WorldWideScience

Sample records for scaled oscillation frequencies

  1. Observation of multi-scale oscillation of laminar lifted flames with low-frequency AC electric fields

    KAUST Repository

    Ryu, Seol

    2010-01-01

    The oscillation behavior of laminar lifted flames under the influence of low-frequency AC has been investigated experimentally in coflow jets. Various oscillation modes were existed depending on jet velocity and the voltage and frequency of AC, especially when the AC frequency was typically smaller than 30 Hz. Three different oscillation modes were observed: (1) large-scale oscillation with the oscillation frequency of about 0.1 Hz, which was independent of the applied AC frequency, (2) small-scale oscillation synchronized to the applied AC frequency, and (3) doubly-periodic oscillation with small-scale oscillation embedded in large-scale oscillation. As the AC frequency decreased from 30 Hz, the oscillation modes were in the order of the large-scale oscillation, doubly-periodic oscillation, and small-scale oscillation. The onset of the oscillation for the AC frequency smaller than 30 Hz was in close agreement with the delay time scale for the ionic wind effect to occur, that is, the collision response time. Frequency-doubling behavior for the small-scale oscillation has also been observed. Possible mechanisms for the large-scale oscillation and the frequency-doubling behavior have been discussed, although the detailed understanding of the underlying mechanisms will be a future study. © 2009 The Combustion Institute.

  2. A novel optogenetically tunable frequency modulating oscillator.

    Directory of Open Access Journals (Sweden)

    Tarun Mahajan

    Full Text Available Synthetic biology has enabled the creation of biological reconfigurable circuits, which perform multiple functions monopolizing a single biological machine; Such a system can switch between different behaviours in response to environmental cues. Previous work has demonstrated switchable dynamical behaviour employing reconfigurable logic gate genetic networks. Here we describe a computational framework for reconfigurable circuits in E.coli using combinations of logic gates, and also propose the biological implementation. The proposed system is an oscillator that can exhibit tunability of frequency and amplitude of oscillations. Further, the frequency of operation can be changed optogenetically. Insilico analysis revealed that two-component light systems, in response to light within a frequency range, can be used for modulating the frequency of the oscillator or stopping the oscillations altogether. Computational modelling reveals that mixing two colonies of E.coli oscillating at different frequencies generates spatial beat patterns. Further, we show that these oscillations more robustly respond to input perturbations compared to the base oscillator, to which the proposed oscillator is a modification. Compared to the base oscillator, the proposed system shows faster synchronization in a colony of cells for a larger region of the parameter space. Additionally, the proposed oscillator also exhibits lesser synchronization error in the transient period after input perturbations. This provides a strong basis for the construction of synthetic reconfigurable circuits in bacteria and other organisms, which can be scaled up to perform functions in the field of time dependent drug delivery with tunable dosages, and sets the stage for further development of circuits with synchronized population level behaviour.

  3. Automatic oscillator frequency control system

    Science.gov (United States)

    Smith, S. F. (Inventor)

    1985-01-01

    A frequency control system makes an initial correction of the frequency of its own timing circuit after comparison against a frequency of known accuracy and then sequentially checks and corrects the frequencies of several voltage controlled local oscillator circuits. The timing circuit initiates the machine cycles of a central processing unit which applies a frequency index to an input register in a modulo-sum frequency divider stage and enables a multiplexer to clock an accumulator register in the divider stage with a cyclical signal derived from the oscillator circuit being checked. Upon expiration of the interval, the processing unit compares the remainder held as the contents of the accumulator against a stored zero error constant and applies an appropriate correction word to a correction stage to shift the frequency of the oscillator being checked. A signal from the accumulator register may be used to drive a phase plane ROM and, with periodic shifts in the applied frequency index, to provide frequency shift keying of the resultant output signal. Interposition of a phase adder between the accumulator register and phase plane ROM permits phase shift keying of the output signal by periodic variation in the value of a phase index applied to one input of the phase adder.

  4. Control of Full-Scale Converter based Wind Power Plants for damping of low frequency system oscillations

    DEFF Research Database (Denmark)

    Adamczyk, Andrzej Grzegorz; Teodorescu, Remus; Rodriguez, Pedro

    2011-01-01

    Damping of low frequency power oscillations is one of essential aspects of maintaining power system stability. In literature can be found publications on damping capability of Doubly Fed Induction Generator based wind turbines. This paper extends discussion on Wind Power Plant damping capability...

  5. Low-frequency oscillations in Hall thrusters

    International Nuclear Information System (INIS)

    Wei Li-Qiu; Han Liang; Yu Da-Ren; Guo Ning

    2015-01-01

    In this paper, we summarize the research development of low-frequency oscillations in the last few decades. The findings of physical mechanism, characteristics and stabilizing methods of low-frequency oscillations are discussed. It shows that it is unreasonable and incomplete to model an ionization region separately to analyze the physical mechanism of low-frequency oscillations. Electro-dynamics as well as the formation conditions of ionization distribution play an important role in characteristics and stabilizing of low-frequency oscillations. Understanding the physical mechanism and characteristics of low- frequency oscillations thoroughly and developing a feasible method stabilizing this instability are still important research subjects. (review)

  6. High-frequency plasma oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Akhiezer, A I; Fainberg, Y B; Sitenko, A G; Stepanov, K; Kurilko, V; Gorbatenko, M; Kirochkin, U [Academy of Sciences of the Ukrainian SSR (USSR)

    1958-07-01

    It is well known that the electrical conductivity of a plasma, the ion-electron equilibration time, and the time required to heat the electron component of the plasma all increase greatly with increasing temperature. Consequently, the usual method of Joule heating a plasma may be difficult to apply in the region of high temperatures (> 10{sup 6}K), especially if the plasma current alone, without any additional measures, is used to generate magnetic fields for the confinement of the plasma. Therefore, it is of interest to study methods of plasma heating that do not directly use Joule heat, especially methods by which energy is directly supplied to the ion component during the time between collisions. Some of these methods make use of ionic resonance as well as other resonance phenomena which can occur in plasma in an external magnetic field. This paper deals with certain aspects of the theory of high-frequency plasma oscillations.

  7. Dependence of synchronization frequency of Kuramoto oscillators ...

    Indian Academy of Sciences (India)

    Kuramoto oscillators have been proposed earlier as a model for interacting systems that exhibit synchronization. In this article, we study the difference between networks with symmetric and asymmetric distribution of natural frequencies. We first indicate that synchronization frequency of oscillators in a completely connected ...

  8. Phase noise and frequency stability in oscillators

    CERN Document Server

    Rubiola, Enrico

    2009-01-01

    Presenting a comprehensive account of oscillator phase noise and frequency stability, this practical text is both mathematically rigorous and accessible. An in-depth treatment of the noise mechanism is given, describing the oscillator as a physical system, and showing that simple general laws govern the stability of a large variety of oscillators differing in technology and frequency range. Inevitably, special attention is given to amplifiers, resonators, delay lines, feedback, and flicker (1/f) noise. The reverse engineering of oscillators based on phase-noise spectra is also covered, and end-of-chapter exercises are given. Uniquely, numerous practical examples are presented, including case studies taken from laboratory prototypes and commercial oscillators, which allow the oscillator internal design to be understood by analyzing its phase-noise spectrum. Based on tutorials given by the author at the Jet Propulsion Laboratory, international IEEE meetings, and in industry, this is a useful reference for acade...

  9. Dependence of synchronization frequency of Kuramoto oscillators ...

    Indian Academy of Sciences (India)

    2Department of Theoretical Physics, Physical Research Laboratory, ... on the sine of the phase difference between the oscillators and hence, ... we study the change in synchronization frequency as the symmetry is changed under the limit of.

  10. Damped Oscillator with Delta-Kicked Frequency

    Science.gov (United States)

    Manko, O. V.

    1996-01-01

    Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.

  11. Low frequency temperature forcing of chemical oscillations.

    Science.gov (United States)

    Novak, Jan; Thompson, Barnaby W; Wilson, Mark C T; Taylor, Annette F; Britton, Melanie M

    2011-07-14

    The low frequency forcing of chemical oscillations by temperature is investigated experimentally in the Belousov-Zhabotinsky (BZ) reaction and in simulations of the Oregonator model with Arrhenius temperature dependence of the rate constants. Forcing with temperature leads to modulation of the chemical frequency. The number of response cycles per forcing cycle is given by the ratio of the natural frequency to the forcing frequency and phase locking is only observed in simulations when this ratio is a whole number and the forcing amplitude is small. The global temperature forcing of flow-distributed oscillations in a tubular reactor is also investigated and synchronisation is observed in the variation of band position with the external signal, reflecting the periodic modulation of chemical oscillations by temperature.

  12. High frequency oscillations in brain hemodynamic response

    Science.gov (United States)

    Akin, Ata; Bolay, Hayrunnisa

    2007-07-01

    Tight autoregulation of vessel tone guarantees proper delivery of nutrients to the tissues. This regulation is maintained at a more delicate level in the brain since any decrease in the supply of glucose and oxygen to neuronal tissues might lead to unrecoverable injury. Functional near infrared spectroscopy has been proposed as a new tool to monitor the cerebrovascular response during cognitive activity. We have observed that during a Stroop task three distinct oscillatory patterns govern the control of the cerebrovascular reactivity: very low frequency (0.02-0.05 Hz), low frequency (0.08-0.12 Hz) and high frequency (0.12-0.18 Hz). High frequency oscillations have been shown to be related to stress level of the subjects. Our findings indicate that as the stress level is increased so does the energy of the high frequency component indicating a higher stimulation from the autonomic nervous system.

  13. Sustaining GHz oscillation of carbon nanotube based oscillators via a MHz frequency excitation

    International Nuclear Information System (INIS)

    Motevalli, Benyamin; Taherifar, Neda; Liu, Jefferson Zhe

    2016-01-01

    There have been intensive studies to investigate the properties of gigahertz nano-oscillators based on multi-walled carbon nanotubes (MWCNTs). Many of these studies, however, revealed that the unique telescopic translational oscillations in such devices would damp quickly due to various energy dissipation mechanisms. This challenge remains the primary obstacle against its practical applications. Herein, we propose a design concept in which a GHz oscillation could be re-excited by a MHz mechanical motion. This design involves a triple-walled CNT, in which sliding of the longer inner tube at a MHz frequency can re-excite and sustain a GHz oscillation of the shorter middle tube. Our molecular dynamics (MD) simulations prove this design concept at ∼10 nm scale. A mathematical model is developed to explore the feasibility at a larger size scale. As an example, in an oscillatory system with the CNT’s length above 100 nm, the high oscillatory frequency range of 1.8–3.3 GHz could be excited by moving the inner tube at a much lower frequency of 53.4 MHz. This design concept together with the mechanical model could energize the development of GHz nano-oscillators in miniaturized electro-mechanical devices. (paper)

  14. Low-frequency oscillations in radiative-convective models

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qi; Randall, D.A.

    1991-12-31

    Although eastward propagation is usually regarded as an essential feature of the low-frequency ``Madden-Julian oscillation`` observed in the tropical atmosphere, many observations indicate that there is an important stationary or quasi-stationary component of the oscillation. Yasunari (1979), for example, investigated the stationary 30--60 day variation in upper tropospheric cloudiness in the Asian summer monsoon region. In a case study of the 30--60 day oscillation. Hsu et al. (1990) found a strong stationary oscillation of the divergence, outgoing longwave mdiadon and other fields. A recent observational study by Weickmann and Khalsa (1990) offers further evidence that the Madden-Julian oscillation has an important stationary component. In this paper, we present evidence that intraseasonal oscillations can be produced by local radiative and convective processes. This suggests that the observed propagating Madden-Julian wave is produced by interactions between these local processes and the large scale motion field, and is not essential for the existence of the observed oscillation.

  15. Low-frequency oscillations in radiative-convective models

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qi; Randall, D.A.

    1991-01-01

    Although eastward propagation is usually regarded as an essential feature of the low-frequency Madden-Julian oscillation'' observed in the tropical atmosphere, many observations indicate that there is an important stationary or quasi-stationary component of the oscillation. Yasunari (1979), for example, investigated the stationary 30--60 day variation in upper tropospheric cloudiness in the Asian summer monsoon region. In a case study of the 30--60 day oscillation. Hsu et al. (1990) found a strong stationary oscillation of the divergence, outgoing longwave mdiadon and other fields. A recent observational study by Weickmann and Khalsa (1990) offers further evidence that the Madden-Julian oscillation has an important stationary component. In this paper, we present evidence that intraseasonal oscillations can be produced by local radiative and convective processes. This suggests that the observed propagating Madden-Julian wave is produced by interactions between these local processes and the large scale motion field, and is not essential for the existence of the observed oscillation.

  16. TOWARDS THRESHOLD FREQUENCY IN CHAOTIC COLPITTS OSCILLATOR

    DEFF Research Database (Denmark)

    Lindberg, Erik; Tamasevicius, Arunas; Mykolaitis, Gytis

    2007-01-01

    A novel version of chaotic Colpitts oscillator is described. Instead of a linear loss resistor, it includes an extra inductor and diode in the collector circuit of the transistor. The modified circuit in comparison with the common Colpitts oscillator may generate chaotic oscillations at the funda......A novel version of chaotic Colpitts oscillator is described. Instead of a linear loss resistor, it includes an extra inductor and diode in the collector circuit of the transistor. The modified circuit in comparison with the common Colpitts oscillator may generate chaotic oscillations...

  17. The continuous wave NQR spectrometer with equidistant frequency scale

    Directory of Open Access Journals (Sweden)

    Samila A. P.

    2010-10-01

    Full Text Available The phase binding frequency of marginal oscillator to frequency synthesizer which includes a phase detector, are used for linearization of the frequency sweep. For spectrum calibration the circuit is designed which forms «scale rule» of the frequency tags with an interval of 10 and 100 kHz.

  18. A low-frequency chip-scale optomechanical oscillator with 58 kHz mechanical stiffening and more than 100th-order stable harmonics.

    Science.gov (United States)

    Huang, Yongjun; Flores, Jaime Gonzalo Flor; Cai, Ziqiang; Yu, Mingbin; Kwong, Dim-Lee; Wen, Guangjun; Churchill, Layne; Wong, Chee Wei

    2017-06-29

    For the sensitive high-resolution force- and field-sensing applications, the large-mass microelectromechanical system (MEMS) and optomechanical cavity have been proposed to realize the sub-aN/Hz 1/2 resolution levels. In view of the optomechanical cavity-based force- and field-sensors, the optomechanical coupling is the key parameter for achieving high sensitivity and resolution. Here we demonstrate a chip-scale optomechanical cavity with large mass which operates at ≈77.7 kHz fundamental mode and intrinsically exhibiting large optomechanical coupling of 44 GHz/nm or more, for both optical resonance modes. The mechanical stiffening range of ≈58 kHz and a more than 100 th -order harmonics are obtained, with which the free-running frequency instability is lower than 10 -6 at 100 ms integration time. Such results can be applied to further improve the sensing performance of the optomechanical inspired chip-scale sensors.

  19. Spontaneous low-frequency oscillations in cerebral vessels

    DEFF Research Database (Denmark)

    Schytz, Henrik W; Hansson, Andreas; Phillip, Dorte

    2010-01-01

    ). Analysis of CA by measurement of spontaneous oscillations in the low-frequency spectrum in cerebral vessels might be a useful tool for assessing risk and investigating different treatment strategies in carotid artery disease (CAD) and stroke. We reviewed studies exploring spontaneous oscillations...

  20. Synchronization of Phase Oscillators in Networks with Certain Frequency Sequence

    International Nuclear Information System (INIS)

    Feng Yuan-Yuan; Wu Liang; Zhu Shi-Qun

    2014-01-01

    Synchronization of Kuramoto phase oscillators arranged in real complex neural networks is investigated. It is shown that the synchronization greatly depends on the sets of natural frequencies of the involved oscillators. The influence of network connectivity heterogeneity on synchronization depends particularly on the correlation between natural frequencies and node degrees. This finding implies a potential application that inhibiting the effects caused by the changes of network structure can be balanced out nicely by choosing the correlation parameter appropriately. (general)

  1. Dependence of synchronization frequency of Kuramoto oscillators on symmetry of intrinsic frequency in ring network

    Science.gov (United States)

    Saha, Arindam; Amritkar, R. E.

    2014-12-01

    Kuramoto oscillators have been proposed earlier as a model for interacting systems that exhibit synchronisation. In this article we study the difference between networks with symmetric and asymmetric distribution of natural frequencies. We first indicate that the synchronisation frequency of the oscillators is independent of the natural frequency distribution for a completely connected network. Further we analyse the case of oscillators in a directed ring-network where asymmetry in the natural frequency distribution is seen to shift the synchronisation frequency of the network. We also present an estimate of the shift in the frequencies for slightly asymmetric distributions.

  2. Multiple time scale analysis of pressure oscillations in solid rocket motors

    Science.gov (United States)

    Ahmed, Waqas; Maqsood, Adnan; Riaz, Rizwan

    2018-03-01

    In this study, acoustic pressure oscillations for single and coupled longitudinal acoustic modes in Solid Rocket Motor (SRM) are investigated using Multiple Time Scales (MTS) method. Two independent time scales are introduced. The oscillations occur on fast time scale whereas the amplitude and phase changes on slow time scale. Hopf bifurcation is employed to investigate the properties of the solution. The supercritical bifurcation phenomenon is observed for linearly unstable system. The amplitude of the oscillations result from equal energy gain and loss rates of longitudinal acoustic modes. The effect of linear instability and frequency of longitudinal modes on amplitude and phase of oscillations are determined for both single and coupled modes. For both cases, the maximum amplitude of oscillations decreases with the frequency of acoustic mode and linear instability of SRM. The comparison of analytical MTS results and numerical simulations demonstrate an excellent agreement.

  3. Frequency modulation of neural oscillations according to visual task demands.

    Science.gov (United States)

    Wutz, Andreas; Melcher, David; Samaha, Jason

    2018-02-06

    Temporal integration in visual perception is thought to occur within cycles of occipital alpha-band (8-12 Hz) oscillations. Successive stimuli may be integrated when they fall within the same alpha cycle and segregated for different alpha cycles. Consequently, the speed of alpha oscillations correlates with the temporal resolution of perception, such that lower alpha frequencies provide longer time windows for perceptual integration and higher alpha frequencies correspond to faster sampling and segregation. Can the brain's rhythmic activity be dynamically controlled to adjust its processing speed according to different visual task demands? We recorded magnetoencephalography (MEG) while participants switched between task instructions for temporal integration and segregation, holding stimuli and task difficulty constant. We found that the peak frequency of alpha oscillations decreased when visual task demands required temporal integration compared with segregation. Alpha frequency was strategically modulated immediately before and during stimulus processing, suggesting a preparatory top-down source of modulation. Its neural generators were located in occipital and inferotemporal cortex. The frequency modulation was specific to alpha oscillations and did not occur in the delta (1-3 Hz), theta (3-7 Hz), beta (15-30 Hz), or gamma (30-50 Hz) frequency range. These results show that alpha frequency is under top-down control to increase or decrease the temporal resolution of visual perception.

  4. Improvement of the low frequency oscillation model for Hall thrusters

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chunsheng, E-mail: wangcs@hit.edu.cn; Wang, Huashan [Yanshan University, College of Vehicles and Energy, Qinhuangdao 066004, Hebei (China)

    2016-08-15

    The low frequency oscillation of the discharge current in Hall thrusters is a major aspect of these devices that requires further study. While the existing model captures the ionization mechanism of the low frequency oscillation, it unfortunately fails to express the dynamic characteristics of the ion acceleration. The analysis in this paper shows this is because of the simplification of the electron equation, which affects both the electric field distribution and the ion acceleration process. Additionally, the electron density equation is revised and a new model that is based on the physical properties of ion movement is proposed.

  5. Frequency and amplitude stabilization in MEMS and NEMS oscillators

    Science.gov (United States)

    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.

  6. Seismology and geodesy of the sun: low-frequency oscillations

    International Nuclear Information System (INIS)

    Dicke, R.H.

    1981-01-01

    The hourly averages of the solar ellipticity measured from June 13 to September 17, 1966, are analyzed for indications of solar oscillations with periods in excess of 2 h ν -1 . Nothing significant is found for frequencies ν > 0.1 hr -1 but for lower frequencies the power spectrum shows a very complex structure containing about 20 strong narrow peaks. The complexity is illusionary. The signal apparently consists of only two frequencies. The complexity is due to aliasing by the window function with its basic 24-h period, with many observational days missing, and with different numbers of hourly averages for the various observational days. Both signal frequencies are apparently due to odd-degree spherical harmonic oscillations of the sun

  7. Frequency comb generation in a continuously pumped optical parametric oscillator

    Science.gov (United States)

    Mosca, S.; Parisi, M.; Ricciardi, I.; Leo, F.; Hansson, T.; Erkintalo, M.; Maddaloni, P.; De Natale, P.; Wabnitz, S.; De Rosa, M.

    2018-02-01

    We demonstrate optical frequency comb generation in a continuously pumped optical parametric oscillator, in the parametric region around half of the pump frequency. We also model the dynamics of such quadratic combs using a single time-domain mean-field equation, and obtain simulation results that are in good agreement with experimentally observed spectra. Moreover, we numerically investigate the coherence properties of simulated combs, showing the existence of correlated and phase-locked combs. Our work could pave the way for a new class of frequency comb sources, which may enable straightforward access to new spectral regions and stimulate novel applications of frequency combs.

  8. Low-cost precise measurement of oscillator frequency instability based on GNSS carrier observation

    Science.gov (United States)

    Kou, Yanhong; Jiao, Yue; Xu, Dongyang; Zhang, Meng; Liu, Ya; Li, Xiaohui

    2013-03-01

    Global navigation satellite systems (GNSS) receivers can be used in time and frequency metrology by exploiting stable GNSS time scales. This paper proposes a low-cost method for precise measurement of oscillator frequency instability using a single-frequency software GNSS receiver. The only required hardware is a common radio frequency (RF) data collection device driven by the oscillator under test (OUT). The receiver solves the oscillator frequency error in high time resolution using the carrier Doppler observation and the broadcast ephemeris from one of the available satellites employing the onboard reference atomic frequency standard that is more stable than the OUT. Considering the non-stable and non-Gaussian properties of the frequency error measurement, an unbiased finite impulse response (FIR) filter is employed to obtain robust estimation and filter out measurement noise. The effects of different filter orders and convolution lengths are further discussed. The frequency error of an oven controlled oscillator (OCXO) is measured using live Beidou-2/Compass signals. The results are compared with the synchronous measurement using a specialized phase comparator with the standard coordinated universal time (UTC) signal from the master clock H226 in the national time service center (NTSC) of China as its reference. The Allan deviation (ADEV) estimates using the two methods have a 99.9% correlation coefficient and a 0.6% mean relative difference over 1-1000 s intervals. The experiment demonstrates the effectiveness and high precision of the software receiver method.

  9. Dynamics of multi-frequency oscillator ensembles with resonant coupling

    Science.gov (United States)

    Lück, S.; Pikovsky, A.

    2011-07-01

    We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed.

  10. Activation barrier scaling and crossover for noise-induced switching in micromechanical parametric oscillators.

    Science.gov (United States)

    Chan, H B; Stambaugh, C

    2007-08-10

    We explore fluctuation-induced switching in parametrically driven micromechanical torsional oscillators. The oscillators possess one, two, or three stable attractors depending on the modulation frequency. Noise induces transitions between the coexisting attractors. Near the bifurcation points, the activation barriers are found to have a power law dependence on frequency detuning with critical exponents that are in agreement with predicted universal scaling relationships. At large detuning, we observe a crossover to a different power law dependence with an exponent that is device specific.

  11. Broad-scale small-world network topology induces optimal synchronization of flexible oscillators

    International Nuclear Information System (INIS)

    Markovič, Rene; Gosak, Marko; Marhl, Marko

    2014-01-01

    The discovery of small-world and scale-free properties of many man-made and natural complex networks has attracted increasing attention. Of particular interest is how the structural properties of a network facilitate and constrain its dynamical behavior. In this paper we study the synchronization of weakly coupled limit-cycle oscillators in dependence on the network topology as well as the dynamical features of individual oscillators. We show that flexible oscillators, characterized by near zero values of divergence, express maximal correlation in broad-scale small-world networks, whereas the non-flexible (rigid) oscillators are best correlated in more heterogeneous scale-free networks. We found that the synchronization behavior is governed by the interplay between the networks global efficiency and the mutual frequency adaptation. The latter differs for flexible and rigid oscillators. The results are discussed in terms of evolutionary advantages of broad-scale small-world networks in biological systems

  12. Photoinduced High-Frequency Charge Oscillations in Dimerized Systems

    Science.gov (United States)

    Yonemitsu, Kenji

    2018-04-01

    Photoinduced charge dynamics in dimerized systems is studied on the basis of the exact diagonalization method and the time-dependent Schrödinger equation for a one-dimensional spinless-fermion model at half filling and a two-dimensional model for κ-(bis[ethylenedithio]tetrathiafulvalene)2X [κ-(BEDT-TTF)2X] at three-quarter filling. After the application of a one-cycle pulse of a specifically polarized electric field, the charge densities at half of the sites of the system oscillate in the same phase and those at the other half oscillate in the opposite phase. For weak fields, the Fourier transform of the time profile of the charge density at any site after photoexcitation has peaks for finite-sized systems that correspond to those of the steady-state optical conductivity spectrum. For strong fields, these peaks are suppressed and a new peak appears on the high-energy side, that is, the charge densities mainly oscillate with a single frequency, although the oscillation is eventually damped. In the two-dimensional case without intersite repulsion and in the one-dimensional case, this frequency corresponds to charge-transfer processes by which all the bonds connecting the two classes of sites are exploited. Thus, this oscillation behaves as an electronic breathing mode. The relevance of the new peak to a recently found reflectivity peak in κ-(BEDT-TTF)2X after photoexcitation is discussed.

  13. U.S. Hail Frequency and the Global Wind Oscillation

    Science.gov (United States)

    Gensini, Vittorio A.; Allen, John T.

    2018-02-01

    Changes in Earth relative atmospheric angular momentum can be described by an index known as the Global Wind Oscillation. This global index accounts for changes in Earth's atmospheric budget of relative angular momentum through interactions of tropical convection anomalies, extratropical dynamics, and engagement of surface torques (e.g., friction and mountain). It is shown herein that U.S. hail events are more (less) likely to occur in low (high) atmospheric angular momentum base states when excluding weak Global Wind Oscillation days, with the strongest relationships found in the boreal spring and fall. Severe, significant severe, and giant hail events are more likely to occur during Global Wind Oscillation phases 8, 1, 2, and 3 during the peak of U.S. severe weather season. Lower frequencies of hail events are generally found in Global Wind Oscillation phases 4-7 but vary based on Global Wind Oscillation amplitude and month. In addition, probabilistic anomalies of atmospheric ingredients supportive of hail producing supercell thunderstorms closely mimic locations of reported hail frequency, helping to corroborate report results.

  14. The effect of near-surface convection on oscillation frequencies of stars

    Science.gov (United States)

    Hanasoge, Shravan

    2015-08-01

    Measurements of oscillation frequencies of the Sun and stars can provide important independent constraints on their internal structure and dynamics. Seismic models of these oscillations are used to connect structure and rotation of the star to its resonant frequencies, which are then compared with observations, the goal being that of minimizing the difference between the two. Even in the case of the Sun, for which structure models are highly tuned, observed frequencies show systematic deviations from modelled frequencies, a phenomenon referred to as the “surface term”. The dominant source of this systematic effect is thought to be vigorous near-surface convection, which is not well accounted for in both stellar modelling and mode-oscillation physics. Here we bring to bear the method of homogenization, applicable in the asymptotic limit of large wavelength (in comparison to the correlation scale of convection), to characterize the effect of small-scale surface convection on resonant-mode frequencies in the Sun. We show that the full oscillation equations, in the presence of temporally stationary 3-D flows, can be reduced to an effective “quiet-Sun” wave equation with altered sound speed, Brünt-Väisäla frequency and Lamb frequency. We derive the modified wave equation and relations for the appropriate averaging of three dimensional flows and thermal quantities to obtain the properties of this effective medium. Using flows obtained from three dimensional numerical simulations of near-surface convection, we quantify their effect on solar oscillation frequencies, and find that they are shifted systematically and substantially. We argue therefore that consistent interpretations of resonant frequencies must include modifications to the wave equation that effectively capture the impact of vigorous hydrodynamic convection.

  15. Low-frequency oscillations at high density in JFT-2

    International Nuclear Information System (INIS)

    Maeno, Masaki; Katagiri, Masaki; Suzuki, Norio; Fujisawa, Noboru

    1977-12-01

    Low-frequency oscillations in a plasma were measured with magnetic probes and Si surface-barrier detectors, and behaviour of the high density plasmas was studied. The plasma current profile in the phase of decreasing density after the interruption of gas input is more peaked than during gas input. The introduction of hydrogen during a discharge results in a reduction of the impurities flux. The increase of density by fast gas input is limited with a negative voltage spike. Immediately before a negative voltage spike, oscillations of m=1,2 grow, leading to the spike. (auth.)

  16. Seismology and geodesy of the sun: Low-frequency oscillations.

    Science.gov (United States)

    Dicke, R H

    1981-04-01

    The hourly averages of the solar ellipticity measured from June 13 to Sept. 17, 1966, are analyzed for indications of solar oscillations with periods in excess of 2 hr nu 0.1 hr(-1) but for lower frequencies the power spectrum shows a very complex structure containing about 20 strong narrow peaks. The complexity is illusionary. The signal apparently consists of only two frequencies. The complexity is due to aliasing by the window function with its basic 24-hr period, with many observational days missing, and with different numbers of hourly averages for the various observational days. Both signal frequencies are apparently due to odd-degree spherical harmonic oscillations of the sun.

  17. Dynamics of multi-frequency oscillator ensembles with resonant coupling

    International Nuclear Information System (INIS)

    Lueck, S.; Pikovsky, A.

    2011-01-01

    We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed. -- Highlights: → Kuramoto model is generalized on the case of resonantly interacting oscillators having frequency ratio 2:1. → Regimes of full and partial synchrony, as well as non-synchronous ones are reported. → Analytical description is developed on the basis of the Watanabe-Strogatz approach.

  18. Dynamics of multi-frequency oscillator ensembles with resonant coupling

    Energy Technology Data Exchange (ETDEWEB)

    Lueck, S. [Department of Physics and Astronomy, Potsdam University, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany); Pikovsky, A., E-mail: pikovsky@stat.physik.uni-potsdam.de [Department of Physics and Astronomy, Potsdam University, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany)

    2011-07-11

    We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2:1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed. -- Highlights: → Kuramoto model is generalized on the case of resonantly interacting oscillators having frequency ratio 2:1. → Regimes of full and partial synchrony, as well as non-synchronous ones are reported. → Analytical description is developed on the basis of the Watanabe-Strogatz approach.

  19. Trapped Ion Oscillation Frequencies as Sensors for Spectroscopy

    Directory of Open Access Journals (Sweden)

    Wilfried Nörtershäuser

    2010-03-01

    Full Text Available The oscillation frequencies of charged particles in a Penning trap can serve as sensors for spectroscopy when additional field components are introduced to the magnetic and electric fields used for confinement. The presence of so-called “magnetic bottles” and specific electric anharmonicities creates calculable energy-dependences of the oscillation frequencies in the radiofrequency domain which may be used to detect the absorption or emission of photons both in the microwave and optical frequency domains. The precise electronic measurement of these oscillation frequencies therefore represents an optical sensor for spectroscopy. We discuss possible applications for precision laser and microwave spectroscopy and their role in the determination of magnetic moments and excited state lifetimes. Also, the trap-assisted measurement of radiative nuclear de-excitations in the X-ray domain is discussed. This way, the different applications range over more than 12 orders of magnitude in the detectable photon energies, from below μeV in the microwave domain to beyond MeV in the X-ray domain.

  20. Are the North Atlantic oscillation and the southern oscillation related in any time-scale?

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, R.; Ribera, P.; Hernandez, E. [Universidad Complutense de Madrid (Spain). Facultad de Ciencias Fisicas; Gimenoo, L. [Fac. Ciencias, Univ. Vigo, Ourense (Spain)

    2000-02-01

    The north Atlantic oscillation (NAO) and the southern oscillation (SO) are compared from the standpoint of a possible common temporal scale of oscillation. To do this a cross-spectrum of the temporal series of NAO and SO indices was determined, finding a significant common oscillation of 6-8 years. To assure this finding, both series were decomposed in their main oscillations using singular spectrum analysis (SSA). Resulting reconstructed series of 6-8 years' oscillation were then cross-correlated without and with pre-whitened, the latter being significant. The main conclusion is a possible relationship between a common oscillation of 6-8 years that represents about 20% of the SO variance and about 25% of the NAO variance. (orig.)

  1. Resonant behavior of a fractional oscillator with fluctuating frequency

    Science.gov (United States)

    Soika, Erkki; Mankin, Romi; Ainsaar, Ain

    2010-01-01

    The long-time behavior of the first moment for the output signal of a fractional oscillator with fluctuating frequency subjected to an external periodic force is considered. Colored fluctuations of the oscillator eigenfrequency are modeled as a dichotomous noise. The viscoelastic type friction kernel with memory is assumed as a power-law function of time. Using the Shapiro-Loginov formula, exact expressions for the response to an external periodic field and for the complex susceptibility are presented. On the basis of the exact formulas it is demonstrated that interplay of colored noise and memory can generate a variety of cooperation effects, such as multiresonances versus the driving frequency and the friction coefficient as well as stochastic resonance versus noise parameters. The necessary and sufficient conditions for the cooperation effects are also discussed. Particularly, two different critical memory exponents have been found, which mark dynamical transitions in the behavior of the system.

  2. Frequency scaling for angle gathers

    KAUST Repository

    Zuberi, M. A H; Alkhalifah, Tariq Ali

    2014-01-01

    Angle gathers provide an extra dimension to analyze the velocity after migration. Space-shift and time shift-imaging conditions are two methods used to obtain angle gathers, but both are reasonably expensive. By scaling the time-lag axis of the time-shifted images, the computational cost of the time shift imaging condition can be considerably reduced. In imaging and more so Full waveform inversion, frequencydomain Helmholtz solvers are used more often to solve for the wavefields than conventional time domain extrapolators. In such cases, we do not need to extend the image, instead we scale the frequency axis of the frequency domain image to obtain the angle gathers more efficiently. Application on synthetic data demonstrate such features.

  3. Dependence of the colored frequency noise in spin torque oscillators on current and magnetic field

    Science.gov (United States)

    Eklund, Anders; Bonetti, Stefano; Sani, Sohrab R.; Majid Mohseni, S.; Persson, Johan; Chung, Sunjae; Amir Hossein Banuazizi, S.; Iacocca, Ezio; Östling, Mikael; Åkerman, Johan; Gunnar Malm, B.

    2014-03-01

    The nano-scale spin torque oscillator (STO) is a compelling device for on-chip, highly tunable microwave frequency signal generation. Currently, one of the most important challenges for the STO is to increase its longer-time frequency stability by decreasing the 1/f frequency noise, but its high level makes even its measurement impossible using the phase noise mode of spectrum analyzers. Here, we present a custom made time-domain measurement system with 150 MHz measurement bandwidth making possible the investigation of the variation of the 1/f as well as the white frequency noise in a STO over a large set of operating points covering 18-25 GHz. The 1/f level is found to be highly dependent on the oscillation amplitude-frequency non-linearity and the vicinity of unexcited oscillation modes. These findings elucidate the need for a quantitative theoretical treatment of the low-frequency, colored frequency noise in STOs. Based on the results, we suggest that the 1/f frequency noise possibly can be decreased by improving the microstructural quality of the metallic thin films.

  4. Dependence of the colored frequency noise in spin torque oscillators on current and magnetic field

    International Nuclear Information System (INIS)

    Eklund, Anders; Sani, Sohrab R.; Chung, Sunjae; Amir Hossein Banuazizi, S.; Östling, Mikael; Gunnar Malm, B.; Bonetti, Stefano; Majid Mohseni, S.; Persson, Johan; Iacocca, Ezio; Åkerman, Johan

    2014-01-01

    The nano-scale spin torque oscillator (STO) is a compelling device for on-chip, highly tunable microwave frequency signal generation. Currently, one of the most important challenges for the STO is to increase its longer-time frequency stability by decreasing the 1/f frequency noise, but its high level makes even its measurement impossible using the phase noise mode of spectrum analyzers. Here, we present a custom made time-domain measurement system with 150 MHz measurement bandwidth making possible the investigation of the variation of the 1/f as well as the white frequency noise in a STO over a large set of operating points covering 18–25 GHz. The 1/f level is found to be highly dependent on the oscillation amplitude-frequency non-linearity and the vicinity of unexcited oscillation modes. These findings elucidate the need for a quantitative theoretical treatment of the low-frequency, colored frequency noise in STOs. Based on the results, we suggest that the 1/f frequency noise possibly can be decreased by improving the microstructural quality of the metallic thin films

  5. Lyapunov exponent of the random frequency oscillator: cumulant expansion approach

    International Nuclear Information System (INIS)

    Anteneodo, C; Vallejos, R O

    2010-01-01

    We consider a one-dimensional harmonic oscillator with a random frequency, focusing on both the standard and the generalized Lyapunov exponents, λ and λ* respectively. We discuss the numerical difficulties that arise in the numerical calculation of λ* in the case of strong intermittency. When the frequency corresponds to a Ornstein-Uhlenbeck process, we compute analytically λ* by using a cumulant expansion including up to the fourth order. Connections with the problem of finding an analytical estimate for the largest Lyapunov exponent of a many-body system with smooth interactions are discussed.

  6. High frequency oscillations evoked by peripheral magnetic stimulation.

    Science.gov (United States)

    Biller, S; Simon, L; Fiedler, P; Strohmeier, D; Haueisen, J

    2011-01-01

    The analysis of somatosensory evoked potentials (SEP) and / or fields (SEF) is a well-established and important tool for investigating the functioning of the peripheral and central human nervous system. A standard technique to evoke SEPs / SEFs is the stimulation of the median nerve by using a bipolar electrical stimulus. We aim at an alternative stimulation technique enabling stimulation of deep nerve structures while reducing patient stress and error susceptibility. In the current study, we apply a commercial transcranial magnetic stimulation system for peripheral magnetic stimulation of the median nerve. We compare the results of simultaneously recorded EEG signals to prove applicability of our technique to evoke SEPs including low frequency components (LFC) as well as high frequency oscillations (HFO). Therefore, we compare amplitude, latency and time-frequency characteristics of the SEP of 14 healthy volunteers after electric and magnetic stimulation. Both low frequency components and high frequency oscillations were detected. The HFOs were superimposed onto the primary cortical response N20. Statistical analysis revealed significantly lower amplitudes and increased latencies for LFC and HFO components after magnetic stimulation. The differences indicate the inability of magnetic stimulation to elicit supramaximal responses. A psycho-perceptual evaluation showed that magnetic stimulation was less unpleasant for 12 out of the 14 volunteers. In conclusion, we showed that LFC and HFO components related to median nerve stimulation can be evoked by peripheral magnetic stimulation.

  7. Power Scaling of Laser Oscillators and Amplifiers Based on Nd:YVO4

    OpenAIRE

    Yarrow, Michael James

    2006-01-01

    This thesis presents a strategy for power and brightness scaling in diode-end-pumped, master-oscillator-power-amplifier laser systems, based on Nd:YVOIssues relating to further power and brightness scaling are discussed as well as the potential applications of these laser sources as pump sources for frequency conversion in optical parametric devices.

  8. Fast oscillations in cortical-striatal networks switch frequency following rewarding events and stimulant drugs.

    Science.gov (United States)

    Berke, J D

    2009-09-01

    Oscillations may organize communication between components of large-scale brain networks. Although gamma-band oscillations have been repeatedly observed in cortical-basal ganglia circuits, their functional roles are not yet clear. Here I show that, in behaving rats, distinct frequencies of ventral striatal local field potential oscillations show coherence with different cortical inputs. The approximately 50 Hz gamma oscillations that normally predominate in awake ventral striatum are coherent with piriform cortex, whereas approximately 80-100 Hz high-gamma oscillations are coherent with frontal cortex. Within striatum, entrainment to gamma rhythms is selective to fast-spiking interneurons, with distinct fast-spiking interneuron populations entrained to different gamma frequencies. Administration of the psychomotor stimulant amphetamine or the dopamine agonist apomorphine causes a prolonged decrease in approximately 50 Hz power and increase in approximately 80-100 Hz power. The same frequency switch is observed for shorter epochs spontaneously in awake, undrugged animals and is consistently provoked for reward receipt. Individual striatal neurons can participate in these brief high-gamma bursts with, or without, substantial changes in firing rate. Switching between discrete oscillatory states may allow different modes of information processing during decision-making and reinforcement-based learning, and may also be an important systems-level process by which stimulant drugs affect cognition and behavior.

  9. LOW-FREQUENCY OSCILLATIONS IN XTE J1550-564

    International Nuclear Information System (INIS)

    Rao Fengyun; Belloni, Tomaso; Stella, Luigi; Zhang Shuangnan; Li Tipei

    2010-01-01

    We present the results of a timing analysis of the low-frequency quasi-periodic oscillation (QPO) in the Rossi X-Ray Timing Explorer data of the black hole binary XTE J1550-564 during its 1998 outburst. The QPO frequency is observed to vary on timescales between ∼100 s and days, correlated with the count rate contribution from the optically thick accretion disk: we studied this correlation and discuss its influence on the QPO width. In all observations, the quality factors (ν 0 /FWHM) of the fundamental and second harmonic peaks were observed to be consistent, suggesting that the quasi-periodic nature of the oscillation is due to frequency modulation. In addition to the QPO and its harmonic peaks, a new 1.5ν component was detected in the power spectra. This component is broad, with a quality factor of ∼0.6. From this, we argue that the peak observed at half the QPO frequency, usually referred to as 'sub-harmonic', could be the fundamental frequency, leading to the sequence 1:2:3:4. We also studied the energy dependence of the timing features and conclude that the two continuum components observed in the power spectrum, although both more intense at high energies, show a different dependence on energy. At low energies, the lowest-frequency component dominates, while at high energies the higher-frequency one has a higher fractional rms. An interplay between these two components was also observed as a function of their characteristic frequency. In this source, the transition between the low/hard state and the hard-intermediate state appears to be a smooth process.

  10. Pulse-coupled Belousov-Zhabotinsky oscillators with frequency modulation

    Science.gov (United States)

    Horvath, Viktor; Epstein, Irving R.

    2018-04-01

    Inhibitory perturbations to the ferroin-catalyzed Belousov-Zhabotinsky (BZ) chemical oscillator operated in a continuously fed stirred tank reactor cause long term changes to the limit cycle: the lengths of the cycles subsequent to the perturbation are longer than that of the unperturbed cycle, and the unperturbed limit cycle is recovered only after several cycles. The frequency of the BZ reaction strongly depends on the acid concentration of the medium. By adding strong acid or base to the perturbing solutions, the magnitude and the direction of the frequency changes concomitant to excitatory or inhibitory perturbations can be controlled independently of the coupling strength. The dynamics of two BZ oscillators coupled through perturbations carrying a coupling agent (activator or inhibitor) and a frequency modulator (strong acid or base) was explored using a numerical model of the system. Here, we report new complex temporal patterns: higher order, partially synchronized modes that develop when inhibitory coupling is combined with positive frequency modulation (FM), and complex bursting patterns when excitatory coupling is combined with negative FM. The role of time delay between the peak and perturbation (the analog of synaptic delays in networks of neurons) has also been studied. The complex patterns found under inhibitory coupling and positive FM vanish when the delay is significant, whereas a sufficiently long time delay is required for the complex temporal dynamics to occur when coupling is excitatory and FM is negative.

  11. High-Frequency Network Oscillations in Cerebellar Cortex

    Science.gov (United States)

    Middleton, Steven J.; Racca, Claudia; Cunningham, Mark O.; Traub, Roger D.; Monyer, Hannah; Knöpfel, Thomas; Schofield, Ian S.; Jenkins, Alistair; Whittington, Miles A.

    2016-01-01

    SUMMARY Both cerebellum and neocortex receive input from the somatosensory system. Interaction between these regions has been proposed to underpin the correct selection and execution of motor commands, but it is not clear how such interactions occur. In neocortex, inputs give rise to population rhythms, providing a spatiotemporal coding strategy for inputs and consequent outputs. Here, we show that similar patterns of rhythm generation occur in cerebellum during nicotinic receptor subtype activation. Both gamma oscillations (30–80 Hz) and very fast oscillations (VFOs, 80–160 Hz) were generated by intrinsic cerebellar cortical circuitry in the absence of functional glutamatergic connections. As in neocortex, gamma rhythms were dependent on GABAA receptor-mediated inhibition, whereas VFOs required only nonsynaptically connected intercellular networks. The ability of cerebellar cortex to generate population rhythms within the same frequency bands as neocortex suggests that they act as a common spatiotemporal code within which corticocerebellar dialog may occur. PMID:18549787

  12. Monlinear fish-scale metamaterial via coupled duffing oscillators

    OpenAIRE

    Kochetov, Bogdan; Tuz, Vladimir; Mladyonov, Pavel; Prosvirnin, Sergey; Kochetova, Lyudmila

    2012-01-01

    The dynamic system of two coupled Duffing oscillators is considered in order to predict the optical response of the nonlinear planar fish-scale metamaterial. The direct numerical calculation of meta material response confirms the correctness of the proposed model

  13. A precise measurement of the $B^0$ meson oscillation frequency

    CERN Document Server

    Aaij, Roel; Adeva, Bernardo; Adinolfi, Marco; Affolder, Anthony; Ajaltouni, Ziad; Akar, Simon; Albrecht, Johannes; Alessio, Federico; Alexander, Michael; Ali, Suvayu; Alkhazov, Georgy; Alvarez Cartelle, Paula; Alves Jr, Antonio Augusto; Amato, Sandra; Amerio, Silvia; Amhis, Yasmine; An, Liupan; Anderlini, Lucio; Anderson, Jonathan; Andreassi, Guido; Andreotti, Mirco; Andrews, Jason; Appleby, Robert; Aquines Gutierrez, Osvaldo; Archilli, Flavio; d'Argent, Philippe; Artamonov, Alexander; Artuso, Marina; Aslanides, Elie; Auriemma, Giulio; Baalouch, Marouen; Bachmann, Sebastian; Back, John; Badalov, Alexey; Baesso, Clarissa; Baldini, Wander; Barlow, Roger; Barschel, Colin; Barsuk, Sergey; Barter, William; Batozskaya, Varvara; Battista, Vincenzo; Bay, Aurelio; Beaucourt, Leo; Beddow, John; Bedeschi, Franco; Bediaga, Ignacio; Bel, Lennaert; Bellee, Violaine; Belloli, Nicoletta; Belyaev, Ivan; Ben-Haim, Eli; Bencivenni, Giovanni; Benson, Sean; Benton, Jack; Berezhnoy, Alexander; Bernet, Roland; Bertolin, Alessandro; Bettler, Marc-Olivier; van Beuzekom, Martinus; Bien, Alexander; Bifani, Simone; Billoir, Pierre; Bird, Thomas; Birnkraut, Alex; Bizzeti, Andrea; Blake, Thomas; Blanc, Frédéric; Blouw, Johan; Blusk, Steven; Bocci, Valerio; Bondar, Alexander; Bondar, Nikolay; Bonivento, Walter; Borghi, Silvia; Borsato, Martino; Bowcock, Themistocles; Bowen, Espen Eie; Bozzi, Concezio; Braun, Svende; Britsch, Markward; Britton, Thomas; Brodzicka, Jolanta; Brook, Nicholas; Buchanan, Emma; Bursche, Albert; Buytaert, Jan; Cadeddu, Sandro; Calabrese, Roberto; Calvi, Marta; Calvo Gomez, Miriam; Campana, Pierluigi; Campora Perez, Daniel; Capriotti, Lorenzo; Carbone, Angelo; Carboni, Giovanni; Cardinale, Roberta; Cardini, Alessandro; Carniti, Paolo; Carson, Laurence; Carvalho Akiba, Kazuyoshi; Casse, Gianluigi; Cassina, Lorenzo; Castillo Garcia, Lucia; Cattaneo, Marco; Cauet, Christophe; Cavallero, Giovanni; Cenci, Riccardo; Charles, Matthew; Charpentier, Philippe; Chefdeville, Maximilien; Chen, Shanzhen; Cheung, Shu-Faye; Chiapolini, Nicola; Chrzaszcz, Marcin; Cid Vidal, Xabier; Ciezarek, Gregory; Clarke, Peter; Clemencic, Marco; Cliff, Harry; Closier, Joel; Coco, Victor; Cogan, Julien; Cogneras, Eric; Cogoni, Violetta; Cojocariu, Lucian; Collazuol, Gianmaria; Collins, Paula; Comerma-Montells, Albert; Contu, Andrea; Cook, Andrew; Coombes, Matthew; Coquereau, Samuel; Corti, Gloria; Corvo, Marco; Couturier, Benjamin; Cowan, Greig; Craik, Daniel Charles; Crocombe, Andrew; Cruz Torres, Melissa Maria; Cunliffe, Samuel; Currie, Robert; D'Ambrosio, Carmelo; Dall'Occo, Elena; Dalseno, Jeremy; David, Pieter; Davis, Adam; De Aguiar Francisco, Oscar; De Bruyn, Kristof; De Capua, Stefano; De Cian, Michel; De Miranda, Jussara; De Paula, Leandro; De Simone, Patrizia; Dean, Cameron Thomas; Decamp, Daniel; Deckenhoff, Mirko; Del Buono, Luigi; Déléage, Nicolas; Demmer, Moritz; Derkach, Denis; Deschamps, Olivier; Dettori, Francesco; Dey, Biplab; Di Canto, Angelo; Di Ruscio, Francesco; Dijkstra, Hans; Donleavy, Stephanie; Dordei, Francesca; Dorigo, Mirco; Dosil Suárez, Alvaro; Dossett, David; Dovbnya, Anatoliy; Dreimanis, Karlis; Dufour, Laurent; Dujany, Giulio; Dupertuis, Frederic; Durante, Paolo; Dzhelyadin, Rustem; Dziurda, Agnieszka; Dzyuba, Alexey; Easo, Sajan; Egede, Ulrik; Egorychev, Victor; Eidelman, Semen; Eisenhardt, Stephan; Eitschberger, Ulrich; Ekelhof, Robert; Eklund, Lars; El Rifai, Ibrahim; Elsasser, Christian; Ely, Scott; Esen, Sevda; Evans, Hannah Mary; Evans, Timothy; Falabella, Antonio; Färber, Christian; Farley, Nathanael; Farry, Stephen; Fay, Robert; Ferguson, Dianne; Fernandez Albor, Victor; Ferrari, Fabio; Ferreira Rodrigues, Fernando; Ferro-Luzzi, Massimiliano; Filippov, Sergey; Fiore, Marco; Fiorini, Massimiliano; Firlej, Miroslaw; Fitzpatrick, Conor; Fiutowski, Tomasz; Fohl, Klaus; Fol, Philip; Fontana, Marianna; Fontanelli, Flavio; Forshaw, Dean Charles; Forty, Roger; Frank, Markus; Frei, Christoph; Frosini, Maddalena; Fu, Jinlin; Furfaro, Emiliano; Gallas Torreira, Abraham; Galli, Domenico; Gallorini, Stefano; Gambetta, Silvia; Gandelman, Miriam; Gandini, Paolo; Gao, Yuanning; García Pardiñas, Julián; Garra Tico, Jordi; Garrido, Lluis; Gascon, David; Gaspar, Clara; Gauld, Rhorry; Gavardi, Laura; Gazzoni, Giulio; Gerick, David; Gersabeck, Evelina; Gersabeck, Marco; Gershon, Timothy; Ghez, Philippe; Gianì, Sebastiana; Gibson, Valerie; Girard, Olivier Göran; Giubega, Lavinia-Helena; Gligorov, V.V.; Göbel, Carla; Golubkov, Dmitry; Golutvin, Andrey; Gomes, Alvaro; Gotti, Claudio; Grabalosa Gándara, Marc; Graciani Diaz, Ricardo; Granado Cardoso, Luis Alberto; Graugés, Eugeni; Graverini, Elena; Graziani, Giacomo; Grecu, Alexandru; Greening, Edward; Gregson, Sam; Griffith, Peter; Grillo, Lucia; Grünberg, Oliver; Gui, Bin; Gushchin, Evgeny; Guz, Yury; Gys, Thierry; Hadavizadeh, Thomas; Hadjivasiliou, Christos; Haefeli, Guido; Haen, Christophe; Haines, Susan; Hall, Samuel; Hamilton, Brian; Han, Xiaoxue; Hansmann-Menzemer, Stephanie; Harnew, Neville; Harnew, Samuel; Harrison, Jonathan; He, Jibo; Head, Timothy; Heijne, Veerle; Heister, Arno; Hennessy, Karol; Henrard, Pierre; Henry, Louis; Hernando Morata, Jose Angel; van Herwijnen, Eric; Heß, Miriam; Hicheur, Adlène; Hill, Donal; Hoballah, Mostafa; Hombach, Christoph; Hulsbergen, Wouter; Humair, Thibaud; Hussain, Nazim; Hutchcroft, David; Hynds, Daniel; Idzik, Marek; Ilten, Philip; Jacobsson, Richard; Jaeger, Andreas; Jalocha, Pawel; Jans, Eddy; Jawahery, Abolhassan; Jing, Fanfan; John, Malcolm; Johnson, Daniel; Jones, Christopher; Joram, Christian; Jost, Beat; Jurik, Nathan; Kandybei, Sergii; Kanso, Walaa; Karacson, Matthias; Karbach, Moritz; Karodia, Sarah; Kecke, Matthieu; Kelsey, Matthew; Kenyon, Ian; Kenzie, Matthew; Ketel, Tjeerd; Khanji, Basem; Khurewathanakul, Chitsanu; Kirn, Thomas; Klaver, Suzanne; Klimaszewski, Konrad; Kochebina, Olga; Kolpin, Michael; Komarov, Ilya; Koopman, Rose; Koppenburg, Patrick; Kozeiha, Mohamad; Kravchuk, Leonid; Kreplin, Katharina; Kreps, Michal; Krocker, Georg; Krokovny, Pavel; Kruse, Florian; Krzemien, Wojciech; Kucewicz, Wojciech; Kucharczyk, Marcin; Kudryavtsev, Vasily; Kuonen, Axel Kevin; Kurek, Krzysztof; Kvaratskheliya, Tengiz; Lacarrere, Daniel; Lafferty, George; Lai, Adriano; Lambert, Dean; Lanfranchi, Gaia; Langenbruch, Christoph; Langhans, Benedikt; Latham, Thomas; Lazzeroni, Cristina; Le Gac, Renaud; van Leerdam, Jeroen; Lees, Jean-Pierre; Lefèvre, Regis; Leflat, Alexander; Lefrançois, Jacques; Lemos Cid, Edgar; Leroy, Olivier; Lesiak, Tadeusz; Leverington, Blake; Li, Yiming; Likhomanenko, Tatiana; Liles, Myfanwy; Lindner, Rolf; Linn, Christian; Lionetto, Federica; Liu, Bo; Liu, Xuesong; Loh, David; Longstaff, Iain; Lopes, Jose; Lucchesi, Donatella; Lucio Martinez, Miriam; Luo, Haofei; Lupato, Anna; Luppi, Eleonora; Lupton, Oliver; Lusardi, Nicola; Lusiani, Alberto; Machefert, Frederic; Maciuc, Florin; Maev, Oleg; Maguire, Kevin; Malde, Sneha; Malinin, Alexander; Manca, Giulia; Mancinelli, Giampiero; Manning, Peter Michael; Mapelli, Alessandro; Maratas, Jan; Marchand, Jean François; Marconi, Umberto; Marin Benito, Carla; Marino, Pietro; Marks, Jörg; Martellotti, Giuseppe; Martin, Morgan; Martinelli, Maurizio; Martinez Santos, Diego; Martinez Vidal, Fernando; Martins Tostes, Danielle; Massafferri, André; Matev, Rosen; Mathad, Abhijit; Mathe, Zoltan; Matteuzzi, Clara; Mauri, Andrea; Maurin, Brice; Mazurov, Alexander; McCann, Michael; McCarthy, James; McNab, Andrew; McNulty, Ronan; Meadows, Brian; Meier, Frank; Meissner, Marco; Melnychuk, Dmytro; Merk, Marcel; Michielin, Emanuele; Milanes, Diego Alejandro; Minard, Marie-Noelle; Mitzel, Dominik Stefan; Molina Rodriguez, Josue; Monroy, Ignacio Alberto; Monteil, Stephane; Morandin, Mauro; Morawski, Piotr; Mordà, Alessandro; Morello, Michael Joseph; Moron, Jakub; Morris, Adam Benjamin; Mountain, Raymond; Muheim, Franz; Müller, Dominik; Müller, Janine; Müller, Katharina; Müller, Vanessa; Mussini, Manuel; Muster, Bastien; Naik, Paras; Nakada, Tatsuya; Nandakumar, Raja; Nandi, Anita; Nasteva, Irina; Needham, Matthew; Neri, Nicola; Neubert, Sebastian; Neufeld, Niko; Neuner, Max; Nguyen, Anh Duc; Nguyen, Thi-Dung; Nguyen-Mau, Chung; Niess, Valentin; Niet, Ramon; Nikitin, Nikolay; Nikodem, Thomas; Novoselov, Alexey; O'Hanlon, Daniel Patrick; Oblakowska-Mucha, Agnieszka; Obraztsov, Vladimir; Ogilvy, Stephen; Okhrimenko, Oleksandr; Oldeman, Rudolf; Onderwater, Gerco; Osorio Rodrigues, Bruno; Otalora Goicochea, Juan Martin; Otto, Adam; Owen, Patrick; Oyanguren, Maria Aranzazu; Palano, Antimo; Palombo, Fernando; Palutan, Matteo; Panman, Jacob; Papanestis, Antonios; Pappagallo, Marco; Pappalardo, Luciano; Pappenheimer, Cheryl; Parkes, Christopher; Passaleva, Giovanni; Patel, Girish; Patel, Mitesh; Patrignani, Claudia; Pearce, Alex; Pellegrino, Antonio; Penso, Gianni; Pepe Altarelli, Monica; Perazzini, Stefano; Perret, Pascal; Pescatore, Luca; Petridis, Konstantinos; Petrolini, Alessandro; Petruzzo, Marco; Picatoste Olloqui, Eduardo; Pietrzyk, Boleslaw; Pilař, Tomas; Pinci, Davide; Pistone, Alessandro; Piucci, Alessio; Playfer, Stephen; Plo Casasus, Maximo; Poikela, Tuomas; Polci, Francesco; Poluektov, Anton; Polyakov, Ivan; Polycarpo, Erica; Popov, Alexander; Popov, Dmitry; Popovici, Bogdan; Potterat, Cédric; Price, Eugenia; Price, Joseph David; Prisciandaro, Jessica; Pritchard, Adrian; Prouve, Claire; Pugatch, Valery; Puig Navarro, Albert; Punzi, Giovanni; Qian, Wenbin; Quagliani, Renato; Rachwal, Bartolomiej; Rademacker, Jonas; Rama, Matteo; Rangel, Murilo; Raniuk, Iurii; Rauschmayr, Nathalie; Raven, Gerhard; Redi, Federico; Reichert, Stefanie; Reid, Matthew; dos Reis, Alberto; Ricciardi, Stefania; Richards, Sophie; Rihl, Mariana; Rinnert, Kurt; Rives Molina, Vincente; Robbe, Patrick; Rodrigues, Ana Barbara; Rodrigues, Eduardo; Rodriguez Lopez, Jairo Alexis; Rodriguez Perez, Pablo; Roiser, Stefan; Romanovsky, Vladimir; Romero Vidal, Antonio; Ronayne, John William; Rotondo, Marcello; Rouvinet, Julien; Ruf, Thomas; Ruiz Valls, Pablo; Saborido Silva, Juan Jose; Sagidova, Naylya; Sail, Paul; Saitta, Biagio; Salustino Guimaraes, Valdir; Sanchez Mayordomo, Carlos; Sanmartin Sedes, Brais; Santacesaria, Roberta; Santamarina Rios, Cibran; Santimaria, Marco; Santovetti, Emanuele; Sarti, Alessio; Satriano, Celestina; Satta, Alessia; Saunders, Daniel Martin; Savrina, Darya; Schael, Stefan; Schiller, Manuel; Schindler, Heinrich; Schlupp, Maximilian; Schmelling, Michael; Schmelzer, Timon; Schmidt, Burkhard; Schneider, Olivier; Schopper, Andreas; Schubiger, Maxime; Schune, Marie Helene; Schwemmer, Rainer; Sciascia, Barbara; Sciubba, Adalberto; Semennikov, Alexander; Sergi, Antonino; Serra, Nicola; Serrano, Justine; Sestini, Lorenzo; Seyfert, Paul; Shapkin, Mikhail; Shapoval, Illya; Shcheglov, Yury; Shears, Tara; Shekhtman, Lev; Shevchenko, Vladimir; Shires, Alexander; Siddi, Benedetto Gianluca; Silva Coutinho, Rafael; Silva de Oliveira, Luiz Gustavo; Simi, Gabriele; Sirendi, Marek; Skidmore, Nicola; Skwarnicki, Tomasz; Smith, Edmund; Smith, Eluned; Smith, Iwan Thomas; Smith, Jackson; Smith, Mark; Snoek, Hella; Sokoloff, Michael; Soler, Paul; Soomro, Fatima; Souza, Daniel; Souza De Paula, Bruno; Spaan, Bernhard; Spradlin, Patrick; Sridharan, Srikanth; Stagni, Federico; Stahl, Marian; Stahl, Sascha; Stefkova, Slavomira; Steinkamp, Olaf; Stenyakin, Oleg; Stevenson, Scott; Stoica, Sabin; Stone, Sheldon; Storaci, Barbara; Stracka, Simone; Straticiuc, Mihai; Straumann, Ulrich; Sun, Liang; Sutcliffe, William; Swientek, Krzysztof; Swientek, Stefan; Syropoulos, Vasileios; Szczekowski, Marek; Szczypka, Paul; Szumlak, Tomasz; T'Jampens, Stephane; Tayduganov, Andrey; Tekampe, Tobias; Teklishyn, Maksym; Tellarini, Giulia; Teubert, Frederic; Thomas, Christopher; Thomas, Eric; van Tilburg, Jeroen; Tisserand, Vincent; Tobin, Mark; Todd, Jacob; Tolk, Siim; Tomassetti, Luca; Tonelli, Diego; Topp-Joergensen, Stig; Torr, Nicholas; Tournefier, Edwige; Tourneur, Stephane; Trabelsi, Karim; Tran, Minh Tâm; Tresch, Marco; Trisovic, Ana; Tsaregorodtsev, Andrei; Tsopelas, Panagiotis; Tuning, Niels; Ukleja, Artur; Ustyuzhanin, Andrey; Uwer, Ulrich; Vacca, Claudia; Vagnoni, Vincenzo; Valenti, Giovanni; Vallier, Alexis; Vazquez Gomez, Ricardo; Vazquez Regueiro, Pablo; Vázquez Sierra, Carlos; Vecchi, Stefania; van Veghel, Maarten; Velthuis, Jaap; Veltri, Michele; Veneziano, Giovanni; Vesterinen, Mika; Viaud, Benoit; Vieira, Daniel; Vieites Diaz, Maria; Vilasis-Cardona, Xavier; Vollhardt, Achim; Volyanskyy, Dmytro; Voong, David; Vorobyev, Alexey; Vorobyev, Vitaly; Voß, Christian; de Vries, Jacco; Waldi, Roland; Wallace, Charlotte; Wallace, Ronan; Walsh, John; Wandernoth, Sebastian; Wang, Jianchun; Ward, David; Watson, Nigel; Websdale, David; Weiden, Andreas; Whitehead, Mark; Wilkinson, Guy; Wilkinson, Michael; Williams, Mark Richard James; Williams, Matthew; Williams, Mike; Williams, Timothy; Wilson, Fergus; Wimberley, Jack; Wishahi, Julian; Wislicki, Wojciech; Witek, Mariusz; Wormser, Guy; Wotton, Stephen; Wright, Simon; Wyllie, Kenneth; Xie, Yuehong; Xu, Zhirui; Yang, Zhenwei; Yu, Jiesheng; Yuan, Xuhao; Yushchenko, Oleg; Zangoli, Maria; Zavertyaev, Mikhail; Zhang, Liming; Zhang, Yanxi; Zhelezov, Alexey; Zhokhov, Anatoly; Zhong, Liang; Zhukov, Valery; Zucchelli, Stefano

    2016-07-21

    The oscillation frequency, $\\Delta m_d$, of $B^0$ mesons is measured using semileptonic decays with a $D^-$ or $D^{*-}$ meson in the final state, in a data sample of $pp$ collisions collected by the LHCb detector corresponding to an integrated luminosity of 3.0$\\mbox{fb}^{-1}$. A combination of the two decay modes gives $\\Delta m_d = (505.0 \\pm 2.1 \\pm 1.0) \\rm \\,ns^{-1}$, where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is compatible with the current world average and has similar precision.

  14. Nested synchrony – a novel cross-scale interaction among neuronal oscillations

    Directory of Open Access Journals (Sweden)

    Simo eMonto

    2012-09-01

    Full Text Available Neuronal interactions form the basis for our brain function, and oscillations and synchrony are the principal candidates for mediating them in the cortical networks. Phase synchrony, where oscillatory neuronal ensembles directly synchronize their phases, enables precise integration between separated brain regions. However, it is unclear how neuronal interactions are dynamically coordinated in space and over time. Cross-scale effects have been proposed to be responsible for linking levels of processing hierarchy and to regulate neuronal dynamics. Most notably, nested oscillations, where the phase of a neuronal oscillation modulates the amplitude of a faster one, may locally integrate neuronal activities in distinct frequency bands. Yet, hierarchical control of inter-areal synchrony could provide a more comprehensive view to the dynamical structure of oscillatory interdependencies in the human brain.In this study, the notion of nested oscillations is extended to a cross-frequency and inter-areal model of oscillatory interactions. In this model, the phase of a slower oscillation modulates inter-areal synchrony in a higher frequency band. This would allow cross-scale integration of global interactions and, thus, offers a mechanism for binding distributed neuronal activities.We show that inter-areal phase synchrony can be modulated by the phase of a slower neuronal oscillation using magnetoencephalography. This effect is the most pronounced at frequencies below 35 Hz. Importantly, changes in oscillation amplitudes did not explain the findings. We expect that the novel cross-frequency interaction could offer new ways to understand the flexible but accurate dynamic organization of ongoing neuronal oscillations and synchrony.

  15. Measurement of the Bs0-Bs0 oscillation frequency.

    Science.gov (United States)

    Abulencia, A; Acosta, D; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arguin, J-F; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Bachacou, H; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bellettini, G; Bellinger, J; Belloni, A; Ben Haim, E; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carlsmith, D; Carosi, R; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chapman, J; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Chu, P H; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciljak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Cruz, A; Cuenca Almenar, C; Cuevas, J; Culbertson, R; Cyr, D; DaRonco, S; D'Auria, S; D'Onofrio, M; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; Dell'Orso, M; Delli Paoli, F; Demers, S; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Di Giovanni, G P; Di Ruzza, B; Dionisi, C; Dittmann, J R; DiTuro, P; Dörr, C; Donati, S; Donega, M; Dong, P; Donini, J; Dorigo, T; Dube, S; Ebina, K; Efron, J; Ehlers, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Flores-Castillo, L R; Foland, A; Forrester, S; Foster, G W; Franklin, M; Freeman, J C; Frisch, H J; Furic, I; Gallinaro, M; Galyardt, J; Garcia, J E; Garcia Sciveres, M; Garfinkel, A F; Gay, C; Gerberich, H; Gerdes, D; Giagu, S; Giannetti, P; Gibson, A; Gibson, K; Ginsburg, C; Giokaris, N; Giolo, K; Giordani, M; Giromini, P; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Gresele, A; Griffiths, M; Grinstein, S; Grosso-Pilcher, C; Group, R C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, S R; Hahn, K; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, M; Harper, S; Harr, R F; Harris, R M; Hatakeyama, K; Hauser, J; Hays, C; Heijboer, A; Heinemann, B; Heinrich, J; Herndon, M; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ishizawa, Y; Ivanov, A; Iyutin, B; James, E; Jang, D; Jayatilaka, B; Jeans, D; Jensen, H; Jeon, E J; Jindariani, S; Jones, M; Joo, K K; Jun, S Y; Junk, T R; Kamon, T; Kang, J; Karchin, P E; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Kobayashi, H; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kovalev, A; Kraan, A; Kraus, J; Kravchenko, I; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kuhlmann, S E; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; LeCompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Lindgren, M; Lipeles, E; Liss, T M; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Loverre, P; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; MacQueen, D; Madrak, R; Maeshima, K; Maki, T; Maksimovic, P; Malde, S; Manca, G; Margaroli, F; Marginean, R; Marino, C; Martin, A; Martin, V; Martínez, M; Maruyama, T; Mastrandrea, P; Matsunaga, H; Mattson, M E; Mazini, R; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; von der Mey, M; Miao, T; Miladinovic, N; Miles, J; Miller, R; Miller, J S; Mills, C; Milnik, M; Miquel, R; Mitra, A; Mitselmakher, G; Miyamoto, A; Moggi, N; Mohr, B; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Nachtman, J; Naganoma, J; Nahn, S; Nakano, I; Napier, A; Naumov, D; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nigmanov, T; Nodulman, L; Norniella, O; Nurse, E; Ogawa, T; Oh, S H; Oh, Y D; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagliarone, C; Palencia, E; Paoletti, R; Papadimitriou, V; Paramonov, A A; Parks, B; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pinera, L; Pitts, K; Plager, C; Pondrom, L; Portell, X; Poukhov, O; Pounder, N; Prakoshyn, F; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Pursley, J; Rademacker, J; Rahaman, A; Rakitin, A; Rappoccio, S; Ratnikov, F; Reisert, B; Rekovic, V; van Remortel, N; Renton, P; Rescigno, M; Richter, S; Rimondi, F; Ristori, L; Robertson, W J; Robson, A; Rodrigo, T; Rogers, E; Rolli, S; Roser, R; Rossi, M; Rossin, R; Rott, C; Ruiz, A; Russ, J; Rusu, V; Saarikko, H; Sabik, S; Safonov, A; Sakumoto, W K; Salamanna, G; Saltó, O; Saltzberg, D; Sanchez, C; Santi, L; Sarkar, S; Sartori, L; Sato, K; Savard, P; Savoy-Navarro, A; Scheidle, T; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Schwarz, T; Scodellaro, L; Scott, A L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Sexton-Kennedy, L; Sfiligoi, I; Shapiro, M D; Shears, T; Shepard, P F; Sherman, D; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Sinervo, P; Sisakyan, A; Sjolin, J; Skiba, A; Slaughter, A J; Sliwa, K; Smith, J R; Snider, F D; Snihur, R; Soderberg, M; Soha, A; Somalwar, S; Sorin, V; Spalding, J; Spezziga, M; Spinella, F; Spreitzer, T; Squillacioti, P; Stanitzki, M; Staveris-Polykalas, A; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Stuart, D; Suh, J S; Sukhanov, A; Sumorok, K; Sun, H; Suzuki, T; Taffard, A; Takashima, R; Takeuchi, Y; Takikawa, K; Tanaka, M; Tanaka, R; Tanimoto, N; Tecchio, M; Teng, P K; Terashi, K; Tether, S; Thom, J; Thompson, A S; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tokar, S; Tollefson, K; Tomura, T; Tonelli, D; Tönnesmann, M; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tsuchiya, R; Tsuno, S; Turini, N; Ukegawa, F; Unverhau, T; Uozumi, S; Usynin, D; Vaiciulis, A; Vallecorsa, S; Varganov, A; Vataga, E; Velev, G; Veramendi, G; Veszpremi, V; Vidal, R; Vila, I; Vilar, R; Vine, T; Vollrath, I; Volobouev, I; Volpi, G; Würthwein, F; Wagner, P; Wagner, R G; Wagner, R L; Wagner, W; Wallny, R; Walter, T; Wan, Z; Wang, S M; Warburton, A; Waschke, S; Waters, D; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, G; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, T; Yang, C; Yang, U K; Yang, Y C; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zetti, F; Zhang, X; Zhou, J; Zucchelli, S

    2006-08-11

    We present the first precise measurement of the Bs0-Bs0 oscillation frequency Deltams. We use 1 fb-1 of data from pp collisions at sqrts=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3600 fully reconstructed hadronic Bs decays and 37,000 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with Bs0-Bs0 oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to Bs0-Bs0 oscillations, we measure Deltams=17.31(-0.18)+0.33(stat)+/-0.07(syst) ps-1 and determine |Vtd/Vts|=0.208(-0.002)+0.001(expt)-0.006(+0.008)(theor).

