficiency and high peak power laser system with short-pulse and good beam quality has been demonstrated by using a master oscillator power amplifier with two-pass amplification configuration. The master oscillator, end-pumped with a fiber-coupled laser diode array, provides low power but excellent beam quality pulses, and the amplifier boosts the pulse energy by orders without significant beam quality degradation. Short pulses of 8.5 ns with energy up to 130 mJ and approximately diffraction limited beam quality have been demonstrated.

  11. Resolving longitudinal amplitude and phase information of two continuous data streams for high-speed and real-time processing

    Directory of Open Access Journals (Sweden)

    A. Guntoro

    2009-05-01

    Full Text Available Although there is an increase of performance in DSPs, due to its nature of execution a DSP could not perform high-speed data processing on a continuous data stream. In this paper we discuss the hardware implementation of the amplitude and phase detector and the validation block on a FPGA. Contrary to the software implementation which can only process data stream as high as 1.5 MHz, the hardware approach is 225 times faster and introduces much less latency.

  12. Surrogate data modeling the relationship between high frequency amplitudes and Higuchi fractal dimension of EEG signals in anesthetized rats.

    Science.gov (United States)

    Spasic, Sladjana; Kalauzi, Aleksandar; Kesic, Srdjan; Obradovic, Milica; Saponjic, Jasna

    2011-11-21

    We used spectral analysis and Higuchi fractal dimension (FD) to correlate the EEG spectral characteristics of the sensorimotor cortex, hippocampus, and pons with their corresponding EEG signal complexities in anesthetized rats. We have explored the quantitative relationship between the mean FDs and EEG wide range high frequency (8-50 Hz) activity during ketamine/xylazine versus nembutal anesthesia at surgical plane. Using FD we detected distinct inter-structure complexity pattern and uncovered for the first time that the polygraphically and behaviorally defined anesthetized state at surgical plane as equal during experiment in two anesthetic regimens, is not the same with respect to the degree of neuronal activity (degree of generalized neuronal inhibition achieved) at different brain levels. Using the correlation of certain brain structure EEG spectral characteristics with their corresponding FDs, and the surrogate data modeling, we determined what particular frequency band contributes to EEG complexities in ketamine/xylazine versus nembutal anesthesia. In this study we have shown that the quantitative relationship between higher frequency EEG amplitude and EEG complexity is the best-modeled by surrogate data as a 3rd order polynomial. On the base of our EEG amplitude/EEG complexity relationship model, and the evidenced spectral differences in ketamine versus nembutal anesthesia we have proved that higher amplitudes of sigma, beta, and gamma frequency in ketamine anesthesia yields to higher FDs.

  13. DC-current induced magneto-oscillations in very high-mobility 2D electron gas

    Science.gov (United States)

    Yang, C. L.; Zhang, Chi; Du, R. R.; Pfeiffer, L. N.; West, K. W.

    2007-03-01

    We report on a systematic experimental study of DC-current induced magneto-oscillations [1] using Hall bar samples of very high-mobility (8-20 x 10^6 cm^2/Vs) GaAs/AlxGa1-xAs heterostructures. Previously we show that remarkable nonlinear resistance and 1/B oscillations can arise when a high bias current (Ix) is passed through a Hall bar (width w), and the effect can be explained by a Zener tunneling model in the presence of a tilting Hall field [1]. Data of resistance Rxx≡Vx/Ix, differential resistance rxx≡Vx/Ix, and rxx'≡rxx/Ix in higher mobility samples, which show higher order oscillations, have confirmed the validity of this model. Our temperature dependent date show that this effect can persist to kBT>φc, where φc is the cyclotron energy. [1] Yang et al, Phys. Rev. Lett. 89, 076801 (2002).

  14. Linearization of conservative nonlinear oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Belendez, A; Alvarez, M L [Departamento de Fisica, IngenierIa de Sistemas y TeorIa de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, E; Pascual, I [Departamento de Optica, FarmacologIa y AnatomIa, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es

    2009-03-11

    A linearization method of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force which allows us to obtain a frequency-amplitude relation which is valid not only for small but also for large amplitudes and, sometimes, for the complete range of oscillation amplitudes. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of the technique.

  15. High Power Room Temperature Terahertz Local Oscillator Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The motivation of the proposed SBIR is to develop, demonstrate and commercialize a compact, low-mass, high output power (1-10 milliwatt), tunable source of CW THz...

  16. Novel high-frequency, high-power, pulsed oscillator based on a transmission line transformer.

    Science.gov (United States)

    Burdt, R; Curry, R D

    2007-07-01

    Recent analysis and experiments have demonstrated the potential for transmission line transformers to be employed as compact, high-frequency, high-power, pulsed oscillators with variable rise time, high output impedance, and high operating efficiency. A prototype system was fabricated and tested that generates a damped sinusoidal wave form at a center frequency of 4 MHz into a 200 Omega load, with operating efficiency above 90% and peak power on the order of 10 MW. The initial rise time of the pulse is variable and two experiments were conducted to demonstrate initial rise times of 12 and 3 ns, corresponding to a spectral content from 4-30 and from 4-100 MHz, respectively. A SPICE model has been developed to accurately predict the circuit behavior and scaling laws have been identified to allow for circuit design at higher frequencies and higher peak power. The applications, circuit analysis, test stand, experimental results, circuit modeling, and design of future systems are all discussed.

  17. Design of High Frequency Power Oscillator Board Based on Rotary Encoder Control

    Directory of Open Access Journals (Sweden)

    Jiang Shifen

    2013-06-01

    Full Text Available Accurate and stable high frequency pulse power supply is studied to improve high-speed wedm machine tool's efficiency. Regarding to the shortcomings of traditional digital circuit high frequency oscillator board, we design a high frequency power oscillator board based on rotary encoder control, control accuracy and high-frequency waveform by programming, adjusting the frequency and display. It has six brakes of processing function, it also includes feedback function of emulsification oil. The high frequency will be shutdown and the emulsification oil will be changed if there is too much metal dust in emulsification. It has been proved by practice that high-frequency circuit board is simple and reliable and can greatly increase efficiency of wire cutting.

  18. Novel High Temperature Capacitive Pressure Sensor Utilizing SiC Integrated Circuit Twin Ring Oscillators

    Science.gov (United States)

    Scardelletti, M.; Neudeck, P.; Spry, D.; Meredith, R.; Jordan, J.; Prokop, N.; Krasowski, M.; Beheim, G.; Hunter, G.

    2017-01-01

    This paper describes initial development and testing of a novel high temperature capacitive pressure sensor system. The pressure sensor system consists of two 4H-SiC 11-stage ring oscillators and a SiCN capacitive pressure sensor. One oscillator has the capacitive pressure sensor fixed at one node in its feedback loop and varies as a function of pressure and temperature while the other provides a pressure-independent reference frequency which can be used to temperature compensate the output of the first oscillator. A two-day repeatability test was performed up to 500C on the oscillators and the oscillator fundamental frequency changed by only 1. The SiCN capacitive pressure sensor was characterized at room temperature from 0 to 300 psi. The sensor had an initial capacitance of 3.76 pF at 0 psi and 1.75 pF at 300 psi corresponding to a 54 change in capacitance. The integrated pressure sensor system was characterized from 0 to 300 psi in steps of 50 psi over a temperature range of 25 to 500C. The pressure sensor system sensitivity was 0.113 kHzpsi at 25C and 0.026 kHzpsi at 500C.

  19. An experiment to detect gravity at sub-mm scale with high-Q mechanical oscillators

    CERN Document Server

    Haiberger, L; Wenz, H; Schiller, S

    2005-01-01

    Silicon double paddle oscillators are well suited for the detection of weak forces because of their high Q factor (about 10^5 at room temperature). We describe an experiment aimed at the detection of gravitational forces between masses at sub-mm distance using such an oscillator. Gravitational excitation is produced by a rotating aluminium disk with platinum segments. The force sensitivity of this apparatus is about 10 fN at room temperature for 1000 s averaging time at room temperature. The current limitations to detection of the gravitational force are mentioned.

  20. a Network of Oscillators Emulating the Italian High-Voltage Power Grid

    Science.gov (United States)

    Fortuna, Luigi; Frasca, Mattia; Sarra Fiore, Angelo

    2012-10-01

    In this paper, a dynamical model based on Kuramoto-like oscillators is used to represent the Italian high-voltage power grid. Nodes of the network are generators/substations, while links are the physical connections between generators/substations. The normal operating regime of the power grid corresponds to the regime in which the oscillations of all the nodes are synchronized. We studied the conditions for synchronization and the effect of dynamical perturbations on the nodes. The analysis allows to define several dynamical parameters assessing the dynamical robustness of the network.

  1. High-frequency current oscillations in graphene-boron nitride resonant tunnel diodes

    Science.gov (United States)

    Greenaway, Mark; Gaskell, Jenn; Eaves, Laurence; Novoselov, Kostya; Mishchenko, Artem; Geim, Andre; Fromhold, Mark

    The successful realisation of multilayer graphene-hBN-graphene resonant tunnelling diodes (graphene- RTDs) with negative differential conductance (NDC) and MHz current oscillations offers the exciting possibility of exploiting them as high-frequency oscillators and mixers. In this paper, we examine their potential for generating higher frequencies by simulating the oscillations in the tunnel current and charge that arise when the device is biased in the NDC region and placed in a resonant circuit. Using the Bardeen transfer Hamiltonian method, we examine the effect on the device characteristics of the twist angle, θ, between the two graphene electrodes, the hBN barrier thickness and of the carrier density in the graphene electrodes, which can be adjusted by chemical doping or by an applied bias voltage. The simulations accurately reproduce our recently-reported measurements on these RTDs (Fig. 4,). The results of simulations show that frequencies of tens of GHz are achievable by optimising the device parameters. Leverhulme Trust, UK.

  2. Submillimeter sources for radiometry using high power Indium Phosphide Gunn diode oscillators

    Science.gov (United States)

    Deo, Naresh C.

    1990-01-01

    A study aimed at developing high frequency millimeter wave and submillimeter wave local oscillator sources in the 60-600 GHz range was conducted. Sources involved both fundamental and harmonic-extraction type Indium Phosphide Gunn diode oscillators as well as varactor multipliers. In particular, a high power balanced-doubler using varactor diodes was developed for 166 GHz. It is capable of handling 100 mW input power, and typically produced 25 mW output power. A high frequency tripler operating at 500 GHz output frequency was also developed and cascaded with the balanced-doubler. A dual-diode InP Gunn diode combiner was used to pump this cascaded multiplier to produce on the order of 0.5 mW at 500 GHz. In addition, considerable development and characterization work on InP Gunn diode oscillators was carried out. Design data and operating characteristics were documented for a very wide range of oscillators. The reliability of InP devices was examined, and packaging techniques to enhance the performance were analyzed. A theoretical study of a new class of high power multipliers was conducted for future applications. The sources developed here find many commercial applications for radio astronomy and remote sensing.

  3. High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy.

    Science.gov (United States)

    Zweiphenning, W J E M; van 't Klooster, M A; van Diessen, E; van Klink, N E C; Huiskamp, G J M; Gebbink, T A; Leijten, F S S; Gosselaar, P H; Otte, W M; Stam, C J; Braun, K P J; Zijlmans, G J M

    2016-01-01

    High frequency oscillations (HFOs; > 80 Hz), especially fast ripples (FRs, 250-500 Hz), are novel biomarkers for epileptogenic tissue. The pathophysiology suggests enhanced functional connectivity within FR generating tissue. Our aim was to determine the relation between brain areas showing FRs and 'baseline' functional connectivity within EEG networks, especially in the high frequency bands. We marked FRs, ripples (80-250 Hz) and spikes in the electrocorticogram of 14 patients with refractory temporal lobe epilepsy. We assessed 'baseline' functional connectivity in epochs free of epileptiform events within these recordings, using the phase lag index. We computed the Eigenvector Centrality (EC) per channel in the FR and gamma band network. We compared EC between channels that did or did not show events at other moments in time. FR-band EC was higher in channels with than without spikes. Gamma-band EC was lower in channels with ripples and FRs. We confirmed previous findings of functional isolation in the gamma-band and found a first proof of functional integration in the FR-band network of channels covering presumed epileptogenic tissue. 'Baseline' high-frequency network parameters might help intra-operative recognition of epileptogenic tissue without the need for waiting for events. These findings can increase our understanding of the 'architecture' of epileptogenic networks and help unravel the pathophysiology of HFOs.

  4. High frequency oscillations are associated with cognitive processing in human recognition memory.

    Science.gov (United States)

    Kucewicz, Michal T; Cimbalnik, Jan; Matsumoto, Joseph Y; Brinkmann, Benjamin H; Bower, Mark R; Vasoli, Vincent; Sulc, Vlastimil; Meyer, Fred; Marsh, W R; Stead, S M; Worrell, Gregory A

    2014-08-01

    High frequency oscillations are associated with normal brain function, but also increasingly recognized as potential biomarkers of the epileptogenic brain. Their role in human cognition has been predominantly studied in classical gamma frequencies (30-100 Hz), which reflect neuronal network coordination involved in attention, learning and memory. Invasive brain recordings in animals and humans demonstrate that physiological oscillations extend beyond the gamma frequency range, but their function in human cognitive processing has not been fully elucidated. Here we investigate high frequency oscillations spanning the high gamma (50-125 Hz), ripple (125-250 Hz) and fast ripple (250-500 Hz) frequency bands using intracranial recordings from 12 patients (five males and seven females, age 21-63 years) during memory encoding and recall of a series of affectively charged images. Presentation of the images induced high frequency oscillations in all three studied bands within the primary visual, limbic and higher order cortical regions in a sequence consistent with the visual processing stream. These induced oscillations were detected on individual electrodes localized in the amygdala, hippocampus and specific neocortical areas, revealing discrete oscillations of characteristic frequency, duration and latency from image presentation. Memory encoding and recall significantly modulated the number of induced high gamma, ripple and fast ripple detections in the studied structures, which was greater in the primary sensory areas during the encoding (Wilcoxon rank sum test, P = 0.002) and in the higher-order cortical association areas during the recall (Wilcoxon rank sum test, P = 0.001) of memorized images. Furthermore, the induced high gamma, ripple and fast ripple responses discriminated the encoded and the affectively charged images. In summary, our results show that high frequency oscillations, spanning a wide range of frequencies, are associated with memory processing and

  5. Vernier effect within a versatile femtosecond optical parametric oscillator for broad-tunable, high-repetition-rate oscillator

    CERN Document Server

    Jin, Yuwei; Harren, Frans J M; Mandon, Julien

    2015-01-01

    Within a synchronously pumped optical parametric oscillator (SPOPO), the inherent synchronism between the pump and the resonating signal is the magic to partly transfer the coherence property of the pump to the signal. In our demonstration, Vernier effect is observed within a femtosecond SPOPO by simply detuning the FSR of the cavity, generating signal pulses at tunable repetition rate from several GHz to 1 THz with a maximum 22.58 nm full width half maximum (FWHM) bandwidth supporting 160 fs pulses covering the C- and L-bands of the telecom wavelength region. This technique offers a simple method of active ?filtering of dense frequency comb lines instead of using Fabry-P?erot (FP) cavities with complex locking system for astro-comb generation. Beside, as a promising source for frequency combs with tunable and large comb-spacing, it offers potential opportunities for applications such as high speed coherent data transmission, line-by-line pulse shaping, optical clocks and precision metrology.

  6. High Energy Asymptotics of the Scattering Amplitude for the Schrödinger Equation

    Indian Academy of Sciences (India)

    D Yafaev

    2002-02-01

    We find an explicit function approximating at high energies the kernel of the scattering matrix with arbitrary accuracy. Moreover, the same function gives all diagonal singularities of the kernel of the scattering matrix in the angular variables.

  7. Application of high stability oscillators to radio science experiments using deep space probes

    Science.gov (United States)

    Kursinski, Emil R.

    1990-01-01

    The microwave telecommunication links between the earth and deep space probes have long been used to conduct radio science experiments which take advantage of the phase coherency and stability of these links. These experiments measure changes in the phase delay of the signals to infer electrical, magnetic and gravitational properties of the solar system environment and beyond through which the spacecraft and radio signals pass. The precision oscillators, from which the phase of the microwave signals are derived, play a key role in the stability of these links and therefore the sensitivity of these measurements. These experiments have become a driving force behind recent and future improvements in the Deep Space Network and spacecraft oscillators and frequency and time distribution systems. Three such experiments which are key to these improvements are briefly discussed and relationship between their sensitivity and the signal phase stability is described. The first is the remote sensing of planetary atmospheres by occultation in which the radio signal passes through the atmosphere and is refracted causing the signal pathlength to change from which the pressure and the temperature of the atmosphere can be derived. The second experiment is determination of the opacity of planetary rings by passage of the radio signals through the rings. The third experiment is the research for very low frequency gravitational radiation. The fractional frequency variation of the signal is comparable to the spatial strain amplitude the system is capable of detecting. A summary of past results and future possibilities for these experiments are presented.

  8. Application of high stability oscillators to radio science experiments using deep space probes

    Science.gov (United States)

    Kursinski, Emil R.

    1990-01-01

    The microwave telecommunication links between the earth and deep space probes have long been used to conduct radio science experiments which take advantage of the phase coherency and stability of these links. These experiments measure changes in the phase delay of the signals to infer electrical, magnetic and gravitational properties of the solar system environment and beyond through which the spacecraft and radio signals pass. The precision oscillators, from which the phase of the microwave signals are derived, play a key role in the stability of these links and therefore the sensitivity of these measurements. These experiments have become a driving force behind recent and future improvements in the Deep Space Network and spacecraft oscillators and frequency and time distribution systems. Three such experiments which are key to these improvements are briefly discussed and relationship between their sensitivity and the signal phase stability is described. The first is the remote sensing of planetary atmospheres by occultation in which the radio signal passes through the atmosphere and is refracted causing the signal pathlength to change from which the pressure and the temperature of the atmosphere can be derived. The second experiment is determination of the opacity of planetary rings by passage of the radio signals through the rings. The third experiment is the research for very low frequency gravitational radiation. The fractional frequency variation of the signal is comparable to the spatial strain amplitude the system is capable of detecting. A summary of past results and future possibilities for these experiments are presented.

  9. Study of High and Low Amplitude Wave Trains of Cosmic Ray Diurnal Variation during Solar Cycle 23

    Indian Academy of Sciences (India)

    Ambika Singh; Anil Kumar Tiwari; S. P. Agrawal

    2010-06-01

    A detailed study has been conducted on the long-term changes in the diurnal variation of cosmic rays in terms of high and low amplitude wave trains event (HAEs/LAEs) during the period 1996–2008 (solar cycle 23), using the neutron monitor data from Kiel neutron monitoring station. As such, 17 HAE and 48 LAE cases have been detected and analyzed. These HAEs appear quite dominantly during the declining phase as well as near the maximum of the solar activity cycle 23. In contrast, the low amplitude events (LAEs) are inversely correlated with solar activity cycle. In fact, LAEs appear quite dominantly during the minimum phase of the solar activity. When we compare our results for diurnal phase with that observed on an annual average basis, we notice no significant diurnal phase shift for HAEs as well as for LAEs. Moreover, we find that the high-speed solar wind streams (HSSWS) do not play any significant role in causing these variations. These results are discussed on the basis of that observed in earlier cycles.

  10. Energy dependence of r.m.s amplitude of low frequency broadband noise and kHz quasi periodic oscillations in 4U 1608-52

    Science.gov (United States)

    Mandal, Soma

    2016-07-01

    The neutron star low mass X-ray binary 4U 1608-52 is known to show kHz QPOs as well as low frequency broad band noise. The energy dependence of the fractional r.m.s of these variations reflect the underlying radiative mechanism responsible for the phenomena. In this work we compute the energy depedence for 26 instances of kHz QPO observed by RXTE. We typically find as reported before, that the r.m.s increases with energy with slope of ˜0.5. This indicates that the variation is in the hot thermal compotonization component and in particular the QPO is likely to be driven by variation in the thermal heating rate of the hot plasma. For the same data, we compute the energy dependent r.m.s variability of the low frequency broad band noise component by considering the light curves. In contrast to the behaviour seen for the kHz QPO, the energy dependence is nearly flat i.e. the r.m.s. is energy independent. This indicates that the driver here may be the soft photon source. Thus the radiative mechanism driving the low frequency broad band noise and the high frequency QPO are different in nature.

  11. High amplitude vortex-induced pulsations in a gas transport system

    NARCIS (Netherlands)

    Kriesels, P.C.; Peters, M.C.A.M.; Hirschberg, A.; Wijnands, A.P.J.; Iafrati, A.; Riccardi, G.; Piva, R.; Bruggeman, J.C.

    1995-01-01

    High Reynolds number, low Mach number gas flows in pipe systems with closed side branches exhibit spectacular low frequency self-sustained pulsations driven by periodic vortex shedding at specific values of the Strouhal number. A detailed study is presented of the behaviour of the flow in a system w

  12. Kondo Breakdown and Quantum Oscillations in SmB_{6}.

    Science.gov (United States)

    Erten, Onur; Ghaemi, Pouyan; Coleman, Piers

    2016-01-29

    Recent quantum oscillation experiments on SmB_{6} pose a paradox, for while the angular dependence of the oscillation frequencies suggest a 3D bulk Fermi surface, SmB_{6} remains robustly insulating to very high magnetic fields. Moreover, a sudden low temperature upturn in the amplitude of the oscillations raises the possibility of quantum criticality. Here we discuss recently proposed mechanisms for this effect, contrasting bulk and surface scenarios. We argue that topological surface states permit us to reconcile the various data with bulk transport and spectroscopy measurements, interpreting the low temperature upturn in the quantum oscillation amplitudes as a result of surface Kondo breakdown and the high frequency oscillations as large topologically protected orbits around the X point. We discuss various predictions that can be used to test this theory.

  13. High performance ring oscillators from 10-nm wide silicon nanowire field-effect transistors

    KAUST Repository

    Huang, Ruo-Gu

    2011-06-24

    We explore 10-nm wide Si nanowire (SiNW) field-effect transistors (FETs) for logic applications, via the fabrication and testing of SiNW-based ring oscillators. We report on SiNW surface treatments and dielectric annealing, for producing SiNW FETs that exhibit high performance in terms of large on/off-state current ratio (~108), low drain-induced barrier lowering (~30 mV) and low subthreshold swing (~80 mV/decade). The performance of inverter and ring-oscillator circuits fabricated from these nanowire FETs are also explored. The inverter demonstrates the highest voltage gain (~148) reported for a SiNW-based NOT gate, and the ring oscillator exhibits near rail-to-rail oscillation centered at 13.4 MHz. The static and dynamic characteristics of these NW devices indicate that these SiNW-based FET circuits are excellent candidates for various high-performance nanoelectronic applications. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

  14. Observations of high-frequency and high-wavenumber solar oscillations

    Science.gov (United States)

    Fernandes, D. N.; Scherrer, P. H.; Tarbell, T. D.; Title, A. M.

    1992-01-01

    Doppler shift measurements of the Na D1 absorption line reveal solar oscillations in a new regime of frequency and wavenumber. Oscillations of vertical velocities in the temperature minimum and low chromosphere of the sun are observed with frequencies ranging up to 9.5 mHz. The fundamental modes appear with wavenumbers up to 5.33/Mm (equivalent spherical harmonic degree 3710). No evidence for chromospheric modes of 3-minute period is reported.

  15. Numerical simulations of transverse oscillations in radiatively cooling coronal loops

    CERN Document Server

    Magyar, N; Marcu, A

    2015-01-01

    We aim to study the influence of radiative cooling on the standing kink oscillations of a coronal loop. Using the FLASH code, we solved the 3D ideal magnetohydrodynamic equations. Our model consists of a straight, density enhanced and gravitationally stratified magnetic flux tube. We perturbed the system initially, leading to a transverse oscillation of the structure, and followed its evolution for a number of periods. A realistic radiative cooling is implemented. Results are compared to available analytical theory. We find that in the linear regime (i.e. low amplitude perturbation and slow cooling) the obtained period and damping time are in good agreement with theory. The cooling leads to an amplification of the oscillation amplitude. However, the difference between the cooling and non-cooling cases is small (around 6% after 6 oscillations). In high amplitude runs with realistic cooling, instabilities deform the loop, leading to increased damping. In this case, the difference between cooling and non-cooling...

  16. Experience with high frequency oscillation ventilation during the 2009 H1N1 influenza pandemic in Australia and New Zealand.

    Science.gov (United States)

    Boots, R J; Lipman, J; Lassig-Smith, M; Stephens, D P; Thomas, J; Shehabi, Y; Bass, F; Anthony, A; Long, D; Seppelt, I M; Weisbrodt, L; Erickson, S; Beca, J; Sherring, C; McGuiness, S; Parke, R; Stachowski, E R; Boyd, R; Howet, B

    2011-09-01

    During the 2009 H1N1 pandemic, large numbers of patients had severe respiratory failure. High frequency oscillation ventilation was used as a salvage technique for profound hypoxaemia. Our aim was to compare this experience with high frequency oscillation ventilation during the 2009 H1N1 pandemic with the same period in 2008 by performing a three-month period prevalence study in Australian and New Zealand intensive care units. The main study end-points were clinical demographics, care delivery and survival. Nine intensive care units contributed data. During 2009 there were 22 H1N1 patients (17 adults, five children) and 10 non-H1N1 patients (five adults, five children), while in 2008, 18 patients (two adults, 16 children) received high frequency oscillation ventilation. The principal non-H1N1 high frequency oscillation ventilation indication was bacterial or viral pneumonia (56%). For H1N1 patients, the median duration of high frequency oscillation ventilation was 3.7 days (interquartile range 1.8 to 5) with concomitant therapies including recruitment manoeuvres (22%), prone ventilation (41%), inhaled prostacyclins (18%) and inhaled nitric oxide (36%). Seven patients received extracorporeal membrane oxygenation, six having H1N1. Three patients had extracorporeal membrane oxygenation concurrently, two as salvage therapy following the commencement of high frequency oscillation ventilation. In 2008, no high frequency oscillation ventilation patient received extracorporeal membrane oxygenation. Overall hospital survival was 77% in H1N1 patients, while survival in patients having adjunctive extracorporeal membrane oxygenation was similar to those receiving high frequency oscillation ventilation alone (65% compared to 71%, P = 1.00). Survival rates were comparable to published extracorporeal membrane oxygenation outcomes. High frequency oscillation ventilation was used successfully as a rescue therapy for severe respiratory failure. High frequency oscillation ventilation

  17. Large-amplitude jumps and non-Gaussian dynamics in highly concentrated hard sphere fluids.

    Science.gov (United States)

    Saltzman, Erica J; Schweizer, Kenneth S

    2008-05-01

    Our microscopic stochastic nonlinear Langevin equation theory of activated dynamics has been employed to study the real-space van Hove function of dense hard sphere fluids and suspensions. At very short times, the van Hove function is a narrow Gaussian. At sufficiently high volume fractions, such that the entropic barrier to relaxation is greater than the thermal energy, its functional form evolves with time to include a rapidly decaying component at small displacements and a long-range exponential tail. The "jump" or decay length scale associated with the tail increases with time (or particle root-mean-square displacement) at fixed volume fraction, and with volume fraction at the mean alpha relaxation time. The jump length at the alpha relaxation time is predicted to be proportional to a measure of the decoupling of self-diffusion and structural relaxation. At long times corresponding to mean displacements of order a particle diameter, the volume fraction dependence of the decay length disappears. A good superposition of the exponential tail feature based on the jump length as a scaling variable is predicted at high volume fractions. Overall, the theoretical results are in good accord with recent simulations and experiments. The basic aspects of the theory are also compared with a classic jump model and a dynamically facilitated continuous time random-walk model. Decoupling of the time scales of different parts of the relaxation process predicted by the theory is qualitatively similar to facilitated dynamics models based on the concept of persistence and exchange times if the elementary event is assumed to be associated with transport on a length scale significantly smaller than the particle size.

  18. High-frequency climatic oscillations recorded in a Holocene coral reef at Leizhou Peninsula, South China Sea

    Institute of Scientific and Technical Information of China (English)

    余克服; 刘东生; 沈承德; 赵建新; 陈特固; 钟晋梁; 赵焕庭; 宋朝景

    2002-01-01

    A detailed study of the Goniopora reef profile at Dengloujiao, Xuwen County, Leizhou Peninsula, the northern coast of the South China Sea suggests that a series of high-frequency, large-amplitude and abrupt cold events occurred during the Holocene Hypsithermal, an unusual phenomenon termed "Leizhou Events" in this paper. This period (corresponding to 14C age of 6.2-6.7 kaBP or calendar age of 6.7-7.2 kaBP), when the climatic conditions were ideal for coral reefs to develop, can be divided into at least nine stages. Each stage (or called a "climate optimum"), lasting about 20 to 50 a, was terminated by an abrupt cold nap and (or) a sea-level lowering event in winter, leading to widespread emergence and death of the Goniopora corals, and growth discontinuities on the coral surface. Such a cyclic process resulted in the creation of a >4m thick Goniopora reef flat. During this period, the crust subsided periodically but the sea level was rising.The reef profile provides valuable archives for the study of decadal-scale mid-Holocene climatic oscillations in the tropical area of South China. Our results provide new evidence for high-frequency climate instability in the Holocene Hypsithermal, and challenge the traditional understanding of Holocene climate.

  19. Shifted Landau ladders and low field magneto-oscillations in high-mobility GaAs 2D hole systems

    Science.gov (United States)

    Zhang, Po; Wang, Jianli; Zhang, Chi; Du, Rui-Rui; Pfeiffer, L. N.; West, K. W.

    2017-03-01

    We present well-developed low-field magneto-resistance oscillations originating from zero-field spin splitting (ZFSS) of heavy holes in high mobility GaAs/AlGaAs quantum wells. This low field oscillation is 1/B-periodic and emerges before the onset of Shubnikov-de Haas oscillations. The effect can be explained by resonant scattering between two Landau ladders shifted by the ZFSS gap, which in turn can be measured by comparing with the hole cyclotron energy. A front gate is fabricated to tune the ZFSS and hence the oscillation period.

  20. The dark side of high-frequency oscillations in the developing brain.

    Science.gov (United States)

    Le Van Quyen, Michel; Khalilov, Ilgam; Ben-Ari, Yehezkel

    2006-07-01

    Adult brain networks generate a wide range of oscillations. Some of these are behaviourally relevant, whereas others occur during seizures and other pathological conditions. This raises the question of how physiological oscillations differ from pathogenic ones. In this review, this issue is discussed from a developmental standpoint. Indeed, both epileptic and physiological high-frequency oscillations (HFOs) appear progressively during maturation, and it is therefore possible to determine how this program corresponds to maturation of the neuronal populations that generate these oscillations. We review here important differences in the development of neuronal populations that might contribute to their different oscillatory properties. In particular, at an early stage, the density of glutamatergic synapses is too low for physiological HFOs but an additional drive can be provided by excitatory GABA, triggering epileptic HFOs and the cascades involved in long-lasting epileptogenic transformations. This review is part of the INMED/TINS special issue "Nature and nurture in brain development and neurological disorders", based on presentations at the annual INMED/TINS symposium (http://inmednet.com/).

  1. Linear drag law for high-Reynolds-number flow past an oscillating body

    Science.gov (United States)

    Agre, Natalie; Childress, Stephen; Zhang, Jun; Ristroph, Leif

    2016-07-01

    An object immersed in a fast flow typically experiences fluid forces that increase with the square of speed. Here we explore how this high-Reynolds-number force-speed relationship is affected by unsteady motions of a body. Experiments on disks that are driven to oscillate while progressing through air reveal two distinct regimes: a conventional quadratic relationship for slow oscillations and an anomalous scaling for fast flapping in which the time-averaged drag increases linearly with flow speed. In the linear regime, flow visualization shows that a pair of counterrotating vortices is shed with each oscillation and a model that views a train of such dipoles as a momentum jet reproduces the linearity. We also show that appropriate scaling variables collapse the experimental data from both regimes and for different oscillatory motions into a single drag-speed relationship. These results could provide insight into the aerodynamic resistance incurred by oscillating wings in flight and they suggest that vibrations can be an effective means to actively control the drag on an object.

  2. Low amplitude insult project: PBX 9501 high explosive violent reaction experiments

    Energy Technology Data Exchange (ETDEWEB)

    Idar, D.J.; Lucht, R.A.; Straight, J.W.; Scammon, R.J.; Browning, R.V.; Middleditch, J.; Dienes, J.K.; Skidmore, C.B.; Buntain, G.A.

    1998-12-31

    The Modified Steven test geometry has been used with several different target designs to investigate the mechanical loading behavior of PBX 9501 to a low velocity impact. A 2 kg. mild steel spigot projectile is launched via a new powder driven gun design, from {approximately} 20 to 105 m/s, at lightly confined, steel targets. Brief descriptions of the gun design and operation are given. The threshold velocity to reaction for various target designs, different PBX 9501 lots, and different high explosive (HE) thicknesses are reported and compared. Various diagnostics have been employed to evaluate the pressure profile and timing, and target strain behavior relative to projectile impact. The violence of reaction, as measured by both passive and active techniques, is reported relative to a steady state detonation in PBX 9501. Experimental results suggest slightly different ignition mechanisms dominate based on (HE) thickness, resulting in delayed reactions from {approximately} 0.2- to 2.8-ms after impact. Post-test analyses of the PBX 9501 are briefly summarized.

  3. Low amplitude insult project: PBX 9501 high explosive violent reaction experiments

    Energy Technology Data Exchange (ETDEWEB)

    Idar, D.J.; Lucht, R.A.; Straight, J.W.; Scammon, R.J.; Browning, R.V.; Middleditch, J.; Dienes, J.K.; Skidmore, C.B.; Buntain, G.A.

    1998-12-31

    The Modified Steven test geometry has been used with several different target designs to investigate the mechanical loading behavior of PBX 9501 to a low velocity impact. A 2 kg. mild steel spigot projectile is launched via a new powder driven gun design, from {approximately} 20 to 105 m/s, at lightly confined, steel targets. Brief descriptions of the gun design and operation are given. The threshold velocity to reaction for various target designs, different PBX 9501 lots, and different high explosive (HE) thicknesses are reported and compared. Various diagnostics have been employed to evaluate the pressure profile and timing, and target strain behavior relative to projectile impact. The violence of reaction, as measured by both passive and active techniques, is reported relative to a steady state detonation in PBX 9501. Experimental results suggest slightly different ignition mechanisms dominate based on (HE) thickness, resulting in delayed reactions from {approximately} 0.2- to 2.8-ms after impact. Post-test analyses of the PBX 9501 are briefly summarized.

  4. Topographic movie of intracranial ictal high-frequency oscillations with seizure semiology: epileptic network in Jacksonian seizures.

    Science.gov (United States)

    Akiyama, Tomoyuki; Chan, Derrick W; Go, Cristina Y; Ochi, Ayako; Elliott, Irene M; Donner, Elizabeth J; Weiss, Shelly K; Snead, O Carter; Rutka, James T; Drake, James M; Otsubo, Hiroshi

    2011-01-01

    We developed a technique to produce images of dynamic changes in ictal high-frequency oscillations (HFOs) >40 Hz recorded on subdural electroencephalography (EEG) that are time-locked to the ictal EEG and ictal semiology video. We applied this technique to Jacksonian seizures to demonstrate ictal HFO propagation along the homunculus in the primary sensory-motor cortex to visualize the underlying epileptic network. We analyzed intracranial ictal EEGs from two patients with intractable Jacksonian seizures who underwent epilepsy surgery. We calculated the degrees of increase in amplitude within 40-80, 80-200, and 200-300 Hz frequency bands compared to the interictal period and converted them into topographic movies projected onto the brain surface picture. We combined these data with the ictal EEGs and video of the patient demonstrating ictal semiology. The ictal HFOs began in the sensory cortex and appeared concomitantly with the sensory aura. They then propagated to the motor cortex at the same time that focal motor symptoms evolved. As the seizure progressed, the ictal HFOs spread or reverberated in the rolandic region. However, even when the seizure became secondarily generalized, the ictal HFOs were confined to the rolandic region. In both cases, there was increased amplitude of higher frequency bands during seizure initiation compared to seizure progression. This combined movie showed the ictal HFO propagation corresponding to the ictal semiology in Jacksonian seizures and revealed the epileptic network involved in seizure initiation and progression. This method may advance understanding of neural network activities relating to clinical seizure generation and propagation. Wiley Periodicals, Inc. © 2010 International League Against Epilepsy.

  5. High-amplitude THz and GHz strain waves, generated by ultrafast screening of piezoelectric fields in InGaN/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; van Capel, P.J.S.; Turchinovich, Dmitry

    2010-01-01

    Screening of large built-in piezoelectric fields in InGaN/GaN quantum wells leads to high-amplitude acoustic emission. We will compare acoustic emission by quantum wells with different thicknesses with photoluminescence; indicating screening.......Screening of large built-in piezoelectric fields in InGaN/GaN quantum wells leads to high-amplitude acoustic emission. We will compare acoustic emission by quantum wells with different thicknesses with photoluminescence; indicating screening....

  6. How to record high-frequency oscillations in epilepsy: A practical guideline.

    Science.gov (United States)

    Zijlmans, Maeike; Worrell, Gregory A; Dümpelmann, Matthias; Stieglitz, Thomas; Barborica, Andrei; Heers, Marcel; Ikeda, Akio; Usui, Naotaka; Le Van Quyen, Michel

    2017-08-01

    Technology for localizing epileptogenic brain regions plays a central role in surgical planning. Recent improvements in acquisition and electrode technology have revealed that high-frequency oscillations (HFOs) within the 80-500 Hz frequency range provide the neurophysiologist with new information about the extent of the epileptogenic tissue in addition to ictal and interictal lower frequency events. Nevertheless, two decades after their discovery there remain questions about HFOs as biomarkers of epileptogenic brain and there use in clinical practice. In this review, we provide practical, technical guidance for epileptologists and clinical researchers on recording, evaluation, and interpretation of ripples, fast ripples, and very high-frequency oscillations. We emphasize the importance of low noise recording to minimize artifacts. HFO analysis, either visual or with automatic detection methods, of high fidelity recordings can still be challenging because of various artifacts including muscle, movement, and filtering. Magnetoencephalography and intracranial electroencephalography (iEEG) recordings are subject to the same artifacts. High-frequency oscillations are promising new biomarkers in epilepsy. This review provides interested researchers and clinicians with a review of current state of the art of recording and identification and potential challenges to clinical translation. Wiley Periodicals, Inc. © 2017 International League Against Epilepsy.

  7. Detection of high frequency oscillations and damping from multi-slit spectroscopic observations of the corona

    CERN Document Server

    Samanta, T; Sindhuja, G; Banerjee, D

    2015-01-01

    During the total solar eclipse of 11 July 2010, multi-slit spectroscopic observations of the solar corona were performed from Easter Island, Chile. To search for high-frequency waves, observations were taken at a high cadence in the green line at 5303 A due to [Fe xiv] and the red line at 6374 A due to [Fe x]. The data are analyzed to study the periodic variations in the intensity, Doppler velocity and line width using wavelet analysis. The data with high spectral and temporal resolution enabled us to study the rapid dynamical changes within coronal structures. We find that at certain locations each parameter shows significant oscillation with periods ranging from 6 - 25 s. For the first time, we could detect damping of high-frequency oscillations with periods of the order of 10 s. If the observed damped oscillations are due to magnetohydrodynamic (MHD) waves then they can contribute significantly in the heating of the corona. From a statistical study we try to characterize the nature of the observed oscillat...

  8. High-resolution dipole (e, e) study for optical oscillator strengths of helium

    Institute of Scientific and Technical Information of China (English)

    凤任飞; 杨炳忻; 武淑兰; 邢士林; 张芳; 钟志萍; 郭学哲; 徐克尊

    1996-01-01

    The optical oscillator strengths of helium have been studied by a high-resolution dipole (e, e) method on the recently built high-resolution fast-electron energy-loss spectrometer. The difficulties of optical measurement have been avoided and the experimental precision has been improved by using this method. The optical oscillator strength density spectrum corresponding to the 1S n’P transitions and ionization of helium has been measured in the energy loss range of 21 - 26 eV. And the same work corresponding to the autoionization resonance region has been done in energy loss ranges of 59-67 eV and 69-74 eV. The above results have also been compared with those of the previous work.

  9. High-frequency oscillations in small magnetic elements observed with Sunrise/SuFI

    CERN Document Server

    Jafarzadeh, Shahin; Stangalini, M; Steiner, O; Cameron, R H; Danilovic, S

    2016-01-01

    We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca II H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high-frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, although overlapping, period distributions. Two independent estimates give a height difference of approximately 450+-100 km between the two atmospheric layers sampled by the employed spectral bands. ...

  10. Amplitude differences in high-frequency fMRI signals between eyes open and eyes closed resting states.

    Science.gov (United States)

    Yuan, Bin-Ke; Wang, Jue; Zang, Yu-Feng; Liu, Dong-Qiang

    2014-01-01

    Recent studies employing rapid sampling techniques have demonstrated that the resting state fMRI (rs-fMRI) signal exhibits synchronized activities at frequencies much higher than the conventional frequency range (high-frequency fluctuations between different resting states. Here, we acquired rs-fMRI data at a high sampling rate (TR = 400 ms) from subjects with both eyes open (EO) and eyes closed (EC), and compared the amplitude of fluctuation (AF) between EO and EC for both the low- and high-frequency components. In addition to robust AF differences in the conventional low frequency band (high-frequency (primarily in 0.1-0.35 Hz) differences. The high-frequency results without covariates regression exhibited noisy patterns. For the data with nuisance covariates regression, we found a significant and reproducible reduction in high-frequency AF between EO and EC in the bilateral PSMC and the supplementary motor area (SMA), and an increase in high-frequency AF in the left middle occipital gyrus (MOG). Furthermore, we investigated the effect of sampling rate by down-sampling the data to effective TR = 2 s. Briefly, by using the rapid sampling rate, we were able to detect more regions with significant differences while identifying fewer artifactual differences in the high-frequency bands as compared to the down-sampled dataset. We concluded that (1) high-frequency fluctuations of rs-fMRI signals can be modulated by different resting states and thus may be of physiological importance; and (2) the regression of covariates and the use of fast sampling rates are superior for revealing high-frequency differences in rs-fMRI signals.

  11. Investigation of non-uniform airflow signal oscillation during high frequency chest compression

    OpenAIRE

    Lee Jongwon; Lee Yong W; Warwick Warren J; Sohn Kiwon; Holte James E

    2005-01-01

    Abstract Background High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. Methods The computational model, which is based on previous ph...

  12. Self-stabilization of high-frequency oscillations in semiconductor superlattices by time-delay autosynchronization.

    Science.gov (United States)

    Schlesner, J; Amann, A; Janson, N B; Just, W; Schöll, E

    2003-12-01

    We present a scheme to stabilize high-frequency domain oscillations in semiconductor superlattices by a time-delayed feedback loop. Applying concepts from chaos control theory we propose to control the spatiotemporal dynamics of fronts of accumulation and depletion layers which are generated at the emitter and may collide and annihilate during their transit, and thereby suppress chaos. The proposed method only requires the feedback of internal global electrical variables, viz., current and voltage, which makes the practical implementation very easy.

  13. Ictal high-frequency oscillations at 80-200 Hz coupled with delta phase in epileptic spasms.

    Science.gov (United States)

    Nariai, Hiroki; Matsuzaki, Naoyuki; Juhász, Csaba; Nagasawa, Tetsuro; Sood, Sandeep; Chugani, Harry T; Asano, Eishi

    2011-10-01

    Previous studies of epileptic spasms reported that ictal events were associated with high-frequency oscillations (HFOs) or delta waves involving widespread regions. We determined whether ictal HFOs at 80-200 Hz were coupled with a phase of slow-wave, whether ictal slow-waves were diffusely or locally synchronous signals, and whether the mode of coupling between HFOs and slow-wave phases differed between ictal and interictal states. We studied 11 children who underwent extraoperative electrocorticography (ECoG) recording. The phases and amplitudes of slow-waves were measured at the peak of ictal and interictal HFOs in the seizure-onset sites. Ictal HFOs were locked tightly to the phase of slow-wave at ≤1 Hz. Ictal slow-waves propagated from the seizure-onset site to other regions. In contrast, interictal HFOs in the seizure-onset site were loosely locked to the phase of slow-wave at ≤1 Hz but tightly to that of ≥3-Hz. Ictal slow-waves coupled with HFOs can be explained as near-field and locally synchronized potentials generated by the neocortex rather than far-field potentials generated by subcortical structures. Ictal slow-waves in epileptic spasms may be generated by a mechanism different from what generates interictal HFOs-slow-wave complexes.

  14. Measurements of Tune Shifts with Amplitude at LEP

    CERN Document Server

    Müller, A S

    1999-01-01

    The beam orbit system of the LEP electron-positron collider is able to store the beam position over 1000 turns following a deflection by a horizontal kicker. A precise analysis of such 1000-turn data for many beam position monitors was used to study the dependence of the tune on the horizontal amplitude. The horizontal tune shift with amplitude was determined from the decay of the beam oscillation for various LEP optics. This parameter turned out to be an important issue for the LEP high energy optics.

  15. Resurgence of oscillation in coupled oscillators under delayed cyclic interaction

    Science.gov (United States)

    Bera, Bidesh K.; Majhi, Soumen; Ghosh, Dibakar

    2017-07-01

    This paper investigates the emergence of amplitude death and revival of oscillations from the suppression states in a system of coupled dynamical units interacting through delayed cyclic mode. In order to resurrect the oscillation from amplitude death state, we introduce asymmetry and feedback parameter in the cyclic coupling forms as a result of which the death region shrinks due to higher asymmetry and lower feedback parameter values for coupled oscillatory systems. Some analytical conditions are derived for amplitude death and revival of oscillations in two coupled limit cycle oscillators and corresponding numerical simulations confirm the obtained theoretical results. We also report that the death state and revival of oscillations from quenched state are possible in the network of identical coupled oscillators. The proposed mechanism has also been examined using chaotic Lorenz oscillator.

  16. Predicting the onset of high-frequency self-excited oscillations in a channel with an elastic wall

    Science.gov (United States)

    Ward, Thomas; Whittaker, Robert

    2016-11-01

    Flow-induced oscillations of fluid-conveying elastic-walled channels arise in many industrial and biological systems including the oscillation of the vocal cords during phonation. We derive a system of equations that describes the wall displacement in response to the steady and oscillatory components of the fluid pressure derived by Whittaker et al. (2010). We show that the steady pressure component results in a base state deformation assumed to be small in magnitude relative to the length of the channel. The oscillation frequency of the elastic wall is determined by an eigenvalue problem paramterised by the shape of the base state deformation, the strength of axial tension relative to azimuthal bending, F , and the size of non-linear stretching effects from the wall's initial deformation, K . We determine the slow growth or decay of the normal modes in each by considering the energy budget of the system. The amplitude of the oscillations grow or decay exponentially with a growth rate Λ, which may be expressed in terms of a critical Reynolds number Rec . We use numerical simulations to identify three distinct regions in parameter regimes space and determine the stability of oscillations in each.

  17. A note for the mechanism of high-frequency oscillation instability resulted from absorbing boundary conditions

    Institute of Scientific and Technical Information of China (English)

    XIE Zhi-nan; LIAO Zhen-peng

    2008-01-01

    In this paper the explanation of the mechanism of high-frequency oscillation instability resulted from absorbing boundary conditions is further improved. And we analytically prove the proposition that for one dimensional dis- crete model of elastic wave motion, the module of reflection factor will be greater than 1 in high frequency band when artificial wave velocity is greater than 1.5 times the ratio of discrete space step to discrete time step. Based on the proof, the frequency band in which instability occurs is discussed in detail, showing such high-frequency waves are meaningless for the numerical simulation of wave motion.

  18. High-endurance megahertz electrical self-oscillation in Ti/NbOx bilayer structures

    Science.gov (United States)

    Li, Shuai; Liu, Xinjun; Nandi, Sanjoy Kumar; Venkatachalam, Dinesh Kumar; Elliman, Robert Glen

    2015-05-01

    Electrical self-oscillation is reported for a Ti/NbOx negative differential resistance device incorporated in a simple electric circuit configuration. Measurements confirm stable operation of the oscillator at source voltages as low as 1.06 V, and demonstrate frequency control in the range from 2.5 to 20.5 MHz for voltage changes as small as ˜1 V. Device operation is reported for >6.5 × 1010 cycles, during which the operating frequency and peak-to-peak device current decreased by ˜25%. The low operating voltage, large frequency range, and high endurance of these devices makes them particularly interesting for applications such as neuromorphic computing.

  19. High-energy terahertz wave parametric oscillator with a surface-emitted ring-cavity configuration.

    Science.gov (United States)

    Yang, Zhen; Wang, Yuye; Xu, Degang; Xu, Wentao; Duan, Pan; Yan, Chao; Tang, Longhuang; Yao, Jianquan

    2016-05-15

    A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning in a wide frequency range. Through the special optical design with a galvano-optical scanner and four-mirror ring-cavity structure, the maximum THz wave output energy of 12.9 μJ/pulse is achieved at 1.359 THz under the pump energy of 172.8 mJ. The fast THz frequency tuning in the range of 0.7-2.8 THz can be accessed with the step response of 600 μs. Moreover, the maximum THz wave output energy from this configuration is 3.29 times as large as that obtained from the conventional surface-emitted THz wave parametric oscillator with the same experimental conditions.

  20. Proposal to Measure Hadron Scattering with a Gaseous High Pressure TPC for Neutrino Oscillation Measurements

    CERN Document Server

    Andreopoulos, C; Bordoni, S; Boyd, S; Brailsford, D; Brice, S; Catanesi, G; Chen-Wishart, Z; Denner, P; Dunne, P; Giganti, C; Gonzalez Diaz, D; Haigh, J; Hamacher-Baumann, P; Hallsjo, S; Hayato, Y; Irastorza, I; Jamieson, B; Kaboth, A; Korzenev, A; Kudenko, Y; Leyton, M; Luk, K-B; Ma, W; Mahn, K; Martini, M; McCauley, N; Mermod, P; Monroe, J; Mosel, U; Nichol, R; Nieves, J; Nonnenmacher, T; Nowak, J; Parker, W; Raaf, J; Rademacker, J; Radermacher, T; Radicioni, E; Roth, S; Saakyan, R; Sanchez, F; Sgalaberna, D; Shitov, Y; Sobczyk, J; Soler, F; Touramanis, C; Valder, S; Walding, J; Ward, M; Wascko, M; Weber, A; Yokoyama, M; Zalewska, A; Ziembicki, M

    2017-01-01

    We propose to perform new measurements of proton and pion scattering on argon using a prototype High Pressure gas Time Projection Chamber (HPTPC) detector, and by doing so to develop the physics case for, and the technological readiness of, an HPTPC as a neutrino detector for accelerator neutrino oscillation searches. The motivation for this work is to improve knowledge of final state interactions, in order to ultimately achieve 1-2% systematic error on neutrino-nucleus scattering for oscillation measurements at 0.6 GeV and 2.5 GeV neutrino energy, as required for the Charge-Parity (CP) violation sensitivity projections by the Hyper-Kamiokande experiment (Hyper-K) and the Deep Underground Neutrino Experiment (DUNE). The final state interaction uncertainties in neutrino-nucleus interactions dominate cross-section systematic errors, currently 5–10% at these energies, and therefore R&D is needed to explore new approaches to achieve this substantial improvement.