  16. Numerical prediction of the natural frequency of an Oscillating Water Column operating under resonant conditions

    Directory of Open Access Journals (Sweden)

    Marco Torresi

    2016-12-01

    Full Text Available Among the different technologies developed in order to harness wave energy, the Oscillating Water Column devices are the most accredited for an actual diffusion. Recently, Boccotti has patented the REWEC1 (REsonant sea Wave Energy Converter solution 1, a submerged breakwater that performs an active coast protection, embedding an Oscillating Water Column device, which is capable of operating under resonant conditions with that sea state, which gives the highest yearly energy contribution. The REWEC1 dynamic behavior can be approximated by means of a mass-spring-damper system. According to this approximation, a criterion for evaluating the oscillating natural frequency of the REWEC1 has been derived. This criterion has been validated against both experimental results and computational fluid dynamics simulations, performed on a REWEC1 laboratory-scale model. The numerical simulations have shown a good agreement between measurements and predictions.

  17. Input-dependent frequency modulation of cortical gamma oscillations shapes spatial synchronization and enables phase coding.

    Science.gov (United States)

    Lowet, Eric; Roberts, Mark; Hadjipapas, Avgis; Peter, Alina; van der Eerden, Jan; De Weerd, Peter

    2015-02-01

    Fine-scale temporal organization of cortical activity in the gamma range (∼25-80Hz) may play a significant role in information processing, for example by neural grouping ('binding') and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes

  18. Damping of Inter-Area Low Frequency Oscillation Using an Adaptive Wide-Area Damping Controller

    DEFF Research Database (Denmark)

    Yao, Wei; Jiang, L.; Fang, Jiakun

    2013-01-01

    This paper presents an adaptive wide-area damping controller (WADC) based on generalized predictive control (GPC) and model identification for damping the inter-area low frequency oscillations in large-scale inter-connected power system. A recursive least-squares algorithm (RLSA) with a varying...... forgetting factor is applied to identify online the reduced-order linearlized model which contains dominant inter-area low frequency oscillations. Based on this linearlized model, the generalized predictive control scheme considering control output constraints is employed to obtain the optimal control signal...... conditions and different disturbances, but also has better robustness against to the time delay existing in the remote signals. The comparison studies with the conventional lead-lag WADC are also provided....

  19. Characteristics of low-frequency oscillation intensity of airsea turbulent heat fluxes over the northwest Pacific

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on the daily turbulent heat fluxes and related meteorological variables datasets (1985-2006) from Objectively Analyzed air-sea Fluxes (OAFlux) Project of Woods Hole Oceanographic Institution (WHOI), characteristics of low-frequency oscillation intensity of air-sea turbulent heat fluxes over the northwest Pacific are analyzed by linear perturbation method and correlation analysis. It can be concluded that: 1) the distribution of low-frequency oscillation intensity of latent heat flux (LHF) over the northwest Pacific is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea humidity gradient (Δq′) as well as mean air-sea humidity gradient ( Δ q), while the distribution of low-frequency oscillation intensity of sensible heat flux (SHF) is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea temperature gradient (ΔT′). 2) The low-frequency oscillation of turbulent heat fluxes over the northwest Pacific is the strongest in winter and the weakest in summer. And the seasonal transition of low-frequency oscillation intensity of LHF is jointly influenced by those of low-frequency oscillation intensity of Δq′, low-frequency oscillation intensity of anomalous wind speed (U′), Δ q and mean wind speed (U ), while the seasonal transition of low-frequency oscillation intensity of SHF is mainly influenced by those of low-frequency oscillation intensity of ΔT′ and U . 3) Over the tropical west Pacific and sea areas north of 20°N, the low-frequency oscillation of LHF (SHF) is mainly influenced by atmospheric variables qa′ (Ta′) and U′, indicating an oceanic response to overlying atmospheric forcing. In contrast, over the tropical eastern and central Pacific south of 20°N, qs′ (Ts′) also greatly influences the low-frequency oscillation of LHF (SHF).

  20. Nonlinear oscillations of the FitzHugh-Nagumo equations under combined external and two-frequency parametric excitations

    International Nuclear Information System (INIS)

    Tatchim Bemmo, D.; Siewe Siewe, M.; Tchawoua, C.

    2011-01-01

    The continuous FitzHugh-Nagumo (FHN for short) model is transformed into modified van der Pol oscillator with asymmetry under external and two-frequency parametric excitations. At the first, the dependence of the solutions on a combined external and two-frequency parametric stimulus forcing is investigated. By using the multiple scale method, ranges of applied current and/or parametric forcing in which nonlinear oscillations are observed are described. Second, when the multiple scale method cannot be used, we numerically prove that in the modified van der Pol oscillator with asymmetry under external and two-frequency parametric excitations, chaos and periodic solution depending on the combination between different frequencies of the model should appear. We also show that the amplitude of the oscillations can be reduced or increased. To do this, we perform the study of the FHN model by choosing a range of parameters exhibiting Hopf bifurcation and two qualitative different regimes in phase portrait. - Highlights: → We model both external and two-frequency parametric excitations in FHN equations. → We examine effects of harmonic forcing on coupled nonlinear oscillator. → Jump and hysteresis phenomena are observed in the dynamical response. → By increasing the constant stimulus we obtain limit cycle. → Some combinations of frequencies produce limit cycle and chaos for other.

  1. LOW-FREQUENCY OSCILLATIONS IN GLOBAL SIMULATIONS OF BLACK HOLE ACCRETION

    International Nuclear Information System (INIS)

    O'Neill, Sean M.; Reynolds, Christopher S.; Coleman Miller, M.; Sorathia, Kareem A.

    2011-01-01

    We have identified the presence of large-scale, low-frequency dynamo cycles in a long-duration, global, magnetohydrodynamic (MHD) simulation of black hole accretion. Such cycles have previously been seen in local shearing box simulations, but we discuss their evolution over 1500 inner disk orbits of a global π/4 disk wedge spanning two orders of magnitude in radius and seven scale heights in elevation above/below the disk midplane. The observed cycles manifest themselves as oscillations in azimuthal magnetic field occupying a region that extends into a low-density corona several scale heights above the disk. The cycle frequencies are 10-20 times lower than the local orbital frequency, making them potentially interesting sources of low-frequency variability when scaled to real astrophysical systems. Furthermore, power spectra derived from the full time series reveal that the cycles manifest themselves at discrete, narrowband frequencies that often share power across broad radial ranges. We explore possible connections between these simulated cycles and observed low-frequency quasi-periodic oscillations (LFQPOs) in galactic black hole binary systems, finding that dynamo cycles have the appropriate frequencies and are located in a spatial region associated with X-ray emission in real systems. Derived observational proxies, however, fail to feature peaks with rms amplitudes comparable to LFQPO observations, suggesting that further theoretical work and more sophisticated simulations will be required to form a complete theory of dynamo-driven LFQPOs. Nonetheless, this work clearly illustrates that global MHD dynamos exhibit quasi-periodic behavior on timescales much longer than those derived from test particle considerations.

  2. Measurement of the B$_{d}^{0}$ meson oscillation frequency

    CERN Document Server

    Acciarri, M; Aguilar-Benítez, M; Ahlen, S P; Alpat, B; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alverson, G; Alviggi, M G; Ambrosi, G; Anderhub, H; Andreev, V P; Angelescu, T; Antreasyan, D; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Baksay, L; Ball, R C; Banerjee, S; Banicz, K; Barillère, R; Barone, L; Bartalini, P; Baschirotto, A; Basile, M; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biland, A; Bilei, G M; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böck, R K; Böhm, A; Borgia, B; Boucham, A; Bourilkov, D; Bourquin, Maurice; Boutigny, D; Brambilla, Elena; Branson, J G; Brigljevic, V; Brock, I C; Buijs, A; Burger, J D; Burger, W J; Busenitz, J K; Buytenhuijs, A O; Cai, X D; Campanelli, M; Capell, M; Cara Romeo, G; Caria, M; Carlino, G; Cartacci, A M; Casaus, J; Castellini, G; Castello, R; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada-Canales, M; Cesaroni, F; Chamizo-Llatas, M; Chan, A; Chang, Y H; Chaturvedi, U K; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chen, M; Chiefari, G; Chien, C Y; Choi, M T; Cifarelli, Luisa; Cindolo, F; Civinini, C; Clare, I; Clare, R; Cohn, H O; Coignet, G; Colijn, A P; Colino, N; Costantini, S; Cotorobai, F; de la Cruz, B; Csilling, Akos; Dai, T S; D'Alessandro, R; De Asmundis, R; De Boeck, H; Degré, A; Deiters, K; Denes, P; De Notaristefani, F; DiBitonto, Daryl; Diemoz, M; Van Dierendonck, D N; Di Lodovico, F; Dionisi, C; Dittmar, Michael; Dominguez, A; Doria, A; Dorne, I; Dova, M T; Drago, E; Duchesneau, D; Duinker, P; Durán, I; Dutta, S; Easo, S; Efremenko, Yu V; El-Mamouni, H; Engler, A; Eppling, F J; Erné, F C; Ernenwein, J P; Extermann, Pierre; Fabre, M; Faccini, R; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Ferguson, T; Fernández, D; Ferroni, F; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Forconi, G; Fredj, L; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; Gau, S S; Gentile, S; Gerald, J; Gheordanescu, N; Giagu, S; Goldfarb, S; Goldstein, J; Gong, Z F; Gougas, Andreas; Gratta, Giorgio; Grünewald, M W; Gupta, V K; Gurtu, A; Gutay, L J; Hangarter, K; Hartmann, B; Hasan, A; Hebbeker, T; Hervé, A; Van Hoek, W C; Hofer, H; Hoorani, H; Hou, S R; Hu, G; Ilyas, M M; Innocente, Vincenzo; Janssen, H; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Kasser, A; Khan, R A; Kamyshkov, Yu A; Kapinos, P; Kapustinsky, J S; Karyotakis, Yu; Kaur, M; Kienzle-Focacci, M N; Kim, D; Kim, J K; Kim, S C; Kim, Y G; Kinnison, W W; Kirkby, A; Kirkby, D; Kirkby, Jasper; Kiss, D; Kittel, E W; Klimentov, A; König, A C; Korolko, I; Koutsenko, V F; Krämer, R W; Kramer, T; Krenz, W; Kuijten, H; Kunin, A; Ladrón de Guevara, P; Landi, G; Lapoint, C; Lassila-Perini, K M; Laurikainen, P; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Lee Jae Sik; Lee, K Y; Leggett, C; Le Goff, J M; Leiste, R; Lenti, M; Leonardi, E; Levchenko, P M; Li Chuan; Lieb, E H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lu, W; Lü, Y S; Lübelsmeyer, K; Luci, C; Luckey, D; Ludovici, L; Luminari, L; Lustermann, W; Ma Wen Gan; Macchiolo, A; Maity, M; Majumder, G; Malgeri, L; Malinin, A; Maña, C; Mangla, S; Marchesini, P A; Marin, A; Martin, J P; Marzano, F; Massaro, G G G; Mazumdar, K; McNally, D; Mele, S; Merola, L; Meschini, M; Metzger, W J; Von der Mey, M; Mi, Y; Mihul, A; Van Mil, A J W; Mirabelli, G; Mnich, J; Monteleoni, B; Moore, R; Morganti, S; Mount, R; Müller, S; Muheim, F; Nagy, E; Nahn, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Nippe, A; Nowak, H; Organtini, G; Ostonen, R; Pandoulas, D; Paoletti, S; Paolucci, P; Park, H K; Pascale, G; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Peach, D; Pei, Y J; Pensotti, S; Perret-Gallix, D; Petrak, S; Pevsner, A; Piccolo, D; Pieri, M; Pinto, J C; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Postema, H; Produit, N; Prokofev, D; Prokofiev, D O; Raghavan, R; Rahal-Callot, G; Rancoita, P G; Rattaggi, M; Raven, G; Razis, P A; Read, K; Ren, D; Rescigno, M; Reucroft, S; Van Rhee, T; Riemann, S; Riemers, B C; Riles, K; Rind, O; Ro, S; Robohm, A; Rodin, J; Rodríguez-Calonge, F J; Roe, B P; Röhner, S; Romero, L; Rosier-Lees, S; Rosselet, P; Van Rossum, W; Roth, S; Rubio, Juan Antonio; Rykaczewski, H; Salicio, J; Sánchez, E; Santocchia, A; Sarakinos, M E; Sarkar, S; Sassowsky, M; Sauvage, G; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Schmitz, P; Schneegans, M; Schöneich, B; Scholz, N; Schopper, Herwig Franz; Schotanus, D J; Schwenke, J; Schwering, G; Sciacca, C; Sciarrino, D; Sens, Johannes C; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shukla, J; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Sopczak, André; Soulimov, V; Smith, B; Spillantini, P; Steuer, M; Stickland, D P; Sticozzi, F; Stone, H; Stoyanov, B; Strässner, A; Strauch, K; Sudhakar, K; Sultanov, G G; Sun, L Z; Susinno, G F; Suter, H; Swain, J D; Tang, X W; Tauscher, Ludwig; Taylor, L; Ting, Samuel C C; Ting, S M; Tonisch, F; Tonutti, M; Tonwar, S C; Tóth, J; Tully, C; Tuchscherer, H; Tung, K L; Ulbricht, J; Uwer, U; Valente, E; Van de Walle, R T; Vesztergombi, G; Vetlitskii, I; Viertel, Gert M; Vivargent, M; Völkert, R; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Vorvolakos, A; Wadhwa, M; Wallraff, W; Wang, J C; Wang, X L; Wang, Y F; Wang, Z M; Weber, A; Wittgenstein, F; Wu, S X; Wynhoff, S; Xu, J; Xu, Z Z; Yang, B Z; Yang, C G; Yao, X Y; Ye, J B; Yeh, S C; You, J M; Zalite, A; Zalite, Yu; Zemp, P; Zeng, Y; Zhang, Z; Zhang, Z P; Zhou, B; Zhou, Y; Zhu, G Y; Zhu, R Y; Zichichi, Antonino

    1996-01-01

    Time-dependent \\Bd-\\Bbd\\ mixing is studied using 1.5 million hadronic Z decays collected by L3. Semileptonic B decays are selected by requiring at least one reconstructed lepton in both thrust hemispheres. Charge correlations between the tagged leptons are studied as a function of proper time. The proper time of the b-hadron decay is measured by reconstructing the production and decay vertices using a silicon microvertex detector. The measured \\Bd\\ meson oscillation frequency corresponds to a mass difference \\Dmd\\ between the two \\Bd\\ mass eigenstates of \\begin{displaymath} \\Dmd = \\left( 0.496 ^{+ 0.055}_{- 0.051}\\ \\mathrm{(stat)} \\pm{ 0.043}\\ \\mathrm{(syst)} \\right)\\ \\mathrm{ps}^{-1}. \\end{displaymath}

  3. Spontaneous Low Frequency Oscillations in Acute Ischemic Stroke

    DEFF Research Database (Denmark)

    Phillip, Dorte; Schytz, Henrik Winther; Iversen, Helle Klingenberg

    2014-01-01

    Background and purpose: Continuous wave near infrared spectroscopy (NIRS) is a non-invasive bed-side optical method to detect changes in oxygenated (oxyHb) and deoxygenated hemoglobin (deoxyHb) in the outermost layers of the cerebral cortex. Cortical oxyHb low frequency oscillations (LFOs) in the 0.......09-0.11 Hz range are affected by changes in cerebral autoregulation (CA), which is altered following stroke. We examined oxyHb LFOs at bed-side as a marker of CA in the subacute phase in stroke patients with or without recombinant tissue plasminogen activator thrombolytic therapy. Methods: We recruited 29...... patients admitted to the stroke unit with symptoms of ischemic stroke. 11/29 patients received thrombolytic therapy. NIRS examination was conducted 2 days (median time) from stroke onset. NIRS optodes were placed on each side of the head with a 3 cm source-detector distance. Using transfer function...

  4. The role of low-frequency intraseasonal oscillations in the ...

    Indian Academy of Sciences (India)

    We analyze the dynamical features and responsible factors of the low-frequency intraseasonal time scales which influenced the nature of onset, intensity and duration of active/break phases and withdrawal of the monsoon during the anomalous Indian summer monsoon of 2002 – the most severe drought recorded in recent ...

  5. General Forced Oscillations in a Real Power Grid Integrated with Large Scale Wind Power

    OpenAIRE

    Ping Ju; Yongfei Liu; Feng Wu; Fei Dai; Yiping Yu

    2016-01-01

    According to the monitoring of the wide area measurement system, inter-area oscillations happen more and more frequently in a real power grid of China, which are close to the forced oscillation. Applying the conventional forced oscillation theory, the mechanism of these oscillations cannot be explained well, because the oscillations vary with random amplitude and a narrow frequency band. To explain the mechanism of such oscillations, the general forced oscillation (GFO) mechanism is taken int...

  6. An oscillation phenomenon of low frequency reverberation in the shallow water and its physical explanation

    Institute of Scientific and Technical Information of China (English)

    LI; Fenghua; LIU; Jianjun; LI; Zhenglin; ZHANG; Renhe

    2005-01-01

    An oscillation phenomenon of the low frequency reverberation intensity was observed in several shallow water reverberation experiments. This phenomenon cannot be explained by the widely used incoherent reverberation theory. In this paper, to explain the observed oscillation phenomenon, a normal mode based coherent reverberation theory is presented. The theoretical analysis and numerical results show that modal interference can cause the regular oscillation phenomenon of the low frequency reverberation intensity, and the oscillation frequency is determined by the normal mode eigen-values. A new method to estimate the bottom sound speed based on the oscillation frequency of reverberation intensity was presented in this paper. The experimental results at three different sites indicate that the bottom sound speed estimated from the oscillation frequency of reverberation intensity agrees with that inverted from Matched Field Processing (MFP) well.

  7. Modulation linearization of a frequency-modulated voltage controlled oscillator, part 3

    Science.gov (United States)

    Honnell, M. A.

    1975-01-01

    An analysis is presented for the voltage versus frequency characteristics of a varactor modulated VHF voltage controlled oscillator in which the frequency deviation is linearized by using the nonlinear characteristics of a field effect transistor as a signal amplifier. The equations developed are used to calculate the oscillator output frequency in terms of pertinent circuit parameters. It is shown that the nonlinearity exponent of the FET has a pronounced influence on frequency deviation linearity, whereas the junction exponent of the varactor controls total frequency deviation for a given input signal. A design example for a 250 MHz frequency modulated oscillator is presented.

  8. On the frequency scalings of RF guns

    International Nuclear Information System (INIS)

    Lin, L.C.; Chen, S.C.; Wurtele, J.S.

    1995-01-01

    A frequency scaling law for RF guns is derived from the normalized Vlasov-Maxwell equations. It shows that higher frequency RF guns can generate higher brightness beams under the assumption that the accelerating gradient and all beam and structure parameters are scaled with the RF frequency. Numerical simulation results using MAGIC confirm the scaling law. A discussion of the range of applicability of the law is presented. copyright 1995 American Institute of Physics

  9. Scaling Features of Multimode Motions in Coupled Chaotic Oscillators

    DEFF Research Database (Denmark)

    Pavlov, A.N.; Sosnovtseva, Olga; Mosekilde, Erik

    2003-01-01

    Two different methods (the WTMM- and DFA-approaches) are applied to investigate the scaling properties in the return-time sequences generated by a system of two coupled chaotic oscillators. Transitions from twomode asynchronous dynamics (torus or torus-Chaos) to different states of chaotic phase ...

  10. Selection of mother wavelets for the detection of the oscillation frequencies in power signals of nuclear reactors

    International Nuclear Information System (INIS)

    Amador G, R.; Castillo D, R.; Ortiz V, J.

    2007-01-01

    Diverse types of transitory events can lead to oscillations of power in nuclear reactors. In such events, the power monitors provide a signal that contains important characteristics of the transitory one, as the oscillation frequency, tendencies, changes and the instants or periods in those that important events are presented. This characteristics are detected by means of diverse analysis techniques, as Autoregressive methods, Fourier Transform, Fourier Transform in Short Time, Wavelets Transform, among others. Presently work is used the one Wavelets Continuous Transform because it allows to carry out studies of the stationary, quasi-stationary and transitory signals in the Time-scale and Time-scale-spectrum planes. Contrary to other similar works, this work describes a methodology for the selection of the scales and the Wavelet mother to be applied the one Wavelets Continuous Transform, with the objective of detecting to the dominant frequencies of the system. To prove the proposal a broadly well-known real signal of an event of power oscillations it has been used. The obtained results correspond to three families of Wavelets mothers that fulfilled the conditions of scales and central frequency of the proposal. The results show that the value of the certain frequency oscillation in this work is practically the same one reported in other studies with other techniques. (Author)

  11. Power system low frequency oscillation monitoring and analysis based on multi-signal online identification

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The advance in the wide-area measurement system (WAMS) is driving the power system to the trend of wide-area monitoring and control.The Prony method is usually used for low frequency oscillation online identification.However,the identified amplitude and phase information is not sufficiently used.In this paper,the amplitude is adopted to detect the occurrence of the oscillation and to obtain the mode observability of the sites.The phase is adopted to identify the oscillation generator grouping and to obtain the mode shapes.The time varying characteristics of low frequency oscillations are studied.The behaviors and the characters of low frequency oscillations are displayed by dynamic visual techniques.Demonstrations on the "11.9" low frequency oscillation of the Guizhou Power Grid substantiate the feasibility and the validation of the proposed methods.

  12. Cross-frequency coupling of brain oscillations in studying motivation and emotion

    OpenAIRE

    Schutter, Dennis J. L. G.; Knyazev, Gennady G.

    2011-01-01

    Research has shown that brain functions are realized by simultaneous oscillations in various frequency bands. In addition to examining oscillations in pre-specified bands, interactions and relations between the different frequency bandwidths is another important aspect that needs to be considered in unraveling the workings of the human brain and its functions. In this review we provide evidence that studying interdependencies between brain oscillations may be a valuable approach to study the ...

  13. Effect of section shape on frequencies of natural oscillations of tubular springs

    Science.gov (United States)

    Pirogov, S. P.; Chuba, A. Yu; Cherentsov, D. A.

    2018-05-01

    The necessity of determining the frequencies of natural oscillations of manometric tubular springs is substantiated. Based on the mathematical model and computer program, numerical experiments were performed that allowed us to reveal the effect of geometric parameters on the frequencies of free oscillations of manometric tubular springs.

  14. Cross-frequency coupling of brain oscillations in studying motivation and emotion

    NARCIS (Netherlands)

    Schutter, D.J.L.G.; Knyazev, G.G.

    2012-01-01

    Research has shown that brain functions are realized by simultaneous oscillations in various frequency bands. In addition to examining oscillations in pre-specified bands, interactions and relations between the different frequency bandwidths is another important aspect that needs to be considered in

  15. Frequency analysis of the 5.65-min oscillations in the rapidly oscillating Ap star HD 134214

    International Nuclear Information System (INIS)

    Kreidl, T.J.; Kurtz, D.W.

    1986-01-01

    High-speed photometric observations of HD 134214 obtained during 35 hr of observation in 1985 from Lowell Observatory and the South African Astronomical Observatory are presented. A frequency analysis of these data indicate the presence of only one frequency of oscillation in this star at f 1 = 2.94960 + - 0.00004 mHz. This is the highest frequency which is demonstrably not a harmonic of a lower frequency yet discovered in a rapidly oscillating Ap star. This frequency is above the critical frequency calculated for A star models by previous authors. The phase shift has been calculated for HD 134214 for simultaneous B and V observations obtained on three nights from Lowell Observatory. (author)

  16. Non-Axisymmetric Oscillation of Acoustically Levitated Water Drops at Specific Frequencies

    International Nuclear Information System (INIS)

    Chang-Le, Shen; Wen-Jun, Xie; Bing-Bo, Wei

    2010-01-01

    A category of non-axisymmetric oscillations of acoustically levitated water drops was observed. These oscillations can be qualitatively described by superposing a sectorial oscillating term upon the initial oblate shape resulting from the effect of acoustic radiation pressure. The oscillation frequencies are around 25 Hz for the 2-lobed mode and exactly 50 Hz for the 3- and 4-lobed modes. These oscillations were excited by the disturbance from the power supply. For the same water drop, higher mode oscillations were observed with more oblate initial shape, indicating that the eigenfrequencies of these non-axisymmetric oscillations decrease with increasing initial distortion. The maximum velocity and acceleration within the oscillating drop can attain 0.3m·s −1 and 98.7m·s −2 respectively, resulting in strong fluid convection and enhanced heat and mass transfer. (condensed matter: structure, mechanical and thermal properties)

  17. Cross-frequency coupling of brain oscillations in studying motivation and emotion.

    Science.gov (United States)

    Schutter, Dennis J L G; Knyazev, Gennady G

    2012-03-01

    Research has shown that brain functions are realized by simultaneous oscillations in various frequency bands. In addition to examining oscillations in pre-specified bands, interactions and relations between the different frequency bandwidths is another important aspect that needs to be considered in unraveling the workings of the human brain and its functions. In this review we provide evidence that studying interdependencies between brain oscillations may be a valuable approach to study the electrophysiological processes associated with motivation and emotional states. Studies will be presented showing that amplitude-amplitude coupling between delta-alpha and delta-beta oscillations varies as a function of state anxiety and approach-avoidance-related motivation, and that changes in the association between delta-beta oscillations can be observed following successful psychotherapy. Together these studies suggest that cross-frequency coupling of brain oscillations may contribute to expanding our understanding of the neural processes underlying motivation and emotion.

  18. Low frequency noise in resonant Josephson soliton oscillators

    DEFF Research Database (Denmark)

    Hansen, Jørn Bindslev; Holst, T.; Wellstood, Frederick C.

    1991-01-01

    The noise in the resonant soliton mode of long and narrow Josephson tunnel junctions (Josephson transmission lines or JTLs) have been measured in the frequency range from 0.1 Hz to 25 kHz by means of a DC SQUID. The measured white noise was found, to within a factor of two, to be equal...... to the Nyquist voltage noise in a resistance equal to the dynamic resistance RD of the current-voltage characteristic of the bias point. In contrast, measurements of the linewidth of the microwave radiation from the same JTL showed that the spectral density of the underlying noise voltage scaled as R D2/RS where...

  19. Self-excited nonlinear plasma series resonance oscillations in geometrically symmetric capacitively coupled radio frequency discharges

    International Nuclear Information System (INIS)

    Donko, Z.; Schulze, J.; Czarnetzki, U.; Luggenhoelscher, D.

    2009-01-01

    At low pressures, nonlinear self-excited plasma series resonance (PSR) oscillations are known to drastically enhance electron heating in geometrically asymmetric capacitively coupled radio frequency discharges by nonlinear electron resonance heating (NERH). Here we demonstrate via particle-in-cell simulations that high-frequency PSR oscillations can also be excited in geometrically symmetric discharges if the driving voltage waveform makes the discharge electrically asymmetric. This can be achieved by a dual-frequency (f+2f) excitation, when PSR oscillations and NERH are turned on and off depending on the electrical discharge asymmetry, controlled by the phase difference of the driving frequencies

  20. Twin peak high-frequency quasi-periodic oscillations as a spectral imprint of dual oscillation modes of accretion tori

    Science.gov (United States)

    Bakala, P.; Goluchová, K.; Török, G.; Šrámková, E.; Abramowicz, M. A.; Vincent, F. H.; Mazur, G. P.

    2015-09-01

    Context. High-frequency (millisecond) quasi-periodic oscillations (HF QPOs) are observed in the X-ray power-density spectra of several microquasars and low-mass X-ray binaries. Two distinct QPO peaks, so-called twin peak QPOs, are often detected simultaneously exhibiting their frequency ratio close or equal to 3:2. A widely discussed class of proposed QPOs models is based on oscillations of accretion toroidal structures orbiting in the close vicinity of black holes or neutron stars. Aims: Following the analytic theory and previous studies of observable spectral signatures, we aim to model the twin peak QPOs as a spectral imprint of specific dual oscillation regime defined by a combination of the lowest radial and vertical oscillation mode of slender tori. We consider the model of an optically thick slender accretion torus with constant specific angular momentum. We examined power spectra and fluorescent Kα iron line profiles for two different simulation setups with the mode frequency relations corresponding to the epicyclic resonance HF QPOs model and modified relativistic precession QPOs model. Methods: We used relativistic ray-tracing implemented in the parallel simulation code LSDplus. In the background of the Kerr spacetime geometry, we analyzed the influence of the distant observer inclination and the spin of the central compact object. Relativistic optical projection of the oscillating slender torus is illustrated by images in false colours related to the frequency shift. Results: We show that performed simulations yield power spectra with the pair of dominant peaks that correspond to the frequencies of radial and vertical oscillation modes and with the peak frequency ratio equal to the proper value 3:2 on a wide range of inclinations and spin values. We also discuss exceptional cases of a very low and very high inclination, as well as unstable high spin relativistic precession-like configurations that predict a constant frequency ratio equal to 1:2. We

  1. Low frequency steady-state brain responses modulate large scale functional networks in a frequency-specific means.

    Science.gov (United States)

    Wang, Yi-Feng; Long, Zhiliang; Cui, Qian; Liu, Feng; Jing, Xiu-Juan; Chen, Heng; Guo, Xiao-Nan; Yan, Jin H; Chen, Hua-Fu

    2016-01-01

    Neural oscillations are essential for brain functions. Research has suggested that the frequency of neural oscillations is lower for more integrative and remote communications. In this vein, some resting-state studies have suggested that large scale networks function in the very low frequency range (frequency characteristics of brain networks because both resting-state studies and conventional frequency tagging approaches cannot simultaneously capture multiple large scale networks in controllable cognitive activities. In this preliminary study, we aimed to examine whether large scale networks can be modulated by task-induced low frequency steady-state brain responses (lfSSBRs) in a frequency-specific pattern. In a revised attention network test, the lfSSBRs were evoked in the triple network system and sensory-motor system, indicating that large scale networks can be modulated in a frequency tagging way. Furthermore, the inter- and intranetwork synchronizations as well as coherence were increased at the fundamental frequency and the first harmonic rather than at other frequency bands, indicating a frequency-specific modulation of information communication. However, there was no difference among attention conditions, indicating that lfSSBRs modulate the general attention state much stronger than distinguishing attention conditions. This study provides insights into the advantage and mechanism of lfSSBRs. More importantly, it paves a new way to investigate frequency-specific large scale brain activities. © 2015 Wiley Periodicals, Inc.

  2. Testing Scaling Relations for Solar-like Oscillations from the Main Sequence to Red Giants Using Kepler Data

    DEFF Research Database (Denmark)

    Huber, D.; Bedding, T.R.; Stello, D.

    2011-01-01

    ), and oscillation amplitudes. We show that the difference of the Δν-νmax relation for unevolved and evolved stars can be explained by different distributions in effective temperature and stellar mass, in agreement with what is expected from scaling relations. For oscillation amplitudes, we show that neither (L/M) s......We have analyzed solar-like oscillations in ~1700 stars observed by the Kepler Mission, spanning from the main sequence to the red clump. Using evolutionary models, we test asteroseismic scaling relations for the frequency of maximum power (νmax), the large frequency separation (Δν...... scaling nor the revised scaling relation by Kjeldsen & Bedding is accurate for red-giant stars, and demonstrate that a revised scaling relation with a separate luminosity-mass dependence can be used to calculate amplitudes from the main sequence to red giants to a precision of ~25%. The residuals show...

  3. Constant Switching Frequency Self-Oscillating Controlled Class-D Amplifiers

    DEFF Research Database (Denmark)

    Nguyen-Duy, Khiem; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    The self-oscillating control approach has been used extensively in class-D amplifiers. It has several advantages such as high bandwidth and high audio performance. However, one of the primary disadvantages in a self-oscillating controlled system is that the switching frequency of the amplifier...... varies with the ratio of the output voltage to the input rail voltage. In other words, the switching frequency varies with the duty cycle of the output. The drop in the frequency results in lower control bandwidth and higher output voltage ripple, which are undesirable. This paper proposes a new self-oscillating...... control scheme that maintains a constant switching frequency over the full range of output voltage. The frequency difference is processed by a compensator whose output adjusts the total loop gain of the control system. It has been proven by simulation that a con-stant switching frequency self-oscillating...

  4. Investigation of switching frequency variations and EMI properties in self-oscillating class D amplifiers

    OpenAIRE

    Nielsen, Dennis; Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael A. E.

    2009-01-01

    Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in these amplifiers is self-oscillation. A parameter of key interest in self-oscillating amplifiers is the switching frequency, which is known for its variation. Knowledge of switching frequency variations is of great importance with respect to electromagnetic interference (EMI). This paper will investigate, whether the switching frequenc...

  5. Optical parametric amplification and oscillation assisted by low-frequency stimulated emission

    OpenAIRE

    Longhi, Stefano

    2016-01-01

    Optical parametric amplification/oscillation provide a powerful tool for coherent light generation in spectral regions inaccessible to lasers. Parametric gain is based on a frequency {\\it down-conversion} process, and thus it can not be realized for signal waves at a frequency $\\omega_3$ {\\it higher} than the frequency of the pump wave $\\omega_1$. In this work we suggest a route toward the realization of {\\it up-conversion} optical parametric amplification and oscillation, i.e. amplification ...

  6. Stimulus-dependent modulation of spontaneous low-frequency oscillations in the rat visual cortex.

    Science.gov (United States)

    Huang, Liangming; Liu, Yadong; Gui, Jianjun; Li, Ming; Hu, Dewen

    2014-08-06

    Research on spontaneous low-frequency oscillations is important to reveal underlying regulatory mechanisms in the brain. The mechanism for the stimulus modulation of low-frequency oscillations is not known. Here, we used the intrinsic optical imaging technique to examine stimulus-modulated low-frequency oscillation signals in the rat visual cortex. The stimulation was presented monocularly as a flashing light with different frequencies and intensities. The phases of low-frequency oscillations in different regions tended to be synchronized and the rhythms typically accelerated within a 30-s period after stimulation. These phenomena were confined to visual stimuli with specific flashing frequencies (12.5-17.5 Hz) and intensities (5-10 mA). The acceleration and synchronization induced by the flashing frequency were more marked than those induced by the intensity. These results show that spontaneous low-frequency oscillations can be modulated by parameter-dependent flashing lights and indicate the potential utility of the visual stimulus paradigm in exploring the origin and function of low-frequency oscillations.

  7. Wind/PV Generation for Frequency Regulation and Oscillation Damping in the Eastern Interconnection

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yong [Univ. of Tennessee, Knoxville, TN (United States); Gracia, Jose R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hadley, Stanton W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Yilu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2013-12-01

    This report presents the control of renewable energy sources, including the variable-speed wind generators and solar photovoltaic (PV) generators, for frequency regulation and inter-area oscillation damping in the U.S. Eastern Interconnection (EI). In this report, based on the user-defined wind/PV generator electrical control model and the 16,000-bus Eastern Interconnection dynamic model, the additional controllers for frequency regulation and inter-area oscillation damping are developed and incorporated and the potential contributions of renewable energy sources to the EI system frequency regulation and inter-area oscillation damping are evaluated.

  8. Modulation of low-frequency oscillations in GaAs MESFETs' channel current by sidegating bias

    Institute of Scientific and Technical Information of China (English)

    DING Yong; LU Shengli; ZHAO Fuchuan

    2005-01-01

    Low-frequency oscillations in channel current are usually observed when measuring the GaAs MESFET's output characteristics. This paper studies the oscillations by testing the MESFET's output characteristics under different sidegate bias conditions. It is shown that the low-frequency oscillations of channel current are directly related to the sidegate bias. In other words, the sidegate bias can modulate the oscillations. Whether the sidegate bias varies positively or negatively, there will inevitably be a threshold voltage after which the low-frequency oscillations disappear. The observation is strongly dependent upon the peculiarities of channel-substrate (C-S) junction and impact ionization of traps-EL2 under high field. This conclusion is of particular pertinence to the design of low-noise GaAs IC's.

  9. Oscillation mode frequencies of 61 main-sequence and subgiant stars observed by Kepler

    DEFF Research Database (Denmark)

    Appourchaux, T.; Chaplin, W. J.; García, R. A.

    2012-01-01

    Solar-like oscillations have been observed by Kepler and CoRoT in several solar-type stars, thereby providing a way to probe the stars using asteroseismology Aims. We provide the mode frequencies of the oscillations of various stars required to perform a comparison with those obtained from stella...

  10. Clustering of Cochlear Oscillations in Frequency Plateaus as a Tool to Investigate SOAE Generation

    DEFF Research Database (Denmark)

    Epp, Bastian; Wit, Hero; van Dijk, Pim

    2016-01-01

    of coupled oscillators (OAM) [7] are also found in a transmission line model (TLM) which is able to generate realistic SOAEs [2] and if these frequency plateaus can be used to explain the formation of SOAEs. The simulations showed a clustering of oscillators along the simulated basilar membrane Both, the OAM...

  11. Investigation of switching frequency variations and EMI properties in self-oscillating class D amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Knott, Arnold; Pfaffinger, Gerhard

    2009-01-01

    Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in these amplifiers is self-oscillation. A parameter of key interest in self-oscillating amplifiers is the switching frequency, which is kno...

  12. Low and high frequency Madden-Julian oscillations in austral summer: interannual variations

    Energy Technology Data Exchange (ETDEWEB)

    Izumo, Takeshi [Research Institute For Global Change (JAMSTEC), Yokohama (Japan); LOCEAN, IRD-CNRS-UPMC, Paris (France); Masson, Sebastien; Vialard, Jerome; Madec, Gurvan [LOCEAN, IRD-CNRS-UPMC, Paris (France); Boyer Montegut, Clement de [IFREMER, Brest (France); Behera, Swadhin K. [Research Institute For Global Change (JAMSTEC), Yokohama (Japan); Takahashi, Keiko [Earth Simulator Center (JAMSTEC), Yokohama (Japan); Yamagata, Toshio [Research Institute For Global Change (JAMSTEC), Yokohama (Japan); University of Tokyo, Tokyo (Japan)

    2010-09-15

    The Madden-Julian oscillation (MJO) is the main component of intraseasonal variability of the tropical convection, with clear climatic impacts at an almost-global scale. Based on satellite observations, it is shown that there are two types of austral-summer MJO events (broadly defined as 30-120 days convective variability with eastward propagation of about 5 m/s). Equatorial MJO events have a period of 30-50 days and tend to be symmetric about the equator, whereas MJO events centered near 8 S tend to have a longer period of 55-100 days. The lower-frequency variability is associated with a strong upper-ocean response, having a clear signature in both sea surface temperature and its diurnal cycle. These two MJO types have different interannual variations, and are modulated by the Indian Ocean Dipole (IOD). Following a negative IOD event, the lower-frequency southern MJO variability increases, while the higher-frequency equatorial MJO strongly diminishes. We propose two possible explanations for this change in properties of the MJO. One possibility is that changes in the background atmospheric circulation after an IOD favour the development of the low-frequency MJO. The other possibility is that the shallower thermocline ridge and mixed layer depth, by enhancing SST intraseasonal variability and thus ocean-atmosphere coupling in the southwest Indian Ocean (the breeding ground of southern MJO onset), favour the lower-frequency southern MJO variability. (orig.)

  13. 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.

  14. Changes in frequency of spontaneous oscillations in procerebrum correlate to behavioural choice in terrestrial snails

    Directory of Open Access Journals (Sweden)

    Elena Samarova

    2009-08-01

    Full Text Available The aim of our study was to understand functional significance of spontaneous oscillations of local field potential in the olfactory brain lobe of terrestrial snail, the procerebrum (PC. We compared changes in frequency of oscillations in semi-intact preparations from snails trained to percept the same conditioned odor as positive (associated with food reinforcement or negative (associated with noxious reinforcement. In vivo recordings in freely behaving naïve snails showed a significant decrease of spontaneous PC oscillations frequency during a stage of tentacle withdrawal to odor presentation. In in vitro preparations from naïve snails, a similar decrease in frequency of the PC oscillations to odor presentation was observed. Changes in frequency of the oscillations to cineole presentations in the “aversive” group of snails (demonstrating withdrawal were much more pronounced than in naïve snails. No significant difference in responses to 5 and 20% cineole was noted. Changes in the spontaneous oscillations frequency in the snails trained to respond with positive reaction (approach to cineole depended on the concentration of the applied odor, and these responses were qualitatively similar to responses of other groups during the first 10 s of responses to odor, but significantly different (increase in PC oscillations frequency from the responses of the aversively trained and naïve snails in the interval 11-30 s, which corresponds to the end of the tentacle withdrawal and timing of decision making (approach or escape in the free behaving snails. Obtained results suggest that frequency of the PC lobe spontaneous oscillations correlate to the choice of behavior in snails: withdrawal (decrease in frequency or approach (increase in frequency to the source of odor.

  15. Synchronously Pumped Optical Parametric Oscillator with Intracavity Difference Frequency Mixing

    Science.gov (United States)

    1998-06-29

    departing from the Rrpubbc of Panama when traveling on official orders." * " De eonfortnidad con el Parrafo 5u) del Articulo XVII del Acuerdo para U...isotopic photochemistry using an optical parametric oscillator and a down converter," J. Opt. ( Paris ), , no. 14, pp. 43-48, 1983. [4] J. D. Kafka, M. L...isotopic photochemistry using an optical parametric oscillator and a down converter," J. Opt. ( Paris ), , no. 14, pp. 43-48, 1983. [4] J. D. Kafka, M. L

  16. Analysis of Power System Low Frequency Oscillation Based on Energy Shift Theory

    Science.gov (United States)

    Zhang, Junfeng; Zhang, Chunwang; Ma, Daqing

    2018-01-01

    In this paper, a new method for analyzing low-frequency oscillation between analytic areas based on energy coefficient is proposed. The concept of energy coefficient is proposed by constructing the energy function, and the low-frequency oscillation is analyzed according to the energy coefficient under the current operating conditions; meanwhile, the concept of model energy is proposed to analyze the energy exchange behavior between two generators. Not only does this method provide an explanation of low-frequency oscillation from the energy point of view, but also it helps further reveal the dynamic behavior of complex power systems. The case analysis of four-machine two-area and the power system of Jilin Power Grid proves the correctness and effectiveness of the proposed method in low-frequency oscillation analysis of power system.

  17. Optical parametric amplification and oscillation assisted by low-frequency stimulated emission.

    Science.gov (United States)

    Longhi, Stefano

    2016-04-15

    Optical parametric amplification and oscillation provide powerful tools for coherent light generation in spectral regions inaccessible to lasers. Parametric gain is based on a frequency down-conversion process and, thus, it cannot be realized for signal waves at a frequency ω3 higher than the frequency of the pump wave ω1. In this Letter, we suggest a route toward the realization of upconversion optical parametric amplification and oscillation, i.e., amplification of the signal wave by a coherent pump wave of lower frequency, assisted by stimulated emission of the auxiliary idler wave. When the signal field is resonated in an optical cavity, parametric oscillation is obtained. Design parameters for the observation of upconversion optical parametric oscillation at λ3=465 nm are given for a periodically poled lithium-niobate (PPLN) crystal doped with Nd(3+) ions.

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

    DEFF Research Database (Denmark)

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

    2013-01-01

    interconnection network between the switches which provides self-oscillating and interleaved operation. A design approach to ensure zero voltage switching (ZVS) condition of the MOSFET devices is provided. To verify the proposed method, an 11 W, 50 MHz prototype was built using low-cost VDMOS devices...

  19. Investigation of switching frequency variations in self-oscillating class D amplifiers

    OpenAIRE

    Nielsen, Dennis; Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael A. E.

    2009-01-01

    Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in class D amplifiers is known as self-oscillation. An parameter of key interest in self-oscillating class D amplifiers is the switching frequency, which can be directly related to the performance of the amplifier. This paper will clearify the myth of the switching frequency through investigation of its dependency on modulation index and ...

  20. Stereotyped high-frequency oscillations discriminate seizure onset zones and critical functional cortex in focal epilepsy.

    Science.gov (United States)

    Liu, Su; Gurses, Candan; Sha, Zhiyi; Quach, Michael M; Sencer, Altay; Bebek, Nerses; Curry, Daniel J; Prabhu, Sujit; Tummala, Sudhakar; Henry, Thomas R; Ince, Nuri F

    2018-01-30

    High-frequency oscillations in local field potentials recorded with intracranial EEG are putative biomarkers of seizure onset zones in epileptic brain. However, localized 80-500 Hz oscillations can also be recorded from normal and non-epileptic cerebral structures. When defined only by rate or frequency, physiological high-frequency oscillations are indistinguishable from pathological ones, which limit their application in epilepsy presurgical planning. We hypothesized that pathological high-frequency oscillations occur in a repetitive fashion with a similar waveform morphology that specifically indicates seizure onset zones. We investigated the waveform patterns of automatically detected high-frequency oscillations in 13 epilepsy patients and five control subjects, with an average of 73 subdural and intracerebral electrodes recorded per patient. The repetitive oscillatory waveforms were identified by using a pipeline of unsupervised machine learning techniques and were then correlated with independently clinician-defined seizure onset zones. Consistently in all patients, the stereotypical high-frequency oscillations with the highest degree of waveform similarity were localized within the seizure onset zones only, whereas the channels generating high-frequency oscillations embedded in random waveforms were found in the functional regions independent from the epileptogenic locations. The repetitive waveform pattern was more evident in fast ripples compared to ripples, suggesting a potential association between waveform repetition and the underlying pathological network. Our findings provided a new tool for the interpretation of pathological high-frequency oscillations that can be efficiently applied to distinguish seizure onset zones from functionally important sites, which is a critical step towards the translation of these signature events into valid clinical biomarkers.awx374media15721572971001. © The Author(s) (2018). Published by Oxford University Press on

  1. Solid state Ka-band pulse oscillator with frequency electronic switching

    Directory of Open Access Journals (Sweden)

    Dvornichenko V. P.

    2015-08-01

    Full Text Available Transmitting devices for small radars in the millimeter wavelength range with high resolution on range and noise immunity. The work presents the results of research and development of compact pulse oscillators with digital frequency switching from pulse to pulse. The oscillator consists of a frequency synthesizer and a synchronized amplifier on the IMPATT diode. Reference oscillator of synthesizer is synchronized by crystal oscillator with digital PLL system and contains a frequency multiplier and an amplifier operating in pulse mode. Small-sized frequency synthesizer of 8 mm wave lengths provides an output power of ~1.2 W per pulse with a frequency stability of no worse than 2•10–6. Radiation frequency is controlled by three-digit binary code in OOL levels. Synchronized amplifier made on IMPATT diodes provides microwave power up to 20 W in oscillator output with microwave pulse duration of 100—300 ns in an operating band. The oscillator can be used as a driving source for the synchronization of semiconductor and electro-vacuum devices of pulsed mode, and also as a transmitting device for small-sized radar of millimeter wave range.

  2. Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

    International Nuclear Information System (INIS)

    Huang, Houbing; Zhao, Congpeng; Ma, Xingqiao

    2017-01-01

    We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

  3. Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Houbing, E-mail: hbhuang@ustb.edu.cn; Zhao, Congpeng; Ma, Xingqiao, E-mail: xqma@sas.ustb.edu.cn

    2017-03-15

    We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

  4. Oscillations and Stability of Plasma in an External High-Frequency Electric Field

    International Nuclear Information System (INIS)

    Aliev, Ju.M.; Gorbunov, L.M.; Silin, V.P.; Uotson, H.

    1966-01-01

    A theory is developed for the oscillations and stability of plasma in a strong external HF electric field. The kinetic equation with self-congruent reciprocity is linearized for weak deviations from the ground state. Since the latter depends on an external HF field, the linearized equation obtained has coefficients with a periodic time dependence. From this equation and also from Maxwell's equations there is derived a dispersion equation for plasma oscillations that represents the zero value of the infinite order determinant, and that is solved both for external field frequencies considerably exceeding the electron Langmuir frequency and for frequencies that are less. The external HF field changes the oscillation branches in a plasma without an external field, and also leads to a new low-frequency oscillation branch. Movement of particles in the HF field gives spatial dispersion. If the frequency of the field exceeds the election Langmuir frequency, the plasma oscillations are stable. At frequencies less than this level there occurs a build-up of low-frequency oscillations. Here the maximum of the build-up occurs when the external field frequencies approach the electron Langmuir frequency and is equal to the product of the Langmuir frequency and the one-third power of the electron-ion mass ratio. Away from the resonance, -the increment of build-up has the same order of magnitude as the ion Langmuir frequency. An external magnetic field increases the number of possible natural plasma oscillations and thereby increases the possibility of resonance with the external HF field. Allowance for the thermal motion of the particles enables one to determine the attenuation of the oscillations in question. Expressions for the decrements are derived. The effect of the external HF field on a plasma in which there are beams is also discussed. An HF field has a destabilizing effect on a system of this kind, since on the one hand there can be a build-up of fresh, low-frequency

  5. Microbubble generator excited by fluidic oscillator's third harmonic frequency

    Czech Academy of Sciences Publication Activity Database

    Tesař, Václav

    2014-01-01

    Roč. 92, č. 9 (2014), s. 1603-1615 ISSN 0263-8762 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : fluidic oscillator * microbubble generation * fluidic feedback loop Subject RIV: BK - Fluid Dynamics Impact factor: 2.348, year: 2014 http://dx.doi.org/10.1016/j.cherd.2013.12.004

  6. Parametric and scaling studies of condensation oscillation in subcooled water of the in-containment refueling water storage tank

    International Nuclear Information System (INIS)

    Lee, Jun Hyung; No, Hee Cheon

    1999-01-01

    Condensation oscillation by jetting the steam into subcooled water through spargers is studied. To provide a suitable guideline for oscillation phenomena in the IRWST of the next generation reactor, scaling methodology is introduced. Through scaling methodology and subsequent tests, it shows that the volume of steam cavity determines the dynamic characteristics of condensation oscillation. The second-order linear differential equation for frequency analysis is derived and its results are compared with those from the test data. Two types of condensation phenomena exist according to steam flow rates. At subsonic jet, condensation interface becomes irregular in shape and upper system volumes affect the dynamic characteristics of condensation oscillation. At sonic jet, a regular steam cavity forms at the exit of discharge holes. Parametric effects and subsequent dynamic responses of the pool tank are investigated through experiments in applicable test ranges. When the temperature of pool water becomes lower, the amplitude becomes larger. Critical parameters are derived from the scaling methodology and are system volume, cavity volume, discharge hole area, and density ration. It is found that system friction factors affect frequency components of condensation oscillation. Oscillations of a steam cavity occur mainly on the face of the axial direction and pressure amplitudes become larger than that of the lateral direction

  7. Design and construction of an oscillator with a higly stable frequency

    International Nuclear Information System (INIS)

    Jardon, A.H.

    1978-01-01

    An instrument producing pulses with a highly stable frequency was considered necessary for time measurement at the INEN Plasma Physics Program. For this purpose an oscillator with a higly stable frequency which is a measurement instrument was designed and constructed since it can be used as a reference for the measurement of frequency, time, length and phase. The parameters required for this oscillator were as follows: aging lesser than 1 part/10 9 , for sampling period of 0.1 sec.; frequency change equal or smaller than 1 part/10 9 for normal temperature fluctuations found in the laboratory (10 0 C-30 0 C); frequency 1 MHz; amplitude 2 V. After the oscillator was built the parameters were not verified and therefore its characteristics are not exactly known; the reported partial results show that the approximations used for the design are generally valid. (author)

  8. Frequency-dependent transient response of an oscillating electrically actuated droplet

    International Nuclear Information System (INIS)

    Dash, S; Kumari, N; Garimella, S V

    2012-01-01

    The transient response of a millimeter-sized sessile droplet under electrical actuation is experimentally investigated. Under dc actuation, the droplet spreading rate increases as the applied voltage is increased due to the higher electrical forces induced. At sufficiently high dc voltages, competition between the electrical actuation force, droplet inertia, the retarding surface tension force and contact line friction leads to droplet oscillation. The timescale for the droplet to attain its maximum wetted diameter during step actuation is analyzed. Systematic experiments are conducted over a frequency range of 5–200 Hz and actuation voltages of 40–80 V rms to determine the dependence of droplet oscillation on these parameters. The response of the droplet to different actuation frequencies and voltages is determined in terms of its contact angle and contact radius variation. The frequency of the driving force (equal to twice the frequency of the applied electrical signal) determines the mode of oscillation of the droplet which, together with its resonance characteristics, governs whether the droplet contact angle and contact radius vary in phase or out of phase with each other. In addition to the primary frequency response at the electrical forcing frequency, the droplet oscillation exhibits sub-harmonic oscillation at half of the forcing frequency that is attributed to the parametric nature of the electrical force acting on the triple contact line of the droplet. (paper)

  9. 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.

  10. 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

    2016-01-01

    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. PMID:27482084

  11. Nonreciprocity in the dynamics of coupled oscillators with nonlinearity, asymmetry, and scale hierarchy

    Science.gov (United States)

    Moore, Keegan J.; Bunyan, Jonathan; Tawfick, Sameh; Gendelman, Oleg V.; Li, Shuangbao; Leamy, Michael; Vakakis, Alexander F.

    2018-01-01

    In linear time-invariant dynamical and acoustical systems, reciprocity holds by the Onsager-Casimir principle of microscopic reversibility, and this can be broken only by odd external biases, nonlinearities, or time-dependent properties. A concept is proposed in this work for breaking dynamic reciprocity based on irreversible nonlinear energy transfers from large to small scales in a system with nonlinear hierarchical internal structure, asymmetry, and intentional strong stiffness nonlinearity. The resulting nonreciprocal large-to-small scale energy transfers mimic analogous nonlinear energy transfer cascades that occur in nature (e.g., in turbulent flows), and are caused by the strong frequency-energy dependence of the essentially nonlinear small-scale components of the system considered. The theoretical part of this work is mainly based on action-angle transformations, followed by direct numerical simulations of the resulting system of nonlinear coupled oscillators. The experimental part considers a system with two scales—a linear large-scale oscillator coupled to a small scale by a nonlinear spring—and validates the theoretical findings demonstrating nonreciprocal large-to-small scale energy transfer. The proposed study promotes a paradigm for designing nonreciprocal acoustic materials harnessing strong nonlinearity, which in a future application will be implemented in designing lattices incorporating nonlinear hierarchical internal structures, asymmetry, and scale mixing.

  12. Non-linear frequency and amplitude modulation of a nano-contact spin torque oscillator

    OpenAIRE

    Muduli, P. K.; Pogoryelov, Ye.; Bonetti, S.; Consolo, G.; Mancoff, Fred; Åkerman, Johan

    2009-01-01

    We study the current controlled modulation of a nano-contact spin torque oscillator. Three principally different cases of frequency non-linearity ($d^{2}f/dI^{2}_{dc}$ being zero, positive, and negative) are investigated. Standard non-linear frequency modulation theory is able to accurately describe the frequency shifts during modulation. However, the power of the modulated sidebands only agrees with calculations based on a recent theory of combined non-linear frequency and amplitude modulation.

  13. On the surface physics affecting solar oscillation frequencies

    DEFF Research Database (Denmark)

    Houdek, G.; Trampedach, R.; Aarslev, M. J.

    2017-01-01

    . In this Letter, we address the physical processes of turbulent convection that are predominantly responsible for the frequency differences between standard models and observations, also called 'surface effects'. We compare measured solar frequencies from the Michelson Doppler Imager instrument on the SOlar...... physics in our model computation, we are able to reproduce the observed solar frequencies to less than or similar to 3 mu Hz without the need of any additional ad hoc functional corrections....

  14. High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

    International Nuclear Information System (INIS)

    Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Danilovic, S.; Stangalini, M.; Steiner, O.

    2017-01-01

    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, 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.

  15. Constant Switching Frequency Self-Oscillating Controlled Class-D Amplifiers

    OpenAIRE

    Nguyen-Duy, Khiem; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    The self-oscillating control approach has been used extensively in class-D amplifiers. It has several advantages such as high bandwidth and high audio performance. However, one of the primary disadvantages in a self-oscillating controlled system is that the switching frequency of the amplifier varies with the ratio of the output voltage to the input rail voltage. In other words, the switching frequency varies with the duty cycle of the output. The drop in the frequency results in lower contro...

  16. Internal oscillation frequencies and anharmonic effects for the double sine-Gordon kink

    DEFF Research Database (Denmark)

    Salerno, M.; Samuelsen, Mogens Rugholm

    1989-01-01

    A simple derivation of the small oscillation frequency around 4π-kink solutions of the double sine-Gordon equation is presented. Small corrections to these frequencies due to anharmonic effects are also numerically and analytically investigated. The analysis is based on energetic considerations...

  17. High frequency spin torque oscillators with composite free layer spin valve

    International Nuclear Information System (INIS)

    Natarajan, Kanimozhi; Arumugam, Brinda; Rajamani, Amuda

    2016-01-01

    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.

  18. 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.

  19. Minimization of switching frequency oscillation of voltage inverter

    Czech Academy of Sciences Publication Activity Database

    Večerka, Tomáš

    2011-01-01

    Roč. 56, č. 2 (2011), s. 125-140 ISSN 0001-7043 Institutional research plan: CEZ:AV0Z20570509 Keywords : switching frequency * pulse-width modulation * induction motors Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  20. Frequency scaling of linear super-colliders

    International Nuclear Information System (INIS)

    Mondelli, A.; Chernin, D.; Drobot, A.; Reiser, M.; Granatstein, V.

    1986-06-01

    The development of electron-positron linear colliders in the TeV energy range will be facilitated by the development of high-power rf sources at frequencies above 2856 MHz. Present S-band technology, represented by the SLC, would require a length in excess of 50 km per linac to accelerate particles to energies above 1 TeV. By raising the rf driving frequency, the rf breakdown limit is increased, thereby allowing the length of the accelerators to be reduced. Currently available rf power sources set the realizable gradient limit in an rf linac at frequencies above S-band. This paper presents a model for the frequency scaling of linear colliders, with luminosity scaled in proportion to the square of the center-of-mass energy. Since wakefield effects are the dominant deleterious effect, a separate single-bunch simulation model is described which calculates the evolution of the beam bunch with specified wakefields, including the effects of using programmed phase positioning and Landau damping. The results presented here have been obtained for a SLAC structure, scaled in proportion to wavelength

  1. Characteristics of low-frequency oscillation intensity of air-sea turbulent heat fluxes over the northwest Pacific

    Institute of Scientific and Technical Information of China (English)

    LI Gen; REN BaoHua; ZHENG JianOiu; WANG Jun

    2009-01-01

    Based on the daily turbulent heat fluxes and related meteorological variables dataeets (1985-2006) from Objectively Analyzed air-sea Fluxes (OAFlux) Project of Woods Hole Oceanographic Institution (WHOI), characteristics of low-frequency oscillation intensity of air-sea turbulent heat fluxes over the northwest Pacific are analyzed by linear perturbation method and correlation analysis. It can be concluded that: 1) the distribution of low-frequency oscillation intensity of latent heat flux (LHF) over the northwest Pacific is mainly affected by that of low-frequency oscillation intensity of anomalous air-eea humidity gradient (△q') as well as mean air-eea humidity gradient (△q), while the distribution of low-frequency oscillation Intensity of sensible heat flux (SHF) is mainly affected by that of low-frequency oscillation intensity of anomalous air-sea temperature gradient (△T'). 2) The low-frequency oscillation of turbulent heat fluxes over the northwest Pacific is the strongest in winter and the weakest in summer. And the seasonal transition of low-frequency oscillation intensity of LHF is jointly influenced by those of low-frequency oscillation intensity of △q', low-frequency oscillation intensity of anomalous wind speed (U'), △q and mean wind speed (U), while the seasonal transition of low-frequency oscillation intensity of SHF is mainly influenced by those of low-frequency oscillation Intensity of △T' and U. 3) Over the tropical west Pacific and sea areas north of 20ON, the low-frequency oscillation of LHF (SHF) is mainly influenced by atmospheric variables qa' (Ta') and U', indicating an oceanic response to overlying atmospheric forcing. In contrast, over the tropical eastern and central Pacific south of 20°N, qs' (Ts') also greatly influences the low-frequency oscillation of LHF (SHF).

  2. Streaming Velocities and the Baryon Acoustic Oscillation Scale.

    Science.gov (United States)

    Blazek, Jonathan A; McEwen, Joseph E; Hirata, Christopher M

    2016-03-25

    At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the baryon acoustic oscillation (BAO) peak is dramatically enhanced (by a factor of ∼5) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation.

  3. Dependence of Helium II viscosity properties on oscillation frequency

    International Nuclear Information System (INIS)

    Nadirashvili, Z.S.; Tsakadze, J.S.

    1979-01-01

    The causes of a discrepancy in the results of measurements of He II viscosity below Tapprox. =1.6 K obtained with different measurement methods are investigated. It is shown that to obtain correct results in oscillation experiments, the condition delta>>lambda/sub ph/ should obtain, where delta is the depth of viscous wave penetration and lambda/sub ph/ is the phonon free path length. Results of viscosity measurements at different ratios delta/lambda/sub ph/ (by a wire viscometer) are presented. It is shown that for the condition delta>>lambda/sub ph/, the results obtained are in good agreement with the results of Andronikashvili (in which delta/lambda/sub ph/>100). If the mentioned relation is not satisfied, then as the value of the ratio delta/lambda/sub ph/ is decreased, the value measured for the viscosity is increasingly lower than the results of Andronikashvili

  4. Effects of dendritic load on the firing frequency of oscillating neurons.

    Science.gov (United States)

    Schwemmer, Michael A; Lewis, Timothy J

    2011-03-01

    We study the effects of passive dendritic properties on the dynamics of neuronal oscillators. We find that the addition of a passive dendrite can sometimes have counterintuitive effects on firing frequency. Specifically, the addition of a hyperpolarized passive dendritic load can either increase, decrease, or have negligible effects on firing frequency. We use the theory of weak coupling to derive phase equations for "ball-and-stick" model neurons and two-compartment model neurons. We then develop a framework for understanding how the addition of passive dendrites modulates the frequency of neuronal oscillators. We show that the average value of the neuronal oscillator's phase response curves measures the sensitivity of the neuron's firing rate to the dendritic load, including whether the addition of the dendrite causes an increase or decrease in firing frequency. We interpret this finding in terms of to the slope of the neuronal oscillator's frequency-applied current curve. We also show that equivalent results exist for constant and noisy point-source input to the dendrite. We note that the results are not specific to neurons but are applicable to any oscillator subject to a passive load.

  5. Aperture scaling effects with monolithic periodically poled lithium niobate optical parametric oscillators and generators.

    Science.gov (United States)

    Missey, M; Dominic, V; Powers, P; Schepler, K L

    2000-02-15

    We used elliptical beams to demonstrate aperture scaling effects in nanosecond single-grating and multigrating periodically poled lithium niobate (PPLN) monolithic optical parametric oscillators and generators. Increasing the cavity Fresnel number in single-grating crystals broadened both the beam divergence and the spectral bandwidth. Both effects are explained in terms of the phase-matching geometry. These effects are suppressed when a multigrating PPLN crystal is used because the individual gratings provide small effective subapertures. A flood-pumped multigrating optical parametric generator displayed a low output beam divergence and contained 19 pairs of signal and idler frequencies.

  6. Dendritic calcium conductances generate high-frequency oscillation in thalamocortical neurons

    OpenAIRE

    Pedroarena, Christine; Llinás, Rodolfo

    1997-01-01

    Cortical-projecting thalamic neurons, in guinea pig brain slices, display high-frequency membrane potential oscillations (20–80 Hz), when their somata are depolarized beyond −45 mV. These oscillations, preferentially located at dendritic sites, are supported by the activation of P/Q type calcium channels, as opposed to the expected persistent sodium conductance responsible for such rhythmic behavior in other central neurons. Short hyperpolarizing pulses reset the phase and transiently increas...

  7. Relaxation oscillations induced by amplitude-dependent frequency in dissipative trapped electron mode turbulence

    International Nuclear Information System (INIS)

    Terry, P.W.; Ware, A.S.; Newman, D.E.

    1994-01-01

    A nonlinear frequency shift in dissipative trapped electron mode turbulence is shown to give rise to a relaxation oscillation in the saturated power density spectrum. A simple non-Markovian closure for the coupled evolution of ion momentum and electron density response is developed to describe the oscillations. From solutions of a nonlinear oscillator model based on the closure, it is found that the oscillation is driven by the growth rate, as modified by the amplitude-dependent frequency shift, with inertia provided by the memory of the growth rate of prior amplitudes. This memory arises from time-history integrals common to statistical closures. The memory associated with a finite time of energy transfer between coupled spectrum components does not sustain the oscillation in the simple model. Solutions of the model agree qualitatively with the time-dependent numerical solutions of the original dissipative trapped electron model, yielding oscillations with the proper phase relationship between the fluctuation energy and the frequency shift, the proper evolution of the wave number spectrum shape and particle flux, and a realistic period

  8. Voluntary reduction of force variability via modulation of low-frequency oscillations.

    Science.gov (United States)

    Park, Seoung Hoon; Casamento-Moran, Agostina; Yacoubi, Basma; Christou, Evangelos A

    2017-09-01

    Visual feedback can influence the force output by changing the power in frequencies below 1 Hz. However, it remains unknown whether visual guidance can help an individual reduce force variability voluntarily. The purpose of this study, therefore, was to determine whether an individual can voluntarily reduce force variability during constant contractions with visual guidance, and whether this reduction is associated with a decrease in the power of low-frequency oscillations (0-1 Hz) in force and muscle activity. Twenty young adults (27.6 ± 3.4 years) matched a force target of 15% MVC (maximal voluntary contraction) with ankle dorsiflexion. Participants performed six visually unrestricted contractions, from which we selected the trial with the least variability. Following, participants performed six visually guided contractions and were encouraged to reduce their force variability within two guidelines (±1 SD of the least variable unrestricted trial). Participants decreased the SD of force by 45% (P  0.2). The decrease in force variability was associated with decreased low-frequency oscillations (0-1 Hz) in force (R 2  = 0.59), which was associated with decreased low-frequency oscillations in EMG bursts (R 2  = 0.35). The reduction in low-frequency oscillations in EMG burst was positively associated with power in the interference EMG from 35 to 60 Hz (R 2  = 0.47). In conclusion, voluntary reduction of force variability is associated with decreased low-frequency oscillations in EMG bursts and consequently force output. We provide novel evidence that visual guidance allows healthy young adults to reduce force variability voluntarily likely by adjusting the low-frequency oscillations in the neural drive.

  9. Dynamic modulation of epileptic high frequency oscillations by the phase of slower cortical rhythms.

    Science.gov (United States)

    Ibrahim, George M; Wong, Simeon M; Anderson, Ryan A; Singh-Cadieux, Gabrielle; Akiyama, Tomoyuki; Ochi, Ayako; Otsubo, Hiroshi; Okanishi, Tohru; Valiante, Taufik A; Donner, Elizabeth; Rutka, James T; Snead, O Carter; Doesburg, Sam M

    2014-01-01

    Pathological high frequency oscillations (pHFOs) have been proposed to be robust markers of epileptic cortex. Oscillatory activity below this frequency range has been shown to be modulated by phase of lower frequency oscillations. Here, we tested the hypothesis that dynamic cross-frequency interactions involving pHFOs are concentrated within the epileptogenic cortex. Intracranial electroencephalographic recordings from 17 children with medically-intractable epilepsy secondary to focal cortical dysplasia were obtained. A time-resolved analysis was performed to determine topographic concentrations and dynamic changes in cross-frequency amplitude-to-phase coupling (CFC). CFC between pHFOs and the phase of theta and alpha rhythms was found to be significantly elevated in the seizure-onset zone compared to non-epileptic regions (pfrequency oscillations at which pHFO amplitudes were maximal was inconsistent at seizure initiation, yet consistently at the trough of the low frequency rhythm at seizure termination. Amplitudes of pHFOs were most significantly modulated by the phase of alpha-band oscillations (p<0.01). These results suggest that increased CFC between pHFO amplitude and alpha phase may constitute a marker of epileptogenic brain areas and may be relevant for understanding seizure dynamics. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. TESTING SCALING RELATIONS FOR SOLAR-LIKE OSCILLATIONS FROM THE MAIN SEQUENCE TO RED GIANTS USING KEPLER DATA

    Energy Technology Data Exchange (ETDEWEB)

    Huber, D.; Bedding, T. R.; Stello, D. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Hekker, S. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Mathur, S. [High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); Mosser, B. [LESIA, CNRS, Universite Pierre et Marie Curie, Universite Denis, Diderot, Observatoire de Paris, 92195 Meudon cedex (France); Verner, G. A.; Elsworth, Y. P.; Hale, S. J.; Chaplin, W. J. [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom); Bonanno, A. [INAF Osservatorio Astrofisico di Catania (Italy); Buzasi, D. L. [Eureka Scientific, 2452 Delmer Street Suite 100, Oakland, CA 94602-3017 (United States); Campante, T. L. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Kallinger, T. [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Silva Aguirre, V. [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching (Germany); De Ridder, J. [Instituut voor Sterrenkunde, K.U.Leuven (Belgium); Garcia, R. A. [Laboratoire AIM, CEA/DSM-CNRS, Universite Paris 7 Diderot, IRFU/SAp, Centre de Saclay, 91191, Gif-sur-Yvette (France); Appourchaux, T. [Institut d' Astrophysique Spatiale, UMR 8617, Universite Paris Sud, 91405 Orsay Cedex (France); Frandsen, S. [Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Houdek, G., E-mail: dhuber@physics.usyd.edu.au [Institute of Astronomy, University of Vienna, 1180 Vienna (Austria); and others

    2011-12-20

    We have analyzed solar-like oscillations in {approx}1700 stars observed by the Kepler Mission, spanning from the main sequence to the red clump. Using evolutionary models, we test asteroseismic scaling relations for the frequency of maximum power ({nu}{sub max}), the large frequency separation ({Delta}{nu}), and oscillation amplitudes. We show that the difference of the {Delta}{nu}-{nu}{sub max} relation for unevolved and evolved stars can be explained by different distributions in effective temperature and stellar mass, in agreement with what is expected from scaling relations. For oscillation amplitudes, we show that neither (L/M){sup s} scaling nor the revised scaling relation by Kjeldsen and Bedding is accurate for red-giant stars, and demonstrate that a revised scaling relation with a separate luminosity-mass dependence can be used to calculate amplitudes from the main sequence to red giants to a precision of {approx}25%. The residuals show an offset particularly for unevolved stars, suggesting that an additional physical dependency is necessary to fully reproduce the observed amplitudes. We investigate correlations between amplitudes and stellar activity, and find evidence that the effect of amplitude suppression is most pronounced for subgiant stars. Finally, we test the location of the cool edge of the instability strip in the Hertzsprung-Russell diagram using solar-like oscillations and find the detections in the hottest stars compatible with a domain of hybrid stochastically excited and opacity driven pulsation.

  11. Simultaneously Suppressing Low-Frequency and Relaxation Oscillation Intensity Noise in a DBR Single-Frequency Phosphate Fiber Laser

    International Nuclear Information System (INIS)

    Xiao Yu; Li Can; Xu Shan-Hui; Feng Zhou-Ming; Yang Chang-Sheng; Zhao Qi-Lai; Yang Zhong-Min

    2015-01-01

    Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward transfer function, which relates the laser output intensity to the pump modulations, is measured and analyzed. A custom two-path feedback system operating at different frequency bands is designed to adjust the pump current directly. The relative intensity noise is decreased by 20 dB from 0.2 to 5kHz and over 10 dB from 5 to 10 kHz. The relaxation oscillation peak is suppressed by 22 dB. In addition, a long term (24 h) laser instability of less than 0.05% is achieved. (paper)

  12. Thin-film piezoelectric-on-silicon resonators for high-frequency reference oscillator applications.

    Science.gov (United States)

    Abdolvand, Reza; Lavasani, Hossein M; Ho, Gavin K; Ayazi, Farrokh

    2008-12-01

    This paper studies the application of lateral bulk acoustic thin-film piezoelectric-on-substrate (TPoS) resonators in high-frequency reference oscillators. Low-motional-impedance TPoS resonators are designed and fabricated in 2 classes--high-order and coupled-array. Devices of each class are used to assemble reference oscillators and the performance characteristics of the oscillators are measured and discussed. Since the motional impedance of these devices is small, the transimpedance amplifier (TIA) in the oscillator loop can be reduced to a single transistor and 3 resistors, a format that is very power-efficient. The lowest reported power consumption is approximately 350 microW for an oscillator operating at approximately 106 MHz. A passive temperature compensation method is also utilized by including the buried oxide layer of the silicon-on-insulator (SOI) substrate in the structural resonant body of the device, and a very small (-2.4 ppm/ degrees C) temperature coefficient of frequency is obtained for an 82-MHz oscillator.

  13. 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.

  14. General Forced Oscillations in a Real Power Grid Integrated with Large Scale Wind Power

    Directory of Open Access Journals (Sweden)

    Ping Ju

    2016-07-01

    Full Text Available According to the monitoring of the wide area measurement system, inter-area oscillations happen more and more frequently in a real power grid of China, which are close to the forced oscillation. Applying the conventional forced oscillation theory, the mechanism of these oscillations cannot be explained well, because the oscillations vary with random amplitude and a narrow frequency band. To explain the mechanism of such oscillations, the general forced oscillation (GFO mechanism is taken into consideration. The GFO is the power system oscillation excited by the random excitations, such as power fluctuations from renewable power generation. Firstly, properties of the oscillations observed in the real power grid are analyzed. Using the GFO mechanism, the observed oscillations seem to be the GFO caused by some random excitation. Then the variation of the wind power measured in this power gird is found to be the random excitation which may cause the GFO phenomenon. Finally, simulations are carried out and the power spectral density of the simulated oscillation is compared to that of the observed oscillation, and they are similar with each other. The observed oscillation is thus explained well using the GFO mechanism and the GFO phenomenon has now been observed for the first time in real power grids.

  15. Computational Re-design of Synthetic Genetic Oscillators for Independent Amplitude and Frequency Modulation.

    Science.gov (United States)

    Tomazou, Marios; Barahona, Mauricio; Polizzi, Karen M; Stan, Guy-Bart

    2018-04-25

    To perform well in biotechnology applications, synthetic genetic oscillators must be engineered to allow independent modulation of amplitude and period. This need is currently unmet. Here, we demonstrate computationally how two classic genetic oscillators, the dual-feedback oscillator and the repressilator, can be re-designed to provide independent control of amplitude and period and improve tunability-that is, a broad dynamic range of periods and amplitudes accessible through the input "dials." Our approach decouples frequency and amplitude modulation by incorporating an orthogonal "sink module" where the key molecular species are channeled for enzymatic degradation. This sink module maintains fast oscillation cycles while alleviating the translational coupling between the oscillator's transcription factors and output. We characterize the behavior of our re-designed oscillators over a broad range of physiologically reasonable parameters, explain why this facilitates broader function and control, and provide general design principles for building synthetic genetic oscillators that are more precisely controllable. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  16. Resonator as high frequency electromagnetic field oscillation generator

    International Nuclear Information System (INIS)

    Svoroba, O.V.; Scherbina, V.O.

    2007-01-01

    The problem of finding the u(x-vector) field potential in a specific waveguide with generalized corrugated core geometry is considered. The perturbation is brought to the system by high energy electron beam, injected in a waveguide. It is shown that the Neumann spectral problem can be reduced to finding Green approximation solution, and how it can be solved by the discretization technique. Considered parameterization allow to optimize the u(x-vector) field for specific frequency tuning. This method can be used as plasma heating method for thermonuclear temperature control

  17. 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.

  18. Weak wide-band signal detection method based on small-scale periodic state of Duffing oscillator

    Science.gov (United States)

    Hou, Jian; Yan, Xiao-peng; Li, Ping; Hao, Xin-hong

    2018-03-01

    The conventional Duffing oscillator weak signal detection method, which is based on a strong reference signal, has inherent deficiencies. To address these issues, the characteristics of the Duffing oscillatorʼs phase trajectory in a small-scale periodic state are analyzed by introducing the theory of stopping oscillation system. Based on this approach, a novel Duffing oscillator weak wide-band signal detection method is proposed. In this novel method, the reference signal is discarded, and the to-be-detected signal is directly used as a driving force. By calculating the cosine function of a phase space angle, a single Duffing oscillator can be used for weak wide-band signal detection instead of an array of uncoupled Duffing oscillators. Simulation results indicate that, compared with the conventional Duffing oscillator detection method, this approach performs better in frequency detection intervals, and reduces the signal-to-noise ratio detection threshold, while improving the real-time performance of the system. Project supported by the National Natural Science Foundation of China (Grant No. 61673066).

  19. Flow and pressure drop fluctuations in a vertical tube subject to low frequency oscillations

    International Nuclear Information System (INIS)

    Pendyala, Rajashekhar; Jayanti, Sreenivas; Balakrishnan, A.R.

    2008-01-01

    Heat transfer and other equipment mounted on off-shore platforms may be subjected to low frequency oscillations. The effect of these oscillations, typically in the frequency range of 0.1-1 Hz, on the flow rate and pressure drop in a vertical tube has been studied experimentally in the present work. A 1.75 m-long vertical tube of inner diameter 0.016 m was mounted on a plate and the whole plate was subjected to oscillations in the vertical plane using a mechanical simulator capable of providing low frequency oscillations in the range of 8-30 cycles/min at an amplitude of 0.125 m. The effect of the oscillations on the flow rate and the pressure drop has been measured systematically in the Reynolds number range 500-6500. The induced flow rate fluctuations were found to be dependent on the Reynolds number with stronger fluctuations at lower Reynolds numbers. The effective friction factor, based on the mean pressure drop and the mean flow rate, was also found to be higher than expected. Correlations have been developed to quantify this Reynolds number dependence

  20. Flow and pressure drop fluctuations in a vertical tube subject to low frequency oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Pendyala, Rajashekhar; Jayanti, Sreenivas [Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Balakrishnan, A.R. [Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)], E-mail: arbala@iitm.ac.in

    2008-01-15

    Heat transfer and other equipment mounted on off-shore platforms may be subjected to low frequency oscillations. The effect of these oscillations, typically in the frequency range of 0.1-1 Hz, on the flow rate and pressure drop in a vertical tube has been studied experimentally in the present work. A 1.75 m-long vertical tube of inner diameter 0.016 m was mounted on a plate and the whole plate was subjected to oscillations in the vertical plane using a mechanical simulator capable of providing low frequency oscillations in the range of 8-30 cycles/min at an amplitude of 0.125 m. The effect of the oscillations on the flow rate and the pressure drop has been measured systematically in the Reynolds number range 500-6500. The induced flow rate fluctuations were found to be dependent on the Reynolds number with stronger fluctuations at lower Reynolds numbers. The effective friction factor, based on the mean pressure drop and the mean flow rate, was also found to be higher than expected. Correlations have been developed to quantify this Reynolds number dependence.

  1. Cannabinoid Receptors Mediate Methamphetamine Induction of High Frequency Gamma Oscillations in the Nucleus Accumbens

    Science.gov (United States)

    Morra, Joshua T.; Glick, Stanley D.; Cheer, Joseph F.

    2012-01-01

    Patients suffering from amphetamine---induced psychosis display repetitive behaviors, partially alleviated by antipsychotics, which are reminiscent of rodent stereotypies. Due to recent evidence implicating endocannabinoid involvement in brain disorders, including psychosis, we studied the effects of endocannabinoid signaling on neuronal oscillations of rats exhibiting methamphetamine stereotypy. Neuronal network oscillations were recorded with multiple single electrode arrays aimed at the nucleus accumbens of freely moving rats. During the experiments, animals were dosed intravenously with the CB1 receptor antagonist rimonabant (0.3 mg/kg) or vehicle followed by an ascending dose regimen of methamphetamine (0.01, 0.1, 1, and 3 mg/kg; cumulative dosing). The effects of drug administration on stereotypy and local gamma oscillations were evaluated. Methamphetamine treatment significantly increased high frequency gamma oscillations (~ 80 Hz). Entrainment of a subpopulation of nucleus accumbens neurons to high frequency gamma was associated with stereotypy encoding in putative fast-spiking interneurons, but not in putative medium spiny neurons. The observed ability of methamphetamine to induce both stereotypy and high frequency gamma power was potently disrupted following CB1 receptor blockade. The present data suggest that CB1 receptor-dependent mechanisms are recruited by methamphetamine to modify striatal interneuron oscillations that accompany changes in psychomotor state, further supporting the link between endocannabinoids and schizophrenia spectrum disorders. PMID:22609048

  2. Investigation on multi-frequency oscillations in InGaAs planar Gunn diode with multiple anode-cathode spacings

    Science.gov (United States)

    Li, B.; Alimi, Y.; Ma, G. L.

    2016-12-01

    Current oscillations in an AlGaAs/InGaAs/AlGaAs-based two-dimensional electron gas (2DEG)-based hetero-structure have been investigated by means of semiconductor device simulation software SILVACO, with an interest on the charge domain formation at large biases. Single-frequency oscillations are generated in planar Gunn diodes with uniform anode and cathode contacts. The oscillation frequency reduces as the applied bias voltage increases. We show that it is possible to create multiple, independent charge domains in a novel Gunn diode structure with designed multiple anode-cathode spacings. This enables simultaneous generation of multiple frequency oscillations in a single planar device, in contrast to traditional vertical Gunn diodes where only single-frequency oscillations can be achieved. More interestingly, frequency mixing in multiple-channel configured Gunn diodes appeared. This proof-of-concept opens up the possibility for realizing compact self-oscillating mixer at millimeter-wave applications.

  3. High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI

    Energy Technology Data Exchange (ETDEWEB)

    Jafarzadeh, S. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Solanki, S. K.; Cameron, R. H.; Danilovic, S. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Stangalini, M. [INAF-Osservatorio Astronomico di Roma, I-00040 Monte Porzio Catone (RM) (Italy); Steiner, O., E-mail: shahin.jafarzadeh@astro.uio.no [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany)

    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{sup −1} and 31 ± 2 km s{sup −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.

  4. Frequency-Splitting-Free Synchronous Tuning of Close-Coupling Self-Oscillating Wireless Power Transfer

    Directory of Open Access Journals (Sweden)

    Po Hu

    2016-06-01

    Full Text Available The synchronous tuning of the self-oscillating wireless power transfer (WPT in a close-coupling condition is studied in this paper. The Hamel locus is applied to predict the self-oscillating points in the WPT system. In order to make the system operate stably at the most efficient point, which is the middle resonant point when there are middle resonant and split frequency points caused by frequency-splitting, the receiver (RX rather than the transmitter (TX current is chosen as the self-oscillating feedback variable. The automatic delay compensation is put forward to eliminate the influence of the intrinsic delay on frequency tuning for changeable parameters. In addition, the automatic circuit parameter tuning based on the phase difference is proposed to realize the synchronous tuning of frequency and circuit parameters. The experiments verified that the synchronous tuning proposed in this paper is effective, fully automatic, and more robust than the previous self-oscillating WPT system which use the TX current as the feedback variable.

  5. High-frequency oscillations and seizure activity and in the human anterior nucleus of the thalamus

    Czech Academy of Sciences Publication Activity Database

    Rektor, I.; Doležalová, I.; Chrastina, J.; Jurák, Pavel; Halámek, Josef; Brázdil, M.

    2015-01-01

    Roč. 56, S1 (2015), s. 29-30 ISSN 0013-9580. [International Epilepsy Congress /31./. 05.09.2015-09.09.2015, Istanbul] Institutional support: RVO:68081731 Keywords : high-frequency oscillations * anterior nucleus of the thalamus Subject RIV: FS - Medical Facilities ; Equipment

  6. A 60 GHz Frequency Generator Based on a 20 GHz Oscillator and an Implicit Multiplier

    NARCIS (Netherlands)

    Zong, Z.; Babaie, M.; Staszewski, R.B.

    2016-01-01

    This paper proposes a mm-wave frequency generation technique that improves its phase noise (PN) performance and power efficiency. The main idea is that a fundamental 20 GHz signal and its sufficiently strong third harmonic at 60 GHz are generated simultaneously in a single oscillator. The desired 60

  7. Interictal high-frequency oscillations indicate seizure onset zone in patients with focal cortical dysplasia

    Czech Academy of Sciences Publication Activity Database

    Brázdil, M.; Halámek, Josef; Jurák, Pavel; Daniel, P.; Kuba, R.; Chrastina, J.; Novák, Z.; Rektor, I.

    2010-01-01

    Roč. 90, 1-2 (2010), s. 28-32 ISSN 0920-1211 R&D Projects: GA MŠk ED0017/01/01 Institutional research plan: CEZ:AV0Z20650511 Keywords : epilepsy * hgh-frequency oscillations * intracerebral EEG Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery Impact factor: 2.302, year: 2010

  8. A microwave exciter for Cs frequency standards based on a sapphire-loaded cavity oscillator.

    Science.gov (United States)

    Koga, Y; McNeilage, C; Searls, J H; Ohshima, S

    2001-01-01

    A low noise and highly stable microwave exciter system has been built for Cs atomic frequency standards using a tunable sapphire-loaded cavity oscillator (SLCO), which works at room temperature. This paper discusses the successful implementation of a control system for locking the SLCO to a long-term reference signal and reports an upper limit of the achieved frequency tracking error 6 x 10(-15) at tau = 1 s.

  9. Sinusoidal oscillators with lower gain requirements at higher frequencies based on an explicit tanh(x) nonlinearity

    KAUST Repository

    Elwakil, Ahmed S.

    2009-04-28

    Two novel sinusoidal oscillator structures with an explicit tanh(x) nonlinearity are proposed. The oscillators have the attractive feature: the higher the operating frequency, the lower the necessary gain required to start oscillations. A nonlinear model for the two oscillators is derived and verified numerically. Spice simulations using AMS BiCMOS 0.35 μ model parameters and experimental results are shown. Copyright © 2009 John Wiley & Sons, Ltd.

  10. 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

  11. 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

    2002-01-01

    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

  12. Structural control of metamaterial oscillator strength and electric field enhancement at terahertz frequencies

    DEFF Research Database (Denmark)

    Keiser, G. R.; Seren, H. R.; Strikwerda, Andrew C.

    2014-01-01

    The design of artificial nonlinear materials requires control over internal resonant charge densities and local electric field distributions. We present a MM design with a structurally controllable oscillator strength and local electric field enhancement at terahertz frequencies. The MM consists...... of a split ring resonator (SRR) array stacked above an array of closed conducting rings. An in-plane, lateral shift of a half unit cell between the SRR and closed ring arrays results in an increase of the MM oscillator strength by a factor of 4 and a 40% change in the amplitude of the resonant electric field...

  13. Dynamics of a nonlinear oscillator and a low-amplitude frequency-modulated wave

    International Nuclear Information System (INIS)

    White, R.C.; McNamara, B.

    1987-01-01

    When the frequency of a small amplitude plane wave is varied slowly over a large enough bandwidth and this wave is incident upon a nonlinear oscillator, the resulting perturbed motion can exhibit stochastic behavior. Applications for the study of this system are wide and varied. We apply Lie-transform perturbation theory and mapping techniques in the analysis of the stochastic transition and the consequent induced diffusion in the oscillator phase space. A constant of the motion to the first order in a peturbation parameter is calculated, a mapping approximation is derived, and diffusion calculations from the mapping are given. Copyright 1987 Academic Press, Inc

  14. Dust Storms in North China in 2002: A Case Study of the Low Frequency Oscillation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The low frequency oscillation in both hemispheres and its possible role in the dust weather storm events over North China in 2002 are analyzed as a case study. Results show that the Aleutian Low is linked with the Circumpolar Vortex in the Southern Hemisphere on a 30-60-day oscillation, with a weak Circumpolar Vortex tending to deepen the Aleutian Low which may be helpful for the generation of dust storm events.The possible mechanism behind this is the inter-hemispheric interaction of the mean meridional circulation,with the major variability over East Asia. The zonal mean westerly wind at high latitudes of the Southern Hemisphere in the upper level troposphere may lead that of the Northern Hemisphere, which then impacts the local circulation in the Northern Hemisphere. Thus, the low frequency oscillation teleconnection is one possible linkage in the coupling between the Southern Hemisphere circulation and dust events over North China. However, the interannual variation of the low frequency oscillation is unclear.

  15. Analysis of the analytic formulae application area for free oscillation frequency calculation in isochronous cyclotrons

    International Nuclear Information System (INIS)

    Kiyan, I.N.; Taraszkiewicz, R.

    2005-01-01

    Selection of optimal analytic formulae for calculation of free oscillation frequencies of the particles in isochronous cyclotrons, ν r (r) and ν z (r), and their application area are described. The selected formulae are used in the program BORP SR - Betatron Oscillation Research Program Second Release - written in C++ with the help of MS Visual C++ .NET. The free oscillation frequencies, calculated by using the program, are used for the evaluation of the modeled regimes of the work of the AIC144 isochronous cyclotron. The analytic formulae were selected by comparing the results of the calculations performed by using formulae adduced by T.Stammbach, Y.Jongen - S.Zaremba, V.V.Kolga with the results of the calculations performed by using the CYCLOPS iterative program, developed by M.M.Gordon. The least difference in the calculation results was obtained for the analytic formulae adduced by V.V.Kolga. The ν r (r) calculation difference ranged from -0.5 to 1.5% and the ν z (r) calculation difference ranged from -5 to 4% for the working radii of the isochronous cyclotron. As the beam was obtained, the selected analytic formulae can be successfully used in the program BORP SR for free oscillation frequency calculation during the evaluation of the modeled regimes of the work of different isochronous cyclotrons

  16. Kinetic energy dissipation of a tuning fork immersed in superfluid helium at different frequencies of oscillations

    International Nuclear Information System (INIS)

    Gritsenko, I.A.; Klokol, K.A.; Sokolov, S.S.; Sheshin, G.A.

    2016-01-01

    An experimental study is made of the drag coefficient, which is the characteristics of energy dissipation during oscillations of the tuning forks, immersed in liquid helium. The experiments were performed in the temperature range from 0.1 to 3.5 K covering both the range of a hydrodynamic flow, and the ballistic regime of transfer of thermal excitations of superfluid helium below 0.6 K. It is found that there is the frequency dependence of the drag coefficient in the hydrodynamic limit, when the main dissipation mechanism is the viscous friction of the fluid against the walls of the oscillating body at temperatures above 0.7 K. In this case, the drag coefficient is proportional to the square root of the frequency of oscillation, and its temperature dependence in He II is determined by the respective dependence of the normal component density of the normal component and the viscosity of the fluid. At lower temperatures, the dependence of drag coefficient on the frequency is not available, and the magnitude of the dissipative losses is determined only by the temperature dependence of the density of the normal component. At the same time in the entire range of temperatures value of dissipative losses depends on the geometry of the oscillating body.

  17. Are All Oscillators Created Equal? In vitro Performance Characteristics of Eight High-Frequency Oscillatory Ventilators.

    Science.gov (United States)

    Tingay, David G; John, Jubal; Harcourt, Edward R; Black, Don; Dargaville, Peter A; Mills, John F; Davis, Peter G

    2015-01-01

    The mode of waveform generation and circuit characteristics differ between high-frequency oscillators. It is unknown if this influences performance. To describe the relationships between set and delivered pressure amplitude (x0394;P), and the interaction with frequency and endotracheal tube (ETT) diameter, in eight high-frequency oscillators. Oscillators were evaluated using a 70-ml test lung at 1.0 and 2.0 ml/cm H2O compliance, with mean airway pressures (PAW) of 10 and 20 cm H2O, frequencies of 5, 10 and 15 Hz, and an ETT diameter of 2.5 and 3.5 mm. At each permutation of PAW, frequency and ETT, the set x0394;P was sequentially increased from 15 to 50 cm H2O, or from 20 to 100% maximum amplitude (10% increments) depending on the oscillator design. The x0394;P at the ventilator (x0394;PVENT), airway opening (x0394;PAO) and within the test lung (x0394;PTRACH), and tidal volume (V(T)) at the airway opening were determined at each set x0394;P. In two oscillators the relationships between set and delivered x0394;P were non-linear, with a plateau in x0394;P thresholds noted at all frequencies (Dräger Babylog 8000) or ≥10 Hz (Dräger VN500). In all other devices there was a linear relationship between x0394;PVENT, x0394;PAO and x0394;PTRACH (all r2 >0.93), with differing attenuation of the pressure wave. Delivered V(T) at the different settings tested varied between devices, with some unable to deliver V(T) >3 ml at 15 Hz, and others generating V(T)>20 ml at 5 Hz and a 1:1 inspiratory-to-expiratory time ratio. Clinicians should be aware that modern high-frequency oscillators exhibit important differences in the delivered x0394;P and V(T). © 2015 S. Karger AG, Basel.

  18. Damping of Low Frequency Power System Oscillations with Wind Power Plants

    DEFF Research Database (Denmark)

    Adamczyk, Andrzej Grzegorz

    of wind power plants on power system low frequency oscillations and identify methods and limitations for potential contribution to the damping of such oscillations. Consequently, the first part of the studies focuses on how the increased penetration of wind power into power systems affects their natural...... oscillatory performance. To do so, at first a generic test grid displaying a complex inter-area oscillation pattern is introduced. After the evaluation of the test grid oscillatory profile for various wind power penetration scenarios, it is concluded that full-converter based wind power plant dynamics do......-synchronous power source. The main body of the work is devoted to the damping control design for wind power plants with focus on the impact of such control on the plant operation. It can be expected that the referred impact is directly proportional to the control effort, which for power processing devices should...

  19. A daily oscillation in the fundamental frequency and amplitude of harmonic syllables of zebra finch song.

    Directory of Open Access Journals (Sweden)

    William E Wood

    Full Text Available Complex motor skills are more difficult to perform at certain points in the day (for example, shortly after waking, but the daily trajectory of motor-skill error is more difficult to predict. By undertaking a quantitative analysis of the fundamental frequency (FF and amplitude of hundreds of zebra finch syllables per animal per day, we find that zebra finch song follows a previously undescribed daily oscillation. The FF and amplitude of harmonic syllables rises across the morning, reaching a peak near mid-day, and then falls again in the late afternoon until sleep. This oscillation, although somewhat variable, is consistent across days and across animals and does not require serotonin, as animals with serotonergic lesions maintained daily oscillations. We hypothesize that this oscillation is driven by underlying physiological factors which could be shared with other taxa. Song production in zebra finches is a model system for studying complex learned behavior because of the ease of gathering comprehensive behavioral data and the tractability of the underlying neural circuitry. The daily oscillation that we describe promises to reveal new insights into how time of day affects the ability to accomplish a variety of complex learned motor skills.

  20. North-south asymmetry of ultra-low-frequency oscillations of Earth's electromagnetic field

    Science.gov (United States)

    Guglielmi, Anatol; Klain, Boris; Potapov, Alexander

    2017-12-01

    In the paper, we present the result of an experimental study of north-south asymmetry of ultralow-frequency electromagnetic oscillations IPCL. This study is based on observations made at Mirny Observatory (Antarctica). IPCLs are excited in the dayside sector of the auroral oval in the range 3-10 min periods and represent one of the most powerful types of oscillations of Earth's magnetosphere. These oscillations were discovered in the 1970s during IPhE AS USSR polar expeditions organized by Prof. V.A. Troitskaya. We have shown that IPCL activity in Mirny depends on the inclination (north-south asymmetry) of interplanetary magnetic field (IMF) lines to the plane of the geomagnetic equator before the front of the magnetosphere. The result suggests a controlling exposure of IMF on the magnetospheric oscillations and gives rise to the hypothesis that IPCLs are forced oscillations of a nonlinear dynamical system whose major structural elements are dayside polar cusps. The paper is dedicated to the memory of Professor V.A. Troitskaya (1917-2010).

  1. Servo-controlled pneumatic pressure oscillator for respiratory impedance measurements and high-frequency ventilation.

    Science.gov (United States)

    Kaczka, David W; Lutchen, Kenneth R

    2004-04-01

    The ability to provide forced oscillatory excitation of the respiratory system can be useful in mechanical impedance measurements as well as high frequency ventilation (HFV). Experimental systems currently used for generating forced oscillations are limited in their ability to provide high amplitude flows or maintain the respiratory system at a constant mean pressure during excitation. This paper presents the design and implementation of a pneumatic pressure oscillator based on a proportional solenoid valve. The device is capable of providing forced oscillatory excitations to the respiratory system over a bandwidth suitable for mechanical impedance measurements and HVF. It delivers high amplitude flows (> 1.4 l/s) and utilizes a servo-control mechanism to maintain a load at a fixed mean pressure during simultaneous oscillation. Under open-loop conditions, the device exhibited a static hysteresis of approximately 7%, while its dynamic magnitude and phase responses were flat out to 10 Hz. Broad-band measurement of total harmonic distortion was approximately 19%. Under closed-loop conditions, the oscillator was able to maintain a mechanical test load at both positive and negative mean pressures during oscillatory excitations from 0.1 to 10.0 Hz. Impedance of the test load agreed closely with theoretical predictions. We conclude that this servo-controlled oscillator can be a useful tool for respiratory impedance measurements as well as HFV.

  2. Investigation of low-frequency-oscillating water flow in metal foam with 10 pores per inch

    Science.gov (United States)

    Bağcı, Ö.; Arbak, A.; De Paepe, M.; Dukhan, N.

    2018-01-01

    In this study, oscillating water flow in metal foam with open cells is investigated experimentally. The metal foam sample has a porosity of 88% and 10 pores. The water was oscillated in the test section with three frequencies between 0.116 Hz and 0.348 Hz, which are considered low for water oscillation, and three flow displacements ranging between 74.35 mm and 111.53 mm. The combinations of frequencies of displacements were studied for their impacts of dimensional and non-dimensional pressure loss quantities. To this purpose, friction factor was correlated as a function of kinetic Reynolds number. The same metal foam sample was studied by exposing it to steady-state water flow to investigate its permeability and drag coefficient in low-velocity flow regimes. The friction factor distribution for oscillating flow was found to be over that found for steady state. The outcomes of the study are important for studying heat transfer under the same flow conditions.

  3. Low Frequency Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster

    Science.gov (United States)

    Jorns, Benjamin A.; Hofery, Richard R.

    2013-01-01

    The oscillations from 0-100 kHz in a 6-kW magnetically shielded thruster are experimen- tally characterized. Changes in plasma parameters that result from the magnetic shielding of Hall thrusters have the potential to significantly alter thruster transients. A detailed investigation of the resulting oscillations is necessary both for the purpose of determin- ing the underlying physical processes governing time-dependent behavior in magnetically shielded thrusters as well as for improving thruster models. In this investigation, a high speed camera and a translating ion saturation probe are employed to examine the spatial extent and nature of oscillations from 0-100 kHz in the H6MS thruster. Two modes are identified at 8 kHz and 75-90 kHz. The low frequency mode is azimuthally uniform across the thruster face while the high frequency oscillation is concentrated close to the thruster centerline with an m = 1 azimuthal dependence. These experimental results are discussed in the context of wave theory as well as published observations from an unshielded variant of the H6MS thruster.

  4. The forgotten role of central volume in low frequency oscillations of heart rate variability.

    Directory of Open Access Journals (Sweden)

    Manuela Ferrario

    Full Text Available The hypothesis that central volume plays a key role in the source of low frequency (LF oscillations of heart rate variability (HRV was tested in a population of end stage renal disease patients undergoing conventional hemodialysis (HD treatment, and thus subject to large fluid shifts and sympathetic activation. Fluid overload (FO in 58 chronic HD patients was assessed by whole body bioimpedance measurements before the midweek HD session. Heart Rate Variability (HRV was measured using 24-hour Holter electrocardiogram recordings starting before the same HD treatment. Time domain and frequency domain analyses were performed on HRV signals. Patients were retrospectively classified in three groups according to tertiles of FO normalized to the extracellular water (FO/ECW%. These groups were also compared after stratification by diabetes mellitus. Patients with the low to medium hydration status before the treatment (i.e. 1st and 2nd FO/ECW% tertiles showed a significant increase in LF power during last 30 min of HD compared to dialysis begin, while no significant change in LF power was seen in the third group (i.e. those with high pre-treatment hydration values. In conclusion, several mechanisms can generate LF oscillations in the cardiovascular system, including baroreflex feedback loops and central oscillators. However, the current results emphasize the role played by the central volume in determining the power of LF oscillations.

  5. The forgotten role of central volume in low frequency oscillations of heart rate variability.

    Science.gov (United States)

    Ferrario, Manuela; Moissl, Ulrich; Garzotto, Francesco; Cruz, Dinna N; Tetta, Ciro; Signorini, Maria G; Ronco, Claudio; Grassmann, Aileen; Cerutti, Sergio; Guzzetti, Stefano

    2015-01-01

    The hypothesis that central volume plays a key role in the source of low frequency (LF) oscillations of heart rate variability (HRV) was tested in a population of end stage renal disease patients undergoing conventional hemodialysis (HD) treatment, and thus subject to large fluid shifts and sympathetic activation. Fluid overload (FO) in 58 chronic HD patients was assessed by whole body bioimpedance measurements before the midweek HD session. Heart Rate Variability (HRV) was measured using 24-hour Holter electrocardiogram recordings starting before the same HD treatment. Time domain and frequency domain analyses were performed on HRV signals. Patients were retrospectively classified in three groups according to tertiles of FO normalized to the extracellular water (FO/ECW%). These groups were also compared after stratification by diabetes mellitus. Patients with the low to medium hydration status before the treatment (i.e. 1st and 2nd FO/ECW% tertiles) showed a significant increase in LF power during last 30 min of HD compared to dialysis begin, while no significant change in LF power was seen in the third group (i.e. those with high pre-treatment hydration values). In conclusion, several mechanisms can generate LF oscillations in the cardiovascular system, including baroreflex feedback loops and central oscillators. However, the current results emphasize the role played by the central volume in determining the power of LF oscillations.

  6. Persistent hyperdopaminergia decreases the peak frequency of hippocampal theta oscillations during quiet waking and REM sleep.

    Directory of Open Access Journals (Sweden)

    Kafui Dzirasa

    Full Text Available Long-term changes in dopaminergic signaling are thought to underlie the pathophysiology of a number of psychiatric disorders. Several conditions are associated with cognitive deficits such as disturbances in attention processes and learning and memory, suggesting that persistent changes in dopaminergic signaling may alter neural mechanisms underlying these processes. Dopamine transporter knockout (DAT-KO mice exhibit a persistent five-fold increase in extracellular dopamine levels. Here, we demonstrate that DAT-KO mice display lower hippocampal theta oscillation frequencies during baseline periods of waking and rapid-eye movement sleep. These altered theta oscillations are not reversed via treatment with the antidopaminergic agent haloperidol. Thus, we propose that persistent hyperdopaminergia, together with secondary alterations in other neuromodulatory systems, results in lower frequency activity in neural systems responsible for various cognitive processes.

  7. Direct measurement of density oscillation induced by a radio-frequency wave

    International Nuclear Information System (INIS)

    Yamada, T.; Ejiri, A.; Shimada, Y.; Oosako, T.; Tsujimura, J.; Takase, Y.; Kasahara, H.

    2007-01-01

    An O-mode reflectometer at a frequency of 25.85 GHz was applied to plasmas heated by the high harmonic fast wave (21 MHz) in the TST-2 spherical tokamak. An oscillation in the phase of the reflected microwave in the rf range was observed directly for the first time. In TST-2, the rf (250 kW) induced density oscillation depends mainly on the poloidal rf electric field, which is estimated to be about 0.2 kV/m rms by the reflectometer measurement. Sideband peaks separated in frequency by ion cyclotron harmonics from 21 MHz, and peaks at ion cyclotron harmonics which are suggested to be quasimodes generated by parametric decay, were detected

  8. Oscillations of non-isothermal N/S boundary with a high frequency and large amplitude

    International Nuclear Information System (INIS)

    Bezuglyj, A.I.; Shklovskij, V.A.

    2016-01-01

    Within the framework of the phenomenological approach based on the heat balance equation and the dependence of the critical temperature of the superconductor on the current value theoretically investigated the impact of high-frequency current of high amplitude and arbitrary shape on the non-isothermal balance of the oscillating N/S interface in a long superconductor. We introduce a self-consistent average temperature field of rapidly oscillating non-isothermal N/S boundary (heat kink), which allows to go beyond the well-known concept of mean-square heating and consider the impact of current waveform. With regard to experiments on the effects of microwave high-power radiation on the current-voltage characteristics (CVC) of superconducting films, we give the classification of the families of the CVC for inhomogeneous superconductors which carry a current containing a high frequency component of large amplitude. Several characteristics have hysteresis of thermal nature.

  9. Electric-field assisted spin torque nano-oscillator and binary frequency shift keying modulation

    Science.gov (United States)

    Zhang, Xiangli; Chen, Hao-Hsuan; Zhang, Zongzhi; Liu, Yaowen

    2018-04-01

    Electric-controlled magnetization precession introduces technologically relevant possibility for developing spin torque nano-oscillators (STNO) with potential applications in microwave emission. Using the perpendicularly magnetized magnetic tunnel junction (MTJ), we show that the magnetization oscillation frequency can be tuned by the co-action of electric field and spin polarized current. The dynamical phase diagram of MTJ-based STNO is analytically predicted through coordinate transformation from the laboratory frame to the rotation frame, by which the nonstationary out-of-plane magnetization precession process is therefore transformed into the stationary process in the rotation frame. Furthermore, using this STNO as a microwave source, we numerically demonstrate that the bit signal can be transmitted by a binary frequency shift keying (BFSK) modulation technique. The BFSK scheme shows good modulation features with no transient state.

  10. Impact of excitation waveform on the frequency stability of electrostatically-actuated micro-electromechanical oscillators

    Science.gov (United States)

    Juillard, J.; Brenes, A.

    2018-05-01

    In this paper, the frequency stability of high-Q electrostatically-actuated MEMS oscillators with cubic restoring forces, and its relation with the amplitude, the phase and the shape of the excitation waveform, is studied. The influence on close-to-the carrier frequency noise of additive processes (such as thermomechanical noise) or parametric processes (bias voltage fluctuations, feedback phase fluctuations, feedback level fluctuations) is taken into account. It is shown that the optimal operating conditions of electrostatically-actuated MEMS oscillators are highly waveform-dependent, a factor that is largely overlooked in the existing literature. This simulation-based study covers the cases of harmonic and pulsed excitation of a parallel-plate capacitive MEMS resonator.

  11. ON THE HIGH-FREQUENCY QUASI-PERIODIC OSCILLATIONS FROM BLACK HOLES

    International Nuclear Information System (INIS)

    Erkut, M. Hakan

    2011-01-01

    We apply the global mode analysis, which has been recently developed for the modeling of kHz quasi-periodic oscillations (QPOs) from neutron stars, to the inner region of an accretion disk around a rotating black hole. Within a pseudo-Newtonian approach that keeps the ratio of the radial epicyclic frequency κ to the orbital frequency Ω the same as the corresponding ratio for a Kerr black hole, we determine the innermost disk region where the hydrodynamic modes grow in amplitude. We find that the radiation flux emerging from the inner disk has the highest values within the same region. Using the flux-weighted averages of the frequency bands over this region we identify the growing modes with highest frequency branches Ω + κ and Ω to be the plausible candidates for the high-frequency QPO pairs observed in black hole systems. The observed frequency ratio around 1.5 can therefore be understood naturally in terms of the global free oscillations in the innermost region of a viscous accretion disk around a black hole without invoking a particular resonance to produce black hole QPOs. Although the frequency ratio (Ω + κ)/(Ω) is found to be not sensitive to the black hole's spin which is good for explaining the high-frequency QPOs, it may work as a limited diagnostic of the spin parameter to distinguish black holes with very large spin from the slowly rotating ones. Within our model we estimate the frequency ratio of a high-frequency QPO pair to be greater than 1.5 if the black hole is a slow rotator. For fast rotating black holes, we expect the same ratio to be less than 1.5.

  12. Power system low frequency oscillation mode estimation using wide area measurement systems

    Directory of Open Access Journals (Sweden)

    Papia Ray

    2017-04-01

    Full Text Available Oscillations in power systems are triggered by a wide variety of events. The system damps most of the oscillations, but a few undamped oscillations may remain which may lead to system collapse. Therefore low frequency oscillations inspection is necessary in the context of recent power system operation and control. Ringdown portion of the signal provides rich information of the low frequency oscillatory modes which has been taken into analysis. This paper provides a practical case study in which seven signal processing based techniques i.e. Prony Analysis (PA, Fast Fourier Transform (FFT, S-Transform (ST, Wigner-Ville Distribution (WVD, Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT, Hilbert-Huang Transform (HHT and Matrix Pencil Method (MPM were presented for estimating the low frequency modes in a given ringdown signal. Preprocessing of the signal is done by detrending. The application of the signal processing techniques is illustrated using actual wide area measurement systems (WAMS data collected from four different Phasor Measurement Unit (PMU i.e. Dadri, Vindyachal, Kanpur and Moga which are located near the recent disturbance event at the Northern Grid of India. Simulation results show that the seven signal processing technique (FFT, PA, ST, WVD, ESPRIT, HHT and MPM estimates two common oscillatory frequency modes (0.2, 0.5 from the raw signal. Thus, these seven techniques provide satisfactory performance in determining small frequency modes of the signal without losing its valuable property. Also a comparative study of the seven signal processing techniques has been carried out in order to find the best one. It was found that FFT and ESPRIT gives exact frequency modes as compared to other techniques, so they are recommended for estimation of low frequency modes. Further investigations were also carried out to estimate low frequency oscillatory mode with another case study of Eastern Interconnect Phasor Project

  13. Effect of the imposition of low-frequency mechanical oscillations on the extraction efficiency

    Directory of Open Access Journals (Sweden)

    Ju. I. Shitshatskij

    2018-01-01

    Full Text Available It was shown that the effective transfer of the target component from the raw material occurs under a turbulent regime conditions provided by applying mechanical oscillations to a two-phase system: solid-liquid. Due to this hydrodynamic situation, not only external but also internal diffusion is intensified in the extractor. The method for intensifying the extraction process using low-frequency mechanical oscillations in the case when the vibrational motion is performed by a device with a cheese whey containing suspended porous particles was studied in the work. The experiments were carried out on the laboratory equipment with a supply to a two-phase energy system from the outside, the source of which in the first case was an electromagnet, in the second - a mechanical drive with an eccentric device. Schemes of equipment were also presented in the work. The regime parameters varied in the following ranges: temperature - 40-60 оС, oscillation frequency - 30 - 40 osc / s, amplitude - 1 - 6.5 mm. In the extraction process, the current concentration of extractive substances was obtained from the material balance equation. Extraction curves obtained from experimental data were presented. Increasing extraction of extractive substances in time was observed, it being more intense with the increasing frequency of oscillations. It was found that the growth of the amplitude does not have a significant influence on the change of these indices. The intensity of oscillations was up to 260 mm / s. At the same time, the yield of extractive substances in particular from lupine in the form of grits was 25%, and the duration of the process was 18 min. The experiments showed that the application of the chosen extraction method results into a significant acceleration of the process (up to 2.5 times as compared to extraction in a dense layer. It is concluded that due to the imposition of mechanical oscillations on the surface and in the pores of the solid phase

  14. Radio frequency regenerative oscillations in monolithic high-Q/V heterostructured photonic crystal cavities

    International Nuclear Information System (INIS)

    Yang, Jinghui; Gu, Tingyi; Zheng, Jiangjun; Wei Wong, Chee; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee

    2014-01-01

    We report temporal and spectral domain observation of regenerative oscillation in monolithic silicon heterostructured photonic crystals cavities with high quality factor to mode volume ratios (Q/V). The results are interpreted by nonlinear coupled mode theory (CMT) tracking the dynamics of photon, free carrier population, and temperature variations. We experimentally demonstrate effective tuning of the radio frequency tones by laser-cavity detuning and laser power levels, confirmed by the CMT simulations with sensitive input parameters

  15. A one-parametric formula relating the frequencies of twin-peak quasi-periodic oscillations

    Science.gov (United States)

    Török, Gabriel; Goluchová, Kateřina; Šrámková, Eva; Horák, Jiří; Bakala, Pavel; Urbanec, Martin

    2017-12-01

    Timing analysis of X-ray flux in more than a dozen low-mass X-ray binary systems containing a neutron star reveals remarkable correlations between frequencies of two characteristic peaks present in the power-density spectra. We find a simple analytic relation that well reproduces all these individual correlations. We link this relation to a physical model which involves accretion rate modulation caused by an oscillating torus.

  16. Update on the mechanisms and roles of high-frequency oscillations in seizures and epileptic disorders

    Czech Academy of Sciences Publication Activity Database

    Jiruška, Přemysl; Alvarado-Rojas, C.; Schevon, C.A.; Staba, R.; Stacey, W.; Wendling, F.; Avoli, M.

    2017-01-01

    Roč. 58, č. 8 (2017), s. 1330-1339 ISSN 0013-9580 R&D Projects: GA MZd(CZ) NV15-29835A; GA ČR(CZ) GA14-02634S Institutional support: RVO:67985823 Keywords : high-frequency oscillations * epilepsy * ripples * fast ripples * ictogenesis * epileptogenesis * seizures * interneurons * computer models Subject RIV: FH - Neurology OBOR OECD: Neurosciences (including psychophysiology Impact factor: 5.295, year: 2016

  17. Intracerebrally recorded high frequency oscillations: Simple visual assessment versus automated detection

    Czech Academy of Sciences Publication Activity Database

    Pail, M.; Halámek, Josef; Daniel, P.; Kuba, R.; Tyrlíková, I.; Chrastina, J.; Jurák, Pavel; Rektor, I.; Brázdil, M.

    2013-01-01

    Roč. 124, č. 10 (2013), s. 1935-1942 ISSN 1388-2457 R&D Projects: GA ČR GAP103/11/0933; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : High frequency oscillations * Spikes * Ripples * Temporal lobe epilepsy * Extratemporal lobe epilepsy * Seizure onset zone * Epileptogenic zone Subject RIV: FH - Neurology Impact factor: 2.979, year: 2013

  18. A dual resonant rectilinear-to-rotary oscillation converter for low frequency broadband electromagnetic energy harvesting

    Science.gov (United States)

    Deng, Wei; Wang, Ya

    2017-09-01

    This paper reports a dual resonant rectilinear-to-rotary oscillation converter (RROC) for low frequency broadband electromagnetic energy harvesting from ambient vibrations. An approximate theoretical model has been established to integrate the electromechanical coupling into a comprehensive electromagnetic-dynamic model of the dual resonant RROC. Numerical simulation has proved the nature of dual resonances by revealing that both the rectilinear resonance and the rotary resonance could be achieved when the stand-alone rectilinear oscillator (RLO) and the stand-alone rotary oscillator (RTO) were excited independently. Simulation on the magnetically coupled RROC has also shown that the rectilinear resonance and the rotary resonance could be obtained simultaneously in the low-frequency region (2-14 Hz) with well-defined restoring torque (M r ) and the initial rotation angle of the RLO (ψ). The magnetic interaction patterns between the rectilinear and the RTOs have been categorized based on aforementioned simulation results. Both simulation and experimental results have demonstrated broadband output attributing from the dual resonances. Experimental results have also indicated that the RROC could have wide bandwidth in a much lower frequency region (2-8 Hz) even without the rotary resonance as long as the system parameters are carefully tuned. Parameter analysis on different values of M r and ψ are experimentally carried out to provide a quantitative guidance of designing the RROC to achieve an optimal power density.

  19. ANALYSIS OF LOW-FREQUENCY OSCILLATIONS FOR THE SOUTH CHINA SEA SUMMER MONSOON IN 1998

    Institute of Scientific and Technical Information of China (English)

    徐国强; 朱乾根

    2003-01-01

    With NCEP/NCAR reanalysis daily data and SST for 1998, the paper investigates the features of summer monsoon low-frequency oscillation (LFO) over the South China Sea (SCS). Results show that SCS summer monsoon onset is enhanced because of its LFO. Low-frequency (LF) low-level convergence (divergence) region of SCS is in the LF positive (negative) rainfall area. LFO of the SCS region migrates from south to north in the meridian and from west to east in zonal direction. LF divergence of SCS is vertically compensating to each other between high and low level.

  20. OSCILLATION CRITERIA FOR A FOURTH ORDER SUBLINEAR DYNAMIC EQUATION ON TIME SCALE

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Some new criteria for the oscillation of a fourth order sublinear and/or linear dynamic equation on time scale are established. Our results are new for the corresponding fourth order differential equations as well as difference equations.

  1. Convective heat transfer in single-phase flow in a vertical tube subjected to axial low frequency oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Pendyala, Rajashekhar; Jayanti, Sreenivas; Balakrishnan, A.R. [Indian Institute of Technology Madras, Department of Chemical Engineering, Chennai, Tamil Nadu (India)

    2008-05-15

    The effect of oscillations on the heat transfer in a vertical tube has been studied experimentally. A vertical tube was mounted on a plate and the whole plate was subjected to oscillations in the vertical plane using a mechanical oscillator to provide low frequency oscillations. A section of the tube in the middle is subjected to a constant heat flux. The effect of the oscillations on the heat transfer coefficient has been examined. It was found that the heat transfer coefficient increased with oscillations in the laminar regime. In turbulent flow regime (Re > 2,100) it is found that the effect of oscillations did not show any change. A correlation has been developed for enhancement of the local Nusselt number in terms of the effective acceleration and Reynolds number. Using this, an expression has been proposed to calculate the mean Nusselt number as a function of the tube length. (orig.)

  2. Populations of striatal medium spiny neurons encode vibrotactile frequency in rats: modulation by slow wave oscillations.

    Science.gov (United States)

    Hawking, Thomas G; Gerdjikov, Todor V

    2013-01-01

    Dorsolateral striatum (DLS) is implicated in tactile perception and receives strong projections from somatosensory cortex. However, the sensory representations encoded by striatal projection neurons are not well understood. Here we characterized the contribution of DLS to the encoding of vibrotactile information in rats by assessing striatal responses to precise frequency stimuli delivered to a single vibrissa. We applied stimuli in a frequency range (45-90 Hz) that evokes discriminable percepts and carries most of the power of vibrissa vibration elicited by a range of complex fine textures. Both medium spiny neurons and evoked potentials showed tactile responses that were modulated by slow wave oscillations. Furthermore, medium spiny neuron population responses represented stimulus frequency on par with previously reported behavioral benchmarks. Our results suggest that striatum encodes frequency information of vibrotactile stimuli which is dynamically modulated by ongoing brain state.

  3. Frequency of gamma oscillations in humans is modulated by velocity of visual motion

    Science.gov (United States)

    Butorina, Anna V.; Sysoeva, Olga V.; Prokofyev, Andrey O.; Nikolaeva, Anastasia Yu.; Stroganova, Tatiana A.

    2015-01-01

    Gamma oscillations are generated in networks of inhibitory fast-spiking (FS) parvalbumin-positive (PV) interneurons and pyramidal cells. In animals, gamma frequency is modulated by the velocity of visual motion; the effect of velocity has not been evaluated in humans. In this work, we have studied velocity-related modulations of gamma frequency in children using MEG/EEG. We also investigated whether such modulations predict the prominence of the “spatial suppression” effect (Tadin D, Lappin JS, Gilroy LA, Blake R. Nature 424: 312-315, 2003) that is thought to depend on cortical center-surround inhibitory mechanisms. MEG/EEG was recorded in 27 normal boys aged 8–15 yr while they watched high-contrast black-and-white annular gratings drifting with velocities of 1.2, 3.6, and 6.0°/s and performed a simple detection task. The spatial suppression effect was assessed in a separate psychophysical experiment. MEG gamma oscillation frequency increased while power decreased with increasing velocity of visual motion. In EEG, the effects were less reliable. The frequencies of the velocity-specific gamma peaks were 64.9, 74.8, and 87.1 Hz for the slow, medium, and fast motions, respectively. The frequency of the gamma response elicited during slow and medium velocity of visual motion decreased with subject age, whereas the range of gamma frequency modulation by velocity increased with age. The frequency modulation range predicted spatial suppression even after controlling for the effect of age. We suggest that the modulation of the MEG gamma frequency by velocity of visual motion reflects excitability of cortical inhibitory circuits and can be used to investigate their normal and pathological development in the human brain. PMID:25925324

  4. Symmetries and invariants of the oscillator and envelope equations with time-dependent frequency

    Directory of Open Access Journals (Sweden)

    Hong Qin

    2006-05-01

    Full Text Available The single-particle dynamics in a time-dependent focusing field is examined. The existence of the Courant-Snyder invariant, a fundamental concept in accelerator physics, is fundamentally a result of the corresponding symmetry admitted by the harmonic oscillator equation with linear time-dependent frequency. It is demonstrated that the Lie algebra of the symmetry group for the oscillator equation with time-dependent frequency is eight dimensional, and is composed of four independent subalgebras. A detailed analysis of the admitted symmetries reveals a deeper connection between the nonlinear envelope equation and the oscillator equation. A general theorem regarding the symmetries and invariants of the envelope equation, which includes the existence of the Courant-Snyder invariant as a special case, is demonstrated. As an application to accelerator physics, the symmetries of the envelope equation enable a fast numerical algorithm for finding matched solutions without using the conventional iterative Newton’s method, where the envelope equation needs to be numerically integrated once for every iteration, and the Jacobi matrix needs to be calculated for the envelope perturbation.

  5. Cantilever-detected high-frequency ESR measurement using a backward travelling wave oscillator

    International Nuclear Information System (INIS)

    Tokuda, Y; Hirano, S; Ohmichi, E; Ohta, H

    2012-01-01

    Our cantilever-detected electron spin resonance (ESR) technique is motivated for terahertz ESR spectroscopy of a tiny single crystal at low temperature. In this technique, ESR signal is detected as deflection of a sample-mounted cantilever, which is sensitively detected by built-in piezoresistors. So far, ESR detection at 315 GHz was succeeded using Gunn oscillator. In this study, we combine our ESR technique with a backward traveling wave oscillator (BWO), which can cover a wide frequency range 120-1200 GHz, to achieve better spectral resolution. Experiments were carried out at 4.2 K for a single crystal of Co Tutton salt with a newly constructed optical system. We successfully observed two ESR absorption lines in BWO frequencies up to 370 GHz. From multi-frequency measurements, the observed ESR lines shifted linearly with BWO frequency, being consistent with paramagnetic resonance. The estimated g values are g 1 = 3.00 and g 2 = 3.21. The spin sensitivity was estimated to ∼10 12 spins/gauss at 370 GHz.

  6. Measurement of acoustic glitches in solar-type stars from oscillation frequencies observed by Kepler

    Energy Technology Data Exchange (ETDEWEB)

    Mazumdar, A. [Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088 (India); Monteiro, M. J. P. F. G.; Cunha, M. S. [Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Ballot, J. [CNRS, Institut de Recherche en Astrophysique et Planétologie, 14 avenue Edouard Belin, F-31400 Toulouse (France); Antia, H. M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Basu, S. [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 065208101 (United States); Houdek, G.; Silva Aguirre, V.; Christensen-Dalsgaard, J.; Metcalfe, T. S. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Mathur, S. [High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); García, R. A. [Laboratoire AIM, CEA/DSM, CNRS, Université Paris Diderot, IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France); Salabert, D. [Laboratoire Lagrange, UMR7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d' Azur, F-06304 Nice (France); Verner, G. A.; Chaplin, W. J. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Sanderfer, D. T. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Seader, S. E.; Smith, J. C. [SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States)

    2014-02-10

    For the very best and brightest asteroseismic solar-type targets observed by Kepler, the frequency precision is sufficient to determine the acoustic depths of the surface convective layer and the helium ionization zone. Such sharp features inside the acoustic cavity of the star, which we call acoustic glitches, create small oscillatory deviations from the uniform spacing of frequencies in a sequence of oscillation modes with the same spherical harmonic degree. We use these oscillatory signals to determine the acoustic locations of such features in 19 solar-type stars observed by the Kepler mission. Four independent groups of researchers utilized the oscillation frequencies themselves, the second differences of the frequencies and the ratio of the small and large separation to locate the base of the convection zone and the second helium ionization zone. Despite the significantly different methods of analysis, good agreement was found between the results of these four groups, barring a few cases. These results also agree reasonably well with the locations of these layers in representative models of the stars. These results firmly establish the presence of the oscillatory signals in the asteroseismic data and the viability of several techniques to determine the location of acoustic glitches inside stars.

  7. Determination of delayed neutrons source in the frequency domain based on in-pile oscillation measurements

    International Nuclear Information System (INIS)

    Yedvab, Y.; Reiss, I.; Bettan, M.; Harari, R.; Grober, A.; Ettedgui, H.; Caspi, E. N.

    2006-01-01

    A method for determining delayed neutrons source in the frequency domain based on measuring power oscillations in a non-critical reactor is presented. This method is unique in the sense that the delayed neutrons source is derived from the dynamic behavior of the reactor, which serves as the measurement system. An algorithm for analyzing power oscillation measurements was formulated, which avoids the need for a multi-parameter non-linear fit process used by other methods. Using this algorithm results of two sets of measurements performed in IRR-I and IRR-II (Israeli Research Reactors I and II) are presented. The agreement between measured values from both reactors and calculated values based on Keepin (and JENDL-3.3) group parameters is very good. (authors)

  8. Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator

    International Nuclear Information System (INIS)

    Zhu Jiang-Feng; Xu Liang; Lin Qing-Feng; Zhong Xin; Han Hai-Nian; Wei Zhi-Yi

    2013-01-01

    We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624–672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech 2 pulse profile. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  9. Controlled X-ray pumping in a wide range of piezo-electric oscillation frequencies

    CERN Document Server

    Navasardyan, M A; Galoyan, K G

    1986-01-01

    In case of Laue diffraction the transmitted X-ray reflection in shown to be effectively controllable in the perfect quartz single crystal when it generates ultrasonic oscillations at the resonance frequency or in its vicinity. The maximum effective amplitude of applied sinusoidal oscillations is equal to 70 V. The pumping degree depends on the voltage amplitude. In this work monochromatic K subalpha sub 1 and K subalpha sub 2 molybdenum lines satisfying the thin crystal condition, mu t<=1, are used (mu is the linear absorption coefficient of the sample for the given wavelength and t is its thickness). The radiation was reflected from different planes such as (1011), (1011), (2022) etc. The complete pumping strongly restricts the structural factor possibilities in estimating the intensity of diffracted X-rays in case of considerable deformations in the bulk of perfect single crystal.

  10. Decadal summer drought frequency in China: the increasing influence of the Atlantic Multi-decadal Oscillation

    International Nuclear Information System (INIS)

    Qian, Chengcheng; Yu, Jin-Yi; Chen, Ge

    2014-01-01

    Decadal variations in summer drought events during 1956–2005 are examined over Eastern China to identify their leading variability modes and their linkages to the Pacific Decadal Oscillation (PDO), Atlantic Multi-decadal Oscillation (AMO), and global warming. The PDO influence is found to dominate China drought frequency from the 1960s to early 1990s via modulating the Western Pacific Subtropical High and the Mongolian High. The four-pole drought pattern produced by the PDO diminished after the early 1990s, being replaced by a dipolar drought pattern that is produced by the AMO via a Eurasian wave train emanating from North Atlantic to China. The increasing influence of the AMO on China drought since the early 1990s is further shown to be a consequence of global warming. This study indicates that the early 1990s is a time when the Atlantic began to exert a stronger influence on climate over China and even larger part of Asia. (letter)

  11. Measurements of the B0-anti-B0 Oscillation Frequency in Hadronic B Decays

    Energy Technology Data Exchange (ETDEWEB)

    Raven, Gerhard

    2001-07-25

    B{sup 0}{bar B}{sup 0} flavor oscillations have been studied in 20.7 fb{sup -1} of e{sup +}e{sup -} annihilation data collected in 1999 and 2000 with the BABAR detector at center-of-mass energies near the {Upsilon}(4S) resonance. The event sample consists of one B{sup 0} meson fully reconstructed in a hadronic decay mode, while the flavor of the recoiling B{sup 0} in the event is determined with a tagging algorithm that exploits the correlation between the flavor of the heavy quark and the charges of its decay products. By fitting the time development of the observed mixed and unmixed final states, the B{sup 0}{bar B}{sup 0} oscillation frequency, {Delta}m{sub d}, is determined to be 0.519 {+-} 0.020 {+-} 0.016 {Dirac_h} ps{sup -1}.

  12. Numerical Investigation and Experimental Demonstration of Chaos from Two-Stage Colpitts Oscillator in the Ultrahigh Frequency Range

    DEFF Research Database (Denmark)

    Bumeliene, S.; Tamasevicius, A.; Mykolaitis, G.

    2006-01-01

    A hardware prototype of the two-stage Colpitts oscillator employing the microwave BFG520 type transistors with the threshold frequency of 9 GHz and designed to operate in the ultrahigh frequency range (300–1000 MHz) is described. The practical circuit in addition to the intrinsic two-stage oscill......A hardware prototype of the two-stage Colpitts oscillator employing the microwave BFG520 type transistors with the threshold frequency of 9 GHz and designed to operate in the ultrahigh frequency range (300–1000 MHz) is described. The practical circuit in addition to the intrinsic two......-stage oscillator contains an emitter follower acting as a buffer and minimizing the influence of the load. The circuit is investigated both numerically and experimentally. Typical phase portraits, Lyapunov exponents, Lyapunov dimension and broadband continuous power spectra are presented. The main advantage...

  13. Altered low frequency oscillations of cortical vessels in patients with cerebrovascular occlusive disease – a NIRS study

    DEFF Research Database (Denmark)

    Phillip, Dorte; Iversen, Helle K; Schytz, Henrik W

    2013-01-01

    Analysis of cerebral autoregulation by measuring spontaneous oscillations in the low frequency spectrum of cerebral cortical vessels might be a useful tool for assessing risk and investigating different treatment strategies in carotid artery disease and stroke. Near infrared spectroscopy (NIRS...

  14. Measurements of natural frequency and damping constant of single steam bubble oscillating in water

    International Nuclear Information System (INIS)

    Morioka, Mikio

    1983-01-01

    The natural frequency fsub(n) and damping constant delta of a bubble in liquid have been determined by observing the resonance of the bubble to forced oscillation. The bubble was retained under a rigid plate horizontal disk, and the oscillation was applied by underwater speaker. The applied frequency f was kept constant while letting the bubble increase its volume and vary its radius R. Bubble resonance was detected by observing wrinkles appearing on the bubble due to surface waves. Resonance curves relating the amplitude of bubble radius variation to the intensity of applied oscillation is derived theoretically. Good agreement was seen between the data obtained from experiment and the theoretically derived resonance curves at test to the validity of the method proposed of determining fsub(n) and delta from bubble resonance. The values of delta and of the resonant bubble radius R 0 of large steam bubbles (8.5mm< R<11.5mm) in water were determined at f=270, 290 and 358 Hz. The results support the assumption that for large bubbles the value of fsub(n) is little influenced by the exchange of mass between liquid and gaseous phases through evaporation and condensation accompanying bubble pressure oscillation. On the other hand, delta is found to be one order of magnitude higher than calculated for steam bubbles without taking into evaporation and condensation the interphase exchange of mass. The effect brought on delta by the interphase mass exchange can be taken into account by adding a new constant deltasub(ph) to the terms constituting the total damping constant. (author)

  15. Chronic ketamine reduces the peak frequency of gamma oscillations in mouse prefrontal cortex ex vivo

    Directory of Open Access Journals (Sweden)

    James M. McNally

    2013-09-01

    Full Text Available Abnormalities in EEG gamma band oscillations (GBO, 30-80 Hz serve as a prominent biomarker of schizophrenia (Sz, associated with positive, negative and cognitive symptoms. Chronic, subanesthetic administration of antagonists of N-methyl-D-aspartate receptors (NMDAR, such as ketamine, elicits behavioral effects and alterations in cortical interneurons similar to those observed in Sz. However, the chronic effects of ketamine on neocortical GBO are poorly understood. Thus, here we examine the effects of chronic (5 daily i.p. injections application of ketamine (5 and 30 mg/kg and the more specific NMDAR antagonist, MK-801 (0.02, 0.5, and 2 mg/kg, on neocortical GBO ex vivo. Oscillations were generated by focal application of the glutamate receptor agonist, kainate, in coronal brain slices containing the prelimbic cortex. This region constitutes the rodent analogue of the human dorsolateral prefrontal cortex, a brain region strongly implicated in Sz-pathophysiology. Here we report the novel finding that chronic ketamine elicits a reduction in the peak oscillatory frequency of kainate-elicited oscillations (from 47 to 40 Hz at 30 mg/kg. Moreover, the power of GBO in the 40-50 Hz band was reduced. These findings are reminiscent of both the reduced resonance frequency and power of cortical oscillations observed in Sz clinical studies. Surprisingly, MK-801 had no significant effect, suggesting care is needed when equating Sz-like behavioral effects elicited by different NMDAR antagonists to alterations in GBO activity. We conclude that chronic ketamine in the mouse mimics GBO abnormalities observed in Sz patients. Use of this ex vivo slice model may be useful in testing therapeutic compounds which rescue these GBO abnormalities.

  16. Broadband electromagnetic power harvester from vibrations via frequency conversion by impact oscillations

    International Nuclear Information System (INIS)

    Yuksek, N. S.; Almasri, M.; Feng, Z. C.

    2014-01-01

    In this paper, we propose an electromagnetic power harvester that uses a transformative multi-impact approach to achieve a wide bandwidth response from low frequency vibration sources through frequency-up conversion. The device consists of a pick-up coil, fixed at the free edge of a cantilever beam with high resonant frequency, and two cantilever beams with low excitation frequencies, each with an impact mass attached at its free edge. One of the two cantilevers is designed to resonate at 25 Hz, while the other resonates at 50 Hz within the range of ambient vibration frequency. When the device is subjected to a low frequency vibration, the two low-frequency cantilevers responded by vibrating at low frequencies, and thus their thick metallic masses made impacts with the high resonance frequency cantilever repeatedly at two locations. This has caused it along with the pick-up coil to oscillate, relative to the permanent magnet, with decaying amplitude at its resonance frequency, and results in a wide bandwidth response from 10 to 63 Hz at 2 g. A wide bandwidth response between 10–51 Hz and 10–58 Hz at acceleration values of 0.5 g and 2 g, respectively, were achieved by adjusting the impact cantilever frequencies closer to each other (25 Hz and 45 Hz). A maximum output power of 85 μW was achieved at 5 g at 30 Hz across a load resistor, 2.68 Ω.

  17. An Analysis of Decentralized Demand Response as Frequency Control Support under CriticalWind Power Oscillations

    Directory of Open Access Journals (Sweden)

    Jorge Villena

    2015-11-01

    Full Text Available In power systems with high wind energy penetration, the conjunction of wind power fluctuations and power system inertia reduction can lead to large frequency excursions, where the operating reserves of conventional power generation may be insufficient to restore the power balance. With the aim of evaluating the demand-side contribution to frequency control, a complete process to determine critical wind oscillations in power systems with high wind penetration is discussed and described in this paper. This process implies thousands of wind power series simulations, which have been carried out through a validated offshore wind farm model. A large number of different conditions have been taken into account, such as frequency dead bands, the percentages of controllable demand and seasonal factor influence on controllable loads. Relevant results and statistics are also included in the paper.

  18. Frequency-agile terahertz-wave parametric oscillator in a ring-cavity configuration.

    Science.gov (United States)

    Minamide, Hiroaki; Ikari, Tomofumi; Ito, Hiromasa

    2009-12-01

    We demonstrate a frequency-agile terahertz wave parametric oscillator (TPO) in a ring-cavity configuration (ring-TPO). The TPO consists of three mirrors and a MgO:LiNbO(3) crystal under noncollinear phase-matching conditions. A novel, fast frequency-tuning method was realized by controlling a mirror of the three-mirror ring cavity. The wide tuning range between 0.93 and 2.7 THz was accomplished. For first demonstration using the ring-TPO, terahertz spectroscopy was performed as the verification of the frequency-agile performance, measuring the transmission spectrum of the monosaccharide glucose. The spectrum was obtained within about 8 s in good comparison to those of Fourier transform infrared spectrometer.

  19. The effects of extra-low-frequency atmospheric pressure oscillations on human mental activity

    Science.gov (United States)

    Delyukov, A. A.; Didyk, L.

    Slight atmospheric pressure oscillations (APO) in the extra-low-frequency range below 0.1 Hz, which frequently occur naturally, can influence human mental activity. This phenomenon has been observed in experiments with a group of 12 healthy volunteers exposed to experimentally created APO with amplitudes 30-50 Pa in the frequency band 0.011-0.17 Hz. Exposure of the subjects to APO for 15-30 min caused significant changes in attention and short-term memory functions, performance rate, and mental processing flexibility. The character of the response depended on the APO frequency and coherence. Periodic APO promoted purposeful mental activity, accompanied by an increase in breath-holding duration and a slower heart rate. On the other hand, quasi-chaotic APO, similar to the natural perturbations of atmospheric pressure, disrupted mental activity. These observations suggest that APO could be partly responsible for meteorosensitivity in humans.