  1. Nano-structural characteristics of carbon nanotube-polymer composite films for high-amplitude optoacoustic generation

    Science.gov (United States)

    Baac, Hyoung Won; Ok, Jong G.; Lee, Taehwa; Jay Guo, L.

    2015-08-01

    We demonstrate nano-structural characteristics of carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite films that can be used as highly efficient and robust ultrasound transmitters for diagnostic and therapeutic applications. An inherent architecture of the nano-composite provides unique thermal, optical, and mechanical properties that are accommodated not just for efficient energy conversion but also for extraordinary robustness against pulsed laser ablation. First, we explain a thermoacoustic transfer mechanism within the nano-composite. CNT morphologies are examined to determine a suitable arrangement for heat transfer to the surrounding PDMS. Next, we introduce an approach to enhance optical extinction of the composite films, which uses shadowed deposition of a thin Au layer through an as-grown CNT network. Finally, the transmitter robustness is quantified in terms of laser-induced damage threshold. This reveals that the CNT-PDMS films can withstand an order-of-magnitude higher optical fluence (and extinction) than a Cr film used as a reference. Such robustness is crucial to increase the maximum-available optical energy for optoacoustic excitation and pressure generation. All of these structure-originated characteristics manifest the CNT-PDMS composite films as excellent optoacoustic transmitters for high-amplitude and high-frequency ultrasound generation.

  2. Multi-fluid approach to high-frequency waves in plasmas: I. Small-amplitude regime in fully ionized medium

    CERN Document Server

    Martínez-Gómez, David; Terradas, Jaume

    2016-01-01

    Ideal MHD provides an accurate description of low-frequency Alfv\\'en waves in fully ionized plasmas. However, higher frequency waves in many plasmas of the solar atmosphere cannot be correctly described by ideal MHD and a more accurate model is required. Here, we study the properties of small-amplitude incompressible perturbations in both the low and the high frequency ranges in plasmas composed of several ionized species. We use a multi-fluid approach and take into account the effects of collisions between ions and the inclusion of Hall's term in the induction equation. Through the analysis of the corresponding dispersion relations and numerical simulations we check that at high frequencies ions of different species are not as strongly coupled as in the low frequency limit. Hence, they cannot be treated as a single fluid. In addition, elastic collisions between the distinct ionized species are not negligible for high frequency waves since an appreciable damping is obtained. Furthermore, Coulomb collisions be...

  3. Nano-structural characteristics of carbon nanotube-polymer composite films for high-amplitude optoacoustic generation.

    Science.gov (United States)

    Baac, Hyoung Won; Ok, Jong G; Lee, Taehwa; Guo, L Jay

    2015-09-14

    We demonstrate nano-structural characteristics of carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite films that can be used as highly efficient and robust ultrasound transmitters for diagnostic and therapeutic applications. An inherent architecture of the nano-composite provides unique thermal, optical, and mechanical properties that are accommodated not just for efficient energy conversion but also for extraordinary robustness against pulsed laser ablation. First, we explain a thermoacoustic transfer mechanism within the nano-composite. CNT morphologies are examined to determine a suitable arrangement for heat transfer to the surrounding PDMS. Next, we introduce an approach to enhance optical extinction of the composite films, which uses shadowed deposition of a thin Au layer through an as-grown CNT network. Finally, the transmitter robustness is quantified in terms of laser-induced damage threshold. This reveals that the CNT-PDMS films can withstand an order-of-magnitude higher optical fluence (and extinction) than a Cr film used as a reference. Such robustness is crucial to increase the maximum-available optical energy for optoacoustic excitation and pressure generation. All of these structure-originated characteristics manifest the CNT-PDMS composite films as excellent optoacoustic transmitters for high-amplitude and high-frequency ultrasound generation.

  4. Capture into resonance of coupled Duffing oscillators.

    Science.gov (United States)

    Kovaleva, Agnessa

    2015-08-01

    In this paper we investigate capture into resonance of a pair of coupled Duffing oscillators, one of which is excited by periodic forcing with a slowly varying frequency. Previous studies have shown that, under certain conditions, a single oscillator can be captured into persistent resonance with a permanently growing amplitude of oscillations (autoresonance). This paper demonstrates that the emergence of autoresonance in the forced oscillator may be insufficient to generate oscillations with increasing amplitude in the attachment. A parametric domain, in which both oscillators can be captured into resonance, is determined. The quasisteady states determining the growth of amplitudes are found. An agreement between the theoretical and numerical results is demonstrated.

  5. Influence of magnetic arc oscillation and current pulsing on microstructure and high temperature tensile strength of alloy 718 TIG weldments

    Energy Technology Data Exchange (ETDEWEB)

    Sivaprasad, K. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai (India); Ganesh Sundara Raman, S. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai (India)]. E-mail: ganesh@iitm.ac.in; Mastanaiah, P. [Defence Research and Development Laboratory, Hyderabad (India); Madhusudhan Reddy, G. [Defence Metallurgical Research Laboratory, Hyderabad (India)

    2006-07-25

    The aim of the present work is to study the effect of magnetic arc oscillation and current pulsing on the microstructure and high temperature tensile strength of alloy 718 tungsten inert gas weldments. The magnetic arc oscillation technique resulted in refined Laves phase with lesser interconnectivity. The full benefits of current pulsing in breaking the dendrites could not be realized in the present study due to relatively higher heat input used in the welding process. In the direct aged condition weldments prepared using magnetic arc oscillation technique exhibited higher tensile strength due to the presence of refined and lesser-interconnected Laves particles. In the solution treated and aged condition, magnetic arc oscillated weldments exhibited lower tensile strength compared with the weldments made without arc oscillation due to the presence of large amounts of finer {delta} needles.

  6. The influence of temperature dynamics and dynamic finite ion Larmor radius effects on seeded high amplitude plasma blobs

    Science.gov (United States)

    Held, M.; Wiesenberger, M.; Madsen, J.; Kendl, A.

    2016-12-01

    Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic finite Larmor radius effects. We find that the maximal radial blob velocity increases with the square root of the initial pressure perturbation and that a finite Larmor radius contributes to highly compact blob structures that propagate in the poloidal direction. An extensive parameter study reveals that a smooth transition to this compact blob regime occurs when the finite Larmor radius effect strength, defined by the ratio of the magnetic field aligned component of the ion diamagnetic to the \\boldsymbol{E}× \\boldsymbol{B} vorticity, exceeds unity. The maximal radial blob velocities agree excellently with the inertial velocity scaling law over more than an order of magnitude. We show that the finite Larmor radius effect strength affects the poloidal and total particle transport and present an empirical scaling law for the poloidal and total blob velocities. Distinctions to the blob behaviour in the isothermal limit with constant finite Larmor radius effects are highlighted.

  7. High-frequency chest wall oscillation. Assistance to ventilation in spontaneously breathing subjects.

    Science.gov (United States)

    Calverley, P M; Chang, H K; Vartian, V; Zidulka, A

    1986-02-01

    In five supine normal subjects breathing spontaneously, we studied the effects of high-frequency chest wall oscillation (HFCWO), which was achieved by oscillating the pressure in an air-filled cuff wrapped around the lower thorax. Oscillations of 3.5 and 8 Hz (in randomized order) were applied for 15 minutes each at both maximal (mean of 90 to 102 cm H2O) and half-maximal peak tolerable cuff pressures. Fifteen minutes of control spontaneous ventilation preceded each HFCWO maneuver. The HFCWO resulted in a significant decrease in spontaneous minute ventilation (VES) at maximal and half-maximal pressures by 35 and 40 percent, respectively, at 3 Hz and by 26 and 35 percent, respectively, at 5 Hz, with little change in VES at 8 Hz. This occurred despite an unchanging arterial carbon dioxide tension at all frequencies. Arterial oxygen pressure increased at 3 Hz at maximal pressure but remained statistically unchanged at 3 Hz at half-maximal pressure and at 5 Hz and 8 Hz both at maximal and half-maximal pressures. We conclude that HFCWO may potentially assist ventilation in spontaneously breathing man without requiring an endotracheal tube.

  8. Plane-wave transverse oscillation for high-frame-rate 2-D vector flow imaging.

    Science.gov (United States)

    Lenge, Matteo; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Liebgott, Hervé

    2015-12-01

    Transverse oscillation (TO) methods introduce oscillations in the pulse-echo field (PEF) along the direction transverse to the ultrasound propagation direction. This may be exploited to extend flow investigations toward multidimensional estimates. In this paper, the TOs are coupled with the transmission of plane waves (PWs) to reconstruct high-framerate RF images with bidirectional oscillations in the pulse-echo field. Such RF images are then processed by a 2-D phase-based displacement estimator to produce 2-D vector flow maps at thousands of frames per second. First, the capability of generating TOs after PW transmissions was thoroughly investigated by varying the lateral wavelength, the burst length, and the transmission frequency. Over the entire region of interest, the generated lateral wavelengths, compared with the designed ones, presented bias and standard deviation of -3.3 ± 5.7% and 10.6 ± 7.4% in simulations and experiments, respectively. The performance of the ultrafast vector flow mapping method was also assessed by evaluating the differences between the estimated velocities and the expected ones. Both simulations and experiments show overall biases lower than 20% when varying the beam-to-flow angle, the peak velocity, and the depth of interest. In vivo applications of the method on the common carotid and the brachial arteries are also presented.

  9. Effectiveness of treatment with high-frequency chest wall oscillation in patients with bronchiectasis

    OpenAIRE

    Nicolini, Antonello; Cardini, Federica; Landucci, Norma; Lanata, Sergio; Ferrari-Bravo, Maura; Barlascini, Cornelius

    2013-01-01

    Background High-frequency airway clearance (HFCWC) assist devices generate either positive or negative trans-respiratory pressure excursions to produce high-frequency, small-volume oscillations in the airways. HFCWC can lead to changes in volume of 15–57 ml and in flow up to 1.6 L/s, which generate minimal coughing to mobilize secretions. The typical treatment lasts 20–30 minutes, and consists of short periods of compression at different frequencies, separated by coughing. The aim of this stu...

  10. Tunable, high-power, continuous-wave dual-polarization Yb-fiber oscillator.

    Science.gov (United States)

    Zeil, Peter; Pasiskevicius, Valdas; Laurell, Fredrik

    2015-06-29

    We demonstrate a high-power, dual-polarization Yb-fiber oscillator, by separately locking the two linear polarization states defined by slow and fast axis of a polarization-maintaining gain fiber with volume Bragg gratings. Dual-line lasing is achieved with a tunable wavelength separation from 0.03 to 2 THz, while exceeding output powers of 78 W over the entire tuning range, maintaining a high beam-quality with M(2)<1.2. With this laser configuration we achieve a peak-to-peak power variation of <1% for the dual-line signal and <3% for the individual signals.

  11. Effects of Changes in Lung Volume on Oscillatory Flow Rate During High-Frequency Chest Wall Oscillation

    Directory of Open Access Journals (Sweden)

    Scott J Butcher

    2007-01-01

    Full Text Available BACKGROUND: The effectiveness of high-frequency chest wall oscillation (HFCWO in mucolysis and mucous clearance is thought to be dependant on oscillatory flow rate (Fosc. Therefore, increasing Fosc during HFCWO may have a clinical benefit.

  12. LDRD final report on Bloch Oscillations in two-dimensional nanostructure arrays for high frequency applications.

    Energy Technology Data Exchange (ETDEWEB)

    Lyo, Sungkwun Kenneth; Pan, Wei; Reno, John Louis; Wendt, Joel Robert; Barton, Daniel Lee

    2008-09-01

    We have investigated the physics of Bloch oscillations (BO) of electrons, engineered in high mobility quantum wells patterned into lateral periodic arrays of nanostructures, i.e. two-dimensional (2D) quantum dot superlattices (QDSLs). A BO occurs when an electron moves out of the Brillouin zone (BZ) in response to a DC electric field, passing back into the BZ on the opposite side. This results in quantum oscillations of the electron--i.e., a high frequency AC current in response to a DC voltage. Thus, engineering a BO will yield continuously electrically tunable high-frequency sources (and detectors) for sensor applications, and be a physics tour-de-force. More than a decade ago, Bloch oscillation (BO) was observed in a quantum well superlattice (QWSL) in short-pulse optical experiments. However, its potential as electrically biased high frequency source and detector so far has not been realized. This is partially due to fast damping of BO in QWSLs. In this project, we have investigated the possibility of improving the stability of BO by fabricating lateral superlattices of periodic coupled nanostructures, such as metal grid, quantum (anti)dots arrays, in high quality GaAs/Al{sub x}Ga{sub 1-x}As heterostructures. In these nanostructures, the lateral quantum confinement has been shown theoretically to suppress the optical-phonon scattering, believed to be the main mechanism for fast damping of BO in QWSLs. Over the last three years, we have made great progress toward demonstrating Bloch oscillations in QDSLs. In the first two years of this project, we studied the negative differential conductance and the Bloch radiation induced edge-magnetoplasmon resonance. Recently, in collaboration with Prof. Kono's group at Rice University, we investigated the time-domain THz magneto-spectroscopy measurements in QDSLs and two-dimensional electron systems. A surprising DC electrical field induced THz phase flip was observed. More measurements are planned to investigate this

  13. Pulsation and Long-Term Variability of the High-Amplitude δ Scuti Star AD Canis Minoris

    Institute of Scientific and Technical Information of China (English)

    Pongsak Khokhuntod; Jian-Ning Fu; Chayan Boonyarak; Kanokwan Marak; Li Chen; Shi-Yang Jiang

    2007-01-01

    Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006.High-quality photometric data provided in the literature were used to analyze the pulsation of the star,with the derived multiple frequencies fitted to our new data.Besides the dominant frequency and its harmonics,one low frequency(2.27402 cd-1)is discovered,which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light.Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature.we analyzed the long-term variability of AD CMi with the O-C technique.The results provide the updated value of period of 0.122974478 days.and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system.of which some parameters are hereby deduced.

  14. Teaching and Assessment of High-Velocity, Low-Amplitude Techniques for the Spine in Predoctoral Medical Education.

    Science.gov (United States)

    Channell, Millicent King

    2016-09-01

    Although national didactic criteria have been set for predoctoral education and assessment in osteopathic manipulative treatment, there is no criterion standard for teaching methods and assessments of osteopathic manipulative treatment competence in colleges of osteopathic medicine. This issue is more pressing with the creation of the single graduate medical education accreditation system by the American Osteopathic Association and Accreditation Council for Graduate Medical Education, which introduced the creation of "osteopathic recognition" for residencies that want to incorporate osteopathic principles and practice into their programs. Residencies with osteopathic recognition may include both osteopathic and allopathic graduates. Increased standardization at the predoctoral level, however, is recommended as osteopathic principles and practice training applications are expanded. The objectives of this article are to review the standards for teaching osteopathic medical students high-velocity, low-amplitude (HVLA) techniques for the spine; to review and discuss the methods used to assess medical students' proficiency in using HVLA; and to propose baseline standards for teaching and assessing HVLA techniques among medical students.

  15. Pulsation and Long-Term Variability of the High-Amplitude δ Scuti Star AD Canis Minoris

    Science.gov (United States)

    Khokhuntod, Pongsak; Fu, Jian-Ning; Boonyarak, Chayan; Marak, Kanokwan; Chen, Li; Jiang, Shi-Yang

    2007-06-01

    Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006. High-quality photometric data provided in the literature were used to analyze the pulsation of the star, with the derived multiple frequencies fitted to our new data. Besides the dominant frequency and its harmonics, one low frequency (2.27402 c d-1) is discovered, which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light. Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature, we analyzed the long-term variability of AD CMi with the O-C technique. The results provide the updated value of period of 0.122974478 days, and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system, of which some parameters are hereby deduced.

  16. The Kep-Cont Mission: Continuing the observation of high-amplitude variable stars in the Kepler field of view

    CERN Document Server

    Molnár, L; Kolenberg, K; Borkovits, T; Antoci, V; Vida, K; Ngeow, C C; Guzik, J A; Plachy, E; Castanheira, B

    2013-01-01

    As a response to the Kepler white paper call, we propose to keep Kepler pointing to its current field of view and continue observing thousands of large amplitude variables (Cepheid, RR Lyrae and delta Scuti stars among others) with high cadence in the Kep-Cont Mission. The degraded pointing stability will still allow observation of these stars with reasonable (better than millimag) precision. The Kep-Cont mission will allow studying the nonradial modes in Blazhko-modulated and first overtone RR Lyrae stars and will give a better view on the period jitter of the only Kepler Cepheid in the field. With continued continuous observation of the Kepler RR Lyrae sample we may get closer to the origin of the century-old Blazhko problem. Longer time-span may also uncover new dynamical effects like apsidal motion in eclipsing binaries. A continued mission will have the advantage of providing unprecedented, many-years-long homogeneous and continuous photometric data of the same targets. We investigate the pragmatic detai...

  17. Patient-centered outcomes of high-velocity, low-amplitude spinal manipulation for low back pain: a systematic review.

    Science.gov (United States)

    Goertz, C M; Pohlman, K A; Vining, R D; Brantingham, J W; Long, C R

    2012-10-01

    Low back pain (LBP) is a well-recognized public health problem with no clear gold standard medical approach to treatment. Thus, those with LBP frequently turn to treatments such as spinal manipulation (SM). Many clinical trials have been conducted to evaluate the efficacy or effectiveness of SM for LBP. The primary objective of this paper was to describe the current literature on patient-centered outcomes following a specific type of commonly used SM, high-velocity low-amplitude (HVLA), in patients with LBP. A systematic search strategy was used to capture all LBP clinical trials of HVLA using our predefined patient-centered outcomes: visual analogue scale, numerical pain rating scale, Roland-Morris Disability Questionnaire, and the Oswestry Low Back Pain Disability Index. Of the 1294 articles identified by our search, 38 met our eligibility criteria. Like previous SM for LBP systematic reviews, this review shows a small but consistent treatment effect at least as large as that seen in other conservative methods of care. The heterogeneity and inconsistency in reporting within the studies reviewed makes it difficult to draw definitive conclusions. Future SM studies for LBP would benefit if some of these issues were addressed by the scientific community before further research in this area is conducted.

  18. Asteroseismology of KIC\\,11754974: a high-amplitude SX\\,Phe pulsator in a 343-day binary system

    CERN Document Server

    Murphy, S J; Kurtz, D W; Suarez, J C; Handler, G; Balona, L A; Smalley, B; Uytterhoeven, K; Szabo, R; Thygesen, A O; Elkin, V; Breger, M; Grigahcene, A; Guzik, J A; Nemec, J M; Southworth, J

    2013-01-01

    The candidate SX Phe star KIC 11754974 shows a remarkably high number of combination frequencies in the Fourier amplitude spectrum: 123 of the 166 frequencies in our multi-frequency fit are linear combinations of independent modes. Predictable patterns in frequency spacings are seen in the Fourier transform of the light curve. We present an analysis of 180 d of short-cadence Kepler photometry and of new spectroscopic data for this evolved, late A-type star. We infer from the 1150-d, long-cadence light curve, and in two different ways, that our target is the primary of a 343-d, non-eclipsing binary system. According to both methods, the mass function is similar, f(M)=0.0207 +/- 0.0003 Msun. The observed pulsations are modelled extensively, using separate, state-of-the-art, time-dependent convection (TDC) and rotating models. The models match the observed temperature and low metallicity, finding a mass of 1.50-1.56 Msun. The models suggest the whole star is metal-poor, and that the low metallicity is not just a...

  19. A novel high amplitude piezoceramic actuator for applications in magnetic resonance elastography: a compliant mechanical amplifier approach

    Science.gov (United States)

    Arani, Arvin; Eskandari, Amiraslan; Ouyang, Puren; Chopra, Rajiv

    2017-08-01

    Piezoceramic actuators are capable of precise positioning with high force, but suffer from limited displacement range, which has hindered their application in the field of magnetic resonance elastography (MRE). The objective of this study was to investigate the feasibility of using a mechanical amplifier in combination with a piezoceramic actuator for the application of endorectal prostate MRE. A five-bar symmetric structure was designed in ANSYS® and manufactured out of brass. Laser vibrometer measurements were used to characterize the amplitude of the CMA actuator while attached to masses in the 0-325 g range and over operating frequencies of 90-500 Hz. The response of the CMA was investigated while mechanically coupled to a balloon type endorectal coil. The resonant frequency of the prototype CMA actuator was predicted within 10% error using ANSYS simulations. The amplification ratio of the CMA actuator was measured to be 10 with the laser vibrometer and 7.6 ± 1.7 (max: 9.2, min: 6.5) using MRE, at a vibration frequency of 200 Hz. Laser vibrometer data also showed that the CMA actuator’s performance did not change whether it was connected to an empty or inflated endorectal. The feasibility of performing endorectal prostate MRE with a CMA actuator was successfully demonstrated in a human volunteer.

  20. A photometric monitoring of bright high-amplitude delta Scuti stars. II. Period updates for seven stars

    CERN Document Server

    Derekas, A; Székely, P; Alfaro, E J; Csák, B; Mészáros, S; Rodríguez, E; Rolland, A; Sarneczky, K; Szabó, G M; Szatmary, K; Varadi, M; Kiss, C; Meszaros, Sz.; Szabo, Gy.M.; Kiss, Cs.

    2003-01-01

    We present new photometric data for seven high-amplitude delta Scuti stars. The observations were acquired between 1996 and 2002, mostly in the Johnson photometric system. For one star (GW UMa), our observations are the first since the discovery of its pulsational nature from the Hipparcos data.The primary goal of this project was to update our knowledge on the period variations of the target stars. For this, we have collected all available photometric observations from the literature and constructed decades-long O-C diagrams of the stars. This traditional method is useful because of the single-periodic nature of the light variations. Text-book examples of slow period evolution (XX Cyg, DY Her, DY Peg) and cyclic period changes due to light-time effect (LITE) in a binary system (SZ Lyn) are updated with the new observations. For YZ Boo, we find a period decrease instead of increase. The previously suggested LITE-solution of BE Lyn (Kiss & Szatmary 1995) is not supported with the new O-C diagram. Instead o...

  1. Autoresonance versus localization in weakly coupled oscillators

    Science.gov (United States)

    Kovaleva, Agnessa; Manevitch, Leonid I.

    2016-04-01

    We study formation of autoresonance (AR) in a two-degree of freedom oscillator array including a nonlinear (Duffing) oscillator (the actuator) weakly coupled to a linear attachment. Two classes of systems are studied. In the first class of systems, a periodic force with constant (resonance) frequency is applied to a nonlinear oscillator (actuator) with slowly time-decreasing stiffness. In the systems of the second class a nonlinear time-invariant oscillator is subjected to an excitation with slowly increasing frequency. In both cases, the attached linear oscillator and linear coupling are time-invariant, and the system is initially engaged in resonance. This paper demonstrates that in the systems of the first type AR in the nonlinear actuator entails oscillations with growing amplitudes in the linear attachment while in the system of the second type energy transfer from the nonlinear actuator is insufficient to excite high-energy oscillations of the attachment. It is also shown that a slow change of stiffness may enhance the response of the actuator and make it sufficient to support oscillations with growing energy in the attachment even beyond the linear resonance. Explicit asymptotic approximations of the solutions are obtained. Close proximity of the derived approximations to exact (numerical) results is demonstrated.

  2. Gamma oscillations in human primary somatosensory cortex reflect pain perception.

    Directory of Open Access Journals (Sweden)

    Joachim Gross

    2007-05-01

    Full Text Available Successful behavior requires selection and preferred processing of relevant sensory information. The cortical representation of relevant sensory information has been related to neuronal oscillations in the gamma frequency band. Pain is of invariably high behavioral relevance and, thus, nociceptive stimuli receive preferred processing. Here, by using magnetoencephalography, we show that selective nociceptive stimuli induce gamma oscillations between 60 and 95 Hz in primary somatosensory cortex. Amplitudes of pain-induced gamma oscillations vary with objective stimulus intensity and subjective pain intensity. However, around pain threshold, perceived stimuli yielded stronger gamma oscillations than unperceived stimuli of equal stimulus intensity. These results show that pain induces gamma oscillations in primary somatosensory cortex that are particularly related to the subjective perception of pain. Our findings support the hypothesis that gamma oscillations are related to the internal representation of behaviorally relevant stimuli that should receive preferred processing.

  3. Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations in a Young, Extremely Red L-type Brown Dwarf

    Science.gov (United States)

    Lew, Ben W. P.; Apai, Daniel; Zhou, Yifan; Schneider, Glenn; Burgasser, Adam J.; Karalidi, Theodora; Yang, Hao; Marley, Mark S.; Cowan, Nicolas B.; Bedin, Luigi R.; Metchev, Stanimir A.; Radigan, Jacqueline; Lowrance, Patrick J.

    2016-10-01

    Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs, but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here, we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-K s = 2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy, we find a best-fit rotational period (13.20 ± 0.14 hr) with a larger amplitude at 1.1 μm than at 1.7 μm. This is the third-largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentative trend between the wavelength dependence of relative amplitude, possibly proxy for small dust grains lofted in the upper atmosphere, and the likelihood of large-amplitude variability. By assuming forsterite as a haze particle, we successfully explain the wavelength-dependent amplitude with submicron-sized haze particle sizes of around 0.4 μm. W0047 links the earlier spectral and later spectral type brown dwarfs in which rotational modulations have been observed; the large amplitude variations in this object make this a benchmark brown dwarf for the study of cloud properties close to the L/T transition.

  4. LC Oscillator Driver for Safety Critical Applications

    CERN Document Server

    Horsky, Pavel

    2011-01-01

    A CMOS harmonic signal LC oscillator driver for automotive applications working in a harsh environment with high safety critical requirements is described. The driver can be used with a wide range of external components parameters (LC resonance network of a sensor). Quality factor of the external LC network can vary two decades. Amplitude regulation of the driver is digitally controlled and the DAC is constructed as exponential with piece-wise-linear (PWL) approximation. Low current consumption for high quality resonance networks is achieved. Realized oscillator is robust, used in safety critical application and has low EMC emissions.