  20. Numerical investigations of single bubble oscillations generated by a dual frequency excitation

    International Nuclear Information System (INIS)

    Guédra, Matthieu; Inserra, Claude; Gilles, Bruno; Béra, Jean-Christophe

    2015-01-01

    The oscillations of a single bubble excited with a dual frequency acoustic field are numerically investigated. Computations are made for an air bubble in water exposed to an acoustic field with a linearly varying amplitude. The bubble response to an excitation containing two frequencies f 1 = 500 kHz and f 2 = 400 kHz at the same amplitude is compared to the monofrequency case where only f 1 is present. Time-frequency representations show a sharp transition in the bifrequency case, for which the low frequency component f 2 becomes resonant while the high frequency component f 1 is strongly attenuated. The temporal evolution of the power spectra reveals that the resonance of the low frequency component is correlated with the time varying mean radius of the bubble. It is also observed that the total power of the bubble response in the bifrequency case can reach almost twice the power obtained in the monofrequency case, which indicates a strong enhancement of the cavitating behavior of the bubble for this specific frequency combination. (paper)

  1. Multifaceted roles for low-frequency oscillations in bottom-up and top-down processing during navigation and memory.

    Science.gov (United States)

    Ekstrom, Arne D; Watrous, Andrew J

    2014-01-15

    A prominent and replicated finding is the correlation between running speed and increases in low-frequency oscillatory activity in the hippocampal local field potential. A more recent finding concerns low-frequency oscillations that increase in coherence between the hippocampus and neocortical brain areas such as prefrontal cortex during memory-related behaviors (i.e., remembering the correct location to visit). In this review, we tie together movement-related and memory-related low-frequency oscillations in the rodent with similar findings in humans. We argue that although movement-related low-frequency oscillations, in particular, may have slightly different characteristics in humans than rodents, placing important constraints on our thinking about this issue, both phenomena have similar functional foundations. We review four prominent theoretical models that provide partially conflicting accounts of movement-related low-frequency oscillations. We attempt to tie together these theoretical proposals, and existing data in rodents and humans, with memory-related low-frequency oscillations. We propose that movement-related low-frequency oscillations and memory-related low-frequency oscillatory activity, both of which show significant coherence with oscillations in other brain regions, represent different facets of "spectral fingerprints," or different resonant frequencies within the same brain networks underlying different cognitive processes. Together, movement-related and memory-related low-frequency oscillatory coupling may be linked by their distinct contributions to bottom-up, sensorimotor driven processing and top-down, controlled processing characterizing aspects of memory encoding and retrieval. Copyright © 2013. Published by Elsevier Inc.

  2. The Information Content of Anisotropic Baryon Acoustic Oscillation Scale Measurements

    OpenAIRE

    Ross, Ashley J.; Percival, Will J.; Manera, Marc

    2015-01-01

    Anisotropic measurements of the Baryon Acoustic Oscillation (BAO) feature within a galaxy survey enable joint inference about the Hubble parameter $H(z)$ and angular diameter distance $D_A(z)$. These measurements are typically obtained from moments of the measured 2-point clustering statistics, with respect to the cosine of the angle to the line of sight $\\mu$. The position of the BAO features in each moment depends on a combination of $D_A(z)$ and $H(z)$, and measuring the positions in two o...

  3. Hippocampal Ripple Oscillations and Inhibition-First Network Models: Frequency Dynamics and Response to GABA Modulators.

    Science.gov (United States)

    Donoso, José R; Schmitz, Dietmar; Maier, Nikolaus; Kempter, Richard

    2018-03-21

    Hippocampal ripples are involved in memory consolidation, but the mechanisms underlying their generation remain unclear. Models relying on interneuron networks in the CA1 region disagree on the predominant source of excitation to interneurons: either "direct," via the Schaffer collaterals that provide feedforward input from CA3 to CA1, or "indirect," via the local pyramidal cells in CA1, which are embedded in a recurrent excitatory-inhibitory network. Here, we used physiologically constrained computational models of basket-cell networks to investigate how they respond to different conditions of transient, noisy excitation. We found that direct excitation of interneurons could evoke ripples (140-220 Hz) that exhibited intraripple frequency accommodation and were frequency-insensitive to GABA modulators, as previously shown in in vitro experiments. In addition, the indirect excitation of the basket-cell network enabled the expression of intraripple frequency accommodation in the fast-gamma range (90-140 Hz), as in vivo In our model, intraripple frequency accommodation results from a hysteresis phenomenon in which the frequency responds differentially to the rising and descending phases of the transient excitation. Such a phenomenon predicts a maximum oscillation frequency occurring several milliseconds before the peak of excitation. We confirmed this prediction for ripples in brain slices from male mice. These results suggest that ripple and fast-gamma episodes are produced by the same interneuron network that is recruited via different excitatory input pathways, which could be supported by the previously reported intralaminar connectivity bias between basket cells and functionally distinct subpopulations of pyramidal cells in CA1. Together, our findings unify competing inhibition-first models of rhythm generation in the hippocampus. SIGNIFICANCE STATEMENT The hippocampus is a part of the brain of humans and other mammals that is critical for the acquisition and

  4. Highly Stable Wideband Microwave Extraction by Synchronizing Widely Tunable Optoelectronic Oscillator with Optical Frequency Comb

    Science.gov (United States)

    Hou, D.; Xie, X. P.; Zhang, Y. L.; Wu, J. T.; Chen, Z. Y.; Zhao, J. Y.

    2013-12-01

    Optical frequency combs (OFCs), based on mode-locked lasers (MLLs), have attracted considerable attention in many fields over recent years. Among the applications of OFCs, one of the most challenging works is the extraction of a highly stable microwave with low phase noise. Many synchronisation schemes have been exploited to synchronise an electronic oscillator with the pulse train from a MLL, helping to extract an ultra-stable microwave. Here, we demonstrate novel wideband microwave extraction from a stable OFC by synchronising a single widely tunable optoelectronic oscillator (OEO) with an OFC at different harmonic frequencies, using an optical phase detection technique. The tunable range of the proposed microwave extraction extends from 2 GHz to 4 GHz, and in a long-term synchronisation experiment over 12 hours, the proposed synchronisation scheme provided a rms timing drift of 18 fs and frequency instabilities at 1.2 × 10-15/1 s and 2.2 × 10-18/10000 s.

  5. FREQUENCY CATASTROPHE AND CO-EXISTING ATTRACTORS IN A CELL Ca2+ NONLINEAR OSCILLATION MODEL WITH TIME DELAY*

    Institute of Scientific and Technical Information of China (English)

    应阳君; 黄祖洽

    2001-01-01

    Frequency catastrophe is found in a cell Ca2+ nonlinear oscillation model with time delay. The relation of the frequency transition to the time delay is studied by numerical simulations and theoretical analysis. There is a range of parameters in which two kinds of attractors with great frequency differences co-exist in the system. Along with parameter changes, a critical phenomenon occurs and the oscillation frequency changes greatly. This mechanism helps us to deepen the understanding of the complex dynamics of delay systems, and might be of some meaning in cell signalling.

  6. A precise measurement of the [Formula: see text] meson oscillation frequency.

    Science.gov (United States)

    Aaij, R; Abellán Beteta, C; Adeva, B; Adinolfi, M; Affolder, A; Ajaltouni, Z; Akar, S; Albrecht, J; Alessio, F; Alexander, M; Ali, S; Alkhazov, G; Alvarez Cartelle, P; Alves, A A; Amato, S; Amerio, S; Amhis, Y; An, L; Anderlini, L; Anderson, J; Andreassi, G; Andreotti, M; Andrews, J E; Appleby, R B; Aquines Gutierrez, O; Archilli, F; d'Argent, P; Artamonov, A; Artuso, M; Aslanides, E; Auriemma, G; Baalouch, M; Bachmann, S; Back, J J; Badalov, A; Baesso, C; Baldini, W; Barlow, R J; Barschel, C; Barsuk, S; Barter, W; Batozskaya, V; Battista, V; Bay, A; Beaucourt, L; Beddow, J; Bedeschi, F; Bediaga, I; Bel, L J; Bellee, V; Belloli, N; Belyaev, I; Ben-Haim, E; Bencivenni, G; Benson, S; Benton, J; Berezhnoy, A; Bernet, R; Bertolin, A; Bettler, M-O; van Beuzekom, M; Bien, A; Bifani, S; Billoir, P; Bird, T; Birnkraut, A; Bizzeti, A; Blake, T; Blanc, F; Blouw, J; Blusk, S; Bocci, V; Bondar, A; Bondar, N; Bonivento, W; Borghi, S; Borsato, M; Bowcock, T J V; Bowen, E; Bozzi, C; Braun, S; Britsch, M; Britton, T; Brodzicka, J; Brook, N H; Buchanan, E; Bursche, A; Buytaert, J; Cadeddu, S; Calabrese, R; Calvi, M; Calvo Gomez, M; Campana, P; Campora Perez, D; Capriotti, L; Carbone, A; Carboni, G; Cardinale, R; Cardini, A; Carniti, P; Carson, L; Carvalho Akiba, K; Casse, G; Cassina, L; Castillo Garcia, L; Cattaneo, M; Cauet, Ch; Cavallero, G; Cenci, R; Charles, M; Charpentier, Ph; Chefdeville, M; Chen, S; Cheung, S-F; Chiapolini, N; Chrzaszcz, M; Cid Vidal, X; Ciezarek, G; Clarke, P E L; Clemencic, M; Cliff, H V; Closier, J; Coco, V; Cogan, J; Cogneras, E; Cogoni, V; Cojocariu, L; Collazuol, G; Collins, P; Comerma-Montells, A; Contu, A; Cook, A; Coombes, M; Coquereau, S; Corti, G; Corvo, M; Couturier, B; Cowan, G A; Craik, D C; Crocombe, A; Cruz Torres, M; Cunliffe, S; Currie, R; D'Ambrosio, C; Dall'Occo, E; Dalseno, J; David, P N Y; Davis, A; De Aguiar Francisco, O; De Bruyn, K; De Capua, S; De Cian, M; De Miranda, J M; De Paula, L; De Simone, P; Dean, C-T; Decamp, D; Deckenhoff, M; Del Buono, L; Déléage, N; Demmer, M; Derkach, D; Deschamps, O; Dettori, F; Dey, B; Di Canto, A; Di Ruscio, F; Dijkstra, H; Donleavy, S; Dordei, F; Dorigo, M; Dosil Suárez, A; Dossett, D; Dovbnya, A; Dreimanis, K; Dufour, L; Dujany, G; Dupertuis, F; Durante, P; Dzhelyadin, R; Dziurda, A; Dzyuba, A; Easo, S; Egede, U; Egorychev, V; Eidelman, S; Eisenhardt, S; Eitschberger, U; Ekelhof, R; Eklund, L; El Rifai, I; Elsasser, Ch; Ely, S; Esen, S; Evans, H M; Evans, T; Falabella, A; Färber, C; Farley, N; Farry, S; Fay, R; Ferguson, D; Fernandez Albor, V; Ferrari, F; Ferreira Rodrigues, F; Ferro-Luzzi, M; Filippov, S; Fiore, M; Fiorini, M; Firlej, M; Fitzpatrick, C; Fiutowski, T; Fohl, K; Fol, P; Fontana, M; Fontanelli, F; C Forshaw, D; Forty, R; Frank, M; Frei, C; Frosini, M; Fu, J; Furfaro, E; Gallas Torreira, A; Galli, D; Gallorini, S; Gambetta, S; Gandelman, M; Gandini, P; Gao, Y; García Pardiñas, J; Garra Tico, J; Garrido, L; Gascon, D; Gaspar, C; Gauld, R; Gavardi, L; Gazzoni, G; Gerick, D; Gersabeck, E; Gersabeck, M; Gershon, T; Ghez, Ph; Gianì, S; Gibson, V; Girard, O G; Giubega, L; Gligorov, V V; Göbel, C; Golubkov, D; Golutvin, A; Gomes, A; Gotti, C; Grabalosa Gándara, M; Graciani Diaz, R; Granado Cardoso, L A; Graugés, E; Graverini, E; Graziani, G; Grecu, A; Greening, E; Gregson, S; Griffith, P; Grillo, L; Grünberg, O; Gui, B; Gushchin, E; Guz, Yu; Gys, T; Hadavizadeh, T; Hadjivasiliou, C; Haefeli, G; Haen, C; Haines, S C; Hall, S; Hamilton, B; Han, X; Hansmann-Menzemer, S; Harnew, N; Harnew, S T; Harrison, J; He, J; Head, T; Heijne, V; Heister, A; Hennessy, K; Henrard, P; Henry, L; Hernando Morata, J A; van Herwijnen, E; Heß, M; Hicheur, A; Hill, D; Hoballah, M; Hombach, C; Hulsbergen, W; Humair, T; Hussain, N; Hutchcroft, D; Hynds, D; Idzik, M; Ilten, P; Jacobsson, R; Jaeger, A; Jalocha, J; Jans, E; Jawahery, A; Jing, F; John, M; Johnson, D; Jones, C R; Joram, C; Jost, B; Jurik, N; Kandybei, S; Kanso, W; Karacson, M; Karbach, T M; Karodia, S; Kecke, M; Kelsey, M; Kenyon, I R; Kenzie, M; Ketel, T; Khanji, B; Khurewathanakul, C; Kirn, T; Klaver, S; Klimaszewski, K; Kochebina, O; Kolpin, M; Komarov, I; Koopman, R F; Koppenburg, P; Kozeiha, M; Kravchuk, L; Kreplin, K; Kreps, M; Krocker, G; Krokovny, P; Kruse, F; Krzemien, W; Kucewicz, W; Kucharczyk, M; Kudryavtsev, V; K Kuonen, A; Kurek, K; Kvaratskheliya, T; Lacarrere, D; Lafferty, G; Lai, A; Lambert, D; Lanfranchi, G; Langenbruch, C; Langhans, B; Latham, T; Lazzeroni, C; Le Gac, R; van Leerdam, J; Lees, J-P; Lefèvre, R; Leflat, A; Lefrançois, J; Lemos Cid, E; Leroy, O; Lesiak, T; Leverington, B; Li, Y; Likhomanenko, T; Liles, M; Lindner, R; Linn, C; Lionetto, F; Liu, B; Liu, X; Loh, D; Longstaff, I; Lopes, J H; Lucchesi, D; Lucio Martinez, M; Luo, H; Lupato, A; Luppi, E; Lupton, O; Lusardi, N; Lusiani, A; Machefert, F; Maciuc, F; Maev, O; Maguire, K; Malde, S; Malinin, A; Manca, G; Mancinelli, G; Manning, P; Mapelli, A; Maratas, J; Marchand, J F; Marconi, U; Marin Benito, C; Marino, P; Marks, J; Martellotti, G; Martin, M; 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Pappalardo, L L; Pappenheimer, C; Parkes, C; Passaleva, G; Patel, G D; Patel, M; Patrignani, C; Pearce, A; Pellegrino, A; Penso, G; Pepe Altarelli, M; Perazzini, S; Perret, P; Pescatore, L; Petridis, K; Petrolini, A; Petruzzo, M; Picatoste Olloqui, E; Pietrzyk, B; Pilař, T; Pinci, D; Pistone, A; Piucci, A; Playfer, S; Plo Casasus, M; Poikela, T; Polci, F; Poluektov, A; Polyakov, I; Polycarpo, E; Popov, A; Popov, D; Popovici, B; Potterat, C; Price, E; Price, J D; Prisciandaro, J; Pritchard, A; Prouve, C; Pugatch, V; Puig Navarro, A; Punzi, G; Qian, W; Quagliani, R; Rachwal, B; Rademacker, J H; Rama, M; Rangel, M S; Raniuk, I; Rauschmayr, N; Raven, G; Redi, F; Reichert, S; Reid, M M; Dos Reis, A C; Ricciardi, S; Richards, S; Rihl, M; Rinnert, K; Rives Molina, V; Robbe, P; Rodrigues, A B; Rodrigues, E; Rodriguez Lopez, J A; Rodriguez Perez, P; Roiser, S; Romanovsky, V; Romero Vidal, A; W Ronayne, J; Rotondo, M; Rouvinet, J; Ruf, T; Ruiz Valls, P; Saborido Silva, J J; Sagidova, N; Sail, P; 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Wimberley, J; Wishahi, J; Wislicki, W; Witek, M; Wormser, G; Wotton, S A; Wright, S; Wyllie, K; Xie, Y; Xu, Z; Yang, Z; Yu, J; Yuan, X; Yushchenko, O; Zangoli, M; Zavertyaev, M; Zhang, L; Zhang, Y; Zhelezov, A; Zhokhov, A; Zhong, L; Zhukov, V; Zucchelli, S

    2016-01-01

    The oscillation frequency, [Formula: see text], of [Formula: see text] mesons is measured using semileptonic decays with a [Formula: see text] or [Formula: see text] meson in the final state. The data sample corresponds to 3.0[Formula: see text] of pp collisions, collected by the LHCb experiment at centre-of-mass energies [Formula: see text] = 7 and 8[Formula: see text]. A combination of the two decay modes gives [Formula: see text], where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is consistent with the current world average and has similar precision.

  7. The importance of individual frequencies of endogenous brain oscillations for auditory cognition - A short review.

    Science.gov (United States)

    Baltus, Alina; Herrmann, Christoph Siegfried

    2016-06-01

    Oscillatory EEG activity in the human brain with frequencies in the gamma range (approx. 30-80Hz) is known to be relevant for a large number of cognitive processes. Interestingly, each subject reveals an individual frequency of the auditory gamma-band response (GBR) that coincides with the peak in the auditory steady state response (ASSR). A common resonance frequency of auditory cortex seems to underlie both the individual frequency of the GBR and the peak of the ASSR. This review sheds light on the functional role of oscillatory gamma activity for auditory processing. For successful processing, the auditory system has to track changes in auditory input over time and store information about past events in memory which allows the construction of auditory objects. Recent findings support the idea of gamma oscillations being involved in the partitioning of auditory input into discrete samples to facilitate higher order processing. We review experiments that seem to suggest that inter-individual differences in the resonance frequency are behaviorally relevant for gap detection and speech processing. A possible application of these resonance frequencies for brain computer interfaces is illustrated with regard to optimized individual presentation rates for auditory input to correspond with endogenous oscillatory activity. This article is part of a Special Issue entitled SI: Auditory working memory. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Spatiotemporal frequency characteristics of cerebral oscillations during the perception of fundamental frequency contour changes in one-syllable intonation.

    Science.gov (United States)

    Ueno, Sanae; Okumura, Eiichi; Remijn, Gerard B; Yoshimura, Yuko; Kikuchi, Mitsuru; Shitamichi, Kiyomi; Nagao, Kikuko; Mochiduki, Masayuki; Haruta, Yasuhiro; Hayashi, Norio; Munesue, Toshio; Tsubokawa, Tsunehisa; Oi, Manabu; Nakatani, Hideo; Higashida, Haruhiro; Minabe, Yoshio

    2012-05-02

    Accurate perception of fundamental frequency (F0) contour changes in the human voice is important for understanding a speaker's intonation, and consequently also his/her attitude. In this study, we investigated the neural processes involved in the perception of F0 contour changes in the Japanese one-syllable interjection "ne" in 21 native-Japanese listeners. A passive oddball paradigm was applied in which "ne" with a high falling F0 contour, used when urging a reaction from the listener, was randomly presented as a rare deviant among a frequent "ne" syllable with a flat F0 contour (i.e., meaningless intonation). We applied an adaptive spatial filtering method to the neuromagnetic time course recorded by whole-head magnetoencephalography (MEG) and estimated the spatiotemporal frequency dynamics of event-related cerebral oscillatory changes in the oddball paradigm. Our results demonstrated a significant elevation of beta band event-related desynchronization (ERD) in the right temporal and frontal areas, in time windows from 100 to 300 and from 300 to 500 ms after the onset of deviant stimuli (high falling F0 contour). This is the first study to reveal detailed spatiotemporal frequency characteristics of cerebral oscillations during the perception of intonational (not lexical) F0 contour changes in the human voice. The results further confirmed that the right hemisphere is associated with perception of intonational F0 contour information in the human voice, especially in early time windows. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  9. Exploring the time-frequency content of high frequency oscillations for automated identification of seizure onset zone in epilepsy.

    Science.gov (United States)

    Liu, Su; Sha, Zhiyi; Sencer, Altay; Aydoseli, Aydin; Bebek, Nerse; Abosch, Aviva; Henry, Thomas; Gurses, Candan; Ince, Nuri Firat

    2016-04-01

    High frequency oscillations (HFOs) in intracranial electroencephalography (iEEG) recordings are considered as promising clinical biomarkers of epileptogenic regions in the brain. The aim of this study is to improve and automatize the detection of HFOs by exploring the time-frequency content of iEEG and to investigate the seizure onset zone (SOZ) detection accuracy during the sleep, awake and pre-ictal states in patients with epilepsy, for the purpose of assisting the localization of SOZ in clinical practice. Ten-minute iEEG segments were defined during different states in eight patients with refractory epilepsy. A three-stage algorithm was implemented to detect HFOs in these segments. First, an amplitude based initial detection threshold was used to generate a large pool of HFO candidates. Then distinguishing features were extracted from the time and time-frequency domain of the raw iEEG and used with a Gaussian mixture model clustering to isolate HFO events from other activities. The spatial distribution of HFO clusters was correlated with the seizure onset channels identified by neurologists in seven patient with good surgical outcome. The overlapping rates of localized channels and seizure onset locations were high in all states. The best result was obtained using the iEEG data during sleep, achieving a sensitivity of 81%, and a specificity of 96%. The channels with maximum number of HFOs identified epileptogenic areas where the seizures occurred more frequently. The current study was conducted using iEEG data collected in realistic clinical conditions without channel pre-exclusion. HFOs were investigated with novel features extracted from the entire frequency band, and were correlated with SOZ in different states. The results indicate that automatic HFO detection with unsupervised clustering methods exploring the time-frequency content of raw iEEG can be efficiently used to identify the epileptogenic zone with an accurate and efficient manner.

  10. Low Noise Frequency Comb Sources Based on Synchronously Pumped Doubly Resonant Optical Parametric Oscillators

    Science.gov (United States)

    Wan, Chenchen

    Optical frequency combs are coherent light sources consist of thousands of equally spaced frequency lines. Frequency combs have achieved success in applications of metrology, spectroscopy and precise pulse manipulation and control. The most common way to generate frequency combs is based on mode-locked lasers which has the output spectrum of comb structures. To generate stable frequency combs, the output from mode-locked lasers need to be phase stabilized. The whole comb lines will be stabilized if the pulse train repetition rate corresponding to comb spacing and the pulse carrier envelope offset (CEO) frequency are both stabilized. The output from a laser always has fluctuations in parameters known as noise. In laser applications, noise is an important factor to limit the performance and often need to be well controlled. For example in precision measurement such as frequency metrology and precise spectroscopy, low laser intensity and phase noise is required. In mode-locked lasers there are different types of noise like intensity noise, pulse temporal position noise also known as timing jitter, optical phase noise. In term for frequency combs, these noise dynamics is more complex and often related. Understanding the noise behavior is not only of great interest in practical applications but also help understand fundamental laser physics. In this dissertation, the noise of frequency combs and mode-locked lasers will be studied in two projects. First, the CEO frequency phase noise of a synchronously pumped doubly resonant optical parametric oscillators (OPO) will be explored. This is very important for applications of the OPO as a coherent frequency comb source. Another project will focus on the intensity noise coupling in a soliton fiber oscillator, the finding of different noise coupling in soliton pulses and the dispersive waves generated from soliton perturbation can provide very practical guidance for low noise soliton laser design. OPOs are used to generate

  11. Low frequency acoustic properties of bilayer membrane acoustic metamaterial with magnetic oscillator

    Directory of Open Access Journals (Sweden)

    Nansha Gao

    2017-07-01

    Full Text Available A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis (FEA results agree well with the experimental results. It is proved that the sound transmission losses (STLs of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control. Keywords: Bilayer membrane acoustic metamaterial, Low frequency sound insulation, Sound transmission loss, Magnet oscillator

  12. Distinguishing low frequency oscillations within the 1/f spectral behaviour of electromagnetic brain signals.

    Science.gov (United States)

    Demanuele, Charmaine; James, Christopher J; Sonuga-Barke, Edmund Js

    2007-12-10

    It has been acknowledged that the frequency spectrum of measured electromagnetic (EM) brain signals shows a decrease in power with increasing frequency. This spectral behaviour may lead to difficulty in distinguishing event-related peaks from ongoing brain activity in the electro- and magnetoencephalographic (EEG and MEG) signal spectra. This can become an issue especially in the analysis of low frequency oscillations (LFOs) - below 0.5 Hz - which are currently being observed in signal recordings linked with specific pathologies such as epileptic seizures or attention deficit hyperactivity disorder (ADHD), in sleep studies, etc. In this work we propose a simple method that can be used to compensate for this 1/f trend hence achieving spectral normalisation. This method involves filtering the raw measured EM signal through a differentiator prior to further data analysis. Applying the proposed method to various exemplary datasets including very low frequency EEG recordings, epileptic seizure recordings, MEG data and Evoked Response data showed that this compensating procedure provides a flat spectral base onto which event related peaks can be clearly observed. Findings suggest that the proposed filter is a useful tool for the analysis of physiological data especially in revealing very low frequency peaks which may otherwise be obscured by the 1/f spectral activity inherent in EEG/MEG recordings.

  13. Distinguishing low frequency oscillations within the 1/f spectral behaviour of electromagnetic brain signals

    Directory of Open Access Journals (Sweden)

    Sonuga-Barke Edmund JS

    2007-12-01

    Full Text Available Abstract Background It has been acknowledged that the frequency spectrum of measured electromagnetic (EM brain signals shows a decrease in power with increasing frequency. This spectral behaviour may lead to difficulty in distinguishing event-related peaks from ongoing brain activity in the electro- and magnetoencephalographic (EEG and MEG signal spectra. This can become an issue especially in the analysis of low frequency oscillations (LFOs – below 0.5 Hz – which are currently being observed in signal recordings linked with specific pathologies such as epileptic seizures or attention deficit hyperactivity disorder (ADHD, in sleep studies, etc. Methods In this work we propose a simple method that can be used to compensate for this 1/f trend hence achieving spectral normalisation. This method involves filtering the raw measured EM signal through a differentiator prior to further data analysis. Results Applying the proposed method to various exemplary datasets including very low frequency EEG recordings, epileptic seizure recordings, MEG data and Evoked Response data showed that this compensating procedure provides a flat spectral base onto which event related peaks can be clearly observed. Conclusion Findings suggest that the proposed filter is a useful tool for the analysis of physiological data especially in revealing very low frequency peaks which may otherwise be obscured by the 1/f spectral activity inherent in EEG/MEG recordings.

  14. Filterless low-phase-noise frequency-quadrupled microwave generation based on a multimode optoelectronic oscillator

    Science.gov (United States)

    Teng, Yichao; Zhang, Pin; Zhang, Baofu; Chen, Yiwang

    2018-02-01

    A scheme to realize low-phase-noise frequency-quadrupled microwave generation without any filter is demonstrated. In this scheme, a multimode optoelectronic oscillator is mainly contributed by dual-parallel Mach-Zehnder modulators, fiber, photodetector, and microwave amplifier. The local source signal is modulated by a child MZM (MZMa), which is worked at maximum transmission point. Through properly adjusting the bias voltages of the other child MZM (MZMb) and the parent MZM (MZMc), optical carrier is effectively suppressed and second sidebands are retained, then the survived optical signal is fed back to the photodetector and MZMb to form an optoelectronic hybrid resonator and realize frequency-quadrupled signal generation. Due to the high Q-factor and mode selection effect of the optoelectronic hybrid resonator, compared with the source signal, the generated frequency-quadrupled signal has a lower phase noise. The approach has verified by experiments, and 18, 22, and 26 GHz frequency-quadrupled signal are generated by 4.5, 5.5, and 6.5 GHz local source signals. Compared with 4.5 GHz source signal, the phase noise of generated 18 GHz signal at 10 kHz frequency offset has 26.5 dB reduction.

  15. Nonlinear oscillation and interfacial stability of an encapsulated microbubble under dual-frequency ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yunqiao [MOE Key Laboratory of Hydrodynamics, Department of Engineering Mechanics, Shanghai Jiao Tong University, Shanghai 200240 (China); Calvisi, Michael L [Department of Mechanical and Aerospace Engineering, University of Colorado, Colorado Springs, CO 80918, United States of America (United States); Wang, Qianxi, E-mail: yunqiaoliu@sjtu.edu.cn [School of Mathematics, University of Birmingham, Birmingham B15 2TT (United Kingdom)

    2017-04-15

    Encapsulated microbubbles (EMBs) are widely used in medical ultrasound imaging as contrast-enhanced agents. However, the potential damaging effects of violent collapsing EMBs to cells and tissues in clinical settings have remained a concern. Dual-frequency ultrasound is a promising technique for improving the efficacy and safety of sonography. The system modeled consists of the external liquid, membrane and internal gases of an EMB. The microbubble dynamics are simulated using a simple nonlinear interactive theory, considering the compressibility of the internal gas, viscosity of the liquid flow and viscoelasticity of the membrane. The radial oscillation and interfacial stability of an EMB under single- and dual-frequency excitations are compared. The simulation results show that the dual-frequency technique produces larger backscatter pressure at higher harmonics of the primary driving frequency—this enriched acoustic spectrum can enhance blood-tissue contrast and improve the quality of sonographic images. The results further show that the acoustic pressure threshold associated with the onset of shape instability is greater for dual-frequency driving. This suggests that the dual-frequency technique stabilizes the encapsulated bubble, thereby improving the efficacy and safety of contrast-enhanced agents. (paper)

  16. Model based PI power system stabilizer design for damping low frequency oscillations in power systems.

    Science.gov (United States)

    Salgotra, Aprajita; Pan, Somnath

    2018-05-01

    This paper explores a two-level control strategy by blending local controller with centralized controller for the low frequency oscillations in a power system. The proposed control scheme provides stabilization of local modes using a local controller and minimizes the effect of inter-connection of sub-systems performance through a centralized control. For designing the local controllers in the form of proportional-integral power system stabilizer (PI-PSS), a simple and straight forward frequency domain direct synthesis method is considered that works on use of a suitable reference model which is based on the desired requirements. Several examples both on one machine infinite bus and multi-machine systems taken from the literature are illustrated to show the efficacy of the proposed PI-PSS. The effective damping of the systems is found to be increased remarkably which is reflected in the time-responses; even unstable operation has been stabilized with improved damping after applying the proposed controller. The proposed controllers give remarkable improvement in damping the oscillations in all the illustrations considered here and as for example, the value of damping factor has been increased from 0.0217 to 0.666 in Example 1. The simulation results obtained by the proposed control strategy are favourably compared with some controllers prevalent in the literature. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  17. Long-Period Oscillations of Hydraulic Fractures: Attenuation, Scaling Relationships, and Flow Stability

    Science.gov (United States)

    Lipovsky, B.; Dunham, E. M.

    2013-12-01

    Long-period seismicity due to the excitation of hydraulic fracture normal modes is thought to occur in many geological systems, including volcanoes, glaciers and ice sheets, and hydrocarbon reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluid within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis that accounts for quasi-dynamic elasticity of the fracture wall, as well as fluid drag, inertia, and compressibility. We consider symmetric perturbations and neglect the effects of stratification and gravity. In the long-wavelength or thin-fracture limit, dispersive guided waves known as crack waves propagate with phase velocity cw=√(G*|k|w/ρ), where G* = G/(1-υ) for shear modulus G and Poisson ratio υ, w is the crack half-width, k is the wavenumber, and ρ is the fluid density. Restoring forces from elastic wall deformation drive wave motions. In the opposite, short-wavelength limit, guided waves are simply sound waves within the fluid and little seismic excitation occurs due to minimal fluid-solid coupling. We focus on long-wavelength crack waves, which, in the form of standing wave modes in finite-length cracks, are thought to be a common mechanism for long-period seismicity. The dispersive nature of crack waves implies several basic scaling relations that might be useful when interpreting statistics of long-period events. Seismic observations may constrain a characteristic frequency f0 and seismic moment M0~GδwR2, where δw is the change in crack width and R is the crack dimension. Resonant modes of a fluid-filled crack have associated frequencies f~cw/R. Linear elasticity provides a link between pressure changes δp in the crack and the induced opening δw: δp~G δw/R. Combining these, and assuming that pressure changes have no variation with crack dimension, leads to the scaling law relating seismic moment and oscillation frequency, M0~(Gwδp/ρ)f0

  18. Effective deep brain stimulation suppresses low frequency network oscillations in the basal ganglia by regularizing neural firing patterns

    Science.gov (United States)

    McConnell, George C.; So, Rosa Q.; Hilliard, Justin D; Lopomo, Paola; Grill, Warren M.

    2012-01-01

    Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for the motor symptoms of Parkinson’s disease (PD). The effects of DBS depend strongly on stimulation frequency: high frequencies (>90Hz) improve motor symptoms, while low frequencies (basal ganglia were studied in the unilateral 6-hydroxydopamine lesioned rat model of PD. Only high frequency DBS reversed motor symptoms and the effectiveness of DBS depended strongly on stimulation frequency in a manner reminiscent of its clinical effects in persons with PD. Quantification of single-unit activity in the globus pallidus externa (GPe) and substantia nigra reticulata (SNr) revealed that high frequency DBS, but not low frequency DBS, reduced pathological low frequency oscillations (~9Hz) and entrained neurons to fire at the stimulation frequency. Similarly, the coherence between simultaneously recorded pairs of neurons within and across GPe and SNr shifted from the pathological low frequency band to the stimulation frequency during high frequency DBS, but not during low frequency DBS. The changes in firing patterns in basal ganglia neurons were not correlated with changes in firing rate. These results indicate that high frequency DBS is more effective than low frequency DBS, not as a result of changes in firing rate, but rather due to its ability to replace pathological low frequency network oscillations with a regularized pattern of neuronal firing. PMID:23136407

  19. Effective deep brain stimulation suppresses low-frequency network oscillations in the basal ganglia by regularizing neural firing patterns.

    Science.gov (United States)

    McConnell, George C; So, Rosa Q; Hilliard, Justin D; Lopomo, Paola; Grill, Warren M

    2012-11-07

    Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for the motor symptoms of Parkinson's disease (PD). The effects of DBS depend strongly on stimulation frequency: high frequencies (>90 Hz) improve motor symptoms, while low frequencies (basal ganglia were studied in the unilateral 6-hydroxydopamine lesioned rat model of PD. Only high-frequency DBS reversed motor symptoms, and the effectiveness of DBS depended strongly on stimulation frequency in a manner reminiscent of its clinical effects in persons with PD. Quantification of single-unit activity in the globus pallidus externa (GPe) and substantia nigra reticulata (SNr) revealed that high-frequency DBS, but not low-frequency DBS, reduced pathological low-frequency oscillations (∼9 Hz) and entrained neurons to fire at the stimulation frequency. Similarly, the coherence between simultaneously recorded pairs of neurons within and across GPe and SNr shifted from the pathological low-frequency band to the stimulation frequency during high-frequency DBS, but not during low-frequency DBS. The changes in firing patterns in basal ganglia neurons were not correlated with changes in firing rate. These results indicate that high-frequency DBS is more effective than low-frequency DBS, not as a result of changes in firing rate, but rather due to its ability to replace pathological low-frequency network oscillations with a regularized pattern of neuronal firing.

  20. How do the multiple large-scale climate oscillations trigger extreme precipitation?

    Science.gov (United States)

    Shi, Pengfei; Yang, Tao; Xu, Chong-Yu; Yong, Bin; Shao, Quanxi; Li, Zhenya; Wang, Xiaoyan; Zhou, Xudong; Li, Shu

    2017-10-01

    Identifying the links between variations in large-scale climate patterns and precipitation is of tremendous assistance in characterizing surplus or deficit of precipitation, which is especially important for evaluation of local water resources and ecosystems in semi-humid and semi-arid regions. Restricted by current limited knowledge on underlying mechanisms, statistical correlation methods are often used rather than physical based model to characterize the connections. Nevertheless, available correlation methods are generally unable to reveal the interactions among a wide range of climate oscillations and associated effects on precipitation, especially on extreme precipitation. In this work, a probabilistic analysis approach by means of a state-of-the-art Copula-based joint probability distribution is developed to characterize the aggregated behaviors for large-scale climate patterns and their connections to precipitation. This method is employed to identify the complex connections between climate patterns (Atlantic Multidecadal Oscillation (AMO), El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) and seasonal precipitation over a typical semi-humid and semi-arid region, the Haihe River Basin in China. Results show that the interactions among multiple climate oscillations are non-uniform in most seasons and phases. Certain joint extreme phases can significantly trigger extreme precipitation (flood and drought) owing to the amplification effect among climate oscillations.

  1. Laser Raman spectroscopy of the effect of solvent on the low-frequency oscillations of organic molecules

    Science.gov (United States)

    Brandt, N. N.; Chikishev, A. Yu.; Dolgovskii, V. I.; Lebedenko, S. I.

    2007-09-01

    The effect of solvent on low-frequency oscillations is studied using an example of the 1,1,2,2-tetrachloroethane (TCE) and 1,1,2,2-tetrabromoethane (TBE) molecules, which exhibit torsional oscillations in the terahertz range. Dimethylsulfoxide (DMSO) and carbon tetrachloride (CTC) are used as solvents. It is demonstrated that a decrease in the concentration of the substance under study in the TBE/CTC, TCE/DMSO, and TCE/CTC mixtures leads to a frequency shift of the low-frequency oscillation. The shift is not observed in the TBE/DMSO mixture but a decrease in the TBE concentration causes significant broadening of the low-frequency line.

  2. Low-frequency oscillations in default mode subnetworks are associated with episodic memory impairments in Alzheimer's disease.

    Science.gov (United States)

    Veldsman, Michele; Egorova, Natalia; Singh, Baljeet; Mungas, Dan; DeCarli, Charles; Brodtmann, Amy

    2017-11-01

    Disruptions to functional connectivity in subsystems of the default mode network are evident in Alzheimer's disease (AD). Functional connectivity estimates correlations in the time course of low-frequency activity. Much less is known about other potential perturbations to this activity, such as changes in the amplitude of oscillations and how this relates to cognition. We examined the amplitude of low-frequency fluctuations in 44 AD patients and 128 cognitively normal participants and related this to episodic memory, the core deficit in AD. We show higher amplitudes of low-frequency oscillations in AD patients. Rather than being compensatory, this appears to be maladaptive, with greater amplitude in the ventral default mode subnetwork associated with poorer episodic memory. Perturbations to default mode subnetworks in AD are evident in the amplitude of low-frequency oscillations in the resting brain. These disruptions are associated with episodic memory demonstrating their behavioral and clinical relevance in AD. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Allometric scaling relationship between frequency of intestinal ...

    Indian Academy of Sciences (India)

    2013-02-27

    Feb 27, 2013 ... 2Department of Basic Sciences, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran. 3School of Electrical and Computer Engineering, College of Engineering, University of Tehran, ... The question is, what kind of relationship can be ... allometric scaling has been used to predict human clinical.

  4. Nonstandard scaling law of fluctuations in finite-size systems of globally coupled oscillators.

    Science.gov (United States)

    Nishikawa, Isao; Tanaka, Gouhei; Aihara, Kazuyuki

    2013-08-01

    Universal scaling laws form one of the central issues in physics. A nonstandard scaling law or a breakdown of a standard scaling law, on the other hand, can often lead to the finding of a new universality class in physical systems. Recently, we found that a statistical quantity related to fluctuations follows a nonstandard scaling law with respect to the system size in a synchronized state of globally coupled nonidentical phase oscillators [I. Nishikawa et al., Chaos 22, 013133 (2012)]. However, it is still unclear how widely this nonstandard scaling law is observed. In the present paper, we discuss the conditions required for the unusual scaling law in globally coupled oscillator systems and validate the conditions by numerical simulations of several different models.

  5. Experiments and characterization of low-frequency oscillations in a granular column

    Science.gov (United States)

    Oyarte Gálvez, Loreto; Rivas, Nicolás; van der Meer, Devaraj

    2018-04-01

    The behavior of a vertically vibrated granular bed is reminiscent of a liquid in that it exhibits many phenomena such as convection and Faraday-like surface waves. However, when the lateral dimensions of the bed are confined such that a quasi-one-dimensional geometry is formed, the only phenomena that remain are bouncing bed and the granular Leidenfrost effect. This permits the observation of the granular Leidenfrost state for a wide range of energy injection parameters and more specifically allows for a thorough characterization of the low-frequency oscillation (LFO) that is present in this state. In both experiments and particle simulations we determine the LFO frequency from the power spectral density of the center-of-mass signal of the grains, varying the amplitude and frequency of the driving, the particle diameter, and the number of layers in the system. We thus find that the LFO frequency (i) is inversely proportional to the fast inertial timescale and (ii) decorrelates with a typical decay time proportional to the slow dissipative timescale in the system. The latter is consistent with the view that the LFO is driven by the inherent noise that is present in the granular Leidenfrost state with a low number of particles.

  6. Cross-frequency synchronization connects networks of fast and slow oscillations during visual working memory maintenance.

    Science.gov (United States)

    Siebenhühner, Felix; Wang, Sheng H; Palva, J Matias; Palva, Satu

    2016-09-26

    Neuronal activity in sensory and fronto-parietal (FP) areas underlies the representation and attentional control, respectively, of sensory information maintained in visual working memory (VWM). Within these regions, beta/gamma phase-synchronization supports the integration of sensory functions, while synchronization in theta/alpha bands supports the regulation of attentional functions. A key challenge is to understand which mechanisms integrate neuronal processing across these distinct frequencies and thereby the sensory and attentional functions. We investigated whether such integration could be achieved by cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography, we found that CFS was load-dependently enhanced between theta and alpha-gamma and between alpha and beta-gamma oscillations during VWM maintenance among visual, FP, and dorsal attention (DA) systems. CFS also connected the hubs of within-frequency-synchronized networks and its strength predicted individual VWM capacity. We propose that CFS integrates processing among synchronized neuronal networks from theta to gamma frequencies to link sensory and attentional functions.

  7. 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.

  8. 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

  9. Interplay of intrinsic and synaptic conductances in the generation of high-frequency oscillations in interneuronal networks with irregular spiking.

    Science.gov (United States)

    Baroni, Fabiano; Burkitt, Anthony N; Grayden, David B

    2014-05-01

    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 of

  10. Measurement of the Bs anti-Bs oscillation frequency using semileptonic decays

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, Vivek [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2007-05-01

    This thesis reports a time dependent measurement of the B$0\\atop{s}$-$\\bar{B}$$0\\atop{s}$ oscillation frequency Δms using semileptonic decays B$0\\atop{s}$ → D$-\\atop{s}$ℓ+X. We use a data sample of 1 fb-1 of pp collisions at √s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron Collider to reconstruct ~ 61, 500 semileptonic B$0\\atop{s}$ decays. This analysis of B$0\\atop{s}$-$\\bar{B}$$0\\atop{s}$ mixing has a sensitivity of 19.4 ps-1 and shows an evidence of B$0\\atop{s}$ oscillations at Δms ~17.75 ps-1 with an amplitude significance of ~2. In combination with the analyses of ~ 8,700 hadronic B$0\\atop{s}$ decays at CDF, we have made the first direct observation of time-dependent B$0\\atop{s}$-$\\bar{B}$$0\\atop{s}$ flavor oscillations measuring Δms = 17.77$+0.09\\atop{-0.10}$ (stat) ± 0.07 (syst) ps -1. The obtained value of Δms agrees with the Standard Model expectation. When combined with the world average values for Δmd, m$\\bar{B}$0s and m $\\bar{B}$0s, along with other theoretical input, this result yields the ratio of CKM matrix elements |Vtd/Vts| = 0.2060 ± 0.0007 (exp)$+0.0081\\atop{-0.0060}$ (theor).

  11. Scaling and parametric studies of condensation oscillation in an in-containment refueling water storage tank

    International Nuclear Information System (INIS)

    Lee, Jun Hyung; No, Hee Cheon

    2001-01-01

    The purpose of this paper is to study the condensation oscillation phenomena by steam-jetting into subcooled water through a sparger, implementing a scaling methodology and the similarity correlation between the test facility and model prototype. In additon, the results of this study can provide suitable guidelines for sparger design utilized in the IRWST for the Advanced Passive Reactor 1400 (APR 1400). To corroborate the scaling methodology, various experimental tests were conducted. The scaling-related parameters experimentally considered were water temperatures, mass flux, discharge system volumes, tank sizes, source pressure, steam-jetting directions, and numbers of sparger discharge holes. To preserve the scaling similarity, the thickness of the minimum water volume created by the boundary layer that encloses the steam cavity was found to be equal to the maximum length of the steam cavity formed. Four key scaling parameters were identified and empirically correlated with the maximum amplitude of pressure oscillation. They are as follows: Volume of the steam cavity, flow restriction coefficient, discharge hole area, and density ratio of steam to water. Variations of the oscillation amplitude were small when steam-jetting directions were altered. The concept of a reduction factor was introduced for estimating the oscillation amplitude of the multi-hole sparger with test data from a single-hole sparger

  12. Spontaneous high-frequency (10-80 Hz) oscillations during up states in the cerebral cortex in vitro.

    Science.gov (United States)

    Compte, Albert; Reig, Ramon; Descalzo, Vanessa F; Harvey, Michael A; Puccini, Gabriel D; Sanchez-Vives, Maria V

    2008-12-17

    High-frequency oscillations in cortical networks have been linked to a variety of cognitive and perceptual processes. They have also been recorded in small cortical slices in vitro, indicating that neuronal synchronization at these frequencies is generated in the local cortical circuit. However, in vitro experiments have hitherto necessitated exogenous pharmacological or electrical stimulation to generate robust synchronized activity in the beta/gamma range. Here, we demonstrate that the isolated cortical microcircuitry generates beta and gamma oscillations spontaneously in the absence of externally applied neuromodulators or synaptic agonists. We show this in a spontaneously active slice preparation that engages in slow oscillatory activity similar to activity during slow-wave sleep. beta and gamma synchronization appeared during the up states of the slow oscillation. Simultaneous intracellular and extracellular recordings revealed synchronization between the timing of incoming synaptic events and population activity. This rhythm was mechanistically similar to pharmacologically induced gamma rhythms, as it also included sparse, irregular firing of neurons within the population oscillation, predominant involvement of inhibitory neurons, and a decrease of oscillation frequency after barbiturate application. Finally, we show in a computer model how a synaptic loop between excitatory and inhibitory neurons can explain the emergence of both the slow (network. We therefore conclude that oscillations in the beta/gamma range that share mechanisms with activity reported in vivo or in pharmacologically activated in vitro preparations can be generated during slow oscillatory activity in the local cortical circuit, even without exogenous pharmacological or electrical stimulation.

  13. Safety and effectiveness of the high-frequency chest wall oscillation vs intrapulmonary percussive ventilation in patients with severe COPD

    Directory of Open Access Journals (Sweden)

    Nicolini A

    2018-02-01

    Full Text Available Antonello Nicolini,1 Bruna Grecchi,2 Maura Ferrari-Bravo,3 Cornelius Barlascini4 1Respiratory Diseases Unit, Hospital of Sestri Levante, Sestri Levante, Italy; 2Rehabilitation Unit, ASL4 Chiavarese, Chiavari, Italy; 3Statistics Unit, ASL4 Chiavarese, Chiavari, Italy; 4Health Medicine Unit, Hospital of Sestri Levante, Sestri Levante, Italy Purpose: Chest physiotherapy is an important tool in the treatment of COPD. Intrapulmonary percussive ventilation (IPV and high-frequency chest wall oscillation (HFCWO are techniques designed to create a global percussion of the lung which removes secretions and probably clears the peripheral bronchial tree. We tested the hypothesis that adding IPV or HFCWO to the best pharmacological therapy (PT may provide additional clinical benefit over chest physiotherapy in patients with severe COPD. Methods: Sixty patients were randomized into three groups (20 patients in each group: IPV group (treated with PT and IPV, PT group with (treated with PT and HFCWO, and control group (treated with PT alone. Primary outcome measures included results on the dyspnea scale (modified Medical Research Council and Breathlessness, Cough, and Sputum scale (BCSS, as well as an evaluation of daily life activity (COPD Assessment Test [CAT]. Secondary outcome measures were pulmonary function testing, arterial blood gas analysis, and hematological examinations. Moreover, sputum cell counts were performed at the beginning and at the end of the study. Results: Patients in both the IPV group and the HFCWO group showed a significant improvement in the tests of dyspnea and daily life activity evaluations (modified Medical Research Council scale, BCSS, and CAT compared to the control group, as well as in pulmonary function tests (forced vital capacity, forced expiratory volume in 1 second, forced expiratory volume in 1 second/forced vital capacity%, total lung capacity, residual volume, diffusing lung capacity monoxide, maximal inspiratory

  14. 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.

  15. Low-frequency blood pressure oscillations and inotrope treatment failure in premature infants.

    Science.gov (United States)

    Vesoulis, Zachary A; Hao, Jessica; McPherson, Christopher; El Ters, Nathalie M; Mathur, Amit M

    2017-07-01

    The underlying mechanism as to why some hypotensive preterm infants do not respond to inotropic medications remains unclear. For these infants, we hypothesize that impaired vasomotor function is a significant factor and is manifested through a decrease in low-frequency blood pressure variability across regulatory components of vascular tone. Infants born ≤28 wk estimated gestational age underwent prospective recording of mean arterial blood pressure for 72 h after birth. After error correction, root-mean-square spectral power was calculated for each valid 10-min data frame across each of four frequency bands ( B1 , 0.005-0.0095 Hz; B2 , 0.0095-0.02 Hz; B3 , 0.02-0.06 Hz; and B4 , 0.06-0.16) corresponding to different components of vasomotion control. Forty infants (twenty-nine normotensive control and eleven inotrope-exposed) were included with a mean ± SD estimated gestational age of 25.2 ± 1.6 wk and birth weight 790 ± 211 g. 9.7/11.8 Million (82%) data points were error-free and used for analysis. Spectral power across all frequency bands increased with time, although the magnitude was 20% less in the inotrope-exposed infants. A statistically significant increase in spectral power in response to inotrope initiation was noted across all frequency bands. Infants with robust blood pressure response to inotropes had a greater increase compared with those who had limited or no blood pressure response. In this study, hypotensive infants who require inotropes have decreased low-frequency variability at baseline compared with normotensive infants, which increases after inotrope initiation. Low-frequency spectral power does not change for those with inotrope treatment failure, suggesting dysfunctional regulation of vascular tone as a potential mechanism of treatment failure. NEW & NOTEWORTHY In this study, we examine patterns of low-frequency oscillations in blood pressure variability across regulatory components of vascular tone in normotensive and

  16. Analysis of hysteresis characteristics and low frequency oscillation in gas discharge plasma

    International Nuclear Information System (INIS)

    Matsunaga, Yasushi; Kato, Tomokazu

    1997-01-01

    Hysteresis of gas discharge plasma and nonlinear oscillation of low frequency, caused by the trapped ion, are analyzed. Mainly, the hysteresis and emergence of multiple-steady states are discussed by a simple model of chemical-reaction system. It is shown that a function describing the energy balance has three different real roots. The condition for plural roots depends on the ratio of the bulk energy increase to the surface energy loss of plasma. The criterion contains the non-thermodynamic variables such as conductivity and surface quantities. Examination of stabilities of three-obtained solutions by using linear analysis of differential equations manifests that a root represents a saddle point and other two roots represent stable points. (author)

  17. Measurement of the $B_{d}^{0} - \\overline{B}_{d}^{0}$ oscillation frequency

    CERN Document Server

    Acciarri, M; Aguilar-Benítez, M; Ahlen, S P; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Ambrosi, G; Anderhub, H; Andreev, V P; Angelescu, T; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Baksay, L; Ball, R C; Banerjee, S; Banerjee, Sw; Banicz, K; Barczyk, A; Barillère, R; Barone, L; Bartalini, P; Baschirotto, A; Basile, M; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Bhattacharya, S; Biasini, M; Biland, A; Bilei, G M; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böck, R K; Böhm, A; Boldizsar, L; Borgia, B; Bourilkov, D; Bourquin, Maurice; Boutigny, D; Braccini, S; Branson, J G; Brigljevic, V; Brock, I C; Buffini, A; Buijs, A; Burger, J D; Burger, W J; Busenitz, J K; Cai, X D; Campanelli, M; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Castellini, G; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada-Canales, M; Cesaroni, F; Chamizo-Llatas, M; Chang, Y H; Chaturvedi, U K; Chekanov, S V; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chen, M; Chiefari, G; Chien, C Y; Cifarelli, Luisa; Cindolo, F; Civinini, C; Clare, I; Clare, R; Cohn, H O; Coignet, G; Colijn, A P; Colino, N; Costantini, S; Cotorobai, F; de la Cruz, B; Csilling, Akos; Dai, T S; D'Alessandro, R; De Asmundis, R; Degré, A; Deiters, K; Denes, P; De Notaristefani, F; DiBitonto, Daryl; Diemoz, M; Van Dierendonck, D N; Di Lodovico, F; Dionisi, C; Dittmar, Michael; Dominguez, A; Doria, A; Dova, M T; Drago, E; Duchesneau, D; Duinker, P; Durán, I; Dutta, S; Easo, S; Efremenko, Yu V; El-Mamouni, H; Engler, A; Eppling, F J; Erné, F C; Ernenwein, J P; Extermann, Pierre; Fabre, M; Faccini, R; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Fenyi, B; Ferguson, T; Ferroni, F; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisk, I; Forconi, G; Fredj, L; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gau, S S; Gentile, S; Gerald, J; Gheordanescu, N; Giagu, S; Goldfarb, S; Goldstein, J; Gong, Z F; Gougas, Andreas; Gratta, Giorgio; Grünewald, M W; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hartmann, B; Hasan, A; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hirschfelder, J; Van Hoek, W C; Hofer, H; Hoorani, H; Hou, S R; Hu, G; Innocente, Vincenzo; Jenkes, K; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Kasser, A; Khan, R A; Kamrad, D; Kamyshkov, Yu A; Kapustinsky, J S; Karyotakis, Yu; Kaur, M; Kienzle-Focacci, M N; Kim, D; Kim, D H; Kim, J K; Kim, S C; Kinnison, W W; Kirkby, A; Kirkby, D; Kirkby, Jasper; Kiss, D; Kittel, E W; Klimentov, A; König, A C; Kopp, A; Korolko, I; Koutsenko, V F; Krämer, R W; Krenz, W; Kunin, A; Lacentre, P E; Ladrón de Guevara, P; Landi, G; Lapoint, C; Lassila-Perini, K M; Laurikainen, P; Lavorato, A; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Lee, H J; Leggett, C; Le Goff, J M; Leiste, R; Leonardi, E; Levchenko, P M; Li Chuan; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lu, W; Lü, Y S; Lübelsmeyer, K; Luci, C; Luckey, D; Luminari, L; Lustermann, W; Ma Wen Gan; Maity, M; Majumder, G; Malgeri, L; Malinin, A; Maña, C; Mangeol, D J J; Mangla, S; Marchesini, P A; Marin, A; Martin, J P; Marzano, F; Massaro, G G G; McNally, D; Mele, S; Merola, L; Meschini, M; Metzger, W J; Von der Mey, M; Mi, Y; Migani, D; Mihul, A; Van Mil, A J W; Milcent, H; Mirabelli, G; Mnich, J; Molnár, P; Monteleoni, B; Moore, R; Moulik, T; Mount, R; Muheim, F; Muijs, A J M; Nahn, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Niessen, T; Nippe, A; Nisati, A; Nowak, H; Oh, Yu D; Opitz, H; Organtini, G; Ostonen, R; Palit, S; Palomares, C; Pandoulas, D; Paoletti, S; Paolucci, P; Park, H K; Park, I H; Pascale, G; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Peach, D; Pei, Y J; Pensotti, S; Perret-Gallix, D; Petersen, B; Petrak, S; Pevsner, A; Piccolo, D; Pieri, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Postema, H; Produit, N; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Raja, N; Rancoita, P G; Rattaggi, M; Raven, G; Razis, P A; Read, K; Ren, D; Rescigno, M; Reucroft, S; Van Rhee, T; Riemann, S; Riles, K; Rind, O; Robohm, A; Rodin, J; Roe, B P; Romero, L; Rosier-Lees, S; Rosselet, P; Van Rossum, W; Roth, S; Rubio, Juan Antonio; Ruschmeier, D; Rykaczewski, H; Salicio, J; Sánchez, E; Sanders, M P; Sarakinos, M E; Sarkar, S; Sauvage, G; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Schneegans, M; Scholz, N; Schopper, Herwig Franz; Schotanus, D J; Schwenke, J; Schwering, G; Sciacca, C; Sciarrino, D; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shukla, J; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Soulimov, V; Smith, B; Spillantini, P; Steuer, M; Stickland, D P; Stone, H; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Susinno, G F; Suter, H; Swain, J D; Tang, X W; Tauscher, Ludwig; Taylor, L; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tuchscherer, H; Tung, K L; Uchida, Y; Ulbricht, J; Uwer, U; Valente, E; Vesztergombi, G; Vetlitskii, I; Viertel, Gert M; Vivargent, M; Vlachos, S; Völkert, R; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Vorvolakos, A; Wadhwa, M; Wallraff, W; Wang, J C; Wang, X L; Wang, Z M; Weber, A; Wu, S X; Wynhoff, S; Xu, J; Xu, Z Z; Yang, B Z; Yang, C G; Yao, X Y; Ye, J B; Yeh, S C; You, J M; Zalite, A; Zalite, Yu; Zemp, P; Zeng, Y; Zhang, Z; Zhang, Z P; Zhou, B; Zhou, Y; Zhu, G Y; Zhu, R Y; Zichichi, Antonino; Ziegler, F

    1998-01-01

    Time-dependent ${\\mathrm{B^{0}}\\mbox{-}\\bar{\\mathrm{B}} ^{0}}$ mixing is studied using about two million hadronic Z decays registered by L3 in 1994 and 1995. For this study three techniques are used. Tagging of the b-quark charge at decay time is performed by identifying leptons from semileptonic B decays. The flavour of the b quark at production time is determined from the charge of the lepton in the opposite hemisphere or by using a jet-charge technique. The proper time of the B-particle decay is obtained by reconstructing the production and decay vertices or by a measurement of the lepton impact parameter. The combined result for the frequency of ${\\mathrm{B_d^0}}$ meson oscillations is \\begin{displaymath} {\\Delta m_d} = 0.444 \\pm 0.040 \\ \\mathrm{ps}^{-1}. \\end{displaymath} \\end{abstract} \\end{document}

  18. NMDA receptor antagonist-enhanced high frequency oscillations: are they generated broadly or regionally specific?

    Science.gov (United States)

    Olszewski, Maciej; Dolowa, Wioleta; Matulewicz, Pawel; Kasicki, Stefan; Hunt, Mark J

    2013-12-01

    Systemic administration of NMDA receptor antagonists, used to model schizophrenia, increase the power of high-frequency oscillations (130-180Hz, HFO) in a variety of neuroanatomical and functionally distinct brain regions. However, it is unclear whether HFO are independently and locally generated or instead spread from a distant source. To address this issue, we used local infusion of tetrodotoxin (TTX) to distinct brain areas to determine how accurately HFO recorded after injection of NMDAR antagonists reflect the activity actually generated at the electrode tip. Changes in power were evaluated in local field potentials (LFPs) recorded from the nucleus accumbens (NAc), prefrontal cortex and caudate and in electrocorticograms (ECoGs) from visual and frontal areas. HFO recorded in frontal and visual cortices (ECoGs) or in the prefrontal cortex, caudate (LFPs) co-varied in power and frequency with observed changes in the NAc. TTX infusion to the NAc immediately and profoundly reduced the power of accumbal HFO which correlated with changes in HFO recorded in distant cortical sites. In contrast, TTX infusion to the prefrontal cortex did not change HFO power recorded locally, although gamma power was reduced. A very similar result was found after TTX infusion to the caudate. These findings raise the possibility that the NAc is an important neural generator. Our data also support existing studies challenging the idea that high frequencies recorded in LFPs are necessarily generated at the recording site. Copyright © 2013 Elsevier B.V. and ECNP. All rights reserved.

  19. 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.

  20. Abnormal excitability and episodic low-frequency oscillations in the cerebral cortex of the tottering mouse.

    Science.gov (United States)

    Cramer, Samuel W; Popa, Laurentiu S; Carter, Russell E; Chen, Gang; Ebner, Timothy J

    2015-04-08

    The Ca(2+) channelopathies caused by mutations of the CACNA1A gene that encodes the pore-forming subunit of the human Cav2.1 (P/Q-type) voltage-gated Ca(2+) channel include episodic ataxia type 2 (EA2). Although, in EA2 the emphasis has been on cerebellar dysfunction, patients also exhibit episodic, nonmotoric abnormalities involving the cerebral cortex. This study demonstrates episodic, low-frequency oscillations (LFOs) throughout the cerebral cortex of tottering (tg/tg) mice, a widely used model of EA2. Ranging between 0.035 and 0.11 Hz, the LFOs in tg/tg mice can spontaneously develop very high power, referred to as a high-power state. The LFOs in tg/tg mice are mediated in part by neuronal activity as tetrodotoxin decreases the oscillations and cortical neuron discharge contain the same low frequencies. The high-power state involves compensatory mechanisms because acutely decreasing P/Q-type Ca(2+) channel function in either wild-type (WT) or tg/tg mice does not induce the high-power state. In contrast, blocking l-type Ca(2+) channels, known to be upregulated in tg/tg mice, reduces the high-power state. Intriguingly, basal excitatory glutamatergic neurotransmission constrains the high-power state because blocking ionotropic or metabotropic glutamate receptors results in high-power LFOs in tg/tg but not WT mice. The high-power LFOs are decreased markedly by acetazolamide and 4-aminopyridine, the primary treatments for EA2, suggesting disease relevance. Together, these results demonstrate that the high-power LFOs in the tg/tg cerebral cortex represent a highly abnormal excitability state that may underlie noncerebellar symptoms that characterize CACNA1A mutations. Copyright © 2015 the authors 0270-6474/15/355664-16$15.00/0.

  1. Scaling Laws in the Transient Dynamics of Firefly-like Oscillators

    International Nuclear Information System (INIS)

    Rubido, N; Cabeza, C; Marti, A; Ramirez Avila, G M

    2011-01-01

    Fireflies constitute a paradigm of pulse-coupled oscillators. In order to tackle the problems related to synchronisation transients of pulse-coupled oscillators, a Light-Controlled Oscillator (LCO) model is presented. A single LCO constitutes a one-dimensional relaxation oscillator described by two distinct time-scales meant to mimic fireflies in the sense that: it is capable of emitting light in a pulse-like fashion and detect the emitted by others in order to adjust its oscillation. We present dynamical results for two interacting LCOs in the torus for all possible coupling configurations. Transient times to the synchronous limit cycle are obtained experimentally and numerically as a function of initial conditions and coupling strengths. Scaling laws are found based on dimensional analysis and critical exponents calculated, thus, global dynamic is restricted. Furthermore, an analytical orthogonal transformation that allows to calculate Floquet multipliers directly from the time series is presented. As a consequence, local dynamics is also fully characterized. This transformation can be easily extended to a system with an arbitrary number of interacting LCOs.

  2. MIPAS observations of longitudinal oscillations in the mesosphere and the lower thermosphere: climatology of odd-parity daily frequency modes

    Directory of Open Access Journals (Sweden)

    M. García-Comas

    2016-09-01

    Full Text Available MIPAS global Sun-synchronous observations are almost fixed in local time. Subtraction of the descending and ascending node measurements at each longitude only includes the longitudinal oscillations with odd daily frequencies nodd from the Sun's perspective at 10:00. Contributions from the background atmosphere, daily-invariant zonal oscillations and tidal modes with even-parity daily frequencies vanish. We have determined longitudinal oscillations in MIPAS temperature with nodd and wavenumber k = 0–4 from the stratosphere to 150 km from April 2007 to March 2012. To our knowledge, this is the first time zonal oscillations in temperature have been derived pole to pole in this altitude range from a single instrument. The major findings are the detection of (1 migrating tides at northern and southern high latitudes; (2 significant k = 1 activity at extratropical and high latitudes, particularly in the Southern Hemisphere; (3 k = 3 and k = 4 eastward-propagating waves that penetrate the lower thermosphere with a significantly larger vertical wavelength than in the mesosphere; and (4 a migrating tide quasi-biennial oscillation in the stratosphere, mesosphere and lower thermosphere. MIPAS global measurements of longitudinal oscillations are useful for testing tide modeling in the mesosphere and lower thermosphere region and as a lower boundary for models extending higher up in the atmosphere.

  3. Analysis on voltage oscillation of a mid-frequency series resonant inverter for DRMP coils on J-TEXT

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Long-jian, E-mail: liulongjian001@yeah.net [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Yu, Ke-xun; Zhang, Ming; Nan, Jie-yin; Jiang, Guo-zhong; Rao, Bo; Li, Xuan [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2016-01-15

    Highlights: • The reason of high-voltage oscillation of a series resonant inverter for DRMP coils is analyzed. • The condition or method for reduction of high-voltage oscillation is discussed. • The considerations of dead time and switch frequency for reduction of high-voltage oscillation are discussed. - Abstract: This paper deals with the voltage oscillation of an AC power supply for generating dynamic magnetic perturbation (DRMP) on J-TEXT. The power supply is a series resonant inverter with a matching transformer. It was noted that the high-voltage oscillation at transformer primary side is caused by an interaction between the line inductance and the stray capacitance of the matching transformer at switching transitions. In order to reduce the high-voltage oscillation and consider the requirement for soft-switching technique simultaneously, the switching frequency should be chosen properly by fine-tuning. The dead time should be chosen according to the relative size of minimum required dead time for protection and the optimal dead time.

  4. A critical oscillation constant as a variable of time scales for half-linear dynamic equations

    Czech Academy of Sciences Publication Activity Database

    Řehák, Pavel

    2010-01-01

    Roč. 60, č. 2 (2010), s. 237-256 ISSN 0139-9918 R&D Projects: GA AV ČR KJB100190701 Institutional research plan: CEZ:AV0Z10190503 Keywords : dynamic equation * time scale * half-linear equation * (non)oscillation criteria * Hille-Nehari criteria * Kneser criteria * critical constant * oscillation constant * Hardy inequality Subject RIV: BA - General Mathematics Impact factor: 0.316, year: 2010 http://link.springer.com/article/10.2478%2Fs12175-010-0009-7

  5. An observational search for large-scale organization of five-minute oscillations on the sun. [coronal holes or sector structure relationships

    Science.gov (United States)

    Dittmer, P. H.; Scherrer, P. H.; Wilcox, J. M.

    1978-01-01

    The large-scale solar velocity field has been measured over an aperture of radius 0.8 solar radii on 121 days between April and September, 1976. Measurements are made in the line Fe I 5123.730 A, employing a velocity subtraction technique similar to that of Severny et al. (1976). Comparisons of the amplitude and frequency of the five-minute resonant oscillation with the geomagnetic C9 index and magnetic sector boundaries show no evidence of any relationship between the oscillations and coronal holes or sector structure.

  6. 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

  7. Temperature oscillation and the sloshing motion of the large-scale circulation in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Xi, Heng-Dong; Chen, Xin; Xia, Ke-Qing

    2017-11-01

    We report an experimental study of the temperature oscillation and the sloshing motion of the large-scale circulation (LSC) in turbulent Rayleigh-Bénard convection in water. Temperature measurements were made in aspect ratio one cylindrical cell by probes put in fluid and embedded in the sidewall simultaneously, and located at the 1/4, 1/2 and 3/4 heights of the convection cell. The results show that the temperature measured in fluid contains information of both the LSC and the signature of the hot and cold plumes, while the temperature measured in sidewall only contains information of the LSC. It is found that the sloshing motion of the LSC can be measured by both the temperatures in fluid and in sidewall. We also studies the effect of cell tilting on the temperature oscillation and sloshing motion of the LSC. It is found that both the amplitude and the frequency of the temperature oscillation (and the sloshing motion) increase when the tilt angle increases, while the off-center distance of the sloshing motion of the LSC remains unchanged. This work is supported by the NSFC of China (Grant Nos. 11472094 and U1613227), the RGC of Hong Kong SAR (Grant No. 403712) and the 111 project of China (Grant No. B17037).

  8. On the (Frequency) Modulation of Coupled Oscillator Arrays in Phased Array Beam Control

    Science.gov (United States)

    Pogorzelski, R.; Acorn, J.; Zawadzki, M.

    2000-01-01

    It has been shown that arrays of voltage controlled oscillators coupled to nearest neighbors can be used to produce useful aperture phase distributions for phased array antennas. However, placing information of the transmitted signal requires that the oscillations be modulated.

  9. Scaling and Parametric Studies of Condensation Oscillation in an In-Containment Refueling Water Storage Tank

    International Nuclear Information System (INIS)

    Lee, Jun Hyung; No, Hee Cheon

    2003-01-01

    The purpose of this paper is to study the condensation oscillation phenomena by steam-jetting into subcooled water through a multihole sparger, implementing a scaling methodology and the similarity correlation between the test facility and model prototype. To corroborate the scaling methodology, various experimental tests were conducted. The thickness of the boundary layer that encloses the steam cavity was found to be equal to the maximum length of the steam cavity formed. Three key scaling parameters were identified and correlated with the maximum amplitude of pressure oscillation: flow restriction coefficient, area ratio of discharge hole to steam cavity, and density ratio of water to steam. Variations of the oscillation amplitude were small when steam-jetting directions were altered. The concept of a reduction factor was introduced for estimating the oscillation amplitude of the multihole sparger with test data from a single-hole sparger. The results of this study can provide suitable guidelines for sparger design utilized in the in-containment refueling water storage tank for the Advanced Power Reactor 1400

  10. A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements

    International Nuclear Information System (INIS)

    Hlondo, L. R.; Lalremruata, B.; Punte, L. R. M.; Rebecca, L.; Lalnunthari, J.; Thanga, H. H.

    2016-01-01

    Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power are studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.