  5. High-resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph

    Science.gov (United States)

    Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu, B.; Martínez-Sykora, J.; Carlsson, M.; Hansteen, V.; Kleint, L.; Cheung, M.; Golub, L.; Saar, S.; Testa, P.; Weber, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kankelborg, C.; Jaeggli, S.; McIntosh, S. W.

    2014-05-01

    We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slit-jaw images and the spectra of several emission lines formed in the transition region and chromosphere. We first apply a single Gaussian fit to the profiles of the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the sunspot. The intensity change is ~30%. The Doppler shift oscillation reveals a sawtooth pattern with an amplitude of ~10 km s-1 in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and ~12 s, respectively. The line width suddenly increases as the Doppler shift changes from redshift to blueshift. However, we demonstrate that this increase is caused by the superposition of two emission components. We then perform detailed analysis of the line profiles at a few selected locations on the slit. The temporal evolution of the line core is dominated by the following behavior: a rapid excursion to the blue side, accompanied by an intensity increase, followed by a linear decrease of the velocity to the red side. The maximum intensity slightly lags the maximum blueshift in Si IV, whereas the intensity enhancement slightly precedes the maximum blueshift in Mg II. We find a positive correlation between the maximum velocity and deceleration, a result that is consistent with numerical simulations of upward propagating magnetoacoustic shock waves.

  6. High sensitivity, low-systematics atom interferometers using Bragg diffraction and Bloch oscillations

    CERN Document Server

    Estey, Brian; Müller, Holger; Kuan, Pei-Chen; Lan, Shau-Yu

    2014-01-01

    We describe a new scheme for atom interferometry based on both large-momentum transfer Bragg beam splitters and Bloch oscillations. Combining the advantages of previous approaches to recoil-sensitive interferometers, we increase the signal and suppress a systematic phase shift caused by Bragg diffraction at least 60-fold, matching experiment to theory; the systematic shift can be eliminated from Mach-Zehnder interferometers. We demonstrate high contrast, interference with up to 4.4 million radians of phase difference between freely evolving matter waves, and a resolution of $\\delta \\alpha/\\alpha=0.33\\,$ppb$\\sqrt{\\rm 6h}$ available to measurements of the fine structure constant.

  7. InP Gunn Diodes with Current Limiting Contact for High Efficiency Gunn Oscillators

    Science.gov (United States)

    Kim, Mi-Ra; Rhee, Jin-Koo; Lee, Chang-Woo; Chae, Yeon-Sik; Choi, Jae-Hyun; Kim, Wan-Joo

    We fabricated and examined current limiting effect for InP Gunn diodes with stable depletion layer mode operation of diodes for high efficiency Gunn oscillators. Current limiting at the cathode was achieved by a shallow Schottky barrier at the interface. We discussed fabrication procedure, the results for negative differential resistance and rf tests for InP Gunn diodes. It was shown that the fabricated Gunn diodes have the output power of 10.22dBm at a frequency of 90.13GHz. Its input voltage and corresponding current were 8.55V and 252mA, respectively.

  8. High-Q wavelength division multiplexed optoelectronic oscillator based on a cascaded multi-loop topology

    Science.gov (United States)

    Charalambous, Georgios; Hasanuzzaman, G. K. M.; Perentos, Andreas; Iezekiel, Stavros

    2017-03-01

    A WDM optoelectronic oscillator (OEO) based on a cascaded optical multi-loop configuration and multiple photodiodes is proposed and demonstrated experimentally. By employing up to three lasers widely separated in wavelength along with two cascaded multi-loop fiber sections and two photodiodes, we demonstrate OEO topologies that scale up to six effective loops revealing an ultra-high quality factor in excess of 1010 and a phase noise performance down to -119 dBc/Hz at 10 kHz offset

  9. Low-amplitude, high-frequency electromagnetic field exposure causes delayed and reduced growth in Rosa hybrida.

    Science.gov (United States)

    Grémiaux, Alexandre; Girard, Sébastien; Guérin, Vincent; Lothier, Jérémy; Baluška, František; Davies, Eric; Bonnet, Pierre; Vian, Alain

    2016-01-15

    It is now accepted that plants perceive high-frequency electromagnetic field (HF-EMF). We wondered if the HF-EMF signal is integrated further in planta as a chain of reactions leading to a modification of plant growth. We exposed whole small ligneous plants (rose bush) whose growth could be studied for several weeks. We performed exposures at two different development stages (rooted cuttings bearing an axillary bud and 5-leaf stage plants), using two high frequency (900MHz) field amplitudes (5 and 200Vm(-1)). We achieved a tight control on the experimental conditions using a state-of-the-art stimulation device (Mode Stirred Reverberation Chamber) and specialized culture-chambers. After the exposure, we followed the shoot growth for over a one-month period. We observed no growth modification whatsoever exposure was performed on the 5-leaf stage plants. When the exposure was performed on the rooted cuttings, no growth modification was observed on Axis I (produced from the elongation of the axillary bud). Likewise, no significant modification was noted on Axis II produced at the base of Axis I, that came from pre-formed secondary axillary buds. In contrast, Axis II produced at the top of Axis I, that came from post-formed secondary buds consistently displayed a delayed and significant reduced growth (45%). The measurements of plant energy uptake from HF-EMF in this exposure condition (SAR of 7.2 10(-4)Wkg(-1)) indicated that this biological response is likely not due to thermal effect. These results suggest that exposure to electromagnetic field only affected development of post-formed organs.

  10. The Origin of Type I Spicule Oscillations

    CERN Document Server

    Jess, D B; Christian, D J; Mathioudakis, M; Keys, P H; Keenan, F P

    2011-01-01

    We use images of high spatial and temporal resolution, obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope, to reveal how the generation of transverse waves in Type I spicules is a direct result of longitudinal oscillations occurring in the photosphere. Here we show how pressure oscillations, with periodicities in the range 130 - 440 s, manifest in small-scale photospheric magnetic bright points, and generate kink waves in the Sun's outer atmosphere with transverse velocities approaching the local sound speed. Through comparison of our observations with advanced two-dimensional magneto-hydrodynamic simulations, we provide evidence for how magnetoacoustic oscillations, generated at the solar surface, funnel upwards along Type I spicule structures, before undergoing longitudinal-to-transverse mode conversion into waves at twice the initial driving frequency. The resulting kink modes are visible in chromospheric plasma, with periodicities of 65 -220 s, and amplitud...

  11. GNSS Signal Tracking Performance Improvement for Highly Dynamic Receivers by Gyroscopic Mounting Crystal Oscillator.

    Science.gov (United States)

    Abedi, Maryam; Jin, Tian; Sun, Kewen

    2015-08-31

    In this paper, the efficiency of the gyroscopic mounting method is studied for a highly dynamic GNSS receiver's reference oscillator for reducing signal loss. Analyses are performed separately in two phases, atmospheric and upper atmospheric flights. Results show that the proposed mounting reduces signal loss, especially in parts of the trajectory where its probability is the highest. This reduction effect appears especially for crystal oscillators with a low elevation angle g-sensitivity vector. The gyroscopic mounting influences frequency deviation or jitter caused by dynamic loads on replica carrier and affects the frequency locked loop (FLL) as the dominant tracking loop in highly dynamic GNSS receivers. In terms of steady-state load, the proposed mounting mostly reduces the frequency deviation below the one-sigma threshold of FLL (1σ(FLL)). The mounting method can also reduce the frequency jitter caused by sinusoidal vibrations and reduces the probability of signal loss in parts of the trajectory where the other error sources accompany this vibration load. In the case of random vibration, which is the main disturbance source of FLL, gyroscopic mounting is even able to suppress the disturbances greater than the three-sigma threshold of FLL (3σ(FLL)). In this way, signal tracking performance can be improved by the gyroscopic mounting method for highly dynamic GNSS receivers.

  12. A high-density ERP study reveals latency, amplitude, and topographical differences in multiple sclerosis patients versus controls.

    LENUS (Irish Health Repository)

    Whelan, R

    2012-02-01

    OBJECTIVE: To quantify latency, amplitude and topographical differences in event-related potential (ERP) components between multiple sclerosis (MS) patients and controls and to compare ERP findings with results from the paced auditory serial addition test (PASAT). METHODS: Fifty-four subjects (17 relapsing remitting (RRMS) patients, 16 secondary progressive (SPMS) patients, and 21 controls) completed visual and auditory oddball tasks while data were recorded from 134 EEG channels. Latency and amplitude differences, calculated using composite mean amplitude measures, were tested using an ANOVA. Topographical differences were tested using statistical parametric mapping (SPM). RESULTS: In the visual modality, P2, P3 amplitudes and N2 latency were significantly different across groups. In the auditory modality, P2, N2, and P3 latencies and N1 amplitude were significantly different across groups. There were no significant differences between RRMS and SPMS patients on any ERP component. There were topographical differences between MS patients and controls for both early and late components for the visual modality, but only in the early components for the auditory modality. PASAT score correlated significantly with auditory P3 latency for MS patients. CONCLUSIONS: There were significant ERP differences between MS patients and controls. SIGNIFICANCE: The present study indicated that both early sensory and later cognitive ERP components are impaired in MS patients relative to controls.

  13. Energy substrates that fuel fast neuronal network oscillations

    Directory of Open Access Journals (Sweden)

    Lukas V. Galow

    2014-12-01

    Full Text Available Fast neuronal network oscillations in the gamma-frequency band (30-100 Hz provide a fundamental mechanism of complex neuronal information processing in the hippocampus and neocortex of mammals. Gamma oscillations have been implicated in higher brain functions such as sensory perception, motor activity and memory formation. The oscillations emerge from precise synapse interactions between excitatory principal neurons such as pyramidal cells and inhibitory GABAergic interneurons, and they are associated with high energy expenditure. However, both energy substrates and metabolic pathways that are capable to power cortical gamma oscillations have been less defined. Here, we investigated the energy sources fueling persistent gamma oscillations in the CA3 subfield of organotypic hippocampal slice cultures of the rat. This preparation permits superior oxygen supply as well as fast application of glucose, glycolytic metabolites or drugs such as glycogen phosphorylase inhibitor during extracellular recordings of the local field potential. Our findings are: (i gamma oscillations persist in the presence of glucose (10 mmol/L for greater than 60 minutes in slice cultures while (ii lowering glucose levels (2.5 mmol/L significantly reduces the amplitude of the oscillation. (iii Gamma oscillations are absent at low concentration of lactate (2 mmol/L. (iv Gamma oscillations persist at high concentration (20 mmol/L of either lactate or pyruvate, albeit showing significant reductions in the amplitude. (v The breakdown of glycogen significantly delays the decay of gamma oscillations during glucose deprivation. However, when glucose is present, the turnover of glycogen is not essential to sustain gamma oscillations. Our study shows that fast neuronal network oscillations can be fueled by different energy-rich substrates, with glucose being most effective.

  14. Energy substrates that fuel fast neuronal network oscillations.

    Science.gov (United States)

    Galow, Lukas V; Schneider, Justus; Lewen, Andrea; Ta, Thuy-Truc; Papageorgiou, Ismini E; Kann, Oliver

    2014-01-01

    Fast neuronal network oscillations in the gamma-frequency band (30--100 Hz) provide a fundamental mechanism of complex neuronal information processing in the hippocampus and neocortex of mammals. Gamma oscillations have been implicated in higher brain functions such as sensory perception, motor activity, and memory formation. The oscillations emerge from precise synapse interactions between excitatory principal neurons such as pyramidal cells and inhibitory GABAergic interneurons, and they are associated with high energy expenditure. However, both energy substrates and metabolic pathways that are capable to power cortical gamma oscillations have been less defined. Here, we investigated the energy sources fueling persistent gamma oscillations in the CA3 subfield of organotypic hippocampal slice cultures of the rat. This preparation permits superior oxygen supply as well as fast application of glucose, glycolytic metabolites or drugs such as glycogen phosphorylase inhibitor during extracellular recordings of the local field potential. Our findings are: (i) gamma oscillations persist in the presence of glucose (10 mmol/L) for greater than 60 min in slice cultures while (ii) lowering glucose levels (2.5 mmol/L) significantly reduces the amplitude of the oscillation. (iii) Gamma oscillations are absent at low concentration of lactate (2 mmol/L). (iv) Gamma oscillations persist at high concentration (20 mmol/L) of either lactate or pyruvate, albeit showing significant reductions in the amplitude. (v) The breakdown of glycogen significantly delays the decay of gamma oscillations during glucose deprivation. However, when glucose is present, the turnover of glycogen is not essential to sustain gamma oscillations. Our study shows that fast neuronal network oscillations can be fueled by different energy-rich substrates, with glucose being most effective.

  15. Influence of hydrodynamic thrust bearings on the nonlinear oscillations of high-speed rotors

    Science.gov (United States)

    Chatzisavvas, Ioannis; Boyaci, Aydin; Koutsovasilis, Panagiotis; Schweizer, Bernhard

    2016-10-01

    This paper investigates the effect of hydrodynamic thrust bearings on the nonlinear vibrations and the bifurcations occurring in rotor/bearing systems. In order to examine the influence of thrust bearings, run-up simulations may be carried out. To be able to perform such run-up calculations, a computationally efficient thrust bearing model is mandatory. Direct discretization of the Reynolds equation for thrust bearings by means of a Finite Element or Finite Difference approach entails rather large simulation times, since in every time-integration step a discretized model of the Reynolds equation has to be solved simultaneously with the rotor model. Implementation of such a coupled rotor/bearing model may be accomplished by a co-simulation approach. Such an approach prevents, however, a thorough analysis of the rotor/bearing system based on extensive parameter studies. A major point of this work is the derivation of a very time-efficient but rather precise model for transient simulations of rotors with hydrodynamic thrust bearings. The presented model makes use of a global Galerkin approach, where the pressure field is approximated by global trial functions. For the considered problem, an analytical evaluation of the relevant integrals is possible. As a consequence, the system of equations of the discretized bearing model is obtained symbolically. In combination with a proper decomposition of the governing system matrix, a numerically efficient implementation can be achieved. Using run-up simulations with the proposed model, the effect of thrust bearings on the bifurcations points as well as on the amplitudes and frequencies of the subsynchronous rotor oscillations is investigated. Especially, the influence of the magnitude of the axial force, the geometry of the thrust bearing and the oil parameters is examined. It is shown that the thrust bearing exerts a large influence on the nonlinear rotor oscillations, especially to those related with the conical mode of the

  16. The M-current contributes to high threshold membrane potential oscillations in a cell type-specific way in the pedunculopontine nucleus of mice

    Directory of Open Access Journals (Sweden)

    Csilla eBordas

    2015-04-01

    Full Text Available The pedunculopontine nucleus is known as a cholinergic nucleus of the reticular activating system, participating in regulation of sleep and wakefulness. Besides cholinergic neurons, it consists of GABAergic and glutamatergic neurons as well. According to classical and recent studies, more subgroups of neurons were defined. Groups based on the neurotransmitter released by a neuron are not homogenous, but can be further subdivided.The PPN neurons do not only provide cholinergic and non-cholinergic inputs to several subcortical brain areas but they are also targets of cholinergic and other different neuromodulatory actions. Although cholinergic neuromodulation has been already investigated in the nucleus, one of its characteristic targets, the M-type potassium current has not been described yet.Using slice electrophysiology, we provide evidence in the present work that cholinergic neurons possess M-current, whereas GABAergic neurons lack it. The M-current contributes to certain functional differences of cholinergic and GABAergic neurons, as spike frequency adaptation, action potential firing frequency or the amplitude difference of medium afterhyperpolarizations. Furthermore, we showed that high threshold membrane potential oscillation with high power, around 20 Hz frequency is a functional property of almost all cholinergic cells, whereas GABAergic neurons have only low amplitude oscillations. Blockade of the M-current abolished the oscillatory activity at 20 Hz, and largely diminished it at other frequencies.Taken together, the M-current seems to be characteristic for PPN cholinergic neurons. It provides a possibility for modulating gamma band activity of these cells, thus contributing to neuromodulatory regulation of the reticular activating system.

  17. Effects of changes in lung volume on oscillatory flow rate during high-frequency chest wall oscillation

    OpenAIRE

    Scott J Butcher; Pasiorowski, Michal P; Jones, Richard L

    2007-01-01

    BACKGROUND: The effectiveness of high-frequency chest wall oscillation (HFCWO) in mucolysis and mucous clearance is thought to be dependant on oscillatory flow rate (Fosc). Therefore, increasing Fosc during HFCWO may have a clinical benefit.OBJECTIVES: To examine effects of continuous positive airway pressure (CPAP) on Fosc at two oscillation frequencies in healthy subjects and patients with airway obstruction.METHODS: Five healthy subjects and six patients with airway obstruction underwent 1...

  18. Neural responses to the mechanical parameters of a high velocity, low amplitude spinal manipulation: effect of preload parameters

    Science.gov (United States)

    Reed, William. R.; Long, Cynthia R.; Kawchuk, Gregory N.; Pickar, Joel G.

    2014-01-01

    Objective The purpose of this study was to determine how the preload that precedes a high velocity low amplitude spinal manipulation (HVLA-SM) affects muscle spindle input from lumbar paraspinal muscles both during and after the HVLA-SM. Methods Primary afferent activity from muscle spindles in lumbar paraspinal muscles were recorded from the L6 dorsal root in anesthetized cats. HVLA-SM of the L6 vertebra was preceded either by no preload or by systematic changes in the preload magnitude, duration, and the presence or absence of a downward incisural point (DIP). Immediate effects of preload on muscle spindle responses to the HVLA-SM were determined by comparing mean instantaneous discharge frequencies (MIF) during the HVLA-SM’s thrust phase with baseline. Longer lasting effects of preload on spindle responses to the HVLA-SM were determined by comparing MIF during slow ramp and hold movement of the L6 vertebra before and following the HVLA-SM. Results The smaller compared to the larger preload magnitude and the longer compared to the shorter preload duration significantly increased (P=0.02 and P=0.04) respectively) muscle spindle responses during the HVLA-SM thrust. The absence of preload had the greatest effect on the change in MIF. Interactions between preload magnitude, duration and DIP often produced statistically significant but arguably physiologically modest changes in the passive signaling properties of the muscle spindle following the manipulation. Conclusion Because preload parameters in this animal model were shown to affect neural responses to an HVLA-SM, preload characteristics should be taken into consideration when judging this intervention’s therapeutic benefit in both clinical efficacy studies and in clinical practice. PMID:24387888

  19. Design and analysis of a high power moderate band radiator using a switched oscillator

    Science.gov (United States)

    Armanious, Miena Magdi Hakeem

    Quarter-wave switched oscillators (SWOs) are an important technology for the generation of high-power, moderate bandwidth (mesoband) wave forms. The use of SWOs in high power microwave sources has been discussed for the past 10 years [1--6], but a detailed discussion of the design of this type of oscillators for particular waveforms has been lacking. In this dissertation I develop a design methodology for a realization of SWOs, also known as MATRIX oscillators in the scientific community. A key element in the design of SWOs is the self-breakdown switch, which is created by a large electric field. In order for the switch to close as expected from the design, it is essential to manage the electrostatic field distribution inside the oscillator during the charging time. This enforces geometric constraints on the shape of the conductors inside MATRIX. At the same time, the electrodynamic operation of MATRIX is dependent on the geometry of the structure. In order to generate a geometry that satisfies both the electrostatic and electrodynamic constraints, a new approach is developed to generate this geometry using the 2-D static solution of the Laplace equation, subject to a particular set of boundary conditions. These boundary conditions are manipulated to generate equipotential lines with specific dimensions that satisfy the electrodynamic constraints. Meanwhile, these equipotential lines naturally support an electrostatic field distribution that meets the requirements for the switch operation. To study the electrodynamic aspects of MATRIX, three different (but interrelated) numerical models are built. Depending on the assumptions made in each model, different information about the electrodynamic properties of the designed SWO are obtained. In addition, the agreement and consistency between the different models, validate and give confidence in the calculated results. Another important aspect of the design process is understanding the relationship between the geometric

  20. High-frequency oscillations in distributed neural networks reveal the dynamics of human decision making

    Directory of Open Access Journals (Sweden)

    Adrian G Guggisberg

    2008-03-01

    Full Text Available We examine the relative timing of numerous brain regions involved in human decisions that are based on external criteria, learned information, personal preferences, or unconstrained internal considerations. Using magnetoencephalography (MEG and advanced signal analysis techniques, we were able to non-invasively reconstruct oscillations of distributed neural networks in the high-gamma frequency band (60–150 Hz. The time course of the observed neural activity suggested that two-alternative forced choice tasks are processed in four overlapping stages: processing of sensory input, option evaluation, intention formation, and action execution. Visual areas are activated fi rst, and show recurring activations throughout the entire decision process. The temporo-occipital junction and the intraparietal sulcus are active during evaluation of external values of the options, 250–500 ms after stimulus presentation. Simultaneously, personal preference is mediated by cortical midline structures. Subsequently, the posterior parietal and superior occipital cortices appear to encode intention, with different subregions being responsible for different types of choice. The cerebellum and inferior parietal cortex are recruited for internal generation of decisions and actions, when all options have the same value. Action execution was accompanied by activation peaks in the contralateral motor cortex. These results suggest that high-gamma oscillations as recorded by MEG allow a reliable reconstruction of decision processes with excellent spatiotemporal resolution.

  1. A noninvasive high frequency oscillation ventilator: Achieved by utilizing a blower and a valve.

    Science.gov (United States)

    Yuan, YueYang; Sun, JianGuo; Wang, Baicun; Feng, Pei; Yang, ChongChang

    2016-02-01

    After the High Frequency Oscillatory Ventilation (HFOV) has been applied in the invasive ventilator, the new technique of noninvasive High Frequency Oscillatory Ventilation (nHFOV) which does not require opening the patient's airway has attracted much attention from the field. This paper proposes the design of an experimental positive pressure-controlled nHFOV ventilator which utilizes a blower and a special valve and has three ventilation modes: spontaneous controlled ventilation combining HFOV, time-cycled ventilation combining HFOV (T-HFOV), and continuous positive airway pressure ventilation combining HFOV. Experiments on respiratory model are conducted and demonstrated the feasibility of using nHFOV through the control of fan and valve. The experimental ventilator is able to produce an air flow with small tidal volume (VT) and a large minute ventilation volume (MV) using regular breath tubes and nasal mask (e.g., under T-HFOV mode, with a maximum tidal volume of 100 ml, the minute ventilation volume reached 14,400 ml). In the process of transmission, there is only a minor loss of oscillation pressure. (Under experimental condition and with an oscillation frequency of 2-10 Hz, peak pressure loss was around 0%-50% when it reaches the mask.).

  2. High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

    Science.gov (United States)

    Jafarzadeh, S.; Solanki, S. K.; Stangalini, M.; Steiner, O.; Cameron, R. H.; Danilovic, S.

    2017-04-01

    We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca ii H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, though overlapping, period distributions. Two independent estimates give a height difference of approximately 450 ± 100 km between the two atmospheric layers sampled by the employed spectral bands. This value, together with the determined short travel times of the transverse and longitudinal waves provide us with phase speeds of 29 ± 2 km s‑1 and 31 ± 2 km s‑1, respectively. We speculate that these phase speeds may not reflect the true propagation speeds of the waves. Thus, effects such as the refraction of fast longitudinal waves may contribute to an overestimate of the phase speed.

  3. High-Frequency and Type-C QPOs from Oscillating, Precessing Hot, Thick Flow

    CERN Document Server

    Fragile, P Chris; Blaes, Omer

    2016-01-01

    Motivated by recent studies showing an apparent correlation between the high-frequency quasi-periodic oscillations (QPOs) and the low-frequency, type-C QPO in low-mass, black hole X-ray binaries (LMXBs), we explore a model that explains all three QPOs in terms of an oscillating, precessing hot flow in the truncated-disk geometry. Our model favors attributing the two high-frequency QPOs, often occurring in a near 3:2 frequency ratio, to the breathing and vertical epicyclic frequency modes of the hot, thick flow, although we can not rule out the Keplerian and m=-1 radial epicyclic modes. In either case, the type-C QPO is attributed to precession. The correlation of the QPOs comes from the fact that all three frequencies are associated with the same geometrical structure. While the exact QPO frequencies are sensitive to the black hole mass and spin, their evolution over the course of an outburst is mainly tied to the truncation radius between the geometrically thin, optically thick disk and the inner, hot flow. ...

  4. Interplay of intrinsic and synaptic conductances in the generation of high-frequency oscillations in interneuronal networks with irregular spiking.

    Directory of Open Access Journals (Sweden)

    Fabiano Baroni

    2014-05-01

    Full Text Available High-frequency oscillations (above 30 Hz have been observed in sensory and higher-order brain areas, and are believed to constitute a general hallmark of functional neuronal activation. Fast inhibition in interneuronal networks has been suggested as a general mechanism for the generation of high-frequency oscillations. Certain classes of interneurons exhibit subthreshold oscillations, but the effect of this intrinsic neuronal property on the population rhythm is not completely understood. We study the influence of intrinsic damped subthreshold oscillations in the emergence of collective high-frequency oscillations, and elucidate the dynamical mechanisms that underlie this phenomenon. We simulate neuronal networks composed of either Integrate-and-Fire (IF or Generalized Integrate-and-Fire (GIF neurons. The IF model displays purely passive subthreshold dynamics, while the GIF model exhibits subthreshold damped oscillations. Individual neurons receive inhibitory synaptic currents mediated by spiking activity in their neighbors as well as noisy synaptic bombardment, and fire irregularly at a lower rate than population frequency. We identify three factors that affect the influence of single-neuron properties on synchronization mediated by inhibition: i the firing rate response to the noisy background input, ii the membrane potential distribution, and iii the shape of Inhibitory Post-Synaptic Potentials (IPSPs. For hyperpolarizing inhibition, the GIF IPSP profile (factor iii exhibits post-inhibitory rebound, which induces a coherent spike-mediated depolarization across cells that greatly facilitates synchronous oscillations. This effect dominates the network dynamics, hence GIF networks display stronger oscillations than IF networks. However, the restorative current in the GIF neuron lowers firing rates and narrows the membrane potential distribution (factors i and ii, respectively, which tend to decrease synchrony. If inhibition is shunting instead

  5. Ion-Acoustic Instability in the Presence of High Frequency Oscillations

    DEFF Research Database (Denmark)

    Juul Rasmussen, Jens; Sandu, D.; Schrittwieser, R.

    1977-01-01

    Measurements are presented of a standing ion-acoustic wave instability, which is excited by a positively biased grid inserted perpendicularly into the plasma column of a single-ended Q-machine, under the influence of a high frequency signal superimposed onto the positive voltage at the grid....... The experimental results show that in certain regions of the frequency and amplitude of the h.f. signal the ion wave instability is stabilized or destabilized. A possible explanation of these effects is presented....

  6. Fe I OSCILLATOR STRENGTHS FOR TRANSITIONS FROM HIGH-LYING EVEN-PARITY LEVELS

    Energy Technology Data Exchange (ETDEWEB)

    Den Hartog, E. A.; Lawler, J. E.; Brewer, N. R. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Ruffoni, M. P.; Pickering, J. C. [Blackett Laboratory, Imperial College London, London SW7 2BW (United Kingdom); Lind, K., E-mail: eadenhar@wisc.edu [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden)

    2015-01-01

    New radiative lifetimes, measured to ±5% accuracy, are reported for 31 even-parity levels of Fe I ranging from 45061 cm{sup –1} to 56842 cm{sup –1}. These lifetimes have been measured using single-step and two-step time-resolved laser-induced fluorescence on a slow atomic beam of iron atoms. Branching fractions have been attempted for all of these levels, and completed for 20 levels. This set of levels represents an extension of the collaborative work reported in Ruffoni et al. The radiative lifetimes combined with the branching fractions yields new oscillator strengths for 203 lines of Fe I. Utilizing a 1D-LTE model of the solar photosphere, spectral syntheses for a subset of these lines which are unblended in the solar spectrum yields a mean iron abundance of (log[ε(Fe)]) = 7.45 ± 0.06.

  7. Fe I Oscillator Strengths for Transitions from High-lying Even-Parity Levels

    CERN Document Server

    Hartog, E A Den; Lawler, J E; Pickering, J C; Lind, K; Brewer, N R

    2014-01-01

    New radiative lifetimes, measured to $\\pm$ 5 % accuracy, are reported for 31 even-parity levels of Fe I ranging from 45061 cm$^{-1}$ to 56842 cm$^{-1}$. These lifetimes have been measured using single-step and two-step time-resolved laser-induced fluorescence on a slow atomic beam of iron atoms. Branching fractions have been attempted for all of these levels, and completed for 20 levels. This set of levels represents an extension of the collaborative work reported in Ruffoni et al. (2014). The radiative lifetimes combined with the branching fractions yields new oscillator strengths for 203 lines of Fe I. Utilizing a 1D-LTE model of the solar photosphere, spectral syntheses for a subset of these lines which are unblended in the solar spectrum yields a mean iron abundance of = 7.45 $\\pm$ 0.06.

  8. Magnetoencephalography Detection of High-Frequency Oscillations in the Developing Brain

    Directory of Open Access Journals (Sweden)

    Kimberly eLeiken

    2014-12-01

    Full Text Available 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 noninvasive technique of MEG. MEG detection of high-frequency brain signals may open a new window for the study of developing brain function.

  9. Determination of frequencies of oscillations of cloud cavitation on a 2-D hydro- foil from high-speed camera observations

    Institute of Scientific and Technical Information of China (English)

    Patrik ZIMA; Tom FRST; Milan SEDL; Martin KOMREK; Rostislav HUZLK

    2016-01-01

    A method is presented to determine significant frequencies of oscillations of cavitation structures from high-speed camera recordings of a flow around a 2-D hydrofoil. The top view of the suction side of an NACA 2412 hydrofoil is studied in a transparent test section of a cavitation tunnel for selected cloud cavitation regimes with strong oscillations induced by the leading-edge cavity shedding. The ability of the method to accurately determine the dominant oscillation frequencies is confirmed by pressure measure- ments. The method can resolve subtle flow characteristics that are not visible to the naked eye. The method can be used for non- invasive experimental studies of oscillations in cavitating flows with adequate visual access when pressure measurements are not available or when such measurements would disturb the flow.

  10. Reduction of Sub-Harmonic Oscillations in Flyback Converter for High Power Factor

    Directory of Open Access Journals (Sweden)

    Mr.M.SubbaRao,

    2011-03-01

    Full Text Available For High power factor (HPFoperation of flyback converter in continuous conduction mode(CCM, a variety of current mode control techniques, such as peak current control, Average current control andcharge control techniques has been analyzed. But these are suffer from stability problem due to presence of sub-harmonic oscillations and noise immunity. This can be overcome by using slope compensationtechnique, but it increases complexity .So the proposed technique in this paper i.e., a Single-Reset Integrator based line current shaping controller is a simple and accurate line current shaping controllerwith reduced sub-harmonic oscillations. In this paper presents the comparison between charge control technique with proposed control i.e., A Single-Reset Integrator based line current shaping controller for a 200 W,140V A.C input and 48V D.C output single phase flyback converter for HPF.MATLAB/Simulink software is used for implementation and simulation results shows the performance of proposed controller.

  11. Critical parameters and universal amplitude ratios of two-dimensional spin-S Ising models using high- and low-temperature expansions

    CERN Document Server

    Butera, P

    2003-01-01

    For the study of Ising models of general spin S on the square lattice, we have combined our recently extended high-temperature expansions with the low-temperature expansions derived some time ago by Enting, Guttmann and Jensen. We have computed for the first time various critical parameters and improved the estimates of others. Moreover the properties of hyperscaling and of universality (spin S independence) of exponents and of various dimensionless amplitude combinations have been verified accurately. Assuming the validity of the lattice-lattice scaling, from our estimates of critical amplitudes for the square lattice we have also obtained estimates of the corresponding amplitudes for the spin S Ising model on the triangular, honeycomb, and kagome` lattices.

  12. Large-amplitude Fourier transformed high-harmonic alternating current cyclic voltammetry: kinetic discrimination of interfering Faradaic processes at glassy carbon and at boron-doped diamond electrodes.

    Science.gov (United States)

    Zhang, Jie; Guo, Si-Xuan; Bond, Alan M; Marken, Frank

    2004-07-01

    Significant advantages of Fourier transformed large-amplitude ac higher (second to eighth) harmonics relative to responses obtained with conventional small-amplitude ac or dc cyclic voltammetric methods have been demonstrated with respect to (i) the suppression of capacitive background currents, (ii) the separation of the reversible reduction of [Ru(NH(3))(6)](3+) from the overlapping irreversible oxygen reduction process under conditions where aerobic oxygen remains present in the electrochemical cell, and (iii) the kinetic resolution of the reversible [Ru(NH(3))(6)](3+/2+) process in mixtures of [Fe(CN)(6)](3-) and [Ru(NH(3))(6)](3+) at appropriately treated boron-doped diamond electrodes, even when highly unfavorable [Fe(CN)(6)](3-) to [Ru(NH(3))(6)](3+) concentration ratios are employed. Theoretical support for the basis of kinetic discrimination in large-amplitude higher harmonic ac cyclic voltammetry is provided.

  13. Fine structure of high-power microwave-induced resistance oscillations

    Science.gov (United States)

    Shi, Q.; Zudov, M. A.; Dmitriev, I. A.; Baldwin, K. Â. W.; Pfeiffer, L. Â. N.; West, K. Â. W.

    2017-01-01

    We report on observation of a fine structure of microwave-induced resistance oscillations in an ultraclean two-dimensional electron gas. This fine structure is manifested by multiple secondary sharp extrema, residing beside the primary ones, which emerge at high radiation power. Theoretical considerations reveal that this fine structure originates from multiphoton-assisted scattering off short-range impurities. Unique properties of the fine structure allow us to access all experimental parameters, including microwave power, and to separate different contributions to photoresistance. Furthermore, we show that the fine structure offers a convenient means to quantitatively assess the correlation properties of the disorder potential in high-quality systems, allowing separation of short- and long-range disorder contributions to the electron mobility.

  14. High-Power Blue Light Generation by External Frequency Doubling of an Optical Parametric Oscillator

    Institute of Scientific and Technical Information of China (English)

    毕勇; 张鸿博; 孙志培; 包照日格图; 李惠清; 孔宇鹏; 林学春; 王桂玲; 张杰; 侯玮; 李瑞宁; 崔大复; 许祖彦; 宋立维; 章萍; 崔建峰; 樊仲维

    2003-01-01

    We report on an all-solid-state high-power quasi-continuous blue light source by the frequency doubling of a signal wave from an optical parametric oscillator(OPO).A 50-mm-long LiB3O5(LBO)crystal is used for the OPO,which is pumped by a diode-pumped Nd:YAG green laser(10kHz,50ns).Tunable blue emission in a new nonlinear crystal BiB3O6(BiBO)is obtained with a wavelength range from 450 to 495 nm.The average power of the signal output is as high as 9.3 W from 924 to 970nm.The maximum output of the blue laser with the second harmonic walk-off compensation is 1.3 W average power at 470nm for 6.2 W of OPO signal light at 940nm.

  15. High frequency optoelectronic oscillators based on the optical feedback of semiconductor mode-locked laser diodes.

    Science.gov (United States)

    Haji, Mohsin; Hou, Lianping; Kelly, Anthony E; Akbar, Jehan; Marsh, John H; Arnold, John M; Ironside, Charles N

    2012-01-30

    Optical self seeding feedback techniques can be used to improve the noise characteristics of passively mode-locked laser diodes. External cavities such as fiber optic cables can increase the memory of the phase and subsequently improve the timing jitter. In this work, an improved optical feedback architecture is proposed using an optical fiber loop delay as a cavity extension of the mode-locked laser. We investigate the effect of the noise reduction as a function of the loop length and feedback power. The well known composite cavity technique is also implemented for suppressing supermode noise artifacts presented due to harmonic mode locking effects. Using this method, we achieve a record low radio frequency linewidth of 192 Hz for any high frequency (>1 GHz) passively mode-locked laser to date (to the best of the authors' knowledge), making it promising for the development of high frequency optoelectronic oscillators.

  16. DEMONSTRATION OF 3D EFFECTS WITH HIGH GAIN AND EFFICIENCY IN A UV FEL OSCILLATOR

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Benson; George Biallas; Keith Blackburn; James Boyce; Donald Bullard; James Coleman; Cody Dickover; David Douglas; Forrest Ellingsworth; Pavel Evtushenko; Carlos Hernandez-Garcia; Christopher Gould; Joseph Gubeli; David Hardy; Kevin Jordan; John Klopf; James Kortze; Robert Legg; Matthew Marchlik; Steven Moore; George Neil; Thomas Powers; Daniel Sexton; Michelle D. Shinn; Christopher Tennant; Richard Walker; Anne Watson; Gwyn Williams; Frederick Wilson; Shukui Zhang

    2011-03-01

    We report on the performance of a high gain UV FEL oscillator operating on an energy recovery linac at Jefferson Lab. The high brightness of the electron beam leads to both gain and efficiency that cannot be reconciled with a one-dimensional model. Three-dimensional simulations do predict the performance with reasonable precision. Gain in excess of 100% per pass and an efficiency close to 1/2NW, where NW is the number of wiggler periods, is seen. The laser mirror tuning curves currently permit operation in the wavelength range of 438 to 362 nm. Another mirror set allows operation at longer wavelengths in the red with even higher gain and efficiency.

  17. Damping of nonlinear standing kink oscillations: a numerical study

    CERN Document Server

    Magyar, N

    2016-01-01

    We aim to study the standing fundamental kink mode of coronal loops in the nonlinear regime, investigating the changes in energy evolution in the cross-section and oscillation amplitude of the loop which are related to nonlinear effects, in particular to the development of the Kelvin-Helmholtz instability (KHI). We run idea, high-resolution three-dimensional (3D) magnetohydrodynamics (MHD) simulations, studying the influence of the initial velocity amplitude and the inhomogeneous layer thickness. We model the coronal loop as a straight, homogeneous magnetic flux tube with an outer inhomogeneous layer, embedded in a straight, homogeneous magnetic field. We find that, for low amplitudes which do not allow for the KHI to develop during the simulated time, the damping time agrees with the theory of resonant absorption. However, for higher amplitudes, the presence of KHI around the oscillating loop can alter the loop's evolution, resulting in a significantly faster damping than predicted by the linear theory in so...

  18. Amplitude dependent closest tune approach

    CERN Document Server

    Tomas Garcia, Rogelio; Franchi, Andrea; Maclean, Ewen Hamish; CERN. Geneva. ATS Department

    2016-01-01

    Recent observations in the LHC point to the existence of an amplitude dependent closest tune approach. However this dynamical behavior and its underlying mechanism remain unknown. This effect is highly relevant for the LHC as an unexpectedly closest tune approach varying with amplitude modifies the frequency content of the beam and, hence, the Landau damping. Furthermore the single particle stability would also be affected by this effect as it would modify how particles with varying amplitudes approach and cross resonances. We present analytic derivations that lead to a mechanism generating an amplitude dependent closest tune approach.

  19. Effectiveness of treatment with high-frequency chest wall oscillation in patients with bronchiectasis.

    Science.gov (United States)

    Nicolini, Antonello; Cardini, Federica; Landucci, Norma; Lanata, Sergio; Ferrari-Bravo, Maura; Barlascini, Cornelius

    2013-04-04

    High-frequency airway clearance (HFCWC) assist devices generate either positive or negative trans-respiratory pressure excursions to produce high-frequency, small-volume oscillations in the airways.HFCWC can lead to changes in volume of 15-57 ml and in flow up to 1.6 L/s, which generate minimal coughing to mobilize secretions. The typical treatment lasts 20-30 minutes, and consists of short periods of compression at different frequencies, separated by coughing.The aim of this study was to find the more efficacious treatment in patients with bronchiectasis: traditional techniques of chest physiotherapy (CPT) versus high frequency oscillation of the chest wall in patients with bronchiectasis. 37 patients were enrolled. Seven of them were excluded. Computer randomization divided the patients into three groups: - 10 patients treated with HFCWO by using the Vest® Airway Clearance System; - 10 patients treated with traditional techniques of air way clearance (PEP bottle, PEP mask, ELTGOL, vibratory positive expiratory pressure); - 10 patients received medical therapy only (control group). To be eligible for enrollment, participants had to be between 18 and 85 years old and have a diagnosis of bronchiectasis, confirmed on high resolution computed tomography. lack of informed consent, signs of exacerbation, cystic fibrosis. Before the treatment, each patient had blood tests, sputum volume and cell count, pulmonary function tests and on the quality of life inventories (MMRC, CAT, BCSS). The results were processed through the covariance analysis, performed with the R-Project statistical program. It has been considered a positive result p airway clearance, this treatment should be included among the principal options in chest physiotherapy. The study was registered as ChiCTR-TRC-12002134 at http://www.chictr.org.

  20. A new delirium phenotype with rapid high amplitude onset and nearly as rapid reversal: Central Coast Australia Delirium Intervention Study

    Directory of Open Access Journals (Sweden)

    Regal PJ

    2015-02-01

    , and 45%/80% for the Delirium Index. General medicine and geriatric medicine groups had similar outcomes.Conclusion: This delirium phenotype selects for a rapid high amplitude critical decline in attention, executive function, IADL, and apathy that recovers almost as rapidly.Keywords: delirium, inattention, executive function, dementia

  1. Vibrational resonance in the Morse oscillator

    Indian Academy of Sciences (India)

    K Abirami; S Rajasekar; M A F Sanjuan

    2013-07-01

    The occurrence of vibrational resonance is investigated in both classical and quantum mechanical Morse oscillators driven by a biharmonic force. The biharmonic force consists of two forces of widely different frequencies and with $ \\gg $. In the damped and biharmonically driven classical Morse oscillator, by applying a theoretical approach, an analytical expression is obtained for the response amplitude at the low-frequency . Conditions are identified on the parameters for the occurrence of resonance. The system shows only one resonance and moreover at resonance the response amplitude is 1/ where is the coefficient of linear damping. When the amplitude of the high-frequency force is varied after resonance the response amplitude does not decay to zero but approaches a nonzero limiting value. It is observed that vibrational resonance occurs when the sinusoidal force is replaced by a square-wave force. The occurrence of resonance and antiresonance of transition probability of quantum mechanical Morse oscillator is also reported in the presence of the biharmonic external field.

  2. Oscillation effects upon film boiling from a sphere.

    Science.gov (United States)

    Schmidt, W. E.; Witte, L. C.

    1972-01-01

    Heat transfer rates from a silver-plated copper sphere, 0.75 in. in diameter, were studied by high speed photography during oscillations of the sphere in saturated liquid nitrogen and Freon-11. The oscillation frequencies ranged from zero to 13 Hz, and the amplitude-to-diameter ratio varied from zero to 2.67. The sphere was supported by a thin-walled stainless steel tube and carried a thermocouple attached near the lower stagnation point. A Fastax WF-3 16mm movie camera was used at about 2000 frames/sec. The differences in the vapor removal process at lower and higher oscillation frequencies are discussed.

  3. Laser Beam Welding with High-Frequency Beam Oscillation: Welding of Dissimilar Materials with Brilliant Fiber Lasers

    Science.gov (United States)

    Kraetzsch, Mathias; Standfuss, Jens; Klotzbach, Annett; Kaspar, Joerg; Brenner, Berndt; Beyer, Eckhard

    Brilliant laser beam sources in connection with a high frequent beam oscillation make it now possible to join metallic material combinations, which have been conventionally non-laser weldable up to now. It concerns especially such combinations like Al- Cu, where brittle intermetallic phases occur. Extreme small weld seam with high aspect ratio leads to very short meld pool life time. These allow an extensive reduction of the heat input. On the other side the melting behavior at metallic mixed joint, seam geometry, meld pool turbulence and solidification behavior can be influenced by a high frequent time-, position- and powercontrolled laser beam oscillation.

  4. Movement-related beta oscillations show high intra-individual reliability.

    Science.gov (United States)

    Espenhahn, Svenja; de Berker, Archy O; van Wijk, Bernadette C M; Rossiter, Holly E; Ward, Nick S

    2017-02-15

    Oscillatory activity in the beta frequency range (15-30Hz) recorded from human sensorimotor cortex is of increasing interest as a putative biomarker of motor system function and dysfunction. Despite its increasing use in basic and clinical research, surprisingly little is known about the test-retest reliability of spectral power and peak frequency measures of beta oscillatory signals from sensorimotor cortex. Establishing that these beta measures are stable over time in healthy populations is a necessary precursor to their use in the clinic. Here, we used scalp electroencephalography (EEG) to evaluate intra-individual reliability of beta-band oscillations over six sessions, focusing on changes in beta activity during movement (Movement-Related Beta Desynchronization, MRBD) and after movement termination (Post-Movement Beta Rebound, PMBR). Subjects performed visually-cued unimanual wrist flexion and extension. We assessed Intraclass Correlation Coefficients (ICC) and between-session correlations for spectral power and peak frequency measures of movement-related and resting beta activity. Movement-related and resting beta power from both sensorimotor cortices was highly reliable across sessions. Resting beta power yielded highest reliability (average ICC=0.903), followed by MRBD (average ICC=0.886) and PMBR (average ICC=0.663). Notably, peak frequency measures yielded lower ICC values compared to the assessment of spectral power, particularly for movement-related beta activity (ICC=0.386-0.402). Our data highlight that power measures of movement-related beta oscillations are highly reliable, while corresponding peak frequency measures show greater intra-individual variability across sessions. Importantly, our finding that beta power estimates show high intra-individual reliability over time serves to validate the notion that these measures reflect meaningful individual differences that can be utilised in basic research and clinical studies. Copyright © 2016 The

  5. Temporal Characteristics of High-Frequency Lower-Limb Oscillation during Freezing of Gait in Parkinson’s Disease

    Directory of Open Access Journals (Sweden)

    Don A. Yungher

    2014-01-01

    Full Text Available A cardinal feature of freezing of gait (FOG is high frequency (3–8 Hz oscillation of the legs, and this study aimed to quantify the temporal pattern of lower-body motion prior to and during FOG. Acceleration data was obtained from sensors attached to the back, thighs, shanks, and feet in 14 Parkinson’s disease patients performing timed-up-and-go tasks, and clinical assessment of FOG was performed by two experienced raters from video. A total of 23 isolated FOG events, defined as occurring at least 5 s after gait initiation and with no preceding FOG, were identified from the clinical ratings. The corresponding accelerometer records were analyzed within a 4 s window centered at the clinical onset of freezing. FOG-related high-frequency oscillation (an increase in power in the 3–8 Hz band >3 SD from baseline followed a distal to proximal onset pattern, appearing at the feet, shanks, thighs, and then back over a period of 250 ms. Peak power tended to decrease as the focus of oscillation moved from feet to back. There was a consistent delay (mean 872 ms between the onset of high frequency oscillation at the feet and clinical onset of FOG. We infer that FOG is characterized by high frequency oscillation at the feet, which progresses proximally and is mechanically damped at the torso.

  6. Temporal Characteristics of High-Frequency Lower-Limb Oscillation during Freezing of Gait in Parkinson's Disease

    Science.gov (United States)

    Yungher, Don A.; Morris, Tiffany R.; Dilda, Valentina; Shine, James M.; Naismith, Sharon L.; Lewis, Simon J. G.; Moore, Steven T.

    2014-01-01

    A cardinal feature of freezing of gait (FOG) is high frequency (3–8 Hz) oscillation of the legs, and this study aimed to quantify the temporal pattern of lower-body motion prior to and during FOG. Acceleration data was obtained from sensors attached to the back, thighs, shanks, and feet in 14 Parkinson's disease patients performing timed-up-and-go tasks, and clinical assessment of FOG was performed by two experienced raters from video. A total of 23 isolated FOG events, defined as occurring at least 5 s after gait initiation and with no preceding FOG, were identified from the clinical ratings. The corresponding accelerometer records were analyzed within a 4 s window centered at the clinical onset of freezing. FOG-related high-frequency oscillation (an increase in power in the 3–8 Hz band >3 SD from baseline) followed a distal to proximal onset pattern, appearing at the feet, shanks, thighs, and then back over a period of 250 ms. Peak power tended to decrease as the focus of oscillation moved from feet to back. There was a consistent delay (mean 872 ms) between the onset of high frequency oscillation at the feet and clinical onset of FOG. We infer that FOG is characterized by high frequency oscillation at the feet, which progresses proximally and is mechanically damped at the torso. PMID:25101189

  7. The vertical oscillations of coupled magnets

    Science.gov (United States)

    Kewei, Li; Jiahuang, Lin; Yang, Kang Zi; Liang, Samuel Yee Wei; Wong Say Juan, Jeremias

    2011-07-01

    The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for high school students. This paper is adapted from the winning solution to Problem 14, Magnetic Spring, as presented in the final round of the 23rd IYPT in Vienna, Austria. Two magnets were arranged on top of each other on a common axis. One was fixed, while the other could move vertically. Various parameters of interest were investigated, including the effective gravitational acceleration, the strength, size, mass and geometry of the magnets, and damping of the oscillations. Despite its simplicity, this setup yielded a number of interesting and unexpected relations. The first stage of the investigation was concerned only with the undamped oscillations of small amplitudes, and the period of small amplitude oscillations was found to be dependent only on the eighth root of important magnet properties such as its strength and mass. The second stage sought to investigate more general oscillations. A numerical model which took into account magnet size, magnet geometry and damping effects was developed to model the general oscillations. Air resistance and friction were found to be significant sources of damping, while eddy currents were negligible.

  8. The vertical oscillations of coupled magnets

    Energy Technology Data Exchange (ETDEWEB)

    Li Kewei; Lin Jiahuang; Kang Zi Yang [Raffles Institution, 1 Raffles Institution Lane, Singapore 575954 (Singapore); Liang, Samuel Yee Wei [Anglo-Chinese School Independent, 121 Dover Road, Singapore 139650 (Singapore); Juan, Jeremias Wong Say, E-mail: likewei92@gmail.com [NUS High School of Mathematics and Science, 20 Clementi Avenue 1, Singapore 129957 (Singapore)

    2011-07-15

    The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for high school students. This paper is adapted from the winning solution to Problem 14, Magnetic Spring, as presented in the final round of the 23rd IYPT in Vienna, Austria. Two magnets were arranged on top of each other on a common axis. One was fixed, while the other could move vertically. Various parameters of interest were investigated, including the effective gravitational acceleration, the strength, size, mass and geometry of the magnets, and damping of the oscillations. Despite its simplicity, this setup yielded a number of interesting and unexpected relations. The first stage of the investigation was concerned only with the undamped oscillations of small amplitudes, and the period of small amplitude oscillations was found to be dependent only on the eighth root of important magnet properties such as its strength and mass. The second stage sought to investigate more general oscillations. A numerical model which took into account magnet size, magnet geometry and damping effects was developed to model the general oscillations. Air resistance and friction were found to be significant sources of damping, while eddy currents were negligible.

  9. A high-field magnetic resonance imaging spectrometer using an oven-controlled crystal oscillator as the local oscillator of its radio frequency transceiver.

    Science.gov (United States)

    Liang, Xiao; Tang, Xin; Tang, Weinan; Gao, Jia-Hong

    2014-09-01

    A home-made high-field magnetic resonance imaging (MRI) spectrometer with multiple receiving channels is described. The radio frequency (RF) transceiver of the spectrometer consists of digital intermediate frequency (IF) circuits and corresponding mixing circuits. A direct digital synthesis device is employed to generate the IF pulse; the IF signal from a down-conversion circuit is sampled and followed by digital quadrature detection. Both the IF generation and the IF sampling use a 50 MHz clock. An oven-controlled crystal oscillator, which has outstanding spectral purity and a compact circuit, is used as the local oscillator of the RF transceiver. A digital signal processor works as the pulse programmer of the spectrometer, as a result, 32 control lines can be generated simultaneously while an event is triggered. Field programmable gate array devices are utilized as the auxiliary controllers of the IF generation, IF receiving, and gradient control. High performance, including 1 μs time resolution of the soft pulse, 1 MHz receiving bandwidth, and 1 μs time resolution of the gradient waveform, is achieved. High-quality images on a 1.5 T MRI system using the spectrometer are obtained.