  11. The role of high-frequency oscillations in epilepsy surgery planning.

    Science.gov (United States)

    Gloss, David; Nevitt, Sarah J; Staba, Richard

    2017-10-05

    Epilepsy is a serious brain disorder characterized by recurrent unprovoked seizures. Approximately two-thirds of seizures can be controlled with antiepileptic medications (Kwan 2000). For some of the others, surgery can completely eliminate or significantly reduce the occurrence of disabling seizures. Localization of epileptogenic areas for resective surgery is far from perfect, and new tools are being investigated to more accurately localize the epileptogenic zone (the zone of the brain where the seizures begin) and improve the likelihood of freedom from postsurgical seizures. Recordings of pathological high-frequency oscillations (HFOs) may be one such tool. To assess the ability of HFOs to improve the outcomes of epilepsy surgery by helping to identify more accurately the epileptogenic areas of the brain. For the latest update, we searched the Cochrane Epilepsy Group Specialized Register (25 July 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (CRSO, 25 July 2016), MEDLINE (Ovid, 1946 to 25 July 2016), CINAHL Plus (EBSCOhost, 25 July 2016), Web of Science (Thomson Reuters, 25 July 2016), ClinicalTrials.gov (25 July 2016), and the World Health Organization International Clinical Trials Registry Platform ICTRP (25 July 2016). We included studies that provided information on the outcomes of epilepsy surgery for at least six months and which used high-frequency oscillations in making decisions about epilepsy surgery. The primary outcome of the review was the Engel Class Outcome System (class I = no disabling seizures, II = rare disabling seizures, III = worthwhile improvement, IV = no worthwhile improvement). Secondary outcomes were responder rate, International League Against Epilepsy (ILAE) epilepsy surgery outcome, frequency of adverse events from any source and quality of life outcomes. We intended to analyse outcomes via an aggregated data fixed-effect model meta-analysis. Two studies representing

  12. Microwave frequency tuning in heterogeneous spin torque oscillator with perpendicular polarizer: A macrospin study

    Science.gov (United States)

    Bhoomeeswaran, H.; Vivek, T.; Sabareesan, P.

    2018-04-01

    In this article, we have theoretically devised a Spin Torque Nano Oscillator (STNO) with perpendicular polarizer using macro spin model. The devised spin valve structure is heterogeneous (i.e.) it is made of two different ferromagnetic materials [Co and its alloy CoFeB]. The dynamics of magnetization provoked by spin transfer torque is studied numerically by solving the famous Landau-Lifshitz-Gilbert-Slonczewski [LLGS] equation. The results are obtained for the perpendicular polarizer and for that particular out of plane orientation we vary the free layer angle from 10° to 90°. The obtained results are highly appealing, because frequency range is available in all the tilt angles of free layer and it is exceptionally tunable in all free layer tilt angles with zero applied field. Moreover, the utmost operating frequency of about 83.3 GHz and its corresponding power of 4.488 µW/mA2/GHz is acquired for the free layer tilt angle θ = 90° with the solid applied current density of 10 × 1010 A/m2. Also, our device emits high quality factor of about 396, which is remarkably desirable for making devices. These pioneering results provides a significant development for future spintronic based devices.

  13. On one-parametric formula relating the frequencies of twin-peak quasi-periodic oscillations

    Science.gov (United States)

    Török, Gabriel; Goluchová, Kateřina; Šrámková, Eva; Horák, Jiří; Bakala, Pavel; Urbanec, Martin

    2018-01-01

    Twin-peak quasi-periodic oscillations (QPOs) are observed in several low-mass X-ray binary systems containing neutron stars. Timing the analysis of X-ray fluxes of more than dozen of such systems reveals remarkable correlations between the frequencies of two characteristic peaks present in the power density spectra. The individual correlations clearly differ, but they roughly follow a common individual pattern. High values of measured QPO frequencies and strong modulation of the X-ray flux both suggest that the observed correlations are connected to orbital motion in the innermost part of an accretion disc. Several attempts to model these correlations with simple geodesic orbital models or phenomenological relations have failed in the past. We find and explore a surprisingly simple analytic relation that reproduces individual correlations for a group of several sources through a single parameter. When an additional free parameter is considered within our relation, it well reproduces the data of a large group of 14 sources. The very existence and form of this simple relation support the hypothesis of the orbital origin of QPOs and provide the key for further development of QPO models. We discuss a possible physical interpretation of our relation's parameters and their links to concrete QPO models.

  14. Humidification during high-frequency oscillation ventilation is affected by ventilator circuit and ventilatory setting.

    Science.gov (United States)

    Chikata, Yusuke; Imanaka, Hideaki; Onishi, Yoshiaki; Ueta, Masahiko; Nishimura, Masaji

    2009-08-01

    High-frequency oscillation ventilation (HFOV) is an accepted ventilatory mode for acute respiratory failure in neonates. As conventional mechanical ventilation, inspiratory gas humidification is essential. However, humidification during HFOV has not been clarified. In this bench study, we evaluated humidification during HFOV in the open circumstance of ICU. Our hypothesis is that humidification during HFOV is affected by circuit design and ventilatory settings. We connected a ventilator with HFOV mode to a neonatal lung model that was placed in an infant incubator set at 37 degrees C. We set a heated humidifier (Fisher & Paykel) to obtain 37 degrees C at the chamber outlet and 40 degrees C at the distal temperature probe. We measured absolute humidity and temperature at the Y-piece using a rapid-response hygrometer. We evaluated two types of ventilator circuit: a circuit with inner heating wire and another with embedded heating element. In addition, we evaluated three lengths of the inspiratory limb, three stroke volumes, three frequencies, and three mean airway pressures. The circuit with embedded heating element provided significantly higher absolute humidity and temperature than one with inner heating wire. As an extended tube lacking a heating wire was shorter, absolute humidity and temperature became higher. In the circuit with inner heating wire, absolute humidity and temperature increased as stroke volume increased. Humidification during HFOV is affected by circuit design and ventilatory settings.

  15. Large-scale network dynamics of beta-band oscillations underlie auditory perceptual decision-making

    Directory of Open Access Journals (Sweden)

    Mohsen Alavash

    2017-06-01

    Full Text Available Perceptual decisions vary in the speed at which we make them. Evidence suggests that translating sensory information into perceptual decisions relies on distributed interacting neural populations, with decision speed hinging on power modulations of the neural oscillations. Yet the dependence of perceptual decisions on the large-scale network organization of coupled neural oscillations has remained elusive. We measured magnetoencephalographic signals in human listeners who judged acoustic stimuli composed of carefully titrated clouds of tone sweeps. These stimuli were used in two task contexts, in which the participants judged the overall pitch or direction of the tone sweeps. We traced the large-scale network dynamics of the source-projected neural oscillations on a trial-by-trial basis using power-envelope correlations and graph-theoretical network discovery. In both tasks, faster decisions were predicted by higher segregation and lower integration of coupled beta-band (∼16–28 Hz oscillations. We also uncovered the brain network states that promoted faster decisions in either lower-order auditory or higher-order control brain areas. Specifically, decision speed in judging the tone sweep direction critically relied on the nodal network configurations of anterior temporal, cingulate, and middle frontal cortices. Our findings suggest that global network communication during perceptual decision-making is implemented in the human brain by large-scale couplings between beta-band neural oscillations. The speed at which we make perceptual decisions varies. This translation of sensory information into perceptual decisions hinges on dynamic changes in neural oscillatory activity. However, the large-scale neural-network embodiment supporting perceptual decision-making is unclear. We addressed this question by experimenting two auditory perceptual decision-making situations. Using graph-theoretical network discovery, we traced the large-scale network

  16. Radio Frequency Transistors Using Aligned Semiconducting Carbon Nanotubes with Current-Gain Cutoff Frequency and Maximum Oscillation Frequency Simultaneously Greater than 70 GHz.

    Science.gov (United States)

    Cao, Yu; Brady, Gerald J; Gui, Hui; Rutherglen, Chris; Arnold, Michael S; Zhou, Chongwu

    2016-07-26

    In this paper, we report record radio frequency (RF) performance of carbon nanotube transistors based on combined use of a self-aligned T-shape gate structure, and well-aligned, high-semiconducting-purity, high-density polyfluorene-sorted semiconducting carbon nanotubes, which were deposited using dose-controlled, floating evaporative self-assembly method. These transistors show outstanding direct current (DC) performance with on-current density of 350 μA/μm, transconductance as high as 310 μS/μm, and superior current saturation with normalized output resistance greater than 100 kΩ·μm. These transistors create a record as carbon nanotube RF transistors that demonstrate both the current-gain cutoff frequency (ft) and the maximum oscillation frequency (fmax) greater than 70 GHz. Furthermore, these transistors exhibit good linearity performance with 1 dB gain compression point (P1dB) of 14 dBm and input third-order intercept point (IIP3) of 22 dBm. Our study advances state-of-the-art of carbon nanotube RF electronics, which have the potential to be made flexible and may find broad applications for signal amplification, wireless communication, and wearable/flexible electronics.

  17. Constructive influence of noise flatness and friction on the resonant behavior of a harmonic oscillator with fluctuating frequency.

    Science.gov (United States)

    Laas, Katrin; Mankin, Romi; Rekker, Astrid

    2009-05-01

    The influences of noise flatness and friction coefficient on the long-time behavior of the first two moments and the correlation function for the output signal of a harmonic oscillator with fluctuating frequency subjected to an external periodic force are considered. The colored fluctuations of the oscillator frequency are modeled as a trichotomous noise. The study is a follow up of the previous investigation of a stochastic oscillator [Phys. Rev. E 78, 031120 (2008)], where the connection between the occurrence of energetic instability and stochastic multiresonance is established. Here we report some unexpected results not considered in the previous work. Notably, we have found a nonmonotonic dependence of several stochastic resonance characteristics such as spectral amplification, variance of the output signal, and signal-to-noise ratio on the friction coefficient and on the noise flatness. In particular, in certain parameter regions spectral amplification exhibits a resonancelike enhancement at intermediate values of the friction coefficient.

  18. Frequency hopping due to acousto-electric interaction in ZnO based surface acoustic wave oscillator

    Science.gov (United States)

    Dasgupta, Daipayan; Sreenivas, K.

    2011-08-01

    A 36 MHz surface acoustic wave delay line based oscillator has been used to study the effect of acousto-electric interaction due to photo generated charge carriers in rf sputtered ZnO film under UV illumination (λ = 365 nm, 20-100 μW/cm2). Design aspects for developing a delay line based SAW oscillator are specified. The observed linear downshift in frequency (2.2 to 19.0 kHz) with varying UV intensity (20-100 μW/cm2) is related to the fractional velocity change due to acousto-electric interaction. UV illumination level of 100 μW/cm2 leads to a characteristic frequency hopping behavior arising due to a change in the oscillation criteria, and is attributed to the complex interplay between the increased attenuation and velocity shift.

  19. Ih tunes theta/gamma oscillations and cross-frequency coupling in an in silico CA3 model.

    Directory of Open Access Journals (Sweden)

    Samuel A Neymotin

    Full Text Available Ih channels are uniquely positioned to act as neuromodulatory control points for tuning hippocampal theta (4-12 Hz and gamma (25 Hz oscillations, oscillations which are thought to have importance for organization of information flow. contributes to neuronal membrane resonance and resting membrane potential, and is modulated by second messengers. We investigated oscillatory control using a multiscale computer model of hippocampal CA3, where each cell class (pyramidal, basket, and oriens-lacunosum moleculare cells, contained type-appropriate isoforms of . Our model demonstrated that modulation of pyramidal and basket allows tuning theta and gamma oscillation frequency and amplitude. Pyramidal also controlled cross-frequency coupling (CFC and allowed shifting gamma generation towards particular phases of the theta cycle, effected via 's ability to set pyramidal excitability. Our model predicts that in vivo neuromodulatory control of allows flexibly controlling CFC and the timing of gamma discharges at particular theta phases.

  20. 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.

  1. A MULTI-SITE CAMPAIGN TO MEASURE SOLAR-LIKE OSCILLATIONS IN PROCYON. II. MODE FREQUENCIES

    International Nuclear Information System (INIS)

    Bedding, Timothy R.; Bruntt, Hans; Kiss, Laszlo L.; Kjeldsen, Hans; Campante, Tiago L.; Appourchaux, Thierry; Bonanno, Alfio; Chaplin, William J.; Garcia, Rafael A.; Martic, Milena; Mosser, Benoit; Butler, R. Paul; O'Toole, Simon J.; Kambe, Eiji; Izumiura, Hideyuki; Ando, Hiroyasu; Sato, Bun'ei; Hartmann, Michael; Hatzes, Artie

    2010-01-01

    We have analyzed data from a multi-site campaign to observe oscillations in the F5 star Procyon. The data consist of high-precision velocities that we obtained over more than three weeks with 11 telescopes. A new method for adjusting the data weights allows us to suppress the sidelobes in the power spectrum. Stacking the power spectrum in a so-called echelle diagram reveals two clear ridges, which we identify with even and odd values of the angular degree (l = 0 and 2, and l = 1 and 3, respectively). We interpret a strong, narrow peak at 446 μHz that lies close to the l = 1 ridge as a mode with mixed character. We show that the frequencies of the ridge centroids and their separations are useful diagnostics for asteroseismology. In particular, variations in the large separation appear to indicate a glitch in the sound-speed profile at an acoustic depth of ∼1000 s. We list frequencies for 55 modes extracted from the data spanning 20 radial orders, a range comparable to the best solar data, which will provide valuable constraints for theoretical models. A preliminary comparison with published models shows that the offset between observed and calculated frequencies for the radial modes is very different for Procyon than for the Sun and other cool stars. We find the mean lifetime of the modes in Procyon to be 1.29 +0.55 -0.49 days, which is significantly shorter than the 2-4 days seen in the Sun.

  2. 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.

  3. Resection of individually identified high-rate high-frequency oscillations region is associated with favorable outcome in neocortical epilepsy

    Czech Academy of Sciences Publication Activity Database

    Cho, J.R.; Koo, D.L.; Joo, E.Y.; Seo, D.W.; Hong, S.-Ch.; Jiruška, Přemysl; Hong, S.B.

    2014-01-01

    Roč. 55, č. 11 (2014), s. 1872-1883 ISSN 0013-9580 R&D Projects: GA MZd(CZ) NT14489 Institutional support: RVO:67985823 Keywords : epilepsy surgery * high-frequency oscillations * neocortical epilepsy Subject RIV: FH - Neurology Impact factor: 4.571, year: 2014

  4. Low-Frequency Oscillations and Transport Processes Induced by Multiscale Transverse Structures in the Polar Wind Outflow: A Three-Dimensional Simulation

    Science.gov (United States)

    Ganguli, Supriya B.; Gavrishchaka, Valeriy V.

    1999-01-01

    Multiscale transverse structures in the magnetic-field-aligned flows have been frequently observed in the auroral region by FAST and Freja satellites. A number of multiscale processes, such as broadband low-frequency oscillations and various cross-field transport effects are well correlated with these structures. To study these effects, we have used our three-dimensional multifluid model with multiscale transverse inhomogeneities in the initial velocity profile. Self-consistent-frequency mode driven by local transverse gradients in the generation of the low field-aligned ion flow and associated transport processes were simulated. Effects of particle interaction with the self-consistent time-dependent three-dimensional wave potential have been modeled using a distribution of test particles. For typical polar wind conditions it has been found that even large-scale (approximately 50 - 100 km) transverse inhomogeneities in the flow can generate low-frequency oscillations that lead to significant flow modifications, cross-field particle diffusion, and other transport effects. It has also been shown that even small-amplitude (approximately 10 - 20%) short-scale (approximately 10 km) modulations of the original large-scale flow profile significantly increases low-frequency mode generation and associated cross-field transport, not only at the local spatial scales imposed by the modulations but also on global scales. Note that this wave-induced cross-field transport is not included in any of the global numerical models of the ionosphere, ionosphere-thermosphere, or ionosphere-polar wind. The simulation results indicate that the wave-induced cross-field transport not only affects the ion outflow rates but also leads to a significant broadening of particle phase-space distribution and transverse particle diffusion.

  5. Hydrogen-antihydrogen oscillations: Signature of intermediate mass scales in GUTs

    Directory of Open Access Journals (Sweden)

    Uptal Sarkar

    1983-01-01

    Full Text Available Hydrogen-antihydrogen oscillations and the double nucleon decay (pp, np and nn into two antileptons are discussed in the context of SO(10, E(6 and SU(16 GUTs. It is shown that the intermediate mass scales of the GUTs concerned govern the amplitude of these processes which are found to compete with the other baryon nonconserving processes in SU(16 GUT.

  6. Electrodiagnostic applications of somatosensory evoked high-frequency EEG oscillations: Technical considerations.

    Science.gov (United States)

    Simpson, A J; Cunningham, M O; Baker, M R

    2018-03-01

    High frequency oscillations (HFOs) embedded within the somatosensory evoked potential (SEP) are not routinely recorded/measured as part of standard clinical SEPs. However, HFOs could provide important additional diagnostic/prognostic information in various patient groups in whom SEPs are tested routinely. One area is the management of patients with hypoxic ischaemic encephalopathy (HIE) in the intensive care unit (ICU). However, the sensitivity of standard clinical SEP recording techniques for detecting HFOs is unknown. SEPs were recorded using routine clinical methods in 17 healthy subjects (median nerve stimulation; 0.5 ms pulse width; 5 Hz; maximum 4000 stimuli) in an unshielded laboratory. Bipolar EEG recordings were acquired (gain 50 k; bandpass 3Hz-2 kHz; sampling rate 5 kHz; non-inverting electrode 2 cm anterior to C3/C4; inverting electrode 2 cm posterior to C3/C4). Data analysis was performed in MATLAB. SEP-HFOs were detected in 65% of controls using standard clinical recording techniques. In 3 controls without significant HFOs, experiments were repeated using a linear electrode array with higher spatial sampling frequency. SEP-HFOs were observed in all 3 subjects. Currently standard clinical methods of recording SEPs are not sufficiently sensitive to permit the inclusion of SEP-HFOs in routine clinical diagnostic/prognostic assessments. Whilst an increase in the number/density of EEG electrodes should improve the sensitivity for detecting SEP-HFOs, this requires confirmation. By improving and standardising clinical SEP recording protocols to permit the acquisition/analysis of SEP-HFOs, it should be possible to gain important insights into the pathophysiology of neurological disorders and refine the management of conditions such as HIE. Copyright © 2018. Published by Elsevier Inc.

  7. The effects of static quartic anharmonicity on the quantum dynamics of a linear oscillator with time-dependent harmonic frequency: Perturbative analysis and numerical calculations

    International Nuclear Information System (INIS)

    Sarkar, P.; Bhattacharyya, S.P.

    1995-01-01

    The effects of quartic anharmonicity on the quantum dynamics of a linear oscillator with time-dependent force constant (K) or harmonic frequency (ω) are studied both perturbatively and numerically by the time-dependent Fourier grid Hamiltonian method. In the absence of anharmonicity, the ground-state population decreases and the population of an accessible excited state (k = 2.4, 6 ... ) increases with time. However, when anharmonicity is introduced, both the ground- and excited-state populations show typical oscillations. For weak coupling, the population of an accessible excited state at a certain instant of time (short) turns out to be a parabolic function of the anharmonic coupling constant (λ), when all other parameters of the system are kept fixed. This parabolic nature of the excited-state population vs. the λ profile is independent of the specific form of the time dependence of the force constant, K t . However, it depends upon the rate at which K t relaxes. For small anharmonic coupling strength and short time scales, the numerical results corroborate expectations based on the first-order time-dependent perturbative analysis, using a suitably repartitioned Hamiltonian that makes H 0 time-independent. Some of the possible experimental implications of our observations are analyzed, especially in relation to intensity oscillations observed in some charge-transfer spectra in systems in which the dephasing rates are comparable with the time scale of the electron transfer. 21 refs., 7 figs., 1 tab

  8. Very low frequency oscillations of heat load and recycling flux in steady-state tokamak discharge in TRIAM-1M

    International Nuclear Information System (INIS)

    Zushi, H.; Sakamoto, M.; Hanada, K.; Iyomasa, A.; Nakamura, K.; Sato, K.N.; Idei, H.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Hasegawa, M.; Matsuo, Y.; Kuramoto, K.; Sugata, T.; Maezono, N.; Hoshika, H.; Sasaki, K.

    2004-01-01

    Plasma wall interaction (PWI) driven relaxation oscillations are investigated in the steady state discharge for 5 hours. The oscillation frequency was about 10 -3 Hz and each perturbation lasted for about 300 s. The heat load, recycling flux and impurity influx were varied from a few % to several tens of %. The largest variation of 70% was seen on the Mo XIII (molybdenum), although the influx of Mo I was only 20 %. Although the input rf power is kept constant during the discharge, the coupling between the rf and plasma was increased by about 10%. The current drive efficiency is decreased by 24 % in spite of current ramp. The toroidal and poloidal profiles of the recycling flux were also changed. During the last relaxation phase, the plasma was finally terminated. The current reduction (> 4 kA) was not recovered by intense local perturbation of the recycling superposed on the relaxation oscillation. (authors)

  9. Very low frequency oscillations of heat load and recycling flux in steady-state tokamak discharge in TRIAM-1M

    Energy Technology Data Exchange (ETDEWEB)

    Zushi, H.; Sakamoto, M.; Hanada, K.; Iyomasa, A.; Nakamura, K.; Sato, K.N.; Idei, H.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Hasegawa, M. [Kyushu Univ., Research Institute for Applied Mechanics (Japan); Matsuo, Y.; Kuramoto, K.; Sugata, T.; Maezono, N.; Hoshika, H.; Sasaki, K. [Kyushu Univ., Interdisciplinary Graduate School of Engineering Sciences (Japan)

    2004-07-01

    Plasma wall interaction (PWI) driven relaxation oscillations are investigated in the steady state discharge for 5 hours. The oscillation frequency was about 10{sup -3} Hz and each perturbation lasted for about 300 s. The heat load, recycling flux and impurity influx were varied from a few % to several tens of %. The largest variation of 70% was seen on the Mo XIII (molybdenum), although the influx of Mo I was only 20 %. Although the input rf power is kept constant during the discharge, the coupling between the rf and plasma was increased by about 10%. The current drive efficiency is decreased by 24 % in spite of current ramp. The toroidal and poloidal profiles of the recycling flux were also changed. During the last relaxation phase, the plasma was finally terminated. The current reduction (> 4 kA) was not recovered by intense local perturbation of the recycling superposed on the relaxation oscillation. (authors)

  10. 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.

  11. Investigation of switching frequency variations in self-oscillating class D amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Knott, Arnold; Pfaffinger, Gerhard

    2009-01-01

    Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in class D amplifiers is known as self-oscillation. An parameter of key interest in self-oscillating class D amplifiers is the switching fre...

  12. Enhanced detection of a low-frequency signal by using broad squeezed light and a bichromatic local oscillator

    Science.gov (United States)

    Li, Wei; Jin, Yuanbin; Yu, Xudong; Zhang, Jing

    2017-08-01

    We experimentally study a protocol of using the broadband high-frequency squeezed vacuum to detect the low-frequency signal. In this scheme, the lower sideband field of the squeezed light carries the low-frequency modulation signal, and the two strong coherent light fields are applied as the bichromatic local oscillator in the homodyne detection to measure the quantum entanglement of the upper and lower sideband for the broadband squeezed light. The power of one of the local oscillators for detecting the upper sideband can be adjusted to optimize the conditional variance in the low-frequency regime by subtracting the photocurrent of the upper sideband field of the squeezed light from that of the lower sideband field. By means of the quantum correlation of the upper and lower sideband for the broadband squeezed light, the low-frequency signal beyond the standard quantum limit is measured. This scheme is appropriate for enhancing the sensitivity of the low-frequency signal by the aid of the broad squeezed light, such as gravitational waves detection, and does not need to directly produce the low-frequency squeezing in an optical parametric process.

  13. The Influence of the External Signal Modulation Waveform and Frequency on the Performance of a Photonic Forced Oscillator.

    Science.gov (United States)

    Sánchez-Castro, Noemi; Palomino-Ovando, Martha Alicia; Estrada-Wiese, Denise; Valladares, Nydia Xcaret; Del Río, Jesus Antonio; de la Mora, Maria Beatriz; Doti, Rafael; Faubert, Jocelyn; Lugo, Jesus Eduardo

    2018-05-21

    Photonic crystals have been an object of interest because of their properties to inhibit certain wavelengths and allow the transmission of others. Using these properties, we designed a photonic structure known as photodyne formed by two porous silicon one-dimensional photonic crystals with an air defect between them. When the photodyne is illuminated with appropriate light, it allows us to generate electromagnetic forces within the structure that can be maximized if the light becomes localized inside the defect region. These electromagnetic forces allow the microcavity to oscillate mechanically. In the experiment, a chopper was driven by a signal generator to modulate the laser light that was used. The driven frequency and the signal modulation waveform (rectangular, sinusoidal or triangular) were changed with the idea to find optimal conditions for the structure to oscillate. The microcavity displacement amplitude, velocity amplitude and Fourier spectrum of the latter and its frequency were measured by means of a vibrometer. The mechanical oscillations are modeled and compared with the experimental results and show good agreement. For external frequency values of 5 Hz and 10 Hz, the best option was a sinusoidal waveform, which gave higher photodyne displacements and velocity amplitudes. Nonetheless, for an external frequency of 15 Hz, the best option was the rectangular waveform.

  14. The Influence of the External Signal Modulation Waveform and Frequency on the Performance of a Photonic Forced Oscillator

    Directory of Open Access Journals (Sweden)

    Noemi Sánchez-Castro

    2018-05-01

    Full Text Available Photonic crystals have been an object of interest because of their properties to inhibit certain wavelengths and allow the transmission of others. Using these properties, we designed a photonic structure known as photodyne formed by two porous silicon one-dimensional photonic crystals with an air defect between them. When the photodyne is illuminated with appropriate light, it allows us to generate electromagnetic forces within the structure that can be maximized if the light becomes localized inside the defect region. These electromagnetic forces allow the microcavity to oscillate mechanically. In the experiment, a chopper was driven by a signal generator to modulate the laser light that was used. The driven frequency and the signal modulation waveform (rectangular, sinusoidal or triangular were changed with the idea to find optimal conditions for the structure to oscillate. The microcavity displacement amplitude, velocity amplitude and Fourier spectrum of the latter and its frequency were measured by means of a vibrometer. The mechanical oscillations are modeled and compared with the experimental results and show good agreement. For external frequency values of 5 Hz and 10 Hz, the best option was a sinusoidal waveform, which gave higher photodyne displacements and velocity amplitudes. Nonetheless, for an external frequency of 15 Hz, the best option was the rectangular waveform.

  15. Time-dependent scaling patterns in high frequency financial data

    Science.gov (United States)

    Nava, Noemi; Di Matteo, Tiziana; Aste, Tomaso

    2016-10-01

    We measure the influence of different time-scales on the intraday dynamics of financial markets. This is obtained by decomposing financial time series into simple oscillations associated with distinct time-scales. We propose two new time-varying measures of complexity: 1) an amplitude scaling exponent and 2) an entropy-like measure. We apply these measures to intraday, 30-second sampled prices of various stock market indices. Our results reveal intraday trends where different time-horizons contribute with variable relative amplitudes over the course of the trading day. Our findings indicate that the time series we analysed have a non-stationary multifractal nature with predominantly persistent behaviour at the middle of the trading session and anti-persistent behaviour at the opening and at the closing of the session. We demonstrate that these patterns are statistically significant, robust, reproducible and characteristic of each stock market. We argue that any modelling, analytics or trading strategy must take into account these non-stationary intraday scaling patterns.

  16. SELECTIVE MODAL ANALYSIS OF POWER FLOW OSCILLATION IN LARGE SCALE LONGITUDINAL POWER SYSTEMS

    Directory of Open Access Journals (Sweden)

    Wirindi -

    2009-06-01

    Full Text Available Novel selective modal analysis for the determination of low frequency power flow oscillation behaviour based on eigenvalues with corresponding damping ratio, cumulative damping index, and participation factors is proposed. The power system being investigated consists of three large longitudinally interconnected areas with some weak tie lines. Different modes, such as exciter modes, inter area modes, and local modes of the dominant poles are fully studied to find out the significant level of system damping and other factors producing power flow instability. The nature of the energy exchange between area is determined and strategic power flow stability improvement is developed and tested.

  17. Periodic rotation noise induced by the crosstalk between two beat-frequency signals in multi-oscillator ring laser gyros

    International Nuclear Information System (INIS)

    Lu, Guangfeng; Wang, Zhiguo; Fan, Zhenfang; Luo, Hui

    2014-01-01

    Periodic rotation noise in the outputs of multi-oscillator ring laser gyros (MRLGs) is investigated in this paper for the first time. It is proved theoretically and experimentally that noise is induced by the crosstalk between two beat-frequency signals, which are combined from the left and right circularly polarized counter-propagating beams in MRLGs. Theoretical analysis and experimental results also indicate that the fundamental frequency of this noise is equal to the frequency difference between the two beat-frequency signals and the amplitude of the fundamental component is proportional to the crosstalk ratio between the two beat-frequency signals. Further, the amplitude of the nth-order component is proportional to the nth power of the crosstalk ratio. (paper)

  18. Damping of Low Frequency Oscillation in Power System using Robust Control of Superconductor Flywheel Energy Storage System

    International Nuclear Information System (INIS)

    Lee, Jung Pil; Kim, Han Gun

    2012-01-01

    In this paper, the robust superconductor flywheel energy storage system(SFESS) controller using H control theory was designed to damp low frequency oscillation of power system. The main advantage of the controller is that uncertainties of power system can be included at the stage of controller design. Both disturbance attenuation and robust stability for the power system were treated simultaneously by using mixed sensitivity problem. The robust stability and the performance for uncertainties of power system were represented by frequency weighted transfer function. To verify control performance of proposed SFESS controller using control, the closed loop eigenvalue and the damping ratio in dominant oscillation mode of power system were analyzed and nonlinear simulation for one-machine infinite bus system was performed under disturbance for various operating conditions. The results showed that the proposed SFESS controller was more robust than conventional power system stabilizer (PSS).

  19. Study of the B s0overlineBs0 oscillation frequency using D s- ℓ + combinations in Z decays

    Science.gov (United States)

    Buskulic, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Lucotte, A.; Minard, M.-N.; Odier, P.; Pietrzyk, B.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Delfino, M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Juste, A.; Martinez, M.; Orteu, S.; Pacheco, A.; Padilla, C.; Pascual, A.; Perlas, J. A.; Riu, I.; Sanchez, F.; Teubert, F.; Colaleo, A.; Creanza, D.; de Palma, M.; Gelao, G.; Girone, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Marinelli, N.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Alemany, R.; Bazarko, A. O.; Bonvicini, G.; Cattaneo, M.; Comas, P.; Coyle, P.; Drevermann, H.; Forty, R. W.; Frank, M.; Hagelberg, R.; Harvey, J.; Janot, P.; Jost, B.; Kneringer, E.; Knobloch, J.; Lehraus, I.; Lutters, G.; Martin, E. B.; Mato, P.; Minten, A.; Miquel, R.; Mir, Ll. M.; Moneta, L.; Oest, T.; Pater, J. R.; Pusztaszeri, J.-F.; Ranjard, F.; Rensing, P.; Rolandi, L.; Schlatter, D.; Schmelling, M.; Schneider, O.; Tejessy, W.; Tomalin, I. R.; Venturi, A.; Wachsmuth, H.; Wagner, A.; Wildish, T.; Ajaltouni, Z.; Barrès, A.; Boyer, C.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Rossignol, J.-M.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Wäänänen, A.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Bourdon, P.; Rougé, A.; Rumpf, M.; Valassi, A.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Focardi, E.; Parrini, G.; Corden, M.; Georgiopoulos, C.; Jaffe, D. E.; Antonelli, A.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Casper, D.; Chiarella, V.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Curtis, L.; Dorris, S. J.; Halley, A. W.; Knowles, I. G.; Lynch, J. G.; O'Shea, V.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Thompson, A. S.; Thomson, F.; Thorn, S.; Turnbull, R. M.; Becker, U.; Geweniger, C.; Graefe, G.; Hanke, P.; Hansper, G.; Hepp, V.; Kluge, E. E.; Putzer, A.; Rensch, B.; Schmidt, M.; Sommer, J.; Stenzel, H.; Tittel, K.; Werner, S.; Wunsch, M.; Abbaneo, D.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Dornan, P. J.; Moutoussi, A.; Nash, J.; Sedgbeer, J. K.; Stacey, A. M.; Williams, M. D.; Dissertori, G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Betteridge, A. P.; Bowdery, C. K.; Colrain, P.; Crawford, G.; Finch, A. J.; Foster, F.; Hughes, G.; Sloan, T.; Williams, M. I.; Galla, A.; Greene, A. M.; Kleinknecht, K.; Quast, G.; Renk, B.; Rohne, E.; Sander, H.-G.; van Gemmeren, P.; Zeitnitz, C.; Aubert, J. J.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Bujosa, G.; Calvet, D.; Carr, J.; Diaconu, C.; Etienne, F.; Konstantinidis, N.; Payre, P.; Rousseau, D.; Talby, M.; Sadouki, A.; Thulasidas, M.; Trabelsi, K.; Aleppo, M.; Ragusa, F.; Abt, I.; Assmann, R.; Bauer, C.; Blum, W.; Dietl, H.; Dydak, F.; Ganis, G.; Gotzhein, C.; Jakobs, K.; Kroha, H.; Lütjens, G.; Lutz, G.; Männer, W.; Moser, H.-G.; Richter, R.; Rosado-Schlosser, A.; Schael, S.; Settles, R.; Seywerd, H.; Denis, R. St.; Wiedenmann, W.; Wolf, G.; Boucrot, J.; Callot, O.; Cordier, A.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jacquet, M.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Nikolic, I.; Park, H. J.; Park, I. C.; Schune, M.-H.; Simion, S.; Veillet, J.-J.; Videau, I.; Azzurri, P.; Bagliesi, G.; Batignani, G.; Bettarini, S.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; Dell'Orso, R.; Fantechi, R.; Ferrante, I.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Marrocchesi, P. S.; Messineo, A.; Palla, F.; Rizzo, G.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Vannini, C.; Verdini, P. G.; Walsh, J.; Blair, G. A.; Bryant, L. M.; Cerutti, F.; Chambers, J. T.; Gao, Y.; Green, M. G.; Medcalf, T.; Perrodo, P.; Strong, J. A.; von Wimmersperg-Toeller, J. H.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Maley, P.; Norton, P. R.; Thompson, J. C.; Wright, A. E.; Bloch-Devaux, B.; Colas, P.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Trabelsi, A.; Vallage, B.; Black, S. N.; Dann, J. H.; Johnson, R. P.; Kim, H. Y.; Litke, A. M.; McNeil, M. A.; Taylor, G.; Booth, C. N.; Boswell, R.; Brew, C. A. J.; Cartwright, S.; Combley, F.; Koksal, A.; Letho, M.; Newton, W. M.; Reeve, J.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Büscher, V.; Cowan, G.; Grupen, C.; Minguet-Rodriguez, J.; Rivera, F.; Saraiva, P.; Smolik, L.; Stephan, F.; Apollonio, M.; Bosisio, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Musolino, G.; Rothberg, J.; Wasserbaech, S.; Armstrong, S. R.; Bellantoni, L.; Elmer, P.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; González, S.; Grahl, J.; Greening, T. C.; Harton, J. L.; Hayes, O. J.; Hu, H.; McNamara, P. A.; Nachtman, J. M.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Schmitt, M.; Scott, I. J.; Sharma, V.; Walsh, A. M.; Wu, Sau Lan; Wu, X.; Yamartino, J. M.; Zheng, M.; Zobernig, G.; Aleph Collaboration

    1996-02-01

    A lower limit on the oscillation frequency of the B s0overlineBs0 system is obtained from approximately four million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1995. Leptons are combined with opposite sign D s- candidates reconstructed in seven different decay modes as evidence of semileptonic B s0 decays. Criteria designed to ensure precise proper time reconstruction select 277D s-ℓ + combinations. The initial state of these B s0 candidates is determined using an algorithm optimized to efficiently utilise the tagging information available for each event. The limit at 95% confidence level on the B s0overlineBs0 oscillation frequency is Δms > 6.6 ps -1. The same data is used to update the measurement of the B s0 lifetime, τs = 1.54 -0.13+0.14 (stat) ± 0.04 (syst) ps.

  20. Kinetic Scale Structure of Low-frequency Waves and Fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    López, Rodrigo A.; Yoon, Peter H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, MD 20771 (United States); Araneda, Jaime A., E-mail: rlopezh@umd.edu, E-mail: yoonp@umd.edu [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile)

    2017-08-10

    The dissipation of solar wind turbulence at kinetic scales is believed to be important for the heating of the corona and for accelerating the wind. The linear Vlasov kinetic theory is a useful tool for identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, and ion-acoustic (or kinetic slow), and their possible roles in the dissipation. However, the kinetic mode structure in the vicinity of ion-cyclotron modes is not clearly understood. The present paper aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. The theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion-Bernstein modes versus quasi-modes. The spontaneous emission theory and simulation also confirm the findings of the Vlasov theory in that the kinetic Alfvén waves can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high-beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave–particle interactions.

  1. Internal differential rotation of the Sun: the P-modes frequency splitting in the measurements of brightness oscillations

    International Nuclear Information System (INIS)

    Didkovskij, L.V.

    1989-01-01

    a 12-DAY SERIES OF TWO-DIMNIONAL IMAGES OF SOLAR BRIGHTNESS OSCILLATIONS EIGENFREQUENCIES in the range of 6-32 degrees. The rotational frequency splitting of separate modes as a function of inner turn-points radius of acoustic waves is found. The results of the analysis shw fast rotation of the central region of the Sun and non-monotonous trend of angular rotation velocity varitions with radius of the boundary of solar core

  2. Scaling laws and fluctuations in the statistics of word frequencies

    Science.gov (United States)

    Gerlach, Martin; Altmann, Eduardo G.

    2014-11-01

    In this paper, we combine statistical analysis of written texts and simple stochastic models to explain the appearance of scaling laws in the statistics of word frequencies. The average vocabulary of an ensemble of fixed-length texts is known to scale sublinearly with the total number of words (Heaps’ law). Analyzing the fluctuations around this average in three large databases (Google-ngram, English Wikipedia, and a collection of scientific articles), we find that the standard deviation scales linearly with the average (Taylor's law), in contrast to the prediction of decaying fluctuations obtained using simple sampling arguments. We explain both scaling laws (Heaps’ and Taylor) by modeling the usage of words using a Poisson process with a fat-tailed distribution of word frequencies (Zipf's law) and topic-dependent frequencies of individual words (as in topic models). Considering topical variations lead to quenched averages, turn the vocabulary size a non-self-averaging quantity, and explain the empirical observations. For the numerous practical applications relying on estimations of vocabulary size, our results show that uncertainties remain large even for long texts. We show how to account for these uncertainties in measurements of lexical richness of texts with different lengths.

  3. Scaling laws and fluctuations in the statistics of word frequencies

    International Nuclear Information System (INIS)

    Gerlach, Martin; Altmann, Eduardo G

    2014-01-01

    In this paper, we combine statistical analysis of written texts and simple stochastic models to explain the appearance of scaling laws in the statistics of word frequencies. The average vocabulary of an ensemble of fixed-length texts is known to scale sublinearly with the total number of words (Heaps’ law). Analyzing the fluctuations around this average in three large databases (Google-ngram, English Wikipedia, and a collection of scientific articles), we find that the standard deviation scales linearly with the average (Taylor's law), in contrast to the prediction of decaying fluctuations obtained using simple sampling arguments. We explain both scaling laws (Heaps’ and Taylor) by modeling the usage of words using a Poisson process with a fat-tailed distribution of word frequencies (Zipf's law) and topic-dependent frequencies of individual words (as in topic models). Considering topical variations lead to quenched averages, turn the vocabulary size a non-self-averaging quantity, and explain the empirical observations. For the numerous practical applications relying on estimations of vocabulary size, our results show that uncertainties remain large even for long texts. We show how to account for these uncertainties in measurements of lexical richness of texts with different lengths. (paper)

  4. Electronically tunable RC sinusoidal oscillators

    International Nuclear Information System (INIS)

    Florescu, Valeriu

    2008-01-01

    This paper presents two types of active configurations for realizing electronically tunable RC sinusoidal oscillators. The type-1 network employs two grounded scaled resistances KR 1 and KR 2 , where K is scaling factor. The frequency of oscillation W 0 is controlled conveniently by adjusting K, since W 0 appears in the form W 0 =1/K √ R 1 C 1 R 2 C 2 . For realizing the scaled resistances, an active configuration is proposed, which realizes KR 1 =R 1 /(1+f(V B )), where f(V B ) denotes a function of a controlling voltage V B . Thus the frequency tuning can be effected by controlling a voltage V B . The type-2 oscillator uses two periodically switched conductances. It is shown that the tuning of oscillation frequency can be done by varying the pulse width-to-period ratio (t/T) of the periodically switched conductances. (author)

  5. High-Frequency Oscillations Recorded on the Scalp of Patients With Epilepsy Using Tripolar Concentric Ring Electrodes.

    Science.gov (United States)

    Besio, Walter G; Martínez-Juárez, Iris E; Makeyev, Oleksandr; Gaitanis, John N; Blum, Andrew S; Fisher, Robert S; Medvedev, Andrei V

    2014-01-01

    Epilepsy is the second most prevalent neurological disorder ([Formula: see text]% prevalence) affecting [Formula: see text] million people worldwide with up to 75% from developing countries. The conventional electroencephalogram is plagued with artifacts from movements, muscles, and other sources. Tripolar concentric ring electrodes automatically attenuate muscle artifacts and provide improved signal quality. We performed basic experiments in healthy humans to show that tripolar concentric ring electrodes can indeed record the physiological alpha waves while eyes are closed. We then conducted concurrent recordings with conventional disc electrodes and tripolar concentric ring electrodes from patients with epilepsy. We found that we could detect high frequency oscillations, a marker for early seizure development and epileptogenic zone, on the scalp surface that appeared to become more narrow-band just prior to seizures. High frequency oscillations preceding seizures were present in an average of 35.5% of tripolar concentric ring electrode data channels for all the patients with epilepsy whose seizures were recorded and absent in the corresponding conventional disc electrode data. An average of 78.2% of channels that contained high frequency oscillations were within the seizure onset or irritative zones determined independently by three epileptologists based on conventional disc electrode data and videos.

  6. Altered modulation of gamma oscillation frequency by speed of visual motion in children with autism spectrum disorders.

    Science.gov (United States)

    Stroganova, Tatiana A; Butorina, Anna V; Sysoeva, Olga V; Prokofyev, Andrey O; Nikolaeva, Anastasia Yu; Tsetlin, Marina M; Orekhova, Elena V

    2015-01-01

    Recent studies link autism spectrum disorders (ASD) with an altered balance between excitation and inhibition (E/I balance) in cortical networks. The brain oscillations in high gamma-band (50-120 Hz) are sensitive to the E/I balance and may appear useful biomarkers of certain ASD subtypes. The frequency of gamma oscillations is mediated by level of excitation of the fast-spiking inhibitory basket cells recruited by increasing strength of excitatory input. Therefore, the experimental manipulations affecting gamma frequency may throw light on inhibitory networks dysfunction in ASD. Here, we used magnetoencephalography (MEG) to investigate modulation of visual gamma oscillation frequency by speed of drifting annular gratings (1.2, 3.6, 6.0 °/s) in 21 boys with ASD and 26 typically developing boys aged 7-15 years. Multitaper method was used for analysis of spectra of gamma power change upon stimulus presentation and permutation test was applied for statistical comparisons. We also assessed in our participants visual orientation discrimination thresholds, which are thought to depend on excitability of inhibitory networks in the visual cortex. Although frequency of the oscillatory gamma response increased with increasing velocity of visual motion in both groups of participants, the velocity effect was reduced in a substantial proportion of children with ASD. The range of velocity-related gamma frequency modulation correlated inversely with the ability to discriminate oblique line orientation in the ASD group, while no such correlation has been observed in the group of typically developing participants. Our findings suggest that abnormal velocity-related gamma frequency modulation in ASD may constitute a potential biomarker for reduced excitability of fast-spiking inhibitory neurons in a subset of children with ASD.

  7. Spontaneous high frequency diameter oscillations of larger retinal arterioles are reduced in type 2 diabetes mellitus

    DEFF Research Database (Denmark)

    Bek, Toke; Jeppesen, Peter; Kanters, Jørgen K.

    2013-01-01

    Diabetic retinopathy is characterized by morphological changes in the retina secondary to disturbances in retinal blood flow. Vasomotion is a mechanism for regulating blood flow by spontaneous oscillations in the diameter of retinal resistance arterioles, and has been shown to be disturbed outside...... the eye in diabetic patients. Therefore, the purpose of the present study was to characterize spontaneous oscillations in the diameter of retinal arterioles in normal persons and in persons with different severity of diabetic retinopathy....

  8. Synchronization, non-linear dynamics and low-frequency fluctuations: Analogy between spontaneous brain activity and networked single-transistor chaotic oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Minati, Ludovico, E-mail: lminati@ieee.org, E-mail: ludovico.minati@unitn.it, E-mail: lminati@istituto-besta.it [Scientific Department, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan (Italy); Center for Mind/Brain Sciences, University of Trento, Trento (Italy); Chiesa, Pietro; Tabarelli, Davide; Jovicich, Jorge [Center for Mind/Brain Sciences, University of Trento, Trento (Italy); D' Incerti, Ludovico [Neuroradiology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan (Italy)

    2015-03-15

    In this paper, the topographical relationship between functional connectivity (intended as inter-regional synchronization), spectral and non-linear dynamical properties across cortical areas of the healthy human brain is considered. Based upon functional MRI acquisitions of spontaneous activity during wakeful idleness, node degree maps are determined by thresholding the temporal correlation coefficient among all voxel pairs. In addition, for individual voxel time-series, the relative amplitude of low-frequency fluctuations and the correlation dimension (D{sub 2}), determined with respect to Fourier amplitude and value distribution matched surrogate data, are measured. Across cortical areas, high node degree is associated with a shift towards lower frequency activity and, compared to surrogate data, clearer saturation to a lower correlation dimension, suggesting presence of non-linear structure. An attempt to recapitulate this relationship in a network of single-transistor oscillators is made, based on a diffusive ring (n = 90) with added long-distance links defining four extended hub regions. Similarly to the brain data, it is found that oscillators in the hub regions generate signals with larger low-frequency cycle amplitude fluctuations and clearer saturation to a lower correlation dimension compared to surrogates. The effect emerges more markedly close to criticality. The homology observed between the two systems despite profound differences in scale, coupling mechanism and dynamics appears noteworthy. These experimental results motivate further investigation into the heterogeneity of cortical non-linear dynamics in relation to connectivity and underline the ability for small networks of single-transistor oscillators to recreate collective phenomena arising in much more complex biological systems, potentially representing a future platform for modelling disease-related changes.

  9. Synchronization, non-linear dynamics and low-frequency fluctuations: Analogy between spontaneous brain activity and networked single-transistor chaotic oscillators

    International Nuclear Information System (INIS)

    Minati, Ludovico; Chiesa, Pietro; Tabarelli, Davide; Jovicich, Jorge; D'Incerti, Ludovico

    2015-01-01

    In this paper, the topographical relationship between functional connectivity (intended as inter-regional synchronization), spectral and non-linear dynamical properties across cortical areas of the healthy human brain is considered. Based upon functional MRI acquisitions of spontaneous activity during wakeful idleness, node degree maps are determined by thresholding the temporal correlation coefficient among all voxel pairs. In addition, for individual voxel time-series, the relative amplitude of low-frequency fluctuations and the correlation dimension (D 2 ), determined with respect to Fourier amplitude and value distribution matched surrogate data, are measured. Across cortical areas, high node degree is associated with a shift towards lower frequency activity and, compared to surrogate data, clearer saturation to a lower correlation dimension, suggesting presence of non-linear structure. An attempt to recapitulate this relationship in a network of single-transistor oscillators is made, based on a diffusive ring (n = 90) with added long-distance links defining four extended hub regions. Similarly to the brain data, it is found that oscillators in the hub regions generate signals with larger low-frequency cycle amplitude fluctuations and clearer saturation to a lower correlation dimension compared to surrogates. The effect emerges more markedly close to criticality. The homology observed between the two systems despite profound differences in scale, coupling mechanism and dynamics appears noteworthy. These experimental results motivate further investigation into the heterogeneity of cortical non-linear dynamics in relation to connectivity and underline the ability for small networks of single-transistor oscillators to recreate collective phenomena arising in much more complex biological systems, potentially representing a future platform for modelling disease-related changes

  10. Oscillating red giants in eclipsing binary systems: empirical reference value for asteroseismic scaling relation

    Science.gov (United States)

    Themeßl, N.; Hekker, S.; Southworth, J.; Beck, P. G.; Pavlovski, K.; Tkachenko, A.; Angelou, G. C.; Ball, W. H.; Barban, C.; Corsaro, E.; Elsworth, Y.; Handberg, R.; Kallinger, T.

    2018-05-01

    The internal structures and properties of oscillating red-giant stars can be accurately inferred through their global oscillation modes (asteroseismology). Based on 1460 days of Kepler observations we perform a thorough asteroseismic study to probe the stellar parameters and evolutionary stages of three red giants in eclipsing binary systems. We present the first detailed analysis of individual oscillation modes of the red-giant components of KIC 8410637, KIC 5640750 and KIC 9540226. We obtain estimates of their asteroseismic masses, radii, mean densities and logarithmic surface gravities by using the asteroseismic scaling relations as well as grid-based modelling. As these red giants are in double-lined eclipsing binaries, it is possible to derive their independent dynamical masses and radii from the orbital solution and compare it with the seismically inferred values. For KIC 5640750 we compute the first spectroscopic orbit based on both components of this system. We use high-resolution spectroscopic data and light curves of the three systems to determine up-to-date values of the dynamical stellar parameters. With our comprehensive set of stellar parameters we explore consistencies between binary analysis and asteroseismic methods, and test the reliability of the well-known scaling relations. For the three red giants under study, we find agreement between dynamical and asteroseismic stellar parameters in cases where the asteroseismic methods account for metallicity, temperature and mass dependence as well as surface effects. We are able to attain agreement from the scaling laws in all three systems if we use Δνref, emp = 130.8 ± 0.9 μHz instead of the usual solar reference value.

  11. Isocurvature modes and Baryon Acoustic Oscillations II: gains from combining CMB and Large Scale Structure

    International Nuclear Information System (INIS)

    Carbone, Carmelita; Mangilli, Anna; Verde, Licia

    2011-01-01

    We consider cosmological parameters estimation in the presence of a non-zero isocurvature contribution in the primordial perturbations. A previous analysis showed that even a tiny amount of isocurvature perturbation, if not accounted for, could affect standard rulers calibration from Cosmic Microwave Background observations such as those provided by the Planck mission, affect Baryon Acoustic Oscillations interpretation, and introduce biases in the recovered dark energy properties that are larger than forecasted statistical errors from future surveys. Extending on this work, here we adopt a general fiducial cosmology which includes a varying dark energy equation of state parameter and curvature. Beside Baryon Acoustic Oscillations measurements, we include the information from the shape of the galaxy power spectrum and consider a joint analysis of a Planck-like Cosmic Microwave Background probe and a future, space-based, Large Scale Structure probe not too dissimilar from recently proposed surveys. We find that this allows one to break the degeneracies that affect the Cosmic Microwave Background and Baryon Acoustic Oscillations combination. As a result, most of the cosmological parameter systematic biases arising from an incorrect assumption on the isocurvature fraction parameter f iso , become negligible with respect to the statistical errors. We find that the Cosmic Microwave Background and Large Scale Structure combination gives a statistical error σ(f iso ) ∼ 0.008, even when curvature and a varying dark energy equation of state are included, which is smaller that the error obtained from Cosmic Microwave Background alone when flatness and cosmological constant are assumed. These results confirm the synergy and complementarity between Cosmic Microwave Background and Large Scale Structure, and the great potential of future and planned galaxy surveys

  12. A single-layer flat-coil-oscillator (SFCO)-based super-broadband position sensor for nano-scale-resolution seismometry

    Energy Technology Data Exchange (ETDEWEB)

    Gevorgyan, Samvel [Department of Physics, Yerevan State University, 1 Alex Manoogian Street, Yerevan 0025 (Armenia); Institute for Physical Researches, National Academy of Sciences, Gitavan IFI, 0203 Ashtarak-2 (Armenia)], E-mail: gevs_sam@web.am; Gevorgyan, Vardan [Department of Physics, Yerevan State University, 1 Alex Manoogian Street, Yerevan 0025 (Armenia); Institute for Physical Researches, National Academy of Sciences, Gitavan IFI, 0203 Ashtarak-2 (Armenia); International Scientific-Educational Center, National Academy of Sciences, 24-D Marshal Baghramyan av., Yerevan 0019 (Armenia); Karapetyan, Gagik [Department of Physics, Yerevan State University, 1 Alex Manoogian Street, Yerevan 0025 (Armenia); Institute for Physical Researches, National Academy of Sciences, Gitavan IFI, 0203 Ashtarak-2 (Armenia)

    2008-05-15

    A new class super-broadband, nano-scale-resolution position sensor is tested. It is used as an additional sensor in seismograph. It enables to extend the band and enhance the sensitivity of the available technique by at least an order of magnitude. It allows transferring of mechanical vibrations of constructions and buildings, with amplitudes over 1 nm, into detectable signal in a frequency range starting practically from quasi-static movements. It is based on detection of position changes of a vibrating normal-metallic plate placed near the flat coil-being used as a pick-up in a stable tunnel diode oscillator. Frequency of the oscillator is used as a detecting parameter, and the measuring effect is determined by a distortion of the MHz-range testing field configuration near a coil by a vibrating plate, leading to magnetic inductance changes of the coil, with a resolution {approx}10 pH. This results in changes of oscillator frequency. We discuss test data of such a position sensor, installed in a Russian SM-3 seismometer, as an additional pick-up component, showing its advantages compared to traditional techniques. We also discuss the future of such a novel sensor involving substitution of a metallic coil by a superconductive one and replacement of a tunnel diode by an S/I/S hetero-structure-as much less-powered active element in the oscillator, compared to tunnel diode. These may strongly improve the stability of oscillators, and therefore enhance the resolution of seismic techniques.

  13. Higgs mass scales and matter-antimatter oscillations in grand unified theories

    International Nuclear Information System (INIS)

    Senjanovic, G.

    1982-01-01

    A general discussion of mass scales in grand unified theories is presented, with special emphasis on Higgs scalars which mediate neutron-antineutron (n-anti n) and hydrogen-antihydrogen (H-anti H) oscillations. It is shown that the analogue of survival hypothesis for fermions naturally makes such particles superheavy, thus leading to unobservable lifetimes. If this hypothesis is relaxed, an interesting possibility of potentially observable n-anti n and H-anti H transitions, mutually related arises in the context of SU(5) theory with spontaneously broken B-L symmetry

  14. A real scale simulator for high frequency LEMP

    Science.gov (United States)

    Gauthier, D.; Serafin, D.

    1991-01-01

    The real scale simulator is described which was designed by the Centre d'Etudes de Gramat (CEG) to study the coupling of fast rise time Lightning Electromagnetic pulse in a fighter aircraft. The system capability of generating the right electromagnetic environment was studied using a Finite Difference Time Domain (FDTD) computer program. First, data of inside stresses are shown. Then, a time domain and a frequency domain approach is exposed and compared.

  15. Efficient Spectral Power Estimation on an Arbitrary Frequency Scale

    Directory of Open Access Journals (Sweden)

    F. Zaplata

    2015-04-01

    Full Text Available The Fast Fourier Transform is a very efficient algorithm for the Fourier spectrum estimation, but has the limitation of a linear frequency scale spectrum, which may not be suitable for every system. For example, audio and speech analysis needs a logarithmic frequency scale due to the characteristic of a human’s ear. The Fast Fourier Transform algorithms are not able to efficiently give the desired results and modified techniques have to be used in this case. In the following text a simple technique using the Goertzel algorithm allowing the evaluation of the power spectra on an arbitrary frequency scale will be introduced. Due to its simplicity the algorithm suffers from imperfections which will be discussed and partially solved in this paper. The implementation into real systems and the impact of quantization errors appeared to be critical and have to be dealt with in special cases. The simple method dealing with the quantization error will also be introduced. Finally, the proposed method will be compared to other methods based on its computational demands and its potential speed.

  16. A PK-PD model of ketamine-induced high-frequency oscillations

    Science.gov (United States)

    Flores, Francisco J.; Ching, ShiNung; Hartnack, Katharine; Fath, Amanda B.; Purdon, Patrick L.; Wilson, Matthew A.; Brown, Emery N.

    2015-10-01

    Objective. Ketamine is a widely used drug with clinical and research applications, and also known to be used as a recreational drug. Ketamine produces conspicuous changes in the electrocorticographic (ECoG) signals observed both in humans and rodents. In rodents, the intracranial ECoG displays a high-frequency oscillation (HFO) which power is modulated nonlinearly by ketamine dose. Despite the widespread use of ketamine there is no model description of the relationship between the pharmacokinetic-pharmacodynamics (PK-PDs) of ketamine and the observed HFO power. Approach. In the present study, we developed a PK-PD model based on estimated ketamine concentration, its known pharmacological actions, and observed ECoG effects. The main pharmacological action of ketamine is antagonism of the NMDA receptor (NMDAR), which in rodents is accompanied by an HFO observed in the ECoG. At high doses, however, ketamine also acts at non-NMDAR sites, produces loss of consciousness, and the transient disappearance of the HFO. We propose a two-compartment PK model that represents the concentration of ketamine, and a PD model based in opposing effects of the NMDAR and non-NMDAR actions on the HFO power. Main results. We recorded ECoG from the cortex of rats after two doses of ketamine, and extracted the HFO power from the ECoG spectrograms. We fit the PK-PD model to the time course of the HFO power, and showed that the model reproduces the dose-dependent profile of the HFO power. The model provides good fits even in the presence of high variability in HFO power across animals. As expected, the model does not provide good fits to the HFO power after dosing the pure NMDAR antagonist MK-801. Significance. Our study provides a simple model to relate the observed electrophysiological effects of ketamine to its actions at the molecular level at different concentrations. This will improve the study of ketamine and rodent models of schizophrenia to better understand the wide and divergent

  17. Method to minimize the low-frequency neutral-point voltage oscillations with time-offset injection for neutral-point-clamped inverters

    DEFF Research Database (Denmark)

    Choi, Uimin; Lee, Kyo-Beum; Blaabjerg, Frede

    2013-01-01

    This paper proposes a method to reduce the low-frequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a time-offset to the three phase turn-on times. The proper time-offset is simply calculated considering the phase currents and dwell...

  18. Frequency effects on the scale and behavior of acoustic streaming.

    Science.gov (United States)

    Dentry, Michael B; Yeo, Leslie Y; Friend, James R

    2014-01-01

    Acoustic streaming underpins an exciting range of fluid manipulation phenomena of rapidly growing significance in microfluidics, where the streaming often assumes the form of a steady, laminar jet emanating from the device surface, driven by the attenuation of acoustic energy within the beam of sound propagating through the liquid. The frequencies used to drive such phenomena are often chosen ad hoc to accommodate fabrication and material issues. In this work, we seek a better understanding of the effects of sound frequency and power on acoustic streaming. We present and, using surface acoustic waves, experimentally verify a laminar jet model that is based on the turbulent jet model of Lighthill, which is appropriate for acoustic streaming seen at micro- to nanoscales, between 20 and 936 MHz and over a broad range of input power. Our model eliminates the critically problematic acoustic source singularity present in Lighthill's model, replacing it with a finite emission area and enabling determination of the streaming velocity close to the source. At high acoustic power P (and hence high jet Reynolds numbers ReJ associated with fast streaming), the laminar jet model predicts a one-half power dependence (U∼P1/2∼ ReJ) similar to the turbulent jet model. However, the laminar model may also be applied to jets produced at low powers-and hence low jet Reynolds numbers ReJ-where a linear relationship between the beam power and streaming velocity exists: U∼P∼ReJ2. The ability of the laminar jet model to predict the acoustic streaming behavior across a broad range of frequencies and power provides a useful tool in the analysis of microfluidics devices, explaining peculiar observations made by several researchers in the literature. In particular, by elucidating the effects of frequency on the scale of acoustically driven flows, we show that the choice of frequency is a vitally important consideration in the design of small-scale devices employing acoustic streaming

  19. Landslide scaling and magnitude-frequency distribution (Invited)

    Science.gov (United States)

    Stark, C. P.; Guzzetti, F.

    2009-12-01

    Landslide-driven erosion is controlled by the scale and frequency of slope failures and by the consequent fluxes of debris off the hillslopes. Here I focus on the magnitude-frequency part of the process and develop a theory of initial slope failure and debris mobilization that reproduces the heavy-tailed distributions (PDFs) observed for landslide source areas and volumes. Landslide rupture propagation is treated as a quasi-static, non-inertial process of simplified elastoplastic deformation with strain weakening; debris runout is not considered. The model tracks the stochastically evolving imbalance of frictional, cohesive, and body forces across a failing slope, and uses safety-factor concepts to convert the evolving imbalance into a series of incremental rupture growth or arrest probabilities. A single rupture is simulated with a sequence of weighted ``coin tosses'' with weights set by the growth probabilities. Slope failure treated in this stochastic way is a survival process that generates asymptotically power-law-tail PDFs of area and volume for rock and debris slides; predicted scaling exponents are consistent with analyses of landslide inventories. The primary control on the shape of the model PDFs is the relative importance of cohesion over friction in setting slope stability: the scaling of smaller, shallower failures, and the size of the most common landslide volumes, are the result of the low cohesion of soil and regolith, whereas the negative power-law tail scaling for larger failures is tied to the greater cohesion of bedrock. The debris budget may be dominated by small or large landslides depending on the scaling of both the PDF and of the depth-length relation. I will present new model results that confirm the hypothesis that depth-length scaling is linear. Model PDF of landslide volumes.

  20. Energy Conservation Using Dynamic Voltage Frequency Scaling for Computational Cloud

    Directory of Open Access Journals (Sweden)

    A. Paulin Florence

    2016-01-01

    Full Text Available Cloud computing is a new technology which supports resource sharing on a “Pay as you go” basis around the world. It provides various services such as SaaS, IaaS, and PaaS. Computation is a part of IaaS and the entire computational requests are to be served efficiently with optimal power utilization in the cloud. Recently, various algorithms are developed to reduce power consumption and even Dynamic Voltage and Frequency Scaling (DVFS scheme is also used in this perspective. In this paper we have devised methodology which analyzes the behavior of the given cloud request and identifies the associated type of algorithm. Once the type of algorithm is identified, using their asymptotic notations, its time complexity is calculated. Using best fit strategy the appropriate host is identified and the incoming job is allocated to the victimized host. Using the measured time complexity the required clock frequency of the host is measured. According to that CPU frequency is scaled up or down using DVFS scheme, enabling energy to be saved up to 55% of total Watts consumption.

  1. Verification of frequency scaling laws for capacitive radio-frequency discharges using two-dimensional simulations

    International Nuclear Information System (INIS)

    Vahedi, V.; Birdsall, C.K.; Lieberman, M.A.; DiPeso, G.; Rognlien, T.D.

    1993-01-01

    Weakly ionized processing plasmas are studied in two dimensions using a bounded particle-in-cell (PIC) simulation code with a Monte Carlo collision (MCC) package. The MCC package models the collisions between charged and neutral particles, which are needed to obtain a self-sustained plasma and the proper electron and ion energy loss mechanisms. A two-dimensional capacitive radio-frequency (rf) discharge is investigated in detail. Simple frequency scaling laws for predicting the behavior of some plasma parameters are derived and then compared with simulation results, finding good agreements. It is found that as the drive frequency increases, the sheath width decreases, and the bulk plasma becomes more uniform, leading to a reduction of the ion angular spread at the target and an improvement of ion dose uniformity at the driven electrode

  2. Low-frequency photocurrent oscillations in InP in magnetic field

    International Nuclear Information System (INIS)

    Slobodchikov, S.V.; Salikhov, Kh.M.; Kovalevskaya, G.G.

    1994-01-01

    Results of investigations of magnetic field effect on the oscillating photocurrent in InP crytals are presented. It is shown that the magnetic field plays the part of an additional source of photocarrier injection in the sample bulk. 3 refs., 2 figs

  3. A Multi-Site Campaign to Measure Solar-Like Oscillations in Procyon. II. Mode Frequencies

    DEFF Research Database (Denmark)

    Bedding, Timothy R.; Kjeldsen, Hans; Campante, Tiago L.

    2010-01-01

      We have analyzed data from a multi-site campaign to observe oscillations in the F5 star Procyon. The data consist of high-precision velocities that we obtained over more than three weeks with 11 telescopes. A new method for adjusting the data weights allows us to suppress the sidelobes in the p...

  4. New Canonic Active RC Sinusoidal Oscillator Circuits Using Second-Generation Current Conveyors with Application as a Wide-Frequency Digitally Controlled Sinusoid Generator

    OpenAIRE

    Abhirup Lahiri

    2011-01-01

    This paper reports two new circuit topologies using second-generation current conveyors (CCIIs) for realizing variable frequency sinusoidal oscillators with minimum passive components. The proposed topologies in this paper provide new realizations of resistance-controlled and capacitor-controlled variable frequency oscillators (VFOs) using only four passive components. The first topology employs three CCIIs, while the second topology employs two CCIIs. The second topology provides an advantag...

  5. Spanish adaptation of social withdrawal motivation and frequency scales.

    Science.gov (United States)

    Indias García, Sílvia; De Paúl Ochotorena, Joaquín

    2016-11-01

    To adapt into Spanish three scales measuring frequency (SWFS) and motivation for social withdrawal (CSPS and SWMS) and to develop a scale capable of assessing the five motivations for social withdrawal. Participants were 1,112 Spanish adolescents, aged 12-17 years. The sample was randomly split into two groups in which exploratory and confirmatory (CFA) factor analyses were performed separately. A sample of adolescents in residential care (n = 128) was also used to perform discriminant validity analyses. SWFS was reduced to eight items that account for 40% of explained variance (PVE), and its reliability is high. SWMS worked adequately in the original version, according to CFA. Some items from the CSPS were removed from the final Spanish version. The newly developed scale (SWMS-5D) is composed of 20 items including five subscales: Peer Isolation, Unsociability, Shyness, Low Mood and Avoidance. Analyses reveal adequate convergent and discriminant validities. The resulting SWFS-8 and SWMS-5D could be considered useful instruments to assess frequency and motivation for social withdrawal in Spanish samples.

  6. Two-oscillator model of trapped-modes interaction in a nonlinear bilayer fish-scale metamaterial

    OpenAIRE

    Tuz, Vladimir R.; Kochetov, Bogdan A.; Kochetova, Lyudmila A.; Mladyonov, Pavel L.; Prosvirnin, Sergey L.

    2014-01-01

    We discuss the similarity between the nature of resonant oscillations in two nonlinear systems, namely, a chain of coupled Duffing oscillators and a bilayer fish-scale metamaterial. In such systems two different resonant states arise which differ in their spectral lines. The spectral line of the first resonant state has a Lorentzian form, while the second one has a Fano form. This difference leads to a specific nonlinear response of the systems which manifests itself in appearance of closed l...

  7. Frequency-dependent changes in amplitude of low-frequency oscillations in depression: A resting-state fMRI study.

    Science.gov (United States)

    Wang, Li; Kong, Qingmei; Li, Ke; Su, Yunai; Zeng, Yawei; Zhang, Qinge; Dai, Wenji; Xia, Mingrui; Wang, Gang; Jin, Zhen; Yu, Xin; Si, Tianmei

    2016-02-12

    We conducted this fMRI study to examine whether the alterations in amplitudes of low-frequency oscillation (LFO) of major depressive disorder (MDD) patients were frequency dependent. The LFO amplitudes (as indexed by amplitude of low-frequency fluctuation [ALFF] and fractional ALFF [fALFF]) within 4 narrowly-defined frequency bands (slow-5: 0.01-0.027Hz, slow-4: 0.027-0.073Hz, slow-3: 0.073-0.198Hz, and slow-2: 0.198-0.25Hz) were computed using resting-state fMRI data of 35 MDD patients and 32 healthy subjects. Repeated-measures analysis of variance (ANOVA) was performed on ALFF and fALFF both within the low frequency bands of slow-4 and slow-5 and within all of the four bands. We observed significant main effects of group and frequency on ALFF and fALFF in widely distributed brain regions. Importantly, significant group and frequency interaction effects were observed in the ventromedial prefrontal cortex, inferior frontal gyrus, precentral gyrus, in a left-sided fashion, the bilateral posterior cingulate and precuneus, during ANOVA both within slow-4 and slow-5 bands and within all the frequency bands. The results suggest that the alterations of LFO amplitudes in specific brain regions in MDD patients could be more sensitively detected in the slow-5 rather than the slow-4 bands. The findings may provide guidance for the frequency choice of future resting-state fMRI studies of MDD. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  8. Simultaneous temporally resolved DPIV and pressure measurements of symmetric oscillations in a scaled-up vocal fold model

    Science.gov (United States)

    Ringenberg, Hunter; Rogers, Dylan; Wei, Nathaniel; Krane, Michael; Wei, Timothy

    2017-11-01

    The objective of this study is to apply experimental data to theoretical framework of Krane (2013) in which the principal aeroacoustic source is expressed in terms of vocal fold drag, glottal jet dynamic head, and glottal exit volume flow, reconciling formal theoretical aeroacoustic descriptions of phonation with more traditional lumped-element descriptions. These quantities appear in the integral equations of motion for phonatory flow. In this way time resolved velocity field measurements can be used to compute time-resolved estimates of the relevant terms in the integral equations of motion, including phonation aeroacoustic source strength. A simplified 10x scale vocal fold model from Krane, et al. (2007) was used to examine symmetric, i.e. `healthy', oscillatory motion of the vocal folds. By using water as the working fluid, very high spatial and temporal resolution was achieved. Temporal variation of transglottal pressure was simultaneously measured with flow on the vocal fold model mid-height. Experiments were dynamically scaled to examine a range of frequencies corresponding to male and female voice. The simultaneity of the pressure and flow provides new insights into the aeroacoustics associated with vocal fold oscillations. Supported by NIH Grant No. 2R01 DC005642-11.

  9. LOW-FREQUENCY QUASI-PERIODIC OSCILLATION FROM THE 11 Hz ACCRETING PULSAR IN TERZAN 5: NOT FRAME DRAGGING

    International Nuclear Information System (INIS)

    Altamirano, D.; Van der Klis, M.; Wijnands, R.; Ingram, A.; Linares, M.; Homan, J.