  10. Mechanical models of amplitude and frequency modulation

    Energy Technology Data Exchange (ETDEWEB)

    Bellomonte, L; Guastella, I; Sperandeo-Mineo, R M [GRIAF - Research Group on Teaching/Learning Physics, DI.F.TE.R. -Dipartimento di Fisica e Tecnologie Relative, University of Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy)

    2005-05-01

    This paper presents some mechanical models for amplitude and frequency modulation. The equations governing both modulations are deduced alongside some necessary approximations. Computer simulations of the models are carried out by using available educational software. Amplitude modulation is achieved by using a system of two weakly coupled pendulums, whereas the frequency modulation is obtained by using a pendulum of variable length. Under suitable conditions (small oscillations, appropriate initial conditions, etc) both types of modulation result in significantly accurate and visualized simulations.

  11. Theoretical Study on Auto-Oscillating Combustion in Self-propagating High Temperature Synthesis

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jin-yong; FU Zheng-yi; WANG Wei-min; ZHANG Qing-jie

    2003-01-01

    Oscillating combustion is one of classic phenomenon in SHS. But the cause of its formation in a set of complex processes is unclear yet. With a two-step chemical reaction assumption and effects of other thermal dynamic factors, an auto- oscillating combustion hes been gained in a solid SHS process on the macro- humogenous and micro- heterogonous model. Numerical solution shows that the change of chemical reaction is the main cause of the oscillating combustion.

  12. PULSE AMPLITUDE DISTRIBUTION RECORDER

    Science.gov (United States)

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  13. Directly diode-pumped high-energy Ho:YAG oscillator.

    Science.gov (United States)

    Lamrini, Samir; Koopmann, Philipp; Schäfer, Michael; Scholle, Karsten; Fuhrberg, Peter

    2012-02-15

    We report on the high-energy laser operation of an Ho:YAG oscillator resonantly pumped by a GaSb-based laser diode stack at 1.9 μm. The output energy was extracted from a compact plano-concave acousto-optically Q-switched resonator optimized for low repetition rates. Operating at 100 Hz, pulse energies exceeding 30 mJ at a wavelength of 2.09 μm were obtained. The corresponding pulse duration at the highest pump power was 100 ns, leading to a maximum peak power above 300 kW. Different pulse repetition rates and output coupling transmissions of the Ho:YAG resonator were studied. In addition, intracavity laser-induced damage threshold measurements are discussed.

  14. Long-Term Operating Experience with High-Power Gyrotron Oscillators

    Science.gov (United States)

    Felch, Kevin

    2005-10-01

    High-power, megawatt-class gyrotron oscillators have now been used in electron cyclotron heating (ECH) experiments for several years. The long periods of sustained operation have provided important information about the design limits that had initially been placed on the key elements of the gyrotron. In particular, observations made on recent 110 GHz, 1 MW gyrotrons used in ECH experiments on DIII-D at General Atomics indicate that several of the important components of the device, including the electron guns, interaction cavities and diamond output windows, have performed quite well, while analyses of the electron beam collectors on some of the devices indicate that design limits have often been exceeded. Observations made on these gyrotrons will be summarized and plans to address problem areas will be discussed.

  15. Detecting and characterizing high-frequency oscillations in epilepsy: a case study of big data analysis.

    Science.gov (United States)

    Huang, Liang; Ni, Xuan; Ditto, William L; Spano, Mark; Carney, Paul R; Lai, Ying-Cheng

    2017-01-01

    We develop a framework to uncover and analyse dynamical anomalies from massive, nonlinear and non-stationary time series data. The framework consists of three steps: preprocessing of massive datasets to eliminate erroneous data segments, application of the empirical mode decomposition and Hilbert transform paradigm to obtain the fundamental components embedded in the time series at distinct time scales, and statistical/scaling analysis of the components. As a case study, we apply our framework to detecting and characterizing high-frequency oscillations (HFOs) from a big database of rat electroencephalogram recordings. We find a striking phenomenon: HFOs exhibit on-off intermittency that can be quantified by algebraic scaling laws. Our framework can be generalized to big data-related problems in other fields such as large-scale sensor data and seismic data analysis.

  16. Detecting and characterizing high-frequency oscillations in epilepsy: a case study of big data analysis

    Science.gov (United States)

    Huang, Liang; Ni, Xuan; Ditto, William L.; Spano, Mark; Carney, Paul R.; Lai, Ying-Cheng

    2017-01-01

    We develop a framework to uncover and analyse dynamical anomalies from massive, nonlinear and non-stationary time series data. The framework consists of three steps: preprocessing of massive datasets to eliminate erroneous data segments, application of the empirical mode decomposition and Hilbert transform paradigm to obtain the fundamental components embedded in the time series at distinct time scales, and statistical/scaling analysis of the components. As a case study, we apply our framework to detecting and characterizing high-frequency oscillations (HFOs) from a big database of rat electroencephalogram recordings. We find a striking phenomenon: HFOs exhibit on-off intermittency that can be quantified by algebraic scaling laws. Our framework can be generalized to big data-related problems in other fields such as large-scale sensor data and seismic data analysis.

  17. Self-sustained photothermal oscillations in high-finesse Fabry-Perot microcavities

    Science.gov (United States)

    Konthasinghe, Kumarasiri; Velez, Juan Gomez; Hopkins, Adam J.; Peiris, Manoj; Profeta, Luisa T. M.; Nieves, Yamil; Muller, Andreas

    2017-01-01

    We report the experimental investigation of a regime of microscopic Fabry-Perot resonators in which competing light-induced forces—photothermal expansion and photothermal refraction—acting oppositely and on different timescales lead to self-sustained persistent oscillations. Previously concealed as ordinary thermo-optic bistability—a common feature in low-loss resonator physics—these dynamics are visible as fast pulsations in cavity transmission or reflection measurements at sufficiently high time resolution. Their underlying mathematical description is shared by many slow-fast phenomena in chemistry, biology, and neuroscience. Our observations are relevant in particular to microcavity applications in atom optics and cavity quantum electrodynamics, even in nominally rigid structures that have not undergone lithography.

  18. High-Frequency Oscillations in a Solar Active Region observed with the Rapid Dual Imager

    CERN Document Server

    Jess, D B; Mathioudakis, M; Bloomfield, D S; Keenan, F P

    2007-01-01

    High-cadence, synchronized, multiwavelength optical observations of a solar active region (NOAA 10794) are presented. The data were obtained with the Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak using a newly developed camera system : the Rapid Dual Imager. Wavelet analysis is undertaken to search for intensity related oscillatory signatures, and periodicities ranging from 20 to 370 s are found with significance levels exceeding 95%. Observations in the H-alpha blue wing show more penumbral oscillatory phenomena when compared to simultaneous G-band observations. The H-alpha oscillations are interpreted as the signatures of plasma motions with a mean velocity of 20 km/s. The strong oscillatory power over H-alpha blue-wing and G-band penumbral bright grains is an indication of the Evershed flow with frequencies higher than previously reported.

  19. High-power terahertz radiation from surface-emitted THz-wave parametric oscillator

    Institute of Scientific and Technical Information of China (English)

    Li Zhong-Yang; Yao Jian-Quan; Xu De-Gang; Zhong Kai; Wang Jing-Li; Bing Pi-Bin

    2011-01-01

    We report a pulsed surface-emitted THz-wave parametric oscillator based on two MgO:LiNbC>3 crystals pumped by a multi-longitudinal mode Q-switched Nd:YAG laser. Through varying the phase matching angle, the tunable THz wave output from 0.79 THz to 2.84 THz is realized. The maximum THz-wave output was 193.2 nJ/pulse at 1.84 THz as the pump power density was 212.5 MW/cm2, corresponding to the energy conversion efficiency of 2.42 ×10-6 and the photon conversion efficiency of about 0.037%. When the pump power density changed from 123 MW/cm2 to 148 MW/cm2 and 164 MW/cm2, the maximum output of the THz-wave moved to the high frequency band. We give a reasonable explanation for this phenomenon.

  20. Fiber optical parametric oscillator based on highly nonlinear dispersion-shifted fiber

    Institute of Scientific and Technical Information of China (English)

    Sigang YANG; Kenneth K. Y. WONG; Minghua CHEN; Shizhong XIE

    2013-01-01

    The development of fiber optical parametric oscillators (FOPO) based on highly nonlinear dispersion- shifted fiber is reviewed in this paper. Firstly, the background and motivation are introduced, and it is pointed out that the FOPO is promising to act as optical source in non-conventional wavelength bands. Subsequently, the context focuses principally on the problem of inherent multiple-longitudinal-mode characteristic of FOPO and the corresponding solutions to it. The primary technique is by locking the phase of multiple longitudinal modes. The first reported actively mode locked FOPO is also presented in this article. However, it is not probable to realize passively mode locked FOPO because of the random phase dithering of the pump required for suppressing stimulated Brillouin scattering. Furthermore, a regeneratively mode locked FOPO is demonstrated, which can generate wide band tunable radiation in non- conventional wavelengths. Besides mode locked FOPO, the single-longitudinal-mode FOPO is also introduced. Finally, potential future directions are discussed.

  1. Study on low-phase-noise optoelectronic oscillator and high-sensitivity phase noise measurement system.

    Science.gov (United States)

    Hong, Jun; Liu, An-min; Guo, Jian

    2013-08-01

    An analytic model for an injection-locked dual-loop optoelectronic oscillator (OEO) is proposed and verified by experiments in this paper. Based on this theoretical model, the effect of injection power on the single-sideband phase noise of the OEO is analyzed, and results suggest that moderate injection is one key factor for a balance between phase noise and spur for OEO. In order to measure superlow phase noise of OEOs, a cross-correlation measurement system based on the fiber delay line is built, in which high linear photodetector and low-phase-noise amplifier are used to improve systematic sensitivity. The cross-correlation measurement system is validated by experiments, and its noise floor for the X band is about -130 dBc/Hz at 1 kHz and -168 dBc/Hz at 10 kHz after a cross correlation of 200 times.

  2. Anterior Thalamic High Frequency Band Activity Is Coupled with Theta Oscillations at Rest

    Directory of Open Access Journals (Sweden)

    Catherine M. Sweeney-Reed

    2017-07-01

    Full Text Available Cross-frequency coupling (CFC between slow and fast brain rhythms, in the form of phase–amplitude coupling (PAC, is proposed to enable the coordination of neural oscillatory activity required for cognitive processing. PAC has been identified in the neocortex and mesial temporal regions, varying according to the cognitive task being performed and also at rest. PAC has also been observed in the anterior thalamic nucleus (ATN during memory processing. The thalamus is active during the resting state and has been proposed to be involved in switching between task-free cognitive states such as rest, in which attention is internally-focused, and externally-focused cognitive states, in which an individual engages with environmental stimuli. It is unknown whether PAC is an ongoing phenomenon during the resting state in the ATN, which is modulated during different cognitive states, or whether it only arises during the performance of specific tasks. We analyzed electrophysiological recordings of ATN activity during rest from seven patients who received thalamic electrodes implanted for treatment of pharmacoresistant focal epilepsy. PAC was identified between theta (4–6 Hz phase and high frequency band (80–150 Hz amplitude during rest in all seven patients, which diminished during engagement in tasks involving an external focus of attention. The findings are consistent with the proposal that theta–gamma coupling in the ATN is an ongoing phenomenon, which is modulated by task performance.

  3. Using Fast Vibrations to Quench Friction-induced Oscillations

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    1999-01-01

    -frequency excitation. It appears that high-frequency excitation can effectively cancel the negative slope in the friction-velocity relationship, and may thus prevent self-excited oscillations. To accomplish this it is sufficient that the (nondimensional) product of excitation amplitude and frequency exceeds the veloc...... change under the action of fast vibrations....

  4. Lung pressures and gas transport during high-frequency airway and chest wall oscillation.

    Science.gov (United States)

    Khoo, M C; Ye, T H; Tran, N H

    1989-09-01

    The major goal of this study was to compare gas exchange, tidal volume (VT), and dynamic lung pressures resulting from high-frequency airway oscillation (HFAO) with the corresponding effects in high-frequency chest wall oscillation (HFCWO). Eight anesthetized paralyzed dogs were maintained eucapnic with HFAO and HFCWO at frequencies ranging from 1 to 16 Hz in the former and 0.5 to 8 Hz in the latter. Tracheal (delta Ptr) and esophageal (delta Pes) pressure swings, VT, and arterial blood gases were measured in addition to respiratory impedance and static pressure-volume curves. Mean positive pressure (25-30 cmH2O) in the chest cuff associated with HFCWO generation decreased lung volume by approximately 200 ml and increased pulmonary impedance significantly. Aside from this decrease in functional residual capacity (FRC), no change in lung volume occurred as a result of dynamic factors during the course of HFCWO application. With HFAO, a small degree of hyperinflation occurred only at 16 Hz. Arterial PO2 decreased by 5 Torr on average during HFCWO. VT decreased with increasing frequency in both cases, but VT during HFCWO was smaller over the range of frequencies compared with HFAO. delta Pes and delta Ptr between 1 and 8 Hz were lower than the corresponding pressure swings obtained with conventional mechanical ventilation (CMV) applied at 0.25 Hz. delta Pes was minimized at 1 Hz during HFCWO; however, delta Ptr decreased continuously with decreasing frequency and, below 2 Hz, became progressively smaller than the corresponding values obtained with HFAO and CMV.

  5. High-resolution observations of the shock wave behavior for sunspot oscillations with the interface region imaging spectrograph

    Energy Technology Data Exchange (ETDEWEB)

    Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; Golub, L.; Saar, S.; Testa, P.; Weber, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); De Pontieu, B.; Martínez-Sykora, J.; Kleint, L.; Cheung, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P. [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Org. ADBS, Bldg. 252, Palo Alto, CA 94304 (United States); Carlsson, M.; Hansteen, V., E-mail: hui.tian@cfa.harvard.edu [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); and others

    2014-05-10

    We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slit-jaw images and the spectra of several emission lines formed in the transition region and chromosphere. We first apply a single Gaussian fit to the profiles of the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the sunspot. The intensity change is ∼30%. The Doppler shift oscillation reveals a sawtooth pattern with an amplitude of ∼10 km s{sup –1} in Si IV. The Si IV oscillation lags those of C II and Mg II by ∼6 and ∼25 s, respectively. The line width suddenly increases as the Doppler shift changes from redshift to blueshift. However, we demonstrate that this increase is caused by the superposition of two emission components. We then perform detailed analysis of the line profiles at a few selected locations on the slit. The temporal evolution of the line core is dominated by the following behavior: a rapid excursion to the blue side, accompanied by an intensity increase, followed by a linear decrease of the velocity to the red side. The maximum intensity slightly lags the maximum blueshift in Si IV, whereas the intensity enhancement slightly precedes the maximum blueshift in Mg II. We find a positive correlation between the maximum velocity and deceleration, a result that is consistent with numerical simulations of upward propagating magnetoacoustic shock waves.

  6. Magnetoencephalography detection of high-frequency oscillations in the developing brain.

    Science.gov (United States)

    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.

  7. Formation of the peak amplitude of blood flow oscillations at a frequency of 0.1 Hz in the human cardiovascular system by the noise effect on the heart

    Science.gov (United States)

    Grinevich, Andrey A.; Tankanag, Arina V.; Chemeris, Nikolay K.

    2017-04-01

    In the framework of our previous hypothesis about the participation of structural and hydrodynamic properties of the vascular bed in the formation of the 0.1-Hz component of blood flow oscillations in the human cardiovascular system and on the basis of the reduced hydrodynamic model, the role of additive stochastic perturbations of the operation of the single-chamber pump that simulates the heart was investigated. It was shown that aperiodic noise modulation of the rigidity of the walls of the pump or its valves generates low-frequency oscillations of pressure of arterial vascular bed with the spectral components at a frequency close to 0.1 Hz.

  8. Simulations of Oscillating Hydrofoils in Array Configurations

    Science.gov (United States)

    Franck, Jennifer; Simeski, Filip; Spaulding, Arianne

    2016-11-01

    The vortex and wake interactions of multiple oscillating foils are investigated computationally for energy harvesting applications. Oscillating with high pitch and heave amplitudes to maximize power production, the elliptical-shaped foils generate large coherent vortices at the leading and trailing edge, which are shed downstream to create a large highly structured wake of vortices with alternating sign. Downstream foils oscillate within the large organized wake at a relative phase angle to the lead foil such that power efficiency is optimized. When placed directly downstream of one another, the optimal phase of a second foil is to avoid interactions with the first foil's wake, generating less than half of the total power of the first foil. However, when placed in a staggered configuration the downstream foil has an increase in efficiency through constructive vortex-foil interactions. Funded by ARPAe.

  9. Detection of forced oscillations in power systems with multichannel methods

    Energy Technology Data Exchange (ETDEWEB)

    Follum, James D. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

    2015-09-30

    The increasing availability of high fidelity, geographically dispersed measurements in power systems improves the ability of researchers and engineers to study dynamic behaviors in the grid. One such behavior that is garnering increased attention is the presence of forced oscillations. Power system engineers are interested in forced oscillations because they are often symptomatic of the malfunction or misoperation of equipment. Though the resulting oscillation is not always large in amplitude, the root cause may be serious. In this report, multi-channel forced oscillation detection methods are developed. These methods leverage previously developed detection approaches based on the periodogram and spectral-coherence. Making use of geographically distributed channels of data is shown to improved detection performance and shorten the delay before an oscillation can be detected in the online environment. Results from simulated and measured power system data are presented.

  10. Optimal operating points of oscillators using nonlinear resonators.

    Science.gov (United States)

    Kenig, Eyal; Cross, M C; Villanueva, L G; Karabalin, R B; Matheny, M H; Lifshitz, Ron; Roukes, M L

    2012-11-01

    We demonstrate an analytical method for calculating the phase sensitivity of a class of oscillators whose phase does not affect the time evolution of the other dynamic variables. We show that such oscillators possess the possibility for complete phase noise elimination. We apply the method to a feedback oscillator which employs a high Q weakly nonlinear resonator and provide explicit parameter values for which the feedback phase noise is completely eliminated and others for which there is no amplitude-phase noise conversion. We then establish an operational mode of the oscillator which optimizes its performance by diminishing the feedback noise in both quadratures, thermal noise, and quality factor fluctuations. We also study the spectrum of the oscillator and provide specific results for the case of 1/f noise sources.

  11. The Detection of Phase Amplitude Coupling during Sensory Processing

    Directory of Open Access Journals (Sweden)

    Robert A. Seymour

    2017-09-01

    Full Text Available There is increasing interest in understanding how the phase and amplitude of distinct neural oscillations might interact to support dynamic communication within the brain. In particular, previous work has demonstrated a coupling between the phase of low frequency oscillations and the amplitude (or power of high frequency oscillations during certain tasks, termed phase amplitude coupling (PAC. For instance, during visual processing in humans, PAC has been reliably observed between ongoing alpha (8–13 Hz and gamma-band (>40 Hz activity. However, the application of PAC metrics to electrophysiological data can be challenging due to numerous methodological issues and lack of coherent approaches within the field. Therefore, in this article we outline the various analysis steps involved in detecting PAC, using an openly available MEG dataset from 16 participants performing an interactive visual task. Firstly, we localized gamma and alpha-band power using the Fieldtrip toolbox, and extracted time courses from area V1, defined using a multimodal parcelation scheme. These V1 responses were analyzed for changes in alpha-gamma PAC, using four common algorithms. Results showed an increase in alpha (7–13 Hz–gamma (40–100 Hz PAC in response to the visual grating stimulus, though specific patterns of coupling were somewhat dependent upon the algorithm employed. Additionally, post-hoc analyses showed that these results were not driven by the presence of non-sinusoidal oscillations, and that trial length was sufficient to obtain reliable PAC estimates. Finally, throughout the article, methodological issues and practical guidelines for ongoing PAC research will be discussed.

  12. High-peak-power, high-repetition-rate intracavity optical parametric oscillator at 1.57μm

    Institute of Scientific and Technical Information of China (English)

    Yuye Wang; Degang Xu; Yizhong Yu; Wuqi Wen; Jingping Xiong; Peng Wang; Jianquan Yao

    2007-01-01

    We report a high-peak-power, high-repetition-rate diode-side-pumped Nd:YAG Q-switched intracavity optical parametric oscillator (IOPO) at 1.57μm with a type-Ⅱ non-critically phase-matched x-cut KTP crystal. The average power of 1.15 W at 1.57μm is obtained at 4.3-kHz repetition rate. The peak power of the pulses amounts to 33.4 kW with 8-ns duration. The average conversion efficiency from Q-switched 1.064-μm-wavelength input power to OPO signal output power is up to 10.5%.

  13. High frequency chest wall oscillation in patients with chronic air-flow obstruction.

    Science.gov (United States)

    Piquet, J; Brochard, L; Isabey, D; de Cremoux, H; Chang, H K; Bignon, J; Harf, A

    1987-12-01

    In order to assess high frequency chest wall oscillation (HFCWO) as a way to assist spontaneous breathing in obstructive lung disease, we studied 12 patients with severe and stable COPD. HFCWO at 5 Hz were applied by means of an inflatable vest. In order to avoid any discomfort, oscillations were applied only during the expiratory phase of the spontaneous breathing cycle. We compared gas exchange and pattern of breathing during control and HFCWO periods, each lasting 15 min. Minute ventilation did not change, but the pattern of breathing was markedly altered during HFCWO: breathing frequency decreased (p less than 0.001) from 18 +/- 6/min during control to 14 +/- 5/min, whereas tidal volume increased (p less than 0.01) from 600 +/- 200 ml during control to 860 +/- 400 ml. Secondary to this change in the pattern of breathing, arterial PO2 increased slightly (p less than 0.01) from 54 +/- 7 mm Hg during control to 57 +/- 8 mm Hg during HFCWO, and arterial PCO2 significantly (p less than 0.01) decreased from 46 +/- 6 mm Hg during control to 43 +/- 7 mm Hg during HFCWO. In addition, duty cycle (Ti/Ttot) decreased (p less than 0.001) from 0.37 +/- 0.03 s during control to 0.29 +/- 0.05 s during HFCWO. Such a decrease in duty cycle suggest that inspiratory muscle work was facilitated under HFCWO. In 8 patients, we obtained the tension-time index (TTdi), or the product of duty cycle and Pdi/Pdimax, and found that this index significantly decreased (p less than 0.05) from 0.06 +/- 0.03 during control to 0.04 +/- 0.02 during HFCWO.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. Efficient, high-power, ytterbium-fiber-laser-pumped picosecond optical parametric oscillator.

    Science.gov (United States)

    Kokabee, O; Esteban-Martin, A; Ebrahim-Zadeh, M

    2010-10-01

    We report a high-power picosecond optical parametric oscillator (OPO) synchronously pumped by a Yb fiber laser at 1.064 μm, providing 11.7 W of total average power in the near to mid-IR at 73% extraction efficiency. The OPO, based on a 50 mm MgO:PPLN crystal, is pumped by 20.8 ps pulses at 81.1 MHz and can simultaneously deliver 7.1 W of signal at 1.56 μm and 4.6 W of idler at 3.33 μm for 16 W of pump power. The oscillator has a threshold of 740 mW, with maximum signal power of 7.4 W at 1.47 μm and idler power of 4.9 W at 3.08 μm at slope efficiencies of 51% and 31%, respectively. Wavelength coverage across 1.43-1.63 μm (signal) and 4.16-3.06 μm (idler) is obtained, with a total power of ~11 W and an extraction efficiency of ~68%, with pump depletion of ~78% maintained over most of the tuning range. The signal and idler output have a single-mode spatial profile and a peak-to-peak power stability of ±1.8% and ±2.9% over 1 h at the highest power, respectively. A signal pulse duration of 17.3 ps with a clean single-peak spectrum results in a time-bandwidth product of ~1.72, more than four times below the input pump pulses.

  15. Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations In a Young, Extremely Red L-type Brown Dwarf

    CERN Document Server

    Lew, Ben W P; Zhou, Yifan; Schneider, Glenn; Burgasser, Adam J; Karalidi, Theodora; Yang, Hao; Marley, Mark S; Cowan, N B; Bedin,; R., L; Metchev, Stanimir A; Radigan, Jacqueline; Lowrance, Patrick J

    2016-01-01

    Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-Ks=2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy we find a best-fit rotational period (13.20$\\pm$0.14 hours) with a larger amplitude at 1.1 micron than at 1.7 micron. This is the third largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentativ...

  16. High resolution millimeter wave digitally controlled oscillator with reconfigurable distributed metal capacitor passive resonators

    NARCIS (Netherlands)

    Wu, W.; Long, J.R.; Staszewski, B.

    2014-01-01

    A novel and useful millimeter-wave digitally controlled oscillator (DCO) that achieve a tuning range greater than 10% and fine frequency resolution less than 1 MHz. Switched metal capacitors are distributed across a passive resonator for tuning the oscillation frequency. To obtain sub-MHz frequency

  17. Oscillator Based on Lumped Double Ladder Circuit with Band Edge Degeneracy

    CERN Document Server

    Oshmarin, Dmitry; Othman, Mohamed A K; Sloan, Jeff; Radfar, Mohammad; Green, Michael M; Capolino, Filippo

    2016-01-01

    An oscillator design based on a periodic, double ladder resonant circuit is proposed. The circuit exhibits a degenerate band edge (DBE) in the dispersion diagram of its phase-frequency eigenstates, and possesses unique resonance features associated with a high Q-factor resonance, compared to a single ladder or a conventional LC tank circuit. This oscillator is shown to have an oscillation threshold that is half that of a single LC ladder circuit having the same total quality factor, and thus is more robust than an LC oscillator in the presence of losses. It is also shown that the output and amplitude of the double-ladder oscillator is much less sensitive to the output loading compared to single-ladder oscillators. We show the analysis and design of such oscillators that potentially lead to enhancing the efficiency of RF components and sources.