    2012-01-01

    We report on six RXTE observations taken during the 2010 outburst of the 11 Hz accreting pulsar IGR J17480–2446 located in the globular cluster Terzan 5. During these observations we find power spectra which resemble those seen in Z-type high-luminosity neutron star low-mass X-ray binaries, with a quasi-periodic oscillation (QPO) in the 35-50 Hz range simultaneous with a kHz QPO and broadband noise. Using well-known frequency-frequency correlations, we identify the 35-50 Hz QPOs as the horizontal branch oscillations, which were previously suggested to be due to Lense-Thirring (LT) precession. As IGR J17480–2446 spins more than an order of magnitude more slowly than any of the other neutron stars where these QPOs were found, this QPO cannot be explained by frame dragging. By extension, this casts doubt on the LT precession model for other low-frequency QPOs in neutron stars and perhaps even black hole systems.

  10. Low-frequency Quasi-periodic Oscillation from the 11 Hz Accreting Pulsar in Terzan 5: Not Frame Dragging

    Science.gov (United States)

    Altamirano, D.; Ingram, A.; van der Klis, M.; Wijnands, R.; Linares, M.; Homan, J.

    2012-11-01

    We report on six RXTE observations taken during the 2010 outburst of the 11 Hz accreting pulsar IGR J17480-2446 located in the globular cluster Terzan 5. During these observations we find power spectra which resemble those seen in Z-type high-luminosity neutron star low-mass X-ray binaries, with a quasi-periodic oscillation (QPO) in the 35-50 Hz range simultaneous with a kHz QPO and broadband noise. Using well-known frequency-frequency correlations, we identify the 35-50 Hz QPOs as the horizontal branch oscillations, which were previously suggested to be due to Lense-Thirring (LT) precession. As IGR J17480-2446 spins more than an order of magnitude more slowly than any of the other neutron stars where these QPOs were found, this QPO cannot be explained by frame dragging. By extension, this casts doubt on the LT precession model for other low-frequency QPOs in neutron stars and perhaps even black hole systems.

  11. The impact of the winter North Atlantic Oscillation on the frequency of spring dust storms over Tarim Basin in northwest China in the past half-century

    International Nuclear Information System (INIS)

    Zhao Yong; Huang Anning; Zhou Yang; Huang Ying; Zhu Xinsheng

    2013-01-01

    The relationship between the frequency of spring dust storms over Tarim Basin in northwest China and the winter North Atlantic Oscillation (NAO) is investigated by using the observed dust storm frequency (DSF) and the 10 m wind velocity at 36 stations in Tarim Basin and the National Centers for Environment Prediction/National Center for Atmospheric Research reanalysis data for the period 1961–2007. The spring DSF (winter NAO) index shows a clear decreasing (increasing) linear trend over 1961–2007. The winter NAO correlates well with the subsequent spring DSF over Tarim Basin on both interannual and interdecadal time scales and its interannual to interdecadal variation plays an important role in the spring DSF. Two possible physical mechanisms are identified. One is related to the large scale anomalous circulations in spring in the middle to high troposphere modulated by the winter NAO, providing the background of dynamical conditions for the dust storm occurrences. The other is related to the shifts in the local horizontal sea level pressure (SLP) gradients and 10 m wind speed, corresponding to changes in the large scale circulations in spring. The decrease in the local 10 m wind speed due to the reduced horizontal SLP gradients over Tarim Basin during the strong winter NAO years contributes to the decline of the DSF in the subsequent spring. (letter)

  12. Measurement of the $B^0$ Lifetime and Oscillation Frequency using $\\overline{B}^{0} \\to D^{*+}l^{-}\\overline{\

    CERN Document Server

    Abbiendi, G.; Ainsley, C.; Akesson, P.F.; Alexander, G.; Allison, John; Anderson, K.J.; Arcelli, S.; Asai, S.; Ashby, S.F.; Axen, D.; Azuelos, G.; Bailey, I.; Ball, A.H.; Barberio, E.; Barlow, Roger J.; Baumann, S.; Behnke, T.; Bell, Kenneth Watson; Bella, G.; Bellerive, A.; Benelli, G.; Bentvelsen, S.; Bethke, S.; Biebel, O.; Bloodworth, I.J.; Boeriu, O.; Bock, P.; Bohme, J.; Bonacorsi, D.; Boutemeur, M.; Braibant, S.; Bright-Thomas, P.; Brigliadori, L.; Brown, Robert M.; Burckhart, H.J.; Cammin, J.; Capiluppi, P.; Carnegie, R.K.; Carter, A.A.; Carter, J.R.; Chang, C.Y.; Charlton, David G.; Clarke, P.E.L.; Clay, E.; Cohen, I.; Cooke, O.C.; Couchman, J.; Couyoumtzelis, C.; Coxe, R.L.; Csilling, A.; Cuffiani, M.; Dado, S.; Dallavalle, G.Marco; Dallison, S.; de Roeck, A.; de Wolf, E.; Dervan, P.; Desch, K.; Dienes, B.; Dixit, M.S.; Donkers, M.; Dubbert, J.; Duchovni, E.; Duckeck, G.; Duerdoth, I.P.; Estabrooks, P.G.; Etzion, E.; Fabbri, F.; Fanti, M.; Feld, L.; Ferrari, P.; Fiedler, F.; Fleck, I.; Ford, M.; Frey, A.; Furtjes, A.; Futyan, D.I.; Gagnon, P.; Gary, J.W.; Gaycken, G.; Geich-Gimbel, C.; Giacomelli, G.; Giacomelli, P.; Glenzinski, D.; Goldberg, J.; Grandi, C.; Graham, K.; Gross, E.; Grunhaus, J.; Gruwe, M.; Gunther, P.O.; Hajdu, C.; Hanson, G.G.; Hansroul, M.; Hapke, M.; Harder, K.; Harel, A.; Harin-Dirac, M.; Hauke, A.; Hauschild, M.; Hawkes, C.M.; Hawkings, R.; Hemingway, R.J.; Hensel, C.; Herten, G.; Heuer, R.D.; Hill, J.C.; Hocker, James Andrew; Hoffman, Kara Dion; Homer, R.J.; Honma, A.K.; Horvath, D.; Hossain, K.R.; Howard, R.; Huntemeyer, P.; Igo-Kemenes, P.; Ishii, K.; Jacob, F.R.; Jawahery, A.; Jeremie, H.; Jones, C.R.; Jovanovic, P.; Junk, T.R.; Kanaya, N.; Kanzaki, J.; Karapetian, G.; Karlen, D.; Kartvelishvili, V.; Kawagoe, K.; Kawamoto, T.; Keeler, R.K.; Kellogg, R.G.; Kennedy, B.W.; Kim, D.H.; Klein, K.; Klier, A.; Kluth, S.; Kobayashi, T.; Kobel, M.; Kokott, T.P.; Komamiya, S.; Kowalewski, Robert V.; Kress, T.; Krieger, P.; von Krogh, J.; Kuhl, T.; Kupper, M.; Kyberd, P.; Lafferty, G.D.; Landsman, H.; Lanske, D.; Lawson, I.; Layter, J.G.; Leins, A.; Lellouch, D.; Letts, J.; Levinson, L.; Liebisch, R.; Lillich, J.; List, B.; Littlewood, C.; Lloyd, A.W.; Lloyd, S.L.; Loebinger, F.K.; Long, G.D.; Losty, M.J.; Lu, J.; Ludwig, J.; Macchiolo, A.; Macpherson, A.; Mader, W.; Marcellini, S.; Marchant, T.E.; Martin, A.J.; Martin, J.P.; Martinez, G.; Mashimo, T.; Mattig, Peter; McDonald, W.John; McKenna, J.; McMahon, T.J.; McPherson, R.A.; Meijers, F.; Mendez-Lorenzo, P.; Menges, W.; Merritt, F.S.; Mes, H.; Michelini, A.; Mihara, S.; Mikenberg, G.; Miller, D.J.; Mohr, W.; Montanari, A.; Mori, T.; Nagai, K.; Nakamura, I.; Neal, H.A.; Nisius, R.; O'Neale, S.W.; Oakham, F.G.; Odorici, F.; Ogren, H.O.; Oh, A.; Okpara, A.; Oreglia, M.J.; Orito, S.; Pasztor, G.; Pater, J.R.; Patrick, G.N.; Patt, J.; Pfeifenschneider, P.; Pilcher, J.E.; Pinfold, J.; Plane, David E.; Poli, B.; Polok, J.; Pooth, O.; Przybycien, M.; Quadt, A.; Rembser, C.; Renkel, P.; Rick, H.; Rodning, N.; Roney, J.M.; Rosati, S.; Roscoe, K.; Rossi, A.M.; Rozen, Y.; Runge, K.; Runolfsson, O.; Rust, D.R.; Sachs, K.; Saeki, T.; Sahr, O.; Sarkisyan, E.K.G.; Sbarra, C.; Schaile, A.D.; Schaile, O.; Scharff-Hansen, P.; Schroder, Matthias; Schumacher, M.; Schwick, C.; Scott, W.G.; Seuster, R.; Shears, T.G.; Shen, B.C.; Shepherd-Themistocleous, C.H.; Sherwood, P.; Siroli, G.P.; Skuja, A.; Smith, A.M.; Snow, G.A.; Sobie, R.; Soldner-Rembold, S.; Spagnolo, S.; Sproston, M.; Stahl, A.; Stephens, K.; Stoll, K.; Strom, David M.; Strohmer, R.; Stumpf, L.; Surrow, B.; Talbot, S.D.; Tarem, S.; Taylor, R.J.; Teuscher, R.; Thiergen, M.; Thomas, J.; Thomson, M.A.; Torrence, E.; Towers, S.; Toya, D.; Trefzger, T.; Trigger, I.; Trocsanyi, Z.; Tsur, E.; Turner-Watson, M.F.; Ueda, I.; Vachon, B.; Vannerem, P.; Verzocchi, M.; Voss, H.; Vossebeld, J.; Waller, D.; Ward, C.P.; Ward, D.R.; Watkins, P.M.; Watson, A.T.; Watson, N.K.; Wells, P.S.; Wengler, T.; Wermes, N.; Wetterling, D.; White, J.S.; Wilson, G.W.; Wilson, J.A.; Wyatt, T.R.; Yamashita, S.; Zacek, V.; Zer-Zion, D.

    2000-01-01

    The lifetime and oscillation frequency of the B0 meson has been measured using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP. The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the production flavour of the B0 mesons was determined using a combination of tags from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d = 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first error is statistical and the second systematic.

  13. Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator.

    Science.gov (United States)

    Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H; Davies, A Giles; Vitiello, Miriam S

    2016-03-15

    Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.

  14. Selective visual scaling of time-scale processes facilitates broadband learning of isometric force frequency tracking.

    Science.gov (United States)

    King, Adam C; Newell, Karl M

    2015-10-01

    The experiment investigated the effect of selectively augmenting faster time scales of visual feedback information on the learning and transfer of continuous isometric force tracking tasks to test the generality of the self-organization of 1/f properties of force output. Three experimental groups tracked an irregular target pattern either under a standard fixed gain condition or with selectively enhancement in the visual feedback display of intermediate (4-8 Hz) or high (8-12 Hz) frequency components of the force output. All groups reduced tracking error over practice, with the error lowest in the intermediate scaling condition followed by the high scaling and fixed gain conditions, respectively. Selective visual scaling induced persistent changes across the frequency spectrum, with the strongest effect in the intermediate scaling condition and positive transfer to novel feedback displays. The findings reveal an interdependence of the timescales in the learning and transfer of isometric force output frequency structures consistent with 1/f process models of the time scales of motor output variability.

  15. Fluidic low-frequency oscillator with vortex spin-up time delay

    Czech Academy of Sciences Publication Activity Database

    Tesař, Václav; Smyk, E.

    2015-01-01

    Roč. 90, April (2015), s. 6-15 ISSN 0255-2701 R&D Projects: GA ČR GA13-23046S; GA ČR GA14-08888S Institutional support: RVO:61388998 Keywords : fluidics * oscillator * vortex chamber Subject RIV: BK - Fluid Dynamics Impact factor: 2.154, year: 2015 http://www.sciencedirect.com/science/article/pii/S0255270115000252

  16. New Canonic Active RC Sinusoidal Oscillator Circuits Using Second-Generation Current Conveyors with Application as a Wide-Frequency Digitally Controlled Sinusoid Generator

    Directory of Open Access Journals (Sweden)

    Abhirup Lahiri

    2011-01-01

    Full Text Available This paper reports two new circuit topologies using second-generation current conveyors (CCIIs for realizing variable frequency sinusoidal oscillators with minimum passive components. The proposed topologies in this paper provide new realizations of resistance-controlled and capacitor-controlled variable frequency oscillators (VFOs using only four passive components. The first topology employs three CCIIs, while the second topology employs two CCIIs. The second topology provides an advantageous feature of frequency tuning through two grounded elements. Application of the proposed circuits as a wide-frequency range digitally controlled sinusoid generator is exhibited wherein the digital frequency control has been enabled by replacing both the capacitors by two identical variable binary capacitor banks tunable by means of the same binary code. SPICE simulations of the CMOS implementation of the oscillators using 0.35 μm TSMC CMOS technology parameters and bipolar implementation of the oscillators using process parameters for NR200N-2X (NPN and PR200N-2X (PNP of bipolar arrays ALA400-CBIC-R have validated their workability. One of the oscillators (with CMOS implementation is exemplified as a digitally controlled sinusoid generator with frequency generation from 25 kHz to 6.36 MHz, achieved by switching capacitors and with power consumption of 7 mW in the entire operating frequency range.

  17. Neutron-antineutron oscillation and baryonic majoron: low scale spontaneous baryon violation

    Energy Technology Data Exchange (ETDEWEB)

    Berezhiani, Zurab [Universita dell' Aquila, Dipartimento delle Scienze Fisiche e Chimiche, L' Aquila (Italy); INFN, Laboratori Nazionali Gran Sasso, L' Aquila (Italy)

    2016-12-15

    We discuss the possibility that baryon number B is spontaneously broken at low scales, of the order of MeV or even smaller, inducing the neutron-antineutron oscillation at the experimentally accessible level. An associated Goldstone particle-baryonic majoron can have observable effects in neutron to antineutron transitions in nuclei or dense nuclear matter. By extending baryon number to an anomaly-free B - L symmetry, the baryo-majoron can be identified with the ordinary majoron associated with the spontaneous breaking of lepton number, and it can have interesting implications for neutrinoless 2β decay with the majoron emission. We also discuss the hypothesis that baryon number can be spontaneously broken by QCD itself via the six-quark condensates. (orig.)

  18. LOCO - a linearised model for analysing the onset of coolant oscillations and frequency response of boiling channels

    International Nuclear Information System (INIS)

    Romberg, T.M.

    1982-12-01

    Industrial plant such as heat exchangers and nuclear and conventional boilers are prone to coolant flow oscillations which may not be detected. In this report, a hydrodynamic model is formulated in which the one-dimensional, non-linear, partial differential equations for the conservation of mass, energy and momentum are perturbed with respect to time, linearised, and Laplace-transformed into the s-domain for frequency response analysis. A computer program has been developed to integrate numerically the resulting non-linear ordinary differential equations by finite difference methods. A sample problem demonstrates how the computer code is used to analyse the frequency response and flow stability characteristics of a heated channel

  19. Frequency comb generation by a continuous-wave-pumped optical parametric oscillator based on cascading quadratic nonlinearities.

    Science.gov (United States)

    Ulvila, Ville; Phillips, C R; Halonen, Lauri; Vainio, Markku

    2013-11-01

    We report optical frequency comb generation by a continuous-wave pumped optical parametric oscillator (OPO) without any active modulation. The OPO is configured as singly resonant with an additional nonlinear crystal (periodically poled MgO:LiNbO3) placed inside the OPO for phase mismatched second harmonic generation (SHG) of the resonating signal beam. The phase mismatched SHG causes cascading χ(2) nonlinearities, which can substantially increase the effective χ(3) nonlinearity in MgO:LiNbO3, leading to spectral broadening of the OPO signal beam via self-phase modulation. The OPO generates a stable 4 THz wide (-30 dB) frequency comb centered at 1.56 μm.

  20. Self-oscillating Galvanic Isolated Bidirectional Very High Frequency DC-DC Converter

    DEFF Research Database (Denmark)

    Pedersen, Jeppe Arnsdorf; Madsen, Mickey Pierre; Knott, Arnold

    2015-01-01

    This paper describes a galvanic isolated bidirectional Very High Frequency (VHF = 30 MHz - 300MHz) ClassE converter. The reason for increasing the switching frequency is to minimize the passive components in the converter. To make the converter topology bidirectional the rectifier has to be synch......This paper describes a galvanic isolated bidirectional Very High Frequency (VHF = 30 MHz - 300MHz) ClassE converter. The reason for increasing the switching frequency is to minimize the passive components in the converter. To make the converter topology bidirectional the rectifier has...

  1. Studies of Sub-Synchronous Oscillations in Large-Scale Wind Farm Integrated System

    Science.gov (United States)

    Yue, Liu; Hang, Mend

    2018-01-01

    With the rapid development and construction of large-scale wind farms and grid-connected operation, the series compensation wind power AC transmission is gradually becoming the main way of power usage and improvement of wind power availability and grid stability, but the integration of wind farm will change the SSO (Sub-Synchronous oscillation) damping characteristics of synchronous generator system. Regarding the above SSO problem caused by integration of large-scale wind farms, this paper focusing on doubly fed induction generator (DFIG) based wind farms, aim to summarize the SSO mechanism in large-scale wind power integrated system with series compensation, which can be classified as three types: sub-synchronous control interaction (SSCI), sub-synchronous torsional interaction (SSTI), sub-synchronous resonance (SSR). Then, SSO modelling and analysis methods are categorized and compared by its applicable areas. Furthermore, this paper summarizes the suppression measures of actual SSO projects based on different control objectives. Finally, the research prospect on this field is explored.

  2. Chromospheric oscillations

    NARCIS (Netherlands)

    Lites, B.W.; Rutten, R.J.; Thomas, J.H.

    1995-01-01

    We show results from SO/Sacramento Peak data to discuss three issues: (i)--the spatial occurrence of chromospheric 3--min oscillations; (ii)--the validity of Ca II H&K line-center Doppler Shift measurements; (iii)--the signi ?cance of oscillation power and phase at frequencies above 10 mHz.

  3. US Mains Stacked Very High Frequency Self-oscillating Resonant Power Converter with Unified Rectifier

    DEFF Research Database (Denmark)

    Pedersen, Jeppe Arnsdorf; Madsen, Mickey Pierre; Mønster, Jakob Døllner

    2016-01-01

    This paper describes a Very High Frequency (VHF) converter made with three Class-E inverters and a single ClassDE rectifier. The converter is designed for the US mains (120 V, 60 Hz) and can deliver 9 W to a 60 V LED. The converter has a switching frequency of 37 MHz and achieves an efficiency...

  4. Suppression of mechanical resonance in digital servo system considering oscillation frequency deviation

    DEFF Research Database (Denmark)

    Chen, Yangyang; Yang, Ming; Hu, Kun

    2017-01-01

    High-stiffness servo system is easy to cause mechanical resonance in elastic coupling servo system. Although on-line adaptive notch filter is effective in most cases, it will lead to a severer resonance when resonance frequency deviated from the natural torsional frequency. To explain...

  5. The impact research of control modes in steam turbine control system (digital electric hydraulic to the low-frequency oscillation of grid

    Directory of Open Access Journals (Sweden)

    Yanghai Li

    2016-01-01

    Full Text Available Through the analysis of the control theory for steam turbine, the transfer function of the steam turbine control modes in the parallel operation was obtained. The frequency domain analysis indicated that different control modes of turbine control system have different influence on the damping characteristics of the power system. The comparative analysis shows the direction and the degree of the influence under the different oscillation frequency range. This can provide the theory for the suppression of the low-frequency oscillation from turbine side and has a guiding significance for the stability of power system. The results of simulation tests are consistent with the theoretic analysis.

  6. Low Frequency Quasi-periodic Oscillations in the High-eccentric LMXB Cir X-1: Extending the WK Correlation for Z Sources

    Energy Technology Data Exchange (ETDEWEB)

    Bu, Qingcui; Chen, Li [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Belloni, T. M. [INAF-Osservatorio Astronomico di Brera, Via E, Bianchi 46, I-23807 Merate (Italy); Qu, Jinlu, E-mail: buqc@mail.bnu.edu.cn, E-mail: tomaso.belloni@brera.inaf.it, E-mail: chenli@bnu.edu.cn, E-mail: qujl@ihep.ac.cn [Laboratory for Particle Astrophysics, CAS, Beijing 100049 (China)

    2017-06-01

    Using archival Rossi X-ray Timing Explorer ( RXTE ) data, we studied the low-frequency quasi-periodic oscillations (LFQPOs) in the neutron star low-mass X-ray binary (LMXB) Cir X-1 and examined their contribution to frequency–frequency correlations for Z sources. We also studied the orbital phase effects on the LFQPO properties and found them to be phase independent. Comparing LFQPO frequencies in different classes of LMXBs, we found that systems that show both Z and atoll states form a common track with atoll/BH sources in the so-called WK correlation, while persistent Z systems are offset by a factor of about two. We found that neither source luminosity nor mass accretion rate is related to the shift of persistent Z systems. We discuss the possibility of a misidentification of fundamental frequency for horizontal branch oscillations from persistent Z systems and interpreted the oscillations in terms of models based on relativistic precession.

  7. Low- and high-frequency cortical brain oscillations reflect dissociable mechanisms of concurrent speech segregation in noise.

    Science.gov (United States)

    Yellamsetty, Anusha; Bidelman, Gavin M

    2018-04-01

    Parsing simultaneous speech requires listeners use pitch-guided segregation which can be affected by the signal-to-noise ratio (SNR) in the auditory scene. The interaction of these two cues may occur at multiple levels within the cortex. The aims of the current study were to assess the correspondence between oscillatory brain rhythms and determine how listeners exploit pitch and SNR cues to successfully segregate concurrent speech. We recorded electrical brain activity while participants heard double-vowel stimuli whose fundamental frequencies (F0s) differed by zero or four semitones (STs) presented in either clean or noise-degraded (+5 dB SNR) conditions. We found that behavioral identification was more accurate for vowel mixtures with larger pitch separations but F0 benefit interacted with noise. Time-frequency analysis decomposed the EEG into different spectrotemporal frequency bands. Low-frequency (θ, β) responses were elevated when speech did not contain pitch cues (0ST > 4ST) or was noisy, suggesting a correlate of increased listening effort and/or memory demands. Contrastively, γ power increments were observed for changes in both pitch (0ST > 4ST) and SNR (clean > noise), suggesting high-frequency bands carry information related to acoustic features and the quality of speech representations. Brain-behavior associations corroborated these effects; modulations in low-frequency rhythms predicted the speed of listeners' perceptual decisions with higher bands predicting identification accuracy. Results are consistent with the notion that neural oscillations reflect both automatic (pre-perceptual) and controlled (post-perceptual) mechanisms of speech processing that are largely divisible into high- and low-frequency bands of human brain rhythms. Copyright © 2018 Elsevier B.V. All rights reserved.

  8. Frequency-dependent changes in local intrinsic oscillations in chronic primary insomnia: A study of the amplitude of low-frequency fluctuations in the resting state.

    Science.gov (United States)

    Zhou, Fuqing; Huang, Suhua; Zhuang, Ying; Gao, Lei; Gong, Honghan

    2017-01-01

    New neuroimaging techniques have led to significant advancements in our understanding of cerebral mechanisms of primary insomnia. However, the neuronal low-frequency oscillation remains largely uncharacterized in chronic primary insomnia (CPI). In this study, the amplitude of low-frequency fluctuation (ALFF), a data-driven method based on resting-state functional MRI, was used to examine local intrinsic activity in 27 patients with CPI and 27 age-, sex-, and education-matched healthy controls. We examined neural activity in two frequency bands, slow-4 (between 0.027 and 0.073 Hz) and slow-5 (0.010-0.027 Hz), because blood-oxygen level dependent (BOLD) fluctuations in different low-frequency bands may present different neurophysiological manifestations that pertain to a spatiotemporal organization. The ALFF associated with the primary disease effect was widely distributed in the cerebellum posterior lobe (CPL), dorsal and ventral prefrontal cortex, anterior cingulate cortex, precuneus, somatosensory cortex, and several default-mode sub-regions. Several brain regions (i.e., the right cerebellum, anterior lobe, and left putamen) exhibited an interaction between the frequency band and patient group. In the slow-5 band, increased ALFF of the right postcentral gyrus/inferior parietal lobule (PoCG/IPL) was enhanced in association with the sleep quality (ρ = 0.414, P  = 0.044) and anxiety index (ρ = 0.406, P  = 0.049) of the CPI patients. These findings suggest that during chronic insomnia, the intrinsic functional plasticity primarily responds to the hyperarousal state, which is the loss of inhibition in sensory-informational processing. Our findings regarding an abnormal sensory input and intrinsic processing mechanism might provide novel insight into the pathophysiology of CPI. Furthermore, the frequency factor should be taken into consideration when exploring ALFF-related clinical manifestations.

  9. Analysis on oscillating actuator frequency influence of the fluid flow characterization for 2D contractile water jet thruster

    Science.gov (United States)

    Shaari, M. F.; Abu Bakar, H.; Nordin, N.; Saw, S. K.; Samad, Z.

    2013-12-01

    Contractile body is an alternative mechanism instead of rotating blade propeller to generate water jet for locomotion. The oscillating motion of the actuator at different frequencies varies the pressure and volume of the pressure chamber in time to draw in and jet out the water at a certain mass flow rate. The aim of this research was to analyze the influence of the actuating frequency of the fluid flow in the pressure chamber of the thruster during this inflation-deflation process. A 70mm × 70mm × 18mm (L × W × T) 2D water jet thruster was fabricated for this purpose. The contractile function was driven using two lateral pneumatic actuators where the fluid flow analysis was focused on the X-Y plane vector. Observation was carried out using a video camera and Matlab image measurement technique to determine the volume of the flowing mass. The result demonstrated that the greater actuating frequency decreases the fluid flow rate and the Reynolds number. This observation shows that the higher frequency would give a higher mass flow rate during water jet generation.

  10. Damping control strategies of inter-area low-frequency oscillation for DFIG-based wind farms integrated into a power system

    DEFF Research Database (Denmark)

    Li, Hui; Liu, Shengquan; Ji, Haiting

    2014-01-01

    on the power system stabilizer (PSS) control method. Transient simulation on different damping gain coefficients are conducted for justification. Following the OTEF mechanism analysis, an additional fuzzy damping control strategy with the active/reactive power loop is proposed by identifying the oscillation......This study investigates the inter-area low-frequency damping control strategies of a doubly fed induction generator (DFIG)-based wind farm through oscillation transient energy function (OTEF) analysis. Based on the OTEF descent expressions, the feasibility of damping the inter-area low...... oscillation of the wind turbine shaft. The proposed additional fuzzy control strategy with the active/reactive power loop has better damping performance than the presented PSS control, especially for damping the inter-area low-frequency oscillation....

  11. The Response of African Land Surface Phenology to Large Scale Climate Oscillations

    Science.gov (United States)

    Brown, Molly E.; de Beurs, Kirsten; Vrieling, Anton

    2010-01-01

    Variations in agricultural production due to rainfall and temperature fluctuations are a primary cause of food insecurity on the African continent. Analysis of changes in phenology can provide quantitative information on the effect of climate variability on growing seasons in agricultural regions. Using a robust statistical methodology, we describe the relationship between phenology metrics derived from the 26 year AVHRR NDVI record and the North Atlantic Oscillation index (NAO), the Indian Ocean Dipole (IOD), the Pacific Decadal Oscillation (PDO), and the Multivariate ENSO Index (MEI). We map the most significant positive and negative correlation for the four climate indices in Eastern, Western and Southern Africa between two phenological metrics and the climate indices. Our objective is to provide evidence of whether climate variability captured in the four indices has had a significant impact on the vegetative productivity of Africa during the past quarter century. We found that the start of season and cumulative NDVI were significantly affected by large scale variations in climate. The particular climate index and the timing showing highest correlation depended heavily on the region examined. In Western Africa the cumulative NDVI correlates with PDO in September-November. In Eastern Africa the start of the June-October season strongly correlates with PDO in March-May, while the PDO in December-February correlates with the start of the February-June season. The cumulative NDVI over this last season relates to the MEI of March-May. For Southern Africa, high correlations exist between SOS and NAO of September-November, and cumulative NDVI and MEI of March-May. The research shows that climate indices can be used to anticipate late start and variable vigor in the growing season of sensitive agricultural regions in Africa.

  12. High energy single frequency Yb:YAG crystalline fiber waveguide master oscillator power amplifier, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall objective is to demonstrate the concept of Yb:YAG crystalline fiber MOPA laser and investigation the technical feasibility toward 50 mJ single frequency...

  13. Oscillator monitor

    International Nuclear Information System (INIS)

    McNeill, G.A.

    1981-01-01

    Present high-speed data acquisition systems in nuclear diagnostics use high-frequency oscillators to provide timing references for signals recorded on fast, traveling-wave oscilloscopes. An oscillator's sinusoidal wave shape is superimposed on the recorded signal with each cycle representing a fixed time increment. During data analysis the sinusoid is stripped from the signal, leaving a clean signal shape with known timing. Since all signal/time relationships are totally dependant upon working oscillators, these critical devices must have remote verification of proper operation. This manual presents the newly-developed oscillator monitor which will provide the required verification

  14. Feedforward and feedback frequency-dependent interactions in a large-scale laminar network of the primate cortex.

    Science.gov (United States)

    Mejias, Jorge F; Murray, John D; Kennedy, Henry; Wang, Xiao-Jing

    2016-11-01

    Interactions between top-down and bottom-up processes in the cerebral cortex hold the key to understanding attentional processes, predictive coding, executive control, and a gamut of other brain functions. However, the underlying circuit mechanism remains poorly understood and represents a major challenge in neuroscience. We approached this problem using a large-scale computational model of the primate cortex constrained by new directed and weighted connectivity data. In our model, the interplay between feedforward and feedback signaling depends on the cortical laminar structure and involves complex dynamics across multiple (intralaminar, interlaminar, interareal, and whole cortex) scales. The model was tested by reproducing, as well as providing insights into, a wide range of neurophysiological findings about frequency-dependent interactions between visual cortical areas, including the observation that feedforward pathways are associated with enhanced gamma (30 to 70 Hz) oscillations, whereas feedback projections selectively modulate alpha/low-beta (8 to 15 Hz) oscillations. Furthermore, the model reproduces a functional hierarchy based on frequency-dependent Granger causality analysis of interareal signaling, as reported in recent monkey and human experiments, and suggests a mechanism for the observed context-dependent hierarchy dynamics. Together, this work highlights the necessity of multiscale approaches and provides a modeling platform for studies of large-scale brain circuit dynamics and functions.

  15. Low Frequency (11 mHz) Oscillations in H1743-322: A New Class of Black Hole QPOs?

    Science.gov (United States)

    Altamirano, D.; Strohmayer, T.

    2012-01-01

    We report the discovery of quasi-periodic oscillations (QPO) at approx 11 mHz in two RXTE observations and one Chandra observation of the black hole candidate HI743-322. The QPO is observed only at the beginning of the 2010 and 2011 outbursts at similar hard color and intensity, suggestive of an accretion state dependence for the QPO. Although its frequency appears to be correlated with Xray intensity on timescales of a day, in successive outbursts eight months apart we measure a QPO frequency that differs by less than approximately equals 0.0015 Hz while the intensity had changed significantly. We show that this 11 mHz QPO is different from the so-called Type-C QPOs seen in black holes and that the mechanisms that produce the two flavors of variability are most probably independent. We compare the 11 mHz QPO with other variability phenomena seen in accreting black holes and neutron stars and conclude that although at 1-2 orders of magnitude lower in frequency, they best resemble the so-called "1 Hz" QPOs seen in dipping neutron star systems. If confirmed, H1743-322 is the first black hole showing this type of variability. Given the unusual characteristics and the hard-state dependence of the 11 mHz QPO, we speculate that these oscillations might instead be related to the radio jets observed in HI743-322. It remains unexplained, however, why similar QPOs have not yet been identified in other black holes and why they have only been seen in the last two outbursts of HI743-322.

  16. Spontaneous and visually-driven high-frequency oscillations in the occipital cortex: Intracranial recording in epileptic patients

    Science.gov (United States)

    Nagasawa, Tetsuro; Juhász, Csaba; Rothermel, Robert; Hoechstetter, Karsten; Sood, Sandeep; Asano, Eishi

    2011-01-01

    SUMMARY High-frequency oscillations (HFOs) at ≧80 Hz of nonepileptic nature spontaneously emerge from human cerebral cortex. In 10 patients with extra-occipital lobe epilepsy, we compared the spectral-spatial characteristics of HFOs spontaneously arising from the nonepileptic occipital cortex with those of HFOs driven by a visual task as well as epileptogenic HFOs arising from the extra-occipital seizure focus. We identified spontaneous HFOs at ≧80 Hz with a mean duration of 330 msec intermittently emerging from the occipital cortex during interictal slow-wave sleep. The spectral frequency band of spontaneous occipital HFOs was similar to that of visually-driven HFOs. Spontaneous occipital HFOs were spatially sparse and confined to smaller areas, whereas visually-driven HFOs involved the larger areas including the more rostral sites. Neither spectral frequency band nor amplitude of spontaneous occipital HFOs significantly differed from those of epileptogenic HFOs. Spontaneous occipital HFOs were strongly locked to the phase of delta activity, but the strength of delta-phase coupling decayed from 1 to 3 Hz. Conversely, epileptogenic extra-occipital HFOs were locked to the phase of delta activity about equally in the range from 1 to 3 Hz. The occipital cortex spontaneously generates physiological HFOs which may stand out on electrocorticography traces as prominently as pathological HFOs arising from elsewhere; this observation should be taken into consideration during presurgical evaluation. Coupling of spontaneous delta and HFOs may increase the understanding of significance of delta-oscillations during slow-wave sleep. Further studies are warranted to determine whether delta-phase coupling distinguishes physiological from pathological HFOs or simply differs across anatomical locations. PMID:21432945

  17. Applications of wind generation for power system frequency control, inter-area oscillations damping and parameter identification

    Science.gov (United States)

    Wilches-Bernal, Felipe

    Power systems around the world are experiencing a continued increase in wind generation as part of their energy mix. Because of its power electronics interface, wind energy conversion systems interact differently with the grid than conventional generation. These facts are changing the traditional dynamics that regulate power system behavior and call for a re-examination of traditional problems encountered in power systems like frequency response, inter-area oscillations and parameter identification. To address this need, realistic models for wind generation are necessary. The dissertation implements such models in a MATLAB-based flexible environment suited for power system research. The dissertation continues with an analysis of the frequency response of a test power system dependent mainly on a mode referred to as the frequency regulation mode. Using this test system it is shown that its frequency regulation capability is reduced with wind penetration levels of 25% and above. A controller for wind generation to restore the frequency response of the system is then presented. The proposed controller requires the WTG to operate in a deloaded mode, a condition that is obtained through pitching the wind turbine blades. Time simulations at wind penetration levels of 25% and 50% are performed to demonstrate the effectiveness of the proposed controller. Next, the dissertation evaluates how the inter-area oscillation of a two-machine power system is affected by wind integration. The assessment is performed based on the positioning of the WTG, the level of wind penetration, and the loading condition of the system. It is determined that integrating wind reduces the damping of the inter-area mode of the system when performed in an area that imports power. For this worst-case scenario, the dissertation proposes two controllers for wind generation to improve the damping of the inter-area mode. The first controller uses frequency as feedback signal for the active power control

  18. Improved measurement of the $B^0_d$--$\\overline{B}^0_d$ Oscillation frequency

    CERN Document Server

    Buskulic, Damir; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Minard, M N; Nief, J Y; Odier, P; Pietrzyk, B; Casado, M P; Chmeissani, M; Crespo, J M; Delfino, M C; Efthymiopoulos, I; Fernández, E; Fernández-Bosman, M; Garrido, L; Juste, A; Martínez, M; Orteu, S; Padilla, C; Park, I C; Pascual, A; Perlas, J A; Riu, I; Sánchez, F; Teubert, F; Colaleo, A; Creanza, D; De Palma, M; Gelao, G; Girone, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Marinelli, N; Nuzzo, S; Ranieri, A; Raso, G; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Tricomi, A; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Alemany, R; Bazarko, A O; Bonvicini, G; Bright-Thomas, P G; Cattaneo, M; Comas, P; Coyle, P; Drevermann, H; Forty, Roger W; Frank, M; Hagelberg, R; Harvey, J; Janot, P; Jost, B; Kneringer, E; Knobloch, J; Lehraus, Ivan; Lutters, G; Martin, E B; Mato, P; Minten, Adolf G; Miquel, R; Mir, L M; Moneta, L; Oest, T; Pacheco, A; Pusztaszeri, J F; Ranjard, F; Rensing, P E; Rizzo, G; Rolandi, Luigi; Schlatter, W D; Schmelling, M; Schmitt, M; Schneider, O; Tejessy, W; Tomalin, I R; Venturi, A; Wachsmuth, H W; Wagner, A; Ajaltouni, Ziad J; Barrès, A; Boyer, C; Falvard, A; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rosnet, P; Rossignol, J M; Fearnley, Tom; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Rensch, B; Wäänänen, A; Kyriakis, A; Markou, C; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Zachariadou, K; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Rougé, A; Rumpf, M; Valassi, Andrea; Verderi, M; Videau, H L; Candlin, D J; Parsons, M I; Focardi, E; Parrini, G; Corden, M; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Casper, David William; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Curtis, L; Dorris, S J; Halley, A W; Knowles, I G; Lynch, J G; O'Shea, V; Raine, C; Reeves, P; Scarr, J M; Smith, K; Teixeira-Dias, P; Thompson, A S; Thomson, F; Thorn, S; Turnbull, R M; Becker, U; Geweniger, C; Graefe, G; Hanke, P; Hansper, G; Hepp, V; Kluge, E E; Putzer, A; Schmidt, M; Sommer, J; Stenzel, H; Tittel, K; Werner, S; Wunsch, M; Abbaneo, D; Beuselinck, R; Binnie, David M; Cameron, W; Dornan, Peter J; Moutoussi, A; Nash, J; Sedgbeer, J K; Stacey, A M; Williams, M D; Dissertori, G; Girtler, P; Kuhn, D; Rudolph, G; Betteridge, A P; Bowdery, C K; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Sloan, Terence; Williams, M I; Galla, A; Giehl, I; Greene, A M; Hoffmann, C; Jakobs, K; Kleinknecht, K; Quast, G; Renk, B; Rohne, E; Sander, H G; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Bencheikh, A M; Benchouk, C; Bonissent, A; Bujosa, G; Calvet, D; Carr, J; Diaconu, C A; Etienne, F; Konstantinidis, N P; Payre, P; Rousseau, D; Talby, M; Sadouki, A; Thulasidas, M; Trabelsi, K; Aleppo, M; Ragusa, F; Bauer, C; Berlich, R; Blum, Walter; Büscher, V; Dietl, H; Dydak, Friedrich; Ganis, G; Gotzhein, C; Kroha, H; Lütjens, G; Lutz, Gerhard; Männer, W; Moser, H G; Richter, R H; Rosado-Schlosser, A; Schael, S; Settles, Ronald; Seywerd, H C J; Saint-Denis, R; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Choi, Y; Cordier, A; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Höcker, A; Jacholkowska, A; Jacquet, M; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Nikolic, I A; Park, H J; Schune, M H; Simion, S; Veillet, J J; Videau, I; Zerwas, D; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Ciulli, V; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Palla, Fabrizio; Sanguinetti, G; Sciabà, A; Spagnolo, P; Steinberger, Jack; Tenchini, Roberto; Tonelli, G; Vannini, C; Verdini, P G; Walsh, J; Blair, G A; Bryant, L M; Cerutti, F; Chambers, J T; Gao, Y; Green, M G; Medcalf, T; Perrodo, P; Strong, J A; Von Wimmersperg-Töller, J H; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Maley, P; Norton, P R; Thompson, J C; Wright, A E; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Marx, B; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Black, S N; Dann, J H; Johnson, R P; Kim, H Y; Litke, A M; McNeil, M A; Taylor, G; Booth, C N; Boswell, R; Brew, C A J; Cartwright, S L; Combley, F; Köksal, A; Lehto, M H; Newton, W M; Reeve, J; Thompson, L F; Böhrer, A; Brandt, S; Cowan, G D; Grupen, Claus; Minguet-Rodríguez, J A; Rivera, F; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Musolino, G; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Elmer, P; Feng, Z; Ferguson, D P S; Gao, Y S; González, S; Grahl, J; Greening, T C; Hayes, O J; Hu, H; McNamara, P A; Nachtman, J M; Orejudos, W; Pan, Y B; Saadi, Y; Scott, I J; Walsh, A M; Wu, X; Yamartino, J M; Zheng, M; Zobernig, G

    1997-01-01

    The time dependence of $B^0_d--\\bar{B}^0_d$ oscillations is measured by the ALEPH experiment at LEP, using three techniques, two of which are updates of previous measurements. In all cases the charge of the decaying $b$ quark and its decay time are measured in one hemisphere of the event; the quark charge at production is tagged mainly using the opposite hemisphere. The first method uses the charge correlation between a $D^{*-}$ and a lepton in the opposite hemisphere; if no lepton is present, the produced quark charge is determined from the hemisphere charges. In the second method, the decay time is measured using a lepton in one hemisphere and the initial state is inferred from the opposite-hemisphere jet charge. The third method uses a lepton in each hemisphere. The data used were collected from 1991 to 1994. The combined result is $\\Delta m_d = 0.436\\pm 0.033\\, {\\rm ps}^{-1}$

  19. Analysis and damping control of power system low-frequency oscillations

    CERN Document Server

    Wang, Haifeng

    2016-01-01

    This book presents the research and development results on power systems oscillations in three categories of analytical methods. First is damping torque analysis which was proposed in 1960’s, further developed between 1980-1990, and widely used in industry. Second is modal analysis which developed between the 1980’s and 1990’s as the most powerful method. Finally the linearized equal-area criterion analysis that is proposed and developed recently. The book covers three main types of controllers: Power System Stabilizer (PSS), FACTS (Flexible AC Transmission Systems) stabilizer, and ESS (Energy Storage Systems) stabilizer. The book provides a systematic and detailed introduction on the subject as the reference for industry applications and academic research.

  20. Micro-scale piezoelectric vibration energy harvesting: From fixed-frequency to adaptable-frequency devices

    Science.gov (United States)

    Miller, Lindsay Margaret

    hundred milliwatts and are falling steadily as improvements are made, it is feasible to use energy harvesting to power WSNs. This research begins by presenting the results of a thorough survey of ambient vibrations in the machine room of a large campus building, which found that ambient vibrations are low frequency, low amplitude, time varying, and multi-frequency. The modeling and design of fixed-frequency micro scale energy harvesters are then presented. The model is able to take into account rotational inertia of the harvester's proof mass and it accepts arbitrary measured acceleration input, calculating the energy harvester's voltage as an output. The fabrication of the micro electromechanical system (MEMS) energy harvesters is discussed and results of the devices harvesting energy from ambient vibrations are presented. The harvesters had resonance frequencies ranging from 31 - 232 Hz, which was the lowest reported in literature for a MEMS device, and produced 24 pW/g2 - 10 nW/g2 of harvested power from ambient vibrations. A novel method for frequency modification of the released harvester devices using a dispenser printed mass is then presented, demonstrating a frequency shift of 20 Hz. Optimization of the MEMS energy harvester connected to a resistive load is then presented, finding that the harvested power output can be increased to several microwatts with the optimized design as long as the driving frequency matches the harvester's resonance frequency. A framework is then presented to allow a similar optimization to be conducted with the harvester connected to a synchronously switched pre-bias circuit. With the realization that the optimized energy harvester only produces usable amounts of power if the resonance frequency and driving frequency match, which is an unrealistic situation in the case of ambient vibrations which change over time and are not always known a priori, an adaptable-frequency energy harvester was designed. The adaptable-frequency harvester

  1. Method to Minimize the Low-Frequency Neutral-Point Voltage Oscillations With Time-Offset Injection for Neutral-Point-Clamped Inverters

    DEFF Research Database (Denmark)

    Choi, Ui-Min; Blaabjerg, Frede; Lee, Kyo-Beum

    2015-01-01

    time of small- and medium-voltage vectors. However, if the power factor is lower, there is a limitation to eliminate neutral-point oscillations. In this case, the proposed method can be improved by changing the switching sequence properly. Additionally, a method for neutral-point voltage balancing......This paper proposes a method to reduce the low-frequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a time offset to the three-phase turn-on times. The proper time offset is simply calculated considering the phase currents and dwell...

  2. Separation control with fluidic oscillators in water

    Science.gov (United States)

    Schmidt, H.-J.; Woszidlo, R.; Nayeri, C. N.; Paschereit, C. O.

    2017-08-01

    The present study assesses the applicability of fluidic oscillators for separation control in water. The first part of this work evaluates the properties of the fluidic oscillators including frequency, cavitation effects, and exerted thrust. Derived from the governing internal dynamics, the oscillation frequency is found to scale directly with the jet's exit velocity and the size of the fluidic oscillator independent of the working fluid. Frequency data from various experiments collapse onto a single curve. The occurrence of cavitation is examined by visual inspection and hydrophone measurements. The oscillation frequency is not affected by cavitation because it does not occur inside the oscillators. The spectral information obtained with the hydrophone provide a reliable indicator for the onset of cavitation at the exit. The performance of the fluidic oscillators for separation control on a bluff body does not seem to be affected by the presence of cavitation. The thrust exerted by an array of fluidic oscillators with water as the working fluid is measured to be even larger than theoretically estimated values. The second part of the presented work compares the performance of fluidic oscillators for separation control in water with previous results in air. The array of fluidic oscillators is installed into the rear end of a bluff body model. The drag improvements based on force balance measurements agree well with previous wind tunnel experiments on the same model. The flow field is examined by pressure measurements and with particle image velocimetry. Similar performance and flow field characteristics are observed in both water and air.

  3. Oscillation Performance and Wide‐area Coordination Control of Power System with Large‐scale Wind Farms

    DEFF Research Database (Denmark)

    Su, Chi

    and residue identification. Simulation results show the effectiveness of this damping controller under different operating conditions of the SSSC. Influence of a direct‐drive‐full‐convertor based wind farm ancillary frequency control and voltage control on power system oscillation performance is investigated...... oscillation mode damping ratio, respectively. The former controller is implemented in individual wind turbines; the latter controller is implemented in the wind farm level as a supplementary damping controller. Finally, the coordinating selection and parameter design strategy for PSS is extended for all types...... to this problem need to be implemented in the power systems. On the other hand, wind power especially largescale wind farms are increasingly integrated into modern power systems and bring new challenges to power system operation and control. The influence of wind power integration on system oscillation...

  4. Modulating wind power plant output using different frequency modulation components for damping grid oscillations

    DEFF Research Database (Denmark)

    2017-01-01

    A method, controller, wind power plant, and computer program product are disclosed for operating a wind power plant comprising a plurality of wind turbines, the wind power plant producing a plant power output. The method comprises receiving a modulation request signal indicating a requested...... modulation of the plant power output, the requested modulation specifying a modulation frequency. The method further comprises generating a respective power reference signal for each of at least two wind turbines of the plurality of wind turbines selected to fulfill the requested modulation, Each generated...... power reference signal includes a respective modulation component corresponding to a portion of the requested modulation and having a frequency different than the modulation frequency....

  5. Theoretical oscillation frequencies for solar-type dwarfs from stellar models with <3D >-atmospheres

    DEFF Research Database (Denmark)

    Jørgensen, Andreas Christ Sølvsten; Weiss, Achim; Mosumgaard, Jakob Rorsted

    2017-01-01

    We present a new method for replacing the outermost layers of stellar models with interpolated atmospheres based on results from 3D simulations, in order to correct for structural inadequacies of these layers. This replacement is known as patching. Tests, based on 3D atmospheres from three......, and the mismatch in T-eff and log g between the un-patched model and patched 3D atmosphere. We find the eigen frequencies to be unaltered by the patching depth deep within the adiabatic region, while changing the patching quantity or the employed atmosphere grid leads to frequency shifts that may exceed 1 mu Hz....... Likewise, the eigen frequencies are sensitive to mismatches in T-eff or log g. A thorough investigation of the accuracy of a new scheme, for interpolating mean 3D stratifications within the atmosphere grids, is furthermore performed. Throughout large parts of the atmosphere grids, our interpolation scheme...

  6. Design of Weighted Wide Area Damping Controller (WWADC Based PSS for Damping Inter-Area Low Frequency Oscillations

    Directory of Open Access Journals (Sweden)

    Saleh M. Bamasak

    2017-09-01

    Full Text Available Wide Area Measurement System (WAMS can extend and effectively improve the power system stabilizers (PSS capability in damping the inter-area low frequency oscillations in interconnected bulk power systems. This paper proposes the implementation of Weighted Wide Area Damping Controller (WWADC in which weighted factors are introduced for each remote feedback signals. Modal analysis approach is implemented for the purpose of identifying the optimal location as well as the input signals’ optimal combination of WWADC. Based on the linearized model, Differential Evolution (DE algorithm is applied to search for optimal controller parameters and optimal weighted factors. The successful application of the proposed approach is achieved in two power networks; the two-area 4-machine system and the IEEE-39 bus 10-machine system. The analysis of the eigenvalue and non-linear time domain simulations indicate that damping the inter-area oscillations and improving the system stability irrespective of the severity and the location of the disturbances can be effectively achieved by WADC

  7. Cortical drive of low-frequency oscillations in the human nucleus accumbens during action selection.

    Science.gov (United States)

    Stenner, Max-Philipp; Litvak, Vladimir; Rutledge, Robb B; Zaehle, Tino; Schmitt, Friedhelm C; Voges, Jürgen; Heinze, Hans-Jochen; Dolan, Raymond J

    2015-07-01

    The nucleus accumbens is thought to contribute to action selection by integrating behaviorally relevant information from multiple regions, including prefrontal cortex. Studies in rodents suggest that information flow to the nucleus accumbens may be regulated via task-dependent oscillatory coupling between regions. During instrumental behavior, local field potentials (LFP) in the rat nucleus accumbens and prefrontal cortex are coupled at delta frequencies (Gruber AJ, Hussain RJ, O'Donnell P. PLoS One 4: e5062, 2009), possibly mediating suppression of afferent input from other areas and thereby supporting cortical control (Calhoon GG, O'Donnell P. Neuron 78: 181-190, 2013). In this report, we demonstrate low-frequency cortico-accumbens coupling in humans, both at rest and during a decision-making task. We recorded LFP from the nucleus accumbens in six epilepsy patients who underwent implantation of deep brain stimulation electrodes. All patients showed significant coherence and phase-synchronization between LFP and surface EEG at delta and low theta frequencies. Although the direction of this coupling as indexed by Granger causality varied between subjects in the resting-state data, all patients showed a cortical drive of the nucleus accumbens during action selection in a decision-making task. In three patients this was accompanied by a significant coherence increase over baseline. Our results suggest that low-frequency cortico-accumbens coupling represents a highly conserved regulatory mechanism for action selection. Copyright © 2015 the American Physiological Society.

  8. Wavelet based comparison of high frequency oscillations in the geodetic and fluid excitation functions of polar motion

    Science.gov (United States)

    Kosek, W.; Popinski, W.; Niedzielski, T.

    2011-10-01

    It has been already shown that short period oscillations in polar motion, with periods less than 100 days, are very chaotic and are responsible for increase in short-term prediction errors of pole coordinates data. The wavelet technique enables to compare the geodetic and fluid excitation functions in the high frequency band in many different ways, e.g. by looking at the semblance function. The waveletbased semblance filtering enables determination the common signal in both geodetic and fluid excitation time series. In this paper the considered fluid excitation functions consist of the atmospheric, oceanic and land hydrology excitation functions from ECMWF atmospheric data produced by IERS Associated Product Centre Deutsches GeoForschungsZentrum, Potsdam. The geodetic excitation functions have been computed from the combined IERS pole coordinates data.

  9. Determination of frequencies of oscillations of cloud cavitation on a 2-D hydrofoil from high-speed camera observations

    Czech Academy of Sciences Publication Activity Database

    Zima, Patrik; Fürst, T.; Sedlář, M.; Komárek, M.; Huzlík, R.

    2016-01-01

    Roč. 28, č. 3 (2016), s. 369-378 ISSN 1001-6058 R&D Projects: GA ČR GA13-23550S Institutional support: RVO:61388998 Keywords : unsteady cavitation * oscillation frequency * high-speed camera observation Subject RIV: BK - Fluid Dynamics Impact factor: 1.174, year: 2016 http://ac.els-cdn.com/S1001605816606406/1-s2.0-S1001605816606406-main.pdf?_tid=dee3b8f4-4a62-11e6-9d83-00000aacb361&acdnat=1468570098_ce8b727c766e0f96ee20d505e7058102

  10. The effects of age on the spontaneous low-frequency oscillations in cerebral and systemic cardiovascular dynamics

    International Nuclear Information System (INIS)

    Peng, Tingying; Rowley, Alex B; Payne, Stephen J; Ainslie, Philip N; Murrell, Carissa; Thomas, Kate; Cotter, James D; Williams, Michael J A; George, Keith; Shave, Rob

    2008-01-01

    Although the effects of ageing on cardiovascular control and particularly the response to orthostatic stress have been the subject of many studies, the interaction between the cardiovascular and cerebral regulation mechanisms is still not fully understood. Wavelet cross-correlation is used here to assess the coupling and synchronization between low-frequency oscillations (LFOs) observed in cerebral hemodynamics, as measured using cerebral blood flow velocity (CBFV) and cerebral oxygenation (O 2 Hb), and systemic cardiovascular dynamics, as measured using heart rate (HR) and arterial blood pressure (ABP), in both old and young healthy subjects undergoing head-up tilt table testing. Statistically significant increases in correlation values are found in the interaction of cerebral and cardiovascular LFOs for young subjects (P 2 Hb and ABP–O 2 Hb), but not in old subjects under orthostatic stress. The coupling between the cerebrovascular and wider cardiovascular systems in response to orthostatic stress thus appears to be impaired with ageing

  11. An Optical Low-frequency Quasi-Periodic Oscillation in the Kepler Light Curve of an Active Galaxy

    Science.gov (United States)

    Mushotzky, Richard; Smith, Krista Lynne; Boyd, Patricia; Wagoner, Robert

    2018-01-01

    We report the discovery of a candidate quasi-periodic oscillation (QPO) in the optical light curve of KIC 9650712, a Seyfert 1 galaxy in the original Kepler field. After the development and application of a pipeline for Kepler data specific to active galactic nuclei (AGN), one of our sample of 21 AGN selected by infrared photometry and X-ray flux demonstrates a peak in the power spectrum at 10-6.58 Hz, corresponding to a temporal period of 44 days. >From optical spectroscopy, we measure the black hole mass of this AGN as log M = 8.17 M_sun. Despite this high mass, the optical spectrum of KIC 9650712 bears many similarities to Narrow Line Seyfert 1 (NLS1) galaxies, including strong Fe II emission and a low [O III]/Hβ ratio. So far, X-ray QPOs have primarily been seen in NLS1 galaxies. Finally, we find that this frequency lies along a correlation between low-frequency QPOs and black hole mass from stellar and intermediate mass black holes to AGN, similar to the known correlation in high-frequency QPOs.

  12. On the Effects of Frequency Scaling Over Capacity Scaling in Underwater Networks—Part I

    DEFF Research Database (Denmark)

    Shin, Won-Yong; Roetter, Daniel Enrique Lucani; Médard, Muriel

    2013-01-01

    power-limited network. Interestingly, it is shown that the upper bound is intrinsically related to the attenuation parameter but not the spreading factor. Furthermore, we propose an achievable communication scheme based on the nearest-neighbor MH transmission, which is suitable due to the low......In this two-part paper, information-theoretic capacity scaling laws are analyzed in an underwater acoustic network with n regularly located nodes on a square, in which both bandwidth and received signal power can be limited significantly. Parts I and II deal with an extended network of unit node...... parameter that depends on the frequency scaling as well as the transmission distance. Upper and lower bounds on the capacity scaling are then derived. In Part I, we show that the upper bound on capacity for extended networks is inversely proportional to the attenuation parameter, thus resulting in a highly...

  13. Terahertz-Frequency Spin Hall Auto-oscillator Based on a Canted Antiferromagnet

    Science.gov (United States)

    Sulymenko, O. R.; Prokopenko, O. V.; Tiberkevich, V. S.; Slavin, A. N.; Ivanov, B. A.; Khymyn, R. S.

    2017-12-01

    We propose a design of a terahertz-frequency signal generator based on a layered structure consisting of a current-driven platinum (Pt) layer and a layer of an antiferromagnet (AFM) with easy-plane anisotropy, where the magnetization vectors of the AFM sublattices are canted inside the easy plane by the Dzyaloshinskii-Moriya interaction (DMI). The dc electric current flowing in the Pt layer creates due to the spin Hall effect, a perpendicular spin current that, being injected in the AFM layer, tilts the DMI-canted AFM sublattices out of the easy plane, thus exposing them to the action of a strong internal exchange magnetic field of the AFM. The sublattice magnetizations, along with the small net magnetization vector mDMI of the canted AFM, start to rotate about the hard anisotropy axis of the AFM with the terahertz frequency proportional to the injected spin current and the AFM exchange field. The rotation of the small net magnetization mDMI results in the terahertz-frequency dipolar radiation that can be directly received by an adjacent (e.g., dielectric) resonator. We demonstrate theoretically that the radiation frequencies in the range f =0.05 - 2 THz are possible at the experimentally reachable magnitudes of the driving current density, and we evaluate the power of the signal radiated into different types of resonators. This power increases with the increase of frequency f , and it can exceed 1 μ W at f ˜0.5 THz for a typical dielectric resonator of the electric permittivity ɛ ˜10 and a quality factor Q ˜750 .

  14. Alleviation SSR and Low Frequency Power Oscillations in Series Compensated Transmission Line using SVC Supplementary Controllers

    Science.gov (United States)

    Kumar, Sanjiv; Kumar, Narendra

    2017-06-01

    In this work, supplementary sub-synchronous damping controllers (SSDC) are proposed for damping sub-synchronous oscillations in power systems with series compensated transmission lines. Series compensation have extensively been used as effective means of increasing the power transfer capability of a transmission lines and improving transient stability limits of power systems. Series compensation with transmission lines may cause sub-synchronous resonance (SSR). The eigenvalue investigation tool is used to ascertain the existence of SSR. It is shown that the addition of supplementary controller is able to stabilize all unstable modes for T-network model. Eigenvalue investigation and time domain transient simulation of detailed nonlinear system are considered to investigate the performance of the controllers. The efficacies of the suggested supplementary controllers are compared on the IEEE first benchmark model for computer simulations of SSR by means of time domain simulation in Matlab/Simulink environment. Supplementary SSDC are considered in order to compare effectiveness of SSDC during higher loading in alleviating the small signal stability problem.

  15. Altered low frequency oscillations of cortical vessels in patients with cerebrovascular occlusive disease – a NIRS study

    Directory of Open Access Journals (Sweden)

    Dorte ePhillip

    2013-12-01

    Full Text Available Analysis of cerebral autoregulation by measuring spontaneous oscillations in the low frequency spectrum of cerebral cortical vessels might be a useful tool for assessing risk and investigating different treatment strategies in carotid artery disease (CAD and stroke. Near infrared spectroscopy (NIRS is a non-invasive optical method to investigate regional changes in oxygenated (oxyHb and deoxygenated hemoglobin (deoxyHb in the outermost layers of the cerebral cortex. In the present study we examined oxyHb low frequency oscillations (LFOs, believed to reflect cortical cerebral autoregulation, in 16 patients with both symptomatic carotid occlusive disease and cerebral hypoperfusion in comparison to healthy controls. Each hemisphere was examined with 2 NIRS channels using a 3 cm source detector distance. Arterial blood pressure (ABP was measured via a finger plethysmograph. Using transfer function analysis ABP-oxyHb phase shift and gain as well as inter-hemispheric phase shift and amplitude ratio were assessed. We found that inter-hemispheric amplitude ratio was significantly altered in hypoperfusion patients compared to healthy controls (P= 0.010, because of relatively lower amplitude on the hypoperfusion side. The inter-hemispheric phase shift showed a trend (P = 0.061 towards increased phase shift in hypoperfusion patients compared to controls. We found no statistical difference between hemispheres in hypoperfusion patients for phase shift or gain values. There were no differences between the hypoperfusion side and controls for phase shift or gain values. These preliminary results suggest an impairment of autoregulation in hypoperfusion patients at the cortical level using NIRS.

  16. THE ENERGY DEPENDENCE OF THE CENTROID FREQUENCY AND PHASE LAG OF THE QUASI-PERIODIC OSCILLATIONS IN GRS 1915+105

    International Nuclear Information System (INIS)

    Qu, J. L.; Lu, F. J.; Lu, Y.; Song, L. M.; Zhang, S.; Wang, J. M.; Ding, G. Q.

    2010-01-01

    We present a study of the centroid frequencies and phase lags of quasi-periodic oscillations (QPOs) as functions of photon energy for GRS 1915+105. It is found that the centroid frequencies of the 0.5-10 Hz QPOs and their phase lags are both energy dependent, and there exists an anticorrelation between the QPO frequency and phase lag. These new results challenge the popular QPO models, because none of them can fully explain the observed properties. We suggest that the observed QPO phase lags are partially due to the variation of the QPO frequency with energy, especially for those with frequency higher than 3.5 Hz.

  17. A robust single-beam optical trap for a gram-scale mechanical oscillator.

    Science.gov (United States)

    Altin, P A; Nguyen, T T-H; Slagmolen, B J J; Ward, R L; Shaddock, D A; McClelland, D E

    2017-11-06

    Precise optical control of microscopic particles has been mastered over the past three decades, with atoms, molecules and nano-particles now routinely trapped and cooled with extraordinary precision, enabling rapid progress in the study of quantum phenomena. Achieving the same level of control over macroscopic objects is expected to bring further advances in precision measurement, quantum information processing and fundamental tests of quantum mechanics. However, cavity optomechanical systems dominated by radiation pressure - so-called 'optical springs' - are inherently unstable due to the delayed dynamical response of the cavity. Here we demonstrate a fully stable, single-beam optical trap for a gram-scale mechanical oscillator. The interaction of radiation pressure with thermo-optic feedback generates damping that exceeds the mechanical loss by four orders of magnitude. The stability of the resultant spring is robust to changes in laser power and detuning, and allows purely passive self-locking of the cavity. Our results open up a new way of trapping and cooling macroscopic objects for optomechanical experiments.

  18. Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping

    Energy Technology Data Exchange (ETDEWEB)

    Coffer, J.; Encalada, N.; Huang, M.; Camparo, J. [Physical Sciences Laboratories, The Aerospace Corporation 2310, E. El Segundo Blvd., El Segundo, California 90245 (United States)

    2014-10-28

    We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.

  19. Wavelet analysis of low frequency plasma oscillations in the magnetosheath of Mars

    Science.gov (United States)

    Franco, A.; Echer, E.; Bolzam, M. J. A.; Fraenz, M.

    2017-09-01

    Wavelet analysis was employed to identify the major frequencies present in the Martian magnetosheath. The Morlet wavelet transform was selected and applied to the density and temperature data, obtained from the Analyzer of Space Plasmas and Energetic Atoms experiment (ASPERA-3), onboard the Mars Express (MEX). From a preliminary study of 836 magnetosheath crossings, observed in the years of 2005 and 2006, we have found 2357 periods with enhanced power between 5 and 60 mHz for the electron density data. The principal frequencies observed were in the range 5-20 mHz, where we found about 60 % of the frequencies identified. For electron temperature data, we have found about 57.5% of the periods with enhanced power were in the same range as for the density. This is an ongoing work which is part of a PhD Thesis which aims to study all the electron density and temperature data in the Mars magnetosheath during the MEX interval (2004-2015).

  20. Small-scale structure and the Lyman-α forest baryon acoustic oscillation feature

    Science.gov (United States)

    Hirata, Christopher M.

    2018-02-01

    The baryon-acoustic oscillation (BAO) feature in the Lyman-α forest is a key probe of the cosmic expansion rate at redshifts z ˜ 2.5, well before dark energy is believed to have become significant. A key advantage of the BAO as a standard ruler is that it is a sharp feature and hence is more robust against broad-band systematic effects than other cosmological probes. However, if the Lyman-α forest transmission is sensitive to the initial streaming velocity of the baryons relative to the dark matter, then the BAO peak position can be shifted. Here we investigate this sensitivity using a suite of hydrodynamic simulations of small regions of the intergalactic medium with a range of box sizes and physics assumptions; each simulation starts from initial conditions at the kinematic decoupling era (z ˜ 1059), undergoes a discrete change from neutral gas to ionized gas thermal evolution at reionization (z ˜ 8), and is finally processed into a Lyman-α forest transmitted flux cube. Streaming velocities suppress small-scale structure, leading to less violent relaxation after reionization. The changes in the gas distribution and temperature-density relation at low redshift are more subtle, due to the convergent temperature evolution in the ionized phase. The change in the BAO scale is estimated to be of the order of 0.12 per cent at z = 2.5; some of the major uncertainties and avenues for future improvement are discussed. The predicted streaming velocity shift would be a subdominant but not negligible effect (of order 0.26σ) for the upcoming DESI Lyman-α forest survey, and exceeds the cosmic variance floor.

  1. Motor network plasticity and low-frequency oscillations abnormalities in patients with brain gliomas: a functional MRI study.

    Directory of Open Access Journals (Sweden)

    Chen Niu

    Full Text Available Brain plasticity is often associated with the process of slow-growing tumor formation, which remodels neural organization and optimizes brain network function. In this study, we aimed to investigate whether motor function plasticity would display deficits in patients with slow-growing brain tumors located in or near motor areas, but who were without motor neurological deficits. We used resting-state functional magnetic resonance imaging to probe motor networks in 15 patients with histopathologically confirmed brain gliomas and 15 age-matched healthy controls. All subjects performed a motor task to help identify individual motor activity in the bilateral primary motor cortex (PMC and supplementary motor area (SMA. Frequency-based analysis at three different frequencies was then used to investigate possible alterations in the power spectral density (PSD of low-frequency oscillations. For each group, the average PSD was determined for each brain region and a nonparametric test was performed to determine the difference in power between the two groups. Significantly reduced inter-hemispheric functional connectivity between the left and right PMC was observed in patients compared with controls (P<0.05. We also found significantly decreased PSD in patients compared to that in controls, in all three frequency bands (low: 0.01-0.02 Hz; middle: 0.02-0.06 Hz; and high: 0.06-0.1 Hz, at three key motor regions. These findings suggest that in asymptomatic patients with brain tumors located in eloquent regions, inter-hemispheric connection may be more vulnerable. A comparison of the two approaches indicated that power spectral analysis is more sensitive than functional connectivity analysis for identifying the neurological abnormalities underlying motor function plasticity induced by slow-growing tumors.

  2. Short Meditation Trainings Enhance Non-REM Sleep Low-Frequency Oscillations.

    Science.gov (United States)

    Dentico, Daniela; Ferrarelli, Fabio; Riedner, Brady A; Smith, Richard; Zennig, Corinna; Lutz, Antoine; Tononi, Giulio; Davidson, Richard J

    2016-01-01

    We have recently shown higher parietal-occipital EEG gamma activity during sleep in long-term meditators compared to meditation-naive individuals. This gamma increase was specific for NREM sleep, was present throughout the entire night and correlated with meditation expertise, thus suggesting underlying long-lasting neuroplastic changes induced through prolonged training. The aim of this study was to explore the neuroplastic changes acutely induced by 2 intensive days of different meditation practices in the same group of practitioners. We also repeated baseline recordings in a meditation-naive cohort to account for time effects on sleep EEG activity. High-density EEG recordings of human brain activity were acquired over the course of whole sleep nights following intervention. Sound-attenuated sleep research room. Twenty-four long-term meditators and twenty-four meditation-naïve controls. Two 8-h sessions of either a mindfulness-based meditation or a form of meditation designed to cultivate compassion and loving kindness, hereafter referred to as compassion meditation. We found an increase in EEG low-frequency oscillatory activities (1-12 Hz, centered around 7-8 Hz) over prefrontal and left parietal electrodes across whole night NREM cycles. This power increase peaked early in the night and extended during the third cycle to high-frequencies up to the gamma range (25-40 Hz). There was no difference in sleep EEG activity between meditation styles in long-term meditators nor in the meditation naïve group across different time points. Furthermore, the prefrontal-parietal changes were dependent on meditation life experience. This low-frequency prefrontal-parietal activation likely reflects acute, meditation-related plastic changes occurring during wakefulness, and may underlie a top-down regulation from frontal and anterior parietal areas to the posterior parietal and occipital regions showing chronic, long-lasting plastic changes in long-term meditators.

  3. Short Meditation Trainings Enhance Non-REM Sleep Low-Frequency Oscillations.

    Directory of Open Access Journals (Sweden)

    Daniela Dentico

    Full Text Available We have recently shown higher parietal-occipital EEG gamma activity during sleep in long-term meditators compared to meditation-naive individuals. This gamma increase was specific for NREM sleep, was present throughout the entire night and correlated with meditation expertise, thus suggesting underlying long-lasting neuroplastic changes induced through prolonged training. The aim of this study was to explore the neuroplastic changes acutely induced by 2 intensive days of different meditation practices in the same group of practitioners. We also repeated baseline recordings in a meditation-naive cohort to account for time effects on sleep EEG activity.High-density EEG recordings of human brain activity were acquired over the course of whole sleep nights following intervention.Sound-attenuated sleep research room.Twenty-four long-term meditators and twenty-four meditation-naïve controls.Two 8-h sessions of either a mindfulness-based meditation or a form of meditation designed to cultivate compassion and loving kindness, hereafter referred to as compassion meditation.We found an increase in EEG low-frequency oscillatory activities (1-12 Hz, centered around 7-8 Hz over prefrontal and left parietal electrodes across whole night NREM cycles. This power increase peaked early in the night and extended during the third cycle to high-frequencies up to the gamma range (25-40 Hz. There was no difference in sleep EEG activity between meditation styles in long-term meditators nor in the meditation naïve group across different time points. Furthermore, the prefrontal-parietal changes were dependent on meditation life experience.This low-frequency prefrontal-parietal activation likely reflects acute, meditation-related plastic changes occurring during wakefulness, and may underlie a top-down regulation from frontal and anterior parietal areas to the posterior parietal and occipital regions showing chronic, long-lasting plastic changes in long-term meditators.

  4. 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 t...... 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....

  5. Application of modified homotopy perturbation method and amplitude frequency formulation to strongly nonlinear oscillators

    Directory of Open Access Journals (Sweden)

    seyd ghasem enayati

    2017-01-01

    Full Text Available In this paper, two powerful analytical methods known as modified homotopy perturbation method and Amplitude Frequency Formulation called respectively MHPM and AFF, are introduced to derive approximate solutions of a system of ordinary differential equations appear in mechanical applications. These methods convert a difficult problem into a simple one, which can be easily handled. The obtained solutions are compared with numerical fourth order runge-kutta method to show the applicability and accuracy of both MHPM and AFF in solving this sample problem. The results attained in this paper confirm the idea that MHPM and AFF are powerful mathematical tools and they can be applied to linear and nonlinear problems.

  6. Anisotropic frequency response of critical density fluctuation of NIPA gel under oscillation shear

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Masaaki [Research Reactor Institute, Kyoto University, Osaka 590-0494 (Japan)]. E-mail: sugiyama@rri.kyoto-u.ac.jp; Vigild, Martin E. [Danish Polymer Centre, Technical University of Denmark, 2800 Lyngby (Denmark); Fukunaga, Toshiharu [Research Reactor Institute, Kyoto University, Osaka 590-0494 (Japan); Itoh, Keiji [Research Reactor Institute, Kyoto University, Osaka 590-0494 (Japan); Mori, Kazuhiro [Research Reactor Institute, Kyoto University, Osaka 590-0494 (Japan); Sato, Takashi [Department of Engineering Physics and Mechanics, Kyoto University, Kyoto 606-8501 (Japan); Annaka, Masahiko [Department of Chemistry, Kyushu University, Fukuoka 812-8581 (Japan)

    2006-11-15

    A relation between rheology and structure of high density NIPA gel around a critical point on volume phase transition was studied by a simultaneous rheology and small-angle neutron scattering measurement. Just below the critical temperature, the NIPA gel showed softening: G{sup '} and G{sup '}' get closer (G{sup '}>G{sup '}'). At this temperature, the density fluctuation enhanced along the shear direction corresponding to the shear frequency but not to the shear strength. It means that this anisotropy is different from that observed in a statically stretched gel.

  7. EMC Investigation of a Very High Frequency Self-oscillating Resonant Power Converter

    DEFF Research Database (Denmark)

    Pedersen, Jeppe Arnsdorf; Knott, Arnold; Andersen, Michael A. E.

    2016-01-01

    This paper focuses on the electromagnetic compatibility (EMC) performance of a Very High Frequency (VHF) converter and how to lower the emissions. To test the EMC performance a VHF converter is implemented with a Class-E inverter and a Class-DE rectifier. The converter is designed to deliver 3 W...... the regulations. This converter shows to be well below the levels for conducted emission even without filtering. For the radiated emissions the converter is above the limits without input and output filters. Several designs with different ways to lower the emissions are implemented and the different layouts...

  8. On the Effects of Frequency Scaling over Capacity Scaling in Underwater Networks

    DEFF Research Database (Denmark)

    Shin, Won-Yong; Roetter, Daniel Enrique Lucani; Médard, Muriel

    2013-01-01

    that there exists either a bandwidth or power limitation, or both, according to the operating regimes (i.e., path-loss attenuation regimes), thus yielding the upper bound that follows three fundamentally different information transfer arguments. In addition, an achievability result based on the multi-hop (MH......) transmission is presented for dense networks. MH is shown to guarantee the order optimality under certain operating regimes. More specifically, it turns out that scaling the carrier frequency faster than or as is instrumental towards achieving the order optimality of the MH protocol....

  9. 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.

  10. IRIS Arrays: Observing Wavefields at Multiple Scales and Frequencies

    Science.gov (United States)

    Sumy, D. F.; Woodward, R.; Frassetto, A.

    2014-12-01

    The Incorporated Research Institutions for Seismology (IRIS) provides instruments for creating and operating seismic arrays at a wide range of scales. As an example, for over thirty years the IRIS PASSCAL program has provided instruments to individual Principal Investigators to deploy arrays of all shapes and sizes on every continent. These arrays have ranged from just a few sensors to hundreds or even thousands of sensors, covering areas with dimensions of meters to thousands of kilometers. IRIS also operates arrays directly, such as the USArray Transportable Array (TA) as part of the EarthScope program. Since 2004, the TA has rolled across North America, at any given time spanning a swath of approximately 800 km by 2,500 km, and thus far sampling 2% of the Earth's surface. This achievement includes all of the lower-48 U.S., southernmost Canada, and now parts of Alaska. IRIS has also facilitated specialized arrays in polar environments and on the seafloor. In all cases, the data from these arrays are freely available to the scientific community. As the community of scientists who use IRIS facilities and data look to the future they have identified a clear need for new array capabilities. In particular, as part of its Wavefields Initiative, IRIS is exploring new technologies that can enable large, dense array deployments to record unaliased wavefields at a wide range of frequencies. Large-scale arrays might utilize multiple sensor technologies to best achieve observing objectives and optimize equipment and logistical costs. Improvements in packaging and power systems can provide equipment with reduced size, weight, and power that will reduce logistical constraints for large experiments, and can make a critical difference for deployments in harsh environments or other situations where rapid deployment is required. We will review the range of existing IRIS array capabilities with an overview of previous and current deployments and examples of data and results. We

  11. Nonlinear asteroseismology: insight from amplitude and frequency modulations of oscillation modes in compact pulsators from Kepler photometry

    Directory of Open Access Journals (Sweden)

    Zong Weikai

    2017-01-01

    Full Text Available Nonlinear mode interactions are difficult to observe from ground-based telescopes as the typical periods of the modulations induced by those nonlinear phenomena are on timescales of weeks, months, even years. The launch of space telescopes, e.g., Kepler, has tremendously changed the situation and shredded new light on this research field. We present results from Kepler photometry showing evidence that nonlinear interactions between modes occur in the two compact pulsators KIC 8626021, a DB white dwarf, and KIC 10139564, a short period hot B subdwarf. KIC 8626021 and KIC 10139564 had been monitored by Kepler in short-cadence for nearly two years and more than three years without interruption, respectively. By analyzing these high-quality photometric data, we found that the modes within the triplets induced by rotation clearly reveal different behaviors: their frequencies and amplitudes may exhibit either periodic or irregular modulations, or remain constant. These various behaviors of the amplitude and of the frequency modulations of the oscillation modes observed in these two stars are in good agreement with those predicted within the amplitude equation formalism in the case of the nonlinear resonant mode coupling mechanism.

  12. Feasibility of recording high frequency oscillations with tripolar concentric ring electrodes during pentylenetetrazole-induced seizures in rats.

    Science.gov (United States)

    Makeyev, Oleksandr; Liu, Xiang; Wang, Liling; Zhu, Zhenghan; Taveras, Aristides; Troiano, Derek; Medvedev, Andrei V; Besio, Walter G

    2012-01-01

    As epilepsy remains a refractory condition in about 30% of patients with complex partial seizures, electrical stimulation of the brain has recently shown potential for additive seizure control therapy. Previously, we applied noninvasive transcranial focal stimulation via novel tripolar concentric ring electrodes (TCREs) on the scalp of rats after inducing seizures with pentylenetetrazole (PTZ). We developed a close-loop system to detect seizures and automatically trigger the stimulation and evaluated its effect on the electrographic activity recorded by TCREs in rats. In our previous work the detectors of seizure onset were based on seizure-induced changes in signal power in the frequency range up to 100 Hz, while in this preliminary study we assess the feasibility of recording high frequency oscillations (HFOs) in the range up to 300 Hz noninvasively with scalp TCREs during PTZ-induced seizures. Grand average power spectral density estimate and generalized likelihood ratio tests were used to compare power of electrographic activity at different stages of seizure development in a group of rats (n= 8). The results suggest that TCREs have the ability to record HFOs from the scalp as well as that scalp-recorded HFOs can potentially be used as features for seizure onset detection.

  13. The dielectric calibration of capacitance probes for soil hydrology using an oscillation frequency response model

    Directory of Open Access Journals (Sweden)

    D. A. Robinson

    1998-01-01

    Full Text Available Capacitance probes are a fast, safe and relatively inexpensive means of measuring the relative permittivity of soils, which can then be used to estimate soil water content. Initial experiments with capacitance probes used empirical calibrations between the frequency response of the instrument and soil water content. This has the disadvantage that the calibrations are instrument-dependent. A twofold calibration strategy is described in this paper; the instrument frequency is turned into relative permittivity (dielectric constant which can then be calibrated against soil water content. This approach offers the advantages of making the second calibration, from soil permittivity to soil water content. instrument-independent and allows comparison with other dielectric methods, such as time domain reflectometry. A physically based model, used to calibrate capacitance probes in terms of relative permittivity (εr is presented. The model, which was developed from circuit analysis, predicts, successfully, the frequency response of the instrument in liquids with different relative permittivities, using only measurements in air and water. lt was used successfully to calibrate 10 prototype surface capacitance insertion probes (SCIPS and a depth capacitance probe. The findings demonstrate that the geometric properties of the instrument electrodes were an important parameter in the model, the value of which could be fixed through measurement. The relationship between apparent soil permittivity and volumetric water content has been the subject of much research in the last 30 years. Two lines of investigation have developed, time domain reflectometry (TDR and capacitance. Both methods claim to measure relative permittivity and should therefore be comparable. This paper demonstrates that the IH capacitance probe overestimates relative permittivity as the ionic conductivity of the medium increases. Electrically conducting ionic solutions were used to test the

  14. Searching for an oscillating massive scalar field as a dark matter candidate using atomic hyperfine frequency comparisons

    OpenAIRE

    Hees, A.; Guéna, J.; Abgrall, M.; Bize, S.; Wolf, P.

    2016-01-01

    We use six years of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but pr...

  15. Influence of the Basset force on the resonant behavior of an oscillator with fluctuating frequency

    Energy Technology Data Exchange (ETDEWEB)

    Rekker, A., E-mail: Astrid.Rekker@tlu.ee; Mankin, R., E-mail: Romi.Mankin@tlu.ee [Institute of Mathematics and Natural Sciences, Tallinn University, 29 Narva Road, 10120 Tallinn (Estonia)

    2015-10-28

    The influence of hydrodynamic interactions, such as Stokes and Basset forces, on the dynamics of a harmonically trapped Brownian tracer is considered. A generalized Langevin equation is used to describe the tracer’s response to an external periodic force and to dichotomous fluctuations of the stiffness of the trapping potential. Relying on the Shapiro-Loginov formula, exact expressions for the complex susceptibility and for the response function are presented. On the basis of these exact formulas, it is demonstrated that interplay of a multiplicative colored noise and the Basset force induced memory effects can generate a variety of cooperation effects, such as multiresonance versus the driving frequency, as well as stochastic resonance versus noise parameters. In particular, in certain parameter regions the response function exhibits a resonance-like enhancement at intermediate values of the intensity of the Basset force. Conditions for the appearance of these effects are also discussed.

  16. Influence of the Basset force on the resonant behavior of an oscillator with fluctuating frequency

    Science.gov (United States)

    Rekker, A.; Mankin, R.

    2015-10-01

    The influence of hydrodynamic interactions, such as Stokes and Basset forces, on the dynamics of a harmonically trapped Brownian tracer is considered. A generalized Langevin equation is used to describe the tracer's response to an external periodic force and to dichotomous fluctuations of the stiffness of the trapping potential. Relying on the Shapiro-Loginov formula, exact expressions for the complex susceptibility and for the response function are presented. On the basis of these exact formulas, it is demonstrated that interplay of a multiplicative colored noise and the Basset force induced memory effects can generate a variety of cooperation effects, such as multiresonance versus the driving frequency, as well as stochastic resonance versus noise parameters. In particular, in certain parameter regions the response function exhibits a resonance-like enhancement at intermediate values of the intensity of the Basset force. Conditions for the appearance of these effects are also discussed.

  17. Influence of the Basset force on the resonant behavior of an oscillator with fluctuating frequency

    International Nuclear Information System (INIS)

    Rekker, A.; Mankin, R.

    2015-01-01

    The influence of hydrodynamic interactions, such as Stokes and Basset forces, on the dynamics of a harmonically trapped Brownian tracer is considered. A generalized Langevin equation is used to describe the tracer’s response to an external periodic force and to dichotomous fluctuations of the stiffness of the trapping potential. Relying on the Shapiro-Loginov formula, exact expressions for the complex susceptibility and for the response function are presented. On the basis of these exact formulas, it is demonstrated that interplay of a multiplicative colored noise and the Basset force induced memory effects can generate a variety of cooperation effects, such as multiresonance versus the driving frequency, as well as stochastic resonance versus noise parameters. In particular, in certain parameter regions the response function exhibits a resonance-like enhancement at intermediate values of the intensity of the Basset force. Conditions for the appearance of these effects are also discussed

  18. Nonstationary oscillation of gyrotron backward wave oscillators with cylindrical interaction structure

    International Nuclear Information System (INIS)

    Chen, Shih-Hung; Chen, Liu

    2013-01-01

    The nonstationary oscillation of the gyrotron backward wave oscillator (gyro-BWO) with cylindrical interaction structure was studied utilizing both steady-state analyses and time-dependent simulations. Comparisons of the numerical results reveal that the gyro-BWO becomes nonstationary when the trailing field structure completely forms due to the dephasing energetic electrons. The backward propagation of radiated waves with a lower resonant frequency from the trailing field structure interferes with the main internal feedback loop, thereby inducing the nonstationary oscillation of the gyro-BWO. The nonstationary gyro-BWO exhibits the same spectral pattern of modulated oscillations with a constant frequency separation between the central frequency and sidebands throughout the whole system. The frequency separation is found to be scaled with the square root of the maximum field amplitude, thus further demonstrating that the nonstationary oscillation of the gyro-BWO is associated with the beam-wave resonance detuning

  19. Measurement of the $B^0_s-\\overline{B}^0_s$ oscillation frequency $\\Delta m_s$ in $B^0_s \\to D^-_s (3)\\pi$ decays

    CERN Document Server

    INSPIRE-00258707; Adeva, B.; Adinolfi, M.; Adrover, C.; Affolder, A.; Ajaltouni, Z.; Albrecht, J.; Alessio, F.; Alexander, M.; Alkhazov, G.; Alvarez Cartelle, P.; Alves Jr, A.A.; Amato, S.; Amhis, Y.; Anderson, J.; Appleby, R.B.; Aquines Gutierrez, O.; Archilli, F.; Arrabito, L.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Bachmann, S.; Back, J.J.; Bailey, D.S.; Balagura, V.; Baldini, W.; Barlow, R.J.; Barschel, C.; Barsuk, S.; Barter, W.; Bates, A.; Bauer, C.; Bauer, Th.; Bay, A.; Bediaga, I.; Belous, K.; Belyaev, I.; Ben-Haim, E.; Benayoun, M.; Bencivenni, G.; Benson, S.; Benton, J.; Bernet, R.; Bettler, M.O.; van Beuzekom, M.; Bien, A.; Bifani, S.; Bizzeti, A.; Bjornstad, P.M.; Blake, T.; Blanc, F.; Blanks, C.; Blouw, J.; Blusk, S.; Bobrov, A.; Bocci, V.; Bondar, A.; Bondar, N.; Bonivento, W.; Borghi, S.; Borgia, A.; Bowcock, T.J.V.; Bozzi, C.; Brambach, T.; van den Brand, J.; Bressieux, J.; Brett, D.; Brisbane, S.; Britsch, M.; Britton, T.; Brook, N.H.; Brown, H.; Buchler-Germann, A.; Burducea, I.; Bursche, A.; Buytaert, J.; Cadeddu, S.; Caicedo Carvajal, J.M.; Callot, O.; Calvi, M.; Calvo Gomez, M.; Camboni, A.; Campana, P.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cattaneo, M.; Charles, M.; Charpentier, Ph.; Chiapolini, N.; Ciba, K.; Cid Vidal, X.; Ciezarek, G.; Clarke, P.E.L.; Clemencic, M.; Cliff, H.V.; Closier, J.; Coca, C.; Coco, V.; Cogan, J.; Collins, P.; Constantin, F.; Conti, G.; Contu, A.; Cook, A.; Coombes, M.; Corti, G.; Cowan, G.A.; Currie, R.; D'Almagne, B.; D'Ambrosio, C.; David, P.; De Bonis, I.; De Capua, S.; De Cian, M.; De Lorenzi, F.; de Miranda, J.M.; De Paula, L.; De Simone, P.; Decamp, D.; Deckenhoff, M.; Degaudenzi, H.; Deissenroth, M.; Del Buono, L.; Deplano, C.; Deschamps, O.; Dettori, F.; Dickens, J.; Dijkstra, H.; Diniz Batista, P.; Donleavy, S.; Dosil Suarez, A.; Dossett, D.; Dovbnya, A.; Dupertuis, F.; Dzhelyadin, R.; Eames, C.; Easo, S.; Egede, U.; Egorychev, V.; Eidelman, S.; van Eijk, D.; Eisele, F.; Eisenhardt, S.; Ekelhof, R.; Eklund, L.; Elsasser, Ch.; d'Enterria, D.G.; Esperante Pereira, D.; Esteve, L.; Falabella, A.; Fanchini, E.; Farber, C.; Fardell, G.; Farinelli, C.; Farry, S.; Fave, V.; Fernandez Albor, V.; Ferro-Luzzi, M.; Filippov, S.; Fitzpatrick, C.; Fontana, M.; Fontanelli, F.; Forty, R.; Frank, M.; Frei, C.; Frosini, M.; Furcas, S.; Gallas Torreira, A.; Galli, D.; Gandelman, M.; Gandini, P.; Gao, Y.; Garnier, J-C.; Garofoli, J.; Garra Tico, J.; Garrido, L.; Gaspar, C.; Gauvin, N.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gibson, V.; Gligorov, V.V.; Gobel, C.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gordon, H.; Grabalosa Gandara, M.; Graciani Diaz, R.; Granado Cardoso, L.A.; Grauges, E.; Graziani, G.; Grecu, A.; Gregson, S.; Gui, B.; Gushchin, E.; Guz, Yu.; Gys, T.; Haefeli, G.; Haen, C.; Haines, S.C.; Hampson, T.; Hansmann-Menzemer, S.; Harji, R.; Harnew, N.; Harrison, J.; Harrison, P.F.; He, J.; Heijne, V.; Hennessy, K.; Henrard, P.; Hernando Morata, J.A.; van Herwijnen, E.; Hicks, E.; Hofmann, W.; Holubyev, K.; Hopchev, P.; Hulsbergen, W.; Hunt, P.; Huse, T.; Huston, R.S.; Hutchcroft, D.; Hynds, D.; Iakovenko, V.; Ilten, P.; Imong, J.; Jacobsson, R.; Jaeger, A.; Jahjah Hussein, M.; Jans, E.; Jansen, F.; Jaton, P.; Jean-Marie, B.; Jing, F.; John, M.; Johnson, D.; Jones, C.R.; Jost, B.; Kandybei, S.; Karacson, M.; Karbach, T.M.; Keaveney, J.; Kerzel, U.; Ketel, T.; Keune, A.; Khanji, B.; Kim, Y.M.; Knecht, M.; Koblitz, S.; Koppenburg, P.; Kozlinskiy, A.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krocker, G.; Krokovny, P.; Kruse, F.; Kruzelecki, K.; Kucharczyk, M.; Kukulak, S.; Kumar, R.; Kvaratskheliya, T.; La Thi, V.N.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lambert, R.W.; Lanciotti, E.; Lanfranchi, G.; Langenbruch, C.; Latham, T.; Le Gac, R.; van Leerdam, J.; Lees, J.P.; Lefevre, R.; Leflat, A.; Lefrancois, J.; Leroy, O.; Lesiak, T.; Li, L.; Li Gioi, L.; Lieng, M.; Liles, M.; Lindner, R.; Linn, C.; Liu, B.; Liu, G.; Lopes, J.H.; Lopez Asamar, E.; Lopez-March, N.; Luisier, J.; Machefert, F.; Machikhiliyan, I.V.; Maciuc, F.; Maev, O.; Magnin, J.; Malde, S.; Mamunur, R.M.D.; Manca, G.; Mancinelli, G.; Mangiafave, N.; Marconi, U.; Marki, R.; Marks, J.; Martellotti, G.; Martens, A.; Martin, L.; Martin Sanchez, A.; Martinez Santos, D.; Massafferri, A.; Mathe, Z.; Matteuzzi, C.; Matveev, M.; Maurice, E.; Maynard, B.; Mazurov, A.; McGregor, G.; McNulty, R.; Mclean, C.; Meissner, M.; Merk, M.; Merkel, J.; Messi, R.; Miglioranzi, S.; Milanes, D.A.; Minard, M.N.; Monteil, S.; Moran, D.; Morawski, P.; Mountain, R.; Mous, I.; Muheim, F.; Muller, K.; Muresan, R.; Muryn, B.; Musy, M.; Mylroie-Smith, J.; Naik, P.; Nakada, T.; Nandakumar, R.; Nardulli, J.; Nasteva, I.; Nedos, M.; Needham, M.; Neufeld, N.; Nguyen-Mau, C.; Nicol, M.; Nies, S.; Niess, V.; Nikitin, N.; Oblakowska-Mucha, A.; Obraztsov, V.; Oggero, S.; Ogilvy, S.; Okhrimenko, O.; Oldeman, R.; Orlandea, M.; Otalora Goicochea, J.M.; Owen, P.; Pal, B.; Palacios, J.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Parkes, C.; Parkinson, C.J.; Passaleva, G.; Patel, G.D.; Patel, M.; Paterson, S.K.; Patrick, G.N.; Patrignani, C.; Pavel-Nicorescu, C.; Pazos Alvarez, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perego, D.L.; Perez Trigo, E.; Perez-Calero Yzquierdo, A.; Perret, P.; Perrin-Terrin, M.; Pessina, G.; Petrella, A.; Petrolini, A.; Pie Valls, B.; Pietrzyk, B.; Pilar, T.; Pinci, D.; Plackett, R.; Playfer, S.; Plo Casasus, M.; Polok, G.; Poluektov, A.; Polycarpo, E.; Popov, D.; Popovici, B.; Potterat, C.; Powell, A.; du Pree, T.; Prisciandaro, J.; Pugatch, V.; Puig Navarro, A.; Qian, W.; Rademacker, J.H.; Rakotomiaramanana, B.; Rangel, M.S.; Raniuk, I.; Raven, G.; Redford, S.; Reid, M.M.; dos Reis, A.C.; Ricciardi, S.; Rinnert, K.; Roa Romero, D.A.; Robbe, P.; Rodrigues, E.; Rodrigues, F.; Rodriguez Perez, P.; Rogers, G.J.; Roiser, S.; Romanovsky, V.; Rouvinet, J.; Ruf, T.; Ruiz, H.; Sabatino, G.; Saborido Silva, J.J.; Sagidova, N.; Sail, P.; Saitta, B.; Salzmann, C.; Sannino, M.; Santacesaria, R.; Santinelli, R.; Santovetti, E.; Sapunov, M.; Sarti, A.; Satriano, C.; Satta, A.; Savrie, M.; Savrina, D.; Schaack, P.; Schiller, M.; Schleich, S.; Schmelling, M.; Schmidt, B.; Schneider, O.; Schopper, A.; Schune, M.H.; Schwemmer, R.; Sciubba, A.; Seco, M.; Semennikov, A.; Senderowska, K.; Sepp, I.; Serra, N.; Serrano, J.; Seyfert, P.; Shao, B.; Shapkin, M.; Shapoval, I.; Shatalov, P.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, O.; Shevchenko, V.; Shires, A.; Coutinho, R.Silva; Skottowe, H.P.; Skwarnicki, T.; Smith, A.C.; Smith, N.A.; Sobczak, K.; Soler, F.J.P.; Solomin, A.; Soomro, F.; Souza De Paula, B.; Spaan, B.; Sparkes, A.; Spradlin, P.; Stagni, F.; Stahl, S.; Steinkamp, O.; Stoica, S.; Stone, S.; Storaci, B.; Straticiuc, M.; Straumann, U.; Styles, N.; Subbiah, V.K.; Swientek, S.; Szczekowski, M.; Szczypka, P.; Szumlak, T.; T'Jampens, S.; Teodorescu, E.; Teubert, F.; Thomas, C.; Thomas, E.; van Tilburg, J.; Tisserand, V.; Tobin, M.; Topp-Joergensen, S.; Tran, M.T.; Tsaregorodtsev, A.; Tuning, N.; Ukleja, A.; Urquijo, P.; Uwer, U.; Vagnoni, V.; Valenti, G.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vecchi, S.; Velthuis, J.J.; Veltri, M.; Vervink, K.; Viaud, B.; Videau, I.; Vilasis-Cardona, X.; Visniakov, J.; Vollhardt, A.; Voong, D.; Vorobyev, A.; Voss, H.; Wacker, K.; Wandernoth, S.; Wang, J.; Ward, D.R.; Webber, A.D.; Websdale, D.; Whitehead, M.; Wiedner, D.; Wiggers, L.; Wilkinson, G.; Williams, M.P.; Williams, M.; Wilson, F.F.; Wishahi, J.; Witek, M.; Witzeling, W.; Wotton, S.A.; Wyllie, K.; Xie, Y.; Xing, F.; Yang, Z.; Young, R.; Yushchenko, O.; Zavertyaev, M.; Zhang, L.; Zhang, W.C.; Zhang, Y.; Zhelezov, A.; Zhong, L.; Zverev, E.; Zvyagin, A.

    2012-01-01

    The $B^0_s$-$\\overline{B}^0_s$ oscillation frequency $\\Delta m_s$ is measured with 36 pb$^{-1}$ of data collected in $pp$ collisions at $\\sqrt{s}$ = 7 TeV by the LHCb experiment at the Large Hadron Collider. A total of 1381 $B^0_s \\rightarrow D_s^- \\pi^+$ and $B^0_s \\rightarrow D_s^- \\pi^+\\pi^-\\pi^+$ signal decays are reconstructed, with average decay time resolutions of 44~fs and 36~fs, respectively. An oscillation signal with a statistical significance of 4.6\\,$\\sigma$ is observed. The measured oscillation frequency is $\\Delta m_s$ = 17.63 $\\pm$ 0.11 (stat) $\\pm$ 0.02 (syst)~ps$^{-1}$.

  20. Observable N–¯N oscillation, high-scale see-saw and origin of matter

    Indian Academy of Sciences (India)

    Department of Physics and Center for String and Particle Theory, University of ... oscillation to be quite plausible theoretically if small neutrino masses are to be ..... S L Glashow, The future of elementary particle physics, in Proceedings of the ...

  1. REPRODUCING THE CORRELATIONS OF TYPE C LOW-FREQUENCY QUASI-PERIODIC OSCILLATION PARAMETERS IN XTE J1550–564 WITH A SPIRAL STRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Varniere, Peggy [APC, AstroParticule et Cosmologie, Universite Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Lonie Duquet, F-75205 Paris Cedex 13 (France); Vincent, Frederic H., E-mail: varniere@apc.univ-paris7.fr [Observatoire de Paris/LESIA, 5, place Jules Janssen, F-92195 Meudon Cedex (France)

    2017-01-10

    While it has been observed that the parameters intrinsic to the type C low-frequency quasi-periodic oscillations are related in a nonlinear manner among themselves, there has been, up to now, no model to explain or reproduce how the frequency, the FWHM, and the rms amplitude of the type C low-frequency quasi-periodic oscillations behave with respect to one another. Here we are using a simple toy model representing the emission from a standard disk and a spiral such as that caused by the accretion–ejection instability to reproduce the overall observed behavior and shed some light on its origin. This allows us to prove the ability of such a spiral structure to be at the origin of flux modulation over more than an order of magnitude in frequency.

  2. 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.

  3. Arc Length Coding by Interference of Theta Frequency Oscillations May Underlie Context-Dependent Hippocampal Unit Data and Episodic Memory Function

    Science.gov (United States)

    Hasselmo, Michael E.

    2007-01-01

    Many memory models focus on encoding of sequences by excitatory recurrent synapses in region CA3 of the hippocampus. However, data and modeling suggest an alternate mechanism for encoding of sequences in which interference between theta frequency oscillations encodes the position within a sequence based on spatial arc length or time. Arc length…

  4. The effect of methylphenidate on very low frequency electroencephalography oscillations in adult ADHD.

    Science.gov (United States)

    Cooper, Ruth E; Skirrow, Caroline; Tye, Charlotte; McLoughlin, Grainne; Rijsdijk, Fruhling; Banaschweski, Tobias; Brandeis, Daniel; Kuntsi, Jonna; Asherson, Philip

    2014-04-01

    Altered very low-frequency electroencephalographic (VLF-EEG) activity is an endophenotype of ADHD in children and adolescents. We investigated VLF-EEG case-control differences in adult samples and the effects of methylphenidate (MPH). A longitudinal case-control study was conducted examining the effects of MPH on VLF-EEG (.02-0.2Hz) during a cued continuous performance task. 41 untreated adults with ADHD and 47 controls were assessed, and 21 cases followed up after MPH treatment, with a similar follow-up for 38 controls (mean follow-up=9.4months). Cases had enhanced frontal and parietal VLF-EEG and increased omission errors. In the whole sample, increased parietal VLF-EEG correlated with increased omission errors. After controlling for subthreshold comorbid symptoms, VLF-EEG case-control differences and treatment effects remained. Post-treatment, a time by group interaction emerged; VLF-EEG and omission errors reduced to the same level as controls, with decreased inattentive symptoms in cases. Reduced VLF-EEG following MPH treatment provides preliminary evidence that changes in VLF-EEG may relate to MPH treatment effects on ADHD symptoms; and that VLF-EEG may be an intermediate phenotype of ADHD. Further studies of the treatment effect of MPH in larger controlled studies are required to formally evaluate any causal link between MPH, VLF-EEG and ADHD symptoms. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Source conductance scaling for high frequency superconducting quasiparticle receivers

    Science.gov (United States)

    Ke, Qing; Feldman, M. J.

    1992-01-01

    It has been suggested that the optimum source conductance G(sub s) for the superconductor-insulator-superconductor (SIS) quasiparticle mixer should have a l/f dependence. This would imply that the critical current density of SIS junctions used for mixing should increase as frequency squared, a stringent constraint on the design of submillimeter SIS mixers, rather than in simple proportion to frequency as previously believed. We have used Tucker's quantum theory of mixing for extensive numerical calculations to determine G(sub s) for an optimized SIS receiver. We find that G(sub s) is very roughly independent of frequency (except for the best junctions at low frequency), and discuss the implications of our results for the design of submillimeter SIS mixers.

  6. Effects of electron beam parameters and velocity spread on radio frequency output of a photonic band gap cavity gyrotron oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ashutosh, E-mail: asingh.rs.ece@iitbhu.ac.in [Faculty of Physical Sciences, Institute of Natural Sciences and Humanities, Shri Ramswaroop Memorial University, Lucknow-Deva Road, Uttar Pradesh 225003 (India); Center of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Jain, P. K. [Center of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2015-09-15

    In this paper, the effects of electron beam parameters and velocity spread on the RF behavior of a metallic photonic band gap (PBG) cavity gyrotron operating at 35 GHz with TE{sub 041}–like mode have been theoretically demonstrated. PBG cavity is used here to achieve a single mode operation of the overmoded cavity. The nonlinear time-dependent multimode analysis has been used to observe the beam-wave interaction behavior of the PBG cavity gyrotron, and a commercially available PIC code “CST Particle Studio” has been reconfigured to obtain 3D simulation results in order to validate the analytical values. The output power for this typical PBG gyrotron has been obtained ∼108 kW with ∼15.5% efficiency in a well confined TE{sub 041}–like mode, while all other competing modes have significantly low values of power output. The output power and efficiency of a gyrotron depend highly on the electron beam parameters and velocity spread. The influence of several electron beam parameters, e.g., beam voltage, beam current, beam velocity pitch factor, and DC magnetic field, on the PBG gyrotron operations has been investigated. This study would be helpful in optimising the electron beam parameters and estimating accurate RF output power of the high frequency PBG cavity based gyrotron oscillators.

  7. A simple frequency-scaling rule for animal communication

    Science.gov (United States)

    Fletcher, Neville H.

    2004-05-01

    Different animals use widely different frequencies for sound communication, and it is reasonable to assume that evolution has adapted these frequencies to give greatest conspecific communication distance for a given vocal effort. Acoustic analysis shows that the optimal communication frequency is inversely proportional to about the 0.4 power of the animal's body mass. Comparison with observational data indicates that this prediction is well supported in practice. For animals of a given class, for example mammals, the maximum communication distance varies about as the 0.6 power of the animal's mass. There is, however, a wide spread of observed results because of the different emphasis placed upon vocal effort in the evolution of different animal species.

  8. Evaluation of the Atlantic Multidecadal Oscillation Impact on Large-Scale Atmospheric Circulation in the Atlantic Region in Summer

    Science.gov (United States)

    Semenov, V. A.; Cherenkova, E. A.

    2018-02-01

    The influence of the Atlantic Multidecadal Oscillation (AMO) on large-scale atmospheric circulation in the Atlantic region in summer for the period of 1950-2015 is investigated. It is shown that the intensification of the summer North Atlantic Oscillation (NAO) with significant changes in sea level pressure anomalies in the main centers of action (over Greenland and the British Isles) occurred while the North Atlantic was cooler. Sea surface temperature anomalies, which are linked to the AMO in the summer season, affect both the NAO index and fluctuations of the Eastern Atlantic/Western Russia (EAWR) centers of action. The positive (negative) phase of the AMO is characterized by a combination of negative (positive) values of the NAO and EAWR indices. The dominance of the opposite phases of the teleconnection indices in summer during the warm North Atlantic and in its colder period resulted in differences in the regional climate in Europe.

  9. Scale-free amplitude modulation of neuronal oscillations tracks comprehension of accelerated speech

    NARCIS (Netherlands)

    Borges, Ana Filipa Teixeira; Giraud, Anne Lise; Mansvelder, Huibert D.; Linkenkaer-Hansen, Klaus

    2018-01-01

    Speech comprehension is preserved up to a threefold acceleration, but deteriorates rapidly at higher speeds. Current models posit that perceptual resilience to accelerated speech is limited by the brain’s ability to parse speech into syllabic units using δ/θ oscillations. Here, we investigated

  10. Searching for an Oscillating Massive Scalar Field as a Dark Matter Candidate Using Atomic Hyperfine Frequency Comparisons.

    Science.gov (United States)

    Hees, A; Guéna, J; Abgrall, M; Bize, S; Wolf, P

    2016-08-05

    We use 6 yrs of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions, and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed.

  11. Karhunen-Loève (PCA) based detection of multiple oscillations in multiple measurement signals from large-scale process plants

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Wickerhauser, M.V.

    2007-01-01

     In the perspective of optimizing the control and operation of large scale process plants, it is important to detect and to locate oscillations in the plants. This paper presents a scheme for detecting and localizing multiple oscillations in multiple measurements from such a large-scale power plant....... The scheme is based on a Karhunen-Lo\\`{e}ve analysis of the data from the plant. The proposed scheme is subsequently tested on two sets of data: a set of synthetic data and a set of data from a coal-fired power plant. In both cases the scheme detects the beginning of the oscillation within only a few samples....... In addition the oscillation localization has also shown its potential by localizing the oscillations in both data sets....

  12. Nano-Scale Devices for Frequency-Based Magnetic Biosensing

    Science.gov (United States)

    2017-01-31

    show the basic measurement setup (the field is applied perpendicular to the disk plane). A radiofrequency signal is injected across the disk (disks...shown in Fig. 7(a). A spectrum analyser (S.A.) (or a high frequency oscilloscope) is used to measure the radiofrequency STO output signal with Fig...crystals and, via electrical measurements , in magnetic-vortex-containing, isolated micro- and nano-devices. Via micromagnetic simulations, we have largely

  13. Pattern formation in arrays of chemical oscillators

    Indian Academy of Sciences (India)

    Chemical oscillators; phase flip; oscillation death. PACS No. 05.45 .... array oscillate (with varying amplitudes and frequencies), while the others experience oscillation death .... Barring the boundary cells, one observes near phase flip and near ...

  14. Phase inversion and frequency doubling of reflection high-energy electron diffraction intensity oscillations in the layer-by-layer growth of complex oxides

    Science.gov (United States)

    Mao, Zhangwen; Guo, Wei; Ji, Dianxiang; Zhang, Tianwei; Gu, Chenyi; Tang, Chao; Gu, Zhengbin; Nie*, Yuefeng; Pan, Xiaoqing

    In situ reflection high-energy electron diffraction (RHEED) and its intensity oscillations are extremely important for the growth of epitaxial thin films with atomic precision. The RHEED intensity oscillations of complex oxides are, however, rather complicated and a general model is still lacking. Here, we report the unusual phase inversion and frequency doubling of RHEED intensity oscillations observed in the layer-by-layer growth of SrTiO3 using oxide molecular beam epitaxy. In contacts to the common understanding that the maximum(minimum) intensity occurs at SrO(TiO2) termination, respectively, we found that both maximum or minimum intensities can occur at SrO, TiO2, or even incomplete terminations depending on the incident angle of the electron beam, which raises a fundamental question if one can rely on the RHEED intensity oscillations to precisely control the growth of thin films. A general model including surface roughness and termination dependent mean inner potential qualitatively explains the observed phenomena, and provides the answer to the question how to prepare atomically and chemically precise surface/interfaces using RHEED oscillations for complex oxides. We thank National Basic Research Program of China (No. 11574135, 2015CB654901) and the National Thousand-Young-Talents Program.

  15. Advanced Heat Transfer Studies in Superfluid Helium for Large-scale High-yield Production of Superconducting Radio Frequency Cavities

    CERN Document Server

    Peters, Benedikt J; Schirm, Karl-Martin; Koettig, Torsten

    Oscillating Superleak Transducers (OSTs) can be used to localize quenches in superconducting radio frequency cavities. In the presented work the occurring thermal effects during such events are investigated both theoretically and experimentally. In the theoretical part the entire heat transfer process from the heat generation to the detection is covered. The experimental part focuses on the effects in superfluid helium. Previous publications observed the detection of an OST signal that was faster than the second sound velocity. This fast propagation could be verified in dedicated small scale experiments. Resistors were used to simulate the quench spots under controlled conditions. The three dimensional propagation of second sound was linked to OST signals for the first time, which improves the understanding of the OST signal and allows to gather information about the heating pulse. Additionally, OSTs were used as a tool for quench localisation on a real size cavity. Their sensitivity as well as the time resol...

  16. Attention-induced deactivations in very low frequency EEG oscillations: differential localisation according to ADHD symptom status.

    Directory of Open Access Journals (Sweden)

    Samantha J Broyd

    Full Text Available BACKGROUND: The default-mode network (DMN is characterised by coherent very low frequency (VLF brain oscillations. The cognitive significance of this VLF profile remains unclear, partly because of the temporally constrained nature of the blood oxygen-level dependent (BOLD signal. Previously we have identified a VLF EEG network of scalp locations that shares many features of the DMN. Here we explore the intracranial sources of VLF EEG and examine their overlap with the DMN in adults with high and low ADHD ratings. METHODOLOGY/PRINCIPAL FINDINGS: DC-EEG was recorded using an equidistant 66 channel electrode montage in 25 adult participants with high- and 25 participants with low-ratings of ADHD symptoms during a rest condition and an attention demanding Eriksen task. VLF EEG power was calculated in the VLF band (0.02 to 0.2 Hz for the rest and task condition and compared for high and low ADHD participants. sLORETA was used to identify brain sources associated with the attention-induced deactivation of VLF EEG power, and to examine these sources in relation to ADHD symptoms. There was significant deactivation of VLF EEG power between the rest and task condition for the whole sample. Using s-LORETA the sources of this deactivation were localised to medial prefrontal regions, posterior cingulate cortex/precuneus and temporal regions. However, deactivation sources were different for high and low ADHD groups: In the low ADHD group attention-induced VLF EEG deactivation was most significant in medial prefrontal regions while for the high ADHD group this deactivation was predominantly localised to the temporal lobes. CONCLUSIONS/SIGNIFICANCE: Attention-induced VLF EEG deactivations have intracranial sources that appear to overlap with those of the DMN. Furthermore, these seem to be related to ADHD symptom status, with high ADHD adults failing to significantly deactivate medial prefrontal regions while at the same time showing significant attenuation of

  17. Nitric Oxide Modulation of Low-Frequency Oscillations in Cortical Vessels in FHM – a NIRS Study

    Science.gov (United States)

    Schytz, Henrik W.; Hansen, Jakob M.; Phillip, Dorte; Selb, Juliette; Boas, David A.; Ashina, Messoud

    2013-01-01

    Background The pathophysiological alterations in patients with familial hemiplegic migraine (FHM) are not yet fully known. The headache characteristics in patients with FHM mutations have been examined in a series of glyceryl trinitrate (GTN) provocation studies in FHM patients, but the cortical vascular response to GTN in FHM patients has never been investigated before. Objective To investigate changes in spontaneous low-frequency oscillations (LFO) of cortical vessels in response to the nitric oxide donor GTN by near-infrared spectroscopy in FHM patients. Methods Twenty-three FHM patients without known mutations and 9 healthy controls received a continuous intravenous infusion of GTN 0.5 μg/kg/minute over 20 minutes. Using near-infrared spectroscopy, we recorded oxygenated hemoglobin (oxyHb) LFO amplitude bilateral at the frontal cortex at baseline and 15 minutes and 40 minutes after start of the GTN infusion. Results GTN changed oxyHb LFO amplitude in FHM patients (P = .002), but not in healthy controls (P = .121). Only in FHM patients with coexisting common migraine types did GTN infusion induced changes in LFO amplitudes (P < .001), where post-hoc analysis revealed an increase in LFO amplitude 15 minutes (P = .003) and 40 (P = .013) minutes after start of infusion compared with baseline. Interestingly, GTN infusion induced no changes in LFO amplitude in patients with a pure FHM phenotype (P = .695). Conclusion FHM patients with a mixed phenotype (coexisting common type of migraine) showed an increase in oxyHb LFO amplitude during GTN infusion, whereas FHM patients with pure phenotype showed no changes. These data suggest possible differences in frontal cortical nitric oxide vascular sensitivity between FHM patients with a mixed phenotype and patients with pure FHM. PMID:22352839

  18. RIPPLELAB: A Comprehensive Application for the Detection, Analysis and Classification of High Frequency Oscillations in Electroencephalographic Signals

    Science.gov (United States)

    Alvarado-Rojas, Catalina; Le Van Quyen, Michel; Valderrama, Mario

    2016-01-01

    High Frequency Oscillations (HFOs) in the brain have been associated with different physiological and pathological processes. In epilepsy, HFOs might reflect a mechanism of epileptic phenomena, serving as a biomarker of epileptogenesis and epileptogenicity. Despite the valuable information provided by HFOs, their correct identification is a challenging task. A comprehensive application, RIPPLELAB, was developed to facilitate the analysis of HFOs. RIPPLELAB provides a wide range of tools for HFOs manual and automatic detection and visual validation; all of them are accessible from an intuitive graphical user interface. Four methods for automated detection—as well as several options for visualization and validation of detected events—were implemented and integrated in the application. Analysis of multiple files and channels is possible, and new options can be added by users. All features and capabilities implemented in RIPPLELAB for automatic detection were tested through the analysis of simulated signals and intracranial EEG recordings from epileptic patients (n = 16; 3,471 analyzed hours). Visual validation was also tested, and detected events were classified into different categories. Unlike other available software packages for EEG analysis, RIPPLELAB uniquely provides the appropriate graphical and algorithmic environment for HFOs detection (visual and automatic) and validation, in such a way that the power of elaborated detection methods are available to a wide range of users (experts and non-experts) through the use of this application. We believe that this open-source tool will facilitate and promote the collaboration between clinical and research centers working on the HFOs field. The tool is available under public license and is accessible through a dedicated web site. PMID:27341033

  19. High frequency chest wall oscillation for asthma and chronic obstructive pulmonary disease exacerbations: a randomized sham-controlled clinical trial

    Directory of Open Access Journals (Sweden)

    Lewis Stephanie

    2011-09-01

    Full Text Available Abstract Background High frequency chest wall oscillation (HFCWO is used for airway mucus clearance. The objective of this study was to evaluate the use of HFCWO early in the treatment of adults hospitalized for acute asthma or chronic obstructive pulmonary disease (COPD. Methods Randomized, multi-center, double-masked phase II clinical trial of active or sham treatment initiated within 24 hours of hospital admission for acute asthma or COPD at four academic medical centers. Patients received active or sham treatment for 15 minutes three times a day for four treatments. Medical management was standardized across groups. The primary outcomes were patient adherence to therapy after four treatments (minutes used/60 minutes prescribed and satisfaction. Secondary outcomes included change in Borg dyspnea score (≥ 1 unit indicates a clinically significant change, spontaneously expectorated sputum volume, and forced expired volume in 1 second. Results Fifty-two participants were randomized to active (n = 25 or sham (n = 27 treatment. Patient adherence was similarly high in both groups (91% vs. 93%; p = 0.70. Patient satisfaction was also similarly high in both groups. After four treatments, a higher proportion of patients in the active treatment group had a clinically significant improvement in dyspnea (70.8% vs. 42.3%, p = 0.04. There were no significant differences in other secondary outcomes. Conclusions HFCWO is well tolerated in adults hospitalized for acute asthma or COPD and significantly improves dyspnea. The high levels of patient satisfaction in both treatment groups justify the need for sham controls when evaluating the use of HFCWO on patient-reported outcomes. Additional studies are needed to more fully evaluate the role of HFCWO in improving in-hospital and post-discharge outcomes in this population. Trial Registration ClinicalTrials.gov: NCT00181285

  20. RIPPLELAB: A Comprehensive Application for the Detection, Analysis and Classification of High Frequency Oscillations in Electroencephalographic Signals.

    Directory of Open Access Journals (Sweden)

    Miguel Navarrete

    Full Text Available High Frequency Oscillations (HFOs in the brain have been associated with different physiological and pathological processes. In epilepsy, HFOs might reflect a mechanism of epileptic phenomena, serving as a biomarker of epileptogenesis and epileptogenicity. Despite the valuable information provided by HFOs, their correct identification is a challenging task. A comprehensive application, RIPPLELAB, was developed to facilitate the analysis of HFOs. RIPPLELAB provides a wide range of tools for HFOs manual and automatic detection and visual validation; all of them are accessible from an intuitive graphical user interface. Four methods for automated detection-as well as several options for visualization and validation of detected events-were implemented and integrated in the application. Analysis of multiple files and channels is possible, and new options can be added by users. All features and capabilities implemented in RIPPLELAB for automatic detection were tested through the analysis of simulated signals and intracranial EEG recordings from epileptic patients (n = 16; 3,471 analyzed hours. Visual validation was also tested, and detected events were classified into different categories. Unlike other available software packages for EEG analysis, RIPPLELAB uniquely provides the appropriate graphical and algorithmic environment for HFOs detection (visual and automatic and validation, in such a way that the power of elaborated detection methods are available to a wide range of users (experts and non-experts through the use of this application. We believe that this open-source tool will facilitate and promote the collaboration between clinical and research centers working on the HFOs field. The tool is available under public license and is accessible through a dedicated web site.

  1. Numerical Simulation of Unsteady Large Scale Separated Flow around Oscillating Airfoil

    OpenAIRE

    Isogai, Koji; 磯貝, 紘二

    1991-01-01

    Numerical simulations of dynamic stall phenomenon of NACA0012 airfoil oscillating in pitch near static stalling angle are performed by using the compressible Navier-Stokes equations. In the present computations, a TVD scheme and an algebraic turbulence model are employed for the simulations of the unsteady separated flows at Reynolds number of 1.1x105. The hysteresis loops of the unsteady pitching moment during dynamic stall are compared with the existing experimental data. The flow pattern a...

  2. Updated Global Analysis of Neutrino Oscillations in the Presence of eV-Scale Sterile Neutrinos

    Energy Technology Data Exchange (ETDEWEB)

    Dentler, Mona [U. Mainz, PRISMA; Hernández-Cabezudo, Alvaro [KIT, Karlsruhe, IKP; Kopp, Joachim [CERN; Machado, Pedro [Fermilab; Maltoni, Michele [Madrid, IFT; Martinez-Soler, Ivan [Madrid, IFT; Schwetz, Thomas [KIT, Karlsruhe, IKP

    2018-03-28

    We discuss the possibility to explain the anomalies in short-baseline neutrino oscillation experiments in terms of sterile neutrinos. We work in a 3+1 framework and pay special attention to recent new data from reactor experiments, IceCube and MINOS+. We find that results from the DANSS and NEOS reactor experiments support the sterile neutrino explanation of the reactor anomaly, based on an analysis that relies solely on the relative comparison of measured reactor spectra. Global data from the $\

  3. Study of the B$_{s}^{0}\\overline{B}_{s}^{0}$ oscillation frequency using D$_{s}^{-}$l$^{+}$ combinations in Z decays

    CERN Document Server

    Buskulic, Damir; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Minard, M N; Odier, P; Pietrzyk, B; Casado, M P; Chmeissani, M; Crespo, J M; Delfino, M C; Efthymiopoulos, I; Fernández, E; Fernández-Bosman, M; Garrido, L; Juste, A; Martínez, M; Orteu, S; Pacheco, A; Padilla, C; Pascual, A; Perlas, J A; Riu, I; Sánchez, F; Teubert, F; Colaleo, A; Creanza, D; De Palma, M; Gelao, G; Girone, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Marinelli, N; Nuzzo, S; Ranieri, A; Raso, G; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Alemany, R; Bazarko, A O; Bonvicini, G; Cattaneo, M; Comas, P; Coyle, P; Drevermann, H; Forty, Roger W; Frank, M; Hagelberg, R; Harvey, J; Janot, P; Jost, B; Kneringer, E; Knobloch, J; Lehraus, Ivan; Lutters, G; Martin, E B; Mato, P; Minten, Adolf G; Miquel, R; Moneta, L; Oest, T; Pater, J R; Pusztaszeri, J F; Ranjard, F; Rensing, P E; Rolandi, Luigi; Schlatter, W D; Schmelling, M; Schneider, O; Tejessy, W; Tomalin, I R; Venturi, A; Wachsmuth, H W; Wagner, A; Wildish, T; Ajaltouni, Ziad J; Barrès, A; Boyer, C; Falvard, A; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rossignol, J M; Fearnley, Tom; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Wäänänen, A; Kyriakis, A; Markou, C; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Zachariadou, K; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Rougé, A; Rumpf, M; Valassi, Andrea; Verderi, M; Videau, H L; Candlin, D J; Parsons, M I; Focardi, E; Parrini, G; Corden, M; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Casper, David William; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Curtis, L; Dorris, S J; Halley, A W; Knowles, I G; Lynch, J G; O'Shea, V; Raine, C; Reeves, P; Scarr, J M; Smith, K; Thompson, A S; Thomson, F; Thorn, S; Turnbull, R M; Becker, U; Geweniger, C; Graefe, G; Hanke, P; Hansper, G; Hepp, V; Kluge, E E; Putzer, A; Rensch, B; Schmidt, M; Sommer, J; Stenzel, H; Tittel, K; Werner, S; Wunsch, M; Abbaneo, D; Beuselinck, R; Binnie, David M; Cameron, W; Dornan, Peter J; Moutoussi, A; Nash, J; Sedgbeer, J K; Stacey, A M; Williams, M D; Dissertori, G; Girtler, P; Kuhn, D; Rudolph, G; Betteridge, A P; Bowdery, C K; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Sloan, Terence; Williams, M I; Galla, A; Greene, A M; Kleinknecht, K; Quast, G; Renk, B; Rohne, E; Sander, H G; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Bencheikh, A M; Benchouk, C; Bonissent, A; Bujosa, G; Calvet, D; Carr, J; Diaconu, C A; Etienne, F; Konstantinidis, N P; Payre, P; Rousseau, D; Talby, M; Sadouki, A; Thulasidas, M; Trabelsi, K; Aleppo, M; Ragusa, F; Abt, I; Assmann, R W; Bauer, C; Blum, Walter; Dietl, H; Dydak, Friedrich; Ganis, G; Gotzhein, C; Jakobs, K; Kroha, H; Lütjens, G; Lutz, Gerhard; Männer, W; Moser, H G; Richter, R H; Rosado-Schlosser, A; Schael, S; Settles, Ronald; Seywerd, H C J; Saint-Denis, R; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Cordier, A; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Jacquet, M; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Nikolic, I A; Park, H J; Park, I C; Schune, M H; Simion, S; Veillet, J J; Videau, I; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Ciulli, V; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Palla, Fabrizio; Rizzo, G; Sanguinetti, G; Sciabà, A; Spagnolo, P; Steinberger, Jack; Tenchini, Roberto; Tonelli, G; Vannini, C; Verdini, P G; Walsh, J; Blair, G A; Bryant, L M; Cerutti, F; Chambers, J T; Gao, Y; Green, M G; Medcalf, T; Perrodo, P; Strong, J A; Von Wimmersperg-Töller, J H; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Maley, P; Norton, P R; Thompson, J C; Wright, A E; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Marx, B; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Black, S N; Dann, J H; Johnson, R P; Kim, H Y; Litke, A M; McNeil, M A; Taylor, G; Booth, C N; Boswell, R; Brew, C A J; Cartwright, S L; Combley, F; Köksal, A; Lehto, M H; Newton, W M; Reeve, J; Thompson, L F; Böhrer, A; Brandt, S; Büscher, V; Cowan, G D; Grupen, Claus; Minguet-Rodríguez, J A; Rivera, F; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Musolino, G; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Bellantoni, L; Elmer, P; Feng, Z; Ferguson, D P S; Gao, Y S; González, S; Grahl, J; Greening, T C; Harton, J L; Hayes, O J; Hu, H; McNamara, P A; Nachtman, J M; Orejudos, W; Pan, Y B; Saadi, Y; Schmitt, M; Scott, I J; Sharma, V; Walsh, A M; Wu Sau Lan; Wu, X; Yamartino, J M; Zheng, M; Zobernig, G

    1996-01-01

    A lower limit on the oscillation frequency of the BsBsbar system is obtained from approximately four million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1995. Leptons are combined with opposite sign Ds- candidates reconstructed in seven different decay modes as evidence of semileptonic Bs decays. Criteria designed to ensure precise proper time reconstruction select 277 Ds-,l+ combinations. The initial state of these Bs candidates is determined using an algorithm optimized to efficiently utilise the tagging information available for each event. The limit at 95\\% confidence level on the BsBsbar oscillation frequency is delta_m_s > 6.6 ps^-1. The same data is used to update the measurement of the Bs lifetime, tau_s = 1.54 +0.14 (stat) +0.04 (syst) ps. -0.13 -0.04

  4. Precision measurement of the $B^0_s - \\bar{B}^0_s$ oscillation frequency with the decay $B^0_s \\to D^-_s \\pi^+$

    CERN Document Server

    Aaij, R; Adeva, B; Adinolfi, M; Adrover, C; Affolder, A; Ajaltouni, Z; Albrecht, J; Alessio, F; Alexander, M; Ali, S; Alkhazov, G; Alvarez Cartelle, P; Alves Jr, A A; Amato, S; Amerio, S; Amhis, Y; Anderlini, L; Anderson, J; Andreassen, R; Appleby, R B; Aquines Gutierrez, O; Archilli, F; Artamonov, A; Artuso, M; Aslanides, E; Auriemma, G; Bachmann, S; Back, J J; Baesso, C; Balagura, V; Baldini, W; Barlow, R J; Barschel, C; Barsuk, S; Barter, W; Bauer, Th; Bay, A; Beddow, J; Bedeschi, F; Bediaga, I; Belogurov, S; Belous, K; Belyaev, I; Ben-Haim, E; Benayoun, M; Bencivenni, G; Benson, S; Benton, J; Berezhnoy, A; Bernet, R; Bettler, M -O; van Beuzekom, M; Bien, A; Bifani, S; Bird, T; Bizzeti, A; Bjørnstad, P M; Blake, T; Blanc, F; Blouw, J; Blusk, S; Bocci, V; Bondar, A; Bondar, N; Bonivento, W; Borghi, S; Borgia, A; Bowcock, T J V; Bowen, E; Bozzi, C; Brambach, T; van den Brand, J; Bressieux, J; Brett, D; Britsch, M; Britton, T; Brook, N H; Brown, H; Burducea, I; Bursche, A; Busetto, G; Buytaert, J; Cadeddu, S; Callot, O; Calvi, M; Calvo Gomez, M; Camboni, A; Campana, P; Campora Perez, D; Carbone, A; Carboni, G; Cardinale, R; Cardini, A; Carranza-Mejia, H; Carson, L; Carvalho Akiba, K; Casse, G; Cattaneo, M; Cauet, Ch; Charles, M; Charpentier, Ph; Chen, P; Chiapolini, N; Chrzaszcz, M; Ciba, K; Cid Vidal, X; Ciezarek, G; Clarke, P E L; Clemencic, M; Cliff, H V; Closier, J; Coca, C; Coco, V; Cogan, J; Cogneras, E; Collins, P; Comerma-Montells, A; Contu, A; Cook, A; Coombes, M; Coquereau, S; Corti, G; Couturier, B; Cowan, G A; Craik, D C; Cunliffe, S; Currie, R; D'Ambrosio, C; David, P; David, P N Y; De Bonis, I; De Bruyn, K; De Capua, S; De Cian, M; De Miranda, J M; De Paula, L; De Silva, W; De Simone, P; Decamp, D; Deckenhoff, M; Del Buono, L; Derkach, D; Deschamps, O; Dettori, F; Di Canto, A; Dijkstra, H; Dogaru, M; Donleavy, S; Dordei, F; Dosil Suárez, A; Dossett, D; Dovbnya, A; Dupertuis, F; Dzhelyadin, R; Dziurda, A; Dzyuba, A; Easo, S; Egede, U; Egorychev, V; Eidelman, S; van Eijk, D; Eisenhardt, S; Eitschberger, U; Ekelhof, R; Eklund, L; El Rifai, I; Elsasser, Ch; Elsby, D; Falabella, A; Färber, C; Fardell, G; Farinelli, C; Farry, S; Fave, V; Ferguson, D; Fernandez Albor, V; Ferreira Rodrigues, F; Ferro-Luzzi, M; Filippov, S; Fiore, M; Fitzpatrick, C; Fontana, M; Fontanelli, F; Forty, R; Francisco, O; Frank, M; Frei, C; Frosini, M; Furcas, S; Furfaro, E; Gallas Torreira, A; Galli, D; Gandelman, M; Gandini, P; Gao, Y; Garofoli, J; Garosi, P; Garra Tico, J; Garrido, L; Gaspar, C; Gauld, R; Gersabeck, E; Gersabeck, M; Gershon, T; Ghez, Ph; Gibson, V; Gligorov, V V; Göbel, C; Golubkov, D; Golutvin, A; Gomes, A; Gordon, H; Grabalosa Gándara, M; Graciani Diaz, R; Granado Cardoso, L A; Graugés, E; Graziani, G; Grecu, A; Greening, E; Gregson, S; Grünberg, O; Gui, B; Gushchin, E; Guz, Yu; Gys, T; Hadjivasiliou, C; Haefeli, G; Haen, C; Haines, S C; Hall, S; Hampson, T; Hansmann-Menzemer, S; Harnew, N; Harnew, S T; Harrison, J; Hartmann, T; He, J; Heijne, V; Hennessy, K; Henrard, P; Hernando Morata, J A; van Herwijnen, E; Hicks, E; Hill, D; Hoballah, M; Hombach, C; Hopchev, P; Hulsbergen, W; Hunt, P; Huse, T; Hussain, N; Hutchcroft, D; Hynds, D; Iakovenko, V; Idzik, M; Ilten, P; Jacobsson, R; Jaeger, A; Jans, E; Jaton, P; Jing, F; John, M; Johnson, D; Jones, C R; Jost, B; Kaballo, M; Kandybei, S; Karacson, M; Karbach, T M; Kenyon, I R; Kerzel, U; Ketel, T; Keune, A; Khanji, B; Kochebina, O; Komarov, I; Koopman, R F; Koppenburg, P; Korolev, M; Kozlinskiy, A; Kravchuk, L; Kreplin, K; Kreps, M; Krocker, G; Krokovny, P; Kruse, F; Kucharczyk, M; Kudryavtsev, V; Kvaratskheliya, T; La Thi, V N; Lacarrere, D; Lafferty, G; Lai, A; Lambert, D; Lambert, R W; Lanciotti, E; Lanfranchi, G; Langenbruch, C; Latham, T; Lazzeroni, C; Le Gac, R; van Leerdam, J; Lees, J -P; Lefèvre, R; Leflat, A; Lefrançois, J; Leo, S; Leroy, O; Lesiak, T; Leverington, B; Li, Y; Li Gioi, L; Liles, M; Lindner, R; Linn, C; Liu, B; Liu, G; Lohn, S; Longstaff, I; Lopes, J H; Lopez Asamar, E; Lopez-March, N; Lu, H; Lucchesi, D; Luisier, J; Luo, H; Machefert, F; Machikhiliyan, I V; Maciuc, F; Maev, O; Malde, S; Manca, G; Mancinelli, G; Marconi, U; Märki, R; Marks, J; Martellotti, G; Martens, A; Martin, L; Martín Sánchez, A; Martinelli, M; Martinez Santos, D; Martins Tostes, D; Massafferri, A; Matev, R; Mathe, Z; Matteuzzi, C; Maurice, E; Mazurov, A; McCarthy, J; McNab, A; McNulty, R; Meadows, B; Meier, F; Meissner, M; Merk, M; Milanes, D A; Minard, M -N; Molina Rodriguez, J; Monteil, S; Moran, D; Morawski, P; Morello, M J; Mountain, R; Mous, I; Muheim, F; Müller, K; Muresan, R; Muryn, B; Muster, B; Naik, P; Nakada, T; Nandakumar, R; Nasteva, I; Needham, M; Neufeld, N; Nguyen, A D; Nguyen, T D; Nguyen-Mau, C; Nicol, M; Niess, V; Niet, R; Nikitin, N; Nikodem, T; Nomerotski, A; Novoselov, A; Oblakowska-Mucha, A; Obraztsov, V; Oggero, S; Ogilvy, S; Okhrimenko, O; Oldeman, R; Orlandea, M; Otalora Goicochea, J M; Owen, P; Oyanguren, A; Pal, B K; Palano, A; Palutan, M; Panman, J; Papanestis, A; Pappagallo, M; Parkes, C; Parkinson, C J; Passaleva, G; Patel, G D; Patel, M; Patrick, G N; Patrignani, C; Pavel-Nicorescu, C; Pazos Alvarez, A; Pellegrino, A; Penso, G; Pepe Altarelli, M; Perazzini, S; Perego, D L; Perez Trigo, E; Pérez-Calero Yzquierdo, A; Perret, P; Perrin-Terrin, M; Pessina, G; Petridis, K; Petrolini, A; Phan, A; Picatoste Olloqui, E; Pietrzyk, B; Pilař, T; Pinci, D; Playfer, S; Plo Casasus, M; Polci, F; Polok, G; Poluektov, A; Polycarpo, E; Popov, D; Popovici, B; Potterat, C; Powell, A; Prisciandaro, J; Pugatch, V; Puig Navarro, A; Punzi, G; Qian, W; Rademacker, J H; Rakotomiaramanana, B; Rangel, M S; Raniuk, I; Rauschmayr, N; Raven, G; Redford, S; Reid, M M; dos Reis, A C; Ricciardi, S; Richards, A; Rinnert, K; Rives Molina, V; Roa Romero, D A; Robbe, P; Rodrigues, E; Rodriguez Perez, P; Roiser, S; Romanovsky, V; Romero Vidal, A; Rouvinet, J; Ruf, T; Ruffini, F; Ruiz, H; Ruiz Valls, P; Sabatino, G; Saborido Silva, J J; Sagidova, N; Sail, P; Saitta, B; Salzmann, C; Sanmartin Sedes, B; Sannino, M; Santacesaria, R; Santamarina Rios, C; Santovetti, E; Sapunov, M; Sarti, A; Satriano, C; Satta, A; Savrie, M; Savrina, D; Schaack, P; Schiller, M; Schindler, H; Schlupp, M; Schmelling, M; Schmidt, B; Schneider, O; Schopper, A; Schune, M -H; Schwemmer, R; Sciascia, B; Sciubba, A; Seco, M; Semennikov, A; Senderowska, K; Sepp, I; Serra, N; Serrano, J; Seyfert, P; Shapkin, M; Shapoval, I; Shatalov, P; Shcheglov, Y; Shears, T; Shekhtman, L; Shevchenko, O; Shevchenko, V; Shires, A; Silva Coutinho, R; Skwarnicki, T; Smith, N A; Smith, E; Smith, M; Sokoloff, M D; Soler, F J P; Soomro, F; Souza, D; Souza De Paula, B; Spaan, B; Sparkes, A; Spradlin, P; Stagni, F; Stahl, S; Steinkamp, O; Stoica, S; Stone, S; Storaci, B; Straticiuc, M; Straumann, U; Subbiah, V K; Swientek, S; Syropoulos, V; Szczekowski, M; Szczypka, P; Szumlak, T; T'Jampens, S; Teklishyn, M; Teodorescu, E; Teubert, F; Thomas, C; Thomas, E; van Tilburg, J; Tisserand, V; Tobin, M; Tolk, S; Tonelli, D; Topp-Joergensen, S; Torr, N; Tournefier, E; Tourneur, S; Tran, M T; Tresch, M; Tsaregorodtsev, A; Tsopelas, P; Tuning, N; Ubeda Garcia, M; Ukleja, A; Urner, D; Uwer, U; Vagnoni, V; Valenti, G; Vazquez Gomez, R; Vazquez Regueiro, P; Vecchi, S; Velthuis, J J; Veltri, M; Veneziano, G; Vesterinen, M; Viaud, B; Vieira, D; Vilasis-Cardona, X; Vollhardt, A; Volyanskyy, D; Voong, D; Vorobyev, A; Vorobyev, V; Voß, C; Voss, H; Waldi, R; Wallace, R; Wandernoth, S; Wang, J; Ward, D R; Watson, N K; Webber, A D; Websdale, D; Whitehead, M; Wicht, J; Wiechczynski, J; Wiedner, D; Wiggers, L; Wilkinson, G; Williams, M P; Williams, M; Wilson, F F; Wishahi, J; Witek, M; Wotton, S A; Wright, S; Wu, S; Wyllie, K; Xie, Y; Xing, F; Xing, Z; Yang, Z; Young, R; Yuan, X; Yushchenko, O; Zangoli, M; Zavertyaev, M; Zhang, F; Zhang, L; Zhang, W C; Zhang, Y; Zhelezov, A; Zhokhov, A; Zhong, L; Zvyagin, A

    2013-01-01

    A key ingredient to searches for physics beyond the Standard Model in $B^{0}_{s}$ mixing phenomena is the measurement of the $B^{0}_{s}$-$\\bar{B}^{0}_{s}$ oscillation frequency, which is equivalent to the mass difference $\\Delta m_{s}$ of the $B^{0}_{s}$ mass eigenstates. Using the world's largest $B^{0}_{s}$ meson sample accumulated in a dataset, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment at the CERN LHC in 2011, a measurement of $\\Delta m_{s}$ is presented. A total of about 34,000 $B^{0}_{s}\\rightarrow D^{-}_{s}\\pi^{+}$ signal decays are reconstructed, with an average decay time resolution of 44 fs. The oscillation frequency is measured to be $\\Delta m_{s}$ = 17.768 $\\pm$ 0.023 (stat) $\\pm$ 0.006 (syst) ps$^{-1}$}, which is the most precise measurement to date.

  5. Contribution of large-scale circulation anomalies to changes in extreme precipitation frequency in the United States

    International Nuclear Information System (INIS)

    Yu, Lejiang; Zhong, Shiyuan; Pei, Lisi; Bian, Xindi; Heilman, Warren E

    2016-01-01

    The mean global climate has warmed as a result of the increasing emission of greenhouse gases induced by human activities. This warming is considered the main reason for the increasing number of extreme precipitation events in the US. While much attention has been given to extreme precipitation events occurring over several days, which are usually responsible for severe flooding over a large region, little is known about how extreme precipitation events that cause flash flooding and occur at sub-daily time scales have changed over time. Here we use the observed hourly precipitation from the North American Land Data Assimilation System Phase 2 forcing datasets to determine trends in the frequency of extreme precipitation events of short (1 h, 3 h, 6 h, 12 h and 24 h) duration for the period 1979–2013. The results indicate an increasing trend in the central and eastern US. Over most of the western US, especially the Southwest and the Intermountain West, the trends are generally negative. These trends can be largely explained by the interdecadal variability of the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation (AMO), with the AMO making a greater contribution to the trends in both warm and cold seasons. (letter)

  6. Sinusoidal oscillators with lower gain requirements at higher frequencies based on an explicit tanh(x) nonlinearity

    KAUST Repository

    Elwakil, Ahmed S.; Ozoguz, Serdar; Salama, Khaled N.

    2009-01-01

    model for the two oscillators is derived and verified numerically. Spice simulations using AMS BiCMOS 0.35 μ model parameters and experimental results are shown. Copyright © 2009 John Wiley & Sons, Ltd.

  7. Sensory information in local field potentials and spikes from visual and auditory cortices: time scales and frequency bands.