  18. High-quality sandwiched black phosphorus heterostructure and its quantum oscillations.

    Science.gov (United States)

    Chen, Xiaolong; Wu, Yingying; Wu, Zefei; Han, Yu; Xu, Shuigang; Wang, Lin; Ye, Weiguang; Han, Tianyi; He, Yuheng; Cai, Yuan; Wang, Ning

    2015-06-23

    Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices. The family of two-dimensional materials was recently joined by atomically thin black phosphorus which possesses high theoretical mobility and tunable bandgap structure. However, degradation of properties under atmospheric conditions and high-density charge traps in black phosphorus have largely limited its actual mobility thus hindering its future applications. Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ∼1,350 cm(2)V(-1) s(-1) at room temperature and on-off ratios exceeding 10(5). At low temperatures, the mobility even reaches ∼2,700 cm(2)V(-1) s(-1) and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields. Importantly, the sandwiched heterostructures ensure that the quality of black phosphorus remains high under ambient conditions.

  19. An analysis of high cloud variability: imprints from the El Niño-Southern Oscillation

    Science.gov (United States)

    Li, King-Fai; Su, Hui; Mak, Sze-Ning; Chang, Tiffany M.; Jiang, Jonathan H.; Norris, Joel R.; Yung, Yuk L.

    2017-01-01

    Using data from the International Satellite Cloud Climatology Project (ISCCP), we examine how near-global (60°N-60°S) high cloud fraction varies over time in the past three decades. Our focus is on identifying dominant modes of variability and associated spatial patterns, and how they are related to sea surface temperature. By performing the principal component analysis, we find that the first two principal modes of high cloud distribution show strong imprints of the two types of El Niño-Southern Oscillation (ENSO)—the canonical ENSO and the ENSO Modoki. Comparisons between ISCCP data and 14 models from the Atmospheric Model Intercomparison Project Phase 5 (AMIP5) show that models simulate the spatial pattern and the temporal variations of high cloud fraction associated with the canonical ENSO very well but the magnitudes of the canonical ENSO vary among the models. Furthermore, the multi-model mean of the second principal mode in the AMIP5 simulations appears to capture the temporal behavior of the second mode but individual AMIP5 models show large discrepancies in capturing observed temporal variations. A new metric, defined by the relative variances of the first two principal components, suggests that most of the AMIP5 models overestimate the second principal mode of high clouds.

  20. Hidden focal EEG seizures during prolonged suppressions and high-amplitude bursts in early infantile epileptic encephalopathy.

    Science.gov (United States)

    Al-Futaisi, Amna; Banwell, Brenda; Ochi, Ayako; Hew, Justine; Chu, Bill; Oishi, Makoto; Otsubo, Hiroshi

    2005-05-01

    We report on a 27-month-old female with atypical early infantile epileptic encephalopathy (EIEE), who developed tonic spasms, partial seizures and myoclonic jerks along with episodic bradycardia at 5 days. We recorded digital electroencephalography (EEG) using either an 11-channel neonatal montage or 19 channel scalp electrodes, at 200 Hz sampling rate, and a single reference for a minimum of 30 min. At 18 days EEG showed suppression-burst (SB) patterns during wakefulness and sleep. Tonic spasms concomitant with bursts recorded as brief, low-amplitude fast waves. EEG at 8 months showed increased amplitude of bursts to 1 mV and extension of suppression periods to 65 s. By increasing recording sensitivity, we detected focal epileptiform discharges of slow rhythmic sharp and slow waves building to 30 microV during suppression periods. Status epilepticus occurred at 16 months. EEG at 27 months returned to the previous SB pattern with rare partial seizures. This report is the first to demonstrate clinically silent focal EEG seizures during prolonged suppression periods in atypical EIEE by off-line digital EEG. Digital EEG sensitivity can reveal covert electrical activity during suppression periods in epileptic neonates and infants.

  1. Effects of nicotine stimulation on spikes, theta frequency oscillations, and spike-theta oscillation relationship in rat medial septum diagonal band Broca slices

    Institute of Scientific and Technical Information of China (English)

    Dong WEN; Ce PENG; Gao-xiang OU-YANG; Zainab HENDERSON; Xiao-li LI; Cheng-biao LU

    2013-01-01

    Aim:Spiking activities and neuronal network oscillations in the theta frequency range have been found in many cortical areas during information processing.The aim of this study is to determine whether nicotinic acetylcholine receptors (nAChRs) mediate neuronal network activity in rat medial septum diagonal band Broca (MSDB) slices.Methods:Extracellular field potentials were recorded in the slices using an Axoprobe 1A amplifier.Data analysis was performed offline.Spike sorting and local field potential (LFP) analyses were performed using Spike2 software.The role of spiking activity in the generation of LFP oscillations in the slices was determined by analyzing the phase-time relationship between the spikes and LFP oscillations.Circular statistic analysis based on the Rayleigh test was used to determine the significance of phase relationships between the spikes and LFP oscillations.The timing relationship was examined by quantifying the spike-field coherence (SFC).Results:Application of nicotine (250 nmol/L) induced prominent LFP oscillations in the theta frequency band and both small-and large-amplitude population spiking activity in the slices.These spikes were phase-locked to theta oscillations at specific phases.The Rayleigh test showed a statistically significant relationship in phase-locking between the spikes and theta oscillations.Larger changes in the SFC were observed for large-amplitude spikes,indicating an accurate timing relationship between this type of spike and LFP oscillations.The nicotine-induced spiking activity (large-amplitude population spikes) was suppressed by the nAChR antagonist dihydro-β-erythroidine (0.3 μmol/L).Conclusion:The results demonstrate that large-amplitude spikes are phase-locked to theta oscillations and have a high spike-timing accuracy,which are likely a main contributor to the theta oscillations generated in MSDB during nicotine receptor activation.

  2. A review of crustacean sensitivity to high amplitude underwater noise: Data needs for effective risk assessment in relation to UK commercial species.

    Science.gov (United States)

    Edmonds, Nathan J; Firmin, Christopher J; Goldsmith, Denise; Faulkner, Rebecca C; Wood, Daniel T

    2016-07-15

    High amplitude anthropogenic noise is associated with adverse impacts among a variety of organisms but detailed species-specific knowledge is lacking in relation to effects upon crustaceans. Brown crab (Cancer pagurus), European lobster (Homarus gammarus) and Norway lobster (Nephrops norvegicus) together represent the most valuable commercial fishery in the UK (Defra, 2014). Critical evaluation of literature reveals physiological sensitivity to underwater noise among N. norvegicus and closely related crustacean species, including juvenile stages. Current evidence supports physiological sensitivity to local, particle motion effects of sound production in particular. Derivation of correlative relationships between the introduction of high amplitude impulsive noise and crustacean distribution/abundance is hindered by the coarse resolution of available data at the present time. Future priorities for research are identified and argument for enhanced monitoring under current legislative frameworks outlined. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  3. Automatic Detection and Classification of High-Frequency Oscillations in Depth-EEG Signals.

    Science.gov (United States)

    Jrad, Nisrine; Kachenoura, Amar; Merlet, Isabelle; Bartolomei, Fabrice; Nica, Anca; Biraben, Arnaud; Wendling, Fabrice

    2017-09-01

    Interictal high-frequency oscillations (HFOs [30-600 Hz]) have proven to be relevant biomarkers in epilepsy. In this paper, four categories of HFOs are considered: Gamma ([30-80 Hz]), high-gamma ([80-120 Hz]), ripples ([120-250 Hz]), and fast-ripples ([250-600 Hz]). A universal detector of the four types of HFOs is proposed. It has the advantages of 1) classifying HFOs, and thus, being robust to inter and intrasubject variability; 2) rejecting artefacts, thus being specific. Gabor atoms are tuned to cover the physiological bands. Gabor transform is then used to detect HFOs in intracerebral electroencephalography (iEEG) signals recorded in patients candidate to epilepsy surgery. To extract relevant features, energy ratios, along with event duration, are investigated. Discriminant ratios are optimized so as to maximize among the four types of HFOs and artefacts. A multiclass support vector machine (SVM) is used to classify detected events. Pseudoreal signals are simulated to measure the performance of the method when the ground truth is known. Experiments are conducted on simulated and on human iEEG signals. The proposed method shows high performance in terms of sensitivity and false discovery rate. The methods have the advantages of detecting and discriminating all types of HFOs as well as avoiding false detections caused by artefacts. Experimental results show the feasibility of a robust and universal detector.

  4. A survey of strong high-frequency sea level oscillations along the US East Coast between 2006 and 2011

    Directory of Open Access Journals (Sweden)

    S. Pasquet

    2013-02-01

    Full Text Available A systematic survey of high-frequency sea level oscillations (<6 h measured between 2006 and 2011 along the US East Coast is performed. Raw 1-min resolution sea level data is used. After performing a data quality check, the nine most intense events, with maximum recorded wave heights ranging from 40 to 100 cm, are identified. Focusing on three of these events enables us to recognize two different generation mechanisms: (i topographically-trapped edge waves which are found to be a significant contributor to the strongest observed oscillations, and (ii standing waves, which occur over enclosed shallow waters and may result in significant wave heights of up to 100 cm. A reproduction of the observed oscillations is a part of a future work, which will include an assessment of a generating force in the atmosphere, allowing for a better prevention of potential flooding along the US East Coast.

  5. Coronal Loop Oscillations Observed with AIA - Kink-Mode with Cross-Sectional and Density Oscillations

    CERN Document Server

    Aschwanden, Markus J

    2011-01-01

    A detailed analysis of a coronal loop oscillation event is presented, using data from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) for the first time. The loop oscillation event occurred on 2010 Oct 16, 19:05-19:35 UT, was triggered by an M2.9 GOES-class flare, located inside a highly inclined cone of a narrow-angle CME. This oscillation event had a number of unusual features: (i) Excitation of kink-mode oscillations in vertical polarization (in the loop plane); (ii) Coupled cross-sectional and density oscillations with identical periods; (iii) no detectable kink amplitude damping over the observed duration of four kink-mode periods ($P=6.3$ min); (iv) multi-loop oscillations with slightly ($\\approx 10%$) different periods; and (v) a relatively cool loop temperature of $T\\approx 0.5$ MK. We employ a novel method of deriving the electron density ratio external and internal to the oscillating loop from the ratio of Alfv\\'enic speeds deduced from the flare trigger delay and...

  6. Characteristics and mechanism of sub-seasonal zonal oscillation of western Pacific subtropical high and South Asian high

    Science.gov (United States)

    Ren, Xuejuan

    2016-04-01

    The Asian monsoon circulations, like the western Pacific subtropical high (WPSH) at 500hPa and South Asian high (SAH) in the upper level, demonstrate sub-seasonal zonal oscillation. The WPSH is characterized by anomalously westward extension of its western edge with anomalous low-level anti-cyclonic circulation over the coastal region prior and eastward retreat with low-level cyclonic anomalies afterward, contributing persistent heavy rainfall over the Middle-lower reaches of the Yangtze River Valley. The coastal SST anomalies linked with zonal movement of WPSH shows cooling phase to warming phase variations. A local air-sea interaction on sub-seasonal time-scale in the western North Pacific region, which may be responsible for generating WPSH's sub-seasonal zonal oscillation. The SAH's eastward extension is featured by eastward propagation of wavetrain across the Eurasian continent. When the SAH extends to its easternmost position, a strong negative PV (positive geopotential height) center prevails to the east of the Tibetan Plateau at 200hPa. The causes of SAH's eastward extension are examined by performing potential vorticity (PV) diagnosis with emphasis on the joint role of diabatic heating feedback/rainfall and midlatitude wavetrain. The PV diagnosis indicates that the anomalous heating/rainfall and ascending motion generate negative PV anomalies at 200hPa directly over north China-east Mongolia. While anomalous cooling and descending motion produce positive PV anomalies over south China. Those south/north dipolar structure of PV generation indicates large value of meridional gradient of PV anomalies. As a consequence, the negative PV anomalies over the north lobe are transported southwardly by the advection of climatological northerly located to the east and southeast of the Tibetan Plateau.

  7. Angle-dependent magnetoresistance and quantum oscillations in high-mobility semimetal LuPtBi

    KAUST Repository

    Xu, Guizhou

    2017-03-14

    The recent discovery of ultrahigh mobility and large positive magnetoresistance in topologically non-trivial Half-Heusler semimetal LuPtBi provides a unique playground for studying exotic physics and significant perspective for device applications. As an fcc-structured electron-hole-compensated semimetal, LuPtBi theoretically exhibits six symmetrically arranged anisotropic electron Fermi pockets and two nearly-spherical hole pockets, offering the opportunity to explore the physics of Fermi surface with a simple angle-related magnetotransport properties. In this work, through the angle-dependent transverse magnetoresistance measurements, in combination with high-field SdH quantum oscillations, we achieved to map out a Fermi surface with six anisotropic pockets in the high-temperature and low-field regime, and furthermore, identify a possible magnetic field driven Fermi surface change at lower temperatures. Reasons account for the Fermi surface change in LuPtBi are discussed in terms of the field-induced electron evacuation due to Landau quantization.

  8. Neurosteroids modulate epileptiform activity and associated high-frequency oscillations in the piriform cortex.

    Science.gov (United States)

    Herrington, R; Lévesque, M; Avoli, M

    2014-01-03

    Allotetrahydrodeoxycorticosterone (THDOC) belongs to a class of pregnane neurosteroidal compounds that enhance brain inhibition by interacting directly with GABAA signaling, mainly through an increase in tonic inhibitory current. Here, we addressed the role of THDOC in the modulation of interictal- and ictal-like activity and associated high-frequency oscillations (HFOs, 80-500 Hz; ripples: 80-200 Hz, fast ripples: 250-500 Hz) recorded in vitro in the rat piriform cortex, a highly excitable brain structure that is implicated in seizure generation and maintenance. We found that THDOC: (i) increased the duration of interictal discharges in the anterior piriform cortex while decreasing ictal discharge duration in both anterior and posterior piriform cortices; (ii) reduced the occurrence of HFOs associated to both interictal and ictal discharges; and (iii) prolonged the duration of 4-aminopyridine-induced, glutamatergic independent synchronous field potentials that are known to mainly result from the activation of GABAA receptors. Our results indicate that THDOC can modulate epileptiform synchronization in the piriform cortex presumably by potentiating GABAA receptor-mediated signaling. This evidence supports the view that neurosteroids regulate neuronal excitability and thus control the occurrence of seizures.

  9. Amplitude metrics for cellular circadian bioluminescence reporters.

    Science.gov (United States)

    St John, Peter C; Taylor, Stephanie R; Abel, John H; Doyle, Francis J

    2014-12-01

    Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary

  10. High power, high repetition rate, few picosecond Nd:LuVO₄ oscillator with cavity dumping.

    Science.gov (United States)

    Gao, Peng; Guo, Jie; Li, Jinfeng; Lin, Hua; Yu, Haohai; Zhang, Huaijin; Liang, Xiaoyan

    2015-12-28

    We investigate the potential use of Nd:LuVO4 in high average power, high repetition rate ultrafast lasers. Maximum mode-locked average power of 28 W is obtained at the repetition rate of 58 MHz. The shortest pulse duration is achieved at 4 ps without dispersion compensation. With a cavity dumping technique, the pulse energy is scaling up to 40.7 μJ at 300 kHz and 14.3 μJ at 1.5 MHz.

  11. Eliminating the effect of phase shift between injection current and amplitude modulation in DFB-LD WMS for high-precision measurement.

    Science.gov (United States)

    Wei, Wei; Chang, Jun; Liu, Yuanyuan; Chen, Xi; Liu, Zhaojun; Qin, Zengguang; Wang, Qiang

    2016-05-01

    Phase shift between the injection current and amplitude modulation due to the characteristics of diode lasers is discussed in this paper. Phase shift has no apparent regularity, but it has an obvious effect on measurement results, especially for high-precision measurement. A new method is proposed to suppress the influence of this phase shift. Water vapor is chosen as the target gas for experiment in this paper. A new detection system with the new method applied is presented and shows much better performance than the traditional wavelength modulation spectroscopy detection system. Phase shift fluctuation between the injection current and amplitude modulation is suppressed from 0.72 deg to 0.07 deg; accuracy is improved from 0.88 ppm to 0.16 ppm.

  12. High frequency spin torque oscillators with composite free layer spin valve

    Energy Technology Data Exchange (ETDEWEB)

    Natarajan, Kanimozhi; Arumugam, Brinda; Rajamani, Amuda

    2016-07-15

    We report the oscillations of magnetic spin components in a composite free layer spin valve. The associated Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation is studied by stereographically projecting the spin on to a complex plane and the spin components were found. A fourth order Runge–Kutta numerical integration on LLGS equation also confirms the similar trajectories of the spin components. This study establishes the possibility of a Spin Torque Oscillator in a composite free layer spin valve, where the exchange coupling is ferromagnetic in nature. In-plane and out-of-plane precessional modes of magnetization oscillations were found in zero applied magnetic field and the frequencies of the oscillations were calculated from Fast Fourier Transform of the components of magnetization. Behavior of Power Spectral Density for a range of current density is studied. Finally our analysis shows the occurrence of highest frequency 150 GHz, which is in the second harmonics for the specific choice of system parameters.

  13. A new high sensitivity search for neutron-antineutron oscillations at the ESS

    CERN Document Server

    Milstead, David

    2015-01-01

    A sensitive search for neutron-antineutron oscillations can provide a unique probe of some of the central questions in particle physics and cosmology: the energy scale and mechanism for baryon number violation, the origin of the baryon-antibaryon asymmetry of the universe, and the mechanism for neutrino mass generation. A remarkable opportunity has emerged to search for such oscillations with the construction of the European Spallation Source (ESS). A collaboration has been formed which has proposed a search at the ESS, which would provide a sensitivity to the oscillation probability which is three orders of magnitude greater than that achieved at an ILL experiment at which the present best limit on free neutron-antineutron oscillations was obtained.

  14. High frequency spin torque oscillators with composite free layer spin valve

    Science.gov (United States)

    Natarajan, Kanimozhi; Arumugam, Brinda; Rajamani, Amuda

    2016-07-01

    We report the oscillations of magnetic spin components in a composite free layer spin valve. The associated Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation is studied by stereographically projecting the spin on to a complex plane and the spin components were found. A fourth order Runge-Kutta numerical integration on LLGS equation also confirms the similar trajectories of the spin components. This study establishes the possibility of a Spin Torque Oscillator in a composite free layer spin valve, where the exchange coupling is ferromagnetic in nature. In-plane and out-of-plane precessional modes of magnetization oscillations were found in zero applied magnetic field and the frequencies of the oscillations were calculated from Fast Fourier Transform of the components of magnetization. Behavior of Power Spectral Density for a range of current density is studied. Finally our analysis shows the occurrence of highest frequency 150 GHz, which is in the second harmonics for the specific choice of system parameters.

  15. High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy

    Directory of Open Access Journals (Sweden)

    W.J.E.M. Zweiphenning

    2016-01-01

    Significance: ‘Baseline’ high-frequency network parameters might help intra-operative recognition of epileptogenic tissue without the need for waiting for events. These findings can increase our understanding of the ‘architecture’ of epileptogenic networks and help unravel the pathophysiology of HFOs.

  16. Numerical Simulation on Seismic Response of the Filled Joint under High Amplitude Stress Waves Using Finite-Discrete Element Method (FDEM

    Directory of Open Access Journals (Sweden)

    Xiaolin Huang

    2016-12-01

    Full Text Available This paper numerically investigates the seismic response of the filled joint under high amplitude stress waves using the combined finite-discrete element method (FDEM. A thin layer of independent polygonal particles are used to simulate the joint fillings. Each particle is meshed using the Delaunay triangulation scheme and can be crushed when the load exceeds its strength. The propagation of the 1D longitude wave through a single filled joint is studied, considering the influences of the joint thickness and the characteristics of the incident wave, such as the amplitude and frequency. The results show that the filled particles under high amplitude stress waves mainly experience three deformation stages: (i initial compaction stage; (ii crushing stage; and (iii crushing and compaction stage. In the initial compaction stage and crushing and compaction stage, compaction dominates the mechanical behavior of the joint, and the particle area distribution curve varies little. In these stages, the transmission coefficient increases with the increase of the amplitude, i.e., peak particle velocity (PPV, of the incident wave. On the other hand, in the crushing stage, particle crushing plays the dominant role. The particle size distribution curve changes abruptly with the PPV due to the fragments created by the crushing process. This process consumes part of wave energy and reduces the stiffness of the filled joint. The transmission coefficient decreases with increasing PPV in this stage because of the increased amount of energy consumed by crushing. Moreover, with the increase of the frequency of the incident wave, the transmission coefficient decreases and fewer particles can be crushed. Under the same incident wave, the transmission coefficient decreases when the filled thickness increases and the filled particles become more difficult to be crushed.

  17. Influence of inherent parameter of stabilized UHF oscillators on autodyne response formation at a strong reflected signal

    Directory of Open Access Journals (Sweden)

    Noskov V. Ya.

    2011-08-01

    Full Text Available Results of an autodyne response analysis in UHF oscillators stabilized by the external high-Q cavity in the case of the strong signal when the reflected wave amplitude commen-surable with the own oscillation amplitude. Coupling between the basic operation cavity and the stabilizing cavity is implemented as a pass-reflecting filter with a resistive bond. Key relations are obtained, which describe the autodyne response to the own re-reflected radiation from a target. The load and oscillating system influence on autodyne response formation is fulfilled.

  18. Finite amplitude effects on drop levitation for material properties measurement

    Science.gov (United States)

    Ansari Hosseinzadeh, Vahideh; Holt, R. Glynn

    2017-05-01

    The method of exciting shape oscillation of drops to extract material properties has a long history, which is most often coupled with the technique of acoustic levitation to achieve non-contact manipulation of the drop sample. We revisit this method with application to the inference of bulk shear viscosity and surface tension. The literature is replete with references to a "10% oscillation amplitude" as a sufficient condition for the application of Lamb's analytical expressions for the shape oscillations of viscous liquids. Our results show that even a 10% oscillation amplitude leads to dynamic effects which render Lamb's results inapplicable. By comparison with samples of known viscosity and surface tension, we illustrate the complicating finite-amplitude effects (mode-splitting and excess dissipation associated with vorticity) that can occur and then show that sufficiently small oscillations allow us to recover the correct material properties using Lamb's formula.

  19. On the excitation of Goodwin's oscillations

    Science.gov (United States)

    Antonova, A. O.; Reznik, S. N.; Todorov, M. D.

    2014-11-01

    We consider the necessary condition for excitation of long-periodic Goodwin's oscillations and short-periodic sawtooth oscillations in the Goodwin model with fixed delay in the induced investment. Also, using the method of equivalent linearization we evaluate the amplitude of steady-state oscillation.

  20. Fiber Optical Parametric Oscillator for High Power, High Efficiency Short-Wavelength Generation

    Science.gov (United States)

    2010-12-05

    integrals. Thus, it should now be possible to avoid SRS, despite a drop to 1 3 of the intrinsic FWM interaction strength with crossed polarizations, relative...10) The wavelengths, λj , are the resonance wavelengths at which the specific medium absorbs light, while the constants, Bj , indicate the strength of...commercial fibers have been investigated within the project. Among these are the Sumit- omo highly-nonlinear fiber (HNLF), the Corning SMF28 fiber and

  1. Tunable High-Intensity Electron Bunch Train Production Based on Nonlinear Longitudinal Space Charge Oscillation

    Science.gov (United States)

    Zhang, Zhen; Yan, Lixin; Du, Yingchao; Zhou, Zheng; Su, Xiaolu; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Shi, Jiaru; Chen, Huaibi; Huang, Wenhui; Gai, Wei; Tang, Chuanxiang

    2016-05-01

    High-intensity trains of electron bunches with tunable picosecond spacing are produced and measured experimentally with the goal of generating terahertz (THz) radiation. By imposing an initial density modulation on a relativistic electron beam and controlling the charge density over the beam propagation, density spikes of several-hundred-ampere peak current in the temporal profile, which are several times higher than the initial amplitudes, have been observed for the first time. We also demonstrate that the periodic spacing of the bunch train can be varied continuously either by tuning launching phase of a radio-frequency gun or by tuning the compression of a downstream magnetic chicane. Narrow-band coherent THz radiation from the bunch train was also measured with μ J -level energies and tunable central frequency of the spectrum in the range of ˜0.5 to 1.6 THz. Our results pave the way towards generating mJ-level narrow-band coherent THz radiation and driving high-gradient wakefield-based acceleration.

  2. Tunable High-Intensity Electron Bunch Train Production Based on Nonlinear Longitudinal Space Charge Oscillation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhen; Yan, Lixin; Du, Yingchao; Zhou, Zheng; Su, Xiaolu; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Shi, Jiaru; Chen, Huaibi; Huang, Wenhui; Gai, Wei; Tang, Chuanxiang

    2016-05-05

    High-intensity trains of electron bunches with tunable picosecond spacing are produced and measured experimentally with the goal of generating terahertz (THz) radiation. By imposing an initial density modulation on a relativistic electron beam and controlling the charge density over the beam propagation, density spikes of several-hundred-ampere peak current in the temporal profile, which are several times higher than the initial amplitudes, have been observed for the first time. We also demonstrate that the periodic spacing of the bunch train can be varied continuously either by tuning launching phase of a radiofrequency gun or by tuning the compression of a downstream magnetic chicane. Narrow-band coherent THz radiation from the bunch train was also measured with μJ-level energies and tunable central frequency of the spectrum in the range of ~0.5 to 1.6 THz. Our results pave the way towards generating mJ-level narrow-band coherent THz radiation and driving high-gradient wakefield-based acceleration.

  3. COMPARISON OF HIGH-FREQUENCY OSCILLATION VENTILATION WITH CONVENTIONAL MANDATORY VENTILATION IN ANIMAL ARDS MODEL

    Institute of Scientific and Technical Information of China (English)

    SHI Guo-chao; HUANG Shao-guang; LI Min; DENG Wei-wu; WAN Huan-ying

    2005-01-01

    Objective To compare effect of high-frequency oscillation ventilation (HFOV) and conventional mandatory ventilation (CMV) on lung injury development in rabbit with acute respiratory distress syndrome (ARDS). Methods Animals that underwent saline lung lavage to produce lung injury were randomized to one of the two treatment groups (HFOV or CMV, n=6). PaCO2 was maintained between 35-45mmHg and arterial oxygen saturation (SaO2) was maintain >88% by adjusting corresponding ventilator parameters. Ventilation period was 6h. Lung fluids were aspirated before and at the end of ventilation for cell analysis. Then the animals were euthanized, lung tissue was removed for wet/dry weight measurement, light and electron microscopic examination.Results The difference of artery blood gas analyses(pH, PaO2, PaCO2) between HFOV and CMV was insignificant. The difference between HFOV and CMV in cytological examination of lung fluids, wet/dry weight measurement was also insignificant. But compared with CMV,HFOV not only reduced the area of lung injury, but also reduced lung injury score in light and electron microscopic examination. Conclusion When same artery blood gas analysis was obtained, HFOV significantly reduced lung injury development in ARDS animal than CMV. As a lung protection strategy, HFOV can be used in the treatment of ARDS.

  4. Epileptiform synchronization and high-frequency oscillations in brain slices comprising piriform and entorhinal cortices.

    Science.gov (United States)

    Hamidi, S; Lévesque, M; Avoli, M

    2014-12-05

    We employed field potential recordings in extended in vitro brain slices form Sprague-Dawley rats containing the piriform and entorhinal cortices (PC and EC, respectively) to identify the characteristics of epileptiform discharges and concomitant high-frequency oscillations (HFOs, ripples: 80-200Hz, fast ripples: 250-500Hz) during bath application of 4-aminopyridine (4AP, 50μM). Ictal-like discharges occurred in PC and EC either synchronously or independently of each other; synchronous ictal discharges always emerged from a synchronous "fast" interictal background whereas asynchronous ictal discharges were preceded by a "slow" interictal event. In addition, asynchronous ictal discharges had longer duration and interval of occurrence than synchronous ictal discharges, and contained a higher proportion of ripples and fast ripples. Cutting the connections between PC and EC made synchronicity disappear and increased ictal discharges duration in the EC but failed in changing HFO occurrence in both areas. Finally, antagonizing ionotropic glutamatergic receptors abolished ictal activity in all experiments, increased the duration and rate of occurrence of interictal discharges occurring in PC-EC interconnected slices while it did not influence the slow asynchronous interictal discharges in both areas. Our results identify some novel in vitro interactions between olfactory (PC) and limbic (EC) structures that presumably contribute to in vivo ictogenesis as well.

  5. Design of a high efficiency relativistic backward wave oscillator with low guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaoze; Song, Wei; Tan, Weibing; Zhang, Ligang; Su, Jiancang; Zhu, Xiaoxin; Hu, Xianggang; Shen, Zhiyuan; Liang, Xu; Ning, Qi [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

    2016-07-15

    A high efficiency relativistic backward wave oscillator working at a low guiding magnetic field is designed and simulated. A trapezoidal resonant reflector is used to reduce the modulation field in the resonant reflector to avoid overmodulation of the electron beam which will lead to a large momentum spread and then low conversion efficiency. The envelope of the inner radius of the slow wave structure (SWS) increases stepwise to keep conformal to the trajectory of the electron beam which will alleviate the bombardment of the electron on the surface of the SWS. The length of period of the SWS is reduced gradually to make a better match between phase velocity and electron beam, which decelerates continually and improves the RF current distribution. Meanwhile the modulation field is reduced by the introduction of nonuniform SWS also. The particle in cell simulation results reveal that a microwave with a power of 1.8 GW and a frequency of 14.7 GHz is generated with an efficiency of 47% when the diode voltage is 620 kV, the beam current 6.1 kA, and the guiding magnetic field 0.95 T.

  6. High-Reliability Pump Module for Non-Planar Ring Oscillator Laser

    Science.gov (United States)

    Liu, Duncan T.; Qiu, Yueming; Wilson, Daniel W.; Dubovitsky, Serge; Forouhar, Siamak

    2007-01-01

    We propose and have demonstrated a prototype high-reliability pump module for pumping a Non-Planar Ring Oscillator (NPRO) laser suitable for space missions. The pump module consists of multiple fiber-coupled single-mode laser diodes and a fiber array micro-lens array based fiber combiner. The reported Single-Mode laser diode combiner laser pump module (LPM) provides a higher normalized brightness at the combined beam than multimode laser diode based LPMs. A higher brightness from the pump source is essential for efficient NPRO laser pumping and leads to higher reliability because higher efficiency requires a lower operating power for the laser diodes, which in turn increases the reliability and lifetime of the laser diodes. Single-mode laser diodes with Fiber Bragg Grating (FBG) stabilized wavelength permit the pump module to be operated without a thermal electric cooler (TEC) and this further improves the overall reliability of the pump module. The single-mode laser diode LPM is scalable in terms of the number of pump diodes and is capable of combining hundreds of fiber-coupled laser diodes. In the proof-of-concept demonstration, an e-beam written diffractive micro lens array, a custom fiber array, commercial 808nm single mode laser diodes, and a custom NPRO laser head are used. The reliability of the proposed LPM is discussed.

  7. The penetration of plasma clouds across magnetic boundaries the role of high frequency oscillations

    CERN Document Server

    Hurtig, T; Raadu, M A; Hurtig, Tomas; Brenning, Nils; Raadu, Michael A.

    2004-01-01

    Experiments are reported where a collisionfree plasma cloud penetrates a magnetic barrier by self-polarization. We here focus on the resulting anomalous magnetic field diffusion into the plasma cloud, two orders of magnitude faster than classical, which is one important aspect of the plasma cloud penetration mechanism. Without such fast magnetic diffusion, clouds with kinetic beta below unity would not be able to penetrate magnetic barriers at all. Tailor-made diagnostics has been used for measurements in the parameter range with the kinetic beta ? 0.5 to 10, and with normalized width w/r(gi) of the order of unity. Experimental data on hf fluctuations in density and in electric field has been combined to yield the effective anomalous transverse resistivity eta(EFF). It is concluded that they are both dominated by highly nonlinear oscillations in the lower hybrid range, driven by a strong diamagnetic current loop that is set up in the plasma in the penetration process. The anomalous magnetic diffusion rate, ca...

  8. High-Frequency Quasi-Periodic Oscillations from GRS 1915+105

    CERN Document Server

    Belloni, Tomaso M

    2013-01-01

    We report the results of a systematic timing analysis of all archival Rossi X-Ray Timing Explorer (RXTE) observations of the bright black-hole binary GRS 1915+105 in order to detect high-frequency quasi-periodic oscillations (HFQPO). We produced power-density spectra in two energy bands and limited the analysis to the frequency range 30-1000 Hz. We found 51 peaks with a single trial significance larger than 3 sigma. As all but three have centroid frequencies that are distributed between 63 and 71 Hz, we consider most of them significant regardless of the number of trials involved. The average centroid frequency and FWHM are 67.3 +/- 2.0 Hz and 4.4 +/- 2.4 Hz respectively. Their fractional rms varies between 0.4% and 2% (total band detections) and between 0.5% and 3% (hard ban detections). As GRS 1915+105 shows large variability on time scales longer than 1s, we analysed the data in 16s intervals and found that the detections are limited to a specific region in the colour-colour diagram, corresponding to state...

  9. Decreased Modulation of EEG Oscillations in High-Functioning Autism during a Motor Control Task

    Science.gov (United States)

    Ewen, Joshua B.; Lakshmanan, Balaji M.; Pillai, Ajay S.; McAuliffe, Danielle; Nettles, Carrie; Hallett, Mark; Crone, Nathan E.; Mostofsky, Stewart H.

    2016-01-01

    Autism spectrum disorders (ASD) are thought to result in part from altered cortical excitatory-inhibitory balance; this pathophysiology may impact the generation of oscillations on electroencephalogram (EEG). We investigated premotor-parietal cortical physiology associated with praxis, which has strong theoretical and empirical associations with ASD symptomatology. Twenty five children with high-functioning ASD (HFA) and 33 controls performed a praxis task involving the pantomiming of tool use, while EEG was recorded. We assessed task-related modulation of signal power in alpha and beta frequency bands. Compared with controls, subjects with HFA showed 27% less left central (motor/premotor) beta (18–22 Hz) event-related desynchronization (ERD; p = 0.030), as well as 24% less left parietal alpha (7–13 Hz) ERD (p = 0.046). Within the HFA group, blunting of central ERD attenuation was associated with impairments in clinical measures of praxis imitation (r = −0.4; p = 0.04) and increased autism severity (r = 0.48; p = 0.016). The modulation of central beta activity is associated, among other things, with motor imagery, which may be necessary for imitation. Impaired imitation has been associated with core features of ASD. Altered modulation of oscillatory activity may be mechanistically involved in those aspects of motor network function that relate to the core symptoms of ASD. PMID:27199719

  10. Decreased Modulation of EEG Oscillations in High-Functioning Autism During a Motor Control Task

    Directory of Open Access Journals (Sweden)

    Joshua Benjamin Ewen

    2016-05-01

    Full Text Available Autism spectrum disorders (ASD are thought to result in part from altered cortical excitatory-inhibitory balance; this pathophysiology may impact the generation of oscillations on EEG. We investigated premotor-parietal cortical physiology associated with praxis, which has strong theoretical and empirical associations with ASD symptomatology. 25 children with high-functioning ASD (HFA and 33 controls performed a praxis task involving the pantomiming of tool use, while EEG was recorded. We assessed task-related modulation of signal power in alpha and beta frequency bands. Compared with controls, subjects with HFA showed 27% less left central (motor/premotor beta (18-22 Hz event-related desynchronization (ERD (p = 0.030, as well as 24% less left parietal alpha (7-13 Hz ERD (p = 0.046. Within the HFA group, blunting of central ERD attenuation was associated with impairments in clinical measures of praxis imitation (r = -0.4; p = 0.04 and increased autism severity (r = 0.48; p = 0.016. The modulation of central beta activity is associated, among other things, with motor imagery, which may be necessary for imitation. Impaired imitation has been associated with core features of ASD. Altered modulation of oscillatory activity may be mechanistically involved in those aspects of motor network function that relate to the core symptoms of ASD.

  11. Redox oscillation affecting mercury mobility from highly contaminated coastal sediments: a mesocosm incubation experiment

    Directory of Open Access Journals (Sweden)

    Emili A.

    2013-04-01

    Full Text Available Mercury (Hg mobility at the sediment-water interface was investigated during a laboratory incubation experiment on highly contaminated sediments (up to 23 μg g−1 of the Gulf of Trieste. Undisturbed sediment was collected in front of the Isonzo River mouth, which inflows Hg-rich suspended material originating from the Idrija (NW Slovenia mining district. Since hypoxic and anoxic conditions at the bottom are frequently observed, a redox oscillation was simulated in the laboratory at in situ temperature, using a dark flux chamber. Temporal variations of several parameters were monitored simultaneously: dissolved Hg and methylmercury (MeHg, O2, NH4+, NO3−+NO2−, PO43−, H2S, dissolved Fe and Mn, dissolved inorganic and organic carbon (DIC and DOC. Benthic fluxes of Hg and MeHg were higher under anoxic conditions while re-oxygenation caused concentrations of MeHg and Hg to rapidly drop, probably due to re-adsorption onto Fe/Mn oxyhydroxides and enhanced demethylation. Hence, during anoxic events, sediments of the Gulf of Trieste may be considered as an important source of dissolved Hg species for the water column. However, re-oxygenation of the bottom compartment mitigates Hg and MeHg release from the sediment, thus acting as a natural “defence” from possible interaction between the metal and the aquatic organisms.

  12. Shock Wave-Boundary Layer Interaction in Forced Shock Oscillations

    Institute of Scientific and Technical Information of China (English)

    Piotr Doerffer; Oskar Szulc; Franco Magagnato

    2003-01-01

    The flow in transonic diffusers as well as in supersonic air intakes becomes often unsteady due to shock wave boundary layer interaction. The oscillations may be induced by natural separation unsteadiness or may be forced by boundary conditions. Significant improvement of CFD tools, increase of computer resources as well as development of experimental methods have again.drawn the attention of researchers to this topic.To investigate the problem forced oscillations of transonic turbulent flow in asymmetric two-dimensional Laval nozzle were considered. A viscous, perfect gas flow, was numerically simulated using the Reynolds-averaged compressible Navier-Stokes solver SPARC, employing a two-equation, eddy viscosity, turbulence closure in the URANS approach.For time-dependent and stationary flow simulations, Mach numbers upstream of the shock between 1.2 and 1.4 were considered. Comparison of computed and experimental data for steady states generally gave acceptable agreement. In the case of forced oscillations, a harmonic pressure variation was prescribed at the exit plane resulting in shock wave motion. Excitation frequencies between 0 Hz and 1024 Hz were investigated at the same pressure amplitude.The main result of the work carried out is the relation between the amplitude of the shock wave motion and the excitation frequency in the investigated range. Increasing excitation frequency resulted in decreasing amplitude of the shock movement. At high frequencies a natural mode of shock oscillation (of small amplitude) was observed which is not sensitive to forced excitement.

  13. Human gamma oscillations during slow wave sleep.

    Directory of Open Access Journals (Sweden)

    Mario Valderrama

    Full Text Available Neocortical local field potentials have shown that gamma oscillations occur spontaneously during slow-wave sleep (SWS. At the macroscopic EEG level in the human brain, no evidences were reported so far. In this study, by using simultaneous scalp and intracranial EEG recordings in 20 epileptic subjects, we examined gamma oscillations in cerebral cortex during SWS. We report that gamma oscillations in low (30-50 Hz and high (60-120 Hz frequency bands recurrently emerged in all investigated regions and their amplitudes coincided with specific phases of the cortical slow wave. In most of the cases, multiple oscillatory bursts in different frequency bands from 30 to 120 Hz were correlated with positive peaks of scalp slow waves ("IN-phase" pattern, confirming previous animal findings. In addition, we report another gamma pattern that appears preferentially during the negative phase of the slow wave ("ANTI-phase" pattern. This new pattern presented dominant peaks in the high gamma range and was preferentially expressed in the temporal cortex. Finally, we found that the spatial coherence between cortical sites exhibiting gamma activities was local and fell off quickly when computed between distant sites. Overall, these results provide the first human evidences that gamma oscillations can be observed in macroscopic EEG recordings during sleep. They support the concept that these high-frequency activities might be associated with phasic increases of neural activity during slow oscillations. Such patterned activity in the sleeping brain could play a role in off-line processing of cortical networks.

  14. Comparison of high-frequency chest wall oscillation and oscillating positive expiratory pressure in the home management of cystic fibrosis: a pilot study.

    Science.gov (United States)

    Oermann, C M; Sockrider, M M; Giles, D; Sontag, M K; Accurso, F J; Castile, R G

    2001-11-01

    Enhanced airway clearance is thought to result in better-maintained pulmonary function in cystic fibrosis (CF). Postural drainage, percussion, and vibration (PDPV) have been the primary airway clearance technique (ACT) employed in CF for over 40 years. Two new airway clearance modalities are high-frequency chest wall oscillation (HFCWO) and oscillating positive expiratory pressure (OPEP). This pilot study was undertaken to evaluate the efficacy of these techniques during home use, assess patient satisfaction with them as compared to PDPV, and assess the feasibility of performing a definitive comparative trial. The prospective, randomized, multicenter crossover trial was conducted at three urban academic CF Care Centers. Twenty-nine CF patients, 9-39 years of age, participated. Subjects performed 4 weeks each of HFCWO and OPEP following 2-week lead-in/washout periods. Spirometry, lung volumes, National Institutes of Health and Petty Scores, and a satisfaction survey were performed at baseline and after each treatment period. An ACT preference survey was completed at the conclusion of the study. Twenty-four subjects completed both therapies. There were no statistically significant differences between therapies for spirometry, lung volumes, or clinical scores. No significant safety issues arose during the study period. Compliance between therapies was similar. Significant differences among therapies existed in patient satisfaction. Given a choice of therapy, 50% of subjects chose HFCWO, 37% OPEP, and 13% PDPV. This study suggests that HFCWO and OPEP are safe and as effective as patients' routine therapies when used for airway clearance in a home setting. Patient satisfaction and preference differ among ACTs and should be considered when prescribing home therapy. A definitive, multi-center, comparative study evaluating long-term efficacy of these techniques is feasible.

  15. Oscillations of moments in high-energy nucleus-nucleus collisions

    Institute of Scientific and Technical Information of China (English)

    YANG; Hongyan(

    2001-01-01

    [1]Bialas, A., Peschanski, R., Moments of rapidity distributions as a measure of short-range fluctuations in high-energy colli-sions, Nucl. Phys. B, 1986, 273: 703-718.[2]Wu Yuanfang, Liu Lianshou, Self-affinity of multiplicity fluctuation in the phase space of multiparticle production, Phys. Rev.Lett., 1993, 70: 3197-3200.[3]Zhang Yang, The study of intemittency and multifractal in high energy collisions, Doctor Thesis, Institute of Particle Physics,Hua-Zhong Normal University, 1995.[4]Dremin, I. M. , Quantum chromodynamics and multiplicity distributions, Physics-Uspekhi, 1994, 37(8): 715-736.[5]Dremin, I. M., Arena, V., Boca, G. et al., Cumulant to factorial moment ratio and multiplicity data, Phys. Len. B,1994, 336: 119-124.[6]Ugoccioni, R., Stuctures in multiplicity distributions and oscillations of moments, in Proceedings of the 26th International Symposium on Multiparticle Dynamics (eds. Dias de Deus, J. , Sa, P. , Pimenta, M. et al. ), Singapore: World Scientific,1997, 208-219.[7]Capella, A., Dremin, I. M., Nechitailo, V. A. et al., Moment analysis of multiplicity distributions, Z. Phys. C, 1997,75: 89-94.[8]Dremin, I. M. , Nechitailo, V. A., Biyajima, M. et al. , Comparative analysis of multiplicity distributions in inelastic pro-cesses for different colliding particles and nuclei, Phys. Lett. B, 1997, 403: 149-154.[9]Wang Shaoshun, Zhang Jie, Wang Zhaomin et al., Cumulant to factorial moment ratio of multiplicity distributions of pp inter-actions at 400GeV/c, Phys. Rev. D, 1997, 56: 1-5.[10]Kittel, W., Chekanov, S. V., Mangeol, D. J. et al., Multiplicities, fluctuations and QCD, interplay between soft and hard physics? Nucl. Phys. Proc. Suppl., 1999, 71: 90-99.[11]Adamovich, M. I., Aggarwal, M. M., Alexandrov, Y. A. et al., (EMU01 Collaboration) Rapidity density distribution in 16O, 28Si, 32S, 197Au, and 208Pb induced heavy-ion interactions at 4A-200A GeV, Phys. Rev. Lett., 1992, 69: 745-748.[12]Cai Xu, Huang

  16. Restoration of oscillation in network of oscillators in presence of direct and indirect interactions

    Energy Technology Data Exchange (ETDEWEB)

    Majhi, Soumen; Bera, Bidesh K. [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India); Bhowmick, Sourav K. [Department of Electronics, Asutosh College, Kolkata-700026 (India); Ghosh, Dibakar, E-mail: diba.ghosh@gmail.com [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India)

    2016-10-23

    The suppression of oscillations in coupled systems may lead to several unwanted situations, which requires a suitable treatment to overcome the suppression. In this paper, we show that the environmental coupling in the presence of direct interaction, which can suppress oscillation even in a network of identical oscillators, can be modified by introducing a feedback factor in the coupling scheme in order to restore the oscillation. We inspect how the introduction of the feedback factor helps to resurrect oscillation from various kinds of death states. We numerically verify the resurrection of oscillations for two paradigmatic limit cycle systems, namely Landau–Stuart and Van der Pol oscillators and also in generic chaotic Lorenz oscillator. We also study the effect of parameter mismatch in the process of restoring oscillation for coupled oscillators. - Highlights: • Amplitude death is observed using direct and indirect coupling. • Revival of oscillation using feedback parameter is discussed. • Restoration of oscillation is observed in limit cycle and chaotic systems.

  17. CD147 reinforces [Ca2+]i oscillations and promotes oncogenic progression in hepatocellular carcinoma.

    Science.gov (United States)

    Tang, Juan; Guo, Yun-Shan; Yu, Xiao-Ling; Huang, Wan; Zheng, Ming; Zhou, Ying-Hui; Nan, Gang; Wang, Jian-Chao; Yang, Hai-Jiao; Yu, Jing-Min; Jiang, Jian-Li; Chen, Zhi-Nan

    2015-10-27

    Oscillations in intracellular Ca2+ concentrations ([Ca2+]i) mediate various cellular function. Although it is known that [Ca2+]i oscillations are susceptible to dysregulation in tumors, the tumor-specific regulators of [Ca2+]i oscillations are poorly characterized. We discovered that CD147 promotes hepatocellular carcinoma (HCC) metastasis and proliferation by enhancing the amplitude and frequency of [Ca2+]i oscillations in HCC cells. CD147 activates two distinct signaling pathways to regulate [Ca2+]i oscillations. By activating FAK-Src-IP3R1 signaling pathway, CD147 promotes Ca2+ release from endoplasmic reticulum (ER) and enhances the amplitude of [Ca2+]i oscillations. Furthermore, CD147 accelerates ER Ca2+refilling and enhances the frequency of [Ca2+]i oscillations through activating CaMKP-PAK1-PP2A-PLB-SERCA signaling pathway. Besides, CD147-promoted ER Ca2+ release and refilling are tightly regulated by changing [Ca2+]i. CD147 may activate IP3R1 channel under low [Ca2+]i conditions and CD147 may activate SERCA pump under high [Ca2+]i conditions. CD147 deletion suppresses HCC tumorigenesis and increases the survival rate of liver-specific CD147 knockout mice by regulating [Ca2+]i oscillations in vivo. Together, these results reveal that CD147 functions as a critical regulator of ER-dependent [Ca2+]i oscillations to promote oncogenic progression in HCC.

  18. Scattering amplitudes in gauge theories

    CERN Document Server

    Henn, Johannes M

    2014-01-01

    At the fundamental level, the interactions of elementary particles are described by quantum gauge field theory. The quantitative implications of these interactions are captured by scattering amplitudes, traditionally computed using Feynman diagrams. In the past decade tremendous progress has been made in our understanding of and computational abilities with regard to scattering amplitudes in gauge theories, going beyond the traditional textbook approach. These advances build upon on-shell methods that focus on the analytic structure of the amplitudes, as well as on their recently discovered hidden symmetries. In fact, when expressed in suitable variables the amplitudes are much simpler than anticipated and hidden patterns emerge.   These modern methods are of increasing importance in phenomenological applications arising from the need for high-precision predictions for the experiments carried out at the Large Hadron Collider, as well as in foundational mathematical physics studies on the S-matrix in quantum ...

  19. Interlimb coupling strength scales with movement amplitude.

    Science.gov (United States)

    Peper, C Lieke E; de Boer, Betteco J; de Poel, Harjo J; Beek, Peter J

    2008-05-23

    The relation between movement amplitude and the strength of interlimb interactions was examined by comparing bimanual performance at different amplitude ratios (1:2, 1:1, and 2:1). For conditions with unequal amplitudes, the arm moving at the smaller amplitude was predicted to be more strongly affected by the contralateral arm than vice versa. This prediction was based on neurophysiological considerations and the HKB model of coupled oscillators. Participants performed rhythmic bimanual forearm movements at prescribed amplitude relations. After a brief mechanical perturbation of one arm, the relaxation process back to the initial coordination pattern was examined. This analysis focused on phase adaptations in the unperturbed arm, as these reflect the degree to which the movements of this arm were affected by the coupling influences stemming from the contralateral (perturbed) arm. The thus obtained index of coupling (IC) reflected the relative contribution of the unperturbed arm to the relaxation process. As predicted IC was larger when the perturbed arm moved at a larger amplitude than did the unperturbed arm, indicating that coupling strength scaled with movement amplitude. This result was discussed in relation to previous research regarding sources of asymmetry in coupling strength and the effects of amplitude disparity on interlimb coordination.

  20. Potential contribution of wind farms to damp oscillations in weak grids with high wind penetration

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, R.D. [Universidad Nacional de la Patagonia San Juan Bosco (Argentina); Universidad Nacional de La Plata (Argentina); Laboratorio de Electronica Industrial, Control e Instrumentacion (LEICI), Facultad de Ingenieria, P.O. Box 91, 1900 La Plata (Argentina); Mantz, R.J. [Universidad Nacional de La Plata (Argentina); Comision de Investigaciones Cientificas de la Provincia de Buenos Aires (CICpba) (Argentina); Battaiotto, P.E. [Universidad Nacional de La Plata (Argentina)

    2008-08-15

    In Argentinean Patagonia, there exists a growing interest in understanding local problems associated with the increasing of wind energy penetration in the grid. Recent papers show that some of these power quality problems can be reduced by the proper control of the wind farms. In this way, this work deals with the impact and potential contribution of wind generation on the damping of the electromechanical oscillations called inter- and intra-area oscillations. For gaining qualitative insights and understandings on this complex subject, a test system that allows to isolate the oscillations modes is considered. The analysis shows that new control concepts for wind farm can efficiently contribute to the power system damping. (author)