    Science.gov (United States)

    Belitski, Andrei; Panzeri, Stefano; Magri, Cesare; Logothetis, Nikos K; Kayser, Christoph

    2010-12-01

    Studies analyzing sensory cortical processing or trying to decode brain activity often rely on a combination of different electrophysiological signals, such as local field potentials (LFPs) and spiking activity. Understanding the relation between these signals and sensory stimuli and between different components of these signals is hence of great interest. We here provide an analysis of LFPs and spiking activity recorded from visual and auditory cortex during stimulation with natural stimuli. In particular, we focus on the time scales on which different components of these signals are informative about the stimulus, and on the dependencies between different components of these signals. Addressing the first question, we find that stimulus information in low frequency bands (50 Hz), in contrast, is scale dependent, and is larger when the energy is averaged over several hundreds of milliseconds. Indeed, combined analysis of signal reliability and information revealed that the energy of slow LFP fluctuations is well related to the stimulus even when considering individual or few cycles, while the energy of fast LFP oscillations carries information only when averaged over many cycles. Addressing the second question, we find that stimulus information in different LFP bands, and in different LFP bands and spiking activity, is largely independent regardless of time scale or sensory system. Taken together, these findings suggest that different LFP bands represent dynamic natural stimuli on distinct time scales and together provide a potentially rich source of information for sensory processing or decoding brain activity.

  8. The influence of sea surface temperature anomalies on low-frequency variability of the North Atlantic Oscillation

    Energy Technology Data Exchange (ETDEWEB)

    Manganello, Julia V. [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States)

    2008-05-15

    The influence of sea surface temperature anomalies (SSTA) on multi-year persistence of the North Atlantic Oscillation (NAO) during the second half of the twentieth century is investigated using the Center for Ocean-Land-Atmosphere Studies (COLA) Atmospheric GCM (AGCM) with an emphasis on isolating the geographic location of the SSTA that produce this influence. The present study focuses on calculating the atmospheric response to the SSTA averaged over 1988-1995 (1961-1968) corresponding to the observed period of strong persistence of the positive (negative) phase of the decadal NAO. The model response to the global 1988-1995 average SSTA shows a statistically significant large-scale pattern characteristic of the positive phase of the NAO. Forcing with the global 1961-1968 average SSTA generates a NAO of the opposite polarity compared to observations. However, all large-scale features both in the model and observations during this period are weaker in magnitude and less significant compared to 1988-1995. Additional idealized experiments show that over the northern center of the NAO the non-linear component of the forced response appears to be quite important and acts to enhance the positive NAO signal. On the other hand, over the southern center where the model response is the strongest, it is also essentially linear. The 1988-1995 average SSTA restricted to the western tropical Pacific region produce a positive NAO remarkably similar in structure but stronger in magnitude than the model response to the global and tropical Indo-Pacific 1988-1995 forcing. A 200-hPa geopotential height response in these experiments shows a positive anomaly over the southern center of the NAO embedded in the Rossby wave trains propagating from the western tropical Pacific. Indian Ocean SSTA lead to much weaker positive NAO primarily through the effect on its northern center. SST forcing confined to the North Atlantic north of equator does not produce a response statistically different

  9. Seizure-induced alterations in fast-spiking basket cell GABA currents modulate frequency and coherence of gamma oscillation in network simulations

    Energy Technology Data Exchange (ETDEWEB)

    Proddutur, Archana; Yu, Jiandong; Elgammal, Fatima S. [Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, Newark, New Jersey 07103 (United States); Santhakumar, Vijayalakshmi, E-mail: santhavi@njms.rutgers.edu [Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, Newark, New Jersey 07103 (United States); Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, Newark, New Jersey 07103 (United States)

    2013-12-15

    Gamma frequency oscillations have been proposed to contribute to memory formation and retrieval. Fast-spiking basket cells (FS-BCs) are known to underlie development of gamma oscillations. Fast, high amplitude GABA synapses and gap junctions have been suggested to contribute to gamma oscillations in FS-BC networks. Recently, we identified that, apart from GABAergic synapses, FS-BCs in the hippocampal dentate gyrus have GABAergic currents mediated by extrasynaptic receptors. Our experimental studies demonstrated two specific changes in FS-BC GABA currents following experimental seizures [Yu et al., J. Neurophysiol. 109, 1746 (2013)]: increase in the magnitude of extrasynaptic (tonic) GABA currents and a depolarizing shift in GABA reversal potential (E{sub GABA}). Here, we use homogeneous networks of a biophysically based model of FS-BCs to examine how the presence of extrasynaptic GABA conductance (g{sub GABA-extra}) and experimentally identified, seizure-induced changes in g{sub GABA-extra} and E{sub GABA} influence network activity. Networks of FS-BCs interconnected by fast GABAergic synapses developed synchronous firing in the dentate gamma frequency range (40–100 Hz). Systematic investigation revealed that the biologically realistic range of 30 to 40 connections between FS-BCs resulted in greater coherence in the gamma frequency range when networks were activated by Poisson-distributed dendritic synaptic inputs rather than by homogeneous somatic current injections, which were balanced for FS-BC firing frequency in unconnected networks. Distance-dependent conduction delay enhanced coherence in networks with 30–40 FS-BC interconnections while inclusion of gap junctional conductance had a modest effect on coherence. In networks activated by somatic current injections resulting in heterogeneous FS-BC firing, increasing g{sub GABA-extra} reduced the frequency and coherence of FS-BC firing when E{sub GABA} was shunting (−74 mV), but failed to alter average

  10. Seizure-induced alterations in fast-spiking basket cell GABA currents modulate frequency and coherence of gamma oscillation in network simulations

    International Nuclear Information System (INIS)

    Proddutur, Archana; Yu, Jiandong; Elgammal, Fatima S.; Santhakumar, Vijayalakshmi

    2013-01-01

    Gamma frequency oscillations have been proposed to contribute to memory formation and retrieval. Fast-spiking basket cells (FS-BCs) are known to underlie development of gamma oscillations. Fast, high amplitude GABA synapses and gap junctions have been suggested to contribute to gamma oscillations in FS-BC networks. Recently, we identified that, apart from GABAergic synapses, FS-BCs in the hippocampal dentate gyrus have GABAergic currents mediated by extrasynaptic receptors. Our experimental studies demonstrated two specific changes in FS-BC GABA currents following experimental seizures [Yu et al., J. Neurophysiol. 109, 1746 (2013)]: increase in the magnitude of extrasynaptic (tonic) GABA currents and a depolarizing shift in GABA reversal potential (E GABA ). Here, we use homogeneous networks of a biophysically based model of FS-BCs to examine how the presence of extrasynaptic GABA conductance (g GABA-extra ) and experimentally identified, seizure-induced changes in g GABA-extra and E GABA influence network activity. Networks of FS-BCs interconnected by fast GABAergic synapses developed synchronous firing in the dentate gamma frequency range (40–100 Hz). Systematic investigation revealed that the biologically realistic range of 30 to 40 connections between FS-BCs resulted in greater coherence in the gamma frequency range when networks were activated by Poisson-distributed dendritic synaptic inputs rather than by homogeneous somatic current injections, which were balanced for FS-BC firing frequency in unconnected networks. Distance-dependent conduction delay enhanced coherence in networks with 30–40 FS-BC interconnections while inclusion of gap junctional conductance had a modest effect on coherence. In networks activated by somatic current injections resulting in heterogeneous FS-BC firing, increasing g GABA-extra reduced the frequency and coherence of FS-BC firing when E GABA was shunting (−74 mV), but failed to alter average FS-BC frequency when E GABA

  11. Ancillary Frequency Control of Direct Drive Full-Scale Converter Based Wind Power Plants

    DEFF Research Database (Denmark)

    Hu, Weihao; Su, Chi; Fang, Jiakun

    2013-01-01

    This paper presents a simulation model of a wind power plant based on a MW-level variable speed wind turbine with a full-scale back-to-back power converter developed in the simulation tool of DIgSILENT Power Factory. Three different kinds of ancillary frequency control strategies, namely inertia...... control strategies are effective means for providing ancillary frequency control of variable speed wind turbines with full-scale back-to-back power converters....... emulation, primary frequency control and secondary frequency control, are proposed in order to improve the frequency stability of power systems. The modified IEEE 39-bus test system with a large-scale wind power penetration is chosen as the studied power system. Simulation results show that the proposed...

  12. Low-frequency scaling applied to stochastic finite-fault modeling

    Science.gov (United States)

    Crane, Stephen; Motazedian, Dariush

    2014-01-01

    Stochastic finite-fault modeling is an important tool for simulating moderate to large earthquakes. It has proven to be useful in applications that require a reliable estimation of ground motions, mostly in the spectral frequency range of 1 to 10 Hz, which is the range of most interest to engineers. However, since there can be little resemblance between the low-frequency spectra of large and small earthquakes, this portion can be difficult to simulate using stochastic finite-fault techniques. This paper introduces two different methods to scale low-frequency spectra for stochastic finite-fault modeling. One method multiplies the subfault source spectrum by an empirical function. This function has three parameters to scale the low-frequency spectra: the level of scaling and the start and end frequencies of the taper. This empirical function adjusts the earthquake spectra only between the desired frequencies, conserving seismic moment in the simulated spectra. The other method is an empirical low-frequency coefficient that is added to the subfault corner frequency. This new parameter changes the ratio between high and low frequencies. For each simulation, the entire earthquake spectra is adjusted, which may result in the seismic moment not being conserved for a simulated earthquake. These low-frequency scaling methods were used to reproduce recorded earthquake spectra from several earthquakes recorded in the Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation Models (NGA) database. There were two methods of determining the stochastic parameters of best fit for each earthquake: a general residual analysis and an earthquake-specific residual analysis. Both methods resulted in comparable values for stress drop and the low-frequency scaling parameters; however, the earthquake-specific residual analysis obtained a more accurate distribution of the averaged residuals.

  13. Climatic signals and frequencies in the Swedish Time Scale, River Aangermanaelven, Central Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Sander, Mikkel

    2003-03-01

    to attribute some of the variation in the reconstructed Qmax to snow accumulation changes. The reconstructed Qmax series holds a centennial length waveform, which is interpreted in terms of the late Holocene climate succession, i.e. the Roman Warm Period, Dark Ages Cold Period, Medieval Warm Period, Little Ice Age and Contemporary Warm Period. Non-stationary frequencies in the sub decadal, decadal and centennial bands have been detected in the 2000 year long geometric mean varve series. Sub decadal frequencies are tentatively interpreted as forced by the North Atlantic Oscillation. Decadal frequencies are interpreted as sunspot forcing. Centennial frequencies are tentative interpreted as Suess cycle forcing. Missing varves in the STS (minimum 500 years) have previously been postulated on the grounds of an independent calibrated radiocarbon calendar age obtained from varve deposits and its correlation to the GRIP Ice Core. However, an evaluation of the STS by cross correlation does not support the presence of a centennial error in the post glacial part of STS. Additional analyses on the relationship between reconstructed discharge and other climate (-derived) proxies have been tested, including temperature, tree rings, atmospheric indices, sea-ice extent, C-14 production variation, global temperature reconstructions and volcanic eruptions. These analyses were mostly internally contradictive and non-conclusive.

  14. Large scale modulation of high frequency acoustic waves in periodic porous media.

    Science.gov (United States)

    Boutin, Claude; Rallu, Antoine; Hans, Stephane

    2012-12-01

    This paper deals with the description of the modulation at large scale of high frequency acoustic waves in gas saturated periodic porous media. High frequencies mean local dynamics at the pore scale and therefore absence of scale separation in the usual sense of homogenization. However, although the pressure is spatially varying in the pores (according to periodic eigenmodes), the mode amplitude can present a large scale modulation, thereby introducing another type of scale separation to which the asymptotic multi-scale procedure applies. The approach is first presented on a periodic network of inter-connected Helmholtz resonators. The equations governing the modulations carried by periodic eigenmodes, at frequencies close to their eigenfrequency, are derived. The number of cells on which the carrying periodic mode is defined is therefore a parameter of the modeling. In a second part, the asymptotic approach is developed for periodic porous media saturated by a perfect gas. Using the "multicells" periodic condition, one obtains the family of equations governing the amplitude modulation at large scale of high frequency waves. The significant difference between modulations of simple and multiple mode are evidenced and discussed. The features of the modulation (anisotropy, width of frequency band) are also analyzed.

  15. Combining agreement and frequency rating scales to optimize psychometrics in measuring behavioral health functioning.

    Science.gov (United States)

    Marfeo, Elizabeth E; Ni, Pengsheng; Chan, Leighton; Rasch, Elizabeth K; Jette, Alan M

    2014-07-01

    The goal of this article was to investigate optimal functioning of using frequency vs. agreement rating scales in two subdomains of the newly developed Work Disability Functional Assessment Battery: the Mood & Emotions and Behavioral Control scales. A psychometric study comparing rating scale performance embedded in a cross-sectional survey used for developing a new instrument to measure behavioral health functioning among adults applying for disability benefits in the United States was performed. Within the sample of 1,017 respondents, the range of response category endorsement was similar for both frequency and agreement item types for both scales. There were fewer missing values in the frequency items than the agreement items. Both frequency and agreement items showed acceptable reliability. The frequency items demonstrated optimal effectiveness around the mean ± 1-2 standard deviation score range; the agreement items performed better at the extreme score ranges. Findings suggest an optimal response format requires a mix of both agreement-based and frequency-based items. Frequency items perform better in the normal range of responses, capturing specific behaviors, reactions, or situations that may elicit a specific response. Agreement items do better for those whose scores are more extreme and capture subjective content related to general attitudes, behaviors, or feelings of work-related behavioral health functioning. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Single ICCII Sinusoidal Oscillators Employing Grounded Capacitors

    Directory of Open Access Journals (Sweden)

    J. W. Horng

    2011-09-01

    Full Text Available Two inverting second-generation current conveyors (ICCII based sinusoidal oscillators are presented. The first sinusoidal oscillator is composed of one ICCII, two grounded capacitors and two resistors. The oscillation condition and oscillation frequency can be orthogonally controllable. The second sinusoidal oscillator is composed of one ICCII, two grounded capacitors and three resistors. The oscillation condition and oscillation frequency can be independently controllable through different resistors.

  17. Gate-Recessed AlGaN/GaN MOSHEMTs with the Maximum Oscillation Frequency Exceeding 120 GHz on Sapphire Substrates

    International Nuclear Information System (INIS)

    Kong Xin; Wei Ke; Liu Guo-Guo; Liu Xin-Yu

    2012-01-01

    Gate-recessed AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) on sapphire substrates are fabricated. The devices with a gate length of 160 nm and a gate periphery of 2 × 75 μm exhibit two orders of magnitude reduction in gate leakage current and enhanced off-state breakdown characteristics, compared with conventional HEMTs. Furthermore, the extrinsic transconductance of an MOSHEMT is 237.2 mS/mm, only 7% lower than that of Schottky-gate HEMT. An extrinsic current gain cutoff frequency f T of 65 GHz and a maximum oscillation frequency f max of 123 GHz are deduced from rf small signal measurements. The high f max demonstrates that gate-recessed MOSHEMTs are of great potential in millimeter wave frequencies. (cross-disciplinary physics and related areas of science and technology)

  18. Phase synchronization in a two-mode solid state laser: Periodic modulations with the second relaxation oscillation frequency of the laser output

    International Nuclear Information System (INIS)

    Hsu, Tzu-Fang; Jao, Kuan-Hsuan; Hung, Yao-Chen

    2014-01-01

    Phase synchronization (PS) in a periodically pump-modulated two-mode solid state laser is investigated. Although PS in the laser system has been demonstrated in response to a periodic modulation with the main relaxation oscillation (RO) frequency of the free-running laser, little is known about the case of modulation with minor RO frequencies. In this Letter, the empirical mode decomposition (EMD) method is utilized to decompose the laser time series into a set of orthogonal modes and to examine the intrinsic PS near the frequency of the second RO. The degree of PS is quantified by means of a histogram of phase differences and the analysis of Shannon entropy. - Highlights: • We study the intrinsic phase synchronization in a periodically pump-modulated two-mode solid state laser. • The empirical mode decomposition method is utilized to define the intrinsic phase synchronization. • The degree of phase synchronization is quantified by a proposed synchronization coefficient

  19. Network-state modulation of power-law frequency-scaling in visual cortical neurons.

    Science.gov (United States)

    El Boustani, Sami; Marre, Olivier; Béhuret, Sébastien; Baudot, Pierre; Yger, Pierre; Bal, Thierry; Destexhe, Alain; Frégnac, Yves

    2009-09-01

    Various types of neural-based signals, such as EEG, local field potentials and intracellular synaptic potentials, integrate multiple sources of activity distributed across large assemblies. They have in common a power-law frequency-scaling structure at high frequencies, but it is still unclear whether this scaling property is dominated by intrinsic neuronal properties or by network activity. The latter case is particularly interesting because if frequency-scaling reflects the network state it could be used to characterize the functional impact of the connectivity. In intracellularly recorded neurons of cat primary visual cortex in vivo, the power spectral density of V(m) activity displays a power-law structure at high frequencies with a fractional scaling exponent. We show that this exponent is not constant, but depends on the visual statistics used to drive the network. To investigate the determinants of this frequency-scaling, we considered a generic recurrent model of cortex receiving a retinotopically organized external input. Similarly to the in vivo case, our in computo simulations show that the scaling exponent reflects the correlation level imposed in the input. This systematic dependence was also replicated at the single cell level, by controlling independently, in a parametric way, the strength and the temporal decay of the pairwise correlation between presynaptic inputs. This last model was implemented in vitro by imposing the correlation control in artificial presynaptic spike trains through dynamic-clamp techniques. These in vitro manipulations induced a modulation of the scaling exponent, similar to that observed in vivo and predicted in computo. We conclude that the frequency-scaling exponent of the V(m) reflects stimulus-driven correlations in the cortical network activity. Therefore, we propose that the scaling exponent could be used to read-out the "effective" connectivity responsible for the dynamical signature of the population signals measured

  20. Network-state modulation of power-law frequency-scaling in visual cortical neurons.

    Directory of Open Access Journals (Sweden)

    Sami El Boustani

    2009-09-01

    Full Text Available Various types of neural-based signals, such as EEG, local field potentials and intracellular synaptic potentials, integrate multiple sources of activity distributed across large assemblies. They have in common a power-law frequency-scaling structure at high frequencies, but it is still unclear whether this scaling property is dominated by intrinsic neuronal properties or by network activity. The latter case is particularly interesting because if frequency-scaling reflects the network state it could be used to characterize the functional impact of the connectivity. In intracellularly recorded neurons of cat primary visual cortex in vivo, the power spectral density of V(m activity displays a power-law structure at high frequencies with a fractional scaling exponent. We show that this exponent is not constant, but depends on the visual statistics used to drive the network. To investigate the determinants of this frequency-scaling, we considered a generic recurrent model of cortex receiving a retinotopically organized external input. Similarly to the in vivo case, our in computo simulations show that the scaling exponent reflects the correlation level imposed in the input. This systematic dependence was also replicated at the single cell level, by controlling independently, in a parametric way, the strength and the temporal decay of the pairwise correlation between presynaptic inputs. This last model was implemented in vitro by imposing the correlation control in artificial presynaptic spike trains through dynamic-clamp techniques. These in vitro manipulations induced a modulation of the scaling exponent, similar to that observed in vivo and predicted in computo. We conclude that the frequency-scaling exponent of the V(m reflects stimulus-driven correlations in the cortical network activity. Therefore, we propose that the scaling exponent could be used to read-out the "effective" connectivity responsible for the dynamical signature of the population

  1. Oscillations in stellar atmospheres

    International Nuclear Information System (INIS)

    Costa, A.; Ringuelet, A.E.; Fontenla, J.M.

    1989-01-01

    Atmospheric excitation and propagation of oscillations are analyzed for typical pulsating stars. The linear, plane-parallel approach for the pulsating atmosphere gives a local description of the phenomenon. From the local analysis of oscillations, the minimum frequencies are obtained for radially propagating waves. The comparison of the minimum frequencies obtained for a variety of stellar types is in good agreement with the observed periods of the oscillations. The role of the atmosphere in the globar stellar pulsations is thus emphasized. 7 refs

  2. Rayleigh-type parametric chemical oscillation

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Shyamolina; Ray, Deb Shankar, E-mail: pcdsr@iacs.res.in [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2015-09-28

    We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

  3. Rayleigh-type parametric chemical oscillation.

    Science.gov (United States)

    Ghosh, Shyamolina; Ray, Deb Shankar

    2015-09-28

    We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

  4. Scaling of graphene field-effect transistors supported on hexagonal boron nitride: radio-frequency stability as a limiting factor

    Science.gov (United States)

    Feijoo, Pedro C.; Pasadas, Francisco; Iglesias, José M.; Martín, María J.; Rengel, Raúl; Li, Changfeng; Kim, Wonjae; Riikonen, Juha; Lipsanen, Harri; Jiménez, David

    2017-12-01

    The quality of graphene in nanodevices has increased hugely thanks to the use of hexagonal boron nitride as a supporting layer. This paper studies to which extent hBN together with channel length scaling can be exploited in graphene field-effect transistors (GFETs) to get a competitive radio-frequency (RF) performance. Carrier mobility and saturation velocity were obtained from an ensemble Monte Carlo simulator that accounted for the relevant scattering mechanisms (intrinsic phonons, scattering with impurities and defects, etc). This information is fed into a self-consistent simulator, which solves the drift-diffusion equation coupled with the two-dimensional Poisson’s equation to take full account of short channel effects. Simulated GFET characteristics were benchmarked against experimental data from our fabricated devices. Our simulations show that scalability is supposed to bring to RF performance an improvement that is, however, highly limited by instability. Despite the possibility of a lower performance, a careful choice of the bias point can avoid instability. Nevertheless, maximum oscillation frequencies are still achievable in the THz region for channel lengths of a few hundreds of nanometers.

  5. A case study of the intraseasonal oscillation traversing the TOGA-COARE LSD. [large-scale domain

    Science.gov (United States)

    Vincent, Dayton G.; Schrage, Jon M.; Sliwinski, L. D.

    1993-01-01

    The paper presents examination of tree intraseasonal (30-60 day) oscillations (ISOs) that occurred during the southern summer season (December 1, 1985 - February 28, 1986) traversing the Large-Scale Domain (LSD) TOGA-COARE, the region which also plays an important role in ENSO, Australian monsoon, and extratropical circulations. Data presented include Hovmoeller diagrams of 5-day running means of 250-mb velocity potential anomalies and OLR anomalies; graphs of five-day running means of OLR in precipitable water (W) per sq m, averaged over 10 x 10 deg boxes centered on 5 S and (1) 145 E, (2) 155 E, (3) 165 E, and (4) 165 D, indicating the midpoint of each ISO; and vertical profiles of zonal wind in m/s averaged over the time period that each ISO spends in the 10 x 10 deg box centered at 5 S, and 175 E and 145 E.

  6. The effects of high-frequency oscillations in hippocampal electrical activities on the classification of epileptiform events using artificial neural networks

    Science.gov (United States)

    Chiu, Alan W. L.; Jahromi, Shokrollah S.; Khosravani, Houman; Carlen, Peter L.; Bardakjian, Berj L.

    2006-03-01

    The existence of hippocampal high-frequency electrical activities (greater than 100 Hz) during the progression of seizure episodes in both human and animal experimental models of epilepsy has been well documented (Bragin A, Engel J, Wilson C L, Fried I and Buzsáki G 1999 Hippocampus 9 137-42 Khosravani H, Pinnegar C R, Mitchell J R, Bardakjian B L, Federico P and Carlen P L 2005 Epilepsia 46 1-10). However, this information has not been studied between successive seizure episodes or utilized in the application of seizure classification. In this study, we examine the dynamical changes of an in vitro low Mg2+ rat hippocampal slice model of epilepsy at different frequency bands using wavelet transforms and artificial neural networks. By dividing the time-frequency spectrum of each seizure-like event (SLE) into frequency bins, we can analyze their burst-to-burst variations within individual SLEs as well as between successive SLE episodes. Wavelet energy and wavelet entropy are estimated for intracellular and extracellular electrical recordings using sufficiently high sampling rates (10 kHz). We demonstrate that the activities of high-frequency oscillations in the 100-400 Hz range increase as the slice approaches SLE onsets and in later episodes of SLEs. Utilizing the time-dependent relationship between different frequency bands, we can achieve frequency-dependent state classification. We demonstrate that activities in the frequency range 100-400 Hz are critical for the accurate classification of the different states of electrographic seizure-like episodes (containing interictal, preictal and ictal states) in brain slices undergoing recurrent spontaneous SLEs. While preictal activities can be classified with an average accuracy of 77.4 ± 6.7% utilizing the frequency spectrum in the range 0-400 Hz, we can also achieve a similar level of accuracy by using a nonlinear relationship between 100-400 Hz and <4 Hz frequency bands only.

  7. Investigation of scaling laws in frequency-dependent minor hysteresis loops for ferromagnetic steels

    International Nuclear Information System (INIS)

    Kobayashi, S.; Tsukidate, S.; Kamada, Y.; Kikuchi, H.; Ohtani, T.

    2012-01-01

    Scaling laws in dynamical magnetic minor hysteresis loops have been investigated in the magnetizing frequency range of 0.05-300 Hz for various steels including Cr-Mo-V steel subjected to creep, cold rolled steels, and plastically deformed Ni. Although scaling laws in the medium magnetization range found previously fail in the high magnetization frequency regime owing to a significant contribution of eddy currents, a scaling power law of the relation between remanence and remanence work of minor loops, associated with a constant exponent of approximately 1.9, holds true in a very low magnetization regime, irrespective of magnetization frequency and investigated materials. The coefficient of the law is proportionally related to Vickers hardness over the wide frequency range. These observations demonstrate that the scaling analysis of dynamical minor loops enables us to evaluate materials degradation in a short measurement time with low measurement field and high sensitivity to defect density. - Highlights: → We performed hysteresis scaling for dynamical minor loops in ferromagnetic steels. → An universal scaling power law with an exponent of 1.9 was observed. → Coefficient of the scaling law reflects defect density due to creep and deformation. → This method is useful for on-line non-destructive evaluation.

  8. Non-stationary analysis of the frequency and intensity of heavy precipitation over Canada and their relations to large-scale climate patterns

    Science.gov (United States)

    Tan, Xuezhi; Gan, Thian Yew

    2017-05-01

    In recent years, because the frequency and severity of floods have increased across Canada, it is important to understand the characteristics of Canadian heavy precipitation. Long-term precipitation data of 463 gauging stations of Canada were analyzed using non-stationary generalized extreme value distribution (GEV), Poisson distribution and generalized Pareto (GP) distribution. Time-varying covariates that represent large-scale climate patterns such as El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Pacific decadal oscillation (PDO) and North Pacific Oscillation (NP) were incorporated to parameters of GEV, Poisson and GP distributions. Results show that GEV distributions tend to under-estimate annual maximum daily precipitation (AMP) of western and eastern coastal regions of Canada, compared to GP distributions. Poisson regressions show that temporal clusters of heavy precipitation events in Canada are related to large-scale climate patterns. By modeling AMP time series with non-stationary GEV and heavy precipitation with non-stationary GP distributions, it is evident that AMP and heavy precipitation of Canada show strong non-stationarities (abrupt and slowly varying changes) likely because of the influence of large-scale climate patterns. AMP in southwestern coastal regions, southern Canadian Prairies and the Great Lakes tend to be higher in El Niño than in La Niña years, while AMP of other regions of Canada tends to be lower in El Niño than in La Niña years. The influence of ENSO on heavy precipitation was spatially consistent but stronger than on AMP. The effect of PDO, NAO and NP on extreme precipitation is also statistically significant at some stations across Canada.

  9. AUTOMATIC FREQUENCY CONTROL SYSTEM

    Science.gov (United States)

    Hansen, C.F.; Salisbury, J.D.

    1961-01-10

    A control is described for automatically matching the frequency of a resonant cavity to that of a driving oscillator. The driving oscillator is disconnected from the cavity and a secondary oscillator is actuated in which the cavity is the frequency determining element. A low frequency is mixed with the output of the driving oscillator and the resultant lower and upper sidebands are separately derived. The frequencies of the sidebands are compared with the secondary oscillator frequency. deriving a servo control signal to adjust a tuning element in the cavity and matching the cavity frequency to that of the driving oscillator. The driving oscillator may then be connected to the cavity.

  10. Effects of equilibrium point displacement in limit cycle oscillation amplitude, critical frequency and prediction of critical input angular velocity in minimal brake system

    Science.gov (United States)

    Ganji, Hamed Faghanpour; Ganji, Davood Domiri

    2017-04-01

    In the present paper, brake squeal phenomenon as a noise resource in automobiles was studied. In most cases, the modeling work is carried out assuming that deformations were small; thus, equilibrium point is set zero and linearization is performed at this point. However, the equilibrium point under certain circumstances is not zero; therefore, huge errors in prediction of brake squeal may occur. In this work, large motion domains with respect to linearization importance were subjected to investigation. Nonlinear equations of motion were considered and behavior of system for COF's model was analyzed by studying amplitude and frequency of limited cycle oscillation.

  11. On the relation between the frequency of oscillation of a virtual cathode and injected current in one-dimensional grounded drift space

    International Nuclear Information System (INIS)

    Kumar, Raghwendra; Puri, R.R.; Biswas, D.

    2004-01-01

    The relationship between the injected current density j 0 and the dominant fundamental oscillation frequency f of a virtual cathode in a one-dimensional grounded infinite planar drift space of length L is determined numerically. If the electrons, each of mass m e and charge e, are injected with velocity v 0 , it is found that for vertical bar j 0 vertical bar >>m e v 0 3 /18π vertical bar e vertical bar L 2 , f∼√(vertical bar j 0 vertical bar) which is in contrast to the relation f∼vertical bar j 0 vertical bar reported by earlier workers

  12. Nature's Autonomous Oscillators

    Science.gov (United States)

    Mayr, H. G.; Yee, J.-H.; Mayr, M.; Schnetzler, R.

    2012-01-01

    Nonlinearity is required to produce autonomous oscillations without external time dependent source, and an example is the pendulum clock. The escapement mechanism of the clock imparts an impulse for each swing direction, which keeps the pendulum oscillating at the resonance frequency. Among nature's observed autonomous oscillators, examples are the quasi-biennial oscillation and bimonthly oscillation of the Earth atmosphere, and the 22-year solar oscillation. The oscillations have been simulated in numerical models without external time dependent source, and in Section 2 we summarize the results. Specifically, we shall discuss the nonlinearities that are involved in generating the oscillations, and the processes that produce the periodicities. In biology, insects have flight muscles, which function autonomously with wing frequencies that far exceed the animals' neural capacity; Stretch-activation of muscle contraction is the mechanism that produces the high frequency oscillation of insect flight, discussed in Section 3. The same mechanism is also invoked to explain the functioning of the cardiac muscle. In Section 4, we present a tutorial review of the cardio-vascular system, heart anatomy, and muscle cell physiology, leading up to Starling's Law of the Heart, which supports our notion that the human heart is also a nonlinear oscillator. In Section 5, we offer a broad perspective of the tenuous links between the fluid dynamical oscillators and the human heart physiology.

  13. One-dimensional modelling of limit-cycle oscillation and H-mode power scaling

    DEFF Research Database (Denmark)

    Wu, Xingquan; Xu, Guosheng; Wan, Baonian

    2015-01-01

    To understand the connection between the dynamics of microscopic turbulence and the macroscale power scaling in the L-I-H transition in magnetically confined plasmas, a new time-dependent, one-dimensional (in radius) model has been developed. The model investigates the radial force balance equati...

  14. Nonlinear dynamics of a thin liquid film on an axially oscillating cylindrical surface subjected to double-frequency forcing.

    Science.gov (United States)

    Haimovich, Ory; Oron, Alexander

    2013-05-01

    The nonlinear dynamics of a thin axisymmetric liquid film on a horizontal cylindrical substrate subjected to an axial double-frequency forcing that consists of two components of different amplitudes and frequencies and a possible phase shift is considered in this paper. A nonlinear evolution equation governing the spatiotemporal dynamics of the film interface has been derived in the long-wave limit. Similar to the case of a single-frequency forcing considered in our earlier work, there exists a critical forcing amplitude below which the film undergoes a long-time capillary rupture typical for a static cylinder, whereas above it the film remains continuous. We find that it is possible to arrest the rupture even if the forcing parameters of each of the two components correspond separately to the domain where rupture takes place. It is shown that the critical forcing amplitude is easily determined via a single-frequency case when the two forcing frequencies are equal. In the case of different forcing amplitudes and frequencies, the variation of the critical forcing amplitude as a function of the frequency ratio exhibits a unique behavior displaying the emergence of spikes. A related case of an amplitude-modulated single-frequency forcing is also addressed here. For a sufficiently small frequency of the amplitude modulation, a significant increase of the pattern amplitude is observed. In the case of commensurate forcing frequencies, the flow is found to be quasiperiodic.

  15. arXiv GeV-scale hot sterile neutrino oscillations: a derivation of evolution equations

    CERN Document Server

    Ghiglieri, J.

    2017-05-23

    Starting from operator equations of motion and making arguments based on a separation of time scales, a set of equations is derived which govern the non-equilibrium time evolution of a GeV-scale sterile neutrino density matrix and active lepton number densities at temperatures T > 130 GeV. The density matrix possesses generation and helicity indices; we demonstrate how helicity permits for a classification of various sources for leptogenesis. The coefficients parametrizing the equations are determined to leading order in Standard Model couplings, accounting for the LPM resummation of 1+n 2+n scatterings and for all 2 2 scatterings. The regime in which sphaleron processes gradually decouple so that baryon plus lepton number becomes a separate non-equilibrium variable is also considered.

  16. Acute hypoxia diminishes the relationship between blood pressure and subarachnoid space width oscillations at the human cardiac frequency.

    Directory of Open Access Journals (Sweden)

    Magdalena Wszedybyl-Winklewska

    Full Text Available Acute hypoxia exerts strong effects on the cardiovascular system. Heart-generated pulsatile cerebrospinal fluid motion is recognised as a key factor ensuring brain homeostasis. We aimed to assess changes in heart-generated coupling between blood pressure (BP and subarachnoid space width (SAS oscillations during hypoxic exposure.Twenty participants were subjected to a controlled decrease in oxygen saturation (SaO2 = 80% for five minutes. BP and heart rate (HR were measured using continuous finger-pulse photoplethysmography, oxyhaemoglobin saturation with an ear-clip sensor, end-tidal CO2 with a gas analyser, and cerebral blood flow velocity (CBFV, pulsatility and resistive indices with Doppler ultrasound. Changes in SAS were recorded with a recently-developed method called near-infrared transillumination/backscattering sounding. Wavelet transform analysis was used to assess the relationship between BP and SAS oscillations.Gradual increases in systolic, diastolic BP and HR were observed immediately after the initiation of hypoxic challenge (at fifth minute +20.1%, +10.2%, +16.5% vs. baseline, respectively; all P<0.01, whereas SAS remained intact (P = NS. Concurrently, the CBFV was stable throughout the procedure, with the only increase observed in the last two minutes of deoxygenation (at the fifth minute +6.8% vs. baseline, P<0.05. The cardiac contribution to the relationship between BP and SAS oscillations diminished immediately after exposure to hypoxia (at the fifth minute, right hemisphere -27.7% and left hemisphere -26.3% vs. baseline; both P<0.05. Wavelet phase coherence did not change throughout the experiment (P = NS.Cerebral haemodynamics seem to be relatively stable during short exposure to normobaric hypoxia. Hypoxia attenuates heart-generated BP SAS coupling.

  17. Coordinated learning of grid cell and place cell spatial and temporal properties: multiple scales, attention and oscillations.

    Science.gov (United States)

    Grossberg, Stephen; Pilly, Praveen K

    2014-02-05

    A neural model proposes how entorhinal grid cells and hippocampal place cells may develop as spatial categories in a hierarchy of self-organizing maps (SOMs). The model responds to realistic rat navigational trajectories by learning both grid cells with hexagonal grid firing fields of multiple spatial scales, and place cells with one or more firing fields, that match neurophysiological data about their development in juvenile rats. Both grid and place cells can develop by detecting, learning and remembering the most frequent and energetic co-occurrences of their inputs. The model's parsimonious properties include: similar ring attractor mechanisms process linear and angular path integration inputs that drive map learning; the same SOM mechanisms can learn grid cell and place cell receptive fields; and the learning of the dorsoventral organization of multiple spatial scale modules through medial entorhinal cortex to hippocampus (HC) may use mechanisms homologous to those for temporal learning through lateral entorhinal cortex to HC ('neural relativity'). The model clarifies how top-down HC-to-entorhinal attentional mechanisms may stabilize map learning, simulates how hippocampal inactivation may disrupt grid cells, and explains data about theta, beta and gamma oscillations. The article also compares the three main types of grid cell models in the light of recent data.

  18. Search for GeV-Scale Sterile Neutrinos Responsible for Active Neutrino Oscillations and Baryon Asymmetry of the Universe

    Directory of Open Access Journals (Sweden)

    S. N. Gninenko

    2012-01-01

    Full Text Available Standard Model fails to explain neutrino oscillations, dark matter, and baryon asymmetry of the Universe. All these problems can be solved with three sterile neutrinos added to SM. Quite remarkably, if sterile neutrino masses are well below the electroweak scale, this modification—Neutrino Minimal Standard Model (νMSM—can be tested experimentally. We discuss a new experiment on search for decays of GeV-scale sterile neutrinos, which are responsible for the matter-antimatter asymmetry generation and for the active neutrino masses. If lighter than 2 GeV, these particles can be produced in decays of charm mesons generated by high energy protons in a target, and subsequently decay into SM particles. To fully explore this sector of νMSM, the new experiment requires data obtained with at least 1020 incident protons on target (achievable at CERN SPS in future and a big volume detector constructed from a large amount of identical single modules, with a total sterile neutrino decay length of few kilometers. The preliminary feasibility study for the proposed experiment shows that it has sensitivity which may either lead to the discovery of new particles below the Fermi scale—right-handed partners of neutrinos—or rule out seesaw sterile neutrinos with masses below 2 GeV.

  19. Perturbation analysis of complete synchronization in networks of phase oscillators.

    Science.gov (United States)

    Tönjes, Ralf; Blasius, Bernd

    2009-08-01

    The behavior of weakly coupled self-sustained oscillators can often be well described by phase equations. Here we use the paradigm of Kuramoto phase oscillators which are coupled in a network to calculate first- and second-order corrections to the frequency of the fully synchronized state for nonidentical oscillators. The topology of the underlying coupling network is reflected in the eigenvalues and eigenvectors of the network Laplacian which influence the synchronization frequency in a particular way. They characterize the importance of nodes in a network and the relations between them. Expected values for the synchronization frequency are obtained for oscillators with quenched random frequencies on a class of scale-free random networks and for a Erdös-Rényi random network. We briefly discuss an application of the perturbation theory in the second order to network structural analysis.

  20. Time and frequency domain analyses of the Hualien Large-Scale Seismic Test

    International Nuclear Information System (INIS)

    Kabanda, John; Kwon, Oh-Sung; Kwon, Gunup

    2015-01-01

    Highlights: • Time- and frequency-domain analysis methods are verified against each other. • The two analysis methods are validated against Hualien LSST. • The nonlinear time domain (NLTD) analysis resulted in more realistic response. • The frequency domain (FD) analysis shows amplification at resonant frequencies. • The NLTD analysis requires significant modeling and computing time. - Abstract: In the nuclear industry, the equivalent-linear frequency domain analysis method has been the de facto standard procedure primarily due to the method's computational efficiency. This study explores the feasibility of applying the nonlinear time domain analysis method for the soil–structure-interaction analysis of nuclear power facilities. As a first step, the equivalency of the time and frequency domain analysis methods is verified through a site response analysis of one-dimensional soil, a dynamic impedance analysis of soil–foundation system, and a seismic response analysis of the entire soil–structure system. For the verifications, an idealized elastic soil–structure system is used to minimize variables in the comparison of the two methods. Then, the verified analysis methods are used to develop time and frequency domain models of Hualien Large-Scale Seismic Test. The predicted structural responses are compared against field measurements. The models are also analyzed with an amplified ground motion to evaluate discrepancies of the time and frequency domain analysis methods when the soil–structure system behaves beyond the elastic range. The analysis results show that the equivalent-linear frequency domain analysis method amplifies certain frequency bands and tends to result in higher structural acceleration than the nonlinear time domain analysis method. A comparison with field measurements shows that the nonlinear time domain analysis method better captures the frequency distribution of recorded structural responses than the frequency domain

  1. Cross-sectional fluctuation scaling in the high-frequency illiquidity of Chinese stocks

    Science.gov (United States)

    Cai, Qing; Gao, Xing-Lu; Zhou, Wei-Xing; Stanley, H. Eugene

    2018-03-01

    Taylor's law of temporal and ensemble fluctuation scaling has been ubiquitously observed in diverse complex systems including financial markets. Stock illiquidity is an important nonadditive financial quantity, which is found to comply with Taylor's temporal fluctuation scaling law. In this paper, we perform the cross-sectional analysis of the 1 min high-frequency illiquidity time series of Chinese stocks and unveil the presence of Taylor's law of ensemble fluctuation scaling. The estimated daily Taylor scaling exponent fluctuates around 1.442. We find that Taylor's scaling exponents of stock illiquidity do not relate to the ensemble mean and ensemble variety of returns. Our analysis uncovers a new scaling law of financial markets and might stimulate further investigations for a better understanding of financial markets' dynamics.

  2. Low-scale seesaw and the CP violation in neutrino oscillations

    Science.gov (United States)

    Penedo, J. T.; Petcov, S. T.; Yanagida, Tsutomu T.

    2018-04-01

    We consider a version of the low-scale type I seesaw mechanism for generating small neutrino masses, as an alternative to the standard seesaw scenario. It involves two right-handed (RH) neutrinos ν1R and ν2R having a Majorana mass term with mass M, which conserves the lepton charge L. The RH neutrino ν2R has lepton-charge conserving Yukawa couplings gℓ2 to the lepton and Higgs doublet fields, while small lepton-charge breaking effects are assumed to induce tiny lepton-charge violating Yukawa couplings gℓ1 for ν1R, l = e , μ , τ. In this approach the smallness of neutrino masses is related to the smallness of the Yukawa coupling of ν1R and not to the large value of M: the RH neutrinos can have masses in the few GeV to a few TeV range. The Yukawa couplings |gℓ2 | can be much larger than |gℓ1 |, of the order |gℓ2 | ∼10-4-10-2, leading to interesting low-energy phenomenology. We consider a specific realisation of this scenario within the Froggatt-Nielsen approach to fermion masses. In this model the Dirac CP violation phase δ is predicted to have approximately one of the values δ ≃ π / 4 , 3 π / 4, or 5 π / 4 , 7 π / 4, or to lie in a narrow interval around one of these values. The low-energy phenomenology of the considered low-scale seesaw scenario of neutrino mass generation is also briefly discussed.

  3. A Comprehensive Analysis of the Correlations between Resting-State Oscillations in Multiple-Frequency Bands and Big Five Traits.

    Science.gov (United States)

    Ikeda, Shigeyuki; Takeuchi, Hikaru; Taki, Yasuyuki; Nouchi, Rui; Yokoyama, Ryoichi; Kotozaki, Yuka; Nakagawa, Seishu; Sekiguchi, Atsushi; Iizuka, Kunio; Yamamoto, Yuki; Hanawa, Sugiko; Araki, Tsuyoshi; Miyauchi, Carlos Makoto; Sakaki, Kohei; Nozawa, Takayuki; Yokota, Susumu; Magistro, Daniele; Kawashima, Ryuta

    2017-01-01

    Recently, the association between human personality traits and resting-state brain activity has gained interest in neuroimaging studies. However, it remains unclear if Big Five personality traits are represented in frequency bands (~0.25 Hz) of resting-state functional magnetic resonance imaging (fMRI) activity. Based on earlier neurophysiological studies, we investigated the correlation between the five personality traits assessed by the NEO Five-Factor Inventory (NEO-FFI), and the fractional amplitude of low-frequency fluctuation (fALFF) at four distinct frequency bands (slow-5 (0.01-0.027 Hz), slow-4 (0.027-0.073 Hz), slow-3 (0.073-0.198 Hz) and slow-2 (0.198-0.25 Hz)). We enrolled 835 young subjects and calculated the correlations of resting-state fMRI signals using a multiple regression analysis. We found a significant and consistent correlation between fALFF and the personality trait of extraversion at all frequency bands. Furthermore, significant correlations were detected in distinct brain regions for each frequency band. This finding supports the frequency-specific spatial representations of personality traits as previously suggested. In conclusion, our data highlight an association between human personality traits and fALFF at four distinct frequency bands.

  4. A Comprehensive Analysis of the Correlations between Resting-State Oscillations in Multiple-Frequency Bands and Big Five Traits

    Directory of Open Access Journals (Sweden)

    Shigeyuki Ikeda

    2017-06-01

    Full Text Available Recently, the association between human personality traits and resting-state brain activity has gained interest in neuroimaging studies. However, it remains unclear if Big Five personality traits are represented in frequency bands (~0.25 Hz of resting-state functional magnetic resonance imaging (fMRI activity. Based on earlier neurophysiological studies, we investigated the correlation between the five personality traits assessed by the NEO Five-Factor Inventory (NEO-FFI, and the fractional amplitude of low-frequency fluctuation (fALFF at four distinct frequency bands (slow-5 (0.01–0.027 Hz, slow-4 (0.027–0.073 Hz, slow-3 (0.073–0.198 Hz and slow-2 (0.198–0.25 Hz. We enrolled 835 young subjects and calculated the correlations of resting-state fMRI signals using a multiple regression analysis. We found a significant and consistent correlation between fALFF and the personality trait of extraversion at all frequency bands. Furthermore, significant correlations were detected in distinct brain regions for each frequency band. This finding supports the frequency-specific spatial representations of personality traits as previously suggested. In conclusion, our data highlight an association between human personality traits and fALFF at four distinct frequency bands.

  5. Summer planetary-scale oscillations: aura MLS temperature compared with ground-based radar wind

    Directory of Open Access Journals (Sweden)

    C. E. Meek

    2009-04-01

    Full Text Available The advent of satellite based sampling brings with it the opportunity to examine virtually any part of the globe. Aura MLS mesospheric temperature data are analysed in a wavelet format for easy identification of possible planetary waves (PW and aliases masquerading as PW. A calendar year, 2005, of eastward, stationary, and westward waves at a selected latitude is shown in separate panels for wave number range −3 to +3 for period range 8 h to 30 days (d. Such a wavelet analysis is made possible by Aura's continuous sampling at all latitudes 82° S–82° N. The data presentation is suitable for examination of years of data. However this paper focuses on the striking feature of a "dish-shaped" upper limit to periods near 2 d in mid-summer, with longer periods appearing towards spring and fall, a feature also commonly seen in radar winds. The most probable cause is suggested to be filtering by the summer jet at 70–80 km, the latter being available from ground based medium frequency radar (MFR. Classically, the phase velocity of a wave must be greater than that of the jet in order to propagate through it. As an attempt to directly relate satellite and ground based sampling, a PW event of period 8d and wave number 2, which appears to be the original rather than an alias, is compared with ground based radar wind data. An appendix discusses characteristics of satellite data aliases with regard to their periods and amplitudes.

  6. Composable Dynamic Voltage and Frequency Scaling and Power Management for Dataflow Applications

    NARCIS (Netherlands)

    Goossens, Kees; She, Dongrui; Milutinovic, A.; Molnos, Anca; Lopez, S.

    2010-01-01

    Composability means that the behaviour of an application, including its timing, is not affected by the absence or presence of other applications. It is required to be able to design, test, and verify applications independently. In this paper we de﬿ne composable dynamic voltage and frequency scaling

  7. High-frequency, scaled graphene transistors on diamond-like carbon

    NARCIS (Netherlands)

    Wu, Y.; Lin, Y.M.; Bol, A.A.; Jenkins, K.A.; Xia, F.; Farmer, D.B.; Zu, Y.; Avouris, Ph.

    2011-01-01

    Owing to its high carrier mobility and saturation velocity, graphene has attracted enormous attention in recent years In particular, high-performance graphene transistors for radio-frequency (r.f.) applications are of great interest. Synthesis of large-scale graphene sheets of high quality and at

  8. Composable dynamic voltage and frequency scaling and power management for dataflow applications

    NARCIS (Netherlands)

    Goossens, K.G.W.; She, D.; Milutinovic, A.; Molnos, A.M.

    2010-01-01

    Composability means that the behaviour of an application, including its timing, is not affected by the absence or presence of other applications. It is required to be able to design, test, and verify applications independently. In this paper we define composable dynamic voltage and frequency scaling

  9. ON THE GEOMETRIC NATURE OF LOW-FREQUENCY QUASI-PERIODIC OSCILLATIONS IN NEUTRON-STAR LOW-MASS X-RAY BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Homan, Jeroen; Remillard, Ronald A. [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue 37-582D, Cambridge, MA 02139 (United States); Fridriksson, Joel K., E-mail: jeroen@space.mit.edu [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands)

    2015-10-10

    We report on a detailed analysis of the so-called ∼1 Hz quasi-periodic oscillation (QPO) in the eclipsing and dipping neutron-star low-mass X-ray binary EXO 0748–676. This type of QPO has previously been shown to have a geometric origin. Our study focuses on the evolution of the QPO as the source moves through the color–color diagram in which it traces out an atoll-source-like track. The QPO frequency increases from ∼0.4 Hz in the hard state to ∼25 Hz as the source approaches the soft state. Combining power spectra based on QPO frequency reveals additional features that strongly resemble those seen in non-dipping/eclipsing atoll sources. We show that the low-frequency QPOs in atoll sources and the ∼1 Hz QPO in EXO 0748–676 follow similar relations with respect to the noise components in their power spectra. We conclude that the frequencies of both types of QPOs are likely set by (the same) precession of a misaligned inner accretion disk. For high-inclination systems like EXO 0748–676 this results in modulations of the neutron-star emission due to obscuration or scattering, while for lower-inclination systems the modulations likely arise from relativistic Doppler-boosting and light-bending effects.

  10. Vibrational frequency scaling factors for correlation consistent basis sets and the methods CC2 and MP2 and their spin-scaled SCS and SOS variants

    Energy Technology Data Exchange (ETDEWEB)

    Friese, Daniel H., E-mail: daniel.h.friese@uit.no [Centre for Theoretical and Computational Chemistry CTCC, Department of Chemistry, University of Tromsø, N-9037 Tromsø (Norway); Törk, Lisa; Hättig, Christof, E-mail: christof.haettig@rub.de [Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44801 Bochum (Germany)

    2014-11-21

    We present scaling factors for vibrational frequencies calculated within the harmonic approximation and the correlated wave-function methods coupled cluster singles and doubles model (CC2) and Møller-Plesset perturbation theory (MP2) with and without a spin-component scaling (SCS or spin-opposite scaling (SOS)). Frequency scaling factors and the remaining deviations from the reference data are evaluated for several non-augmented basis sets of the cc-pVXZ family of generally contracted correlation-consistent basis sets as well as for the segmented contracted TZVPP basis. We find that the SCS and SOS variants of CC2 and MP2 lead to a slightly better accuracy for the scaled vibrational frequencies. The determined frequency scaling factors can also be used for vibrational frequencies calculated for excited states through response theory with CC2 and the algebraic diagrammatic construction through second order and their spin-component scaled variants.

  11. Oscillations of disks

    CERN Document Server

    Kato, Shoji

    2016-01-01

    This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...

  12. Relationship between the Arctic oscillation and surface air temperature in multi-decadal time-scale

    Science.gov (United States)

    Tanaka, Hiroshi L.; Tamura, Mina

    2016-09-01

    In this study, a simple energy balance model (EBM) was integrated in time, considering a hypothetical long-term variability in ice-albedo feedback mimicking the observed multi-decadal temperature variability. A natural variability was superimposed on a linear warming trend due to the increasing radiative forcing of CO2. The result demonstrates that the superposition of the natural variability and the background linear trend can offset with each other to show the warming hiatus for some period. It is also stressed that the rapid warming during 1970-2000 can be explained by the superposition of the natural variability and the background linear trend at least within the simple model. The key process of the fluctuating planetary albedo in multi-decadal time scale is investigated using the JRA-55 reanalysis data. It is found that the planetary albedo increased for 1958-1970, decreased for 1970-2000, and increased for 2000-2012, as expected by the simple EBM experiments. The multi-decadal variability in the planetary albedo is compared with the time series of the AO mode and Barents Sea mode of surface air temperature. It is shown that the recent AO negative pattern showing warm Arctic and cold mid-latitudes is in good agreement with planetary albedo change indicating negative anomaly in high latitudes and positive anomaly in mid-latitudes. Moreover, the Barents Sea mode with the warm Barents Sea and cold mid-latitudes shows long-term variability similar to planetary albedo change. Although further studies are needed, the natural variabilities of both the AO mode and Barents Sea mode indicate some possible link to the planetary albedo as suggested by the simple EBM to cause the warming hiatus in recent years.

  13. Dependence of exponents on text length versus finite-size scaling for word-frequency distributions

    Science.gov (United States)

    Corral, Álvaro; Font-Clos, Francesc

    2017-08-01

    Some authors have recently argued that a finite-size scaling law for the text-length dependence of word-frequency distributions cannot be conceptually valid. Here we give solid quantitative evidence for the validity of this scaling law, using both careful statistical tests and analytical arguments based on the generalized central-limit theorem applied to the moments of the distribution (and obtaining a novel derivation of Heaps' law as a by-product). We also find that the picture of word-frequency distributions with power-law exponents that decrease with text length [X. Yan and P. Minnhagen, Physica A 444, 828 (2016), 10.1016/j.physa.2015.10.082] does not stand with rigorous statistical analysis. Instead, we show that the distributions are perfectly described by power-law tails with stable exponents, whose values are close to 2, in agreement with the classical Zipf's law. Some misconceptions about scaling are also clarified.

  14. Simulation of particle diffusion in a spectrum of electrostatic turbulence. Low frequency Bohm or percolation scaling

    International Nuclear Information System (INIS)

    Reuss, J.D.; Misguich, J.H.

    1996-02-01

    An important point for turbulent transport consists in determining the scaling law for the diffusion coefficient D due to electrostatic turbulence. It is well-known that for weak amplitudes or large frequencies, the reduced diffusion coefficient has a quasi-linear like (or gyro-Bohm like) scaling, while for large amplitudes or small frequencies it has been traditionally believed that the scaling is Bohm-like. The aim of this work consists to test this prediction for a given realistic model. This problem is studied by direct simulation of particle trajectories. Guiding centre diffusion in a spectrum of electrostatic turbulence is computed for test particles in a model spectrum, by means of a new parallelized code RADIGUET 2. The results indicate a continuous transition for large amplitudes toward a value which is compatible with the Isichenko percolation prediction. (author)

  15. A novel scaling law relating the geometrical dimensions of a photocathode radio frequency gun to its radio frequency properties

    Science.gov (United States)

    Lal, Shankar; Pant, K. K.; Krishnagopal, S.

    2011-12-01

    Developing a photocathode RF gun with the desired RF properties of the π-mode, such as field balance (eb) ˜1, resonant frequency fπ = 2856 MHz, and waveguide-to-cavity coupling coefficient βπ ˜1, requires precise tuning of the resonant frequencies of the independent full- and half-cells (ff and fh), and of the waveguide-to-full-cell coupling coefficient (βf). While contemporary electromagnetic codes and precision machining capability have made it possible to design and tune independent cells of a photocathode RF gun for desired RF properties, thereby eliminating the need for tuning, access to such computational resources and quality of machining is not very widespread. Therefore, many such structures require tuning after machining by employing conventional tuning techniques that are iterative in nature. Any procedure that improves understanding of the tuning process and consequently reduces the number of iterations and the associated risks in tuning a photocathode gun would, therefore, be useful. In this paper, we discuss a method devised by us to tune a photocathode RF gun for desired RF properties under operating conditions. We develop and employ a simple scaling law that accounts for inter-dependence between frequency of independent cells and waveguide-to-cavity coupling coefficient, and the effect of brazing clearance for joining of the two cells. The method has been employed to successfully develop multiple 1.6 cell BNL/SLAC/UCLA type S-band photocathode RF guns with the desired RF properties, without the need to tune them by a tiresome cut-and-measure process. Our analysis also provides a physical insight into how the geometrical dimensions affect the RF properties of the photo-cathode RF gun.

  16. Oscillator phenomena in the solar atmosphere and radiation modulation in microwaves

    International Nuclear Information System (INIS)

    Vaz, A.M.Z.

    1983-05-01

    An overview of the principal known descriptions of oscillations in the solar atmosphere at different ranges of periods was developed. Particular attention was given to oscillations with time scale of seconds, associated to active regions or bursts. 1.5 quasi-periodic oscillations were detected by the first time at more than one microwave frequency simultaneously (22 GHz and 44 GHz), with high sensitivity and high time resolution, superimposed on a burst on Dec. 15, 1980. An advance phase of 0,3s between the oscillations in the frequencies of 22 GHz and 44 GHz was discovered. The proposed mechanism to explain such oscillations is based on oscillations of the magnetic field at the source. These oscillations modulate the gyro-synchrotron emission from high energy electrons trapped in the magnetic structure. The phase difference is attributed to the influence of the optical thickness of the gyro-synchrotron emission at 22 GHz. (Author) [pt

  17. Theta-frequency resonance at the cerebellum input stage improves spike-timing on the millisecond time-scale

    Directory of Open Access Journals (Sweden)

    Daniela eGandolfi

    2013-04-01

    Full Text Available The neuronal circuits of the brain are thought to use resonance and oscillations to improve communication over specific frequency bands (Llinas, 1988; Buzsaki, 2006. However, the properties and mechanism of these phenomena in brain circuits remain largely unknown. Here we show that, at the cerebellum input stage, the granular layer generates its maximum response at 5-7 Hz both in vivo following tactile sensory stimulation of the whisker pad and in acute slices following mossy fiber-bundle stimulation. The spatial analysis of granular layer activity performed using voltage-sensitive dye (VSD imaging revealed 5-7 Hz resonance covering large granular layer areas. In single granule cells, resonance appeared as a reorganization of output spike bursts on the millisecond time-scale, such that the first spike occurred earlier and with higher temporal precision and the probability of spike generation increased. Resonance was independent from circuit inhibition, as it persisted with little variation in the presence of the GABAA receptor blocker, gabazine. However, circuit inhibition reduced the resonance area more markedly at 7 Hz. Simulations with detailed computational models suggested that resonance depended on intrinsic granule cells ionic mechanisms: specifically, Kslow (M-like and KA currents acted as resonators and the persistent Na current and NMDA current acted as amplifiers. This form of resonance may play an important role for enhancing coherent spike emission from the granular layer when theta-frequency bursts are transmitted by the cerebral cortex and peripheral sensory structures during sensory-motor processing, cognition and learning.

  18. A study of B0-B0(bar) oscillations frequency and determination of flavor-tagging efficiency using semileptonic and hadronic B0 decays

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, Barbara

    2000-10-13

    B{sup 0}{bar B}{sup 0} flavor oscillations are studied in e{sup +}e{sup -} annihilation data collected with the BABAR detector at center-of-mass energies near the {Upsilon}(4S) resonance. One B is reconstructed in a hadronic or semileptonic decay mode, and the flavor of the other B in the event is determined with a tagging algorithm that exploits the relation between the flavor of the heavy quark and the charges of its decay products. Tagging performance is characterized by an efficiency {epsilon}{sub i} and a probability for mis-identification, w{sub i}, for each tagging category. We report a determination of the wrong-tag probabilities, w{sub i}, and a preliminary result for the time-dependent B{sup 0}{bar B}{sup 0} oscillation frequency, {Delta}m{sub d} = 0.512 {+-} 0.017 {+-} 0.022 {Dirac_h} ps{sup -1}.

  19. Fourier analysis of the parametric resonance in neutrino oscillations

    International Nuclear Information System (INIS)

    Koike, Masafumi; Ota, Toshihiko; Saito, Masako; Sato, Joe

    2009-01-01

    Parametric enhancement of the appearance probability of the neutrino oscillation under the inhomogeneous matter is studied. Fourier expansion of the matter density profile leads to a simple resonance condition and manifests that each Fourier mode modifies the energy spectrum of oscillation probability at around the corresponding energy; below the MSW resonance energy, a large-scale variation modifies the spectrum in high energies while a small-scale one does in low energies. In contrast to the simple parametric resonance, the enhancement of the oscillation probability is itself an slow oscillation as demonstrated by a numerical analysis with a single Fourier mode of the matter density. We derive an analytic solution to the evolution equation on the resonance energy, including the expression of frequency of the slow oscillation.

  20. A Conspiracy of Oscillators

    DEFF Research Database (Denmark)

    Hjorth, Poul G.

    2008-01-01

    We discuss nonlinear mechanical systems containing several oscillators whose frequecies are all much higher than frequencies associated with the remaining degrees of freedom. In this situation a near constant of the motion, an adiabatic invariant, exists which is the sum of all the oscillator...... actions. The phenomenon is illustrated, and calculations of the small change of the adiabatic invariant is outlined....

  1. Large-scale derived flood frequency analysis based on continuous simulation

    Science.gov (United States)

    Dung Nguyen, Viet; Hundecha, Yeshewatesfa; Guse, Björn; Vorogushyn, Sergiy; Merz, Bruno

    2016-04-01

    There is an increasing need for spatially consistent flood risk assessments at the regional scale (several 100.000 km2), in particular in the insurance industry and for national risk reduction strategies. However, most large-scale flood risk assessments are composed of smaller-scale assessments and show spatial inconsistencies. To overcome this deficit, a large-scale flood model composed of a weather generator and catchments models was developed reflecting the spatially inherent heterogeneity. The weather generator is a multisite and multivariate stochastic model capable of generating synthetic meteorological fields (precipitation, temperature, etc.) at daily resolution for the regional scale. These fields respect the observed autocorrelation, spatial correlation and co-variance between the variables. They are used as input into catchment models. A long-term simulation of this combined system enables to derive very long discharge series at many catchment locations serving as a basic for spatially consistent flood risk estimates at the regional scale. This combined model was set up and validated for major river catchments in Germany. The weather generator was trained by 53-year observation data at 528 stations covering not only the complete Germany but also parts of France, Switzerland, Czech Republic and Australia with the aggregated spatial scale of 443,931 km2. 10.000 years of daily meteorological fields for the study area were generated. Likewise, rainfall-runoff simulations with SWIM were performed for the entire Elbe, Rhine, Weser, Donau and Ems catchments. The validation results illustrate a good performance of the combined system, as the simulated flood magnitudes and frequencies agree well with the observed flood data. Based on continuous simulation this model chain is then used to estimate flood quantiles for the whole Germany including upstream headwater catchments in neighbouring countries. This continuous large scale approach overcomes the several

  2. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Directory of Open Access Journals (Sweden)

    M. Guevara-Bertsch

    2016-03-01

    Full Text Available We investigate the variation of the oscillation frequency of the Mg2+ and O2− ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  3. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Bertsch, M.; Avendaño, E. [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Ramírez-Hidalgo, G. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Sección de Física Teórica, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Chavarría-Sibaja, A.; Araya-Pochet, J. A. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Herrera-Sancho, O. A., E-mail: oscar-andrey.herrera@uibk.ac.at [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstr. 21a, 6020 Innsbruck (Austria)

    2016-03-15

    We investigate the variation of the oscillation frequency of the Mg{sup 2+} and O{sup 2−} ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  4. Determination of frequencies of atomic oscillations along the fourth order symmetry axis in indium arsenide according to thermal diffusion scattering of X-rays

    International Nuclear Information System (INIS)

    Orlova, N.S.

    1978-01-01

    Intensity of diffusion scattering of X-rays from the plane of a monocrystal of indium arsenide has been measured on the monochromatized CuKsub(α)-radiation. The samples are made of Cl indium arsenide monocrystal of the n-type with the 1x10 18 cm -3 concentration of carriers in the form of a plate with the polished parallel cut-off with the +-5' accuracy. The investigations have been carried out on the URS-5 IM X-ray diffractometer at room temperature in vacuum. Intensities of thermal diffusion scattering of the second order have been calculated by the two-atomic chain model with different mass and four interaction paramaters. Based upon the analysis of intensity of single-phonon diffusion scattering the curves of frequencies of atomic oscillations along the direction [100] have been determined. The values of frequencies obtained experimentally on the thermal diffusion scattering of X-rays are in a satisfactory agreement with the calculated data. The frequencies obtained are compared with the results of calculation and the analysis of multiphonon spectra of IR-absorption made elsewhere

  5. A chip-scale, telecommunications-band frequency conversion interface for quantum emitters.

    Science.gov (United States)

    Agha, Imad; Ates, Serkan; Davanço, Marcelo; Srinivasan, Kartik

    2013-09-09

    We describe a chip-scale, telecommunications-band frequency conversion interface designed for low-noise operation at wavelengths desirable for common single photon emitters. Four-wave-mixing Bragg scattering in silicon nitride waveguides is used to demonstrate frequency upconversion and downconversion between the 980 nm and 1550 nm wavelength regions, with signal-to-background levels > 10 and conversion efficiency of ≈ -60 dB at low continuous wave input pump powers ( 25 % in existing geometries. Finally, we present waveguide designs that can be used to connect shorter wavelength (637 nm to 852 nm) quantum emitters with 1550 nm.

  6. DETECTION OF VERY LOW-FREQUENCY, QUASI-PERIODIC OSCILLATIONS IN THE 2015 OUTBURST OF V404 CYGNI

    Energy Technology Data Exchange (ETDEWEB)

    Huppenkothen, D. [Center for Data Science, New York University, 726 Broadway, 7th Floor, New York, NY 10003 (United States); Younes, G.; Kouveliotou, C. [Department of Physics, The George Washington University, Washington, DC 20052 (United States); Ingram, A.; Van der Klis, M. [Anton Pannekoek Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Göğüş, E. [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Bachetti, M. [INAF/Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047 Selargius (Italy); Sánchez-Fernández, C.; Kuulkers, E. [European Space Astronomy Centre (ESA/ESAC), Science Operations Department, E-28691 Villanueva de la Cañada, Madrid (Spain); Chenevez, J. [DTU Space—National Space Institute, Technical University of Denmark, Elektrovej 327-328, DK-2800 Lyngby (Denmark); Motta, S. [University of Oxford, Department of Physics, Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raanana 43537 (Israel); Gehrels, N. [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Tomsick, J. A. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Walton, D. J., E-mail: daniela.huppenkothen@nyu.edu [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)

    2017-01-01

    In 2015 June, the black hole X-ray binary (BHXRB) V404 Cygni went into outburst for the first time since 1989. Here, we present a comprehensive search for quasi-periodic oscillations (QPOs) of V404 Cygni during its recent outburst, utilizing data from six instruments on board five different X-ray missions: Swift /XRT, Fermi /GBM, Chandra /ACIS, INTEGRAL ’s IBIS/ISGRI and JEM-X, and NuSTAR . We report the detection of a QPO at 18 mHz simultaneously with both Fermi /GBM and Swift /XRT, another example of a rare but slowly growing new class of mHz-QPOs in BHXRBs linked to sources with a high orbital inclination. Additionally, we find a duo of QPOs in a Chandra /ACIS observation at 73 mHz and 1.03 Hz, as well as a QPO at 136 mHz in a single Swift /XRT observation that can be interpreted as standard Type-C QPOs. Aside from the detected QPOs, there is significant structure in the broadband power, with a strong feature observable in the Chandra observations between 0.1 and 1 Hz. We discuss our results in the context of current models for QPO formation.

  7. Climate, orography and scale controls on flood frequency in Triveneto (Italy

    Directory of Open Access Journals (Sweden)

    S. Persiano

    2016-05-01

    Full Text Available The growing concern about the possible effects of climate change on flood frequency regime is leading Authorities to review previously proposed reference procedures for design-flood estimation, such as national flood frequency models. Our study focuses on Triveneto, a broad geographical region in North-eastern Italy. A reference procedure for design flood estimation in Triveneto is available from the Italian NCR research project "VA.PI.", which considered Triveneto as a single homogeneous region and developed a regional model using annual maximum series (AMS of peak discharges that were collected up to the 1980s by the former Italian Hydrometeorological Service. We consider a very detailed AMS database that we recently compiled for 76 catchments located in Triveneto. All 76 study catchments are characterized in terms of several geomorphologic and climatic descriptors. The objective of our study is threefold: (1 to inspect climatic and scale controls on flood frequency regime; (2 to verify the possible presence of changes in flood frequency regime by looking at changes in time of regional L-moments of annual maximum floods; (3 to develop an updated reference procedure for design flood estimation in Triveneto by using a focused-pooling approach (i.e. Region of Influence, RoI. Our study leads to the following conclusions: (1 climatic and scale controls on flood frequency regime in Triveneto are similar to the controls that were recently found in Europe; (2 a single year characterized by extreme floods can have a remarkable influence on regional flood frequency models and analyses for detecting possible changes in flood frequency regime; (3 no significant change was detected in the flood frequency regime, yet an update of the existing reference procedure for design flood estimation is highly recommended and we propose the RoI approach for properly representing climate and scale controls on flood frequency in Triveneto, which cannot be regarded

  8. An adjustable multi-scale single beam acoustic tweezers based on ultrahigh frequency ultrasonic transducer.

    Science.gov (United States)

    Chen, Xiaoyang; Lam, Kwok Ho; Chen, Ruimin; Chen, Zeyu; Yu, Ping; Chen, Zhongping; Shung, K Kirk; Zhou, Qifa

    2017-11-01

    This paper reports the fabrication, characterization, and microparticle manipulation capability of an adjustable multi-scale single beam acoustic tweezers (SBAT) that is capable of flexibly changing the size of "tweezers" like ordinary metal tweezers with a single-element ultrahigh frequency (UHF) ultrasonic transducer. The measured resonant frequency of the developed transducer at 526 MHz is the highest frequency of piezoelectric single crystal based ultrasonic transducers ever reported. This focused UHF ultrasonic transducer exhibits a wide bandwidth (95.5% at -10 dB) due to high attenuation of high-frequency ultrasound wave, which allows the SBAT effectively excite with a wide range of excitation frequency from 150 to 400 MHz by using the "piezoelectric actuator" model. Through controlling the excitation frequency, the wavelength of ultrasound emitted from the SBAT can be changed to selectively manipulate a single microparticle of different sizes (3-100 μm) by using only one transducer. This concept of flexibly changing "tweezers" size is firstly introduced into the study of SBAT. At the same time, it was found that this incident ultrasound wavelength play an important role in lateral trapping and manipulation for microparticle of different sizes. Biotechnol. Bioeng. 2017;114: 2637-2647. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.